tag:blogger.com,1999:blog-31035748990926460312024-03-26T23:38:04.587-07:00Tankograd2014 - 2023Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.comBlogger18125tag:blogger.com,1999:blog-3103574899092646031.post-91348496961686243182022-10-21T07:08:00.026-07:002023-04-13T06:26:02.912-07:00MT-LB<h2 style="text-align: center;">
MT-LB</h2>
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghDWW8vQXyzhBQGvoW8uZ-Np32KHLBIKxoX5rCQhmj4YCWjuQlB9V2Ul_L75UZle-KaO4CLkE16OI7EQv9bZoRrv-8ec0Ou12zGj8ZCfRQKlbBNri9P1QdtJnv81-Qh1wndZqS0sNYlq-3c_eVnBHHF4Kx6hurcLqXWEcG1oWIpfbvWtu13TK-dLXdlg/s773/mt-lb%20towing%20guns%20to%20firing%20positions.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="345" data-original-width="773" height="286" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghDWW8vQXyzhBQGvoW8uZ-Np32KHLBIKxoX5rCQhmj4YCWjuQlB9V2Ul_L75UZle-KaO4CLkE16OI7EQv9bZoRrv-8ec0Ou12zGj8ZCfRQKlbBNri9P1QdtJnv81-Qh1wndZqS0sNYlq-3c_eVnBHHF4Kx6hurcLqXWEcG1oWIpfbvWtu13TK-dLXdlg/w640-h286/mt-lb%20towing%20guns%20to%20firing%20positions.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The MT-LB was developed by KhTZ (Kharkov Tractor Plant) as a successor to the AT-P and AT-L prime movers. It is worth noting that the KhTZ factory is distinct from the more famous KhPZ (Kharkov Locomotive Plant), responsible for the T-34, T-54, T-64, and so on. The MT-LB was intended for a tactical tractor-transporter role, acting as a prime mover for both anti-tank guns and artillery pieces. At the time it entered service, the most modern anti-tank gun available in the USSR was the 100mm T-12. Thanks to its lightweight design, this gun could be dependably towed by even the AT-P (<i>Артиллерийский Тягач - Полубронированный</i>, or Artillery Tractor - Semi-armoured), but even so, the size and payload capacity of the AT-P was too limited to effectively serve as the prime mover for the T-12, and the semi-armoured prime mover concept was becoming questionable due to the proliferation of tactical nuclear weapons. </div><div><br /></div><div>In contrast to the AT-P, the AT-L (<i>Артиллерийский Тягач - Лёгкий</i>, or Artillery Tractor - Light) was ostensibly providing untroubled service as a prime mover for heavy mortars and 122mm howitzers, but after some years of use in the army, hull cracking was observed due to vibrations from the suspension. On top of this, it was found in 1959 that its capacity for modernization was limited, as the level of mobility could not be feasibly improved by fitting a larger, more powerful engine because it led to the hull becoming excessively nose-heavy. </div><div><br /></div><div>With the AT-P and AT-L not performing to the desired level and lacking future prospects, the army found a need for a replacement for both vehicles. This was despite the fact that both vehicles had only recently entered service; the AT-P in 1954, and the AT-L in 1952. Given the need to fulfill the roles of two different prime movers, the successor vehicle in development at KhTZ was aptly named the MT-L (<i>Многоцелевой Тягач - Легкий</i>, or Multi-purpose Tractor - Light). </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJMOA-RIdO9SXW_IrhI7a28w6Iza-Bbgs2g-pUmHESIimWmfa03oE48JlwwGti_CqkfkkD8veAGSGPNMGhoW1dtUcWQ7MrE--4stXXzI206fAaw1TtTbb0MjyJRdsbaTiMIxlcAuhHfYA9j_cOluJbiAzpTavmmJnEOk0gWmdT_krxTZ8A-qbYHfaLrQ/s737/mt-l.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="322" data-original-width="737" height="280" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJMOA-RIdO9SXW_IrhI7a28w6Iza-Bbgs2g-pUmHESIimWmfa03oE48JlwwGti_CqkfkkD8veAGSGPNMGhoW1dtUcWQ7MrE--4stXXzI206fAaw1TtTbb0MjyJRdsbaTiMIxlcAuhHfYA9j_cOluJbiAzpTavmmJnEOk0gWmdT_krxTZ8A-qbYHfaLrQ/w640-h280/mt-l.jpg" width="640" /></a></div><div><br /></div><div>When the MT-L was still in development, the perceived need for a basic level of protection for a combat prime mover led to the Army's insistence on a fully enclosed armoured hull complete with NBC protection for the new vehicle, resulting in the creation of the MT-LB. With the addition of armour, the weight of the vehicle rose, although it was kept under control by the lowering of the vehicle silhouette. Compared with the 8.5-ton curb weight of the MT-L, the 9.7-ton curb weight of the MT-LB indicates that the weight gain was relatively limited despite the retention of almost all preexisting features; only the winch of the MT-L was removed in the MT-LB.</div><div><br /></div><div>Testing was carried out in the regions customarily used by the Soviet military, including the Arctic and Turkmenistan for cold and hot climate trials. On 25 December 1964, the development cycle of the MT-LB concluded and it was accepted into service in the Soviet Army alongside the MT-L. KhTZ began the process of retooling its AT-L production line to switch to MT-LB production, which was handled with difficulty, as the assembly line for AT-Ls had been maintaining an average production rate of 5 vehicles a day to meet demand. Under such circumstances, the idea of producing both the MT-L and MT-LB simultaneously only complicated matters. As there was a considerable difference in the hulls of the two vehicles, it was decided that the capacity of the KhTZ plant was to be concentrated into a single production line dedicated solely to the MT-LB, and the technical documentation for the MT-L was transferred to the Semipalatinsk Machine-Building Plant, where the technology was used to improve the plant's products. With this decision, the MT-L was effectively discontinued, and the success of the MT-LB was secured. According to the article "<i>Универсальный Солдат Многоцелевой Транспортер-Тягач МТ-ЛБ</i>" in the No.5 2014 issue of the "<i>Наука и Техника</i>" magazine, serial production of MT-LB at KhTZ officially began in 1966, but the first batch of vehicles was delivered only in 1967.</div><div><br /></div><div>To gain a better technical understanding of the MT-LB and the advancement it represented, it is necessary to first look at its predecessor, the AT-P. The creation of the AT-P was initiated on the basis of providing a modern successor to the successful T-20 "Komsomolets" and Universal Carrier prime movers, the latter of which was fairly ubiquitous in the Red Army thanks to Lend-Lease deliveries from Britain. The Universal Carrier and T-20 "Komsomolets" were both very basic vehicles, being more or less a container for an engine and its drivetrain. The accommodations for crew and passengers were spartan, simple clutch-brake steering was used, and the design followed civilian automotive conventions more than military conventions. This can be seen in their hulls, being built on a chassis with the armour plates riveted to a load-bearing frame upon which the drivetrain was installed, rather than having a monocoque construction. The AT-P was, in turn, a more modern iteration of the T-20, sharing its basic design and most of its design characteristics while introducing some modern ones, such as dispensing with the chassis concept in favour of a monocoque load-bearing hull and replacing the suspension bogies with individually sprung roadwheels. As the successor to the AT-P, the MT-LB completely diverged from this design heritage. </div><div><br /></div><div><div>The MT-LB was not a rudimentary prime mover like the AT-P and T-20. It was fitted with all of the requisite features for operation in cold environments, NBC-contaminated combat zones, for crossing water obstacles, for self defence, and had full armour protection with internal space for a full unit of fire for an anti-tank gun. This was the most major advance over the AT-P, which was considered semi-armoured because its cargo compartment was open-topped and the few crates of ammunition it could carry had to be tied down externally on the sponsons regardless of whether a full passenger load was carried or not, as shown below. Additional features of the MT-LB included a self-replenishing pneumatic system for windshield washing, for operating the on-board pneumatic brakes, and for the pneumatic brakes of a towed trailer (if present). </div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjjyCB5ZYj2Qoqje9b-IBy08-Yt0O6WB6ZyXwZqVjl9BubG1CdHpC8eTUhDcMmXf7oDaw90cZkwKV42Fk__sDrcSrDDPm6g51LaSlkDuvDEhTMn8a7UuMidcn2FwJ6vL2vdFAC1Vd_--IwoqGB5w_UVOxgeOsq40EDfBskQnuPa7GToaLxVyonVfUpE0Q/s802/at-p%20towing%20d-48.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="488" data-original-width="802" height="244" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjjyCB5ZYj2Qoqje9b-IBy08-Yt0O6WB6ZyXwZqVjl9BubG1CdHpC8eTUhDcMmXf7oDaw90cZkwKV42Fk__sDrcSrDDPm6g51LaSlkDuvDEhTMn8a7UuMidcn2FwJ6vL2vdFAC1Vd_--IwoqGB5w_UVOxgeOsq40EDfBskQnuPa7GToaLxVyonVfUpE0Q/w400-h244/at-p%20towing%20d-48.jpeg" width="400" /></a></div><div><br /></div><div>Prior to developing the MT-L and MT-LB, the KhTZ plant was responsible for the AT-L light artillery prime mover and GT-T amphibious prime mover, both of which were unarmoured tractor-transporters. Several major elements of the GT-T formed the basis for the design of the MT-L, which in turn made their way to the MT-LB. The most prominent design elements in common between the two vehicle families was the suspension, and the watertight monocoque load-bearing steel hull. The familial connection between the GT-T and the MT-LB was further deepened when the updated GT-TB model was later introduced, featuring an adapted version of the YaMZ-238 engine originally used in the MT-LB. </div><div><br /></div><div>However, the form of mid-engine, front-transmission layout used in the GT-T was not used in the MT-L. The GT-T had its engine sharing the crew cabin, with the crew seats placed astride the engine, which was imperfect in many respects but allowed for a completely free cargo bed. The same layout was used in the AT-P. Instead, the MT-L used the drivetrain layout of the ATS-59, even including a similar rear winch. Additionally, the gearbox and steering mechanism unit was derived from the type used in the AT-L, which entered service in 1947. Overall, there were very few novel ideas implemented in the MT-L, but its design was innovative in that it combined many successful features taken from existing prime movers. In fact, the mid-engined layout - which is rarely encountered in the present day and could be considered the most distinguishing feature of the MT-LB - was wholly typical of Soviet tracked tractor-transporters.</div><div><br /></div><div>Unlike most armored combat vehicles, tracked tractor-transporters are used, as a rule, with variable loads, so the layout must be designed to provide a satisfactory weight distribution across the suspension without a load, and optimal weight distribution with a load, so that the traction and ride quality is maximized at all times. For this reason, the placement of the engine in the middle of the hull, slightly forward of the geometric center of the track base, was particularly advantageous. This also has the minor benefit of limiting the maximum ground pressure for a given load.</div><div><div><br /></div><div><div><br /></div><div>As older prime movers were gradually decommissioned as they reached the end of their service lives, the demand for the MT-LB in the Soviet Army during the early 1970's reached a point that the production capacity of KhTZ was not enough to accommodate the volume of orders, not just domestically, but also in the armies of Warsaw Pact countries. To fill this demand, the BETA factory in Bulgaria and the Stalowa Wola Steelworks plant in Poland were commissioned with licences to produce the MT-LB, and MT-LBs commenced licensed mass production in 1972 in Bulgaria, then in Poland in 1976.</div><div><br /></div><div>Having the combination of a large load capacity, a relatively large cargo compartment, excellent weight balance, high power reserve, a basic level of armour protection and a high degree of operational commonality with domestic light and medium trucks, the MT-LB was frequently taken as the basis for lightweight specialized military vehicles. This differentiated it from similar vehicles made as personnel carriers, which tended to be designed with smaller gross weight ratings, adequate for passengers and a small complement of equipment, but no more. With the MT-LB, many modifications could be added without violating the buoyancy reserve and without needing automotive upgrades to maintain the same level of performance.</div><div><br /></div><div>As an example of this, the BRDM-2 was rated for a combat weight of 7 tons, and it only meets its rated performance metrics as-is. The Strela-1 modification, built on the basis of the BRDM-2 hull, required weight-saving measures such as the removal of the belly wheels and their drive system in order to maintain the same combat weight of 7 tons. With the MT-LB, a much heavier system could be fitted, with the resulting Strela-10 vehicle weighing 12.3 tons without violating the specifications of the basic MT-LB. In fact, the weight of 12.3 tons reached the 20% limit of the reserve buoyancy required to maintain a safe swimming capability, but not the limit of other parameters. </div><div><br /></div><div><br /></div><div>Following the MT-LB, the MT-LBu variant was created to function as a basis for support vehicles, ranging from artillery fire control posts, to mobile headquarters for air defence units, and even radar stations. To accommodate this equipment, a new enlarged hull (taller by 485mm, longer by 800mm) with 7 roadwheel pairs and a revised layout (reverting to the MT-L layout) was used. </div><div><br /></div><div>The MT-LBu will not be covered in this article for the time being, partly because it is largely the same as the basic MT-LB while also being substantially different, and partly because some features of the MT-LBu are somewhat indeterminate, as changes are made on an individual basis depending on the requirements of the modification. Generally speaking, an MT-LBu is usually unarmed, but a machine gun for self-defence may be fitted on specialized models that faced some danger of attack from enemy reconnaissance probes or exploitation forces. For instance, the 1V13, 1V14 and 1V16 artillery battery fire control vehicles were armed with a pintle-mounted DShKM, theoretically allowing them to serve as a base of fire for troops while the howitzers or guns of the battery fire upon the armoured vehicles of the enemy force with direct fire. </div><div><br /></div><div>Although it is often lauded for its versatility in contemporary literature, the original MT-LB was largely confined to its role as an artillery prime mover during its service in the Soviet Army. In the 1980's, it started to see some use in northern Russia as cargo carriers to remote areas thanks to its high cross-country mobility, and after the dissolution of the Soviet Union, this practice saw a boon as private civilian ownership of MT-LBs became possible. In its original capacity as a military vehicle, the MT-LB was, for the most part, not a pure armoured personnel carrier or a pure tractor, but an artillery prime mover, however vague that distinction may be. Only the MT-LBu can be said to have taken on a wide variety of roles during its time in the Soviet Army, which is due to the fact that it was specifically designed to do so.</div><div><br /></div><div>Rather than the MT-LB, it was the MT-LBu that became the de facto tracked platform for light specialized systems in supporting roles. The next increment in weight class was the GM-123, an older but capable medium tracked vehicle repurposed from the abandoned SU-100P hull that found a range of uses in specialized roles. Other notable lightly-armoured medium platforms were the GM-575 and its modifications (578, 568) in 1967, and the GM-569 series and its modifications (567, 577, 579) in 1978, both made specifically for army tactical air defence systems.</div><div><br /></div><div>Unlike the MT-LBu, the MT-LB itself was only occasionally used as a basis for specialized vehicles; the notable were the Strela-10 and "Shturm-S". It may be surmised that this was partly due to the limited scope for unification within the niche of light tactical combat vehicles, and partly because the BMP had just entered service, and its hull was more suitable for specialized vehicles operating in, or ahead of the frontline.</div><div><br /></div><div>The main variants of the MT-LB in the Soviet Union were the:</div><div><ol style="text-align: left;"><li>MT-LBV</li><li>MT-LB with self-entrenchment equipment (allegedly exclusively imported from Poland)</li><li>MT-LBVM</li><li>Modifications 32, 35 and 49</li></ol></div><div></div><blockquote><div>The MT-LBV, entering service in 1972, introduced new roadwheel swing arms, fenders and mudguards to accommodate a wider set of tracks. </div></blockquote><blockquote><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirFy6XFpTRtfHP6rzzz-uLtgjINbgzvyI4gbxPpIU2aD9KcRLoFI0jUcDpiVbBExcYWmjrJgXGqe5msqdJI1ZNLcSaTB5mWHJVm212TKMar59tbOBTRJGKBqn7tCimlHjx9PNnuhoeSI7O8H2uWoblUwB3CYNc2KZ3PrQzcKFZ8PxO2YMvZeLDQ4X7Lw/s800/ttgm_ris_2_copy.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="284" data-original-width="800" height="228" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirFy6XFpTRtfHP6rzzz-uLtgjINbgzvyI4gbxPpIU2aD9KcRLoFI0jUcDpiVbBExcYWmjrJgXGqe5msqdJI1ZNLcSaTB5mWHJVm212TKMar59tbOBTRJGKBqn7tCimlHjx9PNnuhoeSI7O8H2uWoblUwB3CYNc2KZ3PrQzcKFZ8PxO2YMvZeLDQ4X7Lw/w640-h228/ttgm_ris_2_copy.jpg" width="640" /></a></div><div><br /></div><div>The MT-LBVM model, entering service in 1982, replaced the machine gun turret with a 12.7mm NSVT heavy machine gun weapon station.</div></blockquote><blockquote><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjOSz1HDx7aSxlGcF86poRRGcPDtVs3I1XYrRpaO0AZM98BjfFPgIRSKG8y7sz8V8ctmefIgFi4_DOwL7m9S85IFpjQLjHFZUKtdcDDaDnTAxm4ONh6UFtB8nhAC_JPvd8jYesPibet6AI6oGAvYVV-2D9q1G4bShlsAwAMKqRaNyzF1lvgbAYqr5Skkg/s800/ttgm_ris_3_copy.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="297" data-original-width="800" height="238" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjOSz1HDx7aSxlGcF86poRRGcPDtVs3I1XYrRpaO0AZM98BjfFPgIRSKG8y7sz8V8ctmefIgFi4_DOwL7m9S85IFpjQLjHFZUKtdcDDaDnTAxm4ONh6UFtB8nhAC_JPvd8jYesPibet6AI6oGAvYVV-2D9q1G4bShlsAwAMKqRaNyzF1lvgbAYqr5Skkg/w640-h238/ttgm_ris_3_copy.jpg" width="640" /></a></div><div>Modifications 32, 35 and 49 are simplified versions of the MT-LB, primarily made for cargo ferrying purposes. These three models are shown in ascending order below. On Modification 35, there is a large circular hole on the hull roof with an unknown purpose.</div></blockquote><div></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinPKy0g5-xOts83KCEykwsYWgzQ5XtRTSZihAdFcUag7woGoepwvf3t6zurpOHvOZMH_gCdSLQT_2S19DPt__FMSEGT5mWDxWA7D7xodtwDdn69DirZFtGwPMLpaXK4R5etTi_Uppy8J7rYDHn246E0yLYXV5Vq6SKS5FkkCLQUH7ELaLsLOVsa4Dx_w/s1329/32.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="574" data-original-width="1329" height="173" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinPKy0g5-xOts83KCEykwsYWgzQ5XtRTSZihAdFcUag7woGoepwvf3t6zurpOHvOZMH_gCdSLQT_2S19DPt__FMSEGT5mWDxWA7D7xodtwDdn69DirZFtGwPMLpaXK4R5etTi_Uppy8J7rYDHn246E0yLYXV5Vq6SKS5FkkCLQUH7ELaLsLOVsa4Dx_w/w400-h173/32.png" width="400" /></a></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0qmD5zP_EwxbovtrzR6RIFBnX4e74Alw6hOo4fz-E4lUg_fPwiNq1C-3Gz-HZPHqyH6GnlnS0oQLChuonbsgsAv2IROsLj6BpIfuCeRNAeqNMtBTfvTO2Skm0fD_AnzRFpG9iyH-ySR9nLDR6aM9oURZIpULNHVYDPINNZEN-nuYyPUQRfIbw3lc1iw/s1298/35.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="615" data-original-width="1298" height="190" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0qmD5zP_EwxbovtrzR6RIFBnX4e74Alw6hOo4fz-E4lUg_fPwiNq1C-3Gz-HZPHqyH6GnlnS0oQLChuonbsgsAv2IROsLj6BpIfuCeRNAeqNMtBTfvTO2Skm0fD_AnzRFpG9iyH-ySR9nLDR6aM9oURZIpULNHVYDPINNZEN-nuYyPUQRfIbw3lc1iw/w400-h190/35.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgVYoMz9AqJ7ZszAwJxiC66d3JARZV1BMCxoG9LX6YLiqwPaosvbip_3DEK0zwQh-f3IKIPfKOU-2z_FvT4zrIlAB5CBdxS8beksTiuliLSN--wfScjIn2gNyuJyVFplWcftpNscMzxb4EI5Fwo5VQOg0WrhZGy1hVCLk1n8dXv-WQshSDNirqaJDe9KA/s1319/49.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="566" data-original-width="1319" height="171" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgVYoMz9AqJ7ZszAwJxiC66d3JARZV1BMCxoG9LX6YLiqwPaosvbip_3DEK0zwQh-f3IKIPfKOU-2z_FvT4zrIlAB5CBdxS8beksTiuliLSN--wfScjIn2gNyuJyVFplWcftpNscMzxb4EI5Fwo5VQOg0WrhZGy1hVCLk1n8dXv-WQshSDNirqaJDe9KA/w400-h171/49.png" width="400" /></a></div><div><br /></div><div><br /><div>According to the analysts of the Central Scientific Research Institute of armament and military equipment of Ukraine, there are between 40 to 50 thousand MT-LB vehicles of various models in service with 42 armed forces throughout the world. <a href="https://army.ric.mil.ru/Stati/item/318241/">An article</a> on the Russian Ministry of Defence website makes a similar claim that more than 44,000 MT-LB and MT-LBu vehicles were produced, including for the armies of more than two dozen foreign countries.</div><div><br /></div><div>In its role as an artillery prime mover, the MT-LB had no analogues in the world at the time it entered service. That said, the reason it had no analogues was because towed artillery was being phased out in favour of self-propelled artillery at the time, and efforts were focused in this direction among all of the major military powers of the world. In terms of its design, it was technically deficient in many of the design details relevant to combat vehicles, sharing more in common with utility vehicles such as contemporary domestic military trucks and artillery prime movers.</div><div><br /></div><div><br /></div><div>The MT-LBVM modification, which entered service in 1982, was created based on feedback from Afghanistan. The modifications consisted of a new remote weapon station with an 12.7mm NSVT machine gun instead of the original 7.62mm turret. Its combat weight rose only negligibly, to 10.5 tons. This feedback was related to the use of MT-LBs as tracked personnel carriers in direct combat, like BTRs, and the MT-LBVM was likewise intended for this role. In this configuration, MT-LBs have served as tracked replacements for wheeled BTRs in motor rifle units stationed in the Far East and Northern Russia, where impassable terrain severely restricted the choice of transportation. In this regard, the MT-LBVM did not have any analogues in the world at the time, as the closest equivalent was the Bv 206S which only entered service in the early 2000's. </div><div><br /></div>
<h3 style="text-align: left;"><span style="font-size: large;">INDEX</span></h3>
<hr />
<ol style="text-align: left;">
<li><a href="#ergonomics">Ergonomics</a></li>
<li><a href="#firingports">Firing Ports</a></li>
<li><a href="#ventilation">Ventilation</a></li>
<li><a href="#heater">Heater</a></li>
<hr />
<li><a href="#commander">Commander's Station</a></li>
<li><a href="#armament">Armament</a></li>
<li><a href="#tkb-01-1">TKB-01-1 Turret</a></li>
<li><a href="#tkb">TKB Turret</a></li>
<hr />
<li><a href="#protection">Protection</a></li>
<hr />
<li><a href="#driver">Driver's Station</a></li>
<li><a href="#cargo">Cargo</a></li>
<li><a href="#mobility">Mobility</a></li>
<li><a href="#engine">Engine</a></li>
<li><a href="#engineaccessories">Engine Accessories</a></li>
<li><a href="#cooling">Cooling</a></li>
<li><a href="#fuel">Fuel System</a></li>
<li><a href="#transmission">Transmission</a></li>
<li><a href="#steering">Steering System</a></li>
<li><a href="#suspension">Suspension</a></li>
<li><a href="#water">Water Obstacles</a></li>
</ol>
<hr /><p></p>
<div class="separator" style="clear: both;"><br /></div><div><div><div>Special thanks to <a href="https://crib-blog.blogspot.com/">Cate</a> from the CRIB blog and Lottie from the Australian Armour & Artillery Museum Cairns for photos, measurements and other assistance.</div><div><br /></div><div><br /></div><div><a href="https://www.blogger.com/null" id="ergonomics"></a><h3 style="text-align: left;"><span style="font-size: large;">ERGONOMICS</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhW6Y9EAfuepXWC9smKROCx7PAfKQ9x0oLywjrDXyciUM8nJu712YbVBxPsCC3UdCXid__8cNNKfkUTSs7bSBvS0_YBDgtC4gfBeZ0hj-jpJWpXCqy675EatsPdgDaA2gisu1lXlsxOOxqhAaT_QUZ9WFD1eMh0P3JcIr_CzHuOYsaLy6H1cYUu6E3lZQ/s951/mt-lb%20seats.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="566" data-original-width="951" height="380" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhW6Y9EAfuepXWC9smKROCx7PAfKQ9x0oLywjrDXyciUM8nJu712YbVBxPsCC3UdCXid__8cNNKfkUTSs7bSBvS0_YBDgtC4gfBeZ0hj-jpJWpXCqy675EatsPdgDaA2gisu1lXlsxOOxqhAaT_QUZ9WFD1eMh0P3JcIr_CzHuOYsaLy6H1cYUu6E3lZQ/w640-h380/mt-lb%20seats.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The crew consists of 2 people - driver and commander. When used as an armoured personnel carrier, there are a total of 11 seating spaces available in the cargo compartment. This passenger capacity gave ample surplus space for a motorized infantry squad, which was composed of only 7 men during the periods relevant to the MT-LB (post-1964).</div><div><div><div><br /></div><div>The seating layout in the cargo compartment consists of two benches, seating four people each, supplemented by a fold-out seat just behind the engine compartment corridor. There are an additional two fold-out seats in the corridor itself. The walls and ceiling have no linings for insulation, radiation shielding or otherwise; the only lining present is the rubber anti-slip floor mats.</div><div><br /></div><div>The passengers in the cargo compartment sit facing inward, with the possibility of fully outstretching their legs in the span of space between the benches. The person occupying the supplementary fold-out seat sits opposite the duct of the heater. The benches are rectangular floor fuel tanks with a contoured upper surface, complete with thick foam cushions. The <a href="https://miniteh.com/articles/Obzory/MTLB---tehnicheskie-harakteristiki-i-osobennosti-vezdehoda">photo below</a> shows the cargo compartment benches of an MT-LB without the cushions and backrests.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqXEa8sCRZq33pRnURct8PJPhEuYSZPz2xhNTFpU00-GDi7YJFFaNR61xNFYUOFRZaZvWSifKKwpdQYmxnM_WiyHQk9Lvh9s9KL3yqIHkIdBAKK8lX-WsbIU-Mt3aiXfvNmAOgoc1OqbgTMjwwrsHpEUe6fgAfaTa0nA_HlzyFP0geiD-k48QJo_nGiw/s800/370-7c0cba01b99971637143d7ab48f88f5d.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="500" data-original-width="800" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqXEa8sCRZq33pRnURct8PJPhEuYSZPz2xhNTFpU00-GDi7YJFFaNR61xNFYUOFRZaZvWSifKKwpdQYmxnM_WiyHQk9Lvh9s9KL3yqIHkIdBAKK8lX-WsbIU-Mt3aiXfvNmAOgoc1OqbgTMjwwrsHpEUe6fgAfaTa0nA_HlzyFP0geiD-k48QJo_nGiw/w640-h400/370-7c0cba01b99971637143d7ab48f88f5d.jpg" width="640" /></a></div><div><br /></div><div>The backrests of the benches are folding sheet steel panels with a cushion. When carrying cargo instead of passengers, the backrests are folded down onto the benches to provide a level surface to place cargo. </div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-TQqSBHTWVas/YK2gZO6qmxI/AAAAAAAATHg/EXzYJFBhncU5Ax-mMRZ_W8eXebA_pBMBACLcBGAsYHQ/s640/MT-LBinsideright.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="475" data-original-width="640" height="297" src="https://1.bp.blogspot.com/-TQqSBHTWVas/YK2gZO6qmxI/AAAAAAAATHg/EXzYJFBhncU5Ax-mMRZ_W8eXebA_pBMBACLcBGAsYHQ/w400-h297/MT-LBinsideright.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8Wiu_lMShUg7QDPUG5WazE2oS2P-caIc3Tygo8T0yOE4FzrI2nLptWdiGRi86AXT2ad9_Dvxc8iZz571YvBQ8A5XUZNFAjWimM76PMqiRhxCnP5SOToNvhu_jGo8wG4-bFlFvtjEzUPzt_qEjDXXmgBgVgGjpeoxd6RehQcs-sGIP-M2hvbkmMcHpsw/s1136/cushions.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="829" data-original-width="1136" height="293" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8Wiu_lMShUg7QDPUG5WazE2oS2P-caIc3Tygo8T0yOE4FzrI2nLptWdiGRi86AXT2ad9_Dvxc8iZz571YvBQ8A5XUZNFAjWimM76PMqiRhxCnP5SOToNvhu_jGo8wG4-bFlFvtjEzUPzt_qEjDXXmgBgVgGjpeoxd6RehQcs-sGIP-M2hvbkmMcHpsw/w400-h293/cushions.gif" width="400" /></a><br /></div><div><br /></div></div><div><br /></div><div>With the engine offset to the port side of the hull, the void on the starboard side formed a narrow corridor between the crew compartment and the cargo compartment. The other two seats are hinged to the engine compartment partition, and unfold into this corridor between the crew cabin and the cargo compartment. Two passengers sit may facing forward in this corridor. The void in the engine compartment partition for the space for these seats is the space under the right cylinder bank and exhaust manifold of the YaMZ-238 engine. </div><div><div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjSCyPTFK721asQnVHkRFpUx581iGmhjas3YvyBY6lrAqbw2dUWyABOeoG7oZGX3SpbS7HF8RHn-tn1WCKp_a5Fxrqhh2Pn4Mal5IaGIKlkkKPhJZO8v6GnX5jlxBGNEZhP980g4fUiNOxl4pF5mmsMvhIuVjifO2xazR8ejymStefF67OSUGOmuE8RLg/s640/7f38e885583c.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="640" data-original-width="480" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjSCyPTFK721asQnVHkRFpUx581iGmhjas3YvyBY6lrAqbw2dUWyABOeoG7oZGX3SpbS7HF8RHn-tn1WCKp_a5Fxrqhh2Pn4Mal5IaGIKlkkKPhJZO8v6GnX5jlxBGNEZhP980g4fUiNOxl4pF5mmsMvhIuVjifO2xazR8ejymStefF67OSUGOmuE8RLg/w300-h400/7f38e885583c.jpg" width="300" /></a></div><div><br /></div></div></div></div><div>The corridor has a width of 450mm and a full length of 1,300mm. When folded out, the seats take up almost the entire width in the corridor.</div><div><br /></div><div>To reduce the impact of engine heating on the temperature at this corridor, which would otherwise be very high because it is next to the right exhaust manifold, the engine compartment partition is insulated with a spaced reflector sheet in addition to an asbestos lining, whereas the other partitions have only an asbestos lining. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAHIzE78y1PeYkjhODwU8BNXWG9VXOrqD9k4RrjUNYtWA__uDj7guG6VYaWQ2-qdhWzTsQ8t3Ide_yfyrUps4aU992PlbWRB5j9m0kMN_r-U_u5zmqFxKwyBSVsJoaQnEG-Ddaoxp78RAzq9i6Q0fj-y8vyqbc71Isk6NPUWLnxUK4Z2WjwZfG6cv23A/s1024/mtlb-39.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAHIzE78y1PeYkjhODwU8BNXWG9VXOrqD9k4RrjUNYtWA__uDj7guG6VYaWQ2-qdhWzTsQ8t3Ide_yfyrUps4aU992PlbWRB5j9m0kMN_r-U_u5zmqFxKwyBSVsJoaQnEG-Ddaoxp78RAzq9i6Q0fj-y8vyqbc71Isk6NPUWLnxUK4Z2WjwZfG6cv23A/w400-h300/mtlb-39.jpg" width="400" /></a></div><div><br /></div><div>The image below shows the three types of seats available in the cargo compartment. From left to right, these are the corridor seats, the supplementary seat, and the benches. The fold-out seats are largely the same in basic design, and are the same in terms of ergonomics. The seats are around an inch lower than the benches, giving slightly more headroom.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwJmxDIyIMOSXFjWfY3gtxH415AadUlOB57dso69CkKnfBuH7FqiZygMbZzbMC__fmTBej85pcq-HJaSOHzwaB4q2BhVpiPOdYde_k7tPvvsK9O2bfZDZDNY8DdP0OXeRPIO_8Ds-FlFXPoKo5AEN1bWXNco8HAAJ6MnnS7MNeo16q6N5VOz9ylwSnVw/s693/mt-lb%20passenger%20seats.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="290" data-original-width="693" height="268" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwJmxDIyIMOSXFjWfY3gtxH415AadUlOB57dso69CkKnfBuH7FqiZygMbZzbMC__fmTBej85pcq-HJaSOHzwaB4q2BhVpiPOdYde_k7tPvvsK9O2bfZDZDNY8DdP0OXeRPIO_8Ds-FlFXPoKo5AEN1bWXNco8HAAJ6MnnS7MNeo16q6N5VOz9ylwSnVw/w640-h268/mt-lb%20passenger%20seats.jpg" width="640" /></a></div><div><br /></div><div><div><br /></div><div>When transporting a gun crew while carrying an allocation of ammunition, two passengers would be seated here in order to clear up space on the left half of the cargo compartment for ammunition crates. For instance, when transporting the 6-man crew of a T-12 anti-tank gun, all 6 men can be seated on the right half of the hull and all can leave through the right rear door in single file, leaving the left half for ammunition. An example of this packing layout is depicted in the drawing below.</div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4EJQaDoBtxO7SFgyG7z9EY0BpxRFzYVqvtFaCGitOPwO7mlul0XKJOgMCwZcWK65NJr0hBQCf12I5LwM3Rxtii2nYNlB8YIiLxSjzMbACU0cBlFAGWQijtxCU_Fn861-my2tbDAEbaRXtZa9aJ12Ca0dgjKMbWMzvgJozPR0JwB6jxbqN65RZ7XV7FQ/s1391/seating%20option.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="869" data-original-width="1391" height="250" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4EJQaDoBtxO7SFgyG7z9EY0BpxRFzYVqvtFaCGitOPwO7mlul0XKJOgMCwZcWK65NJr0hBQCf12I5LwM3Rxtii2nYNlB8YIiLxSjzMbACU0cBlFAGWQijtxCU_Fn861-my2tbDAEbaRXtZa9aJ12Ca0dgjKMbWMzvgJozPR0JwB6jxbqN65RZ7XV7FQ/w400-h250/seating%20option.png" width="400" /></a></div></div><div><br /></div></div><div>When used to transport cargo, there are no passengers and no practical utility in allowing the crew to move between the crew and the cargo compartments, so this passage could be used as additional cargo space. When under heavy fire from the front, it also provides the crew with the invaluable option of evacuating the vehicle through the rear doors. </div></div></div><div><br /></div><div>Because most of the cargo compartment roof is allocated as cargo space, the passengers are limited to only two roof hatches, occupying under a third of the available roof space. The roof hatches have a square shape and are quite large, which is beneficial in emergency situations such as when exiting the vehicle with a life jacket, but they are not long enough to allow more than one person to pass through or stand in the opening. For mounted combat, the maximum number of passengers firing from the hatches is two. As the hatches open forward, they could also help in providing small arms protection for passengers opting to fight from the hatches.</div><div><br /></div><div style="text-align: center;"><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7wElFxgavn0ny1y092weNYqyJmRPcux6ckaNCZIO-ef1rOlAio82Pz73vuF4e0SfDP-E6sYVmNjGASQES6f8X-2JGQip5GHxhD5v6AZUhZ5ahMWnpYUtQ3XeimRTlnMwUvklbQrzgV7jflUl5hQKQ4_RLCeRogy7URa4LpkLlXBaWA7n8-OIBT2npHA/s1000/org_cylc715.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="678" data-original-width="1000" height="271" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7wElFxgavn0ny1y092weNYqyJmRPcux6ckaNCZIO-ef1rOlAio82Pz73vuF4e0SfDP-E6sYVmNjGASQES6f8X-2JGQip5GHxhD5v6AZUhZ5ahMWnpYUtQ3XeimRTlnMwUvklbQrzgV7jflUl5hQKQ4_RLCeRogy7URa4LpkLlXBaWA7n8-OIBT2npHA/w400-h271/org_cylc715.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg6uHDoaMtW8FG_9QtzLSmDXq841usUKvQNg6-SCEG_Ck67uSKY3CPAfjv6QlrZEXV8igPVoDmcWmvB665qZqnuNGx1u5T34Immeu4_7_BFidEzp4OXK6hOM6uJ5P2S1mpyMYh8yYtQ_W1sq6zVOQJjtGscOfB44coJ9sYRrZF-KNUplsn07knpFafxfA/s800/ttgm_02_copy.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="426" data-original-width="800" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg6uHDoaMtW8FG_9QtzLSmDXq841usUKvQNg6-SCEG_Ck67uSKY3CPAfjv6QlrZEXV8igPVoDmcWmvB665qZqnuNGx1u5T34Immeu4_7_BFidEzp4OXK6hOM6uJ5P2S1mpyMYh8yYtQ_W1sq6zVOQJjtGscOfB44coJ9sYRrZF-KNUplsn07knpFafxfA/w400-h213/ttgm_02_copy.jpg" width="400" /></a></div></div><div><br /></div><div>A strong example of the vehicle's design focus as a prime mover can be seen in its hull layout, particularly the location of the engine. Although this layout is not volumetrically inefficient, nor is it impractical for accommodating passengers, it is highly inefficient in terms of providing the maximum length of free space for a given total hull length. Although the corridor next to the engine compartment allows men to be seated or additional cargo to be stowed, the contiguous length of the cargo compartment is only 40% of the total structural length of the hull. This is in contrast to the BTR-60, 70 and 80 where the crew and passengers all occupy a single contiguous compartment that spans around 65-70% of the hull structural length. The same is true for truck-type personnel carriers with a conventional front-engine layout like the BTR-152.</div><div><br /></div><div>It is also not optimal in terms of integrating a turreted weapons module, particularly ones occupying a substantial swept radius of space below the turret ring. This is immediately apparent in the hull of the 2S1 "Gvozdika", which was adapted from the MT-LB. By retaining the same powertrain without revising the hull layout, it was not possible to mount a 3-man turret and have rear ammunition racks without extending the hull and suspension by one roadwheel. In contrast, during the development of the 2S1, one of the competing proposals based on an extended Object 765 (BMP) hull was not only able to integrate the turret, but had rear rack space for an additional 20 cartridges.</div></div><div> </div><div><div><div>The structural height of the MT-LB hull without its machine gun turret is 1,211mm. That is, the height from the hull belly to the roof plates is 1,211mm, excluding the thickness of the plates themselves, and excluding any additional height from hatches or external fittings. Considering the armour plate thickness of 7mm on both the belly and roof, the internal height is 1,197mm. </div><div><br /></div><div>For reference, according to data in the U.S Army the IFV Task Force Study, which was carried out in 1978, the M113A1 has an internal hull height of 1,206.5mm at the cargo compartment, which is a large difference from the structural hull height of 1,422mm due to the thick aluminium roof (1.5") and belly (1.1") plates, tall torsion bar housings (5.4"), and false floor paneling (0.5") on top of the torsion bar housings to provide a flat floor surface in the cargo compartment.</div><div><br /></div><div>The nominal dimensions of the cargo compartment, according to an MT-LB manual, are 2,605 x 1,948 x 1,150 mm. These dimensions are measured from the engine compartment firewall to the rear doors for length, between the fuel tanks in the sponsons for width, and between the reinforcing beams on the floor and the surface of the ceiling for height. In practice, the benches, which are not removable to free up cargo space, reduces the actual height available for cargo along half of the given cargo compartment width. The nominal cargo space is calculated to be 5.8 cubic meters, but the actual space is somewhat less when the seats are taken into account. This is practically the same as the cargo space in an M113.</div><div><br /></div><div>The benches are placed 500mm behind the engine compartment firewall, leaving empty space in front of the left bench for loose stowage and a space in front of the right bench for the supplementary fold-out seat. The remaining 315mm of space between the benches and the rear doors is taken up by the track tensioning mechanisms for each idler wheel. </div><div><br /></div><div>The length of the benches is 1,790mm. This is exactly the length required to fit four men with a 50th percentile shoulder width in shoulder-to-shoulder seating. The maximum height of the benches from the floor is 300mm, which can be seen in the cross-sectional drawing below, where the top surface of the bench is shown to be only a little higher than the axis of the towing hitch, itself 260mm from the floor*. The minimum headroom, when measured from bench surface to ceiling, is 860mm. When measured from the surface of the dip in the bench, the headroom is 950mm. All measurements regarding passenger seating were kindly provided by Lottie of the Australian Armour & Artillery Museum Cairns.</div><div><br /></div><div>*<i>MT-LBVM manual lists a nominal height of 667mm to towing hitch, and nominal ground clearance of 400mm </i></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_-xWv-57MjDr6hzIiwstes_p0VPWQTOIRZVPed6-PyB5IDlPmzZAzP_tLK4gEUmtxJElYP8Mxv9GqJMKnRDj7787KMdOXyZk2j4PDd4GLEo3gpemvdJJJytKNefd8ba1Qev8aTjnoSZGj-r70CTpK-zzntFz0vhSxpk7bpwba47Zr9xNUAJdc2j_BMw/s1280/cross%20section.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="425" data-original-width="1280" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_-xWv-57MjDr6hzIiwstes_p0VPWQTOIRZVPed6-PyB5IDlPmzZAzP_tLK4gEUmtxJElYP8Mxv9GqJMKnRDj7787KMdOXyZk2j4PDd4GLEo3gpemvdJJJytKNefd8ba1Qev8aTjnoSZGj-r70CTpK-zzntFz0vhSxpk7bpwba47Zr9xNUAJdc2j_BMw/w640-h212/cross%20section.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div><div>The seated headroom, when taking into account the contour of the dip in the bench and the compression of the foam cushion when sat on, can be expected to be around 890mm. This means that when the passengers are sitting in an erect posture, the height of the cargo compartment is nominally sufficient to accommodate a contemporary 50th percentile Soviet male, who would have a standing height of 170cm, or a 30th percentile American adult male, according to data from a 1966 U.S Army anthropometric study conducted with Army personnel. According to the 1966 data, a 30th percentile male would have an erect seated height of 888.1mm. According to the 1974 ergonomics monograph "<i>Обитаемость Объектов Бронетанковой Техники</i>", which references anthropometric data of Soviet military personnel in the tank forces, the statistical average seated height is 891mm, with a standard deviation of 30mm. Using two standard deviations to describe the maximum seated height, it was determined to be 952mm, although actual measurements showed that the actual tallest seated height among real servicemen was 940mm.</div><div><br /></div><div><br /></div><div>In practice, passengers belonging to those percentile groups will likely not be able to sit in an erect posture due to the discomfort of a lack of head clearance in off-road driving and especially if the passengers are wearing helmets, which will add over an inch to their height. This can be seen in the photos below. Note that the passenger on the right (with the red armband) is not seated on a bench in this MT-LBVM for some reason, but on the ammunition racks for 12.7mm ammo boxes. Because of this, the reinforcing frame on the ceiling interferes with his headroom.</div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQOPSltxc3RjYtujV0oG9z0pyIrYRxsaPFCBQrIJm0A9yoh50q6-h347dLzgLgT7eWVw4bjQf_mynGUBIbqVpnJaKv7sDF33Hxz64kGwfNlHivDLp4m8vjQGPUxpB_q4HsNUtfFxUUk_UBbgiTX3qfmimJee3LHQgh5HonXnh76m1yokgexklfCtvKDg/s1000/entry.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="666" data-original-width="1000" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQOPSltxc3RjYtujV0oG9z0pyIrYRxsaPFCBQrIJm0A9yoh50q6-h347dLzgLgT7eWVw4bjQf_mynGUBIbqVpnJaKv7sDF33Hxz64kGwfNlHivDLp4m8vjQGPUxpB_q4HsNUtfFxUUk_UBbgiTX3qfmimJee3LHQgh5HonXnh76m1yokgexklfCtvKDg/w400-h266/entry.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEixTVkpzG6EJUQChuCmjsBpj2hkXSDtw0pwvvPRpcQrRPNTUknUWZevC6nJV2MandRmX8PhT4YUb7c-zuwbkwBs851xTsCS2V6W3sY9lXCGfX6qYJ7UedIO6rmZtLVy9sUZonrDYsVBwT7vH1uC_F1NVfq_HtmYXjw29PRQM9ArMcrljPPpGOWo5CkLrw/s1000/inside.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="666" data-original-width="1000" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEixTVkpzG6EJUQChuCmjsBpj2hkXSDtw0pwvvPRpcQrRPNTUknUWZevC6nJV2MandRmX8PhT4YUb7c-zuwbkwBs851xTsCS2V6W3sY9lXCGfX6qYJ7UedIO6rmZtLVy9sUZonrDYsVBwT7vH1uC_F1NVfq_HtmYXjw29PRQM9ArMcrljPPpGOWo5CkLrw/w400-h266/inside.jpg" width="400" /></a></div><div><br /></div><div>Based on the seat height, it can be surmised that although it is possible for the passengers to fully outstretch their legs in the span of space between the benches, the seats were designed with a conventional upright seating posture in mind, and as such, were built with a relatively high popliteal height to accommodate the legs. Because of this design decision, the cargo compartment may feel shorter than the driver's positions in domestic tanks where the politeal height of the seat is much shorter, despite the MT-LB hull actually being structurally taller than domestic tank hulls. For comparison, the M113A1 has a 990mm of headroom, despite the interior hull height being almost identical. This was achieved by sacrificing popliteal height with lower benches, only 216mm above the floor. </div><div><br /></div><div>In principle, the MT-LB accommodates the same demographic of soldiers as the BMP, which should not be surprising since combat vehicles were designed according to the same ergonomic guidelines. In the case of the BMP, it has a structural hull height of 1,175mm and a seated headroom space of 890mm, according to West German technical drawings, or 892mm (35.125") with a seat height of 267mm (10.5") according to the IFV Task Force Study. Although the hull is slightly shorter, the same headroom is provided by having lower seats with thinner cushions, at the expense of legroom. </div></div><div><br /></div></div><div><br /></div><div>On the MT-LBV, the possibility of using a standard vehicle as a casualty evacuation vehicle was provided by the implementation of special mounting brackets to secure standard stretchers, which have a length of 2,200mm with a handle diameter of 42mm. The cargo compartment can fit four stretchers, one on the floor between the benches, and three in a second tier above the benches. This is equal to an medevac-configured M113, although the stretcher placement is different.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMDy61TB-FIxyFGHvgpcHMe1Un4iuWimpkp-7ppeFR8Nu-_5F5Hbaxdh2madUJy7ZIDOhjHiKXFpAf2iN_8YxcnVeWOFvNbtwityCD261TNJx5JPNRqnEXCYMofaYZ1VjgbxZMLPABmGVy_10gizeoTYJVycmhHmFtn5XMtwogcrj3U40-TXdTZtb_PQ/s2173/stretchers%20(2).png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1293" data-original-width="2173" height="380" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMDy61TB-FIxyFGHvgpcHMe1Un4iuWimpkp-7ppeFR8Nu-_5F5Hbaxdh2madUJy7ZIDOhjHiKXFpAf2iN_8YxcnVeWOFvNbtwityCD261TNJx5JPNRqnEXCYMofaYZ1VjgbxZMLPABmGVy_10gizeoTYJVycmhHmFtn5XMtwogcrj3U40-TXdTZtb_PQ/w640-h380/stretchers%20(2).png" width="640" /></a></div><br /><div>It is worth noting that the MT-LBV is not a battlefield ambulance when used this way, as an ambulance provides space and facilities for paramedics to deliver emergency treatment inside the vehicle. </div><div><br /></div><div><br /></div><div><div>Passengers ingress and egress the MT-LB through two rear doors. Each door is 910mm wide and 820mm tall. The width of the doors is reasonable, as they make use of all the available hull width, but the height of the rear doors was partly restricted by the large reinforcing strut for the towing hitch, making it necessary to climb through the doors owing to their ground level rather than simply stepping into the cargo compartment. The main upside to having double doors of this design is that at least one door is available when a mortar base plate is carried, and it allows everyone in the cargo compartment to dismount as quickly as possible while a gun or a trailer is hooked to the towing hitch, since both doors can be freely opened over the carriage legs of a towed item.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-8dy1D9A4TCE/X5hmAfw9KlI/AAAAAAAAR1Q/Exksmj9XY_kgFW8NKFgmxRsl3xzodvgRgCLcBGAsYHQ/s2048/exiting.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1367" data-original-width="2048" height="268" src="https://1.bp.blogspot.com/-8dy1D9A4TCE/X5hmAfw9KlI/AAAAAAAAR1Q/Exksmj9XY_kgFW8NKFgmxRsl3xzodvgRgCLcBGAsYHQ/w400-h268/exiting.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWz2DYjdAuKDU-3ut6rs1tpbucCYAX5C2cbj9zmmPLZE1wL7GrM1zkV4ZBcevTT5_JqLLKxBEFP4k02PPi2QHBM0iT31cLEQthDaWL1IbCNg_B-9haFqmB_THwGLqe4gPyRL2J_kP4yCNi99LRTDCmbOMZFgp7HtEPbh0_ELUwL6-J-ULC4IskZ1GNQQ/s1369/2018%20mt-lb%20mortar.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="917" data-original-width="1369" height="268" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWz2DYjdAuKDU-3ut6rs1tpbucCYAX5C2cbj9zmmPLZE1wL7GrM1zkV4ZBcevTT5_JqLLKxBEFP4k02PPi2QHBM0iT31cLEQthDaWL1IbCNg_B-9haFqmB_THwGLqe4gPyRL2J_kP4yCNi99LRTDCmbOMZFgp7HtEPbh0_ELUwL6-J-ULC4IskZ1GNQQ/w400-h268/2018%20mt-lb%20mortar.png" width="400" /></a></div></div><div><br /></div><div>There is only a single B-2 vision block and a single TNPO-170 periscope fitted to the cargo compartment. The B-2 vision block is on the right, next to the right firing port. Its position is considerably lower than the eye level of seated passengers, so it is too low to be comfortably used for general observation when seated, but it is placed conveniently enough for someone manning the firing port. Similarly, the TNPO-170 in the right rear door is only comfortable to use by someone manning the firing port. The periscope is embedded in the door within a pocket, so that there is no gap in the door armour. Structurally, there is no real reason for the periscope mount to have been designed for an upright periscope and not inverted, which could have placed it at eye level. It could be speculated that passenger vision was simply not a serious consideration given the nature of the MT-LB, unlike in the BMP where the passengers were infantry, needing situational awareness to avoid becoming disoriented when disembarking into combat. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi3AqirLgPO0mlyzJe8M7d8W9_M7LI9L22aDrtMtmSp50J-3lQZU30a38fJrWw-EwEiVLDKKyBXmHTkhwRS4HvqKXEpGPmXvVtTwXiNhyLQiru7sOFnUK9_9spOQPRdtIul3hFDnqvcZnHHeA-5zPyURC53IFynfnfkk8Ml_Izg9b505cCFOfxJDzjPZA/s552/b-2%20vision%20block%20passengers.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="241" data-original-width="552" height="175" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi3AqirLgPO0mlyzJe8M7d8W9_M7LI9L22aDrtMtmSp50J-3lQZU30a38fJrWw-EwEiVLDKKyBXmHTkhwRS4HvqKXEpGPmXvVtTwXiNhyLQiru7sOFnUK9_9spOQPRdtIul3hFDnqvcZnHHeA-5zPyURC53IFynfnfkk8Ml_Izg9b505cCFOfxJDzjPZA/w400-h175/b-2%20vision%20block%20passengers.jpg" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhiAgFLYQIit7ywFPLg6ZpNTh3c0CVleMt9DsrsuggUgFRBu4tkhaUoFFsg5H01Ly5Wu_Byo01t91WxU1mkPApznoOnLpFumqMs2JTzKRTVa8C46pTGdBxgCT8GHNK3_eAnqsKYcUHJmJfSG_JNcILFi1_OvM24CJ6lDrK0h2HlgRjfzkWiogw0i-KoUQ/s361/right%20door.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="293" data-original-width="361" height="260" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhiAgFLYQIit7ywFPLg6ZpNTh3c0CVleMt9DsrsuggUgFRBu4tkhaUoFFsg5H01Ly5Wu_Byo01t91WxU1mkPApznoOnLpFumqMs2JTzKRTVa8C46pTGdBxgCT8GHNK3_eAnqsKYcUHJmJfSG_JNcILFi1_OvM24CJ6lDrK0h2HlgRjfzkWiogw0i-KoUQ/s320/right%20door.jpg" width="320" /></a></div><div><br /></div><div>There are very few interior lighting devices distributed in the cargo compartment. Although the driver and commander are adequately furnished with one PK-201A dome light each, supplemented with additional lamps to illuminate instrument panels, the cargo compartment is only provided with a single PK-201A dome light. Together with the small number of vision devices for passengers, this means that the cargo compartment will be quite dark when all hatches are closed.</div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="firingports"></a><h3 style="text-align: left;"><span style="font-size: large;">FIRING PORTS</span></h3><br /><div>There are a total of four firing ports available in the cargo compartment of the MT-LB, providing a modicum of under-armour fighting capability in contaminated environments. There is a firing port on each side of the cargo compartment, and a B-2 vision block next to the right firing port. The empty space in the sponson where the vision block and firing port are located grants plenty of room to swing a rifle around when firing out, but this space is otherwise not used for anything, and can be used to stow personal effects, machine gun ammunition, or anything else needed by the crew or passengers.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-QPjePLWPRTk/YLIpnlw6trI/AAAAAAAATPs/Fk48mE72FEQTgDG5GAbGkJaqQNX0aOh_ACLcBGAsYHQ/s1280/81981ffd150aa85474aceba1eb204ae6.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="1280" height="300" src="https://1.bp.blogspot.com/-QPjePLWPRTk/YLIpnlw6trI/AAAAAAAATPs/Fk48mE72FEQTgDG5GAbGkJaqQNX0aOh_ACLcBGAsYHQ/w400-h300/81981ffd150aa85474aceba1eb204ae6.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjb81vX0nb2DwDZBYGgAbG9gw63tV2P3hMtCWnMhv3PL7FTwPScvZ8Rq4NKw_METXEuWUAEYGeKAUpqorkBq1qEvsRFfFcpvjrbt-i7q1znC-v2zguBFUvivh-FhNqH4A5k5mhdF982v8nuLpb2uhwBgg3F1bB3hUqvmYCJeD6oTeQC54DZZVbV5KjwSg/s640/95eb32a28049.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="480" data-original-width="640" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjb81vX0nb2DwDZBYGgAbG9gw63tV2P3hMtCWnMhv3PL7FTwPScvZ8Rq4NKw_METXEuWUAEYGeKAUpqorkBq1qEvsRFfFcpvjrbt-i7q1znC-v2zguBFUvivh-FhNqH4A5k5mhdF982v8nuLpb2uhwBgg3F1bB3hUqvmYCJeD6oTeQC54DZZVbV5KjwSg/w400-h300/95eb32a28049.jpg" width="400" /></a><br /></div><div><br /></div>When not in use, an armoured teardrop-shaped cover is closed over the firing ports.</div><div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIdDM59ypnUqUR5dGuw0tQiziWuxGHlubkwpvtnGTg9-pnJg_Zfy2YME9IkjnYkv3jLAHLb4GyctgkWh0xuecD07Z7p-1pXftfIVC23EEoCMCuxI0vELVaLPzKlP5x_Y68eKzhBBtzCXbvRPiHlVSzqfJHdfTIKTQsiyag4EmC9h7p7dB4vPQOWtrjkw/s1439/firing%20port%20closed.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1439" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIdDM59ypnUqUR5dGuw0tQiziWuxGHlubkwpvtnGTg9-pnJg_Zfy2YME9IkjnYkv3jLAHLb4GyctgkWh0xuecD07Z7p-1pXftfIVC23EEoCMCuxI0vELVaLPzKlP5x_Y68eKzhBBtzCXbvRPiHlVSzqfJHdfTIKTQsiyag4EmC9h7p7dB4vPQOWtrjkw/w400-h300/firing%20port%20closed.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1gYRVmTZbpC1-HlixvpRG8d_fF6VZcawKACu76EU3WsGqtOM5nBqirtj8mkhIpxNONy1014oiVkMveIJJfTqsUTxYK7_SEPyRRmc8b1pFieP-fKYyLfcv0cPoHp7j2yvybdMwqYaw1HAiY5sKJWhiFleyi4J89CKjdKcuHypYK8z4Gj2tPOcw8cFJKg/s1438/firing%20port%20opened.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1438" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1gYRVmTZbpC1-HlixvpRG8d_fF6VZcawKACu76EU3WsGqtOM5nBqirtj8mkhIpxNONy1014oiVkMveIJJfTqsUTxYK7_SEPyRRmc8b1pFieP-fKYyLfcv0cPoHp7j2yvybdMwqYaw1HAiY5sKJWhiFleyi4J89CKjdKcuHypYK8z4Gj2tPOcw8cFJKg/w400-h300/firing%20port%20opened.png" width="400" /></a></div><div><br /></div><div><br /></div><div>There are another two firing ports embedded in the rear doors. They are also closed with a cover when not in use.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJOiycu0MRO4HDi9ojAPTUcADwYh6SCSdSHPB6rJQnGzM99KSUUaaUJXdetbVaeGVGhemnozkh5E4RzhgiGWHM2yDkY-mrL_oxl5tFjiZm3DoZHd6ZsyiHVc7YG5bQq8bys2c6vtmkwlZ-m6hCnn9N_oRAijlZ2QzbQqw3F0ThbaMD1zn9gxJ9xuVfPQ/s2560/b1aMya2DNuc.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1920" data-original-width="2560" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJOiycu0MRO4HDi9ojAPTUcADwYh6SCSdSHPB6rJQnGzM99KSUUaaUJXdetbVaeGVGhemnozkh5E4RzhgiGWHM2yDkY-mrL_oxl5tFjiZm3DoZHd6ZsyiHVc7YG5bQq8bys2c6vtmkwlZ-m6hCnn9N_oRAijlZ2QzbQqw3F0ThbaMD1zn9gxJ9xuVfPQ/w400-h300/b1aMya2DNuc.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>Due to the lack of fume extraction or additional ventilation at each firing port like in a BMP, it would have been impractical to sustain the use of the four firing ports beyond a few magazines from each rifle. </div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="ventilation"></a><h3 style="text-align: left;"><span style="font-size: large;">VENTILATION</span></h3><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhvGd6DMcC2O7wwqLQZxmwVWr59YPiF8FnvGpx9SrHjIVLs4I6hSWmunrwuiL_NEDjp7Lw8agVCvceZwcFMD2W21Ro5sBlWu9jjILTtOg_ASgRMAXRO4EQwICbjF90dGecleHR-xcTnVZwa7vs7p5urSmiMA7XnSu6WrhKiB7-VJBXYCm6Id69eiV7heg/s2251/supercharger%20original%20mt-lb.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1397" data-original-width="2251" height="398" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhvGd6DMcC2O7wwqLQZxmwVWr59YPiF8FnvGpx9SrHjIVLs4I6hSWmunrwuiL_NEDjp7Lw8agVCvceZwcFMD2W21Ro5sBlWu9jjILTtOg_ASgRMAXRO4EQwICbjF90dGecleHR-xcTnVZwa7vs7p5urSmiMA7XnSu6WrhKiB7-VJBXYCm6Id69eiV7heg/w640-h398/supercharger%20original%20mt-lb.png" width="640" /></a></div><div><br /></div><div>The primary means of ventilation in an MT-LB is a supercharger. It provides a normal blower mode to provide air circulation for general ventilation, and a supercharger mode to purify the air of radioactive dust and create an overpressure inside the vehicle in the event that the air is contaminated by nuclear fallout. The ventilator is turned on with a switch on the driver's instrument panel, with an additional switch to turn on the supercharger mode. To use the ventilator, the intake hood is first opened with a handle, which also tugs on a pullcord to open the dust vent. The intake hood is located just behind the commander's TKB-01-1 turret.</div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_QA2eXbp7NvQM28MjT8h4aZgPI4ZpSRgTaDmIvepynRTaj9OoMsLUFtO4DHz8Q3AvkOKd3WJGnwCFac8puS-IM_Jr2It19789_C7_CChG6gSQFtMZOXN5B48PunFFEvTkFYxLKJdgh3jTn9WSOtMKAdG7ZkxYwfpM-UCFukhAeUIORQC7QW_SpbXsKg/s2194/early%20supercharger.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1082" data-original-width="2194" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_QA2eXbp7NvQM28MjT8h4aZgPI4ZpSRgTaDmIvepynRTaj9OoMsLUFtO4DHz8Q3AvkOKd3WJGnwCFac8puS-IM_Jr2It19789_C7_CChG6gSQFtMZOXN5B48PunFFEvTkFYxLKJdgh3jTn9WSOtMKAdG7ZkxYwfpM-UCFukhAeUIORQC7QW_SpbXsKg/w640-h316/early%20supercharger.png" width="640" /></a></div><div><br /></div><div>To read more on the supercharger ventilator used in Soviet armoured fighting vehicles of the period, visit this <a href="https://thesovietarmourblog.blogspot.com/p/supercharger-ventilator.html">Tankograd article</a>.</div><div><br /></div><div>The supercharger mode would not only be used to filter out radioactive particles, but also to purify dusty air in general use, whenever the MT-LB travels through a dry and dusty area. In humid environments, the dehumidified air also helps improve comfort inside the vehicle by displacing humid air, although it does not function as effectively as an air conditioner that dehumidifies interior air by recirculating it. The blower end of the ventilator is aimed toward the cargo compartment, which is presumably good for the passengers, but less so for the two crew members seated up front.</div><div><div><br /></div><div>At some point in the mid 1970's, this dust-filtering ventilator was replaced with an FVU, or filter-ventilator unit. The main difference is that a HEPA filter is incorporated as a second filter stage to purify the air after dust separation. This class of vehicular collective HEPA filter (FPT-50, 100, 200) did not enter mass production in the USSR until the end of the 1960's, so throughout the 1960's and early 1970's, collective protection from chemical and biological agent was absent except for a few vehicles such as the T-72. For the MT-LB, the FVU was not present in a 1974 manual, but appeared in a 1976 manual.</div><div><br /></div><div>The new FVU consists of the supercharger and filter cartridge connected in series. The same air intake and the same controls were retained, but the entire assembly was now contained in a box. For normal ventilation needs, including overpressure ventilation, the FPT-200M filter cartridge is bypassed to avoid unnecessary filter expenditure. The ventilator is turned on with a switch on the driver's instrument panel, and by turning a handle on the lower side of the box, marked (21) in the drawing below, the connecting duct between the supercharger and the filter cartridge is sealed shut and the flow of air from the fan is diverted to a vent hole on the underside of the box.</div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpYOjVBua1kXFql4CsB1RC2SrJcwReEKf8dd9ZWHCIv8xwkRmIpdtnBH_p6JzTRhtfHP0UTQRrSNuhqvOViOf9AiAUpaJKkclfk7yQQW8UpG4apQjo-EDS_sKIDy27XdZwxk2_DhfOQn0Qvi3T_vM9yvlDjyP29SrGdxPfGyA8a60DzXVw_64O682kpw/s2238/fvu%20mt-lb.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1096" data-original-width="2238" height="314" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpYOjVBua1kXFql4CsB1RC2SrJcwReEKf8dd9ZWHCIv8xwkRmIpdtnBH_p6JzTRhtfHP0UTQRrSNuhqvOViOf9AiAUpaJKkclfk7yQQW8UpG4apQjo-EDS_sKIDy27XdZwxk2_DhfOQn0Qvi3T_vM9yvlDjyP29SrGdxPfGyA8a60DzXVw_64O682kpw/w640-h314/fvu%20mt-lb.png" width="640" /></a></div><div><br /></div><div>The FVU not only introduced a HEPA filter, but also had a new high-efficiency dust separator with a VNSTs-200 supercharger. As its name indicates, the VNSTs-200 supercharger produces an airflow rate of 200 cubic meters per hour (117 CFM), and the same is true for the FPT-200M. Like the previous model of supercharger, the VNSTs-200 is used to purify dust from the air and create an overpressure inside the occupied spaces of the vehicle. The supercharger is a centrifugal compressor fan that delivers a flow of air into an annular array of cyclone filters at high velocity, where dust particles are centrifugally separated from the air owing to their high inertia relative to air, and purified air exits the front end of each cyclone via a central tube. The dust exits the cyclones from the rear end where it is then piped to an exhaust hole in the hull wall, where it is vented out along with only 10-15% of the total outgoing air.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiaPmyi3tzGOaUyehTtz-Vok3wbVwRR92b14MCWJBXxy-VTybYd3HOhUKQPA8L6jvMEtC32D6veKk746mKWtRLHViJyHaERqUoxsbXMnMvp8fmF_4xqsWGnu9scEFmU5YelxRRzKAaIOzvh5MnuAkr6dprvvdRORrYhz_zrL3M1ULM0asoaufU0NaPjgw/s1501/vnsts-200.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1501" data-original-width="1337" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiaPmyi3tzGOaUyehTtz-Vok3wbVwRR92b14MCWJBXxy-VTybYd3HOhUKQPA8L6jvMEtC32D6veKk746mKWtRLHViJyHaERqUoxsbXMnMvp8fmF_4xqsWGnu9scEFmU5YelxRRzKAaIOzvh5MnuAkr6dprvvdRORrYhz_zrL3M1ULM0asoaufU0NaPjgw/w285-h320/vnsts-200.png" width="285" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8nv1OZtOgcsYUZ-qdu98TZMOvUjwpHG2I_1u0W4u_Iwo3uelom40g5thPlb7u2qSCab9XwFuuLHs-0uH9WeVoi2RSn7ZO5s3k2o9L1wcgDJwSSzhuzxQ8YOQDr7ddKeL9gA2hXCfhI1Y3ej40sbQDidnxLVi1KsgYlUDgCwaGdBTutSthVKRRgWTjIw/s387/fvu.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="271" data-original-width="387" height="280" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8nv1OZtOgcsYUZ-qdu98TZMOvUjwpHG2I_1u0W4u_Iwo3uelom40g5thPlb7u2qSCab9XwFuuLHs-0uH9WeVoi2RSn7ZO5s3k2o9L1wcgDJwSSzhuzxQ8YOQDr7ddKeL9gA2hXCfhI1Y3ej40sbQDidnxLVi1KsgYlUDgCwaGdBTutSthVKRRgWTjIw/w400-h280/fvu.png" width="400" /></a></div><div><br /></div><div><br /></div><div>After dust separation, air is ducted to the FPT-200M HEPA filter cartridge. Air enters the cylindrical cartridge from one end, passes through the annular filter and exits through a side vent in the cartridge, exiting the FVU box from a slot on its underside. The HEPA filter should not be used with humid air, so the moisture separation action of the supercharger is important for its proper function. Unlike in the case of the earlier ventilator, where the blower would help circulate air in the cargo compartment, the downward-facing vents of the FVU box make it less ineffective as a ventilator.</div></div><div><br /></div><div><br /></div><div><div>Early MT-LBs fitted with only the dust-filtering ventilator can be identified by the square hood of the dust vent slit, as shown in the image on the left below. Later MT-LBs with an FVU lack this slit, instead having a small hooded dust vent hole just behind the commander's vision block, as seen in the image on the right below, courtesy of Vitaly Kuzmin. </div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEijZjBXuWHDPm-GK8rlNDRUoc8nOlK56dNjbyAIQFwRqa6ZxwPQMkcYReRR7BMfNrANiTBUKBXgdj07Ez3KP9sE4wbgMSEqNzTyXEqXn6cJ_z-BLT7dij7k0Ejn9-EQvkU1OewNC-pxU9rjTi2gP5Fqp9IWGLJ0fOOgdEEQnntau3jrBcEmzzRBMukoEw/s2768/%D0%9C%D0%A2-%D0%9B%D0%91.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1968" data-original-width="2768" height="285" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEijZjBXuWHDPm-GK8rlNDRUoc8nOlK56dNjbyAIQFwRqa6ZxwPQMkcYReRR7BMfNrANiTBUKBXgdj07Ez3KP9sE4wbgMSEqNzTyXEqXn6cJ_z-BLT7dij7k0Ejn9-EQvkU1OewNC-pxU9rjTi2gP5Fqp9IWGLJ0fOOgdEEQnntau3jrBcEmzzRBMukoEw/w400-h285/%D0%9C%D0%A2-%D0%9B%D0%91.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiD99DTfz9pCjQVgkiYh-d5cKmE7fSv2ICWY-n2MrCt4F78f5OZxrBZJ4e5oibtVOnaNSBji0xS7TO_-MwH2KoBva2jcQo70J-7BsTKcVUu0ojkFID0QpJ4YTKpREuj95j8GNRAME-w6YrIyyj1zfoFl8bXb-VmAGUPx51qZEQ36yni3WSAVKm8rj0-ng/s718/exhaust%20hole.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="458" data-original-width="718" height="255" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiD99DTfz9pCjQVgkiYh-d5cKmE7fSv2ICWY-n2MrCt4F78f5OZxrBZJ4e5oibtVOnaNSBji0xS7TO_-MwH2KoBva2jcQo70J-7BsTKcVUu0ojkFID0QpJ4YTKpREuj95j8GNRAME-w6YrIyyj1zfoFl8bXb-VmAGUPx51qZEQ36yni3WSAVKm8rj0-ng/w400-h255/exhaust%20hole.jpg" width="400" /></a><br /></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="heater"></a><h3 style="text-align: left;"><span style="font-size: large;">HEATER</span></h3><div>The personnel heater is distinct from the engine preheater, which is located in the engine compartment. Heating of the cargo compartment is provided by an OV-65G heater-ventilator, a device that was later installed in various heavy duty trucks for cabin heating. As the FVU of the MT-LB would only blow cold air into the cargo compartment in winter, the OV-65G was designed to take over the role of a ventilator. It is used exclusively for space heating, and is not used for engine preheating. Hot air is delivered from the outlet through a set of ducts, as shown in the image below.</div><div><br /></div><div><img border="0" data-original-height="4544" data-original-width="9152" height="318" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirH9NWCgngkuD_qM8g8X0DIvQcg8_0b7MId3t4yvNyZh8EIOX-Qzd0iGCC_lCJDv22U4iAFpTXvPuMGxZZoSId6Gk8_KVFOZ4KyFIftFjR5ITUpwLp76lY43Y3Lx8wXAPcHs-fJLRhfGUNDBZOy1GF0Paw1ruWEs14N7Nf1rm0AJ-f6c5zJlZe6jS9KQ/w640-h318/old%20heater.png" style="color: #0000ee; text-align: center;" width="640" /></div><div><br /></div><div><div>This, however, is an early variant of the heater ducts for the cargo compartment, which is rarely encountered on existing vehicles in the present day. A new duct design was introduced at some point after the late 1960's, and this design is found on the vast majority of MT-LB samples.</div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiDpWEjjhhA90bNVU1j8N1IiCnExDVWJLiBaqifD2bCFLPIEpMOIWWpusBG1Fto760_jTi8ZBuxVjkT5BYXce7ynfiK7HH4rIv0u4qNxUszlZs9NJbVRT8UTkEUZbcUFA9N6Pv4RXBBXHUH8grP0Pl5uf-LO_3t0JvH7ml2IkVQ4ClZ50_xzTTAhz8RqA/s2977/heater.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1217" data-original-width="2977" height="262" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiDpWEjjhhA90bNVU1j8N1IiCnExDVWJLiBaqifD2bCFLPIEpMOIWWpusBG1Fto760_jTi8ZBuxVjkT5BYXce7ynfiK7HH4rIv0u4qNxUszlZs9NJbVRT8UTkEUZbcUFA9N6Pv4RXBBXHUH8grP0Pl5uf-LO_3t0JvH7ml2IkVQ4ClZ50_xzTTAhz8RqA/w640-h262/heater.png" width="640" /></a></div><div><br /></div></div></div><div><br /></div><div>According to the specifications, the OV-65G is a 132 W fuel-burning heater (or 108 W on 12 V electrical system) with an airflow volume of 250 cubic meters per hour (147 CFM), or 220 cubic meters per hour (129.5 CFM) on 12 V. It has a maximum heating capacity of 6,000 kcal/h, with an air heating temperature differential of +95°C. It consumes 1 liter of fuel per hour. The cylindrical heater-ventilator has an air intake with a centrifugal forced induction fan on one end to draw air from the cargo compartment, and the other end is the outflow vent for the heated air. Fuel is piped into the burner from a fuel line and external air is supplied through a tube on the underside of the heater-ventilator, connected to an intake on the roof of the hull by a rubber hose. Exhaust gasses exit from an outlet on the top of the heater-ventilator, out the roof. The heater-ventilator has its own, separate 5-liter fuel tank inside the engine compartment, with a fuel pump located inside the heater-ventilator driven by the same motor as the blower fan.</div><div><br /></div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-epzMGx-EvqU/YK0c6STVqbI/AAAAAAAATG0/7dhxortZNLYeiCtuQCmWY4-l2gCvXPMjQCLcBGAsYHQ/s467/ob-65%2Bheater%2Band%2Bcontrol%2Bpanel.png" style="margin-left: 1em; margin-right: 1em;"></a><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-epzMGx-EvqU/YK0c6STVqbI/AAAAAAAATG0/7dhxortZNLYeiCtuQCmWY4-l2gCvXPMjQCLcBGAsYHQ/s467/ob-65%2Bheater%2Band%2Bcontrol%2Bpanel.png" style="margin-left: 1em; margin-right: 1em;"></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiLywc6UVmw7RotAq6QS3SleMneZfe7laTvZIx_mTbbi-XGpuItuCEGrDUuNZioMA_zn3gAnmhVtvURgNkCflXRWMlNbWkt47ax6pfPWJZjpbZIH3aL3O0AnnnvjVy0G4VRl8x_5TCSeXlILfNVFSQ2QckBUcwdFMl1Q4h_7nUMgJDNPjoIEuHpKx--Ww/s396/ob-65%20heater%20and%20control%20panel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="199" data-original-width="396" height="161" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiLywc6UVmw7RotAq6QS3SleMneZfe7laTvZIx_mTbbi-XGpuItuCEGrDUuNZioMA_zn3gAnmhVtvURgNkCflXRWMlNbWkt47ax6pfPWJZjpbZIH3aL3O0AnnnvjVy0G4VRl8x_5TCSeXlILfNVFSQ2QckBUcwdFMl1Q4h_7nUMgJDNPjoIEuHpKx--Ww/w320-h161/ob-65%20heater%20and%20control%20panel.png" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiOL9nGruS4KPCptSFp_vGXAK-nzSRMKArjQtz5N-SUZBeJKmxMbk6mms3j6siFGxghBG7NNjKlzCC_faQWkTEbSfENyx3LJ_C8xt21gxl0cuyAUPdgq51VNtj8iMwL-mDorXuaUw1DYXgyOExhMaWrNZi3jZsdfS0ZrQBARXstSav91bdG7Wn-gtZhhg/s4364/ov-65g.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2640" data-original-width="4364" height="194" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiOL9nGruS4KPCptSFp_vGXAK-nzSRMKArjQtz5N-SUZBeJKmxMbk6mms3j6siFGxghBG7NNjKlzCC_faQWkTEbSfENyx3LJ_C8xt21gxl0cuyAUPdgq51VNtj8iMwL-mDorXuaUw1DYXgyOExhMaWrNZi3jZsdfS0ZrQBARXstSav91bdG7Wn-gtZhhg/w320-h194/ov-65g.png" width="320" /></a></div></div></div><div><br /></div><div>The heater-ventilator supplies a flow of hot air down an air duct leading to the floor of the cargo compartment, where hot air is distributed to the feet of the bench seats via a central duct. The compartment is then heated by forced convection; as hot air rises, an updraft is created that circulates warm air throughout the compartment, both heating and ventilating it. Additionally, air is also delivered to the driver's compartment by a pipe that runs across the engine compartment via the left sponson, next to the radiator intake and exhaust ducts. In the driver's compartment, the pipe passes along the front left corner of the sponson and curves behind the instrument panel to blow hot air at the driver's feet. The ductwork of the heating system is shown in the diagram below.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyOeeBCiPgc0ilZOm-Sh9m840angU0-bTEdK8ONXDEsvW63lggIt0BGMvXH9451XSsvripAwVgpPsRFG9u2ecSjNzAlx1RSpUqMDc0he-lI_KGesFznB2xfCte6K8eP7GD4eq8NxUvgTKDvvQScG7Z43DL_ZhPC5n7-YIO4NjnGIXMykblo201ir8b9w/s1254/heater.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="798" data-original-width="1254" height="408" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyOeeBCiPgc0ilZOm-Sh9m840angU0-bTEdK8ONXDEsvW63lggIt0BGMvXH9451XSsvripAwVgpPsRFG9u2ecSjNzAlx1RSpUqMDc0he-lI_KGesFznB2xfCte6K8eP7GD4eq8NxUvgTKDvvQScG7Z43DL_ZhPC5n7-YIO4NjnGIXMykblo201ir8b9w/w640-h408/heater.gif" width="640" /></a></div><div><br /></div><div><br /></div><div>The hot air duct is the silver duct prominently visible in the photo on the left below, and the air outlets along the central floor duct on the floor are also faintly visible. The photo on the right prominently shows the outlets on the central floor duct. Before it reaches the central floor duct, the silver-coloured duct has a small vent on its underside to blow at the feet of the passenger seated at the supplementary fold-out seat next to the right bench. In the early variant of the heating duct, there is a separate branch of the duct with an outlet for this purpose.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-sbwsAhQxekM/YK0i7Ev077I/AAAAAAAATHE/JmPuEmtrGkA7vp8HMX3F8McAPOQALg1TgCLcBGAsYHQ/s800/mt-lb%2Bsilver%2Bheating%2Bduct.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="528" data-original-width="800" height="264" src="https://1.bp.blogspot.com/-sbwsAhQxekM/YK0i7Ev077I/AAAAAAAATHE/JmPuEmtrGkA7vp8HMX3F8McAPOQALg1TgCLcBGAsYHQ/w400-h264/mt-lb%2Bsilver%2Bheating%2Bduct.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-o3mVwB0ghqI/YK2deTP_RyI/AAAAAAAATHY/x1Qx7zQECA8yFVK1n7nzgiLTrbFHGB6swCLcBGAsYHQ/s1024/cargo%2Bcompartment.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="683" data-original-width="1024" height="268" src="https://1.bp.blogspot.com/-o3mVwB0ghqI/YK2deTP_RyI/AAAAAAAATHY/x1Qx7zQECA8yFVK1n7nzgiLTrbFHGB6swCLcBGAsYHQ/w400-h268/cargo%2Bcompartment.jpg" width="400" /></a></div><div><br /></div><div>The duct to the driver's compartment is shown in the image below. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhSMW4gfy2_xr0zzJRQjLD1PClDPryzzlsjwq1Nvx7bhKCpo2DyjB3JFwFcPwFI8sXAdpXdYQPvfHC6_VaKZ8io_FVJWAGORJLbRZEvgE4EraF_eXrbFjt1cEyJcsH7s9yy4mfmxq-fC90QefG3fXXgJ66G7SWEiJcj0CM_voZ3BWJTUoOS0LhZFnr6PQ/s1920/exhaust%20duct%20gap.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhSMW4gfy2_xr0zzJRQjLD1PClDPryzzlsjwq1Nvx7bhKCpo2DyjB3JFwFcPwFI8sXAdpXdYQPvfHC6_VaKZ8io_FVJWAGORJLbRZEvgE4EraF_eXrbFjt1cEyJcsH7s9yy4mfmxq-fC90QefG3fXXgJ66G7SWEiJcj0CM_voZ3BWJTUoOS0LhZFnr6PQ/w400-h225/exhaust%20duct%20gap.png" width="400" /></a></div><div><br /></div><div>The ducting system, along with the torsion bar covers, serve a dual purpose as a structural reinforcement frame for the thin hull belly. The use of these structural elements for multiple functions can be considered to be quite a good design solution to offset the parasitic weight of reinforcing members, which would otherwise not be needed if thicker armour was used to form the monocoque hull. Strangely enough, however, there is no partition to cover the heater-ventilator, so whoever is seated on the bench directly in front of it will probably feel quite hot.</div><div><br /></div><div>The downside to this ducting arrangement is that even though the passengers seated in the cargo compartment and the driver have good heating, the commander does not enjoy any direct heating. Even the passengers sitting in the engine compartment corridor have the heat of the engine. </div><div><br /></div></div><div>In warm weather, when the heater is not needed, the duct is unbolted and stowed on the engine compartment firewall to free up space for cargo, people and equipment. It is also possible to use the heater-ventilator as a ventilation blower with no heating. The blower fan in the OV-65B and the fuel pump are both powered by the same electric motor, but the fan is driven at one end and the pump at the other via a clutch. When the heater-ventilator is turned on, it is the motor that is turned on, which starts the fan but not the fuel pump, which is turned on separately by engaging its clutch, and only after the glow plug is switched on. If used simply as a blower fan, the OV-65G provides additional air circulation in the cargo compartment and driver's compartment together with the supercharger ventilator, likely flowing as drawn in the image below.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_75MfV8F3oofwB9PB59ihEZNX5s2IBppyrbhLfCB95xqL6CPc-8tJIbsNY_DBS5UIAL2qKTNIuQt1e27B6H9CE08f0-b5d0MuYKim4BaIhPy3h2yP2cmzt2zoq8VQOABuHm24uneJSmkBlUNFiUxmW4GGCTR25XuDM_ogvztDc24Dthvwvko88u-O4g/s1940/ventilation%20diagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1010" data-original-width="1940" height="334" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_75MfV8F3oofwB9PB59ihEZNX5s2IBppyrbhLfCB95xqL6CPc-8tJIbsNY_DBS5UIAL2qKTNIuQt1e27B6H9CE08f0-b5d0MuYKim4BaIhPy3h2yP2cmzt2zoq8VQOABuHm24uneJSmkBlUNFiUxmW4GGCTR25XuDM_ogvztDc24Dthvwvko88u-O4g/w640-h334/ventilation%20diagram.png" width="640" /></a></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="commander"></a><h3 style="text-align: left;"><span style="font-size: large;">COMMANDER'S STATION</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJLiIAj_-jXUOpMUBqDAqGTC3ILzq7HA75YyIzHUpSOFJoa_kWviy_5gLj8MJVPcnvXHALfV_LewWDyLm2sb664VUNlzvmS1qq7fKnaA0t9xTuRN8zS8Vc9avuGr07vpuaVnYvqmSFAY89eadl0TbmesXS53QolVApPoWUy7bWqsRPj9_kVw4oWB7I_g/s640/3a7f60d6239f.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="480" data-original-width="640" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJLiIAj_-jXUOpMUBqDAqGTC3ILzq7HA75YyIzHUpSOFJoa_kWviy_5gLj8MJVPcnvXHALfV_LewWDyLm2sb664VUNlzvmS1qq7fKnaA0t9xTuRN8zS8Vc9avuGr07vpuaVnYvqmSFAY89eadl0TbmesXS53QolVApPoWUy7bWqsRPj9_kVw4oWB7I_g/w640-h480/3a7f60d6239f.jpg" width="640" /></a></div><div><br /></div><div>The commander of an MT-LB is provided with two seating positions. His station is directly underneath the TKB-01-1 turret. Here, he has direct access to the radio, his control panel and his only magnified observation device, which is the sight for his machine gun. His second position is on a seat straddling the driveshaft cover that divides his station from the driver's station, where a hatch is located overhead. This jockey seat is spring loaded so that it stays folded up and flat against the backrest when not in use. Due to the height of the driveshaft cover, it is not possible to sit here when the hatch is closed. Seated here, he has a free view of his surroundings above the hatch to navigate by eye, which more often than not means that he spends most of his time in this position. To ingress and egress from the vehicle, the commander has to use this hatch. On the MT-LBVM, the replacement of the TKB-01-1 turret with a new NSVT turret provided the commander with an additional semicircular overhead hatch, allowing the commander to stand up directly in his station without using the center hatch, but more importantly, allowing him to reload the machine gun. </div><div><br /></div><div>Note that the new NSVT turret has no name, with one manual simply stating that the TKB-01-1 turret was replaced with an NSVT-12.7 machine gun. However, the generic TKB designation is sometimes used to refer to the new turret, and as such, the same convention will be used in this article. </div><div><br /></div><div>Since the crew area at the front of the hull is shared by only two people, and the width of the hull is more than enough for three people in side-by-side seating, there is quite a surplus of room, particularly for the commander, as the driveshaft cover does not symmetrically bifurcate the crew area. On the commander's side, the width from the driveshaft cover to the hull side wall is 910mm. When measured to the sponson, it varies from 1,290mm to the point just ahead of the ventilator to 1,060mm at the windshield, due to the slope of the sponson cheek. This is substantially wider than the driver's station.</div><div><br /></div><div>However, due to the offset location of the gearbox relative to the centerline of the hull, a wide void was left on the left of the gearbox, which allowed a bulge to be added between the driver's pedals and the left steering brake, thereby providing the necessary space to depress the clutch and brake pedals. On the commander's side, there was only a narrow void, not nearly large enough to expand the commander's legroom, but it was put to use as a stowage space for two 250-round ammunition boxes for the PKT machine gun. </div><div><br /></div><div>The commander's hatch was installed on the hull roof between the TKB-01-1 turret and the driver's hatch. On earlier models of the MT-LB and its variants, the hatch, which was of a more polygonal design, opened by hinging rearward, and it could be locked in the upright position. When locked open in this way, the commander could sit on the center seat and expose his upper torso above the hatch opening. On later models of the MT-LB, the commander's hatch was revised to use the same hatch as the driver's, merely reversed so that it would hinge forward and lock in the upright position to function as a shield for the commander, which is customary for Soviet vehicles.</div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhxLMIT-DTrrrioKmZr2xTVO2evxziOsecdBxCrgmccTx_gYwlGqqx4g7hjNeYo_DmMeNDyuHZD4S9RHLZ-Dc-fO_LbdsE_i7kjpw3uOfG5A6SfihYeWtIUc6_atfovyVz0zMOvhPqDoAog0f1hfjkytZF9FmDJQ9IjCzrAaMYoPFiKpLrKBhy_XKKgLw/s1476/mt-lb%20towing%20mt-12.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="819" data-original-width="1476" height="356" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhxLMIT-DTrrrioKmZr2xTVO2evxziOsecdBxCrgmccTx_gYwlGqqx4g7hjNeYo_DmMeNDyuHZD4S9RHLZ-Dc-fO_LbdsE_i7kjpw3uOfG5A6SfihYeWtIUc6_atfovyVz0zMOvhPqDoAog0f1hfjkytZF9FmDJQ9IjCzrAaMYoPFiKpLrKBhy_XKKgLw/w640-h356/mt-lb%20towing%20mt-12.jpg" width="640" /></a></div><div><br /></div><div>Both types of hatches are simple hinged hatches with no spring assist, likely because they are light enough to not warrant it. The hatch design was standard for virtually all postwar Soviet light vehicles, with an upturned lip on the perimeter of the hatch opening and a downturned lip on the perimeter of the hatch to form a physical barrier against bullet splash and leaks, particularly heavy water splashing when crossing water obstacles. Both hatches have a lock to keep them upright when opened, consisting of spring-loaded pawl which rests against the lip of the hatch openin under spring tension when the hatch is closed. When the hatch is opened by 90 degrees, the pawl catches on the raised lip around the perimeter of the hatch opening as shown in the <a href="https://www.reddit.com/r/TankPorn/comments/os0eq2/here_are_most_of_the_pictures_i_took_at_the/">image below</a>, blocking the hatch from hinging back. To release the hatch, the pawl is pulled away from the lip by a ring pull, freeing the hatch to be pulled back and closed. The hatch is prevented from hinging further forward (or backward, in the case of the early model) by a nub welded onto the hinge.</div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwfhqpBe2eoCBc2XngKaG-xhcpgRbESnhlJgiHOlsVpUTc29RnM1CTaDQlkvhPyPiwqikE8vI_mi6I1BJ7HuUx8-lhwcswpdNhf0BA7MOFiziXXvJ8Q-MWfHjMBHAXsy_doP9uRwPZO_SKnwbvuTCavWAXclMNcBcklzYO3TX1b7bsRixl80Z8BDK6RA/s3968/commander's%20hatch.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="3968" height="166" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwfhqpBe2eoCBc2XngKaG-xhcpgRbESnhlJgiHOlsVpUTc29RnM1CTaDQlkvhPyPiwqikE8vI_mi6I1BJ7HuUx8-lhwcswpdNhf0BA7MOFiziXXvJ8Q-MWfHjMBHAXsy_doP9uRwPZO_SKnwbvuTCavWAXclMNcBcklzYO3TX1b7bsRixl80Z8BDK6RA/w640-h166/commander's%20hatch.jpg" width="640" /></a></div><div><br /></div><div>The lock was borrowed from the AT-P, shown in the image below taken from an AT-P manual.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDXU6Vt73X4DJmLSftGXTeQZxyNjEEfagZM9vJt7Pg1-C6Yn8z9ho4gQ8IWN6GjYv23iYCKrU_eFSDQ8zCKEgWxB_cWmQ6Uw_Ewpeoe51enmgVxJZ-HVA3r1qFOoBBZ9mJZd16esR01A0h5bVPV2XIoJujr4CbjX_RAEEerBT-ac47pGtP0wi-RRofKw/s1126/hatch%20lock.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1070" data-original-width="1126" height="304" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDXU6Vt73X4DJmLSftGXTeQZxyNjEEfagZM9vJt7Pg1-C6Yn8z9ho4gQ8IWN6GjYv23iYCKrU_eFSDQ8zCKEgWxB_cWmQ6Uw_Ewpeoe51enmgVxJZ-HVA3r1qFOoBBZ9mJZd16esR01A0h5bVPV2XIoJujr4CbjX_RAEEerBT-ac47pGtP0wi-RRofKw/w320-h304/hatch%20lock.png" width="320" /></a></div><div><br /></div><div>Directly in front of the commander is the R-123 radio, the standard radio for all armoured vehicles of the time. It is fitted on a shelf beneath the windshield, placed at a convenient position. The MT-LB is fitted with the R-124 intercom system, allowing internal communication between the commander, driver and one passenger in the cargo compartment. The R-123 radio and its power supply unit can be seen in the image on the left below, <a href="https://www.reddit.com/r/TankPorn/comments/os0eq2/here_are_most_of_the_pictures_i_took_at_the/">from Reddit user "BT-42"</a>. The image on the right below showing the empty shelf for the radio and its power unit was taken from <a href="https://youtu.be/UFZU1qWFPGM">this video</a>.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhOtLUwuR4XIXMTB9UL5O0dyxq1fR1JoM-7KymBtB7NXKUF7RbxEXApGS19rnIYGrmtdj-YsxWffZMhHpn6E39VlFFcceZKH3hxJx6XT-vAJq8B-V5q4u95UT3hN2YkAiRqvXgkwQFWRspWAj8bhl7DGeclrGUFNvtWIvbppNDpWmuk8S1Nrw9i7Lwyjw/s3968/905zik4omkd71.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2976" data-original-width="3968" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhOtLUwuR4XIXMTB9UL5O0dyxq1fR1JoM-7KymBtB7NXKUF7RbxEXApGS19rnIYGrmtdj-YsxWffZMhHpn6E39VlFFcceZKH3hxJx6XT-vAJq8B-V5q4u95UT3hN2YkAiRqvXgkwQFWRspWAj8bhl7DGeclrGUFNvtWIvbppNDpWmuk8S1Nrw9i7Lwyjw/s320/905zik4omkd71.jpg" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5M4S9GWqQE5JnQwGjsrS3VY1FKFt1B6UgswUKTPWYYmPbaqPOMS_E1L-6nGPbpZV-JxbogF3q38Z61_GahiyM5sD74Fx3nplqI8jlXGNOtrPSEWdYaxZRfpK4MHUSdddVIQFyVeK9e2FzyfD9qSuxX3tNJRBjz0jnjvG4yjIWrpgSGrR6eGL1Jo4Dpg/s1920/commander's%20compartment%20front.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5M4S9GWqQE5JnQwGjsrS3VY1FKFt1B6UgswUKTPWYYmPbaqPOMS_E1L-6nGPbpZV-JxbogF3q38Z61_GahiyM5sD74Fx3nplqI8jlXGNOtrPSEWdYaxZRfpK4MHUSdddVIQFyVeK9e2FzyfD9qSuxX3tNJRBjz0jnjvG4yjIWrpgSGrR6eGL1Jo4Dpg/w400-h225/commander's%20compartment%20front.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The front wall of his station underneath the radio is a removable partition between the crew compartment and the transmission compartment, where the commander's control panel is fitted. The control panel has three power switches for his front-facing headlight, the heating for his windshield, and turn on power to his turret. With such a sparse selection of controls, the commander has very little physical authority over the essential functions of the vehicle. Next to the control panel is the commander's A-1 communications switchbox.</div><div><br /></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWseUAZu5fs37dDJYpfnTxY-de6Txi8d2NeuEW5zvAe8gwWGgczlM9uXjJcnSbQUA3ioOLSvcK4SSl0_uY8amIr8fY_1dXvWfXtV8kl7Ft2SKKxEBdx172FyQsimAZ1FZlqD4Gu13YKjlQL2IDAdSUnCGNiFPQ1O1bMxf5px85hvSx0TDTEsrIBiD33g/s640/0a2b9c112e4e.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="480" data-original-width="640" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWseUAZu5fs37dDJYpfnTxY-de6Txi8d2NeuEW5zvAe8gwWGgczlM9uXjJcnSbQUA3ioOLSvcK4SSl0_uY8amIr8fY_1dXvWfXtV8kl7Ft2SKKxEBdx172FyQsimAZ1FZlqD4Gu13YKjlQL2IDAdSUnCGNiFPQ1O1bMxf5px85hvSx0TDTEsrIBiD33g/s320/0a2b9c112e4e.jpg" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhZH6UVvXb_GgiK1Bo_ltW4eRsc80o9n9GxcYpi3kbRcLwqHt1t2yKuFVTX4lzqbfAvRWqbRSzGRx1WIybpVEKmNWM8HTo-H0RzR5IbMb5ulGt6IaeW8N3qX8Uyc0TtS4gHS4d8HLTo_ehFySW3x4hC7N0KYjiO0y936XVLAp_NWiGY0o0s-wUZNjw_gw/s1346/commander's%20control%20panel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1158" data-original-width="1346" height="275" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhZH6UVvXb_GgiK1Bo_ltW4eRsc80o9n9GxcYpi3kbRcLwqHt1t2yKuFVTX4lzqbfAvRWqbRSzGRx1WIybpVEKmNWM8HTo-H0RzR5IbMb5ulGt6IaeW8N3qX8Uyc0TtS4gHS4d8HLTo_ehFySW3x4hC7N0KYjiO0y936XVLAp_NWiGY0o0s-wUZNjw_gw/s320/commander's%20control%20panel.png" width="320" /></a><br /></div><div><br /></div><div><br /></div>The A-1 communications switchbox is the commander's switchbox for the communication system and the plug-in point for his headset. It is the master switchbox for the two other switchboxes in the vehicle within the intercom and radio circuit, allowing the headsets of the driver and commander to be connected to the radio, and for all three headsets to be connected to the intercom. The listening volume control knob for all headsets is also located on the A-1. The driver has an A-2 communications switchbox on the wall between the two windshields to switch between the intercom and radio. Additionally, there is an A-4 communications switchbox in the cargo compartment, next to the right firing port. It is connected to the intercom only, and is connected via the A-2 switchbox. This allows a squad leader or towed gun crew leader seated to talk to the crew, and be cued to disembark. When connected to the intercom, the user exchanges his helmet for a headset stowed near the A-4 switchbox. <br /><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgLWqHdT9eLCK9YUvF62MlaPHeSnDckITEr0_GQ8tWlfAaVPDSKRF-PFXqpW59aoeIyfDeEksauDUh1gsKejbETiu_DUGDwVoRXzZqx_2-oH2CnDiAzcjDfydUc473idyPp2lqffZ7yy-546lggiSn0wfmfcqwcep673YBKUsYW_oHPsAB8YAzSf_Hjcw/s2208/intercom.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1078" data-original-width="2208" height="312" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgLWqHdT9eLCK9YUvF62MlaPHeSnDckITEr0_GQ8tWlfAaVPDSKRF-PFXqpW59aoeIyfDeEksauDUh1gsKejbETiu_DUGDwVoRXzZqx_2-oH2CnDiAzcjDfydUc473idyPp2lqffZ7yy-546lggiSn0wfmfcqwcep673YBKUsYW_oHPsAB8YAzSf_Hjcw/w640-h312/intercom.png" width="640" /></a></div><div><br /></div><div><div>The commander is provided with a total of five vision devices in the MT-LB(V) and MT-LBVM. When his hatch is closed, his primary means of observing his surroundings is by the windshield to his direct front, two 54-36-5SB.BM periscopes in the 11 o'clock and 1 o'clock positions, and a B-2 vision block aimed to the right (shown below). The B-2 vision block is fitted with a large thickness of ballistic glass, but even so, it may not provide the same level of protection as the steel armour of the hull. The upside to its large size, however, is that it provides a large field of view. In the combat modifications of the MT-LB proposed by Muromteplovoz, the slits for the vision blocks were patched over and the vision blocks were replaced with periscopes, presumably improving protection in these zones. Bafflingly, in the MT-LBVMK, which is a minor modification of the MT-LBVM with the replacement of the NSVT with the Kord (using an adaptor pin), only the B-2 vision block in the cargo compartment was patched over and replaced with a periscope.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPhfg_S0BINQ7mRGzPoa-9tJrJTSNYlJ8efNmMk4GGYe9ZyzBO_RFt-WJF5SKro_qpjD-JCHWbBSqFbkQTo8-6C7wj0Y42qYbiQUm5lRn7OIilTUMdqwF-l6Dv7-h80TULuPWMpGjazEvoX42A-2Sp4D4wDtP9YPHCvWzv8itAulxiy2XhLn5-7Ei-xg/s581/b-2%20vision%20block.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="269" data-original-width="581" height="185" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPhfg_S0BINQ7mRGzPoa-9tJrJTSNYlJ8efNmMk4GGYe9ZyzBO_RFt-WJF5SKro_qpjD-JCHWbBSqFbkQTo8-6C7wj0Y42qYbiQUm5lRn7OIilTUMdqwF-l6Dv7-h80TULuPWMpGjazEvoX42A-2Sp4D4wDtP9YPHCvWzv8itAulxiy2XhLn5-7Ei-xg/w400-h185/b-2%20vision%20block.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcHg9yVuWFWnVFjkqHB-dmSpjqfl0MnRI-fG2rtoM2U7qyJFqx8rJ7-FW7ozyKCcZ7Uy3D1klOhCAxCpSSTzitlQUc1zPdhZ-c6yFcdtCDOpJinA8ajFq2V3TBHqmjASlXxdjCDJM41fGU1Qvy75toLsBgm3vIroWA64-PmZGlz5gYocG3dze87E7Npw/s1920/b-2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1038" data-original-width="1920" height="216" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcHg9yVuWFWnVFjkqHB-dmSpjqfl0MnRI-fG2rtoM2U7qyJFqx8rJ7-FW7ozyKCcZ7Uy3D1klOhCAxCpSSTzitlQUc1zPdhZ-c6yFcdtCDOpJinA8ajFq2V3TBHqmjASlXxdjCDJM41fGU1Qvy75toLsBgm3vIroWA64-PmZGlz5gYocG3dze87E7Npw/w400-h216/b-2.png" width="400" /></a><br /></div><div><br /></div></div><div>When seated at his station, the commander has good forward visibility as there is a windshield directly in front of him, supplemented by two periscopes, and the B-2 vision block in the side of the hull grants a view to the right. For all-round vision, the commander can use the PP-61B sight installed in his machine gun turret. The sight has a large field of view and permits easy scanning in azimuth using the rotation of the turret, although it does not have a high magnification. In the case of the MT-LBVM, the commander would use his PZU-5 anti-aircraft sight instead. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xpw8r3QVBYk/XymWA8Q7PII/AAAAAAAARbM/68c51exnLogLs4HkLtG1OeEV5Cjueg8PgCLcBGAsYHQ/s1024/left%2Bperiscope.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://1.bp.blogspot.com/-xpw8r3QVBYk/XymWA8Q7PII/AAAAAAAARbM/68c51exnLogLs4HkLtG1OeEV5Cjueg8PgCLcBGAsYHQ/w400-h300/left%2Bperiscope.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-FuQB7VnCLbQ/XymWdpZ0IZI/AAAAAAAARbU/iZ7j1YxI4qU8RPfutUb4Mj3IvEdqjpqTwCLcBGAsYHQ/s600/04RussianMTLBGunnersPosition.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="531" data-original-width="600" height="354" src="https://1.bp.blogspot.com/-FuQB7VnCLbQ/XymWdpZ0IZI/AAAAAAAARbU/iZ7j1YxI4qU8RPfutUb4Mj3IvEdqjpqTwCLcBGAsYHQ/w400-h354/04RussianMTLBGunnersPosition.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>The two 54-36-5SB.BM periscopes use the same periscope unit as the 54-36-317-R periscopes in the driver's station of a T-54, T-55 and T-62, even featuring the same fixed handle, but they differ in the mounting system and do not provide the possibility of quickly cleaning the windows by quick-releasing the periscope and rubbing it up and down against a cleaning pad inside the housing. Nevertheless, the handles for doing so are still present on the 54-36-5SB.BM periscope. When riding around on rough terrain, the handle on each periscope allows the commander to steady himself with both hands.</div><div><br /></div><div>The windshield is not armoured, and does not protect from firearms or artillery fragments other than small fragments and debris. When opened, the windshield cover functions as a visor, keeping rain and direct sunlight off the windshield. The windshields are each fitted with an SL-231B wiper to deal with any rain and snow blown onto the windshield, albeit only on a small swept arc. The windshield is a laminated glass assembly with built-in heating. </div><div><br /></div><div><br /></div><div>The commander's seat is mounted to the torsion bar cover of the first roadwheel pair. The seat is rather unusual in that it is a double swivel seat, in addition to standard features like backrest angle adjustment and seat height adjustment. Not only is the seat itself rotatable on its swivel, but the base of the seat itself has a swivel, allowing the seat to be positioned with an offset like in the photo on the left below. The reason for allowing the base to swivel is unclear, but it may have been to allow the seat to be pushed out of the way when moving in and out of the engine compartment corridor. It is very likely that the seat swivel feature was implemented to allow the commander to comfortably operate the machine gun turret, particularly when he must traverse it more than 90 degrees in either direction. The seat cannot be adjusteed in height, but the angle of the backrest can be adjusted in either direction, with the option of folding the backrest forward and flat onto the seat cushion.</div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-D2nRNObqMCY/Xx2fRGySphI/AAAAAAAARVo/Wfl-hGD39z86h9gYsrBYZE_vvi8hGQj-QCLcBGAsYHQ/s1600/view%2Bof%2Bthe%2Bcommander%2527s%2Bseat%2Bthrough%2Bthe%2Bpassage.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1053" height="400" src="https://1.bp.blogspot.com/-D2nRNObqMCY/Xx2fRGySphI/AAAAAAAARVo/Wfl-hGD39z86h9gYsrBYZE_vvi8hGQj-QCLcBGAsYHQ/w264-h400/view%2Bof%2Bthe%2Bcommander%2527s%2Bseat%2Bthrough%2Bthe%2Bpassage.jpg" width="264" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj7XP7Q7YEiCbKAU2Ys3dVyjN8vMl9TsoBjB2DtD-Vv6zUh5XnfW7HB2Rwno0O1pwAbzngYYkpott4HaQoXUseSJMu5IXhCdTJyQLNdzJMMcDkEnkTJ-3rZUYaL9yR19_ek2l4EqpLUevbQsEi9dDP01P978aL2bNadlu0GbShvHqVGuSnbuTrST5wovg/s800/commander's%20seat.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="627" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj7XP7Q7YEiCbKAU2Ys3dVyjN8vMl9TsoBjB2DtD-Vv6zUh5XnfW7HB2Rwno0O1pwAbzngYYkpott4HaQoXUseSJMu5IXhCdTJyQLNdzJMMcDkEnkTJ-3rZUYaL9yR19_ek2l4EqpLUevbQsEi9dDP01P978aL2bNadlu0GbShvHqVGuSnbuTrST5wovg/w314-h400/commander's%20seat.gif" width="314" /></a><br /></div>
<div><br /></div><div>With the installation of the TKB turret on the MT-LBVM, the seat was slightly modified by the addition of a cushion on the rear of the backrest. According to the manual, the commander is expected to fold the backrest flat against the seat and sit on the backrest to reach the optical sight in the turret, which is due to the increased height of the sight eyepiece in the new turret. Aside from this change, the seat remained the same.</div></div><div><br /></div><div>The metal base of the seat is 280mm from the floor at the highest point, and the seat cushion is 330mm from the floor. When seated normally (and not using the turret for combat in the case of the MT-LBVM), the free space above the commander effectively gives him more headroom than the passengers in the cargo compartment despite his slightly taller seat, to approximately the same extent as the driver, who has a raised cupola, or more. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEig2at5iJiQk9IArZCkZ7Rif2k3TSKaFlzpONwhTDwtr2Y25LC7AGQnMJj5pOp-QwhlVvUait2c4xCVnIhXVc93m6QZ-rrmN-sCVKxWC4e9egwWriRbhFNhAh22nl14PWvoBChslVQdzTHexDYX8ltFrYCTpgpbEUtpbodUvTJ3ubFhQBDHVDe2Qt0Ayg/s4160/commander's%20seat%203.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="4160" data-original-width="3120" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEig2at5iJiQk9IArZCkZ7Rif2k3TSKaFlzpONwhTDwtr2Y25LC7AGQnMJj5pOp-QwhlVvUait2c4xCVnIhXVc93m6QZ-rrmN-sCVKxWC4e9egwWriRbhFNhAh22nl14PWvoBChslVQdzTHexDYX8ltFrYCTpgpbEUtpbodUvTJ3ubFhQBDHVDe2Qt0Ayg/w300-h400/commander's%20seat%203.jpg" width="300" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhOIv1xkJEya9VkmDQ6pZYbvwM15K1IDJFsGHPfuiXzBk9JNbhG3WuuYIBszgrPkZwAgAy0jdzSEOceHguSEM8lVDigUNhznAgJZlSvhv_23Gxu8fVsadnK41kkqbIIOjTLxGvaqmx0WQD_QlAakhLLZFR-yjBEIjDsR7D5HH7bj151eXP-ldxz3-5wrw/s4160/commander's%20station.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="4160" data-original-width="3120" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhOIv1xkJEya9VkmDQ6pZYbvwM15K1IDJFsGHPfuiXzBk9JNbhG3WuuYIBszgrPkZwAgAy0jdzSEOceHguSEM8lVDigUNhznAgJZlSvhv_23Gxu8fVsadnK41kkqbIIOjTLxGvaqmx0WQD_QlAakhLLZFR-yjBEIjDsR7D5HH7bj151eXP-ldxz3-5wrw/w300-h400/commander's%20station.jpg" width="300" /></a></div><div><br /></div><div><br /></div><div>The metal base of the jockey seat in the middle is 550mm from the floor, and its cushion is only 20mm thick. The driveshaft cover is only around 260mm wide, and the jockey seat atop it is around the same width. Seated here, a commander of average height should expose only his head above the rim of the hatch, which gives him a free view towards the front and sides if the hatch is of the early type that hinges opens to the rear. If the hatch is of the later type that hinges open to the front, the commander has a much more restricted forward view in the tall gap between the hatch and the rim of the hatch opening. With a forward-opening hatch, the best position for the commander would be to sit on the hull roof, resting his feet on the jockey seat, or standing on the driveshaft cover. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5R_L4TKNO__Z7prdpkO_98eKulA-b7v4cES4FVf9wy9gbPS6PG4YWb7RIj6pPbh9UrnaiNsxmkefYji6trksBc7URHhK57m6YMm1QDfIzvGvCW4o3JgQy0meRQcoS0XSSZuPCNx-vHi8kv7OwSHwZfHwoRRfYxeNpkyMdFvVREjaj-1DxGSsNPdAcYQ/s4160/jockey%20seat.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="4160" data-original-width="3120" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5R_L4TKNO__Z7prdpkO_98eKulA-b7v4cES4FVf9wy9gbPS6PG4YWb7RIj6pPbh9UrnaiNsxmkefYji6trksBc7URHhK57m6YMm1QDfIzvGvCW4o3JgQy0meRQcoS0XSSZuPCNx-vHi8kv7OwSHwZfHwoRRfYxeNpkyMdFvVREjaj-1DxGSsNPdAcYQ/s320/jockey%20seat.jpg" width="240" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjYVg4abBbGxAxLHQfyGhfDo0pcySVSxU9m9pASPhagT4kAvMCiD8ZcBbRKXx_Y0vqJeS1DiBwv3q0qCUj4Wl3HI-PLrpVSchw57fIrDHHZd7Sn20dp2tZpAR2vy69FULKbdJlcbl0SCf_ckFx7ut9yXisKtclGu4nWXbOVl6JUjiW3Y5spS4PSW8SGVw/s1200/golomyanny_island_06-1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjYVg4abBbGxAxLHQfyGhfDo0pcySVSxU9m9pASPhagT4kAvMCiD8ZcBbRKXx_Y0vqJeS1DiBwv3q0qCUj4Wl3HI-PLrpVSchw57fIrDHHZd7Sn20dp2tZpAR2vy69FULKbdJlcbl0SCf_ckFx7ut9yXisKtclGu4nWXbOVl6JUjiW3Y5spS4PSW8SGVw/w400-h266/golomyanny_island_06-1.jpg" width="400" /></a></div></div><div><br /></div><div><br /></div><div>It is important to note that, unlike purpose-built combat vehicles with a dedicated gunner, the commander was not furnished with a fire correction optic, which would have been a TKN-3B for the MT-LB. The commander's vision in combat is mainly limited by the fact that he is not provided with such a device, like his counterparts in combat vehicles such as BTRs, BMPs and tanks, where such a periscope was necessary for fire correction purposes. Moreover, not only did the commander lack the surveillance capability offered by the 5x magnification of such a device, he also lacked night vision.</div><div>
<br />Nevertheless, the all-round vision of the commander can be considered good relative to the commanders of older Soviet combat vehicles like the BTR-60PA and the BTR-50P. Like on an MT-LB, the commander of a BTR-60PA had a windshield in front of him, but it was only supplemented by a single vision slit in the hull side plate and a single rotatable TPKU-2 binocular periscope, while the commander of a BTR-50P had just three fixed generla vision periscopes arrayed in a 120-degree forward arc, and the squad commander was provided with an MK-4 rotating periscope with the option of installing a TKN-1 night vision periscope. Even when compared to contemporary vehicles such as the BTR-60PB, which had been upgraded with a more comprehensive set of vision devices, the MT-LB is quite good. If the three vehicle families are judged according to the quantity of vision devices and the breadth of view offered, the MT-LB compares favourably, especially considering that he has a swivel seat which allows him to comfortably achieve all-round vision using his machine gun sight, whereas these vehicles had fixed forward-facing seats.</div><div>
<br />
However, compared to foreign armoured personnel carriers, the MT-LB was unremarkable or deficient in this regard. For example, the M24A2 cupola of the M113 had five periscopes covering a 180-degree forward arc, and the cupola could rotate so it was very easy for the commander to obtain an all-round view of his surroundings. The cupola of the French AMX-VCI was very similar as it was also rotatable and had five periscopes covering a 180-degree forward arc.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">ARMAMENT</span></h3><h3 style="text-align: left;"><span style="font-size: large;">MT-LB, MT-LBV</span></h3><div><br /></div><div>The MT-LB was armed with a single 7.62mm machine gun in a turret for self defence purposes. If it were an armoured personnel carrier expected to take part in battle against enemy troops, a single 7.62mm machine gun would be wholly inadequate. Indeed, although the early BTR-60 models (BTR-60P, BTR-60PA) had just a single forward-facing pintle-mounted SGMB machine gun, there was the option of replacing it with a DShKM and even the possibility of mounting two additional SGMB machine guns on the sides. This was followed by an upgrade to a turreted KPVT and PKT pairing, making it possible to fight lightly armoured vehicles on favourable terms. However, the MT-LB was not built to be an armoured personnel carrier, as that role was already filled by the BTR-50P and BTR-60P. For the needs of towed gun crews, who were armed only with AKM assault rifles, a single 7.62mm machine gun provided a reasonable self-defence capability.</div><div><br /></div><div>For the MT-LB and MT-LBV, an ammunition load of 1,000 rounds was specified until at least 1976. However, manuals from the 1980's list an increased ammunition load of 1,500 rounds, possibly a revision made as a result of experiences in Afghanistan.</div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="tkb-01-1"></a><h3 style="text-align: left;"><span style="font-size: large;">TKB-01-1 TURRET</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-qpYSGtHLwi0/Xx3DztcFfpI/AAAAAAAARWM/lLb5N0ilHrM2hnKnQtVsIZB-NvuvMeJqACLcBGAsYHQ/s1098/mt-lb%2Btkb-01-1%2Bmachine%2Bgun%2Braised.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="547" data-original-width="1098" height="318" src="https://1.bp.blogspot.com/-qpYSGtHLwi0/Xx3DztcFfpI/AAAAAAAARWM/lLb5N0ilHrM2hnKnQtVsIZB-NvuvMeJqACLcBGAsYHQ/w640-h318/mt-lb%2Btkb-01-1%2Bmachine%2Bgun%2Braised.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The MT-LB has a PKT machine gun installed in a small turret operated by the vehicle commander for self-defence purposes. Its main function is to serve as the base of fire for an artillery gun crew if they come under infantry attack, whereby each gun crew member becomes a rifleman while defending the gun emplacement or retreating from it. It also grants the possibility of the MT-LB serving as an overwatch weapon against an enemy infantry screening force moving ahead of their tanks, preventing the infantry from closing in and overruning the gun emplacement. With the exception of the RPG (the anti-tank weapon in this case would be the artillery piece) and the RPD or RPK organic to a Soviet motorized infantry squad, this transforms an artillery gun crew into the equivalent of a BTR-40 or BTR-152 squad in terms of firepower.</div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-9Scow6RQj1s/Xp7_0gD-9FI/AAAAAAAAQm4/nuGk_IlskMQmrMr7sYVPSA9-PE7OyiqgwCEwYBhgLKs0DAL1OcqwWoQHEA2J5Y2CNk5A0ByHT1tCH1um0VvaAPTpxI36zwMkgYJs_YVirjFrMxUfreHQHGR2QG3LTN2Zw_55Kkt05_Dm4jzCOFJjUyLvj3Fk5pkcU2Hriu219xpEqUqcbVXjTBr8RHFqgncKtbBHyz-4WNqIQuefF27TWuYFjHVSSN3qgrvyOLR5KGOnCb0e-4Q0OEv9aEvFcwTwJ5aIUGxQROgAvgGTQ84wr7Wlt0u6vLWGvz2xlUmk5enwX-vEIKgTZTgXTyV-q3RzKYd-GsFmRlSumh3qGGMtBi2CCOCWPf10l56WQhH60xOU_KVDc0c1QXlICrwOcgyKJL9FnnuZj2e2XXe-jgacIs8-75hbGgpYKmU2N82p22CYWGLnvHh8wGWyrJ0QJ4n2cAtoG_paemW9F8hxgXP7DYmCMADtWkbN4Z0WfZ98JJwv1dki0iyAf-qoJaLbOkCzxsmx-E9Hf8lyk8YhH8k9TF_QmlL1iDrMVmZ3ifT6mDbZT2nHLsRNJnseGHjeXW9oJRsRBYMDaWsXzSr6DuYQ3IWaqJjmojs3Z0K-kUddw-1iIGR63QO5TPIKi0we0Xs8TgJZoTFEC8ecMNFn2TeMwnoj89AU/s1600/turret.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="986" data-original-width="1120" height="351" src="https://1.bp.blogspot.com/-9Scow6RQj1s/Xp7_0gD-9FI/AAAAAAAAQm4/nuGk_IlskMQmrMr7sYVPSA9-PE7OyiqgwCEwYBhgLKs0DAL1OcqwWoQHEA2J5Y2CNk5A0ByHT1tCH1um0VvaAPTpxI36zwMkgYJs_YVirjFrMxUfreHQHGR2QG3LTN2Zw_55Kkt05_Dm4jzCOFJjUyLvj3Fk5pkcU2Hriu219xpEqUqcbVXjTBr8RHFqgncKtbBHyz-4WNqIQuefF27TWuYFjHVSSN3qgrvyOLR5KGOnCb0e-4Q0OEv9aEvFcwTwJ5aIUGxQROgAvgGTQ84wr7Wlt0u6vLWGvz2xlUmk5enwX-vEIKgTZTgXTyV-q3RzKYd-GsFmRlSumh3qGGMtBi2CCOCWPf10l56WQhH60xOU_KVDc0c1QXlICrwOcgyKJL9FnnuZj2e2XXe-jgacIs8-75hbGgpYKmU2N82p22CYWGLnvHh8wGWyrJ0QJ4n2cAtoG_paemW9F8hxgXP7DYmCMADtWkbN4Z0WfZ98JJwv1dki0iyAf-qoJaLbOkCzxsmx-E9Hf8lyk8YhH8k9TF_QmlL1iDrMVmZ3ifT6mDbZT2nHLsRNJnseGHjeXW9oJRsRBYMDaWsXzSr6DuYQ3IWaqJjmojs3Z0K-kUddw-1iIGR63QO5TPIKi0we0Xs8TgJZoTFEC8ecMNFn2TeMwnoj89AU/s400/turret.png" width="400" /></a></div><div><br /></div><div>Housing the machine gun inside a small turret was the optimal design solution given the constraints of the MT-LB hull design. The machine gun turret fulfilled the same function as the bow machine gun of the AT-P prime mover, but the TKB-01-1 was capable of greater firepower as it could conduct all-round fire and provided the operator with better visibility, more ergonomic controls and a magnified optic. The TKB-01-1 was also directly analogous to a bow machine gun in that the operator controls the machine gun by hand rather than a geared mechanism, which allows the operator to manually stabilize his view and quickly lay the machine gun on a target. This was made easy due to the light weight, and thus low moment of inertia of a 7.62mm machine gun, enhanced by the long control handles, acting as a lever, although this is likely much less intuitive to control than a machine gun on a ball or pintle mount. A turreted system, particularly a non-intrusive type like the TKB-01-1, also increases the internal space available to the operator compared to a bow machine gun, where a rather large swept volume must be allocated inside the vehicle to accommodate the traversing arc of the weapon.</div><div><br /></div><div>The turret is capable of 360-degree traverse, and the machine gun can be depressed by -5 degrees or elevated by +35 degrees, with the possibility of locking the machine gun at any elevation angle within this range. This is sufficient for engaging virtually all relevant ground targets, including infantry in high elevation positions at close ranges, but it is not suitable for air targets except low flying helicopters. That said, the basic premise of using a 7.62mm machine gun against air targets is somewhat suspect, so it is perhaps fair to say that an elevation limit of +35 degrees is sufficient for dealing with virtually all relevant threats. It is worth noting that the range of elevation is not drastically more than a traditional bow machine gun, but even so, the TKB-01-1 has an advantage in that the sight is fixed, and only the periscopic head elevates. Thanks to this, the operator can maintain a fixed, comfortable position on the eyepiece regardless of the elevation angle of the machine gun, unlike a sighted bow machine gun where the operator would have to contort in awkward ways to aim at the elevation extremes.</div><div><br /></div><div>The commander elevates the machine gun using a set of two large control handles affixed to the machine gun cradle by a shared stem, and fires it using a thumb trigger button. On the left of the control handle stem is a gun elevation lock handle, marked (21) in the drawing below, also fitted to the cradle on the same crosspin, and loosely resting a clamp against a track fixed to the turret, marked (4) in the drawing on the left below. On the right of the control handle stem is symmetrically mirrored elevation lock handle. When the machine gun is free to elevate, the elevation lock handle will be at the same angle as the stem of the control handles, but when pulled back, the clamp is tightened against the track to lock the machine gun in elevation. The drawing below does not accurately portray how far the elevation lock handles must be pulled to clamp the machine gun firmly in place. The image on the right below, taken from <a href="https://youtu.be/5xeXQlMkt6w">a military film</a> shared by the VHU YouTube channel, shows the control handles.</div><div><br /></div><div style="text-align: center;"><div class="separator" style="clear: both;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhmuCKnbtqRf82zlLUyQ-h0ux3dW58vKkrLC63bpGctNpxvWXV-dr9q1dgTILQ6xiwhCqis3YNJiQknG-Xf_ryfflht1EbYgvhtEg1OPfQFdCN51oWd0jtMouWkyyKgPe17OGYxGxzfWgxs7Fg_b3neP4fqie14TQfVBIKZMcEdPmpX-ndJmTLgiDwYhg/s1475/turret%20controls.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1475" data-original-width="1363" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhmuCKnbtqRf82zlLUyQ-h0ux3dW58vKkrLC63bpGctNpxvWXV-dr9q1dgTILQ6xiwhCqis3YNJiQknG-Xf_ryfflht1EbYgvhtEg1OPfQFdCN51oWd0jtMouWkyyKgPe17OGYxGxzfWgxs7Fg_b3neP4fqie14TQfVBIKZMcEdPmpX-ndJmTLgiDwYhg/w296-h320/turret%20controls.png" width="296" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRa_dVZrP9-k4bioq18a15hVpTF3YjyeMlNpDdvQtLoorUISremUbvlPmSH82CAMC17OFjgyj_A8uPFeyMzPE4ejpGhwj9o-ygt7nG8HZBv8-H-SJeiYWGLzfD-0g41zFL8CUXywnODl0srsnJ6UA4kD5ZSoqqOOqvL5okqh-D2-U1jPuYgbVBBAscHQ/s1920/snar-10%201.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRa_dVZrP9-k4bioq18a15hVpTF3YjyeMlNpDdvQtLoorUISremUbvlPmSH82CAMC17OFjgyj_A8uPFeyMzPE4ejpGhwj9o-ygt7nG8HZBv8-H-SJeiYWGLzfD-0g41zFL8CUXywnODl0srsnJ6UA4kD5ZSoqqOOqvL5okqh-D2-U1jPuYgbVBBAscHQ/w400-h225/snar-10%201.png" width="400" /></a></div><div style="text-align: left;"><br /></div><div style="text-align: left;">The image on the right below, <a href="https://www.reddit.com/r/TankPorn/comments/os0eq2/here_are_most_of_the_pictures_i_took_at_the/">from Reddit user "BT-42"</a>, shows the two elevation lock handles (behind and above the eyepiece of the sight) pulled sharply back relative to the control handles to keep the machine gun locked in place.</div><div style="text-align: left;"><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_9O7YYgCHxVg6J2KeSGRuJkoOZZE19Kxx-jzpbx6ASYD-cIDXFlr14vL15DtL8Va2NY0QWtU3xPFWzRvteNZ71RYbIUheD5BmTI5kIa5VwnYzqce8XhuXwwDyuB7FF8JeimJ1MDF-MRNk00mEO2W804DI_7aF0PhQ31cgT0BSOkesaDOSxe7KCinREA/s1153/turret%20controls%202.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="826" data-original-width="1153" height="286" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_9O7YYgCHxVg6J2KeSGRuJkoOZZE19Kxx-jzpbx6ASYD-cIDXFlr14vL15DtL8Va2NY0QWtU3xPFWzRvteNZ71RYbIUheD5BmTI5kIa5VwnYzqce8XhuXwwDyuB7FF8JeimJ1MDF-MRNk00mEO2W804DI_7aF0PhQ31cgT0BSOkesaDOSxe7KCinREA/w400-h286/turret%20controls%202.gif" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhslNM66wG5i7WyGLQX0TePfui6MJsSdVudvndZ5QOU7vx1qRqbmFo5qI78US2LC9EGmmD4XBKw5iLrjzMKzRbzo32DXKdECxHB6J6BIaZT8GP5Cq6OVv9Vi9WeLxSe8QqiAFmJkS5JQmaQA3pIHO81Men3WB47lCGiUMMBFZRhgI0m8DwfgVE-7QXpxA/s2049/control%20handles%20behind%20eyepiece.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1402" data-original-width="2049" height="274" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhslNM66wG5i7WyGLQX0TePfui6MJsSdVudvndZ5QOU7vx1qRqbmFo5qI78US2LC9EGmmD4XBKw5iLrjzMKzRbzo32DXKdECxHB6J6BIaZT8GP5Cq6OVv9Vi9WeLxSe8QqiAFmJkS5JQmaQA3pIHO81Men3WB47lCGiUMMBFZRhgI0m8DwfgVE-7QXpxA/w400-h274/control%20handles%20behind%20eyepiece.jpg" width="400" /></a><br /></div><div style="text-align: left;"><br /></div><div style="text-align: left;">The set of controls described was the type used in the majority of MT-LBs. There was a design preceding this type, where the elevation lock handles were much longer, and there was only a single large control handle for the commander to elevate the machine gun. This early type is shown in the photo on the left below. The later type is shown in contrast on the right below. It is not known when the switch to the more common two-handle type was made.</div><div style="text-align: left;"><br /></div><div><a href="https://1.bp.blogspot.com/-D2nRNObqMCY/Xx2fRGySphI/AAAAAAAARVo/Wfl-hGD39z86h9gYsrBYZE_vvi8hGQj-QCLcBGAsYHQ/s1600/view%2Bof%2Bthe%2Bcommander%2527s%2Bseat%2Bthrough%2Bthe%2Bpassage.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1053" height="400" src="https://1.bp.blogspot.com/-D2nRNObqMCY/Xx2fRGySphI/AAAAAAAARVo/Wfl-hGD39z86h9gYsrBYZE_vvi8hGQj-QCLcBGAsYHQ/w264-h400/view%2Bof%2Bthe%2Bcommander%2527s%2Bseat%2Bthrough%2Bthe%2Bpassage.jpg" width="264" /></a><a href="https://blogger.googleusercontent.com/img/a/AVvXsEia0xiH0lwsVEWZUBwoVRLUhugWhX6CoTI9KG9xz8WRJtap65Lbr2o9lF7nbNgTNXXoLclti-4NgS0VaZfPlNupOaUVLY39VKvOpMwoguF-3HLExl-PLb_jdKmtYpkDB7BqdpNSST7WKmEpn9UzO4ldCytlFM7SCVtwGStY9poxrvNF2AfZfJNHag_NfA=s960" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="720" height="400" src="https://blogger.googleusercontent.com/img/a/AVvXsEia0xiH0lwsVEWZUBwoVRLUhugWhX6CoTI9KG9xz8WRJtap65Lbr2o9lF7nbNgTNXXoLclti-4NgS0VaZfPlNupOaUVLY39VKvOpMwoguF-3HLExl-PLb_jdKmtYpkDB7BqdpNSST7WKmEpn9UzO4ldCytlFM7SCVtwGStY9poxrvNF2AfZfJNHag_NfA=w300-h400" width="300" /></a></div></div><div><div><br /></div><div><div>The turret is very small, having a height of just 264.5mm and a maximum external diameter of 798mm. This was made practical by the small dimensions of the PKT, being a 7.62mm machine gun. The armour protection offered by the turret matches the protection level of the MT-LB itself, but due to its small size, the turret weighs just 109 kg with all internal equipment installed, though not including ammunition. The wall of the turret is a single 14mm plate bent into the shape of a truncated cone.</div><div><br /></div><div>The main advantage of having a small turret rather than an external remotely controlled machine gun is that it enabled the commander to operate and access the machine gun without leaving the vehicle. This made it possible to clear stoppages and reload it from under armour. A secondary benefit is that the machine gun itself was better protected from damage, particularly from shell or mortar bomb splinters. At the same time, by having a turret built solely to house the machine gun, the weight and silhoutte of the turret was drastically smaller than a traditional turret, which makes it much easier to control manually and it improves the concealability of the vehicle. </div><div><br /></div><div>In practice, the use of a turret rather than a simple pintle mount for the machine gun such as on early BTR-60 models effectively increased the firepower provided by the same weapon, because it served to isolate the operator from the outside environment, thus rendering enemy suppressive fire ineffective or less effective at the very least, while nullifying the issue of operators being unwilling to expose themselves to sniper fire - an issue which manifested when M113 armoured personnel carriers saw action in Vietnam and was only partly ameliorated by the addition of a gun shield. The same issue led to vehicles such as the Ferret scout car receiving a fully enclosed machine gun turret to replace its pintle-mounted machine gun.</div><div><br /></div><div>The disadvantage of this method of laying the machine gun is that the shot dispersion obtained from it will be much greater than when it is fitted onto a fixed mount as a tank coaxial machine gun. According to the manual, the dispersion of a PKT or PKTM fired from the TKB-01-1 turret is considered normal if the radius of 80% of the impacts (R80) from a 10-round burst at 100 meters does not exceed 15 cm, equating to an angular dispersion of 1.5 mils. For comparison, the norm for a PKT or PKTM on a fixed mount is for 80% of a 10-round burst to fit within a 14 x 16 cm rectangle at 100 meters. Relatively speaking, the difference in the size of the dispersion area is enormous - fired from the TKB-01-1 turret, the 80% dispersion area is 707 sq.cm, whereas a PKT(M) fired from a fixed mount has an 80% dispersion area of just 224 sq.cm; over three times smaller. The precision of fire from the TKB-01-1 is somewhere between a PK fired from its bipod (R50 of 15.5cm, R100 of 35.5cm) and a PKS, which is a PK fired from a tripod (R50 of 7.3cm, R100 of 16cm). In terms of precision, it could be considered roughly equivalent to a free pintle mount. However, it is likely that when the elevation lock is used, the dispersion can be improved.</div><div><br /></div><div>In practice, the possible ramifications are that the amount of ammunition needed to destroy point targets may be increased, and the effective beaten zone produced by the PKT(M) in the TKB-01-1 may be more constrained with regard to target area and range; while a tank coaxial PKT(M) may be capable of providing a high fire density on a small infantry unit concentrated on a narrow frontage at long range, the larger beaten zone from the PKT(M) in the TKB-01-1 may result in an insufficient fire density to effectively deal with the same target under the same conditions. </div></div><div><br /></div><div>There is a dome light on the turret ceiling, located directly above the ammunition box, allowing the commander to conveniently handle the reloading and operation of the machine gun. Power to the turret is transmitted via a brush and a contact ring integrated into the turret ring. Power must be turned on for the commander to turn on the dome light, use the electric solenoid trigger on his machine gun control handles, and to use the sight window heater in cold weather. <span> </span><span> </span></div><div><span><br /></span></div><div><span>The machine gun and the turret controls can be swung up to the maximum elevation angle of +35 degrees and locked using a travel lock on the turret roof in non-combat conditions to free up space in front of the commander. </span></div><div><br /></div><div><br /></div></div><div>The machine gun is sighted using the PP-61B periscopic sight, which is essentially identical to the more ubiquitous PP-61AM used on the BTR-60PB, differing only in that the PP-61B has a different glass insert with a range scale marked for the PKT alone instead of a KPVT and a PKT combination. The sight has a fixed 2.6x magnification and a large field of view of 23 degrees, and is well suited for low light conditions with an exit pupil diameter of 6mm. The aperture window on the turret is electrically heated to prevent fogging. The aperture window is the only protection provided for the sight embrasure in the turret; there is no shield to prevent fragments or a bullet from passing through the embrasure.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgZiKZGqhAaOUHAJIy9jtkY_8DBhVOrTp-l7u4_PEJIItUjPRHZkNdTrA1ffQpHVqeI4le8B3_YaCG2TutvK60-m9BQMtpupexIbMXEUDwscB8nOgd0DBbdy1mNdGjZZhpsqLO5h6jCSsGz7x8l9WhWfHOKdtAw-_jmk4WGB_8WrP9ttDmItgMw5jg9RQ=s1402" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1397" data-original-width="1402" height="319" src="https://blogger.googleusercontent.com/img/a/AVvXsEgZiKZGqhAaOUHAJIy9jtkY_8DBhVOrTp-l7u4_PEJIItUjPRHZkNdTrA1ffQpHVqeI4le8B3_YaCG2TutvK60-m9BQMtpupexIbMXEUDwscB8nOgd0DBbdy1mNdGjZZhpsqLO5h6jCSsGz7x8l9WhWfHOKdtAw-_jmk4WGB_8WrP9ttDmItgMw5jg9RQ=s320" width="320" /></a><a href="https://1.bp.blogspot.com/-vaIx4nXTF9I/XyLaqg5SLRI/AAAAAAAARY8/16dpsTyXdMUIYROl8QHX6BCJSkbBylfpwCLcBGAsYHQ/s2048/viewfinder.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1536" data-original-width="2048" height="300" src="https://1.bp.blogspot.com/-vaIx4nXTF9I/XyLaqg5SLRI/AAAAAAAARY8/16dpsTyXdMUIYROl8QHX6BCJSkbBylfpwCLcBGAsYHQ/w400-h300/viewfinder.jpg" width="400" /></a></div></div><div><br /></div><div><br /></div><div>Having a magnified optic for the machine gun effectively increases its firepower as it extends the effective range of fire by aiding in the observation of enemy forces, the sensing of shots fired downrange, and by making it easier to adjust fire thanks to the range scales marked in the viewfinder. </div><div><br /></div><div>Normally, the most significant downside of a fully enclosed turret is the reduction in the occupant's visibility, especially if the turret is not large enough to provide the occupant with multiple vision devices for an all-round view. This is the case in the much larger turret of the Ferret Mk. 2 scout car, which accommodates the upper torso of the commander, but has only a single forward-facing periscope that serves as the machine gun sight (via an unmagnified collimator). The TKB-01-1 avoids this issue by being particularly short so that when operating the machine gun, the commander's head does not intrude into the turret. The PP-61B sight has a periscopicity of 285mm, and as the viewing window is installed halfway up the height of the turret, this means that the commander's eye level is 153mm below the turret ring, or around half a foot. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj3NFSvMNTx5PwJZJvO4GdryedTqIGOzL9nDmxHjEf8nR3DG7O-eGLKXY_knjgbEUKTfD1RZCjlDIl4fvxseohrlXzcWLCFuEe-wFK4axCegmiZ3qlV4vyUzcf6KqtvpAPDm3N-PVExNtD7w8XL01Zb9Pb0QUJ_L0k3f44CIBC9zuRdKzz7FcBbyAHQKg/s1920/snar-10%203.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj3NFSvMNTx5PwJZJvO4GdryedTqIGOzL9nDmxHjEf8nR3DG7O-eGLKXY_knjgbEUKTfD1RZCjlDIl4fvxseohrlXzcWLCFuEe-wFK4axCegmiZ3qlV4vyUzcf6KqtvpAPDm3N-PVExNtD7w8XL01Zb9Pb0QUJ_L0k3f44CIBC9zuRdKzz7FcBbyAHQKg/w400-h225/snar-10%203.png" width="400" /></a></div><div><br /></div><div>The same design solution of having an uninhabited turret was used for the machine gun turret developed for the BTR-60PB, later shared with the BRDM-2, but differing in the scale due to the much larger bulk of the 14.5mm KPVT.</div><div><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgw-kxx438HeQnO3RzGHshx5TEa4wSDrcjuu6C_olXIu3PV7U5_SUc-INky5akhV9haBYXm3-T3ffsn-N-zHi2EQG0nLMhXxfuOAqm7n3Sw3q1-L7216Bb5VDnPnV9a9AVSHmjR9J2zJ_V3e35Ij8KzR2qjwOq8CnqhyTZPNq1YWG-d78xJet_u5q0KQg/s1170/turret%20cross%20section.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="835" data-original-width="1170" height="456" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgw-kxx438HeQnO3RzGHshx5TEa4wSDrcjuu6C_olXIu3PV7U5_SUc-INky5akhV9haBYXm3-T3ffsn-N-zHi2EQG0nLMhXxfuOAqm7n3Sw3q1-L7216Bb5VDnPnV9a9AVSHmjR9J2zJ_V3e35Ij8KzR2qjwOq8CnqhyTZPNq1YWG-d78xJet_u5q0KQg/w640-h456/turret%20cross%20section.png" width="640" /></a></div></div><div><br /></div><div><br /></div><div>Because the commander's eye level is well below the level of the hull ceiling, he can freely use the vision devices embedded in the MT-LB hull when operating the machine gun turret without needing to adjust the height of his seat. To achieve a more complete all-round view, he must rely on the machine gun sight and rotate the turret. With a field of view of 23 degrees, it would serve quite adequately as a general observation device.</div><div><br /></div><div>Due to the large weight of the 250-round ammunition box, the mounting cradle, the machine gun itself, and the additional weight of any collected spent casings, the weapon system is rather rear-heavy. To properly balance the entire setup, there is a coil spring equilibrator on the turret ceiling, which is hooked onto the gun mask. The machine gun recoils a short distance against a buffer spring on its mount, providing some recoil absorbtion and damping the firing vibration.</div><div><br /></div><div>The machine gun is fed with 250-round boxes, a standard capacity for all armoured vehicles armed with PKT machine guns. The ammunition boxes are the same as those used in turreted BTRs, having a tall and narrow shape designed to fit more easily into narrow one-man turrets, as opposed to the square-shaped boxes used on pintle-mounted PKBs and tank coaxial PKTs. A total of four boxes are carried, one mounted next to the gun, and three more tucked in the front right corner of the commander's station. Spent cases and belt segments are ejected to the left, diverted by a deflector and collected in a fabric bag hanging beneath the machine gun. It is large enough to hold a thousand cases and their belt segments, which is the full combat load specified for the MT-LB, and it has a zipper along its bottom to empty out its contents. The photo below (courtesy of <a href="https://urban3p.ru/blogs/29492/">Viktor Viktor from Urban3r</a>) shows the sheet steel hood affixed to the machine gun mount to serve as a case and belt deflector.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-lhMGm1qHIug/XyLgv5HgUMI/AAAAAAAARZE/XzOINHQi5o4m7Nhy4oLfR-If4WzeYiGQACLcBGAsYHQ/s1024/turret%2Binterior.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://1.bp.blogspot.com/-lhMGm1qHIug/XyLgv5HgUMI/AAAAAAAARZE/XzOINHQi5o4m7Nhy4oLfR-If4WzeYiGQACLcBGAsYHQ/w400-h300/turret%2Binterior.jpg" width="400" /></a></div><div><br /></div><div><div>To reload the machine gun, it must be cranked to its maximum elevation angle as the low clearance afforded by the turret ceiling would otherwise prevent the top cover from being opened.</div><div><br /></div><div><br /></div><div><div>The drawing on the left below shows the box and the spring catch on its side for hooking onto a box holder to secure the box firmly in place, and the image shown on the right below (courtesy of <a href="https://forum.guns.ru/forummessage/85/211107.html">user akstore</a>), shows the carrying handle lifted.</div><div><br /></div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-AngF5G_UF4A/XyJsEMAm2fI/AAAAAAAARYk/7k2gYQKjNOI88w8jmUB2QtVcKoHF3Ii7QCLcBGAsYHQ/s1825/250%2Bround%2Bbox.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1825" data-original-width="1585" height="400" src="https://1.bp.blogspot.com/-AngF5G_UF4A/XyJsEMAm2fI/AAAAAAAARYk/7k2gYQKjNOI88w8jmUB2QtVcKoHF3Ii7QCLcBGAsYHQ/w348-h400/250%2Bround%2Bbox.png" width="348" /></a><a href="https://1.bp.blogspot.com/-MtZM8CoKJz0/XyJsIxZYhgI/AAAAAAAARYo/lXSvJga0Ivc7_cwEhrMHnSxcw4DlByvOwCLcBGAsYHQ/s500/pkt%2Bammo%2Bbox.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="500" data-original-width="291" height="400" src="https://1.bp.blogspot.com/-MtZM8CoKJz0/XyJsIxZYhgI/AAAAAAAARYo/lXSvJga0Ivc7_cwEhrMHnSxcw4DlByvOwCLcBGAsYHQ/w233-h400/pkt%2Bammo%2Bbox.jpg" width="233" /></a></div><div><br /></div></div></div><div><br /></div><div>The main drawback of the machine gun turret compared to a pintle mount is the inability to replace the barrel of the PKT without dismounting it beforehand. When the heat limit of the PKT barrel in continuous fire (500 rounds) is reached, the most practical option is to allow it to cool, rather than dismounting the machine gun to swap out the barrel. </div><div><br /></div></div><div><br /></div><div>The barrel shroud on the turret encloses the barrel up to the gas tube port. There are no issues with propellant gasses being vented into the shroud, because unlike the infantry guns, the PKT and PKTM were built with a proprietary, fully contained gas system, where the gas ported from the barrel is purged from the gas tube simply by returning up the port and back into the barrel when the pressure drops after the bullet has left the muzzle. Unfortunately, however, there is no fume extractor effect like in tank guns because the gas port is perpendicular to the bore axis, and so a substantial volume of fumes can enter the crew compartment via the receiver due to the open-bolt operating system of the machine gun.</div><div><br /></div><div>The necessity of dealing with the issue of fume extraction was one of the ramifications of an enclosed turret such as the TKB-01-1, as by having this instead of an external mount, gunpowder fumes can accumulate rapidly during sustained fire, not just from the machine gun itself, but also emanating from the spent cartridge casings collected in the spent casing bag. The turret has no built-in ventilator to extract these fumes under normal combat conditions, relying instead on the high air flow rate developed by the supercharged ventilator when it is set to the overpressure mode. An air outlet built into the right rear quadrant of the turret wall (marked in the section A-A in the drawing below), fitted with a valve tuned specifically to open under the specified overpressure generated by the ventilator, ensures a controlled flow of air through the turret, around the machine gun, and through the outlet, thus extracting fumes. Given the close proximity between the turret and the ventilator, ventilation of the commander's station should be fairly strong while the machine gun is in use. Because the supercharger is in operation even in the basic ventilation mode of the ventilator, then as long as all hatches are closed, fume extraction is provided. The photo on the right below, taken from the <a href="https://www.net-maquettes.com/pictures/mt-lbv/">Net Maquettes</a> website, shows the bump on the right rear quadrant of the TKB-01-1 turret for the air outlet. </div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-BDv8l_4yfFY/Xp8AvMwgbHI/AAAAAAAAQnA/ZGJV1Z_gT40cdWi_WCJCEeRKn-i-YggCQCLcBGAsYHQ/s1600/turret%2Btop%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1345" data-original-width="1468" height="291" src="https://1.bp.blogspot.com/-BDv8l_4yfFY/Xp8AvMwgbHI/AAAAAAAAQnA/ZGJV1Z_gT40cdWi_WCJCEeRKn-i-YggCQCLcBGAsYHQ/s320/turret%2Btop%2Bview.png" width="320" /></a><a href="https://1.bp.blogspot.com/-B4DBBkcLszs/YK36YzpKrqI/AAAAAAAATH0/UhQmc_aCcs8UmxT4CrGXZKJRZDIZF9pRgCLcBGAsYHQ/s800/22433957583_0b208e85a8_c.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://1.bp.blogspot.com/-B4DBBkcLszs/YK36YzpKrqI/AAAAAAAATH0/UhQmc_aCcs8UmxT4CrGXZKJRZDIZF9pRgCLcBGAsYHQ/w400-h300/22433957583_0b208e85a8_c.jpg" width="400" /></a></div><div><br />Firing the machine gun is done by pressing the thumb trigger button on the right handle. It is a solenoid switch which, when pressed, energizes the solenoid trigger mechanism on the PKT machine gun, causing it to fire.<br /><br /></div><div><br /></div><div>The turret ring can be locked facing forward with a spring-loaded stopper for travel. To unlock the turret, the commander pulls out the stopper and locks it in the open position with by screwing in a nut. The race ring of the turret ring is mounted to a cast steel platform with bolts, and the armoured turret walls not only cover the turret ring itself but also overlap with the platform. The gap in the race ring is protected with fragment traps, to ensure that any bullet splash or other forms of fragmentation cannot jam the turret ring by traveling through the gap between the turret armour and the turret platform.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-wFhfuCff8Aw/XyJlZiTEPgI/AAAAAAAARYQ/xa1RjCwVjEwiYYiP1GMegahYRKu7i6OjACLcBGAsYHQ/s1629/mtlb%2Bturret%2Bring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1595" data-original-width="1629" src="https://1.bp.blogspot.com/-wFhfuCff8Aw/XyJlZiTEPgI/AAAAAAAARYQ/xa1RjCwVjEwiYYiP1GMegahYRKu7i6OjACLcBGAsYHQ/s320/mtlb%2Bturret%2Bring.png" width="320" /></a><a href="https://1.bp.blogspot.com/-8K2dsKD5R7c/XyJleDvl1eI/AAAAAAAARYU/MUQSbnDI9Ms2fhSm9wS56ejArIYhhRecQCLcBGAsYHQ/s1006/turret%2Bring%2Brace%2Bring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="709" data-original-width="1006" height="283" src="https://1.bp.blogspot.com/-8K2dsKD5R7c/XyJleDvl1eI/AAAAAAAARYU/MUQSbnDI9Ms2fhSm9wS56ejArIYhhRecQCLcBGAsYHQ/w400-h283/turret%2Bring%2Brace%2Bring.png" width="400" /></a></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="tkb"></a><h3 style="text-align: left;"><span style="font-size: large;">MT-LBVM</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhOFxy-bgYbnNzcASN39avyoIMB-O1X5q_O0Wj9GG-2iNKVxEZhNW_87XYvrvcIpm3wLWGjzTatWNiZ-Y3ZnXX8Ii3--rUhnmUGfgVLk6OEGHOU0RS_GLZ3qI6324b5R2qLpvrIGuVYShJqdB8wkdkCoK2bXpA6qjmyf_7969YI0hnJRkRTlSpJzo3lJg/s1276/MT-LBVM%20cropped.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="776" data-original-width="1276" height="244" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhOFxy-bgYbnNzcASN39avyoIMB-O1X5q_O0Wj9GG-2iNKVxEZhNW_87XYvrvcIpm3wLWGjzTatWNiZ-Y3ZnXX8Ii3--rUhnmUGfgVLk6OEGHOU0RS_GLZ3qI6324b5R2qLpvrIGuVYShJqdB8wkdkCoK2bXpA6qjmyf_7969YI0hnJRkRTlSpJzo3lJg/w400-h244/MT-LBVM%20cropped.jpg" width="400" /></a></div><div><br /></div><div><div>On the MT-LBVM, a new turret with an externally mounted NSVT machine gun was fitted, along with a complement of 1,050 rounds of ammunition in 7 proprietary 150-round boxes, with one carried on the gun mount and 6 rack spaces allocated in the center of the cargo compartment. By stowing ammunition this way, cargo space was restricted on the MT-LBVM, which made it impossible to tow an anti-tank gun or howitzer together with its ammunition and crew without stowing most of the ammunition externally, on the roof. The 150-round box is shown below.</div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhiacR6E17OKjp-urvMuafU4y7Mk1Cwtu7cXsXj-usMamgCz0vpBgn5c5XFDhmmg3VrO9QlhgP3e5IB1xOmnpFLwo542AVpqXtpb1faAJI6BZMzu5U6MOyFlOPFM7NTSWa_ANDeeaYUMI_2wchVaKY92DWaNqH0n-ZhOEJ98awXfrBVAQsZ1XUHnTyycg/s1344/150%20round%20box.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="894" data-original-width="1344" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhiacR6E17OKjp-urvMuafU4y7Mk1Cwtu7cXsXj-usMamgCz0vpBgn5c5XFDhmmg3VrO9QlhgP3e5IB1xOmnpFLwo542AVpqXtpb1faAJI6BZMzu5U6MOyFlOPFM7NTSWa_ANDeeaYUMI_2wchVaKY92DWaNqH0n-ZhOEJ98awXfrBVAQsZ1XUHnTyycg/s320/150%20round%20box.png" width="320" /></a></div><div><br /></div><div>Beginning from around the late 2000's, a new standard practice for MT-LBVMs and MT-LBVMKs was observed. Instead of the original proprietary 150-round box, they use a box adaptor enabling standard 50-round infantry ammunition boxes to be loaded onto the mount. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLqws6mgcT8FO7tAHSHHhbAkZLwcLMm17DBTQNId1VKgi6keWfBGfWt7zVcZeUkFqS_ANHUZLMVbvCeaPjJLXRNgXJnD6xefO83l7CHHCg6qJWamLtmJIddTIsqLcEE5b0C0lXlk6ZxfIf0sTTQUJgfvtrr0K5QauJjA_h3BCv6n73CDu5me2lutlAHQ/s4000/IMG_01291.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3000" data-original-width="4000" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLqws6mgcT8FO7tAHSHHhbAkZLwcLMm17DBTQNId1VKgi6keWfBGfWt7zVcZeUkFqS_ANHUZLMVbvCeaPjJLXRNgXJnD6xefO83l7CHHCg6qJWamLtmJIddTIsqLcEE5b0C0lXlk6ZxfIf0sTTQUJgfvtrr0K5QauJjA_h3BCv6n73CDu5me2lutlAHQ/w400-h300/IMG_01291.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-J9uPzD2RKM9EE7CnAxngXFRLJghJry1yrt5qysCqjqEuvR1-5NYKFjdQAyy0JcUzyLhaDw4gT_mp2qrZndWNyP3Jk_6EufRLBfSUWODJjFNq2kgJiq25kgqpP9nh3sgdYPgugbAec_4yNNVsjnsJn91ApJ1ryfLWn9Nre8e5A_bsZYHlWq9Yq89bhA/s800/original.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="515" data-original-width="800" height="258" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-J9uPzD2RKM9EE7CnAxngXFRLJghJry1yrt5qysCqjqEuvR1-5NYKFjdQAyy0JcUzyLhaDw4gT_mp2qrZndWNyP3Jk_6EufRLBfSUWODJjFNq2kgJiq25kgqpP9nh3sgdYPgugbAec_4yNNVsjnsJn91ApJ1ryfLWn9Nre8e5A_bsZYHlWq9Yq89bhA/w400-h258/original.jpg" width="400" /></a><br /></div><div><br /></div><div>The photo below shows the ammunition racks occupied not by the specified 150-round boxes, but by pairs of standard 50-round boxes for the infantry DShK or NSV machine guns. When using these smaller boxes, there is a net loss of 300 rounds to the combat load. </div><div><br /></div><div>There are ceiling brackets directly above the central ammunition racks for stowing the NSVT machine gun when it needs to be dismounted for extended periods, such as when transporting the MT-LBVM by rail.</div><div class="separator" style="clear: both; text-align: center;"><div style="text-align: left;"><br /></div><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6yrjRUuLf_2UZUXZhtua0lOX_iAUmE3rnZZsQj2mUlHF_mMbJtNZmfYptdSIKIEoep84RSYNCSu622mv0IWVte-wN-o_6mQMPYExWxOizBT6ZLmHz-Uoejgn8GJxV8IOIw7cmNoLR-YnddipD9v5qHbET_ShG0HWNW3OLSCcffYtKcY1emxNIlro05g/s1107/IMG_01531.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="830" data-original-width="1107" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6yrjRUuLf_2UZUXZhtua0lOX_iAUmE3rnZZsQj2mUlHF_mMbJtNZmfYptdSIKIEoep84RSYNCSu622mv0IWVte-wN-o_6mQMPYExWxOizBT6ZLmHz-Uoejgn8GJxV8IOIw7cmNoLR-YnddipD9v5qHbET_ShG0HWNW3OLSCcffYtKcY1emxNIlro05g/w400-h300/IMG_01531.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFl7Xzy7pMKjQnxzw97RoRaFxLtx-gjoIFX0B3mjy7FM9POxypgtDr5qVMb7lURev_qZJbolHFotHYJ_amKhKv8QhxKP4ugyg7almqm_YxhPNJaWyyuCIGSX6yZ1my9wwO91-YXJkQCxby7iOH7zbgdEQmMlMODoJOFqxE7FGzX0F6iYa19Awm5yAXig/s1664/racks.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1216" data-original-width="1664" height="293" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFl7Xzy7pMKjQnxzw97RoRaFxLtx-gjoIFX0B3mjy7FM9POxypgtDr5qVMb7lURev_qZJbolHFotHYJ_amKhKv8QhxKP4ugyg7almqm_YxhPNJaWyyuCIGSX6yZ1my9wwO91-YXJkQCxby7iOH7zbgdEQmMlMODoJOFqxE7FGzX0F6iYa19Awm5yAXig/w400-h293/racks.png" width="400" /></a><br /></div><div><br /></div><br /><h3 style="text-align: left;"><span style="font-size: large;">TKB TURRET (NSVT)</span></h3></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgrll96ouUIJyP7eU5GY5x0b-LowUJZ07Xnbt7gWYHToK0lR8PJU8h5dBdxjey3yRod7158kT9NgOAaa6Zz3Q4gs70k2FhIM5TUq6vOmDJ1wb7XOlZKI4c92cgU9fzugEeLH1qe4S3JwlDpE3T5KWWRqCTALmzimxIYpazhZ5frH1y_DnmjLzFRMBeAhg/s1531/turret.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1467" data-original-width="1531" height="307" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgrll96ouUIJyP7eU5GY5x0b-LowUJZ07Xnbt7gWYHToK0lR8PJU8h5dBdxjey3yRod7158kT9NgOAaa6Zz3Q4gs70k2FhIM5TUq6vOmDJ1wb7XOlZKI4c92cgU9fzugEeLH1qe4S3JwlDpE3T5KWWRqCTALmzimxIYpazhZ5frH1y_DnmjLzFRMBeAhg/s320/turret.png" width="320" /></a></div><div><br /></div><div>The NSVT machine gun is a 12.7x108mm machine gun with a rate of fire of 700-800 rounds per minute, and a nominal effective slant range of 1,500 meters against low-flying air targets, and an effective range of 1,500-2,000 meters against ground targets. However, in practice, the effective range of the NSVT on the MT-LBVM will tend to be much shorter due to factors that will be detailed later.</div><div><br /></div><div>On the TKB turret, the NSVT is fitted on a cantilever mount and controlled from within the turret using hand cranks. To facilitate the cantilever mount of the machine gun, there is a heavy equilibrator spring installed underneath and between the gun and the ammunition box, held inside a perforated frame. The mount permits a maximum elevation of 75 degrees and depression of -3 to -4 degrees. </div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTnksJGeErkw31ffisTQfXxoS6OmndPSLAMkPXPspoKT8IWywH_7uDf6-aLaKqOq6RTzzd-oEPb-wB-W9jifyHEJ83qZF9YJbvTXmutGT5rkLF8_UfX5jMv2yyvPE6L23mcGO0gkCg8pQK8qDddArznbB94bFZThZgGzfY81h0WnRVbm6TnQGYueSkpg/s1374/equilibrator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="720" data-original-width="1374" height="210" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTnksJGeErkw31ffisTQfXxoS6OmndPSLAMkPXPspoKT8IWywH_7uDf6-aLaKqOq6RTzzd-oEPb-wB-W9jifyHEJ83qZF9YJbvTXmutGT5rkLF8_UfX5jMv2yyvPE6L23mcGO0gkCg8pQK8qDddArznbB94bFZThZgGzfY81h0WnRVbm6TnQGYueSkpg/w400-h210/equilibrator.png" width="400" /></a></div><div><br /></div><div>On its cradle, the machine gun is mounted semi-rigidly, where its front mounting rails are not slotted into locks but simply ride in open-ended grooves, and the rear mounting eye is pinned to a shock absorber. Unlike most domestic 12.7mm machine gun mounts on armoured vehicles, there is no reciprocating recoil absorbing cradle, only the shock absorber, consisting of a stack of textolite buffer rings on a shank. The shock absorber is only mildly compressed during recoil, so there is very little displacement to dissipate recoil energy.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTFl8zl9W9i4O1xevmvzjD__RGfGMf5erq1IcHVG9GIVE8BVdYytrBIRq5B0BbBiaicTDqC93DdmysQbKlG891ZtP8dGSMAvgZcFPDrbvWLWmul0qsqNSGRfMcXyXtKIkwRdNsqiYdkMQ8MwcgoPSteil3l0z3jqV5KUjGgHIOiaDA9NlOj4gmc8KgXw/s1387/gun%20cradle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1203" data-original-width="1387" height="348" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTFl8zl9W9i4O1xevmvzjD__RGfGMf5erq1IcHVG9GIVE8BVdYytrBIRq5B0BbBiaicTDqC93DdmysQbKlG891ZtP8dGSMAvgZcFPDrbvWLWmul0qsqNSGRfMcXyXtKIkwRdNsqiYdkMQ8MwcgoPSteil3l0z3jqV5KUjGgHIOiaDA9NlOj4gmc8KgXw/w400-h348/gun%20cradle.png" width="400" /></a></div><div><br /></div><div>The machine gun is fed from the right, and the belt hanging between the ammunition box and the machine gun is protected from snagging on vegetation by a brush guard. The machine gun and its external fittings are not provided with any other form of protection, which is a relatively common shortcoming of externally mounted machine guns. Spent casings are ejected to the front and the spent belt exits from the left, where it is collected in a canvas bag for later reuse. When reloading, the commander elevates the machine gun to allow him to place a belt into the feed tray without getting out of the hatch and leaning over the top cover.</div><div><br /></div><div><br /></div><div>Aiming of the machine gun is done using the PZU-5 sight. It is a specialized anti-aircraft sight, with a 1x magnification and a very wide field of view of 50 degrees. It provides lead rings for aircraft traveling at up to 300 m/s, but no range scales or any markings appropriate for firing upon ground targets. The head of the sight is articulated by the gun mount with an external rod linkage. Together with its unmagnified view, the PZU-5 was an awkward choice for the MT-LBVM, especially in comparison to the NSV on the 6U6 universal infantry mount which was furnished with an 1OP81 sighting scope with a 3.5x magnification to engage ground targets in addition to the anti-aircraft reflector sight. Similarly, when used with the 6T7 infantry tripod mount, an NSV could be issued with an SPP optical sight with a variable magnification of 3-6x. Compared to these infantry mounts, the lack of a magnified sight in the TKB turret would have severely hamstrung the commander's ability to leverage the long range of 12.7mm rounds in combat conditions. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcdemHqO5j4WOCp8qm2QoBvmqAlR-yBZr16ACY4sVJkISw0nUyCHZvKKmyFz9RqVBTLYmu4t5YpohtLpBbsJwiav9rgKBNUdRTZcjWX7KZh1Wq6A57PeOraIy5f8uGifdVsrmNcoHGYvh2tvGm-fdj3lMl6ExqXde97Wfv79EG1IZgosgh9EV6ffqNag/s2141/sight%20head%20articulation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1291" data-original-width="2141" height="386" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcdemHqO5j4WOCp8qm2QoBvmqAlR-yBZr16ACY4sVJkISw0nUyCHZvKKmyFz9RqVBTLYmu4t5YpohtLpBbsJwiav9rgKBNUdRTZcjWX7KZh1Wq6A57PeOraIy5f8uGifdVsrmNcoHGYvh2tvGm-fdj3lMl6ExqXde97Wfv79EG1IZgosgh9EV6ffqNag/w640-h386/sight%20head%20articulation.png" width="640" /></a></div><div><br /></div><div>As the drawing above shows, the eyepiece of the PZU-5 sight is below the turret ring, but it hangs much higher than the PP-61B, such that the commander's head will be inside the turret when he is looking through the sight. This is due to the low periscopicity of the PZU-5, which was not an issue when it was originally used in a tank cupola, such as the remote weapon station cupola of the T-64B where the eyepiece will be at the same level as the periscopes and the eyepieces of the TKN-3. </div><div><br /></div><div>Moreover, the horizontal positioning of the PZU-5 was also another bad compromise, and in more than one way. Firstly, there was a compromise between left and right eye dominant operators, as the sight is positioned so that the axis of the eyepiece coincides with the bore axis of the machine gun, which can be seen in the right image of the drawing above. It therefore does not favour one eye over another, but this also means that it is not particularly comfortable to use the sight with either eye, as the commander must twist his body to position his head properly regardless. Secondly, by increasing the penetration of the sight stem into the turret for the sake of positioning the eyepiece centrally, half of the turret volume became wasted space, as the sight stem physically prevents the front half of the turret from being used to accommodate the commander's head, or accommodate a larger hatch.</div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEihnRKK7YsAatdP3p4dakfnSfyCr6abljGh5ocXl5mB5LrT57NCqALrKTI6azpVh4p6jq3LlZQS-QJ37UHlPXhahtn0bUx5CLkMRDV4ZN1yVws726A8tPe9likt-omraR2D0TLB0r7ZJGQtMKKX5EdZlN1rmE1SYaA_MUC8XjNE7hWSeYWCS7ufE_-z6g/s1420/turret%20profile%20cross%20section.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="864" data-original-width="1420" height="390" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEihnRKK7YsAatdP3p4dakfnSfyCr6abljGh5ocXl5mB5LrT57NCqALrKTI6azpVh4p6jq3LlZQS-QJ37UHlPXhahtn0bUx5CLkMRDV4ZN1yVws726A8tPe9likt-omraR2D0TLB0r7ZJGQtMKKX5EdZlN1rmE1SYaA_MUC8XjNE7hWSeYWCS7ufE_-z6g/w640-h390/turret%20profile%20cross%20section.png" width="640" /></a></div><br /><div>Besides using the PZU-5 sight, an alternate method of aiming the machine gun is to stand in the open hatch and use the iron sights while operating the controls in the turret. The controls are simple handwheels.</div><div><br /></div><div>The traverse mechanism, shown below, possesses an intermediate degree of complexity, having a more refined design than the simplest hand cranks but lacking selectable gears for fine and coarse gun laying like the traverse mechanisms of larger, heavier turrets. Despite the light weight of the turret, a considerable gear reduction was needed in the traverse mechanism because the cantilever mount of its NSVT machine gun made the turret imbalanced and it introduced a large moment of inertia, particularly when a loaded ammunition box is present on the mount. This increased the effort needed to rotate the turret, particularly if the vehicle was on a slope. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0qb9xCPWOd27esBXQzgA3SU_cx22TxfbstLADwHa7sdJMWlXrOLOFdavEdzs9KlUPg7PkHxJgzfLTM360rjkgzjMxI7vDIlov5rjO8GaA6TkIdPmTnCaGcI6vj0-U7MZvZ0F3Hfipn8H3HuHhWMgJbXQb1oqk1lIawcoUXK9b5S2xJSwMMavCx59AXw/s1597/traverse%20mechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1597" data-original-width="1433" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0qb9xCPWOd27esBXQzgA3SU_cx22TxfbstLADwHa7sdJMWlXrOLOFdavEdzs9KlUPg7PkHxJgzfLTM360rjkgzjMxI7vDIlov5rjO8GaA6TkIdPmTnCaGcI6vj0-U7MZvZ0F3Hfipn8H3HuHhWMgJbXQb1oqk1lIawcoUXK9b5S2xJSwMMavCx59AXw/w359-h400/traverse%20mechanism.png" width="359" /></a></div><div><br /></div>The necessary gear reduction was obtained entirely from the difference in the diameter of the flywheel upon which the handle is installed and the diameter of the drive gear, which drives a pinion in mesh with the turret ring. The pinion is not visible in the diagram above. To reduce backlash and increase the smoothness of the mechanism, there is a backlash regulator fitted parallel to the drive gear which controls the position of the pinion in the gear train. By turning a tensioner, the pinion can be moved laterally between the drive gear and the turret ring, shortening the distance between their centers and tightening the mesh between their teeth. Four springs maintain the tightness of the mesh as the turret is traversing and when it is vibrating under the recoil of the machine gun.</div><div><br /></div><div>The firing trigger is on the traverse handle. The top cover of the traverse flywheel is used to accommodate switches to control power to the trigger, PZU-5 sight heater, and its illumination. Between the cover and flywheel is a rotary firing circuit disconnect that prevents the machine gun from being fired when its barrel intersects with the radio antenna, and a warning lamp, marked (5) in the drawing below, lights up.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhBzsas8lP2oGadntNJ4nBu0n8rJjelBnGUNXzwYkTccypWkSw4d-WfC0XgdFiDUTScQ9opD35zd_BNdFe-XX8FBgGJZje3M7bblQmFNwKDyiiV4Q-D0aPY8uGbfEubmVhmJyv-_fqDZ0ad2VpzdT9OXPRj7iHMI54TK-GuMu8FsjFGSfYvBNmrlwPtNQ/s1299/traverse%20mechanism%20switches.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="977" data-original-width="1299" height="301" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhBzsas8lP2oGadntNJ4nBu0n8rJjelBnGUNXzwYkTccypWkSw4d-WfC0XgdFiDUTScQ9opD35zd_BNdFe-XX8FBgGJZje3M7bblQmFNwKDyiiV4Q-D0aPY8uGbfEubmVhmJyv-_fqDZ0ad2VpzdT9OXPRj7iHMI54TK-GuMu8FsjFGSfYvBNmrlwPtNQ/w400-h301/traverse%20mechanism%20switches.png" width="400" /></a></div><div><br /></div><div>The elevation mechanism is a simple and direct worm gear drive. The elevation handle turns the worm gear, turning the geared head of the machine gun mount trunnion pin, thus raising or lowering the machine gun. Because a driven gear cannot rotate the worm gear, the elevation mechanism intrinsically fixes the gun in elevation unless the commander is controlling it. This provides a tighter elevation lock than the clamp-type braking mechanisms used on the anti-aircraft machine gun mounts on domestic tanks and in the elevation mechanisms of turreted BTR and BRDMs.<br /><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlS6_NDpPIy9aajWVpWls6EgEjkbXzh_kk_YuvX8MrWi8U-1PaHRSmGvQ35tZnQFPWAL_W3OWcfGzjI6F5RRvK4bXuHuKxkdL2q_syQx3XJFzQGc8ff-1Lb1FiQQ-tYn-cFQ33UR5d6OJb295OPcJlSNDtSedYRHzzdFqzsxoWpcFbIEgBY6zIHJd6bw/s1644/elevation%20mechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1644" data-original-width="1396" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlS6_NDpPIy9aajWVpWls6EgEjkbXzh_kk_YuvX8MrWi8U-1PaHRSmGvQ35tZnQFPWAL_W3OWcfGzjI6F5RRvK4bXuHuKxkdL2q_syQx3XJFzQGc8ff-1Lb1FiQQ-tYn-cFQ33UR5d6OJb295OPcJlSNDtSedYRHzzdFqzsxoWpcFbIEgBY6zIHJd6bw/w340-h400/elevation%20mechanism.png" width="340" /></a></div><div><br /></div><div>The turret can be locked facing forward with a stopper, functioning as the main travel lock. The gun elevation, being driven by a worm gear, does not require a travel lock. When marching over distances too short to justify stowing the machine gun away in the cargo compartment, the turret is locked and the machine gun is kept at a level elevation.</div><div><br /></div><div>According to the manual, the dispersion of the NSVT when fired from the TKB turret is considered normal if the average radius of 80% of the impacts (R80) from three 10-round bursts at 100 meters does not exceed 60 cm, equating to an angular dispersion of 6 mils. For comparison, the dispersion from an NSV fired from the 6U6 universal mount (shown below), which also has a cantilever mount, is considered normal when the R80 dispersion of two 10-round bursts at 100 meters does not exceed 30 cm. With a doubling of the angular dispersion, the size of the dispersion area was quadrupled, which is even worse than the degradation of dispersion of the PKT in the TKB-01-1 turret relative to a fixed mount, despite the lack of geared gun laying mechanisms which are present on the TKB turret. It can be surmised that the recoil absorption of the gun cradle is ineffective, and the turret of the MT-LBVM is too light to adequately damp the recoil of the NSVT, leading to unstable recoil.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhuJshD7aDXf4wUz7wYswkOTp2o2WeVTqGnxm_OfSHN7saB9ldNZLWx1wxaegc8yGS9yubeHlX6PvYk7xBk2DtLQIMA8CbHSGKMfNyFbDRkESplDTT90msrQE8H76_lTgSxWVv2kA9HRUGk_w02lO-DjZzJJGrocSH7mcOl1bNzFXScxj0BaBy0TUlEcw/s2728/nsv%20on%206u6.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1442" data-original-width="2728" height="211" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhuJshD7aDXf4wUz7wYswkOTp2o2WeVTqGnxm_OfSHN7saB9ldNZLWx1wxaegc8yGS9yubeHlX6PvYk7xBk2DtLQIMA8CbHSGKMfNyFbDRkESplDTT90msrQE8H76_lTgSxWVv2kA9HRUGk_w02lO-DjZzJJGrocSH7mcOl1bNzFXScxj0BaBy0TUlEcw/w400-h211/nsv%20on%206u6.png" width="400" /></a></div><div><br /></div><div>Its large dispersion, together with the lack of a magnified sight, made the NSVT of the MT-LBVM a highly unrefined weapon and a somewhat questionable upgrade over the preceding PKT. The need for the commander to exit his hatch to reload the machine gun is also a potential issue when fighting ground targets. Only when engaging air targets will the performance of the NSVT reach a modicum of acceptability, as the TKB turret could at least provide the utility of local air defence while under armour. Even so, due to the doubled dispersion relative to the infantry NSV on the 6U6 mount, it is unlikely that engaging aircraft at the rated 1,500-meter effective slant range is viable with the MT-LBVM. When engaging ground targets as fire support for an infantry unit, it may be best to have a mix of MT-LBV and MT-LBVM.</div><div><br /></div><div>That said, when used at ranges where ammunition expenditure will not be extravagant, the destructive power of 12.7mm AP-I and API-T bullets enables an MT-LBVM to function as a credible fire support vehicle against lightly armoured vehicles and enemy forces in buildings or behind light cover. In the original context of its creation based on Soviet Army experience in Afghanistan, the poor shot dispersion and lack of magnification may not have been an issue when repelling ambushes, as the weapon system is still more than accurate enough to respond within and beyond the 300-meter effective range of RPGs and Kalashnikov rifles. Nevertheless, this is too niche of a justification, particularly in light of the design shortcomings of the turret.</div><div><br /></div><div><br /></div><div>
<a href="https://www.blogger.com/null" id="protection"></a><h3>
<span style="font-size: large;">PROTECTION</span></h3>
<div>The MT-LB features a low level of protection, sufficient only for stopping 7.62mm ball rounds and light artillery fragments. Although a heavy truck would be more than capable of towing artillery pieces, a tracked prime mover with protection from bullets and shell splinters was needed to complement artillery pieces obligated to take part in direct fighting such as the 85mm D-48 anti-tank gun and 100mm BS-3 field gun. Being of a small size was also an important feature, as the prime mover of an anti-tank gun would often be concealed close to the gun emplacement in case it is needed for a quick escape. </div><div><br /></div><div>The hull was constructed in such a way that all large sections were formed from smaller plates welded together. The lower sides and both halves of the sponsons are made from two plates, the roof is made from four plates, and the front of the hull itself has a complex shape. The hull belly consists of a five plates forming the flat belly and two pairs of smaller angled plates on the bow and aft sections welded together to join the floor to the front and rear of the hull. The use of thin and small plates generally tends to make it much easier to arrange production compared to large plates, but even so, the hull cannot be considered to have a cheap construction owing to the added labour costs of the extensive welding work.</div><div><br /></div><div>The low height of the MT-LB was a fundamental component of its protection scheme, customary of all Soviet combat vehicles, and particularly so for an anti-tank gun prime mover. With a height of just 1,865mm to the turret roof (when loaded, with ground clearance of 400mm), and a hull height of just 1,600mm, the MT-LB is very low-slung and is easy to conceal. A low height reduced the probability of being hit, and more importantly, it also had a positive effect on the concealability of the vehicle. This was generally true for all vehicles that were expected to be targeted by direct fire weapons, even if they were not expected to take part in combat. As an artillery prime mover, the MT-LB had to be within close proximity to a concealed gun emplacement in case the crew must quickly relocate it, and for this purpose, the low silhouette of the MT-LB facilitated its concealment to help camouflage not only itself, but also the position of the anti-tank gun from enemy reconnaissance. When the gun or howitzer is deployed and in action, the MT-LB has to stay separated from the artillery piece at a distance of 100-150 meters, preferably concealed so as to not reveal the position of the gun battery.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgtYgVMDw4jE3U1HXvr9Z_31KaDc3ZIPbXqHvaVRubHJMSh34Iys5fynyCAWJrxVNxjtRpelW_YUT6o7B3GLdfhtJd6-jM1xzpQs-2Uo3F-xxHFuoYivskBnNoWRKB7M-q5CcKxYVDUeFD0d8q0lWXwv1c7IG_jJwS7XA57NOPPhdXQTCUKROyA3TBo6g/s1772/12593913_572974909538437_3603601771440474840_o.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1181" data-original-width="1772" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgtYgVMDw4jE3U1HXvr9Z_31KaDc3ZIPbXqHvaVRubHJMSh34Iys5fynyCAWJrxVNxjtRpelW_YUT6o7B3GLdfhtJd6-jM1xzpQs-2Uo3F-xxHFuoYivskBnNoWRKB7M-q5CcKxYVDUeFD0d8q0lWXwv1c7IG_jJwS7XA57NOPPhdXQTCUKROyA3TBo6g/w400-h266/12593913_572974909538437_3603601771440474840_o.jpg" width="400" /></a></div><div><br /></div><div><div>The height reduction was achieved by rearranging the layout of components, without drastically changing any part of the drivetrain. The most major change was repositioning the crew so that, instead of sitting in a cabin directly over the gearbox, the seats were placed astride the prop shaft to the gearbox. The fuel system was also revised so that there were no longer fuel tanks under the floor panels of a cargo bed. Instead, it was distributed to the sponsons and to the two benches. The winch was removed, so that the space next to the engine compartment could be used to seat more passengers, who were previously seated in the crew cabin behind the driver and commander. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiOwsSxOjqx1sml4mj9NksnJRFztt_m6Fzjs_z4ZLKX05zltlwFwZG-TEOEKwtFZDQke5wXgdIn2ph8trLySTM43FcvjfS6mL9pzOBOiAzMFx-Mry6AJZlh4SC0s2ZXPjbZrhD21tahy5Z3C-HGs-6mc-F28W9p82mQk3t5BryFjY9pQYWBONHGeYy17A/s767/powertrain%20layout.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="177" data-original-width="767" height="148" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiOwsSxOjqx1sml4mj9NksnJRFztt_m6Fzjs_z4ZLKX05zltlwFwZG-TEOEKwtFZDQke5wXgdIn2ph8trLySTM43FcvjfS6mL9pzOBOiAzMFx-Mry6AJZlh4SC0s2ZXPjbZrhD21tahy5Z3C-HGs-6mc-F28W9p82mQk3t5BryFjY9pQYWBONHGeYy17A/w640-h148/powertrain%20layout.png" width="640" /></a></div><div><br /></div><div><br /></div><div>On the other hand, the MT-LBu, which was designed to be a universal tracked platform for rear echelon units, could afford to have a much taller superstructure with a greatly expanded interior volume, because rear echelon units were not expected to take direct part in fighting enemy forces, making the large silhouette of the MT-LBu largely irrelevant. </div></div><div><br /></div><div><br /></div><div>With a curb weight of just 9.7 tons, the MT-LB was 4.5 tons lighter than the BTR-50P, which had considerably thicker armour, but 1 ton heavier than than the BTR-60PA. Much of this difference is due to the large weight of a tracked suspension compared to a wheeled suspension, but it is also important to note that the MT-LB can be said to have slightly better front protection. </div><br />The armour consisted of welded 2P armour-grade high hardness steel plates set at various obliquities. The upper and lower glacis of the hull, together with the sloping "cheeks" connecting the upper glacis to the sponsons, all have a thickness of 14mm, while all other plates have a thickness of 7mm. This includes the sponson floor plates, the hull roof, and hull belly.<div><br /></div><div>The upper plate, including the windshield covers, is sloped at 54 degrees. The transmission compartment roof and access panel are both 7mm thick, and sloped at 80 degrees. The lower glacis is sloped at 45 degrees, making it nominally weaker than the upper glacis, but it is supplemented by the trim vane. The trim vane is of an unknown material and thickness. The sides are flat on the lower half of the hull, but the sponsons are sloped at 23 degrees. The rear is slightly tilted by a few degrees, but is effectively flat.</div><div><br /></div><div><br /></div><div>Frontally, the armour is only immune to 7.62mm armour-piercing rounds (B-32 AP-I) at point blank range in a limited frontal arc of 90 degrees, which is largely due to the low thickness of the lower side armour. On the sides, protection from 7.62mm armour-piercing rounds is guaranteed only within an arc of 150 degrees and at a range of 250 meters. The sides and rear do not provide all-round protection from 7.62mm armour-piercing rounds, only ball ammunition. Protection from 12.7mm armour-piercing bullets is provided at point blank range but in a narrow arc of unknown size. Owing to the thin, flat lower sides, 12.7mm B-32 can pierce the armour from no less than 400 meters at an impact angle of 45 degrees, as the table below shows, with a probable limit of around 500 meters. With this in mind, the protected frontal arc from point blank range is likely to be no more than 60 degrees. </div><div><br /></div><div>The table below from the 1992 paper "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a257674.pdf">LAV Armor Plate Study</a>" shows the ballistic limit of three thicknesses of MIL-DTL-46100 high hardness steel armour plates against 12.7mm B-32 armour-piercing bullets at an obliquity of 45 degrees. The third row lists an extra-hardened plate (XH) that does not represent the armour standard and it should be ignored. From the table, it can be seen that the velocity limit of 12.7mm B-32 on a 6.31mm plate at 45 degrees is 1,886 ft/s, corresponding to a range of 700 meters, and the velocity limit on a 7.31mm plate at 45 degrees is 2,176 ft/s, corresponding to a range of 400 meters. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-QUd08n8bgII/XMWViJa-0mI/AAAAAAAANyE/hCWI5hr_nEsEXfQ5hOucXU6HU7XvV1YYACLcBGAs/s1045/12.7mm%2Bpenetration%2Bmil-dtl-46100.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="569" data-original-width="1045" height="348" src="https://2.bp.blogspot.com/-QUd08n8bgII/XMWViJa-0mI/AAAAAAAANyE/hCWI5hr_nEsEXfQ5hOucXU6HU7XvV1YYACLcBGAs/w640-h348/12.7mm%2Bpenetration%2Bmil-dtl-46100.png" width="640" /></a></div><div><br /></div><div>Officially, the armour protects the vehicle from machine gun fire as well as from artillery shell splinters. The extent of its artillery protection will be limited to shells optimized for a high quantity of lighter fragments to improve soft target performance, or any shells with a naturally low number of heavy fragments. In general, this describes smaller caliber mortar bombs up to 120mm in caliber, 105mm to 122mm artillery shells and artillery rockets, but not 152mm or 155mm HE-Frag shells or HE-Frag rockets with heavy preformed fragments optimized to defeat light armour, such as the S-13OF aviation rocket. Ideally, for a prime mover of light artillery systems, the MT-LB would mainly be exposed only to weapons of a similar caliber and range when attacked with artillery fire, but in practice, with the U.S Army's move toward standardizing on the M109 155mm self-propelled howitzer, and the Bundeswehr and the British Army following suit by adopting the M109, 105mm howitzers stopped being the most numerous reference threat for the 1970's and the following decades. </div><div><br /></div><div>The only notable factor in favour of the survivability of the MT-LB is that, when used as a prime mover for anti-tank guns, it primarily contends with the weapons available to the target (90mm, 105mm tank guns) to return fire and whatever light artillery is available for close support, with a reaction time quick enough to respond to a sudden call for fire. As a rule, this meant mortars up to 120mm in caliber, which was true even during WW2.</div><div><br /></div><div><br /></div><div>Overall, the protection profile was typical of the low end of Soviet lightly armoured vehicles of the period, corresponding closely if not directly to the BRDM-2. It was significantly inferior to most foreign armoured personnel carriers with light armour, most prominently the M113, which, on top of providing better bullet protection, also provided much better fragment protection owing to the favourable characteristics of aluminium armour. The MT-LB was also highly deficient in terms of mine protection, having no structural features adapted to resist mine blasts under the tracks. The conventional method of joining the belly plates to the side presents a weld seam close to the suspension, increasing the risk of rupture, and the use of high hardness steel to form the hull was also unfavourable in resisting blast damage. The best-protected aspect of the MT-LB is its front, where its ability to withstand .50 caliber machine gun fire is somewhat disproportionate to its all-round weakness. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjs9ZNICNlH7Zl4jAYppQ6_HqmEp9WbURj3UgGvw4JJc0M-gJtoXnygcauOYF_IKsLvUhXpiRJisQj1fS6UI4XPJ-C5CNvEuxViYwBAUqnHeqy0_8XSfF71JC4k11OgiHocMbOU2IUgS0sic145U93KDtrDLyzu3iZF4zc9-oxEF8Li_VxZVC13opS09Q/s916/cracked%201.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="916" data-original-width="705" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjs9ZNICNlH7Zl4jAYppQ6_HqmEp9WbURj3UgGvw4JJc0M-gJtoXnygcauOYF_IKsLvUhXpiRJisQj1fS6UI4XPJ-C5CNvEuxViYwBAUqnHeqy0_8XSfF71JC4k11OgiHocMbOU2IUgS0sic145U93KDtrDLyzu3iZF4zc9-oxEF8Li_VxZVC13opS09Q/s320/cracked%201.png" width="246" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKUpxW1c0Z5jFSonuqYLgxXodq9g2b10GzrMYxoOKBECKujKzyMxzSxhvpPrzRB76n_p0hrgXVMNHBmEt1xi7E7lvPM0njCiEJo4CITh1X3fGQ0EE8yWdG2YhWgoCab7RFQyE8LNUaw1M90rYcoPHj35px7xMRtvsQoWZnPbOQNlVhKPxN1dh3VdWj5A/s1280/cracked%202.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="1280" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKUpxW1c0Z5jFSonuqYLgxXodq9g2b10GzrMYxoOKBECKujKzyMxzSxhvpPrzRB76n_p0hrgXVMNHBmEt1xi7E7lvPM0njCiEJo4CITh1X3fGQ0EE8yWdG2YhWgoCab7RFQyE8LNUaw1M90rYcoPHj35px7xMRtvsQoWZnPbOQNlVhKPxN1dh3VdWj5A/w400-h300/cracked%202.png" width="400" /></a></div><div>
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<div><div>Aside from the myriad of drainage points, there are two access panels in the belly, one large and one small. The small hatch is positioned underneath the power takeoff mechanism ahead of the clutch, and the large shaft is positioned underneath the engine. These access hatches may weaken the belly to mine blast to some extent, although there is hardly any mine protection at all to begin with. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-g4PCHRZnWb8/YLIOa3tEoXI/AAAAAAAATPk/OxAQ0ksdNLcwphHusx2CW2G4cM8ysWPZQCLcBGAsYHQ/s1800/mt-lb%2Bbelly.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="848" data-original-width="1800" height="302" src="https://1.bp.blogspot.com/-g4PCHRZnWb8/YLIOa3tEoXI/AAAAAAAATPk/OxAQ0ksdNLcwphHusx2CW2G4cM8ysWPZQCLcBGAsYHQ/w640-h302/mt-lb%2Bbelly.png" width="640" /></a></div></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUM7-ui28gt3rDbBuWBaIX37HZD1hn-y68cSK7S0FRSTe1mIhfl-_pu278HHLfV2Ex8kk8IfPn_jFKjha9JnUWLxZlzYehd9TElfscglfk-XqFVAzYCAzCHisfXSsVbL2Jg4jR7HuFreiAnqlA0_emm0Jypzz36LqI8otbD1VlffIEnb2vqE93YOxVtA/s1087/belly.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="433" data-original-width="1087" height="254" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUM7-ui28gt3rDbBuWBaIX37HZD1hn-y68cSK7S0FRSTe1mIhfl-_pu278HHLfV2Ex8kk8IfPn_jFKjha9JnUWLxZlzYehd9TElfscglfk-XqFVAzYCAzCHisfXSsVbL2Jg4jR7HuFreiAnqlA0_emm0Jypzz36LqI8otbD1VlffIEnb2vqE93YOxVtA/w640-h254/belly.jpg" width="640" /></a></div><br /><div><br /></div><div>To put out fires in the vehicle, there is a single OU-2 portable carbon dioxide fire extinguisher. No other form of fire protection is available.</div><div><br /></div><div><br /></div><div><a href="https://www.blogger.com/null" id="driver"></a><h3 style="text-align: left;"><span style="font-size: large;">
DRIVER'S STATION</span></h3></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgChtutTApn7MBoiB4-eAdlQdjomzEr5UbstxDbdUbE94E-ckqg3gjfmPpAMu32xR8IcZcupEo8xpRVpUhYMSyxoagrcKuwkYD0QraSEBTWp5f9dqBPwmXLID9JEqgW35jtoWrm3X-RMxrLPhfa7xNvP5bTU1NWNFekeUCtW-Qmfgewn-2MJe-nSmsUFg/s1600/a-view-of-the-drivers-position-inside-a-soviet-mt-lb-multi-purpose-tracked-73408a-1600.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1053" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgChtutTApn7MBoiB4-eAdlQdjomzEr5UbstxDbdUbE94E-ckqg3gjfmPpAMu32xR8IcZcupEo8xpRVpUhYMSyxoagrcKuwkYD0QraSEBTWp5f9dqBPwmXLID9JEqgW35jtoWrm3X-RMxrLPhfa7xNvP5bTU1NWNFekeUCtW-Qmfgewn-2MJe-nSmsUFg/w264-h400/a-view-of-the-drivers-position-inside-a-soviet-mt-lb-multi-purpose-tracked-73408a-1600.jpg" width="264" /></a><a href="https://1.bp.blogspot.com/-2pVSJPSN4iI/XyQ5PSHoRXI/AAAAAAAARZs/FDYcDuXsqhsfC5kPuSalpYFBKqGeOWrXACLcBGAsYHQ/s1600/a-view-of-the-drivers-position-inside-a-soviet-mt-lb-multi-purpose-tracked-0bd3e6-1600.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1053" height="400" src="https://1.bp.blogspot.com/-2pVSJPSN4iI/XyQ5PSHoRXI/AAAAAAAARZs/FDYcDuXsqhsfC5kPuSalpYFBKqGeOWrXACLcBGAsYHQ/w263-h400/a-view-of-the-drivers-position-inside-a-soviet-mt-lb-multi-purpose-tracked-0bd3e6-1600.jpg" width="263" /></a></div></div><div><br /></div><div>The driver's station in the MT-LB is simple but spacious, although not as spacious as the commander's station. The driver has a conventional set of controls, with a pair of steering levers and three pedals. His station is also slightly unusual in that his hatch is mounted on a raised cupola. Unlike in many tanks, his instrument panel is placed directly in front of him, thanks to the free space afforded by the shelf underneath the windshield. At the driver's station, the available width between the driveshaft cover to the hull side wall is 780mm. From driveshaft cover to the sponson, there is an additional 380mm of width where the sponson is the widest, but only 150mm of additional width at the front where the drivers panel is located due to the inward slope.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmlOw6obHMljHp5YbXSzEAkdrKj7IvrPxbvJZuUToFid0jcDARKyr9EQ8dGca1wrNlukQctFxBEbuoNKZMQvQbJVt8ZCnlt35eO8YiIB-foDI_MZYdNXBOY-VJRvJO3mIs34BrRMgGdrbYSy7zIxPBV-d21PRYTuQSanu-sm6bs_X1JdH6KEcnPnyuSg/s781/driver's%20seat.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="781" data-original-width="653" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmlOw6obHMljHp5YbXSzEAkdrKj7IvrPxbvJZuUToFid0jcDARKyr9EQ8dGca1wrNlukQctFxBEbuoNKZMQvQbJVt8ZCnlt35eO8YiIB-foDI_MZYdNXBOY-VJRvJO3mIs34BrRMgGdrbYSy7zIxPBV-d21PRYTuQSanu-sm6bs_X1JdH6KEcnPnyuSg/s320/driver's%20seat.gif" width="268" /></a></div><div><br /></div><div><div>The driver's seat is slightly adjustable in height, allowing a head-out driving position when raised to its highest setting for taller drivers. Setting the seat height is done by twisting an adjustment screw. The maximum range of motion is up to around 85mm, which can lead to issues for shorter drivers wanting to drive from an open hatch or taller drivers needing more headroom. Moreover, the adjustment mechanism does not allow quick changes in seat height, so it is not possible to rapidly transition from a head-out driving position to a closed-hatch combat driving position. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiY3uXSKpf9nLkM2cobGrnCsxOr25WdjPwI0lc7P22xcDXE2V34MOidFWM_aIFOUS4RkBSAnQ3dDGBCbrEdoF5hWpP3haLDzjbrexwQGpvgZiDrhEMpSzNfa4Ccl0AZMVPlPZI2bVLy0UWYVmtrFgAHhNbYmuNpupmO2hdg9_ObMOiQ1sKDnPfRIK8ZdA/s4160/driver's%20station%20seat.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="4160" data-original-width="3120" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiY3uXSKpf9nLkM2cobGrnCsxOr25WdjPwI0lc7P22xcDXE2V34MOidFWM_aIFOUS4RkBSAnQ3dDGBCbrEdoF5hWpP3haLDzjbrexwQGpvgZiDrhEMpSzNfa4Ccl0AZMVPlPZI2bVLy0UWYVmtrFgAHhNbYmuNpupmO2hdg9_ObMOiQ1sKDnPfRIK8ZdA/w300-h400/driver's%20station%20seat.jpg" width="300" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHoGRGmS0QKcrEbdAMNsPkHReTcFsOuFmO-OPAVH0gEdjrVANJifT9ydHN9fn_Agv4cnRnjHBuWfWRATSvDYEcHa5KJIyJIuab-cXtH_2JLXWzKJqfP6ohBpuSDciAcHexwRIDQfJm1aHU1AiyEB2L2anfo5NOTNerZ9Fgi4o93m_T5xrwerYIUgZDAg/s4160/driver's%20seat%20adjustment%20screw.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="4160" data-original-width="3120" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHoGRGmS0QKcrEbdAMNsPkHReTcFsOuFmO-OPAVH0gEdjrVANJifT9ydHN9fn_Agv4cnRnjHBuWfWRATSvDYEcHa5KJIyJIuab-cXtH_2JLXWzKJqfP6ohBpuSDciAcHexwRIDQfJm1aHU1AiyEB2L2anfo5NOTNerZ9Fgi4o93m_T5xrwerYIUgZDAg/w300-h400/driver's%20seat%20adjustment%20screw.jpg" width="300" /></a></div></div><br /><div>In the lowest seat position, the metal base of the seat is 270mm from the floor and the cusion is 340mm from the hull floor. Between the seat and the ceiling at lowest seat height setting, there is 857mm of space, but the driver's available headroom is actually larger due to a cupola, in addition to a slightly domed hatch. Relative to the ceiling, the raised cupola over the driver's hatch provides an additional 70-80mm of headroom, together with the domed hatch. Altogether, the actual available headroom is 930-950mm, taking into account the compression of the thick foam seat cushion.</div></div><div><br /></div><div><div>Because the seat only raises straight up or down, it is evident that the clutch and brake pedals had to be positioned in such a way that the driver could reach them and fully depress them regardless of the seat position. This likely explains why these pedals were placed quite high off the floor, as illustrated in the images below. This may make it more tiring when braking when driving in a closed-hatch position.</div><div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3QHNDTAVK-DQojZmK_P-GXASfsjpS4Oy7Yp47Eb3vOXIYvEVWLlAjzMZ2qKxZjo5LLKmNjKaWoUh3pwKlNuk1EEoHp9dc72KlBUq04TiuyHwUDCnL0mKtwI-snkZJkDXmErXnITq6tX5DhUhOjOoEDvHRtkOi4leiBdI3gkCVudT1KwnZ1nUkbywY7A/s1920/mt-lb%20trainer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3QHNDTAVK-DQojZmK_P-GXASfsjpS4Oy7Yp47Eb3vOXIYvEVWLlAjzMZ2qKxZjo5LLKmNjKaWoUh3pwKlNuk1EEoHp9dc72KlBUq04TiuyHwUDCnL0mKtwI-snkZJkDXmErXnITq6tX5DhUhOjOoEDvHRtkOi4leiBdI3gkCVudT1KwnZ1nUkbywY7A/w400-h225/mt-lb%20trainer.png" width="400" /></a></div></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEha-02XO9Btol0qBXft3LhRx1W9XMXVTU6OzW6Ulkz7YmuEdV-D1_AZEjahLFOp1rDvidxXWJ0X_yp7WlWe_FZ7LsjYE2-cjzUz7Ya-t9nuxNVzGaYpKLIcOxK4Ctyy7ijs4OdGHNIKBp3Qr8zazwnOrBIvNvabWchtQcOokSYB1dcPDFOlG7T3Hh1bhw/s1920/mt-lb%20trainer%202.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEha-02XO9Btol0qBXft3LhRx1W9XMXVTU6OzW6Ulkz7YmuEdV-D1_AZEjahLFOp1rDvidxXWJ0X_yp7WlWe_FZ7LsjYE2-cjzUz7Ya-t9nuxNVzGaYpKLIcOxK4Ctyy7ijs4OdGHNIKBp3Qr8zazwnOrBIvNvabWchtQcOokSYB1dcPDFOlG7T3Hh1bhw/w400-h225/mt-lb%20trainer%202.png" width="400" /></a></div><div><br /></div></div><div>The accelerator pedal is of the same design as found in the BTR-60 series, BRDM-2, and in domestic trucks, and is placed on the floor in the same way, which is another point of commonality that the MT-LB shared with domestic automobile design practice. The clutch and brake pedals are proprietary, however. The steering levers are situated between the driver's legs, like in an M113, but unlike in an M113, the handles of the levers are horizontal.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcnOca9LKgDmg7NLIL_E2ECrtX0fTezEFC9JjmQ7QGrvC4Gfa3cUoXSJSTVB9xrtZFArsB0in3KdfHbT1o0yuzZPoGnxHSTIpms5ZWe0ydBfCfuWNaRyEPqtp3-JTwrXKnhcLMk1Out52o0CK8UakFsu9Jt5Qb1S4O-YJuGGZbQWEbe8_HVD-Z1N8YFw/s1200/f029ff41ff29ebde1dccb3b6468df289.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="899" data-original-width="1200" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcnOca9LKgDmg7NLIL_E2ECrtX0fTezEFC9JjmQ7QGrvC4Gfa3cUoXSJSTVB9xrtZFArsB0in3KdfHbT1o0yuzZPoGnxHSTIpms5ZWe0ydBfCfuWNaRyEPqtp3-JTwrXKnhcLMk1Out52o0CK8UakFsu9Jt5Qb1S4O-YJuGGZbQWEbe8_HVD-Z1N8YFw/w400-h300/f029ff41ff29ebde1dccb3b6468df289.jpg" width="400" /></a></div><div><br /></div><div>Interestingly enough, when the driver's position was moved during the rearrangement of the MT-L layout to form the MT-LB layout, the system of linkages for the gearbox gear shifting mechanism was completely unchanged. As such, the gear shift lever was now in a location that was too far for the driver to reach without leaning forward and to the right. The designers used the most rudimentary solution to this issue, which was to attach a lever extension. </div><div><br /></div><div>The driver is provided with a personal fan for additional ventilation, which is a feature that is curiously absent for the commander's station. Unfortunately, unlike the majority of Soviet ground vehicles, it is not a DV-3 fan.</div><div><br /></div><div><br /></div><div>The driver's cupola is a protrusion on the roof where his hatch is installed, and the driver's three TNPO-170 periscopes are fitted on its front edge. The TNPO-170 periscope has a total range of vision of 94 degrees in the horizontal plane and 23 degrees in the vertical plane. Two versions of the driver's cupola exist. The early type, depicted in the drawing on the left below, was a single steel plate stamped into a smoothly sloping bulge like an overturned soup plate, and the hatch fitted atop it was smaller and more squarish in shape. The later type, shown on the right below, was a larger flat-sided structure constructed of smaller welded plates, accommodating a larger pill-shaped hatch. The switch to the flat-sided cupola occured at the same time that the commander's central hatch was switched to a forward-hinging type. The early cupola type can be seen in <a href="https://i.imgur.com/tH2wIl2.jpg">this photo</a>. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidH5CZGVgdsnIWh9Er936G7lnvf7Yv5EkejJ6sE4i456UzMriD6GZL4bH8-_2Im6VxxXYt7gmLdvbnnuRf7fiaiEOLaqlSR3-psYxSUp9Sc1GA65_GJ3ZlNwtrG2pprGdIc2uY3w2ErksaJrJKLzHHhqm-yzDfDR9IaOjX-8o-aEvK3MIXuBFl-SACzA/s739/driver's%20cupola%20early.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="739" data-original-width="697" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidH5CZGVgdsnIWh9Er936G7lnvf7Yv5EkejJ6sE4i456UzMriD6GZL4bH8-_2Im6VxxXYt7gmLdvbnnuRf7fiaiEOLaqlSR3-psYxSUp9Sc1GA65_GJ3ZlNwtrG2pprGdIc2uY3w2ErksaJrJKLzHHhqm-yzDfDR9IaOjX-8o-aEvK3MIXuBFl-SACzA/s320/driver's%20cupola%20early.png" width="302" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTR7RkgB2oMwQCjy3l5CPSG0q7K_oyW2FACdXuzLtI3IGORcq7UUA4tJ4MKhrZxoaEZBPTA1iFFWQaG4O7uDpNb7Lq72G6JS2MhBxXHNDNB4M6YoGkS7WFpxydidD64W2Jqk66zHV_HQ-JjdvBIjPt2r29Xg7hxfk9kmyuvTar5WjFAXpTCE29U_DNJg/s414/driver's%20cupola.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="414" data-original-width="385" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTR7RkgB2oMwQCjy3l5CPSG0q7K_oyW2FACdXuzLtI3IGORcq7UUA4tJ4MKhrZxoaEZBPTA1iFFWQaG4O7uDpNb7Lq72G6JS2MhBxXHNDNB4M6YoGkS7WFpxydidD64W2Jqk66zHV_HQ-JjdvBIjPt2r29Xg7hxfk9kmyuvTar5WjFAXpTCE29U_DNJg/s320/driver's%20cupola.png" width="298" /></a></div></div><div><br /></div><div>With the change in the cupola design, the shape of the rear of the protective hoods for the three periscopes was modified accordingly. In both cases, the cupola provided additional headroom without any apparent physical need for it, as the TNPO-170 periscopes are tall enough that even the driver had the ceiling directly above him, he would be able to look through the viewing windows of the periscopes while wearing a helmet and holding his head upright. As such, it may be fair to say that the cupola is one of the few creature comforts included in the MT-LB solely for the sake of comfort alone.</div><div><br /></div><div>The windshield is glass. The rim of the driver's windshield has an anti-splash rim, preventing bullet splash (fragments) from slipping through the edges of the windshield and its armoured cover. The windshield is very small compared to the windshields of most armoured vehicles that have one, including the likes of the BTR-60 series, but even so, it offers the driver a wide field of view compared to his front-facing TNPO-170 periscope and a great deal of convenience when driving in situations where it is either not desirable to drive from an open hatch or fully closed down. For instance, when entering a combat zone but not receiving fire, it is too dangerous to drive from an open hatch, but not dangerous enough to avoid using the windshield. It is also beneficial for non-combat driving in winter such as when using the MT-LB for administrative or logistical tasks, as the driver can stay in the warmth of the vehicle for the entire duration, rather than suffering from a frostbitten face and sapping the heat from the cabin if he were to drive from an open hatch.</div><div><br /></div><div>The vision dead zone when looking through the windshield is not formally specified, but can be calculated to be around 4.5 meters from the top edge of the windshield to no more than 8 meters from the bottom edge, where the 80-degree slope of the transmission compartment roof dictates the dead zone. A windshield height of 1,400-1,600mm from ground level is used for this estimation. The photo on the right below shows the view from the driver's seat at eye level, showing that the angle of the transmission compartment roof was harmonized with the driver's head position so as to not obscure the driver's view. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-6hqTSSjlgFc/XyQ5EvY2zYI/AAAAAAAARZo/sYLdUSjQIUk6UjQHYnDfu_uEVi312l5gwCLcBGAsYHQ/s1200/driver%2Blooking%2Bthrough%2Bwindshield.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="799" data-original-width="1200" height="266" src="https://1.bp.blogspot.com/-6hqTSSjlgFc/XyQ5EvY2zYI/AAAAAAAARZo/sYLdUSjQIUk6UjQHYnDfu_uEVi312l5gwCLcBGAsYHQ/w400-h266/driver%2Blooking%2Bthrough%2Bwindshield.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjEUWAFB7xVSD5-GhrOW2gJk6dyGN3WiNQxsQ9fxnh1QTjR5CGJ2XFxCLN0OHUBnxCgaoixnm4ecRbGiQmFF3nN0YEWB45vzfbpU4FLQ54ZuodJL-ZBTAaQTw0PVqv9iYD0d6skSE-zxAXCMUR9JjQd-aCwYO0tw9Ehf48TV_ia33SpcrC9AD4UysblMw/s2048/driver's%20view.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1536" data-original-width="2048" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjEUWAFB7xVSD5-GhrOW2gJk6dyGN3WiNQxsQ9fxnh1QTjR5CGJ2XFxCLN0OHUBnxCgaoixnm4ecRbGiQmFF3nN0YEWB45vzfbpU4FLQ54ZuodJL-ZBTAaQTw0PVqv9iYD0d6skSE-zxAXCMUR9JjQd-aCwYO0tw9Ehf48TV_ia33SpcrC9AD4UysblMw/w400-h300/driver's%20view.jpg" width="400" /></a><br /></div><div><br /></div><div><br /></div><div>Like in the commander's station, the driver also has a B-2 vision block on the side wall of his station to look out. The driver's B-2 vision block also provides him with a line of sight to the vehicle's only side mirror, allowing him a modicum of visibility when reversing. The side mirror frame is a very simple set of rods bolted together into a tripod. By unscrewing two of the bolts, the frame can be turned upside down, tucked behind the left headlight for rail transport. It may also be adjusted so that the side mirror is viewed from the driver's left TNPO-170 periscope instead of the B-2 vision block, as seen in <a href="https://youtube.com/shorts/PurrZbq1Wpk?feature=share">this video clip</a>.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgekL_EqtBFTjkA8H8Y7mbBa5Qo4LnKFqJfq3epi-WuedXaYTW55uJiUET6YbVGB8y_iT9h5vo_mshL97a64nDxsceeIfTBBbaZ9ynzGW-3LyEftF6W417P_rFH45pwRL-Qq0103vsuqHp6T3LfobKinS0T3ERcHuSoE1B2nLJnVLnhMvHdbVLLpa9pQ/s1169/soviet_mt-lb.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="500" data-original-width="1169" height="171" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgekL_EqtBFTjkA8H8Y7mbBa5Qo4LnKFqJfq3epi-WuedXaYTW55uJiUET6YbVGB8y_iT9h5vo_mshL97a64nDxsceeIfTBBbaZ9ynzGW-3LyEftF6W417P_rFH45pwRL-Qq0103vsuqHp6T3LfobKinS0T3ERcHuSoE1B2nLJnVLnhMvHdbVLLpa9pQ/w400-h171/soviet_mt-lb.jpeg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKLEPgWSyDzOIPxG9POtE0SZkccBaTFEeD5hBFJqziMlMnXl2bjxd7vTdaQ3ApquC2-pZ69XhoPHO4F0_qbzDk22ODlpujHubMOsJ-lSFvVguJ2LwEoFjpaNI0SCDlNybu9z20VcNmTqLBnyiDdYqRwojttqcLO-nmySFK5M29_g-7ylQUMJ2QUGakEw/s960/czech%20image001_7.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="540" data-original-width="960" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKLEPgWSyDzOIPxG9POtE0SZkccBaTFEeD5hBFJqziMlMnXl2bjxd7vTdaQ3ApquC2-pZ69XhoPHO4F0_qbzDk22ODlpujHubMOsJ-lSFvVguJ2LwEoFjpaNI0SCDlNybu9z20VcNmTqLBnyiDdYqRwojttqcLO-nmySFK5M29_g-7ylQUMJ2QUGakEw/w400-h225/czech%20image001_7.jpg" width="400" /></a></div><br /><div><br /></div><div>In general, it can be said that the high mobility potential of the MT-LB is not constrained by driver visibility for the standards of the time. The inability to quickly switch from a head-out to a closed-hatch driving position is not ideal for combat situations, which is a recurring theme for the MT-LB. In most other situations, however, the additional visibility afforded to the driver by the windshield enabled him to get the most out of the vehicle while remaining almost fully under armour. </div><div><br /></div><div>For general illumination, there are two FG-122N headlights on the corners of the hull. For additional illumination, there is a movable FG-16N headlight installed between the two windshields. It can be swivelled by either the driver or the commander, and it can be held at any position on its gimbal by a spring tension lock. It may be swivelled from side to side to illuminate objects that are not covered by the fixed headlights, or it may be aimed forwards to better illuminate the area ahead to extend the viewing range of the driver. </div><div><br /></div><div><div>For nighttime driving, the driver is equipped with the TVN-2B binocular infrared night vision periscope. It has a fixed 1x magnification and a 30-degree field of view. To use the TVN-2B, the driver must first swap out the middle TNPO-170 periscope and then plug the power terminals of the TVN-2B into a socket, marked (2) in the drawing below, from the BT-6-26 power supply box, marked (6) in the drawing below. </div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhi5XLU3R_co5ViFAbKUfsR27skj50ZGfcSNorIZIjSQQg4BCqjDv4wjyIZzeD3vW3FSl4pS6WtdH9fIQ-P3p_qIIA9xaRy1Je-XhniTv3IovaEe5gkunV38w2KHx2K8L3dgR1uctSwWzOodRAfhBO4tSEqsKPJ7BZ523Kq_Hu-L3K8Pl3HuwHbjLCfeg/s1390/tvn-2b%20wiring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1072" data-original-width="1390" height="309" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhi5XLU3R_co5ViFAbKUfsR27skj50ZGfcSNorIZIjSQQg4BCqjDv4wjyIZzeD3vW3FSl4pS6WtdH9fIQ-P3p_qIIA9xaRy1Je-XhniTv3IovaEe5gkunV38w2KHx2K8L3dgR1uctSwWzOodRAfhBO4tSEqsKPJ7BZ523Kq_Hu-L3K8Pl3HuwHbjLCfeg/w400-h309/tvn-2b%20wiring.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMMAy285ChLqOQdO0Ly8IZC2jdJGeZYrbXN5Xe67L5GLwPqwKPCJZjBLjku2LcB962gI7EQsR0F9dr4ticfblKkyv3vYGFa-1FkuuvGJATUra3IQzgxbHbnUfZS8mqykwBrwAVpow92XjzqljvdIBcyiHbH7TsruM7suaDGRLpdoxOxJj1ajRpXwFwvQ/s1315/tvn-2b%20installed.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1315" data-original-width="781" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMMAy285ChLqOQdO0Ly8IZC2jdJGeZYrbXN5Xe67L5GLwPqwKPCJZjBLjku2LcB962gI7EQsR0F9dr4ticfblKkyv3vYGFa-1FkuuvGJATUra3IQzgxbHbnUfZS8mqykwBrwAVpow92XjzqljvdIBcyiHbH7TsruM7suaDGRLpdoxOxJj1ajRpXwFwvQ/s320/tvn-2b%20installed.png" width="190" /></a><br /></div><div><br /></div><div><br /></div><div>When driving with the TVN-2B night vision periscope, an additional FG-200 IR headlight must be fitted on a post next to the left vision block, adjacent to the horn, as shown in the diagram on the left below. The photo on the right below (image from <a href="https://www.recomonkey.com/Land-Platforms/IFV-APC/MT-LB/MT-LB">RecoMonkey</a>, author unknown) shows an MT-LB with the IR headlight fitted. The range of vision is limited to 60 meters and only when the infrared headlight is on, as the periscope utilizes a single-stage gen 0 photocathode amplifier for each eye, so illumination is mandatory to form an adequate image. It is not possible to navigate at night using only the night vision periscope, as the driver will be unable to see the landscape and recognize landmarks.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4RsfzxCq11qz951RtzhftOWOu3UQGWrdC86tsYZZJ3eyqe_pyELT96Se9JRwGK4rAjhC-hWtlkK3yPfTkUpcdQSzHMN5Mfm6bIJhvvbRv9eHqpA12Q460w7mK6Uwaw9zU6gxH7pJJknk8WsFOVcoCpazCXnUjTSIG6JCtjz7UMd8q_GUqfhaJTOfyMQ/s788/fg-125.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="532" data-original-width="788" height="270" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4RsfzxCq11qz951RtzhftOWOu3UQGWrdC86tsYZZJ3eyqe_pyELT96Se9JRwGK4rAjhC-hWtlkK3yPfTkUpcdQSzHMN5Mfm6bIJhvvbRv9eHqpA12Q460w7mK6Uwaw9zU6gxH7pJJknk8WsFOVcoCpazCXnUjTSIG6JCtjz7UMd8q_GUqfhaJTOfyMQ/w400-h270/fg-125.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhXe9BeGwwm1V-4ESgl10rzlF_Y9vrP_XyviiqPkVLtobKvLWFZyJTvcbqu5I_ds9QLHHFND7wUr5uiNgEc6dfekpecy8csvlunmhvUNcEQ8EZwVkaOhWHIWhhvdlBnAyRI7IlPsv69EDMGnbkAHOhKVDGL2XV1Xn3L53i0omW1Vyz5cMxZw9XwurL5NQ/s1280/i-s4v278c-X2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhXe9BeGwwm1V-4ESgl10rzlF_Y9vrP_XyviiqPkVLtobKvLWFZyJTvcbqu5I_ds9QLHHFND7wUr5uiNgEc6dfekpecy8csvlunmhvUNcEQ8EZwVkaOhWHIWhhvdlBnAyRI7IlPsv69EDMGnbkAHOhKVDGL2XV1Xn3L53i0omW1Vyz5cMxZw9XwurL5NQ/w400-h266/i-s4v278c-X2.jpg" width="400" /></a></div></div><div><br /></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="cargo"></a><h3 style="text-align: left;"><span style="font-size: large;">CARGO</span></h3><div><br /></div><div>The cargo compartment is the primary space for stowing cargo. It provides a fully enclosed, protected volume, and when cargo is placed on the floor space, the center of gravity of the vehicle is raised minimally. As mentioned earlier in the Ergonomics section of this article, the nominal dimensions of the cargo compartment are 2,605 x 1,948 x 1,150 mm and the nominal cargo space is calculated to be 5.8 cubic meters. Modification 49, one of the simplified MT-LB models, had no passenger seating and no commander's station, and was lightened to 9.3 tons. The two fuel tank benches were removed to free up floor space and the same fuel capacity was maintained by enlarging the right sponson fuel tank. </div><div><br /></div><div>The full displacement of the MT-LB is 14.6 cubic meters, inclusive of the transmission compartment and engine compartments. In contrast, the MT-LBu had a total useful volume of 13 cubic meters, enabling it to provide a passenger and cargo space almost as large as the entire internal volume of the MT-LB. This allowed free movement within the vehicle and the free installation of bulky equipment (as a rule, mechanical and with analogue electronics) used in command posts, mobile radar installations, and other special purpose vehicles.</div><div><br /></div><div>To supplement this, the roof over the cargo compartment was designed to accommodate additional cargo. The perimeter of this cargo space has a number of racks with loopholes, used to secure crates with tie-downs. The roof space is narrower than the internal width of the cargo compartment, and is only a little over two thirds as long. The maximum weight of cargo that can be carried on the roof is not specified in any documentation, but it is known that a basic MT-LB can support a ZU-23-2 on its roof together with its two crewmen, which amounts to a load of over a ton.</div><div><br /></div><div><div>One factor that intrinsically limits the size of the cargo that can be carried in the MT-LB is that its rear doors are limited in size, which consequently limits the size and nature of cargo that can be accommodated inside the cargo compartment compared to a ramp spanning the entire height and width of the compartment. With the backrests of the benches folded down, the rear doors essentially define the maximum dimensions of any container that can be passed into the cargo compartment and rested on the benches. Containers that span the full height of the cargo compartment from floor to ceiling could theoretically fit, but can't be brought into the compartment through the rear doors.</div><div><br /></div><div>In actual use, the ramifications of the rear door size are more theoretical than practical. As a tactical tractor-transporter, the loading and unloading of cargo would invariably be done by hand due to the low-capacity of the vehicle. For individual ammunition crates containing two cartridges each, such as the crate shown below for 100mm HEAT rounds for the MT-12 anti-tank gun, this was practical. </div><div><br /></div><div>The MT-LB is unsuitable for transporting large volumes of cargo internally. Its fully armoured hull was also a part of this limitation, as it effectively limits cargo access to the rear doors, making it infeasible to load up the cargo compartment with forklifts or cranes. This is in contrast to trucks, where forklifts can be used to load the entire length of the bed by folding down the side panels, or pallets can be lowered onto the bed from above. The volume of cargo that can be carried by trucks far exceeds the MT-LB, which makes the mechanization of loading and unloading cargo worthwhile. For its primary role as an artillery prime mover in particular, the unit of fire carried in and on the vehicle would all be in the form of individual crates containing two cartridges each, such as the crate shown below for 100mm HEAT rounds for the MT-12.</div><div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwjyKkvZbAGCRs58avo5sWX-7pgXMkmCmCF-pgwOM-BklJF8zlvMRr2CHo5aDAiG4gbLr3a_a2nxGoGU2O0pbSlnEhNHQCY6OSHU33aHnGoplu8s7ZkD1qNp-AXkyOktBRJllCwUwYZa2xk_PmRCPHSAyzskyskZ6lkgiMPX2ymUBb60a8Cs9w3c3YXw/s2925/yashik.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2013" data-original-width="2925" height="275" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwjyKkvZbAGCRs58avo5sWX-7pgXMkmCmCF-pgwOM-BklJF8zlvMRr2CHo5aDAiG4gbLr3a_a2nxGoGU2O0pbSlnEhNHQCY6OSHU33aHnGoplu8s7ZkD1qNp-AXkyOktBRJllCwUwYZa2xk_PmRCPHSAyzskyskZ6lkgiMPX2ymUBb60a8Cs9w3c3YXw/w400-h275/yashik.png" width="400" /></a></div><br /><div>Funnily enough, despite the MT-LB being primarily a prime mover for T-12 and MT-12 guns, the cargo compartment does not readily accommodate 100x913mm cartridges. With a length of 2,605mm, the cargo compartment is not long enough for two crates of 100x913mm cartridges to be placed end-to-end. As such, more creative stacking layouts need to be devised to stow the specified unit of fire while also accommodating the full gun crew of 6 or 7 men (for the T-12 and MT-12 respectively). The possibility of stowing some of the ammunition on the hull roof is not excluded. On the roof, the width of the stowage area demarcated by the tie-down brackets is just wide enough for 100x913mm ammunition crates, as the photo below shows. Stowing external cargo in this way not only creates the risk of losing some of it to damage from enemy fire, but compared to the sponson spaces on the AT-P, it increases the influence of the external cargo on the center of gravity of the vehicle. </div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhvmfTh1jmJJTNB_gHdBcCxY2U8JMGZ-OAPZB2sb8-athXUGR6r6C-CE8pCvDH2q1fvMTuGk2P791JUiPYEMtMNWg8v8JLMcaontw4CLL16xz8HLed82Hb22eoxtYKyeLUdRuMo0arVAbWSpyxDro8w0zBe0GrfuVH48FHuBQgiIlGTAjorcgp18FwBQw/s960/transporting%20mt-12%20gun%20with%20crew%20and%20ammunition.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="640" data-original-width="960" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhvmfTh1jmJJTNB_gHdBcCxY2U8JMGZ-OAPZB2sb8-athXUGR6r6C-CE8pCvDH2q1fvMTuGk2P791JUiPYEMtMNWg8v8JLMcaontw4CLL16xz8HLed82Hb22eoxtYKyeLUdRuMo0arVAbWSpyxDro8w0zBe0GrfuVH48FHuBQgiIlGTAjorcgp18FwBQw/w400-h266/transporting%20mt-12%20gun%20with%20crew%20and%20ammunition.jpg" width="400" /></a></div></div></div><div><br /></div><div>Due to the low thickness of the plates used to construct the monocoque steel hull of the MT-LB, the structure was extensively reinforced on most surfaces. The rigidity of the floor was augmented by U-beams. The longitudinal beams have no purpose other than structural reinforcement, but the transverse beams serve as covers for the torsion bars. Similarly, the thin roof - which was welded together from several plates - was reinforced with a cruciform frame and supported along the sponsons with struts to allow the MT-LB to haul heavy cargo on its roof. The shape of the hull at its cargo compartment contributed to this by having its sponsons shaped into a shallow arch. Additionally, it is possible to fit a load-bearing column under the center of the cruciform frame to bear the weight of heavy cargo carried on the roof.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirbvSQrcvjtjJvlZVIAT5qlRGzHXpM2IegmK25fyv-mF1yyag95SbFRpZkpuZL130AcgrB0ug3q6n0Ab1RM2u_JWhZGGQsWt80oJ8MXpf-e4CgIDyI8FlOYNAWCBGm06jnanT75uQWEPZkf7Ev2jMsUStj_C1nxlgCMuh0wLc96pD7pJSmHT2wgITUcQ/s1920/floor%20reinforcements.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirbvSQrcvjtjJvlZVIAT5qlRGzHXpM2IegmK25fyv-mF1yyag95SbFRpZkpuZL130AcgrB0ug3q6n0Ab1RM2u_JWhZGGQsWt80oJ8MXpf-e4CgIDyI8FlOYNAWCBGm06jnanT75uQWEPZkf7Ev2jMsUStj_C1nxlgCMuh0wLc96pD7pJSmHT2wgITUcQ/w400-h225/floor%20reinforcements.png" width="400" /></a></div><div><br /></div><div>When used as a prime mover, the MT-LB can tow a trailer or an artillery system weighing up to 6.5 tons while also carrying a nominal load of 2 tons of cargo internally or on the cargo deck. When driving without towing a load, the vehicle is rated to carry 2.5 tons of cargo, but it may only do so at the expense of its amphibious capability. If there is a need to preserve its ability to swim, a maximum of 2 tons may be carried. This is noted in the technical manual for the MT-LB, the military academy coursework of the Kazakh Al-Farabi National University, in the book "<i>Советская бронетанковая техника 1945 - 1995</i>", the article "<i>МТ-ЛБ. Служба продолжается</i>" by Sergey Suvorov in the May 2005 issue of the "<i>Техника и вооружение</i>" magazine, and a variety of other sources. </div><div><br /></div><div>With its increased weight compared to the AT-P, the roles of the MT-LB could be expanded. At the same time, with a towing capacity of 6.5 tons and a nominal maximum cargo capacity of 2.5 tons, the MT-LB firmly remained within the light prime mover class. With its relatively large load-bearing capacity, the MT-LB was particularly suitable for hauling cargo across terrain impassable to trucks. If used as a personnel carrier, the large surplus loading capacity ensures that its offroading mobility remains high and the safety margin when swimming is improved by the increased reserve buoyancy.</div><div><br /></div><div><div>Considering that the vehicle has a curb weight of just 9.7 tons (no crew, loaded with standard set of spare parts, accessories, coolant, oil, and fuel), this nominal cargo load amounted to 25.7% of the weight of the vehicle itself, which was not only superior to the 21.7% load capacity of the AT-P, but is also better than all foreign contemporaries. In real terms, this cargo capacity makes the MT-LB comparable to a lower-end 4x4 or 4x2 medium truck, but if rated according to payload efficiency, its performance is comparable to light trucks or pickup trucks rather than medium trucks. The heavier and more voluminous MT-LBu had a correspondingly larger cargo capacity of 4 tons, and given that its curb weight was 11.3 tons, the cargo rating amounted to an astonishing 35.4% of the vehicle's weight, which is excellent for a tracked vehicle.</div><div><br /></div><div>The closest foreign counterpart to the MT-LB and MT-LBu in terms of cargo carrying capabilities was the M113, which is to be expected because its power-to-weight ratio was the closest to matching that of the MT-LB. The TACOM Standard Military Vehicle Characteristic Data Sheets from June 1962 state that the M113 has a cargo load of 3,860 lb (1.75 tons). Given that the basic M113 has a curb weight of 8.6 tons, this is 20% of the vehicle's weight. For comparison, the basic FV432 Mk. 1 has a laden weight (gross vehicle weight) of 14,770 kg and an unladen weight of 13,252 kg, giving it a cargo capacity of 1.5 tons, amounting to just 11% of the vehicle's weight. The FV432 Mk. 1 was followed closely by the Swedish Pbv 302, which was only specified to carry 1.2 tons, and with a curb weight of 11.1 tons, this meant that it could carry 10.8% of its own weight. All cargo loads or gross vehicle weighs were rated according to the limit for retaining amphibious capability. </div><div><br /></div><div>All three foreign vehicles are distinguished from the MT-LB by the fact that they were personnel carriers, and as such, only had a cargo capacity sufficient for carrying a full crew and passenger load with their standard allotment of ammunition and personal equipment while retaining their mobility characteristics and remaining amphibious. </div><div><br /></div><div><br /></div><div><div>The maximum cargo capacity of the MT-LBV was reduced to just 1.5 tons and the maximum towed load was reduced only 4 tons, ostensibly in spite of the increase in traction that its wide tracks afforded. This is because the mobility characteristics of the MT-LBV were evaluated on more challenging terrain, including deep snow and swampy terrain, which placed harsher limits on how much it could haul. On the MT-LBVM, the cargo and towing capacity was technically unchanged, but officially, the tractor-transporter role was de-emphasized in favour of its new role as an armoured personnel carrier. Instead of a cargo load rating, the manual specifies its cargo load as a function of the passengers it can carry, specifying a load capacity of only 1,300 kg. Of that, the driver accounts for 100 kg, the ammunition accounts for 200 kg, and ten passengers accounts for 1,000 kg. Alternatively, a ton of cargo is carried. In both cases, the specified weights strangely omit the weight of the commander.</div></div><div><br /></div><div>As a side note, the nominal rated cargo capacity of Modification 49 is 2.4 tons, and maximum rated capacity is 2.9 tons.</div><div><br /></div><div><br /></div><div><div>The loading limits according to the center of gravity of the vehicle based on the swimming safety threshold and limiting factors on land are given in the graph below, taken from the 1977 No. 2 issue of the "<i>Вестник Бронетанковой Техники</i>" journal, the article "<i>Метод Анализа Компоновочных Схем И Параметров Вгм, Создаваемых На Базе Многоцелевого Гусеничного-Шасси</i>". The swimming safety thresholds describe a basic level of maneuverability, buoyancy, stability afloat, operability of the main components while on water, and so on. The limiting factors on land are based on the maximum permissible load on any given roadwheel, the power to weight ratio, and so on.</div><div><br /></div><div>The gross vehicle weight (GVW) limit is up to 13.2 tons if the center of gravity is within 2.55 to 2.6 meters behind the drive sprocket, which is a point just behind the engine. Realistically, however, this limit is inevitably exceeded when the full length of the cargo compartment is used to hold the load, which makes this impractical.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjfy2i9P8FHtucwqWU8NzKM6K3X6npsdxOjbafsuiw9xWgbUpd-E2Hfl8XsYiCEtq3hPiKSBjIzE55lRAYDgmrD7Ap1TpM8yz4xswC47UXMaADJ5R78BhYriLGX0QCRZwhPmC6GPNAmnuIMWTovpWxBqGCIYhGsPN_9kB629GAzW1kl-wQ5dBnq2bZ-Q/s2196/position%20of%20cog%20according%20to%202%20parameters.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="647" data-original-width="2196" height="188" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjfy2i9P8FHtucwqWU8NzKM6K3X6npsdxOjbafsuiw9xWgbUpd-E2Hfl8XsYiCEtq3hPiKSBjIzE55lRAYDgmrD7Ap1TpM8yz4xswC47UXMaADJ5R78BhYriLGX0QCRZwhPmC6GPNAmnuIMWTovpWxBqGCIYhGsPN_9kB629GAzW1kl-wQ5dBnq2bZ-Q/w640-h188/position%20of%20cog%20according%20to%202%20parameters.png" width="640" /></a></div><br /><div><div>One of the limitations on the load-carrying capacity of the MT-LB is that each roadwheel has a maximum permissible load limit of just 1,100 kgf. As a matter of fact, the roadwheels simply do not have a structural load limit of 1,100 kgf; when driving at high speed on rough terrain, they most certainly experience much greater loads. This most likely refers to the maximum average load on a roadwheel, considering a distributed weight of 13.2 tons over twelve suspension units, taking into account that while the middle roadwheels bear the highest static loading, the front and rear roadwheels bear the strongest dynamic loads and are the most stressed overall. </div><div><br /></div><div>It is, of course, completely possible to load more cargo than allowed according to the center of gravity, power-to-weight, and roadwheel loading limits, provided that mobility characteristics such as maneuverability, driving range and speed are sacrificed. While suspension loading is inevitably a factor, terrain plays a large part. In general, when driving on good quality dirt roads or on paved roads, the load limit can be relaxed without worsening the lifespan of the suspension. For instance, the ZIL-131 truck was rated to carry a load of 5 tons while towing a load of 4 tons when driving on paved roads, but when driving on dirt roads or off-roading, it can carry only 3.5 tons while towing 4 tons. Needless to say, due to the tracked suspension of the MT-LB, the expectations for its off-roading capability exceed the ZIL-131, which in turn places greater limits on its onboard cargo load.</div></div><div><br /></div><div>Indeed, if mobility characteristics can be sacrificed, then the official rating given in the manual appears to be at least ultimately dependent on space rather than structural or suspension loading limits, as the TM-126, a demilitarized modification of the MT-LB used in the USSR, is specified to carry 4,000 kg of cargo in its expanded cargo compartment, which differed only in an increased height. Moreover, the MT-L was also specified to carry 4,250 kg of cargo, although this required the winch and some fittings in its cargo bed to be removed, lightening the vehicle but mostly freeing up the full bed for more space.</div><div><br /></div><div><div>According to a technical manual for the MT-LB, the center of gravity of the vehicle is 2,267mm behind the axis of the drive sprocket when the vehicle is without cargo. With a driver and a cargo load of 2 tons, the center of gravity is shifted rearwards to 2,575mm from the axis of the drive sprocket. With the MT-LBV, the center of gravity of the vehicle is 2,296mm behind the axis of the drive sprocket when the vehicle is without cargo and 2,510mm with cargo. This is almost the exact midpoint of the distance between the axis of the drive sprocket and the idler wheel. When fully loaded, the height of the center of mass from ground level is 1.1 meters. When partially loaded for rail transport, the center of gravity of the MT-LB is 2,332mm behind the axis of the drive sprocket and 836mm above ground level. With the MT-LBV, the center of gravity of the vehicle is 2,296mm behind the axis of the drive sprocket when the vehicle is without cargo and 2,510mm with cargo, on account of its lighter rated cargo load.</div><div><br /></div><div>With the MT-LBVM, the center of gravity of the vehicle is 2,293mm behind the axis of the drive sprocket when the vehicle is without cargo and 2,438mm with cargo.</div></div><div><br /></div><div><br /></div><div><div>During state testing, the average speed of the MT-LB a full cargo load and with a 6.5-ton trailer on dirt roads reached 26-32 km/h, which was almost one and a half times higher than the AT-L.</div></div></div></div><div><br /></div><div>The main downside of the MT-LB in its primary role as a prime mover for anti-tank guns is that even with the ability to carry a cargo load of 2 tons while swimming, its amphibious capability does not include provisions for transporting a gun over water. Although it is more than capable of ferrying the gun crew and ammunition across water, the guns themselves must be left behind unless a bridge is available. As such, the amphibious capability was only meaningful for specialized combat modifications of the MT-LB designed to follow frontline units in maneuvers. </div><div><div><br /></div><div><br /></div><div><div><div><div>In terms of towing capacity, 6.5 tons was enough for the operational role of the MT-LB. In the Soviet Army, the MT-LB was most often used to tow lighter artillery pieces. The T-12 anti-tank gun, weighing only 2.75 tons, was manageable even for the AT-P. Heavier guns and howitzers like the MT-12 (3.1 tons), D-30 (3.2 tons) and BS-3 (3.65 tons) could still be towed by the MT-LB with ease. The D-20 howitzer, weighing 5.7 tons, was the heaviest artillery piece that could be supported by the MT-LB without a negative impact in its mobility specifications. For the MT-LBV, a towing limit of 4 tons still theoretically allows it to tow almost all of the aforementioned guns, excluding only the D-20.</div></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-7Z1I9PIg95c/X7_T8dzBPZI/AAAAAAAASJ0/AMrQmBt9d3cL8npM6lSGM-d7HASkPXnuACLcBGAsYHQ/s1003/towing%2Bbs-3%2B1944.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="609" data-original-width="1003" height="389" src="https://1.bp.blogspot.com/-7Z1I9PIg95c/X7_T8dzBPZI/AAAAAAAASJ0/AMrQmBt9d3cL8npM6lSGM-d7HASkPXnuACLcBGAsYHQ/w640-h389/towing%2Bbs-3%2B1944.jpg" width="640" /></a></div><div><br /></div></div><div><br /></div></div><div><div>The MT-LB featured a special shock-damping towing hitch to tow trailers and artillery pieces with less of an impact on ride quality. This type of towing hitch had been established as a basic feature for domestic prime movers for over a decade by the time the MT-LB entered service. The towing hitch is spring-loaded to damp longitudinal shocks when traveling over rough ground, particularly where it is possible for the wheels of the towed gun or trailer to be caught in a pothole. The hitch can be pushed forwards by 30mm or pulled backward by 55mm against a heavy coil spring, installed inside the reinforcing strut that runs across the hull. A shock absorber is present between the stem of the towing hitch and the spring, consisting of washers sandwiched by rubber buffer rings. The shock absorber begins to be compressed only after 25mm of travel by the towing hitch in either direction.</div><div><br /></div><div>The shock damping provided by the towing hitch works both ways - it regulates the intensity of the load on the engine from the varying resistance of the towed item and the load on the brakes when stopping (for trailers or guns without brakes), and it helps to protect the chassis of the towed trailer. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkNHhKIhdhdxzldnZrTf4uM4owyskXPufg8M4ou5Cal_GJVbZSelz7NIX4eOMKuW5o_xvj7WnPnmrSA2Z3IgjZOO8HgUyeqsj6QEnvvuuKYfSlD0fAK7xnn_qhZW9Vzm88SEyDc9pGn2osIP5J0UGAuDHTVaXgwjoNiURY1Clap9QF84W4Nd93Z1VPKQ/s1443/towing%20hitch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1059" data-original-width="1443" height="294" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkNHhKIhdhdxzldnZrTf4uM4owyskXPufg8M4ou5Cal_GJVbZSelz7NIX4eOMKuW5o_xvj7WnPnmrSA2Z3IgjZOO8HgUyeqsj6QEnvvuuKYfSlD0fAK7xnn_qhZW9Vzm88SEyDc9pGn2osIP5J0UGAuDHTVaXgwjoNiURY1Clap9QF84W4Nd93Z1VPKQ/w400-h294/towing%20hitch.png" width="400" /></a></div><br /><div><br /></div><div>Two traction force figures are available from MT-LB manuals. One manual states that the tractive force, with a coefficient of adhesion of 0.8, is 7,270 kgf without load and 8,790 kgf with a load. </div><div><br /></div><div>Another manual states that the tractive force, with a coefficient of adhesion of 0.8 and a coefficient of resistance to movement of 0.04, is 7,448 kgf without a load and 8,968 kgf with a load.</div><div><div><br /></div></div></div><div><br /></div><br />
<a href="https://www.blogger.com/null" id="mobility"></a><h3>
<span style="font-size: large;">MOBILITY</span></h3>
<div><br /></div><div>The mobility characteristics of the MT-LB were quite high for its time, in spite of the limitations of its suspension. The drivetrain layout consists of a longitudinally mounted engine with a transversely mounted gearbox. The engine - the heaviest component of the drivetrain - is mounted almost exactly on top of the longitudinal axis of the hull, with an offset to the left by 60mm. The auxiliary systems such as the cooling system and engine preheater are mounted to the left of the engine compartment. In total, the engine compartment was measured to take up 1.5 meters of width and 1.3 meters of length.</div><div><br /></div><div>The installation of the powertrain was of the conventional type, where all major assemblies were individually mounted, aligned and then connected. Maintenance and minor repairs were done with the major components in-situ. Astonishingly enough, the AT-P had an integrated quick-replace powerpack where the engine, clutch, gearbox and steering unit were structurall combined into a single module. This feature, which was exceedingly rare in Soviet vehicle building practice, did not make it to the MT-LB, although understandably so due to its powertrain layout.</div><div><br /></div><div>The maximum operating altitude is 2,000 meters above sea level, and the operating temperature range is -45°C to +45°C. An environmental humidity of 98% is permitted at a temperature of +15°C to +25°C. The vehicle can climb a 35-degree slope or a 25-degree side slope on dry soil, while carying the rated cargo load. It is rated to cross a 2.5-meter trench, and overcome a vertical obstacle with a height of 0.7 meters. This is despite the axis of the drive sprocket being only around 0.61 meters above ground level, implying that to climb such an obstacle, the MT-LB is driven into the obstacle to lift itself up on its sloping lower glacis, allowing the tracks to find purchase on the obstacle to climb over. </div><div><br /></div><div>The ground clearance of the MT-LB is 425mm at its curb weight and 395mm when fully laden. The nominal ground clearance is usually expressed as 400mm. This ground clearance is unremarkable, and would have been even for a tank, which is contrary to expectations of the cross-country mobility of the MT-LB. In fact, with two large access hatches on the hull belly underneath the gearbox and the engine, at the front half of the hull, the driver must take particular care when driving over rough ground so as not to dent or rip the access hatches off on a stump, rocks, rubble, and so on. </div><div><br /></div><div>According to the manual, the maximum speed of the MT-LB without a towed load but with an onboard load is 60 km/h, while the maximum speed when driving with a trailer is 45 km/h. With a trailer, the speed limit is highly dependent on what the trailer is, or indeed, what the towed artillery piece is. Note that, for postwar domestic guns like the D-44, D-48, T-12 and MT-12, the speed limit on a paved road is 60 km/h, as determined by the heat limit of the tyres. Finally, the average speed of movement on a dry dirt road of average quality with a load and with a trailer is 26-32 km/h. The average speed on snow and swampy or muddy terrain is not officially listed.</div><div><br /></div><div>In the article "<i>Универсальный Солдат Многоцелевой Транспортер-Тягач МТ-ЛБ</i>", it is claimed that the average speed of the MT-LBV on deep snow and swampy terrain exceeded that of the MT-LB by 9-18 km/h. However, the manual states that 9-18 km/h is the average speed of the MT-LBV when loaded by 1,500 kg and when towing a trailer over deep snow or swampy terrain. It can only be assumed that an MT-LB under the same circumstances will either have a lower average speed, or it might only be able to bear a greatly lightened load, or it might bog down entirely. </div><div><br /></div><div>As mentioned earlier, the layout of the MT-LB allowed the vehicle to be optimally balanced when performing its primary function as a prime mover, and its stability when driving off-road was additionally enhanced by its low height and long and wide track base. Having the center of gravity aligned so exactly with the center of the track base also increases the safety factor when making a turn at high speeds on terrain with a low coefficient of adhesion, as the intensity of skidding due to understeer or oversteer is minimized, if it occurs. Conversely, this also increases the steering resistance when making a turn, which is already high due to the large inertia resisting a turn at high speed, thereby increasing the load on the engine. However, as a rule in automotive design, the increased turning resistance cannot be considered a downside at all, as the safety factor provided by a driver having firm control over his vehicle is always the first priority.</div><div><div><div><br /></div><div>The effect of having the center of gravity aligned with the midpoint of the track base is that it improves the steering dynamics of the vehicle, especially at high speeds and when moving on muddy or icy terrain. When afloat, the concentration of the drivetrain weight in the nose and middle of the vehicle was also beneficial as the rear half would have a surplus of buoyant force owing to the voluminous and empty cargo compartment. If it is afloat without a cargo load, the nose end of the vehicle is noticeably tipped down, but with cargo, the vehicle is level with the water's surface.</div><div><br /></div></div></div><div><br /></div><div>Additionally, the MT-LB can be transported by the An-12B. Owing to its modest weight, two can be carried in the cargo bay.</div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="engine"></a><h3 style="text-align: left;"><span style="font-size: large;">YaMZ-238V (M)</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiHYe0MopOYL0_Zod7XQb-dSvfzOALknstYjyIjpEy0ycQRhmaBkQIcDhhtGZZe7wQEMgErT5O7g3Z8BIaIST1JxSe7jk3Gpga9oTyBBxDdLQv8PQUm3z_Y0DuOyn_BWqPiIOEs4ua7hz9_7i18qBcRjHKbkFgSYSX5BmLpa1vAOFznTNIABlM6_zc-UA/s857/yamz-238%20profile%20cutaway.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="682" data-original-width="857" height="255" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiHYe0MopOYL0_Zod7XQb-dSvfzOALknstYjyIjpEy0ycQRhmaBkQIcDhhtGZZe7wQEMgErT5O7g3Z8BIaIST1JxSe7jk3Gpga9oTyBBxDdLQv8PQUm3z_Y0DuOyn_BWqPiIOEs4ua7hz9_7i18qBcRjHKbkFgSYSX5BmLpa1vAOFznTNIABlM6_zc-UA/s320/yamz-238%20profile%20cutaway.png" width="320" /></a></div><div><br /></div><div><br /></div><div>On the basis of the need to carry out long marches and sustained high traction to tow heavy loads, it was decided to use an automobile engine with a long service lifespan. This role was fulfilled by the YaMZ-238, which produced the necessary torque and had the durability to withstand high loading, but was deficient in many aspects of its performance partly as a consequence of acquiescing to these priorities. The YaMZ-238V is a specific variant of the YaMZ-238 made for the MT-LB, differing from the basic version by modifications in the air intake, the absence of a built-in radial cooling fan in the standard configuration for trucks with a conventionally placed front engine, and a different alternator. These modifications can be seen mainly on the front end of the engine, where the power takeoff gearbox and belt drives are situated. </div><div><br /></div><div>The YaMZ-238V is a V-shaped 8-cylinder, water-cooled, four-stroke diesel engine with a rather large displacement of 14.86 liters and a rated power of 240 hp. It is naturally aspirated. The V-angle is 90 degrees, which is the ideal balance angle for a V8 engine. The two cylinder groups are symmetric, with 1,858 cc of displacement in each cylinder. Fuel is delivered by direct injection. The compression ratio is 16.5, which is quite typical for its class, with some examples such as the 6V-53 having a slightly higher compression ratio of 17. It is a pushrod engine with a gear-driven camshaft. There are two valves per cylinder. It has aluminium alloy pistons with a surface area of 132.7 sq.cm, and the crankshaft and connecting rods are made of machined steel. The YaMZ-238 is a slightly undersquare engine, with a cylinder bore diameter of 130mm and a piston stroke length of 140mm.</div><div><br /></div><div>The YaMZ-238M is a multifuel variant of the YaMZ-238V with the ability to run on gasoline. Its characteristics are the same as the basic model when fueled with diesel, but if it is running on gasoline, both the power and torque characteristics degrade slightly, with the rated power diminishing to 220 hp.</div><div><br /></div><div>The engine has a gray iron crankcase, giving it a much higher specific weight than high-performance engines with aluminium crankcases that are more commonplace among military combat vehicles. For tractors, a heavy engine contributes to the total load pressing down on the ground at the tracks or wheels, increasing the friction force, and thereby increasing the tractive force. This is the primary method of increasing drawbar pull. The close relationship between axle load and traction is one of the major reasons why the large weight of diesel engines relative to gasoline engines is not seen as a drawback, but rather, as a favourable trait for tractors, tractor-trailers and other prime movers. It is also partly for axle loading purposes that wheeled tractors have large, ballasted rear wheels.</div><div><br /></div><div>According to the article "<i>К вопросу выбора размерности для семейства перспективных танковых двигателей с высокой объемной мощностью при допустимой теплонапряженности</i>" in the 1967 No. 5 issue of the "<i>Вестник Бронетанковой Техники</i>" journal, the mean piston speed of the YaMZ-238 is 9.8 m/s. Of particular note is the fact that the cylinders and pistons of the YaMZ-238 experience very low thermal stress owing to the low power to surface area ratio, which makes the engine less demanding in terms of cooling, facilitating longevity during marches with a towed load. On the other hand, this also meant that the MEP of the engine was low, only 7.6 bar.</div><div><br /></div><div>The primary merit of the YaMZ-238 was its durability, as its weight came from its strongly reinforced construction, suitable for long-term work moving heavy loads. It also had relatively good fuel economy, which can be attributed to the low combustion chamber surface area relative to its displacement, on account of the large 1,858 cc displacement and the undersquare design of the engine. </div><div><br /></div><div>However, although the weight of a strongly reinforced engine may be an acceptable compromise for civilian tractors, a heavy engine mostly presents downsides for a military tractor-transporter such as the MT-LB. Firstly, the large weight of the engine reduces the onboard cargo capacity; secondly, it reduces the permissible armour weight, which is important for a frontline combat vehicle; thirdly, it has a net negative effect on the high-speed off-roading capability of the vehicle. It could be argued that the increased traction available due to the weight of the engine is beneficial when towing a heavy gun or howitzer, and that the increased sprung mass of the vehicle improves ride smoothness, but in practice, the MT-LB also carries the gun crew and ammunition, and the increased weight of the engine simply means that less cargo can be carried. As such, from a weight standpoint, the YaMZ-238 engine was not the ideal choice for a tractor-transporter. The primary justifications for its use were its good torque and power output, and the availability of the engine. </div><div><br /></div><div>At the midpoint of the development of the MT-LB, the YaMZ-238 had just recently entered mass production (June 1962). It was created alongside the YaMZ-236 as a family of universal workhorse diesel engines for civilian and military use, first seeing use in MAZ and KrAZ heavy trucks such as the MAZ-500 and KrAZ-255, and in the "Kirovets" tractor. During their shared development cycle, the YaMZ-238 lagged behind the YaMZ-236 by several months, although the projects were nominally progressing in parallel. In terms of design, however, the YaMZ-238 was evidently shown favour, as the 90-degree V-angle shared by both engines was ideal for the balance of V8 engines but not V6 engines, which require a 60-degree V-angle. While both engines became highly successful in their niches within the USSR, there was particularly high demand for the YaMZ-238 in heavy vehicles; as time went on, the number of military and civilian applications for the YaMZ-238 steadily expanded to include buses, combine harvesters, and off-road trucks, namely those made by the Ural automobile plant. </div><div><br /></div><div>With this level of proliferation, the engine had become deeply embedded in the national economy, and the success of the engine also led to some older military prime movers being upgraded with the YaMZ-238, the main example being the GT-TB update of the GT-T prime mover. All of these peripheral developments made the MT-LB easier to maintain, as the status of the engine as an industrial standard meant that trained mechanics were easy to find throughout the USSR, and spares for both the YaMZ-236 and YaMZ-238 were plentiful.</div><div><br /></div><div><br /></div><div>The engine features a combination splash and forced lubrication system, with a wet sump. The main journals and connecting rod journals are lubricated under pressure, and splash lubrication is used for the cylinders. The use of a wet sump system contributed to the height of the engine, as the sump (oil pan) has to be rather large by its nature. In fact, the entire engine is tipped forward relative to the hull by 3.5 degrees on its mount to provide clearance for the sump, which has a characteristic hump shape to accommodate the oil filter intake. In turn, the gearbox is also tipped forward by 3.5 degrees. </div><div><div><br /></div><div>An engine preheater is fitted for heating the engine crankcase via the coolant, as well as heating the engine and gearbox oil systems. It is the PZhD-44B or PZhD-44L diesel boiler with a heating capacity of 32,000 kcal/h. The PZhD-44B model consumes 6.6 kg (±0.5 kg) of fuel per hour, while the newer PZhD-44L model consumes 5-6 kg of fuel per hour, and the rated time needed to preheat the engine at an air temperature of 45°C to a starting temperature of 50-60°C is 30 minutes.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFGVaSjINgIVMgOD9SHTY4PZQKz8Qe4bWsdykaX89Nv-6wyaS1453Av3u8PALk1OXWZL-9tMboGooMrTk7YXu-nYfXw4fB0voO_bfSirJ-w3mUTmL0NnuARPm9Y6zIpCPhlO5Rtf-yn35WKEQBvPpfgHzOK2mktXSO0Kt2mtvbH9zFHHyqXym_lD16pw/s3309/engine%20preheating%20system.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1377" data-original-width="3309" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFGVaSjINgIVMgOD9SHTY4PZQKz8Qe4bWsdykaX89Nv-6wyaS1453Av3u8PALk1OXWZL-9tMboGooMrTk7YXu-nYfXw4fB0voO_bfSirJ-w3mUTmL0NnuARPm9Y6zIpCPhlO5Rtf-yn35WKEQBvPpfgHzOK2mktXSO0Kt2mtvbH9zFHHyqXym_lD16pw/w640-h266/engine%20preheating%20system.png" width="640" /></a></div><div> </div><div><br /></div><div>A number of accessories are directly mounted to the engine. There is an air cleaner on the crankcase at the rear of the engine, directly above the flywheel, and the alternator and the fuel supply group (a high pressure pump, a booster pump, a regulator and an automatic injection advance clutch) are placed in the valley between the cylinders. The starter is placed at the left of the flywheel. A fine fuel filter, and the coarse and fine oil filters are installed at the front of the engine together with the compressor and water pump. The clutch is firmly bolted to the engine as a single unit. The dry weight of the full engine unit, which is inclusive of all built-in accessories and the clutch, is 1,135 kg. The weight of the engine alone, without the clutch and accessories, is not known.</div></div><div><br /></div><div>The size of the engine is unknown. According to the <a href="https://www.ymzmotor.ru/catalog/dvigateli/ymz-v8/euro-0/ymz-238vm/">YaMZ website</a>, the overall dimensions of the YaMZ-238VM are 1,225 x 1,005 x 1,035 mm (L x W x H). The length is inclusive of the clutch unit. For comparison, the dimensions of the 6V53 engine are 991 x 1,016 x 940 mm (L x W x H). It is worth noting that although the YaMZ-238V is longer - which is to be expected given that its length figure includes the clutch and that the YaMZ-238 is a V8 with a much larger cylinder bore (130mm vs 98mm), when the length is divided by the cylinder count, it actually turns out to be a proportionately shorter engine even before taking the bore size difference and the clutch into account. It is also worth noting that the right row of cylinders is displaced ahead of the left row by 35mm due to the conventional layout of the connecting rods in series on the crankshaft. This slightly increases the length of the engine, and introduces a small bending moment in the crankshaft. Aside from the length, the width of the engine is also well within reason. </div><div><br /></div><div>Only the height of the engine could be seen as an issue for a compact engine compartment. The large height of the engine is particularly pronounced when it is installed inside the MT-LB owing to the limited height of its hull. Due to the accessories mounted on top of the engine, and the clearance needed below it, the engine takes up the entirety of the available vertical space in the engine compartment. </div><div><br /></div><div>The YaMZ-238V has a four-point mounting system with shock absorbing, vibration damping mounts. There are two cross pins with rubber bushings held by horizontal clamp-type mounts at the rear of the engine (toward front of the vehicle), and at the front of the engine, there are two vertical shank bolt mounts with thick rubber cushions. The engine mounting frame is welded to the reinforcing U-beams along the floor of the hull, two of which are the covers of two torsion bar pairs. Owing to its well-damped mount and its perfect primary and secondary balance, the engine runs relatively smoothly and quietly in the MT-LB. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQxTIBuWuqLYr9Om3Z5Z5uNWsA_fHUyPiOx3mosPQD-34NlwHFSN8PDcz0kD8SeSq8E72HoNJxhiEzDk-U44ucQqozvu0gYiz0rMnarLBbnClqZExF-AfCO7QUT3LzaOGvBP5AfepjjsXwcE4j12YFFzwtyIqcnahubTHwH4rRus5_A6-V0YLB0R4eRA/s4588/yamz-238.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2464" data-original-width="4588" height="344" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQxTIBuWuqLYr9Om3Z5Z5uNWsA_fHUyPiOx3mosPQD-34NlwHFSN8PDcz0kD8SeSq8E72HoNJxhiEzDk-U44ucQqozvu0gYiz0rMnarLBbnClqZExF-AfCO7QUT3LzaOGvBP5AfepjjsXwcE4j12YFFzwtyIqcnahubTHwH4rRus5_A6-V0YLB0R4eRA/w640-h344/yamz-238.png" width="640" /></a></div><div><div><br /></div></div><div><br /></div><div>The engine has a rated power output of 240 hp at a speed of 2,100 RPM and a peak torque of 883 N.m at a speed of 1,500 RPM. The idling speed of the engine is 450-550 RPM, and the maximum governed speed is 2,225-2,275 RPM. Given that the vehicle has a curb weight of only 9.7 tons, the YaMZ-238 provided an excellent gross power-to-weight ratio of 24.74 hp/ton. With 2 tons of cargo and two crew members, represented as a nominal weight of 100 kg each, the gross power-to-weight ratio is 20.17 hp/ton, which is still good.</div><div><br /></div><div>The specific fuel consumption is 175 g/hp.h, achieved at a speed of around 1,350 RPM. The nominal fuel consumption rate is 90-120 kg per 100 km or 43-44 kg per engine-hour, while the oil consumption is 2% of the fuel consumption. Converting from kilograms to liters, using the known density of the standard DL grade diesel fuel for summertime, the fuel consumption is 77-103 liters per 100 km, or 37.0-37.8 liters per engine-hour. This nominal rate was determined by a long-term military trial on a track consisting of a variety of terrain and road types.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrt6nKWq6Sjt8c-bpPH2NYZxWjGc7ibeouvJeLi-qs8GYU43VvA_C3gr5eRnv67EAJSmxlhgTA0tWUZ0RUrK7DRchMUpH7gNHqwUolQMWbpKtBNel7Th10-sibKCV6X3GR6c8siYkgWpZbLBc9rVgtBbXTr8RrBhqVlLfKFs5KFCLdf3KUOU3qmyBgjQ/s454/yamz-236%20(1)%20and%20238%20(2)%20power%20chart.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="454" data-original-width="398" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrt6nKWq6Sjt8c-bpPH2NYZxWjGc7ibeouvJeLi-qs8GYU43VvA_C3gr5eRnv67EAJSmxlhgTA0tWUZ0RUrK7DRchMUpH7gNHqwUolQMWbpKtBNel7Th10-sibKCV6X3GR6c8siYkgWpZbLBc9rVgtBbXTr8RrBhqVlLfKFs5KFCLdf3KUOU3qmyBgjQ/s16000/yamz-236%20(1)%20and%20238%20(2)%20power%20chart.png" /></a></div><div><br /></div><div><br /></div>The YaMZ-238 develops a rather low specific power of 16.15 hp/l, which is to be expected due to its large displacement and low speed. When comparing it to the 6V53 of the M113A1 and M113A2, the rated power is only 13.2% higher, and the specific power is drastically inferior (16.15 hp/l to 40.61 hp/l). In general, for engines meant for lightly loaded vehicles, a high specific power is achieved by designing the engine for higher speeds, usually at the cost of low-end power.</div><div><br /></div><div>For instance, it is written in the book "Opposed Piston Engines: Evolution, Use, and Future Applications" that, when running on diesel, the K60 generates a power output of 210 hp (157 kW) at a crankshaft speed of 2,380 RPM (final geared output speed of 3,750 RPM) and it only produces a maximum torque of 488 N.m. The large difference in torque is not only problematic in terms of net power at typical running speeds, but is also indicative of deficient load-bearing capability, especially in difficult terrain. The same was true for the <a href="http://afvdb.50megs.com/usa/pics/m113/chrysler75mcurve71.jpg">Chrysler 75M gasoline engine</a> used in the original M113, which put out 209 hp at 4,000 RPM but had a maximum torque of just 433 Nm. In contrast, the 6V53 diesel engine of the M113A1 and M113A2 generated 212 hp at 2,800 RPM and had a much more reasonable torque output of 607 N.m at 1,800 RPM. </div><div><br /></div><div>For engines intended for tractors, trucks and other heavily loaded vehicles, low-end torque is emphasized for the sake of more low-end power, because the task of hauling a load becomes uneconomical if a high-revving engine is used, as it would need to be driven at a high rotating speed to develop the power needed for the task. Diesel engines are favoured for these classes of vehicles mainly for this reason, and the YaMZ-238 was designed with this role in mind. </div><div><br /></div><div>Moreover, when driving cross-country and when towing or transporting a load, the engine is rarely running at its peak power, and when accelerating, the transmission tends to be upshifted around the rated speed (either automatically or manually), so the engine is able to develop its rated power for only a fraction of the total driving time in each gear. Rather, because the engine accelerates together with the vehicle, it is important to look at the entire power curve leading up to the speed at which the rated power is developed. As the table below shows, the power curve of the slower-running YaMZ-238 is much more favourable for the purposes of a prime mover, cargo transporter or personnel carrier operating in bad terrain, and in virtually all circumstances, the average power delivered by the YaMZ-238 is much greater owing to the shape of its power curve. </div><div><br /></div><div><br /></div><div><div><table border="1"><tbody><tr><td style="text-align: center;"><b> Engine speed (rpm) </b></td><td style="text-align: center;"><b> 6V53 (hp) </b></td><td style="text-align: center;"><b> YaMZ-238 (hp) </b></td><td style="text-align: center;"><b> Power difference </b></td></tr><tr><td style="text-align: center;">1,500</td><td style="text-align: center;">125</td><td style="text-align: center;">186</td><td style="text-align: center;">48.8%</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">1,600</span></td><td style="text-align: center;">136</td><td style="text-align: center;">199</td><td style="text-align: center;">46.3%</td></tr><tr><td style="text-align: center;">1,700</td><td style="text-align: center;">145</td><td style="text-align: center;">209</td><td style="text-align: center;">44.1%</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">1,800</span></td><td style="text-align: center;">153</td><td style="text-align: center;">218</td><td style="text-align: center;">42.5%</td></tr><tr><td style="text-align: center;">1,900</td><td style="text-align: center;">162</td><td style="text-align: center;">227</td><td style="text-align: center;">40.1%</td></tr><tr><td style="text-align: center;">2,000</td><td style="text-align: center;">170</td><td style="text-align: center;">235</td><td style="text-align: center;">38.2%</td></tr><tr><td style="text-align: center;">2,100</td><td style="text-align: center;">177</td><td style="text-align: center;">240</td><td style="text-align: center;">35.6%</td></tr></tbody></table></div><div><br /></div><div><br /></div><div>No data is available for the 6V53 below 1,500 RPM, but when the existing data is graphed using the best fitting curve (r^2 = 0.996), it can be extrapolated that the gap between the YaMZ-238 and 6V53 is widens at the same rate down to idling speed. In practice, the net power available at the gearbox can vary greatly, and the best case scenario for the 6V53 is when the vehicle is cruising or accelerating gently, where the transmission permits the torque converter lockup clutch to engage so that there is no power lost to the torque converter, thus improving fuel economy. Refer to <a href="https://thesovietarmourblog.blogspot.com/p/m113-torque-converter-and-transmission.html">this page on the TX-series transmissions on the M113 series</a> for more details on how a torque converter affects the net power available at the gearbox, even with a gearbox that has a torque converter lockup in all gears.</div><div><br /></div><div><br /></div><div>On top of its favourable power curve, the YaMZ-238 has a notable advantage in fuel consumption, as the 6V53 has a specific fuel consumption of 188 g/hp.h compared to the 175 g/hp.h rate achieved by the YaMZ-238. Additionally, the fuel consumption rate will also tend to be much lower for an MT-LB in practice, as its good power curve allows it to drive at an efficient engine speed at higher gears even while towing a heavy load, whereas an M113 would tend to require the engine to be driven at high speeds with the gearbox in a low gear under the same circumstances.</div><div><br /></div><div>However, in spite of its good power curve, the YaMZ-238 loses out in terms of engine dynamics. To quantify the qualities of the engine dynamics, two metrics are used - engine flexibility (adaptability) and engine elasticity. The engine flexibility (adaptability) coefficient is 1.086, obtained by finding the ratio of the peak torque to the torque developed at the rated power. This figure is also known as the torque backup, torque reserve or torque rise when expressed as a percentage. In this case it is 8.6%. High engine flexibility is important for negotiating terrain that imposes high fluctuating engine loads rather than constant loads, and is therefore responsible for providing a high cross-country speed. </div><div><div><br /></div><div>Additionally, to quantify the characteristics of the power band, the engine elasticity coefficient is used. The wider the power band, the lower (better) the coefficient. For the YaMZ-238, the coefficient is 0.71, as determined by dividing the engine speed for peak torque by the engine speed for peak power. A wide power band contributes to the ease of driving the tank in various types of terrain, because it means that downshifting is often not necessary when the tank slows down as the engine produces a large amount of power at a wide range of speeds.</div></div><div><br /></div><div>In both metrics of the performance of the engine's dynamics, the YaMZ-238 is poor. It is surpassed in both respects by a considerable margin by the 6V53, which had a flexibility coefficient of 1.126 and an elasticity coefficient of 0.64 (the same as all other 53-series engines). However, the turbocharged 6V53T, which provided more power and matched the YaMZ-238 in torque, had drastically worsened dynamics, with a flexibility coefficient of 1.093 and an elasticity coefficient of 0.786.</div><div><br /></div><div><br /></div><div><a href="https://www.blogger.com/null" id="engineaccessories"></a><h3><span style="font-size: large;">ENGINE ACCESSORIES</span></h3><div><br /></div><div><div><div>The engine accessories were installed in a layout similar to a truck engine. Unlike the engines used in domestic tanks and other military tracked combat vehicles, the starter and the alternator are separate devices on the YaMZ-238 series. The starter is placed under the left cylinder bank, and connects to the flywheel. The G290 alternator is mounted on top of the engine, and is driven by a belt from a power takeoff at the rear end of the engine crankshaft. The G290 is a three-phase synchronous AC alternator rectified to produce a DC output. It has a rated output of 3.75 kW. </div><div><br /></div><div>There are four belted drive connections on the engine, two belts at the camshaft for the engine to drive the alternator and air compressor, and two belts for the engine to drive the cooling fan and coolant pump. Smooth wedge-type belts are used, with the transmittable force limit controlled by a spring-loaded tensioner. The same type of belts with the same width can be found in a number of Soviet trucks, and can be used in the MT-LB. Belts of a non-standard length can be used as long as tension is adjusted appropriately. Tensioner adjustment is depicted in the drawing below. An interesting feature of the drive belt system inherited from standard design practice in domestic trucks is that two separate drive belts are used for more heavily loaded units, which in this case were the alternator and cooling fan. This may have been a way of standardizing on a single belt size for all connections. It may also provide an additional element of redundancy to improve the reliability of the belt drive, on top of the natural tendency of such belts to slip rather than break when the loading force exceeds the maximum friction force.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2LR2j9KXuhtmzroaT71mLEiSQ8iVd7yluUcavq1XLM0jkaIkJ5v4XMu9NiLUnTJqORLY69pZ8p-2NFsaufdZc6peLsnA4HTfe5o83SYMUuNi5r4TxzvxddZDtYROMu_Zp2BKb2wKdPrF6HuEvkgwfaFOUWm5qZul3h-pilRXc8npzu4-eNhaN1lFXMw/s1495/belted%20drives.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1495" data-original-width="1097" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2LR2j9KXuhtmzroaT71mLEiSQ8iVd7yluUcavq1XLM0jkaIkJ5v4XMu9NiLUnTJqORLY69pZ8p-2NFsaufdZc6peLsnA4HTfe5o83SYMUuNi5r4TxzvxddZDtYROMu_Zp2BKb2wKdPrF6HuEvkgwfaFOUWm5qZul3h-pilRXc8npzu4-eNhaN1lFXMw/w294-h400/belted%20drives.png" width="294" /></a></div><div><br /></div><div>The engine access panel is very large, and its opening follows the entire perimeter of the engine compartment (excluding the cooling system) without any overhang of the hull roof. In this way, it is very similar to the bonnet of a truck.</div><div><br /></div>Additionally, a notable advantage of the MT-LB drivetrain layout is that the front of the engine can be accessed quite easily by removing the rear engine compartment firewall. With the firewall removed, a mechanic is free to service or replace the belt drive mechanisms without needing to dismantle anything, unlike a typical car or truck where there tends to be very little free space in the engine bay for such tasks, which is also true for trucks equipped with the YaMZ-238, as the radial cooling fan is directly in front of the belt drives. The access available to the belt drives is shown in the <a href="https://litnik.in.ua/walkaround/bronetekhnika/mt-lb-walkaround-ot-pepsa-chast-1">photo below</a>. The firewalls on the side and front of the engine compartment can also be removed to access a few other components. Only the left side of the engine compartment is largely inaccessible, requiring the engine to be removed. <br /><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-H5e2KxkmQsbxycPcFDqCLq08mF0P4O8Yqhkbs8D8Jfg0pdzl0xCneGHnEOVB1R6P8E0J7RomM9xpIQLrHLhSo3lA_PB44gPPAOTZCLSr3_WBBtGi7n28-LRkX3kS8PBRy769Kx5ICYZonJDp4hRjKfvjEmzXR5L-KQZKlnfq1UEKIGt6oabL8HamwQ/s1024/mtlb-19.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-H5e2KxkmQsbxycPcFDqCLq08mF0P4O8Yqhkbs8D8Jfg0pdzl0xCneGHnEOVB1R6P8E0J7RomM9xpIQLrHLhSo3lA_PB44gPPAOTZCLSr3_WBBtGi7n28-LRkX3kS8PBRy769Kx5ICYZonJDp4hRjKfvjEmzXR5L-KQZKlnfq1UEKIGt6oabL8HamwQ/w640-h480/mtlb-19.jpg" width="640" /></a></div></div><div><br /></div></div><div><br /></div><div><div>The power supply system operates at a nominal voltage of 24 V and a load current limit of 120 A. This likens it to a truck electrical system and distinguishes it from domestic tanks and other armoured fighting vehicles, with the exception of the BTR-60 and BTR-70 which also operate on 24 V, and like the MT-LB, use engines and engine accessories meant for trucks and specialized wheeled vehicles.</div><div><br /></div><div>There are two 6ST-140 lead-acid batteries, connected in series. Each battery has a voltage of 12 V and a capacity of 140 Ah, thus providing an operating voltage of 24 V at a capacity of 140 Ah. The design of the 6ST-140 battery is rather interesting as it is actually a wooden box containing a battery bank, consisting of six smaller, individual self-contained batteries. The lid of the box contains built-in conductor plates to connect the batteries and the two terminals for wiring up the battery unit. </div></div></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">AIR INTAKE</span></h3><div><br /></div><div>The engine air supply system was conventional for Soviet military vehicles. It features a two-stage air cleaner with a multicyclone precleaner, and an oil mesh filter pack for fine particle separation. The inlet pipe to the air cleaner leads to the air intake on the engine access panel, so that air enters from above, passes into the cyclones, then travels upward into the oil mesh filters before exiting from the side. The air cleaner assembly is rather tall, and together with the alternator, it is partly responsible for the height at the engine compartment. It does, however, facilitate convenient access to the oil mesh filters for cleaning, and the same can be said for access to the alternator for servicing. </div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlc1SK_dkGcgoMxCHtDVrmaObAYmozfqzgl4dPuaz9fdMu2JUWeHIykNQC5J5zpEaaCKZeraIfjPLWpKFQ45M12oy0pdCI63ouY9-iDVWr21WSyHK0cIbhEiNUgZc7giUZnxCScaaQOgx_ftyynNXxveDv75GAQw5ehSi9XirNwSWuZT--mu8gFsdBqA/s1200/MT-LB_YaMZ_238_1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="797" data-original-width="1200" height="426" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlc1SK_dkGcgoMxCHtDVrmaObAYmozfqzgl4dPuaz9fdMu2JUWeHIykNQC5J5zpEaaCKZeraIfjPLWpKFQ45M12oy0pdCI63ouY9-iDVWr21WSyHK0cIbhEiNUgZc7giUZnxCScaaQOgx_ftyynNXxveDv75GAQw5ehSi9XirNwSWuZT--mu8gFsdBqA/w640-h426/MT-LB_YaMZ_238_1.jpg" width="640" /></a></div> </div><div><br /></div><div>The air intake on the engine access panel consists of a protective cap on top of a hole, and more often than not, there is also an additional intake hood bolted onto the cap. The hood is a simple metal cover with a mushroom dome top, the underside of which is covered with a mesh. This hood is intended to reduce the dust ingested when driving in dusty environments, eliminate water ingestion when crossing water obstacles, and eliminate the ingestion of leaves and pine needles when traveling in forest environments. When not in use, the hood is kept in the transmission compartment, but in practice, it is almost always fitted since there is practically no reason to not use it.</div><div><br /></div><div>Since the engine access panel is routinely opened for various reasons, a spring-loaded sealing mechanism was integrated to the inlet flange of the inlet pipe to connect the air cleaner to the air intake. When the access panel is closed, the seal is pressed tightly against the intake opening.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgO4bsd7O8GcHvoUxnflz2iHh-BLQmQUKXgLhWKGTYWSfMILA6Gn01u52aJ7JgolD8Hgrv2nqB-LVPA7VCvdSal12Yzy3XeOU5G4OaFc9GdlWRJhNvh4x30eb_JiZ13LMbkEqwGEGqElcgUEURPXvEiOgvJ35CtwPCYtrC_hfX20DwNJQ5zuij71B80sQ/s1809/air%20intake%20hood.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1809" data-original-width="1219" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgO4bsd7O8GcHvoUxnflz2iHh-BLQmQUKXgLhWKGTYWSfMILA6Gn01u52aJ7JgolD8Hgrv2nqB-LVPA7VCvdSal12Yzy3XeOU5G4OaFc9GdlWRJhNvh4x30eb_JiZ13LMbkEqwGEGqElcgUEURPXvEiOgvJ35CtwPCYtrC_hfX20DwNJQ5zuij71B80sQ/w216-h320/air%20intake%20hood.png" width="216" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEivF_6vtuOjpo8V4ZTI84Qzq2vykjXgGy1odqtdEKSA8h3F7Cx_7c3RV2Ke-BVYrHld1jhihrlD6IBnVsAdKGZwDupRo5sZ3LuTrfnn4VcwyqkU-IeLUjoW4y9vLbSCEqNz75MJUTw30vd2RYY78mbFL0mY5dwMSzqJb1YTOt1yI73VPlQbVIiPO9r-zg/s800/air%20cleaner.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="712" data-original-width="800" height="356" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEivF_6vtuOjpo8V4ZTI84Qzq2vykjXgGy1odqtdEKSA8h3F7Cx_7c3RV2Ke-BVYrHld1jhihrlD6IBnVsAdKGZwDupRo5sZ3LuTrfnn4VcwyqkU-IeLUjoW4y9vLbSCEqNz75MJUTw30vd2RYY78mbFL0mY5dwMSzqJb1YTOt1yI73VPlQbVIiPO9r-zg/w400-h356/air%20cleaner.jpg" width="400" /></a><br /></div><div><br /></div><div>When it is desirable for the engine to induct heated air, such as during winter, a flap on the side of the air inlet pipe can be opened by pulling a handle on the engine compartment firewall behind the commander. Opening this flap allows the engine to draw air from both the atmosphere and the engine compartment, which is heated by the engine itself. </div><div><br /></div><div>The disadvantage of the overall layout of the air intake system is that the inducted air has to make multiple sharp turns while travelling to the engine, which results in a higher intake air pressure.</div><div><br /></div><div>The air filters and air purifier cyclones for the engine require cleaning after 25-30 engine-hours.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">PNEUMATIC SYSTEM</span></h3><div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh4rr4aT6zom2jSD5ezHZoH93FQSMmiwIwEXcQIlbgTHy0DMh_-3QJqkzCfqhj2ZHRWwV7FUI4Z_RcrK3OogP94QPOjZA3cNczm2Yun9mJ7SYKDf4YvMmq3Wf9fE18fAbGjdC33OMrfdXgvUkb1ybfpwrEroiFnGrhMJncl-_WWMTqCZintGJyJYPNpzg/s6696/pneumatic%20system.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="4304" data-original-width="6696" height="412" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh4rr4aT6zom2jSD5ezHZoH93FQSMmiwIwEXcQIlbgTHy0DMh_-3QJqkzCfqhj2ZHRWwV7FUI4Z_RcrK3OogP94QPOjZA3cNczm2Yun9mJ7SYKDf4YvMmq3Wf9fE18fAbGjdC33OMrfdXgvUkb1ybfpwrEroiFnGrhMJncl-_WWMTqCZintGJyJYPNpzg/w640-h412/pneumatic%20system.png" width="640" /></a></div><div><br /></div><div>It is a light duty compressor of a standard model, standardized between the a wide range of wheeled vehicles such as the BTR-60 series, BRDM-2, ZIL-131, Ural-375 and some tracked prime movers like the ATS-59. In the textbook "<i>Основы Теории И Конструкции Танков, Боевых Машин Пехоты Бронетранспортеров И Армейских Автомобилей:</i> <i>Часть Вторая</i>", it is referred to as the ZIL-131 compressor. The only difference in the compressors used in these vehicles is in how they are mounted and the diameter of the belt wheel to regulate the compressor crankshaft speed when used together with different engines. It is much different from the AK-150 series compressors used in domestic tanks, which generate an operating pressure of 150 kgf/sq.cm. The compressor generates and maintains a pressure of only 6-7.9 kgf/sq.cm (588-774 kPa) in the pneumatic system. A total of 43 liters is stored in two compressed air bottles, mounted in the transmission compartment.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDArRr0-xsVnFa2DdfA6U6P_TCVHTo8Vz0HOxCM5N_v9Z6qZFc7rxn6EafmyEOpgIKynKVfTck8dMWTL20J3UuzLExXAYG7Y6PFinqhURUM2NHASMwaxluldtIcV7Lv7TDq-Vnz-3LhKYGnRcobhbB5WAaHZGDe1zquezoHOV0jMr4RuIeOeIp38QPtg/s4581/compressor.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2757" data-original-width="4581" height="241" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDArRr0-xsVnFa2DdfA6U6P_TCVHTo8Vz0HOxCM5N_v9Z6qZFc7rxn6EafmyEOpgIKynKVfTck8dMWTL20J3UuzLExXAYG7Y6PFinqhURUM2NHASMwaxluldtIcV7Lv7TDq-Vnz-3LhKYGnRcobhbB5WAaHZGDe1zquezoHOV0jMr4RuIeOeIp38QPtg/w400-h241/compressor.png" width="400" /></a></div><div><br /></div><div><br /></div><div>Unlike the pneumatic systems used in domestic tanks, the pneumatic system in the MT-LB is limited to auxiliary features within the vehicle itself. It serves to power the pneumatic brakes and to operate the windshield washers. There is no air start system for the engine. Like other prime movers, the pneumatic system in the MT-LB was mainly fitted to power the pneumatic brakes of a towed trailer, if such a system is present.</div></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="cooling"></a><div><h3><span style="font-size: large;">COOLING SYSTEM</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIkciUGKR1zXFTJmzacbV7liKPSn92NaLhYbq53OAQTm4qGCxqB6Uk5V5yz35r9de_Icp6FG62rPQ5CXr1_2lWzx-0nDQQvtD5Lpw-ennEMiKBVJ6sTNrvvu6yI9SFx28sBI28BlTsv-M7Wppt6oNOem0UB_1VodVhQh0e6rrgSzvichkJbdV4p_IBpw/s2049/preheating%20system.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1101" data-original-width="2049" height="344" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIkciUGKR1zXFTJmzacbV7liKPSn92NaLhYbq53OAQTm4qGCxqB6Uk5V5yz35r9de_Icp6FG62rPQ5CXr1_2lWzx-0nDQQvtD5Lpw-ennEMiKBVJ6sTNrvvu6yI9SFx28sBI28BlTsv-M7Wppt6oNOem0UB_1VodVhQh0e6rrgSzvichkJbdV4p_IBpw/w640-h344/preheating%20system.png" width="640" /></a></div></div><br /><div><br /></div><div><div>The cooling system of the engine is of a conventional type, with aluminium radiators and a normal operating coolant temperature of 75-98°C, and the maximum temperature is 105°C. 55 liters of coolant is used in the system. The cooling system is interconnected with the preheater, as the coolant pipelines are shared. This also means that when preheating the engine, some heat will be lost to the environment through the radiators, thus increasing the preheating time. To mitigate this, a set of ballistic louvers over the radiators can be closed.</div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8-PDQ830BrNpdvDeOeZS-Neh-lulvSnUFpgj7aIr8jdGaeja-9kq9i8ONYwEGR-excXLnwMAaafiYMv50F3_angTehZbR04nsAlJAfwbafYD1vVk1WhEIXewbCndjVVBHgn7GcYotYyQDGEs2HxBxOMAlgXx387WJEMhXmv6WBRrbcyqWX491twaWSA/s4096/cooling%20system%20diagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3832" data-original-width="4096" height="598" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8-PDQ830BrNpdvDeOeZS-Neh-lulvSnUFpgj7aIr8jdGaeja-9kq9i8ONYwEGR-excXLnwMAaafiYMv50F3_angTehZbR04nsAlJAfwbafYD1vVk1WhEIXewbCndjVVBHgn7GcYotYyQDGEs2HxBxOMAlgXx387WJEMhXmv6WBRrbcyqWX491twaWSA/w640-h598/cooling%20system%20diagram.png" width="640" /></a></div><div><br /></div><div>The ballistic louvers protecting the radiator intake are shown below. The radiator area is 1,202mm long and 415mm wide. Each individual louver is hinged and connected to a bar, and the intake can be shut by pushing forward a handle connected to this bar. The handle is behind the driver's left shoulder. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgf9dHCR6eqJTje8Dzv0tfM3ho_o4YEGpmEjlHa2xOZTdl3_BG3DYD5xB_qE7qB0j_SudhMPAm0-NKvunOdvjg60gU0xhktrBkY6TmUo00j_DSJ_BJmC68A4T4cYv1GrttjnklpQwotPCLrB84KMHqvu4uDQnOlXx5xdXL6kYHjm5Fxu47zMfkiQG8qag/s1955/radiator%20louvers.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1005" data-original-width="1955" height="330" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgf9dHCR6eqJTje8Dzv0tfM3ho_o4YEGpmEjlHa2xOZTdl3_BG3DYD5xB_qE7qB0j_SudhMPAm0-NKvunOdvjg60gU0xhktrBkY6TmUo00j_DSJ_BJmC68A4T4cYv1GrttjnklpQwotPCLrB84KMHqvu4uDQnOlXx5xdXL6kYHjm5Fxu47zMfkiQG8qag/w640-h330/radiator%20louvers.png" width="640" /></a></div></div><div><br /></div><div>The oil radiators of the engine and the gearbox are stacked on top of the water radiator for the engine. Air is drawn through the radiators via the intake louvers, where it is ducted to the centrifugal cooling fan and is then expelled. It is worth noting that the cooling fan evacuates any water that enters the radiator duct from the radiator intake by its strong airflow, but when the engine is at rest and the fan is off, rain water can accumulate in the ductwork since it is directly underneath the radiators, and the intake is ducted to the fan. In the long term, this can result in premature corrosion, so a drainage port on the underside of the housing has to be opened when the MT-LB is parked for long periods. This is done with a pullstring mechanism in the driver's station. The image below, taken from <a href="https://youtu.be/J5W5gAW9-wQ">a video</a>, shows the intake duct to the cooling fan.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifnJt2jhYb6ahALeje2CjwCNTYpvLa_kFcDRnl8PKn29gQ8wjL4zBv6VmxOvvD26IlqR3iJAvByVv3fX5QSGXW5eQrD9xLW15n2EaUGU-Jn87oyhTFSBNWkdH3YF66OJVa-A5mH6GhFFdXh33OwVtWYuqhHGBGTtiChwaqpEpg3X05zWd24MLpTFS__g/s1920/radiator%20intake%20duct.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifnJt2jhYb6ahALeje2CjwCNTYpvLa_kFcDRnl8PKn29gQ8wjL4zBv6VmxOvvD26IlqR3iJAvByVv3fX5QSGXW5eQrD9xLW15n2EaUGU-Jn87oyhTFSBNWkdH3YF66OJVa-A5mH6GhFFdXh33OwVtWYuqhHGBGTtiChwaqpEpg3X05zWd24MLpTFS__g/w400-h225/radiator%20intake%20duct.png" width="400" /></a></div><div><br /></div><div>The cooling fan is powered by a belt drive from the engine via a reduction gearbox. The fan gearbox is mounted coaxially to the engine, so like the engine, it is also tipped forward by 3.5 degrees. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjUqSnc5XPpY12n4CJAzaxq1ZiQsVn1HwjY4Yyh_uw8JIULpkPHxs0KUsAPecF611YR5J6gjqHStOXd_l82x_-rwcM28rd7BrdbDhMVnDZjMdVGBI3RwkUE1wT7BRL_mlXJmRiTUhrX4DiBndEYtZRWNWOi94C5lmuTh2Ide3Y7QSEfrRADjCp2rTAKJA/s800/cooling-system.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="656" data-original-width="800" height="328" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjUqSnc5XPpY12n4CJAzaxq1ZiQsVn1HwjY4Yyh_uw8JIULpkPHxs0KUsAPecF611YR5J6gjqHStOXd_l82x_-rwcM28rd7BrdbDhMVnDZjMdVGBI3RwkUE1wT7BRL_mlXJmRiTUhrX4DiBndEYtZRWNWOi94C5lmuTh2Ide3Y7QSEfrRADjCp2rTAKJA/w400-h328/cooling-system.jpg" width="400" /></a></div><div><br /></div><div>The cooling fan system was implemented in a fairly innovative way. Air flows in through the center and exits radially. To direct the outflow, the fan housing has a spiral shape and is ducted to the exhaust outlet, shared with the engine exhaust. Here, the relatively cool air from the radiator mixes with the engine exhaust, cooling it down before it is expelled. More importantly, due to the combination of the low density of the hot radiator exhaust air and its high velocity as it is blown past the engine exhaust port, a low pressure zone is created for the engine exhaust, leading to a significant reduction in exhaust backpressure. In doing so, the net engine power is increased. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj3UqIfTTScZdhg14JZdGsLg_5Wg2HmEIxvQoAIhBmqd6lEt7YK_OmXXzpe7PEJI1lItkxQyASVbcUJq39ZjXy9UkI8fa5i815piFbYabf3ek7TSpPPXI9sORFo08YZAkTFwG3Mov5rSPPOQQ0uVBMIHg0j9vdSq8hV9w2MEmhe8p7UNLGEW-AsM3GOsg/s2226/profile%20view.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="720" data-original-width="2226" height="208" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj3UqIfTTScZdhg14JZdGsLg_5Wg2HmEIxvQoAIhBmqd6lEt7YK_OmXXzpe7PEJI1lItkxQyASVbcUJq39ZjXy9UkI8fa5i815piFbYabf3ek7TSpPPXI9sORFo08YZAkTFwG3Mov5rSPPOQQ0uVBMIHg0j9vdSq8hV9w2MEmhe8p7UNLGEW-AsM3GOsg/w640-h208/profile%20view.png" width="640" /></a></div><br /><div>However, aside from the advantages of the design, it is also important to note that with this implementation, the radiator and the exhaust are placed side-by-side, which is generally undesirable because it introduces the possibility of exhaust recirculation in the cooling system, where heated air from the exhaust re-enters the radiator under the strong draft created by the cooling fan due to its close proximity. This would normally have a negative impact on the cooling efficiency of the system, although it is mitigated when the vehicle is in forward motion by the incoming stream of air and the angle of the exhaust flaps, as shown in the image on the left below (courtesy of <a href="https://fotosn.ru/2021/02/01/%D0%BC%D0%B5%D0%B4%D0%B8%D1%86%D0%B8%D0%BD%D1%81%D0%BA%D0%B8%D0%B9-%D0%BC%D1%82-%D0%BB%D0%B1-%D0%B2-%D0%BF%D1%83%D1%81%D1%82%D1%8B%D0%BD%D0%B5/">Lex Kitaev</a>), or when it is moving forward with the engine at high speed, where the strong jet of exhaust blows clear of the hull. At low engine speeds and when idling, the air stream is too mild, but the weak exhaust is only able to open the flaps partly, and in this position, the flaps work to deflect the exhaust gasses rearward, as shown in the image on the right below. In this way, exhaust recirculation can be virtually eliminated in all circumstances except when the vehicle is moving in reverse. The primary issue with this solution is that the flaps will introduce some additional losses on their own by increasing the exhaust backpressure, varying with how widely they are opened.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhaD7m2vA_Xnc6mPAPyDQC_Ck9t0i7xBB9IX2SxkRlR_Teracrodu6Vv6BLwNHWD7h576ZowiZqTPYTSKeQyJ0rhH3uvd0AwCJGe_QbgoKeW6diFlJlAtZ6vT5dJj1FR8KWUe4z0biA1aJZ2_T2HiQbb7RX4vJIQTxQx2lNICPGXyf3CMwad7PsIw5fbA/s1240/14.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="827" data-original-width="1240" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhaD7m2vA_Xnc6mPAPyDQC_Ck9t0i7xBB9IX2SxkRlR_Teracrodu6Vv6BLwNHWD7h576ZowiZqTPYTSKeQyJ0rhH3uvd0AwCJGe_QbgoKeW6diFlJlAtZ6vT5dJj1FR8KWUe4z0biA1aJZ2_T2HiQbb7RX4vJIQTxQx2lNICPGXyf3CMwad7PsIw5fbA/w400-h266/14.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1q_1HKslCdmyivSZpE7YNjUXUfifd6ZL0fwHcA41dqZ_bBlYOEq5Gxjn97NQJltjmDnlUleZjt4kgEr9j-O9SKLk9ANxtwcscHnkN3g3JGl_EKnOYhNLmUzkeBu1WDcG9DMpYxZTKO8X7NMkkSZZP_qeBGSUi9NysazhtgeT9AfKFZaqkRbT6odRnmg/s3657/MTLBV%C2%A04.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2407" data-original-width="3657" height="264" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1q_1HKslCdmyivSZpE7YNjUXUfifd6ZL0fwHcA41dqZ_bBlYOEq5Gxjn97NQJltjmDnlUleZjt4kgEr9j-O9SKLk9ANxtwcscHnkN3g3JGl_EKnOYhNLmUzkeBu1WDcG9DMpYxZTKO8X7NMkkSZZP_qeBGSUi9NysazhtgeT9AfKFZaqkRbT6odRnmg/w400-h264/MTLBV%C2%A04.png" width="400" /></a><br /></div><div><br /></div><div>The exhaust is mainly protected from bullets and fragments by a set of internal vanes angled to shield the exhaust port from ground level threats. The flaps do not provide any notable protection due to their low thickness. With the engine running, the flaps only serve to prevent the exhaust flow from blowing forward, but when turned off, the flaps fall to fully close over the exhaust port to prevent rain accumulation inside the exhaust ducts. </div><div><br /></div></div><div><br /></div><a href="https://www.blogger.com/null" id="fuel"></a><h3 style="text-align: left;"><span style="font-size: large;">FUEL SYSTEM</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHPNWUt1C99qW5IzliMJKLQoOTjpeAS-HNVbKNwJksf9yito001Djwo9_9SXvW3hbx8YG2Cio9fGSt962_YaDKFBRJKWQAxXRmMXcz9xywU38bB1i2AkwYM2aUeqgBbVNt8sktkzzMhMi5H8XocTir6WPFpn_gCPm6bQw8UNavnu5rB0Qwks-yuO4OzQ/s9000/fuel%20system%201.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="8433" data-original-width="9000" height="600" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHPNWUt1C99qW5IzliMJKLQoOTjpeAS-HNVbKNwJksf9yito001Djwo9_9SXvW3hbx8YG2Cio9fGSt962_YaDKFBRJKWQAxXRmMXcz9xywU38bB1i2AkwYM2aUeqgBbVNt8sktkzzMhMi5H8XocTir6WPFpn_gCPm6bQw8UNavnu5rB0Qwks-yuO4OzQ/w640-h600/fuel%20system%201.png" width="640" /></a></div><div><br /></div><div><br /></div><div>A total of 520 liters of fuel is carried in an MT-LB, spread across four fuel tanks located in the cargo compartment. The fuel system is divided into two groups, left and right. There is a sponson fuel tank as well as a floor fuel tank on each side. Each side contains 260 liters of fuel. The sponson and floor tank in each group is interconnected, and both groups are connected to a single fuel pump.</div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGbDMpGr9YV7uzYJjh1eIPGkDmFWOJ4zxl6jMpT6wMMDVtEgq4xjTf0OxRBnZrdwLw0GTsbIKQRKfCsuGiVxtirdjkzv5rPodSuk0Vl81wILYM8ikHsD6i6fGllP_khCFoHONCe-fCbKCtWRdS_52hy-r4VzmcAM4wxK3qScC0S6gxQZHkT4wUJmBLvQ/s2201/mt-lb%20fuel%20system.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1403" data-original-width="2201" height="408" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGbDMpGr9YV7uzYJjh1eIPGkDmFWOJ4zxl6jMpT6wMMDVtEgq4xjTf0OxRBnZrdwLw0GTsbIKQRKfCsuGiVxtirdjkzv5rPodSuk0Vl81wILYM8ikHsD6i6fGllP_khCFoHONCe-fCbKCtWRdS_52hy-r4VzmcAM4wxK3qScC0S6gxQZHkT4wUJmBLvQ/w640-h408/mt-lb%20fuel%20system.png" width="640" /></a></div><br /><div>The onboard fuel provided the MT-LB with a nominal driving range of 500 km on paved roads. If fitted with the YaMZ-238M engine, the driving range with gasoline is 350-380 km. The nominal fuel consumption rate while carrying out unspecified on-site "work" is 8 liters per hour, or 13.5 liters per hour when doing trenching work. The fuel consumption rate while towing a nominal load is 110 liters per 100 km, or 31.5 liters per engine-hour.</div><div><div><br /></div></div></div><div>When driving with a full fuel load, both right and left fuel tank groups are drained simultaneously by an equal amount. The fuel outflow is from the floor tanks, so if the sponson tanks are filled, they function by replenishing the floor tanks. The effect is that the sponson tanks are emptied first, which can drastically reduce the vulnerability of the MT-LB to fuel fires if it is under enemy attack, as the sponson tanks would tend to be empty or near-empty while the floor tanks are very difficult to hit.</div><div><br /></div><div>Different grades of diesel may be used depending on the weather conditions. In non-winter weather conditions where the ambient temperature is above 0°C, the DL grade "summer" diesel fuel is used. It has a density of 0.86 kg/liter at a nominal temperature of 20°C and has a flash point of 62°C. In winter conditions where the ambient temperature is -30°C and above, the DZ grade "winter" diesel fuel is used. It has a density of 0.84 kg/liter and has a flash point of 40°C. In arctic conditions where the ambient temperature is -50°C and above, the DA grade "arctic" diesel fuel is used. It has a density of 0.83 kg/liter and has a flash point of 35°C. The DA grade is essentially a slightly heavier form of kerosene. If the temperature drops below 0°C during the course of an operation and DZ grade fuel is not immediately available, it was possible to adapt DL grade fuel for winter use in field conditions by adding kerosene.</div><div><br /></div><div>Because the floor fuel tanks had to support cargo, it is of a particularly robust design with thick inner partitions, such that despite having a much smaller capacity than the sponson tanks, the floor tanks weigh 28.5 kg each - more than double the sponson tanks (12.9 kg).</div><div><br /></div><br /><div><br /></div><a href="https://www.blogger.com/null" id="transmission"></a><h3 style="text-align: left;"><span style="font-size: large;">TRANSMISSION</span></h3><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-y6xLf0K8jdJok_dACsO_Y-fulp2qNBYx9t4eGITMeLMD17yDECzhVnyW-89e_ysJiBvqXFALuOSgfVS2JvNL7aDC2-9-lscuNy72CwV7Wcgz9pWThsTm94-8mFgHwnF8Hbk_qH3ODnB6dUpwrqKolnLOZV4dIR_g1ajlYBsoYzVI_bUkQCOf_c4OBA/s8360/gearbox%20view.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="4944" data-original-width="8360" height="378" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-y6xLf0K8jdJok_dACsO_Y-fulp2qNBYx9t4eGITMeLMD17yDECzhVnyW-89e_ysJiBvqXFALuOSgfVS2JvNL7aDC2-9-lscuNy72CwV7Wcgz9pWThsTm94-8mFgHwnF8Hbk_qH3ODnB6dUpwrqKolnLOZV4dIR_g1ajlYBsoYzVI_bUkQCOf_c4OBA/w640-h378/gearbox%20view.png" width="640" /></a></div><div><br /></div><div>The transmission of the MT-LB is housed entirely within the nose of the hull. The transmission is a fully mechanical, manual type, consisting of a synchromesh gearbox with an integral steering mechanism, two stopping brakes, and the final drives. Like the engine compartment, access to the transmission compartment and all the parts within is made easy by a large access panel. Additionally, removing the transmission compartment partition at the commander's station provides access to the rear of the gearbox, where some linkages are located.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEixPXRF7b1dYQ8yJeSs9SQH2VhBrIllXRRd4ANqzmAYHYSo08DZ-Hq3Tms65Y3_auuMx0zxjUC0alpbJttGlCiinbyHOR2RSgmyJSntx5s2KsH47frFuDCz7gdxvTCKtCXNGPFymVFBA8L1NhbDU7PI8tDXs30XXi0gyyYDN1cVzY4f8JQe1LTJKVHdDQ/s1280/stowed%20stuff.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="1280" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEixPXRF7b1dYQ8yJeSs9SQH2VhBrIllXRRd4ANqzmAYHYSo08DZ-Hq3Tms65Y3_auuMx0zxjUC0alpbJttGlCiinbyHOR2RSgmyJSntx5s2KsH47frFuDCz7gdxvTCKtCXNGPFymVFBA8L1NhbDU7PI8tDXs30XXi0gyyYDN1cVzY4f8JQe1LTJKVHdDQ/w400-h300/stowed%20stuff.png" width="400" /></a></div><div><br /></div><div>For the purposes of a prime mover, the use of a manual transmission was not entirely ideal compared to a transmission with a torque converter in terms of ease of driving. With a torque converter, engine stalling becomes much more difficult, and very low speed driving becomes much more practical. For a prime mover, it may be necessary to drive at very low speeds when navigating a difficult path while carrying or towing a heavy load, so a great deal of torque is desirable for confident driving along with protection from stalling, which could be ensured by a torque converter. At the same time, from an economical point of view, the enormous losses in a torque converter at such low speeds makes it highly unattractive to have them in prime movers that are routinely driven this way. Moreover, it could be argued that the high gear reduction for low speed driving is adequately provided by the steering mechanism with the gearbox in 1st gear.</div><div><br /></div><div>The clutch is installed onto the engine as a single unit, as shown in the <a href="https://youtu.be/YrZV31rdIvw">image on the right below</a>, and a cardan shaft connects the clutch output shaft to the gearbox, which then connects to the final drives. The clutch is a multidisc dry friction type with cermet friction pads, with a special friction disc hub designed to provide torsional damping, limiting the vibrations transmitted from the gearbox, prolonging the lifespan of the clutch itself along with the engine under conditions of heavy load. The general design of the clutch is very similar to Soviet truck clutches of the time, which is a trait that is shared with wheeled BTRs. While lighter trucks used a single-disc type, including the dual-engined BTR-60 and BTR-70 series (which had one clutch for each engine), two-disc clutches of this design were used on heavier trucks like the Ural 4320. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwDTMEk5eyFi2axQoOgwVf9_4DtGYjvCdOB6fhp409YnNCOsAcFOwT5T0OpsOcP10Pb9PdUKlJTRRb7ajdhqZgrifjtkGXbCHcY6RLEb4TakDIV4aW4j6bZEdV_ZpgtraVYw1p1m8rUMkw9u98PIrlJ3McP5AMHMlkM2yBzKB3CdG2Wn0j5qEE408Qvg/s3933/clutch%20cross%20section.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3933" data-original-width="2817" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwDTMEk5eyFi2axQoOgwVf9_4DtGYjvCdOB6fhp409YnNCOsAcFOwT5T0OpsOcP10Pb9PdUKlJTRRb7ajdhqZgrifjtkGXbCHcY6RLEb4TakDIV4aW4j6bZEdV_ZpgtraVYw1p1m8rUMkw9u98PIrlJ3McP5AMHMlkM2yBzKB3CdG2Wn0j5qEE408Qvg/w286-h400/clutch%20cross%20section.png" width="286" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEixCAto-Ycdt0Wpy0Z8B7I4QDgJPOVRUCS1QupGTYEJyM-33iOIdL4QMWlVTgmDc5FIMtOl-RugDei4H85LsP1mtxGaxrjFkuRRrKIFZXl_AkWfuTvgdL752vr3aErNTAScE97gvjQEVWtvssLRFy_MdTL4vHDUKlRQG9EnpJwLUaX6yBjKzfdbZqexCw/s779/yamz-238%20engine%20installation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="779" data-original-width="501" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEixCAto-Ycdt0Wpy0Z8B7I4QDgJPOVRUCS1QupGTYEJyM-33iOIdL4QMWlVTgmDc5FIMtOl-RugDei4H85LsP1mtxGaxrjFkuRRrKIFZXl_AkWfuTvgdL752vr3aErNTAScE97gvjQEVWtvssLRFy_MdTL4vHDUKlRQG9EnpJwLUaX6yBjKzfdbZqexCw/w258-h400/yamz-238%20engine%20installation.png" width="258" /></a><br /></div><div><br /></div><div>There is a bevel gear splined to the drive shaft on the clutch, which is part of a power takeoff mechanism integrated ahead of the clutch. The mechanism consists of a mating bevel gear which drives the bilge pump. The bilge pump is the protrusion beneath the clutch in the image on the right above. The blanked-off socket on the left of the clutch was formerly the power takeoff for the winch in the MT-L.</div><div><br /></div><div>The gearbox is a two-shaft mechanical type with a conventional layout, sometimes referred to as an "all-indirect" gearbox layout. The first shaft is the input shaft, and the parallel second shaft is the output shaft. Steering is done using steering levers.</div><div><br /></div><div>Although the use of a mechanical transmission with steering units was a common theme for Soviet tracked vehicles, the MT-LB transmission has a number of peculiarities that should not be overlooked. The main feature of the transmission is its steering mechanism, which provides a discrete steering radius in each gear and is capable of neutral steering. The neutral steering capability is provided by differential action, which is only possible when the gearbox is set to neutral. The steering mechanism consists of left and right units, made integral to the gearbox to minimize weight and the occupied volume, as well as to improve reliability and ease of servicing. </div><div><br /></div><div>Nevertheless, the gearbox was not intrinsically optimized for compact armoured vehicles, as it has a conventional layout with parallel shafts. This makes it somewhat larger and heavier than a planetary gearbox of the same load-bearing capacity. It does not possess intrinsic advantages in efficiency or ease of shifting, nor is its form ideal for integrating the planetary steering mechanisms chosen for this transmission, as they should ideally be packaged with a planetary gearbox in single cylindrical housing, like in the Allison Cross Drive transmission family. Its main advantage is in its simplicity of manufacture and functional similarity to ordinary automotive gearboxes, making it easy for domestic tractor and truck factories to produce, and to do so at a low cost. Its form and function also makes it simple for mechanics familiar with tractor and truck gearboxes to work with it.</div><div><br /></div><div>The gearbox crankcase is made from aluminium. The complete gearbox assembly, complete with gear selector control rods and including the steering units, has a dry weight of 376.6 kg, and measures 124 x 68 x 40 cm (L x W x H). The total volume occupied by the assembly is 0.337 cubic meters. The weight and size of this gearbox are within the expected range for medium duty trucks equipped with engines rated for a similar maximum torque of 800-1,000 Nm, but it is naturally inferior to planetary gearboxes in this regard. For instance, compared to something like the TX100-1 automatic gearbox of the M113, which has a dry weight of just 140 kg, the MT-LB gearbox is very heavy, especially since the clutch is not included in this weight. The MT-LB gearbox is also slightly oversized and overweight relative to conventional automotive gearboxes in the sense that it has fewer gears than the closest equivalent truck gearbox of the same class, but this can be attributed to the built-in steering mechanism.</div><div><br /></div><div>The gearbox was a further development of <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkQ8qerz_2RPySzPYqS7oS8tXYBEv6mVyq8RIkDGIF6t7a5kek4-P44971vJ2Mncy_NnGvxg6e7gCqFugK1BcKCeUdX0fXwOKZYzIbJ3XcP4kw2umKbB1EUTKrahpwajLjFShj86nJNtamuuxcn26THMM8Q0cqriBdUv39fII9B88HTDOCyq6yLn-DWw/s1135/at-l%20transmission.png">the gearbox from the AT-L</a> light artillery prime mover, which is a trait that it shares in common with the GT-T amphibious prime mover, also a product of KhTZ. Kinematically, its design differs in that it was rearranged to accommodate an additional gear pair to provide six forward gears instead of five, and gear synchronization was implemented in all gears except 1st and reverse. These retained a sliding gear mechanism. The addition of a sixth gear mainly served as a means to reach a higher top speed, rather than to narrow down the gear spacing compared to the AT-L. In fact, with a top speed of 41.9 km/h in fifth gear, the gear spacing of the AT-L gearbox was slightly narrower, although with a 135 hp engine and a similar weight to the MT-LB, its automotive performance was not comparable. Nevertheless, when a larger number of gears and a larger gear range is provided, the driver is better able to choose the optimal gear for any given load and terrain conditions to allow the vehicle to travel at an ideal engine speed in terms of fuel economy.</div><div><br /></div><div>The shape of the gearbox, with its side-by-side arrangement of driveshafts, was dictated by its location and the shape of the vehicle hull, in the same way that ordinary car gearboxes use an over-and-under arrangement to minimize width, so as to fit between the driver and front passenger seats. Having a side-by-side arrangement of shafts rather than the conventional over-and-under arrangement, there tends to be an advantage in the reliability, consistency and cooling effect of splash lubrication, since the gears on both shafts are bathed in oil. As such, all gears take part in lifting and splashing the lubricant with their teeth, and the lubricant is immediately passed to the meshing teeth because the gear teeth rotate upwards at the mating point. Moreover, as there is no need to lift the lubricant to a higher level, the gearbox may be less sensitive to low-viscosity oil or a low quality oil that loses viscosity quickly at elevated temperatures. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgl_5OgQylPhH325mFbwEWaJHM_VcS2zY0ixAtFVQ1GJLbLIreR7Kn1KGgIJj6nsWbQWAfJwFIQnCKVpdCBqRR4dTJUUE1lVa-GIt38i3O8uJVXx9Isz4KC5Xn3XnO2PoEP0YYgN-zUMjvlOIdc64ary5y5pEeQV6q_oJy7nv8O2xj83ip61iZbs9Mq4g/s4441/lubrication%20scheme.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2845" data-original-width="4441" height="410" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgl_5OgQylPhH325mFbwEWaJHM_VcS2zY0ixAtFVQ1GJLbLIreR7Kn1KGgIJj6nsWbQWAfJwFIQnCKVpdCBqRR4dTJUUE1lVa-GIt38i3O8uJVXx9Isz4KC5Xn3XnO2PoEP0YYgN-zUMjvlOIdc64ary5y5pEeQV6q_oJy7nv8O2xj83ip61iZbs9Mq4g/w640-h410/lubrication%20scheme.png" width="640" /></a></div><div><br /></div><div>Besides whatever natural advantages that the layout of the gearbox may have afforded it, the lubrication system of the gearbox is highly developed. It is a dry sump type, with combined splash and forced lubrication. Splash lubrication is used for the gears themselves, while forced lubrication is provided for the bearings of the input bevel gear, the bearings of the planetary steering units, the bearings of the 3rd to 6th gears, the synchronizer cones and selector couplings, and the bearings of the steering input shaft. The bearings and selector sleeves for the reverse, 1st and 2nd gears are lubricated only by the splashing oil of their gears.</div><div><br /></div><div>The 3rd and 4th gear selector, and the 5th and 6th gear selector, are both lubricated via their selector forks, which are connected to the pressurized lubrication circuit. To lubricate the selector fork groove on the outer sleeve, the synchronizer cone, and the selector hub within the synchronizer cone, the hollow selector fork has two channels, one which squirts oil into the groove and another that squirts oil onto the synchronizer. Some of the oil squirted onto the synchronizer passes through holes on its body, where it can reach the selector hubs. Both driveshafts in the gearbox are also hollow, and are connected to the lubrication circuit. Oil passes into the hollow shafts and permeate through the bearings of the gears via small channels, and the output shaft has the additional responsibility of connecting to the steering units on its ends. This forms an oil path leading to the bearings of the sun gear, and to the planet gears via the hollow planet carrier arms, thus providing full bearing lubrication of both planetary steering units, which is otherwise difficult to achieve as the bearings are enveloped by the ring gear and are therefore largely inaccessible to oil splash from the sun gear.</div><div><br /></div><div>In the gearbox, oil circulates by being drawn from the sump through two filter intakes and then returned by flowing out from the various lubrication spray points and from a return line connected to the oil reservoir. Compared to ordinary car, truck and tractor gearboxes, a dry sump system with forced lubrication meant that the lubricant was kept constantly cooled and filtered, which is normally absent in rudimentary splash lubrication systems. Filtration and cooling of the lubricant prevents overheating of both the lubricant and the gears, and the removal of contaminants (dirt, dust, fine metal particles, etc) has a strongly positive effect on the lifespan of the bearings and gears.</div><div><br /></div><div>Moreover, the gearbox crankcase is partitioned into four sections by cast internal walls. This can be seen in the <a href="https://vezdehodmarket.ru/catalog/4114-remont-uzlov-i-agregatov-/item-4115-remont-glavnoy-peredachi-mt-lb-s-ispytaniem-na-stende.html">photo below</a>. These partitions mainly serve as intallation points for the bearings of the driveshafts, but they also serve as a means of limiting the difference in the oil bath level when the vehicle is on a side slope. Without partitions, a side tilt causes oil to pool up at one end of the gearbox, potentially leaving some gears unlubricated unless the issue is addressed by having a high oil level (impractical due to the dry sump), which in turn introduces the issue of high churning losses.</div><div><br /></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJLJFiNUShurrnNwE44klJ_6NdyaodclNiaP8uzzYayywZ4MhWITfWyFI_KAU2V8ImGtpoBv-5D3pFay9EnPrNvrAAVlxyrMTyaKKLb-s7UOgBHcnnXqkjoLEHuJH_XC49u9A8Cuku-OYo-DChYc11c4HwA7lUiKuNY-9Usl0rA2ohQEplEDEWL7TBxQ/s644/666200447_.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="382" data-original-width="644" height="380" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJLJFiNUShurrnNwE44klJ_6NdyaodclNiaP8uzzYayywZ4MhWITfWyFI_KAU2V8ImGtpoBv-5D3pFay9EnPrNvrAAVlxyrMTyaKKLb-s7UOgBHcnnXqkjoLEHuJH_XC49u9A8Cuku-OYo-DChYc11c4HwA7lUiKuNY-9Usl0rA2ohQEplEDEWL7TBxQ/w640-h380/666200447_.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The propeller shaft from the engine transfers power to the gearbox via a spiral bevel gear with a small step-up ratio of 0.905. A pair of opposed tapered roller bearings are used for the prop shaft to ensure the proper alignment of the bevel gear and to handle the thrust load that arises from the spiral cut of the bevel gear, although the load is rather limited due to the small spiral angle of the gears. This type of bearing arrangement is normally used for car differentials because the alignment of the prop shaft and the connected housing is not structurally guaranteed due to flexing of the shaft, the gearbox, or both at the same time, since the differential moves with the wheels relative to the chassis on a suspension. This is not a major factor for the MT-LB because all parts of the drivetrain are installed to the hull on rigid mounts, so no major flexing is anticipated.</div><div><br /></div><div>The gearbox has six gear pairs to provide six forward gear settings and one reverse gear setting; the 1st gear setting is not provided by a reduction gear pair between the drive and output shafts. Rather, 1st gear is achieved by disengaging the output shaft, allowing power to flow to the output shafts only via the steering input. As there are seven gear settings, there are seven gear engagement mechanisms, four of which are selectors with cone synchronizers for the 3rd to 6th gear pairs - the 1st gear, 2nd gear and reverse gear settings are only in constant mesh, and are engaged by sliding gear selectors. This was to simplify the gearbox without major negative consequences, as synchronization is not as important when shifting to the 1st, 2nd or reverse gears from a standstill since it is assumed that the clutch has been disengaged for some time before setting off, and there is not much of a speed difference between the two shafts. Many older cars with a manual gearbox generally lacked a synchronizer for the 1st and reverse gears for the same reason. It is a particularly minor issue for the MT-LB because when in neutral, the output shaft is rotating idly due to the steering input, so shifting from a standstill is intrinsically easier. However, double declutching would still be needed needed when downshifting to 2nd gear, which is an inconvenience. </div><div><br /></div><div>The MT-LB is normally started in 2nd gear. The 1st gear is skipped except when carrying out tasks that require an enormous amount of drawbar pull, such as overcoming difficult obstacles, recovering a stuck vehicle, bulldozing the earth, or towing a heavy load up a steep incline. This practice was commonplace even for vehicles that were much heavier than the MT-LB, operating on a much lower power-to-weight ratio.</div><div><br /></div><div><div>The output shaft is shown in the drawing below. As mentioned earlier, the gearbox houses two integral planetary steering mechanisms (right and left) within its aluminium crankcase. The ends of the output shaft serve as the ring gears of the steering units, the end of the output axle is the planet carrier, and the sun gear is driven by the steering input. The steering input is a spur gear pair between the sun gear and a pinion connected to the input shaft by a steering clutch and brake unit. The input is closed by default. If the steering clutch and brake unit is activated, the steering input is kinematically disconnected from the input shaft and braked. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrVkWWYbcL4RL04RrgstsplX5F55-aqlEyFRUCsZS8zIAISG_b_y5gpGMdkae94OeLfjtcCvKOXAd-K8H2ebbUYEYdZMaeVUvfWaXcpQt6Q6nEncN_MTdAwkPEVhU2_6_pvw7TI-ug4StddcpRmiBeTONWfjDBQauL4rWPSJE0lFIQo2OhzIqY1HII0Q/s4441/gearbox%20output%20shaft.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2333" data-original-width="4441" height="336" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrVkWWYbcL4RL04RrgstsplX5F55-aqlEyFRUCsZS8zIAISG_b_y5gpGMdkae94OeLfjtcCvKOXAd-K8H2ebbUYEYdZMaeVUvfWaXcpQt6Q6nEncN_MTdAwkPEVhU2_6_pvw7TI-ug4StddcpRmiBeTONWfjDBQauL4rWPSJE0lFIQo2OhzIqY1HII0Q/w640-h336/gearbox%20output%20shaft.png" width="640" /></a></div></div><div><br /></div><div><div>The input shaft is shown in the drawing below. Steering clutch and brake units are attached to the ends of the input shaft of the gearbox, corresponding to the left and right planetary steering mechanisms. These units are external to the gearbox and can be removed for clutch or brake maintenance without needing to open the gearbox crankcase. The steering clutch is a dry multi-disc type consisting of four steel clutch discs on steel hubs, and the steering brake is a band brake.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgteILLDQKW6AeHYAfKbLxXHor9ocRT8Oo1EIiHJO6VnJYXRvXLOANgvqpdnLNQfevAx-b75hStzR-MZ2p3oN46LTAGtMbZseGYJFAZt-Nh9WrMIroagLFteLGUM5GVbAMOeJbQbiPLedC6obdapppXzQOQeDwZnwA_7FCuZ3GG6qi7sCFB_5KO7_hJtw/s4544/gearbox%20input%20shaft.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2080" data-original-width="4544" height="292" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgteILLDQKW6AeHYAfKbLxXHor9ocRT8Oo1EIiHJO6VnJYXRvXLOANgvqpdnLNQfevAx-b75hStzR-MZ2p3oN46LTAGtMbZseGYJFAZt-Nh9WrMIroagLFteLGUM5GVbAMOeJbQbiPLedC6obdapppXzQOQeDwZnwA_7FCuZ3GG6qi7sCFB_5KO7_hJtw/w640-h292/gearbox%20input%20shaft.png" width="640" /></a></div><div><br /></div></div><div><br /></div><div>The synchronizers are of the so-called "inertial" type, the same as conventional synchronizers. The synchronizer cone is a two-ended cone clutch which synchronizes the speed of a gear to its shaft by friction between the cone surface and a receptable surface on the gear. An example of this type of synchronizer is depicted in drawing (а) on the left below. The selector hub (1), which is splined to the shaft on its inner side, is responsible for engaging the gear by meshing with its teeth. The hub is controlled by the selector sleeve, which rotates together with the synchronizer (2) and connects to the selector hub via rods (4) passing through holes in the synchronizer body. Each hole is wide in the middle and narrow at the ends. When the gear and shaft speeds are not properly synchronized, the friction force from the synchronizer cone sliding against the gear creates a torque, pressing the cone against the rod, jamming it against the shoulder between the wide and narrow regions. This is depicted in drawing (б). Once the speeds are synchronized, the frictional moment drops sharply and the rod is able to slide over the shoulder and into the narrow end, bringing the selector hub along with it and thus mating it to the gear. The holes in the synchronizer body can be seen in the image on the right below.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDlbeD5Je6eqVId_OXuIgwwpMwPI9vLR8_Jy3i19EdhNzKiMdpEfKuKgY6B4Xwohse0lEtFsHKvcPn9Vb5IcGr-9Qetyd5rOTI4rD7dWSxJxpQ4oT-j-VStyqyVylfcjXlkbeBo9FXcdCLQXGKJ-5zkMWNOmZMMOXVzeXyiFgVkVeBJbsCVMd8uh7YVA/s2289/synchro.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1798" data-original-width="2289" height="251" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDlbeD5Je6eqVId_OXuIgwwpMwPI9vLR8_Jy3i19EdhNzKiMdpEfKuKgY6B4Xwohse0lEtFsHKvcPn9Vb5IcGr-9Qetyd5rOTI4rD7dWSxJxpQ4oT-j-VStyqyVylfcjXlkbeBo9FXcdCLQXGKJ-5zkMWNOmZMMOXVzeXyiFgVkVeBJbsCVMd8uh7YVA/w320-h251/synchro.png" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEijKpZ4Vk5xzLM31RWT51FtoANQNXl6rLlOV_JSIQfHLoPDTIQuv5VyBmsLkYqjAoFJC1HE-nw6aqWFgQY0aUV3os8oTISyzxLJUd3xYWY1PYy7CwVVnha23rdVmC6ABYoFxdHEk2S0pR-av8M1KuEb9fXNNraQ2ChgB3q9bmU6F4JIAEUpHCY3m7LJcw/s500/DMzhgDIyDHRaGdz8.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="238" data-original-width="500" height="190" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEijKpZ4Vk5xzLM31RWT51FtoANQNXl6rLlOV_JSIQfHLoPDTIQuv5VyBmsLkYqjAoFJC1HE-nw6aqWFgQY0aUV3os8oTISyzxLJUd3xYWY1PYy7CwVVnha23rdVmC6ABYoFxdHEk2S0pR-av8M1KuEb9fXNNraQ2ChgB3q9bmU6F4JIAEUpHCY3m7LJcw/w400-h190/DMzhgDIyDHRaGdz8.jpg" width="400" /></a><br /></div><div><br /></div><div><br /></div><div><div>Power can flow through the gearbox in two paths. The main path is from the input bevel gear to the input shaft and then to the output shaft through one of the selected gears, and then to the output axles via the ring gears of the steering units. The second path is the steering input, which is the path from the input shaft to the sun gears of the steering units. In reverse and in all forward gears from 2nd gear to 6th gear, power flows from the engine to the final drives through both paths. In 1st gear, power flows from the engine to the final drives in one stream only; from the steering input. </div><div><br /></div><div><div><div>When both power streams arrive at the planetary set, both will be rotating in the same direction. The sun gear, rotating at a reduced rate relative to the input shaft due to the step-down ratio of its steering input gear, and the ring gear, rotating at an increased rate relative to the input shaft due to the step-up ratio of the 2nd to 6th gears. As both the sun gear and ring gear rotate in the same direction, speed summation occurs, and the planet carrier acquires a larger speed. Due to the high reduction ratio obtained from the two reducing gear sets in the steering unit, the maximum speed possible from the steering inputs alone is low, only 4 km/h at an engine speed of 2,100 RPM.</div><div><br /></div><div>In reverse, the power flow is almost the same as in the 2nd to 6th gears, with the exception that the ring gear is turning in the opposite direction to the sun gear. As such, speed subtraction occurs instead of speed summation.</div></div><div><br /></div></div><div><br /></div><div>The kinematic scheme below allows the power flow within the gearbox to be visualized clearly. Note that, when compared to a scheme of the <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEivkBAlC30szNDDiBo_cqjtvxltZ17xHJa_g22xcFL6pHwfeJQFxWK7BGPJ-ELlKgJQINXU6_2BhJmRt9dd4Le2dnOL97dHxTutOkOwN4cP-PzULykGGpbtmC1lmaQCI3iB6atJXpyJZ3m8T7a3krg8aK9PG8fMlF7cxHkNVyzcH-fbbj6goJf_KPl5zA/s1367/atl%20steering%20mechanism.png">AT-L gearbox</a>, the similarity is obvious. </div><div><br /></div><div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjha83aBVujGsqxL7rxjKtTr6JSVgmmozxnhqnQJAvfLRnWba3xEiBIK_gxDoOrLSHAqYvIeGdC224MxnVWzuRq976f8lNzJc3elkAzOZVKhLU_dbJm1Yr_gLfHNEvZYdyRA_cnG6n9ZGBun8pAGm266QwnSHI9dKNhpH80V0XNU45EHAvMWAas96MdRw/s4469/transmission.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3171" data-original-width="4469" height="454" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjha83aBVujGsqxL7rxjKtTr6JSVgmmozxnhqnQJAvfLRnWba3xEiBIK_gxDoOrLSHAqYvIeGdC224MxnVWzuRq976f8lNzJc3elkAzOZVKhLU_dbJm1Yr_gLfHNEvZYdyRA_cnG6n9ZGBun8pAGm266QwnSHI9dKNhpH80V0XNU45EHAvMWAas96MdRw/w640-h454/transmission.png" width="640" /></a></div><div><div><br /></div><div>Note that the 1st gear is obtained by firmly locking the output shaft to the crankcase using the selector sleeve. This method of obtaining a 1st gear setting has a few design benefits, the main one being that it was simply the most convenient approach, providing both the necessary reduction using the existing steering units and the ability to steer by declutching and then braking one of the steering units, followed by braking the axle to perform a clutch-brake turn. A secondary advantage is that it reduces the size of the gearbox, as implementing a 1st gear setting with the same high reduction via a simple meshing gear pair on the drive input would otherwise require a prohibitively large driven gear on the output shaft, or a layshaft to provide compound gearing. Additionally, it reduces the losses from having an additional gear pair in constant mesh on the driveshafts, helping to offset the losses to the steering input gears and planetary steering units.</div></div></div></div><div><br /></div><div>In neutral, the output axles do not receive any power. On each side, the steering input continues to supply power to the sun gear of the steering unit, but the power is simply delivered through the planets and to the ring gear, causing the output shaft to rotate idly. The output axles, connected to the planet carrier, receive no power because the planets possess a torque but no translational movement. To induce translational movement and thereby rotate the planet carrier, there must be a tangential force acting directly upon the axis of the planets. </div><div><br /></div><div>One of the notable traits of the steering unit is that there is only a single planet. This allowed the designers to bypass the issues of load sharing which arise if the product is not built to the high demands on the gear machining tolerances, absence of manufacturing errors, and high demands on the precision of the fit. The unequal loading and vibration issues that arise are most intense in spur planetary gears, although tight machining tolerances are also easiest to achieve with spur gears. By having only one planet in the system, the design forfeits the load-distributing advantages of a conventional planetary gear set, but greatly simplifies the production of the gearbox, and allows the maximum mechanical efficiency to be achieved. </div><div><br /></div><div>The available gear speeds are as follows.</div><div><div> <table border="1"><tbody><tr><td style="text-align: center;"><b> Gear </b></td><td style="text-align: center;"><b>Rated Speed (km/h)</b></td></tr><tr><td style="text-align: center;"><span style="font-size: small;">1</span></td><td style="text-align: center;"><span style="font-size: small;">4</span></td></tr><tr><td style="text-align: center;"><span style="font-size: small;">2</span></td><td style="text-align: center;"><span style="font-size: small;">12</span></td></tr><tr><td style="text-align: center;"><span style="font-size: small;">3</span></td><td style="text-align: center;">20.7</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">4</span></td><td style="text-align: center;">34.1</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">5</span></td><td style="text-align: center;">46.8</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">6</span></td><td style="text-align: center;">61.5</td></tr><tr><td style="text-align: center;">R</td><td style="text-align: center;">6.3</td></tr></tbody></table></div></div><div><br /></div><div>The gear ratios available from the gearbox are listed below. Ratio figures are taken from "Analysis of curvilinear motion of tracked vehicles with electromechanical dual-flux transmissions" except for the 1st and reverse gears, which were calculated by the author. All overall gear ratios were calculated. Note that the ratios given for gears 4 to 6 cannot be reasonably resolved into fractions, as they would imply that an impossible number of gear teeth are present. For the purposes of this article, these figures are accepted as they come from a credible source, but they should be considered purely nominal.</div><div><br /></div><div><div>The indicated gear ratio is the ratio of the single relevant gear pair alone, without including the reduction at the steering unit, and without the summing ratio of the steering unit. The indicated overall gear ratio is calculated by including all gearing elements from the bevel gear to the final drive, and any summing or subtracting action in the steering unit. The overall gear ratio is calculated by taking the bevel input ratio of 0.905, the ratio of the selected gear in the gearbox, the summation ratio in the steering unit, and the reduction ratio of the final drive. <br /> <table border="1"><tbody><tr><td style="text-align: center;"><b> Gear </b></td><td style="text-align: center;"><b>Gear ratio</b></td><td style="text-align: center;"><b>Overall gear ratio</b></td></tr><tr><td style="text-align: center;"><span style="font-size: small;">1</span></td><td style="text-align: center;">9.6 </td><td style="text-align: center;">52.128</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">2</span></td><td style="text-align: center;">3.125</td><td style="text-align: center;">16.969</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">3</span></td><td style="text-align: center;">1.5</td><td style="text-align: center;">8.145</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">4</span></td><td style="text-align: center;">0.833</td><td style="text-align: center;">4.523</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">5</span></td><td style="text-align: center;">0.585</td><td style="text-align: center;">3.176</td></tr><tr><td style="text-align: center;">6</td><td style="text-align: center;">0.435</td><td style="text-align: center;">2.362</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">R</span></td><td style="text-align: center;">2.444</td><td style="text-align: center;">33.4</td></tr></tbody></table></div><div><br /></div></div><div><div>The given gear ratios are applicable to the first power stream for all gears except 1st gear, which receives power only from the steering units. The high gear ratio of 9.6 was achieved by compound gearing, with the first reduction applied by the steering input, and the second reduction applied in the steering unit itself. When the 1st gear is engaged, the output shaft is locked in place, turning the ring gear of each planetary steering unit into a reactionary. The only power flowing to the output shafts is from the steering inputs. The first reduction occurs when the input shaft drives the sun gear at a fixed ratio of around 3.0-3.1 (no firm data available). The sun gear rotates the planets, which crawl around the static ring gear, driving the planet carrier at a reduction of around 3.1-3.2. A compound reduction of 9.6 is thereby obtained. </div></div><div><br /></div><div>It is interesting to note that gears 2-5 all have a smaller reduction than the same gears in the gearbox of the AT-L, on top of having an additional 6th gear. This is indicative of the leeway granted by the much better power to weight ratio of the MT-LB, but considering the large difference in torque output between these two vehicles, it also shows that the MT-LB is capable of much higher drawbar pull. </div><div><br /></div><div>The design of the gearbox facilitated smaller and lighter gears in two ways: by utilizing the bevel gear input to create an overdrive, which slightly reduced the torque flowing through the gears, and by having very modest gear ratios, with a maximum reduction of 3.125 in 2nd gear. As shown in the gear table, gears 4, 5 and 6 are all overdrive gears with a large step-up ratio, completely unlike the vast majority of tracked vehicle gearboxes, particularly the gearboxes of tanks, which may not feature an overdrive gear at all. In fact, the ratios implemented in the MT-LB gearbox are similar to those of a 6-speed gearbox for a sports car, aside from the large spacing between the 1st and 2nd gears. Rather than implementing large gear reductions in the gearbox itself, which would have highly stressed drivetrain components downstream of the gear pairs involved, the necessary gear reductions were accomplished at the final drives, which have a high reduction ratio of 6 for this reason.</div><div><br /></div><div>This meant that even the maximum tangential force transmitted through the most heavily loaded gears in the gearbox and steering units was very mild. The gears and drive shafts could therefore be lightened, reducing the rotating mass and the overall gearbox weight. The lightening of the gears and shafts also meant that the moment of inertia that the gear selectors and synchronizers must overcome to engage a gear is reduced, thus decreasing the wear and tear experienced by the shifting mechanisms. Additionally, because the gearbox carries out minimal torque multiplication, the torque received at the final drives is small, allowing the gears of the final drives themselves to be reduced in bulk and weight (although the axles must still be very strong to withstand the torsional load). This design approach was not new in the Soviet Union by the time the MT-LB was designed, but its successful application can be credited with the light weight of the transmission, despite its high drawbar pull.</div><div><br /></div><div>The overdrive bevel gear in particular was not traditional practice in designing a bevel gear connection between a longitudinally mounted engine and a perpendicular gearbox. In the Christie tanks of the 1930's, which were notable for having this type of engine-gearbox layout (and likely being the first to feature it), the bevel gear input was used as a reduction gear. This persisted in various military tracked vehicles, most notably in tanks derived from, or influenced by Christie designs, including the Soviet BT tank series, the T-34, and various British cruiser tanks, up to the Centurion, although it was by no means limited to this loose lineage. A reduction bevel gear input can also be found in the gearbox of the KV-1, and in at least some of the experimental would-be successors to the KV-1. Additionally, the engine-gearbox layout itself was relatively uncommon. The conventional automotive practice of having a gearbox in series with the engine was dominant, being the layout used in virtually all tractors as well as the majority of tanks built in the first half of the 20th century. In such a layout, the change in the rotational direction was accomplished downstream of the gearbox, either at the crown gear of a differential, or simply at an axle, if the vehicle used clutch-brake steering.</div><div><br /></div><div>The total gearing range of the gearbox is 22. At the same time, due to the method used to achieve the steep reduction of the 1st gear, the speed range ratio (maximum shaft speed divided by minimum shaft speed) of any given power shaft within the gearbox is low, especially relative to the gearing range.</div><div><br /></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="steering"></a><h3 style="text-align: left;"><span style="font-size: large;">STEERING SYSTEM</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiX0_1o6wEoHXhsN5TZQePfT64AA9dUHEE_aNgJkDx54v2ONyL80l2aAqLv1RaAk_zoUMObpHmhxLEFEIvxnuHPcGDVoKmBd6L6PoVVfDy1Bh2TyLqY18QtqUue0kl84lhJ5eMhzN4vojYV6VbkwUWI3zs_9izoaMNVkJSk2622q74lxAigMqraOIQ9PA/s2271/steering%20mechanism%20top.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1415" data-original-width="2271" height="249" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiX0_1o6wEoHXhsN5TZQePfT64AA9dUHEE_aNgJkDx54v2ONyL80l2aAqLv1RaAk_zoUMObpHmhxLEFEIvxnuHPcGDVoKmBd6L6PoVVfDy1Bh2TyLqY18QtqUue0kl84lhJ5eMhzN4vojYV6VbkwUWI3zs_9izoaMNVkJSk2622q74lxAigMqraOIQ9PA/w400-h249/steering%20mechanism%20top.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGZPjU4SAwFSLZcSSiqsig-rDuE_bJsz9lTU-TtlzY7rSe2xvsIPvsKh38zJyyImBr_qtrnwro2V6EhY-oYhlYxsLDShyZzjEWxhipQheEX2HdE6AacP7ovRSCxiI9Bw9mG7_qgxqpwdJYVuz5pTTWJm42qpb2DnUx1eMyO65tS7L8FFoJ-tO3BU351w/s2264/steering%20mechanism%20profile.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1236" data-original-width="2264" height="219" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGZPjU4SAwFSLZcSSiqsig-rDuE_bJsz9lTU-TtlzY7rSe2xvsIPvsKh38zJyyImBr_qtrnwro2V6EhY-oYhlYxsLDShyZzjEWxhipQheEX2HdE6AacP7ovRSCxiI9Bw9mG7_qgxqpwdJYVuz5pTTWJm42qpb2DnUx1eMyO65tS7L8FFoJ-tO3BU351w/w400-h219/steering%20mechanism%20profile.png" width="400" /></a></div><br /><div><br /></div><div>Although the weight of the MT-LB was light enough for a simple clutch-brake steering system like in the PT-76 to be viable in terms of driver fatigue, this steering system was no longer modern enough to meet demands in mobility. The main issues were that the braking losses would be high, too much speed is lost when making a turn, steering lacked precision, and a transmission with regenerative steering is essential for a vehicle intended for high speed travel in difficult terrain. Moreover, clutch-brake steering can be problematic when driving on terrain with low surface integrity, as when one track is de-clutched and braked, all of the torque from the engine is transmitted to the running track so that it outputs all of the tractive force. On swampy ground or snow, this greatly increases the risk of losing traction because the terrain cannot support high tractive force, so steering in such conditions can be ineffective, particularly in lower gears where the torque output is already high.</div><div><br /></div><div><br /></div><div>When the steering levers are in the initial or '0' position, the steering clutches are engaged, and the steering brakes are disengaged. In this condition, the steering inputs convey power to the steering units. In the '1' position, the steering clutch is disengaged and the steering brake is engaged. In the '2' position, the steering clutch remains disengaged, but the steering brake is disengaged, and then the stopping brake is engaged. For this behaviour to be possible, the steering clutches and brakes are regulated by a control mechanism, one for each set of steering inputs. When a steering lever is pulled back, it does not directly tighten the brake bands or pull the clutch plate, but rather, pushes upon camming surfaces under spring tension to manipulate the cranks for the clutch and brake in discrete steps. Due to the small forces involved in controlling these modules, which in turn is due to the light weight of the MT-LB, the steering levers require little effort despite the lack of power assist.</div><div><br /></div><div>When a steering lever is being pulled to the '1' position, there is an intermediate position where the steering clutch is disengaged abruptly via the control mechanism, perceivable as a loss of spring resistance on the lever, but the steering brake band has not begun tightening. When pulled further, the steering brake is tightened by the force on the steering lever, and the lever enters position '1' when the brake is fully tightened, which is also accompanied by a loss of spring resistance on the lever. By releasing the clutch abruptly, the control mechanism prevents the clutch from slipping. This greatly extends the lifespan of the steering clutches, particularly in the hands of novice drivers. Owing to the use of a steel-on-steel clutch, even a multi-disc type, this measure to prolong the clutch lifespan was probably more important than it otherwise would be, as thin steel discs warp more readily under the heat of slippage. After the clutch is disengaged, the clutch engagement crank is unaffected by further motion of the steering lever toward the '1' and '2' positions.</div><div><br /></div><div>When the clutch is released, the steering input ceases to transmit power, but without the application of the steering brake, the sun gear of the steering unit does not turn into a reactionary. As a result, power flow to the output axle stops, as the planetary set becomes incomplete. The power input from the ring gear only drives the free sun gear idly via the planets. This therefore de-clutches the output axle, and the track becomes unpowered. By de-clutching one track, it is possible to make the vehicle turn in a free radius. Because the track is disengaged abruptly, there is an abrupt transition into a turn, but once in the turn, the track slows down only at a gentle rate (affected by terrain resistance), so the MT-LB can be steered for small course corrections this way, even while towing a heavy load since there is no loss of engine power as the full torque of the engine is simply transmitted to the remaining powered track.</div><div><br /></div><div>When the steering brake is fully tightened as the steering lever enters position '1', the sun gear is converted from a power input into a reactionary member. Speed summation no longer occurs in the planetary steering unit. Driven only by the ring gear, the rotational rate of the planet carrier is reduced, and the speed of the track is thereby reduced. At the rated engine speed of 2,100 RPM, this is equivalent to a loss of 4 km/h at the track. The speed difference between the two tracks initiates a turn. At low gears, the speed difference is the highest due to the large contribution of the steering input to the total axle speed, resulting in the tightest turn radius. For instance, at 2nd gear, cutting off the steering input results in a 33.3% speed reduction, whereas at 6th gear, cutting off the steering input results in only a 6.5% speed reduction. In reverse, the steering levers work in reverse. When pulling the right tiller, the right steering unit increases the reverse speed of the right track, causing the vehicle to turn to the left, and vice versa. </div><div><br /></div><div>The track speeds at the rated engine speed of 2,100 RPM in various gears are tabulated below.</div><div><div><br /> <table border="1"><tbody><tr><td style="text-align: center;"><b> Gear </b></td><td style="text-align: center;"><b>Rated track speed (km/h)</b></td><td style="text-align: center;"><b>Rated track speed without steering input (km/h)</b></td></tr><tr><td style="text-align: center;"><span style="font-size: small;">1</span></td><td style="text-align: center;"><span style="font-size: small;">4</span></td><td style="text-align: center;">-</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">2</span></td><td style="text-align: center;">12</td><td style="text-align: center;">8</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">3</span></td><td style="text-align: center;">20.7</td><td style="text-align: center;">16.7</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">4</span></td><td style="text-align: center;">34.1</td><td style="text-align: center;">30.1</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">5</span></td><td style="text-align: center;">46.8</td><td style="text-align: center;">42.8</td></tr><tr><td style="text-align: center;">6</td><td style="text-align: center;">61.5</td><td style="text-align: center;">57.5</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">R</span></td><td style="text-align: center;"><span style="font-size: small;">6.3<br /></span></td><td style="text-align: center;">10.3</td></tr></tbody></table></div><div><br /></div><div><br /></div></div><div>The turn radii at various gears is tabulated below. Although the steering mechanism technically provides fixed turn radii, in practice, drivers must note that due to track skid when off-roading (especially at high speeds), the turn radius may not directly correspond to the theoretical figure, normally exceeding it by some amount but never falling below it. As such, fixed turn radii figures, not just for the MT-LB but for all vehicles, tend to be described as minimums rather than being definitive figures. </div><div><div><div><br /> <table border="1"><tbody><tr><td style="text-align: center;"><b> Gear </b></td><td style="text-align: center;"><b>Turn Radius (meters)</b></td></tr><tr><td style="text-align: center;"><span style="font-size: small;">N</span></td><td style="text-align: center;"><span style="font-size: small;">1.25</span></td></tr><tr><td style="text-align: center;"><span style="font-size: small;">1</span></td><td style="text-align: center;"><span style="font-size: small;">2.5</span></td></tr><tr><td style="text-align: center;"><span style="font-size: small;">2</span></td><td style="text-align: center;">7.5</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">3</span></td><td style="text-align: center;">13</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">4</span></td><td style="text-align: center;">21.35</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">5</span></td><td style="text-align: center;">29.3</td></tr><tr><td style="text-align: center;">6</td><td style="text-align: center;">38.6</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">R</span></td><td style="text-align: center;"><span style="font-size: small;">3.9</span></td></tr></tbody></table><br /></div><div><br /></div><div><div>When a steering lever is pulled to the '2' position, the steering brake is released by a reversal crank in the control mechanism and the lever begins to tighten the stopping brake. The clutch remains disengaged. Due to the force needed to stop the vehicle without power-assisted brakes, the pulling distance for the levers to reach the '2' position is quite long, providing the necessary mechanical advantage to tighten the brake bands. It is possible to carry out a clutch-brake turn in any gear. The turn radius of a clutch-brake turn is the width between the two tracks, or 2.5 meters.</div><div><br /></div><div>With this set of controls, the steering mechanism is able to provide a discrete turn radius in each gear and the supplementary capability of a clutch-brake turn in all gears. </div><div><br /></div><div><div>It is interesting to note that, with the slow-down of the tracks when the steering levers are in the '1' position, the transmission effectively has a low-range setting, nominally doubling the number of gear settings available to the vehicle. From the perspective of automotive design, having high and low ranges was not strictly necessary, because six forward gears is sufficient for virtually all tasks that the vehicle could be expected to perform. In practice, however, the low-range mode can be used to temporarily boost traction for short periods when overcoming a serious obstacle in low gear, and it is particularly useful in this application because the relative increase in torque is significant, unlike at the higher gears where the speed reduction is relatively small and the relative increase in torque is also correspondingly smaller. One notable application for this feature is to obtain additional torque while climbing a steep and uneven hill without downshifting, which must be avoided to prevent the engine from stalling. Additional torque may be needed to overcome a rock while climbing the hill, or simply to continue climbing if the gradient of the hill increases towards its peak. </div><div><br /></div><div>It is also worth noting that when driving this way at low gears, steering can be accomplished by either returning one steering lever to the '0' position, or pulling it further back to the '2' position to perform a clutch-brake steer. When moving across rough terrain and towing a heavy load in this condition, clutch-brake steering is preferable because the body of the vehicle acts as a second class lever, with the locked track acting as the fulcrum, the load being at the towing hitch between the two tracks, and the effort applied through the running track, which is conveying the full torque from the engine. The drawbar pull is approximately doubled in this way, helping a towed gun or trailer overcome ruts, ride over a bump while being towed uphill, or surmount some other obstacle, which generally tend to be much more challenging for a wheeled carriage than a tracked vehicle.</div></div><div><div><br /></div></div></div><div><br /></div><div>Unlike some differential steering systems, the transmission provides stable rectilinear motion, which is to say that it does not induce a self-steering effect when the two tracks are on surfaces with different traction characteristics. That is, differences in the moment of resistance between the left and right axles do not have any influence whatsoever on the power flow in the transmission. This characteristic is shared with the steering system of the Panther, and is due to the fact that in rectilinear motion, the transmission has only one degree of freedom, although the manner in which this was achieved is completely different. With only one degree of freedom, it was possible to avoid the self-steering effect and the loss of traction on poor surfaces. Examples of steering mechanisms with two degrees of freedom during rectilinear motion include the Merritt-Brown triple differential system of the Centurion and the Allison cross drive series, used in a wide range of tracked vehicles, including the M113. Because of this, they provide unstable rectilinear motion, </div></div></div><div><br /></div><div><br /></div><div><div><br /></div><div>With one degree of freedom, it is impossible for the speed of either track to differ from their geared speeds, since it is impossible for the ring or sun gears of the planetary sets to change in rotational rate, as they are directly geared to the engine via fixed gears. Given that the ring and sun gears rotate at a fixed rate relative to the engine, the planets cannot rotate at any speed other than the speed imparted by the ring and sun gears (as doing so would require the teeth of the planets to intersect through the teeth of the ring and sun gears). The orbiting rate of the planets is thereby directly proportional to the ring and sun gears, and thus, the rotating rate of the output shaft is also fixed. This allows torque to be split unevenly between the two tracks. This is due to the fact that the conservation of energy also means that engine power - which is defined as energy transferred over time - is conserved. When both tracks have a speed that is fixed by the geartrain, the rotational rate is effectively constant, so the only pathway for the power to flow between the two tracks is via torque.</div><div><br /></div><div>This ensures that if, for instance, the left track drives over a patch of ice while the right track remains on hard soil, no change in the speed of the left track occurs. In fact, due to the fixed gearing that connects the track to the engine, the track speed will not change regardless of how much or how little traction is supported by the surface, which can be very small in the case of ice, particularly if the track has already slipped and is applying traction by sliding friction rather than static friction or shear force (via grousers penetrating the ice). Moreover, all the torque available from the engine is transmitted to the ground via the track with traction, so no power is wasted. This is analogous to a car with a fixed differential. For the sake of an example: if, for instance, the engine produced 100 Nm and both axles have a direct gearing to convey 100 Nm, but the maximum reaction torque that may arise is also 100 Nm, in keeping with Newton's third law of motion. If both tracks push against the same sturdy surface, the tracks will obtain equal reaction torques, amounting to 50 Nm each and adding up to 100 Nm. Because both tracks convey a torque of 100 Nm, even if one track has lost traction completely, as long as the other has not, the track with traction will receive a reaction torque of 100 Nm and the vehicle will be propelled by the same power.</div><div><br /></div><div><br /></div><div>In steering mechanisms with two degrees of freedom, such as the Merritt-Brown and Cross Drive systems, there is a steering input which takes the form of a separate, independent differential drive mechanism parallel to the gearbox, connected to planetary steering units that are functionally identical to the MT-LB steering units. The steering input links the two planetary steering units, driving the sun gear while the gearbox output drives the ring gear, just like in the MT-LB. When the steering mechanism is not in use during rectilinear motion, the steering mechanism is not connected to the engine, but they still interlink the two steering units. When driving on homogeneous terrain where both tracks can receive an equal and opposite reaction force to the tractive force they transmit to the ground, both axles receive the same reaction torque from the tracks, and so the two planet carriers rotate at the same rate. However, if, say, the left track meets a patch of ice, the reaction torque at the left axle drops while the right axle has the same reaction torque, and so a torque imbalance arises in the system. This leads to the classical textbook axiom for cars with a differential - the torque available at both axles is equal to the torque at the wheel with the least traction. To express this in a more technically sound perspective, it can be said that the torque available at an axle is limited to the reaction torque obtained from the opposite axle.</div><div> </div><div>From this, it is evident that any loss of tractive force from one track is also doubled by the differential, up to the extreme case where if one track loses traction completely, the entire system also loses traction completely. The large contact patch of a tracked suspension makes this scenario highly unlikely in the real world, so becoming bogged down is not such a major concern as with ordinary road cars, but nevertheless, the downside of experiencing considerable losses of traction from driving over uneven terrain with a low friction coefficient or weak integrity remains an issue. That said, although a full loss of traction at one track is not frequently encountered in real life, it can occur in extreme circumstances such as when crossing an anti-tank obstacle or overcoming a natural obstacle of similar difficulty. <a href="https://www.youtube.com/watch?v=wmPPIzeqwFg">In this video</a>, for example, a full loss of traction of one of the tracks and its subsequent idle winding can be seen at 7:05, 7:25 at 12:37, where the loss of traction is partly due to the loss contact with the ground over most of the contact patch. </div><div><br /></div></div><div><br /></div><div>This steering mechanism provides regenerative steering - that is, recuperation of the power from the inside track by transferring it to the outside track. This preserves the thrust-to-weight ratio of the machine in a turn. For comparison, the crossdrive hydromechanical transmission in M113 APCs provided regenerative steering with infinite turn radii by smoothly varying the position of the steering levers, achieved by slipping a left or right steering clutch in the steering differential, but had no ability to neutral steer.</div><div><br /></div><div>Overall, having a discrete turn radius in each gear, the option of a clutch-brake turn in all gears, and easy gear shifting with a synchronized gearbox can be considered sufficient for an MT-LB to realize the full potential of its engine power and give drivers more confidence on rugged terrain. The provision of neutral steering may be credited as a positive point as well, but on poor terrain, where the MT-LB is most attuned to operate, the risk of throwing a track when performing neutral turns - particularly for vehicles with a relatively long ground contact length such as the MT-LB - means that the usefulness of this feature is rather uncertain. </div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">BRAKES</span></h3><div><br /></div><div>The stopping brakes are band brakes. The stopping brake mechanism is very similar to the steering brake mechanism, but larger in diameter for the large stopping brake rotor (330mm vs 250mm). They serve as steering brakes in the transmission's clutch-brake steering mode, as service brakes and as parking brakes. The only way to mechanically engage the brake is with the steering tillers. To provide sufficient braking force to stop the vehicle even at high speeds, a diaphragm-type pneumatic braking actuator was fitted parallel to the brake band tightening mechanism on each side, activated by the brake pedal; the brake pedal has no mechanical connection to the brake mechanism whatsoever. The circular diaphragm braking actuators are depicted by dashed outlines in the drawing below.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhI43eD-K5jQH1gpRm-o_asYhMwDN05zwL7gcPXvefCoSwVIdfdrBQSJ5TVMJGGoELiOPjP0zK28Hv9YMAvtutoG5I52sYscqF0kWz0CtzmcsRizC5Xl8J26hDJQtmYGQEMbcuZPkFT-KAarhj9UcX7cMYvimmbeShg9_qE4SGO2USYt2GmE0b4IfzWaQ/s4385/brakes.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2925" data-original-width="4385" height="426" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhI43eD-K5jQH1gpRm-o_asYhMwDN05zwL7gcPXvefCoSwVIdfdrBQSJ5TVMJGGoELiOPjP0zK28Hv9YMAvtutoG5I52sYscqF0kWz0CtzmcsRizC5Xl8J26hDJQtmYGQEMbcuZPkFT-KAarhj9UcX7cMYvimmbeShg9_qE4SGO2USYt2GmE0b4IfzWaQ/w640-h426/brakes.png" width="640" /></a></div><div><br /></div><div>The brake pedal controls the valve system to the pneumatic actuators on both brakes, and the steering levers control the band tightening mechanism by control rods. Diaphragm-type actuators are often favoured for this application because a diaphragm allows reliable sealing of the air chamber, provides a high push force, and the limited range of motion of the diaphragm is sufficient for brakes. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjF_tUP-No4oce5knjMGlLmi5W0_ViEFFL3ZCEUPrwwuoy0I98LR3ACGENNgiScuxCIeazov53zdpauIcB38-yjZ-wGE8IWSuZQT6Z46K7JfrTsa6v95nYqZd6nETUZy6TYbIJcF1BcJAF7yoAkHba3EAT2DG9wDV8q4m3w8wGPPjy8JAhyqxf72O_vaA/s2089/pneumatic%20brake.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2057" data-original-width="2089" height="315" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjF_tUP-No4oce5knjMGlLmi5W0_ViEFFL3ZCEUPrwwuoy0I98LR3ACGENNgiScuxCIeazov53zdpauIcB38-yjZ-wGE8IWSuZQT6Z46K7JfrTsa6v95nYqZd6nETUZy6TYbIJcF1BcJAF7yoAkHba3EAT2DG9wDV8q4m3w8wGPPjy8JAhyqxf72O_vaA/s320/pneumatic%20brake.png" width="320" /></a></div><div><br /></div><div>The pneumatic braking mechanism allows the driver to precisely control the braking force by controlling the pressure within the brake actuator with the deflection angle of the brake pedal. To provide consistent feedback to the driver, the mechanism functions in such a way that the pedal resistance is consistent to the pedal deflection angle regardless of the available air pressure, although it cannot ensure that the braking force is unchanged, as that depends on whether the pneumatic system of the MT-LB is operating at normal parameters. However, with this braking configuration, drivers must be aware that in the event of a pneumatic system failure and emergency stopping is needed, the brake pedal cannot be used and that instead, the driver must use the tillers.</div><div><br /></div><div>A ram-air intake on the transmission compartment access panel allows cool air to enter and circulate inside the compartment, primarily for the sake of cooling the service brakes. There are no outlet vents near the service brakes to induce a draft across the brake rotors, and the central location of the ram-air intake does not facilitate good airflow over the brakes, especially since the intake is shaped to direct the incoming air directly downwards. The gearbox itself does not greatly benefit from this rudimentary method of air cooling, as it already has its own oil cooler. The intake can be opened and closed from the crew compartment with a push-pull handle. When closed, it is watertight enough to not pose an issue when the vehicle is swimming.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">FINAL DRIVES</span></h3><div><br /></div><div>The use of a planetary final drive was commensurate with the role of the MT-LB as a prime mover, but like the steering units, the planetary gear set includes only one planet. To provide the necessary gear strength to handle the torque of the engine, multiplied by the gearbox, the planet has a large face width and tooth thickness. The sun gear delivers the output from the gearbox, the planet carrier is the axle of the drive sprocket, and the final drive housing itself serves as the reactionary ring gear.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjUsu9YKwNN8UXPg6XTSSVm-5rjlbRUqpFuiEq7TxJ3Oqbly3luK-lvdsYBI7V6g0oHs0Mv0KvYeQevpPd_0p3RBkKYCf8aCAI3XVhtzX7e8lBLRk8X45OWn0rtRUfU03AvkZnKAkv4g0WMidwf58P1pEdxIN7skHkdwt53oqRbWS58VWv6P3CK8DLPCA/s3039/final%20drive%20with%20drive%20sprocket.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2597" data-original-width="3039" height="341" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjUsu9YKwNN8UXPg6XTSSVm-5rjlbRUqpFuiEq7TxJ3Oqbly3luK-lvdsYBI7V6g0oHs0Mv0KvYeQevpPd_0p3RBkKYCf8aCAI3XVhtzX7e8lBLRk8X45OWn0rtRUfU03AvkZnKAkv4g0WMidwf58P1pEdxIN7skHkdwt53oqRbWS58VWv6P3CK8DLPCA/w400-h341/final%20drive%20with%20drive%20sprocket.png" width="400" /></a></div><div><br /></div><div>In general, the torque rating of final drives is designed according to the maximum torque flowing through the overtaking track when it is turning the vehicle uphill at the maximum specified roll angle. In this condition, when steering normally, regenerative torque from the lagging track increases the tractive force at the overtaking track, placing it under increased stress due to the high cumulative load. The final drive is maximally stressed in the case of a clutch-brake turn, where the overtaking track is conveying the entire torque output of the engine. For a prime mover intended for the role of a tractor-transporter, an intrinsically strong final drive was necessary, since the load on the drivetrain tends to be particularly large from a combination of a towed load and onboard cargo. This is distinct from tracked vehicles such as tanks, which are not specified to carry any cargo beyond its own combat load, and are only permitted to tow other tanks over relatively gentle terrain. As such, the use of a single-planet planetary final drive instead of a typical set of three is very unusual, as load distribution would be desirable for a large safety margin, even if a single planet was technically sufficient.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-c3n0xzZbOc4/X1hEEogsV6I/AAAAAAAARjo/t1mJ5fiDVqw_tYSCR09-748qkVL5K6ZngCLcBGAsYHQ/s1600/transmission%2Band%2Bdrive%2Bshaft.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1053" data-original-width="1600" height="264" src="https://1.bp.blogspot.com/-c3n0xzZbOc4/X1hEEogsV6I/AAAAAAAARjo/t1mJ5fiDVqw_tYSCR09-748qkVL5K6ZngCLcBGAsYHQ/w400-h264/transmission%2Band%2Bdrive%2Bshaft.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="suspension"></a><h3 style="text-align: left;"><span style="font-size: large;">SUSPENSION</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgt-2xkJIPZMNTPBB7seTlAjLyD8WYk0tD5GhLeJRn6eVINUmlIaVJwVD4eh6RjHlVYcOq7xlX2rE8DwV-0XwnS9TQ-iuk3nzYddQLHr2lvhaylNKioaKXw28-UrI_8rIY0lkXTqLPAAQ4QXo3l3w4JsXhp355Sa98yNOSI4dPA77OlWm1ZPQRZ1jI02w/s3600/suspension.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3012" data-original-width="3600" height="335" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgt-2xkJIPZMNTPBB7seTlAjLyD8WYk0tD5GhLeJRn6eVINUmlIaVJwVD4eh6RjHlVYcOq7xlX2rE8DwV-0XwnS9TQ-iuk3nzYddQLHr2lvhaylNKioaKXw28-UrI_8rIY0lkXTqLPAAQ4QXo3l3w4JsXhp355Sa98yNOSI4dPA77OlWm1ZPQRZ1jI02w/w400-h335/suspension.png" width="400" /></a></div><div><br /></div><div>Contrary to expectations with the high power-to-weight ratio and good transmission characteristics, the design of the suspension was somewhat dated. It consists of six roadwheels on each side, with torsion bar suspension and an unsupported track. The first and last roadwheel on each side has a shock absorber and volute spring bump stop. To reach the bump stops, the first and last roadwheel swing arms have a protruding arm. Single-pin tracks are used.</div><div><br /></div><div>Trailing swing arms are used for all roadwheel pairs except the last, which have leading swing arms, creating a zone with an enlarged open floor area in the cargo compartment. This zone does not actually free up any height for larger cargo because the space is bisected by a reinforcing beam, and the maximum size of cargo is limited by the small rear doors regardless. Rather, this feature of the suspension was merely a holdover from the MT-L, which used the open floor area for more convenient placement of its floor fuel tanks that were additionally closed off by load-bearing floor panels for supporting cargo. </div><div><br /></div><div>The use of unsupported track could be considered the primary distinguishing feature of the MT-LB suspension against the backdrop of the myriad of very similar suspensions on other Soviet light tracked vehicles. The disadvantages of an unsupported track are that it tends to impart greater dynamic loads on the engine due to tension fluctuations, and the tracks can be thrown against the sponsons during high-speed off-road driving can be violent enough to slap the sponsons, leading to damage and noise.</div><div><br /></div><div>The suspension of the MT-LB is visually and structurally very similar to the suspension of the PT-76, mainly down to the most obvious details such as the number of roadwheels. This has led to the misconception that the suspension is the same, or that the MT-LB itself was derived from the PT-76, but in fact, the suspension was a separate design that simply shared the same basic primary characteristics. The parts for the suspension are all proprietary, bearing product indices, and there is no direct interchangeability with the PT-76. Structurally, the most obvious difference was that the MT-LB used different shock absorbers, a different tensioning mechanism on its idler wheels, and it had full-length torsion bars that span the entire width of the hull, whereas the PT-76 used torsion bars that were a few inches short of the full width of the hull. </div><div><br /></div><div>The torsion bars have a diameter of 36mm. Each bar weighs 17.68 kg.</div><div><br /></div><div>Front mudguards are fitted as standard, but the MT-LB suspension did not have any form of dust or mud splash suppression other than the hydrodynamic paneling kit for amphibious operations.</div><div><br /></div><div><br /></div><div>The roadwheels are 670mm in diameter. The axle hub is a casting of AMG6 grade aluminium, onto which a pair of stamped aluminium discs are welded which are then closed with a welded rim to form a watertight hollow cavity, thus forming the wheel. A rubber rim, 112mm wide, is then bonded on. 38KhS grade steel wear rings are screwed to the rim, acting as sacrificial elements to rub against the guide horns of the track when the vehicle is in motion, eliminating wear on the aluminium wheel itself. The hollow cavity in the discs provide additional buoyancy when swimming. This was an old and well-established design practice by this point in the history of Soviet light tracked prime mover production, with hollow wheels present even on vehicles not designed to swim, including the AT-P, the predecessor of the MT-LB.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhYc7aedu3fxuetGYqw0TmrLVtR2jwKy-u9h-SeMl52yHNJvPcf2kKs-9I0u5jUF3747SjhHTQVq-UgZr19hXakylJWXgnt20s1A9lF7Mggi2q0s_gNa0gj2xaBgpdhUzhH5ge3lVAl8BfR_oJd-bHidWcmhoVIrAektucggyI567AyOyzu1oi2foXDZw/s1716/suspension%202.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1716" data-original-width="1436" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhYc7aedu3fxuetGYqw0TmrLVtR2jwKy-u9h-SeMl52yHNJvPcf2kKs-9I0u5jUF3747SjhHTQVq-UgZr19hXakylJWXgnt20s1A9lF7Mggi2q0s_gNa0gj2xaBgpdhUzhH5ge3lVAl8BfR_oJd-bHidWcmhoVIrAektucggyI567AyOyzu1oi2foXDZw/w335-h400/suspension%202.png" width="335" /></a></div><div><br /></div><div>A pair of roller bearings are fitted to each wheel and the outer end is sealed with a hubcap while the inner end, connected to the swing arm, is sealed with a labyrinth seal. Each wheel weighs 43.42 kg, which is slightly heavier than a 41.09 kg roadwheel from a BMP-1, but indicates that it is proportionately very similar to the BMP roadwheel in the sturdiness of its construction, considering that the BMP roadwheel diameter is only 600mm. The ball bearings are lubricated with grease, which is unsurprising as it was the chosen solution on the great majority of Soviet tracked vehicles. The swing arms on each roadwheel are fitted with textolite bushings for vibration damping.</div><div><br /></div><div>The table below lists the axle load on each suspension unit for the MT-LB. The axle loads will be the same for the MT-LBV, because the tracks, although heavier, are an unsprung mass. According to the article "<i>Метод Анализа Компоновочных Схем И Параметров Вгм, Создаваемых На Базе Многоцелевого Гусеничного-Шасси</i>", published in the 1977 No. 2 issue of the "<i>Вестник Бронетанковой Техники</i>" journal, the maximum permissible load on the rim of a roadwheel is 1,100 kgf. As mentioned in the "Cargo" section, this most likely refers to the maximum average load on a roadwheel, considering a distributed weight of 13.2 tons over twelve suspension units, taking into account that while the middle roadwheels bear the highest static loading, the front and rear roadwheels bear the strongest dynamic loads and are the most stressed overall. </div><div><br /></div><div><div><div> <table border="1"><tbody><tr><td style="text-align: center;"><b> Roadwheel </b></td><td style="text-align: center;"><b> Axle load (empty vehicle) </b></td><td style="text-align: center;"><b> Axle load (loaded to 10.3 tons) </b></td></tr><tr><td style="text-align: center;"><span style="font-size: small;">1</span></td><td style="text-align: center;">960</td><td style="text-align: center;">780</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">2</span></td><td style="text-align: center;">810</td><td style="text-align: center;">865</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">3</span></td><td style="text-align: center;">723</td><td style="text-align: center;">930</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">4</span></td><td style="text-align: center;">632</td><td style="text-align: center;">855</td></tr><tr><td style="text-align: center;"><span style="font-size: small;">5</span></td><td style="text-align: center;">540</td><td style="text-align: center;">885</td></tr><tr><td style="text-align: center;">6</td><td style="text-align: center;">457</td><td style="text-align: center;">910</td></tr></tbody></table></div><div><br /></div></div><div><br /></div><div>Owing to the lack of a counterbalance to the weight of the transmission and engine when the MT-LB is not carrying cargo, the front roadwheels, particularly the first roadwheel pair, are much more heavily loaded relative to the rest of the roadwheels when the vehicle is empty. Relative to the third roadwheel when the vehicle is lightly loaded, the peak load on the first roadwheel pair is not particularly high, which presumably explains why the first suspension pair did not require special reinforcement. However, considering that the load limit on each roadwheel is 1,100 kgf, the roadwheels are apparently working near their limit at all times.</div></div><div><br /></div><div>A highly noteworthy trait of the MT-LB suspension is that, aside from the first and last units, none of the suspension units have a hard stop. This generally implies that, if the vehicle is somehow falls onto a sturdy protruding obstacle such as a tree stump or a large boulder the size of a small boulder, some of the wheels may be deflected far enough to break their torsion bars, particularly the middle wheels. According to experienced MT-LB drivers, the suspension is capable of supporting the weight of a loaded vehicle with only the middle wheels resting on a tree stump, indicating that the range of motion is large enough, and the vehicle light enough, that the lack of hard stops does not pose issues in everyday use.</div><div><br /></div><div>Another interesting feature of the suspension unit is that the swing arm length and wheel diameter coincided in such a way that it is possible for a torsion bar swap to be carried out without removing the wheel, which is a relatively uncommon feature for tracked vehicles. This is largely due to the long swing arms, even relative to the roadwheel diameter.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-0v7hxQsLl8HwXr-bXNlBehs0WW5UZ6bMapmgz8z5oCQbAE-EB_G88dfZYE_-d2IZTVwMyL5h7_ZZ2WkDwp9BMBeNh2mw3dUda1NX4MyCSORzvKt4T7nV2uo3FGNBGKDrVjJ-b6J73w4I3ijy3-UctqWlbzVMVcbmBUx8EV31ORZ6ZXXNq9eUPBt2vQ/s3096/torsion%20bar%20replacement.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2196" data-original-width="3096" height="284" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-0v7hxQsLl8HwXr-bXNlBehs0WW5UZ6bMapmgz8z5oCQbAE-EB_G88dfZYE_-d2IZTVwMyL5h7_ZZ2WkDwp9BMBeNh2mw3dUda1NX4MyCSORzvKt4T7nV2uo3FGNBGKDrVjJ-b6J73w4I3ijy3-UctqWlbzVMVcbmBUx8EV31ORZ6ZXXNq9eUPBt2vQ/w400-h284/torsion%20bar%20replacement.png" width="400" /></a></div><div><br /></div><div>The idler wheel is 510mm in diameter, and its design is somewhat uncommon in that its two discs are very narrow. A somewhat unusual feature of the idler is that the idler wheel adjustment mechanism is inside the cargo compartment, rather than outside the hull. The mechanism does not make use of a worm gear, instead having a screw to raise or lower the inner end of the swing arm where a tensioner arm is splined to the swing arm axle, thereby lowering or raising the idler wheel at the other end. To adjust the tension, the nut on top of the tensioning screw, marked (11) in the diagram below, is twisted with a wrench to turn the tensioning screw (after a retention cap over the nut is released). Once the idler wheel has been lowered to the maximum extent, the tensioner arm (17) will rest against the top of the frame, and the tensioning screw (18) will not be able to raise it any further. Further twisting the nut will unscrew the tensioning screw, to the point where it can be entirely removed from the tensioning mechanism. The tensioner arm and the tensioner screw alone are shown together in <a href="https://st2.stpulscen.ru/images/product/422/501/305_big.jpg">this image</a>. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6C2ha0YB7YAknTPvNpn-3KUW8upRzruJ9CkJJ9zceH9f4mM_SsdLn1ai5T2j50Ztpcb5M3Vk3EW8taOYejnFAcQQ8ADiZSVE9w9lUEtoMUuqQMAz9F5SFu9DFlsbv4dYJH8eifwA9M3Iti5-KkrMCFsgSgp597j57YDppcIj6HfYauoJMC7Nc_ikJDg/s2226/track%20tensioning%20mechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1256" data-original-width="2226" height="226" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6C2ha0YB7YAknTPvNpn-3KUW8upRzruJ9CkJJ9zceH9f4mM_SsdLn1ai5T2j50Ztpcb5M3Vk3EW8taOYejnFAcQQ8ADiZSVE9w9lUEtoMUuqQMAz9F5SFu9DFlsbv4dYJH8eifwA9M3Iti5-KkrMCFsgSgp597j57YDppcIj6HfYauoJMC7Nc_ikJDg/w400-h226/track%20tensioning%20mechanism.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEijhPVpMQ46PGWaeIO_o8YFn6GCdPes5kZEVKrLujaEBaSk6vGaUh0eNIuZZrKLNmq10ilvoggqsMYLr21UR-mfnXnVK7WLVTQrBcD8_1HDdeu7EoYxxQEEsHTYMfKVcUnpQeXshawKRAC1f8WBiVS-sbJ3WtjcdO1fpkgVpNb7oVI53wdJ8sGPzNeouQ/s912/track%20tensioning%202.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="778" data-original-width="912" height="273" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEijhPVpMQ46PGWaeIO_o8YFn6GCdPes5kZEVKrLujaEBaSk6vGaUh0eNIuZZrKLNmq10ilvoggqsMYLr21UR-mfnXnVK7WLVTQrBcD8_1HDdeu7EoYxxQEEsHTYMfKVcUnpQeXshawKRAC1f8WBiVS-sbJ3WtjcdO1fpkgVpNb7oVI53wdJ8sGPzNeouQ/s320/track%20tensioning%202.png" width="320" /></a><br /></div><div><br /></div><div>In the article "<i>Отечественные гусеничные транспортеры</i>" published in the February 2015 issue of the "<i>Техника и вооружение</i>" magazine, it is claimed that the design of the idler wheel, consisting of two thin discs, works to break up ice on the tracks. </div><div><br /></div><div>The drive sprocket is 604mm in diameter, with a pitch diameter of 530mm.</div><div><br /></div><div><br /></div><div><div>Two types of single-pin tracks are available for the MT-LB, an open-joint all-metal type, or OMSh (below, left), and a closed type with a rubber bushing, or RMSh (below, right). The ground contact length is 3.7 meters regardless of the tracks used (the distance between the axis of the drive sprocket and the idler wheel is 5,125mm). This is substantially more than similar vehicles like the M113 (2.67 m) on account of the longer, squatter hull of the MT-LB. This, of course, also amounts to an increase in the weight of the tracks and the rotating mass of the suspension system, while also leading to an increased turning resistance. </div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuYuCcw-QNC90voT9hy5rEewlWsjBrjWZBwNUKpDrQOFQWIh6jfDf91YgEZOdDc2hw2zTXWB8LtZ9Yd_6D80ZkWvmJZTKFq1sA2xoraQJWFYFAu7MM_PVkOewxR-FprqzcazpSTyMj8IcYgQY-RSOh1_6-wR-yw1KEhNd-naQcG9anSefYn3yo8MeZ2g/s1657/omsh.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1657" data-original-width="1127" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuYuCcw-QNC90voT9hy5rEewlWsjBrjWZBwNUKpDrQOFQWIh6jfDf91YgEZOdDc2hw2zTXWB8LtZ9Yd_6D80ZkWvmJZTKFq1sA2xoraQJWFYFAu7MM_PVkOewxR-FprqzcazpSTyMj8IcYgQY-RSOh1_6-wR-yw1KEhNd-naQcG9anSefYn3yo8MeZ2g/w273-h400/omsh.png" width="273" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhb2gliteceieVXX5Bvk5PMQ10JK-scovJt1qUiL79ZwopotIQBrr9MxOe2ztinWKdEqGHkNbFrUNZTfM0g6Vq2bNxPqi6syqyXcQSxOM08IZgVQS20AnZU6Psy5Mz_6AI-FVPvNf_nfKdyIEbqeDwVpbjlVjt8kShE79B1SkiQWpNnQgw4Ywc0gWKwog/s1498/rmsh.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1498" data-original-width="1078" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhb2gliteceieVXX5Bvk5PMQ10JK-scovJt1qUiL79ZwopotIQBrr9MxOe2ztinWKdEqGHkNbFrUNZTfM0g6Vq2bNxPqi6syqyXcQSxOM08IZgVQS20AnZU6Psy5Mz_6AI-FVPvNf_nfKdyIEbqeDwVpbjlVjt8kShE79B1SkiQWpNnQgw4Ywc0gWKwog/w288-h400/rmsh.png" width="288" /></a></div><div><br /></div><div>The width of the OMSh tracks is 350mm, and the track pitch is 111mm. The design of the tracks is very similar to the tracks of the AT-L, although it is wider by 50mm and has a smaller pitch. The track links are cast Hadfield steel. The nominal service life of the tracks is 3,000 km. To improve traction on snow and swampy ground, the track surface was designed with <a href="https://cache3.youla.io/files/images/780_780/59/8c/598c42b893800085bf325b72.jpg">aggressive grousers</a>. The RMSh tracks have the same width but a slightly shorter pitch. The exact pitch length is unknown, as is the service life of the track. </div><div><br /></div><div><div>With a set of new OMSh tracks, there would be 108 track links on each side, whereas with the RMSh tracks, there would be 122 track links on each side. A set of OMSh tracks weighs 693.91 kg, and a set of RMSh tracks weighs 885.7 kg. With OMSh tracks, the tracks weigh 13.7% of the vehicle weight (based on curb weight) and with RMSh tracks, 17.5% of the vehicle weight. This is quite high for a lightly armoured vehicle, but is largely due to the low curb weight of the MT-LB, being a transporter without a serious weapons module. For comparison, one set of tracks for a BMP-1 weighs 625 kg, but the BMP-1 weighs 12.6 tons combat loaded, giving a proportional track weight of just 10%. With a fully loaded MT-LB, the proportional weight of its tracks falls much closer to this figure.</div><div><br /></div><div>With RMSh tracks, the shorter pitch leads to some increase in the mean maximum pressure (MMP) exerted by the MT-LB on top of its added rotating mass, owing to the smaller area of the track links. For a tracked suspension, the traction developed is not constant across the length of the ground contact patch, but varies by the load on each roadwheel, the area of the track link(s) directly underneath the roadwheel bearing the load, and the track tension available to distribute the load between the track links. With a shorter pitch, this meant that the RMSh track must increase the MMP of the MT-LB, although to an unknown extent, and driving performance on soft terrain can be expected to have worsened. </div><div><br /></div><div>However, the RMSh track is more durable, immune to accelerated track pin wear when driving on sandy terrain, has favourable winding characteristics, generates less noise and vibration owing to its shorter pitch, and permits the vehicle to reach a high speed much more easily. Its added rotating mass is compensated by the reduction in rolling resistance, which is significant and is responsible for making the RMSh type more suitable for travelling at higher speeds.</div></div><br /><div>On the MT-LBV, OMSh tracks with increased width were fitted, accompanied by wider fenders. The new 560mm-wide tracks greatly enhanced mobility in particularly harsh terrain, such as on thin ice, on marshy ground or on deep snow. However, with a total weight of over 2 tons for a set of two tracks, they added a great deal of rotating mass to the suspension. Their design structurally incorporated duckbill extensions and also added small extensions on the inner side of the track to further increase the ground contact area. These tracks are of the OMSh type and have the same pitch as the standard OMSh track, and as such, 108 links are needed per side. They can be used on vehicles with drive sprockets meant for the standard OMSh track, and the same number of links per side is used. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4c7aQFaLsB7tx7VdWyMWRP--zu_Ods56CXGwdIRpyXUoFILHESy7BkbpoH7uqK3b6eiNTsqm42FmZ7ZtdRDFU8A6jAeWFxBX_Ueff8p9niX4CAfQ6XsxjWko1lajWY-4-uxLl-THQZNf3tt1myRc0aTa_kL0aGJ7rpCPrCJoLmPs8zy62Z6oMV7vbYw/s1630/wider%20track.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1630" data-original-width="832" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4c7aQFaLsB7tx7VdWyMWRP--zu_Ods56CXGwdIRpyXUoFILHESy7BkbpoH7uqK3b6eiNTsqm42FmZ7ZtdRDFU8A6jAeWFxBX_Ueff8p9niX4CAfQ6XsxjWko1lajWY-4-uxLl-THQZNf3tt1myRc0aTa_kL0aGJ7rpCPrCJoLmPs8zy62Z6oMV7vbYw/w204-h400/wider%20track.png" width="204" /></a></div><div><br /></div><div>With the wider and heavier track, the MT-LBV is also capable of a higher drawbar pull due to the increased tractive force it can put out, especially in softer terrain where the larger area of grousers available on the track distributes traction across a larger soil area, reducing shear stress and thus increasing the obtainable soil thrust.</div><div><br /></div><div><div>All three types of track have mounting holes for cleats, which are an optional accessory for use on very slippery terrain. Each cleat is individually fitted, two on each track link. It is not recommended to drive above 3rd gear when using these cleats, or drive further than 6-8 km at a time. As such, they are meant for temporary use, limited to helping when carefully crossing regions of difficult terrain at low speed, after which they should be removed when more robush paths are available. They are not comparable in purpose to the optional grousers fitted in place of the rubber track pads on many American and German tank tracks. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJjt95_9Y2Yzs67dxMHYUAHT5VBYvciE8ge5ux6MghaX451dHE00MNSVLSQBvVllN7z7zOzS3Z0aW1MaLF4hZY90DHM3xgnzwmMmNh_dC6qbE-Lb26OESAmYx61hAZMhSnbZuFjA2SGgc2ifgcO8wa_17ixvz0TnXL9FL1abJVIKhuHO1qHurtbt-zfQ/s854/track%20cleats.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="778" data-original-width="854" height="292" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJjt95_9Y2Yzs67dxMHYUAHT5VBYvciE8ge5ux6MghaX451dHE00MNSVLSQBvVllN7z7zOzS3Z0aW1MaLF4hZY90DHM3xgnzwmMmNh_dC6qbE-Lb26OESAmYx61hAZMhSnbZuFjA2SGgc2ifgcO8wa_17ixvz0TnXL9FL1abJVIKhuHO1qHurtbt-zfQ/s320/track%20cleats.png" width="320" /></a></div><div><br /></div></div><div><br /></div><div>With the standard tracks, the MT-LB exerts a nominal ground pressure of 0.443 kgf/sq.cm when loaded with the maximum rated onboard cargo of 2.5 tons. This is considerably lower than the ground pressure of a standing infantryman, and also much lower than the 0.549 kgf/sq.cm ground pressure of the M113A1, measured based on its combat weight according to technical manual TM-55-2350-224-14. As another point of comparison, the gground pressure of the BMP-1 is 0.6 kgf/sq.cm.</div><div><br /></div><div>Thanks to its wider tracks, the MT-LBV exerts a nominal ground pressure of only 0.244 kgf/sq.cm at its curb weight or 0.28 kgf/sq.cm when loaded with a crew and 1.5 tons of cargo - two times lower than that exerted by a standing infantryman and equivalent to the loaded ground pressure exerted by the much larger DT-10 and DT-30 series articulated all-terrain vehicles when loaded to their rated cargo of 10 and 30 tons respectively. This gives it excellent terrain-crossing abilities across most landscapes. However, while excellent for a conventional all-purpose armoured military vehicle, this is still incomparable to specialized vehicles such as the Bv 206, which has a limiting ground pressure of 0.13 kgf/sq.cm - less than half that of the MT-LBV.</div><div> </div><div><br /></div><div>Thanks to the flotation of the wider track, MT-LBVs are capable of being regularly driven in seemingly impassable terrain, such as shown in the <a href="https://nagolovu-voenny.livejournal.com/17061.html">image below</a> purportedly showing a driving course for training MT-LBV drivers. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhR4cAsq-hkuDhfiI_SAAcpJfa7fV85LLxpBxFJWgTt-GjfkwfseFmsCgOAnavYE5Tu1PJo5mL_FIB6FfEyQznJl4aPkC5j0a5kNJM08RdnrTwyLOcnMkZNjYVSZEHLAD5oTvlYghKQbTD33nEZWXExTZYP6iwmInwxs6V9uqt7x-e_WZv1iQiLNRR-0w/s900/mt-lbv%20driving.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="675" data-original-width="900" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhR4cAsq-hkuDhfiI_SAAcpJfa7fV85LLxpBxFJWgTt-GjfkwfseFmsCgOAnavYE5Tu1PJo5mL_FIB6FfEyQznJl4aPkC5j0a5kNJM08RdnrTwyLOcnMkZNjYVSZEHLAD5oTvlYghKQbTD33nEZWXExTZYP6iwmInwxs6V9uqt7x-e_WZv1iQiLNRR-0w/s320/mt-lbv%20driving.jpg" width="320" /></a></div><div><br /></div><div><br /></div><div>The added weight of the tracks would not have a negative effect on the traction of the vehicle, as the greater weight pressing upon the ground will increase the friction force. Even so, the MT-LBV was rated for a much smaller towed load than the MT-LB for unknown reasons. </div><div><br /></div><div><br /></div><div>By calculating the weights of the individual suspension elements, including tracks, idler and drive sprockets, complete wheels, swing arms, torsion bars, mud scrapers, hydraulic shock absorbers, but excluding the volute spring bump stops, the total weight of the suspension is no less than 2,631.39 kg with OSh tracks, or 3,014.97 kg with RMSh tracks.</div><div><br /></div><div><br /></div>
<br /><a href="https://www.blogger.com/null" id="water"></a><h3 style="text-align: left;"><span style="font-size: large;">
WATER OBSTACLES</span></h3>The MT-LB is readily amphibious. Because the engine and transmission are at the front of the hull, it was not feasible to implement water jets for propulsion in water. Instead, the MT-LB is propelled by its tracks. Special hydrodynamic grilles are fitted behind the idlers at the rear of the hull to enhance the directivity of the flowing water around the tracks, and special panels are installed around the front of the hull to prevent water from flowing forward. When not in use, this equipment is carried externally on special stowage points with straps. When swimming, the metacentric height of the vehicle is 0.5 meters, and the minimum reserve buoyancy is 20%, which is met when the vehicle is loaded with 2 tons. The maximum immersion depth of the hull is 0.3 meters to its roof.<br /><br />
<div>To prepare for crossing water obstacles, the wave breaker is raised, the shielded air intake tube is fitted over the air intake if it was not already fitted, a splash guard is fitted over the radiator and exhaust outlets, fender panels are installed around the drive sprockets, and the rear hydrodynamic grilles are lowered and clamped in place. For an MT-LBV, the wider tracks required wider fender panels and rear hydrodynamic grilles. The specified preparation time for a water crossing operation by swimming is 20 minutes.</div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiE8F0JlK55vBDHbA2-u31Xbrsa6uR06T0bTzk8GltIIRc6gbc0I-VCtqcLnxKrSf-J9ffFiuKstr64eJ0H2Uy32fzDnWcg2ozlULd537ZsVPBXYly_DYCL8xN-g29B_epgw3IUpxzPz2zezmV9WbzP0uRRoGK0VS7gXBWmvoEl1YH-gnns409sJUxSNA/s1254/front%20fender.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="966" data-original-width="1254" height="309" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiE8F0JlK55vBDHbA2-u31Xbrsa6uR06T0bTzk8GltIIRc6gbc0I-VCtqcLnxKrSf-J9ffFiuKstr64eJ0H2Uy32fzDnWcg2ozlULd537ZsVPBXYly_DYCL8xN-g29B_epgw3IUpxzPz2zezmV9WbzP0uRRoGK0VS7gXBWmvoEl1YH-gnns409sJUxSNA/w400-h309/front%20fender.png" width="400" /></a></div><div><br /></div><div>Forward propulsion is provided by the rearward flow of water dragged by the retreating run (the lower run) of the tracks. The efficiency of the track in ploughing water rearward is quite low, so the rear hydrodynamic grilles were made to increase the directivity of the rearward flow of water. The grilles work by receiving the upward flow of water from the rear sloping part of the retreating run, and redirecting it rearward. The flat-faced front fender panels have the opposite function, working to sharply reduce the efficiency of the returning run (top run) of the tracks in ploughing water forward. An MT-LB fitted with these panels is shown in the images below, courtesy of <a href="https://monk-of-war.medium.com/">Monk of War</a>.</div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhnS-AIDv5ohEripe7uSxYf_SOnnLLg52sHd-Y-iIANVQaVDeAOjSe_0QOOs9OEBazWkd2iRmuO6L5DKvaZI-QvxLSuXgIWBVy3UzRJU8U4CyjfhUXXsg91TOuZQQgA5D-g6hQfpdten3nZvJ89W9286vdJfgTNM7EWXy4ELSHxX1ejCrhKP1nH-uE2ug/s2816/P1210576.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1880" data-original-width="2816" height="268" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhnS-AIDv5ohEripe7uSxYf_SOnnLLg52sHd-Y-iIANVQaVDeAOjSe_0QOOs9OEBazWkd2iRmuO6L5DKvaZI-QvxLSuXgIWBVy3UzRJU8U4CyjfhUXXsg91TOuZQQgA5D-g6hQfpdten3nZvJ89W9286vdJfgTNM7EWXy4ELSHxX1ejCrhKP1nH-uE2ug/w400-h268/P1210576.JPG" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEja0Rt1g4fnoyvkdi0pUo8x3BijWTNuVUwG6UQzCN_6fhYq-MFKmXIb7qF9mI1XXjV3e4Ps80OQykpRWZ_xwOsXiyUFnGQFTFi3Ijn_PWmQSqwWjr2QSOehYcQ0gRzR283X2DDw6r5Kf9mNIrhUXgtZ5VN68xuYnS4Yo9inXgBPOMSqsifIUxdfCq0teg/s2816/P1210577.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1880" data-original-width="2816" height="268" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEja0Rt1g4fnoyvkdi0pUo8x3BijWTNuVUwG6UQzCN_6fhYq-MFKmXIb7qF9mI1XXjV3e4Ps80OQykpRWZ_xwOsXiyUFnGQFTFi3Ijn_PWmQSqwWjr2QSOehYcQ0gRzR283X2DDw6r5Kf9mNIrhUXgtZ5VN68xuYnS4Yo9inXgBPOMSqsifIUxdfCq0teg/w400-h268/P1210577.JPG" width="400" /></a></div><br /></div><div>Without the panels around the drive sprockets, the efficacy of water jet propulsion is significantly reduced, because the forward flow of water dragged by the returning run of the track neutralizes the forward thrust from the rearward flow of water dragged by the retreating run of the track, leaving the redirected flow of water through the hydrodynamic grilles as the only source of forward propulsion.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8R-mvRaedtPFXabmWO21_DG5LU9GJVTE54YFCGdmQU659dIMOEJyf0NSKJrihAIAi8IHc9covZDjNAfZPiC9aZ5yXTLBiM4AfppuFRNX37J2_0Ltmqq-UGddFB2FjVfsOIEdXe9b9uVsBDeMVoW5BvSDaZx-TGmunhR8MpP53MJ001mNod1XV2htK8Q/s898/swimming.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="277" data-original-width="898" height="198" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8R-mvRaedtPFXabmWO21_DG5LU9GJVTE54YFCGdmQU659dIMOEJyf0NSKJrihAIAi8IHc9covZDjNAfZPiC9aZ5yXTLBiM4AfppuFRNX37J2_0Ltmqq-UGddFB2FjVfsOIEdXe9b9uVsBDeMVoW5BvSDaZx-TGmunhR8MpP53MJ001mNod1XV2htK8Q/w640-h198/swimming.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The lower half of each of the grilles is shaped to direct water inward. When both tracks are running, the opposing inward flows from both tracks eliminates any turning effect. When one track is stopped, the inward flow from the opposite track increases the turning force, enabling the vehicle to turn more tightly than if it only had a direct rearward flow from one track.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2f69yCJbfX1rSVQ2z3x4NbRCMFok-RRrgFqMOL4tP_p9YSHvYND_S10X-TpL_sgYZR9t_WiZ6sjU_94B9GuFijc135rp90cc8KvVJC5S_Tk0z2OJoePhtFO5LA4ctqDprG4a0N7EtK4Rs6NpA2YzFXicxFEwQklFtB_kYJ6SyAtPDh-mznFkmEQVZog/s500/otvaga2004_mt-lb_03-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="363" data-original-width="500" height="290" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2f69yCJbfX1rSVQ2z3x4NbRCMFok-RRrgFqMOL4tP_p9YSHvYND_S10X-TpL_sgYZR9t_WiZ6sjU_94B9GuFijc135rp90cc8KvVJC5S_Tk0z2OJoePhtFO5LA4ctqDprG4a0N7EtK4Rs6NpA2YzFXicxFEwQklFtB_kYJ6SyAtPDh-mznFkmEQVZog/w400-h290/otvaga2004_mt-lb_03-2.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>The top speed achieved while swimming with a nominal cargo load (presumably 2 tons) is 5-6 km/h. The top speed in reverse is unspecified. The vehicle can be driven into a water obstacle at a downhill slope of 20 degrees, but exit at an uphill slope of no more than 15 degrees.</div><div><br /></div><div>Like all other amphibious Soviet vehicles, the MT-LB features a bilge pump to bail water out of the hull. According to the article "<i>Универсальный Солдат Многоцелевой Транспортер-Тягач МТ-ЛБ</i>", when the bilge pump is running, the MT-LB can allegedly be kept afloat with a loss of buoyancy of up to 30%, although the author does not specify what a "loss of buoyancy" means.</div><div><br /></div><div>The permissible wave height when swimming is 0.5 meters, but when fording a water obstacle, it is only 0.15 meters, probably due to concerns of water ingress when the vehicle is not prepared for swimming. Splash protection when swimming is provided by the shielded air intake tube and the boxy splash guard over the radiator and exhaust outlets.</div><div><br /></div>
</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhbWxmMpjZaqClIHBhMoxuM_81DX58pwBP3E5Qws3WJWAQGwzVmQ5weGzXQJgqVPb4aUVXsmwbYs7GmYhIewe9aioXPrJMyrq1nbHyrupWSiTcAaI4cWSV2GzzRETfZg_BrKBvCaZpTqYQst_kzEvE8gFTDgDS8nqC7n0SBISjdclcA-R2D0oWUy8eiew/s2695/splash%20guard.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1975" data-original-width="2695" height="294" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhbWxmMpjZaqClIHBhMoxuM_81DX58pwBP3E5Qws3WJWAQGwzVmQ5weGzXQJgqVPb4aUVXsmwbYs7GmYhIewe9aioXPrJMyrq1nbHyrupWSiTcAaI4cWSV2GzzRETfZg_BrKBvCaZpTqYQst_kzEvE8gFTDgDS8nqC7n0SBISjdclcA-R2D0oWUy8eiew/w400-h294/splash%20guard.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhY_ic1DwoaSTRvOvDdnfoatVdG4GyrGDrgtjr9Yn3ZdJxJ-BGTUC6cMyPfBAhCGkf0X704tpCCOYBkuHRUwX9XnDNcvDmrhF9BtngVnwtFKxB0eFtAv_1ptouygiLn2VcbshVOr4GB1SyJ-w6QklHeCv054WZLDUGO1TEOTWlK1oJVkPtg5R78FfkNIg/s2452/tube.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2024" data-original-width="2452" height="264" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhY_ic1DwoaSTRvOvDdnfoatVdG4GyrGDrgtjr9Yn3ZdJxJ-BGTUC6cMyPfBAhCGkf0X704tpCCOYBkuHRUwX9XnDNcvDmrhF9BtngVnwtFKxB0eFtAv_1ptouygiLn2VcbshVOr4GB1SyJ-w6QklHeCv054WZLDUGO1TEOTWlK1oJVkPtg5R78FfkNIg/s320/tube.png" width="320" /></a><br /></div><div><br /></div><div>As an aside, it is interesting to note that the plugs for the drainage holes were borrowed from the BTR-60 series or at least were of the same standard design. In the BTR-60, these plugs were not simply drainage plugs as they are on the MT-LB, but were made to drain water from various points in the hull into the intake ducts of the bilge pump, which is why they were designed to be open from the inside and have a twist handle to screw the stopper. The intake ducts of the bilge pump were of the same thickness of the BTR hull belly, mitigating the vulnerability posed by the exposed drainage holes. In the MT-LB, the stoppers are the only sealing element to plug the drainage holes in the hull belly. </div><div><br /><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWKGsoNMe4OqJMswIekCt2bDIiGbCNUipShwaVPRONUUe2cR6tctVUmlAAR7RHpn524lsdwp04aHAyX31kYWrotOX_3JQ2rh8VtVNBHIUVyjcMGlz7QJCMBpzl_NwNjs0khgL4dXc99D0_Uh8Ibz7PTnzTNPABEShrHMoDjL_J26_X4WgfwVWnBleeVg/s1030/plug.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1030" data-original-width="738" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWKGsoNMe4OqJMswIekCt2bDIiGbCNUipShwaVPRONUUe2cR6tctVUmlAAR7RHpn524lsdwp04aHAyX31kYWrotOX_3JQ2rh8VtVNBHIUVyjcMGlz7QJCMBpzl_NwNjs0khgL4dXc99D0_Uh8Ibz7PTnzTNPABEShrHMoDjL_J26_X4WgfwVWnBleeVg/w229-h320/plug.png" width="229" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1suYNZXPZYgBoPtRc4gaJAOD81FYXnc9XBQRqgHubLd-_uIFsSahXwANRiveAytt4ytiNLOu7Qq3ALOuiiMIZIATAiXb9HZI0DNDsWPe5gNwAYzRxfU9_fJ2Kjg7OJ3riri5t9OmoUS1_4sXHhR_ORYHYUyxqiKRXu77x0Ldzw4DkT16O00NQeLEfwA/s1024/mtlb-22.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="768" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1suYNZXPZYgBoPtRc4gaJAOD81FYXnc9XBQRqgHubLd-_uIFsSahXwANRiveAytt4ytiNLOu7Qq3ALOuiiMIZIATAiXb9HZI0DNDsWPe5gNwAYzRxfU9_fJ2Kjg7OJ3riri5t9OmoUS1_4sXHhR_ORYHYUyxqiKRXu77x0Ldzw4DkT16O00NQeLEfwA/w240-h320/mtlb-22.jpg" width="240" /></a><br /><br /></div></div><div>Owing to the location of three of these drainage holes near the right and left ends of the hull, there can be a noticeable weakening of the belly to heavy anti-personnel mines detonating under the nearside edge of the tracks. The location of all drainage holes is shown in the drawing below, but the sizes are greatly exaggerated and the positioning is inexact. For instance, one of the drainage holes marked in the drawing below (11) is actually located right up against the side hull wall, as the image on the right above shows.</div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-g4PCHRZnWb8/YLIOa3tEoXI/AAAAAAAATPk/OxAQ0ksdNLcwphHusx2CW2G4cM8ysWPZQCLcBGAsYHQ/s1800/mt-lb%2Bbelly.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="848" data-original-width="1800" height="302" src="https://1.bp.blogspot.com/-g4PCHRZnWb8/YLIOa3tEoXI/AAAAAAAATPk/OxAQ0ksdNLcwphHusx2CW2G4cM8ysWPZQCLcBGAsYHQ/w640-h302/mt-lb%2Bbelly.png" width="640" /></a></div></div></div></div></div><br /></div>Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com13tag:blogger.com,1999:blog-3103574899092646031.post-88340750404534232132021-07-21T13:26:00.259-07:002023-10-21T03:07:34.466-07:00Soviet ATGMs <head>
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<div style="text-align: center;"><a href="https://1.bp.blogspot.com/-ebZrj26cSsA/YLax7dSJd5I/AAAAAAAATRA/rJE_L2fA0fM46ngjvpvJSBwY07yGRG_OwCLcBGAsYHQ/s2048/Soviet_ATGM%2527s.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1580" data-original-width="2048" height="494" src="https://1.bp.blogspot.com/-ebZrj26cSsA/YLax7dSJd5I/AAAAAAAATRA/rJE_L2fA0fM46ngjvpvJSBwY07yGRG_OwCLcBGAsYHQ/w640-h494/Soviet_ATGM%2527s.jpg" width="640" /></a></div><p><br /></p><p>After the conclusion of the Second World War, at a time when the exploration of new technologies such as jet propulsion and nuclear bombs was being actively pursued by all of the world's major military powers, heavy investments were made in researching the means of guided payload delivery in the U.S and the USSR. The primary applications of this technology were in anti-aircraft missiles to destroy bombers and in long-range ballistic missiles, both of which were given the utmost attention as they were viewed as being the deciding factors in a potential future conflict.</p><p>However, in the USSR during the early to mid-1950's, the concept of guided anti-tank weapons was not fully appreciated by the military and the state, so all domestic projects were created exclusively under the private initiatives of design bureaus. There were several of these anti-tank missile projects, developed under the name "UPS", which stood for "guided anti-tank projectile". A large variety of guidance technologies were tested with working prototypes, from wire guidance to television guidance, but none progressed beyond the experimental stage, and there was no directive from the state to pursue further developments.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-q5tVmXaZ_-c/YKuCKns-zxI/AAAAAAAATGI/EhxmI-XIK5YfD9wDjrSqJCDtpZ3SOOByACLcBGAsYHQ/s1304/ups-1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="577" data-original-width="1304" height="178" src="https://1.bp.blogspot.com/-q5tVmXaZ_-c/YKuCKns-zxI/AAAAAAAATGI/EhxmI-XIK5YfD9wDjrSqJCDtpZ3SOOByACLcBGAsYHQ/w400-h178/ups-1.png" width="400" /></a><a href="https://1.bp.blogspot.com/-g9rS15h9390/YKuCKvznLqI/AAAAAAAATGE/AmpNngaIvS4dusyTIUqdLz-_2wwARtW4QCLcBGAsYHQ/s1324/ups.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="648" data-original-width="1324" height="196" src="https://1.bp.blogspot.com/-g9rS15h9390/YKuCKvznLqI/AAAAAAAATGE/AmpNngaIvS4dusyTIUqdLz-_2wwARtW4QCLcBGAsYHQ/w400-h196/ups.png" width="400" /></a></div><p>After intelligence reports on the use of SS.10 ATGMs by French forces against Egypt during the Suez Crisis arrived, great interest was aroused in the ministry of defence, resulting in a total reevaluation of priorities regarding ATGM technology. In 1956, the Council of Ministers issued a resolution titled "<i>development of work on the creation of guided anti-tank weapons</i>", officially commencing the familiarization process for this new technology among the specialists of the country; intelligence reports and technical data from foreign sources were transferred to research institutes, and intense research programmes kicked off. In fact, according to Alexander Shirokorad, manuals on the Cobra, SS.10 and SS.11 were acquired, and some live samples of foreign ATGMs were even obtained for study. In the book "<i>Отечественные бронированные машины. 1946-1965 гг.</i>", it is specified that research was undertaken on samples of captured German experimental X-7 "Rotkäppchen" ATGMs and the French SS.11.</p><p>On May 8, 1957, another decree from the Council of Ministers titled "<i>On the creation of new tanks, self-propelled tank destroyers and guided rocket weapons for them</i>" was issued. This officially launched the rapid development of tank, man-portable and heavy missile systems, with the tank missile systems being seen as promising alternatives for high-powered guns. From this, a series of domestic First Generation missile systems was born. </p><p>Despite the late start, Soviet ATGM development progressed extremely rapidly, qualitatively matching the best NATO missile systems by 1960 with the "Falanga" and then the "Malyutka" in 1963. Even the "Shmel", having an exceptionally conservative design, had some merit in its ease of manufacture and simplicity, as this gave it a high reliability rate that not all ATGMs shared. This led to a rather interesting situation where by the turn of the decade, the USSR joined the Swedes, Germans, and Swiss as major contenders in the international ATGM market, second only to France, while the U.S - the single most influential Western military force in the event of a major European war - was not even in the running. During the 1960's, the USSR occupied a relatively large market share largely thanks to its captive market among the Warsaw Pact nations as well as Soviet market domination in Africa (where the Soviet share of weapons imports sometimes reached 100%), supplemented by a few Arab clients and a few Asian clients, including Vietnam. Following the unprecedented mass deployment of ATGMs during the 1973 Yom-Kippur war, international interest in Soviet ATGMs exploded, influenced by somewhat alarmist reporting from Western military journals and magazines, and further buoyed by erroneous Soviet claims of up to 800 Israeli tanks being destroyed by the "Malyutka". It was also because of this conflict that every ATGM became known as a "Sagger" among NATO nations and in Israel. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ry5h2ejBvkE/YOU3SPjeeWI/AAAAAAAATvw/KSkhEtPjf7UBwLi_qd_fzV5onb9zlZtdQCLcBGAsYHQ/s2264/increased%2Binterest%2Bin%2BATGMs.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1048" data-original-width="2264" height="296" src="https://1.bp.blogspot.com/-ry5h2ejBvkE/YOU3SPjeeWI/AAAAAAAATvw/KSkhEtPjf7UBwLi_qd_fzV5onb9zlZtdQCLcBGAsYHQ/w640-h296/increased%2Binterest%2Bin%2BATGMs.png" width="640" /></a></div><p>In the aftermath of the 1973 war, the USSR surpassed France in terms of export volume as well as the size of the customer base, gaining a plethora of clients in the Middle East, Asia and also gaining Yugoslavia. According to a 1980 SIPRI yearbook, there were a cumulative total of 11 clients who ordered the MILAN in the period between 1970-1980, the earliest order being in 1976 (to the U.K), followed by Belgium, Spain, and so on. During this same period, 17 clients ordered "Malyutka" and "Fagot" ATGMs from the USSR. In terms of the scale of domestic use, the Soviet Army surpassed the French Army as the most prolific individual operator of ATGM systems during the 1960's by virtue of its sheer size and industrial capacity.</p><p>This article will examine the seven major Soviet anti-tank guided missiles that entered service and saw widespread use. </p><p><br /></p>
<h3 style="text-align: left;"><span style="font-size: large;">INDEX</span></h3>
<hr />
<ol style="text-align: left;">
<li><a href="#firstgeneration">First Generation</a></li>
<li><a href="#aerodynamics">Aerodynamic Considerations</a></li>
<li><a href="#manual">Manual Guidance Considerations</a></li>
<hr />
<li><a href="#shmel">3M6 "Shmel"</a></li>
<li><a href="#shmeldesign">General Design Features</a></li>
<li><a href="#shmelaerodynamics">Aerodynamics</a></li>
<li><a href="#shmelguidance">Guidance System</a></li>
<li><a href="#shmelsteering">Steering</a></li>
<li><a href="#shmelengine">Engine</a></li>
<li><a href="#shmelwarhead">Warhead</a></li>
<hr />
<li><a href="#falanga">3M11 "Falanga"</a></li>
<li><a href="#falangadesign">General Design Features</a></li>
<li><a href="#falangaaerodynamics">Aerodynamics</a></li>
<li><a href="#falangaguidance">Guidance System</a></li>
<li><a href="#falangasteering">Steering</a></li>
<li><a href="#falangaengine">Engine</a></li>
<li><a href="#falangawarhead">Warhead</a></li>
<hr />
<li><a href="#malyutka">9M14 "Malyutka"</a></li>
<li><a href="#malyutkadesign">General Design Features</a></li>
<li><a href="#malyutkaaerodynamics">Aerodynamics</a></li>
<li><a href="#malyutkaguidance">Guidance System</a></li>
<li><a href="#malyutkaengine">Engine</a></li>
<li><a href="#malyutkasteering">Steering</a></li>
<li><a href="#malyutkawarhead">Warhead</a></li>
<hr />
<li><a href="#secondgeneration">Second Generation</a></li>
<li><a href="#guidanceconsiderations">Guidance considerations</a></li>
<hr />
<li><a href="#fagot">9M111 "Fagot"</a></li>
<li><a href="#fagotdesign">General Design Features</a></li>
<li><a href="#fagotaerodynamics">Aerodynamics</a></li>
<li><a href="#fagotguidance">Guidance System</a></li>
<li><a href="#fagotsteering">Steering</a></li>
<li><a href="#fagotejection">Ejection Charge</a></li>
<li><a href="#fagotengine">Engine</a></li>
<li><a href="#fagotwarhead">Warhead</a></li>
<hr />
<li><a href="#konkurs">9M113 "Gaboy"</a></li>
<li><a href="#konkursdesign">General Design Features</a></li>
<li><a href="#konkursaerodynamics">Aerodynamics</a></li>
<li><a href="#konkursguidance">Guidance System</a></li>
<li><a href="#konkurssteering">Steering</a></li>
<li><a href="#konkursejection">Ejection Charge</a></li>
<li><a href="#konkursengine">Engine</a></li>
<li><a href="#konkurswarhead">Warhead</a></li>
<hr />
<li><a href="#kokon">9M114 "Kokon"</a></li>
<li><a href="#kokondesign">General Design Features</a></li>
<li><a href="#kokonaerodynamics">Aerodynamics</a></li>
<li><a href="#kokonguidance">Guidance System</a></li>
<li><a href="#kokonsteering">Steering</a></li>
<li><a href="#kokonejection">Ejection Charge</a></li>
<li><a href="#kokonengine">Engine</a></li>
<li><a href="#kokonwarhead">Warhead</a></li>
<hr />
<li><a href="#metis">9M115 "Metis"</a></li>
<li><a href="#metisdesign">General Design Features</a></li>
<li><a href="#metisaerodynamics">Aerodynamics</a></li>
<li><a href="#metisguidance">Guidance System</a></li>
<li><a href="#metissteering">Steering System</a></li>
<li><a href="#metisengines">Engines</a></li>
<li><a href="#metiswarhead">Warhead</a></li></ol>
<hr /><p></p>
<p><br /><a href="https://www.blogger.com/null" id="firstgeneration"></a></p><h3 style="text-align: left;"><span style="font-size: large;">FIRST GENERATION</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-spQ2Irnnkyc/YLauoqGaVQI/AAAAAAAATQ4/6yHCRHKFGTkNyXCxLkoE9eDvLxEpDCYmACLcBGAsYHQ/s959/soviet%2BATGM%2Bposter.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="959" data-original-width="729" height="640" src="https://1.bp.blogspot.com/-spQ2Irnnkyc/YLauoqGaVQI/AAAAAAAATQ4/6yHCRHKFGTkNyXCxLkoE9eDvLxEpDCYmACLcBGAsYHQ/w486-h640/soviet%2BATGM%2Bposter.jpg" width="486" /></a></div><p>The decree from the Council of Ministers, "<i>On the creation of new tanks, self-propelled tank destroyers and guided rocket weapons for them</i>" contained a list of eight ATGM projects to be pursued. All eight projects were distinct from one another in fundamental ways, from the guidance method to the aerodynamic scheme. The large number of systems ordered was due to the novelty and complexity of the task; there was no institutional experience in developing guided weapons of such a small size, and hardly any backlog of research to indicate the most promising design solutions to implement. As such, the intent was to assign a wide diversity of projects to multiple design bureaus and choose the best designs to introduce into service and to use as the basis for further work. There was no unified vision for what an ideal ATGM would look like, so the concepts were developed in a piecemeal fashion. There was at least one missile conceptualized for each conceivable application, from man-portable, self-propelled, heavy missile tank, medium missile tank, and an add-on missile for existing tanks.</p><p>OKR "Shmel" was the least ambitious research and development project, created with the intent of providing a basic failsafe option in case the other projects failed to produce workable products. The task of developing the "Shmel" system, listed as "Topic 7", was assigned to the Kolomna Special Design Bureau (SKB) in a decree issued by the Council of Ministers on May 27, 1957. SKB later became KBM. The creation of a control system for the ATGM was assigned to the famous TsNII-173 research institute, which had extensive experience in the development of steering drives and remote control systems for various guided vehicles. The development of the "Falanga" system was carried out under "Topic 8" by OKB-16, which later became KB Tochmash. After the initial round of development concluded, OKR "Malyutka" was borne out of the failure of the "Shmel" to fulfill the requirements of its original tactical niche. Of the two, only the "Malyutka" was a true man-portable system, as a number of design simplifications were made to "Shmel" which severely bloated its weight and dimensions, but these simplifications were commensurate with the spirit of the desire to have at least one failsafe ATGM option in service and were thus tolerated.</p><p><br /></p><p>This article will explore the three first generation ATGMs that went into service in the Soviet Army. These were:</p><p></p><ol style="text-align: left;"><li>3M6 "Shmel"</li><li>3M11 "Falanga"</li><li>9M14 "Malyutka"</li></ol><p><br /></p><p>As with many attempts to classify technology into discrete generations, the dividing line between missiles of the first and second generations is rather blurred, as there are very few primary technologies that conclusively distinguish a first generation ATGM from a second generation model. The only tangible feature that is shared among all first generation ATGMs without exception but not present in second generation models, is that they were launched in a lofted trajectory, and not directly towards the target. </p><p>In the long period between the advent of the first ATGM, the French SS.10, in 1956 to the adoption of the first second generation ATGM in 1972, a number of technical innovations made their way into first generation systems that became standard on the following generation. Even the distinction between manual (MCLOS) and semi-automatic (SACLOS) control is not a useful distinguisher, as this technology is related to the launcher rather than the missile itself. First generation ATGMs have been used with SACLOS guidance quite extensively, most notably with the limited deployment of "Malyutka-P" systems by Syrian and Egyptian forces during the 1973 Arab-Israeli war. A lack of containerization, which was a universal feature of second generation missiles, is also not a useful distinguishing feature, as the Bantam and Swingfire ATGMs were both packed in hermetically sealed launch containers. </p><p>In practical terms, the most meaningful identification of a first generation ATGM is made by taking a holistic view of their technical details rather than individually, as the generation following them was borne out of the desire to combine all of their best characteristics without the drawbacks thereof. Very few first generation ATGMs had advantages that so thoroughly overwhelmed their downsides to justify continued use. The longest-lasting models in Soviet service were the "Malyutka" and "Falanga", both of which achieved a level of technical excellence that placed them on the border between the two generations, allowing them to endure the transition in their careers not merely out of expediency and cost, but for their own technical merits.</p><p><br /><a href="https://www.blogger.com/null" id="aerodynamics"></a></p><h3 style="text-align: left;"><span style="font-size: large;">AERODYNAMIC CONSIDERATIONS</span></h3><p style="text-align: left;">At the most basic level, an anti-tank guided missile is an aircraft - a flying machine, in the technical sense of the term. With that, it possesses most of the design challenges associated with flying machines, the most basic of which is the ability to maintain a given altitude, as the effects of gravity must be counteracted by some means. Being rocket-propelled weapons, the first inclination of a designer may be to rely on rocket thrust for this purpose, but this is not practical. As the missile will be flying directly towards a target situated on the ground, the missile will be oriented almost parallel to the ground, which inherently limits the vertical thrust component of its rocket engine to a near-negligible amount. Instead, wings are needed to support the weight of the missile, which is achieved by having the aerofoil of the wings produce a lift force that is equal to the downward force from the mass of the missile under acceleration by gravity; its weight. This ensures that the missile is capable of level flight - that is, it can maintain a given altitude. On top of that, the missile must also be capable of changing its flight vector so that its trajectory can be steered towards a target in both the horizontal and vertical axes. The missile must therefore have steering mechanisms, which can either rely on aerodynamic control surfaces or on the manipulation of rocket thrust. When these two basic features are present, it can be considered a guided weapon, and the military definition of a missile is satisfied. However, in order to have an effective missile, a number of aerodynamic considerations must be taken into account in its design. </p><p style="text-align: left;"><br /></p><h3 style="text-align: left;">STABILITY</h3><p>The first and most important aerodynamic consideration in the design of an ATGM is its aerodynamic stability. In particular, high static and dynamic stability have special importance to MCLOS systems because it improves the controllability of the missile in the presence of wind and other irregularities. The most important metric for controllability is the ability of the missile to maintain a given flight attitude, dictated by the operator, which requires the missile to resist changes in pitch whenever they are induced by external forces. The main issue is crashing the ATGM into the ground, because tanks are low-profile targets, usually requiring the missile to be travelling no more than 1-2 meters above ground level, and potentially less than a meter above the ground, if the tank is in a hull-down position. A crash may be caused by a tailwind, which reduces the relative airspeed and thus the lift, a strong downdraft, which may physically displace the missile downward, or an updraft, which induces the missile to steer into the direction of the air current, causing it to nosedive into the ground. These forms of external influence can cause a missile flying close to the ground to crash before the operator can even react, and the resistance of an ATGM to this aerodynamic interference is primarily governed by static stability. </p><p>With a positive margin of static stability, the missile resists changes in its flight vector. If its attitude is disturbed by a wind, it will return to its original attitude on its own, and thus the flight vector remains the same. With negative static stability, the missile will accelerate in whichever direction it is directed, whether by intentional control or by external factors, and with neutral static stability, the missile will not resist a change in its attitude nor will it accelerate any changes. If the original attitude was changed, it will simply remain in its new attitude and the flight vector changes accordingly. This applies equally to the pitch and yaw axes. Resistance to crosswinds is also important for all types of ATGMs because it can cause a miss, particularly on moving targets, so yaw stability has its own importance even if it is not as critical as pitch stability.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-CiPo-8qRbV4/YPtowpL-93I/AAAAAAAAUCU/izZUWWVTmT0Svo49v6BSGNOsD4eCx58hACLcBGAsYHQ/s1995/atgm%2Bstatic%2Bstability.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="845" data-original-width="1995" height="272" src="https://1.bp.blogspot.com/-CiPo-8qRbV4/YPtowpL-93I/AAAAAAAAUCU/izZUWWVTmT0Svo49v6BSGNOsD4eCx58hACLcBGAsYHQ/w640-h272/atgm%2Bstatic%2Bstability.png" width="640" /></a></div><p>If the missile possesses static stability, the next issue is dynamic stability, which defines the oscillatory behaviour of the missile after the initial disturbance. The behaviour of a missile with negative, neutral and positive dynamic stability is shown in the drawing below in red, blue and green lines respectively, with the black axis indicating the original flight vector of the missile. With negative dynamic stability, the missile accelerates in its oscillation, each swing becoming more and more violent (divergent oscillation). Neutral dynamic stability simply means that the missile oscillates at the same period and amplitude as its initial recovery arc when the missile responded to the disturbance (undamped oscillation). With positive dynamic stability, the oscillations of the missile are damped. Essentially, the margin of static stability dictates the initial amplitude of the oscillation, and if the missile possesses dynamic stability, the margin of dynamic stability dictates how strongly the oscillation is damped.</p><p>In all cases, it was ideal for the missile to be heavily damped, especially in the case of early MCLOS missiles. Removing or at least suppressing the oscillation of the missile about its heading simplifies guidance and reduces the dispersion of the missile during its approach to the target. It also reduces the likelihood of errant terrain, or even fuselage collision, for missiles launched from aircraft. In all of the Soviet ATGMs explored in this article, intrinsic dynamic stability came entirely from aerodynamic damping. Additional artificial damping could come from operator inputs, but there was no integral system of artificial damping, as found in self-contained guidance systems.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ZMDUw1m3jKY/YPtqMEY7lYI/AAAAAAAAUCc/qbTR-QZzbwosKSo63Y1icJ7rD6BY2YAtACLcBGAsYHQ/s2910/atgm%2Bdynamic%2Bstability.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1058" data-original-width="2910" height="232" src="https://1.bp.blogspot.com/-ZMDUw1m3jKY/YPtqMEY7lYI/AAAAAAAAUCc/qbTR-QZzbwosKSo63Y1icJ7rD6BY2YAtACLcBGAsYHQ/w640-h232/atgm%2Bdynamic%2Bstability.png" width="640" /></a></div> <p></p><p>To ensure controllability and resistance to crashing, all ATGMs have positive static stability and positive dynamic stability, but with varying margins depending on their design parameters. Both forms of aerodynamic stability are essential in providing controllability, even in SACLOS missiles which are automatically steered by the guidance computer. Furthermore, as ATGMs are almost always symmetrical in design, or spin in flight, they possess the same level of stability in both the yaw and pitch axes. With positive static stability, the missile is able to execute a vertical steering command, changing its flight vector up or down, left or right, and once the steering command is removed, the missile will return to its original vector under the balancing moments generated by the lift forces of the missile lifting surfaces, which are designed to be in equilibrium about the center of gravity of the missile when it is traveling at a specific angle of attack, known as the equilibrium angle. The missile will also tend to return to this attitude if disturbed by wind, not only by pitch steering commands.</p><p>Static and dynamic stability is achieved by placing the center of gravity of the missile ahead of its center of pressure, where the sum of all aerodynamic lift forces act upon the missile. The further the center of gravity is forward of the center of lift, the larger the margin of stability, because the moment arm is longer and thus, the balancing force generated by the wings will create a larger balancing moment. An excessively large margin of stability is undesirable, because an ATGM has a finite load capacity, and its steering mechanism generates a finite steering force. If the steering moment is only slightly greater than the balancing moment, the control responsiveness of the missile is poor, and is normally felt by the operator as a sluggish response. Moreover, it is disadvantageous to design an ATGM with powerful steering mechanisms to generate a steering moment powerful enough to overcome an enormous balancing moment, as that would only increase the parasitic mass of the missile. It is best to ensure a good balance, and this must be ensured at the very beginning of the design process. In general, the lighter the missile, the easier it is to obtain a favourable compromise.</p><p>Furthermore, it is important that the center of gravity changes as little as possible during flight, so as to not compromise either the stability or control responsiveness of the missile. To that end, the center of gravity of ATGMs is universally defined by the position of its rocket engine, so that as its fuel depletes over the course of the flight, the depletion occurs at the center of gravity, so the balance is shifted as little as possible, although the total lack of change is usually not guaranteed since rear end-burning solid fuel engines are predominant among ATGMs.</p><p><br /></p><h3 style="text-align: left;">LEVEL FLIGHT</h3><p>The second aerodynamic consideration is the ability of the missile to maintain altitude in all operating conditions - that is to say, it must be capable of level flight. Level flight is attained when two critical conditions are met: </p><p></p><ol><li>Achieving equilibrium between the missile weight and its aerodynamic lift</li><li>Achieving equilibrium between thrust and air resistance</li></ol><p></p><p>The two are interlinked, as the lift generated from aerofoil wings is proportional to the airflow over the wing. By generating enough thrust to equal air resistance, thus maintaining a fixed air speed, the lift produced does not change, and a level altitude can be maintained. However, the reference point for level flight is usually not set at normal conditions (+20°C). Because ATGMs are required to operate in extremely cold weather, as low as -40°C or even -50°C, engine thrust which matches air resistance at normal conditions will be insufficient at such low temperatures, as the fuel will have a lower energy content, generating reduced thrust, whereas the air resistance it must overcome will be greater due to the increased density of the air. Such a missile would have to fly at an increased angle of attack, and by doing so, suffer from high induced drag and poor pitch responsiveness. If the operator manages to keep the missile flying, it would not be capable of achieving its specified maximum range, which is normally a cause for rejection by the military testing commission. Because of this, the sustainer engine of most if not all ATGMs with a dual-thrust propulsion system will produce a surplus of thrust at normal conditions (+15-21°C), so that they meet the thrust requirement for level flight in extreme cold. Consequently, they have a tendency to climb when used at temperatures above -50°C or -40°C if a pitch-down command is not periodically given. Only the earliest ATGMs were designed without consideration for temperature differences, namely the 3M6 and the SS.10. It became a standard design feature in French ATGMs beginning with the SS.11, and domestically, it began with the 3M11 "Falanga".</p><p><br /></p><h3 style="text-align: left;">RELATIONSHIP BETWEEN LIFT AND ANGLE OF ATTACK</h3><p>For a given wing design, the greater the airspeed or the greater the angle of attack, the greater the lift. This means that, for a given wing design, a slow ATGM must assume a high angle of attack to produce enough lift to remain in level flight, and conversely, a faster ATGM can fly at an angle of attack closer to 0 degrees. For a given angle of attack, a faster ATGM can also afford to have smaller wings with a smaller lift coefficient, which also reduces the lift-induced drag and is thus more supportive of higher speeds. For low-velocity missiles, mainly ATGMs of the first generation, the low lift from the low air speed can be compensated by enlarging the wings, or by increasing the angle of attack of the missile to increase the lift coefficient of the wings. Most first generation ATGMs were designed with very large wings for this reason, as illustrated in the image below. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-bICw-ERn1AQ/YPq3tUgRltI/AAAAAAAAUCE/yxiFApHzrw4jsmeD4LT2MqikNCGzwerhACLcBGAsYHQ/s2248/foreign%2BATGMs.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="698" data-original-width="2248" height="198" src="https://1.bp.blogspot.com/-bICw-ERn1AQ/YPq3tUgRltI/AAAAAAAAUCE/yxiFApHzrw4jsmeD4LT2MqikNCGzwerhACLcBGAsYHQ/w640-h198/foreign%2BATGMs.png" width="640" /></a></div><p>An increased angle of attack is naturally needed when an ATGM is launch, as the missile must not drop to the ground or hit an obstacle during the time it accelerates to the velocity needed for level flight. For this reason, virtually all early ATGMs are launched from an elevated rail, and the majority of SACLOS missiles assume a positive angle of attack during their boost phase immediately after leaving the container. During sustained flight, however, an increased angle of attack harms the penetration potential of the warhead, especially on sloped armour. </p><p>For instance, the SS.10 and ENTAC missiles both require a positive angle of attack for level flight. The necessary angle of attack for both missiles is 6-7 degrees, while a higher velocity missile such as the Vickers Vigilant flies at an angle of attack of +5 degrees. As to the effect of the angle of attack, one way or another, it compromised the penetration power of the warhead as the incident angle of the shaped charge jet on an armour plate is increased, particularly on steeply sloped armour. If an SS.10 struck a steel armour plate measuring 200mm thick and sloped at 60 degrees, it would not have to perforate 400mm, which is the geometric LOS thickness, but rather, face an effective thickness of 492mm.</p><p>From this, it is clear that special caution must be exercised when reading penetration figures for first generation ATGMs, as they tend to be reported according to the maximum achievable penetration at an optimum standoff, in addition to having been done in static tests, without acknowledging the attitude of the missile in real flight conditions. To escape these pernicious effects, ATGMs benefit from having wings of the largest practical size, and as quick of a flight speed as possible, thus producing a great deal of lift without resorting to a high angle of attack.</p><p>For missiles that decelerate during flight for whatever reason, whether it is due to sustainer engine burnout (Falanga series) or simply due to the lack of a dual-thrust engine (TOW), the angle of attack can increase considerably during the course of its flight. The TOW missile series, for instance, relies on a short but powerful boost engine to bring it up to nearly 300 m/s, wherein a distance of around 300 meters is covered, but the missile is left to glide for the remainder of its trajectory. For earlier TOW models with a maximum range of 3,000 meters, the speed of the missile falls to around 140 m/s by the end of its flight, and for later TOW models with a maximum range of 3,750 meters, it is as low as around 105 m/s. The small wings, which are adequate during the first few seconds of flight, gradually lose their effectiveness as the missile speed declines. To compensate for the gradual reduction in air speed, the missile must, axiomatically, increase its angle of attack. Determining a single exact angle of attack is somewhat futile for the TOW, because it increases during the gradual deceleration of the missile during its flight. In the specific case shown in the images below, taken from <a href="https://www.youtube.com/watch?v=2xlOFavFZDQ">a Raytheon promotional video showing a wireless (radio-guided) TOW-2A</a>, it is around +5 degrees.</p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both;"><a href="https://1.bp.blogspot.com/-ktdjGrjLdKg/YKr1BpeirnI/AAAAAAAATFs/l03MK1h7p84DT4CNXD5rJ-phHLm3lTZAQCLcBGAsYHQ/s1200/angle%2Bof%2Battack%2Bterminal%2Bphase.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="675" data-original-width="1200" height="225" src="https://1.bp.blogspot.com/-ktdjGrjLdKg/YKr1BpeirnI/AAAAAAAATFs/l03MK1h7p84DT4CNXD5rJ-phHLm3lTZAQCLcBGAsYHQ/w400-h225/angle%2Bof%2Battack%2Bterminal%2Bphase.gif" width="400" /></a><a href="https://1.bp.blogspot.com/-nL8oeX44cbY/YJWPbiw79NI/AAAAAAAAS6w/_NZXwzJP0oAp5EIzKXGLs668UulRA995QCLcBGAsYHQ/s1920/tow%2Bpitch%2Bup%2B2%2Bangle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://1.bp.blogspot.com/-nL8oeX44cbY/YJWPbiw79NI/AAAAAAAAS6w/_NZXwzJP0oAp5EIzKXGLs668UulRA995QCLcBGAsYHQ/w400-h225/tow%2Bpitch%2Bup%2B2%2Bangle.png" width="400" /></a></div></div><p>The most serious implication of this behaviour is that the penetration power of the warhead also degrades according to range, proportionate to the change in its angle of attack. A missile impacting the upper edge of a tank turret might have its shaped charge jet fail to enter the tank at all, and missiles impacting sloped armour, particularly sloped reactive armour panels, could have their effectiveness eroded considerably by a combination of increased armour thickness and stronger disruptive effect from the reactive armour. From this, it is plain to see that the perceived property of HEAT warheads in maintaining a consistent penetration power regardless of velocity or range is not the entire truth. For this reason, penetration data based on static testing may substantially overrepresent the real penetration capability. </p><p><br /><a href="https://www.blogger.com/null" id="manual"></a></p><h3 style="text-align: left;"><span style="font-size: large;">MANUAL GUIDANCE</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-6Z1FPC8sCLI/YKUlSHwg8_I/AAAAAAAATBI/dv875RvRMOg-esiPB834t81Bh9Rvwa3zwCLcBGAsYHQ/s1944/hit%2Bprobability.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1657" data-original-width="1944" height="341" src="https://1.bp.blogspot.com/-6Z1FPC8sCLI/YKUlSHwg8_I/AAAAAAAATBI/dv875RvRMOg-esiPB834t81Bh9Rvwa3zwCLcBGAsYHQ/w400-h341/hit%2Bprobability.png" width="400" /></a></div><p><br /><br />In piloted aircraft, flight control for a collision course with a target occurs in a two-point mode where the pilot simply aligns his aircraft at the target. With three-point control, the operator visually tracks both the missile and the target, and steers the missile until his line of sight with the missile is aligned with his line of sight of the target. When firing at a static target, the guidance process is at its simplest. First generation ATGMs are designed to be launched at a lofted trajectory, gaining an altitude of several meters (normally around 6 meters) to ensure that collision with obstacles is impossible, and the task of the operator is to gently lower the missile until it is superimposed onto the target, whereupon it impacts and (hopefully) destroys it. The main source of interference in this process is a crosswind. Because it is propelled throughout its entire flight, the missile will tend to steer into the crosswind, rather than being carried along with it, as a bullet would. To negate a crosswind, the operator observes the direction of the wind before launch, and once the missile is airborne, he periodically inputs a brief steering correction in the opposite direction whenever the missile begins to drift.</p><p>However, missile guidance is complicated by the fact that, despite the static and dynamic stability of a missile, it will possess a certain amount of inertia from each steering motion, in both the pitch and yaw axes. For example, whenever a horizontal steering input is made and then the control joystick is returned to the neutral position, the missile will stabilize itself to its original flight vector due to its inherent dynamic stability, but there is still a sideways moment of inertia from the prior steering moment. Owing to this inertia, the missile will drift to the side at a rate that is only slowly damped by air resistance. To correct this, a steering input of the same magnitude and period (duration) as the previous input is made, but in the opposite direction. The counter-momentum nullifies the side inertia of the missile and returns it to a direct trajectory.</p><p>In the Vickers Vigilant, and later on, the Swingfire, the nullification of inertia was done automatically by the control panel. The magnitude and period of an input is recorded, and when the control thumbstick is returned to the neutral position, an opposite input of the same magnitude and period is made. This made the guidance process faster and easier, as it is one fewer task for the operator to deal with.</p><p>Beyond these basic guidance principles, there are also good practices to increase the probability of a hit.</p><p>If a steering correction is to be made to align a missile with the target, then the operator must make a gentle deflection of the control joystick in the appropriate direction for a short period, return the joystick to the neutral position, and then input the same deflection for the same period in the opposite direction, and return the joystick to the neutral position again. For the operator to become accustomed to this method of steering, he must undergo training until he is familiar with the steering dynamics on a reflexual level, and he must have good hand-eye coordination. According to the textbook, only up to 10% of trainees were discovered to be capable of guiding missiles to the required accuracy standards. To properly guide the missile, calmness is of critical importance, as hasty, jerky steering inputs must be avoided if possible. The image below shows an incorrect method of guiding an MCLOS missile (solid black line), and the correct method (dotted line).</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-kQr8undOdF8/YKUm6Cr_q0I/AAAAAAAATBQ/rZ_aApWyNF0pmvzCN_dyxz4scVQj0f7QACLcBGAsYHQ/s1358/trajectory%2Band%2Bcontrol%2Bsignal.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1358" data-original-width="581" height="400" src="https://1.bp.blogspot.com/-kQr8undOdF8/YKUm6Cr_q0I/AAAAAAAATBQ/rZ_aApWyNF0pmvzCN_dyxz4scVQj0f7QACLcBGAsYHQ/w171-h400/trajectory%2Band%2Bcontrol%2Bsignal.png" width="171" /></a></div><p>In the incorrect method, the sequence of events is as follows: </p><p></p><ul><li>Point A: the missile is assumed to have deviated to the left, and the operator wishes to return it to the direct LOS between himself (O) and the target (Ц). The operator gently deflects the joystick to the right, but he sees that the missile is still moving to the left, albeit at a slower rate.</li><li>Point B: in response, he jerks the control joystick to the right, and the missile rapidly turns right.</li><li>Point C: the missile has reached the LOS between the operator and the target, but it has overshot due to the excessive violence of the earlier steering command.</li></ul><p></p><p>Seeing this, the operator attempts to bring it back to the left by jerking the control joystick to the left, then to the right, and with such violent maneuvers, the missile is never properly aligned to the target, and it invariably misses. </p><p>To adjust the flight trajectory of the missile correctly, the operator must gently deflect the joystick to the right while observing the missile. It will slow down in its leftward motion, then begin to move to the right. Once it is aligned with the line of sight between the operator and the target, the operator inputs a gentle steer-left command, and the missile hits its target.</p><p>This dynamic between the human operator and the missile and the strong influence of good hand-eye coordination has serious design implications. The first and most obvious design consideration is that the steering system should be capable of bringing the missile to bear on a target that is off-angle to the initial launch direction of the missile, so it should be capable of imparting a strong steering moment, and the missile components should be capable of withstanding the lateral accelerations produced when such maneuvers are made. At the same time, the steering system should be precise enough that the operator can make gentle and minute adjustments to the flight trajectory of the missile. The second design consideration is that it must be feasible for the operator to guide the missile onto target even at a close range without being too taxing on his reaction time and ability to make fine inputs under great time stress. This was solved in virtually all first generation ATGMs by having a thrust surplus from the sustainer stage of their engines, which is also a cold weather performance factor as detailed in the previous section. By having an accelerating flight profile, the amount of time available to the operator to engage a target at close range is increased, yet the missile can reach a target at long range without an excessively long flight time.</p><p><br /></p><p>Live missile launches at the gunnery range was permitted only after the trainee completed around 1,000 simulated launches. Though this figure is rather dramatic, it is important to keep in mind that the flight time of a missile such as the "Malyutka" to its maximum range is just 25 seconds. Given that each engagement could last a maximum of 25 seconds, the total time spent in a simulator can be up to 7 hours, but the real training duration is undoubtedly less, because simulated engagements at closer ranges (around 2 km) were predominant.</p><p><br /><a href="https://www.blogger.com/null" id="shmel"></a></p><h3 style="text-align: left;"><span style="font-size: large;">"Shmel" ("Bumblebee")</span></h3><h3 style="text-align: left;"><span style="font-size: large;">3M6</span><span style="font-size: x-large;"> </span></h3><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both;"><a href="https://1.bp.blogspot.com/-Knj0lhWKnj4/YKt6aVXHAWI/AAAAAAAATF8/_qHR6htumyogvMUAxLWeSfecPBuzRmQZACLcBGAsYHQ/s2048/shmel%2Bcover.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1980" height="320" src="https://1.bp.blogspot.com/-Knj0lhWKnj4/YKt6aVXHAWI/AAAAAAAATF8/_qHR6htumyogvMUAxLWeSfecPBuzRmQZACLcBGAsYHQ/s320/shmel%2Bcover.png" /></a></div></div><p>The urgency of the Soviet ATGM programme can be best appreciated by looking at the development period of the "Shmel" in comparison with its direct counterpart, the SS.10. The SS.10 began development in 1946, had its first unguided flight tests in 1949, and entered service in 1955 - a total period of 9 years. For comparison, the "Shmel" project began in 1957, it had its first unguided launch tests in April 1958, proceeded to controlled launches in June 1958, and was demonstrated to the military in August 1959. Overall, the development of the 3M6 was 3 times shorter than the SS.10 along every milestone in its timeline.</p><p>The 3M6 missile entered service on the 8th of January 1960 as an integral component of the 2K15 and 2K16 missile systems incorporating it, implemented on the 2P26 and 2P27 missile carriers respectively. The 2P26 was made for, and procured by the VDV, while the 2P27 was procured by the Ground Forces. The 3M6 was the first Soviet ATGM to enter service, followed shortly by the 3M11 missile of the 2K8 "Falanga" system which entered service several months later, on the 30th of August 1960. A production line was set up in the Degtyaryov factory, almost simultaneously and in parallel with the production line of the S-75 missile, and the first serially produced batch of missiles was delivered to the Soviet Army in 1961. Mass production of the 3M6, along with the 2P26 and 2P27, lasted from from 1961 to 1966. </p><p>In some sources, such as the article "<i>Первые ОКР по противотанковым и танковым управляемым ракетам</i>" by I. Pavlov and A. Sorokina, published in the September 2018 issue of the "<i>Техника и вооружение</i>" magazine, it is stated that the continued production of 3M6 missiles until 1966 was purely for replenishing existing stocks expended in training and to support the demand from export clients. The modernization of the "Shmel" was cancelled due to the appearance of the "Malyutka" system, which surpassed it in all technical characteristics and had great potential for future developments.</p><p>Interestingly enough, in a rather unusual turn of events, the "Shmel" ATGM was very quickly approved for export and licenced production among the Warsaw Pact nations and the GDR, despite guided anti-tank missiles being an entirely new military technology. The 3M6 enjoyed much greater longevity among these export clients than in the Soviet Army, serving to form the backbone of the ATGM arsenal of those militaries prior to the mass introduction of "Malyutka" systems in the early 1970's. Poland, for example, received 3M6 launchers in 1962, and technical manuals translated from the Soviet originals were approved in 1962 and were published by 1963. The USSR granted Poland the licence to produce the 3M6 in 1963, and exported 2P26 and 2P27 tank destroyers until 1966. According to the article "<i>Przeciwpancerne pociski kierowane w ludowym Wojsku Polskim</i>" (<i>Anti-tank guided missiles in the Polish People's Army</i>) published in the February 2021 issue of the Polish technology magazine "<i>Nowa Technika Wojskowa</i>", local production of the 3M6 began in 1965, and by early 1967, the Polish People's Army posessed 8 2P26 tank destroyers and 72 2P27 tank destroyers. Mass production of 3M6 missiles continued from 1965 to 1972, and they continued to be used until 1979 at the latest. </p><p>Like in the USSR, local improvement projects were not carried out amongst the licenced manufacturers of the "Shmel" in the Warsaw Pact, presumably because the export and grants for licenced production of the "Malyutka" began in a timely manner.</p><p>Though "Shmel" missile systems were mass-produced in the USSR and issued to the troops, the predominant impact of the system was to build up valuable expertise in the Kolomna design bureau and to give the Soviet Army a degree of operational familiarity with ATGMs. In the latter context, the "Shmel" served the same purpose as the SS.10 in the U.S.A, where it was procured by the U.S Army as the MGM-21A in 1960 after domestic attempts to create a workable ATGM system stalled. </p><p><br /><a href="https://www.blogger.com/null" id="shmeldesign"></a></p><h3 style="text-align: left;"><span style="font-size: large;">GENERAL DESIGN FEATURES</span></h3><p style="text-align: center;"><br /></p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-hdPHdFEGx2U/YKJoON0pHNI/AAAAAAAAS_c/junzDxL6sqQCeIglnouG2wf4tPkcKLLGgCLcBGAsYHQ/s1589/3m6%2Bparts.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1274" data-original-width="1589" height="321" src="https://1.bp.blogspot.com/-hdPHdFEGx2U/YKJoON0pHNI/AAAAAAAAS_c/junzDxL6sqQCeIglnouG2wf4tPkcKLLGgCLcBGAsYHQ/w400-h321/3m6%2Bparts.png" width="400" /></a><a href="https://1.bp.blogspot.com/-GugPWdZoWsY/YKJoOGfHWkI/AAAAAAAAS_g/vxdJ4oNZH1wXxSYoPLE0ccLb9Vs8rywfgCLcBGAsYHQ/s2048/shmel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1395" data-original-width="2048" height="272" src="https://1.bp.blogspot.com/-GugPWdZoWsY/YKJoOGfHWkI/AAAAAAAAS_g/vxdJ4oNZH1wXxSYoPLE0ccLb9Vs8rywfgCLcBGAsYHQ/w400-h272/shmel.png" width="400" /></a></p><p>A conservative design philosophy was adopted for the 3M6, whereby the decision was made to implement the flying wing aerodynamic scheme, wire guidance, dual-stage engine and spoiler steering system of the SS.10 as it was a proven missile system, so naturally, the technological solutions it used were considered to have the lowest technical risk. The intent was to ensure that if all other ATGM development projects failed, the Soviet Army could be guaranteed to have at least one basic, functional ATGM system. That said, the design concept was the only similarity between the 3M6 and the SS.10 - the former was by no means a physical copy of the latter and the two do not even share a visual resemblance, as the 3M6 was a domestic design in all respects. </p><p>If the "Shmel" did not distinguish itself by its technological sophistication or innovation, it was at least reliable, having a failure rate of less than 2.5% according to the article "<i>Первые ОКР по противотанковым и танковым управляемым ракетам</i>".</p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-qSh0jSMsXzw/YIwt2gDdN4I/AAAAAAAAS5g/cUOcbIVVFqoGYPi2GivHsG9EuzfQjZPBQCLcBGAsYHQ/s864/3m6%2Bcolour%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="367" data-original-width="864" height="272" src="https://1.bp.blogspot.com/-qSh0jSMsXzw/YIwt2gDdN4I/AAAAAAAAS5g/cUOcbIVVFqoGYPi2GivHsG9EuzfQjZPBQCLcBGAsYHQ/w640-h272/3m6%2Bcolour%2Bdrawing.png" width="640" /></a></p><p>The diameter of the 3M6 fuselage is 136mm and its total length is 1,150mm. The complete missile weighs 24 kg. Far too heavy to be carried by infantry, the 3M6 was only used from missile carriers, those being the 2P26 tank destroyer based on the GAZ-69, and 2P27 tank destroyer based on the BRDM-1. In terms of its weight and performance, the 3M6 was stuck in an unhappy medium, being far too heavy for an infantry system like the SS.10, yet also lacking the high performance of a heavy ATGM, not even having advantages in stowage capacity compared to missiles like the SS.11 due to its large, obtrusive wings. In terms of capabilities and combat load, the closest analogue to the 2P26 would be the French <a href="http://www.m201.com/versions/SS10E.jpg">missile carrier based on the M201 jeep (known as Jeep SS.10)</a>, which carried three SS.10 ATGMs instead of the four "Shmels" on the 2P26.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-KAgKTdiZVZU/YKVeRUZ_5BI/AAAAAAAATCA/3gbUQMUzmW48XSw5r0fXmy9xkOHZ0YlMwCLcBGAsYHQ/s1791/loading%2B3m6%2Bonto%2B2p27.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1134" data-original-width="1791" height="253" src="https://1.bp.blogspot.com/-KAgKTdiZVZU/YKVeRUZ_5BI/AAAAAAAATCA/3gbUQMUzmW48XSw5r0fXmy9xkOHZ0YlMwCLcBGAsYHQ/w400-h253/loading%2B3m6%2Bonto%2B2p27.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-TCemMfv_7TQ/YKYmzCitCII/AAAAAAAATCo/_nuoIUgac_cL_z2De0hbJp23u4BghjWkACLcBGAsYHQ/s424/loading%2B2p26.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="402" data-original-width="424" src="https://1.bp.blogspot.com/-TCemMfv_7TQ/YKYmzCitCII/AAAAAAAATCo/_nuoIUgac_cL_z2De0hbJp23u4BghjWkACLcBGAsYHQ/s320/loading%2B2p26.jpg" width="320" /></a><br /></div><p style="text-align: left;"><br /></p><p style="text-align: left;">Internally, the layout of the 3M6 has a straightforward layout consisting of a warhead section, a guidance section, and an engine section, fitted sequentially in series. The warhead section consists of the shaped charge warhead and its fuzing system. Vacuum tube electronics were used for the guidance equipment. It is worth noting again that, although the 3M6 was directly inspired by the SS.10, it differs considerably in its layout, as the SS.10 has its guidance equipment arranged in the same fuselage compartment as the rocket engine, which also has a completely different design. Overall, it is impossible to view the 3M6 as a copy of anything, even superficially.<br /></p><p style="text-align: left;"><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-7yCGagB_iz4/YKWI2rHkOkI/AAAAAAAATCI/Mqnli8r4jXwEkN4nLSt5AQovfrhzcfEggCLcBGAsYHQ/s2048/3m6%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1366" height="400" src="https://1.bp.blogspot.com/-7yCGagB_iz4/YKWI2rHkOkI/AAAAAAAATCI/Mqnli8r4jXwEkN4nLSt5AQovfrhzcfEggCLcBGAsYHQ/w266-h400/3m6%2Bcross%2Bsection.png" width="266" /></a><a href="https://1.bp.blogspot.com/-NnMTX3cOTwI/YLDg3-YihvI/AAAAAAAATMo/Qs3B2i0APvIEk5MGE-UjAkPw24tsHxUOwCLcBGAsYHQ/s655/shmel%2Bcutaway%2Binstructional%2Bmodel.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="655" data-original-width="434" height="400" src="https://1.bp.blogspot.com/-NnMTX3cOTwI/YLDg3-YihvI/AAAAAAAATMo/Qs3B2i0APvIEk5MGE-UjAkPw24tsHxUOwCLcBGAsYHQ/w265-h400/shmel%2Bcutaway%2Binstructional%2Bmodel.jpg" width="265" /></a></div><p><a href="https://www.blogger.com/null" id="shmelaerodynamics"></a><br /></p><h3 style="text-align: left;"><span style="font-size: large;">AERODYNAMICS</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DjzLgoh3f8o/YMTRTsiHAoI/AAAAAAAATbw/HSAxHgHGD-oknIzPBUEly_6-FCpIWtcPACLcBGAsYHQ/s572/421.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="400" data-original-width="572" src="https://1.bp.blogspot.com/-DjzLgoh3f8o/YMTRTsiHAoI/AAAAAAAATbw/HSAxHgHGD-oknIzPBUEly_6-FCpIWtcPACLcBGAsYHQ/s320/421.jpg" width="320" /></a></div><p>Aerodynamically, 3M6 had a tailless delta aerodynamic scheme, with four large, fixed, cropped delta wings (also known as clipped delta). The wingspan is 750mm. As the missile is tailless, the wings provide lift, flight stabilization and steering all at once. The wings are symmetrical aerofoils, being flat plates with wedge-shaped leading and trailing edges, a shape known as a modified double wedge aerofoil. The construction of the wings consist of an aluminium alloy skin bonded to a plastic foam filler. The production process of the wings was detailed in the article "<i>Первенец противотанкового ракетостроения родился на ЗиДе</i>" published in the March 20, 2019 issue of the "<i>Дегтяревец</i>" Degtyarov factory newsletter by V.A. Golunov. Phenoplast (phenolic resin) is backfilled into the space between the aluminium wing skins, and then heat-activated adhesive is wadded in. With that done, the wing blank would be installed in a metal mould, and then heated in a heating cabinet, which expands the phenoplast into a phenolic foam and activates the glue, and thus the entire wing cavity is filled. This type of thin wing has very low drag in theory, but it also generates limited lift, and in practice, the low aspect ratio of the wing translates to high induced drag. Thin, stubby wings are normally used on supersonic aircraft and are not the most aerodynamically efficient shape for a subsonic missile.</p><p>From a design and production standpoint, however, it is among the simplest and lightest practical aerofoils, and it is a popular choice of aerofoil on the foreign ATGMs such as the SS.10 and the Cobra. Due to the low lift coefficient of this aerofoil, a large surface area is needed, resulting in the distinctive large wings present on these first generation ATGMs. The only simpler construction is to have no aerofoil at all, which is the case with the <a href="https://pbs.twimg.com/media/EdN43eTUEAAdcVO.jpg">ENTAC</a>, which used simple steel plates as wings, or the Bantam, which had composite plastic plates for wings. On the other side of the spectrum, there is the <a href="https://www.globalsecurity.org/jhtml/jframe.html#https://www.globalsecurity.org/military/world/europe/images/mosquito-image06.jpg|||Mosquito%20ATGM">Mosquito ATGM</a> which has a high camber, flat bottomed aerofoil, an optimal shape for subsonic wings. </p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jo9moQGFbA0/YKVEB_kD6cI/AAAAAAAATBo/zHIM5PnCyFQAq1YotGSSRZle_vT8kjWYgCLcBGAsYHQ/s1521/wings.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1521" data-original-width="1173" height="400" src="https://1.bp.blogspot.com/-jo9moQGFbA0/YKVEB_kD6cI/AAAAAAAATBo/zHIM5PnCyFQAq1YotGSSRZle_vT8kjWYgCLcBGAsYHQ/w309-h400/wings.png" width="309" /></a><a href="https://1.bp.blogspot.com/-oa7R3BbMsBg/YKtuYCEzJ0I/AAAAAAAATF0/16lXsihjMsYoo_11qo5eHnFpBBslQhynACLcBGAsYHQ/s2048/3m6%2Bcutaway%2Bpavlov%2Bsorokina.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1053" height="400" src="https://1.bp.blogspot.com/-oa7R3BbMsBg/YKtuYCEzJ0I/AAAAAAAATF0/16lXsihjMsYoo_11qo5eHnFpBBslQhynACLcBGAsYHQ/w206-h400/3m6%2Bcutaway%2Bpavlov%2Bsorokina.png" width="206" /></a><br /><br /></div><p>Immediately after launch, the missile is automatically rolled clockwise by 45 degrees to change the wing profile from a cruciform to an "X" under the influence of a hard-coded program in the steering system. This allows all four wings to generate lift, though the lift coefficient of each wing is reduced due to the smaller horizontal span as compared to a level wing. The X-wing shape balances out roll forces from the wings on both sides, and has neutral roll stability. That is, the missile will not self-correct to its original orientation if a roll angle is induced, nor will it amplify any induced roll. On the 3M6, roll stabilization is provided by the gyroscopic steering system which detects changes in roll angle and automatically stabilizes the missile using aileron spoilers throughout its flight trajectory.</p><p>Unlike tailless delta wing designs on aircraft, where the tips are twisted to a lower angle of attack than the rest of the wing to provide pitch stability, the wings on 3M6 are flat, so the net lift force has an upwards vector. As the center of gravity of the missile is ahead of the center of lift from the delta wings, this would cause the missile to overturn if not continuously trimmed. Trim is automatically applied by the onboard autopilot via the spoilers based on changes to the missile attitude measured by the gyroscope.</p><p>Interestingly enough, the 3M6 was the only Soviet ATGM to have fixed wings, not only in service, but also among all experimental missiles in development in the country. The advantages of folding wings were universally understood, but as the design priority of "Shmel" project was conservatism, it emulated the international practices in this regard. Conversely, virtually all MCLOS missiles in the NATO repertoire had fixed wings with the sole exception of the Swingfire, which was an unusually late addition to the first generation family and is an atypical design overall. The Swedish Bantam ATGM also had folding wings, but Sweden was not a NATO member.</p><p>The wings have a moderate sweep angle of 45 degrees, less than the optimal range for supersonic flight but well within the range of approximately 30-50 degrees for subsonic, high lift applications. Currently, delta wings with moderate sweep angles are very popular for light propeller-driven UAVs which fly at low velocity and require high lift, for the same design reasons that justify their use on the "Shmel".</p><p>Because the wings are not asymmetric aerofoils, and they are not structurally affixed at a positive angle of attack, they do not generate lift if the missile itself is at a neutral angle of attack. To fly on a level trajectory, the missile must maintain a positive angle of attack of a few degrees, wherein both the fuselage itself and the large wings can provide enough lift at the cruising velocity of 110 m/s. The angle of attack is not regulated automatically by any onboard systems based on the internal gyroscope - it was calculated based on early test flights, and it is achieved by using a hard-coded program in the operator's control panel that automatically pitches the missile up at regular intervals. The pitch-up signal is additive to the pitch commands entered by the operator via the joystick. This program is active 0.8 seconds after launch (timed to activate after booster burnout) and acts throughout the flight of the missile. </p><p><br /></p><p>It is not known what the angle of attack is taken by the 3M6 during trimmed flight, but its large wings, with a presumably high lift coefficient, would combine with the relatively high speed of the missile to produce a great deal of lift, more than the smaller wingspans of the French ATGM trio are capable of. This, in turn, implies that the necessary angle of attack to maintain trimmed flight would be lower for 3M6. Beyond this, little else can be said of the flight attitude of the missile.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-uYvGLVGZUh8/YKUXKn7_5cI/AAAAAAAATBA/Lj7zh_wXdfElNdBcq-Lc0ZHXz49tnqohwCLcBGAsYHQ/s366/2P27%2Bfiring%2BShmel.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="263" data-original-width="366" src="https://1.bp.blogspot.com/-uYvGLVGZUh8/YKUXKn7_5cI/AAAAAAAATBA/Lj7zh_wXdfElNdBcq-Lc0ZHXz49tnqohwCLcBGAsYHQ/s16000/2P27%2Bfiring%2BShmel.jpg" /></a></div><p>Due to the massive wingspan of the missile, the operator had to be closely adhere to the rules of the three-point guidance technique to avoid accidentally clipping a wingtip on the ground, which would invariably lead to a crash. The placement of tracers on two wingtips helped in this regard by allowing the operator to track the missile by two opposite points marking its maximum dimensions. Moreover, the large surface area of the wings makes the missile very susceptible to being blown off course by wind. According to the technical manual for the 2P27 tank destroyer, firings are not recommended in crosswinds of 8 m/s, or when gusts of crosswinds of up to 12 m/s are present.</p><p>In principle, the use of a hard-coded program for this task has a number of inherent shortcomings. The main issue is that the calculated angle of attack needed for level flight would only apply for a set of standard conditions, and deviations from these conditions, such as when firing the missiles from high altitudes or in cold weather, would cause the missile to either drift upwards or slowly descend. Moreover, there is no ability to automatically apply corrections in the event that a headwind causes the missile to generate excess lift and pitch up. Stable flight under such conditions would be entirely dependent on the static and dynamic stability of the aerodynamic design of the missile.</p><p><br /></p><p><a href="https://www.blogger.com/null" id="shmelguidance"></a><br /></p><h3 style="text-align: left;"><span style="font-size: large;">GUIDANCE SYSTEM</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-t9O-Kd1-KBA/YKYmj8cJksI/AAAAAAAATCk/Y17QaCPTLZQwEQGenMPquxAlWFG7EBCUgCLcBGAsYHQ/s2048/polish%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1401" data-original-width="2048" height="274" src="https://1.bp.blogspot.com/-t9O-Kd1-KBA/YKYmj8cJksI/AAAAAAAATCk/Y17QaCPTLZQwEQGenMPquxAlWFG7EBCUgCLcBGAsYHQ/w400-h274/polish%2Bcross%2Bsection.png" width="400" /></a></div><p>The guidance system consists of the T-70M thermal battery, a pair of command wire coils stored in bobbins, the gyroscope, a simpler roll correction circuit, and a signal amplifier. </p><p>The T-70M thermal battery is of the molten salt type. It serves as the onboard power source for the control unit (autopilot) and for actuating the spoilers. Since the first use of thermal batteries on the German V-1 bomb, this type of power source established itself as the de facto standard for single-use applications, including guided missiles. The main advantage is that the electrolyte could be stored in a solid state at a wide range of temperatures for long periods of time with no electrical discharge whatsoever, and be activated on command by the transformation of the electrolyte into a partially molten state by intense heating, normally provided by a pyrotechnic charge, which is the case in the 3M6 missile. The primary drawback of thermal batteries is their low power density and heavy weight, increasing the parasitic payload in a missile. The T-70M battery provides a current of 2.2 A at a voltage of 22-26 V for 30 seconds. Upon pressing the launch button on the control console, the pyrotechnic heaters of the T-70M battery would be ignited, and the battery becomes fully operational within 2-3 seconds. The gyroscope and on-board missile control equipment are also activated during the 2-3 second preparation period, and once it elapses, the missile is launched.</p><p>Curiously enough, the use of a thermal battery was an innovation that was not found on the SS.10 or SS.11, which used troublesome wet and dry cell batteries respectively. The battery of the SS.10 had to be primed before combat, as the electrolyte would have settled during storage or transport, while the three dry cell batteries of the SS.11 were stowed separately and had strict servicing requirements as well, described in the COMHART book as being "very penalizing". Though the main issue with wet and dry cell batteries was not disclosed, the most likely issues are self-discharge and possible electrolyte leakage during high accelerations. It was only a few years later that the SS.11 was upgraded with a thermal battery, with the SS.11 B1 model in 1965. The SS.10 was not provided a battery upgrade before it was discontinued. </p><p>The gyroscope in the 3M6 is a rate gyro, with two degrees of freedom. The gyroscope is spun to its operating speed just before launch by an electric motor powered by the launch platform itself, rather than the thermal battery in the missile. Once it is spun up, the motor is disengaged, the power supply is cut, and the missile launches with the gyroscope rotor continuing to spin under inertia. The gyroscope is paired with a potentiometer to generate reaction signals in the roll axis. Deviations in the roll angle of the missile generate a feedback voltage, which is processed by the autopilot program by amplification and the resultant reaction signal for a roll correction is generated. Roll corrections are made using the ailerons to ensure that the four wings are always oriented in an X-shape. Due to the need for correct roll stabilization, the firing platform for the missile must not exceed a roll angle of 3 degrees, so when preparing a firing position for a 2P26 or 2P27, a flat patch of ground is ideal, but if the ground is not flat, then the crew must use pioneering tools to flatten it as much as possible. </p><p>The command wires, held in two bobbins, are 2,300 meters long. Both bobbins and both wires are identical and are interchangeable. The surplus length of 300 meters was to provide the operator with enough freedom to guide the missile on a curved flight path, which is needed to align the trajectory of the missile to the operator's line of sight when firing remotely, or when engaging a moving target. This is because the launchers and optics on the 2P26 and 2P27 tank destroyers have a very limited traverse arc, and so the missile needs a larger margin of maneuverability to hit targets that are not more or less in front of the launcher. Because the steering system is electrically powered, and the nominal operating time of the battery exceeds the 21-second flight time of the 3M6 to 2,000 meters, there is no real obstacle in achieving this. </p><p>Voltage pulses of a specific width are used to communicate steering information in the command signal. The command signal generated from the guidance unit is in the form of a rectified sine wave of a fixed amplitude transmitted down each of the two wires; one wire for each steering axis. One wire is used to transmit up and down pitch signals, and the other is used for left and right yaw signals. The amplitude of the control signal is fixed. The rectification of the sine wave into negative and positive pulses is used as the means of differentiating the sign of the command. That is, a positively rectified waveform in the pitch control channel would communicate a pitch-up command, while a negatively rectified waveform would communicate a pitch-down command. Information about the magnitude of the steering intensity (inputted by varying the deflection angle of the operator's joystick) is controlled by varying the pulse duration (width).</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-bD7hX4Z1KK4/YKVSFRCOnUI/AAAAAAAATB4/QU8sYb_upHU8tGdbmJXPNqQJrFG5ws6hQCLcBGAsYHQ/s1409/3m6%2Bwire%2Bbobbins%2Band%2Bguidance%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="749" data-original-width="1409" height="213" src="https://1.bp.blogspot.com/-bD7hX4Z1KK4/YKVSFRCOnUI/AAAAAAAATB4/QU8sYb_upHU8tGdbmJXPNqQJrFG5ws6hQCLcBGAsYHQ/w400-h213/3m6%2Bwire%2Bbobbins%2Band%2Bguidance%2Bsection.png" width="400" /></a><a href="https://1.bp.blogspot.com/-m198BEVoXCk/YPEN-B1xplI/AAAAAAAAT78/3UT01puu9l8CjajBnb2zOBdiJyFF0TeRACLcBGAsYHQ/s1161/wire%2Bbobbin.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="519" data-original-width="1161" height="179" src="https://1.bp.blogspot.com/-m198BEVoXCk/YPEN-B1xplI/AAAAAAAAT78/3UT01puu9l8CjajBnb2zOBdiJyFF0TeRACLcBGAsYHQ/w400-h179/wire%2Bbobbin.png" width="400" /></a></div><p>The wires are steel, with an insulated cladding, and a diameter of 0.16mm. Based on colour photos, the cladding is very likely to be plastic, as the wires for inert mockups have a blue cladding whereas the wires for live missiles have a yellowish green cladding. At the same time, however, the visible length of wire on missiles installed on launchers appears too thick to match the known wire diameter of 0.16mm, so it appears that the initial portion is either bimetallic or has additional insulative protection to prevent burn damage from the exhaust of the missile booster engine. The remainder of the wire is most likely to be simple enameled wire, based on the fact that a sample of guidance wire was apparently stolen and used as fishing wire by <a href="https://www.currenttime.tv/a/north-korea-spy-story-kgb-archives/29957126.html">an employee of a factory that once produced the 3M6</a>. Enameled wires are simply wire filaments coated in a layer of varnish for insulation, and would have the same colour as the wire material, in this case a silvery grey. This is similar to the SS.10, which used enameled steel wires measuring 0.15mm in diameter. The end connectors on the two wires are locked onto protruding contacts on the launch rail manually during loading. These contacts can be seen in the two photos below. The two wires are unwound from the bobbins at a speed of more than 1,000 turns per second.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-H033nbLY628/YLCLmmI_n6I/AAAAAAAATMY/TDmM6EuJFIEY0uVQHvtTqiCW2O1ci263wCLcBGAsYHQ/s750/launch.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="750" height="320" src="https://1.bp.blogspot.com/-H033nbLY628/YLCLmmI_n6I/AAAAAAAATMY/TDmM6EuJFIEY0uVQHvtTqiCW2O1ci263wCLcBGAsYHQ/w400-h320/launch.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-UnnASC883p8/YLCLmWu5CgI/AAAAAAAATMU/t0-Qu6gEvEU9YhSmTzvfi_Va4edHUK-wwCLcBGAsYHQ/s800/loading%2B3m6.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="605" data-original-width="800" height="303" src="https://1.bp.blogspot.com/-UnnASC883p8/YLCLmWu5CgI/AAAAAAAATMU/t0-Qu6gEvEU9YhSmTzvfi_Va4edHUK-wwCLcBGAsYHQ/w400-h303/loading%2B3m6.jpg" width="400" /></a></div><p>If a command wire is severed during flight for any reason, the missile control system automatically executes a self-destruct program that steers the missile down and to the left to prevent an uncontrolled flight.</p><p>Some two-wire systems have a small possibility of shorting out when the electrical impedance of a wire is more than the electrical impedance of the water between the neighbouring wire, causing a short circuit to form. If the insulation is poor or compromised, this particular issue can arise due to the extremely low thickness of the wire cores used in guidance wires, making them filament-like. It is a particularly serious issue for the TOW, because its wires are not insulated enameled copper, but merely enameled steel. The electrical resistance of a wire increases as its thickness decreases due to the lower cross-sectional area through which current can pass, so if the guidance wires are submerged, the resistance of the water may be less than the resistance of the remaining length of wire ahead of the point of submergence. If the resistance of the water is less, a steering signal transmitted down one of the wires will be routed up the neighouring wire and back to the launcher, causing a short circuit in the guidance system. The severity of the issue is determined by the tautness of the wires and the height of the launcher above the water surface, which determines if and where the wire sags low enough to become immersed in the water.</p><p><br /></p><p>Steering was accomplished using a joystick with a two-axis rheostat mechanism, allowing the steering input to have a variable magnitude in any direction. When the control joystick is deflected to the right and left up to 40 degrees, the steering intensity coefficient of the generated command in the yaw axis (either yaw-left or yaw-right) smoothly changes from 0 to 0.6-0.8 until the joystick reaches 40 degrees, whereupon the intensity jumps to 0.95 or more. When the control jostick is deflected away from the operator by up to 40 degrees, the coefficient of the pitch-up command smoothly changes from 0.36 ± 0.06 (the coefficient of the trimmed flight command) to 0.6-0.8. When the control joystick is deflected towards the operator, the trimmed flight command is gradually nullified, with the steering intensity coefficient reaching 0 once the angle of deviation of the joystick is approximately 25 degrees, and with a further deflection of the joystick up to 40 degrees, the pitch-down command coefficient smoothly varies from 0.1-0.3. The maximum pitch command is presumably equal to an angle of attack that is just below the stall angle of the wing.</p><p>The control panel can be dismounted from the vehicle, mounted to a platform with a binocular sight, and then used by the missile operator from outside the vehicle. One of the most important reasons for this capability is to enhance the concealment of the launch vehicle by having it parked on a flat piece of ground in a defilade position while the operator guides the missile from a more advantageous vantage point. Otherwise, it can be problematic to properly position the vehicle for combat, as it must not be parked in such a way that the roll angle exceeds 3 degrees, but choosing such flat ground can increase the difficulty of camouflaging the vehicle. Dismounted operation does, however, unavoidably increase the firing preparation time considerably, from 10 seconds (when firing from a halt) to 2 minutes and 30 seconds.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-k6AMap5f5qY/YPEfRrzes9I/AAAAAAAAT8E/rvww8f2-jLgIoy-lveQb0ed2Ngii3NkHACLcBGAsYHQ/s1404/dismounted%2Bcontrol%2Bpanel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1062" data-original-width="1404" height="303" src="https://1.bp.blogspot.com/-k6AMap5f5qY/YPEfRrzes9I/AAAAAAAAT8E/rvww8f2-jLgIoy-lveQb0ed2Ngii3NkHACLcBGAsYHQ/w400-h303/dismounted%2Bcontrol%2Bpanel.png" width="400" /></a></div><p>Observation of the missile and the target could be done with the naked eye or through the special 8x binocular sight. The binoculars are virtually the same as a regular pair of field binoculars, differing only in that it has a mount and a special reticle. The missile was fitted with a pair of T-17 tracers to permit observation. T-17 tracers are small, measuring only 17mm in diameter (hence the designation of T-17), and are located on the tips of the two single-spoiler wings. Each of the tracers generates a light intensity of 18,000 candelas with a total burn time of 30 seconds.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-mcA6lzl9J1M/YJb_8iMgckI/AAAAAAAAS7k/8Ne4KucD3RkklSHpFIAwwaHCasSpazuiQCLcBGAsYHQ/s2523/t-17%2Btracer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1246" data-original-width="2523" height="198" src="https://1.bp.blogspot.com/-mcA6lzl9J1M/YJb_8iMgckI/AAAAAAAAS7k/8Ne4KucD3RkklSHpFIAwwaHCasSpazuiQCLcBGAsYHQ/w400-h198/t-17%2Btracer.png" width="400" /></a></div><p>In order to avoid collision with the ground during the first 2-3 seconds after launch from the potential attempts of overzealous operators to immediately align the missile with the target, inputs in the vertical plane are blocked by the control unit. The operator is only allowed to steer the missile in the horizontal plane. The missile is automatically guided by a special autopilot program in the control unit to fly to a predetermined altitude during these 2-3 seconds, whereupon the operator can then steadily lower it down to his line of sight to the target. This program ensures that the missile does not accidentally impact any terrain features during its initial trajectory, where it is most sensitive to tailwinds and crosswinds. The former reduces the relative airspeed and thus the lift of the missile, the latter can blow the missile off course and into obstacles such as boulders and small trees. When engaging targets at a sufficiently long range, it was recommended for operators to keep the missile at an altitude of 4-8 meters to avoid clipping obstructions on the ground, and then lower the missile onto the target within 500-700 meters before impact.</p><p>With all of the flight control limitations, it is perhaps not too surprising that control of the missile required a strong training regimen and frequent practice, even for an MCLOS system. In the book "<i>Отечественные противотанковые комплексы</i>" (<i>Domestic Anti-tank Systems</i>), author Rostislav Angelsky states that the difficulty of controlling the missile was a factor in the short lifespan of the "Shmel" system. Testing personnel of the military testing commission and specialists from the TsNII-173 design bureau could operate the missile system almost without misses by the end of military acceptance tests, but after a three-week break, the same people could only score a hit in one of every four launches. Guidance was accomplished with the control set described earlier, consisting of a control panel featuring a joystick and a pair of binoculars affixed to a pedestal. This set of equipment directly mirrored that of the earlier SS.10. The image below, taken from the book "<i>ПТУР сухопутных войск</i>" by G.N. Dimitriev, shows an NVA dismounted 2P27 operator guiding a "Shmel", with the launch vehicle parked some distance behind him.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ZhxPrpV6LHE/YOjR9eOo9QI/AAAAAAAAT0Y/yqVm0NTpc4MFmjt60UmQZEB9EZ-opiGMQCLcBGAsYHQ/s1249/shmel%2Boperator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="421" data-original-width="1249" height="216" src="https://1.bp.blogspot.com/-ZhxPrpV6LHE/YOjR9eOo9QI/AAAAAAAAT0Y/yqVm0NTpc4MFmjt60UmQZEB9EZ-opiGMQCLcBGAsYHQ/w640-h216/shmel%2Boperator.png" width="640" /></a></div><p>Based on the results obtained by the state testing commission, the probability of hitting a target was 50-80%. The large variance can be attributed to the fact that the testing commission operators honed their skills by simply receiving practical training via the tests, and their proficiency level greatly improved in the period between the beginning and the end of the tests. </p><p>The zone of action of the 3M6 is largely limited by its launch platform, the 2P27. It featured a traversible launcher with a limited horizontal arc of 24 degrees (±12 degrees) and a traversible sight with a horizontal arc of 48 degrees (±24 degrees). Although it is possible to guide the missile in an arc exceeding the traversing limits of the launcher thanks to the wider reach of the sight, it is still necessary for the sight to be aligned with the launcher so that the operator can capture the missile during its initial trajectory, before gradually turning the sight by up to an additional 12 degrees to the left or right. The launch control system has a "ready" signal light to indicate when the sight and launcher are aligned, and the light goes out when the operator turns the sight off alignment by more than 1 degree. When using the full capabilities of the system, the maximum engagement arc is 48 degrees. If the sight is not turned more than ±12 degrees, then the engagement arc is defined by the width of the viewing arc through the sight, giving an arc of 36 degrees. The zone of action when fighting from a 2P27 is marked as Zone 1 in the diagram below.</p><p>Aiming the missile in an arc exceeding the viewing arc of the optical sight is only feasible when the system is fired remotely from a dismounted position, with the operator manning an external control post. The operator aims the sight at the target and mentally notes the landmarks that appear within the viewfinder of the sight. When the missile is launched, the operator visually captures the missile with the naked eye and steers it until it is near the predetermined landmarks, allowing it to be tracked through the sight. This method of guidance increases the zone of action to 98 degrees (±49 degrees). Due to the time needed to complete this maneuver, combined with the relatively high initial speed of the missile due to its boost stage, the minimum range of the missile system is increased to at least 1,000 meters. The probability of hit diminishes near the limits of the zone of action, demarcated into Zones 2 and 3 where the hit probabilities are 0.65 and 0.50 respectively. This is because the operator has less time to control the missile in altitude as he is preoccupied with aligning it into the viewfinder of his sight, increasing the chances of the missile overflying the target or having the operator accidentally steer it into the ground.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-v-_IXl11Ssg/YFgeMT7e7KI/AAAAAAAAS3M/1VHZ2uWM-wALRAA12rJcUiEpQFTHAy21wCLcBGAsYHQ/s1482/zone%2Bof%2Boperation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1448" data-original-width="1482" height="626" src="https://1.bp.blogspot.com/-v-_IXl11Ssg/YFgeMT7e7KI/AAAAAAAAS3M/1VHZ2uWM-wALRAA12rJcUiEpQFTHAy21wCLcBGAsYHQ/w640-h626/zone%2Bof%2Boperation.png" width="640" /></a></div><p>The curved trajectory of the missile, particularly at the extremes of the engagement arc, made it necessary to pack 2,300 meters of wire. Without it, the maximum range of the missile in Zones 2 and 3 would be less than 2,000 meters. As a side effect, the maximum range within Zone 1 can be greater than 2,000 meters. In the pamphlet "<i>Przeciwpancerny Pocisk Kierowany 3M6</i>" published by the Polish Ministry of National Defence in 1976, the so-called "effective engagment range" of the 3M6 is considered to be 2,200 meters.</p><p>The long minimum range of 600 meters, partly caused by the inhibition of operator control during the first 2-3 seconds of missile flight, and partly caused by the delay before the operator can visually acquire the missile in his sight, could only be achieved without degradation in hit probability if the target was within a 6-degree arc in front of the launcher. This can be problematic when engaging a crossing target. If the desired 0.8 hit probability is to be achieved in a larger arc of 48 degrees, the minimum range is 1,000 meters. This long minimum range of 600 meters was shared by the SS.10, which is unsurprising given the close similarity in kinematics between the two missiles. </p><p><br /><a href="https://www.blogger.com/null" id="shmelsteering"></a></p><h3 style="text-align: left;"><span style="font-size: large;">STEERING</span></h3><p>All four wings have a spoiler that can alternately function as a rudder or an elevon, depending on which pair of spoilers are activated. Two wings, forming the upper right and lower left portions of the "X" layout, feature a second spoiler placed at the end of the wing, which functions as ailerons. These only permit roll corrections to be made according to signals generated from the onboard autopilot, and do not respond directly to any steering commands made by the missile operator.</p><p>Each spoiler assembly is housed in a bakelite casing screwed onto the wings, which also feature a pair of wing fences to prevent lateral overflow from the spoilers when they are in operation. The spoiler casings are streamlined with a teardrop shape. Superficially, the overall form of the design is the same as the spoilers used in the SS.10 and ENTAC missiles, but the French type had a metal casing, a different aerodynamic form with a pointed casing, narrower spoilers and cruder fences. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-AMiLi834kGw/YKQdyNbVFKI/AAAAAAAATA4/tVQ4oUFMPv4CJo1XuXYJeoCOzCL503XKACLcBGAsYHQ/s1024/IMG_1256.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://1.bp.blogspot.com/-AMiLi834kGw/YKQdyNbVFKI/AAAAAAAATA4/tVQ4oUFMPv4CJo1XuXYJeoCOzCL503XKACLcBGAsYHQ/w400-h300/IMG_1256.JPG" width="400" /></a><a href="https://1.bp.blogspot.com/-L2JkFC6s-bQ/YKYj8KQt4MI/AAAAAAAATCc/lMXIe9X0Nj0OXyWw2kQTyOClDiHDLykRACLcBGAsYHQ/s671/interceptor.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="632" data-original-width="671" height="301" src="https://1.bp.blogspot.com/-L2JkFC6s-bQ/YKYj8KQt4MI/AAAAAAAATCc/lMXIe9X0Nj0OXyWw2kQTyOClDiHDLykRACLcBGAsYHQ/w320-h301/interceptor.png" width="320" /></a><br /></div><p>Each spoiler used in the 3M6 missile is a plate that is raised through the skin of the wing, interrupting the air flow. The accumulated excess pressure propagates forward, upstream of the flow, and generates a distributed excess pressure on the wing surface in front of the spoiler. This results in an increase in drag, a loss in lift and a change in the pressure differential between the upper and lower surfaces of the wing, which can be used to either roll or steer the missile. The use of wing fences enhances the effectiveness of spoilers by preventing the excess pressure from generating a lateral flow across the wing, dissipating the pressure. The pressure on the lower surface of the wing also decreases when the spoiler is raised, due to the reduction in circulation around the aerofoil. This increases the magnitude of the pressure differential and thus the moment of force pushing down upon the wing. </p><p>The diagram below illustrates the excess pressure that propagates forward of a raised spoiler, and the nature of its intensity. In this case, the structure shown is a symmetric wing with a bidirectional spoiler, representing the wing of 3M6, rather than an asymmetrical wing with an upper spoiler as found on aircraft. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ne_NwgOaae0/YFrB-5V5mmI/AAAAAAAAS3k/N4tBV-W737gDM50NNImty70PPaMaTEPBACLcBGAsYHQ/s989/spoiler%2Bplate.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="371" data-original-width="989" height="150" src="https://1.bp.blogspot.com/-ne_NwgOaae0/YFrB-5V5mmI/AAAAAAAAS3k/N4tBV-W737gDM50NNImty70PPaMaTEPBACLcBGAsYHQ/w400-h150/spoiler%2Bplate.png" width="400" /></a></div><p>The fundamental principle of steering by inducing a pressure differential on the wing is identical to how rudders on wings function, only the mechanical means differ. Spoilers were used primarily for the sake of capitalizing on their sheer simplicity; the actuator of each spoiler is a pair of electromagnets, with the spoiler attached to a hinged armature. It is, essentially, identical to the most rudimentary <a href="https://en.wikipedia.org/wiki/Electric_bell">electric bell</a>. Each electromagnet is used to raise the spoiler on one side of the wing. This device was simpler than servomotors to control rudder deflection, and with a more modest demand on power. The control architecture was also of the utmost simplicity. </p><p>On the 3M6, the spoiler plate is swung between the raised and lowered positions at a fixed frequency of 10 Hz using a bang-bang control scheme, where one of the two electromagnets in the spoiler completes the cycle of pulling the spoiler armature towards itself and releasing it at a rate of 10 times a second. The power supplied to the electromagnet is the amplified signal received from the operator's control unit. The signal, having a rectified square waveform and a certain pulse width, is amplified by the missile guidance system, and is then transitted to the electromagnets. The armature is raised to a fixed height, while the length of time it is left in the raised position is regulated by the pulse widths of the modulated control signal. Each time the armature of the spoiler is released by the electromagnet, the spoiler is returned to its recessed position in the center by a spring. A bang-bang system is the simplest control scheme and one of the most popular types, being a universal standard for heaters and refrigerators. The image below shows an example of how a bang-bang control scheme is applied in a heater to maintain a desired temperature by achieving an average between a set of upper and lower thresholds. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-V_ixatgpvf4/YPXTNi_BzVI/AAAAAAAAT-w/aNds3oQkKJUJL9iogelcz0wwseWOaptYACLcBGAsYHQ/s850/bang%2Bbang.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="631" data-original-width="850" height="297" src="https://1.bp.blogspot.com/-V_ixatgpvf4/YPXTNi_BzVI/AAAAAAAAT-w/aNds3oQkKJUJL9iogelcz0wwseWOaptYACLcBGAsYHQ/w400-h297/bang%2Bbang.png" width="400" /></a></div><p>Cross section A-A shows a longitudinal cross section of a roll stabilization spoiler, and cross-section B-B shows a longitudinal cross section of a steering spoiler. The curved spoiler plates of both units are of a similar thickness, but the armatures are hinged at different points, and the roll stabilization spoiler has a shorter height limit. Knowing that the intensity of the steering effect is dependent on the height of a raised spoiler, this implies that roll corrections were limited to fine adjustments only.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-H_kQaflYUrM/YKVAYr_3HdI/AAAAAAAATBg/RkEYV08mYTk17peY_k9IlTahiGWPAI5-QCLcBGAsYHQ/s958/spoiler%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="322" data-original-width="958" height="135" src="https://1.bp.blogspot.com/-H_kQaflYUrM/YKVAYr_3HdI/AAAAAAAATBg/RkEYV08mYTk17peY_k9IlTahiGWPAI5-QCLcBGAsYHQ/w400-h135/spoiler%2Bcross%2Bsection.png" width="400" /></a></div><p>The higher a spoiler is raised, the larger the effect. This is shown in the graph below, taken from the thesis "<a href="https://core.ac.uk/download/pdf/40024336.pdf">Aerodynamic Performance of Low Form Factor Spoilers</a>". This is used as the basis of the steering system in 3M6. By varying the pulse width of the steering signal to adjust the spoiler activation period, the average steering force generated by the spoiler is proportionately varied, allowing the turning force to be finely controlled, giving the steering precision needed to hit tank-sized targets at long range. The control joystick of the 9S41 control station, used in both the 2P26 and 2P27 tank destroyers, could be deflected by up to 40 degrees with a smooth progressive adjustment in steering intensity throughout. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-wNwqjb06o3I/YFnbSTMnFHI/AAAAAAAAS3c/gKWJeddknuQ6OpA-Um58rurDcUbE9vZbACLcBGAsYHQ/s1387/spoiler.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="635" data-original-width="1387" height="183" src="https://1.bp.blogspot.com/-wNwqjb06o3I/YFnbSTMnFHI/AAAAAAAAS3c/gKWJeddknuQ6OpA-Um58rurDcUbE9vZbACLcBGAsYHQ/w400-h183/spoiler.png" width="400" /></a></div><p>When the operator's control joystick is gently deflected to one side, the pulse width of the signal transmitted over the guidance wire is small. The corresponding pair of spoilers are activated and oscillate at a frequency of 10 Hz, but the plates spend less time in the raised position. Due to the shorter period of spoiler extension above the surface of the wing, the resultant steering force is also small. If the joystick is further deflected, the extension time is increased, and the steering force increases accordingly.</p><p style="text-align: left;">The characteristics of spoilers for missile steering are corroborated and further explored in the book "<i>Armements Antichars Missiles Guidés Et Non Guidés</i>" by COMHART (<i>Comité pour l'Histoire de l'Armement Terrestre</i>). It is noted in the book that wind tunnel tests showed that, compared to traditional rudders, the increase in aerodynamic drag is low if the dimensions of the spoiler and its casing are well optimized and if the gains in simplification compared to traditional rudder steering surfaces are taken into account. In addition, it is reported that for the SS.10, the low flight speeds and the simplicity of the general aerodynamics of the missile made the drag penalty even more negligible.</p><p>Furthermore, by placing the spoilers at the trailing edge of the wing rather than along the midpoint, behind the leading edge, where the local dynamic pressure and interference effects are largest, the braking effect of this type of spoiler is minimized.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-FPqqvUiwrVE/YIw3oeXt5eI/AAAAAAAAS54/CWwlKHDFZPINjiwS-hsxK-W2lN6egD31gCLcBGAsYHQ/s2048/cross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1054" data-original-width="2048" height="330" src="https://1.bp.blogspot.com/-FPqqvUiwrVE/YIw3oeXt5eI/AAAAAAAAS54/CWwlKHDFZPINjiwS-hsxK-W2lN6egD31gCLcBGAsYHQ/w640-h330/cross%2Bsection.png" width="640" /></a></div><p><br /></p><p><br /><a href="https://www.blogger.com/null" id="shmelengine"></a></p><h3 style="text-align: left;"><span style="font-size: large;">ENGINE</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-EEpCFu2NFNM/YKVKow8mwXI/AAAAAAAATBw/wn7Lc5C1A78YavzskaTdy2w1Y0vslF2OQCLcBGAsYHQ/s2576/engine.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1221" data-original-width="2576" height="190" src="https://1.bp.blogspot.com/-EEpCFu2NFNM/YKVKow8mwXI/AAAAAAAATBw/wn7Lc5C1A78YavzskaTdy2w1Y0vslF2OQCLcBGAsYHQ/w400-h190/engine.png" width="400" /></a><a href="https://1.bp.blogspot.com/-gqWCsX-rqKA/YKaZ58ETEWI/AAAAAAAATDM/1NCyX0wMbQEv8UHgtDRUo353RkMudMkVwCLcBGAsYHQ/s1821/p0037.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1059" data-original-width="1821" height="233" src="https://1.bp.blogspot.com/-gqWCsX-rqKA/YKaZ58ETEWI/AAAAAAAATDM/1NCyX0wMbQEv8UHgtDRUo353RkMudMkVwCLcBGAsYHQ/w400-h233/p0037.png" width="400" /></a><br /><br /></div><p>Propulsion was provided by a dual-chamber, dual-thrust engine consisting of separate booster and sustainer chambers. The sustainer is contained in the large forward chamber and the jet of combustion products is routed through a central nozzle, which extends through the length of the booster chamber. The fuel block of the booster engine is wrapped around the sustainer engine nozzle, and the combustion products exit via an annular array of nozzles surrounding the central sustainer nozzle. As the cross-section drawing on the left above shows, the throat of the nozzle for the sustainer engine has a molybdenum insert, where erosion is strongest, but the rest of the nozzle is merely a flared pipe. The annular nozzles for the booster engine do not have molybdenum inserts or any kind of refractory metal insert, which is a cost-saving measure as erosion is a non-issue for the booster, given its short burn time. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-zO5tdguvd-w/YMSKwbsAeSI/AAAAAAAATbg/gmv4gyOxU9oQvjrPwQCo5IViqy4UHA3igCLcBGAsYHQ/s567/dual%2Bchamber%2Bannular%2Bengine.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="202" data-original-width="567" height="143" src="https://1.bp.blogspot.com/-zO5tdguvd-w/YMSKwbsAeSI/AAAAAAAATbg/gmv4gyOxU9oQvjrPwQCo5IViqy4UHA3igCLcBGAsYHQ/w400-h143/dual%2Bchamber%2Bannular%2Bengine.png" width="400" /></a></div><p>The booster generates the necessary thrust to accelerate the missile to 110-115 m/s in 0.6 seconds, followed by the sustainer which generates a thrust equivalent to air resistance, thus sustaining a 110 m/s cruising speed. It can be surmised that the 3M6 does not have an accelerating flight profile at a normal operating temperature, because one of the general instructions for missile operators is to observe if the missile descends or ascends after launch when it appears in the binocular sight, and to input a pitch adjustment accordingly. This strongly indicates that the sustainer engine was calibrated to produce a thrust equal to air resistance for level flight at normal temperature, and will generate a surplus at elevated temperatures and a deficit at lower temperatures. </p><p>The total burn time of the sustainer is 20 seconds, though the thrust developed by the engine drops off in the last few seconds. The flight time of the missile to its nominal maximum range of 2,000 meters is 18 seconds, giving the missile an average speed of 110 m/s. The maximum limit of 2,300 meters can be reached without a debilitating degradation in performance, as the onboard battery continues to function normally beyond 2,000 meters, and so flight corrections are still possible. The hard range limit of 2,300 meters is enforced only by the wire length. Interestingly enough, it is noted in the article "<i><a href="https://web.archive.org/web/20140701211610/http://waronline.org/IDF/Articles/firstATGM.htm#TTX">ПТУР первого поколения в АОИ</a></i>" (<i>First Generation ATGMs in the IDF</i>) that the speed of the 3M6 at its maximum range (2,300 m) will be 74 m/s, implying that the high induced drag of the missile rapidly degrades its kinematic performance beyond its nominal maximum range of 2,000 m. </p><p>This was principally the same as the propulsion system of the SS.10 missile, as the SS.10 was also designed without consideration for low temperature action. It had a booster engine that provided a thrust of about 2,000 N for 0.65 seconds, and its sustainer engine gave a thrust of 95 N for 18 seconds to sustain a cruising speed of 80 m/s, rather than to provide an accelerating effect. The SS.10 engine has a boost-sustain thrust ratio of 21, which was likely duplicated in the 3M6. Kinematically, the two differences between 3M6 and the SS.10 are in their respective flight velocity profiles and in the greater average speed of the 3M6.</p><p>The choice of an intense boost stage lasting for a very short period minimized the launch dispersion of missiles under various environmental conditions, particularly windy conditions. With a predictable trajectory, an operator could visually acquire the missile in his sight more rapidly and begin guiding it. A high launch dispersion is highly undesirable as the missile may not enter the operator's view in his sight after launch, forcing the operator to search for it with his naked eyes. </p><p><br /><a href="https://www.blogger.com/null" id="shmelwarhead"></a></p><h3 style="text-align: left;"><span style="font-size: large;">3N13 WARHEAD</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-yOmJKDh6gb4/YJAa-Nn5SxI/AAAAAAAAS6M/twADJF_hqUcL2_h3KevSkOHWHmg7_6RJACLcBGAsYHQ/s2048/warhead%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1128" data-original-width="2048" height="352" src="https://1.bp.blogspot.com/-yOmJKDh6gb4/YJAa-Nn5SxI/AAAAAAAAS6M/twADJF_hqUcL2_h3KevSkOHWHmg7_6RJACLcBGAsYHQ/w640-h352/warhead%2Bsection.png" width="640" /></a></div><p style="text-align: left;"><br />The warhead section consists of the shaped charge warhead, the EMGK fuze, and the metal fairing containing the entire assembly. In total, the warhead section has a weight of 5.4 kg. It is important to note that this is the weight of the entire warhead section, not of the 3N13 shaped charge itself. Together with the conical nose fairing of the warhead, the EMGK fuze gives the "Shmel" a nondescript profile, practically indistinguishable from the nose profiles of a variety of anti-tank grenades, tank-fired HEAT shells, and a few other ATGMs like the West German Cobra. There is no resemblance whatsoever to the more streamlined, ogive fairings of the French first generation ATGMs.</p><p style="text-align: left;">The EMGK fuze is a percussion spitback fuze with a mechanical percussion primer and a tetryl relay. Its firing train has a two-stage electro-pyrotechnic arming mechanism. The first stage consists of a microswitch that is only tripped when the missile is launched from the appropriate launch rail. The second is a mechanical safety shutter between the percussion mechanism and the tetryl relay, which ensures that the firing train is physically blocked before the missile has traveled a certain distance from the launcher and thus the non-functioning of the fuze. This shutter is opened when the sustainer engine is ignited, whereby propellant gasses vented from the sustainer engine are ported to the nose of the missile fuselage via a gas tube, to shift the shutter of the firing train. The image below shows the fuze in its unarmed (left) and armed (states). As the diagram on the left shows, if the striker is pushed before the mechanical shutter is shifted, the striker head is stopped in an empty cavity in the shutter, and is simply returned to its place by a coil spring.</p><div style="text-align: center;"><img border="0" data-original-height="1289" data-original-width="2048" height="251" src="https://1.bp.blogspot.com/-MUjb-oDK-6k/YJApF6EFtQI/AAAAAAAAS6U/BuVfTn9WENYClCFIGDJQGtUROqrs0qOZwCLcBGAsYHQ/w400-h251/fuze.png" style="color: #0000ee;" width="400" /></div><p>Once the tetryl relay is detonated, the shock causes the spitback charge to detonate, forming an EFP out of the concave lining on the base of the spitback charge. The EFP travels down the apex tube of the funnel-shaped shaped charge liner into a receptacle in the base section of the EMGK fuze, impacting a relay charge, which then subsequently sets off a detonator charge. The detonator charge acts as a booster charge that is necessary to detonate the insensitive main charge. Though this firing train may seem convoluted, the only moving parts in the fuze mechanism are the striker and the safety shutter. All other portions are chemical in nature.</p><p>Due to the use of a very conservative striker-based percussion fuze design rather than a piezoelectric type, the 3M6 may have fuzing issues on highly sloped armour surfaces, and it is certainly not graze-sensitive. That said, this was not unusual. Even the SS.10, which had a streamlined crush fuze integrated into the ogival aerodynamic fairing, still relied on having only the tip of the nose crush against an internal electrical contact, limiting the permissible impact angle. </p><p><br /></p><p>The 3N13 warhead has a copper shaped charge cone, a filling of A-IX-1 and features a wave shaper. A-IX-1 was the first and most widely used hexogen formulation in the USSR, and is known as Gekfol (Гекфол), which is a portmanteau of hexogen (гексоген) and phlegmatizer (флегматизатор). </p><p>It is evident from cross sectional drawings and photos that the diameter of the warhead is slightly smaller than the 136mm diameter of the missile fuselage, but the real diameter is not known. The built-in standoff distance is around 2 CD. </p><p>In terms of diameter, the 3N13 warhead could be considered to be of a respectable size, close to the fuselage diameter. Based on cutaway drawings taken from the technical manual, the charge diameter is around 110mm, making it equivalent in same size to the 110mm warhead of the SS.10. It is stated in the book "<i>Armements Antichars Missiles Guidés Et Non Guidés</i>" by COMHART the SS.10 warhead used a hexolite explosive charge composed of an RDX/TNT mix with a 63% RDX content. It is equivalent to Comp. B, and substantially weaker than phlegmatized hexogen compositions such as A-IX-1, with a lower detonation velocity by around 10% (7,900-8,000 m/s). It is credited with a penetration of 400mm RHA or 200mm on a plate sloped at 60 degrees. The larger 125mm warhead of the SS.11, filled with the same hexolite charge, was credited with 500mm of penetration in the COMHART book. </p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-I9ik4-gAwRQ/YIwvyCmS6eI/AAAAAAAAS5s/w_pcDi38MZo9dB6xl9CtDttuRM6STujDgCLcBGAsYHQ/s1809/3n13%2Bwarhead.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1355" data-original-width="1809" src="https://1.bp.blogspot.com/-I9ik4-gAwRQ/YIwvyCmS6eI/AAAAAAAAS5s/w_pcDi38MZo9dB6xl9CtDttuRM6STujDgCLcBGAsYHQ/s320/3n13%2Bwarhead.png" width="320" /></a></div><p><br /></p><p>According to the tactical-technical characteristics listed in the technical manual for the 3M6, the penetration of the warhead is not less than 150mm RHA at 60 degrees (300mm LOS). In the article "<i>Первые ОКР по противотанковым и танковым управляемым ракетам</i>", it is reported that a penetration of 300mm is achieved in more than 90% of cases, meaning that it is the guaranteed penetration rather than an average. </p><p>Taken at face value, a penetration power of 300mm RHA is very conservative given the technologies implemented in the warhead design and the caliber of its shaped charge. In page 131 of the book "<i>Боеприпасы И Средства Поражения: Энциклопедия XXI век</i>" (<i>Ordnance and Means of Destruction: Encyclopedia of the 21st Century</i>), the penetration of 3M6 "Shmel" is given as 300-400mm instead. Additionally, the article "<i>Полет «Шмеля»</i>" (<i>Flight of the "Bumblebee"</i>) in the "<i>Оружие</i>" magazine, the penetration is listed as 300-380mm of steel. The textbook "<i>Средства поражение и боеприпас: Учебник</i>" (<i>Means of destruction and ammunition: a Textbook</i>) by the Bauman Moscow State Technical University also attributes the 3M6 with a penetration of 380mm, but notes that this is the penetration on a normal angle, i.e. at a flat plate.</p><p>As explored earlier during the "Aerodynamics" section, due to the attitude of the 3M6 in trimmed flight, the penetration will be exponentially worsened by increasing armour obliquity, as the effect of each additional degree is amplified.</p><p>Interestingly enough, the high penetration figures for the SS.10, SS.11 and ENTAC published in the book "<i>Armements Antichars Missiles Guidés Et Non Guidés</i>" by COMHART do not take this approach to reporting penetration power, instead listing only the average perforation limit on a flat impact. Penetration figures on sloped plate are either not given, or are given in such a way so as to subvert the fact that these ATGMs have a positive angle of attack of 6-7 degrees in trimmed flight.</p><p>It is reported in the book that the 130mm warhead of ENTAC (shaped charge diameter of 120mm) has a perforation limit of 650mm (5 CD) of 80 kgf/sq.mm (784 N/sq.mm) steel, which is 230 BHN medium hardness armour steel. This number is abnormally high for a 130mm shaped charge with a hexolite filler (Comp. B), provided with only a little over 1 CD of built-in standoff distance (140-150mm), and with no wave shaper. Indeed, the ENTAC is only stated to have a penetration power in excess of 20 inches (~508mm) of steel in page 17 of FM 23-6 "Antitank Guided Missile (ENTAC)", a much more realistic figure that is far short of the figure claimed in the COMHART book. </p><p>The 650mm figure for the perforation limit was most likely obtained in static testing on a highly sloped plate without simulating its pitch angle of 6 degrees, thus effectively angling the internal warhead downwards by 6 degrees and reducing the LOS thickness of armour accordingly. The real penetration figure is most likely to match the ~508mm figure given in FM 23-6.</p><p>Taking all of these facts into consideration, it is highly likely that the average penetration of 3M6 on a flat impact is at least 400mm, comparable to the SS.10, and it could be somewhat higher since a more effective explosive filler and a wave shaper were included in the 3N13 warhead. The average penetration on a plate sloped at 60 degrees should also be higher than 150mm.</p><p><br /></p><p>For storage and transport, the warhead section is detached from the missile fuselage and stowed in a separate holder, allowing the dimensions of the packing crate to be reduced. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-bW0_9s4O90E/YKaXqrGf8aI/AAAAAAAATDE/plOUAnfO6rYlNphxlhiJV3qgBwUImx22QCLcBGAsYHQ/s1947/box.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="799" data-original-width="1947" height="164" src="https://1.bp.blogspot.com/-bW0_9s4O90E/YKaXqrGf8aI/AAAAAAAATDE/plOUAnfO6rYlNphxlhiJV3qgBwUImx22QCLcBGAsYHQ/w400-h164/box.png" width="400" /></a></div><p><br /><a href="https://www.blogger.com/null" id="falanga"></a></p><h3 style="text-align: left;"><span style="font-size: large;">"Falanga" ("Phalanx")</span></h3><h3 style="text-align: left;"><span style="font-size: large;">3M11, 9M17, 9M17M, 9M17P</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-RYtJNJeAwlc/YNwZWqb9X2I/AAAAAAAATqI/qWk4ScVVNDw0EQ9z4-1gLSn0jCudubQsACLcBGAsYHQ/s640/AT-2%2Bswatter.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="478" data-original-width="640" height="299" src="https://1.bp.blogspot.com/-RYtJNJeAwlc/YNwZWqb9X2I/AAAAAAAATqI/qWk4ScVVNDw0EQ9z4-1gLSn0jCudubQsACLcBGAsYHQ/w400-h299/AT-2%2Bswatter.jpg" width="400" /></a></div><p>Originally named the PUR-62, it received the official GRAU designation of 3M11 when it entered service. The 3M11 itself has no known name, but it is sometimes referred to as the "Falanga". The PUR-62 was developed under Topic No. 8 "Falanga" by the NII-642 research institute as a radio-guided man-portable missile system, but due to a reshuffling of the management at the institute, with the reassignment of the lead designer to work on strategic missile systems at NII-1 GKOT (State Committee for Defense Technology), the "Falanga" project was officially handed over to the OKB-16 design bureau (now known as KB Tochmash) by a decree issued by the USSR Council of Ministers on July 4, 1959. The head of the design bureau, A. E. Nudelman, personally led a team to undertake the project. The government decree also mandated that "Falanga" was to be changed from a man-portable system to a self-propelled one. The weight limit of the missile was increased to 30 kg, and the maximum range was set to 2.5 km. </p><p>At OKB-16, the "Falanga" progressed rapidly into a working system only months later. This was because OKB-16 had been working on Topic No. 2 "Drakon" and No. 5 "Korall" since 1957, and as they were both radio-controlled self-propelled ATGM systems, the bureau had already accumulated substantial experience in this field. The "Drakon" project was a heavy ATGM project for arming missile tanks, while the "Korall" project was a medium ATGM project for increasing the firepower of light tanks armed with conventional guns. "Drakon" was reassigned to a different design bureau, and "Korall" was terminated, leaving OKB-16 to focus exclusively on "Falanga". The BRDM was used as the missile carrier, and the system was assigned the GRAU index of 2K8. </p><p>Along with the "Shmel", the "Falanga" was demonstrated to the leadership of the Soviet Army on August 28, 1959. Even before the demonstrations were concluded, the decision was made to bring the "Falanga" into production in 1960 with an order of 1,000 missiles and 25 tank destroyers. Factory tests began on October 15, 1959. Aside from teething troubles encountered at the beginning of the tests, a positive result was achieved, with a hit rate of 80% with 27 launches made. After eliminating all the identified shortcomings of the 2K8 "Falanga" system on August 30, 1960, it was put into service. Serial production began the same year.</p><p>The "Falanga" family of missiles was fairly successful, largely due to its integration on helicopters, most notably the Mi-24 series. Initially, the "Falanga" was restricted in use to the Soviet Army exclusively - as an example of the restrictions on the "Falanga" system, the Mi-8TV, adapted from its original utility configuration and armed with four 9M17M missiles, was modified into the Mi-8TVK variant with six 9M14M "Malyutka-M" launchers for export. Even the GDR received this downgraded system. Needless to say, in terms of export, the "Falanga" never came close to reaching that of its direct competitor, the AS.11 (the helicopter version of the SS.11).</p><p>However, upon the replacement of the "Falanga" with the "Shturm", and with the creation of the downgraded Mi-25 export model based on the Mi-24D, the Soviet Army ceased to become the most prominent user of the system. Export sales of the Mi-25 ensured a lasting demand for 9M17P missiles abroad and kept the production line for missiles open until 1990, at the collapse of the USSR. This three-decade span in production coincidentally matched that of the SS.11, the direct counterpart of the "Falanga".</p><p>Taking into account his experience working with aviation design bureaus and knowledge of trends in the development of world aviation, chief designer Nudelman proposed to create a helicopter ATGM system on the basis of the 2K8 system as the 2K8 was nearing the end of its development. In 1960, tests on integrating the "Falanga" on an Mi-1 utility helicopter began, but the obsolescence of the Mi-1 cut those plans short. Instead, the Mi-4 was adopted as the new launch platform, and the Mi-4AV was created as a result, followed by the Mi-8, then the Mi-24. </p><p>Compared to its career as a helicopter ATGM system, the "Falanga" series had relatively limited success as a ground forces weapon. "Falanga" systems were issued to the anti-tank regiment integral to a Soviet tank or combined arms army, and in the anti-tank brigade organic to artillery divisions. The main requirement of such high level units was a long firing range and high mobility to respond to threats when they were needed, which is naturally solved by deploying heavy ATGMs on highly mobile, self-propelled systems, which can be either a ground vehicle or an aircraft; this was the fundamental concept behind arming helicopters with the "Falanga". </p><p>The 3M11 was used in 2K8 "Falanga" system of the 2P32 tank destroyer based on the BRDM, and in the 9P124 tank destroyer based on the BRDM-2, which supplanted the 2P32 in 1963 as part of a broader effort to replace the BRDM platform. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://cdn.discordapp.com/attachments/643519782791938058/1027214227586416660/unknown.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="633" data-original-width="800" height="317" src="https://cdn.discordapp.com/attachments/643519782791938058/1027214227586416660/unknown.png" width="400" /></a></div><p>Unlike the "Shmel", the 3M11 was considered to have ample modernization potential, and the design bureau proposed a modernization project to the chairman of the military industrial complex to increase the missile range and armour penetration on May 25, 1963. A week later, the project was approved and on the 8th of December 1964, the 2K8M "Falanga-M" system replaced the 2K8, bringing with it the improved 9M17 missile as a replacement for the 3M11. The largest improvement was in the engine, which granted a greatly improved range of 4 km, but improvements were also made to the guidance system. The new "Falanga-M" system differed from the basic type in that it had an improved radio command system, which was needed to take advantage of the expanded maximum range. The modernized 2P32M and 9P124M tank destroyers were the principal missile carriers featuring this system. Ground-based "Falanga" systems were considered heavy anti-tank weapons, and were exclusively issued to the anti-tank regiments of combined arms armies. </p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-1mHWALBXFiU/YLa0Ei1X6MI/AAAAAAAATRI/zVr3VGNZ2dQiniNTpKQWPDSMzMSGwxdugCLcBGAsYHQ/s600/9P124.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="359" data-original-width="600" height="239" src="https://1.bp.blogspot.com/-1mHWALBXFiU/YLa0Ei1X6MI/AAAAAAAATRI/zVr3VGNZ2dQiniNTpKQWPDSMzMSGwxdugCLcBGAsYHQ/w400-h239/9P124.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-kVMH005e3dk/YMIkCTS8zyI/AAAAAAAATY4/iOs1UBhy_sUNHD0hg35scG45GzbCxnq7gCLcBGAsYHQ/s1957/9p137%2Bfleyta%2Btank%2Bdestroyer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1152" data-original-width="1957" height="235" src="https://1.bp.blogspot.com/-kVMH005e3dk/YMIkCTS8zyI/AAAAAAAATY4/iOs1UBhy_sUNHD0hg35scG45GzbCxnq7gCLcBGAsYHQ/w400-h235/9p137%2Bfleyta%2Btank%2Bdestroyer.png" width="400" /></a></p><p>Later, the 9M17 missile was modernized again, with improved steering responsiveness, becoming the 9M17M which entered service in 1967 in conjunction with the K-4V helicopter weapons suite used on the Mi-4AV, and then later incorporated in the 9P153 "Falanga-MV" system of the Mi-8TV, and the same "Falanga-MV" system of the Mi-24A. The 9M17M was developed with control improvements specifically meant for improved helicopter operation, though the missile could also be used on ground launchers with total interchangeability. The final modernization effort was the 2K8P "Falanga-P" system in 1973, implemented exclusively on the 9P137 "Falanga-P" tank destroyer, shown in the photo below. It included the new 9M17P missile, and was capable of SACLOS guidance. It was created as an interim solution to the ongoing work for a second generation heavy ATGM to replace the "Falanga" series, which had been delayed because the requirement had stipulated that the replacement was to be supersonic. Sources do not disclose much about the 9P137, but with the success of the "Konkurs" missile system in testing and its adoption in 1974, followed by the "Shturm-S" in 1979, the obscurity of the 9P137 implies that its career in the Soviet Army was brief. The image below, taken from the March 2019 issue of the "<i>Техника и вооружение</i>" magazine, shows a rare colour photograph of the 9P137.</p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-FPUVdzLwLtI/YNwGLPgpZgI/AAAAAAAATpo/ZmieLc2iOmwghGN7a63T5opuDIpRjzoLwCLcBGAsYHQ/s2048/falanga-p.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1760" data-original-width="2048" height="344" src="https://1.bp.blogspot.com/-FPUVdzLwLtI/YNwGLPgpZgI/AAAAAAAATpo/ZmieLc2iOmwghGN7a63T5opuDIpRjzoLwCLcBGAsYHQ/w400-h344/falanga-p.png" width="400" /></a></p><p>The 9M17P was also used in the 9P145 "Falagna-PV" ATGM system of the Mi-24D, which entered service on March 29, 1976. SACLOS guidance was provided by the "Raduga-F" stabilized ATGM system of these helicopters, with the "F" suffix denoting "Falanga". </p><p>Altogether, the "Falanga" series persisted for a surprisingly long service career chiefly thanks to the 9M17P, as the Mi-8TV and Mi-24D continued to be operated in meaningful numbers up til the collapse of the USSR. Despite its design anachronisms, being a first generation ATGM at its core, the performance characteristics of the missile were not far behind much more modern missiles like the TOW series, and this - to an extent - justified its retention long past its replacements had arrived.</p><p>The "Falanga" was officially retired from service in 1997. After the dissolution of the Soviet Union, there was very limited use of the "Falanga" in the Russian military. Existing 9M17M and 9M17P missiles were expended by converting them into inexpensive target drones for short-ranged anti-air defence practice, mainly for ZU-23-2 guns and Strela-10 missile systems. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-yUNYIuFmAx8/YMVEPuoybXI/AAAAAAAATcA/KMLHREIf1pYPI46_uAGdzSsd3o7EQH7BQCLcBGAsYHQ/s588/drone.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="557" data-original-width="588" src="https://1.bp.blogspot.com/-yUNYIuFmAx8/YMVEPuoybXI/AAAAAAAATcA/KMLHREIf1pYPI46_uAGdzSsd3o7EQH7BQCLcBGAsYHQ/s320/drone.jpg" width="320" /></a></div><p>More than 24,000 missiles of the "Falanga" series were exported to 16 client nations, almost all of them as part of ammunition supply contracts for Mi-25 helicopters. The only missile exports for ground launchers were to Egypt and Syria, to complement their small contingent of 2P32 tank destroyers, all delivered in early 1973 in preparation for the upcoming war with Israel.</p><p>At the MAKS-99 expo, several modernization options were presented for export still operating legacy Mi-25 helicopters armed with the "Falanga-PV" ATGM system. These were the 9M17P1 and 9M17P2, featuring enhanced HEAT warheads capable of penetrating 400mm RHA at 60 degrees, and more interestingly, there was also the 9M17PM2 fitted with a very powerful 9N114M2 combined EFP and FAE warhead.</p><p><br /><a href="https://www.blogger.com/null" id="falangadesign"></a></p><h3 style="text-align: left;"><span style="font-size: large;">GENERAL DESIGN FEATURES</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-92TiTau3lfI/YMIt4ITxh7I/AAAAAAAATZI/Oubqsx5R4MwEbedFDX5-JVIRJvebv4BnACLcBGAsYHQ/s2048/3m11%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1129" data-original-width="2048" height="352" src="https://1.bp.blogspot.com/-92TiTau3lfI/YMIt4ITxh7I/AAAAAAAATZI/Oubqsx5R4MwEbedFDX5-JVIRJvebv4BnACLcBGAsYHQ/w640-h352/3m11%2Bcross%2Bsection.png" width="640" /></a></div><p>The layout of the missile places the warhead at the front, with the onboard power source and guidance system behind it, followed by the rocket engine which defines the center of mass of the missile, and then finally ending in the radio receiver at the tail. </p><p>Owing to its design roots as a heavy ATGM for vehicle carriers, the "Falanga" was naturally quite large, even compared to the 3M6 "Shmel", measuring 1,150mm in length and 140mm in diameter while also being heavier, weighing 28.5 kg. The new 9M17 missile was heavier still, weighing 31 kg, but boasted considerably improved characteristics. Its dimensions were identical to the 3M11.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ncPMsUteXMA/YKghSb6JDXI/AAAAAAAATEE/YY18ls4owB8NEmuYjQRu-m3vG4HRgR-MwCLcBGAsYHQ/s792/2p32%2Bfalanga.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="557" data-original-width="792" height="281" src="https://1.bp.blogspot.com/-ncPMsUteXMA/YKghSb6JDXI/AAAAAAAATEE/YY18ls4owB8NEmuYjQRu-m3vG4HRgR-MwCLcBGAsYHQ/w400-h281/2p32%2Bfalanga.png" width="400" /></a><a href="https://1.bp.blogspot.com/-xFY6w99wfVg/YIrfw3Q0ZRI/AAAAAAAAS5I/JEpuJi7gqDsvj745DKP0aSH718PxI7E5gCLcBGAsYHQ/s773/falanga%2Bmissile%2Bsize.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="511" data-original-width="773" height="265" src="https://1.bp.blogspot.com/-xFY6w99wfVg/YIrfw3Q0ZRI/AAAAAAAAS5I/JEpuJi7gqDsvj745DKP0aSH718PxI7E5gCLcBGAsYHQ/w400-h265/falanga%2Bmissile%2Bsize.png" width="400" /></a></div><p><br /></p><p>As a heavy ATGM, the only foreign counterpart to the 3M11 during the 1960's was the French SS.11, which was four years older but remained the state of the art in its class among its NATO userbase. This was not only a matter of classification, but in practical terms, as the 3M11 series reached a level of performance that could be rightfully considered a rival to the SS.11, later exceeding it with the 9M17. More importantly, its capabilities were great enough to justify its role as a heavy ATGM system.</p><p>Though the "Falanga" series of missiles was not containerized, like all other examples of MCLOS ATGMs, this did not mean that the missiles could be stored in open air. For storage and transport, the missiles were kept inside special watertight wooden crates with a shock-absorbent mount for the missile and a large dessicant satchel, which is necessary because the crates are not hermetically sealed like containerized ATGMs. The full unit weighed a total of 60 kg - double the weight of the missile alone. </p><p><br /></p><p>The process of checking and ensuring the proper amount of pressure in the missile would have been problematic for the ground forces, for whom the concept of containerization was particularly important for the sake of reducing the missiles into the equivalent of an artillery round - a single, self-contained, maintenance-free unit that can be loaded and fired without any special procedures.</p><p>For helicopters, the nature of their operation was much more accommodating of these idiosyncrasies. Helicopters, as a rule, are supported by a ground crew, and their combat missions are discrete periods of action, after which they return to their airfield and are undergo a round of checks. The slow depressurization of the ATGM power source is thus reduced from a critical issue to an inconvenience - another item on the preflight checklist. Similarly, the lack of containerization is also a much less important issue, as the missiles would be stored at the airfield and handled by personnel trained for non-containerized weapons.</p><p>When fired from a helicopter, the decidedly disadvantageous nuances of a first generation ATGM are also largely solved or at least ameliorated. First of all, the long minimum range becomes a completely irrelevant issue due to the nature of helicopter tactics, and secondly, there is practically no chance of the missile colliding with the ground in the initial part of its trajectory, as the helicopter can be expected to be several meters or tens of meters off the ground. The lofted trajectory of the missile during its boost phase may even help clear forest canopies, if the helicopter is firing while hovering behind a treeline.</p><p>Aside from minor shortcomings like having a slightly longer launch delay - over a second longer than most second generation ATGMs - the performance metrics of the "Falanga-PV" made it viable even among its younger peers. On the contrary, its wireless radio guidance system gave it a number of operational advantages over other heliborne ATGM systems like the TOW and HOT, which had certain firing restrictions due to their control wires. </p><p>However, the main advantage of a wireless command link - the lack of flight speed restrictions - was not exploited by the "Falanga" in any meaningful way, as its peak flight speed was relatively modest, even though it was the highest of all ATGMs at the time it entered service.</p><p><br /><a href="https://www.blogger.com/null" id="falangaaerodynamics"></a></p><h3 style="text-align: left;"><span style="font-size: large;">AERODYNAMICS</span></h3><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-MKRhVGTM0JA/YL3nBy5IPjI/AAAAAAAATXw/2GqENCYdGxc4HTUdwiUguMzgnL5gBX8NgCLcBGAsYHQ/s476/9m17%2Baerodynamic%2Bscheme.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="224" data-original-width="476" height="189" src="https://1.bp.blogspot.com/-MKRhVGTM0JA/YL3nBy5IPjI/AAAAAAAATXw/2GqENCYdGxc4HTUdwiUguMzgnL5gBX8NgCLcBGAsYHQ/w400-h189/9m17%2Baerodynamic%2Bscheme.png" width="400" /></a></p><p>The "Falanga" series uses a canard aerodynamic scheme. The wings have a cropped delta shape, and all four are almost identical in shape and composition. They have a hollow fiberglass structure with a foam filler, are foldable and each has a rudder on the trailing edge. The thick wing roots are also hollow. Unlike the 3M6, a slightly more optimized, thicker symmetric aerofoil was used for the wings of the "Falanga" series. The leading edge has an rounded shape while the trailing edge is wedge-shaped, and the thickness of the wing declines towards the tip. The wing is thickest at the root due to structural reasons, as the root bears the cantilever load generated by the lift force of the entire wing.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-FQfC3ufXS1M/YMNiGgHgEdI/AAAAAAAATaA/mquFScBg81so5VOKYu3tS29T9ThkJsnHQCLcBGAsYHQ/s1295/9m17p%2Bwings.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="912" data-original-width="1295" height="283" src="https://1.bp.blogspot.com/-FQfC3ufXS1M/YMNiGgHgEdI/AAAAAAAATaA/mquFScBg81so5VOKYu3tS29T9ThkJsnHQCLcBGAsYHQ/w400-h283/9m17p%2Bwings.png" width="400" /></a><a href="https://1.bp.blogspot.com/-BYfigNJZwLA/YMNsVKRiSXI/AAAAAAAATaQ/IerjWwInOw82WhWwLFWOLdI8Hwsu05I3wCLcBGAsYHQ/s1086/9m17p%2Bin%2Bcontainer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1037" data-original-width="1086" src="https://1.bp.blogspot.com/-BYfigNJZwLA/YMNsVKRiSXI/AAAAAAAATaQ/IerjWwInOw82WhWwLFWOLdI8Hwsu05I3wCLcBGAsYHQ/s320/9m17p%2Bin%2Bcontainer.png" width="320" /></a><br /></div><p>When mounted on the launcher, the missile is laid with the wings in an "X" form to conserve internal space in the carrier, and immediately after launch, the missile is automatically rolled counterclockwise by 135 degrees to change the wing profile from an "X" to a cruciform. This also orients the canards to be level in the horizontal plane. The missile does not spin in flight, and has automatic roll stabilization via the onboard gyroscope to ensure that the proper orientation is maintained at all times. The wings are numbered 1-4 as a reference for correct loading orientation. The No. 1 and No. 3 wings are the top and bottom vertical wings, and the No. 2 and No. 4 wings are the right and left horizontal wings. </p><p>With the wings deployed, the wingspan is 700mm. With the wings folded, the width and height of the missile is 262mm and 255mm respectively. When folded, a pair of wings are bounded together with a plastic band to lock them in place. To deploy a wing, the plastic band is cut and the wing is flipped onto the wing root until a detent in the base of the wing is moved across a locking pin in the hollow wing root, whereupon it is permanently locked open. The missile cannot be returned to its packing box once it is deployed in its combat-ready configuration, and long-term storage of the missile in open air is not feasible, so preparations for combat must be deliberate.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-aAfgF8ltyPE/YMNxwCvjH_I/AAAAAAAATaY/x3kQtNCsZpMcRShUmKh7lbUZdn2g8duZgCLcBGAsYHQ/s762/on%2Blauncher.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="511" data-original-width="762" height="269" src="https://1.bp.blogspot.com/-aAfgF8ltyPE/YMNxwCvjH_I/AAAAAAAATaY/x3kQtNCsZpMcRShUmKh7lbUZdn2g8duZgCLcBGAsYHQ/w400-h269/on%2Blauncher.jpg" width="400" /></a></div><p></p><p>Two fixed canards at the warhead section provide the necessary lifting force in front of the center of gravity of the missile to balance out the moment of lift from the main wings. Functionally, these canards are equivalent to the horizontal stabilizers on the tail of a conventional aircraft, but in aerodynamic jargon, the positive pitching moment produced by lifting canards means that they are considered destabilizers. The canards are asymmetrical aerofoils, having a sloping top surface on the trailing edge, while the bottom surface is flat. The rest of the canard surface is a simple flat plate, as shown in the photo on the left below, from <a href="https://www.kpopov.ru/military/spb_art_missile.htm#ancor7">an unknown author on the kpopov.ru website</a>.</p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-036ansv5yvw/YMSz6Dszc5I/AAAAAAAATbo/LX1Wctgi2hUHu2iUOhaNWkJEIgSTqxyBwCLcBGAsYHQ/s694/canard.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="463" data-original-width="694" height="266" src="https://1.bp.blogspot.com/-036ansv5yvw/YMSz6Dszc5I/AAAAAAAATbo/LX1Wctgi2hUHu2iUOhaNWkJEIgSTqxyBwCLcBGAsYHQ/w400-h266/canard.png" width="400" /></a><a href="https://1.bp.blogspot.com/-hJeIosR6cEI/YLa2Lmp_L7I/AAAAAAAATRg/zVwsHZnCqkwVTGBGF-MV6yBXElDny7xDQCLcBGAsYHQ/s1393/3m11.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="880" data-original-width="1393" height="253" src="https://1.bp.blogspot.com/-hJeIosR6cEI/YLa2Lmp_L7I/AAAAAAAATRg/zVwsHZnCqkwVTGBGF-MV6yBXElDny7xDQCLcBGAsYHQ/w400-h253/3m11.png" width="400" /></a></div></div><p>Because the canards contribute lift, the amount of lift needed from the wings is reduced, and consequently, the size of the wings can also be reduced. As the canards are fixed, their contribution in lift is also fixed, as is the ratio of lifting forces between the canards and the wings. This means that as the missile changes its angle of attack or experiences a change in its flight speed, the moments of lift always remain balanced. However, the additional lift generated by the canards also shifts the center of pressure considerably forward. This issue was solved quite creatively - like all ATGMs at the time, observation of the missile in flight is permitted by tracers. On the "Falanga" series, a pair of particularly large tracers were used, protruding prominently from the wing roots of the No. 2 and No. 4 wings. The size and location of these tracers was an unusual design solution to incorporate them as additional lifting body structures, increasing the amount of lift generated behind the center of gravity of the missile. This shifts the center of pressure towards the rear, ensuring that it is behind the center of gravity, making the "Falanga" an aerodynamically stable design.</p><p>Besides the wings and canards, the shape of the nose of the missile is also worth noting, as contrary to common expectation, the rounded shape is similar to the conical noses of most first generation ATGMs in terms of aerodynamic efficiency for subsonic flight. The image on the left below, taken from the 1965 textbook "<a href="http://ftp.demec.ufpr.br/disciplinas/TM240/Marchi/Bibliografia/Hoerner.pdf%20Dr.-Ing%20S.%20F.%20Hoerner">Fluid-Dynamic Drag</a>" by Dr.-Ing S. F. Hoerner, shows the relationship between ogived, hemispherical and blunt noses in their forebody pressure drag coefficients for cylindrical bodies. On the first shape from the left, an ogive, a negative forebody drag is observed due to suction forces. A blunt nose results in relatively low forebody drag, on par with a pointed nose, though still 20 times more than a hemispherical nose. The pressure drag on the nose itself is influenced in a similar way to the forebody drag, as shown in the image on the right below, from the article "<a href="https://www.airplanesandrockets.com/rockets/model-rocketry-new-look-american-modeler-may-1961.htm">Model Rocketry's New Look</a>" from the May 1961 issue of the American Modeler magazine. A blunt nose experiences twice as much drag as a hemispherical nose - a difference that is an order of magnitude less severe than in the case of forebody drag. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-leHNyQr00mo/YMOr5vb-CFI/AAAAAAAATa4/qAV6zkc1J-8-7gWo7NyqSJ-GCre0KNNbQCLcBGAsYHQ/s1204/drag%2Bcoefficient%2Bof%2Bshapes.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="677" data-original-width="1204" height="225" src="https://1.bp.blogspot.com/-leHNyQr00mo/YMOr5vb-CFI/AAAAAAAATa4/qAV6zkc1J-8-7gWo7NyqSJ-GCre0KNNbQCLcBGAsYHQ/w400-h225/drag%2Bcoefficient%2Bof%2Bshapes.png" width="400" /></a><a href="https://1.bp.blogspot.com/-_YN6lU2A6yI/YMOtHb78NkI/AAAAAAAATbA/OvHfvRmSk1MCSvr1gEKbqMxpfL7OLmWHgCLcBGAsYHQ/s499/model-rocketry-new-look-american-modeler-may-1961-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="244" data-original-width="499" height="195" src="https://1.bp.blogspot.com/-_YN6lU2A6yI/YMOtHb78NkI/AAAAAAAATbA/OvHfvRmSk1MCSvr1gEKbqMxpfL7OLmWHgCLcBGAsYHQ/w400-h195/model-rocketry-new-look-american-modeler-may-1961-2.jpg" width="400" /></a><br /></div><p><br /></p><p>The shape of the 3M11 nose is roughly represented in the line drawing below, keeping in mind that the drawing is only a loose tracing of the overall form of the missile. The drawing is taken from "<i>Российское ракетное оружие 1943-1993</i>" by A.V. Karpenko. On the 9M17, the shape of the nose was slightly modified, removing the ridge behind the rounded nose. This presumably streamlined the overall shape. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-BQA4qTCbGlY/YOjMgbKO7TI/AAAAAAAAT0I/LP3f35xCvFIEikUOKHB-TQwdPsTO4BlNQCLcBGAsYHQ/s1485/3m11%2Bline%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="729" data-original-width="1485" height="196" src="https://1.bp.blogspot.com/-BQA4qTCbGlY/YOjMgbKO7TI/AAAAAAAAT0I/LP3f35xCvFIEikUOKHB-TQwdPsTO4BlNQCLcBGAsYHQ/w400-h196/3m11%2Bline%2Bdrawing.png" width="400" /></a></div><p></p><p>Because the wings are symmetrical aerofoils, "Falanga" missiles must fly at a positive angle of attack for its lifting surfaces to generate lift in trimmed (level) flight. On the other hand, its combination of large wings and canards is unique if compared to other first generation ATGMs, and should provide the missile with more lift than a conventional tailless delta wing missile, possibly reducing the necessary angle of attack for the "Falanga" to less than the 6-7 degrees needed by the French first generation ATGMs or the 3M6. No information is available on the angle of attack of "Falanga" missiles throughout its flight profile, although it can be safely inferred that it varies considerably from its boost, sustain and glide stages.</p><p>Once launched at boost, the missile acquires an increased angle of attack for reliable launch and to gain altitude, and it continues to climb on its own for most of its flight due to the constant acceleration from the sustainer engine. This is not counteracted by a progrom in the control unit, so the operator needs to manually apply a pitch-down correction in order to bring the missile to level flight. After engine burnout, the missile will begin to descend as it loses speed. The operator must manually intervene to stabilize the missile again, paying constant attention to the missile altitude and increasing the pitch intermittently until target impact. The tendency for the missile to climb is particularly pronounced when it is launched from high-speed helicopters such as the Mi-24A or Mi-24D. If launched at a cruising speed of 100-200 km/h, the missile flies with an additional velocity of 27-55 m/s, so it gains altitude much more rapidly compared to a hovering launch or a static launch from a ground vehicle. </p><p>As with virtually all other first generation ATGMs, the "Falanga" series has an aerodynamic design providing positive static and dynamic stability. However, during the boost phase, when the fuel of the booster engine is not yet expended, the positive static margin of the missile is small, according to the engineering textbook "<i>Основы Устройства И Функционирования Противотанковых Управляемых Ракет</i>" by V. V. Vetrov et al., published for the Tula state university by the KBP design bureau. This is because the center of gravity of the missile is further rearward than normal, as the fuel block of the booster engine is yet to be fully combusted, and so the center of gravity is closer to the center of pressure than normal. It is noted in the textbook that the static margin is close to the minimum permissible amount, so when launching, the missile is a little sensitive to crosswinds. Whether this was enough to be noticeable or problematic, perhaps causing the operator to fail to capture the missile in his optic promptly, is not detailed. The unusual launch procedure of rolling the missile by 135 degrees counter-clockwise into its cruciform attitude, instead of a shorter 45-degree roll, may have been designed to compensate for crosswind sensitivity during the initial boost phase by zeroing out the induced yaw from a crosswind blowing across one side of the missile. </p><p><br /><a href="https://www.blogger.com/null" id="falangaguidance"></a></p><h3 style="text-align: left;"><span style="font-size: large;">GUIDANCE SYSTEM</span></h3><p>The guidance system in all "Falanga" series missiles includes a gyroscope, a power source, the radiocommunications equipment, and an onboard autopilot. The autopilot is linked to the gyroscope, and automatically performs roll corrections when a deviation is detected by the gyroscope.</p><p>The missile is electrically connected to the launcher by two multi-pin connectors on the tail. The rubber cup seen on "Falanga" launchers is a weather shield to help protect the connectors from water ingress when a missile is loaded. This connection delivers the launch signals. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xhTs1Wkw0s8/YMIjm34CnFI/AAAAAAAATYw/zSTTXPDLb4Q2q1-_V8wdHp10ijsKQTgAQCLcBGAsYHQ/s1956/3m11%2Bon%2B2p32.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1169" data-original-width="1956" height="239" src="https://1.bp.blogspot.com/-xhTs1Wkw0s8/YMIjm34CnFI/AAAAAAAATYw/zSTTXPDLb4Q2q1-_V8wdHp10ijsKQTgAQCLcBGAsYHQ/w400-h239/3m11%2Bon%2B2p32.png" width="400" /></a><a href="https://1.bp.blogspot.com/-iTvPBe0JQW0/YMI8RyExT8I/AAAAAAAATZQ/O07gtQf2Cp0pzXZHhbPF-bXN4tlhOVBSgCLcBGAsYHQ/s943/9m17p%2Btail%2Band%2Btracers.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="739" data-original-width="943" height="251" src="https://1.bp.blogspot.com/-iTvPBe0JQW0/YMI8RyExT8I/AAAAAAAATZQ/O07gtQf2Cp0pzXZHhbPF-bXN4tlhOVBSgCLcBGAsYHQ/w320-h251/9m17p%2Btail%2Band%2Btracers.png" width="320" /></a></div><p>On the 3M11, the onboard power supply was pneumatic, relying on a reservoir of pressurized air for both steering and for electrical power. Instead of a battery, a continuous stream of compressed air was fed to a turbine generator, thus providing power to the onboard electronic equipment, mainly to accommodate the electrical power needs of the radio control equipment, but also for the gyroscopic guidance system and for the electronic valves of the steering system. The air reservoir is a short cylinder with rounded ends. An ideal vessel for this purpose would be a sphere, but a sphere has poor volumetric efficiency inside a cylindrical missile fuselage. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-X9RofQSX5B4/YN5r8V2K8mI/AAAAAAAATsk/7pRwToOc_YoiB7ymp6H8xgZ6zazBxKAVACLcBGAsYHQ/s1775/9m17m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1383" data-original-width="1775" height="311" src="https://1.bp.blogspot.com/-X9RofQSX5B4/YN5r8V2K8mI/AAAAAAAATsk/7pRwToOc_YoiB7ymp6H8xgZ6zazBxKAVACLcBGAsYHQ/w400-h311/9m17m.png" width="400" /></a><a href="https://1.bp.blogspot.com/-jp25Py_d6oc/YN5sSOMLI_I/AAAAAAAATss/nze3xcOAou4PbimwDuw9yNRu6teGWCy-ACLcBGAsYHQ/s829/cropped%2B9m17p%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="565" data-original-width="829" height="272" src="https://1.bp.blogspot.com/-jp25Py_d6oc/YN5sSOMLI_I/AAAAAAAATss/nze3xcOAou4PbimwDuw9yNRu6teGWCy-ACLcBGAsYHQ/w400-h272/cropped%2B9m17p%2Bcross%2Bsection.png" width="400" /></a><br /></div><p><br /></p><p>Using air for the onboard power supply has a number of merits, mainly because air compressed to a high pressure provides a much higher energy density than any battery, and in theory, this also gave the advantage of consolidating the power sources of the missile into one medium, simplifying its design. Above all else, the main justification is that the power demands of a radio command system are higher than a wired system, as it must receive and strongly amplify the weak signal current of the radio command link, a task which is simplified in a wire link because the wire allows a strong current to be delivered. The desire to implement alternatives to thermal batteries was not unprecedented, as their low power density incurred a considerable weight penalty; where a wet cell battery weighing several tens of grams is sufficient, a thermal battery weighing several hundred grams would be needed. However, a pneumatic power supply was an imperfect substitute, as it brought a gradual depletion of air pressure even if the missile operator made no steering commands, intrinsically limiting the intensity and frequency of steering commands that could be made. Beginning with the 9M17, the pneumatic power supply system was replaced with a T-158B molten salt thermal battery.</p><p>The gyroscope is a two-axis type with a single degree of freedom, used to detect deviations in roll angle. The gyroscope in the 3M11 was spun electrically, with an electric drive powered by the turbine generator. An electric drive is perhaps the slowest method of spinning up a gyroscope, and indeed, the delay between the pressing of the launch trigger and the departure of a 3M11 missile from its launch rail was unusually long; a full 5 seconds. This was improved upon in the 9M17 by a new pyrotechnically-driven gyroscope, which gave the advantage of a quicker spin-up time, shortening the launch delay to 3.5 seconds. This method of gyroscope spin-up became standard for all subsequent models, but one more gyroscope modification was introduced in 1967. When the 9M17M was introduced that year for helicopter use, it brought some changes to steering control system, particularly the gyroscopic roll stabilization channel. It became capable of compensating for the roll angle of the launch platform to ensure that it could correctly roll into the correct cruciform orientation after launch, which was an important adaptation for helicopters, as it was somewhat more challenging to maintain a level orientation than a ground launcher. </p><p>Though the power supply becomes operational and the gyroscope is spun up before launch, the radio command system only activates after the missile is airborne, due to an inertial switch requiring an acceleration of 9 g to activate. The radio antenna itself is only powered on near the end of the boost phase, when the acceleration has lowered to a threshold value of 4-6 g. Mirroring this, on the launch platform, the firing relay on the launcher sends a signal to switch on the transmitter antenna only after a preprogrammed delay of 0.6 seconds following missile departure, which is sensed by the launcher via the loss of an electrical connection with the missile. This delay is primarily meant to prevent an overenthusiastic operator from prematurely steering the missile (and potentially crashing it) before it has reached a safe altitude above ground level, but it may also serve as a protective measure against the initial voltage spike when the battery begins discharging. </p><p>Because the rocket engine is located between the tail section and power source, and the engine occupies the entire diameter of its section in the fuselage, the tail is powered by a cable in a protective tube laid outside the fuselage. Next to the electrical tube is an air tube which connects the air reservoir to the rudder steering mechanism. Both tubes are situated on the underside of the fuselage, as shown in the photo below, taken from the "valka" online forum.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://www.valka.cz/files/zbran__037.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="511" data-original-width="762" height="268" src="https://www.valka.cz/files/zbran__037.jpg" width="400" /></a></div><p>Command signals are transmitted by a radio link. Unlike a wire link, radio command is unaffected by terrain and electrical obstacles, and there are no limitations to firing over water, either fresh or salt water, or firing over electrical wires. The use of radio guidance also seemed to be a promising solution to the problem of wire breakages and insufficient unspooling speeds, which limited missile flight speeds. However, a radio command link also introduces an additional point of vulnerability to interference, namely radio interference, on top of visual interference and fire suppression on the operator. Another downside is that the radioelectronic equipment needed to operate on a radio command link was rather bulky, weighing much more than a simple spool of wire and occupying much more space. </p><p>The image below, from the engineering textbook "<i>Основы Устройства И Функционирования Противотанковых Управляемых Ракет</i>" by V. V. Vetrov et al., is a control flow diagram representing the operating steps of a radio command missile.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-q35Ot41CJeA/YNeGEAnxcKI/AAAAAAAATh0/J4cEpVcw5kE2K-2VLZxhjykldWCStzoHQCLcBGAsYHQ/s1865/generic%2Bradio%2Bcontrol.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="289" data-original-width="1865" height="100" src="https://1.bp.blogspot.com/-q35Ot41CJeA/YNeGEAnxcKI/AAAAAAAATh0/J4cEpVcw5kE2K-2VLZxhjykldWCStzoHQCLcBGAsYHQ/w640-h100/generic%2Bradio%2Bcontrol.png" width="640" /></a></div><p style="text-align: center;">(1) command generator, (2) encoder, (3) magnetron, (4) transmitter antenna, (5) receiving antenna, (6) radio receiver, (7) decoder, (8) amplifier</p><p><br /></p><p>As discussed previously for the "Shmel", a wire-guided ATGM system has only components (1) and (8), linking them by the eponymous wire. Though these components are all electronic, and have no moving parts, hardening the radioelectronic equipment in the missile to withstand launch acceleration is an engineering challenge that is otherwise unnecessary.</p><p>On the "Falanga" series, all of the radio equipment was contained in the 9B373 radiocommunications unit, at the tail of the missile fuselage. The radio system receives command signals, converts it into useable electrical command signals, then amplifies them, and the resulting signals are relayed as control signals to the rudder or elevator actuators. The gyroscope of the missile has its own, dedicated roll control channel that bypasses the radio command system architecture, only interacting so far as to add its own roll commands on top of yaw commands received through the radio link.</p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-YlnGwZmJWCs/YLh9pFrv01I/AAAAAAAATTA/Mtbuh7MVbUA9ZCPI2Q6XdTH_MrqOYOJygCLcBGAsYHQ/s1993/falanga%2Btail%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1163" data-original-width="1993" height="234" src="https://1.bp.blogspot.com/-YlnGwZmJWCs/YLh9pFrv01I/AAAAAAAATTA/Mtbuh7MVbUA9ZCPI2Q6XdTH_MrqOYOJygCLcBGAsYHQ/w400-h234/falanga%2Btail%2Bsection.png" width="400" /></a></p><p>The 9B373 unit contains all of the radio and signal processing equipment for receiving and interpreting command signals, with individual tasks distributed to discrete blocks in the unit. </p><ul style="text-align: left;"><li>Block 1S: Antenna and filter block. Converts the radio signal into an electric signal</li><li>Block 1F: Frequency filter alone. It is a subcomponent of Block 1S.</li><li>Block 1P: Preamplifier block. Amplifies the weak signal passed from Block 1S to a strength suitable for further processing.</li><li>Block 1D: Decoder block. Transforms the signal to a usable format.</li><li>Block 1M: Amplifier block. Greatly amplifies the decoded signal for use as control signals in the missile steering mechanism.</li><li>Block 1DP: Transmitter overload bypass.</li></ul><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-fcDbSpBp5n0/YMUAYM1lpGI/AAAAAAAATb4/LuIFFYo5JKw8MorMGhASiyINJqDpDbe1ACLcBGAsYHQ/s2048/9b373%2Bblock%2Bdiagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1502" data-original-width="2048" height="470" src="https://1.bp.blogspot.com/-fcDbSpBp5n0/YMUAYM1lpGI/AAAAAAAATb4/LuIFFYo5JKw8MorMGhASiyINJqDpDbe1ACLcBGAsYHQ/w640-h470/9b373%2Bblock%2Bdiagram.png" width="640" /></a></div><p>The filter in all "Falanga" series missiles would be tuned to one of three possible frequencies to reject noise and other signals which may interfere with the guidance of the missile, including jamming signals. It functions as a band-pass, combining a high pass and low pass filter to reject frequencies outside a narrow range, within which the signal frequency lies, as shown in the diagram below adapted from the handbook "Missile Engineering Handbook - Principles of Guided Missile Design" (1958). Encoded pulse-modulated microwave radio signals with a vertical polarization are used in the command link. The amplitude is fixed, while the period between pulses contains information on the magnitude and direction of the steering commands. It is known that the microwave spectrum is used because the radio emitter relies on a magnetron, but the specific frequency ranges are not disclosed even in the technical manual for the 9B373 unit. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-KXww-1nu63s/YNYACR9eLjI/AAAAAAAATgc/hNBx2D3KxBINfadkenjB39zeIYolmK6awCLcBGAsYHQ/s3810/falanga%2Bband%2Bpass%2Bfilter%2Bconcept.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="826" data-original-width="3810" height="138" src="https://1.bp.blogspot.com/-KXww-1nu63s/YNYACR9eLjI/AAAAAAAATgc/hNBx2D3KxBINfadkenjB39zeIYolmK6awCLcBGAsYHQ/w640-h138/falanga%2Bband%2Bpass%2Bfilter%2Bconcept.png" width="640" /></a></div><p>A narrow E-plane horn antenna is used as the receiver, that then passes into a waveguide with a rectangular cross section. It is made of aluminum alloy. A horn antenna accommodates a wide range of frequencies and has very high directivity, aiding in signal reception at long distances while also minimizing the reception of signals from unwanted directions. The waveguide behind the antenna contains a parallel resonance circuit, which functions as a very narrow band pass filter tuned to a single, specific operating frequency. The filter is a passive unit, built into the waveguide itself and tuned before missile assembly at the factory. It cannot be configured without disassembling the tail section, as the filter is simply a piece of hardware. The receiver antenna is protected from water ingress by a distinctive white rectangular radome made from polyurethane foam.</p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both;"><a href="https://1.bp.blogspot.com/-FENUN_rAZBw/YMO5jArZ1-I/AAAAAAAATbQ/OGAboJn9HuQ-A-F5SfuV3-tG-Rw9VphdwCLcBGAsYHQ/s1400/dsc_7566.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="933" data-original-width="1400" height="266" src="https://1.bp.blogspot.com/-FENUN_rAZBw/YMO5jArZ1-I/AAAAAAAATbQ/OGAboJn9HuQ-A-F5SfuV3-tG-Rw9VphdwCLcBGAsYHQ/w400-h266/dsc_7566.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-2gM1f5WEbr0/YMssJYfns3I/AAAAAAAATck/i2Q7-JQTqbUeimzOJJZBsgHwQWFjHNpLQCLcBGAsYHQ/s2048/block%2B1f.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1559" data-original-width="2048" height="305" src="https://1.bp.blogspot.com/-2gM1f5WEbr0/YMssJYfns3I/AAAAAAAATck/i2Q7-JQTqbUeimzOJJZBsgHwQWFjHNpLQCLcBGAsYHQ/w400-h305/block%2B1f.png" width="400" /></a><br /><br /></div></div><p>The design of the receiver block provides three layers of security from jamming and interference, both achieved using hardware alone. The first security layer is the fact that the receiver is highly directional, so that the reception strength is maximum for signals emitted directly behind the missile. This is strongly influenced by the use of an E-plane horn, which has lessened directivity in the vertical plane, to support the reception of signals over a wider elevation arc - allowing the launcher to be situated at a variety of altitudes - and has extremely high directivity in the horizontal axis, so that sources of interference downrange of the missile are hardly received at all. The second basic layer of security is the frequency filter in the radio receiver. The third layer is the provision of three frequency options, which is related to the first layer because horn antennas support a very wide bandwidth, so the three possible frequencies can vary greatly from one another. </p><p>When loading a tank destroyer or a helicopter, the missile operator must take note of the frequency code for each missile he brings into battle and he must switch his control unit accordingly. The frequency code is marked by the number of rings painted on the tail. The rings can be white or black, depending on which provides more contrast against the primary colour of the tail. For instance, the 9M17P in the photo below has two white rings, indicating frequency code 2.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--DHL71uty58/YMImo32f0xI/AAAAAAAATZA/ABMByT8qn74xGidD58sPGiQ4sLACtPVcgCLcBGAsYHQ/s1955/9m17p%2Bon%2Blauncher.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="888" data-original-width="1955" height="290" src="https://1.bp.blogspot.com/--DHL71uty58/YMImo32f0xI/AAAAAAAATZA/ABMByT8qn74xGidD58sPGiQ4sLACtPVcgCLcBGAsYHQ/w640-h290/9m17p%2Bon%2Blauncher.png" width="640" /></a></div><p>This was essentially a rather crude and cumbersome - though not ineffective - measure to ensure that the radio commands transmitted to a missile fired from one 2P32 tank destroyer in a platoon (consisting of three vehicles) would not interfere with the missiles fired from the other members of the platoon. Theoretically, three missiles could be airborne at the same time and fly in crossing trajectories without cross-interference. However, this was a decidedly unwieldy approach to this issue, because it relies on the assumption that the units of fire delivered at ammunition resupply points would have the correct number of missiles with the correct frequency code for each vehicle in a platoon.</p><p>The transmitter antenna for the command signals must be placed on either the missile launcher or the sight of the missile system, with the prerequisite that it is aligned to the launcher, ensuring that the emitted signal is correctly directed towards the missile. The radio transmitter on the launch platform is either a horn antenna (helicopters) or a circular lens antenna (ground vehicles), both allowing directional transmission of the command signals only towards the missile. </p><p>To have some chance of introducing some noise into the command link, a powerful directed signal at the correct frequency range (corresponding to the operating frequency of the missile) and polarization must be emitted towards the missile from its rear aspect. But before this can even occur, the ATGM launch must first be detected, identified as a "Falanga", then the high-velocity missile must be tracked by this hypothetical jammer as it travels to its target. Needless to say, the feasibility of jamming a radio datalink of this type is an immense technical challenge, possibly an insurmountable one. Indeed, this form of jamming is only applicable to radio command-guided surface-air missiles, which are usually furnished with a large number of receiver antennas with very low directivity, arrayed along the sides of the fuselage, because they must perform relatively intense maneuvers in open sky. </p><p>Above all, historically, directed radio jamming of small and fast projectiles was never employed in any form throughout the Cold War by either NATO or the Warsaw Pact, and is likely still impractical today. With that in mind, a "Falanga" operator was effectively guaranteed a jamming-free control link with the missile. The only forms of radio jamming utilized in a significant capacity were intended for communications sets equipped with omnidirectional antennas, most often whip antennas, and were entirely unsuitable for radio-guided ATGMs. The combination of all of these factors indicates that radio jamming would have been largely ineffective against "Falanga" if it was used in combat against an opponent capable of employing such measures. </p><p>Once the signal is received and preamplified, the decoding block transforms it into usable information. When a steering input is made on the operator's control joystick (MCLOS) or generated automatically by the sighting system (SACLOS), the cipher in the launcher control system converts the inputs into pulse modulated signals, encoding the steering commands with varying signs and periods denoting the direction and intensity of the steering command, respectively. This is sent to the magnetron, which generates the corresponding pulsed radio signal that is then transmitted to the missile via the antenna. The decoder in the 9B373 unit is designed to convert the waveform signs and periods into the corresponding control signals for each of the steering rudders. Finally, the control signals are amplified and transmitted to the steering mechanism by the amplifier block. The flow diagram below shows the process flow of the decoder block, from receiving the preamplified signal from Block 1P, to delivering the decoded signal to Block 1M, the amplifier block. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Jr0ThK9xKZE/YN6-lKJKtpI/AAAAAAAATtQ/llBVx034tCAKuxJyYi5N_hqWYquwV4iAgCLcBGAsYHQ/s2048/1d%2Bflow%2Bdiagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1252" data-original-width="2048" height="392" src="https://1.bp.blogspot.com/-Jr0ThK9xKZE/YN6-lKJKtpI/AAAAAAAATtQ/llBVx034tCAKuxJyYi5N_hqWYquwV4iAgCLcBGAsYHQ/w640-h392/1d%2Bflow%2Bdiagram.png" width="640" /></a></div><p><br /></p><p>The signal received by the antenna contains pulse packets emitted in short intervals, forming groups of three packets, which are spaced between one another by specific lengths of time (periods). Each group is a special marker, denoting either a cycle, a yaw, or a pitch group, in that exact order. Cycle markers demarcate the beginning and end of each cycle, and within them, the yaw and pitch markers mark the intensity of the desired steering action. The direction of the steering action is indicated by the polarity of the yaw and pitch pulses. Negative pitch pulses command the missile to pitch downwards, and negative yaw pulses command the missile to steer left, and vice versa. </p><p>The third square pulse packet of every group is taken as the reference point for initial processing. However, the decoder does not know what marker each group indicates, because they all consist of the same three square pulse packets, with the same period between each pulse packet. However, it knows the period between each cycle group, which is fixed. To identify the cycle markers, the decoder block must therefore perform signal gating. The decoder transforms the values of the gating pulses in the temporal distribution of the adopted impulse ciphers into a steady square waveform, the cyclic period of which is determined by the time distribution.</p><p>Firstly, the decoder identifies the third pulse packet in each group via its cycle concurrency, yaw concurrency and pitch concurrency systems. Gating pulses are emitted, and if the gating pulses are not aligned with the cycle markers, then constructive interference does not occur, and no feedback pulse is formed. The decoder block relays a compatibility error signal to the preamplifier block, which introduces a phase shift into the signal sent to the decoder. This process is repeated until the gating pulses coincide with the cycle markers of the modified signal. </p><p>In the absence of an input signal, the decoder generates a "zero" signal. The "zero" signal ensures that no steering actions are made.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DUvW8m10ed8/YN7E8jpoOoI/AAAAAAAATtY/6_2NbsPTQ_MbAPnw0kC25nWoLEUa-TPAgCLcBGAsYHQ/s1357/decoder.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1357" data-original-width="1345" height="400" src="https://1.bp.blogspot.com/-DUvW8m10ed8/YN7E8jpoOoI/AAAAAAAATtY/6_2NbsPTQ_MbAPnw0kC25nWoLEUa-TPAgCLcBGAsYHQ/w396-h400/decoder.png" width="396" /></a></div><p><br /></p><p>Rows 1-2 show the work of Block 1P, preamplifying the signal received from the filter of Block 1S. The decoder identifies the third pulse in each cycle, yaw and pitch group by a concurrency operation, and uses it as the marker. The intensity of the steering action in the yaw axis is determined by t2, and in the pitch axis by t'2. Intensity is obtained by passing a steady voltage through the pulses, and having the pulses trigger the voltage to flip to a negative amplitude, thus forming a rectangular waveform. The waveform is inverted, and the period of the positive section of the waveform is taken as the value of the steering intensity magnitude. </p><p>The full work of the decoder block is shown in the chart below, additionally showing the results of the amplifier block, which amplifies the yaw and pitch periods to a higher amplitude (voltage).</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xxLzw8k6zrw/YN2oFz0o0xI/AAAAAAAATrg/qwqNkuFT8GMTeD1sqPXlAQmQ3YZnRlknwCLcBGAsYHQ/s1396/command%2Bsignal.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1396" data-original-width="1156" height="400" src="https://1.bp.blogspot.com/-xxLzw8k6zrw/YN2oFz0o0xI/AAAAAAAATrg/qwqNkuFT8GMTeD1sqPXlAQmQ3YZnRlknwCLcBGAsYHQ/w331-h400/command%2Bsignal.png" width="331" /></a></div><p><br /></p><p>Observation of the missile in flight is permitted by a pair of tracers. The tracers on 3M11 have an unknown designation. Beginning with the 9M17, the old tracers were replaced by 9Kh46 tracers to provide a longer illumination time, reflecting the considerably longer range of the 9M17. The burn time of the tracers is 30 seconds, providing a tracing time well in excess of the flight time of the missile. The 9M17P differed from preceding models by having the pyrotechnic tracers replaced with 9Kh419 electric lamps. When shooting during the day, observation is carried out by a white-light tracer, and when shooting at dusk, by an incandescent lamp located in the back of the tracer-lamp. The incandescent lamp is powered by a constant voltage from the on-board power supply system. Switching between the "Day" and "Twilight" operating modes is carried out by the operator on the launch unit of the combat vehicle's launch equipment.</p><p><br /></p><p>Because the sustainer engine gives a surplus of thrust, the ATGM enters a gentle climb climb after booster burnout, so once it appears in the operator's field of vision, he must input a pitch-down command to neutralize the climb. Due to the lofted trajectory, the missile had a long minimum range of 600 meters, a trait it shared with other first generation ATGMs.</p><p>Unlike ground platforms, the long minimum range is inconsequential to a helicopter. The root cause of the minimum range - the lofted trajectory - is not required on a helicopter, and unlike the launch rails on a ground-based tank destroyer, the helicopter launch rails are not elevated. The delay before the operator can visually acquire the missile in his sight is therefore shorter. The main issue, rather, is that because a helicopter normally fires its ATGMs from at least treetop level (around 40 meters on average), and sometimes much higher, the operator's sight naturally tends to be aimed slightly downwards, which can introduce complications in finding the missile promptly just as on a ground launcher. </p><p>On the other hand, helicopter launches can increase the range of the missile thanks to the potential energy afforded by a high altitude. For instance, the AS.11 (the helicopter variant of the SS.11) is credited with a range of 3,500 meters rather than 3,000 meters, which is its range when fired from the ground, and this is because when fired from a helicopter, the downwards trajectory raises the speed of the missile and thus allows the finite burn time of its sustainer engine to last for a greater distance, before the steering control from its TVC system is lost upon engine burnout. As such, the missile carries 3,500 meters of wire. Being radio guided, the maximum range of the "Falanga" system when fired from an advantageous altitude is not limited at all by wire.</p><p>The precision and intensity of the steering system was sufficient to permit targets moving at 40 km/h to be hit at the maximum range of 2.5 km with a probability of 0.6-0.7. Stationary targets are engaged with a hit probability of 0.75. As for the 9M17P, the nominal hit probability was 0.9 against a target moving at up to 60 km/h. Strangely enough, it is reported in the 1976 document "<a href="https://apps.dtic.mil/sti/citations/ADA076648">Target Presentation Methodology for Tactical Field Evaluations</a>" by a U.S Army research institute that the so-called AT-2 "Swatter" is easier to control than both "Shmel" and "Malyutka", being the most responsive and accurate of the three. The basis for this belief is somewhat unclear.</p><p>Owing to the much quicker and more systematic detection and control of the IR guidance computer, the 9M17P has a minimum range of 450 meters when used in the SACLOS mode. If used in the MCLOS mode, the 9M17P has the same minimum range of 600 meters as the preceding models, as there are no differences in the guidance method.</p><p><br /><a href="https://www.blogger.com/null" id="falangasteering"></a></p><h3 style="text-align: left;"><span style="font-size: large;">STEERING</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-B3N2MQw6w74/YN5q-CtH6YI/AAAAAAAATsc/xiKT9x84fcgUanNN_1Me0wDWRQ_ThVA_gCLcBGAsYHQ/s896/rudder%2Bon%2Bwing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="578" data-original-width="896" height="258" src="https://1.bp.blogspot.com/-B3N2MQw6w74/YN5q-CtH6YI/AAAAAAAATsc/xiKT9x84fcgUanNN_1Me0wDWRQ_ThVA_gCLcBGAsYHQ/w400-h258/rudder%2Bon%2Bwing.png" width="400" /></a></div><p>Steering and roll control was accomplished using rudders on each of the four wings. The rudders are deflected using pneumatic actuators. Due to the long range and high cruising velocity of the missile, the rudders required a substantial amount of power to allow the missile to perform maneuvers throughout its flight, which made it impractical to use electric servos. </p><p>The rudders (elevators) on the horizontal wings (No. 2 and No. 4) are linked in deflection to execute pitch commands. The rudders on the vertical wings (No. 1 and No. 3) can be synchronized to be deflected in both directions, either having both deflected in the same direction to steer the missile in yaw or in opposite directions to generate roll. </p><p>Air from the reservoir, pressurized to 200 atm, is ported into a distribution manifold, where the pressure is reduced to 4-6 atm by a pressure regulator. The pneumatic actuators operate at a nominal pressure of 5 atm on all "Falanga" missiles. In the book "<i>Отечественные противотанковые комплексы</i>" (<i>Domestic Anti-tank Systems</i>), it is reported that during development, the pneumatic system was not well sealed to prevent leakage, as after 10-12 days, the reservoir would begin to lose pressure. The leakage issue was never completely solved, and it is not known how much of an improvement was made after the 3M11 entered service. With the 9M17 model, an entirely new air reservoir was introduced as part of a new reservoir-engine structure, a comprehensive upgrade to both the rocket engine and the steering system.</p><p>The new air reservoir of the 9M17 provided an increased capacity, with a pressure of 260 atm. The raised capacity was presumably necessary to exploit the increased range of the missile, in addition to offloading the task of supplying electrical power to a thermal battery, which conserves the air supply for the steering system.</p><p><br /></p><p>The gradual loss of pressure in storage made it necessary to carry out pre-combat checks and repressurize the missiles if necessary. This could be done by the ground crew servicing a helicopter or by the operator in a ground-based tank destroyer, but it is undesirable for a tank destroyer to carry out these checks during combat rather than when restocking its ammunition, as the preperation period for an engagement would require an additional 2-3 minutes for these preparations. Otherwise, a 2P32 tank destroyer could transition from its travelling configuration to its combat configuration in 30 seconds, and hit a target within a minute. Failure to perform this check on an ATGM with a reduced air pressure would presumably lead to the premature loss of rudder authority before the missile has reached its maximum range, potentially causing a preventable miss. </p><p>Before mounting the missile onto the launch rail, the ground crew had to remove the missile, unfold the wings, check the air pressure, the condition of the tracers and pipelines, and then set the letter and the code marked on the missile into the guidance system, before finally loading the missile. The whole procedure took 12-15 minutes. The only other ATGM to use pneumatic actuators for steering is the TOW. However, the TOW series has a classical aeroplane layout, with wings at the midsection and all-moving fins at the tail, serving as both stabilizer fins as well as the control surfaces. Like the "Falanga", powerful actuators were needed to move the control fins, and to supply this power, it was built with a remarkably advanced helium reservoir bottle pressurized to 400 atm, while electricity was supplied by two thermal batteries. Not only is helium an expensive gas for such a purpose, but leak-free long-term storage of helium also requires a special vessel and seals, as its small atomic size makes it difficult to eliminate leakages. All this was, however, successfully implemented, allowing the TOW series to avoid the inconvenient servicing requirements that "Falanga" demanded. </p><p><br /></p><p>The actuator for each rudder is housed in the fuselage, allowing the wing itself to maintain a streamlined form. To connect each rudder to its turning mechanism, there is a shank in each wing root, so that when a wing is deployed during unpacking, the bottom end of the rudder hinge pin connects to the shank as the wing is locked onto the wing root. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-NwIg0d4hi0A/YN1E9zw-9eI/AAAAAAAATq4/xWcGwv9yAUMVCObeDxNjm-conzr6y8OvgCLcBGAsYHQ/s1797/pneumatic%2Bsteering%2Bdrive.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="985" data-original-width="1797" height="350" src="https://1.bp.blogspot.com/-NwIg0d4hi0A/YN1E9zw-9eI/AAAAAAAATq4/xWcGwv9yAUMVCObeDxNjm-conzr6y8OvgCLcBGAsYHQ/w640-h350/pneumatic%2Bsteering%2Bdrive.png" width="640" /></a></div><p>A bang-bang control scheme is used to regulate the intensity of the steering action. On top of this, there is a rheostat feedback system for the elevators, serving as the means to maintain a certain elevator deflection angle. In the article "<i>Фаланге продлевают жизнь</i>", the author V. G. Shaleev, an engineer-designer of the Kovrov Mechanical Plant, notes that when cruising in trimmed flight, without pitch commands on the control joystick from the operator, the neutral position of the pitch rudders (elevators) is a positive tilt of 5 degrees. That is, the elevators are designed to be tilted by +5 degrees while the pressure in the elevator actuator is in equilibrium. </p><p>The elevator actuator is a double-acting piston; a piston with two opposing chambers, allowing force to be applied in two opposing directions. To change the pitch angle of the missile, one chamber of the elevator piston is pressurized by the electronically controlled distributor valve. The valve receives a control signal from the signal amplifier of the 9B373 unit, which is a rectangular waveform with either a positive or negative sign. For instance, to pitch down, the elevator must deflect downwards, and this is done by pressurizing the bottom cylinder to move the piston upwards. The control signal, which was inverted by the decoder system before amplification, will have a negative sign, and a certain period. Upon receiving this signal, the electronic valve opens the valve to the bottom cylinder until the period of the control signal elapses (the waveform falls to 0 V), whereupon the valve is closed and the chamber is bled. The longer the period of the control signal, the higher the pressure that accumulates in the piston, and the larger the angle of deflection shall be. While the piston is bled, the elevator returns to its original, straightened position due to the correcting moment from the incoming air flow. </p><p>Moreover, the movement of the piston shifts a rheostat contact up or down. The rheostat is used in conjunction with a constant voltage generator to ensure that the top chamber of the piston is kept pressurized to a specific level to maintain an elevator deflection of +5 degrees. If no control signals are received but the elevator is offset from its trimming position by, let's say, 2 degrees (+7 degrees), the constant voltage passing through the rheostat is modified with a net difference of -2 V. Upon receiving this signal, the electronic valve bleeds the top chamber until the elevator angle is corrected back to the predetermined +5 degree trim angle, whereupon the voltage returns to 0 V and no further actions are taken.</p><p>The same bang-bang control scheme is used for the steering rudders, except two opposing single-acting pistons are used instead of a single dual-acting piston. </p><p>On the topic of pneumatic actuators, another parallel with the TOW series can be made - the low atomic weight of helium means that its power density is incredibly high - one liter of air compressed to 260 atm weighs 300 grams, whereas the same volume of helium compressed to this pressure weighs just 40 grams. While air would have an advantage in driving a rotary pneumatic actuator due to its high molecular weight and thus high mass flow rate, for the linear pneumatic actuators used in both the TOW and "Falanga", where pressure is the governing parameter, this is irrelevant. In a comparison between these two ATGMs, the TOW series has an overwhelming technological superiority. </p><p><br /></p><p>Aerodynamically, the rudders function as normal control surfaces, as on aircraft. When a rudder is tilted upwards, the flow of air is impeded over the elevator surface, generating increased pressure over the local region above the rudder, propagating on the wing upstream of the rudder, while the change in the aerofoil geometry increases flow velocity below the rudder and thus decreases the pressure. The pressure differential between the area above and below the rudder produces in a downward reaction force (marked γ in the drawing below) acting just ahead of the boundary between the rudder and the wing. Because this downward force is applied far behind the center of lift from the wings, it pitches the wing upward. In turn, this pitches the entire missile upward. The same principle applies to both steering axes of the missile.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-0t8e3NymfFA/YKgdK5N604I/AAAAAAAATD8/YipJ_6GwDyU5Rn1OW0bNukdTGtYXrH8FACLcBGAsYHQ/s561/rudders.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="389" data-original-width="561" height="278" src="https://1.bp.blogspot.com/-0t8e3NymfFA/YKgdK5N604I/AAAAAAAATD8/YipJ_6GwDyU5Rn1OW0bNukdTGtYXrH8FACLcBGAsYHQ/w400-h278/rudders.png" width="400" /></a></div><p>Due to the participation of the wing surface itself in the steering effect, trailing edge rudders produce a greater steering lift force for a given surface area compared to all-moving rudders, though only at subsonic speeds. At subsonic speeds, the advantage in lift coefficient provided by trailing edge rudders is enormous, but degrades rapidly in the transonic speed range until the relationship reverses entirely just below Mach 1. This is due to the airflow over the wing becoming supersonic along the leading edge while the wing itself is travelling at transonic speed, which inhibits the propagation of excess pressure upstream of the trailing edge rudder. The comparative effectiveness of both forms of aerodynamic control surface is shown in the graph below, where (2) denotes trailing edge rudders and (1) denotes an all-moving rudder of equal surface area. The unit of the y-axis is the partial derivative of the lift coefficient with respect to the deflection angle of the lifting surface. From this, it can be stated that at subsonic speeds, for a given deflection angle of a trailing edge rudder, the lift force generated is much higher than an equivalent all-moving rudder.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HuvgYKPm55g/YOooOpVqX7I/AAAAAAAAT1M/6Qs4-iH6jY4tGAHGucDZph4Fhfhg1dEZgCLcBGAsYHQ/s658/efficiency%2Bof%2Btrailing%2Bedge%2Brudders%2Bvs%2Ball-moving%2Brudder%2Bfins%2Bacross%2Bmach%2Brange.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="427" data-original-width="658" height="260" src="https://1.bp.blogspot.com/-HuvgYKPm55g/YOooOpVqX7I/AAAAAAAAT1M/6Qs4-iH6jY4tGAHGucDZph4Fhfhg1dEZgCLcBGAsYHQ/w400-h260/efficiency%2Bof%2Btrailing%2Bedge%2Brudders%2Bvs%2Ball-moving%2Brudder%2Bfins%2Bacross%2Bmach%2Brange.png" width="400" /></a></div><p>In concept, the use of aerodynamic rudders rather than a TVC system as found on the SS.11 has little merit. At the high speeds achieved by both systems, up to 230 m/s for the "Falanga" and up to 200 m/s for the SS.11, aerodynamic control surfaces are totally viable, as the high airspeed generates high lift that translates to strong steering moments, but at the same time, this is accompanied by increased resistance. With that, the effort required to move the control surfaces increases strongly, hence the need for powerful pneumatic actuators as on the "Falanga". There is also a strong dependence on airspeed to achieve the desired steering responsiveness and effectiveness, but as the airspeed varies, so too does the steering responsiveness.</p><p>In the final kilometer of flight at faraway targets (3-4 km), the flight speed of a 9M17 series missile is reduced due to deceleration from the lack of propulsion, leading to a gradual reduction in the effectiveness of the rudders. The ATGM reacts more slowly to the steering commands, in particular to pitch-up commands, so only slow and smooth steering inputs are possible. This is not a critical drawback if the principles of the 3-point guidance method are followed by the operator, as the missile should be in level flight above the target, clearing any ground obstructions by a few meters and not obscuring the operator's view of the target by the tracer flare or engine smoke. The terminal phase should therefore involve the operator to gently lowering the missile until the image of the tracer is superimposed on top of the image of the target. When engaging a moving target, the missile should be level with the target in the chase profile, and only yaw steering commands are needed, not pitch-up commands.</p><p>With TVC steering, the continuous thrust of the rocket engine would provide a predictable, quick steering response at all points along the flight trajectory, as long as the engine continues to burn with a constant thrust. This system is, of course, not compatible with the "Falanga", because the missile coasts during its final kilometer. In this specific context, the reduced steering responsiveness beyond 3 km is still an improvement over the SS.11, which would lose all steering functionality entirely once it reached its maximum range of 3 km as engine burnout renders the thrust vectoring system inoperable.</p><p>In terms of specific design detail, the maximum speed of the "Falanga" was indirectly limited by the use of rudders as control surfaces, as higher speeds will encroach upon the low transonic flight regime. At 230 m/s, the maximum speed of the 9M17 series is only Mach 0.67, well below the critical Mach 0.75-0.80 range for transonic flight. As the rudders are on the trailing edge, the magnitude and precision of the steering moment generated is negatively affected by transonic flight, not only due to the speed of the airflow discussed earlier, but also due to laminar flow separation occuring ahead of the trailing edge leading to turbulent flow over the rudders. This has a negative impact on the steering responsiveness of the missile, particularly if the missile has a large positive angle of attack. </p><p>Overall, the high efficiency of trailing edge rudders in subsonic flight made it the most optimal steering solution for the "Falanga" missiles, as they were heavy subsonic missiles that required considerable force to steer. The use of these rudders also allowed the steering mechanism to cope well with the deceleration of the missile, which is not the case with the TOW series. On the TOW, the all-moving steering fins would be highly efficient for only a brief period just after engine burnout, when the missile is travelling at almost 300 m/s, but the amount of lift producible declines sharply as the missile decelerates. In fact, the universal use of trailing edge rudders on subsonic aircraft, predominantly civilian aircraft, is directly influenced by the optimal characteristics of this steering solution for subsonic flight. However, needless to say, this does not mean that trailing edge rudders are the optimal form of steering control surface for all ATGMs, as the flight parameters differ considerably across the diverse range of ATGM models produced over history.</p><p><br /><a href="https://www.blogger.com/null" id="falangaengine"></a></p><h3 style="text-align: left;"><span style="font-size: large;">ENGINE</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-mXATuIOhDo0/YLUBKiszTeI/AAAAAAAATQg/QzzVVvL-uR44O6FWidl4tfe1xgGyZeTSQCLcBGAsYHQ/s587/8.PTUR-Falanga-M-v-moment-puska..jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="405" data-original-width="587" height="276" src="https://1.bp.blogspot.com/-mXATuIOhDo0/YLUBKiszTeI/AAAAAAAATQg/QzzVVvL-uR44O6FWidl4tfe1xgGyZeTSQCLcBGAsYHQ/w400-h276/8.PTUR-Falanga-M-v-moment-puska..jpg" width="400" /></a></div><p>The propulsion system of the 3M11 consisted of a dual-chamber, dual thrust engine with separate booster and sustainer chambers. The engine casing is made from steel. The exhaust jets exit through two oblique nozzles protruding between the wing roots at the top right and bottom left quadrants. The flight profile is largely conventional, relying on the booster to bring the missile to a high velocity, which is then maintained by the sustainer, but the 3M11 differs in that the sustainer does not burn for the entire duration of its flight. </p><p>The booster brings the 3M11 to an unknown speed, and the sustainer engine takes over until engine burnout occurs at 1.5 kilometers, whereupon a maximum of 230 m/s is reached, and the missile is left to glide for the remaining kilometer before eventually self-destructing. This means that 40% of the flight profile is unpropelled. Because the sustainer engine is placed at the center of gravity of the missile, the static margin changes minimally during the flight of the missile, and once the sustainer charge burns out, positive static stability is maintained for the rest of its flight. </p><p>A more extreme form of this mode of flight was later used by the TOW, where the booster brings the missile to a near-transonic speed of ~300 m/s within 1.5 seconds, wherein a distance of 300 meters is crossed, and the missile is left to glide for the remaining 2.7 km, or 90%, of its trajectory.</p><p>The time of flight to its maximum range of 2,500 meters is 16.6 seconds, giving the 3M11 an average flight speed of 150 m/s, which is considerably lower than its maximum speed due to the short working period of the engine. It is worth noting that a number of different sources list 150 m/s as the maximum speed rather than the average speed, including articles such as "<i>Первые ОКР по противотанковым и танковым управляемым ракетам</i>" published in the November 2018 edition of the "<i>Техника и вооружение</i>" magazine, but this is incorrect. Even in the article, a flight time of 16.6 seconds is cited along with a maximum speed of 150 m/s, but these two figures are mutually incompatible. </p><p>For comparison, the SS.11, the direct counterpart to the 3M11, accelerates to 110 m/s during its boost phase and continues accelerating to a final speed of 200 m/s at its maximum range, whereupon the sustainer engine burns out. Though its maximum speed is nominally lower, the average speed was 9 m/s quicker.</p><p>Without a wire of finite length, it is not clear what limits the range of the 3M11 to 2,500 meters. Nevertheless, the maximum range was rather underwhelming considering that the more conservative "Shmel" was already capable of engaging targets out to 2,200-2,300 meters, at least in theory, and the "Malyutka" infantry ATGM would soon enter service with a 3,000-meter range.</p><p>On the 9M17, a new 9D117 solid fuel dual-thrust engine was introduced. The engine was combined with the pressurized air reservoir into a single structure; a single steel vessel partitioned into two chambers. In the engine chamber, dual-thrust functionality was achieved by using retardant coating to modify the burn rate of the solid fuel block, instead of having two structurally separate engines. The savings in weight and space allowed the new engine to hold almost double the weight of fuel. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-k7ZbIUkgiTM/YMR2uaFW01I/AAAAAAAATbY/QLkJReXVseQfL592QqGg4d0aBC-OkxO0wCLcBGAsYHQ/s647/single%2Bchamber%2Bengine.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="259" data-original-width="647" height="160" src="https://1.bp.blogspot.com/-k7ZbIUkgiTM/YMR2uaFW01I/AAAAAAAATbY/QLkJReXVseQfL592QqGg4d0aBC-OkxO0wCLcBGAsYHQ/w400-h160/single%2Bchamber%2Bengine.png" width="400" /></a></div><p></p><p>At the start of the burn, the booster and sustaining charges are simultaneously ignited. The total combustion surface is constant during the boost phase, and once the booster charge has burned out, the combustion surface is decreased, reducing the burn rate and therefore the thrust produced, thereby switching the engine to its sustainer phase. The disadvantage of rockets with a dual-thrust engine containing a starting and sustaining charge in one combustion chamber, or both stages combined into one charge with a variable combustion surface, is that the entire engine chamber must be capable of withstanding the pressure developed by the boost stage. This is achieved with thicker walls, which increases the weight of the engine. In a dual-chamber engine, where the booster is contained in its own isolated chamber, only the booster chamber must have thickened walls, while the sustainer can have a thinner chamber.</p><p>That said, the mass and volume advantages of consolidating both stages into a single chamber yields a net reduction in engine mass, which allows a greater amount of fuel to be packed into the engine. The maximum speed of the 9M17 remained 230 m/s, the same as the 3M11, but due to the longer burn time of the engine, the maximum range of the 9M17 reached 4 km. These characteristics, surpassing the "Malyutka" series, finally made the "Falanga" series worthy of the classification of "heavy" ATGM and justified its continued service and development. For the 9M17M, the slightly updated 9D117M solidfuel engine was used. The changes made are unknown.</p><p>With the new 9D117 engine, burnout occurs at a distance of 3 km, leaving the final kilometer to be crossed by gliding, like 3M11. However, compared to 3M11, the final kilometer is proportionately shorter, being 25% of the total flight distance instead of 40%. Thanks to this, the average speed increased to 170 m/s, allowing the missile to reach its target at its maximum range of 4 km in 23.5 seconds. The average speed of 170 m/s achieved by the missile is shared by the late TOW model, the ITOW, and the TOW-2 series. Unlike the "Falanga" series, the TOW series saw the opposite development, where the range was extended by 750 meters over the basic TOW without increasing the engine burn time, instead relying entirely on increasing its angle of attack to exploit the improved lift-to-drag ratio to extend the glide distance, leading to a drop in average speed from the basic TOW (187 m/s).</p><p><br /><a href="https://www.blogger.com/null" id="falangawarhead"></a></p><h3 style="text-align: left;"><span style="font-size: large;">WARHEAD </span></h3><h3 style="text-align: left;"><span style="font-size: large;">3N18 (HEAT)</span></h3><p><br /></p><p>The original 3M11 was fitted with the 3N18 warhead. The warhead weighs 6 kg, but the explosive charge alone is 3.6 kg of an unspecified compound. The most likely option is A-IX-1, as it was the standard filler for all HEAT warheads developed in the USSR at the time. The diameter of the shaped charge can be assumed to be around 140mm. Unlike the 3N13 warhead of the "Shmel", a very modern design approach was taken for the "Falanga", whereby the warhead casing was integrated as an aerodynamic body. By utilizing the warhead casing itself as a component of the fuselage rather than housing it as a separate unit, the shaped charge diameter can be increased for a given maximum fuselage diameter. The 3M11 was the first to use this approach to warhead design, and it became a universal practice for future ATGM designs both domestically and abroad. For instance, the casing of all TOW warheads up to the TOW 2A is the integral skin of the missile fuselage, having a thickness of ~1mm. This also simplifies the task of determining its penetration power, because the diameter of the warhead and the diameter of the shaped charge can be considered interchangeable.</p><p>Moreover, "Falanga" distinguished itself in that unlike the warheads of 3M6 "Shmel" and 9M14 "Malyutka", the warhead is affixed to the fuselage and screwed in place at the factory, and is not meant to be dismounted for storage.</p><p>The 3V8 fuze is used. It is inertially armed after launch, once the "Falanga" has travelled a distance of 70-200 meters from the launcher. It is notable for being the first graze-sensitive crush fuze to be used on an ATGM, but it works on a different principle compared to more modern membrane-type crush fuzes. In 3V8, a piezoelectric element is used to convert mechanical stress to a voltage, but instead of a single element placed at the tip of the nose, the 3V8 fuzing system features a ring of piezoelectric elements wedged between the nose fairing and the crushing cylinder. The location of the piezoelectric element is highlighted in the cross sectional image below. The copper shaped charge liner is electrically isolated from the nose fairing by an insulated ring, preventing a short circuit in the fuzing system.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-TjL1XxfhXY8/YLbwuxBgTmI/AAAAAAAATSM/keuaEWutzfwesMiyEMYbfJqydMmHOetTQCLcBGAsYHQ/s970/3v8%2Bfuze%2Bpiezoelectric%2Belement.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="780" data-original-width="970" height="323" src="https://1.bp.blogspot.com/-TjL1XxfhXY8/YLbwuxBgTmI/AAAAAAAATSM/keuaEWutzfwesMiyEMYbfJqydMmHOetTQCLcBGAsYHQ/w400-h323/3v8%2Bfuze%2Bpiezoelectric%2Belement.png" width="400" /></a></div><p>When the missile impacts a target, the blunt steel nose fairing is deformed inwards and pushes against the crushing cyclinder. This closes the circuit formed between the nose, the crushing cylinder, the piezoelectric element, the shaped charge liner, and the base fuze. The crushing cylinder imparts a pressure on the piezoelectric elements, thus generating a voltage that travels down the copper shaped charge liner and reaches the detonator in the base fuze, thus detonating the shaped charge. Due to the blunt nose shape and the small clearance between the crushing cylinder and the inner diameter of the nose fairing, it can be seen that 3V8 will function if the missile grazes an obstacle on the edge of the nose, which would otherwise lead to a failure to fuze and the destruction of the warhead on a missile with a conventional nose fuze. This also means that the "Falanga" series of missiles is immune to defuzing or destruction by slat armour. In the article "<i>Фаланге продлевают жизнь</i>", it is stated that the warhead functions at an impact angle of 70 degrees, though this is unlikely to be the absolute fuzing angle limit given the fuze design.</p><p>3V8 was made insensitive to plywood panels up to 5mm thick, branches with a diameter of 8-10mm and steel meshes with a wire diameter of 1.5-2mm and gaps of less than 10x10mm. This gave a modicum of insurance against premature detonations if the missile is used in lightly vegetated areas. It has a self-destruct mechanism. </p><p>According to the book "<i>Первые Отечественные Противотанковые Ракетные Комплексы</i>" (<i>First Domestic Anti-Tank Rocket Complexes</i>), the nose section of the missile was given its shape to permit stowage inside the BRDM for the 2P32 tank destroyer. This partly explains the short built-in standoff distance afforded by the nose section.</p><p>Beginning with the 9M17, the newer 3V8M fuze was used. Visually, it can be distinguished by the change to a slightly more rounded nose shape without an annular protrusion ahead of the canards, and internally, the main difference was a prolonged timer for the self-destruct mechanism to account for the increased range of the missile. The piezoelectric ring is located in an annular protrusion on the 3M11 nose, just ahead of the canards. When the nose shape was modified on the 9M17, the nose became rounder and more streamlined, but a protruding ring remained on the same location.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-k0Xmh6jzQgY/YLa3M4xOADI/AAAAAAAATRo/83FmfcGFEKQ9RWBNRsIoZSanUw4Vs9-KQCLcBGAsYHQ/s1433/3m11%2Bside.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="764" data-original-width="1433" height="214" src="https://1.bp.blogspot.com/-k0Xmh6jzQgY/YLa3M4xOADI/AAAAAAAATRo/83FmfcGFEKQ9RWBNRsIoZSanUw4Vs9-KQCLcBGAsYHQ/w400-h214/3m11%2Bside.png" width="400" /></a><a href="https://1.bp.blogspot.com/-FuKZALFxPog/YLb_YwTyw7I/AAAAAAAATSU/PIidg4qyI08RVZ_l8fQNuljQEEw4zXH7QCLcBGAsYHQ/s518/9m17m%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="225" data-original-width="518" height="174" src="https://1.bp.blogspot.com/-FuKZALFxPog/YLb_YwTyw7I/AAAAAAAATSU/PIidg4qyI08RVZ_l8fQNuljQEEw4zXH7QCLcBGAsYHQ/w400-h174/9m17m%2Bdrawing.png" width="400" /></a><br /></div><p>The rated penetration power of the 3M11 was 250mm RHA at 60 degrees, sometimes expressed simply as 500mm. Penetration on a flat target was not listed in the tactical-technical characteristics of the missile, but it is safe to assume that it would be somewhat less than its penetration at 60 degrees. All mentions of the penetration at 0 degrees in various sources and in websites are simply expressions of the line-of-sight penetration depth rather than the true penetration at a flat impact angle. The built-in standoff distance is tiny - just around half the diameter of the shaped charge cone, or 0.5 calibers, but even this modest amount is at least sufficient for a penetration depth of 4 CD, as shown by the 1965 findings of DiPersio et al. from the BRL presented in the graph below. The reference charge used to produce the results in the graph was an aluminium-cased shaped charge with a conical copper liner and Octol filler, without a wave shaper. Based on this reference, a penetration of 500mm RHA on a flat impact is totally feasible for the 3N18 warhead.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-lCJNH8rtCB0/YKmGDCJ_KCI/AAAAAAAATEo/esle0usIqXkSxBRni1hvmAVUmfReyQh3gCLcBGAsYHQ/s2048/shaped%2Bcharge%2Bgraph.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1549" data-original-width="2048" height="303" src="https://1.bp.blogspot.com/-lCJNH8rtCB0/YKmGDCJ_KCI/AAAAAAAATEo/esle0usIqXkSxBRni1hvmAVUmfReyQh3gCLcBGAsYHQ/w400-h303/shaped%2Bcharge%2Bgraph.png" width="400" /></a></div><p>Against a sloped target plate, the nose impacts on its edge rather than head-on, effectively creating additional standoff distance for the shaped charge warhead. The larger the obliquity of the target plate, the larger the additional standoff, to the extent that total standoff may reach or even exceed the amount provided by a typical fixed conical fairing with a point impact fuze. This is shown in the drawing below, taken from the engineering textbook "<i>Основы Устройства И Функционирования Противотанковых Управляемых Ракет</i>".</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-wWtuHOwB7JM/YFnSfAbwsrI/AAAAAAAAS3U/InfMrwbbSX0VZ9tOgT9Ms6XnwdRTqPlxgCLcBGAsYHQ/s1820/blunt%2Bwarhead.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="708" data-original-width="1820" height="155" src="https://1.bp.blogspot.com/-wWtuHOwB7JM/YFnSfAbwsrI/AAAAAAAAS3U/InfMrwbbSX0VZ9tOgT9Ms6XnwdRTqPlxgCLcBGAsYHQ/w400-h155/blunt%2Bwarhead.png" width="400" /></a></div><p>It was reported in the article "<i>ПТУР Первого поколения</i>" (First generation ATGMs), published in the September 2000 edition of the "<i>Техника и вооружение</i>" magazine, that at the beginning of its serial production, against steel armour placed at 60 degrees, the 3M11 missile penetrated 220mm of armour with a 90% probability or 250mm of armour with a 65% probability. This is further expanded upon in the article "<i>Первые ОКР по противотанковым и танковым управляемым ракетам</i>" in the November 2018 edition of the same magazine, with author Sergey Suvorov reporting that the penetration of 250mm was achieved only at a 60% rate as of 1961 instead of the required 90%. During the course of of mass production, the 3N18 warhead was upgraded to increase the consistency of its performance, but significant improvements were not achieved.</p><p>Based on testing results of the Kontakt-1 reactive armour, detailed in the article "<i><a href="http://armor.kiev.ua/Tank/dz/1968/">Динамическая защита. Израильский щит ковался в... СССР?</a></i>", the 3N18 warhead set up on a static rig was determined to have a non-perforation limit of 290mm RHA at 70 degrees reached 848mmmm, or 6 calibers. At this target obliquity, the standoff distance is around 1.9-2.0 CD, and the penetration depth achievable should be slightly less than 848mm, based on the BRL penetration-standoff graph. This lends credence to the reported results. </p><p>Adding on to that, it is stated in "<i>Armements Antichars Missiles Guidés Et Non Guidés</i>" that the second generation of French ATGMs, namely the MILAN and HOT, achieved a penetration of 5 calibers, having a 73/27 hexolite charge (73% RDX, 27% TNT) and a built-in standoff of ~2 calibers. Given that the 3N18 warhead has a more powerful phlegmatized RDX charge instead of hexolite, the reported non-perforation limit of 6 CD at a standoff of 1.9-2.0 CD can be considered highly credible.</p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">9N114 (HEAT)</span></h3><p>Following the 3M11, a new 9N114 warhead was fitted to all subsequent "Falanga" models. According to the tactical-technical characteristics, the rated penetration power of the 9N114 warhead used in the 9M17, 9M17M and 9M17P was 280mm RHA at 60 degrees, or 560mm in line-of-sight thickness. It is stated in the article "<i>ПТУР Первого поколения</i>" that this was achieved at a 90% rate. 9N114 contains a TG-20 explosive filler. TG-20 is a compound consisting of 20% TNT and 80% RDX. This mixture has a much higher RDX content than Composition B, and most closely resembles the 73/27 hexolite formula used by the French military.</p><p>According to a 1979 Soviet report titled "<i><a href="http://btvt.info/5library/vbtt_1979_03_probivaemost.htm">Выбор Кумулятивных Снарядов Для Испытания Брони</a></i>" (<i>Selection of Cumulative Shells for the Evaluation of Armour</i>), the average penetration of the 9N114 warhead in armour plate is 560mm (4 CD) with a maximum of 655mm (4.68 CD) and a minimum of 425mm (3.04 CD). These figures were tabulated based on the performance of the warhead at both 0 and 60 degrees. The very wide variance between the minimum and maximum penetration can be attributed to the nuances of the blunt nose and small built-in standoff, in particular the low minimum penetration. At a flat impact where the standoff is smallest, the real average ought to be between the nominal average and the minimum, around 490-500mm. At 60 degrees, the real average ought to be between the nominal average and the maximum, around 600-610mm. </p><p>However, it is still unclear if the penetration figures given in the official tactical-technical characteristics table were based on live fire tests, which would induce some penetration loss on sloped armour due to the positive angle of attack, or if they were merely based on static tests.</p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">9N114M2 (EFP-FAE)</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-0z1lq-0KiB4/YJnphGzwRdI/AAAAAAAAS80/j6kgRk2XRr8bSjBjtcmLQVuvcSQol_hTwCLcBGAsYHQ/s507/9m17m2%2Bcolour%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="158" data-original-width="507" src="https://1.bp.blogspot.com/-0z1lq-0KiB4/YJnphGzwRdI/AAAAAAAAS80/j6kgRk2XRr8bSjBjtcmLQVuvcSQol_hTwCLcBGAsYHQ/s16000/9m17m2%2Bcolour%2Bdrawing.png" /></a></div><p>The 9N114M2 warhead, used on 9M17P2 is a combined EFP and FAE (thermobaric) warhead, intended for the destruction of light armour, field fortifications and buildings. The fuze and casing of the warhead was taken directly from the 9N114. This modification increased the total missile weight by 0.5 kg, but otherwise, all parameters remained the same as in a basic 9M17P missile. 9N114M2 was finished development and passed preliminary tests in 2000 at the Federal State Unitary Enterprise, known as GosNIIMash.</p><p>Besides the FAE effect of the warhead, it also featured a concave copper liner that would form a forward-firing EFP. It penetrates 100-120mm RHA at a flat angle, or 50mm RHA at an angle of 60 degrees. It also penetrates 500-600mm of concrete. The blasting power is equivalent to 7.5 kg of TNT. Alone, the blast effect is more than enough to destroy lightly armoured vehicles such as armoured cars or APCs. The EFP is presumably meant to enhance the demolition effect of the explosive charge when attacking bunkers, or to enable penetration to be achieved on the side armour of MBTs with the subsequent ingress of the powerful blast wave and explosion products. A similar concept was applied in the TBG-7 thermobaric-EFP grenade for the RPG-7, though a completely different warhead form was used.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DOWv04xC4RE/YFswrnxhAQI/AAAAAAAAS3s/uNlsvyRhh-Mzokr3Z-Cc5CTT_zJsy4O8wCLcBGAsYHQ/s782/9m17m2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="556" data-original-width="782" height="285" src="https://1.bp.blogspot.com/-DOWv04xC4RE/YFswrnxhAQI/AAAAAAAAS3s/uNlsvyRhh-Mzokr3Z-Cc5CTT_zJsy4O8wCLcBGAsYHQ/w400-h285/9m17m2.png" width="400" /></a><a href="https://1.bp.blogspot.com/-P6N8O4UxUFA/YJnpn-337KI/AAAAAAAAS84/DQndLXpimxU3Q3ES509W5oEQRP8eYSVFwCLcBGAsYHQ/s602/pic_25.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="344" data-original-width="602" height="229" src="https://1.bp.blogspot.com/-P6N8O4UxUFA/YJnpn-337KI/AAAAAAAAS84/DQndLXpimxU3Q3ES509W5oEQRP8eYSVFwCLcBGAsYHQ/w400-h229/pic_25.jpg" width="400" /></a><br /></div><p><br /></p><p><br /><a href="https://www.blogger.com/null" id="malyutka"></a></p><h3><span style="font-size: large;">"Malyutka" ("Baby")</span></h3><h3 style="text-align: left;"><span style="font-size: large;">9M14, 9M14M, 9M14P(1)</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Ldzt9pnqvDM/YPiI_agr3TI/AAAAAAAAUB8/jwOt4l5MkY4KVBJmoVOgHnDxOqGagK0lgCLcBGAsYHQ/s661/malyutka.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="661" data-original-width="500" height="400" src="https://1.bp.blogspot.com/-Ldzt9pnqvDM/YPiI_agr3TI/AAAAAAAAUB8/jwOt4l5MkY4KVBJmoVOgHnDxOqGagK0lgCLcBGAsYHQ/w303-h400/malyutka.jpg" width="303" /></a></div><p>Officially, work on the "Malyutka" project began on July 6, 1961, with a target weight of 8-10 kg, a minimum range of 300-500 meters and a maximum of 3,000 meters, and an armour penetration power of 180-200mm at 60 degrees. Man-portable and self-propelled versions were to be made. The task was assigned to Kolomna SKB design bureau (later known as KBM), the bureau responsible for the "Shmel". The design team was headed by S. P. Nepobedimiy, the same engineer responsible for the "Shmel" project. Along with the missile itself, both a man-portable and a self-propelled system were to be created according to the decree. The "Malyutka" family, consisting of the missile itself, the 9K11 man-portable system and the 9K14 self-propelled system, was accepted in service on the 16th of September, 1963. </p><p>The development cycle of the "Malyutka" from its official project start to its acceptance into service - less than 2 years - is probably the shortest of any guided missile system in history, at least among peacetime projects, a remarkable achievement that was also noted in the article "<i>Тяжелый путь к легкой ракете</i>" published in the March 2019 issue of the "<i>Техника и вооружение</i>" magazine. This was strongly influenced by the fact that the designer was already working on the concept since 1959, and work was later accelerated by the heat of competition.</p><p>The Kolomna SKB design bureau, led by B. I. Shavyrin, had been working on the SKB-129 missile since July 4, 1959, under the mandate of government resolution No. 734-347 on the task of creating an infantry ATGM system to replace "Shmel", which was clearly no longer able to fill the role once it entered its final development stage. At the time, the goal was to create an ATGM weighing 6-8 kg with an armor penetration of 150mm at an angle of 60 degrees, a minimum range of 300 meters and a maximum of 2,000-2,500 m. It is interesting to note that these parameters closely resembled that of the Franco-German MILAN, formerly the SS.9, which would begin development abroad in the next few years, though the SKB-129 had potential for even better performance with further refinement. On the 30th of May, 1960, the Council of Ministers issued a decree for the Kolomna SKB to begin work on the "Skorpion" project, in light of the failure of the "Shmel" project by the same bureau to deliver a man-portable system. </p><p>Work on the "Skorpion" began, but as the refined SKB-129 showed great promise, on January 30, 1961, during a meeting with the GKOT, Shavyrin unilaterally recommended to cease work on the "Skorpion" project, instead proposing to further the development of the SKB-129. This led to the official cancellation of "Skorpion" , and the government issued a decree on July 6, 1961 titled "<i>On carrying out work on the ATGM "Malyutka" and "Ovod"</i>". The "Ovod" project was assigned to the Tula TsKB-14 design bureau, which later became KBP Tula. Why a rival project was launched is unknown. Perhaps it was to ensure that a backup would be available in case "Malyutka" failed, or to create a sense of urgency to speed up development, mirroring the events in the development of the PK machine gun. Regardless of the reason, the effect of introducing a competitor was entirely positive - work on the "Malyutka" progressed at a breakneck pace; testing of 60 missiles took place in November 1961, and then the self-propelled system was tested in August 1962. Full system maturity was achieved by 1963, and it was accepted into service with mass production commencing the same year. The 9K11 man-portable system was deployed as a battalion level asset, in the anti-tank platoon of motorized rifle battalions mounted on BTRs. There were four 9K11 anti-tank teams in the anti-tank platoon, accompanied by an SPG squad armed with three SPG-9 recoilless guns.</p><p>Production began in 1963, ending only in 1984, at least in the USSR. Licenced and unlicenced production continued abroad for some time, most notably in China and Serbia. The introduction of the 9M14 "Malyutka" and the various launch systems created on its basis can be singularly credited with the overall increase in ATGM proliferation in the Warsaw Pact, from manpack systems to wheeled tank destroyers to helicopters. The subsequent export and licenced production of the "Malyutka" among the Warsaw Pact nations also brought them an overall ATGM density advantage over NATO forces.</p><p>At the time of its introduction to the Soviet Army, the "Malyutka" was not only the most capable ATGM available domestically, it was also the most sophisticated design in the world. Indeed, it would not be outlandish to suggest that it is the best ATGM design of all time, when viewed in a historical context. Compared to the "Shmel" and the "Falanga", the "Malyutka" had superior range, a slightly shorter minimum range, more than adequate penetration power, was vastly more compact, fully man-portable (without stretching the definition of the term), and was more responsive in its flight control, but despite all of this, it was also lighter, cheaper and simpler in construction. By all measurable metrics, the "Malyutka" was outstanding.</p><p>Qualitatively, one of the closest contenders would have been the Vickers Vigilant ATGM system, the only reason being that it had a more developed MCLOS guidance system that zeroed out operator inputs, simplifying the guidance process. However, even the Vigilant was inferior by a wide margin in all other respects, being heavier, having less than half the range (1,371 meters), a slightly slower average flight speed (110 m/s), a more prominent flight attitude of +5 degrees, and no use of long-distance infantry transportation in service. In fact, it was predominantly used as an add-on missile system on the turrets of Ferret scout cars in the ground forces, and on a small scale, it was deployed by the airborne forces on Land Rovers in the same role as the 2P26 "Shmel". In that form, the system was really a mechanized tank destroyer, with an optional dismounted launch capability in the same way as any other missile carrier. In fact, reflecting its role, the Vigilant was replaced by the Swingfire, which was also not used as a man-portable system; the first man-portable system in the British Army was the MILAN, acquired in 1977. In this sense, the "Malyutka" was truly unique among its contemporary international counterparts in that it actually fulfilled the demands of infantry portability, where no other ATGM system in the world could.</p><p>Like "Shmel", the export and licenced production of "Malyutka" in foreign countries was cleared fairly rapidly and deliveries to Egypt and Syria took place in the buildup to the 1973 war, but acquisition was delayed among Warsaw Pact nations for many years, and the "Shmel" remained the main Warsaw Pact ATGM for the entirety of the 1960's. Once export to these nations began in the early 1970's, the "Malyutka" became a singularly dominant ATGM system, not only amongst the Warsaw Pact nations, but internationally. In Poland, the first appearance of "Malyutka" systems in mass quantity was in 1974, in the form of the 9P133 "Malyutka-P" tank destroyer. Other clients received less sophisticated models. The Hungarian Army only acquired the original 9M14 missile in 1975, a full 12 years after it was first introduced. The Chinese managed to obtain an unknown quantity of 9M14 missiles in the early 1970's and reverse-engineered the design in 1973 to create a close copy known as the HJ-73. However, the mass deployment of this missile in the PLA only began in 1979 due to the technological limitations of the Chinese weapons industry at the time.</p><p>In terms of the density of launch platforms, the primary deployment method of the 9M14 in the Soviet Army was the 9K11 infantry ATGM system. The 9K11 system consists of a launcher pack and two missile packs, carried by a three-man team consisting of one missile operator and two missile bearers. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEiS_GJ93Q2ZLVkEad9dStgb1t3BYDvXjsTymNoBJLcvoQsdHncoSOHuDLfJDUYsunKtA5o5OPdEygz8WBOSCOPyxQ0DFv-lYkmoNn6OSasm3EFH9O75RRkh2hcGRo0G_3dIhgkp21rX4VBsMYlSkprw7yfQajjOEdEQ0RfgBReo65RAskA0eyJgUkqshA=s1781" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1313" data-original-width="1781" height="472" src="https://blogger.googleusercontent.com/img/a/AVvXsEiS_GJ93Q2ZLVkEad9dStgb1t3BYDvXjsTymNoBJLcvoQsdHncoSOHuDLfJDUYsunKtA5o5OPdEygz8WBOSCOPyxQ0DFv-lYkmoNn6OSasm3EFH9O75RRkh2hcGRo0G_3dIhgkp21rX4VBsMYlSkprw7yfQajjOEdEQ0RfgBReo65RAskA0eyJgUkqshA=w640-h472" width="640" /></a></div><p>However, the majority of the firepower in Soviet Army units was carried in the self-propelled tank destroyers made for the "Malyutka", complete with salvo-firing capability and a dismounted remote firing capability. The 9P110 "Malyutka" with the 9K14 ATGM system was the first self-propelled system to use the missile, created to replace the earlier 2P27 "Shmel" tank destroyer. By using the same 9M14 missiles as the battalion level anti-tank assets, the anti-tank units at every level of a Soviet motor rifle or tank division were thereby standardized on a single, universal ATGM system. This feature was preserved when the BMP-1 entered service a few years later. As for the 9P110, its large capacity of 14 missiles was one of the requirements set in the tactical-technical characteristics mandated for the self-propelled version of the "Malyutka" system, which was made possible by the modest dimensions of the missile, especially compared to earlier domestic models.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-CwXjVHyDM8E/YNor3_pZIYI/AAAAAAAATnA/tk_Jp_DwfmoCEuiFWr4M-Gvbqie92UhJACLcBGAsYHQ/s700/652.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="479" data-original-width="700" height="274" src="https://1.bp.blogspot.com/-CwXjVHyDM8E/YNor3_pZIYI/AAAAAAAATnA/tk_Jp_DwfmoCEuiFWr4M-Gvbqie92UhJACLcBGAsYHQ/w400-h274/652.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-Y89jnaknkA8/YOvhUpKuzyI/AAAAAAAAT34/KlI8L97u3BU7CczoL3olY1e0CoY--E3RwCLcBGAsYHQ/s1241/9p110%2Bremote%2Bfiring.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="1241" src="https://1.bp.blogspot.com/-Y89jnaknkA8/YOvhUpKuzyI/AAAAAAAAT34/KlI8L97u3BU7CczoL3olY1e0CoY--E3RwCLcBGAsYHQ/s320/9p110%2Bremote%2Bfiring.jpg" width="320" /></a><br /></div><p>Following the success of the original "Malyutka" missile in 1963, developmental work on its modernization began immediately, leading to the creation of the 9M14M "Malyutka-M" missile and its adoption by the Soviet Army in 1966. The modernized missile featured a more effective 9N110M warhead. In connection with this, the 9P122 "Malyutka-M" tank destroyer based on the BRDM-2 entered service in 1968. It featured the slightly modified 9K14M "Malyutka-M" ATGM system, but had no intrinsic firepower advantage over the 9P110, though it supplanted it as part of the Army-wide switch to the new BRDM-2 armoured car. The "Malyutka-M" displaced the basic system in the Soviet Army and formed the basis for the fleets of tank destroyers operated abroad, with large export orders from the Warsaw Pact and other nations, most notably Egypt and Syria, which purchased enormous volumes of both launchers and missiles in the process of rearming in preparation for the 1973 Arab-Israeli war. </p><p>In 1969, the 9M14P "Malyutka-P" ATGM entered service. It was a modernization of the 9M14M missile that was adapted for the SACLOS guidance principle as part of the new 9K14P ATGM system installed in the 9P133 tank destroyer. There were no radical design changes; only a new set of tracers was fitted. The development of the "Malyutka-P" was initiated in parallel with the development of the future generation of containerized ATGM systems as an interim solution. By ensuring maximum commonality with the 9M14M, the production rate of the 9M14P could be maximized with low costs, while the missile itself could benefit from the reliability and simplicity of the existing base design. Export deliveries of the 9P133 to Poland took place in 1974.</p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-14A-nDKpFMg/YPiIx8BV7SI/AAAAAAAAUB4/yBFCOBCLRK4vP1cu_IUFeuUQPSExpiKPACLcBGAsYHQ/s1078/9p133.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="749" data-original-width="1078" height="278" src="https://1.bp.blogspot.com/-14A-nDKpFMg/YPiIx8BV7SI/AAAAAAAAUB4/yBFCOBCLRK4vP1cu_IUFeuUQPSExpiKPACLcBGAsYHQ/w400-h278/9p133.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-lzSzdA7PPXE/YOvgCTRTY4I/AAAAAAAAT3w/6DZu5PgQoYwGZvDzh3ot5SKrzdxsED7VACLcBGAsYHQ/s1252/nva%2B9p133.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="887" data-original-width="1252" height="284" src="https://1.bp.blogspot.com/-lzSzdA7PPXE/YOvgCTRTY4I/AAAAAAAAT3w/6DZu5PgQoYwGZvDzh3ot5SKrzdxsED7VACLcBGAsYHQ/w400-h284/nva%2B9p133.jpg" width="400" /></a></div></div><br /></div><p>The "Malyutka-P" was not the first SACLOS missile to enter service in the world, being preceded domestically by the 3M7 "Drakon" of the IT-1 missile tank (November 6, 1968), and also preceded by the American Shillelagh gun-launched missile and the French SS.11 TCA "Harpon" system (TCA - automatic remote control), which appeared in around 1967 and saw limited service on upgraded AMX-13 light tanks. As with the SS.11 TCA "Harpon", the SACLOS guidance equipment of the 9M14P was too bulky to be man-portable, so it was only possible to use it in the SACLOS mode on the 9P133. If used in the 9K11 infantry system, it would have to be guided in its backup manual mode. Similarly, the BMP-1 lacked the room for a control unit and as such, it never received one.</p><p>Like the "Harpon", the creation of the "Malyutka-P" system was predominantly influenced by the desire to put an interim SACLOS missile system into service while work on the second generation replacement progressed. In the case of the "Harpon" specifically, it was an interim to the second generation HOT project which had been underway since 1964 as a replacement for the SS.11. As interim solutions tended to be, the 9P133 "Malyutka-P" was highly successful, having a combination of excellent penetration power, high ammunition capacity, long range, salvo-firing capability, and many more positive qualities. The "Malyutka-P" simply had the distinction of being the most widespread first generation SACLOS missile, being made in large quantities not only for the Soviet Army, but for Warsaw Pact clients. In fact, the "Malyutka-P" was exported in such huge quantities, that it became the backbone of the anti-tank missile units of the Polish Army. It was entirely thanks to the "Malyutka-P" that production of the missiles continued until 1984, as demand was still strong among the clients in the Warsaw Pact and from further abroad. </p><p>In the 1990's, a proposal for the modernization of existing "Malyutka" missiles to the "Malyutka-2" was launched by KBM, with the warhead to be exchanged for a new type to enhance its range, and the solid fuel engine refurbished with a new fuel for greater thrust to make up for the heavier warhead. This modernization option was aimed at export customers exclusively.</p><p><br /><a href="https://www.blogger.com/null" id="malyutkadesign"></a></p><h3 style="text-align: left;"><span style="font-size: large;">GENERAL DESIGN FEATURES</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-WdFC3Oopu5A/YNosN9aqfUI/AAAAAAAATnI/7ahS_6z1YFog5JMcTxncy2B9QApz--koQCLcBGAsYHQ/s2774/9m14m%2Bcutaway.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1134" data-original-width="2774" height="262" src="https://1.bp.blogspot.com/-WdFC3Oopu5A/YNosN9aqfUI/AAAAAAAATnI/7ahS_6z1YFog5JMcTxncy2B9QApz--koQCLcBGAsYHQ/w640-h262/9m14m%2Bcutaway.png" width="640" /></a></div><p>The layout of the "Malyutka" series is conventional, with the warhead situated in the nose, the engine in the center, and the entire guidance system housed in the tail. The guidance system consists of a wire spool, gyroscope and commutator assembly, and the gas-driven actuators of the thrust-vectoring nozzles. The gyroscope and control unit are housed inside a compartment placed behind the sustainer engine, and the wire is wound around the sustainer engine. Aside from the general layout, which is shared between a large number of missiles created both before and after the "Malyutka" itself, the missile has nothing in common with any of the ATGMs developed and manufactured outside the USSR. In terms of capability, the model that comes closest to the 9M14 is the Mamba, which is almost a decade younger, having entered service in 1972.</p><p>To reduce the weight of the missile, fiberglass was used liberally in its design. It was used to form the casing of the warhead, the stabilizer fins, the fuselage, and many other smaller components. One of the requirements was for the missile to have a weight of 8-10 kg to ensure that it could be easily carried on foot by infantry teams from the anti-tank platoon organic to a motor rifle battalion, who would ride to battle on APCs but dismount to deploy their missiles. Although the final product went slightly over the limit with a weight of 10.9 kg, it was still light enough for the specified role. With the 9M14P model, the weight increased slightly to 11.4 kg.</p><p>The emphasis on weight and cost-saving for non-essential components helped reduce the unit price of each "Malyutka", without sacrificing performance. This approach was far from unique at the time, as several other foreign missiles competing against the SS.10 on the international arms market had also targeted low prices as a selling point. The German Cobra ATGM took this to the extreme, using cheap and relatively weak ABS plastic for several components, and even using coated cardboard for its wings and part of its fuselage. Despite the sheer simplicity of the Cobra missile, it was merely 0.6 kg lighter than the Malyutka. However, although the missile is fairly lightweight on its own, it is important to recognize that the complete kit carried by the anti-tank team had to include much more than the missiles alone. </p><p>The missile is stored in a fiberglass suitcase, also containing the launch rail, connectors, and a 15-meter control wire spool, used to link the launcher to the operator's control panel. The fuselage is pre-mounted to the launch rail to save time during the fire preparation process. The complete set forms the 9P111 suitcase-launcher unit. It serves as a shock-resistant protective casing for both the missile and the extension cable, used to connect the launch system to the operator's control panel. The 9M14P can only fit into 9P111P suitcases, which have a modified internal contour to accommodate the specific shape of the 9M14P, but it remains suitable for storing older 9M14 and 9M14M missiles. Up to four 9P111(P) suitcase-launchers can be connected to a 9S415 control panel, although only two missiles are carried in a standard 3-man team. The entire 9P111 unit weighs 18.1 kg. The image on the right below, from the February 2021 issue of the "<i>Nowa Technika Wojskowa</i>" magazine, shows an opened 9P111 suitcase-launcher, represented in the drawing from the 9K11 manual shown on the left.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/---mMVFSRRVA/YNlT-DNY5HI/AAAAAAAATj8/PiQ6qHdCV1Mwzjvg1HlKOnRTAmI3s9RfwCLcBGAsYHQ/s1700/9p111%2Binside.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1224" data-original-width="1700" height="288" src="https://1.bp.blogspot.com/---mMVFSRRVA/YNlT-DNY5HI/AAAAAAAATj8/PiQ6qHdCV1Mwzjvg1HlKOnRTAmI3s9RfwCLcBGAsYHQ/w400-h288/9p111%2Binside.png" width="400" /></a><a href="https://1.bp.blogspot.com/-aawlRNtmEsM/YNwOoY-5hzI/AAAAAAAATqA/goc6ihqfld00VxPnDt5-Qe7WQT-tqDEXQCLcBGAsYHQ/s1691/9p111%2Bnowa.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1326" data-original-width="1691" src="https://1.bp.blogspot.com/-aawlRNtmEsM/YNwOoY-5hzI/AAAAAAAATqA/goc6ihqfld00VxPnDt5-Qe7WQT-tqDEXQCLcBGAsYHQ/s320/9p111%2Bnowa.png" width="320" /></a></div><p>When comparing the Cobra - or rather, the Mamba - to the "Malyutka" in their fullness, container and all, a very marginal difference is also found. The full Mamba container weighs 17.8 kg, only a measly 0.3 kg lighter than a 9P111, but rather than being a convenient compact backpack, the Mamba container is an enormous fiberglass crate with a carrying handle on top.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HqjFWRFtfq4/YNwj7VlWcCI/AAAAAAAATqQ/gNxMNri5ffkq7XJv8afrPjiry6x3CkgaACLcBGAsYHQ/s2596/9p111%2Bvs%2Bmamba.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1212" data-original-width="2596" height="298" src="https://1.bp.blogspot.com/-HqjFWRFtfq4/YNwj7VlWcCI/AAAAAAAATqQ/gNxMNri5ffkq7XJv8afrPjiry6x3CkgaACLcBGAsYHQ/w640-h298/9p111%2Bvs%2Bmamba.png" width="640" /></a></div><p>Other man-portable ATGMs were normally kept in a box-launcher, with no real provisions for infantry transportation. One exception was the ENTAC, which could be carried on a packboard with shoulder straps, by using rope to tie down the box-launcher to the packboard. Without the packboard, the ENTAC launch set is not actually very heavy - only 18.6 kg. With the packboard, it is somewhat heavier, but this would have been far more convenient for transportation over long distances than holding it by the carrying handle, though at the same time, the sheer size of such a contraption is almost comical, especially compared to the 9P111 suitcase-launcher. Moreover, the box-launcher leaves much of the missile exposed, not affording it physical or environmental protection it like the watertight 9P111.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-KVhk58yBxx4/YOVhs3-ETJI/AAAAAAAATv4/NbNQBX2i6fIkRS8F-ghtfr1LR2PIz8p4QCLcBGAsYHQ/s760/entac%2Bmissile%2Bon%2Bpackboard.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="760" data-original-width="394" height="400" src="https://1.bp.blogspot.com/-KVhk58yBxx4/YOVhs3-ETJI/AAAAAAAATv4/NbNQBX2i6fIkRS8F-ghtfr1LR2PIz8p4QCLcBGAsYHQ/w208-h400/entac%2Bmissile%2Bon%2Bpackboard.png" width="208" /></a><a href="https://1.bp.blogspot.com/-H2gV2oWkqYA/YNlIiZb4F2I/AAAAAAAATjc/Gf2aqdCcTjYRIIq8lVoWKaWx0sKsswA7QCLcBGAsYHQ/s1308/9p111%2Bpack.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1308" data-original-width="580" height="400" src="https://1.bp.blogspot.com/-H2gV2oWkqYA/YNlIiZb4F2I/AAAAAAAATjc/Gf2aqdCcTjYRIIq8lVoWKaWx0sKsswA7QCLcBGAsYHQ/w178-h400/9p111%2Bpack.png" width="178" /></a></div><p>During the fire preparation process for the 9K11 system, the missile bearer must place the suitcase lid on the ground, then dock the warhead to the missile fuselage, place the launch rail (with the missile on it) onto the suitcase lid, deploy the wings, then bring the cable spool back to the operator's position and connect the launcher to the control panel. The overturned lid of the 9P111 suitcase-launcher is used, because when pressed deeply into sand or soil until the upper surface is flush with the ground, it becomes a stable firing platform. This was more convenient than staking the corners of a launch platform into the ground with a hammer, which was the only method possible with box-launchers. When operating on frozen ground or other types of terrain where it is impossible to press the suitcase lid into the ground, it is instead braced against the ground with a set of guy ropes and stakes. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-N7uTVwldusw/YOVqy-f-_0I/AAAAAAAATwA/GtHQG9DYVGIZ0CgEGLlzloY9pMm1yHRuQCLcBGAsYHQ/s700/9k11%2Bdeployed.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="460" data-original-width="700" height="263" src="https://1.bp.blogspot.com/-N7uTVwldusw/YOVqy-f-_0I/AAAAAAAATwA/GtHQG9DYVGIZ0CgEGLlzloY9pMm1yHRuQCLcBGAsYHQ/w400-h263/9k11%2Bdeployed.png" width="400" /></a><a href="https://1.bp.blogspot.com/-ScKKuuTNM2g/YOvdKtXnB-I/AAAAAAAAT3o/5lhIiffzlZwjKS2r0UX5TfR-PJy96O9owCLcBGAsYHQ/s1200/setting%2Bup%2B%25282%2529.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="801" data-original-width="1200" height="268" src="https://1.bp.blogspot.com/-ScKKuuTNM2g/YOvdKtXnB-I/AAAAAAAAT3o/5lhIiffzlZwjKS2r0UX5TfR-PJy96O9owCLcBGAsYHQ/w400-h268/setting%2Bup%2B%25282%2529.jpg" width="400" /></a></div><p>In cold conditions, the launch characteristics of the missile will differ from the norms due to a combination of colder (less energetic) rocket fuel and greater air resistance due to the increased air density. The main concern is ensuring that the missile launches properly and acquires sufficient altitude during the boost phase, so that it doesn't fly too low before the operator can effectively gain control, increasing the risk of a crash. For this reason, there are two sets of slots in the launcher lid for the support legs of the launch rail. When operating at an air temperature above zero, the legs are set in the forward slot, giving the launch rail an elevation angle of 1-20 mils (~7 degrees), and at air temperatures below zero, the rear slot is used, placing the rail at an elevation angle of 1-30 mils (~ 8 degrees).</p><p>Some separation between the launchers and the control panel is needed to avoid having the exhaust gasses of a launched missile interfere with the operator's view. The operator's 9S415 control panel can be located up to 15 meters from the launcher, and the operator can be fully concealed behind cover thanks to the 9Sh16 monocular periscopic sight, as opposed to the telescopic binoculars used on the "Shmel". In combat, the advantage of separating the operator from the launcher by such a great distance was that the launcher could be concealed in a full defilade, which would virtually eliminate the faint launch signature of the missile during its boost stage, thus exposing virtually nothing to enemy observers.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-u6k_CjWIjMo/YNlTOq2kHzI/AAAAAAAATj0/zcDF3MNcB1M_jmHrt-hf3DR9bhY6qg7vwCLcBGAsYHQ/s2548/9k11%2Bin%2Bcombat%2Bposition.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1212" data-original-width="2548" height="304" src="https://1.bp.blogspot.com/-u6k_CjWIjMo/YNlTOq2kHzI/AAAAAAAATj0/zcDF3MNcB1M_jmHrt-hf3DR9bhY6qg7vwCLcBGAsYHQ/w640-h304/9k11%2Bin%2Bcombat%2Bposition.png" width="640" /></a></div><p>According to a manual for the 9K11 system, the time needed to deploy from the transport configuration to the combat configuration is 1 minute 40 seconds, and the time needed to pack up into the transport configuration is 2 minutes.</p><p>The lengthy setup process and even lengthier repacking process almost made the "Malyutka" system a static defensive weapon, not entirely dissimilar to a towed anti-tank gun. Indeed, going by the nominal figures printed in the tactical-technical characteristics, anti-tank guns such as the D-48 and T-12 can be packed up into their transport configurations in a shorter time than a 9K11 missile system, at least in theory. This was very different from second generation man-pack ATGM systems which involved simply setting up a launcher and loading it as necessary. The disadvantages of the "Malyutka" were shared with all other examples of the first generation, and these shortcomings were identified as the main points for improvement with the following generation of man-portable ATGMs. The role of heavy anti-tank guns in the Soviet Army during the age of self-propelled and man-portable anti-tank missile systems is discussed in <a href="https://thesovietarmourblog.blogspot.com/2020/12/soviet-towed-anti-tank-guns.html">a separate Tankograd article</a>. </p><p>Unlike its successors, the 9M14 was not containerized in the strictest sense of the term, even though it was carried in watertight and shock-resistant suitcase-launchers, because the equipment inside the suitcase was reusable and the same suitcase could be used for up to 10 launchers whereas the missiles themselves were reloads, which would be transported to the front lines in sealed wooden crates. As the missiles could not be stored in the open for long periods, the unwieldy crate served as the container. This was, of course, a suboptimal solution. When stowed inside a tank destroyer like the 9P110, the missiles were simply kept on racks in the open. All this made it impossible to treat the 9M14 as being administratively equivalent to artillery cartridges once delivered to the front and handled by soldiers.</p><p>The production cost of a "Malyutka" was among the lowest in the world, around the same level as a Cobra, owing to a combination of its production-friendly design, and also to the economic nuances of the USSR to some extent. </p><p><br /><a href="https://www.blogger.com/null" id="malyutkaaerodynamics"></a></p><h3 style="text-align: left;"><span style="font-size: large;">AERODYNAMICS</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-5jnT74HgFsM/YNosnAApHDI/AAAAAAAATnQ/wErxJ3MeqRoN1ioqF4l2lzvwDSCSlTgjQCLcBGAsYHQ/s1309/aerodynamic%2Bforces%2Bon%2Bmissile.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="619" data-original-width="1309" height="189" src="https://1.bp.blogspot.com/-5jnT74HgFsM/YNosnAApHDI/AAAAAAAATnQ/wErxJ3MeqRoN1ioqF4l2lzvwDSCSlTgjQCLcBGAsYHQ/w400-h189/aerodynamic%2Bforces%2Bon%2Bmissile.png" width="400" /></a></div><p><br /></p><p>As with all previous ATGM projects, both serial and experimental, the 9M14 and its variants all have four wings. For increased portability, the wings were made to be foldable, but unlike the type found on the "Falanga", it was possible to return the wings to the folded position after deploying them. The folding wings, along with the wing roots and the casing around the wire spool are made from AG-4 fiberglass. The wings are hollow with a foam core, and the wing roots are solid but have lightening voids as shown in the drawing on the right below. They have a parallelogram planform, with wedge-shaped leading and trailing edges, otherwise known as a modified double wedge aerofoil. It is a symmetric aerofoil shape, which is the expected type for a rotating missile. No lift is produced when the missile has no angle of attack, and asymmetric aerofoils would merely induce roll rather than lift on a rotating fuselage, so by the nature of its design, the "Malyutka" must be oriented at a positive angle of attack in trimmed flight. However, the required angle is very small - around 1 degree, or more precisely, 0.01741 radians. This can be calculated with Equation 0 given in the research paper "<a href="https://scindeks-clanci.ceon.rs/data/pdf/1820-0206/2014/1820-02061401003M.pdf">Aerodynamic Compensation of the Modified Guided Anti-Tank Missile Configuration</a>" using standard air density, coefficients from Table 1, and the lateral thrust data given in Table 13 of the paper "<a href="https://www.researchgate.net/publication/291680304_Side_Force_Determination_in_the_Rocket_Motor_Thrust_Vector_Control_System">Side Force Determination in the Rocket Motor Thrust Vector Control System</a>".</p><p>During launch, a clockwise roll is induced in the "Malyutka" at a rotation speed of 8.5 RPS, and to maintain this speed during cruising flight, each wing is offset by 3.25 degrees. The images presented below, depicting the wings of a 9M14P (left) and a 9M14M (right), shows the angling of the wings and the protruding tabs on the fuselage, which are the guides for the missile when loading it onto a launch rail. </p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-avxP9WnT5tw/YNowI1j63eI/AAAAAAAATng/f4yS4k4B368a_bJ3OnreyZzy5Ie33Ox1ACLcBGAsYHQ/s2048/9m14p%2Bwings.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1558" height="400" src="https://1.bp.blogspot.com/-avxP9WnT5tw/YNowI1j63eI/AAAAAAAATng/f4yS4k4B368a_bJ3OnreyZzy5Ie33Ox1ACLcBGAsYHQ/w304-h400/9m14p%2Bwings.png" width="304" /></a><a href="https://1.bp.blogspot.com/-IFQiADoNba0/YMOEGI06rKI/AAAAAAAATag/_MjiJEEnODkCZ8aFXjytB9ENoVvAeCZwACLcBGAsYHQ/s1868/fin%2Bassembly.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1868" data-original-width="1309" height="400" src="https://1.bp.blogspot.com/-IFQiADoNba0/YMOEGI06rKI/AAAAAAAATag/_MjiJEEnODkCZ8aFXjytB9ENoVvAeCZwACLcBGAsYHQ/w280-h400/fin%2Bassembly.png" width="280" /></a></div></div><p>When folded, the four wings are divided into two pairs that are bounded together with a plastic clip each, holding them in place. To deploy a wing, the clip is simply removed and the wings are flipped onto their wing roots until a detent in the side of the wing is moved across a locking pin, whereupon it is locked open. To unlock the wings and fold them away, a button on the side of the wing root is pressed inward (towards the fuselage) to push the detent pin back into its recess, freeing the wing. The plastic retainer clip is then reused to hold the wings in place.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-YBbbF8kTzR8/YOPO-TWFPxI/AAAAAAAATvY/5sUPLxNIDSYQX4RDlFwKK6ulnfK8yXC9ACLcBGAsYHQ/s520/malyutka%2Bwings.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="390" data-original-width="520" height="300" src="https://1.bp.blogspot.com/-YBbbF8kTzR8/YOPO-TWFPxI/AAAAAAAATvY/5sUPLxNIDSYQX4RDlFwKK6ulnfK8yXC9ACLcBGAsYHQ/w400-h300/malyutka%2Bwings.gif" width="400" /></a></div><p>Each wing has a fixed wing root, but the remainder of the wing is hinged. The two parts have different sweep angles, forming a planform known as the crescent-shaped wing. Naturally, to bear the lift forces of the wing, the root is the thickest part of the wing. This also allows it to house the detent pin for the unfolding mechanism of the wing, shown in the image below. The left diagram shows the detent pin when the wing is folded, and the right diagram shows the wing unfolded and locked open. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-EPnPzkAYtsw/YNvBS_IPpcI/AAAAAAAATo4/DDdRJRXg2gwgps-sDxkY__2bXbAaBthCgCLcBGAsYHQ/s1408/detent%2Bpins.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="848" data-original-width="1408" height="241" src="https://1.bp.blogspot.com/-EPnPzkAYtsw/YNvBS_IPpcI/AAAAAAAATo4/DDdRJRXg2gwgps-sDxkY__2bXbAaBthCgCLcBGAsYHQ/w400-h241/detent%2Bpins.png" width="400" /></a></div><p>The aerodynamic nuances of crescent-shaped wings are listed in the 1954 article "<a href="http://web.archive.org/web/20171116132542/https://www.flightglobal.com/FlightPDFArchive/1954/1954%20-%201386.PDF">Aerodynamics of the Crescent Wing</a>" in Flight International magazine, though only some are relevant to an ATGM. In commercial aviation, the crescent planform was created primarily to ensure that a uniform critical mach number would be maintained along the entire span of the wing, and it is primarily for this reason that commercial airliners often feature a greater sweep angle at the wing root, although the crescent planform itself is not used due to structural expenses. However, given that the "Malyutka" travels well below the transonic speed range where this becomes an issue, this has no influence on the missile whatsoever. The only relevant factor listed in the article that may affect the "Malyutka" is that the crescent wing planform is reported to have better performance in high-speed stall conditions, particularly in high-g turns. Additionally, sweeping the wing root at a larger angle helps reduce interference drag. The manufacturing issues associated with crescent wings in the aviation industry are not relevant for ATGM wings, which have a radically different structural design. In this case, being solid fiberglass rather than hollow sections with a riveted metal skin over spars.</p><p>The center of gravity of the "Malyutka" lies in the front half of its sustainer engine, close to the geometric center of the wing roots. The static and dynamic stability of the missile is provided by the fact that the center of lift from the wings is further back than the wing roots, owing to the crescent wing design. </p><p>The use of folding wings was the primary factor for the large reduction in total missile dimensions, making it possible to reduce each missile into a convenient size for the backpack "suitcase" containers, made famous during the 1973 Yom Kippur war, and also making it feasible to carry a very large number of 9M14 missiles in vehicles like the 9P122 tank destroyer, not only in storage, but also on the launcher, permitting salvoes of up to six missiles in sequence. With the wings folded, the maximum width and height of the missile are both 185mm. When deployed, the wingspan is 393mm.</p><p>Aside from the wings, the other aspects of the missile are streamlined to a reasonable extent. Base drag is reduced by the boattailed shape of the guidance system housing, which protrudes behind the fuselage in between the two engine nozzles. The exhaust stream from the nozzles also ameliorates the formation of a wake behind the fuselage, which is the root cause of base drag. Moreover, the pointed conical nose is acceptable for a subsonic projectile in terms of both forebody drag and pressure drag, although it is not the ideal shape. The ideal nose for subsonic flight is an ogive, as found on French missiles such as the SS.10, SS.11 and ENTAC, as well as on the fuselage noses of commercial aircraft.</p><p>The image on the below, taken from the 1965 textbook "<a href="http://ftp.demec.ufpr.br/disciplinas/TM240/Marchi/Bibliografia/Hoerner.pdf%20Dr.-Ing%20S.%20F.%20Hoerner">Fluid-Dynamic Drag</a>" by Dr.-Ing S. F. Hoerner, shows the relationship between ogived, hemispherical and blunt noses in their forebody pressure drag coefficients for cylindrical bodies. On the first shape from the left, an ogive, a negative forebody drag is observed due to suction forces. An elongated cone nose results in relatively low forebody drag, on par with a rounded blunt nose. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-leHNyQr00mo/YMOr5vb-CFI/AAAAAAAATa4/qAV6zkc1J-8-7gWo7NyqSJ-GCre0KNNbQCLcBGAsYHQ/s1204/drag%2Bcoefficient%2Bof%2Bshapes.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="677" data-original-width="1204" height="225" src="https://1.bp.blogspot.com/-leHNyQr00mo/YMOr5vb-CFI/AAAAAAAATa4/qAV6zkc1J-8-7gWo7NyqSJ-GCre0KNNbQCLcBGAsYHQ/w400-h225/drag%2Bcoefficient%2Bof%2Bshapes.png" width="400" /></a></div><p>The spin rate of the "Malyutka" is dependent on the thrust of the booster engine, which imparts the initial rolling moment, and the wings, which generates a rolling moment that varies with its lift force, which in turn is dependent on the airspeed. As the energy of the rocket engine grows or declines with temperature, so too does the spin rate:</p><p></p><ul style="text-align: left;"><li>+15°C: 8.3 RPS</li><li>+50°C: 10.1 RPS</li><li>-40°C: 5.9 RPS</li></ul><p></p><p>The nominal spin rate of 8.5 RPS normally cited in various sources is achieved at a temperature of +20°C. By having a spin of moderate speed, it became possible to implement a simpler control system, using the gyroscope to dynamically coordinate the actuation of the steering mechanism in the roll axis. But not only that - by maintaining an equilibrium spin, potential sources of flight instabilities from the asymmetry of external and internal fittings of the missile are cancelled out, and the propulsive force from the symmetrically opposed twin sustainer engine nozzles is aligned to the axis of the missile fuselage such that any diverging forces are canceled out. The issue of aerodynamic asymmetries is particularly important for the "Malyutka", because on the 9M14 and 9M14M, there is only a single tracer, placed opposite to the tabs for the launch rail. It is self-evident that the form drag of one side of the missile will not be equal to its opposite, hence the need for an equilibrium spin. By extension, the elimination of this drag inequality on the 9M14P due to the use of symmetrical tracers implies that the flight stability of the missile improved.</p><p>The use of spin was, however, conditional on the limits of the shaped charge warhead, which typically suffers when the spin rate exceeds approximately ~25 RPS, and the spin rate cannot be arbitrarily chosen, as the natural frequency of the missile must be avoided. A spin rate that crosses or is sustained at the natural frequency generates resonance, disturbing its flight vector, reducing control authority over the missile and potentially causing a crash. The natural frequency of the 9M14 missile is 2.5 Hz (2.5 RPS). By providing a minimum spin rate of 5.9 RPS at the lowest rated operating temperature of the missils system, it is guaranteed that resonance will never occur within the operating parameters of the system. </p><p><br /></p><p><br /><a href="https://www.blogger.com/null" id="malyutkaguidance"></a></p><h3 style="text-align: left;"><span style="font-size: large;">GUIDANCE SYSTEM</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-TGVgfsVb05U/YNuMCWrAW1I/AAAAAAAAToQ/7EVqEfnW-IEDqF-rA8-l491U08fJws5hQCLcBGAsYHQ/s3003/guidance%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="923" data-original-width="3003" height="196" src="https://1.bp.blogspot.com/-TGVgfsVb05U/YNuMCWrAW1I/AAAAAAAAToQ/7EVqEfnW-IEDqF-rA8-l491U08fJws5hQCLcBGAsYHQ/w640-h196/guidance%2Bsystem.png" width="640" /></a></div><p>The guidance system of the 9M14, and all other variants of the "Malyutka" missile series, is of the utmost simplicity. In this regard, a particularly noteworthy feature of the "Malyutka" system is that it uses a single-wire command link - the second missile in the world to do so, after the Vickers Vigilant. This facilitated the simplification and lightening of the missile; traits that influenced the proliferation of later single-wire link designs on the MILAN, HOT and Dragon. The image above shows a block diagram of the entire system. Within the missile, the three components of the system are the gyroscope and commutator assembly (gyro-coordinator), a rectifier, and the two solenoids of the steering mechanism. All of the concepts applied in the control circuit of the missile are simple, core topics in electronics engineering, and overall, the complexity of the circuit design is at the level of a high school project. The electronics circuit, consisting of the rectifier, capacitors, diodes and the gyro-coordinator unit are connected using point-to-point wiring, which is not conducive to automated assembly as printed circuit board systems are, but this method of wiring is justified by the great simplicity of the circuit, which simplifies assembly by hand and allows weight to be saved by omitting circuit boards. The following list describes the system blocks in the guidance system:</p><p></p><ul style="text-align: left;"><li>ПУ - control panel</li><li>ИПН - rectangular control voltage generator</li><li>СУ - summing amplifier</li><li>РУ - control joystick</li><li>В - wire core connectors</li><li>К - wire</li><li>Р - rectifier</li><li>Г - gyroscope</li><li>PM - steering mechanism</li></ul><p></p><p>The only blocks housed in the missile itself are the wire (in its spool), the gyroscope and commutator assembly, the rectifier and the steering mechanism. The wire is cross-connected to the rectifier and the gyroscope and commutator assembly for signal processing, and the output, a control signal, is passed to the steering mechanism. Power to the missile is sourced from the summing amplifier in the operator's 9S415 control panel. It takes the two signals from the control joystick, one from each movement axis, and combines the two voltages into a single output voltage. The voltage is then passed down the command wire via one of the three wire cores.</p><p>Given that a wire link in a conventional wire-guided ATGM is used as the medium for transmitting pulses of electrical power to actuate the steering mechanism, as detailed in the earlier section on the 3M6, the use of a wire link as the means for providing power, as well as steering commands, is a rather straightforward logical step, yet also a radical one. It was made possible by the extremely modest power demands of the 9M14, mainly thanks to its use of a highly efficient thrust vector control system for steering, requiring less power than aerodynamic control surfaces. Another radical difference is that the "Malyutka" system features a single-wire command link, instead of two wires and two channels for vertical and horizontal steering control like 3M6 and some other roll-stabilized conventional ATGMs. </p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEj05_wcRRqKpBr6qaQyrkFCO4I2o2rRBhzHL7i5o6fsyyAtpZbyayDRUzGbYiDdd8BkVhDZjLW-lPugm8HyonbSpLl9F_9TayFW1ouyqQ4M9OinarErvNvOcFM9XF7rEIriJrI5CYnQImtzyMU3Jpd2XoHGQu1QwuyFZSDZyTt6HTmmMSuy62vxwpsxzQ=s1875" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1263" data-original-width="1875" height="270" src="https://blogger.googleusercontent.com/img/a/AVvXsEj05_wcRRqKpBr6qaQyrkFCO4I2o2rRBhzHL7i5o6fsyyAtpZbyayDRUzGbYiDdd8BkVhDZjLW-lPugm8HyonbSpLl9F_9TayFW1ouyqQ4M9OinarErvNvOcFM9XF7rEIriJrI5CYnQImtzyMU3Jpd2XoHGQu1QwuyFZSDZyTt6HTmmMSuy62vxwpsxzQ=w400-h270" width="400" /></a><a href="https://1.bp.blogspot.com/-_JPF4ORSi0g/YNuP7zl7l3I/AAAAAAAAToY/v-0vK3R-SWs9fcV4ZQeStEy93cDs_TRLACLcBGAsYHQ/s2048/wire.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1430" data-original-width="2048" height="279" src="https://1.bp.blogspot.com/-_JPF4ORSi0g/YNuP7zl7l3I/AAAAAAAAToY/v-0vK3R-SWs9fcV4ZQeStEy93cDs_TRLACLcBGAsYHQ/w400-h279/wire.png" width="400" /></a></div></div><p>The single command wire is stored in a spool around the sustainer engine. It contains a twisted triple-strand enameled copper wire core in a fiber-reinforced body and then shielded with an insulating fabric jacket, giving the copper cores a total of two layers of insulation. In truth, the construction of the command wire is that of a cable rather than a wire, which would be a single conductive line covered in a single layer of insulation. Each of the three enameled copper wires forming the core have a diameter of 0.12mm, making the overall wire (or cable) several times thicker than the wires used in the 3M6 and several foreign ATGMs. From a design standpoint, the main disadvantage of a copper command wire compared to a steel command wire is that the tensile strength is vastly lower. This means that a thicker core is needed, and fibers with high tensile strength are needed for reinforcement to prevent wire breaks, thus resulting in a heavier wire, even before considering the higher density of copper. The upside is that by having a thick-cored copper cable, the resistance of the wire is greatly reduced compared to a steel wire due to the inversely proportional relationship between resistance and the cross sectional area of a conductor, and the multiple layers over the cores give far better insulation to resist interference should the wire be strung over bushes, tree limbs, or a fire. </p><p>A much lower wire resistance grants the possibility of powering the missile via the wire, and to do so without a strongly amplified power source. This lightens the weight of the control panel, reduces the power demand, and permits a longer range to be achieved.</p><p>The wire is 3,100 meters long. Due to the use of thrust vectoring for steering, excess wire length is only useful for supporting a curved or non-linear trajectory rather than extending the maximum range, as control is lost once the rocket engine burns out anyway.</p><p>Power to the missile, as well as the control system, is supplied by an 11FG-400 rechargeable wet cell battery housed in the operator's control panel. It is a nickel-cadmium battery of a somewhat considerable size, weighing 2.4 kg. Two batteries are included in the full kit of each 9K11 system, to be used alternately. One battery is for use, installed in the control panel, and the second battery is kept at the charging station in the regimental workshop. If not discharged in combat but kept installed in the control panel, the battery slowly self-discharges, and has to be replaced with a fully charged one before combat. In a European climate, with temperatures of -40°C to +35°C, the battery is swapped out once every 30 days, or once every 15 days at temperatures of +35°C to +50°C. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-qwn1s2YnIao/YNmCK64drRI/AAAAAAAATkc/5vYfDnou9hwKFaCyfnHy80oKFsJRYBUIACLcBGAsYHQ/s1797/11fg-400%2Bbattery.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1029" data-original-width="1797" height="229" src="https://1.bp.blogspot.com/-qwn1s2YnIao/YNmCK64drRI/AAAAAAAATkc/5vYfDnou9hwKFaCyfnHy80oKFsJRYBUIACLcBGAsYHQ/w400-h229/11fg-400%2Bbattery.png" width="400" /></a></div><p>The battery has a charge of 1.5 Ah and provides a 12 V DC voltage and a 1.5 A current. Its service lfie is rated for 20 charge-discharge cycles. Due to the discharge characteristics of nickel-cadmium batteries, the operating voltage remains steady, allowing each "Malyutka" missile to receive its rated power supply throughout its entire flight without fluctuations, which could otherwise interfere with the operator's control. The operator determines if the battery attached to his control panel is combat-ready by turning on the power switch and checking the voltmeter attached to the side of the control panel. According to a manual for the 9K11 system, after being stored for 30 days at a temperature range of -10°C to +35°C, the battery will have a remaining charge of 0.6 Ah, and meets the service life rating of 20 charge-discharge cycles. It is rated for no less than 60 missile launches in this state, which reflects all but the most extreme climatic conditions. Presumably, at least 150 launches can be made with a full charge of 1.5 Ah. If stored outside this temperature range of -10°C to +35°C, the service life of the battery is slashed by two thirds, and it can only retain a charge of 0.6 Ah at the end of the its storage period, degrading further to 0.3 Ah if charged and discharged persistently in these temperature extremes.</p><p>When mounted on a vehicle such as the BMP-1 or an Mi-8TVK helicopter, the launcher is plugged into the electrical network of the vehicle itself via the onboard guidance system.</p><p>With one of the three wire cores used for power, the other two cores are used to transmit an AC command signal. To use this command signal, the bridge rectifier in the missile first processes it. The rectifier converts the AC voltage of the command signal into the DC voltage necessary to power the distributor rings in the gyroscope. The charging and discharging of the capacitors across the rectifier output smoothens the wave form, filtering the signal received from the control panel. The rectifier is also used to distribute the command signal between the solenoids of the steering mechanism. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-gsW43ydrCWI/YNoPh_efTdI/AAAAAAAATmE/IeE9dtrncFgyTa-t999NgstOk_-hbLe3QCLcBGAsYHQ/s1512/rectifier.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1512" data-original-width="1298" height="400" src="https://1.bp.blogspot.com/-gsW43ydrCWI/YNoPh_efTdI/AAAAAAAATmE/IeE9dtrncFgyTa-t999NgstOk_-hbLe3QCLcBGAsYHQ/w344-h400/rectifier.png" width="344" /></a><a href="https://1.bp.blogspot.com/-H4UZNU30sl0/YNmq-P9Jc6I/AAAAAAAATkk/KSmk8LhrAKsPxSrdyt7S_zB3gcva7lQfwCLcBGAsYHQ/s2048/control%2Bcircuit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1730" height="400" src="https://1.bp.blogspot.com/-H4UZNU30sl0/YNmq-P9Jc6I/AAAAAAAATkk/KSmk8LhrAKsPxSrdyt7S_zB3gcva7lQfwCLcBGAsYHQ/w338-h400/control%2Bcircuit.png" width="338" /></a></div><p>A rate gyroscope is used in the missile. It acquires a spin rate of 27,000 RPM during launch via a length of tape connected to the launch rail. When the missile accelerates off the launch rail, the tape is rapidly unwound and this spins up the gyroscope. Almost whimsical in its simplicity, this method of spinning up a gyroscope was the most common at the time, being used in ATGMs like the ENTAC and Cobra. The gyroscope is rigidly fixed in place before launch by a mechanical arrestor. The arrestor is connected to the launch rail when the missile itself is fitted to it, and upon launch, the arrestor is pulled away by the movement of the missile and the gyroscope is free to spin. Because the gyroscope is spun by a tape upon launch, and there is no onboard thermal battery requiring a warm-up period, the "Malyutka" missile has no firing delay. When the launch button is pressed, the missile is launched almost instantly.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-7WwPkCba3F4/YNlLLHFkecI/AAAAAAAATjs/Wojc7KzOP3EGQ4FakfL869dPPq8s0QxHQCLcBGAsYHQ/s2672/9m14%2Bgyroscope.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1177" data-original-width="2672" height="282" src="https://1.bp.blogspot.com/-7WwPkCba3F4/YNlLLHFkecI/AAAAAAAATjs/Wojc7KzOP3EGQ4FakfL869dPPq8s0QxHQCLcBGAsYHQ/w640-h282/9m14%2Bgyroscope.png" width="640" /></a></div><p>Once the gyroscope is spun up, it is uncaged, and it begins to perform its function as a gyro-coordinator to coordinate the reception and distribution of control signals from the operator's control panel to the steering nozzles of the missile.</p><p>To coordinate the rotation of the missile with the control signals issued by the operator, the gyroscope is fitted with a commutator. It consists of a four-segment slip ring, acting as an interrupter, rotating about two static distributor rings affixed to the gyroscope frame, which receive power from the rectifier, as detailed earlier. This is represented in the image on the left below. The two inner rings and the two vertical lines (brush contacts) are gyroscopically stabilized and maintain a fixed roll position, while the four-segment slip ring, which is the outer ring in the image, is connected to the missile steering system and thus rotates together with the missile. The horizontal line in the image is not significant. This mechanism functions as the angular coordinator by which the polarity of the steering commands are modified before being delivered to the steering mechanism. The slip ring is supplied with the rectified signals from the control panel via brushes, positive signals on brush contact 1 and negative signals on brush contact 2. The simplest commutator is shown in the image on the right below, taken from the introductory book "<i>Противотанковые Реактивное Оружие</i>" published by the Soviet Ministry of Defence in 1964.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9389Tl0EXx0/YNuEcn7OkkI/AAAAAAAATn4/0H_OUAsG2boa4XxCMvDtxqZJlaTamFy3wCLcBGAsYHQ/s642/slip%2Bring%2Bcontacts.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="598" data-original-width="642" src="https://1.bp.blogspot.com/-9389Tl0EXx0/YNuEcn7OkkI/AAAAAAAATn4/0H_OUAsG2boa4XxCMvDtxqZJlaTamFy3wCLcBGAsYHQ/s320/slip%2Bring%2Bcontacts.png" width="320" /></a><a href="https://1.bp.blogspot.com/-u6NHyrXL-7U/YPIsa6QkAQI/AAAAAAAAT8s/ZFAaRqxOALUzLDKAXkAPicskLLxhSeSDQCLcBGAsYHQ/s1104/simplest%2Bgyro-coordinator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1104" data-original-width="1044" height="320" src="https://1.bp.blogspot.com/-u6NHyrXL-7U/YPIsa6QkAQI/AAAAAAAAT8s/ZFAaRqxOALUzLDKAXkAPicskLLxhSeSDQCLcBGAsYHQ/s320/simplest%2Bgyro-coordinator.png" /></a><br /></div><p>The simplest commutator consists of a four-segment slip ring that is stabilized by the gyroscope on its axis (2), and the control signals are received by the steering mechanism via brushes (1) which are connected to the body of the missile, which rotates in flight and thus causes the brushes to rub around the slip ring. Since the ring sectors maintain a strictly defined position, the steering actuators operate only when the steering units are in the correct position, whether they may be aerodynamic rudders or a TVC nozzle. If there are four aerodynamic rudders, as in this case, then two pairs of rudders will exchange functions when the missile makes a 90-degree turn; the horizontal rudders operate like the vertical ones, and conversely. This is considered a two-axis steering system. </p><p>The commutator of the "Malyutka" adds an additional increment of complexity on top of this simple commutator as it is designed for a hinged TVC nozzle, which is a single-axis steering system, rather than two pairs of aerodynamic rudders or a two-axis TVC nozzle as found on the SS.11. With this mechanism, the magnitude of the output signal will be nullified in the first 90-degree turn, and then the next 90-degree turn reverses its polarity. The image on the right shows the four positions of the slip ring relative to the fixed axis of the gyro-coordinator at rotation angles of 0° (360°), 90°, 180° and 270°, respectively. As a result, if, for instance, a "yaw-left" steering command is executed while the nozzles are horizontally level, the nozzle will be deflected to the left relative to the missile and remain deflected while the missile completes a 180-degree turn, and then they are deflected to the right relative to the missile. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-1PAIdVoFOIc/YNuGtL4C8oI/AAAAAAAAToE/e7Sr9xhWr5cINxdfsK3REJ6fwXgG2ammwCLcBGAsYHQ/s1903/commutator%2Btable.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="551" data-original-width="1903" height="116" src="https://1.bp.blogspot.com/-1PAIdVoFOIc/YNuGtL4C8oI/AAAAAAAAToE/e7Sr9xhWr5cINxdfsK3REJ6fwXgG2ammwCLcBGAsYHQ/w400-h116/commutator%2Btable.png" width="400" /></a><a href="https://1.bp.blogspot.com/-JvpxWHONGB8/YNuGtA9--CI/AAAAAAAAToA/b77nZK7oNGA0NEImdcecXVU0N5WlgrMvwCLcBGAsYHQ/s1832/slip%2Bring%2Bdiagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="682" data-original-width="1832" height="149" src="https://1.bp.blogspot.com/-JvpxWHONGB8/YNuGtA9--CI/AAAAAAAAToA/b77nZK7oNGA0NEImdcecXVU0N5WlgrMvwCLcBGAsYHQ/w400-h149/slip%2Bring%2Bdiagram.png" width="400" /></a></div><p>Overall, the gyroscope and its attached coordinator mechanism had to be built to a fairly high quality standard, although it was still mechanically simple and cheap. At the time, the only simpler gyroscope in use on any other ATGM was that of the Cobra, but the guidance system of that missile was so problematic that it gave it a reputation among its users in the IDF where it was issued in the 755th division, as it was considered capricious and too difficult to control. Its nicknames among the soldiers were "טיל מטורף" (<i>til metoraf</i>) meaning "insane missile" and "טיל לא ממושמע" (<i>til lo memushma</i>) meaning "undisciplined missile". On the other end of the spectrum, the Vickers Vigilant was the most extravagant of all, having two gas-spun gyroscopes, one for yaw sensing and one for pitch sensing, with a commutator of its own, although its guidance system was not as responsive, as the missile spun at only 4 RPS. </p><p>During the initial trajectory of the "Malyutka", operator control of the missile is blocked by the 9S415 control panel for 0.8 seconds as it executes its automatic control program. Immediately after launch, the control unit is programmed to automatically guide the missile to a fixed altitude of 6 meters, which is reached at a range of 200 meters from the launcher. This is achieved by a hard-coded program in the control panel, which runs automatically every launch, transmitting a gentle "up" command, then transmitting a "down" command of the same intensity after a short delay to level off the orientation of the missile. This was intended to ensure that the missile would be clear of any ground obstacles under all circumstances. The initial trajectory of the 9M14, as well as the ideal trajectories when guiding the missile, is shown in the image below from the <a href="https://milimoto.wordpress.com/2019/05/02/ppk-z-systemem-kierowania-mclos-tor-lotu-pocisku/">milimoto blog</a>, originally sourced from the article "<i>Szkolenie operatorów przeciwpancernych pocisków kierowanych</i>" (<i>Training of anti-tank guided missile operators</i>).</p><div><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-3_6fz0BJ_bo/YNwKJ3nklzI/AAAAAAAATp4/iolSXUEaGxMXnW8pmPbSD3LbXAFvFsY-ACLcBGAsYHQ/s1347/ppk_tor_lotu_d.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1347" data-original-width="1000" height="640" src="https://1.bp.blogspot.com/-3_6fz0BJ_bo/YNwKJ3nklzI/AAAAAAAATp4/iolSXUEaGxMXnW8pmPbSD3LbXAFvFsY-ACLcBGAsYHQ/w477-h640/ppk_tor_lotu_d.jpg" width="477" /></a></p><p>To permit observation of the missile in flight, the 9M14 and 9M14M have a single 9Kh44 pyrotechnic tracer fitted externally on its fuselage. A tracer is needed because the jet from the sustainer engine is flameless and has minimal smoke, and is thus totally insufficient for this purpose at all ranges. To avoid temporarily blinding the missile operator when firing at night or in low light conditions, two pyrotechnic compositions were used - the main composition which emits a brighter light, and a low-intensity composition at the end of the tracer that emits a dim light, burning for the first second of missile flight after launch. In total, the tracer burns for 27.1 seconds under normal conditions. This enables observation of the missile trajectory throughout maneuvering flight, or well in excess of its nominal maximum range of 3 km.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-8XaA9bPJC4M/YNvCHOif31I/AAAAAAAATpA/xftZi6PGBa42gt4fBmWuAldDDpnr6YyFACLcBGAsYHQ/s2583/9kh44.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1217" data-original-width="2583" height="189" src="https://1.bp.blogspot.com/-8XaA9bPJC4M/YNvCHOif31I/AAAAAAAATpA/xftZi6PGBa42gt4fBmWuAldDDpnr6YyFACLcBGAsYHQ/w400-h189/9kh44.png" width="400" /></a></div><br /><p>On the 9M14P, the only redesign implemented to adapt the missile for SACLOS guidance was the change from the single 9Kh44 tracer to a pair of external 9Kh416 tracers installed symmetrically at the rear of the fuselage. As the missile spins during its flight, the flame of the two spinning tracers generates a signature that appears as a helix to the naked eye and appears as a point to the photodetector of the launch unit. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-eSRUy8K5l6A/YNvHwJcXnXI/AAAAAAAATpQ/jZbLtvjaf243lF_xwskMvrwBzOfnlPaxwCLcBGAsYHQ/s2048/9kh416%2Btracer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1274" data-original-width="2048" height="249" src="https://1.bp.blogspot.com/-eSRUy8K5l6A/YNvHwJcXnXI/AAAAAAAATpQ/jZbLtvjaf243lF_xwskMvrwBzOfnlPaxwCLcBGAsYHQ/w400-h249/9kh416%2Btracer.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ELJ9icl2kac/YNvEFCwTluI/AAAAAAAATpI/7SiiBGlm6-gnhFOhmP2GQ3FrY4U_cH4sgCLcBGAsYHQ/s1009/tracer%2Bmount.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1009" data-original-width="957" height="200" src="https://1.bp.blogspot.com/-ELJ9icl2kac/YNvEFCwTluI/AAAAAAAATpI/7SiiBGlm6-gnhFOhmP2GQ3FrY4U_cH4sgCLcBGAsYHQ/w190-h200/tracer%2Bmount.png" width="190" /></a><a href="https://1.bp.blogspot.com/-i6XRiqK9xWA/YNoWcDvxfNI/AAAAAAAATms/EHdhJBmeYTojTo4S1Yky33obHToDbqz2wCLcBGAsYHQ/s1261/9kh416%2Btracer%2Bmounted.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1248" data-original-width="1261" height="198" src="https://1.bp.blogspot.com/-i6XRiqK9xWA/YNoWcDvxfNI/AAAAAAAATms/EHdhJBmeYTojTo4S1Yky33obHToDbqz2wCLcBGAsYHQ/w200-h198/9kh416%2Btracer%2Bmounted.png" width="200" /></a></div></div><p><br /></p><p>The tracer generates an energetic red flame, necessary to ensure observation in bad weather conditions out to the maximum range of 3,000 meters. To prevent the tracer from blinding the missile operator during launch, especially in low light conditions, the tracer starts with a slow burn for the first 0.5-1.0 seconds.</p><p><br /><a href="https://www.blogger.com/null" id="malyutkaengine"></a></p><h3 style="text-align: left;"><span style="font-size: large;">ENGINE</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-11vDod6gBuE/YNoI9JeTchI/AAAAAAAATl0/EOXXe-2JvJcLahpNsdNqdqb2ej3jJsZ2ACLcBGAsYHQ/s2048/engine.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1092" data-original-width="2048" height="342" src="https://1.bp.blogspot.com/-11vDod6gBuE/YNoI9JeTchI/AAAAAAAATl0/EOXXe-2JvJcLahpNsdNqdqb2ej3jJsZ2ACLcBGAsYHQ/w640-h342/engine.png" width="640" /></a></div><div><p>The somewhat unusual layout of the two-stage engine was determined by the need to fit the command wire spool and the steering system components within a streamlined cylindrical fuselage, while at the same time avoid disrupting the center of gravity of the missile as the fuel of the sustainer engine is spent. For this reason, the sustainer engine was designed in such a way to define the center of gravity of the missile. The booster engine was placed ahead of the center of the missile, so that its full expenditure during the boost stage has no effect on the center of gravity. </p><p>The missile is launched by the booster engine. It has four nozzles arranged symmetrically around the base of the warhead section of the missile. The booster engine nozzles are offset at a very small angle of 50' (0.83 degrees) to impart a spin of 8.5 RPS to the missile during launch. After the booster engine burns out, this spin rate is sustained by the wings. The casing of the booster engine, which serves as the combustion chamber, is made out of aluminum alloy and covered with a thin layer of V-58 insulation coating. Due to the short burn time of the booster engine, a heavier and more robust combustion chamber was not needed despite the enormous pressure and thrust it develops, nor would it be desirable, as once the booster charge burns out, the booster engine is nothing but a parasitic payload.</p><p>The energy of the rocket engine grows and declines with temperature</p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-6rcAoPj_gL8/YN1duiJ0kCI/AAAAAAAATrA/iBeqnr5ngts_jtGXr26iBpBZ7N6g-T8hwCLcBGAsYHQ/s1720/variance%2Bin%2Bfuel%2Bburn%2Brate%2Bwith%2Btemperature.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="939" data-original-width="1720" height="219" src="https://1.bp.blogspot.com/-6rcAoPj_gL8/YN1duiJ0kCI/AAAAAAAATrA/iBeqnr5ngts_jtGXr26iBpBZ7N6g-T8hwCLcBGAsYHQ/w400-h219/variance%2Bin%2Bfuel%2Bburn%2Brate%2Bwith%2Btemperature.png" width="400" /></a></p><p>Due to the short burn time of the booster, it is somewhat less affected by temperature, ensuring that the missile receives a sufficient thrust to get airborne under all temperature conditions.</p><table border="1"><tbody><tr><td style="text-align: center;"><b> Temperature </b></td><td style="text-align: center;"><b> Burn time </b></td><td style="text-align: center;"><b> Thrust </b></td></tr><tr><td style="text-align: center;"><span style="text-align: left;">+15°C</span></td><td style="text-align: center;">0.68 s</td><td style="text-align: center;"> 202 kgf (1,981 N) </td></tr><tr><td style="text-align: center;"><span style="text-align: left;">+50°C</span></td><td style="text-align: center;">0.61 s</td><td style="text-align: center;">227 kgf (2,226 N)</td></tr><tr><td style="text-align: center;"><span style="text-align: left;">-40°C</span></td><td style="text-align: center;">0.81 s</td><td style="text-align: center;">168 kgf (1,647 N)</td></tr></tbody></table><p><br />The four nozzles of the booster engine are situated to blow between the four wings at the tail of the fuselage. When the missile is installed on a launch rail, the nozzles are laid out in a cruciform. Distributing the thrust of the engine across four nozzles, and having three of the four nozzles not aimed directly at the ground, and the fourth nozzle aiming through the launch rail to blow onto the suitcase launcher lid, may have had some slight positive influence on the launch signature of the missile. This effect is shown in the image below, showing an HJ-73, a Chinese-made derivative of the 9M14M.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ImyKXld60_o/YNvq3U6_9XI/AAAAAAAATpg/us_Nsm2ecOoLlPCwhdIWAzZpSz2hj5aXgCLcBGAsYHQ/s900/hj-73.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="900" height="266" src="https://1.bp.blogspot.com/-ImyKXld60_o/YNvq3U6_9XI/AAAAAAAATpg/us_Nsm2ecOoLlPCwhdIWAzZpSz2hj5aXgCLcBGAsYHQ/w400-h266/hj-73.jpg" width="400" /></a></div><br /><p>In a case of almost trivial, but admirable design simplification and weight savings for electrical contacts, the engine ignition circuits are connected in parallel with other systems. The booster engine igniter circuit is connected in parallel to the tracer igniter, and the sustainer engine igniter circuit is in parallel to the arming circuit of the warhead fuze. </p><p>The image below, taken from the study "<a href="https://www.researchgate.net/publication/318446799_PREGLED_DOSADASNIH_RADOVA_NA_MODERNIZACIJI_POGONSKE_GRUPE_RAKETE_MALUTKA_-_AN_OVERVIEW_OF_RECENT_WORKS_ON_MALUTKA_ANTITANK_ROCKET_MISSILE_MOTOR_GROUP_MODERNIZATION">An Overview of Recent Works on Malutka Antitank Rocket Missile Motor Group Modernization</a>" by Nikola Gligorijevic et al. from the Military Technical Institute Belgrade, shows the full engine assembly on a test stand.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-SFma7hmrvNc/YOMsvJ7ro7I/AAAAAAAATvI/OoVsJw880wEMrfYRt6eRZ08NT7KoRyoHQCLcBGAsYHQ/s1866/rocket%2Bengine%2Bon%2Btest%2Bstand.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1399" data-original-width="1866" height="300" src="https://1.bp.blogspot.com/-SFma7hmrvNc/YOMsvJ7ro7I/AAAAAAAATvI/OoVsJw880wEMrfYRt6eRZ08NT7KoRyoHQCLcBGAsYHQ/w400-h300/rocket%2Bengine%2Bon%2Btest%2Bstand.png" width="400" /></a></div><p>The solid fuel sustainer engine is located in the center of the missile fuselage and its two nozzles are located at the rear the fuselage. The sustainer engine has a steel combustion chamber, needed due to its long burn time. The inner half of the aluminium booster engine chamber was incorporated into the casing of the steel sustainer engine chamber. To blow past the guidance section of the missile, located in the tail of the fuselage, the nozzles of the sustainer engine are greatly elongated aft of the throat. The sustainer engine is integral to the flight and steering of the missile, because the steering is accomplished using thrust vector control, and so a continuous thrust must be provided by the sustainer engine throughout the entire flight of the missile for it to remain controlled. </p><p>Due to the short burn time of the booster, it is somewhat less affected by temperature, ensuring that the missile receives a sufficient thrust to get airborne under all temperature conditions.</p><table border="1"><tbody><tr><td style="text-align: center;"><b> Temperature </b></td><td style="text-align: center;"><b> Burn time </b></td><td style="text-align: center;"><b> Thrust </b></td></tr><tr><td style="text-align: center;"><span style="text-align: left;">+15°C</span></td><td style="text-align: center;">27.1 s</td><td style="text-align: center;"> 8.1 kgf (79 N) </td></tr><tr><td style="text-align: center;"><span style="text-align: left;">+50°C</span></td><td style="text-align: center;">25.1 s</td><td style="text-align: center;">9.0 kgf (88 N)</td></tr><tr><td style="text-align: center;"><span style="text-align: left;">-40°C</span></td><td style="text-align: center;">30.3 s</td><td style="text-align: center;">7.1 kgf (70 N)</td></tr></tbody></table><p><br /></p><p>RNDSI-5K is used in the sustainer engine. The fuel has a density of 1.58 g/cc, and has an energy density of 799 kJ/kg and a specific impulse of 2,186 N.s/kg. Out of the entire range of solid fuel compounds used in domestic ATGMs, the specific impulse of RNDSI-5K is one of the highest, but at the same time, its specific smokiness index is also one of the highest. This means that the loss of visual transparency per unit weight of burned fuel is high. This was balanced out by the low fuel consumption rate of the sustainer engine, due to the long burn time corresponding to a long flight time, over which only a modest amount of thrust is required. Consequently, the volume of smoke produced is also small.</p></div><div style="text-align: left;"><p>The data and image presented below are taken from the study "<a href="https://www.researchgate.net/publication/291680304_Side_Force_Determination_in_the_Rocket_Motor_Thrust_Vector_Control_System">Side Force Determination in the Rocket Motor Thrust Vector Control System</a>", by Nikola Gligorijevic et al. from the Military Technical Institute Belgrade, show the full engine assemblies on test stands. The nominal thrust of the sustainer engine is 95 N. The thrust produced is maintained at a steady level throughout the 24-second cruising stage of the "Malyutka", until the maximum range of 3 km is reached whereby the full 27.1-second burn time of the sustainer engine elapses, the thrust rapidly plummets within 3 seconds, and the missile becomes ineffective. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ZDEmu5dlPBU/YKOg_-qcp5I/AAAAAAAATAE/q0Sm8DeuExoguRtEOL9NPiX_IGu-z0GdgCLcBGAsYHQ/s1752/malyutka%2Bsustainer%2Bengine%2Bthrust%2Bcurve.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1294" data-original-width="1752" height="295" src="https://1.bp.blogspot.com/-ZDEmu5dlPBU/YKOg_-qcp5I/AAAAAAAATAE/q0Sm8DeuExoguRtEOL9NPiX_IGu-z0GdgCLcBGAsYHQ/w400-h295/malyutka%2Bsustainer%2Bengine%2Bthrust%2Bcurve.png" width="400" /></a></div><p>During its short burn time, the booster engine propels the missile to a velocity of ~105 m/s. The constant thrust from the sustainer engine is in excess of the air resistance, and as such, imparts a further, slow acceleration to a peak velocity of 120-130 m/s whereby the thrust matches the air resistance, as shown in the graph below, taken from a <a href="https://www.mycity-military.com/Artiljerija-municija-i-protivoklopna-sredstva/PORS-Drug_2.html#p978418">MyCity Military forum post</a> (original source unknown). The original series is represented by the black line. Red, green and blue lines represent three variants of the modernized "Malyutka-2" series. The surplus of sustainer thrust at normal operating conditions is so that at the lowest boundary of the operating temperature (-40°C), where the air density is higher while the thrust is reduced, the missile does not lose altitude in level flight. It also ensures that when steering corrections are made, the missile does not inadvertently lose altitude, because the TVC steering system involves the reduction of longitudinal thrust by conversion to lateral thrust when it is activated. At the same time, because the thrust is kept constant, the steering response from the TVC system is completely consistent throughout the flight.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-cVhm7EFOWOE/YOMo9AKJFaI/AAAAAAAATvA/IAg3fXmyyn4OjMt9AT_V-fGJIX-P1aDxwCLcBGAsYHQ/s573/malyutka%2Bflight%2Bspeed.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="349" data-original-width="573" src="https://1.bp.blogspot.com/-cVhm7EFOWOE/YOMo9AKJFaI/AAAAAAAATvA/IAg3fXmyyn4OjMt9AT_V-fGJIX-P1aDxwCLcBGAsYHQ/s16000/malyutka%2Bflight%2Bspeed.png" /></a></div><p>The concept of having surplus thrust is applied in most ATGMs. As a point of comparison, the Cobra accelerates to 80 m/s in 0.4 seconds, whereupon the sustainer engine is activated, slowly accelerating the missile with a small surplus of thrust until the missile reaches a cruising velocity of 95 m/s at 1 km. As for the Mamba, its booster takes it to 55 m/s, and the sustainer accelerates the missile intensely to a peak of 140 m/s at 2 km, the maximum range of the system. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-amDfdMQgmKs/YMKMqTJLiBI/AAAAAAAATZY/2cxH9Irl4FIkSKLqwzPl54QLqZiXZQw1QCLcBGAsYHQ/s1708/flight%2Bvelocity%2Band%2Btime%2Bgraph.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="773" data-original-width="1708" height="290" src="https://1.bp.blogspot.com/-amDfdMQgmKs/YMKMqTJLiBI/AAAAAAAATZY/2cxH9Irl4FIkSKLqwzPl54QLqZiXZQw1QCLcBGAsYHQ/w640-h290/flight%2Bvelocity%2Band%2Btime%2Bgraph.png" width="640" /></a></div><p><br /></p><p>With a maximum range of 3,000 meters, the "Malyutka" reached an outstanding level of performance for a missile of its size, particularly in 1963. It surpassed all foreign counterparts in this regard, even matching the range of heavy ATGMs such as the SS.11 and the TOW. More importantly, this specific maximum range figure is tactically meaningful, as it would have allowed the missile operator to engage the vast majority of targets he was likely to encounter in Western Europe. According to the book "<i>Armements Antichars Missiles Guidés Et Non Guidés</i>" by COMHART, a French general study of the most likely battle sites in Western Europe revealed a clear predominance of valleys, with peak-to-peak distances of around 3,000 meters. This influenced a desired within the French military for ATGMs with a 3,000-meter maximum range, though this was not achieved in the MILAN.</p><p>The 9M14 and 9M14M takes 25 seconds to reach its maximum range of 3,000 meters, giving it an average velocity of 120 m/s, which is excellent for a man-portable missile. With the 9M14P, the flight time rose to 26 seconds on account of its greater weight, degrading its average velocity slightly to 115 m/s.</p><p>For example, the book "<i>Armements Antichars Missiles Guidés Et Non Guidés</i>" states that the ENTAC missile had an average flight velocity of 85 m/s and required 23 seconds to travel to its maximum range of 2,000 meters, while the U.S Army field manual FM 23-6 states that the ENTAC has an average flight velocity of 80 m/s and it required 25 seconds to reach 2,000 meters, even including a <a href="https://i.imgur.com/oBmqPmw.png">flight time-distance table</a> on page 64.</p><p><br /></p><p><a href="https://www.blogger.com/null" id="malyutkasteering"></a></p><h3 style="text-align: left;"><span style="font-size: large;">STEERING</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--uyMvPcRCnc/YNuwiLGjJnI/AAAAAAAATog/nuYPouSo404FTaGGzPDMK4ng_PHDjprlwCLcBGAsYHQ/s2035/steering%2Bmechanism%2B1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1581" data-original-width="2035" height="311" src="https://1.bp.blogspot.com/--uyMvPcRCnc/YNuwiLGjJnI/AAAAAAAATog/nuYPouSo404FTaGGzPDMK4ng_PHDjprlwCLcBGAsYHQ/w400-h311/steering%2Bmechanism%2B1.png" width="400" /></a><a href="https://1.bp.blogspot.com/-6LO2mqFvUfc/YMNJLtFe0zI/AAAAAAAATZk/Kop7p08Nepwjnk_JHHwl6LTaCjCqDk1PwCLcBGAsYHQ/s830/malyutka%2BTVC%2Bactuator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="792" data-original-width="830" src="https://1.bp.blogspot.com/-6LO2mqFvUfc/YMNJLtFe0zI/AAAAAAAATZk/Kop7p08Nepwjnk_JHHwl6LTaCjCqDk1PwCLcBGAsYHQ/s320/malyutka%2BTVC%2Bactuator.png" width="320" /></a><br /><br /></div><p>To steer, the "Malyutka" series of missiles features a thrust vector control (TVC) nozzle mechanism utilizing a hinged nozzle. The use of TVC was a suitable solution for a missile of its class, as the fairly modest speed of the "Malyutka" - relative to the second generation missiles that succeeded it - makes thrust vectoring an inherently more efficient method as compared to aerodynamic control surfaces, which would have to be of a large size to generate similar steering forces. The thrust vectoring nozzles are actuated using a gas drive, with gas supplied by the rocket engine itself via a bleeder port. An electromagnetic valve is used to control the gasses from the rocket engine. This solution fills the need for high actuator torque to move the nozzles without incurring penalties in power consumption, and it was specifically the triviality of the power requirements that was the instrumental factor allowing the missile to omit an onboard power source. The photo below, from "<a href="https://archive.kippur-center.org/idf-archive-files/1975-383-122.pdf?fbclid=IwAR1I0YdohSCoob-4KUEgzpbC0yHt3Cp3x3auX-_C9g5-xpqexk8OCLyELa0">Report no. 28, Armor Corps Conclusions Team</a>", shows the tail of a "Malyutka" missile with its gyroscope compartment removed, revealing the rear end of the steering system.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgu0CoLFH65DKuRhhbGATRLwSDdiJsV09hUx7OG8ZnrU2uwyvni8V75BNcJo6-oxVg4DCoCvbwMdr6HwPI1RDmkhUVogsx8u6PVAZIZat7iTKKiWOh62uGgYA9QP2V1T9A6oE0naCzeyU74lDfbhgHIRugPaj8lHDZ4WykVT3el77j4U_rp-9fHkeXO5g=s2156" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1588" data-original-width="2156" height="295" src="https://blogger.googleusercontent.com/img/a/AVvXsEgu0CoLFH65DKuRhhbGATRLwSDdiJsV09hUx7OG8ZnrU2uwyvni8V75BNcJo6-oxVg4DCoCvbwMdr6HwPI1RDmkhUVogsx8u6PVAZIZat7iTKKiWOh62uGgYA9QP2V1T9A6oE0naCzeyU74lDfbhgHIRugPaj8lHDZ4WykVT3el77j4U_rp-9fHkeXO5g=w400-h295" width="400" /></a></div><p>The electromagnetic valve is a two-way solenoid, consisting of one valve armature with two opposing electromagnet coils. In terms of its design and construction, the simplicity of the valve system is on par with the steering spoilers used in the 3M6, the Cobra, and the French family of first generation ATGMs. The solenoid of the steering nozzles receive the amplified signal from the gyroscope potentiometer, with a voltage of 90 V.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-YbqZvEti-Qs/YOdDoCFf5mI/AAAAAAAATyQ/ClaXXhKp2ZcNs-kaJ5vSMt2eoteo3WjIACLcBGAsYHQ/s1962/solenoid%2Bvalve.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1372" data-original-width="1962" height="280" src="https://1.bp.blogspot.com/-YbqZvEti-Qs/YOdDoCFf5mI/AAAAAAAATyQ/ClaXXhKp2ZcNs-kaJ5vSMt2eoteo3WjIACLcBGAsYHQ/w400-h280/solenoid%2Bvalve.png" width="400" /></a></div><p>The mechanism is compact, lightweight, has a low power consumption, and is simple in both its construction and operating principle. Compared to a jet tab, the power demands are essentially the same - a pair of electromagnets is used in both, acting as solenoids. The mechanism is, however, larger and heavier than a jet tab. Comparing it to the bulky jetavator mechanism of the Swingfire, the hinged nozzle of the "Malyutka" is evidently lighter and far more compact, even in relative terms. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-v0x7crQj74M/YNw7n6BWReI/AAAAAAAATqY/M6SIspe_kS872LFVteJCFRb1LKDBopB8gCLcBGAsYHQ/s2558/swingfire%2Bjetavator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1230" data-original-width="2558" height="193" src="https://1.bp.blogspot.com/-v0x7crQj74M/YNw7n6BWReI/AAAAAAAATqY/M6SIspe_kS872LFVteJCFRb1LKDBopB8gCLcBGAsYHQ/w400-h193/swingfire%2Bjetavator.png" width="400" /></a></div><p>The 9Kh113M retarder provides the necessary time delay in pressurizing the steering mechanism after the sustainer engine is started. Its purpose is to eliminate unacceptable deflections within the launch trajectory, before the control panel has completed its launch program and relinquished control to the operator. Within 0.45-0.9 seconds after the ignition signal is delivered to the sustainer engine, the regulator burns out and propellant gasses begin to flow into the steering mechanism, pressurizing it to its operating pressure of 15-25 kg/sq.cm.</p><p><br /></p><p>The steering system has a bang-bang control scheme. The nozzles have two positions - on and off. When no steering commands are made, the left solenoid is energized and keeps the valve in the flight position. Once a steering command is made, the amplified control signal arrives to the right solenoid, and the two nozzle nozzles are simultaneously deflected at an angle of 14 degrees in either direction from the longitudinal axis of the missile fuselage. The vectoring system operates at 16 Hz, which is to say that there are two steering impulses generated each second, or two impulses per missile rotation (8.5 RPS). The delay between the reception of the control signal and the actuation of the jet nozzles by their servomotors is 11-16 milliseconds, or 0.011-0.016 seconds. For comparison, the actuation delay for the Vickers Vigilant is 0.4 seconds.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9TLeFbBMA_s/YNoKkCTyHZI/AAAAAAAATl8/1i0z4xAN8ekz23d8ioIBE6szTnLOkHqUACLcBGAsYHQ/s893/sustainer%2Bnozzle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="524" data-original-width="893" height="235" src="https://1.bp.blogspot.com/-9TLeFbBMA_s/YNoKkCTyHZI/AAAAAAAATl8/1i0z4xAN8ekz23d8ioIBE6szTnLOkHqUACLcBGAsYHQ/w400-h235/sustainer%2Bnozzle.png" width="400" /></a></div><p><br /></p><p>As discussed earlier, the rocket engine burn rate varies with the temperature, and therefore energy, of its fuel. The resultant variance in thrust also affects the steering intensity of the TVC system, as the lateral thrust is also higher. </p><p>To steer the missile upwards, it is necessary to also aim the engine nozzles upwards. This is because the thrust from the nozzles must be used as a steering moment to pivot the missile about its center of gravity. When the nozzles are aimed upwards, the resultant torque acting from behind the missile center of gravity causes the nose of the missile to pitch up, as shown in the drawing below. The center of gravity of the missile is marked by the label (Цт). </p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-YuHnt4gVHFo/YNotp3E9nEI/AAAAAAAATnY/GVl8QmBGB3IE229oPCZArgaBbfy5wUheQCLcBGAsYHQ/s1608/force%2Bdiagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1360" data-original-width="1608" height="339" src="https://1.bp.blogspot.com/-YuHnt4gVHFo/YNotp3E9nEI/AAAAAAAATnY/GVl8QmBGB3IE229oPCZArgaBbfy5wUheQCLcBGAsYHQ/w400-h339/force%2Bdiagram.png" width="400" /></a></p><p style="text-align: left;">Because the steering system is a single-axis system, the nozzle will be deflected in one direction over the span of a 180-degree turn, and the resulting "sweep" generates a net steering force in the desired direction. For example, the image on the left below shows how the missile makes a right turn. Once the nozzles are in the 12 o'clock position, they are deflected to the right relative to the missile. Because the missile is currently upside down (the dotted line shows the orientation of the missile), the nozzles are therefore deflected upwards. As the missile rotates clockwise by 180 degrees during its flight, the nozzles "sweep" a 180-degree arc to the right, generating a progressively variable pitch-up and yaw-right moment, followed by a pitch-down and yaw-right moment. The opposing pitching moments result in a net zero pitching moment, leaving only the yaw moment, thus steering the missile to the right. However, the initial pitching is not completely unfelt, as it will impart a spiralling trajectory to the missile. The image on the right below shows how a diagonal right-up turn is made. The command signal is identical, but phase shifted by 90 degrees (φ).</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-8D8BmoXfkKg/YPKRa7mUtII/AAAAAAAAT9Y/rpWbZPi5x7k6gwTUfA6lnLdqnyBqQ90TwCLcBGAsYHQ/s1265/example%2B2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1265" data-original-width="1249" height="320" src="https://1.bp.blogspot.com/-8D8BmoXfkKg/YPKRa7mUtII/AAAAAAAAT9Y/rpWbZPi5x7k6gwTUfA6lnLdqnyBqQ90TwCLcBGAsYHQ/s320/example%2B2.png" /></a><a href="https://1.bp.blogspot.com/-lxhXiLZHob8/YPKRbBtP5qI/AAAAAAAAT9c/QxeHSMujdk8T9rmSf9bomxr3h9AFwpq-QCLcBGAsYHQ/s1387/example%2B3.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1071" data-original-width="1387" height="309" src="https://1.bp.blogspot.com/-lxhXiLZHob8/YPKRbBtP5qI/AAAAAAAAT9c/QxeHSMujdk8T9rmSf9bomxr3h9AFwpq-QCLcBGAsYHQ/w400-h309/example%2B3.png" width="400" /></a></div><p style="text-align: left;">The phase shifting is applied to the command signal by the operator's control panel. The return signal that arrives to the control panel from the missile is a feedback signal, which is generated by the polarity reversal from the commutator of the gyro-coordinator. To illustrate how this functions, an example is given in a 9M14M technical manual where the maximum command "up" command is inputted on the control joystick and the response of the control system is detailed in four steps, iterating through the four 90-degree turns made by the missile. Firstly, when the operator pushes the control joystick away from himself to its maximum deflection angle, the maximum "Up" command will be formed in the summing amplifier, and a voltage with a positive polarity will travel down the wire link and its current will flow through the EM2 electromagnet coil (right coil). When the current enters the EM2 coil, the vertically arranged nozzles will be switched from right to left relative to the fixed axis defined by the gyroscope. The aims the nozzles upwards, producing the desired steering effect.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Ba-06YTbnIk/YNvRbD3CdBI/AAAAAAAATpY/Fv7C2GFNhFcFJFtcGeOBtbzEMP4juiVsQCLcBGAsYHQ/s2855/zero%2Bposition.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1101" data-original-width="2855" height="246" src="https://1.bp.blogspot.com/-Ba-06YTbnIk/YNvRbD3CdBI/AAAAAAAATpY/Fv7C2GFNhFcFJFtcGeOBtbzEMP4juiVsQCLcBGAsYHQ/w640-h246/zero%2Bposition.png" width="640" /></a></div><p>When the projectile is rotated by 90 degrees during its flight, the control panel will receive a feedback signal indicating "Position to the right", so the control panel will not change the control signal. The current in the control circuit will continue to flow in the same direction, so the nozzles will continue to be rotated at its present position.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-eSSTbkjDrsE/YNoV5bsgprI/AAAAAAAATmc/LiIYMMqO_poz3TfETAs7gTXr48th9fjYwCLcBGAsYHQ/s2048/expanded%2Bcircuit%2Bdiagram%2B1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1189" data-original-width="2048" height="372" src="https://1.bp.blogspot.com/-eSSTbkjDrsE/YNoV5bsgprI/AAAAAAAATmc/LiIYMMqO_poz3TfETAs7gTXr48th9fjYwCLcBGAsYHQ/w640-h372/expanded%2Bcircuit%2Bdiagram%2B1.png" width="640" /></a></div><p style="text-align: left;">When the missile is rotated 180 degrees, the control panel will receive a "down position" feedback signal. This signal from the gyroscope commutator, combined with the "up" command signal, will cause a change in the polarity in the control circuit. The current will flow in the opposite direction through the EM1 coil. This triggers the steering mechanism to snap the nozzles from the right position to the left position. Because the missile itself has reversed its roll orientation, reversing the deflection direction of the nozzles returns it to the same direction as when it started.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-vF9JvBt5QrI/YNoV5ZjgI6I/AAAAAAAATmY/4t3HYZRiQ8I2JKJuIKDR3b-4ylq60vzsgCLcBGAsYHQ/s2658/expanded%2Bcircuit%2Bdiagram%2B2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1183" data-original-width="2658" height="284" src="https://1.bp.blogspot.com/-vF9JvBt5QrI/YNoV5ZjgI6I/AAAAAAAATmY/4t3HYZRiQ8I2JKJuIKDR3b-4ylq60vzsgCLcBGAsYHQ/w640-h284/expanded%2Bcircuit%2Bdiagram%2B2.png" width="640" /></a></div><p>When the missile is rotated by 270 degrees, the control panel will receive a feedback signal "left position". The control panel will not change the control signal when the command "up" is given if it has received the "left position" feedback signal, and the current in the control circuit will continue to flow in the same direction and the nozzles will not change their position.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-dhJP_UylUXU/YNoV5RxdqqI/AAAAAAAATmU/FNqr_1KZbGAyTJSB-TMuJHU8G_UpYzAsACLcBGAsYHQ/s2048/expanded%2Bcircuit%2Bdiagram%2B3.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1195" data-original-width="2048" height="374" src="https://1.bp.blogspot.com/-dhJP_UylUXU/YNoV5RxdqqI/AAAAAAAATmU/FNqr_1KZbGAyTJSB-TMuJHU8G_UpYzAsACLcBGAsYHQ/w640-h374/expanded%2Bcircuit%2Bdiagram%2B3.png" width="640" /></a></div><p style="text-align: left;">When completing the turn of 360 degrees, the projectile is in its original position once again, so the nozzles must be reversed from the left position to the right position. From here, the nozzle switching cycle will be repeated as long as the maximum "up" command continues to be received from the control handle.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-f97UBx6QMpk/YN0kUu_Rk6I/AAAAAAAATqg/VeEeKjjXA2AiK7Of1SYjXuPBaV2bUyyMgCLcBGAsYHQ/s703/moving%2Bdeflector.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="512" data-original-width="703" src="https://1.bp.blogspot.com/-f97UBx6QMpk/YN0kUu_Rk6I/AAAAAAAATqg/VeEeKjjXA2AiK7Of1SYjXuPBaV2bUyyMgCLcBGAsYHQ/s320/moving%2Bdeflector.png" width="320" /></a><br /></div><p><br /></p><p>A rocket nozzle is subject to a few different losses. According to the report "<a href="https://www.diva-portal.org/smash/get/diva2:7328/FULLTEXT01.pdf">Flow Processes In Rocket Engine Nozzles With Focus On Flow Separation and Side-Loads</a>", rocket nozzle loss mechanisms fall into three categories: </p><p></p><ul style="text-align: left;"><li>Geometric or divergence losses</li><li>Viscous effects losses</li><li>Chemical kinetic losses</li></ul><p></p><p>Assuming that chemical kinetic losses are equal for a given rocket engine using a specific fuel, the main source of losses from a thrust vectoring system are divergence losses and viscous effects losses. The use of moving nozzles, as opposed to jet deflector vanes, jet tabs or secondary fluid jets, is more efficient from a thrust loss standpoint because it preserves axial flow and does not induce flow instabilities in the jet, which falls under the category of viscous effects. The table below, from Chapter 16 of the aeronautical engineering textbook "<a href="http://mae-nas.eng.usu.edu/MAE_5540_Web/propulsion_systems/subpages/Rocket_Propulsion_Elements.pdf">Rocket Propulsion Elements (Seventh Edition)</a>" by George P. Sutton and Oscar Biblarz, shows the relative merits and demerits of various thrust vector control mechanisms for rockets.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-1KcOvgkFRYU/YNn7uECPbKI/AAAAAAAATls/Y590GFh2rekrSiVKQCKIPmco4bTj_0mSwCLcBGAsYHQ/s2048/different%2Bforms%2Bof%2Btvc.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1509" height="640" src="https://1.bp.blogspot.com/-1KcOvgkFRYU/YNn7uECPbKI/AAAAAAAATls/Y590GFh2rekrSiVKQCKIPmco4bTj_0mSwCLcBGAsYHQ/w472-h640/different%2Bforms%2Bof%2Btvc.png" width="472" /></a></div><p>It must be noted that "gimbal or hinge" in this case does not refer to gimballing or hinging the nozzle, but the entire rocket engine. The specific type of TVC nozzle used in the "Malyutka" is a hinged movable nozzle, which does not match the description of either type listed in the table. The typical disadvantages listed for conventional examples of this class of mechanism, including issues such as a high actuation forces, and variable actuation forces, were specifically solved by the use of a gas bleedoff from the rocket engine to supply the actuation force, and a bang-bang control scheme to ensure predictability. Compared to other thrust vectoring methods used in ATGMs, such as jetavators (Swingfire) and jet tabs (SS.11, MILAN, HOT), the hinged movable nozzle solution is a particularly efficient one. In the study "<a href="https://www.researchgate.net/publication/291680304_Side_Force_Determination_in_the_Rocket_Motor_Thrust_Vector_Control_System">Side Force Determination in the Rocket Motor Thrust Vector Control System</a>", it is concluded from a semi-empirical analysis of a sample "Malyutka" nozzle that:</p><p></p><blockquote>The calculation showed a very high efficiency of the Maljutka TVC system with the dome deflector [nozzle]. The degree of its efficiency is estimated at about η ≈ 0.95 . There is a very close agreement with the measured thrust values during the dynamic flight tests of the modernized Maljutka rocket.</blockquote><p></p><p>With η being a measure of how efficiently axial thrust is converted into lateral thrust. With a TVC system efficiency of ~0.95, the hinged nozzle of the "Malyutka" is probably the most thrust-efficient TVC design used in any ATGM. This is not a trivial factor, because over the 25-second flight of the missile to its maximum range, multiple steering corrections are needed even when engaging a static target. Against a moving target, the issue is particularly important. Minimizing the thrust losses ensures that the missile does not decelerate excessively by the time it reaches its target or before, which would compromise the hit probability and penetration performance, as reduced velocities require an increased angle of attack.</p><p>The images below, taken from the study, shows the nozzle (left), and the nature of the jet flow in the nozzle of a "Malyutka" missile (right), when the thrust vectoring system is activated.</p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-0pOASxH9j1c/YNn3lrAmLfI/AAAAAAAATlk/ZGlDerrzWQEmyD0eIFlULcfGQA4UlDjGACLcBGAsYHQ/s1829/malyutka%2Bnozzle%2Brender.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1478" data-original-width="1829" height="324" src="https://1.bp.blogspot.com/-0pOASxH9j1c/YNn3lrAmLfI/AAAAAAAATlk/ZGlDerrzWQEmyD0eIFlULcfGQA4UlDjGACLcBGAsYHQ/w400-h324/malyutka%2Bnozzle%2Brender.png" width="400" /></a><a href="https://1.bp.blogspot.com/-cjfjXE5a9KM/YNnsRoN3RsI/AAAAAAAATlc/g73nuGHiizM0DsFoVl8JQtMliI9X2FpgQCLcBGAsYHQ/s1943/malyutka%2Bnozzle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1488" data-original-width="1943" height="306" src="https://1.bp.blogspot.com/-cjfjXE5a9KM/YNnsRoN3RsI/AAAAAAAATlc/g73nuGHiizM0DsFoVl8JQtMliI9X2FpgQCLcBGAsYHQ/w400-h306/malyutka%2Bnozzle.png" width="400" /></a></div></div><br /><p>Other methods of redirecting the thrust vector rely on inducing flow divergence to generate asymmetric thrust, but flow divergences lead to a loss of thrust. This is normally due to the turbulent flow and scattering of the jet. For instance, the thrust vectoring nozzle of the MILAN and HOT missiles functions chiefly by introducing a phenomenon known as boundary layer separation in the jet flow. This was achieved by introducing a tab into the jet stream. In the sustainer phase (right), only the tab induces a bow shockwave in the stream, because the jet plume is too narrow to touch the second deflector tab. When the engine is in the boost phase (left), the larger jet plume means that the tab generates two shockwaves - an oblique shock on the boundary layer between the stream and the tab, and a bow shock between the stream and a fixed second deflector tab in the opposite direction, reducing the steering effect to the same level as in the sustainer phase. The effect of the shockwave is to cause boundary layer separation in the jet flow, and thus introduce a lateral load, an off-center thrust vector, which steers the missile. The images below, taken from the book "<i>Armements Antichars Missiles Guidés Et Non Guidés</i>", shows the shape of the flow from a MILAN rocket nozzle.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-3onmZEP3wEM/YNnmq8Xj3HI/AAAAAAAATlQ/AkPNM8xd54gYEmsRgaB7ruJpuWKabr7SgCLcBGAsYHQ/s1080/TVC%2Bbooster.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="746" data-original-width="1080" src="https://1.bp.blogspot.com/-3onmZEP3wEM/YNnmq8Xj3HI/AAAAAAAATlQ/AkPNM8xd54gYEmsRgaB7ruJpuWKabr7SgCLcBGAsYHQ/s320/TVC%2Bbooster.png" width="320" /></a><a href="https://1.bp.blogspot.com/-kcWDI2ZZhhA/YNnmq33xnAI/AAAAAAAATlM/xbG11MDWppkIwBLhi5WLoDy_csu5WwuBwCLcBGAsYHQ/s1092/TVC%2Bsustainer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="801" data-original-width="1092" src="https://1.bp.blogspot.com/-kcWDI2ZZhhA/YNnmq33xnAI/AAAAAAAATlM/xbG11MDWppkIwBLhi5WLoDy_csu5WwuBwCLcBGAsYHQ/s320/TVC%2Bsustainer.png" width="320" /></a></div><p><br /></p></div><p>Owing to the quick launch velocity and the lofted trajectory of the missile in its initial stage of flight, the minimum range was quite substantial, as with all other contemporary MCLOS missiles. The closest practical distance for hitting a tank-sized target at ground level is 400 meters. However, a minimum range of 500 meters, as listed in various manuals and other documents, is necessary to ensure the nominal hit probability of 90% is achieved. Due to the introduction of an automated guidance system beginning with the 9P122 missile carrier, with automatic optical infrared capture of the missile, the 9M14P missile was considered to have a minimum range of 400 meters.</p><p>The 500-meter minimum range given in the official tactical-technical characteristics can be achieved with the infantry-portable systems only when the launchers are aligned with the target within an arc of 11.52 degrees (±96 Soviet mils), equal to a firing zone width of just 100 meters. In the initial phase of the missile flight (500 - 700 meters), it is advisable to control the guidance with the naked eye, since the missile can leave the field of view of the sight when using high magnification optics. The viability of hitting a crossing target within this zone is dependent on the operator taking the time to mark out the borders of the engagement zone with landmarks using the azimuth scale of his rotating sight, and then firing the missile at an opportune moment once the target has entered the zone. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-XsHqTqTRylU/YKPHolr_ZPI/AAAAAAAATAw/towIflJBq3kIV0UvGj8pp0jRFqwztrmnACLcBGAsYHQ/s2048/operational%2Bzone.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1275" height="400" src="https://1.bp.blogspot.com/-XsHqTqTRylU/YKPHolr_ZPI/AAAAAAAATAw/towIflJBq3kIV0UvGj8pp0jRFqwztrmnACLcBGAsYHQ/w249-h400/operational%2Bzone.png" width="249" /></a></div><p>The entire engagement zone shown in the manuals for both man-portable and vehicle-borne systems represent the zone where the nominal hit probability can be achieved. The missile can be steered outside the given zone, but the minimum range increases and the hit probability degrades because the operator becomes occupied with changing the trajectory of the missile, and has less time to apply the three-point guidance technique methodically. Instead of making wide turns with the missile to engage targets in a wider arc, which was necessary with the earlier 3M6 "Shmel" ATGM due to the limited firing arcs of the 2P26 and 2P27, the "Malyutka" family of tank destroyers were fitted with panoramic sights and synchronized launchers, allowing direct firing trajectories within a very wide engagement arc. </p><p>The minimum range of 500 meters can be achieved at any point of the fring arc of a 9P122 tank destroyer, as the launcher and sight are both rotatable. This is shown in the drawing below, taken from the article "<i>Тяжелый путь к легкой ракете</i>" published in the March 2019 edition of the "<i>Техника и вооружение</i>" magazine.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-uWJt3vrcu8Y/YKOyPWcUCZI/AAAAAAAATAc/Wtux8zhsqlsQzNgaspvpzql_hNA3c_Z4gCLcBGAsYHQ/s2048/malyutka%2Bfiring%2Barc%2B9p122%2Bfull%2Barc.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1336" data-original-width="2048" height="261" src="https://1.bp.blogspot.com/-uWJt3vrcu8Y/YKOyPWcUCZI/AAAAAAAATAc/Wtux8zhsqlsQzNgaspvpzql_hNA3c_Z4gCLcBGAsYHQ/w400-h261/malyutka%2Bfiring%2Barc%2B9p122%2Bfull%2Barc.png" width="400" /></a></div><p>If a minimum range of 500 meters is obligatory when firing "Malyutka" remotely from a dismounted control station, the maximum engagement arc at 500 meters is 43.68 degrees. The minimum range progressively increases if the required engagement arc is expanded to 75 degrees, which would also require the launcher to be rotated 15 degrees to one side. The engagement arc shrinks if the 500-meter minimum range is maintaned because of the horizontal offset between the operator and the launcher, which makes it more difficult for the operator to visually acquire the missile during launch. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-oIdgODVj4s8/YKOyxtv3ypI/AAAAAAAATAo/0KVNaOZ7dUEz4ytK75lGf7qKX23D3GeZQCLcBGAsYHQ/s2048/malyutka%2Bfiring%2Barc%2B9p122%2Bremote.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1691" data-original-width="2048" height="330" src="https://1.bp.blogspot.com/-oIdgODVj4s8/YKOyxtv3ypI/AAAAAAAATAo/0KVNaOZ7dUEz4ytK75lGf7qKX23D3GeZQCLcBGAsYHQ/w400-h330/malyutka%2Bfiring%2Barc%2B9p122%2Bremote.png" width="400" /></a></div><p>When firing a "Malyutka" remotely from a dismounted control station with a less demanding minimum range of 1,000 meters, the engagement arc is greatly expanded to 135 degrees. This is achieved with launcher rotation of up to 45 degrees on each side.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-gT70U-n2yXM/YKOyau6qlNI/AAAAAAAATAg/hxABpEY4ewA6f-shzCZTQbQPDGPhuQiQQCLcBGAsYHQ/s2048/malyutka%2Bfiring%2Barc%2B9p122.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1435" data-original-width="2048" height="280" src="https://1.bp.blogspot.com/-gT70U-n2yXM/YKOyau6qlNI/AAAAAAAATAg/hxABpEY4ewA6f-shzCZTQbQPDGPhuQiQQCLcBGAsYHQ/w400-h280/malyutka%2Bfiring%2Barc%2B9p122.png" width="400" /></a></div><p>If portable launching stations are to be used from missile tank destroyers against distant targets, it is naturally quite likely that some preparations are also made to have the vehicles located in a full defilade, to launch the missiles over terrain features with the operator lying on an elevated vantage point. The nature of such anti-tank defences ameliorates the extension of the minimum range, particularly if the vehicles are deployed as the last echelon in a layered defence. </p><p>The use of a rotating launcher effectively eliminated the engagement arc issues of first generation ATGMs when fired and guided from under armour in a fixed position, and helped increase the engagement arc when firing remotely from a dismounted station. With examples such as the Raketenjagdpanzer and the various Soviet ATGM carriers, rotating launchers became the international standard in the 1960's, not only for conventional MCLOS missiles, but also for vehicles armed with the Swingfire, which implemented a unique low-velocity launch method to permit missile reorientation in mid-air before accelerating to a high velocity after a predetermined delay. This was necessary to achieve a wide engagement arc for the fixed launchers of the aborted man-portable Swingfire proposal and for the FV102 Striker (1972) tank destroyer as that had horizontally fixed launchers, but was redundant on the FV438 Swingfire (1972) as it had a rotating launcher turret, as did the modified Ferret Swingfire in 1968 for the airborne forces.</p><p><br /><a href="https://www.blogger.com/null" id="malyutkawarhead"></a></p><h3 style="text-align: left;"><span style="font-size: large;">WARHEAD</span></h3><p>The warhead is a separate module that is affixed to the fuselage via a locking ring which engages with internal tabs. It would only be attached during the preparation for firing in the case of the man-pack 9K11 missile system, but otherwise, the missiles were stowed in their assembled form in various Malyutka tank destroyers such as on the 9P110, 9P122, Mi-2 helicopters, and the BMP-1. The ability to dismantle the missile was an important man-portability factor, but the external lever for the locking ring is a source of parasitic drag. Such a feature was only acceptable on the 9M14 because, like most other first generation ATGMs, its velocity was low enough that the increase to total drag was within permissible levels. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xjrJgN6s4fA/YNuy0vPaOxI/AAAAAAAAToo/V5OF68q8B7kJJLrVx3AdiSDYC_PzYACdACLcBGAsYHQ/s1765/9m14p%2Bwarhead%2Bslot.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1003" data-original-width="1765" height="228" src="https://1.bp.blogspot.com/-xjrJgN6s4fA/YNuy0vPaOxI/AAAAAAAAToo/V5OF68q8B7kJJLrVx3AdiSDYC_PzYACdACLcBGAsYHQ/w400-h228/9m14p%2Bwarhead%2Bslot.png" width="400" /></a></div><p><br /></p><p>The three warheads developed for the "Malyutka" were used in the following missiles:</p><p></p><ul style="text-align: left;"><li><b>9N110</b> - 9M14</li><li><b>9N110M</b> - 9M14M, 9M14P (optional)</li><li><b>9N110M1</b> - 9M14P (standard</li><li><b>9N110M2</b> - 9M14P1</li></ul><p></p><p>The casing of all warheads used from the original 9M14 up to the 9M14P1, is fiberglass. Needless to say, the fragmentation effect is close to nil. The blast of the explosive filler is the main destructive element against light field fortifications while the shaped charge jet causes the bulk of the damage.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-pxG-r57F8MY/YLf84s7zgSI/AAAAAAAATSg/L5StL7npF7oWmGMl2MoUcX19fjw9TxJOQCLcBGAsYHQ/s2048/9n110m%2Bfuzing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1502" data-original-width="2048" height="294" src="https://1.bp.blogspot.com/-pxG-r57F8MY/YLf84s7zgSI/AAAAAAAATSg/L5StL7npF7oWmGMl2MoUcX19fjw9TxJOQCLcBGAsYHQ/w400-h294/9n110m%2Bfuzing.png" width="400" /></a></div><p>The 9N110 and 9N110M warheads are equipped with the 9E212 point-initiating, base-detonating (PI-BD) piezoelectric fuze. Even though the "Malyutka" has a conventional conical nose with a protruding tip, resembling a stereotypical tank-fired HEAT shell with a piezoelectric element in the tip, the piezoelectric elements of the 9E212 warhead are actually located around the rim of the nose fairing, like the "Falanga" series. Sixteen piezoelectric elements are arranged in a ring. The tip of the nose itself is hollow, with a central passage so as to not interfere with the shaped charge jet in any way, as a conventional nose fuze would, albeit only to a minor extent.</p><p>A layer of silver is applied to the inner surface of the fiberglass shaped charge warhead casing, creating a conductive layer which allows an electrical circuit to form between the piezoelectric elements and the base detonator. Within this circuit, the piezoelectric element serves as the power source. On its front end, a steel contact connects its positive terminal to the copper shaped charge liner, which connects to the base detonator via a spring-loaded contact probe at its apex. On its rear end, the element is connected to the silvered surface of the warhead casing, leading to a second contact on the base detonator. </p><p>When the nose of the warhead strikes a hard obstacle, the impact generates a compression wave in the material, which travels at the sound speed of the fiberglass until it reaches the piezoelectric element. The element converts the stress of the shockwave to a voltage, initiating the base detonator and detonating the warhead. An impact of sufficient violence is needed, or the current from the piezoelectric elements will not be enough to detonate the warhead. This prevents undesirable detonations when the missile strikes soft obstacles such as leaves, thin branches, heavy rain droplets, and so on. Because of this arrangement, the "Malyutka" fuzes on grazing impacts, and is immune to simple anti-RPG measures such as slat armour, fence armour, and other structures designed to crush the fuze of an RPG-7 grenade. One source states that the functioning limit of the fuze on angled surfaces is 73 degrees.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Clr4xtVFEM4/YNu8aeA9xQI/AAAAAAAATow/sFP15jtcwhsI-7-GAUo4NxeatrcuJeLHwCLcBGAsYHQ/s2048/9e212%2Bfuze%2Bbase%2Bdetonator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1237" data-original-width="2048" height="241" src="https://1.bp.blogspot.com/-Clr4xtVFEM4/YNu8aeA9xQI/AAAAAAAATow/sFP15jtcwhsI-7-GAUo4NxeatrcuJeLHwCLcBGAsYHQ/w400-h241/9e212%2Bfuze%2Bbase%2Bdetonator.png" width="400" /></a></div><p>After launch, the fuze is armed by a pyrotechnic delay mechanism at a distance of between 70 to 200 meters, giving the "Malyutka" a technical minimum range of 200 meters. The safety mechanism keeps the piezoelectric system short-circuited and connects the detonator to the circuit. During launch, an arming signal is transmitted to the base detonator via a wire contact. This signal ignites the pyrotechnic delay charge, which burns out at some point while the missile is airborne, at no less than 70 meters and no more than 200 meters - pyrotechnic delay mechanisms generally have limited consistency. The charge then initiates a small explosive squib which shifts a spark detonator into position behind the booster charge, and removes the short circuit of the piezoelectric circuit. The warhead is thereby armed.</p><p>The warhead section weighs 2.6 kg in total, inclusive of the fuze and the shaped charge warhead itself. The shaped charge itself features a copper shaped charge liner, a wave shaper made of solid polystyrene, and a filler of A-IX-1 weighing 2.2 kg. The 9M14 missile, with the 9N110 warhead, is officially rated for a penetration of 200mm RHA at 60 degrees in the tactical-technical characteristics. The 9M14, and all of the subsequent models, could easily pierce the thickest armour on any NATO main battle tank at the time each of them entered service. </p><p>A-IX-1 has a detonation velocity of 8.24 km/s, much higher than Composition B, and almost as high as deeply phlegmatized HMX compositions such as the various Octol formulas used in the French military. </p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">9N110M</span></h3><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-tlcpk8WG1j8/YLf9MudYtmI/AAAAAAAATSs/xBVmGwdZ0kINuk4zstEXzSdRd_ppY45agCLcBGAsYHQ/s2695/9n110m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1081" data-original-width="2695" height="160" src="https://1.bp.blogspot.com/-tlcpk8WG1j8/YLf9MudYtmI/AAAAAAAATSs/xBVmGwdZ0kINuk4zstEXzSdRd_ppY45agCLcBGAsYHQ/w400-h160/9n110m.png" width="400" /></a></p><p>With the newer 9M14M and 9M14P models, the upgraded 9N110M warhead was installed. It still contains an A-IX-1 filler. The changes introduced in the 9N110M are somewhat unclear.</p><p>Officially, the 9N110M is rated for a penetration of 230mm RHA at 60 degrees. Other data, such as its average and maximum penetration, is not known. Its penetration power in reinforced concrete is 1,000mm. In pure concrete, the penetration power is 1,500mm. When attacking bunkers and other hardened buildings, the 9M14M and 9M14P can be considered capable of achieving up to 1,500mm of penetration if there is no rebar in the path of the jet.</p><p>As an indicator of its design sophistication, the ability of the 9M14M to penetrate a LOS thickness of 460mm of RHA steel meant that the missile already surpassed the American BGM-71A TOW missile system that entered service four years later (1970) which could only penetrate 430mm RHA with its 5-inch (127mm) warhead.</p><p>In the study "<i>Ocena Skuteczności Działania Ładunków Kumulacyjnych Na Podstawie Rozwiązań Numerycznych</i>" (<i>Assessment of the Effectiveness of Shaped Charges Based on Numerical Solutions</i>), it is stated that in order to get penetration depths of 6 to 8 calibers, the standoff distance must be 5.5 to 7 calibers. This is effectively equivalent to the peak penetration performance obtainable from a precision copper shaped charge with a 60-degree cone angle, with an Octol explosive charge, as used by W. Walters and J. Zukas for their generic precision HEAT warhead model in the text "<i>Fundamentals of Shaped Charges</i>". </p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">9N110M1, 9N110M2</span></h3><p>With the 9M14P and 9M14P1 missiles, the new 9N110M1 and 9N110M2 warheads were introduced. The 9N110M2 is used only on the 9M14P1, whereas the 9M14P missiles were built and issued with 9N110M1 as standard but could have the warhead swapped out for a 9N110M if needed. The 9N110M2 warhead is a cheaper version of the 9N110M1 with an A-IX-1 filler.</p><p>Both warheads feature a new 9E236 inertially armed fuze, which does not depend on an arming signal from the launcher and therefore lacks an electrical connection to the missile fuselage. The two images below show a side-by-side comparison of the 9N110M (left) and 9N110M1 (right). Both the 9N110M1 and 9N110M2 warheads are functionally identical in this sense. However, because the 9M14P1 lacks an electrical arming circuit for the base fuze, it is incompatible with any warheads fitted with the 9E212 fuze, so it is only possible to use it with the issued 9N110M2.</p><p>The main upgrade of the new warhead design compared to the 9N110M was the change to a new explosive filler, where instead of A-IX-1, Okfol is used. The geometry of the shaped charge liner was also modified in accordance with the new charge design and filler. Another difference is that the geometry of the explosive charge itself also changed slightly, with a slightly less narrow taper. This is visible when comparing the two images below. The 9N110M2 warhead is a variation of the 9N110M1 and featured some improvements, but due to the retention of the A-IX-1 filler, its penetration performance is likely to be between the 9N110M and the 9N110M1. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-tlcpk8WG1j8/YLf9MudYtmI/AAAAAAAATSs/xBVmGwdZ0kINuk4zstEXzSdRd_ppY45agCLcBGAsYHQ/s2695/9n110m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1081" data-original-width="2695" height="160" src="https://1.bp.blogspot.com/-tlcpk8WG1j8/YLf9MudYtmI/AAAAAAAATSs/xBVmGwdZ0kINuk4zstEXzSdRd_ppY45agCLcBGAsYHQ/w400-h160/9n110m.png" width="400" /></a><a href="https://1.bp.blogspot.com/-IeGdUT7uXSo/YLf9Mjxi3aI/AAAAAAAATSw/s5ylq9WI9n033xCeshL6CodYB5ljviwIQCLcBGAsYHQ/s2680/9n110m1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1173" data-original-width="2680" height="175" src="https://1.bp.blogspot.com/-IeGdUT7uXSo/YLf9Mjxi3aI/AAAAAAAATSw/s5ylq9WI9n033xCeshL6CodYB5ljviwIQCLcBGAsYHQ/w400-h175/9n110m1.png" width="400" /></a></div><p><br /></p><p>The Okfol charge, which is specifically Okfol 3.5, has a detonation velocity of 8.7 km/s. It is vastly superior to Composition B (7.89 km/s), and also has a sizeable advantage over Octol (75/25), which has a detonation velocity of 8.48 km/s. The only explosive compound with a higher detonation velocity to be used during the Cold War was LX-14 (8.83 km/s), found in American ATGMs made in the final years of the Cold War, namely the TOW-2 series, Dragon II and Hellfire. </p><p>The velocity of a shaped charge jet, measured at its tip, is a factor of the detonation velocity of its explosive charge. With a copper liner, this relationship is almost 1:1, which is the case for typical precision shaped charges such as the BRL 81mm charge, used as a standardized basic reference point for a modern HEAT warhead. To increase the jet tip velocity beyond the limits of the explosive compound itself, the propagation pattern of the detonation waves must be shaped in such a way that they are incident upon the liner apex first, and at a more favourable angle. This is achieved with a wave shaper, which is an inert explosive lens, normally made from phenoplast or plastic, depending on which is more suitable for the specific explosive compound used in the warhead. The lens transforms the spherical detonation wave so that it will be incident upon the liner at a right angle. Experiments show that when the detonation wave meets the liner at an angle up to a perfect right angle, the jet velocity is increased. The ratio of detonation velocity to jet velocity improves noticeably, to a point where a well-designed wave shaped warhead will produce a jet velocity well in excess of the detonation velocity of its explosive filler.</p><p>Its penetration, according to the official tactical-technical characteristics, is 520mm RHA. Though powerful, the enhanced penetration did not fundamentally change the capabilities of the 9M14P and 9M14P1 missiles. When composite armour became a common feature of NATO main battle tanks in the late 1980's, the usefulness of the "Malyutka" series dropped precipitously. Even if a hit was achieved, the probability of overcoming the frontal armour of these tanks was very low, though still non-trivial. With a penetration power of 460-520mm RHA, the best available "Malyutka" missiles of the 1980's were only capable of defeating the side armour of these tanks at a side angle of more than 30 degrees.</p><p><br /></p><p><br /><a href="https://www.blogger.com/null" id="secondgeneration"></a></p><h3 style="text-align: left;"><span style="font-size: large;">SECOND GENERATION</span></h3><p><br /></p><p>Most examples of first generation ATGMs in service (with the exception of the 3M7 "Drakon") were manually guided (MCLOS), and suffered a number of deficiencies as a consequence - a long minimum range, high training requirements, low hit probability in real combat conditions, and a certain degree of fragility during handling. Such shortcomings led to a certain dissatisfaction in the Soviet military, and as a result, the conceptualization of the replacements for these first generation systems began practically at the same time they entered service. </p><p>One of the primary requirements of the next generation ATGM system was that its missiles had to be containerized, because this could shorten the preparation period for firing, and it provided uncompromised protection for the missiles in field conditions throughout the entire period of its handling, up til the moment it is fired. In the USSR, containerization was the universal factor that distinguished domestic first and second generations. Another common feature of second generation Soviet ATGMs was the shift from tracers to IR beacons. The brightness and glare of tracers was excessive in low light conditions for the operator, and it was not conducive to fast missile acquisition by guidance computers, especially in the presence of visual interference from various light sources on real battlefields. IR beacons emitting light in the near-infrared spectrum were more easily discernible against a variety backdrops. Beyond these two primary features, the technologies utilized in Soviet second generation ATGMs were generally adapted in a piecemeal fashion from models of the previous generation.</p><p>The two most noteworthy Soviet ATGMs of the second generation are the 9M111 and 9M113. These two missiles were developed as a light and heavy ATGM pair, sharing fundamental technologies and design features with built-in cross-compatibility potential. This pair of missiles could be considered a spiritual equivalent to the MILAN and HOT, as they shared some superficial design features and had equivalent roles. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DcfKrZUgBgY/YJ0IkAQrKAI/AAAAAAAAS-E/02s-N2Kyh3AZlYulnnZ7IiSpu3i4TUevgCLcBGAsYHQ/s2833/9m113%2Band%2B9m111m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="747" data-original-width="2833" height="168" src="https://1.bp.blogspot.com/-DcfKrZUgBgY/YJ0IkAQrKAI/AAAAAAAAS-E/02s-N2Kyh3AZlYulnnZ7IiSpu3i4TUevgCLcBGAsYHQ/w640-h168/9m113%2Band%2B9m111m.png" width="640" /></a></div><p>The 9M111 was developed as a replacement for the "Malyutka", which was a product of its time and had all of the drawbacks associated with its generation. It succeeded, and was produced in enormous numbers to meet both domestic and export demand, but unlike the "Malyutka", a self-propelled system such as the 9P122 or 9P133 was not created. This was addressed only some years later, with the appearance of the "Konkurs". According to the article "<i>Противотанкового Комплекс Контейнерного Старта</i>" by Sergey Suvorov, published in the March 2020 issue of the "<i>Техника И Вооружение</i>" magazine, it is stated that, at the same time the "Fagot" was in development, a replacement for the "Falanga" ATGM series was requested, with the requirement that the new system should be supersonic (400-450 m/s), have a range of 4 km, and the total weight should not exceed 35 kg. The task of developing this was assigned to the KBM design bureau in 1968, which undertook this task under OKR "Shturm", taking advantage of their prior experience developing the experimental "Rubin" tank-fired supersonic ATGM. Due to the delays and strong design focus of OKR "Shturm" on becoming an optimized helicopter ATGM system, a void appeared in the replacement for the "Falanga". This void was filled by the "Konkurs", and due to the ubiquity of the role it filled, it was readily exported. Once it entered service, the "Shturm" ATGM system with the "Kokon" missile would have its own share of influence in the Soviet military, as well as in the export market. </p><p>The following Second Generation ATGMs will be examined:</p><p></p><ol style="text-align: left;"><li>9M111 "Fagot"</li><li>9M113 "Gaboy"</li><li>9M114 "Kokon", 9M120 "Ataka"</li><li>9M115 "Metis"</li></ol><p></p><p>The 9M1xx block was designated for the second generation ATGMs of the Soviet Army in the GRAU index. So far, the 9M1xx block has been large enough to categorize all domestic ATGM projects. Interestingly enough, during the Soviet era, almost all sequentially indexed missile projects ended up entering service. The first to be indexed was the 9M111 of the "Fagot" system, followed by the 9M112 for the gun-launched "Kobra" ATGM system. Next, the 9M113 "Gaboy", 9M114 "Kokon", and 9M115 "Metis" took their places, with an additional 9M116 designation allocated for the "Metis" missile itself. Then, there was the 9M117 "Kastet" and 9M119 "Refleks" gun-launched missiles, but nothing is known about 9M118. The 9M119 was the last to be indexed before the fall of the Soviet Union. There are a total of seven Soviet second generation ATGMs. The three Soviet gun-launched ATGMs will be covered in a separate article.</p><p><br /><a href="https://www.blogger.com/null" id="guidanceconsiderations"></a></p><h3 style="text-align: left;"><span style="font-size: large;">GUIDANCE CONSIDERATIONS</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-_WD5reHD_n8/YOu0Z-Szm3I/AAAAAAAAT3A/lM2Qpoe52u84DRZIN61mD5mjMEZJl8w8ACLcBGAsYHQ/s2775/missile%2Bflight%2Btrajectory%2Bin%2BSACLOS%2Bguidance.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="659" data-original-width="2775" height="152" src="https://1.bp.blogspot.com/-_WD5reHD_n8/YOu0Z-Szm3I/AAAAAAAAT3A/lM2Qpoe52u84DRZIN61mD5mjMEZJl8w8ACLcBGAsYHQ/w640-h152/missile%2Bflight%2Btrajectory%2Bin%2BSACLOS%2Bguidance.png" width="640" /></a></div><p>The main guidance consideration for second generation ATGMs is the fact that the steering process itself is automated, while the aiming process remains manual. The guidance loop between the launcher and missile is a PD control loop. The optical tracking system detects the angular position of the missile via its IR beacon and when the missile deviates from the desired aiming point, the equivalent angular error value is generated, and the guidance system issues proportional corrective steering commands until an error is no longer detected. While attempting to stay aligned with the operator's line of sight, dictated by the automatic corrections made by the control system, the missile depends on its dynamic stability to acquire a stable flight trajectory as it approaches the target. Immediately after launch, the missile is usually more sensitive to external disruptions such as crosswinds due to the lower margin of static stability from the unspent booster fuel, and the need to align itself to the operator's line of sight while it is in the boost stage. This means that the missile inherently acquires relatively large disturbances, which reduces its probability of hit. Thus, the probability of hit will be close to 100% if the missile is fired directly at a target located directly in front of it, at a distance approximately equal to its minimum range, but it will suffer a brief dip during its boost stage, before increasing to a stable value for the remainder of its trajectory. These phenomena are illustrated in the graps shown above. </p><p>At firing ranges, the hit probability with 1st generation missiles (MCLOS) ranged from 0.8 to 0.9, but were strongly dependent on operator skill. The real hit probability varies greatly even in calm conditions at a firing range. In combat conditions, the real hit probability ranged from 0.2 to 0.5. </p><p>With 2nd generation missiles (SACLOS), the hit probability at firing ranges was at least 0.9 and could almost reach 1.0, but more importantly, by taking the operator out of the control loop, the real hit probability in combat rose considerably to 0.4-0.7.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-1oRYaETOpsg/YJdG-Nj5shI/AAAAAAAAS8E/1EoFLQ7q4oILV9z-gGiAxqoIo8AZrphcACLcBGAsYHQ/s1842/hit%2Bprobability%2Bgraph.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1272" data-original-width="1842" height="442" src="https://1.bp.blogspot.com/-1oRYaETOpsg/YJdG-Nj5shI/AAAAAAAAS8E/1EoFLQ7q4oILV9z-gGiAxqoIo8AZrphcACLcBGAsYHQ/w640-h442/hit%2Bprobability%2Bgraph.png" width="640" /></a></div><p><br /></p><p><br /><a href="https://www.blogger.com/null" id="fagot"></a></p><h3 style="text-align: left;"><span style="font-size: large;">"Fagot" ("Bassoon")<br />9M111, 9M111-2, 9M111M</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-No1rOgienlQ/YTDyWxKwZDI/AAAAAAAAUJU/QhHk9-EyyOw9Cd-FL7qB0V9FGEFbkXsswCLcBGAsYHQ/s1024/VSU-obstrel-1024x631.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="631" data-original-width="1024" height="394" src="https://1.bp.blogspot.com/-No1rOgienlQ/YTDyWxKwZDI/AAAAAAAAUJU/QhHk9-EyyOw9Cd-FL7qB0V9FGEFbkXsswCLcBGAsYHQ/w640-h394/VSU-obstrel-1024x631.jpg" width="640" /></a></div><p><br /></p><p>Work on a system to replace the newly inducted "Malyutka" began in the TsKB-14 design bureau under private initiative in May 1963 following the rejection of their "Ovod" ATGM system in favour of the "Malyutka", created by their rival, the SKB design bureau in Kolomna. The official launch of OKR "Fagot" only occurred with an official decree by the Council of Ministers issued on May 18, 1966, entrusting the task of creating a second generation infantry ATGM system to TsKB-14. Later in the same year, TsKB-14 was renamed to the KBP Instrument Design Bureau. The requirements given were extremely demanding, and in some cases, too optimistic.</p><p>As a fundamental requirement, the new system was to be guided in the SACLOS mode, and the missiles had to be containerized. The containerized missiles were to be administratively equivalent to artillery ammunition in field conditions, requiring no maintenance, and requiring no special training to use. The weight of the No. 1 pack for the missile operator, consisting of the launcher and one missile, was set at 19 kg, while the No. 2 pack for an ammunition bearer, consisting of two missiles, was set to a weight of 20 kg. By extension, the weight of each "Fagot" missile had to be 10 kg and the combined weight of the launch unit and its accessories had to be 9 kg. The average speed of the missile was to be 180-200 m/s, and the armour penetration was to be 180-200mm RHA at an impact angle of 60 degrees. Very early on, shoulder launching was considered and tested, but abandoned, and it was decided that the system was to be tripod-mounted instead. In the end, the needed weight of the launcher turned out to be vastly underestimated, and the 9M111 missile was also overweight, though by an entirely acceptable margin. The No. 1 pack, consisting of a launcher, designated the 9P135 (shown below), together with a maintenance and accessories kit and a backpack to carry the entire set, had a total weight of 22.5 kg. At this weight, the missile operator could no longer be issued with a missile without violating the individual marching load guidelines, so the two-man team concept was abandoned, reverting to the same three-man team structure as the 9K11. The third man was a second missile bearer, issued with another No. 2 pack. In total, a "Fagot" anti-tank team consisted of one No. 1 pack and two No. 2 packs. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-CTH0U8H102Q/YTDvETWgcAI/AAAAAAAAUJM/AbHmpn0hdRMD5JGgoht0X0FXDJ1bUVgoACLcBGAsYHQ/s2048/9p135.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1345" data-original-width="2048" height="420" src="https://1.bp.blogspot.com/-CTH0U8H102Q/YTDvETWgcAI/AAAAAAAAUJM/AbHmpn0hdRMD5JGgoht0X0FXDJ1bUVgoACLcBGAsYHQ/w640-h420/9p135.png" width="640" /></a></div><p>The first components were ready to undergo factory testing in 1967, but the initial results were not promising, leading to constant reworks. One of the first components to be tested was the warhead, which began testing that year, ending in failure - the measured penetration of the warhead did not match the calculated depth. Tests of other components, carried out from 1967 to 1968, were similarly unsuccessful. In the first prototype, a conventional pyrotechnic tracer flare was used, but because the wire spool was placed around the tracer, the burning slag spat out by the tracer could unpredictably burn the control wire being dispensed around it. The missile would, unsurprisingly, cease to obey steering commands. The last round of factory tests was started in January 1969, but due to the low reliability of the command wire link, the tests were once again deemed unsuccessful. Factory flight tests were repeatedly interrupted for improvements to the missile, and so the testing continued until May 1969. </p><p>A mockup of the missile prototype, which is now used as a museum display, is shown in the photo below on top of a training cutaway of a serial 9M111 missile. The aerodynamic shape of the prototype fuselage was completely different, having an ostensibly more streamlined ogive shape ahead of the warhead, while the warhead itself has a boattailed shape that connects abruptly to the engine section without an aerodynamic fairing over the transition point. The final design has a straight tapered nose, and an aerodynamic fairing between the warhead and the engine.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-IOkbCNQ6Lyo/YOoy1B7G84I/AAAAAAAAT1Y/tCD3mzqGR9oqIWMG6WqHvqCSDeYXfsw8ACLcBGAsYHQ/s600/1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="402" data-original-width="600" src="https://1.bp.blogspot.com/-IOkbCNQ6Lyo/YOoy1B7G84I/AAAAAAAAT1Y/tCD3mzqGR9oqIWMG6WqHvqCSDeYXfsw8ACLcBGAsYHQ/s16000/1.jpg" /></a></div><p>After numerous design revisions, state tests of the "Fagot" system began in July 1969. Finally, it was proven that the system had overcome its design faults, and it passed state tests in March 1970, albeit not without some additional comments from the testing committee which led to a few minor design modifications to the missile. After the design changes were made, the 9K111 "Fagot" portable anti-tank system was officially inducted into service by government decree No. 793-259 on September 22, 1970. Low rate production began the same year, followed by serial production in 1971. The 9K111 was deployed as a battalion level asset, in the anti-tank platoon of motorized rifle battalions mounted on BTRs. It replaced the 9K11 "Malyutka" on a one-to-one basis, placing a total of four 9K111 anti-tank teams in each anti-tank platoon. Although the KBP design bureau failed to meet the original portability goal of accommodating a two-man team, the three-man 9K111 team was the same size as the existing 9K11 "Malyutka" team and split the responsibilities of the team members in the same way, making it simple and organizationally convenient for motor rifle battalions to switch over to the 9K111.</p><p>Throughout the design process, the Tula engineers had a clear set of goals but were working with no frame of reference, as there was simply no other containerized ATGM system known in the 1960's; all existing examples at the time were merely being conceptualized or just beginning their development. In fact, the development of the "Fagot" is an interesting example of convergent thinking with the Franco-German MILAN which was being designed in parallel to the "Fagot". Indeed, the two systems are equivalent in more ways than one, even discounting the fact that they were the only two second generation infantry ATGM systems to be created in the 1970's, so there are no other direct points of comparison. Although there is no traceable relation at all between the two missile systems, there were a number of coincidental similarities even in specific technical solutions. On the foundational level, the basic requirement of having a two-man ATGM team with one launcher and three missiles was the same between the two systems, as was the range requirement of 2,000 meters. Both systems also underwent a brief early conceptualization phase to explore the possibility of shoulder-launching, which was deemed unworkable and then abandoned in favour of a tripod mount. In terms of design, both systems ended up with similar flight characteristics and used the same design solution in the power system, and both were spinning missiles with a single-axis control scheme with a single wire command link, using a two-core wire.</p><p>In the end, even with all the challenges it faced, OKR "Fagot" resulted in a successful product, which not only served in a distinguished career in the Soviet Army, but became an international bestseller closely rivalling the MILAN. The development process itself was also relatively smooth; the "Fagot" project began in May 1963 and the MILAN project began in March 1963, and while both projects made use of existing prototypes, the "Ovod" in the former and the SS.9 in the latter, the "Fagot" managed to enter service in 1970, after a total development period of 7 years and an official development period of just 4 years. Initially, the MILAN had progressed more quickly, with unguided missile firings already taking place in 1965, and the complete ATGM system with working guidance was ready for testing by 1966, and yet, due to the inherent bureaucratic difficulties in managing a binational project, the system entered service only in 1972 after a 9-year development period, throughout which the smoothness of the binational cooperation could only be considered outstanding and exemplary. With that said, the speed at which Soviet ATGM projects matured should be no surprise by now, as this has been a common theme throughout this article. </p><p>Following the original 9M111, the 9M111-2 model was created and entered service in 1974, concurrently with the 9P148 "Konkurs" tank destroyer, with the specific modifications necessary to provide the full range of safety measures when used from the launcher which were not relevant to the 9P135 infantry launcher. In 1980, the 9M111M "Faktoriya" entered service to supplant the original series. The "Faktoriya" featured improved armour penetration and an extended range, at virtually no penalty to any other aspect of the missile system. It was by all means a comprehensive qualitative upgrade over the "Fagot".</p><p>The 9P148 "Konkurs" tank destroyer, originally made to fire the 9M113 "Gaboy", could technically fire all models the "Fagot" series, but it was meant to use only 9M111-2 or the 9M111M. The only reason for a 9P148 to fire the shorter-legged "Fagot" series would be to make use of the larger ammunition capacity in a situation where the engagement range is known to be within the reach of the 9M111-2 or 9M111M, such as an ambush. If loaded exclusively with 9M113 missiles, then 15 were carried in a standard combat load. If a standard mixture was carried instead, then 10 "Fagot" and 10 "Gaboy" missiles could be carried, and both could be loaded on the launcher to be fired selectively depending on the target conditions. A 9P148 carrying a mixed load is shown in the photo below, taken from the book "<i>A Magyar Néphadsereg szárazföldi csapatainak hadrendi változásai 1987-ben</i>".</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-t31OHGX3jOM/YTDskrUNMFI/AAAAAAAAUJE/PJreomBajH0GGIUPCL0eAt7htZk6r-kMACLcBGAsYHQ/s2048/9p148%2Bwith%2Bmix.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1628" data-original-width="2048" height="508" src="https://1.bp.blogspot.com/-t31OHGX3jOM/YTDskrUNMFI/AAAAAAAAUJE/PJreomBajH0GGIUPCL0eAt7htZk6r-kMACLcBGAsYHQ/w640-h508/9p148%2Bwith%2Bmix.png" width="640" /></a></div><p></p><p>Additionally, it is worth mentioning that the 9K111-1 "Konkurs" system with the 9P135M infantry launcher also entered service in 1974, featuring reverse compatibility with "Fagot" missiles. The 9K111-1 "Konkurs" system was responsible for indirectly enhancing the proliferation of the "Fagot", as a 9P135M launcher was included in the BMP-1P and BMP-2, and "Fagot" series missiles were sometimes fired from them as an alternative to the standard "Konkurs" missiles. They were also widespread in the VDV, as 9P135M launchers began to be included with the BMD-1P and BMD-2, as well as the BTR-RD anti-tank vehicle.</p><p><br /><a href="https://www.blogger.com/null" id="fagotdesign"></a></p><h3 style="text-align: left;"><span style="font-size: large;">GENERAL DESIGN FEATURES</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-I97iEknhBaE/YPaBorzpE5I/AAAAAAAAT_k/5A7Qyrq9lbkT5llRopkA81gkKrk-P1AyQCLcBGAsYHQ/s1901/9m111.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="744" data-original-width="1901" height="250" src="https://1.bp.blogspot.com/-I97iEknhBaE/YPaBorzpE5I/AAAAAAAAT_k/5A7Qyrq9lbkT5llRopkA81gkKrk-P1AyQCLcBGAsYHQ/w640-h250/9m111.jpg" width="640" /></a></div><p>The layout of the missile is unconventional, starting with the canard steering mechanism at the nose, followed by the warhead, engine, and finally the guidance section in the tail, where all of the guidance electronics are housed. To connect the wiring at the nose of the missile to the tail, where the guidance system is located, external cable conduits had to be laid over the surface of the missile fuselage, in the same style as the wiring layout of the "Falanga". To reduce the weight of the missile to the furthest possible extent, the use of duralumin and fiberglass was maximized. The only major component made from steel is the rocket engine. An interesting feature of the "Fagot" is that all modules were designed and fitted within their own discrete compartments, dividing the missile sectionally along its longitudinal axis. The photo below shows a dismantled 9M111M "Faktoriya", demonstrating the sequentiality of its layout. This detail differentiates it from a number of first generation ATGMs, where internal components were normally housed inside a fuselage. The prime examples of this are the "Shmel" and "Falanga". In the article "<i>Противотанковые комплексы контейнерного старта: Противотанковый комплекс 9К11 «Фагот»</i>" by Rostislav Angelskiy and S. Suvorov, published in the March 2020 edition of the "<i>Техника и вооружение</i>" magazine, it was noted that there was a pathological resistance to placing the warhead behind the steering mechanism, as the convention of placing the warhead at the very nose of a projectile or missile had been firmly established and was nearly unshakeable. It is perhaps worth noting that unlike the Kolomna KBM design bureau which followed this convention with their "Malyutka", and later their "Kokon", the engineers of Tula KBP proved to be more willing to relocate the warhead wherever it may be more favourable. This was exemplified not only in "Fagot", but in the later 9M119 "Refleks" gun-launched ATGM, and the 9M133 "Kornet".</p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-3HWc6h6R1LQ/YOPRPNVEE9I/AAAAAAAATvg/HNp0GomjowsbDBdWRiqx9R-inbQl0BQTwCLcBGAsYHQ/s1280/9m111%2Bdismantled.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="1280" height="300" src="https://1.bp.blogspot.com/-3HWc6h6R1LQ/YOPRPNVEE9I/AAAAAAAATvg/HNp0GomjowsbDBdWRiqx9R-inbQl0BQTwCLcBGAsYHQ/w400-h300/9m111%2Bdismantled.jpg" width="400" /></a></p><p>The length of the missile is fairly substantial, partly due to its use of a canard layout. The maximum diameter of the missile itself is 120mm and its length is 871mm. The maximum diameter is measured at the obturator ring built into the wire spool housing, necessary to ensure a gas seal as the missile is launched from the container. The wire spool housing itself, and the rocket engine, are less than 120mm in diameter, while the warhead section is only 93mm. As a point of comparison, the MILAN was an ATGM system of the same class, but it featured a slightly smaller missile. Its maximum diameter of 130mm is only nominally larger because it is measured at the hinges of its folding wings - the fuselage itself is only 90mm in diameter. It is somewhat shorter as well, only 798mm. </p><p>The 9M111-2 is a variant intended for increased safety when fired from a 9P148 "Konkurs" tank destroyer. It differs from the basic version by the addition of a special lock designed to ensure that the launch circuits do not receive any signal during an emergency ejection from the launcher guide rails.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Qg6UwanerDk/YOXO7u5FN4I/AAAAAAAATw4/NzFcZclwq_UTI1G4FjI06nTLnc_Vql5agCLcBGAsYHQ/s600/9m111%2Band%2Bcontainer.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="329" data-original-width="600" src="https://1.bp.blogspot.com/-Qg6UwanerDk/YOXO7u5FN4I/AAAAAAAATw4/NzFcZclwq_UTI1G4FjI06nTLnc_Vql5agCLcBGAsYHQ/s16000/9m111%2Band%2Bcontainer.jpg" /></a></div><p>The missile container is manufactured from AG-4S structural grade glass textolite, which is a type of glass textolite using twisted glass fibers impregnated with phenol formaldehyde resin (bakelite). The front end cap is made from cast aluminium, and the rear cap, which is a blow-out cap, is plastic. Alone, the container weighs 2.41 kg, not including its fittings. The container is hermetically sealed at the factory after assembly, and is both watertight and slightly buoyant. This, along with the built-in sling, makes it more convenient to carry by a dismounted missile bearer. As a unit of ammunition, the complete package requires no maintenance for the duration of its guaranteed storage life, and it provides the missile with protection from rough handling. Storage and usage (firing) of missiles that were dropped on concrete from a height of 0.5-1.5 meters is permitted, and if stored in their wooden shipping crates, it is permitted to store and use the missiles after a drop from a height of 1.5-3 meters. </p><p>The container is 1,098mm long, up to 150mm in width and 205mm in height, measured from its connector socket. When two containers are strapped together by the designated attachment points, the two slings of the two containers form the straps of a backpack.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-UyjK9Q4T5pA/YOXN0z_mZ7I/AAAAAAAATww/DCDqOwvwmWkR0PPKm0P7iNnboEAxxt83gCLcBGAsYHQ/s1952/missile%2Bin%2Bcontainer.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="469" data-original-width="1952" height="154" src="https://1.bp.blogspot.com/-UyjK9Q4T5pA/YOXN0z_mZ7I/AAAAAAAATww/DCDqOwvwmWkR0PPKm0P7iNnboEAxxt83gCLcBGAsYHQ/w640-h154/missile%2Bin%2Bcontainer.jpg" width="640" /></a></div><p>In a television interview for the "<i>Ударная сила</i>" show on Russian TV Channel 1, Arkady Shipunov of KBP Tula recounted that early on in the development of the "Fagot", Makarov proposed to use a metal tubular container instead of fiberglass, as Shipunov suggested. Entering the office of Shipunov, Makarov brought a thin-walled steel tube (just 0.8mm thick) as a mockup. To convince Makarov to abandon the idea, Shipunov laid the tube on the floor and jumped on it, flattening the tube completely. Shipunov wordlessly held out the flattened tube, and Makarov relented. A slightly heavier, but far stiffer and tougher glass textolite tube was used in the final product instead.</p><p>The purpose of the container is three-fold:</p><p></p><ol style="text-align: left;"><li>Protect the missile in a hermetically sealed, shock-resistant shell throughout its entire service life</li><li>Provide a tube for the pressure of the ejection system to act upon the missile, launching it without disrupting the operator with the exhaust gasses</li><li>To function as a conduit through which the command wire on the missile is linked to the guidance computer </li><li>To provide power to the guidance equipment</li></ol><p style="text-align: left;">The first and second functions are ensured by the cylindrical construction of the container, and the choice of a rigid, tough material that can absorb an impact and avoid deforming, which would consequently deform or dent the missile within and also ruin the cylindrical shape needed for the container to function as a launch tube. The third function is provided by a six-pin electrical socket which connects to the guidance equipment of the launcher when the container is loaded onto the launcher guide rail. A communication cable runs along the underside of the container, connecting the socket to the front end cap, which in turn anchors the command wire link of the 9M111 missile, forming the connection from guidance computer to the missile.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-dQl6yWqZxJk/YOUuj1KcneI/AAAAAAAATvo/-KegcyycQewj-phYGuqWMP7ZQE6esqBPwCLcBGAsYHQ/s1397/fagot%2Blaunched%2Bwire.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1025" data-original-width="1397" height="294" src="https://1.bp.blogspot.com/-dQl6yWqZxJk/YOUuj1KcneI/AAAAAAAATvo/-KegcyycQewj-phYGuqWMP7ZQE6esqBPwCLcBGAsYHQ/w400-h294/fagot%2Blaunched%2Bwire.png" width="400" /></a></div><p>The fourth function is provided by a pair of T-307 or T-307B thermal batteries housed in the cylindrical compartment underneath the container, serving as the power supply for the 9P135 launcher. According to data provided by the manufacturer, JSC "Energia", each T-307B thermal battery weighs 180 grams. There is no other power supply in the launcher itself, and the pyrotechnic heaters to warm up the batteries to their operating temperature are ignited by the small electrical signal generated in the trigger itself, which contains a linear induction mechanism. This allowed the portable 9P135 launcher to be used indefinitely without worry for charging an integral battery, and by using a disposable thermal battery integral to an equally disposable missile container, the 9K111 system could be issued to hastily trained operators and used without special precautions or maintenance steps. Coincidentally, the same technical solution was later applied in the MILAN, presumably for the same reasons. Blueprints of the MILAN from 1966 reveal that it did not yet have this power system. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ZvDwL1VrOTg/YOd40bSNQiI/AAAAAAAATy4/VsmiTq47RnUfmVQ-6ZHYcavmMhLxDQi7wCLcBGAsYHQ/s1499/thermal%2Bbatteries.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1315" data-original-width="1499" height="351" src="https://1.bp.blogspot.com/-ZvDwL1VrOTg/YOd40bSNQiI/AAAAAAAATy4/VsmiTq47RnUfmVQ-6ZHYcavmMhLxDQi7wCLcBGAsYHQ/w400-h351/thermal%2Bbatteries.png" width="400" /></a></div><p>As a side note, it is interesting that the residual pressure exiting the container after missile launch creates a sound very similar to that made when a person blows air across the opening of a bottle. This is because the container is a Helmholtz resonator.</p><p>Along with its container, the weight of a complete 9M111 unit is 12.8 kg. This is inclusive of accessories such as the carry strap. Alone, the 9M111 missile weighs just 7.6 kg. This is the mass of the missile in its in-flight configuration. </p><p>With the 9M111M "Faktoriya", the entire missile unit was deeply upgraded. The weight of the 9M111M increased to 8 kg, but despite this, the total weight of the containerized unit increased only very slightly to 12.9 kg. It can only be surmised that weight reduction steps were taken in other, unspecified parts of the containerized unit.</p><p>Compared to the 18.1 kg weight of a 9P111 suitcase-launcher, holding a single missile, it is evident that the containerized "Fagot" had tangible advantages in portability. In fact, the complete containerized 9M111 itself already weighs almost as little as a 9M14P missile (11.4 kg) on its own. Each missile pack of two 9M111 missiles borne by the two missile bearers in an anti-tank missile team weighs 25.6 kg (9M111 or 9M111-2) or 25.8 kg (9M111M). This exceeded the original 20 kg requirement by a quarter, though it did not stray into excess. The No. 1 pack containing the 9P135 launcher weighs 22.5 kg (the 9P135 and its spare parts kit alone weighs 22 kg), and is carried by the operator. In total, a full 9K111 "Fagot" set is noticeably heavier and bulkier than the 9K11 "Malyutka", yet at the same time, the number of shots is doubled from 2 to 4 without increasing the size of the anti-tank team. This, combined with the fast setup time and much higher probability of hit owing to its SACLOS system, meant that the total firepower was more than doubled. The weight of the containerized missiles and the launcher also exceed that of the MILAN system, though this was offset by a difference in the team organization. A "Fagot" anti-tank team consists of three men, whereas a MILAN team consists of two men, the operator carrying one missile and the launcher while the assistant operator carries two missiles. The photo below shows an NVA 9K111 team, training with a reduced load of one inert dummy missile per bearer.</p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--AWZdmX6lY4/YOdVy1GXGGI/AAAAAAAATyo/fIbtqxM-Hq080a0upVA3CiGS5Vb33R4JACLcBGAsYHQ/s2048/missile%2Bpack.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1485" data-original-width="2048" height="290" src="https://1.bp.blogspot.com/--AWZdmX6lY4/YOdVy1GXGGI/AAAAAAAATyo/fIbtqxM-Hq080a0upVA3CiGS5Vb33R4JACLcBGAsYHQ/w400-h290/missile%2Bpack.png" width="400" /></a><a href="https://1.bp.blogspot.com/-vvpwhJ7S2UY/YOXC_zEFhJI/AAAAAAAATwg/Api8TW1jWIApL8Iuff5y-37D9lxAThPjwCLcBGAsYHQ/s1951/gdr%2B9k111%2Btraining.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1347" data-original-width="1951" height="276" src="https://1.bp.blogspot.com/-vvpwhJ7S2UY/YOXC_zEFhJI/AAAAAAAATwg/Api8TW1jWIApL8Iuff5y-37D9lxAThPjwCLcBGAsYHQ/w400-h276/gdr%2B9k111%2Btraining.png" width="400" /></a></div></div></div><p>Overall, the "Fagot" can be characterized as having been a powerful infantry ATGM system at the time it entered service. It features a combination of high penetration power and a short flight time, short enough that, in theory, it is possible to fire all four missiles carried in each 9K111 set within one minute, even when engaging targets at maximum range. Officially, the rate of fire is three shots a minute.</p><p><br /><a href="https://www.blogger.com/null" id="fagotaerodynamics"></a></p><h3 style="text-align: left;"><span style="font-size: large;">AERODYNAMICS</span></h3><p><br /></p><p>The 9M111 features a canard aerodynamic layout, where the canards contribute lift and also act as control surfaces to steer the missile in flight. Additionally, the entire section ahead of the engine was shaped to be a lifting body, where additional lift is generated due to the special double-tapered shape of the nose and fairing between the warhead and the engine sections of the fuselage. This shape generates lift more efficiently than a simple cylinder. The same aerodynamic form was implemented in the TOW and ITOW missiles, which were in particular need of additional lift owing to the limited surface area of its wings and steering fins. </p><p>Fundamentally, the use of aerodynamic control surfaces on the 9M111 instead of a TVC mechanism, as found on the "Malyutka", was influenced by the overall lift benefit of the aerodynamic scheme, and by the reasonable effectiveness of control surfaces at the higher cruising speed of the missile. This was not the case for the "Malyutka". The particular choice of canards, rather than tail fins or trailing edge rudders on the wings, was to solve all of the issues associated with implementing aerodynamic control surfaces instead of a TVC system. </p><p>The canards have a trapezoidal planform, and have a thin symmetrical modified double wedge aerofoil. Due to its small surface area, the canards experience a high wing loading, and the use of a supersonic aerofoil lowers its stall point below that of the main wings of the missile. To avoid their wake interfering with the airflow over the wings, the canards are axially offset from the wings by 45 degrees. With canard control surfaces, the aerodynamic layout of the missile could be designed to generate the maximum steering responsiveness for a steering mechanism of minimum size, whilst also producing additional lift, allowing the missile to fly at an attitude closer to a zero-degree angle of attack in level flight. Indeed, the use of lifting canards was the only justifiable implementation of aerodynamic control surfaces on the "Fagot" as opposed to a TVC system, which could have provided the necessary steering force at a minimal weight penalty. In general, aircraft designed with a canard layout have better lifting capacity per unit area of lifting surfaces in all flight attitudes, and have better pitch maneuverability. Moreover, the layout of the missile itself, with the wings placed on the guidance system compartment behind the engine, was to increase the distance between the wings and the center of gravity of the missile, which is defined by the location of the engine, and thus provide a high degree of static stability despite the use of canards.</p><p>Given that the lift force from the wing is much higher than the rest of the fuselage, there is a net moment of lift behind the center of gravity of the missile, which causes the missile to pitch down. To maintain a stable position, the canard, placed near the very end of the nose, generates a lift force that produces a moment of lift in the opposite direction to the wings, as it is on the other side of the center of gravity. The moment of lift is in equilibrium between the three lifting elements because the large wings are a shorter distance behind the center of gravity of the missile, while the canards and lifting body are far forward of it. The lifting surfaces are calibrated so that the moments on both sides of the center of gravity are balanced when the missile is at its trim angle, and disturbances that cause the missile to deviate from this angle in either direction are corrected by a net balancing moment arising mainly from the wing. As such, although the canards reduced the margin of stability, the missile was still designed for stability.</p><p><br /></p><p>In the engineering textbook "<i>Основы Устройства И Функционирования Противотанковых Управляемых Ракет</i>" by V. V. Vetrov et al., published for the Tula state university by the KBP design bureau, the merits of a canard aerodynamic configuration (below, right) in enhancing the dynamic stability of a missile compared to a conventional aerodynamic configuration (below, left) are described in detail. ЦМ refers to the center of gravity, Yδ is the steering force, produced by the elevators acting about the CoG. Yα is the balancing moment, produced by the lift of the wings acting about the CoG. In level flight, Yδ = Yα.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-o3BCkfFFVPI/YOW4kuWsLwI/AAAAAAAATwQ/kBrcqvhCEX8ofaBrqKnCijuxx6gVWM3-gCLcBGAsYHQ/s1870/conventional%2Bvs%2Bcanard%2Baerodynamic%2Bschemes.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1741" data-original-width="1870" height="373" src="https://1.bp.blogspot.com/-o3BCkfFFVPI/YOW4kuWsLwI/AAAAAAAATwQ/kBrcqvhCEX8ofaBrqKnCijuxx6gVWM3-gCLcBGAsYHQ/w400-h373/conventional%2Bvs%2Bcanard%2Baerodynamic%2Bschemes.png" width="400" /></a></div><p>The "conventional" configuration (Обычная) is analogous to conventional aircraft with elevators on the tail, or the TOW, which has all-moving steering rudder and elevator fins. The "canard" configuration (Утка) represents all-moving canards as implemented on "Fagot". In both aerodynamic schemes, it is assumed that both missiles have positive static stability, and positive dynamic stability. A bang-bang control scheme is used in both. In both configurations, a stepwise change in the angle of deflection of the elevator will result in a change in missile attitude; with canards, by positive lift, and with tail fins, by negative lift. In this case, the topic is to study the degree of positive dynamic stability afforded by the two aerodynamic configurations when the altitude of the missile is raised.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-rcflqWvMH7E/YMsFoRa1MHI/AAAAAAAATcc/w9OIMjO_Vto7WoKPUxGmTHtquMmRzMVnwCLcBGAsYHQ/s1536/The%2Breaction%2Bof%2Bthe%2Bnormal%2Band%2Bcanard%2Baerodynamic%2Bschemes%2Bto%2Bthe%2Bstep%2Bdeviation%2Bof%2Bthe%2Brudders.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="867" data-original-width="1536" height="226" src="https://1.bp.blogspot.com/-rcflqWvMH7E/YMsFoRa1MHI/AAAAAAAATcc/w9OIMjO_Vto7WoKPUxGmTHtquMmRzMVnwCLcBGAsYHQ/w400-h226/The%2Breaction%2Bof%2Bthe%2Bnormal%2Band%2Bcanard%2Baerodynamic%2Bschemes%2Bto%2Bthe%2Bstep%2Bdeviation%2Bof%2Bthe%2Brudders.png" width="400" /></a></div><p>In a conventional configuration, a pitch-up maneuver will increase the stabilizing moment, because as the missile nose rotates up, the tail rotates down, and so angle of attack of the tail elevator fins increases. At some point, the pitch angle of the missile reaches the so-called pitch equilibrium angle, where the balancing force from the wings is equal to the pitching moment from the tail elevators, and the elevators become incapable of steering the missile further. When the elevators switch back to their neutral angle, the lift from the wings drives the missile to pitch down until equilibrium between its lifting force and that of the tail elevator fins is returned. Due to inertia, the strong balancing force from the wings causes the missile to overcorrect in its pitch-down motion, but to a lesser degree than the original pitch-up motion, and this pitching motion repeats in an progressively damped oscillatory manner until the pitching motion is fully neutralized. </p><p>However, the textbook states that the static and dynamic stability of the canard configuration is superior. This is counterintuitive, because normally, it is expected that canards would reduce both static and dynamic stability (canards are called destabilizers for this reason), because as the missile pitches up, the angle of attack of the canards increases, progressively increasing the intensity of the pitch-up moment until the canards stall. This would mean that the missile or aircraft is unstable, and would be practically unflyable without a sophisticated fly-by-wire system. In this case, this behaviour was counteracted by having two different aerofoil designs for the canard and the wing. The wings have a thick aerofoil with a higher lift coefficient, while the canards have a thin aerofoil with a lower lift coefficient, so that as the angle of attack increases, the lift force increases at a higher rate on the wing than on the canard, thus creating a tendency for the missile to pitch-down. Morever, the canard configuration of "Fagot" makes use of canard stalling to improve the inertial dampening of the missile.</p><p>When a stepwise change in the elevator angle is made, missiles in both aerodynamic configurations do not merely pitch up until they reach the pitch equilibrium angle, where they would normally be expected to remain. Due to inertia, the missile will exceed the pitch equilibrium angle by a certain oversteer angle until it is fully damped by the balancing moment, whereupon it begins to pitch down. In the case of the "Fagot", the canard is designed to stall if it exceeds the pitch equilibrium angle (the wings do not stall), losing all lift entirely and preventing oversteer. This is why the oscillatory amplitude shown in the graph is smaller than for the conventional configuration. Moreover, because the wing is placed further aft of the center of gravity as compared to the conventional configuration, the balancing moment of the canard configuration is stronger. This improves its static stability. It also means that the pitch-down reaction after the initial-pitch up occurs more violently; the strong balancing force that performs the overcorrection is even stronger than in the conventional configuration. However, this is actually beneficial for a missile, because it hastens the dampening process, allowing the missile to return to level flight around twice as quickly, as shown in the graph. This is an indicator of higher dynamic stability.</p><p>The presence of canards also improves crosswind stability because it presents additional vertical surfaces ahead of the center of gravity. A crosswind can induce yaw on a tailless cropped delta missile by generating a turning moment when blowing upon the wing, but with canards present, the crosswind will impart some force on the canards, and due to the longer moment arm between the canards and the CoG of the missile, the turning moment may be largely neutralized or even completely neutralized. Thus, "Fagot" has a higher resistance to turning into a crosswind, although it will still be physically deflected if the crosswind is strong enough - that effect cannot be neutralized in practice.</p><p><br /></p><p>A unique type of flexible, elastic stainless steel wings were invented for the "Fagot". The engineer responsible for its creation was Nikolai Makarov, the very same Makarov responsible for the PM pistol, who had been retrained as a rocket scientist as part of Premier Khrushchev's heavy-handed pivot from gun to rocket technology, and subsequently assigned to TsKB-14. This innovative wing design had no analogues in the world. The skins of each wing are only 0.2mm thick, though when deployed, the cross section of the aerofoil formed by the skins is quite thick. To fold them away before the missile is packed into the container at the factory, the wings are rolled in a counter-clockwise direction around the guidance system compartment, whereupon the two skins of the elastic wings are flattened together and they fit snugly around the fuselage. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-bvCrxzB8XGY/YOXdyRbY3LI/AAAAAAAATxo/xkKfmmYkIZ0fxQajMljWmysrsWoPS69IgCLcBGAsYHQ/s2048/elastic%2Bwings.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1361" data-original-width="2048" height="266" src="https://1.bp.blogspot.com/-bvCrxzB8XGY/YOXdyRbY3LI/AAAAAAAATxo/xkKfmmYkIZ0fxQajMljWmysrsWoPS69IgCLcBGAsYHQ/w400-h266/elastic%2Bwings.png" width="400" /></a><a href="https://1.bp.blogspot.com/-KUp5wBiddEs/YOXelSqdP4I/AAAAAAAATxw/K4M4AUgCASIO8_smwGyphXvYKI7WAaC7QCLcBGAsYHQ/s1387/wing%2Bstraps.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1287" data-original-width="1387" height="298" src="https://1.bp.blogspot.com/-KUp5wBiddEs/YOXelSqdP4I/AAAAAAAATxw/K4M4AUgCASIO8_smwGyphXvYKI7WAaC7QCLcBGAsYHQ/w320-h298/wing%2Bstraps.png" width="320" /></a></div><p>Before loading into the missile into the container during assembly, the wings are held together with straps. The straps merely serve to support and protect the wings as the missile is propelled down the container during launch, without actually locking them together; once the missile leaves the container, the unfurling of the wings will knock the straps apart.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-uqvHurD9pTY/YOokVADEY7I/AAAAAAAAT1E/Dv4Wrn6tQSsdl-rIaj4ql1-SOO_4HUROwCLcBGAsYHQ/s800/straps%2Bseparating.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="533" data-original-width="800" height="266" src="https://1.bp.blogspot.com/-uqvHurD9pTY/YOokVADEY7I/AAAAAAAAT1E/Dv4Wrn6tQSsdl-rIaj4ql1-SOO_4HUROwCLcBGAsYHQ/w400-h266/straps%2Bseparating.jpg" width="400" /></a></div><p>The wings have a conventional symmetrical circular arc aerofoil. The wings are angled by 2.25 degrees to induce and maintain the 10 RPS spin rate of the missile, and it is the wings alone that are responsible for it, as the engine nozzles are not offset to induce spin, which was likely made possible by the low weight of the missile. A spin has particular importance for the "Fagot", as unlike the "Malyutka", the external cabling on its fuselage is a source of asymmetry in its aerodynamic form. An equilibrium spin is needed to cancel out the asymmetric form and surface drag, which would otherwise induce some yaw.</p><p>Having no hinges, these wings had an advantage in terms of drag. Unlike conventional folding fins, as used in the "Malyutka" and in foreign missiles like the MILAN and TOW, such wings can be lighter as they are hollow, and they facilitate a larger wingspan for a given volume. The larger chord of the wings also gives favourable drag characteristics for subsonic flight, yielding an improved lift-to-drag ratio.</p><p>The downside of this type of wing is that the permissible dynamic pressure is low, chiefly due to the thin skin and hollow structure. The design is structurally limited to generating high lift forces by distributing a low dynamic pressure over a large surface area. The high dynamic pressure generated at supersonic speeds overloads such wings and causes the aerofoil to warp, making them unsuitable for many types of missiles. As such, the elastic wing concept was only applied to future subsonic missiles by KBP Tula such as the 9M133 "Kornet", and not their supersonic products like the 9M117 "Kastet" and 9M119 "Refleks".</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-gDB5sDpUVE4/YOXJMvEEifI/AAAAAAAATwo/UOSDnjTCOqcxS3YLPNjrI4QrHtGpWXA6gCLcBGAsYHQ/s2835/9m111.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1110" data-original-width="2835" height="250" src="https://1.bp.blogspot.com/-gDB5sDpUVE4/YOXJMvEEifI/AAAAAAAATwo/UOSDnjTCOqcxS3YLPNjrI4QrHtGpWXA6gCLcBGAsYHQ/w640-h250/9m111.png" width="640" /></a></div><p><br /></p><p>The large wings, coupled with the high velocity and light weight of the "Fagot", allowed the missile to fly on a level trajectory with a very small positive angle of attack, close to zero.</p><p>The tail of the fuselage, housing the wire spool and the infrared beacon, is cylindrical but ends in a frustum. This forms a minor boattail shape, streamlining the aerodynamic profile of the missile and decreasing base drag to some extent.</p><p><br /></p><p><br /><a href="https://www.blogger.com/null" id="fagotguidance"></a></p><h3 style="text-align: left;"><span style="font-size: large;">GUIDANCE SYSTEM</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-x__t46riTfw/YOX0euRgjCI/AAAAAAAATx4/gDDK_PKMogg_7CAQLUL2avcp4-lkfvwRwCLcBGAsYHQ/s1855/guidance%2Bsystem%2Bblocks.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1117" data-original-width="1855" height="241" src="https://1.bp.blogspot.com/-x__t46riTfw/YOX0euRgjCI/AAAAAAAATx4/gDDK_PKMogg_7CAQLUL2avcp4-lkfvwRwCLcBGAsYHQ/w400-h241/guidance%2Bsystem%2Bblocks.png" width="400" /></a></div><p>The entire set of guidance equipment carried in the missile is housed inside a fiberglass compartment behind the engine and ahead of the tail in a fiberglass casing, on which the missile wings are fitted. The guidance system consists of two thermal batteries, a wire link, the gyroscope (gyro-coordinator), the receiver system and the IR beacon. The block diagram shown above illustrates the logic flow of the control loop.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEhxTxKyU6CU3ggCvJU0L7z3QsKEzlEV5CqJIoMZr9E0b3axA5uzxkwv25lDuidGSHEOQt0AfglnG6dpalsP3kkgf1bRhbRlHCpDUM_YTa51cvelJ2XVNAUxFyI6yPGzv0YJ-W9EBm2nDj_Eivlvj38kVyHHrMZaZLO6mzPlgQj_yIZmZHFNJyDKkmNy7w=s5654" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="4112" data-original-width="5654" height="466" src="https://blogger.googleusercontent.com/img/a/AVvXsEhxTxKyU6CU3ggCvJU0L7z3QsKEzlEV5CqJIoMZr9E0b3axA5uzxkwv25lDuidGSHEOQt0AfglnG6dpalsP3kkgf1bRhbRlHCpDUM_YTa51cvelJ2XVNAUxFyI6yPGzv0YJ-W9EBm2nDj_Eivlvj38kVyHHrMZaZLO6mzPlgQj_yIZmZHFNJyDKkmNy7w=w640-h466" width="640" /></a></div><p>Unlike preceding ATGMs, the electronics in the missile were no longer assembled using point-to-point wiring, but on printed circuit boards (PCB), which can be attributed to the high complexity of the on-board circuitry as shown in the image above. Besides the major self-contained units such as the gyro-coordinator, the wire spool and the thermal batteries, the electronic components are housed in the between two ring-shaped PCBs upon which they are fitted, as shown in the image on the left below. One of the on-board thermal batteries occupies the center of the doughnut-shaped shaped electronics assembly, its case serving as a rigid core on which the electronics assembly is mounted. The two PCBs are braced against each other by reinforcing struts, and the space between the PCBs is filled with polyurethane foam. Combined, these measures give the structure the necessary strength, rigidity and shock protection for the electronics to survive rough handling and the launch acceleration when the missile is fired. The PCBs are connected to a wiring harness leading to the KP5 terminal block, where it connects to the gyro-coordinator, and then to the KP2 terminal block, through which the guidance system interfaces with the launch circuit via the front cap of the missile container, and connects to the steering system at the nose of the missile fuselage. The wiring harness then connects to the other electrically-controlled components of the missile via loose wire leads.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEj3W65CzswJpuStLLrjpaHqNoERBKQICXnBY_BZUaaocreeMKps_qj4I6sYABUPVKZLeNLaLqi2SvOEpWgI8z7N0RHAE1nHYe3Yz6cw9lwpcJ3AwhyNJm8wZ_euuI-T0riTQ9EjDvld954opbyD9aaZiOfEZJK_nGi5kO8CX-j5pc73JqWfAJgVAdrUVQ=s1572" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1360" data-original-width="1572" height="277" src="https://blogger.googleusercontent.com/img/a/AVvXsEj3W65CzswJpuStLLrjpaHqNoERBKQICXnBY_BZUaaocreeMKps_qj4I6sYABUPVKZLeNLaLqi2SvOEpWgI8z7N0RHAE1nHYe3Yz6cw9lwpcJ3AwhyNJm8wZ_euuI-T0riTQ9EjDvld954opbyD9aaZiOfEZJK_nGi5kO8CX-j5pc73JqWfAJgVAdrUVQ=s320" width="320" /></a><a href="https://1.bp.blogspot.com/-eeT-xYim878/YM-VifdkEQI/AAAAAAAATc4/BH7tl7KP-yIukOfDwv0EAyFFuvU8WxgpQCLcBGAsYHQ/s2865/guidance%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1098" data-original-width="2865" height="154" src="https://1.bp.blogspot.com/-eeT-xYim878/YM-VifdkEQI/AAAAAAAATc4/BH7tl7KP-yIukOfDwv0EAyFFuvU8WxgpQCLcBGAsYHQ/w400-h154/guidance%2Bsystem.png" width="400" /></a></div><p>The use of PCBs in the assembly of the electronics of the control equipment offsets the complexity of the circuitry by the ease of production of PCB circuits, as it is possible to highly automate the fitting of components on the boards and automatically solder them by wave soldering. </p><p>Like in the container itself, the onboard power supply of the missile is provided by a pair of T-307 or T-307B thermal batteries, one dedicated to the IR beacon lamp, and the other to the rest of the electric equipment in the missile. According to data provided by the manufacturer, JSC "Energia", the T-307B thermal battery has an output voltage of 15-18 V at a nominal current of 1.5 A. It is rated for a nominal operating time of 17.5 seconds at 15 V. In theory, the power system provides a surplus operating time, given that the missile does not need 17.5 seconds to reach its maximum range, but when placed under heavy electrical load from the steering system, the discharge rate is higher than the nominal figure, so the T-307(B) batteries are only enough to ensure that the maximum range is achieved. The batteries are integral to the signal receiver unit, which is the destination node of the command wire. Ahead of the receiver unit is the gyro-coordinator, and behind the receiver unit is the IR beacon. The image below shows the layout of the missile tail, containing all of the guidance equipment. </p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-D6x-3Aqqo9M/YOvvxY8wD0I/AAAAAAAAT4A/v3AQEDu0F8EeJkXQbpU03VUcnxAAQQifACLcBGAsYHQ/s2048/guidance%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1237" data-original-width="2048" height="386" src="https://1.bp.blogspot.com/-D6x-3Aqqo9M/YOvvxY8wD0I/AAAAAAAAT4A/v3AQEDu0F8EeJkXQbpU03VUcnxAAQQifACLcBGAsYHQ/w640-h386/guidance%2Bsection.png" width="640" /></a></p><p>Unlike the "Malyutka", the need for an onboard power source is likely due to the more demanding power needs of the canard steering actuators and the lamp of the IR beacon. The concept of total design minimalism, exceeding that of the "Malyutka", was later implemented by KBP Tula in their later 9K115 "Metis" ATGM system, which was powered entirely by the thermal battery attached to its missile container. The single thermal battery serviced all the electrical needs of both the launcher, and the missile itself, which had a tracer instead of an IR beacon, no gyroscope, and a new ram-air canard steering mechanism that only required a miniscule amount of power for its solenoid pneumatic valves. Unfortunately, these innovations had not yet been worked out by the era of the "Fagot" project.</p><p>It is worth mentioning that the central placement of the rocket engine interfered with the electrical connection between the nose and the tail of the missile for a multitude of reasons, the main issue being that the nose of the missile serves as the electrical interface for the launch circuitry. As mentioned earlier, the missile container connects to the launcher guide rail via a six-pin socket, and this socket permits a connection between the launcher and the missile. The interface between the container end cap and the missile is in the form of six protruding pins, which enter the six corresponding slots in the missile nose. When the launch trigger is pressed, the six pins, acting as three pairs of positive and negative terminals, complete the ignition circuits of the pyrotechnic heaters of the thermal batteries, one circuit for each battery, and the third pair of pins completes the circuit of the pyrotechnic spin-up mechanism of the gyroscope. The image on the left below shows the inner surface of the container end cap, and the image on the right below shows the corresponding interface on the nose of the 9M111. As the nose of the missile also contains the canard steering mechanism, which contains 4 pairs of electromagnets, the wiring is organized by a distributor board with 14 terminals, 6 for the launch circuits, and 8 for the steering circuits. External cable conduits connect the wiring for these terminals to the tail of the missile, where the guidance system is located.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4Jc9aOiW_7E/YOd0hGci6iI/AAAAAAAATyw/g3frnOV_qEMa8cC-Up3xoNPFHvtVu60CACLcBGAsYHQ/s1821/container%2Bend%2Bcap.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1821" data-original-width="1749" height="320" src="https://1.bp.blogspot.com/-4Jc9aOiW_7E/YOd0hGci6iI/AAAAAAAATyw/g3frnOV_qEMa8cC-Up3xoNPFHvtVu60CACLcBGAsYHQ/w307-h320/container%2Bend%2Bcap.png" width="307" /></a><a href="https://1.bp.blogspot.com/-pot51DwLWqs/YOh1gvUhxuI/AAAAAAAATzI/cHiwcBWuIfcpDU5eB0fxpuzpf7XskFbuwCLcBGAsYHQ/s2048/9m111%2Bnose.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1903" data-original-width="2048" src="https://1.bp.blogspot.com/-pot51DwLWqs/YOh1gvUhxuI/AAAAAAAATzI/cHiwcBWuIfcpDU5eB0fxpuzpf7XskFbuwCLcBGAsYHQ/s320/9m111%2Bnose.png" width="320" /></a></div><p>Within 0.1 seconds of the launch trigger being pressed, the ignition signals are transmitted on all three circuits, and then the miniature explosive bolt on the container front cover is popped open. Approximately 0.5 seconds after the front cover is opened, both onboard batteries will have powered up. Once the onboard thermal batteries power up to their operating voltage of 16 V, arming signals are automatically sent to the warhead and the rocket engine starter circuits, initiating their delayed pyrotechnic arming fuzes, and an ignition signal for the ejection engine in the tail of the container is transmitted to launch the missile. The connector pins on the container end cap can be seen in the image below, together with the conduit for the missile command wire. The initial length of the wire is stretched from the spool at the tail of the missile to the nose, so that it is connected within the container. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-BCtDWnNkSaE/YOh2mTCVLZI/AAAAAAAATzQ/MEahKFrJkp0AmwUYVD5flsYO07ymdjTpgCLcBGAsYHQ/s2048/opened%2Bcontainer%2Bend%2Bcap.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1536" data-original-width="2048" height="300" src="https://1.bp.blogspot.com/-BCtDWnNkSaE/YOh2mTCVLZI/AAAAAAAATzQ/MEahKFrJkp0AmwUYVD5flsYO07ymdjTpgCLcBGAsYHQ/w400-h300/opened%2Bcontainer%2Bend%2Bcap.jpg" width="400" /></a></div><p><br /></p><p>Like the "Malyutka", the command link is a single-wire system, combined with a single-axis control scheme. As the missile already has an onboard power source, the wire has two cores rather than three. One core transmits yaw commands, and the other transmits pitch commands. The core consists of two twisted enamelled copper wires, shielded with a high-tensile plastic jacket. Based on the known wire weight of the 9M113, a two-core wire of this particular design has a specific weight of 0.185 g/m. A 2,000-meter length of wire will therefore weigh around 370 grams, and a 2,500-meter length will weigh around 462 grams. The wire spool, shown in the image on the left below, is functionally the same design as that of the 9M14 "Malyutka". The photo on the right below shows the initial wire section being peeled from the side of the fuselage just after the missile has left the container. </p><p><br /></p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-1HHAyDHiU30/YOh4exdLrQI/AAAAAAAATzY/AkY3Gn4x2QUcYYWWbW53SZdbDVB0BKDRACLcBGAsYHQ/s2048/wire%2Bspool.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1738" height="320" src="https://1.bp.blogspot.com/-1HHAyDHiU30/YOh4exdLrQI/AAAAAAAATzY/AkY3Gn4x2QUcYYWWbW53SZdbDVB0BKDRACLcBGAsYHQ/s320/wire%2Bspool.png" /></a><a href="https://1.bp.blogspot.com/-9ybwyXpGqxE/YOojsmRKZPI/AAAAAAAAT00/g_-AIo6MclMXtehmJKNMmCX3yqQh204FACLcBGAsYHQ/s800/wire%2Bunwinding.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="533" data-original-width="800" height="266" src="https://1.bp.blogspot.com/-9ybwyXpGqxE/YOojsmRKZPI/AAAAAAAAT00/g_-AIo6MclMXtehmJKNMmCX3yqQh204FACLcBGAsYHQ/w400-h266/wire%2Bunwinding.jpg" width="400" /></a></p><p>In the technical manual for the 9K111 system, it is stipulated that when firing over salt water reservoirs or at targets floating on a salt water reservoir, the firing position must be located at an increased elevation relative to the water surface of the reservoir. The table below was given as the guideline for the required elevation for a given firing range. To engage a target situated at a distance of 500 meters, the launcher should be a height of 1.5 meters, at so on.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-KTw1R0UTsww/YNm2CltvTeI/AAAAAAAATks/q9E_Nr_q67kAFDEPswHYt1AO3SKHA8SoQCLcBGAsYHQ/s1765/firing%2Bheight%2Bover%2Bsalt%2Bwater%2Breservoir.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="493" data-original-width="1765" height="178" src="https://1.bp.blogspot.com/-KTw1R0UTsww/YNm2CltvTeI/AAAAAAAATks/q9E_Nr_q67kAFDEPswHYt1AO3SKHA8SoQCLcBGAsYHQ/w640-h178/firing%2Bheight%2Bover%2Bsalt%2Bwater%2Breservoir.png" width="640" /></a></div><p>With the 9M111M, firing out to its extended maximum range of 2,500 meters requires an elevation of 16 meters. </p><p>It is worth noting that this was one of the advantages of a single-wire command link, as opposed to a two-wire link as found on ATGMs like the 3M6 and the TOW. Other missiles with a single-wire link also share the same immunity to interference from fresh water, and are only vulnerable to shallow bodies of salt water. For instance, it is noted in <a href="http://ugcsurvival.com/weaponsmanuals/FM%203-23.24%2020010830-M47%20Dragon%20Medium%20Anti-Tank%20Weapon%20System.pdf">FM 23-24</a>, the field manual for the M47 Dragon ATGM, that:</p><p></p><blockquote>When firing the Dragon over salt water, the gunner must avoid firing at targets beyond 300 meters. Salt water can short-circuit the command link wire. Raising the launcher 0.3 meter (1 foot) increases the distance the Dragon can be fired over water by 100 meters. Fresh water does not affect command-link wire, so the missile normally can be fired over it.</blockquote><p></p><p><br /></p><p>The ability of the MILAN - which also has a single-wire command link - to be fired freely over fresh water was also noted in the book "<i>Armements Antichars Missiles Guidés Et Non Guidés</i>".</p><p>On the "Fagot", the signals conveyed via the wire link to the receiver unit are split into the yaw and pitch channels and then preamplified before being relayed to the gyro-coordinator. The receiver consists of a decoder, polarity inversion, and amplifying (output) stages. The signals arriving from the wire are in the form of square waveforms with a positive or negative polarity to determine the pitch direction, and a different voltage to determine the yaw direction. Signals with a voltage of ±50 V communicate a steer-right command, and signals with a voltage of ±11.5 V communicate a steer-left command. The receiver inverts the polarity of the signal upon reception, so that a positive voltage results in a pitch-down, and a negative voltage results in a pitch up. The reason for this is unclear. </p><p>If the guidance wire is cut or there is a loss of communication for any other reason, the steering system automatically assumes a left-down steering command, causing the missile to self-destruct by diving into the ground. One of the changes brought by the 9M111M "Faktoriya" was the change in the construction of the decoder and amplifier circuits from a traditional point-to-point construction to a set of printed circuit boards, and a switch from conventional connector cables to a ribbon cable, which saved weight. This helped to offset the weight gain from the increased length of wire carried on the missile. </p><p>The gyro-coordinator mechanism distributes the pitch and yaw commands from the receiver into the appropriate phase-shifted commands that are coordinated with the roll position of the missile. The processed signal is sent back to the receiver unit, which then amplifies and transmits it to the appropriate pair of canards. Its purpose is identical to the gyroscope in the "Malyutka". The gyro-coordinator is spun up to its operating speed by a pyrotechnic charge which burns for no more than 0.3 seconds, propelling the rotor via radial vents, like a Catherine wheel firework. This drives the gyro rotor to a speed of 90,000 RPM whereupon a mechanical cutoff is tripped, and the cage of the rotor is released, allowing the rotor to spin under inertia. Connected to the gyroscope frame is a commutator, shown in the drawing on the right below, which has the same function as the commutator found on the "Malyutka".</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-c5i1SupymSw/YM-XEZkw1GI/AAAAAAAATdA/q03_jdOX4zwmSPntE3LYpZVJ2bTw3_xmwCLcBGAsYHQ/s2048/gyroscope.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1259" data-original-width="2048" height="246" src="https://1.bp.blogspot.com/-c5i1SupymSw/YM-XEZkw1GI/AAAAAAAATdA/q03_jdOX4zwmSPntE3LYpZVJ2bTw3_xmwCLcBGAsYHQ/w400-h246/gyroscope.png" width="400" /></a><a href="https://1.bp.blogspot.com/-REfbqOLtvVc/YOjW9du_R6I/AAAAAAAAT0g/cXxTtB7PRsE-syPofX85dweVvR7aD9I3gCLcBGAsYHQ/s1822/commutator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1542" data-original-width="1822" height="271" src="https://1.bp.blogspot.com/-REfbqOLtvVc/YOjW9du_R6I/AAAAAAAAT0g/cXxTtB7PRsE-syPofX85dweVvR7aD9I3gCLcBGAsYHQ/w320-h271/commutator.png" width="320" /></a></div><p>From the moment the cage of the gyroscope rotor is released, the lamellar commutator does not change its position in space, and the current collector contacts, fixed to the fuselage missile and rotating along with it, run around the commutator, receiving the voltages of the control command signals according to the appropriate roll angle sectors. The diagram below shows, from left to right, the canard activation sectors and the corresponding command signals in the pitch and yaw channels.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Us552wNhQX8/YOXbJjXUOWI/AAAAAAAATxY/zutpcUDJMzch2D-sU6j8wcyKL2EfB6mMQCLcBGAsYHQ/s2048/steering%2Bexecution.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1761" height="400" src="https://1.bp.blogspot.com/-Us552wNhQX8/YOXbJjXUOWI/AAAAAAAATxY/zutpcUDJMzch2D-sU6j8wcyKL2EfB6mMQCLcBGAsYHQ/w344-h400/steering%2Bexecution.png" width="344" /></a></div><p>Because there are four canard fins, split into two interlinked pairs, the steering system could smoothly alternate between every two pairs every quarter turn of the missile, rather than having one pair of nozzles be activated every half turn as in the "Malyutka". This means that the "Fagot" has a single-axis control scheme with a two-axis steering mechanism. The downside is that the logic circuit for this operation is much more complex, as steering commands cannot be differentiated merely by introducing a phase shift as in the "Malyutka". When the missile is rotated for every quarter turn, the closed contact pairs of the sensor change and the canards switch roles, i.e. the ones that were executing a pitch command will switch to execute a yaw command after a quarter turn, and vice versa. So, when steering the missile to pitch up, the canards will all become aligned in pitching upwards, and this is also true when steering down, or to the left or right.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-SDtG3LJG4cU/YOXYsyBSZoI/AAAAAAAATxQ/qTSIj6yA5HgNV8p7wel7_c5Keo0x7kLNgCLcBGAsYHQ/s2712/turn.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1160" data-original-width="2712" height="274" src="https://1.bp.blogspot.com/-SDtG3LJG4cU/YOXYsyBSZoI/AAAAAAAATxQ/qTSIj6yA5HgNV8p7wel7_c5Keo0x7kLNgCLcBGAsYHQ/w640-h274/turn.png" width="640" /></a></div><p>To compensate for the phase delay in the processing and execution of commands by the missile guidance system, which occurs due to the speed of its rotation and the inertia of the canards which prevents truly instantaneous turning by the electromagnetic drives, control commands are sent to the projectile with a calculated preemptive angular offset of 10 degrees. Given a missile spin rate of 10 RPS, or 10 Hz, this indicates that the phase delay is 0.0027 seconds, or 2.7 milliseconds. Evidently, the "Fagot" control system is extremely responsive.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-CtwS84NDPOs/YOXVZRNx_lI/AAAAAAAATxI/L7_Ej3SnH84oV9ZLlTu90q5vTo0a463ywCLcBGAsYHQ/s2048/axial%2Bpositions.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1901" data-original-width="2048" height="371" src="https://1.bp.blogspot.com/-CtwS84NDPOs/YOXVZRNx_lI/AAAAAAAATxI/L7_Ej3SnH84oV9ZLlTu90q5vTo0a463ywCLcBGAsYHQ/w400-h371/axial%2Bpositions.png" width="400" /></a></div><p><br /></p><p>Observation of the 9M111 in flight by both the missile operator and the optical tracking module of the launcher is provided by a simple IR beacon consisting of an incandescent bulb with a parabolic reflector. The lamp is not modulated, and is nothing more than a continuous source of light. When the missile is in an unfired state, the spring-loaded flaps are held in place by nitrocellulose gaskets pressed around the circumference of the lamp. Upon firing, the heat from the ejection charge incinerates the gaskets, while the pressure developed in the missile container holds the spring-loaded flaps closed. Once the missile has been ejected from the container, the flaps open under spring tension. At the same time, the inertial circuit switch is armed by the launch acceleration, and once the missile begins to deccelerate from air resistance after leaving the container, the circuit is closed, turning on the lamp. </p><p>To eliminate any fogging that may develop on the lamp at low temperatures just before the missile is launched from the container, there are small vent holes in the tail of the missile that are opened up by the incineration of the nitrocellulose gaskets. These vents permit a small amount of hot gasses from the ejection charge in the missile container to flow behind and around the reflector, thus momentarily preheating the lamp and vaporizing any moisture. During flight, the heat continuously generated by the incandescent bulb itself prevents fogging.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-1vEp04Eu-rA/YOv2C2M4avI/AAAAAAAAT4I/JwIN5c-yOeUov0krXAFLO9GouCuyMzXKACLcBGAsYHQ/s2048/ir%2Bbeacon.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1939" data-original-width="2048" height="303" src="https://1.bp.blogspot.com/-1vEp04Eu-rA/YOv2C2M4avI/AAAAAAAAT4I/JwIN5c-yOeUov0krXAFLO9GouCuyMzXKACLcBGAsYHQ/w320-h303/ir%2Bbeacon.png" width="320" /></a><a href="https://1.bp.blogspot.com/-9QQdLy8_exc/YOh5hm6iwKI/AAAAAAAATzg/0C0VCW9NT301o25LgixxgRpxhfeLx8VUwCLcBGAsYHQ/s1013/9m111%2Btail.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="802" data-original-width="1013" height="316" src="https://1.bp.blogspot.com/-9QQdLy8_exc/YOh5hm6iwKI/AAAAAAAATzg/0C0VCW9NT301o25LgixxgRpxhfeLx8VUwCLcBGAsYHQ/w400-h316/9m111%2Btail.png" width="400" /></a></div></div><p>Overall, the lamp measures 95mm in diameter and is 65mm long. For the light source, an RN 13.5-100 bulb is used. It is an incandescent tungsten filament bulb with a power of 100 W, running on 13.5 volts. The emitted light has an intensity of 2,610 candelas - much dimmer than the beefy pyrotechnic tracers used in the previous generation of ATGMs. The surface of the lamp bulb is covered with an IR filter coating that limits the amount of visible light emitted while allowing IR radiation to pass through. This ensures that the power of the IR emission is intense enough to be registered by the optical tracker of the guidance computer even at the maximum range of the missile, yet the visible light is not overwhelmingly bright for the operator in various lighting conditions. The tip of the bulb itself is obscured by an occluder, so that the bulb only emits light to the sides, to be reflected off the parabolic reflector. This reduces the amount of light emitted radially behind the missile. This helps to reduce the probability of multiple missile launchers receiving mutual interference when multiple missiles are in flight at the same time, as each missile will emit an IR beam that is directly oriented towards their own launcher. This feature also adds an element of stealthiness at night, as tracers or beacons without occluders would illuminate the ground, creating a flight signature that would be clearly visible to enemy forces with night vision equipment.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-1OBpNgCCv7A/YJ1YiXU0IoI/AAAAAAAAS-c/CuV1aMSGiUQBMRZNwflhOy6zV1tZIU1XACLcBGAsYHQ/s1439/9m111%2Bir%2Bbeacon.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1057" data-original-width="1439" height="294" src="https://1.bp.blogspot.com/-1OBpNgCCv7A/YJ1YiXU0IoI/AAAAAAAAS-c/CuV1aMSGiUQBMRZNwflhOy6zV1tZIU1XACLcBGAsYHQ/w400-h294/9m111%2Bir%2Bbeacon.png" width="400" /></a><a href="https://1.bp.blogspot.com/-HMNU4fPX0-0/YKgYr_slJ4I/AAAAAAAATDk/xc0swfQczRkdZHxM_zn_ISJfjXLqDyjgwCLcBGAsYHQ/s603/rn%2B13.5-100.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="603" data-original-width="381" height="320" src="https://1.bp.blogspot.com/-HMNU4fPX0-0/YKgYr_slJ4I/AAAAAAAATDk/xc0swfQczRkdZHxM_zn_ISJfjXLqDyjgwCLcBGAsYHQ/s320/rn%2B13.5-100.jpg" /></a><br /><br /></div><p>The missile enters the field of view of the optical tracking device within 70-75 meters after launch. Prior to the start of operator control, a special program transmits a temorary pitch-up and steer-left command to the missile, which is necessary to ensure that the missile does not lose altitude while its flight speed is low, both by increasing its angle of attack and increasing the vertical thrust component of the rocket engine when it starts. The program was created by taking into account the weight of the missile, its initial velocity upon departure from the container, and the acceleration from the booster engine. The steer-left command also brings the missile into the field of view of the guidance optic more quickly. Once operator control begins, the special program ends. To maintain level flight (without steering corrections), a weight compensation command is automatically generated and periodically transmitted to the missile that prompts it to make a gentle pitch-up motion, and thus maintain its correct trim angle at all times. This weight compensation signal is summed with any operator control commands in the pitch axis.</p><p>Detection of the IR beacon is performed by the 9Sh119(M1) sighting unit of the launcher. The tracking system is essentially a photoelectric goniometer, relying on an IR-sensitive photodetector that is supplied with the IR light from the missile beacon, modulated by an eccentric stroboscopic disc centered on the line of sight. The disc has 100 slots separated by an equal number of opaque sectors, spaced evenly along the surface of the disc, and it spins at a constant rate of 4,500 RPM. The axis of the disc is not coaxial to the photodetector - rather, one of the slots is coaxial to the photodetector, so that when the missile is centered in the line of sight to the target, no modulation occurs. When the missile diverges from the line of sight in any given direction, a unique modulated light signal is generated by the specific interaction with the stroboscopic disc. The modulated light signal is converted into an error signal by the photodetector, which is then processed into a control signal by the missile command system. </p><p>The 9Sh119(M1) sight has two field of view modes, achieved using two identical photodetectors with the same stroboscopic discs, but fitted with different magnifier optics. The photodetector and stroboscopic disc assembly is a goniometer which is used to measure the angular deviation of the missile from the center of the reticle, and generate a corresponding feedback signal. The wide field of view mode allows the system to reliably capture the missile immediately after launch and provide an allowance for initial corrections, and after 4 seconds, when the missile is 500 meters ahead of the launcher, the system automatically switches to the narrow field of view mode. The image on the left below is a block diagram of the 9S451 together with the 9Sh119 sighting unit, showing how the photodetectors (4) and stroboscopic discs (2) are paired with different optics (1). The image on the right shows the kinematic diagram for the disc spinning mechanism.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-c6ZOa2ZZYCg/YPhan0xj8XI/AAAAAAAAUBA/c2sVDJu6BlQM5Vci8exz9Gck8W4M9wLJwCLcBGAsYHQ/s2048/9s451.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1341" data-original-width="2048" height="263" src="https://1.bp.blogspot.com/-c6ZOa2ZZYCg/YPhan0xj8XI/AAAAAAAAUBA/c2sVDJu6BlQM5Vci8exz9Gck8W4M9wLJwCLcBGAsYHQ/w400-h263/9s451.png" width="400" /></a><a href="https://1.bp.blogspot.com/-nNDRT_wdKy8/YPhnRz6IMtI/AAAAAAAAUBQ/rIzDyevz0b8syu9qSU3I6bb_TTOkoZ8UgCLcBGAsYHQ/s2048/stroboscopic%2Bdiscs%2Bturning%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1331" data-original-width="2048" height="260" src="https://1.bp.blogspot.com/-nNDRT_wdKy8/YPhnRz6IMtI/AAAAAAAAUBQ/rIzDyevz0b8syu9qSU3I6bb_TTOkoZ8UgCLcBGAsYHQ/w400-h260/stroboscopic%2Bdiscs%2Bturning%2Bmechanism.png" width="400" /></a><br /></div><p>The optic has a magnification of 10x and a total field of view of 5 degrees. A simple stadiametric rangefinding scale is provided to determine the range to a target with a height of 2.5 meters. The field of view of the wide and narrow tracking channels are marked in the operator's sight as large and medium concentric circles. The large circle has an angular diameter of 2.5 degrees. The medium circle has an angular diameter of 0.5 degrees. A narrow field of view for the missile tracker is preferable as long as a wide field of view is not strictly necessary, as it reduces the vulnerability of the system to IR interference. A wide tracking field of view is a necessity only if the missile lacks responsive steering, which introduces the possibility of the operator traversing the launcher quicker than the missile can turn, leading to a loss of line-of-sight between the tracking optic and the missile beacon. For instance, the wide-view goniometer of the MILAN guidance computer has a field of view of 4.58 degrees (80 mrads) and the narrow-view goniometer has a field of view of 1.15 degrees (20 mrads). The MILAN optic has a 7x magnification and a total field of view of 8.6 degrees (150 mrads).</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-aA8DzCqI0R8/YPhrc_UkXxI/AAAAAAAAUBY/Jt8UyGeA0HYT9I34RXXzG9bY-8XyUG4SwCLcBGAsYHQ/s2048/sight.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1614" data-original-width="2048" height="315" src="https://1.bp.blogspot.com/-aA8DzCqI0R8/YPhrc_UkXxI/AAAAAAAAUBY/Jt8UyGeA0HYT9I34RXXzG9bY-8XyUG4SwCLcBGAsYHQ/w400-h315/sight.png" width="400" /></a></div><p>Strong IR interference, such as the sun or the beam from the IR spotlight of a tank aimed directly at the sight, is likely to cause the system to fail by losing track of the missile IR beacon. By limiting the field of view of the tracker, it becomes difficult to lose the missile unless the operator has his point of aim placed squarely on the source of IR interference. Otherwise, the operator can guide the missile in a raised or offset trajectory, making sure there are no sources of interference within the narrow circle, until the moment just before impact. As a backup option, the 9P148 tank destroyer allows the 9M111 to be guided visually by the operator in the MCLOS mode. This is a somewhat unusual capability, notably absent from contemporary SACLOS missiles such as the MILAN and TOW.</p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">STEERING</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-u9DrSs-FC_w/YOXdhQYBF7I/AAAAAAAATxg/BvIOVfiP5z0XKD-l-ENLrcsdeH5bBSvuQCLcBGAsYHQ/s2048/canard.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1249" data-original-width="2048" height="390" src="https://1.bp.blogspot.com/-u9DrSs-FC_w/YOXdhQYBF7I/AAAAAAAATxg/BvIOVfiP5z0XKD-l-ENLrcsdeH5bBSvuQCLcBGAsYHQ/w640-h390/canard.png" width="640" /></a></div><p>In the article "<i>Противотанковые комплексы контейнерного старта: Противотанковый комплекс 9К11 «Фагот»</i>" by R. Angelskiy and S. Suvorov, published in the March 2020 edition of the "<i>Техника и вооружение</i>" magazine, it was explained that the decision to use a canard steering mechanism was made after a design analysis was made comparing its merits to that of a TVC steering mechanism, as found on "Malyutka". This was related to the launch method selected for the system. Because the missile is ejected from its container by an ejection engine, and its own engine does not start until the missile has reached a safe distance away from the operator, a TVC system did not give any possibility of steering the missile during its initial trajectory. Though less effective at the launch speed of the missile, the use of canard fins made it possible to implement a special repositioning program, which was detailed in the preceding section. The canard fins are non-retractable, as the narrowed nose of the tapered missile fuselage gives enough free space for the fins to clear the container walls. Also, they are active and can respond to commands as soon as the missile is clear of the container, because as mentioned in the previous section, they are powered up as soon as the onboard batteries of the "Fagot" are activated, which occurs before launch.</p><p>Interestingly enough, this problem was "solved" on the MILAN by simply ignoring the issues of exhaust gasses interfering with the operator and the guidance optics.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-RRZIlCUzlK0/YOV6AsqQFqI/AAAAAAAATwI/vXZdmXsZwnYkqBvn4ApmUH62blvN25JTACLcBGAsYHQ/s1920/milan%2Bboost%2Bphase%2Bback%2Bblast.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://1.bp.blogspot.com/-RRZIlCUzlK0/YOV6AsqQFqI/AAAAAAAATwI/vXZdmXsZwnYkqBvn4ApmUH62blvN25JTACLcBGAsYHQ/w400-h225/milan%2Bboost%2Bphase%2Bback%2Bblast.png" width="400" /></a></div><p>To provide steering functionality in both axes, the four canard fins are divided into two mechanically linked pairs. Because the each pair of fins can only deflect in the same direction at any given time, roll control is impossible. Roll stability is thus provided entirely by the equilibrium spin of the missile in flight. The advantage of linking opposing fins into pairs is that this reduced the number of electromagnets to four, two for each pair, rather than eight, which would be two for each individual fin. This was a substantial reduction in mass, though it was not taken to the extreme by leaving only a single pair of canards, as that is not feasible with the actuation limits of electromagnets. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-0l3xy_3HVb4/YOu3aLopPjI/AAAAAAAAT3g/p4IFkt2SHL0VGnS2ybnPPZ-s_NiP0EJuACLcBGAsYHQ/s1563/canard%2Bsteering.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1259" data-original-width="1563" height="323" src="https://1.bp.blogspot.com/-0l3xy_3HVb4/YOu3aLopPjI/AAAAAAAAT3g/p4IFkt2SHL0VGnS2ybnPPZ-s_NiP0EJuACLcBGAsYHQ/w400-h323/canard%2Bsteering.png" width="400" /></a><a href="https://1.bp.blogspot.com/-ldzKiaWR4dI/YN3R5srMGRI/AAAAAAAATsQ/9fs40_eBuIcOmy8q_pSW0IOlyKzJtlNWwCLcBGAsYHQ/s2048/steering%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1879" height="320" src="https://1.bp.blogspot.com/-ldzKiaWR4dI/YN3R5srMGRI/AAAAAAAATsQ/9fs40_eBuIcOmy8q_pSW0IOlyKzJtlNWwCLcBGAsYHQ/w294-h320/steering%2Bmechanism.png" width="294" /></a></div><p>The steering mechanism is extremely simple. It consists of nothing more than a pair of electromagnets, which may alternately attract the armature of a canard fin pair to shift it between two possible deflection angles. If both electromagnets are de-energized, the canard returns to its neutral position via a return spring. Each armature is mounted on rolling bearings between the poles of the electromagnet cores.</p><p>The steering system is controlled in a bang-bang scheme with a deflection angle of ±15 degrees. The intensity of the steering effect is controlled by varying the length of the period when the fins are deflected, which is controlled by pulse width modulation. When a command signal is applied to one of the electromagnets, the canard armature is attracted to the iron core, turning on its bearings, and the fins are thus turned along with it. When the sign of the command signal changes, the signal goes to the opposite electromagnet and the armature is attracted to it, turning the canards in the opposite direction. To minimize the influence of residual magnetization and to prevent the armature from sticking to the poles of the cores, iron cores are used, and non-magnetic pads are glued around them.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-O6t06Dt8NNQ/YN3RJBUZOLI/AAAAAAAATsI/C8j3IUsPQXIBXGTvYQw6BnNGOjHqBLTmACLcBGAsYHQ/s1794/electromagnetic%2Bcanards.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1020" data-original-width="1794" height="228" src="https://1.bp.blogspot.com/-O6t06Dt8NNQ/YN3RJBUZOLI/AAAAAAAATsI/C8j3IUsPQXIBXGTvYQw6BnNGOjHqBLTmACLcBGAsYHQ/w400-h228/electromagnetic%2Bcanards.png" width="400" /></a><a href="https://1.bp.blogspot.com/-4j0lD21MQww/YM97d9fxUbI/AAAAAAAATcw/omemoac95wc5SPwYtB_rYIEbvqBtDiZeQCLcBGAsYHQ/s1481/canard%2Bactuators.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="730" data-original-width="1481" height="198" src="https://1.bp.blogspot.com/-4j0lD21MQww/YM97d9fxUbI/AAAAAAAATcw/omemoac95wc5SPwYtB_rYIEbvqBtDiZeQCLcBGAsYHQ/w400-h198/canard%2Bactuators.png" width="400" /></a></div><p>Moving canards function as steering surfaces by producing excess lift in the desired direction, thus altering the trajectory of the missile. For instance, when pivoted upwards (with the proper synchronization via the gyro-coordinator), the angle of attack of a canard pair relative to the airflow is increased, generating additional lift, causing the entire missile to pitch upwards. The resulting increase in the angle of attack of the missile also raises the lifting force from the wings and increases the vertical thrust component of the rocket engine, thus strongly displacing the missile upward.</p><p>Compared to a TVC system, where lateral forces are provided by the thrust from the engine itself, allowing strong steering moments to be executed without requiring a great deal of electrical power or actuators of a large size, aerodynamic control surfaces have a need for both. To produce the necessary steering moment, the control surfaces ought to be able to produce a lot of lift, which in turn requires either a high airspeed, or a large surface area. In either case, increasing the angle of attack of the canard to execute the steering action creates a corresponding aerodynamic reaction torque, which is caused by the lift force acting about the pivot point of the canard. The reaction torque acts to return the canard to an equilibrium angle, which would be a zero-degree angle of attack, and as such, a high load is imparted on the steering mechanism when it attempts to move the canard. </p><p>The first and most prominent solution to the issue of actuator power was to place the canards at the nose of the missile, practically on its tip. This is so that the distance between fins and the center of gravity of the missile is maximized, and the steering moment arm is therefore also at its maximum. Thus, a large lifting capacity is not needed from the canards. The second solution to keep the steering resistance to a level manageable by electromagnets was to split the lift-producing surface area across more control surfaces of a smaller size, rather than a single pair of two large canards, and make use of the cruciform fin arrangement to double the steering period per missile rotation. This doubled the number of electromagnetic actuators, but allowed electromagnets of less than half the power to cope with the aerodynamic load. Having only a single pair of canard fins was impractical until ram-air actuators were invented later, coupled with an increased flight speed, which considerably improves the lifting efficiency of all-moving control surfaces as discussed earlier in the "Falanga" section of this article. Those practical engineering requirements were only realized in later KBP Tula products such as their gun-launched ATGMs, and the "Kornet".</p><p>The third design solution was in the specific canard design itself. It became a signature of the KBP design bureau, seeing use in almost all of their future, from ATGMs to guided artillery ammunition such as the Kitolov series and the Gran. The design was patented in Russian patent <a href="https://findpatent.ru/patent/222/2222773.html">RU2222773</a>.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GkM-fRjCeAc/YPIxlHtVtBI/AAAAAAAAT80/i8WirxqV3wgDZ184OkqMKL5dGOay0IUpQCLcBGAsYHQ/s699/kbp%2Bcanard.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="463" data-original-width="699" height="265" src="https://1.bp.blogspot.com/-GkM-fRjCeAc/YPIxlHtVtBI/AAAAAAAAT80/i8WirxqV3wgDZ184OkqMKL5dGOay0IUpQCLcBGAsYHQ/w400-h265/kbp%2Bcanard.jpg" width="400" /></a></div><p>This particular planform was chosen to minimize the aerodynamic resistance to the turning motion of the canard, which is raised when the center of pressure of the canard moves as the angle of attack increases. A resistive torque is a result of the center of pressure being behind the pivot point of the canard, so that a torque is generated to oppose the electromagnetic drive whenever the canard is deflected. This is desireable for aircraft largely due to controllability reasons, but human piloting concerns are irrelevant for an ATGM control system. The change in aerodynamic resistance at various angles of attack is shown in the graph below, with curve (1) representing a simple rectangular planform canard and curve (2) representing the patented KBP canard. The graph was produced with empirical testing at Mach 0.7, or 240 m/s, in a wind tunnel. As the graph shows, the resistive aerodynamic force acting on the KBP canard is not only much smaller, but it acts in the opposite direction. The aerodynamic load is therefore small, and the torque requirement of the steering mechanism is also small.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-nbpLNP2_fLU/YPIx60i8wjI/AAAAAAAAT88/-gUV6plpHEAwwbjMqbgNvS6e9q8Z2i5uQCLcBGAsYHQ/s681/lift%2Bcoefficient.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="500" data-original-width="681" height="294" src="https://1.bp.blogspot.com/-nbpLNP2_fLU/YPIx60i8wjI/AAAAAAAAT88/-gUV6plpHEAwwbjMqbgNvS6e9q8Z2i5uQCLcBGAsYHQ/w400-h294/lift%2Bcoefficient.jpg" width="400" /></a></div><p>This, in essence, creates an <a href="https://www.sciencedirect.com/science/article/pii/B9781483200194500144">unstable all-moving control surface</a>. With this type of aerodynamic reaction, it can be seen that the canard will have a natural tendency to become deflected by its own lift force, which is resisted by the spring in the steering mechanism. The actual role of the electromagnet drives is, therefore, to overcome the resistance of the return spring of the canard, and not to overcome the aerodynamic resistance from the canard itself. The result is a net reduction in the load, and thus, a lower actuator power requirement.</p><p>The primary issue with this specific implementation of a canard aerodynamic scheme was that the steering actuators had to be placed in front of the warhead, directly in the path of the shaped charge jet. Although it was universally accepted that nose fuzes on ATGMs had practically no effect on a shaped charge jet, being unsubstantial enough to not disrupt the jet before it impacts the target, this could not be said of the "Fagot" steering mechanism. The solution implemented in the "Fagot" for this issue was to create a controlled disintegration zone. At the moment the missile strikes a target, the nose is flattened upon impact and the screws holding the steering mechanism to the nose are sheared off. While the steering mechanism is stopped on the surface of the target, its rotational inertia from the spin of the missile, no longer restrained by the destroyed fuselage nose, is free to separate the actuators radially, thus clearing a gap in the center that is large enough for the shaped charge jet (which is only a few millimeters wide) to pass through untouched. To provide enough time for the separation to occur, the steering mechanism is spaced around an inch forward of the warhead (estimated based on cutaway photos), and once the warhead crush fuze is deformed by the subsequent collision against the disintegrated steering mechanism, it detonates.</p><p>Though this technical solution solved the issue of jet interference, it was not totally devoid of shortcomings, as the disintegration zone allocated for the steering mechanism in front of the warhead crush fuze reduces the maximum available standoff distance much more than a conventional fuzing solution. Around one inch is lost due to this, or around 0.26 CD. The steering mechanism itself measures around 62mm in length, or 0.71 CD. Note that real measurements are still pending, and only estimates can be made at the moment.</p><p><br /></p><p>Incidentally, it is worth noting that due to the use of a single-axis steering system, some amount of steering force is inevitably transmitted tangentially to the desired axis. For instance, when the missile is turned correctly for a steer-left command to be executed, then the canards snap into position for a quarter turn, which means that the steering force is distributed across an arc of 90 degrees rather than during the exact point when the canards are exactly aligned to the vertical axis of the missile. At the very beginning of the 90-degree turn, the steering action of the canards imparts a steering force with two components, a y-component, and an x-component. Because the angle of the canards relative to the vertical axis of the missile is 45 degrees, the two force components are equal. As the missile turns clockwise, the canards approach the vertical axis, and in doing so, the y-component diminishes until reaching zero, where the x-component is maximum. As the missile continues turning, the y-component increases again until the full 90-degree turn is completed, whereupon the canards snap back to the neutral position. Because the x-component is present throughout the entire turn, the net steering force directs the missile to the left, but the y-component is large enough to redirect the missile tangentially. For this reason, the missile acquires a spiralling trajectory when steering inputs are made. </p><p><br /></p><p>The steering rate of the 9M111 is not known. However, it can be deduced based on the maximum permissible tracking rate of the 9P135(M) launcher, which dictates the maximum steering rate achievable by the missile without the guidance computer losing track of the missile. A high tracking rate is necessary for engaging targets at short range, as an excessively low tracking rate may allow a fast target to cross the field of view of the missile operator faster than his missile can change its trajectory to hit it.</p><p>To search and aim at targets, and to steer the missile in flight, the 9P135(M) launcher has a geared traverse and elevation mechanism. The elevation mechanism is a small handwheel fixed to the launcher that drives the elevation of the launcher by a worm gear; it provides an elevating speed of up to 0.5 degrees per second (with two turns of the handwheel per second). By extension, this limits the maximum altitude displacement rate of the missile to an angular velocity of 0.5 degrees per second. The traverse mechanism provides two traversing speeds - high and low. The main speed used when tracking a target is the low speed mode whereby the operator turns a small handwheel, just as on the elevating mechanism. This provides precise tracking of moving targets with a traversing speed of up to 0.5 degrees per second, which, again, also means that the maximum steering rate of the missile is 0.5 degrees per second. The traverse mechanism incorporates an inertial damper in the form of a flywheel, used to smoothen the operator's input on the handwheel in conjunction with the inertia of the swivelling portion of the launcher.</p><p>Alternately, the operator can switch to the high speed traverse mode by pulling out the traverse mechanism stopper, after which the operator can manually rotate the launcher, up to a traversing speed limit of 1.5 degrees per second. The launcher can, of course, be rotated faster, but the maximum angular tracking speed is 1.5 degrees per second as dictated by the maximum steering velocity of the missile. Manuals for the 9K111 system specify that the transition to the high speed traverse mode should be carried out if the low speed mode does not provide the necessary tracking rate on a fast moving target at short ranges of up to 700 meters. </p><p>For comparison, despite having a TVC steering system, the maneuverability of the MILAN does not surpass the "Fagot". On the contrary, it is somewhat worse. According to a Dutch manual for the MILAN, the maximum tracking rate of the system is not more than 20 mrads per second, or 1.15 degrees per second. The research paper "E Missile And Its Performance - An Analysis" by P. K Kallepelli, et al. corroborates the tracking rate figure of 20 mrads per second. The steering thrust (off-axis thrust) of the MILAN missile is the same in both the boost and sustainer stages of its engine, which eliminates the possibility that this steering rate is achieved near the end of its flight, when the missile is traveling at its peak velocity, because the inertia of the missile is also at its peak and the steering rate will be at a minimum for a given steering thrust. The given maximum change in angular velocity must therefore be true only in the initial seconds of the missile flight. In this case, it can be seen that when engaging targets, the permissible tracking rate of the "Fagot" is no less than 30% higher - 1.5 degrees per second compared to 1.15 degrees per second. As another point of comparison, the ability of the TOW series (including TOW-2A and ITAS) to engage crossing targets is restricted by the kinematic limitations of the missile to around 25 mils per second (1.43 degrees per second) but only up to 900 meters. Beyond this distance, the missile cannot steer hard enough to keep up with the reticle, and if the target continues to be tracked at a rate of 25 mils per second, the missile trajectory diverges further and further until it is lost. Compared to these systems, the higher tracking rate of the 9K111 system may allow the "Fagot" to engage fast moving targets at all ranges more readily than both the MILAN and TOW systems.</p><p>With that in mind, although the 9K111 system was rated to engage (crossing) targets moving at a speed of 60 km/h, and the minimum range is 70 meters, this does not mean that it is possible to engage crossing targets under those conditions. Rather, the target speed limit when firing firing at moving targets is strongly dependent on the distance. Officially, effective engagements at no less than 150 meters are ensured only if the target crossing speed is no more than 20 km/h. At 300 meters, the crossing speed limit is no more than 30 km/h. Only with a distance of at least 300 meters is it possible to effective engage crossing targets moving at up to 60 km/h. These limits exceed the given tracking rate of the missile of 1.5 degrees per second, which implies that the true maximum tracking rate is somewhat higher, which is plausible given that the maximum figure is not actually known. </p><p>It is important to note that the ability of the MILAN to engage moving targets at short range is limited to only 500 meters according to <a href="http://20thcenturyplatoons.com/articles/M47%20Dragon%20assessment.html#title">a Dutch comparative assessment of MILAN and the M47 Dragon</a>. The limitation of the system at short range is also reflected in <a href="https://cdn.discordapp.com/attachments/659750348256182272/879660008076369930/20210824_112933.jpg">a Dutch manual for the MILAN</a>, where the tactical minimum range is listed as being 400 meters. This is particularly noteworthy because the wide-view goniometer of the MILAN guidance computer has a field of view of 4.58 degrees (80 mrads), or 2.29 degrees (40 mrads) to the left and right. The guidance computer operates in the wide-view mode for the first 4.5 seconds of the missile's flight, where it covers a distance of 400 meters according to the Dutch manual, or around 550 meters according to a time-displacement graph in an article titled "MILAN", published in issue 48 of the Armies & Weapons magazine, November 1978. Evidently, the missile is still being tracked in the wide tracking mode during a 400-500 meter engagement. As such, it can be firmly concluded that the field of view of the tracking system is not the limiting factor in the relatively slow tracking rate of the MILAN. Rather, it is a limitation of the missile steering system itself, and interestingly enough, this indicates that the canard steering mechanism of the "Fagot" is more capable than the TVC system of the MILAN.</p><p><br /></p><p><a href="https://www.blogger.com/null" id="fagotejection"></a></p><h3 style="text-align: left;"><span style="font-size: large;">EJECTION ENGINE</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-7LVhJvSRpTA/YJ11TRBUY3I/AAAAAAAAS-0/HZdM7YdrTjwapImOu1NWMCEUKxMAo8xjwCLcBGAsYHQ/s2048/gas%2Bgenerator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1398" data-original-width="2048" height="272" src="https://1.bp.blogspot.com/-7LVhJvSRpTA/YJ11TRBUY3I/AAAAAAAAS-0/HZdM7YdrTjwapImOu1NWMCEUKxMAo8xjwCLcBGAsYHQ/w400-h272/gas%2Bgenerator.png" width="400" /></a></div><p>The ejection system of 9M111 is based on a recoilless gun principle with a fixed ejection charge, called an ejection engine and sometimes even referred to as a rocket engine, but otherwise known as a gas generator in French and some English technical literature. By offloading the task of missile launch to an external engine, important weight savings could be made in the design of the missile itself, freeing up payload capacity for other purposes, including more fuel for a more powerful engine, allowing higher speeds to be achieved. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-hy3KAoGYMvY/YOokB5SKKTI/AAAAAAAAT08/ck_H20Jb77cxdBni-dk80mMULDY9WvEpgCLcBGAsYHQ/s800/flame.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="533" data-original-width="800" height="266" src="https://1.bp.blogspot.com/-hy3KAoGYMvY/YOokB5SKKTI/AAAAAAAAT08/ck_H20Jb77cxdBni-dk80mMULDY9WvEpgCLcBGAsYHQ/w400-h266/flame.jpg" width="400" /></a></div><p>Like any recoilless gun, the missile container is an open-ended tube, allowing gasses inside the container to flow out the rear, as shown in the image below. As dictated by the conservation of momentum, to achieve a truly recoilless effect, the gasses exiting to the rear must possess the same momentum as the missile as it leaves the container, and not only that, but the momentum flow curve must match. Regardless of how propulsion is achieved, whether it is a rocket or a fixed charge, this condition must be satisfied for recoil to be negated. With the "Fagot", a completely recoilless effect is not achieved at all operating temperatures, and a missile launch will still impart a small amount of recoil, especially in colder temperatures. The dynamic balance along the momentum flow curve was matched to within 2 kgf (19 N), which, in all fairness, is almost imperceptible. To eliminate any negative effects from the felt recoil, the mounting rail of the 9P135(M) launcher is a reciprocating assembly containing a soft buffer spring. For maximum stability, the conveniently shaped frame on the front leg of the launcher may be weighed down with sandbags or rocks. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Ezk38LhKEs4/YNNJorenUMI/AAAAAAAATfE/K9xgf9XM9Zo9k6TVqj0-GQaRF-duY1NBACLcBGAsYHQ/s1979/ejection%2Bunit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1295" data-original-width="1979" height="261" src="https://1.bp.blogspot.com/-Ezk38LhKEs4/YNNJorenUMI/AAAAAAAATfE/K9xgf9XM9Zo9k6TVqj0-GQaRF-duY1NBACLcBGAsYHQ/w400-h261/ejection%2Bunit.png" width="400" /></a></div><p>Alone, the ejection engine weighs 1.4 kg. It is made from 30KhGSA grade structural steel, and it contains a 9Kh146M propellant charge. The charge is 0.29 kg of nitrocellulose stick propellant contained in a combustible satchel. The interior vent holes have a diameter of 10mm, and the rearward-facing nozzles have a maximum diameter of 10.5mm. The technical justifications of using nitrocellulose propellant grains in this application are the same as with shoulder-fired grenade launchers - safety and consistence. The main reason is that the mechanical properties (compressive strength, impact toughness) are several times better, giving the propellant grain a higher resistance to mechanical damage, especially during exposure to extreme low temperature conditions during storage and field use, where the grain becomes more brittle. When placed under mechanical stresses, cracks can form in propellant, and these cracks increase surface area and thus the reaction rate of the propellant. Essentially, this can make the combustion dynamics of the engine much more violent, potentially placing the missile operator at risk.</p><p>The ejection engine is a single-chamber pressure vessel that functions by allowing the nitrocellulose propellant to develop a high pressure, then venting the gasses through both ends of the vessel, rearward, and forward into the fiberglass container, at different rates controlled by having different outlets on each end. The maximum pressure developed in the combustion chamber is 37 MPa, while the maximum pressure in the missile container is only 3.3 MPa. Combustion lasts for an average of 0.018 seconds, but the venting period is much longer, and the acceleration of the missile in the container from the gas pressure also takes somewhat more time. The gasses vented into the large free volume inside the fiberglass container exit through six large holes, and the gas develops a low pressure that sets the missile in motion and accelerates it until it reaches the muzzle end of the container. As the missile travels down the length of the container, the free volume for the propellant gasses increases, decreasing the internal pressure and also the propulsive force acting on the missile. </p><p>To generate sufficient rearwards momentum to counteract the recoil of the missile launch, the gasses vented rearward exit through six nozzles, rather than simple holes, whereby they acquire a high velocity. The high velocity increases the rearward momentum. Moreover, the space between the ejection engine and the container forms an annular nozzle, increasing the velocity of the gasses escaping from inside the container. The rubber end cap is blown out during launch.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-6qnrMVKyu5Q/YKE95WF_-GI/AAAAAAAAS_U/7U0B8qT1-jUpy-ujXX9Y0Xez5puyYidHwCLcBGAsYHQ/s2049/9m111%2Bejection%2Bunit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="969" data-original-width="2049" height="189" src="https://1.bp.blogspot.com/-6qnrMVKyu5Q/YKE95WF_-GI/AAAAAAAAS_U/7U0B8qT1-jUpy-ujXX9Y0Xez5puyYidHwCLcBGAsYHQ/w400-h189/9m111%2Bejection%2Bunit.png" width="400" /></a></div><br /><p>Due to the low internal pressure generated inside the missile container, the container walls could afford to be thinned to the minimum permissible thickness for handling purposes. Cross sectional photos show the container has a very thin, uniform thickness across its entire length, discounting the thickened rings where hoops for slings and other fittings are attached. This saves weight. Additionally, the use of the recoilless gun principle improves the performance of the missile itself, as the ejection engine is separate from the missile and is left inside the container, so that it does not constitute a parasitic weight.</p><p>The nominal launch velocity of the 9M111 missile is no less than 75 m/s, with a realistic range of 75-80 m/s depending on the propellant temperature. Due to the increased weight of the 9M111M missile, the nominal launch velocity was lowered to 65 m/s, with a real range of 63-74 m/s. The minimum range of the 9M111 and 9M111-2 is 70 meters. With the 9M111M, this was marginally extended to 75 meters. </p><p>For comparison, the MILAN features a somewhat different ejection mechanism where the container is blown backwards during missile ejection as a counter-recoil ballast, leaving only an electrical connector with a thermal battery to link the guidance wire to the launcher. There is a piston between the base of the missile and the gas generator, serving mainly as a gas seal but also to protect the missile from the hot propellant gasses, and it is captured at the end of the container on a flange once the missile has departed. The missile container - along with the gas generator within - weighs almost as much as the missile and is additionally braked by the rearward propellant thrust, so that it travels rearward at 20 m/s rather than the same velocity as the missile as the conservation of momentum would dictate. Then, the booster stage of the missile engine starts immediately after leaving the container. This is shown in the sequence drawing below.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-VRnaQ49_8UI/YO0Qc6-wRWI/AAAAAAAAT4o/6vGMVME7LawrbKiXhjyZAjEyWmeJl21iACLcBGAsYHQ/s671/ejection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="376" data-original-width="671" height="224" src="https://1.bp.blogspot.com/-VRnaQ49_8UI/YO0Qc6-wRWI/AAAAAAAAT4o/6vGMVME7LawrbKiXhjyZAjEyWmeJl21iACLcBGAsYHQ/w400-h224/ejection.png" width="400" /></a></div><p>The advantage is that the missile can begin controlled flight much more quickly, reducing its minimum range to just 30 meters. However, in reality, this was never actually achieved by the MILAN system because the tracking optic is automatically cut off for the first 0.5 seconds after missile launch to protect it from receiving false readings due to the boost-upon-launch system of the missile. Missile tracking occurs only at 75 meters, according to a Dutch manual for the MILAN system. </p><p>Moreover, because of this launch method, the tube length available for missile acceleration is extremely short. The missile barely moves forward before it reaches the end of the container, whereby the piston is captured, and acceleration ceases. The missile receives a strong launch impulse to achieve a velocity of 75 m/s, the same as the "Fagot", and because the acceleration period is extremely short (0.04 seconds), it is also very violent, reaching 900 g. This is 60-70 times higher than 9M113 and TOW, both heavy ATGMs, and is at the same level as gun-launched supersonic ATGMs like the 9M119 "Refleks". Moreover, because the missile engine ignites while the missile is still physically next to the launch unit, smoke and overpressure is generated right next to the operator's head, and hot gasses are blown into the aperture window of the launcher sight. </p><div><p></p><p>The basic premise of all other containerized launch methods, from the fixed charge of "Fagot" to the in-tube rocket engine burnout of TOW, is to have a soft launch, the objective of which is to avoid having a powerful booster engine ignite near the operator. Indeed, on page 120 of the book "<i>Armements Antichars Missiles Guidés Et Non Guidés</i>", it was mentioned that the strong launch signature and reduced comfort of the operator were the penalties of the launch system used in the MILAN.</p></div><p><br /><a href="https://www.blogger.com/null" id="fagotengine"></a></p><h3 style="text-align: left;"><span style="font-size: large;">ENGINE</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-hPJM52GagWE/YNnImI1I4uI/AAAAAAAATk0/lfxvTG1ASbcOTxgDp4WUBBRLV9nhva_nQCLcBGAsYHQ/s2048/engine%2Bcase.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1392" data-original-width="2048" height="272" src="https://1.bp.blogspot.com/-hPJM52GagWE/YNnImI1I4uI/AAAAAAAATk0/lfxvTG1ASbcOTxgDp4WUBBRLV9nhva_nQCLcBGAsYHQ/w400-h272/engine%2Bcase.png" width="400" /></a></div><p>The "Fagot" features a dual-thrust, single chamber engine with a thin steel (30KhGSA) casing. The casing has a partially welded construction, with a weld-on rear end cap and nozzles, and a threaded front end cap. Its solid fuel block is of an end-burning type. An insulator lining of AG-4V fiberglass with a thermoset plastic binder is present along the two ends of the chamber, with a particularly high thickness on the rear end, as the boost section produces a particularly intense heat. Once the inertial switch is armed by the acceleration of the missile launch and then tripped by the subsequent absence of acceleration, power is able to flow from the onboard battery to the electrical ignition fuze of the engine. This sets off a pyrotechnic delay charge. Once the delay charge burns out, the 9Kh237 ignition device starts the engine after a short delay of approximately 0.15 seconds after launch, or after around 10-15 meters of travel ahead of the launcher. </p><p>The engine nozzles have a diameter of 4.3mm. They contain a molybdenum insert. They are angled 20 degrees from the longitudinal axis of the fuselage, protruding just slightly above the front end of the guidance section. The short length of the nozzles has a positive effect on their efficiency, as providing the highest possible exit velocity allows the gasses to produce the maximum thrust. If nozzles long enough to reach the tail of the missile, were used, there will be a reduction in thrust from viscous (friction) losses.</p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-3E6rpa0D8f0/YOXSnbvzzJI/AAAAAAAATxA/tF2mAp-t8gocv-fdINyxY_ucyooKNCI0ACLcBGAsYHQ/s1265/rocket%2Bengine%2Brear%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1177" data-original-width="1265" height="373" src="https://1.bp.blogspot.com/-3E6rpa0D8f0/YOXSnbvzzJI/AAAAAAAATxA/tF2mAp-t8gocv-fdINyxY_ucyooKNCI0ACLcBGAsYHQ/w400-h373/rocket%2Bengine%2Brear%2Bview.png" width="400" /></a></p><p>The 9Kh145 propellant charge contains a total fuel load of 1.5 kg. The booster charge weighs 0.4 kg, while the sustainer charge weighs 0.9 kg. RNDSI-5K fuel is used in the engine. The dual-thrust regime is accomplished by having partially insulated surfaces on the fuel block to act as combustion inhibitors, which was established as the new standard in engine technology beginning with the 9M17 "Falanga". This separates the fuel block into booster and sustainer sections. The fuel has a density of 1.58 g/cc, and has an energy density of 799 kJ/kg and a specific impulse of 2,186 N.s/kg. As mentioned earlier, in the section on the "Malyutka", the specific impulse of RNDSI-5K is the highest of all fuels used in domestic subsonic ATGMs, and at the same time, its specific smokiness index (2.0) is also the highest in this particular class. This means that the loss of visual transparency per unit weight of burned fuel is high. Compared to the "Malyutka", which uses the same fuel, the total smoke output volume is higher, as the fuel consumption rate is also higher, which was necessary to support the high speed of the missile. According to the study "<i>Оценка Показателей Боевой Эффективности Современных Противотанковых Управляемых Ракет</i>" by P. T. Nugmanov et al., the engine of the 9M111M consumes an average of 0.1 kg of fuel per second. </p><p>To minimize the possibility of the missile colliding with a ground obstacle and to avoid obscuring the target with the rocket exhaust smoke, the preferred guidance technique practiced by trained missile operators is to fire the missile in a raised trajectory. The missile is kept raised above the image of the target as long as possible, and then it is lowered onto the target before impact. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Q13uvD4PKW4/YNnIqGPiLSI/AAAAAAAATk4/j4jJW9dv_a83QSVmKqF8QUfA7rOw82ldQCLcBGAsYHQ/s2048/engine%2527.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1660" data-original-width="2048" height="324" src="https://1.bp.blogspot.com/-Q13uvD4PKW4/YNnIqGPiLSI/AAAAAAAATk4/j4jJW9dv_a83QSVmKqF8QUfA7rOw82ldQCLcBGAsYHQ/w400-h324/engine%2527.png" width="400" /></a></div><br /><p>As is normally observed on most dual-thrust engines for ATGMs, the sustainer is designed to provide sufficient thrust to maintain a constant airspeed at the extreme minimum operating temperature, which in this case is -50°C. Under normal conditions (+20°C), the boost stage of the engine burns for 1.8 seconds while the sustainer stage burns 8 seconds. The total duration of propelled flight is 9.8 seconds, meaning that in the final two hundred meters of its flight, the 9M111 merely coasts to the target under inertia, with a deceleration of around 30 m/s from air resistance. A maximum speed of 240 m/s can be reached, but only at the maximum temperature extreme. Ordinarily, the top speed is 210-215 m/s. An average speed of 186 m/s is achieved during the flight of the missile to its maximum range of 2 km, with a flight time of 10.75 seconds (often rounded up to 11 seconds for simplicity). As the missile continuously accelerates under normal conditions, the average speed increases with distance. At 1,000 meters, for instance, the flight time is 7 seconds, giving an average speed of 142 m/s. The velocity-displacement graph presented below shows the effect of temperature on the flight characteristics of the 9M111. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-LhVjUy-8tOI/YOiA6xtVgQI/AAAAAAAATzo/Zalaf9u34cUH_g9L5OdkGUpOvW1-kmPCwCLcBGAsYHQ/s1934/9m111%2Bvelocity%2Bvariance%2Bwith%2Btemperature.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1934" data-original-width="1573" height="640" src="https://1.bp.blogspot.com/-LhVjUy-8tOI/YOiA6xtVgQI/AAAAAAAATzo/Zalaf9u34cUH_g9L5OdkGUpOvW1-kmPCwCLcBGAsYHQ/w520-h640/9m111%2Bvelocity%2Bvariance%2Bwith%2Btemperature.png" width="520" /></a></div><p>No changes were made to the engine in the creation of the 9M111-2, but in the 9M111M model, the more powerful 9Kh145.010 rocket engine was fitted. The kinematic performance of 9M111M was increased slightly compared to its predecessors. The burn time was the same, but the engine produces slightly more thrust and propels the missile to a higher peak velocity before burnout, thus limiting the impact to its average speed. Its flight time out to 2.5 km is 13.5 seconds, and the average speed is 180 m/s, which is slightly worse than on 9M111 and 9M111-2, but this is solely due to the fact that the maximum range increased by 500 meters, so the "Faktoriya" has a longer period of deceleration. Under normal conditions (+20°C), the boost stage of the "Faktoriya" engine generates 450 N of thrust for 1.8 seconds, developing a chamber pressure of 12 MPa. In the sustainer stage, the engine generates 200 N of thrust for 8 seconds, with a chamber pressure of 4.4 MPa.</p><p>In general, the flight characteristics of the "Fagot" and "Faktoriya" are largely the same as the MILAN, only quicker by a modest margin throughout the entire flight. However, the use of aerodynamic control surfaces instead of a TVC steering system avoided the issue of control cutoff with engine burnout, which is not the case for the MILAN. All models of the MILAN except the MILAN ER have a flight time of 12.5 seconds to 2,000 meters, or 7.3 seconds to 1,000 meters, and its dual-thrust engine produces 265 N of thrust for 1.3 seconds in its boost stage, then 108 N of thrust for 10.7 seconds in the sustainer stage, according to the book "<i>Armements Antichars Missiles Guidés Et Non Guidés</i>" by COMHART. Looking at its total flight time and the total burn time of its rocket engine, a discrepancy is evident, and indeed, it turned out that the missile is unpropelled during the last moments of its 2,000-meter flight, and because the TVC system is nonfunctional, the missile is left unguided, even though the missile carries 2,000 meters of wire. This led to difficulties in hitting moving targets in the last 150 meters, which was an issue raised in an <a href="https://cag.gov.in/uploads/download_audit_report/2010/Union_Compliance_Defence_Army_Ordnance_Factories_12_2010_chap2.pdf">Indian government audit</a>. Because command-guided ATGMs must be guided onto a moving target in a chasing trajectory, the loss of steering control during the final moment before impact would lead to the missile flying behind the target. The only way to compensate is for the operator to manually apply lead on the moving target, which is a less satisfactory guidance technique. This was verified by live fire tests, which led to an official amendment of the maximum range of the missile. The same shortcoming is also reported during a <a href="http://20thcenturyplatoons.com/articles/M47%20Dragon%20assessment.html#fn1-r">Dutch comparative assessment of the M47 Dragon and the MILAN in 1977</a>, where the maximum effective range of the MILAN on moving targets was listed as 1,900 meters and not 2,000 meters.</p><p>It is interesting to note that due to the absence of the 500-meter minimum range of the "Malyutka" system, the zone of action of a 9M111M "Faktoriya" is effectively the same as the "Malyutka" - both have an engagement zone radius of 2,500 meters. However, this does not entirely offset the range difference, because ultimately, this still means that the operator of a 9K111 system must be somewhat closer to the target. Nevertheless, the extended reach of a "Faktoriya" would have had a positive influence on the stealthiness and survivability of an anti-tank team, as a longer standoff distance reduces the probability of being located, both before and after firing.</p><p><br /><a href="https://www.blogger.com/null" id="fagotwarhead"></a></p><h3 style="text-align: left;"><span style="font-size: large;">WARHEAD</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ex2WuM_IDus/YOoyo7OweQI/AAAAAAAAT1U/HhYVZLuwgqIngFEMTdz7Z2JIRN62gypfwCLcBGAsYHQ/s1280/DSC_2184.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1280" height="250" src="https://1.bp.blogspot.com/-ex2WuM_IDus/YOoyo7OweQI/AAAAAAAAT1U/HhYVZLuwgqIngFEMTdz7Z2JIRN62gypfwCLcBGAsYHQ/w400-h250/DSC_2184.jpg" width="400" /></a></div><p>In a television interview for the "<i>Ударная сила</i>" show on Russian TV Channel 1, Anatoliy Kalistov of KBP Tula, who was the chief designer of the "Fagot" and "Gaboy" warheads, detailed that the design requirements placed a specific emphasis on minimal weight and dimensions, while armour penetration was not to compromised. According to Kalistov, every gram saved was paid with a bounty of a Ruble. The lighter the warhead became with every design iteration, the more difficult it was to shave off its weight, and so the bounty was progressively raised to 3 Rubles per gram, then to 10 Rubles per gram, and so on.</p><p>Although it is most convenient to view the reduced warhead diameter as a sign of ignorance on the part of the designers regarding the importance of shaped charge diameter, it is important to keep in mind that missile design is a balance between a large number of parameters, and that a few design solutions can have fundamental incompatibilities with some others. In this case, the fundamental issue is that of shaped charge scaling.</p><p>In their seminal work "Fundamentals of Shaped Charges", Walters and Zukas detail the linearity of shaped charge scaling - that is, the empirically proven direct and linear relationship between the scaling factor of a shaped charge and its penetration depth. Scaling a shaped charge involves maintaining the same geometric shape in all respects; increasing the liner diameter, the charge diameter, charge length, confinement, liner wall thickness, standoff distances, and booster dimensions, all by the same linear scale factor, while keeping all material parameters constant. The final jet parameters will be scaled proportionately in the five following ways, quoted directly from the book:</p><ol><li>The jet tip velocity remains unchanged. This is not surprising since the conical apex angle and the charge-to-mass ratio are unchanged.</li><li>The jet diameter and jet length increase by the linear scale factor.</li><li>The jet mass and total jet kinetic energy increase by the cube of the scale factor.</li><li>The penetration depth and the jet breakup time increase by the linear scale factor.</li><li>Since the hole volume is proportional to the jet kinetic energy, the hole volume should increase by the cube of the scale factor.</li></ol><p></p><p></p><p>When reconciling these facts, it quickly becomes clear that increasing warhead diameter is an extremely costly design solution. If the warhead is scaled by a factor of two, then the charge mass increases by a factor of eight due to the square-cube law while the penetration increases by only a factor of two. The mass and kinetic energy of the jet also increase by a factor of eight owing to the square-cube law, as does the hole volume produced by the jet, but as the goal is to increase hole depth (penetration) rather than width, shaped charge scaling is not the optimal design solution. </p><p>Knowing this, a more accurate perspective can be formed on historical design decisions and their consequences. The sentiment expressed in a number of examples of Russian specialist literature that the penetration power of a warhead ought to be maximized by increasing its size and mass, though obviously correct on a superficial level, is a reductionist view. If a would-be ATGM designer attempted to prioritize this aspect of warhead design, the reality of the square-cube law will quickly quash those idealistic notions. For example, if the existing 9N122 warhead with an official penetration of 400mm were to be scaled up from 87mm to 120mm, the same as the maximum diameter of the missile itself, then the final penetration would increase by the same scale factor of 1.38, giving a final penetration of 552mm, but at the same time, the weight would increase by 2.63 times, to a final weight of 4.62 kg. This is almost heavy as an entire 9M116 "Metis" missile (4.8 kg).</p><p>This is not to mention that a larger warhead will require a longer built-in standoff distance, which also scales linearly to the warhead diameter. If the warhead is enlarged while the standoff distance is left the same, the actual gain in penetration will not be as large as the linear scaling factor would suggest. This appears to have been realized by the engineers of KBP Tula, and as such, a full caliber shaped charge was only implemented with the creation of the "bullpup" layout, which placed the warhead at the rear of the missile and thus gave the maximum possible standoff distance. This layout was pioneered in the 9M119 "Refleks" gun-launched ATGM created in the early 1980's, then it became a signature of the design bureau, seeing use in the "Kornet" and the "Metis-M". </p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">9M111, 9M111-2</span></h3><h3 style="text-align: left;"><span style="font-size: large;">9N122</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-QbM29lur6PQ/YOIi0hOSzvI/AAAAAAAATuw/0VYnFUc9tSgiXE5e-zZtk1Ay6ikzNxuIwCLcBGAsYHQ/s2801/9n122.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1123" data-original-width="2801" height="256" src="https://1.bp.blogspot.com/-QbM29lur6PQ/YOIi0hOSzvI/AAAAAAAATuw/0VYnFUc9tSgiXE5e-zZtk1Ay6ikzNxuIwCLcBGAsYHQ/w640-h256/9n122.png" width="640" /></a></div><p>Compared to the 125mm warhead of the "Malyutka" it replaced, the 9N122 warhead of the 9M111 and 9M111-2 more closely resembles the payload of a shoulder-fired grenade. The warhead weighs 1.76 kg, and it contains 1 kg of explosive filler. The given weight of the warhead does not refer to the shaped charge alone, but the entire warhead assembly, inclusive of the contact plates of its fuzing system, the aerodynamic fairing, the mounting flange behind the warhead, and so on.</p><p>Unlike other domestic ATGMs of the period, the "Fagot" uses an capacitor fuze instead of a piezoelectric fuze. A capacitor fuze works by having a charged capacitor in an opened circuit with the electric detonator. Two closely spaced plates are used as the switch. When the outer plate is deformed inward and touches the inner plate, an electrical path is formed in the circuit, allowing the capacitor to discharge, delivering a current to the electric detonator and thus detonating the warhead. The drawing on the left below shows how the two contact plates on the warhead are connected to the capacitor circuit, and the circuit diagram on the right below shows the fuze circuit, with the yellow circuit indicating the loop of the contact switch mechanism. Contacts 4 and 3 are the contact plates that close the circuit between capacitor C and the ED-05-9 electric detonator. The other portions of the circuit are dedicated to the arming, safety, and the self-destruct mechanisms. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-aUlYeT6WH-Q/YOzpWtGGweI/AAAAAAAAT4Y/K8VppE-t-nQZvbD902YSIE6C6IACI8FdgCLcBGAsYHQ/s1835/warhead%2Bcone.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1595" data-original-width="1835" height="348" src="https://1.bp.blogspot.com/-aUlYeT6WH-Q/YOzpWtGGweI/AAAAAAAAT4Y/K8VppE-t-nQZvbD902YSIE6C6IACI8FdgCLcBGAsYHQ/w400-h348/warhead%2Bcone.png" width="400" /></a><a href="https://1.bp.blogspot.com/-PhTRnJRPmoo/YO0en9o-W1I/AAAAAAAAT4w/zNMJ9mjzVJAtBwcTXO_yZc_2UInpoNtDQCLcBGAsYHQ/s1675/fuze%2Bcircuit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1419" data-original-width="1675" height="339" src="https://1.bp.blogspot.com/-PhTRnJRPmoo/YO0en9o-W1I/AAAAAAAAT4w/zNMJ9mjzVJAtBwcTXO_yZc_2UInpoNtDQCLcBGAsYHQ/w400-h339/fuze%2Bcircuit.png" width="400" /></a><br /></div><p><br /></p><p>When the missile is fired, the acceleration and subsequent deceleration arms and then closes an inertial switch, which closes the electrical circuit of the MB-4-1 electric igniter. It triggers and ignites a delaying pyrotechnic arming charge for the fuze. After 0.2-0.3 seconds, the delay charge burns out, a switch closes the electrical circuit of the capacitor to the onboard power supply and opens the path of the capacitor to the ED-05-9 electric detonator. The capacitor begins to be charged by the onboard battery of the missile at 16 V, and the time needed to charge the capacitor provides an additional arming delay. The 9E234 is fully armed at a distance of 30-75 meters after launch. At the same time, the burnout of the delaying charge also sets off a slow-burning pyrotechnic delay fuze, designed to set off the self-destruction mechanism if the warhead is not detonated on impact with a target. In case of a miss, the warhead is set off by the self-destruct mechanism of the fuze.</p><p>The warhead is a conventional shaped charge with a conical copper liner. The diameter of the liner is unknown. A filler of Okfol is used. According to the article "<i>Главное Противотанковое Оружие Пехоты: История создания и эволюция ПТРК</i>" published in the No. 15, 2019 issue of the "<i>Оружие</i>" magazine as a special edition issue, the diameter of the warhead is 87mm. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-5RwU3M_q9F0/YMNebnxD-GI/AAAAAAAATZ4/bKCui6ZrSQkr5Uu7mFZaIHOfNVYjhRtQwCLcBGAsYHQ/s1149/9n122%2Bwarhead.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1079" data-original-width="1149" src="https://1.bp.blogspot.com/-5RwU3M_q9F0/YMNebnxD-GI/AAAAAAAATZ4/bKCui6ZrSQkr5Uu7mFZaIHOfNVYjhRtQwCLcBGAsYHQ/s320/9n122%2Bwarhead.png" width="320" /></a></div><p>The built-in standoff from the base of the shaped charge liner to the tip of the missile nose is 232mm, based on the drawings in the manual. This is a distance of 2.67 CD. After subtracting the distance occupied by the disintegration of the steering mechanism, around 2-3cm of space is lost, making the actual built-in standoff no more than 2.3-2.4 CD.</p><p>According to the official tactical-technical characteristics, the penetration at 60 degrees is 200mm.</p><p>The average penetration is very likely to be higher than the official value, as this has consistently been the case for ATGMs. For instance, the penetration of 9M113 is officially 250mm RHA at 60 degrees, but it is also indicated in a number of technical sources as being 550-560mm. </p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">9N122M</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-wJ0fLcLZwiI/YOIi5FicsQI/AAAAAAAATu0/btXVorX_A4g8_ix3kdcdbV2furnJRt-QgCLcBGAsYHQ/s2698/9n122m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1165" data-original-width="2698" height="276" src="https://1.bp.blogspot.com/-wJ0fLcLZwiI/YOIi5FicsQI/AAAAAAAATu0/btXVorX_A4g8_ix3kdcdbV2furnJRt-QgCLcBGAsYHQ/w640-h276/9n122m.png" width="640" /></a></div><p style="text-align: left;">The 9N122M warhead for the 9M111M "Faktoriya" provides improved penetration performance, but its charge is slightly larger and heavier as a consequence. It is fitted with the 9E243M fuze. The fuze is identical to the 9E243 in all respects except in the construction of its contact plates, and though it is not confirmed, it is also likely that its self-destruct timer was lengthened to account for the longer range of the 9M111M. The warhead has a diameter of 93mm, a rather specific caliber that was standardized with the 9M116 "Metis" missile, and appears to be tangentially related to the 93mm warhead of the PG-7VL "Luch" grenade. The warhead is also cylindrical in shape, thus also modifying the aerodynamic form of the missile fuselage.</p><p>Alone, the fact that the new warhead appears larger is not an indicator of improved performance in of itself. On the contrary, a cylindrical warhead is normally avoided due to the inability of an explosive mass in the charge tail to contribute to the kinetic energy of the jet, because if the volume of the charge is increased by extending its length beyond the maximum useful length, additional explosive mass no longer contributes to the penetration depth.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ztQwsJhmKko/YOHz3wVwgII/AAAAAAAATuo/Rurm7H-6tPoLULrKwLomlS1_3qBzYb5QwCLcBGAsYHQ/s1304/booster%2Band%2Bcharge%2Bgeometry.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="391" data-original-width="1304" height="120" src="https://1.bp.blogspot.com/-ztQwsJhmKko/YOHz3wVwgII/AAAAAAAATuo/Rurm7H-6tPoLULrKwLomlS1_3qBzYb5QwCLcBGAsYHQ/w400-h120/booster%2Band%2Bcharge%2Bgeometry.png" width="400" /></a></div><p style="text-align: left;">In this case, the loss of the tapered profile was a modification of the wave shaping dynamics of the warhead. As the cross section images show, the tail end of the warhead is fully cylindrical, but at the same time, the gap between the wave shaper and the warhead casing remains practically as small as before, as the wave shaper has increased in diameter and has a modified geometry.</p><p style="text-align: left;">In the new 9E243M fuze, the front contact plate is no longer spaced away from the rear contact plate by an insulated bolt, but is instead incorporated into the skin of the fuselage.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-clVFORCsoSk/YOiSXX6VG9I/AAAAAAAATzw/6IbKqvKAw0wRNXCeEqt33_dViTI5BwsdQCLcBGAsYHQ/s2094/9n122m%2Bin%2Bmissile.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1039" data-original-width="2094" height="318" src="https://1.bp.blogspot.com/-clVFORCsoSk/YOiSXX6VG9I/AAAAAAAATzw/6IbKqvKAw0wRNXCeEqt33_dViTI5BwsdQCLcBGAsYHQ/w640-h318/9n122m%2Bin%2Bmissile.png" width="640" /></a></div><p style="text-align: left;"><br /></p><p style="text-align: left;">The 9N122M warhead is dimensionally interchangeable with the 9N135 warhead of the 9M115 "Metis". In fact, the Bulgarian <a href="http://www.russianarms.ru/forum/index.php?PHPSESSID=k9jo2909m2mhbluf9jo2k73ql4&action=dlattach;topic=1599.0;attach=340105;image">9M111MB</a> and <a href="https://bulgarianmilitary.com/wp-content/uploads/2018/12/Bulgaria-Benefits-from-Conflicts-in-Which-International-Rules-Are-Breached-4.jpg">9M111MB-1</a> variants specifically use the 9N135V warhead rather than the 9N122M of the regular 9M111M. When fitted in the "Metis" missile, the 9N135 warhead differs from the 9N122M in that it uses the 9E132 fuze, which is functionally identical to the 9E234M, except that it has a modified arming circuit, due to the lack of an onboard power source in the 9M115 missile. It should be possible to install the 9E132 in the 9N122M warhead of a 9M111M missile, but at the same time, it is not advisable, as the self-destruct delay was calibrated for the much shorter maximum range of the "Metis". The 9N135V presumably has the same 9E234M fuze of the 9N122M, making it identical in all but name. It is worth noting that despite the labeling of the missiles being in the Latin alphabet, the warhead designation label is in Cyrillic.</p><p style="text-align: left;">According to the official tactical-technical characteristics, the penetration at 60 degrees is 230mm, giving a nominal LOS penetration of 460mm. The average penetration depth is likely to be higher. As a reference, the 93mm warhead of the PG-7VL grenade, made in 1977 for the RPG-7, penetrates 500mm. However, the 9N135 of the "Metis" missile is also rated for a penetration of 460mm.</p></div><div><p> </p><p><br /><a href="https://www.blogger.com/null" id="konkurs"></a></p><h3><span style="font-size: large;">"Konkurs" (Competition)</span></h3><h3><span style="font-size: large;">9M113 "Gaboy", 9M113M "Udar", 9M113M1</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-mgfD77w-U4o/YPsxse6N2zI/AAAAAAAAUCM/ZDEkxd3orCIhpahYmwyfrFDgeww5-LJOgCLcBGAsYHQ/s760/vdv_poligon15.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="507" data-original-width="760" height="427" src="https://1.bp.blogspot.com/-mgfD77w-U4o/YPsxse6N2zI/AAAAAAAAUCM/ZDEkxd3orCIhpahYmwyfrFDgeww5-LJOgCLcBGAsYHQ/w640-h427/vdv_poligon15.png" width="640" /></a></div><p>Though OKR "Fagot" showed great promise, it could not replace the "Falanga-M" as its tactical-technical requirements had been specifically tweaked for the infantry ATGM niche. This gave it an intrinsic limit on its penetration power as well as a much shorter range of 2 km; sufficient for an infantry ATGM system, but not for self-propelled tank destroyers, which were doctrinally required to be deployed at the rear echelons of a layered defence. The KBP design bureau proposed to develop the replacement of the "Falanga" series as an offshoot of the "Fagot", provisionally assigning the project with the codename "Fagot-P". The "Shturm" ATGM system with "Kokon" supersonic missiles was already in progress at this time, but in light of the conceptual focus of the "Shturm" system on arming helicopters, with a very low developmental priority for the ground forces, the proposal was accepted.</p><p>On December 2, 1970, OKR "Konkurs" was officially launched, which would lead to the 9K111-1 "Konkurs" system. This system is a generic term that includes both the 9P148 and the 9P135M launcher, the latter of which was tightly integrated into the new 9P148 tank destroyer, which served as a replacement for the older series of "Falanga" tank destroyers. As with previous tank destroyers, the 9P148 was based on the BRDM-2, and so hull modification 41-08 was created by GAZ for the system. It was designed to have reverse compatibility with "Fagot" missiles, thus filling both roles of the heavy "Falanga" tank destroyers and light "Malyutka" tank destroyers at once. The main component fitted directly into the 9P148 is the 9Sh119M1 sight, and it can be dismantled and fitted onto the portable 9P135M launcher carried in the 9P148. The 9P135M functions as a dismounted launching option for the crew, also with reverse compatibility with the man-portable "Fagot" missiles. Tests began in 1972, and ran smoothly. In 1973, the TOZ plant (Tula Arms Factory) started low rate production of the missiles. On January 18, 1974, the "Konkurs" ATGM system entered service in the Soviet Army, and mass production of both the "Konkurs" systems and the "Gaboy" missiles began. </p><p>The name of the 9M113 missile itself is "Gaboy", inherited from the title of its R&D project (ОКР «Габой»). Humorously enough, this is actually a mispelling of "гобой" (goboy), meaning "oboe", a type of woodwind instrument. However, this name is hardly ever used, as the missile itself is always referred to by its GRAU designation of 9M113 in official documents and in technical manuals. The "Gaboy" name was chosen for the same reason that the "Fagot" (Bassoon) name was given; the primary design feature of these next generation missiles was their containerization, giving them a passing resemblance to woodwind instruments. It is worth noting that even though "Konkurs" is not actually the name of the missile, it is referred to as such even by experts, probably as a matter of preference.</p><p>According to historian Sergey Suvorov, the relationship between the "Fagot" and "Gaboy" was so direct, that the original technical drawings for "Gaboy" were merely "Fagot" blueprints scaled up by a factor of 1.13. The final product had several differences, but the upscaling factor was remained unchanged - the caliber of 9M113 (135mm) is 1.13 times larger than 9M111 (120mm).</p><p>The quick turnaround time was not only achieved by using a proven system as the basis of the new design, but also by the initiative taken by the Tula engineers to reject the idea of a supersonic containerized ATGM. With the strong success of the "Konkurs" as an intermediary to the "Shturm", the military leadership reassessed its requirements and decided to formally implement a subsonic-supersonic mix of heavy ATGMs, with the subsonic system destined to be more predominant owing to the much greater flexibility in launch platforms due to the smaller size and weight inherent to the type. </p><p>In accordance with the premise of a subsonic-supersonic mix, the project for the replacement of the "Gaboy", initiated by KBP in 1988, was a subsonic system focused on implementing a sufficiently powerful warhead to defeat current and future threats, at a minimum increase in weight and cost. This led to the "Kornet", which has seen great success in its own right. The name of the "Kornet", referring to the cornet, was part of the same running theme of naming containerized ATGMs after musical wind instruments.</p><p>"Konkurs" was very prolific in the Soviet Army, being the core anti-tank system for units organized at the army level as well as individual rifle squads, once the BMP-1P and BMP-2 entered service. The 9P148 "Konkurs" was the replacement for the various "Falanga" systems belonging to the anti-tank regiment organic to Soviet combined arms armies, and the 9P148 was also issued to the anti-tank brigade organic to artillery divisions. The only two anti-tank units that did not feature "Konkurs" systems were the anti-tank platoon of BTR motor rifle battalions (armed with "Fagot"), and the fire support platoon of BTR motor rifle companies (sometimes armed with the "Metis", mostly with "Fagot"). During its production run in the Soviet era, over 300,000 units of 9M113 missiles were produced. It surpassed the MILAN and is a contender with the TOW for the distinction of being the most widely produced ATGM during the Cold War, but the lack of precise figures makes it impossible to declare a winner.</p><p><br /></p><p>It is known that the design bureau became engaged in a new project, in compliance with resolution No. 196 issued by the Military Industrial Complex on the 10th of June 1982 to explore the modernization of the "Konkurs" system under the project codename "Udar", the main objective of which was to combat tanks with add-on explosive reactive armour, which was observed on Isreali tanks in Lebanon that same year. Following this, the penetration power of the missile was incrementally improved during the early 1980's with the installation of a new 9N131M warhead, but aside from this, no major new developments went far enough to enter service until much later. It is doubtful if there was any relation between this new warhead and OKR "Udar". The "Udar" project itself culminated in the belated introduction of the 9M113M "Udar" missile by government decree No. 2 on the 4th of January, 1991, only months before the dissolution of the Soviet Union, according to KBP.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-_RkLtL5_YsE/YOjRh8FT5QI/AAAAAAAAT0Q/0v0tNGCS5v8PssxNHJN2jSVg_TEXz_BjQCLcBGAsYHQ/s623/9m113m%2Bline%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="309" data-original-width="623" height="199" src="https://1.bp.blogspot.com/-_RkLtL5_YsE/YOjRh8FT5QI/AAAAAAAAT0Q/0v0tNGCS5v8PssxNHJN2jSVg_TEXz_BjQCLcBGAsYHQ/w400-h199/9m113m%2Bline%2Bdrawing.png" width="400" /></a><a href="https://1.bp.blogspot.com/-vfWy-wjxwpw/YO1j_VqgsBI/AAAAAAAAT5Q/T2ihtkLgRYssgj3eXjRjQizeVV0P3fFtQCLcBGAsYHQ/s300/konkurs_saldk1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="173" data-original-width="300" height="185" src="https://1.bp.blogspot.com/-vfWy-wjxwpw/YO1j_VqgsBI/AAAAAAAAT5Q/T2ihtkLgRYssgj3eXjRjQizeVV0P3fFtQCLcBGAsYHQ/w320-h185/konkurs_saldk1.jpg" width="320" /></a><br /></div><p>The "Udar" missile was packaged along with the "Konkurs" ATGM system production licence sold to India and Iran, where it continues to be produced. It was produced in Russia at TOZ, the Tula Arms Factory. Since its introduction in 1991, over 30,000 units of the 9M113M were produced for export.</p><p>After the creation of the "Udar", KBP worked under their own private initiative on a successor, which led to the 9M113M1. It does not have a developmental name, only the index of 9M113M1. The missile was adopted by the Russian Army in 2004, and has been licenced to India along with the newer "Konkurs-M" system. In domestic use, 9M113M1 appears to be common for the troops still relying on the "Konkurs" system, both infantry and mechanized versions mounted on the BMP-2.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-dLywUO3lyNA/YO1lDxtZsxI/AAAAAAAAT5Y/o_VnqRccZcMYCqTSP1jnGDE4jKESszuGACLcBGAsYHQ/s529/raketa-Konkurs-M.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="300" data-original-width="529" height="227" src="https://1.bp.blogspot.com/-dLywUO3lyNA/YO1lDxtZsxI/AAAAAAAAT5Y/o_VnqRccZcMYCqTSP1jnGDE4jKESszuGACLcBGAsYHQ/w400-h227/raketa-Konkurs-M.png" width="400" /></a></div><p>Since the early 2000's, both the 9M113M and the 9M113M1 have been marketed as part of the "Konkurs-M" system, which consists of the 9P135M launcher and a 1PN86 "Mulat" or 1PN65 "Trakt" thermal sight.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-0F0MiVFg55g/YO1wszLPZgI/AAAAAAAAT5g/kcqLkm7S7RgL-qvV2cP4uy0Q66v9_owugCLcBGAsYHQ/s1128/kbp%2Badvertisement.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="738" data-original-width="1128" height="261" src="https://1.bp.blogspot.com/-0F0MiVFg55g/YO1wszLPZgI/AAAAAAAAT5g/kcqLkm7S7RgL-qvV2cP4uy0Q66v9_owugCLcBGAsYHQ/w400-h261/kbp%2Badvertisement.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-k_OZ9x6TbXc/YO10hSQuE-I/AAAAAAAAT5o/w2XiCZGeyNMW9GpZki3bjTraXkXTK1KYACLcBGAsYHQ/s346/konkurs%2Bm.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="346" data-original-width="319" height="320" src="https://1.bp.blogspot.com/-k_OZ9x6TbXc/YO10hSQuE-I/AAAAAAAAT5o/w2XiCZGeyNMW9GpZki3bjTraXkXTK1KYACLcBGAsYHQ/s320/konkurs%2Bm.jpg" /></a><br /></div><p><br /><a href="https://www.blogger.com/null" id="konkursdesign"></a></p><p><br /></p><h3><span style="font-size: large;">GENERAL DESIGN FEATURES</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jMl63FUk9Ag/YO27o1aqVRI/AAAAAAAAT54/O7mh3pQMeB0KpVafnDS-SyVYxORHeS8YwCLcBGAsYHQ/s1145/9m113.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="694" data-original-width="1145" height="243" src="https://1.bp.blogspot.com/-jMl63FUk9Ag/YO27o1aqVRI/AAAAAAAAT54/O7mh3pQMeB0KpVafnDS-SyVYxORHeS8YwCLcBGAsYHQ/w400-h243/9m113.jpg" width="400" /></a></div><p>Overall, the high degree of unification between the 9M111 and the 9M113 makes it difficult to list the features of the latter without retreating old ground. The layout of the missile is the same unconventional type, having the steering mechanism in the nose, followed by the warhead, engine and guidance system. The major dimensions of the missile are made to a 1.13 scale of the 9M111, with the exception of critical components such as the wings, which required a different scale factor due to the non-linearity of the lift coefficient.</p><p>According to data presented in the engineering textbook "<i>Основы Устройства И Функционирования Противотанковых Управляемых Ракет</i>" by V. V. Vetrov et al., published for the Tula state university by the KBP design bureau, the 9M113 missile alone is 946mm long, and its maximum diameter is 135mm. This is its length without the ejection engine.</p><p>The 9M113 container has the same launcher connector, containing the same two T-307B thermal batteries and six-pin socket. Unlike the straight-walled tubular container of "Fagot", the tail of the 9M113 container is flared to form an annular nozzle, providing additional reverse thrust needed for recoilless operation during the launch of the missile. Rubber shock-absorbing buffer pads are present on both the front and back end caps on the container for impact and fall protection, and the container has a carry handle for convenience. The container has no locking slots to allow two containers to be strapped together, as the portability of each 9M113 was limited to a single missile per person due to its weight. Of course, there is no restriction for a missile bearer to simply carry one container by their handle in each hand, but this is not feasible for long treks. </p><p>If used from a 9P148 missile carrier, then after the missile has hit its target (or self-destructed), the launch system signals an electric igniter in the missile container that, when triggered, ejects the container backwards. Then, when retracting, the launcher pivots backwards, which is to prevent the trailing wires of spent missiles containers from tangling when the launcher is retracted.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jlWiWY1F0f0/YO28aCAX48I/AAAAAAAAT6A/BTg50wd7HtwMcoEHcYP9nBCTo56s2jdlACLcBGAsYHQ/s2174/9m113%2Binside%2Bcontainer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="621" data-original-width="2174" height="182" src="https://1.bp.blogspot.com/-jlWiWY1F0f0/YO28aCAX48I/AAAAAAAAT6A/BTg50wd7HtwMcoEHcYP9nBCTo56s2jdlACLcBGAsYHQ/w640-h182/9m113%2Binside%2Bcontainer.png" width="640" /></a></div><p>Along with its container, the weight of a 9M113 missile is 25 kg. Coincidentally, this is the same weight as the TOW. Alone, the missile weighs just 14.5 kg. Measured along the points of its maximum dimensions, the missile container is 1,263mm long and 188mm in diameter (at the end caps), but with the protruding electrical connector, the maximum height of the container is 230mm. As with 9M111, the containerized 9M113 missile is slightly buoyant, allowing a dismounted infantry team carrying these missiles to cross water obstacles more easily. For comparison, the HOT weighs 32 kg in its container, is 1,300mm long and 175mm in diameter. The missile alone weighs 23 kg. In terms of penetration and flight performance, 9M113 lies in a middle ground between the TOW and the HOT, but exceeds both systems considerably in terms of man-portability.</p><p>According to the engineering textbook "<i>Основы Устройства И Функционирования Противотанковых Управляемых Ракет</i>" by V. V. Vetrov et al., the concept of portable heavy ATGM systems came about when equipping the anti-tank weapons of infantry fighting vehicles. In accordance with the combat tactics of the time, the motorized rifle squad had to be capable of firing at tanks and other hard targets from a launcher placed on top of the vehicle and from the ground, by dismounts. For this purpose, the integral sight of the launch mechanism of both the BMP-1P and BMP-2 was made to be removable, and then combined with the tripod and guidance box to form a complete 9P135M launcher. This launcher could then be carried by two dismounts by a relatively short distance - within 200 to 300 meters - to provide fire support against tanks. To facilitate this, restrictions were imposed on the total weight of the system so that it did not exceed 30 kg, or up to 60 kg when both elements, launcher and missile, are carried together. This requirement cannot be met by a supersonic missile like the "Kokon" of the "Shturm" system, as each containerized missile weighs over 40 kg and is very long, requiring two people holding it by each end. The portability of the "Kokon", and missiles of a similar weight, is limited only to short-distance ferrying from a resupply point to the launch vehicle. This aspect of the 9M113 proved to be an important factor in its popularity in asymmetric conflicts, mainly among insurgent forces which tend to lack the means of mounting large scale mechanized operations and rely on light infantry for almost all combat tasks.</p><p>Restrictions on the weight of heavy missiles like the "Kokon" also exist, but they primarily concern the ease of loading the launch rails of self-propelled tank destroyers with a crew of limited size. By remaining within a reasonable weight for two people, it becomes much easier to handle such missiles in field conditions without trolleys and other tools. </p><p>The 9M113 series can be fired from either the 9P135 or the 9P135M. </p><p></p><p>When fired from a 9P135 or 9P135M launcher, a 9M113 missile can only be guided for up to 3,000 meters, because the two T-307B thermal batteries in the container have a finite operating time of 17.5 seconds at 15 V, which is slightly reduced in practice when the electrical load is higher than the nominal operating parameters of the battery. According to a technical manual for the 9K111 portable anti-tank system, the command link is powered down 16 seconds after launch (t = 16) if the missile container is still connected to the launcher. The operating period is sufficient to power a 9P135(M) long enough for a 9M111M "Faktoriya" to reach its maximum range of 2,500 meters even under the extreme negative temperature requirement of -50°C, but not for the 9M113. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-EoKqY2yWMWQ/YPhaRB4cYvI/AAAAAAAAUA4/Tx5h8gMNH4oJQMTjvAxcmXpu4YnnNnXjwCLcBGAsYHQ/s2021/9k111%2Bttx.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1387" data-original-width="2021" height="275" src="https://1.bp.blogspot.com/-EoKqY2yWMWQ/YPhaRB4cYvI/AAAAAAAAUA4/Tx5h8gMNH4oJQMTjvAxcmXpu4YnnNnXjwCLcBGAsYHQ/w400-h275/9k111%2Bttx.png" width="400" /></a></div><p>An additional limiting factor is that the electrical load is higher, as the same power source is tasked to overcome the greater resistance of the 4 kilometers of wire when the launcher transmits steering commands. The allocated power reserve for each launch is only nominally sufficient for a 9M113 to travel 3 km, according to a 9M113 technical manual. Considering that the 9M113 is faster than 9M111(M), it appears likely that the limit of 3 km is based on the flight time of the missile at a temperature of -50°C. It is possible that the maximum range exceeds 3,000 meters at elevated temperatures, as the increased speed of the missile may allow it to cross a greater distance before the launcher shuts down.</p><p>The 9P135 consists of:</p><p></p><ol><li>9Sh119 periscopic sight</li><li>9S451 control box</li><li>9P155 induction trigger</li><li>9P56 tripod.</li><li>9S469 IR interference detector (optional)</li><li>11FG-400 battery (optional)</li></ol><div>The portable 9K111 "Fagot" system issued to BTR-mounted anti-tank infantry teams are only issued one 9S469 interference detector per six launchers. The interference detector comes with an additional 11FG-400 nickel-cadmium battery, the very same type used in the control panel of the 9K11 "Malyutka" system, but in this case, it is not an important addition as infantry are generally only expected to fire "Fagot" or "Faktoriya" missiles.</div><p>The 9P135M consists of:</p><ol><li>9Sh119M1 periscopic sight</li><li>9S451M control box</li><li>9P155 induction trigger</li><li>9P56M tripod.</li><li>9S469M IR interference system</li><li>11FG-400 battery</li></ol><p>As a means of duplicating the same capabilities offered by the 9P148 launch installation, the 9P135M launcher that is carried in each 9P148 tank destroyer is supplied with a 9S469M interference detection system, which is coupled with a 11FG-400 battery. The 9P148 tank destroyer also features a 9V614 battery charger to keep the 11FG-400 battery charged in combat conditions, allowing it to be used at any time the 9P135M is dismounted. The 11FG-400 can be plugged into the 9S451 control box, taking over the role of the batteries of each mounted missile container and providing sufficient power for the 9M113 to achieve the full 4 km range that the "Konkurs" system is rated for, on each shot of its rated firing cycle. The complete assembly is heavier than the basic 9P135M carried in a BMP, which somewhat degrades its portability, but this is not a major issue for its intended scope. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-NKiy48kc_ic/YNtjlEtaO7I/AAAAAAAATno/hoqvCtqbldofwZJf2lJfg4jpvLTGz2vmQCLcBGAsYHQ/s2048/9sh119m1%2Boptic.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1911" height="400" src="https://1.bp.blogspot.com/-NKiy48kc_ic/YNtjlEtaO7I/AAAAAAAATno/hoqvCtqbldofwZJf2lJfg4jpvLTGz2vmQCLcBGAsYHQ/w374-h400/9sh119m1%2Boptic.png" width="374" /></a><a href="https://1.bp.blogspot.com/-xsf0sYzzdc4/YNtoAIkvs7I/AAAAAAAATnw/-lTr3M2M0K0dKrqQaUFpRMfnMWQI7dguwCLcBGAsYHQ/s2048/9m135m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1786" height="400" src="https://1.bp.blogspot.com/-xsf0sYzzdc4/YNtoAIkvs7I/AAAAAAAATnw/-lTr3M2M0K0dKrqQaUFpRMfnMWQI7dguwCLcBGAsYHQ/w349-h400/9m135m.png" width="349" /></a></div><p>The IR interference detector is designed to interface with the 9S451M, just as in the guidance equipment of the 9P148 tank destroyer. If the 9S469 infrared interference detection system is fitted, a 9P135M launcher can alert the operator of IR interference via a warning tone delivered via his headphones and a warning light in his eyepiece, allowing him to use interference mitigation techniques such as aiming with an offset, or utilize the option of switching to backup MCLOS guidance.</p><p>Thus, if a 9P148 crew chooses to fight while dismounted for whatever reason, they are still able to take advantage of all available guidance features present in the vehicle. A 9P135M launcher with a full set of add-ons is significantly heavier than a basic version, which impedes its portability over long distances. Its purpose is to allow a 9P148 crew to utilize unique firing positions that are exceptionally suitable in terms of stealthiness, field of view and range, but are located in a position that is inaccessible to a vehicle. If such a position is identified, the 9P148 can be parked a short distance away, and the crew sets up the launch position with the 9P135M.</p><p>A single 9P135M launcher is also carried in the BMP-2. The launcher is broken down into its three major components and then integrated into its ATGM system, with its 9Sh119M1 sighting unit and its 9S474 guidance unit plugged into the vehicle, while its 9P56M tripod is stowed in the passenger compartment. The 9Sh119M1 sight from the launcher is installed in the rotating launcher fitted to the BMP-2 turret roof, and the 9S474 guidance unit is mounted behind the commander's seat and connected to the 9Sh119M1 via a cable, which also supplies it with power. Both the 9Sh119M1 and 9S474 are powered by the onboard electrical network of the vehicle, and are linked to the firing safety system of the vehicle. That is, the launch trigger circuit is only closed when all hatches on the vehicle are closed, to prevent injury from backblast overpressure. The circuit diagram for the BMP-2 ATGM system is shown below. The control of the ATGM system is done from the BU-25-2S weapons control panel in the BMP-2, and from there, the ATGM system is turned on by switching the weapons system to the "ATGM" mode, which connects the launcher to the electrical network while simultaneously disconnecting the gun stabilizer. Additionally, the BU-25-2S allows the BMP-2 gunner to switch between operating the ATGM system using the vehicle electrical network or using the integral batteries of the containerized missiles. The latter option can be used as a backup when the vehicle has no power.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Ad9akMfxUVM/YO3ZX0B7MEI/AAAAAAAAT6Y/NPvZgcwn__0zqPZnmz5UiauAbKJQWjlngCLcBGAsYHQ/s1893/bmp-2%2Batgm%2Bsystem%2Bcircuit%2Bdiagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="968" data-original-width="1893" height="328" src="https://1.bp.blogspot.com/-Ad9akMfxUVM/YO3ZX0B7MEI/AAAAAAAAT6Y/NPvZgcwn__0zqPZnmz5UiauAbKJQWjlngCLcBGAsYHQ/w640-h328/bmp-2%2Batgm%2Bsystem%2Bcircuit%2Bdiagram.png" width="640" /></a></div><p><br /></p><p>The 9P135M carried on the BMP-2 is only the basic set, because it lacks the 9S415M IR interference system and the accompanying battery. As such, the full 4,000-meter range of the 9M113 series of missiles can only be exploited when fired directly from the BMP-2, and not when dismounted. This is also true of the BMP-1P, BMD-1P, BMD-2 and BTR-RD. </p><p><br /></p><p><br /><a href="https://www.blogger.com/null" id="konkursaerodynamics"></a></p><h3><span style="font-size: large;">AERODYNAMICS</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-5PNeZm1Ocrw/YJzgIs9Jg-I/AAAAAAAAS90/M-uH4bXnhskwJ9NGza8NZvzCTEJ1mmGPQCLcBGAsYHQ/s1177/aerodynamic%2Bscheme.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="580" data-original-width="1177" height="198" src="https://1.bp.blogspot.com/-5PNeZm1Ocrw/YJzgIs9Jg-I/AAAAAAAAS90/M-uH4bXnhskwJ9NGza8NZvzCTEJ1mmGPQCLcBGAsYHQ/w400-h198/aerodynamic%2Bscheme.png" width="400" /></a></div><p>The aerodynamic design of the 9M113 is almost identical to the 9M111. Almost all features of the fuselage form follow that of the 9M111, with the exception of the nose, which is rounder, almost hemispherical, and the fuselage around the warhead section. Unlike the "Fagot", this section is completely cylindrical. The lift coefficients were presumably adjusted for a higher cruising velocity than "Fagot", hence the difference in the overall shape. However, the basic design is functionally the same. The canards and lifting body shape of the front half of the fuselage provide lift ahead of the center of gravity of the missile, defined by the engine, while the large wings behind the engine produce the majority of lift. The diagram shown above illustrates the aerodynamic factors at play, which are the lift sources (Y) and the moment arms of the lift sources (l), flight velocity (v), flight vector (p), air resistance (x), the center of gravity (Цт), weight (Q), and the three directions of missile rotation in flight (M).</p><p>It is worth noting that when the warhead of the 9M113 was upgraded in the early 1980's, apparently following the precedent of the 9M111M "Faktoriya", the diameter of the front fuselage half increased due to the enlargement of the warhead, with a subsequent modification in the aerodynamic fairing. This can be seen in the two images below. The photo on the left shows an original series 9M113. The photo on the right shows the late series. Aerodynamically, the new form still functioned as a lifting body.</p><p style="text-align: center;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-qkhK6QJfky8/YO3ipAybqYI/AAAAAAAAT6o/pJQI6Azrgukja2mOhbpqnTxYRhOlkEsHACLcBGAsYHQ/s1647/9m113%2Boriginal.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="883" data-original-width="1647" height="215" src="https://1.bp.blogspot.com/-qkhK6QJfky8/YO3ipAybqYI/AAAAAAAAT6o/pJQI6Azrgukja2mOhbpqnTxYRhOlkEsHACLcBGAsYHQ/w400-h215/9m113%2Boriginal.png" width="400" /></a><a href="https://1.bp.blogspot.com/-rRYOihYD8mI/YKrvvY8jOuI/AAAAAAAATFQ/tavumrAx2YoZ2jD2aVJDdPm2scdczm6BQCLcBGAsYHQ/s2561/9m113%2Bin%2Bflight%2Bconfiguration.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="2561" height="160" src="https://1.bp.blogspot.com/-rRYOihYD8mI/YKrvvY8jOuI/AAAAAAAATFQ/tavumrAx2YoZ2jD2aVJDdPm2scdczm6BQCLcBGAsYHQ/w400-h160/9m113%2Bin%2Bflight%2Bconfiguration.png" width="400" /></a></div><p></p><p>The wings are of the same design as those found on "Fagot" and have the same aspect ratio, only differing in size and some specific details in its assembly. The wingspan is 468mm. All four wings are offset by 2 degrees relative to the longitudinal axis of the rocket to induce and maintain the rotation of the missile in flight. Rotating the missile at an arbitrary speed can cause the rotation and pitch of the rocket to coincide, causing unwanted resonance. To eliminate it, the rocket is introduced into forced rotation about the longitudinal axis with a frequency of 5-7 Hz (longitudinal vibration frequency is 2-3 Hz).</p><p>As on the 9M111, the elastic wings are furled and retained by special wing straps that also serve to protect the skin of the wings as the missile is propelled through the container.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-b16qG4euMU8/YKgZoS797QI/AAAAAAAATDs/v67Ofba0zSQfCXMD1xfBy7MO8JOUQtutgCLcBGAsYHQ/s1087/wing%2Bstraps.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="655" data-original-width="1087" height="241" src="https://1.bp.blogspot.com/-b16qG4euMU8/YKgZoS797QI/AAAAAAAATDs/v67Ofba0zSQfCXMD1xfBy7MO8JOUQtutgCLcBGAsYHQ/w400-h241/wing%2Bstraps.png" width="400" /></a><a href="https://1.bp.blogspot.com/-ezI0UuXUsz4/YKgaP2CHJ3I/AAAAAAAATD0/dbzZ_jOL93MNUchdgu-_CglsWCh-Lr7LwCLcBGAsYHQ/s2047/brdm-2%2Bkonkurs%2Bwing%2Bstraps.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1293" data-original-width="2047" height="253" src="https://1.bp.blogspot.com/-ezI0UuXUsz4/YKgaP2CHJ3I/AAAAAAAATD0/dbzZ_jOL93MNUchdgu-_CglsWCh-Lr7LwCLcBGAsYHQ/w400-h253/brdm-2%2Bkonkurs%2Bwing%2Bstraps.jpg" width="400" /></a></div><p>Thanks to the large amount of lift produced by the combination of large wings, canards, and a lifting body fuselage, the attitude of 9M113 in trimmed flight is almost a zero-degree angle of attack. The four frames below, taken from high-speed camera footage demonstrating the "Arena" APS, shows that the angle of the missile is perfectly aligned with the horizontal white stripe on the scale board in the background. It is undoubtedly the same for the 9M111.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4Kj7p-wxswA/YKghs6AW4tI/AAAAAAAATEM/qHNeRm9ZIDAzyGiP8sDfdVBEY5knUJeugCLcBGAsYHQ/s3600/Arena%2Bintercepting%2B9M113.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="620" data-original-width="3600" height="110" src="https://1.bp.blogspot.com/-4Kj7p-wxswA/YKghs6AW4tI/AAAAAAAATEM/qHNeRm9ZIDAzyGiP8sDfdVBEY5knUJeugCLcBGAsYHQ/w640-h110/Arena%2Bintercepting%2B9M113.png" width="640" /></a></div><p><br /></p><p>The 9M113M "Udar" has a slightly modified layout. The nose section of the 9M113M contains the steering mechanism, using a ram-air operating principle, and the precursor charge of the new tandem warhead. The entire nose section is extendible, with a telescoping sleeve that fits over the main warhead which retained its original position.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-8uA_xY6_z2I/YO1gsT0gUjI/AAAAAAAAT5A/gfqar-oR1TszD30uGOS8mEElu5M9c70bgCLcBGAsYHQ/s1581/konkurs%2Band%2Bkonkurs-m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1555" data-original-width="1581" height="394" src="https://1.bp.blogspot.com/-8uA_xY6_z2I/YO1gsT0gUjI/AAAAAAAAT5A/gfqar-oR1TszD30uGOS8mEElu5M9c70bgCLcBGAsYHQ/w400-h394/konkurs%2Band%2Bkonkurs-m.png" width="400" /></a></div><p><br /></p><p>The telescoping nose section, which gained a substantial amount of weight over the original 9M113, requires additional lift due to the presence of a new precursor warhead and the increased caliber of the main warhead, which increased the weight of the missile forward of the center of gravity. By extending the entire nose section and the steering mechanism along with it, the canards are also displaced further from the center of gravity of the missile. This increased the mechanical leverage and thus increased the moment of lift developed from the canards, allowing the missile to remain balanced in level flight without needing canards of a larger size. According to the patent for the "Udar" nose section, Russian patent <a href="https://findpatent.ru/patent/216/2165586.html">RU2165586</a> granted to the KBP Instrument Design Bureau, the increase in the moment arm between the canard fins and the center of gravity of the missile is at least half of the total nose extension distance. </p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-NjKVocSuka8/YJ1N57X5AeI/AAAAAAAAS-U/Xask1RyoBsg67DuKZcPX6OYtV-K9hM7WQCLcBGAsYHQ/s1575/9m113m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1350" data-original-width="1575" height="343" src="https://1.bp.blogspot.com/-NjKVocSuka8/YJ1N57X5AeI/AAAAAAAAS-U/Xask1RyoBsg67DuKZcPX6OYtV-K9hM7WQCLcBGAsYHQ/w400-h343/9m113m.png" width="400" /></a></p><p><br /></p><p>A similar principle was utilized in the 9M113M1, but to supplement the steering canards, four fixed lifting canard fins were added, placed adjacent to the steering canards. The photo below, by <a href="https://missilery.info/gallery/vystavka-vooruzheniy-oboronekspo-2014-v-ramkah-foruma-tehnologii-v-mashinostroenii-2014">S.V. Gurov</a> of the "Ракетная техника" website, shows these additional canards. Like the steering canards, they spring-loaded to fold snugly against the fuselage surface when the missile is inside the container.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-CvdcmJFJEA8/YKWSUDr5F3I/AAAAAAAATCQ/XqKjOiBqs1Mo3GYWalYtnMcl-r7agPqawCLcBGAsYHQ/s1067/9m113m%2Bcanards.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1067" height="240" src="https://1.bp.blogspot.com/-CvdcmJFJEA8/YKWSUDr5F3I/AAAAAAAATCQ/XqKjOiBqs1Mo3GYWalYtnMcl-r7agPqawCLcBGAsYHQ/w320-h240/9m113m%2Bcanards.jpg" width="320" /></a><a href="https://1.bp.blogspot.com/-D3Is--KC0r8/YO3ajGmdovI/AAAAAAAAT6g/a64lwJjodVQaDVbhJG2qnYlwKX_gHo0qACLcBGAsYHQ/s1920/kavkaz%2B2020%2B9m113m1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://1.bp.blogspot.com/-D3Is--KC0r8/YO3ajGmdovI/AAAAAAAAT6g/a64lwJjodVQaDVbhJG2qnYlwKX_gHo0qACLcBGAsYHQ/w400-h225/kavkaz%2B2020%2B9m113m1.png" width="400" /></a><br /><br /></div><p><br /></p><p><br /><a href="https://www.blogger.com/null" id="konkursguidance"></a></p><h3><span style="font-size: large;">GUIDANCE SYSTEM</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-7wHE1ObQHAU/YO25oIVfDnI/AAAAAAAAT5w/jToOv3U7ClgzRAmxgFHvnSku3GZyGVzGQCLcBGAsYHQ/s1048/block%2Bdiagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="615" data-original-width="1048" height="235" src="https://1.bp.blogspot.com/-7wHE1ObQHAU/YO25oIVfDnI/AAAAAAAAT5w/jToOv3U7ClgzRAmxgFHvnSku3GZyGVzGQCLcBGAsYHQ/w400-h235/block%2Bdiagram.png" width="400" /></a></div><p>The guidance system in a 9M113 are essentially the same as in a 9M111. It consists of the wire link, an onboard power source, a signal receiver, a gyro-coordinator, and an IR beacon. The gyro-coordinator appears to be identical in construction to that found in the "Fagot", although it is not entirely clear if they are interchangeable. The IR lamp is, however, known to be interchangeable. </p><p>For the power source, a single T-417 thermal battery with a larger capacity was used to replace the T-307 series batteries. It has an immense weight of 925 grams. It is designed to provide electrical energy to the onboard equipment of the projectile after being heated to its operating temperature by a pyrotechnic heater. According to data provided by the manufacturer, JSC "Energia", the battery has a very wide discharge range of 0.5-15 A, with a nominal output voltage of 15-22.5 V, rated at 15 V for 26 seconds. The operating voltage of the electrical components immediately connected to the battery is 16 V, and the amperage rating varies considerably. Again, as with the "Fagot", it is worth mentioning that this is more than long enough to ensure the proper operation of all electric elements in the missile beyond its maximum range. </p><p>Like on "Fagot", the wire spool is wound around the tail of the missile. The transmitting end of the wire is connected to a special anchor cable that is connected to the front cover of the container. The spool of wire weighs 740 grams. As with the "Fagot, the wire used for the command link is a two-core wired with two twisted enamelled copper cores, shielded with a high-tensile plastic jacket.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-O3u6mkjbE50/YJvAGt3n1II/AAAAAAAAS9s/Cw3AR0sjzqEUgz9FoW6X21TZFWUegnwJQCLcBGAsYHQ/s2048/wire.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1157" data-original-width="2048" height="362" src="https://1.bp.blogspot.com/-O3u6mkjbE50/YJvAGt3n1II/AAAAAAAAS9s/Cw3AR0sjzqEUgz9FoW6X21TZFWUegnwJQCLcBGAsYHQ/w640-h362/wire.png" width="640" /></a></div><p><br /></p><p>Like the "Malyutka" system, the "Konkurs" features a single-wire guidance link, and permits both pitch and yaw steering despite having only a single guidance channel by having the missile rotate in flight. Moreover, as there is only a single wire, the command system cannot be shorted out by having its wires becoming immersed in water when a missile is fired over a body of water, and indeed, the 9P148 "Konkurs" tank destroyer is capable of firing not only over water, but while swimming, which was a considered a strategic priority for the ground forces when fighting a European land war due to the abundance of rivers and lakes. The firing range from water, over water, or at targets floating in water, is unlimited.</p><p>However, there is a special addendum regarding salt water reservoirs or lakes. Instead of shorting out, the issue with salt water is of electrical grounding, as salt water naturally has a very low resistance - generally at least a few times lower than fresh water, if not tens of times lower - and the bottom of the reservoir or lake has a ground potential. Instead of travelling down the wire, the steering command signals transmitted by the launcher are grounded via the salt water, due to the porosity of the insulation cladding, leading to a loss of control over the missile.</p><p>In the technical manual for the 9P148, it is stipulated that when firing over salt water reservoirs or at targets floating on a salt water reservoir, the firing position of the 9P148 must be located at an increased elevation relative to the water surface of the reservoir. The table below was given as the guideline for the required elevation for a given firing range.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-nPK8YhZ-RRU/YLPiiS8TwBI/AAAAAAAATQQ/lmF6x-UgGI4EQVQ1LyBF94h9NFgoLsEOwCLcBGAsYHQ/s1445/height%2Bover%2Bsalt%2Bwater.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="560" data-original-width="1445" height="248" src="https://1.bp.blogspot.com/-nPK8YhZ-RRU/YLPiiS8TwBI/AAAAAAAATQQ/lmF6x-UgGI4EQVQ1LyBF94h9NFgoLsEOwCLcBGAsYHQ/w640-h248/height%2Bover%2Bsalt%2Bwater.png" width="640" /></a></div><p>This stipulation only applies to salt water reservoirs or lakes, not when firing out to the sea or from the sea. Gunnery training with 9P148 tank destroyers have been done with <a href="https://youtu.be/TLmxkNdQTko">targets out at sea</a> without issues. </p><p>On the 9M113M, an additional water-repellant coating was added to the wire. The intent of this modification was not specified, but presumably it allows the missile to be fired without restrictions over all bodies of water, including shallow bodies of salt water.</p><p>The steering commands transmitted over the guidance wire are, of course, the same signals used to guide any other "Fagot" series missile as they are both compatible with the same launchers. There is functionally no difference other than the duration of the guided flight period. The processing steps made by the receiver and the gyro-coordinator as also identical. The only additional step made by the receiver unit is that before the guidance command signal is passed to the yaw steering signal (positive polarity) decoder, there is an additional preamplifier stage applied to eliminate the "dip" of the waveform from the discharging and charging cycles caused by wire capacitance when firing at long ranges, over 3,000 meters.</p><p>As with "Fagot", the 9M113 is tracked in flight via its IR beacon. The lamp consists of an incandescent bulb and a parabolic reflector. For the IR beacon, the same lamp as in the 9M111 missile with an RN 13.5-100 infrared bulb was used, but with an extended operating time of 30 seconds due to the increased power supply in 9M113. The diameter of the lamp itself remained 95mm, so the tail of the 9M113 is only larger than the 9M111 because of its larger wire spool, holding the additional two kilometers of wire. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Aauct7ioL-s/YJtWk8NYI2I/AAAAAAAAS9E/a0FbBlUzNA4S0dygEg2fHdlIR7TkZ20HQCLcBGAsYHQ/s2033/lamp.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1343" data-original-width="2033" height="264" src="https://1.bp.blogspot.com/-Aauct7ioL-s/YJtWk8NYI2I/AAAAAAAAS9E/a0FbBlUzNA4S0dygEg2fHdlIR7TkZ20HQCLcBGAsYHQ/w400-h264/lamp.png" width="400" /></a></div><p>The 9M113M has a new IR beacon, still operating at 13.5 V and a power of 100 W, but with an output intensity of 10,000 candelas according to the textbook "<i>Основы Устройства И Функционирования Противотанковых Управляемых Ракет</i>". This may have been related to the coupling of the add-on "Mulat" thermal sight for the "Konkurs-M" system, with which the "Udar" was offered as a comprehensive modernization set. Due to the insensitivity of a thermal viewer to near-IR emissions, a hotter tungsten filament bulb may have been implemented to produce the heat signature needed to permit reliable operator tracking of the missile in his thermal viewfinder. </p><p><br /><a href="https://www.blogger.com/null" id="konkurssteering"></a></p><h3><span style="font-size: large;">STEERING</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-EeZBi8uu-hs/YKxx1ovRAjI/AAAAAAAATGk/bkeGB-x3nfQPyfkk82x07dx4uPI7ELq2wCLcBGAsYHQ/s2048/nose%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1050" data-original-width="2048" height="205" src="https://1.bp.blogspot.com/-EeZBi8uu-hs/YKxx1ovRAjI/AAAAAAAATGk/bkeGB-x3nfQPyfkk82x07dx4uPI7ELq2wCLcBGAsYHQ/w400-h205/nose%2Bsection.png" width="400" /></a><a href="https://1.bp.blogspot.com/-WGUHdJAbeto/YJW8WasVJII/AAAAAAAAS7M/bTo98e8ZhAkDOHdOIswrTexL36BopApTACLcBGAsYHQ/s523/canard.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="394" data-original-width="523" src="https://1.bp.blogspot.com/-WGUHdJAbeto/YJW8WasVJII/AAAAAAAAS7M/bTo98e8ZhAkDOHdOIswrTexL36BopApTACLcBGAsYHQ/s320/canard.png" width="320" /></a></div><p>The steering mechanism of the 9M113 is functionally and mechanically the same as the 9M111, and as such, there is no reason to re-explore the topic. The only noteworthy difference is that the larger diameter of the missile nose section made it impossible to fit the canard fins within the inner diameter of the container, as was the case for the 9M111. To solve this, the canards were modified into flip-out fins. When loaded into the container during assembly at the factory, the fins would simply be folded over while the missile is inserted, and the container wall itself holds the fins in place. Once the nose is clear of the container muzzle, each fin is flipped into the upright position by a small spring at the base.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ncgYy47d-DY/YOuyGclQBvI/AAAAAAAAT24/nMCWH0ObkvogCbpa2Bn2RoSU-yodFjjEQCLcBGAsYHQ/s1280/1153295.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="716" data-original-width="1280" height="224" src="https://1.bp.blogspot.com/-ncgYy47d-DY/YOuyGclQBvI/AAAAAAAAT24/nMCWH0ObkvogCbpa2Bn2RoSU-yodFjjEQCLcBGAsYHQ/w400-h224/1153295.jpg" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><p>Beginning with the 9M113M "Udar", a major redesign was implemented. Rather than electromagnetic actuators, ram-air actuators were implemented. It is also known as an air-dynamic steering drive in Russian. The concept was first put into practice by KBP in the "Metis" missile series in the late 1970's, and it proceeded to become a signature innovation of the design bureau, seeing use on their series of 100mm gun-launched ATGMs starting with the "Kastet", and then the 125mm gun-launched "Refleks" ATGM. Following these, it was also implemented on the "Kornet", completely solidifying the bureau's preference for this type of actuator. For the "Udar" modernization project, the use of a ram-air actuator made it possible to solve the issue of high electrical power requirements and strong steering forces at the same time. </p><p>The use of ram-air actuators was one of the main reasons for the blunt nose shape. The specific type of ram-air actuator used in "Udar" is termed a semi-open type by KBP. This refers to the extent to which the incoming air is allowed to flow within the actuator. An open actuator allows air to freely flow, a semi-open actuator has partially free flow, and a closed actuator allows no flow unless a valve is opened. In principle, ram-air actuators function based on the use of the braking pressure of the incoming air flow.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-P_28pIaeBbw/YOcNNxcIFYI/AAAAAAAATyI/UmxpISk8s0QjVrIjiWwlJR17RK-QpPqsQCLcBGAsYHQ/s1276/KONKURS-M_02.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="473" data-original-width="1276" height="238" src="https://1.bp.blogspot.com/-P_28pIaeBbw/YOcNNxcIFYI/AAAAAAAATyI/UmxpISk8s0QjVrIjiWwlJR17RK-QpPqsQCLcBGAsYHQ/w640-h238/KONKURS-M_02.jpg" width="640" /></a></div><p>Because the air intake is in the center of the nose, the aerodynamic consequences of the rounded blunt nose shape are greatly lessened. Instead of having air collide with a flat surface and then flowing over the rounded edge, which generates a great deal of air resistance, the air flowing into the center of the nose enters the ram-air inlet, so no collision takes place. This makes the peculiar nose shape of the "Udar" surprisingly aerodynamic, approximately on par with a hemispherical or rounded nose like on the original "Gaboy". The same blunt nose shape was used in the 9M116 "Metis", for the same reason of providing an air intake.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Pn4N7SX3_ls/YPiIcUpG6oI/AAAAAAAAUBs/mn6HlYcc7moFjfxq43DjRM-BzSDvPJ07gCLcBGAsYHQ/s1024/UMaFuwNx5kU.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://1.bp.blogspot.com/-Pn4N7SX3_ls/YPiIcUpG6oI/AAAAAAAAUBs/mn6HlYcc7moFjfxq43DjRM-BzSDvPJ07gCLcBGAsYHQ/w400-h300/UMaFuwNx5kU.jpg" width="400" /></a></div><p>Fundamentally, a ram-air actuator relies on the rocket engine of the missile as its power source. It is the rocket engine which propels the missile through the air, and therefore, it is the rocket that powers the actuator. For missiles with a streamlined nose, the presence of air intakes increases the overall drag by about 2-4%, and to ensure the required flight speed, it is necessary to increase the engine thrust, and therefore the fuel supply onboard the rocket. However, rocket fuel has the highest energy density compared to any other form of onboard power source, not to mention that the rocket engine is an existing component, so additional fuel can be accommodated much more easily than an additional battery or some other form of power source. Electrical power is still needed as the means of switching the set of control surfaces actuated by the mechanism. This is normally done by a small electromagnetic valve, which constitutes an extremely modest electrical load, nowhere nearly as demanding as direct mechanical actuators such as the type used in the original "Gaboy" missile. </p><p>The semi-open actuator used in "Udar" is a very simple inverted wedge with the axle of a pair of canard fins as its hinge. The inverted cone has two small air outlets on each side, allowing air entering from the open base to flow out and into the follow fuselage at equal rates. If the outflow is equalized, then the wedge remains in the neutral position, and so do the canards. This is additionally aided by a spring. To turn the canards to one side or the other, a small flap is closed over one of the outlet holes, causing the actuator to deflect towards the opposite outlet due to the redirection of the airflow, which imparts a net pressure on the wedge surface of the unobstructed outlet. For example, referring to the image below - assuming that the image shows the axle of the canards in the horizontal position, then to cause the canards to deflect upwards and thus induce a pitch-up moment on the missile, the actuator wedge must be pushed up. To do this, the lower outlet flap is closed. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-fa-mpjPpS-s/YOu2LBh0NHI/AAAAAAAAT3I/zP_otnTZkW4EHpzTySIoqITsRn224etSQCLcBGAsYHQ/s505/udar%2Bsemi-open%2Bram-air%2Bactuator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="461" data-original-width="505" src="https://1.bp.blogspot.com/-fa-mpjPpS-s/YOu2LBh0NHI/AAAAAAAAT3I/zP_otnTZkW4EHpzTySIoqITsRn224etSQCLcBGAsYHQ/s320/udar%2Bsemi-open%2Bram-air%2Bactuator.png" width="320" /></a></div><p>The increase in the moment arm between the canard fins and the center of gravity of the missile raised the moment of lift to compensate for the weight of the warhead, and it had the same effect in regards to steering, as the steering moment is nothing but an excess of the lifting moment. </p><p>On the 9M113M1, the ram-air actuator was replaced with an electromagnetic drive once again. This regression is unexplained, but it is most likely related to the space limitation imposed by the inclusion of the standoff probe, which makes it more complicated to fit air intakes and the necessary actuators. </p><p><br /><a href="https://www.blogger.com/null" id="konkursejection"></a></p><h3><span style="font-size: large;">EJECTION ENGINE</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Ri8bBWxwJz0/YJts5gdds0I/AAAAAAAAS9M/deCSe0Qfv5YlXBDpUZMFeqKwTaa4OW_pQCLcBGAsYHQ/s2181/ejection%2Bunit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1037" data-original-width="2181" height="304" src="https://1.bp.blogspot.com/-Ri8bBWxwJz0/YJts5gdds0I/AAAAAAAAS9M/deCSe0Qfv5YlXBDpUZMFeqKwTaa4OW_pQCLcBGAsYHQ/w640-h304/ejection%2Bunit.png" width="640" /></a></div><p>The 9Kh180 ejection engine is similar to the 9Kh146 ejection engine of the "Fagot", but differs in having a much larger powder charge to effectively propel the much heavier 9M113 missile while counteracting its recoil. It has six front and fifteen rear nozzles.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-caQspRfbSeo/YPiIT_PCI1I/AAAAAAAAUBo/dui0-MQU5zIHoHm7fspK_8z1RzaqEpDyQCLcBGAsYHQ/s1067/P1010613.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1067" height="300" src="https://1.bp.blogspot.com/-caQspRfbSeo/YPiIT_PCI1I/AAAAAAAAUBo/dui0-MQU5zIHoHm7fspK_8z1RzaqEpDyQCLcBGAsYHQ/w400-h300/P1010613.jpg" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><p>The maximum pressure developed in the combustion chamber is 39 MPa, while the maximum pressure in the missile container is 4 MPa. Combustion lasts for an average of 0.023 seconds, but the depressurization of the ejection engine is much more prolonged, and the acceleration of the missile in the container from the gas pressure takes somewhat more time. </p><p>The ejection engine weighs 2.9 kg, and contains 0.67 kg of 12/1 tr pyroxylin (nitrocellulose) stick powder are used. The propellant burns cleanly, but develops momentary tongues of flame once the missile is ejected from the tube due to the drop in internal pressure. A similar effect can be seen on the M47 Dragon. The flames are largely inconsequential as an unmasking element, as the smoke and dust raised by the backblast are persistent, and they are far more visible from a distance by comparison. However, when firing at night, the opposite is true. The persistent luminance from the flames compared to the momentary flash of the launch is detrimental as it helps enemy observers locate the launcher more easily, whereas the dust and smoke signature is a non-issue. This was the same principle that guided signalling practices used by watchtowers during the medieval period, both in Europe and Asia, for example, in the form of tower houses or keeps in the north of England, or beacon towers as found on the Great Wall of China. During daytime, watchtowers signalled to friendly observers using the smoke from their fire beacons, and at night, when smoke would be poorly visible, the fire beacons were flashed using opaque screens for signalling instead.</p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-feix5aa-FfI/YN7lnwy0RbI/AAAAAAAATtk/tBApDodZsPIK7zA27aerByXMA8a8LlHBQCLcBGAsYHQ/s1007/ejection%2Bunit%2Bmodel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="583" data-original-width="1007" height="231" src="https://1.bp.blogspot.com/-feix5aa-FfI/YN7lnwy0RbI/AAAAAAAATtk/tBApDodZsPIK7zA27aerByXMA8a8LlHBQCLcBGAsYHQ/w400-h231/ejection%2Bunit%2Bmodel.png" width="400" /></a></p><p>The ejection charge ensures that the missile leaves its container at a speed of at least 64 m/s or up to 70 m/s, lower in cold weather and higher in hot weather. Shortly thereafter, the rocket engine of the missile is ignited, 10-15 meters away from the launcher.</p><p>Depending on the operating temperature, the rearward thrust from the ejection engine may not be exactly proportionate to the recoil force produced from the missile launch, and as such, the container can potentially move a short distance under recoil along the guide rails of the 9P135(M) launcher. The system is therefore not a perfect recoilless system under all conditions. The felt recoil is reduced to a minimum by matching the dynamic balance along the momentum flow curve to within 2 kgf (19 N), and it is additionally buffered by the dampening effect of the reciprocating guide rail, which has a soft buffer spring for this reason. On top of that, the weight of the launcher itself has a stabilizing effect. For maximum stability, the conveniently shaped frame on the front leg of the launcher may be weighed down with sandbags or rocks. The momentary vibration from the recoil does not interfere with the guidance of the missile at any point in its flight, though it is noticeable to the operator because it, together with the muzzle and back blast, briefly blurs his vision as the optics are jolted.</p><div><p><br /><a href="https://www.blogger.com/null" id="konkursengine"></a></p><h3><span style="font-size: large;">ENGINE</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-P4EKhwrK5YY/YJcEKBEkzFI/AAAAAAAAS7s/sBthFYlQDx49jmGFhcAoZs8NyfF5Rbo8QCLcBGAsYHQ/s1644/konkurs%2Bengine.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1644" data-original-width="1259" height="640" src="https://1.bp.blogspot.com/-P4EKhwrK5YY/YJcEKBEkzFI/AAAAAAAAS7s/sBthFYlQDx49jmGFhcAoZs8NyfF5Rbo8QCLcBGAsYHQ/w490-h640/konkurs%2Bengine.png" width="490" /></a></div><p>"Konkurs" has a single-chamber dual-thrust 9Kh179 solid fuel engine, using the RNDSI-5K fuel compound. The engine has an aluminium chamber with an insulating liner, and two fixed nozzles. To start the engine, there is a 9Kh237-1 delayed ignition device screwed into the side of the engine chamber. It electrically ignites a booster charge containing DRP-2 black powder after a delay of 0.15 seconds following ejection from the container. The two nozzles of the engine are symmetrically mirrored and are angled by 20 degrees relative to the transverse axis of the missile fuselage, and they are additionally angled by 9 degrees relative to the longitudinal axis to impart a spin to the missile. </p><p>RNDP fuel is used. The solid fuel is shaped into a single block weighing 3.16 kg, and is of an end-burning type. The weight of the 9M113 missile without fuel is 11.34 kg. The fuel has a density of 1.58 g/cc, and has an energy density of 799 kJ/kg and a specific impulse of 2,186 N.s/kg. Overall, the design of the engine is rather typical for rockets of the time, and is not different from that of the "Fagot" in any meaningful way. As before, the two thrust modes was made possible by using a progressive burning fuel and by the application of an inhibitor coating on a part of the solid fuel block surface to separate it into booster and sustainer blocks. The central location of the engine in the missile fuselage ensures that the center of gravity does not shift as the fuel is gradually spent during flight.</p><p>At first, the fuel block burns along the uncoated part of the outer cylindrical surface, the rear end, and the inner channel. The combustion area remains approximately constant, but with the burning out of the uncoated part of the fuel block, it gradually decreases and the cavity from the expended fuel takes on a shape close to a hemisphere. The outline of the hemispheric surface of the sustainer stage is outlined with a dotted curve in the image above. Tapering off the burn rate in this way allows for a smooth transition to the lower burn rate of the remaining fuel, transitioning the engine from the boost stage to the sustainer stage. </p><p>Under normal conditions, in the boost stage of the engine produces 710 N of thrust for 2.5 seconds, and then produces 320 N of thrust for 13 seconds in the sustainer stage. A top speed of 260 m/s may be reached during the flight of the 9M113, making it slightly faster than the 9M111. To reach this speed, the operating temperature must be +50°C. During its operation, the average fuel consumption rate of the engine is 0.15 kg/s. The velocity curve of the 9M113 is, in principle, the same in shape as the 9M111, although real data is lacking. </p><p>The total burn time of the engine is 15.5 seconds, somewhat longer than the 9M111, but only long enough for the missile to reach a flight distance of somewhere over 3,000 meters, close to 3,500 meters. The missile then glides throughout the remainder of its flight to the target, which takes about 3.7 seconds. The average missile speed is 208 m/s. This is based on the total time of 19.2 seconds needed to reach the maximum range of 4 km. </p><p>Owing to the heavier nose section, the 9M113M missile weighs 13.34 kg without fuel. A more energetic engine was therefore fitted. In the boost stage, the engine develops 900 N of thrust for 2 seconds (at a chamber pressure of 12 MPa), and then produces 350 N of thrust for 13 seconds in the sustainer stage (at a chamber pressure of 4.5 MPa). </p><p>For comparison, the HOT missile, which reaches a maximum speed of 240 m/s, takes 17.3 seconds to reach its maximum range of 4 km; nearly two seconds quicker than 9M113. This is because the HOT is ejected from its container at just 20 m/s, and its booster starts before it fully departs the container and then proceeds to continuously accelerate the missile until its maximum range is reached, owing to its dependence on engine thrust for its TVC steering system to function. The immediate boost startup can be seen in the image below, taken from <a href="https://youtu.be/D2jIgR7twmc">archival footage published by the Bundeswehr</a>. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-i0odFkVxY_c/YLPSPFnADPI/AAAAAAAATQI/hUuXWXrDBNwlwfKElq8QkEO95kMwABVewCLcBGAsYHQ/s1920/hot%2Bdeparts%2Bfrom%2Bcontainer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://1.bp.blogspot.com/-i0odFkVxY_c/YLPSPFnADPI/AAAAAAAATQI/hUuXWXrDBNwlwfKElq8QkEO95kMwABVewCLcBGAsYHQ/w400-h225/hot%2Bdeparts%2Bfrom%2Bcontainer.png" width="400" /></a></div><p>This launch method is completely unacceptable for an infantry launcher, as the rocket jets, producing an enormous amount of thrust due to the short boost period, would damage the launcher's optics and seriously injure the missile operator whose head would be next to the container. And indeed, the HOT could not, and was not used from any man-portable launchers. Yet thanks to this launch method, the missile picks up speed very quickly, such that the average speed of the HOT during its first kilometer of flight is 200 m/s, which surpasses the 9M113. With that said, however, in return for the flight time disadvantage of 1.9 seconds at maximum range, the 9M113 was 8.5 kg lighter and could be used from infantry launchers - all in all, quite a bargain.</p><p>Compared to the TOW missile, a number of interesting points can be raised regarding the fundamental natures of their propulsion methods. Firstly, even though 9M113 is a smaller missile, having a maximum diameter of 135mm rather than 148mm and a length of 960mm rather than 1,163mm, with the TOW also weighing 4.3 kg (30%) more, it nevertheless managed to achieve a longer range, better kinematics and a more efficient design. </p><p>The most apparent example of this is the offloading of the ejection mechanism to an external unit housed in the missile container rather than in the missile itself. On the TOW, ejection is provided by an M114 rocket engine housed in the tail of the fuselage, occupying a considerable amount of space (15" long, 2.1" diameter) due to the high thrust needed to launch the missile from its container but serving no purpose once its task is complete, being nothing but a parasitic weight. Even empty, the weight of the launch engine is still 7% of the total missile weight. The single-stage booster engine (7.5" long, 5.8" diameter) also has a similar parasitic effect. Ergo, for the rest of its flight, the missile carries two components that serve no purpose. </p><p><br /><a href="https://www.blogger.com/null" id="konkurswarhead"></a></p><h3><span style="font-size: large;">WARHEAD</span></h3><p></p><p>As the 9M113 missile in general is based upon the 9M111 with an enlargement scale factor of 1.13, the ratio of warhead diameter to maximum diameter should, in theory, have been preserved. The geometry of the warhead also seems to indicate this, as the drawings show that it is essentially an upscaled 9N122 warhead. With this working assumption and some additional facts, a close approximation of the true warhead diameters can be obtained.</p><p><br /></p><h3><span style="font-size: large;">9M113</span></h3><h3><span style="font-size: large;">9N131</span></h3><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-RT8oeT4VrFA/YJuxaMt0X8I/AAAAAAAAS9k/ViySxB5rlj4BCvYEan_YtiplGW0VEhPygCLcBGAsYHQ/s1661/9n131.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1661" data-original-width="1017" height="400" src="https://1.bp.blogspot.com/-RT8oeT4VrFA/YJuxaMt0X8I/AAAAAAAAS9k/ViySxB5rlj4BCvYEan_YtiplGW0VEhPygCLcBGAsYHQ/w245-h400/9n131.png" width="245" /></a></div><br /><p>The original 9N131 warhead, as used on the 9M113 at its time of introduction in 1974, has a tapered charge and the joint between the warhead section with the engine section is covered with an aerodynamic fairing, like on the 9M111. The warhead assembly weighs just 2.75 kg. It is fitted with the 9E243M fuze, which is the same capacitor fuze used later in the 9M111M "Faktoriya", differing only in that a different set of contact plates is used. The skin of the fuselage is the outer plate, and a rounded cup serves as the inner plate. Otherwise, the fuzes are interchangeable. As the contact plates are structurally integrated into the nose of the fuselage, it is only a matter of wiring, connecting one terminal to the skin of the fuselage and the other terminal to the inner plate.</p><p>Unlike the fuzing system used in the "Fagot" series, which left a certain amount of space behind the canard steering mechanism for its disintegration, the issue of the steering mechanism obstructing the path of the shaped charge jet was solved by the increased diameter of the nose, so there is free room in the center of the canard actuators. By leveraging the larger diameter of the nose in this way, it became possible to give the 9N131 warhead as much standoff distance as possible without substantially increasing the length of the missile. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-idDyeuxQjVE/YOil6XwSrEI/AAAAAAAATz4/oKVb94BuzG09qAk2sF5b5kgJmyeYSxO5gCLcBGAsYHQ/s479/nose.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="279" data-original-width="479" height="233" src="https://1.bp.blogspot.com/-idDyeuxQjVE/YOil6XwSrEI/AAAAAAAATz4/oKVb94BuzG09qAk2sF5b5kgJmyeYSxO5gCLcBGAsYHQ/w400-h233/nose.png" width="400" /></a></div><p>Needless to say, this layout also provides the fuze with graze sensitivity. The arming mechanism of the 9E234M is, of course, unchanged from the same fuze in the "Fagot" series, and it also has a pyrotechnic delayed self-destruct mechanism.</p><p>The warhead diameter of the 9N131 is unknown. However, based on the 1.13 scale factor of the missile with the 9M111, it is highly likely that it is 1.13 times larger than the 87mm warhead of the "Fagot", which would mean it is 98mm in diameter. The built-in standoff distance, as measured from the base of the shaped charge liner to the crush fuze at the missile nose, is approximately 177mm. For a warhead with a diameter of 98mm, this amounts to a standoff of 1.8 CD.</p><p>According to the tactical-technical characteristics, the penetration of 9M113 is officially 250mm RHA at 60 degrees, but it is also indicated in a number of technical sources as being 550-560mm. The most common figure, cited in both technical literature and in other secondary sources, is 560mm. The textbook "<i>Основы Устройства И Функционирования Противотанковых Управляемых Ракет</i>" by V. V. Vetrov et al. also credits the 9M113 with 560mm of penetration.</p><p>Hungarian testing on a T-54 using 9M113 missiles confirmed the powerful post-perforation effects of its warhead. A translation of the full original Hungarian article is available in <a href="https://drive.google.com/file/d/1AlWU24NcjQo6JoprENtiZbIaX9osgs_T/view">this link</a>.</p><p>The first hit in the test was on the upper glacis, 5cm under the driver’s periscope. The jet penetrated the plate (200mm RHA), passed through the 25-30cm logs imitating the driver, gunner and commander as well as the firewall separating the fighting and engine compartments, and stopped in one of the left side cylinder head of the engine. The loader might have survived with serious wounds.</p><p>The second shot also hit the upper glacis. The jet went through one of the front fuel tanks, barely missing a stowed cartridge simulant, pierced some stabilizer components hung underneath the 100mm gun, and stopped in the gun breech.</p><p>In both cases, the blast of the missile damaged some external fittings, including the sights, periscopes, and an external fuel tank.</p><p><br /></p><h3><span style="font-size: large;">9N131M</span></h3><p style="text-align: center;"><a href="https://3.bp.blogspot.com/-gVuAYj5ZQ54/V1MTLuDnP8I/AAAAAAAAGhw/hL9h7pLcdjABWtozmhjUB3Gkmv6-HZHDwCLcB/s1600/konkurs.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://3.bp.blogspot.com/-gVuAYj5ZQ54/V1MTLuDnP8I/AAAAAAAAGhw/hL9h7pLcdjABWtozmhjUB3Gkmv6-HZHDwCLcB/w400-h300/konkurs.jpg" width="400" /></a></p><p>An improved 9N131M warhead was introduced in the early 1980's, presumably supplanting the older warhead entirely. It has a straight-walled charge with a longer, more elongated liner, and a new wave shaper. It is, effectively, an enlarged version of the 9N122M warhead, keeping the same proportional geometry in its design. The new warhead design required a small revision of the aerodynamic form of the missile, also mirroring that of the "Faktoriya".</p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both;"><a href="https://1.bp.blogspot.com/-iSl7tEzx4CQ/YKrvvHEZpRI/AAAAAAAATFU/ChNwCIk_elEnlkWlK2hUFDz7cswUQjU0wCLcBGAsYHQ/s1393/6.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="602" data-original-width="1393" height="173" src="https://1.bp.blogspot.com/-iSl7tEzx4CQ/YKrvvHEZpRI/AAAAAAAATFU/ChNwCIk_elEnlkWlK2hUFDz7cswUQjU0wCLcBGAsYHQ/w400-h173/6.jpg" width="400" /></a></div></div><p>9N131M has a calculated external diameter of 105mm, and the shaped charge liner itself has a confirmed diameter of 92.5mm. The 9N131 shaped charge warhead is complete with all of the performance-enhancing features available at the time it entered service: a HMX-based charge, a wave shaper, and a conical copper liner with an acute angle of 50 degrees. The built-in standoff distance is unknown, but it can be assumed to be the same as the original 9N131; approximately 177mm.</p><p>According to the study "<i>Противокумулятивная Стойкость Комбинированных Преград С Керамикой</i>" published in the March 1988 issue of the "<i>Вестник Бронетанковой Техники</i>" military science journal, the penetration channel depth produced by the 9N131M warhead into a semi-infinite RHA block is 631mm ±14mm, based on a sample size of 22 detonations. It was noted in the paper that the penetration depth was determined based on the results of experiments with a confidence level of 95%. As such, the given range is a comprehensive representation of the performance of the warhead, and its average penetration can be considered 631mm RHA.</p><p><br /></p><h3><span style="font-size: large;">9M113M</span></h3><h3><span style="font-size: large;">9N131M</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jS7xis_o6DE/YOuv_QdmuvI/AAAAAAAAT2s/w3byEi81zWwYGDixNMD0uDez8JyCAEkzwCLcBGAsYHQ/s2048/udar.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1365" height="400" src="https://1.bp.blogspot.com/-jS7xis_o6DE/YOuv_QdmuvI/AAAAAAAAT2s/w3byEi81zWwYGDixNMD0uDez8JyCAEkzwCLcBGAsYHQ/w266-h400/udar.jpg" width="266" /></a><a href="https://1.bp.blogspot.com/-I3OJ6G9PIDc/YOuwDx8fW7I/AAAAAAAAT2w/g3O3VZvUg_od5KeYuSWiGBqiXFez1KbJwCLcBGAsYHQ/s800/tandem%2Budar.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="600" height="400" src="https://1.bp.blogspot.com/-I3OJ6G9PIDc/YOuwDx8fW7I/AAAAAAAAT2w/g3O3VZvUg_od5KeYuSWiGBqiXFez1KbJwCLcBGAsYHQ/w300-h400/tandem%2Budar.jpg" width="300" /></a><br /><br /></div><p>The 9N131M warhead of the "Udar" shares its designation with the 9N131M of the earlier improved 9M113 missile. Though strange, it is confirmed that both missiles have drastically different warheads of the same designation. This may be an indication of their shared heritage on the basis of the 1982 developmental work on combating tanks with reactive armour. Based on the known fact that an undeployed 9M113M1 missile has the same dimensions as the basic 9M113 and fits in the same container, its length must be no more than 960mm. </p><p>In this case, the 9N131M is a tandem warhead assembly, integrated into the extendable nose mechanism of the "Udar" missile itself. The basic premise of the "Udar" telescoping nose mechanism is patented in Russian patent <a href="https://findpatent.ru/patent/216/2165586.html">RU2165586</a> granted to the KBP Instrument Design Bureau. The method of creating a telescoping nose section, containing a precursor charge and a canard steering mechanism, is also covered in a KBP patent, <a href="https://findpatent.ru/patent/208/2084809.html">RU2084809</a>. The nose of the 9M113M extends just before launch via a pyrotechnic charge. A representation of the nose in its retracted and extended state is shown in the drawings on the left and right respectively.</p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both;"><a href="https://1.bp.blogspot.com/-vprmKiy9v6k/YO3IphF6eEI/AAAAAAAAT6Q/Uri5PrXyQrE3vy5jFznaTmZR60bR_5KQQCLcBGAsYHQ/s700/retracted%2Bnose.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="492" data-original-width="700" height="281" src="https://1.bp.blogspot.com/-vprmKiy9v6k/YO3IphF6eEI/AAAAAAAAT6Q/Uri5PrXyQrE3vy5jFznaTmZR60bR_5KQQCLcBGAsYHQ/w400-h281/retracted%2Bnose.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-z65iRXv9Sq0/YOwKrfb6HqI/AAAAAAAAT4Q/xjZ1wr_72J8oD-Eaab_0jShKmWYlZ7hBACLcBGAsYHQ/s607/telescoping%2Bnose.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="500" data-original-width="607" height="330" src="https://1.bp.blogspot.com/-z65iRXv9Sq0/YOwKrfb6HqI/AAAAAAAAT4Q/xjZ1wr_72J8oD-Eaab_0jShKmWYlZ7hBACLcBGAsYHQ/w400-h330/telescoping%2Bnose.jpg" width="400" /></a></div></div><p>Within 0.1 seconds after the front cover of the container is popped open, a signal is sent to the ignition fuze of the charge to deploy the nose section. The pyrotechnic extension charge is fitted behind the precursor warhead. It is inside a cuff, which fits inside the liner of the main warhead when the nose section is in the retracted position. The combustion of the charge generates a slight overpressure inside the fuselage cavity, but without damaging the main charge liner as the combustion products from the charge are directed onto the corrugated cuff. The overpressure generates a relatively strong force, with the entire surface of the nose section acting as a piston for the gasses, shearing a retaining pin and thus pushing the entire nose assembly forward. After the nose section has begun to move, the gas pressure inside the fuselage cavity drops sharply, and the entire nose section continues to move mainly by inertia until it reaches a locking ring and is locked in the extended position. The extension mechanism can be seen at work in a number of videos, such as <a href="https://youtu.be/Pr4iKCnj5A0">this video</a> of combat footage in Syria.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-JsSlmvK3ZxU/YO3BfWKIT6I/AAAAAAAAT6I/RtNQ_Mz7iPUa39JX18JfTVqJeLqnK8kyQCLcBGAsYHQ/s1216/9m113m%2Btelescoping%2Bnose.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="662" data-original-width="1216" height="347" src="https://1.bp.blogspot.com/-JsSlmvK3ZxU/YO3BfWKIT6I/AAAAAAAAT6I/RtNQ_Mz7iPUa39JX18JfTVqJeLqnK8kyQCLcBGAsYHQ/w640-h347/9m113m%2Btelescoping%2Bnose.png" width="640" /></a></div><p>When retracted, the base of the canard steering actuator mechanism fits into the cavity of the shaped charge liner of the main warhead. The precursor warhead is placed ahead of the steering actuator unit.</p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-4du-5fwwEBE/YOuqVDAXVXI/AAAAAAAAT2c/r4JWbkYSkXwd_-JKwafSPhQ6vgqzfSYLgCLcBGAsYHQ/s1000/patent%2Bretracted.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="415" data-original-width="1000" height="165" src="https://1.bp.blogspot.com/-4du-5fwwEBE/YOuqVDAXVXI/AAAAAAAAT2c/r4JWbkYSkXwd_-JKwafSPhQ6vgqzfSYLgCLcBGAsYHQ/w400-h165/patent%2Bretracted.jpg" width="400" /></a></p><p>A dual fuzing system is used in the warhead. The precursor charge fitted with the 9E93-1 fuze and the main charge has the 9E93 fuze. When the missile hits the target, the 9E93-1 precursor fuze is triggered and detonates the precursor warhead, and additionally signals the fuze of the main charge via an unknown means. Upon activation, a delay is initiated, and after 300 ± 50 μs, a signal voltage is applied to 9E93 fuze, which triggers the detonation of the main charge. In the given delay period, the missile would have moved 51-72mm forward under its given average velocity of 206 m/s, thus decreasing the standoff distance of the main charge by around 0.37-0.53 CD. The delay figure given by Rastopshin is 250 μs, which is within the range given in the textbook, but may not accurately represent the average delay.</p><p>The extension of the nose provides two functions. Firstly, it protects the main warhead from fragmentation produced by the precursor. Secondly, it greatly increases the available standoff distance available to the main warhead, which allows its penetration power to be exploited to the furthest extent possible. Because the telescoping nose travels its own length when extending, then the additional standoff distance it provides must correspond to the distance between the base of the shaped charge liner and the nose of a conventional 9M113 model, which would be around 177mm. Additionally, the blunt shape of the missile nose provides an enhanced standoff distance on oblique impacts, along the same lines as the warhead of the "Falanga" series. This is shown in the image below, with (F) being the standoff distance for the main charge. It also enhances the penetration of the precursor charge, which may improve performance on passive armour targets.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4Z2NVJ5kt4Y/YOuqVDIG-5I/AAAAAAAAT2g/PyRk0-7dSugYf1Hev5pC5HDPfdsaezy9ACLcBGAsYHQ/s998/patent%2Boblique%2Bimpact.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="394" data-original-width="998" height="252" src="https://1.bp.blogspot.com/-4Z2NVJ5kt4Y/YOuqVDIG-5I/AAAAAAAAT2g/PyRk0-7dSugYf1Hev5pC5HDPfdsaezy9ACLcBGAsYHQ/w640-h252/patent%2Boblique%2Bimpact.jpg" width="640" /></a></div><p>If the precursor charge successfully defeated an ERA panel on the target, any reduction in standoff distance from the delay period of the main charge may be compensated by the dimensions of the ERA panel itself as well as any spacing it may have had. For instance, a Kontakt-1 block is 70mm tall and is spaced 17mm away from the mounting surface. Larger ERA blocks, such as the Bradley Reactive Armour Tile (BRAT) sometimes found on M2A3 Bradleys, are thick boxes containing multiple ERA panels arranged in a slat layout, with one panel in the direct path of a penetrator at any given point. The standoff distance of the main charge in 9M113M increases considerably when attacking such ERA, even ignoring any additional space behind the ERA block.</p><p>The penetration power of the 9M113M missile behind ERA is 650-700mm RHA, as given in the textbook "<i>Конструкция Средств Поражения, Боеприпасов, Взрывателей И Систем Управления Средствами Поражения: Конструкция И Функционирование ПТУР</i>". KBP states that its penetration behind ERA is 750mm RHA, with a probability of 0.5. Both figures can be true at the same time, with the lower figure merely representing less favourable circumstances, or the statistical penetration range at a higher confidence interval.</p><p><br /></p><h3><span style="font-size: large;">9M113M1</span></h3><h3><span style="font-size: large;">9N131M1 (?)</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-MMCIW7Hru0w/YKgCw_3oPUI/AAAAAAAATDU/cy6RoO2h1AoBzN2x57abipgHoAJ0rTBsQCLcBGAsYHQ/s954/9m113m1%2Boverview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="478" data-original-width="954" height="200" src="https://1.bp.blogspot.com/-MMCIW7Hru0w/YKgCw_3oPUI/AAAAAAAATDU/cy6RoO2h1AoBzN2x57abipgHoAJ0rTBsQCLcBGAsYHQ/w400-h200/9m113m1%2Boverview.png" width="400" /></a></div><p>The 9M113M1 features a new warhead of unknown designation. Copper shaped charge liners are used in both the precursor and main charges, with Okfol explosive fillers. Like the 9M113M, the 9M113M1 is no longer than a basic 9M113, and as such, fits into the same stowage racks. Unlike the 9N131M, the new warhead almost doubles the increase in the standoff distance by combining the telescoping nose concept with the more conventional standoff probe concept. Both mechanisms extend just before the missile launch. The extension mechanism and its merits are described in the <a href="http://www.freepatent.ru/patents/2351887">Russian patent No.2351887 granted to the KBP design bureau</a>.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-LBsAG44CXIU/YJnZTyGsSjI/AAAAAAAAS8g/gknALUuWP401lIUnwqeDRxPRhn8tJr4aQCLcBGAsYHQ/s900/1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="635" data-original-width="900" src="https://1.bp.blogspot.com/-LBsAG44CXIU/YJnZTyGsSjI/AAAAAAAAS8g/gknALUuWP401lIUnwqeDRxPRhn8tJr4aQCLcBGAsYHQ/s320/1.jpg" width="320" /></a><a href="https://1.bp.blogspot.com/-lXmN1YfvAWs/YJnZT1gftlI/AAAAAAAAS8k/9Cow-6G8kys5h1KGh-VgitAsJnOdxY6EQCLcBGAsYHQ/s900/2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="428" data-original-width="900" height="190" src="https://1.bp.blogspot.com/-lXmN1YfvAWs/YJnZT1gftlI/AAAAAAAAS8k/9Cow-6G8kys5h1KGh-VgitAsJnOdxY6EQCLcBGAsYHQ/w400-h190/2.jpg" width="400" /></a></div><div><br /></div><p>The nose section is telescoped into the warhead section, and within the cavity ahead of the shaped charge cone, there is a free space which was used for the pyrotechnic extension charge, marked (16) in the drawing on the left above. After pressing the firing trigger, the missile undergoes the same preparation sequence the 9M113, but 0.1 seconds after the front cover of the container is opened, a signal voltage is applied to the electric ignitor of the pyrotechnic extender mechanism, igniting it. </p><p>A ring (17) forms an airtight seal between the charge and the interior of the fuselage, so that when the pyrotechnic charge is ignited, the nose section behaves as a piston, pushing against the end of the warhead section. The available length of space for the gas to expand is merely 20-30mm, as stated in the patent, so the pyrotechnic charge only acts against the piston for a short period before the gasses are vented out into the inside the nose section, before they are released via small holes once the nose has slid a certain distance past the warhead section. Like a short-stroke piston, the nose section continues to move forward under inertia until it is locked on the external detents. When the nose section is stopped, the inertia of the standoff probe allows it to extend forward of the nose section. The image below shows the smoke vented out after the nose was extended by the pyrotechnic extension charge. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-BkaVA3IncMM/YKgDX-ftSgI/AAAAAAAATDc/yeNzkmTOUU0qdb2tYFn3xrd5jb6L6RVygCLcBGAsYHQ/s1920/pyrocharge%2Bsmoke.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://1.bp.blogspot.com/-BkaVA3IncMM/YKgDX-ftSgI/AAAAAAAATDc/yeNzkmTOUU0qdb2tYFn3xrd5jb6L6RVygCLcBGAsYHQ/w400-h225/pyrocharge%2Bsmoke.png" width="400" /></a></div><p>This solution allowed the missile to retain the same dimensions as an original 9M113 and thus retain the same container while providing the maximum standoff distance that is physically feasible, which would not have been possible if there were only an extendable probe as there is only a limited space between the nose of the missile and the shaped charge cone of the warhead to fit a probe. </p><p>By using this photo of the 9M113M1, conveniently taken from a profile view at a distance far enough to not warp the image of the missile, an estimate of the standoff can be obtained by scaling extendable sections with the known wingspan of 468mm. The additional standoff distance afforded by the extended nose section is roughly 202mm, and the extended probe accounts for another 143mm. This is additive to the existing standoff of 185mm when both mechanisms are undeployed. The total standoff can thus be estimated to be approximately 530mm, or around 3.9-4.0 CD. According to data provided by Mikhail Rastopshin, the caliber of the precursor warhead is 60mm, and the fuzing delay for the main warhead is 250 μs. </p><p>A telescoping probe alone, such as the type found on the TOW 2A, has a precursor charge of limited power as the probe must fit into the hollow space in the shaped charge cone when it is retracted. Given that the TOW series shares the same constraint as the "Konkurs" series in that they all have containers of the same length, the comparative merits of the two approaches can be seen in the additional standoff distances provided. Case in point - the telescoping probe grants an additional 343mm (13.5") of standoff distance, or 2.28 CD, while the total is 2.71 CD, after adding 343mm from the probe and 63.5mm (2.5") from the blunt nose fairing.</p><p>The penetration of 9M113M1 is 800mm RHA, achieved with a probability of not less than 0.5. This performance is on par with the TOW-2A, which has a larger 150mm shaped charge warhead.</p><p><br /><a href="https://www.blogger.com/null" id="kokon"></a></p></div><h3 style="text-align: left;"><span style="font-size: large;">"Kokon"</span></h3><h3 style="text-align: left;"><span style="font-size: large;">9M114, 9M114F</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-vcroXAtvaTU/YO81vQAjY2I/AAAAAAAAT64/Yah_DdjeQesqMC7af-eLSir37fbkKHk-wCLcBGAsYHQ/s1280/shturm-s%2Bin%2Bgrass.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="720" data-original-width="1280" height="225" src="https://1.bp.blogspot.com/-vcroXAtvaTU/YO81vQAjY2I/AAAAAAAAT64/Yah_DdjeQesqMC7af-eLSir37fbkKHk-wCLcBGAsYHQ/w400-h225/shturm-s%2Bin%2Bgrass.png" width="400" /></a></div><p>In 1966, the Soviet military set out the task of creating a self-propelled ATGM system with SACLOS guidance, armed with a supersonic missile with a speed of at least 400 m/s that should also be fireable from a dismounted portable launcher. The engagement range was to be 100-4,500 meters, the flight speed 400-450 m/s, and the armour penetration was to be 250mm at 60 degrees - the same basic requirement of heavy ATGMs, shared by the "Falanga". Its weight was to be up to 30.5 kg.</p><p>At the same time, the envisioned supersonic ATGM became the focus of the armament for potential future attack helicopters of the Soviet military, which had a justifiable need for the given characteristics because helicopters were more suitable as long-range tank destroyers. As a rule, it was possible to detect and identify targets from the air at maximum ranges, unlike ground-based tank destroyers which are routinely obstructed by the terrain, greenery, and artificial obstacles like buildings. Moreover, the envisioned supersonic speed was considered an important lethality and survivability factor because a shorter flight time would greatly reduce the exposure time for the launcher while also shortening the window of opportunity for the target to react. The exposure time factor was critical for helicopters, as minimizing the time spent within view of enemy anti-air assets would not only improve the survivability of the helicopter from return fire, but also eliminate the possibility of forewarning the target by sound, as it takes less time for the missile to reach its target than the sound of its launch and flight. A shorter time of flight also meant a higher rate of fire, increasing the lethality of each engagement.</p><p>Due to the closely interlinked ideas on the deployment of future helicopters and the desired traits of future ATGMs, the missile became a de facto helicopter ATGM. Work on the V-24 project began under the mandate of a decree issued by the USSR Council of Ministers on May 6, 1968. On the same day, the government also issued decree No. 309-119, on the official start of the development of the new supersonic ATGM system, named "Shturm". Though the word has multiple possible contextual meanings, the name "Shturm" is specifically translated as "assault", according to the <a href="https://www.kbm.ru/en/enterprise/history/">KBM website</a>. The missile received the NATO codename AT-6 "Spiral".</p><p>The task of developing "Shturm" was assigned to the KBM design bureau on the basis of the bureau's prior experience in experimenting with supersonic heavy ATGMs for missile tanks, and the project was headed by chief designer S. P. Nepobedimiy, who previously led the teams responsible for the "Shmel" and "Malyutka". The design bureau undertook the task with the approach of reusing multiple elements of existing systems with modifications to harmonize and adapt them for the specific technical tasks of the new ATGM. Among the reused elements were the supersonic canards developed for the "Strela-2" MANPADS missile by KBM a few years earlier, the gyroscopic commutator from the "Malyutka", the steering actuators from the "Malyutka", the fuzing system from the "Falanga", and the pulse encoded radio command system from the "Agona" project by KB Tochmash. The only completely new components designed for the "Kokon" were its HEAT warhead, its rocket engine, and the IR transponder unit. It was presumably thanks to this design approach that work progressed at a blistering pace despite the technical challenges inherent in the creation of guided supersonic missile systems.</p><p>In 1969, just one year after official work commenced, unguided live tests of the "Kokon" began using a grounded Mi-8 as the launch platform. Two years later, in 1970, guided tests began, using the optical and radioelectronic guidance equipment from the abandoned experimental "Rubin" heavy missile tank project. While progress on the missile itself was fairly swift, work on the dedicated heliborne "Shturm-V" (V for helicopter) control system intended for the Mi-24 was not, owing to the difficulties in the structural integration of the system into the helicopter, leading to the refinement of the helicopter itself, which evolved from having the "greenhouse" cockpit of the Mi-24A to the more familiar double bubble canopy cockpit. It is worth bearing in mind that these changes were essentially unrelated to the design of the 9M114 missile itself, which was essentially mature by this point. The same issues with the control system also delayed the creation of the "Falanga-PV" helicopter SACLOS missile system, which was why the Mi-24D model entered service concurrently with the Mi-24V in 1976 despite being armed with the outmoded "Falanga-P", a missile that had previously entered service in the ground forces as part of the 2K8P system in 1973. </p><p>The tests of the 9K113 "Shturm-V" system were carried out using the new helicopter design beginning in 1972. As an example, a prototype of the Mi-24V with the "Shturm-V" system in 1973 is shown in the photo below, taken from the article "<i>Противотанковые комплексы контейнерного старта: ПТРК «Штурм»</i>" by R. Angelskiy and S. Suvorov, published in the May 2020 edition of the "<i>Техника и вооружение</i>" magazine. The tests were finally concluded in November 1975, and serial production of the 9M114 began later the same year at the Izhevsk Mechanical Plant to equip the helicopters, which would also begin production shortly thereafter.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-dKGoYvjjbRw/YOHHeWGKJlI/AAAAAAAATug/gXyQ8R8juEU0x01mMwEU_5oiiBf9Uz8jACLcBGAsYHQ/s2048/mi-24v%2Bin%2B1973.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1222" data-original-width="2048" height="382" src="https://1.bp.blogspot.com/-dKGoYvjjbRw/YOHHeWGKJlI/AAAAAAAATug/gXyQ8R8juEU0x01mMwEU_5oiiBf9Uz8jACLcBGAsYHQ/w640-h382/mi-24v%2Bin%2B1973.png" width="640" /></a></div><p>At the time it entered service, its only direct foreign counterpart was the TOW, compared to which the "Kokon" was clearly superior as a helicopter ATGM, having an overwhelming range, speed, guidance link, and striking power advantage. The HOT was a much more serious competitor, as it held the advantage in armour penetration over "Kokon", though it was still soundly beaten in kinematic performance and in the suitability of the command link.</p><p>From the beginning of the project until its introduction into service in 1976, the "Shturm" project took a total of 8 years. Despite the protracted work needed to realize the goals of the "Shturm" project, it still managed to enter service and begin serial production in a shorter time, and before its direct counterpart, the Franco-German HOT, which was planned from the start to be a high-subsonic weapon. In fact, this was formalized in its name (<i>Haut subsonique, Optiquement téléguidé, tiré d'un Tube</i>) when the bilateral agreement on joint work was made between the French and Germans in 1964. Indeed, a direct parallel can be made between these two ATGM projects.</p><p>It is reported in the book "<i>Armements Antichars Missiles Guidés Et Non Guidés</i>" by COMHART that the HOT achieved "operational qualification" in 1972, which is around the same time the 9M114 itself was mature, but there was a period of deliberation from 1973-1975 before the decision to launch serial production was made. This was the period when decisions were made to procure systems with HOT such as the Bo-105 PAH-1 and the Jaguar 1, and the adoption of the HOT was delayed by the development process for these new combat vehicles, in much the same was as the 9M114 being delayed for want of its helicopter control system. Adoption and serial production of the HOT took place only in 1978, concurrent with the Jaguar 1, giving the HOT project a total development period of 14 years despite being a technically simpler missile with lower developmental risk.</p><p><br /></p><p>Aside from the Mi-24 series, the only other helicopter launch platform for "Kokon" missiles created during the Cold War was the Ka-29, which entered service in 1984. For whatever reason, the "Shturm-V" did not replace the "Falanga-MV" system for armed utility helicopters such as the Mi-8TV; a variant of the Mi-8 with a "Shturm-V" system was not created during the Soviet era. The first such model was the Mi-8AMTSh, a deeply modified armoured gunship variant, which was introduced into service only in in the late 2000's. In 1979, the 9K114 "Shturm-S" ground-based ATGM system entered service on the 9P149 tank destroyer, based on the MT-LB hull. The creation of the "Shturm-S" was put on the backburner to focus all efforts on the "Shturm-V", and the urgency of a ground forces option was diminished even further by the success of the "Konkurs" in 1974. </p><p>Although the "Kokon" missile ostensibly had a greater potential for proliferation than the 9M113, as it had launch platforms on both ground and air, their usage could be considered relatively limited outside of the Mi-24 series. "Konkurs" systems was much more common in the Soviet military simply due to its high concentration in lower level units, down to BMP squads beginning with the BMP-1P and BMP-2, whereas the "Shturm-S" tank destroyer was only deployed in the anti-tank artillery regiment of combined arms armies and the anti-tank artillery brigade of the reserves, as it was the direct successor to the "Falanga".</p><p><br /></p><p>During the early 1980's, the 9M114F missile with a thermobaric warhead entered service. This was the first time an alternative warhead option for an ATGM entered service in the Soviet Army, and its creation was driven by the specific combat environment in Afghanistan - as the enemy had no armoured vehicles, a HEAT warhead did not offer the most useful destructive capabilities. </p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-fJrEG3ON_Kc/YNOKn7Jtd8I/AAAAAAAATfc/TsgHfSAV2yczTjNiueFvmIcRPIZz5YlGQCLcBGAsYHQ/s600/9m114f%2Bafghanistan.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="352" data-original-width="600" src="https://1.bp.blogspot.com/-fJrEG3ON_Kc/YNOKn7Jtd8I/AAAAAAAATfc/TsgHfSAV2yczTjNiueFvmIcRPIZz5YlGQCLcBGAsYHQ/s16000/9m114f%2Bafghanistan.jpg" /></a></div><p><br /></p><p><br /><a href="https://www.blogger.com/null" id="ataka"></a></p><h3 style="text-align: left;"><span style="font-size: large;">"ATAKA"</span></h3><div><span style="font-size: large;"><b>9M120, 9M120F, 9M120F-1</b></span></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-8BEjzbwQvJA/YOugZCM386I/AAAAAAAAT2E/2xezL-ZcKxAZip-VIgIH1aC7WbCQuQIbwCLcBGAsYHQ/s513/mi-28%2Bwith%2Bataka.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="513" data-original-width="500" height="400" src="https://1.bp.blogspot.com/-8BEjzbwQvJA/YOugZCM386I/AAAAAAAAT2E/2xezL-ZcKxAZip-VIgIH1aC7WbCQuQIbwCLcBGAsYHQ/w390-h400/mi-28%2Bwith%2Bataka.jpg" width="390" /></a></div><p>The 9M120 "Ataka", a further development of the 9M114 with improvements in range and the lethality of its warhead, entered service in May 1996. OKR "Ataka" was started under the private initiative of the recently privatized KBM shortly after the fall of the USSR. The basis of the work was to increase the range of the missile and increase its lethality, using a new tandem HEAT warhead developed by the RFYaTs-VNIIEF, the Russian Federal Nuclear Center - All-Russian Research Institute of Experimental Physics. The center was diversifying beyond nuclear weapons and ventured into the field of anti-tank warhead design in either <a href="http://vniief.ru/en/missionareas/Non-nuclear+weapons/">the late 1980's</a> or <a href="https://web.archive.org/web/20090603010339/http://www.vniief.ru:80/directions/weapons/cumulative/">the early 1990's</a>, according to different versions of the Russian Federal Nuclear Center VNIIEF website. Based on an advertisement by the company titled "Shturm", printed in the January 1993 issue of the "<i>Техника и вооружение</i>" magazine, the "Ataka" was formerly referred to simply as "variant 1" of the modernized "Shturm" system offered by the company. In the advertisement, it is stated that all new technical solutions implemented in the missile had undergone bench tests, and individual parameters were tested during flight tests. Moreover, it is stated that Russian parties were ready to consider the issue of upgrading the "Shturm" for mass production according to requirements, and that the deadline for completing the work was no more than two years. The focus of the development for the "Ataka" was to implement a modern helicopter ATGM system for the new Mi-28N attack helicopter, although the missile itself was made to have full reverse compatibility with existing "Shturm" ATGM systems. State tests were passed and the "Ataka" missile entered service in May 1996. This was just shortly before the first flight test of the Mi-28N, equipped with the "Ataka-VN" ATGM system, carried out later that same year. Subsequently, a large number of systems have been created to use the "Ataka" missile, including the "Ataka-V", "Ataka-T", and modernizations of the existing "Shturm" series, including the "Shturm-SM", "Shturm-VU", and "Shturm-VK".</p><p>When it began mass production or proliferated in any way is unknown. Likewise, the origin of the name itself is unknown, but like "Shturm", the word "Ataka" means "assault". Its NATO codename of AT-9 "Spiral-2" accurately reflects the rather straightforward relationship between it and the original "Kokon". Following the precedent of the 9M114F, the "Ataka" was created with three warhead options, which were the tandem HEAT for the 9M120, thermobaric for the 9M120F and continuous-rod HE for the 9M120F-1. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GZpQwBxemCU/YN64uGBJNmI/AAAAAAAATs8/p5aCIo8pOmoHqM_bv4EdDYvPvb11SJYVACLcBGAsYHQ/s850/9m120.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="145" data-original-width="850" height="69" src="https://1.bp.blogspot.com/-GZpQwBxemCU/YN64uGBJNmI/AAAAAAAATs8/p5aCIo8pOmoHqM_bv4EdDYvPvb11SJYVACLcBGAsYHQ/w400-h69/9m120.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-vM4QxWL6t18/YN64uOOKIbI/AAAAAAAATs4/zfEplfHLcTYVaYWpLIQVwEqrQsb7iMOxACLcBGAsYHQ/s706/9m120f.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="161" data-original-width="706" height="91" src="https://1.bp.blogspot.com/-vM4QxWL6t18/YN64uOOKIbI/AAAAAAAATs4/zfEplfHLcTYVaYWpLIQVwEqrQsb7iMOxACLcBGAsYHQ/w400-h91/9m120f.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--pU8rGeyq_k/YN64uCQbKUI/AAAAAAAATs0/dzx9qJVt3ekaGlZv4W8x0fi1LuXigtS9QCLcBGAsYHQ/s714/9m120f-1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="146" data-original-width="714" height="81" src="https://1.bp.blogspot.com/--pU8rGeyq_k/YN64uCQbKUI/AAAAAAAATs0/dzx9qJVt3ekaGlZv4W8x0fi1LuXigtS9QCLcBGAsYHQ/w400-h81/9m120f-1.png" width="400" /></a></div><p>Indeed, in accordance with the goals of OKR "Ataka", the only difference with the 9M120 was in the implementation of a new tandem warhead with a powerful precursor charge, and minor modifications in the launch circuit due to the new fuze of the warhead. Everything else, from the radiocommunications equipment, to the rocket engine, to the steering mechanism, and even the fuselage itself, is the same as the "Kokon". The missile is reverse compatible with the "Shturm" ATGM system. After the dissolution of the USSR, the privatized KBM began to advertise the "Ataka" missile series as the "<a href="http://web.archive.org/web/20040508090820/http://www.kbm.ru/ru/product/ptrk/shturm-ataka">Shturm-Ataka</a>" system, in reference to its intended launch platform. The photo below, from the <a href="http://maks.sukhoi.ru/">MAKS Sukhoi website</a> (unaffiliated with either organization), shows the 9M120 advertised with a "Shturm-Ataka" poster at MAKS 2003. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-7xzMTo8drvk/YNI28H3GsGI/AAAAAAAATeo/wjGhb3Sd-aEPSg5MtQ8mMIkIORjTHpcGACLcBGAsYHQ/s1024/maks%2B2003.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://1.bp.blogspot.com/-7xzMTo8drvk/YNI28H3GsGI/AAAAAAAATeo/wjGhb3Sd-aEPSg5MtQ8mMIkIORjTHpcGACLcBGAsYHQ/w400-h300/maks%2B2003.jpg" width="400" /></a></div><p><br /></p><p>A number of elusive variants of the "Shturm-Ataka" family under a number of designations are known to exist, including models such as the 9M114M, 9M120M and 9M120D. Some data is also given in various examples of specialist literature, but at present, none of these have entered service. The most commonly cited claims credit these versions with various combinations of extended range and enhanced penetration figures, which are entirely bogus. It is, however, possible that 9M114M was the original designation or a provisional designation for the 9M120.</p><p>In the mid-2000's, KBM launched the new 9M120-1 series with a dual channel radio-laser guidance system, unified with the "Khrizantema" ATGM system. The 9M120-1 series is capable of guided flight under command via a radio link, or laser beam riding, with reverse compatibility with all other existing Russian laser-guiding sights. When used in the laser beam riding mode, its maximum guided range is extended by a kilometer. Otherwise, the tactical-technical characteristics were identical to the basic 9M120 series. Thanks to the retention of the radio link, the 9M120-1 series can be used in legacy "Shturm" platforms, which lack a laser guidance system, or it can be used in modern systems that lack a radio command channel, but have a laser guidance system. </p><p>The replacement for the "Shturm", initiated in the mid-1980's, entered service only after the dissolution of the USSR as the "Khrizantema", also a supersonic ATGM system. Like its predecessor, it is a unified ground and airborne ATGM system for the Russian army, recently procured as the "Khrizantema-S" tank destroyer, and currently poised to become a new helicopter ATGM for the "Khrizantema-V" system of the Mi-28NM. However, even in the current year (2021), the number of "Khrizantema" ATGM systems in service is miniscule, and for better or worse, the "Ataka" retains its status as the most common supersonic heavy ATGM in the Russian Army arsenal.</p><p><br /><a href="https://www.blogger.com/null" id="kokondesign"></a></p><h3 style="text-align: left;"><span style="font-size: large;">GENERAL DESIGN FEATURES</span></h3><div class="separator" style="clear: both; text-align: center;"><img border="0" data-original-height="1341" data-original-width="2048" height="420" src="https://1.bp.blogspot.com/-m_Se8Ob4iUc/YNYmckNftAI/AAAAAAAAThU/VXNysIPDhMYeH8eq4EqjiT6bYz4ZSc2dQCLcBGAsYHQ/w640-h420/kokon%2Bcross%2Bsection.png" style="color: #0000ee;" width="640" /></div><p>The layout of the missile is conventional. The warhead is situated at the front, followed by the steering mechanism, the rocket engine, and finally the radio command equipment in the tail of the fuselage, behind the nozzles of the rocket engine. In terms of its overall design, the 9M114 "Kokon" is best described as an amalgamation of the "Malyutka" and "Falanga", the former being an earlier product of KBM and the latter being a product of KB Tochmash. Distinct traces of both products are found everywhere in the missile except in the engine, which was the only completely unique assembly. Otherwise, the missile was almost designed and built from off-the-shelf products, including KB Tochmash inventions. In fact, the cooperation between the two bureaus was so close that 9M114 shares the radio equipment of the 9M112M "Agona" GLATGM for 125mm guns, which was developed by KB Tochmash along with the 9M112 "Kobra" family and the rest of its variants.</p><p>The distinguishing technical features of the "Kokon" were its high supersonic speed and its long nominal maximum range of 5,000 meters, both of which were identified as critical factors in the success of engagements by helicopters. The long range of 5,000 meters meant that attack helicopters would be able to fire upon enemy forces protected by short-ranged air defence systems with almost total impunity. Using the Stinger MANPAD system and the Gepard SPAAG as examples, as the two were the most dangerous threats in this category in the 1980's, the importance of a range advantage becomes clear when considering that the former has a hard range limit of 3.8 km against low-flying targets when fired from ground level, and the 35mm guns of the latter have a maximum effective range of 4 km against helicopters (3.5 km against slow fixed wing aircraft). If a conventional subsonic ATGM with a 4 km range were used in place of a system like "Shturm-V", then practically all attempts to engage defended targets would place the helicopter in a great deal of danger. The same goal of remaining out of range of short-range AA systems drove the requirement for a missile engagement range of 6-8 km for an Mi-24 successor in the early 1980's. It was envisioned that with this extended range requirement, the helicopter would be able to remain outside the engagement range of the next layer in the air defence bubble, which would include missile SHORAD systems such as the "Roland", "Chapparal" and "Rapier".</p><p>An increased standoff distance can also have beneficial effects in terms of detectability, as the detection of a hovering helicopter in plain view is not necessarily guaranteed, even in the absence of factors such as concealment by terrain. The graph below illustrates the variation in the probability of detecting a typical helicopter (4.2 m tall, 2.2 m wide) close in dimensions to an Mi-24 silhouetted against the sky with visual means in three visibility conditions, according to testing and analyses conducted by the U.S Army. The only factors involved in this test condition were the contrast of the helicopter against a sky background, range, and visibility conditions. Extinction coefficients, which represent visibility conditions, are as follows:</p><p></p><ul style="text-align: left;"><li>0.03: Very clear day</li><li>0.05: Clear</li><li>0.5: Light haze</li></ul><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HbuITq-RB1c/YO02lhpcV4I/AAAAAAAAT44/PVyhzFZ26JAI7-fSrNuQva5SOJB9YyiDACLcBGAsYHQ/s1313/probability%2Bof%2Bdetecting%2Ba%2Bhelicopter%2Bsilhouetted%2Bagainst%2Bthe%2Bsky%2Bin%2Bideal%2Bconditions.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1259" data-original-width="1313" height="384" src="https://1.bp.blogspot.com/-HbuITq-RB1c/YO02lhpcV4I/AAAAAAAAT44/PVyhzFZ26JAI7-fSrNuQva5SOJB9YyiDACLcBGAsYHQ/w400-h384/probability%2Bof%2Bdetecting%2Ba%2Bhelicopter%2Bsilhouetted%2Bagainst%2Bthe%2Bsky%2Bin%2Bideal%2Bconditions.png" width="400" /></a></div><p>The source of the graph is the textbook "Engineering Design Handbook - Vulnerability of Guided Missile Systems to Electronic Warfare" published by the U.S Army Materiel Command.</p><p>The total length of the missile assembly, including the attached ejection engine, is 1,830mm. In flight, the missile alone is 1,613mm in length. With such a length but a diameter of only 130mm, the "Kokon" is a very slender missile, primarily because of the large volume of rocket fuel carried in its powerful engine. This is particularly evident in the image below, taken from the book "<i>ПТУР сухопутных войск</i>" by G.N. Dimitriev.</p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-0gFZF65qn5Y/YLanaeczyiI/AAAAAAAATQw/BmA0r3TrTJIpB4gjaVOZ1PM4d8W1IEBBACLcBGAsYHQ/s1024/9M17%2Band%2B9M114.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="661" data-original-width="1024" height="412" src="https://1.bp.blogspot.com/-0gFZF65qn5Y/YLanaeczyiI/AAAAAAAATQw/BmA0r3TrTJIpB4gjaVOZ1PM4d8W1IEBBACLcBGAsYHQ/w640-h412/9M17%2Band%2B9M114.jpg" width="640" /></a></p><p>Despite the enormous power of the rocket engine, the "Kokon" weighs only 31.4 kg, placing it at the same level as the 9M17 missiles of the "Falanga" series. The full weight of the missile in its container, together with the ejection engine, is 46.5 kg, which is much heavier, but unlike the "Falanga", this assembly is a self-contained launch mechanism so that a bulky rail and electrical connectors are not needed. On top of that, the benefits of containerization and maintenance-free operation - particularly for the ground forces - do not need to be reiterated. Compared to subsonic heavy ATGMs like the TOW (full unit weight of 25.5 kg, missile weight of 18.4 kg) and the HOT (full unit weight of 32 kg, missile weight of 23 kg), the impact of supersonic performance on missile weight can clearly be seen.</p><p>The 9M120 "Ataka" shares the same dimensions as the 9M114 in all respects, and is also reverse compatible for both ground and air launch platforms of the "Shturm" system. It weighs slightly more, 33.5 kg on its own, and the full containerized unit weighs 48.5 kg. Again, this weight refers to the sum of the weights of the missile, its ejection engine, and the container.</p><p>As usual for ATGMs of the second generation, the container is made of <a href="https://viam.ru/sites/default/files/scipub/1972/1972-196176.pdf">TS 8/3-250</a> grade glass textolite with an epoxy binder. It is 1,840mm long and has a diameter of 188mm or a maximum of 230mm, depending on the point of measurement. There are eight metal reinforcing bands embedded into the fiberglass container, forming the distinct ribs along its surface. Four of the bands are concentrated along the base of the container, where additional reinforcement is needed due to the initial pressure spike during missile launch, and the remaining four are distributed along the remaining length of the container.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-1L_EZ9gMdcE/YNOpO_G5CnI/AAAAAAAATfk/fD856aJ0TEsHFNC7OyWhALpT3UYq5yJvACLcBGAsYHQ/s950/9m120%2Bataka%2Bdisplay.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="347" data-original-width="950" height="234" src="https://1.bp.blogspot.com/-1L_EZ9gMdcE/YNOpO_G5CnI/AAAAAAAATfk/fD856aJ0TEsHFNC7OyWhALpT3UYq5yJvACLcBGAsYHQ/w640-h234/9m120%2Bataka%2Bdisplay.jpg" width="640" /></a></div><p>The bottom of the container has two single-pin electrical sockets to receive the launch signal. In a welcome departure from the multi-pin electrical interface of the "Falanga", the launch process was simplified to such an extent that it functioned by simply having a voltage applied at two points - the circuit of the ejection engine, and the circuit of the missile power source. Both were pyrotechnic mechanisms with an electric primer.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-hxZVijz-Njk/YNgfUlU4CZI/AAAAAAAATi0/BCNakm0fsqgd9vdEWUF2iFpv-nrpwxVtACLcBGAsYHQ/s2853/container%2Bunderside.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1102" data-original-width="2853" height="248" src="https://1.bp.blogspot.com/-hxZVijz-Njk/YNgfUlU4CZI/AAAAAAAATi0/BCNakm0fsqgd9vdEWUF2iFpv-nrpwxVtACLcBGAsYHQ/w640-h248/container%2Bunderside.png" width="640" /></a></div><p><br /></p><p>The missile is secured inside the container by a special lock at its base, which is popped open by a pyrotechnic squib during the launch sequence. The container itself is secured to the guide rail by a lever lock.</p><p><br /><a href="https://www.blogger.com/null" id="kokonaerodynamics"></a></p><h3 style="text-align: left;"><span style="font-size: large;">AERODYNAMICS</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DToZKKJTLSQ/YNA1gObx7aI/AAAAAAAATdQ/cu0A1Z8m_-s0mfeOPZZIKd9u6bDO4ikSQCLcBGAsYHQ/s500/9%25D0%259C114%2B%25281%2529.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="172" data-original-width="500" height="220" src="https://1.bp.blogspot.com/-DToZKKJTLSQ/YNA1gObx7aI/AAAAAAAATdQ/cu0A1Z8m_-s0mfeOPZZIKd9u6bDO4ikSQCLcBGAsYHQ/w640-h220/9%25D0%259C114%2B%25281%2529.jpg" width="640" /></a></div><p><br /></p><p>Unlike subsonic missiles of the first and second generations, for which aerodynamic streamlining was desirable but not critical to the function of the weapon, the design of the "Kokon" was formulated with a strong focus on streamlining to support its supersonic flight profile. As the speed of a projectile increases, the air resistance it experiences increases exponentially, sharply increasing the demand on engine power to overcome this air resistance. To prevent the missile from bloating to an impractical weight while meeting the requirements on speed and range, yet simultaneously meeting the same penetration power requirement of the "Falanga", the only feasible option was to minimize parasitic drag and reduce the cross sectional area of the missile. Its diameter was set at 130mm for this reason, according to the book "<i>Первые Отечественные Противотанковые Ракетные Комплексы</i>", and the surface of its fuselage was made to be totally free from non-essential protrusions. The difference between the "Kokon" and first generation ATGMs, including the three Soviet models examined earlier in this article, is very apparent - the missile lacks protruding nozzles, clasps to secure the detachable warhead, external tracers, thick wings, or external cabling. Additionally, the nose of the "Kokon" is a spherical blunted tangent ogive, a shape that is well-suited for supersonic speeds. </p><p>On the "Ataka", a telescoping probe containing a precursor warhead is present, with straight vanes along its nose to generate additional lift for weight compensation. The vanes are essentially symmetrical aerofoils, behaving somewhat like lifting canards. The tapered fairing between the probe and the warhead also functions as a lifting body to compensate for the increased warhead weight. </p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-sKuWkixtgKk/YMOV0xeSwDI/AAAAAAAATao/2emWwqmS8XI7zm-_mMeLgbMrY0SDpDY1ACLcBGAsYHQ/s4110/9m120-1_raketa_v_polete_jpg_1418283456.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="765" data-original-width="4110" height="120" src="https://1.bp.blogspot.com/-sKuWkixtgKk/YMOV0xeSwDI/AAAAAAAATao/2emWwqmS8XI7zm-_mMeLgbMrY0SDpDY1ACLcBGAsYHQ/w640-h120/9m120-1_raketa_v_polete_jpg_1418283456.jpg" width="640" /></a></p><p>However, the streamlined aerodynamics of the missile are somewhat spoiled by the completely flat base, made to accommodate the infrared beacon, a mandatory requirement for its radio SACLOS guidance system. The entirely flat-ended cylindrical shape of the missile base is a source of intense base drag, which substantially increases the total drag experienced by the missile and is likely its most major design shortcoming. Gas flow from a rocket nozzle at the base could have ameliorated this issue, but because the engine nozzles are on the sides of the fuselage, as other equipment already occupies the tail, the "Kokon" and "Ataka" do not benefit from the elimination of base drag that a few other missiles do. Indeed, a nozzle at the base can have a very sizeable impact on reducing the base drag of a missile, as the slide below shows, taken from a publicly accessible <a href="http://mae-nas.eng.usu.edu/MAE_6530_Web/New_Course/launch_design/Section3.3.pdf">lecture slide from the Utah State University</a>. This is because the high-pressure exhaust plume largely eliminates the formation of a low-pressure wake. Rather, it effectively functions as a gaseous "tail" behind the base, around which the air arriving from the fuselage will flow and eventually dissipate.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jClIudmlLVg/YNT9bOOLo-I/AAAAAAAATgE/dsti5GIUp00cce_dN099GonCdNtVDVtPACLcBGAsYHQ/s2048/slide.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1524" data-original-width="2048" height="297" src="https://1.bp.blogspot.com/-jClIudmlLVg/YNT9bOOLo-I/AAAAAAAATgE/dsti5GIUp00cce_dN099GonCdNtVDVtPACLcBGAsYHQ/w400-h297/slide.png" width="400" /></a></div><p>Although a flat, non-boattailed fuselage base was far from unusual - in fact, it was the norm among ATGMs - its negative consequences are magnified by the supersonic flight regime of the "Kokon", as the lecture slide shows. </p><p>Unlike the 9M111 and 9M113, which had a lifting body nose design, the streamlined cylindrical form of the "Kokon" was not designed to create additional lift, which was likely not necessary given the high airspeed. The two lifting surfaces of the missile are its canards and wings, both of which are spring loaded, and are deployed when the missile exits its container. The supersonic speed of the 9M114 allowed the use of relatively small and thin wraparound wings, placed far to the rear of the fuselage, with a distance of 1,367.5mm from the nose to the leading edge. Wraparound wings, or fins, if used as such, are commonly found on tube-launched rockets due to their greater compactness compared to folding straight fins. The first use of such wings on rocket weapons was on the M-21 unguided rocket for the Soviet BM-21 "Grad" rocket artilley system, developed in the 1950s and produced since 1960, followed a few years later by the American Hydra 70 family of unguided rockets in the mid 1960's. Wraparound fins are not to be confused with the elastic flexible fins used on grenades such as the various WW2-era Panzerfausts and the PG-2 of the RPG-2, as those are straight fins that merely happen to be flexible enough to wrap around a tail boom. </p><p>The wings on the "Kokon" and "Ataka" have a rectangular planform, and the aerofoil shape is a modified double wedge. Naturally, the aerofoil is symmetrical, because the missile rotates in flight. The total surface area is 0.0246 sq.m, and the specific wing loading over two wings is 12,600 N/sq.m. Even with a smaller lift coefficient due to the smaller area of the wings, the much higher airspeed of the "Kokon" compared to subsonic ATGMs favours such wings as they are able to produce the necessary amount of lift without incurring the high induced drag of larger wings. The wingspan of both the "Kokon" and "Ataka" series is 325mm.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-u_PGvAFdmE4/YLQDEfVqEuI/AAAAAAAATQY/UMrRmCkPWCcRUZq6r7vMEijI1isIT9AYgCLcBGAsYHQ/s879/wings.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="753" data-original-width="879" src="https://1.bp.blogspot.com/-u_PGvAFdmE4/YLQDEfVqEuI/AAAAAAAATQY/UMrRmCkPWCcRUZq6r7vMEijI1isIT9AYgCLcBGAsYHQ/s320/wings.png" width="320" /></a></div><p>The four wings are grouped in two pairs, each pair occupying nearly one half of the fuselage surface. One of the two wings in each pair has a slightly longer span than the other, allowing the two wings to overlap when folded. In the image above, it can be seen that the longer wings are situated on the top right and bottom left quadrants, as seen from behind with the missile upright, as mounted on a launcher. This design has three functional purposes. Firstly, it allows each wing to have a span equal to almost half the circumference of the fuselage, thus increasing the wingspan while still having four wings. Conventional wraparound wings do not overlap, and as such, the wingspan is limited to a quarter of the fuselage circumference. </p><p>Secondly, this folding pattern gives clearance to the rocket engine nozzles, which had to be made as a pair of symmetrically opposed oblique nozzles rather than a straight rear nozzle as the radio equipment and IR lamp of the missile already occupies the tail end of the fuselage. Each group of wings covers the rocket engine nozzle on their side of the fuselage, and when unfolded after launch, the nozzle is revealed.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-RLm7bqBGPHk/YNgfyHdvlaI/AAAAAAAATjA/pqL43C6nxMsMiE_JObR-asC7-Qk7fJDggCLcBGAsYHQ/s1024/kokon.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://1.bp.blogspot.com/-RLm7bqBGPHk/YNgfyHdvlaI/AAAAAAAATjA/pqL43C6nxMsMiE_JObR-asC7-Qk7fJDggCLcBGAsYHQ/w400-h300/kokon.jpg" width="400" /></a></div><p>Thirdly, the slight asymmetry in wing spans yields a rolling moment, continuing to impart spin after the missile engine burns out. This is the mechanism by which the desired spin rate is maintained in flight. It is also worth noting that wraparound wings have a tendency to generate a rolling moment even when they are made in a standard symmetrical layout.</p><p>According to the 1983 research paper "<a href="https://arc.aiaa.org/doi/pdf/10.2514/3.25603">Aerodynamics of Wraparound Fins</a>" from the Technion-Israel Institute of Technology, citing the results of an international research programme centered at the Eglin Air Force Base in 1969, the static longitudinal aerodynamic characteristics of symmetric wraparound wing are the same as straight fins for the same given projected area. It was therefore concluded in the research programme that wraparound wings could be used interchangeably with flat wings, but with the very strange caveat that warparound wings would generate a rolling moment even though they theoretically shouldn't. Moreover, a non-linear positive relationship was found between the area of the wing and the rolling moment generated, which is shown in the figure below with the wing area expressed in terms of span.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-JFOG1hyafU4/YNCt1TwXrzI/AAAAAAAATdw/hbzD3wJS7lsd71LT_rpTgNP0Np3PdePZACLcBGAsYHQ/s1775/rolling%2Bmoment.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="975" data-original-width="1775" height="220" src="https://1.bp.blogspot.com/-JFOG1hyafU4/YNCt1TwXrzI/AAAAAAAATdw/hbzD3wJS7lsd71LT_rpTgNP0Np3PdePZACLcBGAsYHQ/w400-h220/rolling%2Bmoment.png" width="400" /></a></div><br /><p>The unusual behaviour of wraparound wings regarding induced roll moments and the reversal of these moments at varying air speeds have also been noted in other research papers, such as the 2009 study "<a href="https://www.researchgate.net/publication/270492345_Anomalies_in_the_Flow_over_Projectile_with_Wrap-around_Fins">Anomalies in the Flow over Projectile with Wrap-around Fins</a>". </p><p>While the induced spin can be problem for weapons for which non-rotating flight is essential, this phenomenon can instead be leveraged in applications where spin is needed, at a minimum of induced drag. All in all, it can be seen that the slightly asymmetrical wings, and the use of large wings, reaching a span of around 160 degrees, are efficient design features that maximize the induced rolling moment. </p><p>In flight, the missile spins clockwise at a rate of 8-20 RPS. The high 20 RPS spin rate is imparted by the ejection engine during missile launch, then maintained by the combination of the wings and the offset nozzles of the booster engine. During the gradual deceleration of the missile as its engine winds down, the airspeed over the wings also diminishes, which leads to a reduction in the rotational moment from the wraparound wings. By the end of the 5,000-meter flight trajectory, the spin rate will be reduced to no less than 8 RPS.</p><p>Aside from the factors already mentioned, other factors, such as aerodynamic heating, which is a concern for aircraft travelling at high supersonic speeds, are only a negligible factor in the construction of the missile fuselage, given its very short flight time. However, it may be a concern for the wing design, being an additional reason to omit the use of flexible wings with a thin skin as used on the 9M111, 9M113, and other KBP products. </p><p><br /><a href="https://www.blogger.com/null" id="kokonguidance"></a></p><h3 style="text-align: left;"><span style="font-size: large;">GUIDANCE SYSTEM</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Br7g2EXOzBI/YNYyI4AWIyI/AAAAAAAAThk/im8sgokSobsXPyJxx30zue8g8RO-PALHgCLcBGAsYHQ/s2048/9m114%2Bcontrol%2Bflow%2Bdiagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1539" data-original-width="2048" height="480" src="https://1.bp.blogspot.com/-Br7g2EXOzBI/YNYyI4AWIyI/AAAAAAAAThk/im8sgokSobsXPyJxx30zue8g8RO-PALHgCLcBGAsYHQ/w640-h480/9m114%2Bcontrol%2Bflow%2Bdiagram.png" width="640" /></a></div><p>The guidance system consists of the power source, the gyroscope, the radio command equipment, and the infrared beacon. The 9B611M radio unit is housed in the tail of the fuselage, on which the missile wings are fitted. As the image below shows, the gyroscope (2) and the power source (5, 7) are located behind the warhead, at the canard section of the fuselage. It shares the space with the steering mechanism and the electrical starter for the rocket engine of the missile. Control commands from the guidance system in the tail are transmitted to the steering mechanism near the nose of the fuselage by cables in an insulated tube that runs through the center of the rocket engine. Though the presence of a tube through the rocket engine has some deleterious effects on the internal dynamics of the rocket engine, it circumvents the aerodynamic consequences of placing the cables externally. Even so, it is still probably the least efficient design solution implemented in the 9M114, because the great length of the rocket engine meant that the cable tube must also be very long, wasting both volume and weight.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-0v7KnDhGLfk/YNf4x8sLP3I/AAAAAAAATic/ItuG190t4r80-Zjb7vxOpuyvRzBlEmT0wCLcBGAsYHQ/s932/canard%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="719" data-original-width="932" src="https://1.bp.blogspot.com/-0v7KnDhGLfk/YNf4x8sLP3I/AAAAAAAATic/ItuG190t4r80-Zjb7vxOpuyvRzBlEmT0wCLcBGAsYHQ/s320/canard%2Bsection.png" width="320" /></a></div><p>Like the original 3M11 "Falanga", the "Kokon" departed from the domestic design norm of using a thermal battery as the onboard power source, using a turbine generator instead. Specifically, a single-stage turbo-alternator was used together with a slow-burning solid fuel pyrotechnic charge which provided a high velocity gas flow, providing even more power than the compressed air solution used in "Falanga". The generator has a nominal output of 12.6 V AC. To accommodate the electrical needs of different modules in the missile, transformer-rectifiers are used with the generator to supply DC power at voltages of +1700 V, +180 V and -27 V. The generator, together with the pyrotechnic cartridge, are located behind the warhead. Gasses from the pyrotechnic system are also used as the power source for the steering canards of the missile, with electronic valves controlling the gas flow into a pneumatic actuator - another core design feature shared with "Falanga". </p><p>The pyrotechnic charge (below, left) contains a 9Kh181 charge, which is NDP-2MK propellant. It is electrically ignited during the launch sequence, and the turbine generator (below, right) starts up. Power is supplied to the steering mechanism immediately, and within 0.7 seconds, the radio equipment is fully powered up. Power is also delivered to the ignition circuit of the rocket engine, which is set off after launch by an inertial circuit breaker. Soot and slag is removed from the gasses dispensed from the cartridge by a filter consisting of a baffle and a metal sieve, and the gas pressure is maintained by a regulator. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-14_tOcjuQRg/YNYqKGYajkI/AAAAAAAAThc/R1_MRdvBEQIoSYfJupveBTQEaQZQ7J3LQCLcBGAsYHQ/s2048/pyrotechnic%2Bpower%2Bsource.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1199" data-original-width="2048" height="234" src="https://1.bp.blogspot.com/-14_tOcjuQRg/YNYqKGYajkI/AAAAAAAAThc/R1_MRdvBEQIoSYfJupveBTQEaQZQ7J3LQCLcBGAsYHQ/w400-h234/pyrotechnic%2Bpower%2Bsource.png" width="400" /></a><a href="https://1.bp.blogspot.com/-F0D72OIOphk/YNf5SMe-pXI/AAAAAAAATik/i1ZGj_fVelo0eGydIB1gEKFsGRMbbDcpwCLcBGAsYHQ/s2048/turbogenerator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1760" data-original-width="2048" src="https://1.bp.blogspot.com/-F0D72OIOphk/YNf5SMe-pXI/AAAAAAAATik/i1ZGj_fVelo0eGydIB1gEKFsGRMbbDcpwCLcBGAsYHQ/s320/turbogenerator.png" width="320" /></a><br /><br /></div><p>The use of a pyrotechnic power source instead of a battery has several advantages, mainly in power density, as the chemical energy contained in combustible fuel is higher than pressurized gas and much higher than any form of battery. This allows either more power for a given weight and volume, or meeting a certain power requirement while keeping within strict dimensional limits. The latter was the case for the 9M114. An average chamber pressure of 6-10 MPa is generated, with a peak of 24 MPa - almost the same as the 260 atm (26.34 MPa) compressed air reservoir in a 9M17 missile. This is not a particularly important metric, as the volume of gas released from the combustion of the solid pyrotechnic fuel is much larger, a great deal of thermal energy is involved. More importantly, the combustion gasses have a much higher mass flow rate, due to the high molecular weight of the gaseous combustion products compared to air, which makes it particularly efficient in turning a turbo-alternator because momentum transfer is the governing parameter of the work of pneumatic rotary devices. Another important advantage is that, as a chemical compound with a stability that is at least equal to the other fuels and explosives in the missile itself, the pyrotechnic cartridge maintains its rated performance throughout the entire shelf life of the missile and requires no checks, unlike the compressed air reservoir of "Falanga" missiles.</p><p>Besides its role in supplying electrical power, having the vented pyrotechnic gasses supply pressurized gas to the pneumatic actuators of the steering mechanism extracts the maximum amount of useful work available from the system, improving its mass and energy efficiency characteristics. Another advantage is that there is almost no startup period; power is delivered almost instantaneously once the pyrotechnic cartridge is set off. A thermal battery, for example, requires a certain amount of time to heat up to its working temperature, and it needs noticeably more time to do so in cold weather. </p><p>The most major downside is that the pyrotechnic cartridge discharges constantly once activated and its burn rate is essentially fixed. In this case, the operating time is no less than 12.5 seconds, presumably at a temperature of +50°C. However, this is greatly ameliorated by the fact that a missile has a finite operating time, and in the case of the "Kokon", this time is very short due to its supersonic flight regime. The limited endurance of a pyrotechnic cartridge compared to a battery, which discharges on demand (when an electrical load is applied), is therefore not problematic. </p><p><br /></p><p>The steering system operates on a single-axis control scheme, so to convert the control commands issued over the radio datalink into control signals for the appropriate steering axis, a gyro-coordinator was needed. The 9B511 gyro-coordinator used in the missile performs spin rate compensation to properly execute the steering commands throughout the entire flight trajectory of the missile. A single-axis steering system was chosen to save weight and size, according to the book "<i>Отечественные противотанковые комплексы</i>" (<i>Domestic Anti-tank Systems</i>).</p><p>The three-axis gyroscope in the 9M114 and 9M120 is a rate gyroscope, functioning in roll. Its function is the same as in any other spinning ATGM - to serve as a reference point in the roll axis, reversing the polarity of the control signal in accordance with the required deflection of the steering mechanism and thus properly coordinate the execution of steering commands. During the launch process, it is spun up to its operating speed by the gasses of a special pyrotechnic charge to acquire the current attitude of the missile for its reference. The charge burns for a total of 0.24-0.53 seconds, developing a chamber pressure of 20 MPa, venting a stream of gas onto a turbine rotor and thus spinning up the gyroscope within 0.3-0.4 seconds.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DgceXuPusNE/YNfv-t2krUI/AAAAAAAATiU/bJFNF6ReWw4SH5eQRFkIyu3lAYzB3eyOQCLcBGAsYHQ/s2048/9m114%2Bgyroscope.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1397" data-original-width="2048" height="435" src="https://1.bp.blogspot.com/-DgceXuPusNE/YNfv-t2krUI/AAAAAAAATiU/bJFNF6ReWw4SH5eQRFkIyu3lAYzB3eyOQCLcBGAsYHQ/w640-h435/9m114%2Bgyroscope.png" width="640" /></a></div><p>Functionally, the coordinator mechanism functions the same way as in the "Malyutka", though with a modified commutator design. Firstly, there is a current collector affixed on the axis of the outer frame of the gyro assembly, and does not rotate in flight, being gyroscopically stabilized. Two brushes, attached to the current collector, connect the collector to the two slip rings of a sensor which rotates with the missile. One brush is offset relative to the other at an angle of 90 degrees. As the missile rotates in flight, the brushes of the current collector run around the slip rings of the sensor, removing from them two sawtooth pulses of the information signal, offset in phase relative to each other by an angle of 90 degrees, in one full rotation of the missile.</p><p>Another difference between this gyro-coordinator and that of the "Malyutka" is the inclusion of a phase regulator, which is a mechanical governor designed to rotate the gyroscope unit relative to the current collector by an angle proportional to any changes in the rocket spin rate. Thus, the sawtooth pulses of the control signal will have an angle of less than 90 degrees. This, in effect, performs a phase shift on the control signal, and thereby introduces an automatic compensation of signal mistiming before the commands are executed by the steering mechanism. </p><p>The phase regulator is a centrifugal inertial mechanism, consisting of two flyweights connected by a spindle and a sleeve; in other words, it is a classical centrifugal governor, as found on older automobile engines, except that it functions in the reverse manner. When the spin rate of the missile is at its highest (20 RPS), the flyweights have the largest centrifugal force and the flywheel arms are spun at their widest span, completely overcoming the pushing force of the sleeve spring. As the missile gradually decelerates, its spin rate diminishes, and its centrifugal forces along with it, the flywheel arms impart a smaller force on the sleeve spring, causing the sleeve to shift proportionately and rotate the gyroscope unit. This issue did not exist in the "Malyutka" because its spin rate was fixed, thanks to its constant flight speed.</p><p><br /></p><p>The use of a radio command link for the "Shturm" ATGM system was one of the first technical solutions to be finalized for the "Shturm" R&D project. Command wires are not suitable for supersonic missiles due to the quadratic growth of wire tension with increasing projectile speed, so only wireless options could be considered. The fastest ATGM to feature wire guidance is the TOW, which briefly reaches a peak speed of almost 300 m/s, and resists wire breaks by using high-tensile steel wires, but even this is the limit - to achieve better range and velocity performance, a radio command link has been implemented on the latest TOW models and is being explored further. </p><p>Morevoer, there are a few advantages to a wireless link that are specific to aircraft. When fired from a cruising helicopter, an ATGM can exceed its nominal maximum range due to the increased initial speed, especially if the helicopter is also at a high altitude. For example, it was noted in the report "Testing of the TOW Missile-Configured AH-1T Helicopter" that a TOW fired at 100 kts (185.2 km/h) can travel 3,206 meters, but the limited length of wire carried prevents the additional range from being exploited. This is not an issue with a radio command link. Firing is permitted by the "Shturm-V" system with the launch platform moving at up to 300 km/h (162 kts) and at an altitude of up to 3,000 meters, thus allowing an Mi-24 to fire a "Kokon" even while traveling near its top speed, and gain the kinematic benefits thereof. With the "Ataka" missile, the maximum altitude increased to 4,000 meters.</p><p>Besides its critical role in permitting the "Kokon" to reach its high supersonic speeds, a radio link has no firing restrictions related to terrain, either for the ground-based "Shturm-S" or the heliborne "Shturm-V". A common warning found in field manuals for wire-guided ATGMs is to never position the launcher in such a way that the missile travels over power lines, through bushes or bush fires, or through tree limbs or other obstructions, as any of these could damage the wire and interfere with missile guidance. With that in mind, it is worth noting that helicopters not only routinely fire over such obstructions, but one of the main tactics is to hide beneath the treeline of a forest before popping up to fire, which, needless to say, introduces multiple obstructions in the path of a command wire. The ability to fire freely over bodies of water is also an advantage, though less important for helicopters than for the "Shturm-S" tank destroyer, which can even fire while afloat.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jF2kw8PMX3M/YN7rmi-YZfI/AAAAAAAATtw/GL6nYvsY-GcX19gZAky0HpG9_28sd0InwCLcBGAsYHQ/s900/shturm-s.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="339" data-original-width="900" height="242" src="https://1.bp.blogspot.com/-jF2kw8PMX3M/YN7rmi-YZfI/AAAAAAAATtw/GL6nYvsY-GcX19gZAky0HpG9_28sd0InwCLcBGAsYHQ/w640-h242/shturm-s.jpg" width="640" /></a></div><p>0.2 seconds after launch, the launch unit begins acquiring the beacon of the missile, and 0.55 seconds after launch, guidance begins. To receive the radio signals, a horn antenna is placed at the tail of the missile, embedded into the parabolic reflector of the IR beacon next to the bulb of the beacon. The photo below, by Russian historian A. V. Karpenko, shows the horn antenna at the tail of the 9M120 "Ataka".</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-q4HITMTGtn0/YNgA0P27keI/AAAAAAAATis/tXNYDKkYxy04VUMTWXnC7wfocVDfcQJoQCLcBGAsYHQ/s732/karpenko%2Bataka.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="612" data-original-width="732" src="https://1.bp.blogspot.com/-q4HITMTGtn0/YNgA0P27keI/AAAAAAAATis/tXNYDKkYxy04VUMTWXnC7wfocVDfcQJoQCLcBGAsYHQ/s320/karpenko%2Bataka.png" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhEEbVKzDSIddXqAmY-QkLrgWLY8CUlyCL5M_7aRW_9TyGYwwq6qNWHYYiWDq3MoINAojkGMvLvkA3g47AKBnNbN7u7iGX343z1DPPCYKkXwOUl8dmE1JD8YDl0kar1jmuz2H-qUOKLsfmp23QQd1kG6Byfc2J_7eoVDmAqARimBmkCcPsaccl9L9Dqjg/s928/kokon%20beacon.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="604" data-original-width="928" height="260" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhEEbVKzDSIddXqAmY-QkLrgWLY8CUlyCL5M_7aRW_9TyGYwwq6qNWHYYiWDq3MoINAojkGMvLvkA3g47AKBnNbN7u7iGX343z1DPPCYKkXwOUl8dmE1JD8YDl0kar1jmuz2H-qUOKLsfmp23QQd1kG6Byfc2J_7eoVDmAqARimBmkCcPsaccl9L9Dqjg/w400-h260/kokon%20beacon.png" width="400" /></a><br /><br /></div><p>The horn antenna is a conical horn, with a cylindrical waveguide at its base. A conical horn was used, unlike the E-plane horn of "Falanga", because the antenna is connected to the radio receiver by a coaxial cable. The radio receiver receives and processes command signals sent by the emitter of the launch system. The receiver contains a signal filter, decoder, and amplifier. Additionally, the radio receiver has a secondary coupling to an access port that allows an artificial microwave signal to be inputted using special testing equipment to verify the functionality of the radio control system when carrying out service life checks.</p><p>As on the "Falanga" series, a microwave radio command link is used. It is a pulsed radio datalink, utilizing pulse periods to encode steering commands. The amplitude is fixed, while the period between predetermined points in the signal is varied to convey information on the magnitude and direction of the steering commands. Although the "Kokon" and "Ataka" have a single-channel steering system, as discussed in the following section, the radio command link is still fundamentally the same type as used in the "Falanga". It is merely the execution of steering commands that differs, and that is achieved by gyroscopically coordinating the steering mechanism.</p><p>The 9B611M radio unit is the receiver of the radio command datalink, and it performs decoding and conversion of the pulsed radio signal to a control signal (a DC voltage), which is amplified and transmitted to the gyroscopic commutator, before finally being passed on to the canard steering mechanism. Interestingly enough, the 9B611M radio unit is a common module shared with the 9M112M "Agona" GLATGM for 125mm guns, and was adapted from the 9B611 unit used in the original 9M112 "Kobra". Even with the new 9M120 "Ataka", the same 9B611M radio unit was retained.</p><p><br /></p><p>Signal filtering is done with a tunable bandpass filter. The radio control system provides five selectable frequencies and two selectable signal code settings. Unlike the fixed frequency sets offered by the older "Falanga" system, the operating frequency of the "Kokon" and "Ataka" missiles can be switched between any of the five available options at will before launch, and each frequency has one code, giving a total of ten possible combinations. This prevents cross-interference from occuring between all helicopters in a squadron of up to 10 if they all have one missile airborne at the same time, and because the frequencies are not hardware dependent, this makes all missiles interchangeable between helicopters and the only action needed is for all helicopters to be designated one frequency each before leaving on a sortie. The same is true for a company of "Shturm-S" tank destroyers.</p><p>As with a wired command link, the radio command link functioned as the medium by which pulse width modulated control signals are delivered to the missile. In order for pulse durations of not just one, but two steering axes to be represented in a signal, a chronological reference point has to be included in the signal. This was achieved by gating the pulsed signal into cycles of a fixed duration, demarcated by periodical reference points, cycle markers. Each cycle is a discrete data packet containing a pitch command and a yaw command.</p><p>Each cycle has a fixed period (T). Within each cycle, there is a cycle marker, a yaw marker and a pitch marker. They are all represented as a group of two radio pulses. The cycle marker is distinguished by the very short period between its two pulses (T1). The yaw marker has a period (T2) that is longer than the cycle marker. The pitch marker has a period (T3) that is longer than the yaw marker. Thus, the encoding rule, which is shared between all signal frequencies and codes, is that T1 < T2 < T3. The image below, from the engineering textbook "<i>Основы Устройства И Функционирования Противотанковых Управляемых Ракет</i>" by V. V. Vetrov et al., shows two sample command cycles in sequence.</p><p>The specific period between the two pulses in each of the three markers is coded. That is, just before a missile is launched, the "Shturm" control system communicates with the missile decoder unit and programs it to recognize the specific set of periods of T1, T2, and T3. These are thus considered a cycle code, a yaw code, and a pitch code respectively. A "Kokon" or "Ataka" missile that receives a signal with the wrong codes will reject it. As there are two sets of codes, the possibility of successful directed jamming is reduced, even if the jamming frequency matches the selected operating frequency of the missile.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-hBBVtYERiT0/YNfFeboonFI/AAAAAAAATiE/zOHKq2lxPdsQbEGv5knXpeCd6HCvuA1ygCLcBGAsYHQ/s1860/code%2Bpulses.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="588" data-original-width="1860" height="202" src="https://1.bp.blogspot.com/-hBBVtYERiT0/YNfFeboonFI/AAAAAAAATiE/zOHKq2lxPdsQbEGv5knXpeCd6HCvuA1ygCLcBGAsYHQ/w640-h202/code%2Bpulses.png" width="640" /></a></div><br /><p>The steering sign and the magnitude of the command is determined by the position of the pitch and yaw markers. When no steering command is made, both markers are placed in the middle of the cycle and the pulses are summed into a group of three pulses; the second pulse in each group overlap together. This is different from the method used in the radio system of the "Falanga", which uses a more complex system to generate a voltage to serve as an artificial midpoint that occludes any steering pulses with no magnitude or sign. Rather, in this encoding format, the third peak of this group is the measuring point for both the pitch and yaw markers. If a pitch or yaw command is made by the operator, the corresponding marker is shifted either left or right by a certain amount. A left shift encodes a negative sign to the signal, and a right shift encodes a positive sign. The magnitude of the shift, as measured by the length of the period of the steering marker from the pulse marker, encodes the magnitude of the command. </p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-dEXUvAFCNlk/YNfghdFlr3I/AAAAAAAATiM/1B7dOr5uEiMz2sr3-1mxRR_R6aGJ44G5ACLcBGAsYHQ/s2017/zero%2Bcommand.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1005" data-original-width="2017" height="318" src="https://1.bp.blogspot.com/-dEXUvAFCNlk/YNfghdFlr3I/AAAAAAAATiM/1B7dOr5uEiMz2sr3-1mxRR_R6aGJ44G5ACLcBGAsYHQ/w640-h318/zero%2Bcommand.png" width="640" /></a></div><p><br /></p><p>The diagram below shows an example of a steering command. The command is a pitch-up and steer-left at maximum intensity. The yaw marker has a left shift (-) and its relative period is at its minimum. The pitch marker has a right shift (+) and its relative period is at its maximum.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-MmcKKEGI34Y/YNeUAH1B5fI/AAAAAAAATh8/sd3EyPsdL3AwNMldHDoGArgJM9_1T-41ACLcBGAsYHQ/s1566/maximum%2Bup%2Band%2Bleft%2Bcommand.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="679" data-original-width="1566" height="278" src="https://1.bp.blogspot.com/-MmcKKEGI34Y/YNeUAH1B5fI/AAAAAAAATh8/sd3EyPsdL3AwNMldHDoGArgJM9_1T-41ACLcBGAsYHQ/w640-h278/maximum%2Bup%2Band%2Bleft%2Bcommand.png" width="640" /></a></div><p><br /></p><p>This system is more efficient, secure and flexible than that of the "Falanga", which had more processing steps for the same functions, and had no options for protecting the datalink with coded signals.</p><p>After processing at the gyroscopic comparator, the control signal is amplified by the 9B511 gyro-coordinator unit before arriving at the steering mechanism in the form of two pulses with a sawtooth waveform, phase-shifted relative to each other by 90 degrees. In the 9M120 "Ataka", 9B511M was used. Its differences from the basic model are unknown.</p><p>In addition with these elements of the guidance system, there is also the IR beacon, which is referred to as an IR transponder rather than a simple beacon, because it emits response IR signals corresponding to the command signals received from the launch unit. The beacon contains an <a href="https://festima.ru/docs/72284475/allrussia/lampa-impulsnaya-stroboskopicheskaya-isk200">ISK-200</a> capillary discharge xenon flash lamp, later replaced by the ISK-200-1 lamp in the 9M120 series. Its ignition voltage is 1,700 V, and it emits pulsed flashes with an intensity of 310 cd. The lamp is essentially a gas-discharge lamp, but <a href="http://forumcnc.ru/index.php?threads/%D0%9C%D1%83%D0%B7%D0%B5%D0%B9-%D1%8D%D0%BB%D0%B5%D0%BA%D1%82%D1%80%D0%BE%D0%BD%D0%BD%D1%8B%D1%85-%D0%BB%D0%B0%D0%BC%D0%BF.130252/page-99#post-729828">its design is extremely unusual</a>. It used almost exclusively in the "Kokon" and "Ataka" alone.</p><p>Unlike the ordinary incandescent lamp used in the 9M111 and 9M113, the ISK-200 naturally has stronger near-IR emissions than visual emissions, so a filter was not necessary. The emissions also readily penetrate battlefield obscurants, making it more difficult to suppress a "Kokon" using artificial and natural smoke obscurants. More interestingly, the "Kokon" was the first domestic ATGM to have a pulse modulated IR beacon, also being a transponder beacon, followed some years later by the 125mm gun-launched 9M112M "Agona" and 9M128 "Zenit" missiles for the "Kobra" ATGM system of the T-64B and T-80B. A pulse modulated IR beacon was only used in foreign missiles some years later, beginning with the TOW-2 which entered service in 1983, using pulsed frequency modulation. </p><p>Pulse modulated beacons are characterized by having a discontinuous flash cycle containing periodic pulses of variable period and position (frequency modulation). In the case of the "Shturm" ATGM system, frequency modulation is the specific form of modulation used. The flash of the beacon is controlled according to clock synchronization pulses encoded into the radio control signal. The lamp begins flashing only when command signals from the launcher, containing the clock synchronization pulses, arrive at the 9B611M unit. The IR photodetector of the guidance system captures the flash pattern of the transponder beacon to verify it is the correct recipient of its command signal, and in this way, a launcher is able to distinguish its missile amongst sources of IR interference, including other missiles that are within the field of view of the guidance system optic. IR signatures that do not match the synchronization codes are rejected as noise. </p><p>The blinking of the modulated IR beacon can be seen in <a href="https://youtu.be/Dnx4LSq1c-8">combat footage</a> taken from Mi-28N helicopters released by the Russian Ministry of Defence. The flash signature is clearly visible in a thermal imaging channel even through the smoke trail from the rocket engine. The lamp therefore functions as both an IR beacon as well as a thermal beacon, which is a useful additional layer of security for modern launch platforms of the "Shturm-Ataka" family. However, there was no way to utilize the thermal signature of the flash lamp on a "Kokon" for guidance during the Soviet era due to the absence of thermal imaging sights for "Shturm" launch platforms.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-w8KBCD7TCJU/YNX6tSQSrWI/AAAAAAAATgM/Y5YT46f6BMYett8WLJN15cGo2Tkb-z3kwCLcBGAsYHQ/s1034/beacon%2Band%2Bradioelectronics%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="635" data-original-width="1034" height="246" src="https://1.bp.blogspot.com/-w8KBCD7TCJU/YNX6tSQSrWI/AAAAAAAATgM/Y5YT46f6BMYett8WLJN15cGo2Tkb-z3kwCLcBGAsYHQ/w400-h246/beacon%2Band%2Bradioelectronics%2Bsection.png" width="400" /></a><a href="https://1.bp.blogspot.com/-CWCZ_Dk85lg/YNX-mQ1E3_I/AAAAAAAATgU/oq-sY4o4-aQ9Ytc2pGr9Rm2Y-uitJdLhwCLcBGAsYHQ/s1200/9m120-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" src="https://1.bp.blogspot.com/-CWCZ_Dk85lg/YNX-mQ1E3_I/AAAAAAAATgU/oq-sY4o4-aQ9Ytc2pGr9Rm2Y-uitJdLhwCLcBGAsYHQ/s320/9m120-2.jpg" width="320" /></a></div><br /><p>The modulation of the beacon is set when the operating frequency and signal code is selected by the missile operator. In total, there are ten possible beacon flash codes, corresponding to the operator's selection. This means that, in theory, up to ten "Kokon" or "Ataka" missiles may appear in the tracking optic without causing the system to lose control of the correct one from confusion. It also means that jamming of the guidance process of the missile by infrared optical interference from soft-kill active protection systems becomes much more difficult, though not impossible. The system is not fully immune, because an infrared source of sufficient intensity can still overwhelm the signature of the beacon if the two overlap. The lack of contrast making the missile appear as if it was lost. For comparison, the IR beacon on the TOW missile is modulated to flash at a frequency of 5 kHz. All basic TOW infrared beacons operate on the same frequency. Because the same frequency is used for all TOW missiles, it was not possible to have two missiles in flight within 300 meters of each other, making volley fire difficult. It is only possible to fire multiple TOW missiles at different targets in a criss-crossing pattern.</p><p>The image below shows the light of the IR beacon. It is tinted blue due to the digital camera detecting both the visual and infrared light from the beacon. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-soUB7qxasZk/YNOqflaQ3zI/AAAAAAAATfs/9IUlQZfxIJkcISOfdqqw1SlasSOKfhcSgCLcBGAsYHQ/s1200/IR%2Bbeacon.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="266" src="https://1.bp.blogspot.com/-soUB7qxasZk/YNOqflaQ3zI/AAAAAAAATfs/9IUlQZfxIJkcISOfdqqw1SlasSOKfhcSgCLcBGAsYHQ/w400-h266/IR%2Bbeacon.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-9fhYiK5__go/YNYN4zZqh_I/AAAAAAAAThE/TRdg77F3UE46z1-ldytzJgs7b_PSws8XgCLcBGAsYHQ/s800/ukraine%2Brefurbished%2B9m114.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="240" src="https://1.bp.blogspot.com/-9fhYiK5__go/YNYN4zZqh_I/AAAAAAAAThE/TRdg77F3UE46z1-ldytzJgs7b_PSws8XgCLcBGAsYHQ/w320-h240/ukraine%2Brefurbished%2B9m114.jpg" width="320" /></a></div><p>In addition to a high resistance to optical interference and high noise immunity, the missile and its guidance system are also quite precise. According to the article "<i>Отечественные Противотанковые Управляемые Ракеты И Комплексы</i>" published in the No. 4 2016 issue of the "<i>Армии и Флота Обозрение</i>" magazine, the angular dispersion of the "Shturm-S" system does not exceed 0.6 minutes of arc (0.17 mils) at its maximum range (4 km).</p><p>On the 9M120-1 series, a photodetector was added to the guidance section, protruding from the parabolic reflector of the IR beacon like the radio horn antenna. Guidance is achieved in the laser beam riding mode rather than SACLOS radio command. The main advantages brought by this system are interference-related. As a pulse-modulated beam of coherent light, the laser guidance beam readily penetrates battlefield obscurants such as smoke, dust, fog and rain, which would otherwise degrade the tracking accuracy of conventional SACLOS guidance equipment attempting to track an IR beacon. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4GI5vPNeqDg/YNgfpMDhhNI/AAAAAAAATi8/G_AsIHlN38gfOxpFnSgrXLHrwfwiNJWHQCLcBGAsYHQ/s2048/_ach_m_jpg_1418283457.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1194" data-original-width="2048" height="234" src="https://1.bp.blogspot.com/-4GI5vPNeqDg/YNgfpMDhhNI/AAAAAAAATi8/G_AsIHlN38gfOxpFnSgrXLHrwfwiNJWHQCLcBGAsYHQ/w400-h234/_ach_m_jpg_1418283457.jpg" width="400" /></a></div><p>As the laser beam riding system of the 9M120-1 is merely a retrofit onto the 9M120, the main merits of such a system, such as compactness, weight savings and power savings, were not realized. </p><p><br /></p><p>When the ground-based version of the "Shturm" system was in development, the designers ran into difficulties with dust and smoke obscuration. Firstly, the smoky engine exhaust during its powerful boost phase would obscure the operator's view of the target. This was solved by launching the missile in a lofted trajectory, keeping it above the operator's line of sight until the boost phase transitions to the sustainer phase, whereupon the missile is brought down to the line of sight of the operator's optic by an automatic altitude readjustment program in the guidance computer. This increased the minimum range to 400 meters. This is the default operating mode of the "Kokon" when launched from a "Shturm-S".</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-mJsktQyWw-U/YNYHd6phy7I/AAAAAAAATgk/p3kWAHwTpSI6t1AQfNHDGR153MyuB9D3gCLcBGAsYHQ/s1035/shturm-s%2Bflight%2Bprofile.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="121" data-original-width="1035" height="76" src="https://1.bp.blogspot.com/-mJsktQyWw-U/YNYHd6phy7I/AAAAAAAATgk/p3kWAHwTpSI6t1AQfNHDGR153MyuB9D3gCLcBGAsYHQ/w640-h76/shturm-s%2Bflight%2Bprofile.png" width="640" /></a></div><p>Furthermore, the missile raised a dust trail as it traveled over dry ground. This was caused by a combination of the exhaust gasses emitted from the oblique nozzles, and the sonic shockwave from the supersonic missile itself. This issue was completely absent when launched from helicopters, but a "Shturm-S" tank destroyer, normally situated in a hull-down position during combat, had its launch post raised just a meter above ground level. According to the results of studies by TsAGI specialists, a dust trail can form when the missile flies at an altitude of less than 6 meters. To prevent this from occurring, the "Shturm-S" guidance equipment includes a special "Dust" mode, whereby the launcher automatically introduces a certain angular offset in its tracking algorithm to ensure that the missile flies at an altitude of at least 6 meters above the operator's line of sight. The missile then descends back onto the line of sight at a distance of 500-700 meters from the target. The range to the target is measured using stadiametric rangefinder markings in the operator's sight and inputted to the system in 500-meter increments via a dial. Unlike in the case of ballistic weapons, even grossly incorrect measurements due to the low precision of a stadia rangefinder have a lessened impact, due to the large 500-700 meter error margin granted by the program.</p><p>It is worth noting that both of these operating modes are features provided by the 9K114 "Shturm-S" system itself, and are not built into the missile. The "Kokon" and "Ataka" are fully interchangeable between ground and airborne launch platforms.</p><p>The hit probability of the "Shturm" systems is 0.75-0.9, including against targets moving at up to 80 km/h. This can be considered quite high, and is competitive with the best foreign heavy ATGMs of the time, though it is, of course, a highly contextual metric. For instance, the TOW attained a hit probability as high as 0.97 against a fixed target out to its maximum range of 3,000 meters, but when evaluated against a moving target from 65-3,000 meters, the hit probability was 0.71. </p><p><br /><a href="https://www.blogger.com/null" id="kokonsteering"></a></p><h3 style="text-align: left;"><span style="font-size: large;">STEERING</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--iizVR-4u3g/YOBsOXeiNHI/AAAAAAAATuY/fxAUsOLrtI053MjF9TYLg8xbsKT925ZCgCLcBGAsYHQ/s456/kokon.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="90" data-original-width="456" src="https://1.bp.blogspot.com/--iizVR-4u3g/YOBsOXeiNHI/AAAAAAAATuY/fxAUsOLrtI053MjF9TYLg8xbsKT925ZCgCLcBGAsYHQ/s16000/kokon.jpg" /></a></div><p>Steering is effected by a pair of all-moving canards, which serve as both elevators and rudders. The canards have the same design as the canards of the "Strela-2" MANPADS missile, developed a few years before the start of the "Kokon" project at the Kolomna design bureau. This is made possible because, like several other Soviet ATGMs, including the earlier "Malyutka" and "Strela-2" designed by KBM, a single-axis steering system was implemented, whereby steering commands are executed by steering elements that work only on one axis, and the desired direction is controlled by timing the control signal with the rotation of the missile. The same concept was later applied in the RIM-116 Rolling Airframe Missile used by the U.S Navy. In this way, the number of steering mechanisms is halved. The steering mechanism of the "Kokon" is functionally the same as that of the "Malyutka", having an almost identical design with elements recycled directly from the "Malyutka" system, differing only in structural details. </p><p>A high steering moment (either a pitch or yaw moment) is provided by the large distance between the canards and the center of gravity of the missile. During assembly at the factory, the canards are folded into the fuselage and held with sellotape as the missile is loaded into its container, and flip forward under a combination of centrifugal force and spring tension once they are clear of the container when the missile is launched.</p><p>Due to the high airspeeds that the control surfaces must operate in, the amount of resistance is equally enormous. At the same time, the limited burn time of the rocket engine did not allow the use of its gasses to pressurize the steering mechanism, or to use a TVC system, which would have been suitable for providing the needed steering force due to the high thrust of a supersonic missile engine. To solve this, the concept of a pyrotechnic power source was implemented in conjunction with a repurposed variation of the known and proven nozzle deflector mechanism of the "Malyutka". A pyrotechnically-powered gas actuator was also used in the 9M112 "Kobra" ATGM and its variants made by KB Tochmash, also supersonic missiles, to solve the very same technical challenges. </p><p>The steering mechanism, shown in the diagram below, is clearly identical to that of a "Malyutka". A two-way solenoid valve is used to regulate the flow of high-pressure gasses into a dual-acting piston, which functions as the actuator. The canards are linked to the piston by a connecting rod, and the two canard fins are mechanically linked together by a crossbar, so that their movement is symmetrically mirrored. That is, they can deflect in the same direction simultaneously, in either direction, but cannot deflect in opposite directions. They are thus incapable of executing roll corrections. The roll rate of the "Kokon" and "Ataka" is therefore decided entirely by the rolling moment induced by the wraparound wings. Control of the canards is done using a bang-bang control scheme.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-YyE2qGIdwZE/YN1CM1uJsyI/AAAAAAAATqw/J_riZsvCosEQNTl-uFNabDuf6faIuq4cwCLcBGAsYHQ/s2048/canard%2Bactuator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1335" data-original-width="2048" height="418" src="https://1.bp.blogspot.com/-YyE2qGIdwZE/YN1CM1uJsyI/AAAAAAAATqw/J_riZsvCosEQNTl-uFNabDuf6faIuq4cwCLcBGAsYHQ/w640-h418/canard%2Bactuator.png" width="640" /></a></div><p>When the control signal is applied to the left or right electromagnet windings, the armature valve is shifted by magnetic attraction, allowing gas to flow into one of the two piston chambers while opening a bleeder opening to vent pressure from the opposite chamber. Additionally, when the armature is shifted left or right, a small amount of gas enters a special return cavity behind the armature, creating a small opposing force to push the armature in the opposite direction, but it is less than the force of attraction of the armature by the electromagnet, so the armature stays in position as long as the electromagnet is energized by the control signal. This is so that when switching the deflection position of the canard fins as the missile rotates in flight, the armature is immediately shot towards the opposite electromagnet, when its previous electromagnet is demagnetized.</p><p>There is no return spring in the mechanism to return the armature to the neutral position. If no control signal is present, the armature is returned to the neutral position by the equalization of pressure on both ends due to the automatic straightening of the canard fins by aerodynamic forces. When the polarity of the control signal is reversed, the current switches from flowing in, say, the left electromagnet coil to flowing in the right coil, the armature will move towards the right coil instantaneously. The movement translates into the rotation of the canard fins via a connecting rod acting as a second class lever. The canards are deflected at extremes of 15 degrees in either direction.</p><p>The steering mechanism is shown in the photo below, provided by internet user Wiedzmin.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEjJtVzY8CfDE1Oe6dxFswcHlQrfUL1HIvWh5NL9EUwIUHFxD-WnK4Fhp7laM-0TTyMysJ5zlFuYhFecZm7PZvjRbI4Y9eonRk98rymoFN5WrWwgWc4tPninZDA47mJMxEBU_m-zkImW7mcVuhMqGH_3Iddd2Hd-Q_bqeTYJAXE91xUDvJNxxXao3zX9HQ=s4000" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="4000" data-original-width="1846" height="640" src="https://blogger.googleusercontent.com/img/a/AVvXsEjJtVzY8CfDE1Oe6dxFswcHlQrfUL1HIvWh5NL9EUwIUHFxD-WnK4Fhp7laM-0TTyMysJ5zlFuYhFecZm7PZvjRbI4Y9eonRk98rymoFN5WrWwgWc4tPninZDA47mJMxEBU_m-zkImW7mcVuhMqGH_3Iddd2Hd-Q_bqeTYJAXE91xUDvJNxxXao3zX9HQ=w296-h640" width="296" /></a></div><p>As a design choice, the use of all-moving surfaces for the canard fins was the optimal solution for the "Kokon". Compared to the alternative, which would be trailing edge rudders, all-moving surfaces have a much higher efficiency in generating lift at supersonic speeds. This is shown in the graph below, where (2) denotes a trailing edge rudder and (1) denotes an all-moving rudder of equal surface area. The unit of the y-axis is the partial derivative of the lift coefficient with respect to the deflection angle of the lifting surface.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HuvgYKPm55g/YOooOpVqX7I/AAAAAAAAT1M/6Qs4-iH6jY4tGAHGucDZph4Fhfhg1dEZgCLcBGAsYHQ/s658/efficiency%2Bof%2Btrailing%2Bedge%2Brudders%2Bvs%2Ball-moving%2Brudder%2Bfins%2Bacross%2Bmach%2Brange.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="427" data-original-width="658" height="260" src="https://1.bp.blogspot.com/-HuvgYKPm55g/YOooOpVqX7I/AAAAAAAAT1M/6Qs4-iH6jY4tGAHGucDZph4Fhfhg1dEZgCLcBGAsYHQ/w400-h260/efficiency%2Bof%2Btrailing%2Bedge%2Brudders%2Bvs%2Ball-moving%2Brudder%2Bfins%2Bacross%2Bmach%2Brange.png" width="400" /></a></div><div><br /></div><p><br /><a href="https://www.blogger.com/null" id="kokonejection"></a></p><h3 style="text-align: left;"><span style="font-size: large;">EJECTION ENGINE</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-2qwWcYlbWjM/YNImsf6a1sI/AAAAAAAATeg/R1ELnWoCaCoZjYhQpPu0rW6xefdd5_sqQCLcBGAsYHQ/s2048/ejection%2Bunit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1453" data-original-width="2048" height="454" src="https://1.bp.blogspot.com/-2qwWcYlbWjM/YNImsf6a1sI/AAAAAAAATeg/R1ELnWoCaCoZjYhQpPu0rW6xefdd5_sqQCLcBGAsYHQ/w640-h454/ejection%2Bunit.png" width="640" /></a></div><p>On the "Kokon" and "Ataka" series, missile ejection is provided by a small solid fuel rocket engine, 217mm in length and weighing around 3.5 kg, attached to the base of the missile. The ejection engine contains the 9Kh182 charge, consisting of 1.1 kg of NDSI-2K propellant sticks. It is activated by an electrically triggered pyrotechnic ignition capsule. Once the launch button is pressed, the capsule begins to burn, venting its exhaust gasses out of a port in the missile container, and the ejection engine is started within a second. </p><p style="text-align: center;"><img border="0" data-original-height="400" data-original-width="924" height="278" src="https://1.bp.blogspot.com/-F9iZjSL-U2s/YNOFm5qa6XI/AAAAAAAATfU/6PEKrKY_ItocUrp9xYGouROv1R-liFFmwCLcBGAsYHQ/w640-h278/9m120%2Bstartup.png" style="color: #0000ee;" width="640" /></p><p>Once ignited, the ejection engine acts only long enough to propel the missile down the length of the container, burning out just before it exits the muzzle end, whereupon the engine is decoupled from the missile. The engine trails behind the missile for the first few meters of its flight, but quickly decelerates from air resistance and eventually falls to the ground. The 9M114 is ejected to a nominal initial velocity of 55 m/s or up to a maximum of 70 m/s, depending on the propellant temperature.</p><p>NDSI-2K propellant provides a very high nominal specific impulse of 2,320 N.s/kg. It is used in the form of solid sticks, 28 of which are packed into the engine. The engine itself produces a nominal specific impulse of 1,728 N.s/kg, and the total impulse delivered will be between 1,922.8 to 1,957.1 N.s, within a range of -50°C to +50°C. Within this temperature range, the ejection engine will produce a peak thrust of 45,000 N for 0.065 seconds or up to 61,000 N of thrust for 0.030 seconds, accelerating the 35 kg missile and engine assembly to a velocity of 55-70 m/s. During this time, it also imparts a rotational acceleration of up to 900 rev/s^2, giving the missile a spin of 20 RPS upon its departure.</p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-1zw_ffWU9jY/YMOj2clOaEI/AAAAAAAATaw/3PynwTzN7hoSv5b-OZuCZ5C0THPBLNX5wCLcBGAsYHQ/s1200/artilleriya7.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="759" data-original-width="1200" height="253" src="https://1.bp.blogspot.com/-1zw_ffWU9jY/YMOj2clOaEI/AAAAAAAATaw/3PynwTzN7hoSv5b-OZuCZ5C0THPBLNX5wCLcBGAsYHQ/w400-h253/artilleriya7.jpg" width="400" /></a></p><p>The body of the engine is a one-piece stamped steel structure, shaped like a cup. The curved top of the engine fits inside the hollow space of the parabolic reflector of the IR beacon on the tail of the missile, complete with two holes to fit around the bulb at the center of the beacon and the radio receiver antenna next to it, as shown in the drawing below. A raised band around the base of the engine seals the container bore and prevents the rocket exhaust from leaking forwards, where it could damage or contaminate the IR beacon with soot, which is otherwise unprotected.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-oF_j1jIPSNg/YTrlXxU7UUI/AAAAAAAAUK8/R5BjoW2T8TQn3CV-GfQFXB2eaT5TGc5uQCLcBGAsYHQ/s545/engine%2Btop.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="506" data-original-width="545" height="297" src="https://1.bp.blogspot.com/-oF_j1jIPSNg/YTrlXxU7UUI/AAAAAAAAUK8/R5BjoW2T8TQn3CV-GfQFXB2eaT5TGc5uQCLcBGAsYHQ/s320/engine%2Btop.png" width="320" /></a></div><p>Although it develops enormous thrust, the short burn time made it unnecessary to fit the inner surface of the engine with an insulating liner. It is fitted to the 9M114 via a special frame welded to engine body, and the open end is closed by a threaded nozzle cap. The nozzle cap has a central nozzle and 8 peripheral nozzles, which are slanted by 9.5 degrees tangentially to impart a slow initial spin to the missile. On the 9M120 "Ataka", the ejection engine was upgraded to a new model with 15 rear nozzles, but retaining the same 9Kh182 fuel charge. This modification allowed the engine to develop a stronger impulse, necessary to launch the heavier missile at the same velocity as the lighter 9M114. Presumably, a modified ejection charge was also needed for the 9M120-1 series to accommodate the new laser receiver embedded in the parabolic reflector of the IR beacon. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xpCfvsipXWo/YNSbjGH94nI/AAAAAAAATf8/3YoHRSngg0Q_hcBIbVMRC0LiMEDJx1huACLcBGAsYHQ/s1200/wMEsmNcnAbU.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="630" data-original-width="1200" height="336" src="https://1.bp.blogspot.com/-xpCfvsipXWo/YNSbjGH94nI/AAAAAAAATf8/3YoHRSngg0Q_hcBIbVMRC0LiMEDJx1huACLcBGAsYHQ/w640-h336/wMEsmNcnAbU.jpg" width="640" /></a></div><p><br /></p><p>Compared to a recoilless gun principle as implemented in the 9M111 and 9M113, a rocket launch method gives some benefit in terms of propellant weight, because the volume of the container behind the missile is not filled with pressurized gasses as the means of propulsion. Additionally, in a recoilless gun system, the forward-moving gasses acting upon the missile also contribute to the total forward momentum that needs to be counteracted by the rearward flow, so in theory, the back blast is increased, though only slightly because the operating pressure is low. In practice, a missile launched by a rocket engine must also take into account the fact that the rocket engine itself has a non-trivial mass, contributing decidedly more momentum than the gasses acting upon a missile ejected using the recoilless gun principle. In practice, both launch methods are valid, but their suitability is highly contextual.</p><p>In the case of the "Kokon" and "Ataka", there are a number of more relevant design nuances beyond these simple issues. First and foremost, the long slender fuselage of the missile meant that its container had to be uniquely long and voluminous. This creates conditions that are intrinsically more favourable to a rocket ejection system, as unlike a missile ejected using a fixed charge at the base of the container, the growing free volume behind the missile during its launch does not create a demand for an linearly proportional increase of combustion products to maintain pressure, nor does it restrict the force imparted on the missile from declining internal pressure. The thrust developed by a rocket engine is (effectively) constant. This allows a heavy load to be accelerated to the desired velocity over a long distance, thus keeping the firing impulse low. In this case, the firing impulse refers to change in the momentum of the missile, which is equal to the rate of the change in the momentum of the propellant gasses traveling in the opposite direction.</p><p>On the other hand, the rocket ejection method suffers from two main drawbacks, both of which were addressed by the designers. Firstly, the variable location of the rocket nozzle within the container makes it so that the point of peak internal pressure in the container is not limited to a single section, but distributed to the entire length of the container. The internal pressure developed in the container is at its peak in the region surrounding the exit flow from the rocket nozzle, and drops off downstream of the gas flow. As the rocket engine travels down the length of the container, the entire container experiences the peak pressure developed behind the rocket nozzle, making it necessary to reinforce the entire length of the container to withstand the pressure loading, thereby increasing the weight of the structure. This issue seems to have been fairly mild for the "Kokon", as it appears to have been adequately solved by the addition of metal hoops embedded at strategic points along the container, half of them concentrated around the base. The low thickness of the container, and the hoops embedded in it, can be seen with close inspection in the photo below, taken by Vitaly Kuzmin.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-WDdttQJCTEs/YNIUlSmkfCI/AAAAAAAATeY/mVIo0SUFE0o6AUYji9JJESbj3RyFFqoDwCLcBGAsYHQ/s2247/kuzmin%2Bphoto%2B9m114.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="525" data-original-width="2247" height="150" src="https://1.bp.blogspot.com/-WDdttQJCTEs/YNIUlSmkfCI/AAAAAAAATeY/mVIo0SUFE0o6AUYji9JJESbj3RyFFqoDwCLcBGAsYHQ/w640-h150/kuzmin%2Bphoto%2B9m114.png" width="640" /></a></div><p>Secondly, a rocket engine increases the parasitic weight during launch, because the rocket engine itself contributes to the total mass of the missile being propelled. This means that more thrust is needed to achieve a certain launch velocity, and more importantly, the weight of the expended engine has no purpose but to burden the missile during its flight. As such, a more powerful engine is needed to propel the missile after its launch. The prime example of a missile that never resolved this issue in its design is the TOW series. Fortunately, on the 9M114 and 9M120, the ejection engine is a disposable component that separates from the missile after launch, so that it does not contribute any parasitic weight once the missile is in flight. The most serious issue was therefore eliminated. </p><p><br /><a href="https://www.blogger.com/null" id="kokonengine"></a></p><h3 style="text-align: left;"><span style="font-size: large;">ENGINE</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-hFZku7MfYyQ/YNR3DijRPvI/AAAAAAAATf0/JXmwdeAO3jsW9iLkw_r82kIhMHtE9dMJwCLcBGAsYHQ/s2048/engine.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1397" data-original-width="2048" height="436" src="https://1.bp.blogspot.com/-hFZku7MfYyQ/YNR3DijRPvI/AAAAAAAATf0/JXmwdeAO3jsW9iLkw_r82kIhMHtE9dMJwCLcBGAsYHQ/w640-h436/engine.png" width="640" /></a></div><p>The engine is a single-chamber, dual-thrust type. It is lined with DSV-R plastic heat insulation layer, and the engine nozzles are titanium, also with a DSV-R lining in addition to the customary molybdenum throat insert. The use of titanium was due to its low coefficient of thermal expansion - around half that of stainless steel. To impart spin to the missile, the nozzles are angled by 15 degrees tangentially to the longitudinal axis. </p><p>The fuel is made in the form of a single solid fuel block with a central channel, and the two thrust modes are achieved with insulated fuel surfaces. The booster section is termed the 9Kh184 charge, and behind it is the 9Kh183 sustainer. An EV-ED-8 electric igniter with a pyrotechnic delay charge is designed to start the engine, and have it achieve full ignition at a distance of 8-10 m after launch. The igniter is electrically initiated by an inertial circuit breaker, which is tripped when the missile ceases to accelerate once the ejection engine burns out. After a delay of 0.09 seconds, the pyrotechnic charge burns out and reaches the fuel block, thus starting the engine. The engine is ignited, its gasses destroy the nozzle plugs, forming distinct puffs of ejecta from the engine nozzles, shown in the photo below. The engine start-up phase will transition to a steady state burn once it reaches 8-10 meters. </p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-1wNlRvx7giM/YKzXsL2YL0I/AAAAAAAATGs/asQprID8ZFITBs4gpgYjO8SBtEz8AvdogCLcBGAsYHQ/s685/shturm-s%2B%25282%2529.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="456" data-original-width="685" height="266" src="https://1.bp.blogspot.com/-1wNlRvx7giM/YKzXsL2YL0I/AAAAAAAATGs/asQprID8ZFITBs4gpgYjO8SBtEz8AvdogCLcBGAsYHQ/w400-h266/shturm-s%2B%25282%2529.jpg" width="400" /></a></p><p>The 9Kh183 sustainer is a charge of RNDP fuel, while the 9Kh184 booster is a charge of NDSI-2K fuel. The total mass of fuel carried in the engine is 9.82 kg, meaning that the mass of the missile without fuel is 21.68 kg. According to the study "<i>Оценка Показателей Боевой Эффективности Современных Противотанковых Управляемых Ракет</i>" by P. T. Nugmanov et al., the engine consumes an average of 1.95 kg of fuel per second. The proportion of missile weight and volume taken up by the rocket engine is plainly visible in cross sectional views of the missile, such as the one shown below.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9u5cqICID8s/YO3q3Lfx5eI/AAAAAAAAT6w/L2V8mE3gdxAl6Avg3qrtEdTsinq8jeCigCLcBGAsYHQ/s3865/9m114%2Bmodel%2Bin%2Bcontainer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="749" data-original-width="3865" height="124" src="https://1.bp.blogspot.com/-9u5cqICID8s/YO3q3Lfx5eI/AAAAAAAAT6w/L2V8mE3gdxAl6Avg3qrtEdTsinq8jeCigCLcBGAsYHQ/w640-h124/9m114%2Bmodel%2Bin%2Bcontainer.png" width="640" /></a></div><p>As mentioned earlier, NDSI-2K fuel, also used in the ejection engine, has a very high nominal specific impulse of 2,320 N.s/kg. Evidently it is used in the booster stage of the engine because a very high specific impulse is precisely what was needed to break the sound barrier. However, it could not be used for the sustainer, because it is a very smoky fuel. Its smokiness coefficient, defined as the loss of visual transparency per square meter per kilogram of fuel, is 3.8, making it the highest of all fuels used in any domestic ATGM. Given a smokiness coefficient of 1.4, the large fuel mass of 9.82 kg, and the prodigious fuel consumption rate, this means that the 9M114 and 9M120 produce a rather large volume and density of smoke. The slightly shorter burn time of the booster, combined with the raised trajectory of the missile during its initial flight trajectory (giving it the 400-meter minimum range) are compensatory measures to prevent the smoke from obscuring the operator's line of sight to the target when the missile is launched. After its initial trajectory is flown, it transitions to the sustainer engine.</p><p>RNDP fuel has a density of 1.58 g/cc, and has an energy density of 79 kJ/kg and a specific impulse of 2,159 N.s/kg. The choice of RNDP, which is a ballistite propellant, for the sustainer was due to its particular balance of power and smokelessness. Its smokiness coefficient is 1.4, placing it in a favourable point between the NDP-2MS fuel (1.1) used in domestic supersonic GLATGMs and the RNDSI-5K fuel (2.0) used in domestic subsonic ATGMs. </p><p>It is also worth noting that ballistite fuel requires a high combustion rate for stable engine operation, as it requires a relatively high pressure to maintain a steady burn. This was compatible with the needs of a supersonic missile, as high specific fuel consumption rate supports a very high thrust, but the efficiency of the engine was deliberately reduced to some extent by lowering the chamber pressure via an increased nozzle choke diameter, according to the research paper "<i>Оценка Показателей Боевой Эффективности Современных Противотанковых Управляемых Ракет</i>" (<i>Evaluation of the Combat Efficiency Indicators of Modern ATGMs</i>). Lowering the chamber pressure of a rocket engine fundamentally reduces its thrust. In this case, a reduction in the chamber pressure serves to lower the structural load on the engine, allowing thinner casing walls to be used.</p><p><br /></p><p>The 9Kh184 booster develops a thrust of 5,500-7,000 N for 2 seconds, followed by the 9Kh183 sustainer which generates 1,800-3,600 N of thrust for 3 seconds. During the boost phase, the internal pressure in the engine peaks at 16 MPa and declines to 10 MPa. In the sustainer phase, the pressure is 6 MPa and drops to 4 MPa, followed by engine burnout. The minimum pressure of 4 MPa, or 40.7 kgf/sq.cm, was not chosen arbitrarily - according to Russian patent <a href="https://patents.google.com/patent/RU2380346C2/en">No. 2380346C2</a>, 40 kgf/sq.cm is the critical threshold for stable engine operation with ballistite propellant. </p><p>The enormous thrust developed by the booster accounts for most of the fuel consumption, which is necessary to overcome the enormous rise in drag as the missile approaches the sound barrier because of air compressibility effects. The maximum speed of the missile is 550 m/s, achieved at the point of booster cutoff, which occurs at a distance of around 615 meters after launch. The sustainer maintains the speed of the missile at 550 m/s during its 3-second operating period, during which the missile travels an additional 1,650 meters, but once it burns out, the missile is left unpropelled, only gliding for the remaining 2.7 km of its trajectory. </p><p>A cruising speed of up to 550 m/s (Mach 1.6) is beneficial to the kinematic performance of the missile, as the drag coefficient of a projectile invariably reaches its peak in the transonic range but declines as the speed exceeds Mach 1. The specific shape of the drag curve will differ, but for projectiles optimized for supersonic flight, the benefit of exceeding Mach 1 is accentuated. In this case, at no point during its 5-kilometer flight will the "Kokon" fall below Mach 1, making it a fully supersonic system. </p><p>According to the textbook, "<i>Конструкция Средств Поражения, Боеприпасов, Взрывателей И Систем Управления Средствами Поражения: Конструкция и функционирование ПТУР</i>" (<i>Design of Weapons, Ammunition, Fuses, and Control of Destructive Devices: Design and Functioning of ATGMs</i>) by the Penza Artillery Engineering Institute, the 9M120 shares the same engine as the 9M114. However, at the same time, the 9M120 is attributed with a maximum range of 6 km according to a wide variety of credible sources, including advertisements by KBM, and also the aforementioned textbook. In the article "<i>Противотанковые комплексы контейнерного старта: ПТРК «Штурм»</i>" published in the May 2020 issue of the "<i>Техника и вооружение</i>" magazine, it is explained that the range of 6 km is achieved when launched from a helicopter, and that when launched from the ground, the maximum range is 5.5 km. Given that the engine of the 9M120 does not differ from the 9M114, this indirectly confirms that the 9M114 also benefits from an increased range when fired from a helicopter (at a high altitude), though confirmation is not really needed as it is expected behaviour from all air-launched missiles. Furthermore, it must therefore be inferred that the extended probe of the 9M120 conferred some aerodynamic advantage that, when combined with the larger inertia of the heavier missile, allowed it to remain supersonic for an additional 500 meters of flight when fired from the ground. </p><p style="text-align: left;">At present, the data for the flight time of a "Kokon" is known from a data table given in an advertisement titled "Shturm" from the recently privatized KBM, printed in the January 1993 issue of the "<i>Техника и вооружение</i>" magazine. At that time, the "Ataka" was still in development as a modernization option for the "Shturm" system, and is known in the table as "Shturm variant 1". </p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-H6CU7uazm38/YOuOQPyCxJI/AAAAAAAAT18/AjWe6WnL69gt9E5AWB_90najFxuP47FnACLcBGAsYHQ/s1964/shturm%2Badvertisement.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1442" data-original-width="1964" height="294" src="https://1.bp.blogspot.com/-H6CU7uazm38/YOuOQPyCxJI/AAAAAAAAT18/AjWe6WnL69gt9E5AWB_90najFxuP47FnACLcBGAsYHQ/w400-h294/shturm%2Badvertisement.png" width="400" /></a></p><p>The following lists the flight time of a 9M114 missile beyond the first 5 seconds of propelled flight, where a distance of 2,260 meters is traversed. </p><table border="1"><tbody><tr><td style="text-align: center;"><b> Distance (m) </b></td><td style="text-align: center;"><b>Cumulative time (s)</b></td></tr><tr><td style="text-align: center;">3,000</td><td style="text-align: center;"><span style="font-size: small;">7.5</span></td></tr><tr><td style="text-align: center;">4,000</td><td style="text-align: center;"><span style="font-size: small;">10.7</span></td></tr><tr><td style="text-align: center;">5,000</td><td style="text-align: center;"><span style="font-size: small;">14.5</span></td></tr></tbody></table><p>The following table lists the flight time for an "Ataka". The flight time figures at 3, 4 and 5 km are sourced from the data presented in the KBM table. The flight time figure at 6 km is taken from secondary sources. As the table shows, the missile has only a negligibly lower flight speed out to 4 km compared to a basic "Kokon". </p><table border="1"><tbody><tr><td style="text-align: center;"><b> Distance (m) </b></td><td style="text-align: center;"><b>Cumulative time (s)</b></td></tr><tr><td style="text-align: center;">3,000</td><td style="text-align: center;"><span style="font-size: small;">7.7</span></td></tr><tr><td style="text-align: center;">4,000</td><td style="text-align: center;"><span style="font-size: small;">10.75</span></td></tr><tr><td style="text-align: center;">5,000</td><td style="text-align: center;"><span style="font-size: small;">14.5</span></td></tr><tr><td style="text-align: center;">6,000</td><td style="text-align: center;">17.6</td></tr></tbody></table><p>The average speed of a 9M114 during its 14.5-second flight to 5 km is 344 m/s. This is just above the speed of sound, so it is self-evident that if the missile were to exceed 5 km, it would transition to subsonic flight, likely destabilizing the missile and rendering its lifting surfaces ineffective. The time taken to travel to 4 km is less than half the time needed by an ITOW (22 + 1.4 seconds), almost half the time needed by a 9M113 (19.2 seconds), and almost 7 seconds shorter than the HOT (17.3 seconds). The average speed may be increased if the missile is launched from altitude at a ground target, giving the kinematic advantages of a lower air density and gravitational acceleration. An average speed of 350-400 m/s quoted by some sources may be referring to "Kokon" missiles launched in this condition.</p><p><br /></p><p><br /></p><p><br /><a href="https://www.blogger.com/null" id="kokonwarhead"></a></p><h3 style="text-align: left;"><span style="font-size: large;">WARHEAD</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-vefRdX6AQPM/YNYLnhks2YI/AAAAAAAATg0/VNeoj8w1Tzg02EqE88lX5ePxfDxqmLClACLcBGAsYHQ/s503/9m114%2Band%2B114f.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="235" data-original-width="503" src="https://1.bp.blogspot.com/-vefRdX6AQPM/YNYLnhks2YI/AAAAAAAATg0/VNeoj8w1Tzg02EqE88lX5ePxfDxqmLClACLcBGAsYHQ/s16000/9m114%2Band%2B114f.png" /></a></div><br /><p>The warhead is a self-contained module, allowing a "Kokon" to have different warhead options installed during production without any changes to the rest of the missile. This was effectively the entire extent of the difference between the 9M114 and 9M120.</p><p>Given a fixed missile length, the standoff distance of the shaped charge is not at its maximum potential due to the placement of the canard steering mechanism behind the warhead rather than ahead of it, as in the 9M111 or 9M113 designs by Tula. Because of this adherance to a conventional missile layout, the "Kokon" could not outperform the 9M113 "Gaboy" despite having a larger 130mm HEAT warhead.</p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">KOKON</span></h3><h3 style="text-align: left;"><span style="font-size: large;">9M114</span></h3><h3 style="text-align: left;"><span style="font-size: large;">9N132 (HEAT)</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Nu4XXXg1eHI/YN72W3FR2EI/AAAAAAAATt4/hW5v4JPVxy8hmMx_LdiHOpTDdpTtE1I4ACLcBGAsYHQ/s1000/9n132.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="333" data-original-width="1000" height="212" src="https://1.bp.blogspot.com/-Nu4XXXg1eHI/YN72W3FR2EI/AAAAAAAATt4/hW5v4JPVxy8hmMx_LdiHOpTDdpTtE1I4ACLcBGAsYHQ/w640-h212/9n132.gif" width="640" /></a></div><p><br /></p><p>Weighing 5.3 kg, the 9N132 warhead contains 2.2 kg of explosive filler. As with earlier Soviet shaped charges, the full range of technological innovations made by the industry was implemented. The warhead has a steep liner cone angle, a variable thickness liner, a wave shaper, and a dual-explosive filler, consisting of an A-IX-10 base and a main filler of Okfol.</p><p>The A-IX-10 charge at the base is a secondary charge, acting as a detonation relay (booster) as well as a second form of wave shaper - a reactive explosive lens. The concept applied is the same as inert explosive lenses; to modify the direction of the detonation wave so that it is focused towards the apex of the liner. An explosive with a different detonation velocity is needed for this effect to occur, hence the use of A-IX-10. It is an alternative to A-IX-1 with a different phlegmatizer, sharing the same phlegmatizer content of 5%. It is among the Gekfol family of RDX-based explosives, and is known as Gekfol-5 (Hexfol-5). Its detonation velocity is the same as A-IX-1, which is 8.24 km/s. The combined inert and reactive lensing technology induces the detonation wave of the fast explosive (Okfol) to travel as an annular plane wave parallel to the conical liner.</p><p>This concept is also expressed in one of the wave shaping methods described in <a href="https://patents.google.com/patent/US2809585A/en?oq=2809585">U.S patent 2,809,585A</a>, filed in 1949. A booster of tetryl is placed behind an inert wave shaper, while the shaped charge cone is surrounded by pentolite. The same concept of using a slower explosive (tetryl) as the booster and a faster explosive (pentolite) as the main charge is applied in the patent.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-TOjUYJamX0M/YON6mF2L1pI/AAAAAAAATvQ/ZpgumdTo4A0S5NMaA-lxaDMJ1XOAgYltwCLcBGAsYHQ/s925/1949.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="925" data-original-width="617" height="320" src="https://1.bp.blogspot.com/-TOjUYJamX0M/YON6mF2L1pI/AAAAAAAATvQ/ZpgumdTo4A0S5NMaA-lxaDMJ1XOAgYltwCLcBGAsYHQ/s320/1949.png" /></a></div><p><br /></p><p>Other ATGMs began the same wave shaping concept a around a decade later, include the MILAN 2 from 1984, featuring a so-called "2nd generation shaped charge" consisting of a 73/23 hexolite (73% RDX, 27% TNT) booster and a main charge of 85/15 Octol (85% HMX, 15% TNT).</p><p>The 9N132 warhead of a 9M114 section includes the 9E243 fuzing system. Its inertial arming mechanism arms the warhead at a distance of 20-100 m from the launcher. It is a piezoelectric crush fuze with the same fundamental design as the piezoelectric fuze of the "Falanga". By the time the "Kokon" entered service, this type of fuze was no longer the most capable, being surpassed in impact angle performance and grazing sensitivity by electrostatic crush fuzes such as the type used on 9M111 and 9M113, as well as the MILAN and HOT. It is implied in the textbook "<i>Основы Устройства И Функционирования Противотанковых Управляемых Ракет</i>" that the retention of this specific form of piezoelectric fuze, used in the two previous KB Tochmash and KBM missiles, the "Falanga" and "Malyutka" respectively, was because it was a "branded" or "signature" product. Notwithstanding the fact that the textbook was published by KBP, a rival to these two bureaus, the evidence seems to indicate that this is true.</p><p>The photo below, by S. M. Ganin, shows a cross section of the warhead.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-2TnAGvYQuBk/YNYRjZFC72I/AAAAAAAAThM/4VFLkGoduR8DIb5XsQ5tmCiRRz6RQiIHwCLcBGAsYHQ/s810/9e243.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="365" data-original-width="810" height="288" src="https://1.bp.blogspot.com/-2TnAGvYQuBk/YNYRjZFC72I/AAAAAAAAThM/4VFLkGoduR8DIb5XsQ5tmCiRRz6RQiIHwCLcBGAsYHQ/w640-h288/9e243.png" width="640" /></a></div><p>A ring-shaped array of piezoelectric elements, clamped between the two silver rings clearly visible in the photo above, converts mechanical stress to a voltage when crushed. The piezoelectric element serves as a power source in a circuit formed between the detonator at the base of the warhead, the shaped charge liner, the focusing cone, the crushing cylinder and the casing of the warhead. When not in action, the circuit is kept open by the space between the nose fairing and the crushing cylinder. The liner is insulated from the casing of the warhead by an insulator insert to ensure that a short-circuit does not occur. When the missile impacts a hard obstacle, the nose is driven inward to push against the crushing cylinder, completing the fuze circuit and transmitting the shock of the impact to the piezoelectric ring via the crushing cylinder. The resulting voltage, transmitted to the base fuze via the shaped charge liner, detonates the warhead instantaneously. </p><p>Due to the reduced diameter of the piezoelectric ring relative to the fuselage, it is doubtful if 9E243 provides graze-sensitive activation like most other ATGMs. The main advantage of this specific fuze design is that, as stated in its technical description, it ensures the operation of the warhead against targets located behind camouflage and light shelters - bushes, branches, nylon and steel nets. This is presumably due to the high resistance of the nose to inward deformation due to its arch shape, a trait shared with the "Falanga" warhead design. This was presumably an intentional choice, made so that the advantages of radio guidance in being unaffected by bushes, foliage and other terrain features would not be spoiled by the premature detonation of the warhead on these aforementioned features. </p><p>The 9N132 warhead has a charge diameter equal to the fuselage, 130mm, and the built-in standoff distance is around 1.8 CD. This is quite similar to the HOT, which had a 136mm warhead with the same built-in standoff of 1.8 CD (247mm), though the HOT warhead is filled with a somewhat weaker 75/25 hexolite charge. The copper shaped charge liner has a diameter of 115mm, with an internal diameter of 108mm. Its thickness is progressively varied from 2.4mm at the base to 1.6mm at the apex. The apex angle of the cone is 43 degrees, which is within the typical range for Soviet high performance shaped charges. These design features are well known to enhance penetration performance compared to charges with a thicker liner and a shallower angle. The HOT, for instance, has a constant liner thickness of 3mm and cone angle of 60 degrees.</p><p>The penetration of the 9N132 warhead, as rated for a target obliquity of 60 degrees, is 280mm, giving a line-of-sight penetration depth of 560mm. This is the official figure, as given in the tactical-technical characteristics, and is likely referring to the guaranteed penetration performance. </p><p>In a Soviet era report, there is some information about the penetration of the 9N132 warhead, which was ascertained to record a control during trials of experimental ERA. This was presented in the list below. The test was intended to be on ERA placed on top of an armour steel plate meant to behave as a semi-infinite thickness target. As such, these control tests were also conducted on a semi-infinite RHA block, so the following list shows the penetration capability of the warhead, not its perforation capability, which is the more common figure encountered. The perforation thickness limit should be expected to be around a centimeter greater than a given penetration depth.</p><p>At 60 degrees:</p><p></p><ul style="text-align: left;"><li>Maximum depth: 776mm</li><li>Average depth: 597mm</li></ul><p></p><p>At 65 degrees:</p><p></p><ul style="text-align: left;"><li>Maximum depth: 703mm</li><li>Average depth: 534mm</li></ul><p></p><p><br /></p><p>The degradation in performance at 65 degrees, and presumably at higher angles, may possibly be due to slight deformations of the warhead and the liner when the nose impacts the target at a highly oblique angle. The high deviation between the maximum and the average is, however, rather inexplicable. Nevertheless, a "Kokon" perforating above 700mm RHA should be considered statistically significant during combat.</p><p>A penetration depth of around 600mm corresponds to the figures given by some Russian authors in books and specialist literature, where the 9M114 is credited with a penetration of 560-600mm. An average penetration of 600mm represents a relative depth of just 4.6 CD, which is a highly unremarkable level of performance, but is completely consistent with the limitations of the missile layout where the warhead is placed at the nose.</p><p>In practice, this performance is functionally at the same level as the 9M113 (modernized), offering no fundamental advantage against the new tanks in the NATO repertoire in the 1980's. Against such threats, a high probability of kill from a frontal aspect can only be achieved with multiple hits, given that the frontal arc protection of these next generation NATO tanks was formulated with warheads of similar power as a reference. The nominal protection level of the Leopard 2, M1 Abrams and Challenger generally ranged from 600-700mm RHA against HEAT, with few exceptions.</p><p>For comparison, the mean (average) penetration of the slightly larger HOT warhead at its built-in standoff distance is 700-711mm, which was determined by static testing using a special rotating rig that detonated the warhead while spinning it at the same rate as the missile itself in flight (9 RPS). Considering the sizeable advantages of the 9M114 in warhead power in all but six millimeters of diameter, how the HOT achieves a much higher average is something of a mystery. It may be an indication that the production tolerances for the HOT liner are vastly finer, but even a drastic difference cannot account for the disparities.</p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">9M114F</span></h3><h3 style="text-align: left;"><span style="font-size: large;">9N132F (THERMOBARIC)</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-usKOhhyxfuo/YNYLrLFtNHI/AAAAAAAATg4/I2SVTHjqqCogvzQsjcyyrydkDG_ZwOppACLcBGAsYHQ/s400/warhead.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="245" data-original-width="400" src="https://1.bp.blogspot.com/-usKOhhyxfuo/YNYLrLFtNHI/AAAAAAAATg4/I2SVTHjqqCogvzQsjcyyrydkDG_ZwOppACLcBGAsYHQ/s16000/warhead.jpg" /></a></div><p><br /></p><p>The total weight of the warhead increased to 6 kg. No information is available on its blast yield, but based on the very similar 9M120F that succeeded it, it is likely that its high-explosive effect is equivalent to 9.5 kg of TNT in the open. </p><p>The warhead retains the same 9E243 fuzing system of the 9N132. The hollow space around the crushing cylinder was modified to house a separate, additional fuze for the thermobaric fuel charge, which requires a timed ignition after being vaporized by the core HE charge.</p><p>Unlike the 9M114, which was of very limited use in Afghanistan, the thermobaric warhead of the 9M114F proved to be an extremely successful modification, as it was created with the specific nature of the target environment in mind - the local thick-walled mud buildings and caves. Mujahideen fighters taking shelter in these hardy structures were difficult to dislodge, but fuel-air ordinance detonated inside, or a short distance outside the mouth of these structures, could kill the inhabitants by the enormous blast overpressure prolonged by the long impulse period of this type of explosive, and magnified by the structure walls.</p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">ATAKA</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-nLrDRHCSUpc/YNI4gBgr8CI/AAAAAAAATew/9jzcrC_FFU45YmYaKa84se_DBI2wHpnvACLcBGAsYHQ/s343/ataka%2Bwarheads.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="343" data-original-width="250" src="https://1.bp.blogspot.com/-nLrDRHCSUpc/YNI4gBgr8CI/AAAAAAAATew/9jzcrC_FFU45YmYaKa84se_DBI2wHpnvACLcBGAsYHQ/s16000/ataka%2Bwarheads.jpg" /></a></div><br /><p>There are three warhead options within the "Ataka" series, namely the 9M120 or 9M120-1 with a tandem HEAT warhead, 9M120F or 9M120-1F with a thermobaric warhead, and 9M120F-1 or 9M120-1F-1 with a HE-Frag warhead.</p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">9M120, 9M120-1</span></h3><h3 style="text-align: left;"><span style="font-size: large;">9N143 (TANDEM HEAT)</span></h3><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-CD7y-IqGgpo/YMqfmZikgII/AAAAAAAATcM/kvmjFA55tCoNa_mmmUcecnB5DBpxyUtbACLcBGAsYHQ/s1289/ataka%2Bretracted.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1057" data-original-width="1289" height="328" src="https://1.bp.blogspot.com/-CD7y-IqGgpo/YMqfmZikgII/AAAAAAAATcM/kvmjFA55tCoNa_mmmUcecnB5DBpxyUtbACLcBGAsYHQ/w400-h328/ataka%2Bretracted.png" width="400" /></a><a href="https://1.bp.blogspot.com/-xa6jproV7x4/YMqfmb02BSI/AAAAAAAATcI/6pZUnlolAU4Wio7Vk_E0MbBBjAdd3IZYwCLcBGAsYHQ/s1292/ataka%2Bextended.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1059" data-original-width="1292" height="328" src="https://1.bp.blogspot.com/-xa6jproV7x4/YMqfmb02BSI/AAAAAAAATcI/6pZUnlolAU4Wio7Vk_E0MbBBjAdd3IZYwCLcBGAsYHQ/w400-h328/ataka%2Bextended.png" width="400" /></a><br /></p><p>The 9N143 tandem warhead is the warhead of the 9M120 and 9M120-1. It weighs 7.4 kg and has a main charge explosive mass of 2.75 kg. Note that the weight of 7.4 kg refers to the weight of the entire warhead assembly as shown in the image on the right above, and essentially represents the weight of the payload that the missile delivers to the target. The weight of the two shaped charges alone is unknown. A liner of progressive thickness was used in the main charge.</p><p>One of the primary features of the 9N143 warhead is that its dimensions do not exceed that of the original 9N132 for the 9M114, so that the missile itself shares the same dimensions, allowing it to fit within the same container. The diameter of the main charge is still 130mm, unchanged from the "Kokon", but the extendable probe is of a very substantial diameter and contains a 68mm precursor warhead according to data presented by Mikhail Rastopshin. With the probe retracted, the 9M120 measures 1,830mm in total length like the 9M114, and when the probe is extended, it is 2,100mm long. The probe is thus responsible for an additional 270mm of standoff distance. When retracted, the base of the precursor charge fits snugly in the cavity of the main charge liner, forming an extremely densely packed assembly. This is shown in the photo below, provided by internet user Wiedzmin.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgP07PxiICPqvYNc1CAbCI1nBlbC60cdMjuOb745mEunzpfbeuinuD6J1H_FvW51LPNFz6zkd2gCU4Ml5awwGDD_aUzlcM3wzluieDuGb1jmsREi-oRQC-4orRtB0Zs6kSCXHw244LegG6LExNru39EXMJFZtQ6nY-x0kgGQtVlOCpo6CjTph_toOr2sQ=s2819" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1103" data-original-width="2819" height="250" src="https://blogger.googleusercontent.com/img/a/AVvXsEgP07PxiICPqvYNc1CAbCI1nBlbC60cdMjuOb745mEunzpfbeuinuD6J1H_FvW51LPNFz6zkd2gCU4Ml5awwGDD_aUzlcM3wzluieDuGb1jmsREi-oRQC-4orRtB0Zs6kSCXHw244LegG6LExNru39EXMJFZtQ6nY-x0kgGQtVlOCpo6CjTph_toOr2sQ=w640-h250" width="640" /></a></div><p>The telescoping probe mechanism and the fuzing system is detailed in Russian patent <a href="https://patenton.ru/patent/RU2292007C1">RU2292007C1</a>, held by the Russian Federal Nuclear Center VNIIEF, which was the institute responsible for the research and design work for the warhead. Figure 1 of the patent shows the layout of the warhead with the telescopinc probe retracted into the cone of the primary charge.</p><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-2snHoj4ahf8/YOuFpmpCo-I/AAAAAAAAT10/JysjUNM4sOYcFmC_hMEiv-a5VSTz6pISACLcBGAsYHQ/s2048/ataka%2Bprobe%2Bretracted.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1040" data-original-width="2048" height="325" src="https://1.bp.blogspot.com/-2snHoj4ahf8/YOuFpmpCo-I/AAAAAAAAT10/JysjUNM4sOYcFmC_hMEiv-a5VSTz6pISACLcBGAsYHQ/w640-h325/ataka%2Bprobe%2Bretracted.png" width="640" /></a></p><p>The probe is extended during the 1-second startup period between the pressing of the launch button and the ignition of the ejection engine. To extend the two telescoping sections of the probe, the leading section is pushed forward first using direct gas impingement, and then the trailing section is pulled forward by the momentum of the leading section. </p><p>When the launch trigger is pressed, an electric signal is first sent to the extension mechanism of the standoff probe, and after a short interval, just long enough for the probe to lock into position, the "Ataka" is launched as usual. The signal received by the extension mechanism is an ignition signal to trigger the ignition of a small pyrotechnic extension charge in a cap affixed to the leading section of the telescoping probe, just behind the precursor charge. The resulting gasses fill the space between the leading section of the probe and the trailing section, generating enough pressure to shear a set of locking pins, thus freeing the precursor to be pushed forward into position. At the same time, the trailing section also moves backwards by a very short distance, and in doing so, shears off the locking pins that prevent it from moving forward. Once the precursor is stopped in its extended position, it transfers its forward momentum to the trailing section, which kicks it forward into its extended position. Special friction brake rings are fitted to ensure that both the leading and trailing sections are smoothly braked at the end of their movement, so as not to induce vibrations which may jolt parts of the mechanism out of alignment.</p><p>The images shown below capture the moment just after the probe is fully extended, as the ejection engine starts to launch the missile.</p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both;"><a href="https://1.bp.blogspot.com/-6u1sR5p5TVY/YMD_aycJZxI/AAAAAAAATYQ/uZJPeu_8D_IJVQD1GihY36k866hNi2HaACLcBGAsYHQ/s1028/9m120%2Bbefore%2Bexiting%2Btube.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="640" data-original-width="1028" height="249" src="https://1.bp.blogspot.com/-6u1sR5p5TVY/YMD_aycJZxI/AAAAAAAATYQ/uZJPeu_8D_IJVQD1GihY36k866hNi2HaACLcBGAsYHQ/w400-h249/9m120%2Bbefore%2Bexiting%2Btube.png" width="400" /></a><a href="https://1.bp.blogspot.com/-jUOBFIq-3iU/YMD7m8AUE6I/AAAAAAAATYE/xZanVniaABI_TdL5C0hkPG3grU_lv0uZACLcBGAsYHQ/s550/ataka%2Blaunch.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="390" data-original-width="550" height="284" src="https://1.bp.blogspot.com/-jUOBFIq-3iU/YMD7m8AUE6I/AAAAAAAATYE/xZanVniaABI_TdL5C0hkPG3grU_lv0uZACLcBGAsYHQ/w400-h284/ataka%2Blaunch.jpeg" width="400" /></a></div></div><p>The warhead is fitted with the 9E273 fuze. It is a piezoelectric contact fuze with a self-destruct system. It has essentially the same fundamental mode of operation as the 9E243 fuze detailed earlier, but made to detonate the precursor charge instantaneously followed by the main charge after a short delay. The delay mechanism uses a unique mechanism of sensing the destruction of the precursor charge to ensure that the main charge is protected from the fragments of the precursor, and to ensure that the correct delay is provided. According to the textbook "<i>Конструкция Средств Поражения, Боеприпасов, Взрывателей И Систем Управления Средствами Поражения: Конструкция и функционирование ПТУР</i>", the fuzing delay for the main warhead is around 300 μs. According to data provided by Mikhail Rastopshin, the delay is 220 μs.</p><p>The contact fuze installed in the nose of the precursor charge has an identical layout to the piezoelectric 9E243 fuze, simply scaled down. The fuze for the main charge is a capacitor fuze, and relies on two thin contact membranes as sensing elements. There is no shoulder fuze on the main charge itself, though it may not be necessary, considering the large diameter of the probe. This makes the fuzing design of the warhead substantially different from other ATGMs with a standoff probe such as the TOW-2A, which is fitted with a duplicate crush fuze on the fuselage nose to ensure detonation if the standoff probe misses the target. Although, of course, if the probe does not impact the target, it is questionable if the jet from the main charge would have any effect, given that the probe is axially aligned with the main charge.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-iAZ1yshLLAI/YOuCJbNgdaI/AAAAAAAAT1s/QOIsz07NETQ2gpKBHO0g1TeezJUbmjUHgCLcBGAsYHQ/s1948/ataka%2Btelescoping%2Bprobe.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="843" data-original-width="1948" height="276" src="https://1.bp.blogspot.com/-iAZ1yshLLAI/YOuCJbNgdaI/AAAAAAAAT1s/QOIsz07NETQ2gpKBHO0g1TeezJUbmjUHgCLcBGAsYHQ/w640-h276/ataka%2Btelescoping%2Bprobe.png" width="640" /></a></div><p style="text-align: left;">To act as the switch for the main charge and to protect the liner of the main charge from any potential damage inflicted by the precursor charge, two contact plates separated by a gap of a certain size are placed at the base of the standoff probe. The thin contact plates are electrically insulated from each other and from the standoff probe. When the missile impacts a target, the precursor charge is detonated conventionally, and the ensuing explosion generates an air blast as well as a number of weak fragments. These two elements travel down the probe, and deform the outer contact plate inwards, causing it to touch the inner contact plate. This closes the fuze circuit, thus allowing the capacitor to deliver a current to the base detonator of the main charge, thereby detonating it. In this way, the contact plates are able to sense the detonation of the precursor, and detonate the main warhead after the correct delay. Moreover, it also ensures that the shaped charge liner is fully isolated from the precursor charge, while also ensuring minimal resistance to the jet from the main warhead from fuze parts or debris.</p><p style="text-align: left;">The material, thickness of the outer contact plate and the gap size are the determining factors of the duration of the fuzing delay. They are calibrated to give the desired results by design. According to the patent, the detonating delay of the main charge was chosen to be 200-260 μs on the basis of experimental data to ensure the guaranteed departure of the ERA flyer plates from the path of the shaped charge jet from the main charge. The 220 μs delay figure given by Rastopshin is within the range of the cited delay of 200-260 μs, and is likely to be correct.</p><p>It is interesting to note that, without a shoulder-fuze, a theoretical possibility exists in defeating an "Ataka" with slat armour screens. A slat armour screen calibrated for an RPG-7 grenade tends to have a gap size of around 60-70mm, taking into account the known range of grenade diameters. The 68mm precursor may potentially fit just within the gap, fail to detonate, and thus the main warhead also fails to detonate. The main practical limitation of this is the fact that the thin contact plates may be deformed when the nose of the missile is crushed by the slats, as the crushing effect is the main method by which slat armour defeats RPG grenades.</p><p>The precursor charge has a standoff of around 1.5 CD. Its diameter of 68mm is very substantial, and from the available cross sectional view of the charge shown earlier, it appears to be of a high-penetration design. A shaped charge of this diameter, equal to a LAW grenade or some RPG-7 grenades, is generally capable of piercing around 300mm of RHA on its own, with the given standoff. Moreover, the cross section shows that the liner is not copper, like the main warhead. A steel or aluminium liner for a precursor would be capable of producing a wider hole in the target armour, though not as deep as a copper-lined charge. The width of the hole prevents a slug from becoming wedged in the cavity, and promotes the penetration of the main warhead by providing a less tapered cavity profile.</p><p>According to <a href="http://xn--80ajfng1a1g.xn--p1ai/web/upload/attachments/files/2d00ec25101a4fcb46a0134d13709e4c.pdf">the official tactical-technical characteristics</a>, the penetration with a probability of at least 0.5 is 800mm RHA including after reactive armour. For a 130mm warhead, a penetration power of 800mm RHA translates to 6.1 CD, which is a rather unremarkable level of performance, but is not entirely surprising given the conservative decision to place the warhead at the missile nose. No official figures are given for the penetration of the 9M120 on a target without reactive armour. However, based on the data provided by KBM, the penetration of the so-called modernized "Shturm" missile is 900-950mm RHA. </p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">9M120F, 9M120-1F</span></h3><h3 style="text-align: left;"><span style="font-size: large;">9N143F (THERMOBARIC)</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-2LlOZxdMBCo/YNgg2EmRViI/AAAAAAAATjQ/ZlcmbP3o_u8udS46quIJMouHuqTiaogmACLcBGAsYHQ/s1295/9m120f%2Bwarhead.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1061" data-original-width="1295" height="328" src="https://1.bp.blogspot.com/-2LlOZxdMBCo/YNgg2EmRViI/AAAAAAAATjQ/ZlcmbP3o_u8udS46quIJMouHuqTiaogmACLcBGAsYHQ/w400-h328/9m120f%2Bwarhead.png" width="400" /></a></div><br /><p>It is a thermobaric warhead of unknown weight. Even though no weight difference is specified between the 9M120 and 9M120F, it is unlikely that the 9N143F warhead is the same weight as the 9N143, as it would upset the weight and aerodynamic balancing of the missile and require additional lifting fins, such as the type found on the 9M120 or missile like the "Malyutka-2". It is advertised as having a high-explosive effect equivalent to 9.5 kg of TNT.</p><p><br /></p><h3 style="text-align: left;"><span style="font-size: large;">9M120F-1, 9M120-1F-1</span></h3><h3 style="text-align: left;"><span style="font-size: large;">9N143-OF (CONTINUOUS-ROD)</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-BqecepHv1z0/YNggxTONAfI/AAAAAAAATjM/dFF6FGUzkUoquVrjLvvr45PFrkxU8xKlgCLcBGAsYHQ/s1297/9m120f-1%2Bwarhead.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1060" data-original-width="1297" height="327" src="https://1.bp.blogspot.com/-BqecepHv1z0/YNggxTONAfI/AAAAAAAATjM/dFF6FGUzkUoquVrjLvvr45PFrkxU8xKlgCLcBGAsYHQ/w400-h327/9m120f-1%2Bwarhead.png" width="400" /></a></div><p>The 9N143-OF is a continuous rod warhead with largely unknown specifications. To increase the probability of intercepting aircraft, the warhead was equipped with a milimeter-wave radar proximity fuze, supplemented with a backup contact fuze. The missile is claimed to be capable of hitting aircraft travelling at up to 400 km/h, presumably rated against crossing targets. The operating radius of the radio proximity fuze is 4 meters.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-q1yIxVnFl10/YNDLjWNLcAI/AAAAAAAATd4/7GkNDk0TvrcbdoDBteN7KA7ylYtRLKQRACLcBGAsYHQ/s503/millimeter%2Bband%2Bradar%2Bfuze.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="503" data-original-width="256" height="320" src="https://1.bp.blogspot.com/-q1yIxVnFl10/YNDLjWNLcAI/AAAAAAAATd4/7GkNDk0TvrcbdoDBteN7KA7ylYtRLKQRACLcBGAsYHQ/s320/millimeter%2Bband%2Bradar%2Bfuze.png" /></a></div><p style="text-align: left;"><br /><a href="https://www.blogger.com/null" id="metis"></a></p><h3 style="text-align: left;"><span style="font-size: large;">"Metis"</span></h3><h3 style="text-align: left;"><span style="font-size: large;">9M115 (9M116)</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-YxwWDClZwog/YPWzdnsqGhI/AAAAAAAAT-Y/bRdTpgQ9kz0vtLJlKL6bfhzgjXEVam_FQCLcBGAsYHQ/s1200/polish%2Bpeoples%2Barmy%2Bmetis.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="758" data-original-width="1200" height="404" src="https://1.bp.blogspot.com/-YxwWDClZwog/YPWzdnsqGhI/AAAAAAAAT-Y/bRdTpgQ9kz0vtLJlKL6bfhzgjXEVam_FQCLcBGAsYHQ/w640-h404/polish%2Bpeoples%2Barmy%2Bmetis.jpg" width="640" /></a></div><p style="text-align: left;"><br /></p><p style="text-align: left;">The 9K115 "Metis" ATGM system was developed to fulfil the role of a light, company-level ATGM system with the intention of increasing the firepower of low level units. According to the article "<i>Противотанковые комплексы контейнерного старта: Противотанковый комплекс 9К115 «</i><i>Метис</i><i>»</i>" by R. Angelskiy and S. Suvorov, published in the April 2020 edition of the "<i>Техника и вооружение</i>" magazine, the "Metis" was created under the private initiative of the KBP design bureau. Following the success of the "Fagot" programme in 1970, a battalion-level weapon like the "Malyutka", the design bureau independently came up with a proposal to expand upon the basic design of the missile to create the "Konkurs" system, essentially scaling up the "Fagot" to occupy a higher tactical level, in this case the regimental and divisional level. After this idea received approval from the government and the military, the design bureau sought to repeat the same success a second time, this time exploring the possibility of scaling down the "Fagot" to occupy a lower tactical level. A niche was found at the company level, where there was no anti-tank contingent whatsoever, as all anti-tank weapons (RPG-7, RKG-3) were distributed at the platoon level. To serve as the logical intermediary between the RPG-7 with an effective range of 300 meters and the "Fagot" with a range of 2,000 meters, a range of 1,000 meters was chosen for the "Metis". </p><p style="text-align: left;">As an infantry ATGM system, the "Metis", which was assigned the GRAU index of 9K115, there is no vehicular mount. To support the extremely wide proliferation that a company-level ATGM system would have, the engineers took a bold step in radically reducing the complexity and cost of the expendable half of the system - the missile. The gyroscope, which was the single most expensive component included in all ATGMs, was removed, along with the commutator mechanism and onboard power source. The only remaining components of the guidance system were the wire link, a pyrotechnic tracer, and the steering drive. If not for the presence of a steering drive, the missile could be mistaken for an unguided RPG or SPG grenade. The project started under this design focus and was designated with the developmental name "Svirel", following the same theme as the "Fagot" and "Gaboy" of naming their containerized missiles after wind instruments. In this case, a svirel is an old traditional Slavic reed flute, smaller than a bassoon and an oboe. </p><p style="text-align: left;">At some point, the name was changed from "Svirel" to "Metis", referring to someone descended from two or more different ethnic groups. The meaning of this name in the context of the ATGM system is somewhat nebulous. Live fire tests of the "Metis" began in April 1978, but were initially unsuccessful. Strangely enough, in the article "<i>Противотанковые комплексы контейнерного старта: Противотанковый комплекс 9К115 «</i><i>Метис</i><i>»</i>", it is stated that on New Year's Eve of 1978 (31 December), the missile was successfully fired out to a range of 1.3 km. The system passed state tests in 1979, and entered service on June 19, 1979. The munition itself received two GRAU designations, unlike all previous domestic second generation ATGMs. The entire containerized unit, consisting of the container, the power source, and the missile, is known as the 9M115. The missile alone is the 9M116. The launcher for the missile is the 9P151.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-qSSzFZnIzbg/YPb3SLTwXoI/AAAAAAAAT_0/ZZLDZ3JqBM4yTJWeXe3tG1YrbNutHVNUwCLcBGAsYHQ/s2048/9p151.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1443" data-original-width="2048" height="281" src="https://1.bp.blogspot.com/-qSSzFZnIzbg/YPb3SLTwXoI/AAAAAAAAT_0/ZZLDZ3JqBM4yTJWeXe3tG1YrbNutHVNUwCLcBGAsYHQ/w400-h281/9p151.png" width="400" /></a></div><p>If the "Metis" system was issued, the machine gun platoon organic to a motorized rifle company would be transformed into an anti-tank machine gun platoon, or fire support platoon. Originally, the machine gun platoon contained six PKS or PKSM medium machine guns (GPMG on tripod), but with the introduction of the "Metis", half of the machine guns were replaced with ATGMs. Thus, each platoon contained three "Metis" anti-tank teams and three medium machine guns. They could be attached to the three motorized rifle platoons within the company or deployed organically by forming an anti-tank strongpoint. In accordance with the low tactical level of its intended niche, the system has a short range of 1,000 meters.</p><p style="text-align: left;">In this sense, it differed significantly from the M47 Dragon in the U.S Army which served as the sole squad-level anti-tank weapon, present in all rifle squads of the infantry. This organization was later remodeled, according to FM 7-8 (1992), placing two Dragon anti-armour teams at the platoon level instead. An infantry platoon consists of a platoon HQ, three rifle squads, and one fire support squad with two machine gun teams and two anti-armour teams. An anti-armour team consisted of the missile operator, carrying one tracking unit and one missile, accompanied by an assistant operator who brings one additional missile. This organization was essentially a scaled-down version of the company-level deployment of the "Metis".</p><p style="text-align: left;"><br /></p><p style="text-align: left;">In the late 1980's, KBP sought to improve the firepower of the "Metis" system by introducing a new large caliber tandem warhead missile, patterned after the "Kornet", which would be fully compatible with the original 9P151 launcher. The new 130mm caliber 9M131 missile together with the existing launcher unit formed the "Metis-M" system. The creation of the 9M131 missile was not only intended to be the means of keeping the existing infrastructure and stocks of "Metis" systems viable for the future, but also to replace the "Fagot", just as the "Kornet" was to replace the "Konkurs". The creation of the "Metis-M" effectively halted all further work on modernizing the "Fagot" system in KBP, hence the lack of any new missile models after the 9M111M "Faktoriya". However, it is also worth mentioning that creating a new large caliber tandem warhead version on the basis of the 9M111 series would have been utterly pointless, because it already existed as the 9M113M "Udar" of the "Konkurs" system. The "Metis-M" entered service in 1991, but this appears to have been in name only, as it never saw widespread use. On the contrary, it was only very rarely observed as training mockups in Russian Army academies. </p><p style="text-align: left;">Following this, KBP developed a modernization of the system, the "Metis-M1", diverging from the original premise of providing a company-level unit with an appropriately short-ranged missile system, instead featuring an extended range of 2,000 meters, enough to truly replace the "Fagot" on a one-to-one basis in tactical terms. The most remarkable aspect of the new design is that the complete containerized unit weighs merely 13.8 kg - just under a kilogram heavier than a "Faktoriya" missile. <a href="http://www.kbptula.ru/ru/novosti/novosti-kbp/564-metis-m1-na-vooruzhenii">Since 2004</a>, the "Metis-M1" was mass produced, but not for the Russian Army, as it was not accepted into service for unknown reasons. Mass production was launched only to fulfil foreign contracts, and in this regard, the system has had a mild but steady success, accumulating a modest roster of clients abroad. Much later, on the 2nd of March 2016, the "Metis-M1" was finally taken into service.</p><p style="text-align: left;">Because the "Metis-M" and "Metis-M1" were practically not used and are still very rare in the Russian Army to this day, both missiles will not be covered in this article.</p><p style="text-align: left;"><br /><a href="https://www.blogger.com/null" id="metisdesign"></a></p><h3 style="text-align: left;"><span style="font-size: large;">GENERAL DESIGN FEATURES</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-fVjceKEkvLo/YPFZmC3RVqI/AAAAAAAAT8M/kE5a9lC55aELWUop4yHy-_GP9uA_fBTwACLcBGAsYHQ/s2048/9m116%2Bmissile.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1103" data-original-width="2048" height="344" src="https://1.bp.blogspot.com/-fVjceKEkvLo/YPFZmC3RVqI/AAAAAAAAT8M/kE5a9lC55aELWUop4yHy-_GP9uA_fBTwACLcBGAsYHQ/w640-h344/9m116%2Bmissile.png" width="640" /></a></div><p>The design of the missile, from major nuances such as its near-total lack of electronic equipment, down to its launch method, was simplified to the maximum possible extent. If not for having a steering system, the 9M116 "Metis" missile may as well be an RPG grenade.</p><p style="text-align: left;">Owing to its close relationship with the "Fagot", the design of the 9M116 missile has a form factor that is effectively the same. The steering mechanism is housed in the fuselage nose, followed by the warhead, flight engine, ending in the launch engine. The launch engine serves the same purpose as the guidance section in a "Fagot", functioning as a tailboom for mounting the wings and the wire spool. However, thanks to the simplification of the guidance system, major modifications could be made in the container-missile interface. The previous system used in "Fagot", where a nose contact pad was used to link the gyroscope and onboard battery activation circuits to the launcher, was completely abandoned, as the 9M116 has no gyroscope or onboard batteries. This permitted the cast aluminium front cover of the "Fagot" container to be replaced with a much thinner and much lighter plastic cover. The new launch circuit became much simpler, consisting of two wire leads to join the positive and negative terminals of the rocket engine starter to the launcher. For drop protection, both ends of the container are furnished with three rubber pads along their rim.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-_liRP3ElbCk/YPb1N_5ZK3I/AAAAAAAAT_s/m6gTpQCGeJorbr9HVj0iEdahbpzeaAI0wCLcBGAsYHQ/s2048/9m116%2B%25282%2529.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1167" data-original-width="2048" height="364" src="https://1.bp.blogspot.com/-_liRP3ElbCk/YPb1N_5ZK3I/AAAAAAAAT_s/m6gTpQCGeJorbr9HVj0iEdahbpzeaAI0wCLcBGAsYHQ/w640-h364/9m116%2B%25282%2529.png" width="640" /></a></div><p style="text-align: left;">The container is made of glass textolite with a composite construction consisting of electrical grade SSHR-2M glass textolite (STEF) and structural grade AG-4S glass textolite. The container is 784mm long, up to 138mm in width and 145mm in height, measured from its connector socket. The complete containerized missile unit weighs just 6 kg. The missile alone weighs 4.8 kg. In terms of proportional weight, used as a measure of how much the missile weighs relative to the container, the 9M115 had some advantage over the 9M111. Where the 9M111 had a missile weight (missile + fixed ejection engine) share of 70%, the 9M115 had a missile weight share of 80%.</p><p style="text-align: left;">The container lacks a carrying handle or sling, and lacks the attachment points for one. Rather, each container is meant to be carried in bulk as part of a pack. For this, each container has two pairs of locking tabs on both sides. This allows multiple containers to be stacked and strapped together to form a missile pack. A standard pack consists of three missiles, complete with a special padded pack board and shoulder straps.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ZpvkHW85KIs/YPJkkrLR7aI/AAAAAAAAT9M/FJ26j2Wq3JQEgTe9WSqVoSwx5Wyf_QHawCLcBGAsYHQ/s1808/9f392%2Bmissile%2Bpack.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1808" data-original-width="984" height="400" src="https://1.bp.blogspot.com/-ZpvkHW85KIs/YPJkkrLR7aI/AAAAAAAAT9M/FJ26j2Wq3JQEgTe9WSqVoSwx5Wyf_QHawCLcBGAsYHQ/w217-h400/9f392%2Bmissile%2Bpack.png" width="217" /></a><a href="https://1.bp.blogspot.com/-2A10kDw4Vk4/YPJkkoiFIOI/AAAAAAAAT9I/314Ko4BpiS0wkAGe3gZyoQWdzsFsEgn0gCLcBGAsYHQ/s1975/9m391%2Bpack.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1975" data-original-width="1311" height="400" src="https://1.bp.blogspot.com/-2A10kDw4Vk4/YPJkkoiFIOI/AAAAAAAAT9I/314Ko4BpiS0wkAGe3gZyoQWdzsFsEgn0gCLcBGAsYHQ/w265-h400/9m391%2Bpack.png" width="265" /></a></div><p style="text-align: left;">The containerized missiles were to be treated as equivalent to artillery ammunition in field conditions, and require no special training to use. The weight of the No. 1 pack for the operator, consisting of the launcher and one missile, is 16.5 kg, and the No. 2 pack for an ammunition bearer, consisting of three missiles, is 19 kg.</p><p style="text-align: left;">For comparison, if the Dragon ATGM system was deployed in a two-man infantry team, then the Dragon gunner carries one missile with a tracker unit while the assistant gunner carries one additional missile. Additional missile bearers in larger integrated anti-tank units carry only one missile each. Given an anti-tank team of the same size, the "Metis" permits twice as many missiles to be brought into combat. However, because there were two anti-armour teams per platoon, the grand total number of Dragon missiles (4) is actually the same as a Soviet motorized rifle platoon with an attached "Metis" anti-tank team (4). The advantage of the "Metis" in practice is that each given infantry unit (squad, platoon, company) is not only smaller, but also leaner, as it has a higher density of heavy weapons per person while being more infantry-heavy. </p><p>The electrical connector socket to interface the container with the 9P151 launcher is on the front end of the container and faces rearward, so the missile is loaded from the front rather than from behind. This is due to the unusual placement of its T-457 thermal battery, and the unique method of activating it. Instead of connecting the thermal battery directly to the same socket compartment as on the "Fagot", the thermal battery on the 9M115 container is offset to the left, placing it in front of the trigger mechanism of the launcher. Unlike the inductor trigger of the 9P135 launcher of the "Fagot" system, the 9P151 has a simple mechanical trigger with a striker, and the T-457 thermal battery is activated by percussion. Such a system, almost whimsical in its simplicity, is an interesting though somewhat superficial similarity that the system shares with the RPG-7. The trigger is nothing but a lever for a sear, which releases a cocked striker. The unusual length of the trigger lever is to allow the operator to pull the trigger with his index finger without taking his left hand off the elevation wheel of the launcher. The entirety of the mechanism is shown in the image on the left below, and the placement of the trigger mechanism in relation to the T-457 battery can be clearly seen in the image on the right below.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-bHhe6kCq9L0/YPW9Vv8mzgI/AAAAAAAAT-g/Ln-YuzTeEoIsKVrGP44v7TkImcyNht9zACLcBGAsYHQ/s2048/simple%2Bstriker.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1731" data-original-width="2048" height="338" src="https://1.bp.blogspot.com/-bHhe6kCq9L0/YPW9Vv8mzgI/AAAAAAAAT-g/Ln-YuzTeEoIsKVrGP44v7TkImcyNht9zACLcBGAsYHQ/w400-h338/simple%2Bstriker.png" width="400" /></a><a href="https://1.bp.blogspot.com/-9a-oesu2YL4/YPXYieQoPdI/AAAAAAAAT-4/i2LFquC3R0MgqMhnyVDRaN-GR_6QEqGSACLcBGAsYHQ/s1038/trigger%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="851" data-original-width="1038" height="328" src="https://1.bp.blogspot.com/-9a-oesu2YL4/YPXYieQoPdI/AAAAAAAAT-4/i2LFquC3R0MgqMhnyVDRaN-GR_6QEqGSACLcBGAsYHQ/w400-h328/trigger%2Bmechanism.png" width="400" /></a></div><p>When the trigger is pulled, the striker hits the percussion mechanism of the thermal battery heater unit. The firing pin contained inside the percussion mechanism breaks open a pyrotechnic heating capsule, activating it, causing it to heat the thermal battery up to its operating temperature. Once the launcher receives a voltage from the battery, it powers up and begins the launch startup sequence. First, the launcher transmits a signal to the explosive bolt in the front cover of the container, causing it to pop off. Then the launch signal is transmitted to the ejection engine, and from there, the rest of the missile startup sequence is accomplished by pyrotechnic means. After each trigger pull, the striker has to be manually recocked.</p><p>The 9P151 launcher consists of the 9P152 tripod, 9S817 guidance unit and the 9S816 sighting system, which includes the missile tracker and the optical daylight sight for the operator. The 9S816 sighting system also has some unique design features. The unique position of the optical windows - placed below the missile container - ensures that if the operator has set up his position in such a way that he is in full defilade and the launcher is only raised just high enough to peek over the ground or any obstacle, so that when a missile is fired, it will leave the container with enough vertical clearance to not clip its wing (half-span of 187mm).</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-66w3Vq6QanQ/YPb4YKHo6WI/AAAAAAAAUAE/3TcAW61TMeAUtlXKtb_6DfrT8cBuUvuEQCLcBGAsYHQ/s734/9S816%2Band%2B9S817.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="415" data-original-width="734" height="226" src="https://1.bp.blogspot.com/-66w3Vq6QanQ/YPb4YKHo6WI/AAAAAAAAUAE/3TcAW61TMeAUtlXKtb_6DfrT8cBuUvuEQCLcBGAsYHQ/w400-h226/9S816%2Band%2B9S817.png" width="400" /></a><a href="https://1.bp.blogspot.com/-vsZ7Qg6HtZE/YPb4zd7bT5I/AAAAAAAAUAM/ADu1t_UKHTsUSeoAbDsQbXPRtyt2rAjywCLcBGAsYHQ/s2048/sighting%2Bunit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1115" data-original-width="2048" height="217" src="https://1.bp.blogspot.com/-vsZ7Qg6HtZE/YPb4zd7bT5I/AAAAAAAAUAM/ADu1t_UKHTsUSeoAbDsQbXPRtyt2rAjywCLcBGAsYHQ/w400-h217/sighting%2Bunit.png" width="400" /></a><br /></div><p>To accommodate a wide range of possible postures, the optical eyepiece has a free elbow joint, allowing it to be turned fully upward and flush against the side of the launcher for stowage and trasport, partly lowered for firing from the shoulder, and any range of further lower angles when firing from a prone position depending on the operator's posture. </p><p>It is loaded and fired from the 9P151 launch unit. The 9P151 was designed to ensure accurate missile guidance with the inclusion of a tripod, at the expense of increasing its weight, which is non-trivial at 10 kg. The time needed to deploy the system from a travelling configuration is just 12 seconds, and packing up 20 seconds. However, in an emergency, it is also possible for the missile operator to fire the "Metis" system from the shoulder, by bracing the front of the launcher against a firm obstacle and resting his shoulder against the special curved cutout on the back of the 9P151. This, of course, takes virtually no time at all, as the operator simply points the launcher and shoots. According to guidelines, firing from the shoulder is to be done only in emergencies when there is no time to set up a proper firing position, especially at short ranges when the enemy tank is practically overruning the defence. In such cases, the "Metis" would be used at approximately the same range as an RPG, and in the same way as an RPG.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-BJnbFuokTYg/YPDmecygbmI/AAAAAAAAT7s/q7cz4wwETOAN5qeR1mxksYlpv4SStI4-wCLcBGAsYHQ/s1466/metis-m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1466" height="295" src="https://1.bp.blogspot.com/-BJnbFuokTYg/YPDmecygbmI/AAAAAAAAT7s/q7cz4wwETOAN5qeR1mxksYlpv4SStI4-wCLcBGAsYHQ/w400-h295/metis-m.png" width="400" /></a><a href="https://1.bp.blogspot.com/-qGKzJLGM7nQ/YPDv6aAMMoI/AAAAAAAAT70/Y0-T7pk4hbQ07i6hePntG_qXGUD0PLKKQCLcBGAsYHQ/s1461/firing%2Bfrom%2Bshoulder.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1461" height="295" src="https://1.bp.blogspot.com/-qGKzJLGM7nQ/YPDv6aAMMoI/AAAAAAAAT70/Y0-T7pk4hbQ07i6hePntG_qXGUD0PLKKQCLcBGAsYHQ/w400-h295/firing%2Bfrom%2Bshoulder.png" width="400" /></a></div><p>When fired from the shoulder, the skill of the operator and his state of mind has a much greater influence on the trajectory of the missile. Rather than mechanical controls, the operator must calmly and smoothly turn his upper body to steer the missile, ensuring that no sudden jolts are imparted to the launcher. Overall, the hit probability is expected to be less than when firing from the tripod, though the extent of the performance degradation is unknown; no hit probability data was given in technical literature. However, based on the probability of hit data of the M47 Dragon, which is fired from the shoulder as the standard method of employment, it seems likely that firing from the shoulder is ineffective except at short range.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-WNm6Ph0NcSs/YPX_5dWAjsI/AAAAAAAAT_A/LmLotj9JyoMPlNKYt-nhCEJPkXbFkaQ7gCLcBGAsYHQ/s1274/tow%2Band%2Bdragon%2Bhit%2Bprobability.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="848" data-original-width="1274" height="266" src="https://1.bp.blogspot.com/-WNm6Ph0NcSs/YPX_5dWAjsI/AAAAAAAAT_A/LmLotj9JyoMPlNKYt-nhCEJPkXbFkaQ7gCLcBGAsYHQ/w400-h266/tow%2Band%2Bdragon%2Bhit%2Bprobability.png" width="400" /></a></div><p><br /></p><a href="https://www.blogger.com/null" id="metisaerodynamics"></a><h3 style="text-align: left;"><span style="font-size: large;">AERODYNAMICS</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-_TXNvlEvR8Q/YPDL-Fq7DsI/AAAAAAAAT7c/oxg-EZILafQOB2ttz0My1fhsKwVFBsblACLcBGAsYHQ/s2048/9m116%2Baerodynamics.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1315" data-original-width="2048" height="256" src="https://1.bp.blogspot.com/-_TXNvlEvR8Q/YPDL-Fq7DsI/AAAAAAAAT7c/oxg-EZILafQOB2ttz0My1fhsKwVFBsblACLcBGAsYHQ/w400-h256/9m116%2Baerodynamics.png" width="400" /></a></div><p style="text-align: left;">A canard aerodynamic scheme is used for the 9M116, with a high degree of design unification with the preceding "Fagot" and "Konkurs". As the image above shows, the lifting body shape of the front fuselage section combines with the lift of the canards to counterbalance the lift from the large wings. Due to the short length of the missile fuselage owing to its lack of onboard guidance equipment and power sources, a tail boom was needed for the wings and the wire spool, and this function is provided by the launch engine casing. The general shape and proportions of the "Fagot" was therefore preserved.</p><p style="text-align: left;">However, two major changes from the "Fagot" design were implemented. The first change was the switch from a conventional set of four wings to just three wings, which was done to increase the wingspan for the same wing area, and this was needed for the sake of increasing the distance between the wingtip tracer to the longitudinal axis of the missile. This distance was necessary to ensure that the spiral signature of the tracer could be easily discernable to the guidance sstem at longer distances, where a spiralling light source naturally becomes harder to distinguish from a single wobbling point of light due to the finite resolution limits of the tracking optic, especially in fog and hazy conditions.</p><p style="text-align: left;">The wingspan is 374mm (half-span is 187mm), providing ample lift for a missile of such modest weight. The wings are longitudinally offset at an angle of 2.3 degrees to maintain a spin rate of 7-12 RPS. The spin rate is lowest immediately after launch, but rapidly quickens after the engine starts up and propelled flight begins.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-m9R1wDhF7f0/YPPTGvVOwzI/AAAAAAAAT94/YClA4zur-ZMZI125Cr3AyXhVMlDVUK8GACLcBGAsYHQ/s1800/wing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1696" data-original-width="1800" height="378" src="https://1.bp.blogspot.com/-m9R1wDhF7f0/YPPTGvVOwzI/AAAAAAAAT94/YClA4zur-ZMZI125Cr3AyXhVMlDVUK8GACLcBGAsYHQ/w400-h378/wing.png" width="400" /></a></div><p style="text-align: left;">The second change was in the canard design. The canards of the 9M116 have the same planform as on the "Fagot" and "Konkurs", but are unique in that they have a double-plate design, connected at the ends. The missile has a single-axis control scheme, and a single axis steering system, so there is only one pair of steering canards. There is another pair of fixed canards perpendicular to the steering canards to provide lift. It is somewhat unclear how the double-plate design affects the performance of this control surface, as this topic is not widely explored in technical literature. The most basic assumption that can be made is that doubling the number of control surfaces means that the lifting area is doubled, so the single pair of canards on the missile might be able to produce a steering moment equivalent to four canards, or two canards of double the size. Like the 9M111 series, the height of the canards is limited by the inner diameter of the container, as they do not fold away, so a double-plate design may have been a design solution to circumvent the reduction from two pairs of canards as on the "Fagot", to only a single pair.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-pMarntPDb_M/YPhb4tqsClI/AAAAAAAAUBI/J1lBgVxrC8o7cOxLNSsXV88Qpcu2dzfYgCLcBGAsYHQ/s333/canard.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="319" data-original-width="333" height="384" src="https://1.bp.blogspot.com/-pMarntPDb_M/YPhb4tqsClI/AAAAAAAAUBI/J1lBgVxrC8o7cOxLNSsXV88Qpcu2dzfYgCLcBGAsYHQ/w400-h384/canard.png" width="400" /></a></div><p style="text-align: left;"><br /><a href="https://www.blogger.com/null" id="metisguidance"></a></p><h3 style="text-align: left;"><span style="font-size: large;">GUIDANCE SYSTEM</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-W24Sdjy1VBU/YPIrjw0F92I/AAAAAAAAT8k/daVqSNYA-34vc4sJVTBRrZM7bFILvmYEQCLcBGAsYHQ/s2048/9m115%2Bcircuit%2Bdiagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1678" data-original-width="2048" height="524" src="https://1.bp.blogspot.com/-W24Sdjy1VBU/YPIrjw0F92I/AAAAAAAAT8k/daVqSNYA-34vc4sJVTBRrZM7bFILvmYEQCLcBGAsYHQ/w640-h524/9m115%2Bcircuit%2Bdiagram.png" width="640" /></a></div><p style="text-align: left;">There is essentially no guidance system contained inside the 9M116 missile in any sense of the term, other than the command wire which serves as nothing more than a link between the launcher and the steering mechanism of the missile. Command signals transmitted down the wire link, in the form of an AC pulse width modulated voltage, are used directly as control signals for the steering drive without further processing. For this reason, "command signal" and "control signal" will hereby be used interchangeably, as they are the same. As the circuit diagram above shows, the only electronic component contained in the missile is a voltage multiplier which is connected as a bridge between the missile wire link and the steering mechanism. The voltage multiplier is used to convert the AC command signal into a DC control signal to charge the capacitors of the warhead fuze. </p><p style="text-align: left;">The power supply is, as mentioned earlier, a <a href="https://alpha-energy.ru/ru/catalogs.php?cmid=12839">T-457 thermal battery</a>. The battery is of a similar size and weight as a T-307B battery. It weighs 185 grams, and has an operating time of no less than 10 seconds. It has a dual-voltage output of 14.25 V or 28.5 V and three terminals, allowing a connected system to be supplied with either voltage by being connected to different combinations of its three terminals. The lower voltage is used only for the fuze of the explosive bolt for popping off the front cover of the missile container, which operates at 14 V. The higher voltage is the operating voltage for both the launcher and the missile. Once the thermal battery is struck by the trigger mechanism, it reaches a voltage of 23-26.5 V within 0.38-0.46 seconds, whereupon the launcher automatically switches on the guidance system and transmits the launch signal to the missile launch engine. Thanks to the efficient design of the 9P151 launcher, the single T-457 is sufficient to cover all of its electrical needs as well as the needs of the missile. Operator control is enabled only around 0.3 seconds after the launch of the missile (more exactly, between 0.25-0.38 seconds), as a special program is executed during the first 0.3 seconds to keep the missile at a level altitude with a strong-pitch up command, which is timed to coincide with the immediate period after the launch of the missile. The full launch sequence is shown in the block diagram below, taken from the book "<i>Конструкция Средств Поражения, Боеприпасов, Взрывателей И Систем Управления Средствами Поражения: Конструкция и функционирование ПТУР</i>" by the Penza Artillery Engineering Institute.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-d5m8lBxO6lY/YPInDgyUCiI/AAAAAAAAT8U/X0cKx9CZzJ4XBHFDF7skS3apzsPwoVqggCLcBGAsYHQ/s2048/launch%2Band%2Bflight%2Bprocess%2Bblock%2Bdiagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1316" data-original-width="2048" height="412" src="https://1.bp.blogspot.com/-d5m8lBxO6lY/YPInDgyUCiI/AAAAAAAAT8U/X0cKx9CZzJ4XBHFDF7skS3apzsPwoVqggCLcBGAsYHQ/w640-h412/launch%2Band%2Bflight%2Bprocess%2Bblock%2Bdiagram.png" width="640" /></a></div><p style="text-align: left;">The wire spool on the tail of the missile holds 1,000 meters of two-cored insulated wire. It contains copper cores in a high-tensile polymer jacket, and additionally protected with a layer of water resistant coating. The two cores of the wire are connected to two of the four terminals on the container connection socket. The other two terminals connect the positive and negative leads of the electric starter for the launch engine to the launcher. A separate two-core wire is used to connect the launch engine starter circuit to the launcher, and once the missile is launched, the wire is destroyed.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-WXuO-wkMCKA/YPPTA48NKUI/AAAAAAAAT90/t6wAL_VO3Mw8oKASaaOcA8ePW8eJ9X4kgCLcBGAsYHQ/s1782/wire%2Bspool.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1532" data-original-width="1782" height="344" src="https://1.bp.blogspot.com/-WXuO-wkMCKA/YPPTA48NKUI/AAAAAAAAT90/t6wAL_VO3Mw8oKASaaOcA8ePW8eJ9X4kgCLcBGAsYHQ/w400-h344/wire%2Bspool.png" width="400" /></a></div><p style="text-align: left;">There are no restrictions when firing over water, regardless of whether it is a body of fresh or salt water. This was likely guaranteed by the water resistant coating, but it may also have been influenced by the short range of the missile, as the flight distance may not have been long enough to allow the wire to become submerged in water due to sag.</p><p>Due to the short range of the system, a wire was the most rational choice for the command link, being the cheapest and most straightforward option for the given operating parameters of the weapon system. The determining factor was cost, and the combination of tracer and wire guidance was deeply tied into that design goal. Additionally, having a wire spool was convenient for the fuselage design, because it could be wrapped around the launch engine and the depletion of spool weight during flight counterbalances the depletion of fuel weight in the missile flight engine, not to mention that the short range of the missile means that the wire carried in the spool weighs very little in the first place. For short-ranged, low cost, high-volume weapons like the "Metis", or even the larger "Fagot", wireless command links such as radio or a laser beam riding system are senseless, as almost none of the advantages of such links - discussed previously in this article - are applicable in a meaningful way.</p><p style="text-align: left;">To provide the missile sighting system with a high-contrast point for tracking the missile, a 9Kh434 pyrotechnic tracer is fitted to the end of one of the wings. Before the projectile is launched, the tracer is located between the folded consoles and the engine. Because the wing section is ahead of the launch engine, and there is a gas seal between the engine nozzles and the rest of the missile fuselage, the tracer had to be ignited by a special gas release port on the engine casing, allowing a small stream of exhaust gasses to flow into the tracer. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-I9Hs25_Ap4g/YPIqbeFd5hI/AAAAAAAAT8c/HgZIbIrXG5wToc2-bcbtZhxB5UAWHokUACLcBGAsYHQ/s1800/tracer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1230" data-original-width="1800" src="https://1.bp.blogspot.com/-I9Hs25_Ap4g/YPIqbeFd5hI/AAAAAAAAT8c/HgZIbIrXG5wToc2-bcbtZhxB5UAWHokUACLcBGAsYHQ/s320/tracer.png" width="320" /></a></div><p style="text-align: left;">The main disadvantage of the system used in "Metis" is that it has an implicit reliance on a non-modulated light source (the pyrotechnic tracer) to track the missile, so unlike other second generation ATGMs with an IR beacon, it is not possible to implement a modulated beacon. This inherently limits the resistance of the missile system to IR interference, which can be in the form of the IR dazzlers or a strong light source like the sun. It is also not possible for a launcher to distinguish one "Metis" missile from another, so when two or more launchers are engaging different targets, it is strictly necessary to carry out interlocking fire.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HrX1MoVeZpE/YPgxo1c3zEI/AAAAAAAAUAU/DOXlCkMQnPAi2G2VFZIDoNVAANTewiTlACLcBGAsYHQ/s2048/interlocking%2Bfire.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1132" height="400" src="https://1.bp.blogspot.com/-HrX1MoVeZpE/YPgxo1c3zEI/AAAAAAAAUAU/DOXlCkMQnPAi2G2VFZIDoNVAANTewiTlACLcBGAsYHQ/w221-h400/interlocking%2Bfire.png" width="221" /></a></div><p>The "Metis" has a single-axis steering mechanism, but no gyroscopic commutator mechanism to coordinate the steering axis to the same coordinate reference as the launcher. Instead of a gyroscope to provide this coordinate reference, the launcher itself detects the rotation angle of the missile and executes the steering commands accordingly. This is done simply by having a special algorithm in the guidance circuit to recognize the repeating circular signature of the missile tracer when viewed by the IR-sensitive photodetector through the stroboscopic disc. Similarly, an algorithm is also used to allow the launcher to determine the roll angle of the missile by the position of the tracer relative to its calculated center point. In addition, it also provides the basic function of detecting the angular error of the missile from a fixed reference point, allowing the tracker to determine if the missile has deviated from the operator's line of sight. As with the sight unit of the 9P135, the sighting unit for the 9P151 has two duplicate photodetector and stroboscopic discs, which are fitted with different sets of optics to provide a wide and narrow field of view modes. The wide field of view is used to track the missile immediately after launch, up to a distance of 250 meters, whereby the launcher automatically switches to the narrow field of view mode to track the missile for the remaining distance.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-WpEAcoLk3Ak/YPhXgQB31DI/AAAAAAAAUAw/XQpVJWHkJTAMroxYguPW15zmgXvt13XAwCLcBGAsYHQ/s2048/launcher%2Bblock%2Bdiagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1248" data-original-width="2048" height="390" src="https://1.bp.blogspot.com/-WpEAcoLk3Ak/YPhXgQB31DI/AAAAAAAAUAw/XQpVJWHkJTAMroxYguPW15zmgXvt13XAwCLcBGAsYHQ/w640-h390/launcher%2Bblock%2Bdiagram.png" width="640" /></a></div><p>In terms of logical complexity, the system is clearly more sophisticated than that of a conventional SACLOS guidance system. However, this did not translate to the constructional complexity of the physical device itself. As with the 9P135 of the 9K111 "Fagot", the system relies on two photodetectors and two stroboscopic discs. The cost of materials and labour in the production of such devices are primarily determined by the expense of the optics and photodetectors, rather than the mundane semiconductors used to create the analogue algorithms in circuitry. Without real differences in those expensive components, the cost of building "Metis" launchers cannot be considered higher than conventional SACLOS launchers.</p><p style="text-align: left;">The hit probability of the "Metis" system is 0.91-0.98. It is also rated to hit targets moving at up to 60 km/h moving at various angles relative to the launcher. The ability to engage a crossing tank target is a particular concern for a short ranged missile, because at closer ranges, a moving target can cross the 6-degree field of view of the operator's sight very rapidly, so the permissible speed of the moving target is naturally reduced. The following figures are the limits of the target speed for a target moving obliquely relative to the launcher. It is not known if these figures reflect the limits for achieving the rated hit probability of 0.91-0.98, or if the hit probability declines at shorter ranges.</p><p style="text-align: left;"></p><ul style="text-align: left;"><li>At 150 meters - 15-20 km/h</li><li>At 300 meters - 30 km/h</li><li>At 500 meters - 45 km/h</li><li>From 600 meters to 1,000 meters - 60 km/h</li></ul><p></p><p style="text-align: left;"><br /><a href="https://www.blogger.com/null" id="metissteering"></a></p><h3 style="text-align: left;"><span style="font-size: large;">STEERING MECHANISM</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-dHFRoG23lnk/YPZ-mD4Z-xI/AAAAAAAAT_c/VRcfjftSiKoUT8i9C7QLfD5Md5UsShZXgCLcBGAsYHQ/s1507/ram-air%2Bactuator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1412" data-original-width="1507" height="375" src="https://1.bp.blogspot.com/-dHFRoG23lnk/YPZ-mD4Z-xI/AAAAAAAAT_c/VRcfjftSiKoUT8i9C7QLfD5Md5UsShZXgCLcBGAsYHQ/w400-h375/ram-air%2Bactuator.png" width="400" /></a></div><p style="text-align: left;">' steering mechanism, where the control surfaces act only in one axis, relying on the rotation of the missile to exert control radially, and thus steer the missile in two axes. To provide the necessary torque to actuate the steering canards, the "Metis" was built with a ram-air actuator, the first ATGM in the world to feature such a device. It was chosen for being particularly suitable for an ATGM, particularly one with no onboard power source. Its salient properties of low weight, low complexity, low production demands (8-20% less than simple electromagnetic actuators as on the "Fagot"), high torque and low power requirements made it the ideal form of actuator for its purpose. Its qualities were so convincing that KBP adopted it as their preferred steering solution for almost all future guided weapon projects, including the "Kastet", "Refleks", "Kornet", "Metis-M", "Gran" and "Kitolov", with the sole exception being the "Krasnopol".</p><p style="text-align: left;">This type of ram-air actuator is known as an open-type actuator, because the power flow loop is open. As an open-type actuator has an open power flow loop, this means that the air flows freely relative to the actuator, thus eliminating losses due to friction or damping. In real terms, this is reflected by the fact that air does not enter the steering mechanism via the ram-air intake when no steering action is needed, which limits the penalty in air resistance during flight, and once the steering mechanism is in operation, air passes into the missile fuselage through a ram-air intake and, once the flow of air has performed its function in the actuator, it exits freely via gaps in the fuselage. Because a ram-air actuator uses the incoming air as the working fluid, the power of the actuator is directly proportional to the speed of the missile, which in turn means that the rising aerodynamic resistance to the motion of the control surfaces at higher speeds is overcome by the proportional gain in actuator power.</p><p style="text-align: left;">The operating principle of the actuator in the "Metis" is extremely simple - a pair of electromagnets is used to open and close a cover, which, when opened, will allow the incoming air stream to collide with one of two buckets of the canard armature. The inlet cover is a slotted plastic disc, which can selectively cover the air inlets of both air buckets, or one bucket while leaving the other open. It is used together with a slotted intake grille, shown in the images below, which means that the disc only has to be turned by a small angle to create a large intake opening. The air buckets are placed perpendicularly to the canard axle, so in the image on the left below, the inlets are located on the top and bottom ends of the slotted grille. The grille also serves to prevent the ingestion of foreign objects which could damage the ram-air mechanism, including insects, small pebbles, pieces of wood broken off of branches, and so on.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-M28uvxT_khc/YPhMogD91WI/AAAAAAAAUAk/vIOM9aWlGagrCmp-iKh4IMhckWnmG-4SwCLcBGAsYHQ/s1321/front%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1205" data-original-width="1321" src="https://1.bp.blogspot.com/-M28uvxT_khc/YPhMogD91WI/AAAAAAAAUAk/vIOM9aWlGagrCmp-iKh4IMhckWnmG-4SwCLcBGAsYHQ/s320/front%2Bview.png" width="320" /></a><a href="https://1.bp.blogspot.com/-PU47mQQdPPU/YPhMoQ8IVpI/AAAAAAAAUAg/M0aitJrURYM2SZOX0vaAPKny0WlgQrQqQCLcBGAsYHQ/s300/slotted%2Bdisk%2Bram-air%2Bcover.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="300" data-original-width="299" src="https://1.bp.blogspot.com/-PU47mQQdPPU/YPhMoQ8IVpI/AAAAAAAAUAg/M0aitJrURYM2SZOX0vaAPKny0WlgQrQqQCLcBGAsYHQ/s0/slotted%2Bdisk%2Bram-air%2Bcover.png" /></a></div><p>The turning of the slotted ram-air cover is done by having a rotary armature attached to the end of the disc axle, so that when one of the two electromagnets is energized, one end of the armature is attracted to it, creating a torque and thus turning the cover. This mechanism is shown in the image below. The iron cores of the two electromagnets are marked (7), and the copper wire windings around the cores are marked (8). An insulating pad (10) separates the two electromagnets. In the image below, the armature is attracted to the lower electromagnet, turning the ram-air cover clockwise.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-7TN9uoN5e4E/YPW-W60PKSI/AAAAAAAAT-o/CJSdrclLjaYCL5P7eOZeTbDOeYu8zyhjgCLcBGAsYHQ/s779/electromagnetic%2Bflap%2Bvalve.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="779" data-original-width="777" height="320" src="https://1.bp.blogspot.com/-7TN9uoN5e4E/YPW-W60PKSI/AAAAAAAAT-o/CJSdrclLjaYCL5P7eOZeTbDOeYu8zyhjgCLcBGAsYHQ/s320/electromagnetic%2Bflap%2Bvalve.png" /></a></div><p style="text-align: left;">Also connected to the iron cores is a permanent magnet (11), the role of which is unknown. It is not clear how the armature is held in a neutral position, perpendicular to the electromagnets, ensuring that both ram-air slots are sealed. Some method of locking the armature is needed because, when the missile is launched and accelerates during flight, its fuselage is spun by the torque produced by the rocket engine and wings. Some of this torque is passed to the axle of the ram-air cover via friction through the bearings, which are under compression due to air pressure acting on the blunt surface of the ram-air cover. Due to its light mass, the moment of inertia of the ram-air cover is low, yet it is likely to be great enough that the torque delivered via friction is insufficient to equalize its spin rate with that of the fuselage. It is also unclear how the armature returns to the neutral position once the electromagnet is de-energized.</p><p style="text-align: left;">One possibility is that the permanent magnet is inside a hollow cylinder with an open mouth so that, when the electromagnets are de-energized, the permanent magnet slides into a slot in the armature due to magnetic attraction, and the magnet functions as a lock. When one of the electromagnets is energized, magnetism would be induced in the armature, and by having a pole opposite to the closest end of the permanent magnet, the permanent magnet would be repulsed, receding into the cylinder and thereby unlocking the armature, freeing it to rotate. </p><p style="text-align: left;">The inlet leading to each air bucket is shaped as a nozzle to increase the velocity of the incoming air, and thus the amount of momentum transferred to the bucket. The armature is pinned in the center by the canard axle, and the air buckets are situated at the ends of the armature. When one of the buckets is pushed backwards by the air, the armature is turned on its axis, thus turning the canard. The bucket captures the momentum of the high-velocity air by forcing it to come to almost a complete stop against its flat surface, with no way to flow sideways. The impulse delivered by the air is therefore very high, which also raises the efficiency of the mechanism. This principle is the same as that of a Pelton wheel, used in modern hydroelectric turbines to extract the maximum amount of kinetic energy from a high-velocity fluid (water) by momentum transfer, which is converted to electricity. The specific design of the ram-air mechanism in the "Metis" reflects the simplicity of its function - the inlet and air buckets are made of plastic, and the actuator is a pair of low-power electromagnets. The mechanism is capable of operating at flight speeds as low as 20-30 m/s, which is more than enough to allow the 9M116 missile to begin maneuvering immediately after launch, as the missile is launched at a muzzle velocity of 90 m/s. </p><p style="text-align: left;">Unlike a hydroelectric turbine, which remains fixed while the water is moving into it, thus making the working fluid the power source, a missile experiences the inverse - it travels through standing air and thus relies on generating a relative airspeed through its own flight speed. This means that the power source is not the fluid medium itself, but rather the engine that propels the missile through the fluid. For missiles with a streamlined nose, the presence of air intakes increases the overall drag by about 2-4%, and to ensure the required flight speed, it is necessary to increase the engine thrust, and therefore the fuel supply onboard the rocket. However, as mentioned earlier in the section on the 9M113M "Udar" ATGM, rocket fuel has the highest energy density of all other forms of power storage, and because the rocket engine is an existing component, additional power is easily accommodated by simply increasing the fuel load.</p><p style="text-align: left;">Due to the direct use of the command signal to energize the actuator electromagnets, the response time of the steering mechanism is extremely quick, as shown in the chart below. The first waveform, from the top, is the control signal arriving to the actuator electromagnet. 'U' is a pulsed modulated voltage. The second waveform is the deflection angle of the control armature of the ram-air cover, indicated by the unit 'α'. The third waveform indicates the deflection angle of the canards, measured in 'δ'. When chronologically aligned in this way, it can be clearly seen that the control signal directly introduces a nearly instantaneous proportional deflection of the ram-air cover, resulting in the canards deflecting to its maximum deflection angle in a very short span of time, with an equally short reset time.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--FFeekJNiss/YPgxxTU7BqI/AAAAAAAAUAY/s6T2dldp-ggt4IFDzAkfjENK6QcFI_VpwCLcBGAsYHQ/s2048/control%2Bsignal.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1394" height="640" src="https://1.bp.blogspot.com/--FFeekJNiss/YPgxxTU7BqI/AAAAAAAAUAY/s6T2dldp-ggt4IFDzAkfjENK6QcFI_VpwCLcBGAsYHQ/w436-h640/control%2Bsignal.png" width="436" /></a></div><p style="text-align: left;"><br /><a href="https://www.blogger.com/null" id="metisengines"></a></p><h3 style="text-align: left;"><span style="font-size: large;">ENGINES</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-wjPoWHEndYk/YPO-lnsnwQI/AAAAAAAAT9s/4PLphy9gbpIHRD3vhHS1LgfaxP8C8w1yQCLcBGAsYHQ/s2048/rocket%2Bengine.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1133" data-original-width="2048" height="354" src="https://1.bp.blogspot.com/-wjPoWHEndYk/YPO-lnsnwQI/AAAAAAAAT9s/4PLphy9gbpIHRD3vhHS1LgfaxP8C8w1yQCLcBGAsYHQ/w640-h354/rocket%2Bengine.png" width="640" /></a></div><p style="text-align: left;"><br /></p><p style="text-align: left;">In the technical manual for the missile, both the launch and the flight engines are considered to be structurally combined as a single engine assembly. Missile launch is accomplished with the 9Kh916 rocket engine, attached to the end of the 9Kh917 dual-thrust rocket engine. Both have a casing made from 30KhGSA structural steel. The launch engine is started 0.38-0.46 seconds after the launcher is powered up by the T-457 thermal battery.</p><p style="text-align: left;">The launch engine is analogous to the engines of light disposable grenade launchers, not just in function, but also in general constructional and operational details such as the use of a steel chamber casing, and a burn time that is short enough to ensure in-tube engine burnout. The thin walls of the casing functions as a lightweight tail boom for the missile wings. In total, the entire engine assembly weighs 1 kg. Its chamber has a maximum diameter of 71mm and the complete engine measures 200mm in length.</p><p style="text-align: left;">Its fuel is 225 grams of homogeneous (single base) nitrocellulose propellant. It consists of single-channel tubes of 7/1 TR V/A nitrocellulose propellant. The same propellant is used in the RPG-22 "Netto". The designation of 7/1 TR means that it is a single-channel grain with a burning arch of 0.7mm, TR means that it is in tubular form (rather than granulated powder), and V/A indicates that it is a highly nitrated variant of the compound. This type of propellant is among the simplest forms of solid rocket propellant for practical use, being cheap, easy to produce and safe, but has a relatively modest specific impulse of 1,880 N.s/kg. For comparison, the launch engine of the LAW series featured a more advanced double base propellant consisting of nitrocellulose and nitroglycerine, producing a higher specific impulse of 2,160 N.s/kg, allowing more weight savings to be made.</p><p style="text-align: left;">The engine produces a thrust of 75 kN with a burn time of 10 ms. It develops a peak chamber pressure of 48 MPa. Due to the use of an integrated rocket engine, full dynamic equilibrium is achieved along the momentum flow curve, so the launch of the missile is truly recoilless. This was indirectly responsible for some weight savings, as the containerized missile could be mounted directly onto the 9P151 launcher unit rather than onto a separate buffered guide rail. </p><p style="text-align: left;">The rear end of the engine is capped with a nozzle block consisting of an annular bank of six nozzles, and the 9Kh284 electric ignition mechanism in the center, which is connected to the external T-457 thermal battery via positive and negative leads. When firing the missile, the launch signal arriving to the 9Kh284 device sets off the 9Kh290-1 ignition charge, a simple black powder booster, that will, in turn, ignite the propellant charge. The missile is then launched at a velocity of 90 m/s. During launch, the front cover is popped open but the rear cover is not, so when the ejection engine starts, the rear cover is blown off by the rocket exhaust. </p><p style="text-align: left;"><br /></p><p style="text-align: left;">Once the launch engine burns out, it ignites the 9Kh287 pyrotechnic delayed igniter for the 9Kh917 engine. The delayed igniter sets off the 9Kh291-1 black powder ignition charge after a short delay, long enough to ensure the engine is at least 10 meters ahead of its container when it starts up. To ensure the non-interference of the engine exhaust on the wings, the engine has three nozzles arranged concentrically to blow between the three wings. The nozzles are angled by 8.5 degrees to impart and maintain the spin rate of the missile.</p><p style="text-align: left;">566 grams of propellant is carried in the engine. In the boost stage, it produces a thrust of 240 N for 1.9 seconds, and in the sustainer stage, which lasts for 3.4 seconds, it produces 85 N. The maximum speed reached by the 9M116, presumably at a temperature of +50°C, is 223 m/s. The missile travels to its maximum range of 1,000 meters in 5.6 seconds, giving an average speed of 180 m/s. As the total burn time of the engine is 5.3 seconds, it can be seen that the missile is propelled almost throughout its entire flight. </p><p style="text-align: left;"><br /><a href="https://www.blogger.com/null" id="metiswarhead"></a></p><h3 style="text-align: left;"><span style="font-size: large;">WARHEAD</span></h3><p style="text-align: center;"><a href="https://1.bp.blogspot.com/-2JmMhxXEMEA/YOjHlcyG3gI/AAAAAAAAT0A/ATm6CBalx3wJ2M_lLHz-N5L7WePkNGpMgCLcBGAsYHQ/s2048/9n135.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1151" data-original-width="2048" height="360" src="https://1.bp.blogspot.com/-2JmMhxXEMEA/YOjHlcyG3gI/AAAAAAAAT0A/ATm6CBalx3wJ2M_lLHz-N5L7WePkNGpMgCLcBGAsYHQ/w640-h360/9n135.png" width="640" /></a></p><p style="text-align: left;">The 9M116 missile contains the 9N135 warhead which shares an identical design with the 9E243M of the 9M111M "Faktoriya". Its salient features, including its shape and its contact fuze, have already been discussed previously, so the only detail left to explore is the specific design of its 9E132 capacitor fuze, which differs significantly from the 9E243M of the 9N122M. </p><p style="text-align: left;">The primary difference between the 9E132 and the 9E243M in "Faktoriya" is the power source for the capacitors. Because power is delivered to the "Metis" via the two-core wire link, the wiring for the arming and capacitor circuits changed accordingly. Once the inertial arming switch is closed after the missile is launched out of its container and begins decelerating from air resistance, the fuze charging circuit is closed and a current begins to flow into it via the command wire. At the same time, the pyrotechnic arming charge is ignited, and once it burns out, it mechanically shifts the electric detonator inside the ED-DD electric detonator to align with the booster charge behind the warhead. This closes the firing train and in this condition, the ED-DD electric detonator can set off the warhead. The burnout of the arming charge also ignites the pyrotechnic self-destruct fuze. The self-destruct has a timed delay of 10 seconds.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-XWo0Lw3St_4/YPDQn0HkiII/AAAAAAAAT7k/T7RxrWFYVQUeBLxOxN35olPufGZSbM58gCLcBGAsYHQ/s2048/fuze%2Bcircuit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="2048" height="338" src="https://1.bp.blogspot.com/-XWo0Lw3St_4/YPDQn0HkiII/AAAAAAAAT7k/T7RxrWFYVQUeBLxOxN35olPufGZSbM58gCLcBGAsYHQ/w640-h338/fuze%2Bcircuit.png" width="640" /></a></div><p style="text-align: left;">Charging of the capacitor fuze occurs in the 0.25-0.38 second delay between the launch of the missile and the commencement of operator control. During this time, the launcher automatically executes a special program to keep the missile from plummeting to the ground by sending a persistent pitch-up signal, which increases the angle of attack of the missile and thus provides more lift. The pitch-up signals arriving from the launcher are used as the power source to charge the fuze. To accomplish the task of charging the capacitors, the voltage must be converted from the pulse width modulated AC signal into a DC voltage, before it can then be applied across the capacitors. This function is fulfilled by a voltage multiplier circuit, or more exactly, a voltage doubler, consisting of two diodes (D1, D2) and two capacitors (C1, C2). A voltage doubler is a form of rectifier which takes an AC voltage as the input and outputs a doubled DC voltage.</p><p style="text-align: left;">The doubled DC voltage is used to charge two capacitors, C3 and C4, which are arranged in parallel to increase the total charge to the sum of both individual capacitors. This was necessary due to the weak current in the control signals used to power the circuit, so more capacitors are needed to accumulate the necessary amount of charge to activate the fuze. Capacitors C3 and C4 are thus charged to twice the voltage of the control signals. Once charged, the ED-DD electric detonator is considered armed. The missile will be armed at 15-40 meters ahead of the container. Once the outer contact plate in front of the warhead is crushed inward and touches the inner contact plate, the detonator circuit is closed, and all four capacitors discharge simultaneously into the ED-DD electric detonator. The warhead is thus detonated. </p><p>In the textbook "<i>Конструкция Средств Поражения, Боеприпасов, Взрывателей И Систем Управления Средствами Поражения: Конструкция И Функционирование ПТУР</i>", the "Metis" is credited with a penetration of 460mm, the same as the "Faktoriya". </p><p>More dated Russian literature sources from the 1990's credit the "Metis" with a penetration of either 500mm or 550mm. According to Rostislav Angelskiy in the book "<i>Отечественные противотанковые комплексы</i>", the penetration of the "Metis" is 550mm. The encyclopedia "<i>Боеприпасы И Средства Поражения: Энциклопедия XXI век</i>" also credits the "Metis" with 550mm of penetration. In "<i>ПТУР сухопутных войск</i>" by G.N. Dimitriev, a penetration of 500mm is reported.</p><p style="text-align: left;"><br /></p></div>Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com6tag:blogger.com,1999:blog-3103574899092646031.post-59576252477870928672020-12-27T22:39:00.398-08:002024-02-15T17:01:00.679-08:00Soviet Towed Anti-Tank Guns<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jFs3u7C1Np4/X-yO5Mo8w9I/AAAAAAAASkQ/M-rPiL0u7DkHz-lNr-fNRxmxW6Qrl-zgQCLcBGAsYHQ/s2048/mt-lb%2Btowing%2BMT-12%2Bguns.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1845" height="640" src="https://1.bp.blogspot.com/-jFs3u7C1Np4/X-yO5Mo8w9I/AAAAAAAASkQ/M-rPiL0u7DkHz-lNr-fNRxmxW6Qrl-zgQCLcBGAsYHQ/w576-h640/mt-lb%2Btowing%2BMT-12%2Bguns.png" width="576" /></a></div><div><br /></div><div><br /></div><div><div>The Soviet Union continued to develop and use anti-tank guns long after the concept was deemed obsolete and subsequently abandoned by other major military powers. This seems appropriate as the USSR was among the first to adopt this class of weapon, and their capabilities were greatly appreciated during the Spanish Civil War and in the Great Patriotic War.</div><div><br /></div><div>The first Soviet towed anti-tank gun, the 37mm M1930, was a refinement of the 3.7cm Pak L/45 gun design carried out by the Rheinmetall company under a contract from the Soviet state as part of a large technological transfer programme that included the purchase of a dozen Pak L/45 guns. The technical documentation and the necessary machine tools to build the gun were transferred to the No. 8 factory, where the M1930 began to be mass-produced in 1931 under the factory index of 1-K. This was the first step taken to build up the technical expertise needed to form a domestic anti-tank artillery industry.</div><div><br />The original 3.7cm Pak L/45 was the latest and most advanced gun of its type, not only in Germany but also abroad. It was designed in total secrecy in Germany and began low-rate production in 1929, preceding both the French 25mm mle 1934 and the British 2-pdr. In its native country, it was not further developed until 1934 when political changes prompted the rearmament of Germany to further accelerate, but in the USSR, Soviet engineers began improving the M1930 gun as soon as mass production had been officially established. A new 45mm gun was designed on its basis by swapping out the barrel and modifying the breech assembly. The carriage was also improved. The upgraded product, bearing the factory index of 19-K, entered service in 1932 as the M1932. This was the first major divergence from the original 3.7cm Pak L/45 design, and with it, the USSR effectively leapfrogged the British and French in anti-tank artillery development - at least on paper. </div><div><br /></div><div>The mass production of the gun proceeded badly due to a critical shortage of trained workers and the immaturity of the industry, which was further exacerbated by the intensely ideological nature of the state. After the situation was rectified in 1933, an effort was launched to upgrade the gun in 1934 by replacing the wooden carriage wheels with pneumatic ones and improving the traverse mechanism. These improvements culminated in the adoption of the M1937 gun, the definitive model which served in the Red Army at the outbreak of the so-called Great Patriotic War. Compared to the original 3.7cm gun, it was easier to mass-produce, had considerably better mobility, and its firepower was enhanced by its ability to fire much more powerful ammunition, both in terms of armour penetration power and in anti-personnel capabilities owing to its vastly more powerful fragmentation and canister rounds. It was, arguably, the best in its class in the world.</div><div><br /></div><div>More importantly, however, the efforts leading to the creation of the M1937 catalyzed the rapid maturation of the anti-tank artillery industry. By the start of WWII, the industry was capable of designing original anti-tank artillery pieces from scratch that could rival the quality and capabilities of foreign designs, and organize the mass production of such guns in optimized assembly line factories that enabled huge quantities of high-quality guns to be built. The ZiS-2 is a prime example, being a completely original Soviet counterpart to the 5cm Pak 38 and 6-pdr guns from same time period.</div></div><div><br /></div><div><br /></div><div><div>It is perhaps worth noting that the development cycle of Soviet towed and self-propelled anti-tank guns, divisional guns and tank guns were usually created in separate parallel projects utilizing the same ammunition and sharing the same ballistics, and were often based on existing anti-aircraft or naval guns, as these roles required high ballistic performance. The two most notable examples are the 85mm and 100mm tank guns used in the later half of the Great Patriotic War. On April 15, 1943, the State Defense Committee issued a decree on strengthening the anti-tank defense of the ground forces, leading to an intense effort to place guns of increased power into service. The ballistics of the 85mm mod. 1939 (52-K) anti-aircraft gun were used as the basis for the 85mm D-5 gun borne out of this decree, which entered service very soon afterward in 1943 on tanks and self-propelled guns, but the order to develop a towed 85mm divisional field gun featuring the same ballistics was only issued in 1944 to replace the ZiS-3, later resulting in the D-44. The D-44 had nothing to do with the D-5, being a clean-sheet design, and the D-5 itself also shared nothing with the 52-K gun other than the cartridge and ballistics, having a completely new design and being assembled from proprietary parts This was essentially the same developmental trajectory as towed and self-propelled gun systems in the U.S, Britain and to some extent, Germany. This is exemplified by the towed 3-inch M5 and the self-propelled 3-inch M7 (on the M10) which were created from the ballistics of the M3 anti-aircraft gun, or the 8.8cm KwK 36 which was created from the ballistics of the FlaK 18 anti-aircraft gun. </div><div><br /></div><div>Similarly, the 100mm D10 tank gun entered service in July 1944, followed by the 100mm BS-3 field gun a month later, and then the KS-19 anti-aircraft gun after the war. These three guns shared nothing in common other than the ballistics, which were inherited from the B-24BM (1939) 56-caliber 100mm naval gun.</div></div><div><br /></div><div><br /></div><div>In the aftermath of the Second World War, the appreciation of the value of anti-tank guns led to the continuation of anti-tank gun projects for both the ground forces and airborne forces. A myriad of systems were created, ranging from the basic towed variety to self-moving (SD-44) and self-propelled (ASU-57, SU-85) anti-tank guns. In this article, the following postwar artillery pieces will be examined in chronological order with a heavy emphasis on the context of their use:</div><div><div><div><br /></div><div><ol style="text-align: left;"><li>D-44 divisional gun (GAU index 52-P-367)</li><li>D-48 anti-tank gun (GAU index 52-P-372)</li><li>T-12 anti-tank gun (GRAU index 2A19) </li><li>MT-12 anti-tank gun (GRAU index 2A29)</li></ol></div><div><br /></div><div>The 125mm Sprut-B gun entered service in the Soviet Army, but only in name. It was never procured in any meaningful numbers quantity and was never a serious part of the arsenal. As such, it is not covered in this article. Its self-propelled counterpart, the Sprut-SD, was somewhat more successful, but due to its self-propelled nature, it is also beyond the scope of this article.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">INDEX</span></h3><div><br /></div><hr /><div><ol style="text-align: left;">
<li><a href="#intro">Introduction</a></li>
<li><a href="#design-challenges">Design Challenges</a></li>
<li><a href="#basic">Basic Organization</a></li>
<li><a href="#common">Common Features</a></li>
<li><a href="#common-gun">Recoil Devices</a></li>
<li><a href="#common-carriage">Carriages</a></li>
<li><a href="#common-protection">Protection</a></li>
<li><a href="#gunshield">Gunshield</a></li>
<li><a href="#direct-protection">Direct Fire Protection</a></li>
<hr />
<li><a href="#d44">D-44</a></li>
<li><a href="#d44-deployment">Deployment</a></li>
<li><a href="#d44-mobility">Mobility</a></li>
<li><a href="#d44-carriage">Carriage</a></li>
<li><a href="#d44-protection">Protection</a></li>
<li><a href="#d44-sighting">Fire control</a></li>
<li><a href="#d44-gun">Gun</a></li>
<li><a href="#d44-ammo">Ammunition</a></li>
<hr />
<li><a href="#d48">D-48</a></li>
<li><a href="#d48-deployment">Deployment</a></li>
<li><a href="#d48-mobility">Mobility</a></li>
<li><a href="#d48-carriage">Carriage</a></li>
<li><a href="#d48-protection">Protection</a></li>
<li><a href="#d48-sighting">Fire control</a></li>
<li><a href="#d48-gun">Gun</a></li>
<li><a href="#d48-ammo">Ammunition</a></li>
<hr />
<li><a href="#t12-mt12">T-12, MT-12</a></li>
<li><a href="#mt12-deployment">Deployment</a></li>
<li><a href="#mt12-mobility">Mobility</a></li>
<li><a href="#mt12-carriage">Carriage</a></li>
<li><a href="#mt12-protection">Protection</a></li>
<li><a href="#mt12-sighting">Fire control</a></li>
<li><a href="#mt12-gun">Gun</a></li>
<li><a href="#mt12-ammo">Ammunition</a></li>
</ol>
</div><hr /><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="intro"></a><h3 style="text-align: left;"><span style="font-size: large;">INTRODUCTION</span></h3></div><div><div><br /></div><div>The <a href="https://ru.wikipedia.org/wiki/%D0%98%D0%BD%D0%B4%D0%B5%D0%BA%D1%81_%D0%93%D0%A0%D0%90%D0%A3">GAU classification system for artillery pieces</a> was fairly clear and straightforward, assigning a unique identity for each new design. Firstly, the designation of all artillery pieces would be given a "52" prefix, as Category 52 of the GAU index was reserved for artillery. This would be followed by a "P", denoting a gun. The following digits serve as both a categorization and identification number for the product, the first digit being an indicator of its class of caliber and the following digits being a major and minor number to indicate the firepower group and caliber group number of the cannon. According to the textbook "<i>Индексация и маркировка боеприпасов артиллерии</i>" (<i>Indexation and marking of artillery ammunition</i>), classes 1-7 for conventional guns represent the following calibers: </div><div><div><br /></div><div></div><blockquote><div>Class 1: 20-40mm caliber</div><div>Class 2: 40-60mm caliber</div><div>Class 3: 60-100mm caliber</div><div>Class 4: 100-150mm caliber</div><div>Class 5: 150-200mm caliber</div>Class 6: 200-300mm caliber<div>Class 7: 300mm caliber and above</div></blockquote><div><br /></div><div>Knowing this, the meaning of the 52-P-367 and 52-P-372 indexes can be deciphered easily. It is a gun in caliber class 3, firepower group 6, weapon number 7. For instance, the 52-P-367 (D-44) was preceded by the 52-P-366, which was the 85mm KS-1 anti-aircraft gun from 1944.</div><div><br /></div><div>Artillery ammunition - denoted by the "53" prefix and an abbreviation of their type - built for the guns listed in this index were assigned the same categorization number. For example, the 53-BR-412 shell was named according to the index of the BS-3 field gun (52-P-412), the 53-BR-413D shell was named according to the index of the D54 tank gun (52-P-413), and the 53-BR-415 shell was named according to the index of the KS-19 anti-aircraft gun (52-P-415). All three were Class 4 guns, having a caliber of 100mm, were rifled, and had high ballistics. As such, they belonged to the same firepower group, and the different caliber group numbers serve to distinguish between different ammunition, ensuring that they are only used in the appropriate guns. Caliber group '0' for a projectile indicates that the projectile can be used with all guns of the same caliber.</div></div><div><br /></div><div>In 1956, a new index was introduced to accommodate the ever-increasing quantity of new weapon systems, including rocket-based systems. The directorate itself was renamed from GAU to GRAU, with the 'R' standing for "Rocket". Unlike the old GAU index, the numbering system of the new index served only as an identification number and could not give away any useful details whatsoever on the nature of the weapon, thus better preserving secrecy. The T-12 anti-tank gun was named the 2A19 under this index, with "2A" denoting that it is a gun (or howitzer or fireworks launcher) and the number 19 simply identifying it as the 19th system to be indexed.</div><div><br /></div><div><br /></div><div><div>The artillery pieces discussed in this article can all be categorized as "quick-firing" guns, although this is an antiquated term that only remained in use almost exclusively in the British military and in its former colonies. This term was not used in the USSR, even in manuals printed for British anti-tank guns supplied through Lend-Lease. In "<i><a href="https://www.vancouvergunners.ca/uploads/2/5/3/2/25322670/handbookofartillery.pdf">Handbook of artillery: including mobile, anti-aircraft and trench matériel</a></i>", it is stated that the main distinguishing feature of a "quick-firing" gun is that its carriage is not shifted by recoil when firing. Instead, the gun recoils on the carriage and is automatically returned to battery by a recoil mechanism. Other features may contribute to the rate of fire of a gun, but do not constitute their identifying characteristics. </div><div><br /></div><div>All of the guns examined in this article are field guns, with divisional and anti-tank guns belonging to subcategories of field artillery. According to the Soviet definition, the structure of a towed gun can be divided into three main parts: The gun tube, the recoil mechanism, and the carriage.</div><div><br /></div><div><ol><li>The gun tube ("ствол") is the gun barrel together with a muzzle brake and the breech. </li><li>The recoil mechanism includes the hydraulic buffer and hydropneumatic recuperator installed to the gun tube, forming the complete gun. </li><li>The carriage consists of the suspension, the crossbeam serving as a chassis for the suspension, and the two carriage trails. </li></ol></div><div><br /></div><div>Anti-tank guns are a type of field gun but can be readily identified by being readily concealable and having high ballistic performance, typically superior to the field guns and howitzers. </div></div></div><div><br /></div><div>When a rapid deployment in open terrain is necessary, the prime mover tows the gun to the chosen position and the crew disembarks to decouple the gun and set it up. The driver conceals the prime mover a short distance away, then joins the gun crew as an ammunition handler.</div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="design-challenges"></a><h3 style="text-align: left;"><span style="font-size: large;">DESIGN CHALLENGES</span></h3><div><br /></div><div>Although an increase in firepower is always desirable, the successful use of towed anti-tank guns in battle was conditional on their concealability and their mobility. As the demands on the firepower of a gun increase, the task of balancing the design priorities becomes ever more challenging. Achieving a further increase in firepower with purely conventional means inevitably leads to a further increase in the size of the weapon. Generally speaking, the enormous weight of the anti-tank guns deemed powerful enough to deal with modern threats by the latter half of World War II drove the desire to mount guns onto low-cost vehicles to create self-propelled tank destroyers. However, with the exception of the U.S Army in 1944, tank destroyers never completely replaced towed guns for the major military powers, if not because of the advantages of towed guns, then simply because it was more expedient to build them in large numbers. </div><div><div><br />The USSR was somewhat unusual as they continued to pursue the development of new anti-tank guns throughout the Cold War. Although such guns proved to be the most effective anti-tank weapon on both the Western and Eastern fronts, the increased emphasis on mechanized warfare and the improved armour protection of late war tanks made it doubtful that anti-tank guns could remain small enough to be easily hidden - which was one of their primary advantages - yet powerful enough to handle the new generation of tanks.</div><div><br /></div><div><div>As a rule, postwar Soviet anti-tank guns were exceedingly lightweight, but even so, the necessity of a large caliber to fight modern tanks left no allowances for lightening the weapon to the extent of matching the portability of the infantry crew-served guns like the 45mm M-42.</div><div><br /></div><div>Initially, light towed anti-tank guns were proven and were still viable as wartime tanks were still far from being phased out. For this reason, the 57mm ZiS-2 continued production after the war until 1949, when production finally ended with 3,500 guns delivered from 1946 to 1949. Its continued production was necessary to fully displace all 45mm M-42 guns, which had fallen into total obsolescence by the end of the war and was being pulled from active units to enter long term storage or to be distributed to friendly states as military aid. A similar state of affairs transpired abroad, with equivalent guns such as the British 6-pdr continuing to serve in its original role until it was finally deemed obsolete and pulled out of service in July 1960.</div><div><br /></div><div>Meanwhile, the hand grenades and PTRD rifles of the individual anti-tank soldier were replaced with the RKG-3 and RPG-2 respectively. All of these light weapons were only effective out to a range of several hundred meters, though not because of a decline in armour penetration power at long ranges as with a closed-breech gun, but because of a rapidly diminishing probability of hit. In any case, the effective range of the battalion-level weapons did not deteriorate.</div></div><div><br /></div><div><div>Towed crew-served recoilless guns were widely adopted among the major military powers as a promising replacement for conventional towed anti-tank guns such as the ZiS-2, but they were not a panacea. In the Soviet Army, light anti-tank guns were pulled from high priority units throughout the 1950's beginning with the introduction of the SPG-82 in 1950. In 1954, the 82mm B-10 and 107mm B-11 recoilless guns entered service and took over the role of battalion and regimental-level anti-tank artillery respectively, then they were in turn replaced by the SPG-9 in 1962, which became the definitive weapon of its type for the remainder of the Cold War. </div><div><br /></div><div>Even so, there was no recoilless weapon capable of the same ballistic characteristics of a towed gun, presumably because the backblast would be so immensely powerful that it would be impractical. In the USSR, the trend for recoilless guns was to reduce size and weight by reducing the caliver, increasing mobility, while also improving the firepower by using more sophisticated shaped charge technology and by implementing rocket assisted grenades. The Soviet Army did not pursue the creation of recoilless guns large and powerful enough to replace the likes of the D-48 or T-12, and quite rightly so. Rather, guided missiles were explored.</div></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="foreign"></a><h3 style="text-align: left;"><span style="font-size: large;">FOREIGN DEVELOPMENTS</span></h3><div><br />Abroad, experimental anti-tank guns built to meet these conflicting requirements invariably ended in failure. At the end of WWII, both the U.S and Britain had ongoing projects to meet the requirement for high-powered towed guns, the U.S with their 90mm development programme, which evolved to create the 105mm T8 gun, and the British with their 94mm 32-pdr gun.<br /><br />The only 90mm towed anti-tank gun to enter service and serial production in the U.S was the T8 gun, which entered service as the M26 gun on the M18 carriage. The gun was tall, but even worse was its enormous weight which reached an absurd level for a gun with only slightly greater muzzle energy than Soviet 85mm D-44 divisional gun and the German 8.8cm Flak guns. On page 41 of the book "<i>US Anti-tank Artillery 1941–45</i>" by Steven J. Zaloga, the weight of the 90mm gun when standardized as the M26 gun on the M18 carriage is reported to be 3,515 kg. The image below, taken from the book, shows the 90mm M26 gun. Its enormous weight may be related to its lack of a muzzle brake, a trait it shared with the 76.2mm M5 anti-tank gun which also had a preposterously high combat weight of 2,211 kg, far greater than the ballistically equivalent 75mm Pak 40 which weighed just 1,425 kg. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-q95tJrP1EHI/X5PAbOcB25I/AAAAAAAARzQ/5oRq8TEAGAYowT9k2IyvzXUbiHQCCcRQQCLcBGAsYHQ/s2048/m26%2Bgun%2Bon%2Bm18%2Bcarriage.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1289" data-original-width="2048" height="251" src="https://1.bp.blogspot.com/-q95tJrP1EHI/X5PAbOcB25I/AAAAAAAARzQ/5oRq8TEAGAYowT9k2IyvzXUbiHQCCcRQQCLcBGAsYHQ/w400-h251/m26%2Bgun%2Bon%2Bm18%2Bcarriage.png" width="400" /></a><br /></div><div><br /></div><div><br /></div><div>Ultimately, this line of development was doomed by the fact that something with markedly greater firepower - and hence, even bulkier and heavier - was needed to deal with the new German Tiger II and Jagdtiger emerging in 1944. This task was to be handled by the even more powerful 105mm T8 gun, which was prototyped in 1944 and continued development until 1946, when, after tests in February of that year, the project was ended. The T8 weighed a whopping 8 tons, or around 7.2 metric tons.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-KK2AnU9cnFQ/X5gagIf_DpI/AAAAAAAAR0o/RY3URGLU9i00SaP9-IhcZZIgyHbsHT9tACLcBGAsYHQ/s1311/105mm%2Bt8.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1311" height="390" src="https://1.bp.blogspot.com/-KK2AnU9cnFQ/X5gagIf_DpI/AAAAAAAAR0o/RY3URGLU9i00SaP9-IhcZZIgyHbsHT9tACLcBGAsYHQ/w640-h390/105mm%2Bt8.png" width="640" /></a><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-n0Ba26e2ows/X5gcA3pJsiI/AAAAAAAAR0w/3pkrZ67bFPgWtIeU2M_9Yheh6fMZ9O7ZwCLcBGAsYHQ/s1865/105mmT8.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="554" data-original-width="1865" height="190" src="https://1.bp.blogspot.com/-n0Ba26e2ows/X5gcA3pJsiI/AAAAAAAAR0w/3pkrZ67bFPgWtIeU2M_9Yheh6fMZ9O7ZwCLcBGAsYHQ/w640-h190/105mmT8.png" width="640" /></a></div></div><div><br /></div><div><br /></div><div>The reticence to put new towed anti-tank guns into service was also strongly influenced by the high losses of towed guns in the ETO compared to self-propelled tank destroyers, which drove the replacement of all towed guns in tank destroyer battalions to self-propelled tank destroyers in 1945. Given that the technological limit of this class of weapon had been reached and no future prospects were identified, it is rather unsurprising that the War Department Equipment Board concluded in their study of towed anti-tank guns in May 1946 that "<i>There should be no further development of towed anti-tank guns</i>", thus effectively ending all development of this class of weapon in the U.S. </div><div><br /></div><div><br /></div><div>In the U.K, the difficulties in making the 17-pdr a viable weapon were already quite acute on their own. Developing a replacement that could handle future threats was a monumental task that proved to be insurmountable. The primary issue was the same that plagued the 17-pdr: mobility.</div><div><br /></div><div>The first 150 examples of the 17-pdr were hybrids, consisting of the 17-pdr gun mounted onto the Mk. I carriage of the 25-pdr gun-howitzer. This model was known as the 17/25-pdr gun. It was an intermediate solution to deal with the problem of Tiger tanks in North Africa and brought a number of serious drawbacks. Firstly, though it was relatively light (2,097 kg) and could conduct all-round fire, the gun had practically no traverse arc if used without its rotary firing platform which required preparations to be deployed beforehand. It was also very tall, which was wholly undesirable for an anti-tank gun. As such, the definitive 17-pdr model, the Mk. I, was equipped with a conventional split-trail carriage. However, this gun was unreasonably heavy, having an in-action weight of 2,957 kg (6,520 lbs) or just under 3 tons. This made it extremely challenging for the 7-man crew to manhandle the gun even for short distances, except on paved surfaces.</div><div><br /></div><div>The successor to the 17-pdr Mk. I was to be the 94mm 32-pdr gun. The first attempted solution was to convert the existing 3.7-inch AA gun by mounting it to a more suitable carriage, but the resulting gun and carriage were "monstrously large", as described by Chris Henry in "<i>British Anti-Tank Artillery 1939-45</i>". Two new proprietary carriages were designed for the new gun, complete with proprietary recoil systems and muzzle brakes, but the war ended before the project could be completed. In September 1945, the General Staff declared that there was no longer any requirement for the weapon, effectively ending the further development of not only the 32-pdr itself, but towed anti-tank guns as a whole. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-x8pEQTA8iK0/X6VWMXxvajI/AAAAAAAASCc/BNdM1trex_UPgucXdVkfmp0wV3_66BCKACLcBGAsYHQ/s2558/32-pdr%2Bside%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="971" data-original-width="2558" height="242" src="https://1.bp.blogspot.com/-x8pEQTA8iK0/X6VWMXxvajI/AAAAAAAASCc/BNdM1trex_UPgucXdVkfmp0wV3_66BCKACLcBGAsYHQ/w640-h242/32-pdr%2Bside%2Bview.png" width="640" /></a></div><div><br /></div><div><br /></div><div>As the project was never completed, there is no fixed data on the weight of the 32-pdr gun. However, Ian Hogg states in the book "<i>Allied Artillery of World War Two</i>" that the barrel alone would have weighed 2.5 tons, and that the towed equipment (the entire system) would have had a sensational weight of close to 10 tons, presumably short tons (9 metric tons), far surpassing the weight of even the largest 6-inch heavy guns. Naturally, this made it effectively impossible to move the 32-pdr without the use of a heavy prime mover such as the AEC Matador or Scammell Pioneer. In the photo below, the size of the 32-pdr next to the BL 5.5-inch medium gun (6.19 tons) lends credibility to Hogg's estimation of its 9-ton weight. If correct, Hogg's estimation of the system weight implies an extraordinarily inefficient design, bordering on sabotage. The design of the gun mount and shield in particular is highly suspect, inexplicably having a shape and size that is reminiscent of a naval gun turret. It is especially perplexing that so much trouble arose despite the 32-pdr being a smaller, less powerful gun compared to the Soviet 100mm BS-3 field gun.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Q2ct6St_1T8/X5gSwH6xTqI/AAAAAAAAR0c/Px12ViLKlF8Bv_3LOzUe7DTpttHJ9wQkACLcBGAsYHQ/s1082/32-pdr.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="730" data-original-width="1082" height="270" src="https://1.bp.blogspot.com/-Q2ct6St_1T8/X5gSwH6xTqI/AAAAAAAAR0c/Px12ViLKlF8Bv_3LOzUe7DTpttHJ9wQkACLcBGAsYHQ/w400-h270/32-pdr.png" width="400" /></a></div><div><br /></div><div><br /></div><div>Without a replacement, the 17-pdr continued serving through the Korean War era, predominantly organized under the Royal Artillery anti-tank regiments but also as individual batteries allocated to support an infantry battalion.</div><div><br /></div><div>Though the intended successors to the 17-pdr and the M5 ended in failure, their obsolesence was still evident and the need for replacements remained. To fill this niche, large caliber crew-served recoilless rifles were developed to provide the necessary mobility for the guns to closely support small infantry units. In the U.S, the 105mm M27 recoilless gun entered service in 1952 to replace the 57mm M1 and 3-inch M5 guns under the Battalion Anti-Tank (BAT) weapon programme, followed by the 106mm M40 gun under the same programme in 1955. In Britain, the crew-served 120mm L1 BAT entered service in 1953 to replace the 17-pdr. Both developments shared the same design goals and were intended to fulfill the same tactical objectives.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-PFWBLAd0eVM/X5lcSKHAnRI/AAAAAAAAR2U/BbsvXT_tB6wL1hVNkq9dn60cxwVNtiioACLcBGAsYHQ/s489/120mm%2Bbat.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="272" data-original-width="489" src="https://1.bp.blogspot.com/-PFWBLAd0eVM/X5lcSKHAnRI/AAAAAAAAR2U/BbsvXT_tB6wL1hVNkq9dn60cxwVNtiioACLcBGAsYHQ/s16000/120mm%2Bbat.jpg" /></a></div><div><br /></div><div><br /></div><div><div>Self-propelled tank destroyers were one alternative as they could serve as a convenient platform for large, powerful guns that would otherwise be impractical as a towed weapon, but after the conclusion of the war, the conventional tank destroyer concepts were no longer pursued by the U.S, U.K and France. The need for a large gun to defeat enemy heavy tank was to be met with another heavy tank, or heavy gun tank as they were known in the U.S and U.K. The American M103 and British Conqueror heavy tanks were the products of this line of thought, and they would have been joined by the French AMX-50 if it were not for developmental difficulties. All three sported a high powered 120mm gun firing at a velocity in excess of 1,000 m/s, deemed necessary to ensure the defeat of the armour of the Soviet IS-3. In the context of such vigorous demands on firepower, the abandonment of not only towed anti-tank guns but also tank destroyers in favour of recoilless rifles seemed to be a purely pragmatic decision.</div></div><div><br /></div><div>Large caliber recoilless rifles, firing large caliber HEAT or HESH ammunition, appeared to solve the problem of defeating the armour of heavy tanks, but they were far from a panacea. These weapons were only adequate for short range engagements given their low muzzle velocity, and the probability of kill against heavy tanks was not high even within their most effective firing range. </div><div><br /></div><div>The table below, taken from "<a href="https://apps.dtic.mil/sti/pdfs/AD0389304.pdf">Ordnance Engineering Design Handbook - Artillery Ammunition Series - Section 2, Design for Terminal Effects</a>" shows the probability of a firepower kill on a static IS-3 with a salvo of two shots from a 106mm M40 recoilless gun, using its integral spotting rifle to aim. As the table shows, even at a close range of 500 meters and with two aimed shots, a large caliber recoilless rifle had just a 1 in 3 chance of scoring a firepower kill. The maximum effective range of the weapon - where there would be at least a 50% probability of a firepower kill - would perhaps be only around 200-300 meters, contrary to its official maximum effective range being listed as 1,350 meters; that is merely the maximum direct fire range. If rated for a 55% probability of kill, as per the Soviet definition, the effective range may be no more than 200 meters.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-d62F2JBs8N4/X6bM0NuPBtI/AAAAAAAASDo/UfkualyU25IoNR14-e-VZJTKaZVABiv6QCLcBGAsYHQ/s834/105mm%2Bbat.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="715" data-original-width="834" src="https://1.bp.blogspot.com/-d62F2JBs8N4/X6bM0NuPBtI/AAAAAAAASDo/UfkualyU25IoNR14-e-VZJTKaZVABiv6QCLcBGAsYHQ/s320/105mm%2Bbat.png" width="320" /></a></div><div><br /></div><div><br /></div><div>To gain a better sense of perspective, the instruction for Red Army anti-tank artillerymen during the so-called Great Patriotic War was that guns were to open fire on tanks only from a distance of 600-700 meters while howitzers were to open fire from 400 meters. However, given that a heavy tank such as the IS-3 was practically immune to the Pak 43 and even the APDS ammunition of the 17-pdr at such short ranges, the shortcomings of recoilless guns do not seem debilitating.</div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="basic"></a><div><h3 style="text-align: left;"><span style="font-size: large;">BASIC ORGANIZATION</span></h3><div><br /></div><div>The basic structure of Soviet anti-tank artillery fire platoons, batteries, battalions, regiments and brigades was maintained throughout the entire Cold War. The largest unit of anti-tank artillery organic of a motorized infantry division was a battalion.</div><div><br /></div><div><ol style="text-align: left;"><li>A fire platoon consisted of 2 or 3 guns.</li><li>A battery consisted of 2 or 3 fire platoons.</li><li>A battalion consisted of 3 batteries.</li><li>A regiment consisted of 3 battalions.</li></ol></div><div><br /></div><div>The smallest tactical unit was the fire platoon. Individual anti-tank guns were not to be used in isolation. </div><div><br /></div><div>Outside of motor rifle divisions, a regiment of anti-tank guns was integrated at the army level. An anti-tank regiment could operate independently in the form of an army-level reserve defensive force, covering points of the front where there is a danger from tanks, or they can operate within the framework of a motor rifle infantry division, supporting it at such points as may be necessary, and also operating with the supporting tank group.</div><div><br /></div><div>In a sector where there is a danger of a massed tank attack, the regiment can cover a large zone in both width and depth. The battalions would be arranged so that the batteries would be arranged in two echelons. Each battery forms an anti-tank strongpoint within the effective range of the other batteries, and would be positioned to permit mutual support. This creates overlapping fields of fire, and allows neighbouring anti-tank strongpoints to hit the side armour of the tanks if they launch a focused attack on the neighbouring batteries.</div><div><br /></div><div>Soviet artillery divisions also featured a large contingent of anti-tank artillery. Each division would have an anti-tank brigade composed of four anti-tank battalions.</div><div><br /></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="common"></a><h3 style="text-align: left;"><span style="font-size: large;">COMMON FEATURES</span></h3><div><br /></div><div>Some features of practically did not change throughout the evolution of anti-tank guns from the D-44 to the MT-12. These are the gun operating action, its balancing mechanism, its recoil management system, the carriage.</div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="common-gun"></a><h3 style="text-align: left;"><span style="font-size: large;">GUN</span></h3><div><br /></div><div><div>Unlike modern tank guns which have many built-in counterweights such as a powered elevation mechanism, armoured mantlet, and heavy recoil mechanisms to ensure a short recoil stroke within the confines of the turret, the design of a towed anti-tank gun had to prioritize reducing weight to the maximum extent possible. One example of this is the universal preference for implementing equilibrator mechanisms instead of adding steel ballast plates on the breech end to act as counterweights. Even the simplest and heaviest equilibrators could still offer significant weight savings, particularly for large high-powered field guns. Inside armoured vehicles, space is a more important consideration than weight, so ballast is preferred over equilibrators for balancing tank guns.</div><div><br /></div></div><div><br /></div><div>All Soviet towed guns had a vertically sliding breech. According to Soviet engineering manuals, if the bore axis of a tank cannon from the floor of the fighting compartment is lower than 950-1,000mm, a vertically sliding breech should be used, but if the bore axis is higher than that, a horizontally sliding breech should be used. This is because the convenience of ramming a shell through the breech changes depending on the height of the bore in relation to the height of the average loader (170cm). If the height of the bore axis is 950-1,000mm or less, the chamber will below the elbow of a standing man, so a vertically sliding breech is more convenient and it allows a long ramming staff to be used by someone standing behind the gun. This was particularly relevant for field guns given that such artillery often had to conduct indirect fire, as elevating the barrel would lower the breech even further. </div><div><br /></div><div><br /></div><div><div>Being direct fire weapons first and foremost, a large gun elevation arc was not the highest priority for anti-tank guns. The gun elevation limit is intrinsically limited by the bore axis height and the recoil stroke length of the gun. The lower the bore axis and the larger the recoil stroke, the less it will be able to elevate before striking the ground. If the design of the system creates a conflict between these two mutually exclusive specifications, then the elevation limit would always be sacrificed.</div></div><div><br /></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">RECOIL MANAGEMENT</span></h3><div><br /></div><div><br /></div><div><div>All Soviet anti-tank guns featured a muzzle brake as one of the principal recoil absorption mechanisms. In the textbook "<i>Основи Будови Артилерійських Гармат Та Боєприпасiв</i>" (The Basics of Artillery Guns and Ammunition) by A.Y. Derev'yanchuk, it is stated that during its recoil travel, the rearward momentum of the moving parts of the gun are absorbed by four primary mechanisms. As a rule, the distribution of braking forces across these four mechanisms are:</div><div><div><br /></div><div></div><blockquote><div>Friction: 3 - 5%</div><div>Muzzle brake: 25 - 30% </div><div>Recoil recuperator: 10 - 15%</div><div>The recoil buffer: remainder</div></blockquote><div></div></div><div><br /></div><div>It is important to note that this is only a rough generalization. In the textbook "<i>Курс Артиллерии - Книга 4</i>" (Artillery Course - Book 4) from 1947, it is stated that muzzle brakes able to absorb up to 30-40% of the recoil energy are the most common. </div><div><br /></div><div>As noted by Ian Hogg in the book "<i>Allied Artillery of World War Two</i>", anti-tank guns generally use a muzzle brake so as to save weight in the recoil system and carriage and yet still fire as heavy a charge as possible. The ZiS-3 serves as a good example of the utility of muzzle brakes, as it was ballistically identical to its predecessor, the 76.2mm F-22 USV field gun, but was 24% lighter thanks to a more efficient construction and the use of the lightweight carriage of the 57mm ZiS-2 gun. In turn, these changes were made possible partly due to the use of a double baffle muzzle brake which reduced the recoil force by 30%.</div><div><br /></div><div><br /></div><div>The most contentious feature of muzzle brakes is that the blast and gasses directed sideways cause dust and smoke to be raised across a very broad area across the front of the gun, rather than in a relatively restricted forward cone directly in front of the muzzle. With little dust and smoke forward of the muzzle, observation of the target becomes much easier. In fact, a muzzle brake was often used to solve serious obscuration issues, as was the case during the development of the American 90mm M3 tank gun, and it was the driving force behind the addition of a muzzle brake to 76mm guns, leading to the M1A1C variant. </div><div><br /></div><div>On the other hand, the dust and smoke cloud would be more noticeable to the enemy forces being fired upon owing to its great width, potentially enabling quicker return fire, and the visibility of the blasts to enemy air reconnaissance was also a source of consternation. The issue of muzzle blasts and smoke unmasking the position of guns was routinely expressed as a concern in Russian literature covering the development of artillery systems, while obscuration of the target was rarely ever mentioned in any evaluation of guns with muzzle brakes. In fact, the unmasking factor was sometimes cited as a major justification for the rejection of promising tank gun projects. </div><div><div><br /></div></div><div>The drawbacks of muzzle brakes were essentially unavoidable for most of the towed artillery pieces created in the USSR as there were stringent weight requirements, but it was less of an dilemma for tanks, for which guns without muzzle brakes can be viable, though muzzle brakes would occasionally be implemented to shorten the recoil stroke for internal space considerations. For towed anti-tank guns specifically, the tradeoff can be considered - and was considered - worthwhile. That said, the powerful crew-served recoilless rifles replacing towed guns in foreign armies create enormous forward and back blasts by nature of their design. Compared to this, the unmasking factor that muzzle brakes brought to towed guns is perhaps not quite so serious.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">RECOIL MECHANISM</span></h3><div><br /></div><div>Postwar Soviet anti-tank guns, including the three examples presented in this article, use a modified form of the Schneider independent recoil mechanism. Imperial Russia indirectly took part in the creation of this highly influential system by commissioning Schneider to design a howitzer to a set of specifications. The product of this work was the 152 mm howitzer M1910 howitzer, which served as the basis for many future artillery pieces. Moreover, the chosen caliber of 152mm (6 inches or 60 lines) was standardized in Imperial Russia and its legacy endures til this day. </div><div><br /></div><div>As with any other hydraulic recoil buffer, braking is achieved by using a piston to drive the flow of oil through restricted openings so that a large hydraulic resistance impedes the flow, thus absorbing the energy from the recoil of the gun. </div><div><br /></div><div>The entire volume of all three chambers in the buffer were filled with a fixed volume of oil. The flow of oil from the reservoir to the buffer chamber and the piston is regulated by the cross-sectional area of the ring-shaped restrictor bushing between the piston head and the spindle-shaped control rod. The spindle shape of the control rod generates a flow channel with a variable cross-sectional area as the buffer cylinder slides over the piston. The spindle maximizes the bushing area to generate minimum flow resistance during the firing of a shot, then progressively decreases the bushing area to steadily increase the flow resistance during recoil and decelerate the gun, bringing it to a gentle halt. </div><div><br /></div><div>The drawing on the left below is of a hydraulic buffer, and the drawing on the right is of a recuperator. Both were taken from the textbook "Practical Supplement to the School of the Battery Commander" from the Saumur Artillery School, published in 1918 in English for American artillerymen.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-v0cO4hosH9A/X9jm8evieHI/AAAAAAAAScI/XX_sd9X6H_gd7C6UdwVwu4ewfZiF6Bm5QCLcBGAsYHQ/s1237/schneider%2Bbuffer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="569" data-original-width="1237" height="184" src="https://1.bp.blogspot.com/-v0cO4hosH9A/X9jm8evieHI/AAAAAAAAScI/XX_sd9X6H_gd7C6UdwVwu4ewfZiF6Bm5QCLcBGAsYHQ/w400-h184/schneider%2Bbuffer.png" width="400" /></a><a href="https://1.bp.blogspot.com/-M4BNr0JLAhc/X9jm8VwhoZI/AAAAAAAAScM/drt-_cuPFX074N7_sz6hJN_Kvz5z_M5CQCLcBGAsYHQ/s1224/schneider%2Brecuperator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="486" data-original-width="1224" height="159" src="https://1.bp.blogspot.com/-M4BNr0JLAhc/X9jm8VwhoZI/AAAAAAAAScM/drt-_cuPFX074N7_sz6hJN_Kvz5z_M5CQCLcBGAsYHQ/w400-h159/schneider%2Brecuperator.png" width="400" /></a></div><div><br /></div><div><br /></div><div><div>The pistons of both the recuperator and buffer affixed to the immobile gun cradle, while their cylinders, containing large quantities of spindle oil or hydraulic fluid, were affixed to the recoiling gun assemblies. The replenisher tank for the recuperator also recoiled with the gun. This meant that the recoiling mass of the gun could be increased with no actual weight gain for the system as a whole. </div><div><br /></div><div>Increasing the recoiling mass of a gun gives it more inertia, so that it is more inclined to remain motionless while the projectile travels down the bore. This can have a positive effect on shot dispersion to a limited extent. A heavier recoiling mass also possesses favourable recoil dynamics. Due to the conservation of momentum, the forward momentum of a fired projectile and its propellant gasses will impart a rearward momentum of the same magnitude to both a heavy and light gun, but during free recoil, the velocity of the heavy gun will be less. In turn, this reduces the kinetic energy of the moving gun (recoil energy), so that the buffer mechanism generates a smaller reaction force for a given recoil stroke distance, and due to the lower velocity, the braking time is larger which reduces the recoil impulse. In other words, the recoil of the weapon system as a whole is reduced. </div></div><div><br /></div><div><div>The advantages of the Schneider system, as detailed in the textbook "Theory and Design of Recoil Systems and Gun Carriages" by the United States Army Ordnance Department, are as follows:</div></div><div><br /></div><div><div><ol style="text-align: left;"><li>An increased recoiling mass due to the recuperator sleigh containing the cylinders, recoiling with the gun and thereby decreasing the reaction on the carriage.</li><li>The simplicity of the recoil mechanism, especially from a fabrication point of view.</li></ol></div></div><div><br /></div></div><div>The main disadvantage was that the recoil control was achieved with a spindle-shaped control rod of a fixed shape, and hence, shortening the recoil stroke for high angle firing was not possible. This could be a debilitating issue for howitzers, but not for field guns, and it was completely irrelevant for anti-tank guns. </div><div><br /></div><div>A more serious downside was that the weight of the recoil mechanism shifted the center of gravity below the axis of the barrel, stressing the teeth of the elevating rack during recoil. This was easily solved by adding a clutch to the elevating mechanism that would be released by pulling the firing lever, so this layout was used on guns such as the A-19 field gun, ML-20 howitzer, the German Pak 36, IG 37, Pak 38 and Pak 40, just to name a few. On some cannons, this was solved by rearranging the buffer to be directly under the barrel and the recuperator cylinder above the barrel so that the center of gravity is aligned more closely with the bore axis. This layout was used on the ZiS-2, ZiS-3, the American 3-inch M5, and many other field guns and howitzers.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-CxzYS26aD2o/X9jxDToqSVI/AAAAAAAAScY/ijliCklDL7I_WadZbARmykeoi0-5taQUgCLcBGAsYHQ/s700/over%2Band%2Bunder%2Brecoil%2Bmechanism%2Blayout.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="700" data-original-width="529" height="320" src="https://1.bp.blogspot.com/-CxzYS26aD2o/X9jxDToqSVI/AAAAAAAAScY/ijliCklDL7I_WadZbARmykeoi0-5taQUgCLcBGAsYHQ/s320/over%2Band%2Bunder%2Brecoil%2Bmechanism%2Blayout.png" /></a></div><div><br /></div><div><br /></div><div>The summary of the Schneider system given in the "Theory and Design of Recoil Systems and Gun Carriages" textbook was particularly glowing: </div><div><br /></div><div><blockquote><i>On the whole the Schneider recoil system has proved one of the most satisfactory recoil systems used during the late war, being simple to fabricate and thoroughly rugged, due to its simplicity in design</i></blockquote></div><div><br /></div><div>Due to its compelling advantages, and the ease of bypassing or solving its drawbacks, the Schneider recoil system was copied and used in the vast majority of field guns created after WWI by not only the Americans, who were strongly influenced by French artillery practices, but also the Germans, and the Russians (Soviets) and various minor military powers, with the exception of the British.</div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="common-carriage"></a><h3 style="text-align: left;"><span style="font-size: large;">CARRIAGE</span></h3><div><br /></div><div><br /></div><div>A split trail carriage is a type of tripod carriage, as it has three points of contact with the ground. The two wheels constitute one point of contact, and the two trails are another two points of contact. A tripod is ideal for a firing platform because three points always define a plane, so it is inherently stable and a flat surface is not needed. </div><div><br /></div><div>The length of the trails is determined by the power of the gun, the bore axis height from ground level, and the center of gravity of the weapon system. Because the bore axis is above the center of gravity, the recoil of the gun creates a rotational moment around the fixed anchor (spades), thereby causing the weapon to "jump" on its wheels. This issue is particularly problematic for anti-tank guns as they are powerful guns with strong recoil by nature, and direct fire at gun elevation angles of close to zero is the norm. </div><div><br /></div><div>Firing at high elevation angles greatly reduces the rotational moment and thus bypasses the stability issue to a large extent, which is why howitzers can have short trails. For most artillery systems, firing at elevation angles close to zero is uncommon during combat, and as such, the carriages of such artillery systems would be optimized to provide maximum stability at elevation angles much greater than zero. In the textbook "<i>Курс Артиллерии - Книга 4</i>" (Artillery Course - Book 4) from 1947, it is stated that for an anti-tank gun, the minimum elevation angle at which it reaches maximum stability is 0-5 degrees, which is much more demanding than howitzers as they can afford to only reach maximum stability at a minimum angle of 12-15 degrees. </div><div><br /></div><div>To enhance the stability of the system when firing at low or negative gun elevation angles, the distance between the three points of the carriage must be increased. This essentially means having longer trails, and the more powerful the gun, the longer the trails must be. This is undesirable as it adds weight and it increases the length of the weapon, increasing the turning radius of the prime mover and thus complicating maneuvers in built-up environments. A relatively common solution was to have detachable spades, but this only gave a marginal improvement and it also introduced its own share of complications. For these reasons, minimizing the bore axis height is strongly desirable in all field artillery, but particularly for anti-tank guns as it improves their concealability.</div><div><br /></div><div><br /></div><div>Relative to other forms of artillery carriages, the main disadvantage of a split-trail carriage is that it limits the horizontal firing angles to a forward arc, but the desire for all-round fire was nonsensical for anti-tank guns, and other types of carriages brought their own share of drawbacks. </div><div><br /></div><div>For instance, the cruciform firing platform of the 8.8cm Pak 43 permitted all-round fire, but the suspension had to be dismounted for the gun to be deployed. The inability of deployed guns to instantaneously relocate meant that they were often left behind during a tactical retreat or lost to preventable causes. Similarly, a tripod firing platform as found on the D-30 howitzer could give an all-round firing capability and was stable at all firing angles, particularly when staked deeply to the ground, but it lost all mobility once it was deployed. Not only was it was totally impossible to rapidly uproot the gun once it was deployed, converting it to the transport configuration was also futile as the crew had no way of pushing the gun. </div><div><br /></div><div>Conversely, a split-trail carriage permits a modicum of mobility at all times. There was also a great advantage in user friendliness when deploying the gun, as staking a tripod gun platform to the ground is slow and laborious on frozen ground. A gun with a split-trail carriage could dig its own spades into hard ground with the force of its recoil.</div><div><br /></div><div>In general, the firing arc of a gun or a howitzer mounted on a split-trail carriage does not exceed the angle between the trails. The extremes of the arc are invariably reached just before the breech can be traversed directly over the right or left trail. If traversed above one of the trails, a typical gun would be blocked from elevating, or a vertically sliding breech block would not be able to drop down to open. Exceeding the angle between the split trails is to be avoided completely even if the pintle mount technically allows it, as the recoil would generate an abormal stress on the trails.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-06j7WruiIs8/X6bEYrG22eI/AAAAAAAASDg/scdrcDZ3b98sDf4Q3NjWkJ-h-IIuFMxQgCLcBGAsYHQ/s835/split%2Btrail%2Btraverse%2Barc.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="765" data-original-width="835" height="366" src="https://1.bp.blogspot.com/-06j7WruiIs8/X6bEYrG22eI/AAAAAAAASDg/scdrcDZ3b98sDf4Q3NjWkJ-h-IIuFMxQgCLcBGAsYHQ/w400-h366/split%2Btrail%2Btraverse%2Barc.png" width="400" /></a></div><div><br /></div><div><br /></div><div>Unlike foreign carriage designs, the D-44, D-48 and MT-12 carriages had fixed ground spades on each trail, as opposed to the foldable or detacheable spades as found on guns like the Pak 43/41. The rationale is unclear, but it can be inferred that having carriage trails with a single-piece construction with spades permanently welded onto the structure is structurally stronger and more rigid than a comparable design with a hinged spade or removable spade of comparable weight, as there are no joints that require reinforcement.</div><div><br /></div><div><br /></div><div>Though a gun mounted on a split-trail carriage is able to fire without having been dug in beforehand, it is still always desireable to have the spades obstructed on an obstacle to prevent the gun from rolling backwards too far with every shot. The spades prevent the gun from displacing itself this way by digging themselves into the ground with the recoil of each shot. Furthermore, the stability of the gun can be enhanced by entrenching it. This is done by pushing the wheels into pits dug in the ground, then burying the spades and part of the trails into the ground. Chocks can also be placed behind the wheels. This virtually eliminates movement during recoil, and also lowers the profile of the gun. Hand spades are provided as part of the pioneering tool kit of each gun, and the chocks can be any debris found on the site.</div><div><br /></div><div>As a rule, when preparing a temporary gun emplacement, the spades on each carriage trail should be dug-in before firing to ensure that the recoil of the first shot does not displace the gun rearward. When the crew needs to rapidly move the gun out of its firing position, they can push it forward a short distance to pull the spades out of the ground, join the carriage trails together and deploy the castor wheel, then pull the gun away.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-38suSZAVoM8/X6APTxdeEqI/AAAAAAAAR-U/tMbr4TPcK7spj-YGVlsrwt29s5UCXGr8ACLcBGAsYHQ/s1200/entrenching%2Bmt-12.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="735" data-original-width="1200" height="245" src="https://1.bp.blogspot.com/-38suSZAVoM8/X6APTxdeEqI/AAAAAAAAR-U/tMbr4TPcK7spj-YGVlsrwt29s5UCXGr8ACLcBGAsYHQ/w400-h245/entrenching%2Bmt-12.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-r1z_bDEjKu8/X6FHer4lg1I/AAAAAAAASBU/oD4pJ9c60VUSv1d6RXK8-JheaUcHkVt8ACLcBGAsYHQ/s739/strona_144_d_44.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="424" data-original-width="739" height="229" src="https://1.bp.blogspot.com/-r1z_bDEjKu8/X6FHer4lg1I/AAAAAAAASBU/oD4pJ9c60VUSv1d6RXK8-JheaUcHkVt8ACLcBGAsYHQ/w400-h229/strona_144_d_44.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div><div>A split-trail carriage does not allow rapid all-round fire, as the gun must first be uprooted and then rotated with great effort to fire outside of its initial arc. If a gun pit was dug with an opening for a predetermined firing arc, it becomes impossible to fire outside of that arc. That said, all-round fire is rarely useful for anti-tank guns, even in the event that they are overrun - in such a case, the outcome of the battle is already clear, and it can be expected that the crew abandons the gun. All-round fire is possible with some examples of field artillery, such as the 88mm 25-pdr divisional gun, 105mm L118 light gun and 122mm D-30 howitzer.</div><div><br /></div><div>Part of the rationale for the all-round fire capability of the D-30 howitzer (besides lower response times for fire missions) was to ensure it could react instantaneously to the sudden appearance of enemy tanks from an unexpected direction, with the caveat that the gun is already deployed in the combat configuration; the D-30 did not allow emergency firing in the travel configuration. This capability may have occasionally been useful, based on the experiences of the Red Army during the Great Patriotic War in the event of an enemy breakthrough where the divisional artillery unit may not have realized that a breakthrough occurred, or the direction of the main thrust was unclear, or a smaller force broke off from the main thrust to attack the artillery unit. Given that anti-tank guns were a reserve force that would be deployed specifically to halt or delay a successful breakthrough, the ability to conduct all-round fire was totally unnecessary. </div></div><div><br /></div><div>And so, with practically no contextually relevant downsides, the split-trail layout naturally became the de facto standard for anti-tank gun carriages among all military powers with an artillery design and manufacturing industry. </div><div><br /></div><div><br /></div><div>To increase the convenience of pushing the gun by hand, a castor wheel would be fitted. The first example of Soviet anti-tank artillery to have a castor wheel was the 100mm BS-3 obr. 1944 field gun, in the form of a separate module that could be fitted to the end of the spades, presumably by one man from the gun crew while the six other crew members hold the trails up. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-aS5rh14pOJw/X77MbcZsi8I/AAAAAAAASJg/fxgpnE2WRmUMMXK7XNqsfr-_daW9wBJawCLcBGAsYHQ/s2048/%25D0%25B1%25D1%25813_2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1347" data-original-width="2048" height="420" src="https://1.bp.blogspot.com/-aS5rh14pOJw/X77MbcZsi8I/AAAAAAAASJg/fxgpnE2WRmUMMXK7XNqsfr-_daW9wBJawCLcBGAsYHQ/w640-h420/%25D0%25B1%25D1%25813_2.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>All subsequent anti-tank guns, including all three guns discussed in this article, had a castor wheel integrated to the left carriage trail for ease of deployment and stowage when shifting the gun in and out of its combat configuration. </div><div><br /></div><div>The castor wheel is needed on large and powerful guns, because the system is far too heavy for the crew to push or pull it on the ground by the carriage trails like a wheelbarrow. Given that the carriage has to be heavy enough to withstand the strong recoil of the gun, it naturally provides enough weight to counterbalance the gun for such an arrangement to work, ensuring that the castor wheel maintains contact with the ground and the gun does not tip forwards.</div><div><br /></div><div>Once deployed, the castor wheel converts the carriage to a tricycle. The width of the wheel must be large enough to present a large contact surface, so that the carriage does not sink excessively in soft terrain. Also, the diameter of the wheel should be as large as possible so that less pushing effort is needed from the gun crew to surmount stones, branches or bumps in the terrain, and to reduce the likelihood of the wheel getting stuck in a rut.</div><div><br /></div><div>Curiously enough, Soviet towed guns had an all-steel castor wheel, without even a rubber rim. Outside of the USSR, the U.S was the only nation to put an anti-tank gun with castor wheel into service; the 90mm M26 gun on M18 carriage. Like the other 90mm guns in development at the time, it featured a a pneumatic castor wheel, which would presumably offer better traction and some degree of damping compared to a steel wheel, but suffer from being susceptible to punctures from all manner of hazards.</div><br /><div><br /></div><div><br /><a href="https://www.blogger.com/null" id="common-protection"></a><h3 style="text-align: left;"><span style="font-size: large;">PROTECTION</span></h3></div><div><br /></div><div><div><div>The primary drawbacks of towed anti-tank guns include vulnerability to artillery and air bombardment, large manpower requirement to fully crew each gun together with their prime movers and ammunition supply trucks, inability to shift positions while under fire, and high vulnerability to direct hits. To survive contact with an attacking force, anti-tank units had to capitalize on their stealthiness to maintain the element of surprise. The primary survivability factors for a towed anti-tank gun and its crew were the effective use of camouflage, cover, concealment, secrecy and deception. </div></div></div><div><br /><br />If the gun emplacement is discovered by enemy reconnaissance or by unmasking itself during combat, the gun crew has very little protection from artillery fire and air attack. Napalm in particular can be especially effective, as it is able to disable guns and neutralize their deeply entrenched gun crews by heat and asphyxiation, not to mention the morale effect. </div><div><br /></div><div>In this regard, a towed gun has greatly reduced survivability compared to enclosed or even open-topped tank destroyers. However, a properly dug-in gun emplacement also includes trenches for the crew and dugouts for the ammunition stores, which effectively protects the weapon system from attacks of all types. In this context, the disadvantage of a towed gun is that such fortifications require hours if not days to set up, whereas a tank destroyer is innately protected by virtue of its armour plating. It is much more difficult to protect a gun from being disabled by artillery or air attack, as even when dug into a gun pit, the weapon is always still exposed above ground level.</div><div><br /></div><div><div>If located by artillery observers, a battery of anti-tank guns could be quickly neutralized by enemy artillery, assuming that accurate fire is possible. The article "<span style="color: #0000ee;"><u>The interaction of artillery and heavy infantry weapons</u></span>" published in the August 1941 issue of the Artilleristische Rundschau magazine gives the following guidelines for sudden fire to annihilate an enemy artillery battery, to be fired within 1 minute whenever possible: </div></div><div><div><br /></div><div><div><ul style="text-align: left;"><li>72 rounds for each battery of light field howitzers (75mm)</li><li>60 rounds per 105mm cannon battery</li><li>48 rounds for each heavy battery of field howitzers (150mm)</li></ul></div><div><div><br /></div><div>Realistically, a more common form artillery fire would be neutralizing fire, which does not necessarily destroy the anti-tank battery, but forces the enemy into cover and temporarily prevents them from manning their weapons. In the same German artillery magazine article, it is stated that to neutralize a battery, the ammunition consumption will depend on the circumstances, but light field howitzers must use at least 120 rounds, and heavy field howitzers at least 80.</div></div></div><div><div><br /></div></div><div>Unlike indirect fire artillery batteries that normally have to be set up on flat and open terrain, anti-tank guns were generally less susceptible to being seen by artillery reconnaissance prior to an engagement. This hardly changed throughout the Cold War, as advanced artillery reconnaissance technologies such as counterbattery radars were not applicable to direct fire weapons. Besides aerial reconnaissance, which still depended on manned aircraft, there were few other methods of detecting anti-tank gun positions.</div><div><br /></div><div><br /></div>When suppressed by direct fire, a heavy towed weapon is not only slow to relocate, but if the relocation is prompted by crew members being wounded or killed by enemy fire, the crew has more incentive to flee than to remain under fire at the gun emplacement. It is because of such issues that large numbers of intact towed guns tend to be captured during battles, normally abandoned by their crews. The infantry accompanying a tank force in a typical enemy unit, which could be assumed to be a combined arms unit by default during the Cold War, posed a threat to anti-tank guns if deployed forward of the advancing tanks.</div><div><br />With a dedicated armoured prime mover such as an AT-P or MT-LB, the possibility of fending off an infantry attack was somewhat enhanced owing to the fire support capabilities of the integrated machine gun. This decreases the likelihood of the gun being overrun or at least buys the crew enough time to evacuate from the position.<br /></div><div><br /></div><div>The main defences of a gun crew would be the terrain, field fortifications, their personal weapons (a Kalashnikov) and any other weapons organic to the battery. The only protection element integral to the gun itself is the gun shield.</div><div><br /><br /><a href="https://www.blogger.com/null" id="gunshield"></a><h3 style="text-align: left;"><span style="font-size: large;">GUN SHIELD</span></h3><br />Written guidelines for the design of a gun shield are difficult to find. In general, it is a highly contextual matter, seeming to be an aspect of gun design that is left almost entirely to the discretion of the designer and the fancies of the testing commissions. Nevertheless, it is universally accepted that the purpose of a gun shield is to reduce the probability of a gun being taken out of action by enemy fire by protecting the gun crew, at least as far as the French, Americans, Germans, British and Germans were concerned. </div><div><br /></div><div>A history and justification of early gun shields is provided in article "Shrapnel And Shields", published in the September-October 1906 issue of the Journal of the United States Artillery, Vol. 26 No. 2. The relevant passages from the article are as follows:</div><div><br /></div><div><div><i></i></div></div><blockquote><div><div><i>Till within quite recent years only two essential requirements were considered in the construction of field guns: power and mobility, While in time of war power was especially demanded, peace has always produced a marked tendency towards mobility. Now, to these two prime factors, power and mobility, a third condition has been added: protection. Up to this time protection has been considered not from the</i></div><div><i>technical point of view of construction of material, but as dependent on the tactical employment of artillery (i. e. the disposition of guns behind cover). Therefore it did not receive attention in the designing of field guns.</i></div></div><div><i><br /></i></div><div><div><i>In great battles owing to the increased accuracy of infantry and artillery fire, it is often impossible to obtain sufficient cover by skilful disposition of batteries on the terrain, herce it has become necessary to adapt protection to the piece itself, that is to say, provide the shield. The artillery shield, which could</i></div><div><i>be introduced only with the long recoil carriage, was thus a necessary consequence of the new system of artillery. The resulting increase of weight has not the same influence on the rapidity of fire as formerly, as the 5 cm. gun on long recoil carriage can not be fired appreciably faster than one of 7.5cm. of the same system.</i></div></div><div><i><br /></i></div><div><div><i>Attention had already been drawn to the direct protection of guns by means of armor on the carriages. In 1866 extensive tests were made at Mayence with an armored piece constructed by Schumann, the carriage of which was also designed by him. The adoption of axletree seats for field gun carriages might have suggested the idea of making the backs of these seats of sheet steel, thus providing a kind of shield for the cannoneers protecting them from infantry fire and shrapnel bullets. An invention of this nature was noted in the military press in 1892.</i></div></div><div><i><br /></i></div><div><div><i>From that time on, quite naturally, experiments were made in a systematic, continuous manner to determine the thickness, best metal, etc., for the shields, the necessity for which no longer admitted of any doubt. Likewise experiments were begun on the manufacture of projectiles for efficaciously combatting the shields.</i></div></div></blockquote><div><div><i></i></div></div><div><br /></div><div>The Soviet view point was largely the same, but authoritative military texts never fail to note the additional purpose of protecting the gun itself along with the crew. The textbook "<i>Курс Артиллерии</i>" (Artillery Course) published by the Voenizdat in 1943, devoted a footnote to explaining the purpose of a gun shield, stating that artillery shields are not only intended to protect personnel, but also to protect the gun system itself. It is further elaborated in the textbook "<i>Курс Артиллерии - Книга 4</i>" (Artillery Course - Book 4) that invulnerability of towed artillery from enemy fire is provided by the strength of the structure and shield enclosures that protect the gun crew and fragile parts of the gun from fragments and bullets. Much greater attention is paid to the importance of stealth and deception, noting that an important role is played by the camouflaging of the gun and the creation of shelters for the gun crew in the gun emplacement. In order to disguise the guns, they were made as low as possible and painted in a so-called "protective colour". </div><div><br /></div><div><br /></div><div>The lack of central direction in gun shield design is exemplified in the "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a123077.pdf">Field Artillery Cannon Weapon Systems and Ammunition Handbook</a>" by the U.S Army Field Artillery School, dated October 1981, where it is stated quite plainly that shields installed on (some) towed artillery weapons are constructed to protect the crew from fragmentation or small-arms fire from the front. However, the handbook gives no guidelines whatsoever to dictate their design, despite being the definitive engineering handbook on the topic. Because of this, there is little option other than to make inferences based on some observations. Although gun shields are ostensibly nothing more than simply sheets of steel fastened to the rotating gun mount, their design had their fair share of nuances to consider.</div><div><br /></div><div>Firstly, it ought to be noted that the gunner's station on an artillery piece is invariably situated on the left, and the loader may either stand behind the gunner or stand to the right of the gun when loading it. Standing directly behind the gun while loading it was strictly prohibited for safety reasons and remains strictly prohibited on all artillery pieces. </div><div><br /></div><div>The minimum height of the gun shield appears to be determined by the height of the gun breech when the gun is depressed to its maximum limit. If, by chance, the resultant shield meeting this requirement is not tall enough to cover the gunner while he is in a kneeling position, it seems that gun designers often take the liberty to extend it to ensure that the gunner has protection. This can be seen in the photo below of a Polish T-12 gun, which had been dug-in, making its small silhouette size even smaller. The gun shield is just barely tall enough that take cover behind it, the gunner has to be kneeling and hunched down.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-5xtcyJHutWg/X9-Zmim-YXI/AAAAAAAASiQ/5qRnpBcqc6g9hbIrC5hc_AkdyJu6EDkEACLcBGAsYHQ/s1024/polish%2Bt-12.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="480" src="https://1.bp.blogspot.com/-5xtcyJHutWg/X9-Zmim-YXI/AAAAAAAASiQ/5qRnpBcqc6g9hbIrC5hc_AkdyJu6EDkEACLcBGAsYHQ/w640-h480/polish%2Bt-12.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The width of the gun shield is primarily dictated by the gun traverse arc and it cannot exceed the width over the tyres of the carriage, which often necessitates a sweep angle to ensure full coverage for the gun. As a side effect, fulfilling these criteria tends to ensure that the shield will also be wide enough to protect the gunner from the direct front. This is sufficient as long as the gun is pointed directly at the enemy, but no more. There are virtually no anti-tank guns that have a gun shield wide enough to protect the gunner from a shot coming from even a modest side angle.</div><div><br /></div><div>The firing position for a gun is chosen so that its traverse arc can cover the entire width of the expected enemy front or at least the assigned firing sector for the individual gun. Logically, it follows that if the gun were to receive direct fire from the enemy, it would originate from within the same arc. If the gun is fired upon by an enemy located outside of its traverse arc, then the firing position was either overrun or was poorly chosen.<br /><br />If the gun breech assembly is particularly long but the carriage is narrow, which is often the case for a high velocity large caliber gun, then the gun shield must be swept back to ensure that it provides protection across the entire gun traverse arc without exceeding the maximum permissible width.</div><div><br /></div><div>The 57mm M1 gun serves as a good illustration of this. It was unusual in having a particularly wide carriage which permitted a large traverse arc of 90 degrees, and to provide front protection when the gun was traversed to the extremes of this large arc, the gun was issued with a pair of additional fixed side shields which could be mounted on the carriage. Zaloga states in "<i>U.S Anti-Tank Artillery 1941-1945</i>" that in practice, these shields were rarely used, but nevertheless, the existence of these side shields demonstrates the connection between the gun traverse arc and the necessary shield width.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4zxUmp8qUXY/X6GJdUszZAI/AAAAAAAASBw/QcnFZKXNefE-LvrAEUT29p-T36ScFzX0gCLcBGAsYHQ/s600/57mm%2Bm1%2Bgun%2Bside%2Bshields.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="293" data-original-width="600" src="https://1.bp.blogspot.com/-4zxUmp8qUXY/X6GJdUszZAI/AAAAAAAASBw/QcnFZKXNefE-LvrAEUT29p-T36ScFzX0gCLcBGAsYHQ/s16000/57mm%2Bm1%2Bgun%2Bside%2Bshields.jpg" /></a></div><div><br /></div><div><br /></div><div>Shields also served a secondary purpose of improving crew working conditions by behaving as a blast shield. The drawings below, taken and adapted from the book "<i>Engineering Design Handbook - Gun Series - Muzzle Devices</i>" from the U.S Army Materiel Command, shows the reduction in overpressure afforded by a gun shield.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-RrXBSskKGQo/X5h3moeCPsI/AAAAAAAAR2A/jLIzGBXdyWkdJrs2kswH16XjiMlDX8iMgCLcBGAsYHQ/s3241/gun%2Bshield%2Beffect%2Bon%2Bovepressure%2Bwaves.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="970" data-original-width="3241" height="192" src="https://1.bp.blogspot.com/-RrXBSskKGQo/X5h3moeCPsI/AAAAAAAAR2A/jLIzGBXdyWkdJrs2kswH16XjiMlDX8iMgCLcBGAsYHQ/w640-h192/gun%2Bshield%2Beffect%2Bon%2Bovepressure%2Bwaves.png" width="640" /></a></div><div><br /></div><div><br /></div><div>An anti-tank gun is reasonably well protected from the fragmentation of explosive shells when emplaced in a prepared position. Though the crew is exposed, this is largely irrelevant because the gunner is the only member of the gun crew whose duties involve him being obligated to be directly next to the gun when the gun is in action.<br /></div><div><br /></div><div>By design, all Soviet guns permit all available sighting systems to be installed simultaneously. This is particularly convenient for night fighting because the sight can be set up during the emplacement of the gun, before dusk, and then simply left in its mounting bracket until it is needed. The gunner can switch between any of the three sights at any time, and during night fighting, the gunner always has the option of switching back to the day sight in the event that the night sight malfunctions.<div><br /></div><div><br /></div><div><br /></div><div><div><br /></div><div>Another noteworthy feature is the wavy pattern of the top edge of the shield, commonly observed on Soviet guns. This served to break up the silhouette of the shield into an irregular shape, thus helping it blend in with nature, particularly if the gun was emplaced among rocks and mounds of dirt. This was an additional layer of built-in camouflage, in addition to the so-called "protective colour" of the paint on the gun. The camouflaging effect can be further enhanced by attaching foliage to the gun shield. Even a hasty effort can have a positive effect. The same concept of cutting the edges of gun shields into a rounded or wavy shape was also implemented on some French and British guns, but the vast majority of artillery, including domestic artillery, were built with simple straight-edged shields. Many had completely flat, rectangular shields that seemed to have been designed without any regard for concealability whatsoever.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-iw-SdOFYzrQ/X6GFVsl8-DI/AAAAAAAASBo/V25kdZceyyMcgyU5_Dlpdc0jXlcQGaIowCLcBGAsYHQ/s900/mt-12%2Bhastily%2Bcovered.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="900" height="426" src="https://1.bp.blogspot.com/-iw-SdOFYzrQ/X6GFVsl8-DI/AAAAAAAASBo/V25kdZceyyMcgyU5_Dlpdc0jXlcQGaIowCLcBGAsYHQ/w640-h426/mt-12%2Bhastily%2Bcovered.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The thickness of Soviet gun shields is standardized at 4.5mm. The grade of armour steel used for such shields is unknown. This detail was a holdover from the 37mm M1930 anti-tank gun, the first Soviet towed anti-tank gun. In general, this low thickness of armour stops only light ball rifle rounds and shell splinters. With only few exceptions, all Soviet towed anti-tank guns followed the standard set by the M1930 and retained the same 4.5mm thickness. This standard was not followed by other artillery pieces such as the 122mm M-30 howitzer, which reportedly had a 3.5mm shield according to "<i>Энциклопедия Отечественной Артиллерии</i>" (Encyclopedia of Domestic Artillery) by Russian historian A.V. Shirokorad and confirmed by a measurement on a real specimen.</div><div><br /></div></div><div><br /></div><div><a href="https://www.blogger.com/null" id="direct-protection"></a><h3 style="text-align: left;"><span style="font-size: large;">DIRECT FIRE PROTECTION</span></h3><br />Based on the known penetration characteristics of 7.62x54mm LPS (light ball) bullets, a gun shield constructed from 4.5mm RHA steel should be capable of stopping 7.62mm light ball rounds at a distance of 100 meters. Protection from armour-piercing bullets is not provided. The 7.62x54mm B-32 (AP-I) bullet can perforate a 4.5mm RHA plate at 30 degrees from a distance of 700 to 800 meters, and a .30 caliber M2 AP bullet is capable of perforating 4.5mm of RHA at an impact velocity of 450 m/s, corresponding to a range of 800 meters. Above 700-800 meters, both rounds may be able to achieve partial perforation, so the shield still does not provide adequate protection.<br /><br />According to the "<i>Handbook on German Military Forces</i>" written and published by the U.S War Department, the steel gun shield of the 3.7cm Pak 36 was sloped at 30 degrees and had a thickness of 3/16-inches, or around 4.76mm. In the U.S, the gun shields on all anti-tank guns had a standardized thickness of 6.35mm, regardless of the shape of the shield and its obliquity. According to Shirokorad, the 45mm M-42 anti-tank gun entered service in the Red Army in 1942 with a 7mm gun shield to provide better protection from armour piercing bullets. The weight of the gun shield increased <a href="http://www.russianarms.ru/forum/index.php?action=dlattach;topic=7514.0;attach=58636;image">from 53.7 kg to 79.5 kg</a>.<br /><br />The 5 cm Pak 38, which replaced the Pak 36, had a new gun shield consisting of two 4mm armour plates separated by a 1-inch air gap, sloped at 30 degrees. This spaced armour scheme was used for all future German anti-tank guns for the remainder of the war. Based on <a href="https://dspace.lib.cranfield.ac.uk/bitstream/handle/1826/11910/Terminal_ballistics_of_7.62mm_armour_piercing_projectiles-2016.pdf?sequence=3&isAllowed=y">various studies on similar armour with small air gaps</a>, the spaced gun shield of the Pak 38 and other guns provided a modest increase in mass efficiency compared to a single RHA plate, but ostensibly enough to have have been capable of stopping a 7.62mm armour-piercing bullet from 100 meters and above which would have been a notable improvement over a conventional 6.35mm or 7mm gun shield, achieved with only a small increase in weight.<br /><br /><br />In general, shell splinters are the main threat dictating the protection requirements of gun shields. Direct machine gun fire is not normally used to defeat an anti-tank gun, often because the guns are positioned in such a way that they are too difficult to be engaged with small arms fire. In the U.S Army field manual FM 14-12 "<i>Tank Gunnery</i>" from 1957, simulated anti-tank guns were to be engaged with HE shells from a range of 1,000-1,500 yards during qualifications tests.<br /><br />The lack of a need for armour defeating capability from the coaxial .30 caliber machine guns on U.S tanks is reflected in the conspicuous lack of armour-piercing rounds in a typical ammunition mix. Throughout the Cold War, a mix of 4 ball rounds and 1 tracer round was the standard. Even if armour-piercing rounds were issued, their effective use is predicated on the tank closing in on the gun, which is not only extremely unwise, but more importantly, is against regulations.</div><div><br /><br /><br /><br />According to the article "<i>Development of Protection Technologies</i>" published in the June 2009 issue of Defence Technology Review, ballistic casualties in general war, including World War II, Korea, Vietnam, Israel, and the Falklands were recorded as 59% from projectile fragments, only 19% from bullets, and 22% from other causes.<br /></div><div><br /></div><div><br /></div><div>Direct hits on the gun would be effective, but it is difficult to achieve direct hits on anti-tank guns because as a rule, they are very small, well-concealed and there is always extreme stress on the tank gunner from time pressure when attempting to return fire. Real experience showed that explosive rounds were always the first choice for dealing with anti-tank guns.</div><div><br /></div><div>Information on the effect of the 75mm M48, 3" M42A1 and 76mm M42A1 is given in the report "<a href="https://tankandafvnews.com/2015/10/21/from-the-vault-comparison-of-performance-of-75mm-and-76mm-tank-gun-ammo/">Army Operational Research Group Memorandum No. 415</a>", shared by the Tanks and AFV News website.</div><div><br />The table below, made by the <a href="https://www.ww2armor.org/">WWII Armor historian group</a> with data taken from TM 9-1907 "<i>Ballistic Data, Performance of Ammunition</i>" and organized into an easily readable format, shows the fragment density produced by a 90mm M71 HE shell, which is representative of the shells used by the 90mm guns of postwar U.S medium tanks. Compared to 75mm and 105mm HE, the fragmentation of M71 is low, but at least it has a slight advantage over 75mm HE in the greater density of fragments capable of perforating 1/4 inches of mild steel. Nevertheless, this is largely irrelevant because the gun shields of anti-tank guns constitute much tougher armour than 1/4 inches of mild steel. <br /><br /><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-CDnQVsQRt0w/X48SBM-a3QI/AAAAAAAARyM/q9p48lfwqGkSnyXRVaVm9tZldCuBayLxgCLcBGAsYHQ/s1470/fragment%2Bdata.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="629" data-original-width="1470" height="274" src="https://1.bp.blogspot.com/-CDnQVsQRt0w/X48SBM-a3QI/AAAAAAAARyM/q9p48lfwqGkSnyXRVaVm9tZldCuBayLxgCLcBGAsYHQ/w640-h274/fragment%2Bdata.png" width="640" /></a></div><br /><br />High velocity direct fire guns are less effective against a small target with a low silhouette, such as entrenched anti-tank guns. This is due to the non-optimal fragmentation spray pattern for a HE-Frag shell with a flat trajectory, specifically the low fragment spray density forward and behind the burst. With regard to the American 90mm and British 20-pdr guns specifically, the difficulty in knocking out an anti-tank gun with their HE-Frag shells would have been amplified by a combination of a flat trajectory and poor bursting performance.<br /><br /><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-oHyJjHiTd1o/X48CbZ2KRZI/AAAAAAAARx0/fCtmSBk27XIvsh9fRN0DB2T2auPqE93oQCLcBGAsYHQ/s587/fragment%2Bspray.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="341" data-original-width="587" src="https://1.bp.blogspot.com/-oHyJjHiTd1o/X48CbZ2KRZI/AAAAAAAARx0/fCtmSBk27XIvsh9fRN0DB2T2auPqE93oQCLcBGAsYHQ/s16000/fragment%2Bspray.jpg" /></a></div><div><br /></div><div><br /></div><div>Interestingly enough, the survivability of Soviet anti-tank guns was indirectly enhanced by the proliferation of HESH shells among NATO armies as an alternative to HE shells. </div><div><br /></div><div>According to the figures given in the memorandum "<i><a href="https://cdn.discordapp.com/attachments/714898523497431111/772723493241749504/unknown.png">HEAT vs HESH Paper</a></i>", studies done for the Trilateral Tank Main Armament Evaluation, held from December 1973 to August 1975, showed that the 105mm M393A2 HEP shell had a lethal area of 114 square meters against prone infantry, which is slightly inferior to a Soviet 85mm Frag shell (nominal kill zone of 130 sq.m). Also, HEAT shells were also much less effective owing to their small explosive charge and the non-optimal shape of the warhead. In terms of lethal area, HESH or HEP are considered approximately 40% superior to HEAT of the same caliber, implying that the lethal area of 105mm M456 would be approximately 70 square meters. Incidentally, it is reasonable to surmise that the fragmentation effect of a 90mm HEP shell would be approximately equivalent to this, which is to say that it is just as bad.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HgR6YzHeV4w/X5yVnF3Kr1I/AAAAAAAAR3U/EXnkCJkTACwYvZmnoO3WQI8K26O6syxhwCLcBGAsYHQ/s736/lethal%2Bzone.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="180" data-original-width="736" height="157" src="https://1.bp.blogspot.com/-HgR6YzHeV4w/X5yVnF3Kr1I/AAAAAAAAR3U/EXnkCJkTACwYvZmnoO3WQI8K26O6syxhwCLcBGAsYHQ/w640-h157/lethal%2Bzone.png" width="640" /></a></div><div><br /></div><div><br /></div><div>For comparison, the 100mm OF-412 HE-Frag shell has a nominal kill zone of 200 square meters and the 125mm 3OF19 and 122mm OF-471 HE-Frag shells have a nominal kill zone of 300 and 310 square meters respectively. In Soviet and Russian terminology, the nominal kill zone ("<i>приведенной зоны поражения</i>") of a shell is defined as the the area within which there is a 100% probability of a target being struck by one lethal fragment upon the detonation of the projectile. In this case, the target is considered to be infantrymen in the prone position. In principle, it is equivalent to the so-called "lethal area". In practice, the actual kill zone is much smaller because a "lethal" fragment is merely a fragment that contains enough kinetic energy to produce lethal injuries, but the actual likelihood of causing death is highly dependent on where the target is struck. </div></div><div><br /></div><div>Moreover, <a href="http://btvt.info/1inservice/chieftain/vop_chieftain_ammo.htm">a Soviet study</a> on the firepower of Chieftain tanks was carried out using a captured Iranian Chieftain Mk. 5R with one of the topics being the fragmentation characteristics of 120mm L31A7 HESH shells when fired at soil with a simulated trajectory for an impact angle of 18 degrees, where it was found that the nominal kill zone was only 140 square meters. From this, it can be said that 120mm HESH shells have a fragmentation effect that is only approximately equivalent to a Soviet 85mm Frag shell under the same circumstances, with the 85mm shell impacting at an angle of no less than 20 degrees. The relatively flat trajectory of these shells is detrimental to their fragmentation effect, so in practice, the actual lethal area is smaller. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-a0ueoasL9Ts/X5xYojAz0VI/AAAAAAAAR3M/U_mLtCjIEvoFklKbbBNnADDF1G6MmYvwACLcBGAsYHQ/s1935/lethal%2Bareas.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="635" data-original-width="1935" height="210" src="https://1.bp.blogspot.com/-a0ueoasL9Ts/X5xYojAz0VI/AAAAAAAAR3M/U_mLtCjIEvoFklKbbBNnADDF1G6MmYvwACLcBGAsYHQ/w640-h210/lethal%2Bareas.png" width="640" /></a></div><div><br /></div><div><br /></div><div>With the fuze set to the superquick mode, a HE-Frag shell can be fired at the canopy of trees near an anti-tank gun position with a certainty of detonating on contact with the leaves or the branches. This essentially produces an air burst effect which has a high probability of eliminating the entire gun crew and even possibly disabling the gun itself, preventing it from being brought back into action by nearby infantry. An anti-tank gun hidden at the edge of a forest or placed under a tree in the open can be quickly eliminated this way if it is detected. This is shown in the drawing below. It is worth noting that the scenario shown in the drawing is only for illustrative purposes, as field manuals strongly discourage the use of lone trees and clumps of bushes for concealment, as they stand out in open fields and are the first landmarks to be scrutinized by enemy tank crews.<br /><br /><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-lf6Kvp48vDU/X48Dtk1X1SI/AAAAAAAARx8/6sGYvChaKucqg5IqtKqUpBDor7ab5kW3QCLcBGAsYHQ/s418/treeburst.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="418" data-original-width="354" height="320" src="https://1.bp.blogspot.com/-lf6Kvp48vDU/X48Dtk1X1SI/AAAAAAAARx8/6sGYvChaKucqg5IqtKqUpBDor7ab5kW3QCLcBGAsYHQ/s320/treeburst.jpg" /></a></div><br /><br />It is important to note that HESH shells cannot be used this way due to their base fuze and the built-in fuzing delay, which is incompatible with the high-sensitivity instantaneous-detonation function required to work on tree canopies. Indeed, HE-Frag shells would be also ineffective for this purpose if the fuze were set to the "HE" mode. For a HESH shell to fuze properly, it would have to hit the tree trunk, but achieving such a hit could be harder than hitting the concealed gun itself.</div><div><br /></div><div><br /></div><div>If the trajectory of the HE-Frag shell is flat enough and the terrain permits, there is some chance of successfully performing a ricochet air burst when the fuze is set to the maximum delay mode. Alternatively, it is also feasible to depend on the flat trajectory of the shell by deliberately aiming at a point short of the gun and hope to defeat it by the mine action of a delayed fuze HE shell, and if the shell incidentally goes over the intended impact point, it would either land very close to the gun or strike the gun shield itself, which is also highly desirable. Interestingly enough, it was noted in the U.S Army technical manual TM 9-1907 that a HE-Frag shell with the fuze set to the delayed mode (HE) was especially effective against anti-tank guns because the shell could perforate the thin gun shield and then explode some distance behind the gun, killing all members of the gun crew instantly. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-yILBYh1Exc8/X4_n-swX36I/AAAAAAAARyc/xIq2vhjXbC8C1Tm7RUJ9dDxFQc7h-uxHACLcBGAsYHQ/s387/he%2Beffects.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="239" data-original-width="387" src="https://1.bp.blogspot.com/-yILBYh1Exc8/X4_n-swX36I/AAAAAAAARyc/xIq2vhjXbC8C1Tm7RUJ9dDxFQc7h-uxHACLcBGAsYHQ/s16000/he%2Beffects.png" /></a></div><div><br /></div><div><br />With the fuze in the superquick (Frag) or short delay (HE-Frag) modes, a direct hit on the gun shield from a large high velocity HE-Frag shell would also completely destroy the gun and can be expected to also neutralize at least some of the crew through the destruction of the shield itself. A direct hit with a HE-Frag round was responsible for the destruction of the MT-12 shown in the photo below. The gun shield was shattered by the explosion.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-BTeFWhSOHVc/X6AMvzGpHmI/AAAAAAAAR98/pgzP9T6vpJwReDH4Sz554sT8gYJNVl9iwCLcBGAsYHQ/s800/id4139-01.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="450" data-original-width="800" height="360" src="https://1.bp.blogspot.com/-BTeFWhSOHVc/X6AMvzGpHmI/AAAAAAAAR98/pgzP9T6vpJwReDH4Sz554sT8gYJNVl9iwCLcBGAsYHQ/w640-h360/id4139-01.jpg" width="640" /></a></div><br /><div><br /><div>In general, airbursting ammunition would be the most effective against an anti-tank gun emplacement, but such ammunition would only be available to artillery. The closest approximation to an airbursting round for tank guns was APERS, which became available to tanks armed with 105mm guns in mass quantities as the M494 only in 1973. However, prior to this, the XM494E3 had been approved for low rate initial production in 1968 due to an urgent requirement issued by the Department of the Army, just in time for U.S forces in Vietnam to be issued small quantities of APERS rounds during the final years of the conflict. However, APERS did not produce the same target effect as airbursting HE-Frag shells, because it was designed to detonate in front of the target and it only disperses its flechettes in a narrow forward cone of 20 degrees. If adjusted to detonate above an anti-tank gun position, the built-in fuzing standoff of 75 meters combined with the narrow dispersion cone ensures that the flechettes would merely pass above the heads of the crew rather than spray fragments perpendicularly down onto the crew as an airbursting HE-Frag shell would. To achieve its anti-personnel effect, M494 must be detonated only as high above ground level as its natural trajectory in the direct fire mode would allow.</div><div><br /></div><div>For this reason, the official description of the M494 conspicuously omits any mention of targeting infantry in covered positions, let alone entrenched infantry or fortifications. According to its description, the M494 round was designed for close-in defence against massed infantry assaults, for offensive fire against exposed enemy personnel, and secondary firepower capability is provided against lightly armoured vehicles and low-flying aircraft.</div><br />Canister ammunition such as the 90mm M336 round also cannot be expected to be effective because of the poor penetration power of the flechettes or pellets, which degrades even further when this ammunition is used outside of their maximum effective range of a few hundred meters (300-400 m) such that even relatively thin pine boards can stop the projectiles. For instance, the M336 round with its 2-gram pellets was only rated to produce one complete penetration per 6 square feet of a 1-inch thick pine board on a target 8 feet high and 90 feet wide at a range of 400 feet. At the same distance, a 7.62mm light ball round can be expected to perforate a stack of pine boards ten times thicker or more. With this limited performance in mind, it should be noted that the flechettes used in APERS munitions, which weigh just 0.5 grams each, have even worse armour penetration power.</div><div><br /></div><div>Not only was the pellet density low even at such a short range, but the density of pellets with sufficient penetration power to perforate such a thin pine board is exceptionally small. Given these figures and the known dimensions of Soviet anti-tank guns, only 4-5 of such pellets can be expected to strike the gun, and their relatively thin gun shields can be expected to provide full protection even at near point blank range. At the short ranges where canister ammunition are normally used, it would be much easier to simply obtain a direct hit on the gun itself with a HE-Frag shell.</div><div><br /></div><div><br />With the sole exception of HE shells, all NATO tank gun ammunition was quite poor for the purpose of knocking out anti-tank guns. With the replacement of 90mm and 20-pdr guns by the 105mm L7 and the lack of a HE-Frag shell in its repertoire, the efficiency of NATO tanks against anti-tank guns declined sharply. The generalization that the ammunition available to NATO tanks had a very low efficiency against towed anti-tank guns is quite reasonable. Combat experience during WWII showed that firing explosive shells at the estimated positions of anti-tank guns was effective at suppressing the crew, but generally did not put the guns out of action.</div><div><br /></div><div><br /><br /><a href="https://www.blogger.com/null" id="d44"></a><h3 style="text-align: left;"><span style="font-size: large;">D-44 (52-P-367)</span></h3></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-X7Z4aDle29Y/X7pwo8JrX2I/AAAAAAAASIc/5A7X_udkkBsLAjeCNlnsXbGh5-N02ihJgCLcBGAsYHQ/s690/85mm%2BD-44.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="336" data-original-width="690" height="312" src="https://1.bp.blogspot.com/-X7Z4aDle29Y/X7pwo8JrX2I/AAAAAAAASIc/5A7X_udkkBsLAjeCNlnsXbGh5-N02ihJgCLcBGAsYHQ/w640-h312/85mm%2BD-44.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The 85mm divisional gun D-44 was designed at the OKB-9 design bureau of the No. 9 artillery factory, and produced at factory No. 9, as signified by the "D" index. In addition to improved anti-tank capabilities, better target effects on infantry and fortifications were also desired, as the firepower of the ZiS-3 was deemed unsatisfactory. The closest foreign counterpart of the D-44 was the British 25-pdr, which served as the standard British divisional gun from 1940 until 1967. The D-44 served in the Soviet Army under the same system of organization for divisional artillery as the Red Army during WW2. It was used in this role until the dissolution of the Soviet Union, although by that point, it could only be found in low-readiness units in Southern and Eastern Russia. </div><div><br /></div><div>The ballistics of the existing 85mm 52-K anti-aircraft gun were used, but an entirely new weapon was created. In this regard, the creation of the D-44 did not follow the same developmental trajectory as the BS-3 field gun, which was designed around the barrel of the B-34 naval gun, or foreign examples like the American 3-inch M5 and the 90mm M26 guns, which were created by transplanting the 3-inch M1918 and 90mm M1 anti-aircraft barrels respectively onto new mounts.</div><div><br /></div><div><div>The design documentation for the D-44 was sent from OKB-9 to the No. 92 factory named after Stalin, "<i>Zavod imeni Stalina</i>" (ZiS), where the first prototype was built. As the factory was named after Stalin, the gun received the name as an honorific prefix, making it the ZiS-D-44. After testing, the system was further modified at No. 9 factory. On May 8, 1945, the ZiS-D-44 gun was sent to the Gorokhovets training ground to establish its tactical-technical characteristics. The ZiS-D-44 failed these tests, one of the reasons being the unsatisfactory extraction of cases. It finally entered service in 1946 as the D-44, missing the war entirely. The adoption of the D-44 and its belatedness was in large part due to the novelties of the production technologies involved. The share of stamped and cast components by weight reached 41% compared to 25-30% in previous guns, and a whole host of new production processes were adopted at the plant to launch D-44 production.</div><div><br /></div><div>Factory No. 9 was the only enterprise in the USSR that was engaged in the mass production of the gun, where a total of 10,918 guns were manufactured from 1946 to 1954. During the first year, 474 guns were produced. Although the total figure amounted to only around a tenth of the ZiS-3 production run, it was enough to rearm not only the Soviet Army but also its satellites. During its production run, the D-44 was exported to various Warsaw Pact nations in large quantities, such that the D-44 became a fairly ubiquitous weapon outside the Soviet Union by the late 1950's.</div></div><div><br /></div><div><br /></div><div>The D-44 would be replaced together with the old M-30 howitzer during the 1960's with the introduction of the D-30 howitzer, which served as a comprehensive upgrade to both artillery systems by combining the firepower of a 122mm howitzer with the range of the D-44, as well as by having an all-round fire capability. However, as with many weapon systems, the D-44 was never fully phased out in all motor rifle divisions. The 40th Army brought its D-44 guns into Afghanistan, where it proved to be inadequate as there was a strong demand for more powerful artillery capable of high-elevation fire as well as all-round fire to protect forward operating bases situated deep in the country. Because of these limitations, the D-44 guns of the 40th Army began to be replaced in 1981 by D-30 howitzers.</div><div><br /></div><div><div><div>Outside of Afghanistan, it remained in relatively widespread service. It continued to serve in its role as divisional artillery after the dissolution of the Soviet Union, even taking part in the First Chechen War.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-_lEPL0gp_F4/X9D22SpZBKI/AAAAAAAASXI/pIDL19XPUY0QHZY7uR37DmiNePLizqJWQCLcBGAsYHQ/s510/chechnya%2Bartillery.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="332" data-original-width="510" height="260" src="https://1.bp.blogspot.com/-_lEPL0gp_F4/X9D22SpZBKI/AAAAAAAASXI/pIDL19XPUY0QHZY7uR37DmiNePLizqJWQCLcBGAsYHQ/w400-h260/chechnya%2Bartillery.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/--ZQ5pHG937g/X9DzjaXLnXI/AAAAAAAASW0/OGnkHOW63eo8eUgXgyVc7OaPG0wadCGswCLcBGAsYHQ/s788/d-44%2Bbattery.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="471" data-original-width="788" height="239" src="https://1.bp.blogspot.com/--ZQ5pHG937g/X9DzjaXLnXI/AAAAAAAASW0/OGnkHOW63eo8eUgXgyVc7OaPG0wadCGswCLcBGAsYHQ/w400-h239/d-44%2Bbattery.jpg" width="400" /></a></div><div><br /></div></div></div><div><div><br /></div><div><div>Soon after the D-44 entered service, it was recognized that VDV infantry had the same demands for firepower, but guns of such a weight were impractical without a prime mover. As such, the design bureau of factory No. 9 started work on motorizing the D-44 at the end of 1948. The project was officially approved on the 1st of January 1949, and work on creating a prototype began the same year. The first prototype was ready for factory and field tests in 1950, which continued until the system finally passed military trials in 1954. By decree No. 2329-1105 of the Council of Ministers issued on the 19th of November 1954, the SD-44 gun officially entered service. </div><div><br /></div><div>In 1954, factory No. 9 converted 88 D-44 guns into the SD-44, and in 1955 another 250 were converted. In 1957, another 100 guns were converted and the production line reopened briefly to manufacture 109 new SD-44 guns together with 150 SD-44N guns with night sights. A total of 547 SD-44 guns were created.</div><div><br /></div><div>By motorizing the gun, it could serve as its own prime mover and it could shift positions during combat more easily, in spite of the large increase in weight.</div><div><br /></div><div><br /></div></div><div><br /></div></div><div><br /></div><a href="https://www.blogger.com/null" id="d44-deployment"></a><h3 style="text-align: left;"><span style="font-size: large;">DEPLOYMENT</span></h3><div><div><br /></div><div>As a divisional gun, the D-44 took over the role of the ZiS-3. The term "divisional gun" refers to a specific category of field gun intended for divisional level artillery. It was recognized that divisional guns would also have to serve as anti-tank guns, and being a replacement for the ZiS-3, the D-44 was expected to fulfill this role as well. This meant that the D-44 was not only issued to the artillery regiment organic to the division, but also to the anti-tank artillery battalion in the division.</div></div><div><div><br /></div><div><div>Among the other military powers, divisonal guns were not necessarily issued universally. Although the British Army used the 25-pdr and the Heer used various 75mm guns, in the U.S Army, 105mm howitzers had replaced 75mm field guns by WWII and continued to serve in lieu of field guns after the war. </div><div><br /></div><div>A major aspect of divisional guns was their versatility. The effectiveness of 75mm field guns against tanks was demonstrated in WWI, and from then onward, the anti-tank capabilities of divisional guns became an important consideration. Versatility briefly overtook that of practicality during the early 1930's, when the idea of universal guns took hold due to the influence of Mikhail Tukhachevsky, who envisioned divisional artillery as having the versatility to fight all possible threats on a modern battlefield, including aircraft. As a result of this idea, the F-22 gun entered service in 1936. It was quickly replaced by the F-22 USV model lacking the anti-aircraft capability, and in turn, it was replaced by the ZiS-3 which was a classical 3-inch field gun, albeit one of an exceptionally modern design.</div><div><br /></div><div>A common use for divisional or anti-tank guns, as practiced by all participants of WWII, was to attach the weapons to an infantry unit, and bring them up to provide support with direct fire against bunkers, field fortifications and machine gun nests. Whenever possible, tanks would be used instead, but as real experience showed, units were frequently below their theoretical strength and tanks were simply not available. The D-44 could be used for this purpose as well, but this practice largely died out with the conversion of infantry divisions to motorized infantry divisions in 1957.</div><div><br />After the so-called Great Patriotic War (GPW), divisional artillery continued to serve a secondary role as anti-tank artillery. Though the D-44 was a great improvement over the existing means of anti-tank defence in the Soviet Army, its capabilities against tanks were fundamentally outmoded. Such weapons would have been in great demand throughout the later half of the war, but by the end, it was recognized that 100mm guns were needed to combat existing heavy tanks and future threats. The development of towed 85mm anti-tank guns began in response to the appearance of the Tiger heavy tank and continued to be pursued after 85mm tank guns had successfully entered service for the IS-85, SU-85 and T-34-85, but none had passed trials by the end of the war. This was a somewhat unique situation compared to the prevailing trends. Anti-tank guns in use by the Germans, Americans and British were invariably first fielded as a towed version, which would inevitably be followed by mobility concerns, prompting the installation of the gun onto a vehicle mount.</div></div><div><div><br /></div><div>Having the ability to engage from standoff distances was important. If combat took place at only a few hundred meters, the swiftness of the gun crew became paramount, as the enemy tanks were more likely to spot the position of a hidden gun and the effectiveness of their return fire was drastically increased. Dismounted infantry advancing ahead of the tanks could also spot and suppress the gun, or perhaps even overrun it.</div></div><div><br /></div><div><br /></div><div>As divisional artillery, the importance of the D-44 cannot be understated. It was issued to the 2 gun battalions of the artillery regiment organic to a rifle or motor rifle division. A gun battalion had 2 anti-tank artillery batteries, each consisting of 2 fire platoons with 3 divisional guns, for a total of 12 divisional guns in the battalion, and 24 divisional guns in the regiment. D-44 guns were also issued to the anti-tank battalion in each motor rifle or tank regiment. Overall, a motor rifle division was thoroughly saturated with D-44 guns. Alongside the gun battalions, an artillery regiment also had a howitzer battalion equipped with two batteries of 122mm M-30 howitzers for a total of 12 howitzers.</div></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-luXk0in5TAM/X9ESVobwSWI/AAAAAAAASXU/6yBLkMdft8wVf6_28QNJSJrrdkznc_MMACLcBGAsYHQ/s1600/towed.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="935" data-original-width="1600" height="374" src="https://1.bp.blogspot.com/-luXk0in5TAM/X9ESVobwSWI/AAAAAAAASXU/6yBLkMdft8wVf6_28QNJSJrrdkznc_MMACLcBGAsYHQ/w640-h374/towed.jpg" width="640" /></a></div><div><br /></div><div><div><br /></div></div><div>The D-44 was at the peak of its potency in the immediate aftermath of WWII up til the early 1950's, mainly because Western allies were still entirely reliant on wartime medium tanks of various models, much like the Soviet Army. Compared to the German heavy tanks of late 1944, the firepower needed to combat such tanks was far less demanding. Heavy tanks such as the Conqueror and M103 only entered service in 1955 and 1957 respectively, but ignoring the fact that they were only used in very limited numbers, they were not relevant targets for anti-tank artillery because their role was to provide long range firepower to a force of medium tanks from overwatch positions rather than being the proverbial tip of the spear in a breakthrough.</div><div><br /></div><div>The British Army was mainly equipped with Cromwell and Comet tanks until the late 1950's, while the newly rehabilitated French Army, as well as the armies of other liberated European nations, had been supplied with Sherman tanks via various sources. By the outbreak of the Korean war, the U.S had ceased production of the M26 Pershing and low rate production of the M46 had only recently begun with a total of only 319 tanks completed. At the peak of its saturation during the war in Korea, the ratio of M26 Pershings to M4A3E8 Shermans present was just a little over 1:2. Outside of Korea, the proportion of Sherman tankss of various models was even larger, being the most numerous tank in use by the Western allies by a large margin. Needless to say, these circumstances were favourable for the D-44. </div><div><br /></div><div><br /></div><div>However, the situation did not last. Amidst the backdrop of a rapidly deteriorating relationship with the USSR, further worsened by the situation in Korean, the shortfall in modern tank production sparked the so-called "tank panic". Mass production of the M47 Patton began in 1951 as an interim solution to the lack of modern tanks while the output rate of Centurion tanks was accelerated to fulfill American orders. In fact, over half of all Centurions produced in Britain were purchased by the U.S under the MDAA for distribution among the NATO members in Europe. Though far from being frontally invulnerable to the D-44, these new tanks were nevertheless a troubling new threat. A little while later, the M48 entered service and began rapidly displacing obsolete tanks from the U.S Army tank fleet. Against such tanks, the usefulness of the D-44 was very limited.</div><div><br /></div><div><br /></div><div>Decades after their adoption, D-44 guns could still be used for training purposes, to keep reservists up to date on their skills, if nothing else. The photo below, from the <a href="https://477768.livejournal.com/3364140.html">livejournal user 477768</a>, shows Hungarian artillerymen training with D-44 guns in around 1997-1998.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-mG3ZbZi2BEc/X9-xMQpdWkI/AAAAAAAASis/-aAmRKmM4z4V7LPrTBFw-QaSB23XSDVMgCLcBGAsYHQ/s789/training.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="548" data-original-width="789" height="278" src="https://1.bp.blogspot.com/-mG3ZbZi2BEc/X9-xMQpdWkI/AAAAAAAASis/-aAmRKmM4z4V7LPrTBFw-QaSB23XSDVMgCLcBGAsYHQ/w400-h278/training.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="d44-mobility"></a><h3 style="text-align: left;"><span style="font-size: large;">MOBILITY</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-lRBCUgIYG1c/X9ESeN8-h9I/AAAAAAAASXY/B8-zs2dExAkxTszbS0Jh9PhtOkK2XK_rQCLcBGAsYHQ/s1200/towed%2Bd-44.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="630" data-original-width="1200" height="336" src="https://1.bp.blogspot.com/-lRBCUgIYG1c/X9ESeN8-h9I/AAAAAAAASXY/B8-zs2dExAkxTszbS0Jh9PhtOkK2XK_rQCLcBGAsYHQ/w640-h336/towed%2Bd-44.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The GAZ-63, the standard 4x4 utility truck of Soviet motor rifle infantry, was used as the prime mover of the D-44. Needless to say, the enormous number of guns meant that an equally sizeable fleet of trucks was needed to transport them, and for this reason, cheap, light utility trucks were ideal. The GAZ-63 was replaced by the GAZ-66 in the late 1960's. The D-44 shown being towed in the photo above has a GAZ-66 as its prime mover. A limber was created for the D-44 as part of its technical requirements for transportation by horses, but horse-drawn D-44s were not known to have been used in the Soviet Army. </div><div><br /></div><div>The ability to be towed at high speeds by a mechanized prime mover was a basic requirement for the D-44 and for all modern artillery pieces of the mid-1940's, and to that end, it was equipped with fully rubberized tyres and a torsion bar suspension.</div><div><br /></div><div><div>With its modern suspension and tyres, the D-44 was able to handle rough terrain about as well as any of its its prime mover could. It could reach a maximum speed of 60 km/h, effectively allowing it to be towed at a speed matching that of the trucks used to tow it. The top speed of the GAZ-63, for example, reached 65 km/h. On cobblestone roads and dirt roads, the towing speed can reach up to 35 km/h. Needless to say, the actual speed is highly dependent on the capabilities of the prime mover. Relative to wartime wheeled and tracked artillery prime movers, the prime movers in service with the Soviet Army had a larger load capacity and could thus negotiate rough terrain with more confidence.</div></div><div><br /></div><div>When being towed in its transport configuration, the muzzle and the entire breech end of the weapon would be protected with a canvas wrap.</div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="d44-carriage"></a><h3 style="text-align: left;"><span style="font-size: large;">CARRIAGE</span></h3><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-YSSVD9XmCIo/X9DzAInWIjI/AAAAAAAASWk/E6-sVzGu2oEANl70gGCxZkTybqOSUdEgQCLcBGAsYHQ/s2048/carriage%2Bcrossbeam%2Bcutaway.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1404" data-original-width="2048" height="438" src="https://1.bp.blogspot.com/-YSSVD9XmCIo/X9DzAInWIjI/AAAAAAAASWk/E6-sVzGu2oEANl70gGCxZkTybqOSUdEgQCLcBGAsYHQ/w640-h438/carriage%2Bcrossbeam%2Bcutaway.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The crossbeam of the carriage is a cast steel girder, shown in the drawing above. It serves as the gun mount with a protruding pintle for gun traverse, while its hollow inner volume houses the torsion bars of the suspension. The crossbeam is the hub of the entire weapon, onto which the wheels, trails, and gun are fitted to form a complete weapon.</div><div><br /></div><div>The swing arm on each wheel is a straight axle shaft connected to the end of their respective torsion bar. Gusmatic "GK" airless tyres with a sponge rubber core and the hub assembly from the GAZ-AA truck were used. The rim flange width and rim diameter were 6.5 inches and 20 inches respectively. Ordinary pneumatic tyres with the same specifications could also be mounted, but it was inadvisable as such tyres would suffer frequent punctures in combat conditions from not only fragments and bullets, but flying debris. </div><div><br /></div><div>The tyres are worth mentioning, as the roadwheels of almost all German weapons such as the Pak 43 were merely steel wheels with solid rubber rims, while American and British artillery pieces were fitted with pneumatic tyres. </div><div><br /></div><div>It is also worth noting that the D-44 did not have parking brakes for its wheels, which was fairly typical for a gun of its type as brakes are simply unnecessary, but may be unusual under American artillery practices. According to TM 9-3305 "Principles of Artillery Weapons", all towed artillery weapons have a parking brake engaged manually by their crews, while larger weapons like the 8-inch M1 and 240mm M1 have a service brake, normally a pneumatic type connected to the prime mover. For a D-44 or any other artillery piece with a split-trail carriage, splaying the trails apart would firmly root the gun to a spot, making manually-operated parking brakes totally redundant. The ommission of brakes probably helped saved some weight. </div></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-kyFh_VKr4z8/X8gQgr7Qk0I/AAAAAAAASMQ/aTEEoi07bHoKIHhr3G6tPaoi809AM4fzACLcBGAsYHQ/s2048/carriage.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1136" data-original-width="2048" height="356" src="https://1.bp.blogspot.com/-kyFh_VKr4z8/X8gQgr7Qk0I/AAAAAAAASMQ/aTEEoi07bHoKIHhr3G6tPaoi809AM4fzACLcBGAsYHQ/w640-h356/carriage.png" width="640" /></a></div><div><br /></div><div><br /></div><div>When the carriage trails are unlocked and spread apart, the torsion bar anchors for both carriage wheels are disengaged. This is done by having the trails push in a spring-loaded locking pin on their respective wheel swing arms when they are fully spread.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Q3CoShMa2Mo/X8zG0gQACrI/AAAAAAAASQE/F2Tq11GXmgYnMFZwio6EsoinaFtEBL21gCLcBGAsYHQ/s2048/suspension%2Block%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1246" data-original-width="2048" height="390" src="https://1.bp.blogspot.com/-Q3CoShMa2Mo/X8zG0gQACrI/AAAAAAAASQE/F2Tq11GXmgYnMFZwio6EsoinaFtEBL21gCLcBGAsYHQ/w640-h390/suspension%2Block%2Bmechanism.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The locking pin connects the wheel swing arm with the carriage crossbeam, thus immobilizing it. The wheels remain free to rotate, so the gun can still be moved by its crew if necessary.</div><br /><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-adj9JKEmmuU/X9DyflBQ0II/AAAAAAAASWc/x7meRDszpO0WDwGOIFJgnXzghRjjRvapACLcBGAsYHQ/s3007/suspension%2Blocked.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1046" data-original-width="3007" height="222" src="https://1.bp.blogspot.com/-adj9JKEmmuU/X9DyflBQ0II/AAAAAAAASWc/x7meRDszpO0WDwGOIFJgnXzghRjjRvapACLcBGAsYHQ/w640-h222/suspension%2Blocked.png" width="640" /></a></div><div><br /></div><div><br /></div><div>This feature enhanced the firing accuracy of a hastily emplaced gun by preventing the carriage from swaying and bouncing on its wheels after every shot, thus also suppressing the vibrations of the gun barrel. By extension, a higher firing rate could also be attained, as the gunner would be ready to fire follow-up shots sooner. </div><div><br /></div><div>The long and slender trails of the carriage are of particular note, giving the overall system a total length of 8,340mm, which is over a meter longer than guns like the 3-inch M5 (7.1 m) and 17-pdr (7.35 m). </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-BD4ahMcuI7E/X8nem2A6i2I/AAAAAAAASNI/OK-poNEJSEcFWURU1w8Tjw90n7Q9uZlegCLcBGAsYHQ/s3074/d-44%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1023" data-original-width="3074" height="212" src="https://1.bp.blogspot.com/-BD4ahMcuI7E/X8nem2A6i2I/AAAAAAAASNI/OK-poNEJSEcFWURU1w8Tjw90n7Q9uZlegCLcBGAsYHQ/w640-h212/d-44%2Bdrawing.png" width="640" /></a></div><div><br /></div><div><br /></div><div><div>The weight of the carriage is just 972 kg. Of this, the suspension accounts for 222 kg of weight. This light proprietary carriage was made possible thanks to the high-efficiency muzzle brake used on the gun. </div><div><br /></div><div>Like earlier domestic anti-tank gun carriage designs, the trails were cylindrical tubes rather than box girder sections. This was a design feature originally derived from the original 3.7cm Pak, which can also be seen in later German guns like the Pak 38 and Pak 40. The top and bottom part of the trails are additionally reinforced with quarter-diameter tube sections along a third of their initial length (at the end where they are fitted to the carriage crossbeam).</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-wnznjpnTdUs/X6vVgsl4CwI/AAAAAAAASHE/kv56be6FFD8eCnzSVhqZ-Jf6hH5Cj-ZzQCLcBGAsYHQ/s2984/legs.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1054" data-original-width="2984" height="226" src="https://1.bp.blogspot.com/-wnznjpnTdUs/X6vVgsl4CwI/AAAAAAAASHE/kv56be6FFD8eCnzSVhqZ-Jf6hH5Cj-ZzQCLcBGAsYHQ/w640-h226/legs.png" width="640" /></a></div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">Compared to square tubes, the main advantage of cylindrical tubes is that they are simpler to produce. From an engineering standpoint, square tubes are more suitable as they provide a higher bending strength for the given application, but the tube can be weakened if the corners are welded or riveted, becoming more susceptible to buckling below the design load capacity. Being a single-piece component, cylindrical trails do not have this issue. The SD-44 uses the hollow internal volume of the trails as fuel containers to supplement the main fuel tank. </div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-nDRddjoGZ3c/X7ol6fzBobI/AAAAAAAASIU/O5oDZgyG3xMKzrUmX1tPgzSG0GFfssnUQCLcBGAsYHQ/s2973/carriage%2Bleg%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1058" data-original-width="2973" height="228" src="https://1.bp.blogspot.com/-nDRddjoGZ3c/X7ol6fzBobI/AAAAAAAASIU/O5oDZgyG3xMKzrUmX1tPgzSG0GFfssnUQCLcBGAsYHQ/w640-h228/carriage%2Bleg%2Bcross%2Bsection.png" width="640" /></a></div><div><br /></div><div><br /></div><div><div>When set up in the travel configuration, the carriage trails are clamped together with a crossbar. The same crossbar also serves as the travel lock for the gun, featuring a hole which fits over a protruding lug on the breech housing of the gun to secure it firmly. This design, combining the travel lock with the trail clamp, was necessitated by the lack of recoil guide rails on the gun where the travel lock lugs would normally be placed to interface with the trails, as on the <a href="http://data3.primeportal.net/artillery/yuri_pasholok/57mm_zis-2_at_gun_mod1943/images/57mm_zis-2_at_gun_mod1943_042_of_243.jpg">ZiS-2</a>, <a href="http://data3.primeportal.net/artillery/yuri_pasholok/zis-3_div_gun_mod.1942/images/zis-3_div_gun_mod.1942_031_of_185.jpg">ZiS-3</a>, and <a href="https://war-time.ru/images/blog/artilleriya/pushki/sssr-rossiya/100-mm-bs-3/pod-1/100-mm-pushka-bs-3-foto-11.jpg">BS-3</a>.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-QFC3my4MCrw/X7oloIP_szI/AAAAAAAASIM/neAyxOt8rMMXcSmRuX4qwjDCu3czwv0vACLcBGAsYHQ/s2048/20200221_131153.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="400" src="https://1.bp.blogspot.com/-QFC3my4MCrw/X7oloIP_szI/AAAAAAAASIM/neAyxOt8rMMXcSmRuX4qwjDCu3czwv0vACLcBGAsYHQ/w300-h400/20200221_131153.jpg" width="300" /></a></div><div><br /></div></div><div><br /></div><div>A castor wheel was fitted to the left carriage trail. It could swivel, enabling the crew to steer the gun when pushing it. If not deployed, it could be locked atop the gap between the trails for stowage when the gun is towed. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-f1leVUA6Y1w/X8gSBmMq0vI/AAAAAAAASMY/ohqn3y6i2iMk0PMS5IL6dodqrYalziKGgCLcBGAsYHQ/s2685/castor%2Bwheel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1171" data-original-width="2685" height="280" src="https://1.bp.blogspot.com/-f1leVUA6Y1w/X8gSBmMq0vI/AAAAAAAASMY/ohqn3y6i2iMk0PMS5IL6dodqrYalziKGgCLcBGAsYHQ/w640-h280/castor%2Bwheel.png" width="640" /></a></div><div><br /></div><div><br /></div><div>For the D-44, a castor wheel was not strictly necessary - a 6-man crew could cope with the weight of similar guns by handling it like a wheelbarrow. With a combat weight of 1,725 kg, the weight of the D-44 was 609 kg greater than a ZiS-3, making it over 50% heavier. However, the ZiS-3 was ballistically inferior and it was disproportionately light for its caliber, since it used the lightweight carriage of the ZiS-2. There was no direct equivalent to the D-44 in terms of design characteristics so it is rather difficult to find a fair point of comparison. </div><div><br /></div><div>Compared to the 7.5cm Pak 40 anti-tank gun (1,425 kg) of a smaller caliber but more or less comparable ballistics, the increase in weight is far less pronounced. Older types like as the French 75mm Mle 1897/33 anti-tank gun, for example, weighed 1,500 kg. Another approximate point of reference is the British 25-pdr field gun, an 88mm weapon. Its ballistics were not equivalent to the D-44, having a muzzle velocity of just 532 m/s with a supercharged HE shell or a muzzle velocity of 610 m/s when firing its lighter 20-lb AP shot with the maximum overpressure charge. It did, however, have a weight of 1,633 kg, making it proportionately heavier.</div><div><br /></div><div>In absolute terms, the weight and handiness of the D-44 was extraordinarily light for a gun of its power, considering its design features - it weighs less than half that of the 17-pdr Mk. 1, despite the fact that both guns had the same muzzle energy and both had high efficiency double baffle muzzle brakes. Generally speaking, its weight was roughly equal to pre-war 75mm field guns with poorer ballistics. According to the "Handbook of Artillery: Including Mobile, Antiaircraft, Motor Carriage, and Trench Materiel" prepared in July 1921 by the U.S Ordnance Department, it was considered that 3-inch field guns generally had a weight of about 3,900 pounds (1,769 kg). Such guns were deemed to provide the maximum firepower while remaining mobile enough to be practical for division-level operational maneuvers, hence their designation as divisional guns. </div><div><br /></div><div><br /></div><div>A short scene of a D-44 being pushed can be found in the 1984 Soviet film <a href="https://youtu.be/JW4Eez83zrQ">"<i>Парад планет</i>"</a> (Parade of Planets).</div><div><br /></div><div><br /></div></div><div><div><br /></div></div><div><br /></div><a href="https://www.blogger.com/null" id="d44-protection"></a><h3 style="text-align: left;"><span style="font-size: large;">PROTECTION</span></h3><div><div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-2QnhwVdhOk4/X95m5OVs1zI/AAAAAAAASfo/ZZQqhSDKDFEtKTnEtTPPO6BUdBP31hTcwCLcBGAsYHQ/s1479/parad%2Bplanet%2Bd-44%2Baiming%2Bacross%2Briver.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1079" data-original-width="1479" height="466" src="https://1.bp.blogspot.com/-2QnhwVdhOk4/X95m5OVs1zI/AAAAAAAASfo/ZZQqhSDKDFEtKTnEtTPPO6BUdBP31hTcwCLcBGAsYHQ/w640-h466/parad%2Bplanet%2Bd-44%2Baiming%2Bacross%2Briver.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The primary protection factor of the D-44, as with any other anti-tank gun, was in its stealthiness, and in this respect, it is excellent. It is lower than the 7.5cm Pak 40 gun, which had a bore axis height of 960mm. The compactness of the gun, particularly the small size of its silhouette, is such that even a single row of sparse bushes is enough to completely conceal a gun emplacement.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GodKivT9fCk/X54Bz_rXuqI/AAAAAAAAR4s/YfnBnyH3pZofn1EAChxYvrf-wk4C_gYoQCLcBGAsYHQ/s1000/2213.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="666" data-original-width="1000" height="266" src="https://1.bp.blogspot.com/-GodKivT9fCk/X54Bz_rXuqI/AAAAAAAAR4s/YfnBnyH3pZofn1EAChxYvrf-wk4C_gYoQCLcBGAsYHQ/w400-h266/2213.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-7j-K9dIImDU/X54NKfg77aI/AAAAAAAAR5A/Haa_dmhcODsXS_g1Cef9Nn_mTrztSabBwCLcBGAsYHQ/s1000/277.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="666" data-original-width="1000" height="266" src="https://1.bp.blogspot.com/-7j-K9dIImDU/X54NKfg77aI/AAAAAAAAR5A/Haa_dmhcODsXS_g1Cef9Nn_mTrztSabBwCLcBGAsYHQ/w400-h266/277.jpg" width="400" /></a><br /></div><div><br /></div><div><br /></div><div>Entrenching the gun is needed for maximum stability, and digging a gun pit was a prerequisite for a proper firing emplacement if the D-44 was used for indirect fire. Because of the limited gun elevation capability of the D-44, a recoil pit was not needed for it to fire at its maximum elevation angle, even when using a full charge. As with any other gun with a split-trail carriage, all-round fire is only possible with a delay, as the spades must be uprooted before the gun can be turned.</div></div><div><br /></div><div>Ideally, when used as indirect fire artillery, the gun would be emplaced in a gun pit and covered with camouflage netting and foliage, as that provides the best protection from counterbattery fire and concealment from air reconnaissance. The raised earthen perimeter of the pit protects the crew from the fragments of shells landing outside the pit, and shells landing inside the pit will in turn have their fragments contained within, reducing damage to the surrounding personnel and equipment. Gun pits may also be dug on open ground for direct fire if the terrain does not allow hidden positions to be created.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-edNaSkCbxKM/X7qe-IIWUXI/AAAAAAAASIo/xNqHLpAVYMQ9UG-dm_i-s94bdJ2mrYZxgCLcBGAsYHQ/s876/d-44%2Bin%2Bgun%2Bpit.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="521" data-original-width="876" height="239" src="https://1.bp.blogspot.com/-edNaSkCbxKM/X7qe-IIWUXI/AAAAAAAASIo/xNqHLpAVYMQ9UG-dm_i-s94bdJ2mrYZxgCLcBGAsYHQ/w400-h239/d-44%2Bin%2Bgun%2Bpit.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-l5-Q8P1mPWA/X8ngfba4SGI/AAAAAAAASN4/RkoHaRzzDQowJST_QglDVuoIgrbVMkEuQCLcBGAsYHQ/s2048/d-44%2Bexercises.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1266" data-original-width="2048" height="248" src="https://1.bp.blogspot.com/-l5-Q8P1mPWA/X8ngfba4SGI/AAAAAAAASN4/RkoHaRzzDQowJST_QglDVuoIgrbVMkEuQCLcBGAsYHQ/w400-h248/d-44%2Bexercises.png" width="400" /></a></div><div><br /></div><div><br /></div><div>Aside from its concealability and the protection offered by entrenchments, the gun shield on the D-44 provides some protection from bullets and shell splinters, though its small size, particularly its narrow width, means that it does not provide comprehensive cover. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-FhJy8J1xbMc/X96TdbCCuOI/AAAAAAAASgc/kypwWOQGxfA689FV6cRkK-YCopTSKxduwCLcBGAsYHQ/s2048/shield.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1538" data-original-width="2048" height="300" src="https://1.bp.blogspot.com/-FhJy8J1xbMc/X96TdbCCuOI/AAAAAAAASgc/kypwWOQGxfA689FV6cRkK-YCopTSKxduwCLcBGAsYHQ/w400-h300/shield.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The gun shield is supplemented with a hinged apron plate on the underside of the carriage crossbeam, made to cover the gap between the wheels so that shell fragments do not hit the feet of the crew members, assuming that the ground is uneven enough that there is no gap between the apron plate and the ground. </div><div><br /></div><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-lKLI4N_uKdk/X6ozzJBwm_I/AAAAAAAASEw/EUUCRO3tZAormnuylsR4RaGC-J54gnvEgCLcBGAsYHQ/s600/wavy%2Bshield%2Bd-44.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="401" data-original-width="600" height="267" src="https://1.bp.blogspot.com/-lKLI4N_uKdk/X6ozzJBwm_I/AAAAAAAASEw/EUUCRO3tZAormnuylsR4RaGC-J54gnvEgCLcBGAsYHQ/w400-h267/wavy%2Bshield%2Bd-44.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>Above the gun, the gap in the gun embrasure is covered with a curved plate affixed to the gun cradle, but bizzarely enough, a gap in the embrasure is inexplicably present beneath the gun barrel. When the barrel is fully depressed, the height of the gap is insignificant, but it is greatly enlarged when the gun is elevated. The photo on the left below (courtesy of <a href="https://dishmodels.ru/wshow.htm?mode=P&vmode=T&p=2846&id=155583&tp=w">Andrey Alekseev</a>) shows the rather large gap when the gun is elevated. The photo on the right below, taken from the <a href="https://www.kpopov.ru/military/nn_park_15.htm#ancor11">kpopov website</a>, shows the pneumatic equilibrator of the gun exposed through the gap in the shield. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ncbVsATfLgM/X7woyBULjiI/AAAAAAAASJQ/F_AS-_pHbYI3k3ocGKb5yOyjT_hHgq-fwCLcBGAsYHQ/s1566/under%2Bgun%2Bshield.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1044" data-original-width="1566" height="266" src="https://1.bp.blogspot.com/-ncbVsATfLgM/X7woyBULjiI/AAAAAAAASJQ/F_AS-_pHbYI3k3ocGKb5yOyjT_hHgq-fwCLcBGAsYHQ/w400-h266/under%2Bgun%2Bshield.png" width="400" /></a><a href="https://1.bp.blogspot.com/-_JVEW3C9hNs/X8nIgyopIDI/AAAAAAAASM4/sVQc-W75UewiGZ3IN0nZbXOOJBMo29idgCLcBGAsYHQ/s800/through%2Bgap%2Bin%2Bgun%2Bshield.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="534" data-original-width="800" height="268" src="https://1.bp.blogspot.com/-_JVEW3C9hNs/X8nIgyopIDI/AAAAAAAASM4/sVQc-W75UewiGZ3IN0nZbXOOJBMo29idgCLcBGAsYHQ/w400-h268/through%2Bgap%2Bin%2Bgun%2Bshield.jpg" width="400" /></a><br /><br /></div><div><br /></div><div>When the gun is fully elevated, the gap in the embrasure can be up to 45cm tall. Its width is 26cm. Needless to say, such gaps are to be avoided to prevent shell fragments from damaging or jamming the moving parts of the gun. The incomplete cover around these areas is not uncommon among field artillery, but given the presence of an apron plate to cover the gap beneath the carriage, this omission is rather peculiar.</div><br /><div><br /></div></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-qsy7MDVPT-c/X8ojCHuzeOI/AAAAAAAASPU/OH_akllokGsCmkEd8SZz4LQktZIDWyhQACLcBGAsYHQ/s2048/embrasure%2Bgap%2Bheight.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1152" height="400" src="https://1.bp.blogspot.com/-qsy7MDVPT-c/X8ojCHuzeOI/AAAAAAAASPU/OH_akllokGsCmkEd8SZz4LQktZIDWyhQACLcBGAsYHQ/w225-h400/embrasure%2Bgap%2Bheight.jpg" width="225" /></a><a href="https://1.bp.blogspot.com/-3Pp07SyH-N0/X8ojBzX54sI/AAAAAAAASPQ/-K8MYtkEllM-VBRip5JWswss5YaXzvJngCLcBGAsYHQ/s2048/embrasure%2Bgap%2Bwidth.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1152" height="400" src="https://1.bp.blogspot.com/-3Pp07SyH-N0/X8ojBzX54sI/AAAAAAAASPQ/-K8MYtkEllM-VBRip5JWswss5YaXzvJngCLcBGAsYHQ/w225-h400/embrasure%2Bgap%2Bwidth.jpg" width="225" /></a></div><div><br /></div><div><br /></div><br /><a href="https://www.blogger.com/null" id="d44-sighting"></a><h3 style="text-align: left;"><span style="font-size: large;">FIRE CONTROL</span></h3><div><br /></div><div>The only fire control instrument available was a rangefinder, issued at the battery level. Each gun battery was issued with a rangefinder which would be used to create range reference points, which would then be noted by the commanders of each individual gun. The rangefinder could also be used when coordinated fire at a single point target is needed. In the 1950's, the DS-1 or DS-2 stereoscopic rangefinders would be issued. </div><div><div><br /></div></div><div>Meteorological data such as humidity, air temperature, etc, would be communicated to the battery from a higher level headquarters, which in turn would receive data from a meteorological survey platoon, an asset belonging to the artillery regiment of a motor rifle division. Regular updates in meteorological data are critical for long range indirect fire missions, but it matters less for direct fire purposes as the ballistic corrections are generally minor enough to be ignored.</div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">SIGHTING</span></h3><div><br /></div><div>The D-44 is sighted with a simple telescopic sight for direct fire and a panoramic sight for both indirect and direct fire. The drawing on the left below shows the offset of these two sights from the axis of the gun barrel.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-l2RCjLdQRDo/X9EoYZi4jiI/AAAAAAAASX4/8Q8M5QX8gUAEgGyBH7SeoNuDZGlqJ147QCLcBGAsYHQ/s2048/sighting%2Bparallax.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1900" height="400" src="https://1.bp.blogspot.com/-l2RCjLdQRDo/X9EoYZi4jiI/AAAAAAAASX4/8Q8M5QX8gUAEgGyBH7SeoNuDZGlqJ147QCLcBGAsYHQ/w371-h400/sighting%2Bparallax.png" width="371" /></a></div><div><br /></div><div><br /></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">OP1-7, OP2-7</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GIshibPvtkw/X6WBVtQIh6I/AAAAAAAASC8/0MAs9QRmx4YD8t62tXX10TGEv30xF7IxQCLcBGAsYHQ/s1024/op1-7%2Bposter.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="682" data-original-width="1024" height="426" src="https://1.bp.blogspot.com/-GIshibPvtkw/X6WBVtQIh6I/AAAAAAAASC8/0MAs9QRmx4YD8t62tXX10TGEv30xF7IxQCLcBGAsYHQ/w640-h426/op1-7%2Bposter.jpg" width="640" /></a></div><div><br /></div><div><br /></div>A D-44 was provided with a fixed OP1-7 or OP2-7 telescopic sight for direct fire. The OP1 and OP2 series of sights were standardized sighting units with a replaceable glass pane for viewfinder markings. Both series began to be used only on postwar guns. The OP1-7 and OP2-7 models were a standard OP1 and OP2 sight with markings for the 85mm ammunition of the D-44. The OP2 was a later, improved model from the 1950's.<div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ubuNqyGFwpY/X6Vzm_8axiI/AAAAAAAASC0/Q-8hx9jrZPgJgNv7cl7_UoXVYC6dy-5zwCLcBGAsYHQ/s2530/op2-7.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1243" data-original-width="2530" height="314" src="https://1.bp.blogspot.com/-ubuNqyGFwpY/X6Vzm_8axiI/AAAAAAAASC0/Q-8hx9jrZPgJgNv7cl7_UoXVYC6dy-5zwCLcBGAsYHQ/w640-h314/op2-7.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The OP1-7 had an increased fixed magnification of 3.5x and a field of view of 14 degrees. The relatively low magnification of 3.5x was not necessarily bad - considering its field of view, the optical design of the sight was excellent. For comparison, the No. 43 sight for the 17-pdr anti-tank gun had a slightly lower 3x magnification as well as a slightly smaller field of view of 13 degrees. However, the characteristics of the OP1-7 are somewhat odd considering that the M-42 45mm gun was equipped with the PP9-3 telescope with 5x magnification and a field of view of 8.5 degrees, despite being a smaller gun meant to engage tanks at short ranges.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-_byN7rsu8W8/X9ErB5LToDI/AAAAAAAASYA/QSNpyMu_cM4xURBJQSdIAysOAgW3AZsBACLcBGAsYHQ/s2048/op1-7%2Bcutaway.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1447" data-original-width="2048" height="452" src="https://1.bp.blogspot.com/-_byN7rsu8W8/X9ErB5LToDI/AAAAAAAASYA/QSNpyMu_cM4xURBJQSdIAysOAgW3AZsBACLcBGAsYHQ/w640-h452/op1-7%2Bcutaway.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The odd magnification of the OP1-7 was rectified by its replacement with the OP2-7. The OP2-7 had an increased fixed magnification of 5.5x and a field of view of 11 degrees. According to Soviet figures, an optical sight with 5x magnification allows an observer to see and identify a tank from a distance of 3.0 kilometers. For the purposes of the D-44, this magnification level was more than enough for any combat scenario, especially considering that a hidden anti-tank gun may sometimes be best utilized by delaying fire until the target is at a closer range.</div><div><br /></div><div>In the 1956 book "<i>Taktik im Russlandfeldzug. Erfahrungen und Folgerungen</i>" by <a href="https://de.wikipedia.org/wiki/Eike_Middeldorf">Eicke Middeldorf</a>, republished in 2000 as "<i><a href="http://militera.lib.ru/h/middeldorf/index.html">Русская кампания: тактика и вооружение</a></i>", the assumption is made that in the terrain characteristic of the European theater, an anti-tank gun can fire at tanks on average at a distance of up to 500-700 meters. </div><div><br /></div><div>The design of both the OP1 and OP2 sights is simple, but not crude. They provide a few additional features for ease of use in addition to the essential features of a functional gun sight. Unlike American direct fire sights for field artillery, the OP1 and OP2 permit the setting of the range with an adjustment knob, in addition to the calibration of the crosshair for boresighting. A removable rubber eye cup is provided on both sights to prevent extraneous light or rain from distracting the gunner's vision, while the OP2 also has a browpad for the gunner to ensure proper eye relief. Additionally, the OP2 was supplied with a high-contrast light filter that could be screwed to the end of the sight for better visibility in low light and when searching for targets against certain backdrops.</div><div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-EdDMi4G7Xag/X6Voa6VnmzI/AAAAAAAASCk/mW98o50yqhsTu-AwOVcEZi09i9V1YZZcQCLcBGAsYHQ/s2048/op2-7%2Boptical%2Bscheme.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1084" data-original-width="2048" height="338" src="https://1.bp.blogspot.com/-EdDMi4G7Xag/X6Voa6VnmzI/AAAAAAAASCk/mW98o50yqhsTu-AwOVcEZi09i9V1YZZcQCLcBGAsYHQ/w640-h338/op2-7%2Boptical%2Bscheme.png" width="640" /></a></div></div><div><br /></div><div><br /></div><div>With the increased magnification and the introduction of a high-contrast filter, OP2-7 can be considered to be objectively superior to OP1-7 for combat in realistic conditions, where the lighting conditions can be far from ideal, and for long range gunnery.</div><div><br /></div><div>For fighting at night, both sights have provisions for lighting the viewfinder markings using an externally mounted electric lighting system. The OP1-7 is illuminated with the "Luch-2M" system, whereas the OP2-7 is illuminated with the "Luch-S71" system. Light is provided by a small bulb fitted into a small window at the top of the sight casing. </div><div><br /></div><div>In both the OP1 and OP2 sights, the viewfinder markings, including the range scales, are etched into a vertically sliding glass pane. To use range scales, the large range adjustment knob on the underside of the telescope tube is turned. An internal screw lowers the glass pane, thus lowering the sight markings in the viewfinder of the sight. </div><div><br /></div><div>The OP1-7 sight has a single fixed horizontal thread installed in front of the lenses of the eyepiece group. When the viewfinder markings are adjusted vertically, the superelevation angle for range is selected by aligning the appropriate increment of the range scale with the horizontal thread.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-AtOQgHDhh2g/X8skP1ePLKI/AAAAAAAASP8/DVzq1SmUomgZ9Yhnkj8KPdKys0AOmtawwCLcBGAsYHQ/s2048/op1-7.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2022" data-original-width="2048" height="395" src="https://1.bp.blogspot.com/-AtOQgHDhh2g/X8skP1ePLKI/AAAAAAAASP8/DVzq1SmUomgZ9Yhnkj8KPdKys0AOmtawwCLcBGAsYHQ/w400-h395/op1-7.png" width="400" /></a></div><div><br /></div><div><br /></div>The OP2-7 sight has a slightly different construction. A pair of threads are stretched to form a crosshair in front of the lenses of the eyepiece group. This forms a crosshair in the viewfinder, serving as a reference point of the center of its optical axis.<br /><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-drwnHuTanlo/X6Voe7cFKMI/AAAAAAAASCo/njUMKWfspz0XgJuW3SqHpFYRRxMDBjVgQCLcBGAsYHQ/s2048/op2-7.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1982" height="400" src="https://1.bp.blogspot.com/-drwnHuTanlo/X6Voe7cFKMI/AAAAAAAASCo/njUMKWfspz0XgJuW3SqHpFYRRxMDBjVgQCLcBGAsYHQ/w388-h400/op2-7.png" width="388" /></a></div><div><br /></div><div><br /></div>Once the range is selected, all the gunner must do is elevate the gun until the center chevron is laid onto the target. If deflection has to be applied because of wind or to lead a moving target, the gunner uses the smaller markings on either side of the central chevron as aiming points. <br /><div><br /></div><div>The viewfinders of both the OP1-7 and OP2-7 were marked for reduced charge Frag, full charge Frag, and sharp-nosed AP shells (BR-365K). Evidently, the new 367 ammunition was yet not available at the time the sights were originally issued.</div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">S71-7<br />PG-1</span></h3><div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-XULEJSoRSxU/X4Q1bzj6-yI/AAAAAAAARtc/TNdOueAHAa00cASc-Qm1LC4SHNX0PYmjgCLcBGAsYHQ/s1477/s71-40.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1477" data-original-width="1089" height="400" src="https://1.bp.blogspot.com/-XULEJSoRSxU/X4Q1bzj6-yI/AAAAAAAARtc/TNdOueAHAa00cASc-Qm1LC4SHNX0PYmjgCLcBGAsYHQ/w295-h400/s71-40.png" width="295" /></a></div><div><br /></div></div><div><br /></div><div>The S71 is a range setting device, designed for the adjustment of the gun in elevation, while the PG-1 panoramic sight is for laying the gun in azimuth. Both components are used together as a sighting system to enable the precise laying of the gun in both azimuth and elevation for indirect fire. Beginning in the last years of the GPW, all new field guns, including divisional and anti-tank guns, were fitted with the S71 mechanical sight as a standard feature. The S71-7 modification is simply an S71 sight calibrated for the D-44. The sighting system was designed for field guns, and as such, its elevation range is 0-750 mils, or 0-45 degrees. Howitzers, having an elevation limit greater than 45 degrees by definition, required a different sight. </div><div><br /></div><div>The S71 is essentially a mechanical device designed to convert an input angle (in mils) into a superelevation angle that can be applied to the gun by elevating it. The S71 is rigidly mounted on the gun cradle so that its position shifts together with the gun. On the S71, the coarse adjustment drum is divided into increments of 100 mils per division. A full circle is divided into 6,000 mils under the Soviet definition, so there are 60 increments marked on the drum. The fine adjustment drum is divided into increments of 1 mil per division with 100 increments marked on the drum from 0 to 99. When the deflection of the sight is set to 30-00, the line of sight is parallel to the bore axis of the gun, and increasing the deflection angle above 30-00 offsets the sight counterclockwise whereas decreasing the deflection angle below 30-00 offsets the sight clockwise. </div><div><br /></div><div>The PG-1 is a Hertz panoramic periscope, used primarily for indirect fire with the possibility of direct fire as an emergency backup to the direct fire sight. It serves as both a sighting optic and as a goniometer, with an azimuth scale marked on the rotating panoramic head for the gunner to measure the azimuth angle between two points in the distance with high precision. It is mounted onto a rotating bracket on the S71 sight, so that inputting an angle setting to the S71 rotates the PG-1 optic forward by the corresponding angle. When the gun is elevated, the PG-1 is returned to a level position. </div></div></div><div><div><div><br /></div><div>The PG has a fixed magnification of 3.7x and a field of view of 10 degrees. It is tall enough that the gunner can look over his own head when the periscope head is rotated to look backwards. With these properties, the PG-1M provides a wider field of view than a telescopic sight, but proportionally, the field of view is smaller as the magnification is lower. If fixed facing forward, the sight can serve adequately as an alternative to the telescopic sight for direct fire or even as a supplementary sight for short range engagements. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-BfcvMsll1Ys/X9oVjC79rAI/AAAAAAAAScg/C46JJEg6XHw-RP6Kv7Aa0RYDCUcV8sPqgCLcBGAsYHQ/s2048/pg.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1302" height="320" src="https://1.bp.blogspot.com/-BfcvMsll1Ys/X9oVjC79rAI/AAAAAAAAScg/C46JJEg6XHw-RP6Kv7Aa0RYDCUcV8sPqgCLcBGAsYHQ/s320/pg.png" /></a><a href="https://1.bp.blogspot.com/-aJw_xj-5D4w/X9oXH8IdzDI/AAAAAAAASco/pqaLlV6ra7QRjlpSMPxsEYum_t5jn-w0gCLcBGAsYHQ/s2048/pg-1%2Bviewfinder.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1920" height="320" src="https://1.bp.blogspot.com/-aJw_xj-5D4w/X9oXH8IdzDI/AAAAAAAASco/pqaLlV6ra7QRjlpSMPxsEYum_t5jn-w0gCLcBGAsYHQ/s320/pg-1%2Bviewfinder.png" /></a><br /></div><div><br /></div><div><br /></div><div>The "Luch-S71M" illumination device was used to illuminate the reticle of the optical sight for more effective aiming during darkness. It runs on 3.5 V, 0.26-Amp power supply from an NK-13 battery.</div><div><br /></div><div><div>Alternatively, a K-1 collimator unit may be used instead of the PG-1 in low visibility conditions such as at night or when distant landmarks are obscured with smoke, snow or heavy rain. The K-1 is a separate tripod-mounted unit, intended to be set up behind or to one side of a towed gun and within a certain distance from the PG-1. It is used by aligning an azimuth code in the viewfinder of the the PG-1 with the scale displayed on the K-1 display. The scale containing K-1 markings can be seen in the viewfinder of the PG-1 under the crosshair, as the drawing on the right above shows. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-tDi4-OE9Tbo/X-Ng_l4G49I/AAAAAAAASjo/9599o1Y_Roo7f3NqRq_3tNpw4skZprtNACLcBGAsYHQ/s2048/k-1%2Bon%2Btripod.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1729" data-original-width="2048" height="338" src="https://1.bp.blogspot.com/-tDi4-OE9Tbo/X-Ng_l4G49I/AAAAAAAASjo/9599o1Y_Roo7f3NqRq_3tNpw4skZprtNACLcBGAsYHQ/w400-h338/k-1%2Bon%2Btripod.png" width="400" /></a><a href="https://1.bp.blogspot.com/-xqfJY33CgNo/X-Ng_g5pehI/AAAAAAAASjs/JLKoRbogN-0W5oLcRewi3VjbpLF8tFH4wCLcBGAsYHQ/s2048/k-1%2Bscale.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2001" data-original-width="2048" height="391" src="https://1.bp.blogspot.com/-xqfJY33CgNo/X-Ng_g5pehI/AAAAAAAASjs/JLKoRbogN-0W5oLcRewi3VjbpLF8tFH4wCLcBGAsYHQ/w400-h391/k-1%2Bscale.png" width="400" /></a></div><div><br /></div><div><br /></div>The image below shows how the PG-1 should be aligned with the K1.<br /><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-IZ7RHXmv4TQ/X-NigAu2BSI/AAAAAAAASj4/d5q8p1IW_1Y_05vd-KNkbM1qOMcH2brhQCLcBGAsYHQ/s2048/using%2Bk-1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="2021" height="400" src="https://1.bp.blogspot.com/-IZ7RHXmv4TQ/X-NigAu2BSI/AAAAAAAASj4/d5q8p1IW_1Y_05vd-KNkbM1qOMcH2brhQCLcBGAsYHQ/w395-h400/using%2Bk-1.png" width="395" /></a></div><div><br /></div><div><br /></div></div><div><div>To use the optical-mechanical sighting system, the gunner uses aligns the reticle of the panoramic optic with the tip of a distant landmark. The landmark may be a radio mast, the tallest tree on a hill, a windmill or other similar structures. The battery headquarters, which is responsible for receiving fire missions and generating a ballistic solution for the entire battery, calculates and issues a certain deflection angle relative to the reference point.</div></div><div><div><br /></div><div>The gun elevation angle would be set with an accuracy (maximum error) of 0.5 mils - a large improvement over older mechanical sights that permitted an accuracy of 2 mils. </div></div><div><br /></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">NIGHT SIGHTS</span></h3><div><br /></div><div>1957 was a highly significant year for the ground forces as it marked the widespread introduction of night vision devices for artillery and armoured vehicles. Even the old ZiS-2 gun was modernized with a night sight, creating the ZiS-2N variant. Naturally, the D-44 could also be upgraded with a night sight of its own. Guns that were built or modernized with the necessary provisions for mounting a night sight were renamed as the D-44N, and the installation of a standard APN-3 sight converts it to the "N3" suffix. </div><div><br /></div><div><div>For a weapon such as the D-44, a night sight was not strictly necessary, as a competently organized defence in depth would usually include a minefield at the very least, forcing an exploitation force to halt at a predetermined distance in front of the anti-tank gun emplacements, permitting pre-zeroed artillery to fire illumination shells over this zone while keeping the friendly gun emplacements in the dark. </div><div><br /></div><div>Moreover, as towed guns are static, non-enclosed weapons that are practically silent (except for the brief moment a shot is fired), target acquisition under total darkness can be done by a combination of visual and audio means. One technique is to watch for the muzzle flash of an enemy tank to locate it, then count the number of seconds until the sound of the shot is heard to estimate the range. However, such techniques require the enemy to fire the first shot, which is undesirable, and rely on the assumption that the shot fired by the enemy was aimed somewhere else. </div><div><br /></div><div>The tactical advantage brought by a night sight is that night fighting becomes much more feasible under non-ideal circumstances, which is likely to occur as the primary incentive of conducting offensives at night is to achieve surprise on the tactical level. If artificial illumination is provided intermittently during an engagement, the gunner of a D-44 may alternate between using the OP2-7 sight and his night sight. </div><div><br /></div></div><div>Artillery night sights carry the "APN" designation, standing for "artillery night sight"; a simple naming convention, with tank night sights carrying the "TPN" designation, for example.</div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">APN-2-7</span></h3><div><br /></div><div>Exists, but no information is available. Possibly experimental.</div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;"><br />APN-3-7 "Yablonya"</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-tOH35sSDknA/X54QCmEwfsI/AAAAAAAAR5M/IPBO7b8gDHQTWr8_rEGcLWFPpkW8EfUCQCLcBGAsYHQ/s1024/apn-3.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="682" data-original-width="1024" height="426" src="https://1.bp.blogspot.com/-tOH35sSDknA/X54QCmEwfsI/AAAAAAAAR5M/IPBO7b8gDHQTWr8_rEGcLWFPpkW8EfUCQCLcBGAsYHQ/w640-h426/apn-3.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div><div>The APN-3 is notable for being the first artillery night sight to be listed in the GRAU index - it has the GRAU designation of 1PN1. With the absence of information on the APN-2 series, the APN-3 series appears to have been the first of its type to be adopted by the Soviet Army, produced serially, and issued to the troops. The APN-3 would not only be the first artillery night sight, but also the only one of its type available for field guns meant for anti-tank work. The APN-3-5, APN-3-7, APN-3-55 and APN-3-77 variants were created for the BS-3, D-44N3, ZiS-2N and D-48 guns respectively.</div><div> </div><div>The sight has a fixed magnification of 7.5x and a field of view of 6 degrees. The photo below, taken from the book "<i>A Magyar Néphadsereg szárazföldi csapatainak hadrendi változásai 1987-ben</i>", shows a D-44N operated by the Hungarian People's Army. </div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-tbObja3E3_8/YTD0LpB6IGI/AAAAAAAAUJc/9E7GTo2SBjMgKhXJpRGMH7144hR3RJPTQCLcBGAsYHQ/s2048/d-44n.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1364" data-original-width="2048" height="426" src="https://1.bp.blogspot.com/-tbObja3E3_8/YTD0LpB6IGI/AAAAAAAAUJc/9E7GTo2SBjMgKhXJpRGMH7144hR3RJPTQCLcBGAsYHQ/w640-h426/d-44n.png" width="640" /></a></div><div><br /></div><div><br /></div><div>Pending further research, little can be said about this sight. It uses a single S-1 photocathode (as only Ag-O-Cs photocathodes were described in Soviet literature) and requires illumination from the enormous IR spotlight for effective shooting. In the technical manual for the sight, it is stated that the viewing range with infrared illumination is 800 meters, presumably facilitated by the high magnification of the sight and the much higher gain of a Gen 1 device, as opposed to a Gen 0 device such as the FG1250 of WWII vintage with a 400-meter viewing range. </div><div><br /></div><div>The image below shows the viewfinder markings of an APN-3-7 for legacy ammunition. The reticle consists of a chevron with two vertical dashes for windage adjustments, and below the chevron is a vertical line and a horizontal line in an inverted "T" shape. The gunner adjusts the position of the reticle by turning a range dial to lower the reticle along the range scales until the horizontal line aligns with the desired range for the appropriate ammunition type. The range scale on the left is used for sharp-tipped AP shells (BR-365K), the center scale is used for full-charge Frag shells, and range scale on the right is for wartime APCR.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-VpOpf5c4ZEY/YTPJ29aF7yI/AAAAAAAAUJo/7Hjk8CZ2aVgrAvLlDmxxgi0bepqXusiUwCLcBGAsYHQ/s942/APN3-7.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="942" data-original-width="875" height="400" src="https://1.bp.blogspot.com/-VpOpf5c4ZEY/YTPJ29aF7yI/AAAAAAAAUJo/7Hjk8CZ2aVgrAvLlDmxxgi0bepqXusiUwCLcBGAsYHQ/w371-h400/APN3-7.png" width="371" /></a></div><br /><div><br /></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="d44-gun"></a><h3 style="text-align: left;"><span style="font-size: large;">GUN</span></h3><div><br /></div><div><br /></div><div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-oZwppXVyZn8/X8nfJ5OoyMI/AAAAAAAASNU/azdgbzZL0yoxeRZkF73oCqLwqK4aum6LwCLcBGAsYHQ/s2653/barrel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="789" data-original-width="2653" height="190" src="https://1.bp.blogspot.com/-oZwppXVyZn8/X8nfJ5OoyMI/AAAAAAAASNU/azdgbzZL0yoxeRZkF73oCqLwqK4aum6LwCLcBGAsYHQ/w640-h190/barrel.png" width="640" /></a></div></div><div><br /></div><div><br /></div></div><div><br /></div><div><br /></div><div>The D-44 fires the 85x629mm cartridge. According to A. V. Shirokorad in his encyclopedia "<i>Энциклопедия Отечественной Артиллерии</i>" (Encyclopedia of Domestic Artillery), the creation of the 85mm caliber was driven by the desire to optimize the performance of the existing 76.2mm M1931 anti-aircraft gun by using up the growth potential of its ammunition. The 85mm caliber allegedly emerged because it was the largest projectile diameter that could be fitted into a 76.2x558mm cartridge case, though contrary to this narrative, the resulting 85mm ammunition had a slightly longer and wider case to accommodate a larger weight of propellant, effectively making it an entirely new cartridge. Nevertheless, it shared the same operating pressure of the 76.2mm AA ammunition and had proportionally identical ballistics but weighed considerably more, and could therefore deliver a much larger payload to a higher effective ceiling.</div><div><br /></div><div>Like the D-5 and ZiS-S-53 tank guns that came before it, the D-44 inherited the ballistics of the 52-K gun. Proportionately, the D-44 is ballistically equivalent to guns like the 7.5cm Pak 40, 3-inch M5 and 77mm HV. These guns fire AP shells with effectively the same muzzle velocity of 790 m/s or thereabouts. In terms of raw energy, the direct equivalent of the D-44 was the 17-pdr gun. The 17-pdr and D-44 were both L/55 guns and generated almost the same muzzle energy; firing an APBC round, the D-44 generates 2.988 MJ of kinetic energy at the muzzle, and the 17-pdr generates 2.985 MJ of energy when firing any of its standard 17-pound AP rounds. </div><div><br /></div><div><div>It has a semi-automatic, vertically sliding breechblock, opened with a large lever on the right of the breech. The firing mechanism is completely mechanical, with a firing pin and striker. The breechblock-closing mechanism and the extractor are both spring-loaded, and are cocked by the recoil of the gun. The entire system is totally conventional, with no real differences from any other modern semi-automatic field gun of its time. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Rdo0mmqh7IE/X9iTPc6HDgI/AAAAAAAASbU/K3ttTqFL1YAEy25UNOBNnzUPOFokgsCtACLcBGAsYHQ/s2048/closed%2Bbreech%2Bblock.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1470" height="400" src="https://1.bp.blogspot.com/-Rdo0mmqh7IE/X9iTPc6HDgI/AAAAAAAASbU/K3ttTqFL1YAEy25UNOBNnzUPOFokgsCtACLcBGAsYHQ/w288-h400/closed%2Bbreech%2Bblock.png" width="288" /></a><a href="https://1.bp.blogspot.com/-Et2-Bv7w1iA/X9iTPNKDsoI/AAAAAAAASbQ/DPRRPS2ThMky0V_MvhcnwTy1S5s3QoinwCLcBGAsYHQ/s2048/opened%2Bbreech%2Bblock.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1392" height="400" src="https://1.bp.blogspot.com/-Et2-Bv7w1iA/X9iTPNKDsoI/AAAAAAAASbQ/DPRRPS2ThMky0V_MvhcnwTy1S5s3QoinwCLcBGAsYHQ/w273-h400/opened%2Bbreech%2Bblock.png" width="273" /></a></div><div><br /></div><div><br /></div><div>The action of the breech-opening mechanism is shown in the two drawings below, from recoil (left) to counter-recoil (right). Lever (19) opens the breech block. </div><div><br /></div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-LuCvbyPcCDM/X9ooxNpov1I/AAAAAAAAScw/5Q0rCJW_w6kNW2LDnGpS7eddI_iGOvOBQCLcBGAsYHQ/s2048/recoil.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1921" data-original-width="2048" src="https://1.bp.blogspot.com/-LuCvbyPcCDM/X9ooxNpov1I/AAAAAAAAScw/5Q0rCJW_w6kNW2LDnGpS7eddI_iGOvOBQCLcBGAsYHQ/s320/recoil.png" width="320" /></a><a href="https://1.bp.blogspot.com/-xxlGoDVb3a0/X9ownuRAU-I/AAAAAAAASdA/8kf3QexSPzcifqjp__u6kmeev_QhC7bnwCLcBGAsYHQ/s2048/counterrecoil.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="2044" height="320" src="https://1.bp.blogspot.com/-xxlGoDVb3a0/X9ownuRAU-I/AAAAAAAASdA/8kf3QexSPzcifqjp__u6kmeev_QhC7bnwCLcBGAsYHQ/s320/counterrecoil.png" /></a><br /></div></div><div><br /></div><div><br />The maximum rate of fire is 20 rounds per minute, but the aimed rate of fire is considered to be 10-15 rounds per minute. During tests of the ZiS-D-44 in 1945, the rate of fire that was achieved during indirect fire at an elevation angle of +20° with corrections was 15 rounds per minute. Without corrections, the rate of fire was up to 20-22 rounds per minute. The practical rate of fire, when considering the placement of the ammunition pit at a safe distance from the gun, is unknown.</div><div><div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-MlTFJXqmebU/X9Dl52sYMJI/AAAAAAAASV0/-DKTWPiwXvMyZLSSF4hG8ZLqfQs7Sj08gCLcBGAsYHQ/s1920/loading%2Bd-44.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://1.bp.blogspot.com/-MlTFJXqmebU/X9Dl52sYMJI/AAAAAAAASV0/-DKTWPiwXvMyZLSSF4hG8ZLqfQs7Sj08gCLcBGAsYHQ/w400-h225/loading%2Bd-44.png" width="400" /></a></div><div><br /></div></div></div><div><br /></div><div><div>As to be expected from a modern field gun, both the elevation and traverse controls on the D-44 are located on the left side, allowing a single gunner to lay the gun on target. By the time the D-44 was created, this had become a standard feature of artillery. Only legacy systems like the 122mm M-30 howitzer had separate gun laying controls for 2-man gun laying, with the traverse mechanism situated on the right of the gun cradle and the elevation mechanism on the left.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-sc73FBnBOSI/X9Dn1mcEMRI/AAAAAAAASWE/W-ViWa5rh-QOXxSVEEk1Ya3mfv23ZqvvACLcBGAsYHQ/s2048/elevation%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1447" data-original-width="2048" src="https://1.bp.blogspot.com/-sc73FBnBOSI/X9Dn1mcEMRI/AAAAAAAASWE/W-ViWa5rh-QOXxSVEEk1Ya3mfv23ZqvvACLcBGAsYHQ/s320/elevation%2Bmechanism.png" width="320" /></a><a href="https://1.bp.blogspot.com/-bkkld8wzcVw/X9Dn1uLsr-I/AAAAAAAASWA/BkuVYjC9b5QgFqYBVBGHVbF3uI1LutE_wCLcBGAsYHQ/s2048/traverse%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1105" data-original-width="2048" height="216" src="https://1.bp.blogspot.com/-bkkld8wzcVw/X9Dn1uLsr-I/AAAAAAAASWA/BkuVYjC9b5QgFqYBVBGHVbF3uI1LutE_wCLcBGAsYHQ/w400-h216/traverse%2Bmechanism.png" width="400" /></a></div><div><br /></div><div><br /></div>An interesting feature of the D-44 gun laying controls is that the firing mechanism is triggered via a button installed in the center of the elevation handwheel, as opposed to a lever. Presumably the recoil of the gun is not strong enough that a trigger that needs to be pressed does not pose any danger to the gunner as compared to a trigger that is pulled, away from the direction of recoil and away from the rearward jump of the gun. </div><div><br /></div><div>According to a technical manual for the D-44, it has a swinging mass (elevating mass) of 920 kg. This is defined as the weight of the gun assembly together with the gun cradle (99 kg) and control mechanisms (13 kg), as these comprise the elevating mass of the gun. The specified swinging mass includes the weight of a cartridge, as the gun is assumed to be loaded. Alone, the gun, consisting of the barrel and its breech, weighs 718 kg.</div></div><div><br /></div><div><br /></div><div>The mounting system permits the gun to be traversed by 27 degrees to each side, and the limits of gun depression and elevation are -7 degrees and +35 degrees respectively. It is worth noting that the maximum elevation angle is higher than any other anti-tank gun and it almost matches the ZiS-3 (37 degrees), which is appropriate given the importance of its role as indirect artillery. Because of this, the D-44 could fully exploit the increased energy of its full charge shells, allowing it to outrange the ZiS-3 by over two kilometers and thereby expand the flexibility of divisional artillery and even making it viable as a counterbattery weapon against the 105mm howitzers used by NATO forces.</div><div><div><br /></div><div><br /></div><div>The D-44 was equipped with a pneumatic equilibrator. It was of the push-type, with an oil seal, located to the right of the gun cradle. It consists of the main cylinder with the reservoir of the compensator next to it. The compensator is used to adjust the pressure in the main cylinder. The photo below, from an <a href="http://m.sarov.net/news/?id=31023&switch_to_mobile">unknown source</a>, shows a D-44 without its gun shield, revealing the equilibrator and the way it joints with the gun cradle.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-MVPc6P2vVME/X95hXPDZNbI/AAAAAAAASfY/91YDesD9094GosQhm8XajuaipVG1hqszgCLcBGAsYHQ/s900/d-44%2Bwithout%2Bshield.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="900" height="426" src="https://1.bp.blogspot.com/-MVPc6P2vVME/X95hXPDZNbI/AAAAAAAASfY/91YDesD9094GosQhm8XajuaipVG1hqszgCLcBGAsYHQ/w640-h426/d-44%2Bwithout%2Bshield.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The fact that the equilibrator is a push type indicates that the gun is breech-heavy, differing from the ZiS-3 which was muzzle-heavy. Generally speaking, a pneumatic equilibrator is an ideal type for a field gun and particularly for anti-tank guns, given that it has minimal weight and the relatively limited length of stroke is enough for the limited elevation arcs customary of this class of artillery.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-z9gOgl5ruNQ/X8nVVZCjDaI/AAAAAAAASNA/RCaWgbAs5d8Z7K9rj7Y2K4gpZFzBLx63gCLcBGAsYHQ/s1252/equilibrator%2Bdesign.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1172" data-original-width="1252" height="375" src="https://1.bp.blogspot.com/-z9gOgl5ruNQ/X8nVVZCjDaI/AAAAAAAASNA/RCaWgbAs5d8Z7K9rj7Y2K4gpZFzBLx63gCLcBGAsYHQ/w400-h375/equilibrator%2Bdesign.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The regulator piston had an oil seal which required 0.7 liters of oil, with part of the oil in the compensator. As the drawing on the right below shows, the oil seal is simply a loosely contained quantity of oil that rests between in the expansion chamber between the inner cylinder and outer cylinder. According to the technical manual for the D-44, when the equilibrator is operating at normal pressure (50-60 kgf/sq.cm or 4.9-5.9 MPa), the force on the elevation handwheel when raising and lowering the gun should be almost the same and should not exceed 7 kgf (68-69 N) in steady motion. When the ambient temperature changes, the pressure in the balancing mechanism is regulated with the compensator valve. </div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-eKg3aWuQtUA/X6rM0leo2mI/AAAAAAAASGo/AY_R6lUggzgqLnb9MuEugBlOi0p9tuiKACLcBGAsYHQ/s2048/equilibrator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1727" data-original-width="2048" height="270" src="https://1.bp.blogspot.com/-eKg3aWuQtUA/X6rM0leo2mI/AAAAAAAASGo/AY_R6lUggzgqLnb9MuEugBlOi0p9tuiKACLcBGAsYHQ/w320-h270/equilibrator.png" width="320" /></a><a href="https://1.bp.blogspot.com/-CMDCDorvVeo/X9DvWHNMbbI/AAAAAAAASWU/6JxGdLaow_8ntgh1K1yniZ95MVWfa3NVgCLcBGAsYHQ/s2048/equilibrator%2Bwhen%2Bgun%2Bis%2Blevel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1577" data-original-width="2048" height="308" src="https://1.bp.blogspot.com/-CMDCDorvVeo/X9DvWHNMbbI/AAAAAAAASWU/6JxGdLaow_8ntgh1K1yniZ95MVWfa3NVgCLcBGAsYHQ/w400-h308/equilibrator%2Bwhen%2Bgun%2Bis%2Blevel.png" width="400" /></a><br /></div></div><div><br /></div><div><br /></div><div>The recoling mass of the D-44, which is the weight of the barrel, muzzle brake, breech assembly and recoil mechanism, i.e all of the parts that move during recoil, weighs 785 kg. Compared to 85mm 52-K anti-aircraft gun with the same ballistics, large weight savings had been achieved. The 85mm AA gun obr. 1939 had a recoiling mass of 940 kg, while the D-5 gun used in the SU-85 (D-5S) and early T-34-85 tanks (D-5T) had a recoiling mass of 980 kg, or 25% heavier than the D-44.</div><div><br /></div><div><div>The barrel is placed inside a cast steel cylindrical cradle. The forward half of the cradle serves to provide additional protection for the base of the barrel, where the projectile of a loaded cartridge rests.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-SAeBd_t0kGo/X8ngFR6MPiI/AAAAAAAASNo/tKFETCtHCFcokwB029bgPZHKx44TQzyVQCLcBGAsYHQ/s3100/cradle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1014" data-original-width="3100" height="210" src="https://1.bp.blogspot.com/-SAeBd_t0kGo/X8ngFR6MPiI/AAAAAAAASNo/tKFETCtHCFcokwB029bgPZHKx44TQzyVQCLcBGAsYHQ/w640-h210/cradle.png" width="640" /></a></div><div><br /></div><div><br /></div><div>During recoil, the gun is guided by bronze inserts attached to the walls of the cradle, ensuring that the barrel is axially centered during the initial recoil impulse, before and after the projectile has left the barrel. This provides greater axial stability than older artillery pieces relying on a single guide rail below the gun or symmetrical rails below and above the gun, and was not only used on all Soviet artillery pieces excluding 203mm artillery (B-4M howitzer, 2S7 "Pion"), but also on tank guns. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-OWLCBpE5BuU/X9DslQyFZqI/AAAAAAAASWM/lVDw5S4f3x4JIh0NGDCdyi41sKzq-N4aACLcBGAsYHQ/s2048/d-44%2Bcradle%2Bbronze%2Bguides.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1203" data-original-width="2048" height="235" src="https://1.bp.blogspot.com/-OWLCBpE5BuU/X9DslQyFZqI/AAAAAAAASWM/lVDw5S4f3x4JIh0NGDCdyi41sKzq-N4aACLcBGAsYHQ/w400-h235/d-44%2Bcradle%2Bbronze%2Bguides.png" width="400" /></a></div><div><br /></div></div><div><br /></div><div><div>The total length of the gun, consisting of the barrel, breech assembly and muzzle brake, is 4,685mm or 55 calibers, the same as the 52-K anti-aircraft gun. This is rather short, considering the power of the gun. For reference, the KwK 36 gun had a much longer total length of 62 calibers, but fired its APCBC round at a slightly lower muzzle velocity of 773 m/s due to its lighter propellant charge. Alone, the barrel has a length of 4,146mm, making it an L/48.7 gun. The length of the rifled bore in the barrel is 3,496 mm, or just 41 calibers. </div><div><br /></div><div><br /></div></div><div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-oqykcVEbY3I/X8nfBOBpbsI/AAAAAAAASNQ/yQMv9_dy6IwUKUETHp7K8KkKZs2Wy_IHgCLcBGAsYHQ/s3015/stvol.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1043" data-original-width="3015" height="222" src="https://1.bp.blogspot.com/-oqykcVEbY3I/X8nfBOBpbsI/AAAAAAAASNQ/yQMv9_dy6IwUKUETHp7K8KkKZs2Wy_IHgCLcBGAsYHQ/w640-h222/stvol.png" width="640" /></a></div><br /><div><br /></div></div><div>The chamber has a length of 650mm inclusive of the forcing cone, and it has a volume of 3.94 liters when measured up to the base of an O-365K shell loaded inside.</div><div><br /></div><div>The normal peak pressure of the gun when firing a full charge round is 250 MPa (2,550 kgf/sq.cm), the same as the 76.2mm ammunition for the M1931 anti-aircraft gun. This pressure is reached with the standard AP, APCR and Frag rounds. HEAT and reduced charge Frag rounds produce a lower peak pressure. </div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="d44-recoil"></a><h3 style="text-align: left;"><span style="font-size: large;">RECOIL MECHANISM</span></h3><div><br /></div><div>The recoil mechanism of the D-44 uses the Schneider system, consisting of a hydropneumatic recoil recuperator paired with a recoil buffer. Unlike the original layout of the Schneider system, however, both recoil cylinders were relocated to above the gun. The cylinders of the buffer and recuperator were both affixed to the recoiling gun breech and the pistons were pinned to the gun cradle, to increase the recoiling mass, but there was no sleigh or guide rail. The omission of a heavy steel U-beam rail to guide the gun during recoil, as found on many guns including the 7.5cm Pak 40 and the domestic 100mm BS-3 field gun, gave additional weight savings.</div><div><br /></div><div>A buffer-recuperator pair above the gun cradle reduces the barrel bore axis height and the distance between the bore axis to the recoil mechanism. By not having a large gap between the recoil mechanism and the barrel bore axis, the moment of force generated is minimized which diminishes the reaction forces from the cradle acting on the recoiling gun and also improves the stability of the gun.</div><div><br /></div><div>The hydraulic buffer is shown as the top drawing below. It is filled with 4.75 liters of Steol-M. The hydropneumatic recuperator is shown below. It is filled with 3.4 liters of Steol-M, and is pressurized to 46.45 atm. The recuperator has a concentric compensator tank, simplifying the system compared to a conventional Schneider recuperator with separate, parallel tank.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4820MNihDv0/X9jfCyq2coI/AAAAAAAASb4/7iIX05-r-RIqksZdS0zFTaU97yVVzpTWwCLcBGAsYHQ/s3861/buffer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="814" data-original-width="3861" height="134" src="https://1.bp.blogspot.com/-4820MNihDv0/X9jfCyq2coI/AAAAAAAASb4/7iIX05-r-RIqksZdS0zFTaU97yVVzpTWwCLcBGAsYHQ/w640-h134/buffer.png" width="640" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-7W8fIyOI5ww/X9jfC0NCjhI/AAAAAAAASb8/wAwdDW8m8cs42Jhobwfrz23_OEuDnrU_ACLcBGAsYHQ/s2985/recuperator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1053" data-original-width="2985" height="226" src="https://1.bp.blogspot.com/-7W8fIyOI5ww/X9jfC0NCjhI/AAAAAAAASb8/wAwdDW8m8cs42Jhobwfrz23_OEuDnrU_ACLcBGAsYHQ/w640-h226/recuperator.png" width="640" /></a></div><br /><div><br /></div><div>An additional detail to note is that Steol-M itself is an anti-corrosion solution, but later guns had a chrome lining applied to the inner surface of the cylinder end cap to further increase corrosion resistance.</div><div><br /></div><div>The normal recoil stroke length with a reduced charge round is 515-610 mm, increasing to 580-660 mm with a full charge round. The maximum recoil stroke is 675mm, marked on the indicator slide with the word "stop" to alert the crew that firing with the gun must be ceased immediately. If the recoil stroke of the gun does not reach the minimum threshold of 515mm, the automatic breech opening and ejection mechanism do not work, and the gun reverts to a quarter-automatic mode where the breech would have to be opened manually after each shot by one of the crewmen.</div><div><br /></div><div><br /></div><div>The D-44 uses a TsAKB type double-baffle muzzle brake with flat baffles. The design of the brake is shared with the brake of the ZiS-3 and D-25T. The brake is a one-piece steel casting. In general, muzzle brakes were cast from 35NGML or 30KhNML low-alloy steel grades, both ordinary grades that were commonly used for structural purposes.</div><div><br /></div><div>A muzzle brake of this type was conventional at the time, and remains the most common type found on artillery systems even today. Most of the propellant gasses follow the exiting projectile through the hole in the first baffle but not the second, and hence, a double-baffle brake is universally considered to be the optimal design. Increasing the number of baffles beyond two only brings rapidly diminishing returns. </div><div><br /></div><div><div><br /></div></div><div>When a shot is fired, the propellant gasses exiting the muzzle expand into the free area outside the barrel, whereupon they collide with the baffles. The flowing gasses acting upon the surface area of the baffles generates a pressure by momentum transfer, which in turn creates a braking force, counteracting the recoil force experienced by the gun. Canting the baffles to redirect the gasses rearward can generate a further increase in braking force, at the expense of the working conditions of the gun crew.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-26LnY8alWeo/X6o3FeotyZI/AAAAAAAASE4/FPdlZnwqlMcBOwKh8-gwrKKInzijiV_YQCLcBGAsYHQ/s2059/double%2Bbaffle%2Bmuzzle%2Bbrake.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="879" data-original-width="2059" height="171" src="https://1.bp.blogspot.com/-26LnY8alWeo/X6o3FeotyZI/AAAAAAAASE4/FPdlZnwqlMcBOwKh8-gwrKKInzijiV_YQCLcBGAsYHQ/w400-h171/double%2Bbaffle%2Bmuzzle%2Bbrake.png" width="400" /></a><a href="https://1.bp.blogspot.com/-aTWK9A2xyZA/X9Ei-Bf_ISI/AAAAAAAASXw/ptz7ZEojvr8M8VYFzSQZfLde1qOgi3KWACLcBGAsYHQ/s1167/active%2Bbrake.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="494" data-original-width="1167" height="169" src="https://1.bp.blogspot.com/-aTWK9A2xyZA/X9Ei-Bf_ISI/AAAAAAAASXw/ptz7ZEojvr8M8VYFzSQZfLde1qOgi3KWACLcBGAsYHQ/w400-h169/active%2Bbrake.png" width="400" /></a><br /></div><div><br /></div><div><div><br /></div></div><div>As the muzzle brake still constricts the flow of the propellant gasses, though only to a limited extent, the pressure acting on the exiting projectile does not drop to nil within the length of the brake, so the projectile continues to accelerate. As such, a double baffle brake is responsible for a negligible increase in muzzle velocity. The gas pressure only drops completely at the end of the brake. This is shown in the graph below.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-zlSj4sClCrE/X9x02pgiX0I/AAAAAAAASeg/7CuxmKCvuw4YoSzzIVPS-aZ5YV2frWTQQCLcBGAsYHQ/s1384/gas%2Bpressure%2Bwith%2Bmuzzle%2Bbrake.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="899" data-original-width="1384" height="416" src="https://1.bp.blogspot.com/-zlSj4sClCrE/X9x02pgiX0I/AAAAAAAASeg/7CuxmKCvuw4YoSzzIVPS-aZ5YV2frWTQQCLcBGAsYHQ/w640-h416/gas%2Bpressure%2Bwith%2Bmuzzle%2Bbrake.png" width="640" /></a></div><div><br /></div><div><br /></div><div><div>In terms of its effects on the mechanics of the gun recoil stroke, a muzzle brake can have a positive influence on the dispersion of shots. If the recoil devices are asymmetrically laid out, the asymmetric deflection of the barrel from its reaction forces can be limited by simply reducing the recoil force, thereby also reducing the reaction force. This reduces the "jump" of the gun after a shot and limits the barrel flex, which translates to less intense oscillations at the muzzle after a shot is fired. If the barrel has minimal movement during the next shot, there is less of an increase in dispersion if that shot is fired almost immediately following the first.</div><div><br /></div><div>This is expressed in the "<i>Engineering Design Handbook - Gun Series - Muzzle Devices</i>" as follows</div><div><br /></div><div><i><blockquote>If, during the time the projectile is being propelled down the barrel, the barrel is in motion such that at the time of the shot ejection the muzzle axis has undergone some transverse or angular displacement from its undisturbed position or alternatively the muzzle possesses transverse or angular components of motion at the time of shot ejection, then the flight trajectory of the projectile will be directly affected.</blockquote></i></div></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-dgN94LeN1bM/X9D2jbaXHBI/AAAAAAAASXA/1_sUHFfccVg7GeMNQErkEitYHsf8WcDtQCLcBGAsYHQ/s900/d-44%2Bat%2Bchechnya.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="582" data-original-width="900" height="259" src="https://1.bp.blogspot.com/-dgN94LeN1bM/X9D2jbaXHBI/AAAAAAAASXA/1_sUHFfccVg7GeMNQErkEitYHsf8WcDtQCLcBGAsYHQ/w400-h259/d-44%2Bat%2Bchechnya.jpg" width="400" /></a></div><br /><div><br /></div><div>The muzzle brake does not interfere with the flight of a full-bore projectile during and after its exit from the muzzle, and the TsAKB brake design was compatible with saboted and fin-stabilized projectiles as well. </div><br /><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="d44-ammo"></a><h3 style="text-align: left;"><span style="font-size: large;">AMMUNITION</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-XSnk236jMDs/X9ZMjLLb20I/AAAAAAAASao/598LqBHd4a0whV0B50i8OVCfjSeqJYrlgCLcBGAsYHQ/s905/85mm%2Bt-34-85%2Bammunition.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="905" data-original-width="535" height="400" src="https://1.bp.blogspot.com/-XSnk236jMDs/X9ZMjLLb20I/AAAAAAAASao/598LqBHd4a0whV0B50i8OVCfjSeqJYrlgCLcBGAsYHQ/w236-h400/85mm%2Bt-34-85%2Bammunition.png" width="236" /></a></div><div><br /></div><div><br /></div><div>For the first decade of its service, the D-44 was supplied with the same ammunition as that of the tanks and the self-propelled guns. This included the UBR-365K, UBR-365, and UO-365K rounds, all bearing the 365 series index as they were created according to the ballistics of the 85mm 52-K anti-aircraft gun which had a GAU index of 52-P-365.</div><div><br /></div><div><div>85x629mm cartridges suitable for shooting from the D-44 could also be used without restrictions with 85 mm tank and self-propelled guns of various types, as well as with the 85 mm anti-aircraft gun mod. 1939 (52-K). Some projectiles of the 365th and 367th families were allowed to fire from an 85-mm anti-aircraft gun mod. 1944 (KS-1), but only with a propellant charge specific to this system in the sleeve (i.e., shots completed for the D-44 could not be used for this purpose).</div></div><div><br /></div><div>Ammunition produced during the GPW was marked with "85-39" or just a plain "85" on the cartridge case, indicating an 85mm cartridge with the ballistics of the M1939 anti-aircraft gun. Ammunition produced either during or after 1946 was given an additional "85-Д44" marking together with a "85-СУ и ТАНК" marking. This may serve as a useful method of identifying wartime and postwar ammunition.</div><div><br /></div><div>In the years following the war, a range of new ammunition developed on the basis of German types led to the introduction of an APCBC round and a new APCR round in 1956 alongside domestically designed smoke and Frag rounds. Instead of the wartime 365-series index, the new ammunition was given the 367 index. The internal ballistics of the new ammunition did not differ from the old series, so the D-44 could use existing stockpiles of ammunition and the new 367 series could be used in guns produced during wartime.</div><div><br /></div><div>To further enhance the anti-tank firepower of the D-44, the first generation of Soviet non-rotating, fin-stabilized HEAT ammunition in the 85mm caliber (UBK-367) entered service along with a 76.2mm counterpart (UBK-354) for the ZiS-3. This ammunition was also compatible with the other 85mm guns in use after the war.</div><div><br /></div><div>Aside from these types, the D-44 could also fire the 53-UD-367 smoke and 3UD1 illumination rounds, each with their own reduced charge variant.</div><div><br /></div><div>The KV-4 percussion primer was used with all ammunition. According to the article "<i>85-мм дивизионная пушка Д-44: Начало золотого века советской артиллерии</i>" (<i>85-mm divisional gun D-44: The beginning of the golden age of Soviet artillery</i>) published in the February 2019 edition of the "<i>Техника и вооружение</i>" magazine, the KV-4 primer was rated for a peak pressure of 3,100 kgf/sq.cm, or 304 MPa. This allowed it to function without blowing out if the D-44 was fired with a full charge round at the maximum rated operating temperature of +50°C.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">Frag</span></h3><div><br /></div><div>The focus on Frag shells and the lack of HE-Frag ammunition was a matter of expedience, as the cartridge was adapted from the 52-K anti-aircraft gun. For the anti-aircraft role where airbursting shells were needed to damage high-altitude aircraft, good fragmentation potential was greatly preferred over having a larger explosive mass. Originally, only the conventional steel O-365K shell was available. In 1956, the new O-367A Frag round with a cast iron casing entered service, enhancing the capabilities of the D-44 considerably.</div><div><br /></div><div>With that said, it is worth noting that airburst shelling was not possible with the D-44 as no time-fuzed ammunition was included in its repertoire. The existing O-365 shell for the 52-K anti-aircraft gun, fitted with the T-5 pyrotechnic time fuze, was not authorized for use from a D-44, though it was cleared for use from tank guns during the GPW. </div><div><br /></div><div>Purely high explosive (HE) shells were not used in the artillery of the Soviet Army for calibers under 152mm, because regardless of the efficiency of the shell design, a smaller caliber is simply physically incapable of containing enough explosive mass to destroy well-fortified shelters. For small caliber field guns such as the D-44, the use of Frag shells was quite normal.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">53-UO-365K, 53-UO-367<br />53-O-365K</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-lNuC2OD7qSI/X7qi-wqnXpI/AAAAAAAASI8/cMXUO6vplCANiNJlUT-IL8ie4N7_ApppQCLcBGAsYHQ/s1775/uo-365k.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="607" data-original-width="1775" height="218" src="https://1.bp.blogspot.com/-lNuC2OD7qSI/X7qi-wqnXpI/AAAAAAAASI8/cMXUO6vplCANiNJlUT-IL8ie4N7_ApppQCLcBGAsYHQ/w640-h218/uo-365k.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The UO-365K was one of the two main variations of contact-fuzed 85mm Frag ammunition that was issued as standard for D-44 guns. Compared to the O-365 shell, O-365K was slightly heavier and was fitted with a KTM-1 point-detonating impact fuze or a variant thereof. If the original KTM-1 fuze was replaced with the newer V-429 fuze, an additional "V" suffix would be added to the cartridge designation, becoming the UO-365KV. In addition to the basic UO-365K round, there was also the UO-365KZh which had the iron driving bands replaced with iron-ceramic bands, used during the Great Patriotic War. Compared to shells with conventional copper bands, these bands would erode the barrel bore at a 30% higher rate, but could increase the muzzle velocity very slightly and more importantly, were a viable alternative to circumvent copper shortages. For all variations of the cartridge, the case and explosive filler remained the same. </div><div><br /></div><div>The TNT explosive filler weighs 741 grams. With an overall projectile weight of 9.2 kg, this gives an explosive filler weight proportion of 7.8%. This is firmly within the 5-10% range that defines a fragmentation shell. With this filler weight, the O-365K shell was proportionately equivalent to the 25-pdr Mk. 1D shell, as that had a 7.2% filler weight. The shell casing thickness is 0.21 calibers, which is typical of a fragmentation shell and is at the upper end of the 0.16-0.25 caliber thickness range specified in Russian artillery shell design textbooks.</div><div><br /></div><div><br /></div><div>The muzzle velocity of 793 m/s was achieved with 2.48-2.6 kg of propellant, depending on the brand used. It was possible for a D-44 to reach as far as 15.8 km and deliver good obstacle destruction and even armour penetration performance with O-365K, but the flat trajectory resulting from this high muzzle velocity can degrade the fragmentation efficiency in direct fire and short range indirect fire. This was not necessarily a major issue for the tanks and tank destroyers which were the primary recipients of the UO-365K round during the Great Patriotic War, but for the D-44, a reduced charge variant of the cartridge was needed for plunging fire.</div><div><br /></div><div>This took the form of the UO-367 round, which was fitted with the same O-365K shell but had a lighter propellant charge weighing 1.5 kg or 1.8 kg, depending on the specific brand of powder used. A cardboard tube between the propellant bag and the projectile ensures that the propellant is always in contact with the primer and the burn rate remains consistent.</div><br /><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-qTI9fkVYLOU/X7qjCvHrEEI/AAAAAAAASJA/GfYwQ7yPS7YN20PxciuT6qMtBqv7PjUUQCLcBGAsYHQ/s1781/uo-367.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="605" data-original-width="1781" height="218" src="https://1.bp.blogspot.com/-qTI9fkVYLOU/X7qjCvHrEEI/AAAAAAAASJA/GfYwQ7yPS7YN20PxciuT6qMtBqv7PjUUQCLcBGAsYHQ/w640-h218/uo-367.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The 367 index of the round together with the compatibility marking of 85-Д44 on the case indicates that it was created for the D-44 specifically. It was not issued to tanks or self-propelled artillery.</div><div><br /></div><div>The steel projectile casing is made from S-60 structural carbon steel, a standard steel grade for this purpose with a carbon content of 0.60%, hence the -60 index. Although heat-treated S-60 steel can have a relatively high strength, artillery shell casings built using S-60 steel are not heat treated after forging. This greatly reduced the time and demands on skilled labour required in the manufacturing process, and the resultant low strength yields better fragmentation characteristics. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-8Qj--kI5tNw/X9PCqmMq6hI/AAAAAAAASZo/yw7V0Cga7CsuahmZGckpsCS2Hyph0pzrgCLcBGAsYHQ/s2048/o-365k%2Band%2Bcutaway.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1994" data-original-width="2048" height="390" src="https://1.bp.blogspot.com/-8Qj--kI5tNw/X9PCqmMq6hI/AAAAAAAASZo/yw7V0Cga7CsuahmZGckpsCS2Hyph0pzrgCLcBGAsYHQ/w400-h390/o-365k%2Band%2Bcutaway.png" width="400" /></a></div><div><br /></div><div><br /></div><div>Rather than using high-tensile steel which is a class of low carbon alloy characterized by high strength and ductility, carbon steel is relatively weak and brittle, which is conducive for splinter formation. However, due to the low strength, a thicker casing is required to resist projectile breakup during launch, which means that filler weight of the shell must be diminished. As such, such steel is most practical for fragmentation shells, while high strength steels would be used more often for HE shells. </div><div><br /></div><div>Though HE shells have a larger explosive charge than Frag shells and have a much more useful blast effect by definition, the good ratio of filler to casing weight does not necessarily translate to a more powerful fragmentation effect compared to Frag shells. This is because uing high strength steel for shell casings necessitates a more brisant explosive compound to overcome the aforementioned strength and rupture the casing. But even with more explosive energy, the inefficient splintering characteristics of high strength steel, with elongated grains causing long splinters to be formed, makes Frag shells built with brittle carbon steel the superior choice as far as fragmentation effect is concerned.</div><div><br /></div><div>The tensile strength of S-60 steel is 23-30 kg.f/sq.mm, or 225-294 MPa. The mechanical properties would naturally vary within this range depending on the particular design of the shell and whether heat treatment was applied or not, with different wall thicknesses also having a significant effect. For the O-365K, specific details are not known, but the large thickness of the shell casing walls and the known fact that heat treatment was omitted strongly suggests a low steel strength. For comparison, British artillery shells normally had a casing made from 19-ton steel, referring to the tensile strength in tons per square inch (tsi). 19 tons is equal to 293.4 MPa. This figure is nominally the same as the upper limit of 294 MPa specified for S-60, but the practice of foregoing heat treatment after forging differentiates the O-365K (and other Soviet artillery shells) from other artillery or tank HE shells.</div><div><br /></div><div>Given an impact angle of 20-40 degrees with the ground, an 85mm HE shell has a nominal lethal area of 280 square meters for personnel standing in the open, or 130 square meters for personnel lying prone in the open. For comparison, for an impact angle of 20-50 degrees, a 122mm or 130mm HE-Frag shell produces a nominal lethal area of 800 square meters for personnel standing in the open, and 310 square meters for personnel lying prone in the open. As such, the target effect of a D-44 was very limited compared to the M-30 howitzers used in a rifle division's howitzer battalion, alongside gun battalions armed with the D-44. As a Frag shell, the small filler weight of the O-365K shell makes it largely impotent against field fortifications. The O-365K shell will be much more effective for D-44 guns used in direct fire, where accurate hits on field fortifications are much more likely, but conversely, the small impact angle on the ground in direct fire worsens its fragmentation effect.</div><div><br /></div><div><br /></div><div><b>UO-365K (UO-367)</b></div><div><br /></div><div>Muzzle Velocity: 793 m/s (655 m/s)</div><div>Maximum Range: 15,820 m (13,430 m)</div><div><br /></div><div>Projectile Weight: 9.54 kg</div><div>Explosive charge weight: 0.741 kg</div><div><br /></div><div>Projectile Overall Length: 400mm</div><div>Casing Wall Thickness: 0.21 calibers (17.85mm)</div><div><br /></div><div><br /></div><div>Direct fire at lightly armoured or unarmoured targets such as APCs and trucks is most convenient with the full charge UO-365K round, as its point blank range for a target with a height of 2 meters (representing an M113 APC) is 950 meters.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">53-UO-367A<br />53-O-367</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HjTvAf7NZvI/X7qhtFcfR6I/AAAAAAAASIw/LHt3peq5WrAPIEVpBYkUqliX9ADnCfEqgCLcBGAsYHQ/s1762/uo-367a.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="651" data-original-width="1762" height="237" src="https://1.bp.blogspot.com/-HjTvAf7NZvI/X7qhtFcfR6I/AAAAAAAASIw/LHt3peq5WrAPIEVpBYkUqliX9ADnCfEqgCLcBGAsYHQ/w640-h237/uo-367a.png" width="640" /></a></div><div><br /></div><div><br /></div><div>Introduced in 1956, the UO-367A cartridge has a reduced propellant charge and contains the O-367 cast iron fragmentation shell. It was ballistically matched to the reduced charge UO-367 shell. It was also issued for use in 85mm tank guns in use with the Soviet Army at the time, as indicated by the "85 Д-44, ТАНК, СУ" marking on the cartridge case. This is further corroborated by the sight markings of modernized T-34-85 tanks. </div><div><br /></div><div>O-367 was a Frag shell just like O-365K, but owing to its cast iron casing, it possessed superior fragmentation characteristics at the expense of a small sacrifice in explosive filler weight. Additionally, a full charge variant of UO-367A was not feasible, as a cast iron casing was too fragile to survive a high velocity launch. The muzzle velocity of 655 m/s was similar to the 680 m/s velocity of 76mm O-350A cast iron shells for the ZiS-3, which could be fired with a full charge only because its gun had poorer ballistics.</div><div><br /></div><div>With an explosive filler weight of 670 grams, the explosive weight proportion is just 7% and conversely, the proportion of casing mass is higher to provide a larger fragmentation mass. The projectile casing is made from gray cast iron with a carbon content ranging from 2.7% to 3.3%, with a slightly greater thickness of 0.22 calibers instead of 0.21 calibers for additional fragmentation.</div><div><br /></div><div>To ensure sufficient strength to survive being launched at ordnance velocities, the cast iron was formulated to have a tensile strength in the range of 23-30 kg.f/sq.mm, or 225-294 MPa. However, unlike a forged steel casing, a cast iron casing is invariably more brittle. While the structure of forged steel consists of long, uniform and tightly packed grains, critical in ensuring ductility and strength, cast iron has loosely packed grains of an irregular cuboidal shape. Ideally, the lower strength ensuing from the grain structure of cast iron would be exploited for further improvements in fragmentation potential, but in practice, the material must still be strong enough to survive a high-velocity launch. For cast iron shells, the low ductility is responsible for the enhanced fragmentation behaviour.</div><div><br /></div><div>The formation of elongated fragments (splinters) is undesirable as they are ballistically inefficient, decelerating rapidly in flight due to tumbling and a large projected area. The upside is that the wounds caused by tumbling splinters are very serious within the short effective range. This type of fragmentation is unavoidable with standard high-tensile steels, as the process of fragment formation is characterized by longitudinal fractures forming along the length of the shell, creating long strips of steel which then split into shorter fragments in the shape of splinters, hence the name. Around 80% of the casing mass is formed into splinters, which only contribute a small amount to the total fragmentation effect. Low-elongation fragments are responsible for most of the effect.</div><div><br /></div><div>The two images below show the stark difference in fragmentation efficiency between a Soviet 82mm O-832 cast iron mortar bomb (left) and a Japanese 81mm Type 100 steel mortar bomb (right). Besides the obvious difference in fragment quantity, it can be seen that the cast iron fragments had irregular polygonal shapes with a roughly cubic form, while the steel fragments were generally elongated, the majority of them being splinters. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-IxrzYpzjoIw/X8AT6QCUauI/AAAAAAAASKE/69dkQCWCDEYtvXHIAlmP5Uc17nPB_zRTACLcBGAsYHQ/s2048/o-832%2Bmortar%2Bbomb.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1748" height="400" src="https://1.bp.blogspot.com/-IxrzYpzjoIw/X8AT6QCUauI/AAAAAAAASKE/69dkQCWCDEYtvXHIAlmP5Uc17nPB_zRTACLcBGAsYHQ/w341-h400/o-832%2Bmortar%2Bbomb.png" width="341" /></a><a href="https://1.bp.blogspot.com/-yABbErzbRRM/X8AUlSf2oSI/AAAAAAAASKM/2mrFgTti6CwAyVPx1jQTveVl4_2kKvOAwCLcBGAsYHQ/s500/81mm%2Bjapanese%2Bmortar%2Bbomb.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="500" data-original-width="386" height="400" src="https://1.bp.blogspot.com/-yABbErzbRRM/X8AUlSf2oSI/AAAAAAAASKM/2mrFgTti6CwAyVPx1jQTveVl4_2kKvOAwCLcBGAsYHQ/w309-h400/81mm%2Bjapanese%2Bmortar%2Bbomb.jpg" width="309" /></a><br /></div><br /><div><br /></div><div>In Chapter 1 of the book "Wound Ballistics" by the Medical Department of the U.S Army, the effects of the Type 100 bomb obtained during testing in 1944 was disclosed. Each bomb yielded 542 to 696 fragments, with a mean total of 608.6 fragments per bomb. On the other hand, in the report "Review of Soviet Ordnance Metallurgy" by the Watertown Arsenal, it is stated that tests of the O-832 bomb found that over 10,000 fragments would be produced. Compared to an American steel 82mm M43A1 mortar bomb, the O-832 bomb would produce 9.1 times more hits and 8.1 times more perforations in 1" pine boards within a 40-feet radius. This was despite the M43A1 bomb having a larger share of filler weight.</div><div><br /></div><div>The superb fragmentation effects of cast iron bomb and shell casings was noted in "Wound Ballistics" along with the apparently "crude" construction of the bombs. </div><div><br /></div><div><blockquote><i>Whether it was inadvertent or intentional is debatable, but, in Korea, the Communist use of cruder cast metals in mortar shells seemed greatly to increase the number of fragments per shell and the effectiveness of their antipersonnel mortar fire when compared to conventional steel-walled shells. Often, the number of fragments per shell was many times that described previously for Japanese and German rounds.</i></blockquote></div><div><br /></div><div>Such a comparison is not meant to be scientific or outright conclusive, it merely illustrates the efficiency of cast iron as a casing material in lieu of research material directly pertaining to cast iron artillery shells. No known data is available for the O-367 shell at present, but from the available information, it is reasonable to assume that it offered drastically better anti-personnel performance compared to the O-365K shell. </div><div> </div><div><br /></div><div><div>Muzzle Velocity: 655 m/s</div><div>Maximum Range: 13,430 m</div><div><br /></div><div>Projectile Weight: 9.54 kg</div><div>Explosive charge weight: 0.670 kg</div><div><br /></div><div>Projectile Overall Length: 400mm</div><div>Casing Wall Thickness: 0.22 calibers (18.71mm)</div></div><div><br /></div><div><div><br /></div><div><br /></div><h3 style="text-align: left;">AP</h3><div><br /></div><div>Initially, the D-44 merely fired the same AP and APBC rounds used since the GPW. Though the guns were excellent, the ammunition was of an outdated design. In 1956, new armour-piercing ammunition became available along with the new cast-iron Frag rounds. </div><div><br /></div><div>All 85mm AP shells were APHE, with base charges of varying weights. The base charge in shells produced before 1940 used TNT with an incendiary pellet, but with the invention of A-IX-2, it became the new standard explosive-incendiary compound for APHE and HE-I shells. For the D-44, it can be safely assumed that all ammunition used was loaded with A-IX-2.</div><div><br /></div><div><div>An interesting feature of all 85mm AP rounds is the inclusion of a phlegmatizer liner fitted between the propellant stick bundle and the wall of the cartridge case. The liner is wax paper, impregnated with either paraffin or ceresin wax, based on a description given in the 1970 textbook book <a href="http://rufort.info/lib/latuhin-a-n-sovremennaya-artilleriya-1970/">"<i>Современная артиллерия</i>" (<i>Modern Artillery</i>)</a>. </div><div><br /></div><div>When fired, the propellant gasses vaporizes the phlegmatizer and carries its particles into the barrel where it solidifies as a deposit on the surface of the bore, in a process known as sublimation. The coating forms a protective layer between the bore surface and the hot gasses. Its main purpose is to insulate the bore surface, lowering the rate of heat transfer from the propellant gasses and thus reducing heat erosion. The wax coating deposited on the bore surface is easily scraped away by the driving band of the next shot fired from the gun, so fouling does not occur even with sustained firing. Because of this mechanism, phlegmatizing liners are sometimes referred to as coolant liners, most notably in technical documents from Picatinny Arsenal. </div></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">53-UBR-365K<br />53-BR-365K</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-K1zkBvdM5rE/X9O0D1Kb_cI/AAAAAAAASYs/Ihb5neuGOqo_zVFVVC0MiXNWJHMPAsm1ACLcBGAsYHQ/s2846/ubr-365k.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1105" data-original-width="2846" height="248" src="https://1.bp.blogspot.com/-K1zkBvdM5rE/X9O0D1Kb_cI/AAAAAAAASYs/Ihb5neuGOqo_zVFVVC0MiXNWJHMPAsm1ACLcBGAsYHQ/w640-h248/ubr-365k.png" width="640" /></a></div><div><br /></div><div><br /></div><div>Though the UBR-365K round was clearly anachronistic well before the time the D-44 entered service, being an uncapped AP shell, it was still considered the main armour-piercing round for early guns, as evidenced by the markings in the OP1-7 and OP2-7 sights, where the "AP" ("<i>БР</i>") scale was marked for sharp-headed shells ("<i>ОСТР</i>"). </div><div><br /></div><div>With 2.48-2.6 kg of propellant, depending on the brand used, the 9.2 kg projectile would be propelled to a muzzle velocity of 800 m/s. The lack of a ballistic cap greatly inhibited its long range performance as the shell decelerated at a markedly higher rate than BR-365, an APBC shell. Nevertheless, the trajectory of the shell was still flat enough that the point blank range was effectively the same as BR-365. Its point blank range on a target with a height of 2 meters, 2.7 meters and 3.0 meters is 900, 1,050 and 1,100 meters respectively. In the immediate postwar era where the most common threat tank would be a Sherman, a Centurion or a Patton model of some type, the point blank range against a 3-meter target was directly applicable. </div><div><br /></div><div><div>The forged steel penetrator body was made of low alloy structural steels, with the possible grades varying from 50Kh, KhZNM, 35KhGS, 35KhGSA, and then hardened by heat treatment. 35KhGS was overwhelmingly the most common grade used for sharp-nosed ammunition. 35KhGSA is a variant of 35KhGS with a lower sulfur and phosphorus content. </div></div><div><div><br /></div><div>The shape of the nose is described as a tangent ogive with a caliber radius of 1.45 in a Watertown Arsenal Laboratory report, but the Russian textbook "<i>Устройство и действие боеприпасов артиллерии</i>" states that its radius is 1.53. It is possible that more than one model of BR-365K was produced serially.</div><div><br /></div><div>The base charge is of a modest volume, containing 48 grams of A-IX-2. The explosiveness of A-IX-2 is 1.86 times that of TNT, giving the base charge a potency equivalent to 89 grams of TNT, together with an additional incendiary effect. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-REw373muXIQ/X9Ov5PWnHxI/AAAAAAAASYc/zqIOAiVsSvcEviHOghMgw_QKqi3W3TzggCLcBGAsYHQ/s1391/365k%2Bprojectile.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1391" data-original-width="857" height="400" src="https://1.bp.blogspot.com/-REw373muXIQ/X9Ov5PWnHxI/AAAAAAAASYc/zqIOAiVsSvcEviHOghMgw_QKqi3W3TzggCLcBGAsYHQ/w246-h400/365k%2Bprojectile.png" width="246" /></a><a href="https://1.bp.blogspot.com/-MASyWq4mvuo/X9Ov5ZbajuI/AAAAAAAASYg/SIVpnC9M60s_ZieK5MXQdokDsVD5DeMkQCLcBGAsYHQ/s2048/365k%2Bshell.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1466" height="400" src="https://1.bp.blogspot.com/-MASyWq4mvuo/X9Ov5ZbajuI/AAAAAAAASYg/SIVpnC9M60s_ZieK5MXQdokDsVD5DeMkQCLcBGAsYHQ/w286-h400/365k%2Bshell.png" width="286" /></a></div><div><br /></div></div><div><br /></div><div>Two annular grooves were cut around the circumference of the penetrator body just behind the nose. Upon impact with an oblique plate, the compression waves travelling obliquely down and across the nose of the shell towards the base stresses the entire body. With the localizer grooves, these stresses are concentrated in the grooves, so that upon impact, the inevitable breakup of the penetrator body by shearing is localized to the nose where the grooves are situated, shearing the penetrator along the grooves. The shearing metal compresses the projectile nose and converts the shear stress to a volumetric stress, so that the shear cracks do not spread to the rest of the body and thus reducing the likelihood of shell destruction. The base charge, which is a structural weakening element, remains intact thanks to the grooves, so that it can burst behind the armour plate. </div><div><br /></div>With its sharp nose, BR-365K was most suitable for attacking flat plates of armour of a low to medium hardness. It was ineffective against flat or low-obliquity plates of face-hardened armour due to failure by shatter; localizer grooves do not help prevent shatter. </div><div><br /><div>Their function, as explained in various Soviet technical literature such as the 1970 textbook <a href="http://rufort.info/lib/latuhin-a-n-sovremennaya-artilleriya-1970/">"<i>Современная артиллерия</i>" (<i>Modern Artillery</i>)</a>, was correctly deduced in Watertown Arsenal reports analyzing captured 76mm and 85mm ammunition. </div><div><br /></div><div>Additionally, the localizer grooves ensure that the nose shears off when impacting sloped armour plate, rather than allowing the shell to simply dent the plate and ricochet off. This is more likely with BR-365K and other Soviet sharp-nosed shells than their foreign counterparts, as the metal of the shell is characterized by high toughness rather than high hardness.</div><div><br /></div><div>According to the specifications, detailed in the textbook "<i>Устройство и действие боеприпасов артиллерии</i>", the core of the nose is hardened to a Brinell hardness indentation diameter of <2.9mm (at least 444 BHN) and the base and midsection of the body is hardened to 3.2-3.7mm (269-363 BHN), with the base being the softest. Rather than hardness, the grade of steel used and the heat treatment methods promote higher toughness, reducing the likelihood of failure by shatter. According to the specifications, the nose had to meet this minimum hardness specification, but the penetrator body just behind the nose, a critical zone that had to remain intact, had to reached a hardness of 50 HRC. </div><div><br /></div><div><div>In the Watertown Arsenal Laboratory report "<a href="https://apps.dtic.mil/sti/citations/ADA443218">Metallurgical Examination of Soviet 45mm, 57mm, and 85mm APHE Projectiles FMAM 1121, 1935, and 2175</a>", a metallurgical analysis of a captured BR-365K specimen found that the average Rockwell hardness is 47 HRC from the tip of the nose to the obturating band, and from there the hardness decreases rapidly to approximately 26 HRC at the base. The hardness decreases from surface to center from 50 HRC along the cylindrical surface to approximately 44 HRC in the center of the body. From this, it can be seen that this specimen fully met the specifications.</div><div><br /></div></div><div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-q7lsjImwYjM/X6keglO1_dI/AAAAAAAASEA/iedILlg50okyDQaDQw4SbPPRUmoxixXrgCLcBGAsYHQ/s829/ubr-365k%2Brockwell%2Bhardness.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="829" data-original-width="566" height="400" src="https://1.bp.blogspot.com/-q7lsjImwYjM/X6keglO1_dI/AAAAAAAASEA/iedILlg50okyDQaDQw4SbPPRUmoxixXrgCLcBGAsYHQ/w273-h400/ubr-365k%2Brockwell%2Bhardness.jpg" width="273" /></a><a href="https://1.bp.blogspot.com/-wk6Lm6nvJs4/X9O1FY6D1fI/AAAAAAAASY0/spe_j85vX6Q3OpKgjCsCBRPQ9j3s3exXACLcBGAsYHQ/s3063/365k%2Bcutaway.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3063" data-original-width="1027" height="400" src="https://1.bp.blogspot.com/-wk6Lm6nvJs4/X9O1FY6D1fI/AAAAAAAASY0/spe_j85vX6Q3OpKgjCsCBRPQ9j3s3exXACLcBGAsYHQ/w134-h400/365k%2Bcutaway.png" width="134" /></a><br /></div><div><br /></div></div><div><br /></div><div><br /></div><div><div>The steel was described in the report as being an Mn-Si-Cr steel with a medium carbon content, which matches the chemical composition of <a href="http://metallicheckiy-portal.ru/marki_metallov/stk/35XGSA">35KhGS</a>. It has 0.35% carbon and the main alloying elements are magnesium, silicon and chromium.</div><div><br /></div><div><div>There are numerous indications that the metallurgical design of the shell, namely the choice of a structural steel, was focused on toughness. The grade itself was specified for applications requiring a toughness with high strength, and impact strength. The presence and proportion of each main alloying element had the following purposes: </div><div><br /></div><div></div><blockquote><div>Chromium: gives high strength and resistance to corrosion</div><div>Silicon: increases the level of impact strength</div><div>Manganese: increases resistance to mechanical stress</div></blockquote><div></div><div><br /></div><div>In the Watertown Arsenal Laboratory report, it was observed that the shell was only moderately hardened, and that a reduction in penetration power was to be expected. At the same time, further hardening may also be undesirable. As noted in the report, steels with a 0.32-0.38% carbon content harden to 52-55 HRC upon complete transformation to martensite. However, though hard, martensitic steel is also very brittle, which is an important detail left out in the report. </div><div><br /></div></div></div><div><br /></div><div>Additionally, it was noted that the base of the BR-365K shell was heat-treated to a low hardness but rather than gaining toughness, became embrittled. The ideal practice was described in the report was to fully harden the entire body into martensite, and then apply a differential temper to create a progressive softening and toughening towards the base, allowing the base of the projectile to survive the penetration process intact, and pass behind the target plate. However, the report does not correlate potential issues with the breakup of the base with the presence of the localizer grooves, the purpose of which was to isolate penetrator breakup to the nose region, which may make this type of differential tempering unnecessary for the base to survive intact after armour penetration. But with that said, this a matter that is strongly dependent on the target properties, the impact velocity, and impact angle, so generalizing the behaviour of the shell is difficult. </div></div><div><br /></div><div><div>Contrary to the negative assessment given in the report and the remarks that the least desirable heat treatment method was applied to the base of the shell, the embrittlement of the shell base may have been completely deliberate. A brittle casing around the base charge promotes fragmentation, particularly fragmentation into a larger quantity of smaller splinters, to enhance the probability of striking multiple internal components in a tank. Toughening the shell walls surrounding the base charge would have the same negative effect on fragmentation as on HE or Frag shells.</div><div><br /></div><div><br /></div></div><div><div>According to the Watertown Arsenal Laboratory evaluation, the BR-365K shell was estimated to be effective against slightly undermatching armor up to 60-degree obliquity and against somewhat overmatching armor at 0-30 degrees of obliquity. Specifically, it was estimated that the shell would probably perform almost as well as the 90mm T33 sharp-nosed AP shot against 2 inches of armour sloped at 45-60 degrees and 3-4 inches of armour at 0-30 degrees of obliquity, but probably inferior against "more severe" targets, presumably referring to thicker plates sloped at a greater obliquity.</div><div><br /></div><div><br /></div><div>Muzzle Velocity: 800 m/s</div><div><br /></div><div>Cartridge Mass: 16 kg</div><div>Projectile Weight: 9.2 kg</div><div>Explosive Charge Weight: 0.048 kg</div><div><br /></div><div>Projectile Aspect Ratio: 3.1 calibers</div><div><br /></div></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-BFrrPBauEzA/X9O7OPp7r4I/AAAAAAAASZI/FQx0LK2748wJeYnmnhsEWFG6CH4wFdquQCLcBGAsYHQ/s1046/sharp%2Btipped%2Bpenetration.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1046" data-original-width="762" height="320" src="https://1.bp.blogspot.com/-BFrrPBauEzA/X9O7OPp7r4I/AAAAAAAASZI/FQx0LK2748wJeYnmnhsEWFG6CH4wFdquQCLcBGAsYHQ/w233-h320/sharp%2Btipped%2Bpenetration.png" width="233" /></a></div><div><br /></div><div><br /></div><div>Against sloped armour, the efficacy of BR-365K can be expected to be inferior to BR-365, as its sharp nose is not optimal. Breakup of the ogival nose during impact with a sloped plate is ensured by the presence of the localizer grooves so that when impacting sloped plate, the sharp nose invariably shears off, leaving the remainder of the body with a blunt nose. This is a much more suitable form for defeating sloped armour, but even so, the loss of penetrator mass from the destruction of the nose means that the penetration is inferior to a blunt-nosed shell.</div><div><br /></div><div><br /></div><div><div>Although BR-365K was generally hardened inadequately for FHA targets, it should be borne in mind that FHA had long been abandoned by the time the D-44 entered service, even by Germany during WWII, the only significant user of FHA plate armour on tanks. During <a href="https://i.imgur.com/Uevlj2M.jpg">tests against the medium hardness RHA stee of a Tiger heavy tank in 1945</a>, serially-produced sharp-nosed shells, made with 35KhGS steel, perforated the 82mm side armour twice at a firing distance of 2,000 meters and failed to perforate twice at 2,500 meters. At 2,000 meters, the calculated penetration of BR-365K into FHA is just 66mm. From this, it can be surmised that when attacking homogeneous medium hardness armour, the penetration power of BR-365K can be much higher than the official penetration table indicates. According to British examinations of a captured Tiger, the armour had a uniform hardness of 257-310 BHN.</div><div><br /></div><div>Low hardness, low-strength cast steels also do not pose an issue for BR-365K. According to a <a href="http://btvt.info/5library/vtp_1953_bronja_m26_m46.htm">Soviet metallurgical analysis</a> of an M26 provided by the U.S for evaluation and an M46 captured during the Korean war, the front armour casting had a hardness of just 223-229 BHN. The hardness further dropped to just 210 BHN beginning with the M47 Patton.</div><div><br /></div></div><div><div>The M26 was designed to match the Tiger I and its armour was theoretically capable of shrugging off hits from a KwK 36, at least on its strongest zones. By extension it, along with the M46, could be expected to be well protected from a D-44 firing UBR-365K. However, real experience in Korea showed that the frontal armour was vulnerable. In a number of cases, North Korean T-34-85s using either the wartime UBR-365 blunt-tipped APBC round or UBR-365K sharp-tipped AP round (of which 5 were carried in a standard ammunition load) successfully attacked M26 and M46 tanks from the direct front. They were the most effective out of all weapons used against these tanks, including the 45mm M-42, 57mm ZiS-2 and 76.2mm ZiS-3. Of all hits received from enemy fire, 50% (7 in 14) and 43% (3 in 7) of hits on the M26 and M46 respectively resulted in perforations, with 57mm and 85mm guns being responsible for all 3 successes. All hits were on the frontal armour. </div><div><br /></div><div>Photos of all 3 perforations recorded on M46 tanks were published in the book "Pershing - A History of the Medium Tank T20 Series" by R. P. Hunnicutt. One was from a 57mm AP shell fired from a ZiS-2 at the turret cheek, next to the gun mantlet. The two others, shown below, were from 85mm AP shells of an unknown model. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-49SvVJbXJFY/X6eo9A4oABI/AAAAAAAASDw/B-N9oFlau081yYyHeK8yENMa6D7HC88SwCLcBGAsYHQ/s963/m46%2Bglacis%2Bhit%2Bby%2B85mm.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="780" data-original-width="963" height="324" src="https://1.bp.blogspot.com/-49SvVJbXJFY/X6eo9A4oABI/AAAAAAAASDw/B-N9oFlau081yYyHeK8yENMa6D7HC88SwCLcBGAsYHQ/w400-h324/m46%2Bglacis%2Bhit%2Bby%2B85mm.png" width="400" /></a><a href="https://1.bp.blogspot.com/-M9z2aiXYCeM/X6eo9HQ9JJI/AAAAAAAASD0/T5_WVst2Tnk3jJQ0zFAGZP-Mwp4uVRUfwCLcBGAsYHQ/s972/m46%2Bturret%2Bring%2Bhit%2B85mm.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="737" data-original-width="972" height="304" src="https://1.bp.blogspot.com/-M9z2aiXYCeM/X6eo9HQ9JJI/AAAAAAAASD0/T5_WVst2Tnk3jJQ0zFAGZP-Mwp4uVRUfwCLcBGAsYHQ/w400-h304/m46%2Bturret%2Bring%2Bhit%2B85mm.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The photo on the right shows a perforation through the base of the turret below the gun mantlet, where the armour is 4 inches thick and practically flat, having a nominal angle of 6.5 degrees. The photo on the left shows a perforation through the nose of the upper glacis. Contrary to Hunnicutt's assertion in the book, the towing eye did not act as a shot trap for this hit. The absence of damage to the towing eye and the keyhole shape of the impact crater clearly indicates that it was a straight-on hit on the joint between the upper and lower glaces. In the case of the glacis perforation, it appears that the nose of the one-piece cast hull front is a weakened zone, perhaps due to some peculiarities with its geometry. The perforation of the turret is to be expected, considering that it was 4 inches thick and practically flat. The clean entry hole with minimal damage around the rim is characteristic of a sharp-tipped shell, unlike capped or blunt-nosed shells that crater the armour on impact.</div><div><br /></div><div>It is extremely unlikely that either of the perforations were caused by APCR rounds due to the large size of the entry hole and the absence of an annular crater surrounding the hole, which would be particularly deep and noticeable given the low hardness of the armour. The photo below, shared by <a href="https://twitter.com/AnnQuann/status/1308730507992076289">Lee Ann Quann</a>, shows the characteristic cratering of an APCR round on the turret of a T-54B, the armour of which was cast from a harder and stronger grade of steel. </div></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-qswWjv-S_js/X9O2_GyzH_I/AAAAAAAASZA/WtlquKdCrvMTJcQybRhkIy66jhqW_p6uQCLcBGAsYHQ/s845/vietnamese%2Bt-54b%2Bknocked%2Bout%2Bby%2BAPCR.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="390" data-original-width="845" height="295" src="https://1.bp.blogspot.com/-qswWjv-S_js/X9O2_GyzH_I/AAAAAAAASZA/WtlquKdCrvMTJcQybRhkIy66jhqW_p6uQCLcBGAsYHQ/w640-h295/vietnamese%2Bt-54b%2Bknocked%2Bout%2Bby%2BAPCR.png" width="640" /></a></div><br /><div><br /></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">53-UBR-365<br />53-BR-365</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-fVMvWuVDFhU/X6k1lkxge_I/AAAAAAAASEI/ttk7J3ojrjoYcjXILYxXIvqWziezdGNZwCLcBGAsYHQ/s1761/ubr-365.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="633" data-original-width="1761" height="230" src="https://1.bp.blogspot.com/-fVMvWuVDFhU/X6k1lkxge_I/AAAAAAAASEI/ttk7J3ojrjoYcjXILYxXIvqWziezdGNZwCLcBGAsYHQ/w640-h230/ubr-365.JPG" width="640" /></a></div><div><br /></div><div><br /></div>Shells with a blunt nose were introduced into the Red Army arsenal before World War II with the purpose of defeating cemented plate (face-hardened) and homogeneous high-hardness plate, which were optimal against sharp-nosed shells as they could stop them by shatter failure. For the D-44, having the BR-365 shell in addition to BR-365K gave it a measure of flexibility against the tanks that it was likely to encounter. In the last years of the war, new blunt-nosed shells were developed to defeat the armour of tanks like the Panther, which appeared to represent the most relevant future threat. The 100mm BR-412B and 122mm BR-471B shells were created for this reason. </div><div><br /></div><div><br /></div><div><div>The point blank range on a target with a height of 2.0, 2.7 and 3.0 meters is 950, 1,090 and 1,150 meters respectively. In the immediate postwar era where the most common threat tank would be a Sherman, a Centurion or a Patton model of some type, the point blank range against a 3-meter target was directly applicable.</div><div><br /></div><div><div>The shape of the BR-365 nose corresponds to the 1st type from the right (<i>г</i>). Though it is not completely flat, this rounded shape is considered blunt.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ZPtdKf-Vgpg/X9Y-QSfvOtI/AAAAAAAASag/zE5DgZmnqwAXt68wDLY-bh77l-GkFo8nwCLcBGAsYHQ/s1173/types%2Bof%2Bblunt%2Bnose.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="310" data-original-width="1173" height="106" src="https://1.bp.blogspot.com/-ZPtdKf-Vgpg/X9Y-QSfvOtI/AAAAAAAASag/zE5DgZmnqwAXt68wDLY-bh77l-GkFo8nwCLcBGAsYHQ/w400-h106/types%2Bof%2Bblunt%2Bnose.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The main structural justification for a blunt-nosed projectile is to improve performance on sloped armour plate, by capitalizing on the lower energy needed to perforate the armour by plugging the plate. The improvement largely manifests during the impact phase. On impact, the shoulder of the blunt-nosed projectile, which is close to a right angle, comes into contact with the plate first, followed by the nose, and then the side surface of the projectiles. Because it is the shoulder and nose that first contact the target plate, the reaction force is almost coaxial to the projectile, and the resulting torque pitches the projectile into the plate. This is referred to as a righting torque in the image below. After impact, the projectile forms a dish in the surface of the plate and the following penetration proceeds in much the same manner as with sharp-nosed projectiles. However, during penetration, the reaction force has a smaller vertical component compared to a sharp-nosed projectile because the dishing of the plate tends to be highly localized, unlike a sharp-nosed projectile which tends to form a large dish owing to the large contact area of the ogive. The deflecting torque is therefore lessened compared to a sharp-nosed shell. At the same time, because the deflecting torque is lower, the bending moment is also lower, and because the vertical reaction force is lower, the shear stress is also lessened.</div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgqGlssvQ94fRTXXjM-ddPu5dCU4X41VPzC-T1PIBAhlicnB1MV6v01o3ID9NgRliOSbTkMiai2M1Fi1jUvJFXgq08pviwHzb4x6FB-9B0rlJKvp6UyUJnsgwYkxAPyJbIt0eYZorQEVLK7iBVQKPaMqxpLZ10Vo2V7RNXmRPr9rb1d_dkFNYJvV02AeA=s1558" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1124" data-original-width="1558" height="289" src="https://blogger.googleusercontent.com/img/a/AVvXsEgqGlssvQ94fRTXXjM-ddPu5dCU4X41VPzC-T1PIBAhlicnB1MV6v01o3ID9NgRliOSbTkMiai2M1Fi1jUvJFXgq08pviwHzb4x6FB-9B0rlJKvp6UyUJnsgwYkxAPyJbIt0eYZorQEVLK7iBVQKPaMqxpLZ10Vo2V7RNXmRPr9rb1d_dkFNYJvV02AeA=w400-h289" width="400" /></a></div><div><br /></div><div>Curiously enough, Soviet textbooks only mention localizer grooves when referring to sharp-nosed shells, despite blunt-nosed shells also featuring such grooves. The presence of localizer grooves on a blunt-nosed penetrator appears to not only be redundant as there would be little to no shearing of the nose on impact with an oblique plate, but also possibly counterproductive, serving only to assist penetrator breakup. A possible explanation for their presence is that if breakup does not occur, then if the bending moment (which is lessened compared to a sharp-nosed shell due to the righting torque) is strong enough, it may lead to a ricochet. In such cases, controlled breakup would lead to better penetration performance. At the very least, it can help to ensure that the base of the shell along with its charge survives interaction with armour when attacking plates within the penetration limits of the shell.</div></div><div><br /></div><div>Improved heat-treatment specifications called for a minimum hardness of 45 HRC, a requirement shared with BR-365K shells, but unlike sharp-nosed shells, the entire penetrator body, excluding the base, was treated to a hardness of 50 HRC. </div><div><br /></div><div><br /></div><div>A notable feature of the shell is the voluminous base charge cavity, containing a massive filler of 164 grams of A-IX-2. This is almost three times more than the BR-365K, and is likely responsible for a reduction in the structural integrity of the shell to a great extent. Such a large proportion of explosive filler is otherwise only encountered in small caliber shells. This large charge, taking up 1.78% of the total shell mass, is not only capable of fragmenting the base of the shell after armour perforation, but also generating a meaningful blast and incendiary effect, as it is equivalent to 305 grams of TNT. The charge could possibly even help to burst through armour plate in the event that only partial penetration is achieved, where only a cracked bulge separates the interior of the target from the stopped projectile.</div><div><br /></div><div>Either the MD-5 or MD-7 base fuze would be fitted to the shell.</div><div><br /><div><br /></div></div><div>Muzzle Velocity: 800 m/s</div><div><br /></div><div><div>Cartridge Mass: 16 kg</div><div>Projectile Mass: 9.2 kg</div><div>Explosive Charge Mass: 0.164 kg</div></div><div><br /></div><div>Projectile Aspect Ratio: 4.3 calibers</div><div><br /></div><div><br /></div><div><div><br /></div><div><div>Soviet penetration figures were produced using a semi-empirical methodology where test firings were created to establish reference points from which a penetration table could be calculated using the Jacob DeMarre formula. According to these figures, the penetration of BR-365 is inferior to BR-365K on 0-degree and 30-degree targets at 100 meters, which is to be expected. BR-365 performs better at increased ranges, but this is due to the presence of a ballistic cap, and is not indicative of the merits of its blunt nose. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-PHyNkw4rASE/X9OGilam6CI/AAAAAAAASYM/-xi1hkkbLtYUQtBpA00UAM_3tW2OgXUNwCLcBGAsYHQ/s1200/US_Testing_85mm_Gun_perforation.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="757" height="400" src="https://1.bp.blogspot.com/-PHyNkw4rASE/X9OGilam6CI/AAAAAAAASYM/-xi1hkkbLtYUQtBpA00UAM_3tW2OgXUNwCLcBGAsYHQ/w253-h400/US_Testing_85mm_Gun_perforation.jpg" width="253" /></a><a href="https://1.bp.blogspot.com/-yQZNwsaUWrk/X9OGjk-_mMI/AAAAAAAASYQ/kK31ZgVPhEoH01RDSW0l69E1FFDdAlgmACLcBGAsYHQ/s1200/US_Testing_85mm_Gun_perforation_2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="742" height="400" src="https://1.bp.blogspot.com/-yQZNwsaUWrk/X9OGjk-_mMI/AAAAAAAASYQ/kK31ZgVPhEoH01RDSW0l69E1FFDdAlgmACLcBGAsYHQ/w248-h400/US_Testing_85mm_Gun_perforation_2.jpg" width="248" /></a></div><div><br /></div><div><br /></div><div>The target plate used for testing and calculations was face-hardened steel, also known as Krupp Cemented armour. The DeMarre coefficient K = 2,400 was used to represent the interaction between this type of steel and blunt-tipped shells such as BR-365 at a plate obliquity of 0 to 30 degrees. Validation of the calculated figures was done with live fire testing on a Tiger tank. The results showed that the lower front plate could be pierced from 1,000 meters while the side could be pierced from 1,500 meters, which largely corroborates the calculated figures. When the upper front hull plate was fired upon from 1,500 meters, the shell shattered, leaving a dent 30mm deep and 120mm in diameter. For a blunt-nosed shell on FHA, this is the expected form of projectile failure, and the failure to penetrate is also consistent with the calculated performance, as BR-365 was calculated to penetrate 93mm of FHA at 0 degrees at 1,500 meters.</div></div><div><br /></div><div><br /></div><div>In the absence of real data on the penetration power of BR-365 on contemporary RHA targets, it is necessary to refer to the results of real test firings instead. According to Yugoslavian test results retrieved and published from the Yugoslav archives in Serbia by Bojan Kavedžić, BR-365 could defeat the upper glacis of an M4A3E4 Sherman (obtained by Yugoslavia under the MDAP) at 1,100 meters, the same range that the 7.5cm Pak 40 firing Pzgr. 39 is able to defeat the same armour. Additionally, the front armour of the cast turret could be defeated at 1,000 meters by both rounds. </div><div><div><br /></div><div>At 1,000 meters, a Pzgr. 39 shell fired from a Pak 40 has an impact velocity of 643 m/s (approx) while BR-365 has an impact velocity of 696 m/s. Considering the difference in caliber, the disparity in sectional density and specific impact energy is not as large as the disparity in gross kinetic energy (~25% vs ~58%), but even so, despite its lower specific impact energy, the Pzgr. 39 shell performs the same feat as BR-365. This illustrates the relative inefficiency of the BR-365 shell design. Nevertheless, considering the very large explosive payload that can be delivered to the interior of a tank by BR-365, this can hardly be considered to be bad performance for blunt-nosed shells in general, but is instead indicative of the compromises made in the BR-365 design.</div></div><div><br /></div><div>Considering that the point blank range of BR-365 on a Sherman tank is 1,150 meters, it can be inferred that a D-44 would have had a high probability of a first round kill even when relying on grazing fire or battlesight gunnery. With precision gunnery, made possible by having predetermined range reference points on the battlefield, the first shot kill probability further increases.</div></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">53-UBR-367<br />53-BR-367</span></h3><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xLXrOMcjc7s/X533Wxjdo6I/AAAAAAAAR4I/EnuwyAAWN0EWyUT7o_tm29dOvLpdPo_fQCLcBGAsYHQ/s1381/53-%25D0%25A3%25D0%2591%25D0%25A0-367.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="247" data-original-width="1381" height="114" src="https://1.bp.blogspot.com/-xLXrOMcjc7s/X533Wxjdo6I/AAAAAAAAR4I/EnuwyAAWN0EWyUT7o_tm29dOvLpdPo_fQCLcBGAsYHQ/w640-h114/53-%25D0%25A3%25D0%2591%25D0%25A0-367.JPG" width="640" /></a></div><div><br /></div><div><br /></div><div>Introduced in 1956, the UBR-367 was a product of a large scale ammunition redesign effort from the early 1950's. An entire range of shells of the same layout in the 57mm to 130mm calibers was created during this time. UBR-367 allowed not only the D-44 but all armoured vehicles armed with 85mm guns to perform to their full potential against armoured targets with sloped RHA plate.</div><div><br /></div><div>As with the other cartridges, UBR-367 has a single bundle single-channel stick propellant fitted among loose grains to form a flame channel spanning across the entire length of the charge. Upon the initiation of the primer, the satchel of igniter charge at the base of the casing sends a flame that begins the combustion of the propellant at the base while also projecting a flame down the hollow stick propellant tubes. Flames erupting from the end of the sticks, together with uniform burning rate of the sticks themselves, ensures that the entire propellant charge combusts evenly across its entire length.</div><div><br /></div><div>The point blank range on a target with a height of 2.0, 2.7 and 3.0 meters is 970, 1,100 and 1,160 meters respectively. The difference between its trajectory and the BR-365K shell is slight, and relative to the the BR-365 shell, it is negligible. As such, there is no serious issue with using the same range scale in the OP2-7 sight for all three rounds, as long as the range is within approximately 1,100 meters.</div><div><br /></div><div>The dispersion characteristics of BR-367 are the same as preceding shells, which is excellent. The figures given in the table below represent the 50% dispersion zone of the shot group, synonymous with CEP dispersion or mean dispersion.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEg9bPTCw6bD2Fxehmo2pFe8iL7nhVQvVysEAPO9Hze5EqN_Ubd9EbUFzFI0HpTRvnWWkze7pjia9XQUduNkF5JOrG91wApQ28jfCWCCUn4GCFLRv58NQ6BY5bAA-yj_TYbQIThttVkqmYcar8bHEyctCqGSYxgNyLgN1FQismwlntpf7c7_GEHJ1yMiag=s853" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="214" data-original-width="853" height="160" src="https://blogger.googleusercontent.com/img/a/AVvXsEg9bPTCw6bD2Fxehmo2pFe8iL7nhVQvVysEAPO9Hze5EqN_Ubd9EbUFzFI0HpTRvnWWkze7pjia9XQUduNkF5JOrG91wApQ28jfCWCCUn4GCFLRv58NQ6BY5bAA-yj_TYbQIThttVkqmYcar8bHEyctCqGSYxgNyLgN1FQismwlntpf7c7_GEHJ1yMiag=w640-h160" width="640" /></a></div><div><br /></div><div><br /></div><div>From a detailed observation of its features, it can be seen that the design of the shell follows the same general configuration of other APCBC shells, but unlike the American 76mm M62 or the German Pzgr. 39, the armour-piercing cap is blunt rather than rounded or pointed. The closest analogue in design is the German 7.5cm Pzgr. 39/42 shell, while the material specifications were on the same level as the best foreign shells of the time. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-6f8qBjL15MU/X9Yr9Vi6aTI/AAAAAAAASaY/aYPC1N_7pbI1cq32hj7zRwHbD6s-L7_lACLcBGAsYHQ/s505/ubr-367.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="505" data-original-width="168" height="400" src="https://1.bp.blogspot.com/-6f8qBjL15MU/X9Yr9Vi6aTI/AAAAAAAASaY/aYPC1N_7pbI1cq32hj7zRwHbD6s-L7_lACLcBGAsYHQ/w133-h400/ubr-367.png" width="133" /></a></div><div><br /></div><div><br /></div><div><div>The 60KhНМ and 60Kh2М tool steel grades were used. Compared to earlier shells, more sophisticated heat treatment was employed, providing through hardening, high tempering, hardening and rehardening of the nose, tempering of the shell base, and low-temperature tempering of the entire body. This provided higher hardness and strength. The nose of the shell was treated to a hardness of 57-63 HRC, with the hardness being maximum on the surface of the nose (down to the midsection of the shell) and gradually decreasing into the center of the shell. The base is treated to a Brinell hardness indentation diameter of 3.34-3.6 mm (285-332 BHN). These hardness specifications essentially correspond to that of American shells and to the Pzgr. 39 rot specifications from the later half of the GPW. </div></div><div><br /></div><div>The armour-piercing cap soldered onto the penetrator body serves to prevent both penetrator breakup and shatter, particularly when attacking sloped armour. The presence of a blunt AP cap made localizer grooves uncecessary. 35KhGSA or 46Kh30 could be used for the armour-piercing cap, with 35KhGSA most likely being the predominant grade used on shells of various calibers. Its hardness does not exceed 477 BHN, and the hardness of the base of the cap is 269-321 BHN. The thickness of the armor-piercing cap is ~30mm (0.35 calibers), and the length of the penetrator nose that is covered by the cap is ~83mm (0.98 calibers). To avoid confusion, it should be noted that the AP cap depicted in the drawing shown above (below the subsection title) is not accurate, as it is too small.</div><div><br /></div><div><br /></div><div><div>The cap itself can contribute to penetration on sloped armour, as it is made from hardened steel. On flat armour, an APCBC shell with a blunt cap may be inferior than an uncapped sharp-nosed shell of the same weight, but only if the armour does not cause nose breakup in the uncapped shell. When attacking FHA, the calculated perforation thicknesses published in Soviet penetration tables shows that BR-367 is decidedly superior to both BR-365K and BR-365 on all targets. </div><div><br /></div><div>If BR-365K shells manufactured in the 1950's underwent the same heat-treatment process as BR-367, then in all likelihood, its penetration would have been better than BR-367 on low obliquity targets. This is far from implausible, given that captured 100mm BR-412B shells from the Suez Crisis showed that the improved heat treatment was applied to 100mm shells. </div><div><br /></div></div><div><br /></div><div>The length of the base charge cavity is 1.28 calibers, slightly longer than the BR-365K cavity, but only marginally more voluminous as the shape of the cavity was changed to an ogive rather than a straight cylinder with a hemisphere end. An ogive is structurally sturdier, though more difficult to machine. The weight of the base charge is 50 grams, or 0.55% of the total projectile weight. A charge of this weight is only sufficient for cracking the base of the shell so that after armour perforation, the probability of striking multiple internal components with heavy fragments increases drastically compared to a shell that remains intact after perforation. The image of a BR-367 shown below illustrates the necessity of a base charge for breaking up the shell after armour perforation; under some circumstances, the shell may not break up after penetration or hardly break up enough to generate a strong post-perforation effect.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-53MG0xbETUM/X9SpZQOKhBI/AAAAAAAASaE/1nbn34fcXegh2Tv2lsj4FRmPgo6O_bD6gCLcBGAsYHQ/s775/BR-367%2Bpost%2Bperforation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="775" data-original-width="312" height="400" src="https://1.bp.blogspot.com/-53MG0xbETUM/X9SpZQOKhBI/AAAAAAAASaE/1nbn34fcXegh2Tv2lsj4FRmPgo6O_bD6gCLcBGAsYHQ/w161-h400/BR-367%2Bpost%2Bperforation.png" width="161" /></a></div><div><br /></div><div><br /></div><div>Either the MD-8 or DBR-2 base fuze could be used with BR-367. Both fuzes have an inertial striker with a percussion firing mechanism, and detonate the main charge with a tetryl booster. Both fuzes were fitted with a tracer. The DBR-2 weighs 372 grams. The earliest technical manual for the DBR-2 appears to have been published in 1957, so the use of the MD-8 may have been limited to the earliest BR-367 shells.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-6eXzXTjmaBI/X9PN_GRoP8I/AAAAAAAASZ4/NvjmWV3kCHcC7mbsWdUXlzOV7XFVdxqJQCLcBGAsYHQ/s786/md-8.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="671" data-original-width="786" height="341" src="https://1.bp.blogspot.com/-6eXzXTjmaBI/X9PN_GRoP8I/AAAAAAAASZ4/NvjmWV3kCHcC7mbsWdUXlzOV7XFVdxqJQCLcBGAsYHQ/w400-h341/md-8.png" width="400" /></a><a href="https://1.bp.blogspot.com/-d5i804DSW9M/X85Z8cobMsI/AAAAAAAASUA/Tkd3aNkytcEPfrY72OJD9woDqgkITaHSACLcBGAsYHQ/s2048/dbr-2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1506" height="320" src="https://1.bp.blogspot.com/-d5i804DSW9M/X85Z8cobMsI/AAAAAAAASUA/Tkd3aNkytcEPfrY72OJD9woDqgkITaHSACLcBGAsYHQ/s320/dbr-2.png" /></a></div></div><div><br /></div><div><br /></div><div>According to the technical manuals for the MD-8 and DBR-2, the required deceleration time (effected by armour penetration) to initiate both fuzes is 0.005-0.01 seconds. The delay is regulated by a retardation mechanism so that the fuze detonates the base charge only once deceleration ceases, and with a consistent delay. The resulting effect is that premature bursting of the charge becomes highly unlikely, and the burst occurs at practically the same distance behind an armour plate regardless of the thickness, as long as the plate is thick enough that the deceleration time threshold is reached.</div><div><br /></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-AUGmxOAOz20/X34Z2Ym3m_I/AAAAAAAARrk/_xX1uYHeyt0fS0hTCLRQqX8rs6mHRnIugCLcBGAsYHQ/s1000/german%2Btable.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="348" data-original-width="1000" height="222" src="https://1.bp.blogspot.com/-AUGmxOAOz20/X34Z2Ym3m_I/AAAAAAAARrk/_xX1uYHeyt0fS0hTCLRQqX8rs6mHRnIugCLcBGAsYHQ/w640-h222/german%2Btable.jpg" width="640" /></a></div><br /></div><div><br /></div><div>The BR-367 shell provided the D-44 gun with enough penetration power to fight postwar medium tanks from the side and possibly even from their frontal arc, depending on the tank in question. Some models, like the M47 Patton, were quite weakly armoured overall. Wartime tanks, such as the various Sherman models abundant among postwar militaries, could be fired upon with high confidence of success.</div><div><div><br /></div>A Soviet evaluation of the M48 concluded that domestic guns with a caliber of 85mm or less were ineffective against the armour of the M48, whereas domestic 100mm and 122mm guns firing blunt-nosed APBC shells were considered effective measures, being effective on all parts from various firing angles with the sole exception of the upper glacis.</div><div><br /></div><div>Muzzle Velocity: 805 m/s</div><div><br /></div><div><div>Projectile Mass: 9.2 kg </div><div>Explosive Charge Mass: 0.05 kg</div></div><div><br /></div><div><div>Cartridge Mass: 16 kg</div><div>Projectile Mass: 9.2 kg</div></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">APCR</span></h3><div><br /></div><div>The only subcaliber ammunition available to a D-44 was APCR ammunition. All types of Soviet APCR ammunition were based on German models, but had additional design shortcomings that can only be explained by an underdeveloped munitions industry. This was ameliorated after the war.</div><div><br /></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">52-UBR-365P, 52-UBR-367PK<br />52-BR-365P</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-YKUI8rP6wXw/X9CU10bb9vI/AAAAAAAASVU/31v7DFOn0MswyiSLn-CmB1w5CKqJQkZngCLcBGAsYHQ/s2924/ubr-365p.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1075" data-original-width="2924" height="236" src="https://1.bp.blogspot.com/-YKUI8rP6wXw/X9CU10bb9vI/AAAAAAAASVU/31v7DFOn0MswyiSLn-CmB1w5CKqJQkZngCLcBGAsYHQ/w640-h236/ubr-365p.png" width="640" /></a></div><div><br /></div><div><br /></div><div>Initially, the D-44 would be supplied with the wartime UBR-365P round, originally issued beginning in February 1944. Its design was a direct copy of the German Pzgr. 40, duplicating both the general layout as well as design details such as the solid sand-cast aluminium ballistic cap, unlike other APCR designs such as the 76.2mm BR-354P with a hollow steel ballistic cap. However, unlike the German pattern of arrowhead APCR, a much lighter tungsten carbide core was used in Soviet rounds due to difficulties in producing large cores of adequate quality. </div><div><br /></div><div>The UBR-365P round contains 2.85 kg of propellant. With a muzzle velocity of 1,050 m/s, the point blank range of BR-365P on a target with a height of 2 meters was 1,100 meters. The muzzle velocity of BR-365P was particularly high compared to contemporary APCR rounds owing to its low weight, but on the other hand, it also decelerated rapidly, greatly limiting its effective range against any given target. </div><div><br /></div><div>Alongside the UBR-367P, the more economical UBR-367PK was introduced into service. It consisted of a BR-365P projectile mated to the same propellant charge of the UBR-367P. Otherwise, it was ballistically identical to the wartime UBR-365P. The weight of propellant was reduced to 2.5 kg, but its higher calorific value enabled the same ballistics to be maintained.</div><div><br /></div><div>The body is made of standard structural carbon steel S-55, S-60, st. 08 or st. 10. As with the steel used for Frag shells, the steel for the body would not be heat treated. The hollow tail and annular groove around its midsection help reduce the weight of the body, which would otherwise be parasitic weight that would decrease the effective energy delivered to a target. As with all other APCR or HVAP projectiles, the body is mainly used as a carrier to protect and support the brittle tungsten carbide core as it is fired from the gun, as well as to protect it from damage during rough handling.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-UTjiWfOqSko/X9DcU49PMBI/AAAAAAAASVc/Ha9YrDgzWL4vSGc4-yep8sdOcqdgpG2QACLcBGAsYHQ/s2553/br-365p%2Bcutaway.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2553" data-original-width="1170" height="400" src="https://1.bp.blogspot.com/-UTjiWfOqSko/X9DcU49PMBI/AAAAAAAASVc/Ha9YrDgzWL4vSGc4-yep8sdOcqdgpG2QACLcBGAsYHQ/w184-h400/br-365p%2Bcutaway.png" width="184" /></a><a href="https://1.bp.blogspot.com/-h2zQwzJ4xIQ/X9DcU6sg91I/AAAAAAAASVg/VULOnSJ9ZQAR1DyFIdzcviUdA30h2BoawCLcBGAsYHQ/s1000/german%2Breport%2Bdrawing.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1000" data-original-width="669" height="400" src="https://1.bp.blogspot.com/-h2zQwzJ4xIQ/X9DcU6sg91I/AAAAAAAASVg/VULOnSJ9ZQAR1DyFIdzcviUdA30h2BoawCLcBGAsYHQ/w268-h400/german%2Breport%2Bdrawing.jpg" width="268" /></a></div><div><br /></div><div><br /></div><div>Overall, the BR-365P projectile has a relatively low elongation of 3.22 calibers, which helped save weight. Its tungsten carbide core is 28mm in diameter and 90mm long, giving it an aspect ratio of 3.22. It weighs just 0.648 kg. BR-365P tungsten carbide cores were noted to have high porosity and an irregular grain structure in the report "Review of Soviet Ordnance Metallurgy" by the Watertown Arsenal. These properties decrease the impact strength and toughness of the core, as the pores and irregular grains constitute structural weakenings in the material which facilitate crack formation when the core is stressed. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-hvAJiOhMSgE/X539BVYDqmI/AAAAAAAAR4c/kZYSoQnKljgJSPVSLk31XH4Yj3BOhYwawCLcBGAsYHQ/s647/365p.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="647" data-original-width="251" height="320" src="https://1.bp.blogspot.com/-hvAJiOhMSgE/X539BVYDqmI/AAAAAAAAR4c/kZYSoQnKljgJSPVSLk31XH4Yj3BOhYwawCLcBGAsYHQ/s320/365p.png" /></a><a href="https://1.bp.blogspot.com/-7XDV6Y7dRww/X53__sJkj7I/AAAAAAAAR4k/L2rx9WF6L74l3qthAYF5bLbZywOyGFynwCLcBGAsYHQ/s494/365p%2Bcore.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="494" data-original-width="347" height="320" src="https://1.bp.blogspot.com/-7XDV6Y7dRww/X53__sJkj7I/AAAAAAAAR4k/L2rx9WF6L74l3qthAYF5bLbZywOyGFynwCLcBGAsYHQ/s320/365p%2Bcore.png" /></a></div><br /><div><br /></div><div>The smaller size and weight of the BR-365P core made it more economical to produce in two ways. Firstly, the amount of material used was less, and secondly, the task of sintering large tungsten carbide products in mass quantities was laborious and skill-intensive. Smaller cores, especially those used in small arms bullets and in later APFSDS ammunition were always preferable from a production standpoint. </div><div><br /></div><div>The penetration power of BR-365P was intrinsically limited by the poor quality of its light core, though it was compensated by an increased velocity to a very limited extent. Moreover, although the steel carrier body does not directly influence the penetration capabilities of the projectile, given that its shape is highly inefficient for penetrating armour, it still provides a small contribution by transferring a part of its kinetic energy to the core. This is due to the conservation of momentum, made possible by the physical contact between the body and the core. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-mGNoL3M85Oo/X9UwvI4T_SI/AAAAAAAASaQ/-as9zXevZSQcW5BV0K51KXx8opUm-ACmQCLcBGAsYHQ/s707/apcr%2Bpenetration%2Bprocess%2Billustrated.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="462" data-original-width="707" height="261" src="https://1.bp.blogspot.com/-mGNoL3M85Oo/X9UwvI4T_SI/AAAAAAAASaQ/-as9zXevZSQcW5BV0K51KXx8opUm-ACmQCLcBGAsYHQ/w400-h261/apcr%2Bpenetration%2Bprocess%2Billustrated.png" width="400" /></a></div><div><br /></div><div><br /></div><div>Upon impact, the front end of the body collapses due to the structural weakening created by the reel shape, but the heavier base continues its forward motion, helping to drive the core into the armour like a hammer on a nail. It is not until the steel body loses contact with the core due to its collapse against the surface of the armour that this effect ceases. This mechanism was mentioned in the report "Review of Soviet Ordnance Metallurgy" and the textbook "<i>Устройство и действие боеприпасов артиллерии</i>". A steel plug can be fitted behind the core of an APCR round to take full advantage of this effect, as exemplified by the 76.2mm BR-354P round. <a href="https://i.imgur.com/llegSN8.jpg">A variant of BR-365P with a steel plug</a> was also developed at some point, but was not serially produced. </div><div><br /></div><div><br /></div><div><div>Muzzle velocity: 1,050 m/s</div><div><br /></div><div><div>Cartridge weight 11.42 kg</div><div>Projectile weight: 4.99 kg</div><div>Propellant charge weight: 2.85 kg</div></div><div><br /></div><div>Overall projectile length: 274mm</div><div><div>Core diameter: 28mm</div><div>Core length: 90mm</div></div></div><div>Core weight: 0.648 kg</div><div><br /></div><div><br /></div><div><table style="border-collapse: collapse; border: 1px solid black;"><tbody><tr style="border-collapse: collapse; border: 1px solid black;"><th style="border-collapse: collapse; border: 1px solid black;">Range (m)</th><th style="border-collapse: collapse; border: 1px solid black;">100</th><th style="border-collapse: collapse; border: 1px solid black;">300</th><th style="border-collapse: collapse; border: 1px solid black;">500</th><th>1,000</th><th style="border-collapse: collapse; border: 1px solid black;">1,500</th></tr><tr style="border-collapse: collapse; border: 1px solid black;"><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">Penetration at 0 degrees</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">167mm </td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 152mm </td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 139mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 108mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">83mm</td></tr><tr style="border-collapse: collapse; border: 1px solid black;"><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">Penetration at 30 degrees</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">124mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">114mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 103mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 80mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">62mm</td></tr></tbody></table><div><br /></div><div><br /></div></div><div>Below 500 meters, the penetration of BR-365P was essentially equivalent to a 7.5cm Pzgr. 40 fired from a PaK 40. At 500 meters and beyond, BR-365P was substantially worse. During the famous Yugoslavian tests, it was found that it could defeat the uper glacis of the M4A3E4 Sherman from 1,200 meters, matching the 7.5cm Pzgr. 40 and surpassing BR-365 by 100 meters. However, it only managed to defeat the turret front from 1,250 meters, whereas Pzgr. 40 could do so from 1,500 meters. Unsurprisingly, BR-365P was incapable of defeating the upper glacis of the M47 or the front of its turret, as discovered during the same tests. The frontal arc of the turret was still vulnerable, as BR-365P could still defeat its front-side from 1,000 meters, but in this case, it had no advantage over BR-365. </div><div><br /></div><div>With all this in mind, the usefulness of BR-365P usefulness in a postwar battlefield would have been limited on postwar tanks, but considering that it had only a negligible advantage over BR-365 at the same angles of attack, there was practically no point in issuing UBR-365P rounds at all.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">52-UBR-367P, PZh<br />52-BR-367P, PZh</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-6g4dYrj_z50/X5zw55HprjI/AAAAAAAAR4A/zEkypp0U4rsrDvpgyWd4HrKxMTtqHkO7gCLcBGAsYHQ/s1697/ubr-367p.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="653" data-original-width="1697" height="246" src="https://1.bp.blogspot.com/-6g4dYrj_z50/X5zw55HprjI/AAAAAAAAR4A/zEkypp0U4rsrDvpgyWd4HrKxMTtqHkO7gCLcBGAsYHQ/w640-h246/ubr-367p.png" width="640" /></a></div><div><br /></div><div><br /></div>Entering service in 1949, the UBR-367P round replaced the wartime UBR-365P round issued since February 1944. Unlike the old "arrowhead" design used since 1942 with a design copied from the German 3.7cm Pzgr. 40, the postwar series of APCR ammunition were patterned after the newer 8.8cm Pzgr. 40 round which featured a much more streamlined shape, albeit retaining a reel-shaped steel carrier body. Such type of shot was known as "streamlined" APCR. </div><div><br /></div><div>Like the other propellant charges in the 367 series, the propellant of the UBR-367P round contains a bundle of stick propellant, but instead of a loosely packed bundle, it was fitted to the end of the primer. The function of the bundle remained the same, that is, to ensuring the uniformity of propellant combustion. 2.5 kg of propellant is used, like the UBR-365PK round. According to the article "<i>85-мм дивизионная пушка Д-44: Начало золотого века советской артиллерии</i>" (<i>85-mm divisional gun D-44: The beginning of the golden age of Soviet artillery</i>) published in the February 2019 edition of the "<i>Техника и вооружение</i>" magazine, the peak operating pressure developed by BR-367P is 257.9 MPa (2,630 kgf/sq.cm).</div><div><br /></div><div><br /></div><div><div>For BR-367P, the point blank range on a target with a height of 2 meters is 1,120 meters, almost 200 meters further than the standard APCBC round. Though BR-365P has a higher muzzle velocity, the lower drag of the streamlined BR-367P projectile ameliorates the difference at ranges of 500 meters and above. Beyond 500 meters, BR-367P enjoys a rising advantage in velocity, which, combined with the much greater effectiveness of its core, naturally provided an increase in penetration power.</div><div><br /></div><div><br /></div><table style="border-collapse: collapse; border: 1px solid black;"><tbody><tr style="border-collapse: collapse; border: 1px solid black;"><th style="border-collapse: collapse; border: 1px solid black;">Range (m)</th><th style="border-collapse: collapse; border: 1px solid black;">100</th><th style="border-collapse: collapse; border: 1px solid black;">500</th><th>1,000</th><th style="border-collapse: collapse; border: 1px solid black;">1,500</th></tr><tr style="border-collapse: collapse; border: 1px solid black;"><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">BR-365P (m/s)</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">1,018 </td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 895 </td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 751</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 623</td></tr><tr style="border-collapse: collapse; border: 1px solid black;"><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">BR-367P (m/s)</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">997</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 909</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 803</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 705</td></tr></tbody></table><div><br /></div><div><br /></div></div><div>In a technical manual for the D-44, the maximum effective range of BR-367P was considered to be 2,000 meters - twice as far as BR-365P. Though the definitions of "effective range" are nebulous, this illustrates the degree of improvement brought by the new shot. </div><div><br /></div><div>The dispersion of BR-367P is similar if not identical to BR-367.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEiTgXb0w04EHV8SLsLH163KJdLwSkXgZPxrDszu62PH_26beBVzkB87FPhMWFjX7ebb1gOlcw5QAuskW98Zkt47dzWXB4NpiRUcwL322knhiI9xV89AmGVXrRJKwnKdwLyrR8bqCJhX8uz-086qxP35Q6W5oKB3PvZIme7mhpD1rPOVt_NBxj0WndWAtw=s852" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="217" data-original-width="852" height="165" src="https://blogger.googleusercontent.com/img/a/AVvXsEiTgXb0w04EHV8SLsLH163KJdLwSkXgZPxrDszu62PH_26beBVzkB87FPhMWFjX7ebb1gOlcw5QAuskW98Zkt47dzWXB4NpiRUcwL322knhiI9xV89AmGVXrRJKwnKdwLyrR8bqCJhX8uz-086qxP35Q6W5oKB3PvZIme7mhpD1rPOVt_NBxj0WndWAtw=w640-h165" width="640" /></a></div><div><br /></div><div><br /></div><div><div>A pair of copper driving band were fitted to the base of the body. The body of the BR-367P projectile is made from the same structural carbon steel grades as BR-365P. The body is covered with a steel ballistic cap, and the subcaliber core is secured with a steel cap. The main purpose of the cap is to fix the core firmly to the carrier body and to provide a modicum of drop protection for the brittle core from rough handling. It is most likely too thin to protect from spaced armour, with the possible exception of very thin "Schurzen" type skirts.</div><div><br /></div><div>Compared to the American 76mm M93 HVAP round, the proportional weight of the body is much larger. The smaller parasitic mass of the M93 round can be ascribed to its more sophisticated design consisting of an aluminium body fitted to a steel base. The lag in ammunition technology experienced by the USSR relative to Western military powers was a prevailing theme throughout the Cold War. Nevertheless, the penetration power of M93 was not higher than BR-367P despite its advantageous qualities. There are some possible explanations for this.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-vxtTe2cSwFc/X5zwcXQ66xI/AAAAAAAAR30/tI1vuZxb8DcpyV9Y5rjBxav8qyth6DdigCLcBGAsYHQ/s1514/2.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1251" data-original-width="1514" height="330" src="https://1.bp.blogspot.com/-vxtTe2cSwFc/X5zwcXQ66xI/AAAAAAAAR30/tI1vuZxb8DcpyV9Y5rjBxav8qyth6DdigCLcBGAsYHQ/w400-h330/2.JPG" width="400" /></a><a href="https://1.bp.blogspot.com/-kdK7lNDN9nw/X5zwcaqBA_I/AAAAAAAAR3w/L4Viy5tgOr0Yx95anY-9xFtBrPwP-os0QCLcBGAsYHQ/s1297/br-367p.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1297" data-original-width="474" height="320" src="https://1.bp.blogspot.com/-kdK7lNDN9nw/X5zwcaqBA_I/AAAAAAAAR3w/L4Viy5tgOr0Yx95anY-9xFtBrPwP-os0QCLcBGAsYHQ/s320/br-367p.png" /></a></div><div><br /></div><div><br /></div><div>Compared to BR-365P, the BR-367P projectile has an even smaller elongation of 3.0 calibers, though it was still somewhat heavier overall due to the larger core. Its tungsten carbide core is 35mm in diameter and 140mm long, giving it an aspect ratio of 4.0. It weighs 1.6 kg, which is more than twice the weight of the BR-365P core while the weight of the complete projectile inceased only slightly to 5.3 kg. However, the weight of the core was still lighter than the core of the M93, which weighed 1.79 kg (3.95 lbs). The BR-367P tungsten carbide core shared the same aspect ratio as the 76.2mm BR-354N core, developed in conjunction with BR-367P and sharing the same design features but scaled for a smaller and less powerful gun.</div><div><br /></div><div><div><br /></div><div>Muzzle velocity: 1,020 m/s</div></div><div><br /></div><div><div>Cartridge weight 11.72 kg</div><div>Projectile weight: 5.35 kg</div><div>Propellant charge weight: 2.5 kg</div></div><div><br /></div><div>Overall projectile length: 255mm</div><div><div>Core diameter: 35mm</div><div>Core length: 140mm</div></div><div>Core weight: 1.6 kg</div><div><div><br /></div><div><div><br /></div><div><table style="border-collapse: collapse; border: 1px solid black;"><tbody><tr style="border-collapse: collapse; border: 1px solid black;"><th style="border-collapse: collapse; border: 1px solid black;">Range (m)</th><th style="border-collapse: collapse; border: 1px solid black;">100</th><th style="border-collapse: collapse; border: 1px solid black;">300</th><th style="border-collapse: collapse; border: 1px solid black;">500</th><th>1,000</th><th style="border-collapse: collapse; border: 1px solid black;">1,500</th><th style="border-collapse: collapse; border: 1px solid black;">2,000</th></tr><tr style="border-collapse: collapse; border: 1px solid black;"><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">Penetration at 0 degrees</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">243mm </td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 228mm </td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 213mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 178mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">148mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">121mm</td></tr><tr style="border-collapse: collapse; border: 1px solid black;"><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">Penetration at 30 degrees</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">177mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">166mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 155mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 130mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">108mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">88mm</td></tr></tbody></table><div><br /></div><div><br /></div></div></div><div>Owing to the great improvement in core weight as well as quality, the penetration power of BR-367P was greatly improved compared to the BR-365P, and improved to the extent that it exceeded the 8.8cm Pzgr. 40 fired from a KwK 36 and matched the 76mm M93 HVAP round used in the U.S. </div><div><br /></div><div><br /></div><h3><span style="font-size: large;">HEAT</span></h3><div><br /></div><div>The limitations of conventional 85mm anti-tank munitions against the most modern medium tanks of the 1950's was addressed with new HEAT ammunition. The first example of such ammunition for the D-44 was the UBK-367, entering service in 1953. With it, the relatively modest D-44 became a viable postwar anti-tank gun even when faced with the most dangerous threats on the battlefield. </div><div><br /></div><div>As was expected for postwar HEAT designs, the HEAT shells provided for the D-44 were fin-stabilized. The use of folding fins with a large span rather than fixed fins with a span equal to the projectile diameter, such as the designs used in American HEAT shells, was a design solution to maximize the lift generated by the fins. To give fins the most effective lifting surface, the tail boom should be as small as practical so that a greater portion of the fin is outside of the shell body boundary layer, and the shell body should have a boattail so that smooth uniform flow is presented to the surface.</div><div><br /></div><div><div>It is worth noting that fixed fins are easy and cheap to manufacture to precise tolerances because they have no moving parts, which naturally contributes to reduced shot dispersion. However, fixed fins also impose certain design restrictions. A large amount of space is required between the leading edge of the fins and the shell body to reduce fin-body interference and allow the fins to generate their full lift force. This reduces the projectile volume-to-length ratio. If low drag is important, the long boattail required further reduces the useful projectile volume. This is best exemplified by the <a href="https://i.imgur.com/whnYBR8.jpg">90mm M348 shell</a>, which had a tail extending to the very base of the cartridge case.</div><div><br /></div><div>Folding fins permit projectiles to have a higher volume-to-length ratio than fixed fins designs. Weight and volume savings can thus be obtained, allowing a more powerful charge to be delivered to the target. Moreover, the absence of a long tail boom for the stabilizer fins also increases the rigidity of the projectile, suppresses the vibration and flexing of the tail, and thus prevents damage from scraping against the edges of a muzzle brake. Case in point, the BK-367 shell has a full length of 7.2 calibers, whereas the 90mm M348 shell had a full length of 10.02 calibers. The main disadvantage of folding fins is that they are more complex and expensive to manufacture, and the entire assembly must be built with tight tolerances to minimize the asymmetry of drag forces. </div></div><div><div><br /></div><h3><span style="font-size: large;">53-UBK-367<br />53-BK-367</span></h3><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4GBakOiLOns/X8E2yLHPgXI/AAAAAAAASKU/xBVAPzHJW_w-lb3eguMC3jPDtBQ5tRKUgCLcBGAsYHQ/s1920/cross%2Bsection.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1440" data-original-width="1920" height="300" src="https://1.bp.blogspot.com/-4GBakOiLOns/X8E2yLHPgXI/AAAAAAAASKU/xBVAPzHJW_w-lb3eguMC3jPDtBQ5tRKUgCLcBGAsYHQ/w400-h300/cross%2Bsection.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>Introduced in approximately 1955, the UBK-367(M) round was not only intended for the D-44, but also for tanks and tank destroyers armed with an 85mm gun. At the time of its introduction, this was largely limited to the T-44, modernized T-34-85 tanks and SU-85 self-propelled guns. Due to its great length of 1.3 meters, as compared to just 908mm for a UBR-367 APCBC round, the cartridge may not fit in some ammunition racks. For a D-44, the length of the cartridge was meaningless. </div><div><br /></div><div>Designed to destroy tanks, self-propelled guns and other armoured targets, BK-367(M) had high penetration power and allowed the D-44 to combat practically any tank at the time. It was developed from a project in the late 1940's to provide 76.2mm and 85mm guns with ammunition powerful enough to combat modern tanks, resulting in the UBK-354(M) round in the 76.2mm caliber and UBK-367(M). The GKN percussion spitback fuze is used.</div><div><div><br /></div><div><br /></div><div>Like the 76.2mm BK-354(M) shell for the ZiS-3 and the D-56T tank gun for the PT-76, the muzzle velocity of BK-367(M) is only 550 m/s, owing to a small propellant charge of just 1.3 kg. This modest velocity was a limitation imposed by the deficiencies of the percussion-initiated GKN fuze. </div><div><br /></div><div><div>GKN was specifically designed for 76mm and 85mm fin-stabilized HEAT shells, since it was not possible to use a centrifugal arming mechanism as found in the GKV fuze for spin-stabilized HEAT shells. However, its design was still based on percussion initiation with a striker typical for artillery shells, unlike the piezoelectric fuzes being used abroad in the early 1950's. The initiation delay with a percussion fuze is inherently longer than a piezoelectric type, negatively influencing the penetration power of the HEAT shell, and the fuze is not graze sensitive. </div><div><br /></div><div>Its protective cap must be removed before firing, unless external conditions dictate otherwise. During hailstorms and heavy rain, the cap should be left on. The cap may also prevent the fuze from initiating when passing through thick bushes.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ce41BGdU-iA/X8FvETKz-uI/AAAAAAAASKw/Nj0BZNbklLEvVXirZjaGUVEIL9q133LggCLcBGAsYHQ/s1614/gkn.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1346" data-original-width="1614" height="334" src="https://1.bp.blogspot.com/-ce41BGdU-iA/X8FvETKz-uI/AAAAAAAASKw/Nj0BZNbklLEvVXirZjaGUVEIL9q133LggCLcBGAsYHQ/w400-h334/gkn.png" width="400" /></a></div><div><br /></div><div><br /></div><div>On impact, the large spring-loaded striker is driven back, puncturing the detonator cap. The detonation energy of the initiator cap is transmitted to the initiator charge via a shockwave through the walls of the charge casing, which in turn transmits a shockwave to the booster charge via a membrane. The booster charge sends an explosively formed penetrator (EFP) down the length of the projectile and into the detonator receptable at the apex of the shaped charge liner, finally initiating the primary booster charge and prompting the warhead to explode. The use of an EFP rather than a flame decreases the fuzing delay, which is important during a prolonged delay, because the shaped charge warhead could be deformed as the thin-walled projectile continues its trajectory into a hard target. The fuse works at impact angles up to 60 degrees, which was nominally sufficient for all modern medium tanks of the time, but could be problematic in practice as the target could be positioned obliquely. This performance is the same as the M509 piezoelectric PIBD fuze used in American HEAT shells in the 76-120mm range of calibers.</div></div><div><br /></div><div>The implications of the low muzzle velocity were not positive. It eroded an important advantage of the D-44 over recoilless rifles - ballistics. For comparison, the BK-883 HEAT shell fired from the domestic 107mm B-11 recoilless gun had a muzzle velocity of 400 m/s, while foreign weapons like the 106mm M40 and 120mm BAT recoilless rifles had a muzzle velocity of 500 m/s and 450 m/s respectively, implying that their trajectories were not significantly less flat than BK-367(M). </div><div><br /></div><div><div>Relative to the conventional AP or subcaliber rounds, BK-367(M) had much poorer ballistics, making it much harder to use on distant and moving targets. The point-blank range of the BK-367(M) against a target with a height of 2.0, 2.7 and 3.0 meters is 630, 720 and 760 meters respectively. The maximum sighted range of the shell is 2,000 meters, achieved with a gun superelevation angle of 2°57'. Its performance only appears favourable if compared to smaller caliber crew-served weapons such as the 90mm M67 recoilless rifle which had a muzzle velocity of just 213 m/s. However, the poorer ballistics of M67 were excusable owing to the short-ranged nature of its role.</div><div><br /></div></div><div><br /></div><div>To eliminate the stabilizing spin imparted by the rifling of the gun, the projectile has a slip ring and stabilization is achieved with four flip-out fins made from S-50 or S-60 structural carbon steel. The slip ring is made of S-60 carbon steel and is affixed onto the body by a screw-on wedge collar. A copper obturating band is pressed into the slip ring. The slip ring rotates freely as the projectile travels down the rifled barrel, and the low sliding friction between it and the projectile body reduces the rotational energy induced to the projectile. As a result, the projectile only spins at 10% of the full angular speed from the rifling - fast enough for an equilibrium spin, but slow enough to not influence the shaped charge jet coherence.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYJzNZsywbXizmHdBBEhImU2LW6fnd07b8isC044TYLNIc73_0ROCF88eC0KAw7qza56G2hyRVrXu4ZaOqRYZW8dOY5XLa-KZTR--lNR3k-9YePQnkcTWolL0H5EUGMZI22funDnN0ewU9KnQsqMECjEheDPvD10nN4gd5_bH5-4KjYYDnnb7wj_-kqg/s1836/bk-367m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="682" data-original-width="1836" height="238" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYJzNZsywbXizmHdBBEhImU2LW6fnd07b8isC044TYLNIc73_0ROCF88eC0KAw7qza56G2hyRVrXu4ZaOqRYZW8dOY5XLa-KZTR--lNR3k-9YePQnkcTWolL0H5EUGMZI22funDnN0ewU9KnQsqMECjEheDPvD10nN4gd5_bH5-4KjYYDnnb7wj_-kqg/w640-h238/bk-367m.png" width="640" /></a></div><div><br /></div><div>This solution was better than using a copper slip ring, as the coefficient of sliding friction between dry steel on steel is significantly lower than copper on steel, but it was not the most ideal solution. Nylon obturator bands, as used on American fin-stabilized ammunition of the time, had even less friction on steel and also offered somewhat reduced barrel wear compared to copper bands.</div><div><div><br /></div><div>Before the round is fired, the fins of the projectile are kept tucked in by the neck of the cartridge case, and nothing else. The fins remain closed until the projectile leaves the barrel, since the moment of inertia from the linear acceleration of the projectile acting on the fins is greater than the centrifugal moment until the projectile ceases to accelerate once it leaves the barrel. Once acceleration ceases, the centrifugal moment causes the fins to flip open. The fins are not affected by muzzle brakes, and external perturbations have no real effect on the flight of the projectile. Even the reflection of the muzzle blast shockwave from the surface of the ground has no effect on the opening of the fins. When deployed, the fins are slightly swept back and are stopped from unfurling further by the base of the tail boom. The fins have bevelled surfaces to maintain the spin of the projectile during flight.</div></div><div><br /></div></div><div><br /></div><div>The initial production model suffered from a large dispersion due to a design flaw. BK-367 shells manufactured before 1955 had bevels on both sides of each stabilizer fin. During testing, such projectiles showed a large dispersion of 0.8 mils in the vertical and horizontal planes. Beginning in 1955, new stabilizer fins were built with a one-sided bevel. </div><div><br /></div><div>Similar dispersion issues were present in the 90mm M348 round, which had fixed fins. It was approved for production in 1949-1950. During research and development, the ammunition performed according to specifications with dispersions of 0.3-0.4 mils at 1,000 yards obtained during testing, but the practical use of M348 rounds revealed that the dispersion would increase to 1 mil due to damage to the low-strength fins at the muzzle as the barrel "jumps" from the recoil.</div><div><br /></div><div><br /></div><div>The warhead casing wall has a thickness of 0.09 calibers at the thickest point. The shaped charge liner is an acutely angled cone with a diameter of 60mm and a cone angle of 24 degrees. The liner has the shape of a funnel to permit the flame from the GPV-2 spitback fuze to reach the base detonator. A-IX-1 is used as the explosive filler. An unusual feature of the time was the inclusion of a wave shaper, an inert wave-focusing lens, in the explosive charge to optimize the propagation characteristics of the detonation wave. This improved the penetration power for a given mass of explosive and permitted excellent performance for a shell of limited caliber.</div><div><br /></div><div>According to the penetration data given in the munitions design textbook "<i>Устройство и действие боеприпасов артиллерии</i>", the BK-367 shell with a steel liner penetrates just 230mm of medium hardness armour steel, or RHA, whereas BK-367M penetrates 350mm. The basic variant with a steel liner was essentially a fallback option, serving as a more accessible alternative that could still meet the requirement of perforating the armour of any medium tank (considered to be 200mm) in case copper liners could not be produced due to strategic material shortages.</div><div><br /></div><div><br /></div><div>Muzzle Velocity: 550 m/s</div><div><br /></div><div>Projectile Length (official): 616.75mm (610.83mm without fuze)</div><div><br /></div><div>Projectile Weight: 9.24 kg (9.066 kg without fuze)</div><div>Explosive Filler Weight: 0.979 kg</div><div><br /></div><div><br /></div><div><div><br /></div><div>If judged by penetration power alone, the performance of BK-367M is roughly comparable to contemporary recoilless rifle grenades of a similar caliber such as the 84mm slpsgr m/56 HEAT grenade (310mm RHA) fired from the Carl Gustav. It is also similar to the 90mm M348 shell (304mm RHA flat, 127mm at 60 degrees) and markedly superior to the 90mm M371 HEAT grenade (250mm RHA) fired from the M67. The performance approaches the level of 105mm HEAT shells.</div><div><br /></div><div>The main factors that gave the Soviet design an advantage in penetration power over American HEAT shells were the larger diameter of the shaped charge cone (made possible by a thin warhead casing), the use of a wave shaper, and the superior characteristics of A-IX-1. The detonation velocity of A-IX-1 (8,450 m/s) is significantly higher than Comp. B (7,900 m/s), and the detonation pressure is also higher, 30 GPa compared to 27 GPa.</div></div><div><br /></div><div><br /></div><h3><span style="font-size: large;">3UBK1, 3UBK1M<br />3BK2, 3BK2M</span></h3><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-PJNr0hqfrFY/X9CUVRa6dmI/AAAAAAAASVM/ZspDUZAowcUNBennLFB0NxGQOezc3U50wCLcBGAsYHQ/s3005/ubk1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1046" data-original-width="3005" height="222" src="https://1.bp.blogspot.com/-PJNr0hqfrFY/X9CUVRa6dmI/AAAAAAAASVM/ZspDUZAowcUNBennLFB0NxGQOezc3U50wCLcBGAsYHQ/w640-h222/ubk1.png" width="640" /></a></div></div><div><br /></div><br /><div>Like its predecessor, the UBK1(M) round was not only intended for the D-44, but also for tanks and tank destroyers armed with an 85mm gun. This included the SD-44 self-moving gun, the T-34-85 and the SU-85. The shell design is best described as a refined version of BK-367(M). It was introduced in 1961 as the first in the new series of artillery HEAT shells identified by a sequential 3BK GRAU index, with "3" referring to Category 3 of the GRAU index under which artillery ammunition and rockets were classified, replacing the original Category 53 designation that gave the "53-" prefix for artillery ammunition only. </div><div><br /></div><div>Its main distinguishing factors were a lighter overall weight and the use of a 6-bladed stabilizer fin assembly, which was being used universally for all fin-stabilized ammunition. This permitted a large propellant charge weighing 2.14 kg to be used, propelling the shell to a much higher muzzle velocity of 850 m/s.</div><div><br /></div><div><div>The warhead has a conical liner with an A-IX-1 filler, complete with a wave shaper. A major improvement was the use of the GPV-2 piezoelectric spitback fuze, the latest standardized universal fuze for HEAT shells in a range of calibers from 76.2mm to 115mm. Upon impact, the piezeoelectric element experiences a powerful shockwave and converts the mechanical stresses into an electrical impulse. A potential difference of several kilovolts is produced, which is discharged at the electrodes in the spark gap of the spark detonator. This detonates an initial booster charge, setting off the detonator cap through the walls of the steel cavity by transmitting the shockwave of the explosion. In turn, the detonator cap sets off the booster, sending an EFP into the detonator receptable at the apex of the shaped charge liner. </div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhHOsKOwoXfw2ZUHBUJX5XsGxiQR3RNBeA1OtKm_quVGAjx3CMRFkBlDB3VRS9XlGD6e8LEQNJX5NpdpsCIsR-tWQo6iXVGfYP_VyeUcl1ZN53ZW1xR4qZlgKC3Q9xG-3C2fx5k6kFzmHl908KBgLBgqT2zLTeMktjW9oWTeDtE1IxyIb4ncHkStA-lyg/s1836/bk-2m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="676" data-original-width="1836" height="236" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhHOsKOwoXfw2ZUHBUJX5XsGxiQR3RNBeA1OtKm_quVGAjx3CMRFkBlDB3VRS9XlGD6e8LEQNJX5NpdpsCIsR-tWQo6iXVGfYP_VyeUcl1ZN53ZW1xR4qZlgKC3Q9xG-3C2fx5k6kFzmHl908KBgLBgqT2zLTeMktjW9oWTeDtE1IxyIb4ncHkStA-lyg/w640-h236/bk-2m.png" width="640" /></a></div><div><br /></div><div>The use of a piezoelectric element instead of a mechanical striker enabled the possibility of initiation on grazing impacts if the fuze grazed the target in such a way that the piezoelectric element was stressed. It also reduced the fuzing delay. Based on tests of 3BK5 shells (with the same GPV-2 fuze) in Yugoslavia, the fuze works at impact angles of at least 62 degrees. For comparison, the M509A1 PIBD fuze of the 90mm M431 HEAT shell was demonstrated to have a very high probability of failing to detonate at an impact angle exceeding 60 degrees during the same tests. </div><div><br /></div><div><br /></div><div>To counteract spin from rifling, the projectile uses a steel slip ring secured to the projectile body by a screw-on wedge collar. One difference from the BK-367(M) is that the slip ring features an iron-ceramic obturating band rather than a copper one. This can be expected to increase the bore erosion rate of 3BK2(M) by 30% compared to a conventional shell, but it is also responsible for slightly increasing the muzzle velocity.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Ze6bwPJ6EAc/X8E6DzeVapI/AAAAAAAASKk/47r9x0TyjkkoYOLEjaXU8NtyOspDDxluACLcBGAsYHQ/s1650/3bk2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="358" data-original-width="1650" height="138" src="https://1.bp.blogspot.com/-Ze6bwPJ6EAc/X8E6DzeVapI/AAAAAAAASKk/47r9x0TyjkkoYOLEjaXU8NtyOspDDxluACLcBGAsYHQ/w640-h138/3bk2.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The projectile featured a new stabilizer fin assembly with six fins to provide better shot consistency. 50KhG spring steel was used for the fins. The opening mechanism of the fins remained the same, but the fins have a different design with a canted tip to maintain projectile spin instead of a bevel, and they are not swept back when fully deployed.</div><div><br /></div><div>The length of the projectile increased to 7.4 calibers, but the weight decreased to 7.35 kg. This was largely due to a reduction in the warhead casing thickness from 0.09 calibers to just 0.07 calibers. Additionally, the thickness of the nose fairing cone was also substantially reduced. The casing thickness reduction also permitted the shaped charge cone to be enlarged to 63mm. Based on the penetration data given in the munitions design textbook "<i>Устройство и действие боеприпасов артиллерии</i>", its penetration power with a steel liner (BK2) and copper liner (BK2M) reached 242mm and 282mm respectively. While the penetration with a steel liner was marginally superior, the copper variant had decidedly inferior performance compared to BK-367M.</div><div><br /></div><div>This anomalous reduction in penetration power may be explained by the low thickness of the nose fairing cone. Owing to the nature of the operation of a spitback fuze, even a modern design with a piezoelectric element, there is a delay in the initiation of the explosive charge, during which the nose of the projectile may crumple after impact during the action of the fuze booster charge. The crumpling of the nose should be localized as it is not structurally integral to the warhead itself, so the negative effect on jet formation is not critical, but the reduction in standoff distance explains the poorer penetration power relative to BK-367(M) despite the other positive design qualities.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-u9f2sDxKCIg/X8E4ZWwevsI/AAAAAAAASKc/kGNPZM3z920qPZDkRJwbL1YBIyeHiHurwCLcBGAsYHQ/s1126/bk2m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="524" data-original-width="1126" height="186" src="https://1.bp.blogspot.com/-u9f2sDxKCIg/X8E4ZWwevsI/AAAAAAAASKc/kGNPZM3z920qPZDkRJwbL1YBIyeHiHurwCLcBGAsYHQ/w400-h186/bk2m.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The main upside of the reduced weight is that a much higher muzzle velocity of 850 m/s was achieved. The point blank range on a target with a height of 2 meters is 915 meters, which was a very substantial improvement of almost 300 meters compared to BK-367(M). Velocities higher than 850 m/s only bring very limited, diminishing increases in point blank range. This solved the main issue of BK-367(M), while retaining enough penetration power to fulfill the requirement of combating modern medium tanks, while also having reserve penetration to ensure a meaningful post-perforation effect. As such, despite having inferior penetration, BK2(M) was the superior cartridge overall. It also allowed the D-44 to outclass recoilless rifles, helping to justify the investment into this class of weapon rather than switching entirely to recoilless weapons.</div><div><br /></div><div><br /></div><div><div>Muzzle Velocity: 850 m/s</div><div><br /></div><div>Projectile Length (official): 630.07mm (619.7mm without fuze)</div><div><br /></div><div>Projectile Weight: 7.351 kg (7.221 kg without fuze)</div><div>Explosive Filler Weight: 0.935 kg</div></div><div><br /></div><div><br /></div></div><br /><a href="https://www.blogger.com/null" id="d48"></a><h3 style="text-align: left;"><span style="font-size: large;">D-48 (52-P-372)</span></h3></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-0ZRWAxEVRUg/X96hGhjnM4I/AAAAAAAASg8/fyU3yGNohG8E4TYyq8a-GPXwA337lM_UQCLcBGAsYHQ/s996/victory%2Bmuseum%2Bd-48.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="664" data-original-width="996" height="426" src="https://1.bp.blogspot.com/-0ZRWAxEVRUg/X96hGhjnM4I/AAAAAAAASg8/fyU3yGNohG8E4TYyq8a-GPXwA337lM_UQCLcBGAsYHQ/w640-h426/victory%2Bmuseum%2Bd-48.jpg" width="640" /></a></div><br /><div><br /></div><div>The D-48 was developed by OKB-9, the in-house design bureau of factory No. 9, under the leadership of F. F. Petrov. Its origins date back to the second half of the Great Patriotic War, when a set of tactical-technical requirements were issued in the spring of 1944 with the objective of the project was to match the ballistics of the German Pak 43. A specific requirement was that the muzzle velocity of the full-bore AP shell for the gun could not be lower than 1,050 m/s. It was mandated by the GAU that a necked case from the 100mm B-34 gun with an increased powder charge had to be used instead for economical reasons. </div><div><br /></div><div>The first prototype of the D-48 was delivered for state acceptance tests on the 31st of December 1948. Testing began the next year at the Main Artillery Range, but were suspended after 399 rounds as the high-efficiency muzzle brake was reportedly crippling to the gun crew. After the delivery of a new muzzle brake in the second half of April, tests resumed and continued until June 1949. The new model D-48, modified according to the results of field tests, was completed by the factory in April 1950, and then the gun passed comparative tests along with the 85mm S-6 gun, designed at the TsNII-58 research institute under the leadership of G. V. Grabin. The military ultimately chose the D-48, but tests continued and its adoption only took place in 1953.</div><div><br /></div><div>The first order for 50 guns was issued to factory No. 9 a year later, in 1954, but for unknown reasons, work never began. The design documentation was instead transferred to factory No. 75 in the small Siberian town of Yurga, which had been involved in large gun production during the Great Patriotic War with the manufacture of 122mm D-25 guns in its repertoire, and at the time was engaged in the production of naval gun mounts, anti-tank guns, carriages and mortars. As factory No. 75 was already engaged in the production of D-44 field guns, progress in readying D-48 production was relatively speedy. A pilot batch of 28 guns was built before the end of the year, and the mass production of the D-48 began in earnest in 1955. </div><div><br /></div><div><div>The production rate of the D-48 was marginal compared to other towed weapons, and its production run was extremely brief, ending in 1957. A total of just 819 guns were built. Of that figure, 100 guns were the D-48N model featuring a night vision sight, all produced in 1957. </div><div><br /></div><div></div><blockquote><div>Number of guns produced</div><div>1954: 28</div><div><div>1955: 250</div><div>1956: 251</div><div>1957: 290 (incl. 100 D-48N)</div></div></blockquote><div><div></div><div><div><br /></div><div>As it never saw combat against tanks, the capabilities of the D-48 in its primary role are unknown. However, it is known from Soviet testing that the upper glacis of the Panther could be perforated with 8.8cm Pzgr. 39/43 shells at 600 meters. The ability to perform such a feat with a lightweight, high-velocity towed 85mm gun would have been deeply impressive in late 1943, but given that the D-48 only began mass production in 1955, the permissible standards were rather different. Considering that 100mm AP and APBC shells fired from a D10 could accomplish the same feat at more than twice the range, and that the BS-3 field gun with the same ballistics as the D10 already existed since 1944, it becomes very challenging to justify spending resources on a weapon such as the D-48.</div><div><br /></div></div></div></div><div><div>On the whole, the BS-3 was ostensibly just as good as an anti-tank gun as the D-48, and it would have been redundant to have two guns filling the same role if not quite wasteful due to the introduction of an additional ammunition type into the logistics system of the Soviet artillery forces. The only tangible advantage of the D-48 is that it had a longer point blank range, but this alone was not enough to justify its existence, and conversely, the limitations of the caliber would have made it impossible to fight modern medium tanks from the front - a fact that doomed the fate of the D-48. </div></div><div><br /></div><div><br /></div><div><div>The first guns delivered to the Soviet Army participated in the May Day parade of 1955, towed by AT-P prime movers. This marked the first public appearance of the D-48. It was misidentified as a new 100mm field gun by Western observers and was given the designation of "100-mm field gun M1955". The images below, taken from the report "<a href="https://www.cia.gov/library/readingroom/docs/CIA-RDP81-01043R002200030007-3.pdf">Summary of Significant Soviet Weapons and Equipment</a>" by the U.S Department of The Army, clearly show the D-48 with its asymmetrically rounded gun shield and bulbous muzzle brake.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-uPxhkV8x_Os/X5yhyS3ZPHI/AAAAAAAAR3c/HWENT3ZGooEKk0R0NwP7GnxY2Jj26zkhACLcBGAsYHQ/s1719/d-48%2Btowed%2Bby%2Bat-p.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1203" data-original-width="1719" height="280" src="https://1.bp.blogspot.com/-uPxhkV8x_Os/X5yhyS3ZPHI/AAAAAAAAR3c/HWENT3ZGooEKk0R0NwP7GnxY2Jj26zkhACLcBGAsYHQ/w400-h280/d-48%2Btowed%2Bby%2Bat-p.png" width="400" /></a><a href="https://1.bp.blogspot.com/-Jk46sPYffQc/X5yhyRrxlSI/AAAAAAAAR3g/VQgmOaTdb_0Q0NIvlx6fwgYBdiQWulBJwCLcBGAsYHQ/s2048/100mm%2Bm1955%2Bfield%2Bgun.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1580" data-original-width="2048" height="309" src="https://1.bp.blogspot.com/-Jk46sPYffQc/X5yhyRrxlSI/AAAAAAAAR3g/VQgmOaTdb_0Q0NIvlx6fwgYBdiQWulBJwCLcBGAsYHQ/w400-h309/100mm%2Bm1955%2Bfield%2Bgun.png" width="400" /></a></div><div><br /></div><div><br /></div><div>As was often the case, intelligence reporting on the D-48 was completely incorrect with a mixture of overestimates and underestimates. Evidently, the existence of a new 85mm gun bearing the "D-48" designation was known from military journals, but its characteristics were not. The motorized SD-44 gun was misidentified as the D-48, and as such, it was assumed that its ballistics were identical to the D-44. Unaware of the development of the new 367-series ammunition, the APHE and APCR rounds were listed as penetrating 111mm and 138mm respectively at 500 meters, corresponding to the BR-365K and BR-365P rounds. Aside from that, the quantity of guns produced was grossly overestimated.</div><br /><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HPVrOaYnkzs/X5ykD34YGGI/AAAAAAAAR3o/vi3Jpv8Y6U0PAXULvbSr3uFpLJMsa650gCLcBGAsYHQ/s3219/intel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="977" data-original-width="3219" height="194" src="https://1.bp.blogspot.com/-HPVrOaYnkzs/X5ykD34YGGI/AAAAAAAAR3o/vi3Jpv8Y6U0PAXULvbSr3uFpLJMsa650gCLcBGAsYHQ/w640-h194/intel.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The D-48 was not produced outside of the USSR, and indeed, it was not even produced outside of Yurga. Other than Ukraine, which inherited an unknown quantity of guns that were kept in reserve on its territory before the dissolution of the USSR, only Russia still possesses some D-48 guns, all as museum pieces, monuments, or held in long term storage. The most recent use of the D-48 was in the Ukrainian war where massive losses forced the Ukrainian army to reactivate their reserves, and the restrictions on deploying "heavy artillery" within 50 km of the ATO, defined as having a caliber of 100 or more, made the 85mm D-48 a viable artillery piece.</div><div><br /></div><div>Overall, the D-48 was largely unsuccessful. The design of its carriage served as a basis for the carriage of the more powerful T-12 gun at the No. 75 factory in Yurga, but that was the entire extent of the impact that the D-48 had on Soviet anti-tank artillery. The gun itself was a complete dead end. Its ballistics were more influential, however. Its ballistics were used as the basis of the D-58 gun, made for the experimental Object 906 light tank, and the D-70 gun, used in the serially produced ASU-85. </div></div><div><br /></div><a href="https://www.blogger.com/null" id="d48-deployment"></a><h3 style="text-align: left;"><span style="font-size: large;">DEPLOYMENT</span></h3><div><br /></div><div>The D-48 replaced the D-44 in the anti-tank battalion of motor rifle divisions, and was organized in the same way. It is difficult to determine when it was fully replaced by the T-12 anti-tank gun, but it appeared to have served for at least some time during the 1960's.</div><div><br /></div><div>Although it is not directly explained in any literature why factory No. 9 never began work on producing the D-48, the events at the time show that there were already doubts about the usefulness of towed guns, even in this early stage of the Cold War. For one, the SU-100P self-propelled tank destroyer was in development at the same time as the D-48 and had already passed state trials by 1952, and would be ready for service after the correction of design flaws within the next few years.</div><div><br /></div><div>In the 1950's, the Soviet Army launched a massive modernization effort of its ground forces, with the major focus being the complete motorization of infantry units and their supply chain, leading to the official formation of motorized infantry in 1957. Due to the increased motorization of the infantry, the mobility requirements for divisional artillery increased sharply, and weapons like the SU-100P were much more attractive than towed guns.</div><div><br /></div><div>The SU-100P even managed to enter service in 1955, but only in name, as its career was cut short prematurely by the start of the reorientation from conventional weapons to missile technology led by Nikita Khrushchev. In fact, it is claimed on page 160 of the book "<i>Вооруженные Силы СССР после Второй Мировой войны: от Красной армии к Советской. Часть 1: Сухопутные войска</i>" by V. I. Feskov et al., that the SU-100P was put into service with the intention of replacing the D-48. It was only after the SU-100P was withdrawn that a void in this niche appeared, and without another promising weapon to fill this void, the D-48 had to suffice.</div><div><br /></div><div><br /></div><div>However, the drawbacks of a towed weapon were ameliorated to a great extent by a change in the doctrinal role of heavy anti-tank guns like the D-48. Such guns, organized into anti-tank battalions, were relegated to the reserves of motorized infantry divisions. Under this doctrine, heavy anti-tank guns were expressedly prevented from directly taking part in fighting, as was often the case in WWII. The innately poorer tactical mobility of a towed field gun compared to a fully tracked self-propelled system in difficult terrain was also overcome by deploying them in reserve units.</div><div><div><br /></div><div>An anti-tank battalion was instead used as a defensive reserve in motor rifle divisions, organized into a single anti-tank battalion for a motor rifle division. The anti-tank battalion would normally be held in reserve until the division begins to perform an operational maneuver. When defending against an enemy that has broken through the main forces of the division, the anti-tank guns are brought forward from the reserve and are deployed according to the direction of the main thrust, as determined by the reconnaissance unit organic to the anti-tank battalion. A noteworthy detail is that the enemy tanks are allowed to penetrate deeply behind the lines of the division on purpose, so as to create additional depth with which a stronger defence can be made. </div><div><br /></div><div>The engineer battalion of the division would be used together with the anti-tank battalion to lay minefields rapidly in the path of the enemy thrust, in order to stop them or at least to slow them down in front of the anti-tank guns.</div><div><br />Heavy towed anti-tank guns were also used to protect communications facilities, outposts, forward operating bases, and other important fixed facilities. Due to the static nature of this role, a towed weapon system is fundamentally not worse than a self-propelled system.</div></div><div><br /></div><div><div>In the offensive, the guns of the anti-tank battalion would trail behind the advancing motor rifle battalions and could be deployed in several ways. When the motor rifle battalions attack a hastily prepared defence, the guns could be deployed to protect the flanks and provide security for the supporting units at the rear of the division, with the objective of preventing a potential encirclement. For such tasks, a self-propelled tank destroyer would have been excessive or completely wasteful. To use a tank or tank destroyer in such a role would reduce the number of self-propelled guns available to be concentrated for the main offensive push, both for the breakthrough and to exploit the breakthrough, while completely squandering the mobility of the system by deploying it in fixed defensive positions.</div><div><br /></div><div>If the circumstances at the front permitted, anti-tank guns could be called up to supplement artillery units in providing indirect fire support. Indirect fire was a capability that was also provided by contemporary Soviet assault guns and tank destroyers, but to use self-propelled systems for such a role was wasteful. They could instead be used to reinforce the advancing units in the offense by leveraging their mobility to closely support the infantry or be attached to tank units to enhance their firepower against enemy heavy tanks. </div></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="d48-mobility"></a><h3 style="text-align: left;"><span style="font-size: large;">MOBILITY</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-1N-yAxDdBp0/X5_5bpceHpI/AAAAAAAAR9I/WVH1QWtP3TotnBPFLfSA-2yUU_fg5c88wCLcBGAsYHQ/s887/atp%2Btowing%2Bd-48.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="631" data-original-width="887" height="285" src="https://1.bp.blogspot.com/-1N-yAxDdBp0/X5_5bpceHpI/AAAAAAAAR9I/WVH1QWtP3TotnBPFLfSA-2yUU_fg5c88wCLcBGAsYHQ/w400-h285/atp%2Btowing%2Bd-48.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-GhRP76aSjFA/X8_jEvxYniI/AAAAAAAASU0/_evPiB2Qt0kGuR35USl486JjxUzWgF0IwCLcBGAsYHQ/s2048/d-48%2Btowed.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1509" data-original-width="2048" height="295" src="https://1.bp.blogspot.com/-GhRP76aSjFA/X8_jEvxYniI/AAAAAAAASU0/_evPiB2Qt0kGuR35USl486JjxUzWgF0IwCLcBGAsYHQ/w400-h295/d-48%2Btowed.jpg" width="400" /></a><br /><br /></div><div><br /></div><div>The D-48 would be towed by an AT-P armoured prime mover or a ZiS-151 truck. The newer ZiL-157 may also serve as its prime mover later in its life. It could be towed to a top speed of 60 km/h. On a cobblestone road, the average speed is 35 km/h and the average cross-country speed is 15 km/h. By design, the AT-P was more suitable for combat conditions owing to its small size, armour and integrated bow machine gun, allowing it to bring the gun close to the battlefield and retreat to a hidden position more easily than a truck, and have a much better chance of surviving an artillery bombardment. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-RzULcdrwwO0/X9-WIcp7mqI/AAAAAAAASh4/FdDeX7_Bz6weRf3eirs4BWFlbO-7bURggCLcBGAsYHQ/s1620/at-p%2Btowing%2Bd-48%2Btiv.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1548" data-original-width="1620" height="383" src="https://1.bp.blogspot.com/-RzULcdrwwO0/X9-WIcp7mqI/AAAAAAAASh4/FdDeX7_Bz6weRf3eirs4BWFlbO-7bURggCLcBGAsYHQ/w400-h383/at-p%2Btowing%2Bd-48%2Btiv.png" width="400" /></a></div><div><br /></div><div><br /></div><div><div>The D-48 weighed 2,400 kg in its travelling configuration and 2,350 kg in its combat configuration. This was a large increase in weight over the D-44 and made the system rather burdensome, but for the level of anti-tank firepower provided by the D-48, the level of mobility offered by this weight was unprecedented.<br /><br /></div><div>For comparison, the 8.8 cm Pak 43 towed anti-tank gun with a cruciform carriage had a travelling weight of around 5 tons, though it had an "in-action" weight, or combat weight, of 3,650 kg. That said, the combat weight of the Pak 43 was meaningless since its combat configuration involved the conversion of its cruciform carriage to a firing platform by removing its wheels, rendering it totally immobile. The 8.8cm Pak 43/41 gun is a more relevant point of reference as it was built with a split-trail carriage taken from the 10.5 cm leFH 18 field howitzer. As its carriage was chosen out of expediency rather than for optimal characteristics, the Pak 43/41 had a huge weight of 4,389 kg. The D-48 was also lighter than significantly smaller and less powerful foreign counterparts like the 17-pdr Mk. I anti-tank gun, which had a combat weight of 2,957 kg, despite its smaller 76.2mm caliber. </div></div><div><br /></div><div>The nearest point of reference among domestic artillery was the BS-3. Weighing 3.65 tons in its combat configuration, it was a whopping 1.3 tons heavier than the D-48. The BS-3 was already quite a light gun, being equal in weight to the 8.8cm Pak 43 in its combat configuration while retaining a modicum of mobility thanks to its split-trail carriage, but even so, the BS-3 was comparatively difficult to manhandle as each gun was assigned with the same number of crew members as a D-48. </div><div><br /></div><div>However, despite its advantageous size and weight compared to a BS-3, the D-48 was not more flexible in terms of its towed mobility. The BS-3 was still light enough to not require a heavy artillery tractor, and in fact, its designated prime movers were the same vehicles; the wheeled prime mover was the ZiS-151, and the tracked prime mover could be the wartime Ya-12 or the postwar AT-L or AT-P.</div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="d48-carriage"></a><h3 style="text-align: left;"><span style="font-size: large;">CARRIAGE</span></h3><div><br /></div><div><div><br /></div></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-hNz88BWdIeg/X8oHSUXTSKI/AAAAAAAASPA/0YOJvmmOJo4S7ub2D8h20qyg3xW68dg5ACLcBGAsYHQ/s2048/carriage%2Bcrossbeam.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1336" data-original-width="2048" height="418" src="https://1.bp.blogspot.com/-hNz88BWdIeg/X8oHSUXTSKI/AAAAAAAASPA/0YOJvmmOJo4S7ub2D8h20qyg3xW68dg5ACLcBGAsYHQ/w640-h418/carriage%2Bcrossbeam.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The low weight of the D-48 was achieved thanks to its lightweight split-trail carriage, which had a complete weight of just 1,250 kg. For comparison, the large carriage of the 17-pdr Mk. 1 weighed a whopping 2,132 kg (4,700 lbs). In truth, the carriage of the 17-pdr could serve as a masterclass in poor design, considering that the 17-pdr gun assembly itself weighed just 825 kg, which was actually marginally lighter than the 3-inch M5 (903 kg), not to mention that the gun was only equivalent to a D-44 in muzzle energy, and it was fitted with a high efficiency double baffle muzzle brake.</div><div><br /></div><div>The carriage of the D-48 was derived from the D-44, a fact that is abundantly clear when the carriage crossbeam, shown above, is compared with that of the D-44. The two are not totally identical, however - only a fraction of the parts are interchangeable. It is a cast steel girder with an identical shape and identical layout of parts, with functionally identical components. However, the lack of interchangeability extends even to the suspension, featuring new torsion bars, wheel swing arms and axles together with new tyres. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-fACDg423ays/X9_dbHUWM_I/AAAAAAAASi8/1mEHZfmh3CIQ_OErQcFiUbYcIDbYo7s9QCLcBGAsYHQ/s2048/crossbeam%2Bwith%2Blocked%2Bsuspension.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1124" data-original-width="2048" height="352" src="https://1.bp.blogspot.com/-fACDg423ays/X9_dbHUWM_I/AAAAAAAASi8/1mEHZfmh3CIQ_OErQcFiUbYcIDbYo7s9QCLcBGAsYHQ/w640-h352/crossbeam%2Bwith%2Blocked%2Bsuspension.png" width="640" /></a></div><br /><div><br /></div><div>Gusmatic "GK" airless tyres with a sponge rubber core from the ZiS-5 truck were used. The rim flange width and rim diameter were 7 inches and 34 inches respectively. The external diameter of the tyre was 955mm. The width of the axle track (the distance between the centerline of the two wheels) is 1,475mm, and the maximum width of the gun along the hubcaps of the wheels is 1,780mm. Ordinary pneumatic tyres with the same specifications could be used to replace the GK tyres in an emergency.</div><div><br /></div><div>The ZiS-5 was a historically significant truck of legendary reputation, being the workhorse Soviet commercial and military truck throughout the Great Patriotic War and in the 1950's, with over a million units produced. At the time the D-48 entered production, the ZiS-5 had just ceased production, but it and its offshoots remained extremely prolific and its wheel specifications had become an industry standard. The wheels were well-suited for the weight of the D-48 and they were large enough to ensure sufficient ground clearance and off-road performance.</div><br /><div><br /></div><div>The suspension locking system of the D-48, designed to reduce vibrations and the "jump" of the gun after recoil, remained the same as on the D-44. The parts of the locking pin are interchangeable.</div><div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-_7eb2X4jEn4/X8qlPcJZ0GI/AAAAAAAASPw/XbB9y4xoul8qAnZS-6Q1V-TAjm8DZTZaACLcBGAsYHQ/s2048/suspension%2Block.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2030" data-original-width="2048" height="396" src="https://1.bp.blogspot.com/-_7eb2X4jEn4/X8qlPcJZ0GI/AAAAAAAASPw/XbB9y4xoul8qAnZS-6Q1V-TAjm8DZTZaACLcBGAsYHQ/w400-h396/suspension%2Block.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The primary difference of the D-48 carriage, other than its wheels, was its rectangular trails. The main feature of the trail design is the absence of joints on the corners of the trail. This is unlike the trails of most artillery pieces which are constructed from four separate plates welded or riveted together at the corners. Instead, the D-48 trail design eliminates sharp corners and also avoids having any fastenings contribute to the structural weakening of the trail. The trail consists of a C-beam with rounded corners, reinforced on its top half with a U-beam and on its bottom edge with a flat plate. This is effectively a more efficient form of the common rectangular section design, contributing to the lightening of the weapon system.</div></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--uLp8KMlPjM/X8oHhrD9EDI/AAAAAAAASPE/yJJqekgLG70bKW5vvLi4ORuDbltispmJgCLcBGAsYHQ/s2826/trail.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1113" data-original-width="2826" height="252" src="https://1.bp.blogspot.com/--uLp8KMlPjM/X8oHhrD9EDI/AAAAAAAASPE/yJJqekgLG70bKW5vvLi4ORuDbltispmJgCLcBGAsYHQ/w640-h252/trail.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The only tangible downside to lightening a powerful towed gun is a somewhat reduced platform stability during recoil, as a heavy gun platform is helpful for damping the recoil, reducing gun displacement and "jump" after each shot. Besides digging in the gun for stability, a design alternative implemented in the D-48 is to lengthen the trails, reducing the angle between the bore axis of the gun and the axis of the trail. This reduces the rotational moment from the recoil force, thus damping the "jump" of the gun system after each shot and reducing the bending moment on the carriage trails. This, in turn, makes thinner trails viable, offseting the weight gain from their increased length. Owing to the power of the gun, the trails of the D-48 carriage were lengthened compared to the D-44, bringing the total length of the weapon to 9,195mm.</div><div><div><br /></div><div>However, this solution is not totally free of downsides. Needless to say, a longer towed load is undesirable as it brings additional complications when it is being moved around in built-up or densely wooded areas. Design solutions to counteract the growing length of a gun system with increasing gun caliber and power are typically accompanied by drawbacks. For example, one solution, implemented in the 105mm L119 light gun, is to have a reversible gun mount with no gun shield, allowing the barrel to be locked over the trail for towing. For an anti-tank gun expected to take direct fire, it is not permissible to have no gun shield. Other solutions such as removable spades or folding trails decrease the structural integrity of the trail and can increase the weight of the weapon.</div><div><br /></div></div><div><br /></div><div>As is customary for postwar Soviet field guns, the D-48 carriage has a castor wheel on its left trail. The long trails give more leverage when they are lifted to deploy the castor wheel.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-3O32aXUh1R8/X9-RbozktaI/AAAAAAAAShk/tpHDVAQXIuYTrEgtYT89TTQ-IBMJEJfQwCLcBGAsYHQ/s2048/castor%2Bwheel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1295" data-original-width="2048" height="253" src="https://1.bp.blogspot.com/-3O32aXUh1R8/X9-RbozktaI/AAAAAAAAShk/tpHDVAQXIuYTrEgtYT89TTQ-IBMJEJfQwCLcBGAsYHQ/w400-h253/castor%2Bwheel.png" width="400" /></a></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="d48-protection"></a><h3 style="text-align: left;"><span style="font-size: large;">PROTECTION</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-aOQdrOI9yFI/X9-Us5Nk-BI/AAAAAAAAShw/JGVqBc0NZL0oJ9g_NQai2RXct0ykzRubACLcBGAsYHQ/s600/8091.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="290" data-original-width="600" src="https://1.bp.blogspot.com/-aOQdrOI9yFI/X9-Us5Nk-BI/AAAAAAAAShw/JGVqBc0NZL0oJ9g_NQai2RXct0ykzRubACLcBGAsYHQ/s16000/8091.jpg" /></a></div><br /><div><br /></div><div><div>The height of the gun when measured up to the gun shield is 1,475mm, and the height of the bore axis from ground level is 830 mm. The height of the bore axis of the D-48 was very low, much lower than the BS-3 gun (1,010mm), as was its maximum height as measured to the tallest point of the gun shield (1,800mm). That said, the BS-3 was a long range field gun that had to be able to conduct high angle fire of up to 45 degrees, which would be incompatible with its long maximum recoil stroke of 1,180mm unless the bore axis height was increased. Otherwise, the breech could potentially strike the ground when firing at the maximum elevation angle.</div><div><br /></div><div>Nevertheless, even without comparing the D-48 to such a large gun, its silhouette was exceptionally small. The bore axis height of the D-48 was significantly lower than that of the 8.8cm Pak 43 with a cruciform carriage which had a bore axis height of 914mm when deployed, and it is even lower than the Pak 43/41 which had a split-trail carriage and a bore axis of 1,195mm. For a gun of its power, the low silhouette of the D-48 made it exceptionally concealable.</div></div><div><br /><div>In fact, the bore axis height of the D-48 was even lower than the 57mm ZiS-2, which had a bore axis height of 875mm. The maximum height of the gun was comparable to the 57mm M1 gun, which measured 1,448mm tall. The main downside of such small dimensions is that the gunner must be hunched down to remain behind the cover of the shield and the loaders also have reduced protection when working behind the gun, but on the other hand, this made the D-48 somewhat easier to conceal.</div><div><br /></div><div>Having the gun situated closer to the ground is desirable as it reduces the mechanical advantage of the recoil force, thus reducing the bending and twisting moment on the trails applied during recoil. In turn, this permits a reduction in the wall thickness of the carriage trails needed to withstand the recoil. Moreover, it reduces the stress on the trails, as the torque from the recoil is reduced. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HIYcIbQM73w/X9BvHrvVfoI/AAAAAAAASVE/DAiPym0qA9c_Rs-5LfzaEiT3pEhdjEmKQCLcBGAsYHQ/s960/d-48%2Bknocked%2Bout.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="960" height="320" src="https://1.bp.blogspot.com/-HIYcIbQM73w/X9BvHrvVfoI/AAAAAAAASVE/DAiPym0qA9c_Rs-5LfzaEiT3pEhdjEmKQCLcBGAsYHQ/w400-h320/d-48%2Bknocked%2Bout.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>For a conventional split-trail carriage, lowering the bore axis was practically the only viable solution for these issues. Only a design such as the American experimental 90mm T13 gun on the T9 carriage with the trails hinged to the top of the gun shield could permit better recoil absorption. Interestingly enough, even with this novel design, the T13 was still much heavier than a D-48, weighing in at 3,107 kg.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-oYpk_BEgjTs/X3t5FORs-II/AAAAAAAARqo/dsuKEXpH6H4GE5FhaJZlUb4i-2JvF4OWACLcBGAsYHQ/s782/t9.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="366" data-original-width="782" height="300" src="https://1.bp.blogspot.com/-oYpk_BEgjTs/X3t5FORs-II/AAAAAAAARqo/dsuKEXpH6H4GE5FhaJZlUb4i-2JvF4OWACLcBGAsYHQ/w640-h300/t9.jpg" width="640" /></a></div><div><br /></div></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">SHIELD</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-KN4V0BqKxRE/X95eQr4i84I/AAAAAAAASfQ/Cb5LvfIJ8CgDSR9YPusVPx2iQAVUmKBIACLcBGAsYHQ/s2048/gun%2Bshield.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1362" data-original-width="2048" height="426" src="https://1.bp.blogspot.com/-KN4V0BqKxRE/X95eQr4i84I/AAAAAAAASfQ/Cb5LvfIJ8CgDSR9YPusVPx2iQAVUmKBIACLcBGAsYHQ/w640-h426/gun%2Bshield.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The gun shield of a D-48 is easily identified by the wavy shape of its top edge, characterized by the three curves on the left side of the shield and two on the right. In terms of its protective capabilities, it does not differ from the D-44 gun shield in a meaningful way.</div><div><br /></div>Measurements on a D-48 monument showed that the thickness of the shield is 4.5mm. The vertical slope is 30 degrees and the shield is also swept back in the horizontal axis at around the same angle, apart from the gun embrasure area at the center.</div><div><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-s3EUZ042x6I/XpPw7xAfopI/AAAAAAAAQmI/hsv0i-S4L_8aMSktqdpBvooSeLXXxJyygCLcBGAsYHQ/s1600/20200221_131146.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1200" height="400" src="https://1.bp.blogspot.com/-s3EUZ042x6I/XpPw7xAfopI/AAAAAAAAQmI/hsv0i-S4L_8aMSktqdpBvooSeLXXxJyygCLcBGAsYHQ/w300-h400/20200221_131146.jpg" width="300" /></a><br /></div><div><br /></div><div><br /></div><div>The D-48N was built with a mount for a night sight and an additional viewport cut in the gun shield for its use, covered with an armoured panel, along with a new armoured panel for the telescopic sight viewing slit. The photo below, taken by Vitaly Kuzmin, shows a D-48N with the distinctive bulging panel for the night sight viewport.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-hYOSSlgwNbY/X96sZKn3lmI/AAAAAAAAShc/jGPZpDnBs_4h1OFsdMEy5Cr8VSLI9Zu3wCLcBGAsYHQ/s2048/%25D0%2594-48.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1365" data-original-width="2048" height="426" src="https://1.bp.blogspot.com/-hYOSSlgwNbY/X96sZKn3lmI/AAAAAAAAShc/jGPZpDnBs_4h1OFsdMEy5Cr8VSLI9Zu3wCLcBGAsYHQ/w640-h426/%25D0%2594-48.jpg" width="640" /></a></div><br /><div><br /></div><div><div><a href="https://www.blogger.com/null" id="d48-sighting"></a><h3 style="text-align: left;"><span style="font-size: large;">FIRE CONTROL</span></h3>The fire control instruments used to direct D-48 batteries is unknown, but can be assumed with great certainty to be identical to that used for the D-44. There is no evidence of anti-tank battalions armed with D-48 guns having proprietary fire control instruments. </div><div><br /><h3 style="text-align: left;"><span style="font-size: large;">SIGHTING</span></h3><div>The sighting instruments for the D-48 were practically identical to the D-44, and as such, they will be examined only very briefly. The D-48 was equipped with an OP2-77 direct fire telescopic sight and had the standard S71 mechanical sight with a PG-1 panoramic optic.</div><br /><h3 style="text-align: left;"><span style="font-size: large;">OP2-77 </span></h3><br />To aim the gun for direct fire, the gunner was provided with an OP2-77 telescopic tube sight. It was nothing more than a standard OP2 series telescopic sight with a new viewfinder insert to display the range markings for the ammunition of the D-48.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-N-ZLD1UnJN8/X8_bLxVhsLI/AAAAAAAASUY/33aw-ecqhM0SsQD-EYaLhgM8UqekCvgHwCLcBGAsYHQ/s2743/op2-77.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1146" data-original-width="2743" height="268" src="https://1.bp.blogspot.com/-N-ZLD1UnJN8/X8_bLxVhsLI/AAAAAAAASUY/33aw-ecqhM0SsQD-EYaLhgM8UqekCvgHwCLcBGAsYHQ/w640-h268/op2-77.png" width="640" /></a></div><div><br /></div><div><br /></div><div>It has a fixed magnification of 5.5x and a field of view of 11 degrees. Its viewfinder is only marked for AP and both types of HE-Frag; there is no range scale for HEAT ammunition, even though it could be fired from the D-48. In such cases, a conversion table would normally be used to allow range adjustments based on the range scale of another shell type.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-tAWLJ8Vkkc4/X8_bUlfE0tI/AAAAAAAASUg/vB98SSTfsEs9qqU8KpMohlZn6DVC-p0KgCLcBGAsYHQ/s1345/op2-77%2Bviewfinder.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1345" data-original-width="1333" height="400" src="https://1.bp.blogspot.com/-tAWLJ8Vkkc4/X8_bUlfE0tI/AAAAAAAASUg/vB98SSTfsEs9qqU8KpMohlZn6DVC-p0KgCLcBGAsYHQ/w396-h400/op2-77%2Bviewfinder.png" width="396" /></a><a href="https://1.bp.blogspot.com/-wj6GwizuaMY/X953tbukreI/AAAAAAAASfw/pWRvasFjRp0W9i0bXNN_S0YBK0KSgiFLACLcBGAsYHQ/s604/viewfinder.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="483" data-original-width="604" height="320" src="https://1.bp.blogspot.com/-wj6GwizuaMY/X953tbukreI/AAAAAAAASfw/pWRvasFjRp0W9i0bXNN_S0YBK0KSgiFLACLcBGAsYHQ/w400-h320/viewfinder.jpg" width="400" /></a></div></div><div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">NIGHT SIGHT</span></h3><div><br /></div><div>As mentioned before, the artillery and armoured vehicles of the Soviet ground forces gained a night fighting capability in 1957, and the D-48 was not entirely left out. But because the advent of viable infrared night vision sights only occured after the D-48 was nearing the end of its short production run, the number of guns built with the necessary fittings was very limited. </div><div><br /></div><div>As the basic D-48 lacked the provisions to mount this equipment, the updated model was given a new designation, the D-48N (52-P-372N) to differentiate it from the basic model. D-48N guns were equipped with the APN-3-77 (1PN5) night sights. The APN-3-77 is nothing more than a standard APN-3 series sight with a new viewfinder insert with the range scales for D-48 ammunition.</div></div><div><br /></div><div>The two photos below, from the <a href="https://www.recomonkey.com/Land-Platforms/Artillery/Towed/D-48-85mm/D-48N-85mm">RecoMonkey website</a>, shows the night sight and IR spotlight mounting frame on a D-48N (left) and the power supply control box installed on the gun shield (right), albeit in a rather poor state with the cover missing. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GXAhmnGFP5Q/X-NKBZt0utI/AAAAAAAASjI/juQXkremksoVnYhLw7IS5PG5z8jQCw7RACLcBGAsYHQ/s1280/i-CqXF3Fm-X2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="266" src="https://1.bp.blogspot.com/-GXAhmnGFP5Q/X-NKBZt0utI/AAAAAAAASjI/juQXkremksoVnYhLw7IS5PG5z8jQCw7RACLcBGAsYHQ/w400-h266/i-CqXF3Fm-X2.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-Uur-rrDeCjs/X-NKBfY3pEI/AAAAAAAASjM/pccPakTIzA0ZBGmgCKXG34tMI4WDTmhsACLcBGAsYHQ/s1280/i-X28fNbh-X2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="266" src="https://1.bp.blogspot.com/-Uur-rrDeCjs/X-NKBfY3pEI/AAAAAAAASjM/pccPakTIzA0ZBGmgCKXG34tMI4WDTmhsACLcBGAsYHQ/w400-h266/i-X28fNbh-X2.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>The image below shows the viewfinder markings of an APN-3-77 sight. The reticle consists of a chevron with two vertical dashes for windage adjustments, and below the chevron is a vertical line and a horizontal line in an inverted "T" shape. The gunner adjusts the position of the reticle by turning a range dial to lower the reticle along the range scales until the horizontal line aligns with the desired range for the appropriate ammunition type. The range scale on the left is used for both AP and HE, as they are practically ballistically matched for up to 1.6 km. The range scale on the right is for reduced charge HE.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-wzsR9aHkM38/YTPKBLumGuI/AAAAAAAAUJs/MswywpgRNxQh_BFyjZEHKmt4tKsVYj4NwCLcBGAsYHQ/s946/APN3-77.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="946" data-original-width="926" height="400" src="https://1.bp.blogspot.com/-wzsR9aHkM38/YTPKBLumGuI/AAAAAAAAUJs/MswywpgRNxQh_BFyjZEHKmt4tKsVYj4NwCLcBGAsYHQ/w391-h400/APN3-77.png" width="391" /></a></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="d48-gun"></a><h3 style="text-align: left;"><span style="font-size: large;">GUN</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-kjzYqDXYsGk/X9EdvzZ8u0I/AAAAAAAASXg/uuf1uzSpkPIJtNsp2wNfbDbdHz-QhSSUwCLcBGAsYHQ/s3421/d-48%2Bgun%2Btube%2Band%2Brecoil%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="828" data-original-width="3421" height="154" src="https://1.bp.blogspot.com/-kjzYqDXYsGk/X9EdvzZ8u0I/AAAAAAAASXg/uuf1uzSpkPIJtNsp2wNfbDbdHz-QhSSUwCLcBGAsYHQ/w640-h154/d-48%2Bgun%2Btube%2Band%2Brecoil%2Bmechanism.png" width="640" /></a></div><div><br /></div><div><div><br /></div><div>Fires the unitary 85x708mm cartridge. The muzzle energy was, however, considerably reduced compared to a BS-3 field gun - only 5 MJ compared to 6.36 MJ. The D-48 was effectively a direct equivalent to the 8.8cm Pak 43 gun. It fired a slightly lighter round, but at a higher muzzle velocity.</div></div><div><br /></div><div>The D-48 was effectively an entirely new product with no direct commonality with existing guns. A small portion of its components were unified with the D-44 and BS-3, including the outer casing of the recoil buffer and recuperator, a spring for the breech block, and a large number of nuts and bolts. But aside from such parts, no major assemblies were interchangeable.</div><div><br /></div><div>The D-48 has a semi-automatic action with a vertically sliding breechblock, opened with a large lever on the right of the breech. The firing mechanism is completely mechanical, with a firing pin and striker. The image on the left shows the cocking of the extractor and breech closing mechansim during recoil, and the image on the right shows the resetting of the mechanism during counter-recoil. This mechanism is conspicuously different from that of the D-44.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-sUodCfOMWe0/X96CH984vrI/AAAAAAAASgQ/f3ujRJhz8zcM44JMaDiDWAqehQJtdoINgCLcBGAsYHQ/s2048/in%2Brecoil.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="2030" height="320" src="https://1.bp.blogspot.com/-sUodCfOMWe0/X96CH984vrI/AAAAAAAASgQ/f3ujRJhz8zcM44JMaDiDWAqehQJtdoINgCLcBGAsYHQ/s320/in%2Brecoil.png" /></a><a href="https://1.bp.blogspot.com/-mOscpdOH_oI/X96CH4lq9HI/AAAAAAAASgM/cnEfHQ_vSR05lG04Z_ShWo9QTAQpx4UtwCLcBGAsYHQ/s2048/in%2Bcounter%2Brecoil.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1599" height="320" src="https://1.bp.blogspot.com/-mOscpdOH_oI/X96CH4lq9HI/AAAAAAAASgM/cnEfHQ_vSR05lG04Z_ShWo9QTAQpx4UtwCLcBGAsYHQ/s320/in%2Bcounter%2Brecoil.png" /></a></div><br /><div><br /></div><div><div><br /></div><div>According to the norms, the aimed firing rate of the D-48 is 25 rounds in 3 minutes, giving an average of 8-9 round per minute. The maximum rate of fire is much higher - up to 15 rounds per minute.</div></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--GuvlwPm58g/X955yIO9EOI/AAAAAAAASf4/Oz6Fd8LkvpI7ncEUV4S-J6v93CBjo5OMACLcBGAsYHQ/s2048/traverse%2Band%2Belevation%2Bcontrols.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1221" data-original-width="2048" height="382" src="https://1.bp.blogspot.com/--GuvlwPm58g/X955yIO9EOI/AAAAAAAASf4/Oz6Fd8LkvpI7ncEUV4S-J6v93CBjo5OMACLcBGAsYHQ/w640-h382/traverse%2Band%2Belevation%2Bcontrols.png" width="640" /></a></div><br /><div><br /></div><div><div><br />The mounting system permits the gun to be traversed by 27 degrees to each side, and elevated from a maximum depression angle of -6 degrees to a maximum elevation angle of +35 degrees. This was essentially the same as the D-44 gun, which is quite remarkable considering the large increase in firepower. The traversing arc of 54 degrees was good for a towed anti-tank gun of this caliber and power, and the elevation limit of +35 degrees is far above the requirements of an anti-tank gun. </div></div><div><br /></div><div><br /></div><div>As with the D-44, the gun cradle of the D-48 is a cast steel cylindrical unit with reinforcing ribs for rigidity. Inside the cradle are riveted bronze inserts and half-ring sections to guide the barrel during recoil. These inserts have grooves for lubrication with grease, topped up from lubrication ports on the sides of the cradle.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-8lDa8paZs0U/X96nwyMCWYI/AAAAAAAAShI/rUk-UrbowegBp6c_RGMx-0CLwOJ6IvrkgCLcBGAsYHQ/s2048/cradle%2B1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1372" data-original-width="2048" height="268" src="https://1.bp.blogspot.com/-8lDa8paZs0U/X96nwyMCWYI/AAAAAAAAShI/rUk-UrbowegBp6c_RGMx-0CLwOJ6IvrkgCLcBGAsYHQ/w400-h268/cradle%2B1.png" width="400" /></a><a href="https://1.bp.blogspot.com/-i6sO1HvYHtY/X96n-L7678I/AAAAAAAAShM/9micRW88cz0bdg6uc51rVamb2jjzWYM_ACLcBGAsYHQ/s2048/cradle%2B2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1322" data-original-width="2048" height="259" src="https://1.bp.blogspot.com/-i6sO1HvYHtY/X96n-L7678I/AAAAAAAAShM/9micRW88cz0bdg6uc51rVamb2jjzWYM_ACLcBGAsYHQ/w400-h259/cradle%2B2.png" width="400" /></a><br /></div><div><br /></div><div><div><br /></div><div>The weight of the gun, which consists of the barrel and the breech assembly, amounts to 1,200 kg. The weight of the recoiling parts is 1,265 kg. The weight of the gun tube - which includes the barrel, muzzle brake and the breech assembly - is 1,200 kg. This is 67% greater than the D-44 divisional field gun - a large increase, but well within expectations due to the difference in the barrel length and thickness to accommodate the size and power of the cartridge.</div><div><br /></div></div><div><br />A pneumatic equilibrator of identical design to the D-44 equilibrator was used on the D-48, installed on the right side of the gun at the same location as on the D-44. As before, the equilabrator is a push-type device, which is somewhat counterintuitive as the long barrel implies that the gun should be muzzle-heavy. The normal pressure in the balancing mechanism at a maximum barrel elevation angle is 97 ± 5 kgf/sq.cm (9.512 MPa). This is just under twice the pressure of the D-44 equilibrator, evidently because to the larger weight - particularly the forward weight - of the D-48 due to its long barrel. When the ambient temperature changes, the pressure in the balancing mechanism is regulated with the compensator valve. <br /><br /><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ksUIVfICrQo/X6rMPYIZRPI/AAAAAAAASGY/cHQUvwHuxH8sYHpI_8xkVdD7hjPdoEvPgCLcBGAsYHQ/s2048/equilibrator%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1253" data-original-width="2048" height="245" src="https://1.bp.blogspot.com/-ksUIVfICrQo/X6rMPYIZRPI/AAAAAAAASGY/cHQUvwHuxH8sYHpI_8xkVdD7hjPdoEvPgCLcBGAsYHQ/w400-h245/equilibrator%2Bcross%2Bsection.png" width="400" /></a><a href="https://1.bp.blogspot.com/-5DOYF1oibjU/X6rMPK4SBdI/AAAAAAAASGU/qqzYQKBfFfIt58BOd79yeMndiV_R8AAJACLcBGAsYHQ/s1567/equilibrator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1545" data-original-width="1567" src="https://1.bp.blogspot.com/-5DOYF1oibjU/X6rMPK4SBdI/AAAAAAAASGU/qqzYQKBfFfIt58BOd79yeMndiV_R8AAJACLcBGAsYHQ/s320/equilibrator.png" width="320" /></a></div><div><br /></div><div><br /></div><div><div>The total length of the D-48 gun, including the muzzle brake, is 6,290mm or 74 calibers. It is slightly shorter than the 8.8cm Pak 43 in terms of total length (6,576mm) but due to its marginally smaller caliber, the proportional length is almost the same (74.7 calibers). The rifling has 32 lands and grooves and has a twist of one in 35 calibers. Overall, the barrel has a length of 5,602mm, making the D-48 an L/65.9 gun, and the rifled length of its bore is 4,900mm (57.6 calibers). This is equivalent to the Pak 43 and is 40% longer than the D-44. For comparison, the barrel length of the Pak 43 is 6,017mm (68.37 calibers) and the rifled length of its bore is a 5,125mm (58 calibers). The slightly shorter length of the D-48 barrel is entirely due to the shorter chamber.</div><div><br /></div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-j6f8277B5iY/X9Ed6UZM2lI/AAAAAAAASXk/9AiC8Pjf9EgcTH9DmbGIQnpedIQPnVL4ACLcBGAsYHQ/s2830/barrel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1111" data-original-width="2830" height="252" src="https://1.bp.blogspot.com/-j6f8277B5iY/X9Ed6UZM2lI/AAAAAAAASXk/9AiC8Pjf9EgcTH9DmbGIQnpedIQPnVL4ACLcBGAsYHQ/w640-h252/barrel.png" width="640" /></a></div><div><br /></div></div><div><div><div><br /></div><div>The length of the chamber from the end of the barrel to the start of the rifling, is 702mm. This is slightly shorter than the 720mm length of the BS-3 chamber. However, the chamber capacity is 7.987 liters, which is slightly larger than the 7.9-liter capacity of the BS-3 gun chamber, contrary to expectations given the smaller caliber. </div><div><br /></div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-XnxNWjgVdIE/X3uUla-S22I/AAAAAAAARq0/0dvT17ytvxg6Xg3e6I1OJkF5LUS4Q4oSgCLcBGAsYHQ/s3140/d-48%2Bgun%2Bbarrel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="500" data-original-width="3140" height="102" src="https://1.bp.blogspot.com/-XnxNWjgVdIE/X3uUla-S22I/AAAAAAAARq0/0dvT17ytvxg6Xg3e6I1OJkF5LUS4Q4oSgCLcBGAsYHQ/w640-h102/d-48%2Bgun%2Bbarrel.png" width="640" /></a></div><div><br /></div></div><div><br />When firing an APCBC round, a maximum nominal operating pressure of 304 MPa (3,100 kgf/sq.cm) is developed under standard conditions at a propellant charge temperature of 15°C. This is slightly more than the Pak 43, which was rated for a maximum pressure of 3,000 kgf/sq.cm at the same propellant temperature.</div></div></div></div><div><br /></div><a href="https://www.blogger.com/null" id="d48-recoil"></a><h3 style="text-align: left;"><span style="font-size: large;">RECOIL MECHANISM</span></h3><div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-1icWTHrzpzA/X955-RiPF1I/AAAAAAAASf8/fbGOjC-2FCIR77GMbwtG8aKtWYZRvJKAQCLcBGAsYHQ/s2048/d-48%2Brecoil%2Bsystem.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1365" data-original-width="2048" height="266" src="https://1.bp.blogspot.com/-1icWTHrzpzA/X955-RiPF1I/AAAAAAAASf8/fbGOjC-2FCIR77GMbwtG8aKtWYZRvJKAQCLcBGAsYHQ/w400-h266/d-48%2Brecoil%2Bsystem.jpg" width="400" /></a></div></div><div><br /></div><div><br /></div><div>As with the D-44, the proprietary recoil mechanism of the D-48 uses a hydropneumatic recoil recuperator paired with a recoil buffer. The layout and functions are identical to the type used on the D-44. The buffer contains 4.85 liters of Steol-M synthetic hydraulic fluid while the recuperator is filled with 3.6 liters. The recuperator is pressurized to 55 atm. The gun has a normal recoil stroke length of 720mm, with a maximum of 730mm. When firing reduced charge rounds, the recoil stroke length is reduced to 475-625mm.</div><div><br /></div><div>The drawing on the top, shown below, is the buffer. Below it is the recuperator.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-U57wJ7ZuibY/X9jNYGDcOQI/AAAAAAAASbo/c-xYHM7PS_ALGU_dRrq-gJ3PlSxva0VCgCLcBGAsYHQ/s3287/buffer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="951" data-original-width="3287" height="186" src="https://1.bp.blogspot.com/-U57wJ7ZuibY/X9jNYGDcOQI/AAAAAAAASbo/c-xYHM7PS_ALGU_dRrq-gJ3PlSxva0VCgCLcBGAsYHQ/w640-h186/buffer.png" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Pmy4Tcs6_Xw/X9jNYNcDewI/AAAAAAAASbs/uoLQKK9gnnEjE8si-Sx6dHR73-mto2laACLcBGAsYHQ/s3251/recuperator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="968" data-original-width="3251" height="190" src="https://1.bp.blogspot.com/-Pmy4Tcs6_Xw/X9jNYNcDewI/AAAAAAAASbs/uoLQKK9gnnEjE8si-Sx6dHR73-mto2laACLcBGAsYHQ/w640-h190/recuperator.png" width="640" /></a></div><div><br /></div><div><br /></div><div>An important innovation with the buffer mechansim was the addition of an air pocket in the hollow piston rod. This was done by underfilling the buffer, leaving a small chamber which is filled with pressurized air. The air pocket provides enough free volume for the hydraulic fluid in the buffer to expand as it heats up, thus self-regulating the working volume of fluid. The fluid in the buffer can expand or contract in volume due to changes in temperature from the environmental conditions, leaky seals, or simply from firing the weapon. </div><div><br /></div><div>Overall, the air content takes up 2-3% of the total volume in the buffer. During recoil, the air inside the piston rod is compressed by the pressure of the fluid displaced from the reservoir and allows the fluid to occupy its volume until equilibrium is reached. During counter-recoil, the air decompresses and refills the volume evacuated by the fluid. </div><div><br /></div><div>This feature removed the need to regularly top up the hydraulic fluid or install a fluid replenisher mechanism to regulate the fluid volume in the buffer. A replenisher may not be needed on light guns, but more powerful field guns often required one. They are used on weapons such as the 25-pdr, and the 1981 edition of TM 9-3305 "Principles of Artillery Weapons" states that all medium and heavy guns in service in the U.S Army except the M109(A1) had a replenisher. </div><div><br /></div><div>The drawings on the left and right below show the recoil and counter-recoil cycle of the buffer (left) and recuperator (right). Note the air pocket depicted in the buffer on the top left drawing.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-NgsLHgT_IxM/X6qrhB0fpkI/AAAAAAAASF8/L7y9CmFkBJo5OZ-OCdePG9bjK6gglsYKACLcBGAsYHQ/s2790/recoil%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1127" data-original-width="2790" height="258" src="https://1.bp.blogspot.com/-NgsLHgT_IxM/X6qrhB0fpkI/AAAAAAAASF8/L7y9CmFkBJo5OZ-OCdePG9bjK6gglsYKACLcBGAsYHQ/w640-h258/recoil%2Bmechanism.png" width="640" /></a></div></div><div><br /></div><div><div><br /></div><div>Apart from the recoil system, recoil control was also aided by the somewhat unusual "pepperpot" style muzzle brake. It consisted of an oversized tapered chamber with perforated walls. This brake replaced the double baffle brake originally used on the first D-48 prototype. This type of brake had a high efficiency of 68%.</div><div><br /></div><div>This type of muzzle brake is known as a "reactive" brake owing to its predominant use of gas jets instead of baffles. Almost no writings have been published on the technical details of the specific muzzle brake design of the D-48 gun, so all information must be gained from observations alone.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-0WEehgcRT9Q/X5cSj0yiNrI/AAAAAAAAR0A/tSavpm9ePBkYdT0fQ7ING3DBT4pM26XrgCLcBGAsYHQ/s2048/muzzle%2Bbrake.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1400" data-original-width="2048" height="274" src="https://1.bp.blogspot.com/-0WEehgcRT9Q/X5cSj0yiNrI/AAAAAAAAR0A/tSavpm9ePBkYdT0fQ7ING3DBT4pM26XrgCLcBGAsYHQ/w400-h274/muzzle%2Bbrake.png" width="400" /></a></div><div><br /><br />It is worth noting that the front wall of the oversized chamber may act as a baffle, utilizing the reflection of the muzzle blast shockwave and overpressure from the exiting propellant gasses to generate a forward force. However, the small surface area of this wall inherently limits the efficiency of the muzzle brake as a baffle. Rather, the majority of the braking force produced by this muzzle brake is from gas jets, as the official description of the brake indicates. Angled vent holes drilled into the sides of the chamber redirect the exiting propellant gasses in a rearward direction, thus generating a forward thrust. The mild flaring of the brake may be to facilitate the rearward deflection of gasses. Combined with the front wall acting as a baffle, the efficiency of the brake can be quite high.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GIh-CPznHek/X8Kn1i29f4I/AAAAAAAASLA/LHFzwOA8cLkeJp8mYUwwqTVeuwQkHG0zQCLcBGAsYHQ/s1709/reactive%2Bbrake.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1193" data-original-width="1709" src="https://1.bp.blogspot.com/-GIh-CPznHek/X8Kn1i29f4I/AAAAAAAASLA/LHFzwOA8cLkeJp8mYUwwqTVeuwQkHG0zQCLcBGAsYHQ/s320/reactive%2Bbrake.png" width="320" /></a></div><div><br /></div><div><br /></div><div>Its efficiency of 68% was higher than the majority of common muzzle brakes designs, including the myriad of double baffle brake varieties such as the TsAKB brake used on the D-44, the bulbous brake of the 17-pdr, and the standard German-style design, to name the most well-known. It reaches the efficiency of slotted active-reactive multi-baffle brakes. However, as it was chosen over the original double-baffle prototype brake tested on the earliest D-48 guns, the muzzle blast produced by this brake was evidently not as adverse as baffled high-efficiency brakes.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-8qMjq0QWh1g/X6JYmwmCuMI/AAAAAAAASB4/wrw3jT4XyTg8h7kfGxr_FZ7Y4Wljc5dbgCLcBGAsYHQ/s2048/muzzle%2Bbrake%2Befficiencies.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1813" height="400" src="https://1.bp.blogspot.com/-8qMjq0QWh1g/X6JYmwmCuMI/AAAAAAAASB4/wrw3jT4XyTg8h7kfGxr_FZ7Y4Wljc5dbgCLcBGAsYHQ/w354-h400/muzzle%2Bbrake%2Befficiencies.png" width="354" /></a></div><div><br /><br /></div><div><br /><a href="https://www.blogger.com/null" id="d48-ammo"></a><h3 style="text-align: left;"><span style="font-size: large;">AMMUNITION</span></h3></div><div><br /></div><div>85x708mm ammunition was equivalent to 100x695mm ammunition in bulk, though it was still lighter. This is entirely due to the much lighter projectiles, as the case and propellant charge are closely comparable. The mass of the propellant charge for a full charge round like UBR-372 or UOF-372 is 5.36 kg. This is only marginally less than the 5.5 kg of propellant contained in the 100mm UBR-412 and UOF-412 rounds.<br /><br />A standard unit of fire for the D-48 consisted of 44 AP rounds, 8 full charge HE-Frag rounds and 48 reduced charge HE-Frag rounds. </div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">AP</span></h3><div><br /></div><div>The only AP round created for the D-48 to rely on kinetic energy to break through armour was the UBR-372. Subcaliber ammunition was not available, nor were any created for the later D-70 gun used in the ASU-85.</div><div><br /></div><div>A phlegmatizer was included to reduce bore erosion.</div><div><br /><br /><h3 style="text-align: left;"><span style="font-size: large;">53-UBR-372<br />BR-372</span></h3><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-dCeOqnOHsb0/X85ZrWSIuBI/AAAAAAAAST0/CD9sZ3MmVbEx5fv49XFbbdB46w-CyCDAQCLcBGAsYHQ/s2031/ubr-372.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2031" data-original-width="872" height="640" src="https://1.bp.blogspot.com/-dCeOqnOHsb0/X85ZrWSIuBI/AAAAAAAAST0/CD9sZ3MmVbEx5fv49XFbbdB46w-CyCDAQCLcBGAsYHQ/w274-h640/ubr-372.png" width="274" /></a></div><div><br /></div><div><br /></div><div>In terms of kinetic energy, the BR-372 shell lay in between the 8.8cm Pzgr. 39/43 and 20-pdr APCBC Mk. 1, but on account of its smaller projectile diameter, its specific impact energy is on par with Pzgr. 39/43. Its large propellant charge of 5.56 kg propelled it to the highest muzzle velocity among the three - 1,040 m/s. </div><div><br /></div><div>The point-blank range of the BR-372 against a target with a height of 2, 2.7 and 3.0 meters is 1,200, 1,400 and 1,470 meters respectively. This is effectively identical to the Pzgr. 39/43 round fired from the 8.8cm Pak 43 gun. At distances exceeding this, the BR-372 round has a negligibly flatter trajectory, as the firing table for Pzgr. 39/43 round shows it had a point blank range of 1,400 meters on a target with a height of 2.8 meters. For comparison, the point-blank range of the BS-3 field gun when firing the BR-412D round on a target with a height of 2.7 meters is 1,220 meters. </div><div><br /></div><div>The cartridge is fitted with the new KV-5 percussion primer, undoubtedly because the normal operating pressure of UBR-372 (304 MPa) already reached the maximum rated pressure of the KV-4 primer, so there would be no safety margin whatsoever.</div><div><br /></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9hCmfoljihY/X85ZzOrq_WI/AAAAAAAAST4/vGYX8BwBqusRNnFsu-xi-c247hLELVOSACLcBGAsYHQ/s1466/br-372.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1146" data-original-width="1466" height="313" src="https://1.bp.blogspot.com/-9hCmfoljihY/X85ZzOrq_WI/AAAAAAAAST4/vGYX8BwBqusRNnFsu-xi-c247hLELVOSACLcBGAsYHQ/w400-h313/br-372.png" width="400" /></a></div><div><br /></div><div><br /></div><div>Aside from the name, the BR-372 shell is practically identical to BR-367 and it was fitted with the same DBR-2 base fuze. The design and dimensions of the armour-piercing cap, ballistic cap, penetrator body, and base charge are all basically identical. The only difference was the widening of the copper obturator and driving bands and the corresponding changes in the cuts to the penetrator body to accommodate them. This minor modification gave the shell a slightly greater weight of 9.227 kg, just 27 grams heavier than BR-367. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-rOJ5o0-e8Qw/X9PLGxJiEzI/AAAAAAAASZw/F8CYFs_tTNM0iJKTjTQ3AQ1WXwEangwwgCLcBGAsYHQ/s1443/372%2Band%2B367.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1443" data-original-width="940" height="320" src="https://1.bp.blogspot.com/-rOJ5o0-e8Qw/X9PLGxJiEzI/AAAAAAAASZw/F8CYFs_tTNM0iJKTjTQ3AQ1WXwEangwwgCLcBGAsYHQ/s320/372%2Band%2B367.png" /></a></div><div><br /></div><div><br /></div><div>BR-372 has a total projectile length of 3.64 calibers, excluding the protruding base fuze and tracer. Its AP cap has a length of 0.98 calibers, and has a thickness of 0.35 calibers, covering 0.63 calibers of the penetrator nose. The ballistic cap is attached to the AP cap with a double crimp. The base charge is identical, and the same DBR-2 base fuze is used.</div><div><br /></div><div>The penetration power of BR-372 against FHA, calculated using the deMarre formula with K=2,400, is shown in the table below.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-yKJnAw2sDZs/X9hf1-8szvI/AAAAAAAASbI/RY-jvZbqoKM8AlO_1v2YnxmXik97VvGEwCLcBGAsYHQ/s2048/d-48%2Bpenetration%2Btable.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1526" height="320" src="https://1.bp.blogspot.com/-yKJnAw2sDZs/X9hf1-8szvI/AAAAAAAASbI/RY-jvZbqoKM8AlO_1v2YnxmXik97VvGEwCLcBGAsYHQ/s320/d-48%2Bpenetration%2Btable.jpg" /></a></div><div><br /></div><div><br /></div><div>The penetration of BR-372 at 2,000 meters corresponds to the penetration of BR-367 fired from the D-44 at 100 meters.</div><div><br /></div><div><br /></div><div>Muzzle Velocity: 1,040 m/s</div><div><br /></div><div><div>Cartridge Mass: 21.8 kg</div><div>Projectile Mass: 9.227 kg</div><div>Explosive Charge Mass: 0.05 kg</div></div><div><br /></div><div>Projectile Aspect Ratio: 3.64 calibers</div><div><br /></div><div><br /></div><div>As mentioned earlier, Soviet testing found that the upper glacis of the Panther, which was 85mm thick and sloped at 55 degrees, could be perforated with 8.8cm Pzgr. 39/43 shells at 600 meters. Though not precisely identical to Pzgr. 39/43 in design, BR-372 can be expected to break through the same armour at the same distance. For a D-48, Panther tanks were not a relevant threat whatsoever, but it serves as a good analogue of the Centurion as it had just 76mm RHA sloped at 57 degrees on its upper glacis, with the exception of uparmoured models.</div><div><br /></div><div><div>For comparison, <a href="https://i.imgur.com/V3e3AOZ.jpg">during tests in 1945</a>, the D10 gun firing the BR-412 sharp-nosed AP shell could perforate the upper glacis of the Panther at a range of 1,200 meters but failed at 1,500 meters. Meanwhile, an experimental blunt-nosed shell with a ballistic cap (APBC), most likely BR-412B which was still undergoing development in 1945, could perforate the upper glacis at 1,500 meters but failed at 2,000 meters.</div><div><br /></div><div>That said, the turret of a Centurion was much more vulnerable. The front, being flat and only 6" thick, can be considered enough to stop 8.8cm Pzgr. 39 fired from a Kwk 36 or BR-367 fired from a D-44, but it would be wholly insufficient against the likes of the D-48 out to 2 kilometers. Even glancing blows could achieve a firepower kill with ease. </div><div><br /></div><div><div>Firing trials detailed in Report No. A.T.317. "Centurion Mk. 2 Defensive firing trial" included tests where five shots of 8.8cm APCBC (from a Kwk 43) were fired at a Centurion turret to obtain glancing blows on the sides of the turret at velocities guaranteeing non-perforation, from 764 m/s to 910 m/s and at angles of 60-65 degrees to the normal. With the first hit, the loader's periscope was damaged and the ocular prism and its protective glass of the gunner's sight (AFV sight Mk.1) shattered, and the second hit fractured and jammed the sight body and range drum as well. The fifth hit even managed to knock out the turret traverse gearbox, and the cumulative damage of all five hits cracked the weld between the turret side and the turret roof.</div></div><div><br /></div><div>Moreover, as part of the firing trials, a 17-pdr APCBC shot was fired at the gun mantlet at an angle of 30 degrees to the normal, at a striking velocity of 777 m/s. The shot lodged in the armour, but its impact shattered the prism assembly of the gunner's sight and fractured the mantlet trunnion, completely jamming the mantlet and gun elevating gear. At a range of 3,100 meters, the impact energy delivered by BR-372 will be equal to this test case. It is worth noting that the Mk. 2 was the first serial turret design and its armour scheme was used for all Centurion marks until the Mk. 8, when the "resilient mantlet" was introduced. </div><div><br /></div><div>In essence, any hit from a D-48 on the frontal arc of a Centurion turret will have a very high probability of achieving a firepower kill, with a mantlet hit at any feasible range being likely to achieve a total firepower kill. At combat distances of a kilometer or more, the armour itself is likely to be perforated.</div><br /></div><div>However, by the time the D-48 was being delivered to the troops, the Centurion was far from the best protected tank available to the European NATO member states. There was also the M47 and M48 Patton tanks to consider. </div><div><br /></div><div>According to Yugoslavian test results retrieved and published from the Yugoslav archives in Serbia by Bojan Kavedžić, the upper glacis of the M47 Patton, which had a thickness of 102mm (3 inches) and was sloped at 60 degrees, could be perforated by the M39 round (presumably Pzgr. 39) fired from an 8.8cm Pak 43 at 250 meters while the turret front, having 160mm of rounded armour, could be perforated from 1,250 meters, which is not too bad, all things considered. However, due to the needle-nose shape of the turret, its frontal arc had dismal protection; the M39 round could defeat the turret at any range.</div></div><div><div><br /></div><div>Against a more modern target such as the M48, the BR-372 shell had no chance of defeating the upper glacis. That said, the frontal arc of the hull was still vulnerable overall. As expressed through the 85mm BR-367 round, the lower glacis of an M48 Patton can be perforated (solid curve 1) at an impact velocity of 820 m/s, corresponding to a firing distance of 2,100 meters, and it achieves nominal defeat (dotted curve 2) at an impact velocity of 760 m/s, corresponding to a firing distance of around 2,400 meters.</div><div><br /><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-3o5uXvRiYXE/X4KvCCl4nTI/AAAAAAAARsk/khl3IHs8F440ZfjN5UVySXDPE-3g3jgZgCLcBGAsYHQ/s706/image002.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="325" data-original-width="706" height="294" src="https://1.bp.blogspot.com/-3o5uXvRiYXE/X4KvCCl4nTI/AAAAAAAARsk/khl3IHs8F440ZfjN5UVySXDPE-3g3jgZgCLcBGAsYHQ/w640-h294/image002.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>At a side angle of 45 degrees, the upper side of the hull can be perforated (solid curve 3) at an impact velocity of 900 m/s while the lower side can be perforated (solid curve 5) at an impact velocity of 760 m/s. These velocities correspond to ranges of 1,300 meters and 2,600 meters respectively. </div><div><br /></div><div><br /></div><div>The M48 turret maintains a line-of-sight (LOS) thickness of 7 inches (178mm) with a variable thickness of cast steel sloped at a progressively increasing obliquity from 20 to 45 degrees. In general, the turret armour does not offer sufficient thickness to stop BR-372 from a distance of 1,000 meters. Due to the somewhat unusual design approach taken by the Chrysler Corporation engineers, the turret ring region was particularly weak as the turret was mounted on a raised collar housing the turret ring, while the base of the turret itself had a rather tall, 2-inch deep cut to enable the nuts of the turret ring mounting bolts to be fastened. This region would be vulnerable to BR-372 from a distance exceeding 2,000 meters.</div><div><br /></div><div>As such, while the M48 had sufficient armour to ensure immunity against medium tanks of the previous generation (T-34-85) and light field guns (D-44), modern weapons such as the D-48 were a threat. This is partly because the grade of cast steel used on the M48 did not change from the M47 and remained softer than the armour of the M26 Pershing. According to <a href="http://btvt.info/5library/vbtt_1979_3_patton.htm">Brinell hardness testing of an M48A3</a>, the turret gave an impression diameter of 4.20-4.25 (201-207 BHN) while the hull front gave an impression diameter of 4.15-4.20 (207-212 BHN). This is totally consistent with other sources stating that the nominal hardness of the armour was 210 BHN, meaning that the hardness was not increased from the level reached on the M47.</div><div><div><br /></div><div>The use of low hardness steel was not necessarily detrimental against large caliber steel AP shells, but its effectiveness was conditional on several factors. For armour sloped at a high obliquity, toughness is the critical factor, and low hardness steels tend to be ductile but strong, and therefore tough. However, the steel of the M26 and M46 was abnormally soft and the armour obliquity was very modest. This is especially true for the turret which was practically flat except for the upper and lower edges of the gun mantlet. For such zones, medium or high hardness armour is the most suitable. According to a Soviet study, found that high hardness armour with a thickness of 110-160mm (at 0-55 degrees) and 130-190mm (at 0-50 degrees) had an advantage over medium hardness armour in resisting 75mm and 88mm projectiles with a muzzle velocity of 1,000 m/s.</div><div><br /></div><div><br /></div><div><div>On the upper and lower glacis specifically, the low hardness cast steel used on the M48 tank was optimal for resisting larger caliber APCBC shells as a larger amount of energy would be required to pierce it compared to a smaller caliber one. Although the 100mm BR-412D shell had high penetration performance on flat and sloped RHA plate, ostensibly better than BR-372, the lower glacis of the M48 could be perforated by BR-367 at an impact velocity of 820 m/s whereas BR-412D required an impact velocity of 750 m/s. This means that to accomplish the same task, BR-412D would have to possess 4.4 MJ of kinetic energy whereas BR-367 would require just 3.09 MJ. However, the armour was far less effective against Soviet blunt-tipped shells. BR-412B required an impact velocity of just 660 m/s to perforate the lower glacis, translating to 3.45 MJ of kinetic energy.</div></div><div><br /></div>Nevertheless, efficient or not, the practical reality was that 100mm ammunition still held the firepower advantage. While the modest armour of the lower glacis on an M48 Patton, which was 80mm of cast steel sloped at 54 degrees, could be perforated by BR-372 at a firing distance of 2,100 meters, it could be perforated by BR-412B at 2,500 meters. The same can be said of the M47, as 100mm shells held a firepower advantage over the BR-372 against its armour.</div><div><br /></div><div>According to the Yugoslavian test results cited earlier, the 100mm BR-412B shell fired from a D10-TG could perforate the upper glacis from 750 meters and the turret front from 950 meters. The advantage of the BR-372 shell in penetrating low obliquity armour compared to the BR-412B blunt-tipped APBC shell was evidently responsible for providing better performance against the turret of the M47, but its drastically inferior sloped armour penetration was a serious detriment. This was responsible for its deficient performance against the upper glacis, and in general, low obliquity armour was becoming increasingly difficult to find on the modern battlefield. </div><br /><h3 style="text-align: left;"><span style="font-size: large;">HE-Frag</span></h3><div><br /></div>Field guns and howitzers were required to have a secondary anti-tank capability by design according to Soviet Army doctrine so were supplied with a small stock of anti-tank ammunition in case they faced enemy tanks. Conversely, it was expected that in some cases, anti-tank guns may be required to substitute for divisional guns in indirect fire missions out of necessity because the proper equipment might not be available. Based on the Red Army's experience in the Great Patriotic War, this policy of ensuring that a multipurpose capability existed in all towed artillery was simply pragmatic.</div><div><br />For this reason, HE-Frag rounds were supplied to D-48 guns to ensure that each gun battery was capable of handling the full range of expected threats on the battlefield. HE-Frag rounds were ideal against soft targets, and reduced charge rounds in particular were needed when firing at troops in the open as otherwise, the high velocity of the shell would cause unintentional ground ricochets. The full charge HE-Frag rounds are more suitable for hitting armoured personnel carriers.</div><div><br /></div><div>Unlike the D-44, cast iron shells were not viable. Presumably the high firing velocity would have been too stressful for a cast iron projectile, even with a reduced propellant charge. </div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">UOF-372, UOF-372U<br />OF-372, OF-372U</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-7grKgpskuaI/X8nyMcQsHdI/AAAAAAAASOk/lA6WwmDqsFccsBErsLxgL7caWpK75EwAQCLcBGAsYHQ/s2640/uof-372.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2640" data-original-width="1191" height="400" src="https://1.bp.blogspot.com/-7grKgpskuaI/X8nyMcQsHdI/AAAAAAAASOk/lA6WwmDqsFccsBErsLxgL7caWpK75EwAQCLcBGAsYHQ/w180-h400/uof-372.png" width="180" /></a><a href="https://1.bp.blogspot.com/-tBov3KaPC60/X8nyMeb6LrI/AAAAAAAASOg/0XgFWf1YA7gQpmBE93Zi23M0JFRsPqhzwCLcBGAsYHQ/s2622/uof-372u.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2622" data-original-width="1199" height="400" src="https://1.bp.blogspot.com/-tBov3KaPC60/X8nyMeb6LrI/AAAAAAAASOg/0XgFWf1YA7gQpmBE93Zi23M0JFRsPqhzwCLcBGAsYHQ/w183-h400/uof-372u.png" width="183" /></a></div><div><br /></div><div><br /></div><div>In what appears to be a indexing error, OF-372 was officially classified as a HE-Frag shell (OF) rather than a Frag shell (O) as its characteristics indicate. Both the full and reduced charge rounds are paired with the same OF-372 shell.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbsn5fimWfPPFm3ivWNr7JUwyRyFEREmFIZCqbW8DYimoi61DzVpUu-0d-ArcGeUBMrfXyraffeEx7wVSrEEvUIsb_ssIn0YEXBLsQ4_Zr5ZDpqIEPmcEuWFOPK1JbWvHJPxCN9VFDLB890xlMjiIUdHjPGITnqkiwNKTXENJ_BV3auEBDV2NlHWD8rw/s1274/of-372v.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="595" data-original-width="1274" height="298" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbsn5fimWfPPFm3ivWNr7JUwyRyFEREmFIZCqbW8DYimoi61DzVpUu-0d-ArcGeUBMrfXyraffeEx7wVSrEEvUIsb_ssIn0YEXBLsQ4_Zr5ZDpqIEPmcEuWFOPK1JbWvHJPxCN9VFDLB890xlMjiIUdHjPGITnqkiwNKTXENJ_BV3auEBDV2NlHWD8rw/w640-h298/of-372v.png" width="640" /></a></div><div><br /></div><div>The full charge round with 5.43 kg of propellant generates 3,000 kgf/sq.cm of pressure and the shell attains a muzzle velocity of 1,010 m/s. The reduced charge round had 2.5 kg of propellant, generating 2,800 kgf/sq.cm of pressure and propelling the shell to a much lower muzzle velocity of 770 m/s. With the full charge round, the D-48 could achieve an impressive range of 18,970 meters. The reduced charge round gave a maximum range of 1,4770 meters.</div><div><br /></div><div>OF-372 is differs considerably from the O-365K shell, being shorter and slightly lighter, but having the same weight of explosive filler.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9Khn5srRKIs/X8ntvvX_yhI/AAAAAAAASOI/YiV_QCCPp0cEeksxJWTI40OmhlFpPrnmwCLcBGAsYHQ/s1353/of-372%2Bshell.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1040" data-original-width="1353" height="308" src="https://1.bp.blogspot.com/-9Khn5srRKIs/X8ntvvX_yhI/AAAAAAAASOI/YiV_QCCPp0cEeksxJWTI40OmhlFpPrnmwCLcBGAsYHQ/w400-h308/of-372%2Bshell.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The weight of a complete projectile is 9.66 kg, and it contains 0.74 kg of TNT filler. Compared to O-365, it can be expected that the fragmentation effect is not worse, as the proportion of filler weight is hardly different. The MG-N fuze is used. OF-372V shells are fitted with the V-429 fuze instead.</div><div><br /></div><div><br /></div><div>UO-372 (UO-372U)</div><div><br /></div><div><div>Muzzle Velocity: 1,010 m/s (770 m/s)</div><div><br /></div><div><div>Cartridge Mass: 21.8 kg (18.6 kg)</div><div>Projectile Mass: 9.227 kg</div><div>Explosive Charge Mass: 0.741 kg</div></div><div><br /></div></div><div>Projectile Aspect Ratio: 4.1</div><div><br /></div><div><br /></div><div><h3 style="text-align: left;"><span style="font-size: large;">HEAT</span></h3><div><br /></div>According to the official description for the only HEAT round created for the D-48 (and D-70), it was designed for direct fire at medium and heavy tanks and self-propelled guns, with no mention of infantry in the open, fortifications or bunkers. This is unlike the description given for many tank-fired HEAT shells, which typically include them as viable targets. For the D-48, HEAT ammunition was necessary for fighting modern tanks from the from the direct front and for fighting tanks at long ranges. In this sense, the D-48 had no real advantage over the D-44.<br /><br />While HE-Frag ammunition would be ideal for eliminating dismounted infantry, the limited supply of them meant that HEAT ammunition may be used as a substitute, but with a much weaker effect.<br /><br /><br /><h3 style="text-align: left;"><span style="font-size: large;">3UBK5, 3UBK5M<br />3BK7, 3BK7M</span></h3><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgpBrDXhqdaY41d2XwDEj7lZqPvyAg0WzYTHWehiNmbRXPHJixZWKG4Ji2-VtD3UP97HTk-Lu3pEAXUdQm--jNu6aeUaf7Z92xbpjN-YKfVxW0Kx6woreYV_NpG9HJNBvH_C3jX7UpZXQor-uIEw9Q3US-Dzqa67K9T-y9HZQiZFhZ4pHyd-wPtjIMF-A/s1834/bk-7m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="809" data-original-width="1834" height="282" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgpBrDXhqdaY41d2XwDEj7lZqPvyAg0WzYTHWehiNmbRXPHJixZWKG4Ji2-VtD3UP97HTk-Lu3pEAXUdQm--jNu6aeUaf7Z92xbpjN-YKfVxW0Kx6woreYV_NpG9HJNBvH_C3jX7UpZXQor-uIEw9Q3US-Dzqa67K9T-y9HZQiZFhZ4pHyd-wPtjIMF-A/w640-h282/bk-7m.png" width="640" /></a></div><br />The 3BK7(M) shell design belongs to the same developmental series as 3BK2(M) and shares all of the same major design features, but with differences in minor details. It features a 6-bladed stabilizer fin assembly with a steel slip ring, the GPV-2 piezoelectric spitback fuze, and has the same aerodynamic form.<br /><br />The distinguishing feature of 3BK7(M) among the HEAT shells of the time was its slightly higher muzzle velocity of 925 m/s. The projectile is light, weighing only 7.22 kg. The A-IX-2 explosive charge was also lighter than 3BK2(M), weighing only 0.694 kg. The projectile has a particularly short length of just 6.68 calibers.</div><div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-iIaJa_8fjK0/X8F3tao6QYI/AAAAAAAASK4/MCGJ20y3B5ozZ0kbJntsNOYgmiNF6OoDACLcBGAsYHQ/s1768/BK7.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="390" data-original-width="1768" height="142" src="https://1.bp.blogspot.com/-iIaJa_8fjK0/X8F3tao6QYI/AAAAAAAASK4/MCGJ20y3B5ozZ0kbJntsNOYgmiNF6OoDACLcBGAsYHQ/w640-h142/BK7.jpg" width="640" /></a></div></div><div><br /></div>When firing a fin-stabilized HEAT round from a rifled barrel, the equilibrium spin is imparted through the slip ring on the shell body by the rifling and maintained by canted fins; the slip ring merely serves to drastically reduce spin rather than eliminate it completely. <br /><br />Much like the preceding 85mm HEAT shells for the D-44, the 3BK7(M) projectile uses a steel slip ring, but with several design refinements. The main improvement was the switch from a wedge collar to a simple nut for securing the slip ring, and the obturator band was changed back to copper from the iron-ceramic type used in 3BK2(M). Moreover, the the new design of the shell had the slip ring located around the base of the warhead cavity rather than the solid steel base of the projectile. The simplification of the slip ring assembly and refinement in the design of the warhead casing evidently saved some weight and helped shorten the projectile.</div><div><br /></div><div><br /></div><div>According to the penetration data given in the munitions design textbook "<i>Устройство и действие боеприпасов артиллерии</i>", 3BK7 penetrates 240mm RHA and 3BK7M penetrates 280mm RHA. Officially, 3BK7 is rated to penetrate 192mm of medium hardness armour set at 30 degrees, but the rated penetration for 3BK7M is unknown.</div><div><br /><br /><div>Muzzle Velocity: 925 m/s</div><div><br /></div><div>Projectile Weight: 7.22 kg</div><div>Explosive Filler Weight: 0.694 kg</div><div><br /></div><div><br /></div>Fundamentally, the 3UBK5(M) round had no noteworthy advantage over the 3UBK1(M) round, not even in point blank range despite its higher velocity. </div><div><br /><br /><a href="https://www.blogger.com/null" id="t12-mt12"></a><h3 style="text-align: left;"><span style="font-size: large;">T-12 (2A19), MT-12 (2A29)</span></h3><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-5JHt-JNu5cc/XqOigUuZewI/AAAAAAAAQqU/Co3EeHLaJUgRr4vfWqfEudSWLgvUlrjrQCLcBGAsYHQ/s1600/2%25D0%259019.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="452" data-original-width="1023" height="282" src="https://1.bp.blogspot.com/-5JHt-JNu5cc/XqOigUuZewI/AAAAAAAAQqU/Co3EeHLaJUgRr4vfWqfEudSWLgvUlrjrQCLcBGAsYHQ/s640/2%25D0%259019.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>When it entered service in 1961, the T-12 replaced the D-48 and BS-3 as the primary towed anti-tank gun of the Soviet Army. It is notable for being the first towed smoothbore anti-tank gun as well as the first smoothbore gun anti-tank gun to enter service anywhere in the world. Only a few months later, the T-62 would enter service with an even more potent 115mm smoothbore gun. The T-12 was created by the in-house design bureau of factory No. 75 by V. Ya. Afanasyev and L. V. Korneev. The development of the T-12 started in 1957, in conjunction with the termination of D-48 procurement. Ammunition for the gun began development in 1958.</div><div><br /></div><div>According to the article "<i><a href="http://suse.kemrsl.ru/files/1457508501_Rapira.pdf">РАПИРА. Как рождалась знаменитая пушка</a></i>" (<i>"Rapira": How the famous cannon was born</i>) published by the Donetsk-based YuMZ gazette, the task of creating a 100mm anti-tank gun with high armour penetration was assigned to engineers of factory No. 75 by GRAU. The objective was to overcome the armour protection of existing and prospective tanks of potential enemies. The rationale for the mandate to increase the caliber from 85mm to 100mm is not disclosed in literature, but in general, when limited by the length and design pressure of the barrel, a larger caliber is critical in providing growth in the capabilities of the weapon. For KE munitions, a larger caliber allows a higher muzzle energy to be achieved without requiring higher operating pressures, and for HEAT rounds, a larger shaped charge improves penetration. </div><div><br /></div><div>Factory specialists began by working on an experimental model and performed research work, then proceeded to experimental development. According to <a href="http://www.yumz.ru/about/history/">the website of the Yurginsky Mashzavod</a>, design documentation for the serial production of the T-12 was prepared in 1959. After four years of development, the gun passed military tests in 1961. Under decree No. 749-311 issued on the 17th of July 1961, the T-12 anti-tank gun (2A19) was accepted into service and was assigned the moniker of "Rapira". Alongside it, the 2A19-1 and 2A19-M variants also entered service.</div><div><br /></div></div><div>The 2A19 is the basic version of the T-12. According to the GRAU index, there exists a 2A23 variant, which is a T-12 with no fixture for a night sight. It is unknown if this variant was serially produced for the Soviet Army. The T-12 can be difficult to distinguish from the D-48 with total certainty, since the presence or absence of a night sight mount may not be a reliable indicator because the D-48N variant exists. The images below, taken from the October 1997 issue of the "<i>Техника и вооружение</i>" magazine, shows a D-48 on the left and a T-12 on the right. In the original article, they were misidentified and are labeled as the opposite. From this perspective, the bevel of the D-48 breech is the best identification detail.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jGMJiEIvtL8/X9-XjIoEJsI/AAAAAAAASiA/VhTX63DbbacbStc5OMmpaJ04YgcnbZZJQCLcBGAsYHQ/s2048/d-48%2Bmuseum%2Btiv.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1660" data-original-width="2048" height="324" src="https://1.bp.blogspot.com/-jGMJiEIvtL8/X9-XjIoEJsI/AAAAAAAASiA/VhTX63DbbacbStc5OMmpaJ04YgcnbZZJQCLcBGAsYHQ/w400-h324/d-48%2Bmuseum%2Btiv.png" width="400" /></a><a href="https://1.bp.blogspot.com/-Pi7nkRjHDNI/X9-Xo6RZedI/AAAAAAAASiE/Z3CDf3h84kc3-qSMJ7_-YKjuYs2UNk67wCLcBGAsYHQ/s2048/t-12%2Bmuseum.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1614" data-original-width="2048" height="315" src="https://1.bp.blogspot.com/-Pi7nkRjHDNI/X9-Xo6RZedI/AAAAAAAASiE/Z3CDf3h84kc3-qSMJ7_-YKjuYs2UNk67wCLcBGAsYHQ/w400-h315/t-12%2Bmuseum.png" width="400" /></a><br /></div><div><br /></div><div><br /></div><div>It was replaced by the MT-12, or 2A29 in 1970. The MT-12 can rightfully be considered the zenith of towed anti-tank gun evolution, if not by its technological merits, then by default, as it had no serious competitors, whether domestic or foreign. According to the technical manual for the MT-12, the barrel, the breech block, its opening and closing mechanisms, the recoil mechanism, convoy lights and sighting devices of the MT-12 and T-12 guns have no structural differences. Only the carriage, equilibrator and gun shield was changed.</div><div><br /></div><div>The T-12 and MT-12 was used within the Warsaw Pact and by Soviet satellite states, including the GDR. The photo below shows a Hungarian MT-12.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-x6JrK-vCWVo/X945gbdPVQI/AAAAAAAASew/eMJcuwMNPzkyNgpbaQwER5K4FputJSOyQCLcBGAsYHQ/s960/hungarian%2Bmt-12.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="660" data-original-width="960" height="440" src="https://1.bp.blogspot.com/-x6JrK-vCWVo/X945gbdPVQI/AAAAAAAASew/eMJcuwMNPzkyNgpbaQwER5K4FputJSOyQCLcBGAsYHQ/w640-h440/hungarian%2Bmt-12.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div><div>At the time the T-12 entered service, the 73mm SPG-9 recoilless gun also entered service to replace both the 82mm B-10 and 107mm B-11 as the battalion level anti-tank weapon as it was lighter, fired faster, had a longer range, and still had more than adequate penetration power. Relative to the D-48 that it replaced, the T-12 can be described as the opposite of what the SPG-9 represented. While the light anti-tank weapons became lighter, the heavy guns became heavier.</div></div><div><br /></div><div>The replacement for the D-48 inevitably had to gain weight to cope with modern tank armour. The D-48 was exceptionally light, exceptionally powerful, and exceptionally concealable for a weapon of its power - in all regards, it was essentially an ideal towed anti-tank gun. However, all of that becomes irrelevant if the gun is fundamentally ill-equipped to perform its duty. Interestingly enough, the T-12 entered service with APFSDS and HEAT as the only available ammunition types. Its APFSDS ammunition was the first of its type to receive GRAU designations according to the newly established indexing system, with the 3UBM1 and 3UBM2 both predating the 115mm 3UBM3 round for the T-62. Its HEAT round was the second of its type, being indexed 3UBK2, as it appeared only slightly later than the 85mmm 3UBK1 round. It was followed by the 115mm 3UBK3 round for the T-62. However, the first 100mm HE-Frag round for the T-12 was indexed as 3UOF3, meaning that the 115mm 3UOF1 HE-Frag round for the T-62 predated it. From this, it is known that there was an indeterminate period of several years where the T-12 had no HE-Frag ammunition. Based on the fact that a provisional firing table specifically for 3UOF3 exists, as well as the fact that a revised firing table was published in 1967, it can be deduced that the 3UOF3 only became available in 1967.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ZyXeyUHXE74/X95VhTyhpqI/AAAAAAAASe4/g59vkkefDEYiK4EaG1tphUTwxM5iqR8OACLcBGAsYHQ/s1100/MT-12.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="770" data-original-width="1100" height="448" src="https://1.bp.blogspot.com/-ZyXeyUHXE74/X95VhTyhpqI/AAAAAAAASe4/g59vkkefDEYiK4EaG1tphUTwxM5iqR8OACLcBGAsYHQ/w640-h448/MT-12.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div><div>If evaluated purely in terms of muzzle energy, the performance of the T-12 was far from unprecedented at the time of its introduction. The muzzle energy of the T-12 when firing a subcaliber round was less than a full charge round from a BS-3. As the domestic munitions manufacturing technology improved to the extent that 100mm APDS for the D10 gun became available, the lack of a muzzle energy advantage in the T-12 became apparent. It delivered just 5.33-5.45 MJ of kinetic energy with its APFSDS rounds, while the BS-3 could potentially deliver 5.70 MJ if it were to fire a comparable APDS round, based on the D10 gun firing a 3UBM6 round as a reference. </div><div><br /></div><div>In the specific context of the time period, the advantage of the T-12 over the BS-3 was that it was optimized to fire saboted subcaliber rounds, could have a longer barrel life, and provided the conditions for viable APFSDS ammunition to enter service with existing technology, years before APDS and rifled APFSDS ammunition for the 100x695mm caliber reached maturity. </div><div><br /></div><div>With the discrepancy between the T-12 and the BS-3 being so minor, it is quite evident that the ballistic performance of the T-12 was not at the same level as high velocity 100mm guns like the French SA 47 and the domestic U-8TS. The SA 47 was rated to fire a 15 kg projectile at a muzzle velocity of 1,000 m/s, while the U-8TS (D-54TS) was rated to fire a 16.1 kg projectile at a muzzle velocity of 1,015 m/s. Domestically, the only towed 100mm gun to exceed the muzzle energy of the T-12 and BS-3 was the experimental D-46, developed by the OKB-9 design bureau under the leadership of F. F. Petrov. The D-46, operating at a very high pressure of 392 MPa (4,000 kgf/sq.cm), fired a full-bore AP shell weighing 17 kg at a muzzle velocity of 1,000 m/s.</div><div><br /></div><div>However, the T-12 could match the penetration power of the D54 gun without requiring the enormous performance, which in turn required large gain in weight due to a thickened barrel and breech together with a larger recoil system. Because of this, the 100mm D54 weighed 635 kg more than the D10, gaining a 120 m/s of velocity in return.</div><div><br /></div><div>Among existing in-service guns, the closest counterpart to the T-12 was the Czechoslovakian 100mm vz. 53 anti-tank gun. According <a href="http://www.vhu.cz/100mm-protitankovy-kanon-vzor-53/">to the VHU (Military Historical Institute Prague)</a>, the vz. 53 gun had a muzzle velocity of 955 m/s as compared to the BS-3 with a muzzle velocity of 900 m/s, achieved using a modified APCBC round (1 kg lighter than BR-412D). In technical characteristics, the gun itself did not exceed the BS-3. However, the gun was accompanied by a number of drawbacks - the new carriage and gun cradle gave the gun a tall bore axis height of 1,250mm, and the weight of the gun increased by over 600 kg compared to the BS-3. In a combat configuration, the vz. 53 weighed 4,210 kg, and in a travel configuration, it weighed 4,280 kg. As such, it made for a rather cumbersome anti-tank gun, though it at least had the benefit of not requiring proprietary 100mm ammunition like the T-12.</div><div><br /></div><div>The Romanian 100mm M1977 gun was more optimized for the anti-tank role than the old BS-3 by virtue of having a lighter and shorter carriage, but it was still taller than a T-12, having a bore axis height of 900mm, and it offered no firepower advantage as it was ballistically identical to the BS-3.</div></div><div><br /></div><div><br /></div><div><br /></div><div><div><div>In the article "<i>Отечественная противотанковая артиллерия - Часть II: послевоенная противотанковая артиллерия</i>" (Domestic anti-tank artillery - Part II: postwar anti-tank artillery) published in the October 1997 issue of the "<i>Техника и вооружение</i>" magazine, it is reported that in 1967, Soviet specialists came to the conclusion that the T-12 would not ensure the reliable defeat of the new Chieftain and MBT-70. Therefore, in January 1968, the OKB-9 design bureau headed by F. F. Petrov was instructed to develop a new, more powerful anti-tank gun with the ballistics of the 125mm smoothbore D-81 tank gun, created by the same design bureau. The D-81 itself was created due to the same concern that the 115mm gun of the T-62 would be insufficient against the Chieftain.</div><div><br /></div><div>Work on this project culminated in the creation of the D-13 (2A45) "Sprut" gun. However, though the "Sprut" was officially accepted into service, only a small batch of guns were built and delivered to the Soviet Army, all of which were used for troop trials only. There was no replacement for the T-12 other than its own derivative, the incrementally improved MT-12 from 1970. However, the protection of the Chieftain was greatly exaggerated by Soviet intelligence, and the MBT-70 project failed to yield a replacement for the legacy tanks used by the U.S and West Germany.</div></div><div><br /></div><div>Though the M60A1 and Chieftain could stop the basic APFSDS ammunition of the T-12 on their most resilient zones, at least in theory, the vast majority of their frontal arcs were insufficiently armoured. If the need arose, they could fall back on their HEAT rounds to deal with these tanks. As such, even though the effective range of the gun shrank against these heavily armoured tanks compared to the threat tanks of the 1950's, and the options of firing angles for a successful attack diminished somewhat, the T-12 and MT-12 could still adequately fulfill their role.</div><div><div><br /></div></div><div><br /></div><div>In the 1980's, the situation changed. New main battle tanks were entering service. The MT-12 was even used as the basis of the 2S15 "Norov" tank destroyer with a radar FCS, but after a long development cycle, all work ended with its rejection in December 1985 due to the obsolescence of its gun against the latest MBTs emerging in NATO, and by that time, it was indeed plainly obvious that the old 100mm had exhausted its potential. Existing T-12 and MT-12 guns continued to serve, but with no new guns being built and no replacement planned, it was abundantly clear that the Soviet Army had finally turned its back on the towed anti-tank gun concept.</div></div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="mt12-deployment"></a><h3 style="text-align: left;"><span style="font-size: large;">DEPLOYMENT</span></h3><div><br /></div><div><br /></div><div><div>An anti-tank battalion fielded 3 batteries of 6 guns each, for a total of 18 guns. Each battery consisted of 3 fire platoons, composed of 2 guns each. The reason for using smaller 2-gun fire platoons instead of 3-gun fire platoons is unclear. T-12 and MT-12 guns were organized according to this structure for the entirety of the Cold War.</div></div><div><br /></div><div>The anti-tank gun batteries were strictly treated as a tactical subdivision of their battalion, and could not be attached to motorized rifle subunits such as individual rifle regiments for fire support. This was an important detail that distinguished the use of anti-tank guns in the 1960's from the doctrine of the Great Patriotic War and the immediate postwar era.</div><div><br /></div><div><br /></div><div><div>The downsides of towed anti-tank guns were ameliorated by deploying them as a reserve force, for which they were much more suitable than dedicated tank destroyer vehicles, not just on the basis of their high cost effectiveness, but also because they were simply a more suitable weapon for entrenched firing positions. In the 1944 field manual FM 18-5, "Tactical Employment - Tank Destroyer Units", it is stated: </div><div><div><div><br /></div><div><blockquote><i>Towed guns are more suitable for advanced positions than self-propelled guns, since they are smaller and more easily concealed. If tank destroyers are committed to advance firing positions, it may be impracticable to maneuver them further thereafter.</i></blockquote></div></div><div><br /></div></div><div>It is hardly surprising that towed anti-tank guns were highly valued in the Soviet Army, at least based on the lessons given in Soviet textbooks of the time, and their low manufacturing, training and operating costs made it practical to treat them as expendable assets, which could be used to facilitate the tasks of other, less expendable units.</div><div><br /></div></div><div><div><div>Moreover, it was not only their low cost, but their high cost efficiency relative to a tank of equivalent capabilities that made the continued use of towed anti-tank guns attractive, though it is important to also mention that a gun also has to be paired with a prime mover and its crew. In peacetime, the costs of training and retaining a gun crew can be higher than a tank simply because there are more men to train, but in war, the low training requirements required for the effective use of a gun may make it much easier to field more guns and replace losses. In material costs, it is without question that a towed gun is far cheaper by design. In the book "<i>Taktik im Russlandfeldzug. Erfahrungen und Folgerungen</i>" by Eicke Middeldorf, the cost of anti-tank guns must be curtailed to no more than 5% of a tank, although whether this is true of the majority of guns is unclear, as cost comparisons often are. </div><div><br /></div><div><blockquote><i>Anti-tank guns are a relatively cheap mass-produced anti-tank weapon, so it is necessary to continue to produce them in the required quantity. However, the cost of an anti-tank gun must not exceed 5 percent of the cost of a tank. It must be remembered that any saving by reducing the number of anti-tank guns is an unacceptable mistake. However, in the future it is advisable to replace anti-tank guns with anti-tank guided missiles wherever possible.</i></blockquote></div></div><div><br /></div><div>As the complexity and cost of tanks increased, the cost efficiency advantage of a towed anti-tank gun could be maintained or improved. The main disadvantage of a towed system - mobility - was ameliorated by strictly avoiding the practice of deploying the guns offensively as they had been during WW2, where they were pushed along by their crews to hit enemy strongpoints, advancing together with the troops in assaults. As they were held as a divisional reserve, the low mobility of the T-12 and MT-12 compared to tanks was of little consequence in almost all regards except at the moment of a rapid relocation or retreat.</div></div><div><br /></div><div><div>In the Soviet Army, this limitation was accepted and codified as part of the doctrine on the use of anti-tank guns. The assertion is that: "The mission of the antitank regiment is to stop at nothing in its battle against tanks, even if it involves the sacrifice of a considerable part of its strength. The regiment will have carried out its task even if it loses its guns, provided that it destroys and puts out of action a large number of enemy tanks, and provided that against the loss of the guns can be offset the time gained, the holding of territory, or the restoring of a position."</div><div><br /></div><div><br /></div></div><div>If sufficient numbers of missile tank destroyers were available, a gun battery would be replaced with an ATGM battery consisting of 3 missile tank destroyer platoons with 3 tank destroyers each. These tank destroyers could be the 2P27 "Shmel", 2P32 "Falanga", or the 9P110 "Malyutka". An anti-tank battalion could therefore have a 4-3 gun-missile mix, with 12 guns and 9 ATGM platforms.</div><div><br /></div><div>Though the concept of ATGMs theoretically rendered towed anti-tank guns obsolete, a mixed gun-missile defensive shield had its merits for some time due to the myriad of limitations plaguing contemporary MCLOS (Manually Controlled Line Of Sight) anti-tank guided missiles such as their long minimum range, high operator training requirements, low rate of fire, and slow flight speed, which is related to the low rate of fire. The combination of all these limitations gave targets a relatively large window of opportunity to deploy countermeasures or maneuver out of harm's way. Additionally, the high demands on operator competency was counterproductive to the concept of a reserve defensive force. Anti-tank guns, particularly anti-tank guns firing APFSDS ammunition, would evidently excel where the modern guided missiles of the 1960's fell short, and with the ability to effectively engage soft targets with HE-Frag, anti-tank guns filled a role that missiles left completely open. With a mixed battalion, it could be reasonably argued that a more robust defensive capability was attained compared to a pure gun or pure missile battalion.</div><div><br /></div><div>In the same way, the anti-tank platoon in a motorized infantry battalion from the 1960's was equipped with 2 manpack ATGMs, but the basis of the unit's firepower was still the SPG-9, supplemented with several RPG-7 grenade launchers to cover the dead zones of the ATGM systems.</div><div><br /></div><div><div><div>Even with regard to preparation time to fire, towed anti-tank guns were either not worse or even superior to contemporary man-portable ATGM systems. According to a manual for the 9K11 (Malyutka) missile system, the time needed to transition from the transport configuration to the combat configuration was 1 minute 40 seconds, and the time needed to pack up into the transport configuration was 2 minutes. Meanwhile, the (M)T-12 required just 1 minute to transition between the two configurations, including the unloading of the ammunition crates from the prime mover. Of course, it has to be borne in mind that there can be additional nuances regarding such figures, but even so, it is evident that towed anti-tank guns were not only far from obsolete, but may be a preferable class of weapon for the niche that it occupied.</div></div></div><div><br /></div><div>This situation prevailed far into the 1970's, despite the introduction of new ATGM systems with SACLOS guidance. The sheer quantity of legacy missile systems made it impractical to convert the entire army in short order, given that the anti-tank battalion was only a reserve force, and the ATGM platforms in question were self-propeled systems and not manpack launchers. Infantry anti-tank units were converted to SACLOS systems more readily. </div><div><br /></div><div>The anti-tank platoon in a motorized infantry battalion was initially armed entirely with recoilless guns during the 1950's, with six guns per platoon. When the man-portable 9K11 "Malyutka" ATGM complex became available in 1961, 2 of the gun teams were replaced with ATGM teams, leaving 4 guns (SPG-9). By the 1970's, with the advent of the 9K111 "Fagot" ATGM complex with SACLOS guidance and a minimum range of just 70 meters, the number of ATGM launchers increased to 4 and the platoon was left with just a single SPG-9.</div><div><br /></div><div><br /></div></div><div><div>By the 1980's, the justifications for towed anti-tank guns were becoming flimsier, though new projects such as the MT-12K and MT-12R were devised to maintain their relevance. The MT-12K was intended to provide towed guns with their own ATGM capability, so that they could help whittle down an approaching breakthrough force before they came close enough for the gun to switch to APFSDS. It entered service in 1981 but was exceptionally rare.</div></div><div><br />The MT-12R gun with a radar fire control system was accepted into service in 1980. Deliveries to the Soviet Army took place from 1981 to 1990. The MT-12R features the 1A31 "Ruta" radar FCS, utilizing the RLPK-1 milimeter wave radar for automatic target detection, rangefinding, tracking and engagement. The two photos below, from the <a href="https://477768.livejournal.com/4671769.html">livejournal user 477768</a>, shows MT-12R guns of the 488th anti-tank artillery battalion of the 27th guards motorized rifle division in training in the GSVG, during the 1980's.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-H3H1HFU1xwk/X9-quX1yCdI/AAAAAAAASig/kzWjwkMYxrsQ9eZIjWglP58-qZP00qsbACLcBGAsYHQ/s500/ruta%2Btowed%2B1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="344" data-original-width="500" height="275" src="https://1.bp.blogspot.com/-H3H1HFU1xwk/X9-quX1yCdI/AAAAAAAASig/kzWjwkMYxrsQ9eZIjWglP58-qZP00qsbACLcBGAsYHQ/w400-h275/ruta%2Btowed%2B1.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-zkTv4wBFVz0/X9-qudJU2vI/AAAAAAAASic/qG412tUNjoIOjr3lxzBcqbR5GFLtLk-NACLcBGAsYHQ/s500/ruta%2Btowed%2B2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="335" data-original-width="500" height="268" src="https://1.bp.blogspot.com/-zkTv4wBFVz0/X9-qudJU2vI/AAAAAAAASic/qG412tUNjoIOjr3lxzBcqbR5GFLtLk-NACLcBGAsYHQ/w400-h268/ruta%2Btowed%2B2.jpg" width="400" /></a></div><br /><div><br /></div><div>The tactical deployment methods for these weapons are unknown. The most straightforward organizational structure is to equip entire batteries with the MT-12R to simplify upkeep and allowing the unique capabilities of the gun to be exploited to the fullest extent, as opposed to mixed batteries. This structure was observed in Ukrainian gunnery exercises. Another possibility is that fire platoons would have one MT-12 and one MT-12R.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-aOKA1b0gvtE/X55kJbsmMWI/AAAAAAAAR5s/D2tAo3EbiLkduGAjCOBYpMDId8KGGuq7gCLcBGAsYHQ/s640/ruta%2Bgun.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="442" data-original-width="640" height="276" src="https://1.bp.blogspot.com/-aOKA1b0gvtE/X55kJbsmMWI/AAAAAAAAR5s/D2tAo3EbiLkduGAjCOBYpMDId8KGGuq7gCLcBGAsYHQ/w400-h276/ruta%2Bgun.jpg" width="400" /></a></div><br /><div><br /></div><div>This system had no analogues in the world, and helped prolong the usefulness of the MT-12 by giving it a new tactical niche within its defensive role. It was capable of detecting targets from long ranges at a speed that could not be matched by the contemporary thermal imaging sights of the time, and do so regardless of the weather conditions. It was also capable of accurate fire in the presence of obscurants that would otherwise blind any thermal imaging sighting system. In this sense, it was not only better in a defensive role compared to the tanks available in the Soviet Army, which had only daylight optics or passive night vision, but also superior to the latest tanks of the hypothetical enemy equipped with 1st Generation thermal imaging systems.</div><div><br /></div><div>With the aid of the "Ruta" radar FCS, even the relatively modest capabilities of the 100mm gun would have sufficed against these new tanks at any practical range. With that said, however, newer models of the Abrams began arriving to the troops towards the end of the 1980's and the Challenger 1 was emerging as an additional threat. Although the enhanced armour protection of these new models was only limited to certain zones, the limited prospects of the MT-12 meant that it likely could not have coped with further improvements applied to these tanks if it were to continue serving in its role through the 1990's.</div><div><div><br /></div><div><br /></div><div>MT-12 and MT-12R guns are still retained in the Russian ground forces to this day. Though the number of guns have dwindled considerably, the MT-12 continues to be serve even now with <a href="https://tvzvezda.ru/photo-gallery/201611141143-dfmg.htm#">new crews graduating</a> from at least one training center, at Kolomna. Anti-tank gun batteries are integrated into the combined arms network, and regularly take part in exercises. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-mwTvHLTnBAw/X95Y8wUONCI/AAAAAAAASfI/gYavO_zBqToItYdX35JNuCXm3724oXN_ACLcBGAsYHQ/s1920/mt-12%2Bfiring%2Bexercise.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="360" src="https://1.bp.blogspot.com/-mwTvHLTnBAw/X95Y8wUONCI/AAAAAAAASfI/gYavO_zBqToItYdX35JNuCXm3724oXN_ACLcBGAsYHQ/w640-h360/mt-12%2Bfiring%2Bexercise.png" width="640" /></a></div><br /><div><br /></div><div>The most recent large scale exercise where the MT-12R participated was <a href="https://news.myseldon.com/ru/news/index/216363629">Center-2019</a>, where troops were given the opportunity to train with the all-weather capabilities of the MT-12R in a defensive exercise. The simulated enemy launched an offensive against Russian and Kazakh positions under the cover of a dust storm, but were detected by Orlan-10 UAVs, which transmitted positional data to the artillery command post. MT-12R guns then stopped the enemy advance with aimed fire through the dust storm.</div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="mt12-mobility"></a><h3 style="text-align: left;"><span style="font-size: large;">MOBILITY</span></h3><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-lufvJxovie4/XqMA5yqKTeI/AAAAAAAAQpY/uEplgTJ-EL8ORujSyRMwO1LgKdQ9KwfqACLcBGAsYHQ/s1600/mt-lb%2Btowing%2Bguns%2Bto%2Bfiring%2Bpositions.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="345" data-original-width="773" height="285" src="https://1.bp.blogspot.com/-lufvJxovie4/XqMA5yqKTeI/AAAAAAAAQpY/uEplgTJ-EL8ORujSyRMwO1LgKdQ9KwfqACLcBGAsYHQ/s640/mt-lb%2Btowing%2Bguns%2Bto%2Bfiring%2Bpositions.jpg" width="640" /></a></div><div><br /></div></div><div><br /></div><div>The T-12 was customarily towed by a ZiL-150 truck or an AT-P armoured prime mover. When the MT-LB began serial production in 1966 and began deliveries to the troops in 1967, anti-tank battalions were not given the highest priority on the distribution list as the AT-P was adequately coping with the T-12, so initially, the MT-LB was mainly used for heaviest field guns and howitzers. However, the suspension of the T-12 could not cope with the increased cross-country speed offered by the MT-LB, prompting the creation of the MT-12. When the MT-12 entered service in 1970, the MT-LB was designated as its standard prime mover.</div><div><br /></div><div>When towed by an AT-P, the top speed of the T-12 is 50 km/h or equal to the top speed of the AT-P itself. The top speed, which is reached when towed by a ZiL-157 or any other truck, is 60 km/h. This speed limit was imposed by its tyres. Thanks to its redesigned carriage, the MT-12 had improved traction and platform stability which enabled the prime mover to shift the gun more easily across difficult terrain, and even slightly increased the maximum towing speed. It could be towed at speeds up to 70 km/h on paved roads, 40 km/h on dirt roads, and 25 km/h cross-country. This was considerably speedier than the lighter D-48.</div><div><br /></div><div><div>Bearing in mind that a high cross-country speed cannot be achieved when towing a T-12 with an MT-LB, both guns could be towed without difficulty by the same prime movers. The 3.1-ton weight of the MT-12 was still manageable by the ZiL-157, Ural-375D or other trucks in its class, which is hardly surprising given that they were rated to tow the heavier BS-3. The improved mobility of the MT-12 could only be felt at the operational or tactical level. The photo on the left below, taken from <a href="https://russellphillips.uk/soviet-100mm-t-12/">Russel Phillips' website</a>, shows a T-12 hitched up to an unknown truck, and the photo on the right below shows MT-12 guns being towed by Ural-4320 trucks. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Idnt_7uTpEs/X85ULhnDFxI/AAAAAAAASTk/sIi4QTOFsCwQ4Ij9kfENTsJxz9OlIdnxwCLcBGAsYHQ/s800/T-12.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="301" data-original-width="800" height="150" src="https://1.bp.blogspot.com/-Idnt_7uTpEs/X85ULhnDFxI/AAAAAAAASTk/sIi4QTOFsCwQ4Ij9kfENTsJxz9OlIdnxwCLcBGAsYHQ/w400-h150/T-12.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-FLlji-SbzGs/X85T1hlGkhI/AAAAAAAASTY/sw6oTpy1cUoIg2EpjICh1QruIyX2As5fQCLcBGAsYHQ/s1000/truck%2Btowed.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="539" data-original-width="1000" height="172" src="https://1.bp.blogspot.com/-FLlji-SbzGs/X85T1hlGkhI/AAAAAAAASTY/sw6oTpy1cUoIg2EpjICh1QruIyX2As5fQCLcBGAsYHQ/w320-h172/truck%2Btowed.jpg" width="320" /></a></div><div><br /></div></div><div><div><br /></div><div><div>A T-12 gun crew consists of 6 people, including the driver and commander of the prime mover. The vehicle commander would be the gun commander. The remaining 4 crewmen would be seated in the cargo compartment of the same vehicle. They include the gunner, a loader, and two ammunition handlers.</div><div><br /></div><div>An MT-12 gun crew consists of 7 people. The additional crew member was another ammunition handler, whose strength would have undoubtedly been helpful when manhandling the gun in and out of firing positions, although the weight of the MT-12 was still excessive for 7 men.</div></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-olN-7J0JRKI/X6DzwbQbDxI/AAAAAAAASAQ/S_cH497Ore4ho--BaAoBqgjy36vk-F-KwCLcBGAsYHQ/s2048/mt-12%2Btowed%2Bby%2Bmt-lb.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1367" data-original-width="2048" height="268" src="https://1.bp.blogspot.com/-olN-7J0JRKI/X6DzwbQbDxI/AAAAAAAASAQ/S_cH497Ore4ho--BaAoBqgjy36vk-F-KwCLcBGAsYHQ/w400-h268/mt-12%2Btowed%2Bby%2Bmt-lb.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-cu8Be2glN6c/X6Dzv1lKWNI/AAAAAAAASAM/pelOFE3R6rYAIXxb-bHBLbjHktHSqKozwCLcBGAsYHQ/s960/transporting%2Bmt-12%2Bgun%2Bwith%2Bcrew%2Band%2Bammunition.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="640" data-original-width="960" height="266" src="https://1.bp.blogspot.com/-cu8Be2glN6c/X6Dzv1lKWNI/AAAAAAAASAM/pelOFE3R6rYAIXxb-bHBLbjHktHSqKozwCLcBGAsYHQ/w400-h266/transporting%2Bmt-12%2Bgun%2Bwith%2Bcrew%2Band%2Bammunition.jpg" width="400" /></a></div><div><br /></div></div><div><div><br /></div><a href="https://www.blogger.com/null" id="mt12-carriage"></a><h3 style="text-align: left;"><span style="font-size: large;">CARRIAGE</span></h3><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-2ETMw-Ed9SM/X55rcIcY5ZI/AAAAAAAAR50/hW2Ed4lwNjksV_nBE8SI3kwDIqf8rzbnACLcBGAsYHQ/s2048/carriage%2Bmount.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1220" data-original-width="2048" height="382" src="https://1.bp.blogspot.com/-2ETMw-Ed9SM/X55rcIcY5ZI/AAAAAAAAR50/hW2Ed4lwNjksV_nBE8SI3kwDIqf8rzbnACLcBGAsYHQ/w640-h382/carriage%2Bmount.png" width="640" /></a></div><div><br /></div></div><div><br /></div><div>According to historian A. V. Shirokorad, the carriage of the T-12 was inherited from the D-48, but it is not known precisely how many parts were interchangeable. The trails and the suspension are essentially the same, or at least appear to be, but according to the manual, the carriage was very slightly wider. The width of the axle track (the distance between the centerline of the two wheels) is either 1,475mm or 1,490mm, depending on the wheels fitted, and the maximum width of the gun along the hubcaps of the wheels is 1,795 or 1,810mm, depending on the wheels fitted.</div><div><br /></div><div><div>It was partly because of the carriage that the T-12 was relatively lightweight, weighing only 2,750 kg when configured for transportation and 2,800 kg when set up in its combat configuration (one round loaded, all sighting devices installed). It remained slightly lighter than the 17-pdr Mk. 1 gun, and it was heavier than the D-48 by only 350 kg. Astonishingly enough, it was almost a full ton lighter than a BS-3 field gun (3,650 kg). </div><div><br /></div><div>Though it is reasonable to expect the T-12 to be physically larger than the D-48 due to its larger caliber and its power, its dimensions were only negligibly larger. Its total length in the travelling configuration was 9,480mm, very similar to the 9,195mm total length of the D-48 and 9,370mm length of the BS-3. The larger, heavier carriage of the MT-12 had a longer overall length of 9,650mm. These overall length figures include the extended towing eye, which are folded flush against the right carriage trail when not in use.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-7HzciZP8dR8/X85J0DR39xI/AAAAAAAASR0/MLIoMfCfb9c44FeSOZFhd4El0ztio0POwCLcBGAsYHQ/s1058/cuban%2Bmt-12%2Bgun.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="747" data-original-width="1058" height="452" src="https://1.bp.blogspot.com/-7HzciZP8dR8/X85J0DR39xI/AAAAAAAASR0/MLIoMfCfb9c44FeSOZFhd4El0ztio0POwCLcBGAsYHQ/w640-h452/cuban%2Bmt-12%2Bgun.png" width="640" /></a></div><div><br /></div></div><br /></div><div>The main downside of the new carriage on the MT-12 was the greatly increased weight, raising the total weight to 3,100 kg, but even though the additional weight placed a somewhat greater burden on the prime mover, the tactical mobility of the MT-12 saw a net improvement thanks to the more robust suspension and carriage. </div><div><br /></div><div>Like any other conventional gun, the carriage crossbeam served as the gun mount and traverse pintle. It was constructed as a one-piece cast steel girder with a complex shape. The carriage trails of both the T-12 and MT-12 have a rectangular box shape like that of the D-48, but differing substantially in design.</div><div><br /><br /><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Q8vm0P0WF-M/X47hXxSaEGI/AAAAAAAARxI/AD1n4ILtFMsdkhCQxKGQA4wxi4vMjPdZgCLcBGAsYHQ/s2265/carriage.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="870" data-original-width="2265" height="246" src="https://1.bp.blogspot.com/-Q8vm0P0WF-M/X47hXxSaEGI/AAAAAAAARxI/AD1n4ILtFMsdkhCQxKGQA4wxi4vMjPdZgCLcBGAsYHQ/w640-h246/carriage.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The structure of the box section is a multi-part construction, consisting of two U-beams and two curved corner plates for reinforcement. It follows the same design rationale of the D-48 trail in avoiding sharp corners and fastenings at corners.</div></div><div><br /></div><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-nLpMuKpqgN4/X47hI0AMswI/AAAAAAAARxE/X5K7MjlyKjoub3HKrxZTwLbqAyW66YYEgCLcBGAsYHQ/s882/legs.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="666" data-original-width="882" height="303" src="https://1.bp.blogspot.com/-nLpMuKpqgN4/X47hI0AMswI/AAAAAAAARxE/X5K7MjlyKjoub3HKrxZTwLbqAyW66YYEgCLcBGAsYHQ/w400-h303/legs.png" width="400" /></a></div><div><br /></div></div><div><br /></div><div><div>Like other towed guns of the same weight class, the wheels of the carriage were taken from an existing automobile. The new carriage of the MT-12 replaced the ZiS-5 wheels with the newer "GK" airless tyres from the ZiL-150 truck with a rim flange width and rim diameter of 9 inches and 20 inches respectively. The external diameter of the tyre is 1,034mm. These larger tyres accommodated the increased weight of the MT-12 compared to the T-12. The width of the axle track was increased to 1,920mm, and the maximum width of the gun along the hubcaps of the wheels is 2,320mm.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-6WEEYuAGidE/X59nk40oDaI/AAAAAAAAR6o/bkLgPh6AgysjqgegJ-8AWq3rm1kzLwMsQCLcBGAsYHQ/s1768/carriage%2Bsuspension.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="872" data-original-width="1768" height="316" src="https://1.bp.blogspot.com/-6WEEYuAGidE/X59nk40oDaI/AAAAAAAAR6o/bkLgPh6AgysjqgegJ-8AWq3rm1kzLwMsQCLcBGAsYHQ/w640-h316/carriage%2Bsuspension.png" width="640" /></a></div><div><br /></div><div><div><br /></div>The T-12 had an unusually high ground clearance of 380mm, which presumably helped to improve the towing speed of the gun when moving cross-country. The ground clearance was decreased to 330mm on the MT-12 carriage, despite the use of slightly larger wheels. In any case, the ground clearance exceeded that of trucks but was less than that of the MT-LB.</div></div><div><br /></div><div><br /></div><div>It is claimed on some websites that the difference between the MT-12 and the T-12 was that the suspension was switched to a torsion bar type with automatic locking, but this is not the case. As with the preceding guns, the suspensions of both the T-12 and MT-12 are automatically locked when the gun is set up in its combat configuration. Fully spreading a carriage trail until it is locked on its stopper will lock the suspension of the corresponding wheel by securing the swing arm of the wheel to the carriage crossbeam. This is done by the carriage trail pushing in a spring-loaded stopper pin at the end of its rotation arc, engaging a corresponding slot in the swing arm. Considering the stronger recoil of the (M)T-12 compared to the D-48 and D-44, this feature was more useful than ever. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ulHoJq_H8fA/X552KFbrf4I/AAAAAAAAR58/Mq0XdQ94fqEUWlAZ9PaKqgNShoUi2yQVwCLcBGAsYHQ/s1161/torsion%2Bbar%2Bstopper.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1161" data-original-width="1017" height="400" src="https://1.bp.blogspot.com/-ulHoJq_H8fA/X552KFbrf4I/AAAAAAAAR58/Mq0XdQ94fqEUWlAZ9PaKqgNShoUi2yQVwCLcBGAsYHQ/w350-h400/torsion%2Bbar%2Bstopper.png" width="350" /></a><a href="https://1.bp.blogspot.com/-vdXgWAhjhiE/X56cX3ZJGgI/AAAAAAAAR6Q/OgBiOoevhzUug7RHK1s6YdZUfe-bXPjfwCLcBGAsYHQ/s2048/deploying%2Bcarriage.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="2030" height="400" src="https://1.bp.blogspot.com/-vdXgWAhjhiE/X56cX3ZJGgI/AAAAAAAAR6Q/OgBiOoevhzUug7RHK1s6YdZUfe-bXPjfwCLcBGAsYHQ/w396-h400/deploying%2Bcarriage.png" width="396" /></a><br /></div><div><div><br /><br />The shock absorbers greatly reduce the wear and tear induced by vibration from towing the gun on rough terrain.</div><div><br /><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-22fykJ0NRPE/X4NW-0lREdI/AAAAAAAARtE/6rVPbKTKDpgFo3rT-tTTAMRaT0-kU30pQCLcBGAsYHQ/s1839/shock%2Babsorbers.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="987" data-original-width="1839" height="344" src="https://1.bp.blogspot.com/-22fykJ0NRPE/X4NW-0lREdI/AAAAAAAARtE/6rVPbKTKDpgFo3rT-tTTAMRaT0-kU30pQCLcBGAsYHQ/w640-h344/shock%2Babsorbers.png" width="640" /></a></div></div><div> </div></div><div><br /></div><div><div>Movement in snow is facilitated by the mounting of LO-7 skis under the tyres. It was permitted to fire the gun with the skis mounted, but with some limitations. Firing within the entire traverse arc of 54 degrees is possible but with an elevation limit of only +16 degrees, and to fire at the full elevation angle of +20 degrees, the traverse arc must be limited to 40 degrees. </div><div><br /></div><div><br /></div><div><div>In the travelling configuration, the muzzle and rear end of the gun would be covered with canvas wraps, and more interestingly, a set of signal lamps would be fitted. The set consists of parking signals and a brake light. There is a muzzle lamp, attached to the muzzle cover, and a pair of rear lamps with indicator and brake lamps. They are connected to an MT-LB with power cables. The power cable for the muzzle lamp would be wrapped around the barrel. When the gun is in motion behind the MT-LB, the muzzle and rear parking lights are green. The red brake light, located on the gun shield in the rear light, comes on when braking.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-hHZCRrDcQHg/X9qqCBIXLJI/AAAAAAAASdQ/-TK5GBstPaoVM20yGVNsDV_Emoy0AzAdgCLcBGAsYHQ/s800/mt-12%2Brusty.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://1.bp.blogspot.com/-hHZCRrDcQHg/X9qqCBIXLJI/AAAAAAAASdQ/-TK5GBstPaoVM20yGVNsDV_Emoy0AzAdgCLcBGAsYHQ/w400-h300/mt-12%2Brusty.jpg" width="400" /></a></div><div><br /></div></div><br /><div>Despite its prodigiously light weight for its power, the MT-12 reached the upper limit of feasibility for manual handling by a gun crew. For a standard 7-man gun crew, the weight was only manageable if the terrain was paved or at least hard enough. When the crew is inevitably forced to manually shift the position of the gun for whatever reason, the large weight savings would become greatly appreciated. It also has a positive effect on the transportability of the gun as it permitted general purpose trucks such as the ZiL-131 to carry a full gun crew while towing the gun off-road. <br /></div></div><div><br />The carriages of the T-12 and MT-12 have a hand rail in front of each spade for the convenience of the crew when manhandling the gun. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-TCC7Yx1mqLs/X94oXHEuiTI/AAAAAAAASeo/7razaQqy0cUi3Of3x2-3bHaW4omoTQlTQCLcBGAsYHQ/s1067/castor%2Bwheel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="481" data-original-width="1067" height="180" src="https://1.bp.blogspot.com/-TCC7Yx1mqLs/X94oXHEuiTI/AAAAAAAASeo/7razaQqy0cUi3Of3x2-3bHaW4omoTQlTQCLcBGAsYHQ/w400-h180/castor%2Bwheel.png" width="400" /></a></div><br /><div><br /></div><div>Both the T-12 and MT-12 can be maneuvered on flat ground by their 6 and 7-man crews respectively, with one man holding the handlebar on each carriage trail, one holding the towing bar, and the rest pushing on the shield and the wheels.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-w8giItXZldg/X4x1RRfx1BI/AAAAAAAARwA/PSXJdArITnUna0WzN4C6oWP-EvtWyKwHgCLcBGAsYHQ/s800/1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="533" height="320" src="https://1.bp.blogspot.com/-w8giItXZldg/X4x1RRfx1BI/AAAAAAAARwA/PSXJdArITnUna0WzN4C6oWP-EvtWyKwHgCLcBGAsYHQ/w213-h320/1.jpg" width="213" /></a><a href="https://1.bp.blogspot.com/-xCFq6EPwcvQ/X5hj0H-veuI/AAAAAAAAR1I/JUQatV2gXDk0JMhrfBDBohaVa2U5FGHXwCLcBGAsYHQ/s800/manhandling%2Bmt-12.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="533" data-original-width="800" height="266" src="https://1.bp.blogspot.com/-xCFq6EPwcvQ/X5hj0H-veuI/AAAAAAAAR1I/JUQatV2gXDk0JMhrfBDBohaVa2U5FGHXwCLcBGAsYHQ/w400-h266/manhandling%2Bmt-12.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>Needless to say, the increased weight of the MT-12 made it more difficult to manhandle. This is only marginally counterbalanced by its larger wheels, but at the same time, weight is not the only factor dictating the mobility of a gun. The mere presence of handrails and a castor wheel already makes the MT-12 more handy than a gun like the 17-pdr, which was around 150 kg lighter but was found to have seriously deficient mobility during testing in the USSR partly due to the lack of comfortable handrails on its Mk. 1 carriage. The <a href="https://warspot.ru/5976-dlinnaya-ruka-po-angliyski">testing committee</a> noted that:</div><br /><div><i><blockquote>Transportation of a gun off-road to a distance of up to 500 meters is overwhelming for the strength of the gun crew. A crew of 7 people could transport a gun only up to 100 meters, even over flat terrain. Transport with the strength of the gun crew is even more difficult due to the lack of comfortable handrails.</blockquote></i></div></div><div><div><br /></div><div><br /></div><a href="https://www.blogger.com/null" id="mt12-protection"></a><h3 style="text-align: left;"><span style="font-size: large;">PROTECTION</span></h3><div><br />The height of the gun when measured up to the gun shield is 1,565 mm. MT-12 had a slightly taller gun shield due to more pronounced curves on its top edge, giving the gun a maximum height of 1,600mm. The gun shield was mounted to the gun cradle by a pair of support beams and fastened with two bolts on each support beam. It is not structurally integral to the weapon, and could be removed without any special tools, but it is always left mounted to the gun under normal circumstances. Using 76.2mm guns as a reference, the M5 had a maximum height of 1,615mm and the 17-pdr had a maximum height of 1,600mm, while the 90mm M26 had a maximum height of 1,752mm.</div><div><br /></div><div>The gun shield of the T-12 is just tall enough to cover the gunner when he is kneeling to use the sights, but it is barely wide enough to cover a large gunner even from the direct front. This was alleviated by the much wider shield of the MT-12. The shields of both guns are tall enough to protect a loader working behind the gun. </div><div><br /></div><div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-hsbhpU-WbWQ/X6Da11W8UMI/AAAAAAAAR_A/Q34WiVrVBCgx9Pf2PbvKcAIVx-h6wx8owCLcBGAsYHQ/s933/cropped%2Bimage%2Bt-12.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="415" data-original-width="933" height="284" src="https://1.bp.blogspot.com/-hsbhpU-WbWQ/X6Da11W8UMI/AAAAAAAAR_A/Q34WiVrVBCgx9Pf2PbvKcAIVx-h6wx8owCLcBGAsYHQ/w640-h284/cropped%2Bimage%2Bt-12.png" width="640" /></a></div><div><br /></div><br /><div>The height of the bore axis from ground level is just 810mm for both the T-12 and MT-12. This was not only excellent for a gun of its caliber, but was even lower than the D-48 (830mm). In fact, the (M)T-12 was lower than even the British 6-pdr gun which had a bore axis height of 32", or 813mm (determined by measurement on a museum specimen), and the 5cm Pak 38 gun, which had a bore axis height of 820mm. Of course, 3-10mm is a negligible difference relative to the absolute bore axis height, but it serves to illustrate that the structure of the gun was designed with an intense focus on the most important characteristics of effective anti-tank artillery. In fact, such a low bore axis was completely unprecedented for a heavy towed anti-tank gun. Only the smallest infantry anti-tank guns like the American 37mm M3A1 gun and the domestic 45mm M-42 had a lower bore axis than the T-12, being just 650mm tall and 710mm tall respectively.</div></div><div><br /></div><div>The photo on the left below, taken from <a href="https://477768.livejournal.com/1913325.html">an unknown album</a>, shows an MT-12 being naturally camouflaged by its low silhouette among the surrounding vegetation at the edge of a birch forest.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-pU9I0aikL-o/X59WqRjZRxI/AAAAAAAAR6g/j4ANrBDgqZ8MuMYbbSlM2n6fmylgtvgIwCLcBGAsYHQ/s1024/5_1140632.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="682" data-original-width="1024" height="266" src="https://1.bp.blogspot.com/-pU9I0aikL-o/X59WqRjZRxI/AAAAAAAAR6g/j4ANrBDgqZ8MuMYbbSlM2n6fmylgtvgIwCLcBGAsYHQ/w400-h266/5_1140632.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-Tv6lp4PGSCU/X6AOaDMa7nI/AAAAAAAAR-M/yNi02aLF1sAPZjp3usGwDMM3OqKOpZPfgCLcBGAsYHQ/s800/hillside%2Bgun%2Bposition.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="537" data-original-width="800" height="269" src="https://1.bp.blogspot.com/-Tv6lp4PGSCU/X6AOaDMa7nI/AAAAAAAAR-M/yNi02aLF1sAPZjp3usGwDMM3OqKOpZPfgCLcBGAsYHQ/w400-h269/hillside%2Bgun%2Bposition.jpg" width="400" /></a><br /></div><div><br /></div><div><br /></div><div>Further reductions in silhouette size can be obtained by digging in the wheels, entrenching the gun position and modifying the surrounding landscape for the protection of the crew and for concealment, usually by creating a gun pit surrounded by trenches and fox holes. The image on the left below, taken from a video (<a href="https://www.youtube.com/watch?v=OGFIIGiJjCM">link</a>), shows pits for the wheels being dug. Such positions are considered prepared positions, which provide the best conditions for the work of the crew. Prepared positions are preferable to hastily prepared positions, where the spades are dug in but not buried. Due to the nature of its work and the nature of being a defensive reserve asset, the (M)T-12 would predominantly be used from prepared positions.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-vk4JADnAgLU/X83Qqm0KrmI/AAAAAAAASQc/gy2940y-z8ozKEaGAE1gKwSLRClpRB_awCLcBGAsYHQ/s1919/wheel%2Bpits.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1063" data-original-width="1919" height="221" src="https://1.bp.blogspot.com/-vk4JADnAgLU/X83Qqm0KrmI/AAAAAAAASQc/gy2940y-z8ozKEaGAE1gKwSLRClpRB_awCLcBGAsYHQ/w400-h221/wheel%2Bpits.png" width="400" /></a><a href="https://1.bp.blogspot.com/-3EmZzQM5jSA/X5h0XnkFO-I/AAAAAAAAR14/Syn2PTJfqYAF18mZHpI5KpI3bgm33nCAQCLcBGAsYHQ/s1000/mt-12%2Bloading.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="666" data-original-width="1000" height="213" src="https://1.bp.blogspot.com/-3EmZzQM5jSA/X5h0XnkFO-I/AAAAAAAAR14/Syn2PTJfqYAF18mZHpI5KpI3bgm33nCAQCLcBGAsYHQ/w320-h213/mt-12%2Bloading.jpg" width="320" /></a></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">NBC</span></h3><div><br /></div><div><div>If used in the same way as in the GPW, a towed gun such as the (M)T-12 would have been totally at odds with the strong emphasis that the Soviet Army had on mobility and protection from nuclear, chemical and biological threats. This was overcome by their relegation to the divisional or army reserves. <br /><br />In an environment contaminated by weapons of mass destruction, the crew of a towed gun could be protected inside their sealed prime mover, and be protected by their individual NBC suits when they dismount. However, in combat, the crew can be caught without NBC protection if attacked without warning. Protection from nuclear attack is limited to the sturdiness of the shelters prepared next to the gun emplacement. The image below shows an MT-12 gunner in an NBC suit with mask during the Zapad-81 exercises. <br /><br /><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-M2PzWjwIjeI/X9ppVQxTDmI/AAAAAAAASdI/Sw-y2zF9HFMFRmxIRYiLnrJhQt8Kfo6TACLcBGAsYHQ/s1706/mt-12%2Bzapad%2B81.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1706" height="406" src="https://1.bp.blogspot.com/-M2PzWjwIjeI/X9ppVQxTDmI/AAAAAAAASdI/Sw-y2zF9HFMFRmxIRYiLnrJhQt8Kfo6TACLcBGAsYHQ/w640-h406/mt-12%2Bzapad%2B81.png" width="640" /></a></div><div><br /></div></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">SHIELD</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-TtzDBoMlE0Y/X96YiMSOe0I/AAAAAAAASgs/XIRCZ47wDUo_-B5kJ2rn-3CVxzQlEoYWACLcBGAsYHQ/s1344/Front%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="896" data-original-width="1344" height="266" src="https://1.bp.blogspot.com/-TtzDBoMlE0Y/X96YiMSOe0I/AAAAAAAASgs/XIRCZ47wDUo_-B5kJ2rn-3CVxzQlEoYWACLcBGAsYHQ/w400-h266/Front%2Bview.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The gun shield of the T-12 and MT-12 differ in shape and size, but they provide the same level of ballistic protection. Measurements on a T-12 used as a monument indicated that the thickness is 4.5mm, following the same standard set by the M1930 gun. For both the T-12 and MT-12, the vertical slope is 30 degrees and the shield is also swept back in the horizontal axis at around the same angle.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-yDKSg6RKmNM/X96YzGA7ZAI/AAAAAAAASg0/GzKHVmkY80AVKzDW6FE7fCEFjX3s7Tj6ACLcBGAsYHQ/s2048/t-12%2Bshield.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1152" height="320" src="https://1.bp.blogspot.com/-yDKSg6RKmNM/X96YzGA7ZAI/AAAAAAAASg0/GzKHVmkY80AVKzDW6FE7fCEFjX3s7Tj6ACLcBGAsYHQ/s320/t-12%2Bshield.jpg" /></a></div><div><br /></div><div><br /></div><div>On the T-12, the gun mask was very similar to the simple fixed mask of the D-48, if not the same. When the gun is fully elevated, a gap appears, through which fragments can pass and hit the gun mount. The redesigned shield of the MT-12 incorporated a new gun mask constructed to eliminate the gap beneath the gun at high elevation angles with a folding section between the gun shield and the barrel. The photo on the left below, showing a T-12, was provided by a friend of the author, and the photo on the right below, showing an MT-12, is from the <a href="https://www.kpopov.ru/travel/avtovaz_guns_10.htm#ancor9">kpopov.ru photogallery</a>. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Ok7rmDS8mco/X6DqJfRWq_I/AAAAAAAAR_Y/v6GXh5GlBHoE-tcQPtWB-Ju_KgpPqWGYgCLcBGAsYHQ/s2048/20201029_144004.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1152" height="320" src="https://1.bp.blogspot.com/-Ok7rmDS8mco/X6DqJfRWq_I/AAAAAAAAR_Y/v6GXh5GlBHoE-tcQPtWB-Ju_KgpPqWGYgCLcBGAsYHQ/w180-h320/20201029_144004.jpg" width="180" /></a><a href="https://1.bp.blogspot.com/-AZUOJk1gPIQ/X6DuDPwYJeI/AAAAAAAAR_o/JIkXSPOeKdYbvJI8A-0hsJ4b3ORebpacwCLcBGAsYHQ/s800/dsc_7861.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="530" data-original-width="800" height="320" src="https://1.bp.blogspot.com/-AZUOJk1gPIQ/X6DuDPwYJeI/AAAAAAAAR_o/JIkXSPOeKdYbvJI8A-0hsJ4b3ORebpacwCLcBGAsYHQ/w400-h265/dsc_7861.jpg" width="483" /></a><br /></div><div><br /></div><div><br /></div><div>Both the T-12 and MT-12 have a protective sleeve around the base of the barrel which served a secondary purpose of guiding the gun during recoil, as part of the gun cradle. </div><div><br /></div><div>The gaps between the shield and the wheels when traversed to the extreme right and extreme left positions are less than 3mm.</div><div><br /></div><div>Each sight is installed in separate mounting brackets, and the gun shield has three separate panels that can be folded away to selectively open up observation loopholes for each sight. The telescopic direct fire sight looks through a vertical slit, covered by a narrow folding panel. Above it, the panoramic periscope looks over the gunshield when its large protective panel is folded down, same as the night sight which is also protected by a large panel that also bears the upper half of the direct fire observation slit.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ebE7Xw0iNMA/X6YexhZjjPI/AAAAAAAASDY/jSDTi3M6dQQssvbnDyt95ydB6DLx3aJrwCLcBGAsYHQ/s1701/ukraine%2Bmt-12%2Bwith%2Bop4.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1078" data-original-width="1701" height="406" src="https://1.bp.blogspot.com/-ebE7Xw0iNMA/X6YexhZjjPI/AAAAAAAASDY/jSDTi3M6dQQssvbnDyt95ydB6DLx3aJrwCLcBGAsYHQ/w640-h406/ukraine%2Bmt-12%2Bwith%2Bop4.png" width="640" /></a></div><div><br /></div><div><br /></div><div>Opening all three sight panels on the gun shield gives the gunner good visibility in a wide forward arc without requiring him to stand up. This makes it convenient for him when scanning for targets, as he can simply look up from the telescopic day sight and doing so does not compromise the full-body protection afforded to him by the shield, and even from the direct front, only the gunner's helmet is exposed through the gap in the shield when he is using the sight.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-g2ThXyYmqYA/X5m7vB_HN_I/AAAAAAAAR2o/FpL9e1XyttAQHbhHTGPlmk4rNbCz2nwuwCLcBGAsYHQ/s600/visibility.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="400" src="https://1.bp.blogspot.com/-g2ThXyYmqYA/X5m7vB_HN_I/AAAAAAAAR2o/FpL9e1XyttAQHbhHTGPlmk4rNbCz2nwuwCLcBGAsYHQ/s16000/visibility.jpg" /></a></div><div><br /></div><div><br /></div><div>This feature of the gun shield design is somewhat reminiscent of the 3.7cm Pak shield design which had a collapsible upper half. The upper half consisted of three panels locked together with pins and held upright by mutual support. Collapsing the top half required all three panels to be folded down, which gave the gunner unobstructed visibility, but greatly increased the exposure of both the gunner and the loader to direct fire. Due to the much larger size of the T-12 and MT-12 gun shields, the gunner could be granted good visibility without compromising his protection. </div><div><br /></div><div style="text-align: center;"><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-G95ILJ3c74M/X6DdQSMpMzI/AAAAAAAAR_I/gNaeYDgSUJQX1qpd06AUp1u5u_8uu9_dwCLcBGAsYHQ/s1024/45mm-21.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="673" data-original-width="1024" height="263" src="https://1.bp.blogspot.com/-G95ILJ3c74M/X6DdQSMpMzI/AAAAAAAAR_I/gNaeYDgSUJQX1qpd06AUp1u5u_8uu9_dwCLcBGAsYHQ/w400-h263/45mm-21.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-hoUNOCt0AIw/X6DdQah7XiI/AAAAAAAAR_M/7bKFXJTPT6kQH5HORno8mUPTIJ9YZHbiwCLcBGAsYHQ/s1100/folded%2Bgun%2Bshield.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="701" data-original-width="1100" height="255" src="https://1.bp.blogspot.com/-hoUNOCt0AIw/X6DdQah7XiI/AAAAAAAAR_M/7bKFXJTPT6kQH5HORno8mUPTIJ9YZHbiwCLcBGAsYHQ/w400-h255/folded%2Bgun%2Bshield.png" width="400" /></a></div><div><br /><br /></div><div><br /><a href="https://www.blogger.com/null" id="mt12-sighting"></a><h3 style="text-align: left;"><span style="font-size: large;">FIRE CONTROL</span></h3></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both;"><a href="https://1.bp.blogspot.com/-gfFztF9hbYA/X85SwxanSlI/AAAAAAAASTA/jWTMJcRMnhgY2Am95iFBEAV34zwuQrncwCLcBGAsYHQ/s900/gunner%2Band%2Bcommander.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="900" height="426" src="https://1.bp.blogspot.com/-gfFztF9hbYA/X85SwxanSlI/AAAAAAAASTA/jWTMJcRMnhgY2Am95iFBEAV34zwuQrncwCLcBGAsYHQ/w640-h426/gunner%2Band%2Bcommander.jpg" width="640" /></a></div></div><div><br /></div><div><br /></div><div>Initially, rangefinding for a T-12 battery would be done with a DS-1 or DS-2 stereoscopic rangefinder. Beginning in 1971, they were replaced by the DAK-1 laser rangefinder. In turn, the DAK-1 was replaced by the DAK-2, later supplemented by the DAK-2M. The photo below shows a DAK-2 in use during live fire training involving MT-12 guns by Romanian Army.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-PBCmyH221hs/X9qzS-7jGmI/AAAAAAAASdY/EOwd7wYkeNwvtJ1X4vNo8mJPiQWgFmy9wCLcBGAsYHQ/s800/dak-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="533" data-original-width="800" height="266" src="https://1.bp.blogspot.com/-PBCmyH221hs/X9qzS-7jGmI/AAAAAAAASdY/EOwd7wYkeNwvtJ1X4vNo8mJPiQWgFmy9wCLcBGAsYHQ/w400-h266/dak-2.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>Beginning in 1966, each gun battery would be issued with a PSNR-1 portable ground reconnaissance radar station. Against tanks, its pulse-doppler radar had a detection range of up to 10 km. Naturally, the probability of detection is much higher for moving tank units than for individual tanks. The reconnaissance radar of each battery could be deployed to monitor a designated sector, thus forming an early warning perimeter system. Prior information on the direction of the main thrust taken by the approaching enemy exploitation force would enable each battery to position themselves more favourably to prevent detection and assume more favourable firing angles.</div><div><br /></div><div>The advantages of using a ground radar for battlefield surveillance are listed in the report "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/032532.pdf">Problems of Battlefield Surveillance</a>" from the TEOTA (The Eyes Of The Army) project. Under some circumstances radar is preferable to other means of intelligence gathering. The reasons for this, in an approximate order of importance, are:</div><div><br /></div><div><div></div><blockquote><ol><li>The ability of radar to penetrate darkness, fog, and foul weather for relatively great distances. </li><li>Its ability to detect moving objects by means of the doppler effect. </li><li>Accurate range and high range resolution are directly and linearly obtainable. </li><li>Radar camouflage is considerably more difficult than is optical camouflage. </li><li>Certain weather data, such as cloud base and top indication, can best be gathered by means of radar.</li></ol></blockquote></div><div><br /></div><div>The availability of the PSNR-1 did not mean that each individual gun had the same ability to detect and engage targets in bad weather, of course. However, it could act as a serious force multiplier by greatly eroding the ability of the enemy to launch a surprise offensive, particularly at night.</div><div><br /></div><div>Meteorological data collection for a T-12 or MT-12 battery was still not the responsibility of the individual batteries or the anti-tank battalion of a motor rifle division, but the meteorological survey platoon of artillery regiments.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">SIGHTING</span></h3><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-rz4vBGiUcME/X9q0Sq9oAdI/AAAAAAAASdg/5f3lX0umzCkiAAhcG3wnw3SJ-ji86vDJwCLcBGAsYHQ/s900/pg-1m%2Bfront.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="900" height="266" src="https://1.bp.blogspot.com/-rz4vBGiUcME/X9q0Sq9oAdI/AAAAAAAASdg/5f3lX0umzCkiAAhcG3wnw3SJ-ji86vDJwCLcBGAsYHQ/w400-h266/pg-1m%2Bfront.jpg" width="400" /></a></div><div><br /></div></div><div><br /></div><div>The guns permit all available sighting systems to be installed simultaneously. This is particularly convenient for night fighting because the sight can be set up during the emplacement of the gun, before dusk, and then simply left in its mounting bracket until it is needed. The gunner can switch between any of the three sights at any time.</div><div><br /></div><div>The drawing on the left below shows the offset of the three sights from the axis of the gun barrel, and the drawing on the right below shows the gun cradle with the mounting brackets for the three sights. </div><div><br /><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-u3jHAte1Mgw/X85N9e2tnYI/AAAAAAAASSc/vWJs3XV20t8znsj3T5C79KNnPou8LnFGACLcBGAsYHQ/s628/sight%2Bparallax.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="554" data-original-width="628" height="353" src="https://1.bp.blogspot.com/-u3jHAte1Mgw/X85N9e2tnYI/AAAAAAAASSc/vWJs3XV20t8znsj3T5C79KNnPou8LnFGACLcBGAsYHQ/w400-h353/sight%2Bparallax.png" width="400" /></a><a href="https://1.bp.blogspot.com/-dUarGqb_7jk/X85OEWvaURI/AAAAAAAASSg/XjaPtv-lIroVRd586WFZqp_sgW12J-N_gCLcBGAsYHQ/s1462/cradle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1462" data-original-width="1391" height="320" src="https://1.bp.blogspot.com/-dUarGqb_7jk/X85OEWvaURI/AAAAAAAASSg/XjaPtv-lIroVRd586WFZqp_sgW12J-N_gCLcBGAsYHQ/s320/cradle.png" /></a><br /></div><div><br /></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">OP4-40, OP4M-40, OP4M-40U</span></h3></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-YrdczJtjf2o/XqJ9Sp1UkoI/AAAAAAAAQoU/JYzj2k2o_ZYZptWDzCl_dlReFpbG_PtdgCLcBGAsYHQ/s1600/gunner%2Bat%2Brapira.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="678" data-original-width="1024" height="264" src="https://1.bp.blogspot.com/-YrdczJtjf2o/XqJ9Sp1UkoI/AAAAAAAAQoU/JYzj2k2o_ZYZptWDzCl_dlReFpbG_PtdgCLcBGAsYHQ/w400-h264/gunner%2Bat%2Brapira.jpg" width="400" /></a></div><div><br /></div><div><br />For direct fire, the gunner of a T-12 or MT-12 crew was provided with a fixed telescopic sight. Initially, the T-12 was provided with the OP4-40 sight, which was later supplanted by the OP4M-40. It was functionally identical, differing only in manufacturing details. When 100mm HE-Frag ammunition entered service for the T-12, the OP4M-40U with an additional range scale for HE-Frag accompanied it. Otherwise, all three models of the sight were functionally identical and will be considered as such thereafter. The sight has a fixed magnification of 5.5x and a field of view of 11 degrees, the same as all other artillery direct fire sights. Nominally, an optical sight with 5x magnification allows an observer to see and identify a tank from a distance of 3.0 kilometers. The maximum sighting distance for APFSDS and HEAT ammunition is 3,000 and 3,800 meters respectively.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Nt2LibqwSdA/XijpU6aBoxI/AAAAAAAAP9c/Z0pSRrokQLYfm_FXg8kfCZ3e71ZTvk0_QCLcBGAsYHQ/s1600/op4M-40U.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="884" data-original-width="1600" height="352" src="https://1.bp.blogspot.com/-Nt2LibqwSdA/XijpU6aBoxI/AAAAAAAAP9c/Z0pSRrokQLYfm_FXg8kfCZ3e71ZTvk0_QCLcBGAsYHQ/w640-h352/op4M-40U.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The OP4 series of sights was principally the same in design to the OP2 series, being a simple tube telescope with the same optical configuration, consisting of a 3-lens objective group, 6-lens erector lens group and a 6-lens eyepiece group. The exit pupil diameter is 5.5mm, which is an appropriate size for a day sight.</div><div><br /></div><div>Aside from the basic features already present in the OP2 series, the OP4 featured a more sophisticated system of inputting corrections in deflection by enabling the viewfinder markings to be shifted horizontally. This allowed the adjustment of the aiming mark horizontally as well as vertically, allowing the reticle to be simplified into a single central chevron. </div></div><div><br /></div><div>This was done with an adjustable crosshair in the viewfinder, formed by a pair of threads stretched out in front of the eyepiece lens group. The horizontal line of the crosshair is adjusted to serve as a fixed indicator line for the range scales, and the vertical line of the crosshair is used as a fixed indicator line for the lateral deflection scale. The range adjustment mechanism is located on the bottom of the case, and the lateral adjustment mechanism is located on the left side of the case. The calibration of the vertical crosshair thread is done with a knob on the right side of the case, and the calibration of the horizontal crosshair thread is done with a knob on the top.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-kyc6_KUCSCI/X6YVdOKJFLI/AAAAAAAASDI/2tqYjb1uL9UWYZzZ0idca2eOWvgqPKV8wCLcBGAsYHQ/s1386/op4m-40u%2Baxial%2Badjustment.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1313" data-original-width="1386" height="379" src="https://1.bp.blogspot.com/-kyc6_KUCSCI/X6YVdOKJFLI/AAAAAAAASDI/2tqYjb1uL9UWYZzZ0idca2eOWvgqPKV8wCLcBGAsYHQ/w400-h379/op4m-40u%2Baxial%2Badjustment.png" width="400" /></a></div><div><br /></div><div><br /></div><div><div>The upper half of the deflection scale is marked for the target speed in 5 km/h increments, up to 80 km/h. The lower half indicates the deflection angle in mils, in 1 mil increments. It is used to perform windage adjustments and input fire corrections. With a maximum deflection angle of 20 mils, it is possible to adjust HEAT rounds for a 10 m/s crosswind up to a range of 2,000 meters, where a 19 mil deflection is required. The deflection scale marked for target speed is an interesting feature, target leading is normally done using a mil scale with the lead angle decided by the chosen ammunition type and the target speed. Having a scale marked for target speed means that it is only possible to use one ammunition type - in this case, only APFSDS may be used - but it may allow the gunner to apply lead more intuitively according to the estimated target speed. When applying a deflection angle for ammunition other than APFSDS, the mil scale is used instead of the speed scale. Although generally unecessary, the mil scale may also be used to input windage corrections for APFSDS rounds at very long ranges, as the smallest division of the scale is 1 mil, providing enough sensitivity to account for the very small wind deviation of such ammunition. </div><div><br /></div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Z8FguEhF7X0/XqKBtzHeJYI/AAAAAAAAQo4/dAEAp2F-gpMik8i6ZGPY1u6vzqFBsWjEgCLcBGAsYHQ/s1600/op4M-40U%2Bviewfinder%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1310" data-original-width="1600" height="326" src="https://1.bp.blogspot.com/-Z8FguEhF7X0/XqKBtzHeJYI/AAAAAAAAQo4/dAEAp2F-gpMik8i6ZGPY1u6vzqFBsWjEgCLcBGAsYHQ/s400/op4M-40U%2Bviewfinder%2Bdrawing.png" width="400" /></a><a href="https://1.bp.blogspot.com/-cHnbBpbAMJQ/XqJ9TvGZ1PI/AAAAAAAAQog/dY_NYxNNhUYTLsB_2sOImaNRVQ41Db7pwCLcBGAsYHQ/s1600/viewfinder.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="965" height="317" src="https://1.bp.blogspot.com/-cHnbBpbAMJQ/XqJ9TvGZ1PI/AAAAAAAAQog/dY_NYxNNhUYTLsB_2sOImaNRVQ41Db7pwCLcBGAsYHQ/s400/viewfinder.png" width="400" /></a></div><div><br /></div></div></div><div><br /></div><div>A vertical mil scale marked up to 70 mils is also available in the sight, with 1 mil increments. This primarily served as the means of low-angle indirect fire (fire from closed positions), but it can also be used to input fire corrections in elevation, and it also permits sufficient superelevation for a maximum direct firing range of 3,800 meters with the standard 3OF15 HE-Frag shell. Additionally, the vertical and horizontal mil scales do not merely serve as superelevation and deflection aids; they also provide the gunner with a high precision angular scale for range estimations which can serve as a useful alternative to the stadia rangefinder scale. For example, a commonly-taught technique is to use telephone line poles as a height and position reference, as they have a standardized height. With a vertical mil scale, an accurate range measurement can be obtained. The same technique can be applied with both the vertical and horizontal scales to determine the range to targets of known dimensions, including enemy tanks. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-TH0uimevF10/X85FS4Hud5I/AAAAAAAASRY/MN9WOaXMrVAO_kofGcn4CWGjkboc5NJBgCLcBGAsYHQ/s900/adjusting%2Bop4m-40u%2Bsight.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="900" height="426" src="https://1.bp.blogspot.com/-TH0uimevF10/X85FS4Hud5I/AAAAAAAASRY/MN9WOaXMrVAO_kofGcn4CWGjkboc5NJBgCLcBGAsYHQ/w640-h426/adjusting%2Bop4m-40u%2Bsight.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>Moreover, a stadiametric rangefinder scale is available in the sight viewfinder for precision shooting, and, in the OP4-40 and OP4M-40 sights, the central aiming chevron is flanked with two stadiametric brackets to quickly determine if the target is within the point blank range of the gun when firing APFSDS. There is a bracket for a target with a height of 2.7 meters, representing a typical NATO tank, and a bracket for a target with a height of 1.5 meters, representing a field artillery piece. If the height of the target is equal to or greater than the space between the two chevrons of the bracket, then it is within the point blank range of the gun. If the target is shorter than the space between the chevrons, then the range to it exceeds the point blank range of the gun, and a range measurement using the stadia scale may be warranted. These brackets are absent from the OP4M-40U.</div><div><br /></div><div>The minimum range marked in the stadia rangefinder scale is 1,200 meters, which is also the point blank range of a 3BK3 HEAT round against a target with a height of 2.7 meters. Below the 1,200-meter minimum range, rangefinding would not be needed to use HEAT rounds effectively, while the point blank range of the APFSDS ammunition was far enough for practically all engagements, as very few areas in Europe permitted direct fire above 2 kilometers. </div><div><br /></div><div>In practice, the stadia rangefinder is limited in its measuring accuracy because of the low probability of a tank being completely exposed on open ground without being partially obscured by bushes or tall grass. This is further complicated if the tank is in a hull-down position, but given the doctrinal use of T-12 and MT-12 guns and the availability of bona fide rangefinders for this task, such issues were trivial.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Tj7vM9ycKpM/X7_hZ2Fm3VI/AAAAAAAASJ8/z6UCFvCHVDs_0NVrXFAPKll-MiixJg_8wCLcBGAsYHQ/s1021/stadia%2Brange%2Bmeasurements.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="570" data-original-width="1021" height="224" src="https://1.bp.blogspot.com/-Tj7vM9ycKpM/X7_hZ2Fm3VI/AAAAAAAASJ8/z6UCFvCHVDs_0NVrXFAPKll-MiixJg_8wCLcBGAsYHQ/w400-h224/stadia%2Brange%2Bmeasurements.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The stadia brackets shared the same limitations as the stadia rangefinder scale, but fortunately, on tanks like the M48 and M60A1, the large and prominent commander's cupola made the turret into a more convenient target since the turret height, if measured from above the turret ring up to the cupola, is 1,500mm (M48A3) or 1,470mm (M60A1). This made it a convenient target for ranging with the 1.5 meter stadia bracket. The 1.5 meter bracket may also be used for other targets with a similar height such as the M113, if its height is measured from the hull belly rather than from ground level. </div><div><br /></div><div><br /></div><div>Moreover, the tactical doctrine for the T-12 and MT-12 was such that a battery would normally have the opportunity to first establish range reference points and create zones of fire. As such, the gunner would typically be able to apply precision gunnery for maximum probability of a first round hit. </div><div><div><br /></div></div><div><br /><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">S71-40<br />PG-1M</span></h3><div style="text-align: center;"><br /></div><div style="text-align: center;"><div class="separator" style="clear: both;"><a href="https://1.bp.blogspot.com/-HAL81G9SXVo/X9-zWCpblcI/AAAAAAAASi0/beTAtAE2RzkLQvZFJCDXu0q3nWbZdVrTQCLcBGAsYHQ/s2048/20201029_144021.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1152" data-original-width="2048" height="225" src="https://1.bp.blogspot.com/-HAL81G9SXVo/X9-zWCpblcI/AAAAAAAASi0/beTAtAE2RzkLQvZFJCDXu0q3nWbZdVrTQCLcBGAsYHQ/w400-h225/20201029_144021.jpg" width="400" /></a></div></div><div><br /></div><div><br /></div><div>As with the other two guns covered in this article, the (M)T-12 was equipped with an optical-mechanical sighting system for indirect fire. This system includes the S71-40 mechanical sight with a PG-1M panoramic sight and an optional K-1 collimator. The S71-40 was nothing more than an S71 with a linkage for the T-12 or MT-12 gun, and the PG-1M was functionally identical to the PG-1.</div><div><br /></div><div>The structure of the S71-40 and S71-40U model is similar to the D726-45 mechanical sight for the D-30 howitzer. The range drum of the S71-40 is marked for APFSDS and HEAT, with increments of 50 meters. It permits both ammunition types to be fired to their maximum tabular ranges. The range drum of the S71-40U features additional markings for HE-Frag.</div><div><br /></div><div><br /></div><div>It is also possible to use the PG-1M as a backup sight to the OP4M-40U. It is not particularly suitable for direct fire on point targets owing to the lack of range scales for any ammunition type, but it can be used in emergencies. Its viewfinder is shown in the drawing below.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-G8kAJJv-IaE/X4NRvrICYtI/AAAAAAAARs4/OV5ENj1R_5QimeNFzyf90ZtM0wIWDpiFACLcBGAsYHQ/s880/pg-1m%2Bviewfinder.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="863" data-original-width="880" src="https://1.bp.blogspot.com/-G8kAJJv-IaE/X4NRvrICYtI/AAAAAAAARs4/OV5ENj1R_5QimeNFzyf90ZtM0wIWDpiFACLcBGAsYHQ/s320/pg-1m%2Bviewfinder.png" width="320" /></a></div><br /><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">NIGHT SIGHT</span></h3><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-KFJ-xWlLeto/X4rEK55y3MI/AAAAAAAARvg/67YQGJOGzlYjk3fkWJIY-LjzhaBMCVYMwCLcBGAsYHQ/s769/mt-12%2Bgun%2Bshield%2Bfolded.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="414" data-original-width="769" height="215" src="https://1.bp.blogspot.com/-KFJ-xWlLeto/X4rEK55y3MI/AAAAAAAARvg/67YQGJOGzlYjk3fkWJIY-LjzhaBMCVYMwCLcBGAsYHQ/w400-h215/mt-12%2Bgun%2Bshield%2Bfolded.png" width="400" /></a></div><div><br /></div></div><div><br /></div><div>Standard T-12 and MT-12 guns feature provisions to mount a night sight in the form of a frame protruding from the gun cradle through a gap between the recoil buffer and recuperator. As the basic gun was equipped with a night sight, only the guns supplied with different variations of night sights would be given a new designation with an 'N' suffix. This is different from earlier guns, where the 'N' suffix indicates constructional changes that differentiates it from the basic gun with no mount for a night vision sight.</div><div><br /></div><div>All systems provided for T-12 and MT-12 guns were designed exclusively for passive vision. No infrared spotlight was provided, nor were there any accommodations for one to mounted on the gun. </div><div><br /></div><div>Passive vision was not only desirable for the sake of avoiding the tactical drawbacks of having active illumination sources, but for a towed weapon such as the (M)T-12, a sight offering purely passive night vision also consumes less power than a sighting system that requires a spotlight. Lowering the power consumption allows the sight to be used more freely, which is important owing to the lack of an engine or any means of electricity production on towed guns. </div><div><br /></div><div>The manual for the MT-12 cautions that special attention should be paid to take care of the night sight as it is a complex electro-optical device. During marches, even short ones, the night sight is not mounted to the gun to ensure that its internal components are not worn out by vibrations.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">APNB-40, APN-4-40 </span></h3><div>The basic T-12 (2A19) gun was equipped with the APNB-40 sight. The T-12N was a T-12 gun equipped with the APN-4-40 sight. Unfortunately, the changes made are still unknown. They were passive night sights. The night vision mount on the gun cradle, shown in the photo below (taken by a friend of the author), does not have any provisions whatsoever for supporting an IR spotlight.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-V6ZEOan8KJo/X9s1ABHq3NI/AAAAAAAASdw/MbujHQtxJ-gV_wpygRd5oELt3nmA-wZkACLcBGAsYHQ/s1778/night%2Bsight%2Bmount.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1426" data-original-width="1778" height="514" src="https://1.bp.blogspot.com/-V6ZEOan8KJo/X9s1ABHq3NI/AAAAAAAASdw/MbujHQtxJ-gV_wpygRd5oELt3nmA-wZkACLcBGAsYHQ/w640-h514/night%2Bsight%2Bmount.png" width="640" /></a></div><br /><div><br /></div><div>According to a T-12 manual, the APNB-40 night sight is designed to monitor the battlefield and provide aimed direct fire at tanks, automobiles and other targets in natural night illumination at a distance of up to 1,000 m with an ambient light level of 0.003-0.005 lux (starlight illumination only). With more illumination, the limit of visibility increases, and with a full moon and a cloudless sky, where the ambient light reaches 0.2 lux, the observation and direct fire range reaches 3,000 m.</div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">APN-5-40</span></h3><div><div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-oLrxuivC21c/X47ipR4UV6I/AAAAAAAARxc/pvKTLhA2QlkSFZnsBjhK2_nrsFfqlOKXACLcBGAsYHQ/s2048/t-12%2Bwith%2Bnight%2Bsight.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1378" data-original-width="2048" height="430" src="https://1.bp.blogspot.com/-oLrxuivC21c/X47ipR4UV6I/AAAAAAAARxc/pvKTLhA2QlkSFZnsBjhK2_nrsFfqlOKXACLcBGAsYHQ/w640-h430/t-12%2Bwith%2Bnight%2Bsight.png" width="640" /></a></div><div><br /></div></div><div><br /></div><div>The T-12N5 gun (2A19-1) is a T-12 gun with the APN-5-40 (1PN21A) sight. The APN-5-40 can be identified by its bulky tubular shape, with a cuboidal section in its middle. The image below shows a T-12 equipped with all three of its sights, including an APN-5-40.</div></div><div><br /></div><div>The huge size and weight of the sight, even compared to tank sights, is due to the objective lens group, which has a combination of a large diameter and long focal length. An objective lens with a large diameter is of high importance for a night sight, as a large lens has a higher optical resolution and is is able to gather more light.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DaSOP0bNM8s/X9sx-fSP0CI/AAAAAAAASdo/p7DQIo92hm0iwRKaNZUIaDkAvfbqynxKwCLcBGAsYHQ/s1024/2a19-1%2Bgun%2Bshield.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="684" data-original-width="1024" height="268" src="https://1.bp.blogspot.com/-DaSOP0bNM8s/X9sx-fSP0CI/AAAAAAAASdo/p7DQIo92hm0iwRKaNZUIaDkAvfbqynxKwCLcBGAsYHQ/w400-h268/2a19-1%2Bgun%2Bshield.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>The sight has a fixed 6.8x magnification with a field of view of 5.5 degrees (5°30'). The exit pupil diameter is 7mm, which was considered the ideal size according to contemporary standards, as it was understood at the time that the human pupil dilates to a maximum diameter of 7mm. The night sight was therefore designed to provide the maximum possible light transmission, which, needless to say, is appropriate for its purpose.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjytDYLwZLW5GJYSBoYQNHH6JBzyDmjVkxl2Ox3z4WYcHH4GnphlXfZbU14bN1DVTHJY3RGK5v-2Cya1_Vw0Je5iuIcMAGLUFnHTIBYIRzDf3VziYT4FK4PciCZRZX9vGqy3brsJcBr_Y8fnAEu9KigD_wf6gdvYtmQ-VuddvnbMKq6Gw2TZivZq_9D8LG_/s2894/mt-12%20fully%20equipped.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2661" data-original-width="2894" height="588" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjytDYLwZLW5GJYSBoYQNHH6JBzyDmjVkxl2Ox3z4WYcHH4GnphlXfZbU14bN1DVTHJY3RGK5v-2Cya1_Vw0Je5iuIcMAGLUFnHTIBYIRzDf3VziYT4FK4PciCZRZX9vGqy3brsJcBr_Y8fnAEu9KigD_wf6gdvYtmQ-VuddvnbMKq6Gw2TZivZq_9D8LG_/w640-h588/mt-12%20fully%20equipped.png" width="640" /></a></div><div><br /></div><div><div>The sight control panel has three toggle switches, for powering up the sight itself, turning on the reticle backlight, and for opening or closing the internal shutter for light protection. The brightness of the image (amplification factor) is adjustable.</div><div><br /></div><div>Additionally, the sight contained an internal drum with three slots, two of which contained light filters. By turning the drum with a knob, the gunner could apply a yellow high-contrast filter to aid in target detection in the presence of fog and haze, or a red filter to increase the contrast of the target under high illumination. These filters are only useful as long as enough ambient light is available. Otherwise, the sight is used without a filter.</div></div><div><br /></div><div>To power the sight, a battery pack consisting of a pair of 2KNB-2 nickel–cadmium rechargeable batteries (2.5 V) connected in series was used, providing a total charge of 4 Ah and a voltage of 5 V. At an ambient temperature of +20°C, the APN-5-40 can run continuously for 7-8 hours, dropping to 3-4 hours at an ambient temperature of -40°C.</div><div><br /></div><div><div>The system utilizes a three-stage image intensifier cascade tube with three S-1 photocathodes, connected to a discretely amplified power supply. This level of technology was modern for the 1960's, especially in the context of artillery sighting systems as this type of sight was only used for rifle scopes in the U.S beginning in 1965 with the AN/PVS-1 infantry night sight, somewhat later than the APN-5-40. </div><div><br /></div><div>This type of image intensifier is described in Soviet (Russian) literature as having a gain of 50,000-75,000, meaning that it is capable of amplifying light by 50,000-75,000 times. Such a high gain is necessary for passive viewing with starlight illumination alone, and it is somewhat higher than the gain of 40,000 specified for the AN/PVS-1 "Starlight scope". However, the distortion at the edges of the image field of a multi-stage intensifier tube is high, meaning that the effective field of view can be somewhat smaller than the total field of view. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DdAhiJ1iw1g/X4rAdkXUFUI/AAAAAAAARvQ/J6NUZCZ6R_UowjbVPYY-iXCe70pQufHUgCLcBGAsYHQ/s1432/three%2Bstage%2Bamplifier.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="557" data-original-width="1432" height="155" src="https://1.bp.blogspot.com/-DdAhiJ1iw1g/X4rAdkXUFUI/AAAAAAAARvQ/J6NUZCZ6R_UowjbVPYY-iXCe70pQufHUgCLcBGAsYHQ/w400-h155/three%2Bstage%2Bamplifier.png" width="400" /></a></div><div><br /></div><div><br /></div><div><div>The range of vision depends on the amount of natural night illumination, atmospheric transparency and the contrast between the target and the background. A clear moonlit night with a full moon is considered to generate ambient light of 0.2 lux. On a clear moonless night, with only starlight illumination, only 0.001 lux is available. On the darkest nights (cloudy weather), illumination can drop down to 0.0001 lux.</div><div><br /></div><div>With natural night illumination of 0.003-0.005 lux, considered to be the minimum illumination level available during most nights, and good atmospheric transparency, the APN-5-40 sight permits tanks and vehicles to be detected from 1,000 meters. </div></div></div><div><br /></div><div>The reticle is illuminated, and the range scales for HEAT and HE-Frag permit range adjustment from 0 meters to 2,000 meters, while the AP scale has a longer range limit of 2,400 meters. Adjustments in range are done in the same way as in the direct fire day sight.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">APN-6-40 "Brusnika"</span></h3><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-a3rvGsgFzPs/X4NQrWx1Z3I/AAAAAAAARss/FNRFtOm-WQUe9t3yqDg8C44EihKqdLnmQCLcBGAsYHQ/s883/mt-12%2Bsights.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="575" data-original-width="883" height="260" src="https://1.bp.blogspot.com/-a3rvGsgFzPs/X4NQrWx1Z3I/AAAAAAAARss/FNRFtOm-WQUe9t3yqDg8C44EihKqdLnmQCLcBGAsYHQ/w400-h260/mt-12%2Bsights.png" width="400" /></a><a href="https://1.bp.blogspot.com/-iIPiND4Me5E/X4rCG2P220I/AAAAAAAARvY/HQO-vklnvQsbNdd5TuHUdds9EKLMXWKLQCLcBGAsYHQ/s1440/all%2Bsighting%2Bsystems%2Binstalled.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1075" data-original-width="1440" height="239" src="https://1.bp.blogspot.com/-iIPiND4Me5E/X4rCG2P220I/AAAAAAAARvY/HQO-vklnvQsbNdd5TuHUdds9EKLMXWKLQCLcBGAsYHQ/w320-h239/all%2Bsighting%2Bsystems%2Binstalled.png" width="320" /></a></div><div><br /></div></div><div><br /></div><div>T-12 guns beginning with the serial number 03238 were supplied with the APN-6-40 night sight instead of the APN-5-40. When equipped with the APN-6-40, it is converted to the T-12N6 (2A19-M). </div><div><br /></div><div>It was the standard night sight of the MT-12 (2A29 or 2A29-6), being the default type and likely also the only type to be used with the gun in significant numbers. In training posters or drawings, the MT-12 is only depicted with the APN-6-40. Curiously enough, the GRAU indexing system essentially created a redundancy by having the 2A29 and 2A29-6 codes, since they were the same product (the MT-12) which had no suffix.</div><div><br /></div><div>A battery pack consisting of three 2NKBN-1.5 nickel-cadmium batteries coupled with a voltage amplifier provides power to the sight. It has a charge of 3.5 Ah and a voltage of 7.5 V. The sight can run continuously for 10 hours at an ambient temperature of +15-35°C, but only 1.5 hours at an ambient temperature of -50°C. Under normal conditions where a 10-hour operation time is possible, the sight essentially provides full combat readiness during night time, with no real need to shut down to replace the batteries. </div><div><br /></div><div>The APN-6-40 sight (1PN35), named "Lingonberry", differs from the APN-5-40 in its mechanical automatic flash protection system. By connecting a mechanical shutter in the sight to the trigger lever with a cable, the objective lens of the image converter tube is covered just before the firing pin is struck. This way, the sight is protected from the muzzle flash of its own gun. </div><div><br /></div><div>Like previous sights, the sight is very large, and is tubular in shape to house the large objective lens group, but it can be distinguished from the APN-5-40 by the extended eyepiece tube.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-WtVSmzNHgvA/X9tEjOHLcsI/AAAAAAAASeA/1VewOLZbfhoF-6O1AUb0iRV4wlhXBhsmwCLcBGAsYHQ/s1959/apn-6-40%2Bsight.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="895" data-original-width="1959" height="292" src="https://1.bp.blogspot.com/-WtVSmzNHgvA/X9tEjOHLcsI/AAAAAAAASeA/1VewOLZbfhoF-6O1AUb0iRV4wlhXBhsmwCLcBGAsYHQ/w640-h292/apn-6-40%2Bsight.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The sight has a fixed 6.8x magnification with a field of view of 6.83 degrees (6°50').</div><div><br /></div><div>The detection range for tanks and other vehicles was considered to be 1,000 meters, the same as with all previous night sight models. The reticle in the sight can be adjusted for range and brightness.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-QeiHcbY2INE/X6DxbCkpDwI/AAAAAAAAR_0/KYLisEF_ut0Xil11SX9Z60WvfeXdmkcDACLcBGAsYHQ/s502/mt-12k%2Bwith%2Bemitter.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="393" data-original-width="502" src="https://1.bp.blogspot.com/-QeiHcbY2INE/X6DxbCkpDwI/AAAAAAAAR_0/KYLisEF_ut0Xil11SX9Z60WvfeXdmkcDACLcBGAsYHQ/s16000/mt-12k%2Bwith%2Bemitter.png" /></a></div><div><br /></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">APN-7-40</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ksEEKY0mXZY/X9tBBSfKI3I/AAAAAAAASd4/alpaEwp22N8oeIDd0qZp8iiYprQg7mHzwCLcBGAsYHQ/s1024/apn-7%2Bposter.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="635" data-original-width="1024" height="396" src="https://1.bp.blogspot.com/-ksEEKY0mXZY/X9tBBSfKI3I/AAAAAAAASd4/alpaEwp22N8oeIDd0qZp8iiYprQg7mHzwCLcBGAsYHQ/w640-h396/apn-7%2Bposter.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The APN-7 (1PN53) sight was the last passive night sight specified for the MT-12. Its rarity is to the point of not appearing in any photographs of MT-12s serving in any army.</div><div><br /></div><div>Its optical scheme consists of a catadioptric objective lens group placed in front of the image intensifier tube, with an eyepiece optical group to magnify the image. The objective lens group is made according to the Maksutov-Cassegrain design, permitting a very large objective lens to be implemented with a very short tube. This type of design would normally be used for man-portable systems where compactness is a much more valuable trait. Its use for an artillery sight is somewhat unusual.</div><div><br /></div><div>The power source of the sight is a rechargeable battery pack, consisting of five D-0.55S batteries. It has a charge of 5.5 Ah and a voltage of 7 V supplies the sight with power.</div><div><br /></div><div>Aside from the rather unique optical layout of the sight, an additional improvement was the addition of an automatic electronic flash protection system. A prism on the top of the sight detects the light entering the sight. If the brightness exceeds the level permissible for the photocathode tube, the voltage applied to the first photocathode of the 3-stage cascade tube drops, thus dropping the gain in all three photocathodes, dimming the image. This prevents tube burnout as well as prevents the gunner from being blinded.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCu4BrmcuHABvPD8jkxi7S4p4ry2Uu3vgtlodcWMgZlwoTO-4jEVYxVj51WI-5TPyWmN5HEOxWZj135l8KHRzLQCFhaJTOLPYHcX_vaM6WpRbe3e49j1Ba6kORLDBOua0pplLfMIsPMJVvcvjmaOW9qCgRDJnJreddEzEN4Zw72G1DjdOQbzZuQG1gyw/s749/1pn53.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="494" data-original-width="749" height="264" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCu4BrmcuHABvPD8jkxi7S4p4ry2Uu3vgtlodcWMgZlwoTO-4jEVYxVj51WI-5TPyWmN5HEOxWZj135l8KHRzLQCFhaJTOLPYHcX_vaM6WpRbe3e49j1Ba6kORLDBOua0pplLfMIsPMJVvcvjmaOW9qCgRDJnJreddEzEN4Zw72G1DjdOQbzZuQG1gyw/w400-h264/1pn53.png" width="400" /></a></div><div><br /></div><div><br /></div><div>Prolonged exposure to a bright light, such as a white light spotlight aimed directly at the sight, causes the image intensifier to turn off automatically and remain off for 2-3 seconds, but to prevent damage afterward, the gunner must manually turn off the sight.</div><div><br /></div><div>The sight has a fixed 5.9x magnification with a field of view of 5.3 degrees. These properties are inferior to the preceding sights built to conventional design practices.</div><div><br /></div><div>As with preceding sights, the detection range for tanks and vehicles is 1,000 meters under ambient lighting conditions of 0.003-0.005 lux. From this, it can be said that the large objective lens diameter obtained with the Maksutov-Cassegrain design served only as the means to shorten the overall length of the sight, rather than improve its night vision capabilities.</div><div><br /></div><div>The reticle is somewhat different from older sights in that the zero range point is calibrated for a range of 400 meters for AP, 200 meters for HEAT and 100 meters for HE-Frag. The sight is marked for maximum ranges of 1,200 meters for AP and 2,000 meters for both HEAT and HE-Frag. The reticle can be adjusted in range and brightness.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">1A31 "RUTA"</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ldh4-kOF1vM/X5-CD670rrI/AAAAAAAAR68/mrdqw7PI4U0lwdf2gZGGd6V12MvZzN5EACLcBGAsYHQ/s1024/Ruta_big.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="707" data-original-width="1024" height="276" src="https://1.bp.blogspot.com/-ldh4-kOF1vM/X5-CD670rrI/AAAAAAAAR68/mrdqw7PI4U0lwdf2gZGGd6V12MvZzN5EACLcBGAsYHQ/w400-h276/Ruta_big.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>Very little is known about the "Ruta" system, with nearly all information available to the public originating from <a href="http://library.voenmeh.ru/jirbis2/files/materials/ifour/book2/book_on_main_page/9.9.htm">the encyclopedia of radar systems and complexes</a> featured on the website of the Voenmekh Baltic State Technical University and <a href="http://web.archive.org/web/20121117192127/http://www.npostrela.com/ru/products/museum/88/225/">its entry on the archived digital museum of NPO "Strela"</a>. </div><div><br /></div><div>On the 14th of April 1975, a resolution was issued by the Council of Ministers of the USSR ordering the development of a fire control radar system for the MT-12 under the codename "Ruta". A set of tactical-technical requirements was issued by GRAU. </div><div><br /></div><div>The installation of a radar fire control system on a towed anti-tank gun was completely unprecedented at the time and remains completely unique even today, for a number of good reasons. It was part of a broader effort to enhance the capabilities of anti-tank weapons, particularly at night and in poor weather conditions. It was planned to also upgrade the 9P148 "Konkurs" tank destroyer, used in the ATGM battery organic to anti-tank battalions alongside the MT-12. On the 20th of August 1975, a decree was issued to begin the development of a radar detection and tracking system for the Konkurs ATGM system. </div><div><br /></div><div>The radar fire control system was designed to be unified with "Ruta" to the maximum extent, with a large number of components being interchangeable. It was was based on the "Ruta" system, but with an increased power for better long range performance. The new system not only permitted automatic target tracking, but also automatic missile guidance (ACLOS). The resulting system, dubbed "Konkurs-R", was recommended for adoption by the state testing commission in 1986. However, a number of external factors including the cessation of BRDM-2 production interrupted any such plans, and the project was abandoned.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-K1af-jBu0dE/X5-CLH6autI/AAAAAAAAR7E/7lTEX3AH_IU2GCmfAYt9RZzfvbVQARllQCLcBGAsYHQ/s1024/Konkurs_R_big.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="674" data-original-width="1024" height="264" src="https://1.bp.blogspot.com/-K1af-jBu0dE/X5-CLH6autI/AAAAAAAAR7E/7lTEX3AH_IU2GCmfAYt9RZzfvbVQARllQCLcBGAsYHQ/w400-h264/Konkurs_R_big.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-w4LegT9bPsI/X5-CK4T4nmI/AAAAAAAAR7A/IwwJTITt0BU3t7OpLUp5RKqaTI0fsXcdQCLcBGAsYHQ/s1024/Konkurs_R_rab_mesto_big.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="688" data-original-width="1024" height="269" src="https://1.bp.blogspot.com/-w4LegT9bPsI/X5-CK4T4nmI/AAAAAAAAR7A/IwwJTITt0BU3t7OpLUp5RKqaTI0fsXcdQCLcBGAsYHQ/w400-h269/Konkurs_R_rab_mesto_big.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>In accordance with tactical-technical requirements, all components of the system had to be located on the gun itself and be provided with autonomous power. The set of requirements imposed on the complex (small weight and size characteristics and power consumption, high mechanical strength, high accuracy of target tracking and calculation of the lead correction, a wide scanning sector, etc.) did not allow the use of technical equipment already used on other products, i.e. off-the-shelf solutions. New approaches and new solutions were needed, which were successfully worked out. </div><div><br /></div><div><div>By 1979, the new weapon system was ready for state trials. The operation of the system, including combat work on the MT-12, was carried out by gun crews formed from the conscripts of the spring draft of 1979 who did not have experience with either artillery or radar systems. The gun crews received training on the experimental gun during the state tests. The system successfully passed the tests and was recommended for adoption by the Soviet Army, leading to the adoption of the MT-12R in 1981. Mass production was carried out from 1981 to 1990.</div><div><br /></div><div>Interestingly enough, the 1A31 fire control system was evidently assigned its GRAU index at the same time its requirements were issued followed by the commencement of work on the 1A32 fire control system for the 2S15 "Norov" tank destroyer in May 1976. On the other hand, the fire control system of the T-64B tank was evidently only assigned its GRAU index of 1A33 when the tank entered service a few months later in September 1976.</div></div><div><br /></div><div>The installation of the "Ruta" sight was a simple process but it required the welding of new mounting frames onto the carriage, the gun shield and the gun cradle. The mount for the night vision sight served as a mount for the RLPK-1 radar. The panoramic sight must be removed to accommodate the radar sight and control unit, but the sight mount remained. Only the telescopic day sight could remain installed alongside the radar FCS. The power supply box for the gun was mounted to the right carriage trail, presumably due to space constraints as there is evidently no available room anywhere else on the gun. As the box would no longer be covered by the gun shield once the gun was deployed and the carriage trails spread open, the box mounting frame was armoured.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-bNbJ8JEhvxM/X5__iiwv4II/AAAAAAAAR9Y/KsZCefxUQvA8U-XUl5uCAUNKuyy53qo1wCLcBGAsYHQ/s2048/textbook.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1201" data-original-width="2048" height="235" src="https://1.bp.blogspot.com/-bNbJ8JEhvxM/X5__iiwv4II/AAAAAAAAR9Y/KsZCefxUQvA8U-XUl5uCAUNKuyy53qo1wCLcBGAsYHQ/w400-h235/textbook.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-YcXBatpd254/X6ANXgGw9yI/AAAAAAAAR-E/-DfEn3SNmFArfRd000BS6IJ8BlubnnmGgCLcBGAsYHQ/s800/id4389-07.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="240" src="https://1.bp.blogspot.com/-YcXBatpd254/X6ANXgGw9yI/AAAAAAAAR-E/-DfEn3SNmFArfRd000BS6IJ8BlubnnmGgCLcBGAsYHQ/w320-h240/id4389-07.jpg" width="320" /></a><br /></div></div><div><br /></div><div><br /></div><div>No information is available on the weight of the MT-12R, but it remained well within the limits of an MT-LB and likely the AT-P as well, as that was able to cope with the heavier BS-3 field gun. However, the added weight undoubtedly made the gun much harder to manhandle by its crew, though not to the extent that all mobility is lost, as the use of MT-12R guns in Ukraine has shown.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-QILq8dEpBDE/X5-w58xFJII/AAAAAAAAR7g/KunQSDaf39kHS_2PhetNbiaSs9XJoalYQCLcBGAsYHQ/s1024/Ruta_transport_big.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="306" data-original-width="1024" height="235" src="https://1.bp.blogspot.com/-QILq8dEpBDE/X5-w58xFJII/AAAAAAAAR7g/KunQSDaf39kHS_2PhetNbiaSs9XJoalYQCLcBGAsYHQ/w640-h235/Ruta_transport_big.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>In radar fire control systems of anti-tank guns firing unguided projectiles, the predominant factor in hitting a moving target is to accurately determine the future coordinates of the target at the moment the projectile approaches it. To do this, it is necessary to measure with high accuracy the polar coordinates of the target, the direction and speed of its movement and, taking into account the projectile speed and the range to the target, calculate the correction to the sight (lead point), aim the gun at this lead point and fire. The operator's control panel is on the box below the sight display. The features of the operator's interface with the radar sight are unclear beyond the most basic assumption that there are switches that control the activation of the sight. The function of the brown-coloured handle next to the sight display is unknown, but may be speculated to be the operator's interface for selecting a target. </div><div><br /></div><div>The "Ruta" system consists of the RLPK-1 millimeter-wave radar complex and the power supply unit. RLPK is simply an abbreviation of "radar sighting complex". RLPK-1 consists of the antenna-waveguide system, the computer, and the sighting information transmitter. The antenna fairing seals the antenna and protects it from bullets and fragments. From a visual inspection of its exterior form, it can be determined that behind the fixed yellow plastic parabolic lens, the radar antenna has an internal flat movable reflector. In case the radar FCS fails, the OP4M-40U sight remained as a backup option. </div><div><br /></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xtSw_pkP2D0/X6AIYsfiDuI/AAAAAAAAR9o/I3li5lCap40UxPcpy-A2TasZc0yM_yx4wCLcBGAsYHQ/s960/television%2Bsight.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="463" data-original-width="960" height="308" src="https://1.bp.blogspot.com/-xtSw_pkP2D0/X6AIYsfiDuI/AAAAAAAAR9o/I3li5lCap40UxPcpy-A2TasZc0yM_yx4wCLcBGAsYHQ/w640-h308/television%2Bsight.png" width="640" /></a></div><div><br /></div><div><br /></div>Naturally, as the sighting system was mounted directly to the gun cradle, the radar FCS functioned throughout the entire 54-degree traverse arc and 28-degree elevation arc of the gun, and its vertical scanning arc was limited to -7 degrees in depression and +7 degrees in elevation. The size of its horizontal scanning arc is unknown but likely to be the same. The full scanning sector of the radar is therefore -14 to +28 degrees in the vertical axis and likely to be 68 degrees in the horizontal axis. The vertical scanning sector at any given point is more than enough for direct fire at any practical range, as a target will be within the operating arc of the radar even when the gun is elevated by up to +7 degrees, which provides a firing range of up to around 3.7 km with 3BK3 HEAT rounds or 5.2 km with 3OF15 HE rounds.<br /><div><br /></div><div>It is not known what is displayed to the gunner on the CRT, but based on the salient features of the radar FCS, it is likely to be a C-scope, displaying the target and the projected aiming point on the screen. Given the scant information on the major assemblies of the "Ruta" system, precise details are not known at all. During operation, the screen of the CRT sight is fitted with a rubber cowl, shown in the photos below. It can be seen from the length of the cowl that the gunner's head will be positioned in the same way as when he is using the day sight, merely shifted to the left. As there is no optical sight in the "Ruta" system itself, the gunner will have to switch to his OP4M sight for visual confirmation of targets identified by the radar, and in this context, the convenient position of the radar sight display and its cowl is well thought-out. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgMA9_CI9rXWOpcccxIo5l8QIzS5N4D1oisLlPNLGD0qdu0jz-WlrxuN_vfM4ei_AaRuPzSDJQKjnKnoRMSmLRqmAvlAd1xfNiuKamkab1DlXWST3xDT4pdA9r5lU-WZ9fcL2ox7uv-2i7RjxKDbtfenI36F6cu85JLzU1zt5bmSOyfB8n-AfCTmMNJQg=s1920" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="360" src="https://blogger.googleusercontent.com/img/a/AVvXsEgMA9_CI9rXWOpcccxIo5l8QIzS5N4D1oisLlPNLGD0qdu0jz-WlrxuN_vfM4ei_AaRuPzSDJQKjnKnoRMSmLRqmAvlAd1xfNiuKamkab1DlXWST3xDT4pdA9r5lU-WZ9fcL2ox7uv-2i7RjxKDbtfenI36F6cu85JLzU1zt5bmSOyfB8n-AfCTmMNJQg=w640-h360" width="640" /></a></div><div><br /></div><div>Such rubber cowls are also found on the displays of other sighting systems such as the PNS-24 radar sighting and navigation system <a href="http://aircraft-museum.ucoz.ru/_si/0/74212165.jpg">installed in the Su-24</a>. Otherwise, the screen is covered with a cap. Such cowls are used to eliminate glare on the screen and isolate the operator's vision from external influences such as rain. In the case of an open weapon installation such as a towed gun, such cowls can also be used to enforce light discipline at night by preventing any light from the CRT screen from illuminating the gunner's face, which could reveal the gun's position to enemy air and ground reconnaissance using passive image intensifier sensors. The image on the upper right corner below was taken from <a href="https://youtu.be/fNQ8H0YFC2s">a video by Andrey Popov</a>. The other images have anonymous sources. </div><div><br /></div><div><br /></div><div style="text-align: center;"><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-Hdd8dwg39l8/X6AKwje8YwI/AAAAAAAAR90/omfnvJlpMf0rqEeis2I4xmiWH92ABcq3QCLcBGAsYHQ/s1200/mt-12r%2Briver%2Bguard.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1200" height="300" src="https://1.bp.blogspot.com/-Hdd8dwg39l8/X6AKwje8YwI/AAAAAAAAR90/omfnvJlpMf0rqEeis2I4xmiWH92ABcq3QCLcBGAsYHQ/w400-h300/mt-12r%2Briver%2Bguard.png" width="400" /></a><a href="https://1.bp.blogspot.com/-FDxhqbq_GoM/X6AWrlaHZaI/AAAAAAAAR-c/u7Lp82X04NgqIYWCZLdtbWrdH3S4YzueQCLcBGAsYHQ/s1792/ruta%2Bsight%2Bsleeve.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1792" height="241" src="https://1.bp.blogspot.com/-FDxhqbq_GoM/X6AWrlaHZaI/AAAAAAAAR-c/u7Lp82X04NgqIYWCZLdtbWrdH3S4YzueQCLcBGAsYHQ/w400-h241/ruta%2Bsight%2Bsleeve.png" width="400" /></a></div></div><div><br /></div><div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-9nKeut6P1Nc/X6Aa36aNYXI/AAAAAAAAR-o/QVA8mR9CPikbUvzpWgOmbiC7n3ucjJSBgCLcBGAsYHQ/s800/mt-12%2Bfully%2Bequipped.jpg" style="margin-left: 1em; margin-right: 1em; text-align: right;"><img border="0" data-original-height="800" data-original-width="600" height="400" src="https://1.bp.blogspot.com/-9nKeut6P1Nc/X6Aa36aNYXI/AAAAAAAAR-o/QVA8mR9CPikbUvzpWgOmbiC7n3ucjJSBgCLcBGAsYHQ/w300-h400/mt-12%2Bfully%2Bequipped.jpg" width="300" /></a><a href="https://1.bp.blogspot.com/-xHYyGcCy-MQ/X6Ab4UdDORI/AAAAAAAAR-w/loII8FxjIfoMuEqCl9hV-5vDj0JpqdzKQCLcBGAsYHQ/s687/ruta%2Brear.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="600" data-original-width="687" height="349" src="https://1.bp.blogspot.com/-xHYyGcCy-MQ/X6Ab4UdDORI/AAAAAAAAR-w/loII8FxjIfoMuEqCl9hV-5vDj0JpqdzKQCLcBGAsYHQ/w400-h349/ruta%2Brear.jpg" width="400" /></a></div><br /></div><div><br /></div><div>This system could be used during the day or night and in all weather conditions including heavy rain, fog and in a smoke-obscured battle environment. The sight was designed to automatically detect targets from a range of over 3,500 meters, and detect a moving target within 3 seconds with a probability of 80%. The fire control system could automatically generate a firing solution consisting of a superelevation angle for the selected ammunition and a deflection angle for leading a moving target, and project an aiming point in the gunner's sight. As these processes were fully automated, the reaction time of the gun system was very short, even compared to a modern tank fire control system with a laser rangefinder. Given that the system did not motorize the gun laying controls, the gunner was still responsible for operating the hand cranks to lay the gun onto the aiming point indicated in the sight.</div><div><br /></div><div>In the conclusions of the testing commission during the state trials of the MT-12R, it was noted that during combat, the radar instrument complex could be controlled by a single operator and changes in the size of the gun crew were not needed. Moreover, the work of the gunner is simplified, since all settings for firing are entered automatically.</div><div><br /></div><div>The number of "Ruta" sights delivered to the Soviet Army is unknown, but is unlikely to have been in large numbers. Though the saturation of MT-12R guns may have been higher when they were new, such guns are rarely seen today. However, it has been observed that surprisingly large quantities of MT-12R guns have been used by the Ukrainian ground forces throughout the war in Ukraine, both in training and in actual combat.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-XRuX6lrFZk4/X54yU6RhNNI/AAAAAAAAR5U/tI5s0ibEcx0TGItg5NUzM3hRIxAZL0zOQCLcBGAsYHQ/s1080/1545250669-368.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="720" data-original-width="1080" height="266" src="https://1.bp.blogspot.com/-XRuX6lrFZk4/X54yU6RhNNI/AAAAAAAAR5U/tI5s0ibEcx0TGItg5NUzM3hRIxAZL0zOQCLcBGAsYHQ/w400-h266/1545250669-368.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-4YmX9kqGnBA/X54ytms1VhI/AAAAAAAAR5c/GRcNgSLbNL8iIIg39HyXq13aGQTtGlIsQCLcBGAsYHQ/s1772/12898172_572974996205095_2607248245779186685_o.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1181" data-original-width="1772" height="266" src="https://1.bp.blogspot.com/-4YmX9kqGnBA/X54ytms1VhI/AAAAAAAAR5c/GRcNgSLbNL8iIIg39HyXq13aGQTtGlIsQCLcBGAsYHQ/w400-h266/12898172_572974996205095_2607248245779186685_o.jpg" width="400" /></a></div><br /><div><br /></div><br /><a href="https://www.blogger.com/null" id="mt12-gun"></a><h3 style="text-align: left;"><span style="font-size: large;">GUN</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Sr0t3ydLxnI/X85L5eRBZ6I/AAAAAAAASR8/klQEs8Zae489Rqiz3hmD2H6bsjRwBsGMQCLcBGAsYHQ/s1419/stvol.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="541" data-original-width="1419" height="244" src="https://1.bp.blogspot.com/-Sr0t3ydLxnI/X85L5eRBZ6I/AAAAAAAASR8/klQEs8Zae489Rqiz3hmD2H6bsjRwBsGMQCLcBGAsYHQ/w640-h244/stvol.png" width="640" /></a></div><br /><div><br /></div>The T-12 and MT-12 fire the 100x913mm cartridge. The breech, barrel and recoil mechanism of the T-12 was completely different from the D-48. Although Aleksandr Shirokorad claims in his encyclopedia that the T-12 only differed from the D-48 in the barrel, a simple look at the breech on real guns and in drawings shows that the T-12 has a flat-ended breech housing whereas the D-48 had a distinctly beveled breech housing. The MT-12 introduced a new equilibrator, but was otherwise identical to T-12. The primary distinguishing feature of the gun is, of course, the smoothbore barrel.</div><div><br /></div><div><div>The primary justification for a smoothbore gun is that the nature of barrel wear with a smoothbore barrel is more conducive to a high pressure, high velocity gun. In both cases, the extent of throat erosion is the primary factor that determines the condition of the barrel, but the nature of throat erosion differs. This is due to the fact that the limiting wear for a smoothbore barrel is the thickness of the eroded bore diameter, whereas for a rifled gun, the limiting wear is the longitudinal length of the throat, because the delayed engagement with the rifling lands severely impacts the dispersion characteristics of the ammunition. The limiting type of erosion is shown in the drawing below, taken from the 2004 textbook "<i>Учебник Сержанта Танковых Войск</i>". The throat erodes at a much higher rate than the rest of the bore (excluding the muzzle) regardless of whether the barrel is rifled or not, and in both cases, the throat diameter progressively expands along a certain length due to erosion, but the progression of the eroded length is much faster than the progression of the eroded thickness. For instance, if a given ammunition is capable of eroding a certain thickness from the surface of the throat, then the throat diameter will expand at a nominal rate, with the rate decreasing towards the muzzle end, but the length of the throat affected by erosion can be very long, since the projectile and propellant gasses act on the surface for the entire length of the bore. Given this fundamental limitation, ideally, the service life of a barrel should be determined by the eroded diameter. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEijnlHtB8da32C1ULM6QUJtmxOvfsWkPolRiNkST2dV71Px8xtpoEIyzGBO15MEIChGQqjUphb_8QMcyeReOOrJYT9120EWE60riQyDt7J6HXnEmbHayd1xat_-aM3oNoH4SK-DWbZER3Pkhf1np1geXc7aMUivnWj2YcF0hTuSZdxQhVFLPPyEOENWMQ=s1688" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="771" data-original-width="1688" height="292" src="https://blogger.googleusercontent.com/img/a/AVvXsEijnlHtB8da32C1ULM6QUJtmxOvfsWkPolRiNkST2dV71Px8xtpoEIyzGBO15MEIChGQqjUphb_8QMcyeReOOrJYT9120EWE60riQyDt7J6HXnEmbHayd1xat_-aM3oNoH4SK-DWbZER3Pkhf1np1geXc7aMUivnWj2YcF0hTuSZdxQhVFLPPyEOENWMQ=w640-h292" width="640" /></a></div><div><br /></div><div>Because the length of the eroded throat has an overwhelming effect on the precision of a rifled gun, increasing the longevity of the barrel by increasing the resistance of the bore surface against erosion yields less of an improvement. As such, for guns of increased power, the presence of rifling results in the barrel not being able to fulfill its full service life potential. For a smoothbore, the length of the throat affected by erosion is no longer the primary issue, but rather the throat diameter. Because of this, when comparing two identical guns firing the same ammunition that differ only in one being rifled and the other being a smoothbore, the smoothbore will have a longer service life. </div></div><div><br /></div><div>It is claimed on some websites that the T-12 was converted to the 115mm U-5TS tank gun, but this is completely untrue. The T-12 and MT-12 were not developed into any new artillery systems that went into service serially; they were effectively dead-end designs.</div><div><br /></div><div>As with the preceding anti-tank guns, the T-12 has a semi-automatic vertically-sliding breechblock, with a mechanical firing mechanism. The right side of the breech housing is occupied by the spring-actuated breechblock-closing mechanism and the manual opening lever. The mechanism was not changed on the MT-12. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-lfc27zKPNyo/X9iWfmfzWrI/AAAAAAAASbg/lJTUorOaqTsqLjART5R0ZT8Rz5q0topbACLcBGAsYHQ/s2048/breech%2Bopening%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1167" data-original-width="2048" height="228" src="https://1.bp.blogspot.com/-lfc27zKPNyo/X9iWfmfzWrI/AAAAAAAASbg/lJTUorOaqTsqLjART5R0ZT8Rz5q0topbACLcBGAsYHQ/w400-h228/breech%2Bopening%2Bmechanism.png" width="400" /></a></div><div><br /></div><div><br /></div><div>It is stated in the article "<i><a href="http://suse.kemrsl.ru/files/1457508501_Rapira.pdf">«РАПИРА. Как рождалась знаменитая пушка</a></i>" (<i>"Rapira": How the famous cannon was born</i>) that during testing, the T-12 gun had an issue with incomplete case extraction. After a shot was fired, the case would be ejected weakly and hang from the opened breech, forcing a crew member to manually remove the case before the next round could be loaded. This affected the rate of fire. It turned out that the problem was a relatively high residual pressure in the chamber during ejection, which compressed the steel cases to the chamber walls and increased its static friction. The problem was solved by modifying the recoil buffer to delay the opening of the breech by around 2-3 tenths of a second.</div><div><br /></div><div><br /></div><div><div>Elevation and traverse was actuated with a pair of handwheels, each connected to worm gears at the gun cradle pintle and the pinion of the elevation rack. The layout and design is essentially the same as in any other modern towed artillery piece.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GZ4gTB8uJ1k/X85PRm4N1kI/AAAAAAAASSw/dzb99FBEG84NvhXN-IOdxRo516iEr--DwCLcBGAsYHQ/s2048/traverse%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1207" data-original-width="2048" height="236" src="https://1.bp.blogspot.com/-GZ4gTB8uJ1k/X85PRm4N1kI/AAAAAAAASSw/dzb99FBEG84NvhXN-IOdxRo516iEr--DwCLcBGAsYHQ/w400-h236/traverse%2Bmechanism.png" width="400" /></a><div class="separator" style="clear: both;"><a href="https://1.bp.blogspot.com/-00N0dRBj1KA/X85QF5k9h_I/AAAAAAAASS4/ucIPaI4rKkY-PfTsjeomjbBq8sW5TtJSgCLcBGAsYHQ/s2633/elevation%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="928" data-original-width="2633" height="226" src="https://1.bp.blogspot.com/-00N0dRBj1KA/X85QF5k9h_I/AAAAAAAASS4/ucIPaI4rKkY-PfTsjeomjbBq8sW5TtJSgCLcBGAsYHQ/w640-h226/elevation%2Bmechanism.png" width="640" /></a></div></div><div><br /></div><br /><div>The mechanical firing mechanism of the gun is actuated with a large lever affixed to the recoil guard. A possible explanation for using a lever rather than a button on the elevation handwheel is so that the gunner's hand will not be shoved back by the gun if it jumps during recoil. As always, a recocking mechanism allows the firing pin striker to be recocked whenever necessary.</div><div><br /></div><div>As alluded to earlier, there is an attachment point on the trigger lever mechanism for securing a wire cable connecting to the flash protection shutter of the APN-6-40 night sight so that, when the trigger is pulled, the sight is shielded from the muzzle flash. </div></div><div><div><br />The mounting system of the T-12 permits the gun to be traversed by 27 degrees to each side, and elevated from a maximum depression angle of -6 degrees to a maximum elevation angle of +20 degrees. On the MT-12, the elevation limits were expanded to span -7 degrees to +21 degrees. It is worth noting that the bore axis of the (M)T-12 is so low that when preparing to fire at elevation angles of more than 15 degrees, a pit must be dug under the gun breech of the gun to a depth of 20-30 cm. Otherwise, the recoil causes the breech face to strike the ground, and the breech block may be unable to fully open. The limited maximum elevation angle, combined with the low velocity of the proprietary 100mm HE-Frag ammunition, severely limited the reach of the (M)T-12 gun to just 8.2 kilometers.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-nhrjd4Lf4u0/X85NZyqW4fI/AAAAAAAASSU/YUTYreBwnrgsV5eGp4vcADShePr6NDwlQCLcBGAsYHQ/s547/guns02.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="547" data-original-width="420" height="400" src="https://1.bp.blogspot.com/-nhrjd4Lf4u0/X85NZyqW4fI/AAAAAAAASSU/YUTYreBwnrgsV5eGp4vcADShePr6NDwlQCLcBGAsYHQ/w308-h400/guns02.jpg" width="308" /></a></div><div><br /></div><div><br /></div><div>This range of motion - and especially the full traversing arc of 54 degrees - was not any different from the preceding guns, but considering the increased size and power of the 100mm gun, it was very good. With the low bore axis of 800mm, the T-12 and MT-12 can depress the gun low enough that the muzzle touches the ground.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-mBvRU8x88GU/X32cb335bWI/AAAAAAAARrI/505wEdlWmvkQ9Xm1BCsDypg9yuc4YnvHACLcBGAsYHQ/s1440/mt-12%2Bfull%2Belevation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1076" data-original-width="1440" height="299" src="https://1.bp.blogspot.com/-mBvRU8x88GU/X32cb335bWI/AAAAAAAARrI/505wEdlWmvkQ9Xm1BCsDypg9yuc4YnvHACLcBGAsYHQ/w400-h299/mt-12%2Bfull%2Belevation.png" width="400" /></a><a href="https://1.bp.blogspot.com/-Cb4RUaRz46Y/X32cbx1TFKI/AAAAAAAARrE/foP75NQC9bA0Yf51fbdT5MXvDPEh5zs4QCLcBGAsYHQ/s1440/mt-12%2Bfull%2Bdepression.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1076" data-original-width="1440" height="299" src="https://1.bp.blogspot.com/-Cb4RUaRz46Y/X32cbx1TFKI/AAAAAAAARrE/foP75NQC9bA0Yf51fbdT5MXvDPEh5zs4QCLcBGAsYHQ/w400-h299/mt-12%2Bfull%2Bdepression.png" width="400" /></a></div><div><br /></div></div><div><br /></div><div>The photo below, provided by a friend of the author, shows a view of the recoil devices on a T-12. It can be seen that the location and layout of the recoil mechanism is typical of all Soviet guns, with a hydropneumatic recoil buffer on the top left of the barrel paired with a single recuperator on the top right. The levers and the spring for the breech opening mechanism can also be seen on the right of the breech housing. The recoil mechanism shares a close similarity with that of the D-48, but it was not interchangeable nonetheless. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-SIzA2cbTYTI/X46vy0D2vJI/AAAAAAAARw0/2-3CvAS9YUM1PeZhi0iDDQqa-Qt906OEACLcBGAsYHQ/s2048/right%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="400" src="https://1.bp.blogspot.com/-SIzA2cbTYTI/X46vy0D2vJI/AAAAAAAARw0/2-3CvAS9YUM1PeZhi0iDDQqa-Qt906OEACLcBGAsYHQ/w300-h400/right%2Bview.png" width="300" /></a></div><div><br /></div><div><br /></div><div><div>As with the D-48 recoil mechanism, the buffer features an air pocket filling 2-3% of its internal volume to serve as its self-regulating mechanism instead of a replenisher. The design of the buffer and recuperator was almost the same as that of the D-48, but the components were not interchangeable. The recoil recuperator holds a slightly larger volume of Steol-M, 3.6-4.0 liters, and it is pressurized to 58 atm. </div></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-pVB34E7yi3I/X6rK9XqGYQI/AAAAAAAASGE/GL1NLdpaoPgujim58SBNawocWAJ4N_9EgCLcBGAsYHQ/s2157/recoil%2Bbuffer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="563" data-original-width="2157" height="168" src="https://1.bp.blogspot.com/-pVB34E7yi3I/X6rK9XqGYQI/AAAAAAAASGE/GL1NLdpaoPgujim58SBNawocWAJ4N_9EgCLcBGAsYHQ/w640-h168/recoil%2Bbuffer.png" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-mTjK5XrZbYU/X6rK9a4GmfI/AAAAAAAASGI/aati1Fc-8AAnIolqyqh89Dgi0nUT33HxgCLcBGAsYHQ/s2300/recuperator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="638" data-original-width="2300" height="178" src="https://1.bp.blogspot.com/-mTjK5XrZbYU/X6rK9a4GmfI/AAAAAAAASGI/aati1Fc-8AAnIolqyqh89Dgi0nUT33HxgCLcBGAsYHQ/w640-h178/recuperator.png" width="640" /></a></div><div><br /></div><div><br /></div><div><div>This solution does not increase the size or complicate the design of the recoil mechanism, but is unsustainable when large braking forces are involved because an air-oil mixture is compressible, so that the braking response can be altered significantly. For this reason, this method was only used for the recoil mechanisms of guns with a caliber up to 100mm, where the buffer has only a relatively small volume of liquid. For the T-12 and MT-12, the buffer contains 5.45 liters of Steol-M, and the braking force (due to the braking force) is limited by the long recoil stroke. </div><div><div><br /></div><div>The T-12 and MT-12 both have a normal recoil stroke length of 680mm to 760mm, with a hard stop at 780mm. The minimum stroke length is 675mm. The recoil stroke is a useful illustration of the power of the gun, with its minimum recoil stroke being equal to the maximum limit of the D-44.</div><div><br /></div><div>The original design of the 125mm D-81T tank gun, the 2A26, also utilized a free air pocket as a self-compensating mechanism, but this was soon abandoned due to unresolvable issues with the uniformity of the braking force at high temperatures, owing to the high power of the gun, its large buffer fluid content (8.45 liters) and its very short recoil stroke of just 270-320mm. </div></div></div><div><br /></div><div><br /></div><div>Like preceding guns, the T-12 was equipped with a pneumatic equilibrator located on the right side of the gun. It was of the same design as on the D-48. The photo below, from the Wikimedia Commons, shows the T-12 equilibrator in the same location as its counterpart on a D-48. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-dr4Ma7f7U1g/X6JwHtMlFfI/AAAAAAAASCI/HqfgW6U-XWwTaATgFAULKsVJg9n4v_XhQCLcBGAsYHQ/s2048/equilibrator.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1365" data-original-width="2048" height="266" src="https://1.bp.blogspot.com/-dr4Ma7f7U1g/X6JwHtMlFfI/AAAAAAAASCI/HqfgW6U-XWwTaATgFAULKsVJg9n4v_XhQCLcBGAsYHQ/w400-h266/equilibrator.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>On the MT-12, the pneumatic equilibrator was exchanged for a coil spring equilibrator to enhance its ease of use, since the pneumatic type required calibration in various conditions. The large and rather prominent equilibrator is situated on the right of the breech. A spring equilibrator is by far the simplest, most reliable and most user-friendly type, but the drawbacks are their large weight and volume, particularly when they need to support a heavy gun and function over a large gun elevation arc. This is only somewhat ameliorated by the limited elevation arc of the MT-12. Even so, the massive size of the equilibrator springs and its housing undoubtedly contributed to the significant weight gain of the MT-12 over the T-12.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-dKG8DOxHHGc/X46nM5eFWhI/AAAAAAAARwk/9Ll19EWTIKEA0ux648VaDluuQYcwgV-mwCLcBGAsYHQ/s1995/equilibrator%2Bspring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="979" data-original-width="1995" height="196" src="https://1.bp.blogspot.com/-dKG8DOxHHGc/X46nM5eFWhI/AAAAAAAARwk/9Ll19EWTIKEA0ux648VaDluuQYcwgV-mwCLcBGAsYHQ/w400-h196/equilibrator%2Bspring.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GSHPat0hdHQ/X46nM0fIgRI/AAAAAAAARwo/jAOd22Q9_qItLcykm-WcTal9DYejKG9hgCLcBGAsYHQ/s2183/equilibrator%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="701" data-original-width="2183" height="129" src="https://1.bp.blogspot.com/-GSHPat0hdHQ/X46nM0fIgRI/AAAAAAAARwo/jAOd22Q9_qItLcykm-WcTal9DYejKG9hgCLcBGAsYHQ/w400-h129/equilibrator%2Bcross%2Bsection.png" width="400" /></a></div><div><br /></div><div><br /></div><div>It is a push-type equilibrator, using compression-type coil springs. The additional load of the front-heavy gun acting on the elevation handwheel is relieved by the force exerted by the equilibrator springs pushing on a piston connected to the gun cradle. </div><div><br /></div><div><div><br /></div><div>For both the T-12 and MT-12, the barrel and breech together weigh 1,337 kg. The recoiling assembly, which includes the barrel, breech and recoil mechanism, weighs a total of 1,420 kg. In total, the T-12 gun assembly is slightly heavier than the D-48 and lighter than the BS-3. According to Shirokorad in "<i>Энциклопедия Отечественной Артиллерии</i>", the T-12 gun assembly differed from the D-48 only in the barrel, and that the entire breech and its mechanisms were identical to the D-48. However, the recoil system was not interchangeable, as the new 100mm cartridge generated more energetic recoil. It is even claimed in some secondary sources that the T-12 barrel was created by simply boring out the D-48 barrel, leaving the walls smooth and adding a muzzle brake. However, the massive differences in construction show that this cannot be the case.</div><div><br /></div><div><br /></div><div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-yiOr2jgpmA0/XyJOp2zxUPI/AAAAAAAARYA/ko919nioJzU_rnoVzX2qHuDVH5OVTM9xgCLcBGAsYHQ/s2048/breech%2Band%2Bbarrel.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1759" data-original-width="2048" height="344" src="https://1.bp.blogspot.com/-yiOr2jgpmA0/XyJOp2zxUPI/AAAAAAAARYA/ko919nioJzU_rnoVzX2qHuDVH5OVTM9xgCLcBGAsYHQ/w400-h344/breech%2Band%2Bbarrel.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div><div>The chamber consists of two cylindrical sections connected by a truncated conical ramp, which accommodates the bottleneck of the 100mm cartridges. The transition from the chamber to the barrel bore is formed by a forcing cone. The forcing cone aligns the projectile with the bore and ensures that a gas seal is formed upon firing. When a cartridge is fired, the overcaliber obturator ring on a projectile is squeezed by the forcing cone until it fits into the 100mm caliber of the bore, whereupon the projectile can be propelled down the barrel. With an APFSDS round loaded, the useful chamber volume (the volume which is filled with propellant) is 9.4 liters. With HEAT or practice shells, it is 8.9 liters. With a HE-Frag shell, it is 8.188 liters. For comparison, the chamber capacity of the BS-3 field gun and D10 tank gun (with AP or HE) is 7.9 liters, while the 105mm L7 or M68 guns have a chamber capacity of 6.6 liters, and the 90mm M36 and M41 guns have a chamber capacity of 4.9 liters.</div><div><br /></div><div><div>With a smoothbore barrel, the necessary equilibrium spin is imparted by canted fins. Due to the elimination of stresses incurred by spin, fin-stabilized projectiles can be fired at higher velocities than spin stabilized projectiles, and fin stabilized ammunition generally performs much better in a smoothbore gun than in a rifled one. As such, even though an APFSDS round can be fired from a rifled barrel, a smoothbore could provide optimal internal ballistics.</div><div><br /></div><div>A smoothbore barrel also improved the performance of HEAT shells by completely eliminating all unecessary projectile spin, and improved the performance of subcaliber AP rounds by accommodating increased propellant pressures and higher velocities without accelerated bore erosion.</div></div><div><br /></div><div>The name of the gun, "Rapira", was allegedly chosen owing to the long and thin barrel of the gun resembling a rapier, but even though the barrel is certainly thin, it is not particularly long if the muzzle brake is left out. The total length of the barrel, including the muzzle brake, is 6,300mm, or 63 calibers. The total length of the gun, including the breech assembly, barrel and muzzle brake, is 6,650mm, or 66.5 calibers. For comparison, the barrel and breech assembly of the BS-3 had a total length of 5,960mm inclusive of the muzzle brake, or 5,604mm without the brake, and the barrel alone is 5,350mm long. The (M)T-12 chamber is 915mm long, including the forcing cone. The cartridge case, being 913mm long (less when the rim is excluded), fits almost the entire length of the chamber but leaves a sufficient gap for the obturator ring of the projectile to be pressed against the forcing cone. For all ammunition types, the obturator ring is the copper band affixed just slightly ahead of the cannelures around which the cartridge case is crimped.</div></div><div><br /></div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HK0Avbkn-c8/X5mVLth2MHI/AAAAAAAAR2g/xl3Ug5qVcLYlECCZupr0y5JvWoptSkJjwCLcBGAsYHQ/s2583/barrel%2Band%2Bbreech%2Btotal%2Blength.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="487" data-original-width="2583" height="120" src="https://1.bp.blogspot.com/-HK0Avbkn-c8/X5mVLth2MHI/AAAAAAAAR2g/xl3Ug5qVcLYlECCZupr0y5JvWoptSkJjwCLcBGAsYHQ/w640-h120/barrel%2Band%2Bbreech%2Btotal%2Blength.png" width="640" /></a></div><div><br /></div><div><br /></div><div>Of the total length, the breech has a measured length of 345mm as shown below, and the muzzle brake has a length of around 400mm, estimated based on the drawing above. The barrel is of a monobloc construction with an integral muzzle brake. Excluding the breech and muzzle brake, the barrel alone has a length of around 5,900mm, making the (M)T-12 an L/59 gun, which is considerably longer than the D-48 and BS-3 barrels (5,350mm, L/53.5). However, some of this length comes from the long chamber needed to fit the 100x913mm cartridges, so the difference in shot travel distance inside the barrel is not as large as the barrel length alone suggests. From the known chamber length and the approximate length of the muzzle brake, it can be determined that the bore has a length of around 4,985mm, giving the barrel an effective length that is longer than the rifled length of the BS-3 and D10 barrels (4,630mm) by 355mm, which is considerably smaller than the 550mm difference in gross barrel length. Though there is some uncertainty in the muzzle brake length due to the scaling of the drawing above, it is abundantly clear that the effective length - when judged by the bore length - of the T-12 and MT-12 barrel is only slightly greater than the BS-3 and D10 guns.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-M0Np0ztq0DA/X6E4C8JUVWI/AAAAAAAASBM/CB154i8aSgA4lgWCuAxxTCQFkf24qsKQwCLcBGAsYHQ/s2048/20201103_131720.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1152" data-original-width="2048" height="225" src="https://1.bp.blogspot.com/-M0Np0ztq0DA/X6E4C8JUVWI/AAAAAAAASBM/CB154i8aSgA4lgWCuAxxTCQFkf24qsKQwCLcBGAsYHQ/w400-h225/20201103_131720.jpg" width="400" /></a></div><br /><div><br /></div><div><div>Technologically, the gun barrel does not surpass the performance of other artillery barrels of the time, and this can be seen in the fact that the operating pressure of the gun is not particularly high - when firing a standard APFSDS round, exemplified by the 3UBM1 round, the nominal operating pressure of the T-12 and MT-12 is 328.5 MPa (3,350 kgf/sq.cm) under standard conditions with a propellant temperature of 15°C. This is only 11.6% higher than the BS-3 and D10, which have a nominal operating pressure of 294 MPa (3,000 kgf/sq.cm) when firing AP. From all available evidence, it appears that the higher pressure was merely achieved with a heavier propellant charge of 6.85 kg as compared to the 6.5 kg and 6.585 kg charge used in the APFSDS and APDS rounds for the D10 tank gun. The higher muzzle energy of the T-12 gun can be entirely ascribed to the slightly higher pressure and slightly larger weight of propellant. The significantly larger volume of the chamber itself, standing in at 9.4 liters, was not used to pack more propellant, but instead serves to regulate the maximum chamber pressure.</div><div><br /></div><div><br /></div></div><div><br /></div><div><div><div>The muzzle of the barrel features an integral perforated brake with 80 holes, divided into pairs of 20 holes on each side. In the textbook "<i>Основи Будови Артилерійських Гармат Та Боєприпасiв</i>" (<i>The Basics of Artillery Guns and Ammunition</i>) by A.Y. Derev'yanchuk, this type of brake is described as an integral chamberless honeycomb muzzle brake. A honeycomb muzzle brake is a type of perforated brake with a large number of symmetric round holes arranged in a honeycomb pattern for structural strength, and the lack of a chamber refers to the fact that the internal diameter of the muzzle brake is the same as the barrel bore, being an extension of the barrel itself. According to a technical description of the MT-12 from a textbook publshed by the military faculty of the Saint-Petersburg State University, the brake absorbs around 35% of the recoil force.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-sVKVNn6IqdU/X6DyMar8myI/AAAAAAAAR_8/9pjLrH5aZRMljWVzVEGOUeEBmBPDM6YKwCLcBGAsYHQ/s2048/muzzle%2Bbrake.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1152" data-original-width="2048" height="360" src="https://1.bp.blogspot.com/-sVKVNn6IqdU/X6DyMar8myI/AAAAAAAAR_8/9pjLrH5aZRMljWVzVEGOUeEBmBPDM6YKwCLcBGAsYHQ/w640-h360/muzzle%2Bbrake.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>This type of brake is easy to manufacture. Perforated muzzle brakes of this type are produced by simply designing the gun barrel with an extended bell, and then drilling holes into it after forging the barrel. It is necessary for such a brake to have thickened walls to create a sufficiently long venting channel and to offset the structural weakening incurred by the perforations in conjunction with the honeycomb pattern of the perforations. Moreover, because the brake is integral to the forged barrel structure, it is innately stronger than non-integral brakes as those tend to have more complex shapes formed by casting and are affixed with threads and secured by pins. Any possibility of a brake malfunction or self-detachment are also eliminated with an integral design. Like the bell on a conventional barrel, the large thickness of the brake walls makes it highly resistant to scratches, dents and mechanical damage in general. The acceptable scratch depth is 24mm, equal to the permissible limit for the base of the barrel.</div><div><br /></div><div>The brake was used for boresighting by the conventional method of affixing two strings to form a crosshair, then using a boresighting scope to look through the barrel from the breech end. The gunner lays the gun on a reference point in the landscape, then proceeds to adjust the sights until the line of fire coincidences with the line of sight.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-rzaPSo0mOc8/X5_1TbD6REI/AAAAAAAAR9A/ESu3tOiEPAYF1SUFepEPYCUxFiHGE_XDQCLcBGAsYHQ/s1476/arta3.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1476" data-original-width="1194" height="320" src="https://1.bp.blogspot.com/-rzaPSo0mOc8/X5_1TbD6REI/AAAAAAAAR9A/ESu3tOiEPAYF1SUFepEPYCUxFiHGE_XDQCLcBGAsYHQ/s320/arta3.jpg" /></a><a href="https://1.bp.blogspot.com/-5V4E_L0FcQQ/X6D2uHE58tI/AAAAAAAASAs/blRdhYznkYoq2v-GnHvC-hepmQXWOMCzgCLcBGAsYHQ/s1506/muzzle%2Bbrake%2Bcross.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1232" data-original-width="1506" height="328" src="https://1.bp.blogspot.com/-5V4E_L0FcQQ/X6D2uHE58tI/AAAAAAAASAs/blRdhYznkYoq2v-GnHvC-hepmQXWOMCzgCLcBGAsYHQ/w400-h328/muzzle%2Bbrake%2Bcross.png" width="400" /></a><br /></div><div><br /></div><div><br /></div><div>Although the common perception is that the presence of a muzzle brake on an artillery piece implies that the blast and dust obscuration is worse compared to one with no muzzle device, it is important to make a distinction between muzzle devices that have a blast deflecting function and those without. Muzzle brakes with baffles function as a blast deflectors, and the deflected blast can considerably degrade crew visibility. Though such brakes divert a portion of the radial muzzle blast to the sides, ostensibly reducing the pressure of the downwards blast, the side blast expands in such a way that more obscurants are raised next to the muzzle which is inconvenient for the gunner, who sits offset to the right or left of the gun.</div><div><br /></div><div>The perforations are perpendicular to the barrel and are mirrored, so the jets of propellant gas from the holes are not directed back towards the gun crew and the sideways thrust from one side of the brake cancels out the thrust from the other. The fact that the holes are not canted was confirmed by a friend of the author with a practical experiment: passing a pencil through both ends through one of the holes. The photo below, originally shared <a href="https://sibnarkomat.livejournal.com/23143758.html">by sibnarkomat</a>, shows the muzzle blast of a Polish T-12 gun in a live fire exercise.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DX51JhVhZvs/X8_T-pGDomI/AAAAAAAASUM/aIAV39frzYAWWQKOkIscv73OoimNJ0W2gCLcBGAsYHQ/s1024/polish%2Bt-12.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://1.bp.blogspot.com/-DX51JhVhZvs/X8_T-pGDomI/AAAAAAAASUM/aIAV39frzYAWWQKOkIscv73OoimNJ0W2gCLcBGAsYHQ/w400-h300/polish%2Bt-12.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>Recoil reduction is achieved by redirecting a large proportion of the flow of propellant gasses to the sides of the muzzle so that the main forward jet generated after the projectile leaves the brake produces less rearward thrust, and hence, reduces the recoil force. The desired counter-recoil force was provided by having a large number of perforations from which the gasses are redirected. Relative to a brakes that use canted chamber surfaces or angled vents to produce forward thrust in addition, the braking force of this type of perforated brake is limited. As such, it is generally considered to be a medium efficiency brake. It is reported in the document "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/513629.pdf">Gun Blast and Muzzle Brake Symposium</a>" that a similar <a href="https://cdn.discordapp.com/attachments/607630747519549441/771076633452478544/unknown.png">simple perforated brake</a> achieved a satisfactory efficiency of 40-50% without much increase in blast.</div></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-eiAf9b5ZK1k/X6JaT-ONG4I/AAAAAAAASCA/d4TvpBKfcEEzbwCox0h8za81njhBkJgXgCLcBGAsYHQ/s1298/pepperpot%2Befficiency.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="124" data-original-width="1298" height="62" src="https://1.bp.blogspot.com/-eiAf9b5ZK1k/X6JaT-ONG4I/AAAAAAAASCA/d4TvpBKfcEEzbwCox0h8za81njhBkJgXgCLcBGAsYHQ/w640-h62/pepperpot%2Befficiency.png" width="640" /></a></div><div><br /></div><div><br /></div><div>Moreover, in the report "<i><a href="https://arc.aiaa.org/doi/pdf/10.2514/6.1984-1642">An experimental study of perforated muzzle brakes</a></i>", it was found that a simple perforated muzzle brake could produce a satisfactory braking effect, attenuate the blast overpressure by weakening the muzzle blast waves, and help suppress muzzle flash. It was even found that the brake was even responsible for a 1.5% increase in muzzle velocity compared to a barrel with no brake, presumably because the integral brake functioned as a modicum of additional barrel length. For an APFSDS round, this is equivalent to around 200 meters of range.</div><div><br /></div><div>This type of muzzle brake was a natural choice for this type of gun due to the use of saboted subcaliber AP rounds together with HEAT and HE-Frag rounds stabilized by folding fins. The main issue with using overcaliber muzzle brakes together with these types of ammunition is its influence on the separation mechanics of saboted projectiles or projectiles with unfolding fins. Alternatives to a perforated brake include the multi-baffle design used on the 100mm U-8TS gun on the T-62A and the 122mm M62-T2 gun on the T-10M. Those brakes were not integral, but they were chamberless. The influence of the muzzle blast on the projectile after it leaves the muzzle is minimal, but still a valid concern as it may contribute 6.7% to the dispersion of APFSDS shots. </div><div><br /></div><div>In the article "Gun Blast" by Edward M. Schmidt from the Ballistic Research Laboratory (BRL), published in the "Army R, D & A" journal, Volume 20, Issue 4, the relatively minor effects of a modified muzzle blast from a muzzle brake are explained:</div><div><br /></div><div><div></div><blockquote><div><i>Gas velocities within the propellant gas jet can reach values up to three times the launch velocity of the projectile. Thus, the round is exposed to a high speed flow from the rear, that is, it is effectively in reverse flight. Fin-stabilized projectiles are obviously unstable in such a flow, so BRL has conducted a study of the muzzle blast induced perturbations to the trajectory of a variety of finners.</i></div><div><i><br /></i></div><div><i>The study showed that for a typical tank gun kinetic energy projectile, if the round to round dispersion produced a spread of impacts on target of 0.3 metres at a certain range, only 0.02 metres of the spread could be attributed to muzzle blast induced perturbations. Major contributions to dispersion were related to in-bore and separation mechanics.</i></div></blockquote><div></div></div><div><br /></div><div>In principle, a perforated brake of the type used on the T-12 and MT-12 guns does not enhance the muzzle blast acting on the tail of an exiting projectile, but rather reduces it because the gasses exiting the side holes are expelled as high velocity jets, unlike baffled brakes which produce side blasts.</div><div><br /></div><div><br /></div><div><br /></div>The technical maximum rate of fire of both the T-12 and MT-12 is 14 rounds per minute, which is negligibly less than the 15 rounds per minute limit for the D-48. The aimed rate of fire is considered to be 6 rounds per minute. In U.S evaluations of the gun, the maximum practical rate of fire is considered to be 10 rounds per minute, which should correspond to the firing rate of the gun when only minor adjustments must be applied after every shot, as is the case when firing at a fixed target.</div><div><br /><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-uMNnmSDrRg4/X5hw494ooFI/AAAAAAAAR1o/-rCSB-zlhmQGG4Eir_7sgkueGQh0ytBnACLcBGAsYHQ/s2048/93rd%2BOMPB%2Bmt-12%2Bloading.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1366" data-original-width="2048" height="266" src="https://1.bp.blogspot.com/-uMNnmSDrRg4/X5hw494ooFI/AAAAAAAAR1o/-rCSB-zlhmQGG4Eir_7sgkueGQh0ytBnACLcBGAsYHQ/w400-h266/93rd%2BOMPB%2Bmt-12%2Bloading.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-7YQO8PM6chg/X5hxG8Rc5sI/AAAAAAAAR1s/gPh1DdxX518SDOFGZ5HAx4ZN4nRh3wunQCLcBGAsYHQ/s1000/loading%2Bhe.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="666" data-original-width="1000" height="266" src="https://1.bp.blogspot.com/-7YQO8PM6chg/X5hxG8Rc5sI/AAAAAAAAR1s/gPh1DdxX518SDOFGZ5HAx4ZN4nRh3wunQCLcBGAsYHQ/w400-h266/loading%2Bhe.jpg" width="400" /></a><br /></div><div><br /></div><div><br /></div><div>For comparison, the much heavier BS-3 gun had a maximum rate of fire (without aiming corrections) is 8-10 rounds per minute, which is quite acceptable, but the aimed rate of fire was just 4-5 rounds per minute. According to A. V. Shirokorad, the low practical rate of fire was because the gun jumped a lot with every shot, which endangered the gunner if he did not move away and could even even shake the sights loose. Though the (M)T-12 can also jump violently if fired without being properly dug in beforehand, it was evidently a more stable system than the BS-3 despite being much lighter.</div><div><br /></div><div><div><br /></div></div><br /><a href="https://www.blogger.com/null" id="mt12-ammo"></a><h3 style="text-align: left;"><span style="font-size: large;">AMMUNITION</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-fuo5JVG21YY/X85S6icBBAI/AAAAAAAASTE/b1I5pEpnY6sIGvN93tTMjzwd8bocXItVgCLcBGAsYHQ/s900/ammunition%2Bcrates.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="900" height="266" src="https://1.bp.blogspot.com/-fuo5JVG21YY/X85S6icBBAI/AAAAAAAASTE/b1I5pEpnY6sIGvN93tTMjzwd8bocXItVgCLcBGAsYHQ/w400-h266/ammunition%2Bcrates.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>Naturally, the standard ammunition load for the T-12 and MT-12 was heavily focused on anti-armour work. The MT-LB prime mover of each gun would carry 20 rounds internally for immediate use. Of that, there would be 10 APFSDS rounds, 6 HEAT rounds and 4 HE-Frag rounds. The small allotment of HE-Frag rounds were to be used when fighting troop carriers and dismounted infantry accompanying the enemy tanks. Ammunition carriers would be used to reinforce the ammunition stockpiles of a long-term prepared defensive position and to resupply gun batteries. A standard unit of fire consisted of 80 rounds divided into the same ratio of 50% APFSDS, 30% HEAT and 20% HE-Frag. Needless to say, preparation of a unit of fire for a single T-12 or MT-12 gun battery was a more challenging logistics task than for 85mm guns.</div><div><br /></div><div>The maximum tabular firing ranges of the ammunition and their corresponding firing elevation angles are as follows:</div><div><br /></div><div></div><blockquote><div>APFSDS - 3,000 meters (+0.4 degrees)</div><div>HEAT - 6,000 meters (+20 degrees)</div><div>HE-FRAG - 8,200 meters (+20.18 degrees)</div></blockquote><div></div><div><br /></div><div>It is important to note that in the case of APFSDS and HEAT, the maximum ranges were significantly greater than the tabular ranges, but as they were not represented in the firing tables, it was not possible to conduct aimed fire at their maximum ranges even with the S71 mechanical sight. </div><div><br /></div><div>It is also worth noting that in U.S Army documents detailing enemy weapons and their capabilities, it was noted that if an MT-12 had its trails dug in to provide 45-degree elevation, the maximum range with HE-Frag is extended to 16,000 to 21,000 meters. Additional information on this capability is lacking, but the lack of firing tables for an elevation angle exceeding the maximum tabular angle of +20.18 degrees seems to indicate otherwise.</div><div><br /></div><div>In terms of dimensions, 100x913mm ammunition significantly exceeded all other unitary cartridges for artillery in the Soviet Army at the time. The length of a HE shell is 1,284mm, which would have been totally unacceptable if the T-12 was mounted in an enclosed armoured vehicle.</div><div><br /></div><div><div>4G8 steel cases with a KV-5-U primer are used for all ammunition types. The case has a rim diameter of 147mm and a mouth diameter of 100mm, identical to the D-412 steel case in the 100x695mm caliber used by the BS-3 field gun and D10 tank gun series. However, 4G8 is much longer, having an overall length of 913mm. 4G8 cases weigh 8.1 kg, which is rather counterintuitive given that the much shorter D-412 steel case weighs 8.50 kg.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DdiXwRtgIWk/X85TZrfZieI/AAAAAAAASTM/UOhlaXMa5V4iaGs8ptKtFFulTU_BciENgCLcBGAsYHQ/s650/returning%2Bcases%2Bfor%2Brecycling.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="433" data-original-width="650" height="266" src="https://1.bp.blogspot.com/-DdiXwRtgIWk/X85TZrfZieI/AAAAAAAASTM/UOhlaXMa5V4iaGs8ptKtFFulTU_BciENgCLcBGAsYHQ/w400-h266/returning%2Bcases%2Bfor%2Brecycling.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-AOA0B6ddEM4/X85Tj-2FuOI/AAAAAAAASTQ/9BZjCfAPV18e5fWyCOsEQPCYS3NKDJn4wCLcBGAsYHQ/s1772/disposing%2Bcase.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1181" data-original-width="1772" height="266" src="https://1.bp.blogspot.com/-AOA0B6ddEM4/X85Tj-2FuOI/AAAAAAAASTQ/9BZjCfAPV18e5fWyCOsEQPCYS3NKDJn4wCLcBGAsYHQ/w400-h266/disposing%2Bcase.jpg" width="400" /></a><br /></div><div><br /></div><div><br /></div><div>The length of the case was greatly lengthened with a long, pronounced neck to accommodate the stabilizer fins of the entire range of fin-stabilized ammunition. However, though this may have been a serious issue were the gun mounted in a tank or an enclosed self-propelled tank destroyer, the enormous cartridge length was inconsequential for the T-12 and MT-12.</div><div><br /></div><div>The rim and base diameter of the case is the same as the cases for the 85mm D-48, 100mm BS-3 and 122mm howitzers. This is a significant detail, because it meant that the same dies built to manufacture existing artillery ammunition could also be used to manufacture the new 100mm cartridge case. The process would only differ in that the case had to be drawn more times through the die to produce the required case length and wall thickness. </div><div><br /></div><div>Although the rim diameter is the same between the 4G8 and the D-412, the 4G8 case was not merely a D-412 case with an elongated neck. The tapered section of the neck is much shorter, the body of the case is longer, and the walls were thinner. Even if the long neck is excluded, the capacity of the 4G8 case is substantially larger than the D-412 owing to its length.</div><div><br /></div><div>Minor variations of the 4G8 were used for different ammunition types. The 4G8-1 case was used for APFSDS rounds, whereas the 4G8A case was used for HE-Frag and HEAT rounds that were affixed with a single crimp. </div><div><br /></div></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">PROPELLANT</span></h3><div><br /></div><div>Nitrodiglycol propellant was used for all 100mm ammunition. Propellant sticks were used rather than grains, with two bundles stacked together, separated by a cardboard ring. A flame arrester in the form of a ring-shaped bag with 8/1UG powder is attached to the primer, and a lead wire is packed into the case as a decoppering agent to prevent copper fouling in the barrel bore surfaces, made necessary by the continued use of copper driving bands.</div><div> </div><div>According to "<i>Chemistry and Technology of Explosives Volume III</i>", using nitrodiglycol as an alternative to nitroglycerine provides a number of benefits in terms of nitrocellulose solubility and stability, as well as ease of manufacture. In terms of internal ballistics, the use of nitrodiglycol serves mainly to greatly reduce the calorific value of the propellant, reduce the heat of combustion and thus markedly reduce bore erosion without degrading the pressure characteristics. This, combined with the lack of rifling, would have made the T-12 a highly economical field gun. The use of nitrodiglycol also served as a flash suppressant.</div><div><br /></div><div>The propellant charges for all 100mm ammunition lack a primer tube because it was not necessary for a uniform burn. Propellant in the form of long sticks gives a very uniform burn when ignited with a base primer, because the hollow channels inside and between the sticks permit the flame from the primer to travel the entire length of the charge and thus ignite propellant evenly along the axis of the charge.</div><div><br /></div><div><br /><br /><h3 style="text-align: left;"><span style="font-size: large;">APFSDS</span></h3></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-iUtjHGt9jd0/X85Mnw4SH_I/AAAAAAAASSE/HKKLjWScyvUNLWUVnZ8GN3yrxPmeulgIwCLcBGAsYHQ/s800/loading%2Bapfsds%2Bexercises.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="533" data-original-width="800" height="426" src="https://1.bp.blogspot.com/-iUtjHGt9jd0/X85Mnw4SH_I/AAAAAAAASSE/HKKLjWScyvUNLWUVnZ8GN3yrxPmeulgIwCLcBGAsYHQ/w640-h426/loading%2Bapfsds%2Bexercises.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>In accordance with the Soviet preference for KE ammunition in high performance guns, APFSDS ammunition was the primary anti-tank round for the T-12. Similar ammunition was also being developed abroad during the 1950's, but did not enter service despite the recognition of their various merits. The USSR took the first step, making the T-12 became the first artillery piece in the world to be armed with APFSDS ammunition. The roots of this ammunition in the USSR lay in the research work for expanding the reach of anti-aircraft artillery, carried out by Chief Ballistician V. V. Yavorskiy of the NII-24 research and machine-building institute (NIMI). By a resolution of the Council of Ministers of the USSR in November 1952, NIMI was assigned with task of creating fin-stabilized subcaliber ammunition for smoothbore anti-aircraft artillery, and in 1956, the responsibilities of NIMI were greatly expanded as it was declared as the sole authority for designing and mass producing artillery ammunition for the Soviet military by government decree, and the Pavlograd artillery range was handed over to the institute. In this capacity, Chief Ballistician Yavorskiy applied the work on subcaliber ammunition to anti-tank artillery, resulting in the creation of APFSDS ammunition for the T-12 and the subsequent adaptation of the same projectiles for the 115mm 2A20 (U-5TS) tank gun. The success of the 2A20 and the creation of the 125mm 2A26 gun for the T-64A irreversibly solidified the role of APFSDS ammunition in the Soviet Army. </div><div><br /></div><div>Sticks of DG-4 15/1 propellant was used in APFSDS ammunition up to the 3UBM10 "Kalach" round. It is a nitroglycolic powder. According to <a href="https://sci.house/bazyi-raket-arsenalyi-scibook/markirovka-porohov-tverdyih-raketnyih-topliv-72994.html">the classification index for this type of powder</a>, DG-4 has a calorific value of 820 kCal/kg. For comparison, the triple-base M30 propellant used in a 105mm APDS and HEAT rounds has a much higher calorific value of 950 kCal/kg. The APFSDS ammunition for the 115mm U-5TS tank gun also uses DG-4 propellant, but other domestic APFSDS ammunition was filled with different propellants of various types. Additionally, 100mm APFSDS had a wax paper phlegmatizer liner to reduce barrel wear.</div><div><br /></div><div><br /></div><div>According to the manual for the MT-12, the standard 3BM1 and 3BM2 were considered enough to defeat the frontal armour of medium tanks from up to 2,000 meters and heavy tanks from up to 1,000 meters. A characteristic feature of 100mm APFSDS ammunition was its extraordinarily high velocity. They were the speediest ammunition to see service anywhere in the world for a brief period, until they were surpassed by 115mm APFSDS. It is stated that the flatness of the trajectory at long ranges and the short flight time made it possible to use them to engage highly mobile targets (light tanks, armored personnel carriers, automobiles, etc.) at ranges of up to 3,000 meters. The side armour of any tank would also be vulnerable at such distances, so a tank moving side to side was also a viable target.</div><div><br /></div><div>Moreover, the firing tables show that influence of wind on the trajectory of these high velocity APFSDS rounds was practically negligible, which absolved the simplicity of the (M)T-12 fire control system. The angular correction required for a 10 m/s crosswind reached only 0.9 mils when firing at 3 km, whereas a 3BK3 HEAT round would require a correction of 10.2 mils at the same distance. At typical combat ranges of up to 2 km, the needed corrections are small enough to be ignored, allowing gunners to simply point and fire. This contributes to a higher rate of fire. In combat, one of the only reasons to choose HEAT over APFSDS is that it was forbidden to fire APFSDS rounds when there are friendly troops in front of the firing line within a range of 1,000 meters and in an arc of ±5 degrees, due to the danger posed by the discarded sabot petals.</div><div><br /></div><div>Due to the relatively static nature of anti-tank gun deployment, allowing the creation of range reference points and kill zones, the first hit probability of a T-12 or MT-12 is inherently quite high. The high precision of the gun contributed to this, and the hit probability on both static and moving targets was additionally augmented by the high velocity and flat trajectory of its APFSDS ammunition. </div><div><br /></div><div><br /></div><div>When the T-12 entered service, it was supplied with a steel long rod penetrator round and a cored penetrator round. The former was better suited for highly oblique armour plate, while the latter was best on flat or near-flat armour. These two types of subcaliber penetrator formed the basis of Soviet APFSDS ammunition technology for the next two decades, and managed to remain relevant throughout this time despite their simplicity due to a rather fortuitous onset of stagnation in the development of tanks in the West tied to the collapse of the MBT-70 (KPz-70) project.</div><div><br /></div><div>Throughout the service life of the T-12 and MT-12 guns in the Soviet Army, the troops equipped with these guns only received one new model of APFSDS ammunition, the 3BM24 "Kalach" round with enhanced penetration. The new round did not fundamentally change the capabilities of the gun. It merely improved the probability of kill against existing NATO tanks to varying degrees.</div><div><br /></div><div><div>In the mid to late 1980's, the MT-12 could still be considered reasonably effective for their role thanks to the introduction of a new APFSDS round with a long rod DU penetrator, which broadly matched the capabilities of contemporary 105mm APFSDS and permitted the otherwise obsolete MT-12 to defeat the frontal armour of the M1 Abrams and Leopard 2, as these tanks were only armoured against older threats. </div></div><div><br /></div><div><h3><span style="font-size: large;"><br />PRECISION</span></h3><div><br /></div><div>The T-12 and MT-12 are allegedly considered to be extremely accurate guns by Soviet and modern Russian and Ukrainian artillerymen, earning it the moniker of "sniper artillery". However, the evidence suggests that technically, while it is indeed a highly precise gun, especially relative to conventional artillery, its performance is good, but not extraordinarily good by the standards of tank guns.</div><div><br /></div><div>According to a technical manual for the medium repairs of the MT-12, when zeroing in the gun at 100 meters, APFSDS ammunition is to be used and all holes in the shot group must be within a 130mm square. If the distance between the holes that are furthest apart is measured to be greater than 130mm, then the group should be considered uncountable and abnormal. In terms of angular size, this is equal to a maximum angular dispersion of 1.3 mils.</div><div><br /></div><div>The manual also states that the mean shot dispersion in the horizontal and vertical planes, which is measured as the dimensions of the area where 50% of the shots land, does not exceed 30cm when shooting at 1,000 meters or no more than 25mm when shooting at 100 meters. This translates to an angular dispersion of 0.25 mils at 100 meters, widening to 0.30 mils at 1,000 meters. This is also corroborated by a Ukrainian firing table for the 3BM1, 3BM2 and 3BM24 rounds, which also states that the mean dispersion at 2,000 meters is 0.5 meters in both planes.</div><div><br /></div><div>From this, it can be said that the precision of the T-12 and MT-12 is equivalent to a <a href="http://www.kotsch88.de/tafeln/st_100mm-ke.htm">D10 tank gun firing 3BM8 APDS</a> and is also equivalent or better than foreign guns firing subcaliber ammunition, particularly 105mm guns. </div><div><br /></div><div>For comparison, it is stated in the report "<i><a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a031639.pdf">Performance of Chrome-Plated 105mm M68 Gun Tubes with Discarding Sabot Ammunition</a></i>" that the data accumulated from 563 acceptance tests of M392A2 rounds showed horizontal and vertical standard deviation dispersions of 0.30 and 0.33 mils respectively, for a CEP circle of 0.37 mils. CEP is equivalent to mean dispersion, both being measurements of the 50% dispersion zone of shots. However, guns like the 115mm U-5TS and 125mm 2A26 had better precision. 115mm APFSDS ammunition in particular was highly precise, having a mean dispersion of 0.18 mils in the horizontal plane and 0.23 mils in the vertical plane.</div></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">3UBM1<br />3BM1</span></h3><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-6hjI7W0i8VQ/X46GEWB8ttI/AAAAAAAARwU/xoHKj8YWsA8ThroO3qJigEZxmRgZKpt5ACLcBGAsYHQ/s1666/3ubm1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="769" data-original-width="1666" height="296" src="https://1.bp.blogspot.com/-6hjI7W0i8VQ/X46GEWB8ttI/AAAAAAAARwU/xoHKj8YWsA8ThroO3qJigEZxmRgZKpt5ACLcBGAsYHQ/w640-h296/3ubm1.png" width="640" /></a></div><div><br /></div><div><br /></div><div>As the name indicates, 3UBM1 was the first subcaliber round to be classified in the GRAU index, established in 1956. It allegedly entered service in 1960. An almost completely identical design was used for the slightly larger 3BM3 projectile of the 3UBM3 round, the third APFSDS round to be indexed and the third to be put into service in the Soviet Army. The design of the penetrator is fundamentally quite simple - it essentially a greatly elongated APCR round.</div><div><br /></div><div>Its high muzzle velocity of 1,575 m/s provided for an exceptionally flat trajectory compared to all other available munitions at the time with the sole exception of the 115mm gun of the T-62, as that had an even greater muzzle velocity. With a point blank range of 1,880 meters, 2,130 meters and 2,230 meters against a target with a height of 2.0 meters, 2.7 meters and 3.0 meters respectively, the 3BM1 round allowed a T-12 or MT-12 gun crew to confidently engage tank-sized targets at any practical combat range during an engagement even when relying purely on battlesight gunnery techniques, without needing a rangefinder of any kind. The firing table shown below, digitized by Aleksandr Mandadzhiev, is a firing table for both 3BM1 and 3BM2, as they are considered to be ballistically equivalent.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgp19ol4oaCOYZNBLDYBGlBpT0Fb7nTnqRVMBG2p94pacm4r2LTi5pyd1-EE9cAR1jBjkIv_W1iVtnFn9kSZI5jj-J4jSBohLHB-292rx2FWW8lu8nDMfEbnMLdSrXlwT_SZpiODV5oYW7Ynq5eYwdnGCFEjmviHhosWnWPmMlYaMNL-GIb4lt2ts_KpA=s4555" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3192" data-original-width="4555" height="448" src="https://blogger.googleusercontent.com/img/a/AVvXsEgp19ol4oaCOYZNBLDYBGlBpT0Fb7nTnqRVMBG2p94pacm4r2LTi5pyd1-EE9cAR1jBjkIv_W1iVtnFn9kSZI5jj-J4jSBohLHB-292rx2FWW8lu8nDMfEbnMLdSrXlwT_SZpiODV5oYW7Ynq5eYwdnGCFEjmviHhosWnWPmMlYaMNL-GIb4lt2ts_KpA=w640-h448" width="640" /></a></div><div><br /></div><div><div><br /></div><div>According to the firing tables for the 3BM1, 3BM2 (and 3BM24) rounds, the rate of speed loss is 125 m/s per kilometer of travel (in standard conditions). According to V.A Grigoryan in "<i>Защита танков</i>", the 115mm 3BM3 projectile has a rate of speed loss of up to 128.5 m/s per kilometer. Given the close design similarities, it is unsurprising that the 3BM1 projectile decelerates at almost the same rate, and both suffer from higher deceleration than APDS rounds due to higher drag. For comparison, APDS ammunition in the 100mm and 105mm calibers decelerate at a rate of around 100 m/s per kilometer.</div></div><div><br /></div><div>The photo below, from the user vityz3819 of the guns.ru forum, show the projectile assembly separated from the case and its propellant. The projectile assembly includes the sabot. Considering that the weight of the projectile assembly is 4.3 kg while the in-flight projectile alone weighs 3.38 kg, it can be determined that the sabot weighs 0.92 kg.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-zqy8GHiQpXM/X840E9RbSpI/AAAAAAAASRA/TkHdQsWoRrowHDK9YGQ3sCKkbtGp8egMACLcBGAsYHQ/s1730/broken%2Bup.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="831" data-original-width="1730" height="308" src="https://1.bp.blogspot.com/-zqy8GHiQpXM/X840E9RbSpI/AAAAAAAASRA/TkHdQsWoRrowHDK9YGQ3sCKkbtGp8egMACLcBGAsYHQ/w640-h308/broken%2Bup.JPG" width="640" /></a></div><div><br /></div><div><br /></div><div>To withstand the stresses of launch, the sabot and the bore-riding stabilizer fins on the projectile were made from 40KhFA chrome vanadium steel, a type of high-speed steel normally used for steel cutting tools. The fins have canted surfaces designed to impart a spin of 800-1,000 rotations per minute.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-dklvInJ3064/X5bT8krZKLI/AAAAAAAARzw/X3_uu7U_trc-uX5PvwT3OmtDiwIYgR-bwCLcBGAsYHQ/s1269/3ubm1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="240" data-original-width="1269" height="122" src="https://1.bp.blogspot.com/-dklvInJ3064/X5bT8krZKLI/AAAAAAAARzw/X3_uu7U_trc-uX5PvwT3OmtDiwIYgR-bwCLcBGAsYHQ/w640-h122/3ubm1.png" width="640" /></a></div><div><br /></div><div><br /></div><div><div>The penetrator assembly consists of the steel body of the projectile, which is a rod with a uniform diameter, and an armour-piercing cap screwed onto the steel body that would be covered with a ballistic cap. The armour-piercing cap was affixed with epoxy resin. The tail of the projectile is fitted with a 6-bladed stabilizer fin assembly.</div><div><br /></div><div><a href="https://auremo.org/materials/stal-35hn3ma-35hn3m.html">35KhZNM tool steel</a> is used for the steel projectile body. It is a impact-resistant steel with particularly high toughness as well as high strength and resistance to fatigue fracture. 35KhZNM steel used for APFSDS penetrators was rated for a Brinell impression diameter of 2.6-2.8mm along the nose of the penetrator. This translates to a lower boundary hardness of 477 BHN and an upper boundary hardness of 555 BHN.</div><div><br /></div><div>The armour-piercing cap has a length (thickness) of 0.52 calibers, or 22mm. The armour piercing cap has a hollow cavity that accommodates a small tungsten carbide core weighing 0.45 kg, and its nose is blunt to facilitate the penetration of sloped armour. The cap also protects the core from shattering upon impact. The core is 56mm in length and has a diameter of 32.5 mm. Cores were machined with a 16mm socket to allow it to be fitted onto the steel body of the projectile, then secured with epoxy resin.</div></div><div><br /></div><div>The steel body provides energy to the penetrating core by the conservation of momentum, similar to old APCR ammunition. Because the projectile body is a subcaliber assembly that does not exceed the diameter of the tungsten carbide core, it maintains contact with the core throughout the entire depth of its penetration path in armour, unlike APCR projectiles with a full caliber body, which are inevitably stopped by the armour.</div><div><br /></div><div><br /></div><div>According to the munitions design textbook "<i>Устройство и действие боеприпасов артиллерии</i>", the armour perforation limit of a cored APFSDS shot can be approximated by the Jacob deMarre formula for nickel steel armour, taking coefficient 'K' to be 2,800 and using the diameter (42mm) and weight (3.38 kg) of the full projectile for the variables 'D' and 'Q' respectively, or their equivalents in whatever notation variant is used. It is important that the full projectile weight is used rather than the penetrator alone, because the kinetic energy of the stabilizer fins is transferred to the penetrator by momentum transfer until the very end of the penetration when the fins themselves impact the surface of the armour. This is possible because the tungsten carbide core causes the projectile to behave approximately as a rigid body penetrator rather than an eroding penetrator. </div><div><br /></div><div>It is noted in the textbook that initial reference values for the armour penetration of the round must be determined on experimental firing. In the absence of such data, the known performance of 3BM3 (an identical penetrator design) must be used instead. By normalizing its known penetration with the deMarre formula, it can be observed the thickness exponent should be modified from 1.4 to 1.34.</div><div><br /></div></div><div>Using the normalized deMarre formula, the following results are obtained:</div><div><br /></div><div><div><br /></div><table style="border-collapse: collapse; border: 1px solid black;"><tbody><tr style="border-collapse: collapse; border: 1px solid black;"><th style="border-collapse: collapse; border: 1px solid black;">Range (m)</th><th style="border-collapse: collapse; border: 1px solid black;">Muzzle</th><th style="border-collapse: collapse; border: 1px solid black;">1,000</th><th style="border-collapse: collapse; border: 1px solid black;">2,000</th></tr><tr style="border-collapse: collapse; border: 1px solid black;"><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">Penetration at 0 degrees</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">288mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">253mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 223mm </td></tr><tr style="border-collapse: collapse; border: 1px solid black;"><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">Penetration at 30 degrees</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">233mm (269mm LOS)</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">204mm (235mm LOS)</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 180mm (207mm LOS)</td></tr><tr style="border-collapse: collapse; border: 1px solid black;"><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">Penetration at 60 degrees</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">102mm (204mm LOS)</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">90mm (180mm LOS)</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 79mm (158mm LOS)</td></tr></tbody></table><div> </div></div><div><br /></div><div>It is stated in the textbook that cored APFSDS penetrators have somewhat higher penetration than monobloc steel long rods at an armour obliquity of up to 30 degrees, but have less penetration at an obliquity of 60 degrees and greater.</div><div><br /></div><div>Aside from its penetration power in RHA, it is also important to note that RHA was not the most common type of steel armour on the modern tanks of the time. On the M47, M48, M60, M60A1, AMX-30, Centurion and Chieftain tanks, rolled plates could be encountered only sparingly on the main armoured surfaces, i.e. the turret and hull frontal arcs. The only tanks to use rolled steel armour for major assemblies were the Centurion and Leopard 1 which had their hulls assembled entirely from rolled plates.</div><div><br /></div>All things considered, the use of low hardness steel was not necessarily detrimental, but its effectiveness was strongly conditional on several factors. In fact, low to medium hardness plate is optimal against large caliber steel AP shells even with an undermatching thickness as long as the plate is highly sloped (in general, more than 55 degrees). For armour sloped at a high obliquity, toughness is the critical factor, and low hardness steels tend to be ductile but strong, and therefore tough. </div><div><br /></div><div>However, low hardness steel, particularly low hardness cast steel, is exceptionally poor against subcaliber penetrators of all types. Conversely, high hardness armour has an extremely positive influence on resisting subcaliber penetrators. Soviet research into the effect of armour hardness on cored 115mm APFSDS (3BM3) showed that a 100mm high hardness steel plate set at an angle of 70 degrees had the same penetration channel depth as a 120mm medium hardness steel plate at the same angle, giving a higher mass and thickness efficiency by 23%. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--WkJt5Cvsg0/X6k5ILNrjxI/AAAAAAAASEQ/fnfpsvtAI-YuZ3jJaP_2_1weTt70xdY9wCLcBGAsYHQ/s769/penetration%2Bchannel%2Bpath.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="769" data-original-width="615" height="640" src="https://1.bp.blogspot.com/--WkJt5Cvsg0/X6k5ILNrjxI/AAAAAAAASEQ/fnfpsvtAI-YuZ3jJaP_2_1weTt70xdY9wCLcBGAsYHQ/w512-h640/penetration%2Bchannel%2Bpath.png" width="512" /></a></div><div><br /></div><div><br /></div><div>Moreover, tests with 57mm subcaliber simulants with a tungsten carbide core with a diameter of 19.3 mm at a muzzle velocity of 1,400-1,450 m/s showed that, when the impact angle is 0-40 degrees, high-hardness armour has a 16-25% mass efficiency advantage compared with medium hardness armour. The difference narrows to 10% when the impact angle increases to 70 degrees, but even so, the disadvantage of lowering the hardness is abundantly clear. It can be surmised that the low hardness of 210 BHN on tanks like the M48 and M60 greatly improved the effectiveness of 3BM1, even ignoring the lower resistance of cast steel compared to rolled plates.</div><div><div><div><br /></div><div><br /><h3 style="text-align: left;"><span style="font-size: large;">3UBM2<br />3BM2</span></h3><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-N09do4tW7vY/X6EopauoHPI/AAAAAAAASBE/cBVFgw3lWP4h08DPXrSs5h73_bYI08I9gCLcBGAsYHQ/s2000/3ubm2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="743" data-original-width="2000" height="238" src="https://1.bp.blogspot.com/-N09do4tW7vY/X6EopauoHPI/AAAAAAAASBE/cBVFgw3lWP4h08DPXrSs5h73_bYI08I9gCLcBGAsYHQ/w640-h238/3ubm2.png" width="640" /></a></div><div><br /></div><div><br /></div><div>As the cheaper alternative to 3BM1, it was the twin of the 115mm 3BM4 projectile which was its derivative. 3BM2 lacks a tungsten carbide core. It features only a steel penetrator with a steel armour-piercing cap. When fired, the nominal maximum operating pressure is 328.5 MPa (3,350 kgf/sq.cm). Its muzzle velocity of 1,575 m/s was equal to that of the 3BM1 projectile. 3BM2 is considered to be ballistically matched with 3BM1.</div><div><br /></div><div><div>It was noted in the report "<i>Development of 90mm Shot (Armor Piercing). Fin-Stabilized Discarding Sabot for the Defeat of Armor</i>" that the (steel) APFSDS projectile created from the project had very low costs compared to HEAT and especially compared to APDS. Each APFSDS projectile cost only $25, compared to $40 for a HEAT shell and $125 for an APDS projectile.</div><div><br /></div><div>Being a close analogue to such ammunition, Soviet steel APFSDS ammunition would have shared the same low manufacturing cost. The highly economical nature of solid steel penetrators would have made such ammunition deeply attractive for any large army, and particularly for the Soviet Army given its immense size and the expected ammunition consumption rate of such an army in a major war.</div><div><br /></div></div><div><br /></div><div>Unlike the steel body of the 3BM1 projectile, the steel penetrator of 3BM2 was made from 60KhNM tool steel. 60KhNM steel features high strength and toughness with a high hardness, rated for a Brinell impression diameter of 2.4mm to 2.58mm along the nose of the penetrator. This translates to a lower boundary hardness of 560 BHN and a upper boundary hardness of 653 BHN. At the tail, which only interacts with an armour plate at the very end of the penetration process, the rated impression diameter is 3.0mm to 3.3mm, or a hardness of 340-414 BHN. The armor-piercing tip is made of <a href="http://metallicheckiy-portal.ru/marki_metallov/stk/35XGSA">35KhGSA steel</a>. It is a high quality structural steel with a medium hardness of 388-444 BHN; much softer than the tip of the steel projectile body. It was attached to the steel penetrator by soldering.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-l5rGmrGWmds/X5sKTap-mZI/AAAAAAAAR3E/cgU4TQZQzN8mOdBQoCvD4sdHsC5lhUg6QCLcBGAsYHQ/s1461/3bm2%2Bprojectile.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="379" data-original-width="1461" height="166" src="https://1.bp.blogspot.com/-l5rGmrGWmds/X5sKTap-mZI/AAAAAAAAR3E/cgU4TQZQzN8mOdBQoCvD4sdHsC5lhUg6QCLcBGAsYHQ/w640-h166/3bm2%2Bprojectile.png" width="640" /></a><a href="https://1.bp.blogspot.com/-6UuDgoJYv8o/X5sJ32XFTrI/AAAAAAAAR28/OZnNWTpkEwo5-F2sCOgQniylvV-ZNruJgCLcBGAsYHQ/s814/3bm2%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="253" data-original-width="814" height="198" src="https://1.bp.blogspot.com/-6UuDgoJYv8o/X5sJ32XFTrI/AAAAAAAAR28/OZnNWTpkEwo5-F2sCOgQniylvV-ZNruJgCLcBGAsYHQ/w640-h198/3bm2%2Bcross%2Bsection.png" width="640" /></a></div><div><br /></div><div><br />The length of the full projectile is 525mm and its maximum diameter is 38mm. Its tail is of a much smaller diameter than the nose due to the taper of the penetrator, lowering the average penetrator diameter to 31-32mm. As the <a href="https://studfile.net/preview/8087234/page:20/">No. 11 tracer</a> is standardized among subcaliber projectiles, its diameter of 20mm can be used to ascertain that the penetrator tail has a diameter of just over 20mm. The No. 11 tracer also has a known length of 30.5mm, not inclusive of the built-in cavity behind the tracer compound (an additional centimeter), while the ballistic cap has a length of 35mm as measured from the tip of the armour-piercing cap. After subtracting the ballistic cap and the tracer, it can be estimated that the steel penetrator and its armour-piercing cap have a total length of 470mm. The armour-piercing cap has a length (thickness) of 0.58 calibers, or 22mm. The aspect ratio of the penetrator based on its maximum diameter is 12.4, which qualifies 3BM2 as a bona fide long rod penetrator.<br /><div><br /></div><div><br /></div></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-lP6xQakf6HM/X6EfFJTFkuI/AAAAAAAASA8/dukUYIEgwuIYPCjZ2VPd16by3cUERqAUACLcBGAsYHQ/s399/ballistic%2Bcap%2Bmeasurement.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="252" data-original-width="399" height="253" src="https://1.bp.blogspot.com/-lP6xQakf6HM/X6EfFJTFkuI/AAAAAAAASA8/dukUYIEgwuIYPCjZ2VPd16by3cUERqAUACLcBGAsYHQ/w400-h253/ballistic%2Bcap%2Bmeasurement.png" width="400" /></a></div><div><br /></div><br />The weight of the full projectile is 3.38 kg, including the components that do not contribute to penetration such as the tracer and stabilizer fins. The weight of the stabilizer fin assembly is unknown, but based on the known weight of 3BM4 stabilizer fins, it can be estimated to have a proportional weight of 15%. For the 3BM2 projectile, this means that it weighs 0.507 kg, and indicates that the penetrator alone has a weight of 2.87 kg.</div><div><div><br /></div><div>Thanks to the low weight of the steel "ring" type sabot, its parasitic effect on the effective muzzle energy of the 3BM2 round was limited. It is not entirely clear if the sabot for 3BM2 was interchangeable with the sabot for 3BM1, though they appear identical. Though the maximum diameter of the two projectiles is different, that is largely due to the bulbous cap on the 3BM1 projectile. It seems that interchangeability is likely.</div><div><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-d8bgFLaU_q8/XVrP0Oro2XI/AAAAAAAAO_U/D7DsbdgSDGgtgHdyxoeySGDxWCBibgiYQCLcBGAs/s1600/private%2Bcollector.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="955" data-original-width="1280" height="298" src="https://1.bp.blogspot.com/-d8bgFLaU_q8/XVrP0Oro2XI/AAAAAAAAO_U/D7DsbdgSDGgtgHdyxoeySGDxWCBibgiYQCLcBGAs/w400-h298/private%2Bcollector.jpg" width="400" /></a></div></div><div><br /></div><div><br /></div><div>As mentioned previously, penetration values quoted for the T-12 and MT-12 guns universally refer to 3BM2. The tables below detail its performance from 500-3,000 meters, at armour obliquities of 0 to 60 degrees. The penetration channel has a larger diameter than the steel penetrator rod itself.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-nnY8tkqgANU/X5bUhl2NBhI/AAAAAAAARz4/SGYlT5y_BtA_q90aNr72tIyLjukn8_mwQCLcBGAsYHQ/s820/penetration%2Btable.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="504" data-original-width="820" height="246" src="https://1.bp.blogspot.com/-nnY8tkqgANU/X5bUhl2NBhI/AAAAAAAARz4/SGYlT5y_BtA_q90aNr72tIyLjukn8_mwQCLcBGAsYHQ/w400-h246/penetration%2Btable.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgrbxTIrlQkvLvCLADjlBYhfJokgS6DHY2ZNiIRGr7Ws17trA5t81oBEikVQGTBfltVhono77JuMjrRmVG5gsVAiJJmkUuD7AEAnYf_H6YQ1JU_V9Ld5M9PfNVyFBKqWE1m7goAAcL4lHkCXuH9G0Pkq4dG--2y9Lg8VnUG6kMQw4fAGLK5JFbHfwvrzA=s1902" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1125" data-original-width="1902" height="236" src="https://blogger.googleusercontent.com/img/a/AVvXsEgrbxTIrlQkvLvCLADjlBYhfJokgS6DHY2ZNiIRGr7Ws17trA5t81oBEikVQGTBfltVhono77JuMjrRmVG5gsVAiJJmkUuD7AEAnYf_H6YQ1JU_V9Ld5M9PfNVyFBKqWE1m7goAAcL4lHkCXuH9G0Pkq4dG--2y9Lg8VnUG6kMQw4fAGLK5JFbHfwvrzA=w400-h236" width="400" /></a><br /></div><div><br /></div><div><br /></div><div>It can be seen that the behaviour of 3BM2 is completely consistent with a long rod penetrator, having a better penetration capability as the armour obliquity increases from 0 degrees, although this ceases to be true at 2,500 meters and further. Furthermore, it significantly surpasses 3BM1 in penetration at a 60-degree obliquity at all ranges, but conversely, is inferior on flat and modestly sloped armour. This is fully consistent with the information from the textbook "<i>Устройство и действие боеприпасов артиллерии</i>" that cored APFSDS penetrators have somewhat higher penetration than monobloc steel long rods at an armour obliquity of up to 30 degrees, but have less penetration at an obliquity of 60 degrees and greater.</div><div><br /></div><div>According to calculations using the Lanz-Odermatt perforation formula, 3BM2 should be expected to achieve initial perforation on an additional inch to an inch and a half of thickness. That is, the calculated perforation limit at 500 meters at 0 degrees is 245mm rather than 230mm, and it is 142mm at 60 degrees rather than 125mm. At 1,000 meters, the perforation limit is 225mm at 0 degrees rather than 200mm, and the limit is 131mm at 60 degrees rather than 115mm.</div><div><br /></div><div>It is important to note that this is true for all Soviet steel long rod penetrators, and appears to indicate that the rated penetration figures are according to the guaranteed perforation criteria rather than initial perforation.<br /><br />Domestically, the 115mm 3BMU4 round with the 3BM4 projectile is the closest counterpart to 3BM2. The penetrator was significantly heavier (by 18%) and was fired at a higher velocity, but was otherwise equivalent in design. The penetration of 3BM4 at a distance of 1 km is rated as 250mm RHA on a flat plate and 135mm RHA on a plate sloped at 60 degrees, where its impact velocity would be 1,524 m/s. At 500 meters, the impact velocity of 3BM2 is only 16 m/s less, but with a penetration of 230mm and 125mm on a flat and 60-degree target respectively, it can be clearly seen that its penetration power is greatly affected by the smaller penetrator mass.<br /><br /><br /><div>The main attraction of the 3BM2 round was its greatly enhanced penetration power on oblique armour plate owing to its long rod form and its material properties, allowing eroding penetration rather than rigid body penetration as was the case for other existing munitions at the time. Its penetration power on flat armour was only slightly worse than a full caliber steel APCBC round fired from a ballistically equivalent rifled gun with a muzzle velocity of above 1,000 m/s. On oblique plates, particularly plates sloped at 60 degrees and above, 3BM2 was overwhelmingly superior.</div><div><br /></div><div>This is exemplified by the capabilities of the 100mm D54TS gun. The D54TS <a href="https://i.imgur.com/zDaUClW.png">fired BR-413D, a 16.1 kg APCBC shell at a muzzle velocity of 1,015 m/s</a>, achieving the following penetration values:</div><div> </div><div><br /></div><table style="border-collapse: collapse; border: 1px solid black;"><tbody><tr style="border-collapse: collapse; border: 1px solid black;"><th style="border-collapse: collapse; border: 1px solid black;">Range (m)</th><th style="border-collapse: collapse; border: 1px solid black;">1,000</th><th style="border-collapse: collapse; border: 1px solid black;">2,000</th></tr><tr style="border-collapse: collapse; border: 1px solid black;"><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">Penetration at 0 degrees</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">235mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 200mm </td></tr><tr style="border-collapse: collapse; border: 1px solid black;"><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">Penetration at 60 degrees</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;">85mm</td><td style="border-collapse: collapse; border: 1px solid black; text-align: center;"> 75mm</td></tr></tbody></table><div> </div><div><br /></div><div>The main downside was a reduction in the penetrator mass ejected behind armour compared to rigid body shells, because the penetrator body erodes during penetration, but this does not necessarily correspond to a reduction in the total post-perforation effect. Due to the low efficiency of steel, a very large volume of armour material is displaced during penetration which produces characteristically large penetration channels and ensures that a large mass of armour fragments are ejected behind the plate.</div><br /><br /></div><div>Muzzle velocity: 1,575 m/s<br /><br />Cartridge Mass: 19.34 kg<br />Projectile Mass (with sabot): 4.3 kg<br />Subcaliber Projectile Mass: 3.38 kg<br /><br /><br /><div><br />With this performance, 3BM2 matched the contemporary 105mm L28 APDS round in sloped armour penetration without the use of any tungsten carbide. Foreign APFSDS ammunition of equivalent capabilities were not being used at the time, but experimental models were available for experimental guns. Equivalent APFSDS ammunition fired from the serial 90mm M3A1 gun at a pressure of 47,000 psi (324 MPa) achieves a muzzle velocity of just 1,310 m/s. A closer equivalent to 3BM2 was the American experimental 90mm T82E22 round fired from the experimental T114 gun. Its 3.22 kg steel penetrator was 12% heavier, but it was launched at a lower velocity of 1,524 m/s. With this, it could achieve the following performance:</div><div><br /></div><div></div><blockquote><div>4" at 55 degrees (177mm LOS) - V50 of approx. 3,800 ft/s (1,158 m/s) </div><div>5" at 55 degrees (221mm LOS) - V50 of approx. 4,450 ft/s (1,356 m/s) </div><div>6" at 55 degrees (265mm LOS) - no V50 obtained; one perforation at 5,000 ft/s (MV)</div></blockquote><div></div><div><br /></div><div>As would be expected for a steel penetrator, the T82E22 penetrator produced holes that were 4" (100mm) in diameter, much larger than the 40mm diameter of the penetrator itself.<br /></div><div><br /></div><br /><br /><h3 style="text-align: left;"><span style="font-size: large;">3UBM10<br />3BM24 "Kalach"</span></h3></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-W2MUoHMs8VY/X5AgAhRUb1I/AAAAAAAARyk/nu1CDbF_JMwbqy0xtJh0XmMerbLJbmuFgCLcBGAsYHQ/s2733/kalach.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1151" data-original-width="2733" height="270" src="https://1.bp.blogspot.com/-W2MUoHMs8VY/X5AgAhRUb1I/AAAAAAAARyk/nu1CDbF_JMwbqy0xtJh0XmMerbLJbmuFgCLcBGAsYHQ/w640-h270/kalach.png" width="640" /></a></div><div><br /></div><div><br /></div><div><div>In 1972, a directive to modernize the armour-piercing munitions for anti-tank guns of the 100mm to 125mm calibers was issued. From this, four interlinked research projects were started: "Izomer", "Kalach", "Zastup" and "Zakolka" for 100mm, 115mm and 125mm guns. Owing to the shared developmental background, the 3BM24 "Kalach" projectile shares a near-identical design with its brothers, differing only in scale and the details related with case and gun compatibility. These rounds entered service in 1977-1979, although mass production began in 1975-1976. </div><div><br /></div><div>3BM24 has a cored penetrator, having a tungsten carbide core in the tip like 3BM1. Instead of the complex core used in 3BM1, 3BM24 contains the standard 0.27 kg VN-8 tungsten carbide core, shared with the 115mm 3BM21, 125mm 3BM22 and 100mm 3BM25 rounds. The core is 20mm in diameter and 71mm in length. Instead of a relatively thin steel cap atop the core, a massive VNZh-90 tungsten alloy armour-piercing cap with a blunt tip is fitted. </div><div><br /></div><div>The new features increased the weight of the projectile assembly to 4.55 kg, and the weight of the propellant was marginally reduced by 0.05 kg, presumably so as not to exceed the maximum operating pressure of 3BM1 and 3BM2. Because of this, the muzzle velocity of 3BM24 was reduced to 1,548 m/s.</div><div><br /></div><div><br /></div><div>The sabot is assumed to weigh 0.92 kg, identical to the ring sabot of 3BM1 and 3BM2. From this, the weight of the in-flight projectile is calculated to be 3.63 kg.</div><div><br /></div><div>The projectile is fitted with a slightly modified ring-type sabot with four engagement threads. A new 5-bladed stabilizer fin assembly was implemented, undoubtedly due to the forward shift in the center of gravity due to the heavy tungsten alloy cap. The fins have a longer tip chord which increases their wing area, probably to provide the equivalent lift of the earlier 6-bladed fin design. This explains how the sixth fin was eliminated. </div><div><br /></div><div><div>Despite the shortfall of 27 m/s in velocity, which is a considerable loss as it is equal to 200 meters of distance and adds 0.3 meters to the apogee of the flight trajectory, 3BM24 is still considered to be ballistically matched to 3BM1 and 3BM2 in firing tables, and the point blank range on a target with a height of 2 meters is 1,850 meters - only 30 meters short of the preceding rounds. This can be explained by 3BM24 having a more modest rate of velocity loss compared to 3BM1 and 3BM2 owing to a combination of its greater weight, allowing it to better overcome air resistance, and the slightly reduced drag of its new fin design.</div></div><div><br /></div><div>Indeed, similar characteristics are found when the 125mm 3BM22 shot is compared to the 3BM15 shot. While the 125mm 3BM15 projectile decelerates at a rate of 132.5 m/s per kilometer, 3BM22 decelerates by 105 m/s per kilometer according to Mikhail Rastopshin in the article "<i><a href="https://topwar.ru/1716-nashi-tanki-v-realnoj-vojne-obrecheny.html">Наши танки в реальной войне обречены?</a></i>" (<i>Are our tanks doomed in a real war?</i>). This can be expected to be true of 3BM24 as well.</div><div><br /></div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--O4A3SDG0AY/X3vRNq7HTZI/AAAAAAAARq8/1L1kyNurYIYDDvf9xwB8wDZAEpMz9DhywCLcBGAsYHQ/s2048/3bm24.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1369" height="400" src="https://1.bp.blogspot.com/--O4A3SDG0AY/X3vRNq7HTZI/AAAAAAAARq8/1L1kyNurYIYDDvf9xwB8wDZAEpMz9DhywCLcBGAsYHQ/w268-h400/3bm24.png" width="268" /></a></div><br /><div><br /></div><div>Unfortunately, no penetration data is available. It can only be assumed to be better than 3BM1 on flat targets. Based on the relative performance of 3BM22 and 3BM15, the flat penetration increases by 5% and the penetration on RHA sloped at 60 degrees increases by 13.3%.</div><div><br /></div><div>Regardless, it is extremely unlikely that 3BM24 was sufficient to deal with the frontal armour of any of the three new NATO main battle tanks emerging in the early 1980's: the Leopard 2, Challenger 1, and even the M1 Abrams, which was the most modestly armoured of the three.</div><div><br /></div><div><br /></div><div><div>Muzzle Velocity: 1,548 m/s</div><div><br /></div><div><div>Cartridge Mass: 19.9 kg</div></div></div><div>Complete Projectile Mass: 4.55 kg</div><div><br /></div><div><br /></div><div>3UBM10 was the last APFSDS round created for the (M)T-12 before the creation of the 3UBM15 round. As DU ammunition was not authorized for use unless a major war involving the defence of the country broke out, 3UBM10 remains the most advanced type available for use even to this day - a sad state of affairs, to put it mildly.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">3UBM15<br />3BM34 "Val'shchik"</span></h3><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-dUVeAmnxcvg/X5-2mf-dRsI/AAAAAAAAR7w/4GidiSH0g8U5oqctz8wDpaAgy3VSIsQ7QCLcBGAsYHQ/s540/%25D0%2592%25D1%258B%25D1%2581%25D1%2582%25D1%2580%25D0%25B5%25D0%25BB.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="75" data-original-width="540" src="https://1.bp.blogspot.com/-dUVeAmnxcvg/X5-2mf-dRsI/AAAAAAAAR7w/4GidiSH0g8U5oqctz8wDpaAgy3VSIsQ7QCLcBGAsYHQ/s16000/%25D0%2592%25D1%258B%25D1%2581%25D1%2582%25D1%2580%25D0%25B5%25D0%25BB.jpg" /></a></div><br /><div><br /></div><div><br /></div><div>Having been informed of new Western developments in composite armour technology, GRAU set forth new requirements to defeat future tank armour in the mid-70's. In 1977, work began on new APFSDS projectiles to accomplish this. The new ammunition would be based on totally new design concepts in order to avoid the limitations imposed by the previous composite rounds.</div><div><br /></div><div>This round was allegedly mass-produced but never issued to troops, as DU ammunition was procured only to be stockpiled in case of a major European war. The 125mm "Vant" round shared the same fate. </div><div><br /></div><div>The large increase in sectional density improved its ability to overcome air resistance, so that despite retaining stabilizer fins with a full-bore wingspan, the rate of velocity loss could be reduced somewhat. According to Mikhail Rastopshin in his article "<i><a href="https://nvo.ng.ru/armament/2008-08-01/1_uran.html">Уран конструкторам не помог</a></i>" ("<i>Uranium designs don't help</i>"), the drop in the velocity of 3BM32 at a distance of 2 km is 160 m/s, giving an average velocity loss of 80 m/s per kilometer. For comparison, the 105mm M774 round loses 134 m/s at 2 km, and the 105mm M833 round loses just 107 m/s at 2 km.</div><div><br /></div><div>Though 3BM32 "Vant" is a heavier round for a larger and more energetic gun, it is proportionately very similar to "Val'shchik". As such, it can be reasonably assumed that "Feller" shares the same rate of velocity loss if not less, as the air resistance would be lower at the reduced ordnance velocity of "Feller". </div><div><br /></div><div>However, due to the secrecy surrounding the DU ammunition possessed by the Soviet Army, many basic details about "Val'shchik" are still lacking. Its muzzle velocity remains unknown. A conservative estimate is that the muzzle energy of the 3BM24 round is maintained, which implies that "Val'shchik" has a meager muzzle velocity of around 1,425 m/s. From this, it can be estimated that the impact velocity of "Val'shchik" would be 1,345 m/s at 1 km, and 1,265 m/s at 2 km, and so on.</div><div><br /></div><div>This is based on the assumption that the same weight of the same propellant is used, thus providing no increase in muzzle energy. However, the "Val'shchik" round model photographed by Vasily Fofanov at an arms expo, shown above, clearly has black sticks like the APTs-235P 16/1 high-calorie propellant used in the 125mm 4Zh63 propellant charge. The brown-coloured DG-4 15/1 propellant used in older rounds has a lower calorific value.</div><div><br /></div><div><br /></div><div>The UNTs alloy, known as "Material B", is an alloy of depleted Uranium with nickel and zinc. The use of nickel and zinc in an alloy were typically indicates improved formability, ductility and strength. It also serves to provide corrosion resistance, and indeed, <a href="https://inis.iaea.org/collection/NCLCollectionStore/_Public/08/309/8309718.pdf">nickel and zinc electroplating</a> was studied as a solution for the corrosion issues of the Staballoy (U-0.75%Ti) penetrator used in XM774. Based on calculations using the known properties of the 3BM32 "Vant" penetrator, the density of "Material B" is 18.2 g/cc. This indicates a somewhat higher alloy content compared to Staballoy which has a slightly higher density of 18.6 g/cc on account of its low titanium content of 0.75%. </div><div><br /></div><div>Based on available photos of the projectile assembly, the length of "Val'shchik" does not appear to be particularly impressive but it is slightly longer than the 125mm "Vant" round and is more slender, not just overall, but in terms of its shape. In the photo on the left below, it is the second from the left, while the "Vant" projectile is the fourth from the left. The "Val'shchik" penetrator is a uniform cylinder, lacking the characteristic thickened midsection of the "Vant" penetrator where the sabot interface threads are machined. The projectile has a total length of between 518mm and 548mm, judging by its size in relation to 3BM9 (second from right), 3BM15 (first from right) and 3BM25 (first from left). From the myriad of reference projectiles on display, it can be estimated with reasonable certainty that the penetrator rod has a length of around 410mm.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-PfrMKyno3KI/X5-20CsBlBI/AAAAAAAAR78/a8q23pBx5csGHZl-L30fRcknywpP_PL4wCLcBGAsYHQ/s268/11830620.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="177" data-original-width="268" height="264" src="https://1.bp.blogspot.com/-PfrMKyno3KI/X5-20CsBlBI/AAAAAAAAR78/a8q23pBx5csGHZl-L30fRcknywpP_PL4wCLcBGAsYHQ/w400-h264/11830620.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-lRY8aeEKTIg/X5-20IQKZkI/AAAAAAAAR74/XRE0C7-6Rjge053Y_wPSY7N2BSP2MLN3ACLcBGAsYHQ/s329/%25D0%2592%25D0%25B0%25D0%25BB%25D1%258C%25D1%2589%25D0%25B8%25D0%25BA%2B%25D1%2581%25D0%25BB%25D0%25B5%25D0%25B2%25D0%25B0.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="329" data-original-width="136" height="264" src="https://1.bp.blogspot.com/-lRY8aeEKTIg/X5-20IQKZkI/AAAAAAAAR74/XRE0C7-6Rjge053Y_wPSY7N2BSP2MLN3ACLcBGAsYHQ/w83-h200/%25D0%2592%25D0%25B0%25D0%25BB%25D1%258C%25D1%2589%25D0%25B8%25D0%25BA%2B%25D1%2581%25D0%25BB%25D0%25B5%25D0%25B2%25D0%25B0.JPG" width="109" /></a></div><div><br /></div><div><br /></div><div>The projectile mass is known to be 3.43 kg, so after subtracting the known mass of the stabilizer fins (0.335 kg) and the standard T-20-1 tracer (0.03 kg), the weight of the penetrator alone is 3.06 kg. Knowing these variables, the perforation limit of "Val'shchik" on RHA steel with a hardness of 270 BHN can be calculated using the Lanz-Odermatt formula. </div><div><br /></div><div><br /></div><div>Muzzle Velocity: Unknown, estimated 1,425 m/s</div><div><div><br /></div><div>Complete Projectile Mass: 5.38 kg</div><div><div>Projectile Mass: 3.43 kg</div><div>Sabot Mass: 1.95 kg</div><div>Stabilizer Fin Assembly Mass: 0.335 kg</div></div></div><div><br /></div><div><div>Calculated Penetration</div><div></div><blockquote><div>At muzzle:</div><div>350mm at 0 degrees</div><div>205mm at 60 degrees (410mm LOS)</div><div><br /></div><div>At 1 km:</div><div>330mm at 0 degrees</div><div>193mm at 60 degrees (386mm LOS)</div><div><br /></div><div>At 2 km:</div><div>307mm at 0 degrees</div><div>180mm at 60 degrees (360mm LOS)</div></blockquote><div></div></div><div><br /></div><div><br /></div><div>At least in theory, "Val'shchik" is not worse than M774 in a conservative estimate. Relative to the tank rounds appearing in the mid to late 1980's, its performance was modest, but still nominally sufficient to fight tanks such as the M1, M1IP and M1A1 as well as the Leopard 2 and the Challenger 1 within their frontal arcs from any relevant combat range. The toughest target would have been the frontal turret of the Challenger 1, but even so, the hull would be vulnerable out to 2 km or more. The Leopard 2 and M1 Abrams can be threatened on both the hull and turret frontal arcs on the basis of the fact that the reference threat for the M1 was an early form of composite APFSDS from the late 1960's (XM578), a precursor to the M735 with inferior performance, while the reference threat for the Leopard 2 the 105mm DM13 composite APFSDS round, fired from the Rh105 smoothbore gun. </div><div><br /></div><div><div>For instance, the armour of the M1 Abrams (represented by BRL-1) could be defeated by XM774 from a range of up to 3 km, possibly up to 4 km, according to results published in the report DEFE 70.88 "<i>Future gun tank development</i>". The XM774 round used for these tests closely resembled the final M774 round that entered serial production, as evidenced by its 26mm diameter penetrator instead of the 28mm diameter penetrator of the early XM774. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-0_xigNkdHFw/X5-IoetLECI/AAAAAAAAR7Y/vX1vCYMtxsU8CfF9kwJpJgd6gNRLo202QCLcBGAsYHQ/s861/brl-1%2Band%2Bbrl-2%2Btesting.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="756" data-original-width="861" height="351" src="https://1.bp.blogspot.com/-0_xigNkdHFw/X5-IoetLECI/AAAAAAAAR7Y/vX1vCYMtxsU8CfF9kwJpJgd6gNRLo202QCLcBGAsYHQ/w400-h351/brl-1%2Band%2Bbrl-2%2Btesting.png" width="400" /></a></div><div><br /></div></div><div><br /></div><div><br /><h3 style="text-align: left;"><span style="font-size: large;">HEAT</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-I4ULlhZgscc/X85M_Hv5fhI/AAAAAAAASSM/IjYWF81qsyU4psmXj-4Xqhu9YRFTBsNxwCLcBGAsYHQ/s2048/93rd%2BOMPB%2Bmt-12%2Bloading.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1366" data-original-width="2048" height="426" src="https://1.bp.blogspot.com/-I4ULlhZgscc/X85M_Hv5fhI/AAAAAAAASSM/IjYWF81qsyU4psmXj-4Xqhu9YRFTBsNxwCLcBGAsYHQ/w640-h426/93rd%2BOMPB%2Bmt-12%2Bloading.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>Though the increased diameter and smooth bore of the T-12 permitted much more powerful HEAT shells to be used compared to the D-44 and D-48, it was no more than a supplement to APFSDS, which was firmly established as the main anti-tank munition. In the brief period before the introduction of the 3UOF3 HE-Frag round, HEAT served as a multipurpose shell for targets not suitable for APFSDS.</div><br />As with the D-48, the main purpose of 100mm HEAT rounds were to allow tanks with exceptionally thick armour to be defeated in the event that APFSDS fails or if the stock of APFSDS rounds has been depleted. In the document "<i>Збірник Таблица Стрільбі</i>" (<i>Collection of Firing Tables</i>) from the Sumsy State University and in the technical manual for the MT-12, it is advised that, as a rule, HEAT is to be used from the MT-12 only up to a range of 1,500 meters against moving targets, as firing at longer ranges is less effective due to a decrease in the hit probability. Moreover, HEAT is only to be used if it is impossible to shoot APFSDS. One example of such a circumstance is when friendly troops are advancing in front of the gun within the 10-degree sabot separation arc, as the sabot petals pose a severe danger even to lightly armoured vehicles such as BMPs and BTRs. </div><div><br /></div><div>Naturally, as fin stabilization was firmly established as the most suitable solution for HEAT ammunition, and given that T-12 was a smoothbore gun, all 100mm HEAT shells were fin stabilized. </div><div><br /></div><div>For HEAT rounds, single-channel DG-3 13/1 propellant sticks with a length of 290mm are used, packed into bundles. There are numerous indicators that HEAT ammunition was loaded with a propellant charge that traded off muzzle velocity in favour of thinning the thin walls of the projectile, with the positive side effects being the reduced barrel wear and high penetration performance, and negative side effects being the steeper trajectory and poorer hit probability on moving targets. Not only were HEAT cartridges loaded with a reduced charge so as to not fire at the same pressure as APFSDS ammunition, but DG-3 itself is a nitrodiglycolic propellant with a low calorific value of 750 kCal/kg.</div><div><br /></div><div><br /></div><div><div>Hungarian testing on a T-54 using 3UBK2 HEAT rounds fired from an MT-12 confirmed its ability to confidently defeat the armour of a contemporary medium tank with a powerful post-perforation effect. In one of the shots, the jet perforated the cheek of the turret (at a point where there was more than 200mm of armour), passed through a 25-30cm wooden log representing a crew member, perforated a concrete cartridge simulant in the turret bustle ready rack, and was finally stopped in the turret rear wall. </div><div><br /></div><div>A translation of the original Hungarian article is available in <a href="https://drive.google.com/file/d/1AlWU24NcjQo6JoprENtiZbIaX9osgs_T/view">this link</a>.</div></div><div><br /></div><div><br /><h3><span style="font-size: large;">3UBK2(M)</span></h3><h3><span style="font-size: large;">3BK3(M)</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-tP7eR_0g80w/XijYlbDbAeI/AAAAAAAAP9A/9ppg7IXLU1ka0_nkm75BNq10CiE7hIZLACLcBGAsYHQ/s1600/bk3%2Bheat%2Bshell.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="379" data-original-width="1600" height="150" src="https://1.bp.blogspot.com/-tP7eR_0g80w/XijYlbDbAeI/AAAAAAAAP9A/9ppg7IXLU1ka0_nkm75BNq10CiE7hIZLACLcBGAsYHQ/s640/bk3%2Bheat%2Bshell.png" width="640" /></a></div><br /><br />Entering service in 1961 together with the T-12 gun itself, the 3UBK2 round was the second HEAT cartridge to be categorized under the new GRAU index, following shortly behind the 85m 3UBK1(M) round. The 3BK4 shell for the 115mm U-5TS smoothbore tank gun had the same projectile design, differing only in scale and minor structural details. </div><div><br /></div><div>Unlike the HEAT shells fired from rifled guns, the fins are not opened by centrifugal moment as the projectile does not spin at all before the fins are deployed. Instead, they are opened by the flow of incoming air acting on their beveled surfaces. A 6-bladed fin assembly with an integral No. 12 tracer was fitted to the shell. The burning time of the No. 12 tracer is at least 5 seconds, permitting observation out to at least 2,700 meters, although the effective range is much shorter.</div><div><br /></div><div>The shell is propelled with a reduced charge of 4.75 kg of propellant, generating a peak pressure of just 215.7 MPa (2,200 kgf/sq.cm). However, the low weight of the shell gave it a relatively high muzzle velocity of 975 m/s. Because of this, the trajectory of a 3BK3(M) shell was naturally quite flat, despite the restrictions on its energy retention imposed by its light weight and the drag of the stabilizer assembly. With a point blank range of 1,020 meters for a target with a height of 2.0 meters, the trajectory of a 3BK3(M) shell was flat enough to comfortably engage the most modern low-profile NATO tanks of the time from a distance of a kilometer, which makes it feasible for situations other than ambushes at short distances. The point blank ranges are as follows:</div><div><div><br /></div><div>For a target height of 2.0 m - 1,020 m</div><div>For a target height of 2.7 m - 1,150 m</div><div>For a target height of 3.0 m - 1,200 m</div></div><div><br /></div><div>These figures are from firing table shown below, digitized by Aleksandr Mandadzhiev.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEii4KxcUk5f5XesAmM5gDOEQ4Ck1HdyhWPBm3C3ha7zzoxqrfy3bNb-9pn8-qMumyGvWTV01KQFNbce9ti2o2X6KlYjrEcdASSUNdbLFFpx8IJ8CLZlTwPypswdbtT1n47oDOU6gHRUvBD5ccJHiW7O8zvicnIkmWuZnu-R7w3Lz_HtQmmgNX-InKh0yA=s4560" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3196" data-original-width="4560" height="448" src="https://blogger.googleusercontent.com/img/a/AVvXsEii4KxcUk5f5XesAmM5gDOEQ4Ck1HdyhWPBm3C3ha7zzoxqrfy3bNb-9pn8-qMumyGvWTV01KQFNbce9ti2o2X6KlYjrEcdASSUNdbLFFpx8IJ8CLZlTwPypswdbtT1n47oDOU6gHRUvBD5ccJHiW7O8zvicnIkmWuZnu-R7w3Lz_HtQmmgNX-InKh0yA=w640-h448" width="640" /></a></div><div><br />The focus on lightening can be seen in the design of the shell, with its thin shell casing following the inner taper of the warhead complete with protruding rings for the driving band and obturator ring. For comparison, the 3BK5(M) projectile for the 100mm BS-3 and D10 guns had a thicker shell casing that gave it a significantly larger weight despite sharing many similarities in other aspects. As such, the weight of 3BK3(M) is only 10.07 kg, which is substantially less than the 12.2 kg weight of the 3BK5(M) shell. The reduced mass of the projectile allowed its muzzle velocity to be increased without needing to fire it at a pressure approaching that of APFSDS rounds. A marginal improvement in the point blank range was obtained in this way. This did, however, reduce the sectional density of the projectile and worsened its energy retention at increasing ranges. In practice, however, there was effectively no difference. The flight time of 3BK3(M) to 2 km is 3.2 seconds, identical to 3BK5(M), and its flight time to 3 km is 6.2 seconds, as compared to the 6.0-second flight time of 3BK5(M). When compared to the 105mm OCC F1 (Obus-G) and 105mm M456 rounds, both have inferior long range performance. <br /></div><div><br /></div><div><br /></div><div>Like the fin design of other HEAT shells belonging to the late first generation of postwar designs, the fins are very slightly canted to give the projectile a very slow spin calibrated to function as the equilibrium spin for the projectile and to average out the drag forces from each individual stabilizer fin. This allows the projectile to avoid having increased dispersion from asymmetric forces imparted by irregular fins, perhaps due to differences created by manufacturing tolerances or some external interference on the fins. As the smoothbore barrel does not impart any spin to the projectile, the obligatory equilibrium spin was entirely generated by the stabilizer fins.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-7WVzxTUrQb0/X5_tnOHbRaI/AAAAAAAAR80/x2fN8-QY6IIjTQzb_pGJaTIUfQDiFmA9gCLcBGAsYHQ/s538/long%2Bfin.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="538" data-original-width="412" height="320" src="https://1.bp.blogspot.com/-7WVzxTUrQb0/X5_tnOHbRaI/AAAAAAAAR80/x2fN8-QY6IIjTQzb_pGJaTIUfQDiFmA9gCLcBGAsYHQ/s320/long%2Bfin.png" /></a></div><div><br /><br />The main expense of shaped charge ammunition was the high-precision processing of the liner rather than its material, so the use of a steel liner does not reduce the cost of the shell on its own, but material scarcity during a major war can affect the availability of copper, brass, and other types of metals suitable for shaped charge liners. The shaped charge cone has a steep angle of 28 degrees with an open apex, which is connected to the base detonator. This allows the cone to function as a funnel for the spitback element on the nose fuze.</div><div><br /></div><div>3BK3(M) was fitted with the GPV-2 piezoelectric point-initiating base-detonating spitback fuse. This type of fuze is extremely quick, but an all-electric piezoelectric fuze would be marginally quicker.</div><div><br /></div><div><br /></div><div>The shaped charge cone in 3BK3 has a diameter of 90mm, which is almost a full three centimeters larger than 85mm HEAT shells and even slightly larger than the 88.4mm shaped charge cone of the M456 shell contrary to the external projectile diameter. Moreover, the greatly elongated warhead body of 3BK3 gave the shaped charge a very large built-in standoff distance of 2.75 CD, whereas M456 has a short standoff distance of just 1.78 CD. The magnitude of the design advantages is such that 3BK3 significantly outperforms M456A1 despite having a steel liner instead of a copper one, and despite using a piezoelectric spitback fuze rather than a purely electric piezoelectric fuze.</div><div><br /></div><div><br /></div><div>Officially, 3BK3 is rated to penetrate 350mm of medium hardness steel armour. This is further corroborated by the penetration data given in the munitions design textbook "<i>Устройство и действие боеприпасов артиллерии</i>", indicating a penetration of 350mm RHA. However, there is a significant difference between the average penetration of the shell and the rated penetration, with the rated penetration being much lower and close to the minimum value obtained during tests, presumably to ensure a meaningful post-perforation effect on tanks and other armoured vehicles. </div><div><br />According to a 1979 Soviet report titled "<i><a href="http://btvt.info/5library/vbtt_1979_03_probivaemost.htm">Выбор Кумулятивных Снарядов Для Испытания Брони</a></i>" (<i>Selection of Cumulative Shells for the Evaluation of Armour</i>), the average penetration of the BK3 shell in armour plate is 425mm with a maximum of 500mm and a minimum of 338mm. All of the penetration figures represent the performance at both 0 and 60 degrees. Similarly, the 115mm 3BK4M shell is rated with a penetration of 440mm RHA, but the study credited it with an average penetration of 499mm RHA. </div><div><br /></div><div>The large surplus in penetration power theoretically ensures that all existing tank armour would be strongly overmatched with a residual penetration of nearly up to 200mm when attacking tanks such as the M60A1 and Chieftain. For reference, it is stated in "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a954868.pdf">Comparative Effectiveness of Armor-Defeating Ammunition</a>" that a residual penetrating ability of just 2" (50mm) of armour was necessary for a HEAT shell to be considered effectively lethal.</div><div><br /></div><div><br /></div><div>For the sake of comparison, the average penetration of M456A1 in the same targets was found to be 398mm, and the maximum and minimum penetration were 434mm and 355mm respectively. Considering that foreign data indicates that the average penetration of M456A1 is only 380mm, the advantage of 3BK3 may be even more pronounced. </div><div><br />The high performance of 3BK3(M) can be attributed to a combination of a large built-in standoff distance, a quick-acting piezoelectric fuze, steep cone angle, an explosive filler with a high detonation velocity, and the use of a wave shaper - all features of a modern shaped charge warhead. Despite its ostensibly smaller caliber and its use of a steel liner, the 3BK3 shell had a superior penetration performance compared to the 105mm M456 shell with a copper liner. <br /><br /></div><div><br /></div><div>With this penetration power, the basic 3BK3 shell with a steel liner was potent enough to handle the thickest armour on any NATO tank until the new generation of tanks, namely the M1 Abrams and Leopard 2, appeared in the early 1980's. There is no real difference in efficacy if the 3BK3M shell is used instead, given that the lower penetration of the 3BK3 shell is already enough. It is possible that the increased armour overmatch from the higher penetration power of the 3BK3M shell can increase the probability of kill due to increased post-perforation effects, but on the other hand, the comparatively lower penetration depth of the steel liner in the 3BK3 shell is accompanied by a wider penetration channel. As such, the post-perforation effect of the 3BK3 shell is not necessarily worse.<br /><br /><br />Muzzle Velocity: 975 m/s</div><div><br /></div><div>Projectile Length: 637mm</div><div><br /><div>Projectile Mass: 10.072 kg</div><div>Explosive Filler Mass: 0.84 kg</div><div>Cartridge Weight: 23.056 kg</div><br /><div>Penetration in RHA:</div><div><br /></div><div></div><blockquote><div>350mm at 0 degrees</div><div>250mm at 30 degrees</div><div>170mm at 60 degrees</div></blockquote><div><blockquote>From T-12 manual and <a href="https://i.imgur.com/ya3tdRg.png">Croatian technical manual of ammunition for the T-12</a></blockquote><a href="https://i.imgur.com/ya3tdRg.png"></a></div><div><br /></div><br /><h3 style="text-align: left;"><span style="font-size: large;">3UBK8(M)<br />3BK16(M) "Kadet"</span></h3></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-vDSKXPoI1q4/X5AgHcpZzyI/AAAAAAAARyo/DcEc_mtC7nkWwV7yZcHtw3208svOeKvMACLcBGAsYHQ/s2649/ubk8.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1187" data-original-width="2649" height="286" src="https://1.bp.blogspot.com/-vDSKXPoI1q4/X5AgHcpZzyI/AAAAAAAARyo/DcEc_mtC7nkWwV7yZcHtw3208svOeKvMACLcBGAsYHQ/w640-h286/ubk8.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The "Kadet" round was created in the early to mid-1970's as part of a broader modernization effort to improve artillery and tank ammunition, initiated in the early 1970's. The research and design work was shared between several parallel projects for a series of ammunition for different gun, leading to the simultaneous introduction of the "Kadet", the "Zmeya" round for the 115mm U-TS tank gun and the "Ikra" round for the 100mm D10 tank gun. Together with the "Kalach" round, the appearance of "Kadet" enhanced the firepower of the (M)T-12 incrementally. </div><div><br /></div><div>The 3BK16 and 3BK16M projectiles differ only in the material of the shaped charge liner, the former having a steel liner and the latter having a copper liner. According to a technical manual for the 3UBK8(M) round, both versions of the cartridge can be loaded with an OKFOL or A-IX-1 explosive filler. OKFOL is octogen with 5% of wax as a phlegmatizer. The penetration power of shells loaded with OKFOL will be higher, but the variance in penetration - that is, the difference between the maximum and minimum - would also be higher. No guidelines were given on how these different shells would be issued. It appears to be purely subject to the availability of OKFOL, as the Soviet explosives manufacturing industry only began mass producing octogen (HMX) since 1972. </div><div><br /></div><div>The 3BK16(M) shell was fitted with the V-15 piezoelectric point-initiating base-detonating fuze. Unlike GPV-2, this was a purely electric fuze rather than a piezoelectric spitback fuze. Upon impact with the target, the nose initiator, containing the piezoelectric element, generates a current which is channeled down a funnel in contact with the shaped charge liner, which in turn is connected to the base detonator. To complete the circuit, the other terminal of the piezoelectric element is connected to the shell casing, which contacts the corresponding terminal of the base detonator via its threaded socket. Due to the ommission of a spitback mechanism, the action of the fuze was slightly quickened.</div><div><br /></div><div>Compared to the 3BK3(M) it replaced, the 3BK16(M) shell had a slightly flatter trajectory, having a greater point blank range of around 150 meters for targets with heights of 2.0-3.0 meters. This was mainly achieved due to the lightening of the projectile by 0.5 kg, allowing its muzzle velocity to be raised. From comparing the firing tables of 3BK16(M) and M456, the point blank distances of M456 do not exceed that of 3BK16(M) by more than 100 meters, despite the muzzle velocity of M456 being higher by 100 m/s and being heavier by 1 kg. For example, against a target with a height of 2.1 meters, M456 has a point blank range of 1,300 meters whereas 3BK16(M) has a point blank range of 1,200 meters. This can be attributed to the differences in the projectile spike tip and fin configuration, evidently in favour of the Soviet design.</div><div><br /></div><div>The 5-second burning time of the No. 12 tracer permits observation out to at least 3,150 meters.</div><div><br /></div><div><br /></div><div>Instead of using forged steel as was the case for the conical noses of conventional projectiles, the stepped nose of the projectile body is made from cast 50L-I steel. Casting was used as the nose has a complex shape, consisting of a hollow spike tip and a shoulder screwed onto the warhead casing. An improved fragmentation effect can be expected as a side effect to the switch to a cast casing, although published data is absent for 3BK16.</div><div><br /></div><div><div>Replacing the conical nose with a stepped casing with a spike tip enabled a reduction in the length of the tail required on a fin-stabilized round. The self-stabilizing effect of this projectile shape, sometimes known as shape stabilization, drastically increased the static stability of the shell and thereby decreased the shot dispersion compared to a projectile with an ogival or conical nose, particularly in the presence of wind or turbulence. This is partly due the fact that a spike tip lengthens the distance between the center of pressure and the center of gravity of the projectile compared to an ogive tip, given an unchanged center of gravity. According to the textbook "<i>Устройство и действие боеприпасов артиллерии</i>", the center of pressure is shifted towards the rear by 6-8% of the total length of the projectile, and given that the center of pressure is behind the center of gravity, this effectively meant that the static margin is significantly increased, which translates to a greater degree of static stability. For a fin-stabilized projectile, this means that the fins exert a larger stabilizing moment at any given angle of attack, and thus, smaller fins are needed, or the fins can be located closer to the center of gravity of the projectile to exert the same stabilizing moment by having a shorter tailboom. Both approaches will reduce the lateral displacement of the shell by wind, and allow the shell to be lightened, thus allowing a higher muzzle velocity to be obtained. Both smaller fins and a shorter tailboom were implemented on the 3BK16(M), as the drawings below show.</div><div><br /></div></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-EaN0eEQ1i4Y/X5_FDAbPV5I/AAAAAAAAR8E/vDvbZ7Nd4OYUq0GwjAprkdK_PxIygBVuQCLcBGAsYHQ/s2048/bk16%2Bprojectile.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1296" height="400" src="https://1.bp.blogspot.com/-EaN0eEQ1i4Y/X5_FDAbPV5I/AAAAAAAAR8E/vDvbZ7Nd4OYUq0GwjAprkdK_PxIygBVuQCLcBGAsYHQ/w253-h400/bk16%2Bprojectile.png" width="253" /></a><a href="https://1.bp.blogspot.com/-K6iAweWtM6I/X5_s-pEMfsI/AAAAAAAAR8s/qgRwgSdesBkxEYMnteHFkHhLS8ZrGQdIACLcBGAsYHQ/s534/short%2Bfin.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="534" data-original-width="479" height="400" src="https://1.bp.blogspot.com/-K6iAweWtM6I/X5_s-pEMfsI/AAAAAAAAR8s/qgRwgSdesBkxEYMnteHFkHhLS8ZrGQdIACLcBGAsYHQ/w359-h400/short%2Bfin.png" width="359" /></a><br /></div><div><br /></div><div><br /></div><div><div>However, the primary stabilization mechanism of the spike tip is the interaction of the shock wave formed on its tip (a bow shock) with the surface of the projectile shoulder. The bow shock forms a barrier between the flow of air around the projectile and the flow of air directly around the spike tip and in front of the shoulder of the projectile body. The flow of air in front of the shoulder is stagnant as a result of this separation, and as a result of the shape of the bow shock, this zone acquires a cone shape. Within this cone-shaped stagnant zone, the air is not literally stagnant (motionless), but it primarily moves in a recirculatory manner. This zone is stable and symmetrical with respect to the velocity vector of the projectile. With spikes that are 1.5-2.0 calibers long, the border of the stagnant zone is located at the point of separation of the boundary layer, on the tip of the spike. When the projectile is yawed from external influences, the stagnant zone is shifted asymmetrically with respect to the axis of the projectile. The part of the spike tip located closer to the oncoming flow leaves the stagnant zone and is exposed to the air stream, forming a one-sided shock wave. This shock wave forms at a more acute angle than the symmetric shock wave, such that it touches the shoulder of the projectile body. This is shown on the right half of the drawing below. The air pressure at the contact patch of the shock wave generates a reaction force which acts opposite to the yawing direction of the projectile. This reaction moment thereby acts as a stabilizing moment, and its effect supplements the stabilizing moment of the stabilizer fins. </div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-9EfY77EytiI/X5_Fq_nDChI/AAAAAAAAR8U/XoDZbTKSno4iK_uLJjLHHusCC_HVxx6dQCLcBGAsYHQ/s1420/bk9%2Bshock%2Bfront%2Bcone.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1054" data-original-width="1420" height="297" src="https://1.bp.blogspot.com/-9EfY77EytiI/X5_Fq_nDChI/AAAAAAAAR8U/XoDZbTKSno4iK_uLJjLHHusCC_HVxx6dQCLcBGAsYHQ/w400-h297/bk9%2Bshock%2Bfront%2Bcone.png" width="400" /></a></div><div><br /></div><div>When an undercut (reverse taper) is present on the shoulder, the total component of the flow force is directed at an angle to the longitudinal axis of the projectile, which increases the moment generated by the righting force and thus the static stability of the projectile.</div><div><br /></div><div>As such, on top of the higher static margin, the asymmetric reaction mechanism of the spike tip allowed the static stability of the shell to rise drastically in response to disturbances. This made it possible to switch to a more efficient tail assembly with a shorter aluminium tail boom and smaller, shorter fins while having an overall increase in static stability. The lower drag of the smaller fins helps to compensate for the increased drag of the spike tip shape, but overall, these spike-nosed projectiles invariably suffer from higher drag than equivalent projectiles with ogival or conical heads.</div></div><div><br /></div><div>The most important design feature on the spike was the tapered shape of the fuze, which was used as the mechanism for eliminating dual flow that would otherwise increase drag. On spike-tipped projectiles, a bow shock forms on the blunt tip and a reattachment shock forms at a point below it. If a purely cylindrical spike was used, then dual flow (delayed attachment of the reattachment shock to the bow shock) can occur at certain velocities. Dual flow is a serious issue as it drastically increases the drag experienced by the projectile, and its formation is inconsistent, which means that the ballistic trajectory of the same ammunition can vary wildly from shot to shot. Needless to say, this would be unacceptable for HEAT shells. To eliminate dual flow at a wide range of velocities, a taper was added to the fuze, as in the case of 3BK16, or added to the spike itself. These measures ensure that the reattachment shock reliably forms at a predetermined point on the spike, and that the angle of the reattachment shock is such that it can quickly reattach to the bow shock, as shown in left half of the drawing below.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9EfY77EytiI/X5_Fq_nDChI/AAAAAAAAR8U/XoDZbTKSno4iK_uLJjLHHusCC_HVxx6dQCLcBGAsYHQ/s1420/bk9%2Bshock%2Bfront%2Bcone.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1054" data-original-width="1420" height="297" src="https://1.bp.blogspot.com/-9EfY77EytiI/X5_Fq_nDChI/AAAAAAAAR8U/XoDZbTKSno4iK_uLJjLHHusCC_HVxx6dQCLcBGAsYHQ/w400-h297/bk9%2Bshock%2Bfront%2Bcone.png" width="400" /></a></div><div><br /></div><div><br /></div><div>A common design feature of foreign spike-tipped shells to eliminate dual flow is a small ring placd a short distance behind the tip of the fuze which ensures the early separation of the reattachment shock, but the solution used by NIMI engineers was somewhat more elegant. Though the shock separation ring was an adequate solution, it ceases to function reliably at lower velocities and major inconsistencies arise in the flight trajectory of the projectile. This resulted in ammunition such as the <a href="https://cdn.discordapp.com/attachments/638345814955130890/761126215985135666/unknown.png">105mm M456 round</a> and <a href="https://cdn.discordapp.com/attachments/638345814955130890/761126558710628362/unknown.png">120mm DM12 round</a> having a drastically increased angular dispersion once the velocity drops below 660 m/s, corresponding to a range of 2 km. In the case of M456, the angular dispersion at 3,500 meters (0.62 mils) was triple that of its dispersion at 2,000 meters (0.18 mils), while the angular dispersion of DM12 was more than doubled, from 0.23 mils to 0.54 mils. This limited the usefulness of these HEAT rounds as long-range alternatives to KE rounds against heavily armoured targets.</div><div><br /></div><div>The design of 3BK16(M), as well as other Soviet HEAT rounds developed from the same research project, suffers from increased dispersion only when the projectile is destabilized by the transition from supersonic to subsonic flight. This occurs at 3,400 meters. Crossing the 660 m/s threshold, which occurs at 1,700 meters, has no effect on its dispersion. The dispersion of 3BK16(M) only degrades to 0.6 mils at a range of 4 km, which is the largest distance given in its firing table. For 3BK16(M) to degrade to the same dispersion as M456 at 3.5 km, the distance must exceed 4 km.</div><div><br /></div><div>Unlike most other projectile designs like the 125mm 3BK18 or the 122mm 3BK9, the shoulder of the 3BK16 casing does not have knurls or "teeth". The prominent knurls on other rounds was needed to ensure the smooth loading of the projectile into the gun chamber by a mechanical powered rammer, which can only push the cartridge along the surface of the chamber where the possibility of the projectile getting stuck against the shoulder of the chamber neck may arise. Such knurls were not needed on the 3BK16 shell as a human loader can insert a projectile while taking care not to scrape the shoulder of the projectile against the chamber walls. For the same reason, the 3BK15 and 3BK17 shells for the human-loaded 115mm U-5TS and 100mm D10 tank guns lacked knurls. Aerodynamically, the behaviour of 3BK16 did not differ from the projectile designs incorporating prominent knurls, as the knurls are too small to have a significant influence. </div><div><br /></div><div>Unfortunately, no information on the penetration power of any variant of the 3BK16(M) shell can be found in the public domain. It can only be assumed to be at least equal to 3BK3(M) if not slightly better. Based on the drawings available in the technical manual for the ammunition, the shaped charge cone has a diameter of 85mm and it has a built-in standoff of 2.5 calibers. Based on the semi-empirical precision shaped charge penetration graph produced by Walters and Zukas, based on the results of copper shaped charges fired against 320 BHN armour steel, the nominal penetration of 3BK16M should be expected to be no less than 425mm RHA while the penetration of 3BK16 should be around 380mm.</div><div><br /></div><br /><div>Muzzle Velocity: 1,075 m/s</div><div><br /></div><div>Cartridge Mass: 23.16 kg</div><div><div>Projectile Mass: 9.5 kg</div><div><br /></div></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">HE-Frag</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-s8BA5Mzh0pg/X95YNOz-jtI/AAAAAAAASfA/mXP5EerMeYI3Sg69Ss2Sk2RFc_ywRCbqQCLcBGAsYHQ/s1920/loading%2Bhe-frag.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="360" src="https://1.bp.blogspot.com/-s8BA5Mzh0pg/X95YNOz-jtI/AAAAAAAASfA/mXP5EerMeYI3Sg69Ss2Sk2RFc_ywRCbqQCLcBGAsYHQ/w640-h360/loading%2Bhe-frag.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The HE-Frag ammunition for the T-12 and MT-12 had a reduced propellant charge of just 3.655 kg, with no full charge option. This was the first time for such a situation to exist since the first domestic anti-tank gun, the 45mm 53-K. The cartridges were loaded with the same DG-3 propellant as in HEAT rounds and were packed in the same manner. From all available information, the HE-Frag rounds should be highly economical in terms of barrel life, not only because the gun lacks rifling, but because of the use of a reduced charge of nitrodiglycol propellant. </div><br />A highly unusual feature is the presence of a tracer, permitting trajectory observation. A tracer is normally not incorporated into Soviet HE-Frag shells, even fin-stabilized shells which provide free space in the tail boom. Fire correction with such ammunition was invariably done by merely observing the highly visible explosions on impact (burst on target) around the stationary target, with little consideration for hitting moving vehicles, for which a tracer would be most useful. Other ammunition would be used for that purpose.<br /><br />For HE ammunition, fin stabilization brings few benefits. There is no practical advantage in a non-rotating shell and the additional drag simply reduces its range, but on the other hand, fin stabilization provides the possibility to increase the aspect ratio of the shell beyond the structural limits imposed by spin stabilization. Normally, a high capacity HE shell does not exceed an aspect ratio of 5. However, most fin-stabilized HE shells do not exceed their spin-stabilized counterparts in aspect ratio. </div><div><br /><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-OMHat5fomgI/X8n60uKSs9I/AAAAAAAASOw/3dHBVK37dzQAk48q5EBD9AxhEl7mOtvpwCLcBGAsYHQ/s637/spin%2Band%2Bfin%2Bstabilized.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="617" data-original-width="637" height="388" src="https://1.bp.blogspot.com/-OMHat5fomgI/X8n60uKSs9I/AAAAAAAASOw/3dHBVK37dzQAk48q5EBD9AxhEl7mOtvpwCLcBGAsYHQ/w400-h388/spin%2Band%2Bfin%2Bstabilized.png" width="400" /></a></div><div><br /></div><div><br /></div><div>A large aspect ratio is only feasible for a spin-stabilized shell if the ordnance velocity is high enough to allow a more pointed ogive shape to be implemented, which in turn necessitates thicker casing walls to ensure stabilization. However, this design solution negatively impacts the volume available for the explosive payload and adds casing mass to the shell.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-bIQas8n4CbE/X8n9K_tMhDI/AAAAAAAASO4/y9I1lDbh9FU4JTgXHTf2ogXXQL21LUwrgCLcBGAsYHQ/s1440/optimum%2Bogive%2Bbullet%2Bshapes.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="784" data-original-width="1440" height="348" src="https://1.bp.blogspot.com/-bIQas8n4CbE/X8n9K_tMhDI/AAAAAAAASO4/y9I1lDbh9FU4JTgXHTf2ogXXQL21LUwrgCLcBGAsYHQ/w640-h348/optimum%2Bogive%2Bbullet%2Bshapes.png" width="640" /></a></div><br /><div><br /></div><br /><h3 style="text-align: left;"><span style="font-size: large;">3UOF3<br />3OF15</span></h3></div><div class="separator" style="clear: both; text-align: center;"><img border="0" data-original-height="540" data-original-width="1984" height="174" src="https://1.bp.blogspot.com/-ZblLyrADE28/X33qW_agh9I/AAAAAAAARrc/zvB9LB8zh_k6a9sDqTe3CxbqwouHacbOACLcBGAsYHQ/w640-h174/3of15.png" style="color: #0000ee;" width="640" /></div><div><div><div><br /></div><div><br /></div>The 3UOF3 was the standard HE-Frag round for the T-12 gun. It is fitted with the 6-bladed stabilizer fin assembly of the 3BK3(M) shell, and as such, the tail boom contains a No. 12 tracer though a tracer is not strictly necessary for a HE-Frag shell. </div><div><br /></div><div>Thanks to the use of fin stabilization, the body of the shell was elongated to 5.25 calibers. The effect of this was to increase the explosive payload and enhance the fragmentation effect of the shell by a combination of a more optimal weight ratio of explosives to casing, and the greater length of the shell which slightly increases the altitude of its detonation above ground level. The aspect ratio of 3OF15 is superior to the OF-412 and 3OF32 HE-Frag rounds in service for the BS-3 and D10 guns, both of which had an aspect ratio of 4.9. Detailed dimensions are available in the drawing below, taken from "Projectile and Warhead Identification Guide—Foreign, 1997, NGIC, US".</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCGk7_93bhw4qsdTNlaCTrtOuqHVmRprJlaG4y-JTUC4_mB7K24luvobQsNiUOPuheTiaHDSSNAFXDPS5QKh7LPbHVXW6Y_BeNsdBWYw_XBonBNhFOVqcpKNlo4ede7V0lc33-fhjn3sW0cqKK6f4AE_-5B2dCt8mS_k4L1d52r9NQUN21N78yn173yg/s866/dimensions.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="866" data-original-width="698" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCGk7_93bhw4qsdTNlaCTrtOuqHVmRprJlaG4y-JTUC4_mB7K24luvobQsNiUOPuheTiaHDSSNAFXDPS5QKh7LPbHVXW6Y_BeNsdBWYw_XBonBNhFOVqcpKNlo4ede7V0lc33-fhjn3sW0cqKK6f4AE_-5B2dCt8mS_k4L1d52r9NQUN21N78yn173yg/w323-h400/dimensions.png" width="323" /></a></div><div><br /></div><div><br />Due to its small propellant charge, the projectile is launched at a muzzle velocity of just 700 m/s which is somewhat low considering the relatively high operating pressure of the T-12 gun and the high muzzle velocity of its APFSDS and HEAT ammunition. The velocity alone is not unusually low relative to other reduced charge rounds for high-powered field guns, but the maximum range was negatively impacted due to the increased drag from the stabilizer fins. Because of this, 3OF15 had a maximum range of just 8,200 meters, which is achieved with a gun superelevation angle of +336 mils or +20.18 degrees. For comparison, the OF-412 shell fired from a BS-3 field gun at a reduced charge (600 m/s) reaches a maximum range of 10,200 meters when fired from the same gun elevation angle of +20 degrees. The firing table for 3OF15, digitized by Aleksandr Mandadzhiev, is presented below.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgtxb69N_M2mC1BpzQC-TaNCJUw2lBNtbSxJkhSjdQ8fcU8JtSibaAJxahdDsZ5uAZzV226MmxKpGlY-E7K4nOLJdTB-F4k7GPjz9KSEbEogxF_7mKDY5dLH4Tv5NfGj1ZNFwiTYqhEeIMLjo1py_EsO-on6CNPXuNPKfdrbWt8u8LlXwGjcSm3wm6Tww=s4556" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3210" data-original-width="4556" height="450" src="https://blogger.googleusercontent.com/img/a/AVvXsEgtxb69N_M2mC1BpzQC-TaNCJUw2lBNtbSxJkhSjdQ8fcU8JtSibaAJxahdDsZ5uAZzV226MmxKpGlY-E7K4nOLJdTB-F4k7GPjz9KSEbEogxF_7mKDY5dLH4Tv5NfGj1ZNFwiTYqhEeIMLjo1py_EsO-on6CNPXuNPKfdrbWt8u8LlXwGjcSm3wm6Tww=w640-h450" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEiPff35QNG3oOEd19cUS5y9ZOtJO16-4pmtk66CyNxpAN6wtzG8nY2h-AOIH3mRwdhOlTOBALJCfb3iMggEquGMvI3SMTqrr690tmjLyGqyMujJ7J0rKe6nKFWHsOo9xClWXZUghgeuifYZx_hBbEbfvZRbxJVplEiUQijfRpwY7Rx7acov-54iufisvw=s4557" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3221" data-original-width="4557" height="452" src="https://blogger.googleusercontent.com/img/a/AVvXsEiPff35QNG3oOEd19cUS5y9ZOtJO16-4pmtk66CyNxpAN6wtzG8nY2h-AOIH3mRwdhOlTOBALJCfb3iMggEquGMvI3SMTqrr690tmjLyGqyMujJ7J0rKe6nKFWHsOo9xClWXZUghgeuifYZx_hBbEbfvZRbxJVplEiUQijfRpwY7Rx7acov-54iufisvw=w640-h452" width="640" /></a></div><div><br /></div><div><br /></div><div>The advantage of 3OF15 lay in its larger explosive payload and better filler weight proportion, translating to a combination of a superior HE effect and a much more favourable fragmentation characteristics. The stabilizer fin assembly accounts for 9% of the total weight of the projectile, leaving the weight of the projectile warhead alone to be 15.23 kg, where the warhead casing weighs 12.56 kg, the explosive charge weighs 2.234 kg and the V-429E fuze weighs 0.438 kg. From this, the filler weight proportion is 14.6%, almost high enough to classify 3OF15 as a HE shell under the Soviet definition. Overall, 3OF15 is comparable to a 105mm M1 howitzer shell.</div><div><br />For comparison, the OF-412 shell for the D-10T has a projectile weight of 15.6 kg (casing weight of 13.7 kg) and contains a 1.46 kg TNT explosive charge, meaning that the share of the explosive charge is only 10%, which was good considering its high velocity, but lay on the threshold separating a Frag shell from a HE-Frag shell. Additionally, the 3UOF3 cartridge weighs 29.56 kg, which is marginally less than the 30.2 kg weight of a UOF-412 cartridge despite the 3OF15 shell being heavier.</div><div><br /><br />Muzzle Velocity: 700 m/s<br /><br />Projectile weight: 16.74 kg<br />Explosive charge weight: 2.234 kg<br /><br /><br /><br /><h3 style="text-align: left;"><span style="font-size: large;">3UOF12<br />3OF35</span></h3><div><br /></div></div></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-256RQCTfgTQ/X38C2OwG2gI/AAAAAAAARsE/PQ1IEb-YRFUGP0IWJ0N58fJ-58RPFTh4ACLcBGAsYHQ/s2048/3of35.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1992" data-original-width="2048" height="389" src="https://1.bp.blogspot.com/-256RQCTfgTQ/X38C2OwG2gI/AAAAAAAARsE/PQ1IEb-YRFUGP0IWJ0N58fJ-58RPFTh4ACLcBGAsYHQ/w400-h389/3of35.png" width="400" /></a></div><div><br /></div><div><br /></div><div>3OF35 does not differ structurally from 3OF15. It differs only in the switch from TNT to A-IX-2, which led to a substantial enhancement of its destructive power in terms of both its HE effect and fragmentation effect. The incendiary effect of the A-IX-2 compound supplemented the improved lethality of the blast and fragmentation.</div><div><br /></div><div>The weight of the explosive filler increased to 2.5 kg, despite no changes in the internal volume of the shell. This large improvement was achieved by pressing A-IX-2 rather than casting it, reducing the voids and thereby increasing its bulk density to 1.8 g/cc. This increased the filler weight proportion to 16.4%. This is a considerable improvement, but the effective weight is even larger due to the high explosiveness of A-IX-2. By comparing the Trauzl values, A-IX-2 is 1.86 times more explosive than crystalline TNT (530 ml compared to 285 ml) when used in enclosed casing, which is the most relevant metric for explosive bombs and shells. While a simple comparison of their calorific values shows that A-IX-2 has 1.54 times more heat energy, with a specific heat of explosion of 6.44 MJ/kg compared to a specific heat of explosion of 4.184 MJ/kg for TNT, the amount of explosive heat energy by itself says nothing about the ability of the explosive compound to do work; to transfer its explosive heat energy into the shell casing as kinetic energy. By using explosiveness as a reference point rather than the calorific value alone, a much more meaningful estimation of the blasting and fragmenting capability of an explosive can be made. A higher explosiveness has the effect of increasing energy of the fragments produced from the shell casing, which is also increased due to the higher brisance of A-IX-2. </div><div><br /></div><div>When comparing the fragmentation mass proportion with a lower limit of 0.25 grams (N0.25) and 0.50 grams (N0.5), the greater brisance of A-IX-2 evidently grants a considerable improvement over TNT. An improvement can also be seen when categorically sorting the mass range of fragments into small, medium and large fragment groups when tested empirically using a cylinder made from different grades of steel. With S-60 steel specifically, the grade used for artillery HE-Frag shells, the improvement in fragmentation performance is particularly large, producing 27.8% and 26.7% more fragments weighing 0.25 grams and 0.50 grams respectively. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-XPTBdLuSDZM/YLCRDlECWoI/AAAAAAAATMg/cUnRwA36y5kzm_dzLKYRsVeReser6IlOwCLcBGAsYHQ/s1366/fragmentation%2Bperformance%2Bof%2Bdifferent%2Bsteels%2Bwith%2BTNT%2Band%2BA-IX-2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="690" data-original-width="1366" height="324" src="https://1.bp.blogspot.com/-XPTBdLuSDZM/YLCRDlECWoI/AAAAAAAATMg/cUnRwA36y5kzm_dzLKYRsVeReser6IlOwCLcBGAsYHQ/w640-h324/fragmentation%2Bperformance%2Bof%2Bdifferent%2Bsteels%2Bwith%2BTNT%2Band%2BA-IX-2.png" width="640" /></a></div><br /><div><br /></div><div>The overall mass distribution of fragmentation was thereby considerably improved - the proportion of small fragments increased from 15% to 18%, the proportion of medium fragments increased from 26% to 35%, and that of large fragments decreased from 59% to 47%. In this case, small fragments (µм) were defined as weighing less than 1 gram. Medium fragments (µс) weigh between 1-4 grams, and large fragments (µк) weigh more than 4 grams. With a larger quantity of small and medium fragments, the probability of hitting targets is increased, thus improving the lethality radius. This is also mentioned in a patent where it is stated that, for a shell with an S-60 steel case and a TNT filler, <a href="https://findpatent.ru/patent/215/2153024.html">59% of the total fragments can be expected to have a mass of >4 grams, whereas with A-IX-2 or A-IX-20, only 47% of the total fragments do</a>. Brisance is the critical factor responsible for bursting the casing into finer splinters. Essentially, a larger proportion of the steel case is shattered into smaller and faster fragments, which increases the overall probability of enemy personnel becoming a casualty to the shell strike.</div></div><div><br /><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--vMD1y7MxPU/X5_FU_xTNqI/AAAAAAAAR8M/ltLI-RpTzEsL0OYkitQzYKiW2H5NvR7KACLcBGAsYHQ/s1200/original.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="780" data-original-width="1200" height="260" src="https://1.bp.blogspot.com/--vMD1y7MxPU/X5_FU_xTNqI/AAAAAAAAR8M/ltLI-RpTzEsL0OYkitQzYKiW2H5NvR7KACLcBGAsYHQ/w400-h260/original.jpg" width="400" /></a></div><br /><div><br /></div><div>After the casing is burst by the blasting pressure, the high explosiveness of A-IX-2 does its part in creating a strong fragmentation effect by imparting more energy into the fragments by performing more mechanical work, nominally 1.86 times more than TNT. Thanks to these two factors, supplemented by the secondary factor of a larger explosive mass, the lethal area of a shell filled with A-IX-2 is often between 1.5 to 2.0 times larger than the basic shell with a TNT filler.</div><div><br /></div><div><br /></div><div>Muzzle Velocity: 700 m/s</div><div><br /></div><div>Cartridge Mass: 28.56 kg</div><div>Projectile Mass: 16.74 kg<br />Explosive Charge Mass: 2.538 kg</div><div><br /></div><div><br /></div><div><br /></div><div><br /></div></div></div></div></div>Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com13tag:blogger.com,1999:blog-3103574899092646031.post-32025891145970719622019-09-14T08:59:00.025-07:002023-05-05T07:29:45.625-07:002S1 Gvozdika<head>
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The 2S1 "Gvozdika" was a workhorse self-propelled howitzer of the Soviet Army that served in motorized rifle units at the regimental level as well as in tank units, including the single tank regiment of motorized rifle divisions and tank regiments organized under tank divisions. The 2S1 replaced the towed D-30 howitzer in this role. Tank regiments were the first to receive the new self-propelled system and the BMP-equipped infantry regiments were second in line to be equipped with the 2S1, while BTR-equipped infantry regiments relied entirely on the D-30 until until the end of the Cold War. In practice, this meant that the bulk of the vehicles went to tank divisions as each division had three tank regiments and one infantry regiment fully equipped with BMPs. The 2S1 was also deployed in artillery divisions but their quantity depended on the specific division in question. Most Soviet artillery divisions operated a mixture of 2S1 and 2S3 howitzers with two "heavy" regiments armed with the 2S3 and one "light" regiment armed with the 2S1, but others were entirely equipped with the 2S3.<br />
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While massed assaults with shock units supported by highly concentrated massed artillery support was still part of the foundation of the Soviet Army offensive doctrine, it was emphasized to small unit leaders that they should expect to frequently participate in meeting engagements where the maneuvering forces of the two opposing sides meet unexpectedly and without preparation. The proliferation of the "Gvozdika" at the regimental level in the Soviet Army was designed so that highly mobile lower-level units could be provided with a high degree of self-sufficiency in combat as they could rely on responsive artillery support during fast-paced combat which could not be adequately provided if artillery was only available at a higher level of organization. Moreover, it should be noted that Soviet regiments were comparable to the U.S Army brigade in role, but were somewhat smaller in size which meant that the density of artillery was very high. As such, artillery support was more readily available both for indirect and direct fire purposes as dictated by the specific situation.<br />
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Additionally, it was necessary to replace the towed howitzers of the highly-mobile tank and BMP-equipped units with a self-propelled artillery system simply to keep up the pace of an offensive operation, whereas the BTR-equipped infantry units were less mobile, so the main advantage of having towed howitzers replaced with a self-propelled system would have been wasted. Of course, the idea of implementing self-propelled howitzers was by no means an original one by the late 1960's, but the mobility requirement was only firmly established at that time due to the unprecedented increase in the pace of the offensive.<br />
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During the late 1960's, the armour branch was beginning to receive the T-64, a revolutionary design that is now considered to be the first true main battle tank that boasted of an excellent power to weight ratio, a high top speed, long driving distance, excellent armour protection and a powerful gun. The tracked BMP, another revolutionary design that is now considered to be the first true IFV, was also becoming operational in the Soviet Army. It had excellent mobility that allowed them to keep up with main battle tanks. Without replacing the towed howitzers with self-propelled types, the increased operational mobility brought about by these new advanced tracked combat vehicles would have been nullified, or if the artillery elements were left behind during an advance, then the combat units would be left without artillery support. Both outcomes were unacceptable, so it was clearly necessary to develop a new generation of self-propelled howitzers to complement the recent technological advances of the Soviet Army. Indeed, in the article "<i>Soviet Self-Propelled Artillery</i>" published in the September-October 1978 issue of "<i>Armor</i>" magazine, author Larry W. Williams accurately pointed out that the then-recent introduction of new Soviet self-propelled artillery was not in response to Western developments, but rather, it was in connection with the increased demands of modern warfare.<br />
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However, the advantages of self-propelled howitzers over the towed type had always been evident even if there was no critical need for them until the appearance of main battle tanks and infantry fighting vehicles in the Soviet Army. The late appearance of the Soviet Army's first postwar self-propelled howitzer was partly due to the global obsession with missile technology from the late 1950's to the early 1960's, exacerbated by the personal intervention of Soviet Premier Nikita Khruschev in halting work on tube artillery in favour of focusing on rocketry.<br />
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As part of his large scale pivot towards missile technology and nuclear weapons, Nikita Khrushchev personally intervened to constrict the development of all types of tube artillery in 1955, resulting in most of the work on self-propelled artillery being discontinued. When Khrushchev's reign as Chairman of the Council of Ministers of the USSR was forcibly terminated on October 14, 1964, many of his policies affecting the Soviet military were reversed, one of them being the restriction on the development of self-propelled tube artillery. On the 4th of July 1967, the Central Committee of the CPSU and the Council of Ministers of the USSR issued resolution No. 609-201 decreeing the start of the development of new self-propelled howitzers. In accordance with this decree, the development of the first generation of Soviet postwar self-propelled artillery began. This generation included 122mm and 152mm howitzer systems and a 240mm mortar system, resulting in the creation of the 2S1 "Gvozdika", 2S3 "Akatsiya" and 2S4 "Tyulpan".<br />
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The 122mm D-30 was chosen to be the centerpiece of the new 122mm self-propelled howitzer at the very beginning, mainly to ensure that the commonality of ammunition was maintained when artillery units equipped with the D-30 were rearmed with the new self-propelled howitzer. Although some years had passed since the D-30 entered service, its tactical-technical characteristics were excellent and the artillery branch of the Soviet Army was satisfied with this howitzer so there was no perceived need for improvement. The new self-propelled howitzer would essentially be a D-30 on tracks with light armour to resist counter-battery fire when used in an indirect fire role or gunfire from small arms if it was used for direct fire.<br />
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Of course, a fully rotating turret was considered a mandatory feature as the vehicle needed to be capable of conducting all-round fire on a short notice to provide timely and effective fire support. The D-30 howitzer itself was already capable of all-round fire on a short notice thanks to its tripod mount, which was a noteworthy feature because one of the primary incentives to develop self-propelled guns with rotating turrets in the West was the inability for their towed guns to conduct all-round fire. Indeed, the all-round firing capability of the D-30 later proved to be a highly appreciated asset of Soviet forward bases in Afghanistan where it was the main artillery piece of the Soviet 40th Army as it allowed them to provide artillery support at a moment's notice in any direction - a feature that is still not available in the 105mm L118 and M119 light howitzers used by British and American forces in Afghanistan. It was only logical that the prospective new Soviet self-propelled howitzer would also have a feature that was already implemented in the D-30, unlike vehicles of WWII vintage like the German "Wespe", British "Sexton", American M7 "Priest" and the indigenous ISU-152, SU-122 and SU-76.<br />
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The vehicle also had to have a significant secondary anti-tank capability, and as such, it had to have a reasonably low profile and the ability to conduct direct fire using anti-tank ammunition. This was also a requirement shared by the D-30 howitzer in accordance with modern Soviet doctrine on the uses of artillery, towed or otherwise.<br />
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During the development of the prospective new self-propelled howitzer, a prototype turret with a D-30 in a new mount was created first and the tracked platform upon which it would be installed selected from other existing military vehicles. According to Russian historian A.V Karpenko, the selection was narrowed down to three options out of the myriad of choices in the vast arsenal of the Soviet Army:<br />
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<ol>
<li>A modification of the GM-123 hull with five roadwheels instead of the original seven. This hull traces its roots to the SU-100P experimental tank destroyer and was widely used as a heavy universal tracked chassis in the mid-1960's. The most prominent examples are the 2P24 transporter-erector-launcher (TELAR) and 1S32 radar station of the 2K11 "Krug" surface-to-air missile complex.</li>
<li>A modification of the Object 765 with a stretched hull and seven roadwheels instead of the original six. The Object 765 was the BMP-1.</li>
<li>A modification of the Object 6 with a stretched hull, redesigned powerplant layout, relocated driver's station, and seven roadwheels instead of the original six. The Object 6 was the MT-LB.</li>
</ol>
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The three options all used the same turret with the D-30 howitzer and all had a driving range of 500 km but differed quite significantly in their other properties. The prototype based on the GM-123 hull was quite heavy and had a very large ammunition capacity of 100 rounds. Despite a combat weight of 22.2 tons, it had a high top speed of 70 km/h thanks to its powerful 520 hp engine, but it was not amphibious. Its large weight and work capacity was deemed excessive for a 122mm howitzer system.<br />
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The prototype based on an extended Object 6 hull had a smaller ammunition capacity of 60 rounds and a lighter weight of 15.842. However, it retained the original 240 hp diesel engine of the Object 6 so it was not as quick as the other two options and had a lower top speed of 60 km/h. Like its parent design, it was amphibious with minimal preparation. However, it was an insufficiently stable firing platform.<br />
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The prototype based on an extended Object 765 hull was the preferred choice. It had an ammunition capacity of 60 rounds and it was slightly lighter than the prototype based on the extended Object 6 hull, it was readily amphibious, provided a stable firing platform, was quite speedy and easily transportable. It's worth noting that it was heavier than the BMP-1 itself with a weight of 15.164 tons but did not have an uprated engine, so although its nominal top speed remained the same at 65 km/h, it is quite likely that its acceleration and handling was affected.<br />
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The high tactical-technical characteristics of the Object 765 hull also made it an appealing option for the other artillery systems that were in development at the time. In 1969, the OKB-9 design bureau had a project to unify the "Akatsiya", "Gvozdika" and "Tyulpan" artillery systems on a single chassis based on the Object 765, where the products could have better characteristics than those created on the basis of MT-LB. Moreover, the Object 765 hull in its original configuration with six roadwheels was used as the platform for the new SNAR-10 radar system as it was considered the most suitable for this role. However, further work in this direction was hampered by the categorical refusal of the manufacturers of the Object 765, the Chelyabinsk Tractor Plant (ChTZ), to carry out the modifications needed for the installation of special equipment of any type. Moreover, the chief designer of ChTZ, Hero of Socialist Labor, USSR State Prize laureate P.P. Isakov used his influence to place a total ban on the use of his BMP to accommodate any form of special equipment. This decision also affected the development of the SNAR-10 radar system.<br />
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As a result of Isakov's antics, there was no choice but to continue the development of the "Gvozdika" using the extended Object 6 hull, and in the end, the "Akatsiya" and "Tyulpan" projects used the GM-123 hull. The ban on the use of the BMP as the carrier for special equipment was not lifted until Isakov departed ChTZ to become the director of VNII Transmash in 1974, paving the way for the ARK-1 "Rys" counter-battery radar system to be designed on the basis of the BMP-1 hull.<br />
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The first four prototypes of the 2S1 with the extended Object 6 hull were ready and tested in August 1969. The 2S1 "Gvozdika" was accepted officially into service on the 14th of September, 1971, together with the 2S3 "Akatsiya" with a 152mm howitzer and the 2S4 "Tyulpan" with a 240mm breech-loaded mortar. In connection with the simultaneous adoption of three new self-propelled artillery systems, the SNAR-10 radar reconnaissance system was also adopted at the same time, thus providing the new artillery systems of the Soviet Army with a crucial component of a modern fire control system.<br />
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Despite lagging behind Western nations in the use of self-propelled howitzers by more than a decade, the Soviet Union was able to completely eliminate the gap with their first postwar effort thanks to the maturity of their domestic arms industry. Indeed, when the 2S1 "Gvozdika" entered service, it was not only a very modern example of a self-propelled howitzer, but it easily qualified as one of the best vehicles of its type.<br />
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It is also worth noting that even though the various NATO members had continued to develop and produce new self-propelled tube artillery throughout the 1950's and early 1960's, the Warsaw Pact still retained a numerical advantage in the number of vehicles due to the extremely large stocks of ISU-152 and ISU-122 assault guns left over from the Great Patriotic War. However, despite a major modernization effort for the old ISU-122 and ISU-152 in 1958-59 to turn them into the ISU-122M and ISU-152M, the inherent limitations of these old assault guns made it impossible for them to fulfill modern requirements such as the ability to carry out all-round fire, so it is not surprising that the number of self-propelled guns was constantly dwindling after the conclusion of the Great Patriotic War. Nevertheless, the Warsaw Pact was not in any serious danger of being quantitatively overtaken by NATO in terms of self-propelled artillery as a class of weapons because the Soviet Union developed many highly effective multiple rocket launcher systems like the BM-14 with 140mm rockets and the BM-24 with 240mm rockets to supplement the older BM-8 and BM-13 systems which used 82mm and 132mm rockets respectively. Of course, the BM-21 "Grad" should also be mentioned as being an outstanding example of the superiority enjoyed by the Warsaw Pact in this class of artillery. The graph below, taken from the 1984 edition of "<i><a href="http://insidethecoldwar.org/sites/default/files/documents/NATO%20and%20Warsaw%20Pact%20Force%20Comparisons%201984.pdf">NATO and The Warsaw Pact Force Comparisons</a></i>", shows the advantage held by the Warsaw Pact in the quantity of artillery from 1974 to 1984 as perceived by NATO intelligence.<br />
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With that said, the 2S1 was quite a simple vehicle compared to the modern main battle tanks fielded by the Soviet Army in the early 1970's. By the standards of other self-propelled howitzers, the "Gvozdika" was sophisticated in terms of its overall capabilities, yet it was cheap and simple to operate. Its qualities were not only appreciated in the army of its native country but also by foreign users such as the Finnish Army, who bought a number of vehicles from the ex-NVA in 1991.<br />
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<h3>
<span style="font-size: large;">ERGONOMICS</span></h3>
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The "Gvozdika" has a conventional crew layout with the commander seated at the rear left quadrant of the turret, the gunner seated in front of him at the front left quadrant, and the loader occupying the entire right half of the turret. The driver is seated on the front left corner of the hull with the engine to his right and the transmission and final drives to his front.<br />
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During WWII, the USSR and Nazi Germany carried out independent research on self-propelled artillery design and reached the same conclusion regarding the layout of this type of combat vehicle. The optimal layout would have the engine and transmission placed at the front, the driver would be seated next to the engine and behind the transmission, and the fighting compartment would be in the middle or rear together with the ammunition stowage racks. This provided the best working conditions for the crew and allowed ammunition to be easily passed into the fighting compartment through the hull rear while maintaining compactness of the vehicle. A major benefit of this layout was that the overhang of the gun or howitzer was kept to a minimum or eliminated entirely.<br />
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After the war ended, practically all known self-propelled guns and howitzers created internationally followed this layout regardless of whether they were open-topped or fully enclosed designs, or if they were turreted or not. In the USSR, self-propelled guns were actively being developed immediately after the war and the fruits of these labours were Object 105 (SU-100P) and Object 108 (Object 152G). However, no new Soviet self-propelled howitzers were created, although studies were conducted in the USSR from 1947 to 1953 in this direction.<br />
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The hull was derived the MT-LB, but it was not only lengthened with an additional pair of roadwheels. A basic MT-LB had the commander and driver seated side by side at the front, and had its engine installed in the center of the hull with the drive shaft connecting the engine and transmission passing between the seats of the two crew members. It was already decided that the commander would inhabit the turret of the new prospective self-propelled howitzer during the development of the new vehicle, so the MT-LB layout had to be drastically overhauled. This was the most rational distribution of weight and volume for a self-propelled howitzer, and of course, the lengthened ground contact length of the seven pairs of roadwheels made the "Gvozdika" hull a significantly more stable firing platform compared to the basic MT-LB hull. The MT-LB hull had a length of 6,262mm, whereas the 2S1 hull had a length of 7,260mm.<br />
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With a total length of 7,260mm and a width of 2,850mm, the 2S1 "Gvozdika" exceeds most main battle tanks in length and is ostensibly narrower, but this is only because it uses narrower tracks as a result of its low weight. When the width of its hull is compared to a tank like the T-54, the "Gvozdika" is somewhat wider, having a width of 2,100mm instead of 2,000mm.<br />
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The "Gvozdika" was not particularly tall compared to a Soviet medium or main battle tank as it had a height of 2,285mm when measured up to the turret roof, and its height was extremely modest when compared to typical Western self-propelled howitzers like the M109 as that had a height of 2,896mm when measured up to the turret roof. The "Gvozdika" is much closer to tanks like the Leopard 1 and the Chieftain in this respect. When measured up to the top of the OU-3GA spotlight on the commander's cupola, the "Gvozdika" is 2,740mm tall. Internally, the height of the fighting compartment is around 1,700mm. This is enough for a man of average height to stand with a bowed head but not upright since the standard issue boots and helmet add some additional height.<br />
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The turret ring diameter of the 2S1 was not listed in any publicly available literature that the author could find, but based on the drawings shown in the technical manual, the diameter is around 2,140mm. This is a little larger than the turret ring of the T-10 heavy tank (2,100mm) but smaller than the turret ring of the T-62 (2,245mm). It is worth noting that even though it is significantly smaller than the 2,500mm turret ring of the American M109, it is more than adequate for a self-propelled howitzer with a three-man turret which is an important distinction to make since the M109 had five men inside its turret of which only one was seated. The other four men had to be standing and moving around to carry out their duties. In the "Gvozdika", two of the three crew members in the fighting compartment fought from their seats and the third crew member, the loader, was greatly aided by a rational ammunition layout and a well-designed loading assistance device.<br />
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Thanks to the relatively large dimensions of its thinly armoured hull and turret, the 2S1 had a large internal volume that not only facilitated its amphibious qualities but provided good working conditions for the crew inside the vehicle, particularly for the loader who had enough space in the fighting compartment to move freely.<br />
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Inside, the fighting compartment is well-lit with three dome lights fitted on the turret ceiling. There is one dome light directly above the gunner's seat, one behind the commander's cupola, and one on the ceiling next to the howitzer.<br />
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<h3>
<span style="font-size: large;">VENTILATION</span></h3>
The ventilation system of the 2S1 consists of two filter-ventilator units, an FVU-100 filter-ventilator unit located in the driver's compartment, and an FVU-200 filter-ventilator unit in the turret, installed in a large compartment in the turret bustle behind the commander's station. It can be accessed from outside the turret via a large rectangular hatch on the bustle roof, and its air intake is also located on the roof. It is opened or closed via a servo, with a switch placed in the commander's station. The FVU-100 is an entirely separate unit for the driver with the same functions as the FVU-200, because the driver's compartment is physically partitioned from the fighting compartment. However, to ensure that the overpressure in the vehicle is equalized at all points, the driver's compartment is connected to the fighting compartment by a pipe passing through the cooling system casing to the left of the radiators.<br />
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The FVU-200 filter ventilator unit includes a VNSTs-200 supercharger that pressurizes the air inside the crew compartment including the driver's compartment which is physically isolated from the fighting compartment at the front of the hull. The supercharger is driven by an ED-25 electric motor, which has a direct connection to the impeller of the intake and compressor rotors. To prevent high frequency radio noise from arising in the power supply for the supercharger motor, which can interfere with the radio system, an F-1 radio interference filter is fitted to the power supply unit. The supercharger uses centrifugal separation to filter out coarse particles from the air, and a high air flow is produced to generate an internal overpressure in the vehicle.<br />
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<div><br /></div><div>When operating in an environment contaminated with nuclear, chemical or biological contaminants, the FVU-200 and FVU-100 units are switched to the filtering mode, whereby the air taken into the vehicle first undergoes coarse filtration via the supercharger and then fine filtration via the FTP-200M filter, which is a HEPA filter unit. Only then is the air released into the crew compartment.</div><div><br /></div>For basic ventilation during normal operation in uncontaminated environments, the FVU-200 and FVU-100 units simply act as ducted fan systems, drawing air into the vehicle and distributing it via the air ducts around the crew stations. The FTP-200M filter is bypassed. <br /><br />
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<h3>
<span style="font-size: large;">COMMANDER'S STATION</span></h3>
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The commander in a 2S1 was seated behind the gunner and was separated from the D-32 howitzer by a removable perforated sheet steel recoil guard. In combat, he was responsible for radio communications, relaying target position information to the gunner, and designating targets with his own surveillance instruments. He was also responsible for making the necessary calculations for firing upon map coordinates if the vehicle is used independent of a battery command network.<br />
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The commander's seat was attached to the turret ring. The seat is adjustable in height for the commander's personal comfort and it can be folded down flush against the turret basket. The commander's seat is higher than the gunner's seat, but the amount of headroom provided for him is similar because he has a cupola.<br />
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The cupola protrudes slightly above the turret roof and has the same thickness of armour as the turret, while the commander's hatch has the same thickness as the turret roof. The hatch has a dome-shaped bulge in the center to ensure that the commander has adequate headroom when he is positioned to use the periscopes. Overall, the cupola protrudes almost 20 centimeters above the level of the turret roof.<br />
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The internal surface of the cupola platform was marked with an azimuth ring that divided the full circle of the cupola platform into 6,000 mils (as per the Soviet definition) in major increments of 100 mils that were further divided into minor increments of 20 mils. When the cupola is aimed directly forward at the 12 o'clock position, an indicator needle fixed to the rotating cupola is aligned with the zero position of the fixed azimuth ring. The zero position of the azimuth ring corresponds to the 30-00 mil position. If, for example, the cupola is turned counterclockwise by 500 mils, the cupola will be in the 35-00 mil position and the indicator will point at the number "5" on the azimuth ring.<br />
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This simple and rather imprecise measuring system is only intended to allow the commander to be cued to a target or landmark by the battery commander or for the commander to cue the gunner to a certain bearing with just enough precision to allow the gunner to independently spot a target. For example, if the commander needs the gunner to look at a particular object in the distance, he orders the gunner to traverse the turret to the deflection angle reading of the azimuth ring.<br />
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As usual, the hatch becomes a protective shield for the commander when it is locked in the open position. For maximum protection, the commander can adjust the height of his seat so that he is minimally exposed when standing on it. Ideally, he should only have his head peeking above the edge of the hatch.<br />
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Like all contemporary Soviet tanks, the commander was furnished with a TKN-3B periscope, but this universal device was only supplemented by two TNPO-170A general vision periscopes to cover the forward 120-degree arc. The layout was typical for Soviet armoured fighting vehicles, but this meager array of periscopes would not have been acceptable for a tank. The amount of visibility offered by this cupola layout only corresponded to the commander's cupola of the BMP-1 which had the same number of periscopes in the same layout. It was more than adequate given the role of the "Gvozdika" due to the nature of the role that artillery played, even when used for direct fire. In fact, it could even be considered outstanding when compared with other self-propelled howitzers, since the FV433 "Abbot" had the same number of periscopes in the commander's cupola in the same layout but lacked a magnified periscope with a night vision capability like the TKN-3B. The commander of an M109 had even more limited visibility given that he relied entirely on a single forward-facing periscope.<br />
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In most cases, the advantage in vision and situational awareness that a 2S1 commander enjoyed did not really matter because the vehicle would most often be in a situation where it would be safe to fight with open hatches. As such, the "Gvozdika" would only have a real advantage over a contemporary foreign vehicle of its class when the crews are forced to fight with closed hatches. This may be because of an NBC threat or because of counter-battery fire.<br />
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The TKN-3B periscope in the 2S1 has already been discussed in other Tankograd articles and there is no sense in repeating what has already been said about this ubiquitous family of periscopes in this article. It is only worth mentioning that the target designation feature of the periscope was deleted due to the lack of a need for this feature on a self-propelled howitzer. Moreover, the electrical powered traverse system of the vehicle was quite rudimentary and could not support such a feature. Target designation would have been done with the help of the commander's cupola azimuth ring.<br />
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For communications, the 2S1 was equipped with the R-123 radio. It was mounted to the turret wall just next to where the commander would be seated, with its power supply unit mounted on the turret wall to its left. The R-123 radio had a frequency range of between 20 MHZ to 51.5 MHZ. It was mainly used to communicate with the battery command vehicle and with the other vehicles in the battery.<br />
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The commander's control panel, installed on the turret wall above the R-123 radio, was small and simple. On it were three toggle switches that allowed the commander to turn on the marker lights at the corners of the hull, turn on the supercharged blower of the ventilation unit (to generate an internal overpressure) and turn on the electrical power to the cupola to power up the TKN-3B periscope.<br />
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<h3>
<span style="font-size: large;">GUNNER'S STATION</span></h3>
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Thanks to the relatively large volume of the turret, the gunner of a 2S1 not only had a seat but also had his own backrest, which was not present in a T-54 or T-62 due to the close distance between the gunner and the commander. Generally speaking, the gunner is comfortably seated, but unlike the gunners of Soviet tanks like the T-54, T-62, T-10, T-64 and T-72, 2S1 gunners were not provided with a unity periscope for general observation, so like the commander, he has significantly less overall visibility compared to his tanker counterparts in the Soviet Army. He relies entirely on his sighting instruments to survey his surroundings and he must either turn the turret while looking through the OP5-37 direct fire sight to view his surroundings or use his PG-2 panoramic sight, but generally speaking, he is completely subordinate to the commander during combat. This was not a major issue for a self-propelled howitzer simply because of its role and it is not surprising that the entire crew in the fighting compartment of the 2S1 has worse visibility compared to a tank crew.<br />
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The gunner has a control panel of his own, mounted on the turret wall above the turret azimuth indicator clock. The control panel contains fewer controls than the commander's control panel, but it has many more signal and warning indicators. Besides the three sockets at the bottom of the panel that connect to the turret, the entire panel is devoted to displaying valuable information to the gunner.<br />
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Across the top of the control panel, there is a signal lamp that indicates if the external howitzer travel lock at the front of the vehicle is stowed, a lamp warning that the driver's hatch is open, a lamp warning that the driver's windshield cover is open, a lamp warning that the rear door of the hull is open, and a readiness indicator lamp that signals if the electrical system in the turret is ready for operation. At the center of the panel, there is an instructional drawing that represents the vehicle with labels showing the permissible firing arc when the rear door is open and the size of the dead zone for the turret when the driver's hatch is open. When the turret is within the permissible firing arc of 120 degrees, the howitzer can be fired using its electric firing mechanism while the rear door of the hull is open, but if the turret is outside of this firing arc and the rear door is open, the electric firing mechanism is deactivated. When the turret is traversed while the driver's hatch is open, the electrical traverse mechanism is automatically braked when it reaches the designated sector around the driver's hatch. In this dead zone, turret traverse can only be accomplished manually.<br />
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At the left side of the panel, there is a toggle switch that allows the gunner to activate or deactivate the turret electrical traverse drive, and at the right side of the panel, there is a toggle switch that turns on electrical heating for the gunner's sighting instruments.<br />
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<span style="font-size: large;">SIGHTING INSTRUMENTS</span></h3>
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The 2S1 had basic sighting equipment for indirect and direct fire so that it could complete a fire mission independently of external fire control systems with the same accuracy as traditional artillery systems. However, this was normally not required as there was a network of artillery reconnaissance and fire control equipment to direct the "Gvozdika" more accurately. Like any other artillery complex of the 1970's, fire control was handled by surveillance vehicles like the PRP-3 that operated far forward of the howitzer batteries, and the SNAR-10 ground artillery reconnaissance radar operated at the division level. Moreover, the battery command vehicle integral to each battery carried a DAK-1 laser rangefinder. The main purpose of the laser rangefinder was to measure the range of reference points in the distance, but it could also be used to measure the range to enemy troops for direct fire.<br />
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The two sighting instruments installed in the 2S1 "Gvozdika" were the OP5-37 direct fire telescopic sight and the PG-2 panoramic sight. They were mounted side by side and take up minimal space.<br />
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However, the "Gvozdika" did not have the ability to carry out direct fire missions at night as it had no night vision sights or other suitable gunnery equipment for this purpose.<br />
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<span style="font-size: large;">OP5-37 DIRECT FIRE SIGHT</span></h3>
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The OP5-37 sight was a variant of the common telescopic direct fire sight for artillery pieces, similar to the OP4M-45 sight of the D-30 towed howitzer. It differs in that the OP5 permits only vertical adjustments. The objective assembly of the sight features a rotating mirror mechanism, providing a view parallel to the axis of the howitzer. This system was needed to ensure that the eyepiece is stationary relative to the gunner's head while the objective assembly moves to match the large elevation angle of the howitzer. An advantage of this mechanism is that it is more compact than the articulating mechanism of TSh and TSh2 series tank sights.<div><br /></div><div>Like all Soviet direct fire telescopic sights, the OP5-37 had a fixed 5.5x magnification and a field of view of 11 degrees. It can be elevated from -5 degrees to +20 degrees. The magnification of the sight was noticeably lower than that of a typical Soviet medium tank like the T-55 and T-62 (7x) or a heavy or main battle tank (8x), but it was adequate for the 2S1 due to the limited effective range of the howitzer. The viewfinder of the sight had the same type of markings and the same range adjustment mechanism used in Soviet tank sights since the TSh-16, first used in the later half of the Great Patriotic War.<div><br /></div><div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ktNY0NSR3tk/X9wl-wPSaGI/AAAAAAAASeY/IzjaVFuSmho9FcJ0McncOs0-kpSqyIlwgCLcBGAsYHQ/s1267/OP5%2Bsight%2Boptical%2Bscheme.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="390" data-original-width="1267" height="198" src="https://1.bp.blogspot.com/-ktNY0NSR3tk/X9wl-wPSaGI/AAAAAAAASeY/IzjaVFuSmho9FcJ0McncOs0-kpSqyIlwgCLcBGAsYHQ/w640-h198/OP5%2Bsight%2Boptical%2Bscheme.png" width="640" /></a></div><div><br /></div>
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As the viewfinder below shows, this particular sight was configured to allow direct fire with HE-Frag shells with a full charge and BK13 HEAT shells. It was also possible to fire different ammunition types or HE-Frag shells with reduced charges, but to do this, the gunner must refer to a firing table to obtain the necessary superelevation angle corresponding a desired firing range, and then use the mil scale on the right side of the viewfinder (marked 'ТЫС' in the photo below) to adjust the superelevation of the howitzer.<br />
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To adjust the range, the gunner turns the range adjustment dial protruding beneath the eyepiece of the sight to lower the range scales until the correct range increment aligns with the fixed horizontal line in the viewfinder. The center chevron in the viewfinder lowers together with the range scales, thus generating the ballistic solution. When the chevron is raised and placed onto the target, the howitzer gains the necessary superelevation angle.<br />
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Unlike a TSh-type sight, the OP5-37 was linked to the howitzer by a parallelogram linkage instead of a more direct coaxial linkage. However, due to the howitzer's large range of elevation angles and the rather limited range of angles permitted by the linkage system, the OP5-37 was designed to disconnect from the howitzer when its elevation angle exceeded +20 degrees and reconnect itself when the howitzer returned to this angle. This is done with an induction sensor built into the rotor of the alignment mechanism. When the howitzer is depressed to within the elevation range permitted by the OP5-37, the gunner is informed by signal lights. <div>
<div><br /></div>The parallelogram linkage can be seen in the drawing below connecting the head of the sight to the trunnion pin of the D-32 howitzer.</div><div><br />
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The reason for the use of this type of mechanical link with the howitzer was because the howitzer was recessed rather far into the turret and its pivot point was therefore quite far behind the location of the sight, whereas the gun of a tank like the T-54 had its trunnion pin just behind the embrasure for the gun mask, so its pivot point was directly coaxial with the gunner's telescopic TSh sight.<br />
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The aperture window of the sight was partially shielded from the weather by a sheet metal hood, and the window itself had a manually-actuated wiper for the gunner to clean it of dust and rain.<br />
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<span style="font-size: large;">PG-2 (1OP40) PANORAMIC SIGHT</span></h3>
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The PG-2 was a conventional panoramic sight that could be used for both indirect and direct fire, but its main purpose is to allow fire corrections and target transfer for indirect fire. As one would expect, the sight provides a panoramic view in a full 360-degree circle. The vertical range of motion of the sight is limited to 3.55 degrees in elevation and depression. It had a fixed 3.7x magnification and a field of view of 10.5 degrees.<br />
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When used in its indirect fire role, the PG-2 sight has two range drums for the gunner to traverse the turret to a new bearing with various degrees of precision. The range drums are located behind the eyepiece of the sight, and they are positioned so that the gunner can look through the eyepiece with his right eye and also see the range drums so that he can quickly adjust the deflection of the sight.<br />
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The two range drums are used to measure the deflection angle of the panoramic sight. The bottom drum has the coarse adjustment scale with increments of 100 mils per division. A full circle is divided into 6,000 mils under the Soviet definition, so there are 60 increments marked on the drum. The top drum has the fine adjustment scale with increments of 1 mil per division with 100 increments marked on the drum from 0 to 99. When the deflection of the sight is set to 30-00, the line of sight is parallel to the bore axis of the howitzer, and increasing the deflection angle offsets the sight counterclockwise whereas decreasing the deflection angle offsets the sight clockwise. <br />
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To use the PG-2 to lay the howitzer onto a target, the gunner uses the sight as a goniometer. This was the standard method of gun laying for indirect fire at the time. Radio masts, telephone poles, windmills and other structures of a similar shape were considered to make for the best reference points as they are clearly visible from great distances and are easy to align with the vertical markings in panoramic sights. To use the PG-2 to aim the howitzer in azimuth, an external artillery director informs the battery commander to adjust the howitzers to a certain deflection angle relative to the reference point. For example, if a target is 660 mils to the right of a windmill, then the 2S1 gunner would set the PG-2 sight to the 36-60 setting, thus placing it 660 mils to the left of the bore axis of the howitzer. Then, when the gunner aims at the windmill, the howitzer would be laid 660 mils to the right of the windmill.<br />
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When deployed in a traditional line formation in equal intervals of 20 to 40 meters between each howitzer, it is easier to coordinate each tube to compensate for their own displacement from the firing line. This simplifies the calculations for accurate fire, thus enabling quicker reaction times to be achieved.<br />
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When not in use, the sight was fully retracted into the turret and a cover was closed over it. A rubber sleeve ensures that a hermetic seal is maintained regardless of whether the sight is raised or retracted. This can be seen in the drawing on the left below. The cover that is closed over the panoramic sight has the same armour thickness as the rest of the hull roof. It is manually operated by the gunner, with a handle on the turret ceiling for this purpose.<br />
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The short video clip below shows the PG-2 sight head being pushed through the rubber sleeve. <a href="https://youtu.be/jlESoZhg760">Original video from Denis Mokrushin.</a><br />
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<h3>
<span style="font-size: large;">LOADER'S STATION</span></h3>
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The loader in a 2S1 had little else to do but load the howitzer and arrange the ammunition. In connection with these duties, he was also responsible for setting the fuzes on shells and adjusting the weight of the propellant as required before each round is loaded. For general vision, he is provided with a single MK-4 periscope (Gundlach periscope) which gives him a decent all-round view of his surroundings.<br />
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The image below, taken from a show by TV Zvezda, shows an interesting perspective of a seated 2S1 loader grasping his MK-4 periscope for stability.<br />
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The photo below by Vladimir Yakubov shows the loader's periscope and hatch in more detail together with the ammunition racks affixed to the turret wall.<br />
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Some time after the beginning of the mass production of the 2S1, a circular port was added to the turret wall of the loader's station for the disposal of spent cartridge cases. It served as a safe and convenient opening for the loader to dispose of spent shell casings as he would not need to lift the casing up above his head and forcefully throw it out of his hatch, thus saving him energy and maintaining overhead protection. The photo below shows the port cover as viewed from outside the turret. It has been welded shut in this example, but the simple spring-loaded hinge mechanism can be clearly seen.<br />
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To use it, the loader must first unlock it by unscrewing and removing the crossbar that keeps the port cover tightly sealed, but after this, the loader can simply pick up a spent casing and push it out of the port with its base against the spring-loaded port cover. Once the casing clears the port, the cover automatically closes under spring tension.<br />
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Although it seems to offer a good alternative entryway for fresh cartridges when replenishing the ammunition of the vehicle as it led directly to the loader's station, it was not feasible to use the disposal port for this purpose because there was no way to keep it open without partly dismantling it, and even so, it would be redundant because the rear hatch in the hull was more than good enough.<br />
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<h3>
<span style="font-size: large;">LOADING ASSISTANCE DEVICE</span></h3>
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<a href="https://1.bp.blogspot.com/-dqU0u9YrcZI/XVsBn2hR8mI/AAAAAAAAPAE/88O9yLZyiqkvkaBZzp_HUo2BiaY9q0RLwCLcBGAs/s1600/loading%2Bassistance%2Bdevice.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1144" data-original-width="1212" height="302" src="https://1.bp.blogspot.com/-dqU0u9YrcZI/XVsBn2hR8mI/AAAAAAAAPAE/88O9yLZyiqkvkaBZzp_HUo2BiaY9q0RLwCLcBGAs/s320/loading%2Bassistance%2Bdevice.png" width="320" /></a></div>
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The loader's work was made easier by a powered loading assistance device, but because the weight and size of 122mm ammunition was still quite manageable, a semi-automatic loading system with a mechanized ammunition rack such as the type used in the 2S3 "Akatsiya" was not deemed necessary. As such, the loader had to manually transfer projectiles and propellant charges from the fixed ammunition racks fitted around the vehicle into the loading assistance device. This was first serially implemented on the SU-122-54 tank destroyer and T-10 heavy tank, and it is a feature that the "Gvozdika" shares in common with many other vehicles of its type such as the M109 and the FV433 "Abbot". However, the specific design of the loading assistance device in the 2S1 was particularly good as it required minimal physical effort on the loader's part and most importantly, the device worked at all elevation angles but particularly well when the howitzer was aimed at a high angle.<br />
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The loading assistance device increases the rate of fire of the 2S1 on the whole, but it is most helpful for increasing the sustained rate because it substantially reduces the physical burden on the loader when the howitzer is fired for prolonged periods. Unlike a tank loader who is not expected to have many opportunities to expend his entire supply of ready ammunition, a howitzer loader was expected to expend hundreds of rounds of ammunition over the course of a few hours.<br />
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The two photos below show the loading assistance device from the perspective of the commander. The photo on the left shows the device in its standby position with the tray in the raised attitude, ready to accept a fresh shell, whereas the photo on the right, taken <a href="http://guide.sportsmansguide.com/sg-buyers-log-european-military-surplus-tour-1st-stop-poland/">by John Manion and published in the Sportsman's Guide website</a>, shows the loading tray lowered and ready for ramming while the device remains in the standby position.<br />
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To load the D-32, the loader must first receive the order to load a specific type of ammunition from the commander but in most cases, the loader's job is quite straightforward as he would only need to repeatedly load HE-Frag shells. If the 2S1 is ordered to complete a quick shoot-and-scoot fire mission lasting no longer than 5 minutes in duration, the loader would simply be told to load a specific number of shells in a sustained burst at the maximum possible rate or until the order to cease fire is issued.<br />
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The full loading procedure is demonstrated in a number of videos on YouTube and other video streaming sites, and it can be seen in the short clip shown below.<br />
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When loading, the loader picks up a projectile from the closest ready rack and places it on the loading tray. Then, he shoves the entire loading assistance device against the resistance of a pair of returns springs until the device is locked in place behind the breech, whereupon the ramming cycle immediately begins. The loading tray is automatically moved forward and the tray is tilted down onto the U-shaped channel behind the breech block, aligning the projectile with the barrel chamber, and the rammer simultaneously performs a full stroke to ram the projectile all the way down the gun tube to seat it properly against the rifling.<br />
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Immediately after moving the loading assistance device into position behind the howitzer, the loader locates and retrieves a propellant charge and adjusts the propellant weight unless he has already done so in preparation. By the time the loader has retrieved a propellant charge, the mechanism would have finished the ramming cycle for the projectile. When placing the propellant charge on the freshly vacated loading tray, the loader should ensure that the base of the charge is in contact with the rubber-padded tip of the chain rammer. Finally, the loader presses the big red "ram" button on the recoil guard just next to the howitzer breech, whereby the device sends the chain rammer to perform a short stroke to ram the propellant charge into the gun. Once the rammer is fully retracted, the loading tray is also automatically retracted and the device is immediately pulled back to the ready position by the return spring and locked in place, preparing itself to receive the next shell.<br />
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The firing mechanisms of the howitzer are disconnected by the loader's safety system until the loading process is complete. However, the loader can manually set the status of the howitzer firing mechanism from a control box on the recoil guard in front of the loading assistance device.<br />
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Before the first shot is fired, or rather, before the order to fire is received, the loader can preemptively place a shell on the loading tray and have a propellant charge ready in his hands. This is otherwise known as "laploading". It is safe for the shell to be readied in this manner because the tray is designed to prevent it from accidentally rolling off or sliding out, and it is not problematic for a self-propelled howitzer to be laploaded because the target does not change on the fly in a typical mission. It is only a potential problem for tanks because tanks are most often used for direct fire against a mixture of infantry, soft-skinned vehicles, lightly armoured fighting vehicles, other tanks, and fixed fortifications. This requires the loader to constantly switch between AP or APDS or APFSDS, HEAT, HESH, HE, and so on.<br />
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Unlike tanks, a howitzer is usually called upon to deliver a bombardment of the same ammunition type on a fixed area target, most often using HE shells. By enabling the loader to prepare a shell in advance, the burst rate of fire of the "Gvozdika" in the first minute of a barrage can be slightly higher than the average figures that are usually reported.<br />
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The loading tray of the loading assistance device is helpful in other ways as well. Besides allowing the loader to load more quickly, it also makes it more convenient for him to set the fuze. The fuze of a typical OF-462 shell is set to the HE-Frag mode at the factory and the loader can set it to the HE or Frag mode under orders from the commander. The decision on the most appropriate fuze setting comes from the artillery reconnaissance units.<br />
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The general design of the device is focused on facilitating the loader's work to the maximum extent when the howitzer is used for high elevation indirect fire. Unlike the very similar loading device in the T-10 heavy tank, the loading tray, shown in the drawing below, has tall side walls to ensure that the projectiles and propellant charges held inside are properly aligned with the bore axis and do not fall off regardless of the elevation angle of the howitzer.<br />
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When the howitzer is used for direct fire, the breech would tend to be either close to being completely level, or elevated by +3 degrees while the muzzle end is depressed by -3 degrees, or depressed by up to -3.6 degrees (60 mils) when the muzzle end is elevated by +3.6 degrees to exploit the maximum direct fire range permissible from the OP5-37 sight. At these angles, the loading assistance device is slightly less convenient for the loader to use since he has to lift a shell and a propellant charge to his shoulder level to drop it into the loading tray. In fact, the bump in the turret roof is meant to give the loader more space to do this when the howitzer is fully depressed, as the entire rear end of the howitzer would be quite close to the turret ceiling. The device does not restrict the loader in any sense and it is not an obstacle for the loader, and it is still effective at aiding him in his work, but it requires him to expend more energy to do the same task.<br />
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Once the tray is in position behind the breech, a microswitch is tripped and the chain rammer begins its ramming cycle. As the chain rammer travels forward, the loading tray is pushed forward by an actuator and this action causes it to tilt downwards by slide along a curved rail.<br />
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The loading tray is shown in the drawing below in its two principal loading positions: in the "ready" position and the "ramming" position. The drawing also shows the return springs that pull the device back to the "ready" position after the loading cycle is complete.<br />
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The device was a self-contained unit that could be removed from the recoil guard of the D-32 howitzer to revert to a fully manual loading method, so if the device fails completely, it is possible to load the howitzer manually. The loader inserts the projectile and propellant into the breech by hand and the commander participates by using a ramming staff to replace the powered rammer. To do this, he can fold down his seat and remove the recoil guard separating his station from the howitzer.<br />
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<h3>
<span style="font-size: large;">AMMUNITION STOWAGE</span></h3>
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The vehicle carried 40 rounds of 122mm ammunition of which 24 were in the ready racks in the turret and 16 were in the reserve racks in the rear hull compartment. The ready racks on the turret wall and turret basket hold a propellant charges and projectiles respectively whereas the ready racks in the turret bustle mostly hold propellant charges.<br />
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The projectile racks hold their projectiles by cupping the tapered part of their boattails or by supporting them by the ring at the base. The projectiles are further secured by a quick-release tension latch.<br />
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The ready racks in the turret bustle contain 5 HEAT shells and 17 propellant charges. The HEAT shells were stowed in a special set of slots in the corner of the turret bustle where the greater length of the shells compared to the propellant charges would not interfere with the loader as they would not stick out into the fighting compartment.<br />
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The reserve propellant charge racks occupy both sides of the rear compartment, leaving a large empty space in the middle to allow the loader to retrieve the propellant charges freely. The top half of the rack held 8 propellant charges and the bottom half held 8 projectiles for a total of 16 rounds of ammunition. The two racks in the rear compartment were identical and were installed symmetrically.<br />
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The two photos below show the reserve racks being replenished with a new HE-Frag shell and a new propellant charge.<br />
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<a href="https://1.bp.blogspot.com/-odaUY_dyuYQ/XXV5DFR1IKI/AAAAAAAAPJE/Mfi09LvtAY4sB22uu2ttlEbAJp-vdjtugCLcBGAs/s1600/replenishing%2Breserve%2Bracks.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="719" data-original-width="1280" height="223" src="https://1.bp.blogspot.com/-odaUY_dyuYQ/XXV5DFR1IKI/AAAAAAAAPJE/Mfi09LvtAY4sB22uu2ttlEbAJp-vdjtugCLcBGAs/s400/replenishing%2Breserve%2Bracks.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-BTsCabgoJvI/XVLtr1m1VqI/AAAAAAAAO6g/V5HOicF0NKEQRQY0dNo6fjqzWPoqv79vQCLcBGAs/s1600/ammo%2Bracks.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="265" src="https://1.bp.blogspot.com/-BTsCabgoJvI/XVLtr1m1VqI/AAAAAAAAO6g/V5HOicF0NKEQRQY0dNo6fjqzWPoqv79vQCLcBGAs/s400/ammo%2Bracks.jpg" width="400" /></a></div>
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Besides simply allowing the propellant charge racks to be accessed, the empty space in the rear compartment had a variety of other functions. The most obvious function, of course, was that it could serve as a passageway for the crew to exit through the rear doors, but if the "Gvozdika" was used in a static position for sustained fire, this space would be used to link a conveyor chute from the rear door to the fighting compartment. The conveyor chute, shown in the drawings below, is a simple device with a fixed spine and a sliding tray that moves along the spine. Like a curtain rod, the spine of the conveyor fits over two crossbars that are screwed to special threaded holes at both ends of the compartment.<br />
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When disassembled into three individual parts, the conveyor is stowed inside the vehicle on the floor underneath the reserve ammunition racks. When needed, it is installed by the loader while the other members of the crew go about their own tasks. First, he opens the rear door and then he installs the conveyor crossbars, one of them just behind the frame of the rear door and the other just behind the turret basket. This only takes around 20 seconds to complete, as demonstrated in the short clip below. The <a href="https://youtu.be/jlESoZhg760">original video is by Denis Mokrushin</a>.<br />
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After installing the conveyor, the loader returns to his station and waits for ammunition to be fed into the vehicle. This was the responsibility of the assistant loaders riding in the ammunition carriers accompanying the "Gvozdika" battery.<br />
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Because the partial fence around the turret ring on the loader's side of the turret left an open area near the floor, it was possible for the ammunition supplied externally through the conveyor chute to reach the loader as long as the turret was aimed forward or to the right. If the turret was aimed to the left, the turret basket on the commander and gunner's half of the turret prevented the conveyor from reaching the fighting compartment.<br />
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Because of the restriction on the turret orientation for using the conveyor chute, it was necessary for the artillery battery to know the bearing of the target before positioning the 2S1 howitzers and preparing the ammunition carriers for external loading. This also meant that a 2S1 battery that was set up for sustained fire at a fixed target using an external ammunition supply needed time to readjust its position if it received orders to fire at a new target to the left. That said, the battery could still immediately react to a sudden contact with enemy forces by simply having the conveyors dismounted, thus enabling the turret to freely rotate for all-round fire.<br />
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Depending on the particular ammunition rack that was to be replenished, the crew would either pass ammunition into the vehicle through the rear hatch or through the loader's hatch.<br />
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<h3>
<span style="font-size: large;">RATE OF FIRE</span></h3>
The rate of fire of artillery systems was not only an important measure of the amount of destruction that can be caused, but it was also pivotal to the survival of the system itself. If the artillery system must remain in a single firing position for a prolonged period to complete its mission, its chances of survival drop drastically for a variety of reasons. The most dangerous threat was the counter-battery radar equipment of the enemy as it could track incoming shells and compute the location of the battery with an error margin of just tens of meters. This was sufficiently precise to form fire control commands to direct accurate counter-battery fire. Another threat was aerial reconnaissance, which was more acute for Soviet artillerymen than for their NATO counterparts simply because of the low expectation that the Soviet air force could maintain air superiority. While some local sectors may enjoy a sky controlled by Soviet fighters, it was reasonable for most artillerymen to expect the aircraft over their heads to belong to enemy forces. As such, it was also reasonable to expect that even individual artillery batteries engaged in sustained fire would be visible to enemy air reconnaissance from long distances due to a large smoke signature.<br />
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The most straightforward solution to this problem is to increase the rate of fire of the artillery piece, thus maximizing the weight of the munitions delivered to the target for any given period of time, thus allowing the fire mission to be completed sooner and allowing the battery to immediately relocate to a new firing position before the enemy can respond. Together with all-round armour protection and high mobility, the high rate of fire of the "Gvozdika" helped to increase its destructive effect and improve its own survival rate.<br />
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According to the technical manual for the 2S1 "Gvozdika", the maximum aimed rate of fire for direct fire is 4-5 rounds per minute. Other sources corroborate this figure and further mention that the aimed rate of indirect fire against a fixed target using an external ammunition supply was also 4-5 rounds per minute. However, when attacking different targets placed at different distances and firing upon them with different fire trajectories by varying the howitzer elevation angle, the rate of fire drops to 1.5-2 rounds per minute.<br />
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The sustained rate of fire is reported to be 1.5 to 2 rounds per minute, but this figure is not very meaningful without a further breakdown of the number of shots fired cumulatively over a specific period of time. Fortunately, the technical manual provides this information: the rate of fire with an external ammunition supply in an environment with an ambient air temperature of -10 to +10 degrees Celsius ranges from 4 rounds per minute to 1.67 rounds per minute, so the reported sustained rate of 1.5 to 2 rounds per minute is only true if it is considered the minimum rate or if the gun has been fired continuously for around an hour and is expected to continue firing. Otherwise, the "Gvozdika" can easily sustain a rate of up to 4 rounds per minute for the first ten minutes of continuous sustained fire.<br />
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<table>
<tbody>
<tr>
<td><div style="text-align: center;">
<b>Number of shots fired
</b></div>
</td>
<td><div style="text-align: center;">
<b>Rate of fire
</b></div>
</td>
</tr>
<tr>
<td>40 shots in 10 minutes
</td>
<td>4 rounds per minute
</td>
</tr>
<tr>
<td>50 shots in 20 minutes
</td>
<td>2.5 rounds per minute
</td>
</tr>
<tr>
<td>70 shots in 30 minutes
</td>
<td>2.33 rounds per minute
</td>
</tr>
<tr>
<td>80 shots in 40 minutes
</td>
<td>2 rounds per minute
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<tr>
<td>100 shots in 60 minutes
</td>
<td>1.67 rounds per minute
</td>
</tr>
</tbody></table>
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As mentioned before, the loading assistance device is most helpful for increasing the sustained rate of fire and this can also be seen in foreign artillery systems. For example, the American 155mm M114A1 and M198 towed howitzers are reported to have a sustained rate of fire of 2 rounds per minute in the first 15 minutes and 40 rounds would be fired over a one-hour period for an average rate of just 0.67 rounds per minute, whereas the 155mm M109 self-propelled howitzer is reported to have a sustained rate of fire of 1 round per minute over a one-hour period. In other words, the average rate of fire is higher in the self-propelled system despite the fact that the loaders must operate in a crowded turret instead of an open-air environment.<br />
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With an average rate of fire of 1.67 rounds per minute over a one-hour period, the 2S1 was an excellent sustained fire weapon system. The efficient and ergonomic design of its loading assistance device can be credited for this good performance.<br />
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<h3>
<span style="font-size: large;">POWERED TRAVERSE</span></h3>
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The 2S1 featured a basic electric powered traverse system but lacked a powered elevation drive. The motor for the turret traverse drive was installed just in front of the manual flywheel for manual turret traverse. The system was designed to allow the turret to be turned quickly but imprecisely, and the final lay must be done using the manual turret traverse drive. In terms of the overall capability, the howitzer control system of the 2S1 was not at the level of modern main battle tanks, but was modern for a self-propelled howitzer of its class for the era. Case in point, the FV433 "Abbot" was also limited to having only powered traverse, while the M108 had completely manual controls for both traverse and elevation.<br />
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Its larger cousin the 2S3 "Akatsiya" self-propelled howitzer had a fully powered traverse and elevation system controlled with a pair of control handles, like in a T-54 tank.<br />
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<h3>
<span style="font-size: large;">MANUAL CONTROLS</span></h3>
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The image below, taken from <a href="https://youtu.be/YcAWKnxjjbA">this video</a>, shows the two manual flywheels for turret elevation and howitzer elevation.<br />
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The manual elevation flywheel, shown below, was the only mechanism provided for elevating the howitzer.<br />
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To fire the howitzer, the gunner can either use the electric trigger button on the elevation flywheel handle or pull the trigger lever affixed to the side of the gun cradle.<br />
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<h3>
<span style="font-size: large;">D-32 (2A31) </span></h3>
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The Soviet 122mm caliber was an excellent compromise between the 107mm (4.2-inch) and 152mm (6-inch) calibers that combined a high destructive power against area targets and fortifications, sufficient capacity for the delivery of specialty payloads, good ballistic performance, and a practical size for more advanced fuzing options. It was also the smallest howitzer caliber in the artillery branch of the Soviet Army. The 122mm caliber was first introduced to the Russian arsenal in 1909 when Imperial Russia contracted the development of new howitzers from the German Krupp concern and the French Schneider concern, leading to the adoption of the M1909 and M1910 howitzers designed by the two respective companies. Both howitzers were almost the same in their tactical-technical characteristics and both shared the same 4.8-inch caliber. At the time, the caliber was denoted in the "line" unit, each line being a tenth of an inch. The 122mm caliber was 48 lines, or 4.8 inches. This caliber was chosen as a result of a number of analyses commissioned after the Russo-Japanese war, the conclusions of which indicated that this caliber was necessary to defeat field fortifications and structures.<br />
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During the 1960's and for the rest of the Cold War, the 122mm caliber had no direct counterpart in the West as NATO had standardized on the French 105mm and 155mm calibers, although there was no real effort to standardize on a unified cartridge design. In the context of an international market, the 122mm caliber was an intermediary caliber between the two NATO artillery calibers, but for the Soviet Army, it was the smallest howitzer caliber second to the 152mm although they used field guns in calibers from 100mm (BS-3) to 130mm (M-46).<br />
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The total length of the barrel is 4,270mm, or 35 calibers. This places the D-32 well above the threshold of 30 calibers that distinguishes it as a long-barreled howitzer as opposed to a short-barreled howitzer with a barrel length of less than 30 calibers like the M-30 (22.7 calibers). The mass of the barrel was 955 kg. The rifling consists of 36 grooves and lands with a progressive twist from 3°57 ′ to 7°10′. The height of the bore axis from ground level was 1,890mm.<br />
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The recoiling mass of the D-32 howitzer is 1,440 kg. This figure represents the howitzer itself and excludes its cradle and the loading assistance device attached to the immobile recoil guard, which is fixed to the cradle.<br />
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Like all other Soviet artillery systems of the time, the firing mechanism of the D-32 was electric with a mechanical striker as a backup.<br />
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The howitzer has a semi-automatic vertically sliding breech block, similar to the original D-30 breech block but not identical. This is unlike most Soviet tank guns produced since the end of the Great Patriotic War which had horizontally sliding breech blocks in order to facilitate the loader's work given the relatively small range of elevation angles that were permissible with tank guns. According to Soviet engineering manuals, if the bore axis of a tank cannon from the floor of the fighting compartment is lower than 950-1,000mm, a vertically sliding breech should be used, but if the bore axis is higher than that, a horizontally sliding breech should be used. The reason for this is because the convenience of ramming a shell into the chamber changes depends on the height of the bore axis in relation to the height of the average loader (170 cm). If the height of the bore axis is 950-1,000mm or more, the chamber will be above the elbow level of a standing man, so a horizontally sliding breech is more convenient for the loader when inserting a cartridge into the breech and ramming it in. However, if the bore axis is lower than 950-1,000mm, a breech assembly with a vertically sliding breech block is more convenient for the loader.<br />
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Howitzers like the D-32 are most often fired at high elevation angles and are only occasionally used in a direct fire role. When the howitzer barrel is raised to a high elevation angle, the breech assembly is lowered so that the height of the bore will be quite close to the fighting compartment floor, and because of this, a vertically sliding breech block is preferable over any other type.<br />
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The recoil mechanism of the D-32 included a hydraulic recoil brake with a pneumatic recuperator, filled with either nitrogen or air. These two components were installed above the breech assembly in the same layout as the D-30 howitzer, but with some modifications.<br />
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To accommodate a large elevation angle, the howitzer cradle incorporates a large toothed arc underneath the trunnion pin which interfaces with the worm drive gear of the manual elevation mechanism. This can be seen in the drawings below. The center of gravity of the howitzer is exactly centered on the axis of the trunnion so that it is well-balanced.<br />
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The 2A31 could be depressed by -3 degrees and elevated by +70 degrees, making it a gun-howitzer rather than a pure howitzer, even though the weapon itself and the D-30 it is based on are both designated as howitzers in the Soviet Union. The gun depression limit of -3 degrees is normal for a self-propelled howitzer, but it is less than the -7 degrees limit of the towed D-30. Nevertheless, it should not pose any serious issues even when the vehicle is used for direct fire against point targets such as tanks unless it is deployed improperly.<br />
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<a href="https://1.bp.blogspot.com/-Y4uDbiuRcZM/XfUK8Is7nAI/AAAAAAAAP1U/wh_0OcP3zbAwd77-ebPXainxdopU8pa2gCLcBGAsYHQ/s1600/2s1%2Bfully%2Belevated.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="237" data-original-width="333" src="https://1.bp.blogspot.com/-Y4uDbiuRcZM/XfUK8Is7nAI/AAAAAAAAP1U/wh_0OcP3zbAwd77-ebPXainxdopU8pa2gCLcBGAsYHQ/s1600/2s1%2Bfully%2Belevated.png" /></a><img border="0" data-original-height="1170" data-original-width="1212" height="385" src="https://1.bp.blogspot.com/-17FCWBP_M7Y/XVrxPq5WksI/AAAAAAAAO_w/JvVGSNwKWqUl_m-4YEs5wUeSve9nP4h8ACLcBGAs/s400/d-32%2Bgun%2Belevation.png" width="400" /></div>
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The trunnion pins of the gun cradle are coaxial to the gun bore, of course, as the drawing below shows.<br />
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<a href="https://1.bp.blogspot.com/-v7dwrl4dhDI/XVsBmnXun_I/AAAAAAAAO_8/UFcXE4D-BUE2SDIDO32_3tSZG-TOX6JvwCLcBGAs/s1600/gun%2Bcradle%2Bbreech%2Bface.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="513" data-original-width="503" height="320" src="https://1.bp.blogspot.com/-v7dwrl4dhDI/XVsBmnXun_I/AAAAAAAAO_8/UFcXE4D-BUE2SDIDO32_3tSZG-TOX6JvwCLcBGAs/s320/gun%2Bcradle%2Bbreech%2Bface.png" width="313" /></a></div>
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Unlike tank guns that needed much more compact recoil systems in order to fit entirely inside a tank turret, the 2A31 could have the large buffer and recuperator cylinders of its recoil mechanism protruding far outside the turret as it was only necessary to provide protection from bullets and shell splinters. This was easily achieved with an armoured cowling of a similar design to the one on the D-30.<br />
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Unlike the D-30, the D-32 howitzer used a double baffle muzzle brake. The original D-30 had a slotted muzzle brake with five slots. In 1978, the D-30A model replaced the D-30 and one of the primary differences was the replacement of the original muzzle brake with a double baffle design, very similar to the one used on the D-32. The efficiency of the double baffle brake was less than the slotted type, translating to a more modest reduction in recoil force. For the towed D-30A, the replacement of the original muzzle brake with a less efficient type was because the original slotted brake worked by ejecting a large amount of propellant gasses backwards to counteract the recoil force experienced by the howitzer, which was undesirable because these gasses were ejected towards the howitzer crew thus raising the overpressure of the muzzle blast excessively. However, there was no real reason for the D-32 to have differed from the D-30 in this regard because the crew was fully enclosed inside the turret and would have been shielded from the muzzle blast.<br />
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<a href="https://1.bp.blogspot.com/-b87bfCZvFdU/XW_m27J2v7I/AAAAAAAAPH0/gLVw6qnwVywxiChxNx6qeS2OZWOXid9kQCLcBGAs/s1600/donbas.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="720" data-original-width="1280" height="225" src="https://1.bp.blogspot.com/-b87bfCZvFdU/XW_m27J2v7I/AAAAAAAAPH0/gLVw6qnwVywxiChxNx6qeS2OZWOXid9kQCLcBGAs/s400/donbas.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-tBO8KG9bLJI/XW_mE-JdJvI/AAAAAAAAPHg/09TS8n8BxfYLayKmDSw55lDphZH9Sk86QCLcBGAs/s1600/muzzle%2Bbrake.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="520" data-original-width="693" height="240" src="https://1.bp.blogspot.com/-tBO8KG9bLJI/XW_mE-JdJvI/AAAAAAAAPHg/09TS8n8BxfYLayKmDSw55lDphZH9Sk86QCLcBGAs/s320/muzzle%2Bbrake.jpg" width="320" /></a></div>
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The distinctive fireballs ejected sideways from the double baffle muzzle brake of the D-32 can be appreciated in the photo below.<br />
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<a href="https://1.bp.blogspot.com/-qVnGAUQYwMc/XWc4hqGJOsI/AAAAAAAAPFI/3HQdCzQ-H-0Csb10qeceIJhTY3__f-hqgCLcBGAs/s1600/firing.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="587" data-original-width="1036" height="361" src="https://1.bp.blogspot.com/-qVnGAUQYwMc/XWc4hqGJOsI/AAAAAAAAPFI/3HQdCzQ-H-0Csb10qeceIJhTY3__f-hqgCLcBGAs/s640/firing.jpg" width="640" /></a></div>
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Of course, the muzzle brake can be removed, but a full charge cannot be used in the 2A31 without a muzzle brake installed as the recoil force will overload the recoil mechanism. Nevertheless, the muzzle brake should always be installed regardless of the propellant charge used in the howitzer.<br />
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One imperfection of the D-32 was its inability to use bagged propellant charges. This issue was partly solved by the D-16 which was originally designed to solve the issue of excessive gas contamination from the early prototypes of the D-32, but it was decided that the D-16 did not provide a significant advantage over the D-32 to be worth pursuing further. With the suspension of further work on this improved howitzer, it was decided that full metal casings with improved obturation would continue to be used as this effectively solved the issue of gas contamination. It is not known why semi-combustible propellant charges were not considered as an alternative option. This technology was already in widespread use in the form of 122mm ammunition of the D-25T and M62-T2, 115mm ammunition for the D-68, and 125mm ammunition of the D-81T.<br />
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Although this does not seem to be a significant issue, the cost of producing and transporting metal cases accumulates over time and can become problematic in a protracted large scale conventional conflict, especially for the Soviet Army with its strong focus on artillery. According to data provided by Russian historian Isaev Alexey, during the four years of the Great Patriotic War, the Red Army expended artillery and gun shells at a gargantuan rate yet they were still outpaced by the Germans and Americans by a significant margin, particularly the Americans whose industrial capacity allowed them to produce colossal volumes of ammunition in short periods of time. This was despite the fact that the Red Army's ammunition production capability had been supplemented by valuable American machine tools and shipments of explosives.<br />
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If metal cases for propellant charges could be omitted without compromising the performance of the artillery piece, then it was advisable to do so. Nevertheless, it is worth noting that metal cases for two-part ammunition can be easily reused multiple times because there is no need to mate the case to a projectile, and it is particularly easy to reload cased propellant charges for 122mm artillery rounds because the propellant is held separately in fabric bags of which there are seven, each of equal mass.<br />
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The travel lock for the 2A31 is installed on the roof of the hull, next to the driver's station. The travel lock is remotely controlled from the commander's station. To use it, the howitzer should be kept elevated until the travel lock has been fully erected by its electric motor, and then the howitzer barrel is aligned to the 12 o'clock position and depressed until it is seated properly. The remotely-controlled travel lock clamp is then closed over the barrel.<br />
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One of the staple techniques of boresighting the D-32 in field conditions is to tie two pieces of string into a cross shape around the muzzle. The muzzle brake of the D-32 does not have cross-shaped cuts for this purpose like the 125mm D-81T tank gun, but fixed nubs are provided for tying the string. The howitzer and the direct and panoramic sights are zeroed by aiming the barrel of the howitzer at a landmark at a distance of no less than 1,000 meters and then calibrating the sight until the point of aim in the sights aligns with the point of aim of the howitzer barrel. This ensures that horizontal parallax does not contribute to the dispersion of shots at long range.<br />
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<h3>
<span style="font-size: large;">AMMUNITION</span></h3>
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Being a self-propelled howitzer, the flexibility of the "Gvozdika" as a combat vehicle was reflected by a diverse selection of ammunition types. All of its ammunition could be used in either direct or indirect fire, but of course, anti-tank ammunition was ineffectual unless used exclusively for direct fire.<br />
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A basic combat load consisted of 35 HE-Frag rounds and 5 HEAT rounds, but in practice, the combat loadout was adjusted with various ammunition types to suit the tactical situation. Regardless of the number of specialty ammunition types carried in the "Gvozdika", the number of HEAT rounds did not change.<br />
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<h3>
<span style="font-size: large;">HE-Frag</span></h3>
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The "Gvozdika" mainly carried high-explosive fragmentation (HE-Frag) shells as it was an extremely cheap, highly versatile, reliable and lethal type of ordnance. Various models of HE-Frag rounds were used throughout the service career of the "Gvozdika", but it is particularly interesting to note that, like the D-30, it was mainly supplied with OF-462 shells that were first created for the M-30 short-barreled howitzer.<br />
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A number of fuzes were available for the HE-Frag shells supplied to the 2S1, but variable-delay point-detonating fuzes were the most common type and the RGM was the common model that operated on this principle. The V-90 was another option.<br />
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To use the shells in the "Frag" mode, the fuze is left in the superquick setting and the fuze cap is removed. The shell detonates instantly upon impacting any surface, regardless of whether it is a body of water, a marsh, or snow, thus producing the maximum fragmentation effect on targets standing on top of the surface. The sensitivity of the fuze also allows it to detonate when impacting the canopy of trees, thus allowing the shell to burst above hidden infantry. It was not permitted to fire shells in this fuze setting under conditions of heavy rain or hail as the fuze is sensitive enough to potentially detonate before reaching the target.<br />
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If nothing is done prior to firing the shell, meaning that the fuze is left in the superquick setting and the fuze cap is left on, the shell behaves as a "HE-Frag" shell. The fuze detonates after a delay of 0.027 seconds and produces a combined high-explosive and fragmentation effect. This setting provides a reasonable compromise between the two modes of destruction, allowing field fortifications to be destroyed with near misses while also producing a fragmentation effect to deal with soft-skinned targets standing in the open. If the fuze cap is left on but the fuze is set to the delayed setting, the shell behaves as a "HE" shell. It is detonated after a much longer delay of 0.063 seconds after impact. This enables the shell to explode after penetrating the earth down to an optimal depth, thus displacing the largest possible volume of soil and delivering the maximum shock effect to enemy fortifications which tend to be below ground level by nature. For example, a trench can be destroyed by firing a HE shell at a point just in front of the trench. The shell penetrates the earth at an oblique angle and explodes just next to the wall of the trench (a lucky shot may even explode inside the trench itself), thus demolishing it and killing anyone in the way. Setting the fuze is done by the loader using a special key, but it is the commander who dictates which setting is most suitable for the target.<br />
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According to the technical manual for the 2S1 "Gvozdika", the technical dispersion of HE-Frag rounds in direct fire at 1,000 meters is less than 0.2 meters in both the horizontal and vertical planes.<br />
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When firing at area targets, the direct fire dispersion characteristics are not directly applicable as the drawing below illustrates. While an elliptical dispersion pattern is maintained, the area of the impact zone increases enormously because of the additional factor of distance, which is absent when firing at an upright target placed perpendicular to the ground. Vertical dispersion becomes dispersion in depth, and horizontal dispersion becomes dispersion in width, but the impact area is only elongated in depth and not in width because of distance. At the maximum firing range of 15,200 meters, the mean dispersion of the shells in depth is 32 meters, and the mean dispersion of the shells in width is 10.86 meters. This elliptical zone with an area of 1,092 square meters is where 50% of the shells will land.<br />
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By adjusting the muzzle velocity, different trajectories could be generated.<br />
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To adjust the muzzle velocity of the shells for generating various firing trajectories, the number of propellant charges could be manually adjusted by the loader. Seven propellant bags were contained in each charge housed in a steel casing.<br />
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<h3>
<span style="font-size: large;">OF-462, OF-462Zh</span></h3>
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The projectile weighs 21.76 kg and it contains a 3.675 TNT charge. The fuze weighs 0.438 kg, so after subtracting that and the weight of the filler from the total weight of the complete projectile, the share of the explosive filler is calculated to be 20.8%.<br />
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As a 122mm HE-Frag shell, it is hardly surprising that the explosive payload was between typical NATO 105mm shells and 155mm shells in weight, but the efficiency of each OF-462 shell was higher on a shot-for-shot basis. Case in point, the ubiquitous American 105mm M1 shell had a complete projectile weight of 14.9 kg and could have a 2.3 kg filling of Comp. B or 2.18 kg of TNT when fitted with a conventional M557 point-detonating impact fuze, and the equally ubiquitous American 155mm M107 shell had a complete projectile weight of 43.2 kg could have a 6.98 kg filling of Comp B or 6.62 kg of TNT when fitted with a conventional point-detonating impact fuze. Subtracting the weight of an M557 PD fuze (0.975 kg) from the total projectile weights of these two shells, we find that the share of the explosive filler in the M1 shell is 18.56% with a TNT filler and 19.8% with a Comp. B filler. The share of the explosive filler in the M107 shell is 18.6% with a TNT filler or 19.8% with a Comp. B filler.<br />
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Mass: 21.76 kg<br />
Explosive Charge Mass: 3.675 kg<br />
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Muzzle velocities:<br />
Full Charge: 686 m/s<br />
Reduced Charges: 270-565 m/s<br />
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Maximum Firing Range:<br />
Full Charge: 15,200 meters<br />
Reduced Charge: 12,870 meters<br />
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Maximum Pressure with Full Charge: 245.2 MPa<br />
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Its maximum range of 15.2 kilometers was good, but quite ordinary for a medium velocity howitzer. Although it was nowhere close to reaching the capabilities of the 130mm M-46 counter-battery gun, it still gave the "Gvozdika" a range advantage over 155mm guns like the towed M114 or the M126 of the M109 self-propelled howitzer, both of which had a maximum range of 14.6 kilometers, and its range easily exceeded some 105mm howitzers like the M103 of the M108 which had a maximum range of 11.5 kilometers.<br />
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When the fuze is set to the HE mode, the high explosive action of the shell produces a crater with a depth of 1.3 m and a diameter of 3.3 m in soil of medium density. This is a significantly better result than the M-30 short-barreled howitzer could obtain with the same OF-462 shell, as that could only produce a crater with a depth of 0.7 meters and a diameter of 3.0 meters under the same conditions. The difference can be attributed to the higher impact velocity of shells fired from the D-32 at all ranges. By exploding deeper in the soil, a larger portion of the explosive energy is transmitted into the ground rather than being spent in ejecting soil above the shell. This allows a greater mass of soil to be displaced and as a result, the shell is more effective at destroying trenches. <br />
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If the shell manages to actually enter the trench, there is still a powerful destructive effect because the walls of the trench will collapse from the explosion underneath them unless they are reinforced with logs, and the blast wave kills the soldiers standing inside the trench or they are at least injured by the ejecta that is propelled out of the ground.<br />
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According to CAMD RF 81-12104-9, the 122mm HE shell fired from the M-30 howitzer penetrates 30mm of steel armour sloped at 30 degrees at 1,000 meters. The armour used had a resistance coefficient of 2,360. Based on the characteristics of the shell reported in the table (21.76 kg and muzzle velocity of 515 m/s), an OF-462 shell fired with a full charge was used. The table in the document does not mention the nature of the interaction between the shell and the armour plate, but given the large thickness of the armour plate, it is likely that the shell impacted the armour and the fuze was destroyed, but the shell carried enough kinetic energy to break through. The relatively thin casing of the warhead probably could not survive such an interaction and it would have disintegrated into fragments, which would combine with the fragments of the breached armour plate to destroy anything in its path.<br />
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<h3>
<span style="font-size: large;">3VOF29 (3VOF30)<br />3OF24</span></h3>
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With an explosive filler weight of 3.97 kg, the share of the explosive filler in the 3OF24 shell is 22.87%. This is close to the mathematically optimal figure of 25%, and as such, 3OF24 possesses more favourable fragmentation characteristics. There may have been a further improvement in performance if the forged steel casing is made from an improved steel alloy with better fragmentation characteristics.<br />
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Projectile Mass: 21.76 kg<br />
Explosive Charge Mass: 3.97 kg<br />
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Muzzle velocities:<br />
Full Charge: 686 m/s<br />
Reduced Charges: 270-565 m/s<br />
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<h3>
<span style="font-size: large;">HEAT</span></h3>
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During the so-called Great Patriotic War, the Red Army placed a great emphasis on the dual role played by artillery, both the towed and self-propelled varieties. Weapons like the ZiS-3 and M-30 were not constrained to area bombardment with high explosive shells, but were expected to be serve as anti-tank guns if the situation called for it. For this purpose, they were provided with armour piercing shells according to their suitability. The ZiS-3 and A-19 were fairly powerful guns and thus, were supplied with AP or APBC shells and SU-76 self-propelled guns were often supplied with a small number of APCR rounds as well. Short-barreled howitzers like the M-30 had an inherently limited muzzle velocity, making it ineffective to use such ammunition as they depended on kinetic energy. As such, HEAT ammunition was used instead.<br />
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Even by the time the D-30 entered service, it was expected to fulfill a secondary anti-tank role. This expectation carried over to the 2S1 "Gvozdika". For the D-30 and the "Gvozdika", HEAT ammunition was still the only sensible anti-tank munition given the relatively low energy of the howitzer compared to high-power guns like the D-25T.<br />
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The 2S1 was supplied with fin-stabilized HEAT shells. It could also fired the spin-stabilized 3BR1 shell that was originally developed for the M-30 howitzer, but this shell was ineffective against the modern tanks of the 1960's and 1970's and it was not supplied to the 2S1.<br />
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According to the technical manual for the 2S1 "Gvozdika", the technical dispersion of HEAT rounds at 1,000 meters is less than 0.3 meters in both the horizontal and vertical planes. This is worse than the accuracy of the HE-Frag rounds and doubtlessly contributed to the relatively low maximum effective range of the 2S1 against tanks in direct fire.<br />
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<h3>
<span style="font-size: large;">3VBK12, 3VBK12<br />3BK6, 3BK6M</span></h3>
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The ballistic performance of the D-32 howitzer was sufficient for direct fire purposes against point targets, but it was considerably worse than the 122mm mod. 1931/37 field gun due to its lower muzzle velocity. As such, the "point blank" range, otherwise known as the grazing shot or direct shot range, was considerably shorter. The point blank range for a target with a height of 2.0 meters (representing an armoured personnel carrier) was 780 meters, 870 meters for a 2.5-meter target, and 940 meters for a 3.0-meter target (heavy tank). Of course, the natural vertical dispersion of the shot makes it necessary to estimate the range with some precision to have any real chance of scoring a hit at such ranges. This level of performance was quite ordinary for howitzers. The shell has a filling of A-IX-1 explosive compound.<br />
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For direct fire using the BK6(M) round, the "БК" (HEAT) range scale was provided. A tracer was installed at the base of the stabilizer fin assembly for fire correction purposes.<br />
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Projectile Mass: 21.56 kg<br />
Explosive Charge Mass: 2.159 kg<br />
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<h3>
<span style="font-size: large;">3VBK9, 3VBK9M<br />3BK13, 3BK13M</span></h3>
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The 3BK13 shell was a modern HEAT shell that entered service at around the same time as the 2S1, replacing the older 3BK6 that was primarily supplied to the D-30. The main distinguishing feature is the replacement of the conventional aerodynamic fairing of the projectile with a spike tip. In terms of performance, the 3BK13 mainly differed in having a significantly higher armour penetration power. As usual, the 3BK13 had a steel liner and 3BK13M had a copper liner. The maximum effective range was rated to be 1,500 meters.<br />
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Despite the higher muzzle velocity of 726 m/s, the BK13(M) round did not have a flatter trajectory than the BK6(M) round it replaced due to the higher drag of its spike tip projectile design. In fact, its ballistic trajectory was almost identical up to a range of 940 meters.<br />
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The shell had a filler of A-IX-1.<br />
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Muzzle velocity: 726 m/s<br />
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Projectile Mass: 18.2 kg<br />
Explosive Charge Mass: 1.698 kg<br />
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<h3>
<span style="font-size: large;">PROTECTION</span></h3>
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The protection of artillery batteries was considered to be a crucial aspect in conventional warfare in the Soviet Army. There was a general understanding that there were more challenges to overcome than ever before, particularly since the expected enemy was ahead in terms of self-propelled tube artillery systems and thus had a much better shoot-and-scoot capability than the towed guns of the Soviet artillery forces. Soviet officers, analysts and scientists rated enemy artillery as the foremost threat to their own. The second most serious threat was aircraft, including fixed-wing high performance aircraft as well as rotary aircraft. Third on the list of perceived threats to artillery were enemy<br />
tanks, airborne and small infantry units. Of these, enemy tanks were thought to pose the greatest threat to artillery.<br />
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When the MT-L prime mover was being designed, the need for better protection led to the Army's insistence on having armour on the new vehicle, resulting in the creation and introduction of the MT-LB into widespread service instead of the MT-L.<br />
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However, the addition of armour to prime movers was not a panacea to the serious problem of artillery protection. Enhanced mobility was considered to be the greatest countermeasure against enemy artillery fire and airstrikes. This was the primary incentive behind the decision to replace towed howitzers with a self-propelled vehicle like the 2S1, as such systems enjoyed a considerable improvement in survivability under adverse combat conditions.<br />
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With the advent of the MT-LB, towed weapon systems like the D-30 were no longer particularly vulnerable to enemy artillery fire because the crew, ammunition and other sensitive equipment such as the optical sighting instruments were under armour when in transit. The howitzer itself had armoured shields and cowlings around sensitive components such as the recoil system, so only the rubber tyres could be considered vulnerable. In this specific context, the 2S1 had little advantage in protection compared to a D-30 towed by an MT-LB. However, unlike a towed howitzer, the "Gvozdika" did not force its crew to disembark from their armoured carrier in order to put their howitzer into action, and they did not need to issue emergency calls to their prime movers when it became necessary to shift positions in a hurry. Consequently, a "Gvozdika" crew had a much better chance of surviving an onslaught of counter-battery fire or airstrikes compared to their less-fortunate towed counterparts. According to an article published in the well-known "<i>Военный Вестник</i>" (<i>War Herald</i>) magazine, the timeliness of abandoning a firing position before the arrival of counter-battery fire was identified as the primary condition for the survival of artillery in modern fast-paced combat.<br />
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The advantage in survivability was also maintained when both artillery systems are exposed to direct return fire. The "Gvozdika" was fully enclosed and had enough frontal armour to resist heavy machine guns even at point blank range and the sides could resist machine gun fire from a distance, whereas the D-30 had just a gun shield that offered only limited protection against machine guns, and only in a narrow frontal arc that could sparsely cover the gunner, let alone the rest of the crew. After all, the gun shield was meant for protecting the gun, not the crew.<br />
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The turret and hull of the "Gvozdika" were constructed from welded <a href="http://masters.donntu.org/2008/mech/trifonov/library/s13.htm">2P grade high hardness, high strength armour steel plates</a> with a thickness ranging from 7mm to 20mm. 2P grade plates for this range of thicknesses have a tensile strength of around 1450-1550 MPa and a hardness of around 388-495 BHN. Based on a West German evaluation of a captured BMP-1, which was built from 2P plates, the armour of the 2S1 is likely to have a hardness of 488 BHN or more. The direct foreign equivalent of this grade of steel is MIL-DTL-46100 grade high hardness armour steel for combat vehicles. MIL-DTL-46100 is recognized by the U.S Army to be equivalent to the steel grade used on Soviet armoured personnel carriers and infantry fighting vehicles, and steel plates of this standard were also used to construct the hull of the LAV-25.<br />
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For the hull, two thicknesses of steel plate were used: 7mm and 15mm. The side, rear, roof and belly plates were assembled from 7mm plates. The upper glacis was also 7mm thick, but it was sloped at a very large obliquity, and the stamped steel transmission access hatch occupying a large portion of the upper glacis was also 7mm thick. The lower glacis had a thickness of 15mm. Curved 20mm plates form the front half of the turret, and the rear half - including the bustle - is built from 7mm plates that are only modestly sloped. The hull and turret have the same basic level of protection.<br />
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The author has not yet been able to acquire information on the armour rating of the 2S1 or any published details on its testing, but because the hull of the "Gvozdika" is as thinly armoured as a basic MT-LB and the turret reaches the same standard of protection, it is possible to use the MT-LB as a surrogate for the 2S1.<br />
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According to the article "<i>Транспортер-тягач МТ-ЛБ</i>" (<i>Transporter-Tractor MT-LB</i>) published in the 25th issue of the "<i>Боевые машины мира</i>" magazine in 2014, the frontal armour of the MT-LB hull provided immunity from 7.62x54mm B-32 armour-piercing bullets in a frontal arc of 150 degrees at a range of 250 meters, meaning that the side armour was immune to this bullet at 250 meters at a side angle of 75 degrees where the impact angle of the bullet against the side armour plate would be 15 degrees in a worst case scenario. Only the front of the hull guarantees immunity from this type of threat at all ranges and all angles of attack. 12.7mm caliber armour-piercing ammunition such as the .50 cal M2 AP round and the 12.7mm B-32 bullet can defeat the frontal armour from up to 500 meters because the side angle for the side hull armour would not be sufficient against such a powerful machine gun round, but the front armour itself was not vulnerable.<br />
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The front hull armour of the 2S1 consisted of an upper glacis over the engine and transmission compartment with a thickness of 7mm sloped at 73 degrees, a lower glacis with a thickness of 15mm but sloped at 37 degrees, and a plate over the driver's station with a thickness of 15mm, sloped at 40 degrees. The trim vane increased the protection of the lower glacis of the hull when it was kept in its stowed position since it is a steel sheet, but because it is of unknown thickness and unknown steel grade, its contribution was probably quite modest.<br />
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To evaluate the protection level of the front hull armour, let us compare the area with the weakest armour - the lower glacis - against a fairly common threat: the .50 caliber M2 AP bullet fired from an M2 Browning heavy machine gun. It is known that the .50 caliber M2 AP bullet pierces 0.66 inches of RHA plate sloped at 37 degrees at point blank range under the Navy Criterion, so it would appear that the lower glacis of the 2S1 is vulnerable as it is only 14mm (0.551") thick. However, considering that it is made from high hardness steel and not RHA steel, the effective thickness of the armour is actually 1.3 times higher. In actuality, the 14mm of 2P armour plate is equivalent to 18.2mm (0.716") of RHA plate. The M2 AP bullet would not be capable of reliably defeating the weakest part of the front armour of the 2S1 even at point blank range. When the trim vane is taken into consideration, it is clear that even the weakest part of the front hull armour is sufficiently protected from this threat.<br />
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The side armour of the hull was 7mm thick and completely flat. Overall, the side hull armour can only resist 7.62x54mm LPS light ball bullets with a mild steel core or 7.62x51mm M80 ball bullets with a lead core and full metal jacket from point blank range, and it was also immune from ball bullets of intermediate rifle rounds. It was completely invulnerable to 5.56mm rifles during the Cold War as only M193 light ball ammunition was available for the majority of this period until it was replaced by the M855 steel-cored round in 1983, but the steel core in M855 was made from mild steel and only served to enhance barrier penetration. The armour-piercing performance is insignificantly improved compared to M193.<br />
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However, even armour-piercing bullets of intermediate cartridges could pose a threat to the side armour. The protection from 7.62x39mm BZ steel-cored armour-piercing incendiary (AP-I) bullets fired from a standard AK-47 or AKM rifle was insufficient at close range. This particular bullet was rated to penetrate 7mm of 2P steel with a probability of 80% from a distance of 100 meters, so it could already pose a serious threat to the 2S1 from the side. Naturally, with such results it is not surprising that the side armour only offered a modicum of protection from full power 7.62mm armour-piercing rounds. The rear armour should only offer equal protection as the side armour as it has the same thickness, and the fact that it is tilted at 5 degrees should make no noticeable difference to its protective value as it is practically insignificant.<br />
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The front turret armour of the 2S1 was 20mm thick and sloped at 30 degrees. This granted it immunity from .50 caliber armour piercing bullets even at point blank range. At this angle, the .50 caliber M2 AP bullet pierces 18.6mm of RHA plate under the Navy Criterion, so it already has virtually no chance against this aspect of the turret without even considering that it is made from high hardness steel and not RHA steel. The side of the turret was noticeably more resilient than the side hull armour because of its modest slope of 23 degrees, allowing it to resist the 7.62mm B-32 armour-piercing bullet from 360 meters. The frontal arc of protection from .50 caliber armour-piercing bullets would also be larger compared to the hull thanks to the tougher side armour, but the exact magnitude of the difference is unclear.<br />
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In general, both the hull and turret have low protection against small arms and the hull is particularly vulnerable to armour-piercing bullets on the side and rear even from small caliber rifles. As such, entrenching the vehicle in camouflaged dugouts does not only improve its survivability by reducing its chances of being seen and fired upon, but the dugout itself helps to protect the vehicle by hiding the hull below ground level.<br />
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Unlike the hulls of the Object 124 and the Object 765 (BMP), the MT-LB was never designed for direct combat. For instance, the Object 124 was a self-propelled tank destroyer that was intended for deployment at the front lines where it would be much more exposed to threats from other direct fire weapons, so it was sufficiently armoured to protect against heavy machine guns and even autocannons to some extent. The BMP hull had thinner armour but was angled more sharply, allowing it to resist the same types of weapons. Case in point: the frontal arc of the hull was able to resist 23mm BZ armour-piercing shells from 500 meters. <br />
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The most vulnerable zones of the 2S1 are where ammunition is stowed. The ready racks in the turret are the most exposed, whereas the reserve racks are somewhat safer because they are lower to the ground and harder to hit, especially in a frontal attack. If the ready racks in the turret are detonated by a sufficiently powerful round, it should come as no surprise that the thin armour of the turret would be completely ripped apart by the blast.<br />
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<h3>
<span style="font-size: large;">DRIVER'S STATION</span></h3>
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<a href="https://1.bp.blogspot.com/-gxZvAXA2goo/XX0PaIh9WtI/AAAAAAAAPNo/hAnn85L2gVke7YqTSQ7eK9loEgMOrTyewCLcBGAsYHQ/s1600/steering%2Btillers.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="1280" height="300" src="https://1.bp.blogspot.com/-gxZvAXA2goo/XX0PaIh9WtI/AAAAAAAAPNo/hAnn85L2gVke7YqTSQ7eK9loEgMOrTyewCLcBGAsYHQ/s400/steering%2Btillers.jpg" width="400" /></a></div>
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The driver of the 2S1 is isolated from the rest of the crew. The engine is installed to his right and behind him is the cooling system.<br />
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Like the MT-LB, the "Gvozdika" is steered with two tiller levers with horizontal handlebars. The instrument panel is placed in front of the driver.<br />
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He was provided with three possible methods of observation for driving. When driving around without any expectation of receiving fire, the driver opens his hatch and drives with his head peeking out as is normally done in most tracked vehicles, as shown in the photo below. If it is necessary to have all hatches closed for some reason, the driver reverts to using the windshield in front of him, and if the vehicle comes under fire, the driver closes the armoured windshield cover and navigates using his three periscopes.<br />
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To use the periscopes, the driver must first raise the protective steel shield covering the aperture windows. This is done by pushing up on a lever which connects to the shield by a pair of rods, and this rotates the shield on its hinges by a small distance so that it is clear of the periscopes.<br />
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The photo below shows the driver's periscopes and windshield both opened for viewing.<br />
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When the armoured windshield cover is locked in the open position, it acts as a visor to keep out rain and glare from the sun in the same way as the windshield covers of wheeled troop carriers like the BTR-60 and armoured cars like the BRDM.<br />
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The windshield is made of glass and it is heated. It offers a larger field of view compared to the periscopes, but its view to the right was obstructed by the hump over the transmission compartment. As such, the periscope facing the 1 o'clock direction was still necessary for the driver to see both corners of the vehicle. Additionally, the view from the windshield is somewhat constricted by the overhang of the hull so there is a relatively large dead zone in the front, and the driver does not have a good view skywards because the raised cover is in the way. Also, the front-facing periscope must be removed in order to exploit the view from the windshield as demonstrated in the photo below, or else it would block the driver's view since it is installed at the driver's eye level. Before the howitzer is fired, the windshield cover must be closed, especially if it is being used for direct fire against a target directly in the front relative to the hull.<br />
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The photo below shows the front right and front left headlights of the "Gvozdika", complete with marker lights to mark the corners of the vehicle when travelling in convoys.<br />
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<a href="https://1.bp.blogspot.com/-MQPz-5RrrE8/XWchh4fvArI/AAAAAAAAPEc/KL0tGaoMId4vEz35TXl6-K3tKj6IgMgKACLcBGAs/s1600/right%2Bheadlights.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="520" data-original-width="693" height="300" src="https://1.bp.blogspot.com/-MQPz-5RrrE8/XWchh4fvArI/AAAAAAAAPEc/KL0tGaoMId4vEz35TXl6-K3tKj6IgMgKACLcBGAs/s400/right%2Bheadlights.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-PczV0Z7ftis/XWcgrJKaR7I/AAAAAAAAPEQ/-scciVA_SDsKGfCHiYiE1AM-QjBKBtaCACLcBGAs/s1600/front%2Bleft.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="801" data-original-width="1200" height="266" src="https://1.bp.blogspot.com/-PczV0Z7ftis/XWcgrJKaR7I/AAAAAAAAPEQ/-scciVA_SDsKGfCHiYiE1AM-QjBKBtaCACLcBGAs/s400/front%2Bleft.jpg" width="400" /></a></div>
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<h3>
<span style="font-size: large;">MOBILITY</span></h3>
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Besides its howitzer, one of the other main outstanding characteristics of the 2S1 was its mobility, thanks in part to the original focus on mobility as the design goal of the MT-LB chassis. Thanks to its exceptionally high mobility characteristics, the "Gvozdika" could travel almost anywhere it was required and it could be deployed in the "inaccessible" areas of a battlefield. The light weight of the vehicle greatly contributed to its high mobility characteristics as it became possible to be transported by the ubiquitous An-12 transport plane, one vehicle at a time. The larger Il-76 could carry two 2S1 vehicles at a time.<br />
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The vehicle had a combat weight of 15.7 tons, including a full load of ammunition, fuel, lubricants and other fluids, a complete set of spare parts and the crew members themselves. Naturally, the "Gvozdika" was in a completely different weight class than 152mm or 155mm self-propelled howitzers like the 2S3 "Akatsiya" and the M109, both of which weighed 27.5 tons when loaded for combat. However, it was also much lighter than 105mm self-propelled howitzers like the American M108 which weighed 21 tons, and surprisingly enough, it was even slightly lighter than the smaller British FV433 "Abbot" and French AMX-105B which weighed 16.56 tons and 17 tons respectively.<br />
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The "Gvozdika" was much heavier than an MT-LB as that weighed only 9.7 tons when combat loaded (including spare parts, machine gun ammunition and fuel, but no crew and no cargo), but it was only slightly heavier than an MT-LB towing a D-30 howitzer and loaded with crew and ammunition. An MT-LB configured for this role carried a large amount of cargo internally, increasing its combat weight to 12.2 tons, and together with the D-30 which weighed 3.2 tons together with its carriage, the total weight amounted to 15.4 tons.<br />
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The additional weight of the "Gvozdika" was compensated by supercharging the engine. Instead of the original YaMZ-238 engine that generated a maximum power of 240 hp at 2,100 rpm and maximum torque of 883 N.m at 1,500 rpm, the "Gvozdika" has a YaMZ-238N diesel engine with a power and torque output of 300 hp and 1,079 N.m respectively. This engine was shared with the MT-LBu. It was a V-shaped 8-cylinder four-stroke diesel with a displacement of 14.86 liters, differing only in the addition of a supercharger and the modifications thereof.<br />
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The top speed of the "Gvozdika" is 60 km/h, which is the same as the MT-LB. Officially, the average speed on a paved road is 45 km/h and the average speed when driving on a dirt road is 26-32 km/h. Compared to a D-30 howitzer towed by an MT-LB, the 2S1 does not have an advantage when travelling on paved roads but it was substantially more mobile when moving off-road. The issue was not speed since the D-30 itself had a perfectly serviceable maximum towing speed of 60 km/h with the foam-filled rubber tyres of its carriage, but rather, it was the mismatch between the wheeled carriage and the tracked MT-LB. Although the MT-LB had excellent off-road driving capabilities, it was hampered by the wheeled carriage of the D-30 and the situation only improved slightly when pneumatic tyres were introduced on the newer D-30A model.<br />
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A self-propelled artillery system had a significant advantage over towed artillery in these crucial aspects. It was also possible for a self-propelled system to move immediately after completing its fire mission or at least move after receiving the initial volley of counter-battery fire, thus improving its survivability by 15% to 20% according to the article "<i>К вопросу о живучести артиллерийскдх подразделений</i>" (<i>On the issue of survivability of artillery units</i>) by I. Epifanov in the April 1976 issue of the "<i>Военный Вестник</i>" (<i>War Herald</i>) magazine.<br />
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The photo below shows a Ukrainian "Gvozdika" being serviced under field conditions. The transmission access hatch is more than large enough for a man to stand inside and work freely.<br />
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The vehicle is able to climb a hill with a slope of 35 degrees (70% grade) and negotiate a side slope of 25 degrees. Due to the long overhang of the hull in front of the track, the vehicle is only capable of surmounting a vertical obstacle with a height of 0.7 meters, but the long length of the hull allows it to cross a trench with a width of 3.0 meters.<br />
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The superior driving speed and agility of the 2S1 "Gvozdika" compared to its foreign counterparts was facilitated by the improved visibility provided for its driver. Without good visibility, it would be unsafe for heavy vehicles to be driven at high speed - even those that are relatively light like the "Gvozdika" - due to their specific handling characteristics and the braking response of such vehicles.<br />
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<span style="font-size: large;">SUSPENSION</span></h3>
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The "Gvozdika" has a very similar suspension as the MT-LB, differing mainly in having seven roadwheels instead of six. Almost all individual elements of the suspension such as the tracks, roadwheels, shock absorbers and torsion bars are the same, but most of the swing arms are of a new design. The first and last roadwheels had hydraulic shock absorbers. Like the roadwheels of the PT-76 and BMP-1, these were made from stamped steel and were hollow and as such, they contributed to the buoyancy of the vehicle.<br />
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The 2S1 had a ground clearance of 400mm when combat loaded. An interesting feature of the 2S1 suspension is that, to allow transportation by the An-12, the suspension has a special locking system whereby the second, third, fifth and sixth roadwheels can be secured at a level orientation with a locking pawl on the swing arm. To lock the suspension, a log is tied to the tracks and the vehicle is driven forward to position the log underneath each of the aforementioned wheels to raise them. Once all of the wheels with the transportation locks have been secured, the weight of the vehicle is supported entirely by the remaining wheels (first, fourth and seventh) and this causes them to sag, thus reducing the ground clearance to 300mm. <br />
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The vehicle used the same RMSh tracks as the MT-LB. The width of each track link is 350mm and the pitch is 111mm. The nominal specific ground pressure of the vehicle is 0.492 kg.f/sq.cm or 48.25 kPa. This is slightly higher than the 0.46 kg.f/sq.cm ground pressure of a basic MT-LB, but the difference is nullified if it is compared to a loaded MT-LB with a full D-30 howitzer crew and ammunition. For the 2S1, this low ground pressure allows it to confidently negotiate rough terrain and it was certainly more capable of crossing difficult terrain compared to a D-30 towed by an MT-LB as the carriage of the D-30 was wheeled and its ground clearance was less than the MT-LB, so naturally, it would get bogged down even if the prime mover itself did not.<br />
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However, it should be noted that the 2S1 retained the original narrow tracks throughout its service life whereas the MT-LB was supplemented by the MT-LBV model with a modified suspension that included wider tracks with a width of 565mm. The greater weight of the wider tracks was completely offset by the increased width, giving the MT-LBV an exceptionally low nominal ground pressure of just 0.27 kg.f/sq.cm. In the USSR, this model and its derivatives were mainly used in areas where operational experience had indicated that the narrow tracks of the basic model were insufficient. Nevertheless, if the MT-LBV was used as a prime mover for a towed howitzer, it would still be limited by the wheeled carriage of the howitzer. In other words, the "Gvozdika" still retains its mobility advantage.<br />
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<span style="font-size: large;">FUEL SYSTEM</span></h3>
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The vehicle carries 550 liters of fuel held in six containers located in the sponsons of the hull. The two fuel tanks at the rear corners of the sponsons are placed directly behind the reserve ammunition racks containing propellant charges, and the four fuel tanks forward of this are located in the fighting compartment, just under the turret ring.<br />
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With this amount of fuel, the 2S1 had a driving range of 550 km on paved roads.<br />
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<span style="font-size: large;">WATER OBSTACLES</span></h3>
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Unlike the vast majority of self-propelled howitzers, the 2S1 was a fully amphibious that could swim with only minor preparation. The vehicle could swim at a top speed of just 4.5 km/h. Before swimming, the trim vane had to be erected manually by one of the crew members. When stowed, the trim vane made a modest contribution to the protection of the lower glacis of the hull.<br />
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The "Gvozdika" was rated to cross a water obstacle with a width of 300 meters with a maximum wave height of no more than 150mm and a flow speed of no more than 0.6 m/s, so in other words, the vehicle was capable of swimming across the majority of the rivers found across the entirety of Europe, but only in calm water conditions. If the current was strong, the vehicle might lack enough propulsive force to avoid being swept away. The vehicle was completely unsuitable for seaborne operations such as amphibious landings unless it was transported right up to the beach. Nevertheless, this capability was enough for the scope of the Soviet Army.<br />
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Propulsion in water was provided by the movement of the tracks, and steering was accomplished by the braking of one track or the other to allow the vehicle to pivot around the stopped track. Reverse motion was possible, but at a very low speed because the swimming aids and the design of the vehicle itself were all entirely optimized for forward movement. The high hydrodynamic resistance of the tracks allowed them to generate a relatively strong flow of water as they run, but the efficiency of propulsion is low because the track moves in a loop. The forward propulsive force generated from the rearward movement of the lower track loop is partly countered by the reverse propulsion generated by the forward movement of the upper track loop, and even though the reverse propulsive force was limited by the presence of the hull sponsons and the sprocket wheel well, the reduction in the net forward propulsive force was quite significant. To make up for this, special grilles were installed to direct the flow of water more effectively.<br />
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Swimming forward was done by driving the vehicle in the forward gears and swimming backward was done in the reverse gear. Forward propulsion was heavily aided by a pair of special hydrodynamic grilles installed behind the rear idler of the suspension and a pair of long grilles installed adjacent to the tracks above the first roadwheel and the drive sprocket. These grilles were designed so that much of the water that was displaced by the movement of the tracks was captured by the grilles and directed backwards, thus producing a forward propulsive force. The design of the rear grilles and the shape of its vanes is shown in the photo below, courtesy of <a href="http://serkoff.narod.ru/photoalbum25.html">Andrey Nikolaev</a>.<br />
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As the photo shows, the grilles were slanted inwards; i.e. the rear grilles on the right track were slanted to direct the water flow towards the left and the rear grilles on the left track were slanted to direct the water flow towards the right. This was designed so that when the vehicle was steered in the water, the turning force would be increased. For example, when turning left in the water, the left track was braked while the right track continued to run, and the grilles behind the right track increased the turning force for the vehicle to pivot around the stopped track.<br />
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These rear grilles were normally stowed by folding them up flush against the rear hull surface and then holding it in place with a swinging latch. To release it, a crew member exits the vehicle and taps the latch with a mallet until the grille is freed.<br />
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The two photos below show the front grilles. Note that the vanes curved in such a way that water is only expelled backwards. The photo on the left below is by <a href="http://serkoff.narod.ru/photoalbum25.html">Andrey Nikolaev</a>.<br />
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Rearward motion in water is not supported by these special grilles. Instead, it is achieved with only the hydrodynamic interaction of the tracks with the water. Hence, the vehicle handles poorly in reverse and cannot turn easily. Maneuvering in the water is mainly done with forward motion. When not in use, the front grilles are stowed on the rear of the turret bustle to avoid premature wear and tear, but mainly to avoid damaging them in a collision since they are relative light and flimsy.<br />
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For safety reasons, it was only permitted for 30 rounds to be carried in the vehicle when performing swimming operations. This is not because of weight reasons because the small reduction in total weight by the removal of 10 rounds of ammunition is insignificant relative to the vehicle as a whole, and it has a negligible effect on its flotation. Rather, it is required to balance the distribution of weight more equally so that the center of buoyancy is not shifted excessively to the rear because of the turret. This is because the large volume of the turret does not contribute positively to the buoyancy of the vehicle since it is not submerged so it is just more weight that must be supported by the hull alone, and the turret and ammunition of the "Gvozdika" are all concentrated at the rear of the hull.<br />
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Reserve buoyancy is the amount of watertight volume above the waterline when the vessel is submerged, and a high reserve buoyancy begets a high resistance to water intake and thus, a higher level of safety in rough waters. According to Russian military historian A.V. Karpenko, the "Gvozdika" was designed with a 20% reserve buoyancy margin when combat-loaded, or in other words, 20% of the volume in the "Gvozdika" hull is above the waterline when the vehicle is afloat. For comparison, the MT-LB had a 36% reserve buoyancy margin when fully loaded for combat but without cargo and 22.5% when two tons of cargo is carried, so evidently, the buoyancy characteristics of the "Gvozdika" were slightly worse than a fully loaded MT-LB.<br />
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The small amount of water that enters the hull through the imperfect hatch seals or through small gaps in the joints between plates will be removed by a bilge pump. The bilge pump is particularly helpful if the hull armour is perforated by enemy fire, as the vehicle could otherwise take on water at an excessive rate.<br />
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<br /><br /></div></div></div>Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com14tag:blogger.com,1999:blog-3103574899092646031.post-57241849703085456622019-07-30T14:57:00.286-07:002024-03-23T03:07:02.258-07:00T-10<div><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-umxdx3qa5y4/XF4UKyUapvI/AAAAAAAANUo/0Fc_eq91Mc86fJhgf9_KC7hmIvQFY2I3wCLcBGAs/s1600/red%2Boctober%2Bparade.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="755" data-original-width="1280" height="377" src="https://2.bp.blogspot.com/-umxdx3qa5y4/XF4UKyUapvI/AAAAAAAANUo/0Fc_eq91Mc86fJhgf9_KC7hmIvQFY2I3wCLcBGAs/s640/red%2Boctober%2Bparade.jpg" width="640" /></a></div>
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The T-10 heavy tank was formally revealed to the public in its first and only Red Square appearance on the 7th of November, 1957 in the parade for the 40th anniversary of the Great October Socialist Revolution with the T-10 obr. 1956 model representing the series. The parade was held just one month after the successful launch of Sputnik 1, the first artificial satellite to enter low Earth orbit in human history. Among those that made their first appearance on Red Square were the new R-5M mobile strategic nuclear missile on its transporter, the T-54 medium tank, the ZSU-57-2 self-propelled anti-aircraft gun system, and many others, marking this parade as one of the most grandiose political-military displays of the decade as well as one of the most significant from a military intelligence standpoint.<br />
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The T-10 was the culmination of over a decade of continuous heavy tank development in the Soviet Union and is the most advanced design of its class to see service in its homeland. It was also arguably the sleekest of all Soviet heavy tank designs, having extremely well-sloped armour on both its hull and turret arranged in a rather pleasing way. As a series, the T-10 boasted a level of technological sophistication that was unmatched in the Soviet Army until the T-64 entered service, and even then, there was significant overlap in the capabilities of the two classes. Soviet armoured doctrine saw the heavy tank as a breakthrough weapon capable of operating independently or alongside other armoured vehicles in mixed tank units that can, by design, eliminate any opposition that a medium tank cannot.<br />
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In fact, this was the same general doctrine that dictated the deployment of the M103 heavy tank in the service of the U.S Marines, which made little distinction between heavy and medium tanks in the operational sense. Ken Estes, who is probably the world's foremost expert on the M103 tank series, notes in page 38 of "<i>M103 Heavy Tank: 1950-1974</i>" that "<i>there was no specific doctrine calling for the support of medium tanks in the field by heavy tank units, and in general it was assumed that the specific situation at hand would determine if the heavy tank company would support an infantry regiment in combat, form as part of the division’s antitank plan, or, in the rare case that the tank battalion was used en masse, to operate as part of an armored task force</i>".<br />
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The T-10 was organized into heavy tank regiments which would be integrated into a tank division alongside two medium tank regiments. It could also be organized to form heavy tank divisions, but as the purpose of heavy tank divisions on the strategic scale became uncertain in the USSR during the late 1950's, they were eventually declared obsolete, making heavy tank regiments the largest dedicated unit size for heavy tanks.<br />
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The development of the T-10 was managed by Zhozef Yakovlevich Kotin, the chief designer of the Chelyabinsk Kirov Plant (ChKZ) design bureau who was previously responsible for the IS-2 and the IS-3, and the design work was handled by chief designer M.F Balzhi who had previously been involved in the design of both the IS-3 and IS-4. The new heavy tank was developed to be the direct successor of the IS-3 (Object 703) and IS-4 (Object 701). Needless to say, an evolutionary progression in tank technology is quite natural, but in this instance, it was prompted by the inadequacies of the first postwar heavy tanks. Problems with the IS-3 emerged shortly after it entered service and it was tentatively supplanted by the IS-4, but the IS-4 itself turned out to be rather flawed and it was discontinued just three years after production began. Conceptually, both of these tanks were designed during WWII and were created under late-war requirements with a late-war engineering school of thought which made them less than adequate for the needs of a postwar USSR.<br />
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In the December 2012 edition of the "<i>Отечественные Бронированные Машины 1945-1965</i>" series of articles authored by M.V Pavlov and published in the "<i>Техника И Вооружение</i>" magazine, Pavlov states in page 54 that the IS-4 failed its 1,000 km mobility trial due to the failure of the final drives, destruction of roadwheel and idler wheel bearings, failure of the oil pressure gauges in the engine, premature wear and destruction of the brake pads, failure of the transmission, failure of the hydraulic transmission control mechanism, and more.<br />
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Pavlov also mentioned other severe shortcomings of the tank, such as the unacceptably noisy fans of the cooling system. The whistling noise from the pair of radial cooling fans on the engine deck caused such a high amount of acoustic interference that it actually shortened the range of the onboard radio transceivers, and the fans could reportedly be heard from a staggering distance of 7-8 kilometers while the tank was moving. The concentration of carbon monoxide in the tank from the engine and from propellant fumes was also unacceptably high, making it difficult for the crew to operate the tank effectively. To top it all off, the escalation in weight led to one IS-4 costing almost three times as much as an IS-3 without bringing an equal increase in combat effectiveness. Much of this cost was related to the short supply of thick rolled steel armour plates and the difficulties in assembling a tank with such thick armour.<br />
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This is all the more unfortunate when earlier on, the initial IS-4 design (Object 701) still had a more modest combat weight of 55 tons in its prototypical form and it exceeded the IS-3 in several technical characteristics including tactical mobility such as <a href="https://warspot-asset.s3.amazonaws.com/articles/pictures/000/026/993/source/object257s06-62962667aab1e21b16c41f34e201f4cb.jpg">having a 25% higher average speed when moving cross-country</a> despite being a heavier tank. Mobility trials confirmed that the IS-3 was quicker and the difference in the mobility between the Object 701 and IS-3 continued to increase as the Object 701 gained more armour in later prototypes. At this stage, the IS-7 was still optimistically projected to weigh just 54-56 tons. In actuality, the pursuit of all-round armour protection would cause the IS-4 to bloat to a combat weight of 60 tons and the IS-7 would weigh a staggering 68 tons. The issues that arose from the weight gain made the IS-4 unsustainable; the mass production of the IS-4 was terminated on the 9th of April 1947. The IS-4M modernization was created with the aim of fixing these issues or at least ameliorating them, but not all IS-4 tanks were modified to this standard by the time the programme was terminated on the 22nd of March 1949.<br />
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<a href="https://2.bp.blogspot.com/-TQXvOrKx-Es/XM-S7EK1eUI/AAAAAAAAN5Y/R0IPH7MBY4IZUtjCWIkxmqvMeIy8qO3nQCLcBGAs/s1600/moving%2Bis-4.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="360" data-original-width="640" height="225" src="https://2.bp.blogspot.com/-TQXvOrKx-Es/XM-S7EK1eUI/AAAAAAAAN5Y/R0IPH7MBY4IZUtjCWIkxmqvMeIy8qO3nQCLcBGAs/s400/moving%2Bis-4.jpg" width="400" /></a><a href="https://4.bp.blogspot.com/-aEuffLLoek0/XM-SWDaLulI/AAAAAAAAN5Q/sYD6RXLQ0f8e-cv-n1uD9z7KRTBAdLr6ACLcBGAs/s1600/is-4.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="376" data-original-width="658" height="227" src="https://4.bp.blogspot.com/-aEuffLLoek0/XM-SWDaLulI/AAAAAAAAN5Q/sYD6RXLQ0f8e-cv-n1uD9z7KRTBAdLr6ACLcBGAs/s400/is-4.jpg" width="400" /></a></div>
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On the 9th of April 1952, all IS-4 and IS-4M tanks were withdrawn from their frontline stations and relegated to the Reserves of the Supreme High Command (RVGK) - the strategic reserves - and served in this capacity in the Far Eastern Military District. When the Korean War took off, military units stationed in this district including IS-4 tanks were sent to Primorsky Krai (Manchuria) to secure the border between the USSR and North Korea, and when the Sino-Soviet split occurred, IS-4 units stationed in the Far Eastern Military District were mobilized once again and sent to the Transbaikal region bordering China, and the ones stationed in Manchuria were turned towards also China.<br />
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In practice, the troubles with the IS-4 meant that the IS-3 was the de facto heavy tank of the Soviet Army despite its own flaws which were being gradually ironed out in new tanks during production and later corrected on existing tanks via an expensive refurbishment programme to become the IS-3M.<br />
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The plethora of issues plaguing the IS-4 prompted great skepticism towards the IS-7 as the latter represented an even greater escalation in weight. This had an indirect effect on the eventual rejection of the IS-7 and catalyzed the decision to restrict the weight of all future heavy tanks. On February 18th 1949, the Council of Ministers of the USSR passed resolution No.701-270ss which formally prohibited all further work on heavy tanks with a mass of more than 50 tons. This would allow the crossing of civilian bridges, pontoon bridges, and other tactical bridges for crossing obstacles as these had a weight limit of 50 to 60 tons. It would also allow the heavy tank to be transported piecemeal by rail as the maximum weight capacity set by Soviet railway authority at the time was 55 tons. Attached to resolution No.701-270ss was the order for the LKZ and ChKZ design bureaus to develop a new heavy tank with a weight of 50 tons or less. The Object 730 prototype of the new tank, designed by the ChKZ design bureau with Zhozef Kotin at the helm, was ready for trials just seven months later under the tentative designation of IS-5, not to be confused with the Object 248 prototype from 1944 that was also known as "IS-5".<br />
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The IS-5 had a hull design taken directly from the IS-7 but streamlined and trimmed down for reduced weight at the expense of armour protection. Its turret was a completely original design. The IS-5 had the transmission of the IS-4 and used a similar cooling system driven by a pair of large axial cooling fans on the engine deck in the same style as the IS-4, closely patterned after the cooling fans used on the German Panther tank. The image below shows the IS-5 in its 1949 configuration with all of these features.<br />
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However, the reliability issues of the IS-4 transmission reemerged on the IS-5. The test report noted the following:<br />
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<blockquote class="tr_bq">
"<i>1. Испытание машины начато 22.09.49 г. за это время она прошла 1012 км, из них:</i><i>а) проселочная дорога — 501 км;</i><i>б) пересеченная местность — 511 км.</i> </blockquote>
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<i>2. Двигатель проработал 67 ч 36 мин.</i> </blockquote>
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<i>3. В процессе испытаний получены следующие средние скорости чистого движения:</i> </blockquote>
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<i>а) проселочная дорога 29–27 км/ч;</i> </blockquote>
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<i>б) мокрый луг 17,7-16,5 км/ч;</i> </blockquote>
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<i>в) болотистый луг (движение осуществлялось преимущественно погружением клиренса), пройдено 314 км 12–14 км/ч.</i> </blockquote>
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<i></i><i>На отдельных участках сухого пути получали скорость 31–27 км/ч.</i> </blockquote>
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<i>4. Основные дефекты:</i> </blockquote>
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<i>а) Разрыв и разрушение по швам и целому телу алюминиевых топливных баков после 441 км. Внутренние баки заменены на стальные.</i> </blockquote>
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<i>б) Выход из строя обоих бортовых редукторов по причине закручивания и изгиба ведущих валов.</i> </blockquote>
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<i>5. В настоящее время машина находится на втором техническом осмотре</i>"</blockquote>
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Translated to English:<br />
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<blockquote class="tr_bq">
<i>1. The test of the machine started on 22.9.49 during which it covered 1,012 km, of which:</i><i>a) Country roads - 501 km</i><i>b) Rough terrain - 511 km</i> </blockquote>
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<i>2. The engine worked for 67 h 36 min</i> </blockquote>
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<i>3. During the test, the following average net speeds were obtained:</i> </blockquote>
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<i>a) Country roads 29-27 km/h</i> </blockquote>
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<i>b) Wet meadow 17.7-16.5 km/h</i> </blockquote>
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<i>c) Marshy meadow (the movement was carried out mainly with sunken clearance), covered 314 km at 12-14 km/h</i> </blockquote>
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<i></i><i>On some parts of dry roads, the speed was 31-27 km/h.</i> </blockquote>
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<i>4. Major defects:</i> </blockquote>
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<i>a) Formation of gaps and the destruction at the seams and the whole body of aluminum fuel tanks after 441 km. Internal tanks replaced by steel tanks.</i> </blockquote>
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<i>b) The failure of both final drives due to the tightening and bending of the axles.</i></blockquote>
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<i>5. At this time, the machine is undergoing the second technical inspection </i>(author's note: second level of maintenance as part of a planned maintenance schedule)<i>.</i></blockquote>
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The main emphasis of the test was that the transmission was unreliable. The tank failed its 2,000 km factory warranty trial due to the failure of the transmission, signalling the need for a new and more robust design. As a result, a new 8-stage planetary transmission was installed in the tank. During the course of the redesign, many other refinements were made to the tank, including the replacement of the fan-based cooling system with a forced-ejection cooling system inspired by the IS-7 project. By the time the tank entered service as the T-10, it combined several of the successful design features of the IS-4 running gear with several features from the IS-7, so it can be said to have an amalgamation of all the best parts of its predecessors in a refined form. At that point, the "Object 730" designation had been applied to three modifications of the same tank under three different names.<br />
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Although the T-10 obr. 1953 (right below) was externally similar to the first IS-5 design from April 1949 (left below), the end product had several distinguishing features. The hull underwent minimal modifications, but the turret was given a more rational distribution of armour thicknesses. The armour protection was somewhat increased, and as testing of the tank continued in the mid-1950's, improvements to the casting technology and the distribution of armour mass were continuously made on the production line.<br />
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With the less-than-glamorous history of the IS-3 and IS-4 in mind, the T-10 could be rightfully considered the most successful heavy tank to serve in the Soviet Army during peacetime and was unquestionably a good, solid tank worthy of its place, at least by the standards of typical heavy tanks as the T-10 still had all of the drawbacks commonly associated with its class such as high production and maintenance costs and a somewhat low cost effectiveness relative to its actual combat capability. The strategic decision to impose an artificial weight limit of 50 tons undoubtedly had a large influence on the relatively unproblematic career of the T-10.<br />
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While the IS-4 primarily served in the reserves and only lasted only a few years in active service, the T-10 saw over a decade of active service in the Western Military District as the backbone of Soviet heavy tank divisions before being slowly withdrawn to the strategic reserves during the tail end of the 1960's, and several heavy tank units equipped with T-10M tanks even continued to serve in the GSFG until the late 1970's. Some sources state that the withdrawal of the last T-10M battalion occurred in 1979.</div>
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On the 28th of November 1953, the T-10 officially entered service in the Soviet Army and on the 15th of December 1953, the order was given to put the new heavy tank into mass production under the product code of Object 730. Factory No. 200 was responsible for the manufacture of turrets and hulls. Production of the original T-10 was slow, with only 30 units produced in 1954, 90 units produced in 1955 and 70 units produced in 1956 when the production run ended. Together with the ten pre-production tanks manufactured in 1953 prior to the official induction of the tank into the Soviet Army, the total number of T-10 tanks amounted to only 200 units. This paltry figure was less than a tenth of the total number of IS-3 tanks produced during its own short run and was utterly miniscule compared to the production run of workhorse tanks like the T-54, but even so, even at this early stage the T-10 series already outnumbered the Conqueror of which only 185 examples were built in a longer production run from 1955 to 1959. <br />
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However, these T-10 tanks had a number of issues related to the poor quality control of Factory No. 200 for the manufacture of the cast turrets. In 1954, a whopping 50.9% of the turrets of the tanks delivered to the Soviet Army exceeded the design mass of 6,500 kg by the tolerance limit of 5% (325 kg). This improved to 11.5% by 1955, but it was revealed during extensive live fire tests in the same year that 32% of the tested turrets (22 in total) did not meet the design specifications for ballistic resistance. As such, it was recognized that further refinement of the turret design was still needed in order to curb the wastage of resources and ensure that the design criteria for protection could be met consistently. The two photos below show one of the T-10 tanks built in 1954.<br />
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On the 17th of May 1956, the T-10A entered service and began production at ChKZ under the product code of Object 731. Although this model officially replaced the T-10 on the production line, there was a transitional period of a few months where both models were being produced simultaneously, with many components being shared by both. Less than one year later, the T-10B entered service on the 11th of February 1957 and began production at ChKZ under the product code of Object 733. Only 110 examples of the T-10B model were delivered when on the 26th of September 1957, the T-10M entered service and fully replaced it on the production line the next year. It had the product code of Object 272. Interestingly enough, the T-10M had a combat weight of 51.5 tons so it exceeded the official weight limit by just a hair, but this was likely considered acceptable as it was still well within the 55-ton railway load limit.<br />
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The T-10M obr. 1957 was manufactured simultaneously at both ChTZ and LKZ, but in slightly different forms. The ChTZ factory produced the Object 734 and the LKZ factory produced the Object 272. The two factories produced slightly different models because the ChTZ factory had only recently mastered the production of T-10 hulls when the new Object 272 design from LKZ was adopted as the next primary tank model. Because ChTZ was unable to switch production to the new Object 272 hull rapidly, they had to resort to the compromise solution of mating Object 272 turrets to Object 730 hulls, thus creating the Object 734, known as the Chelyabinsk T-10M as opposed to the original Leningrad T-10M. In 1962, ChTZ was finally prepared to switch to producing Object 272 hulls, so both factories were standardized on the Object 272 specifications. The final modification of the T-10M entered service in 1963 as the T-10M obr. 1963 and the tank continued to be manufactured in this form until 1965.<br />
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From 1953 to 1965, a total of 1,439 T-10 tanks and variants thereof were produced in the USSR. The T-10M lasted the longest on the production lines by far and can be considered the definitive representation of the T-10 series, being not only the most advanced model but also the most numerous by a large margin. Although no modernization programmes to bring earlier T-10 models to the T-10M standard were carried out in the USSR, some tanks were retrofitted with night vision equipment to close the gap in capabilities. Some tanks only received a partial modernization as not all parts and facilities were available for the units equipped with T-10 tanks.<br />
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To put the production figures of the T-10 into perspective, it can be compared to the M103 and the Conqueror. In 1955, the first Conqueror was built in the Royal Ordnance Factory and production continued until 1959, ending with a total of 185 tanks delivered to the British Army. A total of 20 Mark 1 and 165 Mark 2 Conquerors were built.<br />
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The M103 was much more numerous, but the time frame of its deployment was relatively late compared to the T-10. The T43E1 prototype of the M103 heavy tank (it was not designated the M103 yet because it had not been type-classified) entered mass production at approximately the same time as the T-10 but was considered unfit for service in its initial form. The Continental Army Command (CONARC), had finished testing these T43E1 tanks and found them unsatisfactory for issue to the troops as of June 20, 1955. A total of 144 modifications were deemed necessary, but due to the lack of urgency after the conclusion of the Korean War, the Army opted for a simpler refurbishment that applied just 98 of the 144 modifications. The M103 was type classified on the 26th of April 1956 and the first batch of 80 M103 tanks that were modified to the Army standard were operational by the middle of 1957 after troops trials in early 1957 had concluded. By this time, a decade had passed since the production of the IS-3 ceased, the T-10B had already begun mass production and the T-10M was only a year away from replacing it on the production line.<br />
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Only around 300 examples were produced, which is barely more than a fifth of the final size of the T-10 fleet. That said, the U.S Army had abandoned all of their heavy tank projects and moved on from the heavy tank concept and had shifted the focus on a main battle tank that could combine the capabilities of a medium tank and a heavy tank in a new and rather forward-thinking battle doctrine. Ultimately, this would prove to be the correct mindset even though the main battle tank borne from the new doctrine, the M60A1, did not have most of the characteristics that are now considered essential for a tank to truly belong under this classification. Ironically, the new main battle tank that made heavy tanks redundant in the eyes of the U.S Army bureaucracy became a source of upgrades for the M103A1 which was overhauled with a large number of M60 components to become the M103A2.<br />
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When the production of the T-10M ceased in 1965, it ended its eight-year production run and twelve years had passed since the original T-10 was accepted into the Soviet Army. The primary factor in the eventual downfall of the T-10 was not in any particular flaw in its design or in any deficiencies of its technical characteristics. Rather, it was a combination of various new developments in tank technology leading to the obsolescence of heavy tanks as a class. The main domestic threat to the existence of the T-10M was the excellent performance and stellar cost effectiveness of the T-54 medium tank, and the threat was further amplified by the appearance of the T-62 with its powerful 115mm smoothbore gun and APFSDS ammunition which would have been more effective against the armour of tanks like the M60A1 than any full caliber AP shell, thus voiding some of the firepower advantage that the T-10M previously held over medium tanks. The gap in the payload of the HE-Frag shells between the 122mm M62-T2 and the 115mm U-5TS was also much smaller than the gap that existed between it and the 100mm D-10, further eroding more of the credibility of the T-10 series as a viable instrument of war.<br />
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The final blow to the T-10 series and to Soviet heavy tank development in general was dealt by the materialization of the main battle tank concept in the Soviet Union in the form of the T-64 which was not only more mobile than the T-10M, but also more heavily armoured and exceeded it in terms of firepower thanks to an automatically loaded 115mm 2A21 smoothbore cannon with a highly sophisticated fire control system that included a fully stabilized optical rangefinder.<br />
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In 1961, the order to terminate all work on heavy tanks was given by the Council of Ministers, but before this, the induction of new vehicles based on heavy tanks had already begun to wind down. For instance, the well-known Object 268 casemated self-propelled gun based on the T-10 hull had passed state trials during the late 1950's and was ready to formally replace the ISU-152 of WWII vintage, but the new tactical and technological trends in armoured warfare did not favour this class of vehicle. A reevaluation of the heavy tank concept yielded the same conclusions. Not only could main battle tanks accomplish all the tasks that were normally delegated separately to medium and heavy tanks, but the tactical-technical characteristics of a main battle tank exceeded both classes of tanks in all operating characteristics including mobility, firepower and armour protection while remaining within the weight category of medium tanks.<br />
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The T-10M continued to serve as a frontline heavy tank in the GSFG until the end of 1976, after which they began to be withdrawn from Germany. Some were sent to training regiments before eventually being delivered back to the Soviet Union. The photo above shows a T-10M of the GSFG photographed in 1974. The withdrawal of the T-10M in 1976 coincided with the deployment of the T-64A main battle tank to the GSFG in the same year, although some units were reequipped with T-55 medium tanks instead. T-10 tanks of all models entered reserve storage and starting from the mid-1980's, they began to be written off, were stripped and used as hard targets at gunnery ranges, or simply scrapped. On the 23rd of September 1997, a presidential decree was issued to officially remove the T-10 series from service and all tanks remaining in storage were ordered to be scrapped<br />
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Overall, the T-10 was a low-profile tank with good armour protection, a relatively low weight, high mobility characteristics, acceptable crew accommodations, an advanced fire control system and an effective complement of weapons at its disposal. By all metrics of tank quality, the T-10M model was a serious contender for the best tank of its class during its heyday.<br />
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<h3>
<span style="font-size: large;">INDEX</span></h3>
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<ol>
<li><a href="#erg">Ergonomics</a></li>
<li><a href="#vent">Ventilation</a></li>
<li><a href="#comstat">Commander's Station</a></li>
<li><a href="#comms">Communications</a></li>
<li><a href="#gunstat">Gunner's Station</a></li>
<li><a href="#sights">Sighting Complexes</a></li>
<li><a href="#tsh2">TSh2-27 Articulated Telescopic Sight</a></li>
<li><a href="#tps1">TPS1 Stabilized Periscopic sight</a></li>
<li><a href="#tup">TUP-21 Auxiliary Telescopic sight</a></li>
<li><a href="#t2s">T2S-29-14 Stabilized Periscopic Sight</a></li>
<li><a href="#tpn-1">TPN-1-29-14 Night Vision Sight</a></li>
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<li><a href="#loadstat">Loader's Station </a></li>
<li><a href="#ammostow">Ammunition Stowage</a></li>
<li><a href="#loadassist">Loading Assistance Device </a></li>
<li><a href="#d25assist">- for D-25TA, D-25TS</a></li>
<li><a href="#m62assist">- for M62-T2</a></li>
<li><a href="#rof">Rate of Fire</a></li>
<li><a href="#taen-1">TAEN-1 Powered Controls</a></li>
<li><a href="#stabs">Stabilizers </a></li>
<li><a href="#puot">PUOT "Uragan"</a></li>
<li><a href="#puot-2">PUOT-2 "Grom"</a></li>
<li><a href="#puot-2s">PUOT-2S "Liven"</a></li>
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<li><a href="#d-25t">D-25TA, D-25TS </a></li>
<li><a href="#d25ammo">Ammunition, 122x785mm </a></li>
<li><a href="#m62">M62-T2 </a></li>
<li><a href="#m62ammo">Ammunition, 122x759mm </a></li>
<li><a href="#mgs">Coaxial, Anti-Aircraft Machine Guns</a></li>
<li><a href="#dshkmt">DShKM</a></li>
<li><a href="#aadshkmt">Anti-Aircraft DShKM</a></li>
<li><a href="#kpvt">KPVT</a></li>
<li><a href="#aakpvt">Anti-Aircraft KPVT</a></li>
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<li><a href="#prot">Protection</a></li>
<li><a href="#hull">Hull</a></li>
<li><a href="#upglacis">Upper Glacis</a></li>
<li><a href="#lowglacis">Lower Glacis</a></li>
<li><a href="#hatch">Driver's Hatch</a></li>
<li><a href="#sides">Side Armour</a></li>
<li><a href="#belly">Belly Armour</a></li>
<li><a href="#t10turret">T-10, T-10A, T-10B Turrets</a></li>
<li><a href="#t10mturret">T-10M Turret</a></li>
<li><a href="#fire">Firefighting System</a></li>
<li><a href="#smoke">Smokescreening System</a></li>
<hr />
<li><a href="#drivestat">Driver's Station</a></li>
<li><a href="#esc">Escape Hatch</a></li>
<li><a href="#mobile">Mobility</a></li>
<li><a href="#v12-5">V12-5 Engines</a></li>
<li><a href="#v12-6">V12-6 Engines</a></li>
<li><a href="#cool">Cooling System</a></li>
<li><a href="#susp">Suspension</a></li>
<li><a href="#fuel">Fuel System</a></li>
<li><a href="#water">Water Obstacles</a></li>
</ol>
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<a href="https://www.blogger.com/null" id="erg"></a>
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<h3>
<span style="font-size: large;">ERGONOMICS</span></h3>
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It is popularly perceived that Soviet tanks were designed with little attention to comfort or safety and that Western tanks were generally the opposite. Although this is evident to be true in some cases, Soviet tanks generally met and sometimes exceeded the minimum ergonomic requirements stipulated by the U.S Army and were not any less safe to operate than any other tank. It's just that in many cases, American tanks (and tanks of other nations) usually exceeded these minimum requirements by a larger margin. However, the fulfillment of those minimum standards implies that the standards of comfort were sufficient to ensure that the tactical-technical requirements could be met.<br />
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It often goes unmentioned that Soviet tank designers had to pay attention to crew ergonomics while under the obligation to deliver a product that met the challenging set of requirements put forward by the GBTU (Main Directorate of Armoured Forces). However, ergonomics had not been firmly established as a formal science at the time so only basic stipulations were given for the required dimensions of the tank crew stations. Much of it was left to the discretion of the design bureau under the advice of the Main Military Medical Directorate of the Soviet Army.<br />
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The basic external dimensions of the hull did not change during the production run of the entire T-10 tank series. The height of the hull is 1,015mm from the fighting compartment floor to the fighting compartment roof, including the armoured belly and roof themselves. However, the floor underneath the transmission has a bulge with a depth of 47mm, so the maximum height of the hull is 1,046mm when measured from this point.<br />
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The torsion bar housings protrude below the hull belly, but do not protrude below the transmission bulge. Internally, the height of the hull in the fighting compartment measured from the rotating floor is only 835mm while the height of the hull at the driver's compartment is 969mm. The total length of the hull is 6,925mm. The total external width of the hull is 3,162mm when measured across the sponsons, and the width of the lower part of the hull is 1,790mm. These dimensions are nearly identical to the IS-3. The internal width of the hull at the lower half is 1,630mm and the maximum internal width of the hull is 2,810mm as measured across the sponsons.<br />
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One of the most common misconceptions is that the liberal application of sloped armour plating for the construction of the hull led to a reduction in interior volume, but there is no evidence for this. On the contrary, a closer inspection of the configuration of the hull as depicted in the cross-sectional drawing below immediately dispels this widespread misunderstanding and shows quite the contrary.<br />
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<a href="https://4.bp.blogspot.com/-k7VcmHniULo/XC1xsOtQvrI/AAAAAAAAMwM/uDfTOa-gRPcHDryw002uYH52SSYFE03JACLcBGAs/s1600/t-10%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="471" data-original-width="948" height="317" src="https://4.bp.blogspot.com/-k7VcmHniULo/XC1xsOtQvrI/AAAAAAAAMwM/uDfTOa-gRPcHDryw002uYH52SSYFE03JACLcBGAs/s640/t-10%2Bcross%2Bsection.png" width="640" /></a></div>
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The hull belly is constructed from a steel plate pressed into the shape of a tub with steeply sloped sides which are joined to the side hull armour plates. This ostensibly cramps the interior of the tank and reduces the floor space in the hull to a narrow corridor, but in actuality, this space is only used to house the torsion bar suspension. The rotating floor for the three-man turret is mounted on a platform and lies on top of the torsion bar housings (140mm in height from the hull floor), giving the crew the full space provided by the internal width of the hull at the expense of the vertical space. Considering that conventional single torsion bar suspensions already take up almost the same amount of hull height in most cases. The loss of vertical space in this design is thus not directly related to the hull shape, but the torsion bars.</div><div><br /></div><div>Nevertheless, the space underneath the rotating floor is not entirely wasted as small arms ammunition for the crew's personal weapons and some equipment is stored underneath it. The small arms ammunition can be retrieved through an access panel on the 6 o'clock sector of the rotating floor when the turret is locked in the forward position.<br />
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The internal width of the hull is notable, seeing as the rotating floor upon which the loader stands has a diameter close to the internal width of the lower part of the hull. For a lack of a written source, the diameter of the rotating floor is estimated to be 1,570mm based on factory drawings. This is very similar to the rotating floor in the Conqueror heavy tank which had a diameter of 1,625mm or 64 inches and it is considerably wider than the rotating floor of the T-54/55 which was 1,370mm in diameter. The remains of a partially rotted and highly vandalized rotating floor in a dilapidated T-10M can be seen in the photo below (photo from the <a href="https://www.net-maquettes.com/pictures/t-10-heavy-tank/">Net-Maquettes website</a>). The gunner's seat can be seen at the top left corner of the photo in its fully lowered position.<br />
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<a href="https://1.bp.blogspot.com/-BBvkLLzCotg/XOzknq_-qVI/AAAAAAAAOHg/HVhPb0O4ZjgHgjMVAwLj4JsYA9mLDGatwCEwYBhgL/s1600/rotating%2Bfloor.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1023" height="480" src="https://1.bp.blogspot.com/-BBvkLLzCotg/XOzknq_-qVI/AAAAAAAAOHg/HVhPb0O4ZjgHgjMVAwLj4JsYA9mLDGatwCEwYBhgL/s640/rotating%2Bfloor.png" width="640" /></a></div>
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The turret ring diameter of all T-10 variants is 2,100mm. This figure lies squarely between the 2,160mm turret ring diameter of the M103 and 2,032mm turret ring diameter of the Conqueror. It is important to note that the turret ring of the IS-3 is only 1,840mm in diameter which is not only markedly inferior to the T-10 but also only negligibly larger than the 1,825mm diameter of the turret ring of the T-54. With the D-25T gun being a shared feature between the T-10 and IS-3, it is evident that the T-10 turret was markedly superior in the width and length of its fighting compartment.<br />
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The increased length of the fighting compartment helped to ensure that the physical spaces of the commander and gunner do not intersect. Like the vast majority of other tanks, both foreign and domestic, the T-10 places its commander's seat within the turret ring, so the space between the commander and gunner is directly linked to the turret ring diameter. Generally speaking, unless it is balanced out by the addition of more equipment in front of the gunner, a larger turret ring diameter usually meant that there was more space between him and the commander behind him. In the T-10, there is just under a meter of space behind the gunner's seat and more than enough space for the commander to sit with his knees well clear of the gunner's back, unlike in the T-54 where the commander needed to sit with the gunner between his knees. The drawing below shows the fighting compartment of a T-10B with the turret ring marked as a red circle.<br />
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<a href="https://1.bp.blogspot.com/-pJiCbukKYxY/XP_7S2gjTNI/AAAAAAAAOaE/4r0GXmOcKn0FuAK7D9gtugRYoIyhz4J7ACLcBGAs/s1600/highlighted%2Bturret%2Bring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1278" data-original-width="1600" height="510" src="https://1.bp.blogspot.com/-pJiCbukKYxY/XP_7S2gjTNI/AAAAAAAAOaE/4r0GXmOcKn0FuAK7D9gtugRYoIyhz4J7ACLcBGAs/s640/highlighted%2Bturret%2Bring.png" width="640" /></a></div>
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Due to the large diameter of the turret ring and the impressive width of the hull across the sponsons, the internal volume from the perspective of the crew in the fighting compartment is relatively large. The photo below, taken from the <a href="https://www.net-maquettes.com/pictures/t-10-heavy-tank/">Net-Maquettes website</a>, shows a view of the hull from behind the fighting compartment. The rotating floor of the turret can be seen in the bottom left corner.<br />
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<a href="https://1.bp.blogspot.com/-6mw_hZlr7IA/XOznPdUj0MI/AAAAAAAAOIQ/-OEmbLrrBhIhZbpezmO0nea2iIdYBpO5wCLcBGAs/s1600/interior%2Bhull%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1023" height="480" src="https://1.bp.blogspot.com/-6mw_hZlr7IA/XOznPdUj0MI/AAAAAAAAOIQ/-OEmbLrrBhIhZbpezmO0nea2iIdYBpO5wCLcBGAs/s640/interior%2Bhull%2Bview.png" width="640" /></a></div>
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Combined, the hull and turret structures for the T-10 up to the T-10B measure 1,881mm in height. Measured from the ground, the height of the hull is 1,506mm, making it much shorter than an average man. This is a normal height for any tank.<br />
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<a href="https://1.bp.blogspot.com/-ROzqoXZrXqo/XM5rZG78meI/AAAAAAAAN30/k-cPY95QbnU2YMhZ62u9EdvThcMTYQU2QCLcBGAs/s1600/t-10m%2Band%2Bpedestrian.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="395" data-original-width="600" height="420" src="https://1.bp.blogspot.com/-ROzqoXZrXqo/XM5rZG78meI/AAAAAAAAN30/k-cPY95QbnU2YMhZ62u9EdvThcMTYQU2QCLcBGAs/s640/t-10m%2Band%2Bpedestrian.jpg" width="640" /></a></div>
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The total height of the tank measured to the top of the commander's cupola is 2,460mm for the T-10, T-10A and T-10B, and 2,585mm for the T-10M. However, the height of the tanks when measured up to the turret roof was just 2,300mm for the first three models and 2,427mm for the T-10M. When the ground clearance of the tank is taken out of the equation, the structural height of the tank is only 1,807mm for the first three models and only 1,930mm for the T-10M. This was directly comparable to the T-54 and it was considerably shorter than Western medium tanks like the M47 and M48 Pattons and the Centurion, not to mention Western heavy tanks.<br />
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The increased height of the T-10M was entirely due to the slightly taller turret which accommodated a gun depression angle of -5 degrees for its M62-T2 gun instead of the normal -3 degrees for the D-25T series of guns mounted in previous models, although the design of the turret itself is only partly responsible for providing the additional two degrees of depression. A full examination of this topic is provided in the section of this article on the M62-T2 gun. Both the Object 272 from Leningrad and Object 734 from ChTZ shared the same height despite the retention of the basic T-10 hull on the Object 734 since they both shared the same turret.<br />
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Internally, the height of the T-10 fighting compartment in the turret was 1,600mm as measured from the rotating floor to the ceiling of the turret. This is the same as the IS-2, IS-3, T-54, and several other Soviet tanks of the era. The two images below give a good perspective on the height of the tank scaled against Soviet tankers.<br />
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<a href="https://1.bp.blogspot.com/-6xdhknyGg34/XPL6ihkGkII/AAAAAAAAOKc/dkEdzyNOthgWu7gDQYMSxM8WIO_gCqNiACLcBGAs/s1600/group%2Bphoto%2B1974.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="456" data-original-width="650" height="280" src="https://1.bp.blogspot.com/-6xdhknyGg34/XPL6ihkGkII/AAAAAAAAOKc/dkEdzyNOthgWu7gDQYMSxM8WIO_gCqNiACLcBGAs/s400/group%2Bphoto%2B1974.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-WUokpNC8Bh4/XPL6ionVQCI/AAAAAAAAOKY/AKISBjaQX3koNZ9mvmAUbKum8nirrJedQCLcBGAs/s1600/t-10%2Bfilm%2Bstill.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="474" data-original-width="648" height="292" src="https://1.bp.blogspot.com/-WUokpNC8Bh4/XPL6ionVQCI/AAAAAAAAOKY/AKISBjaQX3koNZ9mvmAUbKum8nirrJedQCLcBGAs/s400/t-10%2Bfilm%2Bstill.jpg" width="400" /></a></div>
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Naturally, a side effect of the increased height of the T-10M turret is the increased headroom for the crew, and most importantly, for the loader. The internal height of the T-10M as measured from the rotating floor to the turret ceiling is 1,725mm which is tall enough that standing completely upright may be possible for an average Soviet military age male who would have a height of 1.7 meters. The loader also has a cupola which is raised above the turret roof, so in practice, he could have more headroom if he stands directly underneath his cupola when performing some loading actions.<br />
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For a seated gunner or commander, shoulder height and seated height are the most important dimensions. The amount of space needed for these two crew members to carry out their duties effectively is not large, especially for the gunner who practically does not need to move at all if his controls are well laid out. The commander in a T-10 needs space to operate the radio, read maps, and so on, but in combat, his main tasks are to observes the battlefield through the viewing devices in his cupola, receive orders from his superiors or transmit orders to subordinate tank commanders (as a platoon or company leader) and to micromanage the rest of the crew using verbal commands, neither of which require a large working space. For a loader, however, space is much more important as his duties are inherently much more physical. The most important dimensions for a loader are the standing height, elbow width, and elbow height.<br />
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The width of the hips of an average man is only 350mm but the shoulder width of an average man is 450mm. Immediately it becomes obvious that it is possible to optimize the layout of a tank by narrowing the hull and increasing the width of the turret. The width of the loader's station should be as large as possible at elbow height as a human loader grasping a large caliber cartridge would hold it at elbow height, but generally speaking, the maximization of the internal width of the tank above the hip level of a standing man is beneficial to all the members of the crew, especially the loader.<br />
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Because of such nuances, it is not really possible to accurately express crew conditions by simply looking at the volume of the crew members' stations, although it can certainly be used as a tool for comparing two tanks with similar layouts and internal dimensions to some extent.<br />
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The photo below, from "<i>T-10 Heavy Tank and Variants</i>" by James Kinnear and Stephen Sewell, shows the left side of a T-10M turret. Without actual crew members sitting on the seats for the commander and gunner, it is somewhat difficult to form an accurate perspective on the amount of space provided for the two men but at least the layout of the equipment and furniture can be appreciated from this angle.<br />
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The inclusion of sponsons allowed a turret ring of a larger diameter to be implemented than would otherwise be possible with a hull that had completely vertical sides, that is, unless special platforms extending from the sides of the hull were used to accommodate the turret ring. This is best exemplified by the T-62 medium tank which features a 2,245mm turret ring despite having a hull with a width of only 2,020mm. This design solution enables a turret ring of a larger diameter than the maximum width of the hull to be installed, but there is no possibility of stowing a significant amount of ammunition or equipment in the extensions. The area above the tracks can still be used as a stowage space, but only expendable items such as tools and spare parts or fuel can be placed in these areas due to the lack of armour protection.<br />
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In the drawing above, it can be seen that ammunition is stowed in the hull sponsons and that additional external stowage space is available underneath the sponsons in sheet metal bins. The bins all had the same shape and general dimensions, differing only in length and in the number of hatches. There is a long bin with two hatches, a short bin with one hatch, and one long bin with one hatch.<br />
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The hatches are hinged to open upward, allowing items to be placed inside the bins easily. This was a notable improvement over the IS-7 stowage bins which had an unconventional design that was simple to a fault. It is demonstrated in Nicholas Moran's "Inside the Chieftain's Hatch" video on the IS-7, Part 1.<br />
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Two more stowage bins were added to the fenders on the T-10M model. The additional stowage space was probably appreciated by the crews but unfortunately, the bins also slightly disrupted the sleek prow of the tank. The photo on the left below is <a href="https://www.britmodeller.com/forums/index.php?/topic/235020451-t-10-object-730-soviet-heavy-tank/">from Dave Haskell</a> and the photo on the right below is from the Net-Maquettes website.<br />
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As usual for a Soviet tank of the 1950's, the standard-issue tarpaulin was strapped to the rear of the turret. The tarpaulin was a general-purpose item but it was often used as a tent. One excellent way of using it on cold nights was to turn the turret back and elevate the gun to its highest angle, and then draping the tarpaulin over the gun barrel. The crew would then sleep on the toasty engine deck which would remain warm until daybreak.<br />
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<a href="https://1.bp.blogspot.com/-JQ1qZO0tH7o/XMQf9xWdCvI/AAAAAAAANxs/NHD8iSSvJqEWRhxeoUypSM5tZx_M8cLSwCLcBGAs/s1600/rear%2Bt-10m.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="391" data-original-width="600" height="416" src="https://1.bp.blogspot.com/-JQ1qZO0tH7o/XMQf9xWdCvI/AAAAAAAANxs/NHD8iSSvJqEWRhxeoUypSM5tZx_M8cLSwCLcBGAs/s640/rear%2Bt-10m.jpg" width="640" /></a></div>
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In 1959, the T-10M received an add-on metal stowage bin on the turret bustle. The tarpaulin which previously occupied this area was relocated to the right side of the turret. The beveled shape of the stowage bin was dictated by the need to ensure free air flow to the engine air intake and the radiator intakes on the engine compartment deck.<br />
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The bin is made from light gauge sheet metal so it does not significantly increase the protection of the rear of the turret nor does it offer much protection for its contents from gunfire, shell splinters or fragments, but its location makes it much less likely to suffer damage compared to all other stowage bins on the T-10. It is waterproof when sealed properly and will survive a snorkeling operation. The stowage bin is accessed from single large curved hatch on the top.<br />
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<a href="https://2.bp.blogspot.com/-cviCvJuEcfU/XOKbI-4LU9I/AAAAAAAAN_Q/_7Uxu5gMlqUNkLXIsRn4P7LGGtrY-Bs_wCLcBGAs/s1600/t-10%2Bstowage%2Bbins.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="612" data-original-width="1113" height="218" src="https://2.bp.blogspot.com/-cviCvJuEcfU/XOKbI-4LU9I/AAAAAAAAN_Q/_7Uxu5gMlqUNkLXIsRn4P7LGGtrY-Bs_wCLcBGAs/s400/t-10%2Bstowage%2Bbins.png" width="400" /></a><a href="https://4.bp.blogspot.com/-nAAABRHe8Jg/XOKaEDdFlDI/AAAAAAAAN_I/i0PqCs2uyYQhRefdTqL_h1YIrUmzV-QVwCLcBGAs/s1600/t-10m%2Bbustle%2Bbin%2Bside%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="290" data-original-width="595" height="194" src="https://4.bp.blogspot.com/-nAAABRHe8Jg/XOKaEDdFlDI/AAAAAAAAN_I/i0PqCs2uyYQhRefdTqL_h1YIrUmzV-QVwCLcBGAs/s400/t-10m%2Bbustle%2Bbin%2Bside%2Bview.png" width="400" /></a></div>
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The width of the bustle stowage bin was close to the total width of the turret and it occupied the entire height of the bustle, so it was quite spacious. This bin was mainly used for stowing the personal effects of the crew and it was much more useful in this role than the sponson bins which were more exposed to direct fire and could potentially be blown off if the tank ran over a mine.<br />
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The total internal volume of the tank was 12.72 cubic meters, of which 8.21 cubic meters was allocated for the crew compartment and 4.51 cubic meters for the engine compartment. This was not particularly large compared to contemporary Soviet medium tanks such as the T-54 and T-62. For reference, the total internal volume of the T-54 measured in at 11.4 cubic meters, of which 8.05 cubic meters forms the crew compartment and 3.35 cubic meters forms the engine compartment, and the T-62 has a total internal volume of 12.5 cubic meters and the crew compartment occupies a volume of 9.23 cubic meters. From this, it seemingly appears that the T-10 is more spacious than a T-54 but more cramped than a T-62, but as always, further examination is necessary to gain a more detailed understanding of the true situation.<br />
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Given that many components from the T-10 and the two medium tanks share similar dimensions or are outright identical as is the case with the radio equipment, the main differences lie in the size of the cannon and the ammunition, and immediately the T-10 loses out in spaciousness. The massive 122mm cannon of the T-10 and T-10M is larger than the 100mm cannon of the T-54 and the 30 rounds of bulky 122mm cartridges take up more space than the 34 rounds of 100mm cartridges carried in the T-54. However, the T-10 does not carry any fuel in the fighting compartment whereas the T-54 holds 530 liters of fuel in four internal fuel tanks, two of which occupy useful space in the fighting compartment. As such, the available space in the T-54 is lower by 0.53 cubic meters which somewhat offsets the difference in the size of the gun and ammunition.<br />
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Of the internal volume allocated for the fighting compartment of the T-10, the driver's compartment at the front of the hull occupied 1.35 cubic meters and the fighting compartment occupied 6.86 cubic meters. According to the article "<i>Human Factors and Scientific Progress in Tank Building</i>" by M.N. Tikhonov and I.D. Kudrin, the commander is allocated a volume of 0.871 cubic meters, the gunner is allocated a volume of 0.367 cubic meters, the driver is allocated a volume of 0.650 cubic meters and the loader is allocated a volume of only 0.762 cubic meters. In total, the crew of the turret appears to have 2.0 cubic meters of space and the remaining 4.86 cubic meters of volume is dedicated to the internal equipment of the tank.<br />
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Two hatches were installed on the roof of the turret, one for the commander as a part of his cupola assembly and one for the loader. The gunner is forced to exit through the commander's hatch if the crew is ordered to bail out. This is not ideal in terms of individual crew comfort and the speed of a hasty escape, but this arrangement was normal for manually loaded tanks. For comparison, the Conqueror was equipped with three roof hatches on its turret; one for each crew member stationed within. This was possible because of the unconventional seating arrangement with the commander stationed in the turret bustle, separated from the rest of the turret crew. <a href="http://svsm.org/albums/Conqueror/IMGP7232.jpg">Both hatches were of the lift-and-swing type</a> so that they do not interfere with the commander's view from his cupola if left open for whatever reason. The downside of the unconventional layout that this made for a very long and heavy turret and created an enormous shot trap at the rear of the turret.<br />
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The worst design by far was the turret of the M103. Like in the Conqueror, the commander was seated separately in the bustle in an exceptionally large and long turret and he was provided with his own hatch, but the gunner and two loaders were forced to share a single roof hatch that was officially termed the "front loader's escape hatch" since it was directly over the front right loader's station. The hatch layout of all three tanks can be seen in the drawings below and the size of their turrets can also be appreciated.<br />
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Two 20-liter jerry cans for drinking water were provided in the T-10M. They were stowed side-by-side on the hull wall to the left of the driver, behind the accumulator pack.<br />
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<h3>
<span style="font-size: large;">VENTILATION</span></h3>
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For ventilation, the T-10 featured an intake fan and two exhaust fans that worked to blow air through the crew compartment. The ventilator intake fan is prominently placed on the turret roof, and the two ventilator exhaust fans were installed in the bulkhead between the fighting compartment and the engine compartment. These worked by drawing air from the crew compartment and passing it into the engine compartment. Each fan was driven by an MV-42 electric motor with a power of 175 watts, which is extremely powerful considering that the internal volume of the crew compartment is only 8.21 cubic meters. The two top corners of the drawing below show the two ventilator exhaust fans. The bulkhead is not present in the drawing, revealing the engine and the engine air supply system.<br />
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During combat, the ventilation intake fan on the turret roof acts as a blower that brings fresh air into the fighting compartment, and also serves to remove some propellant fumes after each shot is fired by blowing the fumes downward where they are sucked out of the fighting compartment by the exhaust fans. The drawing below shows the position of the ventilation fan in the turret of a T-10B. Its location is the same in the T-10 and T-10A.<br />
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<a href="https://1.bp.blogspot.com/-Xzyx65_LnZQ/XP_chsplwdI/AAAAAAAAOZQ/sKxg_REn3G8nMP9E25iaLoVyfA14VPVGQCLcBGAs/s1600/t-10a%2Bturret%2Bprofile%2Bcutaway.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="440" data-original-width="1237" height="226" src="https://1.bp.blogspot.com/-Xzyx65_LnZQ/XP_chsplwdI/AAAAAAAAOZQ/sKxg_REn3G8nMP9E25iaLoVyfA14VPVGQCLcBGAs/s640/t-10a%2Bturret%2Bprofile%2Bcutaway.png" width="640" /></a><br />
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The drawing on the left below shows the location of the fan from another perspective and the drawing on the right shows a cross section of the entire ventilator dome, including the S-shaped design of its intake duct. This shape prevents bullets impacting the dome from hitting the fan itself through the duct.<br />
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Naturally, it is desirable to keep the hatches opened in hot weather so that the maximum amount of fresh air can enter the crew compartment, but when the hatches are closed, air can only enter the tank through a few possible intakes: the gaps in the gun mask, the gun barrel bore (if the gun is not loaded), the ventilation intake fan on the turret roof, small gaps in the turret ring between the turret and the hull, gaps in the periscope mountings, and gaps from the imperfect seals of the hatches.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-RQ6FFgBj6O4/YUk0bIYSZAI/AAAAAAAAUMc/5isfjQBbR7QhhGQ57vzjWg6ourbCBzl7gCLcBGAsYHQ/s1104/engine%2Bcompartment%2Bbulkhead.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="479" data-original-width="1104" height="278" src="https://1.bp.blogspot.com/-RQ6FFgBj6O4/YUk0bIYSZAI/AAAAAAAAUMc/5isfjQBbR7QhhGQ57vzjWg6ourbCBzl7gCLcBGAsYHQ/w640-h278/engine%2Bcompartment%2Bbulkhead.png" width="640" /></a></div><div><br />
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Due to the large work capacity of the ventilator exhaust fans, it can be surmised that the air flow through the crew compartment is very strong, which is good for the crew in the summer heat. However, this ventilation system is not ideal in the winter because it simply takes cold air and circulates it in the tank when warmth is needed instead. To circumvent this issue, the exhaust fans can simply be deactivated without closing the shutters for the vents. This allows heat from the running engine to radiate into the fighting compartment, thus providing warmth. The downside is that there is no airflow to remove propellant fumes, so it may still be necessary to turn on the ventilator intake fan during combat.<br />
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In principle, the ventilation system of the T-10 was typical of other Soviet tanks of the immediate postwar era like the T-54, and interestingly enough, it was also quite similar to the M4 and M4A1 variants of the Sherman tank with an air-cooled radial engine. Its cooling system used a pair of large and powerful fans that drew air from the crew compartment and passed it through the engine, thus producing a strong draught in the crew compartment. This was an excellent feature during summer or in the Pacific theatre, but a major issue with this system was that there was no alternate airway for the cooling system, so there was no way to prevent the cooling fans from drawing air from the crew compartment. At night and during winter, this chilled the crew compartment even further and made the crew rather miserable. This unfortunate drawback was mentioned by Dmitriy Loza in his book "<i>Commanding the Red Army's Sherman Tanks: The World War II Memoirs of Hero of The Soviet Union</i>". According to Loza, the crews of the M4 Shermans under his command had the habit of having the commander sit on the left fender next to the driver, who drove with his head out of his open hatch. Naturally, these two men were the most exposed to windchill from the cold night air which had an ambient temperature of 8-10 degrees Celsius according to Loza. To resist the cold, the commander and driver helped themselves to extra portions of alcohol. The ventilation system of the T-10 did not suffer from this problem, but with that said, rations of vodka would still have been appreciated by the crew in cold weather, of course.<br />
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<h3>
<span style="font-size: large;">COMMANDER'S STATION</span></h3>
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The turrets of all T-10 models have a conventional seating arrangement with the commander seated at the rear left quadrant of the turret behind the gunner and adjacent to the loader. The commander's seat is attached to the turret ring and the height can be adjusted between five different positions. If desired, the seat cushion can be folded away to permit easier access the hull without dismantling the entire seat. The seat cushion is round as opposed to <a href="https://i.imgur.com/SHcfX2a.jpg">a more comfortable molded shape like on the M103</a>, so there is not much thigh support. This could make it somewhat uncomfortable for the commander to remain seated for very long periods.<br />
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In a major departure from the IS-3 and IS-4, the commander was given a relatively large conventional cupola with an inclusive hatch. The hatch was much smaller as a consequence, but the number of viewing devices was vastly improved. The cupola offered all-round protection from 12.7mm AP bullets and artillery shell fragments. It has insufficient protection from autocannons, but was unlikely to be hit directly by such weapons due to its low height.<br />
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Unlike an IS-3 or IS-4 commander who was given only a single MK-4 rotating periscope, the commander of a T-10 is furnished with seven fixed TNP periscopes arranged around the circumference of his rotating cupola and one magnified forward-facing binocular periscope which is vertically adjustable, giving him an uninterrupted circular view of the surrounding environment.<br />
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<a href="https://3.bp.blogspot.com/-D2-ddzSCEjo/XL6bcRErSOI/AAAAAAAANuU/uBHjpKPaYx8Fh6cIJppA-egt_OCJqif9QCLcBGAs/s1600/t-10a%2Bcommanders%2Bcupola.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="428" data-original-width="560" height="305" src="https://3.bp.blogspot.com/-D2-ddzSCEjo/XL6bcRErSOI/AAAAAAAANuU/uBHjpKPaYx8Fh6cIJppA-egt_OCJqif9QCLcBGAs/s400/t-10a%2Bcommanders%2Bcupola.png" width="400" /></a></div>
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<br />The TNP periscopes arranged around the commander's cupola are medium sized. The width of the periscope body is 133.5mm and the width of the actual periscope prism is slightly less than that. As shown in the photo below on the right, the periscopes around the circumference of the cupola are covered by a step guard, allowing the commander and gunner to step on the edge of the cupola or grip it when exiting the hatch without fear of damaging the periscope windows. The size of the gaps between each periscope can also be seen. Each of the eight observation devices are installed in 45-degree increments around the perimeter of the cupola.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-RElo_MkVCIs/XD89NYPF4sI/AAAAAAAAM78/U42YiznCCfMMUUO4cqwcYswS_2_HuDYFACLcBGAs/s1600/tnp%2Bperiscope.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="607" data-original-width="856" height="282" src="https://4.bp.blogspot.com/-RElo_MkVCIs/XD89NYPF4sI/AAAAAAAAM78/U42YiznCCfMMUUO4cqwcYswS_2_HuDYFACLcBGAs/s400/tnp%2Bperiscope.png" width="400" /></a><a href="https://1.bp.blogspot.com/-9aHX_P77-1M/XDBE90C-vYI/AAAAAAAAMyI/bdJGtz85k1oK4_4zHc9k67XPTi5RzBu5gCLcBGAs/s1600/commanders%2Bcupola%2Bfilm%2Bscreenshot.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="349" data-original-width="471" height="296" src="https://1.bp.blogspot.com/-9aHX_P77-1M/XDBE90C-vYI/AAAAAAAAMyI/bdJGtz85k1oK4_4zHc9k67XPTi5RzBu5gCLcBGAs/s400/commanders%2Bcupola%2Bfilm%2Bscreenshot.jpg" width="400" /></a></div><div><br /></div>This type of cupola design most closely resembles the cupola of the Centurion tank as both designs can rotate, both have a large number of conventional periscopes arranged radially and both have magnified forward-facing binocular periscopes. However, the Centurion commander's cupola is noticeably larger, having a total diameter of 880mm whereas the T-10 cupola has a total diameter of only 718mm.<br /><br />The greatly improved visibility afforded to a T-10 commander compared to IS-3 and IS-4 commanders reduced his incentive to fight from an open hatch, but if the commander chose to do so regardless, the hatch design gives him much better protection from bullets and shell splinters at the small cost of having a more distinctive silhouette when opened.<br />
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Two cupola types were used in the T-10 series, each type having two iterative models with improvements. The first type, used on the original T-10, was practically built into the turret. The cupola ring mount was first fitted to the hole in the turret roof with bolts, then the cupola itself would be placed on top of it, and then the ball bearings inserted into its race ring to secure the two parts together. It was not possible to simply unbolt the cupola and remove it from the turret without first dismantling it. The cupola race ring was protected by a thick steel collar welded to the turret roof. The electrical connectors in the cupola were connected to the electrical network of the tank with loose wires. An improved cupola design was introduced in the T-10A. The sealing of the cupola was improved, a new traverse lock with two positions (facing forward and backward) was introduced, and most importantly, a new electrical contact ring was implemented to supply power to the commander's target designator system integral to the cupola. The contact ring was a textolite ring with copper-lined grooves, connected to wires embedded inside the textolite, serving as a conductive ring to allow current to flow from the turret to the commander's target designator system via brushes riding on the grooves. The contact ring was placed between the rotating cupola and the fixed ring mount within its own sealed chamber, beneath the race ring. This was done to prevent the ingress of contaminants which could obstruct the grooves of the contact ring or interfere electrically.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Lf8C_iwEieU/YUfeWSlo7II/AAAAAAAAULk/vb9PYzavrNMY0g3pR9JHf0ELfVhY7wJMwCLcBGAsYHQ/s531/t-10a%2Bcupola.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="493" data-original-width="531" height="297" src="https://1.bp.blogspot.com/-Lf8C_iwEieU/YUfeWSlo7II/AAAAAAAAULk/vb9PYzavrNMY0g3pR9JHf0ELfVhY7wJMwCLcBGAsYHQ/s320/t-10a%2Bcupola.png" width="320" /></a></div><div><br /></div><div>The cupola seal consists of a rubber flap which is joined to the cupola, and is pressed against the collar on the turret roof with a steel loop. This creates a fairly tight moisture and dust seal without impeding the rotation of the cupola, as the friction that the commander must overcome is between the steel loop and the steel turret collar, rather than a steel-rubber interface, which would create much more resistance and rapidly wear out the rubber.</div><div><br /></div><div>The commander's hatch is hinged to the cupola roof where the TPKU-2 periscope is installed. The hatch has the shape of a circular segment and has a width of 492mm and a depth (axial width) of around 400mm (excluding the hinges). This is enough for a man of average shoulder width and chest depth, but the hatch opening may be too narrow if thick winter clothing is worn. On average, winter clothing adds four inches to the width of a man. Fabric is a flexible material, of course, so the commander can still squeeze into the hatch with reasonable speed, but the man's belt, holster, harness, binoculars case and document case are all worn on top of his winter uniform and become much more liable to be caught on the edges of the hatch opening. The hatch has a shallow dome shape to increase the headroom in the cupola for the commander. The cupola and the hatch can be seen in the drawings below.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-iY5n6pGzC68/XCorTuiUVOI/AAAAAAAAMtI/hDHu4CIT60QoPHXeI9bZ53fQZvdOu_DpwCLcBGAs/s1600/commander%2527s%2Bcupola.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="994" data-original-width="1417" height="224" src="https://4.bp.blogspot.com/-iY5n6pGzC68/XCorTuiUVOI/AAAAAAAAMtI/hDHu4CIT60QoPHXeI9bZ53fQZvdOu_DpwCLcBGAs/s320/commander%2527s%2Bcupola.png" width="320" /></a><a href="https://4.bp.blogspot.com/-EgoIyWc67Sk/XCorTR96q2I/AAAAAAAAMtE/8v8j1zWFrkEY5RlLwiYtH6Nh86voqDE1gCLcBGAs/s1600/commander%2527s%2Bhatch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="782" data-original-width="1327" height="235" src="https://4.bp.blogspot.com/-EgoIyWc67Sk/XCorTR96q2I/AAAAAAAAMtE/8v8j1zWFrkEY5RlLwiYtH6Nh86voqDE1gCLcBGAs/s400/commander%2527s%2Bhatch.png" width="400" /></a></div><br /></div><div><br /></div><div>The second T-10 cupola type, shown in the drawing below, was used on the T-10B, followed by the T-10M. It differed from the first type in having an entirely new mount, with a spaced collar to protect the cupola race ring. Bolts placed behind the ring guard secure the cupola to the turret. This new design allowed the cupola to be installed or uninstalled without needing to dismantle it, the only requirement is that the rain guard is taken off beforehand.<br />
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The T-10M cupola featured an enlarged hood over the TPKU-2 periscope to further decrease the splashing of rain on the periscope window and to further protect from rain water dripping onto the periscope mount. The new cupola has three traverse lock positions, and a new sealing system with a particularly noteworthy seal tightening feature. Unlike the original cupola which had a rubber flap permanently fitted to the cupola to seal the race ring, the new cupola has a rubber flap fitted to the fixed cupola ring mount which is tightened against the cupola with a cable.<br />
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<div><br /></div><div>The seal tightening mechanism functions by pulling in the cable on a reel, which is twisted by turning a lever and locking it in one of nine positions with a spring-loaded stopper. This can be seen in the drawing on the left below. The greater the angle of the lever, the more the reel is twisted and the tighter the cable presses against the rubber flap. Before tightening the seal, the commander must ensure that the cupola is not moving. The purpose of having this decidedly peculiar feature is not mentioned in the manual for the T-10M, but it is most likely the cupola sealing system for snorkelling. The last major redesign introduced in the new cupola is the electrical contact ring for the commander's target designator system, which was no longer sealed within its own chamber, but was simply fitted to the underside of the cupola ring mount. The same general design was retained, consisting of a textolite ring with copper-lined grooves, touching against the terminals of the cupola contacts. This is shown in the drawing on the right below.</div><div><br /></div><div style="text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-YqewOU3nbbI/YUfpabgFLCI/AAAAAAAAUL0/7TW_V2Qt1FAfFYDZnwFUq16NUZru2hfFACLcBGAsYHQ/s730/t-10m%2Bcupola%2Btop%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="642" data-original-width="730" height="351" src="https://1.bp.blogspot.com/-YqewOU3nbbI/YUfpabgFLCI/AAAAAAAAUL0/7TW_V2Qt1FAfFYDZnwFUq16NUZru2hfFACLcBGAsYHQ/w400-h351/t-10m%2Bcupola%2Btop%2Bview.png" width="400" /></a><a href="https://1.bp.blogspot.com/-b8XFrAPEBIs/YUfo6ZwYfSI/AAAAAAAAULs/m7YchaCkJ2s4KfF-WmqWxd_pSCjzBdCLACLcBGAsYHQ/s519/commanders%2Bcupola%2Bcontacts.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="519" data-original-width="510" height="320" src="https://1.bp.blogspot.com/-b8XFrAPEBIs/YUfo6ZwYfSI/AAAAAAAAULs/m7YchaCkJ2s4KfF-WmqWxd_pSCjzBdCLACLcBGAsYHQ/s320/commanders%2Bcupola%2Bcontacts.png" width="314" /></a></div></div>
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The design of the cupola remained largely unchanged from the T-10B to the T-10M, with the exception of the increased protection of the race ring. This was achieved by increasing the height of the spaced armoured collar surrounding the cupola from 22mm to 33mm. The thickness of the collar remained at 20mm. This upgrade further reduced the possibility of jamming the cupola with concentrated heavy machine gun fire, shell fragments, and other ballistic threats. The design of the periscope step guard was also modified from a fully enclosed cover to a partial cover, but remained interchangeable with the earlier version.<br />
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Unfortunately, there are a few factors that can degrade the commander's visibility. The fact that the commander's cupola is offset to the left side of the turret unavoidably exaggerates the size of the dead zone to the right while reducing the dead zone to the left, and depending on the T-10 model, there may be a number of items on the turret roof which obstruct the commander's view from his cupola. On the T-10 and T-10A, the ventilation dome on the turret roof partly obstructs the commander's view from his TNP periscopes in the 1 o'clock direction, and on all T-10 models, the loader's cupola can obstruct the commander's view to his right, mainly from the dome shape of the loader's hatch. This is illustrated in the cross-sectional drawing below. However, the field of view from the TPKU-2 periscope is almost entirely uninterrupted because it is mounted higher to clear both of the aforementioned obstructions. It is worth mentioning that the anti-aircraft machine gun on the loader's cupola is not an obstruction as it is mounted on a raised pintle, so there is a large gap between the machine gun itself and the top of the loader's cupola, enough to not significantly interfere with the commander's field of view in elevation.<br />
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It is obvious that the T-10 commander enjoys an unparalleled amount of overall visibility compared to his peers in an IS-3 or IS-4, but the cupola design of the T-10 also offers appreciably better vision than the cupola of the IS-2 obr. 1944 which had six vision slits supplemented by an MK-4S rotating periscope (Gundlach periscope) installed in the cupola roof, especially since the T-10 also benefits from having a magnified periscope with a target designation function. The MK-4S had no magnification and as such, it only permitted the commander to spot a tank-type target from a maximum distance of 1,000 meters to 1,500 meters.<br />
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The difference between the IS-2 obr. 1944 and the IS-3 and IS-4 in this particular aspect mirrors the difference between the split-hatch cupola of early M4 Shermans to the "vision cupola" of late model Shermans. During modernization programmes in the 1950's, IS-2, IS-3 and IS-4 tanks were upgraded into IS-2M, IS-3M and IS-4M tanks and had their MK-4S periscope replaced with the <a href="https://2.bp.blogspot.com/-2dxan5PFilk/WFEvrGdx5PI/AAAAAAAAH2k/j2atXVbpWjAwIT1JQcWtAbIpRjbpoESvwCLcB/s1600/tpk-1.gif">TPK-1 periscope</a> with a combined unmagnified viewing window and a magnified 2.5x binocular device, but even with this upgrade, the T-10 still held an advantage because the TPK-1 was a generation behind the TPKU-2 and the upgraded tanks were not retrofitted with a target designation system.<br />
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However, the good all-round visibility from the T-10 cupola does not necessarily make it superior to the cupola of contemporary Soviet medium tanks in practical terms. Beginning with the <a href="https://4.bp.blogspot.com/-EQNx3Z6DjfU/WZa2agscwXI/AAAAAAAAJB4/Wp6g2kkuTJAD9qC34rTjPwYXOQXcLHvnQCLcBGAs/s400/T-54.jpg">T-54 obr. 1949</a>, most Soviet medium and main battle tanks used a cupola with a forward-facing binocular periscope supplemented by four general vision periscopes covering the forward half of the cupola's perimeter. On the T-54 and T-62, two TNPO-170 periscopes were installed in the fixed cupola roof and two 54-36-318-R periscopes were embedded into the commander's hatch itself. Both of these periscopes have a width of 230mm and differ only in that the periscopes embedded in the hatch (54-36-318-R) do not have an internal electric heater for defogging whereas the TNPO-170 does. By comparing the width of the periscope casings alone, the TNP is 51% narrower than the TNPO-170 and 54-36-318-R periscopes. The cast aluminium periscope casings for all three models have a fixed thickness, so the difference in the width of the glass prisms inside the periscopes is not directly proportional to the difference in the width of the periscope casings. In actuality, the glass prisms in the TNPO-170 and the 54-36-318-R are more than 51% wider than the TNP. This is only slightly offset by the lower periscopicity of the TNP periscope.<br />
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In a direct side-by-side comparison, it is evident that the T-54 and T-62 cupolas provide better visibility in the forward half simply by virtue of having the same number of periscopes in the same layout, but with wider periscopes that grant a wider field of view. However, the rearward visibility from the T-54 and T-62 cupolas is non-existent unless the cupola is rotated so that one or more of the periscopes is facing rearward, so the T-10 cupola has a weighty advantage here. On the other hand, the relevance of this advantage in a combat situation is debatable.<br />
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The characteristics of a tank commander's observation practices when buttoned-up in a fixed cupola with eight periscopes and one fixed forward-facing sight in the turret were examined in the 1974 study "<i><a href="http://btvt.info/5library/vbtt_1974_02_obzornost.htm">Некоторые Статистические Характеристики Процесса Наблюдения Командира Танка</a></i>" (<i>Some Statistical Characteristics of a Tank Commander's Observation Processes</i>) by G.G Golub et al. The findings of the study were that 30% of all battlefield observations were carried out using the forward-facing unmagnified periscope and at most, 5% of observations were done using the magnified 8x optic with a stabilized field of view because there was little need given that the topographic range of visibility of targets during the study was 1.0-1.5 km. However, it was also found that in certain tactical situations such as when carrying out a breakthrough mission, the frequency of the use of a magnified optic to search for targets increases up to 50%. Overall, more than 70% of observations were made using only three periscopes at the front of the cupola covering a 100-degree frontal sector and over 95% of observations were made in a 200-degree frontal sector. Most interestingly, the experiments revealed that the highest recorded frequency of usage of the rear-view periscope was only 0.8%. It was also noted that the periscopes installed at more than 110 degrees off the centerline axis of the cupola (8 o'clock) were difficult to use due to neck strain when the tank was in motion. One of the conclusions of the study was that observation devices installed in the commander’s cupola at angles greater than ± 100 degrees (outside the 200-degree frontal arc) were difficult to use.<br />
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Based on these results, it can be seen that in a fixed cupola with all-round visibility, five unmagnified periscopes covering the front 180-degree sector provide 95.3% of the total visibility needs of the commander under various combat conditions. The rear-facing periscopes are rarely used partly because of the lack of a need and partly because of user discomfort. A rotating cupola that provides vision in a 206-degree arc will fulfill 98.1% of the commander's visibility needs under the same combat conditions. So in other words, the increased rearward visibility from the T-10 cupola compared the T-54-style cupola would not necessarily have led to any great advantage in combat. The main upside of having better rearward visibility is a greater ease of navigation during marches, particularly in rough terrain. However, this is a non-combat situation and the commander may stand on his seat with his head outside of his hatch for even better visibility and for safer driving.<br />
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A thick armoured rib is welded to the turret roof in front of the commander's cupola to prevent damage to the protruding periscopes from bullets ricocheting off the turret roof. This is shown in the photo below (taken from the <a href="https://www.net-maquettes.com/pictures/t-10-heavy-tank/">Net-Maquettes website</a>).<br />
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Unlike the commander of a Conqueror or an M103(A1), the commander of a T-10 is not provided with his own optical rangefinder. In order to determine the range to a target, the commander only has a simple stadia rangefinder to rely upon. Conversely, the short base length of the rangefinder on the Conqueror was not conducive to precise range measurement and the stereoscopic device on the M103 is inherently difficult to operate properly owing to human limitations.<br />
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In general, the gunner should be responsible for operating a tank's rangefinding device unless the tank lacks a turret - a fact that was later recognized and put into practice in the creation of most tanks outside the U.S during the 1960's but unappreciated during the development of the entire "Patton" line of medium tanks, the M60 series, and the M103 series. Future tanks like Leopard 1 and Chieftain were also configured in this way, and even though the British Chieftain lacked an optical rangefinder, the gunner was responsible for using the ranging machine gun and later, the laser rangefinder. This was a more efficient division of labour and increased the speed of target acquisition and target switching.<br />
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Instead of a coincidence rangefinder in his cupola, the commander of a T-10 was furnished with a large number of observation devices which gave him a much better all-round view. This was a stark contrast to the commander of a Conqueror who was given <a href="http://svsm.org/albums/Conqueror/IMGP7231.jpg">only three general observation periscopes to cover a 90-degree arc</a>. His cupola - or "Fire Control Turret" as it is officially known - can rotate to nullify this drawback to some extent, but the T-10 cupola rotates as well. Even the M103 was rather deficient in this aspect as the commander's M11 cupola only had four M17 periscopes aimed at the four cardinal directions. Although M17 periscopes are certainly larger than TNP periscopes, this periscope layout created large dead zones in the corners of the cupola.<br />
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<h3>
<span style="font-size: large;">TPKU-2</span></h3>
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The TPKU-2 has a fixed 5x magnification. It has a field of view of 7.5 degrees. According to Soviet studies, an optical sight with 5x magnification allows a tank to be seen and identified from a distance of 3.0 kilometers. This may seem excessive as the normal combat distance generally does not exceed 1.5-2.0 kilometers, but a 5x magnification is necessary because it allows the commander to discern minute details and differentiate specific tank models at such ranges. When viewing with the naked eye or with an non-magnified optic, the commander can see and identify a tank from a maximum distance of 1.5 kilometers but he cannot identify its type and model, nor can he effectively perform fire corrections.<br />
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Due to the standardization of the TPKU-2 periscope for all armoured combat vehicles in the Soviet Army during the early 1950's, the viewing distance and rangefinding capabilities of a T-10 commander were at the normal level of the time. The main distinguishing factor is that the T-10 cupola features a more elaborate control scheme with a counter-rotating mechanism.<br />
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Instead of having handles built into the case of the periscope itself, the control of the elevation angle of the periscope and the rotation of the cupola is done by grasping on two vertical handles. The design of the handles hardly changed throughout the evolution of the T-10 series. The positioning of the handles was changed slightly with the introduction of the T-10A, and essentially remained untouched in all folowing models. <br />
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By grasping both handles, the commander could rotate the cupola and adjust the TPKU-2 in elevation. The left handle was firmly fixed to the cupola and the right handle was attached to the cupola with a hinge and fitted into the mounting fork on the left side of the TPKU-2 periscope. To depress and elevate the periscope, the right handle is moved up and down.<br />
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<br />As with the existing T-54 medium tank series, the T-10 series featured a target designation system beginning with the original T-10 model. Using the target designation system, the commander of a T-10 could direct the gunner to a target, and then allow the gunner to carry on with the rest of the engagement process while the commander searches for other targets independently. The T-54 obr. 1949 was the first tank in the world to have this system with the TPK-1 periscope and it became a standard feature of all Soviet tanks from then on, but the system in the T-10 is more sophisticated as it can cue the gunner in elevation and azimuth, rather than being limited to azimuth only. The purpose of this system is to decrease the reaction time of the tank crew to new threats and reduce the time taken to switch from engaging one target to another.</div><div><br />
The left thumb button activates the target designation system and slews the turret to lay the gun on target in both the horizontal and vertical planes. The point of aim in the TPKU-2 in elevation is inputted to the gun elevation system via a potentiometer in the right cupola handle. The point of aim in azimuth is relayed to the powered turret traverse system by a cupola ring sensor. To initiate target designation, the cupola must be traversed away from the direct forward position. The speed of turret rotation depends on how far the cupola is traversed, with a progressive increase up to the maximum speed when the cupola is traversed up to 10 degrees in each direction away from the direct forward position. Beyond 10 degrees, the turret will always turn at maximum speed and it begins braking as it approaches alignment with the cupola, progressively slowing down to a smooth halt within the 10-degree buffer zone. The precision of the target designator system is ±8.5 mils, which is not enough to directly lay the gunner's reticle onto the target, but is more than enough to place it directly in the center of the gunner's field of view in his sight. The direction of turret rotation always takes the shortest path during target designation.</div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-hu4555ZFiWA/XNcGU3rwBGI/AAAAAAAAN7I/zIF7qMdq8v0tC8CMUn2wRGl5D1zt0Zi3wCLcBGAs/s1600/target%2Bdesignator%2Bbutton.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="363" data-original-width="433" height="268" src="https://1.bp.blogspot.com/-hu4555ZFiWA/XNcGU3rwBGI/AAAAAAAAN7I/zIF7qMdq8v0tC8CMUn2wRGl5D1zt0Zi3wCLcBGAs/w320-h268/target%2Bdesignator%2Bbutton.png" width="320" /></a></div><div><br /></div><div>The progressive turret rotation speed control was achieved by having a rheostat in the azimuth sensor, which differentiates it from the simplr directional sensor in the T-54 cupola. When the cupola turns in either direction, it deflects one of two identical opposing rollers which is held in contact with the cupola surface. Both rollers are linked to a two-way rheostat with gears. The direction that the cupola is turned relative to the turret is sensed according to which roller is deflected. </div><div><br /><div style="text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-K71eWPF5q6w/YUf1UkwZXtI/AAAAAAAAUME/9-gVEKyQqrQi7zUOtY_zk9q_RIwR1mS3gCLcBGAsYHQ/s628/t-10a%2Bcupola%2Bazimuth%2Broller.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="429" data-original-width="628" height="274" src="https://1.bp.blogspot.com/-K71eWPF5q6w/YUf1UkwZXtI/AAAAAAAAUME/9-gVEKyQqrQi7zUOtY_zk9q_RIwR1mS3gCLcBGAsYHQ/w400-h274/t-10a%2Bcupola%2Bazimuth%2Broller.png" width="400" /></a><a href="https://1.bp.blogspot.com/-cS-3qubGJC4/YUf1BKQ4DbI/AAAAAAAAUL8/lUY8zQFuYSQLvxokx3BYip9MiLfEgMIUACLcBGAsYHQ/s411/kinematic%2Bdiagram%2Bof%2Bt-10a%2Bcupola%2Bazimuth%2Broller.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="411" data-original-width="384" height="320" src="https://1.bp.blogspot.com/-cS-3qubGJC4/YUf1BKQ4DbI/AAAAAAAAUL8/lUY8zQFuYSQLvxokx3BYip9MiLfEgMIUACLcBGAsYHQ/w299-h320/kinematic%2Bdiagram%2Bof%2Bt-10a%2Bcupola%2Bazimuth%2Broller.png" width="299" /></a></div></div><div><br /></div><div><br /></div>The cupola azimuth sensor is installed on the turret roof just behind the cupola itself, as shown in the photo below. When the target designating button is pressed, the turret turns towards the commander's point of aim in azimuth until the sensor is returned to the neutral position, whereupon the turret is braked. </div><div><br />
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Interestingly enough, the Conqueror also had a target designating system that was functionally identical.<br />
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The British-Israeli report WO 194-2946 with the title "<i><a href="https://tankandafvnews.com/wo-194-2946-a-technical-assessment-of-the-t-55/">A Technical Assessment of the T-55</a></i>" report reveals some interesting information on the precision of rangefinding through the TPKU-2; from the table in Page 64, the mean error in ranging tank-shaped screens, broadside tanks, oblique tanks and head-on tanks is 14.57%. The tests show that the commander is able to range the target in an average time of 3.34 seconds, and this section of the report concludes that the short time required to obtain a range estimate is unobtrusive to the loading and laying of the gun. This means that by the time the gunner has visually acquired the target, he will be have been informed of the range by the commander and can open fire immediately after forming a ballistic solution. The time taken for the measurements is a relatively close representation of real world conditions as the observers were required to start each test by finding and laying the sights onto the target from a fixed point offset to the left or right of it.<br />
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From the table in <a href="https://tankandafvnews.files.wordpress.com/2016/02/064.jpg">page 121 of the report</a> (page 64 of the photo album), the mean error in ranging tank-shaped screens, broadside tanks, oblique tanks, head-on tanks and hull-down tanks at distances of 800 meters to 3,000 meters is 14.57%. There appears to have been very little correlation between the distance and the time taken for each ranging process.<br />
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It is stated in <a href="https://tankandafvnews.files.wordpress.com/2016/02/065.jpg">page 122 of the report</a> (page 65 of the photo album) that the ranging errors only increased slightly with distance. Surprisingly, the precision of rangefinding against hull-down tanks was hardly affected by the fact that half of the target was out of sight. It is also mentioned on page 123 that the light conditions at various times during the day did not make a significant difference in the ranging process. It could be hypothesized that operator skill and experience in range estimation can make a large difference in overcoming the shortcomings of stadiametric rangefinding.<br />
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For reference, the report notes that unaided range estimation by eye results in a mean error of 25%. This information lines up perfectly with a report on the Fifth Annual Army Human Factors Engineering Conference where it is written that a British study showed that a 25% error was found for unaided visual range estimation. The study also showed that on average, a 15% error was found for range measurements using an optical stereoscopic rangefinder. Additionally, a study conducted by The Human Resources Research Organization (HumRRO) found that only 15% of human subjects could physically use a stereoscopic rangefinder, and a second study conducted with 120 men who were given five weeks of training with stereoscopic rangefinders revealed that only 10% could meet or exceed the required standard of accuracy. Furthermore, independent studies have shown that the stresses induced during combat will have a noticeable negative effect on the accuracy of ranging using stereoscopic rangefinders due to the mentally intensive nature of the task. Also, measuring the range to a moving target or an intermittently disappearing target (due to obstructions, for example) was found to be nearly impossible.<br />
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Although the details of the results from the British study were not provided, a direct comparison between the 15% error figure given and the 14.57% error figure given in the British-Israeli report shows that the stadiametric rangefinder of the TPKU-2 is functionally of equal precision as a stereoscopic rangefinder when both are operated by trained personnel, and the stadia system has the major advantage of only requiring the normal clarity of eyesight expected from a tank commander or gunner rather than needing specially picked operators. The high theoretical ranging accuracy of stereoscopic rangefinders is usually not achieved even during training, let alone in combat conditions.<br />
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On the other hand, an optical coincidence rangefinder is much more practical as it does not require operators with special mental capabilities and it can be just as precise as a stereoscopic type. The British-Israeli report includes data in page 121 showing that when ranging the same targets as the T-55 from 970 meters to 2,520 meters, a "Patton coincidence rangefinder" had a mean range measurement error of only 6.65% at the expense of taking an average of 5.72 seconds for each measurement. It is mentioned that there was a noticeable negative correlation between ranging precision and range, but even so, it is clear that the replacement of a stereoscopic rangefinder with a coincidence type in the M103A2 (the same rangefinder as in the M60) gave it a quantifiable advantage over the entire T-10 series in general. However, the catch is that conversions of M103A1 tanks to the M103A2 standard only began in 1964, so this advantage took a rather long time to materialize.<br />
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<span style="font-size: large;">TKN-1T</span></h3>
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The T-10 was furnished with a TKN-1T active infrared monocular periscope. As the TPKU-2 lacked any provisions for nighttime use, it was necessary to swap it out for the TKN-1T before commencing night operations. The device fits into the same periscope slot without any modification. The angle of elevation is adjusted with the right cupola handle in the same way as the TPKU-2 and the target designation system continues to work with the TKN-1T installed, so the basic mode of fire control does not change when operating at night except for the greatly reduced viewing distance and total reliance on the night vision periscope. As before, to designate a target for the gunner to engage, the commander simple aims at it in the TKN-1T viewfinder and presses the thumb button on the left handle.<br />
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The TKN-1T has a fixed 2.75x magnification, making it only suitable for observation at short distances even if the battlefield is illuminated by other sources of infrared light. The angular field of vision is 10 degrees. The high voltage signal needed to amplify the infrared light is supplied by the BT-2-26T power supply unit.<br />
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Illumination for the periscope is supplied by an OU-3T infrared spotlight. The infrared light from the spotlight illuminates the target, and the reflected light entering the objective lens of the periscope is then amplified by an image intensifier tube operating on 17 kV. The power cable supplies power to the transformer housed in the box on top of the eyepiece, and another cable runs from the transformer to the image intensifier installed inside the device itself. To turn on the OU-3T spotlight, the commander simply flips an on-off toggle switch located on the side of the left handle.<br />
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Using the OU-3T in the active infrared mode will enable the commander to identify tank-type targets at a distance of only 250-300 meters. Due to the short viewing distance, the TKN-1 is generally only suitable for spotting enemy tanks that are also using active infrared illumination, for following the fall of tracers, for observing the impact of shots and for spotting the muzzle flash of enemy tanks. The view through the eyepiece of the TKN-1S is shown in the two photos below (image credit to <a href="http://www.gaz69.ru/ipb/topic/124887-%D0%B1%D1%80%D0%B4%D0%BC-2/?page=5">kmshik from the GAZ 69 forums</a>).<br />
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<a href="https://2.bp.blogspot.com/-c-uQEQjAZS4/XD9AqD4ksfI/AAAAAAAAM8M/SrO12RP88Rgod4iIRkq9ujavfk9IfAf_wCLcBGAs/s1600/tkn-1s%2Bview.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1061" height="301" src="https://2.bp.blogspot.com/-c-uQEQjAZS4/XD9AqD4ksfI/AAAAAAAAM8M/SrO12RP88Rgod4iIRkq9ujavfk9IfAf_wCLcBGAs/s400/tkn-1s%2Bview.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-N5_2YnQCDRQ/XD9AqJNZ4LI/AAAAAAAAM8I/9q_PMvi2kJwoYIlY3QijO9mrSzIvlf9tgCLcBGAs/s1600/tkn-1s.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="841" height="380" src="https://1.bp.blogspot.com/-N5_2YnQCDRQ/XD9AqJNZ4LI/AAAAAAAAM8I/9q_PMvi2kJwoYIlY3QijO9mrSzIvlf9tgCLcBGAs/s400/tkn-1s.jpg" width="400" /></a></div>
<div><br /></div><div><br /></div><div><br /></div><h3><span style="font-size: large;">COMMUNICATIONS</span></h3><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-P4cIz-9LwQU/XP-Kf8ccWeI/AAAAAAAAOZE/juQn2YSmr3kDf67zRX9vx-UUWMghBNetwCLcBGAs/s1600/comm.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="720" data-original-width="985" height="466" src="https://1.bp.blogspot.com/-P4cIz-9LwQU/XP-Kf8ccWeI/AAAAAAAAOZE/juQn2YSmr3kDf67zRX9vx-UUWMghBNetwCLcBGAs/s640/comm.png" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"></div><br /><br />The turret wall on the side of the commander's station is largely occupied by the tank's communication facilities. These include the radio transceiver set, the power supply box for the radio, the communications relay box, the radio antenna frequency tuning box, and a slot in the turret wall for the whip antenna. The bulky radio transceiver and radio power supply box are installed side-by-side on the shelf between the turret wall and the turret ring. This is the same layout as in the T-54 and shares the same disadvantage of decreasing the width of the commander's station with the advantage of providing the commander with free and easy access to the radio transceiver. This is necessary for him to control the communication channel fluidly and also to troubleshoot any issues if they arise. The model of radio transceiver installed in the T-10 series directly corresponded to the models that were standardized at the time of introduction. For the original T-10, the 10RT-26E radio was installed.<br /><br />A fuze box for the tank's electrical network is installed above the radio transceiver, and the radio antenna frequency tuning box is installed above it. It connects the radio transceiver to the whip antenna. For communication between crew members, the tank was equipped with the TPU-47-2 intercom system.<br /><br /><div>Additionally, the tank is equipped with an electric S-58 buzzer (horn) to allow infantry to get the attention of the tank crew. The buzzer is located inside the tank on a bracket above the accumulator battery rack. It is activated by a button located near the left rear marker light.</div><div><br /></div><br /><h3><span style="font-size: large;">10RT-26E</span></h3><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-T_VOXUifgyE/XOorJR5vt8I/AAAAAAAAOFU/TuVwc6pD7MI-xDkeSDU0MmwNFkP6qtm_ACLcBGAs/s1600/10rk-26.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="500" data-original-width="767" height="260" src="https://1.bp.blogspot.com/-T_VOXUifgyE/XOorJR5vt8I/AAAAAAAAOFU/TuVwc6pD7MI-xDkeSDU0MmwNFkP6qtm_ACLcBGAs/s400/10rk-26.jpg" width="400" /></a></div><br /><br />The commander is also in charge of the single <a href="http://www.rv3bc.narod.ru/Stat/10rt-12.htm">10RT-26E</a> short wave radio set mounted to the turret wall next to him. The radio is designed to operate in the 3.75-6.00 MHz frequency range. All Soviet armoured vehicles from the later half of WWII and the immediate postwar period featured a 10RT series radio, but by the early 50's, the series was rendered obsolete by a new government decree allocating the 20.0-22.4 MHz frequency range for the exclusive use of tank radios.<br /><br />The production of the venerable 10RT series ceased entirely in 1956, having been replaced by the R-113 radio set. From January 1957 onward, the new R-113 radio transceiver and R-120 intercom system began replacing the older types on existing T-10 tanks during scheduled maintenance. The T-10A model (introduced in May 1957) came with the new communications suite as standard, as did the T-10B and T-10M.<br /><br /><br /><h3><span style="font-size: large;">R-113</span></h3><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-83O3xVvMQzU/XLurqeSap-I/AAAAAAAANtc/YEb_IbENVQ804XhzewetLBIGn0udaOLiACLcBGAs/s1600/r-113%2Bradio%2Bset.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="545" data-original-width="938" height="370" src="https://1.bp.blogspot.com/-83O3xVvMQzU/XLurqeSap-I/AAAAAAAANtc/YEb_IbENVQ804XhzewetLBIGn0udaOLiACLcBGAs/s640/r-113%2Bradio%2Bset.png" width="640" /></a></div><br /><br />R-113 radio transceiver set. A video of an R-113 radio in operation can be found here (<a href="https://www.youtube.com/watch?v=ithjdm39Ax0">link</a>). The R-113 belonged to the first generation of Soviet tank radios designed in the postwar era and it became the standard tank radio for short to medium range communications. It is a typical VHF radio operating in the 20-22.375 MHz frequency range with a maximum range of 20 km with the whip antenna extended, but the range is reduced to 8-12 km in the presence of high noise interference and it is further reduced to 10 km in the presence of jamming. The R-113 could be tuned to 96 frequencies within the limits of its frequency range. During combat, tanks in tank platoons usually have their radios kept in the simplex receiving mode to receive orders from the platoon leader, while the platoon leader operates his radio in the half duplex mode, although he is often forbidden from transmitting except in emergencies. In general, all tanks mainly operate in the receiving mode to receive orders from the company commander, but in some cases, total radio silence is practiced by tank commanders prior to an attack in order to gain the element of surprise. In such cases, communications may be carried out using signal flags and by relying on pre-practiced drills.<br /><br /><br />The extendable whip antenna for the radio system is located on the side of the turret just next to the commander's cupola, behind the gunner's TPB-51 vision block. The photo below is <a href="https://www.britmodeller.com/forums/index.php?/topic/235020451-t-10-object-730-soviet-heavy-tank/">from Dave Haskell</a>.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-D_jM8zT6J2c/XNc4vliCQ-I/AAAAAAAAN8Q/11Dj3adO6AkET1oquACO2EI77nZo0PCogCLcBGAs/s1600/turret%2Bside.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="425" src="https://3.bp.blogspot.com/-D_jM8zT6J2c/XNc4vliCQ-I/AAAAAAAAN8Q/11Dj3adO6AkET1oquACO2EI77nZo0PCogCLcBGAs/s640/turret%2Bside.jpg" width="640" /></a></div><br /><br />The photo shows the commander of a T-10M tank belonging to the 49th Separate Tank Battalion, Senior Sergeant S.N. Shabalin in his tank while stationed at GSFG in the summer of 1974. In the photo, you can see that he is actually seated on the gunner's seat and his right hand is resting on the commander's seat. The R-113 radio can be seen just behind his right shoulder, and the cables that connect his headset to the communications system are clearly visible.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9FB0ZlP_goY/XECqv9UBLAI/AAAAAAAAM9Q/n0rbsWFMMQgWhwBgkTI-yvuZsUXoeJgxwCLcBGAs/s1600/commander%2Bof%2Bthe%2BT-10M%2Btank%2Bof%2Bthe%2B49th%2BSeparate%2BTank%2BBattalion%252C%2BSenior%2BSergeant%2BS.N.%2BShabalin%2Bin%2Bhis%2Bcombat%2Bvehicle.%2BGSVG%252C%2Bsummer%2Bof%2B1974.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="643" data-original-width="510" height="400" src="https://1.bp.blogspot.com/-9FB0ZlP_goY/XECqv9UBLAI/AAAAAAAAM9Q/n0rbsWFMMQgWhwBgkTI-yvuZsUXoeJgxwCLcBGAs/s400/commander%2Bof%2Bthe%2BT-10M%2Btank%2Bof%2Bthe%2B49th%2BSeparate%2BTank%2BBattalion%252C%2BSenior%2BSergeant%2BS.N.%2BShabalin%2Bin%2Bhis%2Bcombat%2Bvehicle.%2BGSVG%252C%2Bsummer%2Bof%2B1974.jpg" width="316" /></a></div><br />
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The tank also has a supply of 20 signal cartridges. The signal gun can be used in times of emergency, but their main purpose is for the commander to signal other troops to coordinate night battles when total radio silence is needed. The signal shells are bright enough to be visible from a very long distance and can be easily seen by enemy forces, thus revealing the position of the firer. However, the shells do not produce enough light to illuminate objects on the ground.<br />
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<a href="https://www.blogger.com/null" id="gunstat"></a>
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<h3>
<span style="font-size: large;">GUNNER'S STATION</span></h3>
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The gunner's seat is mounted on a fixed tubular post which is bolted to the rotating turret floor. The seat can be adjusted in height and the cushion can be folded down to permit easier access to the hull. The gunner is not provided with a footrest so he simply places his feet on the rotating floor, and although there is no turret basket on any T-10 model, there is a short fence on the perimeter of the rotating floor in front of the gunner to ensure that his feet does not slip off accidentally.<br />
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<a href="https://2.bp.blogspot.com/-nXkrQ_p-KIs/XF66K5WQsuI/AAAAAAAANYA/ZKjO-Lo4gsIUsE87d1W8p65eSA-P1uLcgCLcBGAs/s1600/gunners%2Bseat%2Bt-10m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="662" data-original-width="452" height="320" src="https://2.bp.blogspot.com/-nXkrQ_p-KIs/XF66K5WQsuI/AAAAAAAANYA/ZKjO-Lo4gsIUsE87d1W8p65eSA-P1uLcgCLcBGAs/s320/gunners%2Bseat%2Bt-10m.png" width="217" /></a><a href="https://3.bp.blogspot.com/-4BWed8RyTLs/XF6E4qv1kCI/AAAAAAAANXU/vwftM696GiAr_Pp5yBMdvxwBrpYjf-CqACLcBGAs/s1600/gunners%2Bseat.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="424" data-original-width="614" height="276" src="https://3.bp.blogspot.com/-4BWed8RyTLs/XF6E4qv1kCI/AAAAAAAANXU/vwftM696GiAr_Pp5yBMdvxwBrpYjf-CqACLcBGAs/s400/gunners%2Bseat.png" width="400" /></a></div>
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The gunner only has a single TPB-51 aimed 35 degrees to the left for general vision outside of his sighting devices. The two photos below show the position TPB-51 relative to the night vision sight of the T-10M. The photo on the left below (credit to <a href="http://svsm.org/gallery/t-10/IMGP0477">Vladimir Yakubov</a>) shows the exterior of the tank with the (cracked) square periscope aperture window clearly visible in front of the radio antenna post and to the left of the night vision sight housing, which has been blanked off. The photo on the right below (credit to <a href="http://www.kotsch88.de/al_T-10M.htm">Stefan Kotsch</a>) shows the square hole in the turret roof where the TPB-51 would fit and its close proximity to the opening for the night vision sight.<br />
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<a href="https://1.bp.blogspot.com/-ssedO8zjn-E/XEqF7JzqSpI/AAAAAAAANOM/7u2IL9kPa5AtfWonWJ9vJdSUy41DrCUmQCLcBGAs/s1600/periscopes.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://1.bp.blogspot.com/-ssedO8zjn-E/XEqF7JzqSpI/AAAAAAAANOM/7u2IL9kPa5AtfWonWJ9vJdSUy41DrCUmQCLcBGAs/s400/periscopes.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-xkjjjN69YIg/XEoWnUzJo0I/AAAAAAAANKo/B6lrHrVshqgK6gxCsUYQ7omYywMN_epCACLcBGAs/s1600/gunners%2Bperiscope.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://3.bp.blogspot.com/-xkjjjN69YIg/XEoWnUzJo0I/AAAAAAAANKo/B6lrHrVshqgK6gxCsUYQ7omYywMN_epCACLcBGAs/s400/gunners%2Bperiscope.JPG" width="400" /></a></div>
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As usual, a spare periscope is provided. It is worth noting that the T-54 had an MK-4S periscope in a fully rotating mount where the TPB-51 is installed on the T-10, thus granting its gunner much more freedom in terms of vision. This was replaced with a periscopic night vision sight on the T-54B, but the T-55 compensated by installing a forward-facing general vision periscope on the turret roof above its TSh2-22 sight. In both cases, the presence of a periscope to supplement the articulated telescopic sight was a deliberate design solution to not only provide the gunner with good visibility but also to allow him to see over the edge of cover when the tank is in a turret-down position with only the optical instruments on the roof exposed. In such a position, the gunner's primary sight would be useless for surveillance. The need for such a periscope did not exist for the T-10A, T-10B and T-10M as all of these tanks had a periscopic primary sight, but for the T-10, the lack of a periscope was a tangible drawback. Still, having the TPB-51 to cover the 10 o'clock sector of the turret was certainly better than nothing as it expanded the gunner's view of the surrounding environment.<br />
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To put this into a greater context, it should be mentioned that the gunners of virtually all NATO tanks were not provided with general vision periscopes and had to rely entirely on the view from their sights and the directions given by the commander, or their control of the gun and turret had to be overridden by the commander.<br />
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The gunner's intercom relay switch is on the turret ceiling directly above him. It is a somewhat unusual location, but completely serviceable. The gunner also has access to the turret rotation lock.<br />
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<a href="https://www.blogger.com/null" id="sights"></a>
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<h3>
<span style="font-size: large;">SIGHTING COMPLEXES</span></h3>
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The original T-10 had an articulated telescopic TSh2-27 sight. The design of the sight is principally identical to all others in the TSh2 series, including the TSh2-22 of the T-54 obr. 1951 medium tank, so it was not more advanced than the standard medium tank in the Soviet Army in 1953. One of the chief complaints from users of early T-54 models like the T-54 obr. 1947 and T-54 obr. 1949 (TSh-20) and heavy tanks like the IS-2, IS-3 and IS-4 (TSh-17) was the relatively limited 4x magnification of the TSh series of articulated telescopic sights. As such, the TSh2 series was created with two magnification settings: 3.5x and 7x. By implementing variable magnification in the sight, the gunner could enjoy both wide vision and high power magnification as the situation dictated. The "2" suffix at the end of the "TSh" designation indicates that the TSh2 series belongs to the second generation of articulated telescopic sights produced in the USSR.<br />
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The 7x magnification of the high setting was most likely chosen because it was more ideal from the standpoint of practicality. To better understand this, it should be understood that an optical sight with no magnification would allow the gunner to see and identify a tank from a distance of 1.0-1.5 kilometers. According to Soviet figures, an optical sight with 4x magnification increases this distance to 2.5 kilometers, an optical sight with 5x magnification further increases this range to 3.0 kilometers, and according to the table below, an optical sight with 7x to 8x magnification increases this range to 4.0-5.0 kilometers.<br />
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The table below is from page 12 of the article "<i>Forging the Thunderbolt</i>" published in the January-February 1976 issue of "Armor" magazine. The range figures denote the range at which the respective targets are recognizable by the naked eye or when viewed through a magnified optic.<br />
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Based on this, a 4x sight should have been sufficient for a postwar tank as it already permits a tank gunner to identify a tank from beyond the maximum effective range of his tank gun, but a tank gunner does not only need to be able to identify a target but also engage it. With a 7-8 power optic, a gunner can not only spot tanks from beyond the maximum effective range of his main gun but also discern more minute details to differentiate between different tank models and more importantly, he can lay his reticle precisely on the individual parts of a tank from normal combat distances, i.e. from 1.5 kilometers or perhaps more. The ability to see various soft-skinned vehicles from 4 kilometers or more also allows the gunner to conduct long-range direct fire with HE-Frag shells. A further increase in magnification does not necessarily increase the effective direct-fire range of the main gun due to the limitations in the mechanical accuracy of the weapons. Case in point; at two kilometers, the probability of a first-round hit on an ATGM emplacement with a HE-Frag shell is 20% whereas at three kilometers, the probability drops to less than 5%.<br /><br />Contrary to expectations, the magnification power of T-10 tank sights was higher than that of the Conqueror's No. 10 sight, which had a slightly lower 6x magnification. The disparity widens when the Conqueror is compared to the T-10M, which had a sight with 8x magnification.</div><br /><div><br />
<a href="https://www.blogger.com/null" id="tsh2"></a>
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<h3>
<span style="font-size: large;">T-10<br />TSh2-27, TSh2-27K</span></h3>
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjUaVqEgI6B_eeJ-Vz-tuBwNZOLZgEP7GGQ0gYfahuakusoBbNn31N6c-ktUqiRAb3R-7rqjoSz2_J2FJpLMvFKerYd5Xibiv2tRBlHCRKDPfQp7nUICABuLHjJiSo4yacOgL_MaQG5oXn_khtaM5yogIXbE6DRC3CpbljznpyLFyrjoWFYQZoTUZagvQ/s1023/tsh2-27%20diagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="507" data-original-width="1023" height="199" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjUaVqEgI6B_eeJ-Vz-tuBwNZOLZgEP7GGQ0gYfahuakusoBbNn31N6c-ktUqiRAb3R-7rqjoSz2_J2FJpLMvFKerYd5Xibiv2tRBlHCRKDPfQp7nUICABuLHjJiSo4yacOgL_MaQG5oXn_khtaM5yogIXbE6DRC3CpbljznpyLFyrjoWFYQZoTUZagvQ/w400-h199/tsh2-27%20diagram.png" width="400" /></a></div>
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The TSh2-27 is an articulated telescopic sight with manual range adjustment. The sight can be switched between two magnification settings: 3.5x and 7x. The field of view in the 3.5x setting is 18 degrees and the field of view in the 7x setting is 9 degrees. The low magnification setting would be used to scan for targets or for general observation whereas the high magnification setting would be used for laying the gun on the target, engaging it, and conducting fire correction (if not done by the commander).<br />
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The main characteristics of the sight - magnification and field of view - were excellent for the early 1950's and were still more than adequate during the 1960's, and the ergonomic design of the system was good. The large brow pad surrounds the gunner's forehead and temples, and the eyepiece itself is ringed by more rubber padding. Being an articulated sight, the telescopic tube and eyepiece of the TSh2-27 is mounted to the turret roof and suspended in a fixed position, while only the articulated aperture assembly moves up and down coaxially with the main gun. This allows the gunner to stay in his seat in a comfortable posture while using the sight without needing to follow the eyepiece up and down as the gun is elevated and depressed during operation as in some early WWII era telescopic sights. The height of the eyepiece can be adjusted by adjusting the frame attaching the sight to the turret ceiling.<br />
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An additional feature of the TSh2-27 that the previous generation of TSh sights lacked is a stadia rangefinder. The stadia rangefinder allowed the gunner to independently estimate the range to a target from a range of 1.2-2.8 kilometers. However, as mentioned earlier, the commander is responsible for providing an initial range estimate to the gunner using his own stadia rangefinder.<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1r32dFGv6T4VUHrOH4ayhrJLMMcL2R02oy_CmCLedNHxNR0uGS6BpX_z2ExmU6n87B5InXq2Pjycznpd1RbNRwuUP31P8AIuxaqBiGP24oDnv52JE87bKzluYmdvnFmU-0EypPiXndRY813IdIfV9yaKFeLwhOxMwIMQAlrL07brmRQ3LE05l7GwxjA/s955/tsh2-27%20reticle%20zeroing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="382" data-original-width="955" height="160" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1r32dFGv6T4VUHrOH4ayhrJLMMcL2R02oy_CmCLedNHxNR0uGS6BpX_z2ExmU6n87B5InXq2Pjycznpd1RbNRwuUP31P8AIuxaqBiGP24oDnv52JE87bKzluYmdvnFmU-0EypPiXndRY813IdIfV9yaKFeLwhOxMwIMQAlrL07brmRQ3LE05l7GwxjA/w400-h160/tsh2-27%20reticle%20zeroing.png" width="400" /></a></div>
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The TSh2-27K variant is a slightly modified version of the TSh2-27 with an additional range scale for HEAT rounds. This allowed T-10 tanks to fight tanks much more confidently by relying on modern HEAT ammunition instead of legacy armour-piercing shells. However, there appears to be no TSh2-27 variant with a range scale for APDS rounds, so if T-10 tanks were supplied with 3BM7 APDS rounds, the gunner would need to use firing tables.<br />
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<a href="https://www.blogger.com/null" id="tps1"></a>
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<h3>
<span style="font-size: large;">T-10A, T-10B<br />TPS1</span></h3></div><div>
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When the T-10A entered service in 1956, it came equipped with the highly advanced TPS1 sighting complex. The sight was also carried over to the T-10B when it entered service in 1957. The TPS1 is paired with the PUOT "Uragan" stabilizer on the T-10A and paired with the PUOT-2 "Grom" stabilizer on the T-10B, retaining the same function in both setups with only minor technical nuances. Development of the revolutionary TPS1 began during the early 1950's and concluded in 1955, with mass production beginning in 1956 and ending in 1958. There are two gyroscopes in the sight - one rate gyro to stabilize the field of view of the optical channel and another rate gyro to serve as a reference system for calculating lead.</div><div><br />
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The TPS1 features independent vertical stabilization with a range of elevation of -7.75 degrees to +20.75 degrees and an elevation speed of 0.05 degrees per second to 3 degrees per second. The weapons control scheme of the "Uragan" stabilizer slaved the main gun and coaxial machine gun to the TPS1 and only permitted the weapons to be fired when the elevation angle coincided with the elevation angle of the sight. The accuracy of the independent sight stabilization system was such that the point of aim did not deviate by more than of 0.5 mils during normal operation.<br />
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Thanks to these technological achievements, the gunner could maintain visual contact with a target while the tank is moving across extremely rough terrain even if it is beyond the gun elevation or depression limits of the gun. When firing on the move on undulating terrain, the gunner could track a target and simply hold his finger on the trigger button when he has obtained the ballistic solution, and the fire control system would automatically fire the gun when the tank pitches in such a way that the elevation angle of the gun matches the sight.<br />
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This sophisticated control scheme not only provided an considerable increase in firing accuracy but also partly nullified the disadvantages of the low gun depression limit of the T-10 series and gave the tank an indisputable edge over the newest models of the T-54 series and T-62 series appearing the late 1950's and early 1960's, as these medium tanks had a much simpler fire control system lacking independently stabilized sights.<br />
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The TPS1 could be switched between two magnification settings; 3.1x and 8.0x, and as before, the former setting would be used to scan for targets at short distances or for general observation whereas the latter setting would be used for servicing the target. The field of view in the low magnification setting is 22 degrees and the field of view in the high magnification setting is 8.5 degrees.<br />
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The fire control systems of the T-10A and T-10B lack an optical rangefinder, but the TPS1 features a somewhat innovative stadia rangefinder mechanism. Three stadia rangefinder markings calibrated for different targets are etched on three different locations on a glass disc in 90-degree intervals. The glass disc is placed next to the viewfinder in such a way that one edge of the disc will appear on the right edge of the viewfinder. By turning the rangefinder setting dial located on the right side of the sight, the glass disc is rotated to cycle between the three different rangefinder markings. The rangefinder setting dial is marked (22) in the cutaway drawing above. The three settings are: for a towed anti-tank gun with a height of 1.2 meters, a medium tank with a height of 2.7 meters, and a heavy tank with a height of 3.0 meters. The fourth setting is void and provides the gunner with a less cluttered field of view.<br />
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There are also three fixed range marks for OF-471N rounds on the vertical line below the center chevron. The fixed range marks are calibrated for a distance of 1.0 km, 1.8 km and 2.0 km. This is designed to allow the gunner to use the bracketing gunnery technique to rapidly determine the range to the target at normal combat ranges by immediately firing the first shot without prior range estimation. In this system, bracketing is done by firing at the target with the 1.0 km range mark, determining if the shot went over or short, and then using a range mark for a shorter range if the shot went over or a range mark for a longer range if the shot went short.<br />
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The drawings below show the viewfinder of the sight in the 3.1x magnification setting and in the 8.0x magnification setting with the stadia rangefinder adjusted for a 2.7-meter target.<br />
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Additionally, the gunner has the option to place or remove a high-contrast filter by turning a dial on the left side of the sight, and as usual, illumination for the reticle (including all markings in the viewfinder) with a lightbulb can be turned on for nighttime observation.<br />
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The sight is suspended from the roof of the turret on a special frame.<br />
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Theoretically, it is possible to use the coaxial machine gun as a ranging gun. However, this would not be possible with the stabilizer operating in the automatic mode due to the lag issue which discounts any possibility of exploiting the coaxial machine gun in this way under most situations. Another hurdle is that neither B-32 or BZT were ballistically matched to any 122mm round supplied for the D-25TS.<br />
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Due to the high complexity and sensitivity of the TPS1, a backup sight was deemed necessary to ensure that the tank would not lose its firepower spontaneously during combat from technical issues or from battle damage. As such, the TUP sight (standing for "Simplified Tank Sight") was created and installed in the T-10A and T-10B together with the TPS1.<br />
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<a href="https://www.blogger.com/null" id="tup"></a>
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<h3>
<span style="font-size: large;">TUP-21</span></h3>
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The TUP-21 is a simple fixed telescopic sight. It is meant only as a backup to the much more complex TPS1 primary sight and would not be used except in emergencies. The aperture and erector tube of the sight is mounted to the main gun above the trunnion at a relatively unusual position. This was done because the space directly beside the D-25TS was already occupied by the parallelogram linkages connecting it with the TPS1 sight. Two periscopic extensions redirect the optical path to ensure that the eyepiece is placed at the gunner's eye level.<br />
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To use the sight, the periscopic eyepiece extension must be swiveled from the stowed position to the ready position where the gunner's eye would be (refer to drawing above). When placed in the stowed position, the eyepiece is flush to the recoil guard of the cannon breech and should not interfere with the gunner's workspace. </div><div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4AUjDewAnnWT5hYI8L7Aa3DWgD356y5eY4xwqnZPyFQ3NXR8v85t1k3yQvcp67RDrwYXOWZuS3IZfM7sh5_J6r7GTLRAYYFAPpXeh19TKjD8VQhBdEb5to86f9i-9D4NWpvu9_bL4Dduhm_GisRTqNdC_0OtWhwyyLkyK8kAhbPwbxWHvE4jY28y5Ng/s1515/tup%20in%20t-10a%20tps1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1032" data-original-width="1515" height="436" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4AUjDewAnnWT5hYI8L7Aa3DWgD356y5eY4xwqnZPyFQ3NXR8v85t1k3yQvcp67RDrwYXOWZuS3IZfM7sh5_J6r7GTLRAYYFAPpXeh19TKjD8VQhBdEb5to86f9i-9D4NWpvu9_bL4Dduhm_GisRTqNdC_0OtWhwyyLkyK8kAhbPwbxWHvE4jY28y5Ng/w640-h436/tup%20in%20t-10a%20tps1.png" width="640" /></a></div><div><br /></div>
The drawing on the left shows the T-10B with the PUOT-2 stabilizer and the drawing on the right shows the T-10A with the PUOT stabilizer.<br />
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The TUP-21 has a fixed 4x magnification and a field of view of 12 degrees. As shown in the drawings below, there is a fixed range scale for 'БР/ТУП' rounds for a distance of up to 3,600 meters in increments of 200 meters. This stands for 'armour-piercing blunt-tipped', referring to the BR-471B APBC rounds. To aim with the sight, the gunner first estimates the distance to the target using the reticle markings or receives the range estimate from the commander, and then he simply raises the gun with the manual gun elevation handwheel until the appropriate range mark for the desired ammunition type is laid on the target. Engaging point targets with HE-Frag rounds has to be done by using a conversion chart for the range scales, and engaging targets with the coaxial DShKM would have to be done by simply following the fall of the tracers. To engage moving targets, the gunner first determines the amount of lead needed using the lead markings, and then proceeds with the rest of the procedure as before.<br />
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The distance markings for the TUP-1 somewhat resemble the distance and lead grid found in <a href="http://www.theshermantank.com/wp-content/uploads/recticles-for-m10f-periscopes.png">typical American tank sights of WWII vintage</a>, but differ in that only a single row of lead markings comprised of vertical dashes and small chevrons are provided along the center chevron and two columns of range scales for the coaxial machine gun and the main gun are provided. On American sights, the grid is meant only for one type of AP round from the main gun, and firing from all other ammunition types has to be done using firing tables or by following the tracers in the case of the coaxial machine gun. It was noted in <a href="http://tankarchives.blogspot.com/2019/01/t8-periscopic-sights.html">a Soviet tank technology journal article that the American M8 sight</a> (with an identical reticle layout as all other American tank sights) that the presence of a grid obstructed the gunner's view, although it was convenient to use when lead is required. Although there are no pictures of the view through the TUP-21 viewfinder, it is probably safe to assume that the range scales would also obstruct the gunner's view in the same manner.<br />
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The simplification of the aiming system greatly reduced the precision of fire compared to the TPS1 primary sight, but it was still possible to engage targets from up to two kilometers without serious difficulty and the magnification of the TUP-21 was sufficient for identifying a tank-type target at more than two kilometers. The fixed mounting of the TUP-21 to the main gun eliminates the possibility of a mechanical misalignment and contributes to high accuracy, but the disadvantage is that the eyepiece would follow the gun up and down as it is elevated and depressed, so the gunner must adjust himself to keep his eye on the eyepiece. As such, it would also be much less convenient to use the sight when the main gun stabilizer is active. </div><div>
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Considering these limitations, it is still worth keeping in mind that even though the TS-17 primary sight of the IS-3 has a slightly wider field of view and includes a range adjustment dial, it also has the same fixed 4x magnification. As such, even if a T-10A or T-10B is forced to operate in a degraded mode with only the TUP-21 sight, the sighting system does not regress very far below the level of the IS-3.<br />
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<a href="https://www.blogger.com/null" id="t2s"></a>
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<h3>
<span style="font-size: large;">T-10M<br />T2S-29-14 "Udar"</span></h3>
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The T2S-29-14 was the most advanced sighting complex in the world at the time of its introduction in 1957 and firmly retained that title for the earlier half of the 1960's before being surpassed by another Soviet tank sighting complex. The progress made in implementing the features of the T2S sight was instrumental in the research and development of all future Soviet tank sights and fire control systems. Despite being a more technically complex product, the T2S-29-14 did not have the reliability issues of the TPS1 so it was judged that a backup sight like the TUP-21 was no longer needed. The sight facilitated a maximum direct fire range for APCBC ammunition of 4,000 meters, for HE-Frag ammunition it was 6,000 meters, and for the coaxial KPVT machine gun it was 2,000 meters.<br />
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Like the TPS1, the T2S-29-14 sight could be switched between two magnification settings; 3.1x and 8.0x, and as before, the low magnification setting would be used to scan for targets at short distances or for general observation whereas the high magnification setting would be used when laying the gun on the target, firing at the target and applying corrections. The field of view in the 3.1x magnification setting is 22 degrees and the field of view in the 8.0x magnification setting is 8.5 degrees.<br />
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Besides independent stabilization, the T2S-29-14 sight included a Delta-D system. This system automatically and dynamically measures the speed of the tank using a tachometer to calculate the distance traveled and automatically subtracted this from the range to the target in the ballistic solution. The Delta-D system in the T2S-29-14 also took the orientation of the turret in azimuth as an input and dynamically generated new calculations using a cosine function. For example, if the T-10M was moving diagonally obliquely relative to the gunner's target at a 60° angle, the system would subtract the distance at a rate equivalent to the Cosine of 60 degrees, or 0.5. As such, if the tank was moving at a steady speed of 18 km/h (5 m/s), then the system would subtract the distance at a rate of 2.5 m/s.<br />
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The system would continue to run until it is reset by the gunner, so the gunner could make a single range measurement and fire continuously at the target while the driver performs maneuvers with the tank without needing to update his range measurement. The distance traveled by the tank was calculated by measuring the engine driveshaft speed; it was an odometer, to put it simply, but this system was independent from the driving odometer of the tank.<br />
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The Delta-D system continuously corrected the ballistic solution in the sight according to the change in the distance from the tank to the target, and the automatic lateral lead automatically set the lateral lead needed when firing at a moving target.<br />
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One unusual feature of the T2S-29-14 is the layout of the "Cheburashka" control handles. Typically, the handles are placed below the eyepiece of the sight, preferably somewhere in front of the gunner's chest or midriff. On the T2S-29-14, the control handles are located behind the eyepiece of the sight and the potentiometers of the control box are wrapped around the tube of the eyepiece optical channel, so the gunner must have his hands raised up to eye level to operate the control handles. It is worth noting that although the location of the control handles is certainly unconventional, being unconventional does not necessarily translate to being ergonomically deficient. Gun elevation is controlled in the normal way with the handles twisted forwards and backwards to depress and raise the gun, but to control turret traverse, the handles are turned like a steering wheel in the same way as the control handles - or "Cadillacs" - of an American tank. The index buttons on both the left and right handles are for firing the coaxial machine gun and the thumb buttons on both of the handles are for firing the main gun. Strangely enough, although there are two buttons for the main gun and the coaxial machine gun each, the manual states that the gunner can choose to press one or both of the two buttons to fire the associated weapon and there does not appear to be any difference either way.<br />
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Inputting range data is done by turning the large range adjustment dial located between the control handles and the eyepiece of the sight. It is shown in the drawing above, labeled (36). The sight is zeroed for a distance of 1,000-1,200 meters. In the sight viewfinder, the lead markings are spaced 4 mils apart and both the vertical lines and chevrons are 2 mils tall.<br />
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Thanks to the inclusion of a form of independent horizontal sight stabilization, the T2S-29-14 featured special provisions for engaging moving targets. In this system, the sight head remained locked in traverse to the turret, but a vertical line in the viewfinder, joined to an internal gyroscope, allowed deflection angles to be calculated with the help of ballistic computer and a timer. Using the range data inputted by the gunner, the sight can automatically calculate the amount of lead needed for a moving target and create a new point of aim. The process relies on the internal gyroscope of the sight to create a fixed reference point from which the lateral movement of a moving target can be compared via the horizontal stabilization of the sight. By combining the rate of rotation of the sight (together with the turret) as the gunner tracks the target with a range estimate from either the gunner or commander, the sighting complex can determine the necessary horizontal offset to ensure that the shot will land on the target.<br />
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Initially, the vertical lead indicator line is locked to the reticle and is centered on the central chevron. The central chevron, along with the lead markings, is fixed within the viewfinder and to the sight itself. To determine the lateral lead, the gunner must first activate the lead computing system to unlock the lead indicator line from the reticle. Then, the gunner tracks the target by holding the central chevron on it using the control handles. The vertical lead indicator line is gyroscopically stabilized to maintain its initial bearing, so when the central chevron moves to the right or to the left as the target is being tracked, the static vertical line will appear to shift to the left or to the right relative to the central chevron. The T2S-29-14 sighting complex allows the target to be tracked in this manner until the internal timer finishes its countdown, whereupon the vertical indicator line is locked to the viewfinder and it stops moving relative to the central chevron. The intersection point between the vertical lead indicator line and the lateral lead correction scales becomes the new point of aim. In the drawing below, the tank target seen through the sight appears to be 1,550 meters away and the vertical lead indicator line has stopped at the first secondary chevron. This means that the gunner must use the first secondary chevron as his new aiming point in deflection.<br />
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Unlike the previous sighting complexes used on the T-10, the coaxial KPVT machine gun is ballistically matched to the HE-Frag rounds up to a certain distance. As shown in the drawing above, the range markings for the KPVT and HE-Frag ammunition are similar up until 1.2 kilometers where 14.5mm bullets begin to drop off rapidly as they approach the limits of their effective range. Because of this, it is possible to rapidly and accurately engage point and area targets with HE-Frag shells up to 1.2 km as the margin of error in the range estimation is small enough to be irrelevant due to the explosive nature of the HE-Frag ammunition. Nevertheless, the main method of range determination was with the stadia scales.<br />
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According to a report on the Fifth Annual Army Human Factors Engineering Conference, a British study showed that a 25% error was found for unaided visual range estimation and a 15% error was found for range measurements using a stereoscopic optical rangefinder. Additionally, a study conducted by the The Human Resources Research Organization (HumRRO) found that only 15% of human subjects could use a stereoscopic rangefinder, and a second study conducted with 120 men who were given five weeks of training with stereoscopic rangefinders revealed that only 10% could meet or exceed the required standard of accuracy. Furthermore, studies have shown that the stresses induced during combat will have a noticeable negative effect on the accuracy of ranging using stereoscopic rangefinders due to the mentally intensive nature of the task. Also, measuring the range to a moving target or an intermittently disappearing target (due to obstructions, for example) was found to be nearly impossible.<br />
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Of course, rangefinding from any optical rangefinder is practically impossible if the vehicle is moving over uneven ground unless the rangefinder is stabilized. The first stabilized rangefinder did not come about until 1963, when the TPD-43B independently stabilized sighting system with an integrated optical coincidence rangefinder was introduced with the T-64 main battle tank.<br />
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There is not much information on the opinions of Soviet engineers on the precision of this method of rangefinding, but the normal error margin for the .50 caliber ranging system of the Chieftain is claimed to be 50 meters at a distance of 1,000 meters, which is equivalent to a 5% error. However, the rangefinding system in the Chieftain relies on fixed aiming points in the sights, so the claimed degree of accuracy is most likely not achievable if the range to the target does not coincide exactly with the fixed aiming points.<br />
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It is important to note that the ranging time required for the operation of a ranging machine gun is much less than that required of a stereoscopic rangefinder, and that a ranging machine gun also helps give the gunner the ability to loosely sense and account for wind effects. However, using a stadia rangefinder takes much less time and will allow the gunner to fire the first shot in an engagement.<br />
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In any case, whether by stadia rangefinding or ranging machine gun, the results are much better than from simple visual range estimation with the naked eye. With an error margin of 25%, firing on tank-type targets at ranges greater than a few hundred meters is ineffective; tests showed that at a distance of 1,000 meters to 2,900 meters, the probability of hitting the front silhouette of a tank target with an APCBC round with the M62-T2 was just 6-20% with visual range estimation.<br />
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On a side note, it is worth mentioning that the location of the sight resulted in a local weakening of the frontal turret armour. The reduction in the thickness of the turret casting is evident in the photo below (taken by <a href="http://www.kotsch88.de/al_T-10M.htm">Stefan Kotsch</a>). The only redeeming features are that the sight is quite narrow so the zone of reduced armour thickness is also quite narrow, and the external shaping of the turret casting in front of the sight is unchanged so it is still likely for an impacting projectile to ricochet off the armour, in which case the reduction in armour thickness has much less of an effect.<br />
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<a href="https://1.bp.blogspot.com/-UP_PMC297nQ/XS29f_IZidI/AAAAAAAAOk0/Jo82GlAEoZEkau71mj0OdlbsLfwKTTPlACLcBGAs/s1600/front%2Bleft.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="266" src="https://1.bp.blogspot.com/-UP_PMC297nQ/XS29f_IZidI/AAAAAAAAOk0/Jo82GlAEoZEkau71mj0OdlbsLfwKTTPlACLcBGAs/s400/front%2Bleft.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-exfRXeTEgXE/XEOKrzqTeAI/AAAAAAAANEY/4je4Pq7rCrwXWUPcL9wvpE0w4xrAH6LoQCLcBGAs/s1600/t2s%2Bopening.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://3.bp.blogspot.com/-exfRXeTEgXE/XEOKrzqTeAI/AAAAAAAANEY/4je4Pq7rCrwXWUPcL9wvpE0w4xrAH6LoQCLcBGAs/s400/t2s%2Bopening.JPG" width="400" /></a></div>
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A set of spare parts for the T2S-29-14 are kept in an aluminium box on the turret wall at the loader's station, next to the first-aid kit.<br />
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<h3>
<span style="font-size: large;">TPN-1-29-14</span></h3>
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<a href="https://3.bp.blogspot.com/-Y_vVwAOkzVQ/XF9xgY7HKAI/AAAAAAAANYc/z-YQoorD7w4kZT7JVe0mN8xZEX3epW5dwCLcBGAs/s1600/tpn-1-29-14.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="475" data-original-width="728" height="260" src="https://3.bp.blogspot.com/-Y_vVwAOkzVQ/XF9xgY7HKAI/AAAAAAAANYc/z-YQoorD7w4kZT7JVe0mN8xZEX3epW5dwCLcBGAs/s400/tpn-1-29-14.png" width="400" /></a></div>
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When it entered service in 1958, the T-10M featured the "Luna" night vision sighting system consisting of the TPN-1 sight and the L-2 infrared spotlight. The TPN-1-29-14 is a variant of the TPN-1 sight which was used on the T-54B (TPN-1-22-11), T-62 (TPN-1-41-11), T-64 and T-72 (TPN-1-49-23) and other Soviet tanks. The only noteworthy differences between these modifications are the reticle markings and the design of the linkages that connect the sight to the cannon. The photo below (<a href="https://www.britmodeller.com/forums/index.php?/topic/235020451-t-10-object-730-soviet-heavy-tank/">credit to Dave Haskell</a>) shows the L-2 "Luna" spotlight with the TPN-1-29-14 sight window in the background.<br />
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<a href="https://4.bp.blogspot.com/-t-rYulz46lo/XNc3_0gJ3wI/AAAAAAAAN8E/8UQrWmO3g-0Fd3EmZufCe51SQjwgX1WSACLcBGAs/s1600/luna.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="266" src="https://4.bp.blogspot.com/-t-rYulz46lo/XNc3_0gJ3wI/AAAAAAAAN8E/8UQrWmO3g-0Fd3EmZufCe51SQjwgX1WSACLcBGAs/s400/luna.jpg" width="400" /></a></div>
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The TPN-1-29-14 sight is capable of both active infrared imaging and passive light intensification. Infrared illumination is provided by the L-2 "Luna" spotlight. The spotlight uses an incandescent lamp with an output of 200 Watts and produces infrared light using an IR filter fitted in front of the bulb. Removing the filter reverts the IR spotlight to a normal white light spotlight. Due to the use of an incandescent lamp instead of a xenon arc lamp, the intensity of the emitted light is relatively weak and the viewing range of the night vision system suffers because of it. When not in use, the spotlight has a protective cover installed to ensure that the window is clean and ready for use when needed. The cover does not provide any protection from bullets.<br />
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<a href="https://1.bp.blogspot.com/-S2eQ6IPjZBk/XOG6qpfq7yI/AAAAAAAAN-o/fJ5oXVvfdas8PicjuPuVjde02M-duiAGgCLcBGAs/s1600/gun%2Bmantlet%2Bir%2Blamp.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="578" data-original-width="1210" height="190" src="https://1.bp.blogspot.com/-S2eQ6IPjZBk/XOG6qpfq7yI/AAAAAAAAN-o/fJ5oXVvfdas8PicjuPuVjde02M-duiAGgCLcBGAs/s400/gun%2Bmantlet%2Bir%2Blamp.png" width="400" /></a><a href="https://4.bp.blogspot.com/-CTGDXmJ7ZhI/XOG6q5Y1idI/AAAAAAAAN-s/SSe6fLx84XAqFjWbV97pqnjIfQwZrTaVgCLcBGAs/s1600/gun%2Bmantlet%2Bclose%2Bup.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="887" data-original-width="1600" height="221" src="https://4.bp.blogspot.com/-CTGDXmJ7ZhI/XOG6q5Y1idI/AAAAAAAAN-s/SSe6fLx84XAqFjWbV97pqnjIfQwZrTaVgCLcBGAs/s400/gun%2Bmantlet%2Bclose%2Bup.png" width="400" /></a></div>
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The sight can be used to identify a tank-type target at a maximum distance of 750-800 meters in the active mode with illumination from the "Luna" IR spotlight. The T-54B medium tank entered service in the same year as the T-10M (1957) and it was was equipped with a TPN-1 night vision sight as well, so the T-10M did not have any advantage over its medium counterpart in this particular department.<br />
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The passive mode allows the same type of target to be spotted at ranges of up to 500 meters if the intensity of ambient light is no less than 0.005 lux, which is the typical brightness of a moonless, starlit night with clear skies. The clarity of the image - and thus the distance at which targets can be seen and identified - increases with the brightness of ambient light. Based on research into other 1st Generation night vision systems, the identification distance may be expanded to around 1,000 m on moonlit nights with clear skies (0.05–0.3 lux), and it should be possible to spot tanks at distances of more than 1,300 m during dark twilight hours (3.4 lux), although low magnification and mediocre image resolution complicates target observation at longer ranges. The sensitivity of the image intensifier in the sight should be decreased to provide better image quality during twilight hours.<br />
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Illumination shells and bombs can be used to great effect in conjunction with light intensifying sights like the TPN-1.<br />
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<a href="https://4.bp.blogspot.com/-hpkCKH5j7G4/XF6HY_vbPLI/AAAAAAAANXg/-6X9KEIAWRAtpAueYegjY4ih1kCfc1q_QCLcBGAs/s1600/tpn-1%2Bturret%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="586" data-original-width="727" height="321" src="https://4.bp.blogspot.com/-hpkCKH5j7G4/XF6HY_vbPLI/AAAAAAAANXg/-6X9KEIAWRAtpAueYegjY4ih1kCfc1q_QCLcBGAs/s400/tpn-1%2Bturret%2Bcross%2Bsection.png" width="400" /></a></div>
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When operating at night, the "Liven" stabilizer is switched from the "day" mode to the "night" mode. This switches the stabilization system from a gun-follows-sight scheme where the gun stabilizer is slaved to the independent two-plane stabilizer of the T2S-29-14 primary sight to a sight-follows-gun scheme where the TPN-1-29-14 is slaved to the gun stabilizer. The precision of stabilization is consequently reduced but not significantly enough to have a meaningful effect on combat accuracy due to the relatively short viewing distance provided by the night vision sight. If night fighting is conducted using flare illumination and with the IR spotlight converted to a white light spotlight, the T2S-29-14 primary sight is used instead and the stabilizer is set in the "day" mode.<br />
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The TPN-1-29-14 is installed directly above the T2S-29-14 sight in a circular slot in the turret roof. The eyepiece of the sight is placed directly above the eyepiece of the T2S-29-14. From the outside, the sight is protected by a cast steel armoured hood and the objective window is sealed with a simple armoured cover when not in use. The armoured cover is a simple plate with a handle that slides over the window into a pair of dovetailed tracks. The armoured hood on the T-10 has a sloping roof so that it does not obstruct the commander's view from his cupola periscopes. This was necessary because the sight was not offset to the left of the main sight like on the T-54 and T-62.<br />
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<a href="https://1.bp.blogspot.com/-btn3rSVjzHs/XNc4iKijKeI/AAAAAAAAN8M/z2zcZr_p9YMZUCYvV9IXxZqbgyYJqRWdACLcBGAs/s1600/tpn-1%2Bhood.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="266" src="https://1.bp.blogspot.com/-btn3rSVjzHs/XNc4iKijKeI/AAAAAAAAN8M/z2zcZr_p9YMZUCYvV9IXxZqbgyYJqRWdACLcBGAs/s400/tpn-1%2Bhood.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-Ji_6Gwuh-CE/XEj6cydCaVI/AAAAAAAANJQ/bq-aoqLHC-cx-DjwuQ8lr9_32EBkNbWTwCLcBGAs/s1600/T-10M_070.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://3.bp.blogspot.com/-Ji_6Gwuh-CE/XEj6cydCaVI/AAAAAAAANJQ/bq-aoqLHC-cx-DjwuQ8lr9_32EBkNbWTwCLcBGAs/s400/T-10M_070.JPG" width="400" /></a></div>
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Because the TPN-1-29-14 eyepiece is located above the eyepiece of the T2S sight, the gunner should adjust the height of his seat to maintain a comfortable posture when using the night sight. Interestingly enough, the control handles on the T2S sight would be at the level of the gunner's chest in a much more natural position when he is using the night sight.<br />
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As shown in the drawing below, the ends of the vertical lines and the chevron in the viewfinder are calibrated to predetermined distances. The topmost mark corresponding to a distance of 250 meters for AP round from the M62-T2 cannon only corresponds to a distance of 100 meters for the coaxial KPVT machine gun. The difference in the ballistic drop remains roughly similar with the smallest difference being at the center chevron, where there is a difference of 100 meters. The largest difference is at the lowest vertical line where the points of impact of the cannon and the coaxial machine gun would differ by 250 meters. Again, the mismatch between the ballistic trajectory of the APCBC rounds and 14.5mm bullets is clearly demonstrated. The markings are designed to facilitate quick and reasonably accurate engagement using the battlesight gunnery technique.<br />
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<a href="https://4.bp.blogspot.com/-RB0iGSMoqJ0/XCpt5QSX1VI/AAAAAAAAMuY/7GFdhrOhEKswhdxN9sD1ZHKztY1N56FGQCLcBGAs/s1600/tpn1-29-14.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="728" data-original-width="1096" height="424" src="https://4.bp.blogspot.com/-RB0iGSMoqJ0/XCpt5QSX1VI/AAAAAAAAMuY/7GFdhrOhEKswhdxN9sD1ZHKztY1N56FGQCLcBGAs/s640/tpn1-29-14.jpg" width="640" /></a></div>
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The sight does not include a stadia rangefinder or any other provision for range estimation besides the reticle markings, but this was not considered a debilitating drawback due to the limited viewing distance provided by the TPN-1-29-14. Given that the maximum practical combat distance with the sight was just 800 meters, the center chevron in the reticle (700 m) would serve as the universal battlesight and it could be used to engage practically all types of targets. When firing at tanks, the gunner should aim at the center of the hull. If the target is closer than 700 meters, the shot will land on the upper hull or on the turret. If the target is at 700 meters or more, the shot will land on the center of the hull or on the lower glacis. To engage targets with HE-Frag rounds, the gunner has to either rely on the relatively good point blank range of the OF-472 shell or use the burst-on-target gunnery technique.<br />
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The night vision capabilities of the "Luna" system were generally quite good by the standards of the 1950's, but it was limited by the low output of the incandescent lamp in the L-2 spotlight. An M103A2 with a xenon arc lamp spotlight (fitted since 1967) had a 75-million candlepower output that could illuminate a target at close to two kilometers, but the M103 series lacked any infrared night vision sighting systems, let alone a passive light intensifier system as found in the TPN-1. Despite the large range advantage that such a powerful spotlight could have granted the M103A2, the downsides of relying entirely on white light illumination with no possibility of switching to infrared imaging were much more compelling. Earlier M103 tanks were in a worse position as they only had a Hinds-Crouse incandescent white light spotlight of limited power. The worst by far was the Conqueror as it never had any night vision capability whatsoever. It even lacked infrared headlights for driving, and as such, not only lacked a night fighting capability but also lacked the ability to participate in stealthy night maneuvers.<br />
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In 1960, a small scale programme to upgrade existing T-10 series tanks with modern night vision equipment was started. The quantity of tanks that received the upgrade is unclear, but the upgrade package included the TPN-1-29-14 night sight, the L-2 "Luna" infrared spotlight, the TKN-1T infrared periscope, the OU-3T infrared spotlight, the TVN-1T, the FG-100 infrared headlight, as well as all of the associated electrical equipment. The photo below shows one example of a T-10 upgraded with night vision equipment while retaining all other characteristics of a typical T-10. This variant is known as the T-10 obr. 1960.<br />
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<a href="https://3.bp.blogspot.com/-cwkM_8jIX2A/XEWAogEzOLI/AAAAAAAANGM/kztJCJuL_qgJ3AEU2o1W4OcS5hfMRZ2XQCEwYBhgL/s1600/modernized%2Bt-10%2Bwith%2Bnight%2Bvision.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="938" data-original-width="1600" height="375" src="https://3.bp.blogspot.com/-cwkM_8jIX2A/XEWAogEzOLI/AAAAAAAANGM/kztJCJuL_qgJ3AEU2o1W4OcS5hfMRZ2XQCEwYBhgL/s640/modernized%2Bt-10%2Bwith%2Bnight%2Bvision.png" width="640" /></a></div>
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Due to the lack of an existing periscope opening on the turret roof of the T-10, T-10A and T-10B, the tanks that were retrofitted with a night vision sight had to undergo factory-level modifications. A square-shaped hole had to be cut into the turret roof and a hole had to be made in the turret to fit the electrical fittings to supply power to the external infrared spotlight, which was simply added to the right side of the gun mask by welding. The drawings on the left below show the locations of the equipment of the "Luna" night vision system in the turret of a T-10 obr. 1960 and how the TPN-1-29-14 sight is linked to the D-25T cannon, and the photo on the right below shows the TPN-1-29-14 installed in modernized T-10.<br />
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<a href="https://3.bp.blogspot.com/-kKfXlPrrv0g/XL6g-eaNnqI/AAAAAAAANus/iNYfjJNmxlsNCaa_17ISBLalHmkBpl5MQCLcBGAs/s1600/t-10%2Bmod%2B1960%2Bnight%2Bvision.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="395" data-original-width="461" height="342" src="https://3.bp.blogspot.com/-kKfXlPrrv0g/XL6g-eaNnqI/AAAAAAAANus/iNYfjJNmxlsNCaa_17ISBLalHmkBpl5MQCLcBGAs/s400/t-10%2Bmod%2B1960%2Bnight%2Bvision.png" width="400" /></a><a href="https://3.bp.blogspot.com/-KpZXg7pf3l4/XEvR1UBlqwI/AAAAAAAANO8/wXtEurlAfSQ_2QHJIZ0m6uPPHUokFx-5QCLcBGAs/s1600/tpn-1-29-14%2Bt-10%2Bobr.%2B1956.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="670" data-original-width="927" height="288" src="https://3.bp.blogspot.com/-KpZXg7pf3l4/XEvR1UBlqwI/AAAAAAAANO8/wXtEurlAfSQ_2QHJIZ0m6uPPHUokFx-5QCLcBGAs/s400/tpn-1-29-14%2Bt-10%2Bobr.%2B1956.png" width="400" /></a></div>
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<span style="font-size: large;">LOADER'S STATION</span></h3>
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<span style="font-size: large;">T-10, T-10A, T-10B</span></h3>
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For general vision, the loader is provided with two TPB-51 prismatic periscopes on the sides of the turret, just underneath his cupola. They are aimed in the 2 o'clock and 4 o'clock directions to allow the loader to cover the right side of the turret. This is a notable downgrade from most other Soviet tanks which gave their loaders a rotating MK-4S periscope, but regardless, this seems to be a very minor drawback since the loader is generally more focused on his loading duties and the two TPB-51 periscopes on the sides of the turret are enough to allow him to cover the right side of the turret which is a dead zone for the commander because the commander's cupola is offset to the left of the turret roof.<br />
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However, the loader would generally tend to be occupied with his primary tasks such as reloading the coaxial machine gun frequently as it is fed with relatively small 50-round boxes. Even when not actively loading the cannon or the coaxial machine gun, the loader can replenish his ready racks or rearrange the ammunition in the ready racks to more convenient positions so that he is ready for any sudden contact with enemy forces. Scanning the tank's surroundings from his periscopes is quite an unprofitable use of time by comparison.<br />
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The internal height of the fighting compartment at the loader's station as measured from the rotating floor to the turret ceiling is 1,600mm. This is functionally identical to both the IS-2 and IS-3 which had an internal height of 1,580mm. The loader also has a cupola which is raised above the turret roof, so in practice, he could have more headroom if he stands directly underneath his cupola when performing some loading actions, but conversely, the slope of the turret roof in front of the cupola drastically reduces the loader's headroom if he is not standing under his cupola. This would not be a problem if the loader is retrieving ammunition from the ammunition racks on the fighting compartment floor or from any of the hull racks as he must bend down anyway, but it could make it more difficult to reload and service the coaxial machine gun because the top cover must hinge upward. On T-10 models up to the T-10B, the coaxial DShKM mount is raised above the bore axis of the main gun, so it is quite close to the turret roof, especially when the gun is depressed. The coaxial KPVT in a T-10M is closer to the bore axis of the main gun, but due to its enormous top cover, the clearance issues are similar.<br /><br />
The D-25T series gun breech assembly has a width of 480mm and the gun is aligned with the centerline of the turret. Since the tank has a turret ring diameter of 2,100mm, the maximum width of the loader's station is 810mm. By contrast, the loader's station in an IS-2 and IS-3 had a maximum width of 660mm and 680mm respectively. Even when the loading assistance device integral to the T-10 is factored in, the loader's station in the T-10 is still wider by a noticeable amount.<br />
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According to the article "<i>Human Factors and Scientific Progress in Tank Building</i>", the internal volume of the loader's station in a T-10 is 0.762 cubic meters. This much less than the 1.36 cubic meters of space enjoyed by the loader of a T-55, and it can be explained by the ammunition stowage layout in the T-10. This will be explored later in this article.<br /><br />
The loader's hatch has a diameter of 572mm and a thickness of 20mm. It has a dome shape to provide additional headroom if the loader is standing under his cupola.<br />
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The loader was also responsible for manning the external DShKM anti-aircraft machine gun which is mounted on a fixed pintle attached to his cupola. Besides traversing the cupola, the machine gun can also be aimed independently by swinging it around its pintle. This design is unobtrusive to the loader and it permits a full-sized circular hatch to be installed, giving the loader the largest possible passageway for a given cupola diameter. In this case, the cupola has a diameter of 646mm, the hatch has a diameter of 572mm and the hatch opening has an internal diameter of 540mm, as detailed in the drawings below. This is effectively the same design as the loader's cupola on a T-54. The drawback of this design is that when the DShKM is fitted on its mount, the toothed arc for its elevation mechanism physically blocks the hatch from opening or closing, making it necessary to stow the gun away by turning it to the side.<br />
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However, there is no mechanical assistance for rotating the cupola, so the loader must rely entirely on his upper body strength to shift it. The pintle juts outside the perimeter of the cupola to accommodate the full circular hatch for the loader, but the heavy DShKM machine gun unbalances the cupola with its weight and makes it difficult to rotate the cupola if the tank is on a slope. To solve this issue, the loader's hatch was designed to act as a counterweight when it is fully opened.<br />
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<a href="https://2.bp.blogspot.com/-gBzE40p_dgE/XEoahsPO-AI/AAAAAAAANLg/QRfM1s5-SeQbdhV1O6P1WrC5QwewP0ppQCLcBGAs/s1600/loader%2527s%2Bhatch%2Bside.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="424" data-original-width="1379" height="196" src="https://2.bp.blogspot.com/-gBzE40p_dgE/XEoahsPO-AI/AAAAAAAANLg/QRfM1s5-SeQbdhV1O6P1WrC5QwewP0ppQCLcBGAs/s640/loader%2527s%2Bhatch%2Bside.png" width="640" /></a></div>
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<h3>
<span style="font-size: large;">T-10M</span></h3>
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The new T-10M turret retained the general shape of the previous turret design, but the level of protection was deeply enhanced. One of the measures taken to improve the resilience of the side turret armour was to replace the two TPB-51 prismatic periscopes on the sides of the loader's cupola with a single fixed TNP periscope on the turret roof aimed in the 1 o'clock direction. This is probably less useful than the two smaller square-shaped TPB-51 periscopes on the side of the turret since the loader would be looking in a forward direction while both the gunner and commander would already be scanning the area ahead of the tank through their own, much better viewing devices. The loader also loses the ability to scan the dead zone on the right side of the turret. Still, there is not much combat value in giving the loader more vision than absolutely necessary, so it does not make much of a difference in the grand scheme of things. The loader's single TNP periscope can be seen in the photo below (taken from the <a href="https://www.net-maquettes.com/pictures/t-10-heavy-tank/">Net-Maquettes website</a>).<br />
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The photos below show the loader's cupola of a T-10M. The bulge in the hatch for additional headroom can be seen in both photos. To allow the loader to turn the heavy cupola more easily and to aim the KPVT machine gun with greater precision, a geared traverse mechanism was added on the cupola roof, as part of the anti-aircraft machine gun system. If desired, the cupola could still be turned by physically forcing it, with a fixed handle next to the traverse handwheel to aid the loader. In the photo on the left, the handwheel is clearly visible, but the fixed handle next to it has been broken off. In the photo on the right, fixed handle is still attached to the cupola but the handwheel is gone.<br />
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<br />The handwheel of the traverse mechanism has a fixed gear ratio and would be the primary method of laying the machine gun on target in the horizontal plane, but it is light and coarse enough that the cupola could be traversed rapidly with it. Even with the KPVT being mounted directly to the cupola instead of a pintle combined with the loader's hatch acting as a counterweight when it is opened, the cupola is slightly unbalanced due to the huge weight of the KPVT and its ammunition box, so the handwheel is a basic necessity if the tank is on a slope. A manned KPVT on the loader's cupola of a T-10M can be seen in the photo below, taken during Operation Danube in 1968.<br />
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The Object 268 featured an identical loader's cupola on the roof of its casemate, and a brief overview of the cupola sans the KPVT can be seen in <a href="https://youtu.be/_HQYn-hqMr4?t=655">this video clip from an episode of "The Chieftain's Hatch"</a>.<br />
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A major drawback of the new cupola design was decreased size of the hatch opening, making it more difficult for the loader to ingress and egress through the hatch, especially when wearing winter clothing or when carrying some equipment on his person. The photo below, taken from from "<i>T-10 Heavy Tank and Variants</i>" by James Kinnear and Stephen Sewell, shows the loader's station through his open hatch.<br />
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The T-10 series carries a load of 30 rounds of ammunition, which is slightly more than the 28 rounds carried in an IS-2 or an IS-3. A substantial portion of this ammunition load was stowed in the turret. </div>
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The work of the loader is aided rather than hampered by the division of the cartridges into two parts. For reference, a unitary 122mm AP cartridge of equivalent ballistic characteristics to the existing two-part ammunition of the D-25 series of guns <a href="https://yuripasholok.livejournal.com/3962073.html">would have a length of 1,211mm</a>. Individually, a case with a length of 784mm and an AP projectile with a length of 419mm are both much easier to handle than a unitary cartridge in the confines of the tank. The Conqueror and the M103 both used two-part ammunition for the same reason.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><font size="5">SEMI-COMBUSTIBLE PROPELLANT CHARGES</font></h3>
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Since the D-25T and M-62T2 both use cased ammunition, the loader must deal with the hassle of occasionally disposing of spent shell casings during or after combat. This was also a problem for the M103 and Conqueror, but not the future Chieftain main battle tank which made use of lightweight bagged charges.<br />
<br />To achieve a further increase in the rate of fire, the development of tank ammunition with semi-combustible propellant charges in the Soviet Union began in 1954. Comprehensive testing began in 1955 on IS-3 and T-10 tanks and continued for four years, culminating in the acceptance of the new technology in 1957 and the order to begin production of semi-combustible propellant charges for 122mm HE-Frag and AP ammunition in 1959. Modified ammunition racks and fire protection equipment were approved for installation in the IS-3 and T-10 shortly afterward, and fielded to active tank units in 1961. Future ammunition developed for both the IS-3 and T-10 like HEAT and APDS rounds were only supplied with semi-combustible propellant charges, as metal-cased ammunition had been all but phased out by that point.<br />
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Combustible pyroxylin-cellulose textile impregnated with TNT was used to construct the combustible casings of the new propellant charges for the D-25T. The combustible cases were very hard and could withstand cuts and impacts, but not to the same extent as a metal casing, and of course, the combustible cases will begin to burn when subjected to an open flame for a few seconds whereas a metal casing does not burn at all. The purpose of having a rimmed steel casing stub was to ensure that the semi-combustible charges could be used in guns with a breech designed to operate with cased propellant, which would have been impossible with fully combustible charges.<br />
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The use of semi-combustible propellant charges made the loader's job easier as they were lighter to handle and there would be no need to dispose of spent casings even after long periods of sustained firing as the obturator stubs are several times shorter than a full metal casing. For the 122x785mm and 122x759mm caliber cartridges, a casing stub is a fifth of the length of a full-sized casing. The volume in the tank occupied by spent casings after each shot would be much lower accordingly and they are much easier to throw out of an open hatch. According to the study "<a href="http://btvt.info/5library/vbtt_1963_04_gilzi.htm"><i>Автоматизация Удаления Гильз Из Боевого Отделения Танка</i></a>" published in 1963, creating a special space in a tank for stowing 40 full-sized spent shell casings for a hypothetical tank shell cartridge would require a hypothetical volume of 1,000 liters (1 cu.m) whereas 40 casing stubs for semi-combustible rounds of the same caliber would occupy a volume of only 200 liters. </div><div><br /></div><div>Furthermore, according to Soviet data obtained during the development of semi-combustible propellant charges, it was shown that the substitution of metal-cased cartridges with cartridges using this type of propellant charge had the effect of reducing the concentration of propellant fumes in the fighting compartment by 60%. The combination of the light weight of the semi-combustible charges, small size of the casing stubs and the greatly reduced pollution of the fighting compartment atmosphere from propellant fumes meant that the job of the T-10 loader became much easier and the fighting efficiency of the crew as a whole saw a general improvement. Additionally, the substitution of large brass cases with small steel stubs was economically beneficial. These factors were noted to be the main advantages of semi-combustible charges in the book "<i>Танки и танковые войска</i>" published by the Воениздат (Voenizdat) in 1970.<br />
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British engineers were also experimenting with this type of technology around the same time as their Soviet counterparts, leading to the introduction of light bagged charges for the L11 gun of the Chieftain in the mid to late 1960's. The benefits of semi-combustible propellant casings extended to unitary cartridges as well. For example, a unitary DM12 (105) or M456 HEAT cartridge for the L7 and M68 with a brass casing weighs 21.8 kg whereas a DM12 (120) or M830 HEAT cartridge for the Rh 120 and M256 is barely heavier with a weight of only 24.2 kg despite the large increase in caliber, and this is thanks to the change from brass casings to combustible nitrocellulose casings. However, the use of semi-combustible propellant charges was not the only method of reducing the amount of clutter in the loader's station from spent shell casings while also reducing the concentration of propellant fumes. The Conqueror and the T-62 both solved these two issues by using an automatic spent shell casing ejection mechanism. When combined with a fume extractor and a good ventilation system, the concentration of propellant fumes could be reduced to nearly 0%, but the downside to this solution is that nothing is done about the greater weight of the metal-cased cartridges.<br />
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On the basic T-10 model with the D-25TA cannon, the inclusion of a ventilator intake fan on the turret ceiling above the gun breech was necessary due to the lack of a fume extractor on the D-25TA. When the D-25TS was introduced on the T-10A, the ceiling ventilation fan was omitted as it had become redundant and it slightly weakened the turret roof as it was essentially just a large hole.</div>
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The work done by the engineers at the NII-6 research bureau with the participation of the in-house design bureaus of various tank factories culminated in the universal implementation of caseless ammunition for all subsequent Soviet tanks and tank guns in the mid-1960's including the 115mm 2A21 for the T-62 and 125mm 2A26 (2A46) for the T-64A, T-72 and T-80.<br />
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Tanks that were to be supplied with the new semi-combustible ammunition required modified ammunition racks. The new racks had to be slightly narrower so that the charges did not constantly rattle around or rub against the clips, causing wear and tear by friction. The installation of new ammo racks was a very straightforward process that could be carried out during normal maintenance checkups.<br />
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<span style="font-size: large;">AMMUNITION STOWAGE</span></h3>
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<span style="font-size: large;">T-10</span></h3>
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Due to the large weight of 122mm projectiles, they are mostly stowed in the turret so that the loader does not have to bend down and exert additional effort to lift them up to the cannon breech, and the majority of the much lighter propellant charges are stowed in the hull. This also has the benefit of reducing the likelihood of an ammunition fire as the propellant charges are much more sensitive to open flames as well as impact detonation from fragments, so placing a larger share of the charges in the hull behind the tank's thickest armour where they are less likely to be damaged is generally a good idea, although the stowage layout is not optimal from a safety standpoint as the number of propellant charges stowed in the turret is non-trivial. In this sense, the T-10 is actually a step backward from the IS-3 and IS-2, both of which carried a large number of projectiles in the turret but no propellant charges. In fact, the IS-2 carried all 28 projectiles of its full ammunition load in the turret bustle. This shortcoming of the T-10 is mainly due to the short length of its turret bustle.<br />
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The British Conqueror and Chieftain tanks (both use two-piece ammunition) were also designed with the same safety considerations, but the M103 does not follow this convention as the propellant charges are stowed together with the projectiles in the turret bustle. Interestingly enough, this was repeated in the M48, M60 and M60A1 tank designs which also stowed a large quantity of their unitary ammunition in the turret.<br />
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Overall, the ammunition layout in the T-10 is imperfect but it lacks any major flaws that might impede the loader's work. On the T-10A and T-10B, the turret traverse drive is suspended after every shot until the loader presses his safety switch so that there is no chance of the loader being endangered by unexpected turret movements while he is retrieving ammunition from various racks in the hull.<br />
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A vertical rack for six projectiles is arranged in a row at the front of the turret, next to the coaxial machine gun. These are the same racks as the distinctive type found in the IS-3 turret. These racks hold projectiles in folding trays that are designed to be folded flush against the curved turret wall when not in use so as to not obstruct the loader. When the loader wishes to retrieve a projectile, he simply pulls a lever and the tray folds out, allowing the heavy projectile to slide out. This process is shown in the GIF below, created <a href="https://youtu.be/zUXJ_gKMxRQ">using this video</a> from the "Cross Porcupine" channel. If the GIF loads too slowly, it can be viewed separately <a href="https://i.imgur.com/p0dM7C3.gif">here</a>.<br />
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A potential issue with the front turret projectile racks is that a non-perforating hit from a sufficiently powerful cannon could create a bulge on the back surface of the turret wall or even cause spalling. This would not set off the projectile, but the damage could render it unsafe to fire and the racks may also be knocked open, possibly causing the projectile to drop to the floor and cause a nuisance.<br />
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Two more projectiles are stowed on the turret ring underneath these vertical racks.<br />
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Ten propellant charges are placed vertically on the front right quadrant of the rotating floor.<br />
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As shown in the factory drawing below, the vertical ammunition racks take up almost half of the space on the rotating floor on the loader's side of the turret. The presence of these racks may make it impossible to access the front right hull ammunition racks when the turret is facing the front. Once these vertical ammunition racks are expended, the full length of the turret floor is freed up for the loader and the internal volume of the loader's station increases accordingly.<br />
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Several boxes of ammunition for the coaxial 12.7mm machine gun are stored on the rotating floor of the turret, underneath the main gun. Since the vertical ammunition racks on the rotating floor in front of the loader prevent him from reaching these boxes, the loader must have at least depleted the ammunition racks before being able to access this location.<br />
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Six propellant charges are clipped to each of the sponsons on the sides of the hull.<br />
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<span style="font-size: large;">T-10M</span></h3>
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The loader is provided with a seat attached to the rotating floor. The seat is vertically adjustable by sliding it up and down the seat post and it can also be adjusted between two horizontal positions. The first position places the seat directly underneath the loader's hatch and allows the loader to sit facing the front of the tank. The second position places the seat forward of the loader's hatch and allows the loader to easily load the cannon while seated. The grooves for sliding the seat post horizontally on the mounting point is clearly shown in the drawing below. The simple mechanism for adjusting the seat vertically is also shown. When adjusted to its full height and positioned underneath the hatch, the loader can stand on the seat to operate the anti-aircraft machine gun on his cupola, and if the seat is not needed or wanted, it can be dismantled and stowed away.<br />
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Like the T-10A and T-10B models with the "Uragan" and "Grom" stabilizers, the T-10M with the "Liven" stabilizer will automatically elevate the M62-T2 cannon by 3 degrees after each shot and fix it in place by hydrolock, thereby lowering the breech by 3 degrees from the loader's perspective. With the gun fixed at this angle, it it easier for the loader to load the cannon, especially if the tank is moving. In this condition, the stabilizer limits the maximum traverse speed of the turret to just 5 degrees per second. This helps to ensure the loader's safety from unexpected turret movements while he is retrieving ammunition from the hull.<br />
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Four ready boxes of ammunition were provided for the KPVT coaxial machine gun. One box would be placed next to the machine gun itself, ready to feed, and the other three boxes were stowed in three different locations in the fighting compartment. One box is placed in the rear right corner of the hull next to the engine compartment firewall, one box is placed in front of the front right 122mm ammunition rack, and one box is placed in front of the front left 122mm ammunition rack. If the turret is facing to the right or to the rear, only one of the boxes can be reached by the loader. Otherwise, two of the boxes can be accessed by the loader from his station.<br />
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Five ready boxes of ammunition were provided for the KPVT anti-aircraft machine gun. One box would be placed next to the machine gun itself, ready to feed, one box would be stowed externally on the turret next to the loader's cupola, and the remaining three boxes would be stowed on the turret floor. One box is placed underneath the commander's seat and two boxes are placed underneath the main gun, on top of the sealed zinc boxes of reserve ammunition. Except for the box underneath the commander's seat, all of the ammunition is accessible to the loader who is responsible for manning the anti-aircraft machine gun.<br />
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Depending on the situation, it may be expedient to use the ammunition boxes for the anti-aircraft machine gun to feed the coaxial machine gun as the coaxial is likely to see more frequent use.<br />
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The assisted loading system was retained on the new M62-T2 cannon but the ammunition stowage layout in the tank was revised. Like previous T-10 models, the loader can perform his duties while seated because the ready racks for the 122mm rounds are in the turret.</div>
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Seven projectiles are stowed in a single row along the entire length of the turret bustle. The projectiles are angled away from the loader for his convenience when retrieving them from the bustle racks. When the loader extracts a projectile from these racks, his left hand would be on the base of the projectile to pull it out and his right hand would be holding the tip. The loader could then turn on the spot and immediately lay the projectile on the ramming tray without needing to turn it around in his hands to align it with the cannon. The photo on the left below (from "<i>T-10 Heavy Tank and Variants</i>" by James Kinnear and Stephen Sewell) shows the rear bustle racks from the perspective of the cannon breech, and the photo on the right (<a href="http://www.kotsch88.de/al_T-10M.htm">credit to Stefan Kotsch</a>) below shows the racks from the commander's perspective.<br />
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<a href="https://4.bp.blogspot.com/-1gwuWzy2jlQ/XEKxo9_qO3I/AAAAAAAANCw/KLO4VgRjUukTFurFj14cnfm9IrjD-g2iwCLcBGAs/s1600/kubinka%2Bt-10m%2Bbustle%2Bracks.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="706" data-original-width="1057" height="265" src="https://4.bp.blogspot.com/-1gwuWzy2jlQ/XEKxo9_qO3I/AAAAAAAANCw/KLO4VgRjUukTFurFj14cnfm9IrjD-g2iwCLcBGAs/s400/kubinka%2Bt-10m%2Bbustle%2Bracks.png" width="400" /></a><a href="https://3.bp.blogspot.com/-sXv9F3ya9Y4/XEEVkf68Y4I/AAAAAAAAM_M/flgryoujZCERzNkwbIo8b9v-NfP7AgI3QCLcBGAs/s1600/bustle%2Bracks.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://3.bp.blogspot.com/-sXv9F3ya9Y4/XEEVkf68Y4I/AAAAAAAAM_M/flgryoujZCERzNkwbIo8b9v-NfP7AgI3QCLcBGAs/s400/bustle%2Bracks.JPG" width="400" /></a></div>
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There is also a row of nine projectiles stowed facing down around the turret ring behind the casing deflector of the cannon breech guard. The nine projectiles are stowed in three separate racks mounted on the perimeter of the turret ring on rollers. Once the rack closest to the loader is expended, he can push it out of his way and pull the next rack over to his position, possibly with the commander's help. This gives the loader a consistent source of ready ammunition at the most convenient position.<br />
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<a href="https://1.bp.blogspot.com/-moeQKpwsM_M/W9bSutFvLqI/AAAAAAAAMcc/rjLK0YEf93Anne1tZ8y6lnTjD8Yx_vP9gCLcBGAs/s1600/rolling%2Brack.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="445" data-original-width="608" height="292" src="https://1.bp.blogspot.com/-moeQKpwsM_M/W9bSutFvLqI/AAAAAAAAMcc/rjLK0YEf93Anne1tZ8y6lnTjD8Yx_vP9gCLcBGAs/s400/rolling%2Brack.png" width="400" /></a></div>
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In total, sixteen projectiles are stowed in the two turret racks at the rear of the turret in convenient racks. Once the turret racks are fully expended, he can replenish them using the projectiles stowed on the hull floor.</div>
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For the propellant charges, the loader mainly draws from the supply of charges stowed in the turret bustle of which there are six, and on the turret wall, of which there are two. There are another seven propellant charges in the front right hull rack arranged in two staggered columns and there are six more charges in the right hull sponson. In total, twenty two propellant charges are readily available to the loader in various hull and turret racks, but the most convenient ones are the eight charges stowed in the turret.</div>
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<span style="vertical-align: inherit;"><span style="vertical-align: inherit;">During the initial burst of fire with the M62-T2, the loader takes eight projectiles and eight propellant charges from the turret. To load the remaining eight projectiles in the turret, the loader must take propellant charges from the turret floor and front hull racks in front of him, or from the propellant charges clipped to the sponsons. Because each ammunition type must be paired with a proprietary propellant charge, any of the three propellant charge racks may have to be used. The other four rounds that are readily available are taken from the front hull racks. </span></span>The remaining eight rounds consist of eight propellant charges on the port side of the hull, but there are only five projectiles stowed in this side of the hull. The other three projectiles must be taken from the turret floor.<br />
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<span style="vertical-align: inherit;"><span style="vertical-align: inherit;">It is worth noting that it is possible for the tank commander to load the cannon without leaving his station thanks to the relatively large number of rounds stored near him, although he does not have the assistance of the powered rammer as the mechanism is on the loader's side of the turret. This is a rather minor advantage that would probably never have much effect except in emergency situations, but it is interesting to point out nonetheless.</span></span></div>
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<a href="https://www.blogger.com/null" id="loadassist"></a>
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<h3>
<span style="vertical-align: inherit;"><span style="font-size: large; vertical-align: inherit;">LOADING ASSISTANCE DEVICE</span></span></h3>
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<a href="https://1.bp.blogspot.com/-WFDgMoKLbAs/XP_j5q-ZMkI/AAAAAAAAOZw/k1PfNMN-V6Ah3tv9q4g0f2t3pfDjCTFfQCLcBGAs/s1600/device.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="401" data-original-width="650" height="394" src="https://1.bp.blogspot.com/-WFDgMoKLbAs/XP_j5q-ZMkI/AAAAAAAAOZw/k1PfNMN-V6Ah3tv9q4g0f2t3pfDjCTFfQCLcBGAs/s640/device.png" width="640" /></a></div>
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The loading assistance device in the T-10 traces its roots to an idea by Kotin after personally trying to load 122mm shells in an IS-2 in the field after interrogating the tank crews. In Zhozef Kotin's biography "<i>Конструктор боевых машин</i>" (<i>Designer of War Machines</i>) by N. Popov and M. Ashik et al., it is reported that Kotin claimed in a 1977 interview with the "<i>Военный вестник</i>" magazine (<i>Military Herald</i>) that he made it a personal policy to follow the deployments of his new heavy tanks to the frontline in order to inspect them after battle, and this led to his personal revelation that the 122mm shells of the IS-2 (then known provisionally as the IS-122) were too heavy and a mechanical rammer was needed to assist the tank loader. Here is the relevant paragraph from the book, reprinted verbatim:<br />
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"<i>У меня выработалось твердое правило: с каждой новой или модернизированной машиной самому выезжать на фронт, - рассказывал Ж. Я. Котин корреспонденту журнала "Военный вестник" в 1977 г., - в атаку, правда, я свои танки не водил. А вот по горячим следам, сразу же после боя, надо было посмотреть, как работает новая конструкция, побеседовать с командирами экипажей, механиками-водителями. Такая связь с фронтом давала нам очень многое. Помню, испытывался ИС. Пушка на нем стояла 122-мм. Снаряд тяжелый. Члены экипажей жалуются, что слишком много времени и сил тратят на заряжание. Полез сам в танк, попробовал подать снаряд и убедился: надо что-то делать. На заводе в срочном порядке изготовили специальное приспособление для подачи снарядов в казенную часть…</i>"<br />
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Translated:<br />
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<span style="vertical-align: inherit;"><span style="vertical-align: inherit;">“<i>I have developed a firm rule: to go to the front with each new or modernized machine myself, " - Zh. Ya. Kotin told a correspondent of the Military Herald magazine in 1977 - "I didn’t drive my tanks, though. I was hot on their heels. Immediately after the battle, it was necessary to see how the new design works, to talk with the crew commanders, the driver-mechanics. Such communication with the front gave us a lot. I remember testing the IS. The gun had a 122mm caliber. The shell was heavy. Crew members complain that too much time and effort was spent to load them.</i></span><span style="vertical-align: inherit;"><i> I climbed into a tank, tried to lift a shell and found it was really heavy: I needed to do something. The factory urgently produced a special device for feeding shells into the breech ... </i>"</span></span><br />
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This special device was not fitted to the IS-3 and IS-4 in serial production, but it was reportedly tested as early as 1944 on IS-2 tanks but was rejected for unknown reasons. A loading assistance device was tested in an IS-3 with positive results and a recommendation for service, but it was never fitted to IS-3 tanks. The IS-7 had a highly automated loading system in its turret bustle akin to that of the AMX-13, and naturally, the experience gained from developing this loading system influenced the direction taken by future designers. One of the findings was that the original pneumatic rammer in the IS-7 loading mechanism was unreliable, so it was replaced by a mechanical rigid-chain rammer. This later became standard on all Soviet tanks with assisted loading mechanisms and automatic loaders even until now.<br />
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After a great deal of development and testing on various platforms over several years, loading assistance devices eventually became a standard feature among Soviet tanks with large caliber cannons beginning with the T-10.<br />
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<span style="vertical-align: inherit;"><span style="vertical-align: inherit;">Comparing the T-10 with the Conqueror and the M103, the T-10 is the only one that successfully implemented a powered loading assistance system of any kind. An early prototype of the Conqueror was originally intended to have an autoloader for its 120mm gun but this was scrapped before the tank entered series production, leading to the final tank having only one human loader. On the other side of the pond, the M103 was originally intended to have one loader assisted by a power-loader mechanism in the early stages of its development, but this idea did not come to fruition and the tank was designed to have two human loaders instead. The Soviet Union probably took the lead simply because Kotin had been working on this concept since the late stages of WWII, so there was more time for testing and refinement.</span></span><br />
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One of the most attractive characteristics of the T-10 loading assistance device is its compactness. The device is installed behind the cannon breech, inside the recoil guard which is mounted to the gun mounting cradle. Due to its relatively small size and narrowness, it does not intrude significantly into the loader's space or interfere very much with his work, and it also acts as a recoil guard because it physically separates the loader from the path of the recoiling cannon. The photo on the left below shows the device in a T-10M, taken from "<i>T-10 Heavy Tank and Variants</i>" by James Kinnear and Stephen Sewell. The image on the right below, from "<i>Отечественные Бронированные Машины 1945-65 гг.</i>", shows the device already present on the D-25T of the IS-5. <br />
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<a href="https://4.bp.blogspot.com/-kRJi7KDaHHY/XFyog8oH--I/AAAAAAAANTw/8wtz4vo-YSIOTq9Cl21komqKHeD1BeGWgCLcBGAs/s1600/t-10m%2Brammer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="708" data-original-width="755" height="373" src="https://4.bp.blogspot.com/-kRJi7KDaHHY/XFyog8oH--I/AAAAAAAANTw/8wtz4vo-YSIOTq9Cl21komqKHeD1BeGWgCLcBGAs/s400/t-10m%2Brammer.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiiFlbMfgtubEfX8kpn-zT1xo7mnY0MVwuNH2ujGvXKRpF2VGYQJ94McZbC8w1OwB0mcCBVKXD-ZVVpFRJVsFP8-77hosOPFPleipFBZWv0IT_ZTo0DBDeIbxA_HNMXXvHsi1NbfD4ITzMKk3OYjHgSUxLwX2U9jgReHW4cnJHhFH8obWKPlWdWFPfthw/s1009/is-5%20loading%20device.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="823" data-original-width="1009" height="326" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiiFlbMfgtubEfX8kpn-zT1xo7mnY0MVwuNH2ujGvXKRpF2VGYQJ94McZbC8w1OwB0mcCBVKXD-ZVVpFRJVsFP8-77hosOPFPleipFBZWv0IT_ZTo0DBDeIbxA_HNMXXvHsi1NbfD4ITzMKk3OYjHgSUxLwX2U9jgReHW4cnJHhFH8obWKPlWdWFPfthw/w400-h326/is-5%20loading%20device.png" width="400" /></a></div>
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<a href="https://www.blogger.com/null" id="d25assist"></a>
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<span style="font-size: large;">D-25TA, D-25TS</span></h3>
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<a href="https://1.bp.blogspot.com/-c724GOx0eWM/XkhKn2eoIYI/AAAAAAAAQA0/Vz-s3UHxskELZdViXYmZEez8W9_JYV56wCLcBGAsYHQ/s1600/d-25ta%2Bloaders%2Bassist%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="623" data-original-width="785" height="316" src="https://1.bp.blogspot.com/-c724GOx0eWM/XkhKn2eoIYI/AAAAAAAAQA0/Vz-s3UHxskELZdViXYmZEez8W9_JYV56wCLcBGAsYHQ/s400/d-25ta%2Bloaders%2Bassist%2Bmechanism.png" width="400" /></a></div>
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The loading process for the D-25TA and D-25TS is not more complex than a completely manually-loaded tank gun without assistance. On the contrary, the presence of the loading assistance device enables the loader to bypass what is usually the most physically demanding part of his job. Considering that the mass of an OF-471 HE-Frag shell is 25.25 kg and the propellant charge weighs 16.55 kg for a combined weight of 41.8 kg (92 lbs), ramming the full cartridge into the cannon chamber by hand is no mean feat, especially since the loader must also ensure that he rams the cartridge forcefully enough that the projectile engages the forcing cone in the chamber. By implementing a loading assistance device, the T-10 could fire at a higher rate than its NATO counterparts and sustain its higher rate of fire for a prolonged period of time. This was complicated by the lack of a fume extractor on the original T-10 model as sustained fire at a high rate will eventually flood the fighting compartment of the tank with fumes even with a powerful ventilator fan installed directly over the gun breech. This would not have been a problem for any T-10 model after the original.<br />
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<a href="https://2.bp.blogspot.com/-mId4ZVpzqZg/XCpPNp8dKWI/AAAAAAAAMt8/O4NpfTqncRUG0MNhs0gj0BlqAhxtC01lQCLcBGAs/s1600/ramming%2Btray.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="384" data-original-width="534" src="https://2.bp.blogspot.com/-mId4ZVpzqZg/XCpPNp8dKWI/AAAAAAAAMt8/O4NpfTqncRUG0MNhs0gj0BlqAhxtC01lQCLcBGAs/s1600/ramming%2Btray.jpg" /></a></div>
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The loading assistance device is mounted on a rail and includes a powered chain rammer, the electric motor for the rammer, a microswitch, a loading tray, a handlebar underneath the tray, and a return spring. The rigid chain for the ramming mechanism is stored in a special container underneath the tray, as shown in the drawing below. The powered chain rammer has a rubber-padded tip that contacts the base of the projectile or propellant casing. When loading, the chain rammer is programmed to actuate in two different stroke lengths - when ramming projectiles, the entire length of the chain rammer unfurls and the rammer pushes the projectile deeply into the chamber to engage with the forcing cone at the throat of the barrel in a long stroke. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj3wVnu97fJPk9hzE9G9ZF2zAvTBAreyYBVEnAHhdCKN4djeOVsPyumQsCbIrlGnv1R2oPNXlWNlKK_IMl5uHfxAUYUk0fUOFdoifGPEGC6pRCxoTSMm8QD9wsXcVrKR09q60h3lwRj9fFeug_2dVk7SGevZgn3X_fLAd0e90YpPvSo_JG_7APm8xcgPSXU/s1751/rammer%20scheme.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1363" data-original-width="1751" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj3wVnu97fJPk9hzE9G9ZF2zAvTBAreyYBVEnAHhdCKN4djeOVsPyumQsCbIrlGnv1R2oPNXlWNlKK_IMl5uHfxAUYUk0fUOFdoifGPEGC6pRCxoTSMm8QD9wsXcVrKR09q60h3lwRj9fFeug_2dVk7SGevZgn3X_fLAd0e90YpPvSo_JG_7APm8xcgPSXU/w400-h311/rammer%20scheme.png" width="400" /></a></div><div><br /></div><div>When ramming propellant charges, the chain rammer only unfurls partially to push the charge into the chamber in a short stroke, due to the much shorter travelling distance. In the latter case, the much shorter stroke length takes much less time to complete and minimizes the delay before the gunner can fire the cannon. The loading assistance device slides along the rail it is mounted upon and the handlebar underneath the tray contains the stopper that locks the device in one of two positions: the "ramming" position directly behind the gun breech and in the "ready" position behind and to the right of the gun breech.<br />
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<a href="https://4.bp.blogspot.com/-3OHr4nYo6PM/XFyM0KGswqI/AAAAAAAANSg/MRAgTroINgIFiFgTouNfiQSwEAfk9a7agCLcBGAs/s1600/d-25ts%2Bloading%2Bassistance%2Bdevice.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="535" data-original-width="1029" height="332" src="https://4.bp.blogspot.com/-3OHr4nYo6PM/XFyM0KGswqI/AAAAAAAANSg/MRAgTroINgIFiFgTouNfiQSwEAfk9a7agCLcBGAs/s640/d-25ts%2Bloading%2Bassistance%2Bdevice.png" width="640" /></a></div>
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An MU-431 electric motor serves as the drive unit for the chain rammer. The motor has a power of 400 W and a torque output of 0.78 Nm which is amplified through a worm gear in the rammer unit gearbox. The 122mm 2A31 howitzer of the 2S1 "Gvozdika" and the 152mm 2A33 howitzer of the 2S3 "Akatsiya" which entered service later in 1970 and 1971 respectively both use the same MU-431 motor and have very similar loading assistance devices.<br />
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The device is normally in the "ready" position before loading and when not in use. The loader can switch the operating mode of the loading assistance device between the Automatic and Manual modes. The loader is provided with a control box mounted on the recoil guard of the cannon just next to the opening for the breech block. It can be seen in the drawing on the left below. Referring to the drawing on the right below, the control box has a button for activating the chain rammer for loading a propellant charge (labeled <i>КД</i>) and two signal lights, one to indicate that the system is operating in the manual mode (<i>Р</i>) and one to indicate that the system is operating in the automatic mode (<i>А</i>). When operating in the manual mode, a cover (5) above the signal lights is lifted and two buttons are available to control the chain rammer. There is a button to command the chain rammer to ram a full stroke (<i>КПХ</i>) and a button to command the chain rammer to recede (<i>КОХ</i>). A safety and instruction guide is screwed onto the cover of the control box.<br />
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Before loading the cannon, the loader must ensure that the operating mode of the loading assistance device is switched to the "automatic" setting during normal operation. The signal light (<i>А</i>) will be lit, informing the loader that the system is operational and the cannon is ready to be loaded.<br />
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To load, the loader receives the order to load a specific type of ammunition from the commander and he proceeds to locate a shell of the desired type. He retrieves it and deposits it on the loading tray. Then, he grasps the handlebar underneath the loading tray and pulls it back to unlock the stopper from the "ready" position, and then he proceeds to shove the unlocked device behind the breech until it is locked in place by the stopper, indicating that it is in the "ramming" position. This action tensions the return spring and it trips a microswitch which signals the powered chain rammer to begin pushing the projectile in the gun. The rammer extends a full stroke to ram the projectile all the way down the chamber.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgI-vIIz6qv4yOzUa3OFih_KoE-pYWk_n_vnE63uyFTVT8d7BXWiRbM-4fF5BorcipOkbhV27oER8VqxSk5ryhwVg4pHYCw5wS6YUm3S8nXWwwDBv2gQIfY7yoQKz47on-Ah6xJYSmFSyNnP7YRfr-S_wtKW_-LZNmjgtJRKH6x_dmq9LakXNcNomlBmP86/s678/loading%20assist%20with%20projectile.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="518" data-original-width="678" height="305" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgI-vIIz6qv4yOzUa3OFih_KoE-pYWk_n_vnE63uyFTVT8d7BXWiRbM-4fF5BorcipOkbhV27oER8VqxSk5ryhwVg4pHYCw5wS6YUm3S8nXWwwDBv2gQIfY7yoQKz47on-Ah6xJYSmFSyNnP7YRfr-S_wtKW_-LZNmjgtJRKH6x_dmq9LakXNcNomlBmP86/w400-h305/loading%20assist%20with%20projectile.png" width="400" /></a></div><div>
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Immediately after moving the loading assistance device into position, the loader locates and retrieves a propellant charge corresponding to the desired ammunition type. By the time the loader has retrieved a propellant charge, the mechanism would have finished the ramming cycle for the projectile. When placing the propellant charge on the freshly vacated loading tray, the loader should ensure that the base of the charge is in contact with the rubber-padded tip of the chain rammer, although it is by no means mandatory. To complete the loading procedure, the loader presses the "ram" button (marked "<i>Досылка</i>") on the control box, whereby the device sends the chain rammer to perform a short stroke to ram the propellant charge into the chamber. Once the rim of the propellant charge trips the casing ejector and unlocks the breech block, allowing it to close, the unlocking of the breech block also releases the stopper for the loading assistance device and it is immediately pulled back to the ready position by the return spring.<br />
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Then, the loader presses his safety button on the side of the gun breech assembly. This completes the electrical firing circuit and unblocks the mechanical firing mechanism and signals to the gunner that the cannon is ready to fire. The green light on the loader's control panel is shut off and the red light is turned on, indicating to the loader that the cannon is ready to fire.<br />
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A demonstration of the loading procedure is shown in the two short clips below. The clip does not show the loader pressing his safety button.<br />
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If there are any issues with the loading assistance device or if there is simply a loss of electrical power, the loader can immediately proceed to load the cannon manually in the usual manner. The loading assistance device does not block the loader's access to the gun chamber opening and the breech block mechanism can work independently from the device. If electrical power is available but a malfunction has occurred with the loading assistance device, the loader must switch the system to the "Manual" operating mode before attempting to load the cannon. The signal light (<i>Р</i>) will be lit to indicate that the system is operating in the manual mode. This allows the loader to take advantage of some of the features which can be helpful even in a degraded capacity.<br />
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If using the device manually, the loader can control the chain rammer with the buttons on his control box. He can place the projectile on the tray and shove the tray behind the gun breech as usual, and then he must open the flap on the control box and press the ram button (КПХ) to command the rammer to ram a full stroke. After this, he presses the "recede" button (КОХ), and while the chain recedes, he retrieves a propellant charge. Upon placing the propellant charge on the tray, he presses the "ram" button ("Досылка") to command the rammer to ram a short stroke. The rest of the process - including the recession of the chain rammer - is automatic.<br />
<br />It is worth noting that it is strictly necessary to ram the projectile and propellant charge separately, instead of positioning a projectile at the mouth of the chamber and then ramming it together with the propellant charge in a single stroke. This is due to the fact that the mouth of the propellant case is not capped with a rigid load-bearing cork, and pushing the base of the projectile by the mouth of the brass case may deform its thin walls, potentially causing it to split when the round is fired. Moreover, doing so does not shorten the loading time, because the process of ramming the projectile occurs in parallel to the loader picking up the propellant charge anyway. <br />
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The same system was carried over to the D-25TS, but some modifications were added to enable the loader to load the cannon safely while the tank is on the move with the stabilizers active. With the implementation of the PUOT and PUOT-2 stabilizers, the cannon would no longer remain fixed relative to the tank while the tank moved across rough terrain. Instead, when the tank oscillates from the movement, the cannon would remain level thanks to its vertical stabilizer, but from the loader's perspective as a passenger in the tank, the cannon is constantly elevating and depressing. To ensure that accidents do not occur during the loading process, a safety system was added.<br />
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The loader's safety system was designed to automatically disconnect the electric firing circuit and mechanical firing mechanism of the gun as well as to command the stabilizer system to cease the stabilization of the gun beginning from the moment of the shot until the end of the loading process when the loader's safety button (marked '3') is pressed by the loader to signal that a round has been loaded and that he is clear of the recoil path. Before beginning to load the cannon for the first shot, the safety switch has to be toggled manually, but the system automatically activates for every shot thereafter. The safety system will detect that the firing of a shot from the main gun has occurred by sensing the recoil stroke of the cannon using a lever switch (marked '4') attached to the loader's safety control box that maintains contact with the gun breech via a roller. When the cannon recoils, the roller rides over a special bump on the breech and this deflects the lever switch.<br />
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The electrical and mechanical firing mechanisms can also be disconnected manually without relying on the recoil sensor. To do this, the loader flips the toggle switch (marked '5') on the side of the safety system box.<br />
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<a href="https://www.blogger.com/null" id="m62assist"></a>
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<h3>
<span style="font-size: large;">M62-T2</span></h3>
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The loading assistance device on the M62-T2 is almost completely unchanged from the D-25TS, most notably retaining the loader's safety system to return the cannon to the stabilized mode once the loading process is complete. Some minor differences include the change to a new loader's control box and the relocation of this new box to <a href="https://4.bp.blogspot.com/-NNs45teaAHU/XEE0hIVwgfI/AAAAAAAAM_8/Zigmc1Xk8XYNv_AcVtknGj-R9TcrS-CegCLcBGAs/s1600/T-10M_055.JPG">the top part of the recoil guard above the M62-T2 breech block opening</a>. This was needed because the KPVT coaxial machine gun mounted to the M62-T2 was so long that the back of its receiver almost reached the breech block opening on the side of the breech assembly, making it impossible for the control box to remain in its original location.<br />
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Although the loading assistance device was retained, the context for the necessity of such a device changed slightly - where previously the installation of a loading assistance device on the D-25TA and D-25TS was a huge benefit to the loader, the retention of the loading assistance device for the M62-T2 became more of a necessity due to the increased mass of the ammunition. Although the mass of the AP and the HE-Frag shells increased only slightly, the mass of the propellant charges increased to 20.86 kg for the AP rounds and 20.46 kg for the HE-Frag rounds, and the total weight of the cartridges increased to 45.96 kg for an AP round and 47.76 kg for a HE-Frag round (over 105 lbs). The weight of the AP round was almost the same as an M358 round for the 120mm M58 as that had a weight of 106.15 lbs. Having a powered rammer was also particularly beneficial in the T-10M when seating projectiles in the chamber, as the new 122mm ammunition featured a bottlenecked case, matched by a shoulder in the chamber. Manually ramming a projectile up the shoulder of the chamber to the throat of the barrel would require additional effort, which is worth noting if the loading assistance device breaks down and the loader must carry out his duties entirely by hand. </div><div><br /></div><div>On the bright side, the revised ammunition stowage layout in the T-10M helped improve the ease of loading the M62-T2. Moreover, the weight issue was only valid for the first few years of the service career of the T-10M as the situation with the increasing weight of the ammunition was ameliorated when semi-combustible propellant charges were introduced in 1961. The brass-cased 4ZhN4 charge for the OF-472 round and the brass-cased 4ZhN3 charge for the BR-472 round were replaced with the semi-combustible 4Zh14 and 4Zh15 propellant charges respectively, with the new 4Zh15 charge weighing only 14.77 kg and the 4Zh14 charge weighing only 14.6 kg. The 3VBK-5 HEAT round from 1964 and 3VBM-4 APDS round from 1967 were both fielded with semi-combustible propellant charges and never had brass casings, and the APDS cartridge was particularly light, weighing only 22.7 kg in total.<br />
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<a href="https://www.blogger.com/null" id="rof"></a>
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<h3>
<span style="font-size: large;">RATE OF FIRE</span></h3>
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Compared to a tank where the cannon is completely manually loaded, the number of steps in the loading procedure in the T-10 is not fewer, but the mechanization of the most physically demanding parts of the procedure enables the loader to carry his duties out more rapidly and the reduced rate of exertion makes it possible to sustain a high rate of fire for prolonged periods. It would also eliminate the need to give special physical training to new recruits selected to be loaders.<br />
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It should be possible for a T-10 loader to consistently load a round in less than 10 seconds sustain this rate for a few minutes until the ready racks are completely emptied, and the sustained loading speed using all ammunition racks should be less than 15 seconds, including the time needed to turn the turret to access certain ammunition racks. Based on the official figures, the combat rate of fire (using all ammunition racks) is 3-4 rounds per minute. Under the same criteria, the IS-2 could achieve a combat rate of fire of 2-3 rounds per minute but could actually achieve a maximum rate of fire of up to 5-6 rounds per minute.<br />
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For reference, it should be noted that the 2S1 "Gvozdika" self-propelled howitzer had a very similar loading assistance device that worked identically to the one in the T-10, but with minor differences related to the vertically-sliding breech block of the 2A31 howitzer and the need to load the cannon when it is elevated at high angles for indirect fire. The loading process in a "Gvozdika" is briefly demonstrated in <a href="https://youtu.be/_Jq3Zemc5Yc?t=377">this clip</a> from a show by TV Zvezda. Adding on to that, <a href="https://www.youtube.com/watch?v=WytXyj6cL6k">this video by a Ukrainian artilleryman during combat</a> and <a href="https://www.youtube.com/watch?v=ZbhfJ2KHp78">this video by a Russian artilleryman during live fire training</a> shows the loading process being carried out by real loaders under relatively relaxed conditions. Of course, it should be pointed out that the different pace of the sustained fire and different fire control procedure for artillerymen invalidates the use of the combat rate of fire of "Gvozdika" howitzers as a surrogate for the T-10 and the internal space provided for the loader is not comparable at all.<br />
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The November 2012 edition of the "<i>Отечественные Бронированные Машины 1945-1965</i>" series of articles authored by M.V Pavlov and published in the "<i>Техника И Вооружение</i>" magazine, pages 57-58, states that the IS-3 could be reloaded in an average time of just 9.5 seconds during testing with a well-trained loader at the NIIBT proving grounds when using all the ammunition racks in the tank. This figure excludes the time taken by the loader to expel a shell casing from the tank, the time taken for the gunner to lay the gun, and the time taken during the firing of the cannon itself. With all factors included, the average time between shots was 16.5 seconds for an average aimed rate of fire of 3.6 rounds per minute. Normally, these actions are only included in the reported figures for foreign tanks when evaluating the sustained rate of fire. For example, in the report "<i>Motion Studies of German Tanks</i>", the British Army did not include the disposal of spent casings in any of their evaluations of tank loading speeds and the rate of fire figures given in the report have been erroneously compared with the official figures listed for Soviet tanks. Essentially, a maximum short term (burst) rate of fire figure would be compared with a sustained rate of fire figure, and the results would invariably favour the foreign tanks.<br />
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A further increase could have been achieved if the IS-3 loader simply neglected to dispose of spent shell casings after every shot, and in a realistic combat scenario, the loader would only need to use ammunition from the ready racks as a single engagement rarely lasts long enough for the entire ammunition load of the tank to be expended. The disposal of spent casings is a more contentious issue when evaluating the average aimed rate of fire as tank has a ventilation fan but the D-25T does not have a fume extractor, so the fumes from the unburnt propellant residue inside the cases will accumulate with the fumes entering the fighting compartment from the cannon and eventually the toxicity of the air will reach an unacceptable level. This could be alleviated in the IS-3 by keeping the loader's hatch open, but ideally, the loader should find any chance to discard shell casings after a burst of fire. The need to dispose of spent casings was never solved in the IS-3 or in the Conqueror and M103, but it was solved in the T-10 when semi-combustible ammunition became available.<br />
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All in all, the maximum combat rate of fire of an IS-3 would be around 5-6 rounds per minute when using all ammunition racks. Furthermore, it was noted in the article (p.57) that a further increase in the aimed rate of fire of the IS-3 could be achieved by the mechanization of the loading process. Given that the T-10 features a loading assistance device and has a larger turret with more room for the loader, it is guaranteed that the actual aimed rate of fire will greatly exceed the 2-3 rounds per minute figure listed in the manual and other publications even without a well-trained loader.<br />
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It is very likely that the maximum rate of fire of a T-10 reaches or even exceeds 5-6 rounds per minute and the sustained rate of fire exceeds the 3.6 rounds per minute of the IS-3, but even with the loading assistance device on the D-25TA to reduce loader fatigue, the sustained rate of fire may still not be as high as the average aimed rate of fire as the loader in a T-10 still has to dispose of spent casings due to the lack of a fume extractor on the D-25TA. The loader in a T-10A or T-10B would have much more leeway in this regard as a fume extractor is present on the D-25TS, and all of these problems were eliminated when semi-combustible ammunition began to be supplied in 1961. The revised ammunition layout in the T-10M may contribute to an even higher rate of fire.<br />
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It is worth noting, however, that as a result of the first gamut of live gunnery trials carried out on the IS-5 in 1950, it was found that the rate of fire when using the entire ammunition load of the tank using the loading assistance device was around 1.5 times higher than with purely manual loading. The T-10 differed from the IS-5 in many ways, but not in any way that invalidates this comparison as the loader's station was functionally dentical: the gun was the same D-25TA, the ammunition layout was the same, the seat was in the same location, and so on.<br />
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With that said, the significance of these developments can be difficult to grasp without a reference point, so once again, a comparison with the Conqueror and the M103 is warranted. The main advantage of the Conqueror was that it predominantly fired APDS against armoured targets. Since APDS projectiles are much lighter than full caliber AP projectiles, the loader's burden was slashed accordingly. A secondary advantage was that it had the Mollins casing ejection device that automatically disposed of spent shell casings through a small porthole in the right side of the turret, behind the gunner's station. The ejection mechanism was automatic so the loader did not need to be involved at all, but one of its many disadvantages is that the ejection process took around 5 seconds and the mechanism itself was infamously unreliable.<br />
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Rob Griffin writes in "<i>Conqueror</i>" that the maximum rate of fire obtained during actual trials was 4 rounds per minute if the Mollins casing ejection mechanism was operational, but the rate of fire declined after a few minutes as the ready racks were depleted. Griffin reports that the initial requirement for the Conqueror was to be capable of firing 4 shots in the first minute, 16 rounds in 5 minutes (including the 4 shots in the first minute), and fire all 35 rounds in 55 minutes, but actual tests carried out at a gunnery range in Lulworth showed that this could not be achieved. Translated into rates of fire, the requirements were for a rate of fire of 4 RPM in the first minute, 3 RPM in the next four minutes, and an average rate of 0.38 RPM in the next 50 minutes. The tank would therefore only be required to fire 16 aimed shots in a 5-minute burst, but the fact that it could not achieve this modest firing rate at a gunnery range has extremely negative connotations on what it might achieve in combat conditions. With that said, Griffin also reported in the same book that a loading time as short as 6.5 seconds with HESH was recorded.<br />
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On the other hand, the M103 with its two loaders was able to attain a maximum rate of fire of 5 rounds per minute according to R.P Hunnicutt in "<i>Firepower: A History of the American Heavy Tank</i>" - a figure that is supported by Ken Estes - but the same limitations still applied; the sustained rate of fire using all ammunition racks was completely different from the burst rate of fire in the first minute alone.<br />
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As mentioned earlier in the introduction of this article, it is popularly perceived that Soviet tanks were designed with little attention to comfort or safety and that Western tanks were generally the opposite, but ironically, the loader's station in any T-10 model is objectively safer compared to its two Western counterparts the M103 and the Conqueror. In the T-10, the loader cannot be anywhere near the cannon breech when it recoils as he is physically barred by the recoil guard and the tray of the loading assistance device, whereas in the M103, there is no recoil guard at all to prevent either of the two loaders from being in the path of the recoil stroke when the cannon fires. In fact, the loaders must actually position themselves directly behind the cannon breech in order to carry out their duties, which is hardly reassuring even though there are safety systems in place. The lack of safety measures and the cramped conditions of the loaders' stations can be fully appreciated in <a href="http://www.toadmanstankpictures.com/m103a2_82.jpg">this photo showing the interior of an M103A2 turret from the commander's perspective</a>.<br />
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<a href="https://www.blogger.com/null" id="taen-1"></a>
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<h3>
<span style="font-size: large;">POWERED CONTROLS (T-10)</span></h3>
<h3>
<span style="font-size: large;">TAEN-1</span></h3>
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The T-10 was outfitted with the advanced TAEN-1 automated powered gun laying system for aiming and firing the main gun and coaxial machine gun. Both the turret rotation and the gun elevation drives are electromechanical with manual backups. Naturally, the mechanical clutches of the manual turret rotation and gun elevation mechanisms must be disengaged before using the powered systems.<br />
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The system also facilitated the automatic target designation system of the TPKU periscope operated by the tank commander. When a target is detected by the commander, he places his point of aim on it and he presses the target designator button on his left cupola control handle. This overrides the TAEN-1 system so that it automatically lays the gun on the target designated by the commander in both planes. This was somewhat more sophisticated than the target designation function provided by the EPB-4 powered traverse system of the T-54 obr. 1951 as that system could only lay the gun on the target in the horizontal plane.<br />
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More importantly, the TAEN-1 system provided the gunner with full control of the gun in both planes via a single set of control handles that could produce progressive traverse and elevation speeds by changing the deflection angle of the handles. The system allowed the gunner to quickly traverse the gun onto a target like the conventional powered traverse systems found in contemporary tanks, but unlike the existing control systems at the time, the precision of the TAEN-1 gun laying drives was high enough that the final lay on both planes could be done using the powered controls. By contrast, the less sophisticated control scheme in the EPB-1 powered traverse system as found in the IS-4 and T-54 obr. 1947 and T-54 obr. 1949 only provided the gunner with the ability to use powered traverse to lay the gun in azimuth as gun elevation had to be done manually. The process of laying the gun on target was therefore much more fluid and intuitive with the TAEN-1 system than the EPB-4 system.<br />
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The gunner's control handles are placed directly below the TSh2-27 primary sight and above the manual gun elevation handwheel, as shown below. The photo is taken from "<i>T-10 Heavy Tank and Variants</i>" by James Kinnear and Stephen Sewell.<br />
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Gun elevation and traverse was sensed by a pair of rheostats. The maximum gun elevation and traverse speeds were attained by pushing the handles to their limits of deflection in both axes, but if the gunner desires to lay the gun on target with maximum precision, he could simply nudge the handles lightly in the appropriate direction. The minimum speed of gun laying in both axes was 0.05 degrees per second. To put this into perspective, the time needed for the turret to complete a full rotation at this speed is 2 hours. <br />
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Besides having a more sophisticated fire control system than the heavy tanks preceding it, the T-10 most likely had better firing precision when firing on the move or on short halts thanks to its bundled torsion bars. A suspension with a high damping capacity reduces the oscillations of the hull, reduces the power consumption and errors of the stabilizer, and reduces the vibration of the barrel, contributing to reduced dispersion.<br />
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Vertical:<br />
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Maximum elevating speed: 4° per second<br />
Minimum elevating speed: 0.05° per second<br />
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Horizontal:<br />
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Maximum Turret Traverse Speed: 14.8° per second<br />
Minimum Turret Traverse Speed: 0.05° per second<br />
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In terms of gun laying speed and precision, the TAEN-1 system was sufficient for the needs of a modern tank of the early 1950's. It was more precise than any T-54 variant as those had a minimum traverse speed of only 0.07 degrees per second compared to 0.05 degrees per second. It also provided a 48% quicker maximum turret traverse speed than the EPB-4 powered traverse system of the T-54 obr. 1951 and the STP-1 stabilizer system of the T-54A (1954), both of which were only capable of a turret rotation speed of just 10° per second. The IS-4 heavy tank used the EPB-1 powered traverse system and also had a turret rotation speed of 10° per second.<br />
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<a href="https://www.blogger.com/null" id="stabs"></a>
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<h3>
<span style="font-size: large;">STABILIZERS (T-10A, T-10B, T-10M)</span></h3>
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The T-10 series was consistently outfitted with the most modern stabilization systems in the USSR as they became available and there was a clear technological distinction between the fire control systems of the T-10 series and the T-54 series. Some of the most major differences are related to the higher complexity of the primary sights of the T-10 series (beginning with the T-10A). The cost of the stabilizers installed in the T-10 series was higher, but it was justified as it was proportional to the results that they were capable of producing.<br />
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By contrast, very few foreign tanks had stabilizers at the time, and of those that did, they only permitted accurate fire at short range or were limited to providing the gunner with a stable field of view without the possibility of accurate fire while on the move. The T-10 was certainly the only heavy tank that had a stabilizer. The Conqueror is interesting in this regard as it is sometimes said to have a stabilizer, but in reality it had an extremely limited pseudo-stabilization system where the gunner's controls would be automatically disengaged once the tank exceeded a speed of approximately 2 mph whereupon the gyroscopic stabilization system would activate. The system would keep the gun stable within the elevation angles of +1 to +15 degrees, and the gunner's controls would only return to action after the tank came to a full stop, and only after a delay of three seconds. During this time, the gunner could look through his sights but it would be aimed at the sky, so he would not be able to find a target let alone lay the reticle on it during the three-second interval. Of course, the gunner would have to also find the target after he regained control, so the reaction time of the tank is further extended.<br />
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Although the system incorporated a gyroscopic stabilizer and technically kept the gun "stable" within a very generous range of elevation angles, it stripped the gunner of control and prevented the armament of the tank from being used while it was active. This system also greatly hampered the Conqueror's ability to fire on short halts, rendering the tank much less effective unless it was completely static before contact with the enemy is initiated. This relied on the assumption that Conqueror commanders possessed omniscience regarding the enemy's intentions.<br />
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<a href="https://www.blogger.com/null" id="puot"></a>
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<h3>
<span style="font-size: large;">T-10A</span></h3>
<h3>
<span style="font-size: large;">PUOT "Uragan"</span></h3>
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The PUOT "Uragan" stabilizer is a single-plane stabilizer with fully electric gun elevation and turret rotation drives. Turret rotation was fully powered but not stabilized. This complicates firing on the move, so it was still advisable to fire from a slow crawl or a short halt. With the "Uragan", the ability to accurately fire on tank-sized targets while moving at high speeds had not yet been achieved, although the use of fire gating in the stabilizer was a great step forward towards this goal. Control of the turret and gun is actuated by the TAEN-2 drive system which is controlled through the gunner's control handles, which were of a particularly ergonomic design for their time, being self-contained two-axis mechanisms with a pair of handles for the gunner's two hands like in any modern tank. This set it apart from the turret control systems of foreign tanks, which still used joysticks (Patton family, M103) or separate elevation and traverse handles (Centurion). The electric gun elevation motor is the MI-400 and the amplidyne amplifier for the motor is the EMU-3PM. It interfaces with the elevation gear on a toothed arc on the D-25TA gun - which is shared with the backup manual elevation drive - via a worm gear, which can be seen in the diagram below. Underneath the motor is the amplidyne. The electric turret rotation motor is the MI-22M and the amplidyne amplifier for the motor is the EMU-12PM.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-LDYFzrBSRTc/YRAmX6N-AqI/AAAAAAAAUEQ/vFUPvkGSc7IWyY0SrLnycLKi5lkpIYEDwCLcBGAsYHQ/s1380/uragan%2Bstabilizer%2Bdiagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1123" data-original-width="1380" height="520" src="https://1.bp.blogspot.com/-LDYFzrBSRTc/YRAmX6N-AqI/AAAAAAAAUEQ/vFUPvkGSc7IWyY0SrLnycLKi5lkpIYEDwCLcBGAsYHQ/w640-h520/uragan%2Bstabilizer%2Bdiagram.png" width="640" /></a></div><div><br />
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If the stabilizer is switched from the automatic mode to the semi-automatic mode, all gyroscopic stabilization is disabled and the gunner assumes direct control of the TAEN-2 drives which only provide powered turret traverse and gun elevation. The fire control system essentially regresses to the level of the T-10. The field of view of the sight becomes directly coupled to the elevation of the gun via a parallelogram linkage, and the precision of aiming is downgraded to the level offered by the minimum movement speeds of the turret traverse and gun elevation mechanisms. As examined earlier in the section on the TPS1 primary sight, the "Uragan" system is slaved to the much more precise stabilizer of the TPS1 and the two systems are very tightly intertwined in their operation.<br />
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Unlike the conventional stabilization scheme employed by the contemporary STP-1 stabilizer of the T-54A (1955) where the weapons were stabilized at the highest possible precision and the sights are mechanically linked to the weapons so that they shared the same precision of stabilization, "Uragan" keeps the gun loosely stabilized when the tank is in motion and only maintains the orientation of the gun close to the point of aim of the TPS1 within a limit of ± 2.5 degrees. Corrections are continuously applied, but the gun is only automatically elevated at a speed of 8 mils per second (0.48 degrees per second). If the tank is pitching and diving as it is driven across undulating terrain, the loosely stabilized gun will appear as if it is languidly shifting in the opposite direction of the pitching and diving on its own as shown in the clip on the right below. A tightly stabilized gun would simply appear to be completely level even when the tank is moving at a relatively high speed on rough terrain, as the clip on the left shows on a T-54B.<br />
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When the gunner presses the firing button, "Uragan" verifies if the two systems are in alignment, at which point the gun is fired. The system guarantees that the precision of the alignment between the gun and the point of aim of the TPS1 sight is ± 0.5 mils. The time taken for the verification does not exceed one second. To minimize the lag time as much as possible, the elevation speed is temporarily boosted to 4.0 degrees per second until the gun achieves coincidence with the aim point of the TPS1 sight and the shot is fired. "Uragan" features automatic lag compensation to account to eliminate errors from this phenomenon as well as the lag between the initiation of the electric primer for the main gun cartridges and the moment that the shell exits the muzzle. The fire control system facilitates higher accuracy compared to a conventional gun stabilization scheme where only the gun is tightly stabilized and the sights are linked to the gun. When the tank is static, the gun stabilizer does not need to compensate for the deflection of the gun due to the vertical oscillations induced by movement across uneven ground, so it is able to keep the gun aligned with the point of aim of the sight at all times.<br />
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The stabilizer does not treat the coaxial DShKM machine gun the same as the cannon, mainly because the machine gun is a fully automatic weapon so it was not feasible to control the moment it is fired to the moment that its point of aim aligns with the sights. Furthermore, there was no automatic lag compensation programmed into the stabilizer to account for the lag inherent in the mechanical firing mechanism, so it is not reasonable to expect to hit point targets when the tank is moving except at short ranges. This was because the lag time between the triggering and the actual firing of the DShKM was 10 times longer than that of the cannon. If the machine gun was fired on the move using the same fire gating system as the main gun, most of the bullets would probably hit the ground in front of the target or fly clear over it. However, if the tank is cruising at a modest speed on relatively flat ground, the level of accuracy with the loose stabilization is still better than with no stabilization at all so it is possible to use the coaxial machine gun with reasonable accuracy.<br />
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If the coaxial machine gun is being used in lieu of the main gun to engage vehicles such as trucks and APCs with short bursts, it is more efficient to fire from short halts or using the semi-automatic mode of the stabilizer, i.e. regressing to an unstabilized state with powered controls.<br />
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With that in mind, the question arises as to why the stabilizer for the gun should not be discarded entirely in favour of a free-swinging gun paired with simple powered elevation or manual elevation as backups. There are a multitude of technical reasons, but the simplest is that even if the point of aim of a free-swinging gun may eventually coincide with the point of aim of the sights, it simply cannot be relied upon, not to mention that there is guaranteed to be a long lag before the shot can be fired. Furthermore, a free-swinging gun is subjected to the full amplitude of vibrations transmitted from the suspension of the tank during movement, and the pitching motion of the tank is translated into strong oscillations at the muzzle of the gun barrel. The oscillations take some time to dissipate even after the tank stops to fire, thus increasing the dispersion of shots compared to a fully static tank by several times. A free-swinging gun would also have a significant amount of vertical momentum if it is in motion during the moment of firing, as vertical momentum has a major impact on the uniformity of the recoil cycle and the vertical motion of the gun also imparts a vertical moment on the projectile before it leaves the muzzle. These factors, and several more, add up to severely degrade the accuracy of fire.<br />
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Adding on to all of this, a freely swinging gun is liable to hit the ground in front of the tank when the tank is moving on undulating terrain, and the swinging motion of the gun breech inside the turret is a safety hazard. The gun itself may also be damaged by hitting the hard stops at the limits of its elevation and depression angles. Gun stabilizers, even loose systems like in "Uragan", are effective at damping the errors incurred by having a completely free-swinging gun and ensure that it is not damaged by including braking zones at the limits of its elevation and depression.<br />
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It is particularly noteworthy that the "Uragan" stabilization scheme was the first of its kind to be implemented in mass-produced tanks in 1956 when in the U.S.A and other Western nations, such concepts had not yet progressed beyond the research stage. In the report "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/065653.pdf"><i>Tank Fire Control Systems Study: Evaluation of Some Alternative Systems of Tank Stabilization</i></a>" from April 1955 by Philip I. Brown of the Fire Control Instrument Group, this stabilization scheme was referred to as the "three-switch" proposal and was shown to be the most promising system in terms of fire accuracy in theoretical models. Fundamentally, this scheme provides the highest accuracy that can be achieved from all possible gyroscopic stabilization systems. After its first appearance in "Uragan", this operating scheme was carried over to later models of the T-10 and was implemented on the T-64 (Object 432) in 1963 whereas the first instance of a Western nation managing to operationally implement such a scheme was more than two decades later with the appearance of the Leopard 2 in 1979.<br />
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At the end of 1954, three experimental T-10 tanks equipped with the "Uragan" stabilizer were delivered and on the 14th of February 1955, they were ordered to be sent for testing at the Main Research Site of the State Agrarian University. The tests ran from May 5 to June 18, 1955 and the three tanks drove a total cumulative distance of 2,752 kilometers and fired 1,503 shots.<br />
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During the tests, it was noted that when firing on the move at targets from a distance of 1,000 meters to 1,500 meters at a speed of 18-20 km/h, the accuracy increased by around 5.5 times compared to firing without the use of a stabilizer. The average hit rate on static tank side silhouette targets (maximum width of 7.66 meters, height of 2.37 meters) with the stabilizer turned on was 36.9%. By contrast, the hit rate with the stabilizer turned off was just 6.7%. When firing on short halts with the stabilizer active at targets from a distance of 800 meters to 1,300 meters at a speed of 18–20 km / h, the hit rate on static tank front silhouette targets (maximum width of 3.42 meters, height of 2.37 meters) was 45%. The hit rate for anti-tank gun emplacements with simulated gun crews was 36.6%. Because the global experience on the usage of tanks (as of the 1950's) had shown that the best results were achieved when the maneuverability of tanks was exploited during combat, gun stabilization was considered to be a very important feature for a modern tank in the Soviet Army. The presence of "Uragan" on the T-10A reportedly increased the effectiveness of its 122mm gun by 5-6 times, at least according to whatever metrics were used by Soviet analysts to evaluate "effectiveness".<br />
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With a maximum turret traverse speed of 14 degrees per second, the turret is appreciably quicker to rotate than the turret of a T-54A and all preceding T-54 models, all of which had a turret traverse speed of only 10 degrees per second. The maximum gun elevation speed of 3 degrees per second is somewhat ponderous, but is still acceptable. Using the stabilizer in the semi-automatic mode marginally increases the speed of elevation to 3.6 degrees per second.<br />
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When the stabilizer is operated in the automatic mode, the range of vertical elevation decreased by 30' to 45' (0.5 to 0.75 degrees) at the limits of elevation and depression in order to create braking zones. This feature was incorporated into the stabilizer to ensure that the gun does not slam into the hard stops at high speed at the limits of its elevation range when the tank is travelling across rough terrain. This came at the expense of further decreasing the extremely limited gun depression limit of the T-10A when the stabilizer was used in the automatic mode. Interestingly enough, the Conqueror heavy tank "solved" this problem by using a pseudo-stabilization system that kept the gun elevated at +1 to +15 degrees.<br />
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The stabilizer automatically places the cannon elevation into hydrolock after every shot for the loader's safety. It is unlocked when the loader presses the loader's safety button on the side of the cannon breech, signalling the stabilizer to return to the last elevation angle during the previous shot and resume normal operation with full control returned to the gunner.<br />
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Vertical (semi-automatic mode):<br />
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Maximum elevating speed: 3.0° per second (3.6°)<br />
Minimum elevating speed: 0.05° per second<br />
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Horizontal:<br />
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Maximum Turret Traverse Speed: 14° per second<br />
Minimum Turret Traverse Speed: 0.05° per second<br />
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The stabilizer consumes 2.5 kW of power on average during normal operation.<br />
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<a href="https://www.blogger.com/null" id="puot-2"></a>
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<h3>
<span style="font-size: large;">T-10B</span></h3>
<h3>
<span style="font-size: large;">PUOT-2 "Grom"</span></h3>
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The "Grom" stabilizer offered dual-axis stabilization with the option of switching between automatic and semi-automatic modes. The stabilizer was only used in the T-10B, but the first 20 T-10B tanks had the "Uragan" stabilizer installed due to supply issues. The remaining 90 tanks produced were outfitted with "Grom".</div><div><br /></div><div>Because the gun received a fully independent stabilization system, it became possible to fire the coaxial machine gun accurately on the move in the automatic mode. This makes it vastly more effective against point targets and it could help to improve the overall survivability of the tank as it is now possible for the driver to maneuver the tank while the gunner engages dangerous anti-tank weapons with accurate machine gun fire. This includes towed anti-tank guns, recoilless rifle emplacements, and could even include dangerous armoured vehicles like the M56 "Scorpion" and M551 "Sheridan".<br />
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The horizontal stabilizer was not slaved to the sight with a switching system like the vertical stabilizer. Instead, it works as a conventional stabilizer that attempts to keep the turret aimed at the target in azimuth with maximum precision. This was mainly due to the lack of independent horizontal stabilization in the T2S sight itself, but also because the accuracy benefit of implementing such a system for controlling turret rotation was lower than it was for the gun elevation. The stabilization precision of the PUOT-2 is 1 mil in the vertical plane and 3 mils in the horizontal plane.<br />
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The elevation drive had increased precision with a minimum elevating speed that was five times slower than the elevation drive of the "Uragan" stabilizer - 0.01 degrees per second instead of 0.05 degrees per second. The speed of the turret rotation drive was also very close to the STP-2 "Tsyklon" stabilizer of the T-54B (1956) which had a maximum speed of 15 degrees per second, and its gun laying precision was far higher.<br />
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Vertical:<br />
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Maximum elevating speed: 3° per second<br />
Minimum elevating speed: 0.01° per second<br />
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Horizontal:<br />
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Maximum Turret Traverse Speed: 14° per second<br />
Minimum Turret Traverse Speed: 0.05° per second<br />
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The higher electrical load due to the inclusion of a horizontal stabilizer meant that the 3 kW engine generator of previous T-10 models had to be replaced with a 5 kW generator.<br />
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<a href="https://www.blogger.com/null" id="puot-2s"></a>
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<h3>
<span style="font-size: large;">T-10M</span></h3>
<h3>
<span style="font-size: large;">PUOT-2S "Liven"</span></h3>
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The "Liven" dual-axis stabilizer was installed in the T-10M exclusively. It was more sophisticated than previous stabilization systems, eliminated previous technical drawbacks and facilitated greater accuracy. Structurally, the most major difference is that the gun elevation drive was changed from an electric mechanism to a hydraulic mechanism with a piston actuator to move the gun up and down. As before, the stabilizer could be switched between automatic and semi-automatic modes. The vertical gun stabilization system restricts the maximum gun depression angle to -4.5 degrees instead of the full -5 degrees due to the need for braking zones at the elevation limits of the gun to reduce the shock load on the gun elevation mechanism when the stabilizer is attempting to keep the gun aligned to the T2S sight while the tank moves over rough terrain. When operating in the semi-automatic mode, the maximum gun depression angle is increased to the full limit of -5 degrees as the gun is no longer stabilized, so braking zones were no longer necessary. The stabilization precision of the PUOT-2S is 1 mil in the vertical plane and 3 mils in the horizontal plane.<br />
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The addition of a high-precision vertical gun stabilizer system made it necessary to increase the output of the engine generator from 5 kW to 6.5 kW to handle the higher electrical load.<br />
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After each shot, the cannon is elevated by 3 degrees and fixed by a hydrolock in the elevator piston, thereby lowering the breech by 3 degrees from the loader's perspective. With the gun fixed at this angle, it it easier for the loader to load the cannon, especially if the tank is moving. In this condition, the stabilizer limits the maximum traverse speed of the turret to just 5 degrees per second.<br />
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Due to the high complexity of the system, the training of new cadets in the use of the T-10M was a uniquely difficult task compared to the T-55 or T-62 which lacked independent sight stabilization. For the qualitative study and development of the "Liven", powered simulator cabins to demonstrate the functions of the stabilizer were created and installed in tank schools.<br />
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The maximum turret traverse speed of 18 degrees per second is entirely respectable for a heavy tank. This makes the turret quicker to rotate than the turret of a Conqueror which had a traverse speed of 15 degrees per second and it is equivalent to a basic M103 which had an identical maximum turret traverse speed, but it is outstripped by the M103A2 (21 degrees per second). It takes 20 seconds for a T-10M turret to complete a full rotation.<br />
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Vertical:<br />
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Maximum elevating speed: 4.5° per second<br />
Minimum elevating speed: 0.01° per second<br />
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Horizontal:<br />
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Maximum Turret Traverse Speed: 18° per second<br />
Minimum Turret Traverse Speed: 0.05° per second<br />
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<a href="https://www.blogger.com/null" id="manual"></a>
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<h3>
<span style="font-size: large;">MANUAL CONTROLS</span></h3>
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As usual, all T-10 tanks had a set of manual turret traverse and gun elevation drives. These were worked using hand cranks and power was transmitted via worm gears. In order to use them, the stabilizer must be disabled and the mechanical clutches of both the manual turret rotation and gun elevation mechanisms must be engaged. This ensures that the only input force is from the gunner. The gun elevation mechanism is mounted to the gun cradle of the main gun and the turret rotation mechanism is mounted to the turret ring.<br />
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The elevation wheel handle has an electric thumb trigger for firing the main gun, but there is no way to fire the coaxial machine gun electrically from the gunner's station when operating in manual mode. To do this, the loader would have to manually pull the emergency trigger on the DShKM or KPVT receiver when ordered by the commander, who would be responsible for tightly coordinating the crew in such situations. If all electrical systems in the tank were to fail, the main gun can be fired by pulling the emergency trigger on the side of the cannon itself. These procedures apply for all T-10 models.<br />
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An interesting side effect of the unusual layout of the gunner's control handles on the T2S-29-14 sight of the T-10M is that a lot of space beneath the sight was freed up so there was much more room to use the manual turret traverse and gun elevation handwheels. It is doubtful if this had any real effect on the combat effectiveness of the tank, however.<br />
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<a href="https://www.blogger.com/null" id="d-25t"></a>
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<h3>
<span style="font-size: large;">D-25TA, D-25TS</span></h3>
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With a muzzle energy of 8 MJ, the D-25T was among the most powerful guns of WWII and was still a viable weapon in the immediate postwar period, but the need for a more powerful gun was recognized at the end of WWII when new German heavy tanks and tank destroyers like the Tiger II and the Jagdtiger were captured and inspected. Soviet engineers approached the issue by attempting to create large caliber guns with an increased muzzle velocity. Work on installing more powerful guns in the latest heavy tank projects had already been underway several years before the T-10 entered service, and the 130mm S-53 was one of the options considered. The only reason for the installation of a derivative of the D-25T on the T-10 in 1953 was that other alternatives were still technologically immature. There was no real justification to actively use the D-25 in the postwar era.<br />
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The demolition power of its HE-Frag shells was still a highly persuasive argument against stubborn opposition, but the limited potential of the D-25T against heavily armoured targets made it an inefficient weapon against some of the latest medium tanks of the probable enemy, and it would have struggled against new heavy tanks like the M103 and Conqueror.<br />
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The barrel length is 5,610mm or 46 calibers. The maximum operating pressure of all guns derived from the D-25T including the D-25TA and D-25TS is 270 MPa.<br />
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The D-49 gun installed in the SU-122 casemate tank destroyer otherwise known as the "SU-122-54" was developed in parallel with the D-25TA. The two guns shared many similarities and both used the same loading assistance device. Besides the expected differences such as the different gun cradle, gun laying mechanism and the different mounts for the articulated telescopic sights, the most noteworthy difference is that the D-49 had a fume extractor. In fact, the D-49 was the first Soviet tank gun to have one.</div><div><br /></div><div>To remove or install the gun, the turret is unbolted from the turret ring platform and then its front is raised with a crane until there is sufficient clearance to support it in place with rods. From this position, the gun can be disconnected from the turret ring platform and freely removed, or installed. This process was long, and the use of such a system created a local weakening under the gun mantlet due to the absence of a full turret embrasure. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-6ArrZ2CSu6E/YDfvex0uORI/AAAAAAAASz0/pay6YSh4u5wQF8J3eesvauMfLP6_gTuOACLcBGAsYHQ/s1244/t-10%2Bgun%2Binstallation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="807" data-original-width="1244" height="260" src="https://1.bp.blogspot.com/-6ArrZ2CSu6E/YDfvex0uORI/AAAAAAAASz0/pay6YSh4u5wQF8J3eesvauMfLP6_gTuOACLcBGAsYHQ/w400-h260/t-10%2Bgun%2Binstallation.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9StkU4sOJ5-u7A_QnPjrfsqtYa3HRcgo82OZlik_GUuOD69z74WDuai2JMOxHi7to7XuSju0K4cFG4_ByMBcY-d-BJ7Y1tSAgU8t5L8p23Oa9YU5SDImslJm3MKkKdtY2epMxX-Fd3Akj0z8Qo-A2RSiTuD3--aUvtTT-DwnfRqNLaFNd3FP0ZWtyBA/s1010/fitting%20d-25t%20in%20is-5.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="752" data-original-width="1010" height="297" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9StkU4sOJ5-u7A_QnPjrfsqtYa3HRcgo82OZlik_GUuOD69z74WDuai2JMOxHi7to7XuSju0K4cFG4_ByMBcY-d-BJ7Y1tSAgU8t5L8p23Oa9YU5SDImslJm3MKkKdtY2epMxX-Fd3Akj0z8Qo-A2RSiTuD3--aUvtTT-DwnfRqNLaFNd3FP0ZWtyBA/w400-h297/fitting%20d-25t%20in%20is-5.png" width="400" /></a></div><div><br /></div><div>
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Like the 85mm ZiS-S-53 and 100mm D-10 guns, the recoil mechanism of all D-25 variants is located above the breech. The hydraulic recoil buffer is placed on the left and the hydropneumatic recoil recuperator is placed on the right. Due to the location of the recoil mechanism, the center of mass of the gun is higher than the axis of the gun bore by 35mm. Like all other Soviet tank guns of the time, the asymmetry of the recoil mechanism from the axis of the bore was a negative influence on accuracy.<br />
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The drawing below shows the gun cradle of the D-25TS with the slots for these two recoil devices and a slot for the gun tube. The coaxial machine gun mounting platform is on the right of the gun tube and a toothed arc for the manual elevation mechanism is on the left. The gun is well-balanced and it is designed to maintain equilibrium when it is properly assembled with all standard equipment installed, including the coaxial machine gun, the gun mask, and everything else. It does not require an equilibrator.<br />
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The D-25TA is almost completely identical to the basic D-25T and mainly differs in the inclusion of a loading assistance device and the associated modifications to the breech of the cannon. The elevation mechanism of the D-25TA was also modified to have a more restricted range of gun elevation angles of +17 degrees to -3 degrees. The maximum gun depression limit was not worse than previous heavy tanks, but the maximum gun elevation limit was reduced from the +19 or +20 degrees of the IS-2, IS-3 and IS-4. The maximum gun elevation limit is only slightly better than the M103 and Conqueror heavy tanks which had +15 degrees of gun elevation, but unsurprisingly, the gun depression limit was lower than the -8 degrees and -5 degrees of the M103 and Conqueror respectively. The normal length of the recoil stroke is 490-550mm and the maximum is 570mm, the same as the D-25T. Although quite long by most standards, this is already less than half of the length of the recoil stroke of an A-19 howitzer in a direct fire configuration (1,150mm).<br />
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In terms of overall length, the D-25TA and D-25TS were both very imposing. Despite the large 2,100mm diameter of the T-10 turret ring, the cannon occupied almost its entire length, leaving only a narrow gap between the back of the recoil guard and the turret ring. It was completely impossible for the loader on the right side of the gun to move to the other side of the turret and vice versa for the other two crew members.<br />
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When travelling for long distances or when being prepared for transportation, the turret is rotated to the rear and the gun is affixed to the travel lock to eliminate forward gun overhang and reduce the overall length of the tank. For traveling in road marches, the travel lock can be used but it is more practical to use only the internal travel lock on the turret ceiling as this allows the crew to rapidly prepare for combat without needing to exit the tank.<br />
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The D-25TA was replaced by the D-25TS with the introduction of the T-10A model in 1956, and the mass production of the obsolete D-25TA was discontinued entirely in 1957. As the suffix implies, the D-25TS variant includes a number of stabilizer-related upgrades. It also featured a fume extractor which seriously improved the working conditions of the crew during combat and increase the sustained rate of fire.<br />
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Interestingly enough, late-production D-25TA guns from 1956 and 1957 had a fume extractor. These guns were installed on the very last T-10 tanks manufactured in 1956 prior to being the model being fully displaced by the T-10A on the production line. These late model T-10 tanks had all of the features of a typical T-10 obr. 1955 and still used the original TSh2-27 sight with the same powered control system and were almost indistinguishable if not for the fume extractor on the D-25TA barrel. Examples such tanks are shown in the two photos below.<br />
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On both the D-25TA and D-25TS, the recoil guard is mounted to the mounting cradle and includes a shell casing deflector directly behind the breech of the cannon. The casing deflector is slanted inward to deflect the casings ejected from the cannon toward the floor of the tank. Unfortunately, there is no casing collection bin so the casings will simply roll around on the floor until the loader disposes of them. The loading tray on top of the loading assistance device is only long enough to accommodate either the projectile and the cases of the 122mm cartridge individually, and indeed, the entire recoil guard is quite short like the recoil guard of the D-25T which is due to the fact that the loader inserts the projectile and the propellant of the cartridge separately so there is no reason to have the full space that is needed to position a much longer unitary cartridge behind the breech to ram it in.<br />
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A light sheet metal fairing in the shape of a truncated cone was attached to the end of the gun mask. It is bolted to the gun mask by two small bolts. Its official purpose is unclear, but there is an extended collar on the right side of the fairing that is more or less level with the muzzle brake of the coaxial DShKM machine gun. Naturally, it might be assumed that it is a muzzle blast deflector to prevent the uneven heating of the cannon barrel on one side by the firing of the coaxial machine gun, but a problem with this hypothesis is that the muzzle brake of the DShKM is rotated 90 degrees so the muzzle blast is directed downward and upward instead of sideways. The photo on the left below is taken from "<i>T-10 Heavy Tank and Variants</i>" by James Kinnear and Stephen Sewell.<br />
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The D-25TA uses the same muzzle brake as the standard D-25T, designed by the TsAKB design bureau during WWII. The D-25TS used a slightly modified muzzle brake, but it is not easily distinguishable from the first. The TsAKB muzzle brake has two baffles and resembles the muzzle brake of the ZiS-3, and the D-25TS muzzle brake has an even stronger resemblance. The operating principle of both muzzle brakes is referred to as an active braking system.<br />
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According to pages 308-311 of "<i>Основи Будови Артилерійських Гармат Та Боєприпасiв</i>" ("<i>The Basics of Artillery Guns and Ammunition</i>") by A.Y. Derevyanchuk, a double-baffle muzzle brake works by placing obstacles of a large surface area (the baffles) in front of the muzzle to impede the forward flow of the escaping propellant gasses, thus absorbing the kinetic energy of the propellant gas particles in the form of pressure, effectively causing the gasses to impart a forward force on the barrel which cancels out some of the rearward recoil force. This is illustrated in diagram "A" in the drawing below.<br />
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As in all other cases, the decision to use a muzzle brake on the original D-25 was inspired by the need to fit a gun with the same internal ballistic characteristics as the A-19 howitzer into the confines of a tank turret. To contain such power, the barrel and breech assembly needed to be heavy and the recoil system needed to be enlarged and seriously reinforced, keeping in mind that the length of the recoil stroke needed to be much shorter due to the limited diameter of the turret ring. A muzzle brake could reduce recoil forces enough that the size of the recoil system could be kept under control. The same rationale was behind the universal presence of muzzle brakes on the high velocity 7.5 cm and 8.8 cm tank guns on the German Pz.IV, Pz.V and Pz.VI tanks.<br />
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On the T-10, the main downside to the double-baffle muzzle brake is that the propellant gasses diverted sideways through the baffles will obscure the gunner's vision through his telescopic sight after every shot, which can make it more difficult to observe the fall of his shots. Another downside is that the large blast of smoke may also assist enemy observers in locating the tank's position and identifying it as a heavy tank, but this is situational. When the T-10A model replaced the T-10, the new TPS1 periscopic sight was placed on the turret roof and not in the gun mask, so the gunner's vision would no longer be obscured after every shot and it became a much simpler matter to correct fire.<br />
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<h3>
<span style="font-size: large;">AMMUNITION</span></h3>
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<span style="font-size: large;">122x785mm</span></h3>
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The case length is 785mm and the neck diameter is 125mm. The diameter of the rim is 143.3mm. The case is slightly tapered, but it is very minor. The taper probably only exists to help case extraction since a completely straight-walled casing usually experiences much more friction against the gun chamber, especially after it is fired. On its own, the case is longer than the case of a 100mm cartridge for the D-10T of the T-54 as those have a case length of 695mm. It is also not significantly narrower, as the 100x695mm cases have a rim diameter of 147mm. If the 122mm propellant charge was combined with a projectile to form a unitary cartridge, it would be far too long to handle effectively inside the confines of a tank. Case in point: an experimental unitary version of a 122x785mm AP cartridge had a total length of 1,211mm whereas a 100x695mm AP cartridge has a total length of 910mm.<br />
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Although the use of two-part ammunition of the D-25T was carried over from the A-19 field gun as a matter of expediency, the decision to keep the 122x785mm cartridges split into two parts was completely sensible. Contrary to popular belief, it was not a design flaw that limited the rate of fire of the D-25T.<br />
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A single unified HEAT round was developed that could be fired from both the D-25T and M62. The HEAT round for the D-25T was designated as the 3BK-10, and it entered service in 1964. The 3BK-9 round for the M62 entered service in the same year. Before the introduction of 3BK-10, there were no HEAT rounds available for field guns or tank guns in the 122x785mm caliber.<br />
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The development of APDS ammunition for large caliber tank guns netted the Soviet Army a single unified generation of APDS rounds that all shared the same 55mm tungsten carbide core, but with two different projectile and sabots. The 122mm D-25T and M62-T2 received the 3BM7 and 3BM11 rounds respectively, but the only physical difference between the two is the name. Both rounds not only shared the same 55mm core but also shared the same subcaliber projectile. Functionally, the performance of the two rounds were identical except in velocity, as the D-25T could only manage to launch the 3BM7 round at a muzzle velocity of 1,400 m/s whereas the M62-T2 achieved 1,620 m/s.<br />
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<h3>
HE-Frag</h3>
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The 3VOF1 cartridge was originally supplied with the ZhN-471 propellant charge with the G-471 brass casing. The total weight of the cartridge is 40.25 kg<br />
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When semi-combustible propellant charge technology reached maturity, 54-ZhN-471 was replaced by the 4Zh2 semi-combustible charge. 4Zh2 weighs just 10.02 kg, bringing the total mass of the 3VOF1 cartridge to just 35.1 kg.<br />
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AP</h3>
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The 53-VBR-471B cartridge is paired with the 54-Zh-471 propellant charge. The total weight of the cartridge is 40.0 kg<br />
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When the BR-471B shell is paired with the 4Zh2 semi-combustible propellant charge instead, the cartridge is known as 3VBR2. Thanks to the lighter weight of the 4Zh2 charge of just 10.8 kg, the total weight of the 3VBR2 cartridge is 35.1 kg.<br />
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<h3>
HEAT</h3>
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3VBK6 HEAT cartridges were paired with the 4Zh29 semi-combustible propellant charge. The 4Zh29 charge weighed only 8.07 kg. Steel or brass cased propellant charges for the 3VBK6 cartridge did not enter service.<br />
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APDS</h3>
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Like the 3VBK6 HEAT round, the 3VBK4 APDS round was only ever supplied with a semi-combustible propellant charge. However, the exact details are unknown.</div>
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<span style="font-size: large;">HE-Frag</span></h3>
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<h3>
<span style="font-size: large;">53-VOF-471, 3VOF1<br />53-OF-471N, 53-OF-471NZh</span></h3>
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The OF-471N warhead contains a 3.35 kg filler of TNT. A.V Shirokad writes in "<i>Энциклопедия Отечественной Артиллерии</i>" (<i>Encyclopedia of Domestic Artillery</i>) that the TNT filler weighs 3.8 kg. The difference is due to the fact that <a href="https://www.armedconflicts.com/attachments/1058/Strelivo_pre_122_mm_K.jpg">there were two OF-471N models that existed under the same name</a>, and both could be fitted with different fuzes which affected the amount of explosive compound carried in the warhead. Both models were ballistically matched because they had the same weight of 25 kg. The earlier OF-471N model had a monobloc warhead casing with a threaded nose to accept a fuze, and when fitted with the standard D-1 fuze, the weight of the TNT charge would be 3.35 kg. The later OF-471N model featured a slightly thinner warhead casing that had another separate, threaded front section that extended the projectile by around two inches and increased its internal volume, and thus increased the explosive payload from to 3.8 kg with the D-1 fuze fitted. This newer OF-471N shell is shown in the two photos below. <br />
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<a href="https://1.bp.blogspot.com/-oy3wTtdKopw/XUDzQMqg-YI/AAAAAAAAOtc/V2Due1iLbAU-bVuTGmQLzVZwkDgB3rK7wCLcBGAs/s1600/of-471n%2Bcutaway.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="496" height="400" src="https://1.bp.blogspot.com/-oy3wTtdKopw/XUDzQMqg-YI/AAAAAAAAOtc/V2Due1iLbAU-bVuTGmQLzVZwkDgB3rK7wCLcBGAs/s400/of-471n%2Bcutaway.jpg" width="123" /></a><a href="https://1.bp.blogspot.com/-vy7Scg0OwHA/XUDzQWmw_JI/AAAAAAAAOtg/2i4hz8o_PoYVLcpByv6hoO4wWLuJEPIugCLcBGAs/s1600/of-471n.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="481" height="400" src="https://1.bp.blogspot.com/-vy7Scg0OwHA/XUDzQWmw_JI/AAAAAAAAOtg/2i4hz8o_PoYVLcpByv6hoO4wWLuJEPIugCLcBGAs/s400/of-471n.jpg" width="120" /></a></div>
<div><br /></div><div><br /></div>The three-part casing, with two screw-on nose sections atop the main casing body, is characteristic of artillery shells which are difficult to mass produce as a single-piece forged body due to thickness tolerance control issues. Single-piece casings became standard for smaller shells since 1942-1943, but large caliber shells (122mm and 152mm) continued to be produced with a multi-part casing for much longer. It is desirable to build shell casings as a single forging for production simplicity and structural strength, particularly impact strength for penetrating large thicknesses of material.<br />
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As a 122mm HE-Frag shell, the explosive payload was uniquely large and the projectile itself was particularly heavy. Even the older OF-471N shell with the smaller explosive payload exceeded the explosive payload of the 100mm OF-412 shell fired from the D-10T of the T-54 medium tank by more than two times, and the disparity grew even further when compared to the improved OF-471N model. OF-471N also had a more optimal ratio between the mass of the projectile casing and the explosive charge, so it possesses more favourable fragmentation characteristics. For comparison, the older OF-471N warhead casing weighs 21.46 kg and it contains a 3.35 kg TNT charge so the share of the explosive charge by mass is 15.6%, whereas the OF-412 projectile casing weighs 13.7 kg and contains a 1.46 kg TNT explosive charge, and the share of the explosive charge by mass is just 10.3%. The share of the explosive charge mass for the newer OF-471N was 18.1%. The smaller share of explosive mass in the OF-412 is a side effect of the thicker steel casing needed to withstand the heavy stresses of being launched at a muzzle velocity of 892 m/s. The OF-471N avoids this problem because it was originally an artillery round and it was designed to be launched at a more modest muzzle velocity of 795 m/s. However, OF-471N is significantly inferior to the OF-462 howitzer shell in terms of the filler weight ratio and the size of the lethal area, used in the M-30 and D-30 howitzers.<br />
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An even wider gap is found when foreign medium tank guns are compared, as a 20 pdr. HE shell fired from a British Centurion weighs just 7.8 kg and contains an explosive charge of only 0.6 to 0.75 kg of TNT (Mk. I) or Composition B (Mk. I/I), while a 90mm HE shell fired from the M3 guns of the M47 and M48 Pattons weighs 10.56 kg and contains an explosive charge of 0.925 kg. In other words, the OF-471N shell has 5.6 times more explosive content than the 20 pdr. HE shell and 3.62 times more explosive filler than a 90mm HE shell.<br />
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The OF-471N shell can have the RGM, RGM-2 (1978), or D-1 point-detonating fuzes fitted, but for a postwar tank, the D-1 fuze would usually be used. The D-1 fuze weighs 0.188 kg. The OF-471NZh uses the more modern V-429 fuze instead.<br />
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Muzzle Velocity: 795 m/s<br />
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Projectile Mass: 25 kg<br />
Warhead casing mass: 21.46 kg or 21.0 kg<br />
Explosive Charge Mass: 3.352 kg or 3.804 kg<br />
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To use the shell in the "Frag" mode, the fuze is left in the superquick setting and the fuze cap is removed. The shell detonates instantly upon impacting any surface, regardless of whether it is a body of water, a marsh, or snow, thus producing the maximum fragmentation effect on targets standing on top of the surface. If nothing is done prior to firing the shell, meaning that the fuze is left in the superquick setting and the fuze cap is left on, the shell behaves as a "HE-Frag" shell. The fuze detonates after a delay of 0.027 seconds and produces a combined high-explosive and fragmentation effect. If the fuze cap is left on but the fuze is set to the delayed setting, the shell is behaves as a "HE" shell. It is detonated after a much longer delay of 0.063 seconds after impact. This enables the shell to explode after penetrating the earth down to an optimal depth, thus displacing the largest possible volume of soil and delivering the maximum shock effect to enemy fortifications which tend to be below ground level by nature. For example, a trench can be destroyed by firing a HE shell at a point just in front of the trench. The shell penetrates the earth at an oblique angle and explodes just next to the wall of the trench (a lucky shot may even explode inside the trench itself), thus demolishing it and killing anyone in the way. Setting the fuze is done by the loader using a special key, but it is the commander who dictates which setting is most suitable for the target.<br />
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Being a HE-Frag shell with a point-detonating fuze, OF-471N is most effective against troops in the open, sheltered troops, soft-skinned vehicles, and field fortifications. The lack of an armour-piercing tip and a base fuze means that it is unsuitable for destroying reinforced concrete bunkers. Even when set to behave as a HE shell, the explosion is only capable of creating a large and deep dent in the wall of the bunker without significantly penetrating it. Repeated shots at the same area of the wall will eventually bust the bunker, so it is not impossible, but specialized anti-concrete shells are much more efficient for this purpose. Nevertheless, the effect of a HE shell on hard targets should not be underestimated.<br />
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Even against heavily armoured targets that the OF-471N could never hope to perforate, the blast of the shell could still cause serious injuries to the crew. <a href="https://andrei-bt.livejournal.com/470788.html">A Soviet study</a> found that when firing 122mm AP and HE shells at armoured vehicles with an armour thickness of 240mm, the impact generated shock waves inside the vehicle with a pressure of 0.57-1.52 kg/sq.cm as recorded by sensors placed 200-1,000mm from the surface of the armour plate. The back surface of the plate was not breached or compromised in any way in any of the tests in the study as that would invalidate the results. It was noted in a separate report that a pressure of 0.4-0.6 kg/sq.cm is enough to cause medium injuries to humans, including the temporary loss of consciousness, hearing damage, bleeding from the nose and ears, and fractures or twisting of the limbs. A pressure wave of 0.57-1.52 kg/sq.cm can produce heavy hearing damage and blast injuries to the body, leading to an inability to continue fighting.<br />
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These effects are probably not as intense as that of a HESH shell of comparable caliber detonating against a plate of comparable thickness, but still, the effectiveness of 122mm HE-Frag shells on heavily armoured tanks was proven in combat during WWII.<br />
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When set to the Frag mode, the shell merely detonates on the surface of an armour plate and does not inflict much damage except in certain circumstances, but when set to the HE mode for penetration, OF-471N can tank armour and form extremely large breaches, killing the crew and destroying internal equipment with a large mass of fragments. Thinner plates can be perforated without causing too much damage to the point-detonating fuze that it is unable to function, so the shell may explode behind the plate. But if a sufficiently thick plate is fired at, the shell might perforate without detonating since the point-detonating fuze would be destroyed.<br />
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Soft-skinned targets such as trucks, tractors and cars (Jeeps, Land Rovers) can be destroyed without requiring a direct hit if the shell has the fuze set to the superquick mode. In such cases, the fragmentation deals most of the damage. Armoured personnel carriers, light tanks, armoured cars and other lightly armoured vehicles can also be knocked out by a near miss, although some of the heavier vehicles may require a direct hit or even a direct hit with the shell set in the delayed penetration mode. It is worth noting that even HE-Frag shells in the 76mm caliber were already enough to handle light tanks, not to mention less well-armoured vehicles.<br />
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Soviet testing detailed in "<i>Report on the shooting of German tanks with AP and HE shells from tank guns</i>" from 1942 also indicated that 76.2mm HE-Frag shells fired from an F-34 tank gun proved to be capable of destroying early medium tanks like the Pz.38(t) and Pz.III from distances of up to a kilometer in a side attack. If set to the "Frag" mode mode, the detonation of a 76.2mm shell on the surface of the hull sides of these tanks could not blow through the side armour plate but they would destroy the suspension. Adding on to that, 76mm HE shells from obr. 1931 guns (a high velocity anti-air gun) were reportedly capable of perforating 45 mm of armour at 30 degrees from 500 meters and 50 mm of armour at 30 degrees can be perforated from 300 meters or closer. With that in mind, it is also unsurprising that 85mm HE shells fired from the ZiS-S-53 gun of the T-34-85 were <a href="http://tankarchives.blogspot.com/2019/05/t-34-85-review.html">reported to be capable of knocking out Pz.III tanks from 800 meters</a>.<br />
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It is obvious that 122mm HE-Frag shells can achieve these results and more, but the higher rate of fire obtained from smaller caliber tank guns makes them more efficient on a shot-per-shot basis. On the other hand, a valid counterargument is that a 122mm HE-Frag shell fired in the superquick mode is powerful enough to destroy the suspensions of light vehicles with fragmentation and blast alone while also dealing with dismounted infantry, making it somewhat more efficient, especially at longer ranges where a direct hit is simply not guaranteed. Using the shells in HE mode and aiming for direct hits may not be as viable.<br />
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OF-471N may be capable of defeating the side armour of several contemporary medium and heavy tanks, but the most interesting targets are the Centurion and Conqueror as these tanks had spaced side skirts. For reference, it is interesting to recall that German testing of "Schurzen" spaced armour panels in 1943 found that the spaced panels could detonate 76mm HE-Frag shells fired from ZiS-3 guns. The panels were badly damaged, but they served their purpose by shielding the suspension from the blast and splinters.<br />
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<h3>
<span style="font-size: large;">Armour-Piercing</span></h3>
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<h3>
<span style="font-size: large;">53-VBR-471B</span></h3>
<h3>
<span style="font-size: large;">53-BR-471B</span></h3>
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<a href="https://2.bp.blogspot.com/-Ksu6hw8NJPA/XEf0aLwHm0I/AAAAAAAANJE/COM6T2z5uHAbGu6XibZj8fLoUq1wu7iZgCLcBGAs/s1600/br-471b.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1250" data-original-width="1379" height="362" src="https://2.bp.blogspot.com/-Ksu6hw8NJPA/XEf0aLwHm0I/AAAAAAAANJE/COM6T2z5uHAbGu6XibZj8fLoUq1wu7iZgCLcBGAs/s400/br-471b.jpg" width="400" /></a></div>
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The BR-471B shell was one of two armour-piercing shells originally available to the T-10 in 1953. The BR-471 shell of WWII vintage can skipped over even though wartime stockpiles of this obsolete shell still existed because T-10 tanks were simply not intended to use this shell, given that the TSh2-27 and TPS1 sights were only marked for BR-471B rounds.</div><div>
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Although the BR-471 shell was the standard armour-piercing round for IS-2 tanks during WWII, the BR-471B shell already began supplanting it in 1945, albeit too late to see combat in Europe, and it replaced the BR-471 entirely during the 1950's. The main targets of BR-471 shells during its heyday were German tanks such as Panthers and Tigers, against which it was generally quite successful. Even Tiger II tanks could fall victim to this shell under certain circumstances. However, its performance on sloped armour plate, and its long range energy retention, were both not ideal as it was a simple sharp-tipped projectile.<br />
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The BR-471B shell was superior on both counts as it had a blunt tip underneath a ballistic cap, and the projectile had a more elongated and streamlined shape, giving it a better ballistic coefficient. The BR-471 shell had a worse ballistic coefficient as it did not have a ballistic cap on top of its pointed penetrator body, and it two annular grooves around the midsection of its body that acted as local structural weakened zones where the tip of the shell could break off when impacting highly oblique armour. By allowing the penetrator to fail at predetermined points, the catastrophic failure of the entire penetrator could be avoided. The shell could then continue its interaction with the armour plate as a blunt-tipped shell rather than an ogive-tipped shell. The sensitivity of ricocheting from thinner but highly oblique plates was also reduced.<br />
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<a href="https://1.bp.blogspot.com/-6ajjQO7rTg0/XPV-V4n5mwI/AAAAAAAAOL0/Ht1LjDOMuX472RIebBIf_js06PX7MNYjwCLcBGAs/s1600/blunt%2Bcase.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1124" data-original-width="1558" height="287" src="https://1.bp.blogspot.com/-6ajjQO7rTg0/XPV-V4n5mwI/AAAAAAAAOL0/Ht1LjDOMuX472RIebBIf_js06PX7MNYjwCLcBGAs/s400/blunt%2Bcase.png" width="400" /></a></div>
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BR-471B already had a blunt tip so that when it impacts an oblique plate, an edge of its tip will dig into the plate and the resistance of the armour generates a righting torque, countering the effect of the deflecting force. This can improve performance on sloped armour plate and also increases the plate thickness and obliquity threshold for a ricochet. Moreover, rather than perforating armour through ductile hole formation, blunt-tipped shells tend to defeat armour through plug formation. This requires less energy and, if the target armour has a low toughness, allows the BR-471B penetrator to defeat a greater thickness of armour despite having the same mass and velocity as BR-471. The gap in the penetration power widens at longer distances as BR-471B loses less speed thanks to its superior ballistic coefficient.<br />
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<a href="https://1.bp.blogspot.com/-Aac1NoPoIkw/XUDyiZDABEI/AAAAAAAAOtM/3amXC7h_pqgGHx6T7MZYNznJ7nu7Q-5fQCLcBGAs/s1600/br-471b%2Bscale.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="607" height="400" src="https://1.bp.blogspot.com/-Aac1NoPoIkw/XUDyiZDABEI/AAAAAAAAOtM/3amXC7h_pqgGHx6T7MZYNznJ7nu7Q-5fQCLcBGAs/s400/br-471b%2Bscale.jpg" width="151" /></a></div>
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<br />The body of the BR-471B projectile is made from KhZNM steel. The shape of the body is cylindrical from the driving band to the localizer grooves. Ahead of the frontmost localizer groove, the body is ogived for a length of 1.9 calibers, The base is boattailed. <br /><br />
In the later half of WWII when the 122mm D-25T became the new standard gun of Soviet heavy tanks, the BR-471 and BR-471B shells produced at the time had a hardness of up to 481 BHN. This was considerably lower than the steel armour-piercing shells of German and American production which maintained a hardness of 550-600 BHN, but it was already an improvement over earlier Soviet shells from the earlier half of the war which had a hardness ranging from 351-451 BHN. The quality of the metallurgy of postwar shells was substantially higher than shells produced during wartime as the Soviet munitions industry had managed to improve their hardening technology and methodology during the immediate postwar period, allowing the manufacturers to harden the steel penetrator body more rationally and to increase its overall hardness. BR-471 and BR-471B shells <a href="https://pp.vk.me/c626631/v626631491/3989c/tBOidrUQQWg.jpg">produced in the immediate postwar period were of considerably higher quality</a> with a hardness of up to 590 BHN at the surface near the nose, but this still fell short of the U.S Army standard hardness of 60 HRC (654 BHN) at the nose. Moreoever, 100mm shells captured from SU-100 tank destroyers during the Suez Crisis of 1956 revealed that the hardening of BR-412B shells reached 622 BHN at the tip. This implies that BR-471B shells produced in the late 1940's and early 1950's also had the same standard of quality.<br />
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The explosive charge at the base of the shell was initiated by the MD-8 base fuze in early BR-471B shells. Later BR-471B shells have a DBR base fuze instead, later replaced by the DBR-2.<br />
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<div>
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Muzzle Velocity: 795 m/s<br />
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<br /></div>
Cartridge Mass: 40 kg<br />
Projectile Mass: 25 kg<br />
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Explosive charge: A-IX-2<br />
Explosive Charge Mass: 0.156 kg<br />
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The point blank range of BR-471B is high enough that theoretically, a hit can be guaranteed on a typical medium tank at a range of over a kilometer. The point blank range is 970 m for a target with a height of 2.0 meters (representing an armoured personnel carrier), 1,120 m for a 2.7-meter target (medium tank), and 1,180 meters for a 3.0-meter target (heavy tank). Of course, the natural vertical dispersion of the shot makes it necessary to estimate the range with some precision to have any real chance of scoring a hit at such ranges, and the vertical dispersion increases if the tank is on the move or even if it has just recently stopped since the barrel will oscillate from movement.<br />
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Depending on the source, the penetration of BR-471B shells can vary by a considerable margin. One Soviet source gives the following figures:<br />
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<a href="https://1.bp.blogspot.com/-2_QSSvGfois/XPVmwtTVFhI/AAAAAAAAOLk/EsL44AZd6MoIvUDytguOQaDJqLlplVW_gCLcBGAs/s1600/br-471b%2Band%2Bbr-471.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="516" data-original-width="535" height="385" src="https://1.bp.blogspot.com/-2_QSSvGfois/XPVmwtTVFhI/AAAAAAAAOLk/EsL44AZd6MoIvUDytguOQaDJqLlplVW_gCLcBGAs/s400/br-471b%2Band%2Bbr-471.png" width="400" /></a></div>
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U.S Army testing of captured BR-471B shells obtained from knocked-out IS-3 tanks gave the following results:<br />
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<a href="https://1.bp.blogspot.com/-r_deVw9Z7vU/XPV-M9_p2dI/AAAAAAAAOLw/6uBUd8cDxwEYqPCFBTZjOllTxZGpou0dACLcBGAs/s1600/br-471b.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1176" height="640" src="https://1.bp.blogspot.com/-r_deVw9Z7vU/XPV-M9_p2dI/AAAAAAAAOLw/6uBUd8cDxwEYqPCFBTZjOllTxZGpou0dACLcBGAs/s640/br-471b.png" width="470" /></a></div>
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Although BR-471B may have been effective against late WWII-era tanks, postwar tanks such as the M47 Patton were much more challenging. The M47 was designed as the replacement of the M46 Patton, but it held this title for only a short period before it was supplanted less than a year after entering service by the new M48 Patton medium tank. Still, the M47 was not uncommon among U.S Army tank units until the early 1960's and it formed a massive part of the tank fleets of several NATO members in continental Europe as part of U.S military aid, and as such, it was a militarily significant tank model that the T-10 series was likely to encounter. The cast upper glacis armour of the M47 had a thickness of 100mm at a slope of 60 degrees.</div>
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<div>
The M48 had a more resilient upper glacis with a thickness of 110mm sloped at 60 degrees and an eliptical hull shape providing more efficient protection from armour-piercing projectiles. An impact velocity of 870 m/s was needed to guarantee the defeat the upper glacis armour of the M48 from the front and an impact velocity of 900 m/s is required from an ±18 degree side angle. The limit velocity for satisfactory penetrations of the upper glacis was 820 m/s from the front. The low muzzle velocity of 795 m/s of the BR-471B shell effectively renders it impotent against the upper glacis of the M48 even at point blank range, so a hit to the turret or the lower glacis is necessary.<br />
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The British Centurion tank had somewhat poorer chances of surviving an encounter with a T-10. Its upper glacis armour was merely 75mm thick and sloped at 57 degrees, and its turret was more vulnerable as it had a worse ballistic shape but its armour was not thick enough to compensate.<br />
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With this level of performance, BR-471B was sufficiently powerful against medium tanks of the immediate postwar era but it was already falling into obsolescence in the face of the newer M48 Patton. The addition of appliqué armour on Centurion tanks also made them a much more challenging foe.</div>
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<h3>
<span style="font-size: large;">HEAT</span></h3>
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<div>
<div>
<h3>
<span style="font-size: large;">3VBK-6, 3VBK-6M<br />3BK-10, 3BK-10M</span></h3>
</div>
<div>
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<a href="https://1.bp.blogspot.com/-35oXf80kSNI/XOfona3Na9I/AAAAAAAAOE0/tROSLGdyqtE0irGtAhlkFImTvHX8Q9ZmQCLcBGAs/s1600/3bk-10%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="172" data-original-width="668" height="102" src="https://1.bp.blogspot.com/-35oXf80kSNI/XOfona3Na9I/AAAAAAAAOE0/tROSLGdyqtE0irGtAhlkFImTvHX8Q9ZmQCLcBGAs/s400/3bk-10%2Bdrawing.png" width="400" /></a></div>
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Given that 3BK-10(M) is functionally identical to the 3BK-9(M) round, this segment will only focus on its ballistic performance, which was entirely unremarkable for a projectile of its type. Its muzzle velocity was marginally higher than AP or HE-Frag rounds, but due to the increased drag from the stabilizer fins, higher drag of the spike tip projectile design and the smaller momentum of the lighter projectile, 3BK-10 loses velocity at a more rapid rate compared to spin-stabilized projectiles.</div>
<div>
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Like the 3BK-9 round, A-IX-1 is used for the explosive filler, and the V-15PG point-initiating base-detonating (PIBD) fuze is used.<br />
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The point blank range for a target with a height of 2 meters is just 900 meters.<br />
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<div>
<br />
<h3>
3BK-10 (3BK-10M)</h3>
Muzzle Velocity: 820 m/s<br />
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<div>
Cartridge Mass: 26.13 kg</div>
<div>
Projectile Mass: 18.0 kg</div>
<div>
<br /></div>
<div>
Explosive Charge Mass: 1.334 kg<br />
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<div>
<blockquote class="tr_bq">
Penetration at 0 degrees: 400mm RHA (450mm RHA)<br />
Penetration at 60 degrees: 200mm RHA (220mm RHA) </blockquote>
<blockquote class="tr_bq">
(Official figures)</blockquote>
<blockquote class="tr_bq">
Penetration: 523mm RHA (593mm RHA) </blockquote>
<blockquote class="tr_bq">
(From Soviet study)</blockquote>
</div>
</div>
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<h3>
<span style="font-size: large;">APDS</span></h3>
<h3>
<span style="font-size: large;">3VBM4</span></h3>
<h3>
<span style="font-size: large;">3BM7</span></h3>
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Like the 3VBK-6 HEAT rounds, the 3BM7 rounds had an identical design to their more powerful counterparts for the M62 gun and entered service in the same year. The only functional difference was that the 3BM7 projectile had a lower muzzle velocity of 1,400 m/s as a result of the lower chamber pressure of the D-25TA and D-25TS guns. However, even though 3BM7 did not reach the same level of performance as 3BM11, it was already enough to ensure the defeat of all existing NATO medium and main battle tanks of the 1960's from the front at combat distances of 1,500 to 2,000 meters. The point blank range for a target with a height of 2 meters is given as 1,600 meters.<br />
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Muzzle Velocity: 1,400 m/s<br />
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Projectile Mass: 7.4 kg<br />
Core Mass: 2.82 kg<br />
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Muzzle Energy: 7,252 kJ<br />
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<br />
<blockquote class="tr_bq">
Penetration at 1 km:<br />
300mm at 0 degrees<br />
100mm at 60 degrees </blockquote>
<blockquote class="tr_bq">
Penetration at 2 km:<br />
270mm at 0 degrees<br />
90mm at 60 degrees</blockquote>
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<a href="https://www.blogger.com/null" id="m62"></a>
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<h3>
<span style="font-size: large;">M62-T2</span></h3>
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The M62-T2 is a rifled high-pressure tank gun with a horizontally-sliding breech block. It is chambered for the newly developed 122x759mm caliber and it would turn out to be the only gun chambered for this cartridge that ever entered service. Like the D-25TA, a loading assistance device with a powered chain rammer is installed adjacent the breech of the cannon. The mass of the loading assistance device acts as a counterbalance to the gun mask. However, the design of the M62-T2 was completely different from the D-25 series and it had nothing in common except the diameter of the bore, as even the loading assistance device on the M62-T2 was designed to operate with 122x759mm cartridges only. The M62-T2 gun weighs 2,785 kg, inclusive of the muzzle brake and fume extractor. This is comparable to the American M58 which weighs 2,848 kg. Together with the armoured gun mask, the total weight of the gun assembly is 3,397 kg.<br />
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The ammunition for the M62-T2 is proprietary. It is not possible to fire a shell in the 122x785mm caliber, mainly because the propellant charge would not fit into the chamber designed for a 759mm case. The ballistics of the M62 gun were unified with the D-74 field gun, but despite this, the cartridges were not officially shared. According to a T-10M manual, the cases for the ammunition are only marked for the M62-T2, without mention of the D-74 (index 122-D74).<br />
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One of the factors behind the increased muzzle energy of the M62-T2 compared to the D-25T series is the lengthened barrel. The barrel of the M62-T2 has a length of 6,393mm or 52.4 calibers instead of the 43-caliber barrel of the D-25T series. This was still substantially shorter than the American 120mm M58 which had a barrel length of 7,162mm or 60 calibers. The maximum operating pressure of an 122mm AP shell fired from the M62-T2 is 392 MPa. This is noticeably higher than the 330 MPa nominal chamber pressure and 372 MPa maximum pressure of the M58 gun.<br />
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The gun elevation limit for the M62-T2 is 15 degrees and the gun depression limit is -5 degrees. Compared to the D-25TA and D-25TS, the total range of elevation angles is the same but 2 degrees were taken from the positive elevation and essentially reallocated towards increasing the gun depression limit. This is partly due to the revised location and positioning of the recoil mechanism on the M62-T2 breech assembly.<br />
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The hydraulic recoil buffer is located on the bottom left corner of the breech and the hydropneumatic recoil recuperator is placed next to it in the bottom right corner of the breech. Due to the relocation of the recoil mechanism from above the gun breech to below it, the M62-T2 appears narrower than the D-25T, although its breech assembly had the same width of 480mm. This can be seen in the photo below by Yuri Maltsev.<br />
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The M62-T2 is well-balanced and will maintain equilibrium when all of the standard equipment is installed, including the loading assistance device. As usual, there are a stack of steel ballast plates placed behind the breech to act as removable counterweights. As the barrel bore is progressively worn down with repeated firings over time, the weight of the eroded bore material will shift the center of gravity to the rear, so the ballast plate should be incrementally removed to maintain equilibrium. <br />
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Although a maintaining perfect equilibrium seems to be a relatively trivial quality for a tank gun, it is actually not so simple. For example, the M58 gun on the M89 combination mount in the M103 heavy tank required a large hydraulic equilibrator mechanism with a hydraulic cylinder pressurized to 1,000 psi. This mechanism took up a very large amount of space above the breech assembly and increased the total weight of the gun assembly, not to mention that the failure of the equilibrator seal would leave the gun inoperable by power or manual means due to the immense weight of the gun, making it necessary to apply an overwhelmingly large amount of torque to control the gun should the equilibrator fail. It also made the turret taller than it could have otherwise been.<br />
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<div><br /></div><div><br /></div>Lacking an equilibrator, the L1 gun of the Conqueror, equally unbalanced as the M58 gun from which it was derived, relied on a stabilizer to raise the gun and maintain its elevation angle within a range of +1 to +15 degrees once the tank reaches a speed of 2 mph. If left to swing under its own inertia, the gun elevation mechanism would fail and the gun mount itself was liable to be damaged.<br />
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The safety mechanism of the M62-T2 prevents the firing of a loaded round by any method, mechanical or electrical, until the loader's safety switch is closed. This included the electric trigger system and the mechanical firing pin, both the solenoid-actuated and manually-cocked modes of firing using the trigger on the manual elevation handwheel and using the mechanical trigger lever respectively.<br />
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Despite the considerable increase in power compared to the D-25TA gun, the M62-T2 gun assembly is slightly more compact as its breech assembly has the same width but the recoil guard is shorter. This freed up space behind the recoil guard, most notably increasing the size of the gap between the back of the recoil guard and the turret ring, thus allowing additional racks for 122mm projectiles to be placed on the turret ring.<br />
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Besides that, the mask mount on the end of the gun cradle was modified to accept the new gun mask of the T-10M, and like on the D-25 guns installed in previous T-10 models, a light sheet metal fairing was attached to the end of the gun mask, but again, the reason for this item is unclear.<br />
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Protection from the muzzle blast of the coaxial machine gun may have been a somewhat plausible explanation for the previous tanks, but on the M62-T2, the sheet metal fairing does not even reach the muzzle of the KPVT and the KPVT has a conical flash hider instead of a muzzle brake anyway. The increased length of the fairing compared to the one on the D-25 guns of previous T-10 tanks could indicate that it is intended to be a sleeve for protection against fragmentation, but the low thickness of the fairing means that it would only stop fragmentation that is already too anemic to cause anything other than superficial damage to the gun barrel anyway.<br />
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At some point, a canvas gun mask shroud was added to seal the many small gaps around the gun embrasure. The canvas shroud was mainly useful during daily operation as it completely prevented rain water from entering the turret or dust from collecting in the gaps between moving parts. The photo on the left below is taken from "<i>T-10 Heavy Tank and Variants</i>" by James Kinnear and Stephen Sewell.<br />
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As before, the cannon is installed on a mounting cradle which in turn is installed in the turret with two trunnions. These two trunnion are secured to the turret with two trunnion pins which pass through the entire thickness of the frontal turret casting on either side of the cannon and can be seen externally when the cannon is elevated if a canvas gun mask shroud is not present, as shown in the photo on the left below. The photo on the right below shows the mount for the coaxial KPVT with the right trunnion pin visible underneath the mount (<a href="http://www.kotsch88.de/al_T-10M.htm">photo credit to Stefan Kotsch</a>).<br />
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The normal length of the recoil stroke is 490 to 520mm and the maximum is 560mm. This is the same as the D-25T despite the greatly increased power of the gun. This was partly achieved thanks to a more sophisticated recoil mechanism, but the main design feature that permitted this was the new combined slotted-baffle muzzle brake.<br />
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The muzzle brake had six pairs of slots and it was affixed to the muzzle of the barrel with four bolts as shown in the photo below (<a href="http://armor.kiev.ua/Tanks/Modern/T10/?img=t10_16.jpg.html">credit to Vasily Chobitok</a>.). It is used exclusively on the M62-T2 and is a surefire indicator to distinguish the T-10M from all previous models. The 100mm D-54TS high-velocity cannon had a derivative of this muzzle brake design with four pairs of slots instead of six.<br />
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A slotted-baffle muzzle brake, referred to as an active-reactive muzzle brake, works to counteract recoil force by a combination of the rearward thrust (reactive) from the redirected escaping propellant gasses escaping through the slots and the forward force exerted by the pressure of the escaping propellant gas acting on the baffles (active). The smaller size of the slotted baffles compared to the large baffles of the TsKAB muzzle brake reduces the available surface area that the propellant gasses can act upon, but the relatively large slots reduces the velocity of the escaping propellant gasses which consequently reduce the rearward thrust compared to a purely slotted muzzle brake.<br />
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The efficiency and recoil-damping effectiveness of such muzzle brakes is heavily dependent on the specific design in question, but A. Mashkin states in "<i>Тяжёлый танк Т-10</i>" that the slotted muzzle brake of the M62 gun has a very high efficiency of 70%. The downside to having such an efficient muzzle brake is that the recoil system would likely fail if the gun was fired without it or if the brake was defective in some way. Furthermore, the large volume of propellant gasses ejected to the sides with every shot increases the firing signature of the tank, but like the T-10A and T-10B with the periscopic TPS1 sight, obscuration of the gunner's vision would not be a major concern as the T-10M had the periscopic T2S-29-14 sight, so the high velocity of the propellant gas exiting the muzzle brake slots is helpful for clearing the gunner's view and helps the fumes dissipate more quickly.<br /><br />
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<span style="font-size: large;">122x759mm Caliber</span></h3>
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Like all previous T-10 models, the standard combat loadout for the T-10M was evenly divided between HE-Frag ammunition and armour-piercing ammunition. Fifteen HE-Frag rounds and fifteen APCBC rounds would be carried. When HEAT ammunition became available in 1964, the share of APCBC rounds was reduced to only six, with the other nine having been replaced by HEAT rounds.<br />
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It is worth noting that the shape and ballistic properties of the spin-stabilized 122mm ammunition for the M62 was not the same as the 122mm ammunition for the D-25T, even though they shared the same caliber. The difference in the shape of the projectiles can be seen most clearly when the OF-472 is compared to the OF-471N. The radius of the ogive was increased, the bearing surface length was shortened, and the overall length of the projectile grew slightly. These changes were necessary to counteract the increased drag experienced by the projectiles as they traveled at a considerably higher velocity.<br />
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In the early 1960's, there was a desire to improve the firepower of the T-10M and the most expedient approach was to put an APDS round into service. The muzzle velocity was specified to be around 1,800-1,900 m/s and the armour penetration was calculated to be a whopping 200mm at 60 degrees at a distance of 2,000 meters. However, the chamber pressure of this APDS round reached 451.1 MPa, exceeding the maximum safe chamber pressure of 392 MPa by 15%. When the APDS round was fired during a live fire test in January 1963, the M62-T2 gun mounted on a tracked test platform experienced a catastrophic failure: a piece of the breech was blown off and the breech block itself followed, the gun cradle collapsed, the recoil guard and loading assistance device was demolished and the recoil mechanism was disabled. Needless to say, this APDS round was too powerful for M62-T2 to handle. An APDS round with reduced power had to be developed.<br />
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In 1967, the 3BM11 APDS round for the T-10M entered service. This addition was rather belated given that production of the heavy tank had already ceased completely by 1965, but even so, the availability of another new and more potent ammunition type extended the usefulness of T-10M tanks and made it a viable tool during the remainder of their service life until they could be replaced by new and more effective tanks equipped with powerful smoothbore guns. With the new APDS round, the number of HEAT rounds was reduced and obsolete APCBC rounds were omitted entirely. Beginning in the late 1960's, the combat loadout of each T-10M consisted of 18 HE-Frag shells, 8 APDS shells and 4 HEAT shells.<br />
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<h3>
PROPELLANT CHARGES</h3>
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The propellant charges for the M62-T2 cannon had a bottlenecked tapered case instead of a straight cylindrical case. The cases had a slightly reduced length compared to the straight-walled cases for the D-25T - only 759mm compared to 785mm - but had an increased diameter of 157mm and a rim diameter of 171mm. This made them slightly easier to handle in the confines of the tank, especially with the revised ammunition stowage layout of the T-10M. However, the charges also weighed more due to the increased mass of propellant. It can be assumed that the ergonomic benefits of the reduced length of the propellant charges were largely offset by the increased weight.<br />
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As mentioned before in the article, new semi-combustible propellant charges entered service for the T-10M in 1959. Moreoever, the new HEAT and APDS ammunition appearing in 1964 and 1967 were exclusively supplied with semi-combustible propellant charges. </div>
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HE-Frag</h3>
3VOF-2 cartridges with the OF-472 HE-Frag shell use the 4ZhN4 propellant charge with a brass casing and NDT-2 19/1 propellant. The complete propellant charge weighs 20.25 kg and the brass casing alone weighs 9.75 kg. There is a waxed cardboard liner and obturator to seal the mouth of the casing and to phlegmatize the propellant for barrel cooling purposes, helping to reduce erosion. <br />
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3VOF-16 cartridges with the OF-472 HE-Frag shell use the 4Zh14 semi-combustible propellant charge. Weighing only 14.6 kg, the difference in weight between the 4ZhN4 brass-cased propellant charge and the new 4Zh14 semi-combustible propellant charge amounts to 5.65 kg. A waxed liner was absent as the semi-combustible casing material itself served as the phlegmatizer.<br />
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<h3>
APCBC</h3>
3VBR-1 cartridges with the BR-472 APCBC shell use the 4ZhN3 propellant charge. The charge uses a brass casing with NDT-2 16/1 propellant. There is a waxed cardboard liner and a combustible cork with the shape of a truncated cone is affixed to the mouth of the propellant charge casing. It is 95mm long. The purpose of the cork is to ensure that the projectile is seated in the chamber when the propellant charge is rammed into position, because the projectile would tend to lay short of the forcing cone due to the shorter length of the projectile base behind its driving band relative to the HE-Frag shell. The presence of the cork also serves as a way for the loader to quickly identify it from the 4ZhN4 propellant charge to ensure that the incorrect propellant charge is not incorrectly loaded during the heat of battle, as it is inadmissible to use propellant charges interchangeably. The full propellant charge weighs 20.42 kg.<br />
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3VBR-3 cartridges with the BR-472 shell use the 4Zh15 semi-combustible propellant charge. The charge weighs only 14.77 kg - a very substantial improvement over the 4ZhN3 that undoubtedly made the loader's job easier. The combustible cork that was present at the mouth of the 4ZhN3 casing was replaced with a hollow spacer of the same shape, made from the same cellulose textile as the rest of the combustible casing.<br />
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<a href="https://1.bp.blogspot.com/-BZNMGps5L2w/XEfH3TPpCFI/AAAAAAAANII/1aebOE-Mfi0Rs_S8M7QMIt_f_rO-rRFRwCLcBGAs/s1600/vbr3.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="225" data-original-width="1419" height="100" src="https://1.bp.blogspot.com/-BZNMGps5L2w/XEfH3TPpCFI/AAAAAAAANII/1aebOE-Mfi0Rs_S8M7QMIt_f_rO-rRFRwCLcBGAs/s640/vbr3.png" width="640" /></a></div>
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<br />
<h3>
HEAT</h3>
3VBK-5 cartridges with the 3BK-10 HEAT shell use the Zh26 propellant charge. The length of the Zh26 propellant charge is particularly short due to the presence of the stabilizer fins at the rear part of the projectile, so it had to be short to ensure that the projectile is seated properly in the chamber. However, the mass of propellant was not compromised because no air gaps were left inside the charge casing unlike the 4Zh15 and 4Zh14 propellant charges. The charge was shortened to the extent that no bottlenecking remained, which makes it easy to visually differentiate it from the propellant charges of the other ammunition types.<br />
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<a href="https://3.bp.blogspot.com/-rMiEQplGofk/XEJ2Y9Y2C3I/AAAAAAAANBM/7hH3uVfk_rg2lI4tvrmVxz8TeUhTjKdaACLcBGAs/s1600/3VBK5.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="223" data-original-width="1360" height="104" src="https://3.bp.blogspot.com/-rMiEQplGofk/XEJ2Y9Y2C3I/AAAAAAAANBM/7hH3uVfk_rg2lI4tvrmVxz8TeUhTjKdaACLcBGAs/s640/3VBK5.JPG" width="640" /></a></div>
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<br />
<h3>
APDS</h3>
<br />
3VBM4 cartridges with the 3BM11 APDS shell use the 4Zh46 propellant charge. The hollow nose of the combustible casing of the propellant charge is extended to ensure that the exceptionally short APDS projectile is seated properly and engages with the rifling of the barrel, thus fulfilling the same purpose as the combustible cork found on 4ZhN3 charges. The propellant charge weighs 15 kg.<br />
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<a href="https://4.bp.blogspot.com/-hDoX_m6rW4s/XEJ2YRdMZBI/AAAAAAAANBI/TwShTHNWOOMi51btXi3g1IhXyDhkaHumACLcBGAs/s1600/3VBM4.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="236" data-original-width="1285" height="116" src="https://4.bp.blogspot.com/-hDoX_m6rW4s/XEJ2YRdMZBI/AAAAAAAANBI/TwShTHNWOOMi51btXi3g1IhXyDhkaHumACLcBGAs/s640/3VBM4.jpg" width="640" /></a></div>
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Due to the short length of APDS projectiles, there was an attempt to create a unitary APDS cartridge. This unitary cartridge only slightly exceeded the length of a standard propellant charge for an armour-piercing round so it could be loaded using the loading assistance device. Otherwise, two-piece APDS cartridges had to be loaded manually because the APDS projectile assembly was simply too short to be loaded properly by the chain rammer of the loading assistance device. However, the unitary APDS cartridge remained experimental.<br />
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<a href="https://1.bp.blogspot.com/--eWCrF8fVcM/XUDnxr8gc8I/AAAAAAAAOs8/K9P_zhNAyj0uyOFoE78KmhE1ucqdXyZ6ACLcBGAs/s1600/models.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="743" data-original-width="574" height="320" src="https://1.bp.blogspot.com/--eWCrF8fVcM/XUDnxr8gc8I/AAAAAAAAOs8/K9P_zhNAyj0uyOFoE78KmhE1ucqdXyZ6ACLcBGAs/s320/models.png" width="247" /></a></div>
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<h3>
<span style="font-size: large;">HE-Frag</span></h3>
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<h3>
<span style="font-size: large;">3VOF-2, 3VOF-16</span></h3>
<h3>
<span style="font-size: large;">OF-472</span></h3>
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://3.bp.blogspot.com/-jZvVds-QpFk/XEQnT_GmJDI/AAAAAAAANE8/tD5RVbjm3LQwpkF4Al0_vORl46Pln_oswCLcBGAs/s1600/of-472.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1015" data-original-width="898" height="400" src="https://3.bp.blogspot.com/-jZvVds-QpFk/XEQnT_GmJDI/AAAAAAAANE8/tD5RVbjm3LQwpkF4Al0_vORl46Pln_oswCLcBGAs/s400/of-472.png" width="353" /></a></div>
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<br />The only available types of HE-Frag ammunition for the M62-T2 were the full-charge 3VOF-2 or 3VOF-16, both having the same OF-472 shell. The OF-472 shell was also used for the D-74 field gun. A reduced charge cartridge was available for the D-74, but for the T-10M, only full propellant charges were available. </div><div><br /></div><div>Although the upgrade to the M62-T2 improved the performance of armour piercing rounds, the unfortunate side effect is that the increased operating pressure required HE-Frag projectiles to have thicker walls in order to withstand the increased rate of acceleration inside the barrel. According to the Russian artillery ammunition design textbook "<i>Устройство и действие боеприпасов артиллерии</i>", the wall thickness of OF-472 is 0.17 calibers, as compared to 0.14 calibers for the OF-471N. Because of this, the mass of a complete projectile increased by 2.3 kg compared to the OF-471N shell. </div><div>
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The steel body of the OF-472 projectile weighs 23.34 kg. With a total projectile mass of 27.3 kg and a muzzle velocity of 885 m/s, the muzzle energy of the OF-472 shell is a whopping 10.69 MJ, so it is much more energetic than the 8.08 MJ of the OF-471N shell fired from the D-25T. This is beneficial when firing upon armoured targets, including tanks. However, it paid for the increased kinetic energy with a heavy sacrifice in its explosive payload, having only 3 kg of TNT filler compared to 3.35 kg of TNT in the OF-471N. The share of the explosive charge by mass was sub-optimal - only 11.8%. This is still marginally better than the 100mm OF-412 shell, but it falls far below the 15.6% ratio of the OF-471N shell.<br />
<br />One upside of the OF-472 design is that the sectional density of the projectile increased compared to OF-471N due to the larger weight, which has a positive effect on the ballistic coefficient. With the increased muzzle velocity, the ballistic trajectory of the OF-472 projectile became noticeably flatter and the maximum indirect fire range increased to 16 km despite the reduction in the maximum gun elevation angle from the 17 degrees of the D-25T to the limit of 15 degrees on the M62-T2. This is useful when a higher hit probability on point targets is required, but the flat trajectory is counterproductive when engaging infantry in the open because the fragmentation pattern is negatively affected. It also makes the shell more sensitive to ground ricochets when fired at flat ground at short ranges, so the coaxial KPVT of the T-10M may be needed to take over the anti-infantry role in such circumstances. Also, the increased range of the OF-472 shell is not very useful for a heavy tank like the T-10M as it would be an immense waste of resources to deploy it as a field gun instead of using it in its intended role. Overall, there was little good in the reduction of the explosive payload, but it was unavoidable due to the higher acceleration forces the shell experienced when it was launched from the high-pressure M62-T2 gun.<br />
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<br />
Muzzle Velocity: 885 m/s<br />
<br />
Projectile length (without fuze): 564 mm</div><div>Projectile length (fuzed): 622mm (5.1 calibers)<br />
<br />
Projectile body mass: 23.34 kg<br />
Total projectile mass: 27.3 kg<br />
Explosive filler mass: 3 kg<br />
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<br /></div>
<div>
<h3>
<span style="font-size: large;">APCBC</span></h3>
<br />
<h3>
<span style="font-size: large;">3VBR-1, 3VBR-3<br />BR-472</span></h3>
</div>
<div>
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://2.bp.blogspot.com/-UqiGRvkAt9Y/XEQTi-7d_NI/AAAAAAAANEw/YoDnY9TX-PEoGGdiLLrNmpwWaIrNXtshACLcBGAs/s1600/br-472.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="897" data-original-width="866" height="400" src="https://2.bp.blogspot.com/-UqiGRvkAt9Y/XEQTi-7d_NI/AAAAAAAANEw/YoDnY9TX-PEoGGdiLLrNmpwWaIrNXtshACLcBGAs/s400/br-472.png" width="385" /></a></div>
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When the T-10M entered service, the 3VBR-1 round with the BR-472 shell was only armour-piercing ammunition initially available for the tank. It was not the first capped armour-piercing shell in the 122mm caliber as the BR-471D already existed, but it was the first and last APCBC round in the 122x759mm caliber to be issued in service. Like the BR-471D shell, the nose of the BR-472 armour-piercing cap is blunt and the steel armour-piercing core has an ogived tip.</div><div><br /></div><div>The shell body (19.61 kg) is composed of 60Kh2N2M steel, while the armour-piercing tip (3.5 kg) is made from 48Kh3 (sometimes referred to as 48Kh30) steel. Both are grades of tool steel. According to the Russian munitions design textbook "<i>Устройство и действие боеприпасов артиллерии</i>", compared to earlier shells, more sophisticated heat treatment was utilized, providing through hardening, high tempering, hardening and rehardening of the nose, tempering of the shell base, and low-temperature tempering of the entire body. This provided higher hardness and strength. The nose of the shell was treated to a hardness of 57-63 HRC, with the hardness being maximum on the surface of the nose (down to the midsection of the shell) and gradually decreasing into the center of the shell. The base is treated to a Brinell hardness indentation diameter of 3.34-3.6 mm (285-332 BHN). These hardness specifications essentially correspond to that of American shells and to the Pzgr. 39 rot specifications from the later half of the GPW. </div><div><br /></div><div><br /></div><div>The armour-piercing cap soldered onto the penetrator body serves to prevent both penetrator breakup and shatter, particularly when attacking sloped armour. The presence of a blunt AP cap made localizer grooves uncecessary. Its hardness does not exceed 477 BHN, and the hardness of the base of the cap is 269-321 BHN. </div><div><br /></div><div>The design of the shell is effectively the same as BR-471D, namely in the thickness (0.41 calibers) and length (1.03 calibers) of the armour-piercing cap, and the length of the ballistic cap (1.2 calibers). BR-472 only differs in that its total length is very slightly longer (3.72 calibers), the walls of the explosive cavity are marginally thinner (0.29 calibers), but more importantly, a new set of driving and obturator bands was introduced. The image below shows BR-472 on the left and BR-471D on the right.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-tx8ihahaqFM/YB4WkswCMgI/AAAAAAAAStM/-n6SKTLpE_0LrVrieHJeoPyTm5h5IZ3kwCLcBGAsYHQ/s994/br-472%2Band%2Bbr-471d.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="994" data-original-width="591" height="400" src="https://1.bp.blogspot.com/-tx8ihahaqFM/YB4WkswCMgI/AAAAAAAAStM/-n6SKTLpE_0LrVrieHJeoPyTm5h5IZ3kwCLcBGAsYHQ/w238-h400/br-472%2Band%2Bbr-471d.png" width="238" /></a></div><div><br /></div><div><br /></div><div>The use of a capped shell with a sharp-nosed penetrator to replace the homogeneous blunt-nosed type established in 1945 was a result of the close similarity in impact behaviour on mildly oblique armour and the higher penetrating performance of a sharp-nosed penetrator, particularly on thick and tough, but softer armour. Such armour resists blunt-nosed penetrators well due to a high toughness, allowing it to resist failure by plugging, but is suboptimal for sharp-nosed penetrators, against which an armour plate of higher hardness is usually more effective. Since the armour-piercing cap effectively distributes the shock load across the entire surface of the ogived penetrator tip during impact, the penetrator remains intact throughout the interaction and maintains its tip, with the exception of high-obliquity impacts. Shell shattering or fracturing was also avoided, allowing the shell to exhibit better penetration performance than a homogeneous shell under the same conditions, except on high-obliquity impacts.</div><div>
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In terms of muzzle energy, the BR-472 shell was close to the 12.8cm Pzgr. 39 shell fired from a KwK 44 or a Pak 44 as that fired a 28.3 kg projectile at 950 m/s. Compared to the M358 round fired from the M58 gun of the M103 series, BR-372 is less energetic, though the difference is not as large as the commonly printed values suggest due to the use of a 21°C standard propellant temperature in the U.S, as opposed to a 15°C standard temperature as used in Germany and the USSR.<br />
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A 0.34 kg charge of A-IX-2 is packed at the base of the projectile. A DBR base fuze is screwed into the back of the explosive charge cavity and incorporates a tracer at the end. The tracer does not protrude beyond the rim of the projectile base which has some fairly interesting aerodynamic connotations.<br />
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The increased muzzle velocity of the BR-472 shell extended the point blank range to 1,130 meters for a target with a height of 2 meters. This is the average height of an APC hull. The combined height of the hull and turret of NATO tanks like the Centurion and M48 was 2.3 meters tall on average, but the M48 had a very large cupola that increased the height to 2.7 meters. Naturally, this made them much easier to hit.<br />
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<div>
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Muzzle Velocity: 950 m/s</div>
<div>
<br />
Projectile Length: 488mm<br />
Projectile Mass: 25.1 kg<br />
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Muzzle Energy: 11,326.4 kJ</div>
<div>
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<br />
<blockquote class="tr_bq">
Penetration at 0 degrees: </blockquote>
<blockquote class="tr_bq">
500 m - 265mm<br />
1,000 m - 247mm<br />
1,500 m - 230mm<br />
2,000 m - 214mm</blockquote>
<blockquote class="tr_bq">
Penetration at 30 degrees: </blockquote>
<blockquote class="tr_bq">
500 m - 214mm<br />
1,000 m - 200mm<br />
1,500 m - 186mm<br />
2,000 m - 172mm</blockquote>
</div>
<div>
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With this shell, the M48 Patton medium tank was vulnerable on its upper glacis from 1,000 meters and the frontal armour in general (including the turret) was vulnerable to a frontal shot from a distance of 1,500 meters or more. The more lightly armoured M47 would be even less likely to survive a direct hit from BR-472 at such distances. These tanks formed the bulk of the armoured forces of several NATO armies, the main one being the U.S Army, but just a few years after the T-10M was introduced, the M60A1 main battle tank made its appearance. The strong emphasis on armour obliquity on its turret and hull made it practically impervious to BR-472 except at the normal weakened zones - the lower glacis of the hull, the base of the turret cheeks, and the are below the gun mask.<br />
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The large gun mask of the M103 turret has a thickness of 254mm at the apex of its nose, thinning down to 102mm while gaining a slope of 45 degrees. The penetration figures for BR-472 indicate that this armour can be perforated from a distance of up to 1,500 meters.<br />
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<h3>
<span style="font-size: large;">3VBK-5, 3VBK-5M<br />3BK-9, 3BK-9M</span></h3>
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<a href="https://1.bp.blogspot.com/-Bx7M4MAZ8cU/XOfoP-ybAhI/AAAAAAAAOEs/zrZ41ySxak8JuCzZMv8Op45_sNfsRuuMwCLcBGAs/s1600/3bk-9.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="103" data-original-width="446" src="https://1.bp.blogspot.com/-Bx7M4MAZ8cU/XOfoP-ybAhI/AAAAAAAAOEs/zrZ41ySxak8JuCzZMv8Op45_sNfsRuuMwCLcBGAs/s1600/3bk-9.jpg" /></a></div>
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The relatively high muzzle velocity of the projectile helps to improve the probability of scoring a hit on a distant target, especially a moving target. However, the use of a spike tip and stabilizer fins causes the projectile to experience greater air resistance during flight, so the rate of velocity loss is higher than the spin-stabilized BR-472 projectile and the difference between the velocities of the two shells will increase over distance.<br />
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The point blank range of 3BK-9(M) for a target with a height of 2.0 meters is 1,000 meters. This is a small improvement over the 3BK-10(M) round, but it is less than the point blank range of 1,120 meters for BR-472 for a target of the same height. The flatter trajectory of the 3BK-9(M) shell compared to the 3BK-10(M) shell despite having the same caliber and the same projectile design is due to its marginally larger mass and its higher muzzle velocity, courtesy of the higher pressure and longer barrel of the M62-T2 gun.<br />
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According to a 1979 Soviet report titled <i>"<a href="http://btvt.info/5library/vbtt_1979_03_probivaemost.htm">Выбор Кумулятивных Снарядов Для Испытания Брони</a></i>" (<i>Selection of Cumulative Shells for the Evaluation of Armour</i>), the average penetration of 3BK-9 in armour plate is 523mm with a maximum of 563mm and a minimum of 481mm. All of the penetration figures represent the performance at both 0 and 60 degrees. For comparison, the average penetration of the American 105mm M456A1 in the same targets was found to be 398mm, and the maximum and minimum penetration was 434mm and 355mm respectively. The Soviet 115mm BK-4M shell had an average penetration of 499mm with a maximum of 559mm and a minimum of 418mm.<br />
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The penetration power of 3BK-9M is not known for sure, but based on the performance ratio between the 115mm 3BK-4 (440mm RHA) and 3BK-4M (499mm RHA) and assuming a similar ratio exists between 3BK-9 and 3BK-9M, it can be deduced that the penetration of 3BK-9M is around 593mm and the maximum achievable penetration is around 638mm.<br />
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With such an impressive penetration power, 3BK-9(M) is capable of easily perforated the armour of any tank in the world with a large surplus of energy left to inflict heavy post-perforation damage. Case in point, 3BK-9M could perforate the thickest part of the upper glacis of an M103 twice over and 3BK-9 could do the same to the upper glacis of the Conqueror, so the probability of a mission kill on the first hit should be rather high. This creates a strong incentive for T-10M commanders to choose HEAT when dealing with heavily armoured targets over the BR-472 APCBC, especially since there is a relatively small difference in the ballistics between the two shells and none of the penetration power of HEAT is sacrificed at long range.<br />
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The V-15PG point-initiating base-detonating (PIBD) fuze is used.<br />
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3BK-9 (3BK-9M)<br />
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Muzzle Velocity: 920 m/s<br />
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Cartridge Mass: 31 kg<br />
Projectile Mass: 19.2 kg<br />
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Explosive Charge Mass: 1.7 kg<br />
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Penetration (Official): 450mm RHA</div>
<div>
<br />
Penetration: 523mm RHA (593mm RHA)<br />
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<br />
<h3>
<span style="font-size: large;">APDS</span></h3>
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<h3>
<span style="font-size: large;">3BM11</span></h3>
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<br />
3BM11 was developed during the late 1950's in a programme to increase the firepower of the 100mm D-10 and the M62 cannons. It entered service in 1967. The design of the projectile is almost identical to the 100mm 3BM8 projectile and the tungsten carbide core has the same dimensions. The only structural difference is in the size of the steel jacket and the sabot. The core is made from a tungsten carbide with a 10% nickel binder, designated as VN-10.<br />
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<a href="https://1.bp.blogspot.com/-c3IMSo0BUQo/XEk0NtgDHoI/AAAAAAAANKY/3D6SgYbEhRUhs62G4Nu0wSpKud_PhIHwACLcBGAs/s1600/apds.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="469" data-original-width="1600" height="186" src="https://1.bp.blogspot.com/-c3IMSo0BUQo/XEk0NtgDHoI/AAAAAAAANKY/3D6SgYbEhRUhs62G4Nu0wSpKud_PhIHwACLcBGAs/s640/apds.png" width="640" /></a></div>
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Unfortunately for the T-10M, the appearance of 3BM11 in 1967 was rather belated as the T-62 had already achieved its level of performance on sloped targets several years ago thanks to the virtues of APFSDS ammunition. The APFSDS rounds fired from the U-5TS gun of the T-62 were still inferior in penetration on flat targets, but this was largely irrelevant as armour with complex ballistic shapes and liberally sloped surfaces was the norm for all post-WWII tanks. Interestingly enough, the APFSDS rounds that were in development for the U-5TS were also tested in the M62-T2 cannon at the NIIBT testing grounds at Kubinka, but ultimately, only the smoothbore U-5TS was supplied with the new ammunition.<br />
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The 3BM11 round uses a reel-shaped cup-type sabot that is fundamentally the same as the sabot of the 3BM8 round in its working principle, but has a completely different construction due to the two-part ammunition of the M62-T2 gun. The sabot is joined to the subcaliber projectile by four pins and the base of the projectile is supported by the sabot. When the round is fired, the four pins are responsible for transmitting the rotational force imparted by the rifling to the subcaliber projectile.<br />
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As the entire projectile assembly leaves the muzzle of the barrel, both the sabot and the subcaliber projectile are rotating at the same rate but the sabot experiences much more aerodynamic resistance due to the large cavity at its front end. The sabot decelerates because of this, but the heavier subcaliber projectile carries much more momentum and it is much more streamlined. As a result, the four pins connecting the sabot to the projectile experience a strong shear force and are sheared off almost immediately after the projectile assembly stops accelerating from being propelled in the gun barrel, thus separating the subcaliber projectile from the sabot.<br />
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<a href="https://1.bp.blogspot.com/-hjBcsscJmlA/XOm1FUA-qPI/AAAAAAAAOFI/pGcc619iU288eQ4MYkudZ12LEc_B09FCgCLcBGAs/s1600/4.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="957" height="400" src="https://1.bp.blogspot.com/-hjBcsscJmlA/XOm1FUA-qPI/AAAAAAAAOFI/pGcc619iU288eQ4MYkudZ12LEc_B09FCgCLcBGAs/s400/4.jpg" width="238" /></a><a href="https://1.bp.blogspot.com/-bswa1a7leqM/XOm1FRltfmI/AAAAAAAAOFE/jOvD6xEaHig1LVkIVayzCTab6qGeqkroACLcBGAs/s1600/122mm_3BM11%2BAPDS%2BRound_2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="712" height="400" src="https://1.bp.blogspot.com/-bswa1a7leqM/XOm1FRltfmI/AAAAAAAAOFE/jOvD6xEaHig1LVkIVayzCTab6qGeqkroACLcBGAs/s400/122mm_3BM11%2BAPDS%2BRound_2.jpg" width="277" /></a></div>
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<br />
The four pins connecting the sabot to the projectile do not shear off when the round is fired because the base support offered by the cup spares the pins from the tremendous rate of acceleration, so they are left intact to transmit rotational energy.<br />
<br />
This sabot design is simple in its operation. Compared to the complex sabots of foreign APDS rounds, the 3BM11 cup sabot has only a single separation stage whereas the sabots of rounds like the 105mm L28 and 120mm L15 first have three nose petals separate from centrifugal force before the cup separates from the subcaliber projectile due to air resistance.<br />
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With a muzzle velocity of 1,620 m/s and a higher sectional density than full caliber projectiles owing to its small caliber and the high density of its tungsten carbide core, 3BM11 has an exceptionally flat ballistic trajectory compared to BR-472, even more so than the 3BM7 round for the D-25T. Therefore, the probability of hit would be much higher on distant targets and especially if they are moving. The point blank range for a target with a height of 2.0 meters is given as 1,900 meters. Considering that tanks like the M48 Patton, M60A1 and Leopard 1 have a structural height of 2.3 meters (hull and turret only, ignoring ground clearance and cupolas), the actual point blank range on a typical NATO tank exceeds two kilometers. For comparison, the 100mm 3BM8 round has point blank ranges of 1,680 meters and 1,800 meters for a 2.0-meter target and a 2.3-meter target respectively.<br />
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Muzzle Velocity: 1,620 m/s<br />
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Total projectile assembly length (incl. sabot): 250mm<br />
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Total cartridge mass: 22.7 kg<br />
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Projectile Mass: 7.4 kg<br />
Core Mass: 2.82 kg<br />
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Muzzle Energy: 9,710.3 kJ<br />
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<blockquote class="tr_bq">
Penetration at 2 km: </blockquote>
<blockquote class="tr_bq">
320mm at 0 degrees<br />
190mm at 45 degrees<br />
110mm at 60 degrees</blockquote>
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<blockquote class="tr_bq">
From "<i>Theory and Design of a Tank</i>", P.P. Isakov, 1982</blockquote>
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Penetration at 1 km:<br />
370mm at 0 degrees<br />
140mm at 60 degrees<br />
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Penetration at 2 km:<br />
300mm at 0 degrees<br />
115mm at 60 degrees<br />
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The penetration performance of 3BM11 is ostensibly inferior to L1G APDS from the Conqueror's L1 cannon on flat plates by a large margin, but it is apparently somewhat more effective on plates sloped at 60 degrees. This can be seen in the table below from the British Army Operational Research Group memorandum "<i>Tank Effectiveness, Conqueror, Conway and Charioteer</i>" from June 1954 as shared on the Tanks and AFV News website. According to DEFE 15/1183, the penetration of the "Conqueror APDS" is 125mm at 60 degrees at 1,000 yards.<br />
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As mentioned many times before on Tankograd, it is usually not possible to directly compare the penetration figures given by different sources due to differences in the penetration criteria and test methodology, and this is particularly true when comparing Soviet penetration figures with the figures from any other nation. However, the advantage held by the L1G round is quite far beyond the realms of possibility given that it is a 10.43 kg projectile travelling at a muzzle velocity of 1,280 m/s. The core of L1G is much more substantial than the core of 3BM11 at a weight of 5.44 kg, but due to the large difference in the muzzle velocities, the 3BM11 projectile carries 9.71 MJ of kinetic energy whereas the L1G projectile carries 8.54 MJ of kinetic energy.<br />
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<a href="https://4.bp.blogspot.com/-roajAjYANuk/XD4pxtj6HwI/AAAAAAAAM6k/4gINccDXkF4W6GOum0XnfzHp54bgK15NwCLcBGAs/s1600/gun%2Bpenetration%2Bcomparisons.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="298" data-original-width="739" height="258" src="https://4.bp.blogspot.com/-roajAjYANuk/XD4pxtj6HwI/AAAAAAAAM6k/4gINccDXkF4W6GOum0XnfzHp54bgK15NwCLcBGAs/s640/gun%2Bpenetration%2Bcomparisons.png" width="640" /></a></div>
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Firing tables for 3BM11 are not publicly available and <a href="http://www.kotsch88.de/tafeln/st_100mm-ke.htm">the only available firing table for 3BM8 is incomplete</a>, but according to V.A Grigoryan in "<i>Защита танков</i>" (<i>Tank Protection</i>), 3BM8 has a muzzle velocity of 1,415 m/s and a velocity of 1,202 m/s at 2 km. The average rate of velocity loss from this small set of data comes out to 106.5 m/s per kilometer. It is doubtful that this figure is entirely true because the larger caliber L15A5 APDS projectile fired from the 120mm L11 gun is known to decelerate at a rate of 61 m/s per kilometer, but unfortunately, this is the only known source of information on this topic for the 3BM8. In the absence of better information, there is no choice but to assume that the ballistic characteristics of 3BM11 are similar enough to 3BM8 that these figures apply.<br />
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All of the figures are calculated for an impact velocity of 1,500 m/s. For 3BM11, this corresponds to a distance of 1 km. From the graph, it is shown that the penetration of 3BM11 into RHA at this distance is 400mm at 0 degrees, 370mm at 30 degrees, 310mm at 45 degrees, 150mm at 60 degrees, 100mm at 70 degrees, and 40mm at 80 degrees.<br />
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The graph on the left shows the actual penetration of the munitions across the range of target plate angles, and the graph on the right shows the penetration of the munitions in terms of actual line-of-sight thickness. Based on this data, it can be seen that the performance of 3BM11 actually increases gradually as the target obliquity increases from 0 degrees to around 41 degrees, after which a rapid drop is observed. The decay in penetration performance plateaus as the impact angle reaches 70 degrees, but it plummets again until 82 degrees is reached where it is presumably guaranteed to ricochet.<br />
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<a href="https://1.bp.blogspot.com/-VUjZ15hroqw/XEVxE_XlsuI/AAAAAAAANGA/esMJOWqvyiA737aJbM5ZQhiyIG3X9miiACLcBGAs/s1600/penetration%2Bcomparison.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="868" data-original-width="1600" height="346" src="https://1.bp.blogspot.com/-VUjZ15hroqw/XEVxE_XlsuI/AAAAAAAANGA/esMJOWqvyiA737aJbM5ZQhiyIG3X9miiACLcBGAs/s640/penetration%2Bcomparison.png" width="640" /></a></div>
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3BM11 was evaluated against spaced armour with various plate and air gap thickness configurations. The flash photographs below show the result of 3BM11 defeating a two-layer spaced armour pack set at 30 degrees with an 80mm RHA front plate, a 60mm air gap and a 20mm RHA back plate. The velocity limit of defeat was 1,230 m/s.<br />
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<a href="https://3.bp.blogspot.com/-YBvL302uRHQ/XEVnVuhojHI/AAAAAAAANFM/mV0zqjbW27AgQQMvf7zyMD5AxjPh7Z66wCLcBGAs/s1600/80%2B%252B%2B20%2Bspaced%2Barmour.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1357" data-original-width="1237" height="400" src="https://3.bp.blogspot.com/-YBvL302uRHQ/XEVnVuhojHI/AAAAAAAANFM/mV0zqjbW27AgQQMvf7zyMD5AxjPh7Z66wCLcBGAs/s400/80%2B%252B%2B20%2Bspaced%2Barmour.png" width="363" /></a></div>
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It can be seen that the addition of an 80mm air gap between a 100mm RHA front plate and a 200mm RHA back plate increases the relative effectiveness of the armour by 40% and effectively renders the target proof against 3BM11 except at point blank range as an impact velocity of 1,622 m/s is required to defeat it.<br />
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<a href="https://4.bp.blogspot.com/-cKc7u4Y2dAE/XEVo_BV1HvI/AAAAAAAANFc/eCzBjujI3sQ4WSypE-iJ9e0cPAgdJtbcgCLcBGAs/s1600/penetration%2Binto%2Bspaced%2Btargets.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1008" data-original-width="1600" height="402" src="https://4.bp.blogspot.com/-cKc7u4Y2dAE/XEVo_BV1HvI/AAAAAAAANFc/eCzBjujI3sQ4WSypE-iJ9e0cPAgdJtbcgCLcBGAs/s640/penetration%2Binto%2Bspaced%2Btargets.png" width="640" /></a></div>
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The test result from the shelling of the first two-layer spaced armour configuration listed in the table (20-300-200) is shown in the photo below. The photo on the top shows the crater in the 200mm RHA back plate after it successfully stopped the APDS round at an impact velocity of 1,393 m/s. The photo on the bottom shows the perforation channel of the APDS round in the 200mm RHA back plate at an impact velocity of 1,429 m/s. This test data confirms that the calculated velocity limit of 1,413 m/s for the spaced armour configuration is correct. The second spaced armour configuration with a larger air gap is not significantly more effective than the first, despite the increase in the air gap size by 217%. However, both are 40% more effective than a homogeneous 220mm RHA plate, showing that 3BM11 is sensitive to relatively light spaced armour screens.<br />
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<a href="https://3.bp.blogspot.com/-CdkktkXzZm0/XEVusyzHXGI/AAAAAAAANF0/Mb1pmS1dCvAzanqT5ft7-i4R-UqYuuM2ACLcBGAs/s1600/photographic%2Bevidence%2B20%2B%252B%2B200.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1588" data-original-width="1066" height="400" src="https://3.bp.blogspot.com/-CdkktkXzZm0/XEVusyzHXGI/AAAAAAAANF0/Mb1pmS1dCvAzanqT5ft7-i4R-UqYuuM2ACLcBGAs/s400/photographic%2Bevidence%2B20%2B%252B%2B200.png" width="267" /></a></div>
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But besides simply illustrating the effectiveness of 3BM11 on various spaced armour targets, the table also gives the velocity limits for homogeneous armour plates of the same armour weight. For example, the 20-300-200 spaced armour weighs the same amount as a solid 220mm RHA plate, and the table shows that a 220mm RHA plate can be defeated at an impact velocity of 1,000 m/s.<br />
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From the table, it can be seen that a 300mm RHA dual-layered block made by stacking a 100mm RHA plate on top of a 200mm RHA plate is actually marginally more effective at stopping 3BM11 compared to a solid homogeneous 300mm RHA block; while a solid 300mm block can be defeated at an impact velocity of 1,220 m/s, a dual-layered block can only be defeated at 1,235 m/s. It is known that stacked plates can have a noticeable effect on solid steel AP and APC shots, but in this case, a difference of only 15 m/s indicates that 3BM11 is only negligibly affected.<br />
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<a href="https://2.bp.blogspot.com/-9uLpVF3_kZA/XEkxEuQVr-I/AAAAAAAANKM/CfnujxY6oqEbWPET6wkJLk5-vG_VqWuqgCLcBGAs/s1600/300mm%2Bplate%2Bdefeated.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1136" data-original-width="1217" height="372" src="https://2.bp.blogspot.com/-9uLpVF3_kZA/XEkxEuQVr-I/AAAAAAAANKM/CfnujxY6oqEbWPET6wkJLk5-vG_VqWuqgCLcBGAs/s400/300mm%2Bplate%2Bdefeated.png" width="400" /></a></div>
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At an impact velocity of 1,246 m/s, the 3BM11 core narrowly failed to fully perforate the target and left a large cracked bulge on the rear surface of the 200mm plate. This directly contradicts the data given in the table since 1,246 m/s is in excess of the 1,235 m/s perforation limit, but this can be explained by the fact that the penetration path of the projectile deviated from the perpendicular axis while travelling through the second plate. This phenomenon can be attributed to a few factors such as the possible heterogeneity of the plate quality, quality variances in individual penetrator cores, the sturdiness of the testing rigs, and more.<br />
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At an impact velocity of 1,272 m/s, the 3BM11 core successfully defeats the target as expected, leaving a hole in the plate equivalent to the tungsten penetrator core in diameter. The penetration path is more or less completely straight. Based on the available information, the limit velocity of 1,235 m/s corresponds to a distance of 3.5 kilometers. This shows that the reported penetration of only 300mm or 320mm RHA at 2 km is nowhere near the actual limit of the performance of 3BM11.<br />
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<a href="https://4.bp.blogspot.com/-YspXH47Eb70/XEVqp8OACVI/AAAAAAAANFo/imyTBvY4Gig01aLGM5af6ZvsHVNdSh7eACLcBGAs/s1600/penetration%2Binto%2Bspaced%2Btargets%2B30%2Bdegrees.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1320" data-original-width="1600" height="329" src="https://4.bp.blogspot.com/-YspXH47Eb70/XEVqp8OACVI/AAAAAAAANFo/imyTBvY4Gig01aLGM5af6ZvsHVNdSh7eACLcBGAs/w400-h329/penetration%2Binto%2Bspaced%2Btargets%2B30%2Bdegrees.png" width="400" /></a></div>
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<h3>
<span style="font-size: large;">COAXIAL, ANTI-AIRCRAFT MACHINE GUNS</span></h3>
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<span style="font-size: large;">DShKM</span></h3>
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<a href="https://4.bp.blogspot.com/-WkEeYUddFbg/W856sCUWB4I/AAAAAAAAMao/g6OuhJLAAm4KAmKs5xGV_B3CgM7IWVm7gCLcBGAs/s1600/dshkmt.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="369" data-original-width="1600" height="146" src="https://4.bp.blogspot.com/-WkEeYUddFbg/W856sCUWB4I/AAAAAAAAMao/g6OuhJLAAm4KAmKs5xGV_B3CgM7IWVm7gCLcBGAs/s640/dshkmt.png" width="640" /></a></div>
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The T-10 was equipped with a DShKM heavy machine gun as its co-axial machine gun. The DShKM is an open-bolt single-feed heavy machine gun chambered in the 12.7x108mm cartridge. To fit the machine gun into the gun mask, the front and rear sight blocks were removed, although tanks in museums often seem to have DShKMs with the rear sight block intact. Its great length of 1,588mm and prominent muzzle brake meant that a considerable portion of its barrel had to protrude rather openly outside the gun mask, and due to the gas vent of its long-stroke gas mechanism, the machine gun had to be positioned so that it vents out through the gap between the gun mask and the turret, and the turret seal of the coaxial port is fitted behind the gas vent. It has a barrel length of 967mm and a total barrel length of 1,069 with the large muzzle brake included. The cyclic rate of fire is 600 rounds per minute. This is similar to contemporary machine guns like the M2HB and not inferior to most 7.62mm machine guns, but in practice, the practical rate of fire is expected to be lower than a small caliber machine gun for various reasons, the primary one being the more limited ammunition supply. When installed in the T-10, the large muzzle brake of the DShKM protrudes prominently outside the gun mask as shown in the photo below (from "<i>T-10 Heavy Tank and Variants</i>" by James Kinnear and Stephen Sewell). </div>
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<a href="https://1.bp.blogspot.com/-5SC6AQ5SlHw/XEFAPFJE5LI/AAAAAAAANAU/qocirK5HJKgNm8PZCjZbRoj_rSq9h9SQwCLcBGAs/s1600/coaxial.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="916" data-original-width="1412" height="414" src="https://1.bp.blogspot.com/-5SC6AQ5SlHw/XEFAPFJE5LI/AAAAAAAANAU/qocirK5HJKgNm8PZCjZbRoj_rSq9h9SQwCLcBGAs/s640/coaxial.png" width="640" /></a></div>
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A total of a thousand rounds of 12.7mm ammunition is carried in the tank. 50 rounds are provided in a single non-disintegrating steel belt held in a box, of which six are carried in ready racks. The anti-aircraft machine gun is supplied with a 150 in three boxes. The ammunition boxes for the two machine guns are not interchangeable since the coaxial DShKM feeds from the right whereas the anti-aircraft DShKM feeds from the left, and the types of rounds contained within them are not the same. An additional 550 of reserve ammunition is carried in zinc boxes. These zinc boxes are stowed at the rear of the hull. In order to use the reserve ammunition supply, the loader must collect expended belts or obtain empty belts from somewhere else, reload them with the loose cartridges from the zinc boxes, and lay them into empty ammunition boxes. The main drawback of the DShKM is the limited ammunition capacity compared to an SGMT which is fed from 250-round boxes. With only 50 rounds at the gunner's disposal, the machine gun is limited to a practical rate of fire of 80 rounds per minute. The 11 kg weight of the large 50-round boxes for the DShKM is also greater than the 9.4 kg weight of the 250-round boxes for the SGMT, making them somewhat more difficult to handle inside the confines of a tank.<br />
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<a href="https://1.bp.blogspot.com/-y0OfvpQ0ytU/XQVDgIXW2HI/AAAAAAAAOdA/H-a6MWSsj58C4l1ZWzrKIvGIuovTxgrzACLcBGAs/s1600/dshkm%2Bammo%2Bbox.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="820" data-original-width="656" height="320" src="https://1.bp.blogspot.com/-y0OfvpQ0ytU/XQVDgIXW2HI/AAAAAAAAOdA/H-a6MWSsj58C4l1ZWzrKIvGIuovTxgrzACLcBGAs/s320/dshkm%2Bammo%2Bbox.png" width="256" /></a><a href="https://1.bp.blogspot.com/-I_Ncsii4ycM/XM9IlL0GZbI/AAAAAAAAN44/_HJcKOReLpIBDj7zCqWpbMtTQ3089rGVACLcBGAs/s1600/dshk%2B50-round%2Bbox.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="358" data-original-width="500" height="285" src="https://1.bp.blogspot.com/-I_Ncsii4ycM/XM9IlL0GZbI/AAAAAAAAN44/_HJcKOReLpIBDj7zCqWpbMtTQ3089rGVACLcBGAs/s400/dshk%2B50-round%2Bbox.jpg" width="400" /></a></div>
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The barrel of the DShKM is removable, but it is not possible to do so while the weapon is locked in its coaxial mount. In fact, it is not possible to remove it from inside the tank without exiting. This is because the large muzzle brake is larger than the machine gun port, so removing the machine gun requires the prior removal of the muzzle brake from outside the tank.<br />
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<a href="https://1.bp.blogspot.com/-XRfQ0UD5P5M/W86o7Kv549I/AAAAAAAAMbI/AhSpi-A64Yghz0NfhxPn7v9E9GD0g6hfACLcBGAs/s1600/dshkmt.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="178" data-original-width="523" src="https://1.bp.blogspot.com/-XRfQ0UD5P5M/W86o7Kv549I/AAAAAAAAMbI/AhSpi-A64Yghz0NfhxPn7v9E9GD0g6hfACLcBGAs/s1600/dshkmt.jpg" /></a></div>
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<a href="https://1.bp.blogspot.com/-HHEKuErPVPQ/W858DhTyPSI/AAAAAAAAMa8/SPGU56rHJpYnZdkQdTZLKA43XTQ01t5IQCLcBGAs/s1600/t-10%2Bcoax.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1021" height="300" src="https://1.bp.blogspot.com/-HHEKuErPVPQ/W858DhTyPSI/AAAAAAAAMa8/SPGU56rHJpYnZdkQdTZLKA43XTQ01t5IQCLcBGAs/s400/t-10%2Bcoax.png" width="400" /></a></div>
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The concept of installing a coaxial large caliber machine gun to supplement the main cannon was not new by the time the T-10 began development; the IS-4 had a DShKM as its coaxial weapon and the IS-7 was armed with the particularly powerful KPVT together with a rather excessive number of external 7.62mm machine guns. However, it was by no means a standard practice for Soviet heavy tanks as the IS-2 and IS-3 both had a 7.62mm DTM coaxial machine gun.</div>
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<a href="https://1.bp.blogspot.com/-fHVc6CMbQUg/XEWA4r8KseI/AAAAAAAANGQ/IJUuCYNYxLA993iUZZNDu6kUuOdv4hppgCLcBGAs/s1600/dshkmt%2Bcoaxial%2Bt-10.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="890" data-original-width="1600" height="354" src="https://1.bp.blogspot.com/-fHVc6CMbQUg/XEWA4r8KseI/AAAAAAAANGQ/IJUuCYNYxLA993iUZZNDu6kUuOdv4hppgCLcBGAs/s640/dshkmt%2Bcoaxial%2Bt-10.png" width="640" /></a></div>
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The DShKM retains the same basic functionality as a DTM or SGMT machine gun, but unlike a 7.62mm machine gun, it is suitable for engaging troops behind cover and thin-skinned vehicles at longer distances by virtue of its more powerful cartridge. However, a 12.7mm machine gun is less efficient against troops in the open as the practical rate of fire is lower due to the small ammunition capacity and limited ammunition supply. Even though a direct hit from a 12.7mm bullet of any type is instantly lethal, a direct hit from a 7.62mm bullet achieves practically the same effect and the volume of fire from a 7.62mm machine gun can be much higher, so the probability of scoring a direct hit tends to be higher as well. The DShK was also not originally designed to be used in enclosed combat vehicles, unlike the American M85. Its large width of 161mm was not a problem for external mounts but it took up a lot of space inside a tank, and its operating mechanism was not designed with confined spaces in mind. Nevertheless, it was a robust weapon and it was not troublesome in use.<br />
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Standard B-32 armour-piercing incendiary (AP-I) and BZT armour-piercing incendiary tracer (API-T) rounds were provided for the coaxial DShKM. B-32 and BZT bullets contain 1.03 grams (16 grains) of aluminium-magnesium-barium nitrate incendiary compound in the tip. The mass of the incendiary compound in both bullets is substantially greater than the <a href="https://sites.google.com/site/britmilammo/-50-inch-browning/-50-browning-observation">0.84 grams (13 grains) of magnesium-barium nitrate incendiary compound contained in the British .50 caliber L11A1 and L13A1 spotting bullets</a> used in the British Centurion and Chieftain and is marginally greater than the 0.97 grams of <a href="https://fas.org/man/dod-101/sys/land/bullets3.htm">aluminium-magnesium-barium nitrate incendiary compound (IM 11)</a> contained in the American .50 caliber API-M8 bullet. Beginning in 1954, the B-32 obr. 1954 bullet was slightly lengthened to accommodate an additional incendiary charge behind the steel core to improve the damage inflicted on targets behind armour plates. Combined with the sparking from the impact of the steel core, B-32 rounds could generate an exceptionally good flash signature on hard targets, particularly metal ones. </div><div><br /></div><div>For the coaxial DShKM, the AP-I and API-T rounds are fed in a 3:1 ratio, or in other words, there are three B-32 bullets for every BZT bullet in a standard belt. This is the standard configuration for coaxial machine guns and is similar to the 4:1 mix of M8 AP-I and M20 API-T carried by American tanks, and indeed, similar to any other machine gun. The BZT bullet has a tracer burnout range of 1,500 meters. It is worth noting that without tungsten-cored ammunition, the capabilities of the standard ammunition mix are relatively limited against armoured personnel carriers designed with frontal protection against 12.7mm machine guns. In "<i>Современные Отечественные Патроны, Хроники Конструкторов</i>", the fourth book of the four-part monograph "<i>Боевые Патроны Стрелкового Оружия</i>" by the ballistician V.N. Dvoryaninov, the calculated probability of knocking out an M113 with 7 hits of 12.7mm fire from the front was provided for three different belt compositions to evaluate the usefulness of including tungsten-cored 12.7mm AP-I bullets.<div><br /></div><div><ul style="text-align: left;"><li>Belt option 1 - 3x B-32, 1x BZT-44 (standard belt mix)</li><li>Belt option 2 - 1x B3S, 2x B-32, 1x BZT-44</li><li>Belt option 3 - 3x B3S, 1x BZT-44</li></ul></div><div><br /></div><div>With these three options, the following probabilities of defeat were calculated.</div><div><br /></div><div><table border="1"><tbody><tr><th> Distance (m) </th><th> Belt 1 </th><th> Belt 2 </th><th> Belt 3 </th></tr><tr><td style="text-align: center;">100</td><td style="text-align: center;">0.57</td><td style="text-align: center;">0.68</td><td style="text-align: center;">0.83</td></tr><tr><td style="text-align: center;">200</td><td style="text-align: center;">0</td><td style="text-align: center;">0.31</td><td style="text-align: center;">0.67</td></tr><tr><td style="text-align: center;">300</td><td style="text-align: center;">0</td><td style="text-align: center;">0.12</td><td style="text-align: center;">0.33</td></tr><tr><td style="text-align: center;">400</td><td style="text-align: center;">0</td><td style="text-align: center;">0.10</td><td style="text-align: center;">0.27</td></tr></tbody></table></div><br /><div>As the table shows, a typical burst from a DShKM will be effective on an M113 from the front only at a distance of 100 meters or less. Beyond 100 meters, fire from the machine gun is ineffective without BS or B3S tungsten-cored ammunition, but even so, if the steel-cored AP-I is not fully exchanged for tungsten-cored AP-I on a one-to-one basis, the effectiveness will still be quite low at extended ranges. The coaxial DShKM can only be considered effective against armoured personnel carriers if the T-10 gunner has the opportunity to fire upon the flanks. </div><br />
On a flat RHA target, the armour penetration capability of the 12.7mm B-32 bullet is directly equivalent to .50 caliber APM2 fired from an M2 Browning and is slightly superior to .50 caliber API-M8 and APIT-M20. The APM2 bullet travels at a muzzle velocity of 894 m/s and has a 25.9 gram steel core whereas the B-32 bullet travels at a muzzle velocity of 840 m/s and has a 30.0 gram steel core. The diameter of the steel cores of both bullets is 10.8mm, and as such, the B-32 bullet has a larger sectional density. Unsurprisingly, the larger sectional density and the larger elongation of the B-32 bullet granted it a higher ballistic coefficient, providing better energy retention at distance. Case in point - the impact energy of the APM2 bullet at 914 meters (1,000 yards) is 6,544 J, whereas B-32 has an impact energy of 7,000 J. This can also be observed in the maximum ranges of the B-32 compared to APM2 - the B-32 bullet fired from a DShK can travel up to 7,000 meters, whereas an M2 bullet fired from an M2HB can travel 6,583 meters (7,200 yards). The main advantage of APM2 is at shorter ranges, where its higher muzzle velocity grants a shorter time of flight and a flatter trajectory. For instance, the time of flight to 500 meters is 0.69 seconds for the B-32, but an M2 bullet takes 0.64 seconds to reach the same distance, and while the maximum ordinate of a B-32 bullet at 500 meters is 0.55 meters, the maximum ordinate of an M2 bullet at the same range is 0.5 meters.</div><div><br /></div><div>Information on the penetration power of the 12.7mm B-32 and BZT bullets is available in a 1971 USAARMDL handbook titled "<i>Survivability Design Guide For U.S Army Aircraft Volume II: Classified Data for Small-Arms Ballistic Protection</i>".<br />
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From the table on the left, it can be seen that the penetration of the B-32 bullet at its muzzle velocity in RHA is 29.5mm (1.16") at 0 degrees, 21.8mm (0.86") at 30 degrees, 14.2mm (0.56") at 45 degrees, and 9.1mm (0.36") at 60 degrees. The penetration performance of the BZT bullets is much lower due to the presence of a tracer, as shown in the table on the right. Besides this, it is stated on page 6 of the March 1998 issue of the "<i>Техника И Вооружение</i>" magazine that the penetration of B-32 at a 0 degree angle is 20mm at 350 meters which aligns perfectly with the penetration table, but it is also stated that the BZT bullet achieves the same penetration at a slightly shorter distance of 300 meters which is plainly impossible.<br />
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For comparison, the .50 caliber M2 AP round penetrates 30.5mm of RHA steel at its muzzle velocity of 2,935 ft/s when fired from the 45-inch barrel of an M2HB machine gun under the Navy criterion (full bullet passage through armour plate). Its penetration drops to 19.1mm (0.73") at 30 degrees, 12.7mm (0.5") at 45 degrees, and only 6.35mm (0.25") at 60 degrees. As such, the penetration power of the M2 AP bullet is comparable to the B-32 bullet at 0 degrees, but falls short as the target obliquity increases.<br />
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<div><br /></div><div><br /></div>However, Russian testing of the two bullets on 20mm plates of 2P high hardness steel (MIL-DTL-46100 grade) set at 0 degrees revealed that the M2 bullet has a slight advantage, being able to perforate it at a distance of 450 meters whereas the B-32 bullet manages to do so at 400 meters. Against the same 20mm plate of 2P steel but angled at 20 degrees, the M2 requires a range of 100 meters, but B-32 requires the range to be at point blank (muzzle velocity) to achieve perforation. The V80 standard was used for these tests, requiring that 80% of the bullets could achieve a full perforation instead of only 50% under the V50 standard used by foreign nations. This can be attributed to the fact that the core of the B-32 is made of high hardness carbon steel, rather than the high hardness alloy steel of the APM2 bullet. On softer metal plates less capable of breaking up impacting bullets, B-32 has the advantage. <br /><br />
At 100 meters, the penetration of the B-32 bullet is 26.9mm (1.06") in RHA. However, the 12.7mm B-32 bullet is credited with only 20mm of penetration at 100 meters according to Russian literature. This is because of a difference in the standards used to evaluate penetration performance. This Russian figure is a guaranteed minimum where 90% of all bullets will perforate a 20mm RHA plate at the specified distance and 75% of perforations will ignite 70 octane petrol (Soviet grade B-70) placed behind the plate. The U.S Army uses a V50 rating system where only 50% of hits are required to fully perforate the target. This is typically done with six shots where three complete perforations (a 0.5mm aluminium sheet placed six inches behind the target plate must be pierced) and three partial perforations (bulge or crack at the rear of the target plate) are achieved.<br />
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But besides its armour penetration power and incendiary effects, it is also worth noting that 12.7mm B-32 should be able to defeat a typical single-layer sandbag fortification from around 200 meters which is not possible for a 7.62mm bullet to achieve from any distance. As an example, it is noted in manuals for the M2 machine gun series such as the training document TC 3-22.50 (shown below) that protection from a single shot of .50 cal AP or API-T at 200 meters requires 3 layers of 8 to 10-inch sandbags. Rocks, logs, berms and other forms of natural cover that would otherwise be largely impervious to a burst of 7.62mm bullets are also more readily defeated by 12.7mm rounds. Rapid demolition of brick and concrete structures barring thick reinforced concrete bunkers also became possible thanks to the increased caliber of the coaxial machine gun. Rather than simply suppressing concentrations of entrenched enemy infantry with little hope of scoring a direct hit, a large caliber machine gun combines a powerful psychological effect with a much more tangible destructive effect.<br />
<br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-alpN_N0WbIE/YVMkURV6OXI/AAAAAAAAUQo/dDSPahQPK84ogN3pvWIMc45IsiEYpa_cwCLcBGAsYHQ/s958/protection%2Brequirements.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="686" data-original-width="958" height="458" src="https://1.bp.blogspot.com/-alpN_N0WbIE/YVMkURV6OXI/AAAAAAAAUQo/dDSPahQPK84ogN3pvWIMc45IsiEYpa_cwCLcBGAsYHQ/w640-h458/protection%2Brequirements.png" width="640" /></a></div><br />
However, the primary practical incentive to mount a large caliber machine gun as a coaxial weapon instead of a typical 7.62mm machine gun was to conserve the limited supply of 122mm ammunition available in the tank by providing a useful alternative against light fortifications, structures and lightly armoured vehicles. Given the opportunity, the DShKM would likely have been used to great effect against many lightly armoured vehicles including prime movers, utility vehicles as well as several early Cold War armoured personnel carriers like the M59 and Alvis Saracen, not to mention a wide variety of other vehicles that would probably have been pressed into service in the 1950's if another European conflict flared up. Notable examples include the M3 half-track and Universal Carrier, both of which were very numerous and rather lightly armoured. However, later types such as the American M113 armoured personnel carrier would be a somewhat more challenging target as the 12.7mm caliber had insufficient power to reliably defeat the frontal armour of the M113 and FV432 from beyond 200 meters. According to various Soviet and Russian sources, the maximum effective range of the DShKM on lightly armoured vehicles is claimed to be 500 meters.<br />
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The merits of a heavy machine gun as a coaxial weapon were explored outside of the Soviet Union by practically every major military. The U.S Army made an effort to arm their medium and heavy tanks with a .50 caliber M2HB machine gun alongside the standard M1919 but when the M47 and M103 (both with dual coaxial machine gun mounts) entered service, the M1919 was installed exclusively in practice. The French Army went ahead and armed their AMX-30 main battle tank with a .50 M2HB caliber coaxial machine gun before eventually upgrading it to a 20mm autocannon on the AMX-30B in 1972. Early prototypes of the British Centurion Mk. 1 medium tank were armed with a Polsten 20mm autocannon in an independently elevated mount, but this was scrapped fairly quickly in favour of a 7.92mm BESA machine gun. These mixed results came about due to the lack of an incentive for these tanks to have anything larger than a .30 caliber machine gun for a coaxial weapon since they generally had a plentiful supply of main gun rounds which they could afford to expend on lightly armoured vehicles and a .30 caliber machine gun was enough for practically everything else.<br /></div><br />
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<span style="font-size: large;">ANTI-AIRCRAFT DShKM</span></h3>
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For anti-aircraft work, there is a pintle-mounted DShKM machine gun on a gun cradle attached to the rotating loader's cupola. This is the same design as the loader's cupola of the T-54 obr. 1951 and the anti-aircraft machine gun mount and cradle are interchangeable. As mentioned before in this article in the section on the T-10 loader's station, the pintle attached to the loader's cupola is fixed in place. The machine gun mount is installed in the pintle by simply putting its base pin into the pintle slot and then tightening the pintle clamp. The machine gun can be elevated by 85 degrees and depressed by -5 degrees, making it a useful tool against both ground targets and air targets. Besides the infrared spotlight on the commander's cupola, there are no obstructions on the turret roof to prevent the machine gun from being fully depressed, so the loader is largely guaranteed a free field of fire in azimuth.<br />
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The machine gun mount can be swiveled in a full 360-degree arc about its axis on the pintle, and it can be locked facing any direction. If the machine gun is locked facing backward, it will not overhang the turret so it is less likely to snag onto any obstacles, but it will block the opening of the hatch. Locking it in the forward position allows the loader to aim and fire the machine gun from a natural position out of his hatch. The photo below from "<i>T-10 Heavy Tank and Variants</i>" by James Kinnear and Stephen Sewell shows the loader's cupola with its pintle.<br />
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To aim the machine gun in azimuth, the loader must rotate his entire cupola with his own bodily strength, and to aim it in elevation, the elevation hand wheel is worked to move the machine gun along a toothed arc. There is also a braking mechanism on the elevation hand wheel that acts as an elevation lock for the machine gun. It is actuated by a lever on the handle of the wheel that releases the brake when pressed to allow the machine gun to be elevated and depressed, so once the loader has aimed at a fixed target, he should release the lever to lock the machine gun in place before opening fire for maximum accuracy.<br />
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The loader fires the machine gun by depressing the trigger lever on the fixed handle on the left of the gun mount which pulls on a Bowden cable connected to the trigger on the back of the DShKM receiver. Since the DShKM still retains its spade grips and its original finger trigger when mounted in this configuration, it can be fired manually if needed and it can be used if it is dismounted from the machine gun cradle.<br />
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Due to the cantilever installation of the DShKM, the gun cradle has a pair of large equilibrator springs to ensure that the machine gun can be elevated with a uniform effort throughout its entire 90-degree range. Photo on the left by <a href="http://www.armorjournal.com/index-tanks-T-10-Kubinka.php">Yuri Maltsev from the Armor Journal website</a>.<br />
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The cyclic rate of fire of 600 rounds per minute made the DShKM an adequate weapon for anti-aircraft purposes, but it was inferior to the American M85 in this regard as the M85 had an adjustable rate of fire and it could be set to fire at 800-950 rounds per minute; up to 50% faster than the DShKM. The limited supply of 50 rounds per ammunition box may have been a detriment to the practical rate of fire of the machine gun as there would be too few rounds to put out sustained fire against low-flying aircraft. It may not be an issue when firing at any aircraft making a pass at a short distance as the operator can afford to empty the entire box in one long burst and he will manage to reload before the aircraft comes for another pass. Since the aircraft only appears intermittently, the maximum volume of fire can delivered against it whenever it is needed. It is another matter when firing at ground targets because the time spent reloading generally has a much more direct impact on the volume of fire delivered to the enemy.<br />
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Aiming at ground targets is accomplished with either the standard iron sights on the DShKM or the K-10T anti-aircraft collimator sight. The K-10T facilitates accurate aiming at both ground level and high altitude targets, although the basic leaf sights on the machine gun itself would be more appropriate for aiming at ground targets as it can be adjusted for various distances. According to the manual, the K-10T should be zeroed for a distance of 400 meters. Fire correction would only be possible by observing the fall of the tracers and using the elevation scales in the reticle as a reference. The sight has a tinted screen in front of the collimator display to reduce glare. If it is not needed, it can be flipped down and out of the way. When flipped up, the screen darkens the background enough that there is a high enough contrast for the projected reticle to appear clearly in the operator's vision, allowing him to engage air targets with both eyes open.<br />
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<div><br /></div><div><br /></div><div>The reticle of the K-10T is illuminated via a light collecting lens, which receives environmental light from a front-facing lens and magnifies it to project an illuminated image onto the reflector, with which the operator aims. In low-light conditions, the operator must fit a special battery-powered lamp onto a purpose-built bracket in front of the light collector lens to provide an artificial source of light for the illuminated reticle. </div><div><br /></div><div>For anti-aircraft purposes, the collimator sight has an ideal design and location to provide the operator with a maximum field of view while allowing him to aim regardless of how he is positioned, which changes depending on the elevation angle of the machine gun, as the operator does not need to adjust his head to obtain a correct eye relief as with iron sights. The proper method of aiming with the sight is for the operator to keep both eyes open and look through the sight with his his right eye, allowing his brain to perceive the projected sight reticle in his vision through both eyes. Moreover, as long as the right eye is used to aim and there is 165-250mm of eye relief, the operator's field of view is not obstructed by the stowage box next to the sight. </div>
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The anti-aircraft DShKM uses a different belt with AP-I, API-T and HEI-T rounds in a 1:3:1 ratio.</div>
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<span style="font-size: large;">KPVT</span></h3>
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The KPVT is an open-bolt single-feed heavy machine gun, replacing the DShKT as the coaxial machine gun in the T-10M. It fires the 14.5x114mm cartridge at a cyclic rate of 550-600 rounds per minute. It has a barrel length of 1,348mm, but the total length of the barrel including the conical flash hider and booster assembly is 1,496mm. When configured as the coaxial machine gun, the KPVT from the right and ejects spent casings downward. It can be fired using the control handles on the T2S-29-14 sight or using the firing button on the manual gun elevation handwheel.<br />
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The machine gun cycles by short recoil operation. The reciprocating barrel is shrouded by a rigid air-cooling jacket. Propellant gasses entering the booster assembly at the muzzle push the barrel against the end of the jacket, causing the barrel and barrel assembly to recoil backwards a short distance after every shot which unlocks the bolt and propels it rearward to cycle the feed system. The reciprocation of the barrel assembly also marginally reduces the recoil impulse of the machine gun and makes it more manageable on vehicle mounts, thus fulfilling a similar function as the large muzzle brake on the DShK series to a lesser degree without incurring the drawbacks, such as a large muzzle flash - which the DShK is quite famous for - and a loud firing signature. Additionally, the conical flash suppressor at the muzzle of the gun further reduces the muzzle flash, making it an equally subtle weapon as the DShK despite firing a much more powerful round. For the curious, <a href="https://youtu.be/B2zY6Vsb41s">this video shows the field disassembly of a KPVT</a> and <a href="https://www.youtube.com/watch?v=56kMk1XP2fQ">this video gives an in-depth examination of the machine gun</a> (in Russian)<br />
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A pair of shock absorber springs are integrated in the gun cradle for the KPVT on the coaxial mount. Part of the recoil force is damped by these shock absorbers, leading to reduced vibrations and increased firing accuracy. This is not an unusual feature for a coaxial machine gun mount, but for the KPVT, it has particular relevance as tight dispersion is crucial to attaining a long effective range on point targets, which is one of the main justifications of the increased power of the KPVT compared to the DShKM. </div><div><br /></div><div>One of the main features of the KPVT that differentiates it from the standard KPV infantry machine gun was its forward-ejection mechanism for spent cases, which was considered mandatory for machine guns adapted for tank usage. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-woLNOkBa-ek/XvUyHhNUFYI/AAAAAAAARKw/V7oBs_sT-Vc6jLU2Osy8dAkx-z5Kz41eQCK4BGAsYHg/s1200/KPVT%2Bejection%2Bport.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="565" data-original-width="1200" height="302" src="https://1.bp.blogspot.com/-woLNOkBa-ek/XvUyHhNUFYI/AAAAAAAARKw/V7oBs_sT-Vc6jLU2Osy8dAkx-z5Kz41eQCK4BGAsYHg/w640-h302/KPVT%2Bejection%2Bport.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The cases are ejected downward and pushed forward by a special lever. In a T-10M, the machine gun mount includes a special guide chute under the gun barrel that leads to an ejection port outside the tank, closed by a spring-loaded lid. This chute can be clearly seen in the drawing below. By ejecting spent cases out of the tank, the amount of clutter inside the fighting compartment is significantly reduced and the air contamination from propellant fumes is kept under control. <br />
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The coaxial mount is at the same location next to the gun breech assembly. Owing to its increased size, the KPVT takes up even more space inside the turret of the T-10M in both width and length compared to the DShKM. Its greater length of 2,007mm was only partially offset by having a larger portion of the long barrel exposed outside the gun mantlet, but the receiver of the machine gun still protrudes deeper into the turret compared to the DShKM.<br />
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As the coaxial machine gun, the KPVT is loaded and cycled manually by the loader. Cocking the bolt is done with a large spring-loaded cocking lever. To ready the KPVT for loading, the loader pulls the handlebar backward to pull the bolt to the cocked position. The spring tension assists the loader in overcoming the resistance of the recoil spring and it also keeps the cocking lever in the rearmost position. Then, to load the machine gun, the top cover is opened and the belt is inserted into the feed tray like any other belt-fed machine gun. Once the top cover is closed, the machine gun is ready to fire and the bolt does not need to be recocked for any subsequent reloads as it locks itself in the cocked position after the last shot. The machine gun cradle and the cocking lever can be seen in the photos below (<a href="http://www.kotsch88.de/al_T-10M.htm">courtesy of Stefan Kotsch</a>), although the spring for the cocking lever has been unhooked in the photo and the entire assembly appears worn and disheveled. Spent belt segments are collected in a metal bin placed directly underneath the machine gun. The collection bin is fixed, but there is a sliding trap door on the side to empty the bin when it is full. Again, this can be seen in the photos below.<br />
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The M62-T gun shown below lacks a bore evacuator and it is not fitted for stabilization like the M62-T2 gun, but it shares all of the other features found on the M62-T2. The spent link collector bin for the coaxial KPVT can be clearly seen hanging under the gun. This photo also makes it apparent that the coaxial KPVT machine gun is so long that it almost reaches the breech block opening on the side of the breech assembly. This was the reason why the loading assistance device control box had to be moved from its original position.<br />
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A total of 744 rounds of 14.5mm ammunition is carried in the tank. Of this amount, 200 rounds were provided for the coaxial machine gun and 250 rounds were provided for the anti-aircraft machine gun, all in 50-round boxes. All of the bullets and belts are interchangeable, but the boxes are not. Proprietary ammunition boxes with a distinct "lunch pail" shape were provided for the coaxial KPVT, which feeds from the right whereas the anti-aircraft KPVT feeds from the left and uses standard ammunition boxes. The peculiar ammunition boxes for the coaxial KPVT can be seen marked '21' and '25' in the drawing below. Also, the mix of bullet types for the coaxial and anti-aircraft machine guns are entirely different and may not be well-suited to different targets if exchanged. Another 294 rounds of ammunition are carried in sealed zinc tins as a reserve supply.</div><div>
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A ready supply of 200 rounds for the coaxial machine gun is not particularly large despite the high power of the 14.5mm caliber, but on the other hand, the ready supply for the anti-aircraft machine gun is quite plentiful relative to medium tanks like the T-54 series as those tanks carried a total of 300 rounds for their 12.7mm anti-aircraft machine guns. From another perspective, it could be argued that the total ready supply of 500 rounds for the T-10M is acceptable because is just one box shy of the full 500-round ammunition load for the KPVT of a BRDM-2 or a BTR-60PB, but these light vehicles also included a coaxial PKT machine gun with two thousands rounds of ammunition which invalidates the comparison. On the T-10M, it is quite likely for the entire supply of ammunition for the coaxial machine gun to be expended in a single engagement which would not have been a real problem for preceding tanks such as the IS-3, as that had a DTM for its coaxial machine gun with 756 rounds available at any time in 12 drums with another 1,244 rounds in sealed zinc tins in reserve stowage. On the other hand, the DTM was not an ideal tank machine gun either - experience had shown that it could not provide a sufficient volume of fire due to the relatively small capacity of its 63-round drums and the rapid overheating of the barrel.<br />
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Interestingly enough, issues with the ammunition capacity were recognized very early on. The Object 265 experimental prototype was developed from 1952 to 1953 and several samples were built in 1954 to explore alternative armament options for the T-10. It incorporated two coaxial machine guns: a KPVT and an SGMT - a bona fide belt-fed 7.62mm machine gun. A thousand rounds of ammunition would be carried for the SGMT in 250-round boxes, but the total quantity of 14.5mm ammunition dropped to just 510 rounds. The prototypes passed their state trials, but it was never disclosed if the dual coaxial setup was a more effective alternative to the single KPVT that was finally chosen for the T-10M.<br />
<br /></div><div>Although the cyclic rate of fire of the KPVT is 550-600 rounds per minute, the practical rate of fire is officially listed as 70-80 rounds per minute in the manual. The practical rate is achieved by limiting fire to short bursts of 2-5 rounds. When necessary, long bursts of up to 20 rounds against ground targets may be used, and when engaging aerial targets, the machine gun is fired in long bursts exclusively. For a KPV used in its infantry mount and a KPVT used in a BTR turret, continuous full automatic fire is permitted up to 150 rounds, after which it is necessary to let the barrel cool. However, the barrel jacket of the KPVT mounted in a T-10M is almost entirely recessed inside the turret with most of its length enshrouded by armour. As such, there is almost no flowing air to cool the barrel and hardly any room for convection to occur. Because of this, it is likely that the heat limit of its barrel is less than 150 rounds in continuous fire.</div><div><br /></div>
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In recognition of the issues with the DShKM mount in earlier T-10 models, the inability to remove the machine gun from inside the tank was corrected by implementing a coaxial machine gun port with a larger diameter on the T-10M mask casting. No special design solution was needed because the flash hider of the KPVT has the same diameter as the barrel jacket, making it a simple matter to extricate or install the machine gun in the mount from inside the tank. During snorkeling operations, the KPVT is removed from its mount and a protective watertight cover is closed over the port opening. The photo on the left below is by <a href="http://svsm.org/gallery/t-10/IMGP0477">Vladimir Yakubov</a> and the photo on the right below is by <a href="http://www.kotsch88.de/al_T-10M.htm">Stefan Kotsch</a>. <span style="white-space: pre;">Both photos also show the spring-loaded lid for the spent case ejection port underneath the KPVT barrel.</span></div><div>
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<a href="https://1.bp.blogspot.com/-iwg7RdXuBmk/XEowhA5exKI/AAAAAAAANMc/lAyuuF3jKvovcaonw0PqqHfKBt3svr5EgCLcBGAs/s1600/kpvt%2Bport.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://1.bp.blogspot.com/-iwg7RdXuBmk/XEowhA5exKI/AAAAAAAANMc/lAyuuF3jKvovcaonw0PqqHfKBt3svr5EgCLcBGAs/s400/kpvt%2Bport.jpg" width="400" /></a><a href="https://4.bp.blogspot.com/-oIWARDSYHbA/XEEZ7_seE2I/AAAAAAAAM_g/3fX5s3zmnyom5ZJ4HZPwRMzSQzA48NWpwCLcBGAs/s1600/kpvt%2Bcover%2Bclosed.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://4.bp.blogspot.com/-oIWARDSYHbA/XEEZ7_seE2I/AAAAAAAAM_g/3fX5s3zmnyom5ZJ4HZPwRMzSQzA48NWpwCLcBGAs/s400/kpvt%2Bcover%2Bclosed.JPG" width="400" /></a></div>
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The upgrade to the KPVT was largely influenced by the upgrade to the more powerful M-62T2 cannon which fired full caliber rounds at a higher muzzle velocity than the D-25T series. With a muzzle velocity of 1,000 m/s, the ballistic trajectory of the bullets fired from the KPVT were a close match for the OF-472 shells up to a distance of 1.2 km. As such, the upgrade from the DShKM to the KPVT was not simply for the sake of having more firepower, but was done with practical considerations for the fire control and armament of the tank as a holistic system.<br />
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The bullet types supplied for the coaxial KPVT included the 57-BZ-561S cartridge with the B-32 bullet containing a hardened steel core (AP-I), the 57-BZT-561 cartridge with the BZT bullet containing a downsized hardened steel core and a tracer (API-T), the 57-BZ-562 cartridge with the BS-41 bullet containing a tungsten-carbide (cermet) core (AP-I), and the 57-BZT-562 cartridge with the BST bullet containing a downsized tungsten carbide core and a tracer (API-T). Like the DShKM coaxial machine gun of previous T-10 models, the AP-I and API-T rounds are linked in the same 3:1 ratio in a standard belt for the KPVT. There are no specific instructions on how the bullet types are mixed, but the ballistics of the steel-cored bullets are distinct from the cermet-cored bullets and the tracer bullets only correspond to AP-I bullets of the same core material. As such, a standard mix will either consist of a ratio of three B-32 bullets and one BZT bullet or three BS-41 bullets and one BST bullet. In practice, the types of bullets encountered in combat will depend on availability. The four bullet types can be seen in <a href="http://patronen.su/forum/gallery/2-101214221343.jpeg">this collection of sectioned cartridges</a>. The drawings shown below, courtesy of <a href="https://milimoto.wordpress.com/2019/03/04/pociski-smugowe-w-ukladzie-warszawskim-czesc-2/">Przemysław Konicki</a>, show good cross-section drawings of the four main bullet types used in the KPVT together with a ZP (I-T) bullet which is only used in the anti-aircraft gun.<br />
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The B-32 bullet contained 1.3 grams of aluminium-magnesium-barium nitrate incendiary compound in the tip and the BZT bullet contained 1.56 grams of the same incendiary compound, which is substantially more than the 0.84 grams of magnesium-barium incendiary compound in .50 caliber spotting rounds. The tracer of the BZT bullet burns out at 2,000 meters. These characteristics made the KPVT an excellent ranging machine gun as the flash of the impact would be more visible at long distances and in poor weather conditions.<br />
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The BS-41 bullet also contained 1.3 grams of aluminium-magnesium-barium nitrate incendiary compound in the tip. The BST bullet had an incendiary charge of the same mass in the tip, but had a tracer with a burnout distance of only 1,500 meters. This was due to the greater mass of the cermet core compared to the steel core of the BZT bullet. If used for ranging purposes, the maximum measuring distance would be somewhat shorter than with the BZT bullet paired with the B-32.</div><div><br /></div>In the book "<i>Современные Отечественные Патроны, Хроники Конструкторов</i>", Dvoryaninov published data on the ammunition consumption rates needed by various weapons to knock out an M113 armoured personnel carrier, which were determined as part of military-economic factors by the Soviet military. It was determined that to knock out an M113, a 12.7mm machine gun requires 13 hits using B-32 ammunition or 7 hits using BS ammunition. With a KPVT firing B-32 ammunition, 10 hits are required. Under this premise, tests were carried out to record the ammunition consumption rates needed to ensure that the specified number of hits are achieved. When firing upon an M113 from the front, the following number of rounds must be fired from each respective weapon. <br /><br /><table border="1"><tbody><tr><th> Weapon </th><th> 300 m </th><th> 500 m </th><th> 700 m </th><th>1000 m</th></tr><tr><td style="text-align: center;">NSV (12.7mm BS)</td><td style="text-align: center;">20.4</td><td style="text-align: center;">26.6</td><td style="text-align: center;">-</td><td style="text-align: center;">-</td></tr><tr><td style="text-align: center;">NSV (12.7mm B-32)</td><td style="text-align: center;">-</td><td style="text-align: center;">-</td><td style="text-align: center;">-</td><td style="text-align: center;">-</td></tr><tr><td style="text-align: center;">KPVT (14.5mm B-32)</td><td style="text-align: center;">23</td><td style="text-align: center;">23</td><td style="text-align: center;">-</td><td style="text-align: center;">-<br /></td></tr></tbody></table><div><br /></div><div>When firing upon an M113 from the side, the following number of rounds are needed from each weapon.<br />
<br /><table border="1"><tbody><tr><th> Weapon </th><th> 300 m </th><th> 500 m </th><th> 700 m </th><th>1000 m</th></tr><tr><td style="text-align: center;">NSV (12.7mm BS)</td><td style="text-align: center;">19.6</td><td style="text-align: center;">24</td><td style="text-align: center;">32</td><td style="text-align: center;">59</td></tr><tr><td style="text-align: center;">NSV (12.7mm B-32)</td><td style="text-align: center;">27.3</td><td style="text-align: center;">33.5</td><td style="text-align: center;">-</td><td style="text-align: center;">-</td></tr><tr><td style="text-align: center;">KPVT (14.5mm B-32)</td><td style="text-align: center;">24.5</td><td style="text-align: center;">29.6</td><td style="text-align: center;">37.5</td><td style="text-align: center;">97.6</td></tr></tbody></table>
<br />As the results show, a KPVT firing steel-cored AP-I rounds can be expected to knock out a typical armoured personnel carrier with the expenditure of around half an ammunition box during a 500-meter engagement. Beyond 500 meters, the degradation in hit probability slightly erodes the economical justifications of relying upon the KPVT to engage vehicles as a substitute to the main gun, even when it is capable of penetrating its armour, as up to two 50-round boxes may be needed when engaging targets at a kilometer or more. Overall, the best results are obtained from an NSV machine gun equipped with full belts of tungsten-cored BS rounds, but supplying such quantities of BS rounds is itself an unrealistic option. However, when comparing these two weapons on the basis of their capabilities using standard steel-cored AP-I rounds, the advantage of the KPVT is very stark. By mounting the KPVT as its coaxial weapon, the T-10M was granted the ability to confidently eliminate a wider variety of lightly armoured vehicles from longer distances than was previously possible with the DShKM. Once again, information on the penetration of B-32 bullets come from the 1971 USAARMDL handbook titled "<i>Survivability Design Guide For U.S Army Aircraft Volume II: Classified Data for Small-Arms Ballistic Protection</i>".</div>
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From the table, it can be seen that the penetration of the B-32 bullet in RHA is 32.8mm (1.29") at the muzzle, 30.0mm (1.18") at 100 meters, 26.9mm (1.06") at 300 meters, 23.9mm (0.94") at 500 meters, and 15mm (0.59") at 1,000 meters. Needless to say, a 14.5mm B-32 bullet is much more powerful than a 12.7mm B-32 bullet. Additional information given on page 6 of the March 1998 issue of the "<i>Техника И Вооружение</i>" magazine indicates that 14.5mm B-32 penetrates 20mm RHA at 0 degrees at 800 meters which fits perfectly into the American penetration data.<br />
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Information on the BS-41 tungsten-cored bullet is more scarce, but it is known that its nominal penetration at 0 degrees amounts to 40mm of RHA at 100 meters, 35mm RHA at 350 meters, 32mm RHA at 500 meters, and 20mm RHA at 1,000 meters. According to data provided by Dvoryaninov, BS-41 is guaranteed (≥90%) to perforate 30mm of medium hardness steel (RHA) set at 20 degrees at 350 meters, or 30mm of high hardness steel at 20 degrees at 140 meters. When firing at a flat 30mm RHA target from 100 meters, the probability of igniting a container of gasoline behind the plate is ≥80%. BS-41 is also capable of penetrating 125mm of 5083 aluminium armour (same grade as used on the M113 APC) at 100 meters.<br />
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By having the KPVT, it also became possible to reliably defeat single-layer sandbag fortifications and natural cover from longer distances than was previously possible with the DShKM. Indeed, the PTRD and PTRS anti-tank rifles chambered for the 14.5mm cartridge were often used to defeat light fortifications and machine gun nests during WWII when there were no armoured targets to shoot at. Lightly armoured vehicles like the M113 and FV432 were, of course, prime targets as their frontal armour would not be able to withstand a 14.5mm B-32 bullet even from more than half a kilometer away and their side armour could be defeated from more than a kilometer away, even with a non-perpendicular impact. Light tanks like the AMX-13, M41 Walker Bulldog and M551 Sheridan could also be vulnerable to an attack to their sides from between 500 to 1,000 meters away. If cermet-cored BS-41 bullets are used instead, the range at which the KPVT is effective against lightly armoured vehicles undoubtedly increases, but the lack of a detailed penetration table makes it more troublesome to find the exact limits of its capabilities. However, given that the tracer burnout distance of the BST bullet is 1,500 meters, it is at least known that the maximum effective firing range is somewhat shorter than with the steel-cored B-32 and BZT.<br />
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Officially, the effective range of the KPVT on lightly armoured vehicles is stated to be 1,000 meters and the maximum effective range on unarmoured targets or infantry is 2,000 meters. The burnout of the tracers and the dispersion of the bullets makes it ineffective to open fire further than 2,000 meters except on area targets, but the 122mm main gun is far more appropriate under such circumstances.<br />
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<span style="font-size: large;">ANTI-AIRCRAFT KPVT</span></h3>
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The KPVT installed on the anti-aircraft mount is the same as on the coaxial mount, but configured to feed from the left. The cantilever mounting of the KPVT is made possible by an equilibrator spring, allowing the machine gun to be elevated with uniform effort. A spent belt link collection box is mounted on the right of the machine gun, and spent cartridge casings are ejected downward where they can roll off the roof of the turret. To lay the machine gun precisely on target in the horizontal axis, the loader should use the geared handwheel on the cupola. There is an electric braking system in the geared traverse mechanism and also a pair of stopper pins to fix the cupola in a certain position. Laying the gun in the vertical plane is done with another handwheel, but the gun elevation handwheel has a more complex mechanism with a worm drive and two adjustable gear ratios for fine and coarse laying. The coarse setting allows the machine gun to be elevated rapidly from -5 degrees to 85 degrees, and the fine setting allows the maximum accuracy potential of the machine gun to be obtained - an important consideration when firing at long range with a machine gun. For anti-aircraft work, speed in tracking the target is more important than fine laying so the loader should adapt accordingly.<br />
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<div><br /></div><div><br /></div>To improve the accuracy of automatic fire from the KPVT, the mount features a pair of shock absorbers, each consisting of a large main buffer spring to damp the recoil of the machine gun as it reciprocates in the mount, and a small buffer spring to damp the vibration as it is returned forward after recoiling.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEibPHVM0_JaetmsA0oJGALHhpKGnhjuAzCfDyBIxQ_rkTL4sRnWGKvkAR9iR23ikizqDkL8zV1LNFvMaigAbjN7sN5l3E3mbIfZLbYS0hEr0XOHSrPC8NpYYUyqRw32Gw8IfD3fP0M01us_QMFSWZViX6onXEo4yu93XaKdhPbL4P1ieWhql5aP_AhlDQ=s1116" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="524" data-original-width="1116" height="300" src="https://blogger.googleusercontent.com/img/a/AVvXsEibPHVM0_JaetmsA0oJGALHhpKGnhjuAzCfDyBIxQ_rkTL4sRnWGKvkAR9iR23ikizqDkL8zV1LNFvMaigAbjN7sN5l3E3mbIfZLbYS0hEr0XOHSrPC8NpYYUyqRw32Gw8IfD3fP0M01us_QMFSWZViX6onXEo4yu93XaKdhPbL4P1ieWhql5aP_AhlDQ=w640-h300" width="640" /></a></div><div><br />
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To fire the machine gun, the loader presses the electric thumb trigger on the elevation handwheel handle. When the trigger is depressed, it also engages the electric braking system to freeze the cupola in azimuth so that the firing accuracy against static targets is maximized. The brake can be disabled for firing at moving targets.<br />
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Like the DShKM, the cyclic rate of fire of 600 rounds per minute of the KPVT was reasonable for anti-aircraft purposes but it was not outstanding, and like the smaller machine gun it replaced, the practical rate of fire of the KPVT was also limited by the ammunition supply in the same ways. The probability of hit with the KPVT against aircraft should be higher thanks to the higher muzzle velocity of its bullets and superior sighting instruments, and the probability of inflicting debilitating damage to aircraft should definitely be higher thanks to the larger mass of each 14.5mm bullet compared to their 12.7mm counterparts.<br />
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When using the anti-aircraft machine gun in a combat situation, the loader is effectively limited to 100 rounds of ammunition. One box of 50 rounds is immediately available on the machine gun mount, and another box of 50 rounds is stowed on the right side of the turret for a rapid reload. Another three boxes of reserve ammunition are stowed inside the tank, but two of these are located on the turret floor underneath the main gun and the other is underneath the commander's seat, and as such, they are difficult to access and it is difficult for the loader to transfer the large boxes out of his hatch and onto the anti-aircraft mount or onto the external stowage mount. Practically speaking, this would have to be done in a non-combat situation only. The mount for the externally-stowed anti-aircraft ammunition box is shown in the photo below.<br />
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The mix of bullet types is different from the coaxial KPVT to reflect the poorly-armoured nature of the intended target: fixed-wing jet and propeller-powered aircraft. Non-tracer and tracer rounds are loaded in a 2:1 ratio, with the anti-aircraft belts containing 57-Z-564 cartridges with MDZ bullets containing an explosive-incendiary charge (HE-I) and 57-ZP-561M cartridges with ZP bullets containing an incendiary charge and a tracer (I-T). The two bullet types can be seen in <a href="http://patronen.su/forum/gallery/2-101214221343.jpeg">this collection of sectioned cartridges</a>.<br />
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MDZ bullets are miniaturized explosive bullets detonated by an impact fuze. MDZ bullets are ineffective at defeating armoured targets but are capable of igniting fuel in metal containers with wall thicknesses of 2mm to 8mm via its explosive-incendiary charge (A-IX-2). As such, MDZ bullets can easily perforate the thin skin of aircraft and set internal equipment alight. According to data provided by Dvoryaninov, the reliability of fuzing on a 2mm duralumin sheet at a firing range of 100-1,500 meters is ≥90%, and the nominal probability of igniting TS-1 grade kerosene in a container situated behind a 2mm sheet of duralumin at 100-1,500 meters is ≥80%. MDZ bullets may also be extremely effective against thin-skinned vehicles such as trucks, but a possible issue with the use of MDZ bullets on targets other than aircraft and thin-skinned vehicles is the potentially inconsistent reliability of the fuze on any surface that is softer than sheet metal, including concrete and wood. However, even if the fuze does not initiate, the bullets themselves are more than capable of defeating brick and concrete walls and other forms of light cover with enough residual energy to remain lethal. Interestingly enough, the T-10M manual states that MDZ bullets should only be used on aircraft even though it is clearly also effective against other targets. This unusual instruction may be related to certain legal prohibitions on the use of explosive bullets on humans.<br />
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ZP bullets are incendiary bullets with an inertial fuze and a tracer. Its main purpose is for observation and fire correction, but it is capable of breaching thin sheet metal structures such as the thin aluminium skins of aircraft or car doors to cause fires albeit not to the extent of MDZ bullets. Unlike MDZ bullets, the incendiary charge is placed at the tip and is initiated from the rear by an inertial fuze consisting of a primer, a firing pin and a free-floating lead striker. As the drawing on the right below shows, the bimetallic jacket of the ZP bullet only extends from the base to the end of the fuze mechanism, and the outer copper-washed steel jacket ends just short of the tip of the nose. The tip is made from a thinner metal windshield.<br />
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The sighting system of the anti-aircraft machine gun is more sophisticated than that of lesser types like the DShKM on previous models of the T-10, not to mention the simpler "spider web" iron sights found on foreign tanks. Unlike most anti-aircraft machine gun installations, the sights are not simply attached to the machine gun cradle or to the machine gun itself but are instead installed on an articulated mount offset to the right of the KPVT. The purpose of this setup is to ensure that the vertical alignment between the sights and the machine gun does not shift throughout the entire range of elevation of the machine gun, so vertical parallax does not influence the operator's aim. This gives the anti-aircraft system an additional level of accuracy which was necessary for fully exploiting the longer reach of the 14.5mm caliber.<br />
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For aiming at aircraft and ground targets, the anti-aircraft KPVT on the loader's cupola is furnished with the VK-4 collimator sight and PU-1 magnified telescopic sight. The PU-1 sight is installed in the VK-4 sight housing as an integral component. This combination is also used on the <a href="http://www.russianarms.ru/forum/index.php?action=dlattach;topic=10109.0;attach=315195;image">ZPU-1</a> light towed anti-aircraft system. The concept for a dual-purpose sighting system that combines a collimator sight with a magnified telescopic sight was first used on German anti-aircraft gun installations during WWII.<br />
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The PU-1 is a telescopic sight with a 3.5x magnification and a field of view of 4.5 degrees. It is a slightly modified variant of the PU standard sniper scope that was widely used on the Mosin Nagant 91/30 and SVT during WWII. After the war, the PU was widely used on multiple weapon systems as a simple direct vision aiming device with reticles modified for the ballistics of the corresponding weapon. For example, the ZPU-2 and the ZU-23-2 towed anti-aircraft gun systems also included a PU sight for ground targets to supplement their anti-aircraft sighting instruments.<br />
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The PU-1 sight is intended for use against ground targets and was designed to increase the maximum effective range of the machine gun to two kilometers. Naturally, 14.5mm bullets have no problem reaching this distance while remaining supersonic as their ballistic form is elegant and the muzzle velocity is very high, but it would be practically impossible for the operator to exploit the long reach of the machine gun without a magnified optic due to the inherent limitations of the human eye. Plus, rudimentary range estimation could also be done using the reticle markings of the PU-1. As such, the full potential of the KPVT as an anti-personnel and anti-vehicle weapon was not constricted by deficiencies in the aiming devices.<br />
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The VK-4 is a simple collimator sight with a built-in reticle for aerial targets. The brightness of the internal lamp is adjustable for ease of use in different light conditions. There is a tinted anti-glare glass window in front of the collimator reflector. Together with the sheet metal hood on top of the sight, the machine gun operator's sight will be minimally affected by the sun. The presence of a tinted window also helps to reduce the visual interference from the muzzle flash, especially during twilight hours or at night as it could be blinding. If unneeded, the tinted window can be flipped down on its hinge, as seen in the two photos below.<br />
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The markings for leading aerial targets is shown on the left in the drawing below being compared to a conventional spider sight. The VK-4 can also be used when firing at ground targets, and it may be a favourable alternative to the PU-1 at closer ranges as the small field of view from the PU-1 would be too constricting.<br />
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A rubber pad is placed above the VK-4 sight for the machine gun operator to rest his forehead against while looking through the sights. This is a rather frivolous feature when firing at aircraft using the VK-4 itself since one of the main advantages of collimator sights is that the projected reticle remains on target regardless of the viewer's eye position, but it is needed for the PU-1 scope in order to maintain the proper eye relief.<br />
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Altogether, the replacement of the DShKM machine gun on previous T-10 variants with a KPVT and the addition of a more advanced aiming system resulted in a sharp increase in firepower for the T-10M, particularly against ground targets.<br /></div>
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<h3>
<span style="font-size: large;">PROTECTION</span></h3>
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The mass of armour on the T-10 was 25.55 tons and accounted for 51.1% of the total mass of the tank. This was not particularly high as the T-54 allocated 50% of its mass towards its armour, so the T-10 was not proportionately more armoured compared to the latest Soviet medium tank in terms of mass. The turret of the T-10 alone weighed 6.5 tons and the hull alone weighed 19.05 tons. On the original IS-5 prototype, the turret weighed 6.2 tons and the hull weighed 17.48 tons. In production, the welding processes were carried out by automatic welding machines using large electrodes - a technology developed by NII Stali in 1948.<br />
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For comparison, the M103A2 weighed 58.1 tons but was a much more massive vehicle and its turret especially so. The Conqueror weighed 66 tons and was also a much more massive vehicle, featuring a similarly elongated bustle. Naturally, the larger size of these foreign heavy tanks begot a larger internal volume, and volume is one of the most expensive commodities for a tank as the amount of armour thickness required to protect a given unit volume increases at a rate expressed by the square-cube law. Of course, to give credit where credit is due, the use of a large bustle with a crew member seated within became a convenient counterweight for the large gun and thick frontal turret armour, thus shifting the center of gravity closer to the geometric center of the turret ring which greatly reduces the load on the horizontal turret drives. Most Soviet tanks - including the T-10 series - tended to have front-heavy turrets.<br />
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Several Soviet heavy tank prototypes and concept models featured elliptical hulls as well, including the famous Object 279. An elliptical hull design is not necessarily intended to grant increased protection on its own, but instead improves the efficiency of the distributed armour mass such that more protection can be afforded by a given amount of steel. This is achieved by working out the optimal curvature of the armour and the optimal shape of the structure to account for the probability of being hit by enemy fire. This principle was not easy to apply to tank hulls, but it is naturally much easier to apply to turrets as they are comparatively smaller and lighter structures.<br />
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The M48 is the most prolific tank with a cast elliptical hull, but the M103 was the first tank to have this concept implemented in practice. The concept was largely abandoned on the M60 series as only the sides of the hull were designed according to this principle, leaving the front hull armour to better accommodate a type of composite armour known as "siliceous core armour" which had a protracted development and never managed to enter service.<br />
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The Conqueror had the simplest hull armour configuration with a single upper glacis plate and a single lower glacis plate joined by welds and sloped only in the vertical plane.<br />
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As mentioned during the introduction to this article, the combined height of the hull and turret structures of the T-10, T-10A and T-10B is 1,881mm. This was increased to 2,006mm on the T-10M due to the increased height of the turret. In either case, the structural height of the T-10 series is less than a contemporary medium tank like the M48 Patton and much less than the M103 and Conqueror which had a structural height of 2.84 meters and meters respectively.<br />
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The distribution of hits on tanks changed throughout the years. During WWII, it was found that the hull was hit the most often, sometimes by a large margin. The higher propensity for hits to land on the hull was further exaggerated on the T-34 which had a rather small two-man turret. A wartime report from 1942 by the NII-48 research institute states that for the T-34, 81% of hits were recorded on the hull and 19% of hits were recorded on the turret. During this period, the average range of tank combat generally did not exceed a few hundred meters.<br />
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However, even at short ranges where aiming at specific points of a tank was quite possible with tanks and anti-tank guns, the instructions printed on pamphlets and posters for the gunners of tanks and anti-tank guns alike were generally quite simple and only advised firing on the sides and rear of enemy tanks or to target the tracks. In Soviet pamphlets, information was given on the range at which certain facets of an enemy tank could be defeated with different types of guns. Various pamphlets can be seen in this compilation <a href="http://tankarchives.blogspot.com/2013/06/weak-spots-and-hit-zones.html">posted on Peter Samsonov's blog</a>. There were no official instructions for gunners to target a tank's cupola or something to that effect, but firing machine guns at viewing ports was advised and the cupola was naturally focused on.<br />
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As the caliber and velocity of anti-tank guns and tank guns increased along with the steadily improving quality of optics and vision devices, the combat ranges also increased. By the time the U.S military became directly involved in the battle in Europe, the average distance of a tank battle had increased to around 700 meters. In fact, data from the Aberdeen Proving Ground showed that 80% of all encounters between tanks and other tanks or anti-tank weapons occurred at a distance of less than 1,000 yards. There were practically no encounters beyond 2,000 yards. This is shown in the graph below.<br />
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Due to the dispersion of shots, aiming at specific weak points was still futile, and in fact, scoring a hit was already a challenge. According to the report WO 342/1 titled "<i>Tank and Anti-Tank Warfare: Tanks; Battle Performance and Tactics 1951 Feb - 1953 Sept</i>", the hit probabilities for an M26 Pershing medium tank calculated from combat data showed that from a distance of 350 yards or less, the hit probability on an enemy tank was 85% and from a distance of 350-750 yards, the hit probability was 69% and from a distance of 750-1,150 yards, the hit probability was 46%. Given that a hit on an enemy tank from a distance of 350 yards or less was still not guaranteed, targeting weak points was not viable and the best policy was still to aim at the center of mass of the target.<br />
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<h3>
<span style="font-size: large;">HULL</span></h3>
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<a href="https://3.bp.blogspot.com/-lVxrZD-viVc/XEdTs3-EeVI/AAAAAAAANGg/Lz8MCal2bVQtoPm5BsT8BarcTvMBRNmhACLcBGAs/s1600/object%2B272%2Bt-10m%2Bprofile%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="472" data-original-width="1600" height="188" src="https://3.bp.blogspot.com/-lVxrZD-viVc/XEdTs3-EeVI/AAAAAAAANGg/Lz8MCal2bVQtoPm5BsT8BarcTvMBRNmhACLcBGAs/s640/object%2B272%2Bt-10m%2Bprofile%2Bdrawing.png" width="640" /></a></div>
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The hull design was established with the original IS-5 prototype in 1949 and was based on the hull of the IS-7. It surpassed both the IS-3 and IS-4 in protection, but naturally, it lagged far behind the IS-7 itself. Like the IS-7, the upper glacis of the T-10 had a distinctive "pike nose" shape.<br />
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"Pike nose" shaping is most often described solely as a method to increase the slope of armour plating, but in reality, the history and the consequences of this design solution are somewhat more complex. The main impetus behind the development of this particular armour configuration was the non-ideal geometry of the front hull of the IS heavy tank. The frontal hull armour of the original IS-1 had a stepped configuration not unlike the armour of the Tiger I, but because there was no bow machine gunner or radio operator seated next to the driver, the upper front plate was narrower than the lower front plate and the sponsons were sloped inward to join with the upper front plate, which made it appear to be "pinched". This was inherited from KV-series prototypes. When the tank was uparmoured in the IS-2 obr. 1944 modification, the stepped armour was replaced with a more streamlined sloped plate that extended from the lower glacis to the turret ring. However, the "cheekbones" that joined the sponsons to the upper glacis still existed.</div>
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By using a "pike nose" shape, the upper glacis was eliminated entirely and the "cheekbones" directly joined the sponsons to the lower glacis. This allowed the armour protection in the frontal arc to be improved without increasing the weight of the tank, and indeed, the IS-3 achieved a large improvement in armour protection with practically no real increase in weight over the IS-2 obr. 1944. The "pike nose" also allowed the driver to have his own hatch and it also eliminated the need for a vision port in the middle of the upper glacis.<br />
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It is well known that the slope of armour plating can be increased by introducing a horizontal slope component, which can be either constructional or induced by the lateral angling of the tank hull itself relative to the direction of attack. However, there are diminishing returns when combining two angles. This can be seen from the mathematical expression for a compound angle consisting of angles in two axes:</div>
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Cosine (a) = Cosine (b) x Cosine (c)</div>
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Combining two equal angles in both axes is the most mathematically optimal solution as this generates the largest compound angle. However, this is not necessarily the most practical solution because if an enemy shot impacts the armour at a side angle relative to the longitudinal axis of the tank hull, much of the compound angle is lost.</div>
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The rationale behind the decision to use heavily sloped armour plate instead of a flat plate of equal line-of-sight thickness is obvious with regard to the armour-piercing rounds that were likely to be used against a tank. Practically all armour-piercing ammunition types at the time had reduced effectiveness on highly oblique plates, even HEAT rounds, as the impact fuzes that were available at the time were far from perfect. Furthermore, the mechanism of projectile defeat on oblique armour plate is to cause the penetrator to fail by shattering. Solid steel armour-piercing shot is susceptible to this, as are capped steel shots. APCR, or HVAP as it is known in the U.S, was particularly vulnerable because tungsten carbide is extremely hard but rather brittle and will shatter relatively easily, thus severely limiting its ability to defeat highly oblique armour. The earliest APDS rounds like the British Mk. 1 and Mk. 3 shared the same issue because these rounds still lacked an armour-piercing cap to soften the shock of impact to ensure that the tungsten carbide core does not shatter. Naturally, such rounds will find the frontal hull armour of the T-10 to be a major challenge.<br />
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This also applied to steel full-caliber armour-piercing projectiles and could be mitigated to some extent by placing an armour-piercing cap on top of the steel penetrator, but even so, such projectiles had limited effectiveness when the angle of obliquity was above a certain threshold. The exact threshold depends on the projectile. For the German 8.8cm Pzgr. 39, this was 50 degrees.<br />
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Even if the penetrator does not shatter outright on impact, the deflection force generated by the resistance of the armour plate can cause a ricochet. When a full-caliber AP projectile or an APDS projectile meets an armour plate that is beyond its penetration capability, the projectile impacts the plate and begins to displace armour material, but the strong upwards reaction force from the plate deflects the projectile and it ricochets (often intact but sometimes fragmented), leaving only a shallow crater, usually oval in shape. As plate obliquity increases, the depth of the crater decreases. The projectile retains most of its energy after it ricochets, meaning that most of its energy is not absorbed by the tank and the welds that hold the plate experience much less stress, and less of the impact energy is transferred into the plate in the form of strong vibrations, which bodes well for any internal equipment that happens to be attached to the plate. Sights and other optical devices are particularly sensitive to shock loading, and a firepower kill can be achieved even with a non-perforating hit if the sights are put out of commission by a very energetic projectile.<br />
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A flat plate of equivalent effective thickness may stop the projectile, but the intact or fragmented projectile will be embedded into the armour and all of its kinetic energy will be transferred into the plate. Even if the welds are strong enough to withstand the stress and the armour plate manages to defeat the projectile without spalling, the bulge that tends to form on the back surface of the plate may still cause an inconvenience by damaging any equipment that is attached to it, not to mention that the displacement of a large volume of armour material from a large caliber shell means that any equipment that is installed in an opening that passes through the plate may be affected. Sensitive precision instruments such as gun sights can be the victim to such damage. These concepts are best exemplified by this photo of the front hull armour of a Sherman Jumbo after extensive bombardment.<br />
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<a href="https://1.bp.blogspot.com/-wxX1MkICi7A/XEe0RiXp4AI/AAAAAAAANHY/i4_etQ1s_c09gT41mEMfY9c4v5PBsvESwCLcBGAs/s1600/jumbo%2Btesting.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="635" data-original-width="1038" height="390" src="https://1.bp.blogspot.com/-wxX1MkICi7A/XEe0RiXp4AI/AAAAAAAANHY/i4_etQ1s_c09gT41mEMfY9c4v5PBsvESwCLcBGAs/s640/jumbo%2Btesting.png" width="640" /></a></div>
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The approach taken by the designers at the ChTZ Design Bureau was to create a geometrically complex tank hull that could offer a high level of ballistic protection from a large range of lateral angles that could also accommodate a hatch for the driver. The drawback of this decision was a higher cost of production and high demands on technical expertise, although it should be noted that experience from designing and manufacturing the IS-3 helped to ease the process, as T-10 chief designer M.F Balzhi had previously worked on the IS-3 and IS-4. His experience ameliorated some of the technical issues that arose from the complex hull armour scheme.<br />
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A more thorough understanding of the armour protection of the T-10 can be gained from the March 2014 edition of the "<i>Domestic Armoured Vehicles 1945-1965</i>" series of articles by M.V Pavlov published in the "<i>Техника и вооружение</i>" magazine. The article details the test results of T-10 turrets and hulls produced by <a href="http://www.libinfo.org/index/index.php?id=41765">factory No. 200</a>. Factory No. 200 was a metallurgical facility situated in Chelyabinsk that was established in November 18, 1941 and specialized in the manufacture of hulls and turrets for heavy and medium tanks. Prior to the manufacture of T-10 turrets and hulls, factory No. 200 was responsible for the manufacture of IS-4 hulls and turrets from 1946 to 1948.<br />
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The hull of the T-10 is constructed from 42SM medium hardness armour steel; the very same grade used for the hull of the T-54 medium tank. Medium hardness rolled armour steels such as 42SM are technically specified to have a hardness ranging from 285-341 BHN which is a narrower range compared to the equivalent MIL-A-12560H standard used by the U.S which specifies that the hardness must be within the range of 241 to 388 BHN. For the 120mm plates on the T-10 hull, the hardness should be at the lower end of the technical specifications for Soviet medium hardness armour of around 285 BHN. However, it is reported in the study "<i>Повышение Противоснарядной Стойкости Толстолистовой Серийной Стали 42СМ С Помощью Электрошлакового Переплава</i>" (<i>Enhancement of the Ballistic Resilience of Serial 42SM Steel Using Electroslag Remelting</i>), that while the technical specifications call for a hardness within the range of 285-340 BHN, serially-produced 42SM steel plates are usually processed to a hardness ranging from 293 BHN to 311 BHN. Assuming that this refers to plates with a thickness of 80-100mm as used in the T-54 and in some parts of the T-10, the hardness of such steel plates should be somewhere within this range. It should be noted that Yugoslavian tests found that the armour of the T-54A was hardened to 290 BHN which matches with other information.<br />
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Throughout the rest of this section, the term "conditional defeat" will be used several times. This term is used to describe the defeat of the tank armour by the breakdown of its structure achieved by exceeding the limits of its strength. This can include breaches formed by the cracking or splitting of the armour. Spalling is also a form of conditional defeat as it shows that the shock energy from an impacting projectile was high enough to overcome the tensile strength of the armour material. The successful prevention of conditional defeat indicates that no noticeable amount of damage is dealt to the tank. This term does not imply that the defeat of the tank armour would lead to lethal consequences for the crew. To cause an appreciable amount of damage behind armour, the impact velocity of the penetrating shell should exceed the velocity limit of conditional defeat by some margin.<br />
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<a href="https://www.blogger.com/null" id="upglacis"></a>
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<h3>
<span style="font-size: large;">UPPER GLACIS ARMOUR</span></h3>
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<a href="https://2.bp.blogspot.com/-Ld301gYcVl0/XNcyGxEN_fI/AAAAAAAAN7Y/IGq_1tZ3UuYyZUQWGngixHHI71m8cytFACLcBGAs/s1600/t-10%2Bfront.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="684" data-original-width="1077" height="253" src="https://2.bp.blogspot.com/-Ld301gYcVl0/XNcyGxEN_fI/AAAAAAAAN7Y/IGq_1tZ3UuYyZUQWGngixHHI71m8cytFACLcBGAs/s400/t-10%2Bfront.png" width="400" /></a></div>
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According to factory drawings, the upper glacis armour of all T-10 models has a vertical slope of 55 degrees and a horizontal slope of 40 degrees. The compound angle from these two angles is 64 degrees. With a plate thickness of 120mm, the total line-of-sight (LOS) thickness becomes 273mm when viewed directly from the front. This was substantially thicker than the upper glacis of the IS-2 obr. 1944 and the IS-3 but was ostensibly marginally weaker than the upper glacis of the IS-4 which had a 140mm RHA plate sloped at 61 degrees for a LOS thickness of 288mm. However, unlike the IS-4, the use of thinner 120mm plates simplified quality control, reduced production costs, and facilitated a much larger production volume. Moreover, the penetration of conventional armour-piercing rounds degrades exponentially with plate obliquity, making it more profitable to use thinner plates placed at a larger obliquity than to use thicker plates with a smaller obliquity if the weight of armour is approximately equal. Because of this, the small difference in the LOS thickness does not translate into a difference in the effective thickness. This will be explored further later on.<br />
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The armour scheme of the T-10 was established in the IS-5 prototype and it was unchanged throughout the continuous development of the tank series. After its design was established in 1949, the IS-5 underwent its first live fire tests from May 16 to June 4, 1950. The tests were split into two stages and the tank was fired upon with a 122mm D-25 cannon, a 8.8cm KwK 43 cannon, and a 76mm ZiS-3 field gun. Each of these guns represented distinct classes of varying power within the repertoire of contemporary armies; the D-25 was intended to represent a modern large caliber tank cannon - the most dangerous threat - and the KwK 43 was intended to represent the medium caliber, high velocity tank cannon of a modern medium tank. A total of 74 rounds were fired during the two testing stages. The first stage was intended to test the structural strength of the hull by subjecting it to non-perforating hits. The second was intended to test the strength of the joints between individual parts and assemblies, as well as the resilience of the armour itself towards the three guns.<br />
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It was demonstrated that the frontal armour of the hull could resist 122mm sharp-tipped armor-piercing shells (BR-471) from all distances in a frontal arc of 80 degrees, and it was noted that the level of protection offered by the hull was significantly higher than that of the IS-3 but the turret was approximately comparable to the IS-3.<br />
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The photo on the left below shows the IS-5 before the first stage of testing and the photo on the right shows the IS-5 after the second stage of testing was concluded.<br />
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The front hull armour was only tested using 122mm armour-piercing sharp-tipped shells (BR-471) fired from a D-25 cannon as it was felt that testing with the other calibers was unneeded. The mass of this shell is 25 kg and the nominal muzzle velocity is 795 m/s. As a result of the tests, it was found that the upper glacis could not be pierced by these shells in a frontal arc of ± 40 degrees from a nominal range of 100 meters. When fired upon head-on (0 degrees), the resulting lack of damage from hits at an impact velocity of 797 m/s indicated that the limit of the armour had not even been approached. When fired upon at a side angle of 40 degrees, the upper glacis was at its most vulnerable position as the entire horizontal slope component was negated, leaving only the vertical slope component of 55 degrees. <br />
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<blockquote class="tr_bq">
<ul>
<li>At an impact velocity of 739 m/s (corresponding distance: 800 meters), traces of damage were found on the back surface of the steel plate - at this impact velocity, a smooth bump with a height of 16 mm was formed. </li>
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<ul>
<li>At an impact velocity of 764 m/s (corresponding distance: 400 meters), a bulge of unknown height was created. More importantly, the surface of the bulge had cracks.</li>
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<li>At an impact velocity of 785 m/s (corresponding distance: 100 meters), a partial plug had begun to form and the outline of the plug bulged from the back surface of the plate by 15mm.</li>
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Although the armour was never fully perforated during the tests, the nature of the damage recorded on the 785 m/s and 764 m/s impact velocity test cases were both informative and worrying. The presence of cracks on the bulge formed at a 764 m/s impact velocity indicates that sufficient energy was imparted to cause surface damage. The formation of a partial plug at an impact velocity of 785 m/s indicated that the armour plate had begun to experience shear failure and that a further increase in velocity may give the projectile enough energy to overcome the energy absorption limit of the armour plate.<br />
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For a plug to be formed ahead of the projectile, the total resisting force on the projectile nose must be at least equal to the total shear force acting along the separating surfaces of the plug. If this condition is met, the plug is formed by adiabatic shear and it separates from the armour plate, allowing itself to be driven by the penetrator pushing it from behind. This forms a secondary projectile that can cause additional damage inside the tank. If plugging failure does occur, the total energy that the armour absorbs will be less than in the case of a perforation by ductile hole formation. This is because the failure is localized and does not allow for gross plate plastic deformation, since the deformation of the armour plate would act as an energy absorption mechanism.<br />
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Unfortunately, tests were not done with the German 12.8cm Pak 44 or KwK 44 L/55 guns and the limits of the armour were not tested beyond the capabilities of postwar 122mm AP rounds. However, during quality certification tests in 1955, it was verified that the upper glacis of the hull could withstand the 122mm BR-471B shell at its muzzle velocity (795 m/s).<br />
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It is well known that the British Conqueror and American M103 heavy tanks were developed with the specific goal of countering the Soviet IS-3 and their 120mm guns would most likely have been successful in this regard, but this prognosis is sometimes erroneously projected onto the T-10 simply because the two tanks closely resemble each other geometrically.<br />
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The L1G APDS round was the primary anti-tank round for the Conqueror. The L1G projectile uses the same basic design as the Mk. 3 APDS projectile for the 20 pdr. gun but on a larger scale. The large and heavy tungsten carbide core has an ogived tip and is topped off by a small soft steel nose pad (as opposed to a duralumin nose pad used in the Mk. 1 design), which is only loosely aligned with the core by the steel jacket and ballistic windshield of the projectile. Due to the low performance of the Mk.3 design on sloped armour plate, the<br />
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According to the British Army Operational Research Group (BAORG) memorandum "<i>Tank Effectiveness, Conqueror, Conway and Charioteer</i>" from June 1954, the penetration of L1G APDS on RHA plate sloped at 60 degrees is 118mm and 108mm at 1,000 yards and 2,000 yards respectively. The slope modifiers for "APDS" given in "<i>WWII Ballistics: Armour and Gunnery</i>" seem to represent this type of British APDS from the immediate postwar era as they are a near-perfect match for L1G.<br />
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An APDS round was never fielded for the M103. Its combat loadout consisted of M358 APBC and M469 HEAT rounds. According to Hunnicutt in "<i>Firepower: A History of the American Heavy Tank</i>", the penetration of the M358 APBC round on RHA plate sloped at 60 degrees reached 124mm at a distance of 1,000 yards and 114mm at 2,000 yards. These figures immediately make it clear that M358 was an extremely powerful round and could surpass L1G on highly oblique armour, and indeed, it was noted in Osprey that comparative studies of kinetic damage by experimental APDS rounds fired from the T123 gun on high obliquity armour at realistic battle ranges showed no better results than APCBC rounds. However, it is equally clear that these impressive figures would still be insufficient against the upper glacis armour of the T-10.<br />
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Based on these figures, the chances of piercing the upper glacis armour of the T-10 directly from the front are virtually nil even at point blank range. To defeat the upper glacis armour from 1,000 yards, a Conqueror must fire upon the tank at a ±30 degree side angle or more. According to the slope modifiers for "APDS" given in page 29 of the second edition of "<i>WWII Ballistics: Armour and Gunnery</i>", the upper glacis plates of the T-10 with its compound slope of 64 degrees would have a slope modifier of 4.5 which increases the effective thickness to 540mm RHA. At a ±40 degree side angle where only the vertical slope of 55 degrees is presented towards the direction of attack, the slope modifier degrades to just 2.75, giving the upper glacis plates a respectable effective thickness of 330mm RHA.<br />
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<a href="https://2.bp.blogspot.com/-jOnJn9p5CRs/XOPBge1I2iI/AAAAAAAAOAM/O1Nqu-sFqhM_v9sc_LIFXA9tcEEjP05gQCLcBGAs/s1600/m103%2Bshooting.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="767" data-original-width="1004" height="305" src="https://2.bp.blogspot.com/-jOnJn9p5CRs/XOPBge1I2iI/AAAAAAAAOAM/O1Nqu-sFqhM_v9sc_LIFXA9tcEEjP05gQCLcBGAs/s400/m103%2Bshooting.jpg" width="400" /></a></div>
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The M358 shell would also struggle to defeat the frontal hull armour from a ±40 degree side angle at below 1,000 yards. Other forms of damage such as spalling and the jamming of moving mechanisms could still be possible from M358 given the huge amount of energy delivered by the shell when fired from the M58, so an M103 would maintain some chance of disabling a T-10 with a direct hit to the upper glacis whereas a Conqueror probably would not.<br />
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On the other hand, the frontal hull armour of the IS-3 was created to fulfill the requirement for immunity against German 8.8cm rounds fired from the Pak 43 and KwK 43 L/71 guns. A report of live fire tests conducted in March 1945 (<a href="http://ftr.wot-news.com/2013/10/21/is-3-armor-tests/">CAMD RF 38-11355-2872</a>) shared by Yuri Pasholok shows that it achieved this requirement in full, but the trials also showed that sharp-tipped armour-piercing 122mm rounds (BR-471) fired from a D-25 were already enough to cause issues from certain angles from a distance of close to a kilometer: the armour could resist BR-471 when hit directly from the front, but from a side angle of 40 degrees, the upper glacis was perforated from 900 meters. It was also found that blunt-tipped armour-piercing shells (BR-471B) could perforate the upper glacis from the front at 0 degrees from a distance of 200 meters and less. Although the tests did not include the German 12.8cm Pak 44 or KwK 44 L/55 guns, it is already clear that these guns and other guns of equivalent power like the 120mm L1 and M58 would have been effective at dealing with the IS-3. Furthermore, this can be demonstrated with some simple mathematics.<br />
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With a vertical slope of 56 degrees and a horizontal slope of 30 degrees, the compound angle of the upper glacis plates of the IS-3 is 61 degrees, giving the 110mm upper glacis plates an effective thickness of 227mm. From this, it can be surmised that the upper glacis of the IS-3 would only have a chance of withstanding L1G APDS from a distance of above 1.5 km and only from the direct front, and it would be incapable of stopping M358 even from more than 2.0 km away. Interestingly, the T-54 obr. 1947 (T-54-1) medium tank had a 120mm RHA upper glacis plate sloped at 60 degrees, making it somewhat more resilient than the upper glacis of the IS-3.<br />
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The frontal armour of the IS-4 (Object 701) was originally developed under the same set of requirements as the IS-3 and the early prototypes fulfilled these requirements with a 120mm upper glacis plate sloped at 61 degrees, but the thickness of the plate was later increased to 140mm on the Object 701 #5 and #6 prototypes in order to withstand 10.5cm and 12.8cm rounds as they expected future German tanks to have an even more powerful cannon than the Kwk 43. The uparmoured prototype entered production as the IS-4. Based on the penetration data for L1G and M358, it certainly appears that the earlier decision to provide protection from German 12.8cm guns had fortunately proofed the IS-4 against the future threat of the 120mm L1 and M58. However, the IS-4 had a very limited production run and would not have even faced NATO tanks as they were deployed in the Far East.<br />
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From a historical perspective, the M103 and Conqueror would have been capable of fulfilling their original doctrinal requirement of countering the IS-3, and with the large numbers of IS-2M and IS-3M tanks present in Soviet heavy tank units in the 1950's, there was certainly a niche for the capabilities offered by these tanks and they were arguably a worthwhile investment at the time.<br />
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<a href="https://2.bp.blogspot.com/-w1pjokFvPgA/XLug-xTjj0I/AAAAAAAANtI/X5DpIs5CBSMztcNHOKwyXiJOyrGQBI1LQCLcBGAs/s1600/advancing.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="208" data-original-width="760" height="174" src="https://2.bp.blogspot.com/-w1pjokFvPgA/XLug-xTjj0I/AAAAAAAANtI/X5DpIs5CBSMztcNHOKwyXiJOyrGQBI1LQCLcBGAs/s640/advancing.jpg" width="640" /></a></div>
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Due to the extended service life of the T-10 series as a frontline heavy tank in the form of the T-10M, it is necessary to also consider the effectiveness of the armour against the new APDS rounds being fielded by the opposition forces at the time. A perfect example would be the L15A5 APDS round for the 120mm L11 gun of the Chieftain main battle tank. The new APDS round was created using new technologies that were developed specifically to improve performance on sloped plates and even multilayer armour (to some extent) and as such, L15A5 is inherently much more dangerous to the T-10 series than any previous APDS design. The chart below (<a href="https://tankandafvnews.files.wordpress.com/2016/02/20131231_142533.jpg">full page of report available on the tanksandafvnews site</a>) shows the limit of plate thickness defeated plotted against the obliquity of the target plate.<br />
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From the graph, it can be seen that at an angle of 64 degrees, L15A5 can confidently defeat a 120mm plate at 1,000 yards but it reaches its limit at 2,000 yards. As such, although the upper glacis armour of the T-10 could still be a challenging target at combat distances, it was altogether insufficiently protected, especially if it was not hit directly from the front but from a side angle. The upper glacis armour of the IS-3 would have no chance against this round at any practical distance and the upper glacis of the IS-4 would also be vulnerable from a distance of 2,000 yards or less despite having a nominally thicker LOS thickness of steel. Only the IS-7 would be completely invulnerable to L15A5 from a 60-degree frontal arc and only from more than a thousand yards away.<br />
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Because the standard 20 pdr. and 90mm cannons used by the largest NATO armies (U.K, U.S, West Germany) began to be replaced by the L7 cannon on a wide scale in the early 1960's, it is necessary to explore the level of protection offered from 105mm rounds. The Centurion Mk. 10 entered service in 1959 with the L7 and it could fire L28 APDS rounds. This APDS round was produced under licence in the U.S as the M398 and in West Germany as the DM13, but this round had no chance against the upper glacis of the T-10 even from point blank range. Late APDS designs with a tungsten alloy core and a tilting cap posed a greater threat as they were designed for increased performance on sloped armour. The benchmark model was the British L52 round which was also licence-produced in the U.S as the M728 with minor modifications to the tracer and other miscellaneous components, while the West Germans continued to use the old DM13 round (L28A1 clone) until the DM23 APFSDS round went into service in the early 1980's. The design of the 105mm L52 round for the L7 cannon was largely identical to the 120mm L15A5 round except in scale, so the same slope performance modifiers should be applicable as long as considerations are made for the reduced penetrator to plate thickness ratio.<br />
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A drawing from a Swedish Army handbook titled <a href="http://tanks.mod16.org/wp-content/uploads/2015/09/IMG_4087.jpg">“Arméhandbok del 2” (Army handbook, part 2)</a> that was generously <a href="http://tanks.mod16.org/2015/09/25/armor-penetration-of-swedish-tank-and-anti-tank-weapons/">declassified and shared publicly by Ren Hanxue</a> shows that the Slpprj m/66 round (Swedish name for L52A1) fired from the L7 cannon of the Strv 101/102 will defeat 140mm of RHA at 55 degrees from a distance of 1,000 m. Adding on to this, a Spanish catalog page for a 60mm APFSDS round states that 105mm L52 defeats 120mm of RHA at 60 degrees from 1,830 meters. For comparison, the 120mm L15A5 round penetrates 130mm of RHA at 2,000 meters. Using a slope modifier derived from the L15A5 graph to extrapolate the penetration at 55 degrees and 60 degrees to 64 degrees, it appears that the LOS penetration path of L52A1 in RHA declines to below 230mm at 64 degrees at 1,000 m. It should be emphasized that this is good for an APDS round, but it is not enough to defeat the 273mm LOS thickness of the T-10 upper glacis. However, if the "pike" nose of the upper glacis was hit from a side angle of 10 degrees or more, L52A1 may defeat the armour from 1.8 kilometers away. As such, tanks armed with 105mm guns in the mid-1970's would have had little trouble fighting a T-10.<br />
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105mm APFSDS rounds would have been a serious threat for any T-10 model, but they came too late to be of any relevance for the T-10 as they only began appearing in the late 1970's. More specifically, there was one APFSDS round in service in the late 1970's: the American M735 round from 1978. The British did not create any APFSDS ammunition for the L7 until the early 1980's and in that instance it was only for export (L64), and the West Germans got their first 105mm APFSDS round in 1982 the form of the DM23.<br />
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<a href="https://www.blogger.com/null" id="lowglacis"></a>
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<h3>
<span style="font-size: large;">LOWER GLACIS</span></h3>
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<a href="https://1.bp.blogspot.com/-BfFsa6lhNBA/XEDgkkmIIVI/AAAAAAAAM-s/b2Nea6ajrKE9FtkUb8QqBz0vxaHEvlwhQCLcBGAs/s1600/lower%2Bglacis.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="684" data-original-width="1600" height="272" src="https://1.bp.blogspot.com/-BfFsa6lhNBA/XEDgkkmIIVI/AAAAAAAAM-s/b2Nea6ajrKE9FtkUb8QqBz0vxaHEvlwhQCLcBGAs/s640/lower%2Bglacis.png" width="640" /></a></div>
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Naturally, the lower glacis of the T-10 is less resilient than the upper glacis, so it is a much more attractive target than the upper glacis if it is exposed. Having a plate thickness of 120mm and a slope of 50 degrees, the lower glacis has a LOS thickness of just 187mm and it is only proofed against a comparatively limited variety of armour piercing ammunition, but it is important to point out that the slope angle of 50 degrees was most likely chosen deliberately because the German 8.8cm Pzgr. 39/40 APCBC shell was known to reliably break apart and fail catastrophically on armour plate at impact angles of 50 degrees and above. Full immunity from this round fired from KwK 43 and Pak 43 guns was a basic requirement of the tank along with protection from domestic 122mm shells. Nevertheless, this part of the tank was still be slightly weaker compared to the IS-3 which had a 110mm plate sloped at 55 degrees for a LOS thickness of 192mm and it was also significantly weaker compared to the IS-4 which had a 160mm plate sloped at 40 degrees for a LOS thickness of 209mm.<br />
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Given a thickness to diameter ratio (T:D) of 0.6 for a 90mm projectile against the 120mm plate, the 50 degree slope multiplier of 2.05 for an American 90mm APCBC projectile given in page 37 of "<i>WWII Ballistics: Armour and Gunnery</i>" is applicable for the M82 round for the 90mm M36 and M41 guns which armed the M47 and M48 respectively. Against this round, the lower glacis armour would be equivalent to a perpendicular 246mm RHA plate. This is far beyond the capabilities of M82 even at point blank range. With that, the lower glacis is at least proofed against the standard American tank gun of the period.<br />
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Testing of the IS-5 with sharp-tipped armour-piercing rounds (BR-471) revealed that the velocity limit of immunity against these shells on the frontal arc of ± 30 degrees was 762 m/s, corresponding to a distance of 400 meters. At this impact velocity, a bulge with a height of 17mm was formed on the back surface of the plate. During tests in 1955, it was found that the velocity limit of conditional defeat of the T-10 lower glacis from the 122mm BR-471B shell (muzzle velocity of 795 m/s) from the direct front was 710 m/s. This corresponds to a distance of around 1,050 meters. Combining these two data points together, the lower glacis is resistant to BR-471 at 400 meters and it should be resistant to BR-471B only at 1,100 meters and above.<br />
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The lower glacis has a slope modifier of 2.25 against early APDS and 2.6 against 90mm HVAP, and as such, has an effective thickness of 270mm and 312mm respectively for the two aforementioned projectile types. Based on these figures, the lower glacis armour would be immune to M332 HVAP fired from the M36 and M41 guns only from a range of above 500 yards. However, <a href="http://www.wwiivehicles.com/great-britain/penetration-tables.asp">if the penetration tables from this site are correct</a>, Mk.3 APDS rounds fired from the British 20 pdr. gun would be able to defeat the lower glacis armour from over 2,000 yards away.<br />
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The lower glacis is not thick enough to resist 105mm APDS rounds at any feasible distance according to the figures presented in this <a href="http://tanks.mod16.org/wp-content/uploads/2015/09/IMG_4085-904x684.jpg">Swedish armour penetration diagram</a>, available courtesy of Ren Hanxue. From the diagram, it can be seen that both the Slpprj. m/61 (L28) and Slpprj. m/66 (L52A1) fired from the L7 gun of an Strv 101/102 (Swedish modification of the Centurion) will defeat a 120mm RHA plate angled at 38 degrees from the horizontal (52 degrees from the vertical) from more than three kilometers.<br />
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<a href="https://www.blogger.com/null" id="hatch"></a>
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<h3>
<span style="font-size: large;">DRIVER'S HATCH</span></h3>
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<a href="https://4.bp.blogspot.com/-HSLqsiPpkKE/XNc2gGMYdNI/AAAAAAAAN7o/dVILRKOoDrI6SSWThThGwPj5l6tmYs1kgCLcBGAs/s1600/t-10m%2Bdrivers%2Bhatch.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="426" src="https://4.bp.blogspot.com/-HSLqsiPpkKE/XNc2gGMYdNI/AAAAAAAAN7o/dVILRKOoDrI6SSWThThGwPj5l6tmYs1kgCLcBGAs/s640/t-10m%2Bdrivers%2Bhatch.jpg" width="640" /></a></div>
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The upper glacis deck has a thickness of 60mm and is sloped at 78 degrees for a total LOS thickness of 288mm. The obliquity of the armour is high enough that most fuzed projectiles from the 1950's will consistently fail to initiate on impact. The driver's hatch has the same thickness and is angled at the same obliquity, but it is made from cast steel instead of rolled steel and has a shallow bulge in the center to increase the driver's headroom. The photo above is <a href="https://www.britmodeller.com/forums/index.php?/topic/235020451-t-10-object-730-soviet-heavy-tank/">from Dave Haskell</a>. If the upper glacis deck is compared to the upper glacis, it appears to be more resilient as it has a higher LOS thickness, and this should be true for HEAT and HESH impacts, but because of the presence of the driver's hatch, the entire area should still be somewhat weaker .<br />
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In terms of protection, the driver's hatch theoretically serves as a very sturdy piece of armour with a slope equal to the rest of the upper glacis deck, but it is important to remember that armoured plates that are not rigidly secured tend to have issues with direct impacts from powerful cannons even if the nominal thickness of the plate appears to be enough to deflect the shot. For instance, the driver's hatch of the T-34 was identified as a weakness in combat reports and it remained a weakness albeit a lesser one even after its thickness was increased to 60mm on the T-34 obr. 1941. The issue was that the hatch could be ripped from its hinges or jammed in place even if the shot did not perforate the plate. As such, having the driver's hatch in a position where it is exposed to direct hits on the T-10 created a minor weakened zone in the frontal projection of the tank, and the hole in the hatch for the TPV-51 forward-facing periscope compromises the resistance of the hatch itself to direct hits.<br />
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Case in point: after live fire tests of T-10 hulls with 122mm guns were concluded, it was observed that the driver's hatch was consistently dislocated despite never having been hit directly with cannonfire. During tests August 24 to September 6, 1956, the hatch locking mechanism was broken by the initial battery of shells and the hatch lifting mechanism handle fell off. In a real combat situation, the driver would be unable to exit through the hatch afterwards and he would have to evacuate the tank through the belly escape hatch or through the turret. After the fifth shot to the front hull armour, the hatch popped out and it became impossible to close and lock it. After the live fire tests of the armour plate joints, the hatch together with its locking and lifting mechanism was simply torn out. This occurred during all of the tests. Pavlov writes that the durability of the driver's hatch and hatch mechanism was not considered an issue, although he does not elaborate further. It may be that the high number of direct hits required to cause such damage was not considered plausible in a realistic combat scenario.<br />
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Based on these results, the T-10 may only be considered completely proofed against guns of lower power such as the 90mm M41 that armed the M48 Patton, the 20 pdr. gun of the Centurion Mk. 3, and the 105mm L7 and M68 that armed many NATO tanks during the 1960's. As established earlier, an attack from the 120mm M58 gun of the M103 would probably fail to defeat the upper glacis armour from combat ranges, but with these test results in mind, it is likely that the colossal energy delivered by the M358 projectile may damage the driver's hatch on the first hit and physically incapacitate the crew as well as disable some internal equipment with multiple hits by shock alone.<br />
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The results of possible direct fire tests of the T-10 upper glacis deck and driver's hatch have not yet been published, but the level of resilience can already be appreciated from the available information. Even if the upper glacis deck and driver's hatch armour itself is theoretically capable of stopping a powerful tank shell, debilitating injury to the driver and a subsequent loss of the tank's mobility is quite possible. The T-10 could be considered a downgrade from the IS-3 in this regard as the driver's hatch and upper glacis deck of the IS-3 was much less exposed, as shown in the comparative image below (not to scale). The cost of the IS-3 design was that it had a smaller driver's hatch, among other drawbacks that will be discussed later.<br />
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<a href="https://www.blogger.com/null" id="sides"></a>
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<h3>
<span style="font-size: large;">SIDE ARMOUR</span></h3>
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<a href="https://3.bp.blogspot.com/-LDy588_Xx_o/XNPSxH98ZGI/AAAAAAAAN6w/XREX-0ulXnwk6EQ_Zaj3fxGWxV1H7pzlwCLcBGAs/s1600/cross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="228" data-original-width="321" height="284" src="https://3.bp.blogspot.com/-LDy588_Xx_o/XNPSxH98ZGI/AAAAAAAAN6w/XREX-0ulXnwk6EQ_Zaj3fxGWxV1H7pzlwCLcBGAs/s400/cross%2Bsection.png" width="400" /></a></div>
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The sides of the hull were also tremendously well-armoured, particularly for a tank weighing only 50 tons. Like the front of the hull, this part of the T-10 also left a legacy in the form of the NATO Triple Heavy target which was designed to represent the side armour of a T-10 and it was considered to be the toughest tank armour target to defeat. This target assumed that the T-10 side hull armour was composed of a 10mm high hardness skirt, large mild steel roadwheels with a thickness of 25mm, and an 80mm RHA base armour plate. In reality, the side armour of the T-10 was entirely monolithic, lacked a high hardness skirt, and the roadwheels were also too small to cover the side hull armour.</div><div>
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The sponson upper side armour plate was 120mm thick and sloped at 47 degrees, and the sponson lower side armour was constructed from a single 80mm plate bent outward with a large press to join the hull belly to the sponson side plate. The 80mm plate is sloped at a very steep angle of 62 degrees. These two parts constitute the sponson armour of the T-10, which occupies approximately half of the total height of the hull. </div><div><br /></div><div>The lower half is much weaker as it consists of the flat portion of the 80mm plate that formed the lower sponson armour, and the bottom half is formed from the belly armour plate which was bent upwards to join with the 80mm plate. The drawing below shows how the armour is distributed. As you can see, the level of protection gradually increases as the height tends towards the turret ring area. At the very bottom of the hull, there is only the empty space underneath the rotating floor of the fighting compartment and the probability of hitting this part of the tank is low, so the rather poor protection offered by the thin plate has a minimal effect on the overall survivability of the tank.</div><div>
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<div><br /></div><div><br /></div>It is worth noting that by using a bent 80mm plate which is joined to the sponson plate in a wedge shape rather than having a conventional rectangular sponson, issues with large caliber HE shells potentially bursting the sponson floor plate when impacting the flat side plate can be avoided entirely. <br />
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The 120mm upper sponson side armour plate has an effective thickness of 176mm when viewed perpendicularly, but when viewed from a ± 30 degree side angle, the compound angle is 70 degrees and the effective thickness of the armour increases to 352mm. The sloped 80mm plate of the lower sponson armour has an effective thickness of 170mm when viewed perpendicularly, and when viewed from a ± 30 degree side angle, the compound angle is 76.4 degrees and the effective thickness becomes 341mm. This is only marginally less than the sponson side armour and the higher angle of slope is a major compensating factor as the effectiveness of AP and APDS rounds declines exponentially at higher angles of obliquity. Needless to say, the side armour of the hull at such an angle would have been theoretically immune to any AP or APDS round at the time and remained invulnerable even against the newer L15 APDS of the Chieftain main battle tank.<br />
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Based on the results of the live fire trials, it was found that the velocity limit of conditional defeat for the lower part of the sponson armour (80mm sloped at 62 degrees) against 100mm blunt-tipped shells (BR-412B, muzzle velocity of 895 m/s) were 790 m/s for the starboard side and 793 m/s for the port side. Postwar firing tables show that these velocities correspond to a distance of 1,000 meters. The velocity limit of conditional defeat for the lower part of the hull sides (flat 80mm) was 483 m/s, corresponding to a distance of more than 4,000 meters.<br />
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The lower half of the hull sides is less than half as resilient as the sponson side armour since the plate is 80mm thick but is not sloped at all. This part of the hull has the same protection as the side hull armour of a Soviet medium tank like the T-54. From a 30 degree side angle, the effective thickness of this plate increases to only 160mm.<br />
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The hull belly plate at the lowest part of the hull sides is exceptionally thin, having a thickness of only 16mm. It is sloped at 58 degrees for a line-of-sight (LOS) thickness of 30mm, so it would still be sufficient for heavy machine guns, small caliber autocannons and splinters from large caliber artillery shells if it were hit at a perpendicular angle. From the same side angle, the compound angle is 74.6 degrees which increases the effective thickness of this thin plate to 60mm. But even after accounting for the additional protection offered by the overlapping torsion bar housings and the roadwheels from such an angle of attack, the small thickness of the plate is generally not enough to stop serious anti-tank weaponry. The saving grace of this shortcoming is that not much damage can be done if a shell pierces this part of the tank since there is very little behind the plate, and the thick torsion bars and torsion bar housings can absorb much of the shrapnel. Interestingly enough, weak as it is, this part of the side hull armour is still nominally equivalent to the side hull armour of the AMX-30 and Leopard 1 in LOS thickness (30mm), but it may be more effective since the penetration of power of bullets and shell splinters degrade drastically on oblique plate. </div>
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However, it is worth mentioning that there was a serious caveat to this tremendous level of protection; it was found during live fire testing that the hits of 100mm APBC and HE-Frag shells into the sides of the hull usually split the welds joining the torsion bar housings to the lower side of the hull and the welds attaching the flanges of the support rollers to the side of the hull, and destroyed the closest torsion bar housing and support rollers. The test did not include a full set of roadwheels and tracks as the test was designed to evaluate the structural condition of the tank and not the practical level of protection, but it could be surmised that if the suspension was configured normally, the track would be severed by a shell ricocheting off the sponson lower side plate due to the high obliquity of 62 degrees. Either way, some degradation of the mobility of the tank can be expected from the destruction of one or more suspension elements. So although the side armour of the T-10 could withstand serious punishment, it is quite likely to suffer a mobility kill when powerful anti-tank cannons are fired at its side.<br />
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It is worth noting that at a ± 30 degree side angle, one side of the upper glacis "pike" loses 30 out of its 40 degrees of horizontal slope which makes it a wider target while also reducing its effective thickness down to only 258mm whereas the other side of the upper glacis "pike" gains 30 degrees of additional slope but becomes such a narrow target that the area of its projection is negligible compared to the area of the rest of the tank. From the same side angle, the lower glacis armour gains an additional 30 degrees of slope which increases its effective thickness to 216mm. This is not much compared to the colossal thicknesses that are normally encountered on other parts of the tank, but it is still a formidable thickness of armour and it is nominally thicker than the upper glacis of the T-54. Even at this inopportune angle, the majority of the profile of the hull is still completely immune to L1G APDS from at least 1,000 yards or less.</div>
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<h3>
<span style="font-size: large;">REAR ARMOUR</span></h3>
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The rear of the hull is very thinly armoured in comparison with the front. The transmission access panel at the rear of the hull has a thickness of 50mm and is sloped at an angle of 40 degrees for a LOS thickness of just 65mm. The angle of slope was increased to 55 degrees on the T-10M (LKZ) for a LOS thickness of 87mm. The lower rear hull plate is 60mm thick with a slope of only 20 degrees for a LOS thickness of 64mm, and remained unchanged in all models. This was a reduction from the IS-3 and IS-2 which had 60mm plates sloped at 48 and 41 degrees on the top and bottom halves of their rear hull plates respectively, but it was already enough to resist shelling from medium caliber autocannons.<br />
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The rear hull armour of the IS-4 was simply excessive by comparison, having 100mm plates sloped at various angles from 32 to 39 degrees for a maximum LOS thickness of 128.7mm; twice the LOS thickness of the armour plates of the T-10 at the same locations. For the T-10, having half as much armour at the rear of the hull also halved the weight and the tank could benefit in other aspects without suffering any real loss in protection from a practical standpoint, as the fact of the matter is that direct hits to the rear of the hull from anti-tank weapons were rather rare even when tank combat distances were limited to just a few hundred meters. According to the data presented in the report WO 342/1 detailing the distribution of hits on American tanks during the Korean war, of the 57 hits whose position are known, 35% were on the front of the tank, 60% were on the sides, and 5% on the rear. Data from WWII tank battles shows a similar distribution of hits.<br />
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In the unlikely event that the tanks is attacked from the rear, even the huge thickness of armour on the rear of the IS-4 would be insufficient to deal with the 75mm and 76mm guns of the AMX-13 and M41 Walker Bulldog light tanks, not to mention infantry-portable HEAT weapons like the M20 "Super Bazooka" which had enough penetration power perforate the rear hull armour of an IS-4 twice over. Infantry-portable weapons were particularly relevant as a heavy tank could be attacked from the rear with such weapons after rolling past enemy fortifications, but both the T-10 and IS-4 would only be capable of resisting a glacing hit if either tank were attacked from this direction.<br />
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However, an examination of the hull cannot end here. Besides the sturdiness of the armour against direct-fire weapons, some attention must be directed at its resistance to mines as well.<br />
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<h3>
<span style="font-size: large;">BELLY ARMOUR (MINE PROTECTION)</span></h3>
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Unfortunately, there is a lack of information on the resistance of the T-10 to mine attack, but the sturdiness of the stamped hull belly is not particularly reassuring as it has a thickness of only 16mm. The belly underneath the transmission is even weaker, having a thickness of only 12mm and being completely flat unlike the remaining three quarters of the hull where the belly is shaped like a trough. This is only twice as thick as on a typical armoured personnel carrier and it would be considered abnormally weak for a tank if the rest of the belly were this thin. However, this is acceptable in the sense that differentiated armour thickness is used to mitigate weight gain, as the rear of the hull belly is very unlikely to receive a mine blast compared to the front of the hull belly. To improve the rigidity of this area, additional longitudinal and lateral ribs were stamped into the belly plate underneath the transmission beginning with the T-10M.</div><div><br /></div><div>On the T-10M, the belly plate is a single long plate stamped into a trough shape. It is unclear if the same method was used to form the belly of preceding models, or if they were made from separate plates welded together.</div><div><br /></div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-k7VcmHniULo/XC1xsOtQvrI/AAAAAAAAMwM/uDfTOa-gRPcHDryw002uYH52SSYFE03JACLcBGAs/s1600/t-10%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="471" data-original-width="948" height="317" src="https://4.bp.blogspot.com/-k7VcmHniULo/XC1xsOtQvrI/AAAAAAAAMwM/uDfTOa-gRPcHDryw002uYH52SSYFE03JACLcBGAs/s640/t-10%2Bcross%2Bsection.png" width="640" /></a></div><br /><br />This shape does not qualify as a bona fide "V" belly that is common among modern mine-resistant armoured vehicles, but the trough shape has a similar effect in that the sloping edges direct the blast wave of an underbelly explosion towards the sides and it increases the rigidity of the belly structure as a whole.</div><div><br /></div><div>It is also necessary to take the cylindrical torsion bar housings that protrude beneath the hull belly into consideration. Because around half of the torsion bar housings protrude outside the hull, the bottom half of the housing had to be thickly armoured and there is an external "waffle" pattern ribbing to increase rigidity. The thickness of the exposed parts of the cast torsion bar housing is the same as the hull belly itself and the cylindrical shape together with the "waffle" pattern ribbing makes it more resistant to deformation. Rather than compromising the rigidity of the hull belly, the presence of the torsion bar housings most likely reinforces it, and indeed, in part 10 of the "<i>Отечественные Бронированные Машины 1945-1965</i>" series of articles authored by M.V. Pavlov and published in the March 2009 edition of the "<i>Техника и вооружение</i>" magazine, Pavlov mentions that the torsion bar housings increase the rigidity of the hull belly. That said, although rigidity reduces the likelihood that structural deformation interferes with the normal function of components, rigidity is by itself not a positive attribute in terms of the resistance of the belly to being breached by blast.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-eUTXAFdKGKI/XOpT2LxJJGI/AAAAAAAAOGs/BuKxbXIuheYkaa3oaEtbRTna8Nn_kkAjACLcBGAs/s1600/torsion%2Bbar%2Bhousing%2Bvariable%2Bthickness.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="401" data-original-width="754" height="340" src="https://1.bp.blogspot.com/-eUTXAFdKGKI/XOpT2LxJJGI/AAAAAAAAOGs/BuKxbXIuheYkaa3oaEtbRTna8Nn_kkAjACLcBGAs/s640/torsion%2Bbar%2Bhousing%2Bvariable%2Bthickness.png" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"></div><br /></div><div><br /></div><div>The belly is ostensibly well-protected from mine blast due to its trough shape, previously implemented on the T-54. Executed properly, this shape drastically increases the resistance of a tank hull belly to a mine blast occuring underneath the tracks, with full or partial track overlap over the diameter of the mine. However, in the case of the T-10, the edges of the trough belly shape are far too long, and as a result, the sides of the belly receive shockwave of a mine blast underneath the tracks at an incident angle close to normal. The only positive aspects of this design are that the side surfaces of the belly are distanced further from the ground and from the track, where a mine blast occurs, and that the design may have a partial effect on reducing the severity of a mine blast directly underneath the belly, as the flat center plate of the belly is narrowed due to the trough shape, and thus, the probability of a blast directly underneath the flat zone is somewhat lessened. The width of the sides of the trough-shaped belly is 400mm on each side.<br />
<br />The results of experimental and theoretical analyses on the resistance of the T-10 belly to mine blast damage were presented in the 1969 No. 5 issue of the "<i>Вестник Бронетанковой Техники</i>" journal, in the article "<i>Пути Повышения Противоминной Стойкости Днища Танков</i>". It was noted that the main shortcomings of the T-10 belly design are the low thickness of the belly plate, large surface area of the sloped side projections, the intrusion of the large torsion bar units in the belly plate, as well as the great length of the weld seams connecting the torsion bar units to the belly plate. </div><div><br /></div><div>When an anti-tank mine with a 9 kg TNT charge detonates underneath a track with a partial overlap over half of the diameter of the mine, with the other half exposed to the inner side of the track facing the hull belly, there will be a probability of ~0.5 that the T-10 belly will be breached by the blast. In the best case scenario, to survive a 9 kg TNT mine, the mine must be covered by the track by more than half of its diameter at the moment it detonates. With full track overlap, a mine weighing 12 kg is required to breach the hull. In the worst case scenario, where weld seams are exposed to the blast, the resistance of the belly is drastically less. Even with full overlap of the track on the mine, the welded portion of the belly does not survive a blast of only 6 kg. For comparison - with full overlap of the track on the mine, the T-55 belly requires a 12 kg TNT charge to breach. Without track overlap, a charge of approximately 7.5 kg TNT is required to breach the hull in an underbelly blast. This is shown in the graph on the right in the image below. The y-axis is the weight of the TNT charge, the x-axis is the distance from the track (negative is inward to the hull, positive is away from the hull). The graph lines represent the thickness of the belly plate, with the dashed line represented the welded portion.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjK_CXwx4AwqqKr8tEzHZUwHSZNsxvir223OtLFnCOLaZafa76ooqdcpvNlm8HAeDNBAQkhZYMI4wckhYw3ayIs2EShONc8fQqPtr0lJvaR6rtYFqfA6i9zkRm96-wSvsSqAxCv-OG9rzOEOxvykew_Cg1RjKEmiPOLtLOKXlldvNHBftjEUKg7vbE8aw/s1057/mine%20resistance%20t-55%20and%20t-10.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="1057" height="364" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjK_CXwx4AwqqKr8tEzHZUwHSZNsxvir223OtLFnCOLaZafa76ooqdcpvNlm8HAeDNBAQkhZYMI4wckhYw3ayIs2EShONc8fQqPtr0lJvaR6rtYFqfA6i9zkRm96-wSvsSqAxCv-OG9rzOEOxvykew_Cg1RjKEmiPOLtLOKXlldvNHBftjEUKg7vbE8aw/w400-h364/mine%20resistance%20t-55%20and%20t-10.png" width="400" /></a></div><div><br /></div><div><br /></div><div>It was calculated that overall, the probability of dangerous damage to the belly of a T-10 tank from a 9 kg TNT mine is 1.66 times higher than the probability of dangerous damage to the belly of a T-54 or T-55, accounting for the probabilistic nature of a mine detonating under a zone of the track where it causes the required severity of damage.<br /><br />Besides the structural issues of the belly design, the armour itself posed an issue, as a thickness of 16mm is noticeably less than the belly of the T-54 medium tank (20mm) and the M60A1 main battle tank (19mm), although is effectively the same thickness as the British Centurion medium tank, Conqueror heavy tank, and Chieftain main battle tank. American tanks like the M103 and M48 are in a class of their own in this category as they have double the thickness of belly armour with additional reinforcement on the very front end of the belly to increase the total thickness to 38mm. This, combined with the rounded shape of the hull belly, made these tanks unmatched in mine protection as the M48 proved in Vietnam. <br />
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The British heavy, medium and main battle tank were all designed under the same requirement of surviving a 20 lb anti-tank mine (usually represented by a Mk. 7 mine) underneath the track, and the Centurion tank is known to be incapable of surviving a partially-buried 20 lb mine detonated directly underneath the belly based on declassified reports. Compared to this, the T-10 belly only matches this protection level in the best case scenario, where the mine does not breach weld seams, but in the best case scenario, the resistance of the T-10 belly is significantly higher. It is worth noting that on these British tanks, the only design solution used to improve mine resistance was to slope the hull sides inward, thereby distancing the welded connection between the side and belly plates further from the track.<br /><br />
As a side note, the hull roof over the crew compartment had a thickness of 30mm, but the thickness of the various roof panels covering the engine compartment is only 16mm.
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<h3>
<span style="font-size: large;">T-10, T-10A, T-10B TURRETS</span></h3>
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<a href="https://1.bp.blogspot.com/-dbHuZWJMof8/XPwsiPbWOwI/AAAAAAAAOWU/Rr4XqpAbLyMhwDx-8nmEZikcY1sjzjYtwCLcBGAs/s1600/2nd%2Bstage%2Bturret%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="236" data-original-width="1600" height="94" src="https://1.bp.blogspot.com/-dbHuZWJMof8/XPwsiPbWOwI/AAAAAAAAOWU/Rr4XqpAbLyMhwDx-8nmEZikcY1sjzjYtwCLcBGAs/s640/2nd%2Bstage%2Bturret%2Bview.png" width="640" /></a></div>
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A major impetus for the development of the Kirovets-1 that eventually led to the IS-3 was a tank vulnerability study commissioned by Gen. Nikolai Dukhov. The study found that the most common cause of serious heavy tank losses was hits to the turret, followed by hits to the front of the hull. This prompted the design of a turret with a radically new ballistic shape with a heavy emphasis on armour obliquity, as a result of which the level of armour protection was doubled over the IS-2 turret design. The T-10 turret represents another step forward from the IS-3 design with a more optimal ballistic shape and thicker armour. It is sometimes mistaken for the turret of the IS-3 from some perspectives, but the resemblance is purely superficial as the overall shapes and the curvature of the armour were completely different. However, just like the IS-3 turret, the length of the T-10 turret did not exceed the width of the hull, and because of this, the area of the front projection of the tank did not increase in size when the turret was turned to the side as the photo below (of a T-10M) shows, and therefore, the probability of being hit by incoming fire would not increase. Although this seems trivial, the considerable increase in the projected area of tanks with large turret bustles was a real disadvantage in a combat situation.<br />
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The T-10 turret is constructed from two pieces: the main structure is a large single-piece casting with a slightly curved cast plate welded on top to form a part of the turret roof. The turret weighs 6,500 kg in metal alone. MBL-1 grade steel was used for the turret. It is a softer steel compared to the 70L and 71L grades used for IS and T-34 turrets during WWII because the softer but tougher MBL-1 provided more protection against full-caliber armour-piercing shells. The drawing on the left below shows the turret of the basic T-10 and the drawing on the right below shows the turret of the T-10A. The T-10B shares the same turret with the T-10A. The T-10 and T-10A turrets share the same shape, same distribution of armour thickness and provide an almost identical level of protection.<br />
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The T-10 turret also abandoned the bolted access panel over the cannon breech assembly that could be found on the turret roof of the IS-3 and IS-4. This made the area much more resistant to direct hits and gave the turret greater structural rigidity with the minor downside that it was no longer possible to <a href="https://i.imgur.com/vAgrARj.jpg">remove the cannon from its mount</a> without lifting the turret off the hull. Instead of a bolted access panel, the same area on the T-10 turret roof was solid cast steel with a thickness of 40mm sloped at 85 degrees, and the welded turret roof plate at the rear half of the turret has a thickness of 30mm.<br />
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In December 1954, the roof of the turret was changed after tests were carried out earlier in the year. The triangular weld-on turret roof plate was replaced by an oval-shaped plate of the same thickness. This improved the overall structural strength of the roof against cannon fire. All T-10 turrets produced after December 1954 had this new turret design, and it carried over to the T-10A and T-10B turrets as well.<br />
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Both the T-10 and T-10A turrets share an almost identical oblong embrasure for the coaxial machine gun next to the embrasure for the main gun. The T-10 has the TSh2-27 sight with an articulating head portion so the embrasure in the turret for its aperture window is oblong in shape and quite small. The T-10A and T-10B with the TUP-21 backup sight is mounted directly onto the D-25TS cannon and lacks an articulated head and as such, a narrow but long vertical slit had to be cut into the turret instead.<br />
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On the whole, the T-10 turret is somewhat similar to the T-54 obr. 1949 turret in general shape, except with a more pronounced vertical curvature on all surfaces. From the side, the turret bears a strong resemblance to an egg halved along its longitudinal axis, but from the front and rear, the turret appears to be shaped like an isosceles trapezoid. The shot trap formed by the curvature of the IS-3 turret cheeks was also eliminated by the T-10 turret which had an almost completely convex design, lacking any surfaces from which an impacting shot could potentially ricochet into the turret ring or onto the hull roof. This was not an insignificant improvement considering that AP, HVAP and APDS rounds were still the primary anti-tank munitions carried by the tanks of the probable enemy at the time. The closest equivalent to this development is the progression of the Pz.V "Panther" gun mantlet design from the Ausf. A/D scheme to the Ausf. G scheme with the flattened lower edge.<br />
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According to Mikhail Kolomiets, the front of the turret had a thickness of 275mm to 250 mm, the sides were 157mm to 102 mm thick, and the rear had a thickness of around 90 mm. The front armour thickness figure refers to the thickness of the cheek from a side angle of 30 degrees, rather than from the direct front. As with practically all complex cast turrets, it is extremely difficult to find a reasonably accurate description of the distribution of thicknesses and angles of slope, and it is harder still to distill the true qualities of the armour in text. The biggest challenge lies in the sloping of the armour in two planes. This severely complicates calculations and introduces further variances in armour effectiveness depending on the angle of impact. Based on a review of all available sources, it appears that the most commonly reported thickness figure for the T-10 turret is 250mm, but the compound slope of 20-30 degrees at cheek region affects the protection value.<br />
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<a href="https://3.bp.blogspot.com/-LnGtOnHoUmU/XNrZF61w_HI/AAAAAAAAN-A/18Z3-nokZtYUACeAeorz_tL9JdqjeSqzwCLcBGAs/s1600/t-10%2Barmour%2Bscheme.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="393" data-original-width="1600" height="156" src="https://3.bp.blogspot.com/-LnGtOnHoUmU/XNrZF61w_HI/AAAAAAAAN-A/18Z3-nokZtYUACeAeorz_tL9JdqjeSqzwCLcBGAs/s640/t-10%2Barmour%2Bscheme.png" width="640" /></a></div>
<div><br /></div><div><br /></div>In terms of thickness alone, the T-10 turret does not surpass the IS-3 which had a maximum physical thickness of 249mm at the turret cheeks, but after tests in 1955, it was concluded that the T-10 turret had greater structural strength than the IS-3 turret and was also more resilient. This was most likely because of the use of a better type of steel and improved casting technologies.<br />
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Besides the base armour thickenss of the turret front, it is necessary to also examine the gun mask that covers the embrasure for the main gun. The photo on the left below, by Pavel Lusta, shows the gun mask of an original T-10 while the drawing on the right below shows the gun mask of the T-10A and T-10B. The only real difference is that the former has an embrasure for the TSh2-27 sight whereas the former has an embrasure for the TUP-21 sight. Both gun masks are rounded in shape.<br />
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The gun mask is attached to the front part of the D-25TA and D-25TS gun breech assembly with large bolts and buffered with thick rubber bushings for shock absorption. The size of the embrasure in the turret is no wider than the gun breech assembly, and it is slightly shorter in height. The photos below show the small size of the embrasures in the turret for the coaxial machine gun and the TSh2-27 sight. The replacement of a traditional gun mantlet such as on the T-34, T-34-85, T-44, and IS-2 turrets with a narrow embrasure coupled with an armoured gun mask was a feature that the T-10 shared with postwar Soviet tanks like the IS-3, IS-4 and the T-54 obr. 1949 as this type of construction solved a plethora of structural issues, had a reduced likelihood of jamming from direct hits, and improved the protection of the turret as a whole.<br />
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The armour of the gun mask varies in thickness and overlaps with the turret base armour, but overall, the area covered by the gun mask reaches a similar level of protection as the turret cheeks from a frontal attack and does not exceed it because the base turret armour has two weakened zones. One of them is the edges of the embrasure which have a reduced armour thickness owing to the need to accommodate the trunnions for the gun cradle. The trunnion is marked (1) in the drawing on the left below. As the drawing on the right below shows, the gun mask overlaps with this area and more than doubles the total thickness. The armour thickness reaches its maximum at the base of the turret where the trunnion mounting pins are secured into the turret, marked (2). These pins run through the entire thickness of the turret, so they qualify as another weak point in the armour as a direct hit on the head on the pin might push it out and into the interior of the turret. Fortunately, they are extremely small relative to the overall size of the turret - the surface area of the pins occupy less than 0.5% of the total surface area of the front projection of the turret. The heads of these two pins can be seen from outside the tank if the gun mask is removed like in the photo on the right above.<br />
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The variable thickness of the gun mask reaches its maximum in the area directly in front of the gun breech assembly, as this part is otherwise unprotected by the turret armour. The thinner edges of the gun mask extend outward to cover the vertical slots cut into the turret for the coaxial machine gun and the coaxial telescopic sight. The maximum width of the gun mask is 835mm.<br />
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At the rear of the turret, there is small gap between the turret ring and the wall of the turret bustle. Unlike the M103 and Conqueror turrets which had a large shot trap built into their turret bustles, this gap in the bustle of the T-10 turret is simply a zone of greatly reduced armour thickness. The thickness of the thin floor plate joining the turret ring to the walls of the turret bustle in this gap is not known, but based on the drawing below, it appears to be half the thickness of the hull roof (40mm), so it should be around 20mm. To reduce the vulnerability of this zone, an additional curved armoured rib welded to the underside of the floor plate to act as a spaced armour screen beginning with the T-10A turret. The ideal design would omit gaps and shot traps like the turret of the IS-3, but in this case, the height of the gap is small enough that it is an extremely minor chink in the turret armour.<br />
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<a href="https://3.bp.blogspot.com/-pIOxWrpmsgE/XL6eo8gauzI/AAAAAAAANuk/Ofx31WY2GRwmnXF4VpQiMFFf-I88HaM8gCLcBGAs/s1600/t-10%2Bmod%2B1960.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="490" data-original-width="422" src="https://3.bp.blogspot.com/-pIOxWrpmsgE/XL6eo8gauzI/AAAAAAAANuk/Ofx31WY2GRwmnXF4VpQiMFFf-I88HaM8gCLcBGAs/s1600/t-10%2Bmod%2B1960.jpg" /></a></div>
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Given that the sides of the turret appear to be set at the same angle as the upper side hull plates (47 degrees), the armour at the widest point - next to the commander's station and loader's station - should be set at this angle.<br />
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<a href="https://3.bp.blogspot.com/-LnGtOnHoUmU/XNrZF61w_HI/AAAAAAAAN-A/18Z3-nokZtYUACeAeorz_tL9JdqjeSqzwCLcBGAs/s1600/t-10%2Barmour%2Bscheme.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="393" data-original-width="1600" height="156" src="https://3.bp.blogspot.com/-LnGtOnHoUmU/XNrZF61w_HI/AAAAAAAAN-A/18Z3-nokZtYUACeAeorz_tL9JdqjeSqzwCLcBGAs/s640/t-10%2Barmour%2Bscheme.png" width="640" /></a></div>
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The turret ring race ring is recessed below the surface of the hull roof and there is a set of interleaved rings to seal the gap from bullet splash. To further reduce the probability of a jammed turret, the hull armour plates on the front and sides have a lip with a height of around 27-35mm that covers the small gap between the base of the turret and the surface of the hull roof. It's rather unlikely that this lip is enough to stop a cannon shell, but it is more than enough to reliably keep out heavy machine gun bullets and shell splinters and it may also be enough to resist direct hits from a 20mm autocannon.<br />
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<a href="https://1.bp.blogspot.com/-3LNcpZRlsns/XOzmjwIIGlI/AAAAAAAAOIA/ptVcUzscP6YpDaVgblwujMhj6vlFNo89wCLcBGAs/s1600/raised%2Blip%2Bturret%2Bring%2Bprotection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://1.bp.blogspot.com/-3LNcpZRlsns/XOzmjwIIGlI/AAAAAAAAOIA/ptVcUzscP6YpDaVgblwujMhj6vlFNo89wCLcBGAs/s400/raised%2Blip%2Bturret%2Bring%2Bprotection.png" width="400" /></a></div>
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These details are represented in the drawing below.<br />
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<a href="https://3.bp.blogspot.com/-JdYR8bLws8A/XNjPfRdRb8I/AAAAAAAAN88/wWyOS8vA0KMyUNebAsnLnQwiuAoxwKiZQCLcBGAs/s1600/turret%2Bring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="138" data-original-width="211" src="https://3.bp.blogspot.com/-JdYR8bLws8A/XNjPfRdRb8I/AAAAAAAAN88/wWyOS8vA0KMyUNebAsnLnQwiuAoxwKiZQCLcBGAs/s1600/turret%2Bring.png" /></a></div>
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The interleaved rings around the circumference of the turret ring are clearly shown in the drawing below.<br />
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<a href="https://3.bp.blogspot.com/-IgQsQ22NUFM/XNjEP58JE_I/AAAAAAAAN8s/PuZ7uS2mk0INd3MGB1p2qWVjtZZnk2--ACLcBGAs/s1600/turret%2Bring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="711" data-original-width="1181" height="384" src="https://3.bp.blogspot.com/-IgQsQ22NUFM/XNjEP58JE_I/AAAAAAAAN8s/PuZ7uS2mk0INd3MGB1p2qWVjtZZnk2--ACLcBGAs/s640/turret%2Bring.png" width="640" /></a></div>
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<h3>
<span style="font-size: large;">T-10M TURRET</span></h3>
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<a href="https://4.bp.blogspot.com/-Egp0ALXkjcQ/XL72pJky32I/AAAAAAAANvw/xGq13mZJRJ0diNrAA9iMX3UN6xWFpUNUwCLcBGAs/s1600/t-10m%2Bturret%2Bdrawing.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="314" data-original-width="479" height="261" src="https://4.bp.blogspot.com/-Egp0ALXkjcQ/XL72pJky32I/AAAAAAAANvw/xGq13mZJRJ0diNrAA9iMX3UN6xWFpUNUwCLcBGAs/s400/t-10m%2Bturret%2Bdrawing.jpg" width="400" /></a></div>
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To help control the weight gain from the new features added in the Chelyabinsk T-10M (Object 734) without significantly compromising the protection level of the tank, the thickness of the welded turret roof was reduced from 30mm to 20mm. However, the Leningrad T-10M (Object 272) retained a welded turret roof with a 30mm thickness, and the constructional turret roof had its thickness increased from 40mm to 50mm without changing the angle of slope of 85 degrees. Given that the Object 272 became the standard T-10M design for serial manufacture in both ChTZ and LKZ since 1962, it can be considered the de facto model.<br />
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<a href="https://1.bp.blogspot.com/-a0Q1eFhyYl4/XS291P7kIXI/AAAAAAAAOlA/9v1ijvdlYzwc-caFtKQ8HwZiEi6w5G3BgCLcBGAs/s1600/front.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="266" src="https://1.bp.blogspot.com/-a0Q1eFhyYl4/XS291P7kIXI/AAAAAAAAOlA/9v1ijvdlYzwc-caFtKQ8HwZiEi6w5G3BgCLcBGAs/s400/front.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-JLiacVw1Aww/XS291LveX1I/AAAAAAAAOk8/PG9whr9nQQks7vf_oovV5PzLQ3e7tmgdgCLcBGAs/s1600/profile.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="266" src="https://1.bp.blogspot.com/-JLiacVw1Aww/XS291LveX1I/AAAAAAAAOk8/PG9whr9nQQks7vf_oovV5PzLQ3e7tmgdgCLcBGAs/s400/profile.jpg" width="400" /></a></div>
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Although there were some changes in the shape of the front of the turret, the basic design was more or less unchanged. At the front of the turret next to the gun barrel, the base of the turret has a thickness of 250mm. Physically, this is the thickest section of armour found on the entire turret, but it is completely flat in the horizontal plane. As the turret curves upward to form the roof over the gun breech, the thickness is reduced to 200mm with a vertical slope of 24 degrees, and then transitioning to 135mm with a slope of 49 degrees. Based on these simple figures alone, it appears that the line-of-sight (LOS) armour thickness reduces along the height of the turret, but this is only because the horizontal slope of the turret is completely ignored.<br />
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<a href="https://1.bp.blogspot.com/-TWU6-F3FGJg/XLukLCQH6jI/AAAAAAAANtU/P6J8v6Lq3AUSFxsJwfJ2NdR_DZzLebKsACLcBGAs/s1600/t-10m%2Barmour%2Bdrawing.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="369" data-original-width="1600" height="146" src="https://1.bp.blogspot.com/-TWU6-F3FGJg/XLukLCQH6jI/AAAAAAAANtU/P6J8v6Lq3AUSFxsJwfJ2NdR_DZzLebKsACLcBGAs/s640/t-10m%2Barmour%2Bdrawing.jpg" width="640" /></a></div>
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Like the T-10 and T-10A turrets, the edges of the embrasure in the T-10M turret also had a reduced thickness to accommodate the trunnions, marked (2) in the drawing below. The trunnions and the trunnion mount was of a different, more robust design, but the modified trunnions were still secured to the turret using pins, marked (1) in the drawing below.<br />
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<a href="https://3.bp.blogspot.com/-6F4TtSn9COM/XL7N0NYQJMI/AAAAAAAANvU/czx49zMj5PImOABAsAFVoLNs_2cfFUJHACLcBGAs/s1600/gun%2Bmount%2B.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="485" data-original-width="738" height="262" src="https://3.bp.blogspot.com/-6F4TtSn9COM/XL7N0NYQJMI/AAAAAAAANvU/czx49zMj5PImOABAsAFVoLNs_2cfFUJHACLcBGAs/s400/gun%2Bmount%2B.png" width="400" /></a><a href="https://2.bp.blogspot.com/-fdElyIICFAU/XEEmhRCdfPI/AAAAAAAAM_s/l8BoC0nBBRQ-si8N-dReJplLCf7kwSqUQCLcBGAs/s1600/kpvt%2Bmount.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://2.bp.blogspot.com/-fdElyIICFAU/XEEmhRCdfPI/AAAAAAAAM_s/l8BoC0nBBRQ-si8N-dReJplLCf7kwSqUQCLcBGAs/s400/kpvt%2Bmount.JPG" width="400" /></a></div>
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The trunnion was moved forward relative to the trunnion mounting pins to reflect the different center of gravity of the M62-T2 cannon. Indeed, the entire cannon breech assembly was mounted slightly further forward in the turret, but the thickness of the armoured gun mask was not increased. On the contrary, the overall thickness of the gun mask was significantly reduced to only around 100mm and the amount of protection that it offered was considerably lower. However, the diameter of the M62-T2 gun tube was larger without a corresponding increase in the size of the embrasure, so proportionately speaking, this part of the gun mask of the T-10M covered a slightly smaller surface area and constituted a smaller weakened zone.<br />
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<a href="https://1.bp.blogspot.com/-0beBFrMcCi0/XT__0gONuaI/AAAAAAAAOrA/r3Jhw6qG4n86lrfDwRDURfrONiNlH7r1QCLcBGAs/s1600/t-10%2Bturret%2Bmantlet.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="375" data-original-width="302" height="400" src="https://1.bp.blogspot.com/-0beBFrMcCi0/XT__0gONuaI/AAAAAAAAOrA/r3Jhw6qG4n86lrfDwRDURfrONiNlH7r1QCLcBGAs/s400/t-10%2Bturret%2Bmantlet.png" width="321" /></a><a href="https://3.bp.blogspot.com/-KMNAQT837nE/XD9KbyQlAtI/AAAAAAAAM8c/xJvRm6VALakNqlbfH0MlsN9FuCQISEVkACLcBGAs/s1600/gun%2Bmantlet%2Barea.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="521" data-original-width="597" height="348" src="https://3.bp.blogspot.com/-KMNAQT837nE/XD9KbyQlAtI/AAAAAAAAM8c/xJvRm6VALakNqlbfH0MlsN9FuCQISEVkACLcBGAs/s400/gun%2Bmantlet%2Barea.png" width="400" /></a></div>
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Like the gun masks of previous T-10 models, the gun mask on the T-10M turret was attached to the end of the M62-T2 gun by four large bolts, and like the earlier gun mask designs, the T-10M gun mask has a maximum width of 835m, but the shape of the gun mask was changed. Now, it is no longer rounded but was instead semi-cylindrical as the photo below shows.<br />
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<a href="https://1.bp.blogspot.com/-4p1GzV4EoR0/XO4WUfyR_qI/AAAAAAAAOI0/5wj8BGNpvmc71tX5NYhm1Z9tr62eCF8vwCLcBGAs/s1600/mantlet%2Bprofile.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="767" data-original-width="1023" height="298" src="https://1.bp.blogspot.com/-4p1GzV4EoR0/XO4WUfyR_qI/AAAAAAAAOI0/5wj8BGNpvmc71tX5NYhm1Z9tr62eCF8vwCLcBGAs/s400/mantlet%2Bprofile.png" width="400" /></a></div>
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The lowest edge of the gun mask is flat in the vertical plane but retains the same 24 degrees of horizontal slope.<br />
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<a href="https://1.bp.blogspot.com/-Dhy-07bWkC4/XO4WTfT4CBI/AAAAAAAAOIw/JSQAinwvOeIOjkc86qG7qtpP56NOjjfYACLcBGAs/s1600/gun%2Bmantlet%2Bleft%2Bside.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://1.bp.blogspot.com/-Dhy-07bWkC4/XO4WTfT4CBI/AAAAAAAAOIw/JSQAinwvOeIOjkc86qG7qtpP56NOjjfYACLcBGAs/s400/gun%2Bmantlet%2Bleft%2Bside.png" width="400" /></a><a href="https://1.bp.blogspot.com/-3Bk54tXt-ls/XO4WTWuegvI/AAAAAAAAOIo/JQHNufmxXNEBufrlgCo33tms8BAmsJa_wCLcBGAs/s1600/gun%2Bmantlet.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="767" data-original-width="1023" height="298" src="https://1.bp.blogspot.com/-3Bk54tXt-ls/XO4WTWuegvI/AAAAAAAAOIo/JQHNufmxXNEBufrlgCo33tms8BAmsJa_wCLcBGAs/s400/gun%2Bmantlet.png" width="400" /></a></div>
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The two photos below show the T-10 turret with the gun mask removed. The photo on the right below (from <a href="http://www.primeportal.net/tanks/carrey/t-10/">Carrey on Primeportal.net</a>) gives a closer view of the four large bolt holes which are used to mount the gun mask onto the M62-T2 gun.<br />
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<a href="https://1.bp.blogspot.com/-4vkzlx-d8B8/XT_7SEJBFpI/AAAAAAAAOqw/UYhxy29UZtIxNNx9nUyQhy6N4TIz4-j6gCLcBGAs/s1600/t-10m%2Bwithout%2Bgun%2Bmask.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="575" data-original-width="800" height="287" src="https://1.bp.blogspot.com/-4vkzlx-d8B8/XT_7SEJBFpI/AAAAAAAAOqw/UYhxy29UZtIxNNx9nUyQhy6N4TIz4-j6gCLcBGAs/s400/t-10m%2Bwithout%2Bgun%2Bmask.jpg" width="400" /></a><a href="https://4.bp.blogspot.com/-EtvWcKd8JlQ/XL69uPYS1qI/AAAAAAAANu4/dULwnTD3F6wMi3qb3kavBsDVt2KsvBjLQCLcBGAs/s1600/t-10_015_of_141.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://4.bp.blogspot.com/-EtvWcKd8JlQ/XL69uPYS1qI/AAAAAAAANu4/dULwnTD3F6wMi3qb3kavBsDVt2KsvBjLQCLcBGAs/s400/t-10_015_of_141.jpg" width="400" /></a></div>
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The photo below (from Mikhail Baryatinsky) shows two T-10M tanks being prepared for scrapping. The size of the embrasure for the main gun can be clearly seen.<br />
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<a href="https://3.bp.blogspot.com/-bLjmeFrRnvg/XEoZjzpcHYI/AAAAAAAANLU/w1UuXbQbzQQxZhpK-8FdRVc9PIZv664igCLcBGAs/s1600/cannon%2Bremoved.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="436" data-original-width="700" height="398" src="https://3.bp.blogspot.com/-bLjmeFrRnvg/XEoZjzpcHYI/AAAAAAAANLU/w1UuXbQbzQQxZhpK-8FdRVc9PIZv664igCLcBGAs/s640/cannon%2Bremoved.jpg" width="640" /></a></div>
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The thickness of the T-10M turret next to trunnion mounting pins is 250mm. This zone is the only part of the turret that could be considered close to flat as there is only 16 degrees of horizontal slope with no vertical slope. Overall, the level of protection offered by the T-10M turret is equivalent to the T-10 turrets produced from 1955 to 1956 and onwards.<br />
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The rear of the turret also remained at the same level of protection. The base of the bustle had an armour thickness of 102mm at a flat angle, thinning down to 68mm at an angle of 54 degrees. Combined with the curvature of the turret in the horizontal plane, the armour above the 102mm belt at the base of the bustle is theoretically enough to withstand full-caliber armour-piercing shells from a 57mm high velocity cannon from any range.<br />
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The gap at the base of the turret bustle remained, but the bustle floor plate joining the turret ring to the walls of the turret bustle changed in design. The floor plate in the T-10M turret extends away from the turret ring before sloping upwards to join with the walls of the turret bustle, thus creating additional internal space without adding weight. The curved armour rib welded to the underside of the floor plate was removed, but the level of protection did not change because of the slope of the floor plate. The reason for this change was to accommodate the new ammunition stowage scheme.<br />
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<h3>
<span style="font-size: large;">PROTECTION AGAINST HEAT</span></h3>
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The protection of the hull sides against shaped charges was considered insufficient as the frontal arc of immunity against contemporary HEAT weapons was too narrow. For the PG-2 grenade with an 82mm warhead fired from the RPG-2 (rated penetration of 180mm RHA), the maximum angle of attack where the armour remained immune was just ±26 degrees, meaning that a PG-2 grenade would only fail to perforate the armour when the angle of impact is 26 degrees off from the perpendicular axis in either direction. For the PG-82 grenade with an 82mm warhead fired from the SPG-82 (rated penetration of 175 mm RHA), the maximum angle of attack was ±27 degrees. For the VBK-881 grenade with an 82mm warhead fired from the B-10 recoilless gun (rated penetration of 250mm RHA), the maximum angle of attack was ±22 degrees. For the VBK-883 grenade with a 107mm warhead fired from the B-11 recoilless gun (rated penetration of 290mm RHA), the maximum angle of attack was ±20 degrees.<br />
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For a 76.2mm HEAT shell of unknown type, presumably the BK-354M round for the D-56T gun of the PT-76, the maximum side angle was ±21 degrees. For an 85mm HEAT shell of unknown type, presumably the 3BK-7М round for the D-48 and D-70 anti-tank guns, the maximum side angle was ±15 degrees. However, keep in mind that all of these figures are only for the lower side hull armour which is a flat 80mm plate. As usual, the Soviet criteria for tank protection was extremely strict and only the least protected portion of the side hull projection was considered. If a less pessimistic perspective were adopted instead, it is obvious that the upper side hull armour of 170mm to 176mm would have a decent chance of resisting a shot from an RPG-2 or an SPG-82 at a flat angle. Even against the 85mm HEAT round which had the most potent warhead of all the types tested, the maximum side angle of immunity for the upper hull sides would be around ±56 degrees, so the frontal arc of immunity would be 112 degrees.</div>
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The M371A1 HEAT round fired from the 90mm M67 recoilless rifle penetrated 250mm of armour plate, and the warhead of the M72 LAW (from original up to the A3 model) penetrated 200mm of armour. The original M28 HEAT rocket for the M20 Super Bazooka penetrated 265mm of armour and the newer M35 rocket penetrated 280mm of armour. It is worth noting that the penetration power of all of these weapons deteriorated somewhat on sloped plate due to fuzing issues. These weapons were enough for the frontal armour of a T-34 or even a T-54, but generally speaking, man-portable recoilless rifles and rocket launchers lacked sufficient penetration power to defeat the armour of the T-10 from the front unless the lower glacis armour was hit. The turret could be defeated more easily than the upper glacis, but the rather low overmatch would only result in minor internal damage. Nevertheless, the T-10 was clearly not immune to such weapons, and that fact alone is worrying.<br />
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Larger crew-served weapons like the 106mm M40 recoilless rifle were capable of handily defeating the armour of the T-10 from the front. The M344 HEAT shell penetrates 433mm RHA which gives it an overmatch factor of 100mm against the upper glacis armour, making it an effective countermeasure against the T-10. Nevertheless, the T-10 was still noticeably better protected in this regard compared to its direct counterparts the American M103 and the British FV214 Conqueror. The upper and lower glacis armour of both of these tanks could be pierced by the PG-7V round fired from an RPG-7 which had 260mm of penetration with the basic PG-7 grenade, and the BK-833 round fired from the crew-served 107mm B-11 recoilless gun had 381mm of penetration which is more than enough to pierce the hull armour of both tanks at any location.<br />
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Based on a simple comparison of the LOS thickness of armour and the penetration power, the upper glacis of the T-10 is ostensibly incapable of resisting the 90mm M431 HEAT shell fired from the M36 and M41 guns of the M47 Patton and M48 Patton respectively, and it appears to be completely insufficient against the 105mm HEAT rounds of the L7 such as the M456. However, there are serious caveats - during ballistic tests conducted in Yugoslavia, it was found that 90mm M431 HEAT shells (with the M509A1 fuze) failed to fuze on the upper glacis armour of a T-54A if the tank hull was angled 20 degrees sideways. The resulting compound angle is only 62 degrees but this was apparently sufficient to cause a fuzing failure. It can be expected that the 105mm M456 would perform just as poorly as it uses the same M509 fuze as the M431.<br />
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Because additional angling was required to achieve this effect, this would only count as circumstantial protection for the T-54, but for the T-10 which has a structural 40 degrees of horizontal slope on its upper glacis, a 90mm or 105mm HEAT shell would need to impact the upper glacis from a side angle of at least 36 degrees in order to simply fuze properly, and conversely, the upper glacis of the T-10 would be capable resisting these shells in a 70-degree frontal arc with the same consistency displayed in the Yugo trials. As such, HEAT ammunition for M47, M48 and M60A1 tanks cannot be considered reliable countermeasures against the T-10 hull. The issue with fuzing on highly oblique targets was only remedied in the early to mid 1980's with the M456A2 and 105mm DM12 HEAT rounds. However, the turret of the T-10 would be more vulnerable, especially at its gun mask area. Only the edges of the turret would have a sufficient line of sight thickness to resist HEAT shells as well as a sufficiently steep angle of obliquity to cause fuzing issues.<br />
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The Yugoslavian test results were not a isolated cases. During the Korean War, it was found that M6 Bazookas and M20 recoilless rifles were ineffective against North Korean T-34 tanks despite having a nominally sufficient penetration power to go through the thickest parts of the tank. The issue was that the all-aspect sloping of the hull of the T-34 resulted in frequent fuzing failures, so the warheads simply failed to detonate or they detonated with a significant delay, causing the shaped charge to impact the armour from a very short standoff distance. Broadly speaking, fuzing issues were likely to occur if the angle of impact exceeded 60 degrees.<br />
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The issues with fuzes during the early years of the Cold War were noted by both sides and sometimes led to interesting creations. Indeed, the well-rounded hull of the famous Object 279 depended on the low fuzing reliability of HEAT shells as the primary defense mechanism. By having additional angled inserts added on top of the cast steel hull to increase the relative slope of the armour, Soviet engineers were able to greatly reduce the vulnerability of the tank to HEAT shells without raising its weight to an impractical level. These inserts were rather lightweight so they were not sturdy enough to act as armour against solid shot AP or APDS projectiles, but were just thick enough to ensure that the fuzes of HEAT shells could not pierce the skin and would instead be deflected and destroyed, thus causing the shell to fail to initiate on impact.<br />
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Graze-sensitive fuzes for anti-tank missiles would not suffer from the same issues. Such devices began appearing in the early 1970's and would have been an effective means of defeating the T-10M as it was still in service and would likely have routinely faced NATO anti-tank missile platforms owing to its high priority as a heavy tank. Furthermore, the M456A2 and its West German licence-produced clone the DM12 were no longer susceptible to fuzing issues on highly oblique targets as a new fuze, known as the full-frontal area impact switch (FFAIS), was installed.<br />
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<a href="https://www.blogger.com/null" id="heshprot"></a>
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<h3>
<span style="font-size: large;">PROTECTION AGAINST HESH</span></h3>
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The high obliquity of the upper glacis armour may also useful against HESH or HEP rounds in certain circumstances as it is high enough to be more useful than harmful, but still, the thickness of the armour is insufficient against HESH rounds larger than 90mm in caliber. Moreover, the high obliquity of the T-10 armour may be rather useless if it is attacked from a very long range as the arcing trajectory of HESH rounds - which are slow by nature - will tend to impact at a diving angle.<br />
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In a Soviet document titled "<i><a href="http://btvt.info/5library/vbtt_1977_05_106mm.htm">Воздействие 106-мм Бронебойно-Фугасных Снарядов Безоткатного Орудия На Монолитную Стальную Броню</a></i>", it is reported that the M346 projectile, which has a diameter of 105mm and contains 3.25 kg of Composition A3 but lacks an inert nose cap, is capable of defeating a 120mm plate at 65 degrees. Cannon-fired 105mm HESH rounds should achieve the same result. Needless to say, 120mm HESH is easily capable of defeating a 120mm plate as the graph below shows.</div>
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<a href="https://2.bp.blogspot.com/-yM-FaShrb00/XEDSf80Rq0I/AAAAAAAAM94/KslVnhkdE38xoERqPv3h7SjVWHzI8mLOQCLcBGAs/s1600/l11%2B120mm%2Bhesh%2Bperformance%2Bon%2Bslopes.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="536" data-original-width="1156" height="296" src="https://2.bp.blogspot.com/-yM-FaShrb00/XEDSf80Rq0I/AAAAAAAAM94/KslVnhkdE38xoERqPv3h7SjVWHzI8mLOQCLcBGAs/s640/l11%2B120mm%2Bhesh%2Bperformance%2Bon%2Bslopes.png" width="640" /></a></div>
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However, it must be understood that HESH rounds were not necessarily an effective counter to T-10 tanks as the effectiveness of any given type of ammunition does not hinge entirely on the ability to defeat the armour of the target. It is certainly an integral component of the equation, but it is not the only factor. For HESH rounds, the primary factor that hinders its ability to serve as an effective weapon against T-10 tanks is their poor ballistic performance. Due to the plethora of technical constraints associated with the proper function of squash head warheads, HESH shells must be launched at a low muzzle velocity of around 600 m/s, not more. Combined with the poor aerodynamic form of the HESH projectile, which is another technical constraint related to the squash head design, the ballistic trajectory of HESH shells is extremely pronounced and the shell is extremely sensitive to deflection by crosswinds despite their characteristically high mass.<br />
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As the graph on the left below shows, a HESH (HEP) shell takes a significantly longer time to reach the target compared to four other types of armour-piercing ammunition and has an extremely arced ballistic trajectory. The long flight time makes it much more difficult to hit a moving target. The graph on the right below shows the effect of a 10 m/s crosswind on the deflection of three types of armour-piercing ammunition. APDS rounds are the least affected, making them much easier to use, especially for early Cold War tanks that lack a crosswind sensor, whereas HESH rounds are severely affected by crosswinds.<br />
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<a href="https://1.bp.blogspot.com/-knryzBo5G1o/XUMFNZhtANI/AAAAAAAAOuY/zjt-0DLhtT4KKMBtyoQUqustIWiq5pisACLcBGAs/s1600/trajectory.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="495" data-original-width="757" height="261" src="https://1.bp.blogspot.com/-knryzBo5G1o/XUMFNZhtANI/AAAAAAAAOuY/zjt-0DLhtT4KKMBtyoQUqustIWiq5pisACLcBGAs/s400/trajectory.png" width="400" /></a><a href="https://1.bp.blogspot.com/-34sDvWZVLJM/XUMFNjtogBI/AAAAAAAAOuc/Vzx4CYP_ZVgbCqyRq5sABi7lNcmmu66GgCLcBGAs/s1600/wind%2Bdeflection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="525" data-original-width="768" height="272" src="https://1.bp.blogspot.com/-34sDvWZVLJM/XUMFNjtogBI/AAAAAAAAOuc/Vzx4CYP_ZVgbCqyRq5sABi7lNcmmu66GgCLcBGAs/s400/wind%2Bdeflection.png" width="400" /></a></div>
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Even with a suite of sensors and a ballistic computer that can handle a variety of environmental factors, modern tanks firing HESH shells still have a notably worse probability of hit on tank targets, especially moving targets. Needless to say, tanks such as the M60A1 will find it extremely difficult to use HESH rounds against moving T-10 tanks at long range, whereas most T-10 models that an M60A1 would encounter will tend to have a stabilized gun that can deliver effective return fire, and although Chieftains have a stabilizer, there is no reason for them to use HESH rounds when they have L15 APDS rounds that facilitate a higher probability of hit and have sufficient penetration power to defeat the frontal armour of any T-10.<br />
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<a href="https://www.blogger.com/null" id="fire"></a>
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<h3>
<span style="font-size: large;">FIREFIGHTING</span></h3>
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The PPO firefighting system came standard on the T-10. This was an automated system that was controlled by the driver with two modes of operation: the 'automatic' mode, or the 'semi-automatic' mode. Three carbon dioxide fire extinguisher bottles were provided and each would be expended in a single powerful burst with each activation. The fire extinguisher bottles were placed behind and to the right of the driver's seat.<br />
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In the 'automatic' mode, the system alerts the driver of the source of the fire, shuts off the engine, and cuts off the engine air intake. Then, one of the three fire extinguisher bottles are activated and the entire compartment is flooded with the extinguishing agent. In the 'semi-automatic' mode, the system alerts the driver of the presence of a fire via an audio alarm and a signal light, but takes no action on its own. The driver can then choose whatever action he deems most suitable at the moment. He can control the system from his station and choose to activate any number of bottles.<br />
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Six TD-1 temperature sensors were placed in strategic locations around the engine compartment and oriented at the most probable source of potential fires. The system reacts to a rise in temperature to 180 degrees Celsius and has a response time of 10 seconds. The long response time is due to the inherent limitations of the use of thermocouples as temperature sensors. Naturally, the oxygen content in the engine compartment is quite low due to the high concentration of carbon monoxide and fumes so fires tend to be easier to extinguish as they are already facing partial oxygen deprivation, but fires cannot be detected instantly due to the limitations of the sensors and the lack of any other feedback system to alert the crew, so the fire has more time to spread and this makes it much more difficult to extinguish.<br />
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Because the PPO system only protects the engine compartment, fires in the fighting compartment must be handled manually by the crew using two carbon dioxide OU-2 hand-held fire extinguishers to extinguish fires. The fire extinguishers are placed on the front right corner of the fighting compartment and are most easily reached by the driver, but the loader is able to access them as well. Carbon dioxide is suitable against Class B and C fires, namely fuel and electrical fires, which are the predominant causes of fire in a tank. Although it is not as poisonous as carbon monoxide, carbon dioxide can cause asphyxiation by hypoxia and it is is toxic in high concentrations, so it is unsafe to remain inside the tank after the extinguisher bottles have been discharged.<br />
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In 1964, the "Rosa-2" firefighting system was installed on new T-10M tanks and it began to be retrofitted to older tanks. Like the older system it replaced, "Rosa-2" only covers the engine compartment. The main improvements of "Rosa-2" was in the speed and reliability of extinguishing fires compared to the PPO system. This was achieved by using a halocarbon fire extinguishing agent designated "3.5"; a pressurized combination of ethyl bromide and carbon dioxide. The mixture is very effective at retarding flames, but also highly poisonous and carcinogenic. Three extinguisher bottles were provided, giving the driver three attempts to fight the fire in the engine compartment.<br />
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<a href="https://www.blogger.com/null" id="smoke"></a>
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<h3>
<span style="font-size: large;">SMOKESCREENING SYSTEM</span></h3>
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<a href="https://2.bp.blogspot.com/-OLL_uBhdpOo/XNrTk5O9tQI/AAAAAAAAN9s/A6nKyTTQ4KQ6xASfIV4NL2xq9HUPEXoxQCLcBGAs/s1600/t-10m%2Brear.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="535" data-original-width="750" height="456" src="https://2.bp.blogspot.com/-OLL_uBhdpOo/XNrTk5O9tQI/AAAAAAAAN9s/A6nKyTTQ4KQ6xASfIV4NL2xq9HUPEXoxQCLcBGAs/s640/t-10m%2Brear.jpg" width="640" /></a></div>
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The T-10 was originally provided with a pair of BDSh-5 smoke bombs for generating a defensive smoke screen. The BDSh-5 was developed in 1944 for the T-34-85 and armoured fighting vehicles derived from the T-34. It continued to be used in a number of Soviet tanks until it was withdrawn from service in the 1950's due to the advent of self-generated smoke using the TDA smokescreen system. The BDSh-5 bomb measures 0.45 meters in diameter and 0.65 meters in length. Under conditions of minimal wind, a single BDSh bomb produces enough white smoke to cover an area of 40,000 square meters, or a square of 200 meters in width and length. The bomb burns and produces smoke for five to seven minutes. Smoke pours out of the circular opening on the surface of the cylindrical housing. The bomb is weighted so that the opening is always facing upwards even when floating in water, but it is not conducive for a T-10 to drop a BDSh-5 into water.<br />
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<a href="https://2.bp.blogspot.com/-lNt1Q-v_AQM/XMGXPKaY-lI/AAAAAAAANw8/unxf3T2qXaAgpT-3i-zXTWLL5Io2ksH2QCLcBGAs/s1600/%25D0%2591%25D0%2594%25D0%25A8-5.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="450" data-original-width="800" height="225" src="https://2.bp.blogspot.com/-lNt1Q-v_AQM/XMGXPKaY-lI/AAAAAAAANw8/unxf3T2qXaAgpT-3i-zXTWLL5Io2ksH2QCLcBGAs/s400/%25D0%2591%25D0%2594%25D0%25A8-5.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-PdYrcCqflaw/XMGW02SFaYI/AAAAAAAANw0/qG-t1JpVsiUXSuMYWUUAird7IvyTk08IgCLcBGAs/s1600/bdsh-5%2Bsmoke.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="453" data-original-width="604" height="240" src="https://3.bp.blogspot.com/-PdYrcCqflaw/XMGW02SFaYI/AAAAAAAANw0/qG-t1JpVsiUXSuMYWUUAird7IvyTk08IgCLcBGAs/s320/bdsh-5%2Bsmoke.jpg" width="320" /></a></div>
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When the T-10M was introduced in 1957, it was also dependent on these smoke bombs as its only method of generating a smoke screeen. The photo below shows a pair of BDSh-5 smoke bombs on a T-10M.<br />
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<a href="https://1.bp.blogspot.com/-j_HjqeQk-d8/XVa3QVYODhI/AAAAAAAAO-A/KgynIs046Z0qxLcuvaxd_5wycahOgT_pQCEwYBhgL/s1600/t-10m%2Bbustle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1068" data-original-width="1600" height="426" src="https://1.bp.blogspot.com/-j_HjqeQk-d8/XVa3QVYODhI/AAAAAAAAO-A/KgynIs046Z0qxLcuvaxd_5wycahOgT_pQCEwYBhgL/s640/t-10m%2Bbustle.png" width="640" /></a></div>
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In 1963, the TDA smokescreening system began to be included in new production T-10M tanks (T-10M obr. 1963) and were retrofitted into existing tanks, making BDSh-5 smoke bombs redundant. However, the mounting points and the quick-release mechanism for BDSh-5 smoke bombs were not removed so the option of using them remained after the modifications were made to accommodate fuel drums. The mounting points for smoke bombs are often seen coexisting with the mounting points for fuel drums on the same tank, but not all tanks had the fittings for external fuel drums whereas all have fittings for BDSh-5 smoke bombs.<br />
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<a href="https://4.bp.blogspot.com/-6I5CeFnHK04/XNrTls2yMuI/AAAAAAAAN9w/EJEnCV2IQSID4V2RetWr8CibhZEBCY56ACLcBGAs/s1600/t-10m%2Btransmission%2Baccess%2Bpanel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="579" data-original-width="1078" height="213" src="https://4.bp.blogspot.com/-6I5CeFnHK04/XNrTls2yMuI/AAAAAAAAN9w/EJEnCV2IQSID4V2RetWr8CibhZEBCY56ACLcBGAs/s400/t-10m%2Btransmission%2Baccess%2Bpanel.png" width="400" /></a><a href="https://1.bp.blogspot.com/-gLf2jrEq3TM/XNrTkNlP9jI/AAAAAAAAN9g/ZganL2TTpJYm4dKYoEds-H56EjtPMBI7ACLcBGAs/s1600/t-10m%2Bkiev%2Bchobitok.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="689" data-original-width="1000" height="275" src="https://1.bp.blogspot.com/-gLf2jrEq3TM/XNrTkNlP9jI/AAAAAAAAN9g/ZganL2TTpJYm4dKYoEds-H56EjtPMBI7ACLcBGAs/s400/t-10m%2Bkiev%2Bchobitok.jpg" width="400" /></a></div>
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<a href="https://www.blogger.com/null" id="drivestat"></a>
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<h3>
<span style="font-size: large;">DRIVER'S STATION</span></h3>
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<a href="https://1.bp.blogspot.com/-KyoEUO5PefQ/XO6IcQTPc7I/AAAAAAAAOJQ/9wVECxDA5ssopkamFf3iw-QBbIgn5olHACLcBGAs/s1600/t-10%2Bdrivers%2Bstation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="655" data-original-width="1118" height="233" src="https://1.bp.blogspot.com/-KyoEUO5PefQ/XO6IcQTPc7I/AAAAAAAAOJQ/9wVECxDA5ssopkamFf3iw-QBbIgn5olHACLcBGAs/s400/t-10%2Bdrivers%2Bstation.png" width="400" /></a><a href="https://1.bp.blogspot.com/-BTttL7QKsxo/XP8ZEELyD9I/AAAAAAAAOXU/H1HhyFsmhq02VBrx5OBBDK0GOsNdasI5wCLcBGAs/s1600/drivers%2Bstation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="465" data-original-width="687" height="270" src="https://1.bp.blogspot.com/-BTttL7QKsxo/XP8ZEELyD9I/AAAAAAAAOXU/H1HhyFsmhq02VBrx5OBBDK0GOsNdasI5wCLcBGAs/s400/drivers%2Bstation.png" width="400" /></a></div>
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Like the IS-3 and IS-7, the driver of the T-10 could be provided his own overhead hatch thanks to the geometry of the pike nose glacis design. The inclusion of a personal hatch for the driver is a basic ergonomic necessity of modern tanks that was unfortunately neglected in the IS-2, forcing the driver to ingress and egress the tank through the escape hatch in the belly, or the turret, which could only be done with reasonable speed if the turret was not pointed directly forward or elevated (the breech assembly is large and blocks the path of the driver). The IS-4 design included an overhead hatch for the driver, but it was only to permit the driver to drive with his head out of the hatch, thus eliminating the need for a vision port in the upper glacis as on the IS-2. This provided good driving visibility in non-combat conditions and improved the armour profile of the hull, but the hatch was too small for the driver to pass through. The IS-6 featured a driver's hatch as well, but it was designed as part of the upper glacis in the same configuration as the T-34 which was extremely unsatisfactory as the hatch was very heavy and the contortions required for the driver to pass through the hatch opening were simply not conducive to a quick escape.<br />
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<a href="https://1.bp.blogspot.com/-NNWd50psX18/XOo5fbHZM1I/AAAAAAAAOGE/6hpOO9rCZu4EYWo8SRKpaxw0L2-yNEftwCLcBGAs/s1600/1342289433_hOEl421.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1255" data-original-width="836" height="400" src="https://1.bp.blogspot.com/-NNWd50psX18/XOo5fbHZM1I/AAAAAAAAOGE/6hpOO9rCZu4EYWo8SRKpaxw0L2-yNEftwCLcBGAs/s400/1342289433_hOEl421.jpg" width="266" /></a></div></div><div><br />
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That said, the heavy tank models with a pike nose glacis were not without flaw. The driver's hatch on the IS-3 could not be opened from the outside because the rotatable MK-4 periscope embedded in the hatch was too tall and prevented the hatch from being swung off to the side. To open the hatch, the driver had to pull out the periscope from inside and stow it away before lifting the hatch and swinging it off to the side. This delays a quick escape if the tank were knocked out. Because of this limitation, the driver would be able to enter and exit through his hatch at will but he would first need to enter his station through the turret. Other tanks with rotatable periscopes in the driver's hatch used a <a href="http://www.williammaloney.com/Aviation/MilitaryMuseumOfSouthernNewEngland/CenturionMainBattleTank/images/06CenturionTankDriversHatch.jpg">split-hatch design to overcome this issue</a>.<br />
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To remedy the drawbacks of the IS-3 design, the T-10 uses the same periscope layout as the IS-7 with a more streamlined, low profile TPV-51 prismatic periscope embedded in the driver's hatch that did not need to be removed before opening the hatch. Two TPB-51 prismatic periscopes supplement the forward-facing TPV-51.<br />
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<a href="https://1.bp.blogspot.com/-A-lHVhmKSLc/XQVnQb1mYuI/AAAAAAAAOeE/X3rpm01moFAY0gg_2mOimzYgyKjI9cjTgCLcBGAs/s1600/tpv-51%2Bin%2Bdrivers%2Bstation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="954" data-original-width="1454" height="418" src="https://1.bp.blogspot.com/-A-lHVhmKSLc/XQVnQb1mYuI/AAAAAAAAOeE/X3rpm01moFAY0gg_2mOimzYgyKjI9cjTgCLcBGAs/s640/tpv-51%2Bin%2Bdrivers%2Bstation.png" width="640" /></a></div>
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The TPV-51 could be replaced without the driver leaving the tank by simply pulling the periscope out of its socket in the periscope housing and installing a new one in its place. Visibility from the TPV-51 was much better than the single MK-4S periscope of the IS-3, especially in the horizontal plane. The MK-4S could be rotated, so in theory, the driver of an IS-3 could see everything in front of the tank and beside it, but in practice, the driver needed both hands to use the steering tillers and the gearshift when the vehicle was in motion, so the supposed advantages of this setup do not offset the narrowness of the periscope. For comparison, the width of the TPV-51 periscope is 208mm whereas the width of the MK-4S is only 91mm.<br />
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<a href="https://1.bp.blogspot.com/-oztxHJAiPig/XD8eeGkjubI/AAAAAAAAM68/mo1fiyZl5qs9KumY-NOX1C5XNVOalsA7gCLcBGAs/s1600/tpv-51.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="723" data-original-width="1181" height="243" src="https://1.bp.blogspot.com/-oztxHJAiPig/XD8eeGkjubI/AAAAAAAAM68/mo1fiyZl5qs9KumY-NOX1C5XNVOalsA7gCLcBGAs/s400/tpv-51.png" width="400" /></a></div>
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The two TPB-51 prismatic periscopes are embedded in the top edges of the two "pike" surfaces of the upper glacis and are aimed at the 10 o'clock and 2 o'clock positions. The TPB-51 periscopes are identical to a TPV-51 in all dimensions except that they are square and not rectangular, which is somewhat unusual. It is likely that such periscopes were used so that the size of the holes in the frontal armour plates were minimized to reduce the reduction in structural integrity and the uniformity of armour thickness. The IS-7 uses an identical periscope layout but has TPV-51 periscopes instead of the square TPB-51.<br />
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<a href="https://2.bp.blogspot.com/-38assBCF2hQ/XEEUIDGewbI/AAAAAAAAM-4/7Vy7lixFi-gpczB4d6RgW67YN9FBb_WegCLcBGAs/s1600/drivers%2Bperiscopes.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://2.bp.blogspot.com/-38assBCF2hQ/XEEUIDGewbI/AAAAAAAAM-4/7Vy7lixFi-gpczB4d6RgW67YN9FBb_WegCLcBGAs/s400/drivers%2Bperiscopes.JPG" width="400" /></a><a href="https://3.bp.blogspot.com/-Uv3FrKik8iQ/XD8mEkT_rFI/AAAAAAAAM7U/PbbkDB32aw820d6zBF0Lp8FiwyNzn3f0ACLcBGAs/s1600/tpb-51.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="403" data-original-width="500" height="256" src="https://3.bp.blogspot.com/-Uv3FrKik8iQ/XD8mEkT_rFI/AAAAAAAAM7U/PbbkDB32aw820d6zBF0Lp8FiwyNzn3f0ACLcBGAs/s320/tpb-51.jpg" width="320" /></a></div>
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If damaged, each TPB-51 periscope can be replaced from inside the tank by unbolting it from its frame and then simply inserting a new one into the empty slot. The same is done to replace the TPV-51 periscope in the hatch. A set of two spare TPB-51 periscopes and one spare TPV-51 are carried in the T-10 in aluminium boxes. A dome light is installed on the hull ceiling to the left of the driver's seat. There is a fuze box for the tank's electrical system on the left wall of the driver's station.<br />
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Some accessories were provided for the driver to improve his driving experience. A spring-loaded helical brush could be affixed to the TPV-51 periscope. The helical brush is powered by a small electric motor and continually sweeps up and down the aperture window to clean it from mud, snow or rain. <a href="https://youtu.be/MwDaA15tiO8?t=567">This video of an Object 268 review</a> shows the installation of the brush being demonstrated briefly.<br />
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The combination of three fixed periscopes providing coverage for the forward arc of the tank grants the driver an acceptable level of visibility, although it is worth pointing out that the layout of the driver's periscopes is imperfect. Instead of having two square prismatic periscopes embedded in the upper glacis armour, rectangular periscopes could have been installed in the hatch over the driver's station much like <a href="http://data4.primeportal.net/tanks/jeff_derosa/m1a1_details/images/m1a1_details_137_of_435.jpg">the periscope layout of the M1 Abrams</a>. This would have conceivably provided much better visibility for the driver without any noticeable loss in protection. Nevertheless, the driver has an acceptable level of visibility. As the drawing on the right below shows, the size of the driver's hatch is quite average and it has a bulge behind the TPV-51 periscope to better accommodate the driver's head.<br />
<br /><br /><div>Additionally, an important design feature of the T-10 driver's hatch, inherited from the IS-7 and absent on the IS-3, was the high-strength locking mechanism used to secure the hatch. This was a necessary measure because of the very heavy shock loads that the tank was expected to survive, as it was meant to be protected from 100mm and 122mm shells. The highly reinforced nature of the locking mechanism may also be beneficial against blast and direct hits, which would be an important consideration for the T-10 because the roof and hatch are exposed from ground level and stood a moderately high chance of being struck directly by incoming shells. Rather than a conventional tension lock or a latch, the hatch is locked by a camming mechanism, whereby the hatch is cammed forward and slotted into a groove within the rim of the hatch opening on the roof plate. This means that the plate is not only structurally secured from being pushed inward, like any conventional driver's hatch, but also more secure from popping out.</div><div><br /></div>
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<div><br /></div><div><br /></div>The camming action is carried out using a special locking handle, located to the rear left corner of the hatch. When the hatch is locked, the handle is folded flush against the hull ceiling. In this position, the locking cam, which is a long steel bar that runs across the entire length of the hatch, lying between the hatch and the hull roof plate, will force the hatch forward and thereby wedge it in place. To unlock the hatch, the driver turns the handle to the vertical position, which turns the locking cam so that the hatch is no longer blocked from moving rearward. In this state, the hatch is still locked and cannot move either backwards or upwards, but it is only held from moving backwards by the hatch lifting mechanism.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-bEaMHCO-Q2M/YX8Yod1x99I/AAAAAAAAUUU/fW8YdVxeJL87bIGNhfGMnDlvaMO4qW5WwCLcBGAsYHQ/s693/drivers%2Bhatch%2Boverall%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="552" data-original-width="693" height="319" src="https://1.bp.blogspot.com/-bEaMHCO-Q2M/YX8Yod1x99I/AAAAAAAAUUU/fW8YdVxeJL87bIGNhfGMnDlvaMO4qW5WwCLcBGAsYHQ/w400-h319/drivers%2Bhatch%2Boverall%2Bview.png" width="400" /></a><a href="https://1.bp.blogspot.com/-XEt5jbbT_7Q/YX8dxKgnX-I/AAAAAAAAUUc/ldKNCj7OrOIQnqTRpxOVg_2C6K8APwWOwCLcBGAsYHQ/s598/drivers%2Bhatch%2Bopening%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="544" data-original-width="598" height="364" src="https://1.bp.blogspot.com/-XEt5jbbT_7Q/YX8dxKgnX-I/AAAAAAAAUUc/ldKNCj7OrOIQnqTRpxOVg_2C6K8APwWOwCLcBGAsYHQ/w400-h364/drivers%2Bhatch%2Bopening%2Bmechanism.png" width="400" /></a></div><div>
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Then, to lift the hatch, the driver lifts the opening lever from the locked position (completely vertical) until it is in the opening position (completely horizontal), and in doing so, the lever cams the hatch slightly rearward before it begins to lift it, thus allowing the rim to disengage from the groove in the hull roof plate. To swing the hatch over to the right, the driver pushes against the opening lever until it reaches a stopper, and he then lowers the lever to the locked position. The swinging of the hatch is assisted by a spring, housed in a tube next to the hatch opening mechanism and connected to the hatch hinge pin by a lever arm, as shown in the image on the right above. The spring is marked (21) and the lever arm is (19). It was necessary to include a spring assist mechanism because the hatch is very heavy, which can make it very difficult to open if the tank is banking to the left, so that the driver would have to fight against gravity to swing open the hatch. The spring assist was also borrowed from the IS-7 driver's hatch design. The process is reversed for closing the hatch and locking it in place. </div><div><br /></div><div>Due to the central location of the driver's station, it is not possible for the driver to pass through the hatch opening unless the turret is shifted to one side or the gun is elevated and the same limitations apply when he is driving with his head out of the hatch.<br />
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When driving "unbuttoned" with the turret in the travel position (aimed in the 6 o'clock direction and gun fixed to the travel lock), a curved water deflector attached to the turret bustle prevents rain water from flowing down the surface of the turret bustle and directly into the driver's neck, as shown in the photo below. The driver's hatch itself had a sponge rubber seal along its perimeter that provided a good water seal. This was replaced with a rubber O-ring seal in the T-10M to provide a more reliable hermetic seal.<br />
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The driver's seat is mounted directly on the floor of the hull between the torsion bar housings of the second pair of roadwheels. The gap between the torsion bar housings is 326mm in width, implying that the seat has the same width. It was necessary to install the seat on the floor of the hull and not on top of the torsion bar housings in order to provide the driver with the maximum amount of headroom. The width of the driver's station from shoulder-to-shoulder is 678mm.<br />
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As usual for Soviet tanks, the backrest of the driver's seat is adjustable in inclination with a choice of four positions and it is possible to place the backrest into a reclined position , making it a convenient and convenient place for the driver to sleep. The seat can also be folded forward which is useful when exiting the tank through the hull escape hatch. When the tank is driven with an open hatch, the driver's seat is not only raised but pivoted forward by the raising mechanism. This is because the driver's seat is not directly underneath the hatch but is actually slightly behind it, as mentioned earlier in the "Protection" section of this article.<br />
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To the driver's left, four accumulator batteries are installed on a special rack, and placed to the driver's right is ammunition racks for the 122mm cannon and three fire extinguisher bottles for the automatic firefighting system. The two 5-liter compressed air tanks for the pneumatic engine starting system are mounted to the lower glacis, behind and slightly above the driver's control pedals. These are standard air tanks with an operating pressure of 150 kg/sq.cm.<br />
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As usual, the driver steers the tank with steering tillers. These are placed on either side of the driver's legs and the driver's dashboard is located directly in front of him. The screenshot below (taken from <a href="https://www.youtube.com/watch?v=VYJjEzEeeFg">part 2 of Inside the Chieftain's Hatch: Object 268</a>) shows the dashboard from an Object 268 which does not differ from the T-10. The tachometer gauge is helpfully placed centrally on the dashboard. Strangely enough, there are two warning lights on the edges of the dashboard marked "Out of clearance".<br />
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The push-pull control rods for the various control pedals and levers - e.g. brakes, clutch, gear shift, accelerator, etc - run all the way to the engine compartment on top of the torsion bar housings.<br />
<br />There are a total of three headlights arranged on the upper glacis, two on the right and one on the left, together with an S-58 electric buzzer (horn) on the left side of the upper glacis. The horn is activated by a button located to the right of the driver's instrument panel. Depending on the model of T-10 and the circumstances, the headlights may have IR lamps (FG-100), full white light lamps (FG-10) or blackout lamps (FG-26, FG-102). A variety of combinations of these headlights can be seen in photographs of various T-10 tanks over the years of its career in the Soviet Army, with no discernible pattern.</div><div><br /></div><div>All of these devices are protected by a guard cage. The photo below from <a href="https://www.britmodeller.com/forums/index.php?/topic/235020451-t-10-object-730-soviet-heavy-tank/">from Dave Haskell</a> shows the headlight on the left of the upper glacis.<br />
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<span style="font-size: large;">TVN-1</span></h3>
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The T-10A had the TVN-1 infrared driving periscope as part of its standard equipment in 1956. The tank lacked any other night vision equipment besides this periscope so there was practically no possibility of fighting without additional white light illumination, but having the TVN-1 gave heavy tank units equipped with the T-10 a basic ability to maneuver in complete darkness during nighttime. Most importantly, large columns of tanks on a march would no longer be visible from the air. The periscope had a 1x magnification and a field of view of 30 degrees. The driver views the image through a viewing prism.<br />
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The infrared light source for the periscope is a single FG-10 infrared headlight installed on the right upper glacis plate. The 40 W infrared lamp of the FG-10 provided limited illumination, giving the driver a limited viewing distance of only 30 to 35 meters and curbing the average speed of the tank to only around 15 km/h on a dirt road. It was also challenging for the driver to negotiate obstacles and cross narrow paths. Combat maneuvering would be impossible or at least highly dangerous, so the tank is limited to firing from static positions or from a slow crawl, with the commander giving directions to the driver. The TVN-1 had a very constricted objective lens and provided a limited field of view, as the photos below show. There was a large deadzone in front of the tank due to the limited visibility, so the driver needed to be exceptionally careful when overcoming obstacles and crossing trenches. The TVN-1 lacked a heating system, so fogging could be an issue.<br />
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The T-54 was the first to receive the TVN-1 as the T-54 obr. 1954 variant. The main hurdle in implementing the TVN-1 on the T-10 was compatibility issues.<br />
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<span style="font-size: large;">TVN-2T</span></h3>
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The T-10M received the TVN-2T infrared periscope together with a new FG-100 infrared headlight. The FG-100 still had a 40 W lamp and was interchangeable with the FG-10 in practice, but the new periscope granted an increased viewing distance of 60 meters which made it much easier for the driver to navigate and enabled the tank to be driven at a much higher average speed of up to 25 km/h on dirt roads. The periscope had 1x magnification and a field of view of 30 degrees. One advantage of the TVN-2T over the TVN-1 is that the new design is binocular and therefore gave the driver a modicum of stereoscopic vision. The most apparent downside to the TVN-2T is that because the image is displayed on two eyepieces, the driver must have his face pressed up against the brow pad of the periscope to have the proper eye relief. Due to the layout of the driver's station, the driver would have to lean quite far forward to do this, and it is not a comfortable position for long durations. Another downside is that the periscope still lacked a heating system.<br />
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The TVN-1 or TVN-2T periscope would be installed in the hatch periscope housing next to the slot for the TPV-51 periscope. In order to fit the night vision periscope, new hatches with the appropriate periscope slots had to be installed in lieu of the original T-10 driver's hatch. The TVN-1 could not be installed in a hatch designed for the TVN-2T and vice versa. For both systems, the TPV-51 had to be pulled out of its slot to have armoured plug is inserted in its window to provide protection from bullets as well as to act as a barrier against water, mud and other unwanted foreign objects. Only then could the night vision periscope be installed. All of this could be done without leaving the tank, but this would only be done in a non-combat situation for obvious reasons. The drawing on the left below shows the TVN-1 as it appears when mounted in its slot, and the drawing on the right below shows the TVN-2T in its modified slot. Note the difference in the sealing mechanism for the periscope slot cover - it is absent for the TVN-2T slot.<br />
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Due to the restriction to a single narrow forward-facing vision device, the driver must take much greater caution when maneuvering the tank and the speed of the tank must be limited for safety reasons. The limited visibility range also forces the commander to determine a suitable route using his more powerful TKN-1 night vision device to direct the driver. During combat, the driver would most likely be forced to travel in straight lines and he will find it difficult to maneuver the tank into advantageous positions, such as by finding cover, driving over smoother paths to improve the accuracy of fire for the gunner. It would also be very difficult for him to detect and avoid tank traps.<br />
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On tanks that were equipped with the TVN-1 or the TVN-2T, the periscope could be installed in a special mount with the hatch opened. On the T-10A and T-10B, the TVN-1 would be installed on a special bracket that was clamped to the edge of the hatch opening, and on the T-10M, a simplified quick-detachable mounting system with a dovetail rail was provided on the hull roof in front of the driver's hatch. This feature improved the speed of nighttime maneuvers in non-combat conditions by allowing the driver to navigate with the benefit of having his head out of the hatch and access to a night vision device at the same time. It is also much more comfortable for the driver as he would not need to lean forward to use the periscope in this situation.<br />
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The night vision periscope is quite tall when configured for open-hatch driving and will obstruct the main gun, but this is irrelevant as turret rotation is automatically locked if the driver's hatch is opened. The safety rules for driving with the night vision periscope from an open hatch were the same as in daytime.<br />
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When not in use, the night vision periscope would be stowed inside the tank in a box attached to the wall of the upper glacis.<br />
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When it was introduced, the TVN-2T was fitted to Soviet tanks on a wide scale. The IS-2M, IS-3M and IS-4M were all upgraded with the TVN-2T to bring their night maneuvering capabilities to a modern level, and of course, the standardization of all night vision equipment into a single set running on a standard 27 V power supply was very sensible from a logistics perspective.<br />
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The GPK-48 gryocompass was installed in the T-10 together with the TVN-1 in 1956. It was placed in front of the gear selector lever, to the right of the accelerator pedal. The use of a gyrocompass together with a map gives the crew a rudimentary form of an Inertial Navigation System (INS). It is most useful when it is not possible to navigate by landmarks, such as when crossing rivers by snorkeling or when driving at night. To use it, the driver aims the tank in a specific direction and turns on the gyrocompass to set a reference point. For example, if the tank needs to travel in a perfectly straight line, the driver must steer the tank so that the bearing indicator line remains at the '0' point.<br />
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<h3>
<span style="font-size: large;">ESCAPE HATCH</span></h3>
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A circular escape hatch is installed in the belly of the tank, located behind the driver's seat. It is placed between the torsion bar housings for the second and third roadwheels. Having a diameter of 495mm, the size of the escape hatch is comparable to the commander's cupola hatch and it should certainly be more than enough to facilitate a speedy exit if the situation calls for it. A central post protrudes 84mm above the hatch.<br />
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The escape hatch designs is of the drop-out type. The hatch is secured to the hull belly by two locking lugs at the edges of the hatch which are spring-loaded and by two locking levers which are mounted to the central post. A cable runs between the two locking lugs. When pulled sharply upwards, the cable draws the two locking lugs back into their recesses and this releases the hatch, allowing it to drop free from the hull belly. To reinstall the hatch, someone inside the tank simply pulls it back up through the hatch opening. The beveled surfaces of the locking lugs slide against the edge of the hatch opening to push the lugs inward, and the lugs spring out to lock the hatch in place once they have cleared the edge of the hatch opening.<br />
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<h3>
<span style="font-size: large;">MOBILITY</span></h3>
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From an automotive standpoint, T-10 shared only a few similarities with previous heavy tanks like the IS-4. The suspension was derived from the IS-4, but the T-10 used the V12-5 engine instead of the V-12, the transmission was different, and the cooling system was absolutely unique, having only been implemented on prototypes like the IS-7 in the past.<br />
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Fixed aluminium side skirts were attached to the sponson stowage bins along the entire length of the sides of the hull. These are partial skirts as they only cover the returning track and the tops of the return rollers unlike the full skirts of a Centurion which cover the entire height of the hull. The main purpose of most side skirt designs is to reduce the amount of dust or sand kicked up by the tracks as it can form large clouds that may betray the location of moving tank units to enemy observers, but the effectiveness of the partial skirts in this capacity is probably not as high as full side skirts and the partial skirts are also too narrow to cover much of the crew compartment, so it isn't likely that they will have the chance to fulfill a secondary role as spaced armour screens. Aluminium side skirts were later fitted to the IS-3 and IS-4 as part of the IS-3M and IS-4M modernizations.<br />
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Aluminium mud guards with rubber flaps were fitted over the idler wheels. Beginning with the T-10M, rubber mudflaps were fitted to the nose of the glacis next to the mud guards as shown in the photo below <a href="https://www.britmodeller.com/forums/index.php?/topic/235020451-t-10-object-730-soviet-heavy-tank/">from Dave Haskell</a>.<br />
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A V-shaped splash guard is fitted halfway up the upper glacis, above the towing hooks to prevent water from flowing up the glacis and splashing the driver through his open hatch when the tank is fording a shallow stream.<br />
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As usual, the T-10 came with an unditching log for self-recovery if the crew found themselves stuck and there was not enough traction to escape. Due to the large number of equipment carried on the back of the hull, the unditching log was strapped to the right side of the hull instead of the normal position, behind the drive sprockets.<br />
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The T-10 was driven by the V-12 series of twelve-cylinder supercharged diesel engines with a displacement of 38.88 liters. The engine has roots in the original V-2 engine that powered the IS heavy tank family. Although obviously they were far from identical to the V-2IS engine of the IS-2 and IS-3, the fundamental similarities of the engine design undoubtedly made it easy for older crews and mechanics trained for IS tanks to familiarize themselves when they transferred to a T-10 unit.<br />
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As usual, the engine is mounted on a pair of I-beams on either side of the crankcase that run parallel to the engine crankshaft. Due to the use of short torsion bars, there is a gap between the torsion bar housings on the sides of the hull which the lower part of the engine crankcase occupies. This allowed the engine to be placed inside the engine compartment without needing a raised roof to accommodate its height.<br />
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The powertrain of the T-10 was proprietary. Only some peripheral components like the oil filter and fuel pump were shared with the V-54 engine of the T-54, but the advancements and technical solutions used during the development of the V-12-5 were transferred to the V12 engine project leading to the V12M variant which was fitted to the IS-4M.<br />
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Thanks to a relatively powerful engine and a relatively low combat weight, the top speed of the T-10 reaches 43 km/h, which is respectable for a heavy tank. The average speed when travelling on a dirt road is 24 km/h. When the T-10M entered service with a 750 hp engine, its marginally higher combat weight of 51.5 tons did not offset the advantages gained from the new engine and transmission; the top speed was increased to 50 km/h and the dynamic performance of the tank improved. For comparison, the M103A2 could only manage a top speed of 34 km/h. All T-10 models could surmount a vertical wall with a height of 0.9 meters, and cross a 3-meter trench.<br />
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The increased power of the V12 series demanded a cooling system of a much larger capacity. Externally, the primary distinguishing feature of the V12-5 and V12-6 from other engines is the lack of conventional exhaust manifolds as these engines were designed and tuned to work together with a forced ejection cooling system. Instead, the exhaust manifolds were integrated with the cooling system and they would be connected to the exhaust outlets of the engine using special adaptors.<br />
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On the T-10, T-10A and T-10B, there were two air types of intake vents for the engine. Two small "summer" intake vents were located on the rear corners of the fighting compartment roof and one large "winter" intake vent is located behind the engine access hatch on the engine deck. The "winter" intake is located behind the engine so that the engine is between the intakes of the air cleaners and the source of fresh air. As the air enters the engine compartment, it first passes around the engine, becoming heated in the process, before entering the intakes of the air cleaners. The heating of inducted air during extreme cold weather ensures that fuel vaporizes normally in the combustion chamber, allowing a high combustion efficiency to be maintained. The "summer" intakes allow the engine to draw air from ahead of the engine, allowing the airflow to avoid passing by the engine. This ensures that the heating of the air is kept at the absolute minimum when it is not desired. Needless to say, it is also possible to continue using the "summer" air intake in extreme cold, with the benefit of added engine power due to the high density of cold air, but the fuel efficiency of the engine suffers.<br />
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The "winter" intake grille is armoured with a mesh cover. It is hinged and once opened, the engine oil filter and some parts of the engine and transmission can be accessed.<br />
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By using multiple smaller plates bolted to a superstructure frame to form the engine deck, it was not necessary to remove the entire deck as a single piece in order to replace the engine, transmission, cooling system, or the fuel tanks. Each one of these four components can be replaced after removing only the engine deck panel directly above it.<br />
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On the T-10M, there were two air intake vents for the engine - one for "summer" and one for "winter". The "summer" air intake is hidden by the overhanging turret bustle when the turret is facing forward and the "winter" air intake is in the same location as before. The "winter" air intake remained a hinged hatch that could be opened to access some parts of the transmission. The single large engine access hatch of the previous T-10 models was replaced with two smaller hatches, the larger one permitting access to the coolant reservoir and some parts of the engine and the smaller one permitting access to the oil filter and more parts of the engine. The shapes of the engine deck armoured roof panels were also changed to reflect the reorganization of some internal components.<br />
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The change from a pair of "summer" air intakes at the corners of the fighting compartment hull roof to a single intake on the engine deck hidden under the turret bustle was due to experimental findings that established that the original placement of air intake hatches from the sides of the tank resulted in an unnecessarily high dust intake rate and thus, a larger filtration load on the air filters. The new single intake allowed the same air flow rate but with a significantly reduced dust intake rate.<br />
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The two air cleaners of the engine air supply system protrude slightly into the rear corners of the fighting compartment, so the firewall separating the fighting compartment from the engine compartment has two bumps to cover them. Interestingly enough, the M103 also had its air cleaners installed in such a layout.<br />
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Because of this layout, the length of the crew compartment is slightly shorter than the turret ring implies. Indeed, the great length of the engine compartment in the T-10 series is a trait shared with all preceding Soviet heavy tanks.<br />
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The air cleaners are self-contained units that can only be accessed from inside the tank. Air is received from the engine compartment rather than from an enclosed duct with a specific air intake, and the air is purified by the air cleaners before it is inducted by the engine via the supercharger intake manifold. The supercharger is driven by a power takeoff shaft connected directly to the engine crankshaft by a planetary reduction gear.</div><div><br /></div><div>
The air cleaner is a three-stage unit with a design that was shared with the PT-76, on account of both the T-10 series and the PT-76 having forced ejection cooling systems. The T-54 series was also fitted with a three-stage air cleaner at the time, but differed in having a multi-cyclone inertial dust separator as its first stage, as opposed to the centrifugal inertial dust separator of the T-10 design. <br /><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-nZ_n5IHGcAM/YUk5le5typI/AAAAAAAAUMk/EuniRGc83HMpNfQdqyX_OA5timfnrW_vgCLcBGAsYHQ/s670/engine%2Bair%2Bsupply%2B%25282%2529.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="364" data-original-width="670" height="348" src="https://1.bp.blogspot.com/-nZ_n5IHGcAM/YUk5le5typI/AAAAAAAAUMk/EuniRGc83HMpNfQdqyX_OA5timfnrW_vgCLcBGAsYHQ/w640-h348/engine%2Bair%2Bsupply%2B%25282%2529.png" width="640" /></a></div><a href="https://www.blogger.com/null" id="v12-5"></a><div><br /></div><div><div><br /></div><div>The first stage is a inertial dust separator with automatic dust ejection, powered by the negative pressure from the engine exhaust. Air enters the dust separator drum from the sides, where it passes along a grille with angled slats, causing the air to make an abrupt turn to pass through the holes in the grille. This is illustrated in the drawing on the right below. The air must make an acute turn, greater than 90 degrees, to pass between the slats. Due to the weight of the dust particles suspended in the air, they possess a relatively large amount of inertia, and strongly resist acute changes in direction. As such, while the air is capable of changing its flow direction abruptly to pass through the grille, the dust particles continue their original trajectory with the aid of the suction stream induced by the engine exhaust, as shown as the red line in the drawing, and end up funneled into the ejection chute instead. From there, the dust is extracted from the container and exit the tank via the engine exhaust. </div></div><div><br /></div><br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-X11KZ6Z0Td8/YUlqXv2ObzI/AAAAAAAAUNI/E4CB_e7R_KMXKiChlG50MrSEfYNpiuH_wCLcBGAsYHQ/s678/original%2Bair%2Bcleaner.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="490" data-original-width="678" height="289" src="https://1.bp.blogspot.com/-X11KZ6Z0Td8/YUlqXv2ObzI/AAAAAAAAUNI/E4CB_e7R_KMXKiChlG50MrSEfYNpiuH_wCLcBGAsYHQ/w400-h289/original%2Bair%2Bcleaner.png" width="400" /></a><a href="https://1.bp.blogspot.com/-K9DS0wncRBc/YUmCL9sFM2I/AAAAAAAAUNY/Ga4MM0kdToEpEnak7yReE4fFfhFyVxNJACLcBGAsYHQ/s678/original%2Bair%2Bcleaner.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="490" data-original-width="678" height="289" src="https://1.bp.blogspot.com/-K9DS0wncRBc/YUmCL9sFM2I/AAAAAAAAUNY/Ga4MM0kdToEpEnak7yReE4fFfhFyVxNJACLcBGAsYHQ/w400-h289/original%2Bair%2Bcleaner.png" width="400" /></a><br /></div></div><div><br /></div><div><br /></div><div>With the heaviest dust particles separated, the air proceeds to the second stage of the air cleaner, which consists of oiled felt lamellae. The lower part of the felt lamellae are soaked in a basin of oil while the top part are exposed to the air stream, serving as a trap for dust particles. Because the air lost its momentum when passing through the dust separator grille, the lighter dust particles suspended within the air also lose their momentum, and settle on the bottom of the air cleaner casing. There, they are stuck to the sticky oil surfaces of the lamellae. In the third stage, the finest dust particles are removed by an oiled filter consisting of three steel cassettes filled with steel wool which are coated with a layer of engine oil, held by mesh screens. The density of the wool packing is progressively increased in the direction of the air flow.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://2.bp.blogspot.com/-xla3RahCjO4/XFF5OdyNNYI/AAAAAAAANRc/1v5ho_X9dGUWtUmFl7_RRZ06RCacLa_VgCLcBGAs/s1600/air%2Bcleaner.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="476" data-original-width="712" height="267" src="https://2.bp.blogspot.com/-xla3RahCjO4/XFF5OdyNNYI/AAAAAAAANRc/1v5ho_X9dGUWtUmFl7_RRZ06RCacLa_VgCLcBGAs/s400/air%2Bcleaner.png" width="400" /></a></div><div><div><br /></div><div><br /></div><div>It is worth noting that due to the open air supply of the air cleaners, some power losses can arise due to the induction of heated air even when using the "summer" intake. Some amount of air inside the engine compartment will circulate regardless of which intake is used, and this air will still flow past the engine on its way to the air cleaner, which inevitably draws some heat from the engine. While this may have some effect in cooling the engine, albeit inefficiently, the heated air has a lower density, and thus, the amount of oxygen delivered to the engine combustion chambers is negatively impacted.</div><div><br /></div><div>According to the book "<i>Отечественные Бронированные Машины 1945–1965 ГГ.</i>", this type of three-stage air cleaner was used in the T-10 series until 1960. This is verified by a 1960 technical manual for the T-10M, which is applicable for the Object 272 model as of 1959, the original air cleaner is included as the existing type rather than the newer VTI-8. However, it was also stated in the book that the VTI-8 air cleaner was implemented in the T-10 series by 1956. The most likely explanation is that the VTI-8 only partially replaced the original type from 1956-1960, and a complete replacement did not occur until after 1960.</div><div><br /></div><div>The VTI-8 was designed as part of the new VTI series of two-stage air cleaners, featuring high cleaning efficiency and very low maintenance demands.</div><div><br /></div><div>A multi-cyclone cleaner is used as the first stage of the air filtration system, functioning as the main filtration unit. It consists of 96 micro-cyclones, with the collected dust falling into an ejection duct where it is carried away by the engine exhaust. Due to the lack of moving parts in cyclone filters, and the use of gas suction from the engine exhaust to continuously extract the collected dust, the cyclone system has very low maintenance demands. Even as a pre-filter, the cyclone system handles the bulk of the filtration workload, providing an air purity of at least 99.4% on its own. The second stage is a fine filtration system comprised of three steel mesh filter cassettes of progressively finer meshes. These cassettes are oil filters, with the meshes being coated with a thin layer of engine oil by soaking before being loaded into the air cleaner unit. After passing through the second filter stage, an air purity of around 99.9% is achieved. The nominal dust content after passing through the air cleaner is 0.12%. Each VTI-8 air cleaner supports and airflow rate of 0.38 cubic meters of air per second, for a total of 0.76 cubic meters per second.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-6f2ceRJ9Oqg/YUl5yu1dM-I/AAAAAAAAUNQ/m6ANyFPQoeov0ywjjXmMmI5JQgAc_omDwCLcBGAsYHQ/s400/vti-8.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="301" data-original-width="400" height="241" src="https://1.bp.blogspot.com/-6f2ceRJ9Oqg/YUl5yu1dM-I/AAAAAAAAUNQ/m6ANyFPQoeov0ywjjXmMmI5JQgAc_omDwCLcBGAsYHQ/w320-h241/vti-8.jpg" width="320" /></a><a href="https://1.bp.blogspot.com/-a1IGL8jGXH4/YUlgJsJGpXI/AAAAAAAAUNA/RRf6XhLvdxkFJd2m8NJr_km4m0p0ow0twCLcBGAsYHQ/s1653/t-10%2Bair%2Bcleaner%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1150" data-original-width="1653" height="279" src="https://1.bp.blogspot.com/-a1IGL8jGXH4/YUlgJsJGpXI/AAAAAAAAUNA/RRf6XhLvdxkFJd2m8NJr_km4m0p0ow0twCLcBGAsYHQ/w400-h279/t-10%2Bair%2Bcleaner%2Bsystem.png" width="400" /></a></div></div><br /><div>The time needed between servicing is 46 engine hours. </div><div><br /></div><br />
<h3>
<span style="font-size: large;">V12-5, V12-5B</span></h3>
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The V12-5 series was installed in the T-10 up to the T-10B. It had a maximum power output of 700 hp at an engine speed of 2,100 RPM and had a maximum gross torque output of 2,844 Nm at an engine speed of 1,200 to 1,400 RPM. The net power output at the drive sprockets was 640 hp. Compared to the V-54 engine used in the T-54 series of medium tanks, the V12-5 series gained additional power from a slightly increased crankshaft speed combined with more torque, achieved via supercharging. The use of a supercharger also provided benefits in terms of the flatness of the torque and power curves, which enhanced the load-bearing performance of the engine. In particular, the engine elasticity and flexibility (adaptability) was improved. <br />
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Attached to the engine was an electric generator, a fine fuel filtration system, a fuel pump, an oil filter and a water pump for the engine cooling system. One of the characteristic features of the V12-5 is the AM42-K supercharger fitted to the crankshaft on the opposite end of the powertrain output shaft. The supercharger has a large impeller fan with a diameter of 240mm in order to ensure sufficient pressurization of the air supply to support the high power of the engine.<br />
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The original V12-5 engine was fitted to the original T-10. This engine had the G-731 electric generator to supply electrical power for charging the batteries and to run the equipment in the tank. The output of the generator is 1.5 kW and the operating voltage is 24-29 V. The generator was driven by power takeoff from the engine crankshaft through a power takeoff gear with a hydraulic clutch.<br />
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As the electrical load increased with the number of planned new features, the need for a more powerful generator became evident. Beginning with the T-10A model with the single-plane PUOT stabilizer, the G-731 electric generator was replaced the G-74. The output of the generator is 3 kW. With the introduction of the T-10B model in 1956, the V12-5B variant developed in 1953 was installed to handle the further increase in the electrical load from the new two-plane PUOT-2 stabilizer. The V12-5B was fitted with the G-5 electric generator. It had an output of 5 kW.<br />
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The ST-700 electric starter was installed next to the crankcase. It runs on the 24 V supply from the accumulator batteries carried in the tank and has a power of 15 hp. The engine was normally started using the electric starter but as expected from a Soviet tank, the option of using the compressed air of the pneumatic starting system was also available. Air is supplied by two five-liter air cylinders and the delivery of the air to the engine is controlled by regulator mechanism as shown in the drawing below. The option of inertial starting was also provided. Thanks to these provisions, a T-10 with flat batteries and empty air cylinders could be started under unenviable conditions as long as a suitable owing vehicle was available. Later on, the ST-700 electric starter was replaced by the ST-16M. The ST-16M has the same power output.<br />
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<a href="https://www.blogger.com/null" id="v12-b"></a>
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<h3>
<span style="font-size: large;">V12-6B, V12-6V</span></h3>
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The V12-6B was developed in 1956 and installed in some T-10M tanks when the model entered service in 1957. It has a maximum gross power output of 750 hp at an engine speed of 2,100 RPM and produced a maximum gross torque output of 2,942 Nm at an engine speed of 1,200 to 1,400 RPM. <br />
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The engine includes water channels for the heating system inside its crankcase. This made it non-interchangeable with the V12-5, although many of the peripheral components such as the fuel filters and electric generators could still be shared between the two engines. The AM42-K supercharger was replaced by the UNA-6 which was characterized by a larger impeller fan with a diameter of 297mm designed for the 50 hp increase in the power output of the engine compared to the V12-5. The dry weight of the V12-6B is 1,024 kg.<br />
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The V12-6B retained the same G-5 generator found on the V12-5B. The V12-6V variant entered service in 1958 together with the T-10M, differing only in that it had the G-6.5 generator with an output of 6.5 kW. The larger power supply was needed to handle the increased load from all of the new equipment implemented in the rather sophisticated T-10M.<br />
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In the graph below, the dotted line represents the V12-5 and V12-5B engines and the solid line represents the V12-6B and V12-6V engines. From the top, the first chart shows the power output curve in kilowatts and in horsepower. The second chart shows the torque output curve in kilogram-meters (kg.m) and in Newton-meters (N.m). The third chart shows the relative fuel consumption rate in kilograms per hour (kg/h), and the fourth chart shows the specific fuel consumption rate in grams per kilowatt-hours (g/kW.h).<br />
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All T-10 models are able to climb a hill with a slope of 32 degrees (62.5% grade) and negotiate a side slope of 30 degrees. This is superior to the T-34-85 and is equivalent to the standards of the T-54 medium tank and other modern medium tanks of the time, so there was very little distinction in hill-climbing capabilities between the two classes, at least as far as the Soviet Army was concerned.<br />
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The design weight limit of 50 tons had a positive effect on the mobility of the T-10 and in the mobility of tank units equipped with heavy tanks in general.<br />
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The most immediate effect of the artificial weight limit is that all T-10 models are light enough to make use of all tactical bridges for crossing anti-tank trenches and pontoon bridges for river crossings, although it should still be noted that the lower weight surplus for the T-10 on bridges like the MTU and TMM systems compared to medium tanks like the T-54 and T-62 (36 tons and 37 tons respectively) necessitates greater caution when performing such operations.<br />
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Although the power developed by the V12-5 and V12-6 engines was not outstanding compared to existing foreign counterparts, the relatively light weight of the T-10 series gave it a relatively high power-to-weight ratio and facilitated better fuel economy. With a combat weight of 50 tons, the T-10, T-10A and T-10B had a power to weight ratio of 14 hp/ton. This was directly equivalent to the power-to-weight ratio of a T-54 which weighed 36 tons and had a 520 hp engine. The T-10M was slightly heavier as it weighed 51.5 tons combat loaded but this was fully compensated by the increased power of its engine, giving it a slightly better power to weight ratio of 14.56 hp/ton.<br /><br />
Although by now it may seem that the comparisons with the M103 and Conqueror have become rather incessant and somewhat predictable, they are still important. However, a direct comparison of the power output of the heavy tank engines simply does not suffice as the power output curves are rather different. There are also differences between M103 models themselves; the twelve-cylinder V-shaped AV-1790-5B engine of the M103A1 is a carbureted petrol engine whereas the AVDS-1790-2A of the M103A2 is a supercharged diesel engine.<br />
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The AV-1790-5B has a displacement of 29.36 liters and has a gross power output of 810 hp at 2,800 RPM. It develops 2,169 N.m of gross torque at a relatively high engine speed of 2,200 RPM and a maximum net torque of 1,912 N.m at 2,000 RPM. The diesel AVDS-1790-2A has the same displacement but it has a lower gross power output of 750 hp at 2,400 RPM. It develops 2,318 N.m of gross torque at a lower engine speed of 1,800 RPM with a maximum net torque of 2,135 N.m at 1,750 RPM. The net horsepower of the diesel engine was lower, but the engine not only had a much higher gross torque output - it was also generated at a lower engine speed, thus making for a flatter power curve with more instantaneous power available to the driver. This allowed the tank to overcome rolling resistance more rapidly and thus accelerate more quickly from a standstill. As such, a net improvement in acceleration characteristics was gained.<br />
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However, even with the improved performance of the new diesel engine, the T-10M still surpassed the M103A2 by a considerable margin on paper. Thanks to the large displacement of the engine, 38.88 liters, it was naturally predisposed to producing a great deal of torque, which gives an advantage in the lower end of the power curve. This is shown in the two power curves below. The graph on the top is for the AVDS-1790-2, while the graph on the bottom is for the V12-5 (dotted line) and the V12-6 (solid line). It can be seen that the power of the AVDS-1790-2 at 1,400 RPM reaches 480 hp, whereas the V12-5 attains 560 hp at the same speed, and the V12-6 reaches around 580-590 hp. In this example, it can be seen that despite the fact that the V12-6 and the AVDS-1790-2 engines both have an equal maximum gross power output of 750 hp, the V12-6 surpasses the AVDS-1790-2 by over 100 hp in low end power. The advantage declines as the engine speed rises, up to a gap of 50 hp when the V12-6 reaches its peak at 2,100 RPM, while the AVDS-1790-2 must still continue to speed up to 2,400 RPM to reach its peak power.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GRJEk1CzpQc/YUmVrKo2xuI/AAAAAAAAUNw/l2omFwwakGwEnTCTxyUbky0vd_oP5ShpACLcBGAsYHQ/s316/avds-1790%2B750%2Bhp%2Bpower%2Bcurve.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="263" data-original-width="316" height="333" src="https://1.bp.blogspot.com/-GRJEk1CzpQc/YUmVrKo2xuI/AAAAAAAAUNw/l2omFwwakGwEnTCTxyUbky0vd_oP5ShpACLcBGAsYHQ/w400-h333/avds-1790%2B750%2Bhp%2Bpower%2Bcurve.png" width="400" /></a></div></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-OqcBdrNQgmE/YUmV7Sr2u0I/AAAAAAAAUN4/bNr95XWJCJY97GzEAHHC0Ho0nRyXWXqrQCLcBGAsYHQ/s515/v-12-5%2Band%2Bv-12-6%2Bpower%2Bcurve.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="230" data-original-width="515" height="179" src="https://1.bp.blogspot.com/-OqcBdrNQgmE/YUmV7Sr2u0I/AAAAAAAAUN4/bNr95XWJCJY97GzEAHHC0Ho0nRyXWXqrQCLcBGAsYHQ/w400-h179/v-12-5%2Band%2Bv-12-6%2Bpower%2Bcurve.png" width="400" /></a></div><div><br /></div><div><br /></div><div>In practice, the difference in mobility is unlikely to have a decisive effect on an actual tank duel. Rather, the practical advantage held by the T-10M would be the ability to move more confidently in sub-optimal terrain which may allow the Soviet Army as a whole to gain the strategic initiative in large scale maneuvers.<br />
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Four 6-STEN-140M accumulator batteries are carried in the tank. These are lead-acid batteries with a voltage rating of 12 V and an amperage rating of 140 Ah each. Alternatively, 6-MST-140 and 6-ST-130 accumulator batteries may be used instead. The four batteries are divided into two pairs wired in series and the two pairs are wired in parallel to double the operating voltage and amperage rating to 24 V and 280 Ah respectively if 6-STEN-140M or 6-MST-140 batteries are used. If 6-ST-130 batteries are used, the lower amperage rating of 130 Ah reduces the total capacity to 260 Ah when wired up. The batteries supply 24 volts when the engine is turned off and the G-5 generator supplies 28 V when the engine is running.<br />
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A nozzle-type preheater is installed in the engine compartment to assist in starting the engine in cold weather conditions. The preheater is designed to warm up the engine and the oil before the engine is started electrically or pneumatically, depending on the severity of the weather. Under the worst conditions, a combination of electric and pneumatic starting may be needed. The preheater, shown in the drawing below, is installed in the front right corner of the engine compartment. The circulation of water in the cooling and heating system was provided by an electric pump with a manual hand crank as a backup option in case electrical power is unavailable. To use the manual hand crank, a flap in the engine compartment partition could be opened to insert the crank handle. In the T-10M, the preheater was also used to heat the oil in the transmission.<br />
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The water reservoir of the preheater system is the large container bolted to the floor, and the boiler is the smaller box placed next to it. The pump is mounted above the water reservoir and serves to circulate heated water from the boiler around the engine crankcase and cylinders as well as the engine oil tank and transmission case. The water flow path is shown in the drawing below, taken from a T-10M manual.<br />
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Besides using a preheater, the air intake manifolds of the engine had an integral heating system that burned small amounts of diesel fuel in order to heat up the incoming air. This greatly improved the starting reliability of the engine in extremely cold weather.<br />
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<a href="https://www.blogger.com/null" id="transmission"></a>
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<h3>
<span style="font-size: large;">TRANSMISSIONS</span></h3>
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Three different transmissions were used in the T-10 series. All three transmissions featured regenerative steering with a single variable turn radius in each gear, and with optional clutch-and-brake steering. Only pivot steering was possible; the ability to perform neutral steering was not provided and it was generally not possible on any serially-produced Soviet tank. This basic set of features was a universal feature of Soviet heavy tanks since the IS (IS-1) entered service in 1943. Regenerative steering means that the transmission supplies full power to both tracks so there is minimal energy loss when turning, allowing the T-10 to preserve most of its speed while turning and even more so in muddy or swampy terrain. The optional clutch-and-brake steering system is engaged when the steering tillers are pulled to the maximum deflection and it applies the brake on the track of the corresponding side. Clutch-and-brake steering is used for pivot turning in first gear and it can act as a secondary steering system in all higher gears.</div><div><br /></div><div>The first transmission used in the T-10 (Object 730) was inherited from the IS-7 (Object 260) as of its development in 1947-1948.<br />
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Aside from the transmission itself, it is worth noting that there is a dome light installed on each side of the engine compartment next to the transmission unit. Although it seems fairly mundane, the inclusion of dome lights is only standard for the crew compartment of tanks. It is very rare for dome lights to be provided in the engine compartment and it is a nice bonus for the crew or for the technicians when carrying out repairs or maintenance, especially at night.<br />
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The drawing on the left below shows the original 8-speed transmission of the T-10, T-10A and T-10B. The drawing on the right below shows the 8-speed transmission of the T-10M, uprated for the increased power of the V12-6B engine and fitted with a hydraulic control system.<br />
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<h3>
<span style="font-size: large;">T-10M (Object 272)</span></h3>
<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-QJkmm6ZnfPw/XO1Zr2_Zo4I/AAAAAAAAOIg/wG4G9cCRCngtDTzx8Yp8aVlRtuYIzKGYACLcBGAs/s1600/obj%2B272%2B8-speed.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="301" data-original-width="458" height="262" src="https://1.bp.blogspot.com/-QJkmm6ZnfPw/XO1Zr2_Zo4I/AAAAAAAAOIg/wG4G9cCRCngtDTzx8Yp8aVlRtuYIzKGYACLcBGAs/s400/obj%2B272%2B8-speed.jpg" width="400" /></a></div>
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The new transmission developed for the Object 272 had a planetary three-shaft gearbox with eight forward gears and two reverse gears. The casing of the entire transmission is made from cast aluminium. Gear shifting and de-clutching was done hydraulically. Like the older transmission of the T-10, the Object 272 transmission had dry friction band brakes, but the steering system provided a different variable turn radius in each gear, with the radius being dependent on the terrain resistance, which determines the steering resistance and therefore the response from the differential.</div><div>
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The overall weight of this transmission is 3,811 kg. The gearbox itself weighs 2,118 kg and occupies 0.998 cubic meters, and the final drives weigh 725 kg each. As a whole, the transmission occupied a volume of 1.55 cubic meters. </div><div>
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<h3>
<span style="font-size: large;">T-10M (December 1962)</span></h3>
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Beginning in December 1962, a simplified 6-speed mechanical transmission was implemented on the T-10M. It was also retrofitted to older tanks at the factory during scheduled major overhauls. This transmission was originally designed for the experimental "Object 709" tank and it was developed as a backup option for the T-10M in case the 8-speed hydraulically assisted transmission was not successful.<br />
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The new three-shaft gearbox (one input shaft, two output shafts) had six forward gears and two reverse gears. The use of a three-shaft design instead of a planetary design reduces the length of the transmission yet provides a high torque capacity. The friction clutch is of the multi-disc, dry friction type with steel on asbestos friction surfaces. Later on, the asbestos was replaced by K-15-6 high-performance plastic. The steering system was simplified but still provided progressive turn radii in different gears.<br />
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Overall, the new transmission weighed 311 kg less than the 8-speed transmission of the T-10M (Object 272), had smaller dimensions, and was simpler to manufacture and install. Requiring a volume of only 0.825 cubic meters, the new transmission freed up 0.173 cubic meters of space in the engine compartment. This was taken as an opportunity by the tank designers to increase the internal fuel capacity by 100 liters.<br />
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The photo below shows the armoured transmission access panel at the rear of the hull (credit to <a href="http://www.kotsch88.de/al_T-10M.htm">Stefan Kotsch</a>). The transmission access panel is attached to a pair of hinges and is sprung with a heavy-duty torsion bar so that it is relatively easy to open despite its large armour thickness. This is necessary because the panel is sloped at 55 degrees, so the crew would need to fight against gravity to lift the heavy access panel which would be even heavier if BDSh-5 smoke bombs or additional fuel drums were mounted.<br />
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When opened, the panel is held on fixed stops at an oblique angle. It would probably have been best if the panel could be held in a horizontal position when opened so that it becomes a convenient platform, but the angle of the access panel is dictated by the limits of the torsion bar.<br />
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<a href="https://1.bp.blogspot.com/-MWq3tVDr3lw/XQVRNcJsACI/AAAAAAAAOdk/RgjvypkORAQUPIkWGm2-GCWFhYit5RZCgCLcBGAs/s1600/transmission%2Baccess%2Bpanel%2Bt-10a%2Brange%2Btarget.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="598" data-original-width="1259" height="302" src="https://1.bp.blogspot.com/-MWq3tVDr3lw/XQVRNcJsACI/AAAAAAAAOdk/RgjvypkORAQUPIkWGm2-GCWFhYit5RZCgCLcBGAs/s640/transmission%2Baccess%2Bpanel%2Bt-10a%2Brange%2Btarget.png" width="640" /></a></div>
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Criticism is sometimes directed at the T-10 and other Soviet tanks (including high-profile individuals in the tank enthusiast community) for having an ostensibly excessive level of protection on the rear of the hull, facilitated by a supposedly unnecessary sloped armour configuration. However, this is usually not a valid concern as tanks that featured sloped rear hull armour also had no use for the additional space gained by omitting sloped rear hull armour.<br />
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This is shown in the drawing below. If the sloped transmission access panel was replaced with a flat armour plate of equivalent effective thickness, only the volume of air would be increased as nothing can be installed above the transmission or it would simply obstruct access to the maintenance hatches on the transmission case. Rather, the design implemented on the T-10 allows relatively easy access to the transmission without the need for special tools other than a wrench, and the transmission can be removed through the open access panel without unbolting and removing any of the engine deck panels. The main disadvantage is that having so many bolts to secure the access panel for the sake of armour integrity also makes it a tedious chore to access the transmission for even minor inspections.<br />
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<a href="https://2.bp.blogspot.com/-XsnZ_ejxlSY/XDOChDJeGmI/AAAAAAAAMz0/JUgipSWhvhAe2Lh6QVGbGyUWP7UPfAVTQCLcBGAs/s1600/cross%2Bsection%2Bt-10m%2Bbtvt.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="589" data-original-width="1600" height="234" src="https://2.bp.blogspot.com/-XsnZ_ejxlSY/XDOChDJeGmI/AAAAAAAAMz0/JUgipSWhvhAe2Lh6QVGbGyUWP7UPfAVTQCLcBGAs/s640/cross%2Bsection%2Bt-10m%2Bbtvt.jpg" width="640" /></a></div>
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<a href="https://www.blogger.com/null" id="cool"></a>
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<h3>
<span style="font-size: large;">COOLING SYSTEM</span></h3>
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<a href="https://3.bp.blogspot.com/-xhslv1yv4AM/XDaVRStj4cI/AAAAAAAAM0o/dmQsKyxPWjI4J1iXzYicPcT-iaD8o5EYACLcBGAs/s1600/cooling.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="373" data-original-width="686" height="347" src="https://3.bp.blogspot.com/-xhslv1yv4AM/XDaVRStj4cI/AAAAAAAAM0o/dmQsKyxPWjI4J1iXzYicPcT-iaD8o5EYACLcBGAs/s640/cooling.png" width="640" /></a></div>
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In a departure from previous Soviet heavy tank designs where fan-driven cooling systems were the norm, the T-10 uses a forced ejection-type cooling system. This system was previously implemented on the IS-7 and it was later implemented on the T-64 which had a 10-cylinder opposed-piston engine. The system works by using the exhaust gasses from the engine to draw air through a pair of radiator packs by suction. The radiators are located on both sides of the engine with the two radiator packs mounted on the engine compartment deck, both protected by heavily armoured grilles. A steel mesh screen is bolted on top of the armoured grille to keep out leaves and other debris.<br />
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<a href="https://3.bp.blogspot.com/-GhvMJ7PUQRk/XMX7DnPV_TI/AAAAAAAANy4/9nv6z3V_SAEE1f6eje2YcA-0DMxh5gOoACLcBGAs/s1600/left%2Blouvers.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1094" data-original-width="1275" height="342" src="https://3.bp.blogspot.com/-GhvMJ7PUQRk/XMX7DnPV_TI/AAAAAAAANy4/9nv6z3V_SAEE1f6eje2YcA-0DMxh5gOoACLcBGAs/s400/left%2Blouvers.png" width="400" /></a><a href="https://2.bp.blogspot.com/-d29FdH2JsqI/XMX7Dm2VKUI/AAAAAAAANy0/l9MqZ8mUGJUOcShuMjWJC9PnDMtFAivwACLcBGAs/s1600/right%2Blouvers.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1139" data-original-width="1284" height="353" src="https://2.bp.blogspot.com/-d29FdH2JsqI/XMX7Dm2VKUI/AAAAAAAANy0/l9MqZ8mUGJUOcShuMjWJC9PnDMtFAivwACLcBGAs/s400/right%2Blouvers.png" width="400" /></a></div>
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Unlike the armoured radiator louvers of tanks like the T-54, the grilles are fixed in place and as such, they cannot be sealed from water when performing fording operations, let alone to protect against air attack, napalm attack or Molotov cocktails. As such, the grilles only provide armour protection through their considerable thickness and their shape with the natural drawback of being very heavy.<br />
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Each radiator pack consists of a lamellar-tube oil radiator and a water radiator, with the former placed on top of the latter. The water is used as the engine coolant and the oil is used as the transmission coolant. The oil reservoir is located on the left of the engine underneath the left radiator pack. The coolant reservoir is located on the floor of the fighting compartment in the rear right corner, but there is a pan-shaped expansion tank at the top of the engine where the only coolant filler port is located. The filler port can be accessed from outside the tank without opening the entire engine access panel by simply unscrewing the armoured filler port cap and then opening the filler port cap. The water radiator is shown in the drawing on the left below and the oil radiator is shown in the drawing on the right below.<br />
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The cooling system has no moving parts as it works entirely on the principles of pressure differentials. Exhaust gasses are routed from the engine exhaust manifolds into an expansion chamber, where they can then exit through a special nozzle at high velocity. The high velocity of the gasses emerging from the nozzle creates a suction force due to the pressure differential between the gasses and the atmospheric air above the radiator pack. This draws cool atmospheric air through the radiator pack and into the stream of the exhaust flow, where it mixes with the exhaust gasses and is ejected out of the tank through the diffusor duct. A cross-sectional drawing of the system is shown below.<br />
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The diffusor duct is designed to enable the waste gasses to exit with minimal flow restriction. The entire system does not draw any power directly from the engine, but the expansion chamber which generates the high velocity flow necessary to create high suction forces to circulate air through the radiators also creates a significant amount of backpressure which translates to power losses in the engine.<br />
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A great deal of research was done to develop the nozzles of the forced ejection cooling system. <br />
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<a href="https://1.bp.blogspot.com/-hDY6duHehgY/XPZPvrebDxI/AAAAAAAAOMM/H4tM5Z5-wtMgYBPi5pzLB4BDWVbUiuCVACLcBGAs/s1600/ejector.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="449" data-original-width="953" height="300" src="https://1.bp.blogspot.com/-hDY6duHehgY/XPZPvrebDxI/AAAAAAAAOMM/H4tM5Z5-wtMgYBPi5pzLB4BDWVbUiuCVACLcBGAs/s640/ejector.png" width="640" /></a></div>
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According to the study "<i><a href="http://btvt.info/5library/vbtt_1985_02_poteri.htm">Пути Снижения Затрат Мощности В Системах Танкового Диселя</a></i>" ("<i>Ways to Reduce The Power Costs in Tank Diesel Systems</i>") by S.P Baranov and V.T Nikitin, the cooling system of the T-64A with the 5TDF engine (700 hp) consumes 5.6% of engine power. Given the lack of detailed information on the T-10 in this particular topic, it should be reasonable to assume that the V-12-5 engine of equivalent power to the 5TDF engine will also suffer similar losses since it uses a principally identical cooling system, although it is important to note that the V-12-5 and V-12-6 operate under a higher load due to the much higher weight of the T-10 heavy tank compared to the T-64. Still, it is probably safe to assume that the T-10 follows the Soviet norm of having an efficient cooling system with low power consumption which combines with the high efficiency of the manual mechanical transmission to ensure a high net horsepower at the drive sprockets.<br />
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The exhausts of the filtration system for the engine air supply are also connected to the diffusor duct as a convenient mechanism for the disposal of the larger dust particles. The drum or cyclonic filters only separate the dust without ejecting them, so the dust is removed by suction from the exhaust flow in the diffusor duct.<br />
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Interestingly enough, the mixing of the relatively cool waste air from the radiator pack with the much hotter air from the engine exhaust manifolds would undoubtedly lower the final temperature of the mixture by some amount when it emerges from the diffusor outlet.<br />
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Opening the armoured radiator grilles reveals the radiator packs, and removing the radiator packs will enable access to the sides of the engine. This is shown in the photo below (taken from the <a href="https://www.net-maquettes.com/pictures/t-10-heavy-tank/">Net-Maquettes website</a>), although in this photo, the panel for mounting the armoured grilles has been removed entirely. The mounting points for the diffusor duct can be seen on the curved side armour plate, just above the engine support frame.<br />
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<a href="https://www.blogger.com/null" id="susp"></a>
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<h3>
<span style="font-size: large;">SUSPENSION</span></h3>
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The T-10 had seven pairs of roadwheels with a form of torsion bar suspension known as bundled torsion bars. Unlike conventional rubber-rimmed roadwheels found on the majority of tanks, the entire line of IS heavy tanks including the T-10 used all-metal roadwheels exclusively, and like the tanks that preceded it, the tracks of the T-10 were supported with three return rollers on each side. The total weight of the running gear, including the suspension, is 10,116 kg. It accounts for 19.6% of the total weight of the tank. This is the same share of weight as medium tanks like the T-54. Each return roller had a diameter of 310mm as shown in the drawing below and each weighed 73 kg. The first and seventh roadwheel swing arms had hydraulic shock absorbers for additional shock damping. On the T-10M, an additional pair of hydraulic shock absorbers were added on the second roadwheel swing arms, giving the tank a total of three pairs for both sides.<br />
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The bundled torsion bars of the T-10 were derived from the IS-7 and have fairly unique characteristics. Instead of a single spring rod stretching across the full width of the tank hull, seven individual rods of a much smaller diameter and a much shorter length were bundled together in a large cylindrical housing to form the torsion bar spring. This is shown in the drawing below, taken from a T-10M manual. The drawing below also shows the shock absorber built into the roadwheel swing arm.<br />
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This type of suspension was originally developed at the end of WWII by chief designer Nikolay Shashmurin at factory No. 100 in conjunction with the NII-48 research institue for the IS-7. Further research on bundled torsion bars was continued at the VNII-100 research institute. The bundle consists of a central torsion bar surrounded by 6 peripheral bars. This was a simplification of the bundle design used on the IS-7, which had a central bar and 18 peripheral bars.</div><br /><div><br /></div><div>Like practically all other torsion bars created for Soviet tanks during the 1950's, 45KhNMFA spring steel is used. The length of each torsion bar is only 880mm and the diameter is only 34mm. For reference, the torsion bars of the PT-76B are 38mm in diameter and the torsion bars of the T-54 are 56mm in diameter. By bundling seven smaller rods together to form a torsion bar, the modulus of elasticity was increased to 51,9900 N/m. This is only 4.5% higher (more rigid) than the torsion bars of the T-55 and T-62, and the weight of the T-10 is spread over seven roadwheels on each side instead of five. Additionally, it is claimed in the 21st edition of the "<i>Отечественные бронированные машины 1945-1965 гг.</i>" series (<i>Domestic Armoured Vehicles 1945-1965</i>) by M. V. Pavlov and I. V. Pavlov that a non-linear response could be obtained from bundled torsion bars, approaching that of a progressively hardening suspension, though it is somewhat unclear why this type of torsion bar exhibits this behaviour.</div><div>
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The decision to use bundled torsion bars as opposed to conventional single-rod torsion bars was a matter of contention during the development of the T-10 that apparently led to the dismissal of the former wartime manager of the ChKZ plant and his replacement with a more agreeable plant manager. It was not a matter of limited hull width or any geometric constraint, but a desire to eliminate some of the durability and reliability issues associated with single-rod torsion bars and to use the internal space of the tank in a more efficient manner.<br />
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As mentioned before in this article in the section on the driver's station, the axial distance between the ends of the torsion bar housings is 326mm. This was designed so that the driver's seat could be installed in this gap rather than on top of the torsion bars, thus saving vertical space in the hull and ensuring the the driver had the maximum amount of headroom that was possible in the 1,015mm-tall hull.<br />
<br />The maximum shear stress of the bundle was 1,128 MPa, compared to the maximum shear stress of 978 MPa of the single torsion bar from a T-55. The travel range of the roadwheels was also slightly higher, having a bump travel of 172mm compared to 162mm of travel for the T-55. Besides that, the durability and reliability of the bundled torsion bar was higher due to the extremely low probability of all seven individual torsion bars failing at once. Even if several of the bars were damaged, whether by fatigue or mine attack, the bundle can still function until a replacement is available. In a conventional single-rod torsion bar suspension system there is no redundancy, so damage to a torsion bar will render the entire suspension element useless.<br />
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However, the T-10 was the first and last Soviet tank to implement this approach to suspension design. Due to the increased complexity of the design and greater demands on skilled labour during of manufacturing, as well as the higher cost, bundled torsion bar suspension technology was not further pursued for future tank projects. </div><div><br /></div><div>Moreover, the objective of minimizing the usage of internal vertical hull space was only partly achieved, as the rotating floor of the turret still had to be installed above the large torsion bar housings. As such, even though the driver benefited from the added headroom, the fighting compartment actually lost around ten inches of vertical space which had to be compensated by an increase in the height of the turret. The approach taken by domestic medium tanks was much more reasonable; they all had ribs pressed into the hull belly plate, and the torsion bars were laid into the troughs of these ribs, maximizing the available internal height by reducing space wastage while simultaneously increasing the rigidity of the belly.</div><div>
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Volute spring bump stops are present for every roadwheel. Having volute springs instead of simple fixed metal blocks for bump stops contributes to the smoothness of a ride across rough terrain as the jolts from the roadwheel swing arm reaching their maximum angle of deflection are progressively absorbed. This also contributes to giving the suspension the characteristics of a progressively hardening suspension. Combined with the non-linear spring behaviour of the bundled torsion bars, the total effect meant that the T-10 series had the most advanced suspension of its time, not only among Soviet tanks, but also among all of its international counterparts. Strangely enough, this type of bump stop was not used on medium tanks or main battle tanks.<br />
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The drive sprockets have two sets of fourteen teeth each, and have a pitch diameter of 820mm. A mud scraper is installed next to each drive sprocket to reduce the likelihood of the track being dislocated from the sprocket by an excessive buildup of mud. These features can be seen in the two photos below (credit to <a href="http://www.primeportal.net/tanks/carrey/t-10/index.php?Page=2">Carrey on Primeportal.net</a>), which show the drive sprocket of a T-10M (Object 734) with the original T-10 gearbox and final drives. The large diameter of the sprocket hub, made to accommodate the protruding planetary set in the final drive, can also be clearly seen. Moreover, the sprocket wheel has a solid hub plate, serving as protection for the final drive unit. This increased its weight and moment of inertia compared to conventional sprocket designs with skeletonized hubs and rims.<br />
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<br /></div><div><br /></div><div>The new transmission in the T-10M (Object 272) was accompanied by a new drive sprocket, featuring the same pitch diameter and the same number of teeth, but a narrower hub thanks to the new, more compact final drive unit design.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-i-6pwsMkxxg/YXZAd8qe2YI/AAAAAAAAUS8/dO_yTPDdGhUsDnRXrCo284XUK6Xm8sv8gCLcBGAsYHQ/s893/t-10m%2Bsprocket.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="508" data-original-width="893" height="364" src="https://1.bp.blogspot.com/-i-6pwsMkxxg/YXZAd8qe2YI/AAAAAAAAUS8/dO_yTPDdGhUsDnRXrCo284XUK6Xm8sv8gCLcBGAsYHQ/w640-h364/t-10m%2Bsprocket.png" width="640" /></a></div><div><br /></div>
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As mentioned before, the T-10 series was equipped with cast steel roadwheels measuring 550mm in diameter and weighing 119 kg. The main advantage to these small diameter all-metal roadwheels was that they were very cheap and simple to manufacture and replace, had a relatively small mass, had a long service life, and had low rolling resistance. The same wheel is also used as the idler wheel. Despite its close visual similarity to the earlier model of all-steel roadwheel used in the serial KV and IS heavy tank models, the T-10 roadwheel features a roller bearing and a ball bearing instead of a pair of thrust bearings. In this sense, it also differs from the experimental IS-7 tank, from which the bundled torsion bar suspension of the T-10 was derived.<br />
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Removing the hubcap of these wheels reveals the ball bearings and axle, but this is not necessary when topping up the lubricant as there is a special access point for this purpose. It can be seen in the drawing on the left above.<br />
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These wheels were truly all-metal as they lacked even internal rubber bushings. Furthermore, the track links lacked rubber pads on the inner surfaces so the steel rims of the roadwheels ran on the steel surfaces of the links. This eliminated the durability issues associated with having rubber pads and rubber rims, but the lack of any damping elements in the suspension aside from the torsion bar springs enabled vibrations to be transmitted more readily to the tank and results in reduced efficiency at higher speeds. This has a negative effect on the comfort of the crew and may also be responsible for the accelerated wearing of sensitive equipment, and additionally, the lack of damping elements in the wheels increased the rate of wear on the ball bearings. Because of these issues, all-metal roadwheels were never used on any Soviet tank other than the IS line of heavy tanks. The main reason for this was because of the durability issues of rubber linings when used for a 50-ton tank made to travel at speeds of up to 50 km/h.<br />
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The shock absorbers on the T-10 series were built into a cavity inside the roadwheel swing arm. This was another design solution borrowed from the IS-7 project, providing more evidence of the lineage of the T-10. The shock absorber is of a conventional cylindrical hydraulic type with a restrictor connected to a rotary actuator rather than a linear piston. When the swing arm is deflected upwards by a bump on the road, it pushes the rotary actuator arm upwards, forcing the actuator to push the hydraulic restrictor assembly upwards. This is illustrated in the drawing on the right below.<br />
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The range of vertical deflection (from the resting position with a combat-loaded tank) of the roadwheels on the T-10 is 144mm. The range of deflection of the roadwheels was increased to 172mm on the T-10M to improve the smoothness of the driving experience together with the additional pair of hydraulic shock absorbers. The increase in the range of vertical deflection also required modifications to the shock absorbers as the roadwheel swing arm would otherwise be blocked by the support arm of the shock absorber rotary actuator.<br />
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For comparison, the maximum deflection of the roadwheels on the Conqueror heavy tank is 150mm, but since the tank used a Horstmann suspension system, the two roadwheels of a bogie shared a single spring and if a bogie rode over a bump, the spring would be compressed by both wheels and the maximum deflection of either wheel decreases drastically.<br />
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The ground clearance of the T-10 varies depending on the exact point of measurement since the belly of the hull is marked by the protruding torsion bar housings and the bulge underneath the engine compartment. When measured from the engine compartment bulge, the ground clearance is 456mm.<br />
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The T-10 used OMSh tracks. OMSh stands for open metal-pinned tracks. Its design is essentially a modification of the IS-3 track, modified with a slightly different track surface and given extended bills, which protrude beyond the width of the track pins. This new track remained interchangeable with the IS-3, and conversely, existing IS-3 tracks could be used on the T-10 as well. OMSh tracks were suitable for heavy tracked vehicles with a low maximum speed limit, including the likes of the Centurion, so it was considered to be adequate for the T-10. However, the high stresses of having to support a large load meant that the service life of the T-10's OMSh tracks was just 2,000 km, considerably less than the 3,000-km life of the T-54's OMSh tracks. The same track design was kept throughout the military career of the T-10 series.</div><div><br /></div><div>The nominal figure of 2,000 km is an average obtained from testing on special test tracks in central USSR, representing the service life that can be expected after driving on a variety of road surfaces in summer. If driven exclusively or predominantly on a single road surface, the service life of the tracks can vary considerably. Driving on sand, particularly quartz sand, halves its service life to just 1,000 km, whereas driving in winter conditions increases the service life to 3,000 km. As such, the tracks of a T-10 operating in a temperate, tropical or cold region, where road surfaces will mainly be soil, dirt, clay, mud or frozen earth with snow, can be expected to enjoy a service life exceeding 2,000 km. When operating in desert regions, the service life can be expected to be below average, close to 1,000 km.<br />
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<br />The photo below on the left shows the outer edge of the track with the track pin retainers visible and the photo below on the right shows the heads of the track pins. Photos by <a href="http://www.primeportal.net/tanks/carrey/t-10/index.php?Page=3">Carrey on PrimePortal.net</a>.<br />
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The track links have a width of 720mm and a pitch of 160mm which is quite typical for a heavy tank. For reference, the T96, T97 and T107 series of tracks for the M103 are 710mm in width and the tracks of the Conqueror are 787mm in width, while tracks for most medium tanks and main battle tanks typically have a width of around 600mm, give or take a few centimeters. The ends of the track pins on the outer edge of the tracks are secured with a nut and washer while the ends of the track pins on the inner edge of the tracks are simply held by an oversized head. <br />
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There are 88 track links on each side, each link weighing in at 21 kg. A complete set of tracks weighs 2,147.8 kg and two complete sets weighs 4,395.2 kg. In the 1960's, the roadwheels and OMSh tracks of the T-10 were carried over to the IS-3M when the latter had worn out their old tracks or when they underwent capital repairs. This improved the reliability and serviceability characteristics of the older tank and increased the degree of parts interchangeability between the two main heavy tanks of the Soviet Army while also removing an obsolete product from the production line for spare parts.<br />
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The ground contact length of each set of tracks is 4.55 m for a total nominal ground contact area of 6.55 sq.m with both tracks. The nominal ground pressure for all combat-loaded T-10 variants is 0.77 kg/sq.cm, give or take a few hundredths to account for some minor differences. This placed the T-10 in the same general category as medium tanks like the T-54 which weighed much less but had narrower tracks, although it is interesting to note that every model from the T-54 obr. 1951 until the T-54B had a ground pressure of 0.8 kg/sq.cm and the T-55 had a negligibly higher ground pressure of 0.81 kg/sq.cm.<br />
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For comparison, the nominal ground pressure (NGP) exerted by the Conqueror was 0.847 kg/sq.cm and the pressure of the M103A2 was a whopping 0.929 kg/sq.cm. It's possible that the disadvantage of the Conqueror is not as drastic as the NGP figure implies since it has eight small roadwheels on each side instead of seven like the T-10 and M103, so the difference in the mean maximum pressure (MMP) may not be exactly proportional to the difference in the NGP. Nevertheless, the advantage held by the T-10 in this comparison is quite obvious - it is a heavy tank in role, weight, armour and firepower, but not in mobility. Overall, the tactical mobility of the T-10 was comparable to medium tanks in many respects and the strategic mobility of the T-10 was not significantly worse thanks to the artificial weight limit of 50 tons, but the tank still fell behind in terms of ease of repair and in operating costs. This is entirely expected given the much lower production figures of the heavy tank and the higher complexity of its design.<br />
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For movement through deep mud, marshy or deep snow, track extenders could be bolted to each track link. A full set of 174 extenders weighed 1,265 kg, making the tank significantly heavier but vastly increasing the ground contact area. This lowered the nominal ground pressure from 0.77 kg/sq.cm to just 0.55 kg/sq.cm, thus giving the tank enough flotation to drive atop difficult terrain where the tank would otherwise sink and completely lose traction.<br />
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<a href="https://1.bp.blogspot.com/-olRbaVNgWmo/XP-H7Ti70HI/AAAAAAAAOYw/ezZDkIOD8iYWqtGLbpvoIbCacSIwz74KQCLcBGAs/s1600/track%2Bextensions.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="578" data-original-width="829" height="278" src="https://1.bp.blogspot.com/-olRbaVNgWmo/XP-H7Ti70HI/AAAAAAAAOYw/ezZDkIOD8iYWqtGLbpvoIbCacSIwz74KQCLcBGAs/s400/track%2Bextensions.png" width="400" /></a></div>
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<a href="https://www.blogger.com/null" id="fuel"></a>
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<h3>
<span style="font-size: large;">FUEL SYSTEM</span></h3>
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It has become common knowledge that Soviet tanks generally carried fuel in the fighting compartment and bore the consequences of this design choice, both the good and the bad. However, the T-10 follows the precedent set by its predecessor the IS-3 and stores its entire supply of internal fuel in the engine compartment as shown in the drawings below.<br />
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<a href="https://1.bp.blogspot.com/-5vSD70pMDWo/XC5lG1588GI/AAAAAAAAMxI/RoIy65WSzDU-mVeogiCpdBye7kRm24hXwCLcBGAs/s1600/interior.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="557" data-original-width="629" height="353" src="https://1.bp.blogspot.com/-5vSD70pMDWo/XC5lG1588GI/AAAAAAAAMxI/RoIy65WSzDU-mVeogiCpdBye7kRm24hXwCLcBGAs/s400/interior.png" width="400" /></a></div>
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On the original T-10, the internal fuel was held in three fuel tanks placed in the engine compartment. The total capacity of all the internal fuel tanks is 450 liters. The internal fuel tanks of the T-10 were smaller than the tanks of the IS-2 and IS-3 (520 liters) but they were still at least somewhat larger than the IS-4 (410 liters). However, the relatively small fuel capacity was remedied very early on in the production run of the T-10. The fuel system of the original T-10 is shown below. Beginning in June 1955, the rear internal fuel tanks were replaced with larger tanks with a capacity of 270 liters, increasing the total capacity to 630 liters.<br />
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<a href="https://1.bp.blogspot.com/-3zC5XXS5Ba8/XT_O5iNPJ-I/AAAAAAAAOp4/LfQfBrZcTC4k39D33LsmAgWfHhGDMzz_wCLcBGAs/s1600/t-10%2Bfuel%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1015" data-original-width="1600" height="406" src="https://1.bp.blogspot.com/-3zC5XXS5Ba8/XT_O5iNPJ-I/AAAAAAAAOp4/LfQfBrZcTC4k39D33LsmAgWfHhGDMzz_wCLcBGAs/s640/t-10%2Bfuel%2Bsystem.png" width="640" /></a></div>
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Both the Object 734 and Object 272 variants of the T-10M featured a new layout of internal fuel tanks was used. Fuel was held in six separate tanks, granting a slightly larger total capacity of 640 liters. The two rear internal fuel tanks tucked between the engine and transmission were symmetrically mirrored and located between the engine and the transmission assembly. Each of these tanks holds 160 liters of fuel. The other four fuel tanks hold a total of 320 liters.<br />
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<a href="https://4.bp.blogspot.com/-trIFRSiF5p8/XFF9C8vd2LI/AAAAAAAANRo/Kj6yGdRO658FKL_9DOkBZdfwlDBQQqCAwCLcBGAs/s1600/fuel%2Btanks%2Bmarked.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="648" data-original-width="1097" height="378" src="https://4.bp.blogspot.com/-trIFRSiF5p8/XFF9C8vd2LI/AAAAAAAANRo/Kj6yGdRO658FKL_9DOkBZdfwlDBQQqCAwCLcBGAs/s640/fuel%2Btanks%2Bmarked.png" width="640" /></a></div>
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Beginning in December 1962 when a lighter, simpler and more compact transmission began to be installed in all T-10M models, the total fuel capacity was increased by 100 liters thanks to the increased size of the two rear internal tanks tucked between the engine and transmission. These T-10M tanks had a total internal fuel capacity of 740 liters.<br />
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To augment the internal fuel tanks, a pair of external conformal fuel tanks were fitted the rear corners of the hull with a capacity of 150 liters of fuel each, for a total external fuel load of 300 liters. These conformal fuel tanks are made from stamped sheet aluminium and are connected directly to the fuel system. Like the external fuel tanks found on the track fenders of the T-54 and T-62, the conformal external fuel tanks can be easily removed but this is never done in practice as they are unobtrusive, so they are generally considered permanent fixtures. These fuel tanks were present on the very first T-10 models, but the designed was changed slightly on the T-10M without changing its capacity. The fuel tanks are attached to the hull with two simple latches and are secured to the fenders with sheet metal straps. The photo on the right below is by <a href="http://svsm.org/gallery/t-10/IMGP0477">Vladimir Yakubov</a>.<br />
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<a href="https://3.bp.blogspot.com/-tmPVBdCTN8w/XEp3gZDL7bI/AAAAAAAANNU/Cw0uOfVzhNUiqLZd6RgdL8T7UCCGM452gCLcBGAs/s1600/fuel%2Btanks.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1075" data-original-width="1535" height="280" src="https://3.bp.blogspot.com/-tmPVBdCTN8w/XEp3gZDL7bI/AAAAAAAANNU/Cw0uOfVzhNUiqLZd6RgdL8T7UCCGM452gCLcBGAs/s400/fuel%2Btanks.png" width="400" /></a><a href="https://2.bp.blogspot.com/-7XIAX5lxKRw/XEp1yyq_U7I/AAAAAAAANNI/uTIoi2xzYjEeHEItwxwm4Zf0XR0m98sUACLcBGAs/s1600/t-10m%2Bexternal%2Bfuel%2Btank.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://2.bp.blogspot.com/-7XIAX5lxKRw/XEp1yyq_U7I/AAAAAAAANNI/uTIoi2xzYjEeHEItwxwm4Zf0XR0m98sUACLcBGAs/s400/t-10m%2Bexternal%2Bfuel%2Btank.jpg" width="400" /></a></div>
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On each of the conformal tanks, the fuel line connecting the conformal tanks to the fuel system is located in the bottom inward-facing corner, thus shielding the hose from battle damage. The conformal tanks themselves are a minimal fire hazard in battle due to their location - even if they are destroyed and set alight, the fuel would not leak onto the engine deck or otherwise affect the powertrain. Instead, the burning fuel would harmlessly run off the metal track fenders and the sloped rear hull armour plating. Even the roadwheels and tracks would be minimally affected as they are of an all-metal construction.<br />
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On the first T-10 model with original internal fuel tanks, the addition of the external conformal fuel tanks increased the total fuel capacity to 750 liters, but beginning with the improved June 1955 variant, the total fuel capacity was 930 liters. The total fuel capacity of a T-10M was 940 liters, or 1,040 liters after the December 1962 upgrade.<br />
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Using both the internal fuel supply and the external fuel supply, the driving range of a T-10 with the V-12-5 engine and 8-speed gearbox on a paved asphalt road is 230 km and 185 km when driving cross-country. This is the same as an IS-2 obr. 1944. With the June 1955 upgrade, the driving range increased to 300 km on paved roads and 240 km when driving cross-country.<br />
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Using the internal fuel tanks and the conformal external fuel tanks, the driving range of a T-10M with the V-12-6 engine and 8-speed gearbox on a concrete road is 350 km and its driving range when traveling cross-country is up to 200 km. This is less than a T-54 or a T-62 under the same conditions by around 100 km, but it is a large improvement over previous Soviet heavy tanks and even this relatively short range is already twice that of the Conqueror heavy tank. With the additional 100 liters of fuel that accompanied the simplified transmission with a 6-speed gearbox, the driving range increased to 390 km on a concrete road and 265 km when going cross-country.<br />
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Beginning from September 1959, two additional 200-liter fuel drums could be mounted on the transmission access panel to improve the driving range of the tank on long marches. Each of the fuel drums were mounted on a pair of crescent-shaped racks and secured with metal bands. The fuel drums fittings were at the same level as the mounting points and the quick-release mechanism for the BDSh-5 smoke bomb mounts, so it was not possible to have a pair of fuel drums and a pair of smoke bombs installed simultaneously.<br />
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<a href="https://1.bp.blogspot.com/-jtpiCIz6tSo/XNrPk7x-ooI/AAAAAAAAN9E/lKkr2QlAkFg5XxPzCF2v9y6L2QO6LeNUwCLcBGAs/s1600/t-10%2Bfuel%2Bdrum%2Bbands.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="899" data-original-width="1126" height="318" src="https://1.bp.blogspot.com/-jtpiCIz6tSo/XNrPk7x-ooI/AAAAAAAAN9E/lKkr2QlAkFg5XxPzCF2v9y6L2QO6LeNUwCLcBGAs/s400/t-10%2Bfuel%2Bdrum%2Bbands.png" width="400" /></a><a href="https://4.bp.blogspot.com/-LYFUCpeb50E/XNrPk69o1tI/AAAAAAAAN9I/c3IwE6DQuykR-fa0iHHH3ZOq6M_mUSHhQCLcBGAs/s1600/t-10%2Bfuel%2Bdrums%2Bon%2Bbands.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1211" height="296" src="https://4.bp.blogspot.com/-LYFUCpeb50E/XNrPk69o1tI/AAAAAAAAN9I/c3IwE6DQuykR-fa0iHHH3ZOq6M_mUSHhQCLcBGAs/s400/t-10%2Bfuel%2Bdrums%2Bon%2Bbands.png" width="400" /></a></div>
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Having the two additional fuel drums increased the total fuel capacity of the T-10 to 1,340 liters and expanded the driving range of the heavy tank to more than 500 km on a concrete road. With the additional fuel drums, an original T-10 model with an onboard fuel capacity of 750 liters had a driving range of 460 km. This is only slightly inferior in range to a T-54 equipped with additional fuel drums of its own. The drums were not directly connected to the fuel system of the T-10, so they had to be siphoned manually to replenish the tank's internal fuel supply during a march whenever the opportunity arose.<br />
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The main drawback of the location of the fuel drums is that they prevent the gun travel lock from being moved if they were mounted on the tank. If the travel lock is in the stowed position when the drums are added, then it cannot be used and the tank must use its internal travel lock instead.<br />
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Two more 200-liter fuel drums could be added on the transmission access panel above the standard fuel drum racks, but even though a number of T-10M tanks that participated in Operation Danube in 1968 had these drums, they appear to be non-standard.<br />
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<a href="https://4.bp.blogspot.com/-G4ICtSeFBQA/XNMEuVnQcmI/AAAAAAAAN6Y/EjPZdfvpYnQ2_AZtwnon4PwG6yMae9bhgCLcBGAs/s1600/danube%2Bmoving%2Bt-10m.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="320" src="https://4.bp.blogspot.com/-G4ICtSeFBQA/XNMEuVnQcmI/AAAAAAAAN6Y/EjPZdfvpYnQ2_AZtwnon4PwG6yMae9bhgCLcBGAs/s400/danube%2Bmoving%2Bt-10m.jpg" width="481" /></a><a href="https://3.bp.blogspot.com/-Id4xjLBfJkg/XNMD5rCZrNI/AAAAAAAAN6I/IlKr5DTaki0tROOimvrDVYN8Dt3wjvSJgCLcBGAs/s1600/large%2Bfuel%2Bdrums.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="560" height="320" src="https://3.bp.blogspot.com/-Id4xjLBfJkg/XNMD5rCZrNI/AAAAAAAAN6I/IlKr5DTaki0tROOimvrDVYN8Dt3wjvSJgCLcBGAs/s320/large%2Bfuel%2Bdrums.jpg" width="224" /></a></div>
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<a href="https://www.blogger.com/null" id="water"></a>
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<h3>
<span style="font-size: large;">WATER OBSTACLES</span></h3>
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<a href="https://1.bp.blogspot.com/-1AUn3tdZGaM/XQZB31x8UyI/AAAAAAAAOeU/atS92ewXqcYP3o-y2vPyMw-iupOtaJIUwCLcBGAs/s1600/gsfg%2Bditch.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="446" data-original-width="800" height="356" src="https://1.bp.blogspot.com/-1AUn3tdZGaM/XQZB31x8UyI/AAAAAAAAOeU/atS92ewXqcYP3o-y2vPyMw-iupOtaJIUwCLcBGAs/s640/gsfg%2Bditch.jpg" width="640" /></a></div>
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A V-shaped splash guard is fitted to the upper glacis of the hull to deflect the incoming wave when the tank enters a shallow body of water.<br />
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<a href="https://4.bp.blogspot.com/-oLgqkrC33wE/XMGRQjLrYyI/AAAAAAAANws/jZW-Yjw_uIYecRWTW2pI-eHXQeKcnWbgwCLcBGAs/s1600/t-10m%2Bopvt.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="444" data-original-width="591" height="300" src="https://4.bp.blogspot.com/-oLgqkrC33wE/XMGRQjLrYyI/AAAAAAAANws/jZW-Yjw_uIYecRWTW2pI-eHXQeKcnWbgwCLcBGAs/s400/t-10m%2Bopvt.jpg" width="400" /></a></div>
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Since 1962, T-10M tanks began to be fitted with the OPVT snorkelling system, further reducing the gap in operational mobility between the T-10 and medium tanks. Because the vehicle was not originally designed for snorkeling operations, proprietary covers for the various openings on the engine compartment deck and the hatches had to be issued.<br />
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<span style="vertical-align: inherit;"><span style="vertical-align: inherit;">The equipment of the OPVT system included a snorkel, special exhaust valves, a lid for winter air intakes, bilge pumps, seals for the muzzle brake and gun mask, a venting pipe, an antenna for communications while completely submerged, hatch covers, fume extractor seals, turret seals, and a system for regulating the temperature of the engine when the tank is moving under water. The crew was also provided with IP-46 rebreathers and SLF-58 life jackets for emergency use. OPVT kits began to be retrofitted earlier T-10 models in 1963. It was planned to manufacture 200 kits for the T-10, 140 kits for the T-10A and 20 kits for the T-10B. With this programme, the majority of T-10 tanks would be outfitted with the new system and all tanks in active service would gain increased independence in crossing water obstacles.</span></span><br />
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Here, a T-10 is shown crossing an NZhM-56 pontoon bridge. The NZhM-56 had a very high load capacity , This meant that a heavy tank regiment equipped with T-10 tanks accompanying the two medium tank regiments in a Soviet tank division would be able to cross obstacles using the standard tactical bridging systems of its engineering battalions. These include the PMP truck-based ribbon-type pontoon bridging system (60-ton capacity), TMM truck-based scissor-type span-bridging system (60-ton capacity) and the MTU and MTU20 bridges based on T-54 armoured bridgelayers (50-ton capacity).<br />
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<a href="https://1.bp.blogspot.com/-dpsw03xbfsk/XQAEevAtTOI/AAAAAAAAOaM/0lWhidbpryM4q2D9YFqKRDpxV0ho0A6EACLcBGAs/s1600/bridge%2Bcrossing%2Bt-10.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="937" data-original-width="1600" height="374" src="https://1.bp.blogspot.com/-dpsw03xbfsk/XQAEevAtTOI/AAAAAAAAOaM/0lWhidbpryM4q2D9YFqKRDpxV0ho0A6EACLcBGAs/s640/bridge%2Bcrossing%2Bt-10.png" width="640" /></a></div>
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Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com9tag:blogger.com,1999:blog-3103574899092646031.post-66867349553224114952018-02-24T12:00:00.013-08:002023-05-21T08:16:07.731-07:00PT-76<div class="separator" style="clear: both; text-align: center;">
<a href="https://2.bp.blogspot.com/-jJxpkvz3KeA/WXMep77QWKI/AAAAAAAAIzc/OAcS7fcNXtUcwArS_pIdao1Dt9ysEoPRgCLcBGAs/s1600/pt-76%2Bin%2Bwater.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="667" data-original-width="1000" height="426" src="https://2.bp.blogspot.com/-jJxpkvz3KeA/WXMep77QWKI/AAAAAAAAIzc/OAcS7fcNXtUcwArS_pIdao1Dt9ysEoPRgCLcBGAs/s640/pt-76%2Bin%2Bwater.jpg" width="640" /></a></div>
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The PT-76 is an amphibious light tank, first entering service in the Red Army and Soviet Naval Infantry in 1952 and serially produced until 1967, when it was largely replaced by the much more flexible BMP-1 infantry fighting vehicle. The PT-76 is notable for being the first light tank in the world to be designed as an amphibian, featuring a very large and mostly empty hull for buoyancy and an innovative water jet propulsion system. Originally intended for advance patrols in Red Army tank battalions, the Soviet Navy took an interest in the PT-76 during its development, and went on adopt it for their Naval Infantry as a beach assault vehicle. Although the amphibious tank was withdrawn from Army service long ago, modernized forms of the PT-76 continued to serve in Naval Infantry tank battalions up until the late 2000's, albeit in a very limited capacity. They are currently being replaced by the BMP-3F, but the replacement is moving along at a very slow rate.<br />
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<a href="https://3.bp.blogspot.com/-aVq4CmNS8yE/WWn88V-EbcI/AAAAAAAAIqU/IOkuL_K5QM4ZmwTTc82XOKuTcz02hED9gCLcBGAs/s1600/pt-76%2Bbeach%2Bassault.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="340" data-original-width="637" src="https://3.bp.blogspot.com/-aVq4CmNS8yE/WWn88V-EbcI/AAAAAAAAIqU/IOkuL_K5QM4ZmwTTc82XOKuTcz02hED9gCLcBGAs/s1600/pt-76%2Bbeach%2Bassault.png" /></a></div>
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When used for reconnaissance, the PT-76 would move ahead of the main force - either a tank or motorized infantry division - and carry out forward reconnaissance, and if it encounters resistance, it would fulfill the duties of medium tanks when none are presently available. Because of the abundance of lakes, rivers and waterlogged swampland in Eastern and Central Europe, the PT-76 should, in theory, have plenty of opportunities to exploit its amphibious qualities while the main force was still preparing to cross these types of obstacles. If nothing else, the PT-76 could swim very well indeed.<br />
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<a href="https://3.bp.blogspot.com/-CC6AInXzuho/WmdexbQraNI/AAAAAAAAKkw/RULBmZ1FN5YtbKzVaDhjbpR3akxeP-GYQCLcBGAs/s1600/tank%2Bcomparison.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="701" data-original-width="428" src="https://3.bp.blogspot.com/-CC6AInXzuho/WmdexbQraNI/AAAAAAAAKkw/RULBmZ1FN5YtbKzVaDhjbpR3akxeP-GYQCLcBGAs/s1600/tank%2Bcomparison.gif" /></a></div>
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The PT-76B was formally adopted in January 10, 1958, but mass production only commenced in 1959 and continued until 1967. Production of the original model began in 1952 and ended in the first half of 1959, just seven years later. During its production run, 1,896 PT-76 tanks were manufactured. Production of the PT-76B model commenced in 1959 and ended 1967, 1,143 tanks were produced.<br />
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Special thanks to <a href="https://sean1082.imgur.com/">Sean Murphy</a> for providing excellent photos from his personal collection.<br />
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<h3>
<span style="font-size: large;">INDEX</span></h3>
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<ol>
<li><a href="#comstat">Commander's Station</a></li>
<li><a href="#vision">Vision Devices</a></li>
<li><a href="#tpku-2b">TPKU-2B</a></li>
<li><a href="#tshk">TShK-66</a></li>
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<li><a href="#load">Loader's Station</a></li>
<li><a href="#d-56t">D-56T</a></li>
<li><a href="#stab">Powered Traverse, Stabilizer</a></li>
<li><a href="#ammo">Ammunition</a></li>
<li><a href="#sgmt">SGMT Coaxial Machine Gun</a></li>
<hr />
<li><a href="#prot">Protection</a></li>
<li><a href="#smoke">Smokescreen</a></li>
<li><a href="#nbc">NBC Protection</a></li>
<li><a href="#fire">Fire Fighting</a></li>
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<li><a href="#driver">Driver Station</a></li>
<li><a href="#mob">Mobility</a></li>
<li><a href="#water">Water Obstacles</a></li>
<li><a href="#fuel">Fuel Endurance</a></li>
</ol>
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<a href="https://www.blogger.com/null" id="comstat"></a>
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<h3>
<span style="font-size: large;">COMMANDER'S STATION</span></h3>
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<span style="font-size: large;"><br /></span></div>
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<a href="http://4.bp.blogspot.com/-Q3QIaJ0ftEc/Vj8vkHs7B-I/AAAAAAAAEBQ/PYlvRV-J1hQ/s1600/PT76.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://4.bp.blogspot.com/-Q3QIaJ0ftEc/Vj8vkHs7B-I/AAAAAAAAEBQ/PYlvRV-J1hQ/s640/PT76.jpg" width="640" /></a></div>
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The commander of the PT-76 resides in the turret alongside the loader. He normally enters the truncated cone-shaped turret through the large rectangular hatch which dominates the turret roof, but he has his own personal rotatable cupola and hatch. The hatch gives him the option to survey the battlefield from outside the turret without needing to open the large main hatch, as doing so would not only drastically increase the size of the tank's silhouette, but the movement would be more visible to an enemy observer at long distance. The photo below shows the commanders of a column of marching PT-76s sitting atop the turrets of their tanks, protected from the front by the hatch.<br />
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<a href="https://3.bp.blogspot.com/-oiOhNj2mMCM/WlEffLo1jGI/AAAAAAAAKXE/Kf4EtO1O7k4rR-wbDeRHJTWN64NhvgHWQCLcBGAs/s1600/pt-76%2Bmarch.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="434" data-original-width="635" height="436" src="https://3.bp.blogspot.com/-oiOhNj2mMCM/WlEffLo1jGI/AAAAAAAAKXE/Kf4EtO1O7k4rR-wbDeRHJTWN64NhvgHWQCLcBGAs/s640/pt-76%2Bmarch.jpg" width="640" /></a></div>
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The hatch is only 6mm thick, but it is enough to shield the commander from sniper fire coming from distances of several hundred meters. Ideally, the commander would expose as little of his head as possible while looking through his binoculars over the tip of the hatch. Since the hatch is part of the rotating cupola, it can also be rotated to give the commander protection from whichever direction he chooses.<br />
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The size of the main hatch is exceptionally useful for a quick escape if the tank were to be knocked out, on fire or otherwise inoperable, but the relatively heavy weight of the large hatch makes it difficult to open if both of the crew members in the turret are injured. Nevertheless, available information indicates that the turret was given a large hatch so that the crew could quickly evacuate a sinking tank while wearing the standard emergency bulky breathing apparatus, so it was probably quite justified. Moreover, the weight of the hatch would not be nearly as serious of an issue as on the T-34 obr. 1940, which had a hatch that was somewhat smaller but was 20mm thick.<br />
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The total volume of the fighting compartment is not known, but there are several indications that the work space for the crew in the turret is more than adequate. Aside from the abundance of internal space due to the emptiness of the hull, the most useful indicator is the diameter of the turret ring.<br />
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The turret ring of the PT-76 turret is 1,800mm in diameter. Considering that the armour of the turret is very thin and that the tank is equipped with only a medium pressure 76mm gun, the two men in the turret are quite well accommodated. For comparison, the T-34-85 had a 1,600mm turret ring and seated three men with an 85mm gun while the T-54 had a 1,825mm turret ring and seated three men with a 100mm gun. The PT-76 surpasses both of these medium tanks in this respect and is also more spacious than the M4 Sherman which had a 1,750mm turret ring and seated three men with a medium pressure 75mm gun. In a comparison between the PT-76 and its direct American counterpart the M41 Walker Bulldog, the PT-76 ostensibly loses out as the latter had a slightly larger turret ring diameter of 1,850mm, but the M41 turret was occupied by three crew members and it mounted a somewhat bulkier high-pressure 76mm gun.<br />
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Aside from shooting and commanding the tank, the commander is also in charge of the single <a href="http://www.rv3bc.narod.ru/Stat/10rt-12.htm">10RT-26E short wave radio set</a> placed on the left side of the turret. The radio is designed to operate in the 3.75-6.00 MHz frequency range. The <a href="http://www.rwd-mb3.de/ntechnik/pages/10rt26.htm">10RT-26 and 10RT-26E</a> were the standard radio systems for Soviet armoured vehicles built during the late 40's, but by the early 50's, the series was rendered obsolete by a new government decree allocating the 20.0-22.4 MHz frequency range for the exclusive use of tank radios. The whip antenna for the radio is installed on the turret wall, to the right of the intercom relay box and to the left of the turret traverse flywheel, as you can see on the upper left corner of the photo below.<br />
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When the tank is moving, the whip antenna is retracted to the minimum 1 meter length and the radio has a range of between 7 to 15 km, but when the tank is stationary and has the whip antenna extended to its full length of 4 meters, the radio has a range of between 9 to 20 km. The production of the 10RT series of radios ceased entirely in 1956, and in 1957, a modernization programme was carried out to replace the 10RT-26E with the newer the <a href="http://www.rv3bc.narod.ru/Stat/rtx-r-113.htm">R-113 "Granat" radio set</a> and its accompanying power supply. The programme ran in parallel with similar programmes for tanks like the T-54 and T-10 that have been ongoing since 1954 to standardize the R-113 among all armoured combat vehicles in the Red Army. The R-113 belonged to the first generation of Soviet tank radios designed in the post-war era. It operates in the 20-22.375 MHz frequency range and has a maximum range of 20 km with the whip antenna extended, reduced to 8-12 km in the presence of noise and 10 km in the presence of jamming.<br />
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In 1967, the latest batch of PT-76B tanks were produced with new <a href="http://photo.qip.ru/users/otrok/4169327/?mode=large&sort=rating">R-123 "Magnoliya"</a> radios, and a modernization programme was initiated to equip older PT-76 with the new radio system during scheduled overhauls.<br />
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<a href="https://2.bp.blogspot.com/-6aqKTXiLk-o/WmcVqKiQyjI/AAAAAAAAKj8/a_TnfjlSr3UXUS1x-u6tB_pthpHZ-wlvgCLcBGAs/s1600/pt-76%2Br123.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1588" height="400" src="https://2.bp.blogspot.com/-6aqKTXiLk-o/WmcVqKiQyjI/AAAAAAAAKj8/a_TnfjlSr3UXUS1x-u6tB_pthpHZ-wlvgCLcBGAs/s400/pt-76%2Br123.png" width="396" /></a></div>
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To save room, the radio and accompanying power supply unit are not installed directly on the wall of the turret, but suspended in brackets beneath the turret ring as depicted in the drawing above. With these two bulky pieces of equipment absent from the turret wall, the only pieces of equipment that can be found at chest level of the commander are the intercom relay box, antenna tuning box, turret azimuth indicator and turret traverse mechanism. The mounting bracket for the R-113 and the accompanying <a href="http://otrok.users.photofile.ru/photo/otrok/3638034/xlarge/80813991.jpg">BP-2A power supply unit</a> is shown in the first photo below. The second photo shows an R-123M radio and its accompanying <a href="https://media2.24aul.ru/imgs/5298bc157617f70f54b3fc00/radiostantsiya-r-123m-s-blokom-pitaniya-bp-26-+-soedinitelnyy-5-3455992.jpg">BP-26 power supply unit</a>. Due to various modernization programs over the years since the introduction of the PT-76, it is extremely difficult to find an example equipped with the 10RT-26E radio and its proprietary power supply unit, but it would have been mounted in the same way as the later R-113 and R-123.<br />
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The other silver-coloured box is the frequency tuning box for the antenna. The <a href="http://photo.qip.ru/users/otrok/4190467/102488883/#mainImageLink">R-113</a> and <a href="http://photo.qip.ru/users/otrok/4187195/102372615/#mainImageLink">R-123</a> have proprietary tuning boxes.<br />
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<a href="https://www.blogger.com/null" id="vision"></a>
<h3>
<span style="font-size: large;">VISION DEVICES</span></h3>
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<a href="https://1.bp.blogspot.com/-ZOBTOYuMkn8/XeywA81E15I/AAAAAAAAP0w/1SuQ-8ssErQa95aTY6Rt1U5zl6IL3Gc-gCLcBGAsYHQ/s1600/cupola.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="743" data-original-width="1125" height="263" src="https://1.bp.blogspot.com/-ZOBTOYuMkn8/XeywA81E15I/AAAAAAAAP0w/1SuQ-8ssErQa95aTY6Rt1U5zl6IL3Gc-gCLcBGAsYHQ/s400/cupola.png" width="400" /></a></div>
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The commander has two TNP-B general vision periscopes and one TPKU-2B binocular periscope installed in his cupola to cover a forward 120-degree arc. Unlike a T-34-85 or T-54 style cupola with a half moon hatch and periscopes in a fixed roof, the cupola on the PT-76 has all of its periscopes installed in the one-piece hatch. The cupola is rotatable, thus giving him a full 360-degree view of his surroundings. There are no handles for the commander to grasp when turning the cupola, so he must hold onto one of the periscopes to do so.<br />
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The visibility arc diagram below shows the size of the dead zones in the viewing arcs from the periscopes in the tank. When looking towards the front of the tank, the commander's periscopes have a dead zone of 6 to 8 meters, and when looking towards the left side, the dead zone is 7 to 8 meters. Towards the rear right corner of the hull, the dead zone increases to 11 meters.<br />
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It needs to be emphasized that the PT-76 was designed to be an amphibious tank first and foremost. Its role as a reconnaissance vehicle for the ground forces was more of an afterthought than a part of the initial requirements for the design. According to Baryatinsky, the thinking behind its use as a reconnaissance tank despite the poor optimization of its design was because light amphibious tanks were typically used for reconnaissance as a rule of thumb according to traditional Red Army doctrine from the 1930's. It's easy to see why this doctrine did not fit well with the design of the PT-76; the light amphibious tanks deployed by the Red Army back then were the T-37 and its derivatives - very small, very light, armed only for self defence and crewed by only two men. The PT-76 is not only larger than the T-54, but also slower because of its underpowered engine and unsophisticated clutch-and-brake transmission.<br />
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<a href="https://3.bp.blogspot.com/-zxAWYvEvYMY/Wmdd7gEwBwI/AAAAAAAAKkc/Wtlv6Hkbuq0O6M6URKgO6cE0_RQRPrRPACLcBGAs/s1600/t37.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="348" data-original-width="550" height="252" src="https://3.bp.blogspot.com/-zxAWYvEvYMY/Wmdd7gEwBwI/AAAAAAAAKkc/Wtlv6Hkbuq0O6M6URKgO6cE0_RQRPrRPACLcBGAs/s400/t37.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-VfOHQLSN2lM/WmdeEkoN8fI/AAAAAAAAKkg/KcYiZaYd15cqCsp3jolLoXJdO494TWT5gCLcBGAs/s1600/destroyed%2Bpt-76%2Bvietnam.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="604" data-original-width="907" height="266" src="https://1.bp.blogspot.com/-VfOHQLSN2lM/WmdeEkoN8fI/AAAAAAAAKkg/KcYiZaYd15cqCsp3jolLoXJdO494TWT5gCLcBGAs/s400/destroyed%2Bpt-76%2Bvietnam.jpg" width="400" /></a></div>
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In terms of overall visibility and amenities for observation while under armour, the PT-76 loses out to the majority of armoured vehicles in the Red Army arsenal. In fact, some tanks like the T-10 and T-10A had almost twice as many observation devices as the PT-76, and the common T-54 medium tank had three or four more observation devices, depending on the exact model. Having a combination of two general vision periscopes and one binocular periscope only puts the PT-76 commander on par with a T-44 commander or a commander of an early T-54 model in terms of visibility, whereas T-54 models beginning from 1951 had two additional periscopes embedded in the commander's hatch to provide vision in a much wider 200-degree frontal arc. To be fair, the commander of a PT-76 is also responsible for manning the gunsight, and that grants him an additional observation device, but he still lacks the MK.4 rotatable periscope that was present in earlier T-54 models for the gunner (before it was replaced with a night vision sight), and the fact that the commander must also act as the gunner of the PT-76 worsens the combat potential of the light tank as a whole. All together, the surveillance capabilities of the PT-76 are not only quite lackluster but also inferior to its land-bound counterparts. It goes without saying that the commander's cupola of the American M41 Walker Bulldog beats the cupola of the PT-76 easily in this respect, not to mention the fact that the M41 has a three-man turret and carries a large amount of radio equipment. This is because the M41 was designed to be a reconnaissance vehicle from the very beginning.<br />
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Unlike the BMP-1 that replaced it, a specialized reconnaissance model of the PT-76 was never developed. The tanks that were used in the reconnaissance role were not supplied with special surveillance devices, so the crews had to rely exclusively on the basic equipment that came with the tank. Needless to say, the PT-76 was simply not ideal for this particular role. The BRDM-1 was far more suitable for reconnaissance.<br />
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<a href="https://www.blogger.com/null" id="tpku-2b"></a>
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<h3>
<span style="font-size: large;">TPKU-2</span></h3>
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<a href="https://1.bp.blogspot.com/-391m4l-jqQY/Xeys4DZ80MI/AAAAAAAAP0I/SsgqI354ub0T_a3tmUMdaSrekwKmUl2awCLcBGAsYHQ/s1600/tpku-2%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1089" data-original-width="1600" height="434" src="https://1.bp.blogspot.com/-391m4l-jqQY/Xeys4DZ80MI/AAAAAAAAP0I/SsgqI354ub0T_a3tmUMdaSrekwKmUl2awCLcBGAsYHQ/s640/tpku-2%2Bdrawing.png" width="640" /></a></div>
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The TPKU-2 binocular periscope is fitted on the PT-76B as well as later variants of the PT-76. The TPKU-2B variant was used in the T-54B as well as other Soviet armoured vehicles. This variant differed in that it had two handlebars on each side for the commander to hold on to, while the basic TPKU-2 installed in the PT-76 has no handlebars at all.<br />
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The TPKU-2 periscope was widely used in other light vehicles like the BRDM-1, BTR-60, BTR-70, and many others, not to mention the BTR-50 derived from the PT-76. This simplified periscope lacks the target designation function present in the tank-mounted version, but is otherwise functionally identical. The TPKU-2B has adjustable magnification with the option to choose between either 1x or 5x magnifications. Under 1x magnification, the field of view from the sight is 17.5 degrees. This is reduced to 7.5 degrees under 5x magnification. The general layout of the viewfinder and the reticle is the same as in all other Soviet binocular tank periscopes of the era, including the presence of a stadiametric rangefinder markings. This is enough for the commander to search for targets at short to medium distances, follow up by estimating the range using the stadia rangefinder, and end by switching over to the gun sight and open fire on the target.<br />
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<a href="https://1.bp.blogspot.com/-I6m3QQqTQFI/VtKGHxnr-sI/AAAAAAAAGEo/rycAr09J6m8/s1600/pt-76%2Bhatch.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://1.bp.blogspot.com/-I6m3QQqTQFI/VtKGHxnr-sI/AAAAAAAAGEo/rycAr09J6m8/s320/pt-76%2Bhatch.jpg" width="237" /></a><a href="https://1.bp.blogspot.com/-BjYRBeoRwA0/Wl7vc7j5TsI/AAAAAAAAKhM/D1v-jejvSZo4MyfhsBnruOMmMUb7xIJZgCLcBGAs/s1600/inside%2Bthe%2Bpt-76%2Bturret.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="426" data-original-width="640" height="265" src="https://1.bp.blogspot.com/-BjYRBeoRwA0/Wl7vc7j5TsI/AAAAAAAAKhM/D1v-jejvSZo4MyfhsBnruOMmMUb7xIJZgCLcBGAs/s400/inside%2Bthe%2Bpt-76%2Bturret.jpg" width="400" /></a></div>
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The photo on the right shows a TPKU-2B with two handlebars as used in the tank version, but it is very probable that this is a modification done by the U.S Army after the tank was captured and sent to America.<br />
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<h3>
<span style="font-size: large;">Gun Sight</span></h3>
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<a href="https://www.blogger.com/null" id="tshk"></a>
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<h3>
<span style="font-size: large;">TShK-66, TShK-66P, TShK-2-66</span></h3>
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TShK-66 is an articulated telescopic sight used in the PT-76, and the TShK-66P is a slightly modified variant used in the PT-76 obr. 1957. The TShK-2-66 sight is another modification of the TShK-66, first used in the PT-76B obr. 1959. It differs from previous variants in that it is designed to be stabilized via mechanical linkages to the cannon. By coupling the sight to the stabilized cannon, the gunsight is stabilized vertically in the same way as the elevation mechanism of the cannon.<br />
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Being an articulated telescope, the aperture of the sight is installed co-axially with the trunnion of the cannon mounting cradle so that the raising and lowering of the cannon will raise and lower the aperture by the same amount while the eyepiece of the sight remains fixed. This means that the gunner does not have to move around to keep his eye pressed to the eyepiece when elevating or depressing the cannon for whatever reason. The eyepiece is fixed at a slight downward tilt for better comfort. When using the sight, the gunner's head will be slightly lowered and partly supported by the brow pad, so that the strain on his neck is reduced.<br />
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<a href="https://1.bp.blogspot.com/-kQLWDPC_sjw/Xeys4KTk1AI/AAAAAAAAP0E/Rbcjd-wSRJ0_ceSjkwSRipakUdlLRTLlgCLcBGAsYHQ/s1600/viewfinder.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="773" data-original-width="1285" height="384" src="https://1.bp.blogspot.com/-kQLWDPC_sjw/Xeys4KTk1AI/AAAAAAAAP0E/Rbcjd-wSRJ0_ceSjkwSRipakUdlLRTLlgCLcBGAsYHQ/s640/viewfinder.png" width="640" /></a></div>
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The TShK-66 sight belongs to the same classification as the TSh series (e.g TSh-15, TSh-16, TSh-17) of articulated telescopic sights designed and fielded during WWII. Although the TShK-66 sight was developed at around the same time as the telescopic sights for the T-54 and the post-war IS heavy tank series, the TShK-66 does not feature variable magnification. In this regard, it is identical to the TSh series of articulated tube telescopic sights of the 1943 pattern with a fixed 4x magnification and a 16 degree field of view, but with the additional 'K' at the end to denote the shortened telescopic tube of the sight compared to the normal tank sights. The TShK-66 also lacks stadiametric rangefinder markings, thus firmly placing it in the same classification as the TSh-20 sight for the T-54 obr.1947, and one step below the TSh2-22 for the T-54 obr.1951. Once again, this reinforces the fact that the PT-76 was not only objectively deficient in observational facilities, but also deficient in comparison with its peers from the same year of introduction. To conduct rangefinding, the commander is forced to use his TPKU-2B periscope. This would be fine for the first shot, as it is more convenient to search for targets through the variable magnification binocular optics of the TPKU-2B, but it becomes a liability when a second target has to be engaged, as the commander has to switch from the sight to the TPKU-2B and reacquire the target to estimate the range before switching back to the sight to open fire on it. Since the periscope cannot be expected to be aligned with the sight (as that would defeat the purpose of placing the TPKU-2B in an independent rotating cupola), this forces the commander to move between the periscope and the sight multiple times and thus lose visual contact with the target multiple times in order to ascertain the distance to it. This is completely impractical for a moving target, and highly time consuming even for a static target. Therefore, the only reasonable option would be to estimate the range using the mil markings and fire a ranging shot to the target and rely on the quick hands of the loader to fire a second one.<br />
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Thanks to Sean Murphy for providing the photo below, which may be the first photo of the TShK-66 ever to be uploaded on the Internet.<br />
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As you can see in the photo above, the sight only has markings for AP and HE-Frag shells, and for the co-axial machine gun. There are no markings for APCR or HEAT ammunition. In order to use these ammunition types, he must refer to a pre-calculated range table. It is interesting to note that the range scale for HE-Frag ammunition is tighter than the range scale for AP, showing that HE-Frag rounds have a slightly flatter trajectory.<br />
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<h3>
<span style="font-size: large;">LOADER'S STATION</span></h3>
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The loader is situated on the right side of the turret. He is responsible for loading the cannon and the co-axial machine gun, but he is also responsible for surveying the battlefield when he is not occupied with these duties. To do this, he is provided with a single MK-4S periscope installed in a rotatable race ring mount directly in front of him. Being limited to only one periscope - albeit a rotatable one - severely restricts the loader's perception of the outside world, but it is at least somewhat understandable as he is predominantly focused on servicing the weapons.<br />
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The rotatable mount allows the loader to direct the periscope to look forward and to the right, and the reversible viewfinder of the MK-4S lets him look to the left and rearward, which would otherwise be impossible with the turret wall in the way of the loader's head. Having the periscope is useful for directing the driver when backing up the tank or crossing water obstacles. This is normally done by the commander of a tank, but the redistribution of labour in the PT-76 may be necessary on some occasions because the commander is already quite overworked.<br />
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In terms of working space and general comfort, the loader is reasonably well accommodated as the turret ring diameter of the PT-76 turret is 1,800mm, which is quite large for a thin-skinned tank with a medium pressure 76mm gun. Besides the general roominess of the tank, the loader is provided with a great number of metal loops on the right hull sponson onto which he can strap his personal effects. The loops are visible in the background of the photo on the left below, underneath the dark magenta backrest of the loader's seat.<br />
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The loader's backrest is positioned in such a way that he must sit facing the gun, which may be convenient for loaders who choose to perform their duties while seated. As the photo above shows, the loader's seat is suspended from the turret ring. It can be folded up and out of the way so that the loader is unobstructed if he chooses to carry out his duties while standing.</div><div><br /></div><div>The <a href="https://twitter.com/annquann/status/1267027123669094400?lang=en">image below</a> shows a PT-76 loader from the VPA securing UBR-354P rounds into the ready racks.</div><div><br /></div><div><br /></div><div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-zvAMWV2hW7Y/X538KtCUExI/AAAAAAAAR4U/7Q0y-F4O7EcD0DsLoRg9y62S99yPWeogwCLcBGAsYHQ/s500/vietnamese%2Bpt-76.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="375" data-original-width="500" src="https://1.bp.blogspot.com/-zvAMWV2hW7Y/X538KtCUExI/AAAAAAAAR4U/7Q0y-F4O7EcD0DsLoRg9y62S99yPWeogwCLcBGAsYHQ/s16000/vietnamese%2Bpt-76.jpeg" /></a></div><br />
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There is one dome light on the loader's side of the turret, installed next to the MK-4S periscope. The location of the dome light is convenient for the loader to reload or service the co-axial machine gun in the dark.<br />
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(Photo credit to the <a href="http://modelizmspb.temza.ru/postament/tanks/pt76-1.html">modelizmspb.temza.ru site</a>)<br />
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The roominess of the turret combined with the small size and handiness of the unitary 76.2mm cartridges make the task of loading the D-56T gun extremely straightforward. It should not take more than four seconds to load, unless the loader is unusually sloppy. All of the 76.2mm ammunition is stowed inside the turret basket. There are fourteen rounds in a ready rack directly behind the loader, arranged in such a way that seven rounds are stowed horizontally in a double stack. Another two rounds are clipped to the turret wall directly above this ready rack. The reserve ammunition is stowed in two containers on the rotating turret floor directly underneath the cannon assembly, each holding sixteen rounds, for a grand total of forty rounds. This is not a lot, especially considering the large internal volume of the tank and the small size of the 76.2x385mm cartridge, but it was significantly more than the ammunition capacity of the P-39 (Object 101) prototype, which carried only thirty rounds of ammuntion - an absolutely unacceptable amount, considering the fact that the latest T-54 model at time carried 34 rounds of the much more powerful 100mm caliber.<br />
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Loading the cannon should be quite straightforward. The location of the ready rack and the rounds clipped to the turret wall makes it convenient for the loader to extract a round, turn a little to the right and ram it into the cannon in one fluid motion. This can be done standing or seated, and indeed, the height and orientation of the loader's seat compared to the ready racks would make it quite easy for the loader to do so while seated, as you can see in the photo below (photo credit to <a href="http://www.maquetland.com/article-phototheque/4288-pt-76-interieur-details">Claude Balmefrezol from maquetland.com</a>).<br />
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The reserve racks are placed on the rotating turret floor, but it is shifted so that one of the containers extend out of the perimeter of the floor to increase the available floor space of the loader. These racks are not as convenient to use as they could be, as the angling of the racks to the left (refer to diagram below) prevents the loader from extracting a round and charging it into the cannon in one swift motion. This is because the loader is naturally inclined to extract rounds from these racks using his right hand, when it is his left hand that is used to ram rounds into the cannon chamber. So to load, he must shift his grip on the base of the shell from his right hand to his left hand. The end result is a slight increase in the time needed to load.<br />
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Nevertheless, it appears that the reserve racks are still decent from an ergonomics point of view. Placing the racks underneath the cannon ensures that both the gunner and loader have the maximum possible amount of forward legroom in their respective stations, and this necessitates the angling of the racks so that the loader can access it without needing to crouch below the cannon, which may be impossible or dangerous if the cannon is elevated. Additionally, it can be argued that a high loading rate from these racks is not necessary, as these are the reserve racks and would be most often used to replenish the ready racks.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://4.bp.blogspot.com/-5E-vPOmnKIs/WoTKxVrt1fI/AAAAAAAAK10/M9zTWSTD_cc6MNQeyUF5ej6GYJ13muYwwCLcBGAs/s1600/polish%2Bloader%2Bpt-76.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="795" data-original-width="1133" height="449" src="https://4.bp.blogspot.com/-5E-vPOmnKIs/WoTKxVrt1fI/AAAAAAAAK10/M9zTWSTD_cc6MNQeyUF5ej6GYJ13muYwwCLcBGAs/s640/polish%2Bloader%2Bpt-76.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Polish loader in a PT-76. Photo credit to the <a href="http://www.7ldd.ocalicodzapomnienia.eu/wpis.php?wpisid=33">7th Lusatian Landing Division (7th ŁDD) website</a>.</td></tr>
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According to the manual, the maximum aimed rate of fire is seven rounds per minute, translating to an average period of 8.57 seconds between each shot, but there can be no doubt that most of that time is spent aiming, as <a href="http://2.bp.blogspot.com/-aB-JsIy9KG8/VHKvtnUKyHI/AAAAAAAADms/WmuGC6hfAi8/s1600/penetration-us-intel-1.png">this table</a> lists the maximum rate of fire as fifteen rounds per minute. The huge difference in the aimed rate of fire and the maximum rate of fire shows how much - or rather, how little - time is actually spent loading the cannon when the time needed to aim is taken out of the equation, and it is even more obvious when we take into account the fact that the rate of fire of the T-54 is stated in technical manuals to be seven rounds per minute. Being listed as the "aimed" rate of fire denotes that the commander has to first find the target, estimate the distance and adjust his sights before opening fire, and the loader follows the formal procedure of observing the fall of the shot from his single periscope before reloading the cannon for the next shot. Since the PT-76 has the same fire control system as the T-54, it makes sense that the aimed rate of fire from the PT-76 would be the same as the T-54, since the time needed to load either of their cannons is less than the time needed to aim despite the large difference in caliber. The maximum rate of fire is simply the rate of fire that can be achieved without aiming or without making corrections while the loader loads as quickly as he can. The maximum rate of fire would be true for repeated shots on a single target or for a short and intense burst of artillery fire, whereas the aimed rate of fire would be true if the tank was engaging multiple targets one after another. In a realistic scenario where a platoon of PT-76 tanks is used to support a motorized Naval Infantry company against fixed defences, the actual rate of fire of the tank would most likely be seven rounds per minute or less, as the tank would be firing on the move at multiple targets.<br />
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The implementation of a stabilization system in the PT-76B presumably led to an increase in the aimed rate of fire, as the commander would need less time to lay the gun on the target. The same would apply for firing on the move, as the tank would no longer need to halt before every shot as it could fire accurately while cruising at a slow crawl.<br />
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<h3>
<span style="color: white; font-size: large;">ARMAMENT</span></h3>
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<span style="font-size: large;">D-56T RIFLED GUN</span></h3>
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The PT-76 is equipped with the D-56T rifled gun. The D-56T was a completely new design developed in 1949 by the design bureau <a href="http://www.zavod9.com/?pid=10093">No.9 factory</a>, where it received the designation LB-62T (not to be confused with the LB-76T designed by the No.92 factory and installed in the Object 101). It was later renamed as the D-56T when the Object 740 prototype officially entered service as the PT-76. The cannon is chambered for the 76.2x385mm cartridge used in the ZiS-3 towed divisional gun and F-34 obr.1940 tank gun, and was designed with identical ballistic characteristics. To that end, the barrel measures 42 calibers (3200mm) in length, identical to the ZiS-3 and F-34. However, the barrel is of a distinct design, featuring a characteristic tapered step at the one-third mark of the tube.<br />
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Unlike many of the other tank guns designed in the late 40's, the D-56T has a recoiling mechanism that is reminiscent of more modern guns like the 115mm U-5TS or the 125mm D-81. Instead of having the hydro-pneumatic recoil buffer and hydraulic recuperator mounted on top of the chamber and forward of the breechblock like on the <a href="http://armor.kiev.ua/armor/Tanks/Modern/T54/manual/T54-025.gif">D-10T</a> and <a href="http://i57.fastpic.ru/big/2013/1029/9d/7861ae56f2df910085f4ed6cfcc50c9d.jpg">D-25T</a>, the recoil buffer is mounted in a slot in the lower right corner of the breech block and the recuperator is mounted in a slot in the lower left corner. This frees up valuable space on the top part of the cannon and permits the installation of the gun in a low profile turret, and also helps to somewhat reduce the amount of interior penetration (the length of the gun extending into the turret). Besides its atypical configuration, the recoiling mechanism is also designed with a long recoil stroke to help reduce the recoil impulse to a manageable level. The maximum recoil stroke length is 550mm and the normal recoil stroke length is 470mm to 545mm, depending on the ammunition fired. The drawing below depicts the D-56TM cannon without its mounting cradle and without the recoil buffers.<br />
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The photo below (credit to Stephen Tegner from the <a href="https://www.scalenews.de/pt-76b-objekt-740b-walkaround-394/">scalenews.de</a> walkaround page) offers a better view of the two recoil buffers below the breech block of the D-56T.<br />
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There were guns with better anti-armour performance, like the Ch-51 57mm gun, and the newly developed S-60 57mm autocannon may have offered great firepower against hard and soft targets alike, but the official requirements stipulated that a 76mm gun was to be installed in the Red Army's prospective new amphibious light tank. In hindsight, it may seem that not installing the S-60 on the PT-76 was a mistake, seeing as this class of weapon is now in vogue for light combat vehicles and a relatively recent Russian upgrade package offered for the PT-76 proposes to replace the turret with a new model that mounts a 57mm autocannon based on the S-60, but it should be understood that the requirements set forth by the Ministry of Defence were not arbitrary.
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The PT-76 was to provide fire support for troops during amphibious landings, most often to suppress and eliminate fixed defences on the shore like machine gun and recoilless rifle nests while having enough firepower to deal with the majority of armoured targets, and in the immediate post-war period, the majority of armoured targets that the PT-76 was expected to encounter would be light tanks mixed with a small number of WWII era medium tanks. The PT-76 would not face the modern medium tanks of the enemy unless some sort of tactical error was made. From the front, neither a high velocity 57mm cannon or a medium velocity 76mm cannon would be able to do much against a medium tank using conventional armour-piercing shells, but a 76mm cannon has the option of using HEAT ammunition, so it is capable of dealing with significantly heavier tanks. Against field fortifications and buildings, the high explosive and fragmentation effect of a 76mm HE-Frag shell also makes it more useful than 57mm HE-Frag shells, even if a 57mm autocannon is able to deliver more rounds to the target. One of the primary drawbacks of having high velocity small caliber cannons is the low explosive content of its explosive shells due to the need to have a sufficiently thick casing to withstand the acceleration forces in the barrel. Aside from fixed defences, the PT-76 would have to deal with mechanized transportation for infantry, which most often took the form of unarmoured trucks or thinly armoured half-tracks in the immediate postwar period, and later on, armoured personnel carriers. A quick-firing autocannon is ideal against this type of threat, but a medium velocity tank gun is also effective, and of course, dismounted infantry could be effectively suppressed or eliminated solely with the complementary 7.62mm coaxial machine gun. In this context, a medium pressure large caliber cannon like the D-56T paired with a 7.62mm machine gun appears to be a reasonable choice.<br />
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However, the 76.2x385mm cartridge itself was not the first choice. Cannons chambered for this cartridge were generally considered obsolete in the Red Army, which was increasingly relying on larger and larger guns, whether it be towed, self-propelled or tank mounted. For example, the ZiS-3 divisional gun chambered for the same cartridge was declared obsolete and immediately replaced by the 85mm D-44 after the conclusion of WWII, and the 85mm ZiS-S-53 of the T-34-85 was replaced by the D-10T in its successor, the T-54. This trend was not ignored during the conceptualization of the Red Army's new amphibious light tank in 1947. Originally, the plan was to create a 20-ton tank armed with an 85mm cannon and with the same mobility characteristics as a medium tank. It was intended to have a 400 hp engine and swim with the use of foam-filled aluminium floats, but the engine was not yet ready at the time, and it was realized that the reliance on vulnerable unarmoured floats was not viable for an amphibious light tank, so there was no other choice but to create a tank that could float with the buoyancy of its own hull. The weight of the new concept tank had to be reduced to 15 tons, and because of this, the plans for an 85mm gun had to be scrapped for a 76mm gun.<br />
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The D-56TS modification featured a new hydraulic elevation drive piston as an addition to the simple rack-and-pinion geared manual elevation mechanism, and also added brackets underneath the gun cradle to accommodate the hydraulic pump for the elevation drive. This increased the weight of the gun at the breech end, so the thickness of the fume extractor tube was increased from 3mm to 4mm in order to act as a counterweight.<br />
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The D-56T has a vertically sliding wedge breech, which is highly unusual for a Soviet tank. According to Soviet engineering manuals, if the bore axis of a tank cannon from the floor of the fighting compartment is lower than 950-1,000mm, a vertically sliding breech should be used, but if the bore axis is higher than that, a horizontally sliding breech should be used. This is because the convenience of ramming a shell into the chamber changes depending on the height of the bore in relation to the height of the average loader (170cm). If the height of the bore axis is 950-1,000mm or more, the chamber will be above the elbow of a standing man as evident in the drawing below, so a horizontally sliding breech is more convenient for the loader.
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Under this criteria, having a vertically sliding breech gun in a turreted tank would require a rather tall turret paired with a very short hull (less than 1 meter tall) or some other unusual and impractical solution, and for this reason, most tank guns built in the Soviet Union have a horizontally sliding breech as do many tank guns built abroad, the L7 being a prime example. However, that is not to say that this criteria was strictly enforced or that it made a major difference relative to other factors like the allocated working space for the loader, the weight and size of the ammunition, and so on. Just as there are plenty of tank guns with horizontally sliding breech blocks, there are also plenty of tank guns with vertically sliding breech blocks used in tanks that have the same bore axis height as tanks armed with horizontally sliding breech guns, with examples like the M68, M256, Rh 120 L/44, L11, L30, CN 120-26, and others. In the case of the D-56T, it appears that the decision to use a vertically sliding breech was possibly influenced by the ease of loading from a seated position, since the bore axis height of the D-56T from the floor of the fighting compartment is 1,500mm - nowhere close to being below 1 meter. It is quite probable that there was no real incentive to have a horizontally sliding breech block for a 76mm gun since the cartridges were relatively small and light, and were easy to load anyway.<br />
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All of the D-56T variants are fitted with a muzzle brake. A modern muzzle brake is capable of reducing the recoil force of a recoiling rifle or cannon by up to 80%, but they are limited to around 30% for guns and howitzers as an insurance policy so that the hydraulic recoil system does not fail catastrophically if the cannon is fired with a damaged muzzle brake. The main downside to a muzzle brake is that the smoke and hot gasses diverted sideways has the side effect of obscuring the gunner's vision and also revealing the tank's position. For a light reconnaissance tank with only enough armour to stop machine gun fire, these drawbacks are much more serious than they are for a heavily armoured tank intended for open combat. That said, a muzzle brake was necessary on the D-56T in order to keep the recoil forces low enough for the turret to handle. The original D-56T is fitted with a multi-slotted muzzle brake of considerable length, but from 1957 onward, new production PT-76 tanks were armed with the newer D-56TM cannon with a new updated muzzle brake with a fume extractor.<br />
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The new muzzle brake returned to a double-baffle type like the original ZiS-3, but was of a new style of brakes derived from the muzzle brake of the D-25T designed by the TsAKB design bureau (now referred to as the "TsAKB style" brake, as opposed to the "German style" brake used on earlier D-25T guns). The advantages of slotted-type and baffle-type brakes over each other are debatable and the two types of brakes operate on different principles, but according to "<i>The Basics of Artillery Guns and Ammunition</i>" (Основи Будови Артилерійських Гармат Та Боєприпасiв, А. Й. Дерев’янчук), pages 308-311, double-baffle brakes are typically more efficient and more suitable for tank guns for a variety of reasons. A double-baffle muzzle brake works by placing obstacles of a large surface area (the baffles) in front of the muzzle to impede the forward flow of the escaping propellant gasses, thus absorbing the kinetic energy of the propellant gas particles in the form of pressure, effectively causing the gasses to impart a forward force on the barrel which cancels out some of the rearward recoil force. This is illustrated in diagram "A" in the drawing below. On the other hand, a slotted muzzle brake works entirely by redirecting the escaping propellant gasses at a rearward angle to produce forward thrust much like a rocket, thus creating a braking effect. The small size of the slots forces the escaping propellant gasses to exit at an extremely high velocity, but the angle of the slots is inherently restricted by the need to protect the tank and surrounding infantrymen from the same powerful gasses. Because of this restriction, the amount of thrust produced from each individual slot is low, so a large number of slots is needed to achieve a useful level of recoil reduction. All of this is shown in diagram "B" in the drawing below.<br />
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For the PT-76 specifically, the advantage of a double-baffle muzzle brake over the earlier slotted one is obvious: the tank was required to ferry up to 20 troops on top of its hull during river crossings, and a slotted muzzle brake would have a much higher chance of harming the tank riders than a double-baffle type. This may also be one of the reasons why baffle-type brakes have been the most common design by far in every application, from custom-made competition rifles to large artillery systems. Slotted muzzle brakes have been used on guns and howitzers of calibers ranging from 152mm on the ML-20 to 57mm on the early production variants of the Ch-51 gun, so clearly there is no caliber limitation, but modern guns are invariably fitted with a baffle-style brake. For example, the <a href="https://upload.wikimedia.org/wikipedia/commons/thumb/e/ea/ASU-57.jpg/800px-ASU-57.jpg">early long slotted brake on the Ch-51</a> was quickly replaced by a much more compact <a href="https://upload.wikimedia.org/wikipedia/commons/8/8d/Russian_57-mm_ASU-57_SP_Gun%2C_New_Brunswick_Military_History_Museum%2C_5_Division_Support_Group_Gagetown%2C_New_Brunswick%2C_Canada.JPG">double baffle muzzle brake on the Ch-51M</a>, and all Russian 152mm gun-howitzers produced after the ML-20 - including both towed and self-propelled guns - were fitted with double baffle muzzle brakes as well. Another likely factor behind the popularity of baffle-type brakes over slotted-type brakes may be its compactness, which is important for turreted tanks like the PT-76 as they are sometimes expected to drive into forested areas where a long muzzle brake may hamper the movement of the tank or prevent it from traversing the turret to aim. It also helps to ensure that the muzzle does not dig into the ground and cause malfunctions when driving across rough terrain, although this is not an issue for the PT-76 due to its relatively tall hull and short gun barrel.<br />
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The recoil guard and shell casing deflector can be folded down by a full 90 degrees, thus creating a spacious passageway between the two crew stations in the turret.<br />
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<span style="font-size: large;">POWERED TRAVERSE, STABILIZER</span></h3>
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The first iterations of the PT-76 featured powered electric turret traverse, but no stabilizers. The original PT-76 obr. 1952 had the EPB-4 electric turret drive installed, granting a maximum turret rotation speed of 17 degrees per second. To operate the electric traverse system, the commander was furnished with a KB-4 control unit, which has the appearance of spade grip attached to a black box. The control unit is essentially a complicated rheostat. The spade grip could be rotated with the commander's left hand to different degrees of deflection to control the speed of turret traverse, and returning the handle to the center position while the turret was still in motion reversed the polarity of the electric traverse motor, producing a braking effect until the turret comes to a complete stop. Gun elevation was controlled manually via the gun elevation handwheel, located directly underneath the TShK-66 sight. The lack of powered gun elevation meant that gun laying was relatively slow, but this was typical for all tanks of the era. Besides that, the layout of the KB-4 powered traverse unit and the manual elevation flywheel in the PT-76 is not particularly ergonomic. If we take the height of the commander's head to be at the same level as the eyepiece of the TShK-66 sight, then the powered traverse unit would be slightly above shoulder level and the manual elevation flywheel would be at chest level. This is similar to the layout of the gunner's controls in the T-54, the M41 Walker Bulldog, and the Centurion Mk.III.<br />
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The photo below shows (from left to right) the turret traverse flywheel, the KB-4 control unit, and the gun elevation flywheel.<br />
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To switch from powered electrical turret traverse to manual traverse, the worm gear mechanism must be engaged and the electric traverse motor interface must be disengaged.<br />
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Being an amphibious vehicle meant that the Soviet Naval Infantry finally had dependable firepower to assault shore defences in amphibious landings, but the lack of gun stabilization severely limited the firepower of the PT-76. Upon entering the water, a PT-76 would be unable to return fire against defensive positions on the shore until it reached solid ground, but even then, the tank could only fire accurately during short halts. This was a major issue because the landing ships from which the tanks are launched had limited firepower against hardened point targets.<br />
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<span style="font-size: large;">STP-2P "Zarya"</span></h3>
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Attached to the D-56TS gun of the PT-76B was the STP-2P 'Zarya" two-plane stabilizer system derived from the STP-2 "Tsiklon" stabilizer originally developed and used in the T-54B. The addition of the stabilizer took up a some space inside the turret, most of it by the amplidyne generator, electrical junction boxes and hydraulic pump. Most of the additional equipment was non-intrusive, being located underneath the gun or behind the commander's control handles and sight, but some components (such as the junction boxes) was mounted to the turret walls. A collapsible shoulder guard was added to the gun mount on the commander's side of the turret to ensure that the automatic adjustments of the stabilized gun do not injure him.<br />
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The stabilizer has two modes of operation: automatic and semi-automatic. The automatic mode is the primary mode for combat purposes where the stabilizer performs at its full operational capacity and will continuously stabilize the gun with maximum precision. This mode is the default mode during combat and is used when firing from all positions - stationary, while moving, and during short halts. The semi-automatic mode is an auxiliary operating mode as well as an emergency mode in the event of stabilizer failure where the stabilization system is not used and the system reverts to a powered turret and gun control system instead.<br />
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An autoblocker system in the STP-2P "Zarya" stabilizer automatically hydrolocks the gun elevation drive when the gunner presses the firing button and it maintains the lock until the loader has finished loading the gun and presses his safety button. This is a feature it shares with all other Soviet tank gun stabilizers of the period. During the moment of firing, the gun has to be hydrolocked as the moment of force from the recoil of the gun greatly exceeds the moment of force that can be generated by the gun elevation drive. As such, the stabilizer will fail to keep the gun pointed in the desired elevation angle and the muzzle will tend to be thrown upwards (muzzle rise), causing the gunner to immediately lose sight of the target and making it impossible to observe the fall of the shot. This problem is solved by locking the gun in place. After the gun is loaded and the loader has pressed his safety button, the gun is returned to a stabilized condition for subsequent shots.<br />
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Moreover, the autoblocker system also improves the working conditions of the loader as the breech of the gun does not move up and down relative to the oscillating hull as the tank moves over uneven terrain. Under such conditions, it is not only more difficult to load the gun but also somewhat dangerous, as a particularly steep bump or hole in the road that causes the vehicle to pitch up or dive down can cause the breech to swing in the opposite direction at high speed in response. This could cause injuries to the loader. As such, the inclusion of an autoblocker feature improves the rate of fire of the PT-76B while it is on the move over rough terrain.<br />
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If the PT-76B commander wants to shoot the coaxial machine gun immediately after the D-56TS is fired, then the loader must press his safety button before he starts loading the gun. This returns the gun to a stabilized condition and the commander regains control of the gun elevation drive, permitting him to fire the machine gun while the loader proceeds with loading the gun.<br />
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The STP-2P "Zarya" differs from the STP-2 "Tsiklon" in that it does not have a "loader's assist" feature where the gun is hydrolocked at an elevated angle after the gun completes its recoil cycle. In the T-54, this feature was a convenience for the loader who had to handle large and rather heavy 100mm cartridges, but in the PT-76 where each 76.2mm cartridge was several times smaller and lighter, this feature was not necessary. Also, unlike a T-54B or T-55 with the STP-2 stabilizer, the turret of the PT-76B would not be locked in traverse by the autoblocker system. This feature was necessary for a T-54 as most of the ammunition was stowed in the hull. It would otherwise be too dangerous for the loader to be standing on the rotating turret floor while retrieving ammunition from the hull, as the stabilized turret could turn unexpectedly because of the driver steering the tank in another direction or because of the gunner's inputs. In a PT-76B where all of the ammunition was stowed inside the turret, this feature was redundant.<br />
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Depending on the situation, the PT-76 commander can turn the autoblocker on or off as he sees fit. For instance, the PT-76B manual states that when the tank is afloat in calm waters, the autoblocker system can be switched off. In this case, the gun is only hydrolocked during the moment of firing and it returns to a stabilized condition immediately after the gun has completed its recoil cycle. The combination of calm waters and the low swimming speed makes it unnecessary to keep the gun hydrolocked while the loader performs his duties as the gun does not oscillate by much in such conditions.<br />
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Automatic, Semi-Automatic Modes</h3>
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Maximum Turret Traverse Speed: 20°/sec<br />
Minimum Turret Traverse Speed: 0.1°/sec<br />
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Maximum Gun Elevation Speed: 6°/sec<br />
Minimum Gun Elevation Speed: 0.05°/sec<br />
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The accuracy of stabilization in the vertical plane is 1.0 mil and the accuracy of stabilization in the horizontal plane is 1.5 mils. This is very similar to the performance of the "Tsiklon" stabilizer, and "Zarya" offered a similar improvement in firing accuracy. When approaching a target at a distance of 800-1,200 meters in a straight line, the chances of scoring a hit on the frontal silhouette was increased by 5.25 times, and the chances of scoring a hit on the side silhouette at 1,000 meters was increased by 6.3 times. The chances of scoring a hit while moving at an angle of 15 degrees relative to the target was improved by 4 times. In short, the implementation of "Zarya" enabled the PT-76 to fire at tank-type targets at short to medium range with reasonable accuracy at speeds of between 12 to 25 km/h and effectively open fire at troop concentrations and fixed fortifications at long range at the same speed. More interestingly, it also gave the tank the ability to fire with high accuracy on shore targets while sailing on relatively calm waters, which may be partially attributed to the relatively low maximum sailing speed of the tank and the dampening of the vibrations from the engine by the surrounding water.<br />
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<span style="font-size: large;">AMMUNITION</span></h3>
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The D-56T gun came with a plethora of preexisting ammunition types, all identical to the ammunition used in towed ZiS-3 field guns. The cartridge is 76.2x385mmR (Rimmed).<br />
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The generic ammunition loadout of a PT-76 operating in the 50's consisted of 24 HE-Frag shells, 4 APHE shells, 4 APCR shells and 8 HEAT shells. By the late 70's, this was changed to a mix of 20 HE shells, 4 APHE shells, 4 APCR shells and 12 HEAT shells.<br />
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The small quantity of armour piercing rounds of the same type can make it difficult to engage targets. Beyond the obvious drawback of a limited number of available ammunition, the small quantity of each variety of ammunition complicates the process of using the 'burst on target' gunnery method where the gunner senses the impact of his first shot to correct his aim for the second shot, since the different ammunition types are affected in different ways by the same weather conditions. For example, BK-354M is a fin-stabilized HEAT shell, and the windage adjustments needed for it will be different for the other shell varieties, and the difference in velocities between the four different anti-armour shells makes it difficult to apply corrections from one type to another.<br />
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<span style="font-size: large;">PROPELLANT</span></h3>
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The propellant type for the regular ammunition used in the D-56T is a full charge of 54-A-354 stick powder 9/7. The mass of the normal propellant charge is 1.08 kg, the same as for all other L/40-42 guns chambered for the 76.2x385mm cartridge, but HEAT and APCR ammunition differed. The mass of the 54-A-354K propellant charge for the BK-354/M round is 0.86 kg, the mass of the 54-A-354P propellant charge for the BR-354P is 1.3 kg but this can be substituted with 1.21 kg of 4A41 special charge, and the mass of the 54-A-354N propellant charge for the BR-354N APCR round is 1.4 kg. Reduced charge shells were used for high explosive shells on field guns for high angle shooting, but never for the D-56T.<br />
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All of the ammunition use the standard 54-G-354 brass case.<br />
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<span style="font-size: large;"><b>53-</b>UOF-354M</span></h3>
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<span style="font-size: large;"><b>53-</b>OF-350</span></h3>
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OF-350 is a fairly typical high-explosive fragmentation shell of modern construction that was used extensively during WWII with the ZiS-3 divisional gun and F-34 tank gun. The steel walls of the cavity are cylindrical, as opposed to tapered like on the O-350A fragmentation shell. During the so-called "Great Patriotic War", the shell was sometimes filled with Amatol instead of TNT as a cost-saving measure due to the huge expenditure of TNT during the war, but this was no longer practiced by the time the PT-76 entered service because pure TNT was simply better. Despite the invention and proliferation of more powerful explosives (in terms of detonation velocity) in the late 30's, the OF-350 HE-Frag shell was only filled with TNT during its service with the PT-76 due to the good balance of blasting power, fragmentation effect and cost. Only the O-350A Frag shell used A-IX-2 (73% RDX, 23% Al, 4% phlegmatizing wax) or TGA (40% RDX, 50% TNT, 10% Al) for its explosive filler due to the much higher brisance of these explosives compared to pure TNT, making them much more effective at producing shell splinters and fragmentation. O-350A shells are compatible with the D-56T, and it was probably used in some indeterminate quantity at some indeterminate time, but as a rule of thumb, the PT-76 carried only HE-Frag due to its versatility.<br />
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The maximum range of the OF-350 shell is 12,000 m when fired from the D-56T. This is slightly lower than the maximum range from 76mm field guns, which could send an OF-350 shell out to a distance of 13,000 m at an elevation of 37 degrees (obr. 1942 ZiS-3) or 13,290 m at an elevation of 45 degrees (obr. 1902/30 and obr. 1939 USV). By comparison, the maximum elevation of the D-56T is 30 degrees.<br />
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Muzzle Velocity: 680 m/s<br />
Battlesighting Range for Target Height of:<br />
2.0 m - 820 m<br />
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Maximum Range: 12,000 m<br />
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Total Projectile Mass: 6.21 kg<br />
Explosive Filling Mass: 0.64 kg<br />
Explosive Composition: TNT<br />
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Since the ballistics of OF-350 are quite similar to the AP rounds fielded for the D-56T, the two ammunition types are more or less interchangeable at distances of less than a kilometer. This greatly simplifies the aiming process when engaging lightly armoured vehicles.<br />
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The OF-350 shell was initially capped with the KTM-1 or KTMZ-1-U point-detonating (PD) fuze during the earlier years of its service, but beginning in the early 50's, the newer MG-N point-detonating fuze was available as a replacement and became standard for Soviet 76mm and 85mm artillery and tank shells of the post-war era.<br />
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The MG-N fuze offers the same choice of instantaneous (fragmentation) or delayed (high-explosive) action like the earlier KTM-1, but differs somewhat in the percussion detonation mechanism. For all practical purposes, both fuzes are interchangeable. To choose between fragmentation and high-explosive modes, the loader can take the safety cap off or leave it on. The inertial distance arming system for the KTM-1 is detailed in the two diagrams on the left, and the upper right diagram shows how the fuze behaves without the cap when the shell impacts a target, while the lower right diagram shows how the fuze behaves with the cap.<br />
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<a href="https://2.bp.blogspot.com/-Zd_Nu8weAU4/Wlqnor59M7I/AAAAAAAAKck/_MHwtdSA9R8Q9grAg1RWFPr8QPYkaWb5wCLcBGAs/s1600/ktm-1%2Bfusing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="506" data-original-width="709" height="454" src="https://2.bp.blogspot.com/-Zd_Nu8weAU4/Wlqnor59M7I/AAAAAAAAKck/_MHwtdSA9R8Q9grAg1RWFPr8QPYkaWb5wCLcBGAs/s640/ktm-1%2Bfusing.png" width="640" /></a></div>
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Without going into too much detail, the delay mechanism of the fuze relies on inertia. When the safety cap is taken off the fuze, the piston at the tip is exposed. When the shell impacts an obstacle, the fuze digs in and the piston is pushed back by the material of the obstacle (soil, concrete), driving a firing pin backwards while the percussion detonator at the base of the fuze is thrown forward by inertia (refer to upper right diagram). Under the combined speed of both components moving toward each other, the firing pin and detonator impact in a fraction of a millisecond and the booster is set off by the detonator. If the safety cap is left on, the piston and firing pin do not move when the shell impacts an obstacle, and only the detonator flies forward due to inertia from the deceleration of the shell when it penetrates an obstacle. When the detonator hits the fixed firing pin, the warhead detonates. The time needed for the detonator to reach the firing pin creates a delay of 0.03-0.05 seconds, allowing the shell to penetrate into the target before it explodes.<br />
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When the cap on either the MG-N or KTM-1 fuze is left on (HE mode), a OF-350 shell fired from a distance of 7.5 km can penetrate a brick wall up to 0.75 meters thick or an earthen embankment up to 2.0 meters thick before detonating. Since the fuze works on a delay mechanism, the shell will detonate behind the wall or obstacle if it is less thick than the penetration path of the shell. When the cap is screwed off (Frag mode), the shell explodes instantaneously upon impact with the target or with the ground, producing a spray of up to 670 shell splinters of sufficient energy to injure or kill in an area measuring 30 m wide and 15 m deep.<br />
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Based on a "Report on the shooting of German tanks with AP and HE shells from tank guns" from 1942, a part of which is detailed <a href="http://tankarchives.blogspot.my/2013/05/f-34-vs-german-tanks.html">in this article by Peter Samsonov</a>, 76mm high-explosive fragmentation shells fired from an F-34 tank gun proved to be capable of destroying light tanks like the Pz.38(t) and Pz.III from distances of up to a kilometer. A variety of ammunition types of different calibers was tested, including 76mm HE-Frag. The designation of the 76mm HE-Frag shell used in the testing was not explicitly mentioned, but the generic description of "76мм осколочно-фугасная дальнобойная стальная граната" (76mm long-range steel high-explosive fragmentation grenade) leaves no doubt that 53-OF-350 with a standard KTM-1 fuze was used, as it is the only round for the F-34 that is designated as such. In order to understand the type of damage that can be inflicted on a light tank like an M41 Walker Bulldog, we can use the tests on the Pz.38(t) as an example. It is important to note that the Pz.38(t) used for the tests is either an Ausf. E or F model as evidenced by the presence of appliqué armour on the front (25+25mm) and sides (15+15). The outcome of the tests are shown on pages 30 and 31, as seen below.<br />
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<br />
A total of six HE-Frag shots were fired at the tank at distances of between 800 to 950 meters. Keep in mind that the testing with HE-Frag shells was preceded by a single test of 76mm AP fired at the base of the turret (30+30mm), which severely damaged it. Before testing with 76mm rounds, the Pz.38(t) was bombarded with 37mm, 40mm and 45mm shells which left deep dents and extensive cracking on the plating of the tank. However, the photographs show that the cracks were isolated to the 25mm appliqué armour, so the base 25mm armour of the tank was still sound, and the testing is still valid.<br />
<br />
<ol>
<li>Aimed at the front hull plate (25+25mm, 10°) from 800 meters. The dual-layer 50mm plate was bent inward by 40mm and a weld seam burst 300mm in length.</li>
<li>Aimed at the front of the turret (25+25mm, 10°) from 800 meters. The appliqué armour plate on the front of the turret to the right of the gun mount is torn off its rivets. Fragments of the plate enter the turret. </li>
<li>Aimed at the base of the turret (25+25mm, 17°) from 900 meters. The remainder of the turret front plate is shattered by the shell, and the pieces fall inside the tank.</li>
<li>Aimed at the side of the hull (15+15mm, 0°) from 800 meters. A 200 mm breach is formed in the outer armour plate, 300 mm breach in the inner one. </li>
<li>A second shot at the side of the hull (15+15mm, 0°) from 950 meters. It makes a breach 100 mm in diameter, and results in 90 mm long cracks running through the side armour. </li>
<li>Aimed at the side of the turret (30mm, 10°), from 950 meters. The turret is torn off, and displaced 150 mm. The turret ring is destroyed. The right side of the turret is destroyed.</li>
</ol>
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<div>
The testers concluded that the front hull of the Pz.38(t) could be destroyed with either 76mm AP or HE-Frag shells from a distance of 950 meters. Overall, it was concluded on page 77 that 76 mm HE-Frag shells fired from an F-34 model 1940 gun installed in a T-34 tank can destroy the Pz.38(t) tank and the side or rear hull and turret armour plating (30-20mm) of the Pz.III, StuG, and PzIV from 1000 meters, damaging the tank and crew with the shell fragments and spall. However, the report does not elaborate if the warhead exploded inside the tanks or during the penetration of the plates. The results of these tests are broadly similar to the results of a <a href="http://www.dtic.mil/dtic/tr/fulltext/u2/348021.pdf">British evaluation of the lethality of 76mm HESH on armoured personnel carriers</a>. For the British evaluations, the testers used a Saladin armoured car and a Comet tank as surrogates for the BTR-60P and BTR-50 respectively to determine the effectiveness of 76mm HESH on contemporary Soviet APCs, but did not explicitly identify the 76mm HESH round used in the testing. Since the L29 was the only HESH round in service for the L5A1 low pressure gun at the time of the evaluation, it is all but certain that some variant of the L29 was used, probably <a href="http://jcammo.com/medium-caliber-76-mm-l29-a3-hesh/">L29A3</a>. The projectile has a mass of 4.5 kg and packs 0.9 kg of RDX explosive filling. The most relevant parts of the evaluation are the two pages shown below.<br />
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It is interesting to note that the testers decided to up-armour the Saladin in order to better represent a BTR-60P, when the BTR-60P actually did not have more armour than the Saladin.<br />
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From the results of the tests, it is clear that 76mm HESH behaves much like 76mm HE-Frag on armour plates measuring from 25mm to 32mm thick. On the Saladin target, the thin armour had an appliqué plate welded on to increase the total thickness to 25mm (one inch) in much the same way as the side armour of the Pz.38(t) referenced earlier. Both the Saladin and Comet were consistently breached by 76mm HESH rounds where the armour was between 25-32mm thick, after which the shell exploded on the other side of the plate, indicating that the HESH rounds did not breach the plates with the blasting power of its squash head filling, but with its own kinetic energy, which is surprising since the nose of HESH shells is invariably thin and soft to promote the "squashing" of the explosive filler. Suffice to say, the OF-350 with its thicker steel walls would have no trouble penetrating the side armour plates of an M41 Walker Bulldog, which did not exceed an inch in thickness on the turret and the side of the hull, dropping down to just 19mm on the lower side hull. By extension, this also means that OF-350 is capable of destroying or at least disabling any armoured personnel carrier, armoured car, and light tank fielded during the Cold War. This is very useful since this round comprises the majority of the ammunition carried in the PT-76 in most combat loads.<br />
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<h3>
<span style="font-size: large;"><b>53-</b>UBR-354B APHE</span></h3>
<div>
<span style="font-size: large;"><b>53-</b><b>BR-350B</b></span></div>
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<a href="https://1.bp.blogspot.com/-FpRDleYg7io/Xeys2-oKGHI/AAAAAAAAPz8/BkAwmbSJpvcqCfo6O8zhBYi9k1gQPhJ8QCLcBGAsYHQ/s1600/br-350b.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="830" height="400" src="https://1.bp.blogspot.com/-FpRDleYg7io/Xeys2-oKGHI/AAAAAAAAPz8/BkAwmbSJpvcqCfo6O8zhBYi9k1gQPhJ8QCLcBGAsYHQ/s400/br-350b.png" width="207" /></a></div>
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Before the improved BR-354 became available in the mid-50's, the BR-350B shell of WWII vintage became the only APBC-HE shell available to the PT-76 during the earliest years of its service. The 65-gram explosive filling makes the shell exceptionally lethal once full armour penetration is achieved, and greatly increases the first-hit kill probability on light tanks. While 65 grams may not seem like much, the filling is composed of A-IX-2, which is a potent explosive-incendiary compound, because it contains aluminium as a fuel additive. A-IX-2 consists of 73% RDX, 23% aluminium powder, and 4% of phlegmatizing wax. This explosive compound has a high shattering power, or brisance, allowing it to shatter the base of the shell into multiple fragments as it emerges from an armour plate to devastating effect on personnel and equipment. Thanks to the high brisance, 65 grams of A-IX-2 is more effective in this capacity than the 150 grams of TNT used in the BR-350A shell.<br />
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Besides the damage from fragmentation, the blast itself may have some impact as well, as the aluminium powder in A-IX-2 content produces an incendiary effect because <a href="https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwjU4P3P4YvVAhUKOo8KHSJ1DLMQFggxMAE&url=https%3A%2F%2Fcameochemicals.noaa.gov%2Fchemical%2F14570&usg=AFQjCNEufaQ_AQu0MYMni8bq7_kdHtAQJg">aluminium powder is pyrophoric</a>. The relatively low aluminium content in A-IX-2 means that there will be some unburnt aluminium powder dispersed into the surrounding air, where it will burn at reduced rate due to the reduced oxygen levels and the high concentration of byproducts from the explosion. Augmenting this effect is the fact that the burning of aluminium generates an alumina (aluminium oxide) coating over the surface of the aluminium particles. The alumina acts as an insulation layer, requiring the steady application of heat to penetrate. Since the hotness of the explosion is not maintained, but instead decreases over time, the efficiency of combustion is reduced (Türker 2016, p. 426). This has the effect of extending the duration of combustion, extending the release of heat energy, increasing the explosive impulse, extending the radius of the incendiary effect, and thus increasing the probability of igniting other flammables in the vicinity of the explosion. The unavoidable side effect of the reduced efficiency of combustion is that the detonation velocity is slightly lower (1.54 RE) compared to RDX (1.60 RE).<br />
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The MD-10 base detonating (BD) fuze is used.<br />
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The dimensions for this shell are shown below:<br />
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The deep grooves around the circumference are described as fragmentation grooves to encourage projectile breakup after it passes through armour plate. As usual, the shell has a stamped sheet steel ballistic windshield crimped directly onto the steel penetrator for better aerodynamic performance. Underneath the ballistic cap is the blunt nose of the steel penetrator, meant to improve the performance of the shell on angled armour plates. The hardness rating of the steel penetrator from the tip to the explosive cavity is between 40 to 47 points on the Rockwell C scale, translating to approximately 370 BHN to 451 BHN. This is much softer, and inferior to American APCBC rounds of the same intrinsic design, which are are heat-treated to 600 BHN. For projectiles of this type, steel that is softer than 600 BHN result in a heightened tendency to shatter on impact with hardened armour. This might not make a big difference on the soft cast armour of post-war American tanks, but it may prove troublesome on other tanks and armoured targets.<br />
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The photo on the left shows a complete BR-350B projectile, and the photo on the right is an illustration of the hardness pattern in Rockwell C. These photos, and the hardness information presented above were obtained from the report "Metallurgical Examination of Soviet 76mm APHE Projectile mod. BR-350B, FMAM 2267" from the Watertown Arsenal Laboratory, which you may download here (<a href="http://www.dtic.mil/dtic/tr/fulltext/u2/014698.pdf">link</a>).<br />
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Due to the low hardness of the shell and the poor hardening technique employed during heat treatment, the shell will be more prone to shattering under several conditions, these conditions being:<br />
<br />
<ul>
<li>Very hard armour</li>
<li>Low velocity</li>
<li>Thick armour at low obliquity</li>
</ul>
<br />
Having a relatively low muzzle velocity, the shell will reach the velocity at which shattering initiates more quickly as it decelerates during flight. This means that unless the target armour is particularly thin or particularly soft, BR-350B is inherently unsuitable for long range use.<br />
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<br />
Muzzle Velocity: 655 m/s<br />
Battlesighting Range For Target Height of:<br />
2.0 m - 780 m<br />
2.7 m - 880 m<br />
3.0 m - 920 m<br />
<br />
Mass of Complete Cartridge: 9.12 kg<br />
Shell Mass: 6.5 kg<br />
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<br />
PENETRATION<br />
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<br />
<table border="1">
<tbody>
<tr>
<td>At 60° inclination</td>
<td>At 0°</td>
</tr>
<tr>
<td>100 m - 33.5 mm<br />
500 m - 30.5 mm<br />
1000 m - 22.5 mm<br />
1500 m - 24.5 mm<br />
2000 m - 21.5 mm</td>
<td>100 m - 82 mm<br />
500 m - 75 mm<br />
1000 m - 67 mm<br />
1500 m - 60 mm<br />
2000 m - 53 mm</td>
</tr>
</tbody></table>
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The table below is a firing table for a variety of Soviet 76mm rounds including the BR-350B. Taken from <i>World War II Ballistics: Armor and Gunnery</i>.<br />
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<a href="https://4.bp.blogspot.com/-4jQQX0H4j2Q/WoHtIPogsLI/AAAAAAAAK0I/JdBBmp1EpS44s4Deb9yB7DGE_RvNyAhLQCLcBGAs/s1600/br-350b.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="661" data-original-width="521" height="400" src="https://4.bp.blogspot.com/-4jQQX0H4j2Q/WoHtIPogsLI/AAAAAAAAK0I/JdBBmp1EpS44s4Deb9yB7DGE_RvNyAhLQCLcBGAs/s400/br-350b.jpg" width="315" /></a><a href="https://2.bp.blogspot.com/-kFHNE4gykFI/Wr-t-1HRPxI/AAAAAAAALPc/tBKLyVsvmx8yVpGS6ef4mxHfK6NF6A-FACLcBGAs/s1600/76.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="931" data-original-width="1169" height="317" src="https://2.bp.blogspot.com/-kFHNE4gykFI/Wr-t-1HRPxI/AAAAAAAALPc/tBKLyVsvmx8yVpGS6ef4mxHfK6NF6A-FACLcBGAs/s400/76.jpg" width="400" /></a></div>
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Despite the relatively low power of the shell, it is still enough to soundly defeat the cast steel frontal armour of an M41 Walker Bulldog light tank from between 1000 to 1500 m, and threaten the flanks of any early WWII era medium tank from 1000 m or more. The thin side armour of the British Centurion Mk.3 (51mm) and Chieftain (38mm) compared to the Patton series - even accounting for the steel side skirts - made these tanks especially vulnerable to an ambush by the PT-76. Additionally, BR-350B is theoretically capable of perforating the flat 76mm of side hull armour on the M47 Patton from a distance of 500 meters, but on the other hand, guaranteeing that the shell impacts at an angle that is perfectly perpendicular to the side hull plate is highly improbable even in an ambush scenario. The gunner will be forced to aim for the thinner side armour of the engine compartment (51mm) and hope to set the tank on fire.<br />
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<br />
<h3>
<span style="font-size: large;">53-UBR-354 APBC-HE<br />53-BR-354</span></h3>
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<a href="https://2.bp.blogspot.com/-Cs-3W4XIiYk/WoHmZ3wGUQI/AAAAAAAAKz4/B-BcEzc-1Bw-F9zTCD-PrvbqT7yvIee3wCLcBGAs/s1600/%25D0%2591%25D0%25A0-354.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1536" data-original-width="1401" height="400" src="https://2.bp.blogspot.com/-Cs-3W4XIiYk/WoHmZ3wGUQI/AAAAAAAAKz4/B-BcEzc-1Bw-F9zTCD-PrvbqT7yvIee3wCLcBGAs/s400/%25D0%2591%25D0%25A0-354.jpg" width="363" /></a></div>
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Entered service for the PT-76 in the first half of the 1950's. BR-354 is ballistically matched to BR-350B, so the generic "AP" range scale in the TShK-66 sight of all PT-76 tanks is compatible with the new round.<br />
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Like BR-350B, the BR-354B shell has a solid full-bore steel penetrator with an explosive charge at the base, complete with a fuse, but features an armour piercing cap. The cavity for the explosive charge was downsized and the explosive charge was halved compared to the BR-350B in order to reduce the likelihood of the shell shattering prematurely from lateral stresses as it penetrates thick armour plate.<br />
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The stamped sheet steel ballistic windshield is crimped onto the steel adapter on the tip of the steel penetrator, and in turn the adapter is affixed to the steel penetrator with tin-lead solder. It is possible that the adapter may behave as a ballistic cap on impact with sloped armour, but it is all but certain that it will not help against spaced or composite armour due to its thinness. Its primary purpose is to provide a proper interface to install the ballistic windshield to obtain a streamlined aerodynamic shape, not to absorb the impulse of the shell impacting armour plating.<br />
<br />
The penetration of BR-354 is greatly improved compared to BR-350B, and even exceeds the BR-354P APCR round at medium and long ranges. It is more than enough to deal with any light tank fielded by NATO and it is useful against the side armour of most medium tanks that the PT-76 can be expected to encounter in the 1950's, but it is not powerful enough to defeat the frontal armour of a WWII era Allied medium tank, let alone a post-war tank. In this regard, BR-354 is vastly inferior to the M339 APBC-T round (6.6 kg solid steel projectile at 975 m/s) fired from the high pressure 76mm of the M41 Walker Bulldog, which was enough for the frontal armour of the T-34-85 and some parts of the IS-2 at combat ranges. In comparison, BR-354 only increases the range at which the PT-76 can perforate the side armour of contemporary medium tanks at a flat angle - it does not change the tactical value of the PT-76 in any significant way.<br />
<br />
<br />
Muzzle Velocity: 655 m/s<br />
Battlesighting Range For Target Height of:<br />
2.0 m - 780 m<br />
2.7 m - 880 m<br />
3.0 m - 920 m<br />
<br />
Mass of Complete Cartridge: 9.12 kg<br />
Projectile Mass: 6.5 kg<br />
Mass of Explosive Filling: 0.032 kg<br />
Explosive Composition: A-IX-2<br />
<br />
<br />
Penetration:<br />
<br />
<table border="1">
<tbody>
<tr>
<td>At 0° inclination
</td>
<td>At 30° inclination
</td>
</tr>
<tr>
<td>500 m - 95mm<br />
1000 m - 80mm<br />
1500 m - 70mm<br />
2000 m - 60mm</td>
<td>500 m - 75mm<br />
1000 m - 65mm<br />
1500 m - 55mm<br />
2000 m - 45mm</td>
</tr>
</tbody></table>
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<div>
<span style="font-size: large;"><b>53-UBR-354P APCR</b></span><br />
<span style="font-size: large;"><b>53-</b><b>BR-354P</b></span></div>
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The UBR-354P round was the first Soviet "arrowhead" APCR round with a tungsten carbide core, developed on the basis of 45mm APCR rounds. It entered service in April 1943. The tungsten carbide core was carried inside a carbon steel body, onto which the copper driving band and tracer is fitted. A conical aluminium windshield is crimped on the circumference of the steel body to improve the aerodynamic performance of the projectile. However, the shape of the projectile was not entirely streamlined due to the exposed annular groove around the steel body, which gave the projectile a distinctive arrowhead shape.<br />
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The development of Soviet APCR ammunition began in 1942 based on captured German PzGr. 40 shells. The first examples were developed for the 45mm obr. 1932 and obr. 1937 anti-tank guns due to the ubiquity of these guns in the Red Army arsenal, and the engineers followed up with the design of the BR-350P shell in the fall of 1942 for 76mm field guns. Mass production of APCR rounds for all calibers including for the 76.2x385mm cartridge began in 1943. The original variant of the BR-354P round featured a rather small core held in a large steel body. The bulk of the projectile is steel, with the tungsten carbide core occupying only a small volume of the complete projectile assembly. Strangely, the core in this early BR-354P shell has a much lower elongation than the core of the 45mm BR-240P, which was apparently due to the difficulty in sintering the thicker cores of the BR-354P. The tungsten carbide core measures 72mm in length and weighs 0.48 kg.<br />
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Because of the greatly reduced mass of the projectile compared to other ammunition available for the D-56T, the muzzle velocity of BR-354P is much higher, although the less aerodynamic shape of the projectile generates an accelerated loss in velocity over long distances. Even so, the shell travels faster than the other anti-armour options for the PT-76, which limits the effect of crosswinds and produces a flatter ballistic trajectory, especially at short to medium distances where most tank combat is expected to occur. The reduced flight time also makes it easier to hit moving targets because the margin of error in leading the target is much more generous. Overall, scoring direct hits with BR-354P should be at least slightly easier when compared to other armour-piercing shells, so it may be useful in certain circumstances even when APHE and HEAT is available.<br />
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BR-354P was good enough to reliably defeat the armour of the light tanks operated by NATO forces, but its usefulness is generally quite limited against any combat vehicle with more armour than an M41 Walker Bulldog. The likelihood of a PT-76 knocking out the AMX-30 and Leopard 1 with this shell is low to nil from the front, but BR-354P has enough penetration power to deal with the side armour of most medium tanks. During the "Great Patriotic War", the official maximum effective range of BR-354P was only 500 meters, and the gunners of ZiS-3 field guns and SU-76 self-propelled guns were instructed to fire 500 meters or less. This was largely because of the high deceleration due to the arrowhead shape, gradually eroding its penetration advantage over ordinary AP shells. This did not change after the conclusion of the war, and the maximum effective range remained listed as 500 m.<br />
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Muzzle Velocity: 950 m/s<br />
Battlesighting Range For Target Height of:<br />
2.0 m - 940 m<br />
3.0 m - 1100 m<br />
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Cartridge Mass: 6.3 kg<br />
Projectile Mass: 3.02 kg<br />
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Core Diameter: 27.36mm</div><div>Core Length: 71.63mm<br />
Core Weight: 0.48 kg<br />
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Penetration:<br />
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<td>At 0° inclination</td><td>At 30° inclination</td><td>At 60° inclination</td>
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<td>100 m - 120mm<br />
300 m - 105mm<br />
500 m - 90mm<br />
1000 m - 60mm</td>
<td>100 m - 95mm<br />
300 m - 85mm<br />
500 m - 75mm<br />
1000 m - 50mm</td>
<td>500 m - 40mm (?)<br />
1000 m - 32mm (?)</td>
</tr>
</tbody></table>
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Due to its obsolescent design, the armour penetration power is markedly lower than it should be for a shell fired from a medium pressure gun like the D-56T. The biggest issue is the use of steel for the body of the projectile instead of aluminium, like contemporary American 76mm HVAP rounds. Upon impact, the soft steel body is stripped away from the core and mushrooms out on the surface of the armour plate while the core penetrates the plate on its own, as illustrated in the drawing below. The drawing is taken from the textbook "<i>Артиллерия</i>" (Artillery) published by the USSR Ministry of Defence, page 153. Since the steel body does not contribute to the penetration power of the shell, it is considered to be parasitic mass.<br />
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A type of 76mm APCR shell with a large tungsten carbide core existed, and in fact, there are several known BR-354P variants. The original small core design persisted until the end of the war in 1945, but it was supplemented by two newer variants. One of them is the design with a large core, which probably entered service after the war, and the other is an economical alternative using a bimetallic core composed of a tungsten carbide tip attached to a cylindrical steel slug, as shown in the drawings below. </div><div><br /></div><div>This variant was based on <a href="http://tankarchives.blogspot.my/2013/11/45-mm-apcr-part-2.html">feasibility studies in 1942</a> aimed at reducing the quantity of tungsten needed for the newly developed 45mm APCR shells, due to the limited supply of tungsten. The tungsten carbide tip on this variant of the BR-354P was slightly smaller than the original core, but the addition of the steel slug increases the total kinetic energy of the core due to its mass, so in effect, the rate of deceleration of the bimetallic core inside an armour plate during penetration is lower than the solitary small tungsten carbide core of the earlier design, so better armour penetration can be achieved. The steel slug also presumably contributes to the post-perforation effect by contributing some additional fragments. The objective of reducing the use of tungsten was achieved in the 45mm version albeit with a small reduction in penetration power.<br />
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<div><br /></div><div><br /></div><div>According to a metallurgical report by the Watertown Arsenal Laboratory, the steel slug (known as the "follow-thru plug") weighed 0.33 lbs, or 150 grams. It had a hardness of 385-675 BHN, presumably with the tip having the greatest hardness. The weight of the tungsten carbide core is 1.07 lbs, or 0.485 kg.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-kELXuqGKFb4/X7YaIk16f_I/AAAAAAAASH0/GQNqebKSLgQbgaPsnIm3guJ1q7oy99a9QCLcBGAsYHQ/s1345/metallurgical%2Breport.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="743" data-original-width="1345" height="354" src="https://1.bp.blogspot.com/-kELXuqGKFb4/X7YaIk16f_I/AAAAAAAASH0/GQNqebKSLgQbgaPsnIm3guJ1q7oy99a9QCLcBGAsYHQ/w640-h354/metallurgical%2Breport.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The tungsten carbide core measures 70mm in length while the steel slug is 32.54mm long. Overall, this bimetallic assembly measures weighs 0.635 kg.</div><br />
Scant information on the late BR-354P variant with the enlarged core is available. According to the ammunition design textbook "<i>Устройство и действие боеприпасов артиллерии</i>" published in 1968, the core has a length of 105mm, a diameter of 28mm, and weighs 0.68 kg. According to the table on the left, this round is listed part of the ammunition load of the PT-76B.</div><div><br />
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<br />Another variation of the BR-354P design features a double crimp to secure the ballistic cap to the steel body, but it is unclear how this variant relates to the differences in the core, if at all.<br />
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<h2>
<b style="font-size: x-large;">53-</b><span style="font-size: large;">UBR-354N</span></h2>
<h2>
<b style="font-size: x-large;">53-</b><span style="font-size: large;">BR-354N</span></h2>
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UBR-354N is a post-war APCR round used in the PT-76 as a replacement for the UBR-354P round. The main improvement over the "arrowhead" BR-354P was the greatly improved aerodynamic characteristics of the projectile. It was patterned after the newer 8.8cm PzGr. 40 round, used in the Pak 43 gun during the later half of the Great Patriotic War.</div><div><br /></div><div>Instead of a simple conical ballistic cap over the tip, BR-354N has an ogived aluminium ballistic cap and a cylindrical aluminium sleeve to streamline the steel body of the projectile. Internally, there are not many differences between it and the latest BR-354P variant with the large tungsten carbide core, except that BR-354N has an additional steel cap over its core, used for protection and to secure the core firmly to the steel carrier body. Penetration was improved thanks to a heavier, 0.825 kg tungsten carbide core. It measured 112mm in length and 28mm in diameter. The projectile was also heavier overall, weighing 3.3 kg.</div><div><br /></div><div>The design of the projectile shares much in common with the 85mm BR-367N, which should not be surprising given that both were developed as part of the same research program.<br />
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The maximum effective range is listed as 1,500 meters - a huge improvement over the BR-354P. At 1,500 meters, the penetration of BR-354N is the same as the penetration of BR-354P at 500 meters.<br />
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Muzzle Velocity: 950 m/s<br />
Point Blank Range For Target Height of:<br />
2.0 m - 1,050 m<br />
2.7 m - 1,200 m<br />
3.0 m - 1,250 m<br />
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Cartridge Mass: 6.0 kg<br />
Projectile Mass: 3.3 kg<br />
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Penetration:<br />
<table 1px="" border:="" cellpadding="1" dddddd="" solid=""><tbody>
<tr><td>At 0° inclination</td><td>At 30° inclination</td><td><br /></td></tr>
<tr><td>500 m - 125mm<br />
1000 m - 110mm<br />
1500 m - 90mm<br />
2000 m - 75mm</td><td>500 m - 100mm<br />
1000 m - 90mm<br />
1500 m - 75<br />
2000 m - 65</td></tr>
</tbody></table>
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<b style="font-size: x-large;">53-UBK-354, 53-UBK-354M (HEAT)</b><br />
<h3>
<b style="font-size: x-large;">53-</b><span style="font-size: large;">BK-354, BK-354M</span></h3>
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The UBK-354(M) round was introduced in 1955. In contrast to the outdated spin-stabilized UBP-354A HEAT round that entered service in mid-1942, the UBK-354 round had fin-stabilization, but its technology was not the most modern for its time. The shaped charge liner, for instance, has a flash tube extending from the apex of the cone to the base-detonating fuze like the BP-354A. The need for the flash tube came out of a lack of reliable piezoelectric PIBD fuzes like the M509A1 fuze used in the majority of Cold War-era American HEAT shells from the 76mm M496 to the 152mm M409, so the GPV-1 and GPV-2 spitback fuzes were used instead. The lack of a shaped charge liner apex changes the shape of the liner from an optimal conical shape to a sub-optimal truncated cone, and the presence of the flash tube creates a cylinder of empty air on the axis of the liner. This interferes with the propagation of the blast waves during detonation and has a negative influence on the formation of a precise high velocity shaped charge jet. The flash tubes in HEAT warheads with early spitback type fuzes were designed to funnel and direct the hot gasses from the explosive booster charge of a simple PD fuze into a second booster charge at the base of the warhead, which detonates the explosive charge of the warhead. The flash tube in BK-354 was designed for the same purpose, except that the GPV-1/2 fuze has a shaped charge booster instead of a simple explosive type. The shaped charge booster can be seen in the diagram below, labelled (29).<br />
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Upon impact, the piezeoelectric crystal labelled (4) experiences a powerful shockwave and converts the mechanical stresses into an electrical impulse. A potential difference of several kilovolts is produced, which is discharged at the electrodes in the spark gap of the spark detonator. This detonates an initial booster charge, which sets off the detonator cap through the walls of the steel cavity via the shockwave of the explosion. In turn, the detonator cap sets off the shaped charge booster, sending an explosively formed penetrator (EFP) down the flash tube and into the secondary booster charge. The impact of the EFP is enough to set off the secondary booster charge, and this finally detonates the explosive charge of the warhead. The shaped charge booster is more reliable than the old simple explosive booster, but still slower and less reliable than a purely electric piezoelectric PIBD fuze which skips the cascade of booster detonations in the fuze to directly detonate the secondary booster charge at the base of the warhead via a spark detonator. Since there is a lengthier period between fuze initiation and warhead detonation, the standoff distance between the shaped charge cone and the surface of the target at the moment of detonation will be reduced, potentially limiting the penetration power of the shell.<br />
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The GPV-2 fuze is also used in the 100mm BK-5 HEAT shell and there is evidence that it is effective at very high angles of impact, but besides the different fuze, the warhead in BK-354 does not feature any real improvements over the earlier BP-354A shell, so it appears that the improvement in armour penetration comes mainly from the fin stabilization scheme. The standoff distance is around 2.66 calibers (166mm).</div><div>
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<br />Information given in the munitions design textbook "Устройство и действие боеприпасов артиллерии" shows that the penetration of BK-354 is 209mm and the penetration of BK-354M is 280mm. Furthermore, it is stated in the article "<i>Shaped Charges Versus Armor - Part III</i>" by Joseph E. Backofen in the November-December 1980 issue of Armor magazine that the BK-354M round is capable of penetrating 280mm of RHA steel, coinciding with the information in the textbook. </div><div><br /></div><div>Based on the semi-empirical shaped charge penetration by Walters and Zukas, a standoff distance of 2.66 yields a penetration of 5.0 calibers or more when a precision-made copper shaped charge liner is used on 320 BHN armour steel. With a shaped charge liner diameter of 62.3mm, this implies that BK-354M should be able to penetrate 311mm of RHA steel or more. However, because the spitback mechanism in the GPV-2 fuze introduces an additional delay compared to more modern piezoelectric fuzing systems, the nose of the shell to experiences some deformation during an impact with a hard target causing the standoff distance to decrease slightly. Furthermore, the design of the shaped charge itself with its long spitback receptacle at the apex of the shaped charge liner is not optimal. As such, the penetration power achieved with BK-354M was less than 311mm RHA. </div><div>
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The greater mass and dimensions of the BK-354 projectile compared to earlier conventional AP shells necessitated a 20% reduction in the propellant charge mass from 1.08 kg to 0.9 kg, so the shell has a comparatively low muzzle velocity. Coupled with the added drag from the pop-out stabilizing fins, this generates a more pronounced ballistic arc and reduces the point blank range and the maximum effective range accordingly. As mentioned before, the TShK-66 sight for the PT-76 lacks a range scale for HEAT rounds, so the gunner must refer to a range table.<br />
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Muzzle Velocity: 550 m/s</div><div><br />
Point Blank Range For Target Height of:<br />
2.0 m - 630 m<br />
2.7 m - 730 m<br />
3.0 m - 760 m<br />
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Mass of Complete Cartridge: 9.54 kg<br />
Projectile Mass: 7.027 kg<br />
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Mass of Explosive Filling: 0.74 kg<br />
Explosive Composition: A-IX-1<br /><br />
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<div>
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It is interesting to compare the penetration of M496 HEAT fired by the 76mm M32 gun of the M41 Walker Bulldog to the BK-354M, as both rounds entered service in 1955. M496 has a copper shaped charge liner with a Comp. B explosive filler that is reportedly capable of penetrating 220mm of RHA steel. The performance advantage enjoyed by the Soviet design can be credited to a few factors, the main one being the difference in shaped charge caliber. The M496 shell was designed to be fired at high velocity from the M32 gun of the M41 Walker Bulldog, and as such, <a href="https://bulletpicker.com/images/clip1507.png">it had a heavy steel casing that was 10mm thick</a>. In contrast, the BK-354M shell was designed for a medium pressure cannon so it had a casing with a thickness of 6.35mm. Because of this disparity, the shaped charge liner in the BK-354M shell had a diameter of 62.3mm whereas the M496 had a shaped charge liner with a smaller diameter of 56mm.<br />
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Another advantage of the Soviet shell is that the detonation velocity of A-IX-1 is significantly higher than Comp. B - 8,450 m/s to 7,900 m/s. The detonation pressure of A-IX-1 is also higher - 30 GPa compared to 27 GPa - and the 0.5 kg of Comp. B in the M496 is much lighter than the 0.74 kg charge in the BK-354M.<br />
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Although the nominal penetration power is sufficient for most tank-type threats that the PT-76 may encounter in a European land war, BK-354 is not enough for American medium tanks like the M47 which filled the ranks of many NATO countries like West Germany, France, Belgium, and others. Technically, the 100mm of upper glacis armour on the M47 can be defeated by BK-354, but only for a perfect straight-on hit. Any amount of sideways angling of the hull would render it immune to the shell from the front, and even if the warhead managed to pierce the armour, the beyond-armour performance (spalling, residual cumulative jet particles, etc) will not be enough to do any meaningful damage to the internal equipment or to the crew. The turret of the M47 is nominally thinner, but the complex shape of the casting ensures that even if BK-354 can perforate the armour, the beyond-armour performance will be as weak as on the upper glacis plate. Nevertheless, the penetration power of BK-354 is reliable enough to deal with common tanks like the Centurion Mk. 3 from the front, and capable of inflicting serious damage to any medium or heavy tank from the side on a direct hit. With BK-354M, all medium tanks could be perforated from any practical angle of hit.</div><div>
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By virtue of its indifference toward impact velocity, shaped charges would not be affected by the low chamber pressure of the D-56T gun and the resultant low muzzle velocity, so it is easy to see why the amount of APCR ammunition carried in the PT-76 dropped sharply as soon as HEAT ammunition was available.<br />
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<h3>
<span style="font-size: large;">CO-AXIAL MACHINE GUN</span></h3>
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Like most other armoured vehicles of its time, the PT-76 is armed with an SGMT co-axial machine gun. The machine gun is fed with separate 250-round boxes, of which four are carried in the tank for a total of 1000 rounds of ammunition. The machine gun is fed by one box, and the other three boxes are stowed on an adjacent metal rack to facilitate quick replacement and reloading.<br />
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A thousand cartridges is not a large quantity, especially considering that the PT-76 is typically the only tank available to support Naval Infantry companies, and a large amount of ammunition will have to be expended to suppress and defeat enemy infantry, as mentioned earlier in the section on the D-56T. A thousand rounds is not significantly more than the ammunition load of a motorized infantry platoon, and it is also much less than the 3,500 rounds carried in a T-54. It is even less impressive considering that the only other mounted machine gun available to the common Naval Infantryman at the time was the SGMB or DShK machine gun on a BTR-60, which could carry 2,000 rounds for the for the former and 500 for the latter, supplemented with another 3,000 rounds for a pair of auxiliary SGMB machine guns for the passengers. Fortunately, the PT-76 is spacious enough that several more boxes of ammunition could be placed on the floor of the tank without affecting the work space of the crew, so if, for example, additional boxes were stowed to the right of the driver or in the small space in front of the engine compartment bulkhead, the loader could conceivably replenish his ready racks for the co-ax during a lull in the fighting without any real trouble. Nevertheless, the lack of proper storage racks close to the loader (the empty hull sponsons would be the perfect location) is perplexing given the large surplus of space inside the tank, and the need for improvisation is not an ideal solution.<br />
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<h3>
<span style="font-size: large;">PROTECTION</span></h3>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-ZP_ecvr9WGY/VgpHGAX-SpI/AAAAAAAAD2M/DWHSfqkzkSo/s1600/pt-76%2Barmour%2Btests.png" style="margin-left: auto; margin-right: auto; text-align: center;"><img border="0" height="392" src="https://3.bp.blogspot.com/-ZP_ecvr9WGY/VgpHGAX-SpI/AAAAAAAAD2M/DWHSfqkzkSo/s640/pt-76%2Barmour%2Btests.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Photo from the now-defunct <a href="http://web.archive.org/web/20130613121715/http://www.drostrup.com/Kampvogne.htm">drostrup website</a></td></tr>
</tbody></table>
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The turret and hull are constructed from welded <a href="http://masters.donntu.org/2008/mech/trifonov/library/s13.htm">2P grade high hardness, high strength armour steel plates</a> with thicknesses ranging from 6mm to 15mm. It is a manganese-molybdenum steel with a carbon content of 0.23-0.29%. 2P grade plates for this range of thicknesses have a tensile strength of 1450 MPa and a hardness of 388-495 BHN (average 450 BHN) for plate thicknesses of 8-14mm, representing the plates used in the PT-76. The direct foreign equivalent of this grade of steel is MIL-DTL-46100 high hardness armour steel for combat vehicles, but <a href="https://www.bisalloy.com.au/Products/BISALLOYProtection440steel.aspx#tabs-technical">Bisalloy 450</a> is also a good representation of 2P, since the physical properties of Bisalloy 450 are identical to 2P and it has itself <a href="https://www.researchgate.net/publication/292394134_BALLISTIC_TESTING_OF_AUSTRALIAN_BISALLOY_STEEL_FOR_ARMOR_APPLICATIONS">passed the MIL-DTL-46100 standard</a>. Since MIL-DTL-46100 is recognized by the U.S Army to be equivalent to the steel grade used on Soviet armoured personnel carriers and infantry fighting vehicles, we will be using the ballistic limit data on MIL-DTL-46100 for our assessment of the protection level offered by the PT-76. It is important to note that '2P' grade steel is considered HHA (High Hardness Armour) and not RHA, so a direct comparison between the penetration values of various bullets in RHA and the physical thickness of the armour of the PT-76 is superficial at best, and totally invalid at the worst. For the curious: the steel grade commonly termed "RHA" used as vehicle protection as well as for official proof and acceptance testing purposes is <a href="http://www.usa.arcelormittal.com/~/media/Files/A/Arcelormittal-USA-V2/what-we-do/steel-products/plate-products/Armor.pdf">classified as MIL-DTL-12560</a>. RHA is significantly weaker than HHA against steel cored armour piercing bullets due to lower strength and hardness. It also performs worse than HHA when set at a slope, as the lower hardness makes it less effective at deflecting bullets.</div><div>
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We will be examining the resistance of the armour against .30 caliber M2 AP (30-06 M2) and .50 caliber M2 AP only, as these were the most common types of machine gun ammunition at the time in the arsenals of the probable enemies of the USSR at the introduction of the PT-76. Technically speaking, 7.62x51mm M61 AP would be more common as it was a standardized NATO cartridge, but M61 AP has less penetration than M2 AP, especially on sloped plate, due to the very low elongation of its steel core, its excessively sharp ogived tip, and its low muzzle velocity compared to M2 AP. Case in point: the official penetration of M61 AP at 300 m is 7mm RHA, but the penetration of M2 AP at the same range is 10.3mm RHA. In this respect, the PT-76 is slightly over-armoured because NATO and many non-NATO nations standardized on the less powerful 7.62x51mm caliber during the early 50's. The FN FAL, for example, was the standard battle rifle for most NATO countries in the 50's, and beginning in 1957, the 7.62x51mm caliber began to replace 30-06 as the U.S Army transitioned from the M1 Garand to the M14 battle rifle.<br />
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The military specification documents use V50 to express the penetration in terms of bullet velocity, so to find the range corresponding to the bullet velocities given in the tables, we will have to refer to <a href="https://www.hornady.com/team-hornady/ballistic-calculators/#!/">a ballistic chart calculator</a> for the 30-06 (set ballistic coefficient: 0.451, velocity: 850 m/s, weight: 150 gr) and <a href="http://www.sniperforums.com/forum/cartridges-calibers/6836-14-5x114mm-russian.html">this chart</a> for the .50 cal M2 Ball, which is ballistically identical to M2 AP.<br />
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The original requirements for the armour of the prospective new amphibian were not very demanding, to put it mildly. The intention was to provide all-round protection from .30 caliber machine gun fire, and as such, the side hull armour was required to be only 8mm thick, the front of the turret had to be only 10mm thick, and the belly of the hull had to be 4mm thick for immunity against anti-personnel mines. The Object 740 prototype fulfilled all of these requirements in excess. It is important to note that the Obj. 740 was not the most heavily armoured of the prototypes created to be the new prospective amphibious light tank of the USSR, being surpassed in terms of frontal protection by the K-90 and the P-39 (Object 101). However, the K-90 had poorer all-around protection and the P-39 had a myriad of other issues, and both ultimately lost out to the Obj. 740. The armour profile of the PT-76 is well known and has been illustrated in a convenient format below:<br />
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The sharp vertical sloping of the frontal hull projections was an important aspect of the protection scheme of the tank due to the ricocheting of impacting projectiles combined with a phenomenon known as "shattergap", the latter being a reliable mechanism for projectile defeat. When the sharp-tipped steel core of an armour piercing bullet (M2 AP for .30 cal and .50 cal) impacts an oblique armour plate, the tip experiences an asymmetric force. The part contacting the armour plate encounters strong resistance by the tough and hard plate, but the opposite end of the tip is exposed to nothing but air, and because of this, the high stresses accumulating in the tip are released into the direction of least resistance, leading to the shattering of the tip of the bullet. The higher the obliquity of the armour plate, the more pronounced the effect. At very high angles, the entire bullet is liable to shatter and ricochet, leaving only surface damage on the plate.<br />
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<h3>
<span style="font-size: large;">HULL</span></h3>
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The upper glacis plate was 10mm thick and sloped at 80 degrees, making it essentially impenetrable to any machine gun bullet in service even today, because even a tungsten carbide (cermet) cored 14.5mm BS-41 bullet will ricochet and experience catastrophic destruction on impact with a high hardness steel plate at such an angle. There is no point in finding any references to see how much steel .50 cal M2 AP can penetrate at this angle - it is sure to glance off.<br />
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In order to reduce the weight of the tank, the thickness of the upper glacis plate was reduced from 10mm to 8mm in May 1962. This did not have any appreciable effect on its resistance to machine gun bullets, since the angle of the slope is so high that a ricochet is practically guaranteed even with the slightly thinner plate.<br />
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The lower glacis plate is thicker at 13mm, but less sloped at only 45 degrees. Finding references for ballistic testing on armour plates sloped at this specific angle is extremely difficult, but according to an article titled "Our Planes Can Take It" published in the <a href="https://books.google.com.my/books?id=3CEDAAAAMBAJ&printsec=frontcover#v=onepage&q&f=false">July 1944 issue of Popular Science</a>, a half-inch (12.7mm) plate of homogeneous or face-hardened steel set at 45 degrees can withstand a .50 caliber bullet at 50 yards. Keeping in mind that .50 cal M2 Ball can only penetrate 13mm of homogeneous armour at <i>0 degrees</i> at a distance of 200 m, and that it would definitely penetrate much, much less than that at 45 degrees even at 50 yards, it seems the article is referring to .50 cal M2 AP in this instance.<br />
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Whatever the case may be, a good rule of thumb is that steel cored bullets or cannon shells invariable penetrate less armour in LOS thickness at any angle more than 0 degrees. 13mm of armour sloped at 45 degrees produces a LOS thickness of 18.4mm, and the distance where .50 cal M2 AP penetrates an equivalent thickness of MIL-DTC-46100 rated steel is 200 yards, where a 15.8mm plate sloped at 30 degrees offers a LOS thickness of 18.4mm. It is safe to assume that a 13mm plate angled at 45 degrees is more resilient than a 15.8mm plate angled at 30 degrees, so the maximum distance where .50 cal M2 AP is able to penetrate the lower glacis of the PT-76 should be less than 180 meters (200 yards). If "Our Planes Can Take It" is to be believed, then the bullet will be deflected at a distance as little as 50 yards. A safer bet would be that the lower glacis is immune at 100 m and above, since the term "ballistic limit" implies that the bullet <b>will</b> penetrate at a certain velocity and the corresponding distance. Needless to say, the front of the hull is not a viable target for a .50 caliber machine gun at combat distances, and the chances of getting through are extremely slim even if the tank were one street block away from you (200-274 m), and that's for a head-on shot. If the tank were to be angled a few degrees to the side, defeating the lower glacis would become completely impossible.<br />
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In 1957, the hull was modified with an increased height at the turret ring to ensure that the gun could depress by -4 degrees when aiming behind the tank, over the engine deck. This was done by raising the hull by 60mm at the turret ring, so that the side profile of the tank gained a distinct rearward slope like an M4 Sherman. This had minimal secondary effects on the other characteristics of the tank.<br />
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In October 1962, the hull was raised again by 70mm to improve its buoyancy, and the angle of the lower glacis was increased from 45 degrees to 55 degrees. All PT-76 tanks built in the subsequent years followed the obr. 1962 design.<br />
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The upper side hull plate is 13mm thick, and the lower side hull plate is 10mm thick. The <a href="https://www.researchgate.net/publication/292394134_BALLISTIC_TESTING_OF_AUSTRALIAN_BISALLOY_STEEL_FOR_ARMOR_APPLICATIONS">ballistic limit of .30 cal M2 AP for a 10mm plate of Bisalloy steel with a hardness of 450 BHN at 0 degrees</a> is known to be 702 m/s (2303 ft/s), corresponding to a distance of just under 228 meters (250 yards). Being the weaker half of the side hull plates, this is not too bad, considering that a shooter would have to able to fire at a perfectly perpendicular angle to the side profile, which is not very likely. Even if the shooter is able to line up a shot at the perfect angle, the chances of hitting the exposed parts of the lower side hull are not too high, since half of the plate is concealed under the running gear of the tank as you can see in the photo below, so the chances of successfully damaging the tank from the side is reduced even further. The upper side hull plate is completely immune since .30 cal M2 AP can be stopped <a href="http://www.bulletproofme.com/Ballistic_Protection_Levels.shtml">by half an inch (12.7mm) of high hardness armour at a velocity of 869 m/s</a> - a velocity that is considerably higher than the muzzle velocity of the same bullet from an M1 rifle or an M1919 machine gun. Overall, this means that the side of the PT-76 is generally quite resilient against rifle fire. If the shooter is using a battle rifle or a machine gun loaded with M61 AP, the chances of defeating the side hull plating of the PT-76 are essentially nil.<br />
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If a .50 caliber M2 AP bullet impacts at a perpendicular angle to the lower side hull armour of the PT-76, the 10mm plate can be perforated at a maximum distance of 1200 meters. The upper side hull armour is slightly more resilient, but it can still be perforated at a distance of around 1000 meters. In spite of that, this does not necessarily mean that the tank can be destroyed at such distances with a single M2 Browning heavy machine gun in real combat conditions. The main issue is having the opportunity to fire at the side of a PT-76 at a perfectly flat angle and obtaining repeat hits using only iron sights at such a long distance. In reality, the side plating of the PT-76 can be immune to .50 cal M2 AP at distances as short as 600 meters if the bullet impacts at a 30 degree angle - short enough that a machine gun nest can be easily seen and destroyed by the tank.<br />
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In 1967, the armour scheme was changed again, albeit very slightly. The armour on the hull and turret remained absolutely identical to the 1962 model, but the angled lower plate at the stern of the hull was thickened from 6mm to 8mm. This modification probably helped to improve the protection of the transmission from artillery shell splinters, but the objective was to increase the rigidity of the stern of the hull. This modification had little effect on the legacy of the tank, as the mass production of the PT-76 in the Soviet Union ended in 1967.<br />
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<h3>
<span style="font-size: large;">TURRET</span></h3>
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The turret is made from two curved steel plates of different thicknesses - 15mm and 10mm - welded together to form the front and back walls respectively. The thicker 15mm front plate covers around 3/5 of the circumference of the turret, and the other 2/5 is covered by the thinner back plate. The roof is a single flat plate with a thickness of 6mm. The greater thickness of the armour plate of the turret compared to the front hull armour plating is ostensibly counteracted by the reduced vertical slope compared to the front hull armour, but the curvature of the round turret creates horizontal sloping that must be taken into account as well.<br />
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The V50 ballistic limit for .50 cal M2 AP and 14.5mm B-32 for a MIL-DTL-46100 plate identical to the grade of armour plate used on the PT-76 can be obtained from <a href="http://www.titussteel.com/wp-content/uploads/2011/02/46100E_spec.pdf">this specifications document</a>.<br />
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According to the document, the ballistic limit for .50 cal M2 AP for a 15mm plate (0.59 inches) at 30 degrees is 815.3 m/s (2675 ft/s), which corresponds to a distance of between 250 to 300 yards, or around 250 meters. Since the slope of the armour plating on the turret is slightly more than 30 degrees, we can lower the distance of the ballistic limit to approximately 200 m. Note that the term 'minimum ballistic limit' in the document is defined as the minimum thickness of the plate where a projectile will penetrate it with a probability of 50% at a given velocity, so the estimated ballistic limit of 200 m for the armour plate of the turret could be considered the maximum distance where .50 cal M2 AP will penetrate. However, that does not mean that the turret can be penetrated at 200 meters, because the armour plate on the turret is not only sloped in the vertical plane, but curved in the horizontal plane as well, since the turret is round. The distance at which the turret is completely immune should therefore be below 200 m in realistic conditions.<br />
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The ballistic limit for 14.5m B-32 for the same plate at the same angle is much lower than for the .50 cal round - only 717 m/s (2353 ft/s). According to the firing table for 14.5mm M-44 ball, this corresponds to a distance of between 960-1000 meters (1050-1100 yards), or around 980 meters. Using the same logic as before, this implies that the turret can only guarantee complete immunity from 14.5mm B-32 at a distance of somewhere below 980 meters. This essentially means that the turret can be pierced with a KPV machine gun at the same distances where a man operating a tripod-mounted KPV machine gun can be expected to reliably hit a tank-sized target with iron sights. However, unless the enemy somehow captures and fields 14.5mm weapons en masse, this is hardly a concern for the crew of a PT-76.<br />
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The back of the turret is only protected by 10mm of steel angled at 35 degrees, but this is more than enough to reliably withstand .30 caliber M2 AP rounds at any range. The specified thickness of 10mm (0.393 inches) does not even appear on the table of ballistic limits for .30 cal M2 AP, meaning that the bullet would have to travel at velocities greatly exceeding muzzle velocity to have a chance of penetrating a 10mm plate angled at 30 degrees. Defeating a curved plate angled at 35 degrees would be completely impossible.<br />
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Overall, the PT-76 offers an equivalent or higher level of ballistic resistance compared to a typical armoured personnel carrier, but is considerably lacking in protection compared to a contemporary light tank. Compared side by side to the British FV432 and American M113 tracked armoured personnel carriers, the PT-76 has slightly more protection on all aspects and has much better sloped frontal armour, but the tank has much less armour than an M41 Walker Bulldog. From the perspective of a NATO military, the armour of the PT-76 may be considered deficient as it cannot withstand 14.5mm KPVT fire, but for the Red Army, this makes no difference as the most powerful machine gun available to the enemy is much less potent. Therefore, the PT-76 can be considered immune to heavy machine gun fire from the front, and highly resistant to small caliber rifle fire from the sides. Despite being vulnerable to heavy machine gun fire from the sides, it was never reported to be an issue during the many combat outings of the PT-76. There are no records (that the author was able to find) of any PT-76 ever being knocked out or even damaged by rifle or machine gun fire during the Vietnam war. In fact, it appears that machine gun fire was generally ineffective against the PT-76 and the BTR-50 (which has the same armour scheme as the PT-76) according to personal testimonies from American veterans:<br />
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One of the testimonies comes from these excerpts of <a href="http://www.modernforces.com/veteran_paulk_longgrear.htm">an interview with retired Colonel Paul Longgrear on the infamous Battle of Lang Vei</a>, which took place between February 6-7, 1968. The battle involved a massed NVA attack with sixteen PT-76 tanks.<br />
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<i>Jim Hruska: Why were there so few MGs on the perimeter fire line? Didn’t the camps of the day use Browning A6s for defense?</i><br />
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<i>Col Paul Longgrear (Ret): There was a 50 cal that did engage the tanks (no known damage). I had four 60’s [author's note: M60 machine guns] that killed the crap out of NVA infantry</i><br />
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Several PT-76 tanks were lost to HEAT shells from a single 106mm recoilless rifle during the assault.<br />
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<i>Jim Hruska: The two 106 RRs had 20 HE rounds per gun. If they were there to counter enemy armor then why did they not have HEAT rounds?</i><br />
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<i>Col Paul Longgrear (Ret):The two 106’s were not there to counter enemy armor. Someone sent 100 LAWs to us (just in case) the tanks attacked. There was some speculation that, if there are tanks, they would be used as indirect fire support. Terrain around LV was not conducive to tank running. The 1st 2 or 3 tanks were KIA by 106 – HEAT. The 2nd 106 was not manned during the battle.</i><br />
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As a light tank, the PT-76 can hardly be expected to survive direct hits by large caliber HEAT shells, and neither could any tank from the era, for that matter, so the crux of the issue is whether they were used in such a way so as to minimize the chance of getting hit while maximizing their own potential. This was not the case.<br />
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<i>Jim Hruska: Looking back as a man that commanded a US rifle company in combat and a senior planner do you think that a US rifle company would have blunted the armor thrust? What about a US Army line infantry battalion?</i><br />
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<i>Col Paul Longgrear (Ret): The 16 Russian PT-76s were poorly used and improperly deployed. We could have destroyed them all with two 106’s with HEAT rounds or Molotov cocktails. Any US Rifle Company with prior intel and planning could have destroyed the tanks. There is an aspect I’m not sure if for this question. My Yards did not run and kept the infantry from protecting the tanks. I have questions that US Infantry guys would have done the same. </i><br />
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Even if the armour of the tank was sufficient against gunfire, it was not thick enough to be effective at resisting high explosive shells. For example, take the two PT-76 tanks and single BTR-50 APC destroyed during the failed NVA night assault on a U.S special forces camp at Ben Het on the 3rd of March 1969. There can be no doubt that the attack was extremely daring, since the NVA attack force rushed across an open valley to a camp defended by three entrenched M48 Pattons, relying only on the cover of darkness to approach close enough so that they would not be taken out at long range by the Pattons which were sitting at elevated positions (West Hill) overlooking the valley. However, the location of the attacking vehicles was uncovered when one of the vehicles accidentally ran over an anti-personnel mine. The excerpt below comes from an article describing the attack, and it mentions that the Pattons fired high explosive rounds at the approaching enemy vehicles. A full account of the event is given here (<a href="https://www.facebook.com/UnlikelyWarriors/posts/549524831811877">link</a>).<br />
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"<i>As darkness settled over the camp, the defenders were on high alert, awaiting what they assumed would be a full-force NVA attack by units of unknown size and capabilities. At 2100 hours, the camp began receiving recoilless-rifle fire, followed by heavy mortar and artillery fire. Over the roar of the artillery, the tank crews began to hear the familiar sound of engines, and this time it was coupled with the distinctive rumbling of tracked vehicles. Stovall was scanning the area with a night-vision scope and infrared searchlights when an enemy vehicle was suddenly illuminated. It had detonated an anti-personnel minefield located about 800 meters from the camp’s perimeter, and some portion of the vehicle had caught fire. In the light thrown out by the blaze, three NVA tanks and an armored personnel carrier were visible. The lumbering vehicles were approaching the coils of concertina wire surrounding the camps perimeter and the U.S. tank crews opened fire with high-explosive rounds..</i>"<br />
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The two photos below show one of the two destroyed PT-76 tanks from the battle. This one was clearly hit from the side by one of the aforementioned 90mm HE shells fired by the defending Patton tanks. The shell likely entered from the right and exploded inside the engine compartment, demolishing the roof from the inside. Here's <a href="http://www.war-stories.com/images/it-tastes-like-soap-jay-gearhart-6.jpg">another photo</a> of the same tank, either before or after it was loaded onto the flatbed truck that we see in the photo on the left.<br />
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<a href="https://3.bp.blogspot.com/-H1PaG5Ra0u4/WmjYABxAE9I/AAAAAAAAKl4/Brm80RpYx0ct-ZUsP8rwVgf-G-9VkTJ0QCLcBGAs/s1600/destroyed%2Bpt-76.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="921" data-original-width="1335" height="275" src="https://3.bp.blogspot.com/-H1PaG5Ra0u4/WmjYABxAE9I/AAAAAAAAKl4/Brm80RpYx0ct-ZUsP8rwVgf-G-9VkTJ0QCLcBGAs/s400/destroyed%2Bpt-76.jpg" width="400" /></a><a href="https://2.bp.blogspot.com/-Oi0DeKtC-uU/Wnm76ljnKUI/AAAAAAAAKuM/W6fAAQU-iOMaNcz0jzw6-Fbg2Fv0yk4wACLcBGAs/s1600/ben%2Bhet%2Bpt76.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="624" data-original-width="882" height="282" src="https://2.bp.blogspot.com/-Oi0DeKtC-uU/Wnm76ljnKUI/AAAAAAAAKuM/W6fAAQU-iOMaNcz0jzw6-Fbg2Fv0yk4wACLcBGAs/s400/ben%2Bhet%2Bpt76.jpg" width="400" /></a></div>
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The second PT-76 destroyed in the battle is shown in the two photos below. Almost everything inside the tank is blackened by fire, but the lack of debris inside the hulk itself shows that most of the internal equipment didn't burn down from an inferno, but was blasted away from the tank by an ammunition explosion or something to that effect.<br />
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The condition of the second tank is clearly much worse off compared to the first one even though both tanks were knocked out by the same weapons, but there is a very good explanation for this:<br />
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"<i>The exchange of fire continued briefly, but enemy fire gradually subsided. The NVA vehicles were withdrawing; the expected ground assault was not going to take place. U.S. tanks fired several more HE rounds into one of the enemy hulks, reducing it to a pile of rubble, just as B Company’s 2nd Platoon arrived in relief.</i>"<br />
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Having mentioned anti-personnel mines, it should be noted that the extremely thin hull belly plating of the PT-76 is more than enough for any anti-personnel mine, but not nearly enough for any anti-tank mine. If a PT-76 were to detonate a typical 8-10 kg anti-tank land mine like an <a href="https://fas.org/man/dod-101/sys/land/atm.htm">M15</a> under its tracks, a large part of the belly would be completely obliterated and the tank would probably be flipped over by the blast. Smaller anti-tank mines designed for breaking tracks would be more than capable of puncturing the belly even if they are detonated under the tracks and not directly underneath the tank.<br />
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Besides the threat of mines, it would not be difficult to inflict serious damage on the suspension of the tank with the shell splinters of a 105mm artillery shell detonating close by. 155mm artillery would be particularly lethal as the penetration power of shell splinters produced by a typical 155mm high explosive shell should be enough to perforate the rear armour from 100 meters and the side armour from more than 60 meters (based on STANAG 4569 specifications). Close detonations of 152/155mm artillery shells are known to be powerful enough to completely demolish tank suspensions and knock out external devices, and the PT-76 would be highly vulnerable to such attacks. Airbursting 155mm shells are the most dangerous threat, as the thin roof armour would be easily penetrated by the shell splinters from typical detonation altitudes even at a high obliquity.<br />
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<span style="font-size: large;"><br />SMOKE SCREEN</span></h3>
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The earliest variants of the PT-76 were equipped with two BDSh-5 smoke bombs. The BDSh-5 was developed in 1944 for the T-34-85 and armoured fighting vehicles derived from the T-34. It continued to be used in a number of Soviet tanks until it was withdrawn from service in the 1950's due to the advent of self-generated smoke using the TDA smokescreen system. The PT-76 used the BDSh-5 until 1957 when it received the TDA smokescreen system, whereupon the metal brackets originally intended for the smoke bombs were repurposed for fuel drums.<br />
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The BDSh-5 measures 0.45 meters in diameter and 0.65 meters in length. Under conditions of minimal wind, a single BDSh bomb produces enough white smoke to cover an area of 40,000 square meters, or a square of 200 meters in width and length. The bomb burns and produces smoke for five to seven minutes. The obturating smoke only blocks light in the 400-750 nm wavelength range - the entire spectrum of visible light, encroaching on near infrared. This narrow range of obscured wavelengths is effective at shielding the tank from the naked eye and from white light searchlights, but it is completely ineffective against infrared searchlights like the AN/VSS-1 and AN/VSS-3A, which operate in the 785-1000 nm range. Needless to say, the fog is also completely ineffective at counteracting thermal imaging devices like the AN/VSG-2 Tank Thermal Sight (TTS) installed in the M60A3 (TTS), which <a href="https://patents.justia.com/patent/5369276">operates in</a> the <a href="https://www.forecastinternational.com/archive/disp_old_pdf.cfm?ARC_ID=927">7,600-11,750 nm range</a>.<br />
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Smoke pours out of the circular opening on the surface of the cylindrical housing. The bomb is weighted so that the opening is always facing upwards even when floating in water, ensuring that a dependable flow of smoke is emitted. The ability to float makes BDSh-5 useful when advancing across rivers, as it enables the lead tank to create a smokescreen on a large section of the river to mask the crossing of the landing party as well as the massed forces waiting on the riverbank. After the BDSh-5 has been expended after five to seven minutes, the advance force of PT-76 tanks should be on the other side of the river, and the task of masking the construction of a pontoon bridge or some other type of bridge would be taken over by a specialized smoke generator.<br />
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The PT-76 had a TDA smoke generating system installed since 1955. TDA stands for "Thermal Smoke Apparatus". A smokescreen is created by injecting diesel fuel into a special section of the exhaust manifold. The hot metal of the exhaust manifold evaporates the diesel instantly, turning it into a fine vapour. The smoke generated from the exhaust is actually a fog, as it is formed by the condensation of the hot diesel vapours as it comes into contact with the cool surrounding air. The fog only obturates light in the 400-760 nm wavelength range, so again, it is not effective at blocking infrared imaging devices. Nevertheless, it is useful for covering retreats as well as advances, and it is particularly useful for masking the advance of tank units across rivers. The TDA smokescreen generator is activated by the driver via a control box.<br />
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<span style="font-size: large;">NBC PROTECTION</span></h3>
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When all of the hatches are closed, the only source of air in the fighting compartment comes from the ventilation fan embedded in the back of the turret. The dome-shaped ventilator is located at the very rear of the turret, giving the gunner and loader choice airflow.<br />
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The fan is protected by a frying pan-shaped armoured cover of the same thickness as the armour plating of the rear of the turret. This ventilator provided no protection from NBC contamination whatsoever.<br />
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The PT-76 lacked protection from nuclear, biological and chemical attacks, but this situation was alleviated in the PT-76B. The PT-76B featured a nuclear protection system, referred to as "PAZ", which literally translates to "Anti-Nuclear Protection" (Противоатомная Защита).<br />
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The ventilator fan at the back of the turret was replaced with a new type, but unlike most other tanks in the Red Army at the time, it was not directly replaced with a ventilation system that was capable of creating an overpressure inside the fighting compartment, like the T-54 which had its original ventilator removed entirely. The new ventilator had an automatic self-sealing mechanism to prevent radioactive dust from entering via the air inlet. Other than that, it only had a simple electrical fan. As you can see in the photo below, the appearance of the new ventilator from inside the tank is clearly different from the older type. Credit for the photo goes to <a href="http://www.maquetland.com/article-phototheque/4288-pt-76-interieur-details">Claude Balmefrezol from Maquetland.com</a>.</div>
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Externally, the new ventilator can be distinguished from the older type by the rounded dome-shaped armoured cover, the widened collar around the armoured cover and the presence of three bolts jutting out of the surface of the cover.<br />
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A cross section of the automatic sealing mechanism is shown in the diagram below.<br />
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A supercharger was installed in the hull, next to the driver. It had its own air inlet and filtration system, separate from the engine air intake and the ventilator air inlet. When it is activated, an overpressure is produced inside the tank, preventing the ingress of irradiated particles as well as chemical and biological threats. Air enters through a circular inlet with a mesh screen, and the cyclone filter inside the supercharger ejects dust and other contaminants through an small slit next to the inlet.<br />
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<a href="https://2.bp.blogspot.com/-rm28c5ZmmyE/WpE-QBuGVxI/AAAAAAAAK-w/LY4eBnm5QyAMm-0-sruaFN2vHUY-5YJegCLcBGAs/s1600/pt-76b%2Bair%2Bintake.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://2.bp.blogspot.com/-rm28c5ZmmyE/WpE-QBuGVxI/AAAAAAAAK-w/LY4eBnm5QyAMm-0-sruaFN2vHUY-5YJegCLcBGAs/s320/pt-76b%2Bair%2Bintake.jpg" width="320" /></a><a href="https://3.bp.blogspot.com/-5pCUzwzxfT4/WpFpR6llSBI/AAAAAAAALAA/gzEXEzeD53cVzetjhCijVLUrALmdEZSIwCLcBGAs/s1600/paz%2Bsupercharger.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="567" data-original-width="1187" height="190" src="https://3.bp.blogspot.com/-5pCUzwzxfT4/WpFpR6llSBI/AAAAAAAALAA/gzEXEzeD53cVzetjhCijVLUrALmdEZSIwCLcBGAs/s400/paz%2Bsupercharger.png" width="400" /></a></div>
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However, the system does not offer comprehensive NBC protection as it lacks the sensors needed to detect the presence of chemical and biological agents in the atmosphere, so the crew is not automatically alerted of a threat, even if the system is technically capable of repelling such attacks. The only case where self-protection from such threats is plausible is when a PT-76 company or platoon commander is alerted of a threat by spotting the contamination flags dropped by preceding NBC reconnaissance units, typically mounted on the BRDM-1RKh or the BTR-40RKh (shown below). Then, he would be able to command his company or platoon to manually engage their defences.<br />
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The overpressure system protects the crew from nuclear fallout and biological and chemical contamination, but there is no real protection from radiation. On its own, the steel body of the tank is more than enough to stop ionizing radiation (alpha, beta rays) and reduce gamma radiation transmission from fallout by some amount, but gamma radiation and neutrons from the initial radiation burst of a nuclear explosion can easily pass through the thin steel walls. No anti-radiation lining was installed on the PT-76 during its time in service. In order to sense a nuclear detonation and detect the presence of nuclear fallout, a DP-3B gamma radiation detector (roentgenometer) was installed on the left wall of the driver's station. The DP-3 radiation detector was a very common device for Soviet vehicles of the era, from helicopters to tanks to NBC reconnaissance vehicles like the BRDM-1RKh. The DP-3B is the tank version. The unit comprises an analogue control box and readout display, complete with an ion chamber (mounted on the lower glacis of the tank next to the left idler wheel). The use of an ion chamber instead of a Geiger-Muller tube means that the device is rather less sensitive, hence the need to place the ion chamber in an unusually low position in the hull - to detect radiation from the soil. The range of measurement of DP-3B is from 0.1-500 roentgens/hour.<br />
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The system depends on the penetration of gamma radiation into the tank to detect the detonation of a nuclear device before the blast wave reaches the tank, so that the system is able to activate the countermeasures before the irradiated wind arrives.<br />
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<h3>
<span style="font-size: large;">FIREFIGHTING</span></h3>
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<a href="https://1.bp.blogspot.com/-is2ytnzXokE/WnlNzKcH6sI/AAAAAAAAKts/zbuxeDeV7YYk-Em6fVD28YjEQRnI0gP7wCLcBGAs/s1600/firefighting%2Bpt-76b.png" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" data-original-height="948" data-original-width="1580" height="384" src="https://1.bp.blogspot.com/-is2ytnzXokE/WnlNzKcH6sI/AAAAAAAAKts/zbuxeDeV7YYk-Em6fVD28YjEQRnI0gP7wCLcBGAs/s640/firefighting%2Bpt-76b.png" width="640" /></a><br />
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The "Rosa" fire fighting system was installed in the PT-76B obr. 1959 model is a relatively sophisticated system borrowed directly from the T-55. It has a maximum response time of 50 milliseconds upon detection of a fire. The system can operate in the semi-automatic or the automatic mode, as determined by the driver. When operating in the semi-automatic mode, "Rosa" alerts the driver with an audio signal and a flashing light at the instant that a fire is detected in the engine compartment. The driver has the option to ignore the alert, of course, but he is obligated to immediately discharge the fire extinguishers. The driver can manually activate the fire extinguishers wired to the automatic firefighting system from a red control panel to his right. There is also an additional two OU-2 manually operated carbon dioxide fire extinguishers stowed next to the driver's left foot. These two fire extinguishers will be the only means of eliminating a fire in the fighting compartment. In the 'automatic' mode, "Rosa" alerts the driver of the source of the fire upon detection and immediately closes the radiator louvers, shuts off the engine and cuts off the engine air intake system. Then, the fire extinguishers are activated and the entire compartment is flooded with the extinguishing agent. Two cylinders of fire extinguishing agent are connected to the system, providing a maximum of two doses of fire extinguishing agent to flood the engine compartment and hopefully extinguish the flame.</div>
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"Rosa" employs a halocarbon fire extinguishing agent known under the designation "3.5": a pressurized combination of ethyl bromide and carbon dioxide. The mixture is very effective, but also highly poisonous and carcinogenic, limiting its use to the engine compartment. The system relies on four TD-1 heat sensors to detect a local rise in temperature to at least 180°C, after which the system will react. The four TD-1 heat sensors are arranged so that a fire from any part of the engine compartment will be detected by at least one of the sensors. The covered areas include the fuel tank and oil container in the right sponson, the gearbox and final drives at very back, the oil cooler on the deck, and the engine itself.<br />
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The TD-1 heat sensor uses an array of fifteen thermocouples wired in series to detect changes in ambient temperature. The reaction time of the sensor does not exceed 10 seconds, meaning that it takes a maximum of 10 seconds between detecting the fire to the activation of the fire extinguishing system. The sensors do not guarantee reliable detection of fires in the 60°C to 150°C range of temperature differences due to insufficient contrast, so the fire needs to be close to the sensor. Still, this is much better than the earlier bimetallic sensors employed in early firefighting systems developed during and immediately after WWII.<br />
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A TD-1 thermal sensor is shown below.<br />
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<a href="http://4.bp.blogspot.com/-fFSQLBlxpIM/VlCiUm35SYI/AAAAAAAAEQ0/8uBeX99CmuM/s1600/td-1%2Bfire%2Bsensor.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="282" src="https://4.bp.blogspot.com/-fFSQLBlxpIM/VlCiUm35SYI/AAAAAAAAEQ0/8uBeX99CmuM/s320/td-1%2Bfire%2Bsensor.jpg" width="320" /></a></div>
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The control box for the system is mounted to the "roof" of the driver's station, which is the upper glacis plate. An emergency switch to shut off the engine is placed on the roof next to the driver's GPK-48/59 gyrocompass.<br />
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<a href="https://www.blogger.com/null" id="mobility"></a>
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<h3>
<span style="font-size: large;">MOBILITY</span></h3>
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<a href="https://3.bp.blogspot.com/-X4758hmwCsk/WmM0E5JQ0xI/AAAAAAAAKig/a9MM6yjW9bcehUkoETYCkZbKmkUTMYV1wCEwYBhgL/s1600/pt-76.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="551" data-original-width="1062" height="332" src="https://3.bp.blogspot.com/-X4758hmwCsk/WmM0E5JQ0xI/AAAAAAAAKig/a9MM6yjW9bcehUkoETYCkZbKmkUTMYV1wCEwYBhgL/s640/pt-76.jpg" width="640" /></a></div>
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Unlike most light tanks, the PT-76 is not particularly quick or nimble. Its primary attraction is its ability to swim. Its mobility characteristics are comparable to the T-54 medium tank for the most part, but its low speed was found to be problematic for a tank that is usually tasked for reconnaissance duties. By the late 1950's, it had become clear that the PT-76 was no longer sufficient for the various roles that it was assigned, partly due to its insufficient weaponry, but mostly due to its low speed compared to the T-55, which had been recently upgraded with a more powerful engine. The need for an upgrade was recognized in just a few short years after the adoption of the PT-76 was formalized in 1952, catalyzing the development of various replacements in the late 50's and early 60's, none of which succeeded in replacing the PT-76 for a variety of reasons. As such, the PT-76 fulfilled its service in the Russian army with the original engine.<br />
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The PT-76 is powered by the V-6 diesel engine, putting out 240 hp at 1800 RPM. The name of the engine can be confusing as it is not a V-shaped six-cylinder engine, but actually an inline-six 19.1 liter engine with six vertical cylinders arranged in a row. The V-6 was created by halving the legendary V-2 engine, so there is a great deal of parts interchangeability between the two engines, and the manufacturing of the V-6 was greatly simplified. Like the V-2, the piston diameter in the V-6 is 150mm, with a stroke of 180mm. The creation of the V-6 came from the need for a relatively simple engine for light vehicles with good dynamic characteristics. The decision to create an inline six-cylinder engine was justified by the inherently good balance of this type of engine, making it exceptionally smooth at the operating rev speeds of 1600-1800 rpm, although some vibration can still occur at the idle speed of 500 rpm. The power density of the engine is not particularly high, given that its dry weight is 825 kg and its maximum output is only 179 kW, but it is good enough for an engine of its technological level. Compared to something like the 14.7-liter six-cylinder <a href="http://www.corvair.org/chapters/lvcc/lvcc_newsletters/lvcc_2012_01_fifth_wheel_redacted.pdf">Continental AOS-895-3</a> supercharged gasoline boxer engine, the V-6 is rather large and underpowered. The V-6 has a service life of 250 hours. The engine can be started electrically or with compressed air supplied by two compressed air tanks placed on the left side of the driver's station. In October 1964, the updated V-6B engine for the PT-76B began to be manufactured in mass quantities and was implemented in new production PT-76B tanks in November. The main differences were in the lubrication system, main friction clutch and in the new 6.5 kW G-6.5S generator, replacing the 1.5 kW G-73 generator. The substantially more powerful generator was needed for supplying power to the new two-plane stabilizer system and other electrical equipment.<br />
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The external appearance of the V-6 is depicted in the drawings below. The drawing on the left shows the fuel pump, oil pump, electrical tachometer, the air distribution system for the six cylinders (for pneumatic starting in cold weather), and other assorted essentials. The drawing on the right gives us a good view of the ST-721 electric starter interfacing with the teeth of the flywheel. Behind it is the G-73 direct current generator that supplies electrical power to the tank and charges the lead-acid accumulators.<br />
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<a href="https://2.bp.blogspot.com/-3U6kIQRryXU/Wormgo_EjMI/AAAAAAAAK7o/lwX-jiS2zxku2jOO4DKwW9t5hUOgwRa-wCLcBGAs/s1600/v-6.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="383" data-original-width="417" height="366" src="https://2.bp.blogspot.com/-3U6kIQRryXU/Wormgo_EjMI/AAAAAAAAK7o/lwX-jiS2zxku2jOO4DKwW9t5hUOgwRa-wCLcBGAs/s400/v-6.jpg" width="400" /></a><a href="https://2.bp.blogspot.com/-OwmOReXhHPs/WormtK6aQ-I/AAAAAAAAK7s/OykH1tzP7nw1wV4TTZPnPUReQTxj7mGbACLcBGAs/s1600/v-6.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="368" data-original-width="400" height="367" src="https://2.bp.blogspot.com/-OwmOReXhHPs/WormtK6aQ-I/AAAAAAAAK7s/OykH1tzP7nw1wV4TTZPnPUReQTxj7mGbACLcBGAs/s400/v-6.gif" width="400" /></a></div>
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The gross output of the V-6(B) is 240 hp, but the net output is only around 190 hp. Taking into account the light weight of the new light tank, it was decided that a simple clutch-and-brake steering system would suffice. During the development of the PT-76, it was suggested that the tank should use the transmission and steering system of the T-34, as that was readily available and very simple to manufacture as the tooling still existed. Early prototypes of the Object 740 had this transmission installed, but it was found to be unsuitable in the long term, partially because the design of the transmission was fundamentally obsolete and partially because the tank needed a more complex transmission to transfer power to its waterjets, its mechanical bilge pump and the tracks at the same time. For this purpose, a completely new transmission with a clutch-and-brake steering system was developed for the PT-76.<br />
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The gearbox sits at the back of the engine compartment on the same axis as the engine. It receives power from the engine driveshaft and distributes it through the two friction clutches attached on either side of the gearbox. The side friction clutches connect to a pair of reduction gearboxes on either side, meant for transferring power to the tank's dual waterjets and bilge pumps, but the reduction gearboxes do not interact with the driveshafts until the driver engages it in preparation for swimming, so the driveshafts effectively transfer power directly to the final drives. Shifting the gears is done with a system of mechanical rods.</div>
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A kinematic diagram of the powertrain is available below. Note the power takeoff mechanism from the final drives to the waterjet impeller. When operating the PT-76 in water, the driver steers with the steering levers as usual, and he controls the speed of the tank with the accelerator pedal and by shifting gears.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://4.bp.blogspot.com/-6_XRwSytbFE/Wk_oLITyYEI/AAAAAAAAKWw/ZlXSVkha_BkPt4NB4MZF3y2mmPhfdHwLACLcBGAs/s1600/pt-76%2Btransmission.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="404" data-original-width="640" height="403" src="https://4.bp.blogspot.com/-6_XRwSytbFE/Wk_oLITyYEI/AAAAAAAAKWw/ZlXSVkha_BkPt4NB4MZF3y2mmPhfdHwLACLcBGAs/s640/pt-76%2Btransmission.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">1 - Engine; 2 - Flywheel and main friction clutch; 3 - Drive shaft-gearbox coupling; 4 - Gear box; 5 - Side friction clutches; 6 - Reduction gearbox; 7 - Final drives; 8 - Cardan shafts; 9 - Drives for waterjet impeller; 10 - Impellers; 11 - Drive sprocket; 12 - Drives to bilge pumps</td></tr>
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Removing the transmission first requires that the gearbox is disconnected from the driveshaft and the reducer gearboxes. This is quite time consuming, but not more inconvenient than in any other Soviet tank. The water jet ducts do not interfere with the removal of the gearbox, which can be done with a common engine hoist. Although removing the engine and transmission is relatively straightforward, the lack of a direct coupling between the transmission and the engine to create a single powerpack and the lack of a quick-disconnect between the components can be considered somewhat anachronistic, even if this was the standard configuration for the majority of Soviet armoured vehicles throughout the Cold War. The large engine deck and large access panels makes it easy to service and remove the engine and transmission compared to the M24 Chaffee and the AMX-13 series of light tanks, but it is inferior to the M41 Walker Bulldog by a large margin.<br />
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The radiator is on the engine deck, to the left of the engine and next to the exhaust port. The oil cooler radiator pack is placed on top of the water radiator pack. The maximum permissible temperature of the water is 105°C and 110°C for the oil, beyond which the engine overheats. The lack of a supercharger or turbocharger on the V-6 and the large volume of the engine compartment means that the workload of the cooling system is not very high.<br />
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The cooling system does not use a fan to draw air through the radiator to remove heat, but instead uses a novel pressure differential system. According to Bernoulli's principle, fluids such as air have a lower pressure when flowing at higher velocity compared to fluids flowing at lower velocity. The difference in pressure creates a suction force, which is used in the cooling system of the PT-76 to draw cool air from above the radiator through the cooling tubes of the radiator pack and into the exhaust duct, where it is ejected out of the exhaust port. This cools the water and oil in the radiator and the exhaust gasses at the same time, making it a highly reliable compact system with literally no moving parts. The system was also a part of the engine air respiration system. Similar cooling systems were used in the T-10 heavy tank and T-64 main battle tank and contributed to the compactness of their engine compartments, which allowed significant reductions in the mass of the tanks. The drawback of this type of cooling system is the limited cooling capacity - a problem that has plagued the T-64 since it entered service in 1968 until the present day. In fact, one of the most frequent complaints of T-64 during the Ukrainian civil war (on both sides) is that it overheats too quickly and too often. This is probably not a problem for the PT-76 as it uses a naturally aspirated engine, but it is difficult to be certain since there are practically no PT-76 tanks in service at the moment and it is an enormous challenge trying to find enough people who previously served in one to form a complete picture of the real state of affairs.<br />
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The tank runs on six large diameter (670mm) hollow stamped metal roadwheels with rubber rims. There is a hydraulic shock absorber paired with a volute spring on the first and sixth roadwheels to improve the ride quality over rough terrain. As was typical for post-war Soviet tanks, the wheels were sprung with torsion bars. The first models of the Object 740 prototype used high hardness steel for its torsion bars, but these were found to be unsuitable for the low weight of the tank as they vibrated very strongly when the tank traveled across rough terrain, so softer steel was used as a replacement.<br />
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The roadwheels of earlier variants of the PT-76 were stamped from plain sheet steel and had a smooth surface (see photo above), but later on, a new roadwheel design with stamped radial reinforcement ribs was introduced as the new standard type for newly produced tanks and slowly replaced the older roadwheels over the next few decades as they wore out on older tanks. The roadwheels deserve special attention as they were the first of its type and led to the development of similar hollow wheels for a variety of vehicles used for a variety of purposes. Being hollow and very lightweight, the wheels had positive buoyancy and contributed to the flotation of the tank.<br />
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The all-metal tracks are of a single pin type, with a width of 360mm and pitch of 128mm. There are 96 links on each side. Like most other tracked vehicles produced in the USSR at the time, the tracks on the PT-76 are of an unsupported type.<br />
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The PT-76 has superb flotation on soft ground, allowing it to be driven where most other tanks could not. Compared to its American rival the M41 Walker Bulldog, the PT-76 exerted around 36% less static ground pressure - 0.46 kg/sq.cm against 0.72 kg/sq.cm. This is helpful when travelling on soft snow and muddy terrain, but does not entirely solve the problem of low engine power and it does not take into account the differences in traction from the different track designs. Also, it may be more difficult to maneuver in waterlogged soil and swamps due to the clutch-and-brake steering system. Without regenerative steering, power is lost whenever the driver adjusts the direction of the tank or makes a turn. This may be negligible on paved roads, but can result in the loss of traction when driving on pliant terrain.<br />
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Due to the simple technology and straightforward layout of the powertrain (thanks in no small part to the large volume of the engine compartment), regular maintenance is relatively painless. The only inconvenience is the bolted access panels on the engine deck, which are very large, but have to be completely unbolted to be opened and the panels lack hinges, so they must be lifted off the engine deck and placed somewhere else while maintenance is ongoing. There are four handles on <a href="http://data3.primeportal.net/apc/dave_connolly/russian_pt-76/images/russian_pt-76_37_of_65.jpg">the corners of the engine access panel</a> and <a href="http://data3.primeportal.net/apc/dave_connolly/russian_pt-76/images/russian_pt-76_58_of_65.jpg">two handles the transmission access panel</a> for this purpose.<br />
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<h3>
<span style="font-size: large;">DRIVER-MECHANIC'S STATION</span></h3>
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To the driver's immediate front is the instrument panel and his three periscopes. On his right, there is little of interest except for the two accumulators that are used in the tank's electrical system. The driver is provided with a single dome light, which is located beside the hatch opening mechanism and the firefighting system control box.<br />
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The driver's controls can be seen in the photos below. As you can see, the pedals and steering levers are not installed on the floor of the hull, but on the lower glacis plate. The driver's seat is placed on the floor of the hull, and positioned such that the driver's legs are raised above hip level when he rests his feet on the pedals. This is very apparent from the photo on the right.<br />
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Reading the gauges on the instrument panel is not easy, but the driver can see out of the periscopes with relative ease without needing to lean forward too much. When the angle of the lower glacis plate was changed from 45 degrees to 55 degrees in 1962, the position of the driver's foot controls relative to the height of the seat was lowered accordingly, so that the driver's feet would be at around hip level when resting on the pedals. This would definitely have been more comfortable than before.<br />
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In 1958, a GPK-48 gyrocompass was installed for basic inertial navigation. This was quickly replaced with a GPK-59 gyrocompass on the PT-76B in 1959. Combined with a map, the gyrocompass gave the tank a reliable method of navigation between waypoints.<br />
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There is a circular escape hatch installed in the floor of the hull, to the left of the driver's seat. It is around the same size as the driver's hatch, meaning that it is unusually large compared to the escape hatches on typical Soviet medium and heavy tanks as well as foreign tanks. This was probably influenced by the much more lenient requirements for the belly protection of the PT-76.<br />
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<h3>
<span style="font-size: large;">WATER OBSTACLES</span></h3>
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Exceptional waterborne mobility was the PT-76's defining feature. While
other light tanks were similarly equipped with high-powered guns, many of them much more powerful than the D-56T, the
PT-76 was the only tank of its type that was completely amphibious. It was also the first vehicle of its kind to use water jets for waterborne propulsion, rather than screw propellers.<br />
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The PT-76's amphibious nature made it irreplaceable when conducting ship-to-shore landings, and gave unique opportunities to conduct tactical maneuvers across large rivers.<br />
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Executed properly with air support, artillery barrages and quick hands, the presence of PT-76 tanks in a tank division can help reduce the loss of strategic momentum from water obstacles, and even offers an extra layer of tactical opportunities.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-LqExrR-lkNA/VgpIQs-tq-I/AAAAAAAAD2U/ZeVzdpYRL1Q/s1600/pt-76b%2Briver%2Bassault.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="354" src="https://4.bp.blogspot.com/-LqExrR-lkNA/VgpIQs-tq-I/AAAAAAAAD2U/ZeVzdpYRL1Q/s640/pt-76b%2Briver%2Bassault.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">PT-76B tanks staging a massed river assault</td></tr>
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Two water inlets are located on the underside of the engine compartment behind the second-last roadwheel on either side of the hull. Water passes through an intake screen designed to prevent large debris from entering the waterjet and damaging the pump. The pump inside the waterjet duct has an impeller driven by the engine, which pulls water in and throws it out of the rear ports. The impeller blades have a diameter of 340mm. Stator hydrofoils are placed behind the impeller to eliminate the rotational momentum, and the waterjet duct narrows into a choke near the outlets. This creates a steady jet of high velocity water with an efficient linear flow, as opposed to a disturbed flow that dissipates quickly after leaving the outlet. As mentioned before, steering is accomplished by pulling either the left or right steering levers which shuts the cover on the outlet on the same side as the lever and cuts power to the pump, causing the vehicle to pivot from the thrust of the single remaining waterjet. It is possible to reverse the tank in the water by shifting to the reverse gear, which closes off both covers without cutting power to the two water pumps and simultaneously opening the two forward-facing outlets, thereby directing the flow of water through the forwards-facing outlets only.<br />
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The waterjets are each powered by the engine via a driveshaft from a special reducer gear attached to the gearbox. During tests with the Object 728 special emulation vehicle, the waterjets of the PT-76 were found to produce a traction force of 82 kgf in the first gear, 900 kgf in the second gear and 1650 kgf in the third gear. The driveshaft and reducer gearbox are shown in the two photos below (credit to Stephen Tegner from the <a href="https://www.scalenews.de/pt-76b-objekt-740b-walkaround-394/">scalenews.de</a> walkaround page).<br />
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The opening and closing of the trim vane is carried out by an electric motor but a manual hand crank is also available.<br />
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One of the primary considerations in the design of the shape of the hull was that it needed to be stable during every stage in the process of crossing water obstacles. The tank had to remain stable as it entered the water, whether it be from a riverbank or from the bow ramp of an assault landing ship, and then it needed to resist pitching and rolling by strong currents and waves while swimming. The hull also had to be sturdy and stable enough that the recoil of the cannon could be completely absorbed by the water through the walls of the hull, as the recoil force could not be transferred to the suspension since it was not touching solid ground. This was largely determined by the amount of surplus buoyancy provided by the design of the hull.<br />
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One of the design considerations was that the buoyancy distribution of the hull had to be shifted slightly rearward so that the thrust from the waterjets would not tip the tank nose-down into the water. This is why the PT-76 appears tail-heavy when afloat.<br />
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The large internal volume of the vehicle meant that it had a lot of surplus buoyancy, but it came with the cost of thin armour and a large silhouette. The tank could probably have been made much smaller and it would still be able to float and swim safely, as proven by the more heavily armoured BMP-1 and BMP-2, but the requirement for such a large amount of surplus buoyancy was not arbitrary. It gave the PT-76 a serious seafaring capability as well as the ability to carry some cargo. Even when fully loaded for combat, the tank has a 26% surplus buoyancy, equal to 3.6 cubic meters of displaced water, or 3.6 tons. As a result, the PT-76 is extremely difficult to sink even when travelling through choppy waters, or when it is laden with a large amount of extra cargo, up to 1.8 tons or more. Because of this, the PT-76 is often used to ferry troops across rivers when an amphibious armoured personnel carrier is not available, or if pontoon bridges have not yet been established.<br />
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One of the requirements drawn up by the Ministry of Transport Engineering was that the new amphibious light tank needed to be able to temporarily transport a landing force of 20 men across water obstacles, while the armoured personnel carrier variant based on the amphibious light tank had to be able to transport 25 men across water obstacles as well as on marches. The objective was to ensure that an infantry regiment could be landed on the opposite bank of a river with tank support and a full complement of heavy weapons, thereby improving the chances of successfully defending and holding the riverbank until the main force can cross. Infantry could also be ferried in this manner during ship-to-shore landings, but this was rarely practiced. The photo below shows three PT-76 tanks belonging to the Naval Infantry, each transporting six "black berets" - Soviet Marines.<br />
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Of course, the infantrymen would be extremely vulnerable to machine gun fire, artillery bombardment or air attack, so this method of transportation is only practical under relatively safe conditions. If possible, the PT-76 would be landed directly onto shore on a landing ship like the Ropucha-class LST or landing hovercrafts like the Aist-class hovercraft. As good of a swimmer as it is, the PT-76 is still rather slow in the water, making them easy targets for shore artillery and anti-tank missiles. Shore bombardment from the landing craft can only do so much to suppress enemy defences<br />
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<h3>
<span style="font-size: large;">FUEL ENDURANCE</span></h3>
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The PT-76 has two internal fuel tanks clustered on the right side of the engine compartment. The fuel is split between a large tank holding 150 liters and a smaller tank in the hull sponson holding 100 liters, for a sum total of 250 liters. This afforded the PT-76 a cruising range of 370-400 km on paved roads, or about half that off-road. The PT-76B featured a third internal fuel tank (shown in the drawing below) that could hold 140 liters of fuel, increasing the total fuel capacity to 390 liters, granting the PT-76B a cruising range of 480 km on paved roads.<br />
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This was superior to what most foreign designs of the same role could achieve. For instance, the M41 Walker Bulldog with its high performance 500 hp gasoline engine had a cruising range of only 120 km on roads (corroborated by a Belgian ex-tanker who served on one between 1967 and 1969), but on off-road expeditions, that range could be cut down to only 40 kilometers or so, equivalent to just a few hours of idling and little actual driving. This was important for the PT-76 tanks in Naval Infantry tank battalions, as they was obligated to establish hold a beachhead during amphibious landings with limited logistical support, but it was even more important for the PT-76 tanks in reconnaissance companies, as they had to be inserted ahead of the main landing force and move some distance inland to conduct surveillance. The long travelling range was also crucial for the tanks used in the reconnaissance battalion of tank and motorized rifle divisions as they not only had to march ahead of the tank or motorized rifle regiment, but also patrol far forward of the vanguard in order to carry out their reconnaissance duties.<br />
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To grant the PT-76 an even greater range of travel, additional fuel drums were added during various modernization efforts throughout the latter half of the 50's. Early on, external fuel drums borrowed from the T-34 were mounted on brackets on the engine deck of the PT-76. These fuel drums each have a capacity of 90 liters, and thus increased the total fuel capacity of the PT-76 to 430 liters, boosting the cruising range of the tank to 480-510 km. Later, the flat rectangular external fuel tanks mounted on the fenders of the T-54 were transplanted over to the PT-76 and the PT-76B. These fuel tanks each have a capacity of 95 liters, and increased the total fuel capacity of the PT-76B to 580 liters, increasing the cruising range to 590 km. The advantage of these flat tanks was not the additional 5 liters of fuel, but the flatness that allowed the gun to traverse more easily to face the rear.<br />
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On the water, the PT-76 and PT-76B have a fuel endurance of 100 km and 120 km respectively, although the tank would never have the chance to actually travel such distances in real situations.<br />
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Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com20tag:blogger.com,1999:blog-3103574899092646031.post-39425647575412362112017-12-08T01:45:00.934-08:002024-01-20T08:03:14.779-08:00T-72: Part 2<br />
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Due to the length constraints imposed by Blogger, the original T-72 article was split into two parts. This part covers the second half of the article. You can view the <a href="https://thesovietarmourblog.blogspot.com/2015/05/t-72-soviet-progeny.html">first half here</a>.
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<h3>
TABLE OF CONTENTS, PART 2</h3>
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<ol>
<li><a href="#prot">Protection</a></li>
<li><a href="#commonchar">Common Characteristics</a></li>
<li><a href="#weak">Weakened Zones</a></li>
<li><a href="#weight">Weight Growth</a></li>
<li><a href="#criteria">Protection Criteria</a></li>
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<li><a href="#obj172">Object 172 Series (172M, 172M1, 172M-1)</a></li>
<li><a href="#8010520">80-105-20 Armour</a></li>
<li><a href="#6010550">60-105-50 Armour</a></li>
<li><a href="#applique">Appliqué Armour</a></li>
<li><a href="#steelturret">Monolithic Steel Turret</a></li>
<li><a href="#kvartzturret">"Kvartz" Turret</a></li>
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<li><a href="#obj184">Object 184 Series</a></li>
<li><a href="#reflection1">60-15-15-15-50 Armour</a></li>
<li><a href="#upgradedreflection1">60-10-10-20-20-50 Armour</a></li>
<li><a href="#rpturret">"Reflecting Plate" Turret</a></li>
<li><a href="#nera">Background on NERA</a></li>
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<li><a href="#gill">Gill Armour</a></li>
<li><a href="#skirts">Steel-reinforced Rubber Side Skirts</a></li>
<li><a href="#kontakt1">Kontakt-1</a></li>
<li>Kontakt-5</li>
<li><a href="#relikt">"Relikt" Side Skirts</a></li>
<li><a href="#4s22">4S22 Blocks</a></li>
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<li><a href="#smoke">Smoke Screen</a></li>
<li><a href="#nbc">NBC Protection</a></li>
<li><a href="#fire">Firefighting</a></li>
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<li><a href="#mobility">Mobility</a></li>
<li><a href="#engines">Engines</a></li>
<li><a href="#cool">Cooling System</a></li>
<li><a href="#trans">Transmission</a></li>
<li><a href="#susp">Suspension</a></li>
<li><a href="#water">Water Obstacles</a></li>
<li><a href="#fuel_tanks">Fuel Tanks</a></li>
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<a href="https://www.blogger.com/null" id="prot"></a>
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<h3>
<span style="font-size: large;">PROTECTION</span></h3>
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A good indication of a tank's true survivability is its resistance to catastrophic destruction, which can refer to the tendency for a fire to
start and the likelihood of that fire spreading and consuming the entire vehicle or the possibility of the ammunition exploding or the death of too many crew members for the tank to continue fighting. The reasoning is that the resistance of a tank to a catastrophic kill (K-kill) is quite distinct from the resistance of a tank to a mobility kill (M-kill) or firepower kill (F-kill). All tracked tanks are equally vulnerable (more or less) to the loss of its tracks from enemy anti-tank fire, and all tanks are generally equally vulnerable (more or less) to the loss of their weapons or their sighting systems from enemy fire. The main difference lies in the ability of a tank to withstand direct hits on its armour and its ability to minimize the damage inflicted on the inhabitants of the tank as well as the internal equipment in case the armour fails. In this sense, the T-72 stands on equal footing with many of its contemporaries and surpasses some of its rivals due to a combination of sturdy armour, a rational internal layout, shock damping mounts for internal equipment and the inclusion of an anti-radiation liner that also behaves as a spall liner. However, many modern tanks now include separated ammunition storage, which is something the T-72 lacks and has proven to be an issue in certain circumstances.<br />
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Regardless, the protection level of the T-72 was remarkably high for its time as a result of its combination of thick armour and low silhouette and the low placement of ammunition in the hull reduced the chances of the ammunition suffering a direct hit. The main drawback of the location of the ammunition is that any fuel or hydraulic fluid leakage will inevitably pool on the floor of the hull and if an internal fire is started, it will reach the ammunition eventually. The best practice is for the commander to give the order to bail out and then press the master switch for the fire extinguisher system, thus greatly reducing the chances of an ammunition explosion from occurring before all crew members escape.<br />
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The location of the batteries in the front of the tank as opposed to the engine compartment reduces the chances of the tank losing its electrical power if the engine compartment was hit. This gives the T-72 a better chance of surviving an internal fire as the fire extinguishing system will still have electrical power, and the smoke grenade launching system can still be used to obscure the tank from further attack. If the batteries at the front of the tank were hit by a frontal armour perforation, the tank may not necessarily lose electrical power as the generator in the engine compartment is still intact. The only problem is that the engine cannot be started electrically after it is turned off without a battery replacement, but it is still possible to start the engine with compressed air. The compressed air cylinders are refilled by an engine-driven compressor, so the tank can remain fully autonomous indefinitely without batteries if necessary, as long as it has fuel. This high level of redundancy contributes to a high level of survivability as the tank can still continue to fight after sustaining serious damage.<br />
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Besides a disinclination to internal fires, the survivability of the tank was enhanced by its low profile. Even though it was certainly not the shortest of all Cold War era main battle tanks, it was still an impressively diminutive target. The original T-72 had a height of 2.19 meters (measured up to the turret roof) and the T-72A was the same. The T-72B had a marginally taller turret along with slightly more ground clearance, combining to slightly increase the height of the tank to 2.23 meters. Overall, the tank is shorter than the T-62 and T-54/55 that preceded it, and compared to tanks like the M60A1, the T-72 can only be described as a dwarf.<br />
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Although the tanks produced in the Soviet Union are most famous for emphasizing low size and weight, the reality is that all nations were actively pursuing such reductions and the Leopard 2 and M1 Abrams were examples of West Germany and the U.S making great strides towards this objective. Even so, the T-72 was still slightly shorter than the M1 Abrams and Leopard 2 which had a height of 2.39 meters and 2.48 meters respectively (measured up to the turret roof). In terms of height and overall profile size, it is beaten only by the Strv 103 which also had the upper hand in terms of overall length. By comparison, the Strv 103 had a height of only 1.9 meters when the suspension is in the travelling condition, and having a "bullpup" configuration gave the Strv 103 a uniquely short overall vehicle length without compromising gun barrel length such that its ability to maneuver through dense forests could be better than other tanks. The difference in size can be seen in the drawing below, and the drawing below it comparing the Strv 103 with the M60A1 gives a reference point. Both drawings are taken from "<i>Kampfpanzer: Die Entwicklungen der Nachkriegszeit</i>" by Rolf Hilmes.<br />
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The three film stills below show drawings that superimpose the T-72 on comparable NATO tanks to illustrate the difference in the size. The scale appears to be slightly exaggerated in favour of the T-72 in these drawings; the height of the M60A1 seems to be warped as the turret is depicted is too tall and the commander's cupola is too short. Despite this, these drawings are accurate enough to gain a general impression of the difference in size. These film stills were taken from archival footage from a Czechoslovakian Army training film. <a href="https://www.youtube.com/watch?v=EqYupAqiVro">Original video from the VHU channel</a>.<br />
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However, even though the Strv 103 is shorter than the T-72, the casemate hull is still significantly wider, especially at the top part due to the large sponsons over the tracks. Overall, the area of the frontal silhouette of the Strv 103 including the tracks is 4.25 sq.m whereas the area of the frontal silhouette of the T-72 is only 4.0 sq.m, which also happens to be half of the frontal silhouette of the M60A3 (8.0 sq.m). As such, despite being slightly taller than the Strv 103, the T-72 manages to still present a comparatively smaller frontal projection if both tanks are travelling over open ground. Needless to say, this is not a trivial achievement.<br />
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In a hull-down position where the height of the turret matters more than the tank's full silhouette, the small turret of the T-72 also has an advantage. With a maximum height of just 750mm when measured from the hull roof to the highest point of the turret roof, the T-72 turret is slightly taller than a T-62 turret (720mm) but shorter than a T-54 turret (810mm). The difference between foreign tank turrets is even more noticeable: the Centurion Mk.10 turret had a height of 956mm, the Chieftain turret had a height of 975mm, and the M60A1 turret had a height of 970mm. A large amount of effort was spent to reduce turret heights in the West, resulting in the turret of the M1 Abrams (and all variants thereof) having a height of 900mm. On page 2409 of the "<i>Department of Defense Authorization for Appropriations for Fiscal Year 1983</i>", it is asserted that the projected area of the M1 Abrams turret is equal to the M60A1, but has a lower profile. From the side, the projected area of the M1 turret is stated to be approximately 6% smaller than the M60A1 turret. The M1 turret could have been shorter, but there was a need to have a sufficiently large internal height to accommodate a human loader and some of this height had already been sacrificed because of the short hull with a reclined driver's seat. Together, the combination of a lower turret and hull gave the M1 a smaller overall projected area compared to the M60A1. The Leopard 2 had a conventional driver's seat and a taller hull, so the turrets of all models of the Leopard 2 (excluding the latest models with additional roof armour) could afford to have a reduced height of 830mm, less than the Abrams. The reduction in turret height was a objective worth achieving even if the projected area is not reduced.</div><div>
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Additionally, the difference in the area of the silhouette of the T-72 does not merely manifest from a frontal view, but also when the turret is turned to one side. When the turret is turned to the side such as shown in the drawing below, the area of the silhouette of the turned turret (dark grey) is the same as the area of the silhouette of the turret when it is facing straight forward (light grey). On the other hand, the area of the silhouette of the turret of an M1 Abrams when it is turned (dark grey) is significantly larger than when the turret is facing straight forward (light grey). The same principle is true for turreted tanks with long bustles like the M60A1 and the Leopard 2. Drawing taken from "<i>Kampfpanzer: Die Entwicklungen der Nachkriegszeit</i>" by Rolf Hilmes.<br />
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The increase in the area of the silhouette of the turret has the effect of increasing the chance of receiving a hit on the turret. Additionally, this advantage is non-trivial in a defensive scenario where both tanks are hull-down, dug-in and concealed. The longer turret of an M1 Abrams or Leopard 2 will appear larger to an observer when it is turned away from his direct line of sight, thus making it easier to see. This also has the side effect of causing the movement of the turret to become more obvious, as the change in silhouette size during the rotation of the turret will be more likely to invite the attention of watchful eyes. The lack of any change in the silhouette of a T-72 turret as it rotates renders it harder to notice. Of course, these advantages may be nullified under certain circumstances, such as those facing Iraqi tankers during the first Gulf War. Many T-72M and T-72M1 tanks were dug-in and hull-down, but were easy to see due to the featureless terrain of the desert, especially from the sky. Furthermore, the dug-in tanks baked for hours directly under the hot sun, making them glow brightly in the thermal imaging sights of Coalition tanks and infantry fighting vehicles. These problems are not present in a hypothetical European battlefield due to the abundance of foliage and shade.<br />
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The use of a long turret bustle is not inherently bad, of course. Like any other technical solution, it has its own set of merits and demerits. The merits include better turret balance (because the long bustle behaves as a counterweight to the heavy gun and armour at the front of the turret), and quicker loading speed for both manually loaded tanks and tanks with autoloaders if ammunition is stowed in the bustle. This is confirmed by ergonomics studies on manual loading and by autoloader optimization studies done in the USSR. Of course, the downside to having ammunition stowed in the bustle is that the turret is statistically more likely to be hit so that ammunition stowed inside is also more likely to be hit if the turret armour is defeated, and this is quite an important consideration to make. When the turret of a tank with a long bustle is turned to the side, it becomes possible to hit the bustle from the front. For tanks without compartmentalized ammunition and blowout panels like the M60A1, the thin side armour makes it comparatively easy to perforate the bustle armour compared to the frontal armour, thus making it possible for even obsolete anti-tank weapons to defeat the tank from the frontal arc. This is mostly avoided in the M1 Abrams, but not entirely.<br />
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Offensively, the smaller overall size of the tank made it more difficult to hit when it was on the move in open terrain. Defensively, the low turret made it hard to detect and even harder to hit, and the armour protection of the turret could also be enhanced if the tank is on a reverse slope. The roof of the turret is angled at around 78-80 degrees, so when the tank is on a gentle reverse slope and the gun is laid at the maximum depression angle of -6 degrees, the angle of the turret roof becomes 84-86 degrees (critical ricochet angle for virtually all long rod APFSDS) and the projected area commander's cupola is partly hidden behind the turret cheek armour, thus minimizing the weakened zones of the turret and making the tough frontal protection of the turret even tougher.<br />
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The superior target-finding capabilities of the hypothetical enemy granted by the widespread adoption of thermal imaging technology would also be negated if the tank were hull down, as the hot engine and running gear would be concealed below ground level while the turret may not be hot enough to offer sufficient thermal contrast, especially if it were covered in camouflaging elements like special netting and foliage cloaks or even field expedient solutions like branches. The main factor that gives the surfaces of tank armour a different thermal signature from the surrounding environment is the heating of the steel by solar radiation at a different rate than soil and vegetation, so by covering these surfaces with netting and branches, it is possible to strongly reduce or even eliminate the thermal signature of the tank. On a typical T-72 from the 1980's, a few parts of the tank such as the steel-reinforced rubber side skirts, the plastic gun mask cover, and the anti-radiation cladding on the turret are thermal insulators by design, particularly the anti-radiation cladding as it is designed to resist the heat flash from a nuclear blast. These external components reduce the thermal signature of the tank and may expedite the camouflaging process.<br />
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To summarize, the T-72 was not just a capable offensive tool but also quite formidable when used defensively. The only drawback was the slow reverse speed which prevents the tank from quickly withdrawing from a compromised position and performing an effective tactical retreat. However, the slow reverse speed would not have been an issue when firing from a hull defilade behind a reverse slope or a berm as it is quick enough for the tank to rapidly return to a turret defilade. This is mainly due to the low height of the turret, which means that a lower reverse speed is sufficient to completely hide the turret within the same time period as a tank with a taller turret and a quicker reverse speed.<br />
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Of course, it is not possible to remain completely unseen indefinitely. The formidable armour of the tank is the most obvious major factor in reducing the casualty rate of its crew and ensuring the success of a combat mission, but the criteria for knocking out a tank does not only depend on defeating its armour. In fact, it is not only possible to disable a tank without perforating its armour plating, but also quite common. One of the easiest ways to do so would be to simply de-track the tank, but the tank can still fight albeit from a compromised position. Another effective method of eliminating the combat capability of a tank would be to destroy its observation devices. In that case, the most important objective would be the destruction of the gunner's sights which would prevent the tank from using its weapons.<br />
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The location of the gunner's sight aperture depends on the individual tank, but generally speaking, tanks with a telescopic gun sight have the sight aperture in the gun mantlet or near it, making them vulnerable to damage. For a tank like the T-54, the sight aperture is located in a slit cut into the turret armour next to the gun barrel, directly at the center of mass of the tank where most shots are expected to land. Furthermore, a hit from a solid armour-piercing shot on the well-sloped upper glacis may produce enough secondary fragmentation to damage the sights indirectly, and the detonation of an explosive shell on the upper glacis is quite likely to do so owing to the large amount of fragmentation expected. Tanks with a periscopic gun sight usually have the gun sight aperture located on the turret roof or some other part of the turret above the frontal armour facings. The T-72 belongs in this category as the aperture of its primary sight and night vision sight are both located on the turret roof, making it less likely to be damaged by explosive shells impacting the front of the turret or the upper glacis.<br />
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The T-72 has proven its worth in various conflicts when placed under competent command, but the lack of media coverage on the successes does not help its case. Even though many tanks have been destroyed, often irrecoverably, many more have survived such that the tank's ability to endure severe punishment simply cannot be considered low. To list one <a href="http://42.tut.by/434659">incident</a> in Grozny, in the year 2000, a T-72B with the tail number 611 took 3 hits from Fagot anti-tank missiles and 6 hits from RPGs during 3 days of intense fighting and remained in battle with only minor damage. Most of the hits landed on the sides of the tank, with one rocket impacting the lower rear of the hull. Other cases involving older models such as the T-72A more often ended on a sadder note, but in general, it took several hits from anti-tank grenades and missiles to reduce the combat capacity of a T-72 and at least half a dozen hits on the weakened zones (sides, rear) are usually required for the ammunition to detonate or a fire to start in the tank.<br />
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More examples come from a <a href="http://www.btvt.narod.ru/2/tanks_in_grozny.htm">World of Weapons magazine article (March 2005 issue)</a> on tank action in Grozny containing details on multiple T-72As lost in combat. The 131 Separate Motor Rifle Brigade (OMSBR) tasked with capturing the Grozny rail station sustained many casualties during combat, losing a total of 157 men, 22 tanks, 45 infantry fighting vehicles, 37 cars and all 6 of the Tunguska anti-aircraft systems operated by the air defence division attached to the brigade. While providing supporting fire, the tanks belonging to the brigade received multiple anti-tank grenades from every direction in return for each shot fired. One T-72A with the tail number 533 sustained four or five RPG grenade impacts on the engine compartment, and the tank caught fire. It eventually exploded, long after the crew escaped. Another T-72A, with the tail number 537, withstood six or seven hits from RPG grenades before suffering an ammunition explosion, killing its entire crew instantly. A third T-72A, with the tail number 531, sustained four hits from RPGs before its turret drive failed, and the tank was finally knocked out of action after an APFSDS round fired from 100 meters impacted the turret on the commander's side. A fire was started, but fortunately, the gunner (left hand side of the turret) was only heavily concussed because the bulky breech assembly of the cannon saved him from the spall and fragments entering the turret on the commander's side (right hand side of the turret). Both the gunner and driver were able to escape the tank before it eventually succumbed to the fire and exploded 20 minutes later. None of these tanks had reactive armour installed.<br />
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In another example, a T-72B1 from the 276 Motor Rifle Brigade with the tail number 221 was penetrated twice in combat during the battle for the Grozny hospital in January 16, 1995. After repairs, it was damaged again on January 21, 1995 during combat near the building of the Council of Ministers where it was hit with five RPG grenades. Four of the hits were located on the sides of the hull, one of them on right side, on the fourth roadwheel, and the other three on the left side. The fifth hit was located on the turret, above the gun barrel. The autoloader was damaged by the turret strike, but the tank survived and was sent for an overhaul.<br />
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More interesting examples can be found in the article "<i><a href="http://otvaga2004.ru/tanki/v-boyah/tanki-t72-v-vojnax/">Танки Т-72 В Войнах И Локальных Конфликта</a></i>" (<i>T-72 Tank in Wars and Local Conflicts</i>) by V. Moiseev and V. Murakhovsky and published in the "<i>Arsenal of the Fatherland</i>" magazine, issue 4, 2013. One of them is taken from an after-action report on the death of a tank commander in a T-72 after an attack by RPG-type weapons. The tank was a T-72B1 built in December 1985 in Uralvagonzavod. After being pulled into a repair facility, the tank was inspected and eight damage points were observed. Five of the hits were recorded on the hull, and of these, three were from RPG grenades impacting the sides of the tank in the areas protected by reactive armour, one was from an RPG grenade impacting the rubber side skirt of the tank in an area unprotected by reactive armour, and one was from a fragmentation grenade (possibly a VOG-17M) impacting the rear of the engine compartment. The remaining three hits were recorded on the turret, one on the front, one on the side, and one on the rear.<br />
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It was noted that the tank was in a marching status prior to the attack, having the cannon locked in the travel position and the 12.7mm machine gun locked facing backwards. Also, the commander's hatch was ajar or opened completely, so that the death of the commander was most likely caused by the combined explosion of an anti-tank grenade and the reactive armour occurring outside the tank, given that the armour was not perforated. Overall, the tank remained combat capable despite receiving damage in the autoloader and in the stabilizer system, as the driver and the gunner were still alive at the end of the ordeal and the gun could still be fired using the manual controls.<br />
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In general, photos of destroyed T-72 tanks cannot be said to be proof of the low survivability of the tank, but are instead often indicators of the sheer ferocity of the fight that led to its destruction.<br />
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<h3>
<span style="font-size: large;">COMMON CHARACTERISTICS: HULL</span></h3>
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The protection qualities of the frontal armour depend greatly on the specific model, but there are many characteristics that were shared across all models. This includes the side armour, hull belly armour, hull roof armour, and others. Protection was focused on the frontal arc of the hull.<br />
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The frontal arc of the tank is not the same for the hull and the turret. Various definitions of a tank frontal arc are handily compiled in the drawing below, taken from the article "Elements of Tank Design" by Gerald A. Halbert published in the November-December 1983 issue of the ARMOR magazine. For the hull, the Soviet definition of the frontal arc places the center point of the arc at the centerline off the hull (first from left). For the turret, the center point of the frontal arc is placed at the center of the turret (first from right). When the effective armour protection is given for the turret, it is almost always referring to the frontal arc protection using a reference side angle of 30 degrees under this frontal arc definition. <br />
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The Soviet definitions are used throughout this article and other Tankograd articles.<br />
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Generally speaking, the level of protection was quite formidable although some concessions were made during its development which put it slightly below the level of the T-64A. It is widely known that increasing the volume of a tank leads to an increase in armour mass without an increase in armour thickness because of the need to add armour to protect a larger surface area. This was a source of inefficiencies in the design of the T-72. When the UKBTM design bureau of the Uralvagonzavod factory designed the Object 172 prototype using the T-64A as the foundation of their new tank, one of the modifications made was to replace the compact 5TDF opposed piston engine with the V-46 V-shaped 12-cylinder engine developed by the Chelyabinsk tractor plant (ChTZ). The V-46 engine itself was larger than the 5TDF, but the difference in dimensions was not as significant as the decision to use the conventional centrifugal fan-driven cooling system from the T-54 instead of the ejection-type cooling system of the T-64. The volume of the engine compartment had to be increased by 0.5 cubic meters to accommodate this new equipment, and in turn, the increased volume generated a larger surface area. Added together with the increased mass of the running gear, the weight of the T-72 increased considerably and none of the extra mass went towards thickening the armour. To the contrary, the side hull plating had to be thinned down to 80mm from 85mm in order to put the weight gain in check. This was partly nullified by the larger diameter roadwheels of the T-72 which could cover parts of the hull, but the wheels are made of aluminium and not particularly thick, so this was not a true remedy but merely an unintended bonus.<br />
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The hull side, hull roof, hull belly and rear armour of all T-72 models are identical, regardless of the variant. As stated earlier, the armour of the side of the hull is 80mm thick. Tthe armour on the sides of the engine compartment is 70mm thick. The side armour of the hull is more than enough to withstand 20mm armour-piercing ammunition fired from various aircraft as well as 20mm and 25mm APDS rounds from autocannons.<br />
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There are several zones in the side of the hull that may not be entirely on the same level as the rest of the armour such as the one shown in the photo below. As you can see, the thickness of the steel armour at the drive sprocket and the rear shock absorber is reduced. It is thinner than the side armour of the engine compartment, and even though the shock absorber unit and the drive sprocket are backed by some amount of armour, the level of protection at these zones is not equal to the side of the engine compartment.<br />
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Note that in the first photo, the cut in the armour plate above the shock absorber is angled whereas the same cut is perfectly horizontal in the second photo. This is because of the slight offset of the roadwheels caused by the use of a torsion bar suspension. On the T-72, the roadwheels on the left side of the hull (port) are displaced slightly forward from the roadwheels on the right side (starboard). As such, the roadwheels on the right side of the hull (starboard) are slightly closer to the drive sprocket, so the shock absorber for the sixth roadwheel had to be moved closer to the drive sprocket and angled slightly to facilitate the same range of vertical travel.<br />
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The thickness of the armour at the holes for the installation points for the shock absorbers and the final drives is 40mm. The shock absorber itself has a casing made from armour-grade cast steel and has a considerable bulk which adds some protection on its own, and the final drive is protected by the drive sprocket and the drive sprocket hub.<br />
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Besides these weakened zones, the mounting points for the roadwheels and track support rollers can be considered reinforced zones. The armour thickness at these zones is much greater than the parts of the hull where they are located. The mounting points for the roadwheels are especially thick as they are separate milled blocks of steel welded onto the belly plate. The thickness of steel at the mounting points for the roadwheels probably exceeds 100mm and the thickness of the steel at the mounting points (also thick blocks of milled steel welded) for the track support rollers easily exceeds 100mm.<br />
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The side armour is thickest at the top
half and thins down to just 20mm at the lower quarter of the side hull profile. The upper and lower sides are not the same plate. The upper side armour is a single rolled steel plate whereas the lower side armour is actually a part of the belly armour plate. The belly plate is a large stamped piece of steel, bent into a tub shape and welded to the upper side armour. It joins with the upper side plate at an angle of 32 degrees from the vertical axis. The lower side hull armour has a height of 250mm or 270mm if the thickness of the plate itself is included. The upper side hull occupies around three quarters of the area of the side hull profile and the weaker lower side hull occupies one quarter. This thin strip of the side armour is usually not visible as it is completely concealed behind the roadwheels which add a modicum of spaced armour. The roadwheels cover a height of around 350mm of the lower part of the hull, and thus cover the entirety of the lower hull sides and also cover a part of the upper hull sides as well. The short height of the lower side hull armour makes it statistically unlikely to be hit and the additional protection provided by the roadwheels offsets the reduced thickness of the armour, so overall, it is not a flaw in the protection scheme of the tank. It is worth noting that the side armour of many other tanks are configured in a similar way, including the Leopard 2 as shown on the right next to the T-72 on the left.<br />
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The interior surface of the upper side hull armour is coated in a 45-50mm layer of "Podboi" anti-radiation lining, which can help absorb spall and other secondary penetrator fragments or even stop residual penetration from less energetic projectiles. This is discussed later in the "NBC Protection"
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It is without a doubt that the sides of the tank were only sufficient for a very limited period of the service life of the T-72. Being only 80mm thick, the side armour plate could offer only a fraction of the protective value of the front armour, and this was not a trifling issue. The number of hits sustained by a tank's sides were statistically significant, as shown by the analyses conducted by Dr. Manfred Held in "<i>Warhead Hit Distribution on Main Battle Tanks in The Gulf</i>". The charts below are from the study.<br />
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The sides would have been mostly resistant against 105mm APDS like the L28 round (M392 in the U.S and DM13 in West Germany) at a range of 2,000 meters within a somewhat reasonable 40-degree arc, but this arc is still relatively narrow and it limits the tank's freedom to maneuver in open spaces. At a range of 200 meters, the side armour is only capable of resisting DM13 at a side angle of 17.5 degrees, so the protected frontal arc would only be 35 degrees. The appearance of 105mm APFSDS rendered the side armour completely inadequate as protection against contemporary anti-tank firepower. </div>
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The hull roof is 30mm thick, while the thickness of the hull roof around the turret ring is 20mm. It can be seen in the photo below. The rear armour plate over the engine compartment is 40mm thick, sloped at 30 degrees, and the hull belly is 20mm thick. The thickness of the "Podboi" anti-radiation lining on the hull roof is 50mm. As it is not inhabited by the crew, the engine compartment lacks an anti-radiation lining. </div><div>
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<br />The engine access panel is 20mm thick and is supplemented by a stamped steel radiator cover. The cover is used to seal the radiator during snorkelling operations and it is stowed on top of the engine access panel when not in use. Its contribution to the overhead protection of the engine is limited, but it may prove beneficial against certain threats. For example, the damage from grenades, shells, bombs and other high-explosive ordnance may be reduced by the standoff distance created by the cover. Fragments from airbursting artillery shells may also be negatively affected by the spaced armour effect created by the cover.<br /><br />
The thickness of the hull belly plate is comparable to tanks like the M60 series and is slightly thicker than the 16mm belly plate of the Centurion and Chieftain, but is soundly beaten by the arched 36mm-thick belly of the M48 which was known to have excellent mine protection. The hull belly of the T-72 is only sufficient against explosive charges with a mass of less than 10 kg detonated over the tracks and not directly under the hull. These parts of the hull are most likely constructed from the same steels used in the same locations in the T-54 and T-62: 49 S grade steel for rear armour plate and the hull roof, 43 PSM grade steel for the floor. These grades of steel were first used in the T-54 obr. 1953.<br />
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The hull bottom is constructed from a single plate of rolled steel, which is then stamped into a complex shape with protruding ribs for the installation of torsion bars and a depressed section in the floor to accommodate the driver. Reinforcing nubs were pressed into the plate between every torsion bar rib to improve the stiffness of the floor. The side edges of the plate were bent upward at a 30 degree angle to join with the side hull plate, thus forming a tub shape. This was possible due to the ductility of <a href="https://vdocuments.site/catalogue-of-plates-new1.html">43 PSM steel</a>, which is a soft annealed steel and cannot be considered equivalent to RHA. 43 PSM has a yield strength of 400 MPa, a tensile strength of 600 MPa, and a hardness of 180-250 BHN. The elongation limit of 25% for 43 PSM is very high compared to RHA. These qualities make the steel plate easy to process by stamping and potentially more useful for mine protection because softer steels like 43 PSM <a href="https://pdfs.semanticscholar.org/a7d5/d6bd9df223153cea0d1a09b03ce84bad3c63.pdf">have a reduced resistance to deformation but higher resistance to rupturing</a> compared to high strength and high hardness steels. The rigidity of the belly plate is augmented by the lateral ribs for the torsion bars and the longitudinal embossed nubs on the belly plate.<br />
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Initially, cast turrets for the T-72 were made from MBL-1 cast armour steel with a hardness of 270-290 BHN. This grade of steel was first used in the turret of the T-62. The high hardness armour used in the turret of the T-72B is BTK-1Sh, a high hardness, high strength electroslag remelted (ESR) steel with a hardness of around 450 BHN. The appliqué armour plate installed on the 1983 modification of the T-72A and earlier T-72 variants is not known but it has been credited with a hardness of more than 500 BHN by credible sources. In Poland, an armour grade equivalent to MARS 500 was used. In the USSR, BT-70Sh steel may have been used.<br />
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The upper glacis is a multi-layered armour array angled at 68 degrees. Although the composition of the composite armour was changed many times over the course of the long career of the T-72, the angle of the upper glacis always remained the same. The high obliquity was an advantage against APDS ammunition, HEAT ammunition (due to fuzing issues) and early composite APFSDS rounds including Soviet models, but additional challenges arose when long rod APFSDS ammunition became commonplace in the 1980's due to the increased performance of long rod penetrators on highly oblique armour. But even so, this did not necessarily mean that the high slope of the upper glacis became a detriment - these matters are not so simple when composite armour is involved. The nuances of this design decision are discussed further later on in this article.
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<h3>
<span style="font-size: large;">LOWER GLACIS</span></h3>
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The armour protection of the lower glacis changed very little during the service life of the T-72. The properties of the plate are identical to the other welded plates used for the hull, like the side armour plate and the front plate of the upper glacis. The lower glacis is reported by some sources to be 80mm plate sloped at 61.5 degrees, identical to the T-64A, but it is stated to be 85mm sloped at 60 degrees according to "<i>Kampfpanzer: Technologie Heute und Morgen</i>" by noted German armour expert Rolf Hilmes. The difference in effective thickness between these two figures is minimal and may be explained by possible variations in discrete T-72 models, but the angle of the lower glacis is marked as 61.5 degrees in the Object 172M factory drawings, lending much more credence to the notion that it is also 80mm in thickness (identical in thickness to the T-64A).<br />
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Being a traditionally weak area on most tanks, the relatively poor armour of the lower glacis is largely counteracted by its small size and low exposure to enemy fire. It occupies less than 20% of the total area of the front hull. The low number of hits recorded on the lower parts of tank hulls have been independently verified by multiple sources, as discussed previously in this article in the section on the autoloader of the T-72. Again, it should be noted that statistics on the hit distribution on combat-damaged tanks during WWII showed that 90% of hits were recorded one meter above the ground, as reported by Sergey Gryankin on pages 12-13 in his article "<i>T-54</i>", published in the "<i>Техника-молодёжи</i>" magazine (<i>Technology of the Youth</i>). Moreover, Richard Ogorkiewicz writes on page 394 in "<i>Technology of Tanks</i>" that on average, the first 0.7 meters of a tank's height is covered by the terrain irregularities. If grass or other forms of vegetation are also present, this would mean that the lower glacis of a T-72 would almost always be obscured from direct vision and would usually be physically protected by the terrain due to its low height. Such statistics directly influenced Soviet tank designers in determining the optimal height of the lower glacis.<br />
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The vulnerability of the lower glacis can be reduced even further if the tank is in a hull defilade position behind a natural obstacle. Even if the obstacle does not provide enough resistance to stop an incoming projectile, the fact that it hides the lower part of the tank will shift the point of aim upwards, away from the lower glacis.<br />
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<span style="font-size: large;">LOWER GLACIS WITH DOZER BLADE</span></h3>
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If natural cover is not available and a static defensive position must be created, it is possible to for any T-72 model to self-entrench using the integral dozer blade installed on the lower glacis. Only the Object 172 prototype tanks created from 1968-1970 lacked a dozer blade. 17 tanks of this type were produced, and they were not delivered to the troops. A dozer blade was present on the Object 172M prototypes created during the summer of 1972 for performance trials (shown in the two photos below), and the final Object 172M model that was accepted into service in the Soviet Army as the T-72 Ural on the 7th of August 1973 had a dozer blade.<br />
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The dozer blade can be used for self-entrenchment or to augment existing cover with additional concealment. It also allows the tank to be used as a tractor and a digger for general construction work when specialized vehicles are not available. The blade secured by two rotating latches which are turned with a wrench to release the dozer blade. The dozer blade has a width of 2.14 meters.<br />
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The dozer blade is suspended from the belly of the tank by four structural support rods which can be seen in the two photos above. Two of these can be seen in the photo below. When the dozer blade is unlocked and released, these support rods retract backwards into special troughs to orient the dozer blade at the proper angle for digging.<br />
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With the dozer blade, the T-72 can be used to build a tank trench for itself in 15-20 minutes on soil. On snow, it can take as little as 5 minutes, but conversely, it takes much longer to self-entrench on frozen dirt. Due to the limited width and capacity of the dozer blade, the tank must make a few passes when digging out a suitably sized hole for itself. The tank commander and gunner exit the tank and continuously guide the driver during this process. Further improvements to the tank's firing position can be done by hand with the pioneering tools carried on the tank (spades, picks). </div><div style="font-size: medium;"><br /></div><div>If necessary, the dozer blade can also be used to overcome <a href="https://mykonspekts.ru/2-82208.html">anti-tank trenches</a> by filling them in or creating a ramp. This may be the only option for regular tank units if the engineering company of a tank regiment is not available to support them for whatever reason, or if too much time would be wasted in waiting for support. This greatly reduces the effectiveness of such trenches in delaying an attacking force composed of T-72 tanks as compared to any other tank, excluding the T-80 series and later models of the T-64 series. </div>
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In the total absence of natural cover, the presence of the upper glacis armour array will partly reduce the height of the lower glacis weakened zone. The photos below (left photo courtesy of Stephen Sutton) shows the thickness of the front plate of the upper glacis array by the seam joining it to the lower glacis plate so that you can visualize the approximate reduction in the size of the weakened zone. The tank on the left is a T-72M1 (formerly Iraqi) and the tank on the right is a T-72M, so both have an improved hull armour array with a 60mm front plate. The dozer blade has some overlap with the array which further minimizes gaps in the armour.<br />
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Actual measurements done on a T-72M shows that the distance between the surface of the upper glacis and the edge of the dozer blade is 290mm. Knowing that the upper glacis has a thickness of 215mm on the T-72M, the gap between the area of the lower glacis protected by the dozer blade and the area overlapping with the upper glacis is only 75mm. When viewed from the front, the height of this gap is around 37.5mm, or just one and a half inches. Needless to say, hitting this part of the lower glacis is extremely challenging. On its own, the lower glacis plate is highly vulnerable to 105mm APDS, but this vulnerability is greatly reduced by the aforementioned factors.<br />
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The dozer blade is a very thick and heavy steel plate. According to T-72 manuals, it weighs 200 kg. It is probably made from a high hardness abrasion-resistant or armour grade steel. It is very likely that high hardness armour steel grade is used for the dozer blade of a military vehicle like the T-72 because a high hardness blade can be used to shift abrasive rock and frozen soil as well as provide additional ballistic protection. Case in point - high hardness impact resistant steels like Hardox 500 are standard for bulldozer blades and loader buckets used in mines and construction sites where large quantities of rock must be shifted, and high hardness steel dozer blades are also standard for military combat engineering vehicles. The measurement on the left below (done by Jarosław Wolski) shows that the thickness of the dozer blade on an old Polish T-72M1 is 20mm. The measurement on the right, taken from the <a href="https://www.facebook.com/t72org/photos/?tab=album&album_id=1652076908337757">T-72.org Facebook group</a>, shows that the dozer blade of a T-72M is also around 15-20mm thick, although it is not possible to be sure. The measured dimensions are congruent with the given weight of 200 kg. At an unknown point in the production of the T-72, possibly beginning with the T-72B, the thickness of the dozer blade was increased to 25mm. This increased its weight to 250 kg. The T-90 and T-90A are verified to feature this thickened dozer blade.<br />
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Due to the obscurity of this topic, it is rather difficult to ascertain if the T-72M and T-72M1 differed from their domestic counterparts in the thickness of the dozer blade. However, it seems safe to assume that if the T-72M1 had a dozer blade with a thickness of 20mm, then the T-72A would also have one of the same thickness. It is worth noting that the dozer blade is not simply laid on top of the lower glacis plate, but it is actually slightly spaced. This is shown in the drawing below, taken from a T-80B manual. The T-80B has the same dozer blade installed.<br />
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This is beneficial against AP and APDS ammunition. An armour configuration consisting of a high hardness steel plate on top of an RHA plate at high obliquity is more effective than a solid RHA plate of the same weight, which is not only demonstrable with test firings against laboratory model targets but also in live fire tests. E.g. the solid 118mm RHA upper glacis of the Centurion Mk. 7 and Mk. 8 was found to be noticeably less effective on a thickness basis compared to the uparmoured upper glacis of Centurion Mk. 3 and Mk. 5 tanks, consisting of a 44mm RHA plate welded on top of the 76mm base RHA plate. The presence of an air gap between the two layers can provide an additional benefit against AP and APDS, supplementing the positive effect of layered armour.<br />
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The overlapping section between the upper and lower glacis plates combines with the dozer blade to make the lower glacis a problematic target to defeat. To put the level of protection into perspective, Rolf Hilmes credits the lower glacis of an ex-East German T-72M with 250mm RHA of protection against KE attack, which is incongruous with the combined LOS thickness of the lower glacis and dozer blade on their own (only around 208mm). This appears to be the only published figure on the armour value of the lower glacis. It is worth noting that if Hilmes' figure is correct, then the weakest part of the T-72 hull is nominally more resilient than the frontal armour of a T-54 and is on the same level as the turret armour of the Chieftain tank, especially after the slope of the armour is considered. The additional 5mm of thickness for late T-72 models increased the effective thickness slightly, but did not change the fundamental level of protection.<br />
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In all likelihood, L52A1 or M728 APDS with a penetration of 130mm at 60 degrees at 1 km and 120mm at 60 degrees at 2 km may fail to defeat the lower glacis from a range of approximately 1.5 km and more. The older L28A1 or M392A2 rounds had significantly worse performance on oblique armour and would certainly fail to defeat the lower glacis from 1 km or less. Of course, the L15A4 APDS round fired from the 120mm L11 with a penetration of 130mm RHA at 2 km should succeed against the lower glacis of the T-72 quite easily from any distance. Needless to say, these ranges would be unacceptable for the main armoured surfaces of the tank, but for a minimally exposed target such as the lower glacis, it is a very respectable level of protection, especially when compared to tanks like the Chieftain or M60A1.<br />
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It is worth noting that according to Russian historian Mikhail Pavlov mentions that the lower glacis plate of an Object 432 (T-64) can be nominally defeated by 105mm "subcaliber shells with a muzzle velocity of 1,475 m/s" at a distance of 2,500 meters, which is the same distance limit given for the lower glacis of the T-55 and T-62 (100mm RHA at 55 degrees). The lower glacis of the T-64 is the same as the T-72, but the tank lacks a dozer blade. HEAT rounds of a modest caliber would not face any difficulties in defeating the lower glacis armour, but against HESH, the physical separation of the dozer blade from the lower glacis fulfills the essential role of preventing the transmission of stress waves to the lower glacis plate from the blast, which prevents spalling. The considerable thickness of the blade itself allows it to resist deformation and thus fulfill its function even when impacted by HESH shells of a large caliber, as tests on Conqueror tanks have shown that thinner 14mm spaced plates ("burster plates") were effective at defeating 183mm HESH shells and Malkara missiles (HESH warhead).<br />
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However, all of this is only true if the incoming projectile impacts the middle section of the lower glacis, as the lower part of the lower glacis has a reduced thickness. For the original T-72 Ural model, the reduction in thickness was a necessity because the torsion bars for the first pair of roadwheels are in the way, as you can see in the drawing on the left below (T-72 Ural). However, the geometry of the lower glacis was changed at an unknown time and became even thinner at the area in front of the torsion bars, as shown in the drawing on the right (T-90). Also note that the dozer blade on the T-90 is not spaced from the lower glacis plate, or has so little spacing that it is practically irrelevant.<br />
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<span style="font-size: large;">COMMON CHARACTERISTICS: TURRET</span></h3>
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The turret is a two-piece casting. The walls, base, the bulge for the commander's cupola and some parts of the turret roof are formed from a single casting, onto which the cast roof is welded. The side armour is curved at a considerable rearward angle to form a point at the very back of the turret, forming a teardrop shape. This was especially exaggerated in the T-72B variant due to the larger and thicker turret cheeks, which earned it the humorous "Super Dolly Parton" moniker. The rear of the turret of all T-72 variants have a distinct step joining the turret roof to the bulge at the rear of the turret. This was inherited from the turret design of the T-64A, like so many other details of the T-72 series.<br />
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As there is no discrete transition from the frontal cheek armour to the side armour owing to the complex shape of the cast turret, the turret sides are simply defined as the region of the turret directly next to the crew seats, labelled 'Д' in <a href="http://btvt.narod.ru/raznoe/bulat-leo2.files/image011.jpg">this drawing of a T-64B turret</a>. As mentioned before, the side of the turret has a physical thickness of around 80mm near the base and the curvature of the turret sides provide a minor increase in line-of-sight thickness to around 88mm when viewed perpendicularly. The turret sides becomes negligibly thinner towards the roof, but the curvature of the turret enables the same line-of-sight thickness to be maintained along the entire height of the sides. The amount of vertical sloping is relatively minor as the turret is built with a heavy emphasis on horizontal shaping; the side of the turret is horizontally sloped rearward at an angle of 42 degrees, as measured tangentially to the side of the turret. The LOS thickness of the side armour is therefore 118mm when viewed perpendicularly. The rear of the turret is around 65mm thick, but varies considerably in actual protective value due to the complex shape of the casting. This part of the turret is notably tougher than the T-64 and T-80 pattern of turrets as they are completely flat and therefore have a lower effective thickness.<br />
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With a thick layer of anti-radiation lining backing it and with the storage bins (plus cargo) adding a modicum of resistance, the sides are more
than enough to withstand any 20mm and 23mm shell at point-blank and any 25mm autocannon shell at the higher end of typical combat ranges (in the vicinity of 1,500 m) when hit at a perpendicular angle. This is including the 25mm M919 APFSDS shell. However, the armour is not thick
enough to reliably resist 30mm, 35mm and 40mm shells. In order to do so, the shot must impact the side armour from the frontal arc of the turret and not perpendicularly to the side. The rear of the turret, however, is only sufficient against 20mm autocannons unless it is attacked at a considerable angle of incidence, although the rear armour is actually somewhat pointed due to the teardrop shape of the turret. This would certainly improve the level of protection. From a perpendicular angle of attack, the turret cheeks can still offer a respectable defence due to the large thicknesses of steel, but the sides of the turret over the crew stations provide only a modicum of protection from light shoulder-fired HEAT grenades weapons like the M72 LAW. The presence of stowage bins made it difficult to achieve reliable penetration with such small caliber grenades, particularly when they were fully packed with spare parts and equipment, but it was not a comprehensive remedy.<br />
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On the T-72B3 UBKh, the sides of the turret have been completely covered with an advanced ERA kit capable of defeating tandem warheads at the expense of valuable stowage space and the rear has been reinforced with slat armour.<br />
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The shape of the turret of the T-72A and T-72B is such that the sides will be completely unreachable by enemy fire from within the frontal 70-degree arc. This means that if the side of the turret was shot at an angle of attack of 35 degrees, the thin sides of the turret will be hidden behind the turret cheeks. If the angle of attack is increased to 45 degrees, the sides will be visible, but the angle of incidence will increase to 87 degrees - steep enough to guarantee a ricochet. When the angle of attack is increased to 55 degrees, the angle of incidence is still 77 degrees. This is steep enough that many shaped charge warheads will fail to fuse and APDS projectiles are very likely to ricochet. Even if an attacking projectile manages to dig into the armour, the LOS thickness of the thin side armour from the horizontal angle of the turret alone at such a steep angle of incidence is very formidable at 391mm. This is already enough to resist the majority of shoulder-fired HEAT weapons used by opposing armies. This is also a noticeably higher level of protection than the side turret armour of the Abrams series from the M1 to the M1A2, as that only offers an effective thickness of 380mm RHA against an 81mm shaped charge warhead from a 45-degree side angle. The difference in the level of KE protection is even greater - the homogeneous cast armour at this zone of the T-72 turret would offer between half as much to twice as much protection at 55 degrees based on the calculated thickness efficiency coefficients of the Abrams turret side armour, and the protection provided at 45 degrees is infinitely higher because the angle of incidence is simply too high (87 degrees) whereas the side of the Abrams turret would offer only around 200mm RHA in effective thickness.<br />
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In other words, the turret of the T-72 is a very, very tough nut to crack from a wide range of angles. The unique teardrop shape of the turret makes it possible to present a high thickness of armour across the frontal arc and, more importantly, accomplish this without adding excessive weight to the tank. Indeed, based on the hit distribution data from multiple conflicts during the 20th Century, the teardrop shape is mathematically ideal for conventional large scale mechanized warfare on a fundamental level. This shape could not have been implemented effectively without restricting the turret crew to two men, and in turn, a combat-effective two-man turret design could not have been implemented without an autoloader.<br />
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However, this shape does not come without drawbacks. It is extremely efficient in the distribution of armour mass because it can provide a very high level of protection in its frontal arc with comparatively little armour compared to heavier turrets, but because the vast majority of the mass is disproportionately allocated to the front, the turret also became unbalanced. It is quite the opposite for NATO tanks like the M60A1, Chieftain, Leopard 2, M1 Abrams, AMX-30, and even the Leopard 1 to some extent. For these tanks, the inclusion of a large bustle containing ammunition or other equipment was a convenient counterweight to the frontal armour, thus shifting the center of gravity closer to the geometric center of the turret ring. This not only reduces the load on the horizontal turret stabilization system when the tank is situated on non-level ground and especially so when the tank is in motion over rough terrain, but a balanced turret also generates a more stable load on the stabilizer, making it easier to implement faster and more precise turret rotation drives, and it also reduces the stress on the turret ring from firing the main gun at various gun elevation angles and at various tank orientation angles. For instance, the turret of a basic T-72A weighs 12 tons (including the weapons and a full set of standard equipment) and its center of gravity is 500mm above the level of the turret ring race ring and horizontally offset 430mm from the geometric center of the turret ring. The turret of the T-72B has even heavier frontal armour and is even more unbalanced, and the addition of explosive reactive armour on the frontal arc further exacerbates the issue.
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Tanks like the <a href="https://photos.smugmug.com/Military/Park-Patriot-New-photos-part1/i-Pcz8V8b/0/901fb079/L/ParkPatriot2015part13-012-L.jpg">T-64B</a> and <a href="https://photos.smugmug.com/Military/Park-Patriot-New-photos-part1/i-xV39Zgs/0/0fce64f9/L/ParkPatriot2015part13-057-L.jpg">T-80B</a> used externally-stowed auxiliary equipment as counterweights with limited success. Presently, the relatively new T-72B3 UBKh modernization shifted more weight to the rear of the turret when reactive armour blocks were added to the sides of the turret over the inhabited zones and a slat armour screen was installed over the rear of the turret, but again, the effect is still limited simply due to the massive allocation of armour mass to the turret cheeks. More recently, the approach taken by Uralvagonzavod engineers with the new Proryv-3 turret of the T-90M can be seen in the retention of the teardrop shape and the addition of a segregated ammunition compartment to the bustle to act as a counterweight and to reduce the quantity of ammunition stowed openly in the fighting compartment. This solution is not perfect, but it is a suitable adaptation of the basic teardrop geometry for modern needs.
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Nevertheless, the unbalanced turret of the T-72 is still lighter than the turret of tanks like the M1 Abrams or Leopard 2. The turret of a Leopard 2A4 reportedly weighs 16 tons (fully equipped), and would weigh even more if the designers had decided to provide any serious amount of protection for the sides of the turret bustle. As it stands, that is the weight of a Leopard 2A4 turret with only 80mm of flat RHA steel protecting the sides of the turret bustle (4 times less protection than the sides of the T-72 turret). In this respect, the T-72 turret design certainly has a major advantage and the decision to use a teardrop shape for the turret could be considered eminently justifiable.
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The turret ring of the T-72 is a simplified form of the T-64 turret ring design with the MZ autoloader carousel mounting ring removed. The design was created based on the T-54 and T-62 turret designs which placed the ball bearing race ring of the turret ring above the level of the hull roof in a cutout in the turret armour. This made the structure vulnerable to jamming from direct hits to the lower edge of the turret where the turret ring was located as the thickness of the armour is lower. For the T-72, the hull roof around the turret ring is thinner (20mm) than the hull roof above the driver's station (30mm) to accommodate the turret ring, but even so, the ball bearing race ring is still located in a cutout in the turret armour, above the level of the hull roof. As such, only a limited thickness of turret armour is present in front of the race ring, which poses a problem if an armour piercing round impacts the joint between the turret and the hull as it is much more likely to defeat the armour and jam the turret ring or enter the tank and cause internal damage. The turret ring design is shown in the two drawings below. The drawing on the left shows the rear of the T-72 turret and the drawing on the right shows the front.<br />
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<a href="https://1.bp.blogspot.com/-Es2d5mYEL4g/W_WGpmTmNoI/AAAAAAAAMik/Bu9X4gZhHHAtFMRMyLyNDLDBKfC4CAsBwCEwYBhgL/s1600/turret%2Bring%2Bclose%2Bup%2Brear.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1465" data-original-width="737" height="320" src="https://1.bp.blogspot.com/-Es2d5mYEL4g/W_WGpmTmNoI/AAAAAAAAMik/Bu9X4gZhHHAtFMRMyLyNDLDBKfC4CAsBwCEwYBhgL/s320/turret%2Bring%2Bclose%2Bup%2Brear.png" width="160" /></a><a href="https://1.bp.blogspot.com/-Nq3SF5azjfE/W_WGpkvrchI/AAAAAAAAMig/zLKoDrG9x0s-xyHgsA6NnfQkoIFRJJkYQCEwYBhgL/s1600/turret%2Bring%2Bclose%2Bup.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="807" data-original-width="834" height="309" src="https://1.bp.blogspot.com/-Nq3SF5azjfE/W_WGpkvrchI/AAAAAAAAMig/zLKoDrG9x0s-xyHgsA6NnfQkoIFRJJkYQCEwYBhgL/s320/turret%2Bring%2Bclose%2Bup.png" width="320" /></a></div>
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The difference between the T-64 and the T-72 turret ring designs is apparent when they are compared. The T-72 turret ring is shown on the left with the interior of turret ring facing to the right of the drawing, and the T-64 turret ring is shown on the right with the interior of the turret ring facing to the left of the drawing.<br />
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<a href="https://2.bp.blogspot.com/-JLfbglpEyfA/W_WIggOBOqI/AAAAAAAAMis/bqB2ehX79ZobQXhSLUj_T1xOfiHg0LQTwCLcBGAs/s1600/t-72%2Bturret%2Bring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="399" data-original-width="443" height="360" src="https://2.bp.blogspot.com/-JLfbglpEyfA/W_WIggOBOqI/AAAAAAAAMis/bqB2ehX79ZobQXhSLUj_T1xOfiHg0LQTwCLcBGAs/s400/t-72%2Bturret%2Bring.png" width="400" /></a><a href="https://1.bp.blogspot.com/-vLxMG3JgcBw/W_WJH-9bppI/AAAAAAAAMi0/XaGBGgEykGE0bgUoQ76DgPdv5n0YZU-zACLcBGAs/s1600/t-64%2Bturret%2Bring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1235" data-original-width="1459" height="337" src="https://1.bp.blogspot.com/-vLxMG3JgcBw/W_WJH-9bppI/AAAAAAAAMi0/XaGBGgEykGE0bgUoQ76DgPdv5n0YZU-zACLcBGAs/s400/t-64%2Bturret%2Bring.png" width="400" /></a></div>
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Two rubber gaskets below the ball bearing race ring seal the turret ring from water ingress. A raised collar prevents artillery splinters and bullets from slipping into the gap between the turret and the hull roof. The depression of the hull roof around the turret ring can be seen in the photo below along with the protective collar.<br />
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<a href="https://4.bp.blogspot.com/-Dxo7-hYxcRs/W_cIE0my9FI/AAAAAAAAMk0/O5oK2XQL-GU1MR7OoXCE5aSbLvl3E5RlACLcBGAs/s1600/123724639.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="1280" height="480" src="https://4.bp.blogspot.com/-Dxo7-hYxcRs/W_cIE0my9FI/AAAAAAAAMk0/O5oK2XQL-GU1MR7OoXCE5aSbLvl3E5RlACLcBGAs/s640/123724639.jpg" width="640" /></a></div>
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The merits of various turret ring protection methods are examined in the study "<i><a href="http://btvt.info/5library/vbtt_1968_03_04_barbet.htm">Некоторые Вопросы Проектирования Защиты Стыка Корпуса И Башни</a></i>" by O.I Alekseev et al. It was noted that turret ring designs that required a cutout in the lower part of the turret like the T-54 turret was a liability. Conversely, the solution implemented in the M48 Patton, M60 and M103 where the turret ring was installed in a raised flange cast together with the hull was also assessed to be a non-ideal solution as it still fails to prevent the turret from being jammed by a hit to the joint between the turret and the hull. The low thickness of the flange also results in a low level of armour protection. The best solution was found on the IS-3, T-10, Chieftain, Leopard 1 and M46 Patton. These tanks had the ball bearing race ring recessed below the hull roof, and in the case of the T-10, M46 and Chieftain, the gap between the turret and the hull roof was covered by raised parts of the hull. For example, the Leopard 1 shown below clearly has the turret ring race ring placed below the hull roof (<a href="http://preservedtanks.com/Image.aspx?PhotoID=9831&UniqueID=298&Page=4">photo taken by T. Larkum</a>). The T-72 turret ring design belongs somewhere in between the first and third categories as the ball bearing race ring is still installed in a cutout in the lower part of the turret, but the height of the race ring is reduced compared to the T-54 and T-62.<br />
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<a href="https://2.bp.blogspot.com/-wJgjjmbJtOw/XAlIkvbhpEI/AAAAAAAAMpo/2HmvV1vCImwmoFUJkWOxIfQlOikoReXgACLcBGAs/s1600/leopard%2B1%2Bturret%2Bring.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="799" data-original-width="1200" height="266" src="https://2.bp.blogspot.com/-wJgjjmbJtOw/XAlIkvbhpEI/AAAAAAAAMpo/2HmvV1vCImwmoFUJkWOxIfQlOikoReXgACLcBGAs/s400/leopard%2B1%2Bturret%2Bring.jpg" width="400" /></a></div>
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At the front of the turret, the cast steel gun mask can be considered a common feature of all T-72 variants, although this is not true in the strictest sense as the gun mask is different depending on the model of cannon mounted in the tank. The gun mask is a single solid steel casting that is bolted on the gun mounting cradle. The gun mask has a width of 390mm. It does not contact the gun barrel and does not interfere with the harmonics of the barrel, nor does it have any effect on the dynamics of the recoil stroke of the cannon. The gun mask is connected to the co-axial infrared spotlight on the right of the gun by a set of pushrods that allows the spotlight to be aimed vertically in sync with the tank's night vision sight albeit with a great deal of horizontal parallax if the spotlight is used at a different distance than the distance that it was previously calibrated for.<br />
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The gun mask has a ring of screws around the base of the barrel which are designed for securing a plastic gun mask cover. The cover is meant to prevent rain from ingressing the tank through the gap between the gun mounting cradle and the turret, but it also functions as a seal to prevent the ingress of NBC contaminants. <a href="http://www.primeportal.net/tanks/thomas_voigt/t-72m/index.php?Page=9">The photo below by Thomas Voigt</a> shows the gun mask of a T-72M with a plastic cover.<br />
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<a href="https://3.bp.blogspot.com/-YzyPcEHdmKE/W2l_JsN5kFI/AAAAAAAAMBo/ShdD4PT5O1UQJtUMQuQSKui5PhUVhRTRACLcBGAs/s1600/t-72m_107_of_166.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1600" height="400" src="https://3.bp.blogspot.com/-YzyPcEHdmKE/W2l_JsN5kFI/AAAAAAAAMBo/ShdD4PT5O1UQJtUMQuQSKui5PhUVhRTRACLcBGAs/s400/t-72m_107_of_166.jpg" width="400" /></a></div>
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The ring of screws is also used in tank models with Kontakt-1 reactive armour as the mounting point for a metal frame holding a set of three reactive armour blocks on top of the gun mask, as shown in the photo below of a T-72AV. This contraption is also found on the T-72B.<br />
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<a href="https://1.bp.blogspot.com/-NZatewe4cfg/W20xDveAPEI/AAAAAAAAMMo/TEtd5wIpii8ZOhM1jhQ5inIZuwbaBUwcwCLcBGAs/s1600/t-72av%2Bgun%2Bmask.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="972" data-original-width="1296" height="480" src="https://1.bp.blogspot.com/-NZatewe4cfg/W20xDveAPEI/AAAAAAAAMMo/TEtd5wIpii8ZOhM1jhQ5inIZuwbaBUwcwCLcBGAs/s640/t-72av%2Bgun%2Bmask.png" width="640" /></a></div>
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The gun mask is not meant to stop serious anti-tank weapons, but is instead simply a protective cover for the base of the gun barrel to protect the barrel and breech block from bullets and fragments and blast damage from shells impacting the turret. The gun mask is also designed with protruding edges that overlap the gap between the gun barrel and the turret in order to limit the possibility of bullets and fragments potentially jamming the gun in elevation. Due to the nature of the type of threat, the thickness of the casting is not particularly high, as shown in the photo on the left, below. Measurements on the protruding edges of the gun mantlet are shown in the two photos on the right, below. The measurements were done by Jarosław Wolski.<br />
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<a href="https://3.bp.blogspot.com/-oDFEafRpxqI/W2ly50nmjpI/AAAAAAAAMA0/GvXDBd42zJgXvHM2vyvLu86rC8hZ_L7RgCEwYBhgL/s1600/maska%2Barmaty%2Bt72b%2Bi%2Bt90.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://3.bp.blogspot.com/-oDFEafRpxqI/W2ly50nmjpI/AAAAAAAAMA0/GvXDBd42zJgXvHM2vyvLu86rC8hZ_L7RgCEwYBhgL/s400/maska%2Barmaty%2Bt72b%2Bi%2Bt90.jpg" width="400" /></a><a href="https://2.bp.blogspot.com/-S4-mL2oI4xk/W2l27Xdi-9I/AAAAAAAAMBQ/xhIRW4T6SwEOe-r01l215e8aAzEXYYCfACLcBGAs/s1600/20180806_170506.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="900" height="320" src="https://2.bp.blogspot.com/-S4-mL2oI4xk/W2l27Xdi-9I/AAAAAAAAMBQ/xhIRW4T6SwEOe-r01l215e8aAzEXYYCfACLcBGAs/s320/20180806_170506.jpg" width="180" /></a><a href="https://1.bp.blogspot.com/-O7oQtAZqKx0/W2mAYXOJNzI/AAAAAAAAMB4/c1MGgcC4BmEz-3EKR8hf0P3-LvGOH9G3ACLcBGAs/s1600/20180806_170457.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="900" height="320" src="https://1.bp.blogspot.com/-O7oQtAZqKx0/W2mAYXOJNzI/AAAAAAAAMB4/c1MGgcC4BmEz-3EKR8hf0P3-LvGOH9G3ACLcBGAs/s320/20180806_170457.jpg" width="180" /></a></div>
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The thickness of the thinnest part of the base of the gun mask of the T-72M1 is around an inch. Based on the photo on the left, above, the thickness of the armour wrapped around the gun barrel is around an inch as well. According to <a href="http://gurkhan.blogspot.com/2012/01/blog-post_13.html?utm_source=warfiles.ru">"<i>Возможная Компоновочная Схема Танка</i>" ("<i>Possible Tank Layout Scheme</i>") by S.A. Gusev</a>, the gun mask of the T-72B is only rated to stop 12.7mm B-32 armour piercing rounds from a distance of 100 meters. However, the rounded design of the casting and the thickness of the plate makes it quite obvious that this is the minimum guaranteed level of protection, as there are many sections where the combined thickness and slope of the mask should make it more than sufficient against 12.7mm B-32 at even point blank range.<br />
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The form of the gun mask changed slightly during the evolution of the T-72. The photo on the left shows the gun mask of an early T-72 Ural. <a href="https://www.cybermodeler.com/armor/t-72/t-72_walk.shtml">The photo in the center by Stephen Sutton</a> shows a T-72M1, analogous to the T-72A. The photo on the right shows a T-72B. Note the presence of a large nut in the corner of the gun mask of the T-72 Ural and T-72A. The nut is mirrored on the other side. On the T-72B, there are four nuts arranged at each corner of the gun mask. These nuts are attached to bolts that join the gun mask to the gun mounting cradle.<br />
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<a href="https://4.bp.blogspot.com/-Z_olOCPRy2M/W2tGnbulEKI/AAAAAAAAMIo/KgBXtGRPCmIDCUpyPO5FVX5fMJV8Pus-ACLcBGAs/s1600/ob172m%2Bgun%2Bmask.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="682" height="200" src="https://4.bp.blogspot.com/-Z_olOCPRy2M/W2tGnbulEKI/AAAAAAAAMIo/KgBXtGRPCmIDCUpyPO5FVX5fMJV8Pus-ACLcBGAs/s200/ob172m%2Bgun%2Bmask.jpg" width="130" /></a><a href="https://1.bp.blogspot.com/-gXGl2YZnH-g/W2l7nTiqrhI/AAAAAAAAMBc/WEZzECnuf4IKDyi97fxAlJW10c1gXIUcACLcBGAs/s1600/t-72_09.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="450" data-original-width="600" height="240" src="https://1.bp.blogspot.com/-gXGl2YZnH-g/W2l7nTiqrhI/AAAAAAAAMBc/WEZzECnuf4IKDyi97fxAlJW10c1gXIUcACLcBGAs/s320/t-72_09.jpg" width="320" /></a><a href="https://2.bp.blogspot.com/-p9-SECs9Up0/W2tH_yt8oFI/AAAAAAAAMI0/6QXG_nGR7asL96FYVZ2_w6Z2IBHUWurYgCLcBGAs/s1600/bolts.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="589" data-original-width="785" height="240" src="https://2.bp.blogspot.com/-p9-SECs9Up0/W2tH_yt8oFI/AAAAAAAAMI0/6QXG_nGR7asL96FYVZ2_w6Z2IBHUWurYgCLcBGAs/s320/bolts.jpg" width="320" /></a></div>
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The change in the number of nuts is related to the upgrade to the 2A46M cannon with a quick-detach barrel, although the precise reason is not known.<br />
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<a href="https://1.bp.blogspot.com/-pDFoaOXlX1g/XQ9BCx4qQpI/AAAAAAAAOgU/oBkjUaG2cgwKxLPWtiBRlu1PGKHdNO39wCLcBGAs/s1600/below%2Bgun%2Bmantlet.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1201" data-original-width="1600" height="300" src="https://1.bp.blogspot.com/-pDFoaOXlX1g/XQ9BCx4qQpI/AAAAAAAAOgU/oBkjUaG2cgwKxLPWtiBRlu1PGKHdNO39wCLcBGAs/s400/below%2Bgun%2Bmantlet.jpg" width="400" /></a></div>
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<h3>
<span style="font-size: large;">WEAKENED ZONES</span></h3>
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<a href="https://2.bp.blogspot.com/-z10QiWSowY4/W196Ydi3GCI/AAAAAAAAL3w/bo2qSp07Uy0DTKKDRKPmrZBfIZGtwkQ1wCLcBGAs/s1600/weakened%2Bzones.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="481" data-original-width="600" height="320" src="https://2.bp.blogspot.com/-z10QiWSowY4/W196Ydi3GCI/AAAAAAAAL3w/bo2qSp07Uy0DTKKDRKPmrZBfIZGtwkQ1wCLcBGAs/s400/weakened%2Bzones.jpg" width="400" /></a></div>
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Although the armour scheme of the tank is good, the fact that some parts of the tank have less armour protection than others cannot be ignored when evaluating the overall level of protection. The critical zones of reduced armour protection (weakened zones) are:<br />
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<blockquote class="tr_bq">
Lower glacis (4): <i>The lower glacis has already been discussed, of course, so there is no need to examine it again.</i></blockquote>
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Gunner's primary sight aperture (5): <i>The gunner's primary sight aperture weakened zone is an artifact of the sloped roof of the turret. Due to its periscopic construction, the sight must extend through the roof, which creates a gap in the roof armour. When viewed from the front of the tank, this gap is a narrow area where there is practically no armour, but in fact, the weakened zone includes the turret roof directly around the gap. This is because the gap is a structural weakness that may cause the roof armour to fail when impacted by a kinetic energy penetrator.</i></blockquote>
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Gun mantlet area (2): <i>The gun mantlet area weakened zone exists due to the need for space to accommodate the co-axial machine gun and the mechanical linkages that connect the gunner's primary sight to the cannon.</i></blockquote>
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Turret ring area (3): <i>The turret ring area is simply an inherent weakness created by the joint between the turret and hull. It is practically unavoidable for turreted tank designs.</i></blockquote>
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Commander's cupola (5): <i>The commander's cupola weakened zone is, of course, the cupola itself, which extends above the turret roof and cannot be armoured as thickly as the rest of the turret for obvious reasons.</i></blockquote>
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Driver's periscope area (1): <i>The weakened zone at the driver's periscope is created by the void in the upper glacis necessitated by the installation of the driver's TNPO-168V periscope as well as the need to accommodate the driver's head. This weakened zone is particularly interesting.</i></blockquote>
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The weakened zone at the driver's periscope area can be seen in the cross-sectional drawing of the T-72 Ural shown below. The slope of the upper glacis is interrupted by the periscope, and the composite armour of the upper glacis is supplemented by a thick triangular reinforcing steel wedge to compensate for the reduction in line-of-sight (LOS) thickness caused by the interruption in the slope of the glacis.<br />
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<a href="https://1.bp.blogspot.com/-24paQH05owg/W18eaRltmCI/AAAAAAAAL3M/yypQWv3lyPoZNcRwLA-QKyMaeZPJrxrsACLcBGAs/s1600/t-72%2Bural%2Bupper%2Bglacis%2Barmour.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="196" data-original-width="411" height="190" src="https://1.bp.blogspot.com/-24paQH05owg/W18eaRltmCI/AAAAAAAAL3M/yypQWv3lyPoZNcRwLA-QKyMaeZPJrxrsACLcBGAs/s400/t-72%2Bural%2Bupper%2Bglacis%2Barmour.png" width="400" /></a></div>
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The dimensions of this weakened zone is not available in literature, but it can be deduced from other sources of information. It can be seen from the drawing above that the height of the void is roughly equivalent to the height of the TNPO-168V periscope (274mm), and from the photo on the left below, it can be seen that the width of the void is roughly equivalent to the width of the driver's hatch (530mm). From these dimensions, the area of the void is around 0.145 sq.m. This, however, only considers the upper glacis when struck from the direct front. The reduction in LOS thickness is also apparent if the cutout is attacked from a side angle. Like the front wall of the cutout, the side walls are reinforced, but only along the front half, which has the largest projected area from the side. The side reinforcements are indicated by the large arrows in the photo on the right below. The rear half of the sides of the cutout are not reinforced, having a wall thickness of only 20mm.<br />
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<a href="https://2.bp.blogspot.com/-atiKXUJYgY8/W18jURF5VpI/AAAAAAAAL3Y/arn9GztVs4kUpSkxgaOFQ8BAvWk5IF3WQCLcBGAs/s1600/drivers%2Bperiscope%2Bweak%2Bpoint.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://2.bp.blogspot.com/-atiKXUJYgY8/W18jURF5VpI/AAAAAAAAL3Y/arn9GztVs4kUpSkxgaOFQ8BAvWk5IF3WQCLcBGAs/s400/drivers%2Bperiscope%2Bweak%2Bpoint.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/a/AVvXsEhKFTR4O5A3wO0kkX9_s4CijpBiyL1O5PayDsR_p-7p4qK-7e0ycXdfTO3n07GdGIiGRKxIQQzNnNXMRNXPGVSOD1jHO6-lccSBVxInCv2gZgrwcZ9cYbdWTgta80LlpUV_TCj7T43EGdcntFFtB1pm8ULbQH3AdwqIirSwkgnMSXLyjwbd3cYm3zCoRw=s1024" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://blogger.googleusercontent.com/img/a/AVvXsEhKFTR4O5A3wO0kkX9_s4CijpBiyL1O5PayDsR_p-7p4qK-7e0ycXdfTO3n07GdGIiGRKxIQQzNnNXMRNXPGVSOD1jHO6-lccSBVxInCv2gZgrwcZ9cYbdWTgta80LlpUV_TCj7T43EGdcntFFtB1pm8ULbQH3AdwqIirSwkgnMSXLyjwbd3cYm3zCoRw=w400-h300" width="400" /></a></div></div><div><br /></div><div>The thickness of the rear half of the sides of the cutout can be seen in the drawing below, which shows the driver's hatch mechanism. Although from this perspective it appears as if the upper glacis ends with a flat surface behind the mechanism, the drawing actually does not show the area behind the cylindrical hatch mechanism but rather the side of the driver's cutout in the upper glacis. The glacis armour is to the left of the driver's hatch mechanism, and the right wall of the driver's cutout is to its right, complete with a 10mm anti-radiation lining. Judging by the proportions depicted in the drawing, the side wall of the driver's cutout is a 20mm plate.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-rPqmfA0rSPQ/W2KCJxgfZbI/AAAAAAAAL50/g-khCUyH-X05JOfSiOkdV5vV3K8CEGuBACLcBGAs/s1600/drivers%2Bhatch%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1012" data-original-width="526" height="400" src="https://2.bp.blogspot.com/-rPqmfA0rSPQ/W2KCJxgfZbI/AAAAAAAAL50/g-khCUyH-X05JOfSiOkdV5vV3K8CEGuBACLcBGAs/s400/drivers%2Bhatch%2Bmechanism.png" width="207" /></a></div><div><br /></div><div>Whether the effective thickness declines drastically when the upper glacis is struck from a side angle will depend on the context. Due to the increased impact angle, the protection offered by the upper glacis improves, as does the side aspect of the cutout. While the side aspect of the cutout is undoubtedly thinner than the rest of the upper glacis from this perspective, the increased protection offered by the increased angle may at least provide the side aspect of the cutout with the same or similar protection as the upper glacis from the front. The weakest part of the side aspect is the rear part, which is the top edge of the glacis. This part is significantly weaker, owing to the lack of reinforcement. The only mitigating factor is that it is a smal area.</div>
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Besides that, as illustrated in zone (1), the weakened zone includes an additional area next to the driver's cutout. This is due to a cylindrical hole where an air sampler device for the NBC protection system is fitted, behind the opening and closing mechanism of the driver's hatch. The driver's hatch mechanism itself, situated inside the upper glacis next to the hatch, does not create a weakened zone by itself even though it intersects with the upper glacis armour. The difference in armour protection between the area containing the mechanism and the unaltered upper glacis armour array is more difficult to quantify due to the relatively small size of the mechanism and the fact that the mechanism is constructed from steel, with several telescoping concentric cylinders within that form a nearly solid barrier, so it still contributes to stopping a penetrating projectile. Moreover, it is also worth noting that the cylindrical hole for the air sampler device will also contribute to the weakening of the armour from a side angle, further compounding the lack of reinforcement at this area.</div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEihiQ7piXdS_7b0pYMs6smdIDvR9sm1A41swaHxm8r8bBEsKdMrMIswmfmFvCddtPUwqPooUb3pN6DwuxDQgNtzE4oP4GibuUlifnDOgzbpKjUIHwoFhnhnJSCufBKF-ftRqFVPw1JoqqWmVGuvTpSPBmkgeW11xaDJfq4Kc9HIhxbDjXA3tB0L-VRy3A=s829" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="580" data-original-width="829" height="448" src="https://blogger.googleusercontent.com/img/a/AVvXsEihiQ7piXdS_7b0pYMs6smdIDvR9sm1A41swaHxm8r8bBEsKdMrMIswmfmFvCddtPUwqPooUb3pN6DwuxDQgNtzE4oP4GibuUlifnDOgzbpKjUIHwoFhnhnJSCufBKF-ftRqFVPw1JoqqWmVGuvTpSPBmkgeW11xaDJfq4Kc9HIhxbDjXA3tB0L-VRy3A=w640-h448" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div>
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The dimensions of the weakened zone is not necessarily the same as the dimensions of the driver's periscope area void - the triangular reinforcing wedge in the upper glacis armour in front of the driver's periscope may not only compensate for the reduced LOS thickness, but instead increase the effective armour thickness to a certain extent against APDS and APFSDS ammunition. As such, certain portions of the so-called "weakened zone" are not actually weak when compared to the unaltered upper glacis armour, especially for the earlier armour designs incorporating glass textolite as the interlayer material. This is because the shape of the wedge is such that the thickness of steel increases as the LOS thickness of the upper glacis decreases, thus compensating for the reduction in the thickness of glass textolite. At the apex of the triangular wedge (one third of the height of the weakened zone), the LOS thickness of steel is 390mm. This is nominally enough to resist 120mm APDS rounds and indeed, considering that the unaltered upper glacis armour of the T-72 Ural is only equivalent to 305mm RHA against long rod APFSDS, the driver's periscope "weakened zone" for the T-72 Ural can actually be slightly stronger than the full upper glacis armour array at certain zones against KE threats, although it is undoubtedly still weaker in terms of HEAT resistance.<br />
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Even so, 390mm of solid steel is still more than enough to resist the grenade of an M72 LAW or other grenades with similarly small and light warhead, to list just a few. The resistance of this part of the armour is also higher than the unaltered upper glacis armour in a more nuanced sense due to its flat back surface which would not suffer the same structural shortcomings of a thin 20mm back plate, and as a homogeneous armour block, it avoids the issue of asymmetric forces causing the premature failure of a sloped armour plate. Overall, the dimensions of the weakened zone for a T-72 Ural (relative to the unaltered upper glacis) can be considered to span an area of 530x135mm (0.072 sq.m) - around half of the dimensions of the driver's periscope void itself. To fully understand the magnitude of this figure, it is necessary to take a better look at the total area of the frontal hull:<br />
<br />The projected area of the front hull is 2.08 meters according to <a href="http://gurkhan.blogspot.com/2012/01/blog-post_13.html?utm_source=warfiles.ru">"<i>Возможная Компоновочная Схема Танка</i>" ("<i>Possible Tank Layout Schemes</i>") by S.A. Gusev</a>. Therefore, the void at the driver's periscope area occupies around 7.0% of the total area of the front hull and the actual weakened zone in the case of the T-72 Ural is only 3.4% of the total area. Considering that the area of the upper glacis is approximately 1.48 sq.m and the area of the lower glacis is approximately 0.6 sq.m, the driver's periscope weakened zone seems extremely small, especially when compared to the much larger lower glacis weakened zone on the front of the hull (29% of the total hull area), but again, it must be noted that the location of the driver's periscope at the center of mass of the tank makes it much more vulnerable than its relative size implies.<br />
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The size of the void does not change (0.145 sq.m), but the relative weakness of the driver's periscope area depends greatly on the specific round fired at the tank as well as the specific model of the tank. As the T-72 evolved, the different upper glacis armour designs prompted changes in the internal configuration of the armour in front of the driver's periscope area. For example, while the actual area of the weakened zone on the T-72 Ural is only 0.072 sq.m against 105mm APDS and other threats, the area of the weakened zone on the T-72B against 125mm BM-26 APFSDS is 0.12 sq.m. This area is 5.7% of the total area of the front hull. During live fire testing of the frontal hull armour of a T-72B, it was found that the driver's periscope area weakened zone could be defeated by BM-22 or BM-26 at a distance of 1.7 km at the midpoint of the zone.<br />
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Determining the size of the weakened zone on the lower glacis is somewhat more straightforward although it is still fairly complex in its own right due to the overlapping of the upper glacis composite armour with the lower glacis plate. According to "<i>Возможная Компоновочная Схема Танка</i>", the area of the lower glacis weakened zone that is vulnerable against 100mm BM-8 APDS is 0.33 sq.m, which is 16% of the total area of the front hull. The other 0.23 sq.m is presumably the area where the upper and lower glacis overlap.<br />
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As for the turret, the weakened zones are more numerous than the hull on account of the complex cast construction, although it is clear that the design of the turret can still be considered good. As discussed previously in Part 1 of this article in the section regarding the AZ autoloader, the turret of the T-72 is generally tougher than the front hull armour. This was necessary for the simple fact that most hits land on the turret and not the hull during tank combat, so it is more profitable to distribute a larger share of armour mass to the turret. The size of the turret was also kept to an absolute minimum in order to reduce the probability of receiving a hit, and the teardrop shape of the turret was designed such that the area of the turret projection would remain low from a variety of angles. This was accomplished by the use of an autoloader and ammunition stored in the hull (which is expected to sustain much fewer hits). The area of the turret from the front at a 0 degree angle is 1.7 sq.m, which is smaller than the frontal hull (2.08 sq.m).<br />
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The height of the T-72 turret from the turret ring level up to the top edge of the turret cheek is shown in the photo below to be 380mm. The photo is from the <a href="https://www.facebook.com/t72org/photos/?tab=album&album_id=1652076908337757">T-72.org Facebook group</a>. The height of the turret in this context does not include the height of the turret ring area, so this is not the actual height as measured from the level of the hull roof.<br />
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<a href="https://4.bp.blogspot.com/-2cnnrqV62tk/W2YqNwsHV8I/AAAAAAAAL-s/NJ1SiTiAHcYoj9FXciaUV8xHwBEpqz6lQCLcBGAs/s1600/12006084_1652077578337690_2320124515931494881_n.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="636" data-original-width="960" height="424" src="https://4.bp.blogspot.com/-2cnnrqV62tk/W2YqNwsHV8I/AAAAAAAAL-s/NJ1SiTiAHcYoj9FXciaUV8xHwBEpqz6lQCLcBGAs/s640/12006084_1652077578337690_2320124515931494881_n.jpg" width="640" /></a></div>
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The gap between the hull roof and the turret cheek on all T-72 tank turrets is considered the turret ring weakened zone. This gap has a height of 60mm, as shown by the photo below, taken from the <a href="https://www.facebook.com/t72org/photos/?tab=album&album_id=1652076908337757">T-72.org Facebook group</a>. As the internal turret ring diameter of the tank is 2,162mm, the area of this weakened zone is 0.13 sq.m. The turret ring weakened zone occupies 7.64% of the total area of the turret.<br />
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<a href="https://2.bp.blogspot.com/-O3NLqrRX-OM/W2abGrua-_I/AAAAAAAAL_Q/O-u06avp4n0OHfhe87w0WoBuzpikfwgvgCLcBGAs/s1600/11998827_1652079481670833_349110587450973903_n.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="636" data-original-width="960" height="265" src="https://2.bp.blogspot.com/-O3NLqrRX-OM/W2abGrua-_I/AAAAAAAAL_Q/O-u06avp4n0OHfhe87w0WoBuzpikfwgvgCLcBGAs/s400/11998827_1652079481670833_349110587450973903_n.jpg" width="400" /></a></div>
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The gun mantlet weakened zone is thinner than the turret cheeks, and beginning with the introduction of the "Kvartz" composite turret, the relative weakness of the gun mantlet area became exaggerated as it was still only homogeneous steel, thus making it comparatively more vulnerable to shaped charge attacks. The turret ring area is also just a homogeneous casting, and of a rather low thickness as well. However, it should be understood that the gun mantlet weakened zone still has a formidable thickness of steel. Referring once again to "<i>Возможная Компоновочная Схема Танка</i>", it is reported that live fire testing revealed that the gun mantlet area of the T-72B could be defeated by BM-22 or BM-26 at a distance of 1.65 km. It is known that the armour penetration of these two rounds at a 0 degree impact angle at 2 km is between 420mm RHA to 490mm RHA, depending on the source. Therefore, the thickness of the gun mantlet weakened zone of the T-72B must significantly higher, taking into consideration the reported distance limit of armour defeat (1.65 km instead of 2.0 km). With that in mind, the vulnerability of the gun mantlet area of the T-72B against BM-22 and BM-26 does not necessarily translate to a vulnerability to contemporary 105mm APFSDS or even 120mm APFSDS like DM13 and DM23. Indeed, this so-called "weakened zone" would still be highly resilient to 105mm DM23 and DM33, as well as 105mm M833 and 120mm DM13 and DM23.<br />
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The area of the gun mantlet zone that is vulnerable to BM-26 is 0.29 sq.m, which is 17% of the total area of the turret. The area of the turret ring vulnerable to BM-26 is 0.49 sq.m, which is 29% of the total surface area of the turret. The combined area of the turret roof and the commander's cupola that is vulnerable to BM-26 is 0.26 sq.m, which is 15% of the total surface area of the turret. All taken together, the zones of the 172.10.077SB turret that are vulnerable to BM-26 constitute 61% of the total area. Needless to say, this is highly problematic for a turret that is theoretically immune to not only BM-26 but also much more powerful rounds. Of course, this is a context-specific example and the previous T-72 models do not necessarily have the same weakness when viewed in the appropriate context. For instance, the roof of the T-72 Ural would not be vulnerable to 105mm APDS thanks to its high slope and the physical thickness of steel present at the gun mantlet zone would also be enough for 105mm APDS from certain distances. The proportion of the weakened zones would therefore be much lower.<br />
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The increase in the proportion of weakened zones throughout the evolution of the T-72 can be attributed to two interrelated factors: the appearance of long rod APFSDS and the obsolescent design of the turret itself. It should not be forgotten that the turret of the T-72 is derived from the design of the T-64A turret, which was the direct descendant of the T-64 (Obj. 432) turret that was conceptualized and developed during the late 1950's. At that time, the 105mm L7 had not yet even entered service and contemporary munitions tended to have issues against highly oblique targets. When the new turrets of the T-72A and T-72B succeeded the turret of the T-72 Ural, the increase in protection was mainly focused on the turret cheeks where the composite armour was situated and some other zones saw modest increases in the thickness of steel or minor changes in geometry. No other parts of the turret gained a composite construction. Newer turret designs such as the flatter turret of the T-80U and the welded turret of the T-90A are designed with APFSDS in mind, featuring much flatter roofs that are able to deflect long rod high-elongation APFSDS rounds more readily.<br />
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Of the total area of the silhouette of the tank from the front (4.0 sq.m), the area of the turret occupies a 42.5% share and the hull occupies a 52% share. The remaining 5.5% share is presumably occupied by the tracks.<br />
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The gun mantlet area and the turret ring area have been identified as the most critical weakened zones due to their location at the center of mass of the tank. The main reason is that the gun mantlet area and turret ring area are more likely to be hit due to the preponderance of impacts sustained on the turret compared to the hull whereas the nominally larger lower glacis weakened zone is comparatively less likely to be hit.<br />
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The influence of these weakened zones on the probability of the destruction of the tank is studied in "<i><a href="http://btvt.info/5library/vbtt_1974_06_oslablennie_zoni.htm">Влияние Ослабленных Зон На Поражение Броневой Защиты</a></i>" by A.G. Komyazhenko et al. (<i>Influence of Weakened Zones On Defeat of Armor Protection</i>). The probabilities of armour defeat by 105mm APDS and HEAT fired from an L7 or M68 cannon at the frontal arc of the tank (± 35° for the turret, ± 22° for the hull) were calculated and the effect of increasing the armour protection of the weakened zones up to the level of the base armour were evaluated (for example, bringing the armour of the lower glacis up to the same level as the upper glacis and bringing the armour of the gun mantlet up to the same level as the turret cheeks).<br />
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By referring to Figure 2, it can be seen that the probability of defeat of the tank's armour in its original state with the inclusion of its weakened zones with APDS is around 40% at a distance of 0.5 km, falling to 29% at 1.0 km and 17% at a distance of 1.5 km. The probability of the same with HEAT is around 25% at a distance of 0.5 km, falling to 20% at 1.0 km and around 11% at 1.5 km.<br />
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It was concluded that the greatest reduction in the probability of armour defeat could be achieved with the elimination of the gun mantlet weakened zone. The reduction was 18% for APDS and 12% for HEAT. The second greatest reduction was achieved with the elimination of the turret ring area weakened zone, to the order of 15% for APDS and 12% for HEAT. The elimination of the driver's periscope weakened zone resulted in a reduction of the probability of armour defeat of 12-13% for both ammunition types. Combined, the elimination of all three weakened zones would result in an increase in armour protection of 45% for APDS and 37% for HEAT.<br />
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<h3>
<span style="font-size: large;">WEIGHT GROWTH</span></h3>
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The overall dimensions of the T-72 did not change over time, but as the areal density of the armour increased with each successive model, so did the overall weight of the tanks. It is possible to determine the increase in armour weight of each tank model with only a small margin of error by referring to the increase in the overall weight.<br />
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However, it is important to note that a direct comparison of combat weights between T-72 models will not provide a completely accurate reflection of the actual gain in armour weight. For the sake of accuracy, it is necessary to look at the empty weights of the tanks. The empty weight is defined as the weight of the tank with all of its equipment and weapons installed plus its full complement of tools and spare parts but without fuel, ammunition or crew.<br />
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The three-man crew weigh a little over 210 kg in total, assuming an average weight of 70 kg for each crew member, and when fully topped up, the T-72 carries 1,200 liters of diesel fuel which translates to a weight of 1,032 kg. For a T-72 Ural, the weight of a full ammunition load (including both 125mm and small arms) is approximately 1.25 tons. A T-72A has an increased capacity of 44 rounds of main gun ammunition, so the weight of a full combat load increased to around 1.4 tons. The T-72B carried 45 rounds of main gun ammunition, so the weight of a full combat load was around 1.43 tons. From this, it is possible to estimate the empty weights of all three primary T-72 models.<br />
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<ol>
<li>T-72 Ural (Object 172M) - combat weight of 41 tons and an empty weight of 38.6 tons. </li>
<li>T-72A (Object 172M-1) - combat weight of 41.5 tons and an empty weight of 39.0 tons.</li>
<li>T-72B (Object 184) - combat weight of 44.5 tons with Kontakt-1 or Kontakt-5 ERA, and a combat weight of 43 tons without ERA. It had an empty weight of 41.6 tons.</li></ol>
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With the upgrade from the T-72 Ural to the T-72A, the combat weight rose by 0.5 tons but the actual increase in weight from additional armour was 0.4 tons. From the T-72A to the T-72B, the gain in the empty weight was a whopping 2.6 tons, but the actual gain in armour weight was slightly less because like the T-72A obr. 1983, the T-72B featured additional anti-radiation cladding and had an additional stowage bin on the turret. The actual gain in armour weight was approximately 2.5 tons.</div><div>
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<br />When considering only the empty structure with the integral armour, the weight of the T-72 Ural hull is 13,381 kg and the turret weighs 7,085 kg, for a nominal overall weight of 20,466 kg. The weight of the T-72B hull is 15.3 tons and the turret weighs 8.1 tons, for an overall weight of 25.4 tons according to the journal article "<i>Объемно-Массовый Анализ Защиты Серийных Танков</i>". The proportion of armour by weight therefore ranges from 50% (T-72) to 57% (T-72B) for a combat-loaded tank or 53% (T-72) to 61% (T-72B), if the empty weight is used. For the original T-72, the armour weight proportion was largely the same as earlier all-steel tanks, which invariably had no more than 50% of armour weight, but by the introduction of the T-72B and its deeply upgraded armour, this had totally changed. If the ERA weight is taken into account as part of the armour of the tank, then the T-72B has an armour weight proportion of 58.47% when combat loaded. This is more meaningful for T-72B models equipped with Kontakt-5 than for those with Kontakt-1, as the Kontakt-5 panels on the upper glacis are structurally integral to the hull.</div><div><br /></div><div>
It is worth noting that the weight proportion of the turret is very high relative to the hull, despite the fact that all T-72 models had two-man turrets. Looking at the Yugoslavian M-84 as a surrogate for a late T-72 Ural model, as it was effectively a locally designated T-72M tank, the total weight of the turret is 15 tons and the total weight of the hull is 27 tons. In general, the weight of the turret on all T-72 models is around 55% of the hull weight, both empty and combat loaded.</div><div><br />
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<h3>
<span style="font-size: large;">PROTECTION CRITERIA</span></h3>
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The Soviet criteria for armour protection has a specific definition that distinguishes it from the protection criterion used by foreign armies. Under the Soviet definition, the term "кондиционного поражения" or "nominal defeat" is used. This term is used to describe the defeat of the tank armour by the breakdown of its structure, achieved by exceeding the limits of its strength. It is equivalent to a partial penetration under the definitions of other testing standards. For example, if spall failure is detected, it is indicative that the shock energy from an impacting projectile was high enough to overcome the tensile strength of the armour material. However, spall must not be ejected from the armour. Similarly, if ductile fractures are detected, it is indicative that another form of structural failure has occurred. From external observation, the detection of nominal armour defeat can be carried out by identifying surface cracks or cracked bumps on the back surface of the armour plate.<br />
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This is different from perforating the armour plate, for which the term "сквозное поражение" (perforating defeat) is used. The velocity limit of armour perforation, "пределе сквозное поражение", is expressed as "Vпсп". The definition of the limit of armour perforation in Soviet and Russian technical literature is the same as in all other works on the subject. <a href="http://www.longrods.ch/perflimit.php">The perforation limit</a> of a penetrator is the maximum armour thickness where breakthrough is possible for a given impact velocity. This type of armour perforation yields a very weak post-perforation effect. After achieving breakthrough, the residual penetrator has almost no energy left, so it either sticks to the exit crater or falls to the ground and does not contribute to damaging the internal equipment or crew of a tank, and the energy of the spall ejected from the back surface of the armour is also very low. Due to this, it can be referred to as initial perforation, which distinguishes it from more energetic cases of armour perforation where a large amount of residual energy is retained after breaking through the armour.<br />
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In the textbook "<i>Частные Вопросы Конечной Баллистики</i>" <span style="font-family: "times new roman";">(</span><i style="font-family: "times new roman";">Particular Questions of Terminal Ballistics</i>), it is stated that the rule for converting from the limit of nominal armour defeat to the limit of armour perforation is to subtract 10mm of RHA from the physical armour thickness. To do the opposite, the reverse is applied. For example, if a KE round can achieve nominal defeat on 150mm RHA sloped at 60 degrees, it only achieves armour perforation on 140mm RHA sloped at 60 degrees. According to the textbook, the 10mm RHA thickness was determined by practical experience.<br />
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It is also stated that for composite armour, 20mm of additional physical thickness on the back plate is required to ensure a transition from guaranteed armour perforation to nominal armour defeat. For example, if a hypothetical two-layer spaced armour target is guaranteed to be perforated by a long rod penetrator, adding another 20mm of physical thickness to the back plate will prevent a guaranteed penetration and instead leave the armour vulnerable only to nominal defeat. The inverse is also true. If the same spaced armour can only be nominally defeated by a long rod penetrator, reducing the back plate thickness by 20mm will guarantee that the penetrator perforates the armour.<br />
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It is important to mention that by definition, nominal defeats can only occur for finite thickness plates. A semi-infinite thickness armour block effectively prevents any back surface failure by its nature, and hence, it is impossible for a nominal defeat to be achieved. As such, it is fundamentally meaningless to compare the thickness limit of nominal defeat with thickness limit (penetration depth) of a KE penetrator into semi-infinite steel.<br />
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Along with nominal defeat and initial perforation, another type of armour defeat is the so-called "guaranteed perforation". The guaranteed perforation is defined as the minimum armour thickness that can be perforated by the given penetrator at the given velocity. It can also be defined as the minimum velocity where a given thickness of armour can be perforated. Guaranteed armour perforation is usually accompanied by strong post-perforation effects.<br />
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Note that the three distinct types of armour defeat - nominal defeat, initial perforation, guaranteed perforation - are all important metrics and the relationship between each type must be understood to make sense of how effective thickness is calculated for tank armour.<br />
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The photo on the left below (<i>а</i>) shows the condition of an RHA plate after being subjected to an impact from an APFSDS round at the velocity of its nominal defeat. The stress exceeded the tensile strength limit of the armour material which resulted in a spall failure, but without the ejection of spall from the plate. Only a cracked bump has formed on the back surface of the plate. The photo on the right below (<i>б</i>) shows an example of full armour perforation where fragments are ejected from the armour plate, which requires a higher impact velocity to achieve. The armour obliquity is 30 degrees in both examples.<br />
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If the limit of nominal defeat is reached ("пределе кондиционного поражения"), this is enough for the armour to be considered defeated, and the impact velocity at which the reference threat achieves this is referred to as the velocity limit of nominal defeat, "Vпкп" (Vpkp).<br />
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When evaluating multilayered tank armour, it is very important to understand that its effective thickness will be different depending on the type of armour defeat. Achieving nominal defeat requires significantly less kinetic energy than achieving initial perforation. On page 553 of the textbook "<i>Частные Вопросы Конечной Баллистики</i>", it is stated that in practice, the difference between nominal defeat and initial perforation when testing multilayered armour is 10mm of additional back plate thickness (physical thickness). Similarly, the difference between nominal defeat and guaranteed perforation is 20mm of additional back plate thickness (physical thickness). This can be used as a guideline to differentiate the effective thickness of armour into several different categories, and it also applicable to finite thickness homogeneous armour.<br />
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As an example, according to results obtained using the Lanz-Odermatt calculator, an ideal 105mm M111 APFSDS round has a perforation limit of 160mm RHA (hardness of 270 BHN) sloped at 60 degrees (320mm RHA in LOS thickness) at an impact velocity of 1,359 m/s, corresponding to a range of 2 km. However, in official Soviet era technical documentation and in modern Russian textbooks, M111 is credited with a penetration of 170mm RHA sloped at 60 degrees at a range of 2 km, or a LOS thickness of 340mm RHA. This was determined with live fire tests. The difference between the Soviet figure and the Lanz-Odermatt figure can be fully explained by the fact that the Soviet penetration figure was obtained under the nominal defeat criteria, whereas the Lanz-Odermatt calculation determines the limit of initial perforation. The difference of 20mm RHA in defeated thickness (10mm at 60 degrees) corresponds with the guideline given in the textbook.<br />
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Note that the ideal penetrator model used for the Lanz-Odermatt calculation has a normalized working length of 295mm and it uses a weighted average penetrator diameter of 29.8mm. The three armour-piercing cylinders at the tip of the projectile were normalized into additional working length for the penetrator. The same method of normalizing a non-uniform rod shape into a right cylindrical rod <a href="http://www.longrods.ch/wlength.php">is used by Willi Odermatt as part of the Lanz-Odermatt perforation calculator</a> to convert a frustum into additional working length for the penetrator.<br />
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<h3>
<span style="font-size: large;">AMMUNITION TYPES</span></h3>
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Aside from the three main types of armour defeat, it is also necessary to note that in many cases, the effective thickness figures reported for different tanks often cannot be compared directly due to the use of different ammunition during tests. This is a particularly noteworthy issue when comparing Soviet tanks to foreign tanks with composite armour, as the ammunition used by the respective nations differed wildly.<br />
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In 1979, the first next-generation NATO tank - the Leopard 2 - entered service. It was followed by the M1 Abrams which was type classified in 1981. The KE protection requirement for these two tanks were formed using composite APFSDS ammunition as reference threats and not monobloc rods.<br />
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In the U.S, the XM579E4 round with a tungsten alloy penetrator was used to simulate a future Soviet 115mm gun threat, which was the reference threat for the the KE protection requirement for the M1 Abrams. The penetrator had a teardrop shape that it shared with the later 105mm M735 round, and it represented a level of technology far below that of long rod penetrators. Similarly, the KE protection requirement of the Leopard 2 was formed using DM13 APFSDS ammunition fired from a domestic 105mm Rheinmetall smoothbore gun as the reference threat. The DM13 round was not a long rod penetrator either, as it had a composite construction consisting of two partially jacketed tungsten alloy penetrators with low aspect ratios. It is not possible to compare the effective thickness figures obtained using XM579E4 with those obtained with DM13, let alone with Soviet APFSDS ammunition due to the massive differences in penetrator design.</div>
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<h3>
<span style="font-size: large;">SUMMARY</span></h3>
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With all this in mind, it also important to understand that the effective thickness of composite armour is implicitly contextual. A cautionary statement is given in the conclusion of the research paper "<a href="http://ciar.org/ttk/mbt/papers/symp_19/TB151159.pdf"><i>Definition and Uses of RHA Equivalences for Medium Caliber Targets</i></a>":<br />
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"<i>The protection level of a threat vehicle cannot be defined by one RHA-e value; it depends on several factors: penetrator material, penetrator geometry, target configuration, RHA penetration, and the method and RHA baseline used.</i>"<br />
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To ensure that the conclusions reached in this article are as accurate as possible, the armour of each T-72 model is always evaluated within a specific context unless generalizations are valid, and the threats for each effective thickness value given are always specified.<br />
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As for the definition of "effective thickness" itself, a standard scientific method is used in each case. Given that only the armour itself will be evaluated, the primary metric for rating the effectiveness of the armour is its ability to resist initial perforation by a specific penetrator or type of penetrator. For this, the velocity limit of initial perforation (and the range corresponding to the velocity) is the main concern. To determine the effective thickness of the wide variety of composite armour designs implemented in the T-72 series, the limit of initial perforation against the armour is compared with the limit of initial perforation against RHA placed at the same angle, which may be flat, as in the case of some parts of the turret, or may reach 68 degrees, as on the upper glacis. Based on Soviet studies and modern Russian textbooks, this method was used and is appropriate for the purpose. It is also the method recommended in the research paper "<a href="http://ciar.org/ttk/mbt/papers/symp_19/TB151159.pdf"><i>Definition and Uses of RHA Equivalences for Medium Caliber Targets</i></a>":<br />
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"<i>The final use of the RHA-e should dictate which method is used to define the protection level. If the final use is the perforation range, the range at which the target is just perforated, the V<span style="font-size: xx-small;">L</span>* and the perforation baseline should be used.</i>"<br />
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*Defined in the research paper as the velocity at which the given finite thickness RHA is barely perforated (initial perforation).<br />
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<span style="font-size: large;">OBJECT 172 SERIES (172M, 172M1, 172M-1)</span></h3><div><span style="font-size: large;"><br /></span></div><div><span style="font-size: large;"><div class="separator" style="clear: both; font-size: medium; text-align: center;"><a href="https://1.bp.blogspot.com/-a1xc6TtB-W8/XnHSqRzZjUI/AAAAAAAAQTY/BS7SQIdXOa4aWgHs_AGukqcCC6aOtjsJQCLcBGAsYHQ/s1600/early%2Bural.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="357" data-original-width="450" height="316" src="https://1.bp.blogspot.com/-a1xc6TtB-W8/XnHSqRzZjUI/AAAAAAAAQTY/BS7SQIdXOa4aWgHs_AGukqcCC6aOtjsJQCLcBGAsYHQ/s400/early%2Bural.jpg" width="400" /></a></div><br style="font-size: medium;" /><br style="font-size: medium;" /><span style="font-size: medium;">The T-72 Ural (Object 172M), which entered service in 1973 and began mass production in 1974, inherited the hull upper glacis armour of the T-64A obr. 1969, and the turret was a homogeneous steel casting with a weld-on turret roof. The all-steel turret was closely based on the turret of the T-64A but differed somewhat in the shape of the frontal profile and most of all in the shape of the back half, as it had a distinctive step between the almost-flat rear armour and the heavily sloped roof to house the AZ autoloader ammunition lifter and rammer mechanisms.</span><br style="font-size: medium;" /><br style="font-size: medium;" /><br style="font-size: medium;" /><div class="separator" style="clear: both; font-size: medium; text-align: center;"><a href="https://1.bp.blogspot.com/-BAFMjjxijxM/XnHQS3mt4iI/AAAAAAAAQTQ/kws_GIrlHGoOjglNpGL9JGFaIjt6LKGZwCLcBGAsYHQ/s1600/t-72%2Bural%2Barmour%2Bscheme.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="435" data-original-width="1105" height="250" src="https://1.bp.blogspot.com/-BAFMjjxijxM/XnHQS3mt4iI/AAAAAAAAQTQ/kws_GIrlHGoOjglNpGL9JGFaIjt6LKGZwCLcBGAsYHQ/s640/t-72%2Bural%2Barmour%2Bscheme.png" width="640" /></a></div><div><br /></div></span></div>
<h3 style="text-align: left;">
<span style="font-size: large;">80-105-20 UPPER GLACIS ARMOUR</span></h3></div><div>
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The original upper glacis armour for the Object 172M, or T-72 "Ural", is a three-layer composite consisting of a 105mm layer of glass textolite sandwiched between an 80mm RHA front plate and a 20mm RHA backing plate. The total thickness is 205mm to the normal. The upper glacis is angled at 68 degrees from the vertical axis, producing a total LOS thickness of 547mm. A T-72 model with this armour array can be identified by the presence of four anti-ricochet ribs in front of the driver's periscopes, with three small ribs and one large rib. The number of ribs is an excellent identification feature as it is often possible to see the outlines of the ribs in old low quality photos, particularly photos in digitized documents where the excessive contrast would wash out most other details. The majority of export-model T-72 tanks were built with this upper glacis armour.<br />
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<a href="https://1.bp.blogspot.com/-8aAtgv7mD_o/XndSPyuudxI/AAAAAAAAQaQ/E47ze2uZycAd7_TDPyCJsKnJ-Ype6eGAACLcBGAsYHQ/s1600/t-72%2Bural%2Bin%2Bditch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="461" data-original-width="582" height="316" src="https://1.bp.blogspot.com/-8aAtgv7mD_o/XndSPyuudxI/AAAAAAAAQaQ/E47ze2uZycAd7_TDPyCJsKnJ-Ype6eGAACLcBGAsYHQ/s400/t-72%2Bural%2Bin%2Bditch.png" width="400" /></a></div>
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To form the 105mm glass textolite layer, two glass textolite plates were pressed together. Some publications mention that the 105mm glass textolite interlayer was split evenly into two 52.5mm layers. According to Rolf Hilmes, the 105mm glass textolite interlayer was split into 60mm and 45mm plates as shown in the drawing below, although it is worth mentioning that the photo itself does not support his data. Each layer is a collection of multiple smaller panels of equal dimensions, as shown in cross sections of not only T-72 tanks, but also T-64s and T-80s but may be single large panels. It is quite possible that in the USSR, the glass textolite plates were produced in equal thicknesses whereas tanks produced under licence in Warsaw Pact states or other foreign manufacturers used glass textolite plates of two different thicknesses.</div><div>
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<a href="https://1.bp.blogspot.com/-eDTXvf0mC1k/WtiKbLu2BjI/AAAAAAAALeQ/FSri5d6SQ-UzrCgboyD-y_Fchvd73wnJwCLcBGAs/s1600/t-72%2Barmor.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="548" data-original-width="1286" height="272" src="https://1.bp.blogspot.com/-eDTXvf0mC1k/WtiKbLu2BjI/AAAAAAAALeQ/FSri5d6SQ-UzrCgboyD-y_Fchvd73wnJwCLcBGAs/s640/t-72%2Barmor.png" width="640" /></a></div>
<div><br /></div><div><br /></div><div>The glass textolite interlayer is held in place mainly by its placement between the steel front plate and steel back plate, both welded to the hull structure. During assembly of the complete tank hull, the 80-105-20 array is first assembled as a self-contained sandwich before welding to the tank hull belly, side, and roof plates. Complete armour arrays can be transported individually without needing to keep the layers clamped together with external means. This is provided by the pre-assembly of the lower glacis to the upper glacis array as part of a single front hull block, and by steel studs which pass through the glass textolite interlayer, securing the interlayer and the steel back plate to the front plate. The front end of each stud is welded to the 80mm front plate, and the rear end is welded to the 20mm back plate. It can be surmised that during assembly, the front plate has these studs fitted, the glass textolite interlayer is slotted over them, and then the back plate is secured by welding it to the studs and to the reinforcing structure in front of the driver's cutout. </div><div><br /></div><div>These studs appear to be concentrated around the zones of the armour surface which face empty space, which, in this case, is the driver's station and spaces accessible by the driver, such as cuts in the fuel tanks. Zones which are not secured by steel studs coincide with the spaces occupied by fuel tanks, on both sides of the driver's station. The front hull fuel tanks are not directly braced against the upper glacis, and there is a certain amount of clearance between the fuel tank and the back surface of the upper glacis, ensured by steel spacers screwed onto the upper glacis back plate just above the joint with the lower glacis. As such, the fuel tanks offer no structural support to the 20mm back plate, but the consequences of not limiting the bulging of the back plate at these zones is less severe than in front of the driver.</div><div><br /></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEhjBhxOIsU-EgpTlIAkwYIm2XM6nptgwe39cqYDKOFoh0qxzZHEgTymBqc2oUFEBkjkv4R_M6GnowxcAXcc5qmkaCLsDEP0m54mMI0KYZ1dw9g_ZUHgFKM9mTGbEdIYfmcIZCv263VLAmJ1qehFmrpH7ieFrPWE52x1-oHN9OQqXgCVXT4PBzkXjp1oXg=s2048" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="966" data-original-width="2048" height="302" src="https://blogger.googleusercontent.com/img/a/AVvXsEhjBhxOIsU-EgpTlIAkwYIm2XM6nptgwe39cqYDKOFoh0qxzZHEgTymBqc2oUFEBkjkv4R_M6GnowxcAXcc5qmkaCLsDEP0m54mMI0KYZ1dw9g_ZUHgFKM9mTGbEdIYfmcIZCv263VLAmJ1qehFmrpH7ieFrPWE52x1-oHN9OQqXgCVXT4PBzkXjp1oXg=w640-h302" width="640" /></a></div><br /><br />
It is possible to determine the thickness of the front plate by measuring it at the joint between the upper glacis and the lower glacis. The photo below, taken from an album on the <a href="https://www.facebook.com/t72org/photos/?tab=album&album_id=1652076908337757">T-72.org Facebook group</a>, shows that the front plate is indeed 80mm.<br />
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<a href="https://1.bp.blogspot.com/-uAgPL9hdSeY/XoB-mt0yDFI/AAAAAAAAQf0/e2FV907tw4M0yKuvlhof8g231tqjx3aaACLcBGAsYHQ/s1600/lower%2Bglacis%2Bview.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="636" data-original-width="960" height="265" src="https://1.bp.blogspot.com/-uAgPL9hdSeY/XoB-mt0yDFI/AAAAAAAAQf0/e2FV907tw4M0yKuvlhof8g231tqjx3aaACLcBGAsYHQ/s400/lower%2Bglacis%2Bview.jpg" width="400" /></a></div>
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The areal density of the armour array is 2,616 kg/sq.m, and its weight is equivalent to 333mm of steel. With this information, it is possible to determine the effective thickness of the armour by finding the mass efficiency (ME) coefficients for various threats.<br />
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<h3>
<span style="font-size: large;">BRIEF HISTORY</span></h3>
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The 80-105-20 armour design was developed by NII Stali research institute in the early 1960's, and work was completed in 1962. <a href="http://www.niistali.ru/about-company/about-nii-stali/etapy-puti.php">It is stated on the NII Stali website</a> that in 1962, the institute developed the world's first composite armour with an anti-shaped charge filler for the T-64 tank.<br />
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The first appearance of this armour was not on the T-64, but on the Object 167M developed at UKBTM which was informally referred to as the "T-62B". A technical drawing of the Object 167M, dated May 1962, shows the familiar 80-105-20 armour array, but with some notable differences. The drawing shows that the armour is sloped at 68 degrees and it has a cutout to accommodate the driver's periscopes, but the glass textolite layer is depicted as a single large plate and the armour lacks a reinforcing steel block in front of the driver's periscopes to compensate for the reduced armour thickness. Nevertheless, the most important feature - the layout - is clearly 80-105-20.<br />
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<a href="https://1.bp.blogspot.com/-KM6cHfw7Rms/Xn8FXGih8QI/AAAAAAAAQd4/qyyhqcS-ppwG7dZhrbXgSCVJNwMaFtIJQCLcBGAsYHQ/s1600/object%2B167m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="557" data-original-width="1539" height="230" src="https://1.bp.blogspot.com/-KM6cHfw7Rms/Xn8FXGih8QI/AAAAAAAAQd4/qyyhqcS-ppwG7dZhrbXgSCVJNwMaFtIJQCLcBGAsYHQ/s640/object%2B167m.png" width="640" /></a></div>
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Prior to the Object 167M, the upper glacis armour of its parent design the Object 167 was a 100mm RHA plate sloped at 60 degrees, practically identical to that of the T-62 and T-54 preceding it. However, even though the T-72 used many technologies inherited from the Object 167M, its hull was ultimately derived from the T-64A which also used the 80-105-20 upper glacis armour. Despite the availability of the 80-105-20 armour design in 1962, the T-64 series only began to implement this armour after undergoing an evolutionary process over a four-year span from 1960 to 1964. In 1960, the preliminary sketch of the Object 432 featured an all-steel hull with an 80mm upper glacis plate, sloped at 68 degrees.<br />
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<a href="https://1.bp.blogspot.com/-uzCZ7VzUiG8/Xn8nplDRJyI/AAAAAAAAQeg/qWdXMD5vYE4nOHzjxiwrXaP5WuLQmNzcwCLcBGAsYHQ/s1600/432%2Bpreliminary%2B1960.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="288" data-original-width="462" height="248" src="https://1.bp.blogspot.com/-uzCZ7VzUiG8/Xn8nplDRJyI/AAAAAAAAQeg/qWdXMD5vYE4nOHzjxiwrXaP5WuLQmNzcwCLcBGAsYHQ/s400/432%2Bpreliminary%2B1960.png" width="400" /></a></div>
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In 1961, the design was further refined with the main emphasis on increased protection. The new Object 432 design incorporated a 140mm glass textolite layer behind the 80mm upper glacis plate, forming a two-layer composite armour. When the Object 432 entered low rate production two years later as the T-64 obr. 1963, it had undergone numerous changes but the 80-140 composite armour design was kept. The 140mm glass textolite plate, which had a number of pre-drilled holes, was installed by fitting it over metal studs welded to the 80mm front plate and then securing it in place with fasteners. The fasteners can be seen embedded in recesses in the back surface of the glass textolite plate in interior photos from the driver's station.<br />
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<a href="https://1.bp.blogspot.com/-bLI-vpSZiWE/Xn8RvZfR-aI/AAAAAAAAQeI/OaJN82aTA68gVX_zF80Z-fntwpvJIn_pwCLcBGAsYHQ/s1600/obj%2B432%2B1963%2Bupper%2Bglacis.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="384" data-original-width="1600" height="152" src="https://1.bp.blogspot.com/-bLI-vpSZiWE/Xn8RvZfR-aI/AAAAAAAAQeI/OaJN82aTA68gVX_zF80Z-fntwpvJIn_pwCLcBGAsYHQ/s640/obj%2B432%2B1963%2Bupper%2Bglacis.png" width="640" /></a></div>
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The armour design was only upgraded to the 80-105-20 design in 1964 and it was implemented in production with T-64 obr. 1964 tanks. By this time, the armour had been fully developed into its final configuration with an additional reinforcing steel block in front of the driver's cutout.</div>
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From this timeline of developments, it can be inferred that the 80-140 armour was probably an early effort developed in 1961 by NII Stali before transitioning to the final 80-105-20 design in 1962. In the T-64 series, it is likely that the 80-140 armour was retained until 1964 for no other reason than to avoid another redesign in order to expedite the beginning of production. </div>
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According to the page fragment below, the original requirements for the new prospective medium tank of the USSR dictated that it had to be immune to 100mm armour piercing shells fired at 1,000 m/s (muzzle velocity for 100mm AP shells fired from D-10T is 895 m/s) and 105mm subcaliber shells fired from the American M68 cannon at a distance of 1,000 meters. The armour was also required to be immune to 85mm HEAT as well as 105mm HEAT fired from an M68 cannon. However, these figures were corrected on the very same page. Instead, the armour was required to be immune to 105mm subcaliber shells at 500 meters and 115mm HEAT shells, while the requirement to resist 105mm HEAT shells was crossed out.<br />
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It is noted in the margins that the data on the performance of the M68 was estimated and was subject to change, which may explain the revision of the protection requirement from immunity from 1,000 m to immunity from 500 meters. In the main table, it is written that the required resistance level of the armour was ~330mm RHA against KE threats and ~450mm against HEAT threats. The only subcaliber ammunition available for the 105mm L7 at that time was APDS with tungsten carbide cores, so this was the reference KE threat used at the time.<br />
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To determine the actual value of the armour against KE attack and the context of the protection values given in various authoritative sources, it is necessary to have a deep understanding of the working principles of the armour as a system and to find out its physical characteristics. The characteristics of the interactions between the armour and shaped charge jets will also be studied as part of this comprehensive examination.<br />
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<h3>
<span style="font-size: large;">GENERAL FEATURES OF NOTE</span></h3>
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The high obliquity of the glacis armour presents a mixture of advantages and disadvantages, but the composite nature of the array makes the true value of the armour much more nuanced than it appears at first glance.<br />
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The most obvious advantage of steep angling is that the penetration power of earlier APDS rounds will be drastically reduced and some HEAT warheads may even fail to fuse on impact, but there may be side effects stemming from the ability of long rod penetrators to perforate more armour at higher angles up until the critical ricochet angle, which is usually around 80 degrees and above and depends on the aspect ratio of the penetrator rod as well as the shape of its tip. It is known that the higher penetrative power of long rod penetrators on high obliquity plates is caused by the asymmetry of forces acting on the back of the plate as the penetrator passes through, but the impact and breakout effects for a finite thickness plate are often ignored. In truth, the lower effective thickness of a steel plate at high obliquity is only directly relevant for the steel back plate of a composite armour array, as that back plate must absorb the remnants of a penetrator without failing whereas the other plates in an armour array are usually designed to fail in such a way that the penetrator is damaged in the process.<br />
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Against HEAT warheads, the principle benefit of the high slope of the armour is that some warheads may not detonate properly. During the famous Yugo tests, the 90mm M431 HEAT shell with the M509A1 PIBD fuze was demonstrated to have a very high probability of failing to detonate against the 60-degree upper glacis of the target tank (a T-54) when the tank was angled 20 degrees sideways. Using the <a href="https://html2-f.scribdassets.com/53jsqnovi83p23t5/images/91-ec3900f32a.jpg">compound angle table on page 47 of <i>WWII Ballistics: Armor and Gunnery</i></a>, we find that a 60 degree vertical slope and 20 degree horizontal slope creates a compound angle of 62 degrees. The 68 degree slope of the T-72 upper glacis exceeds this in excess.<br />
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Although 90mm guns were obviously obsolete in the face of the T-72, the newer 105mm M456A2 HEAT shell <a href="https://www.gd-ots.com/wp-content/uploads/2017/11/105mm-M456A2-HEAT-T.pdf">also uses the M509A1 PIBD fuze</a>, so the results of the Yugo tests imply that M456A2 will also struggle to properly fuze on the upper glacis of the T-72. If a shaped charge succeeds at detonating on the upper glacis, it can be handled by the composite armour.<br />
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Quite interestingly, it appears that the high obliquity of the upper glacis also helps reduce the effectiveness of HESH (High-Explosive Squash Head) or HEP (High Explosive Plastic) rounds. Based on this <a href="https://i.imgur.com/EYb8T43.jpg">document fragment</a> shared in <a href="http://tankarchives.blogspot.com/2018/05/compare-and-contrast.html">this Tankarchives post</a>, it appears that HESH shells are most effective at an impact angle of 45 degrees but drop off sharply down to 0mm of penetration at 70 degrees. This most is most likely due to a failure to fuze, but even if the round detonates, it appears that it may not even be enough to cause the 80mm or 60mm steel front plate of the T-72 composite armour to spall. Of course, the low velocity and arced trajectory will reduce the relative impact angle of the round if it is used at long range, but even so, it is clear that the combination of high obliquity and composite layering makes the upper glacis armour extremely resilient to HESH attack. It is preferable to avoid detonating the shell at all, of course, because the power of the explosion can still have some physiological and psychological effects on the crew even if they are not physically harmed by spalling. The explosion may also damage other parts of the tank (periscopes, sights) and render it incapable of normal operation, thus knocking out the tank without actually defeating its armour.<br />
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If the HESH round detonates, the high blast attenuation offered by composite armour would be beneficial to the survival of the crew. By placing multiple layers of materials with drastically different densities and mechanical properties (including sound speed) in the path of the blast waves, the effectiveness of the array in attenuating explosions is significantly improved as compared to homogeneous materials of the same weight. This was quite important seeing as HESH shells were a British favourite during the Cold War. </div><div><br /></div><div><br />A significant point of interest regarding the upper glacis design is the effect it has on top-attack munitions. The large thickness of the armour and the short length of the hull roof above the driver's compartment were the main factors that necessitated a cutout in the armour to accommodate the driver's head and his periscope, leading to the creation of this weakened zone, but this also meant that from above, almost the entire front hull projection was protected by composite armour to varying extents. From above, the relative obliquity is only 22 degrees, so the LOS thickness of armour does not exceed 221mm, but to a submunition with an EFP warhead or a small shaped charge, this is a considerable level of protection. A significant thickness of composite armour exists even at the area where the armour is joined to the hull roof. The overhang of the turret cheeks above the hull roof is also worth mentioning as a protection factor against top-attack bomblets, but for earlier models of the T-72, this consideration is only marginal.</div><div><br /><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-7WxzBUTHaoo/X21j4zvZrnI/AAAAAAAARqE/C4Jk9_6lUpoi8g0k5ze832jee_aowapogCLcBGAsYHQ/s3048/top%2Battack%2Bon%2Bupper%2Bglacis.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1031" data-original-width="3048" height="216" src="https://1.bp.blogspot.com/-7WxzBUTHaoo/X21j4zvZrnI/AAAAAAAARqE/C4Jk9_6lUpoi8g0k5ze832jee_aowapogCLcBGAsYHQ/w640-h216/top%2Battack%2Bon%2Bupper%2Bglacis.gif" width="640" /></a></div><br />
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The majority of interest lies in how the armour interacts with the two major threats - KE attack and HEAT attack. Almost all of the amateur attempts to distill the relative RHA efficiency factor of glass textolite use the thicknesses of each individual component of the armour as given, and almost all of these attempts are fundamentally incorrect.<br />
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Rather, the actual effectiveness of any composite armour (not just the armour of the T-72) in terms of RHA can only be determined by actual live fire testing of specific rounds against the armour or a simulacrum of it to determine its mass efficiency. The velocity limit of armour perforation for the composite armour must be recorded and compared to the velocity limit of the same round for a homogeneous RHA block set at the same obliquity. If round 'x' can successfully perforate a composite armour array at a minimum velocity of 1,500 m/s and round 'x' can also perforate 600mm RHA at a minimum velocity of 1,500 m/s, then the composite armour is equivalent to 600mm RHA against that specific round. However, this is only true for round 'x'. Other rounds with the same penetration power on a homogeneous RHA block may fail against the same composite armour array or perforate it at lower velocities. As such, some degree of uncertainty is always present in any estimation of armour effectiveness, even in the detailed examinations that are presented in this article.<br />
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<h3>
<span style="font-size: large;">BREAKDOWN OF ARMOUR MATERIALS</span></h3>
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Each element of a composite armour array has its own special purpose such that all of the individual layers added together would be more than the sum of its parts.<br />
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Like the T-64A, T-62 and T-54/55 tanks preceding it, the hull of the T-72 was constructed from rolled <a href="https://vdocuments.site/catalogue-of-plates-new1.html">42 SM medium hardness RHA steel</a>. The minimum yield strength of 42 SM steel is 850 MPa, the tensile strength is 1,050 MPa and the elongation limit is 7%. The specified range of hardness for the 42 SM grade is 280-340 BHN, and it can be processed into plates with a thickness ranging from 40mm to 120mm. When processed into 80mm plates for the thickest sections of a T-72 hull, the hardness of 42 SM plates is moderately high for a medium hardness steel.<br />
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In the study "<i><a href="http://btvt.info/5library/vop_1976_btk1.htm">О Путях Повышения Противоснарядной Стойкости Катаной Стальной Брони Для Танков</a></i>" (<i>About the methods of increasing the ballistic resistance of rolled steel armour for tanks</i>), it is stated that increasing the hardness of serially produced medium hardness steels for tanks (42 SM, 52 S) to 340 BHN does not increase the resistance of the steel because it results in a reduction in ductility and toughness. Moreover, medium hardness steel treated to this hardness also exhibits unsatisfactory resistance at a temperature of -40°C in some cases. As such, the hardening of 42 SM steel to 340 BHN was not practiced. In production, 42 SM steel plates are hardened to 302-311 BHN. Both the 80mm front plate and 20mm back plate of the 80-105-20 armour array are constructed from RHA of this specification.<br />
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It is interesting to note that at least one known Chinese armour simulator used to represents a T-72 threat assumed that the 20mm steel back plate was made from high hardness steel. Note that the front plate was assigned a hardness of 300 BHN and the back plate was assigned a hardness of 450 BHN. The thickness of the glass textolite interlayer is slightly thinner and the composition used is not exactly identical.<br />
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Other than the two steel layers in the 80-105-20 armour array, there is the glass textolite interlayer. It is an integral component of the composite armour design and functions mainly as a low-density filler to resist shaped charge jets. Indeed, it has been described in some Soviet engineering studies as an anti-shaped charge filler.<br />
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Glass textolite is a material consisting of layered sheets of glass textile bonded by a resin and pressed together. Glass textolite is not the same as fiberglass, because glass textolites are manufactured using laminated sheets of glass matting bonded together by resin whereas fiberglass is manufactured using continuous glass fibers or chopped strands suspended in resin. Both contain glass fibers, but the use of fiber sheets in glass textolite makes it stronger than regular fiberglass. It is important to realize that the glass textolite used in the Soviet tank armour has very specific properties which were carefully chosen to provide optimal performance, such that it caused some complications during the manufacture of T-72M tanks in Warsaw Pact nations because the grade of glass textolite used in the USSR could not be easily replicated for mass production and it could not be substituted for inferior types.<br />
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Armour-grade glass textolite such as the type used in the T-72 is known generically as STB. This acronym stands for armoured glass textolite; "СТБ - <b>С</b>текло<b>т</b>екстолит <b>Б</b>роневой". The specific grade of STB used in the armour of the T-64 and T-72 is STB-3-02.<br />
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The glass textolite used in the armour of the T-72 is often referred to as "STEF". In the USSR and in Russia, STEF (СТЭФ) is a particular grade of glass textolite with good electrical insulation properties which has been widely used in the field of electronics and electrical engineering, but it is not the specific grade used for armour. The first two letters of the name stand for glass textolite; "СТ - <b>С</b>текло<b>т</b>екстолит" and the last two letters stand for epoxyphenol binder; "ЭФ - <b>Э</b>покси<b>ф</b>енольное связующее". Unlike STEF, the type of glass textolite used for the armour of the T-72 uses a phenolic resin binder. The colloquial use of the term "STEF" to refer to glass textolite armour appears to have originated from books authored by Steven Zaloga before this information became publicly available.<br />
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A U.S Army technical translation of the technical document "<a href="http://www.ciar.org/ttk/mbt/papers/misc/armor.russia.plastics_in_armor_material.742135.1972-05-24.pdf"><i>Plastmassy v bronetankovoy tekhnike</i></a>" (Plastics in Armor Materiél) originally published by the USSR Ministry of Defence in 1965 gives us some information on the glass textolite and fiberglass types used in the Soviet Union that would have been used in the armour of the T-72. The website of the <a href="http://www.eurokompozit.mk/product/en/ballistic-plates-for-military-vehicles-protection/">Eurokompozit company</a> also gives a description of the glass textolite used in the T-72 which we can cross reference with the Soviet document. It mentions woven glass roving (rovings are woven bundles of glass fibers) and special phenolic resin as the matrix material, and the phenolic resin-based glass textolite (steklotekstolite) listed in page 24 of the document "<i>Plastmassy v bronetankovoy tekhnike</i>" matches the description exactly.<br />
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The Eurokompozit website also states that the glass textolite used in the armour uses a specially modified phenolic resin for the matrix. The purpose of the modifications made to the phenolic resin in the glass textolite for the T-72 is not directly explained, but it is well known that glass-reinforced plastics like glass textolite lose a significant amount of strength at very low temperatures where they may become susceptible to brittle failure, but phenol-based GRPs are less sensitive to lower temperatures and are generally more ductile at the cost of reduced mechanical properties compared to GRPs based on epoxide resins. Based on this information, the choice of a phenol-based glass textolite for the armour and the use of a modified phenol resin is probably related to the inflexible requirement for Soviet tanks to be operable in conditions of -50°C to +50°C.<br />
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From this, it can be determined that the density of the glass textolite used in the T-72 is around 1.8 g/cc. Referring to the table of material properties, the specific type of glass textolite used in the armour has a tensile strength of 274.6 MPa, compressive strength of 294.2 MPa, flexural strength of 382.5 MPa and a specific impact strength (toughness) of 4.7-5.4 MPa. Furthermore, the study "<a href="http://btvt.info/5library/vop_1976_vld_t64.htm"><i>О Некоторых Закономерностях, Определяющих Защитные Свойства Трехслойных Преград При Обстреле Сплошными Оперенными Бронебойно-Подкалиберными Снарядами</i></a>" originally published in 1976 describes the glass textolite of the T-64 as having a density of 1.85 g/cc but does not mention the designation or the grade of the glass textolite.<br />
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The table below, taken from from page 260 of the book "<span style="font-family: "times new roman";"><i style="font-family: "times new roman";">Частные Вопросы Конечной Баллистики</i>"</span>, shows that STB-3-02 is a grade of glass textolite with a density of 1.80-1.85 g/cc, which coincides with the previously established densities of the glass textolite used in tank armour.<br />
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<div><br /></div><div><br /></div>In addition to its more obvious role as protection from anti-tank weapons, glass textolite also has a secondary role as radiation shielding. In the journal article "<i>Противорадиационные защитные характеристики стеклопластиков на различных смолах</i>" published in the 1967 No. 3 issue of the "<i>Вестник Бронетанковой Техники</i>" journal, it is detailed that glass textolite functions as radiation shielding in two ways: firstly, it releases much less gamma radiation to the crew via induced radioactivity from neutrons, and secondly, it is effective as a neutron shield due to the boron content of its borosilicate glass fibers. <br />
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The function of the STB interlayer in the composite armour sandwich of the T-72 is straightforward, but the overall operation of the composite armour as a whole is somewhat more complex. Given that the STB primarily serves as a barrier against shaped charge jets, it is appropriate to begin examining the 80-105-20 armour design from the perspective of HEAT protection.<br />
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<h3>
<span style="font-size: large;">SHAPED CHARGE PROTECTION</span></h3>
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The bulk of the protection offered against shaped charges is provided by the STB interlayer, but the steel front plate is necessary to degrade the shaped charge jet (SCJ) into a state where the STB reaches a high efficiency. When a monolithic STB plate is tested against a monolithic armour plate of an equivalent weight with a shaped charge, the SCJ penetrates the STB in the hydrodynamic mode just as it does with steel and thus, the mechanism of jet penetration into STB can be described with the hydrodynamic penetration model. This remains true when a thin steel plate is placed in front of the STB. However, when material of sufficiently high areal density is placed in front of the STB, the form of the continuous jet is disrupted as it is broken up into discrete particles once it has perforated the steel plate and emerges from its back surface, i.e., it becomes discontinuous.<br />
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A discontinuous jet is unable to stretch as a continuous jet normally does when penetrating through a homogeneous material. For a steel-STB-steel composite armour, the steel front plate is penetrated by a stretching jet, but the glass textolite layer behind it will be penetrated by the scattered jet particles. This penetration mode is far less efficient for the jet, and conversely, it increases the mass efficiency of the STB and steel back plate of the armour array. This is mainly applicable for modern precision-made shaped charge warheads. Old spin-stabilized HEAT shells from WWII generate an unstable jet that rapidly loses its cohesiveness partly due to imperfections in the shaped charge liner and partly from the spinning of the warhead. To defeat such a warhead, composite armour does not necessarily require a thick steel front plate.<br />
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This is supported by the study "<a href="http://ciar.org/ttk/mbt/papers/papers.2007-12-21/armor.x.ijie.vol23pp585_595.jet_penetration_into_low_density_targets.mayseless_genussov.1999.pdf"><i>Jet Penetration into Low Density Targets</i></a>". The simulations and experiments detailed in the study involved a 100mm plate of variable density placed in front of a filler of variable density to find the most optimal combination. It was found that the velocity of the shaped charge jet tip emerging from the 100mm front plate tended to be lower as the filler density decreased, and the jet increased in velocity when the density of the 100mm front plate was decreased. As the graph below shows, the most serious reduction in jet tip velocity occurs when low density material is placed behind a 100mm plate with high areal density (m = 500 kg/sq.m). Since the thickness of the plate is fixed at 100mm, achieving the 500 kg/sq.m areal density figure requires the plate to be made from a material with a density of 5.0 g/cc. The relatively high 7.85 g/cc density of steel makes it even more suitable for this purpose, and alloys made from heavy metals such as tungsten and depleted uranium will be even more effective.<br />
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The study goes on to detail that low density materials are more effective against disrupt and disperse jets than continuous jets. The graph above was plotted with the assumption that the jet emerging from the 100mm front plate is continuous, but the mass efficiency of a filler increases as the density of the filler decreases if the jet is already disrupted when it enters the filler. As the graph below shows, the most serious reduction in jet tip velocity occurs when the jet passes through a high areal density plate (500 kg/sq.m) and enters a low density filler, with the biggest reduction in velocity occurring when the filler density falls below 0.3 g/cc.<br />
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The most optimal configuration is to have a front plate of high density in front of a filler of low density. This ensures that the jet is disrupt and disperse as it emerges from the front plate, so that the low density filler performs at an optimum level. This conclusion is reinforced by other studies on the topic of shaped charge jet penetration into multi-layered targets such as "<a href="http://www.detk.com/wp-content/uploads/2013/10/ChouFoster10thISB.pdf"><i>Theory Of Penetration By Jets Of Non-Linear Velocity And In Layered Targets</i></a>" by P. Chou and J. Foster, from which the drawing below was taken. For a dual-layered target composed of an RHA plate stacked with an aluminium plate each with an equal thickness of 50mm each, the residual jet emerging from an RHA-AL target is shorter and slower than the residual jet emerging from an AL-RHA target, indicating that the efficiency of the layering scheme with the high density plate in front of the low density plate is higher and that the behaviour of multi-layered composite armour is anisotropic, i.e, dependent on the direction of attack.<br />
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In the 80-105-20 armour, a filler with an even lower density than glass textolite may be preferable as the mass efficiency would improve, but there may be structural factors that make it a more sensible choice. Considerations such as multi-hit performance and reliability against KE threats play an important role, and it is also worth noting that with a lower density filler, an excessive thickness of interlayer material will be needed to achieve the same level of protection. Due to the volumetric constraints of tank armour, this may not have been a viable option.<br />
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To supplement this, it was concluded in the research paper "<i>Research of protective multilayer titanium and aluminum system for cumulative jet</i>" by Z. Wilk et al., that to optimize the efficiency of a passive composite armour system to, the first layers should have the maximum energy absorption capacity. This is because the majority of the energy of an SCJ is carried in its front part, which interacts with the target during impact and initial penetration. This can be seen in the crater profile of shaped charge penetrations into homogeneous steel.<br />
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In the case of the 80-105-20 armour, the areal density of the front plate is high because of its large thickness, and the energy absorption capacity of RHA is high. Its thickness was more than enough to disrupt the jets of modern precision shaped charge warheads, yielding a high efficiency from the glass textolite filler. Indeed, the 80mm front plate is actually excessively thick for this purpose.<br />
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The back plate behind the glass textolite layers also gains a somewhat increased efficiency from the prior disruption of the shaped charge jet in a similar manner, but with the additional benefit of deflecting the discrete jet particles as they "splash" onto its surface due to the low-high density differential.<br />
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In Chapter 5.11 of the book "<i style="font-family: "times new roman";">Частные Вопросы Конечной Баллистики</i>", it is noted that utilizing multiple alternating layers of steel and STB can increase the resistance of the armour against SCJs, but only to a limited extent. It is concluded that the studies on this type of armour and their use in practice has shown that the increase in shaped charge resistance of steel and glass textolite composite armour was 35-40%.<br />
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From all of this information, it can be deduced that the most optimal armour configuration for defeating shaped charges uses a steel front plate of high thickness with a very thick layer of glass textolite behind it.<br />
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It can be determined that after a shaped charge with a penetration power of 450mm RHA perforates the 80mm front plate (214mm LOS) in the hydrodynamic mode, the remaining 280mm of glass textolite and 53mm of steel provides the equivalent protection of 236mm of RHA steel. The combined weight of the glass textolite layer and the steel back plate is equivalent to 119mm of steel, and as such, the two layers can be represented with a mass efficiency coefficient of 2.00.<br />
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For comparison, the old 80-140 configuration used in the Object 432 design from 1961 to 1963 ostensibly fulfilled the demanded protection requirements as it provided protection equal to 450mm of RHA against shaped charges. This means that after a shaped charge with a penetration power of 450mm RHA perforates the front steel plate (214mm), the remaining 374mm of glass textolite provides the equivalent protection of 236mm of RHA steel, despite having a weight equivalent to only 88mm of steel. The mass efficiency coefficient of the glass textolite is therefore 2.68. From this, it is immediately clear that the glass textolite interlayer and the back plate in the 80-105-20 array behave differently and cannot be generalized into a single coefficient.</div>
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The thinner 105mm glass textolite interlayer had a weight of 66mm, and by applying the same ME coefficient of 2.68, it is determined that it is equivalent to 177mm of RHA. Together with the 80mm heavy front plate which has a LOS thickness of 213mm, the first two layers of the 80-105-20 array can account for 390mm RHA of effective thickness against shaped charges. The remaining 60mm RHA of effective thickness is provided by the 20mm steel back plate, which evidently has an increased efficiency against the disrupted shaped charge jet given that the LOS thickness of the plate itself is 53mm; somewhat less than 60mm. The ME coefficient of the back plate is therefore around 1.13.<br />
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Looking at this design solution from the perspective of mass efficiency against shaped charges, the efficiency of the armour clearly decreased because the effective thickness offered by the new configuration against shaped charges remained at 450mm RHA but the replacement of 35mm of glass textolite with 20mm of steel yielded a net increase in weight of 31mm of steel. Based on the available evidence, this appears to have been a compromise to address the structural issues of the 80-140 composite armour.<br />
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The steel back plate acts as a final barrier against KE threats but aside from this, based on live fire experiments on this type of armour, another important function of the back plate is to behave as a structural support to prevent the glass textolite from delaminating while being penetrated and to limit the deformation of the back surface of the armour due to momentum transfer from the penetrator into the glass textolite. It is known that confining glass textolite somewhat increases its efficiency when it is being penetrated by a long rod projectile.<br />
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In summary, there is an abundance of evidence that establishes the effective thickness of the 80-105-20 armour array to be 450mm RHA, and with an esoteric understanding of the working mechanisms of this type of composite armour, it was possible to determine the ME coefficient of a steel back plate behind the glass textolite layer. While this may seem to be a purely academic exercise, this information can be useful when evaluating the later variations of steel-STB-steel composite armour used in the T-72 series.<br />
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Having an effective thickness of 450mm RHA renders the upper glacis completely immune against 105mm HEAT shells. According to the study "<a href="http://btvt.info/5library/vbtt_1979_03_probivaemost.htm"><i>Выбор Кумулятивных Снарядов Для Испытания Брони</i></a>", the 105mm M456 HEAT round (licence-produced in Germany as the DM12) had an average penetration of 398mm RHA with a minimum of 355mm and a maximum of 434mm, while the French 105mm F1 HEAT shell (Obus-G) had an average penetration of 388mm RHA. However, the 115mm BK-4M HEAT shell with a copper liner easily overmatches 450mm of RHA equivalent armour as it has a penetration power far exceeding 500mm RHA. Evidently, the protection requirement for 105mm HEAT was met, but the requirement for 115mm HEAT was not.<br />
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This level of protection was also sufficient against light shoulder-fired HEAT grenades. It provided full immunity from any 84mm HEAT grenades fired from the ubiquitous Carl Gustaf and any 89mm grenade fired from the LRAC F1.<br />
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Protection was also provided from a limited number of ATGMs, the most prominent being the original TOW missile (1970) which would have also been insufficient against the T-72 as it had only 430mm RHA of penetration. The M47 Dragon ATGM, which was issued to every mechanized infantry squad in the U.S Army, was also inadequate against the 80-105-20 armour as it had a similar penetration power of 430mm RHA. However, the ubiquitous MILAN missile system which entered service in several major NATO armies in 1972 could guarantee the defeat of the 80-105-20 armour array, having a penetration power of 530mm RHA. If the original requirement for protection against 115mm HEAT shells with a copper liner was met, the armour would have been sufficient to resist the MILAN missile.<br />
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<h3>
<span style="font-size: large;">EFFECT ON APDS</span></h3>
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The 68-degree obliquity of the upper glacis armour is beneficial when dealing with APDS rounds as even the most advanced models still had significantly degraded performance at higher angles of impact. For example, in the trials report "<i>Performance of 120mm Gun in Chieftain</i>", the difference in the guaranteed perforation limit of 120mm L15A4 APDS round on RHA sloped at 60 degrees is slightly more than 280mm, whereas on RHA sloped at 68 degrees, it is 267mm. This shows that when the armour obliquity is increased from 60 degrees to 68 degrees, the mass efficiency of monolithic RHA plates increases by around 5%. This justifies the increase in obliquity from preceding tanks like the T-54 and T-62.<br />
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Alone, the 80mm front plate can be considered to be a challenging target as it is almost enough to stop early 105mm APDS on its own, leaving them with almost no energy left after perforation is achieved. West German testing of captured T-55 tanks with 105mm DM13 rounds (L28A1 produced under licence) allowed a graph of the safety limits of the side armour of the tank, 80mm of RHA, to be produced for ranges of 800 meters and 200 meters.<br />
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As shown in the graph, L28A1 can exceed the safety limit of 80mm RHA sloped at 68 degrees when the firing range range is 200 meters, but at 800 meters, the safety limit is nominally higher by a small margin, as it is around 81-82mm. Four shots were used to determine this safety limit. Shot No. 60, which had a muzzle velocity of 1,500 m/s and impacted the hull side at an angle of 68 degrees, only managed to produce a cracked bulge. Shot No. 59, having a muzzle velocity of 1,502 m/s and an impact angle of 70 degrees, also only managed to produce a cracked bulge. Shot No. 61, having a muzzle velocity of 1,497 m/s and an impact angle of 67.5 degrees, successfully perforated the armour. Finally, shot No. 62, having a muzzle velocity of 1,495 m/s and an impact angle of 70 degrees, also successfully perforated the armour. Being an initial perforation limit, this type of perforation is where the penetrator exceeds the protection limit of the plate by a margin that only guarantees a 50% likelihood that the rear surface of plate is breached. The remaining energy in the residual penetrator is naturally very low. This serves to illustrate the limitations of the penetrator against the 80mm front plate of the 80-105-20 array, particularly when the structural support of the glass textolite layer is taken into account. <br />
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It is important to note that these muzzle velocities exceed the actual muzzle velocity of 1,478 m/s rated for L28A1 and all of its foreign clones produced under licence. The average difference of 20 m/s corresponds to a range difference of 200 meters. Going by the actual muzzle velocity, the safety curves should be adjusted downward to 600 meters, and from this, it can be rationalized that the 80mm RHA front plate of the 80-105-20 array cannot stop L28A1 on its own at 500 meters, but may do so at 700-800 meters.<br />
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At 500 meters, L28A1 barely perforates the 80mm front plate, but with such a low perforation margin at this distance, the fragments of the tungsten carbide core can be completely stopped within the 105mm glass textolite layer. The same is true even at an impact velocity far exceeding the muzzle velocity of L28A1. The L52 series does not have more kinetic energy but achieves better performance on multilayered targets due to the greater toughness of its W-Ni-Cu tungsten alloy core, but even so, early W-Ni-Cu alloys used in the late 1960's were reported to have issues with spaced armour due to its vulnerability to fracturing and fragmentation. The particular alloy used in the L52 series had a density of 17 g/cc. Based on its performance on sloped monolithic RHA targets, L52A2 has a somewhat larger perforation margin than L28A1, but still insufficient to overcome the 20mm steel back plate even at its muzzle velocity of 1,426 m/s.<br />
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120mm APDS posed the main threat as the guaranteed perforation of the L15A4 APDS on a steel target at a 68 degree obliquity is around 110mm at 1,000 yards (914 m) and around 100mm at 2,000 yards (1,828 m), so it is obvious that the penetrator core will still have a large amount of kinetic energy after perforating the 80mm front plate of the upper glacis array. The penetrator core was made from the same W-Ni-Cu alloy used in the L52 series.<br />
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After the tungsten carbide or tungsten alloy core of an APDS round breaks through a highly oblique plate of large thickness, it exits in a thoroughly damaged state. A tungsten carbide core in particular will tend to be fragmented into several pieces. During the breakout phase, where the penetrator has almost perforated the plate, the asymmetry of forces acting on the plate due to the different relative thickness of metal above and below the penetrator cause the part of the plate below the penetrator to buckle, resulting in the early structural failure of the plate compared to a vertical plate. In parallel to this, the penetrator also experiences asymmetrical stresses as it penetrates the oblique plate, causing it to fracture into pieces inside the plate and to break apart as it exits due to the sudden release of the built-up stresses. This phenomenon becomes more pronounced at higher obliquity because the asymmetry of forces increases with the angle of the plate. This is not exhibited when the plate is perpendicular to the shot.<br />
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If the target is a single plate, the fractured state of the penetrator core is beneficial as it greatly increases the post-penetration lethality of the shell, but the same phenomenon is hugely disadvantageous against multilayered armour or oblique spaced armour. Similarly, with the oblique composite armour of the T-72, the penetrator would successfully perforate the heavy front plate but the broken pieces (and also the fragments of the armour plate) will have to pass through a very large thickness of glass textolite, expending more energy in the process and leaving less to attack the steel back plate. This is all compounded by the fact that the shape of the individual core fragments after exiting an oblique steel plate is very poor for penetration, especially since the residual velocity of the fragments exiting the heavy front plate will be greatly reduced.<br />
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It is interesting to see that in <a href="https://tankandafvnews.files.wordpress.com/2016/02/20131231_142341.jpg">page 3 of the report "<i>Performance of 120mm Gun in Chieftain</i>"</a>, it is stated that the 120mm APDS ammunition for the Chieftain was "the first high velocity shot of its type which effectively defeats multiple targets", which may be referring to the NATO Heavy Triple target. The enhanced performance came as a result of the switch of the core material from tungsten carbide to tungsten alloy. The L52 round, which used the same W-Ni-Cu alloy, was possibly a derivative of the L15 series or its parent design.<br />
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<h3>
<span style="font-size: large;">APDS PROTECTION</span></h3>
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In the book "<i>Боевые Машины Уралвагонзавода: Танк Т-72</i>", it is stated on page 159 that the armour of the Object 172 and Object 172M are both equivalent to 305mm RHA against subcaliber shells, and the table below from the textbook "<i>Теория И Конструкция Танка: Т. 10. Кн. 2. Комплексная защита</i>" (<i>Tank Theory and Construction - Vol. 10, Book 2: Comprehensive protection</i>) also states that the resistance of this same armour (on the T-64A) is equivalent to 305mm of RHA steel against KE threats and 450mm RHA against shaped charges (row - T-64A; column - "KC").<br />
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On page 77, it is stated that the composite armour of the T-64A tank provided protection from subcaliber rounds (APDS) with a penetration of 110-120mm RHA at 60 degrees (at 2 km) at a range of 0.5 km. This is likely referring to the British 105mm L28A1 and L52A2 APDS rounds. <a href="http://btvt.info/1inservice/m60a1_israel/vop_m60a1_israel_firepower.htm">Testing of captured ammunition in the USSR</a> found that L28A1 and L52A2 perforate 110mm and 120mm RHA respectively at 60 degrees at a range of 2 km.<br />
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In the book "<i>Боевые машины Уралвагонзавода - Т-72</i>", it is stated on page 109 that the protection of the Syrian T-72M tanks used during the 1982 war in Lebanon had a level of protection that corresponded to the Object 172M, which has the 80-105-20 armour array. It is claimed that the turret was equal to 410mm of armour and the hull was equal to 305mm of armour, without more details given.<br />
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By its nature, the effective thickness of 305mm given in these two authoritative sources is almost based on the velocity limit of nominal defeat, rather than initial perforation. By using the guideline given in the textbook "<i>Частные Вопросы Конечной Баллистики</i>" to convert from nominal defeat to initial perforation, the effective thickness of the armour would be around 332mm RHA. This is completely consistent with the requirement for the armour to have an effective thickness of ~330mm RHA. With an effective thickness of ~330mm, the ME coefficient of the armour is 1.0 for the 80-105-20 array.<br />
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The table below, taken from page 62 of the book "<i>Т-72/Т-90. Опыт создания отечественных основных боевых танков</i>" (<i>T-72/T-90. The experience of creating domestic main battle tanks</i>) published by the Uralvagonzavod Research and Production Corporation, gives the distance limit of initial perforation of 105mm APDS and 120mm APDS on the armour of the T-64 (Object 432) tank with the same 80-105-20 upper glacis armour configuration. As the table shows, it is considered outright impossible for 105mm APDS to defeat the upper glacis armour or the frontal turret armour at any range, but 120mm APDS is considered capable of achieving initial perforation on the upper glacis armour at a maximum range of 1,000 meters and the frontal turret armour at 500 meters.<br />
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As stated earlier, L15A4 is guaranteed to perforate a 110mm RHA plate set at 68 degrees (294mm LOS) at a distance of 1,000 yards (914 m), and the perforation limit is above 110mm RHA at 68 degrees. Given that the 80-105-20 armour offers an effective thickness of ~330mm RHA against APDS rounds, L15A4 fails to guarantee perforation of the armour at 1,000 meters, but as described in the table, it is possible to achieve initial perforation. In order for the L15A4 round to guarantee perforation - that is, deliver lethal fragmentation behind the armour - the firing range must be 500 meters or less.<br />
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Overall, the upper glacis armour of the T-72 Ural provided good protection against the tank guns of the expected enemy forces. It was immune to 105mm APDS at point blank range and immune to 120mm APDS from above one kilometer. Given that 105mm APFSDS did not exist for several years after the introduction of the T-72 Ural, the Chieftain was the only credible threat in 1974.<br />
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With this in mind, it is interesting to note that the very early T-64 obr. 1963 relied on the single 80mm RHA plate of its 80-140 composite armour for the bulk of the work of stopping APDS rounds, leaving the 140mm-thick glass textolite layer with the task of stopping the residual core fragments. This was ostensibly enough to fulfill the requirement for protection against 105mm APDS.<br />
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The 80-105-20 armour array provides a guarantee of total immunity against this threat and even extends the scope of the protection level to include 120mm APDS, which emerged as a new threat with the appearance of the Chieftain Mk. 3 in late 1969. It is unlikely that the initial 80-140 armour design would have been capable of this.<br />
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<h3>
<span style="font-size: large;">GENERAL VIEW REGARDING APFSDS</span></h3>
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The T-72 Ural entered service some time before APFSDS ammunition appeared in the inventories of NATO forces, and by the time such ammunition began to be issued to the troops, the 80-105-20 armour design it used had already been replaced and new production T-72 tanks with the improved armour greatly outnumbered the original T-72 Ural production series. Nevertheless, it is still interesting to examine the performance of this early armour design against early APFSDS and even relatively modern long rod APFSDS to form a foundational understanding of the principles involved and to understand the magnitude of the improvements implemented later.<br />
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Moreover, it is also worthwhile to delve into this topic because a large number of exported T-72 models featured this armour design. The Object 172-E, Object 172-E1 and Object 172-E2 export models all featured the 80-105-20 armour design. The Object 172M1-E2 export variant has the hull armour of the T-72 Ural-1 model, as signified by the 172M1 designation. Some T-72M1 tanks exported by Poland or Czechoslovakia even retained the 80-105-20 armour array, while the turret was that of the T-72M1 proper (T-72A). Based on the available information at this time, more than a thousand tanks were built with the 80-105-20 armour design, which is a significant quantity.<br />
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In 1978, the American 105mm M735 round and the West German DM23 (a licence-produced clone of the Israeli M111 "Hetz") entered service and began production. The 80-105-20 armour array of the T-72 Ural could not provide sufficient protection from APFSDS rounds in general, including domestic 115mm steel APFSDS rounds, and these new 105mm round were challenging threats.<br />
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Against APFSDS ammunition, the functions of the individual components of the armour array are similar as for APDS rounds but the influence of the glass textolite interlayer is greatly reduced. The protection of the armour array strongly depends on the 80mm RHA front plate, which not only erodes the penetrator but also damages it as the penetrator achieves breakthrough so that the following layers have an increased efficiency.<br />
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<h3>
<span style="font-size: large;">EFFECT OF NOSE SHAPES</span></h3>
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It is important to consider the fact that certain nose shapes perform better on semi-infinite plate at high obliquity and certain nose shapes perform worse. Conical noses, for example, are rarely found on service ammunition or not at all because conical-nose rods yield the best results on perpendicular plate but perform very poorly at high obliquity, and more importantly, conical noses do not offer nearly enough improvement on perpendicular plates to justify the huge losses in performance on oblique plates. This is supplemented by the fact that even completely flat targets will often be attacked at some angle during real tank battles. All taken together, it is easy to understand why conical noses are never found on any long rod penetrator. Blunt noses are the most popular as they offer the best performance on highly oblique plates with only slightly reduced performance on perpendicular plates, which is largely irrelevant for modern tank armour design anyway. Frustrum-nosed rods offer a compromise between conical and blunt nosed rods, and for this reason it has found some usage, although it is not nearly as widespread as blunt noses.<br />
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This was examined in great detail in the study "<a href="http://www.dtic.mil/dtic/tr/fulltext/u2/a330157.pdf"><i>Effect of Nose Shape on Depleted Uranium (DU) Long-Rod Penetrators</i></a>" by W. Leonard. This study is particularly relevant for American depleted uranium long rod penetrators from the 70's and 80's as the material used for the DU test rod is the same U-3/4% Ti alloy as used in the M774 and M833. The DU test rod is not a replica of the two rods since the aspect ratio is less - 10.0 vs 14.3 and 18.0 respectively - but this does not affect the nature of the effect of nose shape.<br />
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As the tables above show, the effects of nose shape are consistent for both depleted uranium and tungsten alloy rods. For a 1" thick RHA plate sloped at 70.5 degrees, the velocity limit for a DU rod with a blunt tip is 1,088 m/s and the velocity limit for a DU rod with a conical tip is 1,355 m/s. This is a very sizable difference of 267 m/s or 24.5%, meaning that a conical rod of the same mass and aspect ratio would need to have 24.5% higher impact velocity to defeat the same target. The difference between a blunt nose and a frustum cone nose is much less - only 7%. A frustum cone is a reasonable representation of the ogived nose shape used in APFSDS rounds like the M774 and M833. For a 3" thick RHA plate placed perpendicularly, the velocity limit for a DU rod with a blunt tip is 1,373 m/s and the velocity limit for a DU rod with a conical tip is 1,239 m/s. The difference is only 134 m/s or 9.76%, so in other words, the conical rod has a relatively minor advantage compared to the blunt rod.<br />
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The same pattern is observed for tungsten alloy rods. For a 1" thick RHA plate sloped at 70.5 degrees, the velocity limit for a tungsten alloy rod with a blunt tip is 1,186 m/s and the velocity limit for a tungsten alloy rod with a conical tip is 1,470 m/s. The difference is 284 m/s or 24%, which is very significant. The difference between a blunt nose and a frustum cone nose is much less - only 5%. For a 3" thick RHA plate placed perpendicularly, the velocity limit for a tungsten alloy rod with a blunt tip is 1,440 m/s and the velocity limit for a tungsten alloy rod with a conical tip is 1,333 m/s. The difference is only 107 m/s or just 7.4%. This is somewhat relevant for the American M735 round, as the performance of its hemispherical nose is approximating that of a frustum cone nose.<br />
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According to the study "<i>The Penetration Performance of Tungsten Alloy L/D=10 Long Rods With Different Nose Shapes Fired At Rolled Homogeneous Armor</i>" by John Zooks, the effects of nose shapes is largely independent of the penetrator material. The findings reported by Zooks also reaffirms that tungsten alloy rods with short frustum, hemispherical, and blunt noses performed worse than a conical nose rod on a perpendicular impact but better on an oblique impact.<br />
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<h3>
<span style="font-size: large;">CONTRIBUTION OF STEEL FRONT PLATE</span></h3>
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<span style="font-weight: normal;">Long rod penetrators are generally capable of penetrating more armour at a higher obliquity than at a lower obliquity, so the steep 68 degree angle of the upper glacis is ostensibly a drawback, but on the contrary, it enhances the destructive effect on the penetrator. </span><span style="font-weight: normal;">Long rod penetrators are susceptible to fracturing and deforming after perforating oblique armour plates, especially at very high angles. This is due to the asymmetric buildup of stress within the rod during penetration, which is immediately released once the rod emerges from the back surface of the plate. The release of stress generally fractures the rod at the tip but sometimes fractures the entire rod as well, and the asymmetric forces also deflect the rod into a direction perpendicular to the surface of the plate. Thicker plates are more effective and more reliable at producing fractures because the longer duration of penetration causes a bigger buildup of internal stress in the rod, leading to a more severe fracture once the rod exits the back of the plate, but thinner plates can be used in this capacity as well.</span><br />
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<span style="font-weight: normal;">The behaviour of long rods penetrators as they perforate and emerge from behind an armour plate is termed "breakout", and the period is known as the "breakout phase". These umbrella terms describe the behaviour of penetrator rods as well as the damage inflicted onto them, including yawing, tip deformation, fracturing, and so on.</span><br />
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After perforating the thick 80mm steel front plate, a long rod penetrator or a composite penetrator will have its nose deflected downwards due to asymmetric reactionary forces. Depending on the specific penetrator, it can even break up into multiple sections. In any case, the nose shape of the residual penetrator is deformed and has a reduced efficiency against subsequent armour layers.<br />
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<h3>
<span style="font-size: large;">CONTRIBUTION OF GLASS TEXTOLITE INTERLAYER</span></h3>
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Against long rod penetrators made from heavy alloys such as tungsten or depleted uranium, the function and influence of glass textolite (STB) as a part of a multi-layered composite armour array is nuanced. Its first contribution to the overall resistance of the armour is its role as a backing material to support the back surface of the steel front plate, as it is a highly incompressible material. By functioning as back support, the breakout of a penetrator from the steel front plate is delayed and as such, the plate is able to offer slightly greater resistance during the penetration process. After the steel front plate is perforated and when the penetrator impacts the STB itself, a different set of interactions occur.<br />
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The photograph on the left below shows a heavy alloy long rod penetrator passing through a two-layer composite of steel and STB, and the photograph on the right below shows the penetrator passing through three layers of glass textolite placed at an angle. Photograph taken from page 290 and 291 of "<i>Частные Вопросы Конечной Баллистики</i><span style="font-family: "times new roman";">" (</span><i style="font-family: "times new roman";">Particular Questions of Terminal Ballistics</i>) published by Bauman Moscow State Technical University on behalf of NII Stali.<br />
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The behaviour of dual and triple layers of steel-STB composites as well as monolithic glass textolite plates were tested against scale model VNZh-90 tungsten alloy long rod penetrators with an aspect ratio of 10 and 12.5. As the photo on the left shows, the glass textolite layer behind the steel plate was delaminated in the area immediately surrounding the penetration channel, but the three glass textolite plates (solid glass textolite, no steel front plate) shown in the photo on the right show no such damage. This is explained by the fact that a long rod penetrator exiting the back of a steel plate sloped at a high obliquity will be highly bent and deflected, so that a larger surface area interacts with the glass textolite, thus tearing a larger channel as it passes through and resulting in some local delamination.<br />
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For angled and flat three-layer glass textolite target blocks, it was recorded in all cases that the tungsten alloy penetrator was bent and fractured by the time it reached the back of the block. Furthermore, the trajectory of the penetrator changes during penetration and became curved.<br />
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For the composite steel-STB target, it was observed that the tungsten alloy penetrator was fractured and bent as it exited the steel front plate, and that increasing the hardness of the plate increased the severity of the damage experienced by the penetrator. At an impact velocity of 800 m/s to 1,500 m/s, it was found that the residual depth of penetration inside the glass textolite layer was 1.5 to 2.7 rod lengths in the case of an impact with the dual layer composite at an angle of 0 degrees. For an impact at an angle of 60 degrees, the residual depth of penetration was 2.5 to 3.2 rod lengths. In comparing the raw data, the residual penetration into the 60 degree target was 15-65% higher than in the 0 degree target, apparently showing that the composite is less effective at a high angle of obliquity. This was explained by the anisotropic properties of glass fibers in the glass textolite. However, this is compensated by the fact that the penetrator is much more heavily deflected after perforating the steel front plate of an angled dual layer composite target and the trajectory of the penetrator inside the glass textolite layer is heavily curved, so overall, the ballistic resistance of the glass textolite is not worse than for an impact at 0 degrees. This is explained in pages 292 and 293. The relevant paragraphs are shown below:<br />
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"<i>Таким образом, при соударении под углом 60° глубина внедрения возрастает примерно на 15...65% по сравнению с глубиной при соударении по нормали. Однако защитные свойства стеклотекстолита при соударении под углом могут быть не ниже, чем при соударении по нормали вследствие более интенсивного искривления траектории и отклонения движения элемента вдоль слоев преграды, что наблюдалось в лабораторных условиях.</i><br />
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<i>Способность низклоплотных материалов вызывать при соударении изгиб корпуса и разрушение ньоражающего элемента из тяжелого сплава подтверждена и на менее плотных материалах типа полиэтилена. Однако такой эффект наблюдается не всегда и зависит в основном от качества сплава, из которого изготовлен сердечник.</i>"<br />
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Translation:<br />
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"<i>Thus, in the case of an impact at an angle of 60°, the depth of penetration increases by approximately 15 ... 65% compared to the depth at a normal impact. However, the protective properties of glass textolite in an angled impact can not be lower than in a normal impact due to a more intensive curvature of the trajectory and deflection of the motion of the element </i>[author's note: "element" refers to the penetrator]<i> along the barrier layers, which was observed under laboratory conditions.</i><br />
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<i>The ability of low-density materials to cause flexion of the body and the destruction of the striking element of a heavy alloy is confirmed on less dense materials such as polyethylene. However, this effect is not always observed and depends mainly on the quality of the alloy from which the core is made.</i>"<br />
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In other words, the depth of the penetration channel increases but the channel is curved away from the line-of-sight thickness of the armour, so the increased channel depth is irrelevant. It is presumed that if the residual long rod penetrator reaches a hypothetical steel back plate behind the glass textolite layer, the deflected penetrator will impact the plate at an angle greater than the structural 68 degree slope. Furthermore, the second paragraph confirms the previous assertion that decreasing the density of the interlayer (which would increase the efficiency of the composite armour against shaped charges) may result in less reliable protection against long rod penetrators.<br />
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At a high impact velocity on a steel-STB composite target at a high obliquity, it was observed that the contribution of glass textolite layer was very little compared to the steel plate. It was concluded in another study on steel-STB composites on page 423 that the effectiveness of the glass textolite interlayer was very low at an angle of 68 degrees - its resistance was around 20 times lower than steel, and it had a negligible impact on the dynamics of the penetrator as it travels through the armour. Using steel-STB composite targets at different angles, it was found that the armour set at an angle of 30 degrees stopped long rod penetrators of a variety of different diameters at a higher velocity limit than the same armour at 60 degrees. However, the glass textolite is not dead weight against long rod penetrators, as the composite armour did not have less ballistic resistance compared to a monolithic steel armour plate of the same mass. The relevant paragraph is shown below:<br />
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"<i>На рисунке видно, что при внедрении снаряда под углом 60° при скоростях удара до 2000 м/с стойкость стали все время выше стойкости стеклотекстолита. Отсюда можно заключить, что при больших конструктивных углах преграды использование стеклотекстолита в комбинированной броне неэффективно. Однако экспериментально установлено, что на комбинированных преградах со стеклотекстолитом с большими конструктивными углами не наблюдается проигрыша по стойкости по сравнению с монолитной стальной броней равной массы.</i>"<br />
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Translated:<br />
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"<i>The figure shows that when the projectile is deployed at an angle of 60° at impact speeds up to 2,000 m/s, the resistance of the steel is always higher than the strength of the glass textolite. Hence it can be concluded that with large structural angles of obstruction, the use of glass textolite in composite armour is ineffective. However, it has been experimentally established that on the composite targets with glass textolite with large structural angles, there is no loss in durability in comparison with monolithic steel armour of equal mass.</i>"<br />
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It is mentioned in page 290 of "<i>Particular Questions of Terminal Ballistics</i>" that when monolithic glass textolite was divided into two layers of equal total thickness, ricocheting of the tip of long rod penetrators and the fracture of the rods was observed on the contacting boundaries between the two glass textolite layers. This heavily implies that splitting the single 140mm glass textolite into two layers on production model T-64 tanks had the effect of improving the ballistic resistance of the glass textolite interlayer on long rod penetrators, so it appears that the improvements of the Obj. 432SB-2 upper glacis array over the Obj. 432 design were far more nuanced than simply reducing the thickness of glass textolite and adding an additional steel back plate.<br />
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<span style="font-size: large;">CONTRIBUTION OF STEEL BACK PLATE</span></h3>
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Because a dual layered steel and glass textolite composite armour is not less effective than a monolithic steel plate of the same mass, the mass efficiency is not less than 1.0. As such, the 80mm RHA front plate and 105mm glass textolite layer alone should be equivalent to 104mm RHA sloped at 68 degrees in effective thickness (280mm RHA in LOS effective thickness) against both steel and tungsten alloy long rod penetrators. Because the study concerns long rod penetrators and the experiments used monobloc tungsten alloy long rod penetrators with aspect ratios representative of APFSDS rounds from the 1980's, this mass efficiency coefficient is valid against this type of ammunition. However, the 20mm steel back plate, which contributes a LOS thickness of 53mm, does not actually contribute an effective thickness of 53mm.<br />
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The effects of the distribution of the thicknesses of the steel layers in this type of composite armour is studied in "<a href="http://btvt.info/5library/vop_1976_vld_t64.htm"><i>Regarding Some Regularities Defining The Protective Properties of Three-Layered Barriers In The Testing Of Long Rod Armour-Piercing Sub-Caliber Projectiles</i></a>" published in 1976 by O. I. Alekseev. The study used data from live fire tests with 115mm APFSDS rounds with a long rod steel penetrator (3BM6). Based on those results, it was determined that when the steel back plate has a thickness of less than 35-40mm, its mass efficiency was less than 1.0. This was because a thin plate offers significantly less resistance than its thickness implies, and significant deflection of the back plate would also be observed even in the case of a failure to perforate it owing to the lower rigidity of thinner plates. Due to the low mass efficiency of the back plate (ME coefficient of 0.47), the overall mass efficiency of the entire armour array does not reach 1.0. Tests were carried out to determine the nature of the penetrator after perforating the first two layers of the 80-105-20 array, and to determine the characteristics of the interaction between the penetrator and the back plate.<br />
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The photo below shows the remains of the steel penetrator of the 3BM6 round after breaking through an 80mm RHA front plate and the 105mm glass textolite layer, sloped at 68 degrees. In this specific test (with an unknown impact velocity), only the last 120mm of the tail out of the 436mm total length of the penetrator survived the interaction. The diameter of the nose of this penetrator segment is 30mm.<br />
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The ANSYS explicit dynamics analysis test shown below, <a href="https://youtu.be/Eq27qQrWq9g">originally shared by Roman Mashinyan (Роман Машинян)</a>, is a simulation of 3BM6 defeating an 80-105 target at an impact velocity of 1,500 m/s. It replicates the results obtained by the Soviet live fire tests. Apart from the region that is directly interacting with the steel front plate and penetrating it by erosion, the rod maintains its velocity until the moment it breaks out from the plate. Then, velocity equalization occurs and the rod travels at a much lower velocity at the moment it begins to penetrate the glass textolite layer. As it penetrates the glass textolite, the residual penetrator experiences a mild deceleration and is slightly eroded. At the moment the residual rod begins to break out from the glass textolite layer, it has a velocity of just 750 m/s. If a steel back plate were placed behind the glass textolite layer, the impact velocity on the back plate will be 750 m/s.<br />
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Due the low residual velocity, the residual penetrator can no longer penetrate steel armour by erosion as it has fallen to less than 1,192 m/s (the critical velocity for the grade of steel of the 3BM6 penetrator). Moreover, the rod has lost so much of its body length that it no longer qualifies as a long rod penetrator, so the residual penetrator has effectively become a blunt-tipped AP shot with a diameter of 31mm.<br />
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Because the residual penetrator no longer behaves as an eroding long rod penetrator but has instead transitioned into a rigid body penetrator, it behaviour is directly analogous to an AP shot at the given velocity. Due to the lack of erosion, the impact characteristics of the residual penetrator on oblique plates are degraded, although it is still not a trivial threat to the back plate owing to the blunt tip. Besides these structural and material factors, there is still the underlying factor that with residual penetrators in general, it can be expected that they tend to be deflected more dramatically by the high obliquity of the back plate because they possess much less momentum. These positive factors enhance the protection offered by the back plate. This is fundamentally true for any long rod penetrator, depending on its material density. For a tungsten alloy rod with a density of 17.6 g/cc, the velocity of the residual penetrator must be at least 945 m/s for eroding penetration to occur. Below this velocity, eroding penetration does not occur, and the residual penetrator of a tungsten alloy rod with this particular density will not enjoy an increased penetration efficiency against the steel back plate.<br />
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However, this armour design has a significant drawback. Due to momentum transfer from the rod into the glass textolite layer from the penetrating rod, the steel 20mm back plate becomes bulged, as it lacks sufficient rigidity to fully contain the rearward movement of the glass textolite except in the regions closer to the edges where the armour array is welded to the tank hull's roof, bottom and sides. The back plate continues to bulge as the penetrator approaches up to the moment of impact. Due to this bulging effect, the effective obliquity of the 20mm back plate at the point of impact tends to be less than 68 degrees, possibly falling as low as 60 degrees. In truth, because the back plate is supported by metal studs that pin it to the front plate, the severity of the bulging is not only depedent on the amount of momentum delivered into the glass textolite layer but also on the location of a hit.<br />
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Because the residual steel penetrator behaves like an AP shot, it is possible to estimate its penetration power using the DeMarre penetration calculator. For our calculation, the Soviet 3UBR6 steel 30mm AP-T round is used as the reference penetrator. It is confirmed to have an initial perforation limit of 20mm in RHA sloped at 60 degrees from a range of 700 meters, and like the 3BM6 penetrator, it is made from a high hardness steel albeit a softer grade. The variables used for the calculation are as follows:<br />
<blockquote class="tr_bq">
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Caliber: 30mm<br />
Mass: 0.375 kg (steel penetrator only)<br />
Velocity: 817 m/s (velocity at 700 meters)<br />
Penetration: 20mm (at 60 degrees)</blockquote>
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The variables used to represent the 3BM6 residual penetrator are as follows:<br />
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<blockquote class="tr_bq">
Caliber: 31mm<br />
Mass: 0.6 kg<br />
Velocity: 750 m/s</blockquote>
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With these variables, the calculated penetration is 24mm of RHA sloped at 60 degrees. An imperfection of this simple approximation is that the residual penetrator tends to be yawing at the moment it impacts the 20mm back plate, whereas a DeMarre calculation assumes that the reference penetrator and target penetrator are impacting a surface with the same attitude. However, even with an imprecise estimate, it can be seen that the 20mm back plate of the 80-105-20 armour array would be reliably defeated by the residual penetrator at the given initial impact velocity of the 3BM6 rod.<br />
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According <a href="https://1.bp.blogspot.com/-6yNomsLRzpM/XU6A8GiFNCI/AAAAAAAAOy0/sDGAVagqWLATrGri7Z1NNo4wJp_MlrN0QCLcBGAs/s1600/penetration%2Bcomparison.png">to tests on homogeneous plates</a>, the 3BM6 round can nominally defeat around 120mm of RHA sloped at 68 degrees at a velocity limit of 1,500 m/s, equal to around 320mm in LOS thickness. The impact velocity corresponds to a range of 1,500 meters. It is important to note that this is the velocity limit of nominal defeat, not perforation. From this, it is evident that the 80-105-20 armour array provides considerably less than 320mm RHA of equivalent protection against a steel long rod penetrator, so its mass efficiency is well below 1.0 given that the array weight is equal to 333mm of steel. <br />
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As an additional point of reference, the below simulation shows M735 impacting the 80-105-20 armour array at an impact velocity of 1,430 m/s. This velocity corresponds to a distance of 1 km. Although the simulation ends before the residual penetrator has perforated the back plate, it is clear that the armour array is perforated at this impact velocity.<br />
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Due to the hemispherical nose of the M735 penetrator, it has a significantly reduced performance during the impact phase with the 80mm steel front plate compared to the blunt nose of the 3BM6 penetrator, even though 3BM6 is made from steel. A very large portion of the penetrator is lost due to the ricocheting of the nose, which not only results in the loss of mass to contribute towards penetrating the armour, but also leads to a highly deformed and inefficient nose shape during the subsequent penetration phase.<br /><br />
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<br />After perforating the steel front plate and the glass textolite interlayer, the residual penetrator gains a tumbling trajectory and it has become extremely deformed - more so than 3BM6. It impacts the 20mm back plate on its side, and at a velocity well below its critical velocity for erosion. Nevertheless, owing to the low thickness - and therefore low rigidity - of the back plate, the plate bulges considerably before impact occurs. This negatively affects its resistance to the residual penetrator. Despite the large amount of kinetic energy that can be absorbed by a ductile back plate, its ability to pull its own weight within the armour array is inherently hamstrung by its low thickness. <br />
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<span style="font-size: large;">KE PROTECTION</span></h3>
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On page 137 of the book "<i>Т-72/Т-90. Опыт создания отечественных основных боевых танков</i>" (<i>T-72/T-90. The experience of creating a domestic main battle tank</i>), it is stated that a basic T-72 tank [with the 80-105-20 armour array] was only able to resist 115mm APFSDS (of an unknown model) at an impact velocity of 1,400 m/s. Depending on the particular type used, an impact velocity of 1,400 m/s may correspond to a range of 1.5 km or up to 2.2 km, which means that the armour only provides protection against the unspecified 115mm APFSDS from these ranges. Based on this result, it is self-evident that the 305mm RHA of effective thickness offered by the 80-105-20 armour was insufficient protection from APFSDS rounds as even old 115mm steel APFSDS could pose a serious threat. A range of 1.5 km should be considered medium to long range, given that various studies indicated that tank combat distances in Europe can reach a maximum of only 1.8-2.0 km in certain regions, such as the relatively flat fields of Northern Germany.<br />
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It is unsurprising, then, that the more advanced 105mm APFSDS ammunition appearing in the late 1970's and early 1980's could reliably defeat the 80-105-20 armour at any practical range. Against such formidable threats, the primary function of the armour is reduced to simply limiting the post-perforation effect and hopefully reduce crew casualties. The photo below, taken from "<i>History of the 4th Battalion, 37th Armored Regiment in Operation Desert Shield/Storm</i>", shows an Iraqi T-72M tank which was used for target practice by the aforementioned U.S Army battalion. The presence of four anti-ricochet ribs in front of the driver's periscope indicates that this T-72M was built with the old 80-105-20 armour array. Amateur tests were carried out against the captured tank at 1 km, 2 km and 3 km using 105mm M774, M833 and M900 rounds and 120mm APFSDS ammunition.<br />
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According to the book, all 105mm rounds fired successfully perforated the upper glacis at each tested range. An M833 round fired from 2 km is claimed to be responsible for one of the holes in the upper glacis in the photo above. The nature of the perforation indicates that it can be classified as guaranteed perforation, which is unsurprising given the high performance of M833.<br />
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<h3>
<span style="font-size: large;">SUMMARY</span></h3>
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In the context of international developments in armour technology, the 80-105-20 armour scheme certainly deserves much more attention than it currently receives compared to the famous British "Burlington" and "Chobham" armour, considering that it reached a very similar level of efficiency.<br />
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According to the research by Pawel Przezdziecki on "Burlington" armour using declassified documents in U.K archives, the configuration of "Burlington" armour developed in the late 1960's had a mass efficiency coefficient of 2.0-3.0 against shaped charges and reached similar resistance as monolithic steel armour against kinetic energy rounds (APDS). The STB layer in the 80-105-20 armour achieves similar performance, with an ME coefficient of 2.68 against shaped charges and an ME coefficient of 1.0 against long rod penetrators, or more than 1.0 against APDS rounds. As the STB layer is solid, it may also have a better thickness efficiency than contemporary "Burlington" armour as well, given that "Burlington" requires air gaps of substantial size to work.<br />
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Given that the 80-105-20 configuration was developed by NII Stali in the early 1960's and first implemented in low rate production in 1964 on the <a href="http://i.imgur.com/AsVHCqp.jpg">T-64 obr. 1964</a>, it is not a trivial accomplishment that the mass efficiency figures achieved by Soviet steel and glass textolite composite armour technology closely matched that of the most advanced "Burlington" armour technology available in Britain in the late 1960's. As such, it should be considered among the best in the world at the time it was developed. It is simply unfortunate that, having met the objectives for protection against 105mm APDS and HEAT, the armour configuration was not further refined; by the time the T-72 entered service in 1973, the 80-105-20 armour scheme was almost a decade old and had become obsolescent. The insufficient protection of this armour array against modern ATGMs was a clear weakness that may have required appliqué armour to remedy if a major war had erupted in Europe.<br />
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On the whole, this stagnation may have been somewhat acceptable because it was counterbalanced by an equal lack of innovation in 105mm KE and HEAT ammunition during the 1960's and early 1970's. Throughout this period, the most advanced 105mm KE threat was the British L52 APDS round (1966), which was completely inadequate against this armour design. Soviet intelligence on the development of 105mm APFSDS ammunition during the early to mid 1970's resulted in the timely introduction of a revised composite armour scheme.<br />
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<h3>
<span style="font-size: large;">60-105-50 ARMOUR</span></h3>
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In December 1975, the T-72 Ural-1 was accepted for service in the Soviet Army. Initially, this model retained the 80-105-20 armour array as indicated by the presence of four anti-ricochet ribs in front of the driver's periscope, visible in the photo shown above. In 1976, the armour was revised and thickened.<br />
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In the collection of memoirs <span style="font-family: "times new roman";">"</span><i style="font-family: "times new roman";">Life Given to Tanks</i><span style="font-family: "times new roman";">" dedicated to the UKBTM chief designer V.N Venediktov, published in 2010,</span> M.I. Maresev and I.I. Terekhin write that the armour of the T-72 "Ural" was enhanced by redistributing the thickness of the steel armor plates in the upper glacis, which made it possible to increase the protection characteristics of the entire composite array as a whole and introduced the possibility of further improvements. I.I. Terekhin was the department head of the NII Stali branch in the UKBTM design bureau.<br />
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The reinforced armour retained the 105mm glass textolite interlayer, but it now had a 60mm steel front plate and a 50mm back plate instead. The physical thickness increased to 215mm, and the LOS thickness increased to 574mm. Its weight in terms of steel was increased to 360mm due to the additional 10mm of steel thickness in the array. The areal density increased from 2,616 kg/sq.m to 2,826 kg/sq.m. The new armour gradually replaced the older design on the production line over the next three years until the T-72A entered service in July 1979. By then, the T-72 series had completely shifted to the 60-105-50 armour design.</div><div><br /></div><div>One of the structural characteristics of the 60-105-50 array is the omission of steel studs to secure the back plate, presumably due to the much greater stiffness of a 50mm plate compared to the earlier 20mm plate. The lack of visible welded studs on the entire rear surface of the back plate can be seen in the photo below. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEjdAvypEogfMckgYix7HwWgfzh4GjkS8EDe5ktKK11_CeZMKLJXPv0vkgjJ40WbZMGpXVWgHDLcxzCtQnYxesCOkark7oFhV5iSVq9KZnOhSDkXMcuAEhz2KfBvQVLQwPEw8X__wSnmCH7CNIvCqLpaIJdmA9_VH7GsexpZUhovCgTqTGTE8bOYflLT-Q=s2140" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1208" data-original-width="2140" height="362" src="https://blogger.googleusercontent.com/img/a/AVvXsEjdAvypEogfMckgYix7HwWgfzh4GjkS8EDe5ktKK11_CeZMKLJXPv0vkgjJ40WbZMGpXVWgHDLcxzCtQnYxesCOkark7oFhV5iSVq9KZnOhSDkXMcuAEhz2KfBvQVLQwPEw8X__wSnmCH7CNIvCqLpaIJdmA9_VH7GsexpZUhovCgTqTGTE8bOYflLT-Q=w640-h362" width="640" /></a></div><div><br /></div><div>However, the assembly process for the hull front did not change, and the armour array was still a self-contained pack which could be transported individually. To keep the three layers (or more accurately, four, given that the glass textolite interlayer is in two layers) joined together securely, the steel front and back plates are joined along the sides with welded frames. This can be seen in the image below, which shows the front hull assemblies for the PT-91. The PT-91 and its variants have the same armour as a T-72M1 (E5 model), being a derivative of it. </div><div><br /></div><div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-mrPipks4N9w/WZXgMhVEPRI/AAAAAAAAJBQ/yKVNLj9Wuq8dsxLp_DB14L4arodwWgpeQCLcBGAs/s1600/bumar%2Blabedy.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://1.bp.blogspot.com/-mrPipks4N9w/WZXgMhVEPRI/AAAAAAAAJBQ/yKVNLj9Wuq8dsxLp_DB14L4arodwWgpeQCLcBGAs/s400/bumar%2Blabedy.jpg" width="400" /></a></div>
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A T-72 Ural-1 with reinforced upper glacis armour will have three anti-ricochet ribs instead of four. The small rib closest to the periscope was eliminated so that it did not increase the size of the dead zone in front of the tank by obstructing the driver's downward view, which would occur due to the increased thickness of the reinforced armour and therefore the increased height of the ribs relative to the periscope window. As such, only two small ribs and one large rib are present on the reinforced upper glacis. Also, as the armour block in front of the driver's periscope was unchanged, the outline of driver's cutout around the periscope became much more visible as the new armour is slightly raised above the amour block in the cutout, which is also due to the composite armour array being 10mm thicker than the original design. These two identification features can be seen on the T-72 Ural-1 shown in the photo below. This particular example was produced in 1977, as indicated by its turret.<br />
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It is interesting to note that on page 139 of the book "<i>T-72/T-90: Опыт создания отечественных основных боевых танков</i>" published by the Uralvagonzavod corporation in 2013, it is claimed that T-72 hulls began to be built from BTK-1 steel plates beginning in 1976. The scale of the production of such hulls is unknown due to a lack of documentation and other credible sources other than this single book, so it is assumed to be on a small scale or even on an experimental basis.<br />
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There were efforts to improve the effectiveness of steel-STB-steel composite armour in the early 1970's, at least before 1972. The technology was tested on the first prototype of the Object 172-2M experimental tank, an offshoot of the Object 172, first created in 1972 and then tested in 1972-1974. Its upper glacis armour was composed of a 105mm STB interlayer sandwiched by a 70mm RHA front plate and a 40mm RHA back plate, sloped at 70 degrees. The physical thickness of the armour array was 215mm, equal to the 60-105-50 design that came later, but the additional two degrees of slope gave it a greater LOS thickness of 629mm. On the Object 172-2M, the thickened upper glacis armour can be identified by the presence of three anti-ricochet ribs instead of four.<br />
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The armour was equivalent to 394mm of RHA in weight, or in other words, the areal density was 3,093 kg/sq.m. However, based on the effective thickness figures given in the book "<i>T-72/T-90: Опыт создания отечественных основных боевых танков</i>", the mass efficiency of this design was slightly lower as armour was equivalent to only 520mm RHA against HEAT, indicating that the mass efficiency coefficient was 1.32 instead of 1.35 as in the 80-105-20 array. This is likely due to the reduced strength of the glass fibers at increased armour obliquity.<br />
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In the context of such experiments, the 60-105-50 armour was not an entirely original design, merely a further refinement of the armour with a back plate of increased thickness.<br />
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In the memoirs <span style="font-size: small; font-weight: 400;">"</span><i style="font-size: medium; font-weight: 400;">Life Given to Tanks</i><span style="font-size: small; font-weight: 400;">" dedicated to the</span><span style="font-size: small; font-weight: 400;"> UKBTM chief designer V.N Venediktov,</span><span style="font-size: small; font-weight: 400;"> </span><span style="font-size: small; font-weight: 400;">published in 2010, </span>V. D. Tumasov (head of the Department of Armour in UKBTM) writes that since the T-72 began mass production in 1974, the redesigned hull armour was among one of the first major measures taken to modernize the tank. Against the backdrop of the earlier experiments with the Object 172-2M in 1972-74, it is clear that a backlog of research data was already available and the design of the new armour would not have been protracted. However, Tumasov writes that the introduction of the new armour was hindered by bureaucratic red tape, which was only overcome with the intervention of chief designer Venediktov himself.<br />
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<h3>
<span style="font-size: large;">EFFECT ON KE THREATS</span></h3>
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The redistribution of thicknesses of the steel plates in steel-STB-steel armour was done to improve the mass efficiency of the array against long rod penetrators by eliminating the structural deficiencies of a thin back plate. In a relatively recent series of studies compiled in "<i style="font-family: "times new roman";">Particular Questions of Terminal Ballistics</i><span style="font-family: "times new roman";">" 2006 (</span><i style="font-family: "times new roman";">Частные Вопросы Конечной Баллистики</i><span style="font-family: "times new roman";">) published by Bauman Moscow State Technical University on behalf of NII Stali</span>, a multitude of different array layouts with different ratios of layer thicknesses were tested against tungsten alloy long rod penetrators of differing aspect ratios to find the optimal distribution of thicknesses and the optimal obliquity.<br />
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The three-layer array shown below has a 1.2:2.12:1.0 ratio of layer thicknesses with steel front and back plates with a STB interlayer, equivalent to the 60-105-50 armour layout. This layout was placed at an angle of 68 degrees and was tested against two types of tungsten alloy long rod penetrators with equal lengths but different diameters (aspect ratios: UPE-3 = 11.0, UPE-4 = 12.0) and compared to other layouts.<br />
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The resistance experienced by the penetrator is shown in the first graph, the amplitude of normalization of the penetrator is shown in the second graph, and the change in velocity of the penetrator (measured at the tail) is shown in the third graph.<br />
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The penetrator experiences large destabilizing effects inside the steel front and back plates, but remains almost completely steady inside the STB interlayer. Similarly, the velocity of the penetrator drops sharply as it penetrates the steel plates but barely changes as it travels through the STB layer. This graph is useful when simulating the interaction between a long rod penetrator and the 60-105-50 armour as it can be used as a reference when examining the calculated exchange of kinetic energy. Most importantly, it lends validity to such simulations because the graph was created using live fire test data.<br />
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The effects of redistributing the thicknesses of the steel layers is studied in <a href="http://btvt.info/5library/vop_1976_vld_t64.htm">"<i>Regarding Some Regularities Defining The Protective Properties of Three-Layered Barriers In The Testing Of Long Rod Armour-Piercing Sub-Caliber Projectiles</i>"</a> published in 1976 by O.I. Alekseev and I.I. Terekhin.<br />
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The study encompasses a broad range of armour thicknesses for dual and triple layered steel-STB composite armour designs and compares them with homogeneous steel plating of equal weight. Data from live fire testing is used for homogeneous steel targets as well as the multi-layer composite targets. The hardness of the RHA steel for all targets is kept constant at 285-311 BHN and the glass textolite had a density of 1.85 g/cc (the same type used in mass production tanks). 115mm APFSDS rounds with a steel penetrator were used. Ordnance velocities were in the range of 1,000-1,600 m/s. The characteristics of the composite armour were investigated within a narrow range of angles from 60 degrees to 70 degrees, which makes this study fully relevant to the T-72 upper glacis armour.<br />
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It was found that the ME coefficient of the back plate of a steel-STB-steel array reaches 1.0 only if its thickness is 35-40mm. When the thickness of the steel back plate is increased above 20-25mm, the resulting increase in mass efficiency of the entire armour array sharply rose by 2-3 times per unit thickness. To put it more succinctly, for every millimeter of thickness added to the steel back plate, the effective armour thickness increases by 2-3 millimeters. Thus, if the thickness of the back plate is more than 35-40mm, the overall ME coefficient of the entire armour array will rise above 1.0. Most interestingly, it was found that to optimize the mass efficiency of the 80-105-20 armour design, the thickness of the front plate should be reduced to 37-49mm (100-130mm in LOS thickness) with a corresponding increase in the thickness of the back plate to 51-63mm.<br />
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The back plate of the 60-105-50 array is therefore at the lower boundary of the optimum range of thicknesses, but nevertheless, it can be considered to be within the optimum range. Given that the mass efficiency of the armour is mainly dependent on the back plate and not the front plate, the increase in the thickness of the front plate above the optimum range has neither a positive or negative effect. Overall, the mass efficiency of the 60-105-50 armour must be above 1.0. Based on the figures given in the study, and the fact that the 50mm back plate is barely within the optimum range, the calculated ME coefficient of the 60-105-50 armour is 1.07.<br />
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For comparison, the mass efficiency of the 70-105-40 upper glacis armour of the Object 172-2M experimental tank will only be 1.0 because the thickness of its back plate is only 40mm.<br />
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It is important to note that positive ME obtained by increasing the back plate thickness in steel-STB-steel armour is limited to the upper boundary of the optimal range given in the study, and the front plate should not fall below the suggested optimal thickness range. Further decreasing the front plate thickness with an accompanying decrease in back plate thickness may decrease the ME of the array rather than increase it. Testing with 3BM6 showed that for a two-layer spaced armour target with a 20mm steel front plate and a 70mm steel back plate, angled at 65 degrees, the mass efficiency is 4.2-5.7% less than homogeneous steel if the air gap is 70mm or 130mm, or in other words, the ME coefficient is around 0.94-0.96.<br />
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Besides long rod penetrators, it is also necessary to look at the performance of composite penetrators. Unfortunately, if such a study was carried out in the USSR, it has not yet been made available to the public. It is therefore necessary to instead determine the performance of such ammunition against targets that behave similarly to the 60-105-50 armour in principle. The main items of interest are the German 120mm DM13 (1979) and the Soviet 125mm 3BM15 (1972) composite APFSDS rounds.<br />
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A 38mm-caliber APFSDS round was developed for an experimental Rheinmetall 105mm smoothbore gun with the same technology and similar characteristics as the 120mm DM13 round. As such, the 105mm DM13 round can be used as a technological surrogate for the 120mm DM13 round. The Rh105 smoothbore gun was tested in Sweden with DM13 ammunition for evaluation purposes, and thanks the "<a href="https://fromtheswedisharchives.wordpress.com/2019/01/03/rheinmetall-105-cm-smoothbore-performance/"><i>From the Swedish archives</i></a>" blog, the test data is available to the public.<br />
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<a href="https://i.imgur.com/OsIyskL.jpg">When tested against a NATO Medium Single (MS) target</a> (a 130mm RHA plate sloped at 60 degrees) the 105mm DM13 round was able to perforate the target at an impact velocity limit of 1,209 m/s. <a href="https://i.imgur.com/CiE16p5.jpg">Against a NATO Heavy Single (HS) target</a> (a 150mm RHA plate sloped at 60 degrees), the DM13 round was able to perforate the target at an impact velocity limit of 1,329 m/s. <a href="https://i.imgur.com/ZINaoSZ.jpg">Against a NATO Medium Double (MD) target</a> (40mm RHA front plate and 90mm RHA back plate spaced apart by 150mm, sloped at 60 degrees), the DM13 round was able to perforate the target at an impact velocity limit of 1,287 m/s. The drawing below shows the MD target.<br />
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Because the MD target has the same areal density as the MS target and differs only in the inclusion of an air gap, it is clear that simple double-layered oblique spaced armour has a positive mass coefficient against this APFSDS penetrator design. In fact, the velocity limit for the MD target is closer to the velocity limit for the HS target than to the MS target. Based on the velocity difference, the MD target is equivalent to an effective thickness of 289mm of RHA (144.5mm RHA sloped at 60 degrees) against DM13. As such, its mass efficiency coefficient is 1.11.<br />
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For comparison, <a href="https://4.bp.blogspot.com/-HsYb_RGtPYI/WsegHWtjrjI/AAAAAAAALYI/7mWAoRi_9lMUNGwx2TdsiFMisL7n8baAQCLcBGAs/s1600/3bm-15%2Bhigh%2Bobliquity.png">tests using 125mm 3BM15 rounds</a> found that a comparable two-layer spaced target with a 50mm RHA front plate and a 100mm RHA back plate with an air gap of 175mm, all angled at 60 degrees, required a 90 m/s higher velocity to achieve the limit of nominal defeat compared to a single 150mm RHA plate sloped at 60 degrees (equivalent to NATO Single Heavy target), which required an impact velocity of 1,480 m/s. The spaced 50-175-100 armour has an effective thickness equivalent to 165mm RHA sloped at 60 degrees under the nominal defeat standard. To achieve initial perforation, an additional 10mm of back plate thickness is added. In total, the effective thickness is 185mm RHA sloped at 60 degrees under the initial perforation standard. From this, the ME coefficient of the 50-175-100 spaced armour against 3BM15 is 1.23.<br />
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Based on this information, it is possible to gain a more accurate perception of the value of the 60-105-50 armour design against two types of composite APFSDS ammunition available in the late 1970's. The main feature that distinguishes the 60-105-50 armour array from the NATO Medium Double target and the 50-175-100 target is the inclusion of a STB interlayer instead of an air gap. As established earlier in this article, STB has an ME coefficient of 1.0. As such, it skews the weighted ME value of the entire array. Assuming that the mechanism of operation of the armour remains the same with or without a low density filler, it can be calculated that the ME coefficient of the 60-105-50 armour against 105mm DM13 APFSDS under the initial perforation standard is:<br />
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<div style="text-align: center;">
(<b>ME of steel</b> x proportional weight of steel) + (<b>ME of STB</b> x proportional weight of STB)</div>
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(<b>1.11</b> x (110 / 134.74)) + (<b>1.0</b> x (24.74 / 134.74)) = 1.09</div>
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Using the same method, it can be calculated that the ME coefficient of the 60-105-50 armour against 3BM15 under the same standard is 1.19.<br />
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From this, two inferences can be made:<br />
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<ol>
<li>The 60-105-50 armour array has a marginally inferior mass efficiency compared to dual-layer spaced armour against these two different types of composite APFSDS ammunition, but the ME coefficient remains well above 1.0 in both cases.</li>
<li>On a technological level, the composite steel APFSDS ammunition available in the USSR during the early 1970's is noticeably inferior to 105mm DM13 and 120mm DM13 composite tungsten alloy APFSDS when fired against similar two-layer spaced RHA targets.</li>
</ol>
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Logically, it can be concluded that the 60-105-50 armour would therefore have a much higher effective thickness against 3BM15 compared to 105mm DM13. Because the Rh105 smoothbore gun did not enter service, the 105mm DM13 APFSDS round also remained experimental. However, its technology was shared with the 120mm DM13 APFSDS round for the Rh120 L/44 gun, which was introduced into service in the Bundeswehr in 1979 together with the Leopard 2. It was more sophisticated than the contemporary 105mm M735 composite tungsten alloy APFSDS round, featuring a teardrop-shaped penetrator with a hemispherical tip. M735 was type classified in 1978.<br />
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Prior to 1978-1979, the most advanced ammunition available to any NATO nation operating a 105mm gun was the British L52 series, which has already been established as being utterly deficient against the older three-layer armour of the T-72 Ural earlier in this article. The 120mm L15A5 APDS round could pose a threat at a range of under 1 km to the older 80-105-20 armour, but should be unable to defeat the 60-105-50 armour even at point blank range. Overall, the protection level of the 60-105-50 armour vastly overmatched all available APDS ammunition at the time and would still have been proofed against the latest 105mm APFSDS ammunition that appeared two years in the future.<br />
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<h3>
<span style="font-size: large;">KE PROTECTION</span></h3>
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Against a long rod penetrator, the effective thickness of the 60-105-50 armour is not less than 360mm RHA (its own weight in terms of steel). Based on its calculated ME coefficient of 1.07, the effective thickness is estimated to be around 387mm RHA. For comparison, the 70-105-40 upper glacis armour of the Object 172-2M may have a effective thickness equal to its weight of 394mm RHA, which is only marginally greater than the 60-105-50 armour.<br />
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Using the ME coefficient of 1.09 determined earlier from experimental results of 105mm DM13 APFSDS tests against simple two-layer spaced armour, the effective thickness of the 60-105-50 armour would be 393mm RHA against this type of composite penetrator under the initial perforation standard.<br />
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If, for some reason, the 60-105-50 armour array is not attacked with a long rod penetrator or DM13 but is instead attacked with the 3BM15, the ME coefficient can be taken as 1.19, as established earlier. The armour array would therefore have an effective thickness of around 429mm RHA.<br />
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Overall, the calculated effective thickness figures for all three types of APFSDS ammunition are completely consistent with the nature of the respective penetrator designs.<br />
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According to Rolf Hilmes, the upper glacis armour of an ex-East German T-72M provided a protection level of 400mm against KE and 490mm against HEAT. Based on this, the ME coefficient would be 1.1 against KE. The protection figure provided by Hilmes implies that APFSDS ammunition with composite penetrators such as the 120mm DM13 round or the 105mm DM13 APFSDS round was used to test the armour rather than ammunition with monobloc penetrators like 105mm DM23 or 120mm DM23.<br />
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To supplement this, it is stated in the book "<i>Боевые Машины Уралвагонзавода: Танк Т-72</i>", it is stated that the upper glacis armour of the T-72A is equivalent to 360mm RHA against APFSDS threats. This low figure was most likely calculated based on the limit of nominal defeat of the armour against M111.<br />
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M. M. Rastopshin, candidate of technical sciences and a former academician employed by NII Stali, wrote in the article "<i><a href="https://topwar.ru/1716-nashi-tanki-v-realnoj-vojne-obrecheny.html">Наши танки в реальной войне обречены</a>?</i>" (<i>Are our tanks doomed in a real war?</i>) testing in the USSR showed that the 60-105-50 armour was "pierced" from a range of 2 km. However, given M111 can only achieve nominal defeat against the 16-60-105-50 armour array at a range of 500 meters (1,428 m/s) and would have to impact the reinforced armour at more than 1,450 m/s to achieve initial perforation, it is unlikely it can perforate the basic armour with no reinforcement at 2 km. Rather, it is much more likely that at a range of 2 km, M111 may only achieve nominal defeat against the armour array by inflicting structural back plate damage. To achieve initial perforation, it should be necessary to strike the armour at a range of less than 2,000 meters.<br />
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Given the large increase in effective thickness compared to the 80-105-20 armour, M735 is unlikely to defeat this armour even at point blank range as it already struggles against the older and substantially less efficient design.<br />
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<h3>
<span style="font-size: large;">EFFECT ON SHAPED CHARGES</span> </h3>
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Functionally, each layer is identical to the earlier 80-105-20 array. The 60mm steel front plate is penetrated in the hydrodynamic mode, thus behaving as a homogeneous barrier, and it serves to disrupt the jet once it is perforated. In principal, the mass efficiency is unchanged but the effective thickness will be higher due to the increased areal density of the armour. From a technical standpoint, the specific choice of a 60mm plate was justified by a number of parameters.<br />
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As shown earlier, in the study <a href="http://btvt.info/5library/vop_1976_vld_t64.htm">"<i>Regarding Some Regularities Defining The Protective Properties of Three-Layered Barriers In The Testing Of Long Rod Armour-Piercing Sub-Caliber Projectiles</i>"</a>, it was found that to optimize the mass efficiency of the 80-105-20 armour design against a long rod penetrator, the thickness of the front plate should be reduced to 37-49mm (100-130mm in LOS thickness) with a corresponding increase in the thickness of the back plate to 51-63. However, the suggested front plate thickness was not practical because the front plate of the composite armour had to be thick enough to disrupt a shaped charge jet. The minimum permissible thickness, where the plate remains thick enough to fulfill this function, is 60mm when the armour obliquity is 68 degrees (160mm in LOS thickness).<br />
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The 80mm front plate was thicker than necessary for this simple function, and consequently, the back plate thickness was restricted to keep the weight of the armour under control which in turn resulted in a non-optimal array design against KE threats. This is not surprising as the 80-105-20 design appears to have been developed by a simple evolutionary process that began with an 80mm plate sloped at 68 degrees, with the following two layers added over time.<br />
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With this in mind, an increase in armour thickness and weight over the 80-105-20 armour was clearly unavoidable. It was simply a necessity to meet the minimum thickness threshold of 60mm for the front plate and also have a 50mm back plate for optimal performance against long rod penetrators.<br />
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<span style="font-size: large;">HEAT PROTECTION</span></h3>
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With the same ME coefficient of 1.35, the effective thickness of the 60-105-50 armour against shaped charges is 490mm RHA. This supported in the book "<i>Kampfpanzer: Heute und Morgen</i>" by Rolf Hilmes. He credits the T-72M with an effective thickness of 490mm RHA against shaped charges. Additionally, it is stated on page 159 of "<i>Боевые Машины Уралвагонзавода: Танк Т-72</i>" published by the Uralvagonzavod Production Association, the hull armour of the T-72A (the same as the Ural-1 and T-72M1) is equal to 500mm RHA against shaped charges. On the whole, the difference of 10mm in effective thickness between these sources can be considered negligible, and in any case, both values are consistent with the ME coefficient range of 1.35-1.40 reported in the book "<i style="font-family: "times new roman";">Частные Вопросы Конечной Баллистики</i>".<br />
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Additionally, the very similar 60-100-45 armour array of the T-80B hull is reported to have an effective thickness of 480-500mm RHA against HEAT, which strongly supports the calculated and reported protection value of the 60-105-50 array.<br />
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An effective thickness of 490-500mm RHA is only a modest improvement over the previous composite armour design, but it was already enough to resist the 120mm DM12 and M830 HEAT rounds (480mm RHA penetration) used in the future Leopard 2 (1979) and M1A1 Abrams (1985) in addition to the existing 105mm HEAT rounds. However, it was still insufficient for the MILAN missile which had begun proliferating among the European NATO members in the mid-1970's.<br />
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It is interesting to note that the Soviet Army began fielding the 93mm PG-7VL grenade for the RPG-7 beginning in 1977. It could penetrate at least 500mm RHA, making it a serious threat to a T-72 Ural-1 from the direct front. However, outside of the USSR, a light anti-tank grenade with a similar capability was not available until the end of the 1980's. Generally speaking, foreign grenades of this type had a similar level of performance. The 8.4 cm Slpsgr m/75b grenade for the Carl Gustaf has a penetration power of "more than 400mm RHA", and the Swedish AT-4 and the French LRAC F1 both have a penetration power of 420mm RHA.</div><br />
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<span style="font-size: large;">APPLIQUÉ ARMOUR (1983)</span></h3>
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M111 "Hetz" ammunition was acquired by the Soviet Union and extensively examined and tested after the 1982 war in Lebanon (June 1982 - September 1982). A very popular theory is that the ammunition came on board a captured Israeli Magach 4 tank, which was until recently on display in Kubinka. Having captured M111 "Hetz" rounds in sufficient quantity for live fire testing, it was discovered by Soviet specialists that the upper glacis of the T-72 was vulnerable. As a response, the "<i>Reflection</i>" R&D programme (<i>ОКР «Отражение»</i>) was initiated. This programme consisted of the "<i>Reflection-2</i>" research topic on a stopgap solution and the "<i>Reflection-1</i>" research topic on a long-term solution. Work on the "<i>Reflection-2</i>" research topic concluded before the end of 1982. It lead to the development of high hardness appliqué armour plates tailored to each of the Soviet Army's main battle tanks - the T-64, T-72 and T-80. According to the book "<i>Тагильская школа: 80 лет в авангарде мирового танкостроения</i>" by the UVZ corporation, live fire tests of T-72 and T-72A tanks with the appliqué armour created from the "<i>Reflection-2</i>" project with M111 took place from 31 March 1983 to 19 April 1983.<br />
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As part of the "<i>Reflection-2</i>" programme, new-production T-72A tanks received a layer of appliqué armour on the upper glacis during hull construction at the factory and the T-72M1 export variant was created on the basis of this model in the same year. Furthermore, all models of the T-72 series were ordered to have 16mm of appliqué armour welded onto the upper glacis beginning in July 1983. The uparmouring process for existing tanks was authorized to take place during scheduled maintenance at repair facilities across the USSR.<br />
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As explained on page 139 of the book "<i>Т-72/Т-90. Опыт создания отечественных основных боевых танков</i>", the appliqué armour was intended to limit the effective range of M111, but no more. It was merely a temporary stopgap measure to keep the Soviet Army's large fleet of T-72 tanks viable against common 105mm APFSDS threats for the next few years. The limitations of the outdated three-layer armour sandwich design were recognized and work on a much more serious upgrade in armour protection was already underway, thanks to prior intelligence on West German plans to install a 120mm gun on the new Leopard 2 tank. Indeed, the 16mm plate was not only intended to immunize the tank from the new 105mm threat, but also to limit the effective range of the 120mm gun threat.<br />
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Contrary to a widespread myth, there is little evidence that IDF tanks with M111 "Hetz" ammunition destroyed Syrian T-72 tanks from the front during combat or in tests, although at least nine Syrian T-72 tanks (Object 172M-E1) were destroyed during the war. An old, but well-researched and very comprehensive analysis of this topic is provided in the article "<a href="http://armored.byethost17.com/2019/06/07/syrian-t-72-tanks-in-the-1982-lebanon-war/?i=1http://armored.byethost17.com/2019/06/07/syrian-t-72-tanks-in-the-1982-lebanon-war/?i=1"><i>Syrian T-72 tanks in the 1982 Lebanon War</i></a>". Rather, strong evidence has indicated that at best, of the limited number of Syrian T-72s that were deployed, nine tanks were destroyed in one ambush where multiple TOW anti-tank teams mounted on M151 MUTT Jeeps and Cobra helicopter gunships armed with TOW missiles attacked from several directions. The tanks were caught in the open while travelling in a convoy. The photo below shows a convoy of Syrian T-72s.<br />
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<a href="https://1.bp.blogspot.com/-PFSF6VjdePQ/XnHaOwncPoI/AAAAAAAAQTw/qky0wFYizSUodLQq3Fint_NWoe_F_R2RwCLcBGAsYHQ/s1600/syrian%2Bt-72.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="587" data-original-width="1000" height="374" src="https://1.bp.blogspot.com/-PFSF6VjdePQ/XnHaOwncPoI/AAAAAAAAQTw/qky0wFYizSUodLQq3Fint_NWoe_F_R2RwCLcBGAsYHQ/s640/syrian%2Bt-72.jpg" width="640" /></a></div>
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The surviving tanks managed to escape by deploying a smoke screen using their built-in TDA systems (exhaust smokescreening system). IDF tanks were not present for the engagement, and no destroyed tanks were recovered by the IDF, which excluded the possibility of Israeli tests on captured tank hulks.<br />
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Unfortunately, the exact grade of steel used for the 16mm plate is not known. For Polish T-72M1 tanks, 2P steel was specified for the appliqué plate as it was the primary high hardness steel available for armoured vehicle production. 2P has a maximum hardness of 477 BHN.<br />
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The main alternative is BT-70Sh, as it was widely available in the early 1980's and it was readily weldable. It has a specified hardness range of 477-555 BHN, and it reaches a hardness of 534 BHN when processed into the thin plates. There are three possibilities:<br />
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<ol>
<li>Given that T-72M1 tanks directly correspond to T-72A tanks, Soviet T-72A tanks also received 2P appliqué plates.</li>
<li>Both steel grades were used for tanks in the Soviet Army depending on availability.</li>
<li>Exported tanks were specified to receive 2P plates while Soviet tanks received BT-70Sh plates.</li>
</ol>
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<h3>
<span style="font-size: large;">16-60-105-50 UPPER GLACIS ARMOUR</span></h3>
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The T-72M1 export models Object 172M-1-E5 (Warsaw Pact members) and Object 172M-1-E6 (3rd world countries), both cleared for export in 1983, directly corresponded with the T-72A obr. 1983 in turret armour and hull armour, including the appliqué armour plate. The photo below shows the profile view of completed front hull assemblies for PT-91 tanks before final hull assembly. The PT-91 tank and its variants have the same armour as a T-72M1 (E5 model), being a derivative of it. The photo was taken from inside the Bumar-Łabędy plant.<br />
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<a href="https://1.bp.blogspot.com/-mrPipks4N9w/WZXgMhVEPRI/AAAAAAAAJBQ/yKVNLj9Wuq8dsxLp_DB14L4arodwWgpeQCLcBGAs/s1600/bumar%2Blabedy.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://1.bp.blogspot.com/-mrPipks4N9w/WZXgMhVEPRI/AAAAAAAAJBQ/yKVNLj9Wuq8dsxLp_DB14L4arodwWgpeQCLcBGAs/s400/bumar%2Blabedy.jpg" width="400" /></a></div>
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Determining the presence of the 16mm appliqué armour plate on T-72 tanks is a simple task. The tow hook area is a good indicator. If there is a visible cutout around the tow hooks, then the appliqué armour plate is present. This is a good way of distinguishing the T-72A obr. 1982 from the T-72A obr. 1983 and 1984 when the turret is not visible.<br />
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<a href="http://2.bp.blogspot.com/-mEjirHJov4k/VOJ_nkFkOfI/AAAAAAAABOo/ru6FaxTdrmI/s1600/t-72m1_018_of_126.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://2.bp.blogspot.com/-mEjirHJov4k/VOJ_nkFkOfI/AAAAAAAABOo/ru6FaxTdrmI/s1600/t-72m1_018_of_126.jpg" width="400" /></a></div>
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Another indicator is the number of anti-ricochet ribs in front of the driver's periscope. If the tank has the appliqué armour applied, only two ribs will be present. This can be seen in the two photos below. The photo on the left below shows a T-72M1 belonging to the GDR, and the photo on the right shows a standard T-72A obr. 1979 with the appliqué armour.<br />
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<h3>
<span style="font-size: large;">KE PROTECTION</span></h3>
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The addition of the plate increased the weight of the armour array to the equivalent of 403mm of steel and increased the areal density to 3,161 kg/sq.m. The physical thickness of the armour array was increased to 231mm, and the LOS thickness was increased to 617mm.<br />
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It is important to note that 16mm of appliqué armour contributes a considerable LOS thickness of 43mm. Due to the low rate of velocity loss of APFSDS ammunition such as M111 "Hetz", this is equivalent to a decrease in the penetration power from a reduced impact velocity corresponding to a range of 2.5 km against RHA sloped at 68 degrees. By its thickness alone, it is reasonable to expect the 16-60-105-50 armour array to resist M111 at point blank range, given that M111 may achieve initial perforation against the basic 60-105-50 array at less than 2.0 km.<br />
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The change in the mass efficiency from the appliqué plate is dependent on the specific APFSDS round used against the armour array, but in general, the higher hardness and strength of HHS yields the best results for defeating KE threats especially at a high obliquity. This has been shown by a number of studies on the topic of layered steel targets and is additionally reinforced by the previous discussion on steel-STB-steel composite armour where it was found that increasing the hardness of the steel front plate increases the resistance of the armour against long rod penetrators. However, there is no metallurgical bond between the appliqué plate and the 60mm front plate, as the appliqué plate is only attached to the upper glacis by welding it along its edges. To form true dual hardness armour (DHA), it is necessary to roll-bond two plates until they form a strong metallurgical bond, unlike a weld-on plate where there is only static friction on the contact surface between it and the base armour.<br />
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It is reported by <a href="http://btvt.info/3attackdefensemobility/armor.htm">Andrei Tarasenko</a> that the armour of the T-72A with the appliqué plate is equivalent to 405mm of steel against M111. Unfortunately, Tarasenko did not cite any specific source for this information and none of the references listed in the article contain this information. The relevant paragraphs, after omitting Tarasenko's personal opinions, are cited verbatim:<br />
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"<i>В ответ на это по завершении ОКР «Отражение» на танки вышеуказанных типов в ходе капитального ремонта на ремзаводах МО СССР на танках с 1984 года осуществлялось дополнительное усиление верхней лобовой детали. В частности на Т-72А устанавливалась дополнительная плита толщиной 16 мм, что обеспечивало эквивалентную стойкость 405 мм от ОБПС М111 при скорости предела кондиционного поражения 1428 м/с.</i>"<br />
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This translates to:<br />
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<i>"In response to this, after the completion of the OKR</i><i> "Reflection" for tanks of the above types during the overhaul at the Soviet factory of the Ministry of Defense of the USSR, since 1984 an additional reinforcement of the upper glacis was carried out. In particular, the T-72A was equipped with an additional plate with a thickness of 16 mm, which provided [the armour with] the equivalent thickness of 405mm of steel from M111 APFSDS at the velocity limit of nominal defeat of 1428 m/s.</i>"<br />
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The phrasing used by Tarasenko is a non sequitur because the velocity of nominal defeat is not directly related to the equivalent protection value, but nevertheless, assuming that the information is correct, there are two separate premises:<br />
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<ol>
<li>The velocity of nominal defeat is 1,428 m/s</li>
<li>The armour is equivalent to 405mm RHA</li>
</ol>
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According to firing tables for M111, an impact velocity of 1,428 m/s corresponds to a distance of 500 meters under standard testing conditions with a propellant charge temperature of 15°C. This specific range is important, as it was a requirement that the armour should stop 105mm subcaliber rounds at 500 meters.<br />
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For this article, a model of the 16-60-105-50 armour and M111 were created and then numerical simulations were run to determine the critical velocity of initial perforation, based on the reported result at 1,428 m/s. Animations of the simulations were made to help visualize the interaction between M111 and the armour array at an impact velocity of 1,430 m/s. The simulation shown below shows the 16-60-105-50 armour with a 2P appliqué plate.<br />
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<a href="https://1.bp.blogspot.com/-i2EZZEzn0ZE/Xod3XaMtqmI/AAAAAAAAQjU/1lwLHDanmdom3woIKiQ9Xa2_4oyBPCgIgCLcBGAsYHQ/s1600/M111-vs-UPF-T-72A-at-1430-ms-3-s.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="338" data-original-width="640" height="338" src="https://1.bp.blogspot.com/-i2EZZEzn0ZE/Xod3XaMtqmI/AAAAAAAAQjU/1lwLHDanmdom3woIKiQ9Xa2_4oyBPCgIgCLcBGAsYHQ/s640/M111-vs-UPF-T-72A-at-1430-ms-3-s.gif" width="640" /></a></div>
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The result corresponds to an initial perforation rather than nominal defeat.<br />
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The appliqué plate was changed from 2P to BT-70Sh. All other variables were left unchanged. In this case, the penetrator fails to defeat the back plate and instead ricochets back into the STB where it is eventually stopped. The dent in the back plate and the subsequent bulge on its rear surface corresponds to nominal defeat under the Soviet criteria, matching the reported result. For this reason, it is reasonable to expect that BT-70Sh was used for Soviet T-72A tanks.<br />
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<a href="https://1.bp.blogspot.com/-QsSlbwCon08/XnfIrSnpxII/AAAAAAAAQa4/hLYq692WSQMHVGX5VhyCEbZiF0Mamn-DACLcBGAsYHQ/s1600/M111-vs-T-72A-1430-ms%2Bbt-70sh.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="338" data-original-width="640" height="338" src="https://1.bp.blogspot.com/-QsSlbwCon08/XnfIrSnpxII/AAAAAAAAQa4/hLYq692WSQMHVGX5VhyCEbZiF0Mamn-DACLcBGAsYHQ/s640/M111-vs-T-72A-1430-ms%2Bbt-70sh.gif" width="640" /></a></div>
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The main results of the interaction between the penetrator and the two front plates are that over half of the penetrator mass is largely eroded, yaw is induced into the residual penetrator, the residual penetrator is slightly bent, and it has a damaged nose. Due to the combination of yaw and the bending of the residual penetrator, a larger cross sectional area is exposed against the STB interlayer which slightly increases the resistance it experiences while travelling through it. More importantly, the bent and yawing residual penetrator impacts the back plate on its side rather than head-on. This severely reduces its penetration efficiency and conversely, increases the efficiency of the back plate. This corroborates the findings regarding the ME of the 60-105-50 armour design presented earlier in this article.<br />
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Due to the low penetration efficiency of the residual penetrator against the 50mm back plate, a much higher impact velocity is needed to defeat it. According to estimates derived from the simulation, it is necessary for M111 to impact the armour array at a velocity of greater than 1,450 m/s for the residual penetrator to achieve initial perforation. As such, the addition of the 16mm appliqué plate on the 60-105-50 armour array provided full immunity to this round under standard testing conditions. In terms of effective thickness, this means that under the initial perforation standard, the 16-60-105-50 armour is equivalent to more than 405mm RHA. By using the guideline given in the textbook "<i>Частные Вопросы Конечной Баллистики</i>" to convert from nominal defeat to initial perforation, the effective thickness of the armour would be around 432mm.<br />
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Given that the weight of the armour is equivalent to 402mm of steel, an effective thickness of 432mm RHA translates to an ME coefficient of 1.074. This is almost the same as the ME coefficient of 1.07 calculated for the 60-105-50 armour. The marginal increase in ME is almost negligible, but can be attributed to the high hardness of the 16mm appliqué plate.<br />
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At the time the "<i>Reflection-2</i>" project was implemented in 1983, protection from M111 was important as it was also being produced in West Germany and had entered service as the 105mm DM23 round. It was also a good representation of other common 105mm APFSDS rounds available at the time. In 1980, the M774 APFSDS round was type classified and began to be issued in the U.S Army. Due to its higher kinetic energy, M774 should fare better against the 16-60-105-50 armour array compared to M111, but overall, it appears that its performance should be quite similar. It is worth noting that M774 is credited with the ability to defeat 180mm RHA at 60 degrees at 2 km in Russian textbooks.<br />
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However, even though the 16-60-105-50 armour offers guaranteed protection from M111 and should still be quite adequate against M774, by 1983, the U.S Army began issuing the new M833 round. This was a much more challenging threat. It is unlikely that the 16-60-105-50 armour can withstand this round within normal combat ranges.<br />
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Aside from 105mm guns, the Rh120 L/44 gun of the Leopard 2 in the early 1980's was also a serious threat. The DM13 round available in 1979 did not have a monobloc penetrator like M111, but it was still a challenge to resist. In terms of working length, it is not particularly impressive as the combined length of its two-part tungsten alloy penetrator was similar to M111 and its diameter was much smaller. However, the muzzle velocity of DM13 was 190 m/s higher, which enabled it to compensate for its other shortcomings to a large extent. Because of this, the 16-60-105-50 armour is probably not capable of preventing initial perforation by DM13 from below 1,000 meters. However, by 1983, the new DM23 had already appeared and had begun to supplant DM13. It was more potent than M111 as it had a monobloc penetrator with a similar diameter and greater length. Because of its favourable design and high muzzle velocity of 1,640 m/s, it is plainly evident that the 16-60-105-50 armour array should be insufficient against this threat even from 3 km, as DM23 still retains a velocity of 1,475 m/s at this distance.<br />
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Overall, the 16-60-105-50 armour fulfilled the requirement to ensure comprehensive security against the 105mm gun threat with common APFSDS ammunition, but as a stopgap solution, it was inherently limited in its scope. To defend against the latest 105mm APFSDS ammunition and the emerging 120mm gun threat, a completely redesigned armour array was required. This was the objective of the "<i>Reflection-1</i>" research topic.<br />
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In the 2002 book "<i>НИИ Стали - 60 лет в сфере защиты</i>" ("<i>NII Stali - 60 years in the field of protection</i>"), it is detailed that tests in the early 1980's showed that when the penetration power of M111 and the 3BM22 against RHA are equalized, 3BM22 has inferior performance against composite armour targets in practice. That is, to defeat the same composite target, 3BM22 must be fired from a shorter range. Given that 3BM22 decelerates at a much higher rate of 105 m/s per kilometer compared to M111 which decelerates at a rate of 44 m/s per kilometer, the performance gap between the two projectiles is narrower at close range, but even so, it is very likely that the 16-60-105-50 armour array is immune to 3BM22 at point blank range.<br />
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<h3>
<span style="font-size: large;">16-80-105-20 ARMOUR</span></h3>
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<a href="https://1.bp.blogspot.com/-Xh04uMZ33S0/XodwE7mtxqI/AAAAAAAAQjE/21BemqO1fBwLHU7AKFryg9Q6CCaKbjBXQCLcBGAsYHQ/s1600/t-72%2Bural%2Breflection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="350" data-original-width="591" src="https://1.bp.blogspot.com/-Xh04uMZ33S0/XodwE7mtxqI/AAAAAAAAQjE/21BemqO1fBwLHU7AKFryg9Q6CCaKbjBXQCLcBGAsYHQ/s1600/t-72%2Bural%2Breflection.png" /></a></div>
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While it is true that the share of T-72 Urals in the Soviet Army tank fleet was relatively small due to the short period of mass production (1974-1975), it did not matter as the scope of the “Reflection” R&D programme included all T-72 models. As such, even the oldest tanks were upgraded when they were sent for scheduled maintenance at repair facilities. The two photos below show T-72 Ural tanks that were not only upgraded with 16mm of appliqué armour, but also reinforced with Kontakt-1 ERA, given an anti-neutron cladding, new mudguards, a new 2A46M gun, smoke grenade launchers, new stowage bins, and more, thus bringing them up to the standard of a T-72A obr. 1983.<br />
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Interestingly enough, the T-72 series was only specified to receive 16mm of additional armour without any distinction between the original “Ural” series and the later “Ural-1” or T-72A, whereas the T-64 and T-80 series were specified to receive 30mm of additional armour.<br />
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The status of export model T-72 tanks is also not completely clear due to a lack of information. The photo below shows a particularly interesting example - the photo below shows an Iraqi T-72M1 with the 80-105-20 armour array supplemented with a 16mm appliqué armour plate. The origin of this particular tank is unknown. T-72M1 tanks exported from the USSR directly corresponded to the T-72A obr. 1983 in terms of armour protection, and as such, they were built with the 60-105-50 armour array. It is therefore more likely that T-72M1 tanks with the 16-80-105-20 armour array were of Czechoslovakian or Polish origin, or possibly even a local modification.<br />
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The effective thickness of the 16-80-105-20 armour is unknown, but it is reasonable to expect that it is capable of limiting the effective range of M111 to around 1 km.<br />
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<h3>
<span style="font-size: large;">HEAT PROTECTION</span></h3>
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Against shaped charges, the additional LOS thickness of the appliqué plate does not necessarily translate to the same value in effective thickness. The mass efficiency of the array may possibly increase due to the added thickness of the heavy front plate but it is too complex to quantify the changes, not least because the mechanical properties of the plate material must be known. Taking the simplest approach, the LOS thickness of the appliqué plate is simply added on top of the known effective thickness of the original 80-105-20 and 60-105-50 armour arrays, which yields a total effective thickness of 493mm RHA for the former and 532mm RHA for the latter.<br />
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It is stated in the article "<i>Anatomia pancerza Polski czołg PT-91 Twardy</i>" by Jarosław Wolski that for the T-72M1, the addition of the 16mm appliqué armour plate provided a HEAT resistance equivalent to 500-550mm RHA. Broadly speaking, this is congruent with an equivalent thickness of ~530mm RHA.<br />
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Regardless of the exact increase in protection, the reinforced armour was clearly insufficient against modern anti-tank missiles fielded during the early 1980's. The standard TOW and Dragon anti-tank missiles would not be effective against this armour, but they were also ineffective against the original 80-105-20 array so the up-armoured design did not provide any real qualitative improvement. The 16-60-105-50 armour array may be borderline acceptable for resisting a MILAN missile (530mm penetration) if the protection level is closer to the high end estimate of 550mm RHA, but the basic MILAN was an outdated threat by 1983. The newly appearing ITOW (1982) and MILAN 2 (1983) missiles could easily overcome the armour array. A substantial improvement in the mass efficiency was required to achieve a sufficient level of protection from these threats as well as against future threats without encumbering the tank too much. This improvement took the form of Kontakt-1 reactive armour.<br />
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<a href="https://www.blogger.com/null" id="steelturret"></a>
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<h3>
<span style="font-size: large;">MONOLITHIC STEEL TURRET</span></h3>
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<a href="https://3.bp.blogspot.com/-YpHHJ89ZHBI/Wgvl9YM3iMI/AAAAAAAAKHw/Ux30Rc3mVpw9p5lrNJdvcD6Ey1LCId6egCLcBGAs/s1600/image015.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="362" data-original-width="664" src="https://3.bp.blogspot.com/-YpHHJ89ZHBI/Wgvl9YM3iMI/AAAAAAAAKHw/Ux30Rc3mVpw9p5lrNJdvcD6Ey1LCId6egCLcBGAs/s1600/image015.jpg" /></a></div>
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Cast monolithic steel turrets were installed on serially produced T-72 "Ural" tanks. The turret is made from MBL-1 armour-grade cast steel and is assembled from two pieces. The turret front, sides and rear are cast as a single piece, but the roof is a separate piece that is welded on. This slightly degrades the structural integrity of the roof, as the weld seams can be weak points. This is probably some byproduct of the close imitation of the T-64A turret design, since the UVZ plant had already mastered the production of one-piece turrets for the T-62 and demonstrated the ability to produce a one-piece turret with composite armour for the Object 167M.<br />
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Various sources, including a UVZ book on the history of the T-72, state that the T-72 Ural-1 model of 1975 was mainly distinguished by improved hull and turret armour. The improved 60-105-50 hull armour has been examined, but unfortunately, there is no information on the specific modifications were applied to the turret.<br />
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<a href="https://1.bp.blogspot.com/-nimnzcb_f_0/XoB0TLdpNkI/AAAAAAAAQfg/Ed5UK5YEmvY6dNzyrn4ouJTNeEU9YA1aACLcBGAsYHQ/s1600/t-72%2Bural-1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="384" data-original-width="562" src="https://1.bp.blogspot.com/-nimnzcb_f_0/XoB0TLdpNkI/AAAAAAAAQfg/Ed5UK5YEmvY6dNzyrn4ouJTNeEU9YA1aACLcBGAsYHQ/s1600/t-72%2Bural-1.jpg" /></a></div>
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Currently, there is not a large amount of direct information pertaining to the thickness of the turret available to the public. According to the official tactical-technical characteristics, the turret is considered to have a thickness of 410mm. The T-64A has an equivalent monolithic turret (434.10.2.30sb-1SB), for which technical drawings with sectional thicknesses are available. Its LOS thickness ranges from 473mm to 445mm within its frontal arc. The slope of the monolithic steel turret of a former NVA-operated T-72M is 27 degrees from the vertical axis, as measured just behind the IR spotlight.<br />
<br /><br /><div style="text-align: center;"><img border="0" data-original-height="2048" data-original-width="1536" height="320" src="https://1.bp.blogspot.com/-BsJwDfGpa2I/YDUluhHjM1I/AAAAAAAASyY/jf6de7VT8-0YqGjf8wjygtPSqgB29dJLwCLcBGAsYHQ/s320/turret%2Bslope.png" style="color: #0000ee;" /></div><div><br /></div><br />
A direct measurement of a T-72 turret is available courtesy of the <a href="https://www.facebook.com/t72org/photos/?tab=album&album_id=1652076908337757">T-72.org Facebook group</a>. As the tape rule in the photo shows, the thickness of the turret cheek at the edge of the roof is only 310-320mm due to the cutout made on the inner surface of the cheek to accommodate the sight. However, at the middle of the turret cheek or near the base, the measured thickness comfortably exceeds 400mm and reaches 470-480mm or more. It is probably more than 470mm because the perspective of the photo may not allow an accurate reading from the tape rule because of parallax, and parallax from this perspective creates a bias towards a lower reading.<br />
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<a href="https://1.bp.blogspot.com/-OU5-M5xrkSk/XhtoHimr_JI/AAAAAAAAP4U/INfvucZVSXAcNotfInlC21SKK0oGh7nNwCLcBGAsYHQ/s1600/t-72%2Bturret%2Bmeasurement%2Bin%2Bfront%2Bof%2Bsight.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="636" data-original-width="960" height="424" src="https://1.bp.blogspot.com/-OU5-M5xrkSk/XhtoHimr_JI/AAAAAAAAP4U/INfvucZVSXAcNotfInlC21SKK0oGh7nNwCLcBGAsYHQ/s640/t-72%2Bturret%2Bmeasurement%2Bin%2Bfront%2Bof%2Bsight.jpg" width="640" /></a></div>
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To determine the thickness of the turret armour from this measurement, the drawing of the T-72 Ural turret shown below can be used as a reference. The drawing shows the weakened zone next to the gun trunnion for the linkage on the left side of the turret, mirroring the weakened zone for the coaxial machine gun on the right side of the turret, and it also shows the location of the interior surface of the turret cheek. The marked red line in the drawing is positioned this way because the window of the primary sight housing is a few centimeters in front of the sight periscope head itself. From this drawing, it can be seen that the LOS thickness of the armour should be approximately 450mm. However, it is critical to note that the thickness gradually declines from the base of the cheek to the top edge, because the outer surface of the cheek is sloped while the inner surface is mostly flat due to the cutout for the sight. <br />
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<a href="https://1.bp.blogspot.com/-qPa5i4xrTPo/XnJVaUMPf9I/AAAAAAAAQVQ/az_SHtQ1YkcGJFSVy6K09QWNTrwCG6IYwCLcBGAsYHQ/s1600/t-72%2Bural%2Bturret%2Bcheek%2Bthickness.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1189" data-original-width="1600" height="474" src="https://1.bp.blogspot.com/-qPa5i4xrTPo/XnJVaUMPf9I/AAAAAAAAQVQ/az_SHtQ1YkcGJFSVy6K09QWNTrwCG6IYwCLcBGAsYHQ/s640/t-72%2Bural%2Bturret%2Bcheek%2Bthickness.png" width="640" /></a></div>
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Because the two turret cheeks are symmetrical, the commander should also have the same thickness of armour in front of him.<br />
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Besides that, there are other sources of information that may have a larger margin of error. According to a <a href="https://www.cia.gov/library/readingroom/docs/DOC_0000498195.pdf">well known CIA analysis</a> of a diagram from a captured Soviet T-72 manual, the thickness of the turret at the mantlet area is 350mm. This figure is confirmed by Rolf Hilmes in his book "<i>Kampfpanzer: Technologie Heute und Morgen</i>" where he states that the turret is 355mm thick. The mantlet is the area immediately next to the cannon. The area directly next to the machine gun port is already 475mm thick, and from there, the turret only gets thicker, so even the weakest part of the turret can survive a hit from 105mm M392A2 APDS from 500 meters or less and the rest is thick enough to be largely invulnerable to any 105mm APFSDS shell when hit from straight ahead. The diagram is shown below. The areal density of the cheek (475mm) is 3,729 kg/sq.m. The gun mask wrapped around the gun barrel is designed to eliminate the gap between the gun barrel and the turret (depicted in the drawing below), but it is not large enough to be useful against serious anti-tank munitions. It is only designed to prevent machine gun bullets and autocannon shells from entering the gap and potentially jamming the gun. The mask itself is not particularly thick - it is only rated for 12.7mm bullets.<br />
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This weakened zone is very narrow as it only exists to accommodate the co-axial machine gun. It is also not very tall. This can be seen in the photo below of a T-80 turret (T-80 obr. 1976) stripped of much of its internal equipment and its co-axial machine gun. Photo by V<a href="https://sfw.so/1148814589-tank-t-80.html">oLLanD and published on the sfw website</a>. The T-80 obr. 1976 turret is taken directly from the T-64A, and as such, closely resembles the T-72 Ural turret in many respects. In this case, the two turrets are directly equivalent as there are no differences in the cannon mount and co-axial machine gun mount.<br />
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<a href="https://3.bp.blogspot.com/-Eu5qzMJg8Mc/Wwou6Nae0fI/AAAAAAAALoI/Jelsw2N2BVUCdQGPwbIgUY7nHEZCJKw8ACLcBGAs/s1600/1053346042.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="493" data-original-width="726" height="434" src="https://3.bp.blogspot.com/-Eu5qzMJg8Mc/Wwou6Nae0fI/AAAAAAAALoI/Jelsw2N2BVUCdQGPwbIgUY7nHEZCJKw8ACLcBGAs/s640/1053346042.jpg" width="640" /></a></div>
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The area between the gun barrel and the co-axial machine gun is especially weak due to the gun trunnion block. The diagram processed by the CIA is reproduced rather poorly, so an original diagram from a higher quality Soviet T-72A manual gives us a better idea of the armour profile. The trunnion block is highlighted below:<br />
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<a href="https://2.bp.blogspot.com/-odMQDUHB6Lg/WfHJ_zZZERI/AAAAAAAAJ-g/QDRKmaloNcE56NK2WmSgZoQKt3pFISYKQCLcBGAs/s1600/t-72%2Bgun%2Btrunnion.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="315" data-original-width="294" src="https://2.bp.blogspot.com/-odMQDUHB6Lg/WfHJ_zZZERI/AAAAAAAAJ-g/QDRKmaloNcE56NK2WmSgZoQKt3pFISYKQCLcBGAs/s1600/t-72%2Bgun%2Btrunnion.png" /></a></div>
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This is not the actual trunnion of the gun itself, but an armoured block that connects the gun trunnion to the turret. Little is known about the composition of the steel of this armoured block, but based on images showing its surface, it is safe to assume that it is a forged block of high strength steel machined to shape. Combining the cast steel of the turret with the trunnion block, the total physical thickness amounts to only 320mm at the most. <br />
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The diagram appears to show that only the turret cheek on the right has a thickness of 475mm, and the turret cheek on the left appears to be substantially thinner, but both cheeks are equally thick. Both sides of the turret are symmetrical, and the zone on the left of the gun constitutes a weak point on the left side of the mantlet, mirroring the cutout for the machine gun.<br />
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The turret roof over the crew positions is 45mm thick and sloped at 78 degrees, and the thickness of the roof above the gun breech is more than twice as thick, angled at between 78 to 80 degrees. According to "<i>Kampfpanzer: Technologie Heute und Morgen</i>" by Rolf Hilmes, the thickness of the roof plate is 45mm and the angle is 80 degrees at the peak of the roof. The total LOS thickness is at least 210mm. The roof armour alone is more than capable of causing contemporary APDS rounds to ricochet, even though some small areas may still be weaker than the cheeks. When APFSDS rounds began to appear in the late 70's, the invulnerability of the roof was seriously challenged.<br />
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Due to the geometry of the turret, the maximum physical thickness of the cheeks of around 475mm is not replicated anywhere other than the area immediately beside the gun mantlet. The cheeks become progressively thinner as it nears the edge of the frontal profile of the turret, but the line-of-sight thickness from the front increases due to the rounded shape of the cheeks. As such, the 475mm figure is only the minimum thickness of the turret cheeks from the front. From a side angle, however, the relative thickness of the turret cheeks is significantly lower than 475mm, although still extremely formidable. According to <a href="https://www.litmir.me/br/?b=544730&p=5">Baryatinsky</a>, the thickness of the turret cheeks at a side angle of 30 or 35 degrees is 400 to 410mm with a vertical slope of 10 to 25 degrees. The thickness of the side armour of the turret (80mm thick) varies between 395mm to 440mm at a side angle of 20 to 25 degrees. Due to the curvature of the turret, the base sections of the turret cheek is less sloped than the upper sections so the claimed 10 degree vertical slope must be for the thicker 410mm section while the 25 degree vertical slope must be for the thinner 400mm section. According to page 159 of "<i>Боевые Машины Уралвагонзавода: Танк Т-72</i>" published by the Uralvagonzavod Production Association, the LOS thickness of the turret at a 30-degree side angle is 410mm.<br />
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<h3>
<span style="font-size: large;">PROTECTION</span></h3>
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Based on the available information, the effective thickness of turret does not fall below 410mm against KE threats in a 60 degree frontal arc. It is difficult to determine if the cast steel is less efficient than rolled steel in this application, because of the colossal thicknesses involved. It was not possible to experimentally compare cast and rolled plates due to the insurmountable difficulty of producing a rolled plate with a thickness of around 400mm that can match the mechanical properties of a cast plate of the same thickness. In fact, specifications for RHA plates of such a thickness do not even exist. For example, according to the standards set by the MIL-DTL-12560 specifications, the maximum thickness of RHA is merely 6.0 inches (152.4mm). Furthermore, it is not valid to use a stack of plates instead of a single rolled homogeneous plate for such testing as the behaviour of various penetrators can differ on stacks of plates. It is only valid for shaped charge testing.</div><div style="text-align: left;"><br /></div><div style="text-align: left;"><br /></div><div style="text-align: left;">Assuming that the turret casting has a uniform hardness throughout its entire thickness, its effective thickness would be approximately equal to RHA against shaped charges or approximately equal to 0.9 times its physical thickness against subcaliber threats. Interestingly, in the book "<i>Т-72/Т-90. Опыт создания отечественных основных боевых танков</i>" published by the Uralvagonzavod Research and Production Corporation, the effective armour thickness is considered to be the same as the LOS thickness of 410mm from a 30-degree side angle.<br /><br /><br />
The turret cheeks of the T-72 Ural offer a minimum LOS thickness of steel of 450-475mm from the direct front. As the point of aim goes further towards the edges of the turret, the LOS thickness of steel increases due to the curvature of the turret. When shooting at the turret cheeks from a 30 degree side angle, the cheeks can be considered equivalent to 410mm RHA against KE threats. Considering that the 120mm L15A5 APDS round penetrates 355mm of steel at 0 degrees at 914 m, it can be estimated that the L15A5 round does not defeat the armour at any distance.<br /><br />
Aside from the most modern APDS ammunition of the early 1970's, late 105mm APFSDS ammunition such as the 105mm M833 and DM63 APFSDS rounds from the late 1980's will penetrate around 360mm of steel at 0 degrees at 1 km and M900 penetrates around 440mm under the same conditions. In other words, the turret armour of the T-72 Ural provides protection against the most powerful APDS ammunition available in NATO when it was introduced into service, and it still offered a very respectable level of protection against the 105mm APFSDS threat of the future. Penetration figures for the 105mm APFSDS were taken from a <a href="https://pp.vk.me/c625629/v625629491/215c2/IMml2ddeOiU.jpg">Nitrochemie presentation</a>.<br />
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The lack of a composite filling in the turret is disadvantageous when the tank has to deal with HEAT and HESH ammunition, but this is compensated to a large extent by the extreme thickness of the steel. HESH works well on homogeneous plate, but there is a limit to how thick the plate can be. As far as the T-72 is concerned, HESH is no more deadly than any other high explosive round, which is to say that the turret is completely immune.<br />
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On the other hand, the shaped charges of the heavy ATGM systems used by NATO forces in the mid to late-1970's were more likely to succeed. The prolific BGM-71 TOW, which was a heavy anti-tank system issued at the company level in the U.S Army, would have a good chance of breaking through the armour as it could penetrate around 430mm RHA, even though it may not be able to generate much of a post-perforation effect. The MILAN (530mm RHA penetration) would have been able to reliably overcome the turret armour from any angle of attack.<br />
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Medium or light weapons could pose a threat, but they were still largely inadequate against the turret armour. The most dangerous threats were the 84mm Slpsgr m/75b grenade for the Carl Gustaf and the French LRAC F1 as both have a penetration of just over 400mm RHA. They could pose a serious threat to the turret from a side angle of 30 degrees. However, the M47 Dragon ATGM system, which was standard issue for mechanized infantry in the U.S Army (one missile per squad), was the most potent anti-tank weapon available at the platoon level yet it had no chance of defeating the frontal turret armour from any angle as it could penetrate only 330mm RHA. This was confirmed in combat in 1991. The two photos below show an Iraqi T-72 that resisted a hit from an M47 fired by USMC infantry. Even at a large side angle, the turret armour was thick enough to resist the ATGM.<br />
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The armour was also sufficiently thick to prove a challenge for 105mm HEAT shells. According to a Soviet study, the 105mm M456 HEAT round and its West German licence-produced clone DM12 had an average penetration of 398mm RHA with a minimum of 355mm and a maximum of 434mm. M456 is also credited with a penetration of 380mm RHA in other sources. Bearing in mind that cast homogeneous steel armour can be considered to offer the same resistance as RHA against shaped charges, 380-400mm of penetration is far too low to go through the 475mm turret cheek in a head-on attack and it has a low chance of success on a shot from the side at an angle of 30 degrees where the LOS thickness of the turret is 410mm. So despite the lack of composite armour, the frontal arc of the turret could at least fulfill the basic requirement of resisting 105mm subcaliber and HEAT ammunition.<br />
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<a href="https://www.blogger.com/null" id="kvartzturret"></a>
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<h3>
<span style="font-size: large;">"KVARTZ" TURRET</span></h3>
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<a href="https://1.bp.blogspot.com/-I-URVqkTRRM/XnfYnhq0CcI/AAAAAAAAQbM/RY2eUzbR3kYwFviO4uqQruAUoSWsaLXKQCLcBGAsYHQ/s1600/t-72m1%2Bturret%2Bon%2Bstand.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="447" data-original-width="860" height="207" src="https://1.bp.blogspot.com/-I-URVqkTRRM/XnfYnhq0CcI/AAAAAAAAQbM/RY2eUzbR3kYwFviO4uqQruAUoSWsaLXKQCLcBGAsYHQ/s400/t-72m1%2Bturret%2Bon%2Bstand.png" width="400" /></a></div>
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According to Mikhail Baryatinsky in his book "<i><a href="https://rutlib6.com/book/22969/p/3">Т-72: Уральская броня против НАТО</a></i>" (T-72: Ural versus NATO), the T-72 began to receive the "Kvartz" turret from 1977 onward, which would mean that all of these turrets went to the T-72 Ural-1 model as the production life of the Ural-1 was from December 1975 to July 1979. Early batches of turrets had the "Kvartz" armour but also had the extension for the second optic of the TPD-2-49 optical coincidence rangefinder. The photo below, taken from a parade during the Zapad-81 exercises in the USSR, shows T-72 Ural-1 tanks with the 80-105-20 upper glacis armour and early "Kvartz" turrets.<br />
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In 1978, new production T-72 Ural-1 tanks began receiving TPD-K1 sights with an integrated laser rangefinder. New turrets built for these tanks omitted the extension for the second optic of the TPD-2-49 optical coincidence rangefinder.<br />
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A "Kvartz" turret with an anti-neutron cladding (introduced in October 1983) has the product code of 172.10.073SB. Almost all of these turrets were modified from existing turrets. For the sake of convenience, such turrets are hereby referred to by the code 073SB.<br />
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The T-72A was outfitted with this turret since the beginning of its military service 1979, and continued to be manufactured with this turret for five more years until 1984. In the USSR, the production of "Kvartz" turrets only continued for exported T-72M and T-72M1 tanks. This turret was also produced under licence outside of the USSR with the same specifications, so the turrets of such tanks were practically identical to that of Soviet Army T-72 models.<br />
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The composite turret features a cast armour cavity on each cheek filled with a material known as "Kvartz". "Kvartz" translates to "Quartz", so quartz is the main ingredient, but the exact composition of this compound is unknown. Based on an ARMOR journal article penned by James Warford, the armour of captured Iraqi T-72M1 tanks was thoroughly analyzed in the U.S but the composition of the filler has not yet been disclosed to the public. Warford emphasizes that typical sand is probably not used, and he speculates that the name "Kvartz" hints that quartz may be used and recalls the use of quartz gravel as an ingredient in HCR2 add-on armour kits during WWII. The full ARMOR article can be read <a href="http://www.ciar.org/ttk/mbt/armor/armor-magazine/armor-mag.1999.ja/4warford99.pdf">here</a>.<br />
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According to page 4-5 the article "<i>Anatomia pancerza. Polski czołg PT-91 Twardy, Nowa Technika Wojskowa</i>" ("Anatomy of Armour. Polish tank PT-91 Twardy, New Military Technology magazine") published in April 2018 by Jarosław Wolski, the filler used in the T-72M1 turret is sintered quartz. In a recent correspondence with Mr. Wolski, he revealed that the "Kvartz" substance is prepared using quartz sand. It is sintered in a special furnace at a temperature of 1,200°C at high pressure. The resultant material is a solid block of sintered quartz ceramic. The pebble shown in the photo below is apparently a chipped fragment of the "Kvartz" insert from a T-80B (Obj. 219R) turret which is functionally identical to the T-72A turret.<br />
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These prefabricated solid ceramic blocks are then used as the casting mould, around which the molten steel is poured to form the turret itself. To keep the block centered at the desired positions in the mould, three protruding bars are built into the prefabricated blocks. After the steel turret shell has cooled, the bars are cut flush to the turret roof. The use of sintered quartz as the casting mould is only natural given that silica sand is already a standard type of casting sand used for casting steel, and using prefabricated blocks allows the dimensions of the composite armour to be easily controlled. The outlines of the protruding bars are visible in the turret below. Photo from "<i>Nowa Technika Wojskowa</i>", a Polish military news magazine.<br />
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The physical and mechanical properties of the particular form of sintered quartz used in the "Kvartz" insert is difficult to ascertain, not only due to the lack of detailed information on the production process of the material itself, but also because of the lack of information on the raw ingredients. The main focus is on finding the density of the ceramic substance, as that will allow us to determine the areal density of the turret armour array and find the mass efficiency coefficient. This, in turn, will allow us to compare the technological level of the turret with its peers as well as verify or disprove claims regarding the turret armour.<br />
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The bulk density of commercial quartz sand is 1.2 g/cc but the density of pure solid quartz is 2.6 g/cc - the high porosity of sand is responsible for the large difference in density. According to several studies, the density of sintered quartz increases as the sintering temperature increases whereas the porosity decreases. From this, it is guaranteed that "Kvartz" will have a density of between 1.2 g/cc to 2.6 g/cc. Besides quartz sand, however, the compound contains the normal ingredients for a casting mould such as binding clay and some additives. According to a Polish document "<i><a href="http://www.tank-net.com/forums/index.php?showtopic=43899">Odlewnictwo: Technologia wykonywania form i rdzeni - skrypt nr 1747 Politechniki Śląskiej. Gliwice 1993</a></i>" ("<i>Casting. The technology of making molds and cores - script No. 1747 of the Silesian University of Technology. Gliwice City 1993"</i>) on casting technology, 75-85% of the content of the "Kvartz" ceramic blocks used in the turrets of Polish T-72M1 tanks in terms of mass was a material known as "Casting Material Sz01-III", which is a compound made from 70% quartz sand and 30% aluminum oxide and titanium dioxide. Besides that, 12-15% was clay (binding material), and the remainder was an additive made from graphite or ground electrodes with water.<br />
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It is unclear how closely this Polish recipe for "Kvartz" matches the original Soviet type, and it may depend on how much technology transfer was needed to prepare for Polish production of T-72M1 turrets using local manufacturing facilities and equipment. Due to the sheer abundance of quartz sand or silica sand in the commercial market, acquiring the raw ingredients for the "Kvartz" insert will not strain the budget, and the production process itself is fairly straightforward for any country with a modest metalworking industry. The light prerequisites for the production of this type of armour was probably an attractive feature for client states during the Cold War, so it is no surprise that so many second and third-world nations produced the T-72M1 under licence. The extremely favourable performance to cost ratio of this type of armour would also make the T-72M1 highly desired.<br />
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Since the "Kvartz" insert is commonly described as "sandbar" armour or "sand rod" armour, it may be difficult to appreciate the fact that it is actually a ceramic block, and that the armour of the T-72A turret is a simple three-layer ceramic sandwich. However, it is necessary to differentiate it from "siliceous core armour" developed and tested by the U.S Army in the late 1950's. Both types of armour use silicon dioxide as the main ingredient, but siliceous core armour uses fused quartz and not sintered quartz. Fused quartz is a glass, not a ceramic. Fused silica armour utilizes a phenomenon described as "elastic rebound" to defeat shaped charge jets and KE projectiles alike which is only possible due to the physical properties of glass. Although little is known about "Kvartz", there is little doubt that its behaviour will not be anything similar to siliceous core armour.<br />
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Needless to say, the three-layer arrangement of the armour will help it attain greater standards of protection than homogeneous armour of the same mass against shaped charges. As noted with the hull array, the composite nature of the T-72A's turret should also give it an added damping effect against high explosives and high explosive squash heads, but also against the shockwave of nuclear explosions as well as the radiation. The effect of the "Kvartz" filling on long rod penetrators is less clear, but the low density of the sintered compound compared to ceramics like alumina and silicon carbide is not encouraging.<br />
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The thickness of the T-72A turret is known, but we can use the same method employed by the CIA to determine the thickness of the turret of the T-72 Ural. As mentioned before regarding the turret of the T-72 Ural, the CIA determined the thickness of the turret by scaling it against the known length of the barrel of the co-axial machine gun. Comparing the diagram used by the CIA and the diagram from the T-72A manual, we can clearly see that the 73SB turret is thicker. Taking the machine gun barrel to be 680mm long, we find that the thickness of the cast steel around the machine gun barrel is 370mm - just slightly thicker than on the T-72 Ural. The beginning of the turret cheek to the immediate right of the co-axial machine gun measures approximately 514mm, which is 8.2% thicker than on the Ural turret. The lack of a non-metallic filler in the depiction of the turret armour appears to be a security measure.<br />
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Referring to the manual drawing, the turret measures 514mm in LOS thickness at the start of the cheek and increases to around 600mm at the area directly in front of the commander's cupola. According to According to page 159 of "<i>Боевые Машины Уралвагонзавода: Танк Т-72</i>" published by the Uralvagonzavod Production Association, the LOS thickness of the T-72A turret from a side angle of 30 degrees is 530mm.<br />
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A cross-section of the armour of the T-72A is available by referring to a factory blueprint tracing, shown below. The thickness of the center of the turret cheeks at a 38 degree side angle (III) is 540mm. From a 30 degree side angle at the same point, the thickness is higher by the dividend of 540mm by the cosine of 8 degrees, which is 545mm. These figures appear to match quite closely with the 530mm figure claimed by the Uralvagonzavod book as well as other sources by independent Russian historians, who alternately attribute the turret with a thickness of either 530mm or 540mm. The small difference may be explained from minor casting imperfections. From the front at a 0 degree angle, the thickness of the turret increases from 564mm at (III) to more than 700mm at the middle of the turret cheeks (in front of the commander and gunner), and increasing to 900-1,000mm as the cheek progresses to the edge of the inhabited space of the turret. As the thickness figures show, the thickness ratio between the "Kvartz" ceramic filler and the cast steel turret cavity walls is 2.7 to 1.<br />
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The thickness of the cast steel alone is 426mm, which exceeds the armour thickness of the T-72 Ural turret at the same location. Also, it is important to note that the monolithic "Ural" turret was inherently difficult to harden due to its large thickness whereas the cavity walls are individually thinner, and as such, they are readily hardened. Because of this, the cast steel of the "Kvartz" turret should offer a somewhat higher resistance against KE attack.<br />
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The "Kvartz" turret of the T-80B is very similar and even has the same average thickness, but it differs in the ratio of armour elements. From an angle of 30 degrees from the longitudinal axis, the same point on the turret had an average thickness of 530mm. Of this, the first layer is 180mm of cast steel, then 130mm of "Kvartz" filler, and then another 220mm of cast steel.<br />
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The general depiction of the turret in the blueprint tracing seems to agree with the drawing taken from the T-72A manual. Both drawings show that the turret cheek has a thickness of around 510mm at the edge where it joins with the mantlet weakened zone, although the blueprint tracing seems to indicate that the weakened zone is 410mm thick and not 370mm thick as determined from the manual. However, this detail might be explained by a slight asymmetry of the turret, since the two drawings are not depicting the same side of the turret. On the other hand, a factory blueprint would be far, far more accurate than a drawing from a manual as the former is an actual description of the specified thickness and the latter is merely illustrative.<br />
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The subject of the photo is the turret of an ex-GDR T-72M1, purchased by Sweden in the early 90's and used for testing purposes. Many of the vehicles purchased by Sweden during that time are still used today as OPFOR assets for training purposes. Looking closely at the photo below, you will notice that the turret is rusted on the surfaces of the cut, but the filler retains its original colour and some amount of it has fallen out of the cavity. It is worth noting that this particular implementation of ceramic armour ensures that the ceramic component is fully confined from all three axes which ensures optimal performance. The factory drawing confirms the validity of this photo, as shown by the thickness ratio between the "Kvartz" filler and the cast steel walls.<br />
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The steel to filler ratio of 2.7 to 1 is somewhat unusual compared to the distribution of thicknesses in the turret of the T-64 and T-64A, which had <a href="http://btvt.info/3attackdefensemobility/armor.files/432_alum.jpg">almost the same thickness of filler as the steel walls</a> of the composite armour cavity. The low thickness of the filler in the T-72A turret indicates that it has relatively low mass efficiency (ME) but relatively high thickness efficiency (TE) against both KE threats and shaped charges, as the bulk of the work of defeating both types of threats is still accomplished by the sheer thickness of the cast steel of the armour.<br />
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It is worth noting that the lower thickness of the steel cavity walls compared to the monolithic steel cheeks of the T-72 Ural turret has a positive effect on the protection value of the armour because it drastically improves the hardenability of the cast steel. As such, the ME of the cast steel itself may be higher against KE threats.<br />
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The co-axial machine gun port weakened zone did not change in size and the thickness of the cast armour above the machine gun port weakened zone was increased slightly, but this increase did not correspond directly with the increase in thickness of the turret cheeks with the "Kvartz" filling. As such, this part of the gun mantlet is only slightly thicker than the turret of the T-72 Ural at the same location and can be considered an additional weakened zone when compared to the turret cheeks. This detail can be faintly seen in the photo below (credit to <a href="https://meteo.livejournal.com/35006.html">livejournal user meteo</a>), although the angle of the photo is not ideal.<br />
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Unlike the turret cheeks, the interior surface of the mantlet zone has practically no slope. The geometric nuances of the turret design at this location can be seen much more clearly in the photo below. The photo is a screenshot taken from <a href="https://youtu.be/FHO8YLigwmI">this video of a T-72 turret used for ballistic tests displayed at the Parola museum</a>.
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<h3>
<span style="font-size: large;">KE PROTECTION</span></h3>
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The "Kvartz" composite turret should have a mass efficiency greater than the homogeneous cast turret of the T-72A's predecessor although the coefficient may not necessarily be more than 1.0, and this is an important distinction to make due to the fact that the previous homogeneous turret was made from cast steel and not RHA, giving it a mass efficiency coefficient of around 0.9. Whether the numbers credited to the turret are relevant for long rods or APDS remains to be seen, as there is literally no scientific literature in the public domain that describes "Kvartz" armour in the relevant perspective. Still, at least there is no doubt that the "Kvartz" composite turret would be more efficient than homogeneous steel against shaped charges.<br />
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As mentioned before, the total physical thickness of the center of the turret cheek armour from a 30 degree side angle at point (III) is between 545mm ("Wiedzmin" turret drawing) and 530mm (various sources). For the sake of simplicity, the average thickness of 537mm will be taken. Due to the fact that casting imperfections should only be observed in the steel casting and not the "Kvartz" casting core, the thickness of the "Kvartz" filler should be quite consistent whereas the thickness of the steel will vary by a more appreciable amount. Thus, it can be said that of the total thickness, 115mm is "Kvartz" and around 422mm is cast steel. In terms of weight, the estimated density of "Kvartz" (1.8 g/cc) implies that it weighs the same as 26.4mm of steel and has an areal density of 207 kg/sq.m. The cast steel of the turret weighs the same as its thickness indicates, of course, and the areal density is 3,313 kg/sq.m. In total, the weight of the turret is equivalent to 448mm of steel and the areal density is 3,520 kg/sq.m.<br />
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From a 0 degree frontal angle at the same point on the turret face (III), the geometry of the turret reduces the thickness of steel but not the "Kvartz" filler. The thickness of the cast steel is 418mm and the thickness of the filler is 146mm. The total weight of the turret should be equivalent to 451mm of steel and the areal density is 3,540 kg/sq.m. In other words, the armour at 0 degrees will be very similar to the armour at 30 degrees. As such, large differences in the armour equivalence credited to the turret cannot be explained by differences in the angles of impact.<br />
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<blockquote class="tr_bq">
Sergey Suvorov reports that the armour is equivalent to 500mm against armour-piercing subcaliber threats and 560mm against shaped charges in his article <span style="font-family: "times new roman"; font-size: small;">"</span><i style="font-family: "times new roman";">Танки Т-72: Вчера, Сегодня, Завтра</i><span style="font-family: "times new roman"; font-size: small;">"</span>, published in the July 2004 issue of the "<i>Техника и Вооружение</i>" magazine.</blockquote>
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According to "<i>Боевые Машины Уралвагонзавода: Танк Т-72</i>", the resistance of the T-72A turret from a 30 degree side angle is equivalent to 410mm RHA against APFSDS rounds and 500mm against HEAT rounds. This implies a mass efficiency coefficient of 0.915, which is essentially the same as homogeneous cast steel.</blockquote>
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Jarosław Wolski reports in "<i>Anatomia pancerza. Polski czołg PT-91 Twardy</i>" that the turret of a T-72M1 is equal to 400mm RHA against KE attack and 500mm RHA against shaped charge attack at a 30 degree side angle where the physical LOS thickness is 530mm. This implies a mass efficiency coefficient of 0.89 against KE threats, which is essentially the same as homogeneous cast steel.</blockquote>
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<blockquote class="tr_bq">
Wolski also states that from the front at a 0 degree angle, the armour is equivalent to 480mm RHA against KE and 600mm RHA against shaped charges where the physical LOS thickness is 650mm. At that location (referring to the "Wiedzmin" turret drawing), the thickness of the "Kvartz" filler is 146mm and the thickness of the cast steel is 532mm. Wolski's numbers imply a mass efficiency coefficient of 0.85, which is somehow worse than the armour at 30 degrees.</blockquote>
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<blockquote class="tr_bq">
It is mentioned in page 14 of the November 2006 issue of the "<i>Техника и Вооружение</i>" magazine that in 1993, a report published in the specialized magazine "<i>German Airspace</i>" by A. Mann states that the armour protection of the T-72M1 exhibited protection equivalent to 420-480mm of rolled homogeneous armour when tested against modern 105mm and 120mm ammunition from West Germany.</blockquote>
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The resilience of the turret armour against contemporary APDS and kinetic energy projectiles of all sorts should still be very high, definitely high enough to resist 105mm APFSDS from well into the 1980's.<br />
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<span style="font-size: small; font-weight: normal;">According to</span><span style="font-size: small; font-weight: normal;"> first hand accounts on the performance of ex-East German T-72M1s during Canadian testing, found </span><a href="http://www.tank-net.com/forums/index.php?showtopic=40194" style="font-size: medium; font-weight: normal;">here</a><span style="font-size: small; font-weight: normal;">, new experimental 105mm shells, presumably designed in the late 1980's, claimed to be "jazzed up" to match 120mm rounds in performance, failed to perforate the turret armour. It is stated that the impact only formed a "slight [dinner] plate sized bulge </span><span style="font-size: small;"><span style="font-weight: normal;">in the armour and cast some paint flakes around the turret wall". </span></span>The hull armour fared worse, but still quite respectably given the power of the ammunition tested. If this anecdotal account is true, these tests echo the initial relationship between M111 "Hetz" and the T-72A, as "Hetz" was able to defeat the glacis armour at close ranges while the turret was effectively invulnerable.<br />
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The "Kvartz" composite turret apparently appears to be effective against 3BM15 APFSDS. This was demonstrated by a well-known T-72M1 turret test target in the Parola Tank Museum, located at Parola, Finland. Tag (5) in the photo below marks the impact of a 3BM15 shell into the left turret cheek. Photo by Andrej Smirnov.<br />
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<a href="http://2.bp.blogspot.com/-y4aGMUZIg34/VUH15PkXOpI/AAAAAAAACJE/RJmvuy_wzNQ/s1600/3bm-15%2Bhit.png" style="font-family: "times new roman"; margin-left: 1em; margin-right: 1em;"><img border="0" height="335" src="https://2.bp.blogspot.com/-y4aGMUZIg34/VUH15PkXOpI/AAAAAAAACJE/RJmvuy_wzNQ/s640/3bm-15%2Bhit.png" width="640" /></a></div>
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According to <a href="http://legion-afv.narod.ru/USSR/1946_UP/T-72_Parola_2/T-72_Parola_2_015.JPG">a placard underneath the turret</a> at the Parola museum, the shell was stopped completely after digging only 170mm through the multilayer armour. This is rather strange as this would mean that the shell successfully penetrated the outer cast steel wall but then stopped after penetrating only an inch into the "Kvartz" layer. The extremely shallow penetration channel implies that the ceramic "Kvartz" filler somehow destroyed the entire penetrator by interface defeat, but this is rather absurd. Instead, the close-up photo of the penetration cavity shown below indicates that the 3BM15 round initially created a clean, straight tunnel through the outer cast steel wall but was deflected upwards when it reached the "Kvartz" layer. The entire penetrator then became embedded inside the turret cheek. It is extremely likely that the museum staff only measured the depth of the straight tunnel through the outer cast steel wall, leading to a misleading result.<br />
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A more conclusive answer could be obtained if more details of this test were known, but unfortunately, the range (simulated or otherwise) at which the shot occurred is not known, and there is no explanation about how they determined the depth of penetration. The inner wall of the turret was obviously not cut up to examine the armour, so they must have poked a stick into the shell crater until they hit solid resistance. It is possible that the stick was touching the penetrator remnants embedded inside the armour, implying that the round successfully penetrated the outer cast steel wall and the "Kvartz" filler, but stopped somewhere in the cast steel back plate. It is also possible that the perforation of the "Kvartz" layer pulverized the brittle ceramic such that the pulverized debris refilled the hole and gave the illusion of a shallow penetration channel. On the other hand, the statement on the placard can be interpreted to mean that the shell defeated the outer cast steel wall, passed through the "Kvartz" layer and penetrated 170mm into the inner cast steel wall, where it stopped. Either way, this hands-on ballistic test of the turret armour gave a very strange result.<br />
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<span style="font-size: large;">OBJECT 184 SERIES</span></div>
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<a href="https://1.bp.blogspot.com/-IFq6zouM2L0/Xnc2MZ1y3mI/AAAAAAAAQaA/_O5oTF2l9hwcXuLKPJZqRpqY9x3WKhWrwCLcBGAsYHQ/s1600/t-72a%2Bobr.%2B1983%2Bin%2Bmoscow.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="390" data-original-width="516" height="301" src="https://1.bp.blogspot.com/-IFq6zouM2L0/Xnc2MZ1y3mI/AAAAAAAAQaA/_O5oTF2l9hwcXuLKPJZqRpqY9x3WKhWrwCLcBGAsYHQ/s400/t-72a%2Bobr.%2B1983%2Bin%2Bmoscow.png" width="400" /></a><a href="https://3.bp.blogspot.com/-BMm1gTRmWvU/W2vKeTl8MOI/AAAAAAAAMLo/WvJq63Lnfr8-DO7RmB8y5OCqolAQ3GUQQCLcBGAs/s1600/t-72a%2Bobr.%2B1983%2Banother%2Bone.jpg" style="font-size: medium; font-weight: 400; margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="873" data-original-width="1200" height="290" src="https://3.bp.blogspot.com/-BMm1gTRmWvU/W2vKeTl8MOI/AAAAAAAAMLo/WvJq63Lnfr8-DO7RmB8y5OCqolAQ3GUQQCLcBGAs/s400/t-72a%2Bobr.%2B1983%2Banother%2Bone.jpg" width="400" /></a></div>
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<span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;">In the book "<i>T-72/T-90: Опыт создания отечественных основных боевых танков</i>" published by the Uralvagonzavod corporation in 2013, it is stated that immediately after finalizing the improved 60-105-50 armour design and a new turret with a "Kvartz" ceramic filler, the UKBTM design bureau began the development of new armour solutions, catalyzed by the emergence of APFSDS ammunition among NATO member countries in the second half of the 1970's. The main impetus was new information about the 105mm M735 round and the 120mm Rheinmetall smoothbore gun which was reaching maturity at the time. </span></span><span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;">In fact, detailed drawings of the M735 round were available in the article "<i>A Bigger Foot Print</i>" </span></span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">published in the</span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;"> September-October 1978 issue of the "<i>Armor</i>" magazine, and it was assumed that the German DM23 round was M735 produced under licence. The threat was overestimated, as the advertised capabilities of M735</span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;"> were only true under the assumption that the upper glacis armour of the T-72 was a 100mm RHA plate sloped at 70 degrees - it was not known in the U.S that the T-72 already had composite armour.</span><br />
<span style="font-family: "times new roman"; font-size: small; font-weight: 400;"><br /></span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">However, these claims were evidently taken at face value and M735 was assumed to have been specially designed to defeat the first generation of composite armour used in Soviet MBTs, while the APFSDS ammunition of the new 120mm smoothbore gun was perceived to represent the future reference threat.</span><br />
<span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;">In April 1980, preparations for the production of 172.10.077SB turrets with new composite armour began, and in September 1982, it entered low rate production. Mass production began in 1983. The new hull armour entered mass production in early 1983. According to the book "<i>T-72/T-90: Опыт создания отечественных основных боевых танков</i>", all tanks produced at Uralvagonzavod for delivery to the Soviet Army had new turret and hull armour since January 1, 1984. There appears to be no way of distinguishing between "Improved T-72A" tanks built in 1983 and those built in 1984. </span></span><br />
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<span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;">The research and design work on the further improvement of T-72A tanks was done under the research topic of "Совершенствование Т-72А" ("Improved T-72A"). The tanks created in 1983 and 1984 are therefore most accurately referred to as "Improved T-72A" tanks. This term is used in several Russian articles, and the tanks are referred to as such by N.A. Molodnyakov in the collection of memoirs "<i>Life Given to Tanks</i>" dedicated to the UKBTM chief designer V.N Venediktov, published in 2010. </span></span><br />
<span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;">These tanks received the product code "Object 184". While it is certainly quite confusing for one model of tank to have two product codes, this was not unprecedented. The T-72A was accepted into service in 1979 under the product code of Object 172M-1, but the code Object 176 was also used despite the fact that the actual Object 176 was merely an experimental tank used as a testbed for various technologies that were eventually implemented in the T-72 series. In particular, the T-72AV was given the code Object 176V; there is no Object 172M-1V.</span></span><br />
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<span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;">"Improved T-72A" tanks appeared in the 1986 parade in honour of the 69th anniversary of the Great October Socialist Revolution and the turret was given the nickname "Super Dolly Parton" by CIA observers. The new upper glacis armour was visually imperceptible from the exterior of the tank. </span></span><br />
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<span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;">Some tanks were equipped with the 902B system which had only 8 grenades, all installed in a single cluster on the left of the turret, while others had the 902A system with 12 grenades installed in two rows along both turret cheeks, inherited from the T-72A obr. 1979. The two images below show "Improved T-72A" tanks equipped with the 902A system. </span></span></div>
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<span style="font-size: small; font-weight: normal;">The two photos below show another "<i>Improved T-72A</i>" in Belarus. This particular tank was still in active service, participating in various training exercises.</span></div>
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<a href="https://1.bp.blogspot.com/-pdB1bfdZHgk/XneWe5bXR7I/AAAAAAAAQaw/vmSa1htzPCI1dHYpTdMm2ajhhM3cqTPcwCLcBGAsYHQ/s1600/belorussian%2Bt-72a.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="444" data-original-width="606" height="292" src="https://1.bp.blogspot.com/-pdB1bfdZHgk/XneWe5bXR7I/AAAAAAAAQaw/vmSa1htzPCI1dHYpTdMm2ajhhM3cqTPcwCLcBGAsYHQ/s400/belorussian%2Bt-72a.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-JhgzPyE01bo/XnXRUXY8UFI/AAAAAAAAQY0/3Qhm4fJeCooY12crkRSp-bNt2FJv-NU5gCLcBGAsYHQ/s1600/belorussian%2Bt-72a%2B2.jpg" style="font-size: medium; font-weight: 400; margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="461" data-original-width="626" height="293" src="https://1.bp.blogspot.com/-JhgzPyE01bo/XnXRUXY8UFI/AAAAAAAAQY0/3Qhm4fJeCooY12crkRSp-bNt2FJv-NU5gCLcBGAsYHQ/s400/belorussian%2Bt-72a%2B2.jpg" width="400" /></a></div>
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<span style="font-size: small;"><span style="font-weight: 400;">The two photos below show "Improved T-72A" tanks participating in the August 1991 failed coup d'état attempt in Moscow. These vehicles entered service with the 2nd Guards Tamanskaya Motor Rifle Division. The tank in the photo on the left was specifically identified as a T-72A obr. 1983 in the collection of memoirs "<i>Life Given to Tanks</i>".</span></span></div>
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<a href="https://1.bp.blogspot.com/-mxta8fwznHI/XnHU7ibfR4I/AAAAAAAAQTk/XRuXvVN7TeYZ0gYx--sjY9VqjDN9AqCFQCEwYBhgL/s1600/t-72a%2Bobr%2B1984%2Bin%2Bmoscow.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="280" data-original-width="480" height="233" src="https://1.bp.blogspot.com/-mxta8fwznHI/XnHU7ibfR4I/AAAAAAAAQTk/XRuXvVN7TeYZ0gYx--sjY9VqjDN9AqCFQCEwYBhgL/s400/t-72a%2Bobr%2B1984%2Bin%2Bmoscow.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-LrpecjIWFBM/XnHWPX0ztxI/AAAAAAAAQTo/BAAUib52XEMwjsOnvM_1rlDePVlygNocwCLcBGAsYHQ/s1600/USSR-RUSSIA-HISTORY-COUP-1991.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="259" data-original-width="462" height="224" src="https://1.bp.blogspot.com/-LrpecjIWFBM/XnHWPX0ztxI/AAAAAAAAQTo/BAAUib52XEMwjsOnvM_1rlDePVlygNocwCLcBGAsYHQ/s400/USSR-RUSSIA-HISTORY-COUP-1991.jpg" width="400" /></a></div>
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<span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-size: small;"><span style="font-weight: 400;"><span style="font-size: small;">Currently, </span><span style="font-size: small; font-weight: 700;"><span style="font-weight: 400;">tanks with the old 902A system are very rarely encountered in Russia. It is very likely that they were produced in small numbers, and most tanks were instead manufactured with the 902B system in preparation for the installation of Kontakt-1. Upon receiving Kontakt-1, an "<i>Improved T-72A</i>" is converted into a T-72B or T-72B1, depending on whether the tank has the "Svir" missile system installed or just a TPN-3 night vision sight.</span></span></span></span><br />
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<a href="https://1.bp.blogspot.com/-yYUDpp21Dn0/XnPNBYQ0jFI/AAAAAAAAQWo/dXIXGHvcp_4IEdZxNRVACaZCPPOKVsQJQCLcBGAsYHQ/s1600/t-72a%2Bobr%2B1984%2Bfront%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="438" data-original-width="659" height="265" src="https://1.bp.blogspot.com/-yYUDpp21Dn0/XnPNBYQ0jFI/AAAAAAAAQWo/dXIXGHvcp_4IEdZxNRVACaZCPPOKVsQJQCLcBGAsYHQ/s400/t-72a%2Bobr%2B1984%2Bfront%2Bview.png" width="400" /></a><a href="https://1.bp.blogspot.com/-yPmj3H7RMaU/XnPNBTIak-I/AAAAAAAAQWk/QitJZup_I6YmYKN2bcYdGf_W16-So_RJgCLcBGAsYHQ/s1600/moscow%2Bcoup%2Bt-72a%2Bobr%2B1984.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="658" data-original-width="1000" height="262" src="https://1.bp.blogspot.com/-yPmj3H7RMaU/XnPNBTIak-I/AAAAAAAAQWk/QitJZup_I6YmYKN2bcYdGf_W16-So_RJgCLcBGAsYHQ/s400/moscow%2Bcoup%2Bt-72a%2Bobr%2B1984.jpg" width="400" /></a></div>
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<span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-size: small;"><span style="font-weight: 400;">The design of the upper glacis armour array of the "Improved T-72A" represented the first major design change in the upper glacis armour of all Soviet main battle tanks since the addition of a steel back plate to the STB composite armour of the Object 432 obr. 1964. Instead, the new armour features spaced high hardness steel plates as inserts. In the collection of memoirs "Life Given to Tanks", it is stated by V. D. Tumasov (head of the Department of Armour in UKBTM) that the new armour design was a multilayered array of steel and air, as opposed to composite armour with various fillers. This is corroborated in the book "<i>T-72/T-90: Опыт создания отечественных основных боевых танков</i>" published by the Uralvagonzavod corporation in 2013, where the new armour was described as flat parallel plates with inserts made of high hardness steel. In essence, both describe a multilayered spaced armour array with RHA front and back plates with high hardness steel plate inserts. </span></span><br />
<span style="font-size: small; font-weight: 400;"><br /></span><span style="font-size: small; font-weight: 400;">The grade of steel is not mentioned in any source. Judging by the low thickness of the plates and the installation method (lack of welding), any high hardness steel with poor weldability can be used. The widespread BT-70 or BT-70Sh high hardness steel grades are the most likely candidates. </span><br />
<span style="font-size: small; font-weight: 400;"><br /></span><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-size: small;"><span style="font-weight: 400;">Like the upper glacis of a tank with the earlier 60-105-50 armour, the upper glacis of a tank with the "Reflection-1" armour has three anti-ricochet ribs in front of the driver's periscope, with one large rib and two small ribs. This can be seen in the two photos above. Because of this, it is quite difficult to distinguish between a tank with the "Reflection-1" armour and one with 60-105-50 armour. Depending on the context, it may be possible that the lack of a 16mm appliqué armour plate on a post-1984 T-72A tank indicates the presence of the new armour, but this may not be a reliable identifier as it is impossible to confirm that all tanks in the Soviet Army received the appliqué plate during or after 1984.</span></span><br />
<span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-size: small;"><span style="font-weight: 400;">The thickness of the armour remained the same as that of 60-105-50 design. The omission of STB was ordered by UKBTM Chief Designer V. N. Vendiktov. He specified that the increase in armour mass had to be minimal, and that the protection requirement had to be achieved without using glass textolite. One of the reasons was its cost. Glass textolite is produced using laminated glass mats, and glass mats are the most expensive filler for glass reinforced plastics as stated on page 21 of the book "Стеклотекстолит" ("Glass Textolite"). There were also some safety concerns, as glass fibers are dangerous to inhale.</span></span><br />
<span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-size: small;"><span style="font-weight: 400;">The new armour was developed at UKBTM with the participation of NII Stali. The institute was engaged in research in all forms of tank armour, including the refining of existing concepts and the exploration of prospective new ideas. NII Stali was involved in work at all three tank design bureaus, in Nizhniy Tagil, Leningrad and Kharkov, but the choice and implementation of the particular type of armour was made at the discretion of the design bureau. One line of research focused on further developing the existing steel-STB-steel armour technology by adding a high hardness steel plate in the middle of the armour array to split the glass textolite layer into two, with a total of five layers in the armour array. This was the option pursued by the LKZ design bureau in Leningrad and by the Malyshev design bureau in Kharkov. In 1985, this type of armour was implemented in the T-64BV and T-80BV, but in different forms. At this point, not one among the three tanks shared the same armour, unlike in the mid 1970's when all three series featured the same 80-105-20 armour developed by NII Stali.</span></span><br />
<span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-size: small;"><span style="font-weight: 400;">Over the course of the work on the "Reflection-1" project, over thirty mock-ups of different armour configurations were designed, manufactured and tested and 2,500 rounds of ammunition were expended in live fire tests. Multilayered armour arrays with various fillers were considered as well as arrays with no fillers (spaced armour). The objective was to provide protection from M111 as well as from potential KE threats of the future with a simultaneous increase in resistance from HEAT threats. </span></span><br />
<span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-size: small;"><span style="font-weight: 400;">On the 4th of November 1982, the Ministry of Defence issued order No. 620 to implement the "Reflection-1" project. In accordance with this order, the mass production of T-72A hulls with the new armour began in early 1983 and gradually accelerated. Some of these tanks were paired with the new "reflecting plate" turret, and others were not.</span></span><br />
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<span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-size: small;"><span style="font-weight: 400;">Based on available information, the spaced armour array of the "Improved T-72A" was a limited solution that offered better protection from KE threats but no real improvement in shaped charge protection.</span></span><br />
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<span style="font-size: small;"><span style="font-weight: 400;">The photo above shows a destroyed T-72 from the first Chechen war. The glacis array of a destroyed "Improved T-72A" is visible down at the bottom half of the left side of the photo. Note that the spaced steel plates are held by spacers identical to the type used in the earlier 80-105-20 and 60-105-20 armour designs. These ensure proper spacing between the plates and are also the sole mounting points for the spaced plates, as they are not welded along the sides, top or bottom edges and there are no discernible supports elsewhere.</span></span></div>
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<span style="font-size: small;"><span style="font-weight: 400;">The thickness of the internal plates is not known, and the only information that can be gleaned from these photos is that the three plates are spaced equally apart by air gaps of equal size, and the plates all appear to have identical thicknesses.</span></span><br />
<span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-size: small;"><span style="font-weight: 400;">However, because it is known that the total thickness of the armour array is 215mm, it is reasonable to assume that the upper glacis of the "Improved T-72A" has the same thicknesses for the front plate and back plate (60mm and 50mm respectively) and has a 105mm gap in between. The 105mm gap can be divided into seven parts representing three plates and four air gaps of equal thicknesses. Thus, the plates should be around 15mm thick and the air gaps should be around 15mm in size. The estimated armour array would therefore be 60-15-15-15-50.</span></span><br />
<span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span><span style="font-size: small;"><span style="font-weight: 400;">In total, this estimated array has 155mm of steel. Compared to earlier armour designs, it is only marginally heavier. The areal density of the armour is 3,248 kg/sq.m, which is quite high, but not significantly higher than the armour of the T-72A with a 16mm appliqué armour plate as that already has an areal density of 3,161 kg/sq.m. The "Improved T-72A" would therefore not have experienced a noticeable weight gain from the change to the new upper glacis armour design. This is congruent with the design objective for the "Reflection-1" project.</span></span><br />
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<span style="font-size: small;"><span style="font-weight: 400;">In some publications, the upper glacis armour of the tanks seen during the 1986 parade was described as being upgraded with a 20mm appliqué plate, implying that the same 60-105-50 armour was kept but simply reinforced. This claim is self-evidently incorrect. It is most often encountered in English publications from the past two decades, and it </span></span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">may have originated in the article "</span><i style="font-family: "times new roman"; font-size: medium; font-weight: 400;">Танки Т-72: Вчера, Сегодня, Завтра</i><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">" by Sergey Suvorov, published in the July 2004 issue of the </span><span style="font-size: small; font-weight: 400;">"</span><span style="font-size: small; font-weight: 400;">Техника и Вооружение</span><span style="font-size: small; font-weight: 400;">" </span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">magazine.</span><br />
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<span style="font-size: large;">EFFECT ON KE THREATS</span></h3>
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Alone, the combination of a 60mm front plate and 50mm back plate with a 105mm air gap qualifies as spaced armour. As discussed earlier, a two-layer spaced armour of this type achieves an ME coefficient of 1.11 against the 105mm DM13 and 120mm DM13 APFSDS rounds. The three spaced high hardness steel plates serve to further break apart a penetrator before it reaches the back plate, as opposed to the passive resistance offered by the glass textolite interlayer of the old 60-105-50 array. </div>
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The interactions between long rod penetrators and spaced armour have been studied extensively, which is quite natural considering that spaced armour is considered the simplest form of multilayered armour. However, from a conceptual standpoint, many spaced armour experiments do not represent the "Reflection-1" armour accurately as there is no thick back plate for the target setup. For example, one s<span style="font-family: "times new roman";">tudy featured in the book "</span><i style="font-family: "times new roman";">Particular Questions of Terminal Ballistics</i><span style="font-family: "times new roman";">" 2006 (</span><i style="font-family: "times new roman";">Частные Вопросы Конечной Баллистики</i><span style="font-family: "times new roman";">) published by the Bauman Moscow State Technical University on behalf of NII Stali, showed that i</span>t was possible to increase the mass efficiency by redistributing the mass of a single homogeneous steel plate into multiple layers in a spaced armour array, but it was found that there were serious limits to the effectiveness of this type of armour. </div>
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The two graphs shown below illustrate the difference in the velocity limit of nominal defeat and the change in mass efficiency obtained by splitting homogeneous steel plate. The graph on the left (<i>а</i>), shows the change in the velocity limit of nominal defeat for three tested angles. (1) - 0 degrees; (2) - 30 degrees; (3) - 60 degrees. The graph on the right (<i>б</i>) shows the same, but in terms of percentage, where (1) - 0 degrees; (2) - 30 degrees; (3) - 60 degrees. Additionally, graph (b) shows the change in mass efficiency, where (4) - 0 degrees; (5) - 30 degrees; (6) - 60 degrees.</div>
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Splitting a homogeneous steel plate sloped at 60 degrees into two equal layers at the same slope provided a weight saving of around 6%, and splitting it into three equal layers provided the largest weight saving of 13%. Splitting the steel plate into four layers almost completely neutralized the positive effect of spaced armour, and splitting the plate into more than four layers gave a negative effect. While interesting, these findings are mostly irrelevant due to the peculiarities of the experimental setup.</div>
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The steep reduction in mass efficiency from the splitting of a homogeneous armour plate into multiple thinner plates below a certain number of layers can be entirely attributed to to the loss of rigidity in the last few plates in the spaced armour array. As discussed before when examining the 80-105-20 armour array, the 20mm back plate had a significantly lower ME coefficient than RHA steel owing to its excessively low thickness and correspondingly low rigidity. A spaced armour array with layers of thin plates that are of a uniform thickness will be able to break up a long rod penetrator quite effectively in the first layers, but the last layers perform poorly as a backing plate. Because of this, the overall efficiency of the array suffers considerably. In this particular experiment, the specific thicknesses of the armour and the caliber of the long rod penetrator tested against it were the two factors that, combined, produced such a result.</div>
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An optimal spaced armour design with maximum mass efficiency has an array of thin spaced plates and a thick back plate. This avoids the main issue with a multilayered spaced armour array. Because of this structural factor, the "<i>Reflection-1</i>" armour retains the 50mm back plate of the previous 60-105-50 armour design.</div>
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<span style="font-family: "times new roman"; font-size: small;">In the same book, a different study is detailed. Different findings were obtained due to a more realistic experimental setup. It was found that high armour obliquity is required for spaced armour to be effective against long rod monobloc penetrators, that increasing the number of plates in a spaced armour array improves its mass efficiency and that increasing the elongation of a long rod penetrator reduces the effectiveness of the spaced armour array. The relevant paragraph is shown below:</span><br />
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<span style="font-family: "times new roman"; font-size: small;">"</span><i><span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;">Прирост стойкости двух- и многопреградных структур фиксированной толщины неизбежно падает увеличением длины сердечника </span></span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">БПС в связи с соответствующим увеличением МПР, необходимого для </span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">максимально возможного использования эффектов изгиба и разрушения сердечника при пробитии сильно наклоненных преград. На реальном возможных толщинах многопреградных структур следует рассчитывать не более чем на 15% прироста стойкости при воздействии </span><span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;">моноблочных вольфрамовых сердечников с удлинением 15...20 (с использованием броневых сталей средней твердости) Этот прирост при </span></span><span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;">больших углах встречи достигается числом преград от трех до пяти, в зависимости от соотношения МПР и общей толщины преграды. При </span></span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">малых углах встречи разнесение преград малоэффективно.</span></i><span style="font-family: "times new roman"; font-size: 18.72px;">"</span></div>
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<span style="font-family: "times new roman"; font-size: small;"><span style="font-weight: 400;">"</span><span style="font-style: italic;">The increase in the durability of dual and multi-layered structures of a fixed thickness inevitably falls with the increase in the length of the APFSDS penetrator due to the corresponding increase in the MPR </span><span style="font-style: italic;">[air gap between layers]</span><span style="font-weight: normal;"></span><span style="font-style: italic;"> required for the maximum possible use of the bending and fracture effects of the core when penetrating steeply sloped targets. Given the realistic possible thicknesses of multi-layered structures, one should expect no more than a 15% increase in resistance against monobloc tungsten cores with an elongation </span><span style="font-style: italic;">[aspect ratio]</span><span style="font-style: italic;"> of 15-20 (using medium hardness armour steels). This increase at large impact angles is achieved with three to five layers, depending on the ratio of the MPR</span></span><span style="font-family: "times new roman"; font-size: small; font-style: italic;"> and the total thickness of the array. At small impact angles, incorporating air gaps is ineffective.</span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">"</span></div>
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<span style="font-family: "times new roman"; font-size: small;"><br /></span><span style="font-family: "times new roman"; font-size: small;"><br /></span><span style="font-family: "times new roman"; font-size: small;">In other words, a multi-layered spaced armour array is not more effective than a monolithic homogeneous block of armour at small angles of obliquity and the efficiency of highly angled spaced armour array will decrease when the elongation of a long rod penetrator is increased. Compared to a monolithic homogeneous block when attacked with a tungsten long rod penetrator with an aspect ratio of 15-20, a three to five-layer spaced armour array has a mass efficiency of around 1.15. In addition to this, using high hardness and high strength steels yields further improvements in the efficiency of the armour array:</span></div>
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<span style="font-family: "times new roman"; font-size: small;"><br /></span><span style="font-family: "times new roman"; font-size: small;"><br /></span><span style="font-family: "times new roman"; font-size: small;">"<i>Увеличение прочности (твердости) стальных броневых преград при сохранении пластичности приводит к соответствующему повышению противоснарядной стойкости многопреградных структур. Использование броневых сталей повышенной и высокой твердости с пределами текучести 120 ... 130 МПа на структурах, характерных для лобового бронирования танков, обеспечивает дополнительный прирост стойкости 10...15%.</i>"</span></div>
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<span style="font-family: "times new roman"; font-size: small;"><br /></span><span style="font-family: "times new roman"; font-size: small;"><br /></span><span style="font-family: "times new roman"; font-size: small;">"<i>Increasing the strength (hardness) of steel armored barriers while maintaining ductility leads to a corresponding increase in the ballistic resistance of multi-layered structures. The use of high hardness armour steels with yield strengths of 120-130 MPa on structures characteristic for frontal tank armour provides an additional increase in resistance of 10-15%.</i>"</span></div>
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An additional nuance of the armour design to consider is the specific combination of thin high hardness plates and small air gaps which is not replicated in many experimental spaced armour targets. For instance, KE munitions in NATO member nations were invariably tested against the NATO Triple Heavy target which was meant to represent the side armour of a Soviet T-10 heavy tank and as such, included large air gaps between the three layers of the target. This is a completely different form of spaced armour with its own distinguishing characteristics. The differences are major enough that in Russian and Chinese textbooks and other specialist literature, this type of spaced armour is referred to as "shielded armour".</div>
<span style="font-weight: normal;"><br /></span><span style="font-weight: normal;">On the topic of air gaps, it should be noted that the size of the air gap between densely packed spaced plates such as in the 60-15-15-15-50 array has no direct effect on the integrity of the rod. However, this does not mean that the size of air gaps in tank armour is arbitrary; one of the functions of the air gap is to allow the tip of the rod to ricochet up and away from the plate and to allow the shattered fragments of the tip to be ejected away from the penetration crater, preventing them from contributing to the depth of the penetration. Without a sufficiently large air gap, the fragments have nowhere else to go, so they are pushed into the next armour plate and thus, they can still contribute to armour penetration. The small 15mm air gaps in the armour are sufficiently large to prevent this.</span><br />
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<span style="font-weight: 400;">A good example of oblique spaced steel armour arrays can be found in the study "<a href="https://www.researchgate.net/publication/228529929_A_unified_model_for_long-rod_penetration_in_multiple_metallic_plates"><i>A unified model for long-rod penetration in multiple metallic plates</i></a>" by S. Chocron et al. A dense pack of six spaced plates was used for the tests, each plate being 19mm thick and sloped at 65 degrees to the vertical plane. Each plate was separated by an air gap of 25.4mm in length and the distance between the last plate and the RHA witness block was 76.2mm. Long rod projectiles were fired at the armour pack at super-ordnance velocity and the depth of penetration into the witness block was recorded.</span><br />
<span style="font-weight: 400;"><br /></span><span style="font-weight: 400;">Super-ordnance velocity was defined as the range velocities of between 1.72 to 1.78 km/s which exceeds the normal muzzle velocity of 105mm and 120mm guns by around Mach 1 and Mach 0.3 respectively. This simulated hypersonic impacts. Hypervelocity penetrators with a velocity of 2.6 km/s were also tested, but the results of these tests have little relevance to us. The lower the impact velocity of the penetrator, the greater the effect of target and penetrator material strength, and the typical impact velocity range for APFSDS fired from 105-120mm guns at 1.5 km is 1,400-1,500 m/s, so the effect of the strength of the RHA and HHS plates in the "<i>Reflection-1</i>" armour array still remains a highly relevant factor in the overall protective capabilities of the armour under normal conditions.</span><br />
<span style="font-weight: 400;"><br /></span><span style="font-weight: 400;">The pretest assumption was that the spaced steel plates would offer the same resistance as the line-of-sight thickness indicated, i.e each 19mm plate was assumed to possess a resistance of 45mm of steel. However, the experiment showed that the estimated penetration depth into the witness block was 40mm less than predicted.</span><span style="font-weight: 400;"> </span><span style="font-weight: 400;">It was surmised that repeated impacts and breakouts was the cause of the overprediction, and although it was not explicitly mentioned to be a source of penetration loss, it is worth noting that the 1.78 km/s rod was yawed by 2.34 degrees after passing through the spaced plate array, before it impacted the RHA witness plate. This is consistent with all of the other studies concerning spaced armour. The information regarding the yaw of the penetration was included in a different study, "<a href="http://www.dtic.mil/dtic/tr/fulltext/u2/a281384.pdf"><i>Pretest Predictions of Long-Rod Interactions With Armor Technology Targets</i></a>".</span><br />
<span style="font-weight: 400;"><br /></span><span style="font-weight: 400;">As the illustration below shows, the pressure spikes at the moment of impact with a spaced plate and falls rapidly as the rod passes through the physical thickness of the plate. After perforating the plate, the pressure drops down to zero as the rod travels into the air gap before spiking again as the next plate is struck. </span><br />
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<span style="font-weight: 400;"><br /></span><span style="font-weight: 400;">The inability of the penetrator rod to achieve quasi-steady state penetration through spaced plates results in a reduction in the efficiency of the rod.</span><br />
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<span style="font-weight: 400;">According to the experiments, it was deduced that the deformed and fractured tip of the penetrator is a result of structural failure from large stresses, so it was considered to no longer be a part of the rod. For all intents and purposes, the tip was therefore considered to be incapable of contributing to the penetration of the rod, so it was discarded after the perforation of each spaced plate to simulate the detachment of the tip. To simulate the discarded tip, lengths of 1.5 D or 1.8 D were subtracted from the rod, and a loss of 1.8 D was found to generally agree with the results of the super-ordnance penetrator (1.72 km/s) but not the hypervelocity penetrator (2.6 km/s). The analytic model for the hypervelocity penetrator would require a length reduction of as much as 2.0 D to agree with the experimental results. To supplement this, it is stated on page 250 in </span><span style="font-size: small; font-weight: 400;">"</span><i style="font-family: "times new roman";">Particular Questions of Terminal Ballistics</i><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">" 2006 (</span><i style="font-family: "times new roman";">Частные Вопросы Конечной Баллистики</i><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">) that</span><span style="font-weight: 400;"> the length of the rod broken off due to breakout effects for plates at a high obliquity was equal to 1.5 times the LOS thickness of the plate, regardless of the hardness of the plate.</span><br />
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<span style="font-weight: normal;">In total, a significant amount of penetrator material is lost during the impact and breakout phases, which allows a spaced thin plate to reduce the penetration power of a long rod penetrator by more than the LOS thickness of the plate implies. Because of this, an array of multiple thin spaced plates with small air gaps can have a positive mass efficiency.</span></div>
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<span style="font-weight: normal;"><br /></span><span style="font-weight: normal;"><span style="font-weight: normal;"><span style="font-weight: normal;">From this, it is easy to see the advantage of multiple oblique spaced plates of high hardness steel.</span></span><span style="font-weight: 400;"> </span><span style="font-weight: normal;">These results are supported by the findings in studies such as "<i>Oblique Impact of Elongated Projectiles on Massive Targets</i>" by Veldanov et al. and "</span><a href="http://iopscience.iop.org/article/10.1088/0022-3727/35/20/331/pdf" style="font-weight: normal;"><i>Ricochet of a tungsten heavy alloy long-rod projectile from deformable steel plates</i></a><span style="font-weight: normal;">" by Woong Lee et al., and others. </span><span style="font-weight: 400;">Of course, it should not be forgotten that all of the same impact and breakout effects apply to the heavy front plate of the array as it can contribute to the effectiveness of the spaced plates by removing and deforms the tip of long rod penetrators, conditioning them for defeat by the spaced plates. </span></span></div>
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All of these phenomena can be seen in the image below where a two-layer spaced armour target with a small air gap is perforated by a long rod penetrator with a high aspect ratio. The image is a composite of several X-ray photos at different points in time. After passing through both plates, the rod is highly fragmented and the tip is completely missing, having been destroyed as it was deflected off the surfaces of the first and second spaced plates.</div>
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The two waves of penetrator ejecta on the surfaces of the two plates show the large amount of penetrator material removed during the impact phase with the two plates. Furthermore, the amount of ejecta visible on the second plate is clearly more than the ejecta from the first plate, showing that the destruction of the original tip on the surface of the first plate reduced the efficiency of the rod during the following impact with the second plate.</div>
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<span style="font-weight: 400;">As mentioned before, six spaced plates were used in the experimental array, each 19mm thick and spaced an inch apart from each other (25.4mm). The witness block was spaced behind the last plate at a distance of 76.2mm and simulated a semi-infinite target. The entire array was angled at 65 degrees and the total LOS thickness was 270mm. The LOS penetration of the spaced plate array including the penetration depth into the witness block amounted to a total of only 414mm. Compared to the penetration depth of 524mm recorded for the finite thickness plate at a normal impact angle, the difference amounts 110mm RHA. Therefore, the spaced armour array is worth 110mm more armour than its own LOS thickness, implicitly indicating a mass efficiency of 1.26 for the spaced steel plate array. This is despite the fact that long rod penetrators are known to penetrate a greater thickness of sloped armour plate than flat armour plate.</span></div>
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<span style="font-size: small;"><span style="font-weight: 400;">According to <a href="http://btvt.narod.ru/4/armor.htm">an article published by Andrei Tarasenko</a>, the first version of the T-72B hull armour (referring to the "<i>Improved T-72A</i>" from 1984) was 20% more effective than a homogeneous plate by mass, so the ME coefficient is 1.2. In <a href="http://btvt.info/1inservice/t-72B.htm#_%D0%97%D0%B0%D1%89%D0%B8%D1%82%D0%B0">a separate article</a>, the armour is stated to have an effective thickness of 490mm RHA.</span></span><span style="font-size: small; font-weight: 400;"> However, the standard of armour defeat used to determine this coefficient is not known. As such, this effective thickness figure could refer to either nominal defeat or initial perforation. More likely, it refers to the latter. Aside from these articles by Tarasenko, there are no other sources that directly divulge the effective thickness of this armour.</span><br />
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Against shaped charges, the main consequence of switching from a steel-STB-steel composite to a spaced steel armour array was the change in the operating principle of the armour. The "Reflection-1" armour was still a completely passive system, but the interstitial space between the front plate and back plate no longer serves to only absorb the kinetic energy of the SCJ but also functions as additional disruptive elements.<br />
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However, this does not imply that the armour has a higher ME compared to steel-STB-steel composite against shaped charges. On the contrary, this type of spaced armour is generally inferior. This may only be somewhat offset by the fact that the "Reflection-1" armour is only slightly heavier than the 16-60-105-50 armour.<br />
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As mentioned before, increasing the hardness of the steel front plate leads to a reduction in the overall efficiency of the armour array as it reduces the energy absorption capacity of the material and renders it less effective at disrupting the cohesiveness of an SCJ. However, the high hardness of the internal spaced steel plates has no significant effect. The combination of a 60mm RHA front plate and high hardness 15mm spaced plates is therefore not problematic.<br />
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In a study presented in a Chinese textbook on tank armour, a form of spaced armour closely resembling that of the "Reflection-1" design was experimented upon. The primary finding is that the obliquity of the spaced armour array has little to no effect on its effectiveness. Moreover, it was found that the penetration of the shaped charge into the spaced multilayer target is reduced by 15% compared to a monolithic steel target, i.e. the final penetration is 85% of the amount in a monolithic steel target. The reciprocal of 0.85 is calculated to find the ME coefficient: 1.176. The total volume of the holes created in each spaced plate is larger than the volume of the penetration crater created in a monolithic steel target, indicated for the spaced target, a smaller portion of the jet energy was spent increasing the depth of the penetration channel.</div>
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<span style="font-weight: normal;">However, despite the close resemblance of the target used in the experiment to the spaced plates in the "Reflection-1" armour, it is not possible to directly apply the findings of this study because the SCJ is not disrupted before it encounters the target. In the "Reflection-1" armour, the front plate is still thick enough to disrupt and </span>scatter<span style="font-weight: normal;"> the jet of a shaped charge warhead, so the penetration of the jet will not increase due to jet stretching in the air gaps of the spaced armour array, and the penetration efficiency is lower as a whole. This resolves the issue of spaced armour acting as additional standoff for a shaped charge warhead, and it enhances the disruptive effect of the internal spaced plates. As such, it is only possible to conclude that the ME coefficient of the internal spaced plates is more than 1.176, and nothing else.</span></div>
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It is important to note that in the 80-105-20 and 60-105-50 armour designs, the steel back plate has an ME coefficient of 1.13 because it encounters the SCJ only after it has been scattered by perforating the steel front plate. By applying this ME coefficient to the spaced plates and the back plate in the "Reflection-1" array, it is estimated that these layers have an ME coefficient of ~1.33. The overall ME coefficient of the entire armour array is therefore 1.2. This approach is probably far too simple to have yielded an accurate calculation. </div>
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<span style="font-size: small; font-weight: 400;">However, it is stated in </span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">page 286 of the textbook </span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">"</span><i style="font-family: "times new roman"; font-size: medium; font-weight: 400;">Particular Questions of Terminal Ballistics</i><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">"</span><span style="font-size: small; font-weight: 400;"> that a multi-layered NERA armour design is 40% more effective than monolithic steel of the same weight against shaped charges and 10-23% more effective than multi-layered spaced steel armour of the same weight. Based on this, it can be surmised that spaced steel armour would have a mass efficiency of 1.14 to 1.27 compared to homogeneous steel armour. The midpoint of these figures, 1.2, is coincidentally the same as the figure obtained earlier.</span></div>
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<span style="font-size: small; font-weight: 400;">Applying the ME coefficient of 1.2, the "Reflection-1" armour would have an effective thickness of 496mm RHA, which makes it essentially equivalent to the 500mm RHA effective thickness of the basic T-72A.</span><span style="font-size: small;"> This figure is completely congruent with the general requirement for the "Reflection-1" armour to be a significant improvement over the earlier 60-105-50 armour design in terms of resistance to KE threats and to not be inferior in terms of resistance to HEAT threats. </span></div>
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<span style="font-size: small;">The lack of an improvement in shaped charge protection was not considered a significant shortcoming of the armour as the task of countering the existing and upcoming ATGM systems in NATO was left to be handled by "Kontakt-1" ERA. While an improvement in the base armour protection was certainly desirable, the magnitude of the improvement required to make a difference against the new generation of ATGM systems (with a penetration of up to 900mm RHA) required the application of a completely new type of armour with an extremely high mass efficiency. This was, in essence, fulfilled by ERA. </span></div>
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<span style="font-weight: normal;">The upper glacis armour of the T-72B was a further development of the "<i>Reflection-1</i>" project, which had been implemented on T-72 tanks since 1983. T</span><span style="font-weight: 400;">he lighter "<i>Reflection-1</i>" armour (60-15-15-15-50) that was used for the "</span><i style="font-weight: 400;">Improved T-72A</i><span style="font-weight: 400;">" tanks from 1983 and 1984 yielded a very modest gain in weight compared to the 16-60-105-50 armour array, but due to the higher efficiency against KE threats, the effect is that the new armour array approaches or reaches 500mm RHA in effective thickness, which is very good. This was sufficient protection against the 105mm gun threat, but p</span><span style="font-weight: 400;">roviding security from the new APFSDS ammunition developed for the British L11 and L30 rifled 120mm guns and the new 120mm gun observed on the new German Leopard 2 tank was a more difficult task that required a further gain in protection value, which necessitated a gain in armour mass.</span><br />
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The new armour retained a 60mm front plate and a 50mm back plate, but the size of the interstitial space was increased to 110mm. In it, there were two 10mm high hardness steel plates and two 20mm high hardness steel plates, each separated by 10mm air gaps. The overall array scheme of the array is 60-10-10-20-20-50.<br />
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Like the earlier upper glacis armour designs, there are three anti-ricochet ribs in front of the driver's periscope. Externally, there seems to be no identification aid that can be used to distinguish this armour from the "<i>Reflection-1</i>" armour.<br />
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<span style="font-weight: 400;">The photo below shows the exposed glacis armour of a T-72B3 that its idler mount ripped off due to an accident during the 2015 Tank Biathlon. Although the camera angle is not ideal, it can be seen that the layout of the internal spaced plates match the description. The uniform coat of surface rust indicates that these are simply steel plates and not NERA panels. </span></div>
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The two images below show another T-72B that was involved in an accident severe enough to rip off the idler mount, thus exposing the same part of the upper glacis armour.<br />
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<span style="font-size: small;"><span style="font-weight: normal;">Again, it can be clearly seen that the spaced steel plates are not welded to the side hull armour plate by looking at the photo below. The spacing between the plates is maintained by metal spacing brackets similar to the type used in the "<i>Reflection-1</i>" armour, but they are removed in the photo below. This explains why the space between the plates is uneven and some of the plates are in contact with each other, whereas the plates of the damaged T-72B3 seen in the photo above clearly show uniform spacing between the plates.</span></span></div>
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It is likely that BT-70Sh high hardness ESR steel was used, as it is treated a hardness of around 534 BHN when produced in thin plates and is readily weldable. However, the spaced steel plates of the armour arrays described for the "<i>Improved T-72A</i>" and T-72B obr. 1985 variants are not secured to the side hull plates by welding but are suspended by spacers. This means that welding is not an issue, so high hardness steels with poor weldability can be used without structural issues. However, without having clear answers regarding the specific grade of steel used for the spaced plates is used in the T-72B, it is perhaps safer to work under a conservative estimate is that BTK-1Sh steel was used.</div>
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<span style="font-size: small; font-weight: normal;">The total thickness of this array is 220mm which is only 5mm more than the 60-105-50 array of the T-72A and 6mm less than the upgraded 16-60-105-50 array, but the thickness of steel in the array is increased from 110-126mm to 170mm. The total thickness of steel is also greater than in the "<i>Reflection-1</i>" array. At the constructional 68-degree angle of the upper glacis, the physical LOS thickness of steel in the array is 454mm. </span><br />
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The areal density is 3,562 kg/sq.m. From its areal density alone, the armour array would be similar to the armour of the Leopard 2 (~3,500 kg/sq.m), but the actual effective armour value requires the mass efficiency to be known. For instance, since the Leopard 2 is known to use NERA armour, it must have a higher mass efficiency against HEAT threats compared to the spaced steel armour of the T-72B, but it is also known that early NERA designs were largely ineffective against long rod penetrators so the armour may be less effective than the T-72B against KE threats. Knowing the areal densities, the comparative thicknesses of the armour does not matter that much as it is obvious that the thicker array is simply filled with more air than the thinner array.<br />
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As a further development on the "Reflection-1" concept, the heavier and more complex 60-10-10-20-20-50 armour works under the same operating principles against long rod penetrators, differing only in the greater number of layers and the increased complexity. An increase in mass efficiency is expected from this, but the extent of the improvement is not well understood. It is only safe to assume that the ME coefficient of the armour is somewhat above 1.2.<br />
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In the memoirs <span style="font-size: small; font-weight: 400;">"</span><i style="font-size: medium; font-weight: 400;">Life Given to Tanks</i><span style="font-size: small; font-weight: 400;">" dedicated to the</span><span style="font-size: small; font-weight: 400;"> UKBTM chief designer V.N Venediktov,</span><span style="font-size: small; font-weight: 400;"> </span><span style="font-size: small; font-weight: 400;">published in 2010,</span> G. A. Kheifits, a <span style="font-size: small; font-weight: 700;"><span style="font-weight: 400;">leading specialist in the D</span></span>epartment of Armour at UKBTM who was appointed to the State Commission for testing the T-72B tank, describes the live fire tests against mock ups of the T-72B upper glacis and other experimental armour designs developed by the UKBTM design bureau that took place at the proving grounds of the Main Missile and Artillery Directorate (GRAU) in Donguz (in the Southern Urals). At the same time, various armour designs developed by the LKZ design bureau were also being tested at the same proving grounds, including a mock up of the T-80BV upper glacis. The tests were carried out with the 125mm 3BM-32 "Vant" monobloc DU long rod APFSDS ammunition, which was the newest ammunition of its type available in the Soviet Army in 1985.<br />
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<span style="font-size: small;">According to Kheifits, the tests of the T-72B armour designed by UKBTM were successful. Even after increasing the amount of propellant to launch the "Vant" round at its maximum permissible velocity, it was not possible to break through the armour. On the other hand, the armour designed by LKZ was perforated by "Vant" when fired from a standard propellant charge. </span></div>
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Using the Lanz-Odermatt equation, the perforation limit of 3BM32 "Vant" at its muzzle velocity of 1,710 m/s is calculated to be 192mm at 68 degrees (~513mm LOS), with the target being medium hardness RHA (270 BHN). To convert from initial perforation to nominal defeat, a physical thickness of 10mm is added, translating to an effective thickness figure of 540mm. In other words, to resist 3BM32 at its muzzle velocity, the effective thickness of the 60-10-10-20-20-50 armour must equivalent to around 540mm RHA. With the armour having the same weight as 454mm of steel, this implies that the mass efficiency coefficient of the armour is only 1.18 which is less than the 1.2 coefficient of the "<i>Reflection-1</i>" array.<br />
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The so-called "maximum permissible velocity" is assumed to be the muzzle velocity of "Vant" at a charge temperature of +40°C, which is listed as the maximum temperature in a <a href="https://pp.userapi.com/c629124/v629124491/2829/Hrko1f2ISCo.jpg">NIMI (Research Institute of the Machine Industry) catalogue</a>. With 12/7 V/A propellant, the difference in muzzle velocity at 15°C and 40°C is +2.5%. The maximum permissible velocity is therefore around 1,753 m/s. At this velocity, the perforation limit is calculated to be 195mm RHA at 68 degrees (~522mm LOS). Converting to nominal defeat, the effective thickness of the armour would be around 550mm RHA.</div>
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<span style="font-size: small; font-weight: normal;">In the article "<i>П</i></span><i>оложение в Отечественном Танкостроении: </i><span style="font-weight: normal;"><i>Правда и вымыслы</i>" published in the November 2006 issue of the "<i>Журнал Техника и Вооружение</i>" </span><span style="font-weight: normal;">magazine, it is stated on page 14 that the protection of the 1985 model of the T-72B is equivalent to </span>more than<span style="font-weight: normal;"> 550mm RHA against APFSDS rounds. This figure may be referring to either the turret or the hull, but in any case, it is consistent with the estimated effective thickness of the armour based on its performance against 3BM32 in live fire tests.</span><br />
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<span style="font-weight: normal;">Based on this, the ME coefficient of the armour is 1.2, which is not higher than the "<i>Reflection-1</i>" array. This is not consistent with the increased complexity of the armour array, but nevertheless, it is supported by some evidence.</span><br />
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According to Swedish trials, 120mm DM33 perforates a LOS thickness of 530mm RHA at 200 meters and a LOS thickness of 470mm RHA at 2,000 meters, converted from its perforation limits on armour sloped at 60 degrees. Based on this, DM33 should perforate a LOS thickness of 565mm RHA and 500mm RHA against armour set at 68 degrees at 200 meters and 2,000 meters respectively. Based on these figures alone, the 60-10-10-20-20-50 armour is nominally capable of resisting DM33 at a range of around 1,000 meters.</div>
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<span style="font-weight: normal;"><span style="font-weight: normal;">Against armour set at 68 degrees, M829 perforates a LOS thickness of 552mm RHA at its muzzle velocity and a LOS thickness of 522mm RHA at 2,000 meters. From this, it can be estimated that the 60-10-10-20-20-50 armour is nominally capable of resisting M829 at a range of around 500 meters and above.</span></span>
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The 60-10-10-20-20-50 armour is 1.35 times heavier than the 80-105-20 armour used in the T-72 Ural and T-72 Ural-1. However, thanks to a substantial improvement in mass efficiency, the calculated effective thickness is 1.83 times is greater than the 80-105-20 armour.</div>
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Having the same 60mm front plate as the "Reflection-1" armour and a similar spaced plate array, it is reasonable to assume that it has the same mass efficiency as its parent design. However, due to the smaller air gaps between each spaced plate, the armour may offer better protection thanks to the "lip" effect.<br />
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The spaced steel armour array shown below, taken from the research paper "<i>Pancerze Pasywne</i>" (Passive Armour), shows the penetration channel of a densely packed spaced plate array that exhibits the "lip" effect.<br />
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When testing this type of armour, it was observed that additional protection value was provided from the interference of a shaped charge jet by the "lips" formed at the edges of the perforated plates, which are deflected from the neighbouring plate and into the path of the penetrator. It was noted that only slightly better results were observed at high angles of obliquity, and that an improvement can be gained by packing more spaced plates in a smaller space.<br />
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Due to the denser layout of of spaced plates inside the 60-10-10-20-20-50 armour compared to the "<i>Reflection-1</i>" armour, the "lip" effect further enhances the mass efficiency offered by the new armour design against shaped charges. As such, it is reasonable to expect the mass efficiency of the armour to exceed 1.2.</div>
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<span style="font-size: large;">HEAT PROTECTION</span></h3>
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<span style="font-weight: normal;"><br /></span><span style="font-weight: normal;">Based on the available information, the armour would be sufficient against practically all handheld antitank weapons, tank-fired HEAT shells, as well as most older anti-tank missiles like the TOW (430mm penetration), MILAN (530mm penetration), and the domestic 9M113 "Konkurs" missile (550mm penetration) but only by a small margin.</span></div>
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<span style="font-weight: normal;">Due t</span><span style="font-weight: normal;">o the installation of</span><span style="font-weight: normal;"> Kontakt-1 as standard equipment on the T-72B, the upper glacis became completely invulnerable to all of these missiles, and any other single-charge HEAT warhead. </span><span style="font-weight: normal;">The use of tandem warheads would negate Kontakt-1 to a large extent, so missiles like the TOW-2A would be a serious threat to the upper glacis armour.</span></div>
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<h3>
"REFLECTING PLATE" TURRET</h3>
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<span style="font-size: small;"><span style="font-weight: normal;"><span style="font-size: small; font-weight: 700;"><span style="font-weight: 400;">Reflecting plate armour was developed and integrated with a new turret as a result of the collaboration between NII Stali and UVZ. By April 1980, UVZ engineers began undertaking the preparation work for the production of the new turret. </span></span><span style="font-weight: normal;">In </span><span style="font-size: small; font-weight: 400;">September 1982</span><span style="font-weight: normal;">, the new </span><span style="font-size: small; font-weight: 700;"><span style="font-weight: normal;">172.10.077SB (</span></span><i style="font-size: medium; font-weight: normal;">172.10.077СБ</i><span style="font-size: small; font-weight: 700;"><span style="font-weight: normal;">) turret with reflecting plate armour inserts entered low rate production. In early 1983, mass production of the 172.10.077SB turret began</span></span><span style="font-size: small; font-weight: normal;">. Throughout the course of the year, the 172.10.077SB turret gradually replaced the 172.10.0</span><span style="font-size: small; font-weight: 400;">73SB turret with "Kvartz" inserts</span><span style="font-size: small; font-weight: normal;"> for new-production T-72A tanks on the assembly line at Uralvagonzavod. By the 1st of January 1984, all new-production T-72A tanks were built with the new turret. </span></span></span><br />
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<span style="font-weight: normal;">All tanks produced from the 1st of January 1984 until the 23rd of January 1985 had this turret, when the Object 184 and Object 184-1 officially entered service as the T-72B and T-72B1. T-72B tanks produced in 1985 and after had slightly modified turrets that were assigned the code 172.10.100SB. </span><span style="font-weight: 400;">Some differences related to the armour may exist between the 077 and 100 turrets, but they are unconfirmed. For simplicity, they are referred to as "reflecting plate" turrets. </span><br />
<span style="font-size: small;"><span style="font-weight: normal;"></span></span><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span><span style="font-size: small; font-weight: normal;">The article </span><span style="font-size: small; font-weight: normal;">"<i>П</i></span><i style="font-weight: 400;">оложение в Отечественном Танкостроении: </i><span style="font-weight: normal;"><i>Правда и вымыслы</i>" published in the</span><span style="font-size: small; font-weight: normal;"> November 2006 issue of the Russian magazine "</span><span style="font-size: small; font-weight: normal;"><i>Журнал Техника и Вооружение</i>" </span><span style="font-size: small; font-weight: normal;">mentions in page 14 that the protection of the 1985 edition of the T-72B is equivalent to more than 550mm against a KE projectile. This is probably a general descriptor that applies for the frontal arc of the tank including both the turret and the hull, but it is widely accepted that the turret of the T-72B is the stronger of the two, for reasons which we will see later on. Andrei Tarasenko reports that the turret of the T-72B is equivalent to 540mm RHA at a side angle of 30 degrees.</span></div>
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<span style="font-weight: normal;">The turret - dubbed "Super Dolly Parton" by American observers -</span><span style="font-weight: normal;"> retains the same general shape of previous turret models but features thicker and heavier turret cheek armour. The most obvious visual trait of the turret is the prominent cut under each turret cheek. As on the "Kvartz" turret, the cuts ensure that the driver's hatch can be opened even when a cheek is overhanging it.</span><br />
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<span style="font-weight: normal;">Each turret cheek features a large cavity where reflecting plate panels are installed and secured. Compared to the earlier turret design with a "Kvartz" filler, the thickness of the cast steel walls of the armour cavity decreased considerably, giving the composite armour a greater share of the weight. The size of the turret cheeks is fully apparent in the photo below, as is the size of the weakened zone created by the cut in the turret to accommodate the gun cradle trunnions and the coaxial machine gun.</span></div>
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<span style="font-weight: normal;">The use of NERA in the turret was inline with contemporary developments in composite armour technology within the Soviet Union and abroad. At the time when it first began to be used in the Soviet Army on late model T-72A tanks in the 1983-1984 time frame, a different form of NERA was being incorporated into T-62M and T-55AM tanks in the form of "metal-polymer" armour which consisted of steel plates suspended in polyurethane. Abroad, all of the next-generation tanks created by the three major NATO military powers - the United States, West Germany and U.K with the M1 Abrams, Leopard 2 and Challenger 1 respectively - used bulging plate-type NERA technology extensively. </span></div>
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The Russian terminology for non-explosive reactive armour is the same as in the West, being labeled as a "non-explosive dynamic armour" as opposed to "explosive dynamic armour" which is better known as explosive reactive armour in English speaking countries. The operating principles of the two types of "dynamic armour" are recognized as the same, except that one is simply more energetic than the other. The drawing on the left below describes the action of ERA, and the drawing on the right below shows the action of NERA.</div>
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Both types of reactive armour were implemented in the T-72B. It was the first mass-produced tank to do so in the history of tank design.</div>
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<span style="font-size: large;">DIMENSIONS</span></h3>
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The majority of what is now known about the turret armour of the T-72B comes from an article published by James M. Warford in the May 2002 edition of Armor magazine. The photograph above is taken from the article and it is particularly useful as it not only shows the dimensions of the turret cavities in inches, but the inch ruler can be used as a point of reference to accurately determine the thickness of the turret armour using the pixel scaling technique. With this method, it can be seen at the shorter red line, the LOS thickness of the armour directly in front of the crew stations is around 27 to 28 inches, or 686mm to 711mm. It can also be seen from the longer red line that the LOS thickness of the armour at its full thickness is around 34 inches, or 863mm. This is very similar to <a href="http://www.btvt.narod.ru/raznoe/leopard2/2zpv3o5.jpg">a Leopard 2 turret (measured directly by a tape rule)</a>, but of course, the thickness of cast turrets may vary by a small amount due to normal casting imperfections.<br />
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A thickness of 863mm is impressive for any tank, but it is worth noting that the 73SB turret already reaches a LOS thickness of 700mm when viewed from the direct front at the same location. However, because the thickness alone is not very meaningful without information of the composition of the turret armour, it is important to examine this before comparing its armour to other tanks.<br />
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From the drawing below, it can be seen that the external surface of the turret cheeks are vertically sloped at 30 degrees and the bevels along the underside of the cheeks have a reverse slope of 50 degrees, forming a wedge shape. Although the bevels along the underside of the cheeks appear to be weakened zones, they are not thinner than the rest of the armour above it, as the drawing shows. The slope on both halves of the wedge has a rather small overall impact on the armour thickness as it is only on the surface, and its effect on ammunition types such as APDS is overshadowed by the immense thickness of the armour. The entire armour array (including the surfaces of the armour cavities, the cavity inserts and the back plate of the cavity, but excluding the NERA panels themselves) is uniformly sloped at a modest angle of 25 degrees. This slope has to be accounted for when calculating the LOS thickness of the armour array.</div><div>
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<span style="font-weight: normal;"><br /></span></div><div style="font-size: medium;"><span style="font-weight: normal;"><br /></span></div><div style="font-size: medium;"><span style="font-weight: normal;">Because the entire armour array is uniformly sloped at a modest angle of 25 degrees, the reverse slope of the bevels progressively diminishes the armour thickness from the tip of the wedge to the base of the cheek, thus creating a weakened zone. </span></div>
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The photo, taken from the ARMOR article mentioned previously, shows the turret cavity complete with its set of NERA panels. The photo has been rotated to represent the orientation of the turret armour along its longitudinal axis.</div>
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The NERA panels contained within the turret cheek cavities are installed perpendicular to the cavity which is angled at 54-55 degrees from the horizontal axis of the turret, so the obliquity of the panels is 54-55 degrees subtracted from 90 degrees, or 35-36 degrees. Together with the vertical slope of the turret casting, the compound angle of the turret cheek when viewed directly from the front is 58.7 degrees. When viewed from a side angle of 30 degrees, the compound angle is 35 degrees.</div>
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<span style="font-weight: normal;">The wedge plates also serve a secondary purpose: the size of the armour cavity varies slightly between different turrets due to casting imperfections, so depending on the particular turret, the fit of the NERA panels may differ. One turret cheek may even have 19 panels instead of the full set of 20. As a result, the void at the front of the armour cavity could also differ in size. The number of wedge plates is adjusted depending on the size of the void so that the NERA panels are properly secured and the void is filled with layers of steel plates to offset the lack of NERA elements.</span></div>
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<span style="font-weight: normal;">Near the gun mantlet, the thickness increases considerably but loses its slope of 55 degrees. At the edges of the turret cheek cavity, the front wall of the cavity thins down to 90mm as the turret cheek curves into the side of the turret. The rear facing is composed of the 80-90mm cast steel wall of the turret cavity supplemented by a 45mm HHS rolled steel plate placed in front of it. The HHS plate is made from BTK-1Sh high strength, high hardness armour steel.</span></div>
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<span style="font-weight: normal;"><br /></span><span style="font-weight: normal;">The exact thickness of the cast steel turret cavity walls is unknown, but it is known that the rolled steel plate at the back of the cavity is 45mm from the <a href="https://tankandafvnews.files.wordpress.com/2015/06/t-72b-armor-article_jmo_may2002_4.jpg">ARMOR magazine article</a>. To estimate the cast back wall of the armour cavity, the photo below can be used as it has a scale laid on top of the turret cheek with one black or white segment denoting one inch. The back plate should extend from the outer edge of the weld seam of the cavity cover plate to the edge of the armoured housing for the gunner's sight. Here, we can see that this LOS thickness around 6 inches (152mm)</span>. To convert this LOS thickness figure to perpendicular plate, it is multiplied by the cosine of 55 degrees, giving us an actual physical plate thickness of 87mm. The LOS thickness of the armour cavity can also be measured from this photo as the ruler is placed directly on top of it. By measuring from the outer edges of the weld seams, the LOS thickness of the cavity directly underneath the ruler is around 14 inches, or 381mm.</div>
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<span style="font-weight: normal;"><br /><br />The combined total weight of the contents of both cavities is 781 kg.</span></div>
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Each NERA panel may vary greatly in length, but all of them are uniform in their thickness, each module being 30mm thick. The modules are composed of a 6mm rubber interlayer sandwiched between a 21mm steel front plate and a 3mm steel bulging plate. The maximum length of a NERA panel is 280mm. The air gap between each panel is 22mm, and the size of the air gap is enforced by metal spacers built into the high hardness steel front plates of the NERA panels. The entire array is angled at 55 degrees from the longitudinal axis of the turret, or in other words, the array is angled at 35 degrees from the horizontal axis. </div>
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With an 87mm (rounded up to 90mm) back plate, a 45mm high hardness steel strike plate and a 90mm front plate, all angled at a compound angle of 58.7 degrees when the turret cheek is viewed from the front, the total thickness of steel excluding the NERA panels is 433mm. The weight of the seven NERA panels is equivalent to 215.3mm of steel when viewed directly from the front at a relative obliquity of 35 degrees. In total, the weight of the turret armour is equivalent to 648.4mm of steel, or in other words, it has an areal density of 5,090 kg/sq.m.<br />
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It is possible to determine the LOS thickness of the turret armour using the known thicknesses of each component of the armour array and turret cavity. It is known that there are seven NERA panels with a thickness of 30mm together with seven air gaps with a distance of 20mm, and when angled at 35 degrees, this array has a LOS thickness of 427mm. Together with the 433mm of steel from the 45mm back plate and two 90mm cast steel cavity walls, the total LOS thickness is 860mm. This aligns perfectly with the LOS thickness of the armour of 863mm determined earlier using the inch ruler as a scale.<br />
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Moreover, reinforcing the calculated density figure of the turret armour is a simple matter of taking the known LOS thickness of the armour (860mm) and then subtracting the LOS distance of the seven air gaps in the armour (188mm). From this, the turret armour would have a total solid thickness of 672mm, of which a LOS thickness of 51.3mm is rubber. The weight of the rubber is equivalent to 10mm of steel, so 41.3mm is subtracted from 672mm. The equivalent weight figure of 631.7mm is obtained. This is only 2.6% off from the other figure obtained using independent scale measurements on the same tank, thus showing that the margin of error from using the pixel scaling technique on two different photos is easily within acceptable bounds.<br />
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Naturally, the weight and areal density figures of the turret from a 30-degree side angle decreases along with the total LOS thickness of the armour array. From this angle, the equivalent weight of steel contributed by the two 90mm cast steel walls of the armour cavity and the 45mm high hardness steel plate is just 274mm. At this angle, three NERA panels at a relative obliquity of 65 degrees are present, contributing a weight equivalent to 179mm of steel. In total, the weight of the turret at a 30-degree side angle is equivalent to 462mm of steel, equal to an areal density of 3,626 kg/sq.m. The total LOS thickness of the turret armour is 661mm at this side angle. For comparison, the T-72A turret had 426mm of steel and a total thickness of 545mm at the same point at a 30-degree side angle, so although the Object 184 turret was somewhat heavier from this angle, the difference is not nearly as large as the 120mm difference in thickness implies. Nevertheless, the armour was a significant upgrade from the T-72A turret with a "Kvartz" filler. Compared to a Leopard 2 turret cheek which had a LOS thickness of 760mm from a 30-degree side angle, the thickness of the Object 184 turret clearly falls short by a significant amount.<br />
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Depending on the specific point of impact, the LOS thickness of the NERA array alone could differ by quite a significant amount. The image below uses colour coding to show the changing LOS thickness through the NERA array to indicate the number of panels that will be struck by a projectile. The NERA panels are placed in such a way that seven panels will intersect with the path of a penetrator when the turret cheek is hit from the direct front, but if the turret cheek is hit from a 30-degree side angle, the number of NERA panels in the path of the penetrator decreases to just three. However, due to the layout of the NERA panels, a side angle of 30 degrees adds 30 degrees to the structural 35-degree slope of the panels to generate a relative obliquity of 65 degrees. This is in the optimum range of angles for bulging plate-type NERA and the implications on the mass efficiency of the armour array as a whole are quite drastic, offsetting much of the reduction in armour thickness.<br />
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If a projectile impacts the turret directly in front of the gunner's primary sight, the LOS thickness of the cavity is 12 inches, or 305mm. If the projectile impacts slightly further away from the gun mantlet, the LOS thickness of the cavity that it will face is 14 inches, or 356mm. Beyond this point, the cavity walls run in parallel so that the thickness of the cavity is not compromised. The LOS thickness of the cavity is 522mm.</div>
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To estimate the protection level of the turret cheeks, it is necessary to know the equivalent weight of the armour in steel. Moreover, knowing the actual thickness of steel in the armour allows a minimum value to be determined.<br />
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<tr><td>0 degrees</td><td>863mm</td><td>638mm</td><td>648mm (5,090 kg/sq.m)</td></tr>
<tr><td>30 degrees</td><td>661mm</td><td>454mm</td><td>462mm (3,626 kg/sq.m)</td></tr>
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From this, it can be estimated that the turret should be equivalent to not less than 638mm of RHA from the direct front, and from a 30-degree side angle, it should be equivalent to not less than 454mm of RHA. These figures are useful reference data.</div>
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Besides the areas of the turret containing composite armour, the other areas have to be examined to better evaluate the turret as a whole. Given that there was little increase in the armour protection of the turret outside of the gun mantlet zone and the turret cheeks, these other areas no longer met the modern requirements for protection. As shown in the excerpt below, the roof of the turret and the commander's cupola are highly vulnerable to munitions like 3BM22 and 3BM26. At two kilometers, the two rounds have a certified penetration of 170mm RHA at 60 degrees and 200mm RHA at 60 degrees respectively. These rounds can perforate the commander's hatch (cupola protrusion) from 3,900 meters, perforate the turret roof from 3,700 meters and perforate the gun mantlet zone from 1,650 meters.<br />
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On a side note, the driver's periscope area is also a weakened zone and can be perforated from 1,700 meters, and the gun mask can be perforated by 12.7mm B-32 armour piercing rounds from 100 meters. Of course, the T-72 doesn't actually have the type of gun mantlet or gun mask that most people are familiar with. Instead of a large armoured plate like the mantlet of the Panther or M-46, the T-72 merely has a piece of cast armour wrapped around the base of the barrel to prevent fragments from entering the gap between the turret and the gun breech assembly. Based on the reported protection level, this gun mask is primarily meant to protect the gun barrel from the splash of an explosive warhead detonating against the turret cheek, and to prevent shell splinters from jamming the gun elevation system by becoming lodged between the turret and gun breech.<br />
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The turret cheek cavities offer a great deal of modularity and repairability. The NERA panels are simply inserted into the turret cavity one by one. In the field, replacing the bulging armour is a simple matter of cutting off the top at the weld lines (very distinctly seen in the picture below), putting new panels in, and replacing the top. This makes battle damage comparatively easy to repair and also simplifies the installation of upgraded armour inserts in the future, unlike the earlier T-72A which did not have a replaceable insert. The penetration of the "Kvartz" filler in the turret of the T-72A would create voids which cannot be mended because the fillers are prefabricated as complete blocks and incorporated into the turret cheeks during the casting process of the turret itself.</div>
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Aside from that, it must be noted that despite the huge leap in protection relative to the previous T-72 turrets, the Object 184 turret is still as simple to produce as its predecessors since no new technologies were needed to cast the turret and the workmanship required to process the cast turret does not demand any new skills or any retraining. </div>
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<span style="font-size: large;">EFFECT ON SHAPED CHARGES</span></h3>
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Due to the multiple layers of steel plates used for the turret inserts, the armour is expected to have a positive ME coefficient against shaped charges simply due to the spaced armour effect. However, the bulk of the protection against this threat is derived from its reflecting plate armour, a form of non-energetic reactive armour (NERA). To better understand the operating principle of reflecting plate armour, it is useful to first examine conventional bulging plate NERA. </div>
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<b><span style="font-size: large;">CONVENTIONAL BULGING PLATE NERA</span></b></div>
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Essentially, the kinetic energy of the shaped charge jet is used to cause the front and back plates to bulge by absorbing momentum from the jet and spreading it radially via the interlayer. The movement of the bulging plates obliquely against the jet causes severe disruption of the jet along its axis and, thus, reducing its penetration capability.<br />
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When a shaped charge jet penetrates the sandwich, the interlayer is rapidly displaced by deformation from the passage of the jet. The momentum of the moving interlayer material is transferred into the front and back plates of the sandwich, thus propelling them apart and creating a bulging effect localized around the point penetrated by the jet. The images below show the gradual bulging of the front and back plates due to momentum transfer at four points in time, from 5 microseconds to 20 microseconds. In this case, the impact angle of the jet is normal to the NERA panel so the panel practically does not cause any disruptive effect, but the principle of momentum transfer still occurs nonetheless. </div>
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The same process occurs with KE penetrators, but to have a noticeable effect, the NERA panel must be quite thick. Thin panels which are designed to defeat shaped charges generally perform poorly against long rod penetrators. </div>
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It is also possible to omit the front plate of a NERA sandwich and have a two-layer panel composed of an inert front plate with a low Young's modulus (typically an elastomer) combined with a steel back plate, or with the two plates in reversed positions. One early configuration of Chobham armour belonged to this class of NERA. Based on a declassified document describing this armour, the thicknesses of the plastic front plate and steel back plate were in a 2:1 ratio.</div>
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This type of bulging plate NERA can be effective, with optimized designs such as the one shown in the image below being demonstrated to be capable of reducing the penetration of a shaped charge to less than a half of its original value. However, it is not as effective as an optimized sandwich-type NERA.</div>
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The bulging of the front and back plates of the NERA sandwich has the effect of disrupting the shaped charge jet and dispersing it into discrete particles, thus reducing its penetration power when it reaches the main armour plate behind the NERA panel.<br />
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<span style="font-size: small; font-weight: 400;">Contrary to popular belief, the intersection of the bulging plates with the shaped charge jet does not cause a penetration reduction by forcing the jet to penetrate more material. The total virtual thickness of plate material that intersects with the shaped charge jet is far too little to explain the large reduction in the penetration of the jet. In 2004, Dr. Held published "<a href="http://onlinelibrary.wiley.com/doi/10.1002/prep.200400051/epdf"><i>Dynamic Plate Thickness of ERA Sandwiches against Shaped Charge Jets</i></a>" in Volume 29 of Propellants, Explosives, Pyrotechnics, issue No. 4. Held examines the mechanism behind the generation of dynamic plate thickness and concludes that the disruption and destruction of shaped charge jets is the main method of jet defeat by reactive armours. In one example given, a 100mm shaped charge which normally achieves a penetration of 800mm has its penetration depth reduced by 560mm after passing through a 3/3/3 reactive armour sandwich. The total dynamic plate thickness in the path of the jet from the two 3mm flyer plates is 270mm (206mm from the rear plate, 63mm from the front plate). Thus, the ERA reduced the</span><span style="font-size: small;"><span style="font-weight: 400;"> penetration depth achieved by the shaped charge by</span></span><span style="font-size: small; font-weight: 400;"> 70%, but the dynamic thickness from the two 3mm flyer plates only accounts for </span><span style="font-size: small; font-weight: 400;">30% of the reduction. </span><br />
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It is important to note that Held simply defined "dynamic plate thickness" as the virtual plate thickness that intersects with the path of the shaped charge jet. He does not explain how the jet is degraded by the intersection.</div>
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<span style="font-size: small;"><span style="font-weight: 400;">Momentum transfer between the bulging plates and the jet causes particles to be displaced from both the plate and the jet. This is responsible for the keyhole-shaped slot cut into bulging plates, and it results in a loss of jet coherence and mass.</span></span><span style="font-size: small; font-weight: 400;"> However, classifying the interaction as the penetration of the moving plate is inaccurate. In actuality, the moving plate is penetrating the shaped charge jet as much as the jet is penetrating the plate, so the mechanism cannot be described as simple armour penetration by erosion. The most important distinction is that the tip of the cumulative jet will almost always be on the other side of the plate before the plate even begins to move due to the immense speed of the jet tip, so it is not the tip of the jet impacting the edges of the plate as the plate moves obliquely against it, but the midsection of the jet body. The interaction causes the jet to be disintegrated, meaning that the single continuous jet is divided into smaller segments, each with their own discrete velocities. The result is that the armour plate behind the NERA plate will be impacted consecutively by two forms of shaped charge jets: a disembodied continuous jet (jet tip), and a smattering of dispersed jet segments. </span><span style="font-size: small; font-weight: 400;">An effective modern ERA design is capable of propelling a flyer plate at such a high velocity that it intercepts the jet tip and destroys it.</span><br />
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The photos below illustrate the effect of a NERA panel on a shaped charge jet. There is no immediate effect 17 microseconds after the jet had perforated the panel, as the jet is still completely intact. 30 microseconds after perforation, the bulging plates have acted on the jet, perturbing it at several points. 45 microseconds after perforation, the bulging action has stopped and the rear of the jet passes through the hole in the NERA panel without being affected.</div>
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The body of the jet behind the tip is disturbed due to the formation of instabilities caused by the disruption of the shape of the jet. According to "<a href="http://www.diva-portal.org/smash/record.jsf?pid=diva2%3A359769&dswid=9315#sthash.q5b2Lgst.dpbs"><i>The role of Kelvin-Helmholz instabilities on shaped charge jet interaction with reactive armour plates</i></a>", the disruptions experienced by the cumulative jet are Kelvin-Helmholz instabilities. Kelvin-Helmholtz instabilities are formed when there is velocity shear in the continuous flow of a fluid, namely the shaped charge jet.</div>
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This is why a shaped charge jet does not penetrate smoothly into armour plate after passing through a NERA plate. Instead, shallow craters are created on a large area of the surface of the plate from the impact of the particulated jet, and some end up on the inside the deepest crater which is invariably made by the disembodied jet tip. Jet particles that do not impact the tunnel made by the disembodied jet tip do not contribute to the final depth of penetration of the target plate. This is best seen in the four photographs below taken from "<a href="https://www.researchgate.net/publication/263609133_Study_on_Rubber_Composite_Armor_Anti-Shaped_Charge_Jet_Penetration"><i>Study on Rubber Composite Armor Anti‐Shaped Charge Jet Penetration</i></a>". The craters were produced by a shaped charge jet disturbed by a steel-rubber NERA sandwich panel at four different angles.</div>
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The greatest reduction in penetration was achieved when the rubber NERA plate was angled at 60 degrees and the largest amount of jet scattering can also be observed at this angle. It is interesting to note that even at 0 degrees, the NERA plate caused some particulation to occur as evidenced by the shallow pockmarks around the tunnel created by the otherwise untouched shaped charge jet. In this case, the NERA plate acted as simple spaced armour, causing the tip of the jet to lose some material due to the compression of the jet when it passed through the NERA plate and subsequent decompression as it exited. At 30 and 45 degrees, the degree of particulation increased drastically as evident from the much larger surface area covered with pockmarks, but the jet still appears to remain somewhat unperturbed. At 60 degrees, the jet is badly disturbed by the NERA plate and is split into a number of segments. Lateral forces from the bulging plate gives the segments a sideways velocity component, causing them to impact some distance away from the main tunnel created by the disembodied jet tip.<br />
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In the paper "<a href="http://sci-hub.io/10.1016/s0734-743x(97)00082-1">A Parametric Study Of The Bulging Process In Passive Cassettes With 2-D Numerical Simulations</a>", Rosenberg states that the motion of bulging plates is not sensitive to obliquity since the main source of propulsion is the energy transferred into the interlayer. In "<a href="http://onlinelibrary.wiley.com/doi/10.1002/prep.200400065/epdf">Study of Jet Interaction with Interlayer Material of Bulging Armor</a>", Yadav states that the amount of energy transferred into the interlayer depends on the duration of contact between the shaped charge jet and the interlayer during penetration, and on the velocity of the jet - the higher the better.</div>
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There must be some space behind the NERA plate in order for it to perform efficiently. This is because the perturbations to the shaped charge jet do not manifest until a small period of time has passed. Here are several X-ray photographs, taken from Dr. Manfred Held's paper "<a href="http://cdn.preterhuman.net/texts/terrorism_and_pyrotechnics/explosives/Shaped_Charges_Penetrators/Disturbance%20of%20Shaped%20Charge%20Jets%20by%20Bulging%20Armour.pdf">Disturbance of Shaped Charge Jets by Bulging Armour</a>", page 194.<br />
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<a href="https://4.bp.blogspot.com/-_hBqPI1Rx00/WY6i3WUzmcI/AAAAAAAAI8k/x2_H45svLognJbLgSy2sxZnr_vRjNVM4QCLcBGAs/s1600/1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="736" data-original-width="1277" height="230" src="https://4.bp.blogspot.com/-_hBqPI1Rx00/WY6i3WUzmcI/AAAAAAAAI8k/x2_H45svLognJbLgSy2sxZnr_vRjNVM4QCLcBGAs/s400/1.png" width="400" /></a><a href="https://2.bp.blogspot.com/-Em5e-9hVjFs/WY6i4FoRpMI/AAAAAAAAI8o/pg01fsrWZZI3ImBf_uXdWdy3FQPcYQNigCLcBGAs/s1600/2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="733" data-original-width="1318" height="221" src="https://2.bp.blogspot.com/-Em5e-9hVjFs/WY6i4FoRpMI/AAAAAAAAI8o/pg01fsrWZZI3ImBf_uXdWdy3FQPcYQNigCLcBGAs/s400/2.png" width="400" /></a></div>
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The photo below shows three bulging plates shot through by a high power shaped charge jet. Notice that there are keyhole-shaped cuts in the plates, and that the plates are cracked.<br />
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More energetic interlayer materials can improve the reaction speed of the NERA plates and increase the lateral energy imparted onto the jet. Rubber is the earliest and most basic material for this application, and can be considered the least sophisticated.<br />
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In the study <a href="https://www.researchgate.net/publication/242230270_MULTIPLE_CROSSWISE_ORIENTATED_NERA-PANELS_AGAINST_SHAPED_CHARGE_WARHEADS">Multiple Cross-Wise Oriented NERA-Panels Against Shaped Charge Warheads</a>, the effectiveness of NERA panels was investigated in various configurations. Experiments were done with a single panel, two panels mounted in parallel, and two panels mounted crosswise. It is most interesting to compare the results obtained with a single panel and two parallel panels.<br />
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It is important to note that the experimental setups do not represent practical tank armour because the air gap behind the NERA panels is very large - 590mm in the case of the single panel test and 490mm in the case of the two parallel panels. Overall, the experimental setups had a total "thickness" of 900mm, including the NERA panel, the air gap, and the 180mm base armour. Additionally, it must be noted that for the control test, the shaped charge was detonated at a standoff distance of 450mm from the witness block whereas for the single and double NERA panel experiments, the total standoff distance was 870mm from the witness block. The penetration of the 84mm warhead in the witness block at the control standoff distance of 450mm was 410mm, and it was noted in the study that the optimum standoff for the warhead was 350mm and the penetration at this optimum standoff is 450mm of armour steel. From this, it is clear that the large standoff of 870mm used in the NERA experiments was already capable of reducing the penetration of the SCJ by a significant amount independently from the NERA panels. This is a very common flaw in such studies, and it tends to skew the result in favour of the tested NERA panel design such that immense ME coefficients are obtained, which would otherwise be unobtainable in practice.<br />
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Nevertheless, the results are worth studying. It was found that a single NERA panel can decrease the penetration of an 84mm shaped charge warhead from 410mm to just 70mm - a reduction of 83%. Two NERA panels in parallel could reduce the penetration to 60mm - a total reduction of 85%. From this, it can be seen that the second NERA panel is responsible for an additional reduction of only 2%. The very small influence of the second panel is explained by the fact that this type of bulging armour cannot react quickly enough to intercept the tip of a shaped charge jet due to its immense speed. With this type of NERA, it is only possible to cut off the SCJ body trailing behind the tip<span style="text-align: center;"> </span>and reduce its contribution to armour penetration, as shown in the photo below.</div>
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The very small reduction in performance offered by the second NERA plate is almost entirely due to the erosion of the <span style="text-align: center;">SCJ</span> from impacting the material of the panel (two 3mm RHA plates and one 5mm layer of rubber), not by the movement of the plates. This was because the body of the <span style="text-align: center;">SCJ</span> had been disrupted by the first NERA panel, leaving only the disembodied jet tip to continue. The disturbed jet body could not contribute to the final penetration depth.<br />
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Overall, it was demonstrated that NERA panels alone are not enough to stop shaped charges. The SCJ tip is generally too fast to be affected by the movement of the bulging plates, and must be arrested by a back plate or an array of plates of sufficient thickness. It was also demonstrated that there are diminishing returns past a certain number of layers of NERA panels in an armour array as the back layers may not be able to contribute much to the reduction in <span style="text-align: center;">SCJ </span>penetration. In practical tank armour, it is necessary to sharply reduce the size of the air gap between the NERA panel and the back plate of the armour array due to volume constraints, and to compensate for this, the only option is to increase the number of NERA panels. A large array of NERA panels with a small air gap is generally only capable of a fraction of the performance of a single panel separated from the base armour with a large air gap. The main alternative is to increase the thickness of the back plate of the armour array, but it may not be a viable solution due to weight constraints. </div>
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This context is crucial because such details are usually not disclosed outside of esoteric scientific documents, yet it is crucial for determining how effective the armour design will be in practical terms. For example, Polish researcher Pawel Przezdziecki published a wealth of declassified information regarding the development of "Burlington" armour. According to him, the configuration of "Burlington" developed at the turn of the decade from the 1960's to the 1970's had 2-3 times higher mass efficiency than monolithic steel armour against shaped charges and had a similar mass efficiency as monolithic steel armour against KE rounds.<br />
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New "Burlington" armour variants from 1978 had a greatly improved mass efficiency of 1.3-1.5 against KE rounds and more than 3.0 against shaped charges. Taking this information at face value, it seems self-evident that the NERA armour found in modern tanks of the early 1980's like the M1 Abrams, Leopard 2 and Challenger 1 would all match or even exceed these parameters, yet, this was not the case.<br />
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<span style="font-size: large;"><b>REFLECTING PLATE ARMOUR</b></span></div>
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Broadly speaking, this type of NERA is constructed with a thick rigid front plate and a rear bulging plate. It functions with or without an inert interlayer. This type of armour relies on the reflection of shock waves to supply energy for the propulsion of the bulging plate, and as such, it is known as reflecting plate armour. </div>
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<span style="font-size: small; font-weight: 400;">When a shaped charge jet (</span><span style="font-size: small; font-weight: 400; text-align: center;">SCJ)</span><span style="font-size: small; font-weight: 400;"> impacts the plate and begins penetrating it, shock waves propagate from the point of contact between the </span><span style="font-size: small; font-weight: 400; text-align: center;">SCJ</span><span style="font-size: small; font-weight: 400;"> and the plate material, which is a </span><span style="font-size: small; font-weight: 400;">plastically deforming region</span><span style="font-size: small; font-weight: 400;">. The shock waves travel to the boundary between the thick plate and the bulging plate where it is mostly reflected while some of its energy is transferred into the bulging plate. This energy pushes the bulging plate away perpendicularly from the thick plate. </span><br />
<span style="font-size: small; font-weight: 400;"><br /></span><span style="font-size: small; font-weight: 400;">After the bulging plate is propelled away from the back surface of the thick plate, an air gap is created between the two plates which means that the back surface of the thick plate no longer has a steel-steel interface, but instead has a steel-air interface. The additional shock waves generated by the penetrating </span><span style="font-size: small; font-weight: 400; text-align: center;">SCJ</span><span style="font-size: small; font-weight: 400;"> reflect off the boundary, causing fragmented spall to be ejected from the back surface of the thick plate. The stream of spall fragments travels perpendicular to the thick plate. Like conventional bulging plate NERA, the reflecting plate panel must be set at an oblique angle to the SCJ to ensure that the </span><span style="font-size: small; font-weight: 400;">bulging plate and the spall fragments travel obliquely relative to the </span><span style="font-size: small; font-weight: 400; text-align: center;">SCJ</span><span style="font-weight: 400;">.</span><br />
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<span style="font-size: small; font-weight: 400;">As both the bulging plate and the spall fragments travel obliquely relative to the </span><span style="font-size: small; font-weight: 400; text-align: center;">SCJ</span><span style="font-size: small; font-weight: 400;">, their dynamic trajectory intersects with the </span><span style="font-size: small; font-weight: 400; text-align: center;">SCJ</span><span style="font-size: small; font-weight: 400;">. The interaction between these elements is the same as in conventional bulging plate armour, but with a reduced intensity as the energy imparted into the bulging plate by boundary reflection is limited so the momentum of the bulging plate is relatively small, and the spall fragments also have a limited momentum. </span><span style="font-size: small; font-weight: 400;">The intensity of the effect can be enhanced by placing a filler material between the bulging plate from the front plate as shown in the image below. This configuration, which is used in</span><span style="font-size: small; font-weight: 400;"> the Object 184</span><span style="font-size: small; font-weight: 400;"> turret,</span><span style="font-size: small; font-weight: 400;"> is still considered a form of reflecting plate armour.</span><br />
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When a <span style="text-align: center;">SCJ</span> or KE penetrator strikes the thick steel front plate, shock waves propagate from the point of contact until it reaches the back surface, whereupon some of the energy is transmitted into the interlayer and some of the energy is converted into kinetic energy by their reflection at the boundary between the back surface and the inert interlayer. This causes the interlayer to be propelled away from the back surface. The energy that is transmitted into the interlayer propagates to the interface between the interlayer and the bulging layer, and the same process repeats, resulting in the bulging plate being propelled away from the interlayer. Through the propagation and reflection of shock waves, the interlayer and back plate are both propelled away from the thick steel front plate before the <span style="text-align: center;">SCJ</span> or KE penetrator even reaches the interlayer. When the <span style="text-align: center;">SCJ</span> or long rod penetrator reaches the inert interlayer, additional energy is imparted into it by momentum transfer which further accelerates the bulging effect.</div>
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The two factors in the choice of different materials for the interlayer are to change the characteristics of the propagation and reflectance of stress waves between the boundaries, and change the momentum transfer characteristics from the penetrator into the interlayer.<br />
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Additionally, it is stated on page 284 in the textbook "<i><a href="https://www.researchgate.net/publication/309205526_ARMOUR_Materials_theory_and_design">Armour: Materials, Theory, and Design</a></i>" by Paul J. Hazell (professor of Impact Dynamics at UNSW Australia), that it is advantageous for the hole formed by the penetrating jet in the front plate to be as small as possible to maximize the effects of the interaction between the jet and the plate, i.e. material compression and shock wave emanation and propagation. This can be achieved using high-hardness steels for the front plate.<br />
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Because the energy of the <span style="text-align: center;">SCJ</span> is extracted by a combination of shock wave reflection together with momentum transfer instead of momentum transfer alone, a larger amount of energy may be transferred into a reflecting plate armour panel compared to a conventional bulging plate panel. This allows the bulging plate of the reflecting plate armour panel to move at greater velocity, which increases its effectiveness. The reaction time of the reflecting plate armour will be noticeably shorter for the reasons outlined previously. Adding on to those effects, the thick front plate will slow down the jet somewhat before it reaches the interlayer, which creates a larger delay that allows the interlayer and bulging plate to attain a higher velocity before the jet tip eventually reaches it. The drawing below shows the passage of the <span style="text-align: center;">SCJ</span> through reflecting plate armour in three successive stages.</div>
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The first stage shows the <span style="text-align: center;">SCJ</span> penetrating the front plate and the propagation of shock waves, which causes the interlayer and the bulging plate to move. The second stage shows the breakout of the <span style="text-align: center;">SCJ from the back surface of the front plate</span>, causing a further expansion of the rubber interlayer and the subsequent bulging of the thin rear plate. The third stage shows the full extent of the bulging effect after the <span style="text-align: center;">SCJ has perforated the interlayer.</span></div>
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A Chinese analogue of this type of armour was described to have the same operating principles. While the inert interlayer and bulging plate are violently propelled in pursuit of the shaped charge jet, the high hardness steel front plate remains rigidly fixed.</div>
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The unidirectional NERA plate might propel its single bulging plate more violently, since all of the energy absorbed into the inert sandwich layer is used to propel only one plate and not two. Still, the effect of a single bulging plate will be less effective than two plates taken together, because there is one fewer plate to disrupt the cumulative jet. However, this might be compensated by emphasizing more violent expansion in a certain direction, as shown below:</div>
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<span style="text-align: center;">(a) </span><span style="text-align: center;">"Backwards moving" means that the plate bulges </span><span style="text-align: center;">against the direction of travel of the jet. This is known as an "in retreat" or "head-on" type NERA.</span></div>
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<span style="text-align: center;">(b) "Forwards moving" means that the plate bulges</span><span style="text-align: center;"> </span><span style="text-align: center;">in the same direction as the direction of travel of the jet. This is known as an "in pursuit" type NERA.</span></div>
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<span style="text-align: center;">The pictures above are not of an actual simulation of SCJ hitting a NERA panel. The plates pictured were moved by explosives which were detonated before the jet reached the plate, but they achieve the same effect in its essence. The photos above shed light on an extremely important phenomenon, which is integral to the operation of the armour of the T-72B. In the turret, the NERA panels are all of the "in pursuit" type. This maximizes their performance, effectively reversing any </span><span style="text-align: center;">penalties potentially incurred by the unidirectional design, or at least neutralizing the disadvantages.</span></div>
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<span style="text-align: center;"><br /></span><span style="text-align: center;"><br /></span><span style="text-align: center;">The two graphs below show the change in residual penetration depth of a 100mm shaped charge warhead into an armour steel witness block after perforating a NERA panel. The graph on the right is for a single reflecting plate armour panel, and the graph on the left is for conventional NERA panels, with one curve for a single NERA panel and another curve for two parallel NERA panels. For this comparison, the single NERA panel is compared to the single reflecting plate armour panel. In both graphs, the y-axis is the residual penetration in the witness block and the x-axis is the angle of the panels. Note that the angle of the NERA panel given in the left graph is measured from the vertical axis and not the vertical axis. Also, it is worth noting that the standoff distance between the warhead and the conventional NERA panel is 250mm, whereas it is only 150mm on the reflecting plate panel. As such, the comparison is not exact.</span><br />
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<span style="text-align: center;">("三明治" 结构 - single NERA panel)</span><br />
<span style="text-align: center;">(双</span><span style="text-align: center;">"</span><span style="text-align: center;">三明治" 结构</span><span style="text-align: center;"> </span><span style="text-align: center;">- two parallel NERA panels)</span><br />
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<span style="text-align: center;">From a visual comparison of the two graphs, it can be clearly seen that the curve for the single NERA panel and the curve for the reflecting plate panel are identical. </span><span style="text-align: center;">As such, it can be concluded that the influence of obliquity is identical for reflecting plate NERA and conventional NERA.</span><span style="text-align: center;"> In both cases, the difference in penetration power from 45 degrees to 70 degrees is 62%.</span><br />
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<span style="text-align: center;">For the reflecting plate armour panel experiment, the residual penetration of the 100mm shaped charge is around 400mm (extrapolated from curve) when the panel is set at 45 degrees, and it is 150mm when the panel is set at 70 degrees.</span><br />
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For the conventional NERA panel experiment, the residual penetration of the 100mm shaped charge is around 420mm <span style="text-align: center;">when the panel is set at 45 degrees </span><span style="text-align: center;">(extrapolated from curve)</span><span style="text-align: center;">, and it is 160mm when the panel is set at 70 degrees (20 degrees from horizontal). </span><br />
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At all angles from 45 degrees to 70 degrees, the residual penetration of the 100mm shaped charge is marginally less after passing through the reflecting plate armour compared to the conventional NERA. The comparison is not perfect because the standoff distances differ, but even so, it is abundantly clear that reflecting plate armour is not necessarily worse than conventional NERA despite having only one bulging plate instead of two, and on the contrary, it can even slightly outperform conventional NERA against shaped charges.</div>
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Unfortunately, tests were not done for two parallel reflecting plate panels and such information is extremely difficult to obtain in the public domain, so it is difficult to evaluate the effectiveness of this arrangement compared to conventional NERA. Based on the principal operating mechanisms involved, reflecting plate armour will also suffer from diminishing returns when arranged in an array. However, unlike conventional NERA panels, the thicker plates are capable of affecting the SCJ tip by subjecting it to stronger alternating cycles of stress accumulation and stress release, and also by offering a passive barrier that erodes the SCJ tip. Or in other words, it can perform as more effective spaced armour.</div>
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<span style="font-size: large;">EFFECT ON HEAT THREATS</span></h3>
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The X-ray photograph below (from NII Stali) shows a sample of the NERA plates used in the Object 184 turret being tested. The plate in the photo is angled at 68 degrees.</div>
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The bulging plate is very strongly deflected, and it can be seen that large disrupted portions in the jet, like troughs in a sine graph, appear quite often down the length of the jet, indicating the the jet is highly disrupted. It is unfortunate that the photo is so closely focused on the NERA panel, as the tip of the jet is out of frame so its length and condition cannot be observed. It is quite clear that the disturbances in the jet only appear after travelling a certain distance behind the bulging plate, which is completely consistent with Dr. Held's findings in "<a href="http://cdn.preterhuman.net/texts/terrorism_and_pyrotechnics/explosives/Shaped_Charges_Penetrators/Disturbance%20of%20Shaped%20Charge%20Jets%20by%20Bulging%20Armour.pdf">Disturbance of Shaped Charge Jets by Bulging Armour</a>".<br />
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<span style="text-align: center;"><span style="font-family: "times new roman"; text-align: left;"><br /></span></span><span style="text-align: center;"><span style="font-family: "times new roman"; text-align: left;">Based on the available information, the specific design of the reflecting plate panels in an Object 184 turret cavity appears to have been optimized to defeat shaped charge warheads within a fairly broad range of common calibers. In page 286 of the textbook "<i>Particular Questions of Terminal Ballistics</i>" 2006 (<i>Частные Вопросы Конечной Баллистики</i>) published by Bauman Moscow State Technical University on behalf of NII Stali, </span><span style="font-family: "times new roman"; text-align: left;">a</span></span><span style="text-align: center;">n optimal distribution of thicknesses of the five basic elements of a NERA sandwich with a rubber interlayer was formulated based on data accumulated from testing and simulating armour of this type. The study posits that the most rational distribution of thicknesses is as follows:</span></div>
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<li>Steel front plate - thicknesses equal to 0.2-0.5 times the caliber of the HEAT warhead.</li>
<li>Rubber interlayer - thickness equal to 1.0-2.0 times the diameter of the shaped charge jet.</li>
<li>Thin steel bulging plate - thickness equal to 1.5 times the diameter of the shaped charge jet.</li>
<li>Size of the air gap behind the thin steel bulging plate - 0.4 times the caliber of the HEAT warhead.</li>
<li>The optimal angle of the NERA panel - 60 to 70 degrees.</li>
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<div style="font-size: medium; font-weight: normal;">Note that the jet diameter of a typical anti-tank shaped charge warhead is 2.5-3.5mm. Based on this, it appears that the NERA panels in the armour of the T-72B were designed with realistic threats in mind, having a reasonable ratio of thicknesses in each panel and appropriately sized air gaps between each panel. Moreover, the use of BTK-1Sh for the front plate of the reflecting plate armour optimizes its performance against SCJs, as the use of high hardness steel for the front plate is advantageous according to professor Paul Hazell.<br />
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However, there is a major downside to the armour layout. The main issue is that the panels are not placed at the optimum angle - the structural obliquity of the reflecting plate NERA panels from the direct front is just 35 degrees; very far from the ideal range of 60-70 degrees. That said, the number of panels in the path of the penetrator is very large if the turret is hit from the direct front. Also, the turret is not only required to withstand attacks from the direct front, but also from a side angle of up to 30 degrees. Due to the structural obliquity of the NERA panels, aiming at the turret from a side angle of 30 degrees generates a relative obliquity of 65 degrees.<br />
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A more tangible shortcoming of the armour array design is that there is no air gap separating the NERA array from the back plate of the turret armour, and hence, an SCJ may only break up while it travels through the NERA array. This is chiefly due to volumetric constraints. Given a fixed volume for the armour, the only way to introduce an air gap in this location is to remove armour material, which inevitably leads to a net loss in effective thickness even if the mass efficiency of the armour array may rise.<br />
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Aside from the reflecting plate armour itself, some other traits of the turret armour array are worth noting. The thick steel armour in front of the turret cheek cavities slows down an SCJ before it enters the reflecting plate armour array, and thus improve their performance due to the longer interaction time between the bulging plate and the jet tip. This was shown in the study "<a href="http://onlinelibrary.wiley.com.sci-hub.io/doi/10.1002/prep.200500027/pdf">Shaped Charge Optimisation against Bulging Targets</a>" authored by Dr. Held, where it was found that as the velocity of a shaped charge jet tip decreases, the effectiveness of bulging armour increases.<br />
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The velocity of the shaped charge jets was adjusted by varying the thickness of the shaped charge liner without changing the the diameter or the cone angle, which remain at 96mm and 60° respectively. The target was a 10mm steel plate in front of a 2/15/4 bulging armour plate. Shaped charges with liner thicknesses of 1mm, 2mm, 3mm and 4mm were tested. As the thickness of the shape charge liner increases, the jet tip velocity decreases. Jet tip dimeter, however, was unaffected. All warheads were detonated at a standoff of 2 CDs, except for the 2mm liner warhead, which was detonated at 6 CD. This skewed the results slightly, but the shaped charges consistently exhibited more symptoms of disturbance as the liner thickness increases.<br />
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According to the textbook "<i>Частные Вопросы Конечной Баллистики</i>", the increase in mass efficiency for shaped charge protection achieved by multi-layered armour using reflecting plate panels is up to 40% compared to homogeneous steel armour of medium hardness, and the armour is more effective than a spaced steel armour array of the same weight by 10-23%. From these figures, it can be said that the mass efficiency of the armour of the T-72B (depending on the angle of attack) can be as high as 40%, depending on the side angle. Based on the claim that this type of NERA armour is 10-23% more effective than spaced steel armour of the same weight, it can be surmised that spaced steel armour would have a mass efficiency of 1.14 to 1.27 compared to homogeneous steel armour whereas the same armour array with NERA has a mass efficiency of 1.4, so even if NERA were absent, the spaced steel plates alone provide more protection than their weight suggests.</div>
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The relatively low ME coefficient is realistic given that it represents a setup where the reflecting plate panels are part of a multi-layered armour array for a tank. The constraints for actual tank armour include limited internal volume which limits the size of the air gaps and the permissible mounting angle of the internal NERA panels. Due to these real world constraints, much of the efficiency is lost after averaging out the numbers from including thick steel plates into the array. Therefore, a direct comparison between NERA designs examined in various scientific studies and the NERA armour of the T-72B is not valid.</div>
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On page 138 of the book "<i>T-72/T-90: Опыт создания отечественных основных боевых танков</i>" it is stated that according to calculated data from 1982, the frontal arc armour provided protection from shaped charges with a penetration of up to 600-620mm RHA. The effective thickness of the armour may therefore be 630-650mm RHA.<br />
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Based on the earlier discussion on the design and operation of NERA, the mass efficiency coefficient of Russian "multi-layered armour" incorporating NERA against HEAT should be 1.4. Treating the turret armour of the T-72B as such, we can multiply the mass of the armour from a front view (648mm) by 1.4 to obtain 907mm. However, it is unlikely that the full value of the coefficient can be reached because the NERA panels are only set at a relative obliquity of 35 degrees when the turret is impacted from the direct front.<br />
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At a 30-degree side angle, the weight of the armour is greatly reduced and the effective thickness must be lower as a result. However, the NERA panels in the armour cavity reach a relative obliquity of 65 degrees at this angle of attack, so the full mass efficiency coefficient of 1.4 should be applied. The armour should reach an effective thickness of 647mm RHA against shaped charge warheads. Overall, these estimates are in good agreement with the claimed protection value given in the book "<i>T-72/T-90: Опыт создания отечественных основных боевых танков</i>".</div>
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In the NII Stali website guestbook (forum) from 2012-2013, a NII Stali website administrator claimed that a T-72B turret can resist a "Konkurs" ATGM without Kontakt-1. The 9N131 warhead used in the basic 9M113 missile (1974) penetrates 550mm RHA, and the enhanced 9N131M warhead used in the upgraded 9M113 (mid-1980's) penetrates 630mm RHA. Based on the available information, the turret may confidently withstand the former type from a 60-degree frontal arc and it may still resist the latter type, albeit by a small margin. In general, the available information is quite consistent.</div>
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This level of protection is sufficient for common anti-tank missiles and most shoulder-fired anti-tank grenades. It is the same level of protection achieved by the M1 Abrams and Leopard 2, which were tested against a very similar threat. During their development, the XM1 was tested against the 5" BRL precision shaped charge with 636mm of penetration, and the Leopard 2AV was tested against the same 5" BRL precision shaped charge but with 600mm of penetration. The reduced penetration power was achieved by adjusting the stand off distance. The armour of both tanks could resist the threat and were not tested against more powerful warheads. As such, the effective thickness of both the M1 Abrams and Leopard 2 can be considered to reach approximately 650mm RHA at a 30-degree side angle.<br />
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However, even though the effective thickness of the Object 184 turret is good, the main issue is that the contemporary ATGM systems of the mid 1980's could already overcome it. The main threats were the MILAN 2, TOW-2, HOT, and Hellfire missiles. To withstand these weapons, the armour must be supplemented by Kontakt-1 ERA.<br />
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Even shoulder-fired weapons would eventually become a formidable threat. The Panzerfaust 3 (PzF 3) is a good example of this. It began low rate production for evaluation purposes in 1985 and entered mass production at the end of the decade. Weighing in at 2.3 kg, the 110mm caliber warhead of the DM12 round is claimed to be capable of penetrating 700mm RHA in <a href="https://www.bundeswehr.de/de/ausruestung-technik-bundeswehr/ausruestung-bewaffnung/panzerfaust-3">the official website of the Bundeswehr</a> and it is documented in <a href="http://www.dtic.mil/dtic/tr/fulltext/u2/a347474.pdf">a JPRS (Joint Publications Research Service) report from December 1987</a> (pages 17, 19) that Dynamit Nobel representatives credited the PzF 3 with "penetrating armor more than 700mm thick". The improved DM12A1 grenade is claimed to be capable of penetrating "steel armor of approximately 800mm thickness" by <a href="https://www.dutchdefencepress.com/wp-content/uploads/2010/09/Asym_Bedrohung_Eng_email_300810.pdf">Dynamit Nobel Defence in a brochure published in August 2010 (page 13)</a>. The DM12 round was the only available ammunition type at the turn of the decade, and the DM12A1 became available in the early 1990's, after the conclusion of the Cold War.<br />
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The turret of the T-72B should be able to resist this grenade from the direct front, but struggle to do so from a side angle of 30 degrees. From these examples, it is clear that Kontakt-1 is not merely a supplement for the considerable armour of the T-72B but a necessity given the gravity of the threat posed by contemporary NATO weapons.<br />
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After the dissolution of the USSR in 1991, a variety of ex-Soviet hardware found its way into foreign hands. A large number of T-72B tanks were shipped over to the U.S and extensively examined along with other T-72 models as well as samples of Kontakt-5 reactive armour, and T-80U tanks equipped with Kontakt-5 were thoroughly examined in Sweden. As a result of this unprecedented insight into Soviet tank armour, the DM22 round for the Panzerfaust 3-T (Tandem) was developed in 1998 to defeat a "T-72 with ERA" (Kontakt-1) and the DM72 round for the Panzerfaust 3-IT (Improved Tandem) was developed in the same year to defeat the T-80U with ERA (Kontakt-5).</div>
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The DM22 warhead features 800mm of penetration behind ERA and the DM72 warhead features 900mm of penetration behind ERA. Of course, it is immediately obvious that this shows the existence of a gap between the protection level of the T-80U and the "T-72", and also that it implies a certain level of protection for the two tanks. Based on our knowledge of the level of protection offered by the various T-72 models in existence, the "T-72" must be a T-72B by default as no other model has enough armour to require such a powerful warhead.</div>
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In general, the turret armour can simply be described as a complex spaced armour array, as the bulging plates of the reflecting plate panels will not have a significant effect on a long rod penetrator due to their low thickness and the relatively low bulging velocity. It is the same with conventional NERA panels, but unlike those, the thick, high hardness steel front plates of the reflecting plate panels behave as spaced plates.</div>
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The high thickness of steel in front of the reflecting plate armour array can also be advantageous for defeating KE threats. According to <a href="http://below-the-turret-ring.blogspot.my/2017/01/early-m1-abrams-composite-armor.html">German expert Rolf Hilmes</a>, one method to augment the efficacy of NERA against KE threats is to incorporate a heavy armour plate in front of the NERA array, so that the penetrator is shattered or fractured before it enters the array. This may be the function of the heavy cast steel front plate of the turret cheeks. In later iterations of the T-72B, this effect is augmented by Kontakt-5 reactive armour, so that the NERA array in the turret is further amplified.</div>
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The T-72B turret is claimed to have an effective thickness of 550mm RHA against KE threats (<i>Tekhnika i Vooruzhenie Magazine, November 2006 issue, p.14</i>). On page 138 of the book "<i>T-72/T-90: Опыт создания отечественных основных боевых танков</i>" it is stated that according to calculated data from 1982, the frontal arc armour provided protection from APFSDS with an armor penetration of up to 500-520 mm RHA. An effective thickness of 550mm RHA is indeed sufficient to provide protection against KE threats with the given penetration power.<br />
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The reported protection level against KE threats from calculated data is likely to be purely theoretical because in 1982, there was no APFSDS round available in the USSR that could achieve the required performance. Technologically, the most advanced foreign KE round available in the USSR was the M111 "Hetz" and it is known that the testing of prospective tank armour was carried out using M111 ammunition from 1982 onward. Its performance was good, but its penetration power simply does not approach the required level to rate the "<i>Reflection-1</i>" with such a high effective thickness due to the fundamental limitations of its design. One possibility is that an early prototype from the "Vant" research topic was used to test the armour. However, ultimately, it is most likely that this figure simply refers to the results obtained by numerical modeling rather than live fire testing.<br />
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Based on the equivalent weight of the armour at a 30-degree side angle (462mm), this is a mass efficiency coefficient of only 1.19. For comparison, the weight of the 60-10-10-20-20-50 upper glacis armour is equivalent to 454mm of steel and it has an effective thickness of around 560mm RHA against a monobloc long rod penetrator with a high aspect ratio. The presence of bulging plates does not necessarily improve the efficiency of the turret armour, because it is known that this type of NERA has a minimal effect on long rod penetrators with a high aspect ratio.</div>
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Both types of spaced upper glacis armour used on the Object 184 had a higher mass efficiency. This can be attributed to four main factors:</div>
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<li>The use of a cast steel to form the cavity walls of the turret armour instead of RHA steel as on the upper glacis.</li>
<li>The lack of a highly oblique heavy front plate to break up the projectile before it enters the NERA array inside the turret cavity as on the upper glacis. The 90mm cast steel cavity front wall (109mm due to 35-degree turret slope) is inherently less effective than the 60mm RHA upper glacis front plate (160mm due to 68 degree slope) in this role.</li>
<li>The slightly lower obliquity of the NERA panels, 65 degrees, at this angle of attack instead of 68 degrees as on the upper glacis.</li>
<li>Equal or fewer reflecting plate panels in the path of a penetrating projectile compared to the spaced upper glacis armour.</li>
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On the other hand, it is worth noting that the reflecting plate panels are set at a perpendicular angle to the armour cavity walls and the high hardness steel back plate. This is a favourable design for defeating long rod penetrators as the opposing angles of the armour elements is another source of asymmetric force in addition to the main sources already examined in this article.</div>
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If the turret is attacked from the direct front, the thickness of steel is vastly greater, but since the behaviour of NERA and spaced armour is anisotropic, it is not possible to simply divide the effective thickness at a 30-degree side angle (550mm RHA) by the cosine of 30 degrees to obtain the effective protection level from a head-on frontal view, so an accurate estimation cannot be made this way. Figuring out the mass efficiency of the armour is also complicated by the use of cast steel along with the rolled high hardness steel plating and the spaced NERA panels implemented in the armour design. With so many factors to consider at the same time, the margin of error is simply too high, so a more basic method of estimation must be used: </div>
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<li>Considering that the turret armour has a weight equal to 648mm of steel and measures 863mm in LOS thickness, it is not possible for the protection value to exceed 863mm against a long rod penetrator with a high aspect ratio.</li>
<li>Assuming the armour to be a single block of steel with hypothetical cast armour and high hardness armour layers, the mass efficiency benefit from high hardness armour alone should completely cancel out the lower effectiveness of the cast steel cavity walls. As such, the armour should not have a lower effective thickness than its cumulative thickness in steel (638mm).</li>
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While the armour is most likely to have an effective thickness of 550mm RHA at a 30-degree side angle, the same armour may not have the same mass efficiency from a front view. Due to the six total factors listed so far, the mass efficiency coefficient is unlikely to reach 1.19. Assuming a coefficient of 1.0 to 1.1 instead, the armour value would be around 650-710mm RHA.</div>
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In a modern context, the calculated protection value of 650-710mm RHA should not be considered to be too conservative or excessively high because modern long rod penetrators with a penetration power in the range of 600-800mm RHA also tend to be optimized to defeat spaced or other complex armour targets instead of homogeneous steel. </div>
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Based on available information, the turret cheek armour may only be vulnerable to the M829A1 round at combat ranges within its frontal arc. M829A1 had the best performance among all other 120mm tank gun rounds at the time of its introduction and for the remainder of the Cold War. Unless it impacts the front of the turret cheek, it has a high probability of defeating the armour at combat ranges.<br />
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<span style="font-size: large;">GILL ARMOUR</span></h3>
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In addition to solid armour protection elements, the T-72 Ural is also equipped with four flip-out panels on each side of the hull, known as "gill" armour. They are spring-loaded panels with additional reinforced rubber flaps. Of the four panels on each side of the hull, three are mounted to the hull sponsons and one is mounted to the front mudguards. The purpose of these panels was to detonate shaped charge warheads at a great distance from the sides of the tank to allow the shaped charge jet to dissipate before reaching the sides of the hull, thus providing a great deal of protection. These panels took the place of traditional side skirts and were originally found on the T-64A, but were carried over to the T-72 to fulfill the same requirements. Originally, the armour was intended to protect the hull of the T-64A from tank-fired 105mm HEAT rounds within a 70-degree frontal arc, which is the same level of protection provided by the turret according to the official requirements. When attacked from a side angle of 30 degrees, the panels cover the entire side of the tank with some overlap between the "gills", as the photo on the right below shows.</div>
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However, the coverage offered by these "gills" was somewhat limited as gaps will begin to appear past a side angle of 35 degrees from the centerline of the hull. The maximum standoff distance and best coverage is achieved when the "gills" are deployed. Even when folded, however, the panels may still provide a modicum of spaced armour from certain angles, as shown in the photo on the left below. It is interesting to note that the suspension of the T-72 is rather densely packed, so there is hardly any room for a shaped charge jet to slip through without colliding with some part of a track or a roadwheel. Any part of the suspension can act as additional armour in this case, especially the roadwheels.</div>
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Each panel is constructed from hard vulcanized rubber flaps secured to an aluminium sheet. They offer absolutely no protection whatsoever from any type of KE projectile, even bullets from small arms, although it is very clear that there was a lot of missed potential in improving the relatively thin side armour of the tank. Nevertheless, the design of the "gills" makes them a very lightweight accessory to a lightweight main battle tank. As you can see in the two photos below, the thickness of the rubber flaps is 6mm and the thickness of the aluminium sheet is 2mm. These measurements were kindly provided to the author by Jarosław Wolski.</div>
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The primary disadvantage to "gill" armour is that the panels are rather easy to knock off when maneuvering in densely wooded areas. Each gill panel is spring loaded which lets them fold back if they happen to cross paths with a tree trunk or a large bush, but if the tank scrapes its fenders against a firm obstacle such as a tree, boulder or a wall, the bolts holding the panels to the fenders can be sheared off. </div>
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Depending on the exact point of impact on the "gills", the air gap between the panel and the side hull armour can range from 1.8 meters to a whopping 3.5 meters, as shown in the diagram and caption below (taken from "<i>Kampfpanzer: Die Entwicklungen der Nachkriegszeit</i>" by Rolf Hilmes). If a shaped charge warhead struck the center of any one of the panels at a 30 degree side angle from the centerline of the hull, the panel creates around 2.65 meters of air space between the panel and the side armour of the hull. The air gap will be larger if the panel is struck at the outer edge and less if struck at the inner edge, but on average, a great deal of spaced protection will be achieved. Note that the standard complement of four "gill" panels will fully cover the side of the hull including the engine compartment from a 30 degree side angle but covers only the fighting compartment from a 35 degree side angle.</div>
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In summary, the "gill" armour panels would have given the T-72 Ural a great amount of side protection from the various types of guided anti-tank missiles, recoilless guns, tank-fired HEAT rounds, and man-portable rockets fielded during the 1960's within a 70-degree frontal arc, but this may not be true for anti-tank missiles of the 1970's. To fully convey the peculiarities of the effects of spacing on the penetration of shaped charges, the drawing below can be of great help. <span style="font-size: small; font-weight: 700;"><span style="font-weight: normal;">This drawing comes from the article</span><span style="font-weight: 400;"> "<i>Hydrodynamic theory of shaped charge jet penetration</i>" published in 1991 in the Journal of </span></span>Explosives and Propellants by Dr. Manfred Held. The graph is rather faded, but the dotted line plotting the maximum penetration depths in RHA versus the standoff distance is still visible. It shows the depth of penetration of a 100mm shaped charge increasing to a maximum of 700mm (7 CD) when the standoff distance is increased to 0.6 meters, but the penetration drops down to less than 400mm at a standoff of 1.2 meters, around 180mm at 2.4 meters, and less than 50mm at 4.8 meters.</div>
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The normal achievable penetration of the 100mm diameter warhead would probably correspond to the penetration at a 15cm (0.15 m) standoff distance or less, since the typical built-in standoff for a rocket-delivered shaped charge warhead with a typical pointed aerodynamic fairing without a standoff probe or a spike tip is usually between 1 to 2 CD. This implies a penetration of just slightly over 500mm in RHA.</div>
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As you can see in the graph, an additional 0.45 meters of space in front of a 100mm warhead with a built-in standoff of 0.15 meters yields the best penetration obtained from the warhead, and this helps to communicate the peculiarities of shaped charges: spaced armour can be effective, but only when integrated in a complex armour configuration or with a sufficiently large air gap. For example, if an APC with a ~400mm-wide track had a simple sheet metal or rubber side skirt installed to cover the suspension, it would actually become even more vulnerable to a shaped charge grenade due to the increased standoff. Even at 30 degrees, the side skirts of a typical tank would not provide sufficient spacing to defeat a tank-fired HEAT shell. Because of this, the primary incentive to install simple side skirts on tanks was usually to reduce the amount of dust kicked up into the air by the tracks, mainly to reduce the chances of being spotted by enemy forces from faraway distances and also to improve the visibility for other tanks at the back of a single-file formation or a convoy. Protection from shaped charges would not be one of the reasons unless the side skirts were thick armoured panels such as on the M1 Abrams.</div>
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The "gill" armour panels provided more spacing than normal side skirts would, and this makes them genuinely useful as spaced armour screens. If a "gill" armour panel was struck at a 30 degree side angle by the 100mm warhead described in the diagram, the total air space between the panel and the side of the hull would be around 2.8 meters. Considering that the penetration of the 100mm warhead diminishes to only around 180mm with 2.4 meters of air space, the likelihood of the warhead failing to defeat the 160mm side armour (80mm at 60 degrees) with 2.8 meters of air space is quite high. Protection would be guaranteed at angles steeper than 30 degrees since the amount of air space provided would increase drastically. All taken together, the combination of composite armour and spaced armour theoretically gives the frontal arc of the tank hull a high level of protection against shaped charge warheads. However, this is only a hypothetical scenario with a nondescript shaped charge. By comparing the specifications of actual anti-tank missiles with the spacing of "gill" armour, it is clear that the results could vary wildly.</div>
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Older missiles like the SS.11 (1962) using older shaped charge technology form less cohesive jets due to imperfections in the manufacturing of the shaped charge liner, so the shaped charge jet dissipates more quickly over spaces. A missile like the SS.11 will fail to perforate the side armour of the T-72 despite having a 164mm diameter warhead with a 125mm diameter shaped charge that was allegedly capable of 600mm of penetration, whereas the much newer TOW missile (1970) with less penetration was much more likely to go through. It is very much worth noting that the shaped charge liner of the SS.11 is the same diameter as the TOW, yet the SS.11 is advertised to penetrate much much more armour. The only conclusion is that the 600mm figure is bogus and that the penetration of the SS.11 is similar to the 125mm warhead of the 9M14 Malyutka. Besides the TOW, another interesting example is the ITOW from 1982 which has a 127mm warhead (152mm missile body) and a 124.2mm diameter shaped charge with 630mm of penetration compared to only 430mm from the original TOW despite having a reduced explosive filler (2.08 kg vs 2.45 kg). This was achieved by adding an extendable probe to increase the standoff distance to 370mm (14.6 inches) as opposed to only 107mm for the original TOW, by using a more elongated shaped charge liner with a steeper apex angle, and by incorporating a wave shaper in the explosive charge. The implications of these details will be immediately apparent after deciphering the graph below. The graph comes from the 1989 book "<i>Fundamentals of shaped charges</i>" by W.P Walters and J. Zukas. </div>
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For more precise estimations, it is important to keep in mind that the actual shaped charge liner in all HEAT warheads is actually smaller than the diameter of the warhead. This is often ignored for missiles due to the thin skin of the warhead casing, but some missiles like the SS.11 are unique. The SS.11 warhead casing has an external diameter of 164mm, but the shaped charge in the warhead is only 125mm in diameter. If this 125mm warhead impacted the side skirt of the T-72 at an angle of 30 degrees from the axis of the hull, the 2.65 meters of standoff distance from the warhead to the side armour would be equivalent to 21.2 CD or around 22.6 CD when the built-in standoff of the missile nose fairing is accounted for. As shown in the graph for a "standard charge", this cuts down the penetration of the warhead to less than one CD, or in other words, less than 125mm. The 80mm side hull armour of the T-72 will be more than enough to resist such an attack, having 160mm of effective thickness when angled at 30 degrees.</div>
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Tank-fired 105mm HEAT rounds like the M456 required a thick casing due to the high stresses during the acceleration of the projectile in the barrel to reach the final muzzle velocity of 1,025 m/s. As such, it is no surprise that the shaped charge liner has a diameter of only 88.4mm, but the spike tip of the projectile gives it a built-in standoff of around 2 CD. This enabled it to achieve a penetration power of around 4.5 CD (380-400mm), which is verified by other sources. However, if the M456 round impacted a "gill" armour panel, the air gap would be equivalent to a whopping 31.2 CD, or 33.6 CD when the built-in standoff is accounted for. From this, it is abundantly clear that it would have no chance of defeating the side armour of the T-72 at this angle. Even at a side angle of 35 degrees, the penetration losses are simply too high to overcome with an 85mm shaped charge. This allowed the tank to fulfill the same requirement of providing protection from 105mm HEAT rounds in a 70-degree frontal arc that was stipulated for the T-64.</div>
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As another example, the total amount of standoff for the ITOW missile from the 2.65 meters of air space would be 21.3 CD, or 24.3 when considering the built-in standoff distance. If the warhead in the ITOW missile had a shaped charge liner made using older technologies, this would reduce the penetration to less than half of a charge diameter, or just 62mm, but thanks to the superior performance of precision-made shaped charges, the actual penetration of the missile would be around 1.8 CD, or 224mm. There is always a chance that one of the roadwheels or a track link could be in the path of the shaped charge jet, but otherwise, the missile would have enough penetration power to pierce the side hull armour and cause damage. If the obliquity of the side angle is increased to 25 degrees, 3.135 meters of air space is created. This increases the standoff to 25.1 CD or 28.1 CD with the built-in standoff accounted for. At this angle, the ITOW would fail against the side armour of the T-72 by a large margin. Knowing that the M1 Abrams was designed to resist a 127mm ATGM from its 50-degree frontal arc, the T-72 should be considered to have a similar level of protection as the M1 Abrams.</div>
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When "gill" armour was first implemented on the T-64, the most powerful anti-tank missiles at the time were slow, manually guided types with paltry penetration power for their size and weight, so this solution was not simply limited to providing protection from 105mm HEAT shells. However, the forward march of technology gradually eroded the usefulness of the "gill" armour and the fragility of the panels made it less attractive still. Of course, the best case scenario where the "gill" panels create 3.5 meters of air space may have the effect of neutralizing the threat posed by more modern missiles, but this is not possible to achieve consistently and from all angles of attack due to simple geometric constraints. All taken together, it is much easier to understand why this unusual solution was replaced with conventional side skirts after only a few short years, and even so, this was not necessarily a downgrade. By reducing the likelihood of being spotted at long distances from the dust cloud, the likelihood of being targeted by reconnaissance at long distances is consequently reduced.</div>
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The "gill" panels are accompanied by a short rubber skirt which conceals the gap between the returning track and the sponson fuel tanks or stowage bins. These reduce the amount of dust kicked up into the air by the movement of the tracks, but if the "gill" panels are absent, they also provide a certain amount of spaced armour protection. As the photo below shows, even when the "gill" panels are not installed, the side of a T-72 Ural is still reasonably protected as the only gap along the side of the hull is the narrow space between the roadwheels and the return rollers.</div>
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These panels are no longer seen even on original T-72 Ural or early T-72M tanks, having being rapidly replaced with conventional side skirts as seen on the T-72A. This could be due to two reasons already mentioned above; fragility and incomplete coverage. One concrete advantage of the conventional side skirts is that it keeps the amount of dust kicked up by the tracks under control, but why not combine the two? The more conventional side skirts that began to be installed on T-72 tanks since 1975 on the Ural-1 model retained mounting points for "gill" panels and it would be completely possible for a tank to have both types of side screens. However, there does not appear to be any photographic evidence of a T-72 having this combination of features in the Soviet Army. Such a modification seems to only exist on Czech T-72M1 tanks and their derivatives as the photos below show, but even then, it does not appear to be a standard modification for Czech-operated T-72 tanks or even a large scale modification for their T-72M1 tanks as part of some overhaul plan as this combination is rarely seen.</div>
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It is rather likely that the panels were installed as part of a modernization programme, but they simply kept falling off and it became tedious to replace them after every exercise, so they were removed once and for all, leaving only the standard side skirts.</div>
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Interestingly enough, the T-55M, T-55AM and T-62M tanks from 1983 were designed to fit "gill" armour panels as part of the design goal of achieving the same level of protection as the first serial main battle tanks of the Soviet Army, namely the T-64A and T-72. However, this appears to have remained a largely theoretical capability as these tanks were almost never seen with the "gill" panels installed, even in Afghanistan where they would have been effective against light handheld anti-tank weapons.</div>
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<span style="font-size: large;">STEEL-REINFORCED SIDE SKIRTS</span></h3>
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Conventional side skirts were first installed on an experimental basis in 1975 on the T-72 Ural-1 model. They became standard beginning in 1979. They are made from synthetic rubber reinforced with polymer fabric and steel wire mesh. A close inspection of the skirt shows six layers of fabric and six layers of steel alternating within the rubber matrix, with a rubber outer layer on both sides. The high reinforcing substrate content enhances the thermal stability of the material compared to a plain rubber sheet and gives good mechanical properties to resist tearing and for sufficient stiffness to activate grenade fuzes. Moreover, the high hydrogen density of the rubber and polymer fabrics allow the skirt to function as a radiation shield. According to NII Stali, the skirts (2) are considered to be a part of the radiation protection scheme of a tank. </div><div style="text-align: left;"><br /></div><div style="text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-hbCoyCn2rG0/X2IqqPO2N3I/AAAAAAAARmU/rWQg9ZMy2iUwADjqt1j2Yq516vHhqqjXQCLcBGAsYHQ/s1096/chema.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="468" data-original-width="1096" height="171" src="https://1.bp.blogspot.com/-hbCoyCn2rG0/X2IqqPO2N3I/AAAAAAAARmU/rWQg9ZMy2iUwADjqt1j2Yq516vHhqqjXQCLcBGAsYHQ/w400-h171/chema.jpg" width="400" /></a></div><br /><div style="text-align: left;"><br /></div><div style="text-align: left;"><br /></div><div style="text-align: left;">An equally important function of the skirts is their role in reducing the amount of dust ingested by the engine air intake by suppressing the ejection of dust from the sides of the tracks, which would be blown over the engine deck and over the radiator louvres where the air intake is located. This, combined with the aerodynamic shape of the turret, eliminated the formation of a vortex over the engine deck and thus improved the purity of the ingested air in highly dusty conditions. This also has a positive influence on the visibility of a tank unit from long distances as it can reduce the overall dust signature to some extent. The crew also benefits from this because they will be exposed to less dust during long marches, particularly if they ride outside the tank.</div><div style="text-align: left;"><br /></div><div style="text-align: left;">These skirts were 10mm thick and provided complete coverage for the sides of the hull with some overlap over the roadwheels. Each side of the tank had four skirt panels, three of them being identical rectangular panels and one of them being shaped like a right trapezoid at the rear of the hull. Mudguards of a new design were also installed to seamlessly cover the entire side of the hull from end to end. The height of the skirts on the T-72 was the same as the overall height of the "Gill" armour panels. It was sufficient to cover almost all of the hull sides and the remainder was covered by the roadwheels themselves. Mounting points for a full set of four "Gill" panels on each side of the hull were still provided on the new side skirts. Sometime during the production run of the T-72, three wire footholds were added to the bottom edges of the front skirt panels.</div><div style="text-align: left;">
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<span style="font-size: small;"><br /></span><div style="font-size: medium;">Unlike rigid sheet metal side skirts as found on the Centurion and Chieftain series of tanks, a flexible textile skirt is much less likely to fall off during maneuvers in heavily vegetated areas and will not allow the suspension to be clogged by mud or vegetation collected in the gap between the tracks and the skirt - a common complaint of Centurion crews in Korea and Vietnam, with Australian Centurion crews in Vietnam resorting to removing the skirts altogether as standard practice. The textile skirts of the T-72 can also absorb blast pressure just as readily as a metal sheet skirt. These advantages are made all the more attractive by the benefit of a reduced weight due to the much lower density of the textile skirt compared to steel or aluminium sheeting. </div>
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The disadvantage to a skirt of this type is that it may fail to offer enough resistance to set off the fuses of certain anti-tank warheads. For instance, it was found during Hungarian testing of a T-54 retrofitted with the side skirts of a T-55AM (same reinforced textile skirt as the T-72) that a Fagot missile fired at the side of the hull at a perpendicular angle of attack resulted in the missile piercing the skirt and detonating on the surface of the side hull armour. Some fuses for HEAT shells are also known to be rated to be insensitive to plywood obstructions to ensure that the shell does not detonate prematurely on bushes and branches before reaching the target. As such, there is an additional layer of nuance that has to be taken into account when assessing the effectiveness of the side skirts as spacing screens. </div>
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<span style="font-size: small;"><br /></span><span style="font-size: small;">Each skirt panel is secured to the sponson fender by two or three hinges (horizontal cross pins) and each panel is linked to one another by a pair of hinges (vertical cross pins). As such, it is possible to alternatively lift the skirt panels up to a horizontal position or swing them aside depending on which hinges are disconnected. To access the suspension through individual skirt panels, it can be disconnected from its neighbouring panels and lifted upward or disconnected from the fender and swung to the side. The latter option may be more expedient if reactive armour is installed as the weight would make it difficult to lift up the skirt and keep it up. To gain access to the suspension, the entire set of skirts on each side of the tank can be lifted up as an entire unit or individual sections of the skirt could be lifted. If lifted, the skirts are held up by simply putting a metal loop on the side skirt panel onto a hook on the sponson fender.</span><br />
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<a href="https://4.bp.blogspot.com/-ciVbB2CmFdc/XI5l3FU2xzI/AAAAAAAANi4/3pJE7HUMQB05IYURwCrMDubrKaeJtwUdwCLcBGAs/s1600/wheel.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="453" data-original-width="604" height="300" src="https://4.bp.blogspot.com/-ciVbB2CmFdc/XI5l3FU2xzI/AAAAAAAANi4/3pJE7HUMQB05IYURwCrMDubrKaeJtwUdwCLcBGAs/s400/wheel.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-xzi96K8YGEA/XoB0TLLqsdI/AAAAAAAAQfk/GCO1tPy1R2gIlVp6GO6YL5YC5gNBrQCywCLcBGAsYHQ/s1600/mudguard%2Band%2Bskirt.jpg" style="font-size: medium; margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="431" data-original-width="579" height="297" src="https://1.bp.blogspot.com/-xzi96K8YGEA/XoB0TLLqsdI/AAAAAAAAQfk/GCO1tPy1R2gIlVp6GO6YL5YC5gNBrQCywCLcBGAsYHQ/s400/mudguard%2Band%2Bskirt.jpg" width="400" /></a></div>
<span style="font-size: small;"><br /></span><span style="font-size: small;"><br /></span><span style="font-size: small;">The skirts were mounted 745mm away from the side of the hull and could thus still drastically reduce the effectiveness of a small HEAT warhead like the 66mm warhead of the M72 LAW when impacted at a steep angle, though certainly not to the degree that the earlier "gill" armour configuration could achieve. In general, simple side skirts of this type do not contribute enough armour value against contemporary shaped charge weapons to achieve a useful level of protection except under ideal circumstances and are completely useless against KE munitions. Nevertheless, a modicum of protection is provided which may prove useful under certain circumstances. </span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;">For example, a shaped charge warhead for a light shoulder-fired weapon from the 1960's can be handled by this type of armour within a fairly wide range of attack angles. The performance of the warhead of a PG-7V grenade (1961) with 260mm of penetration degrades on spaced armour at a rather high rate, coinciding with the technological level of that time. The chart below from the TRADOC manual "<i>M72 LAW and The RPG-7: Handheld Anti-Tank Weapon Operator Manuals</i>" shows the standoff effect on the penetration of PG-7V.</span><br />
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<a href="https://3.bp.blogspot.com/-y3gbdpo-cQg/XHkkAsQCgcI/AAAAAAAANdE/KIq6U9NapI0iJXGxQMRQBNh-cLbF678rgCLcBGAs/s1600/rpg-7%2Bpenetration%2Bdrop%2Boff.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="502" data-original-width="628" height="320" src="https://3.bp.blogspot.com/-y3gbdpo-cQg/XHkkAsQCgcI/AAAAAAAANdE/KIq6U9NapI0iJXGxQMRQBNh-cLbF678rgCLcBGAs/s400/rpg-7%2Bpenetration%2Bdrop%2Boff.png" width="400" /></a></div>
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<span style="font-size: small; font-weight: normal;">From the TRADOC manual, it can be seen that the PG-7V grenade penetrates around 260mm (10.2") with the built-in standoff distance, marked by the starting point of the solid line. For a T-72 with the textile side skirts, the PG-7V would fail to defeat the side hull armour at an impact angle of 50 degrees and above. At 50 degrees, the air gap would amount to 985mm (3.23') including the skirt itself and the penetration of the grenade would be only 96mm (4.3") whereas the LOS thickness of the side hull armour would be 104mm (4.11"). As such, the protection of the side of the hull can be said to be equivalent to >260mm RHA against an 85mm HEAT warhead with a standard shaped charge liner at the technological level of the early 1960's from a 100-degree frontal arc. </span></div><div style="text-align: left;"><span style="font-size: small; font-weight: normal;"><br /></span></div><div style="text-align: left;"><span style="font-size: small; font-weight: 400;">In the memorandum "<i><a href="https://cdn.discordapp.com/attachments/714898523497431111/772723493241749504/unknown.png">HEAT vs HESH Paper</a></i>", from studies done for the Trilateral Tank Main Armament Evaluation held from December 1973 to August 1975, it was established that when detonated at a standoff distance of above 210mm (built-in standoff is 187mm), the penetration power would fall sharply. This was due to the antiquated method of liner manufacture throughout <a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/b126955.pdf">the entire history of M456 production</a>. This issue was never addressed throughout the Cold War, as the programme to replace M456A2 with the entirely new XM815 projectile never matured. Due to its unusually poor performance, the skirts theoretically enabled the side of a T-72 to resist all M456 models including the M456A2 even up to a side angle of 40 degrees, giving it a protected frontal arc of 80 degrees. However, they would be totally ineffective against a modern weapon such as the German DM12 HEAT round, also used in the U.S under licensed production as the M830.</span></div><div style="text-align: left;"><span style="font-size: small; font-weight: 400;"><br /></span></div><div style="text-align: left;"><span style="font-size: small; font-weight: 400;"><br /></span></div><div style="text-align: left;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-VJNo512hlTU/YBKioatuI-I/AAAAAAAASo8/UDTVvRmmlv4BYyfsSNLWaoKMvUBhj3E5ACLcBGAsYHQ/s1242/standoff.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="882" data-original-width="1242" height="454" src="https://1.bp.blogspot.com/-VJNo512hlTU/YBKioatuI-I/AAAAAAAASo8/UDTVvRmmlv4BYyfsSNLWaoKMvUBhj3E5ACLcBGAsYHQ/w640-h454/standoff.png" width="640" /></a></div><span style="font-size: small; font-weight: normal;"><br /></span></div><div style="text-align: left;"><span style="font-size: small; font-weight: normal;"><br /></span></div><div style="text-align: left;"><span style="font-size: small; font-weight: normal;">Against more modern weapons that are capable of generating more precise and less sensitive shaped charge jets, the effectiveness of the side skirts as spacing screens drops drastically and it quickly becomes apparent that the side hull armour of the T-72 was inadequate against contemporary threats. </span><br />
<span style="font-size: small; font-weight: normal;"><br /></span><span style="font-size: small; font-weight: normal;">Supplementing this is the fact that the T-72M1 hull is rated at 500mm RHA against shaped charges in a 44-degree frontal arc, implying that the side of the hull is equivalent to 500mm RHA at a 22 degree angle where the air gap between the side skirts and the hull side would be 2,015mm, including the skirt itself. This is broadly consistent with the penetration-standoff curve for a precision shaped charge with a cone diameter of 88.4mm such as that found in the 105mm M456 or DM12 HEAT shell. For a 88.4mm shaped charge, a standoff distance of 2,015mm is equivalent to 22.8 CD and together with a built-in standoff of 1.5 CD, the total standoff is 24.3 CD. The penetration at this standoff distance is around 1.8 CD, or around 159mm, so the 80mm side hull armour plate would be more than enough to resist this threat as it has a </span><span style="font-size: small; font-weight: 400;">LOS armour thickness of 213mm at a 22 degree side angle</span><span style="font-size: small; font-weight: normal;">.</span></div><div style="text-align: left;">
<span style="font-size: small; font-weight: normal;"><br /></span><span style="font-size: small; font-weight: normal;">The side of the hull should also be able to resist other HEAT weapons with a similar shaped charge cone diameter at this angle of attack including the 84mm Slpsgr m/75b HEAT</span><span style="font-size: small; font-weight: normal;"> round for the Carl Gustaf ("more than 400mm" RHA penetration), or the 93mm PG-7VL for the RPG-7 (500mm RHA penetration). A larger shaped charge warhead with a cone diameter of 100mm and above should be expected to defeat the side hull armour. The disruptive effect of the skirt material on the shaped charge jet is considered negligible in this simple analysis because it is likely to be practically imperceptible.</span></div><div style="text-align: left;"><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div></h3><h3><div><span style="font-size: small;"><span style="font-weight: 400;">Conversely, the side skirts do not provide enough protection from contemporary ATGMs, at least in theory. For the Milan missile, the skirt provides an air gap of 2,173mm inclusive of the built-in standoff of the missile. Milan retains a penetration of 272mm with a standoff distance of 20 CD and approximately 230-40mm with </span></span><span style="font-size: medium; font-weight: 400;">a standoff distance of </span><span style="font-size: small;"><span style="font-weight: 400;">21 CD, exceeding the LOS thickness of the armour by 17-27mm. The 500mm RHA equivalent protection of the side armour is therefore nominally insufficient to handle the 530mm RHA penetration power of the Milan.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-EdL8PqNM4ac/X2cd0i5TCpI/AAAAAAAARnY/EMPo3mHh2EksGr6cc_Fh9s8hBAFw66BTQCLcBGAsYHQ/s551/milan%2Bpenetration%2Bat%2Bvarious%2Bstandoff%2Bdistances.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="384" data-original-width="551" height="279" src="https://1.bp.blogspot.com/-EdL8PqNM4ac/X2cd0i5TCpI/AAAAAAAARnY/EMPo3mHh2EksGr6cc_Fh9s8hBAFw66BTQCLcBGAsYHQ/w400-h279/milan%2Bpenetration%2Bat%2Bvarious%2Bstandoff%2Bdistances.jpg" width="400" /></a></div><span style="font-weight: 400;"><div><span style="font-size: small;"><br /></span></div><div><span style="font-size: small;"><br /></span></div></span></span><span style="font-size: medium; font-weight: 400;">In practice, however, the obliquity of the hull side armour plate causes the jet to splatter during the impact phase, and when coupled with the loss of jet coherence at such a large tandoff distance, the penetration channel depth can be predicted to reduce while the channel entry hole widens. As such, a diference between theory and practice can be expected.</span></div></h3><h3><div style="text-align: left;">
<span style="font-size: small; font-weight: normal;"><br />On the other hand, the M1 Abrams had more serious requirements for shaped charge protection in the frontal arc of its crew compartment which was fulfilled by incorporating composite armour in the sides of the turret and in its side skirts. The requirements for the side armour over the crew compartment (both hull and turret) in the XM-1 that ended up proceeding into production as the M1 Abrams was required to withstand an 81mm (3.2") HEAT charge at a 45 degree angle. Assuming that this refers to the Ballistics Research Laboratory (BRL) standard 81mm shaped charge with a precision-made copper liner detonated at the standard standoff distance of 147mm, the penetration of the charge would be around 350mm RHA, so the side hull armour would have to be equivalent to slightly more than 350mm RHA when hit at a 45 degree angle. <a href="https://i.imgur.com/2vIipNC.jpg">This is confirmed by this drawing</a> showing that the side turret and side hull armour of the M1A1HA - which was unchanged from the basic M1 - is equivalent to 380mm RHA against an 81mm Hand-held Infantry Weapon (HHIW). Protection against a 127mm ATGM was also required in a 50-degree frontal arc, and as such, the side hull armour achieved an effective thickness of 750mm RHA from a side angle of 25 degrees. It is self-evident that this is a significantly higher level of protection than what the T-72 offers with its simple textile side skirts, but it is important to point out that the difference in effective thickness rapidly declines as the angle of attack declines until there is hardly any difference at all when both tanks are attacked perpendicularly to their side armour.<br /><br /><span style="font-size: small;"><br /></span><span style="font-size: small;"><br /></span><span style="font-size: small; font-weight: normal;">With the growing inadequacy of the "Gill" armour solution against modern anti-tank missiles, the merits of the conventional side skirts became more apparent. When we also consider the lack of durability associated with "gill" panels, it is obvious that the decision to switch to a conventional side skirt was a completely pragmatic one.</span><br /><span style="font-size: small; font-weight: normal;"><br /></span><span style="font-size: small; font-weight: normal;"><br /></span><span style="font-size: small; font-weight: normal;">Besides the large and obvious side skirts, there were also additional flaps mounted to the sponsons. The external sponson fuel tanks and stowage bins were made from stamped sheet steel and were completely exposed on the original T-72 Ural. When conventional side skirts were implemented in the late 70's, steel-reinforced plastic flaps were added along the entire length of both spnsons. The purpose of these flaps is not known, but it could be assumed that they are meant to ensure the detonation of an anti-tank grenade to maximize the protective effects of the sponson fuel tanks and stowage bins. </span></span><br />
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<span style="font-size: small; font-weight: normal;"><span style="font-size: small; font-weight: normal;">On the T-72AV and T-72B, these rubber flaps were replaced by steel plates with mounting points for Kontakt-1 blocks, but the plates disappeared from tanks equipped with Kontakt-5. It appears that the use of steel plates on the T-72AV and T-72B limit the destructive effects that the detonation of a Kontakt-1 block would have on the underlying stowage bins or fuel tanks. The steel plates also presumably had the additional benefit of providing the sponson fuel tanks with protection from small arms and artillery fragments. The photos below show the sponson flaps on a T-72A and the steel sponson plates on a T-72AV. Photos posted to <a href="https://www.dishmodels.ru/wshow.htm?np=4&p=1660&vmode=T#blockpre">dishmodels.ru by Ilya Sterlikov</a>.</span></span><br />
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<span style="font-size: small; font-weight: normal;"><span style="font-size: small; font-weight: normal;">On the T-72B3 UBKh, additional steel plates were added to the sponsons. The primary purpose of these plates appears to be for mounting the new armoured side skirts, but they also offer additional ballistic protection for the sponson fuel cells and stowage bins.</span></span><br />
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<span style="font-size: large;">KONTAKT-1</span></h3>
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<span style="font-size: small;"><span style="font-weight: normal;">Kontakt-1 is a type of explosive reactive armour. Work on the integration of the reactive armour with the T-72 was completed in the summer of 1982 and testing of experimental tanks with this new reactive armour kit were carried out in November 1982. Since 1984, the large-scale fitting of Kontakt-1 on T-72 tanks began. New production tanks would have the ERA mounts installed after final assembly at the factory, and existing tanks would be retrofitted while receiving scheduled maintenance at repair facilities across the USSR. On the T-72, the installation of the reactive armour blocks does not differ between tanks that had the 16mm appliqué armour plate on the upper glacis and those that lacked it.</span></span></div>
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<br /></div><div style="font-size: medium; margin: 0px;">A detailed breakdown of Kontakt-1 is available in <a href="https://thesovietarmourblog.blogspot.com/p/kontakt-1.html">a separate article page</a>.</div><div style="font-size: medium; margin: 0px;"><br /></div>
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<span><span style="font-family: "times new roman"; font-weight: normal;">On page 140 of the book "<i>Т-72/Т-90. Опыт создания отечественных основных боевых танков</i>", it is stated that beginning o</span></span><span style="font-family: "times new roman";">n the 1st of January 1984, ERA became a standard accessory on serially produced T-72 tanks. At the end of the year, ERA kits began to be delivered to tank repair facilities for installation on existing tanks sent in for scheduled maintenance. It is worth noting that the UVZ plant was responsible for the design, production and supply of Kontakt-1 boxes for the whole country, while the 4S20 explosive elements for the ERA were designed, produced and supplied by NII Stali.</span><br />
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<span style="font-family: "times new roman";">Due to the replacement of the Object 172M-1 with the Object 184 on the UVZ production line in 1984, all T-72AV tanks were upgraded from existing tanks rather than new-builds. After the delivery of Kontakt-1 kits to repair facilities, the upgrading of tanks began. </span><span style="font-family: "times new roman";">The first T-72AV tanks entered service in 1985 after their scheduled overhauls in late 1984</span><span style="font-family: "times new roman";">, and after 1985, most T-72A tanks had received ERA during scheduled repairs. </span>By the end of the year, a supply of Kontakt-1 kits had been established to tank repair facilities across the USSR to upgrade existing tanks of all models, and the first T-72AV tanks entered service in 1985 after their scheduled overhauls in late 1984.</div>
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There are two types of Kontakt-1 blocks - full sized and reduced size. The reduced size block is used to protect special areas of the tank, like behind the headlights. A full set of Kontakt-1 for the T-72A consists of 227 blocks. There are 48 blocks mounted on the side skirts on each side of the hull, 70 blocks on the frontal arc and the roof of the turret, and 61 blocks on the upper and lower glacis of the hull. The total weight of the armour kit including the additional fittings and mounting frames amounts to 1,500 kg.<br />
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The drawing below roughly illustrates the zones covered with Kontakt-1 on a T-72AV.<br />
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The installation of Kontakt-1 blocks only requires that there are two threaded posts of the correct specifications. On the T-72AV, special light metal mounting frames are welded to the turret cheeks with threaded holes for bolts, but everywhere else on the tank, threaded female tubes are simply welded to the surface of the armour and the blocks are mounted onto them with bolts<span style="font-weight: normal;">. On T-72 models featuring a 16mm appliqu</span><span style="font-size: small; font-weight: 400;">é</span><span style="font-size: small; font-weight: normal;"> armour plate on the upper glacis, the ERA blocks are mounted in the same way with threaded female tubes welded to the appliqué plate as seen in the photo below.</span></div>
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A disadvantage of the light metal mounting frames used to affix the Kontakt-1 blocks on the turret cheeks is that the detonation of the block on one half of the frame is enough to destroy the frame itself, thus removing the other block in the process. This was the cost of ensuring that the block was installed at the optimum 68-degree angle.</div>
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<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span><span style="font-size: small;"><span style="font-weight: normal;">The ease of installing and replacing the blocks </span><span style="font-weight: normal;">meant that the entire modification could be carried out as part of regular scheduled maintenance and blocks lost to battle damage can be easily replaced. </span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>Unlike the T-64, the Kontakt-1 blocks for the hull sides of the T-72 are mounted directly to the textile side skirts and not to a metal frame that is installed over the existing side skirt, as seen <a href="http://4.bp.blogspot.com/-MgX8MehO_zM/UO7TUlBZfrI/AAAAAAAAEfI/WFrPV0a-bSw/s640/saenko2.jpg">on this T-64BV</a>. The simple mounting system allowed the ERA to be easily installed even in field conditions, deprived of special tools. However, the Kontakt-1 blocks themselves are not sufficiently robust, as they are relatively light and the mounting bolts do not secure the blocks securely enough against physical damage. It was noted in a test report that an inexperienced driver could cause the tank to lose some of the blocks on the side skirts by scraping the hull against obstacles such as</div>
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<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span><span style="font-size: small;"><span style="font-weight: normal;">This does not necessarily mean that the arrangement on the T-72 is inferior. According to an anecdote by a pro-rebel volunteer fighting named "Kurt", the arrangement of ERA blocks on skirts of a T-72 are slightly more resilient to damage but torn blocks are easier to replace on a T-64BV. Neither type lasts longer than a week of intense usage. A translated excerpt from the interview with "Kurt" is available on <a href="http://www.tank-net.com/forums/index.php?showtopic=16675&page=91#entry1296524">this Tank-Net post</a>. A single anecdote is not good enough to form a conclusion, of course, but it is plausible that mounting the Kontakt-1 blocks directly on the flexible skirts is more resistant to damage because the skirt will flex if the tank hits something, thus limiting the damage to the blocks and to the skirt itself.</span></span></div>
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NII Stali published the specifications of the Kontakt-1 kit found on the T-72S. The T-72S is a T-72B model for export. Like T-72M1 models exported with a Kontakt-1 kit such as the Indian T-72M1 "Ajeya", the T-72S has reduced reactive armour coverage on the front and sides of the hull with a total of just 165 blocks instead of the full set of 227. According to <a href="http://web.archive.org/web/20040811180253/http://www.niistali.ru/science/secure.htm">NII Stali</a>, the percentage of the surface area covered by Kontakt-1 on a T-72S is as follows:</div>
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<tr><td>Turret</td><td>Hull Front </td><td>Hull Sides </td></tr>
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62%</div>
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82%</div>
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32%</div>
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The total weight of the Kontakt-1 kit over the three individual surfaces for a T-72S are as follows:</div>
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<tr><td>Turret</td><td>Hull Front </td><td>Hull Sides (total)</td></tr>
<tr><td><div style="text-align: center;">
422 kg </div>
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288 kg</div>
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300 kg</div>
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Note that the figures given by NII Stali for the turret are for the entire turret, not just the frontal arc. Like T-72M1 tanks with a Kontakt-1 kit, the surface area covered by reactive armour on the sides of the T-72S was heavily trimmed down to just 32%. This is provided by just 25 blocks. The upper glacis has a few less blocks compared to the full set and the lower glacis of the hull does not have any Kontakt-1 blocks whatsoever.<br />
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The total weight of the Kontakt-1 kit is 1,010 kg. The surface area of the sides of the hull that are covered was 2.3 times less than on a standard T-72AV.<br />
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<span style="font-size: large;">OBJECT 184</span></h3>
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<span style="font-style: normal;"><span style="font-size: small;">As mentioned earlier, beginning on the 1st of January 1984, new-production T-72 tanks were outfitted with ERA. However, given that </span>T-72 tanks produced from the 1st of January 1984 to the 23rd of January 1985 "</span><i>Improved T-72A</i>" were Object 184 tanks, the installation of Kontakt-1 converts them into a T-72B or T-72B1 obr. 1984, depending on the presence of the "Svir" ATGM system. Examples of a T-72B obr. 1984 include <a href="http://hobby-models.ru/walkaround/t-72-walkaround-chast-1.html" style="font-style: normal;">this particular tank at the Museum-Panorama at Volgograd</a>, which was identified as such by Russian historian A.V. Karpenko. The image below shows a T-72B1 obr. 1984, identified as such in the book <span style="font-family: "times new roman";">"</span><i style="font-family: "times new roman";">Т-72/Т-90. Опыт создания отечественных основных боевых танков</i><span style="font-family: "times new roman";">"</span>.</div>
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The total number of blocks did not change compared to the T-72AV (Object 172M-1), so the total weight of the armour set is similar. However, on the T-72B, the Kontakt-1 blocks on the turret cheeks were fitted without a special mounting frame like on the T-72A or on the T-80B and T-64B. Instead, the blocks are simply mounted following the natural contours of the turret surface. All of the other blocks everywhere else on the tank were affixed onto threaded female tubes welded to the armour surfaces like all previous tank models.</div>
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<span style="font-size: small;"><span style="font-weight: normal;">Coming out of the factory, all T-72B models except the obr. 1989 were outfitted with a set of 227 blocks of Kontakt-1 covering the most of the hull and the forward arc of the turret as well as the turret roof. </span></span></div>
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The upside of the new installation layout is that the total surface area covered by the armour increased, and the vulnerability of the light metal mounting frames to the simultaneous loss of two or more blocks to a single detonation was eliminated, but this came at the expense of reducing the effectiveness of the reactive armour significantly as the blocks are no longer installed at the optimum angle of 68 degrees. By not including the mounting frames on the turret cheeks, the total weight of the armour set also decreased somewhat, although it is unclear what the total weight is. It is only safe to assume that the total weight is slightly less than 1,500 kg. The weight of a T-72B with Kontakt-1 is 44.5 tons, and the weight of the tank without it is around 43 tons.</div>
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There are 48 blocks on each side skirt, 61 blocks on the upper and lower glacis plates, and 70 blocks on the entire front half of the turret and the turret roof. On the hull, the reactive armour layout is identical to the T-72A. Only the layout on the turret differs.</div>
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With the exception of the absence of special mounting frames on the turret cheeks, the method of mounting the Kontakt-1 blocks on the T-72B remained the same as on the T-72A. The process of installing new blocks or replacing damaged mounting bolts is identical. As long as the parts are available, this type of battle damage repair can be done in field conditions with minimal tools.</div>
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If needed, more blocks can be added to the side skirts without any difficulty thanks to the ease of installation, as demonstrated on the T-72B in the photo below.</div>
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The arrangement of blocks on the T-72B provides better coverage of the turret compared to the T-72A at the expense of reduced effectiveness. As mentioned earlier, the blocks on the T-72A are mounted on special metal frames to form a wedge shape around the circumference of the turret cheeks, allowing the reactive armour to perform up to its maximum potential at a high obliquity. However, this arrangement left the turret ring and much of the mantlet area unprotected, a problem which can be considered to be more or less "solved" on the T-72B. The Kontakt-1 blocks on the turret ring of the T-72B are mounted on rails and are easy to remove. They are often removed when not needed during peacetime so that the driver is not obstructed when his head is out of the hatch while driving. </div>
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The presence of Kontakt-1 on this part of the turret solved the coverage issue with the layout on the T-72A turret, although small gaps still exist between the Kontakt-1 blocks on the T-72B turret. Due to the thickness of the Kontakt-1 blocks and the mounting angle, they project far enough to cover the turret ring area which is 60mm tall and has a greatly reduced thickness of steel to accommodate the turret ring race ring. This is another improvement over the earlier ERA layout.</div>
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<h3 style="font-size: medium; font-style: normal;">
<span style="font-size: large;">EFFECTIVENESS</span></h3>
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According to the test results for a T-72A equipped with Kontakt-1 reported in the article "<a href="http://armor.kiev.ua/Tank/dz/1968/"><i>Динамическая защита. Израильский щит ковался в... СССР?</i></a>" (<i>"ERA: Israeli Shield was forged in... USSR?"</i>), the effective thickness of the armour was increased to 850-900mm RHA in a 70-degree frontal arc on the turret and in a 44-degree frontal arc on the hull. This is fully supported by other Soviet and Russian sources.</div>
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According to the information presented in the poster below, the installation of Kontakt-1 was offered for the modernization of T-72M1 tanks to the T-72M1M level. The T-72M1M is a designation that has been used several times to describe completely different T-72 export models. The main difference is that the Kontakt-1 set offered in the package includes only 155 blocks as opposed to the standard 227 blocks of the T-72AV. Instead of 48 blocks on each side skirt, only 25 blocks are installed, and instead of 55 blocks on the upper and lower glacis of the hull, just 40 blocks cover the upper glacis and the lower glacis is left completely unprotected. The turret has just 65 blocks instead of the full set of 70 blocks.</div>
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Thus, the weight of the package is only 1,200 kg instead of 1,500 kg and the exposed surface area is correspondingly higher. However, the effective thickness of the armour would not be less since the T-72M1 is functionally identical to the T-72A in terms of protection, so the information presented in the poster can be used as a surrogate for the T-72A. Only the information on the size of the protected frontal arc may be inaccurate.</div>
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<span style="font-weight: normal;">The poster was taken from the private website of Russian military historian A.V Karpenko. The original source is unknown.</span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">Interestingly, the drawings at the bottom of the poster credit the T-72M1 hull with 500mm RHA of effective thickness in protection against shaped charges in a 44-degree frontal arc, while the turret has the same effective thickness but in a 70-degree frontal arc. Because the frontal arc size is factored into these figures, these figures express the minimum level of protection at the outer boundaries of the frontal arc and do not represent the maximum effective thickness at the toughest parts of the tank, i.e the front of the turret cheeks and the upper glacis.</span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span><span style="font-size: small;"><span style="font-weight: normal;">According to the subheading of the poster, the Kontakt-1 package offers an effective thickness of 850-900mm RHA against the TOW, HOT, MILAN and Dragon anti-tank guided missiles, against the tank-fired 120mm HEAT shells of the M1A1 Abrams and Leopard 2, and against the M72A2 and Panzerfaust-3 shoulder-fired anti-tank grenade launchers. The poster also states that the Kontakt-1 package offers 730-750mm RHA of effective thickness against artillery-fired HEAT rounds, but based on other evidence, this may be referring to tank-fired HEAT shells and there is some slight confusion in the claims. </span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span><span style="font-size: small;"><span style="font-weight: normal;">This information is corroborated by official marketing information provided by NII Stali, the developers and manufacturers of Kontakt-1. The current Russian language version of <a href="http://niistali.ru/products/nauka/dynamic+protection/kontakt_addon/">the NII Stali website</a>, Kontakt-1 provides an armour equivalent of 400-500mm in steel </span></span>against RPGs and ATGMs and 200-250 mm against artillery-fired HEAT shells. An older catalogue, also from NII Stali, states that Kontakt-1 provides an armour equivalent of 450-500mm in steel against RPGs and ATGMs.</div>
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<span style="font-size: small;"><span style="font-weight: normal;">It is extremely important to understand the contextual significance of the effective thickness figures or RHA equivalence figures given in these sources. When Kontakt-1 was tested on experimental T-72A tanks in 1982, the most powerful HEAT charge available at the time was the 140mm 3N18 warhead of the 3M11 "Falanga" missile. When the warhead is set up on a static rig, a LOS thickness of 848mm RHA (290mm RHA target sloped at 70 degrees) is needed to stop it.</span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">Officially, the T-72A with Kontakt-1 was considered to have an effective thickness value of up to 900mm RHA against HEAT because it could successfully stop this threat on its upper glacis and the turret cheeks, which had a base protection of 490mm and 500mm RHA respectively against shaped charges. </span></span>Because a HEAT warhead with a penetration power of above 900mm RHA was not tested, the effective thickness also did not exceed 900mm RHA. Technically, the effective thickness can be higher, and given that Kontakt-1 is rated to provide an additional effective thickness of up to 500mm RHA, the armour of a T-72AV can be equivalent to up to 1,000mm RHA against HEAT, especially if measured in a frontal arc of 60 degrees instead of 70 degrees as per the Soviet specifications.</div>
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<span style="font-size: small;"><span style="font-weight: normal;">A similar method of evaluating effective thickness is used abroad. During the development of the M1 Abrams, the armour of the XM-1 prototype was tested using a standard 5.0" BRL precision shaped charge with a penetration of 636mm RHA was used. During the development of the Leopard 2, the armour of the Leopard 2AV was tested the same 5.0" BRL shaped charge was also used but with a slightly smaller standoff distance so that it yielded 600mm RHA of penetration. </span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">At the same time Kontakt-1 was accepted into service, the TOW-2 missile (1983) also appeared. Its penetration power of 900mm RHA was nominally insufficient to overcome the armour of a T-72AV. Until this point, t</span></span>he most powerful ATGM among the European NATO members at the time was the HOT, which had a penetration power of 720mm RHA. It began to be replaced by the HOT-2 missile in 1985. The HOT-2 had a penetration power of 850mm RHA. All three heavy ATGMs lacked sufficient power to overcome the frontal arc armour of a T-72A tank equipped with Kontakt-1.</div>
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<span style="font-size: small;"><span style="font-weight: normal;">On a T-72B, the total effective thickness of the turret is also equivalent to 900-1,000mm RHA in a 70-degree frontal arc, despite the higher effective thickness of the base armour (650mm instead of 500mm). This is mainly due to the reduced effectiveness of the Kontakt-1 on the T-72B turret because the blocks located at the same point of the turret are only sloped at 30 degrees instead of 68 degrees. </span></span>As discussed earlier in the section regarding the ERA armour on the T-72A, each block can reduce the penetration of a shaped charge warhead by an average of 55% at 0 degrees, by 80% when angled at 60 degrees, and by up to 90% at 68 degrees. NII Stali claims that it can reduce the penetration power of a typical anti-tank missile like the Konkurs (130mm diameter) by up to 86%, or 58% for a 125mm HEAT shell, or up to a whopping 92% for lower velocity shaped charge warheads like the one on the 66mm LAW.<br />
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Based on our earlier research, a V-shaped ERA design like Kontakt-1 reduces the penetration of a shaped charge jet by 55% at a perpendicular impact angle, so the armour is far from useless, but in comparison with the 90% penetration reduction achieved with a Kontakt-1 block angled at 68 degrees, it is a sizable downgrade. Still, the curvature of the turret cheeks remedies this shortcoming to some extent by introducing a horizontal slope. Moreover, the surface of the turret cheeks are also vertically sloped at 30 degrees and the cut on the lower edge of the turret cheeks are vertically sloped at 50 degrees.<br />
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For instance, if a shaped charge warhead impacted the turret directly in front of the gunner's sight of an <span style="font-family: "times new roman";">Object 184 turret</span>, it will hit a Kontakt-1 block that is only angled 10 degrees vertically, which is quite close to flat. In the neighbouring zone, several Kontakt-1 blocks are angled 48 degrees horizontally and 30 degrees vertically (compound angle of 54.6 degrees). In the next zone, several Kontakt-1 blocks are angled 67 degrees horizontally and 30 degrees vertically (compound angle of 70 degrees). These values are based on technical drawings. These three zones constitute the area directly in front of the gunner's station.<br />
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<a href="https://1.bp.blogspot.com/-7GkKiRhtkHc/XnTzVZkprWI/AAAAAAAAQYU/tiPQ8XHsZXsEdg0FAlAGoJjfH1cHAwo9QCLcBGAsYHQ/s1600/cheek.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="713" data-original-width="677" height="320" src="https://1.bp.blogspot.com/-7GkKiRhtkHc/XnTzVZkprWI/AAAAAAAAQYU/tiPQ8XHsZXsEdg0FAlAGoJjfH1cHAwo9QCLcBGAsYHQ/s320/cheek.jpg" width="303" /></a><a href="https://1.bp.blogspot.com/-e1zq1BWiklc/XnTy0n9pp4I/AAAAAAAAQYM/KdOHZNls89AWlyo0DphqehNwDCbB9MY5ACLcBGAsYHQ/s1600/t-72b%2Bkontakt-1%2Bzones.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="339" data-original-width="253" height="320" src="https://1.bp.blogspot.com/-e1zq1BWiklc/XnTy0n9pp4I/AAAAAAAAQYM/KdOHZNls89AWlyo0DphqehNwDCbB9MY5ACLcBGAsYHQ/s320/t-72b%2Bkontakt-1%2Bzones.png" width="237" /></a></div>
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According to Chinese research on a replica of Kontakt-1, it was found that at an impact angle of 45 degrees, the penetration depth of a shaped charge is reduced by 60% and at an impact angle of 68 degrees, it is reduced by 90%. This shows that the effectiveness of Kontakt-1 will vary wildly between 55% to 90% depending on the point of impact on the turret.<br />
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At the reference point on the turret cheek, it is theoretically possible for the total effective thickness to exceed 1,000mm RHA, but there is no way to validate this as there is currently no information regarding the tests of this armour with a HEAT warhead of such power.<br />
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<span style="font-size: small;"><span style="font-weight: normal;">The front of the hull reaches the same total effective thickness of 900-1,000mm RHA, but the effective thickness in its 44-degree frontal arc remains 850-900mm RHA because the side hull armour is the same as the T-72AV. </span></span><br />
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Compared to foreign tanks, the sides of the hull of a T-72 tank with Kontakt-1 have adequate protection from shaped charge weapons and all of its weakened zones throughout the tank were also reinforced in the same way. The turret roof, for example, has a LOS thickness of only 210mm at the weakest zones. Adding Kontakt-1 to these areas immunizes them from the vast majority of shaped charge weapons, especially considering that the slope of the roof is 78 degrees which is very steep indeed. At such a high obliquity, a penetration loss of over 90% can be expected for most types of HEAT weapons, making it very difficult to defeat the roof armour with any contemporary single-charge HEAT warhead.</div>
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As mentioned before, the M1A1HA Abrams has an effective thickness of 750mm RHA against a 127mm ATGM from a 25 degree side angle but only 380mm RHA against an 81mm grenade from a 45 degree side angle. The sharp drop in protection when attacking the armour from a 25 degree side angle (65 degree angle of incidence) to a 45 degree side angle (45 degree angle of incidence) is not explained simply by the natural decrease in LOS thickness as this is a reduction in the obliquity of the angle of incidence of only 20 degrees, thus the LOS thickness was lower by 40.2%, but the drop in the effective thickness was in the order of 49.3%. This is explained by the use of a 38mm steel front plate and two NERA panels placed parallel to the side of the hull. This is because the effectiveness of bulging plates varies exponentially with its obliquity, and as the angle of incidence approaches zero, the effect of the bulging plates also approaches zero.</div>
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If attacked perpendicular to its hull, the side armour of any Abrams variant from the M1 up to the M1A2 would fail against practically all postwar HEAT weapons unless an ERA package is fitted. On the other hand, Kontakt-1 still ensures a 55% reduction in penetration power when hit at a perpendicular angle. Alternatively, Kontakt-1 has been credited to be provide an equivalent thickness of 200-250mm RHA when struck perpendicularly. Together with the air gap of more than 745mm between the Kontakt-1 bricks on the side skirt and the surface of the hull sides, it became possible to reliably resist light shoulder-fired HEAT weapons with a penetration of more than 400mm RHA. This is thanks to the internal angling of the 4S20 explosive elements in a V-shape. As such, not only does a T-72A equipped with Kontakt-1 boast a higher level of protection in a larger frontal arc compared to the NATO's best-protected tanks of the late 1980's, it also avoids suffering a near-total loss of protection when attacked at a perpendicular angle to the sides of the hull. The caveat is, of course, the lack of a multi-hit capability.</div>
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It is possible to exploit the lack of a multi-hit capability by firing multiple rounds against the tank, but for a light shoulder-fired system like the Carl Gustaf where the probability of hit on a static tank is only 50% at 200 meters, there is no guarantee of scoring a successful hit on a tank during combat, let alone hitting the same spot twice. It is important to note that the grenades from a light handheld anti-tank weapon normally have a rather small explosive charge, and are generally incapable of affecting more than two ERA blocks with a single hit. </div>
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Needless to say, it is not a trivial accomplishment that Kontakt-1 could boost the protection of a T-72A tank above the level of the most heavily armoured NATO tanks of the mid-1980's, namely the M1A1HA Abrams and late-model Leopard 2A4 tanks (batch 6 and 7, delivered in 1988-90), especially in terms of side protection.<br />
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Modern HEAT grenades with a tandem warhead can defeat Kontakt-1 and may have enough penetration power to perforate the base armour as well. One example is the PG-29V for the RPG-29 which is rated to penetrate 650mm RHA after ERA.<br />
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<span style="font-size: small;">According to the study "<i><a href="http://btvt.info/5library/vot_1984_dz.htm">Методический Подход К Выбору Характеристик Динамической Бронезащиты Танка</a></i>", the resistance of a T-72M1 or T-72A tank to attacks using all types of HEAT ammunition is increased by an average of 1.8 times with Kontakt-1 and the size of the protected frontal arc was expanded. This was a holistic breakdown of the</span> influence of Kontakt-1 on the armour perforation probability using weighted hit probability data. </div>
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<span style="font-family: "times new roman"; font-weight: normal;">From the perspective of the Soviet state, the addition of reactive armour vastly was extremely valuable as it improved the survivability of existing tanks against the most powerful shaped charge weapons appearing in the first half of the 1980's, and more importantly, could do so at an extremely low cost; the cost of installing Kontakt-1 on a tank amounted to only 1,600 Rubles. This was around half the cost of a SACLOS guided missile such as the 9M113 "Konkurs".</span><br />
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<a href="https://www.blogger.com/null" id="kontakt-5"></a>
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<span style="font-size: large;">KONTAKT-5</span></h3>
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This section is under renovation. A full examination of Kontakt-5 will be posted as a separate page accessible from this article and from the tool bar at the top of the screen.
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<a href="https://www.blogger.com/null" id="relikt"></a>
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<span style="font-size: large;">"RELIKT" SIDE SKIRTS</span></h3>
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<a href="https://2.bp.blogspot.com/-swYwfRacvx0/W6AbVk8tjKI/AAAAAAAAMQk/u9LezqEjhEkRRjssccUxHIWdntxqY-3fACLcBGAs/s1600/4cv5Y.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="720" data-original-width="1280" height="360" src="https://2.bp.blogspot.com/-swYwfRacvx0/W6AbVk8tjKI/AAAAAAAAMQk/u9LezqEjhEkRRjssccUxHIWdntxqY-3fACLcBGAs/s640/4cv5Y.jpg" width="640" /></a></div>
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The fighting compartment and engine compartment of the tank is protected by heavy side skirts incorporating "Relikt" ERA elements. The skirts were originally developed and implemented on the T-90MS (Object 188MS).<br />
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There are six skirt segments on either side of the hull, each with two prominent steel front plates. Like the Kontakt-1 armour package used on earlier T-72 models, the "Relikt" skirts extend up to the fifth roadwheel and thus cover the entire side of the hull from a 70-degree frontal arc. In total, there are twelve skirt segments and twenty four steel plates protecting the sides of the hull. Each skirt segment is attached to the hull sponsons by a pair of hinges, as seen in the photo on the left below. The two photos below are from Vitaly Kuzmin. Additional armoured plates protecting the sponsons were added for this purpose.</div>
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<a href="https://3.bp.blogspot.com/-iERmCjnVkHA/W6AYyqkIwnI/AAAAAAAAMQY/-HYlC1Ui1vg5SlKHbxySdUZI-4m4urmZwCLcBGAs/s1600/T-72B3mod2016-15.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="266" src="https://3.bp.blogspot.com/-iERmCjnVkHA/W6AYyqkIwnI/AAAAAAAAMQY/-HYlC1Ui1vg5SlKHbxySdUZI-4m4urmZwCLcBGAs/s400/T-72B3mod2016-15.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-P7w0zJr-B-A/W6AYIvMedWI/AAAAAAAAMQI/heRhXwyMNgMsdvqj7vxxYz7tWfVzuJMfgCLcBGAs/s1600/T-72B3mod2016-16.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="266" src="https://1.bp.blogspot.com/-P7w0zJr-B-A/W6AYIvMedWI/AAAAAAAAMQI/heRhXwyMNgMsdvqj7vxxYz7tWfVzuJMfgCLcBGAs/s400/T-72B3mod2016-16.jpg" width="400" /></a></div>
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The mounting points for the armoured side skirts can be seen in the photo below.<br />
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<a href="https://2.bp.blogspot.com/-kfcxPGmvLaA/XGZrAEGopeI/AAAAAAAANYk/8bRPg0J0fT0ym960LdKHlSxf2KtkZDrJwCLcBGAs/s1600/mud%2Bguard%2Bt-72b3%2Bobr.%2B2016.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="567" data-original-width="851" height="426" src="https://2.bp.blogspot.com/-kfcxPGmvLaA/XGZrAEGopeI/AAAAAAAANYk/8bRPg0J0fT0ym960LdKHlSxf2KtkZDrJwCLcBGAs/s640/mud%2Bguard%2Bt-72b3%2Bobr.%2B2016.jpg" width="640" /></a></div>
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These heavy skirts are officially listed as a component of "Relikt" reactive armour. This is supported by the fact that the skirts are distinguished from the "soft" fabric bagged-type ERA pouches that are listed as a completely separate item. A purchase agreement memo published in 2015 by the Uralvagonzavod company in accordance with the purchase of the T-72B3 UBKh lists the agreed-upon upgrades and gives the following details:<br />
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"<i>бортовых экранов корпуса с интегрированными модулями динамической защиты типа «Реликт» и решетчатых экранов проекции МТО корпуса.</i>" </blockquote>
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Which translates to: </blockquote>
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"<i>Side screens of the hull with integrated modules of dynamic protection of the type "Relikt" and slat screens on the side projections of the engine compartment.</i>"</blockquote>
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A recently released episode of the <a href="https://youtu.be/J2S1OAzckeM?t=1894">show "<i>Военная приемка</i>" on the T-90M "Proryv"</a> published by TV Zvezda confirms that these side skirts contain explosive elements. It can be seen from close-up photos of the heavy armoured skirts that they are constructed from steel-reinforced rubber skirt material sandwiched between steel plating. The explosive elements are embedded in special cutouts in the middle layers.<br />
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The middle layers appear to be the same type of steel-reinforced rubber that was used for the side skirts found on the T-72 since the mid to late 1970's.<br />
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<a href="https://3.bp.blogspot.com/-ySu9SgZ-Bxs/W6AeMEmwAZI/AAAAAAAAMQw/H6nPpb6GuN80dLr3ZodNzqouneyruT99QCLcBGAs/s1600/skirts.png" style="font-size: 18.72px; font-weight: 700; margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="1273" data-original-width="396" height="640" src="https://3.bp.blogspot.com/-ySu9SgZ-Bxs/W6AeMEmwAZI/AAAAAAAAMQw/H6nPpb6GuN80dLr3ZodNzqouneyruT99QCLcBGAs/s640/skirts.png" width="198" /></a></div>
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The cutout for explosive elements can be seen in the photo below, taken from the <a href="https://vk.com/oldfag_tm?w=wall-69502755_157006">"<i>Олдфаги ТМ</i>" VK group</a>. The thin back plate of the sandwich was removed.<br />
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<a href="https://1.bp.blogspot.com/--Evau75EYY8/XpF5dJnAA4I/AAAAAAAAQko/J6EXBWSPS48jBTTp6xSeE8JeTKCbVKxuQCLcBGAsYHQ/s1600/opened%2B2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1040" data-original-width="1386" height="300" src="https://1.bp.blogspot.com/--Evau75EYY8/XpF5dJnAA4I/AAAAAAAAQko/J6EXBWSPS48jBTTp6xSeE8JeTKCbVKxuQCLcBGAsYHQ/s400/opened%2B2.png" width="400" /></a><a href="https://1.bp.blogspot.com/-1UXUnLGzzDo/XpFxZzv8GkI/AAAAAAAAQkY/O8ik1yKiSuo5I6gSmR90s5y30PRvkL7WACLcBGAsYHQ/s1600/opened%2B1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1509" data-original-width="1263" height="320" src="https://1.bp.blogspot.com/-1UXUnLGzzDo/XpFxZzv8GkI/AAAAAAAAQkY/O8ik1yKiSuo5I6gSmR90s5y30PRvkL7WACLcBGAsYHQ/s320/opened%2B1.png" width="265" /></a></div>
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It is known from <a href="http://www.russianarms.ru/forum/index.php?PHPSESSID=n0601ccbcd0r0cenngl2etetm2&action=dlattach;topic=10994.0;attach=317289;image">an information placard</a> provided by NII Stali at an arms exhibition that a 4S23 explosive element designed for "Relikt" has dimensions of 250x125x7 mm, and there is a stack of two elements in each cutout. As such, the total thickness of the steel-reinforced rubber skirt layer must be more than 14mm. The steel front plate of the sandwich is therefore around 7mm, and the back plate is 1-2mm.<br />
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Each skirt panel appears to be equal in length to a roadwheel, which has a diameter of 250mm, and the height of the panels is around a third of their length. This implies that up to three 4S23 elements can be fitted lengthwise inside each panel and up to two 4S23 elements fitted in height. The total number of elements contained within each skirt panel would be up to eighteen. A layout with angled plates similar to Kontakt-1 is also possible, but not very likely.<br />
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It is known that a similar armoured side skirt sandwich design was experimentally built and tested during the late 1990's on an early prototype of the Object 199, a vehicle now known as the BMPT. <a href="http://www.freepatent.ru/patents/2238508">Russian Patent RF 2238508</a> contains a description of this type of armour as well as two fairly detailed cross sectional drawings showing a similar sandwich configuration with two metal plates sandwiching two inner sheets. Externally, the only visible difference is that the top half of the skirt is slightly inclined, giving it a slightly rounded appearance when mounted.<br />
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<a href="https://1.bp.blogspot.com/-MU88gZLieNo/XpFw-fdv_7I/AAAAAAAAQkQ/pOCDGfNQjnQ4nInxD9yrUk_Mh6FoedOVQCLcBGAsYHQ/s1600/relikt%2Bside%2Bscreens.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="463" data-original-width="640" height="288" src="https://1.bp.blogspot.com/-MU88gZLieNo/XpFw-fdv_7I/AAAAAAAAQkQ/pOCDGfNQjnQ4nInxD9yrUk_Mh6FoedOVQCLcBGAsYHQ/s400/relikt%2Bside%2Bscreens.jpg" width="400" /></a></div>
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A variant of this side skirt design was used on the T-80U and several modernized T-64 models as part of the Kontakt-5 reactive armour set with 4S22 explosive elements embedded in the center layers of the skirts. In this variant, the explosive elements were not merely placed inside special cutouts in under the skirt panels, but held inside a container. <br />
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The great length of each skirt panel (~750mm) is a contributing factor in the effectiveness of the armour as the working length of the flyer plates would be very high. Together with the large air gap between the side skirts and the side hull (even with the suspension in the way), this combination of features innately improves the effectiveness of the armour.
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It is claimed in an old catalogue produced by NII Stali that "Relikt" improves the protection against APFSDS rounds by 1.5 to 1.6 times and by 2.0 times against shaped charges. The difference in protection against shaped charges compared to Kontakt-5 is not large as NII Stali claims that Kontakt-5 improves the protection against such weapons by 1.9-2.0 times. It is also claimed that Kontakt-5 increases the side protection of a T-72M1 tank by 600mm RHA against shaped charges, presumably when attacked at a side angle of 22 degrees. This is most likely in addition to the 500mm of effective thickness provided by the side skirts integral to this model of the T-72 when attacked at a side angle of 22 degrees. Based on this information, the "Relikt" side skirt armour on the T-72B3 should offer an effective thickness in excess of 1,000mm RHA against shaped charges in a 44-degree frontal arc.<br />
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The low protective value of the skirts at a flat angle of attack is probably the reason for the use of the soft bagged ERA pouches.<br />
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For comparison, the heavy ballistic skirts found on the M1 Abrams depend on NERA to achieve a modest level of protection. In a <a href="https://www.cia.gov/library/readingroom/docs/CIA-RDP91B00390R000300220014-8.pdf">well known declassified document</a> showing the "special armour" of the M1 Abrams, it is shown that the side skirts are classified as "special armour". It is stated in the document that the term "special armour" refers to a tri-plate arrangement which is understood to be simple NERA of the bulging plate type, and as seen in the drawing below, the heavy ballistic side skirt is composed of a thick steel front plate with the bulging plate armour elements placed behind it. It is worth noting that the drawing appears to show two thin bulging sandwiches separated by a small air gap behind the steel front plate, with one of them being attached directly to the steel front plate so that there is only one in-pursuit bulging plate. According to measurements, the armoured side skirts on the Abrams have a thickness of 65mm, and are composed of a one inch-thick steel front plate with 38mm of "special armour" behind it.</div>
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Photos of battle-damaged side skirts on M1A1 Abrams tanks confirm the presence of bulging plates by the characteristic bulging of the back plate. It is worth mentioning the requirements for the side armour over the crew compartment (both hull and turret) in the XM-1 that ended up proceeding into production as the M1 Abrams was rated for an 81mm (3.2") HEAT charge at a 45 degree angle. Assuming that this refers to the Ballistics Research Laboratory (BRL) standard 81mm shaped charge with a copper liner detonated at the standard standoff distance of 147mm, the penetration of the charge would be around 350mm RHA, so the level of protection would have to be equivalent to above 350mm RHA when hit at a 45 degree angle. <a href="http://image.noelshack.com/fichiers/2018/10/2/1520357157-m1a1-ha-protection-level.jpg">This is confirmed by this drawing of the M1A2</a> showing that the side turret and side hull armour of the M1A2 (unchanged from the M1) is equivalent to 380mm RHA against an 81mm Hand-held Infantry Weapon (HHIW). This was already insufficient against a PG-7VS grenade (1972) for the RPG-7 with 400mm of penetration into RHA, and the PG-7VL (1977) with 500mm of penetration would provide a relatively high amount of armour overmatch at the given angle to achieve a high probability of killing crew members or even piercing the armoured ammunition rack blast doors. The T-72B3 UBKh offers a much higher level of protection on the sides. An additional factor to consider is the better coverage of the "Relikt" side skirts, which are symmetrical on both sides of the hull and are long enough to protect the engine compartment on both sides when hit from the 70 degree frontal arc of the tank whereas on the Abrams, the starboard side armoured skirts extend up to the fourth roadwheel to protect the hull ammunition compartment from a 45 degree hit, and the port side armoured skirts only extend up to the second roadwheel to protect the fighting compartment from a 45 degree hit.<br />
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Because these new armoured skirts are not laid over the existing skirts like the Kontakt-5 panels of earlier T-72 models but instead replace the skirts entirely, the width of the hull actually decreased marginally compared to earlier T-72 models with Kontakt-1 and Kontakt-5.<br />
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<span style="font-size: large;">SLAT ARMOUR</span></h3>
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<tr><td style="text-align: center;"><a href="https://4.bp.blogspot.com/-sSmYLQqzjGc/W6AoWD6_71I/AAAAAAAAMQ8/GoJP5iB-S6c8OuiEPDObZvLCI5FkIiB8wCLcBGAs/s1600/EBSCybFrASg.jpg" style="font-size: 18.72px; font-weight: 700; margin-left: auto; margin-right: auto; text-align: center;"><img border="0" data-original-height="1067" data-original-width="1600" height="425" src="https://4.bp.blogspot.com/-sSmYLQqzjGc/W6AoWD6_71I/AAAAAAAAMQ8/GoJP5iB-S6c8OuiEPDObZvLCI5FkIiB8wCLcBGAs/s640/EBSCybFrASg.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Photo credit to Vitaly Kuzmin</td></tr>
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The side and rear aspects of the engine compartment are protected with slat armour screens installed over the preexisting textile side skirts. There are three small slat armour screens on each side of the hull and six screens protecting the back of the hull. The six screens at the back are split into a top half and a bottom half with three screens each, and the mounting frame is designed so that either half can be folded over the other half. Folding the top half away as shown in the photo on the left enables additional fuel drums to be carried and folding the bottom half away as shown in the photo on the right grants access to the back of the engine compartment. The photo on the left below is provided by Dmitry Derevyankin from the Dishmodels scale modeling website and the photo on the right below is from <a href="https://yuripasholok.livejournal.com/10734351.html">Yuri Pasholok</a>.</div>
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<a href="https://4.bp.blogspot.com/-YmN4naRXuv4/W6AoWuQbCnI/AAAAAAAAMRA/xIKc-JRX4CQRHFdLcDjvGXr-M8-avNugACLcBGAs/s1600/rear%2Bslat%2Bscreens.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="801" data-original-width="1200" height="266" src="https://4.bp.blogspot.com/-YmN4naRXuv4/W6AoWuQbCnI/AAAAAAAAMRA/xIKc-JRX4CQRHFdLcDjvGXr-M8-avNugACLcBGAs/s400/rear%2Bslat%2Bscreens.png" width="400" /></a><a href="https://3.bp.blogspot.com/-jhNP7vAfIII/W6AuHJ_SnaI/AAAAAAAAMRY/QTKT58jpW_EWhlUjJUGEoBS4mce5kRTggCLcBGAs/s1600/pasholok%2Bslat%2Bscreen.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="266" src="https://3.bp.blogspot.com/-jhNP7vAfIII/W6AuHJ_SnaI/AAAAAAAAMRY/QTKT58jpW_EWhlUjJUGEoBS4mce5kRTggCLcBGAs/s400/pasholok%2Bslat%2Bscreen.jpg" width="400" /></a></div>
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As for the slat armour screens on the sides of the engine compartment, two of them are fixed in place with bolts and one screen can be folded upward. This is most likely designed to facilitate access to the roadwheels. The hinge for one of the slat armour screens can be seen in the photo below. Photo by <a href="https://yuripasholok.livejournal.com/10734351.html">Yuri Pasholok</a>.</div>
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From a profile view, the slat armour screens comprise approximately one third of the protected area of the hull and the other two thirds are covered by the heavy Relikt skirts. The combination of the slat armour screens and the heavy Relikt skirts almost completely covers the entire surface area of the sides of the hull.</div>
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<a href="https://www.blogger.com/null" id="4s22"></a><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><h3 style="font-size: medium;"><span style="font-size: large;">ADDITIONAL 4S22 ERA</span></h3><div><span style="font-size: large;"><br /></span></div></div>
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<a href="https://4.bp.blogspot.com/-BEwWvxAX_dY/XANOlbWLm1I/AAAAAAAAMoA/EUhejRjxvDgOT0y2LUwmlJ-tPFmIPF0EQCLcBGAs/s1600/DHMRk6JXkAMmW_-.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="675" data-original-width="1200" height="225" src="https://4.bp.blogspot.com/-BEwWvxAX_dY/XANOlbWLm1I/AAAAAAAAMoA/EUhejRjxvDgOT0y2LUwmlJ-tPFmIPF0EQCLcBGAs/s400/DHMRk6JXkAMmW_-.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-n7OM36RI0VI/XANKvxBqMiI/AAAAAAAAMnQ/E7uvZjJGDi00mCcg0s_XthC851ziaXsMgCLcBGAs/s1600/T-72B3mod2016-16.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="266" src="https://1.bp.blogspot.com/-n7OM36RI0VI/XANKvxBqMiI/AAAAAAAAMnQ/E7uvZjJGDi00mCcg0s_XthC851ziaXsMgCLcBGAs/s400/T-72B3mod2016-16.jpg" width="400" /></a></div>
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"Soft" ERA blocks were installed on the sides of the hull on top of the "Relikt" side skirts of the T-72B3 UBKh, or T-72B3M as it may be known. Three different sizes were installed. Two small blocks are installed at the front of the side skirts above the first roadwheel, two medium blocks are installed behind them, above the first and second roadwheels, and eight large blocks are installed to cover the rest of the hull, from above the second roadwheel to the fifth roadwheel.<br />
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<a href="https://1.bp.blogspot.com/-iCRNIJ_HGng/XUzCrSxq0KI/AAAAAAAAOxw/ci1hupPsmlU0jB4iNxUD3d457XUuEumqQCLcBGAs/s1600/t-72b3%2Bobr.%2B2016%2Bekaterinburg.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="728" data-original-width="1200" height="388" src="https://1.bp.blogspot.com/-iCRNIJ_HGng/XUzCrSxq0KI/AAAAAAAAOxw/ci1hupPsmlU0jB4iNxUD3d457XUuEumqQCLcBGAs/s640/t-72b3%2Bobr.%2B2016%2Bekaterinburg.jpg" width="640" /></a></div>
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<div style="font-size: medium; font-weight: normal;">Each of these ERA bags consist of a pouch to hold a number of 4S22 explosive elements, spaced apart with special plastic inserts. <a href="https://4.bp.blogspot.com/-uc0vy0amZv8/XANKvhiyBII/AAAAAAAAMnI/it3S7YIxVGk8B5DqrRABNFke8otVaArMwCLcBGAs/s1600/DMQeIy2XcAANEnl.jpg">Each insert resembles a small egg tray</a>, designed to interlock as the diagram below shows. The 4S22 explosive elements are held at the correct angle by a combination of the shape of the pouch and the mutual support of the other elements in the stack.</div>
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<br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidQMEGC-iUgco6m1WHXw8PuxiYLklHULgh9EPg3xqBs3XTRIqntZCvMDwooFNP8FNHmtybB05zhPbw8V-PuPuSHEnzYRixSiqAS2Hf-tJXYWjnkF4TNrE9bLAsX3GykMEQu6BmpVZUxF3AeaNFpaxdcX-9mh8j0_79UOZRDUGapAxB1qJHDxLf7hZvYQ/s1297/soft%20bag.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1297" data-original-width="910" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidQMEGC-iUgco6m1WHXw8PuxiYLklHULgh9EPg3xqBs3XTRIqntZCvMDwooFNP8FNHmtybB05zhPbw8V-PuPuSHEnzYRixSiqAS2Hf-tJXYWjnkF4TNrE9bLAsX3GykMEQu6BmpVZUxF3AeaNFpaxdcX-9mh8j0_79UOZRDUGapAxB1qJHDxLf7hZvYQ/w281-h400/soft%20bag.png" width="281" /></a></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div>
<div style="font-size: medium; font-weight: normal;">The sides of the turret were also uparmoured with ERA blocks. The right side is protected with five blocks while the left side is covered with only four, leaving a gap to accomodate the smoke grenade launchers. These are simple, light metal boxes.</div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-0eSUma1ObuU/X2kwL0DHmTI/AAAAAAAARoY/T_vNOFcF6cAuCRGU_S7a20JM91_SH8EoACLcBGAsYHQ/s1024/ERA%2Bboxes.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="680" data-original-width="1024" src="https://1.bp.blogspot.com/-0eSUma1ObuU/X2kwL0DHmTI/AAAAAAAARoY/T_vNOFcF6cAuCRGU_S7a20JM91_SH8EoACLcBGAsYHQ/s320/ERA%2Bboxes.jpg" width="320" /><br /></a></div><div><br /></div><div><br /></div><div>Inside each box, ten 4S22 explosive elements are fixed on spacer brackets. </div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTSQ0J821o43rhZxUvCXx--l0xiHJhZfHgWmvsOYTIhLeE-P0YBliOA0ID9yRYp2Ua5wjO388Hb3jp6WYGaVQThKAkkflLW7G0ak04OZjV1VCTIzgkZ0npBr3G9ejhyTFIQGqvXSI5Yfo0odSnb3QEP3t4De3b7vYO5PDaj_FY6F7MpDcXDXUsKq9e_Q/s1080/4TlK6KF3otA.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="608" data-original-width="1080" height="360" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTSQ0J821o43rhZxUvCXx--l0xiHJhZfHgWmvsOYTIhLeE-P0YBliOA0ID9yRYp2Ua5wjO388Hb3jp6WYGaVQThKAkkflLW7G0ak04OZjV1VCTIzgkZ0npBr3G9ejhyTFIQGqvXSI5Yfo0odSnb3QEP3t4De3b7vYO5PDaj_FY6F7MpDcXDXUsKq9e_Q/w640-h360/4TlK6KF3otA.jpg" width="640" /></a></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;">The photo on the right below, courtesy of Vitaly Kuzmin, shows the welded frame constructed from hollow structural steel tubes and also shows the air gap separating the ERA block from the turret side.</div>
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<a href="https://3.bp.blogspot.com/-FE8S0gBaeoc/XANM3-2kypI/AAAAAAAAMnw/tZJvq3Vy6_E8EbNbATgmRcGsfFPzmaAygCLcBGAs/s1600/4360007_original.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="266" src="https://3.bp.blogspot.com/-FE8S0gBaeoc/XANM3-2kypI/AAAAAAAAMnw/tZJvq3Vy6_E8EbNbATgmRcGsfFPzmaAygCLcBGAs/s400/4360007_original.jpg" width="400" /></a><a href="https://4.bp.blogspot.com/-H_VS-0CjW8k/XANKv6YFxaI/AAAAAAAAMnM/WX1EjjrI9JwdoHkt5AytBFDSPrEJjFikQCLcBGAs/s1600/DMQeaSNW4AAvuiu.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="266" src="https://4.bp.blogspot.com/-H_VS-0CjW8k/XANKv6YFxaI/AAAAAAAAMnM/WX1EjjrI9JwdoHkt5AytBFDSPrEJjFikQCLcBGAs/s400/DMQeaSNW4AAvuiu.jpg" width="400" /></a></div></div><div>
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<span style="font-size: large;">SMOKESCREEN</span></h3>
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<a href="https://1.bp.blogspot.com/-ZYjYdnrj37Y/WMMNu0cyaUI/AAAAAAAAIhw/V9E1DC3NETslfnj1oQg4eK6uCX611KOpACLcB/s1600/t-72%2Bsmokescreen.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://1.bp.blogspot.com/-ZYjYdnrj37Y/WMMNu0cyaUI/AAAAAAAAIhw/V9E1DC3NETslfnj1oQg4eK6uCX611KOpACLcB/s640/t-72%2Bsmokescreen.JPG" width="640" /></a></div>
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Earlier T-72 models can either lay its own smokescreen by injecting a diesel fuel into the exhaust manifold via the TDA (Thermal Smoke Apparatus), and later variants have the option of using its smoke grenade launchers. TDA is an inexpensive and extremely useful method of providing quick concealment at the cost of 10 liters of diesel per minute of continuous operation. By injecting diesel into the exhaust manifold, the hot manifold evaporates the fuel instantly, and it is ejected from the exhaust port by the exhaust gasses. Upon contacting the cool ambient air, the diesel mist condenses, forming a thick white fog. The fog is opaque to light in the 400-760 nm wavelength range, or in other words. This makes the TDA system a viable method of concealing the tank from anti-tank guided missiles, anti-tank guns and other tanks during daylight hours. The fog does not mask the tank from infrared searchlights like the AN/VSS-1 and AN/VSS-3A, which operate in the 785-1000 nm range, but it is possible to create denser smoke by driving the tank at a higher speeds to increase the fuel consumption rate by 10 times. High density smoke is opaque light in the 400-3000 nm wavelength range, making it effective at concealing the tank from active infrared imaging systems. However, TDA cannot offer any concealment from thermal imaging devices like the AN/VSG-2 Tank Thermal Sight (TTS) installed in the M60A3 (TTS), which <a href="https://patents.justia.com/patent/5369276">operates in</a> the <a href="https://www.forecastinternational.com/archive/disp_old_pdf.cfm?ARC_ID=927">7,600-11,750 nm range</a>.<br />
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The driver should not shift gears when the TDA is in action if he wants to maintain a continuous curtain of fog, as the change in engine load will affect the volume of fog produced. It is not recommended to use the system for more than 10 minutes, and there must be an allowance of 3-5 minutes between each use. If the driver adheres to all of the guidelines, the system can theoretically be used for an infinite number of times (until something eventually breaks). The video screenshot below shows a low-density stream of smoke produced by an idling T-72. The volume of smoke produced when the engine is idling is not useful for screening purposes and it would probably reveal the tank's position more quickly rather than offer useful concealment.<br />
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<a href="http://2.bp.blogspot.com/-00rY9L-HZ-g/VUOarxQK7TI/AAAAAAAACK8/6tuGIHXStJ4/s1600/smokescreen.png"><img border="0" height="472" src="https://2.bp.blogspot.com/-00rY9L-HZ-g/VUOarxQK7TI/AAAAAAAACK8/6tuGIHXStJ4/s1600/smokescreen.png" width="640" /></a></div>
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The two photos below show high-volume, dense smokescreens produced by mobile tanks.<br />
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<a href="https://3.bp.blogspot.com/-uWKHx2s2hPw/W120iExvwpI/AAAAAAAAL2g/OSqjgf-dpFEsI8fYus7jG9OxB0WyDlIgwCLcBGAs/s1600/smokescreen%2Bdeploying.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="720" data-original-width="960" height="240" src="https://3.bp.blogspot.com/-uWKHx2s2hPw/W120iExvwpI/AAAAAAAAL2g/OSqjgf-dpFEsI8fYus7jG9OxB0WyDlIgwCLcBGAs/s320/smokescreen%2Bdeploying.jpg" width="320" /></a><a href="http://3.bp.blogspot.com/-LNK3wIGymH4/VUOm6MMh4MI/AAAAAAAACL0/Uvku1O9drSs/s1600/deploying%2Bsmokescreen.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="205" src="https://3.bp.blogspot.com/-LNK3wIGymH4/VUOm6MMh4MI/AAAAAAAACL0/Uvku1O9drSs/s400/deploying%2Bsmokescreen.png" width="400" /></a></div>
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<h3>
<span style="font-size: large;">"TUCHA" SMOKESCREEN SYSTEM</span><span style="font-size: small;"> </span><span style="font-size: small; text-align: center;"> </span></h3>
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Aside from the TDA system, the
T-72 was equipped with the 902A "Tucha" smoke grenade system beginning with the T-72A obr. 1979. The "Tucha" system can launch several types of caseless 81mm grenades - the 3D6, 3D17, or the 3D6M. The grenade launchers are affixed at an elevation angle of 45 degrees and all of the launchers are parallel to one another. A low pressure propulsion system is used to launch the grenades, which will detonate at varying ranges depending on the grenade model. Twelve grenades are available to the T-72A as part of the 902A system. The T-72AV and the T-72B used the 902B "Tucha" system which has the same operating characteristics as the 902A variant but differs in that it includes only eight grenades.</div><div style="font-size: medium; font-weight: normal;">
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On all variants of the "Tucha" system, the grenade launchers covered by protective rubber caps which are removed before combat. The gunner of the tank is responsible for aiming and firing the grenades by turning the turret towards the threat and aiming with his forward-facing optics. This is done using a control box, shown below, which allows the gunner to customize the number of salvos and the number of grenades launched in each salvo. The system allows the gunner to launch the smoke grenades individually or in salvos of up to four grenades. To aim, the gunner uses the center chevron in his primary sights.<br />
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Earlier T-72 versions with the 902A system had their smoke grenades launchers installed on the turret cheeks. This was a fairly common location for smoke grenade launchers; for example, the Chieftain, Challenger 1 and Challenger 2 all have their smoke grenade launchers mounted directly on their turret cheeks, and a large number of IFVs have their smoke grenades installed on the front of the turret.</div>
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<a href="https://3.bp.blogspot.com/-O4Q9DGeFxfY/WXJf2-L9m2I/AAAAAAAAIxw/ZXMHzAnZ-DYy7sgfJ8Y4TQDsFjDiLXiRgCLcBGAs/s1600/smoke%2Bgrenades%2Bt-72.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="328" data-original-width="500" height="262" src="https://3.bp.blogspot.com/-O4Q9DGeFxfY/WXJf2-L9m2I/AAAAAAAAIxw/ZXMHzAnZ-DYy7sgfJ8Y4TQDsFjDiLXiRgCLcBGAs/s400/smoke%2Bgrenades%2Bt-72.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-PNsNSPvcMiY/WXJgXnN5WcI/AAAAAAAAIx0/wcIDdlvpQ3Af6Jy7Pb1JKuYI58ybEVEXgCLcBGAs/s1600/smoke%2Bright%2Bside.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="298" data-original-width="439" height="271" src="https://3.bp.blogspot.com/-PNsNSPvcMiY/WXJgXnN5WcI/AAAAAAAAIx0/wcIDdlvpQ3Af6Jy7Pb1JKuYI58ybEVEXgCLcBGAs/s400/smoke%2Bright%2Bside.jpg" width="400" /></a></div>
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<br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;">When modernized to the T-72A standard during scheduled repairs, older T-72 models would also receive the 902A system with the smoke grenade launchers installed in the same layout, with minor changes in the position of the launchers to account for the turret geometry. The photo below, taken from <a href="http://www.militaertechnik-der-nva.de/Bestimmungsbuch/5gepKetFhrmitTurm/51/T-72/T-72.html">the militaertechnik-der-nva website</a>, shows a T-72 Ural that received such a modification.</div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-zP4QGbFvEU8/XtCZk7e9jnI/AAAAAAAAQ34/pke6mkW15OwJMrROfv2ZYZz4mrcLHoSVgCK4BGAsYHg/T-72mod1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="308" data-original-width="461" src="https://1.bp.blogspot.com/-zP4QGbFvEU8/XtCZk7e9jnI/AAAAAAAAQ34/pke6mkW15OwJMrROfv2ZYZz4mrcLHoSVgCK4BGAsYHg/d/T-72mod1.jpg" /></a></div><div style="font-size: medium; font-weight: normal;"><br /></div>
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Although it was not uncommon for the smoke grenade launchers to be installed at this part of the turret, it was probably not a very wise idea since a direct hit on the turret cheeks could potentially deprive the tank of the ability to react defensively to an attack by deploying a smoke screen. The issue is not necessarily the loss of the smoke grenades themselves, but also the danger of short-circuiting the system if a damaged launcher is triggered. A warning lamp on the 902A or 902B control panel will light up if the gunner selects a set of smoke grenades that are experiencing technical issues. Due to the lack of armour protection for the grenade launchers, a direct hit from any type of ordnance with more power than a heavy machine gun bullet is practically guaranteed to put the smoke grenade out of commission. The cable that connects the grenade launchers to the launch system are also a weak point as they are exposed on the surface of the turret and they are only shielded with a simple metal tube, so it is possible to cut off an entire bank of grenade launchers by severing the cable tube on the turret. The photo below shows the turret of an ex-NVA T-72M1 after live fire testing in 1993.<br />
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<a href="https://1.bp.blogspot.com/-UPFrRMZc9A4/XLdM85dxggI/AAAAAAAANsQ/11LunFsD1O4oJg0cucuGuHBWvGtkVOIDwCLcBGAs/s1600/turret%2Btesting%2Bapfsds.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="848" data-original-width="1254" height="270" src="https://1.bp.blogspot.com/-UPFrRMZc9A4/XLdM85dxggI/AAAAAAAANsQ/11LunFsD1O4oJg0cucuGuHBWvGtkVOIDwCLcBGAs/s400/turret%2Btesting%2Bapfsds.jpg" width="400" /></a></div>
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With the appearance of Kontakt-1 on tanks like the T-72AV and T-72B, the 902A was exchanged for the 902B system. The grenades were clustered together on the left side of the turret, leaving the frontal arc of the turret clear for the Kontakt-1 blocks. This was a much safer location for the launchers, but having fewer smoke grenades was a disadvantage of its own.<br />
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<a href="https://thesovietarmourblog.blogspot.com/p/81mm-smoke-grenades.html">A more detailed examination of 3D6 and 3D17 smoke grenades is available in this page</a>. During Soviet times, the 3D6 was the only available model. 3D17 only became available in the early 1990's, and more recently, 3D6M grenades are used on T-72B3 tanks.</div>
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<h3>
<span style="font-size: large;">NBC PROTETCION</span></h3>
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Ventilation is controlled from the KUV-11-5-1S ventilation and filtration management box. The ventilation system has a built-in dust ejector at the air inlet to ensure a supply of clean air under normal operating conditions. An FVU, or filter-ventilator unit, is used to provide both normal ventilation to the crew and to generate a filtered internal overpressure. </div>
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The diagram on the right below, taken from the book "<a href="http://ivto.omgtu.ru/wp-content/ivto/biblioteca/uchebnici/Jelektrooborudovanie-tanka-T-72.pdf"><i>Special Electrical Equipment of the T-72</i></a>" published by the military department of the Omsk State University of Technology, shows a cross section of the system. The air outlet for the ventilator in the normal operating mode is marked (21). Air is taken in by the fan, flows through the air booster, and exits through the outlet (21). Under normal operation, the ventilator acts as a simple blower to supply the crew compartment with air, performing no air conditioning whatsoever. When operating in the overpressure mode, the supercharger fan turns on and generates a strong inflow of air. The dust particles in the air are separated from the air stream by the supercharger. A dust ejector is installed at the air inlet to ensure that the centrifugally separated dust is ejected from the air stream, so that clean air is supplied into the crew compartment even under highly dusty conditions. The blower is quite powerful, having a MV-67 fan motor rated for a power of 800 W and spinning at 7,000 RPM. When locked down, the overpressure generated inside the crew compartment is 343.23 Pa, or 35mm of water column.</div><div style="font-size: medium; font-weight: normal;"><br /></div><div>The supercharger is activated via an EK-48 electropneumatic valve, which is triggered by an electric signal from the tank's automatic NBC protection system, firefighting system, by the electric triggers of the gun and coaxial machine gun, as well as by a manual backup switch. When triggered, the valve opens to allow the pressurized air from the tank's pneumatic system to actuate a pneumatic servomotor which switches the airflow pathway in the ventilator unit to the HEPA filter unit.</div>
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The ventilator draws air from a port on the hull roof, located just behind the turret ring. Before crossing water obstacles, the ventilation system is deactivated and the air intake is closed to prevent water from entering the fighting compartment and to prevent damage to the electric motor.</div>
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The ventilator housing and the white pipe leading to the air intake can be seen tucked away in the rear corner of the fighting compartment in the photo below. The air outlet from the filtration system drum is indicated by a red arrow.</div>
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<span style="font-size: large;">GO-27</span></h3>
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Soviet tank designers were very conscious of the dangers of nuclear warfare, especially artillery-fired tactical nuclear weapons. The T-72 perfectly reflected their seriousness, featuring the GO-27 NBC protection system with a filtered ventilation system that is also capable of generating an overpressure. A radiation lining shielded the occupants from penetrating radiation (mainly Gamma rays) and neutrons. The photo above shows the B-1 instrument and control box, the B-2 sensor for gamma radiation detection, and the B-3 power supply unit. </div>
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The dosimeter detects and measures gamma radiation levels. The B-1 instrument and control panel displays the radiation level in rads per hour (rad/h), and is able to measure and display the radiation level in a range between 0.2 to 150 rads per hour. <a href="http://www.bnti.ru/des.asp?itm=4263&tbl=02.02.01.">The system has a measurement accuracy of ± 30%</a>. The B-1 instrument and control panel is shown in the photo below. Photo credit to Leonid Varlamov.<br />
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<a href="https://1.bp.blogspot.com/-BnXTo-9uUNM/WdJf74vMHbI/AAAAAAAAJuE/-UZAo0TcmNAcgSjIfvV8gMT9TrPOU1yrACLcBGAs/s1600/%25D0%2593%25D0%259E-27%2B-%2B%25D0%25BF%25D1%2583%25D0%25BB%25D1%258C%25D1%2582.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="900" height="426" src="https://1.bp.blogspot.com/-BnXTo-9uUNM/WdJf74vMHbI/AAAAAAAAJuE/-UZAo0TcmNAcgSjIfvV8gMT9TrPOU1yrACLcBGAs/s640/%25D0%2593%25D0%259E-27%2B-%2B%25D0%25BF%25D1%2583%25D0%25BB%25D1%258C%25D1%2582.jpg" width="640" /></a></div>
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The system has different reactions depending on the rate of dosage of radiation. The system is able to react instantaneously to a nuclear detonation (classified as a Type "A" radiation threat) and initiate the necessary protective measures.<br />
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<li style="font-size: medium; font-weight: normal;">Type "R": When the tank is exposed to gamma radiation from a radioactively contaminated site and is exposed to a dose rate of 0.85 Rads/h and above, the response time of the system does not exceed 10 seconds.</li>
<li style="font-size: medium; font-weight: normal;">Type "A": In the event that the tank is exposed to a gamma ray flux with a dose rate of 4 Rads/s and, the response time of the system does not exceed 0.1 seconds.</li>
<li style="font-size: medium; font-weight: normal;">Type "O": When biological or chemical contaminants are detected, the response time of the system does not exceed 40 seconds.</li>
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The reaction of the system includes visual and audio signals to alert the crew. The above photo of the B-1 instrument and control box shows three coloured incandescent lights marked "O", "P" (R in Cyrillic) and "A". When any one of the threats is reacted upon, the driver is instantly informed of the type of threat by the colour of the light.<br />
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Once a Type "A" radiation threat is detected, the system immediately activates the air filtration system and initiates the lock down protocol. As part of this protocol, the cooling fan outlet vanes on the engine deck are automatically closed to prevent blast and debris damage, the turret traverse is braked to lock in place to better withstand the blast wave, and more. Due to the immense speed of gamma rays (very close to speed of light) and the quick reaction of the system, the tank will have reacted quick enough to be protected by the time the blast wave from the nuclear explosion arrives. This protects the internal components and the crew from the blast wave itself as well as from exposure to fallout after the initial blast wave.<br />
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A Type "R" radiation threat is a much less serious situation. Type "R" threats are detected when the tank is exposed to radiation from an irradiated environment. The long reaction time of the system to this type of threat is offset by the low danger of minor irradiation.<br />
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Type "O" threats are airborne biological or chemical threats. The system detects contaminants in the air using a cyclone-based air sampler and analyzer. The air inlet for the sampler and analyzer is depicted in the diagram below. Due to the rather long reaction time, the driver is sometimes obligated to manually switch on the chemical and biological threat protection measures when entering contaminated zones, assuming that the tank is preceded by a forward reconnaissance force that included chemical troops mounted on NBC reconnaissance vehicles like the BRDM-2RKh.<br />
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The air inlet is installed just next to the driver's hatch. Photo credit to the <a href="https://www.facebook.com/pg/t72org/photos/?tab=album&album_id=1650261635185951">T-72.org Facebook page</a>.</div>
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The location of the B-2 gamma radiation sensor can be seen in the photo below, taken from <a href="http://www.stvgroup.cz/ru/--/pro-sberatele/vojenska-pasova-technika/tank-t-72-m1">the STV Ground website</a>.<br />
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<a href="https://4.bp.blogspot.com/-AG4kysYNUCI/WedPqSgSFhI/AAAAAAAAJ5U/jD2VjN5fvkEluMneUWq_0wDUAOg3gCEFgCLcBGAs/s1600/go-27.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="533" data-original-width="800" height="266" src="https://4.bp.blogspot.com/-AG4kysYNUCI/WedPqSgSFhI/AAAAAAAAJ5U/jD2VjN5fvkEluMneUWq_0wDUAOg3gCEFgCLcBGAs/s400/go-27.jpg" width="400" /></a></div>
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The B-3 power supply unit is installed just next to the gear shift:<br />
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<h3 style="font-size: medium;">
<span style="font-size: large;">PKUZ-1A Digitized Protection Complex</span></h3>
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The GO-27 system was replaced with the PKUZ-1A in the T-72B3 modernization. The PKUZ-1A was first used in the T-90A, and features improved detection and reaction time to chemical, biological and nuclear threats. The PKUZ-1A analyzes the air outside the tank using an ionizing system.</div>
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The system capable of detecting gamma rays with energies ranging from <a href="http://www.pz-signal.ru/index.php/product/military/54-pribornyj-kompleks-pkuz-1a">0.66 to 1.25 MeV</a>. The system is capable of measuring gamma radiation at dose rates of 0.1 to 500 rads/hour, making it somewhat more versatile than the GO-27. In order to measure the true level of radiation outside the tank, the radiation attenuation coefficient of the armour of the tank and the anti-radiation linings is manually inputted at the factory. This improves the accuracy of the system. Like the GO-27 system, PKUZ-1A automatically executes defensive systems and alerts the crew via visual and audio signals when an NBC threat is detected.</div>
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The PKUZ-1A system comes with a new instrument and control box. The new control panel fulfills the same function as its predecessor, but is more user friendly. The old ammeter-based radioactivity gauge was replaced by a digital LCD segment display for quicker and more precise readings. The old ammeter gauge display could not give an accurate reading if the tank was moving because the vibrations caused the indicator needle to jump around.</div>
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The new control panel can be seen at the right side of the screenshot below.</div>
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<span style="font-size: large;">ANTI-RADIATION CLADDING AND LINER</span></h3>
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<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-5YcuPghWyFE/YDS2yWy7KpI/AAAAAAAASxM/4SUa6AHpeW43bOehrhZQJ6yhBCFRg03qwCLcBGAsYHQ/s2048/Gunners%2Bstation%2Boverview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="400" src="https://1.bp.blogspot.com/-5YcuPghWyFE/YDS2yWy7KpI/AAAAAAAASxM/4SUa6AHpeW43bOehrhZQJ6yhBCFRg03qwCLcBGAsYHQ/w300-h400/Gunners%2Bstation%2Boverview.png" width="300" /></a></div><span style="font-size: small; font-weight: 400;"><br /></span>
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<span style="font-size: small; font-weight: 400;">Anti-radiation measures were among the top priorities regarding crew protection. It was considered no less important than ballistic protection given the nuclear environment that the T-72 was expected to fight in. Compared to foreign developments in radiation protection for tanks, Soviet anti-radiation liners, developed by NII Stali, had the benefit of testing with real nuclear detonations rather than with simulated radiation sources. </span></div><div style="font-weight: normal; text-align: left;"><span style="font-size: small; font-weight: 400;"><br /></span></div><div style="text-align: left;"><span style="font-size: small; font-weight: 400;">One of the built-in protection measures for the crew was the fuel, which attenuates neutrons well due to the high hydrogen content. This is true for all fuels usable by the T-72, including petrol, kerosene and diesel. It is, however, not an efficient form of radiation shielding compared to polyethylene radiation panels, as the density of the fuel is equal to polyethylene, but its hydrogen density is 1.3 times lower. Nevertheless, the presence of large thicknesses of fuel between the crew stations and an external source of radiation has a positive effect. According to tests, detailed in the journal article "<i>О Влиянии Внутренних Баков С Топливом На Уровень Противорадиационной Защиты Экипажей Танков И БМП</i>" published in the sixth 1972 edition of the "<i>Вестник Бронетанковой Техники</i>" journal, which were carried out using a real T-72 tank and a VVR-L-02 reactor as the gamma and neutron source, the presence of fuel in the fuel tanks of the T-72 improves the overall neutron dose attenuation of the tank at the crew stations by an average of 1.37 times. The crew stations were tested from all-round, in 45-degree increments.</span></div><div style="text-align: left;"><span style="font-size: small; font-weight: 400;"><br /></span></div><div style="text-align: left;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEjzFgIbEH28ukfDs9ntIow7kyJGH1a1sP7Dy1IY48qIi1T_Izyf-b_SLIB3yt3k9GCkShQWPTs0bl1fjy2UIHkBmEbZmOsXl2ex-9cI34loirU7R6CkjsWMPj7BHTJlwDEU7x_HknaGajPwvBrp5OtVOH38YniMK3T0sCQClHPuebzIQwlpQEaYbrqPuw=s1521" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="989" data-original-width="1521" height="260" src="https://blogger.googleusercontent.com/img/a/AVvXsEjzFgIbEH28ukfDs9ntIow7kyJGH1a1sP7Dy1IY48qIi1T_Izyf-b_SLIB3yt3k9GCkShQWPTs0bl1fjy2UIHkBmEbZmOsXl2ex-9cI34loirU7R6CkjsWMPj7BHTJlwDEU7x_HknaGajPwvBrp5OtVOH38YniMK3T0sCQClHPuebzIQwlpQEaYbrqPuw=w400-h260" width="400" /></a><a href="https://blogger.googleusercontent.com/img/a/AVvXsEhBDVJoSsgFUjAJUKripDrPqGzRVF0nrgmAveZ45rJQyV_YJVKJr0afpmzxPmW30C8IRA6SiD75eVfKIHi6BAcR0PdiZ2f9zBjIa1ZjKdWPZj-n715rh4Fe07zbed88h0Gc82Ln5dPiyYEV8tz5UXgvW0GwjDonLfZG_v14uhDZR0s6ZzNknfYds4Tfnw=s1161" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1161" data-original-width="1025" height="320" src="https://blogger.googleusercontent.com/img/a/AVvXsEhBDVJoSsgFUjAJUKripDrPqGzRVF0nrgmAveZ45rJQyV_YJVKJr0afpmzxPmW30C8IRA6SiD75eVfKIHi6BAcR0PdiZ2f9zBjIa1ZjKdWPZj-n715rh4Fe07zbed88h0Gc82Ln5dPiyYEV8tz5UXgvW0GwjDonLfZG_v14uhDZR0s6ZzNknfYds4Tfnw=s320" width="283" /></a></div><span style="font-size: small; font-weight: 400;"><br /></span></div><div style="font-weight: normal; text-align: left;"><span style="font-size: small; font-weight: 400;"><br /></span></div><div style="font-weight: normal; text-align: left;"><span style="font-size: small; font-weight: 400;">In addition, the T-72 was fitted with an interior anti-radiation lining nicknamed "Podboi", simply meaning "liner", since the very beginning as a means to keep the crew alive long enough to fulfill a combat mission without requiring a replacement crew. The "Podboi" lining was present on almost all interior surfaces of the tank, excluding the floor of the hull. Instead, underbelly protection was provided by anti-radiation panels on the autoloader carousel cover, coubling as spall protection. The commander's cupola had a cladding called "Nadboi" on the roof instead of a liner, as there was not enough space behind the periscopes to accommodate a sufficient thickness of liner. The cladding had a metal skin for environmental protection. The turret ring extension on the hull sides was also covered with a thick layer of "Nadboi", as this space inside the tank was used for cables, fuel and air lines.</span></div><div style="font-weight: normal; text-align: left;"><br /></div><div style="font-weight: normal; text-align: center;"><br /></div><div style="font-weight: normal; text-align: center;"><div class="separator" style="clear: both; font-size: medium;"><a href="https://1.bp.blogspot.com/-aQFg0v8Ccz0/XlcolVTwJaI/AAAAAAAAQHk/9YMzIdgdJtkG8ivAaJRp5-eNg7hKcsNgwCLcBGAsYHQ/s1600/anti-radiation%2Bhull%2Bexterior.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="681" data-original-width="1024" height="265" src="https://1.bp.blogspot.com/-aQFg0v8Ccz0/XlcolVTwJaI/AAAAAAAAQHk/9YMzIdgdJtkG8ivAaJRp5-eNg7hKcsNgwCLcBGAsYHQ/s400/anti-radiation%2Bhull%2Bexterior.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-yUdmV998pnw/YDen5lfK9tI/AAAAAAAASzk/w3yP5EWDkTEfNarvtmv7iY0FJp0nfwjQwCLcBGAsYHQ/s1288/48.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="859" data-original-width="1288" height="266" src="https://1.bp.blogspot.com/-yUdmV998pnw/YDen5lfK9tI/AAAAAAAASzk/w3yP5EWDkTEfNarvtmv7iY0FJp0nfwjQwCLcBGAsYHQ/w400-h266/48.jpg" width="400" /></a><br /></div><div style="font-size: medium;"><br style="text-align: left;" /></div></div><div style="font-weight: normal; text-align: left;"><span style="font-size: small; font-weight: 400;"><br /></span></div><div style="text-align: left;"><span style="font-size: small; font-weight: 400;">From 1983 onward, the T-72 had an additional set of anti-radiation cladding installed on the exterior of the turret and hull as a response to an announcement by U.S president Ronald Reagan in 1981 that the production of neutron bombs would be restarted. The heavy armour of the T-72 (and tanks in general) provided very good protection from the immediate destructive blast and heat of nuclear weapons including neutron bombs, but the powerful burst of neutron radiation could not be easily blocked even with the existing anti-radiation liner. The thin roof and sides of the turret and hull were particularly vulnerable, being much thinner than the frontal armour of the tank. The "Nadboi" external anti-neutron cladding was therefore concentrated around these areas. The name simply means "cladding". T-72A tanks built in 1983 received the additional cladding at the factory and other tanks were retrofitted at depots during scheduled repairs. The photo on the right below is an example of a T-72A that had the cladding retrofitted, and the photo on the left below shows the same for a T-72B.</span><br />
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<div class="separator" style="clear: both; font-weight: normal; text-align: center;"><a href="https://2.bp.blogspot.com/-pHHecwfC0oo/XHUJCQJFJiI/AAAAAAAANcs/a1HJ-vRRtiElMNc_QoDCpGV3DaOhyIGHQCLcBGAs/s1600/late%2Bmodel%2Bt-72a.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="389" data-original-width="598" height="260" src="https://2.bp.blogspot.com/-pHHecwfC0oo/XHUJCQJFJiI/AAAAAAAANcs/a1HJ-vRRtiElMNc_QoDCpGV3DaOhyIGHQCLcBGAs/s400/late%2Bmodel%2Bt-72a.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-pm-FFhRetT8/YDehttNS5hI/AAAAAAAASzc/QOQK2JQFoAYdoSPguInrmzVWsMAqpFSYgCLcBGAsYHQ/s809/nadboi%2Bon%2Bt-72a.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="607" data-original-width="809" src="https://1.bp.blogspot.com/-pm-FFhRetT8/YDehttNS5hI/AAAAAAAASzc/QOQK2JQFoAYdoSPguInrmzVWsMAqpFSYgCLcBGAsYHQ/s320/nadboi%2Bon%2Bt-72a.jpg" width="320" /></a><br /></div><div><div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">"Nadboi" was also added to several zones on the external surface of the sides of the hull, excluding the area around the driver's compartment. This is because the driver was already protected from radiation from either side by the two large fuel tanks flanking him. The fuel supply system of the engine was arranged such that these frontal fuel tanks were used last, so that the additional protection from these tanks would persist as long as possible. For additional neutron protection, the driver's seat in a T-72B or T-72B1 had an anti-radiation panel added to the back surface of the backrest, and the commander's recoil guard was fitted with an additional anti-radiation panel as well.</span></span></div><div style="font-size: medium; font-weight: normal;"><br /></div><div><span style="font-size: small;"><span style="font-weight: 400;">The lining and cladding are composite materials composed of woven polyethylene panels. Polyethylene has an extremely high density to neutrons and a high resistance to nuclear reaction from neutrons which makes it suitable for particle shielding, as there is little induced radiation. Indeed, for these reaosns UHMWPE is still the preferred neutron shielding material for lightweight applications due to its excellent qualities. The maximum thickness of liner present in the T-72 is 50mm.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">The lining and cladding are fitted on the tank with a special glue and pressed firmly to the tank by special bolts with a washer affixed to the heads. The polymers are impregnated with lead to increase their opacity to gamma radiation, and a sheet of borated polyethylene fabric was added as a response to developments in neutron bomb technology during the 1960's. Borated polyethylene is a type of high density polyethylene infused with boron. According to Anderi Tarasenko, the name of the material is "boron 2EP002". Boron is known to be extremely effective at capturing neutrons thanks to its large absorption cross section, making it suitable for use as radiation shielding. The high cost of boron compounds made it impractical to implement in a high concentration, so it was decided to include only a single layer of borated material in the composite cladding. The location of the layer was such that it reportedly slashed the required boron content by half, but the reduction in radiation dosage remained at the same level as before.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">Due to the large thicknesses of the anti-radiation material installed around the inhabited areas of the tank, the total weight of both the lining and cladding and their fittings is 650 kg.</span></span></div>
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Compared to a tank without anti-radiation liners, the attenuation of penetrating radiation increased by 3-5 times. According to "</span></span><i style="font-size: medium; font-weight: normal;"><a href="http://archive.li/ExYAl#selection-207.0-211.19">Создание танка Т-64 (фрагменты истории)</a></i><span style="font-size: small;"><span style="font-weight: normal;">" (</span></span><i style="font-size: medium; font-weight: normal;">Creation of the T-64 Tank: Fragments of History</i><span style="font-size: small;"><span style="font-weight: normal;">) by V.V Polikarpov, the reduction in radiation dosage from penetrating radiation (neutrons and gamma rays) was by 16 times and the reduction in radiation dosage from an irradiated environment (residual radiation) was by 18 times. The anti-radiation measures installed in the T-72 do not differ from the T-64, so the same level of reduction can be expected.</span></span></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;">From this, it can be determined that the transmission factor (TF) for residual radiation and penetrating radiation (gamma) is 0.05 and 0.06 respectively. For example, a TF of 0.05 means that, for every 100 rads of radiation emitted onto the tank, only 5 rads are received by crew members inside. The maximum permissible dose is considered by the U.S Army to be 150 rads and a lethal dose is 450 rads. Strangely enough, however, it is stated in the 1979 report "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a112303.pdf">Armored Vehicle Shielding Against Radiation</a>" that a standard M60A1 tank provides a TF of 0.1 against gamma radiation and 0.04 against residual radiation, whereas the M60A2 provides a provides a TF of 0.05 against gamma radiation and 0.03 against residual radiation. Both are thus ostensibly equal or better than the T-72, despite having neither any special linings or internal attenuation elements, or thicker armour. This may be due to the use of actual nuclear detonations for tank irradiation tests in the USSR for real measurements and validation of mathematical models, whereas in the U.S, irradiation tests on the M60A1 and M60A2 were merely simulated. News of this practice can be found in the article "TECOM Scientists Measure Radiation Protection of XM1" published in the July-August 1979 issue of the Army RD&A Bulletin.</div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;">With the installation of "Nadboi", the attenuation factor against penetration radiation was further enhanced, so that the detonation of a neutron bomb will have reduced effects on the combat capabilities of the crew and it becomes almost trivial to survive an attack by conventional nuclear weapons such that the likelihood of death from anti-tank guns and missiles is probably higher than from radiation sickness.<br />
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The nature of the laminated construction of the anti-radiation lining also makes it a suitable spall liner. Indeed, UHMWPE fiber sheeting has been widely used for this purpose and more modern formulations such as Spectra fibers are used as an alternative to aramid fibers. <a href="http://www.niistali.ru/products/nauka/protection/splinter-screen/">NII Stali states on their website</a> that as a rule, spall liners made from aramid fibers or from UHMWPE (Ultra High Molecular Weight Polyethylene) reduce the ejection arc of fragments (spall) by a factor of 3 and the reduce the number of fragments by a factor of 10, drastically increasing the survival rate of equipment and crew. Furthermore, a spall liner will not only capture the fragments ejected at the site of armour perforation, but when all internal surfaces of the tank are protected with a spall liner, it can also capture the fragments which otherwise may ricochet off the armour surfaces and cause additional damage. To that end, the high thickness of the lining in many parts of the tank is highly beneficial.</div><div style="font-size: medium; font-weight: normal;">
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The thickness of the "Podboi" lining behind the turret front armour is around 10-20mm and the lining around the sides, rear, and ceiling of the turret is 40-50mm thick. The ceiling in particular has <a href="https://i.imgur.com/R0WfNfQ.jpg">a 41mm thick lining</a>. The hatches have a 50mm lining, with some variances due to the need to make cutouts for the lock handles. The thinness of the lining behind the turret front was due to the high radiation attenuation provided by the large thickness of armour, so a thick anti-radiation lining was not necessary. 50mm of "Podboi" lining is present on the sides of the hull and on the hull ceiling.</div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-k4z1LNgXoOQ/YDS4gj6PRjI/AAAAAAAASxU/Fmabp6PwydAefY6gAeDLVBHj7WYHOnDygCLcBGAsYHQ/s2048/podboi%2Bcommanders%2Bhatch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="320" src="https://1.bp.blogspot.com/-k4z1LNgXoOQ/YDS4gj6PRjI/AAAAAAAASxU/Fmabp6PwydAefY6gAeDLVBHj7WYHOnDygCLcBGAsYHQ/s320/podboi%2Bcommanders%2Bhatch.png" /></a><a href="https://1.bp.blogspot.com/-0kgFmsE00QU/YDS4gRcSuHI/AAAAAAAASxY/-ziOljBV6DcjTxhjEzWTfRQ6hQokWyocACLcBGAsYHQ/s2048/podboi%2Bgunners%2Bhatch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="320" src="https://1.bp.blogspot.com/-0kgFmsE00QU/YDS4gRcSuHI/AAAAAAAASxY/-ziOljBV6DcjTxhjEzWTfRQ6hQokWyocACLcBGAsYHQ/s320/podboi%2Bgunners%2Bhatch.png" /></a></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;">The driver's hatch also features a 40-50mm layer of lining, and the cutout in the upper glacis for the driver's head and his periscope has a 13mm layer of lining to compensate for the reduced thickness of armour. The back surfaces of the upper and lower glacis have no anti-radiation liner. In the case of the upper glacis, it was presumably not necessary due to the large thickness of armour, and the lower glacis has a water tank behind it. With a sufficient amount in the path of the gamma rays, water serves as a reasonably effective radiation shield. </div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-zcvSt20SUAY/YDS7GlJCFOI/AAAAAAAASxw/KTSMbClR8lchRwQKLT8RhVFefYATGW12gCLcBGAsYHQ/s2048/drivers%2Bcutout%2Bradiation%2Bliner.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="320" src="https://1.bp.blogspot.com/-zcvSt20SUAY/YDS7GlJCFOI/AAAAAAAASxw/KTSMbClR8lchRwQKLT8RhVFefYATGW12gCLcBGAsYHQ/s320/drivers%2Bcutout%2Bradiation%2Bliner.png" /></a></div><div style="font-size: medium; font-weight: normal;"><br />
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The cross-sectional drawing below, taken from a CIA report on Soviet tank developments, indicates that the thickness of the "Podboi" lining is around 50mm behind the upper glacis composite armour. However, it appears that this was incorrect information as internal photographs and cross sectional drawings of this part of the hull all indicate that there is no such lining. It is most likely a misidentification based on the presence of air pipes shown in cross-sectional drawings.<br />
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<div><br /></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">Without an additional anti-radiation liner, it must be assumed that the glass textolite interlayer in the upper glacis armour combined with the steel layers of the armour to fulfill the role of a radiation shield.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">The thickness of the anti-radiation lining along the hull sides reaches a maximum of 50mm, but the actual thickness can differ considerably. The maximum thickness is reached at the flanks of the driver's compartment and around the fighting compartment. Local thinning of the liner is present in specific zones for space reasons, which is the case in areas such as the hull sides around the autoloader carousel and the wall behind the front right fuel-ammunition tank. There is no anti-radiation lining on the hull wall behind the battery rack.<br /></span></span><br /><br /><div style="text-align: center;"><img border="0" data-original-height="2048" data-original-width="1536" height="400" src="https://1.bp.blogspot.com/-fOxyhbkSqyg/YDdi97tW72I/AAAAAAAASzU/MHEj2J99nHw2hV9CJgFYsDvYjnSsLpYXACLcBGAsYHQ/w300-h400/hull%2Bside%2Bliner.png" style="color: #0000ee;" width="300" /></div>
<div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">The flammability of the "Nadboi" cladding is unclear, but it is beyond question that it was designed to survive the heat from a nuclear explosion. The cladding would have to fulfill its purpose as neutron and gamma radiation shielding before it gets swept away by the nuclear shockwave and high speed winds (and the debris it carries) since neutrons and gamma radiation will arrive at the tank instantaneously, and the cladding needs to survive the flash of heat from the blast, since heat radiates at the speed of light. To prevent the destruction of the cladding from the heat of the nuclear blast, the outermost layer of the composite material is made from a flameproof material. Since "Nadboi" is often observed to be missing from burnt-out T-64, T-72 and T-80 tanks, it is obvious that the material is still flammable to some degree, although this may not be entirely relevant in a combat situation as the cladding is often burnt off by an external heat source like burning fuel from the wrecked tank. It may be a problem if the tank is attacked with napalm or other flame weapons, but such attacks are rare and would constitute a minor threat compared to more serious anti-tank weapons like recoilless rifles and guided missiles.</span></span></div><div><br /></div><div><span style="font-size: small; font-weight: normal;">In the photo below, a T-64 with external "Nadboi" anti-radiation cladding displays the damage dealt by a 122mm HE-Frag artillery shell. Note the charred chunks of fabric, proving that the cladding is made from textile sheets. More importantly, the cladding has not burned off entirely. The damage is almost entirely localized to the point of impact of the artillery shell, indicating that the cladding does not burn readily when subjected to an intense flash of heat. Instead, it is much more likely that the cladding was stripped off by the blast of the shell and not burnt off.</span></div></div><div style="font-size: medium; font-weight: normal;">
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The screenshots below are taken from a <a href="https://www.youtube.com/watch?v=U1ck-E6hgwg">Czechoslovakian television news channel</a> that showed the aftermath of an infamous tragedy that took place on the 9th of January, 1991, during the withdrawal of Soviet forces from Czechoslovakia. A T-72 was completely destroyed by the delayed detonation of three 125mm HE-Frag shells after an internal fire spontaneously started for unknown reasons. Somehow, <a href="https://ic.pics.livejournal.com/andrei_bt/18425682/685836/685836_original.jpg">all of the other explosive rounds stowed inside the tank failed to explode and most remained largely intact</a>, despite the <a href="https://ic.pics.livejournal.com/andrei_bt/18425682/684582/684582_original.jpg">total destruction of the ammunition carousel</a>. The force of the explosion was such that the turret was thrown 78 meters away, landing on a corner of a nearby tank shed and demolishing it, and the commander's cupola was detached from the turret and <a href="https://ic.pics.livejournal.com/andrei_bt/18425682/687981/687981_original.jpg">landed 142 meters away</a>. In the screenshots below, it can be seen that the "Podboi" lining on the surface of the hull side wall of the fighting compartment (where ammunition was stowed) is destroyed, but the lining on the surface of the wall of the driver's station is only scorched and is otherwise perfectly intact despite the violence of the event.<br />
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<a href="https://3.bp.blogspot.com/-SFqhfBbyJiY/XHT4IP5O1mI/AAAAAAAANcg/POjhkr_HnqMpF_SKSqEmeuDeSGdbXVsIgCLcBGAs/s1600/catastrophic%2Btragedy%2Bside%2Barmour%2B2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1206" height="253" src="https://3.bp.blogspot.com/-SFqhfBbyJiY/XHT4IP5O1mI/AAAAAAAANcg/POjhkr_HnqMpF_SKSqEmeuDeSGdbXVsIgCLcBGAs/s400/catastrophic%2Btragedy%2Bside%2Barmour%2B2.png" width="400" /></a><a href="https://1.bp.blogspot.com/-CZ_14UBynJE/XHT4FzhQwSI/AAAAAAAANcc/-FlMEaB6TYgLLaBewuIPQ7PsCQ02AsKjQCLcBGAs/s1600/catastrophic%2Btragedy%2Bside%2Barmour.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1209" height="253" src="https://1.bp.blogspot.com/-CZ_14UBynJE/XHT4FzhQwSI/AAAAAAAANcc/-FlMEaB6TYgLLaBewuIPQ7PsCQ02AsKjQCLcBGAs/s400/catastrophic%2Btragedy%2Bside%2Barmour.png" width="400" /></a></div>
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The thickness of "Nadboi" on the turret roof is around two inches (45-50mm), and the thickness of the cladding on the turret hatches are just as thick if not more so. This is because of the low thickness of the hatch compared to the turret roof, so there is less steel to absorb incoming radiation. The photo on the left below shows how the mounting studs for Kontakt-1 reactive armour protrude through the "Nadboi" cladding.<br />
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<a href="http://3.bp.blogspot.com/-yAu3imK7Xb4/Vf_7f5vS6lI/AAAAAAAADmY/r2aOwiD1dvI/s1600/t-72%2Banti-radiation%2Bcoating.jpg"><img border="0" height="300" src="https://3.bp.blogspot.com/-yAu3imK7Xb4/Vf_7f5vS6lI/AAAAAAAADmY/r2aOwiD1dvI/s400/t-72%2Banti-radiation%2Bcoating.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-OB61631dw_I/XnSBYs0fEUI/AAAAAAAAQXE/EdyWZdWXeYYmTiNk_Ma-Om6tdiyIgXQzwCLcBGAsYHQ/s1600/nadboi%2Bon%2Bt-72a.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="607" data-original-width="809" height="300" src="https://1.bp.blogspot.com/-OB61631dw_I/XnSBYs0fEUI/AAAAAAAAQXE/EdyWZdWXeYYmTiNk_Ma-Om6tdiyIgXQzwCLcBGAsYHQ/s400/nadboi%2Bon%2Bt-72a.jpg" width="400" /></a></div>
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The circles with four holes that pockmark the surface of the cladding are the metal studs that press the cladding on the surface of the turret. When the cladding material is burnt away, these studs usually remain intact since they are welded to the turret. See the two photos below showing a burnt-out T-72 turret (photo credit to <a href="http://armor-kiev-ua.livejournal.com/35790.html">armour-kiev-ua</a>).</div>
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The shell casing stub ejection hatch is heavily shielded with a 50mm layer of "Podboi" and received another 50mm "Nadboi" layer on its external surface beginning in 1983.</div>
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As mentioned before, the lining and cladding not only function as neutron absorbers, but
they perform admirably as a form of spall liner as well. <a href="https://www.cia.gov/library/readingroom/docs/CIA-RDP00-01872R001001550001-3.pdf">This CIA document</a> reports on page 13 that the anti-radiation liner found on the T-72 and T-64 functions as a spall liner, and Rickard Lindström reports that Swedish trials of purchased
ex-East German T-72M1s led to the conclusion that the anti-radiation liner
was perfectly capable of absorbing the secondary fragments of shaped charge jets.<br />
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Depending on the construction, spall liners may reduce the spray cone
angle of secondary fragments from a shaped charge warhead by up to 50% or more if the armour is
greatly overmatched and it is possible reduce the quantity of secondary fragments by up to 80%. The NII Stali website gives a more optimistic claim that the spray cone angle of secondary fragments (from an unknown type of armour-piercing round) can be reduced by a factor of 3 and the quantity of fragments can be reduced by a factor of 10. Plus, the reduction in the amplitude of a shockwave from an external explosion is in the order of 4.5-5 times for a lightly armoured vehicle. The T-72 is not a "lightly armoured vehicle", of course, but the presence of a spall liner would still help improve the conditions inside the tank if explosive ordnance was detonated outside. If the armour is not perforated by an impacting shell, the spall liner may absorb all of the spall produced from the surface of the armour plate. Either way, the likelihood of injuring the crew or damaging the internal equipment of the tank is greatly reduced, particularly from munitions such as HESH shells which relies exclusively on spall and blast to concuss and injure the crew or damage internal equipment. The anti-radiation lining and cladding should have good performance even against light HEAT grenades on account of its substantial thickness both inside and outside the tank. In fact, this feature has helped to saved lives in at least one confirmed incident:</div>
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<a href="http://1.bp.blogspot.com/-zQC3-bEUZek/VTDS4YcB6gI/AAAAAAAABzQ/3UoxsLSiV6c/s1600/T-72B1%2Bhit%2Bby%2BRPG.%2BSurvived%2Bdue%2Bto%2Bspare%2Bparts%27%2Bbox%2Bacting%2Bas%2Bspaced%2Barmour.jpg"><img border="0" height="438" src="https://1.bp.blogspot.com/-zQC3-bEUZek/VTDS4YcB6gI/AAAAAAAABzQ/3UoxsLSiV6c/s1600/T-72B1%2Bhit%2Bby%2BRPG.%2BSurvived%2Bdue%2Bto%2Bspare%2Bparts'%2Bbox%2Bacting%2Bas%2Bspaced%2Barmour.jpg" width="640" /></a></div>
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<span style="font-size: small; font-weight: normal;"><span style="font-weight: normal;"><br /></span></span><div><span style="font-size: small;"><span style="font-weight: 400;">In this instance, the T-72 was hit in the flank by an RPG attack which also blew off a large section of the external sponson storage bins. The crew survived and the tank only suffered from a minor puncture wound. The anti-radiation cladding on the external surface of the side hull plate at the sponsons would not behave as a spall liner, but it is still additional material in the path of the shaped charge jet, turning the side hull armour into a three-layer sandwich of plastic-steel-plastic measuring 170-175mm thick.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">The presence of the lining is a significant factor in the safety of the carousel ammunition in case of armour perforation, especially from the side, but the low density plastic lining has the additional benefit of attenuating blast waves. </span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">Ordinarily, a steel plate alone provides very good protection from a blast wave, if the structure is strong enough to resist the overpressure. </span></span><span style="font-size: small; font-weight: 400;">By having a medium of low acoustic impedance behind a steel plate of high acoustic impedance, as is the case with a steel-air interface, the energy of a shockwave is absorbed within the armour via a mechanism known as impedance mismatch, rather than transferring the energy through the air and into the crew. </span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">For RHA steel the acoustic impedance is 46 MRayls and the acoustic impedance of air is 413 Rayls. The effect of having a low impedance layer behind the high impedance layer is that the compression waves from an explosion on the front surface of the high impedance medium are reflected back from the boundary with the low impendance medium, and for a combination of two mediums as dissimilar as steel and air, the reflection ratio is very high, so barely any energy is transferred to the air. Almost all of the energy is retained in the form of the reflected waves, which are tensile waves. When the tensile waves intersect with the compression waves trailing them from the front surface of the medium, the constructive interference from the two longitudinal waves generates enormous tensile stress. If the tensile stress exceeds the tensile strength of the medium, in this case a steel plate, the plate fails at the point of intersection of the waves and spall is created.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">For the T-72, the acoustic impedance of the anti-radiation lining can be considered at least as high as polyethylene, which has an impedance of 1.73 MRayls - over 4,000 times higher than air. This permits a much larger share of the wave energy to be transferred into the lining, and in turn, reduces the intensity of the reflected tensile wave by the same amount. By doing so, it reduces the energy of the spall or eliminates spalling entirely if the tensile stress is sufficiently suppressed. If spall is still formed and there is enough energy to eject the scab, it can be captured by the lining. The same process of wave reflection occurs with the waves induced in the anti-radiation lining, and due to the high impedance mismatch between it and the air, little energy is transferred, and the enormous tensile strength of the woven polyethylene fibers strongly resists spalling. In terms of blast attenuation, the total energy transferred through the two layers is less than in the case of a single layer due to the attenuation of wave energy during its propagation through the thickness of the armour layers.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">As such, four protection mechanisms are at play: blast attenuation, prevention of spall, attenuation of spall energy, and capture of spall.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">Close, uninterrupted contact between the steel plate and the anti-radiation lining is crucial in guaranteeing that these phenomena occur as this eliminates the free air interface. Hence, the "Podboi" anti-radiation lining was designed to conform to the shape of the internal surfaces of the tank hull and turret with relatively tight tolerances and was tightly secured with glue and multiple metal studs. If an air gap exists between the surface and the lining, some parts of the protective effect would be compromised as spall formation within the steel plate would not be properly suppressed.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">Additionally, the presence of a liner and a cladding on the metal surfaces of the turret and hull helps to insulate the tank and prevents condensation. This may help preserve the myriad of electric and electronic components in the tank. The "Nadboi" cladding on the turret may be especially useful as heat insulation since the outermost layer is composed of a flameproof material, which naturally implies that it would insulate the tank from solar radiation.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">The "Podboi" lining was partially removed and the "Nadboi" cladding was completely removed beginning with T-72B3 model. There is no documentation on the rationale behind this decision, but it is extremely likely that the loss of the cladding is due to the vastly lower emphasis on a major nuclear war since the end of the Cold War, while the partial removal of the lining is probably directly connected to the Russian Ministry of Defence beginning to procure the 6B15 "Cowboy" protective suit for armoured vehicle crews since 2012. The 6B15 suit includes a 6B15-1 soft armour vest and a 6B15-2 armoured helmet cover, both rated for GOST Class 1, so in effect, they fulfill the same function as the anti-radiation lining. The deletion of the lining can be explained by the need to compensate for the added bulk of the suits and the space taken up by new electrical and electronic equipment.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">Only the some of the side and rear surfaces of the turret interior had the lining removed. The lining on all surfaces of the hull interior was retained. As the image below shows, the lining on the ceiling was retained, and a part of the hull side lining can even be seen.</span></span></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div class="separator" style="clear: both; font-weight: normal; text-align: center;"><a href="https://1.bp.blogspot.com/-K6K1W9gDUKM/X1sXAPskvXI/AAAAAAAARlQ/zULF2htWmiQZknUSGpwfsAQ04HzVkDwxQCLcBGAsYHQ/s854/sosna-u%2Bt-72b3.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="478" data-original-width="854" height="358" src="https://1.bp.blogspot.com/-K6K1W9gDUKM/X1sXAPskvXI/AAAAAAAARlQ/zULF2htWmiQZknUSGpwfsAQ04HzVkDwxQCLcBGAsYHQ/w640-h358/sosna-u%2Bt-72b3.png" width="640" /></a></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;">The photos below, showing a Belorussian T-72B3, give a better overall view of how much was removed from the turret walls. <a href="https://vsr.mil.by/2017/06/07/bronya-krepka-i-tanki-nashi-bystry-vsyo-o-modernizirovannyx-t%E2%80%9172b3/">Photos from the Belorussian Military Gazette</a>. The commander's side of the turret still has some lining, whereas the gunner's side of the turret is completely bare.</div>
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<br />The partial removal of the internal lining and the total removal of the exterior cladding undoubtedly helped to counterbalance the weight gain of the T-72B3 models to a limited extent, given that the total weight of the lining and cladding amounts to 650 kg. <br />
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An automatic fire extinguishing system is present to prevent the spreading of internal fires in the engine and crew compartments. Such systems have been present in all postwar Soviet tanks, and was a basic feature on all T-72 models. The firefighting systems fitted to the T-72 are detailed in <a href="https://thesovietarmourblog.blogspot.com/p/t-72-firefighting-systems.html">a separate article</a>. <br /><br /></div><div style="font-size: medium; font-weight: normal;">From its introduction into service in 1973 until 1990, the T-72 was fitted with the ZETs11-3 system. Beginning in January 1990, the new ZETs13-1 "Iney" system was installed. This system was also used in the T-80U and later on, the T-90.</div><div style="font-size: medium; font-weight: normal;"><br /></div>
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<span style="font-size: small; font-weight: normal;">The T-72 was a true main battle tank, having successfully achieved an excellent compromise of the three principle attributes that govern basic tank design: firepower, protection and mobility. Throughout its career during the Cold War, the T-72 had one of the world's most powerful tank guns, had excellent armour protection, and was reasonably agile compared to its peers. In terms of average travelling speed, the off-road performance of the T-72 was broadly comparable to peers such as the M60A1, Chieftain and Leopard 1 but the T-72 had better acceleration characteristics. However, the T-72 was by no means the best in this category as the T-80 entered service only a few years later, followed by the Leopard 2 and then the M1 Abrams. All of these tanks surpassed the T-72 in acceleration characteristics and top speed by a significant margin, although it should be pointed out that "mobility" is an umbrella term that covers more than just these two aspects.</span></div>
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<span style="font-size: small; font-weight: normal;">Compared to the T-64A from which it was created, the T-72 Ural is a heavier tank. This is despite having the same gun, a very similar weight of armour for both the hull and turret and virtually identical internal equipment. The culprit of this added weight is the running gear, which weighed a total of 6.2 tons in the T-64A but weighed 8.47 tons in the T-72. The difference of 2.27 tons is due to the heavier roadwheels, heavier tracks, heavier cooling system, and the enlarged volume of the engine compartment which required more armour to be added to the tank due to the increased surface area. These factors were counterbalanced by the installation of a more powerful V-shaped engine, thus placing the mobility of the T-72 on a marginally higher level than the T-64A.</span></div>
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<span style="font-size: small; font-weight: normal;">Despite being heavier than the T-64A, the T-72 was still small and lightweight for a tank of its type. This simplified rail transportation and allowed it to safely cross low-capacity bridges and make good use of the large fleet </span><span style="font-size: small; font-weight: normal;">of tactical bridge layers in Soviet army service, including the ones derived from the then-already-antiquated T-54.</span></div>
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<span style="font-size: small; font-weight: normal;">Sw</span><span face=""></span><span style="font-size: small; font-weight: normal;">edish mobility trials of T-72M1s (and MTLBs) in Northern Norrland between 1992 and 1994 yielded positive results. The tanks in question displayed good performance over snow as deep as 0.8 meters although it still failed at times to reliably traverse frozen ice banks.</span></div><div style="font-weight: normal;"><br /></div><div><span style="font-size: small; font-weight: normal;">Trenches with a width of 2.6-2.8 meters can be crossed either by driving slowly or at high speed. With the mud guards on, the T-72 can only climb vertical obstacles measuring at least 0.85 meters in height. When they are removed, the tank can scale obstacles at least as tall as 1.2 meters or more. This is despite such obstacles being not only taller than the idler, but also the top run of the tracks</span><span style="font-size: small;"><span style="font-weight: 400;">. For comparison, the M60A1 is only able to climb a 36" (914mm) vertical obstacle despite the much taller location of its idler wheel. </span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span><span style="font-size: small; font-weight: 400;">The engine deck consists of two panels - the engine access panel, and the radiator panel. The engine access panel is just a simple stamped steel plate, while the radiator panel is made as part of the intake ducting for the radiator packs held within. These two panels are hinged on a crossbar that spans the width of the engine compartment. Both panels are bolted to the hull structure along their perimeter, securing them tightly against unintended water ingress. If needed, the radiator access panel can be opened on its own, without also lifting the radiator pack. This may be done to clean the radiator pack of debris, leaves, etc.</span></span></div><div><br /></div><div><span><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQyKR4n_2cg1PnFX7kyj7BzofkuV-DTk56BELSogNagHj6EvvFzVhGv5C9Zvl_RubzJ1ixsRlVuQDVznx98aNjDIhupTPBZkVDl024WZYJxQ0eyipLf_4oA7eJk2fwezoRxa8OO781Id8GXUY6PyREV9uBczj0JTV1frJ2mqPA_y5lu0NxS7MfYdllPw/s7225/the%20engine%20deck.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3281" data-original-width="7225" height="290" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQyKR4n_2cg1PnFX7kyj7BzofkuV-DTk56BELSogNagHj6EvvFzVhGv5C9Zvl_RubzJ1ixsRlVuQDVznx98aNjDIhupTPBZkVDl024WZYJxQ0eyipLf_4oA7eJk2fwezoRxa8OO781Id8GXUY6PyREV9uBczj0JTV1frJ2mqPA_y5lu0NxS7MfYdllPw/w640-h290/the%20engine%20deck.png" width="640" /></a></div></span></div><div><span><span style="font-size: small; font-weight: 400;"><br /></span></span></div><div><span><span style="font-size: small; font-weight: 400;"><br /></span></span></div><div><span><span style="font-size: small; font-weight: 400;">Having the engine deck panels bolt firmly to the hull is inconvenient in terms of tedium when the panels need to be lifted for access, but in addition to water sealing, this type of engine deck enclosure allows the thick panels to serve as structural members of the hull. This provides the hull with better rigidity when subjected to a mine blast, nuclear explosion, and other similar stresses. Sectioned intake panels, as found on tanks such as the Centurion and Patton series, normally have only one of the panels screwed in place, while the others are secured by an overhanging lip from their neighbouring panel. This makes it much less tedious to open up large areas of the engine deck, but the lack of spring-loaded hinges to support the weight, and the lack of positive fastening, creating loose tolerances, are issues that are not to be neglected. </span></span></div><div><span><span style="font-size: small; font-weight: 400;"><br /></span></span></div><div><span><span style="font-size: small; font-weight: 400;">Each panel can be hinged open on its own, or both panels can be opened together. The minimum angle between the panels is 100 degrees, and as such, only one panel can be fully opened at any one time. To minimize the need for opening the access panels as much as possible, the engine oil, transmission oil and coolant filler ports have their own, separate access ports for oil and coolant checks. The entire engine deck can only be removed as part of an involved process, which involves unbolting not only the deck panels but also the crossbeam between them, and draining the cooling and lubrication systems to empty out the radiator packs, since quick-disconnect couplings were not used.</span></span></div><div><span><span style="font-size: small; font-weight: 400;"><br /></span></span></div><div><span><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_CbfdoFYh4FlgweqkX-MMY9H34e2OUSgb-CM0H1zebRZAsVEkiWuRajU5fW8Dh1Pr3P4e3598gJsoSqa5c6TB6wXcIQQtOrs22FVhhfdIKwu_8pDo1b5ZDrs9Wsgxx9mQ8CXtRAUSyrTLiEwHpfcYukvHQdokTBxEbWyZTGBokUjQvo1UJSEQMyl09Q/s1888/crossbar.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1240" data-original-width="1888" height="263" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_CbfdoFYh4FlgweqkX-MMY9H34e2OUSgb-CM0H1zebRZAsVEkiWuRajU5fW8Dh1Pr3P4e3598gJsoSqa5c6TB6wXcIQQtOrs22FVhhfdIKwu_8pDo1b5ZDrs9Wsgxx9mQ8CXtRAUSyrTLiEwHpfcYukvHQdokTBxEbWyZTGBokUjQvo1UJSEQMyl09Q/w400-h263/crossbar.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlepr1VdtQDkiAcV4mqIMY4l8LqTMRFo1O0H7XpBO4n9b8mn-IcQCAk-BnbcfJE6GCFP4tyXhgww3_hzvd_qlD1U60d3EIS1CrpVpUQZ3eFrvyFsiBvSdY6UiRLZMiXGJnhk1QjTPx19PkJgLV0W1KWTpj-WgKPZQikmiEYxy5VThrzfHUwin2dKRYnw/s2157/engine%20deck%20lifted.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2157" data-original-width="1897" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlepr1VdtQDkiAcV4mqIMY4l8LqTMRFo1O0H7XpBO4n9b8mn-IcQCAk-BnbcfJE6GCFP4tyXhgww3_hzvd_qlD1U60d3EIS1CrpVpUQZ3eFrvyFsiBvSdY6UiRLZMiXGJnhk1QjTPx19PkJgLV0W1KWTpj-WgKPZQikmiEYxy5VThrzfHUwin2dKRYnw/s320/engine%20deck%20lifted.png" width="281" /></a><br /></div><span style="font-size: small; font-weight: 400;"><br /></span></span></div><div><span><span style="font-size: small; font-weight: 400;">Removal of the entire engine deck is done only when it is necessary to replace major internal assemblies such as the engine, the intermediate power transfer gearbox, or the cooling fan mechanism, among others. Otherwise, all other components can be accessed and replaced after opening one of the two access panels. In the case of major powertrain repair or replacement, coupling the two access panels and the radiator pack together into a single unit speeds up the overall process to some extent, as this allows a 1.5-ton crane to remove all three units in one go.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">An interesting feature of the tank is that when driving in peacetime, the external indicator lights of the T-72 can function as a road signalling system, including features such as a turn signal and brake light. An emergency signal can also be given, whereby all marker lights begin flashing. The road signalling system includes marker lights, the KDS 1-2C road signalling system box, an internal warning lamp and switches to activate the signals. The KDS 1-2C box houses the switches to turn the marker lights on and off, as well as activating the left and right turn signals, whereby the left and right marker lights flash until the switch is reset. It also activates the marker lights when the brake pedal is depressed, thus providing a brake light. </span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">The T-72 has been host to several variations of the same type of engine over the years, starting with the V-46, evolving into the V-84, and finally the V-92. All of the T-72 engines to date are V-12 four-stroke diesels with a multifuel capability. They are able to consume low octane gasoline (A-66 and A-72), standard Soviet military-grade diesels, kerosene (TS-1, T-1 and T-2), and petroleum naphta (paint thinner). At temperatures of above 0°C, referred to as "summertime", the DL grade is used. At temperatures of between 0</span></span><span style="font-size: small;">°C</span><span style="font-size: small;"> and -30°C, the DZ grade is used. At temperatures of between -30</span><span style="font-size: small;">°C</span><span style="font-size: small;"> and -50</span><span style="font-size: small;">°C</span><span style="font-size: small;">, the special DA grade is used. The engine power falls by up to 20% when using petrol or kerosene. </span></div>
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driver can switch the type of fuel between gasoline, diesel and jet fuel by simply setting a rotary selector located next to his seat. The engine does not need to be further modified beyond that, but it is inefficient when using petrol. All engines were fitted with the typical complement of accessories such as an oil preheater system, oil filters, and an <a href="https://studfile.net/preview/5955532/page:4/">ST-10-1S starter-generator</a>. The ST-10-1S is a starter motor that doubles as the generator to power the electrical systems of the tank, using the principle of reversing a motor to use it as a generator. The operating speed of the ST-10-1S in the generator mode is between 3,600-6,250 RPM. The generator begins to output its rated power at the nominal electrical load at an engine speed of 900 RPM, and full operating power is achieved at 1,200 RPM. A fluid coupling was used to drive the device in the generator mode, requiring the crankshaft speed to be at least 80 RPM to produce enough oil pressure for the generator to begin producing electricity. When used as a starter motor, the electrical system boosts the input voltage to 48 V to provide the necessary starting power of 14.7 kW while keeping the current low, and thereby reduce the heat stress of the device. Because the ST-10-1s starter-generator is a DC generator, push-starting or tow-starting the T-72 is possible. The weight of all accessories is taken into account in the published weighs of the various engines fitted to T-72 models.</span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div><span><span style="font-size: small; font-weight: 400;">During the creation of the T-72 (Object 172M), the design and tuning of the V-46 engine was made so that the level of mobility would nominally correspond to that of the T-64A. The initial model Object 172 models designed by the UKBTM design bureau were made by converting existing</span></span><span style="font-size: medium; font-weight: 400;"> </span><span style="font-size: small; font-weight: 400;">T-64A hulls delivered from Kharkov, and were fitted with the</span><span style="font-size: small;"><span style="font-weight: 400;"> V-45K engine with a power of 730 hp. Compared to the 5TDF engine of the T-64A, the power output was 30 hp higher, which was needed to compensate for the slightly increased weight of the tank (39 tons vs 38 tons) from the enlarged engine compartment. Following this, drastic changes made in the hull and suspension in the Object 172M design caused the weight of the tank to rise further from 39 tons to 41 tons, and to compensate for this, the V-46 engine was created, rated for 780 hp at 2,000 RPM. If viewed purely in terms of the power to weight ratio from the gross power of the engine, the T-72 was directly equivalent to the T-64A.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">Due to a mandate by the government to standardize the T-72 transmission with the existing T-64A transmission, there was an inherent incompatibility between the engine speed of the engine and the gear ratios of the gearboxes, which would not have allowed the same top speed of 60 km/h to be achieved if the engine were directly connected to the gearboxes, as it was on the T-64A. To solve this issue, the input speed at the gearboxes was increased by a step-down gear in an intermediate power transfer gearbox between the engine and the gearboxes. This raised the input speed at the gearboxes from 2,000 RPM to 2,800 RPM, the same as in the T-64A. Even the powerband of the V-46 was matched to the 5TDF (at the gearbox input). In spite of this, the actual outcome of the switch to the V-46 resulted in a net gain in acceleration performance, because unlike the 5TDF, the V-46 moves from idle to its power band almost immediately due to the lower crankshaft speed of the engine itself.</span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">The main method of starting the engine is via compressed air, with the possibility of electric starting or tow-starting as the auxiliary. Electric starting was not preferred as it added wear and tear to the starter-generator, which could lead to earlier electrical failure. In exceptionally cold weather conditions, the most dependable method of starting is a combination of compressed air and the electric starter. It takes around 20 minutes to start the engine in extremely cold weather, which is much longer than the 3 minutes needed by the GTD-1000T gas turbine engine used on the T-80, but diesel piston engines have their own advantages. </span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><div style="font-size: 18.72px;"><span style="font-size: small;"><span><br /></span></span></div><div class="separator" style="clear: both; font-size: 18.72px; text-align: center;"><a href="http://4.bp.blogspot.com/-qJUMWipChoA/VlCm0GenxBI/AAAAAAAAERg/DdxJxVNoc_g/s1600/air%2Bcanister%2Bfor%2Bcompressed%2Bair%2Bstarting%2Bsystem.jpg"><img border="0" src="https://4.bp.blogspot.com/-qJUMWipChoA/VlCm0GenxBI/AAAAAAAAERg/DdxJxVNoc_g/s1600/air%2Bcanister%2Bfor%2Bcompressed%2Bair%2Bstarting%2Bsystem.jpg" /></a></div></span></span></div><div><span><span style="font-size: small; font-weight: 400;"><div><br /></div><div>The compressed air is stored in a pair of 5-liter bottles installed in the nose of the hull glacis which are continuously maintained at the rated pressure by the AK-150SV compressor. The AK-150SV is a three-stage reciprocating compressor with air cooling. The compressor is powered via a power takeoff shaft from the intermediate power transfer gearbox ("<i>Гитара</i>"), so that it continues to run even if the tank is parked and the gearboxes are shifted to neutral. The gear ratio in the intermediate power transfer gearbox for the air compressor is 0.934. During normal operation, the compressor uses 1.1 to 2.2 kilowatts of power (1.47-2.95 hp) depending on the engine speed. As such, the compressor would reduce the net power delivered through the transmission by an average of around 2 hp when it is running. It has an operating pressure of 150 kg/sq.cm and a capacity of 2,400 liters per hour.</div><div><br /></div><div>The compressed air bottles provide a reservoir of air for the engine starting system and serve as a source of air if the engine is not running. The pneumatic system of the tank is not only used to start the engine, but also to clean the driver's periscope, clean the gunner's primary sight, to evacuate the moisture and oil separator of the air compressor intake oil, clean the engine preheater by purging residue with a jet of compressed air, and for actuating electropneumatic valves to operate the filter-ventilator unit in the crew compartment. It is not known if the compressed air cylinders pose a tangible hazard if the tank armour is struck but not pierced. There is no doubt that the cylinders will explode if penetrated by a shaped charge jet or by heavy metal fragments, but the small size of the cylinders make that unlikely unless a very specific part of the front hull armour is hit.</div><div><br /></div></span></span></div><div><span style="font-size: small;"><span><div><div><span style="font-weight: 400;">In all T-72 models, the engine draws air from the engine compartment itself rather than from any particular intake. The main source of air in the engine compartment is sourced from the engine deck intake, but it is also possible for air to enter the engine compartment from the crew compartment. In this way, the air within the engine compartment always flows from the front to the back, i.e. in through the engine deck intake and the radiator intake, and out through the cooling fan. </span><span style="font-weight: 400;">To minimize the amount of heat permeating around the air cleaner due to its close proximity to the radiator packs, there is an internal partition that separates the air cleaner unit from the cooling system airflow pathway. During winter, the engine deck intake is closed with a cover, thus making the engine air cleaner system induct heated air from the radiators instead. Cooling efficiency is also reduced somewhat, because some amount of heated air recirculates around the engine rather than exiting directly via the cooling fan, but this is desirable as it can help to warm up the auxiliary components. </span></div><div><span style="font-weight: 400;"><br /></span></div><div><div style="font-weight: 400;"><font size="3">The photo on the left below shows the engine access panel intake for T-72 models with a V-46 engine. The photo on the right below shows the intake for T-72 models with a V-84 engine. Unlike the intake at the same location on the preceding T-62, T-55 and T-54 tanks, this intake is nothing more than a hole in the engine access panel which permits air to enter the engine compartment. Because the cooling fan evacuates air inside the engine compartment, the engine compartment is constantly held at a negative temperature, and the resulting pressure differential serves as the main driving force for atmoshpheric air to enter the engine compartment via the engine deck intake, supplemented by the negative pressure from the air cleaner itself due to engine induction. Unlike the preceding T-62, T-55 and T-54 tanks, where all or almost all of the air needed by the engine is sourced from the radiator intakes, no air is taken from the radiator intakes on the T-72.</font></div><div style="font-weight: 400;"><span style="font-size: small;"><br /></span><span style="font-size: small;"><br /></span></div><div class="separator" style="clear: both; font-size: 18.72px; font-weight: 400; text-align: center;"><a href="http://3.bp.blogspot.com/-kRu4S6nBNec/VUTJHD6vHgI/AAAAAAAACSo/KltGWPXcRks/s1600/26434.jpg"><img border="0" height="300" src="https://3.bp.blogspot.com/-kRu4S6nBNec/VUTJHD6vHgI/AAAAAAAACSo/KltGWPXcRks/s1600/26434.jpg" width="400" /></a><a href="http://2.bp.blogspot.com/-VJXPvgrDSLM/VUOux1tPwYI/AAAAAAAACME/6ItUS8SeDlo/s1600/t-72.26974.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://2.bp.blogspot.com/-VJXPvgrDSLM/VUOux1tPwYI/AAAAAAAACME/6ItUS8SeDlo/s1600/t-72.26974.jpg" width="400" /></a></div></div><div><span style="font-weight: 400;"><br /></span></div><div><span style="font-weight: 400;">The air supply of the engine is processed by a two-stage air cleaner system with automatic dust ejection. It is virtually identical to the VTI-4 previously used on the T-54, T-55 and T-62, but features a number of modifications to support the nuances of the V-46 engine. According to V.S. Dubov, writing in the collection of memoirs "<i>Life Given to Tanks</i>", the increase in the air consumption of the engine in the Object 172 compared to the T-62 led to the need to develop a new air cleaner and required the development of a new dust extraction ejector. Before the new air cleaner was designed, deterioration was observed in the original air cleaner and dust ejection system after tests of the Object 172. When creating a new version of the dust ejector, the task was to find the required intake area of the nozzle and position it in the ejector body so that it minimally increased the hydrostatic pressure at the inlet and at the exhaust outflow. Hydrostatic pressure creates resistance, which must be overcome with the energy of the engine itself via its exhaust gasses. In this case, a higher resistance leads to a higher exhaust backpressure, which introduces a power loss.</span></div><div><span style="font-weight: 400;"><br /></span></div><div><span style="font-weight: 400;">The VTI-4 was developed at the VNII-100 research institute for medium tanks, with its first use being in the T-54 from 1953 and onwards. The only difference is that the purified air outlet is a single wide duct that connects to the supercharger intake of the V-46, rather than being two smaller ducts that feed into the engine cylinders as on preceding tanks. </span></div><div><span style="font-weight: 400;"><br /></span></div><div><span style="font-weight: 400;">A multi-cyclone cleaner is used as the first stage of the air filtration system, functioning as the main filtration unit. It consists of 96 micro-cyclones, with the collected dust falling into an ejection duct where it is carried away by the engine exhaust. </span></div><div><span style="font-weight: 400;"><br /></span></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-j6llmgdfFV8/YStN7RHdeDI/AAAAAAAAUIU/r2biSJrGES0-lAIK2RnRTg6sVFFCStT3gCLcBGAsYHQ/s1916/engine%2Bair%2Bcleaner%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1180" data-original-width="1916" height="394" src="https://1.bp.blogspot.com/-j6llmgdfFV8/YStN7RHdeDI/AAAAAAAAUIU/r2biSJrGES0-lAIK2RnRTg6sVFFCStT3gCLcBGAsYHQ/w640-h394/engine%2Bair%2Bcleaner%2Bsystem.png" width="640" /></a></div></div><div><span style="font-weight: 400;"><br /></span></div><div><span style="font-weight: 400;">The dust ejection system uses the negative pressure of the engine exhaust to induce airflow in the dust collection pan, thereby sweeping the dust into the ehxaust outflow. This was done by having the engine exhaust manifolds routed to an exhaust duct where the high velocity exhaust creates a low pressure zone downstream of the exhaust. Each exhaust duct is also narrowed ahead of the exhaust stream to further increase exhaust velociy via the Venturi effect. The air in the dust collector underneath the cyclones, which is upstream of the exhaust, has a high static pressure. The pressure differential</span><span style="font-weight: 400;"> results in a flow of air from the dust collector into the exhaust ducts where the cool dusty air is mixed with the engine exhaust. The mixture then flows out of the exhaust port. This evacuates the dust within the dust collector and simultaneously cools down the exhaust gasses. The drawing below shows the exhaust ducts for both sides of the engine, linked to the two exhaust manifolds.</span></div><div><span style="font-weight: 400;"><br /></span></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HRbRU9ejzt0/YStbdqXlWkI/AAAAAAAAUIc/V5zyT7D9Bhwfhhys5oGmsAKN2JY4T2c5QCLcBGAsYHQ/s1843/air%2Bmixing%2Bducts.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1276" data-original-width="1843" height="445" src="https://1.bp.blogspot.com/-HRbRU9ejzt0/YStbdqXlWkI/AAAAAAAAUIc/V5zyT7D9Bhwfhhys5oGmsAKN2JY4T2c5QCLcBGAsYHQ/w640-h445/air%2Bmixing%2Bducts.png" width="640" /></a></div><span style="font-weight: 400;"><br /></span></div><div><span style="font-weight: 400;"><br /></span></div><div><span><div><font size="3" style="font-weight: 400;"><span><span>Specific details on the strength of the exhaust cooling effect are not known. If exploited properly, the induced airflow from engine exhaust via the Bernoulli principle tends to be very strong, and indeed, this was leveraged by the ejection-type cooling system of the PT-76, T-10 and T-64 series tanks, which lacked cooling fans, instead relying solely on the engine exhaust to induce a flow of air through their radiator packs at a sufficient rate for satisfactory driving performance. However, to use the energy of the exhaust for this purpose would incur power losses due to backpressure, which is the source of the cooling system losses in the aforementioned tanks. And indeed, the VTI-4 air cleaner generates an exhaust resistance of 11.8 kPa, more than twice as high as foreign tank engine exhaust systems (~5 kPa). Due to intense efforts made in reducing power losses, the exhaust resistance of the T-72 is less than that of preceding medium tanks, but still remains higher than foreign tanks. This is, however, largely unavoidable, and would be encountered by any tank equipped with an exhaust cooler for thermal signature suppression purposes. The most common form of exhaust cooler is a venturi ejector, as shown in the drawing below, taken from the "Engineering Design Handbook: Military Vehicle Power-plant Cooling".</span></span></font></div><div><span style="font-weight: 400;"><br /></span></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4ErAZ7G9uOQ/YS3q_jYaiPI/AAAAAAAAUI4/fpXufhNesGkVhhUn87GH3sATTIbShPFLgCLcBGAsYHQ/s693/exhaust%2Bcooler.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="536" data-original-width="693" height="248" src="https://1.bp.blogspot.com/-4ErAZ7G9uOQ/YS3q_jYaiPI/AAAAAAAAUI4/fpXufhNesGkVhhUn87GH3sATTIbShPFLgCLcBGAsYHQ/s320/exhaust%2Bcooler.png" width="320" /></a></div></div><div><span style="font-weight: 400;"><br /></span></div><div><span style="font-weight: 400;">The dust ejection system may also promote better engine aspiration because it generates a flow of air towards the air cleaner. The intensity of the airflow changes dynamically with the exhaust output, which is dependent on the engine speed. As such, when the engine load rises and falls, both the exhaust cooling and intake airflow will rise and fall accordingly. </span></div><div style="font-weight: 400;"><font size="3"><span><span><br /></span></span></font></div><div style="font-weight: 400;"><font size="3"><span><span>An additional nuance to note regarding the exhaust cooling effect is that because the exhaust is cooled after leaving the manifolds and entering the exhaust ducts, the duct surfaces and the exhaust gasses themselves are too cool to evaporate fuel for the engine smokescreening system. As such, the fuel injectors had to be placed at the end of the manifolds, so that the diesel can be evaporated into an aerosol and then cooled as it enters the exhaust ducts, where it condenses and becomes smoke. </span></span></font></div><div><span style="font-size: small;"><span><div style="font-weight: 700;"><br /></div><div style="font-weight: 700;"><span style="font-weight: 400;">Due to the lack of moving parts in cyclone filters, and the use of gas suction from the engine exhaust to continuously extract the collected dust, the cyclone system has very low maintenance demands. Even as a pre-filter, the cyclone system handles the bulk of the filtration workload, providing an air purity of at least 99.4% on its own. The second stage is a fine filtration system comprised of three steel mesh filter cassettes of progressively finer meshes. These cassettes are oil filters, with the meshes being coated with a thin layer of engine oil by soaking before being loaded into the air cleaner unit. After passing through the second filter stage, an air purity of no less than 99.8% is achieved. The nominal dust transmission rate through the specific air cleaner model used in the T-72 is unknown, t</span><span style="font-weight: 400;">he nominal dust transmission rate through the </span><span style="font-weight: 400;">VTI-4 is 0.078%, with an airflow rate of 472 liters per second. </span></div><div style="font-weight: 700;"><span style="font-weight: 400;"><br /></span></div><div style="font-weight: 700;"><span style="font-weight: 400;">After passing through the last filter cassette, the main flow of air enters the supercharger of the engine via a large outlet duct, and some air is diverted out via a secondary air hose into the AK-150 air compressor, where it is used to refill the pneumatic reservoirs of the tank. </span></div></span></span></div></span></div><div><span style="font-weight: 400;"><br /></span></div><div><span style="font-weight: 400;">When the air intake resistance crosses a certain threshold, indicating clogged filter elements, a sensor is tripped and the driver is notified by a warning light on his instrument panel. </span><span style="font-weight: 400;">After the warning light comes on, the tank is allowed to be driven for an additional 5 hours under conditions of </span><span><span style="font-weight: 400;">medium air dustiness or 2 hours under conditions of high air dustiness. The nominal time between servicing under a standard air dust density of 2.5 grams per cubic meter (high dustiness in desert environment) is 400 km according to the research paper "<i>Высокоэффективная система очистки воздуха для военных гусеничных машин</i>" by M.D Borisyuk et al.. According to Sergey Suvorov in </span></span><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">"</span><i style="font-family: "times new roman"; font-weight: 400;">Танки Т-72: Вчера, Сегодня, Завтра</i><span style="font-family: "times new roman"; font-size: small; font-weight: 400;">"</span><span style="font-weight: 400;">, the air cleaner requires cleaning every 1,000 km in winter, and every 500 km in the summer.</span></div><div><span style="font-weight: 400;"><br /></span></div><div><span style="font-weight: 400;">Before cleaning the filter elements, the engine access panel is first opened, then the filter unit top cover is opened, and the retaining brackets are removed. Each of these steps involves unscrewing bolts, which is rather tedious. The elements can then be removed.</span></div></div><div style="font-size: 18.72px; font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-size: 18.72px; font-weight: normal;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-sri2PLEmmCs/YSXAMGahDOI/AAAAAAAAUGU/g3DoALI2trEaEfw5I23A7yy6W2admZIWwCLcBGAsYHQ/s1251/filter%2Bopening.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="817" data-original-width="1251" height="261" src="https://1.bp.blogspot.com/-sri2PLEmmCs/YSXAMGahDOI/AAAAAAAAUGU/g3DoALI2trEaEfw5I23A7yy6W2admZIWwCLcBGAsYHQ/w400-h261/filter%2Bopening.png" width="400" /></a><a href="https://1.bp.blogspot.com/-nU1kNQ8O0Mg/YSXAMK8yaZI/AAAAAAAAUGQ/cjox1JgX1ioKCdm7Vbi_v-ixHCEbUf-3QCLcBGAsYHQ/s1288/filter%2Bremoval.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="902" data-original-width="1288" height="280" src="https://1.bp.blogspot.com/-nU1kNQ8O0Mg/YSXAMK8yaZI/AAAAAAAAUGQ/cjox1JgX1ioKCdm7Vbi_v-ixHCEbUf-3QCLcBGAsYHQ/w400-h280/filter%2Bremoval.png" width="400" /></a></div><span style="font-size: small;"><br /></span></div><div style="font-size: 18.72px; font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-size: 18.72px; font-weight: normal;"><span style="font-size: small;">Cleaning of the filter elements in field conditions is done by hosing them down with a jet of diesel, which is made possible by the inclusion of an MZA-3 fuel filler device in the accessories kit of the T-72. The MZA-3 is a powerful, compact device that can pump out diesel at 60 liters per minute. By connecting it to the fuel of the tank, and connecting its power cable to the external ShR-51 electrical socket on the left rear corner of the T-72 hull, the crew can set up a washing station next to the tank. The elements are then coated with engine oil before being reinstalled. </span></div><div style="font-size: 18.72px; font-weight: normal;"><br /></div><div style="font-size: 18.72px; font-weight: normal;"><span style="font-size: small;"><div><span><span style="font-size: small;"><div style="font-size: 18.72px;"><br /></div><div style="font-size: 18.72px;"><span style="font-size: small;"><span>The engine deck is cool enough that people can ride on top of it.</span></span></div><div style="font-size: 18.72px;"><span style="font-size: small;"><span><br /></span></span><span style="font-size: small;"><span><br /></span></span></div><div class="separator" style="clear: both; font-size: 18.72px; text-align: center;"><a href="https://4.bp.blogspot.com/-DryyKQ9zHgI/WMMMZFP33iI/AAAAAAAAIhk/gyGjzDLeGVAAA7nOJzK3hWWQNjN5ZpcZwCLcB/s1600/t-72%2Bgrozny%2Bdesantnik.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="286" src="https://4.bp.blogspot.com/-DryyKQ9zHgI/WMMMZFP33iI/AAAAAAAAIhk/gyGjzDLeGVAAA7nOJzK3hWWQNjN5ZpcZwCLcB/w400-h286/t-72%2Bgrozny%2Bdesantnik.jpg" width="400" /></a></div><div style="font-size: 18.72px;"><span style="font-size: small;"><span><br /></span></span></div></span></span><span><span style="font-size: small;"><br /></span></span></div><div><span><span style="font-size: small;">The two photos below show the two-layered engine deck opened up to expose the engine, ready to be serviced<span style="font-size: 18.72px;"><span style="font-size: small;">.</span></span></span></span></div><div><span><span style="font-size: small;"><br /></span></span><span><span style="font-size: small;"><br /></span></span></div><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-DkTfPLYC0aw/Wm9luhL80_I/AAAAAAAAKqY/2Jji3CV8yGo90kW9fi4O_3MwiuyRsbYnwCLcBGAs/s1600/t-72%2Bengine%2Bdeck.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://3.bp.blogspot.com/-DkTfPLYC0aw/Wm9luhL80_I/AAAAAAAAKqY/2Jji3CV8yGo90kW9fi4O_3MwiuyRsbYnwCLcBGAs/s400/t-72%2Bengine%2Bdeck.jpg" width="400" /></a><a href="http://3.bp.blogspot.com/-ZdmaZPDPe0w/VUPtGlCZ6GI/AAAAAAAACPE/TmkWP4kHdCw/s1600/engine%2Bdeck%2Bopen.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="261" src="https://3.bp.blogspot.com/-ZdmaZPDPe0w/VUPtGlCZ6GI/AAAAAAAACPE/TmkWP4kHdCw/s400/engine%2Bdeck%2Bopen.png" width="400" /></a></div><div><br /></div><div><br style="font-size: 18.72px;" /></div></span></div></span></span></div><div style="font-weight: normal;">
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<h3 style="font-weight: normal;">
<span style="font-size: large; font-weight: normal;"><b>V-46 (V-46-4, V-46-6)</b></span></h3>
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<a href="https://2.bp.blogspot.com/-wQRuEvmnIBU/VSFHQFEVAHI/AAAAAAAABp0/i57PjV-MOnw/s1600/v466ms_180.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-wQRuEvmnIBU/VSFHQFEVAHI/AAAAAAAABp0/i57PjV-MOnw/s1600/v466ms_180.jpg" /></a><span style="font-size: small;"><span><span style="font-weight: normal;">The
V-46 is a liquid-cooled supercharged diesel engine. It </span></span><span>is a V12 engine with a 60-degree V-angle. The V-46 was </span><span><span>developed in Chelyabinsk by the Chelyabinsk Tractor Plant (ChTZ) as a modern derivative of </span></span><span>the classic V-2 which once powered the iconic T-34 and KV-1, but is otherwise a completely new design. In general, the V-46 and all its descendants are robust and dependable multifuel diesel engines that offer good performance for a tank in the weight class of the T-72. The V-46 produces 780 hp (574 kW) at a rated speed of 2,000 RPM. The engine is rated for a temperature range of -40°C to +50°C. Without preheating, the minimum starting temperature is +5°C.</span></span></div><div style="font-weight: normal;">
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<span style="font-size: small;">The V-46-4 model was used on the T-72 Ural and most other T-72 variants, and the V-46-6, which was first tested in 1976 in the Object 176 experimental tank, was used in the T-72A. Overall, seven modifications of the V-46 engine were made with a range of power ratings from 650 hp to 780 hp. They were installed in T-72 tanks, engineering vehicles based on it, modernized T-55AM and T-62M tanks, self-propelled artillery vehicles, SHORAD systems, and other military tracked vehicles totaling 20 types. The main downside of the V-46 is that it has a high specific oil consumption rate of 8 g/hp.h, which is a trait shared with other V-2 derivatives. This is mainly due to the relatively large clearances in the cylinder group, which is an indication of the state of manufacturing technologies available in the Soviet Union.</span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div><span style="font-size: small; font-weight: 400;"> It has a large bore diameter of 150mm and a piston stroke length of 180mm (left cylinder group) and 186mm (right cylinder group), which is the same as the V-2. The right cylinder bank has a capacity of 19.8 liters and the left bank has a capacity of 19.092 liters, and the total capacity is 38.89 liters. This is usually abbreviated to 38.8 l. The asymmetric cylinder banks was a result of using master-and-slave connecting rods, with the right piston having the slave, or articulated, connecting rod. This allowed the engine length to be minimized, which was not only beneficial in terms of compactness, but also reduced its weight, as the material savings from having a shorter engine block meant less weight. This is in contrast to conventional automotive V-engines which usually have side-by-side connecting rods, which generally increases engine length by 11-14% and introduces additional bending moments that bend the crankpin due to the longitudinal offset between the connecting rods in each pair, increasing stress.</span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div><span style="font-size: small; font-weight: 400;">All of the basic features of the V-46 were inherited directly from the original V-2, including its dual overhead camshaft and variable speed mechanical governor. At the time the V-2 was introduced, these were modern features, but by the time the T-72 was introduced, both features had long become standard among tank engines. </span><span style="font-size: small; font-weight: 400;">The firing order of the engine is 1-12-5-8-3-10-6-7-2-11-4-9, or 1L-6R-5L-2R-3L-4R-6L-1R-2L-5R-4L-5R. The camshaft pairs on both cylinder banks are identical and provide symmetrical valve timing. Injection timing is also symmetrically matched on both sides. Although the right groups of pistons has a longer stroke, the torque delivered is equal between the two piston groups. Altogether, the V-46 corresponds to an ideal even-firing 60-degree V12 engine, with full dynamic balance without needing balancing shafts.</span></div><div style="font-weight: 400;"><span style="font-size: small;"><br /></span></div><div style="font-weight: 400;"><span style="font-size: small;">The V-46 was designed with a large valve overlap of 75 degrees, which provides a strong scavenging effect as the negative pressure from the leaving exhaust gasses are used to accelerate the entry of fresh air into the cylinder. This was an important design change from earlier V-2 engine derivatives, which had a small valve overlap of less than 20 degrees. It functions as a means of completely purging exhaust gasses from the cylinder, and it also provides significant air cooling to the piston head and injector nozzle. The large valve overlap works in tandem with the supercharger to increase engine power, at the expense of creating excessive gaps at idling speeds which reduces fuel economy, owing to the fixed valve timing. </span><span style="font-size: small;"><span>According to operational guidelines, the engine should idle at a speed of 800-900 RPM (no less than 800 RPM), and the minimum idle speed is 600 RPM, which is the minimum stable crankshaft speed, but idling at 600 RPM is not recommended.</span><span> On previous V-2 derivatives, the recommended idle speed was 600 RPM due to the</span><span> lack of a significant valve overlap. </span></span></div><div style="font-weight: 400;"><span style="font-size: small;"><br /></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">A variable speed mechanical </span></span><span style="font-size: small; font-weight: 400;">governor is capable of setting a variable idle speed, to enforce a fixed maximum speed, and to maintain any constant speed between idle and maximum. The driver is provided with two controls to regulate fuel - the hand accelerator, used to set the idle speed which is then automatically maintained by the governor, and the accelerator pedal, which is used to manually increase the engine speed, which the governor will maintain under fluctuating loads by increasing or decreasing the fuel flow in response. If, for example, the driver is keeping his foot on the accelerator pedal at a steady position to maintain an engine speed of 1,900 RPM, then as the tank travels across undulating terrain, the governor will maintain the same engine speed even as the engine load rises when the tank is climbing a mound and then falls as the tank rolls down the opposite side of the mound. Because the engine speed is constant, the tank speed also remains constant, making it easier for the driver to control the tank and increasing the average speed of the tank during cross-country operation. </span></div><div><span style="font-size: small; font-weight: 400;"><br /></span></div><div><span style="font-size: small; font-weight: 400;">Setting the idle speed is done before starting the engine by pushing the hand accelerator to the idle position. The hand accelerator handle knob is shown in the photo below, next to the steering handle and behind the GPK-59 gyrocompass.</span></div><div><span style="font-size: small; font-weight: 400;"><br /></span></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-miw7i3E78mo/VTPjwjs8L9I/AAAAAAAAB6Y/nyZ-9ZuvQkM/s800/gpk-59.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="600" height="400" src="https://3.bp.blogspot.com/-miw7i3E78mo/VTPjwjs8L9I/AAAAAAAAB6Y/nyZ-9ZuvQkM/w300-h400/gpk-59.jpeg" width="300" /></a></div></div><div><span style="font-size: small; font-weight: 400;"><br /></span></div><div><span style="font-size: small; font-weight: 400;">Idling at the 600 RPM minimum speed is possible with the hand accelerator, but not recommended. Idling at an excessively low speed is not conducive to fuel economy, and promotes soot buildup. The recommended idling speed of at least 800 RPM is set by the driver during engine startup by pushing the hand accelerator until resistance is felt, which will be around the middle of the accelerator handle pawl. The handle can be pushed forward beyond the felt resistance to increase the idling speed of the engine to charge the batteries at a quicker rate, when preheating the engine and to keep the engine warm in cold weather, when running the engine on a fuel other than diesel, when the stabilizer needs to be fully powered, and so on. The driver has to observe the tachometer while pushing the handle forward until he observes that the desired speed has been reached, or if a certain voltage is needed, he needs to observe the voltmeter. For example, to reach and sustain 26 V to supply the nominal rated power to the stabilizer, the engine speed should be 1,500-1,600 RPM. When shutting off the engine, the hand accelerator is pulled to the full rear position to cut off the fuel supply. </span></div><div><br /></div><div style="font-weight: normal;"><span style="font-size: small;"><br /><div style="font-size: 18.72px;"><span style="font-size: small;"><span>The N-46 centrifugal supercharger is used on all models of the V-46 series. The air intake of the supercharger is above the end of the crank shaft. It is connected to the air intake filtration unit by a duct. On the opposite end of the engine is the exhaust manifold exit ducts and the air distributor hub of the pneumatic starting system. <br /><br /></span></span><span style="font-size: small;"><span><br /></span></span><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-7rJ6g4Y6_ys/XnfijaNDZcI/AAAAAAAAQbg/2kCuDuyqY28PONpqvCIswXN5TIOIYpIBQCLcBGAsYHQ/s1600/v-46%2Bengine.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="410" data-original-width="1008" height="260" src="https://1.bp.blogspot.com/-7rJ6g4Y6_ys/XnfijaNDZcI/AAAAAAAAQbg/2kCuDuyqY28PONpqvCIswXN5TIOIYpIBQCLcBGAsYHQ/s640/v-46%2Bengine.jpg" width="640" /></a></div><span style="font-size: small;"><span><br /></span></span></div></span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;"><div><span style="font-size: small;">The compression ratio is 14. This ratio is relatively low, but remained within permissible limits for a compression ignition engine because the N-46 supercharger generates a sufficiently high boost pressure of 0.68 bar (0.7 kgf/sq.cm). The total overpressure within the cylinder is 0.804 bar (0.82 kgf/sq.cm) - higher than the supercharger boost pressure alone thanks to the scavenging provided by the valve overlap. The overall pressure, which is inclusive of atmospheric pressure, is therefore 1.817 bar at sea level. The air temperature inside the cylinder at the end of the intake stroke is 128°C. It is because of the high boost provided by the supercharger and scavenging that the fuel efficiency remains relatively high, </span><span>despite the somewhat low compression ratio</span><span>. The specific fuel consumption is 180 g/hp.h at the rated speed, which is the same as the V-55 and AVDS-1790-2 series engines, and lower than the 185 g/hp.h of the MB 838 CaM-500. The minimum specific fuel consumption is around 172 g/hp.h.</span></div><div style="font-size: 18.72px;"><span style="font-size: medium;"><br /></span></div><div style="font-size: 18.72px;"><span style="font-size: small;">Thanks to the use of a cast aluminium engine block, the engine weighs just 980 kg. Its compactness gives the V-46 an exceptionally high specific power of 653 hp/cu.m. </span><span style="font-size: small;">Its mean effective pressure (MEP) is 8.8 bar (9 kgf/sq.cm).</span></div></span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;">As the capacity of the engine is 38.8 liters, which is quite large relative to the power output of the V-46, the engine has a power density of 20.1 hp/l. This is considerably lower than the MB 838 CaM-500 powering the Leopard 1 (22.2 hp/l) and the AVDS-1790-2C powering the M60A1 (25.5 hp/l), but the large displacement of the engine - primarily the long stroke length of the pistons - is responsible for the favourable torque output of the engine and its competitive specific torque. The operating speed range of the engine is 1,300-2,000 RPM, and the maximum crankshaft speed is 2,300 RPM. </span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;">The idle speed of the V-46 is the same as the 5TDF, but because to the step-up gear in the intermediate power transfer gearbox, the idle speed at the BKP input is actually around 1,100-1,200 RPM. </span><span style="font-size: small;">The maximum torque output is 3,090 Nm at an engine speed of 1,300 RPM, dropping to 2,745 Nm at 2,000 RPM. Based on the known torque curve of the Polish S-1000 engine, an uprated derivative of the V-46-6, it can be calculated that the torque of the engine at a speed of just 1,000 RPM is only 2.5% below the peak torque. Thus, the torque curve should be as follows:</span></div><div style="font-weight: normal;"><span style="font-size: medium;"><br /></span></div><div style="font-weight: normal;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-uZiwTTOv4uQ/YVjHUwFQtSI/AAAAAAAAURI/t9yfbo4mem49Am0lwWOskl181ANmcVmMQCLcBGAsYHQ/s1498/v-46%2Btorque%2Bcurve.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="763" data-original-width="1498" height="326" src="https://1.bp.blogspot.com/-uZiwTTOv4uQ/YVjHUwFQtSI/AAAAAAAAURI/t9yfbo4mem49Am0lwWOskl181ANmcVmMQCLcBGAsYHQ/w640-h326/v-46%2Btorque%2Bcurve.png" width="640" /></a></div><span style="font-size: medium;"><br /></span></div><div><span style="font-size: small; font-weight: normal;">As the graph shows, </span><span style="font-size: small;"><span style="font-weight: 400;">the low end of the torque curve is extremely flat, and an enormous amount of torque is obtained even at 1,000 RPM, just marginally higher than the idle speed. In practical terms, this means that the driver of a T-72 has a great deal of power delivered immediately upon stepping on the accelerator pedal, which translates to exceptional driving response. This is not only significant as a measure of responsiveness, but it shows that lowering the speed at which the engine develops peak torque was utilized as the method of improving engine flexibility.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">To quantify the qualities of the engine dynamics, two metrics are used - engine flexibility (adaptability) and engine elasticity. The engine flexibility (adaptability) coefficient is 1.125, which is otherwise known as the torque backup, torque reserve or torque rise when expressed as a percentage. In this case it is 12.5%. Strangely enough, officially, the torque backup of the V-46 is rated as 9-18%, which is obviously not achieved with the given maximum torque and torque at maximum power. This places the V-46 between the MB 838 CaM-500, the 5TDF, and the MB 873 Ka-501 engine in terms of engine flexibility. The MB 838 CaM-500 has a mere coefficient of 1.058 (5.8% torque backup) while the 5TDF engine reaches a more respectable coefficient of 1.095 (9.5% torque backup), whereas the MB 873 has an engine flexibility coefficient of 1.159 (15.9% torque backup). The AVDS-1790-2 series is by far the worst, with a coefficient of just 1.041 (4.1% torque backup). High engine flexibility is important for negotiating terrain that imposes high fluctuating engine loads rather than constant loads, and is therefore responsible for providing a high cross-country speed. </span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">Additionally, to quantify the characteristics of the power band, the engine elasticity coefficient is used. The wider the power band, the lower (better) the coefficient. For the V-46, the coefficient is 0.65, slightly lower (better) than the MB 838 CaM-500 of the Leopard 1 (0.68) substantially lower than the 5TDF (0.73) but slightly higher (worse) than the MB 873 Ka-501 of the Leopard 2 (0.61). Again, the AVDS-1790-2 series performs the worst by far, with an elasticity coefficient of 0.75 (using peak torque speed of 1,800 RPM from Hunnicutt) or 0.79 (using peak torque speed of 1,900 RPM from Teledyne). But even this was already better than the earlier AV-1790-7 series gasoline engine that powered the later M47s and M48s, as that had a ghastly elasticity coefficient of 0.857. A wide power band contributes to the ease of driving the tank in various types of terrain, because it means that downshifting is often not necessary when the tank slows down as the engine produces a large amount of power at a wide range of speeds.</span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">It is worth noting that the peak torque speeds in the chart differ slightly from the official rating, as it shows that peak torque begins at 1,200 and it is maintaned up to 1,400 RPM. This is excellent as the high peak torque is available at a wide range of low engine speeds, so the engine is able to provide a large amount of tractive force to overcome resistances which is necessary for accelerating a heavy vehicle like a tank from a standstill, while the flatness of the torque curve translates to a large amount of power available even at a low engine speed, which ensures that high acceleration performance is achieved and maintained across the power curve. Compared to the 5TDF, the fact that the peak torque of the V-46 is achieved at a much lower engine speed of 1,300 RPM rather than 2,050 RPM gives an advantage in load-bearing characteristics and in acceleration performance, given that both engines idle at 800 RPM. Taking into account the step-up gear, the input speed at the BKPs from the V-46 engine is 1,183 RPM at idle and 1,840 RPM at peak torque. The 5TDF, on the other hand, must accelerate from 800 RPM to 2,050 RPM. Proportionately speaking, the power band of the V-46 starts at a lower engine speed, and the power band is correspondingly wider. </span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div style="font-weight: normal;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-pVk5P_XFtto/X2l7SbKrueI/AAAAAAAARo4/hDhd5I5Fbwk4haJVH6qh57J9Ff_JnCjmACLcBGAsYHQ/s2048/v-46%2Bcharacteristics.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1585" height="400" src="https://1.bp.blogspot.com/-pVk5P_XFtto/X2l7SbKrueI/AAAAAAAARo4/hDhd5I5Fbwk4haJVH6qh57J9Ff_JnCjmACLcBGAsYHQ/w310-h400/v-46%2Bcharacteristics.png" width="310" /></a></div><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div><span style="font-size: small; font-weight: 400;">In the power curve illustrated above, it can be seen that the engine develops 605 hp at 1,400 RPM. For comparison, the AVDS-1790-2 engine series for the M60A1 and M60A3 (among others) manages an output of 486 hp (480 bhp) at the same speed. The difference in low end power is 119 hp - much greater than the difference in the peak powers developed by the two engines, 780 hp compared to the 760 hp (750 bhp) of the AVDS-1790-2 series. This is due to the large deficiency in engine elasticity that the AVDS-1790-2 series suffers from, and it means that despite having a higher rated power output, an AVDS-1790-2 series engine needs to be driven harder under most circumstances to produce the same amount of power as the V-46. Furthermore, when measured by sprocket power, t</span><span style="font-size: small; font-weight: normal;">he power developed by the V-46 is actually at the same level as the MB 838 CaM-500 engine of the Leopard 1 which has a much higher rated power output of 830 hp, even exceeding it at lower engine speeds thanks to the high torque developed by the V-46. And finally, although the V-46 does not surpass these two engines in power and torque density to a noteworthy degree, its light weight and small overall size give it favourable power and torque density characteristics.</span></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;">However, the V-46 is soundly beaten by the advanced MB 873 Ka-501 of the Leopard 2 which has a maximum power output of 1,500 hp and generates a maximum torque of 4,700 Nm at 1,600 RPM. Of course, this is not particularly surprising because the MB 873 is a larger 47.6-liter engine. The light weight of the T-72 only compensates for this to some extent. In terms of handling torque overloads during steady driving, such as when maintaining a cruising speed over rough terrain, when operating a mine plough, when driving over obstacles, up a hill, towing another tank, and so on, the V-46 performs well thanks to a large torque backup of 12.5% and therefore, a good engine flexibility. Having a low peak torque speed of 1,300 RPM and a high torque backup allows the V-46 to provide good acceleration characteristics and retain driving performance when moving in difficult terain. </span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;">Officially, the maximum permissible operating altitude of the V-46 is 3,000 meters. However, Indian forces </span></span><span style="font-size: small;"><span>deployed in the icy mountainous regions of Eastern </span><span>Ladakh have been successfully operating their T-72M1 tanks at altitudes in excess of 4,500 meters.</span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;">V-46 engines delivered to the Soviet Army had a warranty service life of 500 engine hours. The actual service life regularly exceeded the warranty service life. After going through an overhaul, the factory guaranteed an additional 300 engine hours of operation, providing a total warrantied service life of 800 hours, with the service life defined as the 90% exhaustion of its total life. According to a large-scale East German study of the reliability of East German and Czechoslovak T-72M tanks, the useful lifetime of the engine reaches 800 engine hours. Officially, 800 engine hours is considered equivalent to 9,000-10,000 km of travel. For comparison, Simon Dunstan states in "<i>Chieftain Main Battle Tank 1965-2003</i>" that the planned engine service life of the Leyland L60 engine targeted by the "Sundance" reliability improvement programme (1976-1979) was 4,000 miles (~6,400 km), but even this modest goal was rarely achieved despite the maturity of the engine and the tank itself by the time of the "Sundance" programme. This was equivalent to the average lifespan of a V-2 engine (T-34-85) produced in 1944-1945 and would have been considered blatantly unacceptable in the postwar era.</span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">The exhaust port for this engine is characteristically long and narrow, because the exhaust manifolds from both sides of the engine were joined together just before exiting the exhaust port. It has very rudimentary sheet steel cooling fins on top. The fins are arranged so that as the tank drives forward, cool air rushes from one side of the fins to the other, drawing away some heat along the way.</span></span></div>
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<span style="font-weight: normal;"><span style="font-size: small;">The exhaust port connects to the exhaust manifold via a simple duct. The exhaust port is secured onto the duct via a pair of bolts and nuts on either side.</span></span></div>
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<span style="font-weight: normal;"><span style="font-size: small;">The V-46-4 is the variant which the T-72 Ural uses, while the V-46-6 is used in the T-72A. The only difference between the V-46-4 and the V-46-6 is a change in the</span></span><span style="font-size: small; font-weight: normal;"> placement of oil containers</span><span style="font-weight: normal;"><span style="font-size: small;">. </span></span><span style="font-size: small; font-weight: normal;">With the V-46, both the T-72 Ural and T-72A can achieve a nominal top speed of 60 km/h on asphalt and set an average speed of 35 to 40 km/h on dirt roads.</span></div>
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<span style="font-size: small;"><span style="font-weight: normal;"><span style="font-size: large;"><b>V-84 (V-84-1, V-84M, V-84MS)</b></span></span></span></h3>
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<a href="https://3.bp.blogspot.com/-kKYJhO7cV0g/VSFH97vUTyI/AAAAAAAABp8/6z1pELAr6wE/s1600/v84ms_180.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-kKYJhO7cV0g/VSFH97vUTyI/AAAAAAAABp8/6z1pELAr6wE/s1600/v84ms_180.jpg" /></a> <span style="font-size: small;"><span style="font-weight: normal;">The V-84 engine represented the limit of the growth potential provided by superchargers for the engine design. Its power output of 840 hp lay on the boundary of diminishing returns, as further increasing the power also drove up the power losses to the supercharger to an exorbitant degree. The V-84 engine series began mass production in 1984 at the ChTZ motor plant. It differs from its predecessor
mainly by an increase in torque output within the same operating engine speed range, thus producing more power. The basic V-84 was not used in the T-72 models preceding the T-72B, though there is some evidence that "<i>Improved T-72A</i>" tanks built in 1984 were fitted with the new engine. The V-84-1, featuring an air intake heating system for winter starting, was the most numerous version of the engine, being used in the T-72B obr. 1985, and the improved V-84M was used in later T-72B models at the end of the 1980's. The V-84MS was used in T-72B models built or modernized in the 1990's, including T-72BA tanks. The V-84MS was also installed in the T-90 obr. 1992. The V-84 was completely interchangeable with the V-46 and shared a large number of parts, being a derivative of the V-46-6. </span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div><span><span style="font-size: small; font-weight: 400;">With the installation of the V-84-1 in the T-72B, a rise in the losses of net power available to propel the tank had to be solved by imroving the efficiency of the powertrain. M. L. Naumov, who worked as a research engineer in the UKBTM automotive department, states in the collection of memoirs "<i>Life Given to Tanks</i>" that during testing, it was found that after installing the V-84 engine in the T-72A tank for testing, the engine power was reduced by 13-14% and its fuel efficiency was reduced by 15% due to the additional power losses arising from the overloading of the powertrain, which was not designed to handle the increased power. To improve the net power available to the tank, a comprehensive study was made to reduce power losses from inducted air heating, air intake resistance, exhaust backpressure, and the efficiency of the cooling system. As a result, improved assemblies - fully interchangeable with the original models - were developed, thanks to which the net power rose by an additional 50-55 hp.</span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;">The V-84 series produces 840 hp at an engine speed of 2,000 RPM, and the maximum torque developed by the engine reaches 3,335 Nm at a speed of 1,300 RPM. The engine elasticity coefficient is 0.65. Thanks to the retention of the original V-46 engine dimensions, the specific power was increased from 653 hp/cu.m to 700 hp/cu.m. The same N-46-6 centrifugal supercharger from the V-46-6 engine was used. It provides a boost pressure of 0.68 bar (0.7 kgf/sq.cm).</span></span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;">The increased power offsets the added weight of the tanks that have it installed, namely Object 184 tanks which includes "<i>Improved T-72A</i>" tanks produced in 1984 and all T-72B models, allowing it to remain as nimble as its predecessors. There was no improvement in the peak sprocket power-to-weight ratio, however. One side effect of the added power is the increased heat output. Since the cooling fan for the radiator draws power directly from the engine, the increased heat is mostly eliminated, but more heat escapes from the exhaust manifolds. For the upgraded V-84-1 and V-84M models, an intake air heating device was included to facilitate the starting of the engine in cold weather conditions. This device, combined with the use of special low-viscosity oil, made it possible to start the engine at a temperature of -20°C without needing to be preheated first.</span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;">The specific fuel consumption of the V-84 is 182 g/hph at the rated speed. This is marginally more than the V-46 and marginally less than 184 g/hph and 185 g/hph consumption rate of the MB 873 Ka-501 and MB 838 CaM-500 respectively.</span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">Output at rated speed: 840 hp </span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">Rated speed: 2,000 rpm</span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">Idle speed: 800 rpm </span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">Fuel Consumption:</span></span><span style="font-size: small;"><span style="font-weight: normal;"> 247 g/kWh or 182 g/hph</span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">Weight: 1,020 kg</span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">The dynamic characteristics of the V-84 is shown in the chart below, taken from a V-84 technical manual. The power output of the engine rises sharply from around 610 hp to 840 hp as the engine speed increases from 1,300 RPM to 2,000 RPM. At the same time, the relative fuel consumption rate drops to the lowest point of 171 g/hp.h at 1,600 RPM and rises to the highest point of 182 g/hp.h at the rated speed of 2,000 RPM.</span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span><span style="font-size: small;"><span style="font-weight: normal;">As mentioned earlier, the maximum torque output of the V-84-1 is 3,335 Nm at an engine speed of 1,300 RPM. This is much more than 1,922 Nm produced by the 5TDF of the T-64BV but much less than the 4,395 Nm produced by the GTD-1250 of the T-80U and the 5,170 Nm of the AGT-1500 of the M1 Abrams. The increased weight of the T-72B compared to the T-72A was offset (with a surplus) by t</span></span><span style="font-size: small; font-weight: 400;">he higher torque output and better overall dynamic running characteristics of the V-84 engine such that the acceleration characteristics probably increased to the level of the T-72 Ural. </span><span style="font-size: medium;">When using TS-1, T-1 and T-2 jet fuel or A-72 gasoline, the maximum torque output of the V-84 engine is only 900 Nm at 1,300 RPM. As such, the tank accelerates very slowly and cannot climb steep slopes or overcome most natural obstacles, so it is not feasible to operate a T-72B (or any T-72) with non-diesel fuels during combat. As a rule, non-diesel fuels can only be used in emergencies when diesel is completely unavailable. </span></div>
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<span style="font-size: small; font-weight: 400;">When running under normal conditions, the V-84 engine has excellent running characteristics like the V-46, which can be seen in its power curve, producing a very flat torque curve throughout its speed range, almost as flat as the V-46. To illustrate this, t</span><span style="font-size: small;">he graph on the left shows the torque curve of the V-84, taken from a technical manual. The graphs show that the torque output of the V-84 is at the maximum of 3,334 Nm at 1,300 RPM and steadily drops to 2,940 Nm at 2,000 RPM, which gives an engine flexibility (adaptability) coefficient of 1.13. In other words, the high torque generated by the engine is largely retained throughout a wide range of engine speeds, to almost the exact same extent as the V-46, albeit with a larger dropoff at the rated engine speed for peak power. The torque reserve of 11.8% is slightly higher (worse) than the V-46, again owing to the larger dropoff at peak power.</span></div>
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</div><div style="font-weight: normal;"><span style="font-size: small; font-weight: 400;"><br /></span></div><div><span style="font-size: small; font-weight: normal;">Thanks to its flat torque curve, the resulting power curve delivered by the V-84 was also flattened, gaining a more linear rise with engine speed, matching the V-46 power curve in shape. This is shown in the graph on the left below, produced using the power curves for both engines. Though the overall performance across the power curve was still largely the same, there is a slight difference in the sprocket power-to-weight ratio due to the V-84 power curve. The V-84 is able to maintain an identical sprocket power-to-weight ratio on the T-72B only on the lower half of the operating speed range, but because the torque curve has a larger gradient at the tail end of the range, the peak sprocket power-to-weight ratio actually worsened slightly. </span></div><div><span style="font-size: small; font-weight: normal;"><br /></span></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jHxGMusoIPg/YU6VBf_9MaI/AAAAAAAAUPI/TrHsJCw2uxcVczbnUyms_TdWGV4znjljwCLcBGAsYHQ/s1201/V-84%2Bvs%2BV-46.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="610" data-original-width="1201" height="204" src="https://1.bp.blogspot.com/-jHxGMusoIPg/YU6VBf_9MaI/AAAAAAAAUPI/TrHsJCw2uxcVczbnUyms_TdWGV4znjljwCLcBGAsYHQ/w400-h204/V-84%2Bvs%2BV-46.png" width="400" /></a><a href="https://1.bp.blogspot.com/-fElND40Z_0U/YU6XXNQ6qNI/AAAAAAAAUPQ/c8baAn514FM_GIMtfmiOjpBRcNd_8K0VgCLcBGAsYHQ/s1244/t-72b%2Bpower%2Bweight.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="645" data-original-width="1244" height="208" src="https://1.bp.blogspot.com/-fElND40Z_0U/YU6XXNQ6qNI/AAAAAAAAUPQ/c8baAn514FM_GIMtfmiOjpBRcNd_8K0VgCLcBGAsYHQ/w400-h208/t-72b%2Bpower%2Bweight.png" width="400" /></a><br /><br /></div></div><div><span style="font-size: small; font-weight: normal;"><br /></span></div><div><span style="font-size: small; font-weight: normal;">Nevertheless, this is not unsurprising given that the engine is functionally the same aside from the increased torque. When compared to an equivalent diesel engine of a similar power, the flatness of the torque curve still gives the V-84 a great advantage in that it produces a stronger and more uniform acceleration from a standstill,</span><span style="font-size: small;"><span style="font-weight: 400;"> as illustrated in the two graphs below - the top graph shows the power curve of the V-84, and the bottom graph shows the power curve of the MB-838, the engine of the Leopard 1. At an engine speed of 1,300 RPM, the V-84 puts out just a little over 441 kW (600 hp) of power, whereas the MB-838 generates around 380 kW (516 hp). In this case, the difference in low end power is nearly 100 hp, an important gap which would be missed</span></span><span style="font-size: small;"><span style="font-weight: 400;"> if the two engines were compared purely in terms of peak power output (840 hp vs 830 hp). This gap of 100 hp is still maintained at an engine speed of 1,500 RPM, which is the point where the MB 838 develops its maximum torque. From there, the gap gradually diminishes as the engine speeds increase, narrowing to 65 hp at 2,000 RPM where the MB-838 reaches 570 kW (775 hp) while the V-84 puts out 618 kW (840 hp), but even so, it is apparent </span><span style="font-weight: 400;">that despite what the peak power suggests, the actual advantage of the V-84 in power output far exceeds 10 hp</span></span><span style="font-size: medium; font-weight: 400;">. </span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: 400;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: 400;"><br /></span></div><div style="font-weight: normal;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--Ri44nVq-vs/YUmirRPJxAI/AAAAAAAAUOI/HI8usNxYmRsdb5JF7GmezTt3dFZdtrZiQCLcBGAsYHQ/s2760/v-84%2Bpower%2Bcurve.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1139" data-original-width="2760" height="165" src="https://1.bp.blogspot.com/--Ri44nVq-vs/YUmirRPJxAI/AAAAAAAAUOI/HI8usNxYmRsdb5JF7GmezTt3dFZdtrZiQCLcBGAsYHQ/w400-h165/v-84%2Bpower%2Bcurve.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--Ri44nVq-vs/YUmirRPJxAI/AAAAAAAAUOI/HI8usNxYmRsdb5JF7GmezTt3dFZdtrZiQCLcBGAsYHQ/s2760/v-84%2Bpower%2Bcurve.png" style="margin-left: 1em; margin-right: 1em;"></a><a href="https://1.bp.blogspot.com/-Kt2Syl6Jvq0/YUmjNOI8PlI/AAAAAAAAUOQ/s1q5TIsAiS4Lkb-VX9I00F3oKgOGZRvUQCLcBGAsYHQ/s441/MB-838%2Bpower%2Bcurve.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="429" data-original-width="441" height="311" src="https://1.bp.blogspot.com/-Kt2Syl6Jvq0/YUmjNOI8PlI/AAAAAAAAUOQ/s1q5TIsAiS4Lkb-VX9I00F3oKgOGZRvUQCLcBGAsYHQ/s320/MB-838%2Bpower%2Bcurve.png" width="320" /></a></div><span style="font-size: small; font-weight: 400;"><br /></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;">The exhaust outlet for a V-84 type engine is identical in appearance to that of the V-46.</span></span></div>
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<a href="https://2.bp.blogspot.com/-FjtZfnDKDAI/WfhJiCTfVSI/AAAAAAAAKCQ/CDXZych1U0oZVUgkRUD7rs0FugqJoD2KwCLcBGAs/s1600/t-72%2Bexhaust.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1354" data-original-width="1600" height="270" src="https://2.bp.blogspot.com/-FjtZfnDKDAI/WfhJiCTfVSI/AAAAAAAAKCQ/CDXZych1U0oZVUgkRUD7rs0FugqJoD2KwCLcBGAs/s320/t-72%2Bexhaust.png" width="320" /></a></div>
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<span style="font-size: small;"><span style="font-weight: normal;">Like previous variants, the T-72B had a nominal top speed of 60 km/h on asphalt roads and an average speed of 35 to 40 km/h on dirt roads.</span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;"><span style="font-size: large;"><b>V-92 (V-92S2F)</b></span></span></span></h3>
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<a href="https://4.bp.blogspot.com/-vX6RLjpRIt4/VSFIM8bRc0I/AAAAAAAABqE/-eYkA06cigY/s1600/v92s2_180.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-vX6RLjpRIt4/VSFIM8bRc0I/AAAAAAAABqE/-eYkA06cigY/s1600/v92s2_180.jpg" /></a><span style="font-size: small;"><span style="font-weight: normal;">The V-92S2F turbocharged</span></span><span style="font-size: small;"><span style="font-weight: normal;"> engine boasts an
impressive power density combined with higher standards of reliability and fuel economy. Due to the use of a relatively compact turbocharger instead of the N-46 supercharger, the total length of the engine decreased marginally compared to the V-46 and V-84 series, but the weight of the engine increased marginally to 1,100 kg. The main feature of the engine is that it produces a rated power of 1,130 hp at 2,000 RPM. The warrantied service life of the V-92S2F is unknown, but the warranty service life of the less powerful V-92S2 from which it was derived is 650 engine hours.</span></span></div><div style="font-weight: normal;"><span style="font-size: medium;"><br /></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">To drive the turbocharger, new exhaust manifolds were implemented. After passing through the turbine, the exhaust gasses are routed through a duct sitting between the rocker covers. Due to the changes in the exhaust, T-72 tanks equipped with V-46 or V-84 engines require minor modifications to fit the V-92S2F. </span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;">The maximum torque output is 4,521 Nm which is a huge improvement over the V-84 engine and nominally exceeds the GTD-1250 gas turbine engine of late production T-80U tanks. It is close to the MB 873 Ka-501. </span></span><span style="font-size: small; font-weight: normal;">The increased torque output and torque backup greatly improves driving characteristics
across rough terrain and aids in steering, as the torque backup is used to overcome the increased resistance during a turn to ensure that the vehicle does not lose speed compared to straight-line driving. The fuel
efficiency has been substantially improved to just 158 g/hph, fully compensating for the greatly increased power output compared to previous engines, yielding a net increase in driving range without an increase in the fuel capacity of the tank. </span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;">The cylinders and pistons were updated and are more robust compared to previous engines to cope with the added power. The T-72B3 UBKh has the V-92S2F installed along with a new transmission and new dual-pin tracks with improved traction on broken terrain. </span><span style="font-size: small;">The new transmission was presumably needed because the original transmission had insufficient safety margins for an engine with the power of the V-92S2F, and the gearing ratios also had to be different to allow a higher top speed to be achieved with the new engine. The specific power of the V-92S2F engine is 950 hp/cu.m. </span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;">The desired combination of a flat torque curve at the low end, behind the point of peak torque, followed by a downward curve with a large gradient, is naturally provided by electric motors, but in the case of turbocharged engines, can be provided by a smaller and lighter turbocharger which is able to supply its rated boost at the low end of the torque curve. </span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;">For the V-92S2F, the torque at the rated power is 3,967 Nm. From this, it can be calculated that the engine flexibility coefficient (torque backup) is 1.14 (14%). This is only a small improvement over the V-84 and V-46, and still does not reach the same level as the MB 873 Ka-501.</span></div>
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<span style="font-weight: normal;"><span style="font-size: small;">Variants of the T-72 outfitted with the V-92S2F can be identified by the heavily modified exhaust unit, now much narrower but taller, and with different cooling fins. A new exhaust unit was needed because of the new narrower exhaust duct that combined the exhaust flow from the turbocharger. It appears that two variations of this exhaust unit exist. The T-72B3 UBKh uses a different exhaust than other tanks using the same engine.</span></span></div>
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<a href="https://3.bp.blogspot.com/-EMnmdsRQdQk/XANND84hd6I/AAAAAAAAMn0/5wL8Lv3toYkH2IAKx74BFJ_yXhFtU3EiQCLcBGAs/s1600/T-72B3mod2016-102.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="266" src="https://3.bp.blogspot.com/-EMnmdsRQdQk/XANND84hd6I/AAAAAAAAMn0/5wL8Lv3toYkH2IAKx74BFJ_yXhFtU3EiQCLcBGAs/s400/T-72B3mod2016-102.jpg" width="400" /></a><a href="http://3.bp.blogspot.com/-XU6DDUs8bkk/VTfYcWXoDJI/AAAAAAAACCM/9U2W8-tcV1E/s1600/t-90_i11.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://2.bp.blogspot.com/-WHNbHEL1OpU/VTfYe2PK0eI/AAAAAAAACCU/3cJLC65za3w/s1600/t-90_075_of_261.jpg" width="400" /></a></div>
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<span style="font-size: small; font-weight: normal;">With the cooling fins and muffler removed, the exhaust duct itself is just a simple metal duct.</span><br />
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<span style="font-size: small; font-weight: normal;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-dwWzl1YyJoE/WeXr08FolfI/AAAAAAAAJ20/qgSdKFD9nX4X6YORj04Fbu6-SC_C6URBwCLcBGAs/s1600/exhaust%2Bduct.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="525" data-original-width="700" height="240" src="https://3.bp.blogspot.com/-dwWzl1YyJoE/WeXr08FolfI/AAAAAAAAJ20/qgSdKFD9nX4X6YORj04Fbu6-SC_C6URBwCLcBGAs/s320/exhaust%2Bduct.jpg" width="320" /></a><a href="https://4.bp.blogspot.com/-8Zv7OGaiEQo/WeXr3g7KfvI/AAAAAAAAJ24/NYkeYE5h8HcvS9ul6U-zDs0HieC9NM1IQCLcBGAs/s1600/exhaust%2Bduct%2Bsmokey.jpg" style="font-size: 21.9024px; margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="525" data-original-width="700" height="240" src="https://4.bp.blogspot.com/-8Zv7OGaiEQo/WeXr3g7KfvI/AAAAAAAAJ24/NYkeYE5h8HcvS9ul6U-zDs0HieC9NM1IQCLcBGAs/s320/exhaust%2Bduct%2Bsmokey.jpg" width="320" /></a></div>
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<span style="font-size: small; font-weight: normal;">The use of the V-92S2F on the T-72B3M and T-72B3 UBKh coupled with the new transmission boosts its top speed to a blistering 84 km/h on paved roads and allows it to cruise cross-country at a speed of up to 60 km/h on dirt roads. This elevates the tank's mobility to the level of the T-80BV in terms of speed, and gives it something close to parity when moving cross country thanks to the high torque backup.</span></div>
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<span style="font-size: small; font-weight: normal;"><br /></span><h3 style="text-align: left;"><span style="font-size: large;">ENGINE REMOVAL</span></h3></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">To prepare the engine for removal, it is necessary to remove the engine deck by unbolting it and then lifting it off the tank using a crane. From there, the air cleaner unit is removed, then the engine is disconnected from the cooling, lubrication and fuel systems. The engine is then disengaged from the intermediate power transfer gearbox ("<i>Гитара</i>") of the transmission. Following this, the engine is detached from its floor mount which requires the engine compartment firewall to be opened to access the front side of the mount. The engine can then be removed using the same light crane. </span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-L37GoouBboA/YQDhI6w2UDI/AAAAAAAAUDE/1OPFEq3ILusUxFODKBpi3Esc1-kaDVGTwCLcBGAsYHQ/s2048/removing%2Bengine.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1600" height="400" src="https://1.bp.blogspot.com/-L37GoouBboA/YQDhI6w2UDI/AAAAAAAAUDE/1OPFEq3ILusUxFODKBpi3Esc1-kaDVGTwCLcBGAsYHQ/w313-h400/removing%2Bengine.png" width="313" /></a></div><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">According to the book "<i>Основной боевой танк России. Откровенный разговор о проблемах танкостроения</i>" (<i>Main Battle Tanks of Russia. Frank Discussions on the Problems of Tank Building</i>) authored by E.B Vavilonskiy et al., the T-90S, which can be considered a surrogate of any T-72 due to the near-identical design of its powertrain, required a total of 8.5 hours to replace its engine (removal and reinstallment to running condition) during a 2006 demonstration in Saudi Arabia. </span></span><span style="font-size: small; font-weight: 400;">A well designed quick-replace powerpack is far quicker to replace, although they invariably require special resources such as a crane with a high load capacity, and in practice, an ARV like the Bergepanzer 2 is needed to carry out the task. The engine of the T-90S required 3.5 hours to 4.0 hours to remove and requires nothing more than a workhorse truck equipped with a light crane. The TRM-A-70 or TRM-80 mobile workshop based on the ZIL-131 truck was widely used in this role, since it had a boom crane with a capacity of 1.5 tons. ARVs like the BREM-1 are practically never needed to carry out powertrain field repairs, and are instead used much more often for tank recovery in danger zones, which is the primary role of ARVs.</span></div><div><span style="font-size: small;"><span style="font-weight: 400;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: 400;">The average time needed to replace all units installed in the engine compartment is unclear, but it has sometimes been quoted as 3 days. For comparison, the M60A1 needed just 4 hours to have its powerpack replaced. Compared to the Leopard 1 and Leopard 2, the time needed to replace the engine and transmission of a T-72 is is exceptionally long as these two German tanks require only around 35 minutes or less. Well-trained maintenance teams can even replace the powerpack of a Leopard 2 in less than 20 minutes in ideal conditions. The caveat to this is that this restricts all powerpack repairs to be done exclusively by an ARV, as there is no way to access the powerpack components without removing it from the tank, and the only crane with the required load capacity is found on ARVs. It also means that the failure of minor powertrain accessories cannot be solved in the field by the crew, but must involve an ARV and the atention of the maintenance unit personnel. This is the most common form of breakdown, as opposed to a critical engine malfunction or the malfunction of some other major powertrain component, which cannot be repaired rapidly in the field without needing to dispatch a repair team from the maintenance unit. Overall, in practice, the speed advantage of tanks with quickly replaceable powerpacks exists, but is a nuanced compromise.</span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">
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<span style="font-size: x-small;"><span style="font-size: large;"><b>COOLING SYSTEM</b></span></span></h3>
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<span style="font-size: small;"><span style="font-weight: normal;"><div>The cooling system is a closed-circuit, liquid cooling system with forced circulation of the coolant. It has a capacity of 90 liters. The cooling system, depicted in the drawing above, is comprised of a cooling fan, a coolant reservoir, an expansion tank, a water radiator and the radiator water pump. The engine preheater is linked to the cooling circuit. The pump is mounted on the engine itself. The cooling system operates within a moderate temperature range, with a normal (reecommended) coolant temperature of 70-100°C when running on diesel, naphta and kerosene, or 80-100°C when running on gasoline.. The maximum permissible operating temperature is 115°C. When antifreeze is added for cold weather operations, the normal coolant temperature range is 70-90°C when running on diesel, naphta and kerosene, or 80-90°C when running on gasoline. With antifreeze, the maximum operating temperature is 95°C, but driving with a coolant temperature of 105°C is permitted for short periods. The minimum coolant temperature in all cases is 65°C. </div><div><br /></div><div>Coolant temperatures are sensed by either a critical temperature sensor with a response threshold of 112-118°C, which is used when the tank is operating in conditions of +5°C and above, or another critical temperature sensor with a response threshold of 104-109°C, to be used at temperatures lower than +5°C. The sensors are connected to warning lamps on the PV-82 control panel, located in the driver's station. However, it is important to note that the cooling system is not automatically regulated, and the PV-82 control panel is not capable of initiating an automatic engine shutdown if the critical temperatures are exceeded. Corrective actions must be carried out with the personal intervention of the driver. </div><div><br /></div><div>The coolant capacity of 90 liters is only a small increase over the 77-liter capacity of the T-62 cooling system and the 80-liter capacity of the T-55 cooling system, both of which coped with the lighter thermal load of the less powerful V-55 engine. Though the slightly larger capacity is beneficial to the extent that it constitutes additional thermal mass to contain more heat energy and thus regulate the rise in temperature, the cooling system of the T-72 was not a direct copy of the existing designs, instead featuring a number of design changes. The much larger amount of waste heat produced by the engine was handled by the higher efficiency of the cooling fan, a redesigned radiator inlet with no bypass vent to supply air to the engine, and the larger surface area of the radiator packs, made possible by the wider hull of the T-72 compared to preceding medium tanks.</div></span></span>
<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span><span style="font-size: small;"><span style="font-weight: normal;">Water is pumped around the engine and pumped up to the dual radiator packs where it is cooled. Inside the dual-pass radiator packs, water flows in winding aluminium tubes with cooling fins and heat is removed by air sucked in by an engine-driven centrifugal fan at the rear of the engine compartment. Internal turbulators increase the efficiency of heat transfer by inducing turbulence in the flowing water. </span></span><span style="font-size: small;">At ambient temperatures of +5°C and above, the coolant is water with a three-component anticorrosion additive. Although pure water has a higher heat transfer rate and performs better as a heat transfer fluid, pure water poses the threat of serious long-term corrosion for aluminium engines, and on top of this, the vast majority of accessible water sources contain minerals which can lead to scale formation in the cooling pipework, so the use of an anticorrosion additive or antifreeze is mandatory. Between -35°C to +5°C, grade 40 antifreeze is added to the coolant. At temperatures below -35°C, grade 65 antifreeze is used.</span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: 400;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: 400;">Engine oil is also cooled with two similar single-pass radiator packs installed above the water radiators.</span><span style="font-size: small; font-weight: normal;"> The waste heat extracted from the radiator by the air is pulled into the radiator fan and ejected out of the radiator fan outlet at the rear of the hull in an upward direction. Because the radiator pack is located directly beneath the intake grilles, the inlet air temperature for the radiator is exactly equal to the ambient air temperature. Heating of the inlet air, which reduces the heat transfer efficiency, does not occur. Within the airflow path of the cooling system, shown below, the only potential cause for increased inlet temperature is the recirculation of the hot air exiting upwards through the air outlet. When the tank is driven forwards, the formation of a turbulent wake behind the turret, directly over the engine deck, has the potential to circulate the heated air from the cooling fan outlet back towards the radiator inlet. This was mainly addressed by the sloped design of the hull rear and the slanted positioning of the cooling fan, which allows it to blow the waste air to the rear at a 30-degree angle, the same angle as the slope of the rear armour plate. This is in contrast to the T-54/55 and T-62, which had vertically mounted fans that relied on curved outlet vanes to direct the outflow of hot air slightly rearward, though the air stream was still predominantly in an upward direction due to the shape of the duct.</span></div>
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<a href="http://4.bp.blogspot.com/-OAn5k_gaf7c/VUP89O9QQWI/AAAAAAAACQI/CnE755YXySY/s1600/T-72%2Bcooling%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="360" src="https://4.bp.blogspot.com/-OAn5k_gaf7c/VUP89O9QQWI/AAAAAAAACQI/CnE755YXySY/s1600/T-72%2Bcooling%2Bsystem.png" width="640" /></a></div>
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<span style="font-size: small;"><span><div><span style="font-weight: 400;">The rotational speed of the fan is determined by the gearing system in the intermediate power transfer gearbox connecting the fan drive to the engine. As engine speed increases, the rotational speed of the fan increases proportionately. The gearbox for the cooling fan can be adjusted only by moving a selector on the intermediate gearbox manually, after lifting open the radiators. The fan drive has three positions: neutral, low and high. The gear ratios for the fan provided by the intermediate power transfer gearbox are 0.647 (high gear) and 0.773 (low gear). For the most part, the choice of the fan speed is tied to the region and season. The fan is set to the "low" mode as the standard setting for most situations, but the driver can switch to the "high" mode if the ambient temperature is higher than 25°C or if the temperature of the coolant and engine oil is observed to be above the critical temperature during operation. For example, during summer, a driver could set the fan to run on "high" and leave it for the entire season, unless he notices that the coolant temperature is excessively low during routine driving. The fan drive must not be left on neutral if the tank is driven. According to <a href="https://findpatent.ru/patent/219/2199017.html">Russian patent No. 2199017</a>, the power consumption of the cooling fan consumption is 29 kW (38.9 hp) in the "low" mode and 50 kW (67 hp) in the "high" mode. In the "low" mode, the power consumption of the fan is 4.9% of the gross engine power. In the "high" mode, it is 8.6%. Due to the fact that the fan speed is tied to engine speed, these figures represent the maximum power consumption.</span></div><div><span style="font-weight: 400;"><br /></span></div><div><span style="font-weight: 400;">In order to prevent the fan speed from changing abruptly with an abrupt change in engine speed, which could cause damage to the fan, the fan drive is connected to the intermediate power transfer gearbox via a clutch, which transmits a torque of 18-50 kgf (176-490 N). A sudden change in engine speed would cause the clutch disc to slip until the fan speed has equalized with the engine speed, thus ensuring that the light aluminium structure of the fan does not deform under the torque overload. </span></div><div><span style="font-weight: 400;"><br /></span></div><div><span style="font-weight: 400;">Aside from the mechanical fan drive, the intensity of the airflow is also regulated by the position of the fan outlet vanes, which is mechanically controlled by the driver via a selector with a pushrod mechanism. The driver can select between six positions, from fully open, where the vanes are completely parallel to the outlet duct, to fully closed. </span></div><div><span style="font-weight: 400;"><br /></span></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9dCd5l_QoZ8/YUvgyRj_G5I/AAAAAAAAUOY/gBmbbM_bHaUKXLJGhq3NPbszNwVhOyT8ACLcBGAsYHQ/s2048/cooling%2Bfan%2Boutlet%2Bflap%2Bcontrol.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1337" data-original-width="2048" height="418" src="https://1.bp.blogspot.com/-9dCd5l_QoZ8/YUvgyRj_G5I/AAAAAAAAUOY/gBmbbM_bHaUKXLJGhq3NPbszNwVhOyT8ACLcBGAsYHQ/w640-h418/cooling%2Bfan%2Boutlet%2Bflap%2Bcontrol.png" width="640" /></a></div><span style="font-weight: 400;"><br /></span></div><div><span style="font-weight: 400;"><br /></span></div><div><span style="font-weight: 400;">However, the lack of an automatic coolant temperature regulation system limits the efficiency of the cooling system and limits the potential lifespan of the engine in practice. Beginning with the V-92S2F engine, which can be found in the latest versions of the T-72B3 tank, a built-in detuning mechanism is installed. It automatically limits the power output when the engine temperature becomes excessive. This limits the potential for damage from engine overheating if the driver fails to take corrective actions when warned by the temperature sensors. </span></div></span></span>
<span style="font-size: small; font-weight: normal;"><span style="font-weight: normal;"><br />Due to the short path between the radiator pack and the cooling fan, aided by the slanted positioning of the cooling fan, the heating of the other units in the engine compartment by the hot air from the radiator is minimalized, while the open airflow within the compartment promotes the cooling of the transmission and especially the brakes, which are located inside the side gearboxes.<br /><br /></span></span>
<span style="font-size: small; font-weight: normal;"><span style="font-weight: normal;">The oil radiator is shown in the drawing below on the left, and the water radiator is shown on the right. Both radiators are coupled together to form the radiator pack.</span></span></div>
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<a href="https://3.bp.blogspot.com/-M6c29fr8zks/XBUJFUVI4vI/AAAAAAAAMrA/Ksnv4HB7fXISUMfGjDJl63K8kHPmnRweACLcBGAs/s1600/oil%2Bradiator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="980" data-original-width="1600" height="245" src="https://3.bp.blogspot.com/-M6c29fr8zks/XBUJFUVI4vI/AAAAAAAAMrA/Ksnv4HB7fXISUMfGjDJl63K8kHPmnRweACLcBGAs/s400/oil%2Bradiator.png" width="400" /></a><a href="https://3.bp.blogspot.com/-L-PHxBsQ3Xw/XBUIh7p_L6I/AAAAAAAAMq4/mfABI0N4ImQ8khuFgX57Na7i2qDM3kHNACLcBGAs/s1600/water%2Bradiator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="949" data-original-width="1600" height="235" src="https://3.bp.blogspot.com/-L-PHxBsQ3Xw/XBUIh7p_L6I/AAAAAAAAMq4/mfABI0N4ImQ8khuFgX57Na7i2qDM3kHNACLcBGAs/s400/water%2Bradiator.png" width="400" /></a></div>
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<span style="font-size: small;"><span style="font-weight: normal;">This cooling system was previously used in the same configuration on the T-54 and T-62 and was proven to be sound by over two decades of use, experimentation and refinement by the time the T-72 entered service. One drawback is that dust particles kicked up into the air from driving at high speed may be sucked up by the high velocity air stream from the cooling fan, creating a distinctive "rooster tail" dust cloud behind the tank. </span></span><span style="font-size: small;"><span style="font-weight: normal;">The radiator pack, opened for access to the engine compartment, is shown in the two photos below.</span></span></div>
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<a href="https://4.bp.blogspot.com/-DX2LvUx74HI/WXJfYIBFe0I/AAAAAAAAIxs/s2fab57r_eQ8QXhzo7xIMeTyXvja8HyMgCLcBGAs/s1600/radiator%2Bpack.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="372" data-original-width="539" height="276" src="https://4.bp.blogspot.com/-DX2LvUx74HI/WXJfYIBFe0I/AAAAAAAAIxs/s2fab57r_eQ8QXhzo7xIMeTyXvja8HyMgCLcBGAs/w400-h276/radiator%2Bpack.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-ynwsYDAenVc/YBPZELliiTI/AAAAAAAASq0/Zu0TBXSohlIb9wK_60pWo_cvAeoFIZZ0ACLcBGAsYHQ/s2048/t-72%2Bmaintenance%2Bat%2Bacademy.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1965" data-original-width="2048" src="https://1.bp.blogspot.com/-ynwsYDAenVc/YBPZELliiTI/AAAAAAAASq0/Zu0TBXSohlIb9wK_60pWo_cvAeoFIZZ0ACLcBGAsYHQ/s320/t-72%2Bmaintenance%2Bat%2Bacademy.png" width="320" /></a><br /></div>
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<span style="font-size: small;"><span style="font-weight: normal;">Reports indicate that t</span></span><span style="font-size: small; font-weight: normal;">his system may be somewhat limited in extreme hot weather and only sufficient for European summers. The cooling system is designed for maximum cooling efficiency at an ambient temperature of up to 25</span><span style="font-size: small;"><span style="font-weight: normal;">°C, as higher temperatures increase the load on the system, meaning that the cooling fan requires a larger share of engine power. The normal operating range is defined as 5-25°C, within which the cooling fan is set to the "slow" mode unless the coolant and oil temperature reach the critical threshold when driving. At an ambient temperature of 25°C,</span></span><span style="font-size: small; font-weight: 400;"> the engine is expected to work with no loss in power,</span><span style="font-size: small;"><span style="font-weight: normal;"> but it will begin to experience marginal reductions in performance at higher temperatures. </span></span><span style="font-size: small; font-weight: normal;">Overheating becomes a major issue in ambient temperatures of up to 50</span><span style="font-size: small;"><span style="font-weight: normal;">° C, which is sometimes recorded at the Thar desert in India. At temperatures of 45° C and above, the engine will experience a steep reduction in power (up to 33% loss). At such temperatures, the tank must be stopped every 25 kilometers to allow the engine to cool to prevent excessive fatigue. <br />
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<span style="font-size: small; font-weight: normal;">According to the report "<a href="http://btvt.info/5library/vbtt_1985_02_poteri.htm"><i>Пути Снижения Затрат Мощности В Системах Танкового Дизеля</i></a>" ("<i>Ways to Reduce The Power Costs in Tank Diesel Systems</i>") by S.P Baranov and V.T Nikitin, the power consumption of the cooling system of the T-72 is 7.7% when the ambient temperature is higher than the typical operating range of 4</span></span></span><span style="font-size: small; font-weight: 400;">°C</span><span style="font-size: small; font-weight: normal;"> to 30°C. However, when the system is running within the operating temperature range, the power consumption is only 4.9% which is less than the ejection-type cooling system of the T-64A. This is consistent with the known power consumption of the cooling fan. Even when operating above optimal temperatures, the cooling system of the T-72 is more efficient than the fan-type cooling systems of foreign tanks like the M60A1, Leopard 1 and Leopard 2 which consume 14.4%, 14.7% and 14.5% of engine power respectively.</span></div>
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<span style="font-size: small;">In total, the net engine power of the V-46 is 11.5% lower than the gross engine power after adding up the costs of the ambient heating of the inducted air. the air cleaning system, and the cooling system. Aside from that, it is stated in the book "</span><i style="font-size: medium;">Основной боевой танк России: Откровенный разговор о проблемах танкостроения</i><span style="font-size: small;">" (</span><i style="font-size: medium;">Russian main battle tank: A frank conversation about the problems of tank building</i><span style="font-size: small;">) that the net engine power of the V-84 is about 11% lower than its gross power (840 hp). In cold weather, the net engine power can be higher due to the higher density of cold air but it could also be somewhat less, as the air intake heater may be used when running the engine at temperatures from 0 to -20°C. The rarefaction of the air reduces the oxygen density in the air delivered to the combustion chamber, and the power of the engine worsens as a result, but the combustion efficiency of the engine is maintained. If fuel efficiency is less of a concern, intake heating can be ignored.</span><br />
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<span style="font-size: small; font-weight: normal;">Apparently, the V-92 engine series and its accompanying modifications have partially solved the overheating issue at very high ambient temperatures. Specific details are not known to the author, but it could only either be an increase in the power of the centrifugal fan, or a simple modification of the water flow channels in the radiator, as Indian T-90S tanks apparently have.</span><br />
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<span style="font-size: small;"><span style="font-weight: normal;">The photos below show the r</span></span><span style="font-size: small;"><span style="font-weight: 400;">adiator covers opened and closed, exposing the protective louvers within.</span></span><br />
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<span style="font-size: small;"><span style="font-weight: normal;"><a href="http://3.bp.blogspot.com/-YcV4wN96wyY/VUP-eL9t7dI/AAAAAAAACQU/tMorR6tR1us/s1600/t-72_int_28_of_32.JPG"><img border="0" height="400" src="https://3.bp.blogspot.com/-YcV4wN96wyY/VUP-eL9t7dI/AAAAAAAACQU/tMorR6tR1us/s400/t-72_int_28_of_32.JPG" width="300" /></a><a href="http://1.bp.blogspot.com/-_uzcYeUI5OI/VSETJgKV22I/AAAAAAAABpI/0FyIwMbGaLM/s1600/t-72%2Bradiator.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://1.bp.blogspot.com/-_uzcYeUI5OI/VSETJgKV22I/AAAAAAAABpI/0FyIwMbGaLM/s1600/t-72%2Bradiator.jpg" width="300" /></a></span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;"><span style="font-size: small; font-weight: 400;">The photo</span><span style="font-size: small; font-weight: 400;"> below shows the engine compartment with cooling pack and engine access panel removed. </span></span></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;"><a href="http://2.bp.blogspot.com/-1pQtHmRIUN4/VUPJdRPYWlI/AAAAAAAACOI/tHUTnDskHZc/s1600/motor_t-72m.jpg"><img border="0" height="300" src="https://2.bp.blogspot.com/-1pQtHmRIUN4/VUPJdRPYWlI/AAAAAAAACOI/tHUTnDskHZc/s400/motor_t-72m.jpg" width="400" /></a></span></span></div>
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<span style="font-weight: normal;"><span style="font-size: small;"><br /></span></span><span style="font-size: small;"><span style="font-weight: normal;">Note the crossbar to hinge both of the aforementioned accessories. Also note the centrifugal fan at the bottom left corner. It is a riveted aluminium fan with a diameter of 655mm and a width of 205mm, with twenty evenly spaced vanes. It is powered by a driveshaft connected to the gearbox so that it increases or decreases its power in accordance with the engine's mechanical output, thus adjusting for the engine's heat output as well. It is strong enough to throw water out of the engine compartment like a blowhole even while the engine is idling. The use of a mechanical power shaft to transmit power, unlike fan belts as used in some other tanks, eliminates the issue of fan belts snapping under the high stress of driving such a fan.</span></span><br />
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<a href="http://4.bp.blogspot.com/-e_ypsp3s064/VUPcGOPN1-I/AAAAAAAACOw/szmaWSTT21o/s1600/t-72.26363.jpg"><img border="0" height="252" src="https://4.bp.blogspot.com/-e_ypsp3s064/VUPcGOPN1-I/AAAAAAAACOw/szmaWSTT21o/s1600/t-72.26363.jpg" width="400" /></a><a href="https://4.bp.blogspot.com/-MLJh6YwyoyU/XDfunff1myI/AAAAAAAAM3U/IyT_ZPvvjgofiAMLESwu2wG4ZJ2JsEQ2ACLcBGAs/s1600/tumblr_nxaxoxhEFN1rqpszmo4_1280.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="857" data-original-width="1280" height="267" src="https://4.bp.blogspot.com/-MLJh6YwyoyU/XDfunff1myI/AAAAAAAAM3U/IyT_ZPvvjgofiAMLESwu2wG4ZJ2JsEQ2ACLcBGAs/s400/tumblr_nxaxoxhEFN1rqpszmo4_1280.jpg" width="400" /></a></div>
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<span style="font-size: small;"><span style="font-weight: normal;">The use of a centrifugal cooling fan is one of the many conservative design features of the T-72, and in fact, the entire cooling system is fundamentally the same as the design used in the T-54. However, that does not mean that it was no longer viable by the 70's, as the design could still meet the cooling requirements of the V-46 engine in most weather conditions due to design refinements while remaining relatively compact, easy to maintain, and reasonably protected, although there are still a few drawbacks. </span></span></div><div style="font-weight: normal; text-align: left;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal; text-align: left;"><span style="font-size: small;"><span style="font-weight: normal;">By placing the radiator on the engine deck and exposing a large surface area, it becomes more vulnerable to napalm attacks or molotov cocktails, as the cooling fan creates a suction force that can suck in burning gels and liquids through the radiator louvers. This is only marginally compensated by the presence of <a href="https://photos.smugmug.com/Military/T-72B3-walkaround/i-FWzfZ6n/0/492b3400/XL/T-72B3walkaround-74-XL.jpg">optional watertight covers</a>. Keeping these watertight covers shut and configuring the tank to draw air through the fighting compartment prevents the ingress of burning liquids at the cost of accelerating the overheating of the engine. </span></span>The cooling fan itself is well protected, since it is too small to be hit by aerial weapons and it can eject any burning liquid thrown inside it. </div><div style="font-weight: normal; text-align: left;"><br /></div><div style="font-weight: normal; text-align: left;">By contrast, the cooling system of the Leopard 1 may offer better protection against incendiary attack as only the cooling fan is exposed on the engine deck whereas the radiators are not, but the radiators are on the sides of the hull, making them more vulnerable to heavy machine gun fire and artillery shell splinters. The cooling fan itself is barely protected from ballistic attack, but does not need to be, since there is no coolant to leak and it may still function with minor damage.</div><div style="font-weight: normal; text-align: left;">
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<span style="font-size: small;"><span style="font-weight: normal;">In the event of damage from an air attack, maintaining or replacing the radiator is quite simple, since the entire unit can be hinged open. The radiator can be disconnected from the coolant pump quite easily, as the two components are only connected by inflow and outflow hoses.</span></span><br />
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<a href="http://2.bp.blogspot.com/-OKwbmMBu650/VUPWMJHc42I/AAAAAAAACOg/c-B52uWEkCc/s1600/t-72%2Breference-interior%2Bengine%2Bdetails-3-ps.jpg"><img border="0" height="354" src="https://2.bp.blogspot.com/-OKwbmMBu650/VUPWMJHc42I/AAAAAAAACOg/c-B52uWEkCc/s1600/t-72%2Breference-interior%2Bengine%2Bdetails-3-ps.jpg" width="640" /></a></div>
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<span style="font-size: small;"><span style="font-weight: normal;">The louvers that protect the radiator and cooling fan outlet can be shut or opened by turning a lever from the driver's station. Closing these louvers provide additional protection from aerial attack and napalm or makeshift weapons such as Molotov Cocktails.</span></span></div>
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<a href="https://1.bp.blogspot.com/-IugKNCOxdkA/WolOvc9HoCI/AAAAAAAAK6w/3Es8uTsqCiMaq1pNsgvwuVQoBXlopNRZwCLcBGAs/s1600/t-72%2Bengine%2Bdeck.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://1.bp.blogspot.com/-IugKNCOxdkA/WolOvc9HoCI/AAAAAAAAK6w/3Es8uTsqCiMaq1pNsgvwuVQoBXlopNRZwCLcBGAs/s400/t-72%2Bengine%2Bdeck.jpg" width="400" /></a><a href="http://1.bp.blogspot.com/-E4PCr9lX2s4/Vdw0myBK62I/AAAAAAAADNo/cYoPsYGBoR0/s1600/t-72%2Bengine%2Bpanel%2Barmour.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="317" src="https://1.bp.blogspot.com/-E4PCr9lX2s4/Vdw0myBK62I/AAAAAAAADNo/cYoPsYGBoR0/s400/t-72%2Bengine%2Bpanel%2Barmour.png" width="400" /></a></div>
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<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span><span style="font-size: small;"><span style="font-weight: normal;">The photo above shows the engine access panel and armoured cover hinged open. The radiator pack cover panel is stowed on top of the engine access panel when not in use. It may help increase the level of protection by acting as rudimentary spaced armour, although it is not particularly thick.</span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;">
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<h3 style="font-weight: normal;">
<span style="font-size: x-small;"><span style="font-size: large;"><b>TRANSMISSION</b></span></span></h3>
<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-vA_U_3tIGXo/X03cuNLt0BI/AAAAAAAARiE/HJO5KBfZZmQnrE5sxPhy8kpb6Hj-yvg6QCLcBGAsYHQ/s1232/drivetrain.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="687" data-original-width="1232" src="https://1.bp.blogspot.com/-vA_U_3tIGXo/X03cuNLt0BI/AAAAAAAARiE/HJO5KBfZZmQnrE5sxPhy8kpb6Hj-yvg6QCLcBGAsYHQ/s640/drivetrain.png" width="640" /></a></div><div class="separator" style="clear: both; font-weight: normal; text-align: center;"><br /></div><div style="font-weight: normal;">
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<span style="font-size: small;"><span style="font-weight: normal;">The T-72 transmission consists of dual planetary gearboxes with integrated final drives, a type of transmission that is sometimes referred to as a geared dual transmission system, but more generically known as a transmission with side gearboxes, or BKPs. The two gearboxes are connected by a driveshaft which transmits power from the engine via the </span></span>intermediate power transfer gearbox ("<i>Гитара</i>"), marked (5) in the drawing above. The transmission does not have a main clutch. This type of transmission was originally developed for the Object 430 by the Malyshev design bureau in Kharkov. The use of BKPs in the T-72 was for the unification of transmissions with the T-64, not only on the industrial level but also in terms of supply and institutional familiarity. A mechanic trained on T-64s would have been able to service the BKPs on a T-72, and the BKPs in T-72s were interchangeable with those in a T-64, simplifying logistics. Direct interchangeability was possible even though the 5TD series engines used in the T-64 ran at a rated speed of 2,800 RPM whereas the V-46 engine in the T-72 ran at a rated speed of 2,000 RPM, because the intermediate power transfer gearbox in the T-72 geared down the output speed by a factor of 0.706, raising the input speed at the BKPs to 2,832 RPM - equal to the rated speed of the 5TDF. The chosen ratio of 0.706 is slightly higher than the 0.7 gear ratio of the intermediate power transfer gearbox of the T-54, T-55 and T-62.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><span style="font-size: small;"><br /></span></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><span style="font-size: small;"><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-xZ3hcmu30yI/XBa2_Dp-LCI/AAAAAAAAMrU/OTNw-H1UWVcIjWu9aZLpytWsQaxVdh7GACLcBGAs/s1600/transmission.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="422" data-original-width="500" height="270" src="https://2.bp.blogspot.com/-xZ3hcmu30yI/XBa2_Dp-LCI/AAAAAAAAMrU/OTNw-H1UWVcIjWu9aZLpytWsQaxVdh7GACLcBGAs/s320/transmission.jpg" width="320" /></a><a href="https://3.bp.blogspot.com/-EtRxe3ACkOw/XBa2_SDTrfI/AAAAAAAAMrY/kes0Ug7M61Aw-hsxb17AC1B5cRy85Zh3QCLcBGAs/s1600/trans.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="453" data-original-width="500" height="270" src="https://3.bp.blogspot.com/-EtRxe3ACkOw/XBa2_SDTrfI/AAAAAAAAMrY/kes0Ug7M61Aw-hsxb17AC1B5cRy85Zh3QCLcBGAs/s320/trans.jpg" width="320" /></a></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-fJw6Z5vH8fY/XlZZlfKeeEI/AAAAAAAAQHE/jzjPNXNrzgUvb8OSR6HP9wE7puL1-KuQQCLcBGAsYHQ/s1600/transmission%2Bleft%2Bgroup.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1179" data-original-width="1600" height="235" src="https://1.bp.blogspot.com/-fJw6Z5vH8fY/XlZZlfKeeEI/AAAAAAAAQHE/jzjPNXNrzgUvb8OSR6HP9wE7puL1-KuQQCLcBGAsYHQ/s320/transmission%2Bleft%2Bgroup.png" width="320" /></a><a href="https://1.bp.blogspot.com/-L20GPTsaKIA/XlZZlDeJVlI/AAAAAAAAQHA/jNn7FvTTvOorfkyBCovHHkzm8kUXXKmUACLcBGAsYHQ/s1600/transmission%2Bright%2Bgroup.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1179" data-original-width="1600" height="235" src="https://1.bp.blogspot.com/-L20GPTsaKIA/XlZZlDeJVlI/AAAAAAAAQHA/jNn7FvTTvOorfkyBCovHHkzm8kUXXKmUACLcBGAsYHQ/s320/transmission%2Bright%2Bgroup.png" width="320" /></a></div><div><br /></div><span style="font-size: small;"></span></div></span></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;">This type of transmission is extremely compact, extremely durable, extremely reliable, and has a very high mechanical efficiency due to its kinematic simplicity. Alone, the left gearbox weighs 710 kg, the right gearbox weighs 700 kg, and the intermediate power transfer gearbox located between the engine and the gearboxes weighs 320 kg.</span></span><span style="font-size: small;"><span style="font-weight: normal;"> The </span></span>intermediate power transfer gearbox is shown below. The mechanism acts as a step-up gear between the engine and the BKPs, with a ratio of 0.706. It also provides a power takeoff for the AK-150SV air compressor, SG-10-1S starter-generator and the cooling fan. The gear ratio to the fluid coupling of the starter-generator is 0.693. The gear ratio to the air compressor is 0.934. </div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DTGAwuoT9NY/X03dqfeQZQI/AAAAAAAARiM/IR_Ty1oew5IW7-n4ucHwCwUsiaZ2CmoogCLcBGAsYHQ/s1023/gitara.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="718" data-original-width="1023" height="281" src="https://1.bp.blogspot.com/-DTGAwuoT9NY/X03dqfeQZQI/AAAAAAAARiM/IR_Ty1oew5IW7-n4ucHwCwUsiaZ2CmoogCLcBGAsYHQ/w400-h281/gitara.png" width="400" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The service life of the intermediate power transfer gearbox was 11,100 km, while the side gearboxes and the final drives had a service life of 10,800 km. Service life is defined as the 90% exhaustion of the total life of the unit. The long service life of these units ensured that failures were rare and tank availability rates could be kept consistently high.</div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;">T</span>he weight of the transmission including the intermediate power transfer gearbox for the radiator fan, pumps, and the ST-10-1S starter-generator is 1,635 kg. The total weight of the transmission assembly with all accessories, including the hydraulic control system and the lubrication system is 1,870 kg. The image below shows the hydraulic control system and the lubrication system, excluding the oil radiator. The hydraulic servo units on top of the gearboxes are used to actuate the clutches.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Y7MWWvkrd6Y/X03unl76wlI/AAAAAAAARiU/PAVeMqm-MhwtiUqnuddzJWj9bCIrh_BaQCLcBGAsYHQ/s1022/hydraulic%2Bcontrol%2Band%2Blubrication%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="879" data-original-width="1022" height="344" src="https://1.bp.blogspot.com/-Y7MWWvkrd6Y/X03unl76wlI/AAAAAAAARiU/PAVeMqm-MhwtiUqnuddzJWj9bCIrh_BaQCLcBGAsYHQ/w400-h344/hydraulic%2Bcontrol%2Band%2Blubrication%2Bsystem.png" width="400" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The total volume occupied by the transmission assembly is 0.43 cubic meters and the volume occupied by each individual gearbox is 0.09 cubic meters. The side gearboxes only occupy approximately the same space as the epicyclic steering units in a T-54 and the gearbox connecting the two steering units in a T-54 are absent in a T-54, so the difference in the occupied volume is tremendous. It is several times less than double or triple differential transmissions used in foreign tanks while offering all of the same features except neutral steering. When installed inside the engine compartment, each BKP is seated in their proper position by a drum-shaped steel case, which also provides mechanical protection. Once removed from their mounts, the BKPs can be readily disassembled. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">According to technical reports from Sverdlovsk and Nizhny Tagil published in 1973-1974, the manufacture of the transmission of the T-72 requires 721 man-hours. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The gearboxes are each comprised of four planetary gear sets connected to two clutches and four braking clutches, or brakes. Each side gearbox has a range of 8 gears, 7 forward and 1 in reverse. The recommended engine speed range for shifting gears is 1,600-1,900 RPM. The gears are engaged by selectively applying a pair of clutches or brakes on sets of planetary gears, which produces the desired gearing ratio. In the gearbox, the clutches are wet multi-plate friction clutches that join two rotating assemblies together. The brakes are wet multi-plate friction disc brakes that stop a rotating assembly against the casing of the gearbox, which may be done to stop the ring gear of a planetary gear set to change its gear ratio. Fundamentally, the clutch and brake are essentially the same, only their purposes differ. Both use cermet discs on steel rotors (clutches) or stators (brakes). The plates are oil-cooled by a forced lubrication system, which lubricates and removes the heat generated by friction in both the multi-plate clutches and multi-disc brakes. The clutches and brakes are engaged hydraulically, with a hydraulic system that is pressurized via an engine power takeoff from the intermediate power transfer gearbox ("<i>Гитара</i>"). The gearshift mechanism is a rotary hydraulic valve key which changes the flow pathway of the hydraulic network. When a certain gear is selected, hydraulic pressure is routed to the power piston on the two corresponding clutches or brakes, engaging them and producing the desired gear ratio via the planetary gear sets. The hydraulic pressure on the other power pistons is zero. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">In 1st and reverse, the clutches and brakes are engaged at a pressure of 16.5-1.80 kgf/sq.cm. In the normal driving gears, which are the 2nd to 7th gears, the clutches and brakes are engaged at a pressure of 10-11.5 kgf/sq.cm. To prevent the clutch from slipping, stronger thrust is provided by the hydraulic clutch pack pistons, as, with a given coefficient of friction, the torque capacity of a friction clutch increases with the normal force pressing the clutch discs together. In ordinary cars with a dry clutch, the normal force is provided by the springs of the pressure plate, so the torque capacity is fixed. In the BKPs, this force is supplied by the hydraulic system with variable pressure, allowing variable torque capacities.</div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DBFIoQjSEag/X2YqXjRSAtI/AAAAAAAARnQ/mM0_ADingoMXu0UkUZ1rubUxZnIgFGBcACLcBGAsYHQ/s925/%25D0%25A2-72%2B26.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="612" data-original-width="925" height="423" src="https://1.bp.blogspot.com/-DBFIoQjSEag/X2YqXjRSAtI/AAAAAAAARnQ/mM0_ADingoMXu0UkUZ1rubUxZnIgFGBcACLcBGAsYHQ/w640-h423/%25D0%25A2-72%2B26.jpg" width="640" /></a></div><div style="font-weight: normal;"><br /></div><div>The effectiveness of such clutches and brakes is proportional to their diameter; in this case, just over 600mm. Larger discs are needed for multi-plate disc brakes and clutches for heavy vehicles and other high-torque industrial applications due to the higher braking torque afforded by large-diameter discs (due to the increased distance from the axle to the disc) and better heat dissipation.</div><div><div><br /></div><div>The clutch pedal in the driver's station is used to de-clutch both the gearboxes by de-clutching whatever clutches and brakes are currently engaged as the selected gear, and after the driver selects a new gear, releasing the clutch pedal will engage the clutches and brakes corresponding to the selected gear. The clutch mechanism is a hydraulic relay switch, functioning as a pressure release for the entire gearbox. Once the clutch pedal is fully depressed, hydraulic pressure in all clutches and brakes in the gearbox drop to zero, thus disconnecting the gearbox the from the power input shaft. Because the system is a relay for a powered hydraulic drive, the effort needed on the clutch pedal is minimal. The adjustable return spring of the clutch pedal control rod provides most of the resistance felt by the driver.</div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4-mOELHi2IE/YU780zJbqQI/AAAAAAAAUPs/fCUi18eSlPQQdj8XOIj0VDdsWTcmq76dgCLcBGAsYHQ/s1940/clutch%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1540" data-original-width="1940" height="318" src="https://1.bp.blogspot.com/-4-mOELHi2IE/YU780zJbqQI/AAAAAAAAUPs/fCUi18eSlPQQdj8XOIj0VDdsWTcmq76dgCLcBGAsYHQ/w400-h318/clutch%2Bmechanism.png" width="400" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The following table shows the various combinations of clutches and brakes used to actuate the side gearboxes. The clutches are identified as (Ф) and brakes are identified as (Т). For instance, the 1st gear is engaged by activating clutch No. 3 and brake No. 4. The 3rd gear is engaged by clutch No. 3 and brake No. 6. Not shown is the combination of brake No. 4 and brake No. 5, which engages the brake in the gearbox and brakes the track. Only brake No. 4 and No.5 have both a hydraulic power piston and a mechanical drive, allowing control by the gear shift, clutch pedal and steering levers, which are hydraulic, as well as the brake pedal mechanism, which is fully mechanical. All other clutches and brakes have only a hydraulic drive and are controlled by the gear shift, clutch pedal and steering levers exclusively. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-XTkR81asHW0/YUwuOjw3yDI/AAAAAAAAUOw/Gt8RnwAA3b8inywksfN_xiav_YwAHIdwQCLcBGAsYHQ/s602/clutches.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="349" data-original-width="602" height="233" src="https://1.bp.blogspot.com/-XTkR81asHW0/YUwuOjw3yDI/AAAAAAAAUOw/Gt8RnwAA3b8inywksfN_xiav_YwAHIdwQCLcBGAsYHQ/w400-h233/clutches.png" width="400" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The planetary gears engaged by the aforementioned clutches and brakes are shown below. Note that this table does not differentiate between the clutches and brakes, labelling all of them interchangeable as clutches. Also note that the 6th gear is incorrectly labeled as using only planetary gear IV. It should be II and IV. Moreover, the table does not mention that the planetary gear engaged in neutral is the IV gear.</div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-YTUpg4AYEuA/YUwv69RcolI/AAAAAAAAUO4/TeD-A245MtEpGWC5YkfYtqJwPQy3-nrPgCLcBGAsYHQ/s1215/planetary%2Bsets.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="626" data-original-width="1215" height="330" src="https://1.bp.blogspot.com/-YTUpg4AYEuA/YUwv69RcolI/AAAAAAAAUO4/TeD-A245MtEpGWC5YkfYtqJwPQy3-nrPgCLcBGAsYHQ/w640-h330/planetary%2Bsets.png" width="640" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">Normally, the tank is started on the 2nd gear unless the ground is particularly soft, in which case the tank starts on the 1st gear. Thanks to the large amount of torque available from the engine, the tank readily accelerates from a standstill in 2nd gear, as long as the tank is not on a steep slope or the ground is hard enough that it does not offer high resistance. Acceleration from a standstill is done like in any automobile with a manual transmission; according to the manual, bringing the tank into motion is done by releasing the clutch pedal and depressing the accelerator pedal simultaneously. As the engine idles at 800-900 RPM, its speed rises above 1,000 RPM very quickly and it should reach its operating speed of 1,300 RPM by the time the clutch pedal is fully released. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><div>According to the book "<i>Основной боевой танк России. Откровенный разговор о проблемах танкостроения</i>" (<i>Main Battle Tanks of Russia. Frank Discussions on the Problems of Tank Building</i>) authored by E.B Vavilonskiy et al., the powertrain components in the T-72 and T-90 family of tanks was laid out with the idea of providing the maximum possibility of replacing most of the defective components in the field to expedite repairs in the field without the participation of special tools or resources, which may be unavailable for a variety of reasons. </div><div><br /></div><div>Based on repair manuals for the T-72M and T-72B, it can also be concluded that the replacement and repair of components was designed to be achievable with minimal manpower in the repair team. Out of 149 replacement and repair operations, 81 can be done by 2 men and 66 can be done by a single man. Only a single operation requires 3 men, and only the replacement of the engine requires 4 men. Considering that the tank crew consists of 3 men, it can be seen that the operations on multiple components can be done in parallel on each tank, or individual operations can be done by a larger workforce very quickly. For labour-intensive procedures such as engine replacement, the crew assists the repair team assigned by the repair and maintenance battalion.</div></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9gLEmj0N5j0/YA5tD__t31I/AAAAAAAASmk/pUkInZuAvxEMElkq44_8oj3hbZl8I262ACLcBGAsYHQ/s2048/side%2Bgearbox%2Bunit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1536" data-original-width="2048" height="300" src="https://1.bp.blogspot.com/-9gLEmj0N5j0/YA5tD__t31I/AAAAAAAASmk/pUkInZuAvxEMElkq44_8oj3hbZl8I262ACLcBGAsYHQ/w400-h300/side%2Bgearbox%2Bunit.png" width="400" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div>The side gearboxes are coupled to the final drive as a single module. To replace these modules from a T-72, it is necessary to break track, remove the drive sprocket, open the radiator pack on its hinges to disconnect the oil lines, then unbolt the final drive housing from the side hull plate, and finally pull out the entire module with a crane. In field conditions, the crane would normally be provided by a TRM-A-70 or TRM-A-80 mobile workshop based on the ZIL-131 truck with a crane capacity of 1.5 tons. Conceptually, this process is similar to the transmission replacement process of an M4 Sherman, but much less laborious and much less demanding on the load capacity of the crane. The simplicity of the replacement process makes it expedient to swap out broken down transmissions in field conditions. For comparison, the work of removing and reinstalling the transmission unit on a Sherman required no less than 64 man-hours. The same work on the left and right BKP units require just 21 and 16 man-hours respectively, so it is generally quite quick and convenient to carry out parts replacement even at lower levels of organization.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-BZqp7C1TM-M/X2X-ihfmj1I/AAAAAAAARnA/DfUChSb4pu4pznHMwGDsp4YUgsJISpDrwCLcBGAsYHQ/s1920/gearbox.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://1.bp.blogspot.com/-BZqp7C1TM-M/X2X-ihfmj1I/AAAAAAAARnA/DfUChSb4pu4pznHMwGDsp4YUgsJISpDrwCLcBGAsYHQ/w400-h225/gearbox.png" width="400" /></a><a href="https://1.bp.blogspot.com/-6RdOc5iGZho/X2X-iTjp0wI/AAAAAAAARm8/cCrRWF1izdksP7nNXmxC6X14uke77IDjwCLcBGAsYHQ/s1920/removed.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://1.bp.blogspot.com/-6RdOc5iGZho/X2X-iTjp0wI/AAAAAAAARm8/cCrRWF1izdksP7nNXmxC6X14uke77IDjwCLcBGAsYHQ/w400-h225/removed.png" width="400" /></a></div><div><br /></div><div><br /></div>To replace the steering and brake unit on a T-54, T-55 or T-62, the process was vastly more laborious, though no special skills or tools were needed other than a crane. The crew would have to remove the radiator pack and the roof of the engine compartment, remove the cooling fan, disconnect the oil pipes, disconnect the control rods and disengage the clutches of the gearbox drives from the power transfer case and planetary steering unit. Then, the crew has to unbolt and pull out the gearbox itself, and disconnect the final drives from the steering and brake unit, after which the unit can finally be pulled out. Then the whole process would have to be repeated in reverse.</div><div><br /></div><div><br /></div><div><h3 style="text-align: left;"><span style="font-size: large;">STEERING SYSTEM</span></h3><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;">As with the geared steering system of the T-54 and T-62 transmissions, the BKPs of the T-72 allow the tank to be steered by slowing down one track, or by de-clutching one track, or by de-clutching one track and braking it. Clutch-brake steering is used only in 1st gear and reverse. Steering in higher gears is regenerative, as power is delivered to both tracks. As with rectilinear motion, the transmission has one degree of freedom when the tank is turning. Unlike the T-54, T-55 and T-62 transmission which only offers a single turning radius of 8.91 meters regardless of the selected gear (with the additional option of a clutch-brake turn with a radius of 2.64 meters), the T-72 transmission provides multiple turn radii, with each gear providing its own unique turn radius. This is because the transmission is a classical twin-transmission system, whereby each track is provided with its own gearbox, mechanically identical to the other. By shifting one gearbox to the next lower gear in sequence, the inner track is slowed down and a turn is obtained. By giving every two gears in sequence a different relative ratio, one unique turn radius is obtained in each gear. This enabled smoother and more precise steering without the reduced efficiency of other steering mechanisms.</span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;"><br /></span></div><div><span style="font-weight: normal;">For example, if the tank enters a left turn when traveling in 2nd gear, the left BKP is shifted to 1st gear while the right BKP remains in 2nd gear. The ratio of the 2nd gear to 1st gear (4.4 ÷ 8.173) is 0.538, and so the left track will turn at 0.538 times the speed of the right track, which is a large difference. A tight turn is thereby obtained. If the tank enters a left turn when traveling in 3rd gear, the left BKP is shifted to 2nd gear while the right BKP remains in 3rd gear. The ratio of the 3rd gear to 2nd gear (3.485 ÷ 4.4) is 0.792, and so the left track will turn at 0.792 times the speed of the right track. The speed difference is much smaller, and the turn radius is expanded accordingly. </span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;"><div><span style="font-size: x-small;"><span style="font-size: small;">A simple formula can be used to calculate the turn radii at each gear. The turn radius formula is as follows, where the gear ratio difference is obtained by subtracting </span></span>the current gear setting of the BKPs in rectilinear motion from the gear ratio of the next lower gear.</div><div><br /></div><div><span style="font-size: x-small;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-3YoQaOvEcuY/X2lYa1fTmUI/AAAAAAAARos/ZXK8Rx0HBUUISE66F3utgnbW3DWeWz6JQCLcBGAsYHQ/s2717/turn%2Bradius%2Bformula.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="665" data-original-width="2717" height="98" src="https://1.bp.blogspot.com/-3YoQaOvEcuY/X2lYa1fTmUI/AAAAAAAARos/ZXK8Rx0HBUUISE66F3utgnbW3DWeWz6JQCLcBGAsYHQ/w400-h98/turn%2Bradius%2Bformula.png" width="400" /></a></div><div><br /></div><span style="font-size: small;">So, for example, the turn radius of the tank in 2nd gear is 8.173 divided by 8.173 subtracted by 4.400, multiplied by 2.79 meters. The result is 6.04 meters. The turn radius of the tank in 7th gear is 1.467 divided by 1.467 subtracted by 1, multiplied by 2.79 meters. The result is 8.76 meters. It is worth noting that terrain has a major impact, as skidding influences the real turn radius. Although track skidding </span></span>(lateral slip of the tracks) <span style="font-size: x-small;"><span style="font-size: small;">inherently occurs with any steering mechanism that relies on generating a difference in the speeds of two laterally rigid tracks, and this form of steering is called skid-steering for this reason, skidding of the entire tank is undesirable for controllability and safety reasons. On dry soils, the actual obtainable turn radii closely correspond to the tabular values, but the actual turn radii tend to be somewhat larger when driving on other surfaces due to skidding, particularly at high speeds. Based on the reported performance of the T-64, the turn radius can be around 1.3-1.8 times higher than the values</span></span> on dry soils.</div></span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;"><br /></span></div><div><span style="font-size: small;"><br />
<table border="1" style="font-weight: normal;">
<tbody>
<tr>
<td style="text-align: center;"><b><span style="font-size: small;"> Gear </span></b></td><td style="text-align: center;"><b>Turn Radius (meters)</b></td>
</tr>
<tr>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">1</span></span></td>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">2.79</span></span></td>
</tr><tr>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">2</span></span></td>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">6.04</span></span></td>
</tr><tr>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">3</span></span></td>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">13.42</span></span></td>
</tr><tr>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">4</span></span></td>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">13.93</span></span></td>
</tr><tr>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">5</span></span></td>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">10.23</span></span></td>
</tr><tr>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">6</span></span></td>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">10.1</span></span></td>
</tr><tr>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">7</span></span></td>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">8.76</span></span></td>
</tr><tr>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">R</span></span></td>
<td style="text-align: center;"><span style="font-size: small;"><span style="font-weight: normal;">2.79</span></span></td>
</tr>
</tbody></table>
<br /><br /><div>It can be seen that the turn radius begins to tighten in 5th gear, which is counter-productive. It is desirable for a tracked vehicle to have progressively larger turn radii at higher speeds to allow effective steering without skidding and to facilitate gentler steering corrections, and in this regard, an unusual drawback of the BKP steering system is that the turn radius becomes progressively smaller beginning with the 5th gear owing to the decrease of the relative ratio between the 5th and 4th gears, 6th and 5th gears, and the 7th and 6th gears. This was due to the fact that the choice of gear ratios of the BKP transmission was primarily subordinated to ensuring high tractive properties in rectilinear motion, high acceleration by keeping the engine in its power band, and a high top speed, compromising the effectiveness of the turn radii at high speeds. Because of this, precise steering can become more difficult at higher speeds (30 km/h and above) and in conditions of low traction efficiency as an average driver cannot accurately predict how much the tank will skid when turning, and the tank tends to lose more speed with each turn.</div><br /><div><span style="font-size: small;">However, the negative impact of this aspect of the BKP is greatly lessed by the fact that, in all gear settings, the turn radius can be increased by only pulling the steering lever part way between the full forward and full back positions. </span>When the steering lever is initially pulled back from its full forward position, the hydraulic control system instantaneously drops the pressure in the clutches and brakes for the selected gear, disengaging it, while smoothly raising the pressure on the clutches for the lower gear, allowing it to slip. This is done by a modulating rotary spool valve which can vary the clutch pressure by controlling the inflow and outflow rates of the hydraulic fluid, thus controlling the rate of pressure rise from anywhere between a net zero change in pressure to a quick jump to 10-11.5 kgf/sq.cm, whereupon the clutches fully engage. In this way, the turn radius is controlled by hydraulic pressure on the clutch pistons, which in turn is controlled by the angle of the steering lever. The speed of the inner track during the turn will therefore not correspond to the speed in gear, but rather to an intermediate speed. At the same time this is occurring in the BKP of the inner track, the pressure in the clutches and brakes of the overtaking track is raised from 10-11.5 kgf/sq.cm to 16.5-18.0 kgf/sq.cm in a stepwise manner. This is because the regenerative action of the steering system recirculates power to the overtaking track in the form of torque (since the track speed is fixed), so the BKP of the overtaking track has its clutches and brakes engaged at a pressure equivalent to the 1st or reverse gears to prevent the clutches and brakes from slipping due to torque overload. </div><div><br /></div><div><span style="font-size: small;">When steering by clutch slip, the turn radius will therefore be variable between a minimum, which will be fixed turn radius of the selected gear gear settings, and no turn, which is rectilinear motion. Thus, the turn radius will range from the tabular values to infinity. For example, if the tank is moving in 5th gear and the driver turns right by jerking the right steering lever, the tank will enter a turn with a radius of 10.23 meters with minimal delay. If, however, the driver chooses any arbitrary lever position between full forward and full back, the tank can turn in a radius ranging from 10.23 meters to infinity. </span>Small and precise steering adjustments are done this way, and it is also less tiring as the levers are not repeatedly pulled back all the way. In high gears (5th to 7th), the low controllability of the tank when using the full minimum-radius turn makes it much more effective to steer within the intermediate range. </div><br /><div>The downside to utilizing the precision steering feature is that it has a relatively low mechanical efficiency; when a clutch slips, the full sum of the torque arriving at the clutches is still delivered through the clutches even while they are slipping, but the full sum of power is not, due to the mismatch in speed between the engine and the drive sprocket (power is the product of torque and rotationanl speed). Some of the power is lost by conversion into heat. While inefficient, it is permissible to slip the clutches in the BKPs thanks to the fact that they are wet clutches with forced lubrication, and use cermet friction pads with high thermal stability. The film of transmission oil on each disc surface of the multi-disc clutch pack greatly limits mechanical wear and thermal wear is limited by the rejection of waste heat into the flowing transmission oil. Moreover, although it is characterized by much higher power loss compared to steering with engaged clutches, steering by clutch slippage is still regenerative. As the left and right tracks are connected via the transmission drive shaft, the power not transmitted to the inner track flows to the outer track.</div><div><br /></div><div>It is worth noting that the use of slipping wet clutches with hydraulic pressure to obtain a variable turn radius is a technical solution that the BKP shares with the Allison Cross Drive (CD) series. Cross drive transmissions feature a double differential steering mechanism and lack a hydrostatic steering drive, but the turn radii was considered to range from pivot (neutral steer) to infinity, despite the fixed gearing ratio between the main drive and the steering drive. Instead, the cross drive transmission design simply uses the slipping of the left and right steering clutches when steering left and right respectively. As with the BKP design, this is controlled by having the pressure pistons of the clutches be controlled by a hydraulic modulating valve, but rather than steering levers, the driver's steering device is a wobble stick, steering wheel or T-bar, depending on the tank model. </div><div><br /></div><div>The tank slows down during a turn because the inner track is slowed down but the outer track is not sped up. If a higher speed is desired, the driver has to increase fuel flow to the engine with the accelerator pedal to overcome the speed reduction and maintain the same vehicle speed as before entering the turn. The engine speed itself does not fall, because the governor can increase the fuel supply to compensate for the increase in the engine load if the rolling resistance exceeds the torque output of the engine. During a turn, the engine runs at the speed set by the operator via the accelerator pedal and the speed is maintained by the governor regardless of the load on the engine. It will continue to do so as long as the load applied has not reached or exceeded the engine's torque curve, but once a torque overload occurs occurs, the governor ceases to maintain engine speed. Instead, engine flexibility (adaptability), which is dependent on the flatness of the torque curve, plays the primary role in minimizing the fall in engine speed. The curvier (peakier) the torque curve, the less the engine speed needs to fall until equilibrium between torque and load is reached. When turning the tank at high speeds on unpaved surfaces, the overload caused by the turning resistance from both the inertia of the tank and the terrain will be handled by these characteristics. </div><div><br /></div><div>Nevertheless, because of the fundamental limitations of this type of steering system as compared to a differential steering system, exacerbated by the tightening of the turn radii at gears above 4th gear, a tank with BKPs suffers a speed decrease of up to 50% during a turn relative to rectilinear motion. For comparison, the M60A1 with the CD-850-6 transmission experiences a speed decrease of only around 15%.</div><br />Clutch-brake steering is the only method of steering on the 1st and reverse gears. The clutch-brake turn produces a turn radius equal to the width of the tank between the centerline of the tracks, expressed as "B" in the table below, taken from the Polish textbook "<i>Budowa pojazdów gąsienicowych</i>" (Construction of Tracked Vehicles). The </span>width of the tank between the centerline of the tracks is 2.79 meters, and so the turn radius is 2.79 meters. In the 1st and reverse gears, the turn radius is 1B, while in the 2nd gear it is 2.16B, and so on. </div><div><span><br /><br /><div style="font-size: medium; text-align: center;"><a href="https://1.bp.blogspot.com/-PxZtEgkx4cw/X2dNidHXXBI/AAAAAAAARng/6iZsL8yIKUUCwIU-SsG52H4aGrJqqZjlACLcBGAsYHQ/s650/t-72_mech_skret_prom_skret.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="180" data-original-width="650" height="162" src="https://1.bp.blogspot.com/-PxZtEgkx4cw/X2dNidHXXBI/AAAAAAAARng/6iZsL8yIKUUCwIU-SsG52H4aGrJqqZjlACLcBGAsYHQ/w640-h178/t-72_mech_skret_prom_skret.jpg" width="582" /></a><a href="https://1.bp.blogspot.com/-GwJ6zzmsj4w/X2dOvj6rwzI/AAAAAAAARno/cZ9wCjQc3hAugMrJ6FDffdsR_xGVy_5sgCLcBGAsYHQ/s308/track%2Bwidth.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="249" data-original-width="308" height="162" src="https://1.bp.blogspot.com/-GwJ6zzmsj4w/X2dOvj6rwzI/AAAAAAAARno/cZ9wCjQc3hAugMrJ6FDffdsR_xGVy_5sgCLcBGAsYHQ/w200-h162/track%2Bwidth.png" width="200" /></a><br /></div><div style="font-size: medium;"><br /></div><div style="font-size: medium;"><br /></div><div>Theoretically, the turning rate of the tank when turning in 1st gear is around 41.75 degrees per second, allowing the tank to complete a full pivot turn in around 8.6 seconds if the engine ran at 2,000 RPM for the entire duration of the turn. In reverse, the tank would turn at around 23.8 degrees per second under the same circumstances, requiring 15 seconds for a full pivot turn. In practice, due to the need to accelerate from a standstill and then slow down to a stop at the end of the turn, a full pivot turn requires somewhat more time to complete, with real demonstrations showing that around 10 seconds is required. Broadly speaking, this turn rate is on par with tanks capable of neutral steering with on-the-spot turning, but it is nominally slower to tanks like the T-54, T-55 and T-62 which permitted a pivot turn in any gear setting, allowing the driven track to achieve a much higher angular speed, though the highest possible gear setting was still constrained by terrain resistance limitations.</div><div style="font-size: medium;"><br /></div><div style="font-size: medium;">On a final note - when the clutch pedal is depressed or when the gearshift is set to neutral, the steering system does not function. Another important nuance of the steering system is that if a T-72 is being towed, the steering system will not work, because the engine is off and there is no hydraulic pressure in the BKPs. </div><div style="font-size: medium;"><br /></div><div style="font-size: medium;"><br /></div><h3 style="text-align: left;"><span style="font-size: large;">SPEED AND ACCELERATION</span></h3><div style="font-size: medium;"><br /></div><div style="font-size: medium;">According to the manuals for the T-72A and T-72B and the book "<i>Main Battle Tank</i>" (<i>Основные Боевые Танки</i>) published by Arsenal Press in 1993, the tank speeds (at 2,000 RPM) and gear ratios are presented in the table below. Note that the gearbox has a geometric progression from gears 2 to 4, which are the most commonly used gears, allowing the optimum engine speed range to be maintained within these gears. Gears 5 to 7 have no mathematical progression, serving only to increase the speed of the tank on roads, with the 7th gear present only for the sake of providing the desired top speed. The 1st gear is a high reduction gear for circumstances that demand high tractive force. </div><div style="font-size: medium;"><br /></div><div style="font-size: medium;">The final drive gear ratio is 5.454. The overall gear ratio can be found by multiplying the 0.706 gear ratio of the intermediate power transfer gearbox with the selected transmission gear ratio and the final drive gear ratio. Knowing these gear ratios, the tank speeds in each gear can be calculated quite easily. Taking the 1st gear as an example, it can be calculated that the torque is multiplied 31.47 times and the angular speed is reduced by 31.47 times. If the engine is running at 2,000 RPM, the sprocket speed will be 63.55 RPM, and when multiplied with the circumference of the drive sprocket of 1.92 meters, yields a speed of 7.32 km/h. </div></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div>
<div style="font-weight: normal;">
<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
</div>
<table border="1" style="font-weight: normal;">
<tbody>
<tr>
<td style="text-align: center;"><b><span style="font-size: small;">Gears</span>
</b></td>
<td style="text-align: center;"><b><span style="font-size: small;">Tank speeds (km/h)</span>
</b></td>
<td style="text-align: center;"><b> Gear ratios </b>
</td>
<td style="text-align: center;"><b><span style="font-size: small;">Overall gear ratios</span>
</b></td>
</tr>
<tr>
<td style="text-align: center;"><b><span style="font-size: small;">1<br />2<br />3<br />4<br />5<br />6<br />7<br />R</span>
</b></td>
<td><div style="text-align: center;">7.32</div>
<span style="font-size: small;"><div style="text-align: center;">13.59</div></span><div style="text-align: center;">17.16</div>
<span style="font-size: small;"><div style="text-align: center;">21.47</div></span><div style="text-align: center;">29.51</div>
<span style="font-size: small;"><div style="text-align: center;">40.81</div></span><div style="text-align: center;">60</div>
<span style="font-size: small;"><div style="text-align: center;">4.18</div></span></td>
<td><div style="text-align: center;">8.173</div><div style="text-align: center;">4.400</div><div style="text-align: center;">3.485</div><div style="text-align: center;">2.787</div><div style="text-align: center;">2.027</div><div style="text-align: center;">1.467</div><div style="text-align: center;">1.0</div><div style="text-align: center;">14.3</div></td>
<td><div style="text-align: center;">31.47</div><div style="text-align: center;">16.94</div><div style="text-align: center;">13.42</div><div style="text-align: center;">10.73</div><div style="text-align: center;">7.80</div><div style="text-align: center;">5.64</div><div style="text-align: center;">3.85</div><div style="text-align: center;">55.06</div></td>
</tr>
</tbody></table><br /><div style="font-weight: normal;"><span style="font-size: x-small;"><span style="font-size: small; font-weight: normal;"><br /></span></span></div><div><span><span style="font-size: small;">Knowing the overall gear ratio at 7th gear, it can be calculated that the technical maximum speed of the T-72 is 68.8 km/h, achieved by running the engine at its maximum speed of 2,300 RPM. The engine cannot run faster than 2,300 RPM due to its governor. However, reaching the technical maximum speed requires a paved road, because the engine power drops off beyond its rated speed due to a steep decline in torque, making it difficult for the tank to overcome the resistance of rough terrain. The results of the tests of Object 172 tanks in the Turkestan Military District in 1968 showed that the average speed of the tanks on a paved road was 43.4 to 48.7 km/h, and the maximum speed recorded was 65 km/h, presumably achieved by driving down a straight stretch of highway. </span></span></div><div><span><span style="font-size: small;"><br /></span></span></div><div><span><span style="font-size: small;">With this in mind, it is important to note that a T-72B3 reached a speed of 77 km/h on the straight dirt road track during the 2018 Tank Biathlon held in Alabino proving grounds outside of Moscow, and during the 2020 Tank Biathlon, a T-72B3 reached 84 km/h, also on the dirt road track. Because it is known that the V-92S2F engine does not run at a higher speed than prior engines, it is evident that a new transmission with new gear ratios was installed to these participating tanks, and possibly serial T-72B3 tanks as well. This would not be particularly surprising given that the greatly increased torque from the new engine would most likely require gearboxes rated for a higher torque.</span></span></div><div style="font-weight: normal;"><span style="font-size: x-small;"><span style="font-size: small; font-weight: normal;"><br /></span></span></div><div><span><span style="font-size: small;">By examining the speeds permitted by these gear ratios, it can be seen that during the design of the BKP transmission, there are more gears than required to merely keep the engine running within its powerband of 1,300-2,000 RPM. Rather, the ratios were calculated so that when upshifting at an engine speed of 1,900-2,000 RPM from the 2nd gear to a higher gear, up to the 4th gear, the engine speed will not fall below 1,600 RPM</span></span>. This means that when accelerating while the tank is already in motion (not from a standstill) for short dashes from cover to cover in off-road conditions, the engine will always be in the upper end of its powerband, and it will always be delivering close to its peak power. From the 5th gear to the 7th gear, the spacing between the gears is expanded so that the when upshifting at an engine speed of 1,900-2,000 RPM, the engine speed will fall to 1,300-1,400 RPM. This was done to make use of a wider engine speed range to gain a higher top speed, at a small expense to acceleration, as it is important to note that when shifting from 6th to 7th gear, the engine will still be within its powerband, though only by a small margin. This is in stark contrast to the 4HP 250 transmission of the Leopard 1, which has a 4-speed gearbox. Because the Leopard 1 was designed to achieve a top speed of 62 km/h at its rated engine speed of 2,200 RPM (65 km/h when the engine is at its max speed), it is immediately apparent that the gearbox had to be designed to make use of a much wider engine speed range than the 7-speed BKPs. In fact, due to the wide spacing between the gears in the 4HP 250, the engine speed will fall from 2,200 RPM to 1,200 RPM after shifting from 1st to 2nd (a wide gear spacing exists due to the high gearing ratio of the 1st gear, like all other tanks), and then to 1,400 RPM after shifting from 2nd to 3rd, and 3rd to 4th. Because the peak torque of the MB 838 CaM-500 engine is developed at 1,550 RPM, it is evident that the gear ratios were calculated so that upshifting would push the engine well below its power band for the sake of a higher top speed.</div><div><br /></div><div>Ideally, the driver should upshift close to 2,300 RPM in order to maximize the acceleration period in each gear, especially in the first few gears, but this may not be desirable during routine maneuvers for wear and tear reasons. This can be seen in torque-speed chart below, which shows the torque curves of the V-46 in each gear of the transmission at an engine speed of 1,000-2,000 RPM against vehicle speed. The chart also shows the close and uniform spacing between the 2nd, 3rd and 4th gears, where acceleration is highest. The spacing between the 5th, 6th and 7th gears is also quite uniform but noticeably wider, which is responsible for the high top speed, achieved with at the expense of acceleration performance.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-u5Uvmxl31BE/YVodjcssQ2I/AAAAAAAAURY/_JdRFeJtO08rJkDkVSAODKrMdzo2jA_nQCLcBGAsYHQ/s1487/torque%2Bin%2Beach%2Bgear%2BT-72.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="808" data-original-width="1487" height="348" src="https://1.bp.blogspot.com/-u5Uvmxl31BE/YVodjcssQ2I/AAAAAAAAURY/_JdRFeJtO08rJkDkVSAODKrMdzo2jA_nQCLcBGAsYHQ/w640-h348/torque%2Bin%2Beach%2Bgear%2BT-72.png" width="640" /></a></div><div><br /></div><div><br /></div><div>As the chart shows, the crossover point between each gear in sequence from the 2nd to the 7th does not occur at 2,000 RPM, but rather at a speed that, when extrapolated, lies around 2,300 RPM. The chart also shows that there is a steep drop off when shifting from the 1st to the 2nd gear even when the curve is extrapolated out to 2,300 RPM, so a smooth transition is not possible at all. Some acceleration potential will naturally be lost during the upshift. This could be solved by reducing the gearing ratio to a much smaller figure so that the overall ratio would only be around 20, but this was accepted as a calculated loss, which is a design compromise shared with the majority of other tank transmissions, as the 1st gear is usually designated as a special low range gear for bearing heavy loads. On the T-72, the 1st gear is primarily meant for low speed maneuvering in restricted terrain, towing heavy loads, turning sharp corners in tight spaces, climbing obstacles, crossing trenches, climbing very steep hills, getting the tank to move if it is stuck, and any other situation where a great deal of torque is needed. </div><div><br /></div><div><span><span style="font-size: small;"><br /></span></span></div><div><span><span style="font-size: small;">The gear shifting mechanism has an interlocker that is designed to prevent the driver from downshifting in the 7th to 5th gear settings (7th to 6th, 6th to 5th, 5th to 4th) unless the engine speed is below 1,500 RPM. This is accomplished by an electronically controlled actuator on the gear shift lever which mechanically locks the lever against the selector frame until the engine speed is below the minimum threshold. When the lock is active, a red warning light on the left of the driver's TNPO-168V periscope is illuminated to warn the driver. The interlocker was needed because shifting down at an engine speed of above 1,500 RPM in these gears causes the engine to overspeed, exceeding its governed maximum speed of 2,300 RPM. This causes premature wear. Ideally, the driver should downshift at 1,300 RPM or less. Switching off the interlocker is prohibited except in case of emergencies. No interlocker is present when downshifting at the 4th to 1st gears, as the close spacing in the gears makes it very hard to overspeed the engine. In this regard, the 7-speed transmission has a positive effect on the ease of driving, as the speed margins for upshifting and even downshifting (up to the 5th gear) are very flexible. For instance, the driver could safely downshift from the 4th gear to the 3rd gear at a speed of as high as 1,800 RPM without overspeeding the engine, or upshift from the 3rd gear to the 4th gear at a speed of only 1,550-1,600 RPM and still end up at 1,300 RPM in 4th gear - just within the power band.</span></span></div><div><span><span style="font-size: small;"><br /></span></span></div><div><span><span style="font-size: small;">Another merit of the 7-speed transmission is that it provides the driver with enough gearing options to run the engine at its most efficient speed of ~1,600 RPM (where its specific fuel consumption is lowest) when the tank must be driven at a steady speed, such as in convoys. </span></span></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">
<span style="font-size: x-small;"><span style="font-size: small; font-weight: normal;"><br />The unusually slow reverse speed of the T-72 is explained by the immense gearing ratio, enabling a T-72 to extricate itself if it gets stuck in a ditch. It can also be used when towing another tank if success cannot be achieved with the 1st forward gear. No explanation for the slow reverse speed on the T-72 is given in the technical manual, operator's manual or any textbooks, but such a slow speed was not uncommon for tanks of WWII vintage.</span></span></div>
<div style="font-weight: normal;">
<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
<span style="font-size: small;"><span style="font-weight: normal;">The gear shift is the same one used in the T-64 and is shared with that of the T-10 heavy tank. Only sequential upshifting and downshifting is allowed by the gearboxes. Only sequential upshifting and downshifting is permitted, with a mechanical interlock to prevent the driver from skipping gears.</span></span></div>
<div style="font-weight: normal;">
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<a href="https://3.bp.blogspot.com/-HrGCJoVXJs0/WWwRtDthQzI/AAAAAAAAIsY/R4xRqqZPWI8rwA7SwpkyAMj3cyOUY-ENACLcBGAs/s1600/t-72%2Bgear%2Bshift.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="724" data-original-width="1366" height="211" src="https://3.bp.blogspot.com/-HrGCJoVXJs0/WWwRtDthQzI/AAAAAAAAIsY/R4xRqqZPWI8rwA7SwpkyAMj3cyOUY-ENACLcBGAs/s400/t-72%2Bgear%2Bshift.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-GkDVqBI6Rlc/WWwWhRCV76I/AAAAAAAAIso/iJwO3A6E2nETtkmcIyZNh9Kuj3t63somACLcBGAs/s1600/t-64%2Bshifting.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="250" data-original-width="333" height="240" src="https://3.bp.blogspot.com/-GkDVqBI6Rlc/WWwWhRCV76I/AAAAAAAAIso/iJwO3A6E2nETtkmcIyZNh9Kuj3t63somACLcBGAs/s320/t-64%2Bshifting.gif" width="320" /></a></div>
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<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span><span style="font-size: small;"><span style="font-weight: normal;">A new electronic control system was reportedly installed for the transmission in the T-72B3 UBKh. Very little information is available on the new system.</span></span></span></div><div style="font-weight: normal;"><br /></div><div><div style="font-weight: normal;"><span style="font-size: small;"><div><span style="font-size: small;"><span><span style="font-size: small;">The steering levers control the hydraulic servo units, which greatly reduces driver fatigue. The amount of force needed to pull the steering levers is around 16 kgf.</span></span></span></div><div><span style="font-size: small;"><span><span style="font-size: small;"><br /></span></span></span></div><div><span style="font-size: small;"><span><span style="font-size: small;"><br /></span></span></span></div><div><span style="font-size: small;"><span><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-iFIKKoNjVwo/X00-kTf9ZlI/AAAAAAAARhg/oDn3KuacXF0Z1bOktWjXSA-jl-vZtWRBACLcBGAsYHQ/s1364/t-72%2Bsteering%2Bmechanism%2Blinkages.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="791" data-original-width="1364" src="https://1.bp.blogspot.com/-iFIKKoNjVwo/X00-kTf9ZlI/AAAAAAAARhg/oDn3KuacXF0Z1bOktWjXSA-jl-vZtWRBACLcBGAsYHQ/s640/t-72%2Bsteering%2Bmechanism%2Blinkages.png" width="640" /></a></div><span style="font-size: small;"><br /></span></span></span></div><br />The steering levers have two positions, forward and back. To steer, the driver pulls the right or left steering lever back. This causes the side gearbox on the corresponding side of the hull to downshift instantaneously and thus reduce the track speed, or brake if the transmission is in the 1st gear or reverse gear setting. The speed difference between the two tracks causes the tank to turn around the slower track. </span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;">The brake, which is mechanically assisted by a spring, is operated with the brake pedal, or the steering tillers when in the 1st gear, neutral and reverse gears. Slowing down the tank with engine braking is also practical in the T-72 due to its manual transmission, and is the main braking method when moving down a steep descent with the intermittent application of the brake to prevent the engine from overshooting its maximum speed. As in a normal automobile with a manual transmission, engine braking is applied by shifting to a lower gear. This can be done with the gear shift or by pulling both steering levers back and holding them in place until the tank has reached the bottom of the slope. Engine braking also serves as a means of slowing down from high speed on level ground. </span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;">The effort needed on the pedal is mechanically reduced by a pair of coil springs and a reduction mechanism with a variable gear ratio, shown in the image below. When depressed, the brake pedal actuates a pushrod which turns an input cam against an output cam in the reduction mechanism, creating a two-stage multiplication of the driver's pushing force on the </span>control rods for the No. 4 and No. 5 brakes in the BKPs, thereby activating the brake. The reduction mechanism provides a more modest driver pedal force multiplication in the first stage, and the second stage provides a much higher multiplication factor, needed to fully lock up the brakes when the brake pedal is fully depressed. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The use of multi-disc brakes for this purpose is particularly appropriate owing to the high braking forces needed to stop a moving tank. To engage the parking brake, the pedal is held in place with a hook and rack mechanism. The brake pedal mechanism is fully mechanical and is not linked to the hydraulic units of the transmission, and is therefore not boosted by the engine power, unlike the braking mechanism which is engaged by the steering lever (in 1st gear and reverse). This makes the brake pedal a redundant system that can function regardless of the condition of the engine or hydraulic systems, which is an important safety feature for bringing the tank to a stop during emergencies, keeping the tank parked when the engine is off, and braking a broken-down tank while being towed with a towing cable. On the other hand, the lack of a powered booster of any kind could make the brake pedal very heavy to depress when the tank is travelling at high speed and a high braking force is needed to stop it. According to a report on the capabilities of a testbed T-64A equipped with a new hydromechanical transmission, the basic T-64A requires a brake pedal force of 50-100 kgf (490-980 N) to depress. Because it weighs more than a T-64A, a T-72 should be more difficult to stop and thus require more effort on the brake pedal.</div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-LLlcPJEXJmA/YVNgSGv_oeI/AAAAAAAAUQw/DgV1HKFaK7whVFHJduIjlvJaV_qtz978wCLcBGAsYHQ/s2048/mechanical%2Breducer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1425" data-original-width="2048" height="279" src="https://1.bp.blogspot.com/-LLlcPJEXJmA/YVNgSGv_oeI/AAAAAAAAUQw/DgV1HKFaK7whVFHJduIjlvJaV_qtz978wCLcBGAsYHQ/w400-h279/mechanical%2Breducer.png" width="400" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div>Another way to activate the brakes is to shift into 1st gear, and then pull both steering levers back simultaneously, activating the brake on both BKPs hydraulically. Because the hydraulic system directly acts upon the multi-disc brake packs, no force is transmitted into the mechanical brake linkages, and all resistance except the force of the return spring is removed from the brake pedal because the brake packs are already compressed. This can be done to quickly control the brakes without stopping the tank while traversing obstacles at low speed. It is the recommended way of bringing the tank to a full stop on a slope. The engine does not stall when both steering levers are used for braking in 1st gear or reverse gear, because the BKPs are automatically de-clutched. Once the tank is fully stopped, the driver steps on the brake and clutch pedals, releases the steering levers, and shifts into neutral.</div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;">Beginning on January 1, 1978, a pneumatic braking system was installed to the T-72. The mechanism, and the associated modifications to the pneumatic network of the tank, was also installed in all subsequent models of the T-72 series. It is analogous to the pneumatic brake used in heavy trucks and buses, but it is more powerful and provides no fine control over the braking force, as it is either turned on or off. The work is done by a pneumatic cylinder located </span>in the engine compartment, connected to the brake linkages via the input cam of the reduction mechanism. Air enters the piston chamber via the inlet indicated by the red arrow in the drawing below, and the piston rod (14) is pushed out of the cylinder, turning a lever arm on the casing of the mechanism that turns the input cam. Because the brake pedal linkage is splined into the input cam, the activation of the pneumatic cylinder also causes the brake pedal to be depressed. In this way, the driver receives physical feedback on the magnitude of the braking force by sensing how far the pedal is depressed.</div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--dCVpS4aKls/YVCGQv2jGFI/AAAAAAAAUQM/VjGbMTw6qRsdR6VTr4kfANVF_vP0SoaSQCLcBGAsYHQ/s1225/brake%2Bsystem.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="607" data-original-width="1225" height="318" src="https://1.bp.blogspot.com/--dCVpS4aKls/YVCGQv2jGFI/AAAAAAAAUQM/VjGbMTw6qRsdR6VTr4kfANVF_vP0SoaSQCLcBGAsYHQ/w640-h318/brake%2Bsystem.jpg" width="640" /></a></div></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;">The mechanism was designed to brake the tank without using the brake pedal, and it also moves the brake pedal to a more convenient position for later use, after the tank has slowed down. The driver activates the system while the tank is in motion by pressing and holding the brake button on the end of the left steering lever, shown in the image on the right below. This sends an electric signal to two EK-48 electro-pneumatic valves connected in series, releasing a flow of pressurized air to the pneumatic cylinder, turning the linkage for the brake control rods and thus engaging the brakes. The tank is then fully braked, only without any physical effort from the driver. The recommended pressure in the tank's pneumatic system for using the brake is 6.8 MPa (69 kg/sq.cm or 986.2 psi), which is - quite appropriately - vastly higher than pneumatic brakes for commercial heavy veicles, almost 10 times higher. However, because the bore diameter of the pneumatic cylinder is relatively small compared to truck brakes for the sake of compactness, a high braking force is obtained from a relatively low actuator force by having a longer piston stroke to produce more work, which goes through the input cam (1) to the output cam (9) in the reduction mechanism, shown in the image on the left below, to reduce the linkage displacement and thus amplify the actuator force. Under normal conditions, the pressure in the pneumatic system should be no less than 7.4 MPa to ensure that pneumatic starting of the engine is possible, so the pneumatic brake should always be ready to use, and the presence of the AK-150SV air compressor allows the brake to be used in perpetuity.<br /></span><br /></div><div class="separator" style="clear: both; font-weight: normal; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-vvWHobAEeqI/YVCaAuu1qnI/AAAAAAAAUQU/Oo1NrMhF4-0q0itwEqRuzkAdAjugAD7zwCLcBGAsYHQ/s436/brake%2Bforce%2Bmultiplier.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="319" data-original-width="436" height="293" src="https://1.bp.blogspot.com/-vvWHobAEeqI/YVCaAuu1qnI/AAAAAAAAUQU/Oo1NrMhF4-0q0itwEqRuzkAdAjugAD7zwCLcBGAsYHQ/w400-h293/brake%2Bforce%2Bmultiplier.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-Y_ORQzqCq3s/YUwVROaIgNI/AAAAAAAAUOo/Kv4BhRNuqyQx0PIltJt_o53_ZOpZbXHjgCLcBGAsYHQ/s2048/t-72%2Bbrake%2Bbutton.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1630" data-original-width="2048" height="319" src="https://1.bp.blogspot.com/-Y_ORQzqCq3s/YUwVROaIgNI/AAAAAAAAUOo/Kv4BhRNuqyQx0PIltJt_o53_ZOpZbXHjgCLcBGAsYHQ/w400-h319/t-72%2Bbrake%2Bbutton.png" width="400" /></a></div></div><div style="font-weight: normal;"><br /></div><div><span style="font-size: small;">Before releasing the braking button, the driver places his foot on the brake pedal, which will be depressed. Once the braking button is released, the air is evacuated from the system by a release valve and control of the pedal is returned to the driver, so he must step on it to ensure the tank continues to remain braked. If there is no force on the pedal, it will return to its original position under its spring. The addition of this pneumatic braking system was presumably done to ensure that the tank could be forcefully braked while travelling at high speed without requiring excessive effort on the driver's part.</span></div><div><span style="font-size: small;"><br /></span></div><div><span style="font-size: small;">The use of wet multi-plate disc brakes was an exceptionally modern feature at the time. The Patton series used dry multi-plate disc brakes, while most other tanks used more familiar automotive braking technologies such as the T-54/55 and T-62 which used band brakes, or the Leopard 1 and Chieftain which used a single-plate dry friction disc brake with twin calipers. All of these offered acceptable performance but were a suboptimal choice for a hot, enclosed engine compartments compared to a multi-plate brake with forced oil cooling. Moreover, the combination of a hydraulic control system with a mechanical control system, supplemented by a pneumatic actuator, made the T-72 braking system completely unique in the automotive world.</span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;">When starting a tank from a standstill, the driver can shift to the 2nd or 3rd gear and have both steering levers pulled back, thus setting the BKPs to the 1st or 2nd gear. Then, when the driver releases the clutch pedal and accelerates, he can rapidly shift up a gear by returning both steering levers to the forward position without needing to use the clutch pedal. In effect, this essentially duplicates the function of a semi-automatic transmission for one upshift or downshift, and it can be done at any gear setting. It may be exploited to maximize the acceleration of the tank on hard ground, but it is particularly favourable to do this when setting the tank in motion in 1st gear on a slope and in bad terrain because upshifting with this method is faster, reducing the period in which the tank can decelerate while engine power is no longer delivered to the tracks. <br /></span></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><span style="font-size: small;"><br />Due to the use of a manual transmission with a high mechanical efficiency, the net power at the drive sprockets of the T-72 is actually slightly higher than the Leopard 1, and the higher low end torque output of the V-46 engine allows the tank to accelerate very quickly. However, the T-72 generally falls short of the Leopard 1 in terms of steering precision, as its 4HP 250 double differential transmission provides two turn radii per gear, giving the tank a total of 8 turn radii as opposed to the 7 radii available on the T-72. The T-72 can only achieve more than one turn radius in each gear by partially downshifting one track, to make minute steering adjustments. The hydrostatic double differential transmission of the Leopard 2 is even more sophisticated as it provides an infinitely variable turning radius. </span></div></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small;"><span style="font-weight: normal;">
<br />The T-72 is not capable of neutral steering. When the gearshift is set to neutral, the steering system does not function; pulling the steering levers has no effect. The T-72 can only perform a pivot turn, that is, turn by locking one of the two tracks in place while the other drives the tank around it. This method of steering is mechanically simple, but inferior to turning in place whereby both of the tracks receive power and one of the tracks is run at the desired speed while the other is run in the opposite direction. Besides being slower, pivot steering induces strain on the inactive track and pushes soil between it and the road wheels, creating more tension that may cause the track to be dislocated from the suspension if not alleviated by running the track, either by momentarily making the tank go forward or in reverse. This is not an issue on dirt, sand, snow or paved surfaces, but is a possibility if the tank is turned in thick clay.</span></span><br /><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
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<span style="font-size: small; font-weight: normal;"><span style="font-weight: normal;"><br /></span></span><div style="font-weight: normal;"><font>Driving the T-72 is a pleasant experience - at least compared to a T-54 - according to people with firsthand experience. A few of the reasons, besides the fully hydraulic control of the steering system, are the low center of gravity of the tank and the uniform weight distribution on the roadwheels, and indeed, the tank was designed so that the weight distribution is most uniform when the turret is facing forwards. By having all these positive features, oscillations are less pronounced and the handling is easier. The tank is also more stable when moving at high speeds, particularly on harsh terrain. Nevertheless, the tiller system is perhaps inherently less ergonomic than a steering bar or wheel in terms of steering effort. The technical advantages of the tiller system over the slightly more complex steering bar system are that tillers are mechanically simple, durable, provide a great deal of leverage to reduce steering effort, and frees up space for the driver's legs.</font></div><div style="font-weight: normal;"><font><br /></font></div><div><font>Though the tiller steering system can be considered one of the more antiquated aspects of the T-72, it's worth noting that many of its rivals like the AMX-30, Chieftain and Challenger used the same system as well.</font></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><font>With a total power loss of 11-11.5% before the power is transmitted to the gear boxes of the transmission, the T-72 retains a larger share of its engine power than the M60A1, Leopard 1 and Leopard 2. Thus, the net engine power of the T-72 Ural and T-72A is 682 hp, and the net engine power of the T-72B is 712 hp. This is slightly more than the 642 hp of the M60A1, 630 hp of the M48A3, and only slightly less than the 710 hp of the Leopard 1 but much less than the 1,260 hp of the Leopard 2. It is closely equivalent to the Challenger 1 which has a net engine power of 871 hp.</font></div><div style="font-weight: normal;"><font><br /></font></div><div style="font-weight: normal;"><font>However, the modest engine power compared to tanks like the Leopard 2 is somewhat counterbalanced by the lower weight of the T-72, which is lower than both the M60A1 and Leopard 2 for all T-72 variants. Astonishingly, the weight of a combat loaded T-72 Ural (41 tons) is even slightly lower than a combat loaded Leopard 1A1 (41.5). Of course, these power deductions are only for the engine related subsystems. The deductions from the electrical systems of the tank are not yet considered. For example, the ST-10-1S generator on the T-72 generates 10 kW, and this power comes from the engine. The electrical systems of foreign tanks are typically more power-hungry which is often reflected in better performance in certain aspects (quicker turret rotation speed, more powerful infrared spotlights), but also results in slightly lower net power. Transmission losses may also reduce the power available to drive the tracks. A manual transmission with friction side clutches like the type installed in the T-72 has lower parasitic power losses compared to automatic transmissions. The maximum power loss to the transmission in a T-72 at peak engine power is 70 hp, compared to an estimated 200-250 hp in a Leopard 2. The high power losses suffered by the Leopard 2 are due to the low efficiency of hydrostatic double differential transmissions, particularly when steering.</font></div><div style="font-weight: normal;"><font><br /></font></div><div><font style="font-weight: normal;">With a power loss of 11.5% to auxiliary systems and another 8.9% (70 hp) to the transmission, the sprocket power of a T-72 is 620 hp. For comparison, the sprocket powers of the Leopard 2, Leopard 1, Challenger 1, M60A1 and Chieftain Mk. 5 at peak engine power are 1,000 hp, 572 hp, 871 hp, 520 hp and 585 hp respectively. As a result, the actual power-to-weight ratios of these five tanks are quite different than what the net engine powers imply. Additional losses to the electric generator are substantially less for the T-72 - its generator </font><font>has an output of 10 kW, whereas the generator of the M1 Abrams produces 15.6 kW and the generator of the Leopard 2 produces 20 kW.</font><span style="font-size: small; font-weight: normal;"> However, for this comparison, they are omitted.</span></div></span></div>
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<tr><td><b>Tank</b></td><td><b>Gross engine power-to-weight ratio (hp/ton)</b></td><td><b>Sprocket power-to-weight ratio (hp/ton)</b></td></tr>
<tr><td>Leopard 2</td><td>27.20</td><td>18.13</td></tr>
<tr><td>T-72 Ural</td><td>19.00</td><td>15.12</td></tr>
<tr><td>Leopard 1</td><td>20.75</td><td>14.30</td></tr>
<tr><td>Challenger 1</td><td>19.35</td><td>14.05</td></tr>
<tr><td>Chieftain Mk. 5</td><td>13.64</td><td>10.63</td></tr>
<tr><td>M60A1</td><td>15.76</td><td>10.5</td></tr>
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<span style="font-size: small;"><span style="font-weight: normal;">During the evolution of the T-72, the sprocket power-to-weight ratio remained at the same approximate level despite the</span></span><span style="font-size: small; font-weight: 400;"> gradual increase in weight of each new model</span><span style="font-size: small; font-weight: normal;">. For instance, the T-72B obr. 1985 and T-72B obr. 1989 both weighed 44.5 tons, but the sprocket P:W ratio actually increased marginally to 15.22 hp/ton due to the 840 hp engine. The much more recent T-72B3 model weighs 45.6 tons and has the V-84M engine with the same output of 840 hp, so the P:W ratio declined to 14.86 hp/ton. On the most recent T-72 model, the T-72B3 UBKh, the gross P:W ratio increased drastically to 24.3 hp/ton, but the exact sprocket P:W ratio is not known because the losses have not been disclosed. Under the reasonable assumption that the same transmission is still used, the sprocket power is around 900 hp. With a combat weight of 46.5 tons, the sprocket P:W ratio of the T-72B3 UBKh is around 19.35 hp/ton.</span></div>
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<h3 style="text-align: left;"><span style="font-size: large;">ACCELERATION</span></h3>
<div style="font-size: 21.9024px;"><span style="font-size: small;">Acceleration data for the T-72 is somewhat difficult to find. According to the report "<i>Propozycja Poprawy Manewrowości Czołgu Twardy</i>" (<i>Proposal to Improve Maneuverability of the "Twardy" Tank</i>) from the University of Technology in Szczecin, the T-72M1 accelerates to 32 km/h in 10.5 seconds on a paved road. Data for the T-72B from empirical data is available in a journal article "<i>Теплоинерционное кратковременное форсирование мощности танкового двигателя и его технические возможности</i>" by B. I. Vasiliev, S. V. Dorogin, et al. The relevant table is presented below. The time taken for a T-72B with a V-84 engine operating under normal power (840 hp) to accelerate to 30 km/h (T1) is 8.5 seconds on concrete, and 12 seconds on a dirt road. Accelerating to its top speed of 60 km/h (T2) takes 27.6 seconds on concrete, and 38 seconds on a dirt road. Note that the use of a concrete track instead of a paved road may degrade acceleration performance due to higher track slippage, particularly since only metal tracks were available for T-72 tanks.</span></div><div style="font-size: 21.9024px;"><span style="font-size: small;"><br /></span></div><div style="font-size: 21.9024px; text-align: center;"><span style="font-size: small;"><a href="https://topwar.ru/uploads/posts/2022-06/1654035607.jpg" style="font-size: 18.72px; margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="264" data-original-width="800" height="132" src="https://topwar.ru/uploads/posts/2022-06/1654035607.jpg" width="400" /></a></span></div><div style="font-size: 21.9024px;"><span style="font-size: small;"><br /></span></div><div style="font-size: 21.9024px;"><span style="font-size: small;"><div style="font-size: 21.9024px;"><span style="font-size: small;">The acceleration figures for the T-72 are supported by original technical documentation on the acceleration of the T-64 with the 5TDF opposed-piston engine (700 hp). The chart below </span><span style="font-size: small;">(</span><a href="http://btvt.info/4ourarticles/istoria_t64/4_3.htm" style="font-size: medium;">taken from Andrei Tarasenko</a><span style="font-size: small;">)</span><span style="font-size: small;"> shows the drop in engine performance when jet fuel (grey line, </span><span style="font-size: small;">ТС</span><span style="font-size: small;">) and low octane gasoline (white line, A-72) is used instead of diesel (black line, </span><span style="font-size: small;">ДЛ</span><span style="font-size: small;">), but more importantly, the chart shows that </span><span style="font-size: small;">a T-64 (Object 432) running under normal conditions on diesel fuel accelerates from 0 to 32 km/h in 10 seconds, although this was because the BKP transmission was optimized to reach 30 km/h. Reaching 32 km/h required an additional gear shift from 5th to 6th, which misrepresents the tank's acceleration performance.</span><span style="font-size: small;"> The T-72 Ural with the V-46 engine has a marginally higher power-to-weight ratio, better running characteristics, and identical gearboxes, only counterbalanced to some extent by the larger rotating mass in its suspension, so it must have similar acceleration characteristics as the T-64 at the very least, and likely noticeably better. </span></div><div style="font-size: 21.9024px;"><span style="font-size: small;"><br /></span><span style="font-size: small;"><br /></span></div><div class="separator" style="clear: both; font-size: 21.9024px; text-align: center;"><a href="https://3.bp.blogspot.com/-UuoNG5fhgos/XDBvGlM4fsI/AAAAAAAAMyg/f0XDuhsnO9o44JRgBPOT-IXNpML6Cv5ywCLcBGAs/s1600/5tdf%2Bacceleration.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="721" data-original-width="700" height="400" src="https://3.bp.blogspot.com/-UuoNG5fhgos/XDBvGlM4fsI/AAAAAAAAMyg/f0XDuhsnO9o44JRgBPOT-IXNpML6Cv5ywCLcBGAs/s400/5tdf%2Bacceleration.jpg" width="387" /></a></div><div style="font-size: 21.9024px; font-weight: 700;"><span style="font-size: small; font-weight: normal;"></span></div></span></div><div style="font-size: 21.9024px;"><span style="font-size: small;"><br /></span></div><div style="font-size: 21.9024px;"><span style="font-size: small;">By cross-referencing data for the T-64 and the T-72B, there is a strong indication that the acceleration of a T-72 Ural to 32 km/h should be between 8.5 and 10.5 seconds, with 4 gear shifts to bring it from 2nd to 6th gear. If the acceleration time is measured to 30 km/h, a T-72 Ural will likely take around 7 seconds. The performance of a T-72 can be expected to outshine that of a T-64A at all speeds, as the T-64A had the same acceleration dynamics as the T-64, but was slower due to its added weight. For the T-64A, acceleration to 40kph is 16-17 seconds</span></div><div style="font-size: 21.9024px;"><span style="font-size: small;"><br /></span></div><div style="font-size: 21.9024px;"><span style="font-size: small;">The report "<i>Propozycja Poprawy Manewrowości Czołgu Twardy</i>" also states that a "Leopard 2" accelerates to 32 km/h this in 9.5 seconds and the M1A1 Abrams achieves this in 7 seconds. The acceleration figure for the "Leopard 2" presented in the study is most likely erroneous, as the Leopard 2A0 model is known to be capable of accelerating to 32 km/h in 6 seconds. More contemporary sources repeat that the acceleration of the M1 Abrams to 32 km/h as 6.2 seconds. Paul-Werner Krapke states in "<i>Leopard 2: Sein Werden und seine Leistung</i>" that the Leopard 1 accelerates to 32 km/h in 10 seconds on a paved street. Additionally, according to Soviet tests and data sheets from various U.S sources, the M60A1 with the T97E2 track reaches 32 km/h in 15 seconds and reaches 40 km/h in 25 seconds. It is also stated on page 12 of the May-June 1977 issue of "ARMOR" magazine that the M60A3 reaches 32 km/h in 16 seconds, presumably also with T97E2 tracks. With T142 tracks, which began replacing the T97E2 in 1974, the acceleration to 32 km/h and 40 km/h worsened to 17.5 seconds and 30 seconds respectively. For comparison, the XM-1 reaches 32 km/h in 6.2 seconds. </span></div></div><div><div style="font-size: 21.9024px;"><span style="font-size: small;"><br /></span></div><div style="font-size: 21.9024px;"><span style="font-size: small;">Interestingly enough, measuring the acceleration to 32 km/h makes for an informative comparison between the T-72 and the Leopard 1. The T-72 may start from 2nd or 3rd gear, and then shift up a few times to reach the 6th gear and hit a speed of 32 km/h. On the other hand, a Leopard 1 has a torque converter that provides enhanced starting authority, which is promptly locked once the tank is in motion, and the driver only has to upshift twice, to the 3rd gear, but due to the wide spacing between the gears in the 4-speed transmission, the engine speed will fall well below the power band after each shift. Delivery of engine power to the tracks is therefore interrupted up to half as many times as in the T-72, but the engine is forced to work back up to its power band from a much lower speed after each gear shift, where it operates at a low efficiency due to the negative influence of turbolag. Evidently, the non-optimal circumstances faced by these two tanks balance each other out, with the outcome being that both tanks share virtually the same acceleration time to 32 km/h, with the T-72 likely beating the Leopard 1 by a small margin.</span></div><div style="font-size: 21.9024px;">
<span style="font-size: small;"><br /></span><span style="font-size: small;">In terms of acceleration, the T-72 was clearly superior to tanks like the M60A1/M60A3 and was at least on par with the Leopard 1, but was undoubtedly inferior to the new generation of NATO tanks, i.e, the Leopard 2 and M1 Abrams. As a side note, the Polish study also includes figures for the PT-91 "Twardy" which weighs 45.3 tons and has a modern Polish S-12U engine with a power output of 850 hp. The PT-91 reportedly accelerates to 32 km/h in 11.0 seconds, which is congruent with the acceleration figure of the lighter T-72M1 with a less powerful V-46 engine. The acceleration of all four of these modern tanks far outpaces tanks like the T-54 and others of its generation; a basic T-54 requires 18 seconds to reach 32 km/h on a paved road, placing it in the same class as the M48 and M60A1 in this category.</span></div>
<div style="font-size: 21.9024px;"><br /></div><div style="font-size: 21.9024px;"><span style="font-weight: normal;"><span style="font-size: small;">However, it is worth noting that there is a possibility for some doubt to arise regarding these acceleration figures for the T-72 as the acceleration of a generic T-72 model from 0 to 32 km/h is claimed to be 14 seconds <a href="http://www.yugoimport.com/en/proizvodi/pp1000-main-battle-tank-powerpack-unit">in this promotional webpage for the PP1000 powerpack upgrade for the T-72</a>. It is quite likely that the numbers given in the Yugoimport page are for acceleration on a dirt road instead of an asphalt road, or for a tank that weighs substantially more than a basic T-72 model. This may be a T-72M1, as it was likely used as a reference point. This would also match very well with the known acceleration data for a T-72B on a dirt road.</span></span></div>
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<span style="font-size: small; font-weight: normal;">With the available set of data on the acceleration of various tanks on concrete or paved roads, it can be seen that t</span><span style="font-size: small; font-weight: 400;">he sprocket power-to-weight ratios offer a more accurate reflection of the comparative acceleration performances of tanks, and indeed, it is a far better point of comparison than the gross power-to-weight ratios.</span><span style="font-size: small; font-weight: 400;"> It is worth noting that some small discrepancies in the sprocket P:W ratio and the acceleration time in the table can be explained by the presence of a torque converter, which improves acceleration smoothness from a standstill, but at the expense of additional power losses. In the case of the T-72, despite having a marginally higher sprocket P:W ratio than a Leopard 1 and almost the same amount of suspension rolling resistance, it does not possess a quicker acceleration time to 32 km/h. It can be assumed that this is partly because of the number of upshifts needed, and partly because its steel tracks experience slip on concrete, whereas rubber padded tracks experience negligible slip. Based on the data presented previously, a T-72 Ural is likely to reach 30 km/h in around 7 seconds, while a Leopard 1 would require 7-8 seconds, but this would be achieved solely due to a wider gap in sprocket P:W ratio of 15.12 hp/ton against 14.30 hp/ton.</span><br />
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<tr><td><b>Tank</b></td><td><b>Sprocket P:W ratio (hp/ton)</b></td><td><b>Acceleration to 32 km/h (s)</b></td></tr>
<tr><td>Leopard 2</td><td>18.13</td><td>6.0</td></tr>
<tr><td>Leopard 1</td><td>14.30</td><td>10.0</td></tr>
<tr><td>T-72M1</td><td>14.95</td><td>10.5</td></tr>
<tr><td>M60A1</td><td>10.5</td><td>17.5</td></tr>
<tr><td>T-54</td><td>10.75</td><td>18.0</td></tr>
<tr><td>Chieftain Mk. 5</td><td>10.63</td><td>19.0</td></tr>
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<span style="font-size: small;"><span style="font-weight: normal;"><b><span style="font-size: large;">SUSPENSION</span></b></span></span></span></h3>
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<span style="font-size: small;"><a href="https://2.bp.blogspot.com/-8Jjvo7EI9fs/WedH_ugifLI/AAAAAAAAJ4w/bCBC8rUQFJgMBC4v2c8FPpE4lbfBFgSeQCLcBGAs/s1600/t-72%2Bsuspension.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="646" data-original-width="900" height="459" src="https://2.bp.blogspot.com/-8Jjvo7EI9fs/WedH_ugifLI/AAAAAAAAJ4w/bCBC8rUQFJgMBC4v2c8FPpE4lbfBFgSeQCLcBGAs/s640/t-72%2Bsuspension.gif" width="640" /></a></span></div>
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<span style="font-size: small;"><span style="font-weight: normal;"><br />The T-72 has independent suspension using full-length torsion bars, with each bar running across the full width of the hull. The front two wheel housings are affixed to the hull with reinforced bolts to withstand additional stresses when the tank is driven on uneven ground or into ditches. </span></span></span><span><span style="font-size: small;"><span>According to Vasily Chobitok in <a href="http://militaryarticle.ru/tekhnika-i-vooruzhenie/2005/11616-hodovaja-chast-tankov">"<i>Ходовая Часть </i></a></span></span><span style="font-size: small;"><span><i><a href="http://militaryarticle.ru/tekhnika-i-vooruzhenie/2005/11616-hodovaja-chast-tankov">Танков</a></i></span></span><span style="font-size: small;"><a href="http://militaryarticle.ru/tekhnika-i-vooruzhenie/2005/11616-hodovaja-chast-tankov">"</a> (</span><i>The Running Gear of Tanks</i><span style="font-size: small;">), the torsion bars of the T-72 </span>are made from 45KhN2MFASh steel alloy. They are coated with a layer of varnish and then wrapped in a protective insulating tape for scratch protection and </span>to prevent corrosion. Though the composition of the alloy is the same as the 45KhN2MFA alloy used in the torsion bars of the previous generation of medium and heavy tanks, 45KhN2MFASh was processed by electroslag remelting, marked by the "Sh" suffix. The bars are 2,310mm long and 47mm in diameter, and each weighs 31.7 kg.</div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small; font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small; font-weight: normal;">Both the idler wheel and drive sprocket are cast steel components. The idler wheel weighs 197 kg and the drive sprocket weighs 193 kg. The idler wheel has a diameter of 520mm, and the drive sprocket has a diameter of 611mm as measured along its rim (not the tips of the teeth)</span></span>, which defines the point where its circumference is measured to calculate track speed. There are three support rollers on each side, each having a single tyre on the inner side of the track center guides. As such, they function purely as support rollers, and do not assist in retaining the track. Each roller weighs 31 kg. They have a diameter of 204mm.</div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small; font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small; font-weight: normal;">The nominal ground clearance of the T-72 Ural and T-72A is 470mm and was increased to 490mm on the T-72B for improved mobility. The ground clearance is measured from the hull belly, and not the driver's "tub" which protrudes below it and is level with the roadwheel swing arm housings. The minimum ground clearance as measured to the "tub" is 406 mm, or 426 mm on the T-72B.</span><br />
<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span><span style="font-size: small;"><span style="font-weight: normal;">This suspension, inherited from the Object 167, was a departure from the unsupported tracks of the preceding T-54 and T-62 tanks. It consists of </span></span></span>six evenly-spaced roadwheels, 750mm in diameter, with three return rollers on each side of the hull. As a rule, return rollers increase the rolling resistance of a suspension, but in this case, the use of a supported track layout provided the roadwheels with much a larger range of dynamic motion, which was presumably too large for the wheels to accommodate unsupported tracks. Like the roadwheels of the preceding T-54, T-55 and T-62 tanks, forged aluminium stampings are used in their construction, helping to save weight and reduce roling resistance. By the time the T-72 entered service, this had become a standard practice among major tank builders, with the U.S first using aluminium tank roadwheels beginning with the M60, and both Germany and France followed suit with the Leopard 1 and AMX-30. Only the Chieftain continued using steel roadwheels (inherited from the Centurion), with aluminium roadwheels appearing only beginning with the Challenger 1.</div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small;"><span style="font-weight: normal;">The structure of each wheel consists of two stamped aluminium discs bolted together and fastened to a steel hub. Inside the steel hub, a 142220 roller bearing and a 371 ball bearing are fitted. Thick rubberized rims are fitted to the discs, and steel wear plates protect the inner rims of the wheel from the friction of the track center guides. Officially, each wheel is listed as having a </span></span><span style="font-size: small;"><span style="font-weight: normal;">weight of 177 kg, presumably representing the complete wheel unit with the hubcap installed. The first wheel on each side of the hull is reinforced with an additional roller bearing.</span></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small;"><span style="font-weight: normal;">The T-72 Ural used the <a href="https://bmz.ru/172-50-002sb-a-opornyj-katok-dlya-tanka-t-72-prodazha-s-hraneniya">172.50.002sb-A wheel</a>, an 8-spoked design weighing 164.15 kg. Subsequent models with increased weight used the reinforced <a href="https://bmz.ru/katok-opornyj-imr-2-usilennyj-172-50-001sb">172.50.001sb-A wheel</a> with 6 spokes, featuring a different, reinforced roller bearing. The 001sb-A wheel weighs 169.28 kg. On top of that, the swing arm for each roadwheel weighs 87.87 kg. For comparison, the smaller, 660mm-diameter wheels of an M60A1 weighed 125 kg.</span></span></span><br />
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<span style="font-weight: normal;"><a href="http://2.bp.blogspot.com/-TN4dF1XNRyM/VRgYRJ_S59I/AAAAAAAABhI/nj_WLdhNehk/s1600/t-72%2Bwheel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="304" src="https://2.bp.blogspot.com/-TN4dF1XNRyM/VRgYRJ_S59I/AAAAAAAABhI/nj_WLdhNehk/s1600/t-72%2Bwheel.png" width="320" /></a><a href="http://4.bp.blogspot.com/-cWK2SpEDYjU/VRgYQy8cozI/AAAAAAAABhE/wayByA22L-A/s1600/t-72%2Bwheels.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://4.bp.blogspot.com/-cWK2SpEDYjU/VRgYQy8cozI/AAAAAAAABhE/wayByA22L-A/s1600/t-72%2Bwheels.png" width="238" /></a></span></div>
<div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-L6lcgNeB7h0/YEkKOwmxvnI/AAAAAAAAS14/tbL_mJnBJi8_PVTovQSt7_p1_7ECUoqFACLcBGAsYHQ/s619/T-72%2Broadwheel%2Bdisc%2Binner%2Bside.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="457" data-original-width="619" src="https://1.bp.blogspot.com/-L6lcgNeB7h0/YEkKOwmxvnI/AAAAAAAAS14/tbL_mJnBJi8_PVTovQSt7_p1_7ECUoqFACLcBGAsYHQ/s320/T-72%2Broadwheel%2Bdisc%2Binner%2Bside.png" width="320" /></a></div><div><br /></div><div><br /></div><div>The 1st, 2nd and 6th swing arm pairs are reinforced to withstand stronger dynamic loads, and thus weigh 59 kg instead of 55 kg like the 3rd, 4th and 5th swing arm pairs. Together with the swing arm and torsion bar, the complete wheel unit has a nominal weight of 265 kg, similar to the individual wheel weight of a T-54, T-55 and T-62. The large weight of the wheel increases the rotating mass of the suspension, which has a negative influence on the dynamic characteristics of the tank, namely in terms of acceleration and the suspension reaction when steering. Having a larger unsprung mass also makes the tank itself heavier, which is undesirable as well. The main advantage of larger diameter wheels is that rolling resistance is reduced, but due to the heavier powertrain and reduced traction from the RMSh track design compared to the dual-pin RMSh track of the T-64, the advantage is small.</div></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div><span style="font-size: small;"><div style="font-weight: normal;"><span><span style="font-size: small;"><span>The photos below give a good view of the wheels.</span></span><br /></span></div><div style="font-weight: normal;"><span><span style="font-size: small;"><span><br /></span></span></span><span><span style="font-size: small;"><span><br /></span></span></span></div><div class="separator" style="clear: both; font-weight: normal; text-align: center;"><span><a href="http://4.bp.blogspot.com/-sRpvSzToNuk/VSuF0w5jg2I/AAAAAAAABuw/b5WfRVTcv2c/s1600/8.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="265" src="https://4.bp.blogspot.com/-sRpvSzToNuk/VSuF0w5jg2I/AAAAAAAABuw/b5WfRVTcv2c/s1600/8.png" width="640" /></a></span></div><div style="font-weight: normal;"><span></span></div><div class="separator" style="clear: both; font-weight: normal; text-align: center;"></div><div style="font-weight: normal;"><span></span></div><div class="separator" style="clear: both; font-weight: normal; text-align: center;"><span><a href="http://1.bp.blogspot.com/-a1eLSAmMOJ8/VSuF5XtHvII/AAAAAAAABu4/aWtLDAGOq9s/s1600/6.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="267" src="https://1.bp.blogspot.com/-a1eLSAmMOJ8/VSuF5XtHvII/AAAAAAAABu4/aWtLDAGOq9s/s1600/6.png" width="640" /></a></span></div><div style="font-weight: normal;"><br /><span><span style="font-size: small;"><span><br /></span></span></span></div><div style="font-weight: normal;">Due to the close similarity in dimensions between the 810mm roadwheels of the T-54 and the 750mm roadwheels of the T-72 and the fact that the RMSh tracks used by the T-72 were designed to work with both types of wheels, it is ostensibly possible to convert a T-72 to use the older type. The main modification would be to add a few more track links to accommodate the larger diameter. The axle socket of the T-54 wheel has the same diameter of 85mm as the axle socket of the T-72 wheel, and in fact, the wheels of the T-72 share the same internal axle sleeve (54.12.022-2А) as T-54 wheels which ensures cross-compatibility. T-54 wheels are sometimes seen on T-72s in repair depots. However, the suspension interchangeability between the T-72 and older medium tanks was not total, because the tank cannot use old OMSh tracks. The drive sprocket does not work with the OMSh track, and there is no pin retention ramp built into the sides of the hull to hammer the track pins back into place as they work themselves out.</div><div style="font-weight: normal;"><span><br /></span></div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; font-weight: normal; text-align: center;"><a href="https://1.bp.blogspot.com/-9J-Rd35N1ZY/Xm9sVMiph2I/AAAAAAAAQSg/jvwrjqzyrZYnaKGPwP88r7-izq8vKa6SACLcBGAsYHQ/s1600/t-72%2Bdriving%2Bwith%2Bt-54%2Bwheels%2B1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="750" data-original-width="1000" height="300" src="https://1.bp.blogspot.com/-9J-Rd35N1ZY/Xm9sVMiph2I/AAAAAAAAQSg/jvwrjqzyrZYnaKGPwP88r7-izq8vKa6SACLcBGAsYHQ/s400/t-72%2Bdriving%2Bwith%2Bt-54%2Bwheels%2B1.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-hVxqveLKc_k/Xm9sVnKtMBI/AAAAAAAAQSk/kPI3BHobZQ4k_i1h8G43MAo_MEIAUi3gACLcBGAsYHQ/s1600/t-72%2Bdriving%2Bwith%2Bt-54%2Bwheels%2B2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="750" data-original-width="1000" height="300" src="https://1.bp.blogspot.com/-hVxqveLKc_k/Xm9sVnKtMBI/AAAAAAAAQSk/kPI3BHobZQ4k_i1h8G43MAo_MEIAUi3gACLcBGAsYHQ/s400/t-72%2Bdriving%2Bwith%2Bt-54%2Bwheels%2B2.jpg" width="400" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><div><div><span style="font-size: small;">The first, second and last roadwheel on both sides are augmented with hydraulic rotary shock absorbers. The front two shock absorbers are highly beneficial as the tank crosses rough terrain, while the rearmost shock absorber is intended to assist recovery when driving through dips and bumps. Simple bump stops are affixed to the sides of the hull for each swing arm to prevent the arm from overextending beyond the deflection limit of the torsion bar and shock absorber. This type of bump stop simply blocks the further motion of the swing arm without damping the shock forces as a hydraulic or volute spring bump stop would. As such, the cross-country ride would tend to be harder at high speeds compared to a suspension system with damping bump stops.</span></div></div><div><span><br /></span></div><div><div><span><br /></span></div><div class="separator" style="clear: both; text-align: center;"><span><a href="https://2.bp.blogspot.com/-01JdzcM42VE/WhI4XP_760I/AAAAAAAAKKY/TS_GuwRg2sst0ovizh2L-GJbKK_kpZrEgCLcBGAs/s1600/t-72%2Bshock%2Babsorber.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1440" height="300" src="https://2.bp.blogspot.com/-01JdzcM42VE/WhI4XP_760I/AAAAAAAAKKY/TS_GuwRg2sst0ovizh2L-GJbKK_kpZrEgCLcBGAs/w400-h300/t-72%2Bshock%2Babsorber.png" width="400" /></a></span></div><div><span><br /><br /><span style="font-size: small;"><span>A cross section of the shock absorber is illustrated below. The device is compact and relatively light, each filled shock absorber assembly having a weight of 66.6 kg. It is a vane type shock absorber with the vanes splitting the body into two pairs of opposing chambers, with a regulator valve in each vane opening. Vertical motion of the roadwheel swing arm deflects the lever arm of the shock absorber, transforming linear force into torque which is applied to the vane rotor. The rotary motion of the vanes displaces the hydraulic fluid from the high-pressure chamber to the opposing low-pressure chamber via the vane opening. The restriction of fluid flow through a small opening creates a resistance to motion, converting kinetic energy into thermal energy, thus damping the force applied by the roadwheel. The large amount of heat produced by the interaction is absorbed by the tank hull and removed by the flow of cool air. </span></span></span></div><div><br /></div><div><span><br /></span></div><div class="separator" style="clear: both; text-align: center;"><span><a href="https://1.bp.blogspot.com/-kJfhZ0FKjcM/WwA9S0mUPOI/AAAAAAAALmg/y6_4RzAGzfQ2147y-nIXxpzjWckuNCr6gCLcBGAs/s1600/t-72%2Bshock%2Babsorber.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1159" data-original-width="1600" height="288" src="https://1.bp.blogspot.com/-kJfhZ0FKjcM/WwA9S0mUPOI/AAAAAAAALmg/y6_4RzAGzfQ2147y-nIXxpzjWckuNCr6gCLcBGAs/s400/t-72%2Bshock%2Babsorber.png" width="400" /></a><a href="https://3.bp.blogspot.com/-_bL4kR-pYfY/Wv_lUbMtrBI/AAAAAAAALl8/2P7jLlLS0LsQG0xTUQF9DdDmUMK2tFMIgCLcBGAs/s1600/shock%2Babsorber%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="545" data-original-width="811" height="268" src="https://3.bp.blogspot.com/-_bL4kR-pYfY/Wv_lUbMtrBI/AAAAAAAALl8/2P7jLlLS0LsQG0xTUQF9DdDmUMK2tFMIgCLcBGAs/s400/shock%2Babsorber%2Bcross%2Bsection.png" width="400" /></a></span></div><div><span><br /></span></div><div><span><span style="font-size: small;"><span><br /></span></span><span style="font-size: small;"><span>This type of shock absorber was previously used on the T54 and T-62 series, but the shock absorbers of the T-72 have a much greater range of travel so that the load is absorbed progressively over a longer distance. This greatly softens the oscillation of the hull, making it a much smoother ride compared to a T-54/55 or T-62. The larger range of travel is depicted in the drawing below by the dotted lines. Drawing taken from the book "<i>Kampfpanzer: Die Entwicklungen der Nachkriegszeit</i>" by Rolf Hilmes.</span></span><br /></span></div><div><span><br /></span></div><div class="separator" style="clear: both; text-align: center;"></div><div><span><br /></span></div><div class="separator" style="clear: both; text-align: center;"><span><a href="https://2.bp.blogspot.com/-CXitDVfmbRM/Wv5CDDFSkmI/AAAAAAAALlk/rn5M-4xs8vUmyAo2FtMWsxT5O8v6jZniACLcBGAs/s1600/shock%2Babsorbers.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1110" data-original-width="752" height="400" src="https://2.bp.blogspot.com/-CXitDVfmbRM/Wv5CDDFSkmI/AAAAAAAALlk/rn5M-4xs8vUmyAo2FtMWsxT5O8v6jZniACLcBGAs/s400/shock%2Babsorbers.png" width="270" /></a></span></div><div><span><br /></span></div></div></div><div style="font-weight: normal;"><br /></div>
<span style="font-size: small; font-weight: normal;"><span style="font-weight: normal;">The maximum vertical travel of the first roadwheel is 315mm up (bump) to 43mm down (rebound) for a total range of 358mm, and the amount of vertical travel of each of the other roadwheels is variable. This variability was created intentionally by varying the angle of the swing arm installation points. The effect of this is a considerable reduction in the linearity of the overall suspension system despite the linear characteristics of each individual wheel, which is unavoidable as it is an inherent trait of a torsion bar spring. The three shock absorbers on each side of the T-72 suspension are additional non-linear elements that modify the linearity of the suspension system. The non-linearity of the system has a positive effect on ride quality.</span></span></span></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The ranges of travel are listed in the drawing below. Altogether, the bump travel varies from 254-315mm and the rebound travel varies from 43-116mm for an overall travel range of 358-370mm. This was a large improvement compared to the 224mm of overall travel offered by the T-54/55 or T-62 suspensions, and it was achieved by producing the torsion bars using a new steel alloy alongside the increased length of the torsion bars (2,310mm vs 2,180mm). It was also good compared to all foreign tanks of the 1970's, with the closest counterpart in terms of performance being the Leopard 1. The Leopard 1 had a bump travel of 227-279mm and a rebound travel of 128-156mm, giving a larger overall travel range of 383-407mm. However, the relative importance of bump travel with regard to ride quality at high speeds over bumpy terrain far outweighs that of rebound travel, and because of this, the T-72 suspension is not inferior to that of the Leopard 1. </div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span><br />
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<span style="font-size: small;"><a href="https://4.bp.blogspot.com/-5tbpSx8ATkc/WqigXw3TqFI/AAAAAAAALIQ/FTvXVtjL04ElqwQLLLCYQ9MKjMxKttVXACLcBGAs/s1600/t-72%2Bsuspension.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="296" data-original-width="1600" height="118" src="https://4.bp.blogspot.com/-5tbpSx8ATkc/WqigXw3TqFI/AAAAAAAALIQ/FTvXVtjL04ElqwQLLLCYQ9MKjMxKttVXACLcBGAs/s640/t-72%2Bsuspension.png" width="640" /></a></span></div><div style="font-weight: normal;"><span style="font-size: small;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small;"><span style="font-weight: normal;">Compared to the suspensions of the M60A1, AMX-30 and the Chieftain, the difference in performance is very stark. An interesting exception is the Strv 103 as its hydropneumatic suspension offered an exceptionally large</span></span></span> overall wheel travel range of 379-543mm, but gave an unusually bumpy ride (likened to that of a camel ride in a British evaluation) as the vehicle was unstable due to its short track base and the fact that it had just four roadwheels on each side. However, the three next-generation NATO tanks all surpassed the T-72 in ride quality. The M1 Abrams and Leopard 2 both offered excellent damping with much larger overall travel ranges of 481mm and 470mm respectively, though it is important to keep in mind that the difference in rebound travel is disproportionately higher than the bump travel. The bump travel of the M1 Abrams and Leopard 2 suspensions is 381mm and 325-331mm respectively. The Challenger 1 had a hydrogas (hydropneumatic) suspension that offered an overall travel range of 450mm with 350mm of bump travel at a nominal temperature of 20°C. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><span style="font-size: small;">
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<span style="font-size: small;"><span style="font-weight: normal;">In terms of ease of accessibility such as routine maintenance (such as lubrication, as shown below) or the replacement of damaged wheels, the design of the roadwheels and idler wheels of the T-72 is not different than any other type. </span></span><br /><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
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<span style="font-size: small;"><span style="font-weight: normal;"><a href="https://2.bp.blogspot.com/-yYFpqZfO9P0/W122OeiKyAI/AAAAAAAAL20/Z_0lKxCNfIIpATAa6dUDFSgOc7F6t1QAQCLcBGAs/s1600/lubricating%2Bwheels%2Bt-72.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="408" data-original-width="713" height="229" src="https://2.bp.blogspot.com/-yYFpqZfO9P0/W122OeiKyAI/AAAAAAAAL20/Z_0lKxCNfIIpATAa6dUDFSgOc7F6t1QAQCLcBGAs/w400-h229/lubricating%2Bwheels%2Bt-72.png" width="400" /></a><a href="https://1.bp.blogspot.com/-iltYtXyIfmc/YBPchvyNASI/AAAAAAAASq8/4Zr27InkkA8FG4zrpwr7vmZGmqgnqA3zwCLcBGAsYHQ/s2048/t-72a%2Bmaintenance.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1211" data-original-width="2048" height="236" src="https://1.bp.blogspot.com/-iltYtXyIfmc/YBPchvyNASI/AAAAAAAASq8/4Zr27InkkA8FG4zrpwr7vmZGmqgnqA3zwCLcBGAsYHQ/w400-h236/t-72a%2Bmaintenance.png" width="400" /></a><br /></span></span></div>
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<span style="font-size: large;">TRACKS</span></h3>
<div><br /></div><div>Track tension was adjusted in a manner that is familiar to most tankers; a large wrench (the "tanker bar") is fitted onto the protruding nut of a worm gear in the idler wheel housing, marked in the photo below with a white arrow. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-31UP0HEMMBU/X2e6QA36zuI/AAAAAAAARoA/GIHo_4tDtF0h_JqgL0pG1ZuOva2Vw3VXwCLcBGAsYHQ/s1408/1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1118" data-original-width="1408" height="318" src="https://1.bp.blogspot.com/-31UP0HEMMBU/X2e6QA36zuI/AAAAAAAARoA/GIHo_4tDtF0h_JqgL0pG1ZuOva2Vw3VXwCLcBGAsYHQ/w400-h318/1.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><div style="text-align: left;"><br /></div><div style="text-align: left;"><br /></div><div style="text-align: left;">The nut is then twisted to turn the worm gear inside the housing which rotates the idler wheel around its axle, thus shifting it forwards or backwards.</div><div style="text-align: left;"><br /></div><div style="text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jTuILdG407c/X2e9en9yjiI/AAAAAAAARoI/0ebUTY6XsQIcGnOic6b46_jSNjaTZmsjQCLcBGAsYHQ/s2048/idler%2Bwheel%2Badjustment%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1087" data-original-width="2048" height="341" src="https://1.bp.blogspot.com/-jTuILdG407c/X2e9en9yjiI/AAAAAAAARoI/0ebUTY6XsQIcGnOic6b46_jSNjaTZmsjQCLcBGAsYHQ/w640-h341/idler%2Bwheel%2Badjustment%2Bmechanism.png" width="640" /></a></div><br /></div><div><br /></div><br />
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<span style="font-size: large;">RMSh</span></h3>
<span style="font-weight: normal;"><br /></span><div>In 1964, the RMSh track (613.44.22sb) began replacing the older OMSh track for T-54, T-55 and T-62 tanks. It is a live track. Existing tanks would be converted over to the new track during scheduled maintenance at repair facilities by having their drive sprockets replaced. By the 1970's, the RMSh track was the most common type in the Soviet Army. The design of the RMSh was continuously refined, and in 1972 an improved RMSh track was adopted by the Soviet Army. It had a service life of up to 10,000 km. The T-72 used the improved track from the beginning of its service in the Soviet Army, and the improved track was also issued as the new standard for T-55 and T-62 tanks. This was achieved by using a new and improved steel grade with greater wear resistance and strength. Some structural changes were also made to the design of the track itself. As a result, the mine resistance of the new RMSh track was 1.5 times better than the old OMSh track. </div><div><br /></div><div>During mine tests in the late 1970's, it was found that the single-pin RMSh track was more resistant to mine blasting compared to the tracks of the T-64 and Object 219 (T-80). It was determined that 1.4 kg of TNT or its equivalent is required to sever the RMSh track on a T-72. This difference was largely meaningless against most anti-tank mines, including most track-breaker mines with a small explosive mass, but against very light, rocket or helicopter-delivered scatterable track breaker mines of the same class as the domestic PTM-1, a resistance limit of 1.4 kg of TNT provided the tank with a margin of safety. In the event that such a mine is encountered, the tank may retain some mobility to withdraw from the minefield under its own power, keeping the crew out of risk.</div><div><br /></div><div><br /></div><div>Each side of the T-72 requires a set of 97 RMSh track links which may be reduced as the track is worn and eventually stretches. The T-72 uses the same number of RMSh track links as the T-62. The track measures 580mm in width and 137mm in pitch. A rubber bushing is fitted between the pin and the pinhole, both of which are hexagonal. The bushings reduce vibrations, reduce wear and tear and also dampen the noise levels compared to all-metal tracks. The track links are made of G13LA Mangalloy (Hadfield steel). It has a hardness of 170-217 BHN. Each track pin has a diameter of 30mm, and the eyelets for the pins have an external diameter of 38mm.</div></div><div>
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<a href="https://1.bp.blogspot.com/-8BH8jgThIP4/XlZ26Hj38RI/AAAAAAAAQHU/40k64kyZR8I4Xe04kTWrWPfY67qvj8gZgCLcBGAsYHQ/s1600/rmsh%2Btrack.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1477" height="320" src="https://1.bp.blogspot.com/-8BH8jgThIP4/XlZ26Hj38RI/AAAAAAAAQHU/40k64kyZR8I4Xe04kTWrWPfY67qvj8gZgCLcBGAsYHQ/s320/rmsh%2Btrack.jpg" width="295" /></a><a href="http://1.bp.blogspot.com/-dqkyf-lfgRk/VRPb6kU8MaI/AAAAAAAABcs/gL5r_xpeTOI/s1600/T-72%2BIdler%2Band%2Btrack.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="272" src="https://1.bp.blogspot.com/-dqkyf-lfgRk/VRPb6kU8MaI/AAAAAAAABcs/gL5r_xpeTOI/s400/T-72%2BIdler%2Band%2Btrack.png" width="400" /></a></div>
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<span style="font-weight: normal;"><span style="font-weight: normal;"><span style="font-size: small;">The ground contact length is 4,270mm, as opposed to 4,242mm of the T-64 tracks.</span></span><span style="font-size: small;"><span style="font-weight: normal;"> A full set of 97 links weighs just over 1,723 kg for one side, and 3,446 kg for a pair of two tracks. These tracks were simpler than the dual-pin tracks of the T-64A and had better traction on rocky and sandy terrain, but had worse traction in mud and other types of terrain and were not as durable. The RMSh tracks compare unfavourably to the T142 tracks of the M60A1. These tracks are also heavier than the T-64A tracks which weighed just 1,450 kg.</span></span></span></div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-eTnBf_zJBBk/VPMhNGaPpjI/AAAAAAAABSU/f9xmst78lac/s1600/t-72_raac_museum_130_of_151.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://2.bp.blogspot.com/-eTnBf_zJBBk/VPMhNGaPpjI/AAAAAAAABSU/f9xmst78lac/s1600/t-72_raac_museum_130_of_151.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Old drive sprocket</td></tr>
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<br /><br /></div><div>Rubber track pads were not used during the career of the T-72 in the Soviet Army as such pads were found to increase the track mass by approximately 40% and are ineffective when driving over rough terrain. Of course, that is not to say that they do not come with any benefits. On the contrary, it was experimentally established that rubber track pads increased traction on concrete by 40%, and on dry soil by 7%. When moving on roads, the average speed of a tank column can be increased by 10-15%. However, in practice, metal grousers provide better performance when driving cross-country across a variety of surfaces, including mud, snow, sand and soil. </div><div><br />
<h3>
<span style="font-size: large;">UMSh</span></h3>
<span style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
<span style="font-size: small;"><span style="font-weight: normal;">Newer UMSh dual-pin tracks are available, also measuring 580mm in width</span></span><span style="font-size: small;"><span style="font-weight: normal;">. UMSh tracks were specially developed for the T-80 as a necessity because of the uniquely high stresses on the suspension from the high torque from its gas turbine engine and also because of the tank's high average speed across rough terrain. As such, these tracks were the smoothest and most durable of the three types used by the Soviet Union's three main battle tanks. Installation of the newer tracks
requires modified drive sprockets, so only the newer modifications of the T-72 have this installed, including some late production T-72B variants. </span></span></span><br />
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<span style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;">The interior surface of the track pads are rubber-lined so that the rubber rims of the roadwheels roll on a rubber surface rather than a metal one. This prolongs the life of the roadwheels and also helps to reduce the vibrations transmitted to the tank from driving over rough ground. The reduction in vibrations increases the comfort of the crew and improves the accuracy of the weapons while firing on the move, at the expense of slightly increasing the rolling resistance. An entire set of tracks weighs 1,760 kg and the combined weight of a pair of tracks is just under 3,520 kg. There are 80 track links per side.</span></span><br /><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
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<span style="font-weight: normal;"><a href="https://3.bp.blogspot.com/-HyC9IJA1qDk/Wh1fnvTuj6I/AAAAAAAAKO8/y64tWEiWB5AW98MOdpNn3pPI0ZfuOphNgCLcBGAs/s1600/7au2n0iszolo-12.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="266" src="https://3.bp.blogspot.com/-HyC9IJA1qDk/Wh1fnvTuj6I/AAAAAAAAKO8/y64tWEiWB5AW98MOdpNn3pPI0ZfuOphNgCLcBGAs/s400/7au2n0iszolo-12.jpg" width="400" /></a></span></div>
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<span style="font-weight: normal;"></span><span style="font-size: small;"><span style="font-size: small; font-weight: normal;">Because the weight increase is negligible - less than 80 kg - the installation of UMSh tracks did not noticeably increase the weight of the tank. Overall, the effect of replacing the RMSh track with the UMSh track was purely beneficial.</span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-size: small; font-weight: normal;"><br /></span><span style="font-weight: normal;"><span style="font-weight: normal;"><font>The ground contact length with the UMSh tracks is very slightly longer than on the RMSh tracks - 4,290mm instead of 4,270mm. The photo below (</font></span></span></span><font>courtesy of Vitaly Kuzmin) shows a T-72B3 with UMSh tracks and rubber track pads installed for driving on paved roads.</font></div>
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<span style="font-size: small;"><span style="font-weight: normal;">There is a simple mud scraper bolted on to the side of the hull in every T-72, just above the drive sprocket. The scraper helps to prevent loss of traction from excess soil on the tracks, especially sticky mud like clay.</span></span><br />
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<br /><span style="font-size: small;"><span style="font-weight: normal;">The T-72 continued to use the same sheet metal mudguard design until the T-72B variant, when it was replaced by a T-80-style rubber mudguard design. The two mudguard types are interchangeable between all T-72 variants, and indeed, many examples had the new mudguards retrofitted during regular scheduled overhauls. The photo below on the left shows the original sheet metal mudguards on a T-72 Ural and the photo below on the right shows the new mudguard on a modernized T-72 Ural.</span></span></span></span></div>
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<a href="https://2.bp.blogspot.com/-cv69WC4XfxI/W4Q2s2HfZTI/AAAAAAAAMPM/3UVFN_N6eTgqP21G2Je02f4KbsPosvo8wCLcBGAs/s1600/kubinka%2Bkhlopotov.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://2.bp.blogspot.com/-cv69WC4XfxI/W4Q2s2HfZTI/AAAAAAAAMPM/3UVFN_N6eTgqP21G2Je02f4KbsPosvo8wCLcBGAs/s400/kubinka%2Bkhlopotov.jpg" width="400" /></a><a href="https://4.bp.blogspot.com/-VLi5C-sflVs/W4Q2fYeRxwI/AAAAAAAAMPI/JiAe8SlDokozm_5r24vp5JcRIV9012u0QCLcBGAs/s1600/modernized.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="593" data-original-width="790" height="300" src="https://4.bp.blogspot.com/-VLi5C-sflVs/W4Q2fYeRxwI/AAAAAAAAMPI/JiAe8SlDokozm_5r24vp5JcRIV9012u0QCLcBGAs/s400/modernized.jpg" width="400" /></a></div>
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<span style="font-size: small; font-weight: normal;">The reason for the switch is not entirely clear, but it is very likely that the main impetus was the greater durability of a rubber mudguard. It is likely that unlike sheet metal, the rubber flap of the new design could flex and deform elastically under adverse conditions while still maintaining enough rigidity to perform its primary function as a mudguard. The T-90 and T-90A continue to use the new rubberized mudguards to this day.</span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;"><br /></span></div><div style="font-weight: normal;"><span style="font-size: small; font-weight: normal;">The T-72 Ural and T-72A exert 0.83 kg/sq.cm of nominal ground pressure, while the T-72B, being heavier due to its thicker armour and incorporation of ERA, put in 0.898 kg/sq.cm of ground pressure. Compared to its immediate foreign counterparts, the T-72 had little to no advantage in soft terrain, despite being a great deal lighter than all of its adversaries. Against the Chieftain, Leopard 1 and M60A1, the T-72 Ural and T-72A fared slightly better in this respect, but the T-72B was neither better nor worse than its more modern rivals like the Leopard 2, Challenger 1, M60A3 and the M1 Abrams. The weight discrepancy doesn't manifest in this regard, but it becomes much more apparent when we consider the infrastructure of Eastern Europe at the time, especially the bridges - both permanent and temporary ones - which had stricter weight restrictions. Another advantage of the light weight of the T-72 is that it is light enough to be transported on existing rail platforms (the maximum cargo load limit was 55 tons), and also light enough to be compatible with the weight limit of the old MTU-55 bridge layers and TMM truck-based bridge layers, both of which were and still are present in large numbers in the Russian Army Engineers. </span></div>
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<div style="font-weight: normal;"><span style="font-weight: normal;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;">When parked or moving on a hard surface, where the weight of the tank is applied over the single track link directly underneath each roadwheel, the mean maximum ground pressure (MMP) is obtained instead of the nominal ground pressure. Given a fixed vehicle weight, the mean maximum ground pressure is governed by the area of a track link and the number of roadwheels over which the weight is divided rather than the entire track contact area, with the number of roadwheels being the dominant factor. By this metric, the T-72 is significantly inferior to its foreign counterparts, as shown in the table below, with a T-72 having an MMP of 430 kPa as compared to the M60A1 (335 kPa), Leopard 1 (344 kPa), and so on. All tanks are combat-loaded in this comparison. This is not very surprising, as the T-72 has one fewer roadwheel pair, and it uses a single-pin track with a short pitch, unlike the longer-pitched double-pin tracks found on all four foreign tanks compared in the table.</div><div style="font-weight: normal;"><span style="font-weight: normal;"><span style="font-weight: normal;"><br /></span></span></div><div class="separator" style="clear: both; font-weight: normal; text-align: center;"><a href="https://1.bp.blogspot.com/-iFI_BKRFI4I/YSXpzBXpbUI/AAAAAAAAUGw/nT9LtrXwjyQJ_NaJguB-6Uo-mJ2pJsI_QCLcBGAsYHQ/s1909/ground%2Bpressures.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="865" data-original-width="1909" height="290" src="https://1.bp.blogspot.com/-iFI_BKRFI4I/YSXpzBXpbUI/AAAAAAAAUGw/nT9LtrXwjyQJ_NaJguB-6Uo-mJ2pJsI_QCLcBGAsYHQ/w640-h290/ground%2Bpressures.png" width="640" /></a></div><div style="font-weight: normal;"><br /></div><div>Broadly speaking, this is indicative of the difference in the design priorities of these opposing tank designs, as a low mean maximum ground pressure is most relevant for tanks that must drive on paved roads, as a high MMP translates to a high load on rubber track pads, and thus strongly affects the lifespan of track pads, and a high MMP is responsible for more intense damage to roads. Soviet tanks did not use track pads, and did not rely on road networks for long-distance travel, which apparently gave the suspension designers far a much larger allowance in the permissible MMP limit compared to their NATO counterparts.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><span style="font-weight: normal;"><span style="font-weight: normal;">There are, however, mitigating factors which are not addressed by direct comparisons, which are the wheel diameter and the track surface itself. The latter factor is perhaps the most obvious, as on asphalt or concrete, the surface of a metal track, which is grousered, does not distribute the load onto a surface that is directly equal to the surface area of a single track link, but onto the ends of the grouser protrusions, which naturally translates to a very high mean maximum pressure. For this reason, metal tracks penetrate into asphalt and concrete and cause severe damage. The use of rubber track pads for driving on paved roads also has a similar effect, as the contact patch of the rubber pad(s) on a track link are also invariably smaller than the surface area of the track link itself. Indeed, for tracks that were designed to use rubber track pads for both on-road and off-road driving, the dependence on using the protruding track pad as a grouser can mean that the pad contact patch is only half as large as the track link itself, as exemplified by the American T97E1 and T142 tracks for the M60A1.</span></span></div><div style="font-weight: normal;"><span style="font-weight: normal;"><span style="font-weight: normal;"><br /></span></span></div><div><span><span>The factor of wheel diameter is largely irrelevant when driving on paved roads, but on deforming terrain, the diameter of the roadwheels is responsible for distributing the load more evenly when the track is flexed in following the contours of the terrain. This is shown in the diagram below, from the engineering textbook "<i>Расчет И Конструирование Гусеничных Машин</i>", edited by Professor N. A. Nosov. The extent of track flexion is exaggerated in the drawing to illustrate the effect. Compared to the case of the suspension on terrain, the suspension on hard ground exerts a high mean maximum pressure because the track tension has little effect when the track is laid flat on the ground. On deforming terrain, the track redistributes a significant proportion of the load between the wheels, partly due to the terrain conforming to the circumference of the roadwheels and partly via track tension. Due to this, when compared to the nominal ground pressure (dashed line), the MMP is only somewhat larger.</span></span></div><div style="font-weight: normal;"><span style="font-weight: normal;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-weight: normal;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEht78vqIZAvgZdknkm1snUzjkWcPt1IbNMBGcZgguNfgK9VqshG3Nl42u_t-Ye9c_cg8B_mKOIdGfhWdezphTIuz72b0WsGj3DcNp0krs7JNglrVOE9sLPb42Dp5wpqJVszxucvgzJCxhJ7u-oLohW2dboeZqOdhei9xp1E0qtyDeL6VMEXkdjIksV0ZQ=s2711" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="717" data-original-width="2711" height="170" src="https://blogger.googleusercontent.com/img/a/AVvXsEht78vqIZAvgZdknkm1snUzjkWcPt1IbNMBGcZgguNfgK9VqshG3Nl42u_t-Ye9c_cg8B_mKOIdGfhWdezphTIuz72b0WsGj3DcNp0krs7JNglrVOE9sLPb42Dp5wpqJVszxucvgzJCxhJ7u-oLohW2dboeZqOdhei9xp1E0qtyDeL6VMEXkdjIksV0ZQ=w640-h170" width="640" /></a></div><span style="font-weight: normal;"><br /></span></span></div><div><span><span>For a given amount of space between roadwheels, track tension and track pitch, increasing the diameter of the roadwheels can reduce the MMP. With highly tensioned tracks, the tracks deform less and can hold the wheels in compression excessively, which negatively affects off-road mobility. Thus, assuming that track tension is equal between tanks with supported track suspension (unsupported track suspensions generally require slightly less track tension), the other major factor in reducing MMP is the roadwheel diameter. When normalized to a generalized pressure parameter (labeled pressure 'Q' in Table 20 above) which takes into account the flex of the track such that the area through which the load is transmitted to the ground is dependent on the ratio of the diameter of the roadwheel and the pitch of the track, the pressure is much closer to foreign tanks, reaching 183 kPa compared to a pressure of 170-171 kPa for all four foreign tanks. The disadvantage in nominal MPP, which is between 25-38%, translates to a real difference of only 7.6% on terrain when this parameter is considered. This is only a fraction (20-30%) of the difference in nominal MPP. Keeping this in mind, along with the nominal ground pressure, it can be seen that the T-72 may not be significantly inferior to foreign tanks in the most relevant parameters for cross-country travel when using RMSh tracks, depending on the terrain. A T-72B3 with a nominal combat weight of 45.6 tons will have an MMP of 391.7 kPa with its dual-pin tracks, due to the longer track pitch of 164mm.</span></span></div><div><br /></div><div><span><span>Thus, it can be seen that there is a great deal of complexity involved in the subject, and that direct comparisons of nominal figures are usually not valid as comparisons of capability. </span></span>Secondary merits also deserve consideration, as, for instance, the use of tracks with a shorter pitch provides advantages in track noise, vibration, and track life.</div><div style="font-weight: normal;"><br /></div>
<span style="font-size: small; font-weight: normal;"><span style="font-weight: normal;">In total, the suspension, powertrain, and all the associated systems have a combined weight of 8.57 tons. </span></span><span style="font-size: small; font-weight: normal;"><span style="font-weight: normal;">The total weight of the T-72 suspension alone with RMSh tracks is 5,849 kg.</span></span></span></span></div><div><span style="font-weight: normal;"><span style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></span></span></div><div><span style="font-weight: normal;"><span style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
<span style="font-size: small;"><span style="font-weight: normal;">Finally, it is worth noting that if the T-72 were trapped in swamps, bogs or in deep snow, it may escape with the help of an unditching log.</span></span><br />
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<span style="font-weight: normal;"><span style="font-weight: normal;"><a href="http://3.bp.blogspot.com/-OBJOt53_vBU/VQbesZQVBJI/AAAAAAAABX4/AjiK88i9Dow/s1600/Finnish_Army_T-72_Ps264-202_rear.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="360" src="https://3.bp.blogspot.com/-OBJOt53_vBU/VQbesZQVBJI/AAAAAAAABX4/AjiK88i9Dow/s640/Finnish_Army_T-72_Ps264-202_rear.jpg" width="640" /></a></span></span></div><div style="font-weight: normal;"><span style="font-weight: normal;"><span style="font-weight: normal;">
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<span style="font-size: small; font-weight: normal;">B</span><span style="font-size: small; font-weight: normal;">y
tying the log to track pins on both right and left tracks as
illustrated below, the tracks will drag the log along and under them,
thus forcing that section of the track to rise above the mud while
simultaneously giving the track something more solid to drive over. This
allows the tank to get out of the hairiest situations.</span><br />
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<span style="font-weight: normal;"><span style="font-weight: normal;"><a href="http://1.bp.blogspot.com/-emBQ7jgC-tA/VQbYNoQ64fI/AAAAAAAABXc/b99XbXqFvA4/s1600/log.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="275" src="https://1.bp.blogspot.com/-emBQ7jgC-tA/VQbYNoQ64fI/AAAAAAAABXc/b99XbXqFvA4/s1600/log.png" width="320" /></a> </span></span></div>
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<span style="font-size: small; font-weight: normal;">The unditching log was demonstrated in Sweden by an ex-GDR T-72M1 in 1991 as part of a series of tests. Colour photo available on the <a href="http://www.ointres.se/cg-artikel-5.jpg">ointres.se website</a>.</span><br /><span style="font-size: small; font-weight: normal;"><br /></span>
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<a href="https://3.bp.blogspot.com/-oy6c9eGTTmA/Wg7vovD7WxI/AAAAAAAAKIg/PglKVhx94jol_HXjSuArr1NFIS3eg0hCACLcBGAs/s1600/t-72%2Bin%2Bsweden.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="326" data-original-width="800" height="260" src="https://3.bp.blogspot.com/-oy6c9eGTTmA/Wg7vovD7WxI/AAAAAAAAKIg/PglKVhx94jol_HXjSuArr1NFIS3eg0hCACLcBGAs/s640/t-72%2Bin%2Bsweden.jpg" width="640" /></a></div>
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<span style="font-size: small; font-weight: normal;">Here is a video (<a href="https://www.youtube.com/watch?v=YEoaU6aQxMI">link</a>) demonstrating a tank unditching itself using the log.</span><br />
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<a href="https://www.blogger.com/null" id="water"></a>
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<h3>
<span style="font-size: small;"><span style="font-size: large;">WATER OBSTACLES</span></span></h3>
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<a href="https://3.bp.blogspot.com/-kdbCDcqILO4/W2mCXbDpYpI/AAAAAAAAMCM/LO5wMutQAWYsxRwflvHYYh9BnaZPaRi8gCLcBGAs/s1600/16023694837_dba92e6662_o.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="534" data-original-width="841" height="253" src="https://3.bp.blogspot.com/-kdbCDcqILO4/W2mCXbDpYpI/AAAAAAAAMCM/LO5wMutQAWYsxRwflvHYYh9BnaZPaRi8gCLcBGAs/s400/16023694837_dba92e6662_o.jpg" width="400" /></a><a href="https://2.bp.blogspot.com/--tpdZGXIyns/WXJeuaoXAuI/AAAAAAAAIxk/aqqmE8laF7Mk9J7Lm89HQFFfTR2P0N_EACLcBGAs/s1600/snorkel.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="507" data-original-width="319" height="320" src="https://2.bp.blogspot.com/--tpdZGXIyns/WXJeuaoXAuI/AAAAAAAAIxk/aqqmE8laF7Mk9J7Lm89HQFFfTR2P0N_EACLcBGAs/s320/snorkel.jpg" width="200" /></a></div>
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<span style="font-size: small; font-weight: 400;">The T-72 is equipped with the OPVT fording system which includes a snorkel.</span><span style="font-size: small; font-weight: normal;"> The system allows the T-72 to cross deep water obstacles in the same manner as the T-64, which also uses the OPVT system. It is possible for the tank to ford streams with a depth of 1.2 meters without any preparations, but crossing water obstacles with a depth of 1.8 m or more requires additional preparation: the fighting compartment ventilation system must be turned off, the driver's hatch must be closed, the blower valves in the ventilation system must be checked, the water drainage port plug in the belly of the tank must be removed, an outlet valve must be installed in the drainage port, the air pressure valve for the driver's periscope cleaning system must be closed, the engine exhaust outlet must be replaced with a special outlet with valves (shown below on the right), and all open ports on the engine deck must be shut with their respective sealing covers.</span><br />
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<a href="https://1.bp.blogspot.com/-8QICByWJOEs/XnYFhfMwN7I/AAAAAAAAQZU/cxxvR9n7ybYp21-JHEBSvbpJ1IRedFxwwCLcBGAsYHQ/s1600/valves.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1366" height="358" src="https://1.bp.blogspot.com/-8QICByWJOEs/XnYFhfMwN7I/AAAAAAAAQZU/cxxvR9n7ybYp21-JHEBSvbpJ1IRedFxwwCLcBGAsYHQ/s640/valves.png" width="640" /></a></div>
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<div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div><span style="font-size: small;">The deck is taken up by the engine access panel, the engine access panel intake, the radiator louvres and the cooling system air outlets. All of them are provided with </span><span style="font-size: small;">watertight covers integral to the OPVT kit to seal the engine compartment during snorkelling operations. </span></div><div><span style="font-size: small;"><br /></span><span style="font-size: small;"><br /></span></div><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-h94-fddfcxo/VUPtN4wZBOI/AAAAAAAACPM/f_WF8EyluCk/s1600/left%2Band%2Bright.png"><img border="0" height="206" src="https://2.bp.blogspot.com/-h94-fddfcxo/VUPtN4wZBOI/AAAAAAAACPM/f_WF8EyluCk/s1600/left%2Band%2Bright.png" width="640" /></a></div><div><br /></div>
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<span style="font-size: small; font-weight: normal;">Fording a 1.8 meter-deep river can be done with the turret hatches open, although water may splash into the turret as the tank is only 2.23 meters tall. The engine draws in air through the fighting compartment, so if the turret hatches are closed, the circular port in the gunner's hatch (shown below) must be opened to ensure that the engine is sufficiently aspirated and to prevent the asphyxiation of the crew.</span><br />
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<a href="http://2.bp.blogspot.com/-oYj0PmJA4jg/VQa0dOqxO3I/AAAAAAAABWo/tAzNRdIYemw/s1600/26574.jpg" style="font-size: 21.9024px; font-weight: 700; margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="300" src="https://2.bp.blogspot.com/-oYj0PmJA4jg/VQa0dOqxO3I/AAAAAAAABWo/tAzNRdIYemw/s400/26574.jpg" width="400" /></a></div>
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<span style="font-size: small;"><span style="font-weight: normal;">The commander directs the driver when crossing such obstacles as the driver has no way of seeing out of the tank when the hull is completely submerged. The tank is driven in 1st gear.</span></span><br />
<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
<span style="font-size: small;"><span style="font-weight: normal;">When the OPVT system is fully activated and the snorkel is mounted, fording up to a depth of
5 meters is possible, but t</span><span style="font-weight: normal;">horough p</span></span><span style="font-size: small; font-weight: normal;">reparations are necessary in order to do so. The same preparations for crossing an 1.8 meter-deep stream must be followed, and the additional preparations include sealing the edges of all
hatches and various openings and periscopes with a thick
resinous waterproofing paste, as the water pressure at such
depths is simply too much for rubber seals to handle. </span><br />
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<a href="http://3.bp.blogspot.com/-H8c1lWriYCY/VSp4w__n8UI/AAAAAAAABtU/E5eUfT8u56A/s1600/paste.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://3.bp.blogspot.com/-H8c1lWriYCY/VSp4w__n8UI/AAAAAAAABtU/E5eUfT8u56A/s1600/paste.png" width="320" /></a></div>
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<span style="font-size: small;"><span style="font-weight: normal;">The driver must then turn on the bilge pump and remove the bilge pump plug. The pump is located to his left side. The bilge pump expels water from the tank through drainage ports in the belly of the hull at a rate of 100 liters per minute when operating with a back pressure of 4 meters of water, which ensures that the tank is not flooded by minor leaks when snorkelling at a depth of 5 meters.</span></span><br />
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<span style="font-size: small;"><span style="font-weight: normal;">Crew members are each given a closed-circuit IP-5 rebreather and a life jacket. The crew must put on the life jacket before beginning the snorkeling operation as a precautionary measure, but the IP-5 may or may not need to be worn prior to entering water. In most cases, the rebreather is worn inside the tank when the commander gives the order to bail out of the tank while the tank is already underwater.</span></span><br />
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<a href="https://3.bp.blogspot.com/-aVLm0EhqWwM/WZgtRtlPTeI/AAAAAAAAJE0/Gh1a6VJBpu0V9K5Ag89HY31ywMluXZnNwCLcBGAs/s1600/t-72%2Bcrew%2Bsnorkeling.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="712" data-original-width="1043" height="436" src="https://3.bp.blogspot.com/-aVLm0EhqWwM/WZgtRtlPTeI/AAAAAAAAJE0/Gh1a6VJBpu0V9K5Ag89HY31ywMluXZnNwCLcBGAs/s640/t-72%2Bcrew%2Bsnorkeling.png" width="640" /></a></div>
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<span style="font-size: small;"><span style="font-weight: normal;">It comprises a watertight, form fitting gas mask, a chemical respirator chamber containing potassium superoxide (KO2), and a flotation collar. The rebreather uses the chemical reaction between potassium superoxide and carbon dioxide, activated by water from the user's breath reduce the former two to oxygen and potassium carbonate. The freshly produced oxygen gas is mixed into the previously exhaled breath to replenish its oxygen content for rebreathing.</span></span><br />
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<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-nS3nzD9aHNU/VT3zpPsnsSI/AAAAAAAACGA/62LOZN0f2a0/s1600/ip5.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-nS3nzD9aHNU/VT3zpPsnsSI/AAAAAAAACGA/62LOZN0f2a0/s1600/ip5.jpg" /></a></td></tr>
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<span style="font-size: small; font-weight: normal;"><br /></span><span style="font-size: small; font-weight: normal;">To cross water obstacles deeper than 1.8 meters, the snorkel included in the OPVT kit is needed to supply air to the engine as the entire tank would be submerged. The long telescoping snorkel, which is made from steel, is broken down into three sections for stowage. The total length of the assembled snorkel is 3,712mm. It is also possible to fit only one or two snorkel sections rather than all three if the depth of the water obstacle does not warrant the installation of the full snorkel. When installed, it provides ventilation for all three crew members as well as the engine. Air is sucked into the fighting compartment of the tank and into the engine via an air intake fan duct which draws air from the crew compartment. The T-72 can snorkel to a maximum depth of 5 meters.</span><br />
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The ventilation scheme is shown in the drawing below. Due to the very large flow rate of the air sucked through the snorkel to aspirate the engine, the crew compartment is well ventilated. The main disadvantage is that the snorkel has no filtration system, and the normal filtered ventilation system is inoperable while snorkeling. However, even with this downside, the crew is not necessarily vulnerable to such dangers while snorkeling as each crew member must don a closed cycle rebreather system before entering water. This means that the crew never has to breathe contaminated air, although the interior of the tank will be unavoidably contaminated. As such, the short term survival of the crew is at least assured.<br />
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Because the hatch can be simply swung open, installing the snorkel is not difficult. The snorkel is fitted with two floating markers during training exercises to indicate the tank's position underwater to help rescue teams locate the tank if it has stopped underwater.<br />
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<span style="font-weight: normal;"><span style="font-size: small;">The two photos below shows the snorkel being installed during a river crossing exercise.</span></span><br />
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<span style="font-weight: normal;"><span style="font-size: small;"></span></span><a href="http://4.bp.blogspot.com/-DBZwpN28rIY/VUHSmJxm3aI/AAAAAAAACIM/rKD_KlWL_Aw/s1600/combat%2Bsnorkelling.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="238" src="https://4.bp.blogspot.com/-DBZwpN28rIY/VUHSmJxm3aI/AAAAAAAACIM/rKD_KlWL_Aw/s400/combat%2Bsnorkelling.png" width="400" /></a><a href="https://2.bp.blogspot.com/-D7DfhA3HjHs/WZgrmIBoECI/AAAAAAAAJEk/Fex63pe-9dINBsSsDG6zpjZXMb88iiIxgCLcBGAs/s1600/t-72%2Bsnorkel.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="465" data-original-width="800" height="232" src="https://2.bp.blogspot.com/-D7DfhA3HjHs/WZgrmIBoECI/AAAAAAAAJEk/Fex63pe-9dINBsSsDG6zpjZXMb88iiIxgCLcBGAs/s400/t-72%2Bsnorkel.jpg" width="400" /></a></div>
<span style="font-weight: normal;"><span style="font-size: small;"><br /></span></span><span style="font-weight: normal;"><span style="font-size: small;"><br /></span></span>The maximum distance that can be traveled underwater by snorkeling is 1,000 meters. Needless to say, the further the distance, the greater the danger of the operation. Operationally, however, the capability to cross large water obstacles was indispensable.<br />
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<span style="font-weight: normal;"><span style="font-size: small;">Only crews that have passed a water obstacle crossing training programme and have taken part in exercises are allowed to undertake such maneuvers. If radio communication between the tank crew and ground units is interrupted while the tank is snorkeling, it is possible to communicate by passing an antenna up the snorkel. Depending on the situation, the crew may have to bail out of the tank while it is underwater. To do this, the bilge pump is deactivated and the TKN-3 periscope and the TNPO-168V periscope are both pulled out of their respective ports to allow water to flood the tank. Flooding the tank this way takes 1.5 minutes, and after the tank is completely flooded, each members exit the tank through their own hatches. Prior to this, the crew must perform a few safety tasks, like switching on the emergency lighting in the tank, switching off the battery system, releasing the parking brake, or disconnecting their communications devices from the intercom system and taking off their helmets (if IP-5 is not already worn prior to entering the water). </span></span><br />
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<span style="font-size: small;"><span style="font-weight: normal;"><b><span style="font-size: large;">FUEL TANKS</span></b></span></span></h3>
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<span style="font-weight: normal;">Different grades of diesel may be used depending on the weather conditions. In non-winter weather conditions where the ambient temperature is above </span>0°C<span style="font-weight: normal;">, the DL grade "summer" diesel fuel is used. It has a density of 0.86 kg/liter at a nominal temperature of 20°C and has a flash point of 62°C. In winter conditions where the ambient temperature is </span>-30°C and above<span style="font-weight: normal;">, </span>the DZ grade "winter" diesel fuel is used. It has a density of 0.84 kg/liter and has a flash point of 40°C. <span style="font-weight: normal;">In arctic conditions where the ambient temperature is -</span>50°C and above<span style="font-weight: normal;">, </span>the DA grade "arctic" diesel fuel is used. It has a density of 0.83 kg/liter and has a flash point of 35°C. The DA grade is essentially a slightly heavier form of kerosene. If the temperature drops below 0°C during the course of an operation and DZ grade fuel is not immediately available to a tank unit, it was possible to adapt DL grade fuel for winter use in field conditions by adding kerosene. Alternatively, it is also possible to switch from diesel to TS-1 kerosene (jet fuel) as all T-72 engines have a multifuel capability.<br />
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<span style="font-weight: normal;"><span style="font-size: small;">All T-72 variants have a total internal fuel capacity of 705 liters spread across several fuel tanks. Two fuel tanks are located on the two front corners of the hull (flanking the driver). The port side fuel tank (17) extends from the nose of the glacis up to the turret ring and the starboard side fuel tank (18) extends from the nose of the glacis up to the driver's station. Though it has a cutout for the driver's instrument panel, it has a voluminous capacity of 475 liters. The starboard side fuel tank has a capacity of only 158 liters due to the deep cutout for the firefighting system control units, detection and control units for the NBC protection system, and a power supply unit. The fuel level, as displayed to the driver on his instrument panel, is measured by from these two fuel tanks, each equipped with an electronic fuel meter. Behind the starboard side fuel tank is another fuel tank (3) with slots for ammunition. It has a capacity of 237 liters. The crescent-shaped conformal fuel tank directly behind the autoloader carousel, which holds 12 propellant charges, has a capacity of 75 liters. </span></span>These internal fuel tanks are made from stamped sheet steel with a bakelite coating.<br />
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Another 495 liters of fuel is stored in conformal fuel tanks located externally on the starboard side fenders above the tracks. </span></span>As the diagram above shows, the external and internal fuel systems are not interconnected. They each have their own separate fuel lines, but both connect to the same fuel pump. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">These fuel tanks are made from stamped aluminium with an internal bakelite coating and have internal partitions to reduce sloshing. Fuel from the sponson tanks are drained sequentially, beginning with the front tank and ending with the last tank from, as the fuel line is connected to the last tank while the first tank is connected to an air line. With this arrangement, the puncturing of the front tanks does not drain the tanks behind, so that the loss of the entire bank of fuel tanks on the sponson from combat damage is unlikely. The fuel hose between two external fuel tanks can be seen in the photo below.</div><div style="font-weight: normal;">
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<span style="font-weight: normal;"><span style="font-size: small;">The total fuel capacity of the T-72 is 1,200 liters. </span></span>In the summer, the 1,200 liters of fuel carried in a T-72 weighs 1,032 kg.<br />
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Due to the radiation absorbing properties of fuel, it was found that the frontal fuel tanks gave the driver considerable protection from gamma radiation. As such, the front fuel tanks were designed to be drained last. This also has the added bonus of providing additional protection from spall and secondary fragments during combat, especially in conjunction with the 45mm of anti-radiation lining on the hull sides, as it is generally quite unlikely for the tank to be nearly running out of fuel during combat. In an emergency, if any other tank is damaged, 90-100 liters of diesel in the left front fuel tank is sufficient for 1 hour of continuous driving.<br />
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<span style="font-weight: normal;"><span style="font-size: small;">Being entirely separated from each other, the driver is able to shut off and isolate the internal and external fuel tanks from his station. Isolated fuel tanks will be disconnected from both the fuel pump and the air return lines, so the fuel within the tank will be left to sit. This can be beneficial in some circumstances, such as when there is an imminent threat of an internal fire spreading. By shutting off all of the internal fuel tanks, the fuel will not leak out as energetically as it is no longer being drawn by the fuel pump or maybe even stop leaking entirely, depending on the specific location of the damage to the tanks. Without an air return line, a fire in the fuel tanks will extinguish itself rapidly as it consumes the limited volume of oxygen available.</span></span></div><div style="font-weight: normal;"><span style="font-weight: normal;"><span style="font-size: small;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-weight: normal;"><span style="font-size: small;">It is also possible for the driver to shut off all internal fuel tanks, and rely on external fuel only if the situation allows it. This keeps the internal fuel tanks full and prevents the tanks from being filled with air, so that the chances of an internal fire or explosion are minimized.</span></span><br />
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<span style="font-weight: normal;"><span style="font-size: small;">The video below shows a T-72B in Grozny retreating with some of its external sponson fuel cells alight. As you can see, the tank is not disabled by the fire and is perfectly capable of moving under its own power to a safe location where the crew can put out the fire with the fire extinguishers carried inside the tank.</span></span><br />
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<span style="font-weight: normal;"><span style="font-size: small;"><br /></span></span><span style="font-weight: normal;"><span style="font-size: small;">Two externally mounted auxiliary fuel drums can be carried on special mounts at the rear of the tank. </span></span><span style="font-size: small; font-weight: 400;">The auxiliary fuel tank holders are hinged, and may be folded flush to the hull rear when not in use. </span><span style="font-size: small; font-weight: normal;">The standard drums fitted to each T-72 have a capacity of 275 liters and are connected directly to the fuel system, and both can be disconnected by the driver at the same time by the push of a button. With these drums fitted, the maximum fuel capacity of the T-72 is increased to a total of 1,750 liters. Alternatively, it is also possible to use generic 200-liter capacity drums, giving a smaller total capacity of 1,600 liters. </span><br /><span style="font-size: small; font-weight: normal;"><br /></span><br />
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<span style="font-size: small;"><span style="font-weight: normal;">On highways, the T-72 Ural and T-72A can travel 480-500 km on internal fuel alone or around 700 km with additional fuel drums. With the standard 275-l drums, a range of 730 km is possible. With 200-l drums, the range is around 670 km. It is stated in the book "<i>Боевые Машины Уралвагонзавода: Танк Т-72</i>" published by the Uralvagonzavod Production Association, that when using petrol (A-72), the driving range is reduced by 20%. The fuel consumption of a T-72 Ural is 2.4 l/km when driving on paved roads, higher than the T-64A with the less powerful 5TDF engine; a fuel consumption of only 2.0 l/km was recorded during the same tests. However, the T-72 achieved better performance during offroad driving - the fuel consumption was 2.6-4.5 l/km, whereas a figure of 3.0-4.5 l/km was recorded for the T-64A.</span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;">Thanks to improvements in fuel efficiency on the
T-72B3, it can travel 550 km on internal fuel alone or 800 km with
external fuel drums despite having the same fuel capacity as older models. As with all automobiles, fuel efficiency decreases significantly while driving cross-country because the amount of engine power needed to overcome dynamic resistance increases as the harshness of the terrain increases, and so does fuel consumption. </span></span><br />
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<span style="font-size: small;"><span style="font-weight: normal;">Because of the T-72's relatively large fuel capacity and high fuel efficiency, refueling the T-72 isn't even necessary for short continuous operations. This greatly eases the logistical burden on the frontlines.</span></span><br />
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Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com50tag:blogger.com,1999:blog-3103574899092646031.post-40036467309793492832017-03-29T03:22:00.087-07:002023-04-27T12:24:35.771-07:00Field Disassembly: BMP-1<head>
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This is a Field Disassembly article, which means that only the defining characteristics of the BMP-1 will be examined in detail. We will not be exploring the armour protection and mobility of this vehicle in much detail except for its significance in a historical context, as the technical details have already been covered in Tankograd's BMP-2 article.<br />
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The development of the BMP-1 was linked to the development of the tanks in the Soviet Army. In the mid-50's, requirements for a prospective new medium tank were drawn up, and in doing so, it was realized that existing armoured personnel carriers would be left behind during fast-paced offensive maneuvers if the new machine was realized. Moreover, the motorized infantry would not be able to fight effectively in an environment contaminated by weapons of mass destruction. Closer cooperation between tanks and infantry was identified as a mandatory requirement under the new vision of mechanized warfare for the survival of both the tank forces and the infantry, so it was decided that an entirely new class of troop carrier was required for the future Soviet Army.<br />
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From 1959 to 1960, the GBTU (Main Armored Directorate) carried out research work on the development of the concept and the development of basic tactical and technical requirements for the new combat vehicle. During the developmental process, all existing domestic and foreign troop carriers were analyzed with the intent to identify promising solutions, and the objective was to create a Soviet IFV that was superior to the best foreign counterpart that was projected to appear in the late 1960's based on current trends.<br />
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It was to be a fully armored and sealed amphibious vehicle with high off-road mobility that could accommodate 7-10 men. The vehicle had to be fast enough to keep up with tanks and it needed to have the same travelling range as tanks at the very minimum. Full NBC protection was mandatory, and the passengers had to be able to use their personal weapons from within the vehicle without compromising the hermetic seal of the vehicle. When the passengers had to dismount, it was stipulated that they must be able to do so conveniently and with concealment and protection from incoming fire. In addition to the small arms carried by the passengers, the prospective IFV was required to have a powerful rapid-fire weapon with anti-tank capabilities to ensure its ability support infantry during offensive operations and repel the armoured vehicles of the enemy during defensive operations. However, a fire-on-the-move capability was not required.<br />
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Due to the large number of motorized rifle units in the Soviet Army and their high concentration relative to tank units, it was determined that the prospective IFV had to be inexpensive and simple to produce. The size and weight of the IFV had to be as low as possible to minimize metal consumption, it had to have a simple construction for ease of manufacture, and it had to use existing and inexpensive components from the automotive tractor industry.<br />
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Initially, an autocannon with a caliber of 20mm or 23mm was specified as the main armament of the prospective IFV, but this specification was reevaluated in the early 1960's. Instead, the feasibility of autocannons in the 30mm, 37mm and 45mm calibers and medium caliber semi-automatic guns in the 57mm, 76.2mm and 73 mm calibers with rocket-assisted projectiles was investigated. The caliber of the weapon was constrained by its recoil force which had to be within certain limits because an excessively large turret ring would take up too much space and thus reduce the number of passengers or force the size of the vehicle to be increased. As a result of a general directive by Soviet Premier Nikita Khrushchev to reorient the direction of Soviet military weapons technology development from traditional ballistic weapons towards rockets and rocket-assisted weapons, the GBTU chose the 73mm smoothbore gun concept with rocket-assisted grenades. In theory, the decision to install this weapon drastically widened the scope of the prospective IFV, as it provided the capability to destroy any enemy armoured vehicle and also eliminate entrenched enemy targets and machine gun positions in support of dismounted infantry who would be responsible for neutralizing enemy infantry with their own small arms.<br />
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After this decision was made, the Tula KBP Design Bureau (now the KBP Joint Stock Company) designed the 73mm 2A28 cannon and created a prototype one-man turret that featured an autoloader with a capacity of forty rounds and an integrated launch system for the "Malyutka" ATGM, of which four would be carried. The main gun was supplemented by a PKT coaxial machine gun. There was no requirement for a stabilizer, so the prospective IFV could only fire accurately when it was stationary. The turret ring diameter of this turret was 1,380mm, which was considered acceptable. All prospective IFV designs were required to fulfill the criteria put forth by the GBTU and all had to be compatible with the new one-man turret.<br /><br />
The participants of the competition were the design bureaus from Chelyabinsk (ChTZ), Kurgan (KMZ), Altai (ATZ) and Volgograd (ZiL). The Object 765 first prototype was made at ChTZ in 1962, the second in March 1963. In 1963 the vehicle passed factory tests and it was deemed suitable for conducting military tests. In July 1961, the project documentation from the ChTZ, ATZ, KMZ and ZiL design bureaus was evaluated. A total of eleven designs were submitted, of which five met the general requirements and proceeded to military tests at proving grounds in Rzhevka and Kubinka. They were the Object 19, Object 765, Object 911, Object 914, and Object 1200. Most of these prototypical designs incorporated a water jet, and many of them used an identical system to that of the PT-76. Of the five competing prototypes, the Object 765 and Object 914 were the only fully-tracked designs. The Object 1200 had a wheeled chassis in an 8x8 configuration, while the Object 19 and Object 911 both featured a combination of wheels and tracks. The Object 19 had four wheels in a 4x4 configuration that was supplemented by a pair of short retractable tracks between the wheels on each side, whereas the Object 911 had a pair of tracks that occupied the entire length of the hull and were supplemented by four retractable wheels.<br />
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During the course of testing, the Object 911 and Object 19 were eliminated rather quickly as they were found to be extremely complex but lacked any tangible advantage over a fully tracked or wheeled vehicle. The Object 1200 was a very modern design and it was an extremely capable combat vehicle, but it had insufficient off-road mobility compared to tanks due to its wheeled propulsion system. The Object 914 was a fully tracked vehicle and possessed very good tactical-technical characteristics, but its passengers were forced to egress through roof hatches due to its use of a rear engine and transmission. The Object 765 had a number of minor flaws, but it was the only design to fulfill virtually all of the requirements put forth by the GBTU. The layout of the various competing models is shown below.<br />
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In 1965, the Object 765 design was proclaimed as the winner of the competition. Aside from the primary features of the Object 765 that defined it as the world's first true IFV, there were also a number of details that marked its uniqueness among other tracked troop carriers. For instance, it was not steered with tillers like the MT-LB and the BTR-50, but instead had a T-bar steering system with excellent hydraulic assistance. This marked the progressiveness of the BMP among its foreign counterparts as well, as APCs like the British FV432, American M113, French AMX-10P and German Spz. 12-3 were all steered with tillers.<br />
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Sergey Suvorov writes in his book "<i>Боевые машины пехоты БМП-1, БМП-2 и БМП-3. «Братская могила пехоты» или супероружие</i>" (<i>BMP-1, BMP-2 and BMP-3 infantry fighting vehicles. "Mass grave of infantry" or a superweapon</i>) that when it came time for the Object 765 to enter service in the Soviet Army as the BMP, the long term viability of the vehicle came into question due to its high cost and somewhat complex construction. Broadly speaking, a high price tag was part and parcel of the creation of a radically new combat vehicle, but it was considered particularly high in comparison with existing armoured personnel carriers. Although the Object 765 was a lightweight vehicle, it was not as simple to produce as older tracked APCs like the BTR-50P, and its design did not make use of existing components in significant quantities. There was also some debate as to whether or not it offered enough advantages over the much cheaper BTR-60 to warrant its increase in unit price. According to Suvorov, it was determined that in a conventional large scale war, a cheaper wheeled APC like the BTR-60PB was much more cost efficient. A large scale nuclear war - where a vehicle like the BMP would excel - was seen as an increasingly unlikely scenario, mainly due to the fact that the USSR had managed to field submarine-launched ballistic missiles (SLBM) in the early 1960's and had therefore improved their nuclear deterrence capability to such an extent that a mutually assured destruction (MAD) situation was created between the USSR and the USA.<br />
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However, the relatively high price of the BMP was eventually accepted after some motorized infantry tactics were thoroughly reworked to make full use of the capabilities of the new vehicle. The BMP officially entered service in 1966 with mass production beginning in the same year at Kurganmashzavod (Kurgan tractor plant).<br />
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It was decided that only the motorized rifle units in close proximity to NATO forces in Europe would be equipped with the new BMP. The motorized rifle regiments integrated into tank divisions were also equipped with BMPs to maximize their shock action capability. Second line and reserve units would remain equipped with cheaper wheeled BTRs like the BTR-60PB which also entered service in 1966. In the end, the BMP turned out to be the most mass produced IFV in human history with around 40,000 samples - including a number of specialized variants - produced by the time production ended in the USSR in 1983. It was formally replaced by the BMP-2 in 1980.<br />
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In this article, we will only be examining the five primary variants of the generic BMP-1 IFV. The first iteration of the BMP design is the Object 765 Sp.1 from 1966, also known simply as "BMP", without the "-1" suffix. It is characterized by the stubby bow of its hull. The second variant is the Object 765 Sp.2 from 1969. It is distinguished from the BMP by the more elongated bow, and it is the first model to be officially designated as the BMP-1. The third variant is the Object 765 Sp.3 from 1973. This modification introduced a new mode for its autoloader for compatibility with HE-Frag rounds, with manual loading by the gunner. The fourth and final variant is the Object 765 Sp.4 from 1979, better known as the BMP-1P. It is essentially the same as the Object 765 Sp.3 except for the missile system. The BMP-1P has an external 9P135 missile launcher and had all of the control equipment for "Malyutka" missile system removed. The BMP-1P replaced the BMP-1 on KMZ production lines beginning in 1979, and in the same year, all BMP-1s coming into depots for capital overhauls began to be modernized to the BMP-1P standard.<br />
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<span style="font-size: large;">COMMANDER'S STATION</span></h3>
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In a BMP, the commander of the vehicle was also a motorized rifle unit commander. Depending on the specific vehicle in a standard motor rifle company, the vehicle commander may be the commander of the company, of a platoon, be the deputy to the platoon commander, or be the commander of a squad. In a standard platoon, the commander typically dismounts together with the passengers when required and acts as the squad leader, while the platoon commander remains in his vehicle.<br />
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When fighting from inside the vehicle, the commander of a BMP acts as a typical vehicle commander. He issues orders to the rest of the crew and to the passengers, who open fire from their firing ports or dismount from the vehicle only when instructed by the commander. To facilitate his duties, the commander is given a rotating cupola which includes a forward-opening hatch and three periscopes. His primary vision device was the TKN-3B, used not only for general surveillance but also fire correction, when working together with the gunner. The TKN-3B is distinguished from the TKN-3 by the lack of a target cueing system owing to the location of the commander's station. The TKN-3B uses a 2-stage cascading tube light intensifier with 0-generation photocathodes. It has no useful passive viewing capability, depending entirely on illumination from the OU-3GA2 infrared spotlight.<br />
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The hatch is of a semicircular shape and it is locked with a simple latch. Also, the hatch features a safety mechanism linked to the powered traverse system of the turret that locks the turret in place once the latch is unlocked. The system senses this via a spring-loaded solenoid button maintains contact with the latch. The button is disengaged when the latch is turned to the locked position so the turret can turn normally when the hatch is closed. Once the latch is turned to open the hatch, the button is depressed, and this sends an electric signal to the turret traverse system to suspend the traversal of the turret regardless of any inputs on the control handles and the turret is automatically locked in place.<br />
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Besides the hatch, the cupola is fitted with a small array of observation devices. The commander does not have much in the way of surveillance equipment. He is provided with a TKN-3B periscope and two TNPO-180 general purpose periscopes. This is not many, but this is compensated by the fact that the cupola can be rotated a full 360 degrees. The very light weight of the cupola makes it very easy to spin.<br />
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The ergonomic qualities of the commander's station are best described as spartan. Being located in the front of the hull next to the engine compartment, the station is longer than it is wide. The width of the "corridor" where the driver and commander is seated is only 60cm, which is quite narrow, but enough for the commander to operate the TKN-3B and swing it around (with elbows tucked in).<br />
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Because a one-man turret was specified for the BMP, the commander had to be seated in the hull. directly behind the driver. <span style="text-align: center;">This was not particularly unusual for an armoured personnel carrier at the time as they typically did not have a two-man turret, if they had a turret at all, but even so, it</span> was not an ideal position for a vehicle commander given that the role invariably involves a great deal of surveillance.<span style="text-align: center;"> The main drawback is that the commander cannot look towards the rear of the vehicle from the 5 o'clock to 3 o'clock sector. Moreover, </span><span style="text-align: center;">thanks to a combination of its low height and the relatively small turret, it is easy to camouflage the BMP and place it in a turret defilade position behind natural concealment such as bushes, tall grass and soil mounds, but</span><span style="text-align: center;"> the commander's view is completely blocked if the vehicle enters a turret defilade position so the gunner must survey the environment alone from his turret station. However, the commander's location in the vehicle does not prevent him from surveying the battlefield when the vehicle is in a hull defilade position as the commander's cupola is slightly raised and has sufficient clearance to allow the periscopes to peek over an obstacle without needing the vehicle to expose its hull.</span><br />
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<span style="text-align: center;"><br /></span><span style="text-align: center;">Ideally, the commander should be located in the turret alongside the gunner as this allows two crew members to search for targets independently from a turret defilade position and it permits the commander to issue orders and designate targets much more effectively. A turret also offers a taller vantage point for a superior range of vision and a turret tends to be on the center of gravity of the vehicle, thus making hull oscillations less obvious. This helps improve ride quality and ease of observation. </span><span style="text-align: center;">It also enhances the commander's ability to direct the driver and the convenience of a platoon or company commander to marshal other members of the unit.</span><span style="text-align: center;"> The advantage of a two-man turret was recognized and subsequent developments discarded the one-man turret concept. For instance, the Object 768 prototype, designed by the in-house design bureau of the ChTZ factory as the intended successor to the BMP-1 in 1972, featured a two-man turret with a 73mm cannon of increased power. This is shown in the photo below (courtesy of the <a href="http://tankmuseum.ru/bmp-ob768/bmpob768/">tankmuseum.ru website</a> for the Kubinka tank museum) Additionally, t</span>he BRM-1K reconnaissance vehicle based on the BMP-1 also had its commander seated in a large two-man turret and not in the hull.<br />
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<span style="font-size: large;">GUNNER'S STATION</span></h3>
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The gunner's resides in the one-man turret. He is responsible for maintaining the machine gun, cannon, sighting complexes, and autoloader. It is rather cramped in the turret, but this is balanced out to some extent by the lack of a turret basket. This means that the gunner can stretch his legs whenever the turret is not moving, and as he controls the rotation of the turret, he is much more able to ensure the safety of his appendages. There is a corridor beside the turret, joining the passenger space and the front hull space where the commander and driver are situated. When not in combat, the gunner can spread his legs out into this space, with the turret locked in traverse to prevent accidents. <div><br /><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgnNlTJHDLBf6GEKhWgbligUmxyQSi-QayGgX7JmU-RXQ7NXAFPws-i_5Z5cj0onIs5hVXe45jZbfw70nWyht8erJm5oLe83Napj-m9Gd7NGv0zRnh4KQdD7sm9R6XW1aLJTJCFDuwz_5ByDlmSJmanikLqNk7hB6veSIdzblCBXg0GTnvUvy5-7MQzhw/s1288/bmp-1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1288" height="382" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgnNlTJHDLBf6GEKhWgbligUmxyQSi-QayGgX7JmU-RXQ7NXAFPws-i_5Z5cj0onIs5hVXe45jZbfw70nWyht8erJm5oLe83Napj-m9Gd7NGv0zRnh4KQdD7sm9R6XW1aLJTJCFDuwz_5ByDlmSJmanikLqNk7hB6veSIdzblCBXg0GTnvUvy5-7MQzhw/w640-h382/bmp-1.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The turret floor is a flat sheet of aluminium with level edges except in front of the gunner's seat where the edges are bent upwards to form a shallow ridge. This ridge is there to ensure that the gunner's feet do not slip off the floor. There is also a simple sheet metal shin guard stretching from one of the struts connecting the turret floor to the turret to the ammunition and casing container to the right of the gunner. This shin guard prevents the loader from accidentally putting his knees outside the perimeter of the turret floor. All of this is shown in the photo below, taken <a href="http://www.primeportal.net/apc/hans-hermann_buhling/bmp-1_cutaway/index.php?Page=2">by Hans-Hermann Bühling</a>.<br />
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The gunner's hatch opens forward and locks in the upright position which is very typical of a Soviet vehicle. If a gunner of average height stands on his seat with the seat in the lowest setting, his head will be just over the edge of the open hatch, so the hatch itself will be able to provide his torso with frontal protection from bullets while the gunner enjoys the better view gained from having a higher vantage point.<br />
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Due to the installation of the cannon along the center axis of the turret, the gunner's station is confined to the left half of the turret and the right half of the turret is used for electronic equipment. Components of the 9S428 missile guidance system are installed on the turret wall on the right half of the turret.<br />
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The 2A28 "Grom" cannon of the BMP lacks a fume extractor. To remove propellant fumes from the cannon and the coaxial machine gun, the turret has a special ventilator that extracts air from the fighting compartment and expels it out through a vent on the turret roof. The ventilator consists of a single centrifugal extractor fan powered by an electric motor that leads to a vent on the turret roof. There is also a duct that connects the extractor fan inlet to the container on the turret floor for spent propellant charges, thus allowing the system to extract the fumes emitted from these spent charges from propellant residue. The photo below, courtesy of Vladimir Yakubov, shows the extractor fan of the ventilator and the duct that connects the fan inlet to the container on the turret floor.<br />
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The BMP-1 technical manual mentions that the extractor fan is the same as the type used in the propellant fume extraction system for the passenger firing ports. Without this system, it would tend to be quite unpleasant to remain confined inside the small turret of the BMP with all the hatches closed during sustained fire. Even when the weapons are not being fired, this vent continues to help circulate air in the fighting compartment. </div>
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The gunner is provided with a total of five observation devices in his turret: the 1PN22M1 sight aimed directly forward, and four TNPO-170 periscopes arranged around the perimeter of his hatch. Two of the TNPO-170 periscopes are placed on the flanks of the primary sight to provide forward vision which is helpful for seeing targets and maintaining situational awareness, and the other two are placed on the sides of the hatch to allow the gunner to check his surroundings. There is a dead zone in the 2 o'clock sector because a periscope could not be placed directly behind the breech of the 2A28 "Grom" cannon, as that space was needed for loading the cannon. The photos below shows the layout of the periscopes around the gunner's hatch. Photos <a href="http://www.primeportal.net/apc/robert_de_craecker/bmp-1_east_german/index.php?Page=7">by Robert De Craecker</a>.<br />
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When a mounting post was installed on the right side of the turret roof in the BMP-1P modernization for the 9P135M missile launcher, it partially obstructed the view from the TNPO-170 aimed to the right.<br />
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The front-right periscope can also be used to aim the weapons in the event that the primary sight fails. Engaging targets with the coaxial machine gun can be done by following the tracers for fire correction, and the "Malyutka" missile can be guided by eye at shorter distances. With a total of five observation devices, a BMP-1 gunner has good vision in the forward 180-degree sector of the turret but no rearward visibility whatsoever. To see behind the turret, the gunner can open his hatch or traverse the turret to the left or right by until one of the side-facing TNPO-170 periscopes is aimed to the rear. In an active combat situation or in an NBC-contaminated environment, only the latter option is feasible. The lack of rearward visibility for the gunner when he is buttoned up was addressed on the BMP-2 when a rear-view prism was added to the gunner's hatch.<br />
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The good vision from the BMP-1 turret partly compensates for the sub-optimal location of the commander's station and provides the gunner with a high level of independence in target acquisition when the commander dismounts together with the passengers.<br />
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For lighting, there is a PMV-71 dome light located on the turret roof to the left of the gunner's hatch and another one on the turret roof on the opposite side, to the right of the autoloader mechanism. The dome light contains a TN-28-10 incandescent lamp that runs on a voltage of 28 volts and consumes 10 W of power. Each PMV-71 dome light has an output of 10 candelas. For a one-man turret, the amount of illumination is quite good. The gunner has access to a master power relay to control the activation of various electrical systems in the vehicle.<br />
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Although the BMP has an overpressure ventilation system that is capable of providing sufficient ventilation for all of the occupants, the gunner has the good fortune of being able to open two hatches for additional ventilation - his personal roof hatch, and the missile loading hatch. When the missile loading hatch is open and the vehicle is moving forward, the rush of wind is deflected by the hatch directly towards the gunner much like the vent window of old cars.<br />
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The gunner's seat together with its backrest is adjustable in height. A foldable arm guard is installed on the right side of the seat to isolate the gunner from the autoloader mechanism. The top half of the arm guard is folded down to allow the gunner to access the two "Malyutka" missiles stowed in the turret when reloading the missile launcher, and the entire arm guard can be detached from the seat for unobstructed access to the turret interior. The 9V332 control box with its control joystick for the "Malyutka" missile system is folded under the seat when not in use.<br />
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With the introduction of the 902V "Tucha" smoke grenade launcher system on the BMP-1P, new control boxes had to be installed. The gunner was provided with a revised master power relay to turn on the "Tucha" electrical system, and a "Tucha" launch control box to select individual grenades to launch.<br />
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<h3>
<span style="font-size: large;"><br />POWERED CONTROLS</span></h3>
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The 1ETs10M powered gun laying system provides powered turret traverse and gun elevation with satisfactory accuracy using all-electric drives. Gun stabilization was not provided and was never provided to any serially produced BMP-1 variant during its career in the Soviet Army, and later, the Russian Army. The gun can be depressed to -4 degrees and elevated to +30 degrees, but direct fire with the 73mm cannon is only possible from -4 degrees to +15 degrees due to the elevation limits of the 1PN22M1 sight.<br />
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The DGN-3 electric motor is the turret rotation drive. It runs on 24 V and has an output of 300 W. The DVN-1 electric motor is the gun elevation drive. It also runs on 24 V and has an output of 65 W. The maximum speeds of turret rotation and gun elevation are slightly higher than of a T-64 and significantly higher than of a T-62 or T-55, and the mechanical precision of the BMP gun laying system should be very similar to these two tanks. As such, the gun laying system was not only more than sufficiently precise to facilitate the use of the 2A28 cannon out to its maximum effective range of 800 meters but it could also be considered quite modern.<br />
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Vertical:<br />
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Maximum Cannon Elevation Speed: 6° per second<br />
Minimum Cannon Elevation Speed: 0.07° per second<br />
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Horizontal:<br />
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Maximum Turret Traverse Speed: 20° per second<br />
Minimum Turret Traverse Speed: 0.1° per second<br />
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In 1973, the BMP-1 was equipped with the 1ETs10M2 modification of the original powered gun laying system. The new model was adapted to the modification of the autoloader in accordance with the introduction of HE-Frag ammunition for the main gun. The control handles gained a switch to load HE-Frag rounds, or rather, to control the operation of the autoloader so that it selectively loads HEAT rounds if the gunner presses the "K" (HEAT) button, but only rotates the conveyor by one step if the gunner presses the "O" (HE-Frag) button.
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The BMP-1 cannot fire on the move with any guarantee of accuracy unless the vehicle is travelling over a well paved road at low speed. Nevertheless, BMP gunners were trained to fire on the move at low speeds using both the 2A28 cannon and the PKT coaxial machine gun. To maximize training time without needing to cover the costs of maintenance and fuel, the training was often done on simulators. These simulators were platforms built into the ground which the BMP would park on. To simulate the experience of driving over uneven terrain, the platform oscillates at various intensities while the gunner uses the coaxial PKT machine gun to engage pop up targets representing infantry.<br />
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Video footage of a firing exercise taking place can be found on YouTube on yolkhere's channel, here (<a href="https://youtu.be/Y_MHivW1las?t=3m35s">link</a>).<br />
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The short video and the limited amount of information I have gathered doesn't say if gunners were trained to fire the 73mm cannon from the platform, but as far as I know, it was not part of the curriculum. Live fire training at the firing range was more extensive as it involved both tank and infantry-type targets and tested the coordination of the entire crew, not just the skills of the gunner. This made time on the range irreplaceable, not that further evidence was needed.<br />
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Due to the presence of the OU-3GA infrared spotlight on the commander's cupola, a deadzone with an arc of 50 degrees was created. The turret cannot be aimed at the normal angles of gun elevation over this arc, and instead, the gun must be elevated over the spotlight. Another deadzone exists over the rear arc where the gun depression angle over the troop compartment roof is reduced to a maximum of -2 degrees instead of the normal -4 degrees, but this is completely normal for practically all turreted tanks and should not have a significant effect during combat.<br />
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The PU-6 control handles are used with this system. The right handle has a thumb button for firing the "Grom" cannon and the left handle has a thumb button for firing the coaxial machine gun.<br />
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<h3>
<span style="font-size: large;">1PN22M1</span></h3>
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One of the design requirements stipulated for the BMP was that it had to have a sighting system equal in capabilities to the tanks it was to complement, including a night fighting capability. As a result, the 1PN22 combined day-night sight was developed. The original 1PN22 was only used in the prototype turrets installed on the five competing prototypes that took part in the 1961-1965 military competition. After the competition was won by the Object 765 in 1965, the modernized 1PN22M1 sight was created and used on all serially produced BMPs.<br />
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The 1PN22M1 is a relatively advanced sight that features a fixed magnification daytime optic and a night vision channel with a 1st Generation three-stage light amplifier. The gunner looks through the same eyepiece for both the day and night channels, and he can switch between the two channels by rotating an internal mirror. By incorporating two features into one sighting system, Soviet engineers were able to save space inside the small turret and simplify the sighting system without compromising overall effectiveness.<br />
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The head of the sight contains a mirror that is linked to the trunnion of the 2A28 cannon. The viewing window of the sight head is protected by a pane of glass, and an additional protective glass pane can be lowered when launching ATGMs to prevent the main viewing window of the sight from being scorched by the rocket exhaust. After the ATGM leaves the launch rail, the scorched glass pane is raised.<br />
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The night vision system of the 1PN22M1 sight is housed in the left side and bottom of the sight housing. The left "shoulder" of the sight contains a reflector assembly with one mirror and a prism that projects light collected from the objective lens of the sight into the U-42-M light intensifier tube at the bottom of the sight. The amplified image is then reflected to the eyepiece of the sight through four prisms.<br />
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The sight has fixed magnification of 6x and a field of view of 15° in the day channel. The magnification was adequate given the effective range of the main gun and the coaxial machine gun, but from a technical point of view, the capabilities of the sight are exceptional. The magnification power of the 1PN22M1 is directly comparable to that of tanks with larger, high power cannons like the M48, which used the M20 sight with a 6x maximum magnification, though it lacked selectable magnification settings as on the Soviet TSh2 series of sights. With a field of view of 15 degrees, however, the 1PN22M1 provided considerably expanded vision compared to tank sights like the TSh2 series (9 degrees at 7x magnification). The 1PN22M1 offers a notably higher magnification than the PGO-9 periscopic sight used on the SPG-9, which only had a 4.2x magnification with a field of view of 10.5 degrees. This means that a BMP-1 gunner should be able to identify and fire upon targets at a longer range than an SPG-9 gunner, but because the effective range is largely the same, the higher magnification of the 1PN22M1 sight did not give the BMP-1 any major advantage. Needless to say, both the commander and gunner of a BMP-1 have much less visibility when they are buttoned up compared to an SPG-9 crew.<br />
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The viewfinder of the sight is abundantly marked for ballistic drop and lead. Windage was adjusted using the lead scales. The small crosshair at the top of the viewfinder is zeroed for 50 meters, so in practice, it serves as a reference point rather than an actual aiming mark. The viewfinder permits aimed fire out to a maximum range of 1,300 meters for both the PG-15V rounds as well as for the PKT coaxial machine gun. A separate scale for the PKT is not needed because it has very close ballistics to the PG-15V round out to 1,300 meters, allowing the gunner to use the range scale for both weapons interchangeably.<br />
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The point blank range of the PG-15V round fired from the 2A28 is 765 meters for a target with a height of 2 meters, meaning that up to a distance of 765 meters, the trajectory of a PG-15V round will have a total height of 2 meters. In theory, this means that if the target tank is 2 meters tall and within 765 meters of the BMP-1, the gunner can simply aim his crosshair at the roof of the target and open fire with a total guarantee of achieving a hit at some part of the tank. If the tank is 765 meters away, the shot will impact its lower glacis, and if it is 300 meters away, the shot will impact the turret. However, due to a myriad of factors such as the dispersion of shots, it is still necessary to obtain a range reading to maximize the probability of hit. For this reason, the 1PN22M1 sight features a stadiametric rangefinder in its viewfinder.<br />
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The rangefinder scale is intended for a target 2.7 meters in height, starting from 400 meters and ending at 1,300 meters. Below 400 meters, the trajectory of PG-15V rounds is flat enough that the battlesight gunnery technique is sufficiently accurate for achieving a probability of hit exceeding 90%, and fire correction can be accomplished with the burst-on-target gunnery technique if it is truly necessary. There are no range scales between the 50-meter crosshair and the 400-meter range scale. In the stadiametric scale, the target height of 2.7 meters is representative of the height of the average Western tank, including the Chieftain, M48, M60A1, Leopard 1, and even some later combat vehicles like the Marder 1.<br />
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The sight is switched to the night vision channel by redirecting the light collected from the objective lens away from the day channel optical assembly to the reflector assembly located in the left side of the sight. The light then passes through one of six light filters on a revolving disc before entering the light intensifier tube at the bottom of the sight. The gunner chooses the filter by rotating the knob at the bottom left of the sight, shown in the drawing on the left below.<br />
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The light filters are designed to provide the optimal level of contrast in various lighting conditions, including daylight. The designations of the various filters and their purposes are listed in the table below. Filters 'O' and 'KS-17' are intended for use at night under natural illumination from starlight and moonlight. Filter 'NS-10' is intended for use at twilight. Filter 'NS-11' is intended for use in overcast daylight conditions. Filters 'NS-12-1' and 'NS-12' are intended for use during sunny weather.<br />
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The night vision channel has a separate viewfinder reticle design from the daytime channel. The reticle is projected onto the viewfinder using a collimator system with an adjustable brightness. The reticle has greatly simplified lead and range correction scales compared to the day channel reticle. The sight has a fixed magnification of 6.7x and a field of view of 6 degrees in the night channel. As with the day channel, this was excellent performance compared to the tank equivalent. In this case, the standard TPN1 series of night sights, which had a smaller magnification of 5.5x but the same field of view of 6 degrees. <div><br /></div><div>Night vision was provided by a passive image intensifier system running on a 40 kV power supply. The system utilizes a three-stage image intensifier cascade tube with three S-1 converter tubes. This level of technology was modern for the 1960's.</div><div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Y1ut0jEpVCk/XyfD3FqiOTI/AAAAAAAARbE/GGym7BEAL7AGDDI1Wa5WOZXeXJa6u5h4ACLcBGAsYHQ/s2048/three-stage%2Blight%2Bintensifier.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1066" data-original-width="2048" src="https://1.bp.blogspot.com/-Y1ut0jEpVCk/XyfD3FqiOTI/AAAAAAAARbE/GGym7BEAL7AGDDI1Wa5WOZXeXJa6u5h4ACLcBGAsYHQ/s640/three-stage%2Blight%2Bintensifier.png" width="640" /></a></div><div><br /></div><div><br /></div><div>This type of image intensifier has a gain of 50,000-75,000, meaning that it is capable of amplifying light by 50,000-75,000 times. Such a high gain is necessary for Gen 1 image intensifiers to provide practical passive viewing with starlight illumination alone. In the 1PN22M1 sight, glare and flash protection is provided to preserve the intensifier tubes via the automatic reduction of the input voltage on the converter tubes, which leads to a sharp drop in the gain, as a result of which the tubes are not burned out by a sudden flash of bright light and the smearing effect of light sources is reduced. </div><div><br /></div><div>This system enabled the gunner to identify and fire upon a tank-type target at a range of up to 400 meters with an ambient light of 0.005 lux. The maximum viewing range was limited by the inherently low resolution of the image generated by a three-stage image intensifier tube. Another tactical limitation of this type of image intensifier system is that although the image at the center was clear, the edges would be distorted, thus effectively reducing the useful field of view. A technical limitation is the low service life of the converter tubes due to the very high operating voltages.</div><div><br /></div><div>This is the same maximum viewing range of the commander's TKN-3B periscope. At the maximum identification range of 400 meters, the gunner could simply lay the center chevron in the viewfinder on a target and open fire immediately once it is identified and expect a high probability of scoring a first-round hit. When firing at targets at ranges of up to 800 meters, the need for a range estimate arises. This can be done using the reticle markings by comparing its known angular dimensions (in arcminutes) to the dimensions of the image of the target.<br />
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As the markings show, the BMP-1 is theoretically capable of engaging targets up to a distance of 800 meters at night using the 1PN22M, but the center chevron is calibrated for 400 meters as that is the distance limit of the night vision system. It is only practical to fire at targets from further than 400 meters if the target is illuminated by natural or artificial means.<br />
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<h3>
<span style="font-size: large;">1PN22M2</span></h3>
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1PN22M2 was introduced in 1974. From a technical viewpoint, it is identical to the 1PN22M1 in almost every way. The only functional difference is the addition of a scale for HE-Frag rounds which extends far below the original scale for HEAT rounds due to the low velocity of OG-15V HE-Frag rounds. Around the same time, the PGOK-9 sight with compatibility with HE-Frag rounds for the SPG-9 was introduced.<br />
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As you can see in the diagram above, the sight is marked for a maximum direct fire range of only 1,600 meters for HE-Frag. This is the hard limit of the direct fire capabilities of the BMP-1 using OG-15V HE-Frag rounds, and also the maximum range of the rounds.<br />
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<h3>
<span style="font-size: large;">2A28 "GROM"</span></h3>
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The BMP mounts the 73mm 2A28 "Grom" low-pressure smoothbore cannon. The cannon has a vertically sliding breech block with a spring-loaded folding shell casing deflector at the end of the breech assembly. The cannon has a total length of 2,180mm and a gun tube length of 2,117mm, which is longer than the gun tube of the SPG-9 despite the recoilless gun having a longer chamber for the larger propellant charge. The width of the 2A28 breech housing is very narrow - only 213mm. The cannon does not have a fume extractor.<br />
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The barrel life of "Grom" is 1,250 shots. The cannon can elevate between -4 degrees to +30 degrees, but direct fire is only possible from -4 degrees to +15 degrees due to the elevation limits of the 1PN22M1 sight. The breech block can be manually opened with a cam operated by a lever handle located underneath the casing deflector, as shown in the photo below. A recoil guard is attached to the lever.<br />
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"Grom" is incredibly lightweight, weighing only 115 kg on its own. Of course, its weight is not so impressive when compared to the SPG-9, which weighs 49.5 kg with its direct fire sight and without its tripod and aiming mechanism. This was mainly due to the need for a recoil mechanism and a breech to withstand the chamber pressure. When installed inside the BMP-1 turret, the full gun assembly includes the cast steel gun mantlet, the "Malyutka" missile launch platform on top of the recoil buffer sleeve, and a set of rollers for aligning the top of the gun breech with the missile launch platform.</div><div><br /></div><div>Rounds are fired electrically, with a mechanical striker as a backup. <br />
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The recoil mechanism consists of a hydraulic recoil buffer and coil return spring. It is wrapped around the base of the barrel and encased in an armoured sleeve, so it is concentric to the bore axis of the cannon. This is a positive influence on the dispersion characteristics of the cannon. Owing to its low operating pressure and its compact overall design, the "Grom" has a recoil stroke of only 150mm.<br />
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As the drawing below shows, the trunnion and barrel chamber of the "Grom" are at the same location, and because the BMP-1 turret has a protruding gun mount with the trunnion located in front of the turret ring, the cannon only protrudes a short distance into the turret and only the breech can be seen from inside the turret.<br />
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The recoil buffer sleeve also has built-in provisions for mounting the "Malyutka" launching rail. When a missile is mounted on the launcher, the cannon becomes somewhat unbalanced by the weight. The missile itself weighs 10.9 kg and it is located forward of the gun trunnion, making the gun rather front-heavy.<br />
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Even back in 1966, it was a somewhat unusual decision to use a low-velocity cannon in lieu of the typical heavy machine gun or autocannon as was normal for both purpose-built IFVs as well as APCs pressed into service in the IFV role. The convention that was followed by foreign militaries at the time was based on relatively sound reasoning: in a typical skirmish where tanks do not need to be involved, an armoured troop carrier should only face light resistance, and indeed, the ACAV modification of the M113 that was used by U.S forces and the ARVN during the war in Vietnam was only armed with externally-mounted M2 and M60 machine guns with gun shields for protection, and this was deemed to be enough for shock action against light infantry. In most cases, <a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/347543.pdf">even a basic M113 was effective when the opposition was armed only with small arms and small numbers of anti-tank weapons</a>. If additional firepower is desired for a vehicle intended for the same role, a rapid-fire autocannon would be more efficient at dispatching infantry, soft-skinned targets and lightly armoured vehicles compared to a large caliber semi-automatic cannon, but a rapid-fire autocannon has a lower efficiency against dugouts and field fortifications.<br />
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From this, it is evident that the BMP-1 was largely incapable of countering man-portable ATGMs which is a noteworthy drawback as the BMP-1 entered service during an era when such weapons were prolific. The effectiveness of the "Grom" in this role was increased when OG-15V HE rounds were introduced, but even so, another limitation came in the form of the rather short 1,600-meter maximum range of the OG-15V round.<br />
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If the BMP is being used to supplement a breakthrough attempt, it will not be the centerpiece of the attack. Soviet field manuals detail a number of formations to be used against enemy forces in certain situations, and in one of these, it is stated that when tanks are available to support the advance, one tank can be attached to each motorized infantry platoon. The three BMPs of the platoon follow the tank at a distance of 100 to 200 meters, with either dismounted or mounted infantry. The tank will take care of the toughest targets with its cannon, and the BMPs will knock out anti-tank weapons and lightly armoured vehicles in support of the tank. When a motorized infantry platoon with BMPs is operating without tank support, the modest capabilities of "Grom" would be the most potent anti-armour weapon available to the platoon besides the integrated "Malyutka" missile, so avoiding contact with enemy tanks is a priority. If enemy tanks are not encountered, the 73mm cannon will prove most useful against hardened field fortifications, buildings, and fixed weapon emplacements like machine gun and recoilless rifle nests, and so on. The penetration and blast effect of its HEAT grenades would be particularly useful on fortifications that are otherwise completely immune to machine gun fire, like a triple layer of sandbags (a common standard during the Vietnam war) or a double layer of sandbags reinforced with timber.<br />
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Given that the light weight of the BMP-1 allows it to be deployed where tanks cannot go, the firepower of a 73mm cannon becomes particularly meaningful for the troops that are deployed together with the vehicle. From this perspective, there were clear merits to the use of the 73mm "Grom" in the BMP-1. Indeed, there are are a multitude of valid reasons why a weapon like "Grom" is preferable for the BMP rather than a heavy machine gun or a rapid fire autocannon. For one, the firepower of a large caliber cannon is indispensable in many situations. The need for such weapons was met in Vietnam by configuring the M113A1 ACAV with a pintle-mounted 106mm M40A1 recoilless rifle to be operated from the passenger compartment roof hatch. The M113 ACAV with the M40A1 had tremendous firepower but the vehicle provided no protection whatsoever for the gunner and had a severely constrained rate of fire due to the small roof hatch of the passenger compartment and inconvenient location of the weapon itself; the rear of the gun tube extended behind the roof hatch, so the loader has to contort himself to fit each cartridge - almost a meter long and weighing 16.4 kg - through the breech. It was also unsafe for personnel to stand behind or even near the vehicle when the M40A1 is in use due to the colossal back blast and firing signature. The British FV432 "WOMBAT" had an even more powerful <a href="http://s3.amazonaws.com/hmvforum/monthly_2015_07/59dce6a9da23e_WombatLoadingNetheravon.jpg.22847b539ee2c2139eceaaa0be33b415.jpg">120mm L6 "WOMBAT" recoilless rifle</a> mounted in a layout similar to the M113 and thus shared the same fundamental shortfalls, exacerbated by the more massive size (more than 1.1 meters) and weight (27.2 kg) of the cartridges. As such, these vehicles were tactically distinct from the BMP-1 and neither of the two were proper analogues.<br />
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The British Alvis Saladin armoured car and FV101 Scorpion reconnaissance vehicle were both armed with 76mm low pressure guns in fully enclosed turrets, and <a href="https://www.army.gov.au/media-room/media-releases/50-years-service-for-m113-0">the Australian Army developed a closer analogue of the BMP-1 in 1967</a> by mating the fully enclosed turret of the Saladin armoured car with a 76mm L5A1 low pressure gun to the hull of the M113A1, thus creating the Saladin FSV (Fire Support Vehicle). The Saladin FSV is shown in the photo belo. In continuation of this concept, the MSV was created in 1976 by mating the turret of a Scorpion with its 76mm L23 low pressure gun to the M113A1. But even so, these were still fire support vehicles and not pure IFVs. The BMP-1 was completely unique in its combination of traits in 1966 and for better or worse, remained unique throughout the remainder of the Cold War.<br />
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From the perspective of the Bundeswehr, the decision to mount the 20mm HS.820 on the SPz 12-3 and the 20mm Rh202 on the Marder was motivated by the need for sufficient firepower to deal with dismounted infantry and lightly armoured troop carriers. In the Soviet Army, this need was met by using a combination of a 14.5mm KPVT heavy machine gun and a 7.62mm SGMT or PKT general purpose machine gun. This armament scheme was established as the standard armament of Soviet armoured personnel carriers and armoured cars beginning with the BRDM-2 (1962) and the BTR-60PB (1966) which both used the same BPU-1 turret. The KPVT would be used against armoured personnel carriers - such vehicles would typically only have limited protection from 12.7mm machine guns - and infantry behind solid obstacles, and the SGMT or PKT would be used against infantry in the open. Although the KPVT was not as useful in the anti-personnel role as a 20mm or 23mm rapid-fire autocannon as its caliber is too small to deliver an effective explosive payload, it fulfilled the same niche in every other respect and was more than adequate for armoured personnel carriers. With this in mind, an escalation in firepower to encompass tanks as the primary target for an IFV like the BMP-1 is not unusual.<br />
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<h3>
<span style="font-size: large;">ACCURACY</span></h3>
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According to the firing table for the PG-9 grenade fired from the 2A28 cannon, the technical dispersion of the PG-9 grenade is 0.6 mils in both the horizontal and vertical axes. The technical dispersion of the OG-9 grenade fired from the 2A28 is 0.9 mils in the horizontal axis and 1.0 mil in the vertical axis.<br />
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The point blank range of the cannon with PG-9 HEAT grenades against a medium tank target with a height of 2.7 meters is 800 meters. Theoretically, this allows the gunner to neglect the range estimation process and open fire immediately at a tank within 800 meters with a reasonable expectation of scoring a first-round hit, but due to the dispersion of each shot, the reality is that range estimation is still required to achieve a reasonable probability of hit.<br />
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According to comparative data published in the book "<i>БМП-1 (1964-2000): Боевая машина пехоты</i>" by Sergey Malyshev, a basic BMP-1 only has a 35% chance of eliminating an ATGM team with two shots from its cannon at a range of 500 meters. This drops to a measly 10% at a range of 1,000 meters. For comparison, a 30mm autocannon (the 2A72 in this case) has a 100% chance of eliminating an ATGM team with sixteen shots at 500 meters, 50% chance at 2,500 meters, and 40% chance at a range of 4,000 meters. In this comparison, both vehicles are stationary. Against ground targets, the main downside of the 73mm HEAT rounds fired from the "Grom" is that they have an extremely limited fragmentation effect and the explosive charge is not powerful enough to ensure the elimination of soft-skinned targets in the open unless it detonates close to the target.<br />
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According to the same book, the probability of destroying an armoured personnel carrier with two shots from the 2A28 cannon is 80% at a range of 500 meters. This drops to only 25% at a range of 1,000 meters. Keep in mind that the probability of destruction is not the same as the probability of hit, as each hit is not guaranteed to destroy the target.<br />
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Zaloga claims that the "Grom" can achieve a 70% hit rate on a stationary tank-type target at 500 meters in still air, degrading to 50% at 800 meters. This is not high compared to a high velocity tank cannon, but still quite respectable, as this is already somewhat close to the performance level of the T-62 firing 3UBK-3 115mm HEAT shells, as you can see in the TRADOC bulletin diagram below. An M60A1 could achieve an 80% hit rate with its own 105mm HEAT shells at the same range thanks to its optical coincidence rangefinder.<br />
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Without knowing the target that was used to determine the probability of hit data supplied by Zaloga, it is not possible to make any firm conclusions. Nevertheless, the ineffectiveness of the "Grom" cannon at long range is hardly a secret, and its maximum effective range of 800 meters may not even be achievable in practice. During one a live firing trial, a BMP-1 was made to open fire against a stationary T-55 tank at 800 meters. Out of 50 shots, only 17 hit the tank; the others were carried off their trajectory by the wind. This translates to a 34% hit rate.<br />
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Nevertheless, it is worth pointing out that a T-55 is smaller than a typical NATO tank. The British Chieftain tank, for example, is 2.9 meters tall and 3.66 meters wide. The American M60A1 has a similar height of 2.9 meters (not counting the very large commander's cupola) and 3.63 meters wide. The German Leopard 1 was 2.6 meters tall and 3.25 meters wide while the French AMX-30 was by far the smallest at 2.52 meters in height and only 3.1 meters in width. The T-54 is only 2.4 m tall and 3.37 m wide. The probability of hit will be higher at all ranges against a larger target, and vice versa. Therefore, it can be inferred that the "Grom" has a slightly higher than 50% chance of hitting a stationary M60 or Chieftain at a distance of 800 meters under favourable weather conditions when using the standard PG-15V HEAT round. The gunner will have to rely more on the ATGM when engaging tanks at distances exceeding 800 meters, and will become totally dependent on the ATGM when fighting at distances of more than 1,300 meters.<br />
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As a fighting system, the "Grom" cannon was the most potent direct fire weapon organic to a motorized infantry squad equipped with a BMP-1. An RPG-7 with five grenades would be carried by the grenadier in the squad and it would be operated together with the assistant grenadier. The RPG-7 was a powerful weapon in its own right, but it belonged to a different class than that of the "Grom". The penetration power of the original 85mm PG-7V grenade from 1961 was also less compared to the 73mm PG-9 fired by the "Grom" - 260mm RHA compared to 300mm RHA. In 1969, the improved 70mm PG-7VM grenade entered service with a warhead derived from the PG-9 and a modified propulsion system. The deflection of the projectile from crosswinds was decreased by 1.5 times and the accuracy of fire was increased by around 20-25%. But even with these improvements, the probability of hitting targets beyond 300 meters was still a challenge.<br />
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A further examination of the functional precision of the PG-7V rocket grenade when fired from an RPG-7 against tank targets can be found in "<i>Analysis of Rocket-Assisted Aspects of Infantry Antitank Weapons</i>" by Dr. Thomas H. Dawson published in the November-December 1975 issue of the Army Research and Development News Magazine. The article details the technical aspects of the PG-7V rocket itself and considers its advantages and disadvantages, concluding that the drawback of increased wind deflection of the rocket design is completely overshadowed by the greatly reduced margin of error allowed in range estimations due to the increased velocity. It was found that compared to a conventional projectile with a muzzle velocity of 100 m/s, a rocket-assisted grenade like PG-7V with a boosted velocity of 300 m/s decreases the angular elevation (range estimate) error by a factor of more than 10, while the angular deflection (crosswind) error increases only by 3 times.<br />
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The hit probability data presented in the graph below shows the probability of a PG-7V grenade achieving a first round hit on a 2.3 x 2.3 meter square target with the same nominal ranging error of 15% (stadia rangefinder), technical shot dispersion of 2 mils, and the same crosswind of 3 m/s. Compared to a hypothetical conventional grenade with a muzzle velocity of 100 m/s and no rocket booster, the effective range of the PG-7V - defined as the distance at which a 50% hit probability is achieved - is twice that of the conventional grenade. The hit probability of PG-7V reaches 80% at a range of 140 meters, and it is 20% at 300 meters.<br />
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This shows that in a worst-case scenario where a crosswind is present, the effective range of the rocket-assisted grenade is 2 times better than the conventional grenade. When a crosswind is not present, the advantage of the rocket-assisted grenade is even larger.<br />
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This is corroborated by data on the number of shots needed to "defeat" an armoured target in various situations is detailed in page 58 the manual "<i>Наставление по стрелковому делу Ручной противотанковый гранатомет РПГ-7, РПГ-7Д </i>" (<i>Manual on the Matters of Firing Hand-held Anti-tank Grenade Launcher RPG-7, RPG-7D</i>) from 1972. The manual does not specify the type of armoured target or the definition of "defeat", but it can be reasonably assumed that the figures refer to the number of shots needed to hit a tank rather than the number of shots needed to kill a tank, as multiple direct hits are usually needed to knock out a postwar tank. Three types of targets are specified: a frontal aspect of a target moving at 20 km/h, a profile target moving at 20 km/h, and a target situated in a hull-down position.<br />
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At 100 meters, both the original PG-7V round and the improved PG-7VM round needed only one shot on the frontal aspect of a target moving at 20 km/h, one shot is needed on the profile of a target moving at 20 km/h, and one shot is needed for a tank in a prepared hull-down position. When the distance increases to 200 meters, the number of PG-7V rounds needed increases to two for the frontal target and four for the hull-down target, and the higher precision of the PG-7VM round begins to show itself as only three shots are needed for the hull-down target. The gap in accuracy between the PG-7V and the PG-7VM widens as the distance increases, but the limits of the RPG-7 are quite evident as the PG-7VM round achieves a 50% hit probability for the front silhouette and side silhouette of moving tanks at just 200 meters and 300 meters respectively. For comparison, the Carl Gustaf M2 (m/48) achieves the same hit probability against a moving tank at a range of 150 meters.<br />
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In a best-case scenario where the target is a static tank and there is no crosswind, the effective range where the RPG-7 achieves a 50% hit probability reaches 250 meters. The Carl Gustaf M2 (m/48) achieves the same hit probability at a range of 200 meters. The difference can be attributed to the difference in the flight velocities of the grenades fired by the two antitank systems. The RPG-7 launches a rocket-assisted grenade at a muzzle velocity of only 140 m/s but the projectile accelerates to a peak velocity of 300 m/s after it leaves the launcher, after which it starts to decelerate. The Carl Gustaf launches its HEAT grenade at a muzzle velocity of 255 m/s and the grenade experiences a continuous deceleration until it reaches the target.<br />
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At a range of 250 meters, "Grom" has a 90% chance of hitting a stationary tank-type target with its PG-9V grenade. Compared to the RPG-7 carried and operated by the anti-tank grenadier in the squad transported in a BMP-1, the maximum effective range of the "Grom" against a tank-sized target is up to three times higher. Most of the difference can be attributed to the much higher velocity of the PG-9V grenade: the muzzle velocity of the PG-9V is 400 m/s m/s and the maximum velocity is 665 m/s. In comparison, the PG-7VM round remains subsonic throughout its entire flight. The probability of hit with an RPG-7 was therefore much more sensitive to errors in range estimates and it was additionally affected by operator stance, which is a factor that is not relevant for a tripod-mounted weapon like the SPG-9 or the vehicle-mounted "Grom".<br />
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However, the PG-9 grenade had much higher drag than a typical spin-stabilized round fired from a tank gun and was intrinsically limited in its range. Needless to say, "Grom" was far from a match for postwar tank guns and as such, the BMP-1 would be consistently outgunned in any duel with a tank if it relied on its cannon alone. However, the advantage of the BMP-1 against contemporary tanks is that the gunner can fire an ATGM from under armour protection in a turret-down position at ranges where the enemy tank has practically no chance of scoring a direct hit. This is thanks to the combination of a periscopic sight on the turret roof and the mounting of the 9M14 "Malyutka" launch rail on the gun barrel above the level of the turret roof. Even if the BMP is in a hull-down position rather than a turret-down position, the extremely small silhouette of the turret makes it very easy to conceal and very difficult to hit with direct fire at the normal operating ranges of the "Malyutka" missile.<br />
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In other words, the short effective range of the "Grom" was not a problem when considering the full suite of weapons on the BMP-1 in its totality.<br />
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<h3>
<span style="font-size: large;">AUTOLOADER</span></h3>
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The cannon is fed with 40 rounds of ammunition by an autoloader mechanism, all of which is stored in a crescent-shaped conveyor. No additional ammunition was carried in reserve stowage racks. The electrically powered autoloader conveyor is designed to ensure a continuous supply of ammunition for the autoloader.<br />
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The conveyor is essentially a chain with external spokes where the 73mm rounds are attached. The drive sprocket, shown in the drawing on the left below and in the photo on the right below, is directly behind the gunner's seat. The electric motor for the conveyor is installed in the turret.<br />
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<br /><div>To initiate the loading cycle, the gunner presses a switch on his powered gun control handles. Because the autoloader was only capable of loading HEAT rounds, it was not necessary for the conveyor to have any internal memory and it lacked the ability to cycle to an ammunition type of the gunner's choice. The conveyor moves by one step with each loading cycle.</div></div><div><br /></div><div>In 1973, a modification to the autoloader was made so that when the gunner pressed the "K" (HEAT) button on his control handles, the conveyor would cycle until the tip of a HEAT grenade touched a microswitch mounted to the turret ring, positioned at the loading axis. This would trigger the conveyor to brake, and for the loading process to begin. If the gunner pressed the "O" (HE-Frag) button on his control handles, the conveyor would simply run for as long as the button was held down, ignoring any HEAT grenades passing by the microswitch. In this way, the gunner could cycle through the conveyor until he has a HE-Frag grenade within reach. He can then proceed to load it manually. <br />
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To load, the autoloader arm hinges upwards, and the grenade is pitched forward over the gunner's right shoulder and into the breech. To load, the cannon must be elevated by +3 degrees.<br />
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The ammunition conveyor occupies the 1 o'clock to 7 o'clock sector of the perimeter of the turret floor.<br />
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The autoloader elevator arm is shown in the two pictures below. The photo on the left by Robert De Craecker shows a BMP-1 formerly belonging to the NVA.<br />
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The loading tray is shown in the drawing below in its ramming position.<br />
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The time taken to complete a loading cycle is 6 seconds. This figure includes the time taken for the gun to elevate or depress to the proper loading angle and then return to the original elevation angle when gunner pressed the "load" button.<br />
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When the autoloader is not used, the loading speed is theoretically the same. Officially, the crew standards for a BMP-1 gunner mandate that the 2A28 gun loaded in 6 seconds for him to pass with a "satisfactory" mark. To pass with a "good" mark, the procedure must be done within 5 seconds, and to pass with an "excellent" mark, no more than 4 seconds must be taken. The loading time was defined as the period starting with the commander issuing the order to load and ending with the gunner announcing that the gun is ready to fire.<br />
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The manual states that the gunner should not hold his arm close to or in front of the autoloader as this could cause the autoloader to malfunction, presumably due to his jacket getting pinched by the swinging arm, but it is unlikely for the gunner's arm to be "eaten" for the simple fact that the autoloader arm just isn't powerful enough to tear an arm off. However, if there is any truth to the oft-repeated "fact" that Soviet tank autoloaders created an entire generation of armless tank gunners, it should have spawned from the BMP-1. For some reason, the BMP-1 has never been associated with gunners missing arms, even though it is the only Soviet armoured vehicle with an autoloader where this could technically be possible.<br />
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Besides the arm guard installed on the gunner's seat, there is an additional perforated metal shield fixed to the turret to separate the gunner's seat from the autoloader mechanism. It is shown in the drawing below.<br />
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The ammunition stowage simply does not meet modern standards of safety, not to mention that the overall design of the BMP-1 itself is now completely outdated, but the level of safety was quite typical for armoured vehicles of the late 1960's and was not unusual by those standards. Any IFV, modern or otherwise, would burn up if its ammunition were directly struck by an anti-tank weapon. It is worth noting that because the BMP-1 has all of its ammunition in the hull below the turret ring, there is no ammunition in the turret so that a hit to the turret has a minimal chance of causing a catastrophic kill.<br />
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Like the BMP, the AMX-10P carries 325 rounds of ready 20mm ammunition in the fighting compartment below the turret ring in addition to another 475 rounds of reserve ammunition in the hull. The Marder 1 also carries a total of 1,250 rounds of 20mm ammunition in the turret and hull as well, along with its stock of MILAN missiles. It is no different with the Bradley, as it carries hundreds of 25mm rounds in the turret, a few TOW missiles and a Dragon missile in the passenger compartment. If any of these vehicles were to be hit anywhere across the side of the hull with an RPG grenade, the missiles or ammunition may be hit. In this context, the BMP-1 is not much different from any other design of its time.<br />
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Replenishing the autoloader conveyor is done by hand. It takes only a few minutes to stock up a full load of 40 rounds due to the compactness of each 73mm cartridge.<br />
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<h3>
<span style="font-size: large;">73MM AMMUNITION</span></h3>
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Between 1966 to 1973, the standard combat load for the 73mm 2A28 cannon of the BMP-1 consisted of 40 HEAT rounds. The standard combat load for the BMP-1 beginning in 1974 was 16 HE-Frag rounds and 24 HEAT rounds. As one would expect, the loadout can change depending on the tactical situation.<br />
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<h3>
Propellant Charge</h3>
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The only real difference between the ammunition for the "Grom" and the "Kopye" is the means of propulsion - whereas PG-9 rockets were to be fired from an open-ended tube that is the SPG-9 recoilless gun, the PG-15V is fired from a closed-breech gun. As such, PG-15P cased propellant charges were used instead of PG-9P bagged propellant charges. The case is made from galvanized steel. According to the CAT UXO website, the rimmed stub case has a rim diameter of 83mm and a mouth internal diameter of 63mm.<br />
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<h3>
<span style="font-size: large;">PG-15P</span></h3>
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The coupler assembly for both the PG-9P and PG-15P can fit the standard PG-9 grenade and warhead assembly. It is possible for a PG-9V round to be converted to PG-15V rounds by simply swapping out the PG-9P propellant charge for the PG-15P propellant charge. The coupler is designed to ignite the tracer and begin the rocket motor fuze via transferring the primer ignition spark. The EKV-23A primer in the PG-15P charge is an electric-percussion primer. It can be initiated electrically, or mechanically via the striker pin, giving the option to either fire a round normally using the electric trigger on the gunner's control handles, the electric trigger on the manual elevation handwheel, or using the manual lever-operated striker pin incorporated into the breech block of the gun. <br />
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<a href="https://1.bp.blogspot.com/-meIsPEI_nBg/Xdla6298XdI/AAAAAAAAPss/7p1bWY1atu4Wb7TAVHXn4a6L5dfGf-VRACLcBGAsYHQ/s1600/propellant%2Bcharge%2Battachment.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="563" data-original-width="959" height="233" src="https://1.bp.blogspot.com/-meIsPEI_nBg/Xdla6298XdI/AAAAAAAAPss/7p1bWY1atu4Wb7TAVHXn4a6L5dfGf-VRACLcBGAsYHQ/s400/propellant%2Bcharge%2Battachment.png" width="400" /></a></div>
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The entire PG-15P charge weighs just 0.96 kg in total, but the mass of the propellant is only 0.16 kg. Without needing to vent out most of the expanding hot gasses of the propellant charge out the back of the gun tube like in the SPG-9, it became possible to reduce the amount of propellant while maintaining the same muzzle velocity. The small size of the PG-15P is a crucial benefit in the small one man turret, helping to reduce the total length of the rocket to acceptable limits. Nevertheless, the complete cartridge is still quite long.<br />
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<div><br /></div><div><br /></div><div>Upon initiating the primer, the ignition charge (3) held in a perforated tube in the center of the charge is set off. This sends a jet of hot gasses into the PG-9 grenade via the coupler assembly, and at the same time, the flame front exits the perforated tube radially and ignites the propellant charge uniformly. The combusting propellant builds up pressure until the top lid of the PG-15P charge, which is made of aluminium, is breached and the gasses are expelled into the gun chamber, where it can begin to set the PG-9 grenade in motion.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEhY9nwgtPuC_WV0Ks9fgPn56NcK2bv9cPiKOsP8TnC9KNODThUWndtH7CIAIv9KEks4VEwkmt-e4_tLxLSBPNgcgtMQhRS-a55BbStoaqC3OQf-g26l5pH0KjcnP0mQaYChdksuXZ3Rd0FZjRJbgouOjYKNDXcNB4XJNA4e_U96HlfzSn4b7mpC5TxSGg=s1915" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1915" data-original-width="928" height="400" src="https://blogger.googleusercontent.com/img/a/AVvXsEhY9nwgtPuC_WV0Ks9fgPn56NcK2bv9cPiKOsP8TnC9KNODThUWndtH7CIAIv9KEks4VEwkmt-e4_tLxLSBPNgcgtMQhRS-a55BbStoaqC3OQf-g26l5pH0KjcnP0mQaYChdksuXZ3Rd0FZjRJbgouOjYKNDXcNB4XJNA4e_U96HlfzSn4b7mpC5TxSGg=w194-h400" width="194" /></a></div>
<br />As shown in the photo below, the top lid of the charge casing is breached upon firing, but the lid is deformed in such a way that the passage from the casing to the cannon chamber and the barrel is restricted. This reduces the rate of pressure release and thus reduces the chamber pressure by some amount, which translates to a small reduction in the recoil impulse of the cannon.<br />
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<h3>
<span style="font-size: large;">
HEAT</span></h3>
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To deal with all ground targets, including both armoured and unarmoured targets, the PG-15V HEAT round with the PG-9 grenade was the only available option to BMP-1 gunners. It had a pure HEAT grenade only meant for armoured targets, having only a negligible fragmentation effect unlike HEDP grenades. Despite its low efficiency against targets other than armoured vehicles, BMP-1 gunners were instructed to use this round against infantry in the open and in fortified positions for lack of a better option until the OG-15V round became available.</div><div class="separator" style="clear: both; text-align: left;"><div><br />Since the introduction of the OG-15V in 1973, the PG-15V was relegated to a backup role against non-armoured targets. PG-15V itself was replaced by PG-15VS with a more potent armour piercing effect in the same year.</div></div><div class="separator" style="clear: both; text-align: left;"><br /></div>
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<span style="font-size: large;">PG-15V</span></h3>
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<a href="http://3.bp.blogspot.com/-e3Bah37uuAI/ValAWubNXkI/AAAAAAAAC1Y/ITseP_Hv3Wk/s1600/PG-15V-Hollow-charge-ground.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="192" src="https://3.bp.blogspot.com/-e3Bah37uuAI/ValAWubNXkI/AAAAAAAAC1Y/ITseP_Hv3Wk/s640/PG-15V-Hollow-charge-ground.png" width="640" /></a></div>
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The PG-15V cartridge combines the PG-9 fin-stabilized rocket grenade assembly used by the SPG-9 with the proprietary PG-15P propellant charge. Introduced in 1962 alongside the SPG-9 as part of the PG-9V round, the PG-9 was originally intended to fulfill the anti-armour role, but it was initially used for anti-personnel purposes as well due to a lack of options at the time.</div><br /><div>
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The rocket engine is located at the rear of the projectile, in front of the folding stabilizer fins. Rocket propellant is contained inside the cylindrical segment at the middle of the projectile and the exhaust gasses exit from a Venturi nozzle at the rear end of the projectile, unlike an RPG-7 rocket where multiple exhaust nozzles are arranged around the circumference of the rocket just behind the grenade warhead. A raised lip in front of the stabilizer fins acts as a bore obturator.<br />
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<a href="http://1.bp.blogspot.com/-d9N20JoBvqw/ValBCJyA1YI/AAAAAAAAC1g/FhBnkCv2mRI/s1600/PG-15V.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="148" src="https://1.bp.blogspot.com/-d9N20JoBvqw/ValBCJyA1YI/AAAAAAAAC1g/FhBnkCv2mRI/s640/PG-15V.png" width="640" /></a><br />
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Due to the low pressure of the PG-15V round and its low muzzle velocity, the acceleration forces during the launch of the PG-9 grenade were relatively tame. This allowed the thickness of the warhead casing to remain thin and thus allow the diameter of the shaped charge to be maximized. However, the grenade could still acquire a relatively high velocity of 665 m/s thanks to its rocket booster. This allowed it to have a point blank range of 765 meters for a target with a height of 2 meters. For comparison, the BR-350B APBC shell fired from the 76.2mm D-56T gun of the PT-76 had a muzzle velocity of 655 m/s and a point blank range of 780 meters against a target with a height of 2 meters, so it had a marginal point blank range advantage of just 15 meters over the PG-15V. This was due to the lower drag forces experienced by the APBC shell compared to the finned PG-9 grenade. However, when comparing the PG-15V to the 76.2mm BK-354(M) HEAT shell which had a muzzle velocity of just 550 m/s and a point blank range of 630 meters for a target that is 2 meters tall, the relationship is reversed and the PG-15V gains a considerable point blank range advantage.</div><div><br /></div><div>
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In other words, the use of rocket assistance technology allowed Soviet engineers to create a HEAT grenade that had superior ballistic performance to a 76.2mm HEAT shell fired from medium-pressure gun while having superior armour penetration performance.<br />
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The PG-9 warhead has a conical shaped charge liner made from <a href="http://metallicheckiy-portal.ru/marki_metallov/stk/40X">40Kh low alloy steel</a> which is widely used for structural purposes where increased strength is required. Compared to a shaped charge with a copper liner, the effectiveness of a steel liner in penetrating armour is somewhat lower, but the post-perforation effect tends to be substantially greater owing to the larger diameter of the penetration cavity. According to a drawing from a January 1997 edition of "<i>Projectile and Warhead Identification Guide</i>", the shaped charge cone has a diameter of 61.7mm and an apex angle of 60 degrees. The liner has a variable thickness, from 1.27mm near the rim to 1.02mm at the apex. The warhead has 258mm of built-in standoff distance between the shaped charge and the tip of the fuze. The use of a variable thickness liner and a wave shaper was a highly advanced feature for a 1962 grenade, as most foreign HEAT shells of the time still lacked even a wave shaper.<br />
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The casing of the PG-9 grenade is made from aluminium and weighs only 0.9 kg. A light aluminium casing is exceptionally poor at fragmentation compared to the typical steel casings of tank-fired HEAT shells, and indeed, thin aluminium casings are used in offensive hand grenades like the RGN grenade for this reason. The poor fragmentation effect makes the PG-9 highly anemic against dispersed infantry on open ground, but the 0.322 kg explosive charge can still cause significant damage to light fortifications as it is equivalent to a 0.515 kg TNT charge. In practice, the actual blasting effect should be stronger than the explosive weight alone suggests, because according to studies such as "<i><a href="https://iopscience.iop.org/article/10.1088/1742-6596/1507/3/032008/pdf">The analysis of the equivalent bare charge of aluminum cased charge exploding in confined space</a></i>", the reactivity of aluminium casings on TNT charges increases the total energy of the explosion by 18-26%. The combustion of aluminium particles among the other detonation products acts as a fuel additive, increasing the heat of the explosion and thus enhancing the blast loading.</div><div><br /></div><div>In total, the explosive charge is only slightly weaker than a conventional tank-fired 75mm or 76mm HE shell filled with TNT. Heavy concrete barriers, brick and concrete walls, sandbag walls, timber barriers and other types of field fortifications can be destroyed with confidence. When firing at troops in the open, a BMP-1 gunner will have to rely mainly on his PKT coaxial machine gun, as an HE effect is not efficient in open spaces.<br />
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The PG-9V grenade uses the VP-9 piezoelectric point-initiating, base-detonating (PI-BD) fuze. It features an inertial safety mechanism and it has a self-destruct system that automatically detonates the grenade 4-6 seconds after it is armed. The fuze is armed at a distance of 2.5 to 20 meters from the muzzle of the gun by the braking force of the deceleration from air resistance and the deploying stabilizer fins on the grenade. The nose fuze is connected to the base detonator by the aerodynamic fairing connecting the warhead to the fuze, and an internal conductive cone, which links the positive terminal of the element to the negative terminal of the base detonator via the shaped charge cone. On impact with an obstacle, the mechanical stress induced in the piezoelectric element is converted into an electrical current. The current travels down the conductive cone and shaped charge liner, and into the base detonator, setting off the warhead.</div><div><br /></div><div>The metal safety cap on the VP-9 is designed to protect the piezoelectric element. It mainly serves as an additional drop safety measure as it helps to protect the ceramic piezoelectric element from cracking by rough handling. If the safety cap is left on when the grenade is fired, it prevents the fuze from initiating on heavy rain, twigs, and other minor obstacles. An impact on a hard and unyielding object is necessary to initiate the fuze. This makes the grenade unsuitable for firing targets other than vehicles and structures. If the safety cap is removed, the VP-9 behaves as a highly sensitive superquick fuze. It initiates on any obstacle, and the delay of the fuze is the same as any other domestic piezoelectric fuze of its type - less than 0.0001 seconds, though the specific time is unknown. This makes the grenade suitable for firing at personnel in the open as it ensures the maximum fragmentation effect. For the BMP-1, the grenades are usually loaded into the autoloader with the safety cap on.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-FEcMjar03kA/XsUMbG3pnPI/AAAAAAAAQwk/-uGLGsiczmsz-h_GzGgWJF_X4aEEVNHrACK4BGAsYHg/vp-9.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="402" data-original-width="336" height="320" src="https://1.bp.blogspot.com/-FEcMjar03kA/XsUMbG3pnPI/AAAAAAAAQwk/-uGLGsiczmsz-h_GzGgWJF_X4aEEVNHrACK4BGAsYHg/s320/vp-9.jpg" /></a><a href="https://1.bp.blogspot.com/-0nAvvMx3668/XsUNozUORPI/AAAAAAAAQxA/Dt1jZTdi-HonBaTNtrZkhr4KT7oJks3uQCK4BGAsYHg/vp-9%2Bbase%2Bdetonator.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="336" data-original-width="378" src="https://1.bp.blogspot.com/-0nAvvMx3668/XsUNozUORPI/AAAAAAAAQxA/Dt1jZTdi-HonBaTNtrZkhr4KT7oJks3uQCK4BGAsYHg/s320/vp-9%2Bbase%2Bdetonator.jpg" width="320" /></a></div><div><br /></div><div><br /></div><div>In either case, the VP-9 provides instant action even at an impact velocity corresponding to point blank range, thus ensuring that the warhead of the grenade is detonated at the proper standoff distance without any reduction in the standoff distance by the crumpling of the grenade casing. </div><div><br /></div><div>As with any other thin-skinned grenade, it is possible to defeat the PG-9 using slat armour with gaps of an appropriate size, and certain types of chain link fencing can also have the same effect, though the reliability is significantly diminished. If the grenade flies between two slats with a gap less than 73mm wide, the fuze does not initiate, while the slats short-circuit the fuze by crushing the aerodynamic fairing against the conductive cone, and the destroy the warhead itself by cutting through the shaped charge liner. The probability of success for this type of armour tends to be around 0.5-0.6, which is significant, but is too low to be considered a comprehensive armour solution. The majority of light anti-tank grenades, including the HEAT grenades for weapons such as the LAW, LRAC F1, PzF 44, older grenades for the Carl Gustaf to name just a few, will also be defeated due to warhead destruction when flying between the slats. Only some grenade designs feature a shoulder fuze like the m/66 grenade for the Carl Gustaf.</div><div>
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Maximum Chamber Pressure: 73 MPa<br />
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Total Cartridge Mass (incl. propellant charge): 3.49 kg</div><div>
Projectile Mass: 2.53 kg<br />
Grenade Mass: 1.20 kg<br />
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Explosive charge: A-IX-1<br />
Explosive charge mass: 0.322 kg<br />
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Muzzle velocity: 400 m/s<br />
Maximum velocity: 665 m/s<br />
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Penetration: 300mm RHA<br />
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Officially, the PG-9 grenade warhead penetrates 300mm of RHA steel, but this figure actually indicates the thickness of armour that can be perforated with a significant destructive post-perforation effect. This effect is provided when a certain amount of armour overmatch is included. According to a 1979 Soviet report titled <i>"<a href="http://btvt.info/5library/vbtt_1979_03_probivaemost.htm">Выбор Кумулятивных Снарядов Для Испытания Брони</a></i>" (<i>Selection of Cumulative Shells for the Evaluation of Armour</i>), the average penetration of the PG-9 warhead in RHA reaches 326mm. The maximum penetration is 346mm and the minimum penetration is 302mm. <br />
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The high penetration power of the PG-9 grenade relative to its caliber can be credited to the large standoff distance of 258mm, or 4.2 calibers, built into the warhead design. This is much higher than the built-in standoff provided for most other HEAT warheads. <br />
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In theory, the PG-9 grenade was fully capable of reliably defeating the frontal armour any NATO tank that it was expected to encounter in a major European war during the period of influence of the BMP-1, including tanks such as the M60A1, AMX-30, Leopard 1 and Chieftain. Even when NATO obtained a numerically relevant quantity of next-generation tanks like the Leopard 2 and M1 Abrams in the mid-1980's, the large number of legacy tanks serving in the ground forces of NATO militaries allowed the BMP-1 to stay relevant with the PG-9. However, the small margin of defeat against the front of heavily armoured tanks such as the M60A1 and Chieftain made the PG-9 an unreliable weapon.<br />
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The ballistic performance of PG-9 is quite good for a grenade of its class. It has a ballistic coefficient of 2.11. Because of the very high velocity of the rocket grenade, it takes only 1.32 seconds to reach a target at 700 meters. This makes it easier to hit a moving target compared to a lower velocity round. A firing table for the PG-9 round is shown below.<br />
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The first column is distance in meters (in meters), the second column is angle of gun elevation (in degrees), the second is the height of drop (in meters), the third is the total flight time (in seconds), and the fifth column is the speed of the rocket grenade (in meters/second). As you can see from the table, the grenade remains supersonic up to 900 meters and slightly further, and the ballistic drop is less than a meter at a distance of 500 meters, and it takes only 0.9 seconds for the grenade to reach its mark at 500 meters.<br />
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One of the peculiarities of rocket-propelled grenades like the PG-9 is that the deflection dynamics of the projectile from crosswinds will change depending on the state of the rocket engine. When the projectile is still experiencing acceleration from the rocket engine, it accelerates against the direction of the crosswind. In other words, if the crosswind is blowing from right to left, the projectile flies to the right. Once the rocket engine burns out completely, the projectile begins to decelerate and it behaves like a typical fin-stabilized projectile in the cross wind, which is to say that it flies in the direction of the wind. For the PG-9 round, the rocket engine burns out in only a fraction of a second and as such, the projectile ceases to accelerate against the crosswind and begins to normalize in the opposite direction. At 800 meters, the projectile is completely normalized and is oriented parallel to the bore axis of the cannon, and beyond 800 meters, the projectile becomes deflected into the crosswind. These non-intuitive flight characteristics make it extremely difficult to engage targets at ranges beyond 800 meters as the gunner is expected to mentally apply corrections for this phenomenon without the aid of any instruments except the markings in his sight.<br />
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The firing table for PG-9 as fired from the "Grom" shows that the maximum deflection from a 10 m/s crosswind is 6.5 mils at a distance of 500 to 600 meters. Beyond this range, the trajectory of the projectile reverses direction. At 1,150 meters, the point of impact coincides exactly with the point of aim.<br />
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Fortunately, because the maximum effective range against tanks is limited to 800 meters, the reversal in the flight direction of the PG-9 grenade in a crosswind at beyond 800 meters is practically irrelevant. The gunner would only need to apply the basic - and more intuitive - windage corrections when firing at virtually all point targets.<br />
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<a href="https://3.bp.blogspot.com/-y35hsJMy4BM/WKXKRC40lxI/AAAAAAAAIZM/8K4t8hlzb0kHMpOZNFSc6x1JCfVmSTdAACLcB/s1600/pg-15v.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-y35hsJMy4BM/WKXKRC40lxI/AAAAAAAAIZM/8K4t8hlzb0kHMpOZNFSc6x1JCfVmSTdAACLcB/s1600/pg-15v.jpg" /></a></div>
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<h3 style="text-align: left;">
<span style="font-size: large;">PG-15VS, PG-15VS1</span></h3>
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Introduced in 1973, the PG-15VS round with the PG-9S grenade featured an improved warhead, providing superior penetration power while maintaining the same weight as the original PG-9S. The new warhead has a shaped charge liner made from V-95 aluminium alloy constructed using new high-precision manufacturing technologies, and the shaped charge was filled with a more powerful OKFOL explosive charge instead of A-IX-1. OKFOL is composed of 95% HMX and 5% phlegmatizing wax. The PG-15VS1 round had the PG-9S1 grenade. It was a cheaper alternative that featured a modified aluminium shaped charge liner and an A-IX-1 filling. It had a lower penetration power than the PG-9S grenade, but it was an improvement over the basic PG-9. Compared to a copper or steel liner, the penetration power of an aluminium-lined shaped charge is inferior, as the jet will bore a wider but shallower penetration cavity. However, this also results in drastically improved post-perforation damage due to the combination of increased ejecta and internal overpressure from the grenade blast. At the same time, the PG-9S and PG-9S1 grenades manage to achieve an excellent penetration performance by having a very long built-in standoff distance, giving its aluminium shaped charge the necessary conditions to achieve performance equal to much larger caliber HEAT shells with copper and steel liners.<br />
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All other parts of the PG-15VS and PG-15VS1 rounds were identical to the PG-15V and its ballistic characteristics were identical to that of the PG-9. As such, the 1PN22M1 sight did not need to have a new viewfinder disc to be compatible with the new ammunition. PG-15VS replaced the PG-15V in the early 1970's.<br />
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<div><br /></div>According to the study "<i>Противокумулятивная Стойкость Комбинированных Преград С Керамикой</i>" published in the March 1988 issue of the "<i>Вестник Бронетанковой Техники</i>" military science journal, the penetration channel depth produced by the PG-9S grenade into a semi-infinite RHA block is 404mm ±20mm, based on a sample size of 8 detonations. It was noted in the paper that the penetration depth was determined based on the results of experiments with a confidence level of 95%, and the confidence interval is 384mm to 424mm. However, the standoff distance used was 185mm, which is the distance between the liner and the nose of the warhead without the protruding tip of the VP-9 fuze. This may be enough to simulate the minor reduction in standoff during fuze activation and jet formation as the grenade impacts a target.<br />
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The substantial increase in armour penetration performance offered by the PG-15VS increased the probability of knocking out existing tanks with the first shot due to the increased post-perforation effect. With a nominal armour penetration of 400mm RHA, the PG-9S grenade warhead was equivalent in power to the 125mm warhead of the 9M14 "Malyutka" missile, so it was very potent indeed. This improvement was tactically relevant throughout the 1970's because NATO relied entirely on tanks with conventional steel armour that was generally not thick enough to resist any contemporary HEAT weapon worth mentioning. When the Abrams and Leopard 2 were introduced in 1980 and 1979 respectively, one of the basic requirements of their protection was to be immune to a HEAT grenade with the penetration power of the PG-9S within a large frontal arc. For the M1 Abrams specifically, this frontal arc was 90 degrees in size (± 45 degrees). This severely limited the effectiveness of the PG-9S grenade in a frontal attack, making it useful only in a side attack where the angle of impact against the side armour of the tank was less than 45 degrees.</div><div><br /></div><div>Additionally, according to the book "<i>Боеприпасы И Средства Поражения: Энциклопедия XXI век</i>" (<i>Ordnance and Means of Destruction: Encyclopedia of the 21st Century</i>), the penetration of the PG-15VS in brick is 1.5 meters, and its penetration in reinforced concrete is 1 meter.<br />
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<b>PG-15VS (PG-15VS1)</b><br />
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Total mass (incl. propellant charge): ~3.49 kg<br />
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Explosive charge: OKFOL (A-IX-1)<br />
Explosive charge mass: 0.340 kg (0.316 kg)<br />
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Muzzle velocity: 400 m/s<br />
Maximum velocity: 665 m/s<br />
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Penetration: 400mm RHA (350mm RHA)<br />
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Soviet-era stocks of PG-15V rockets have either been used up or have expired, and production for domestic use in Russia has shifted towards the improved PG-15VS for equipping the meager collection of various leftover BMP-1s still in service in rear echelon forces. Since 1999, the Planta chemical plant in Russia has been proceeding with its munitions recycling program designed to reintroduce expired Soviet-era HEAT grenades back into the Russian Armed Forces. Up to 75% of all non-perishable components (including the casing, booster assembly, shaped charge liner, fuze, etc.) could be kept and reused with new rocket propellant and a new explosive charge.<br />
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The remaining BMP-1P vehicles still in use in the Russian Army are armed with PG-15VS or PG-15VS1 rounds, as this is the type that is also supplied for the SPG-9 recoilless guns that are present in the Army.<br />
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<h4 style="text-align: left;"><font size="4">
OG-15V (HE-Frag)</font></h4>
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<div><br /></div><br />Introduced in 1973, the OG-15V round gave the BMP-1 a greatly enhanced anti-personnel capability. With these HE-Frag rounds and HEAT grenades, a BMP-1 was theoretically capable of fulfilling all combat tasks from eliminating infantry in the open and in field fortifications, to destroying tanks. As the OG-15V was significantly shorter than PG-15V, it cannot be loaded by the BMP-1 autoloader but it is much easier to load by hand within the confines of the turret.</div><div><br />
Ballistically, the OG-9 grenade is similar to a mortar shell. It is significantly heavier than a PG-9 grenade and it lacks a rocket motor. Because of this, it is subsonic, with a muzzle velocity of just 290 m/s. Unlike the four long flip-out stabilizing fins of the PG-9 rocket grenade, the eight stabilizing fins on the OG-9 have a much smaller wingspan and gives the grenade the ballistics of a mortar bomb fired at a full charge. Firing tables show that in a 10 m/s crosswind, an OG-9 grenade is deflected by 3 meters.<br /><br /><br />
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<div><br /></div><div><br /></div>The OG-9 warhead uses the GO-2 point-detonating fuze. It has an inertial arming mechanism. It is armed by the deceleration experienced by the projectile from air resistance when it leaves the gun, ensuring that the warhead is only armed at a minimum distance of 2.5 meters from the muzzle. The GO-2 fuze is covered by a safety cap that can be removed by the gunner prior to firing. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-UyPwEr47lpE/XsUQO1keBVI/AAAAAAAAQxc/nd5HedrK_YA4aazQvGEKvH0tD2uIHF36QCK4BGAsYHg/go-9.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1418" data-original-width="617" height="320" src="https://1.bp.blogspot.com/-UyPwEr47lpE/XsUQO1keBVI/AAAAAAAAQxc/nd5HedrK_YA4aazQvGEKvH0tD2uIHF36QCK4BGAsYHg/s320/go-9.jpg" /></a></div><div><br /></div><div><br /></div><div>When the OG-9 grenade is fired with the safety cap on, the fuze is switches from instantaneous impact initiation to inertial initiation, giving the grenade a short delay to allow it to function in the HE mode. When the safety cap is removed prior to firing, the grenade functions in the Frag mode. The need to manually set the fuze mode is one of the reasons why the autoloader of the BMP-1 is not used to load the OG-15V grenade.<br />
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The OG-9G warhead of the grenade has a 0.73 kg filler of A-IX-1. The explosiveness of A-IX-1 is 1.58 times higher than TNT. This is quite good, but it is still slightly lower than pure hexogen due to the presence of a wax phlegmatizer to stabilize the explosive compound. In terms of explosive effect, the OG-9G warhead is equivalent to 1.15 kg of TNT. This is almost twice that of tank-fired 75mm and 76mm HE shells.<br />
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Like the PG-9, the OG-9 grenade uses the same PG-15P propellant charge. The grenade body has a perforated tube section in lieu of a rocket motor. When the PG-15P charge is detonated, the perforated tube of the grenade fills with expanding gasses which results in a reduction in chamber pressure. Due to the low muzzle velocity and the lack of a rocket motor, the OG-15V has a very pronounced arcing ballistic trajectory, similar to a mortar bomb.<br />
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The original video is available here (<a href="https://www.youtube.com/watch?v=7sZtCPsvvX0">link</a>).<br />
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Muzzle velocity: 290 m/s<br />
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Total Cartridge Mass (incl. propellant): 4.59 kg<br />
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Warhead Total Mass: 3.7 kg<br />
Explosive charge: A-IX-1<br />
Explosive charge mass: 0.73 kg<br />
<br /><br />The cast steel casing of the warhead weighs 2.83 kilograms. The walls of the warhead cavity can be seen in the photo below. <a href="https://reibert.info/threads/og-15v-k-gladkostvolnomu-73-mm-orudiju-2a28.416296/">Photo by RaiderBox</a>. With a TNT equivalence of 1.15 kg, the mass of the filler is 40% of the mass of the steel casing. The mass of the explosive charge is quite large for a grenade of its caliber, but the thickness of the steel casing is considerably less than a tank-fired HE shell of a similar caliber. For comparison, the steel casing of the M309 HE shell weighs 5.35 kg. Due to the use of cast steel rather than forged steel, made possible by the low velocity of the grenade, and the relatively thin casing walls, the fragmentation effect is likely to be excellent.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-PRQfWQlc3nI/V3JGHI1GgII/AAAAAAAAG4k/XOr1UiI4Uh00TEKi8nEPnkkMqnNSAqt1QCLcB/s1600/20130927_103027.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://4.bp.blogspot.com/-PRQfWQlc3nI/V3JGHI1GgII/AAAAAAAAG4k/XOr1UiI4Uh00TEKi8nEPnkkMqnNSAqt1QCLcB/s400/20130927_103027.jpg" width="400" /></a></div><div><br /></div><br /></div><div>The OG-9G warhead is considerably more potent than 82mm mortar bombs in terms of explosive payload and casing weight, and has a superior filling to weight ratio. For example, the VO-832DU mortar bomb, used as a standard bomb for all Soviet mortars since the 82mm mortar Mod. 1937, has a full bomb weight of 3.1 kg and a TNT filler weighing just 0.4 kg. The superiority of OG-9G is entirely due to the higher elongation of its warhead.</div><div><br /></div><div>It is also worth mentioning that the OG-9 grenade is launched at around the same velocity as a typical mortar bomb, except that the poor gun elevation of the 2A28 cannon in the BMP-1 restricts its ability to perform long range indirect fire. It is only possible to use the grenade in the direct fire mode. The closest counterpart to this unique combination is the M20 recoilless rifle firing the spin-stabilized M309 HE shell, but the M309 is a modification of the tank-fired M48 shell of WWII vintage. The nominal kill zone of the OG-9 grenade is 83 square meters against infantrymen in the prone or supine position. For comparison, a 30mm HE-I shell has a nominal kill zone of 11 square meters against the same targets. The nominal kill zone of OG-9 is 500 square meters against infantrymen in a standing position.<br /></div><div><br /></div><div>
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Although the OG-9 grenade is primarily intended for the anti-personnel and anti-fortification role, they can also be effective against lightly armoured vehicles and soft-skinned vehicles under certain conditions. The photo on the left is from the <a href="http://www.15thfar.org/morepic.html">15th Artillery Field Regiment website</a> and shows an M113 hit by a B40 anti-tank grenade launcher (RPG-2 clone). The photo on the right is from the <a href="https://www.awm.gov.au/collection/C311008">Australian War Memorial website</a> and shows a destroyed Australian M113A1 from the Vietnam War. According to the AWM, the vehicle was hit three times by 75mm recoilless rifles during Operation Bribie on the 17th of February 1967. In both photos, it is simple to deduce that the large breaches in the armour were caused by an external explosion because the edges of the armour plate around the breach are bent inward. This implies that the explosive payload of grenades in the 70-80mm caliber range is already sufficient to cause serious damage to lightly armoured vehicles.<br />
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The second example is the most interesting because one of the 75mm recoilless rifle rounds struck the passenger compartment roof hatch which was open at the time, and the damage done by the HEAT grenade to the 38mm-thick hatch can be clearly seen. The engine of the M113A1 was destroyed by another round from recoilless rifles. Note that the 75mm M309 HE grenade fired from the M20 recoilless rifle only has 0.676 kg of TNT as its explosive filler and the projectile is launched at a muzzle velocity of just 302 m/s, and the HEAT grenade has even less explosive power. The OG-9 grenade is launched at practically the same muzzle velocity but the explosive charge of its warhead is equivalent to 1.15 kg of TNT. The heavier steel casing of the M309 is irrelevant in this comparison as it is the blasting power of the shell that caused the damage to this M113 and not fragmentation.<br />
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Although HEAT rounds are usually the ammunition of choice when grenadiers are facing armoured vehicles, it is clear that even medium-caliber high explosive shells launched at low velocities can cause enough damage to knock out armoured personnel carriers and other vehicles with a similar level of armour protection. With this in mind, it should be understood that the addition of HE rounds as a new ammunition type to the repertoire of the BMP-1 in 1974 did not necessarily result in a trade-off of anti-armour capabilities in exchange for enhanced anti-personnel and anti-fortification capabilities. Rather, the overall firepower and flexibility of the BMP-1 saw a general increase.<br />
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The OG-15VM grenade became available later on. It was an improved version using a more powerful A-IX-2 explosive charge instead of A-IX-1. This improved the blasting power of the warhead and added an enhanced incendiary effect.<br />
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<h3>
<span style="font-size: large;">PKT</span></h3>
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Although the coaxial machine gun in most IFVs is usually sidelined in favour of their more powerful autocannons when engaging infantry, the BMP is often forced to depend on its PKT when dealing with infantry in the open due to the weak fragmentation effects of the 73mm HEAT grenades. The PKT is mounted to the right of the 73mm 2A28 "Grom" cannon, as it feeds from the right and ejects to the left. </div>
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To facilitate the work of the gunner, the coaxial machine gun in the BMP was fed from an unusually large 2,000 round box as the drawing below shows. This was a departure from the typical ammunition feed systems for the coaxial machine guns of Soviet tanks and armoured personnel carriers. As the BMP must make use of its PKT regularly, the large capacity box is very convenient. Looking abroad, however, it is clear that this was not much of an innovation for 1967. The Marder 1 and the AMX-10 were both introduced in the early 1970's and both had coaxial machine guns fed with 2,000-round boxes, so the BMP can be considered on par with its contemporaries in this regard. Also, the BMP carries additional boxes of machine gun ammunition, but those boxes are meant for hand-held PK and PKM machine guns and cannot be readily used by the coaxial machine gun, as there is no mounting point for 250-round boxes, although it is still possible to load a full belt and leave it hanging - the PK series reportedly has an exceptionally strong feeding mechanism.</div>
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Spent shell casings and link segments fall through a chute and into a metal bin to be collected. This bin is the same one that collects spent casings ejected from the main cannon, but in a different compartment.<br />
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If stoppages occur, the gunner - being the only occupant of the turret - is responsible for correcting them. It is fairly easy to do so due to the close proximity of the machine gun to the gunner's seat even though it is installed to the right of the 2A28 cannon.</div>
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Armour piercing incendiary rounds and armour piercing incendiary tracer ammunition is usually loaded in a 4:1 ratio. The PKT machine gun has a cyclic rate of fire of 650 rounds per minute, and it has a thicker barrel than the infantry-based PK to allow for longer periods of sustained fire. There are two ways to fire the PKT: the left thumbs witch on the control handles, or by depressing the manual trigger lever on the back of the machine gun, on the firing unit just behind the disassembly button.</div>
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In 1969, the PK was replaced by the PKM and the corresponding sub-variants were also replaced with modifications of the PKM, including the replacement of the PKT with the PKTM. The PKTM is mainly distinguished from the earlier PKT by the smooth barrel as opposed to the fluted barrel of the PKT. Internally, the PKTM and the PKT differ in the same way that the basic PK and PKM models differ.<br />
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<h3>
<span style="font-size: large;">BMP-1 (Object 765 sp.1, sp.2, sp.3)</span></h3>
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<span style="font-size: large;">"MALYUTKA" ATGM SYSTEM</span></h3>
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The 9M14 "Malyutka" missile entered service in 1963 as part of the 9K11 system. At the time of the introduction of the BMP-1, the 9K11 "Malyutka" ATGM system was already widespread in the Soviet Army as an infantry-operated system and it posed a a very serious threat to NATO armour despite the inherent limitations of its manual guidance principle. Owing to its high performance characteristics despite its dimunitive size, it was viable for both infantry and mounted systems, including dedicated missile carriers, but for the BMP, the most significant aspect was that it was the first ATGM system to be comprehensively incorporated as part of the primary armament of this class of combat vehicle. This was one of the reasons why the BMP-1 is often said to be more qualified as the first true IFV instead than the Schützenpanzer 12-3 which came much earlier, despite the fact that the Bundeswehr had developed mechanized infantry tactics centering on the IFV concept to go with the SPz 12-3 before the Soviet Army. Even the Marder 1 that entered service years after the BMP did not feature an ATGM launching capability.<br />
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When the BMP-1 entered service in 1966, the original 9M14 missile had been replaced by the improved 9M14M "Malyutka-M". In a 1966 manual for the BMP-1 (Object 765 sp.1), the 9M14M is the specified model in a standard combat load and the descriptions and instructions in the manual all pertain to the 9M14M only, with no mention of the 9M14 whatsoever. Although the older 9M14 could be fired from the BMP-1 without any compatibility issues, it is safe to assume that it was not officially issued to the BMP-1 during its service in the Soviet Army. The "Malyutka" series and its technical details are described in a separate Tankograd article, <a href="https://thesovietarmourblog.blogspot.com/2021/07/soviet-atgms.html#malyutka">"Soviet ATGMs"</a>.<br />
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Owing to the demanding requirements set forth in a government decree on July 6, 1961, the 9M14 "Malyutka" missile that entered service in 1963 surpassed all of its foreign counterparts. One of the requirements was for the missile to have a weight of 8-10 kg to ensure that it could be transported easily by infantry anti-tank teams, and although the final product went slightly over the limit with a weight of 10.9 kg, it was still light enough for the specified role. Moreover, its relatively small dimensions and foldable fins made it much more convenient to transport, especially in fully enclosed vehicles where compactness was a particularly important factor. The closest counterpart to the 9M14 was the French ENTAC missile, which is comically oversized and overweight in comparison with the more sophisticated "Malyutka" despite belonging to the same class of ATGM.<br />
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When installed on the launcher atop the 2A28 cannon and deployed for launch, the 9M14M missile on the BMP-1 is completely exposed and may be damaged. The lack of protection from gunfire and shell fragments was an important consideration, but it was also recognized that the missile could potentially be rendered inoperable in mundane accidents such as in a collision with a tree branch that causes one of the plastic stabilizer fins to break.<br />
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To prevent this type of damage, it was officially forbidden for BMP-1 gunners to keep a missile deployed on the external launcher indefinitely. When going on a march, the launcher would be kept empty and all missiles would be stowed internally. The gunner would only load a missile onto the launcher if it was necessary during combat or if combat was imminent and there was a perceived need.<br />
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The missile comes assembled with a lightweight launch rail that fits onto the launcher on top of the cannon barrel. It is the same launch rail used in the 9P110 and 9P133 tank destroyers. After a missile is launched, the launch rail remains on the launch platform and it must be manually removed by the gunner before the next missile is loaded. The launch rail would be reused when replenishing the ammunition supply of the vehicle. New missiles are attached to the launch rail before they are stowed in the BMP.<br />
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The "Malyutka" launch platform contains electrical connectors that joins the missile guidance system to the missile guidance wire through the launch rail. The missile guidance wire not only transmits steering commands from the operator's joystick to the missile, but also serves as an electrical conduit that supplies the missile with electrical power. The launch platform positions the launch rail at an elevation angle of 3.25 degrees.<br />
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During the launch and throughout the flight of the missile, it maintains a spin rate of 8.5 revolutions per second. Although the performance of shaped charge warheads is negatively affected by spin, this modest rate of spin was far too low to have a noticeable effect on the performance of the missile warhead.<br />
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Among the requirements for the 9M14 missile was that it must penetrate between 180-200mm of RHA steel at an angle of 60 degrees. The final warhead design managed to achieve a penetration of 200mm RHA, which makes it a direct equivalent to the 9M17P "Fleyta-P" missile. Despite the 9M17P having a larger warhead diameter of 142mm, the smaller 125mm warhead of the "Malyutka" could match its performance thanks to a much larger standoff distance built into the missile fairing.<br />
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When launching a missile, the cannon should be elevated to provide the necessary ground clearance to allow the missile to stabilize during flight. The correct elevation is achieved by the gunner placing the crosshair at the bottom of the 1PN22M1 sight viewfinder on the desired target.<br />
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Control of the "Malyutka" missile is achieved using the 9S428 control system which includes the analogue electronic components of the control joystick for the gunner and the electrical connections that connect the missile to the launching system on top of the barrel of the "Grom" cannon.<br />
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Control of the "Malyutka" missile is MCLOS only, and that means that the gunner must steer the missile manually as it flies through the air. This is done via the 9V332 missile systems control box, which has a joystick to steer and a button to launch the missile. When not in use, the joystick is retracted inside the control box. The 9V332 missile systems control box was originally designed for the 9P110 tank destroyer. The box has a non-functioning dial that was originally meant to allow the 9P110 missile operator to select a missile from the six available on the overhead launch rails. As the BMP-1 can only mount one missile at a time, the dial is permanently set at the number one position. To launch a missile, the gunner presses the "launch" button on the left of the control box. The purple bulb in the center of the box is the missile status indicator. If the bulb does not light up, it means that the missile is either not mounted, not mounted properly, or malfunctioning.<br />
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To use the control box, the joystick is extended first. For the best results, the joystick is grasped with both hands and the gunner presses his thumbs against the tip of the joystick to input small corrections when steering the missile. When the joystick is deflected in the four cardinal directions, the missile acquires a directional acceleration corresponding to the deflection angle of the joystick. For example, if the joystick was merely tapped to the left, the missile accelerates a small amount to the left, and if the joystick was pushed to its maximum deflection to the left, the missile accelerates very quickly to the left. The missile maintains its speed after it is steered, so if the gunner returns the joystick to the neutral position, the missile will continue to drift in the direction it was previously steered. The gunner must input a correction in the opposite direction to return the missile to a straight trajectory.<br />
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When a missile is in flight, the gunner is supposed to concentrate on guiding the missile to the target but there are no technical limitations that prevent the gunner from firing the 2A28 cannon or the coaxial machine gun. The missile control system and the turret controls are not linked.<br />
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The control box is installed on a hinged pedestal. When not in use, the box is stowed away by swinging the pedestal underneath the gunner's seat.<br />
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<span style="font-size: large;">GUIDANCE METHOD</span></h3>
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The 9M14M "Malyutka-M" missiles launched from the BMP-1 were to be guided by the gunner using the same three-point method as the missile operators of any other MCLOS missile system. The three-point method includes three reference points, which are the operator, the missile, and the target. The operator tracks the missile and target and attempts to guide the missile into the target while ensuring that the missile never touches the ground, as opposed to a typical SACLOS system where the operator only has to track the target.<br />
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The proper control methods for an MCLOS missile like the 9M14M are detailed in a 1967 Polish article titled "<i>Szkolenie operatorów przeciwpancernych pocisków kierowanych</i>" (<i>Training of anti-tank guided missile operators</i>). The most relevant parts of the article have been extracted below, but the original text can be accessed in <a href="https://milimoto.wordpress.com/2019/05/02/ppk-z-systemem-kierowania-mclos-tor-lotu-pocisku/">this post on the Milimoto blog</a>.<br />
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Figure 10a shows the perfect way to control the missile. It is considered as such because it ensures that the missile never comes in contact with the ground or any bushes or fences on the ground situated between the operator and the intended target. The operator in this case would control the missile at a certain height above ground level and then he would lower it to the line of sight just before it impacts the target. However, this guidance method is not practical for an MCLOS missile as this would require the operator to know the distance between the missile and the target at every point on the flight path, and without a rangefinder on the BMP-1, this was not feasible. Therefore, this guidance method could not be used. It is worth noting that years later, the T-64B obr. 1976 implemented the highly advanced "Kobra" ATGM system with a SACLOS guidance system that attained this trajectory with the use of a guidance computer and the integrated laser rangefinder in the tank's 1G42 sight.<br />
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Figure 10 (b), (c) and (d) show the best ways to guide a missile over various distances. These methods rely on the fact that the missile's flight is gradually lowered to the operator's line of sight with the target at a certain time, just before it impacts the target. From point P<span style="font-size: x-small;">2</span> of the trajectory shown in the drawings above, the projectile is guided by the three-point method (eye-missile-target) in the so-called attack phase where the missile is in the operator's line of sight with the target. When operating a missile in this phase, the operator must focus his attention and steadily steer the missile. The missile is most likely to touch the ground in this phase.<br />
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It is understandable that from the point of view of the operator's psychological capabilities, the attack phase should be as short as possible. In addition, it was calculated that the probability of the missile coming into contact with the ground increases with the passage of the projectile's flight time in the operator's line of sight (because it travels at its minimum altitude during this time). Therefore, guidance time using the three points method at different shooting distances will be different, which will involve the operator having to perform appropriate tracking and flight time assessment activities.<br />
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While observing the firing of an ATGM, there were many cases where operators found a lack of psychological resistance under the influence of emotional tension in guiding the missile while it was approaching the target. Some, under the influence of mental illusions, sought to bring the missile to the line of sight as soon as possible (eye-missile-target). In addition, the operator's high emotional tension led to the fact that such shooting usually ended with a missile hitting the ground. Operators who learned the technique of controlling an ATGM and adhered to the rules of approaching the target during the specified time and at the appropriate height, were able to properly stabilize the missile and smoothly enter the attack phase.<br />
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When engaging a target situated at a distance of more than 500 meters up to 1,000 meters, the gunner can guide the missile using only his forward-facing TNPO-170A general vision periscope. When the target is further than a kilometer away, it is much more practical to switch to the primary sight as there is much more time for the missile to be captured within the field of view of the gunner. The gunner determines which method to use by first estimating the range to the target using the stadia rangefinder incorporated in his 1PN22M1 sight.<br />
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The 6x magnification and the field of view of 15 degrees of the 1PN22M1 sights in the BMP-1 was more than enough to find and engage targets at the maximum aiming range of 1,300 meters of the PG-9 grenade, and based on Soviet requirements, it was also sufficient for finding and engaging targets at 3,000 meters. According to Soviet data, an optical sight with no magnification would allow the gunner to see and identify a tank from a distance of 1.0-1.5 kilometers, while an optical sight with 5x magnification would allow a gunner to do so from 3.0 kilometers. Other data indicates that an optical sight with a magnification of 7-8x would allow a tank to be identified from a distance of 4.0-5.0 kilometers. As such, the magnification of the 1PN22M1 can be considered sufficient for a BMP-1 gunner to fully exploit the maximum range of the 9M14M missile against tanks and other targets of a similar size.<br />
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Nevertheless, it should be noted that a higher magnification would be preferable due to the demanding nature of the MCLOS missile guidance principle. Besides the obvious advantage of being able to identify a camouflaged tank at long range more easily with a higher magnification sight, a more enlarged view of the target and the missile would also allow the gunner to steer the missile more precisely. In this regard, the 9K11 man-packed missile complex had an advantage due to the 8x magnification of its 9Sh16 periscopic sight.<br />
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<span style="font-size: large;">MISSILE LAUNCH</span></h3>
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It should be noted that because the missile is launched from a rail on top of the gun barrel of the 2A28 "Grom", it will be clear of any obstacles as long as the gunner has a clear line of sight to the target from his primary sight. The gunner can verify this using his general vision periscopes. Moreover, because the missile is launched at a slight elevation angle such that it gains altitude immediately upon leaving the launch rail, it is guaranteed that there will be enough ground clearance to ensure that the stabilizer fins do not touch the ground.<br />
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With the gunner's periscopic primary sight and his forward-facing general vision periscopes all on the turret roof and the missile itself being above it, it is possible for a BMP-1 gunner to launch and guide his missiles from a turret defilade position. This is a capability that the BMP-1 shares with missile tank destroyers like the 9P110.<br />
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Due to the elevated launch angle built into the 9M14 and 9M14M missile launch system, the initial 500 meters traveled by the missile after its launch is a dead zone where it is not yet under the complete control of the operator. It is not impossible to hit a target inside this dead zone, but it is very unlikely in combat conditions and should not be attempted unless it is an emergency situation as it would otherwise be a waste of ammunition. An absolute minimum range is set by the warhead fuze which is only armed after the missile has traveled 70-200 meters. Engaging targets inside the 500-meter practical dead zone of the missile is done using the 73mm 2A28 cannon. Even without the dead zone, it is always favourable for a BMP-1 gunner to engage it with his cannon instead of an MCLOS missile as the reaction time with the cannon tends to be quicker.<br />
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It is often stated that the dead zone exists as a consequence of the limitations of the MCLOS guidance principle, but this is not true. The dead zone exists because of a combination of the waiting time for sustainer engine to start, whereby the thrust vectoring control system becomes active, and the time needed by the missile operator to bring the missile down from altitude to a target at ground level. The 9M14P "Malyutka-P" missile with a SACLOS guidance system had a reduced dead zone of 400 meters thanks to the automatic command unit which is able to visually capture the missile and bring it under control more quickly than a human operator, but the dead zone was inherently quite large due to the peculiarities of the launch system. Later SACLOS missiles like the 9M111 "Fagot" and 9M113 "Konkurs" practically removed the dead zone by implementing a different control mechanism along with a gas generator to launch the missiles at a high initial velocity, thus allowing the missiles to be controlled in direct flight towards the target along the line of sight of the command unit optic immediately after launch.<br />
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The operational zone of the 9M14M missile launched from a BMP-1 is much narrower than the same missile launched as part of the 9K11 man-portable complex, but only if the turret of the BMP-1 is not turned to expand the size of the firing arc. Without using the rotation of the turret, the firing arc is only 15 degrees. At a range of 3,000 meters, this arc covers a width of almost 800 meters, so it is enough for slower moving targets such as vehicles being driven cross-country. For the 9K11 complex, the operational width is a whopping 2,240 meters, but this is only achieved if the operator swivels his 9Sh16 periscopic sight. In a BMP-1, the 1PN22M1 sight is fixed to the turret in the horizontal plane, but the gunner can rotate the turret incrementally as the target approaches the edge of his field of view in the sight and thus expand the firing arc of his 9M14M missile to track any moving target.</div><div>
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At night, the 9M14M missile is completely ineffective without external factors to assist the gunner since the night vision module of the 1PN22M1 sight only allows tank-type targets to be identified from a maximum distance of 400 meters with starlight alone. This is less than the practical minimum range of the missile. On a moonlit night with clear skies, it may be possible for a skilled gunner to use the missile, but this is circumstantial. It is only possible to use the missile at night with somewhat consistent results by relying on illumination shells and flares fired over enemy positions. If the opportunity presents itself, gunners can guide a missile towards the light emitted by the headlights of enemy vehicles even in complete darkness.<br />
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In the snippet below from the September-October 1975 issue of the Army Reserve magazine, it is stated that in a poll of Israeli tank crews after the 1973 Arab-Israeli war showed that it was extremely difficult to detect the launch of a "Malyutka" missile but most tank commanders could at least detect the missile itself as it traveled towards them. The caveat is that the missiles were detected at long range in only a minority of cases, so while it is reasonable for a "Malyutka" operator to expect a missile launched at an enemy tank to be detected most of the time, it is not feasible to expect the majority of the enemy tank crews to detect the missile until it is already too late to perform evasive maneuvers or to fire back at the launch site.<br />
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The chances of detecting incoming missiles in a timely manner may be increased if the crews of multiple tanks in a unit focus their attention in the same area, but on the other hand, those chances may plummet if the tank crew is already preoccupied with fighting other enemy forces.<br />
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Based on the experiences of U.S troops in Vietnam, it was possible to distract or agitate the operator of a 9K11 complex by having all nearby personnel fire every weapon available in the general direction of the operator. However, it is reasonable to assume that this tactic was only feasible because of the relatively short combat ranges that were supported by the local environment, and even then, it was not a reliable countermeasure by any means. The same tactic would be even less effective against a BMP-1 gunner who is fully enclosed in an armoured vehicle that offers both physical and psychological protection with a combination of its protection from shell fragments and a certain amount of isolation from the noise of the return fire.<br />
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The Hungarian Army estimated that on average, the probability of achieving a hit on a static tank target with an MCLOS "Malyutka" missile was only 20% to 25%. Nevertheless, this modest figure already indicates an advantage over the SS.11 missile which had a recorded probability of hit of 10% based on American experiences in Vietnam during the 1972 Easter Offensive against NVA tanks. Steven J. Zaloga writes in a 1994 article published in Jane's Intelligence Review that a "Malyutka" operator needed to have fired about 2,300 simulated missile shots before he could be qualified. The gunner would also apparently need to practice at the simulator 50 to 60 times a week to maintain that proficiency standard.<br />
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Due to the extremely large number of shots needed to train a missile operator to proficiency, the only practical option was to rely heavily on simulators with live fire training sessions occupying a much smaller share of the training regime. Nevertheless, the "Malyutka" series of missiles had an inherent advantage over earlier MCLOS missiles that were steered with spoilers like the 3M6 "Shmel" or the SS.10 instead of a thrust vectoring control system in that the missile was more responsive to the operator's commands. This reduced the chances of the operator accidentally steering the missile into the ground when attempting to guide it onto the target, especially if the target is a tank in a hull defilade position. Needless to say, this was beneficial due to the challenging nature of guiding this type of ATGM, and the relatively high flight velocity of the 9M14M had a generally positive influence on its hit probability as there was less time for the target to evade it.<br />
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<h3>
<span style="font-size: large;">LOADING MISSILES</span></h3>
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The relatively light weight of the 9M14M missile and its small dimensions lent itself quite well to relatively quick and easy loading from within the confines of the turret. Arguably easier even in comparison to later IFV designs like the Bradley which forced a passenger to load TOW missiles weighing in excess of 21 kg from the passenger compartment through a large roof hatch. The Bradley could not reload its missiles at all either if no passengers were around to help. For what it's worth, that is a praiseworthy feature of the BMP-1.<br />
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To load a missile, the gunner must elevate the cannon to its limit of +30 degrees, open a small hatch in the turret roof directly above the cannon breech, and then slide the missile with its launch rail onto the launcher. To align the missile launch rail with the launcher, the gunner aligns it on top of a pair of rollers on top of the "Grom" cannon breech before pushing the entire assembly forward.<br />
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When the launch rail is pushed forward far enough, it is automatically locked in place. The missile has its stabilizer fins folded for stowage and to fit through the small hatch in the turret roof, so the next step for the gunner is to unfold the fins. The gunner could do this by reaching his arm out of the loading hatch, but to minimize his exposure outside of the armoured turret, he was provided with a special stick.<br />
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A standard combat load for a BMP-1 includes four 9M14M missiles, of which two are stowed in a ready rack on the turret floor while the remaining two are stowed next to the turret in the passenger compartment. The ready racks are shown in the photo on the left below, and the location of both the ready and reserve racks in the vehicle from a top-down perspective with an arrow to indicate the front of the hull. While in a 9K11 man-portable system, the warhead of the missile would be detached and stowed separately, and then assembled during setup, but for the BMP-1, the missiles are stowed in their assembled form and require only the wings to be deployed. <br />
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The ready racks are in a convenient location for the gunner to rapidly reload the launcher without leaving his seat.<br />
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In case of an unexpected sudden contact with enemy forces while a BMP-1 unit is on a march, the gunner cannot react immediately as he must first complete a number of preparations. According to Sergey Suvorov in his book "<i>Боевые машины пехоты БМП-1, БМП-2 и БМП-3. «Братская могила пехоты» или супероружие</i>" (<i>BMP-1, BMP-2 and BMP-3 infantry fighting vehicles. "Mass grave of infantry" or a superweapon</i>), no more than 50 seconds is needed to complete the full preparation process to launch a missile. This process not only includes the loading of the missile itself, but also the setup of the guidance equipment.<br />
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Officially, the crew standards for a BMP-1 gunner mandate that the ATGM must be readied and fired within 55 seconds for him to pass with a "satisfactory" mark. To pass with a "good" mark, the procedure must be done within 45 seconds, and to pass with an "excellent" mark, no more than 40 seconds must be taken. The procedure is not equivalent to the loading time of a single 9M14M missile as it also involves the readying of the ATGM control system and other tasks. It is described as follows: <br />
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"<i>Обучаемый на месте наводчика-оператора ПТУР на направляющей в боевой укладке, пульт оператора в походпом положении, оружие в боевом положений. При выполнения норматива обучаемый переводит пульт оператора в боевое положеше, устанавливает ПТУР па пусковой кронштейн, наводит пусковую установку в цель и производит пуск ПТУР.</i>"</blockquote>
Translated:<br /><blockquote>
"<i>The trainee is in the gunner's station. The ATGM mockup is stowed in the fighting compartment, the operator's control box [9V332] is stowed away, the gun [the 2A28] is in a combat position. When executing the drill, the trainee transfers the operator's control box to the combat position, installs the ATGM on the launch bracket, directs the launcher to the target, and launches the ATGM.</i>"</blockquote>
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To complete the process in reverse, the time taken for a BMP-1 trainee gunner to achieve a "satisfactory" mark is 35 seconds. A time of 30 seconds is required for a "good" mark is 30 seconds, and a time of 25 seconds is required for an "excellent" mark.<br /><br />
Given the preparation times stated in the official standards for trainee gunners, the 50-second time stated by Suvorov is reasonable. In battle, 50 seconds is a very long time and it is only acceptable if there is a long standoff distance between the BMP and the enemy. At long range, the seriousness of the issue is ameliorated to a large extent by the low probability of a direct hit from enemy fire, which is aided by the small silhouette of the BMP-1 itself. At short ranges such as in an ambush scenario, the gunner can react quickly by returning fire with the 2A28 cannon and there is no need to bring the missile into action, but if the target is beyond the effective range of the 2A28 cannon while still remaining close enough to be able to fire upon the BMP-1 with a high probability of hit, then the crew has no options but to have the driver maneuver the vehicle into a covered position.<br />
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If the presence of the enemy is known or if enemy contact is determined to be probable, the long-range firepower of the BMP-1 can be maximized by having a missile loaded onto the launch rail from the reserve stowage racks, thus keeping the ready racks full. Ideally, the missiles are used with a considerable standoff distance between the BMP-1 and the target to ensure the greatest probability of survival for the operator. According to safety protocols, it is generally not permitted to keep a missile loaded on the launcher rail during long marches for fear that it may be damaged, as the missile is completely unprotected. In field conditions, a missile is kept loaded on the launcher so that it can be used immediately when it is needed.<br />
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If a missile is not already loaded, the maximum rate of fire for the "Malyutka" missiles is two launches in the first two minutes when firing at the maximum range of 3,000 meters, with the first minute being largely taken up by the preparation process (40-55 seconds). After the second round is fired, the gunner must load the launcher with missiles from the reserve racks which can only be done if the turret is turned to the left or to the rear. As such, the combat rate of fire in a non-ideal situation would be less than one launch per minute. If a missile is already loaded, the gunner may be able to launch three missiles in two minutes. All four missiles may be launched in three minutes. The combat rate of fire would therefore be just over one launch per minute. At shorter distances, the flight time of the missile is correspondingly shorter so a somewhat higher overall rate of fire can be expected.<br />
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This rate of fire is nominally less than that of the 9K11 man-portable ATGM complex which can achieve a rate of fire of two rounds per minute when firing at the maximum range of 3,000 meters by having an array of prepared missiles launched consecutively, but on the other hand, the 9K11 complex requires a much longer preparation time as the ATGM team must set up multiple missiles on their individual launchers and then link them to a control unit. Case in point, a 9K11 manual states that for a three-man team with two missiles and one control unit, deploying the missile complex takes 1 minute 40 seconds. A much more unfavourable comparison would be between the BMP-1 and a self-propelled missile tank destroyer like the 9P110 which requires practically no setup time and can launch six missiles consecutively. The BMP-1 has a much slower combat rate of fire by comparison.<br />
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When resupplying the BMP-1, the missile ready racks are replenished with fresh missiles passed into the turret through the gunner's hatch.<br />
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The BMP-1 was never issued with the original 9M14 model. The improved 9M14M model was the basic variant for the BMP-1. All Malyutka-type missiles are compatible with the BMP-1's launcher system.<br />
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<h3>
<span style="font-size: large;">BMP-1P (Object 765 sp. 4)</span></h3>
<h3>
<span style="font-size: large;">"KONKURS" MISSILE SYSTEM</span></h3>
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The Object 765 sp.4, better known as the BMP-1P, had its "Malyutka" missile system replaced with an externally mounted 9P135M launcher post. The joystick control box and the missile launch rail for the "Malyutka" system were removed in this modification. Older BMP models updated to the BMP-1P standard had the missile loading hatch welded in place as shown in the photo on the left below (photo by Yuri Pivkin), while new production turrets did not have a hatch fitted at all, instead having a modified roof construction as shown in the photo on the right below (photo from <a href="http://www.militaertechnik-der-nva.de/Bestimmungsbuch/5gepKetFhrmitTurm/51/BMP/BMP.html">the militaertechnik-der-nva website</a>). </div><div><br /></div><div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-cgvKpkmDtTc/XtCUoSbHAzI/AAAAAAAAQ3g/Gn2kkpNtAW4476Kv_5N_JUTwlBMa6hKEwCK4BGAsYHg/yuri%2Bpivkin%2Bbmp-1p%2Bturret.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="552" data-original-width="736" height="300" src="https://1.bp.blogspot.com/-cgvKpkmDtTc/XtCUoSbHAzI/AAAAAAAAQ3g/Gn2kkpNtAW4476Kv_5N_JUTwlBMa6hKEwCK4BGAsYHg/w400-h300/yuri%2Bpivkin%2Bbmp-1p%2Bturret.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-Ihqms5E21hk/XtCSMrCdqsI/AAAAAAAAQ2w/iGKs2VTZf5wUA_71L6AY0IiISrqxJNoyQCK4BGAsYHg/BMP1PmodDetail.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="307" data-original-width="459" height="268" src="https://1.bp.blogspot.com/-Ihqms5E21hk/XtCSMrCdqsI/AAAAAAAAQ2w/iGKs2VTZf5wUA_71L6AY0IiISrqxJNoyQCK4BGAsYHg/w400-h268/BMP1PmodDetail.jpg" width="400" /></a></div></div><div><br /></div><div><br /></div><div>There are some unique points about the BMP-1P's missile configuration. Firstly, the missile launcher is placed on the turret roof so it was still possible to assume a turret-down position when using the ATGM.<br />
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<div><br /></div><div><br /></div><div>Unlike the "Malyutka" system, it was permitted to keep the launcher loaded with a missile during non-combat operations as the missile is housed in a protective fiberglass container. Nevertheless, it was usually stowed inside the vehicle when it was not needed.</div><br />
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<a href="https://2.bp.blogspot.com/-26go_60fPsU/WLjwz9d_f3I/AAAAAAAAIeU/MwVZnTpZboseIuxvSlssA9CjLlHD8HvCgCLcB/s1600/bmp1p.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="235" src="https://2.bp.blogspot.com/-26go_60fPsU/WLjwz9d_f3I/AAAAAAAAIeU/MwVZnTpZboseIuxvSlssA9CjLlHD8HvCgCLcB/w400-h235/bmp1p.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-Q-FMx-u2wmU/XtCRn7KH6qI/AAAAAAAAQ2c/DBOottOTuSEnHBnvyiHH93rUS1quTp33QCK4BGAsYHg/10901.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="790" data-original-width="1073" height="295" src="https://1.bp.blogspot.com/-Q-FMx-u2wmU/XtCRn7KH6qI/AAAAAAAAQ2c/DBOottOTuSEnHBnvyiHH93rUS1quTp33QCK4BGAsYHg/w400-h295/10901.jpg" width="400" /></a></div>
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<br />The main drawback was the inability to fire missiles from under armour. Besides eliminating its ability to fire a missile in an NBC-contaminated environment, it also became much easier for enemy forces to suppress the BMP with indiscriminate fire if its approximate location is detected. It is worth noting that with the hatch locked in the open position and the gunner's eye placed on the 9P135M launcher eyepiece, the gunner is almost completely shielded by the hatch and only a small part of his head can be seen from the front. In this regard, the operator can be considered well protected, but only from machine gun fire and the fragments of tank shells falling short in front of the BMP. It was not safe for him to operate the ATGM under artillery fire.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ryLLnlZU8ag/XtB5tavbr9I/AAAAAAAAQ1U/7IYfX4YXG-YraQ-XstPUhadWG9NxY7sRQCK4BGAsYHg/lebed.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="824" data-original-width="620" height="400" src="https://1.bp.blogspot.com/-ryLLnlZU8ag/XtB5tavbr9I/AAAAAAAAQ1U/7IYfX4YXG-YraQ-XstPUhadWG9NxY7sRQCK4BGAsYHg/w301-h400/lebed.jpg" width="301" /></a></div><div><br /></div><div><br /></div><div>Regardless, there are certain advantages. For example, the gunner's view is obviously much improved outside the turret, so it is easier to find targets by eye. The placement of the launcher above the turret roof also presents certain tactical advantages. The vehicle can be parked behind a pile of rubble, a hill, a mound, a wall, or even just a particularly large bush, and it will be possible to hide the entire silhouette and still use the vehicle's missile launcher. Still, these advantages are purely circumstantial. It would still be much better to have an under-armour missile launching capability, and preferably the ability to reload under armour too.</div><div>
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The situation with the BMP-1P is not so different than its contemporaries like the Marder 1. The Marder 1 did not even have an ATGM launching capability until it was modernized in 1977, and the upgrade only involved installing a simple launcher post beside the commander's hatch, identical in form and function to the one on the BMP-1P. Also, it should also be pointed out that only one Marder in a platoon of three vehicles was given this modification with a MILAN launching unit and the missiles to use with it. This was purely for doctrinal reasons. The Marder's turret has a two-man crew and it is the commander who operates the ATGM, so the gunner is ostensibly free to carry out other tasks unlike in a BMP-1P, but technical limitations limit the gunner of a Marder in his abilities to contribute. While the commander is operating the ATGM system, the turret is locked in place and the autocannon is disabled. The AMX-10P faces a similar conundrum. Clearly, the simplistic implementation of anti-tank missiles on most of the modern IFVs of the time was a global trend that the BMP-1P simply followed. It is no better or worse than its contemporaries in this regard.<br />
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<h3>
<span style="font-size: large;">AIR DEFENCE</span></h3>
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<a href="https://1.bp.blogspot.com/-2d1sB_XXNT0/Xef-bz3clVI/AAAAAAAAPyQ/fD1Fg7DQPdY6RkkQnbuc7Hv2LXlKumA6QCLcBGAsYHQ/s1600/bmp-1%2Bmanpads.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="268" data-original-width="446" src="https://1.bp.blogspot.com/-2d1sB_XXNT0/Xef-bz3clVI/AAAAAAAAPyQ/fD1Fg7DQPdY6RkkQnbuc7Hv2LXlKumA6QCLcBGAsYHQ/s1600/bmp-1%2Bmanpads.jpg" /></a></div>
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It is also worth noting that as a general rule, low-pressure cannons are completely ineffective against low-flying aircraft, including helicopters, if they only fire conventional ammunition with conventional fuzing systems. However, this was largely ameliorated by the inclusion of the 9K32 "Strela-2" MANPADS system with two 9M32 missiles in the combat load of a standard BMP-1 for one of the passengers to use from one of the roof hatches of the passenger compartment or while dismounted. This system entered service in 1968 and was issued to BMP. In 1970, the 9K32M "Strela-2M" system entered service. It had improved performance characteristics compared to its predecessor and featured the ability to engage jet aircraft in a head-on attack, whereas the "Strela-2" was limited to tail chase attacks only. Newer systems such as the 9K34 "Strela-3" began to be issued in the mid to late 1970's, while the 9K310 "Igla-1" and 9K38 "Igla" became available in the early 1980's.<br />
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Officially, the 9K32 "Strela-2" was specified for the BMP-1 (Object 765 sp.2), while the 9K32 "Strela-2M" was specified for the BMP-1P (Object 765 sp.4). Only the BMP-2 was officially specified to have the 9K34 "Strela-3" system. However, due to the fact that the MANPADS issued to the vehicles are self-contained systems that are used by the passengers, there was no strict policy on their distribution other than the priority of the motorized infantry units. In practice, even the oldest BMP variants could enjoy the enhanced air defence capabilities provided by the latest MANPADS models if sufficient quantities were issued to replace older models. For example, the photo below shows an "Igla" being used by a passenger in a basic BMP-1. This would be an impossible combination if the specifications were strictly followed.<br />
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<a href="https://1.bp.blogspot.com/-EVgG8XXgkvM/XevOCDeKuRI/AAAAAAAAPzQ/EQqdVJK8ef8ZHXOj3UFJcpsymd-Zg4rOgCLcBGAsYHQ/s1600/igla%2Bfired%2Bfrom%2Bbmp-1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="429" data-original-width="769" height="223" src="https://1.bp.blogspot.com/-EVgG8XXgkvM/XevOCDeKuRI/AAAAAAAAPzQ/EQqdVJK8ef8ZHXOj3UFJcpsymd-Zg4rOgCLcBGAsYHQ/s400/igla%2Bfired%2Bfrom%2Bbmp-1.png" width="400" /></a></div>
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Two 9M32 or 9M32M missiles with a single launcher could be carried in each BMP. One missile was stowed on top of the central fuel tank with clips while the other missile was stowed on the left hull wall with clips. If the space on top of the central fuel tank was not used for a missile, it could be used to stow an additional RPG-7 grenade launcher. The location of the two missiles is shown in the drawing below. They are marked in red and labeled (15) and (20).<br />
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<a href="https://1.bp.blogspot.com/-_tSqO6OCBso/XevTKeXjYdI/AAAAAAAAPzY/8itG4szWWvA_654KgHRFJOH17cQ7o0-MACLcBGAsYHQ/s1600/manpads.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="753" data-original-width="1600" height="300" src="https://1.bp.blogspot.com/-_tSqO6OCBso/XevTKeXjYdI/AAAAAAAAPzY/8itG4szWWvA_654KgHRFJOH17cQ7o0-MACLcBGAsYHQ/s640/manpads.png" width="640" /></a></div>
<div><div><br /></div><div><br /></div><div>The short clip below shows a MANPADS being fired from a moving BMP-1.</div><div><br /><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-55mMUPxAO3U/X-2ZesBxd_I/AAAAAAAASkc/uah3_DHPA7suOw1M5qJ1hKVjlCJ-Z0I-QCLcBGAsYHQ/s728/MANPAD.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="546" data-original-width="728" src="https://1.bp.blogspot.com/-55mMUPxAO3U/X-2ZesBxd_I/AAAAAAAASkc/uah3_DHPA7suOw1M5qJ1hKVjlCJ-Z0I-QCLcBGAsYHQ/s320/MANPAD.gif" width="320" /></a></div></div><div><br /></div>
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In the book "<i>Soviet/Russian Armor and Artillery Design Practices: 1945-1995</i>" by the Marine Corps Intelligence Activity and in the book "<i>BMP Infantry Fighting Vehicle 1967–94</i>" by Steven J. Zaloga, it is reported that initially, one missile and one launch unit was issued per two vehicles. The exact timeframe was not specified. Later, each vehicle was issued with one launch unit and two missiles, thus quadrupling the number of missiles available in each BMP-equipped motorized infantry unit. With such a high concentration of anti-aircraft weapons, the ability of each unit to defend itself from air attack is highly noteworthy. This was a valuable capability for the Soviet Army given that the Soviet Air Force was not expected to be capable of maintaining air superiority except in some localized areas.<br />
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<a href="https://1.bp.blogspot.com/-Rhznh8JLfFQ/Xef_uDSiUQI/AAAAAAAAPyc/WF0GFaErVjI06RI9I5V7_DqJZaXOawUXQCLcBGAsYHQ/s1600/bmp%2Bobr%2B1966%2Bstrela-2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="664" data-original-width="1600" height="165" src="https://1.bp.blogspot.com/-Rhznh8JLfFQ/Xef_uDSiUQI/AAAAAAAAPyc/WF0GFaErVjI06RI9I5V7_DqJZaXOawUXQCLcBGAsYHQ/s400/bmp%2Bobr%2B1966%2Bstrela-2.png" width="400" /></a></div>
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Despite its inherent limitations, this type of air defense system could be considered to be a more effective alternative to the rapid-fire autocannons of foreign IFVs against both modern jet-propelled aircraft and helicopters. Against fixed wing jet aircraft, the probability of kill depends on a number of factors including the number of engines; twin-engine aircraft have a high chance of surviving a hit from a MANPADS missile as it would most likely hit one of its engines, leaving the other engine intact. The overall probability of kill against a jet fighter with the "Strela-2" is stated to be 19-25% in the article "<i>Переносный Зенитные Ракетные Комплексы "Стрела-2" и "Стрела-3</i>"" (<i>Man-portable Air Defense Missile Systems</i>) published in the May 1999 issue of the "<i>Техника и вооружение</i>" magazine. The probability of kill of the "Strela-2M" against the same target was 22-25%, and for the "Strela-3" it was 31-33%. The all-new "Igla" series had greatly enhanced performance, with the "Igla-1" achieving a probability of kill of 44-59% against a jet fighter while the "Igla" could achieve a probability of kill of 45-63% against the same target. These figures are repeated in the book "<i>Зенитные ракетные комплексы</i>" (Anti-Aircraft Missile Complexes) by Nikolai Vasilii and Aleksandr Gurinovich.<br />
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Given that two missiles were carried in each BMP, there can be two attempts with an overall probability of hit of 19-25% each, so the theoretical probability of achieving one aircraft kill per BMP using the "Strela-2" can be considered to be 34.9-39.2%, and if the "Strela-3" system was used instead, the probability of one aircraft kill per BMP increases to 52.4-55.1%. Using the newer "Igla-1", the probability of one kill with two missiles increases to 68.6-83.2%. With the much more modern "Igla" the probability of one kill with two missiles increases to 70-86.3%, and indeed, the likelihood of downing one aircraft with a single "Igla" missile is already high enough that two attempts may not be needed.<br />
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To achieve a similar probability of hit with a 20mm autocannon aimed with conventional optical sights, hundreds or even thousands of rounds would be required. Indeed, the primary incentive of developing man-portable air defense missile systems during the 1950's and 1960's was the very low efficiency of conventional guns against jet aircraft which were too fast for a human gunner to engage without computer assistance. For example, on page 20 of the book "<i>Self-Propelled Anti-Aircraft Guns of the Soviet Union</i>" by Mike Guardia, it is stated that a M163 VADS firing a 60-round burst at a MiG-21 in level flight from a range of 1 km with its 20mm M61 Vulcan cannon had a kill-per-burst probability of just 0.08, or 8%. To achieve a probability of kill matching the "Strela-2", six 60-round bursts would be required, expending a total of 360 rounds. To achieve a probability of kill matching the "Strela-3", ten 60-round bursts would be required, expending a total of 600 rounds.<br />
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It is important to note that the M163 VADS fire control system <a href="https://i.imgur.com/Tf9v6dZ.png">included a radar rangefinder and an automatic target lead computer</a>, and the M61 Vulcan cannon installed in the M163 had a high rate of fire of 3,000 rounds per minute. To put this in perspective, a Marder 1 IFV had a 20mm MK.20 Rh 202 autocannon that fired at less than a third of the rate of the M61 Vulcan on the M163. The Marder 1 itself had no optical or laser rangefinder, no firing solution calculator, and it had only simple lead markings in its optical anti-aircraft sight. It was the same for the AMX-10P. These IFVs would probably have to expend their entire ready supply of 20mm ammunition simply to guarantee at least one hit on a fixed-wing aircraft, and to achieve a 50% kill probability may require the expenditure of their entire ammunition supply.<br />
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Moreover, the maximum range of the "Strela-2" was 3.4 km and its maximum altitude was 1.5 km while the "Strela-2M" had an even longer range of 4.3 km and higher maximum altitude of 2.3 km, which is more than double the maximum effective range and altitude of the 20mm MK.20 Rh202 and HS.820 autocannons against air targets. The larger 25mm M242 chain gun of the M2 Bradley had a longer range than these 20mm autocannons, but it was considered to be only suitable for suppressive fire against helicopters at a maximum range of 2,500 meters while FM 3-22.1 (Bradley gunnery field manual) states that too many rounds are required to achieve a kill when firing at air targets beyond 1,700 meters. The 30mm RARDEN autocannon of the FV510 Warrior had a longer range, but the FV510 itself was wholly inadequate against aircraft of all types due to a combination of the extremely low rate of fire of the RARDEN and the severely limited speed of its hand-cranked gun laying system.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-e4qtHHVjBfg/Xe0WKW-MYSI/AAAAAAAAP08/QPI4cDsCcA4Vfi1jhgzmEvLGLNorr1tIQCLcBGAsYHQ/s1600/two%2Bstrela-2m%2Bfiring%2Bfrom%2Bbmp-1.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="653" data-original-width="1198" height="348" src="https://1.bp.blogspot.com/-e4qtHHVjBfg/Xe0WKW-MYSI/AAAAAAAAP08/QPI4cDsCcA4Vfi1jhgzmEvLGLNorr1tIQCLcBGAsYHQ/s640/two%2Bstrela-2m%2Bfiring%2Bfrom%2Bbmp-1.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Two "Strela-2M" missiles fired simultaneously from separate vehicles</td></tr>
</tbody></table>
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The sole advantage held by IFVs with fast-firing 20mm autocannons is their ability to react more quickly to the sudden appearance of enemy aircraft flying at a low altitude. These may be fixed wing aircraft or helicopter gunships. Fighter-bombers attacking with bombs are a viable target, but ground attack aircraft flying missions against armoured vehicles were almost always armed with rockets. Helicopter gunships were universally armed with rockets for such missions, occasionally supplemented with ATGM systems. Unguided rocket systems like the Hydra 70 and S-8 were typically used from a range of up to 2.0 kilometers against point targets and airborne ATGM systems generally had a range of 3.0 kilometers or longer. With a maximum effective range of 1.5 km against aircraft, 20mm autocannons do not offer any standoff distance against such threats.<br />
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<a href="https://1.bp.blogspot.com/-t5PaB6a2xis/XmQKmJ2nunI/AAAAAAAAQJc/TrNqMWjBpSU-agwFG-ChTX5XgQtA-DQOwCLcBGAsYHQ/s1600/commander%2Band%2Bstrela.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="229" data-original-width="400" height="228" src="https://1.bp.blogspot.com/-t5PaB6a2xis/XmQKmJ2nunI/AAAAAAAAQJc/TrNqMWjBpSU-agwFG-ChTX5XgQtA-DQOwCLcBGAsYHQ/s400/commander%2Band%2Bstrela.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-OVH9F03FK8A/XmQK4whrrBI/AAAAAAAAQJs/4nwelyEG4JcG2GM7jv2d8UsCu1bebUAwACLcBGAsYHQ/s1600/strela-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="845" data-original-width="800" height="228" src="https://1.bp.blogspot.com/-OVH9F03FK8A/XmQK4whrrBI/AAAAAAAAQJs/4nwelyEG4JcG2GM7jv2d8UsCu1bebUAwACLcBGAsYHQ/s200/strela-2.jpg" width="214" /></a></div>
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The ideal air defence system is a combination of a fast-firing autocannon of a larger caliber with a MANPAD system operated by a passenger - this was later achieved with the BMP-2 which featured a 30mm autocannon with a range of 3.0 km against air targets and a 9K34 "Strela-3" system with a range of 4.1 km or a 9K310 "Igla-1" system with a range of 5.2 km. Such a combination allows two targets to be engaged simultaneously, or for one target to be engaged by both types of weapons for a higher probability of kill.<br />
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All in all, it can be said that the BMP was not inferior to later foreign IFVs with 20mm autocannons like the AMX-10P and Marder 1, and it could even be considered to be outright superior to much newer IFVs like the M2 Bradley and FV510 Warrior. Only the BMP-2 surpassed the BMP-1 in this regard.<br />
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Besides engaging aircraft with a MANPADS system, it was also possible for the passengers to fire their small arms from the roof hatches at aircraft flying overhead. It would not have been effective, of course, but it was the only option for the passengers of a BMP that was not issued with a MANPADS system.<br />
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<a href="https://1.bp.blogspot.com/-ckPPAK2U6D4/Xef-bzemBjI/AAAAAAAAPyM/39PvVdc2YKAggkX8f43yXFm71cKYFDIbQCLcBGAsYHQ/s1600/bmp-1%2Bair%2Bdefence.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="367" data-original-width="451" src="https://1.bp.blogspot.com/-ckPPAK2U6D4/Xef-bzemBjI/AAAAAAAAPyM/39PvVdc2YKAggkX8f43yXFm71cKYFDIbQCLcBGAsYHQ/s1600/bmp-1%2Bair%2Bdefence.jpg" /></a></div>
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<h3>
<span style="font-size: large;">SMOKESCREENING SYSTEM</span></h3>
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<span style="font-size: large;">902V "Tucha"</span></h3>
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<a href="https://4.bp.blogspot.com/-jnMHGlZP_UQ/WMYcq7nn1II/AAAAAAAAIjY/qsoab2t--20iIoEm6Ua-1c4cikmHOjbJACLcB/s1600/BMP-1_back.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://4.bp.blogspot.com/-jnMHGlZP_UQ/WMYcq7nn1II/AAAAAAAAIjY/qsoab2t--20iIoEm6Ua-1c4cikmHOjbJACLcB/s400/BMP-1_back.JPG" width="400" /></a></div>
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The 902V "Tucha" smokescreening system was a standard feature of the BMP-1P (Object 765 sp.4) and was retrofitted to older BMP models at an unknown rate. Although it appears to be a straightforward modification, the addition of the "Tucha" system involves more work than the installation of the external missile launcher on the BMP-1P since the grenade launching system connects to the vehicle's electrical system and has its own control box. This means that the old master control panel used to power up ancillary systems had to be replaced with an updated one.<br />
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A bank of six 81mm smoke grenade launchers are arranged around the rear of the turret, aimed directly forward. The gunner aimed the grenades using the 1PN22M1 or 1PN22M2 sight. The grenades had to be aimed because they do not produce instantaneous smokescreens for self-concealment but are instead propelled to a range of 200 to 350 meters after launch and emit smoke after landing.<br />
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<a href="https://1.bp.blogspot.com/-Ju7YvJR2180/WNuKR2CJbYI/AAAAAAAAIno/mO56JgsQqzAt2lwZnDLmIcPryY0aN-msgCLcB/s1600/89.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="335" src="https://1.bp.blogspot.com/-Ju7YvJR2180/WNuKR2CJbYI/AAAAAAAAIno/mO56JgsQqzAt2lwZnDLmIcPryY0aN-msgCLcB/s400/89.jpg" width="400" /></a></div>
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<a href="https://thesovietarmourblog.blogspot.com/p/81mm-smoke-grenades.html">A more detailed examination of 3D6 and 3D17 smoke grenades is available in this page</a>. During the career of the BMP-1 in the Soviet Army, the 3D6 was the only smoke grenade type issued.<br />
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<h3>
<span style="font-size: large;">PASSENGER SPACE</span></h3>
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<a href="https://1.bp.blogspot.com/-ee_GVrEmUD0/XmQKmAsMInI/AAAAAAAAQJg/HOd7PCtKrgsV6sr77gY6yYPV9IWXzozfgCLcBGAsYHQ/s1600/bmp-1%2Blayout.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="310" data-original-width="700" height="176" src="https://1.bp.blogspot.com/-ee_GVrEmUD0/XmQKmAsMInI/AAAAAAAAQJg/HOd7PCtKrgsV6sr77gY6yYPV9IWXzozfgCLcBGAsYHQ/s400/bmp-1%2Blayout.jpg" width="400" /></a></div>
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Each passenger was provided an internal space of 0.54 cubic meters. The seating positions of the passengers were designed to accommodate average Soviet adult men of a fighting age, but the percentile requirement for the passengers is not known. In terms of real volume, the BMP-1 was marginally superior to the M113 which provided each of its passengers with an internal space of 0.51 cubic meters. However, the relative volume of the BMP-1 was greater than the real volume suggests due to the considerable anthropomorphic differences between Soviet and American men in the 1960's.<br />
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To fully appreciate this difference, it is necessary to understand that the 95th percentile American ground forces serviceman had a weight of 91.5 kg based on measurements in 1966 and in 1977 with large sample sizes of USMC and U.S Army personnel, whereas the 95th percentile Soviet young adult male (conscription age) had a weight of 81.57 kg according to the USSR Anthropometric Atlas, 1977. Moreover, Soviet young adult males who reach conscription age in the 1960's should be significantly lighter than their juniors in 1977 due to food shortages during their childhood in the 1940's. Naturally, the dimensions of Soviet men were also smaller than their American counterparts including in critical points such as stature, shoulder width, and leg length, all of which are used as guidelines when allocating space for the passengers in a vehicle.<br />
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The significantly smaller bulk and dimensions of young adult Soviet males during the 1960's made the modest internal space of the BMP-1 more comfortable for its passengers relative to the M113, although it was still not luxurious by any standard.<br />
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In the U.S, tests of a captured Syrian BMP-1 trophy from the 1973 Yom Kippur war found that the ergonomics of the passenger compartment met the minimum human engineering standards used by the U.S Army. The BMP-1 was deemed to be acceptable for accommodating only 30th percentile American men, whereas the M2 Bradley was designed to accommodate 95th percentile soldiers under the same standards, using ANSUR (U.S. Army Anthropometric Survey) data from the 1970's. Height was given the most attention in the passenger compartment design, but the seating space was still extremely tight in terms of length and width, especially if the passengers wore their standard PASGT gear.<br /></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-XDWLh6rVhyo/XwaP9aYkouI/AAAAAAAARPg/6y9a2Uzp9GgA__iM01foUUGMd4p6haIDQCK4BGAsYHg/s2048/m2%2Bpassengers.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1365" data-original-width="2048" height="266" src="https://1.bp.blogspot.com/-XDWLh6rVhyo/XwaP9aYkouI/AAAAAAAARPg/6y9a2Uzp9GgA__iM01foUUGMd4p6haIDQCK4BGAsYHg/w400-h266/m2%2Bpassengers.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>Similarly, if the passengers in a BMP-1 wore a 6B2 or 6B3 vest as issued in the 1980's, it becomes excessively cramped for comfort over long periods. However, with all this in mind, it should be clear that the space allocated for the passengers in the BMP-1 was adequate for the demographic it was designed for, and it was on par with comparable personnel carriers from the same period. Since the 1960's, the average height of Russian men has increased quite noticeably such that the average heights of Russian men have equalized with other developed nations. Because of this, it is not surprising that the BMP-1 is considered very cramped by today's standards, especially considering that bulky body armour is normal equipment for soldiers today. This already became a noticeable issue in the 1980's, when body armour became commonplace for Soviet Army soldiers in Afghanistan.</div><div><br /></div><div><br /></div><div>The passengers in a BMP exit through a pair of rear doors. The port side rear door holds 55 liters and the starboard side door holds 67 liters. The port side door has a smaller capacity as it has a firing port built into it.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-NUIaoh2eWJI/XwvgKUck3MI/AAAAAAAARRU/yC09oRh1xo83spjHswG10M9B_qHpzb29gCLcBGAsYHQ/s1000/8307.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="452" data-original-width="1000" height="290" src="https://1.bp.blogspot.com/-NUIaoh2eWJI/XwvgKUck3MI/AAAAAAAARRU/yC09oRh1xo83spjHswG10M9B_qHpzb29gCLcBGAsYHQ/w640-h290/8307.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>Although powered exit ramps were favoured over doors in the West, a pair of doors allowed passengers to dismount quicker compared to a powered ramp. For the BMP-1 specifically, a pair of doors was the most rational design decision given that the passengers were seated in two rows, separated by a divider. In the U.S, the M44 and M75 were the only APCs that allowed passenger egress through a pair of doors. They were replaced by the M59 and then the M113, both of which used a powered ramp with a single embedded door in case of a power outage or mechanical failure with the ramp. The French AMX-10P IFV combined a powered exit ramp with a pair of doors, and the Marder 1 had only a powered ramp with no door. If the powered ramp failed for any reason, the passengers in a Marder 1 would be forced to exit through the roof hatches. </div><div><br /></div><div>In <a href="https://arsenalen.se/katalog/pansarbandvagn-pbv-302/">the entry on the Pbv 302 armoured personnel carrier</a> in the official website of the Swedish Arsenalen museum and in <a href="https://www.ointres.se/pbv_302.htm">the Pbv 302 article on the Ointres website</a> by Rickard Lindstrom, it is stated that Swedish trials found that the passengers could dismount faster with two rear doors instead of a powered ramp like on the M113. Initially, an early prototype of the Pbv 302 had been fitted with a powered ramp inspired by the M113, but they were abandoned shortly afterward. The serial Pbv 302 had two rear doors, like the Soviet BMP and MT-LB.</div><div><br /></div>
</div></div></div></div>Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com33tag:blogger.com,1999:blog-3103574899092646031.post-18921854446078068882017-01-10T07:04:00.018-08:002022-05-02T10:20:45.943-07:00T-54<head>
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As the first postwar medium tank of the Soviet Army, the T-54 was built upon the basis of the Red Army's experiences during the so-called Great Patriotic War. The tank was reasonably advanced for its era but it could never quite be described as being on the cutting edge in terms of technological sophistication. The tank was rationally constructed and technically excellent where the traditional three criteria of mobility, firepower and protection are concerned, but it also had a number of minor drawbacks that may not be immediately obvious at first glance.<br />
<br />At present, the T-54 remains history's most enduring tank, and this is largely due to the sheer quantity of tanks used outside of the USSR. Besides the vast numbers of T-54 tanks fielded by the Soviet Army, thousands of tanks were exported and thousands more were produced by China. Dozens of variants of the basic model have been produced, most of them used by the Soviet Army. Production of the T-55 series for the Soviet Army continued until 1967 when it was fully replaced by T-64 and T-64A tanks, but it continued to be built for export clients until 1979, outlasting the T-62 which did not have the same level of export success.<br />
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As usual, we will only be covering the models used in the USSR but not abroad. We will be examining the most relevant variants of the T-54 except the models designed to fulfill supporting roles like firefighting and bridge laying.<br />
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<a href="https://2.bp.blogspot.com/-Kr8qD5ivKDw/WCbBiOhL-SI/AAAAAAAAHjs/RkRMIwGqLZUgxL_JkQTYraafcOWmv-ZmwCLcB/s1600/MiniArt%2BT-54-1%2B1946%2Bmod%2B%25281%2529.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="253" src="https://2.bp.blogspot.com/-Kr8qD5ivKDw/WCbBiOhL-SI/AAAAAAAAHjs/RkRMIwGqLZUgxL_JkQTYraafcOWmv-ZmwCLcB/s640/MiniArt%2BT-54-1%2B1946%2Bmod%2B%25281%2529.png" width="640" /></a></div>
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There were a few prototype models, but the only one that made it to low rate production and small scale issuance was the T-54 obr. 1947, also known as the T-54-1. T-54-1 was first deployed to units in the Belorussian military district for crew familiarization and exercises, and it was there that a myriad of design flaws were discovered. As they were unfit for frontline use, most, if not all T-54-1s were relegated to reserves or storage soon after its more evolved brothers appeared. In the mid 60's, many T-54-1s and T-54-2s were taken apart and their turrets used as static pillboxes along the Chinese border and as coastal defence guns in the Far East.<br />
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Here are T-54-1 turrets installed on reinforced concrete pillboxes for coastal defence.<br />
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And here are T-54-2 turrets, one used for coastal defence and one on the border. Note the extremely small size and low height of the turret compared to the man.</div>
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The T-54 is a descendant of the legendary but obsolescent T-34, but after numerous revisions, the technical similarities between the two medium tank eroded away and the relationship between the two tanks had become purely historical by the early 1950's. Practically speaking, there was very little in common between the T-34 and the T-54 save that they both share roadwheels of the same diameter and the same track pin retention system (T-34-85 tanks stored in reserves were later modernized with T-54 roadwheels in the 1950's and 1960's). The noteworthy use of a transverse mounting scheme for the engine resulted in an enormous reduction in the volume of the engine compartment, leading to a cascading effect where the reduced volume also resulted in a reduced surface area that required armour protection, and the weight of the tank was consequently reduced. This freed up a considerably surplus of weight that could be distributed to other parts of the tank as additional armour thickness.<br />
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<span style="font-size: large;">ERGONOMICS</span></h3>
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Being smaller yet roomier and more thickly armoured than a T-34, the T-54 is excellent evidence that smaller tanks are not necessarily more cramped than a larger one. The main parameter is volumetric efficiency, in which the T-54 is rated highly. The total internal volume of the T-54 measured in at 11.4 cubic meters, of which 8.05 cubic meters forms the fighting compartment at the front and middle of the tank and the remainder forms the engine compartment. The share of the fighting compartment volume from the total volume is 71.25%, which is much higher than the 60.4% of the M47, 59.2% of the M48 and 60.7% of the M60A1. Of course, the volume of the T-54 fighting compartment is undoubtedly smaller than the aforementioned tanks in real terms: the M47 which is considered somewhat cramped compared to other Cold War era American tanks has a larger fighting compartment with a volume of 9.06 cubic meters. The roomy M48 has a fighting compartment volume of 10.48 cubic meters and the M60A1 is simply luxurious by comparison, having a fighting compartment volume of 11.17 cubic meters. Of course, one cannot ignore the fact that the M47 had five crew members and carried 71 rounds of 90mm ammunition as opposed to the four crew members of the T-54 and 34 rounds of 100mm ammunition, but the M48 and M60A1 have a clear and overwhelming advantage in terms of the volume allocated to each crew member. With this in mind, it can be said that the T-54 has a remarkably efficient allocation of volume and armour but with relatively little actual room due to the small overall size of the tank. Ideally, the efficient layout of the T-54 could have been scaled up, but the small silhouette of the tank was a serious advantage in terms of survivability at the time as it made the tank harder to hit, especially when it is moving.<br />
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Besides the volume allocated to the crew, it is also important to evaluate the furniture inside the tank as its design influences the comfort of the crew. In all T-54 and T-55 models, the turret occupants were seated on seats suspended from the turret ring. The gunner was separated from the D-10T gun by the built-in recoil guard of the gun itself, and a removable fence was attached to the recoil guard to keep the commander away from the recoil of the gun. The gunner's seat did not have a backrest.<br />
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Beginning with the T-55, a new recoil guard was added to the turret that separated the commander from the recoil path of the gun, and the gunner's seat received a backrest. The backrest was mounted to the seat cushion with a pole and it could be removed as the gunner moves from the commander's hatch to his station. However, it is often absent because it can impede a quick exit in an emergency.<br />
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The T-54 has a turret ring diameter of 1,825mm. In all incarnations of the turret design, the structure of the front half of the turret lies close to the turret ring but the structure rear half of the turret lies on top of a shelf. On the commander's side of the turret, this shelf space is taken up by the radio and control boxes, thus making up for the lack of a bustle. By right, the amount of room available in a T-54 turret should be at least comparable to a tank like, say, the Centurion MK. 2 and all subsequent models which shared the same cast turret, which had a 1.88 m turret ring, but as we know from actual comparison, that is not the case. This is at least partially due to the rather large breech of the D-10T gun and the lack of a turret bustle which was used to mount the radio (<a href="https://i.pinimg.com/originals/5b/dc/4f/5bdc4f26d1dd598946d55858f93ac164.jpg">on the loader's side of the turret</a>) in the Centurion, and more significantly, the commander in a Centurion is seated on top of the turret ring on the first step of the two-stepped turret bustle. This can be seen in the photo below.</div>
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With the commander seated this way, more space was created between the commander and gunner. This also allowed the gunner to have his own backrest - a luxury that the T-54 does not have. However, by placing the commander's seat in the turret bustle, the turret also had to be much taller to accommodate him; according to official drawings it is 959mm tall. This increased the overall height of the tank to 2,635mm when measured up to the turret roof, and the total height was 2,972mm. This also added weight; a combat-loaded Centurion Mk.3 weighed a whopping 50.8 tons - equal to a Soviet T-10 heavy tank and weighing 14 tons more than a T-54, yet having less armour than its Soviet medium tank counterpart, a less powerful gun, worse automotive performance, and a much worse travelling range. It was also not as roomy as an M48 Patton which still managed to weigh 5 tons less. Needless to say, there was no chance that such characteristics would have been acceptable for a Soviet medium tank. </div>
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The T-54 turret is slightly wider than the turret of an M46 which had a turret ring of only 1.75 m in diameter, and comparable with the M47, which had a turret ring that measures 1.85 m in diameter. A comparison between these tanks is fitting because they all have a similar needle-nose ballistic shaping with sloped turret sides, unlike the Centurion, which does not have significantly sloped plating on any facet of its turret. All of these tanks had rather narrow turret rings compared to the M48, as that had a 2,160mm diameter turret ring. In a comparison between the T-54 and its closest counterpart, the M48, the T-54 loses out in the amount of internal space available to the crew by a wide margin.<br />
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<a href="https://2.bp.blogspot.com/-O5JfwcwRUI0/WvzcABv_0NI/AAAAAAAALlM/Z99KoqisLKABLnbPQ4RIWaY_mRqz7XTogCLcBGAs/s1600/t-54%2Bturret.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="809" data-original-width="1127" height="457" src="https://2.bp.blogspot.com/-O5JfwcwRUI0/WvzcABv_0NI/AAAAAAAALlM/Z99KoqisLKABLnbPQ4RIWaY_mRqz7XTogCLcBGAs/s640/t-54%2Bturret.png" width="640" /></a></div>
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The low profile of the tank is advantageous when concealing the tank in prepared positions and it is also helpful if the tank is driving across open terrain as it reduces the likelihood of being hit, especially since tanks of that period had poor rangefinding capabilities, but the low profile is not so conducive for the loader. With a maximum internal height of only 1,600mm from the crew compartment floor to the turret ceiling, it was not possible for any of the crew members to stand upright in the turret unless they were particularly short. Nevertheless, the available internal height of the tank was considered enough for a loader by Soviet standards and the D-10T gun was designed with a horizontally-sliding breech as opposed to a vertically-sliding breech with this in mind. From this perspective, the T-54 is directly comparable to the M26 Pershing, M46 and M47 Pattons, but not the Centurion or the M48 Patton.<br />
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According to factory drawings, the Centurion has a total internal height of 2,057mm, but the tank stows a large quantity of ammunition on the floor of the hull underneath a rotating floor which the loader stands on. As such, the actual internal height from the rotating floor to the turret ceiling is 1,816mm - more than enough for an average man to stand up straight inside the tank. This is partly thanks to the fact that the Centurion uses an externally-mounted Horstmann suspension system which conserves the internal space of the tank, although there is no volumetric miracle as the Centurion is a very tall tank in the first place.<br />
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In the case of the M26, M46 and M47, the immense external height of the tanks did not translate into an equally immense internal height in the crew compartment because the turret basket was suspended far above the floor of the hull. For <a href="http://afvdb.50megs.com/usa/pics/pershingcross1.jpg">the M26</a>, the floor was suspended <a href="http://afvdb.50megs.com/usa/pics/m26int.jpg">more than halfway above the hull itself</a> because a large quantity of ammunition was <a href="http://afvdb.50megs.com/usa/pics/pershingammo.jpg">stored on the floor of the hull</a>. It was the same for the M46 and <a href="http://afvdb.50megs.com/usa/pics/m47pattonint.jpg">the M47</a>, both of which stored ammunition on the floor of the hull. Because of this, a large quantity of ammunition could be carried relatively safely in these tanks but the internal height was actually less than the T-54. Furthermore, ammunition was also stowed in vertical racks next to the loader in all of the aforementioned Western tanks, which is convenient for the loader but also takes up a large amount of space as shown <a href="http://afvdb.50megs.com/usa/pics/m47loader.jpg">in this photo of an M47</a>. As such, the horizontal space for the loaders of these tanks is far less than the turret ring diameter suggests, and the cramped conditions for T-54 loaders are perhaps not so cramped in this context.<br />
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<span style="font-size: large;">VENTILATION</span></h3>
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<a href="https://3.bp.blogspot.com/-qkkyGrdJkrM/Wa5NdrOlfwI/AAAAAAAAJRg/z-LSJqYx3-w4r_jeyj4ryFsIW8a0FDzYgCLcBGAs/s1600/ventilator%2Bdome.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1366" height="356" src="https://3.bp.blogspot.com/-qkkyGrdJkrM/Wa5NdrOlfwI/AAAAAAAAJRg/z-LSJqYx3-w4r_jeyj4ryFsIW8a0FDzYgCLcBGAs/s640/ventilator%2Bdome.png" width="640" /></a></div>
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Like all tanks of its era, the T-54 had a ventilation system that supplied airflow globally throughout the tank rather than locally towards each individual crew member. Beginning with the first T-54 model up to the T-54B, crew ventilation was provided by a large exhaust fan installed in the partition between the fighting compartment and the engine compartment. A ventilator intake fan was installed in the turret roof just in front of the loader's hatch to ensure a large supply of air above the gun breech. Both the ventilator intake and exhaust fans were powered by electric motors.<br />
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The dome surrounding the ventilator intake fan is a thick armoured steel casting that is welded to the turret. The heavy steel walls of the dome and the S-shaped ducting enables the dome to protect the motor from machine gun fire and artillery fragments. The drawing on the left below shows a winter cover for the ventilator dome and the drawing on the right below shows a cross section of the dome.<br />
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<a href="https://3.bp.blogspot.com/-_yI_ZWdoMk8/WG5pSur_5YI/AAAAAAAAH_s/I8rSZ4-XvJAhMXAov7dQ-gzudi_gzXG3ACEw/s1600/t-54%2Bventilator%2Bdome.gif" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="252" src="https://3.bp.blogspot.com/-_yI_ZWdoMk8/WG5pSur_5YI/AAAAAAAAH_s/I8rSZ4-XvJAhMXAov7dQ-gzudi_gzXG3ACEw/s320/t-54%2Bventilator%2Bdome.gif" width="320" /></a><a href="https://1.bp.blogspot.com/-F2UTakOwPbU/XVAnX3FLoaI/AAAAAAAAOy8/s5o1Cux0R9AO42nMx8JR5vIumCTR72wSgCLcBGAs/s1600/ventilation%2Bfan.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="180" data-original-width="350" height="205" src="https://1.bp.blogspot.com/-F2UTakOwPbU/XVAnX3FLoaI/AAAAAAAAOy8/s5o1Cux0R9AO42nMx8JR5vIumCTR72wSgCLcBGAs/s400/ventilation%2Bfan.gif" width="400" /></a></div>
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During combat, the ventilation intake fan on the turret roof acts as a blower that circulates fresh air through the loader's station and also serves to clear the air of some propellant fumes after each shot is fired, blowing the fumes downward where they are sucked out of the fighting compartment by the exhaust fan. This is shown in the drawing below. When the hatches on the tank are opened, the exhaust fan ensures that the crew experiences a continuous rush of air, but when the hatches are closed, air can only enter the tank through a few intakes: the gaps in the gun mask, the gun bore (if it is not loaded), the ventilation intake fan on the turret roof, small gaps in the turret ring between the turret and the hull, gaps in the periscope mountings, and gaps from the imperfect seals of the hatches.<br />
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<a href="https://2.bp.blogspot.com/-5sqrhLzB_8g/WE_vJeavjDI/AAAAAAAAH1E/T1eLLO42H1o9yz3_vX3nNh84zLVAGMfWwCLcB/s1600/t-54%2Bmod.%2B1947%2Bventilation%2Bsystem.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-5sqrhLzB_8g/WE_vJeavjDI/AAAAAAAAH1E/T1eLLO42H1o9yz3_vX3nNh84zLVAGMfWwCLcB/s1600/t-54%2Bmod.%2B1947%2Bventilation%2Bsystem.jpg" /></a></div>
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The ventilation exhaust fan blew air from the crew compartment into the engine compartment. When fording deep bodies of water, this fan also serves as the only source of air for the engine and cooling system as the external air intake had to be shut off to prevent the engine from being flooded. The hole in the engine compartment bulkhead for the exhaust fan is shown in the drawing on the right below, and the drawings on the right below show the exhaust fan with the covers closed and the covers opened.<br />
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<a href="https://1.bp.blogspot.com/-iIaQnUJLats/XaXZydMBqpI/AAAAAAAAPYw/obZs0q14CaML8KzlTp6GfP9yISGlGBAygCLcBGAsYHQ/s1600/exhaust%2Bfan.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1409" height="320" src="https://1.bp.blogspot.com/-iIaQnUJLats/XaXZydMBqpI/AAAAAAAAPYw/obZs0q14CaML8KzlTp6GfP9yISGlGBAygCLcBGAsYHQ/s320/exhaust%2Bfan.png" width="281" /></a><a href="https://1.bp.blogspot.com/-wyeOOU0x8EQ/XVKmIgGykFI/AAAAAAAAO6A/eZUsb8UNIusup_FrkrgvDHqc7asGCcZOQCLcBGAs/s1600/bulkhead.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="294" data-original-width="400" height="293" src="https://1.bp.blogspot.com/-wyeOOU0x8EQ/XVKmIgGykFI/AAAAAAAAO6A/eZUsb8UNIusup_FrkrgvDHqc7asGCcZOQCLcBGAs/s400/bulkhead.gif" width="400" /></a></div>
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The loader receives the most airflow thanks to his close proximity to the ventilator intake fan, which is appropriate given his physically demanding duties. In combat, the driver can ensure that he is well ventilated by opening the ventilation porthole in his hatch, and in non-combat situations, it is better for him to drive with an open hatch. The commander's hatch also has a small ventilation porthole that can be opened to allow air to enter and blow down on the commander's shoulders under the suction force of the exhaust fan. Overall, this ventilation system was adequate for most situations, but it was not sufficiently effective at evacuating propellant fumes and it created some potential vulnerabilities. The reliance on small ventilation ports to supply air to the crew members may not have been a problem when the tank was hit by machine gun fire and armour piercing shells, but it presented an entryway for blast overpressure to reach the crew members directly. For instance, a medium caliber explosive shell detonating on the frontal turret armour would not be able to deal significant damage to the tank, but if the driver's ventilation port was open, the blast wave would reach him and some fragments may even find their way through the port. As such, only the commander could safely have the ventilation port in his hatch open during combat. This ventilation system was also incompatible with a collective NBC protection system.<br />
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<a href="https://1.bp.blogspot.com/-49pNK2AWHP4/XVGfzxGn4gI/AAAAAAAAO38/74Y5C1zFoAs3G-ZXiBeJvD1_1txnfcyMQCLcBGAs/s1600/commander%2527s%2Bcupola%2Bhatch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="879" data-original-width="721" height="320" src="https://1.bp.blogspot.com/-49pNK2AWHP4/XVGfzxGn4gI/AAAAAAAAO38/74Y5C1zFoAs3G-ZXiBeJvD1_1txnfcyMQCLcBGAs/s320/commander%2527s%2Bcupola%2Bhatch.png" width="262" /></a><a href="https://1.bp.blogspot.com/-O2kbjD7_Mzw/XVAz1wspDyI/AAAAAAAAOzg/EvmIjVJn5tUJtkyVeTeAWnRs7PaWqSyPACLcBGAs/s1600/driver%2527s%2Bhatch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="458" data-original-width="657" height="278" src="https://1.bp.blogspot.com/-O2kbjD7_Mzw/XVAz1wspDyI/AAAAAAAAOzg/EvmIjVJn5tUJtkyVeTeAWnRs7PaWqSyPACLcBGAs/s400/driver%2527s%2Bhatch.png" width="400" /></a></div>
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In cold weather conditions, using the ventilation system in its normal operating mode is undesirable because it simply takes cold air and circulates it in the tank when warmth is needed instead. It can simply be deactivated and the vents for the exhaust fan can be left open to allow heat from the running engine to radiate into the fighting compartment, but the downside is that there is no airflow to remove propellant fumes. Also, the driver would not be able to experience much heat as he is seated quite far away from the exhaust fan. There is no dedicated heater for the crew, but heat for the fighting compartment may be supplied by the nozzle-type engine and oil preheater placed in the rear left corner fighting compartment, clearly visible in the photo below (credit to Jim Chandler and the Warwickshire Armour Modellers for the photo). The exhaust of this heater is located on the belly of the hull. This heater can only be used if the tank is not in combat or conducting maneuvers.<br />
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<a href="https://3.bp.blogspot.com/-JOQEap1MnFM/WG-7CD4xgFI/AAAAAAAAIC0/n34tf80cy4I7Jcz8NNNy3hi08BzeiI_2gCLcB/s1600/jimchandlert-55.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://3.bp.blogspot.com/-JOQEap1MnFM/WG-7CD4xgFI/AAAAAAAAIC0/n34tf80cy4I7Jcz8NNNy3hi08BzeiI_2gCLcB/s640/jimchandlert-55.jpg" width="640" /></a></div>
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The heater had to be moved slightly when a rotating floor was introduced in the T-54B in order to enable a floor of maximum diameter to be installed, although the floor was still somewhat narrow as it had a diameter of only 1,370mm. This was slightly narrower than the rotating floor of the Centurion Mk.7 which had a diameter of 1,549mm. The difference cannot be considered large because even though the total difference in diameter is 179mm, the actual difference on each half of the turret is only 90mm and Centurion tank loaders were separated from the hull by a turret basket wheras T-54 and T-55 loaders were not. It is the same for other NATO tanks as well.
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The majority of surfaces of the fighting compartment floor was covered with textured rubber matting to prevent slipping. Unlike contemporary Western tanks, the T-54 lacked a turret basket and only had the rotating floor, although the turret basket floor of tanks like the M47 was also quite narrow because the turret basket tapers inward from the turret ring.<br />
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<a href="https://1.bp.blogspot.com/-f9DsDAzfU6s/XPjfkTPyFsI/AAAAAAAAOOk/GxMvdkwDV60VE4OE83KNacdLipuwPgfkgCLcBGAs/s1600/floor%2Band%2Belectrical%2Bfittings.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="914" data-original-width="1600" height="363" src="https://1.bp.blogspot.com/-f9DsDAzfU6s/XPjfkTPyFsI/AAAAAAAAOOk/GxMvdkwDV60VE4OE83KNacdLipuwPgfkgCLcBGAs/s640/floor%2Band%2Belectrical%2Bfittings.png" width="640" /></a></div>
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The lack of a turret basket allowed the gunner to stretch his legs into the driver's compartment when the turret was facing forward, but more importantly, it eliminated the need to store the tank's ammunition supply within the boundaries of a turret basket. In the Centurion, Leopard 1 and M48 (to list only a few), a large quantity of ammunition is stored next to the loader in vertical racks or bins which greatly reduces the available space in the loader's side of the turret. In the case of the M48A5, the loader has only half the space that the turret ring diameter alone suggests, as you can see in the photo on the left below. It is more or less the same for the Leopard 1, as shown in the photo on the right below. A T-54 loader is provided with a similar amount of headroom as its Western counterparts and he has more room in other respects.<br />
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<a href="https://4.bp.blogspot.com/-pIpUh3Xi7rw/W-7aFFN5RZI/AAAAAAAAMd4/DdV27fHn-UQb7IXkNZH9bABRjS6mJpQqACLcBGAs/s1600/m48a5.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="480" data-original-width="640" height="300" src="https://4.bp.blogspot.com/-pIpUh3Xi7rw/W-7aFFN5RZI/AAAAAAAAMd4/DdV27fHn-UQb7IXkNZH9bABRjS6mJpQqACLcBGAs/s400/m48a5.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-I3iQnS_gc-U/W-7aFRU2jZI/AAAAAAAAMd8/Qbc0v4D448QKK0El7yKGAKpI7Oi01bctwCLcBGAs/s1600/leopard%2B1.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="519" data-original-width="780" height="265" src="https://1.bp.blogspot.com/-I3iQnS_gc-U/W-7aFRU2jZI/AAAAAAAAMd8/Qbc0v4D448QKK0El7yKGAKpI7Oi01bctwCLcBGAs/s400/leopard%2B1.JPG" width="400" /></a></div>
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On a side note regarding the rotating floor of the T-54, it seems rather improbable that the loader or anybody else will get his foot ripped off by the heater when the turret turns. It overhangs the rotating floor by only an inch or two and it is in the left rear corner of the fighting compartment, so the loader will only be in its vicinity in a narrow range of turret azimuths. Also, the loader will often be working with ammunition from the hull, so he should be very much aware of anything that might be dangerous.<br />
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Besides the general crampedness of the tank, a minor weakness of the T-54 is the scarcity of storage space. Besides the containers on the track fenders for storing tools and spare parts, there is no dedicated container for the personal effects of the crew. The abundance of external handrails and hooks for camouflage netting made it convenient for the crew to secure their canvas bags around the circumference of the turret (this is standard procedure taught to recruits), but it is not as convenient nor as secure as having proper stowage bins. One of the most common modifications of exported T-54s is the addition of external baskets and bins for stowage.<br />
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The handrails (two large ones on either side of the turret, and two small ones at the base of the rear of the turret. See photo above) make for great footholds to help the crew mount the turret.</div>
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<h3>
<span style="font-size: large;">COMMANDER'S STATION</span></h3>
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<a href="https://1.bp.blogspot.com/-_EMDJ-1Cg1w/XZWyZaWC2_I/AAAAAAAAPRI/F2KDXXbiaHEYHMyvqyPmrweDKw_i2S2HACLcBGAsYHQ/s1600/commanders%2Bstation%2Bt-54%2B1949.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="266" src="https://1.bp.blogspot.com/-_EMDJ-1Cg1w/XZWyZaWC2_I/AAAAAAAAPRI/F2KDXXbiaHEYHMyvqyPmrweDKw_i2S2HACLcBGAsYHQ/s400/commanders%2Bstation%2Bt-54%2B1949.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-kwHexEGI1i0/XPjR6kYXMsI/AAAAAAAAONo/cbp7yiqLslM3eSK9795-TFKlFCmQXTg4ACLcBGAs/s1600/7714628306_9e65db1818_o.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1196" data-original-width="1600" height="298" src="https://1.bp.blogspot.com/-kwHexEGI1i0/XPjR6kYXMsI/AAAAAAAAONo/cbp7yiqLslM3eSK9795-TFKlFCmQXTg4ACLcBGAs/s400/7714628306_9e65db1818_o.jpg" width="400" /></a></div>
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The commander is seated on a padded triangular seat with a padded backrest, and there is also a cushion attached to the turret ring for him to rest his left knee upon. A fold-out footrest is provided. On earlier T-54 models, the lack of a rotating turret floor made this feature mandatory like on older tanks such as the T-34-85. The commander has access to the turret traverse lock, which is placed next to the radio transceiver on the turret shelf. Aside from that, he does not have any direct control over the turret or the weapons other than the target designation system as the T-54 does not provide duplicated controls for the commander. However, the extremely close proximity of the commander to the gunner's controls may allow him to override the gunner in a somewhat more direct way by simply leaning over and using the gunner's turret traverse controls.<br />
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<a href="https://1.bp.blogspot.com/-aa4woAk1Cuk/XVA1rU5ww8I/AAAAAAAAOz0/X752sLd_mkEjqRQkXuT9g0OwB8iQnGNMwCLcBGAs/s1600/commanders%2Bstation.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="430" data-original-width="600" height="286" src="https://1.bp.blogspot.com/-aa4woAk1Cuk/XVA1rU5ww8I/AAAAAAAAOz0/X752sLd_mkEjqRQkXuT9g0OwB8iQnGNMwCLcBGAs/s400/commanders%2Bstation.jpg" width="400" /></a></div>
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In terms of space, the commander is severely restricted in his ability to move forwards and backwards as well as side to side. The small length of his station is because he is seated very close to the gunner in front of him, and the main culprit of the limited width of the commander's station is the location of the radio set. Being placed on the turret shelf just next to the commander, he can access it more easily than if it were installed behind his backrest, but this comes at the cost of restricting his working space above waist level. The narrow width of the commander's station can be seen in the two screenshots below, taken from the video "<a href="https://youtu.be/GSTbIXt2MQk"><i>Танк Т 55 – снаружи, внутри, на ходу</i></a>" from Ivan Zenkevich's channel.<br />
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<a href="https://1.bp.blogspot.com/-sNDvSXgyO98/XPjR6ktoHGI/AAAAAAAAONs/FgRaH0DL1QkoECntZpn35HLhPKwWawc6ACEwYBhgL/s1600/t-55a%2Bcommanders%2Bstation%2Bthrough%2Bhatch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1365" height="225" src="https://1.bp.blogspot.com/-sNDvSXgyO98/XPjR6ktoHGI/AAAAAAAAONs/FgRaH0DL1QkoECntZpn35HLhPKwWawc6ACEwYBhgL/s400/t-55a%2Bcommanders%2Bstation%2Bthrough%2Bhatch.png" width="400" /></a><a href="https://1.bp.blogspot.com/-L6-BLVVwSHU/XPjU5NXe8VI/AAAAAAAAOOI/XcVR0wjrLcUfwQ0pzgHm_teRw5NqCkh7gCLcBGAs/s1600/commanders%2Bleft%2Bside.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1365" height="225" src="https://1.bp.blogspot.com/-L6-BLVVwSHU/XPjU5NXe8VI/AAAAAAAAOOI/XcVR0wjrLcUfwQ0pzgHm_teRw5NqCkh7gCLcBGAs/s400/commanders%2Bleft%2Bside.png" width="400" /></a></div>
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The shoulder guard on the commander's right side isolates him from the recoil path of the D-10T cannon. It is possible to remove the arm guard. This gives the commander some much needed breathing space, but this can only be done in non-combat situations, for obvious reasons. This is also done to enable the commander to move to the loader's station, or vice versa, but to do that, the recoil guard behind the cannon breech assembly must be folded down as well. This is all shown in the two screenshots below, again taken from the video "<a href="https://youtu.be/GSTbIXt2MQk">Танк Т 55 – снаружи, внутри, на ходу</a>" from Ivan Zenkevich's channel.<br />
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<a href="https://4.bp.blogspot.com/-5jAoa_IPzJI/WCVyPD9c2hI/AAAAAAAAHjM/QlrMDdOK7MEpcDb84Ml884JKZjE4AIDGgCEw/s1600/commander%2527s%2Barm%2Bshield.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="222" src="https://4.bp.blogspot.com/-5jAoa_IPzJI/WCVyPD9c2hI/AAAAAAAAHjM/QlrMDdOK7MEpcDb84Ml884JKZjE4AIDGgCEw/s400/commander%2527s%2Barm%2Bshield.png" width="400" /></a><a href="https://2.bp.blogspot.com/-lg5gp1hDP74/WDKR9QZ4ytI/AAAAAAAAHpA/RfYK4iSZUZoHiiU2w17T5Hx9PUuuNH7oQCLcB/s1600/d-10t%2Bfolded.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="223" src="https://2.bp.blogspot.com/-lg5gp1hDP74/WDKR9QZ4ytI/AAAAAAAAHpA/RfYK4iSZUZoHiiU2w17T5Hx9PUuuNH7oQCLcB/s400/d-10t%2Bfolded.png" width="400" /></a></div>
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The commander and the loader can move over to each others' positions with relative ease once the deflector shield is folded down, although the keyword here is "relative". Furthermore, the commander's seat can be folded up for better access to equipment located below the turret ring and for maintenance and stowage purposes.<br />
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In terms of comfort, the commander gets a somewhat better deal than the gunner, who does not have a real backrest. Still, even though the commander has a footrest he has practically no legroom, forcing him to wrap his legs around the gunner. The advantage is that it is easy to nudge the gunner and give him quick orders. The disadvantage is that it quickly becomes very uncomfortable especially in hot weather, but perhaps it would be the opposite in cold weather. Nevertheless, the high level of physical intimacy between the two crew members is not particularly desirable.<br />
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<h3>
<span style="font-size: large;">COMMUNICATIONS</span></h3>
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Originally, the T-54 was provided with a <a href="http://www.rv3bc.narod.ru/Stat/10rt-12.htm">10RT-26E</a> radio transceiver mounted to the turret wall next to him. The radio is designed to operate in the 3.75-6.00 MHz frequency range. All Soviet armoured vehicles from the later half of WWII and the immediate postwar period featured a 10RT series radio, but by the early 50's, the series was rendered obsolete by a new government decree allocating the 20.0-22.4 MHz frequency range for the exclusive use of tank radios.<br />
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The production of the venerable 10RT series ceased entirely in 1956, having been replaced by the R-113 radio set in 1955. Beginning in 1955, all new production T-54s were equipped with the R-113 radio transceiver set. A video of an R-113 radio in operation can be found here (<a href="https://www.youtube.com/watch?v=ithjdm39Ax0">link</a>). The R-113 belonged to the first generation of Soviet tank radios designed in the post-war era. It is a standard VHF radio operating in the 20-22.375 MHz frequency range with a maximum range of 20 km with the whip antenna extended, reduced to 8-12 km in the presence of noise and 10 km in the presence of jamming. For regular tanks in tank platoons, the radio is usually kept in the simplex receiving mode to receive orders from the platoon leader, while the platoon leader operates his radio in the half duplex mode, although he is forbidden from transmitting except in emergencies. In general, all tanks mainly operate in the receiving mode to receive orders from the company commander. The R-113 radio and the BP-2A power supply unit are shown in the photo below.<br />
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The T-54K command tank variant was created in 1959 and came with an additional R-112 radio mounted on the back of the turret. The R-112 operates in the 2.8 - 4.99 MHz frequency range, and has a range of 6 km with a whip antenna and 25 km with a mast antenna. The tank must be stationary to deploy the mast antenna. The R-112 radio allows the T-54K to communicate with the tank commanders of other tank companies as well as battalion commanders. The large size and mass (90 kg) of the radio made it impossible to install it inside the tank without removing something else. In this case, the ammunition rack holding five rounds at the back of the turret behind the deflector shield was removed and the radio is mounted there instead, as shown in the drawing on the right. The single round stored at the back of the hull was also deleted which led to a reduction in the total ammunition capacity from 34 rounds to 28 rounds in the T-54K.<br />
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Communication between crew members was facilitated by the their headsets and laryngophones which were connected to the TPU-47 intercom system. The components of the intercom system can be seen on the wall of the turret at the left side of the photo below. The tank in the photo below does not have a radio. The turret traverse lock can also be seen attached to the turret ring, and the metal loops for personal stowage can be seen on the wall of the hull at the bottom of the photo. Each crew member in the T-54 was allotted some space of personal equipment and each crew member was provided with a <a href="http://img.allzip.org/g/227/orig/11976964.jpg">two-liter aluminium bottle</a> which would be stowed in a special holder near their respective stations. Two clips for stowing two rounds of ammunition can also be seen at the bottom right corner of the photo.<br />
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<span style="font-size: large;">CUPOLAS</span></h3>
Following the precedent set by the T-34-85 and T-44, it was quite natural that the T-54 series would also have this essential design feature. Every variant of the T-54 had a rotating commander's cupola mounted on a separate cast substructure that is bolted onto the turret and multiple cupola designs were implemented throughout the evolution of the tank, ending with the introduction of the T-54A in 1954.<br />
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<span style="font-size: large;">T-54 obr. 1947</span></h3>
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On the T-54 obr. 1947, the commander's cupola protruded very slightly from the turret roof and the roof of the cupola is almost completely flat as shown in the two photos above, taken from the <a href="https://www.net-maquettes.com/pictures/t-54-vol3/?afg533_page_id=3#afg-533">Net-Maquettes</a> scale modelers' website. There was a single MK-4S periscope (also known as a Gundlach periscope) installed centrally on the cupola roof, supplemented by two viewing prisms that were slightly offset to the left and right. The hatch opens forward and can be locked in an upright position to provide frontal protection for the commander. As one would expect, there was a rubber lining on the underside of the hatch to protect the commander's head. This layout was borrowed from the commander's cupola of the T-44, which in turn was taken directly from the T-34-85, but unlike this older design, the cupola of the T-54 obr. 1947 had a much lower profile and omitted direct vision devices entirely in order to enhance the protection of the commander and reduce the overall height of the tank. However, even though it was certainly an improvement in terms of protection, the T-54 obr. 1947 cupola was not a comprehensive upgrade as it suffered from reduced visibility. Keeping its drawbacks in mind, the cupola of the T-34-85 could at least ensure all-round visibility with five viewing slits arranged around the fixed cupola at equidistant intervals to supplement the single MK-4 periscope in the rotating cupola roof. The photo on the left below shows the cupola of a T-34-85 as seen from below, and the photo on the right shows the cupola of a T-54 obr. 1947 from a similar perspective (photo from the <a href="https://urban3p.ru/object18316/gallery">urban3r website</a>).<br />
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Each viewing prism in the T-54 obr. 1947 cupola offered a horizontal field of view of 80 degrees and the full viewing arc from the cupola to the front of the turret was only around 100 degrees. In truth, the full viewing arc could have been wider but the commander's view to the right was partly blocked by the ventilation dome on the turret roof. With just three viewing devices available, the commander was forced to rotate his cupola in order to look towards the side and rear of the turret, but the ability to rotate the cupola does not completely solve the issue of reduced all-round visibility as it would take more time for the commander to scan his surroundings and the commander would not be able to notice his surroundings through his peripheral vision. When not in use, armoured covers could be closed to protect the windows of the fixed viewing prisms from gunfire.<br />
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The central MK-4S periscope was similar to the other two viewing prisms in that it gave an unmagnified view, but it was adjustable in the vertical axis. Unlike the MK-4 periscope in the T-34-85 or T-44 cupola, it was not possible to look backwards from the periscope by using its reverse view feature due to the non-rotating mount and the armoured hood around the periscope head. This distinguishes the MK-4S variant from the original MK-4. The rear view feature of the MK-4 could be used by pulling down a sliding glass prism over the eyepiece window and then turning the periscope to face the rear.<br />
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<br />The MK-4S was obsolete as a primary observation device as it did not provide magnified vision. This limited the commander's viewing range and restricted his ability to conduct fire correction for the gunner. Beginning in 1948, the MK-4S periscope was replaced by the TPK-1 fire correction periscope.<br />
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<h3>
<span style="font-size: large;">MK-4S</span></h3>
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The MK-4S differed from the basic MK-4 by not having a rotating mount with an armoured collar and tin hood.<br />
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The MK-4 was a copy of the British AFV Periscope No.1 Mk.1, also known as the Vickers Mk. 4 periscope, which was actually the Polish Gundlach periscope produced under licence. The Soviet designation of MK-4 was taken directly from the Vickers designation, but of course, the Soviet government did not deem it necessary to pay licencing fees for using the design. However, Soviet engineers introduced a handful of improvements over the original design such as simplifying the overly complex handle and modifying the mounting flange to include a rubber seal. As such, the MK-4 was simpler to produce, more durable, and did not leak when it rained. Interestingly enough, the MK-4 was compatible with the No.1 periscope mounting point on British tanks like the Churchill and Cromwell.<br />
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The periscope can be elevated by 18 degrees and depressed by -12 degrees for a total elevation range of 30 degrees, but to have an all-round view, the T-54 obr. 1947 commander must rotate his entire cupola as the periscope is fixed in traverse. As the MK-4S is a unity periscope with no magnifying power, the early T-54 obr. 1947 suffers from a bad case of short sightedness. <div><br /></div><div>According to Soviet studies (supported by foreign studies), an optical device with no magnification would allow the gunner to see a tank from a maximum distance of 1.0-1.5 kilometers. This is corroborated by actual combat experience during WWII which showed that users could identify tanks up to a distance of 1,000-1,200 meters. This is the same as viewing with the naked eye. Although this seems adequate, it is too limited to permit the commander to perform fire corrections for the gunner and it does not allow the commander to differentiate between different tank models as he simply cannot discern such details. This was sufficient at the time due to the rather short median tank engagement distances during the war, but it was no longer enough in the postwar era. The inadequacy of the MK-4S meant that it was only ever a stopgap solution before the TPK-1 was ready for production.<br />
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<h3>
<span style="font-size: large;">TPK-1</span></h3>
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The TPK-1 periscope began development in the first half of 1944, but it was only ready for mass production after the conclusion of the war and it first entered service in 1948. The TPK-1 was completely interchangeable with the MK-4S as they both shared the same mount, so it was easy to introduce the TPK-1 to tanks that were originally equipped with the older type.<br />
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The TPK-1 was a notable improvement over the old MK-4S for observation at longer distances as it provided a 2.5x magnification power. The requirement set by the GBTU (Directorate of Armoured Forces) was for an effective viewing range of 1,500 meters and easier fire correction than from the venerable MK-4S, and the TPK-1 periscope met those requirements. An internal mirror could be unfolded above the binocular optics to display an unmagnified image through the viewing window above the binocular eyepieces, thus duplicating the function of the MK-4S. This gave the commander the luxury of both a wide-vision 1x periscope and a 2.5x magnified optic in the same device. The photo below shows a T-54 commander looking through this viewing window.<br />
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Although the modest 2.5x magnification of the device is totally inadequate for long range observation in a modern context, studies and records showed that tank combat distances during WWII generally did not exceed a kilometer. In fact, combat data from the Aberdeen Proving Ground showed that 80% of all encounters between tanks and other tanks or anti-tank weapons occurred at a distance of less than 1,000 yards. There were practically no encounters beyond 2,000 yards. From this perspective, the device is quite adequate, although not entirely ideal since a higher magnification would certainly have been appreciated for easier target identification at the upper boundaries of expected combat distances. For long range observation, the commander would have to rely more on his personal 8x30 field binoculars, which were usually of superb quality, as most examples of this line of binoculars made in the USSR were built using tooling plundered from the German Zeiss-Jena factory at the climax of WWII.<br />
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What a pair of 8x30 field binoculars doesn't have, though, is a stadiametric rangefinder. The stadia markings in the TPK-1 viewfinder allowed the commander to rapidly estimate the distance to a typical tank-type target with a height of 2.7 meters, and the additional markings allowed him to estimate lead for the target to a limited extent. These modest features were not insignificant, considering the fact that the MK-4S periscope lacked any mil markings whatsoever and did not permit even basic range estimations.<br />
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That, however, is not the biggest breakthrough from this new device. The most significant feature of the TPK-1 is its ability to designate targets for the gunner. This is done by simply aiming the device at the target and pressing the left thumb button. An electric signal is sent to the turret traverse motor, and by referring to a deflection sensor attached to the cupola ring, the turret is automatically rotated to meet the target. The deflection sensor detects if the cupola is turned away from the 12 o'clock position relative to the turret but does not record the actual azimuth of the cupola. If the sensor detects that the cupola is rotated counter-clockwise relative to the turret, the turret will be rotated counter-clockwise and vice versa. Once the commander has designated a target, the turret will turn until the cupola is once again at the 12 o'clock position relative to the turret - indicating that the turret is facing the same direction as the commander - and the turret traverse motor is halted.<br />
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Turret traverse is only conducted at maximum speed in order to minimize the reaction time of the system. As the gun elevation mechanism lacked power controls, it was still up to the gunner to adjust in elevation. The commander does not need to hold the button to slew the turret all the way to the target. A single click will do. Holding the button will prompt the turret to slew to meet the target and remain slaved to the periscope, thus allowing the commander to commandeer the turret as its movement would then depend on the commander rotating his cupola. Small corrections made by rotating the cupola slightly will not cause the turret to jerk onto the new aiming point even though turret traverse is done at maximum speed by default. This is because the traverse motor will need time to accelerate the turret to its maximum speed (due to inertia), so the turret will turn quite slowly if the arc of rotation is very small. The effect is that the commander can guide the gunner onto target quite gently if he turns the cupola slowly enough.<br />
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This arrangement can be described as a hunter-killer system, making the T-54 the first tank ever to implement such a system, followed by the British Conqueror heavy tank in 1955. The commander of a T-54 is not provided with duplicated firing controls so he cannot override the gunner completely, but this has little bearing on the definition of a hunter killer system. During the early 1950's, the TPK-1 periscope and the associated fire control modifications was retrofitted to IS-2 and IS-3 tanks to modernize them to the IS-2M and IS-3M standard, thus bringing the hunter-killer feature to the Soviet Army's workhorse heavy tanks as well.<br />
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<span style="font-size: large;">T-54 obr. 1949</span></h3>
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To solve the visibility issues of the earlier cupola design, the T-54 obr. 1949 cupola had five viewing prisms of a new design arranged around the circumference of the cupola roof, thus guaranteeing that the commander could easily survey his surroundings without needing to rotate the cupola. Including the central TPK-1 periscope, there were six viewing devices in total, putting it directly on par with the T-34-85 or T-44 cupola design. Moreover, the viewing prisms also had a larger horizontal field of view of 86 degrees instead of 80 degrees. <br />
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However, the diameter of the cupola was not decreased and there was no additional space left for the viewing prisms around the rear half of the cupola, so the commander's hatch was shrunk to accommodate them. The exact dimensions of the hatch are currently not available, but needless to say, the resulting design was far from optimal. The other details of the cupola design such as the periscope mount and the hatch locking mechanism remained largely identical.<br />
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The photos below, taken by <a href="http://svsm.org/gallery/T-54m49">Vladimir Yakubov</a>, shows a T-54 obr. 1949 housed in the Kubinka Armor Museum. The positions of the viewing prisms on the sides and rear of the cupola can be seen.<br />
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Strangely enough, the cupola is shown to be slightly tilted in some drawings, but not in others. If it was really tilted, the small angle probably did not massively affect the balance of the cupola to make it harder to rotate, but it most likely had a minor negative effect on the commander's view of the battlefield through the periscopes.<br />
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<a href="https://1.bp.blogspot.com/-yuYZiQB53ec/XZGmjwPuLRI/AAAAAAAAPPw/LqFPK014sWg4izcdk4pUFozHX5hd6G53QCLcBGAsYHQ/s1600/t-54%2B1949%2Bfront%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="556" data-original-width="622" height="357" src="https://1.bp.blogspot.com/-yuYZiQB53ec/XZGmjwPuLRI/AAAAAAAAPPw/LqFPK014sWg4izcdk4pUFozHX5hd6G53QCLcBGAsYHQ/s400/t-54%2B1949%2Bfront%2Bview.png" width="400" /></a></div>
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<h3>
<span style="font-size: large;">T-54 obr. 1951</span></h3>
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<a href="https://1.bp.blogspot.com/-bxIKUx85oUQ/XZGe0yEyMtI/AAAAAAAAPO4/tJuH-mytze0D1NF-398Vkw5fNpotoegNQCLcBGAsYHQ/s1600/1951%2Bcupola.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="924" data-original-width="717" height="640" src="https://1.bp.blogspot.com/-bxIKUx85oUQ/XZGe0yEyMtI/AAAAAAAAPO4/tJuH-mytze0D1NF-398Vkw5fNpotoegNQCLcBGAsYHQ/s640/1951%2Bcupola.png" width="496" /></a></div>
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The cupola design was changed yet again in the T-54 obr. 1951 model to correct the drawbacks of the earlier design. The viewing prisms used in all of the previous T-54 models were replaced with periscopes, and the cupola layout returned to the same style as the T-54 obr. 1947. The height of the cupola was increased, and the commander's hatch gained a dome shape. This greatly increased the amount of headroom in his station and also made it possible to embed the side and rear view periscopes in the hatch itself. By relocating all of the five general vision periscopes to the rotating cupola with three embedded into the hatch itself, it was possible to increase the size of the hatch back to the same dimensions as the T-54 obr. 1947 without increasing the size of the cupola or compromising on the commander's circular visibility. Furthermore, it was level unlike the cupola of the T-54 obr. 1949.<br />
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The increased height of the cupola had the beneficial side effect of giving the periscopes more clearance from the turret roof, giving the commander a better view over the loader's cupola and the ventilation dome in front of it. This improved the commander's all-round visibility towards the right side of the turret, but came at the expense of making the cupola a slightly more prominent target.</div><div><br /></div><div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-4A5cpdm92jk/YSX_mpGbY2I/AAAAAAAAUG4/OslG607OqV0LjxkDiymcIwOFGpay3zSXACLcBGAsYHQ/s1332/cupola.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="671" data-original-width="1332" height="322" src="https://1.bp.blogspot.com/-4A5cpdm92jk/YSX_mpGbY2I/AAAAAAAAUG4/OslG607OqV0LjxkDiymcIwOFGpay3zSXACLcBGAsYHQ/w640-h322/cupola.png" width="640" /></a></div>
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One drawback of this periscope layout was that the rear view periscope prevented the hatch from being opened unless it was removed. This made it impossible to open the hatch from outside the tank if the periscope was installed. If the commander was already at his station, the need to remove the periscope was an obstacle that complicated a speedy exit through the hatch. There was no real solution for bypassing this issue other than to keep the rear view periscope permanently stowed away.<br />
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<h3>
<span style="font-size: large;">T-54A (and later)</span></h3>
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When the T-54A was created, it was given a new cupola design that remained the final variation to be found on any serial T-54 model and was later used on the T-54B and T-55 series, before also being adopted for the T-62 series and then becoming the template for the commander's cupola of the T-64, T-72 and T-80 main battle tanks.<br />
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The cupola was largely identical to the T-54 obr. 1951 design with modifications made to accommodate the new "Uzor" night vision system consisting of an OU-3 infrared spotlight and the TKN-1 night vision periscope. The modifications included the addition of a mounting point for the OU-3 spotlight above the central periscope hood, a hole in the cupola roof for the actuating rod that joins the TKN-1 periscope to the OU-3 spotlight, and the removal of the rear view periscope in the hatch due to the inconvenience it caused.<br />
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As the photo below shows, the rear periscope in the hatch that could be found on the T-54 obr. 1951 was replaced with a simple steel handlebar.<br />
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<a href="https://1.bp.blogspot.com/-3awqrXzfJvo/XZGdXW4lXaI/AAAAAAAAPOo/csO9_0HtsDkPS0t7233NgyFf_r30EgCRQCLcBGAsYHQ/s1600/hatch.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="356" data-original-width="556" src="https://1.bp.blogspot.com/-3awqrXzfJvo/XZGdXW4lXaI/AAAAAAAAPOo/csO9_0HtsDkPS0t7233NgyFf_r30EgCRQCLcBGAsYHQ/s1600/hatch.jpg" /></a></div>
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The T-54A retained the TPK-1 periscope for fire correction and general observation, but later tanks like the T-54B had the improved TPKUB periscope and later, the TPKU-2B.<br />
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The bolt-on substructure on which the cupola is mounted has a minimum internal race ring diameter of 570mm and the substructure itself has an external diameter of 624mm. The rotating cupola itself fits inside this substructure. As shown in the drawing, the substructure is horizontally slanted by 17 degrees to offset the slope of the T-54 turret roof. This creates a level plane for the cupola to be mounted on, which is important because a tilted cupola makes it extremely difficult for the commander to use the viewing devices and the cupola itself would require more force to rotate.<br />
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The cupola and the cupola hatch are shown in the two drawings below. The hatch itself has a total length and total width of 497mm and 670mm respectively, but the actual opening in the cupola through which the commander can ingress and egress is much smaller as the length of the hatch includes the hinge where it attaches to the cupola and the edge where it overlaps with the lip of the cupola race ring. The actual size of the opening is only approximately 400mm long and the width is 570mm as indicated by the minimum internal diameter of the cupola substructure.<br />
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The height of the exposed cupola excluding the race ring which fits into the cupola substructure is 131mm and the entire cupola is thickly armoured and sloped.<br />
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<a href="https://2.bp.blogspot.com/-CUTwT3E0_zY/XBI-DaN0LvI/AAAAAAAAMqQ/N6MgQkgrSvcYO2Vxml-49fcnUpgTdTq1gCLcBGAs/s1600/commander%2527s%2Bcupola%2Bhatch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="879" data-original-width="721" height="400" src="https://2.bp.blogspot.com/-CUTwT3E0_zY/XBI-DaN0LvI/AAAAAAAAMqQ/N6MgQkgrSvcYO2Vxml-49fcnUpgTdTq1gCLcBGAs/s400/commander%2527s%2Bcupola%2Bhatch.png" width="327" /></a><a href="https://4.bp.blogspot.com/-cBecks10ZGs/XBI-DSbBjdI/AAAAAAAAMqM/G9uLq-ScSN0JLedDdRBVgOT-M9rOODnEACLcBGAs/s1600/commander%2527s%2Bcupola%2B1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="788" data-original-width="705" height="400" src="https://4.bp.blogspot.com/-cBecks10ZGs/XBI-DSbBjdI/AAAAAAAAMqM/G9uLq-ScSN0JLedDdRBVgOT-M9rOODnEACLcBGAs/s400/commander%2527s%2Bcupola%2B1.png" width="357" /></a></div>
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<h3>
<span style="font-size: large;">TPKUB, TPKU-2B</span></h3>
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The commander of an early issue T-54B was equipped with the TPKUB binocular periscope. This was a binocular magnified periscope like the TPK-1, but it lacked the wide vision feature of its predecessor. The TPKUB had a single left handle for the commander to grasp, but the much more common TPKU-2B model that came later had two handles. The left handle on both models contains the target designation button for the tank's hunter-killer system. The new periscope was a step forward over the TPK-1 in the observation range thanks to the increased magnification. Many older T-54 models were retrofitted with the TPKU-2B to bring it up to the same level of technology as the T-54B.<br />
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The sight has two adjustable magnification settings of either 1x or 5x. Under 1x magnification, the field of view from the sight is 17.5 degrees. This is reduced to 7.5 degrees under 5x magnification. The general layout of the viewfinder and the reticle is the same as in previous periscopes. The viewing distance is improved by the higher magnification factor, but the rangefinding capabilities of the periscope are probably not improved at all. A British-Israeli report made available on the tankandafvnews website reveals some interesting information on the precision of rangefinding through the TPKU-2B: from the table in <a href="https://tankandafvnews.files.wordpress.com/2016/02/064.jpg">page 121</a> (page 64 of the photo album), the mean error in ranging tank-shaped screens, broadside tanks, oblique tanks (meaning: angled hull) and head-on tanks is 14.57%. The results of an analysis of the data were somewhat counter-intuitive.<br />
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<a href="https://tankandafvnews.files.wordpress.com/2016/02/065.jpg">Page 122 of the report</a> (page 65 of the photo album) mentions that the precision of rangefinding against hull-down tanks was surprisingly unaffected by the fact that half of the target was out of sight. The report does not say why, but we can conjecture that it is because stadia rangefinding is partly technique and partly guesswork. The full report on tankandafvnews is worth reading in its entirety as it is very enlightening.<br />
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The tests show that the commander is able to range the target in an average time of 3.3 seconds, and this section of the report concludes that the short time required to obtain a range estimate is unobtrusive to the loading and laying of the gun. This means that by the time the gunner has visually acquired the target, he will already know the range, and can open fire without delay.<br />
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Like the TPK-1, the TPKU-2B has a target designation function. The target designation system is a rather simple one; A direction sensor is installed in the 5 o'clock position of the cupola. The direction sensor consists of a roller placed in permanent contact with the cupola race ring, a cam attached to the roller and two switches. The roller is recessed into a notch in the cupola race ring when the cupola is turned to the 0 o'clock position relative to the turret. When the cupola is turned to the right, the motion of the cupola race ring dislodges the roller from the notch and causes the roller to be deflected to the left by friction. The cam attached to the roller also rotates left, causing it to touch the switch on the right (see diagram on the top right, below). The right switch triggers the turret rotation motor to turn the turret to the right until the roller returns to the notch, which would mean that the gun is now facing the same direction as the commander's cupola. The same mechanism is repeated in reverse when the cupola turns to the left. Since the direction sensor is composed of two switches which can only be either on or off, the command to initiate turret rotation is binary. This means that the turret is either turning, or it is not. For that reason, the turret always rotates at maximum speed when the target designation system is activated.<br />
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The binary system also does not allow the commander to precisely lay the gun on target, because precision gun laying is done at the minimum turret rotation speed, which would be 0.07 degrees per second in the case of the T-55. Potentiometers would be needed in order to have a variable speed of turret rotation. However, as mentioned before, small corrections made by rotating the cupola slightly will not cause the turret to jerk onto the new aiming point, even though turret traverse is done at maximum speed by default. This is because the somewhat underpowered traverse motor will need time to accelerate the turret to its maximum speed. There is no vertical deflection sensor attached to the TPKU-2B periscope, so it is not possible for the commander to raise the cannon onto the target from his station.<br />
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<h3>
<span style="font-size: large;"><br />TKN-1, TKN-1S</span></h3>
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The TKN-1 periscope was a monocular night vision surveillance device, and it was the first serially produced device of its kind to be used in the Soviet Army. As the TPK-1 and TPKU-2B periscopes lacked any provisions for effective nighttime use, it was necessary to swap it out for the TKN-1 before commencing night operations. The TKN-1 was introduced in 1954, and was used on the T-54A, T-54B, and later on in the T-55 as the TKN-1S.<br />
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TKN-1 has a fixed 2.75x magnification. This is insufficient for long range observation, but due to the short range provided by the TKN-1. The angular field of vision is 10 degrees. TKN-1 fits in the same slot as the TPKU-2B. Older model T-54s can also use TKN-1, but only if they have been modernized to include the BT-2-26 power supply system.<br />
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The TKN-1 required a source of near infrared light for illumination. This is provided by an OU-3 infrared spotlight that is directed in elevation by a mechanical rod linked to the TKN-1. When the periscope is adjusted to look up and down, the spotlight is rotated around its hinge to follow the commander's line of sight.<br />
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The infrared light from the spotlight illuminates the target, and the reflected light entering the objective lens of the periscope is then amplified by an image intensifier tube operating on 17 kV. The power cable connecting the periscope to the tank's electrical system can be seen on the left side of the periscope, as seen in the photos below (Photo credit to ancientpieces from ebay). The power cable supplies power to the transformer housed in the box on top of the eyepiece, and another cable runs from the transformer to the image intensifier installed inside the optic.<br />
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Using the TKN-1 with the illumination from the OU-3 will enable the commander to identify tank-type targets at a distance of only 250-300 meters. Due to the short viewing distance, the TKN-1 is generally only suitable for spotting enemy tanks that are also using active infrared illumination, for following the fall of tracers, for observing the impact of shots and for spotting the muzzle flash of enemy tanks. The view through the eyepiece of the TKN-1S is shown in the two photos below (image credit to <a href="http://www.gaz69.ru/ipb/topic/124887-%D0%B1%D1%80%D0%B4%D0%BC-2/?page=5">kmshik from the GAZ 69 forums</a>).<br />
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Like the TPKU-2B, the TKN-1 can be used to designate targets by pressing the left thumb button. On the right handgrip is a thumb button to activate the OU-3 infrared searchlight on the cupola. It is not only possible for the sight to be turned to the active infrared imaging mode without turning on the searchlight, it is highly recommended. If enemy tanks have infrared searchlights as well, then the commander will be able to spot them easily without needing to turn on his own, thus remaining hidden. Use of infrared illumination is usually only tactically viable with good coordination and fire control, or when enemy tanks have absolutely no night vision equipment at all.<br />
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<h3>
<span style="font-size: large;">GUNNER'S STATION</span></h3>
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The T-54 gunner sat directly in front of the commander. The gunner's seat was mounted to a frame bolted to the turret wall to the left of the gun cradle and he was provided with a foot rest. His seat could be folded up and to the right and locked flush against the recoil guard of the D-10T gun to permit freer access to the hull, particularly if the gunner wants to crawl out through the escape hatch behind the driver's seat.<br />
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The gunner could determine the orientation of the turret in azimuth by referring to an azimuth ring marked on the turret ring. This was quite typical for many tanks of that era, although some already had more sophisticated clock-type azimuth indicator mechanisms that offered higher measuring precision.<br />
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In all T-54 models up to the T-54A, the gunner was provided with a single MK-4 periscope for general surveillance. It was installed in the turret roof and was positioned to the left of the telescopic primary sight as shown in the photo above. As mentioned before, the MK-4 has a rear view feature, can be rotated independently, and can be elevated by 18 degrees and depressed by -12 degrees. For T-54 gunners, the main benefit of having the MK-4 was the fact that it had a fixed handle and could be elevated and depressed independently of the turret, so when the tank moved over rough ground, the gunner could grasp the handle of the MK-4 firmly and press his forehead against the brow pad to keep a relatively stable view of the terrain. Keeping in mind that early T-54 models lacked a gun stabilizer, this provided the gunner with the ability to continue contributing to the surveillance capabilities of the tank to some degree while most other tanks did not.<br />
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However, the independent rotation and the rear view capability of the MK-4 were not useful for the gunner because of the location of the periscope. The commander's cupola obstructed the gunner's view to the rear, the telescopic primary sight made it difficult for the gunner to look to the left, and the turret wall itself made it difficult to look to the right. As such, the gunner's field of view was not as good as the design of the MK-4 itself implied.<br />
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Nevertheless, the MK-4 gave the gunner unusually good situational awareness compared to many other tanks, but in practice, it was somewhat flawed. After numerous field exercises were conducted by units equipped with the T-54 in the late 40's and early 1950's, it was found out that the MK-4 could not be used for too long when the tank was driving over rough ground as the pitching of the tank could give the gunner motion sickness. It was far more profitable to focus on the operating the main sight instead and leave the MK-4 be until it was needed, like when the tank enters a turret defilade position. The gunner would then use the periscope to observe targets without needing the turret to be exposed and without needing to turn the turret, since the MK-4 could rotate independently.<br />
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On the T-54B model, the MK .4 was replaced by the TPN-1 night vision sight, so its role was taken over by a single fixed forward-facing periscope installed above the TSh2-22 primary sight. This configuration was kept in the T-55 and T-55A. As a result of the loss in the ability to independently rotate the periscope, the gunner's vision deteriorated slightly. However, the T-54A and T-54B already featured gun stabilizers so the gunner had a stable view of the battlefield through his primary sight when the tank was in motion, so the gunner's ability to scan for targets did not decline but instead increased considerably, and the essential ability to scan for targets when in a turret defilade position was maintained. Overall, the gunner was well-equipped for his duties and the T-54 must be considered excellent in this regard.<br />
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Laying the gun in elevation was done using a spirit level affixed next to the gun, and laying the gun in the horizontal plane was facilitated by a turret azimuth indicator, as seen below. The indicator works like a clock with two hands. The indicator can be seen next to the manual turret traverse handwheel in T-54 models beginning from the T-54A (1954).<br />
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The azimuth indicator measures the orientation of the turret according to the Soviet mil definition where a full circle is divided into 6,000 mils and the azimuth reading is divided into tens and hundreds with the 3,000 mil position (30-00) being the 12 o'clock position. For example, if the turret is oriented 180 mils to the left, it is in the 28-20 position, and if the turret is oriented 340 mils to the right, then it is in the 33-40 position. The 00-00 and 60-00 positions are equivalent.<br />
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The ventilation porthole in the commander's cupola allows a panoramic periscope for indirect fire to be installed.<br />
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<h3>
<span style="font-size: large;"><br />TSh-20</span></h3>
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The TSh-20 was an articulated telescopic sight. Most telescopic sights from the WWII era including the TMFD-7 and TOD sights of the T-34 were fixed to the cannon so that if the cannon elevated, the telescope went up and down along with it. This meant that the eyepiece would never be in the same spot as the gunner fiddled around trying to get a firing solution for his target. In the TSh-20, the telescopic aperture is joined to the telescope body with a hinge, optically connected by cleverly placed mirrors. With an articulated telescopic sight, the eyepiece and the main telescope body could stay fixed while only the aperture moved. This eliminated the problem of gunner fatigue and improved firing accuracy, as the gunner will always maintain optimum eye relief. This arrangement was first used in the Soviet weapons industry in the TSh-16, which was installed in the T-34-85.<br />
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The T-34's PT-4-7 sight (below, left) featured a similar system of range adjustment. The horizontal line can be moved while the vertical line remains static, unless lead is applied. The intersection point between the two lines forms the crosshair. As the horizontal line is moved down the range scales to the appropriate distance to the target for a given ammunition type, the crosshair is moved down by the same amount.<br />
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The newer TSh-16 (above, right) offered an improved viewfinder arrangement. The viewfinders on the TSh series of telescopic sights generally have a better layout as all of the "clutter" is concentrated in the top half of the sight picture where there is nothing but sky. This means that the gunner's view of everything from the ground up to the horizon is perfect, but his view of the sky is not, which is obviously not important. Insufficient magnification power of the TSh-16 aside (only 2.5x), the design of the viewfinder was considered sound, so it was carried over to the TSh-20.<br />
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One excellent feature of the TSh-20 sight is the large rubber brow pad. It is large enough to fit around the gunner's forehead and temples - even if he is wearing his helmet - and stiff enough to hold his head in place, so that even if the gunner's body is rocking about, his head will be held firm and his eyes can be glued onto the eyepiece. This is a traditional feature of almost all gun sights on Soviet and Russian tanks, including later sights present on the T-54, which we will discuss later, all the way up to the Sosna-U on the latest T-90MS.<br />
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TSh-20 offers a fixed 4x magnification with a 16° field of view. This is horrible by modern standards, but <i>arguably</i> within acceptable limits for a 1945 product. For example, the M71C for the Pershing had a fixed 5x magnification with a 13° field of view. The extra wide vision arc offered by the TSh-20 enabled the gunner to survey for targets at short to medium distances more easily, but severely handicapped the long range viability of the tank. Whether high magnification was necessary during that particular stage of global tank evolution is not too clear. U.S research showed that the average tank duel in the Korean war occurred at an average distance of only 450 yards (411 m) due to the abundance of natural obstacles and obscurants. In addition to that, Soviet experience and research during WWII showed that almost all tank duels fought by Red Army tanks occurred under 1 kilometer in distance. With heavy, hours-long artillery barrages usually preceding breakthrough assaults, smoke and dust in the air often reduced tank engagement distances to just a few hundred meters, with many tanks only meeting each other at "knife fight" distances (also making head-on collisions, accidental and non-accidental, surprisingly common).<br />
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If the T-54 obr. 1947 came early enough to fight in WWII, or if its sequel was conducted in much the same way, then perhaps TSh-20 is good enough. However, it was impossible not to recognize that tank warfare was evolving and that the requirements for sight magnification had become more demanding.<br />
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<h3>
<span style="font-size: large;">TSh2-22, TSh2B-22</span></h3>
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<a href="https://4.bp.blogspot.com/-sGXEmIvl_SA/WFEtoGEwS4I/AAAAAAAAH2Y/_RvZlA0yWEICrmg5QbwJr4J3L9cvzWg1wCLcB/s1600/tsh2-22.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-sGXEmIvl_SA/WFEtoGEwS4I/AAAAAAAAH2Y/_RvZlA0yWEICrmg5QbwJr4J3L9cvzWg1wCLcB/s1600/tsh2-22.gif" /></a></div>
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TSh2-22 was introduced with the T-54 obr. 1949. Continual field trials of the T-54 obr. 1947 throughout 1948 had shown that one of the chief complaints was the limited magnification of the TSh-20. Consequently, TSh2-22 features variable magnification settings of 3.5x and 7x. By implementing variable magnification in the gun sight, the gunner could enjoy both wide vision and high power magnification, though obviously not at the same time. For an even wider field of view, the MK-4 rotating periscope would more than suffice. The TSh2B-22 sight was a modification of the basic model with new design features that gave it compatibility with the STP-1 gun stabilizer of the T-54A respectively.<br />
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TSh2-22 is directly comparable to the Centurion's No.1 sight which had a variable magnification of 1x or 6x and the M47 Patton's M20 sight, which also had a variable magnification of 1x or 6x. The M20 sight was shared by the M48 as well.<br />
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There are multiple variations of the TSh2-22 viewfinder. An early versions (a) has four scales; three for main gun rounds and one for the coaxial machine gun. Listed from left to right, they are: HE-Frag with a full charge (53-UOF-412), APBC (53-UBR-412B), HE with a reduced charge (53-UOF-412U) and finally, the coaxial machine gun. A late version (b) has just two scales for main gun ammunition: HE with a full charge and APBC, plus one for the coaxial machine gun.<br />
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Moreover, the later version included additional horizontal lead markings and a stadia rangefinder scale to allow the gunner to quickly measure the range in case the commander is preoccupied or if the tank is running in a degraded state with a 3-man crew. It allows the gunner to switch from battlesight gunnery to precision gunnery, which is necessary to ensure a reasonable probability of hit on targets that are beyond the point blank range of the tank's 100mm armour-piercing ammunition. The stadia rangefinder markings start at 1,220 meters, which is the point blank range for the BR-412B and BR-412D rounds against a target with a height of 2.7 meters.<div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ttFGnuqD30k/Xrwqg7W13eI/AAAAAAAAQsc/_v9_fS37j708I8hmdBiT6ToEvRGXgSGigCK4BGAsYHg/stadia%2Brange%2Bmeasurements.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="570" data-original-width="1021" height="224" src="https://1.bp.blogspot.com/-ttFGnuqD30k/Xrwqg7W13eI/AAAAAAAAQsc/_v9_fS37j708I8hmdBiT6ToEvRGXgSGigCK4BGAsYHg/w400-h224/stadia%2Brange%2Bmeasurements.png" width="400" /></a></div><div><br /></div><div><br /></div><div>Another difference is the removal of the range markings on the vertical line below the center chevron. These range markings are meant to be convenient aiming points for common combat distances using APBC shells to aid the gunner if he decides to use the bracketing gunnery technique to engage a target. It is reasonable to assume that with the addition of a stadia rangefinder scale, it became superfluous as it would be slower, less accurate, and more wasteful of ammunition compared to stadia rangefinding. At least, this was the case in other contemporary sights. Multiple viewfinder configurations with various combinations of markings existed and small changes were implemented over time, making it rather difficult to classify the TSh2-22 this way. The markings were etched on a special viewfinder glass disc that could be removed relatively easily and replaced with updated markings when new ammunition became available.<br />
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<a href="https://2.bp.blogspot.com/-bLsI0gCT_pI/XGbxgfiI5bI/AAAAAAAANZc/sNGUvbAZABIxezzyUPr9pEqarmj1KN72QCLcBGAs/s1600/sight.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="739" data-original-width="775" height="381" src="https://2.bp.blogspot.com/-bLsI0gCT_pI/XGbxgfiI5bI/AAAAAAAANZc/sNGUvbAZABIxezzyUPr9pEqarmj1KN72QCLcBGAs/s400/sight.jpg" width="400" /></a><a href="https://4.bp.blogspot.com/-BGopPJTA_Nk/XGbvLWLBlHI/AAAAAAAANZU/OjyRaaQg1jQp2XeQv-2ZyYrhn3-J6JzmwCLcBGAs/s1600/markings.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="538" data-original-width="614" height="350" src="https://4.bp.blogspot.com/-BGopPJTA_Nk/XGbvLWLBlHI/AAAAAAAANZU/OjyRaaQg1jQp2XeQv-2ZyYrhn3-J6JzmwCLcBGAs/s400/markings.jpg" width="400" /></a></div>
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The sight is ordinarily zeroed to a distance of 1,200 meters or more. The drawing below depicts a method of zeroing the sight in field conditions by using a landmark.<br />
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<a href="https://1.bp.blogspot.com/-dmJ5OYNpF9o/WFFaKMp-1dI/AAAAAAAAH4I/W2ccDIO_TMIVLJ3gzYz-1lBaAvabcO0qQCLcB/s1600/tsh.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-dmJ5OYNpF9o/WFFaKMp-1dI/AAAAAAAAH4I/W2ccDIO_TMIVLJ3gzYz-1lBaAvabcO0qQCLcB/s1600/tsh.gif" /></a></div>
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By displaying all of the range scales in the viewfinder and not on an external dial, the gunner can conduct the entire target acquisition procedure without removing himself from the sight and losing visual contact with the target. This problem was solved in the Centurion in a rather creative way; a mirror was placed in front of the gunner's left eye at such an angle that the gunner could see the range drum with his left eye as he adjusted it, and then - by just moving his eyes - return to the sight and resume targeting.<br />
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To use the rangefinder, the gunner only needs to bracket the target tank between the stadia lines and read the figure corresponding to the height of the target, and then turn the range adjustment dial until the horizontal line is on the correct range scale mark for the desired ammunition type. It is also possible for the gunner to use the multitude of chevrons and lines that form the reticle of the sight viewfinder and combine them with his own memorized information of tank widths and lengths to obtain a range estimate.<br />
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The sight aperture port cut into the turret was protected by a pane of glass. This was merely a thin barrier to prevent external debris and water from entering the turret through the aperture. It had no ballistic protection whatsoever.<br />
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<a href="https://1.bp.blogspot.com/-WHgrkI5gEAA/XZYow0aaY4I/AAAAAAAAPRw/FtwuI1v-EEg_nVVuhB9F63cGhlDD-w8GACLcBGAsYHQ/s1600/aperture%2Bport.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="685" data-original-width="1024" height="267" src="https://1.bp.blogspot.com/-WHgrkI5gEAA/XZYow0aaY4I/AAAAAAAAPRw/FtwuI1v-EEg_nVVuhB9F63cGhlDD-w8GACLcBGAsYHQ/s400/aperture%2Bport.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-g5B5gaJLvig/XZYiHes_w1I/AAAAAAAAPRo/9Ig3_wQ9jxQyXwKHu6EWx_DG3oo1y2PYACLcBGAsYHQ/s1600/glass%2Bcover.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="333" data-original-width="250" height="320" src="https://1.bp.blogspot.com/-g5B5gaJLvig/XZYiHes_w1I/AAAAAAAAPRo/9Ig3_wQ9jxQyXwKHu6EWx_DG3oo1y2PYACLcBGAsYHQ/s320/glass%2Bcover.gif" width="240" /></a></div>
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While Soviet-built tanks had a stadium-shaped glass cover that was affixed to a raised lip that is shaped accordingly, Polish-built T-54 tanks used an oval-shaped glass cover. This can be used to identify the origin of the tank regardless of its markings.<br />
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<h3>
<span style="font-size: large;">TSh2B-32</span></h3>
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<a href="https://1.bp.blogspot.com/-CS8xmaLILDk/XVHN--y8l_I/AAAAAAAAO4o/APNzmHUgbPIhYK51bHhCQwiNIMPXpFUJwCLcBGAs/s1600/t-54b%2Binterior.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="246" data-original-width="343" src="https://1.bp.blogspot.com/-CS8xmaLILDk/XVHN--y8l_I/AAAAAAAAO4o/APNzmHUgbPIhYK51bHhCQwiNIMPXpFUJwCLcBGAs/s1600/t-54b%2Binterior.jpg" /></a></div>
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TSh2B-32 was first implemented in the T-54B. The sight was practically identical to the previous articulated telescopic sights with the main difference being that it was designed to connect to the new STP-2 gun stabilizer. This sight continued to be used in the T-55 series as the fire control system did not change. The configuration of the viewfinder markings follows the latest variant of the TSh2B-22. As shown in the photo below, there were range scales for HE-Frag with a full charge, APCBC, HEAT and the coaxial machine gun. Additionally, the markings for HE ammunition with a reduced charge were permanently removed as this type of ammunition had become obsolete.<br />
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<h3>
<span style="font-size: large;">TSh2B-32P</span></h3>
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In January 1965, the TSh2B-32P was installed in the T-54B and T-55. The only difference between it and the TSh2B-32 is the new range scale for 3UBM6 APDS ammunition. The "P" in "TSh2B-32P" stands for "subcaliber". Tanks that had the TSh2B-32 equipped were modified by swapping out the viewfinder glass disc with a new disc with the additional markings to transform them into the TSh2B-32P.<br />
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<a href="https://1.bp.blogspot.com/-crhs6AWc5aY/XaWY-47WICI/AAAAAAAAPX8/3EZGj9D53VkBHMZXTK59YecTiUaNM-LjwCLcBGAsYHQ/s1600/tsh2b-32p.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1533" data-original-width="1453" height="400" src="https://1.bp.blogspot.com/-crhs6AWc5aY/XaWY-47WICI/AAAAAAAAPX8/3EZGj9D53VkBHMZXTK59YecTiUaNM-LjwCLcBGAsYHQ/s400/tsh2b-32p.png" width="378" /></a></div>
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<a href="https://2.bp.blogspot.com/-0OEk5gu8Yd4/WFEVMKMX1-I/AAAAAAAAH2A/48sK0zBRobgw1fUBZ20IDKHoqUycZaDFwCLcB/s1600/tsh2b-32p.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://2.bp.blogspot.com/-0OEk5gu8Yd4/WFEVMKMX1-I/AAAAAAAAH2A/48sK0zBRobgw1fUBZ20IDKHoqUycZaDFwCLcB/s400/tsh2b-32p.png" width="315" /></a><a href="https://3.bp.blogspot.com/-l-5acWF9lzk/V4x1KzHIGMI/AAAAAAAAHHw/vAJRKzHLtgIdiOP6q_EEdRzS00dJ5D8YwCLcB/s1600/t-54%2Bsight.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://3.bp.blogspot.com/-l-5acWF9lzk/V4x1KzHIGMI/AAAAAAAAHHw/vAJRKzHLtgIdiOP6q_EEdRzS00dJ5D8YwCLcB/s400/t-54%2Bsight.jpg" width="382" /></a></div>
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Besides the range scale for subcaliber rounds, there are no other notable differences. It is worth noting that the scale for subcaliber rounds can be used for both APDS (3BM8) rounds and APFSDS (3BM19, 3BM20, 3BM25) rounds due to the very similar ballistic trajectories of both types of ammunition and the low precision of this type of range scale. For instance, the 3BM20 APFSDS shell had a point blank range of 1,690 meters against a target with a height of two meters and a point blank range of 2,040 meters against a target with a height of three meters while the 3BM8 APDS shell had a point blank range of 1,680 meters against a target with a height of two meters and a point blank range of 2,020 meters against a target with a height of three meters. In realistic conditions, this small difference is practically imperceptible.<br />
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<a href="https://2.bp.blogspot.com/-0RHstfTR0Ag/WA8R1v63LHI/AAAAAAAAHcQ/z4WX9YYhlO8pEnVGDFB6bUGFJQQSe7EvgCLcB/s1600/tshsm%2Bsight.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="359" src="https://2.bp.blogspot.com/-0RHstfTR0Ag/WA8R1v63LHI/AAAAAAAAHcQ/z4WX9YYhlO8pEnVGDFB6bUGFJQQSe7EvgCLcB/s640/tshsm%2Bsight.png" width="640" /></a></div>
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<h3>
<span style="font-size: large;">TPN-1-22-11</span></h3>
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<a href="https://1.bp.blogspot.com/-H4E5if4gok0/WFz6tW6DDTI/AAAAAAAAH8c/t6kX4uQGWkUW1ILUOQSwAvwzIrbiql0twCLcB/s1600/t-55%2Bgunners%2Bstation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="425" src="https://1.bp.blogspot.com/-H4E5if4gok0/WFz6tW6DDTI/AAAAAAAAH8c/t6kX4uQGWkUW1ILUOQSwAvwzIrbiql0twCLcB/s640/t-55%2Bgunners%2Bstation.png" width="640" /></a></div>
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In the year 1957, the T-54 entered its tenth year of formal service in the Soviet Army and also the tenth year of its continuous evolution, becoming the T-54B. The T-54B became capable of night fighting with the installation of the TPN-1-22-11 active infrared imaging sight and the accompanying L-2 "Luna" infrared spotlight. Although the performance of the night vision system is far from impressive by modern standards, it was a modern product for its time and the inclusion of a night vision sighting system in the T-54B together with a night vision TKN-1 optic for the commander gave it a distinct edge over the contemporary M48A2 which lacked any form of night vision sighting equipment whatsoever. Only the M60A1 from 1962 was equipped with a night vision sight (M32) and a night vision optic for the commander (M36). The armoured hood for the TPN-1 night sight on the T-54B can be seen in the photo below in front of the commander's cupola.<br />
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<a href="https://1.bp.blogspot.com/-R_vkqYOuAoc/XVGHJ9oPqFI/AAAAAAAAO3c/-E6ibmCGUc0FlsHkINwdm6eqdtnVX2r9gCLcBGAs/s1600/t-54b%2Bcupola.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="390" data-original-width="657" height="378" src="https://1.bp.blogspot.com/-R_vkqYOuAoc/XVGHJ9oPqFI/AAAAAAAAO3c/-E6ibmCGUc0FlsHkINwdm6eqdtnVX2r9gCLcBGAs/s640/t-54b%2Bcupola.jpg" width="640" /></a></div>
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TPN-1-22-11 can operate in either the active infrared imaging mode or the passive light intensification mode. In the active infrared imaging mode, the infrared light supplied by the L-2 "Luna" spotlight mounted coaxially to the main gun is visible through the sight, allowing the gunner to identify a tank-type target at a maximum distance of 750-800 meters. This was quite good for night vision equipment from the 50's. The L-2 "Luna" spotlight uses an incandescent bulb and consumes only 200 W, which is quite weak for a spotlight. In the passive mode, the sight employs a 1st Generation light intensifier tube to amplify ambient light, providing a nominal maximum identification distance of 400 meters for a tank-type target under lighting conditions of no less than 0.005 lux. The sight has an adjustable sensitivity to allow the gunner to obtain the best image under different lighting conditions.<br />
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<a href="https://3.bp.blogspot.com/-va43PaLlGN8/XGbuRiE9DlI/AAAAAAAANY8/mD1AbRcbrrk_8Sz5PQeVcITL2ZudHm78ACLcBGAs/s1600/tpn-1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="761" data-original-width="1019" height="297" src="https://3.bp.blogspot.com/-va43PaLlGN8/XGbuRiE9DlI/AAAAAAAANY8/mD1AbRcbrrk_8Sz5PQeVcITL2ZudHm78ACLcBGAs/s400/tpn-1.png" width="400" /></a></div>
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TPN-1-22-11 has fixed 5.5x magnification, and a narrow field of view of 6 degrees. The magnification is quite reasonable for a night vision device, as the IR sight for the Chieftain only had a 3x magnification. The viewfinder is extremely simple, as you can see below. The tip of the chevron is sighted for BR-412D AP rounds for a distance of 200 m, going down to 400 m at the upper tip of the vertical reticle line below the chevron. A more comprehensive adjustment system was not included as the short range of the TPN-1-22-11 night vision system limited engagement distances to 800 meters or less anyway.<br />
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<a href="https://2.bp.blogspot.com/-71hUJnSZ60M/WFEzZ1MAQoI/AAAAAAAAH20/hlxF8t8kYhIb5HI9P-byZsIX4vX4KuiyACLcB/s1600/tpn.gif" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="314" src="https://2.bp.blogspot.com/-71hUJnSZ60M/WFEzZ1MAQoI/AAAAAAAAH20/hlxF8t8kYhIb5HI9P-byZsIX4vX4KuiyACLcB/s320/tpn.gif" width="320" /></a></div>
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The TPN-1-22-11 has an internal lightbulb to facilitate aiming at night. It is either on or off without the option of dimming, but it can be turned on in either the day mode or the night mode as the gunner wishes. It is preferable to remain in the day mode with an illuminated reticle when operating during sunset or twilight hours.<br />
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TPN-1-22-11 is similar to the telescopic primary sight in that it is not independently stabilized. It is only connected to the main gun by a mechanical linkage as shown in the drawing below. Disregarding its night vision capabilities, the sight is mechanically and optically quite simple.<br />
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<a href="https://4.bp.blogspot.com/-yIrhNUnVVys/WFE1R155k1I/AAAAAAAAH3A/EAtHXkYzN7MxBK_nXqCx-Wd2Gms_N8ThQCLcB/s1600/tpn-1-21-11.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-yIrhNUnVVys/WFE1R155k1I/AAAAAAAAH3A/EAtHXkYzN7MxBK_nXqCx-Wd2Gms_N8ThQCLcB/s1600/tpn-1-21-11.gif" /></a></div>
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During the late 50's, nearly all T-54 obr. 1949 tanks (built and issued from 1949 to 1951) and T-54 obr. 1951 tanks (built and issued from 1952 to 1954) underwent a modernization program to improve its combat capabilities to the level of the T-54B, which was the latest iteration at the time. The technical details for the modernization of older tanks - excluding the troublesome obr. 1947 model - to the standard of the T-54B model was prepared simultaneously with the development of the T-54B itself, thus ensuring that a large part of the Soviet Army's T-54 fleet would be kept up to date at the highest available level of technology. One of the upgrades was the addition of night fighting capabilities via the installation of the TPN-1-22-11 night vision sight and the associated equipment, including the L-2 "Luna" spotlight and a new power supply system to handle the new equipment. The T-54-2 in the two photos below is an example of a tank modernized to T-54B standards. Note the counterweight at the muzzle of the cannon. This will be examined further in the article.<br />
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<a href="https://1.bp.blogspot.com/-ZfHGVE7dKLw/W2uUJb_5gAI/AAAAAAAAMK0/9rI2I-P9A1QM1-L1DhHPOwiA6t8MykaNACLcBGAs/s1600/t-54-2%2Bmodernized.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="530" data-original-width="800" height="265" src="https://1.bp.blogspot.com/-ZfHGVE7dKLw/W2uUJb_5gAI/AAAAAAAAMK0/9rI2I-P9A1QM1-L1DhHPOwiA6t8MykaNACLcBGAs/s400/t-54-2%2Bmodernized.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-cUl8_XwH1Rk/W2uUI0Ais4I/AAAAAAAAMKw/tqqLz-aXhTc_bYr3hjOBTXiDI8iXqThnACLcBGAs/s1600/t-54-2%2Bluna.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="530" data-original-width="800" height="265" src="https://3.bp.blogspot.com/-cUl8_XwH1Rk/W2uUI0Ais4I/AAAAAAAAMKw/tqqLz-aXhTc_bYr3hjOBTXiDI8iXqThnACLcBGAs/s400/t-54-2%2Bluna.jpg" width="400" /></a></div>
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The addition of a night fighting capability to the vast majority of the T-54 tanks in the Soviet Army represented a significant tactical advantage, considering that the M60A1 was only being produced in relatively small numbers during the early 60's and the M48A2 modernization in 1956 did not grant the U.S Army's large fleet of M48 Patton tanks a night fighting capability. Even when the M48 gained a xenon spotlight and the M32 periscope in 1963 as part of the M48A3 upgrade, the T-54 retained an advantage because its night sight had a passive image intensifier mode that made it possible for the gunner to engage targets without turning on its infrared spotlight, whereas the enemy M48A3 and M60A1 tanks were forced to rely entirely on active IR or white light illumination.<br />
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The night vision equipment was tested in a British/Israeli assessment of the T-55, among other things. The full report is available in the <a href="https://tankandafvnews.com/wo-194-2946-a-technical-assessment-of-the-t-55/">Tanks and AFV News site</a>. The relevant page of the report can be viewed here (<a href="https://tankandafvnews.com/wo-194-2946-a-technical-assessment-of-the-t-55/attachment/059/">link</a>). According to the test, TPN-1-22-11 allowed the gunner to see:<br />
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<table border="1" cellpadding="4" cellspacing="0" style="text-align: left;">
<tbody>
<tr>
<td>Target
</td>
<td>Distance (m)
</td>
</tr>
<tr>
<td>Man
</td>
<td>200
</td></tr>
<tr>
<td>Topless Jeep
</td>
<td>400
</td>
</tr>
<tr>
<td>Chieftain (from behind)
</td>
<td>400
</td>
</tr>
</tbody></table>
<div style="text-align: left;">
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<div style="text-align: left;">
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However, the report notes that the equipment was "suspect in nature" and that too much significance should not be attached to the results. This is possible evidence that the night vision equipment was downgraded for export. It is also possible that the sight was somehow damaged or defective. The problem does not lie in insufficient illumination (200 W spotlight), as the TPN-1-22-11 was also tested using the Chieftain's 2 kW infrared spotlight, but this only marginally improved the maximum identification distance to 500 meters when used to identify a Chieftain target tank.<br />
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Another explanation is that the TPN-1-22-11 has lackluster performance simply because it is older than whatever the Chieftain uses by almost a decade, but then, why did the report mention that the equipment was "suspect in nature"?<br />
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<h3>
<span style="font-size: large;"><br />Volna Fire Control System</span></h3>
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The T-55AM deep modernization programme of 1983 involved a total overhaul of the fire control system as well as a base overhaul of the engine and other essential components.<br />
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<a href="https://3.bp.blogspot.com/-6C-CBjt_TjQ/WDARJR9U_QI/AAAAAAAAHog/HKXbYkcuiXESd6z5LnJSoVJY7XLy72ARQCLcB/s1600/229_29.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://3.bp.blogspot.com/-6C-CBjt_TjQ/WDARJR9U_QI/AAAAAAAAHog/HKXbYkcuiXESd6z5LnJSoVJY7XLy72ARQCLcB/s640/229_29.jpg" width="640" /></a></div>
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<h3>
<span style="font-size: large;">TShSM-32PV</span></h3>
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<a href="https://2.bp.blogspot.com/-P_DRbbfYM3o/WFz54jnPNVI/AAAAAAAAH8Q/XHI1GYd4V_cV2IMiMhcwC9XJ00uXkfwCACLcB/s1600/tshcm32pv_950.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="468" src="https://2.bp.blogspot.com/-P_DRbbfYM3o/WFz54jnPNVI/AAAAAAAAH8Q/XHI1GYd4V_cV2IMiMhcwC9XJ00uXkfwCACLcB/s640/tshcm32pv_950.jpg" width="640" /></a></div>
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Introduced as a complement to the Volna fire control system, TShSM-32PV is substantially more advanced than the previous telescopic sights used in the T-54 series. TShSM-32PV features a viewfinder that is very similar to the TPD-K1 in layout, especially with the removal of the range scales and its substitution with a more space efficient dial-type range indicator at the top.<br />
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<a href="https://1.bp.blogspot.com/-n5CtPmuSNaU/WFzoYrQm6BI/AAAAAAAAH8A/Q_bfJ1HZ7kgLq85X2q__slZHBFjRA_e9wCLcB/s1600/tshsm-32pv.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-n5CtPmuSNaU/WFzoYrQm6BI/AAAAAAAAH8A/Q_bfJ1HZ7kgLq85X2q__slZHBFjRA_e9wCLcB/s1600/tshsm-32pv.png" /></a></div>
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The magnification of TShSM-32PV is practically identical to its predecessors; either 3.5x power magnification or 6.9x. The sight offers a field of view of 18 degrees in the low magnification setting and 9 degrees in the high magnification setting. The sight is independently stabilized in the vertical plane with a maximum accuracy of 0.3 mils, which is quite good. At 1000 m, the sight will have a maximum deviation of 0.3 meters from the point of aim.<br />
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Now that the sight is linked to an analogue ballistic computer, additional features had to be implemented in order to add more functionality. An LED tab at the bottom of the viewfinder displays the ammunition type and the range. The range dial at the top of the viewfinder spins (different dial rings spin at different rates via a differential mechanism) to display the range equivalent for different types of ammunition. In the right hand side drawing of the viewfinder above, you can see that the number "140" displayed in the range display tab, and the range dial for BK (HEAT ammunition) set to "14". This means that the target is 1400 meters away, and HEAT is selected. Switching the ammunition type will reset the range dial accordingly.<br />
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The same reticle design was retained in the TShSM-32PV, as was the method of gun laying. Once the range was automatically inputted into the sight via the BV-55 ballistic computer, the reticle drops a certain amount. The gunner must then manually raise the reticle and lay it on target. This is not as convenient as having the cannon raise automatically while the reticle remains static, as was the usual in digitized Western FCS appearing in the late 70's and early 80's. <br />
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<h3>
<span style="font-size: large;">1K13-2</span></h3>
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://2.bp.blogspot.com/-UbvQ56FDHlo/WFz9P78S5dI/AAAAAAAAH8o/FajQWtCp4DMfDg6MBR65rOF5rDVAYyaawCLcB/s1600/1k13.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://2.bp.blogspot.com/-UbvQ56FDHlo/WFz9P78S5dI/AAAAAAAAH8o/FajQWtCp4DMfDg6MBR65rOF5rDVAYyaawCLcB/s640/1k13.jpg" width="512" /></a></div>
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By outfitting the T-55 with the 1K13-2 sight, the tank instantly gained a missile-firing capability. 1K13-2 is significantly TPN-1-22-11 in target engagements capabilities; With a fixed 8x magnification in the daytime channel and 5.5x magnification in the nighttime channel, its effectiveness as a long range daytime observation device rose slightly above the gunner's main telescopic sight, but because 1K13-2 is not integrated with the Volna FCS, its usefulness for long range fire is limited somewhat.<br />
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The sight has a field of view of 5 degrees in the daylight setting or 6°4' in the nighttime setting. It is independently stabilized in the vertical plane, with +20° elevation -7° depression.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-nz4qf5Tf4Rw/VTF7d7JEdII/AAAAAAAAB14/qOKUI-WU3_s/s1600/1k13.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="482" src="https://4.bp.blogspot.com/-nz4qf5Tf4Rw/VTF7d7JEdII/AAAAAAAAB14/qOKUI-WU3_s/s1600/1k13.jpeg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Daytime mode</td></tr>
</tbody></table>
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The sight's active infrared imaging system is slightly improved over the TPN-1-22-11. Now, the viewing range in the active mode is increased to 1200 m, though the light intensification unit has not been improved, meaning that the 1K13-2 sight still has a viewing distance of only 800 m under ambient lighting conditions of no less than 0.005 lux. The identification distance and image clarity improves with increasingly brighter lighting conditions, but excessive brightness can oversaturate the image, and overwhelming brightness can overload and possibly damage the sight.<br />
<div>
<br /></div>
<div>
In accordance with the extended viewing distance in the active infrared mode, the sight is now equipped to adjust the superelevation of the reticle, just like the telescopic sights described before. This is to enhance firing accuracy at ranges above the reasonable range of distances for battlesighting.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-6gQfcRRylJI/VTYLhu28neI/AAAAAAAAB_k/0tagX-P7Qy0/s1600/1k13-4.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://1.bp.blogspot.com/-6gQfcRRylJI/VTYLhu28neI/AAAAAAAAB_k/0tagX-P7Qy0/s1600/1k13-4.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">1K13-2 viewfinder in the passive light amplification mode, aimed at nothing in particular (Photo credit: Stefan Kotsch)</td></tr>
</tbody></table>
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<h3>
<span style="font-size: large;">POWER TRAVERSE, STABILIZERS</span></h3>
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<a href="https://4.bp.blogspot.com/-QZgVnpm1cH0/WHdLlDWJ3eI/AAAAAAAAIIk/HgI11UmT2eEgyQWxUbWFBKU-ik8mmWC3QCLcB/s1600/FnJHQRx.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="438" src="https://4.bp.blogspot.com/-QZgVnpm1cH0/WHdLlDWJ3eI/AAAAAAAAIIk/HgI11UmT2eEgyQWxUbWFBKU-ik8mmWC3QCLcB/s640/FnJHQRx.jpg" width="640" /></a></div>
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The first model of the T-54 was principally equivalent to late WWII tanks in that it featured powered turret traverse and manual gun elevation, but lacked gun stabilization or a powered gun elevation mechanism. The T-54 obr. 1946 pre-production model and T-54 obr. 1947 both used the EPB-1 electromechanical turret rotation system, also used in the IS-4 heavy tank. Beginning in 1948, it was replaced by the EPB-4 which remained standard until 1954 when it was replaced by the much more advanced stabilized STP-1 system.<br />
<br />On all T-54 models, the main gun has an elevation and depression limit of +18 to -5 degrees respectively. This is the hard limit, as stoppers prevent the gun from moving further. With a stabilizer installed and turned on, the limits may differ.<br />
<br />
<h3>
<span style="font-size: large;">EPB-1</span></h3>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://1.bp.blogspot.com/-Lehd8F6vanI/XZMNF_K70OI/AAAAAAAAPQo/PZi5KYqnP4011ePSbq5h7CIOkT947yYqACLcBGAsYHQ/s1600/t-54%2Bobr%2B1947%2Bgunners%2Bcontrols.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="820" data-original-width="1165" height="281" src="https://1.bp.blogspot.com/-Lehd8F6vanI/XZMNF_K70OI/AAAAAAAAPQo/PZi5KYqnP4011ePSbq5h7CIOkT947yYqACLcBGAsYHQ/s400/t-54%2Bobr%2B1947%2Bgunners%2Bcontrols.png" width="400" /></a></div>
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The EPB-1 system provided powered turret traverse at a variable speed, and unlike older powered traverse systems, it permitted relatively precise gun laying thanks to a sufficiently low minimum traverse speed. For maximum precision, the final gun lay could be carried out using the manual controls. Moreover, unlike the powered turret traverse mechanisms of earlier tanks like the T-34, the turret would not continue to rotate after the cessation of input on the control handle due to inertia, as an electric brake was installed to automatically stop the turret when the control handle is in the neutral position or if the gunner releases his grip on it. The brake will also activate to adjust the speed of the turret when the gunner changes the degree of deflection applied on the control handle.<br />
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<a href="https://2.bp.blogspot.com/-6cP4-tpQecI/WHWksxxY89I/AAAAAAAAIGY/3nlQgyv0SYIZipNueRgRyu6RGzeEUCFIACLcB/s1600/epb-1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-6cP4-tpQecI/WHWksxxY89I/AAAAAAAAIGY/3nlQgyv0SYIZipNueRgRyu6RGzeEUCFIACLcB/s1600/epb-1.jpg" /></a></div>
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Control of turret rotation was done with the KB-3A control unit which took the form of a spade grip with a bakelite paddle. The gunner squeezes the paddle and turns the grip clockwise or counter-clockwise to turn the turret to the right or left respectively. The control unit is essentially a rotary rheostat that registered the angle of deflection of the handle and transmitted a signal to an amplidyne amplifier. The amplidyne amplifier would then generate a high voltage proportional to the angle of deflection of the spade grip to power the turret traverse motor, which would then spin the turret at the desired speed. To switch from powered traverse to manual traverse, the powered traverse drive clutch had to be disengaged and the manual drive clutch had to be engaged.<br />
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<a href="https://1.bp.blogspot.com/-QxqLLMjO_48/WHW1YqZNiAI/AAAAAAAAIG0/7Ds16ntyoMszh7P6b61R-fgzPSEj_0yZACLcB/s1600/kb-4%2Bpowered%2Btraverse%2Bhand%2Bgrip.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="379" src="https://1.bp.blogspot.com/-QxqLLMjO_48/WHW1YqZNiAI/AAAAAAAAIG0/7Ds16ntyoMszh7P6b61R-fgzPSEj_0yZACLcB/s400/kb-4%2Bpowered%2Btraverse%2Bhand%2Bgrip.jpg" width="400" /></a></div>
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The KB-3A control unit is located at midriff level of the gunner, close to the gun elevation drive which is just next to the cannon. The gunner's left hand would be on the traverse control grip and his right hand would adjust the elevation of the cannon. A manual turret traverse handwheel was located on the turret ring next to the power traverse control. The triggers for firing the cannon and the coaxial machine gun were both on the elevation handwheel handle. Overall, the layout of the gunner's controls was quite rational and was ergonomic enough that prolonged use was not fatiguing to the gunner, which cannot be said for the layout of the gunner's controls in some other tanks of the same era. The most major drawback to the system was the lack of powered gun elevation, forcing the gunner to elevate the gun manually via the gun elevation handwheel. Despite the ease of using the manual gun elevation drive, this still meant that gun laying was slower when compared to tanks like the M47 and Centurion Mk. 3, although did not mean that the T-54 was imprecise as manual gun elevation was still the most precise method of gun laying available in any tank at the time.<br />
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The turret could be driven by the MPB-52 electric motor at a minimum speed of 0.1 degrees per second and at a maximum speed of 13 degrees per second. For comparison, the MB-20G electric turret traverse motor of the T-34-85 allowed a maximum traverse speed of 25-30 degrees per second or a minimum speed of 12 degrees per second, with the option of a reduction to 1.5-2.0 degrees per second.<br />
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<h3>
<b>Traverse Speeds under Normal Operation</b></h3>
Minimum Traverse Speed: 0.1 deg/sec<br />
Maximum Traverse Speed: 13 deg/sec<br />
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Unlike a modern electric or hydraulic system, it took some time for the MPB-52 motor to accelerate the turret to its maximum speed.<br />
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<h3>
<span style="font-size: large;">EPB-4</span></h3>
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Beginning in 1948, the T-54 used the improved EPB-4 electromechanical turret traverse system. The EPB-4 improved upon the EPB-1 in several aspects, but worked on the same operating principles and had the same control scheme. Control of the turret was done using the KB-4 control unit which had the same appearance as the KB-3A and was operated in an identical manner.<br />
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<h3>
<b>Traverse Speeds under Normal Operation</b></h3>
Minimum Traverse Speed: 0.1 deg/sec<br />
Maximum Traverse Speed: 13 deg/sec<br />
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The main improvement of the EPB-4 drive was the addition of an electronic link to a deflection sensor on the commander's cupola which allowed the commander to rotate the turret using the target designator button on his TPK-1 periscope. Additionally, the maximum turret rotation speed was increased to 11-12 degrees per second while the minimum speed remained at 0.1 degrees per second. When the commander designates a target using his TPK-1 periscope, the drive motor of the EPB-4 system is overcharged and rotates the turret at an increased speed of 13 degrees per second<br />
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<h3>
<span style="font-size: large;">MANUAL CONTROLS</span></h3>
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The photo below, taken from the <a href="https://www.kwsurplus.com/tank.php">K-W Surplus store</a> website, shows the turret traverse handwheel with its clutch control handle. To turn the turret, the clutch handle must be depressed or the handwheel will not engage with the gearing connected to the toothed turret race ring. This was designed so that when the turret was turned with the powered system, the handwheel would not spin as that could injure the gunner because it would spin quite fast due to the gearing ratio. It is worth noting that this configuration took up more space than in the T-34, because the powered traverse system of the T-34 elegantly incorporated the powered traverse control handle and the manual traverse handle into one mechanism so that the handle was automatically disconnected from the manual traverse mechanism when the gunner switched to the powered traverse mode.<br />
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<a href="https://1.bp.blogspot.com/-0wP-AHjeOOs/XaXMzGi3ddI/AAAAAAAAPYo/MKgZ84m0CYwnWgMGVhxhAk66uYB6ZoLAwCLcBGAsYHQ/s1600/intank8.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="336" data-original-width="450" src="https://1.bp.blogspot.com/-0wP-AHjeOOs/XaXMzGi3ddI/AAAAAAAAPYo/MKgZ84m0CYwnWgMGVhxhAk66uYB6ZoLAwCLcBGAsYHQ/s1600/intank8.jpg" /></a></div>
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<h3>
<span style="font-size: large;">STP-1 "Gorizont"</span></h3>
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Introduced on the T-54A which arrived in 1954, the STP-1 stabilizer complex for the D-10TG made the T-54 the second postwar tank to receive a gun stabilizer, albeit without full two-plane stabilization. The Centurion Mk. 3 was the first as it already featured a two-plane stabilization system in 1948. The gunner's sight is coaxially linked to the trunnion pin of the cannon to ensure its stabilization.<br />
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In April 1952, at the TsNII-173 the STP-1 "Gorizont" stabilizer was created for the D-10T gun. In May 1952, the STP-1 "Gorizont" stabilizer was installed in three experimental T-54 tanks that underwent acceptance tests in August of the same year, and in September two of them were used for field tests which they passed.<br />
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The stabilizer system is composed of multiple elements working in concert, but the focal point of our attention is the electric gun elevation control system. The minimum elevation speed is 0.07 degrees per second and the maximum elevation speed is 4.5 degrees per second.<br />
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STP-1 included the new TAEN-3 electromechanical turret rotation drive, but did not include horizontal stabilization. A new EMU-5PM amplidyne amplifier was implemented, which solved the problem of excessively high power consumption. The TAEN-3 electric drive for turret traverse is located above the manual traverse handwheel. The electric motor is mounted horizontally, as opposed to the vertical mounting of the electric motor seen in the STP-2, which we will examine later. The TAEN-3 motor was quite compact.<br />
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The gun lacked horizontal stabilization, meaning that firing on the move could only be done if the tank was travelling in a straight line. The handgrip controllers were updated to the KB-4, pictured below. KB-4 is colloquially known as "Cheburashka", in reference to the large ears of the beloved Russian cartoon mouse. Having a single controller with a pair of handgrips to control the orientation of the tank turret and gun is objectively superior to a separated layout like on the Centurion Mk.5 from an ergonomic point of view.<br />
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<a href="http://1.bp.blogspot.com/-pXLBJfS4ctE/VlCvD-2l2PI/AAAAAAAAERw/YCBFNJ3nuhU/s1600/t-55%2Bmeteor%2Bhandgrips.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="320" src="https://1.bp.blogspot.com/-pXLBJfS4ctE/VlCvD-2l2PI/AAAAAAAAERw/YCBFNJ3nuhU/s320/t-55%2Bmeteor%2Bhandgrips.jpg" width="246" /></a></div>
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Modernized versions of the tank like the T-54A, T-54B, T-55, the T-62 and even the BMP-1, all used the basic design of this controller in some form or another. along with the fire control systems of many other military vehicles.<br />
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<h3>
<b>Automatic Mode</b></h3>
Minimum Traverse Speed: 0.07 deg/sec<br />
Maximum Traverse Speed: 15 deg/sec<br />
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Minimum Gun Elevation Speed: 0.07 deg/sec<br />
Maximum Gun Elevation Speed: 4.5 deg/sec<br />
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STP-1 was decent enough, but partially by virtue of its presence alone. After all, stabilization is better than no stabilization. Various useful safety features were also implemented, including a safety device to keep the cannon under control as the tank hurdles over undulating terrain, so as to prevent the cannon from wildly swinging up and down and potentially damaging itself as well as anybody close by. A feedback system was also installed. By monitoring the load on the stabilizer motor, the stabilization system can detect if the cannon is being pushed up or down by an external force. The stabilization system will then depress or elevate the cannon in the opposite direction until the extraneous load is removed. This prevented the cannon from digging into hard objects like large rocks and concrete walls when the stabilizer was turned on.<br />
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<h3>
<span style="font-size: large;">STP-2 "Tsyklon"</span></h3>
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<a href="https://1.bp.blogspot.com/-6xWmqVBOrm4/WHH5j26KK9I/AAAAAAAAIEM/wwKJBrTDIiAOUaSqHhWAlOa992qP-ly8wCLcB/s1600/25327634524_9872293e3a.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" src="https://1.bp.blogspot.com/-6xWmqVBOrm4/WHH5j26KK9I/AAAAAAAAIEM/wwKJBrTDIiAOUaSqHhWAlOa992qP-ly8wCLcB/s1600/25327634524_9872293e3a.jpg" /></a></div>
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The STP-2 "Tsyklon" stabilizer was designed by the TsNII-173 research institute from 1952-1955 and the D-10T2S variant of the D-10T gun was created with the necessary modifications for the new stabilizer. STP-2 featured a new electric turret drive and featured stabilization in the horizontal plane, which was an big improvement over the STP-1. Small batches of T-54B tanks were built in 1955 and 1956 for field trials and troubleshooting, and the tank officially entered service in 1956. Mass production of the T-54B with its new "Tsyklon" stabilizer began in 1957.<br />
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The presence of two-plane stabilization improved the chance of a hit on the first shot by 2 times compared to a single-plane stabilization system and the overall practical rate of fire reportedly rose by 1.5 times.<br />
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<a href="https://3.bp.blogspot.com/-r6JZE0saN5M/WHWg6_MmV7I/AAAAAAAAIGM/OIXhz7rQRNcZhHJ79H-4-qJLj-_PcmluACLcB/s1600/stp-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="510" src="https://3.bp.blogspot.com/-r6JZE0saN5M/WHWg6_MmV7I/AAAAAAAAIGM/OIXhz7rQRNcZhHJ79H-4-qJLj-_PcmluACLcB/s640/stp-2.jpg" width="640" /></a></div>
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If you happen to be inside a T-54B or a T-55, it may be useful to know that the STP-2 can be distinguished from the STP-1 by the vertically placed electric motor on the turret ring, next to the manual turret traverse handwheel.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-_9A8aAh-e-c/WHdNF0d9ELI/AAAAAAAAIIw/GfyY2XLh1AI6cRLT7u2r3dTCpOeF8o9vQCLcB/s1600/280312_orig.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="426" src="https://1.bp.blogspot.com/-_9A8aAh-e-c/WHdNF0d9ELI/AAAAAAAAIIw/GfyY2XLh1AI6cRLT7u2r3dTCpOeF8o9vQCLcB/s640/280312_orig.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Photo credit belongs to Jim Chandler of the Warwickshire Armour Modellers</td></tr>
</tbody></table>
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The turret traverse motor can be seen again in the photo below. It is the green cylinder in the same position as before.<br />
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<a href="https://1.bp.blogspot.com/-H4E5if4gok0/WFz6tW6DDTI/AAAAAAAAH8c/t6kX4uQGWkUW1ILUOQSwAvwzIrbiql0twCLcB/s1600/t-55%2Bgunners%2Bstation.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="425" src="https://1.bp.blogspot.com/-H4E5if4gok0/WFz6tW6DDTI/AAAAAAAAH8c/t6kX4uQGWkUW1ILUOQSwAvwzIrbiql0twCLcB/s640/t-55%2Bgunners%2Bstation.png" width="640" /></a></div>
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The vertical stabilization system was carried over from the STP-1, but with some differences. Components such as the gyrostabilizer box, amplidyne amplifier and the mounting system for the electronics were modified and rearranged.<br />
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<h3>
<b>Automatic Mode</b></h3>
Minimum Traverse Speed: 0.07 deg/sec<br />
Maximum Traverse Speed: 15 deg/sec<br />
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Minimum Gun Elevation Speed: 0.07 deg/sec<br />
Maximum Gun Elevation Speed: 4.5 deg/sec<br />
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Unfortunately, powered traverse was still quite slow even with the improved turret drive, which was not very powerful compared to the hydraulic systems being used in Patton tanks at that time. According to a T-54B manual, the turret could spin at 15 degrees per second, meaning that it would take 24 seconds to complete a full rotation. This is marginally faster than the Centurion Mk. 7, which took 25 seconds to complete a full 360 degrees, but the M47 tank (no stabilizer) was faster by 14 seconds. A <a href="https://ia801001.us.archive.org/20/items/ComparativeCharacteristicsOfMainBattleTanks/Comparative%20Characteristics%20of%20Main%20Battle%20Tanks.pdf">U.S Armor School document</a> on the T-54B claims that the turret could complete a full rotation in 21 seconds.<br />
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The slow turret traverse speed can be an issue for the tank if it is caught in an ambush, as the crew will not be able to react quickly enough. On the upside, the lack of flammable hydraulic fluid being circulated inside the turret was beneficial towards the survival of the crew and the tank as a whole if it was hit.<br />
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The slow traverse speed can also be a handicap when the tank is turning on the spot or zigzagging at a low speed, because the hull can turn faster than the turret. If this happens, the turret might not be able to catch up, making it jerky. This concern also exists with the vertical stabilization drive, and the ability of the gun stabilizer to maintain a fixed aiming angle is determined by its ability to cope with the oscillations of the hull when it moves over uneven ground. The faster the horizontal and vertical drives, the better the stabilization quality when quick changes of direction are involved, and consequently, the ability of the suspension to absorb vertical displacement is also a factor in stabilization quality. An increase in the speed of the tank would also necessitate faster stabilization drives.<br /><br />
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The minimum speed of both gun elevation and turret traverse is 0.07 degrees per second. The maximum speed of gun elevation is 4.5 degrees per second. The vertical stabilizer is designed to suspend turret traverse and lift the cannon by about 3.5 degrees immediately after firing in order to improve loader access to the breech. This is part of the loader's assist function of the stabilizer, designed to ensure that the loader can load the cannon quickly and safely using ammunition from the hull. The side effect is that the gunner's primary and secondary sights will follow, thus making it impossible for the gunner to observe the effect on the target in certain situations. If the gunner wishes to maintain visual contact with the target at all times, he can request the loader to turns off the loader's assist function of the stabilizer by pressing the loader's safety button before loading a round. This returns full control to the gunner but disables the safety systems built into the D-10T2S that prevent it from firing electrically or mechanically, so the gunner must take more care to ensure that his finger is off the trigger while the gunner is loading.<br />
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A captured T-55 tested by the Israelis in 1969 yielded interesting results. The T-55 was tested on a flat sandy track at a steady speed of 15 km/h. Out of 35 shots, only 3 hit the target - a success rate of only 8.5%. This is better than the quoted value of "3% and below", but still extremely poor. Photos of the report are available on tankandafvnews. The relevant pages are Page 52 (<a href="https://tankandafvnews.files.wordpress.com/2016/02/052.jpg">photo</a>), Page 53 (<a href="https://tankandafvnews.files.wordpress.com/2016/02/053.jpg">photo</a>), Page 54 (<a href="https://tankandafvnews.files.wordpress.com/2016/02/054.jpg">photo</a>).<br />
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The report mentions that STP-2 is only suitable for stabilizing the gunner's line of sight, not firing on the move. The poor performance of STP-2 is most likely due to the lack of range data, but the limits suspension itself definitely has an impact as well, as a hard ground was chosen to induce vibrations to the tank as detailed in Page 52. As a rule, vibrations cannot be eliminated by a gun stabilizer, but are largely handled by the suspension of the tank itself. <br /><br />
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Six of the targets presented a broadside profile (side profile), two of the targets presented a head-on profile, and two of the targets presented an oblique broadside profile (angled profile). All of the targets were paper targets. The visible height of the target ranged from 1.45 meters to 2.45 meters, which would be representative of an average Soviet tank, but not a Western one; the Centurion is 3.01 meters tall, the M48 is 3.10 meters tall, and the M47 is an astonishing 3.35 meters tall.<br />
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At target distances averaging 1200 m with outlying targets at the unusually short distance of 600 m and the unusually long distance of 2140 m, the ratio of the number of hits to the number of rounds fired was obtained. The results are listed below: <br />
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<table border="1" cellpadding="3" cellspacing="1">
<tbody>
<tr>
<td>Crew
</td>
<td>Phase
</td>
<td>Number of Targets Engaged
</td>
<td>Number of Rounds Fired
</td>
<td>Hits
</td>
</tr>
<tr>
<td>A
</td>
<td>1
</td>
<td>5
</td>
<td>12
</td>
<td>2
</td>
</tr>
<tr>
<td>A
</td>
<td>2
</td>
<td>5
</td>
<td>11
</td>
<td>4
</td>
</tr>
<tr>
<td>B
</td>
<td>1
</td>
<td>5
</td>
<td>12
</td>
<td>3
</td>
</tr>
<tr>
<td>B
</td>
<td>2
</td>
<td>5
</td>
<td>11
</td>
<td>3
</td>
</tr>
</tbody></table>
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This test was not to determine the accuracy of the gun and fire control system, unlike the test of the Centurion detailed above. This test was a simulation, with unknown and unexpected target positions, unknown distances to these targets, and so on. Another factor to consider is that these tests were held in the same extremely dusty conditions that so badly affected the crew's ability to sense the point of impact of shots. In Page 55 (<a href="https://tankandafvnews.files.wordpress.com/2016/02/055.jpg">Photo</a>), it was noted that the obscuration after firing lasted for 4-5 seconds, preventing observation of the target (and the fall of the shot), making it nearly impossible to correct fire. In fact, if we scan the details of each shot as analysed and listed in the report, we can see that <u>all of the misses</u> (including the ones involving incorrect horizontal lay) either went high or low. Therefore, the gun was almost always laid correctly on the target, which is some credit to the horizontal stabilizer system of STP-2. The only issue was the ability of the crew to ascertain the range to the target and obtain a ballistic solution.<br />
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Out of 12 shots <a href="https://tankandafvnews.files.wordpress.com/2016/02/079.jpg">in phase A1</a>, there was only one shot where the shell was off target in the horizontal plane. <a href="https://tankandafvnews.files.wordpress.com/2016/02/080.jpg">In phase A2</a>, out of 11 shots, there was, again, only one shot where the shell was off target in the horizontal plane. <a href="https://tankandafvnews.files.wordpress.com/2016/02/080.jpg">In phase B1</a>, out of 12 shots, we have two shots off target in the horizontal plane. <a href="https://tankandafvnews.files.wordpress.com/2016/02/081.jpg">In phase B2</a>, out of 11 shots, we have one shot off target in the horizontal plane. All of the misses were due to the shot going high or low. It is very likely that in less dusty conditions, the T-55 could achieve much, much better accuracy. On a related note, the exclusive use of APDS ammunition for anti-tank purposes in the Centurion MK. 3 greatly contributed to good accuracy at all ranges, as the high velocity of APDS shells partially negated ranging errors.<br />
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From a statistics standpoint, relying on this report to generalize the performance of all T-55 tanks in all conditions will be erroneous. Therefore, I ask the reader not to take any of this data at face value. This test cannot be used to represent the majority of T-55 tanks in real battle, and certainly not T-55 tanks in Europe, where environmental conditions are very different. Take this little analysis as supplementary knowledge.<br />
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<h3>
<span style="font-size: large;">D10-T (TG, T2, T2S)</span></h3>
<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-RLN_v0gh_J0/Xrxye21lI1I/AAAAAAAAQt8/Ip4MtDIUMhslBgycemlIumRjRResFsGWwCK4BGAsYHg/d10-t%2Bgun%2Bfull%2Bassembly.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="117" data-original-width="865" src="https://1.bp.blogspot.com/-RLN_v0gh_J0/Xrxye21lI1I/AAAAAAAAQt8/Ip4MtDIUMhslBgycemlIumRjRResFsGWwCK4BGAsYHg/d/d10-t%2Bgun%2Bfull%2Bassembly.png" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div>
<div><br /></div><div>At the time it entered service on the T-54 obr. 1947, the first serial T-54 model, the D10-T gun had a larger caliber than any other tank gun fielded on a medium tank from the late 1940's to the late 1950's, and more importantly, its ballistic performance was high enough to effectively combat the postwar medium tanks of the Western Allies and even pose a serious threat to heavy tanks like the M103 and Conqueror from their frontal arcs, albeit not from the direct front. </div></div><div><br />
<br />The total length of the gun is 5,608mm. The gun tube has a length of 5,350mm or 53.5 calibers, making the D10 an L/53.5 gun. It is worth noting that in the Soviet Army, the "L/" format is not used to denote lengths and there is no confusion between overall gun length and gun tube length. However, outside of the USSR, this format may be used for either overall gun lengths and gun tube lengths. For example, the German 8.8cm KwK 43 is officially listed as an L/71 gun. However, <a href="http://www.panzerbasics.com/panzer/02_archive/drawings/Tiger_B_3_files/The-C938_8.8cm_KwK43-Stammzeichnung.jpg">the master drawing for the KwK 43</a> shows that this is its full length, measured from the muzzle to the rear face of its breech, whereas the length of the gun tube alone is only 6,010mm, or 68.3 calibers.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-FWkRUCHv6cU/XrxwF3De_XI/AAAAAAAAQtg/f7pETGEdp28CVE3LIRJ8i4VelB4i03GBQCK4BGAsYHg/d10%2Bbreech%2Band%2Bgun%2Btube.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="301" data-original-width="2228" height="86" src="https://1.bp.blogspot.com/-FWkRUCHv6cU/XrxwF3De_XI/AAAAAAAAQtg/f7pETGEdp28CVE3LIRJ8i4VelB4i03GBQCK4BGAsYHg/w640-h86/d10%2Bbreech%2Band%2Bgun%2Btube.png" width="640" /></a></div><div><br /></div><div><br /></div><div>There are 40 lands and grooves in the continuous twist rifling of the D10. </div><div><br /></div><div>The maximum operating pressure of all D10 guns (rated based on AP rounds) is 3,000 kgf/sq.cm, or 294 MPa. This is comparable to the 90mm M36 and M41 guns used on the M47 and M48 Patton respectively. Data provided on page 2-37 of the engineering textbook "<i>Interior Ballistics of Guns</i>" produced by the United States Army Materiel Command, shows that the M318A1 APBC round fired from the M36 or M41 gun had a maximum operating pressure of 44,000 psi, or 303 MPa. However, being L/50 guns, the proportionately shorter barrels of the M36 and M41 hamstrung the potential gain in muzzle velocity, limiting it 914 m/s which is only 2.1% higher than the AP shells fired from a D10. On the other hand, the KwK 43 gun had the same maximum operating pressure of 3,000 kgf/sq.cm as the D10 according to its original design documentation, but due to its proportionately longer barrel, the muzzle velocity of its standard AP round exceeds that of the D10-T by a little over 100 m/s, translating to a difference of 11.7%.</div><div><br /></div><div>The muzzle energy of the D10 series when firing its AP ammunition exceeded that of the KwK 43 by 20%, and naturally, the muzzle energy advantage of the D10 was even larger when compared to the M36 and M41 90mm guns. While the KwK 43 itself lost its relevance after the conclusion of WWII, it was still a good reference point for its particular class, as the domestic 85mm D-48 anti-tank gun and the British 20 pdr gun that was installed in various Centurion tank models since 1948 were both directly equivalent to the KwK 43 in ballistic performance.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-YKx8JsAc3oI/Xrw1dlVCbwI/AAAAAAAAQs0/lCpMidcKlRg-Y0aNnrSuBpAn-UOJJJKbgCK4BGAsYHg/tube%2Bcradle%2Band%2Bbreech.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="794" data-original-width="2685" height="190" src="https://1.bp.blogspot.com/-YKx8JsAc3oI/Xrw1dlVCbwI/AAAAAAAAQs0/lCpMidcKlRg-Y0aNnrSuBpAn-UOJJJKbgCK4BGAsYHg/w640-h190/tube%2Bcradle%2Band%2Bbreech.png" width="640" /></a></div><div><br /></div><div><br /></div><div>To install the STP-1 stabilizer in a T-54 tank, a number of components had to be mounted to the underside of the gun. These were the hydraulic pump for the gun elevation drive, the gyro unit, the electrical transformer and the amplifier. The weight of these components made the gun rear-heavy. To solve this, the fume extractor was placed at the muzzle of the gun to act as a counterweight. A gun featuring all of these modifications was designated as the D10-TG. This gun was used by the T-54A. Later on, the gun was adapted to the "Tsyklon" dual-axis stabilization system, changing the designation to D10-T2S. This model featured only minor changes related to the slight differences in the installation of the stabilizer components under the gun breech.</div><div><br /></div><div>The fume extractor is of a simple sheet metal construction. After a fired projectile has left the muzzle and the bore pressure plummets, the pressurized air contained in the fume extractor rushes out at a speed of approximately 500 m/s.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-B_3oEcibcII/Xrxv0vTqkYI/AAAAAAAAQtM/ibYhgfDA-Tg_RywI7YyBsPxAXvMoRIxJgCK4BGAsYHg/d-10tg%2Bfume%2Bextractor.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="904" data-original-width="3344" height="174" src="https://1.bp.blogspot.com/-B_3oEcibcII/Xrxv0vTqkYI/AAAAAAAAQtM/ibYhgfDA-Tg_RywI7YyBsPxAXvMoRIxJgCK4BGAsYHg/w640-h174/d-10tg%2Bfume%2Bextractor.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The width of the D10 gun breech is not known, but based on technical drawings, its width is identical to that of the R-112 radio installed in command variants of the T-54 series. The R-112 has a width of 422mm, so it is very likely that the D10 breech is around 420mm in width. For comparison, it is known that the width of the 122mm D-25T gun breech is 480mm and the width of the 8.8cm KwK 43 gun breech is 360mm.</div><div>
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In the T-54, the gun mount is slightly offset to the right. This offset appears to be intended to increase the working space for the commander and gunner as a significant amount of space is occupied by the equipment installed on the turret wall, whereas the loader's side of the turret is much less cluttered. </div><div><br />
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<a href="https://1.bp.blogspot.com/-TVo8Z7DRZSU/WBhlHyCxKxI/AAAAAAAAHgY/-8tt_6EaulIh0uywSADVLXiSqozEBonIwCEw/s1600/t-54%2Bseating%2Barrangement.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="400" src="https://1.bp.blogspot.com/-TVo8Z7DRZSU/WBhlHyCxKxI/AAAAAAAAHgY/-8tt_6EaulIh0uywSADVLXiSqozEBonIwCEw/s400/t-54%2Bseating%2Barrangement.jpg" width="370" /></a><a href="https://1.bp.blogspot.com/-fRCqP3uFx3I/WokC2mvfdXI/AAAAAAAAK6E/GZanzWfbb2E1vpGD3v5taetzKIhVDmeFACLcBGAs/s1600/offset%2Bgun.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="434" data-original-width="531" height="325" src="https://1.bp.blogspot.com/-fRCqP3uFx3I/WokC2mvfdXI/AAAAAAAAK6E/GZanzWfbb2E1vpGD3v5taetzKIhVDmeFACLcBGAs/s400/offset%2Bgun.jpg" width="400" /></a></div>
<div><br /></div><div><br /></div>As mentioned before in this article in the section examining the TPN-1-22-11 night vision sight, nearly all T-54 obr. 1949 tanks (built and issued from 1949 to 1951) and T-54 obr. 1951 tanks (built and issued from 1952 to 1954) underwent a modernization program during the late 1950's to improve its combat capabilities to the level of the T-54B, which was the latest iteration at the time. However, the modernized tanks were not to be fitted with a fume extractor which was standard for the D10-TG and D10-T2S. Instead, a counterweight was added to the end of the barrel to simulate the load of a fume extractor to balance the cannon properly for the stabilizer to function. These unusual guns, adapted for the STP-2 "Tsyklon" but with a counterweight in lieu of a fume extractor, were designated D10-T2. The two photos below show two different T-54 models both upgraded to the standard of the T-54B. The photo on top shows a T-54 obr. 1951 and the photo on the bottom shows a T-54 obr. 1949.<br />
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<a href="https://2.bp.blogspot.com/-mGZ52ZeV1zE/WCiE8PlspfI/AAAAAAAAHmE/4Un-690o07ALYa3spIiufkNn0Y6LlNL_gCLcB/s1600/%25D0%25A2-54-%25D0%25B2%25D0%25B8%25D0%25B4-%25D1%2581%25D0%25B1%25D0%25BE%25D0%25BA%25D1%2583.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="191" src="https://2.bp.blogspot.com/-mGZ52ZeV1zE/WCiE8PlspfI/AAAAAAAAHmE/4Un-690o07ALYa3spIiufkNn0Y6LlNL_gCLcB/w400-h191/%25D0%25A2-54-%25D0%25B2%25D0%25B8%25D0%25B4-%25D1%2581%25D0%25B1%25D0%25BE%25D0%25BA%25D1%2583.jpg" width="400" /></a><a href="https://4.bp.blogspot.com/-3qK1vKpNFMc/WCiFXeFPIHI/AAAAAAAAHmQ/XV-nZ_KnsigvTPlG-q_pQ9_BVPs6RjqYACLcB/s1600/SuT5455196.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="176" src="https://4.bp.blogspot.com/-3qK1vKpNFMc/WCiFXeFPIHI/AAAAAAAAHmQ/XV-nZ_KnsigvTPlG-q_pQ9_BVPs6RjqYACLcB/w400-h176/SuT5455196.jpg" width="400" /></a></div>
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The rationale behind the decision to use a counterweight instead of simply retrofitting a fume extractor to the gun barrels of modernized tanks is unclear. There is no conceivable advantage whatsoever in omitting a fume extractor other than expediency. Nevertheless, the widespread implementation of fully stabilized guns and the addition of a night fighting capability was not a trivial matter. The increase in overall combat capabilities was a large boost for the vast tank fleet of the Soviet Army.<br />
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The production of D10-T, D10-TG and D10-T2S guns at the No. 9 plant in Sverdlovsk and the No.172 plant in Perm is documented in the table below.<br />
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<a href="https://2.bp.blogspot.com/-KsLAWHV0LaQ/WiN2FO-NHwI/AAAAAAAAKPc/FKFQ1DiwkdA9MUDh10H1F0t68ohhC4u6wCLcBGAs/s1600/d-10t%2Bproduction.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="267" data-original-width="1089" height="156" src="https://2.bp.blogspot.com/-KsLAWHV0LaQ/WiN2FO-NHwI/AAAAAAAAKPc/FKFQ1DiwkdA9MUDh10H1F0t68ohhC4u6wCLcBGAs/s640/d-10t%2Bproduction.jpg" width="640" /></a></div></div><div><br /></div><div>
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The basic D10-T has a weight of 1,950 kg, including the gun cradle and armoured gun mask of a T-54 obr. 1949 or any model thereafter. Together with the gun cradle and recoil system, it weighs 1,430 kg. On the M60A1, the M68 together with its gun cradle weighs 1,410 kg and the combined weight of the entire gun assembly with the gun mantlet weighs 3,260 kg. On the Leopard 1, the L7A3 with the gun cradle and gun mantlet weighs 2,900 kg. Alone, the breech and gun tube assembly of the M68 and the L7 weigh 1,122 kg and 1,282 kg respectively, but data for the D10-T is not known. From this, it can be seen that the decision to abandon a turret design with a gun mantlet as on the T-54 obr. 1947 in favour of a much more compact gun mask led to a large reduction in the mass of the cannon assembly and thus reduced the work needed to elevate or depress the cannon.</div><div><br />
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To replace the barrel, it is necessary to lift the turret off the turret ring and pull the entire cannon assembly out the back. The turret is designed to tilt forward and stay propped open to make this easier to do in the field, but it is still by no means a quick procedure.<br />
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<a href="https://2.bp.blogspot.com/-OZVDWtMk7jo/V2zO1zTLi7I/AAAAAAAAG04/G9w99nhtGhw0w5PO6b-IgwR5su2mfMWTQCLcB/s1600/8.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="352" src="https://2.bp.blogspot.com/-OZVDWtMk7jo/V2zO1zTLi7I/AAAAAAAAG04/G9w99nhtGhw0w5PO6b-IgwR5su2mfMWTQCLcB/s640/8.jpg" width="640" /></a><br />
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Here's a scene of this procedure being carried out in the field. The gun is being lifted by an engineering vehicle.<br />
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<a href="https://3.bp.blogspot.com/-Lfnb_OIF9Z4/WE5GwIYoV5I/AAAAAAAAH0k/We-hKsOhn68zjJ0qw9rSKSzYRfdY-HqvgCLcB/s1600/t-54%2Bgun%2Breplacement.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://3.bp.blogspot.com/-Lfnb_OIF9Z4/WE5GwIYoV5I/AAAAAAAAH0k/We-hKsOhn68zjJ0qw9rSKSzYRfdY-HqvgCLcB/s640/t-54%2Bgun%2Breplacement.png" width="459" /></a></div>
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<span style="font-size: large;">LOADER'S STATION</span></h3>
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The T-54 is rather short compared to the T-34, so it is quite surprising that the actual available vertical space inside the T-54 is actually quite similar to its predecessor. <a href="http://2.bp.blogspot.com/-cMdb28XA5mA/UpVRoNsbMNI/AAAAAAAAB8Y/Gqna1CDRTdE/s1600/ergonomics-4.jpg">Measuring from floor to turret ceiling, the fighting compartment of a T-34-85 was 1.56 meters in height</a>, or <a href="http://tankarchives.blogspot.my/2015/01/soviet-medium-tank-family.html?m=1">1.585 meters</a>, or 1.55 m, depending on the source. The T-54, on the other hand, had a maximum internal height of 1.6 meters, even though the T-54 is 2.32 meters tall while the T-34-85 is 2.7 meters tall. This wizardry was only possible because a large part of the floor of the T-34-85 is taken up by an ammunition box which stows the majority of the tank's ammunition supply. Being tall enough to stow 85mm shells three rounds deep, the box takes up a considerable portion of the tank's available vertical space. As the floor of a T-54 only needed to accommodate the torsion bars and the false floor, it could have the same internal height as the taller T-34-85. The length and width of the loader's station in the T-54 was also improved over the T-34-85 thanks to the wider turret ring, although any improvement in loading speed were probably cancelled out by the much larger bulk and weight of the 100mm rounds.<br />
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The requirement for at least 1.6 meters of vertical space was not arbitrary. According to an article published in the April 2004 issue of the "<i>Tekhnika i Vooruzhenie</i>" magazine titled "<i>Основы теории и история развития компоновки танка</i>" (<i>Fundamentals of the Theory and History of the Development of Tank Layouts</i>) by Vasily Chobitok, the height of the loader's station should be between 1.6-1.7 m tall and 0.5 m wide with a space of 1 cubic meter to accommodate the loader.<br />
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The commander and gunner can sit down with a reasonably comfortable allotment of headroom, but 1.6 meters is not nearly enough to let a man of average height stand upright, even with the infamous practice of choosing smaller servicemen for tank crews. According to "Foundations of Design of Armament for Self Propelled Guns and Tanks", the average height of a man is stated to be 1.7 meters, so a loader of average height would have to conduct his duties from a seated or half-standing position. As the loader's protruding cupola breaks the turret's sloping profile, he has room to stand a little straighter directly when he is directly underneath the hatch, which, conveniently, is where he needs to be in order to ram rounds into it, but otherwise, the turret is far too low to allow the loader to work with a straightened back. The low ceiling at the front part of the turret is not a problem, as there is no ammunition there that is stored above waist level at the front of the turret. The loader's seat can be unhooked from the turret and relocated to a new position near the rear of the turret, so there are two possible seated positions from which the loader can perform his duties. As usual, the seat can be folded up and out of the way for the loader to stand and move around freely in his station, but the seat can also be unhooked and stowed away for extra space. There are two fire extinguishers at the rear of the turret, directly underneath one of the possible positions for the loader's seat. The loader is also furnished with an MK-4 periscope for general visibility. The periscope is installed in front of the loader's hatch and its aperture window is surrounded by an armoured collar that is a part of its rotating mount.<br />
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The loader is drilled to return to the MK.4 periscope immediately after loading and readying the cannon to help observe the fall of every shot and help search for targets until he is called to load another round by the commander. However, in practice, if the loader is not servicing the cannon, he is either getting another cartridge ready or rearranging the ammunition into the ready racks. The periscope is marginally useful when under threat of imminent contact with the enemy as it grants the tank an extra pair of eyes, but attempting to use a non-magnified periscope to help spot targets is usually a waste of time. The greatest value of the periscope is in the psychological benefit of giving the loader a sense of his surroundings. The extra lighting may be helpful as well, since the loader's station has only one dome light.<br />
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When an IR night sight was installed beginning in 1957, the addition of an IR spotlight on the starboard side of the turret above the coaxial machine gun port had the unfortunate side effect of blocking the loader's view in the 12 o'clock sector. As such, the loader's view was restricted to the right side of the turret only, which limits his ability to assist in finding targets and completely prevents him from observing the fall of shots. However, granting forward vision to the loader is often considered superfluous given that both the gunner and commander would be looking forward and observing the target anyway. As such, the loader would be more helpful if he was focused on scanning the right side of the turret instead.
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<span style="font-size: large;">AMMUNITION STOWAGE</span></h3>
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The T-54 generally had a relatively small ammunition capacity, but not all T-54 models carry the same load of ammunition. All T-54 variants created between 1947 and 1958 could only carry a measly 34 rounds - nearly half that of tanks like the M46 and the Centurion. To be fair, this was compensated by the significantly higher explosive and anti-armour performance of each 100mm shell compared to a 90mm or an 84mm one, but only to a certain extent. By having fewer rounds at their disposal, a T-54 crew must be more mindful of ammunition expenditure as the probability of obtaining a direct hit was low due to the simple fire control system and the lack of high velocity ammunition such as APDS or APFSDS.<br />
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Unlike American and British tanks and post-war German tanks, the loader in the T-54 is situated on the right side of the turret, to the right of the gun. Because of this, he loads with his left hand and not his right hand, which is the dominant side for 90% of the world's population. This has been criticized as an ergonomic failing point as it is thought that this would tire out loaders at a quicker rate, but contrary to this perception, it was never noted to be an issue during combat or during field exercises in the T-54, or in other tanks with left-handed loading including WWII-era German tanks. It is possible that the lack of any quantifiable difference is because neither of the two loading layouts are without flaws. For left-handed loading, the loader holds the base of the cartridge with his left hand and holds the nose of the cartridge with his right arm or cradles it in his right arm. Since unitary cartridges are invariably nose-heavy, this would be most comfortable for the loader. The downside is that the loader must ram the cartridge into the cannon with his left hand. For right-handed loading, the loader holds the heavier end of the cartridge with his left hand and rams it into the cannon with his right hand.<br />
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Rather than left-handed or right-handed loading, the main impediments to a T-54 loader are the length and mass of the 100mm cartridges. This was the main downside to having a more powerful gun than the American Pattons and the British Centurions during the 1950's. The base diameter of each cartridge case is 147.32mm and the length is 692mm. Naturally, the armour-piercing rounds have shorter projectiles and are therefore shorter overall compared to HE-Frag and HEAT rounds, but generally speaking, the cartridges were quite long. For comparison, the cartridges for the 105mm L7 cannon were noticeably more compact, having a base diameter of 147.3mm and a case length of 617mm. The reduced length makes them easier to handle inside the confines of a tank.<br />
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<a href="https://3.bp.blogspot.com/-RQrNMDRSoN8/W_Q2JcAqbfI/AAAAAAAAMhU/JX4UMdnzp8k3VSDODSBmWGWBdDlgbc5iwCLcBGAs/s1600/t-55a%2Bstocking%2Bammo.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1573" height="640" src="https://3.bp.blogspot.com/-RQrNMDRSoN8/W_Q2JcAqbfI/AAAAAAAAMhU/JX4UMdnzp8k3VSDODSBmWGWBdDlgbc5iwCLcBGAs/s640/t-55a%2Bstocking%2Bammo.jpg" width="628" /></a></div>
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A drawing of ammunition placement in a T-54 obr. 1951 is shown below. As the arrangement of ammunition in a T-54 obr. 1949 is practically identical to that of the more historically relevant T-54 obr. 1951, we will only be discussing the latter.<br />
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<a href="https://1.bp.blogspot.com/-NcemboFqCds/WClEfCthvLI/AAAAAAAAHmo/VcIZ_rDPcYsFdvVlXSMYAZSEh4Rlue32gCLcB/s1600/T-54-035.gif" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" src="https://1.bp.blogspot.com/-NcemboFqCds/WClEfCthvLI/AAAAAAAAHmo/VcIZ_rDPcYsFdvVlXSMYAZSEh4Rlue32gCLcB/s1600/T-54-035.gif" /></a></div>
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The 1951 upgrade that brought the new egg-shaped turret also brought improvements in the ammunition stowage scheme. Most notably, the bevelled turret rear was filled out, and this allowed an additional five rounds to be carried. You can see these racks in the photo below.<br />
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<a href="https://2.bp.blogspot.com/-90qgPIFCFl8/WBBMwg9qqiI/AAAAAAAAHdQ/v8uWrfwwhBAdRKEAs0TPIjBNmx-WSxdkACLcB/s1600/t-54%2Bturret%2Brear%2Bammo%2Bracks.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="358" src="https://2.bp.blogspot.com/-90qgPIFCFl8/WBBMwg9qqiI/AAAAAAAAHdQ/v8uWrfwwhBAdRKEAs0TPIjBNmx-WSxdkACLcB/s640/t-54%2Bturret%2Brear%2Bammo%2Bracks.png" width="640" /></a></div>
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The five rounds are stowed crosswise, tip to tail. Three rounds are stowed pointing towards the commander, and two are stowed pointing to the loader. Unfortunately, the turret bustle is too shallow for the loader to avoid the recoil stroke of the cannon when retrieving ammunition from these racks. As such, it is dangerous to extract ammunition from these racks immediately after the cannon has been loaded as the loader will not know when the gunner will decide to fire, making it impractical to lapload using these racks. These racks are deleted from the T-54K command tank variant as the space is taken up by an additional R-112 radio.<br />
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<a href="https://3.bp.blogspot.com/-Vnw-atEJrEE/WG5i5amR1VI/AAAAAAAAH_c/Qfi2q8JNKZkSFzcCieSHg1fXfPEGXtnZgCLcB/s1600/T54-037.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-Vnw-atEJrEE/WG5i5amR1VI/AAAAAAAAH_c/Qfi2q8JNKZkSFzcCieSHg1fXfPEGXtnZgCLcB/s1600/T54-037.gif" /></a></div>
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An additional two rounds are stowed on the turret wall next to the loader. The rounds are mounted facing forward. This was a rather odd design decision, since this forces the loader to hold the base of the shell with his right hand and hold the nose end with his left, even though he can only ram the round in with his left hand. This prevents the loader from extracting the round, turning around and loading the round in one fluid stroke.<br />
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Four rounds are stowed with clips at shin level on the wall of the hull, on the loader's side. These are not very convenient to use in battle if the turret is pointing forward, but they are still easier to access than the ammunition located at the very back of the fighting compartment. If the turret is pointed to the right relative to the hull, these racks will be convenient for the loader as they would then be situated directly in front of him. The presence of these four rounds decreases the available width of floor space available to the loader by 147mm (the base diameter of a 100mm cartridge case) which is somewhat inconvenient.<br />
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<a href="https://1.bp.blogspot.com/-4kcggOaxHJQ/XaYpXZVQIMI/AAAAAAAAPZg/Soz-aK9f8bwId6rPKkxXzMVKYVo_OynZwCLcBGAsYHQ/s1600/t-54%2Bammo%2Bracks%2Bwith%2Bcat.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://1.bp.blogspot.com/-4kcggOaxHJQ/XaYpXZVQIMI/AAAAAAAAPZg/Soz-aK9f8bwId6rPKkxXzMVKYVo_OynZwCLcBGAsYHQ/s400/t-54%2Bammo%2Bracks%2Bwith%2Bcat.jpg" width="400" /></a></div>
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Twenty rounds are stowed in a metal skeleton frame rack at the front of the hull. The loader must squat down to access these racks, but the way they are placed is extremely convenient for him. These racks are placed underneath the flat part of the hull ceiling due to geometric incompatibility with the sloping front part of the hull. Underneath the 60 degree slope of the upper glacis plate, and in front of the ammo racks, is a large triangular fuel tank. <br />
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<a href="https://1.bp.blogspot.com/-Pldcg8-ZyPw/XaYpw8WRgzI/AAAAAAAAPZo/HF6RgMjkSOMb8aBfFJ5v8mysT3sE7dwfACLcBGAsYHQ/s1600/front%2Bammo%2Bracks.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="266" src="https://1.bp.blogspot.com/-Pldcg8-ZyPw/XaYpw8WRgzI/AAAAAAAAPZo/HF6RgMjkSOMb8aBfFJ5v8mysT3sE7dwfACLcBGAsYHQ/s400/front%2Bammo%2Bracks.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-3aPcV0ksDIQ/WFFFTGSUNGI/AAAAAAAAH3g/bvHMO90JyFgrjUjPeCQvYUSb40ngT1lowCLcB/s1600/t-54%2Bfront%2Bhull%2Bammo%2Bracks.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="284" src="https://3.bp.blogspot.com/-3aPcV0ksDIQ/WFFFTGSUNGI/AAAAAAAAH3g/bvHMO90JyFgrjUjPeCQvYUSb40ngT1lowCLcB/s320/t-54%2Bfront%2Bhull%2Bammo%2Bracks.gif" width="320" /></a></div>
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Here it is being used in an FSA-operated T-54.<br />
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Finally, there is a single cartridge stowed on the floor of the hull next to the engine compartment bulkhead. Five 250-round ammunition boxes for the coaxial machine gun are stowed on the floor of the turret, underneath the cannon, and another two boxes are placed next to the front hull ammunition racks, next to the driver's seat.<br />
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The front hull racks are the most convenient to access. They are considered the primary ready racks of the tank. Because the supply of ready rounds in a T-54 were not stowed in the turret bustle racks but were instead stowed in the front hull racks, the spring-loaded support tray featured on the 85mm ZiS-S-53 cannon of the T-34-85 was not implemented on the D10-T. Instead, the horizontally-sliding breech block was more convenient. According to Stefan Kotsch, a former T-55 tank commander in the NVA, the tank crew is trained to point the hull toward an enemy tank in a tank duel. This presents the most heavily armoured zone of the tank to the enemy and naturally makes the front hull racks a convenient source of ammunition to the loader. However, there are additional nuances with the stowage scheme, one of them being that the rounds stowed at the bottom rows of the front hull racks would be harder to access than the rounds stowed at the top rows. The loader would need to take every opportunity available to rearrange the ammunition in such a way that they are convenient to access.</div><div>
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<h3>
<span style="font-size: large;">T-55</span></h3>
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<a href="https://4.bp.blogspot.com/-0l3YQaTE3zs/W_GvUQzlGFI/AAAAAAAAMeo/9bFKaaUOXnsPo41srNIIX0Yotf29KTIsACLcBGAs/s1600/t-55%2Bammo.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="369" data-original-width="708" height="333" src="https://4.bp.blogspot.com/-0l3YQaTE3zs/W_GvUQzlGFI/AAAAAAAAMeo/9bFKaaUOXnsPo41srNIIX0Yotf29KTIsACLcBGAs/s640/t-55%2Bammo.jpg" width="640" /></a></div>
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The T-55 introduced new front hull racks. Instead of a simple metal skeleton frame, these racks are conformal fuel tanks with slots for ammunition. Two rounds had to be sacrificed to make the arrangement work, slashing the total number of rounds stowed in the racks from 20 to 18. The rear hull fuel tank next to the engine compartment bulkhead was removed, but the new conformal fuel tank held 300 liters of diesel which offset removal of the rear hull fuel tank and increased the total fuel capacity of the tank by 100 liters, giving the tank an extended driving range. This was a considerable performance boost, especially since no additional useful internal space was used by the new special fuel tank and a volume of 200 liters was freed up by the removal of the rear hull fuel tank. This was enough space for an additional 11 rounds, so despite losing two slots in the front hull racks, the T-55 could carry 43 rounds of ammunition, which is 9 more rounds than previous T-54 models. Contrary to the commonly held belief that the removal of the bow machine gun enabled more ammunition to be stowed, the extra ammunition was not stowed anywhere near the removed bow machine gun, and the larger ammunition capacity of the T-55 had nothing to do with it at all.<br />
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The photo below shows the front hull ammunition racks in a special T-55 training demonstrator as seen from outside its imitation turret.<br />
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The rear hull ammunition racks can be seen below (some space is being used in a non-historical manner for assorted machine gun ammunition boxes).<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://4.bp.blogspot.com/-i3LuVpVV904/WG_Fc6AW9II/AAAAAAAAIDU/hC4nJl8Bzf0r_8Te0ctr83k_srau792EgCLcB/s1600/6225122_orig.jpg" style="margin-left: auto; margin-right: auto; text-align: center;"><img border="0" height="426" src="https://4.bp.blogspot.com/-i3LuVpVV904/WG_Fc6AW9II/AAAAAAAAIDU/hC4nJl8Bzf0r_8Te0ctr83k_srau792EgCLcB/s640/6225122_orig.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Photo credit to Jim Chandler of the Warwickshire Armour Modellers</td></tr>
</tbody></table>
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It is not as easy to extricate ammunition from these racks as it is from the front hull racks or from the turret racks due to the horizontal arrangement of the ammunition and the presence of the large casing deflector extending almost to the turret ring. Therefore, these racks are considered non-ready racks for reserve ammunition. As these are not ready racks, they are usually filled with HE-Frag rounds as opposed to AP or HEAT rounds which would be stowed in the front hull racks. In the event that the loader must load the cannon when the turret is turned to the right, the rear hull racks will become much easier to access and would become his primary source of ammunition besides the rounds stowed in the turret.<br />
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It is possible for the loader to load the gun from a seated position. To do this comfortably, the seat should be placed in the rear position (facing forward) as this would allow the loader to easily access the two ammunition racks in the turret without any real difficulty. If the loader carries out his duties while seated, there would be no problems with the limited vertical height of the tank and even people of above average height would be able to load the gun with ease, but the limited amount of ammunition stowed in the turret makes it impractical for the loader to remain seated for the entire length of an engagement as he would need to access the ammunition in the hull to replenish the turret ready racks. If the situation is very dire, it would be faster to simply begin taking ammunition from the front hull racks once the turret racks are depleted. The GIF below shows a loader in a T-55A loading an APDS round while seated.<br />
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<a href="https://4.bp.blogspot.com/-lFKBif-kxHQ/XGbz8iJoBrI/AAAAAAAANZo/_lBDag4bciUVzQg5xf5vruu7RkMWBYkFACLcBGAs/s1600/t-55a%2Bloading%2Bapds.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="546" data-original-width="728" height="480" src="https://4.bp.blogspot.com/-lFKBif-kxHQ/XGbz8iJoBrI/AAAAAAAANZo/_lBDag4bciUVzQg5xf5vruu7RkMWBYkFACLcBGAs/s640/t-55a%2Bloading%2Bapds.gif" width="640" /></a></div>
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Experiences in various conflicts throughout the Cold War era have indicated that it is rare for a tank to expend more than 20 rounds of ammunition in a single engagement. Most often, the tank only needs to fire around a dozen rounds before the enemy is either destroyed or routed, keeping in mind that tanks do not operate alone - the firepower of a tank platoon or tank company is very high indeed, especially if tactical numerical superiority is achieved. This knowledge is reflected in the designs of tanks like the Pershing, M46, Centurion, and all the rest. In all of these tanks, and in the tanks that came after, ammunition stowage is divided into two types; ready and non-ready. Ready rounds are stowed in racks close to the loader, so that he can load as quickly as possible during battle. During the lulls between battles, the loader refills the ready racks with ammunition from the non-ready racks. The T-54 is no worse than any of its counterparts in this sense. The total number of rounds available in the ready racks in a T-54 is 29, whereas in the T-55, it is 27 rounds. As you may recall, another four rounds are stowed by the loader's feet at shin level, but they are not necessarily ready rounds in the strictest sense.<br />
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By comparison, a 20-pdr-armed Centurion has 28 ready rounds, according to a U.S Army report <a href="http://worldoftanks.com/en/news/pc-browser/21/The_Chieftains_Hatch_Centurion_III_Pt1/">posted in abridged form</a> by Nicholas "The Chieftain" Moran on the World of Tanks forum. There are 8 rounds in the ready racks in front of the loader and 20 more rounds in the voluminous front hull racks next to the driver. A 105mm-armed Centurion, on the other hand, has only 24 ready rounds in two racks close to the loader. The front hull racks hold 20 rounds as they did before, but now the ready racks in front of the hull only contain 4 rounds. These racks can be seen in the picture below. It can be seen that the ready racks partly obstruct the loader's access to the front hull racks, making it quite difficult to extract ammunition from those racks. The T-54 is more ergonomic in this respect.<br />
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The loader in a T-54 or T-55 is able to reach virtually all of the ammunition in the tank in both ready and non-ready racks, with the insignificant exception of the single cartridge stowed on the floor next to the gunner's seat. That single round is only useful when the turret is pointed directly behind the tank, which would prevent the loader from accessing any of the other hull ammunition racks. Obviously this is a rather inappropriate position for the tank to fight in, so the lack of any ammunition in the hull in such a scenario is not a disadvantage in any way. Furthermore, the low ammunition capacity of the T-54 is not a disadvantage where modern tank combat is concerned, such as in a meeting engagement. However, it can be an issue when meeting engagements become pursuits as the Soviet Army (hypothetically) blitzes across Europe. An adequate stream of supplies must always be maintained in order to keep up the pace of combat operations, and higher dependency on ammunition resupply may prevent some tank units from exploiting gaps in the enemy's defence in certain situations, although it is rather difficult to quantify the effects of lower ammunition capacities.<br />
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A popular myth is that the Soviet Army was ambivalent towards the T-54's relatively low ammunition capacity as it was believed that the tank would be sent to its doom in massed frontal attacks against dug-in NATO tanks and anti-tank weapons, so it only needed enough ammunition for one battle as entire tank fleets could be replaced within hours of its loss. However, this was never mentioned as official policy in any documents or in any Soviet military literature and it was certainly not part of the design requirements of the T-54, or any other Soviet tank for that matter. It must be said that huge losses were expected if the Soviet Army were ever to push into Europe, but that was simply the reality of warfare on such a large scale. The only reason why the T-54 has such a small stock of ammunition compared to NATO tanks is because of the paradox of having a large gun and a small tank at the same time.<br />
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<h3>
<span style="font-size: large;">RATE OF FIRE</span></h3>
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Official Soviet documentation of tank crew norms (battle drills) specifies that loading an Object 137 and Object 155 (a T-54 and T-55 respectively) from the ready racks should take no more than 13 seconds. The "minimum" grade, which is the minimal passing grade, is 13 seconds, and the "good" grade is 11 seconds, while the "excellent" grade is 10 seconds. The standards for loading speed from the other ammunition stores are more lax; when loading from any ammunition rack other than the ready racks, the "minimum" grade is 15 seconds, the "good" grade is 13 seconds, and the "excellent" grade is 12 seconds. However, these numbers are contradicted by the rate of fire figures from the manuals.<br />
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The manual for the T-55A tank states that the combat rate of fire when firing from a standstill is seven rounds per minute and that the expected rate of fire when on the move is four rounds per minute. A 1969 manual for the T-54 (T-54 obr. 1951 with no stabilizer) gives the same numbers - the combat rate of fire is seven rounds per minute when firing from a standstill and four rounds per minute when firing on the move. Considering that the very first prototype of the T-54 had a rate of fire of only 5-6 rounds per minute, and that the T-44 using the ZiS-S-53 along with the T-34-85 could attain a rate of fire of 7-8 rounds per minute, it appears that the newer turret design of the T-54 provided a more conducive working environment for the loader.<br />
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Seven rounds per minute can be considered quite average for a medium tank, albeit one with a 100mm cannon. This amounts to a nominal sustained loading speed of 8.5 seconds per shot, assuming that acquiring a target and aiming at it takes less time than that. However, keep in mind that there is a technicality in the testing procedure. The Soviet measuring criteria calls for the use of all of the ammunition in the tank, not only the rounds from the ready racks. Drawing from only the most convenient ammunition racks and containers, the loader could achieve a higher burst rate of fire.<br />
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However, it should be noted that the combat rate of fire figures given in the manual definitely does not represent the loading speed of the loader. Qualitative analyses of gunnery trials at firing ranges showed that the loading speed does not exceed 7 seconds even when firing on the move, but the actual time between shots was longer due to other factors.<br />
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Reloading while the tank is on the move is more difficult in most variants of the T-54 compared to some other tanks due to the lack of a rotating turret floor, even if that was counter balanced by the rather sluggish spinning speed of the turret. Nevertheless, four aimed shots per minute is not a bad result when compared to other tanks, as you can see in the table below.<br />
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<a href="https://2.bp.blogspot.com/-bv5Vi6jKCaQ/WAtWaNrSQzI/AAAAAAAAHZM/3PfzlRYsAqUt-TiYbUMeLe8RSi7MaGXLwCLcB/s1600/rate%2Bof%2Bfire.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="418" src="https://2.bp.blogspot.com/-bv5Vi6jKCaQ/WAtWaNrSQzI/AAAAAAAAHZM/3PfzlRYsAqUt-TiYbUMeLe8RSi7MaGXLwCLcB/s640/rate%2Bof%2Bfire.png" width="640" /></a><br />
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Older models of the T-54 that lack a stabilizer may have a lower rate of aimed fire when firing on the move as the time taken to acquire the target is much longer due to the need to halt or slow to a crawl in between shots as opposed to the T-54B and T-55 where the gunner can scan for targets while on the move.<br />
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<h3>
<span style="font-size: large;">AMMUNITION</span></h3>
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According to the September issue of the 2008 edition of the "<i>Техника и вооружение</i>" magazine, the ammunition loadout of a typical Soviet T-54 and T-54A consists of 12 HE-Frag rounds, 4 "Shrapnel" rounds, 6 HEAT rounds and 12 AP rounds. The loadout of a Soviet T-55 and T-55A consists of 18 HE-Frag rounds, 4 "Shrapnel" rounds, 6 HEAT rounds and 15 AP rounds. The "Shrapnel" rounds most likely refer to 3USh-1 rounds with the 3Sh5 Flechette shell which contains 1,800 steel flechettes packed in a special casing which is fuzed to break apart during flight to release the flechettes. Due to the rarity of this round, most tanks probably substituted them with standard HE-Frag rounds.<br />
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The standard loadout of a Yugoslavian T-54 consists of 17 HE, 11 AP and 6 HEAT.<br />
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Two types of ammunition casings are available; D-412 steel cases, and Kh-415 brass cases. D-412 weighs 8.50 kg, whereas Kh-415 weighs 6.0 kg. Brass cases are mostly used for AP, APDS, APFSDS and HEAT ammunition to improve firing consistency, while steel cases are mostly used for HE-Frag ammunition as accuracy is slightly less important.<br />
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<h3>
<span style="font-size: large;">HE-Frag</span></h3>
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A tank's target is not necessarily another tank. Most of the time, it isn't. And to that end, the average T-54 tends to have a larger number of HE-Frag ammunition in its loadout compared to its stock of anti-armour ammunition. Out of a total load of 34 rounds, a T-54 with a standard loadout can carry 10 HE rounds and 4 Frag rounds. When the ammunition capacity was increased to 43 rounds in the T-55 upgrade, the number of HE rounds increased to 18 rounds, but the number of Frag rounds remained the same. However, the implementation of HE-Frag rounds made Frag ammunition redundant. The number of HE-Frag rounds carried is the sum of HE and Frag rounds.<br />
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<h3>
<span style="font-size: large;">53-UOF-412</span></h3>
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<span style="font-size: large;">53-OF-412</span></h3>
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The UOF-412 cartridge weighs a total of 30.2 kg. The OF-412 shell itself weighs 15.6 kg while the propellant charge contained within the steel or brass casing weighs 5.5kg. The explosive charge is TNT. Though it was far from unusual to have a TNT filler, more brisant and powerful fillers such as various mixtures of Amatol and A-IX-1 existed, and it is not explained in any literature why TNT continued to be used. Perhaps the most plausible explanation is that TNT was simply easier to cast and much cheaper and the expenditure of HE-Frag shells in times of war was expected to be so high that the cost efficiency of using TNT outweighed all of the drawbacks.<br />
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A 20 pdr. HE shell, for instance, weighs 7.838 kg and contains an explosive charge of 0.6 to 0.75 kg of TNT or Composition B (60% RDX, 40% TNT), depending on the exact model of shell. The OF-412, on the other hand, weighs twice as much at 15.6 kg and contains twice as much explosives with a 1.46 kg TNT explosive charge. For every 100mm HE round that the T-54 carried, a Centurion Mk. 3 would need two 20 pdr. ones to match it in payload. The raw kinetic energy of OF-412 shells is also much higher, not only because it is of a larger caliber and weighs twice as much but also has a higher muzzle velocity of 892 m/s compared to just 602 m/s for a 20 pdr. HE shell. This makes OF-412 very useful against hardened structures as it is capable of penetrating reinforced concrete pillboxes and heavy field fortifications when the PD fuze is set to the "HE" mode for delayed detonation. The range of the shell is also extended, making the T-54 more useful for indirect fire.<br />
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<br />
Muzzle Velocity: 892 m/s<br />
<br />
Cartridge Mass: 30.2 kg<br />
Projectile Mass: 15.6 kg<br />
Explosive Charge Mass: 1.46 kg<br />
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<br />
OF-412 is is topped off with an RGM-6 point detonating (PD) fuse. The fuze is armed only by centrifugal forces, thus making it inert until it has been fired through a rifled gun barrel. There are two fuze settings with three possible firing methods. The superquick setting is marked with an "O" and the delayed setting is marked with a "З" (a Cyrillic "Z").<br />
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The superquick setting detonates the shell 0.027 seconds after impact and the delayed setting detonates the shell 0.063 seconds after impact. Superquick action guarantees reliable detonation in snowy or swampy ground, and delayed action gives a small time allowance for the shell to penetrate its target before detonating. Keeping the (waterproof) safety cap on the fuze has a delaying effect on the fuze (refer to the table above) and switches the round from the "Frag" mode to the "HE" mode. Setting the fuze is the loader's job, but it is the commander who dictates which setting is used. The variety of fuzing possibilities gives OF-412 an added degree of flexibility against targets of all types, meaning that the T-54 has to use fewer rounds overall compared to an early Centurion equipped with the 20 pdr. gun. This offsets the difference in ammunition quantity.<br />
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The delayed fuzing feature is beneficial to overall efficiency when the T-54 is used in an indirect fire role. When RGM-6 fuze is set to the delayed mode, OF-412 can be very useful against underground or dug-in positions, as the shell assumes an arcing ballistic trajectory when shooting at long range.<br />
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The fuze slot at the tip of the shell is also compatible with the <a href="http://jcammo.com/wp-content/themes/directorypress/thumbs//fu-V429.jpg">V-429 variable delay fuse</a> designed in the 60's. The V-429 fuse is point-detonating and armed by centrifugal forces, like RGM-6. The V-429 fuse differs from the V-429E (used in the 115mm U-5TS and 125mm D-81T), which is armed by the braking effect from the unfolding of the stabilizer fins of the shell. Like the RGM-6, the V-429 has two possible settings: superquick and delayed. The main advantages of the V-429 are that it is waterproof even without a waterproofed safety cap, and it has additional safety features to prevent the detonation of the shell even if the fuze is accidentally set off.<br />
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<h3>
<span style="font-size: large;">3UOF10</span></h3>
<h3>
<span style="font-size: large;">3OF32</span></h3>
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3UOF10 is a more modern cartridge, incorporating the 3OF32 shell. This round was introduced in 1975. 3OF32 is designed to produce a more optimal pattern of fragmentation for increased casualties but also remain sturdy enough that it can penetrate reinforced concrete targets without breaking up. The 3OF32 shell is furnished with the V-429 fuze as standard.<br />
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Muzzle velocity: 900 m/s<br />
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Complete round mass: 30.36 kg<br />
Propellant Charge Mass: 5.6 kg<br />
<br />
Mass of Shell: 15.96 kg<br />
Explosive Charge Mass: 1.7 kg<br />
Explosive Type: A-IX-1<br />
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Number of Preformed Fragments and Their Mass:<br />
With a mass of not less than 0.5 g: 1993<br />
With a mass of 0.5 g to 2 g: 814<br />
With a mass of 2 g to 15 g: 928<br />
With a mass exceeding 15 g: 251<br />
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Statistical Average Mass of Fragments: 6.2 g (median is more important, but the statistic is not provided)<br />
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<br />
Velocity of Fragments and Ratio of Fragment Velocities:<br />
100% - at least 1040 m/s<br />
90% - 1060 m/s or more<br />
80% - 1080 m/s or more<br />
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Interestingly, the 3OF32 was later used in the 2A70 low pressure cannon of the BMP-3. In that particular application, the low velocity of the shell further decreases the penetration of the shell into soil and snow, thus improving its fragmentation value, but the low velocity also reduced the energy of the shell and reduced the time allocation for it to penetrate hard obstacles, making it exceedingly unsuitable for bunker busting. It could, however, still be used to remove earth and log fortifications.<br />
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<h3>
<span style="font-size: large;">Armour Piercing (AP)</span></h3>
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Throughout the 1950's, conventional full-caliber steel armour-piercing rounds were the only armour-piercing round available for the T-54, but even after reliable fin-stabilized HEAT shells became available in 1961, conventional full-caliber shells remained the standard ammunition type for dealing with tanks with the less numerous HEAT shell being reserved for more heavily armoured tanks. As a rule, this included heavy tanks like the M103 and the Conqueror or main battle tanks like the M60A1.<br />
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The typical example of this type of ammunition was cheap, reliably lethal, and tended to be more accurate than other types of ammunition. Out of a standard combat load of 34 rounds, a T-54 carried 12 armour piercing rounds and the remainder was taken up by HE-Frag rounds. The T-55 had an expanded ammunition capacity of 43 rounds and carried 15 armour piercing rounds in a standard combat load. When APDS officially became available in 1967, it replaced full caliber steel armour piercing ammunition entirely.<br />
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Throughout the military career of the T-54 series in the USSR and in most of its satellite states, AP shells were preferred over HEAT shells despite the obvious superiority of the latter in armour penetration power. When HEAT became available for the T-54, the ratio between AP and HEAT ammunition was 2:1, and when the T-55 tank was introduced with a larger ammunition capacity, it carried AP and HEAT ammunition in a 2.5:1 ratio. For example, according to ex-NVA tank commander Stefan Kotsch, a standard combat loadout for an NVA T-55 was comprised of 15 APDS rounds, 6 HEAT rounds and 22 HE-Frag rounds. It was the same in the Soviet Army.<br />
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The point blank range for BR-412B and BR-412D is 1,220 m for a target with a height of 2.7 meters, representing a NATO tank. This means that the gunner can set the sight at 1,220 m prior to an engagement, and when an enemy tank is spotted, the gunner simply aims for the center mass of the target. If the target is exactly 1,220 meters away, the shot will land on the turret ring. If the target is closer than 1,220 meters, the shot may land on the turret. If the target is slightly further than 1,220 meters, the shot may land on the hull. Either way, a hit is quite likely within the margin of error provided by the point blank distance. This is a faster method of engaging tank-type targets, and given the high threat posed by tanks, it is probably the preferred gunnery technique employed by most T-54 gunners. For precision gunnery, the range reading obtained by stadiametric rangefinding can be used to further enhance to probability of a hit.<br />
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<h3>
<span style="font-size: large;">53-</span><b><span style="font-size: large;">UBR-412B</span></b></h3>
<h3>
<span style="font-size: large;">53-</span><b><span style="font-size: large;">BR-412B</span></b></h3>
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<br />
When the T-54 entered service in the Soviet Army, there were only two types of armour piercing ammunition available for it. BR-412 AP, and BR-412B APBC. BR-412B was formally introduced sometime around 1946 (apparently, it was already in production by early 1945, but not issued) as a modified version of BR-412, featuring a blunt nose and a ballistic cap to maintain an aerodynamically pointed nose. The shape of the blunt nose is similar to the older 57mm BR-271 APHE-T shot in that it has a small bump on the tip, but the bump is completely flattened and not rounded. As the ballistic properties of the two rounds were different, chiefly due to this ballistic cap, it made little sense to keep the worst of the pair, so the early incarnations of the T-54 were stocked entirely with BR-412B.<br />
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When fired from the D-10T, the probable deviation of BR-412B at a distance of 1 km is 0.3 meters in the horizontal axis and 0.3 meters in the vertical axis. At a distance of 2 km, the probable deviation is 0.5 meters in the horizontal axis and 0.6 meters in the vertical axis.<br />
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The quality of the steel is considered high, and the hardness is respectably high as well. The hardening of the shell progresses uniformly - hardest at the tip and areas close to the surfaces, and slightly softer at the center. In contrast, wartime production 76mm BR-354B for the ZiS-3 gun ranges from 47 points Rockwell C to 38 points (451 BHN to 351 BHN) at the tip alone. Such shells were prone to shattering on impact with hard armour. A hardness of at least 600 BHN at the tip - which BR-412B achieves in excess - is necessary to prevent this from happening. The BR-412B shell is fired from the D-10 series of guns at a chamber pressure of 294.2 MPa.<br />
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Below are two different analyses on different BR-412B samples. Both were done by the Ministry of Munitions in the U.K, but at different times. The one on the right was done in 1963 with ammunition from an unspecified recent conflict, and the one of the left was done in 1958 with ammunition taken from a captured Egyptian SU-100 from the Suez Crisis.<br />
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According to a U.S army document analyzing the Soviet 76mm BR-354B, it was mentioned that American armour piercing shots are generally hardened to approximately Rockwell C 60 (654 BHN) at the nose. By this metric, BR-412B can be considered on par with U.S ammunition.<br />
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With successful armour perforation, the lethality of BR-412B will be high due to the larger mass of the projectile compared to 85mm and 90mm guns firing the same type of shell, and it is further augmented by the 65-gram explosive charge of A-IX-2 at the base of the shell which ensures the complete destruction of the projectile after armour perforation. A British evaluation states that the detonation of the explosive charge has the effect of shattering the rearmost portion of the shell into five to six pieces as the shell exits the rear of an armour plate, supplementing the large spray of secondary projectile fragments and spall from the armour plate itself. As such, the cone of fragmentation is increased in size and a larger number of internal components will be hit. These five to six large chunks of hard steel may also produce even more fragmentation as they impact the interior walls of the target. In addition to that, the high energy of these chunks has a much greater chance of detonating ammunition inside the tank compared to smaller fragments. Contrary to how AP shells with a base charge are often perceived, the explosion will not send fragments in all 360 degrees like a grenade. It must be remembered that the walls surrounding the cavity containing the explosive charge are very thick - too thick to act as an effective fragmentation casing.<br />
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Nevertheless, the killing power of the shell is augmented to some extent by the percussive effect of the blast, which has greater power than that of an F-1 fragmentation grenade (which holds 60 grams of TNT), even though most of it is spent in cracking the base of the shell into several pieces. Confined inside the small spaces of a tank, the effect of the blast is magnified and the incendiary effect of A-IX-2 increases the chance of igniting fuel and ammunition, not to mention burning the crew and internal equipment. While 65 grams may not seem like much, A-IX-2 is a particularly useful explosive-incendiary compound because it contains aluminium as a fuel additive. A-IX-2 consists of 73% RDX, 23% aluminium powder, and 4% phlegmatizing wax. The aluminium powder content produces an incendiary effect, because aluminium powder is used as a fuel additive to increase the heat of combustion (<a href="http://www.sciencedirect.com/science/article/pii/S2214914716300927#">Türker 2016, p. 426</a>).<br />
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The high aluminium content in A-IX-2 means that there will be some unburnt aluminium powder dispersed into the surrounding air, where it will burn at reduced rate due to the reduced oxygen level in the air (and also in the RDX itself, as RDX is oxygen deficient) and due to the increased concentration of gaseous byproducts from the explosion. Augmenting this effect is the fact that the burning of aluminium generates an alumina (aluminium oxide) coating over the surface of the aluminium particles. The alumina acts as an insulation layer, thus delaying the burning of the aluminium itself so that the efficiency of combustion is reduced. This has the effect of extending the duration of combustion and thus increasing the explosive impulse, extending the release of heat energy, increasing the explosive impulse, extending the radius of the incendiary effect, and increasing the probability of igniting other flammables in the vicinity of the explosion. Because of these factors, all HE-I shells for aviation cannons and APHE shells developed in the USSR after 1940 used A-IX-2 exclusively. On the other hand, medium to large caliber HE-Frag shells usually had an A-IX-1 or Trotyl filler, presumably for cost reasons.<br />
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Muzzle velocity: 895 m/s<br />
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Mass of Complete Round: 30.1 kg<br />
Projectile Mass: 15.88 kg<br />
<br />
Mass of Explosive Charge: 0.065 kg<br />
Explosive Charge Type: A-IX-2<br />
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Chamber Pressure: 294.2 MPa<br />
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According to Yugoslavian tests, BR-412B could only defeat the front turret armour of a T-54A at a distance of 500 meters. This means (indirectly) that BR-412B can perforate 200mm of cast steel armour of medium hardness set at an angle of 0-30 degrees at 500 meters. This is well within the figures listed below.<br />
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Penetration at 0 Yards:<br />
<br />
164mm at 30°<br />
133mm at 45°<br />
96mm at 60°<br />
59mm at 70°<br />
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Penetration at 1,000 Yards:<br />
<br />
140mm at 30°<br />
115mm at 45°<br />
82-85mm at 60°<br />
51mm at 70°<br />
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Source: British test report: DEFE 15/1107 "The Performance of Russian SU 100 APHE/T Shot UBR-412B Against Armour Plate"<br />
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All values are for a 50% chance of penetration.<br />
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The British use the V50 standard instead of the Soviet/Russian V80 standard. If the document were Russian, the distance where the shell would be able to penetrate the armour of the tank would be listed as shorter. Besides that, the criteria for what constitutes armour penetration differs substantially from the Russian criteria. The British and American criteria dictates that at least 50% of the projectile mass must end up on the other side of the armour plate per a certain velocity, or in more practical terms, a certain distance (as the function of distance is the derivative of velocity). This forms the basis of the V50 standard. The Russian criteria as manifested in most firing tables dictates that at least 75% of projectile mass must be found on the other side of the armour plate. In actual certification testing, though, an 80% standard is used. This is responsible for the differences in penetration values of Russian ammunition in both military and civilian literature.<br />
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These figures are backed up by this page of the report:<br />
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Each vertical divider on the chart represents 250 meters.<br />
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All values are in V50 standard. The hardness of the target plates is listed below.<br />
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<blockquote class="tr_bq">
Penetration at 0°:<br />
100 m: 235mm<br />
250 m: 226mm<br />
500 m: 211mm<br />
750 m: 197mm<br />
1000 m: 185mm<br />
1250 m: 172mm<br />
1500 m: 161mm<br />
2000 m: 141mm<br />
2500 m: 123mm<br />
3000 m: 108mm </blockquote>
<blockquote class="tr_bq">
(<i>WWII Ballistics: Armour and Gunnery</i>, corroborated with <i>Janes' Ammunition Handbook</i>)</blockquote>
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As usual, the ballistic arc of the shell is not significant enough to affect armour penetration on sloped targets by any significant amount. According to Soviet firing tables reproduced in the CIA report "<a href="https://www.cia.gov/library/readingroom/document/cia-rdp80t00246a028600430001-7"><i>Technical Information on the 100-mm Gun and Other Armament on the T-54 Tank</i></a>" from 1960, the angle of descent of BR-412B and BR-412D is 0.4 degrees at a distance of 1 km and 1 degree at 2 km.<br />
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In terms of penetration power and post-penetration lethality, BR-412B is nominally superior to 90mm M318A1 APCBC. However, the T-54 did not have access to "premium" ammunition like M304 HVAP, though 100mm BR-412P HVAP ammunition was built in some small quantities and was considered for full issuance. Ultimately, regular steel rounds were considered adequate and BR-412P never saw the light of day. For situations where steel AP was inadequate, multipurpose HEAT ammunition could do the job better than tungsten cored HVAP ammunition while simultaneously offering a secondary anti-personnel function thanks to its explosive charge and thick steel casing.<br />
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Once full armour perforation is achieved, the results are utterly devastating. (The photo on the left is actually from a BR-412D penetration, but the effect is much the same).<br />
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As a rule of thumb, the entry channel in a thick armour plate is always larger than the actual caliber of the shell and the exit channel is typically equally large if not more so. A blast of armour fragments is ejected at extremely high speed into the tank, followed by shards of the shell, followed by the shell itself which may or may not be intact. If intact, the explosive filling at the base of the shell detonates and fragments the steel body, creating additional fragmentation and increasing the spray cone angle of fragmentation after clearing the armour plate. The MD-8 fuse embedded in the rear of the shell has a delay to ensure that the explosive charge detonates a certain distance inside the tank past the armour, making it more deadly than if it detonated immediately after perforating the armour plate, or during the penetration phase inside the armour plate.<br />
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Although it was originally intended for defeating increasingly thick German tank armour near the end of the Second World War, the intended targets for the BR-412B shell quickly changed to American tanks. The M26 Pershing, and by extension the M46, both have a 100mm-thick cast steel upper glacis angled at 46 degrees. Factoring in the lower efficiency of cast armour compared to rolled armour and the information from the British tests, it should be vulnerable to BR-412B at a distance in excess of 1.5 km. As for the M47, Yugoslavian ballistic testing found that the 100mm cast steel upper glacis with a slope of 60 degrees can be perforated by BR-412B at a distance of 750 meters. This would not have been an acceptable result by WWII standards as average tank combat distance was between 200-800 meters, but as tank optics improved, this became rather close for comfort. Nevertheless, the T-54 still nominally outranges the M47.<br />
<br />
According to page 25 of <i>WWII Ballistics: Armour and Gunnery</i>, a 100mm cast armour plate within the 220-300 BHN hardness range is 93% as effective as rolled armour with a hardness of 240 BHN at a 0 degree impact angle against 100mm armour piercing projectiles. The book does not list the relative efficiency of cast armour when it is sloped, but this information agrees with the results of the Yugoslavian tests, implying that the efficiency does not change significantly with the angle of the plate.<br />
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The M47 became the mainstay of many European armies including the West German Bundeswehr, but the improved M48 was the backbone of the U.S Army for most of the Cold War. The upper glacis of the M48 is cast steel, 110mm thick sloped at 60 degrees, which is more somewhat formidable than the upper glacis of the M47. 110mm of cast steel should be equivalent to around 102mm of rolled steel, making the upper glacis of the M48 approximately on par with the T-54 itself. A detailed report on the performance of BR-412B against the M48 is detailed in <a href="http://tankarchives.blogspot.com/2017/06/soviets-vs-m48-patton.html">this Tank Archives post</a>, courtesy of Peter Samsonov. The original 1958 report is titled "<i><a href="http://btvt.info/5library/vbtt_1958_02_m48.htm">Броневая Защита Американского Среднего Танка М-48</a></i>". Soviet testing revealed that BR-412B was not capable of penetrating the upper glacis of the M48 even at point blank range, which should not be surprising as the Yugo test report mentions that BR-412B was not capable of perforating the upper glacis of a T-54A. However, the lower glacis of the M48 could be perforated at 2,500 meters. It is interesting to note that the Soviet report concluded that BR-412B needed an impact velocity of 940 m/s to defeat the upper glacis armour of the M48, which is substantially higher than the muzzle velocity achieved by firing BR-412B out of a D-10 or a BS-3 gun. Defeating the upper and lower side hull armour of the M48 from a side angle of 30 degrees (from the longitudinal axis of the tank) is possible from a distance of 500 meters.<br />
<br />
The turret of the M48 is weaker than the upper glacis - mostly because it is not nearly as sloped as the upper glacis - but it is still very well rounded and quite formidable. The thickness of the front turret face at the gun mantlet region varies from 178mm to 100mm, with sloping that ranges from 14 degrees at the very bottom edge of the turret where it is thickest to 56 degrees near the turret roof, where it is much thinner, but no matter what the thickness or slope is, the thickness on the front turret face invariably measures up to exactly 7 inches, or 178mm. The thickness reduces considerably beyond the immediate front turret face, but this is somewhat compensated by additional horizontal slope, although the final LOS thickness is still less than the front turret face. By referring to the penetration values given earlier, we can see that the front turret face cannot be considered well protected against BR-412B.<br />
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<a href="https://4.bp.blogspot.com/-844ll7gXG8Q/WWfYGxN0svI/AAAAAAAAIqA/EBP-TNPOllwqZD4s4_1DCqitDm64DhMVgCLcBGAs/s1600/detroit%2Bm48.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="649" data-original-width="1233" height="336" src="https://4.bp.blogspot.com/-844ll7gXG8Q/WWfYGxN0svI/AAAAAAAAIqA/EBP-TNPOllwqZD4s4_1DCqitDm64DhMVgCLcBGAs/s640/detroit%2Bm48.jpg" width="640" /></a></div>
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The gun shield overlaps the front turret face slightly, but the area of overlap is very small and the gun shield itself is negligibly thin. The most significant portion of the gun shield is 110mm thick, sloped at 30 degrees, which comes out to 127mm in LOS thickness. This should be vulnerable to BR-412B at a distance of more than 1,200 meters.<br />
<br />
Overall, BR-412B should be able to perforate the area near the base of the turret at distances in excess of 1,250 meters, and the area near the roof should be highly vulnerable at a distance of at least 800 meters. This was inexcusable, since BR-412B was by no means new by the time the M48 entered service. For this reason, the Soviet report "<i><a href="http://btvt.info/5library/vbtt_1958_02_m48.htm">Броневая Защита Американского Среднего Танка М-48</a></i>" concluded that 100mm rounds are generally effective against the M48, despite the inability to defeat the upper glacis armour. However, better ammunition in the form of BR-412D became available at the same time that the M48 entered service in the U.S Army.<br />
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<br />
<h3>
<span style="font-size: large;">53-UBR-412D</span></h3>
<h3>
<span style="font-size: large;">53-BR-412D</span></h3>
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<a href="https://4.bp.blogspot.com/-SzTvuwDAdKw/V8G_Rfd8N4I/AAAAAAAAHQA/_mKTqXiEsjYlFbdLx8zQvh47MlLXmI15ACLcB/s1600/br-412d.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-SzTvuwDAdKw/V8G_Rfd8N4I/AAAAAAAAHQA/_mKTqXiEsjYlFbdLx8zQvh47MlLXmI15ACLcB/s1600/br-412d.png" /></a></div>
<br />
<br />
Steel shell with a soft steel armour piercing cap. This shell formally replaced the BR-412B as the standard anti-armour round in 1953, but it came as early as 1951 as an component of the loadout of the T-54 obr. 1951 (the brand new TSh2-22 sight for the T-54 obr. 1951 had a range scale for BR-412D). Both BR-412B and BR-412D continued to be used side by side for some time, so in actuality, BR-412D supplanted the BR-412B rather than replaced it outright in Soviet service. Some former Soviet satellite states were still using BR-412B into the 2,000's until they eventually scrapped their T-54 tanks completely.<br />
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The armour piercing cap prevents the shell from breaking up when it impacts thick steel plate at high velocities. Controlled fracturing of the nose of the shell is beneficial towards penetration on sloped targets, but shattering of the shell will neutralize it completely. This shell is superior to the BR-412B on both low and high obliquity targets, but the difference is most noticeable at low obliquity. In page 10 of "<a href="https://www.slideshare.net/NikoHolkko/bachelors-61286856">Mechanisms of Armour Penetration</a>" by Niko Holkko, it is shown that uncapped APBC and AP shells are more effective on thin plates (0.4 calibers) at all angles compared to APC and APCBC shells, but the inverse is true when the plate thickness reaches 0.45 calibers and above. On a thick plate (1.3 calibers), APC and APCBC rounds vastly outperform APBC at 60 degrees obliquity. In practical terms, the superior penetration on thick sloped armour makes BR-412D a favourable choice when engaging modern tanks of the era such as the M47 and M48.<br />
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<br />
Muzzle Velocity: 887 m/s<br />
<br />
Complete Mass of Round: 30.4 kg<br />
Projectile Mass: 15.88 kg<br />
<br />
Mass of Explosive Charge: 0.061 kg<br />
Explosive Charge Type: A-IX-2<br />
<br />
Chamber Pressure: 294.2 MPa<br />
<br />
Point-blank ranges:<br />
<br />
For a target height of 2.0 m - 1,070 m<br />
For a target height of 2.7 m - 1,220 m<br />
For a target height of 3.0 m - 1,270 m<br />
<br />
<br />
For armour penetration, Zaloga gives these figures (<a href="http://amizaur.prv.pl/www.wargamer.org/GvA/weapons/soviet_guns8.html">Link</a>):<br />
<br />
Penetration at 0°:<br />
100 m: 200mm<br />
500 m: 185mm<br />
1000 m: 170mm<br />
1500 m: 155mm<br />
2000 m: 125mm<br />
<br />
<br />
Penetration at 30°:<br />
100 m: 150mm<br />
500 m: 140mm<br />
1000 m: 130mm<br />
1500 m: 120mm<br />
2000 m: 100mm<br />
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<br />
These values are in Soviet standard. Soviet target plates had a hardness of between 250 to 350 BHN.<br />
<br />
<br />
Penetration at 0°:<br />
100 m: 250mm<br />
1.0 km: 185mm<br />
1.5 km: 170mm<br />
<br />
<br />
(Source unknown)<br />
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The CIA report "<a href="https://www.cia.gov/library/readingroom/document/cia-rdp80t00246a028600430001-7"><i>Technical Information on the 100-mm Gun and Other Armament on the T-54 Tank</i></a>" has this penetration table for the BR-412D:<br />
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<a href="https://2.bp.blogspot.com/-oOfnEL1O6Dw/WMte0QnQ8TI/AAAAAAAAIlk/xHlEWYtoA8kNnkSWIBPTJoievji7VD_zgCLcB/s1600/cia-d-10-1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="382" src="https://2.bp.blogspot.com/-oOfnEL1O6Dw/WMte0QnQ8TI/AAAAAAAAIlk/xHlEWYtoA8kNnkSWIBPTJoievji7VD_zgCLcB/s640/cia-d-10-1.png" width="640" /></a></div>
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Comparing these figures to Zaloga's, we can see a significant discrepancy. The CIA's figures are much higher, especially when we go up to and beyond 2,000 meters. At 500 m and 1,000 m, the CIA's figures are 10mm higher for a 30-degree impact and 15mm higher for a 0 degree impact. At 2,000 meters, the CIA's figures are 20mm (!) higher for a 30-degree impact and a 30mm (!) higher for a 0-degree impact. The figures in the report are apparently taken from Soviet documents.<br />
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According to these figures, BR-412D should be more than capable of perforating the front hull armour of a Leopard 1 at distances in excess of 1,500 meters. The Panther's 82mm upper glacis sloped at 55 degrees was found to be penetrable at a distance of 1,500 meters. As for the M48, the BR-412D should have an effective range of several hundred meters more than the BR-412B when attacking the turret, but the most noticeable advantage is that BR-412D should be able to perforate the upper glacis of the M48 at a distance of around 500 meters, based on the difference in slope modifiers.<br />
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<h3>
<span style="font-size: large;">3UBM8</span></h3>
<div>
<span style="font-size: large;"><b>3BM8</b></span></div>
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<a href="http://3.bp.blogspot.com/-XVGAvJq7B94/VmPs1afNsLI/AAAAAAAAEr4/JTCUfoIO4j4/s1600/01%2B-%2B100mm%2Bx695%2BBM-8%2BAPDS-T%2BRussia.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://3.bp.blogspot.com/-XVGAvJq7B94/VmPs1afNsLI/AAAAAAAAEr4/JTCUfoIO4j4/s400/01%2B-%2B100mm%2Bx695%2BBM-8%2BAPDS-T%2BRussia.JPG" width="72" /></a> <a href="https://1.bp.blogspot.com/-DB2P6qsyEcA/WofbTw3PHFI/AAAAAAAAK5U/SjcCAAHHImMdW2pVSe8aLpu55JratNOjgCLcBGAs/s1600/bm8.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="519" data-original-width="291" height="400" src="https://1.bp.blogspot.com/-DB2P6qsyEcA/WofbTw3PHFI/AAAAAAAAK5U/SjcCAAHHImMdW2pVSe8aLpu55JratNOjgCLcBGAs/s400/bm8.png" width="223" /></a></div>
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3BM8 is an APDS shell for the D-10T that officially entered service in 1967. However, mass production began some years prior to 1967, and the modified TSh2B-32P sight with markings for APDS rounds was introduced in 1965.</div><div><br /></div><div>The development of Soviet anti-tank munitions is highly unusual in that APFSDS rounds entered service before APDS rounds whereas foreign nations invariably put APDS rounds into service before upgrading to APFSDS ammunition later on. The 3BM8 round specifically was part of a unified development effort that led to the introduction of APDS rounds for the 122mm D-25T and M62-T2S guns for T-10 heavy tanks. If the 100mm D-54 gun were to enter service in the late 1950's instead of the 115mm U-5TS smoothbore gun, it would have been supplied with an APDS round almost identical to 3BM8.</div><div><br /></div><div>3BM8 had good performance on vertical plate, possibly as good as 105mm L28 APDS, but its effectiveness on heavily sloped plate was largely unremarkable, although there are certain nuances that can be attributed to its design. Unlike the 105mm L28 APDS series, the penetration depth of 3BM8 into armour plate does not have a linear relationship with the slope of the late. </div><div><br /></div><div>When comparing 3BM8 to the 20 pdr. MK.3 and the 105mm L28, it can be seen that the core of the 3BM8 and the MK.3 is an ogive whereas the L28 has a blunt tip. This is responsible for the better penetration of L28 on sloped armour plate at the expense of some penetration performance on flat armour plate. However, it is worth noting that problems with L28 were encountered during combat, prompting the development of tilting caps.<br />
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As a side note, MK. 3 and the more advanced L28 are similar in that they both have an unsecured cap. The MK.3 projectile has a small blunt steel cap (possibly non-ballistic in function, as it is referred to as a spacer) and the L28 has a conical tungsten carbide cap. For 3BM8, an extraordinarily thick section of low hardness alloy steel in front of the core acts as the armour piercing cap, and the hollow tip of the structure is partially filled with some lightweight metal (probably aluminium) to act as a windscreen. Although it appears to be less elegant than the solution used in the L28 round, the large steel cap may be highly beneficial against simple dual-layered spaced armour as the cap cannot be easily removed by a thin spaced plate: the thickness of the cap is too high to be eroded by a thin spaced plate, and the firm integration of the cap as a part of the jacket for the core makes it more difficult to dislocate the cap or deflect it away from the core after passing through a spaced plate. This is an interesting perspective to consider, as the deficiencies of L28 on thin spaced armour was well known - a thin 10mm steel plate could not only remove the tungsten armour piercing cap but also shatter the tungsten carbide core, making it ineffective on any subsequent plates. The extraordinarily thick steel cap of 3BM8 may have been designed to alleviate this issue, and this is explored later in the article.<br />
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Besides that, the tungsten carbide core in 3BM8 is smaller and lighter than the one in MK. 3 and also lighter to the one in the L28, although the diameter is slightly larger. From left to right: 3BM8, MK.3, L28 with tilting cap. Earlier L28 variants had a core with a blunt tip instead of a hemispherical tip. The hemispherical tip allowed the cap to slide against the tip of the core, which would not have been possible with a blunt tip.<br />
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<a href="http://3.bp.blogspot.com/-tuNTGX8eIx8/VmPsaczUr3I/AAAAAAAAErw/2BK5wJjdfl4/s1600/100mm%2Bbm-8%2Bapds-t.JPG" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="400" src="https://3.bp.blogspot.com/-tuNTGX8eIx8/VmPsaczUr3I/AAAAAAAAErw/2BK5wJjdfl4/s400/100mm%2Bbm-8%2Bapds-t.JPG" width="190" /></a><a href="https://4.bp.blogspot.com/-6Vn3W-GtS1U/WEQa9S__K1I/AAAAAAAAHwE/xQ7YhS7MENgQortqkUlQEpwY29wS1fHJgCLcB/s1600/20%2Bpdr.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://4.bp.blogspot.com/-6Vn3W-GtS1U/WEQa9S__K1I/AAAAAAAAHwE/xQ7YhS7MENgQortqkUlQEpwY29wS1fHJgCLcB/s400/20%2Bpdr.jpg" width="192" /></a><a href="https://2.bp.blogspot.com/-7CFTVJk6Kj4/WEQa8UCt-dI/AAAAAAAAHwA/wOkZ8ccAHUsqpaNutq524FUPu35YOPPNgCEw/s1600/105mm.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://2.bp.blogspot.com/-7CFTVJk6Kj4/WEQa8UCt-dI/AAAAAAAAHwA/wOkZ8ccAHUsqpaNutq524FUPu35YOPPNgCEw/s400/105mm.jpg" width="300" /></a></div>
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The same design of core contained within the 3BM8 projectile is shared by the 122mm 3BM11. The development of the 3BM8 is directly related to the 3BM11, as they were both born out of the same set of requirements. The shared heritage can be seen in their identical designs. 3BM11 appears to be larger than 3BM8, but that is mostly due to an increase in the thickness of the steel sheath over the core, leading to an increase in the overall diameter of the projectile but not in the diameter in the core itself. The sabot has a distinctly larger diameter. 3BM11 penetrates 320mm at 0 degrees and 110mm at 60 degrees, but this is purely due to the higher power of the cannon that fires it.<br />
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<br />
Muzzle Velocity: 1,415 m/s<br />
<br />
Maximum Chamber Pressure: 3,000 kg/sq.cm<br />
<br />
Mass of Complete Round: 20.9 kg<br />
<br />
Projectile Length (incl. sabot): 240mm<br />
Projectile Mass (incl. sabot): 5.7 kg<br />
<br />
Subcaliber Projectile Diameter: 55mm<br />
Subcaliber Projectile Length: 223mm<br />
Subcaliber Projectile Mass: 4.13 kg<br />
<br />
Source for dimensions: (<a href="http://guns.allzip.org/topic/216/845563.html">Link</a>)<br />
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<br />
Core Material: Tungsten carbide<br />
Core Diameter: 50mm<br />
Core Length: 120mm<br />
Core Mass: 2.82 kg<br />
<br />
<br />
Point blank ranges:<br />
<br />
For a target height of 2.0 m - 1,680 m<br />
For a target height of 2.7 m - 1,930 m<br />
For a target height of 3.0 m - 2,020 m<br />
<br />
<br />
<blockquote class="tr_bq">
Penetration at 2.0 km: </blockquote>
<blockquote class="tr_bq">
290mm at 0°<br />
80mm at 60° </blockquote>
<blockquote class="tr_bq">
From "<i>Сустьянцев Колмаков Боевые машины уралвагонзавода танки Т-54 Т-55</i>"</blockquote>
<br />
<blockquote class="tr_bq">
Penetration at 0°: </blockquote>
<blockquote class="tr_bq">
300mm at 2.0 km<br />
240mm at 3.5 km<br />
<br />
Penetration at 30°: </blockquote>
<blockquote class="tr_bq">
240mm at 2.5 km<br />
200mm at 3.5 km<br />
<br />
Penetration at 60°: </blockquote>
<blockquote class="tr_bq">
100mm at 2.0 km<br />
90mm at 2.5 km<br />
75mm at 3.5 km </blockquote>
<blockquote class="tr_bq">
<br />
From "<i>Частные Вопросы Конечной Баллистики</i>"</blockquote>
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All information from official instructional booklet on 3BM8 and 3BK5.<br />
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As seen in the viewfinder of the TShSM-32P sight, APDS ammunition was a huge improvement over the old full-caliber steel AP rounds. According to V. A. Grigoryan in "<i><a href="https://eknigi.org/voennaja_istorija/154326-zashhita-tankov.html">Защита танков</a></i>", 3BM8 has a muzzle velocity of 1,415 m/s and a velocity of 1,202 m/s at 2 km. The rate of velocity loss from this data amounts to 106.5 m/s per kilometer, and the deceleration is -142 m/s^2. In comparison, the 105mm L28 APDS round with a muzzle velocity of 1,478 m/s is reported to have a velocity of 1,381 m/s at 1 kilometer, implying a rate of velocity loss of 97 m/s per kilometer. Given that the rate of velocity decay increases with distance, the aerodynamic performance of 3BM8 can be considered functionally identical to L28 and also to the L36 and L52 which share the same ballistic shape as L28.<br />
<br />
The tables below are taken from page 205 of "<i style="font-family: "times new roman";">Частные Вопросы Конечной Баллистики</i><span face="">" (</span><span face=""><i style="font-family: "times new roman";">Particular Questions of Terminal Ballistics</i>) published by Bauman Moscow State Technical University on behalf of NII Stali. The first column from the left indicates that 3BM8 is the tested projectile and the next three columns from the left list the spaced armour configurations: b1 and b2 denote the thickness of the first and second plates in millimeters, and L denotes the size of the air gap in millimeters. The fourth column from the right lists the velocity limit of 3BM8 for the described spaced armour configuration, and the third column from the right lists the velocity limit for a monolithic plate of the same thickness in steel (b1 + b2). The difference in the velocity limit is listed in the second column from the right. The first column on the right shows the difference in the velocity limits between the spaced armour configuration and a monolithic RHA plate in percentage points, and also represents the improvement in mass efficiency. For example, in the table below for spaced armour targets at a 0 degree obliquity, </span><span face="">3BM8 can defeat a 150-300-90 spaced armour design angled at 0 degrees at an impact velocity of 1,215 m/s, whereas a monolithic 240mm plate (150 + 90) can be defeated at a velocity of 1,050 m/s. The difference in velocity limits amounts to 15.7%, showing that the spaced armour is 15.7% more effective than a monolithic armour plate of the same mass. In terms of distance, a velocity of 1,215 m/s corresponds to a distance of 2 km and a velocity of 1,050 m/s roughly corresponds to a distance of 3.4 km.</span><br />
<span face=""><br /></span>
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<a href="https://4.bp.blogspot.com/-jUyK_lS7bPM/W8D5tphDtMI/AAAAAAAAMYw/nKA9Mf1JC0QC2QAP2bckvT_-RTNwBHEOgCLcBGAs/s1600/100mm%2B0%2Bdegrees.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="753" data-original-width="1600" height="300" src="https://4.bp.blogspot.com/-jUyK_lS7bPM/W8D5tphDtMI/AAAAAAAAMYw/nKA9Mf1JC0QC2QAP2bckvT_-RTNwBHEOgCLcBGAs/s640/100mm%2B0%2Bdegrees.png" width="640" /></a></div>
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<span face=""><br /></span>
<span face="">The table below shows the velocity limit of 3BM8 on similar spaced targets but at an angle of 30 degrees. </span><span face="">From the table below, it can be seen that the effect of increasing the thickness of the spaced plate from 20mm to 50mm to 90mm while maintaining the same amount of spacing and the same 150mm RHA back plate causes a negligible increase in the effectiveness of the spaced armour in terms of mass efficiency: only from 21.5% to 22.5%. Of course, in real terms, the use of a 90mm front plate makes the sloped spaced armour effectively immune to 3BM8 at point blank range whereas a monolithic plate with a thickness of 240mm (90 + 150) under the same conditions could be defeated at a velocity limit of 1,160 m/s, which translates to a distance of roughly 2.5 kilometers. Overall, it can be seen that the increasing the thickness of the back plate of a spaced armour design has a much larger effect than increasing the thickness of the front plate for spaced armour sloped at 30 degrees.</span><br />
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<a href="https://1.bp.blogspot.com/-s4HEoq6Ofls/Wu_AJ5TAwyI/AAAAAAAALhM/fC88v-ICEIwuk169iCuz7ZrEYi3IP26ngCLcBGAs/s1600/3bm8%2B30%2Bdegrees.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="557" data-original-width="1079" height="330" src="https://1.bp.blogspot.com/-s4HEoq6Ofls/Wu_AJ5TAwyI/AAAAAAAALhM/fC88v-ICEIwuk169iCuz7ZrEYi3IP26ngCLcBGAs/s640/3bm8%2B30%2Bdegrees.png" width="640" /></a></div>
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This analysis is reinforced by shooting results at 30 degree targets with 122mm 3BM11, which has the same basic projectile design as 3BM8 and only differs in the increased muzzle velocity when fired out of a 122mm cannon and the shape of the steel jacket around the tungsten carbide core. As seen in the table, the use of a 200mm back plate with a spaced 20mm front plate and a 350mm air gap results in a 42.1% increase in mass efficiency. The use of a spaced 10mm front plate with an 80mm air gap and a 140mm back plate yields practically no improvement in mass efficiency whatsoever, which is the opposite of the expected result for an L28 round. Experiments conducted with L28A1 imitators and L28A1 scale models also showed that the design was highly sensitive to spaced armour. It was shown that a 20-300-50 spaced armour design sloped at 30 degrees yielded a 62.8% increase in mass efficiency, which is quite large compared to the 14.3% increase when 3BM8 was shot at the same target. VK-12 tungsten carbide was used for the L28A1 imitators. VK-12 has a 12% cobalt binder instead of the normal 8% nickel binder of VN-8.<br />
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<a href="https://3.bp.blogspot.com/-QZpRjQJPgGM/W8D30Q7nC1I/AAAAAAAAMYk/jcfs74PcUxgN4KvrSO4l5VWti2KkqfS_gCLcBGAs/s1600/122mm%2B3bm11.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="381" data-original-width="1002" height="241" src="https://3.bp.blogspot.com/-QZpRjQJPgGM/W8D30Q7nC1I/AAAAAAAAMYk/jcfs74PcUxgN4KvrSO4l5VWti2KkqfS_gCLcBGAs/s640/122mm%2B3bm11.png" width="640" /></a></div>
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<br />
The table below shows the velocity limits of 3BM8 for a target angled at 60 degrees in the same format. The data below is obviously quite significant in determining the capabilities of 3BM8 against simple spaced armour such as the type found on upgraded Leopard 1 tanks, but useful data on the velocity limits for monolithic plates is also given. According to the table, the velocity limit for a 100mm monolithic plate (from the table: 20 + 80) is 1,220 m/s, corresponding to a target distance of just under 2 km. Also, the velocity limit for a monolithic 85mm plate (from 40 + 45) is 1,125 m/s which corresponds to a distance of between 2.5-3.0 km, and the velocity limit for a monolithic 90mm plate (10 + 80) is 1,160 m/s, corresponding to a distance of between 2.0-2.5 km. From this data, the 80mm penetration figure for a 60 degree target at 2 km appears to be a guaranteed or a minimum penetration figure and the actual achievable penetration can be much higher at the same distances.<br />
<br />
Regarding the optimization of the spaced armour designs, it can be seen that the most effective configuration in real terms is the 20-300-80 array, which can only be defeated from near-point blank range (velocity limit of 1,400 m/s). However, the most efficient configuration is the 20-300-45 array, which had a 21.1% mass efficiency advantage over a monolithic armour plate of the same mass. However, the 20-300-45 armour could be defeated at a velocity limit of 1,150 m/s and a 65mm plate (20 + 45) could be defeated at a velocity limit of 950 m/s, corresponding to distances of roughly 2.5 km and 4.4 km respectively.<br />
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<a href="https://3.bp.blogspot.com/-wM6-1GjJrHQ/Wu_AKJKXMAI/AAAAAAAALhQ/mVIRYhDxQqIOEcbHNOHcSGU-Uoa_cgFvQCLcBGAs/s1600/3bm8%2B60%2Bdegrees.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="624" data-original-width="1117" height="356" src="https://3.bp.blogspot.com/-wM6-1GjJrHQ/Wu_AKJKXMAI/AAAAAAAALhQ/mVIRYhDxQqIOEcbHNOHcSGU-Uoa_cgFvQCLcBGAs/s640/3bm8%2B60%2Bdegrees.png" width="640" /></a></div>
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The graph below illustrates the change in velocity limit for changes in the thicknesses of the first and second spaced plates. The thickness of the first plate is alternatively expressed in terms of the ratio of the thickness to the diameter of the tungsten carbide core.<br />
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<a href="https://4.bp.blogspot.com/-C4Gq5Fi1bEk/Wu_Kh6LsmVI/AAAAAAAALhk/_iTojmOKUHkCmgjdhB7oJCm_pLW5I89EQCLcBGAs/s1600/graph%2Bof%2Bspaced%2Barmour.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1020" data-original-width="591" height="640" src="https://4.bp.blogspot.com/-C4Gq5Fi1bEk/Wu_Kh6LsmVI/AAAAAAAALhk/_iTojmOKUHkCmgjdhB7oJCm_pLW5I89EQCLcBGAs/s640/graph%2Bof%2Bspaced%2Barmour.png" width="370" /></a></div>
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Although higher than the more commonly cited figure of 80mm at 60 degrees at 2 kilometers, the penetration figures for a 60 degree plate from "<i style="font-family: "times new roman";">Particular Questions of Terminal Ballistics</i><span face="">"</span> still fall short of the claimed performance of the 105mm L52 APDS round from the early 70's (reportedly entered service in 1973 in the U.K, 1974 in the U.S in the form of M728), which is comprised of a tungsten alloy core with a steel armour piercing cap and can reportedly perforate 120mm RHA at 60 degrees at a distance of 1,830 meters (according to a marketing brochure) and penetrate 250mm RHA at 0 degrees at 1,000 meters (according to Janes). The use of softer but much tougher tungsten alloy core in the L52 instead of a tungsten carbide core with exceptionally high hardness but low toughness was aimed at improving the performance of the round on non-monolithic targets, particularly simple dual-layered spaced targets. An increase in performance on oblique targets was also obtained. This improved performance came at the cost of reduced performance on monolithic RHA targets at a flat angle, which is reflected in the penetration figures mentioned earlier - 250mm RHA at 0 degrees at 1 km for L52, and 290mm RHA at 0 degrees at 2 km for 3BM8.<br />
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The merits of the increased performance on sloped and non-monolithic targets are self-evident. At the time, all of the known Soviet medium and heavy threats incorporated heavily sloped armour and there was no indication that Soviet armour designs would trend towards thick and flat homogeneous steel plating in the near future. Similarly, the newest NATO tanks as of 1967 - namely the M60A1 and the Chieftain - also relied heavily on the complex oblique ballistic shaping of their cast hulls and turrets. The design of the 3BM8 penetrator was unsuited for such targets, which is indicative of a large technological gap between the USSR and the West. That said, the side armour of any NATO tank could be defeated by 3BM8 from a high angle of incidence.<br />
<br />
Aside from that, it is clear that 3BM8 boasts greatly improved penetration power compared to the outdated BR-412B and BR-412D rounds at all angles of obliquity, but it could also be argued that the primary benefit of the APDS round was the enhanced probability of achieving a hit on faraway targets and especially moving targets. This advantage arguably carries more weight than the increased penetration power, as despite the increased armour piercing performance, the challenge of defeating the frontal armour of contemporary tanks like the M60A1 and Chieftain would be practically insurmountable at long ranges. If the T-54/55 hoped to defeat these formidable foes from the front in the 1961-1971 time frame, it could only do so with HEAT ammunition. This situation contradicts the common Western narrative that the T-62 was made redundant by the introduction of the 3BM8 round. In truth, the T-54 series only gained the ability to counter NATO's new main battle tanks when it began receiving APFSDS ammunition in 1972.<br />
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<h3>
<span style="font-size: large;">3UBM7</span></h3>
<h3>
<span style="font-size: large;">3BM19</span></h3>
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<a href="https://1.bp.blogspot.com/-5bPTi75fJ-A/W_QvTlfo57I/AAAAAAAAMgc/49rClTA7y5ERSPH4XAENRP22pgo79V9dACLcBGAs/s1600/3%25D0%2591%25D0%259C19.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1356" data-original-width="766" height="640" src="https://1.bp.blogspot.com/-5bPTi75fJ-A/W_QvTlfo57I/AAAAAAAAMgc/49rClTA7y5ERSPH4XAENRP22pgo79V9dACLcBGAs/s640/3%25D0%2591%25D0%259C19.jpg" width="360" /></a></div>
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The 3UBM7 round contained the 3BM19 projectile with a steel penetrator. It was designed as an all-steel alternative to the 3UBM8 round with the 3BM20 projectile that contained tungsten carbide. The impetus behind the creation of this round is unclear, but it is unlikely that it was created solely for training purposes as it is listed as a combat round.<br />
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The shape of the projectile was identical to 3BM20 and the ballistic properties of the cartridge was identical to 3BM20. Although the penetrators of the two projectiles were different, both used the same sabot and stabilizer fin assembly with the same tracer. Compared to the 3BM8 projectile that it replaced, the 3BM19 featured only a slightly higher muzzle velocity of 1,430 m/s, but its kinetic energy was not higher because the weight of the projectile decreased slightly to 4.06 kg. It is therefore not surprising that its ballistic characteristics were very similar to the APDS round it replaced. Having a point blank range of 1,690 meters against a target with a height of two meters, and a point blank range of 2,040 meters against a target with a height of three meters, the trajectory of 3BM20 was only negligibly flatter than 3BM8.<br />
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The three-piece steel sabot designed for the 3BM19 differed significantly from the steel "ring" type sabot for the APFSDS rounds used in the smoothbore 115mm and 125mm guns at the time, and needless to say, it was completely different from the "cup" type sabot of 3BM8. Despite the shorter length of the three-piece sabot and the use of the stabilizer fins of the projectile as contact points, its weight was similar to the sabot of the 3BM8 projectile. Moreover, the penalty for the use of large bore-riding stabilizer fins was high aerodynamic drag. The D-10 gun was evidently not suitable for the extremely light "ring" type sabots used by the 100mm T-12, 115mm U-5TS and 125mm D-81 smoothbore guns.<br />
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At the time, the use of the stabilizer fins as contact points between the projectile and the bore was a universal feature of all Soviet APFSDS rounds but the particular design of the three-piece sabot was unique to the D-10 family of guns due to the presence of rifling, so naturally, it featured some measures to ensure that round could operate normally with rifling. The main design feature to neutralize the effect of the rifling was the copper driving band which was only loosely connected to the sabot so that the friction between the band and the sabot would be very limited. This allowed the driving band to act as a slip ring when the round was fired through the rifled barrel of the D-10 gun, thus preventing the rifling from imparting the full spin rate to the entire projectile (the projectile still spun, but at a greatly reduced rate). There was another ring ahead of the driving band that acted as another contact point with the barrel. Moreover, the stabilizer fins of the projectile itself had flat ends to ensure that they would maintain contact with the lands of the rifling without slipping into the grooves.<br />
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The back surface of the sabot was lined with a thin sheet of rubber. When the projectile assembly is propelled through the barrel, the high energy propellant gasses pushing on the back of the sabot causes the rubber to expand and form a gasket to seal the gap between the rifling lands and grooves. This prevented any propellant gasses from exiting the barrel before the projectile.<br />
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The weight of the 3BM19 projectile itself is unknown, but based on its dimensions, it should be very similar to the 3BM2 projectile for the 100mm smoothbore T-12 towed anti-tank gun as that also had a maximum diameter of 38mm and its overall length was only slightly longer at 535mm. Given that the weight of 3BM2 is 3.38 kg, the 3BM19 projectile most likely weighs 3.3 kg of which approximately 3.0 kg is formed by the steel penetrator rod. Knowing this, it is quite interesting to note that the kinetic energy of the projectile is significantly less than the 3BM8 shell as that weighed 4.13 kg in flight and traveled at practically the same velocity.<br />
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Muzzle Velocity: 1,430 m/s<br />
<br />
Total Projectile Mass (incl. sabot): 4.58 kg<br />
Projectile Mass: ~3.3 kg<br />
<br />
Maximum Projectile Diameter: 38mm<br />
Total Projectile Length: 496mm<br />
<br />
Penetrator Length: 384mm<br />
Maximum Penetrator Diameter: 38mm<br />
Minimum Penetrator Diameter: 30mm<br />
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Firing tables for 3BM19 are not currently available in the public domain, but because its point blank ranges for two and three meter targets are known to be equivalent to 3BM8, it can be easily deduced that its velocity decays at almost the same rate as 3BM8. Working off the assumption that the rate of velocity decay is around 106 m/s, it can be estimated that the impact velocity of 3BM19 at one kilometer is 1,324 m/s and its impact velocity at two kilometers is 1,216 m/s.<br />
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With this data in hand, it is possible to estimate the perforation limit of 3BM19 using the latest revision of the perforation calculator developed by Willi Odermatt based on the well known Lanz-Odermatt equation. However, the calculator can only work if the tapered 3BM19 steel penetrator rod is represented by a simplified cylinder of equal weight with a frustum shape based on available line drawings. After doing so, the following results are obtained:<br />
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<table border="1">
<tbody>
<tr>
<th>Range</th>
<th>Perforation limit at 0°</th>
<th>Perforation limit at 60° (LOS thickness)</th>
</tr>
<tr>
<td>0 m</td>
<td>205mm</td>
<td>120mm (240mm)</td>
</tr>
<tr>
<td>1,000 m</td>
<td>174mm</td>
<td>101mm (203mm)</td>
</tr>
<tr>
<td>2,000 m</td>
<td>141mm</td>
<td>82mm (164mm)</td>
</tr>
</tbody></table>
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From these calculations, it is very clear that 3BM19 falls far short of the penetration power of 3BM8 on flat RHA steel by a huge margin, and the shortfall is only somewhat less pronounced on targets sloped at 60 degrees or may be equal to 3BM8 depending on the source. Assuming that the rather pessimistic penetration figures listed in the book "<i>Сустьянцев Колмаков Боевые машины уралвагонзавода танки Т-54 Т-55</i>" are true, then 3BM19 can match the penetration power of 3BM8 on RHA targets sloped at 60 degrees, but if the (more realistic) figures from "<i>Частные Вопросы Конечной Баллистики</i>" are used instead, then it is evident that 3BM19 does not even come close to achieving a similar result as 3BM8.<br />
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<h3>
<span style="font-size: large;">3UBM8</span></h3>
<h3>
<span style="font-size: large;">3BM20</span></h3>
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://4.bp.blogspot.com/-U4hHmgCl7Bs/W_QwARQDt1I/AAAAAAAAMgw/_Dy0vTxM2iMrGLE6pS6D1KO0XjFdsl_8gCLcBGAs/s1600/100-mm-UBM-8-Round-with-Armour-Piercing-Fin-Stabilized.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="107" data-original-width="515" src="https://4.bp.blogspot.com/-U4hHmgCl7Bs/W_QwARQDt1I/AAAAAAAAMgw/_Dy0vTxM2iMrGLE6pS6D1KO0XjFdsl_8gCLcBGAs/s1600/100-mm-UBM-8-Round-with-Armour-Piercing-Fin-Stabilized.jpg" /></a></div>
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The 3UBM8 round entered service concurrently with the 3UBM7 round in 1972. It was developed under the same research topic as the 3BM15 projectile and as such, it had the same penetrator configuration but the whole projectile was scaled down to better suit the ballistic properties of the aging D-10 cannon. As mentioned before, the 3BM20 projectile shared many similarities with the 3BM19 projectile, most notably sharing the same sabot, stabilizer fin assembly and tracer. The propellant charge was also the same. The only difference was in the penetrator of the projectile. The 3BM20 projectile was externally similar to 3BM19, but it had a tungsten carbide core made from VN-8 carbide and an armour piercing cap in a configuration that was shared with the 3BM15 projectile for the 125mm D-81T gun. This is immediately obvious when the cross section of the tip of the projectile is inspected (shown below).<br />
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<a href="https://1.bp.blogspot.com/-2eWXrLnUfpE/W_QvwhsxI8I/AAAAAAAAMgs/PfPHukUoiSA3_eRdpNlivvgZzJJsVkLZQCEwYBhgL/s1600/3%25D0%2591%25D0%259C20%2B%25D1%2581%25D1%2585%25D0%25B5%25D0%25BC%25D0%25B0.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1362" data-original-width="754" height="640" src="https://1.bp.blogspot.com/-2eWXrLnUfpE/W_QvwhsxI8I/AAAAAAAAMgs/PfPHukUoiSA3_eRdpNlivvgZzJJsVkLZQCEwYBhgL/s640/3%25D0%2591%25D0%259C20%2B%25D1%2581%25D1%2585%25D0%25B5%25D0%25BC%25D0%25B0.jpg" width="354" /></a> </div>
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The tungsten carbide core was also of the same material as that of the 3BM15 projectile, differing only in dimensions. VN-8 indicates that it is a tungsten carbide with an 8% nickel binder.<br />
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The nature of the 3BM20 penetrator gave it far superior performance on sloped targets compared to the obsolete 3BM8 APDS round, but the much lower muzzle velocity of 3BM20 compared to 3BM15 meant that its performance was much lower relative to its bigger brother with all else being roughly equal. Case in point: the muzzle velocity of 3BM20 was only equal to the velocity of 3BM15 at 2.7 kilometers. The ordnance velocity of 3BM20, i.e its impact velocity at typical combat ranges of between 1.5 to 2.0 kilometers, was only 1,200 to 1,300 m/s.<br />
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The length of the 3BM20 projectile is 496mm which is close to the 508mm length of the 3BM2 projectile for the MT-12 towed anti-tank gun, but it is noticeably shorter than the 115mm 3BM6 projectile and the 125mm 3BM15 projectile, as shown in the photo below.<br />
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<a href="https://1.bp.blogspot.com/-byKV08isP4E/W_Qs-0ntnfI/AAAAAAAAMgU/YFwvVPCa0EEy-qwSlo-fOBy_-FUTX5cuwCEwYBhgL/s1600/various%2Bapfsds.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="534" data-original-width="604" height="564" src="https://1.bp.blogspot.com/-byKV08isP4E/W_Qs-0ntnfI/AAAAAAAAMgU/YFwvVPCa0EEy-qwSlo-fOBy_-FUTX5cuwCEwYBhgL/s640/various%2Bapfsds.jpg" width="640" /></a></div>
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<br />
Muzzle Velocity: 1,430 m/s<br />
<br />
Tungsten Penetrator Mass: 0.17 kg<br />
<br />
Total Projectile Mass (incl. sabot): 4.58 kg<br />
Projectile Mass: ~3.3 kg<br />
Maximum Projectile Diameter: 38mm<br />
Projectile Length: 496mm<br />
<br />
Total Penetrator Length: 380mm<br />
Maximum Penetrator Diameter: 38mm<br />
Minimum Penetrator Diameter: 30mm<br />
<br />
Core Material: VN-8 Tungsten carbide<br />
Core Diameter: ~20mm<br />
<br />
<br />
Based on publicly available sources, 3BM20 is reportedly rated to defeat 240mm of flat RHA plate at a distance of two kilometers. This is exactly the same performance as 3BM8 and it confirms that 3BM20 succeeded in its intended purpose of achieving a penetration power similar to 3BM8 while maximizing the conservation of tungsten, as 3BM20 uses only 170 grams of tungsten, which is only 5.7% of the amount used in the 3BM8.<br />
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<h3>
<span style="font-size: large;">3UBM11</span></h3>
<h3>
<span style="font-size: large;">3BM25 "Izomer"</span></h3>
<br />
The order for the modernization of anti-tank munitions for anti-tank guns of the 100mm to 125mm calibers was issued in 1972, and led to the creation of 3BM25 "Izomer" alongside 3BM21 "Zastup for the 115mm U-5TS tank gun, 3BM24 "Kalach" for the 100mm T-12 and MT-12 towed anti-tank guns and 3BM22 "Zakolka" for the 125mm D-81T tank gun. The three-piece sabot was carried over from the 3BM-19. This led to a range of APFSDS rounds built using the same technologies with a close resemblance to one another. In practice, most of the difference in armour-piercing performance comes from the difference in the muzzle velocities. Mass production of the 3UBM11 started in around 1975 or 1976, but it only formally entered service in 1978.<br />
<br />
The internal construction of the "Izomer" projectile is identical to the other APFSDS rounds in the 100-125mm range of calibers. The tungsten carbide core is located at the tip of the projectile behind a VNZh-90 tungsten alloy armour-piercing cap. The remainder of the projectile is made from 35KhZNM tool steel. The 0.27 kg VN-8 tungsten carbide core is the same as the one used in 125mm APFSDS rounds, larger than the 0.17 kg core used in 3BM20. The cross section of the projectile shown below shows the large tungsten alloy armour piercing cap with its blunt tip.<br />
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<a href="https://2.bp.blogspot.com/-0p0QIOUVgT8/W_QwxpKOa7I/AAAAAAAAMhE/ta2nXPEbOlI6sQDEVlN72gKozdy33O1LACLcBGAs/s1600/3%25D0%2591%25D0%259C20.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="274" height="640" src="https://2.bp.blogspot.com/-0p0QIOUVgT8/W_QwxpKOa7I/AAAAAAAAMhE/ta2nXPEbOlI6sQDEVlN72gKozdy33O1LACLcBGAs/s640/3%25D0%2591%25D0%259C20.jpg" width="108" /></a></div>
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<br />
In terms of length and diameter, the 3BM25 projectile appears to be very close to the 3BM20 projectile. However, it is known to be considerably heavier as implied by the larger weight of the complete projectile assembly. Based on the weight difference (5.02 kg as compared to 4.58 kg), the 3BM25 projectile has a weight of around 3.74 kg. Like its predecessor, the 3BM25 projectile has four stabilizer fins.<br />
<br />
<br />
Muzzle velocity: 1,430 m/s<br />
<br />
Total Mass: 20.7 kg<br />
Total Projectile Mass (incl. sabot): 5.02 kg<br />
Projectile Mass: ~3.74 kg<br />
<br />
Total Length: 978mm<br />
<br />
Core Material: VN-8 Tungsten carbide<br />
Core Diameter: 20mm<br />
Core Length: 71mm<br />
<br />
<br />
Information from "<i>Оружие России (2001-2002)</i>".<br />
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<br />
<h3>
<span style="font-size: x-large;">HEAT</span></h3>
<br />
The use of shaped charge ammunition is often viewed as an equalizing factor that virtually invalidated all tank armour for a large part of the Cold War. However, this is only a half-truth. HEAT ammunition was a convenient alternative to conventional steel and subcaliber armour-piercing rounds, but was not a substitute. In fact, throughout the service life of the T-54 and 55, only 6 rounds were carried out of a total load of 34 and 43 rounds respectively. When the ammunition capacity of the tank increased with the introduction of the T-55, the number of HEAT rounds did not increase whereas the number of full caliber steel armour piercing rounds increased from 12 to 15 rounds, the ratio of HEAT rounds to other rounds actually fell. This contradicts the widespread belief that the Soviet army preferred HEAT rounds over KE rounds, and instead shows that the opposite is true.<br />
<br />
Only the French army can be considered to have viewed HEAT ammunition as a universal replacement for all other armour-piercing ammunition types, as the unusual Obus-G HEAT round was the only anti-armour round available to AMX-30 tanks for a considerable length of time. However, it was eventually accepted that HEAT was not only a non-optimal anti-tank round, but that the Obus-G design itself was critically flawed in that it had a high cost due to the high tolerance requirements, but low penetration power and an accuracy advantage that was too minor to be worth the tradeoff.<br />
<br />
That said, HEAT ammunition was valuable for the T-54 as it allowed it to reliably defeat the frontal armour of the M60A1 and the Chieftain at any distance, assuming that it could score a hit.<br />
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<br />
<h3>
<span style="font-size: large;"><b>3UBK4, 3UBK4M</b></span></h3>
<h3>
<span style="font-size: large;"><b>3BK5, 3BK5M</b></span></h3>
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The first HEAT round design for the D-10T, introduced in 1961. The appearance of this round coincided with the appearance of the heavily armoured M60A1 tank. 3BK5 had more than enough penetration power to defeat the strongest parts of the M60A1 and still retain enough residual penetration to be able to eliminate the crew and destroy important equipment.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://4.bp.blogspot.com/-LcVMKv9_AgA/WH3MQZ6DhSI/AAAAAAAAIKk/i8m8EqQQIA8nsH1Gfw_iIgJ2R2gf2y0xgCLcB/s1600/01%2B-%2BBK-5%2BHEAT-T%2Bcartridge%2Bcutaway%2Band%2Bbackside.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://4.bp.blogspot.com/-LcVMKv9_AgA/WH3MQZ6DhSI/AAAAAAAAIKk/i8m8EqQQIA8nsH1Gfw_iIgJ2R2gf2y0xgCLcB/s640/01%2B-%2BBK-5%2BHEAT-T%2Bcartridge%2Bcutaway%2Band%2Bbackside.JPG" width="214" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Photo credit to PzGr40 of the wk2ammo site</td></tr>
</tbody></table>
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<br />
The advantage of 3BK5 over typical armour piercing rounds is slightly offset when taking the poorer ballistic properties of the shell into consideration. Although the shell has a muzzle velocity that is slightly higher than BR-412B and BR-412D armour-piercing shells, it was significantly lighter so the shell carried less kinetic energy as well as momentum which is more important in this context. This means that it slows down more rapidly from aerodynamic drag, which is compounded by the higher drag from the stabilization fins, leading to a larger drop in velocity over distance. As the firing table below shows, the point blank range of 3BK5 is consistently shorter at all distances compared to BR-412B and BR-412B. It also becomes subsonic at a range of 2,550 meters whereas the firing table for BR-412B/D ends at 4,000 meters with the shell still maintaining a velocity of 545 m/s.<br />
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<a href="https://1.bp.blogspot.com/-VDzmNYTpvmc/XPvVDmT-zSI/AAAAAAAAOU8/GOq0rp3S4jEqDxD9I09FyEisvtB4_La2wCLcBGAs/s1600/3bk5%2Bfiring%2Btable.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1169" data-original-width="1600" height="466" src="https://1.bp.blogspot.com/-VDzmNYTpvmc/XPvVDmT-zSI/AAAAAAAAOU8/GOq0rp3S4jEqDxD9I09FyEisvtB4_La2wCLcBGAs/s640/3bk5%2Bfiring%2Btable.jpg" width="640" /></a></div>
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There are two variants of the 3BK5 shell. One is the basic 3BK5, which had a steel liner, and the other is the 3BK5M, which had a wave shaper and a copper liner. The wave shaper was a block of inert material that controlled the propagation of the blast wave to optimize the formation of the cumulative jet of the shaped charge. 3BK5M had improved penetration power. Both the 3BK5 and 3BK5M were introduced simultaneously in 1961.<br />
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<a href="https://2.bp.blogspot.com/-J8q7VJFnwJI/WEZca1FkJ-I/AAAAAAAAHww/ffXt7tco9WoJg3SNX9_u6f-3AhxoQhE1ACLcB/s1600/3bk5.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="237" src="https://2.bp.blogspot.com/-J8q7VJFnwJI/WEZca1FkJ-I/AAAAAAAAHww/ffXt7tco9WoJg3SNX9_u6f-3AhxoQhE1ACLcB/s400/3bk5.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-CRu9D4piDXo/WH3MU11EREI/AAAAAAAAIKo/zk2qYuGC47wvJ2Edvs0VNSUuotUXdniXACLcB/s1600/02%2B-%2BBK-5M%2BHEAT-T%2Bprojectile%2Bin%2Bflight.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="217" src="https://3.bp.blogspot.com/-CRu9D4piDXo/WH3MU11EREI/AAAAAAAAIKo/zk2qYuGC47wvJ2Edvs0VNSUuotUXdniXACLcB/s400/02%2B-%2BBK-5M%2BHEAT-T%2Bprojectile%2Bin%2Bflight.JPG" width="400" /></a></div>
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<br />
Fuse: GPV-2 PIBD<br />
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Muzzle Velocity: 900 m/s<br />
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Total Mass of Cartridge: 25.5 kg<br />
Mass of Projectile: 12.38 kg<br />
Mass of Explosive Charge: 0.990 kg (3BK5), 1.038 kg (3BK5M)<br />
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Penetration (at all ranges):<br />
<br />
180mm RHA at 60 degrees<br />
390mm RHA at 0 degrees<br />
<br />
Chamber Pressure: 235.36 MPa<br />
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Point-blank ranges:<br />
<br />
For a target height of 2.0 m - 960 m<br />
For a target height of 2.7 m - 1,100 m<br />
For a target height of 3.0 m - 1,150 m<br />
<br />
<br />
With each cartridge weighing in at just 25.5 kg, 3BK5 was easier to load than either AP and HE, but not APFSDS. It is interesting to note that during the famous Yugo tests, 90mm M431 HEAT failed to fuze on the upper glacis of the target T-54 if the tank had a side angle of more than 20 degrees, but there were no such remarks to the same effect regarding the 3BK5. It can be inferred with reasonable confidence that 3BK5 with the GPV-2 fuze can handle steep slopes.<br />
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<h3>
<span style="font-size: large;">3UBK9, 3UBK9M</span></h3>
<h3>
<span style="font-size: large;">3BK17, 3BK17M</span></h3>
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<a href="https://1.bp.blogspot.com/-eM5zMHigWMw/W7dQ-MXDM3I/AAAAAAAAMW8/hFUoP-5mgdc3d7aOGxql9P6oGJdcbEBjACLcBGAs/s1600/ikra.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="265" data-original-width="1600" height="106" src="https://1.bp.blogspot.com/-eM5zMHigWMw/W7dQ-MXDM3I/AAAAAAAAMW8/hFUoP-5mgdc3d7aOGxql9P6oGJdcbEBjACLcBGAs/s640/ikra.png" width="640" /></a></div>
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Newer HEAT round, entered service in 1978. The penetration power of this new round was higher thanks to the implementation of new liner manufacturing technologies, but it is quite interesting to note that the mass of the projectile was substantially reduced, allowing the round to achieve a substantially higher muzzle velocity. The increase in muzzle velocity was helpful when engaging moving targets at a distance, but the magnitude of the improvement in hit probability is not likely to be major.<br />
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<br />
Total Length of Cartridge: 1,093mm<br />
Total Mass of Cartridge: 21.9kg<br />
Mass of Projectile: 10.0 kg<br />
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Muzzle velocity: 1,085m/s<br />
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Projectile Mass: 10 kg<br />
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It is worth noting that the short spike tip of the 3BK17(M) round has a protruding ring just behind the tip of the fuse. This is to eliminate an aerodynamic phenomenon known as dual flow, which greatly increases the drag coefficient of the projectile during high velocity flight. However, it is particularly interesting that the 115mm 3BK-15 "Zmeya" round that was designed under the same developmental program as "Ikra" lacks this ring. The ballistic properties of spike tip designs is explored in <a href="https://thesovietarmourblog.blogspot.com/2015/12/t-62.html#heat">Tankograd's T-62 article</a>.<br />
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<h3>
<span style="font-size: large;">COAXIAL MACHINE GUN</span></h3>
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<a href="http://2.bp.blogspot.com/-T6gKzMB36SE/Vk8sfT5RpDI/AAAAAAAAEHk/TuCBCGXbmy4/s1600/sgmt43.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-T6gKzMB36SE/Vk8sfT5RpDI/AAAAAAAAEHk/TuCBCGXbmy4/s1600/sgmt43.gif" /></a></div>
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The T-54 mounts the SGMT on the right side of the main gun as a co-axial weapon. It has a cyclic rate of fire of 600 rounds per minute, and it is fed from a 250-round box of which ten more are stowed inside the tank for a total of 2,750 rounds of ammunition. The SGMT could be fired with the trigger button on the elevation handwheel or the left trigger button on the gunner's handgrip on the T-54A and all subsequent models. Firing the machine gun is also possible with the solenoid trigger button attached to the back of a receiver in case of a total failure of the tank's electrical systems.<br />
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In 1964, the SGMT was swapped out for the PKT machine gun. Naturally, the first model to receive the new machine guns was the T-55A, but existing tanks gradually transitioned to the PKT over time as their original machine guns wore out. The two machine guns were practically indistinguishable in ballistic performance, but the PKT fires at a higher cyclic rate of 800 rounds per minute. Ball and AP-I is linked with API-T in a 4:1 ratio.<br />
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When the bow machine gun was removed beginning with the T-55 model, the ammunition allocated to it was transferred to the coaxial machine gun. As such, it now had 3,500 rounds of ammunition available.<br />
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<a href="https://1.bp.blogspot.com/-rrirlbAzPas/XaYW2hn_AqI/AAAAAAAAPZY/oAAtFzz7odQxs3nNgytnSDbbTRNwhJWZQCLcBGAsYHQ/s1600/machine%2Bgun%2Bcover.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="287" data-original-width="250" src="https://1.bp.blogspot.com/-rrirlbAzPas/XaYW2hn_AqI/AAAAAAAAPZY/oAAtFzz7odQxs3nNgytnSDbbTRNwhJWZQCLcBGAsYHQ/s1600/machine%2Bgun%2Bcover.gif" /></a></div>
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<h3>
<span style="font-size: large;">
BOW MACHINE GUN</span></h3>
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<a href="https://2.bp.blogspot.com/-Iblyh63QowE/WIhBbYkSdGI/AAAAAAAAISw/IoRYBiMDZYML1Q1_4-PUFMnrbr8f5alRACLcB/s1600/SGMT.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-Iblyh63QowE/WIhBbYkSdGI/AAAAAAAAISw/IoRYBiMDZYML1Q1_4-PUFMnrbr8f5alRACLcB/s1600/SGMT.jpg" /></a></div>
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The T-54 has a fixed SGMT machine gun mounted just to the right of the driver (pictured below). This was not unusual in any way, especially considering the roots of the design of the tank. However, what is unique to the T-54 is that there is a bow machine gun, but no dedicated bow machine gunner as the SGMT is aimed and fired by the driver. In this sense, the T-54 was a more forward-thinking design than tanks like the M46 while also being a more silly one.<br />
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<a href="http://4.bp.blogspot.com/-ncACjc1np7w/Vk8ipmAq4VI/AAAAAAAAEHU/N3BJJiAUglU/s1600/t-54%2Bbow%2Bmachine%2Bgun.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://4.bp.blogspot.com/-ncACjc1np7w/Vk8ipmAq4VI/AAAAAAAAEHU/N3BJJiAUglU/s640/t-54%2Bbow%2Bmachine%2Bgun.jpg" width="640" /></a></div>
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Ammunition is supplied by a 250-round box mounted to the right of the gun. Spent ammo belts and casings are ejected into a deflector and fall into a canvas collection bag placed just below the machine gun. Reloading the machine gun is the driver's duty. It is fired using a solenoid thumb trigger on the end of the right steering tiller, but there is no way to aim it at all, other than by steering the tank. It doesn't take much imagination to figure out how effective this would have been in combat. One plausible use for the bow machine gun is for the driver to suppress the area directly in front of the tank without aiming for no other reason than to induce panic in enemy forces by sheer volume of fire. In practice, the ammunition allocated to the bow machine gun probably would be used up by the coaxial machine gun instead.<br />
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<h3>
<span style="font-size: large;">ANTI-AIRCRAFT MACHINE GUN</span></h3>
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<a href="https://1.bp.blogspot.com/-jbq_srxoy5o/XVA1rdbnZlI/AAAAAAAAOz8/B0iL5_QB-rcUwk696z244jHNT6B2DQBgwCLcBGAs/s1600/anti%2Baircraft%2Bgun.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="355" data-original-width="598" height="378" src="https://1.bp.blogspot.com/-jbq_srxoy5o/XVA1rdbnZlI/AAAAAAAAOz8/B0iL5_QB-rcUwk696z244jHNT6B2DQBgwCLcBGAs/s640/anti%2Baircraft%2Bgun.jpg" width="640" /></a></div>
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The original T-54-1 (T-54 obr. 1947) was a departure from the WWII-era policy for medium tanks in that it had a DShKM anti-aircraft machine gun installed on its roof in a simple skate ring mount, shown in the photo above. Prior to the T-54, only the IS-2 heavy tank had such a machine gun, and only in an official capacity from November 1944 onward.Medium and light tanks in the Red Army generally did not have external machine guns of any kind unless field modifications were performed whereas American tanks infamously bristled with machine guns, often installed in impractical positions. The DShKM on the T-54-1 could be rotated along the skate ring, swiveled around its own axis on the pintle mount or both at once. The DShKM could be fixed in any position by locking its pintle mount and elevation gear, and then locking the skate ring in place. It was normally aimed by grasping the spade grips built into the back of the machine gun and swiveling it around. The machine gun can be elevated by 85 degrees and depressed by -5 degrees, making it a useful tool against both ground targets and air targets, but because the machine gun had to be operated by someone standing behind the turret owing to its location, it was not an effective system.<br />
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Beginning with the T-54 obr. 1951 model, the machine gun was relocated to a new ring mount on the loader's cupola. The new mount preserved the same range of elevation provided by the earlier mount, but the method of aiming the machine gun was changed and its new location made it much easier for the loader to operate the machine gun in combat. <br />
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<a href="https://1.bp.blogspot.com/-GlbyVyrbL0c/XQMlj1PaIPI/AAAAAAAAObc/Gi53canMtaMta9m4lodEoVe2n1ynUQk8ACLcBGAs/s1600/dshkmt%2Bmachine%2Bgun.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="399" data-original-width="600" height="265" src="https://1.bp.blogspot.com/-GlbyVyrbL0c/XQMlj1PaIPI/AAAAAAAAObc/Gi53canMtaMta9m4lodEoVe2n1ynUQk8ACLcBGAs/s400/dshkmt%2Bmachine%2Bgun.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-QxzOCH2UPOg/WBhk8i2kSyI/AAAAAAAAHgM/cVjd6yxtFrwgKQbtaC8bCWQSmmSGTS6DQCLcB/s1600/t-54%2Bdshk.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="285" src="https://3.bp.blogspot.com/-QxzOCH2UPOg/WBhk8i2kSyI/AAAAAAAAHgM/cVjd6yxtFrwgKQbtaC8bCWQSmmSGTS6DQCLcB/s400/t-54%2Bdshk.jpg" width="400" /></a></div>
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To aim the machine gun in azimuth, the loader must rotate his entire cupola with his own bodily strength, and to aim it in elevation, the elevation hand wheel is worked to move the machine gun along a toothed arc. There is also a braking mechanism on the elevation hand wheel that acts as an elevation lock for the machine gun. It is actuated by a lever on the handle of the wheel that releases the brake when pressed to allow the machine gun to be elevated and depressede, so once the loader has aimed at a fixed target, he should release the lever to lock the machine gun in place before opening fire for maximum accuracy.<br />
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The loader fires the machine gun by depressing the trigger lever on the fixed handle on the left of the gun mount which pulls on a Bowden cable connected to the mechanical trigger on the back of the DShKM receiver. Since the DShKM still retains its spade grips and its original finger trigger when mounted in this configuration, it can be fired manually if needed and it can be used if it is dismounted from the machine gun cradle.<br />
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This design was retained until the T-55 model omitted an anti-aircraft machine gun entirely, but when the T-55A reintroduced the DShKM due to the threat posed by attack helicopters, it was installed on a new loader's cupola with minimal changes to the operating mechanism of the gun mount.<br />
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<a href="https://1.bp.blogspot.com/-xQ4Jmxgzzkk/XOfjwIy38FI/AAAAAAAAOEY/SDyTOcfQ3Wcd_Ka9aIWRcpdbgqsgoafBACEwYBhgL/s1600/dshk.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="418" data-original-width="604" height="276" src="https://1.bp.blogspot.com/-xQ4Jmxgzzkk/XOfjwIy38FI/AAAAAAAAOEY/SDyTOcfQ3Wcd_Ka9aIWRcpdbgqsgoafBACEwYBhgL/s400/dshk.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-dg-55j97GJ4/XOfjxQZ77QI/AAAAAAAAOEg/79Aq7vYgpKAclpIIKTRvC9KWTE6PZrNRwCEwYBhgL/s1600/nva%2Bt-55%2Bdshk.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1071" data-original-width="1141" height="375" src="https://1.bp.blogspot.com/-dg-55j97GJ4/XOfjxQZ77QI/AAAAAAAAOEg/79Aq7vYgpKAclpIIKTRvC9KWTE6PZrNRwCEwYBhgL/s400/nva%2Bt-55%2Bdshk.jpg" width="400" /></a></div>
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Ammunition was provided in standard 50-round boxes which were stowed outside the turret, on the loader's side. This was so that the loader could easily reach over and retrieve an ammunition box when the machine gun is aimed forward. Although stowing ammunition outside the tank is clearly not an ideal solution as the boxes may be damaged by bullets, blast and fragmentation, there were good reasons for this decision. The most important reason is that there was simply not enough room inside the tank to fit a full load of 300 rounds of 12.7mm ammunition, and another reason is that the loader's hatch is not large enough to permit the easy transfer of the large 50-round boxes from inside the tank to outside. As such, placing the ammunition boxes on the side of the turret was in the best interests of improving the ergonomics of the crew and improving the speed of reloading the anti-aircraft machine gun.<br />
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<a href="https://1.bp.blogspot.com/-nWZpSe99TcQ/XQMlkWYAv5I/AAAAAAAAObk/6HZlZRZHLLMDtiwHyf25mJlZlEZu3lT8wCLcBGAs/s1600/t-55%2Bammo%2Bboxes.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="441" data-original-width="608" height="290" src="https://1.bp.blogspot.com/-nWZpSe99TcQ/XQMlkWYAv5I/AAAAAAAAObk/6HZlZRZHLLMDtiwHyf25mJlZlEZu3lT8wCLcBGAs/s400/t-55%2Bammo%2Bboxes.png" width="400" /></a></div>
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Aiming at ground targets is accomplished with either the standard iron sights on the DShKM or the K-10T anti-aircraft collimator sight. The K-10T facilitates accurate aiming at both ground level and high altitude targets, although the basic leaf sights on the machine gun itself would be more appropriate for aiming at ground targets as it can be adjusted for various distances.<br />
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<a href="https://1.bp.blogspot.com/-IJu0tm1alqQ/XVA1soUmc0I/AAAAAAAAO0I/QGfAuHXZxcMCcsV9VO3dx7aLnAL4sXL8wCLcBGAs/s1600/k-10t.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="269" data-original-width="600" height="286" src="https://1.bp.blogspot.com/-IJu0tm1alqQ/XVA1soUmc0I/AAAAAAAAO0I/QGfAuHXZxcMCcsV9VO3dx7aLnAL4sXL8wCLcBGAs/s640/k-10t.gif" width="640" /></a></div>
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The K-10T is offset to the right in order to allow the ladder-type iron sights to be raised for long-distance fire.<br />
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<a href="https://1.bp.blogspot.com/-xXeTh_YpjYo/XVA1rHFGL7I/AAAAAAAAOz4/gdWhiB0o83sx4yaUTrONmeeRxS-XMBnQQCLcBGAs/s1600/aamg.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="625" data-original-width="500" height="400" src="https://1.bp.blogspot.com/-xXeTh_YpjYo/XVA1rHFGL7I/AAAAAAAAOz4/gdWhiB0o83sx4yaUTrONmeeRxS-XMBnQQCLcBGAs/s400/aamg.gif" width="320" /></a><a href="https://1.bp.blogspot.com/-sYHbVlIOcbo/XOfjx73rzjI/AAAAAAAAOEo/Fviic83dXr8v3HfX8QxeSzMko-VZm5RlgCEwYBhgL/s1600/t-55a%2Bdshkm.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="350" data-original-width="311" src="https://1.bp.blogspot.com/-sYHbVlIOcbo/XOfjx73rzjI/AAAAAAAAOEo/Fviic83dXr8v3HfX8QxeSzMko-VZm5RlgCEwYBhgL/s1600/t-55a%2Bdshkm.jpg" /></a></div>
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One of the drawbacks to the layout of the T-54 turret is that the IR spotlight partially blocks the anti-aircraft machine gun in a narrow 12 o'clock sector in depression. When aiming forward, the tank loader is able to fire straight ahead and apply superelevation for distant targets, but he cannot depress the machine gun more than a few degrees. This was arguably acceptable given that the DShKM was an anti-aircraft machine gun after all, so gun depression was not a high priority. Given that the elevated mounting of the IR spotlight was intended to reduce vertical parallax with the gunner's IR night sight, the drawback of reducing the depression angle of the anti-aircraft machine gun was an acceptable concession and the overall layout represented the best compromise.<br />
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<a href="http://1.bp.blogspot.com/-HeA4SUOytlo/VmM-ZGe3shI/AAAAAAAAEp0/Auj6LtnHP5Q/s1600/t-55a_101_dshk.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="282" src="https://1.bp.blogspot.com/-HeA4SUOytlo/VmM-ZGe3shI/AAAAAAAAEp0/Auj6LtnHP5Q/s400/t-55a_101_dshk.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-pQARm78WA2Q/WC_XYfzbU4I/AAAAAAAAHno/Q6BWK2HjjHU3SeNaSgi4bKY46A7Xp9CdwCLcB/s1600/t-55%2Bloader%2527s%2Bcupola.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://1.bp.blogspot.com/-pQARm78WA2Q/WC_XYfzbU4I/AAAAAAAAHno/Q6BWK2HjjHU3SeNaSgi4bKY46A7Xp9CdwCLcB/s400/t-55%2Bloader%2527s%2Bcupola.jpg" width="400" /></a></div>
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<h3>
<span style="font-size: large;">PROTECTION</span></h3>
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Mass-produced T-54 models had more than twice as much armour compared to the T-34, and earlier prototype models had even more. Original design requirements dictated that the frontal armour had to withstand shots from the 7.5cm L/43 KwK 40 and 8.8cm L/71 KwK 43 which can only be described as a remarkable demand because this was the same requirement for the IS-2, a heavy tank, and also the basic requirement of the IS-3. The specific requirements for the prototype of the T-54, <a href="http://tankarchives.blogspot.my/2014/05/nii-48-experiments-1946.html">as translated by Peter Samsonov from Tankarchives</a>, are:<br />
<br />
<br />
<blockquote class="tr_bq">
<i>1. Determine the armour that will protect the hull and turret from 75 mm and 88 mm shells with the muzzle velocity of 1,000 m/s.</i><br />
<i>2. Improve the shape of the hull from the point of view of robustness and shell resistance.</i><br />
<i>3. Improve the armour of the turret to the point that it resists shells as well as the front of the hull.</i><br />
<i>4. Develop armour screens for the T-54 to protect it from HEAT shells up to 105 mm in caliber inclusive and Faust type anti-tank rockets.</i><br />
<i>5. Develop a robust track and track pin (increase track life to 3000 km).</i><br />
<i>6. Investigate the optimal location for ammunition in the tank.</i></blockquote>
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The original requirement of the T-54 for protection from the Pzgr. 39 round fired from the 8.8cm Pak 43 or KwK 43 at a muzzle velocity of 1,000 m/s was created because it was expected that the Pak 43 and KwK 43 or an equivalent cannon would become the standard cannon for future German medium tanks while the existing Tiger II heavy tank would eventually be replaced with a new design equipped with a 10.5cm or 12.8cm cannon. Even though the war ended before this became a reality, the requirement was not relaxed.<br />
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Out of the total weight of 36 tons for a standard T-54 obr. 1951, 18 tons of weight comes from the armoured plating which occupies a 50% share of the total weight of the tank.<br />
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Aside from armour alone, the protection of a tank also encompasses its survival rate in the event that the armour is defeated.<br />
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Contrary to the popular belief that the tightly packed interior of a T-54 or T-55 tank increases the probability of catastrophic destruction from a single penetrating hit, a Soviet study showed that large open spaces inside tanks actually allows spall and fragments to hit more hit crew and internal equipment due to the larger affected arc.<br />
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In terms of serviceability and survivability, the Israeli experience with Centurions, M48s, M60s, T-54s and T-55s (captured during the 1967 war) showed that the exceptionally voluminous M48 and M60 tanks were the poorest by far. In the book "<i>M60 vs T-62: Cold War Combatants 1956–92</i>", a USMC study is cited on page 35 indicating that the battle damage repair states for the October 1973 war were:<br />
<blockquote class="tr_bq">
<ul>
<li>Centurion - 60% returned to action </li>
<li>T-54 / T-55 - 55% returned to action </li>
<li>M48 / M60 - 19% returned to action</li>
</ul>
</blockquote>
It is worth noting that Israel did not have a steady supply of T-54/55 parts and had to cannibalize other tanks, including captured Syrian and Egyptian ones, to repair battle damage and solve mechanical issues. Despite this, T-54 and T-55 tanks were returned to action at almost the same rate as Centurions, whereas the repair rates for the M48 and M60 was almost a third less than that of the T-54/55.<br />
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<h3>
<span style="font-size: large;">T-54-1 (T-54 obr. 1947)</span></h3>
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As a result of these requirements, the T-54-1 prototype tank had an upper glacis plate measuring 120mm thick, angled at 60 degrees. This was equal in thickness to the armour of the prototype of the IS-2 (cast 120mm armour sloped at 60 degrees) and thicker in total than the upper glacis of a King Tiger as well as the upper glacis of an IS-2 obr. 1944 (cast 100mm amrour sloped at 60 degrees). Even more remarkably, this also exceeded the thickness of the IS-3 upper glacis as that was only 110mm thick and sloped at a compound angle of 61 degrees for a total LOS thickness of 227mm.<br />
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The lower glacis plate was quite formidable as well since its thickness was equal to the upper glacis but only slightly less well angled at 55 degrees, while the side armour was 90mm thick. An important detail in the angle of obliquity of the lower glacis armour is that its slope of 55 degrees was designed to cause the Pzgr. 39 shell to break up reliably upon impact. Tests showed that projectile breakup began to occur at 45 degrees, became quite consistent at 50 degrees, and occurred reliably at angles greater than 50 degrees.<br />
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The turret had a much more complex shape and its distinct appearance makes it one of the many surefire identification marks of a T-54 obr. 1947.<br />
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The turret had a very distinct appearance, but in reality, it was merely a reimagination of the hexagonal design of the T-34-85 and T-44 turrets with increased sloping. The turret bustle was shortened which reduced the amount of space available for ammunition, and it gained a wedge shape with a large bevel along its lower half that formed a shot trap. These bevels were included in the turret to ensure that the driver could drive with his head out of his hatch or exit through his hatch regardless of the orientation of the turret.<br />
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Like the turrets of the T-44 and T-34-85, this design retained a conventional heavy semicircular mantlet where the gunsight and co-axial machine gun was fitted. The thickness of the gun mantlet can be seen in the cross sectional drawing shown below. At its peak thickness, the gun mantlet reached 200mm. The turret cheeks had a lower thickness but were sloped at a much greater angle due to the curvature of the turret, thus ensuring a higher effective thickness.<br />
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The ballistic shaping of this turret was better than the previous versions, but the large shot traps around the turret ring area was considered a huge liability. Other than that, the good angling of the side cheeks of the turret in combination with the well-rounded gunshield provided good protection. The photo below (of an abandoned pillbox turret), provided by Vladimir of Urban3p, shows the curvature of the turret as seen from the gunner's station. The hole at the end is for the TSh-20 telescopic gunsight. By comparing the angle of the wall of the turret to the cannon breech, we can see that the horizontal slope of the turret is quite steep. There is not much in the way of vertical slope, but the turret is rounded. However, the turret ring was protected by rather thin armour in the same way as the T-44 turret, although like the T-44 turret, it had a very low height and was not as exposed as on the T-34-85 turret.<br />
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Even though the front of the turret was considerably more resilient than that of earlier medium tank turrets, it was inferior to the front of the hull due to the rather large thickness of the front hull armour and its steep sloping. The shot traps around its front and rear further compromised the integrity of the tank's overall protection scheme.<br />
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<h3>
<span style="font-size: large;">T-54-2 (T-54 obr. 1949)</span></h3>
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To solve the issues with the 1946 turret, the design bureau of plant No. 183 created a new turret design in 1948 with an entirely new egg shape that omitted the front bevel. This new turret design not only provided a weight reduction, but also better protection from all directions. However, the rear bevel shot trap remained albeit with significant reinforcement. The height of the bevel was reduced, and the turret gained an armoured collar around its rear sector that not only protected the turret ring from direct hits but also prevented shell ricochets from reaching it.<br />
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In 1949, the revised T-54-2, or T-54 obr. 1949, entered production with the new turret. The thickness of the upper glacis armour was reduced to 100mm. The hull side armour was reduced to 80mm. Despite the decreased mass of the frontal hull armour, the level of protection still met the requirements. Having a thickness of 100mm and sloped at 60 degrees, the upper glacis was equal in thickness to the IS-2 obr. 1944 but the crucial difference was that it was made from RHA instead of a high hardness cast steel. As such, the upper glacis of the T-54 obr. 1949 could resist the 8.8cm Pzgr. 39 fired from a Pak 43 or KwK 43 at point blank range whereas the IS-2 obr. 1944 could only resist this round from a distance of more than 450 meters.<br />
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According to a Soviet analysis on the amount of armour required to stop an 8.8cm PzGr. 39/43 armour piercing shell fired from an L/71 Kwk 43 or PaK 43 gun, it was determined that an impact velocity of 1,090 m/s was needed to achieve initial penetration on 100mm of RHA sloped at 60 degrees under the V20 criteria (20% chance of complete perforation). Considering that the muzzle velocity of this shell is 1,000 m/s, the probability of achieving initial perforation was 0%. An impact velocity of 1,160 m/s was required to achieve initial penetration on an 120mm of RHA sloped at 60 degrees.<br />
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Besides the reduction in the hull armour thickness, another significant change was the shift to a new turret design with a narrow gun embrasure instead of a traditional gun mantlet. The width of the embrasure was just 400mm wide. The base of the gun barrel is protected by a simple gun mask that only offers protection against artillery shell splinters and heavy machine gun fire. The gun mask also prevents fragments or bullets from jamming the gun elevation mechanism by becoming lodged between the gun breech block and the turret.<br />
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The gun mask was mounted to an armoured plate affixed to the front end of the gun breech by four large bolts. The gun mask protects the gun breech at all angles of elevation from direct hits and from bullet ricochets or splatter, but when elevated to a high angle, the lower edge of the gun mask clears the base of the turret and and leaves a noticeable gap as the photo on the right above shows (photo by Vladimir Yakubov). This gap can be large enough to allow even small caliber cannon shells to enter, but a heavily sloped internal armoured plate prevents direct damage to the gun breech or the turret ring. When the gun is level, this armoured plate rests behind the base of the turret as the drawing below shows.<br />
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One disadvantage to the lack of a gun mantlet was that a tall slit has to be cut into the armour to accommodate the vertical movement of the co-axial machine gun and the aperture of a telescopic gun sight. As long as a telescopic sight is used, there must be a hole in the armour, but as a gun mantlet moves with the elevation of the cannon, a gun sight aperture embedded in the mantlet only needs a single, small hole. The relatively large slit in the turret of the T-54 increases the size of the weakened zone. Examples of tanks that possess this weakness besides the T-54 include the Chieftain tank, which has a tall vertical slit in the front of the turret for the co-axial machine gun, but the Chieftain bypasses the need for a slit for it's gunner's primary sight by using a periscopic sight.<br />
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To seal the gun embrasure from the weather, a rubberized fabric seal was provided.<br />
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<h3>
<span style="font-size: large;">T-54-3 (T-54 obr. 1951 and onwards)</span></h3>
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In the year 1951, the T-54 finally gained its iconic rounded turret. The turret has been described in many ways, from "overturned soup bowl" to "hemispherical". In truth, it is a unique shape with complex angles that cannot be summarized easily. From above, it is distinctly egg shaped. From the side, it is more oblong than round. Only from the front does it resemble a perfectly rounded overturned soup bowl. From a frontal perspective, the thickness of the turret is roughly uniform in the vertical axis although the actual physical thickness of the casting varies. However, the horizonal slope of the turret vastly increases the effective thickness of the turret at the edges of the turret silhouette. Roughly speaking, the thickness of the front of the turret ranges from 200mm at an angle of around 0 degrees at the base of the turret to 70mm at an angle of 52 degrees at the top edge of the turret, where the frontal armour transitions to the roof. The sides of the turret are 160mm thick at the base where the angle of the slope is none or negligible, but the side armour thins down to 115mm at the upper edge of the side where the slope is 45 degrees. However, these values are only nominal as the complex shape of the turret makes the actual thickness values difficult to describe. Overall, the high thickness of the armour increases its efficiency against contemporary armour piercing ammunition. For example, <i>WWII Ballistics: Armour and Gunnery</i> notes on page 25 that a 195mm cast armour plate with a hardness of 220-300 BHN at an angle of 0 degrees is equivalent to 195mm of rolled homogeneous armour with a hardness of 240 BHN against projectiles in the 50-152mm diameter range, meaning that it is essentially equal to an RHA plate of the same thickness. The commonly cited efficiency coefficient of 0.85-0.95 for cast armour relative to rolled armour is only true for thinner plates in the 50-100mm range.<br />
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Like the previous T-54-2 turret, there is no gun mantlet and the gun is only protected by a cast steel gun mask. The shape of the gun mask is very similar to the type used on the T-54-2, but it is unclear if the same mask design was carried over directly.<br />
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However, cutouts were made in the armour at the slits for the co-axial machine gun and the gunner's telescopic sights now. This created weakened zones where the armour thickness is substantially less than the advertised 200mm. The cutout is shown in the drawing on the right and the cutout for the co-axial machine gun can be seen clearly in the photo on the left. The photo on the left comes from flickr user <a href="https://www.flickr.com/photos/solipsistnation/7714630332">solipsistnation</a>. The combination of reduced thickness and the presence of a hole in the armour makes the co-axial machine gun port and the gunner's sight aperture especially weak to anti-tank fire.<br />
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Production turrets were manufactured by chill casting, but there were issues with casting the entire roof along with the rest of the turret in one piece. To fill in the gap, the roof had to be constructed from two D-shaped rolled steel plates, which were welded onto the cast walls in an automated procedure done by a machine rig. This results in a marginally weaker turret compared to a turret made from a single casting as the roof plates might be ripped off at the weld seams or the seams may burst if the roof was struck by glancing cannon fire. However, using rolled steel plates in this location has the benefit of increasing the chance of a ricochet when struck since rolled steel plates invariably have better ballistic properties than cast steel of the same hardness. An illustration of the chill casting mold is shown below.<br />
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The welds joining the hull roof to the side hull, and the welds joining the hull roof to the glacis plates and to the floor and all the welds in between were strengthened in the T-54-3 compared to the T-54-2. The geometry of the fittings between the armour plates was changed to increase the surface area between the joints and thus improve the strength of the seams. This helped to improve the armour integrity of the hull and thus improve protection without changing the thickness of the plates. The hull roof is 30mm thick.<br />
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The hull and turret were evaluated against anti-tank guns of a myriad of calibers of both domestic and foreign make. The frontal aspect of the tank had to be proofed against common tank guns like the 90mm M3 of the M26 Pershing and the M46, but it was also tested against the tank's own D-10T and the 85mm S-53 of the T-34-85. As the post war reality showed that American 90mm guns would be the main threat to Soviet armour amd not German 88mm guns, the basic requirements for the ability to resist 88mm shells "with a muzzle velocity of 1000 m/s" (referring to PzGr. 39 shell fired from the 88mm KwK 43 L/71) became very convenient as the tank would not have to be uparmoured to deal with the new expected threat. M82 APCBC/HE-T was obtained via lend-lease, and became one of many foreign-made munitions for use in testing.<br />
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The photos below show the armour of a T-54-3 pattern model tested against anti-tank weapons of various calibers. Note that the roadwheels are of the spoked type, indicating that the test vehicle is indeed a T-54 obr. 1951, and not a T-54A or T-54B which were fitted with "star" type roadwheels. <br />
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The photo above shows scallops in the turret from various shell impacts and the photos below show the setup of the testing rig for comprehensive turret and hull testing.<br />
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The sides of the tank turret and hull were tested just as thoroughly as the front, and with weapons of the same variety. Besides large caliber tank shells, the vulnerability of the sides of the tank to large caliber anti-aircraft cannons like the Soviet Army's own 57mm S-60 was also investigated. It is unknown if the widely used Bofors 40mm L/70 was also tested. <br />
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Both the upper and lower glacis plates and the side hull plates are constructed from 42SM armour grade steel. The rear armour plate and the roof plate was made from 49S armour grade steel, and the belly of the tank was made from 43PSM armour grade steel. The cast steel turret was made from 74L CrNiMo armour grade steel, while the two-piece roof welded onto the cast turret was made from 43 PSM steel. The 49S and 43PSM steel plates installed in the roof and belly of the tank was quite thin - only 20mm, so it is quite surprising that these steels are rather soft for their thickness. <a href="http://evstest.vitkovicesteel.com/en/pages/plates-armour-plates">This table</a> states that 49S and 43PSM have a hardness of only 180-250 BHN. The rule of thumb is that thinner plates are easier to harden than thicker plates, so the plates used in the tank are definitely closer to latter than the former, but even so, that is relatively soft for such thin plates. 42SM and 74L, on the other hand, are medium hardness steels that are technically specified to have a hardness ranging from 285-340 BHN. However, it is reported in the study "<i>Повышение Противоснарядной Стойкости Толстолистовой Серийной Стали 42СМ С Помощью Электрошлакового Переплава</i>" (<i>Enhancement of the Ballistic Resilience of Serial 42SM Steel Using Electroslag Remelting</i>), while the technical specifications call for a hardness within the range of 285-340 BHN, serial 42SM steel plates are actually treated to a hardness ranging from 293 BHN to 311 BHN. These steel hardnesses are optimal for resisting armour piercing rounds for the thicknesses of the given plates.<br />
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Foreign appraisals of the steel for the armour of the tank were consistently positive. In the (translated) famous Yugo tests document, for example, it was noted that "T-54A cast parts were 270 BHN (rolled plates were 290 BHN) and were judged to be of excellent quality". From this, we know that 74L cast armour steel has a hardness of 270 BHN, while 42SM has a hardness of 290 BHN. The hardness and thickness of the various armour plates were controlled to offer optimal efficiency against the type of armour piercing shells expected to be used by the perceived enemy.<br />
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The sides of the turret slope inwards at 60 degrees and converge at the gun mantlet, giving it a rounded needle-nose shape. This shape is excellent for an all-steel turret from a ballistic point of view, but the effect on internal space in the turret is somewhat negative, which is compounded by the fact that the turret of the T-54-3 is also dome-shaped. The sides of the turret that slope inwards to form the needle-nose shape are 150mm to 170mm thick, thickest as it transitions from the turret front and thinner as it curves round to the back. The rear part of the turret sides, at the commander's and loader's areas, are around 100mm to 120mm thick, thickest at the bottom and thinner as the steel curves towards the top.<br />
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If we take a close look at the turret wall behind the gunner's primary gunsight, we can see very plainly how the turret immediately assumes a side slope after the gunsight port.<br />
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The photo above also shows that the flat part of the front of the turret is shaped like a right angled triangle. This is the weakest part of the T-54 turret, as it is only sloped in the vertical plane. Aside from the flat triangle, the turret is sloped in three dimensions.<br />
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As you can see in the photo, the area behind the gunner's MK.4 periscope is distinctly more curved than the rest of the commander's station. In other words, the flat part of the turret is much narrower than it appears in exterior photos.<br />
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<h3>
<span style="font-size: large;">VERSUS SPECIFIC AMMUNITION</span></h3>
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Penetrating just 147mm at 0 degrees at a thousand meters' distance, M82 was simply inadequate against the T-54. A large portion of the side of the turret has the potential to shrug off a hit from M82 at close range, and the side hull is largely immune at most angles, unless it is struck straight on.<br />
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Much later on, the M36 gun became available as well, as nearby Yugoslavia operated 319 M47 Patton tanks. According to the famous Yugoslavian tests, the front of the turret could only be perforated by PzGr. 39-1 APCBC fired from the KwK 43 at a dangerously close distance of 600 meters. The upper glacis was totally immune even from a hundred meters, but the sides of the turret can be defeated at a distance of up to 1750 m.<br />
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Fired from the 90mm M3A1, T33 APCBC rounds (shown above) totally fail to defeat the front of the T-54's turret at any range. Shot perpendicularly from the side, the front part of the turret sides can only be defeated at a suicidal range of 250 m. When hot loaded T33 rounds are fired from the higher pressure M36 cannon, the chances improve a bit. The shell is still not capable of getting through the glacis even at a hundred meters, but the front of the turret can now be perforated at 350 m. The frontal part of the side turret can be perforated at 850 m, which is a much more comfortable shooting distance. M304 APDS is mandatory when fighting the T-54, as the front turret can be perforated at 750 m. Nevertheless, the inability to defeat the armour of the T-54 except from the sides can be considered a serious drawback for opposing forces armed with 90mm guns.<br />
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M431 HEAT works well at any range on any part of the T-54, but the killing power is low and the shell has fuzing problems on angled parts of the armour. It has a high probability of failing to detonate if it strikes the upper glacis when the tank is angled 20 degrees sideways. The shell may not work properly on the well rounded shape of the turret, especially the top half. Also, M431 was not introduced until the late 50's. Details on the M431 are available here (<a href="http://www.tank-net.com/forums/index.php?showtopic=28229&page=2">Link</a>). Fuzing issues with other HEAT rounds were also observed on the T-34-85 during the tests. Of special interest is the performance of the 75mm M20 and the 105mm M27 recoilless rifles. The M310 HEAT round fired from the 75mm M20 fails to defeat the upper glacis armour of the T-34-85 (45mm at 60 degrees) if the side angle was 20 degrees or more and it fails to defeat the upper side hull armour (45mm at 40 degrees) if the side angle was 30 degrees or more. The same result was obtained with the 105mm M27 which could not defeat the upper glacis armour with the M52 round if the side armour was more than 20 degrees. Since the upper glacis of the T-54 is sloped at the same angle as the T-34, the same results can be expected. The sides may be more vulnerable, however, as there are only fuel tanks and stowage bins on the track fenders and no sloped armour plating.<br />
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The M82 APCBC/HE-T round packs 200 grams of RDX, but it is largely impotent against the T-54 unless the gunner aimed for the side hull or rear hull and turret. M82 was not included in the Yugo tests, but it is not difficult to predict its performance. According to U.S Army tests detailed here (link), T33 fired from the M3 cannon is capable of defeating the upper glacis (82mm at 55 degrees) of a Panther at a range of up to 1100 yards, but M82 fired from the same cannon cannot repeat the same feat, despite having a capped penetrator. At most, it could deal with the lower glacis - which measured 60mm thick at 55 degrees - at a maximum range of something over 950 yards.<br />
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The T-54 offered the next best chance against itself, behind the long-barreled 88mm KwK 43 as the 100mm BR-412B round is capable of perforating the front of the turret at 500 m and the front part of the side turret at 1000 meters. With BR-412D, a better result may be obtained.<br />
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The M48 will find itself in a rather bad situation in comparison to the T-54 where hull armour is concerned. It is well known that cast armour is significantly weaker than rolled armour, but the extent is not often grasped by many. In the Yugo tests, testing of domestic M47s have shown that the upper glacis, a 100mm cast steel plate sloped at 60 degrees, can be defeated by BR-412B at a distance of 750 meters even though BR-412B is technically only rated to penetrate 96mm of rolled steel angled at 60 degrees at a point blank distance according to a British evaluation using the same metrics of penetration. The 100mm rolled steel upper glacis of the T-54A is unsurprisingly immune to BR-412B from all ranges. The T-54 can be considered arguably on par with the M48 or the M60 tank in terms of hull armour protection.<br />
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There is much more information that can be gleaned from the results of those tests, but only if we pay close attention to detail. The tests involved shooting at the side of the turret from a right angle, but as we know, the turret is sloped inward. If the turret is attacked at a perfectly perpendicular side angle, the front part of the sides of the turret will have a horizontal slope of 30 degrees, thus making the LOS thickness 196mm to 173mm. We know that T33 fired from the M36 cannon is capable of defeating this at 850 m.<br />
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However, a shot coming at the turret from a forward 30 degree angle would also have to face between 173mm to 196mm of LOS armour, because the 60 degree inward angle of the turret sides is reduced to just 30 degrees. This means that if the turret is attacked from its forward arc, it may only be as strong as its side in certain parts. In general, the turret becomes more vulnerable as the incident angle increases from 0 degrees to 30 degrees to 50 degrees and so on, up til a point at 90 degrees where it is as vulnerable as it is at 30 degrees. This is a peculiarity of this type of ballistic shaping, and it is not limited to the T-54. The turret of the M60A1 has the same problem, only it is even further amplified because the cheeks of the M60A1's turret are thinner - only 140mm thick. The T-54's turret can be considered to be extremely resilient to anti-tank guns of its time, but it is not without certain weaknesses.<br />
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<span style="font-size: large;">VS 20 pdr</span></h3>
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According to British tests, Centurion's MK.3 APDS for the 20 pdr. gun would fail to defeat its own upper glacis (76mm at 57 degrees) at a minimum distance of 4400 yards, or 4023 meters. After the addition of a 44mm weld-on applique armour plate, the distance of immunity was decreased to just 850 yards, or 777 meters. This means that MK. 3 APDS can penetrate less than 120mm RHA angled at 57 degrees at 777 meters, and less than 76mm at 57 degrees at 4023 meters.<br />
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According to Swedish archive documents shared by renhanxue, owner and administrator of the Swedish Tank Archives website (tanks.mod16), 20 pdr. APDS (most likely MK. 3) can penetrate 240mm of vertical plate at 500 m, and 95mm at 60 degrees at 1000 yards (914 m), and it fails to penetrate 122mm angled at 60 degrees at 500 m. This is congruous with the aforementioned tests. The hardness of the plate used is unknown. However, the drop in penetration performance is between 4400 yards and 1000 yards is suspiciously small for an APDS round. It is possible that the Centurion's rolled steel plates are softer than the test plates used during the Swedish tests.<br />
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Taken all together, this means that using MK. 3 APDS, a Centurion Mk. 3 should have the ability to defeat the upper glacis plate of a T-54 only from below 900 meters. This makes the Centurion the best performer among all of its Western peers in a hypothetical face-off against Soviet T-54s.<br />
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Let's see how MK. 3 does against shallowly sloped plates:<br />
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So, MK. 3 can confidently defeat 150mm RHA angled at 30 degrees at about 1750 yards, and pierce 120mm RHA angled at 25 degrees at up to 2250 yards. This would allow it to perforate the base of the T-54 obr. 1951 turret in the region around the gun mantlet, but the frontal arc of the turret is still capable of resisting a hit from MK. 3.<br />
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According to Swedish test data provided by renhanxue, 105mm L28 penetrates 200mm RHA at 30 degrees at 1500 m, and 140mm RHA at 55 degrees at 900 m. On the Tank-Net forum, renhanxue states that the British give a penetration value of 120mm RHA at 60 degrees at 1000 yards for L28. Overall, this means that the turret of the T-54 is vulnerable from combat ranges of 1500 meters and beyond, so the 105mm L7 gun is an effective countermeasure against the T-54 in a frontal attack.<br />
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Additionally, any evaluation of the T-54's survivability is not complete without also reviewing the value of its relatively small silhouette. Being quite small for a tank, the T-54 is easy to conceal in vegetated areas. The small surface area of the tank also makes it less time consuming to camouflage.<br />
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Although it is an aspect of the T-54 design that is often criticized, a small silhouette was not only coveted by Soviet tank designers. It was a common goal of practically every major military power that was influenced by statistical probabilities calculated from years' worth of combat data. For example, the height of the M60A1 was recognized as excessive and the M60A2 introduced a low-profile turret design to minimize the projected area of the turret while maximizing protection.<br />
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<a href="https://1.bp.blogspot.com/-UOR-6rUB5mg/XNPsTzuwkMI/AAAAAAAAN7A/fQDroMgYy0cOabuAuVqRyB5T_7t0VyWRACLcBGAs/s1600/m60a2%2Band%2Bt-54b%2Bsilhouette%2Bcomparison.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="819" data-original-width="608" height="640" src="https://1.bp.blogspot.com/-UOR-6rUB5mg/XNPsTzuwkMI/AAAAAAAAN7A/fQDroMgYy0cOabuAuVqRyB5T_7t0VyWRACLcBGAs/s640/m60a2%2Band%2Bt-54b%2Bsilhouette%2Bcomparison.png" width="474" /></a></div>
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<h3>
<span style="font-size: large;">Metal-Polymer Armour</span></h3>
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The add-on armour featured on the T-55AM and its variants is referred to as metal-polymer armour blocks. This type of armour has already been covered in Tankograd's T-62 article. It would be pointless to repeat it all here, so please head over to the <a href="https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiU_LWw7L_RAhWFo5QKHYeHDvYQFggbMAA&url=https%3A%2F%2Fthesovietarmourblog.blogspot.com%2F2015%2F12%2Ft-62.html&usg=AFQjCNE79OF6-xi59Z6CWcSwp7CKkHC1WQ&sig2=nDHT8PDJJXszUzBJMpHE1g">T-62 article</a> to read more. However, the unique geometry of the turret of the T-54 means that the spacing between the turret and the add-on armour blocks is not the same as on the T-62, which is a nuance worth examining.<br />
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As mentioned earlier, the turret of the T-54 had a variable thickness and had a very complex range of sloping angles due to its rounded shape to ensure that the entire height of the turret had an equal thickness of steel. This was designed so that the turret could attain a uniformly high level of protection against steel full caliber shells and APCR rounds with tungsten carbide cores. The shape of the metal-polymer armour blocks on the T-55M and T-55AM turrets was therefore designed accordingly.<br />
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According to Soviet drawings, the total thickness of turret armour including the "Brow" armour blocks amounts to 500mm when measured at the center of the block. At the top of the armour block, the thickness of the cast steel front plate decreases but the metal-polymer composite armour increases and the air gap behind it also increases to compensate. At the bottom of the armour block, the cast steel front plate of the "Brow" armour block is thickest but the metal-polymer composite has its smallest thickness, as does the air gap. Due to the complexly differentiated thickness of the armour elements, the total LOS thickness of the turret differs at the locations where the "Brow" armour block is present.<br />
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The variable thickness of the cast steel front plate can be seen clearly in the photo below, taken from <a href="https://btvtinfo.blogspot.com/2019/08/552.html">Andrei Tarasenko and originally uploaded to his blog</a>. The subject of the photo is a Czechoslovak T-55AM2, but the armour is identical to the Soviet T-55M and T-55AM.<br />
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At the top half of the armour block, the cast steel front plate has a thickness of 71mm, the armour is sloped at an obliquity of 30 degrees and the total thickness of the armour is 280mm. At the bottom half, the cast steel front plate has a thickness of 85mm and the entire armour block is sloped at an obliquity of 15 degrees.<br />
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<a href="https://1.bp.blogspot.com/-07fqDuLJWgA/Wxp3rsnGWEI/AAAAAAAALr0/pVyFP6AVk6U9nix6Vy8NrqGyn806fKPNwCLcBGAs/s1600/hull%2Barmour.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="761" data-original-width="899" height="337" src="https://1.bp.blogspot.com/-07fqDuLJWgA/Wxp3rsnGWEI/AAAAAAAALr0/pVyFP6AVk6U9nix6Vy8NrqGyn806fKPNwCLcBGAs/s400/hull%2Barmour.png" width="400" /></a><a href="https://1.bp.blogspot.com/-DC0ZX1b9hMk/WxpzG2iJWWI/AAAAAAAALro/JAEb_DxaJjc1VwNRMCdOhOvg81ZPh15EwCLcBGAs/s1600/t-55am2%2Barmour.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="693" data-original-width="768" height="360" src="https://1.bp.blogspot.com/-DC0ZX1b9hMk/WxpzG2iJWWI/AAAAAAAALro/JAEb_DxaJjc1VwNRMCdOhOvg81ZPh15EwCLcBGAs/s400/t-55am2%2Barmour.png" width="400" /></a></div>
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The size of the air gap is known thanks to measurements provided by Georg Stark and published in Paul Lakowski's "<i>Modern Armour</i>". It is now known that "<i>Modern Armour</i>" uses very old estimates and figures, but some of the information, like the photo and sketch below, is accurate as it was measured directly on the tank in question.<br />
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<a href="https://3.bp.blogspot.com/-jqZfJAfYuDs/Wg4sjdQcF0I/AAAAAAAAKIA/-bUYxWc4j-AJvNSbzn5UuqhrZN8XsaX2gCLcBGAs/s1600/brow.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="755" data-original-width="1600" height="301" src="https://3.bp.blogspot.com/-jqZfJAfYuDs/Wg4sjdQcF0I/AAAAAAAAKIA/-bUYxWc4j-AJvNSbzn5UuqhrZN8XsaX2gCLcBGAs/s640/brow.png" width="640" /></a></div>
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As the sketch shows, the air gap between the metal-polymer composite block and the turret ranges from 50-60mm at the bottom to around 200mm at the top, directly corresponding to the thickness of the metal-polymer composite block itself. At the top of the armour block where the air gap is 200mm, the turret armour has a thickness of 100-110mm and is sloped at 54 degrees for a LOS thickness of 178mm and the "Brow" armour block itself has a LOS thickness of 323mm. By adding up the cumulative thicknesses of the "Brow" armour block, the air gap and the turret armour, it is calculated that the armour array has a total thickness of 659mm at this location. Using these methods, it is determined that the at the bottom and middle of the turret, the LOS thickness ranges from 480mm to 500mm but it reaches up to 660mm at the top. The turret armour itself remains at a uniform thickness of 170-180mm at these zones.<br />
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The presence of an air gap behind the armour array gives room for KE projectiles to break apart as the buildup of internal stresses from the penetration of the steel front plate and the moving internal plates is suddenly released, thus magnifying the effect of the armour. For shaped charge jets, the air gap gives room for disturbed jet particles to disperse such that they do not contribute to the total penetration depth from the residual jet tip.<br />
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The belly armour was enhanced with rudimentary spaced armour plate welded onto the hull. Six 20mm steel plates were welded onto the front half of the tank belly with the proper spacing of 80mm ensured by a steel frame. Unlike more modern mine and IED protection kits, there is no low-density filler between the spaced plate and the tank belly so there is little blast attenuation aside from the spaced 20mm plate. The main function of the spaced armour would be to prevent the tank belly from being breached by an explosion.<br />
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The drawing on the left below shows the tank's escape hatch with its spaced plate armour and the drawing on the right below sows the spaced belly armour kit from a profile view.<br />
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<a href="https://1.bp.blogspot.com/-h8ZwlYkuTUI/XaYSNkZhYuI/AAAAAAAAPZQ/y_ybc8iRSgs2d2gPTfiBlDCLQUvi6W-fACLcBGAsYHQ/s1600/czech%2Bt-55am%2Bescape%2Bhatch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="771" data-original-width="1600" height="192" src="https://1.bp.blogspot.com/-h8ZwlYkuTUI/XaYSNkZhYuI/AAAAAAAAPZQ/y_ybc8iRSgs2d2gPTfiBlDCLQUvi6W-fACLcBGAsYHQ/s400/czech%2Bt-55am%2Bescape%2Bhatch.png" width="400" /></a></div>
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The separate spaced plate sections can be seen below. There are ports built into the armour for drainage plugs.<br />
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<h3>
<span style="font-size: large;">NBC PROTECTION</span></h3>
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As the T-54 was formulated during the closing years of WWII and was only finalized a few years after its conclusion, no considerations were made for the effects of nuclear destruction. As part of tests carried out between 1952 and 1953 to determine the effects of nuclear weapons on various ground equipment, including tanks, the T-54 tank was exposed to a nuclear explosion from various distances. As it turned out, even at large distances, the turret could be displaced by the sheer power of the nuclear winds even when the turret was locked in the travelling position, causing the gear teeth around the turret ring to break and render the tank unserviceable. As a result of these tests, the turret locking mechanism was strengthened, so that even at around 300 meters' distance from the detonation of a 2 to 15 kiloton bomb, the tank remained serviceable.<br />
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However, it was discovered in subsequent tests that at distances of up to 700 meters, animals (rabbits, dogs) standing in for the tank crew died immediately from the shock wave and overpressure of the blast. As a result of these findings, the requirements for a comprehensive anti-nuclear protection suite for the T-54 were drawn up, and in 1956, the KB-60 design bureau from Kharkov finalized a "PAZ" (Nuclear Protection System) complex and sent the technical documentation to the Uralvagonzavod tank factory for implementation. <br />
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The T-55 was the first Soviet medium tank to feature an NBC protection system. It was an advanced collective type system with automatic and semi-automatic operating modes. A gamma radiation sensor was used to detect the detonation of a nuclear bomb and initiate countermeasures before the shockwave could reach the tank. The system could react 0.3 seconds after detecting a spike in gamma radiation. All openings in the tank would be automatically sealed by heavy steel wedges activated by explosive squibs. The engine and the cooling fan would be stopped, and the armoured louvers over the engine deck would be closed, all done automatically.<br />
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The ventilator intake fan on the turret roof lacked a filtration unit and was insufficiently powerful to create an overpressure inside the tank, and there was no additional space to add these necessary features. As a result, it was replaced by a new ventilator intake system that included a supercharged blower. The supercharger drum is placed right beside the co-axial machine gun, in front of the loader. Not only was it capable of producing an overpressure inside the tank to prevent foreign particles from seeping in, the filtration system could also remove chemical and biological agents, though only when activated, either manually or automatically. In normal operation, the powerful compressor fans are not used, and the ventilation system performs the same basic function as the old dome ventilator.<br />
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The T-55A obr. 1967 provided an additional layer of security from the harmful effects of a nuclear explosion by including a special anti-radiation lining. The anti-radiation material is a lead-impregnated polymer composite textile that is layered and cut into the desired form before it is installed on the surfaces of the tank. It is designed for absorbing gamma radiation - the most dangerous form of radiation as it can penetrate even relatively large thicknesses of steel - but it can also perform a secondary function as a spall liner when present in sufficient thickness.<br />
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The anti-radiation lining is secured onto the internal surfaces of the fighting compartment by bolts. They mainly cover the areas of the tank where the armour thickness is lower and therefore less effective at attenuating gamma radiation and neutrons. The turret ceiling is completely covered by the lining and most of the turret rear and sides are covered. Even the hatches have a layer of anti-radiation lining.<br />
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The commander's cupola and loader's cupola on the T-55A both had relatively high radiation permeability due to their relatively low thickness of armour. As such, a large thickness of anti-radiation lining was needed to ensure a sufficient level of protection, but this thickness was too large to be practical as a lining on the internal surfaces of the cupolas. Instead, the anti-radiation material was installed outside the cupolas in the form of prefabricated conformal blocks and given a sheet steel shell to protect it from the weather and from the initial blast and heat of a nuclear explosion. Anti-radiation material was also added to a small strip of the turret roof joining the two cupolas.<br />
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The large thickness of the anti-radiation blocks on the loader's cupola can be seen in the two photos below. If this amount of material was used as an internal lining instead, it probably be so thick that it may constrict the size of the loader's hatch and it would certainly severely restrict his headroom.<br />
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The commander's cupola received similar treatment. However, the commander's hatch and cupola roof has a noticeably larger thickness of external anti-radiation cladding compared to the loader's hatch, and this is because a lining would have intruded much more into the commander's available headroom than for the loader, who is not confined to a fixed position underneath his cupola.<br />
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The driver's hatch also received an anti-radiation cladding.<br />
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<h3>
<span style="font-size: large;">ESCAPE HATCH</span></h3>
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The T-54 has an escape hatch. It is located behind the driver's seat. It is held in place by four locks. Once all four have been disengaged, the hatch drops down, allowing the crew to crawl out. It is much easier said than done, and it will be nearly impossible to do a quick escape from a hatch of such small size, but having a hatch presents unique tactical opportunities as the crew can exit the tank without being seen by the enemy.<br />
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<span style="font-size: large;">DRIVER'S STATION</span></h3>
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The driver's station in the T-54 was a departure from the T-34 driver's station in that it had less headroom due to the significantly shortened hull, but the driver's comfort and visibility improved because the periscopes were relocated from a hatch on the upper glacis plate to the hull roof. This meant that the driver could be seated in a far more natural posture while driving. There were also other ergonomic improvements were added for the driver's benefit, such as handlebars built into the periscopes for the driver to hold on to as he ingresses or egresses from his station. The driver's station changed very little throughout the evolution of the tank, as exemplified by the two photos above. The photo on the left shows a T-54A and the photo on the right shows a T-55. The only major difference is the absence of a bow machine gun on the latter tank.<br />
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We have already examined most of the components of the driver's station in Tankograd's T-62 article. As the driver's station in a T-62 is almost identical to one from a T-55, there is no point to repeat it here. <a href="https://thesovietarmourblog.blogspot.com/2015/12/t-62.html">Please head over to the T-62 article</a>. However, there are some small historical details that uniquely belong to the T-54.<br />
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The design of the driver's hatch of the T-54 was finalized on the T-54 obr. 1947 and it was retained throughout the production life of the tank series. The design is shown in the drawings below. The thickness of the hatch was equal to the hull roof: 30mm. As mentioned before in the article when examining the ventilation system of the T-54, the driver's hatch had a small ventilation porthole designed to work in conjunction with the ventilation exhaust fan at the back of the fighting compartment, in the engine compartment bulkhead. Besides that, there was a layer of padding on the underside of the center of the hatch to protect the driver's head from a hard knock, and the rim of the hatch opening was lined with rubber on both sides to seal the hatch from the weather and to provide some protection for the driver's head. These details can be seen in the drawings below.<br />
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One side of the hatch opening is slanted which was necessitated by the overhang of the turret over the turret ring. The dimensions of the hatch opening are not particularly large but it is reasonable. It is particularly important to note that the width of the hatch is 486mm which is substantially more than the average shoulder width of an average Soviet Army conscript, so in general, the size of the hatch can be considered sufficient for a tank driver even when wearing winter clothing.<br />
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The driver's sat in a bucket type seat. It had bolsters on the sides and a well-padded cushion and backrest. It could be adjusted in height, with the tallest setting meant for driving with the driver's head outside the hatch. The backrest could be adjusted between just two angles of recline, which is rather unfortunate. However, the backrest can be easily folded fully backward or forward in order to allow the driver to freely move into the fighting compartment or evacuate the tank via the escape hatch behind him.<br />
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The periscopes of the T-54 also deserve some mention. Originally, destroyed periscopes were almost impossible to remove if a powerful shell struck the armour in front of it as the mounting piece would usually be damaged in a most inconvenient way. This was solved in 1953 by using a heat-treated mounting piece of a higher grade of steel, increasing the strength of the welds and by thickening certain components.<br />
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In 1951, the TVN-1 infrared night vision driving periscope was introduced along with an infrared headlight on the T-54 obr. 1951. With the help of the tank commander who was provided with the new TKN-1 night vision monocular periscope, the driver of the T-54 gained the ability to navigate at night more stealthily than if conventional white light headlights were used and tank units could march more confidently at night. When the more capable TVN-2 night vision periscope became available in the late 1950's, the TVN-1 was phased out in favour of the newer type. The two images below show TVN-2 periscopes installed in the appropriate periscope slot.<br />
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For a more detailed examination of the night vision devices, <a href="https://thesovietarmourblog.blogspot.com/2015/12/t-62.html">please head over to Tankograd's T-62 article</a>.<br />
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<h3>
<span style="font-size: large;">MOBILITY</span></h3>
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The mobility characteristics of the T-34-85 were largely retained, but it is somewhat worse than the T-44 due to the large difference in weight. The T-34-85 had a combat weight of 32 tons and with a gross engine output of 500 hp, the tank ostensibly has a power-to-weight ratio of 15.6 hp/ton. The T-44 had a combat weight of 31 tons and an uprated V-44 engine with an output of 520 hp, so it had an increased power-to-weight ratio of 16.8 hp/ton. However, the net power available at the drive sprockets of the T-34-85 is 390 hp after all the power deductions from the cooling system, generator, and other auxiliary equipment are made. The actual power to weight ratio is 12.2 hp/ton.<br />
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Having a gross output of 520 hp, the V-54 engine gave the T-54 obr. 1949 a nominal power-to-weight ratio of 14.65 hp/ton, but the net power is 430 hp so the real power-to-weight ratio is actually 12.2 hp/ton. When the gross powers are compared, the power-to-weight ratio of the T-54 obr. 1949 is 6.3% lower than the T-34-85, but when the net powers are compared, the two tanks are equivalent.<br />
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The engine was installed transversely in the hull and was connected to the transmission by a transfer case that contained the main clutch.<br />
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One of the immediate benefits of the transverse engine position is the increased power transmission efficiency gained by omitting a bevel gear to transmit the driveshaft power to two axles, which is necessary when the engine is installed longitudinally. Alone, a bevel gear incurs a power transmission loss of 4%, as the drawing below shows. The drawing was taken from page 432 of the Soviet tank design handbook "<i>Tank</i>" (1954).<br />
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The transmission was quite compact and its external appearance was similar to the transmission of the T-34. Above it were the water and oil radiator packs and the accompanying radiator fan. This layout made it possible to greatly decrease the volume of the engine compartment by decreasing its length, and most importantly, this design solution did not have any caveats.<br />
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<h3>
<span style="font-size: large;">V-54</span></h3>
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The T-34-85 had a top speed of 55 km/h, while the T-44 had a top speed of 51.1 km/h. The first mass-produced model, the T-54 obr. 1947 had a restrictive top speed of just 43.5 kph. The V-54 was slightly underpowered for the T-54 obr. 1947, so the top speed had to be compromised by adjusting the gearing ratios in the gearbox to preserve the acceleration characteristics of the tank. The T-54 obr. 1949 and the definitive T-54 model, the T-54 obr. 1951, finally settled on a slightly more modest weight which permitted a top speed of 50 km/h to be achieved.<br />
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Fuel is delivered by a direct injection system. The engine has a 14-15:1 compression ratio.<br />
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Not all of the engine's power is used to propel the tank as some power must be transferred to the centrifugal radiator fan for the tank's cooling system, the air cleaning system, and the G-73 electric generator for the tank's electrical systems. The net power available to propel the tank is 430 hp. This constitutes 82-83% of the gross power.<br />
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<h3>
<span style="font-size: large;">V-55</span></h3>
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The V-55 is a modification of the V-54 engine with an increased output. It generates a maximum power output of 580 hp at an engine speed of 2,000 rpm and a maximum torque of 2,254 N.m at an engine speed of 1,200-1,400 rpm.<br />
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Thanks to the increased power of the V-55, the gross power-to-weight ratio of the T-55 increased to 16.1 hp/ton.<br />
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The added power comes from a better optimized compression ratio of 15:1 ±0.5 and an improved fuel injection system. The V-55 was paired with a new and improved VTI-4 air filter which helped by reducing the power loss in extremely dusty environments.<br />
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Aside from the increased automotive performance, the new engine was more robust and reliable. It was delivered to the Soviet Army with a warranty of 350 cumulative hours of engine operation.<br />
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Due to the power allocated to the G-5 electric generator for the tank's electrical systems and the addition of an AK-150 air compressor, the net power available to propel the tank is only 480 hp. This constitutes 82.76% of the gross power.<br />
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In the Soviet tank design handbook "<i>Tank</i>" (1954), it is stated on page 432 that the energy loss from friction from a mechanical (manual) gearbox is 6%. From there, the power is transmitted to the final drives, where an additional power loss of 1% is incurred. With this high level of efficiency, most of the net engine power is transmitted to the drive sprockets with only a small amount becoming heat. In turn, this indirectly increases the power available to propel the tank as it reduces the amount of power that must be allocated to the cooling system.<br />
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The superior gearbox and steering system of the T-54 enabled the tank to get more out of its 520 hp engine by allowing the driver to shift gears much more quickly and also to steer more precisely and with much less effort. Moreover, the new super-compact dry plate clutch transmission enabled the T-54 to retain the agility of the T-34-85 despite having a worse power-to-weight ratio, especially at higher speeds. This is because the T-34-85 was steered via the clutch-and-brake system which robbed the tank of some of its speed with each turn. The top speed and acceleration of the T-54 when travelling in a straight line was worse compared to its predecessor, but when travelling on actual roads or when moving cross-country, the T-54 was comparable.<br />
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According to the official figures presented in manuals, the average speed of the T-34-85 reaches 30 km/h on paved roads and reaches 25 km/h on dirt roads whereas the T-54 obr. 1951 reaches an average speed of 30-33 km/h on paved roads and 20-25 km/h on dirt roads. It is reasonable to assume that these figures were derived from a standardized test where both tanks ran the same course at Kubinka under the same conditions albeit at different points in time, so in all likelihood, these average speed figures should be directly comparable. With that, it can be seen that even though the T-54 cannot reach a top speed as high as the T-34-85, it did not suffer in terms of mobility in realistic conditions where the tank must be navigated through a course that involves maneuvering rather than simply driving in a straight line. The uprated engine of the T-55 tank allowed it to achieve an average speed of 32-35 km/h on paved roads and 22-27 km/h on dirt roads, thus surpassing the T-34-85 by a small margin.<br />
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<h3>
<span style="font-size: large;">TRANSMISSION</span></h3>
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<i>(This section was written by the user "AKMS", administrator of the Milimoto blog. <a href="https://milimoto.wordpress.com/2019/11/24/dwustopniowy-planetarny-mechanizm-skretu/">The original article from which this section was derived can be found here</a>)</i><br />
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The T-54 used a 5-speed manual transmission with a syncromesh gearbox. In the T-54 gearbox, the speeds ranging from the 2nd to 5th are controlled using the synchromesh system, but the 1st gear and the reverse gear still used the less advanced constant mesh system. The lack of a synchromesh system on the 1st gear was typical of old synchromesh gearboxes and it was not a real disadvantage for the T-54 because the driver only engages the 1st gear while the tank is motionless, and when the vehicle is motionless, a synchromesh system is not necessary. It was the same for the reverse gear, and in fact, modern vehicles with manual gearbox typically don't use a synchromesh system in reverse.<br />
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The use of a synchromesh means that driver does not have to use double declutching for gear changes. As there was no need for double declutching, the time required for gear changing is reduced and the amount of driver experience required to drive the tank was also reduced. Because of these advantages, practically every modern passenger car with a manual transmission use a synchromesh system. For comparison, T-34 tanks produced since 1943 used a 5-speed unsynchronized gearbox with a constant mesh system. That means that the T-54 gearbox had a serious advantage over the gearboxes of late production T-34 tanks such as the T-34-85.<br />
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Additionally, in the Polish book "<i>Teoria ruchu pojazdu gąsienicowego</i>" (<i>Theory of tracked vehicle movement</i>) written by Zbigniew Brudziński, it is stated that for a synchromesh gearbox, a gear change typically requires 1.0 to 1.5 seconds. For comparison, a gear change in a unsynchronized constant mesh transmission typically requires 1.5 to 2 seconds. Moreover, Brudziński writes that in an unsynchronized sliding mesh transmission such as the 4-speed gearbox used in early T-34 tanks (up until 1942), a gear change requires 2 to 3 seconds.<br />
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The drawing below shows a top view of the transmission with its kinematic components and connections. The T-54 transmission has 3 parallel shafts located longitudinally relative to transmission body. Due to the transverse mounting of the gearbox, the shafts are located transversely relative to the tank hull. The First shaft works as the power input. It receives power from the engine through an intermediate power transfer mechanism and main clutch (which are located between engine and gearbox). The first shaft transmits power to the second shaft, and the second shaft acts as an intermediate to transfer power to the third shaft, which is the main shaft.<br />
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The gears on the second and third shafts are paired together. The specific pair of gears used for power transmission from the second shaft to third shaft depends on the gear shift lever position. The synchronizers used for engaging gears are located on the third shaft. The third shaft transfers power to the steering mechanism.<br />
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The main clutch is a multi-disc dry clutch. It is is located between engine and gearbox, or more precisely, it is between the gearbox and intermediate power transfer mechanism. The main clutch is used for declutching the gearbox from the engine, like in a typical passenger car with manual gearbox. For declutching, the driver uses the clutch pedal.<br />
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T-54 uses a double-stage epicyclic steering mechanism. Each track has a separate steering mechanism with separate epicyclic steering units. The left steering tiller operates the left epicyclic unit, and the right tiller operates the right epicyclic unit. The two systems are completely isolated, so pulling on one steering tiller has no effect on the other. In both epicyclic units the ring gear works as the power input - power from the engine is delivered to the ring gear via the driveshaft from the gearbox and it transfers power into the rest of the gears. The planet carrier works as the output - it gets power from the ring gear (through the planets) and transfers power to the final drive, which transfers the power to the track via the drive sprocket.<br />
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In the T-54, the steering tillers have 3 main positions. The 1st position allows the track to move at its full forward speed, the 2nd position generates a reduced track speed by engaging a reduction gear, and the 3rd position is used for track de-clutching and braking. When driving the tank, if the driver changes the right tiller position from 1st to 2nd without changing the left tiller position (still in the 1st position), the speed of right track is decreased but left track still moves at its full forward speed. This causes the tank to turn to the right.<br />
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If the tiller is in the 1st position, the clutch of the steering mechanism keeps the sun gear and planet carrier connected, so that one rotation of the ring gear produce one rotation of the sun gear and one rotation of the planet carrier. If the tiller is in the 2nd position, the ring gear is disconnected from the sun gear, and the sun gear is braked by a small internal brake. Thus, the planets rotate around the sun gear and one rotation of the ring gear is faster than one rotation of the planet carrier in a ratio of 1.42. Changing tiller position from the 1st position to the 2nd position decreases the planet carrier speed, but increase the torque on the planet carrier. As a result, the speed of the drive sprocket is reduced but its torque is increased. If the driver puts the steering tiller on the 3rd position, the sun gear is disconnected from the planet carrier but the sun gear is not braked. Instead, the planet carrier is braked by the main brake. In this tiller position the track is braked and de-cluched, so it is disconnected from the drivetrain.<br />
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Regardless of the turning direction, the faster track moves at its full forward speed while the slower track has a lower speed than during a forward ride, and the hull moves at a lower speed than during a forward ride as it turns. In Polish terminology, this idea is categorized as a "second group steering mechanism". Steering mechanims which are included into the second group may be based on side clutches or on epicyclic gearing. Second group steering mechanisms include systems that do not feature regenerative steering (side clutches) and systems which feature regenerative steering (epicyclic gearing).<br />
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When the driver changes the steering tiller from the 1st position to the 2nd position, the track speed is decreased but the torque delivered to the track is increased. As such, the T-54 steering mechanism can be used as a reduction drive that may be used when additional torque is needed. For example, if the driver sees a steep hill, he can pull both tillers from the 1st position into the 2nd position to increase the torque delivered to the tracks to propel the tank until it reaches the top, whereby the driver returns the tillers to the 1st position. This method of torque boosting cannot be used for prolonged periods. According to the Polish army "<i>Podręcznik czołgisty</i>" (<i>Tanker handbook</i>), the driving distance should not be greater than 100-150 meters when using this method. This is enough for climbing hills, extricating another tank from a ditch by towing, knocking over obstacles, or performing some other operation that requires higher torque.<br />
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There are two main turning radii. If the driver wants to gently turn the tank, the first turning radius of 9 meters is used. With both tillers starting in the 1st position for normal forward motion, the driver pulls one tiller to the 2nd position while keeping the other on the 1st position. In this case both tracks move forward relative to the hull but with different speeds. When the first turning radius is being used, the T-54 steering mechanism operates with regenerative steering. Regenerative steering means that during a turn, power is transferred from the slower track into the faster track. That means that the faster track not only receives power from the engine, but also from the slower track. As such, a tank with regenerative steering requires a lower engine power to turn compared to a tank that does not feature regenerative steering idea. The turning radius of the tank does not depend on the selected gear. The drawing and citation below, taken from the Polish book "<i>Teoria ruchu pojazdu gąsienicowego</i>", details the regenerative steering concept in the T-54 steering mechanism:<br />
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From the book, translated by AKMS of the milimoto blog:<br />
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"<i>Power which is transferred from the epicyclic gear of the slower track into main shaft of mechanism, circulates inside closed circuit: axle of faster track sprocket wheel - final drive - vehicle hull - final drive of slower side - epicyclic gear of this side of vehicle - main shaft of mechanism - epicyclic gear of faster side - final drive - axle of sprocket wheel of faster vehicle side. Power transferred from slower track into faster track is called "regenerative steering". This is the recuperation power, which must be additionally generated by the engine if power were not transferred from the slower track into the faster track</i>"<br />
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In other words, in T-54, when the first turning radius is being used, power is transmitted from the engine into the faster track through the gearbox, the faster track moves the hull, hull movement propels the slower track (hull movement powering slower track), and power is transferred from the slower track into the faster track. This situation is visible on the drawing above.<br />
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The transmission permits the tank to execute pivot turns but not neutral turns. A pivot turn is where one track is driven forward or rearward while the other track is stopped with the tank turning around the stopped track, and a neutral turn is where both tracks are driven in opposite directions with the tank turning around the reversing track. When performing a pivot turn, the tank is using its second turning radius. To execute a pivot turn in a T-54, the driver must have one tiller on the 1st or 2nd position while pulling the other tiller to the 3rd position. The tiller placed in the 3rd position causes the corresponding track to be declutched and braked, thus immobilizing it. The tank rotates around the immobilized track, effectively steering the system via the traditional clutch and brake method. In this case there is no regenerative steering. If the propelling track is driven with the steering tiller in the 1st position, the tank performs the pivot turn at its maximum speed for a given gear. When the 2nd position is used, the torque delivered to the propelling track is increased while its speed is decreased and as such, the tank turns more slowly but more firmly.<br />
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Other than a "second group steering mechanism" like in the T-54, Polish terminology also includes the "first group steering mechanism" category. First group steering systems are based on a differential or multiple differentials. In a first group steering mechanism, pulling a tiller decreases the speed of the corresponding track while automatically increasing the speed of the opposite track compared to its normal forward speed. That means that during a turn, the hull moves at a speed equal to its full forward speed. Inside first group of steering systems, there are systems which don't use regenerative steering (braking differential) and systems which use regenerative steering (controlled differential).<br />
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Generally, steering mechanisms belonging to the second group produce a lower hull speed than first group steering mechanisms during a turn, but on the other hand, the load on the engine during a turn is lower when a second group steering mechanism is used compared to a first group steering mechanism. However, it should be emphasized that this is a generalization and there may be exceptions.<br />
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In the T-54 steering mechanism, the main brake is used not only for pivot turns (one tiller in the 1st or 2nd position, another tiller in the 3rd position), but also for vehicle braking during forward motion. The driver can use the steering tillers for braking during forward motion by pulling both tillers to the 3rd position. Of course, if the driver puts both tiller into the 3rd position, the tracks are not only braked but also are disconnected from drivetrain. If driver wants to brake the tank without de-clutching the tracks, he can step on the brake pedal instead. In some Soviet tanks with similar steering mechanism, a brake pedal is not provided. For example, Soviet heavy tanks like the IS-2, IS-3 and T-10 lack a brake pedal. The drivers of these tanks must pull both tillers to the 3rd position to brake, and the side effect of this is that the driver cannot brake the tank without de-clutching both tracks.<br />
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Driving a T-54 is less fatiguing than driving a T-34. Thanks to a hydraulic assist mechanism, the pulling force on the steering tillers is 12 kilogram-force (kgf), compared to around 30 kgf in a typical T-34 (27-36 kgf for a T-34-85). Additionally, in T-54, the clutch pedal is also hydraulically assisted and it also requires 12 kgf to depress. In a T-34, the maximum acceptable force on the clutch pedal is 25 kgf. The data for the T-54 comes from the Polish "<i>Tanker Handbook</i>", and the data for the T-34 comes from a Soviet test and Polish manual from 1961 (T-34-85M manual).<br />
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The transmission casing is made from cast aluminium. It is air-cooled by the centrifugal cooling fan. The power takeoff unit that transfers power from the engine to the tank's auxiliary systems is on top of the transmission casing. The power takeoff unit connects directly to the first shaft of the gearbox which receives power from the engine, and there is no intermediate gearing so the amount of power supplied to the power takeoff unit changes only when the
output of the engine itself changes. The block splits the power between
three smaller drive shafts. One goes to the AK-150 air compressor (if installed), another is connects to the centrifugal cooling fan, and the third connects to the radiator coolant pump.<br />
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The three L-shaped protrusions on the top of the transmission casing are part of the gear shifting system. They are connected to the gear shift lever. The three loops on the corners of the transmission casing are lifting eyes, to be used with a winch to lift the entire unit out of the tank's engine compartment such as shown in the photo below.<br />
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Like many tanks preceding it, the T-54 has the option of using compressed air to start its engine. There are two 5-liter air canisters mounted in the driver's station that are used to inject air into the cylinders of the engine, forcing the pistons into motion. This method is harsh on the engine, but dependable. Starting the engine in the summer is usually done electrically, but in the wintertime, the electric starting system may not be reliable due to piston lockup, so using air is necessary. In the harshest weather conditions, with the most poorly maintained T-54, starting the engine will require a combination of both methods simultaneously.<br />
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However, like the T-34, the compressed air tanks in a T-54 are not refilled automatically, so the reserves of compressed air is limited. This was changed in the T-55, which was equipped with an AK-150 V-shaped air compressor. The AK-150 is a typical two-stage reciprocating compressor, and like any other compressor of its type, the second stage piston is shorter than the first, and the two are linked by a cooling tube for the forced air cooling system used to regulate the heating of the piston cylinders during normal operation. The compressor is powered via an input shaft from the engine that is independent of the gearbox, thus allowing it to continue running even if the tank's gearbox is set to neutral. When it is in normal operation, the compressor uses 1.1 to 2.2 kilowatts of power (1.47-2.95 hp) depending on the engine speed. As such, the compressor would reduce the net power delivered through the transmission by an average of 2 hp when it is running.<br />
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The AK-150 compressor can be seen in the photo of the exposed engine compartment above, partially obscured, and the pneumatic starter system of the T-55 is illustrated in the drawing below.<br />
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It must also be said that the T-54 is extraordinarily light compared
to its foreign counterparts. Weighing in at only metric 36 tons dry, it
is lighter than a generic Centurion tank (52 metric tons) by an entire
16 tons, and lighter than an M48 tank (45 metric tons) by 9 tons, and
despite this, it is comparable in most respects and manages to achieve
superiority in others. The light weight of the tank enables it to not
only exploit bridges intended for light loads, but to also use pontoon
bridges and scissor bridges with impunity, as there will be a large load
surplus. A large convoy of T-54 tanks may cross a pontoon bridge
without needing to take turns.<br />
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The T-54 exerted a ground pressure of 0.8 kg/sq.cm, whereas the newer and heavier T-55 exerted a ground pressure of 0.81 kg/sq.cm.<br />
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<h3>
<span style="font-size: large;">SUSPENSION</span></h3>
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Like the T-44 before it, the T-54 used torsion bars instead of the famous Christie spring suspension of the T-34. The tracks were unsupported and ran directly on top of five large diameter rubber-rimmed roadwheels. The drawing above shows the suspension of a typical T-54 with the shock absorbers behind the first, second and last roadwheels on either side of the hull clearly visible.<br />
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Due to the lack of space above each roadwheel swing arm owing to the lack of support for the returning track, it was not feasible to install a conventional linearly actuated hydraulic shock absorber, so a compact vane-type rotary hydraulic shock absorber was installed. The shock absorber arm is joined to the roadwheel arm by a rod.<br />
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<br />The rotary shock absorber contains four chambers separated by two vanes with constricted openings for hydraulic fluid to pass through. Vertical motion of the roadwheel swing arm deflects the lever arm of the shock absorber, transforming linear force into torque which is applied to the vane rotor. The rotary motion of the vanes displaces the hydraulic fluid from the high-pressure chamber to the opposing low-pressure chamber via the vane opening. The restriction of fluid flow through a small opening creates a resistance to motion, converting kinetic energy into thermal energy, thus damping the force applied by the roadwheel.<br />
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The torsion bars were swapped out for better ones made by electroslag remelted (ESR) steel in the T-55AM modernization and the variants thereof. One reason for this upgrade was simply the desire the improve the mobility of the tank to a more modern standard and improving the quality of the ride, but another reason was the added weight of the tank from the add-on "Brow" armour. The superior steel of the new torsion bars combined with the heavier mass of the modernized tank improved the damping of vibrations.<br />
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<h3>
<span style="font-size: large;">OMSh tracks</span></h3>
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As with earlier Soviet medium tank tracks, the T-54 uses OMSh tracks. OMSh stands for open metal-pinned tracks. The single-pin track links are held together with bare metal pins which are only secured on the inner end of the track by an oversized head. There are no clips or fasteners to retain the pin on the other end of the track, so when the tracks move, the pins gradually come loose and eventually worm their way out of their slots, but only in the direction of the hull. A steel ramp is welded onto the side of the hull just next to the drive sprocket to knock these loose pins back into the track.<br />
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The T-54 obr. 1947 used a proprietary OMSh track design with a width of 580mm that was not carried over to later T-54 models. Beginning with the T-54 obr. 1949, a new OMSh track design was implemented and this came to be the standard design for the T-54 family and its derivatives for the next two decades. These OMSh tracks can be easily identified by the distinctive loop at the end of each track link. The track links are made from cast steel. There are 90 links on each side. The track width remained the same at 580mm and the track pitch is 137mm.<br />
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The requirement for the lifespan of the track was fulfilled by the original OMSh track design of the T-54 prototypes, four years before the new OMSh track for the T-54 obr. 1949 was developed. Recall that the T-54 was developed under a set of six requirements, the fifth being: "<i>Develop a robust track and track pin (increase track life to 3,000 km)</i>". Testing in 1946 revealed that the T-54 prototype drove 20,000 kilometers and wore out 6 pairs of tracks, equating to an average lifespan of 3,333 kilometers per track, thus exceeding the original requirements by an average of 11.1%.<br />
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There were no rubber bushings and no rubber pads on the inner surface of the track links. Furthermore, the open design of the tracks meant that sand and dust could slowly accumulate inside the gap between the track pin and the track link socket. The abrasion from these foreign objects could wear out the track pins which could make them more susceptible to breaking, thus increasing the probability of the tank throwing a track when performing a hard maneuver of some kind. The deficiencies of open-type tracks were recognized and work was done to implement new track designs with an increased lifespan.<br />
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<h3>
<span style="font-size: large;">RMSh</span></h3>
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To improve the lifespan of the tracks, a new RMSh track design was developed by the Omsk Transport Engineering Plant with development concluding in 1962. Beginning in 1966, these new RMSh tracks were fitted to new-production T-55 tanks on a mass scale and the new tracks gradually replaced old OMSh tracks on existing T-54 and T-55 tanks as they wore out during normal use. However, the new track did not become a common sight until much later because large stockpiles of OMSh tracks had been accumulated in the Soviet Army and there was a plentiful supply of spares.<br />
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RMSh stands for rubber-lined metal tracks. The tracks have the same width of 580mm as the previous OMSh track design. The track pitch is 137mm, which is also exactly the same as the previous OMSh track design. The track pins are hexagonal and fit into the rubber-lined track pin sockets in the track links and are fastened at the ends with hexagonal nuts.<br />
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These tracks were not only designed for increased durability but also higher dynamic loads, so they were built heavier and sturdier than the OMSh design. A full set of ninety seven RMSh track links weighs 1,655 kg. Theoretically, the increased mass of the tracks increased the rolling resistance of the tank which translates to a reduction in the acceleration rate, but in actuality, the increased traction and dynamic characteristics of the tracks reduced power loss by 20%. The driving range and the speed of the T-55 also increased by 15% compared to a tank equipped with OMSh tracks. The biggest improvement offered by RMSh tracks is the increased service life, which is around twice that of the OMSh tracks. Thanks to the shock and vibration damping effect of the rubber bushing, the lifespan of the RMSh track was improved to 5,000-6,000 km and the ride quality in the tank also improved. The noise level of the RMSh tracks was also reduced.<br />
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The RMSh track design was also used on the T-62 and it was later carried over to the T-72. Since the T-54/55, T-62 and T-72 became the most numerous tanks in the Soviet Army by a large margin with the T-54/55 and the T-72 being the most and second-most produced tanks in history respectively, the use of the same tracks undoubtedly helped simplify the logistical burden of operating multiple different tank models. It was probably also quite convenient for units transferring from the T-54/55 or T-62 to the T-72.<br />
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<h3>
<span style="font-size: large;">COOLING SYSTEM</span></h3>
Like the T-34 it replaced, the T-54 had a water-cooled engine but the layout of the cooling system was changed to reflect the new design of the engine compartment. The radiator is located on the back half of the engine deck. A large centrifugal fan at the very rear of the engine compartment draws air through the radiator and into the engine compartment from the outside, and then ejects the hot air out through a port, thus cooling the engine. The main flaw in this design is that hot air from the radiator passes into the engine compartment before it exits through the centrifugal fan, so the engine compartment is heated by the hot air and more heat energy is retained overall, making it slightly less efficient. The centrifugal fan can be seen in the photo below.<br />
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As mentioned before, the fan is driven at a very high speed by a shaft from the gearbox. Along with the compressor and generator, the fan comprises one of the parasitic elements reducing the final amount of power that is transmitted to the drive sprockets.<br />
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The radiator pack is rather large. Inside it is a maze of tubes and heat sinks to maximize the loss of heat. The radiator pack is protected from above by an armoured cover, complete with armoured louvers. The armoured louvers can be closed to protect the radiator and the gear box under it from air attack and molotov cocktails, but the consequence of closing them is that the airflow into the radiator is severely restricted, so that less heat is removed from the coolant.<br />
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The armoured cover is hinged and can be lifted up and away, and there are armoured louvers in the armoured cover that can be opened or closed from the driver's station by turning a lever. Closing the armoured louvers will increase protection against air attack and also prevent napalm and other burning liquids from entering the engine compartment, but the louvers cannot be kept closed for prolonged periods as this will make the engine overheat. When the armoured cover is opened, the radiator pack can be lifted up and away in the same manner, and it even has two rubber padded handles for this purpose, as seen in <a href="http://i140.photobucket.com/albums/r13/SaucemanRC51/T-55%20cutaway/131_zpsb8250beb.jpg">this photo</a>. Both the radiator pack and armoured cover are sprung with a torsion bar so that one man can easily lift them open without assistance. Once out of the way, the gear box, transmission, brakes, radiator pump and coolant reservoir can all be accessed. <br />
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One minor disadvantage of the cooling system is that the ejected air is blown out of the centrifugal fan at a high velocity, so that the dust kicked up by the tracks gets sucked into the air stream. The effect is that there is a "rooster tail" of dust spouting from the back of the tank. This tends to be a problem in very dry and dusty conditions like in deserts or in some European summers but not in hot and humid conditions like in South East Asia (including Vietnam). If you happen to be a scout conducting forward observation in a very dry part of the world, faint "rooster tails" in the distance would be a dead giveaway that T-54 tanks are coming your way.<br />
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Swapping out the engine requires the armoured panel above it to be unbolted and shifted out of the way. Then, the engine must be decoupled from the transmission input shaft, and the four bolts that secure the engine crankcase to its mount on the floor of the engine compartment have to be removed. Then, all of the tubes and hoses including the fuel and water tubes have to be disconnected, and then finally, the engine can be lifted.<br />
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Many armour historians have observed that, among other things, one of the main factor behind the T-54's longevity is its automotive reliability and simplicity of maintenance. This is generally true. Quoting from Stefan Kotsch's website (<a href="http://www.kotsch88.de/al_geschichte_T54.htm">link</a>), which uses Russian sources including Uralvagonzavod's official works on the T-54:<br />
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"<i>For example, in the period from October to November 1956, service station no. 20 was tasked to repair 188 tanks T-54. Of these, 18 had tanks, covered with the meantime the engine has change, a driving distance of around 8,000 km. Another 56 tanks reached an average of 6,031 km. The engines on 15 tanks achieved an average operating hours of 600 Mh, an even 696 Mh. Constructor Kartzev presented in 1956 found the tank T-54 can be used without major repair, for replacement of individual modules, certainly achieve a mileage of up to 10,000 km. Thus, the T-54 can be described as one of the most reliable tanks in the world.</i>"<br />
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According to Pat Ware and Brian Delf in "The Centurion Tank", the engine life of the Rolls-Royce Meteor was reported in service to be only around 3,000 miles (4,828 km) before a base overhaul was required. Many other tanks have been deemed "satisfactory" or "perfectly sound", but not many tanks have the same legendary reputation of toughness as the T-54.<br />
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However, this came at a cost. The T-54 is reliable and extremely sturdy, but as we have already learned, the driver's controls were not as user-friendly as contemporary Western tanks which had steering wheels and automatic gearboxes.<br />
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<h3>
<span style="font-size: large;"><br />WATER OBSTACLES</span></h3>
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<a href="https://1.bp.blogspot.com/-q_OHR1_h-f4/WF0oJDyduAI/AAAAAAAAH9E/otGdNxXGP-IxI5fpo-psHUq1YYj8jWOaQCLcB/s1600/polish%2Bt-54%2Bwading.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="476" src="https://1.bp.blogspot.com/-q_OHR1_h-f4/WF0oJDyduAI/AAAAAAAAH9E/otGdNxXGP-IxI5fpo-psHUq1YYj8jWOaQCLcB/s640/polish%2Bt-54%2Bwading.png" width="640" /></a></div>
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In 1958, the T-54 received the OPVT snorkeling system, thus gaining the ability to cross water obstacles as deep as 5 meters.<br />
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<a href="https://3.bp.blogspot.com/-nOMPWgcp5b4/WF0oKDQ8YBI/AAAAAAAAH9I/aJCTjYaBS1gJp4rGMF-rKW13IKyxX6J6QCLcB/s1600/t-55%2Bsnorkelling.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="429" src="https://3.bp.blogspot.com/-nOMPWgcp5b4/WF0oKDQ8YBI/AAAAAAAAH9I/aJCTjYaBS1gJp4rGMF-rKW13IKyxX6J6QCLcB/s640/t-55%2Bsnorkelling.png" width="640" /></a></div>
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If the obstacle is too deep for unassisted fording but too shallow for the full snorkel tube to be used, a shorter snorkel section can be installed, as the photo below showcases.<br />
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<a href="https://1.bp.blogspot.com/-oOlXK7y1V6k/XQMlkXNjVSI/AAAAAAAAObg/0czx2THhi6kOKONWAG1E5P60OTBwsS8QgCLcBGAs/s1600/nva%2Bt-55.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="771" data-original-width="1024" height="480" src="https://1.bp.blogspot.com/-oOlXK7y1V6k/XQMlkXNjVSI/AAAAAAAAObg/0czx2THhi6kOKONWAG1E5P60OTBwsS8QgCLcBGAs/s640/nva%2Bt-55.jpg" width="640" /></a></div>
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When not in use, the OPVT snorkel is stowed away at the back of the tank, underneath the wooden log.<br />
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<a href="https://3.bp.blogspot.com/-O4NK8pO_DpE/WeDENMFgpEI/AAAAAAAAJ1I/P1hWURkU1zY-oM9V6iV7qxdQKakhys7VQCLcBGAs/s1600/opvt.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="261" data-original-width="605" src="https://3.bp.blogspot.com/-O4NK8pO_DpE/WeDENMFgpEI/AAAAAAAAJ1I/P1hWURkU1zY-oM9V6iV7qxdQKakhys7VQCLcBGAs/s1600/opvt.jpg" /></a></div>
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<h3>
<span style="font-size: large;">FUEL SYSTEM</span></h3>
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<span style="font-size: large;">T-54</span></h3>
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<a href="https://1.bp.blogspot.com/-jYHaT5m_KNM/WG3itfCpCPI/AAAAAAAAH-g/1Ujw8NEo8-gAWDUDpmDlpzvbs43fB6CwQCLcB/s1600/t-54%2Bfuel%2Bsystem.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="228" src="https://1.bp.blogspot.com/-jYHaT5m_KNM/WG3itfCpCPI/AAAAAAAAH-g/1Ujw8NEo8-gAWDUDpmDlpzvbs43fB6CwQCLcB/s400/t-54%2Bfuel%2Bsystem.gif" width="400" /></a></div>
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The T-54 obr. 1947 featured four internal fuel tanks and three external fuel tanks on the fenders above the tracks. As shown in the drawing above (depicting the T-54 obr. 1951 fuel system)), the external fender fuel tanks were not connected with the fuel lines of the internal fuel tanks, but both the internal and external fuel tanks are connected to the engine through their separate pipes. This is designed so that the fuel supply to the engine can be switched between the internal fuel tanks, the external fuel tanks or switched off entirely, all done remotely from a rotary switch located in the driver's compartment.<br />
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The internal fuel tanks were located in the crew compartment. There were three interconnected tanks at the nose of the glacis, shown on the left below, and a single large tank in front of the bulkhead between the fighting compartment and the engine compartment, shown on the right below. These four internal fuel tanks had a total capacity of 520 liters, of which 300 liters is held in the two larger front hull fuel tanks in the nose of the glacis, 20 liters is held in the smaller tank between the ammunition racks and the wall of the hull side, and 200 liters was held in held in the rear fuel tank. The T-54 obr. 1951 featured an increased fuel capacity thanks to the addition of a 95-liter fuel tank on the right track fender. This arrangement was retained up to the T-54B model.<br />
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<a href="https://1.bp.blogspot.com/-Zl4R5b1LCg4/XVAshRprHLI/AAAAAAAAOzI/OSs6ryescp4Xh_BMdlJXBdB79ogbBUBowCLcBGAs/s1600/rear%2Bfuel%2Btank.gif" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="411" data-original-width="400" height="200" src="https://1.bp.blogspot.com/-Zl4R5b1LCg4/XVAshRprHLI/AAAAAAAAOzI/OSs6ryescp4Xh_BMdlJXBdB79ogbBUBowCLcBGAs/s200/rear%2Bfuel%2Btank.gif" width="194" /></a><br />
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<span style="font-size: large;">T-55</span></h3>
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<a href="https://1.bp.blogspot.com/-mDkh-YdwXPY/XVAshQUvhXI/AAAAAAAAOzE/9T_8y9MqJR0fOipsaZDHpu55eCwCzWfWwCLcBGAs/s1600/t-55%2Bfuel%2Bsystem.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="207" data-original-width="484" height="170" src="https://1.bp.blogspot.com/-mDkh-YdwXPY/XVAshQUvhXI/AAAAAAAAOzE/9T_8y9MqJR0fOipsaZDHpu55eCwCzWfWwCLcBGAs/s400/t-55%2Bfuel%2Bsystem.jpg" width="400" /></a></div>
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The T-55 modernization introduced new conformal fuel tanks that replaced the front hull ammunition racks in the tank. These new tanks held 300 liters of fuel. The rear hull fuel tank of earlier T-54 models was removed and replaced with ammunition racks. The loss of this rear hull fuel tank reduced the fuel capacity by 200 liters, but because the new conformal fuel tanks held 300 liters, a net increase of 100 liters was gained. An additional 280 liters of fuel was carried in the external fuel tanks located on the right track fender, like older T-54 models. Thanks to the additional fuel reserve, the driving range of the T-55 was expanded to 485-500 km on paved roads and 290-320 km when driving cross-country.</div>
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The T-54 had good fuel economy and a long driving range which was an advantage that was further accentuated by the T-55. Beginning with the T-54B, the driving range of the tank could be enhanced by two removable 200-liter fuel drums mounted at the rear of the tank. These fuel drums were not connected to the fuel network so the fuel must be siphoned into the fuel system manually, as was the case with the T-34. Doing so would require the tank unit to make a short halt which would delay the pace of the march, but not as much as completely stopping the unit and waiting for refueling trucks. Even so, this was recognized as a limitation and the T-72 was designed to have quick-detachable fuel drums that were connected to the fuel system.<br />
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In the absence of tank transporter lorries or appropriate rail transport, the T-54 could cover 500 km on a paved road under its own power. If the two external 200-liter fuel drums were fitted, the driving range of the T-54 and the T-55 on paved roads increased to 600 and 650-715 km respectively. Travelling across dirt roads and rough terrain will reduce the travelling range by almost half, as a rule of thumb.<br />
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The Centurion, in comparison, consumed fuel at an eye-watering rate of just 0.27 to 0.52 miles to the gallon, giving a range of just 33 to 62 miles. When Stalin closed down all avenues of entry to West Berlin in 1948 (nearly starting WWIII in the process), it became clear that Centurions would not be able to reach the city from their bases in West Germany without needing to refuel en route and waste precious time. This problem was only solved in 1963 with the installation of a bolt-on 109-gallon fuel tank at the rear of the tank, but the T-54 still maintained a huge - only now slightly smaller - advantage in road range and more importantly, fighting endurance.<br />
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<span style="font-size: large;">DISTRIBUTION</span></h3>
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It is impossible to discuss the T-54/55 without mentioning that it is the most widely produced tank design in the history of tanks. About 60,000 examples have been produced in the USSR alone, and tens of thousands more have been produced in satellite states. Copies and derivatives of the design, including the Chinese Type 59 and Type 69 boost the total number of tanks even further, making the T-54 the most produced tank in human history. The absurdly high production figures for the T-54 series gave the Soviet Army a decisive numerical superiority during the Cold War and ensured the longevity of the tank in the years to come. For comparison, Simon Dunstan stated that the production of the Centurion Mk. 3/5 medium tank ran from 1946 to 1958, during which 2,833 Mk. 3 tanks (1946-56) and 221 Mk. 5 tanks (1955-58) were manufactured. Three facilities were responsible for Centurion final assembly: Vickers Armstrong and the Royal Ordnance Factories at Leeds and Dalmuir. According to Spencer Tucker, a total of 4,423 Centurions of all types were built, of which 2,500 were exported.<br />
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Currently, the T-54 is in service in Russia as hard targets on firing ranges all over the country. A few examples are were serving in the Far East as coastal defence guns as recently as 2012, but since then, virtually all existing T-54 tanks have dismantled and melted down for their steel. Almost all of the examples that actively served in the Far East were leftover T-55A tanks equipped with KDT-1 laser rangefinders, but even these are now almost never seen outside of storage facilities.<br />
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</div></div></div><br /><div><br /></div>Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com63tag:blogger.com,1999:blog-3103574899092646031.post-7419438683365030912016-05-27T07:15:00.042-07:002023-05-09T01:23:11.768-07:00BMP-2 <head>
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<h2 style="text-align: center;">
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This iteration of the BMP family is technically excellent in the application of available technologies and features, especially when compared to its predecessor, the BMP-1, but some view the BMP-2 is nothing more than a "rehash" of the old and obsolete BMP-1 design. While that is technically true, the sentiment behind such an accusation points to an incorrect mindset. The BMP-2 is a product improved BMP-1, but it is not quite the same thing as its predecessor. Far from it. It is so heavily modified that the only similarities are in the general layout and the powertrain. Even the hull was structurally different due to the use of a new steel. The most obvious difference between the BMP-2 and its predecessor is, of course, the new turret, now armed with a deadly 30mm autocannon. The modifications resulted in an almost entirely different vehicle with greatly expanded capabilities. However, the BMP-2 never got past the lack of a modern thermal imaging system like the M2 Bradley's ISU (Integrated Sighting Unit), and it only got worse as time went on, as the BMP-2 stagnated technologically while its contemporaries continually evolved.<br />
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From 1980 to 1989, the factory now known as Kurganmashzavod produced a total of 14,000 BMP-2 models of all types. At the peak of production in 1989, between 1,800 to 1,900 units exited factory gates every year - triple the maximum annual rate of production of the M2 Bradley. These production numbers ensured that many Soviet motorized infantry units were equipped with fully armoured and highly mobile troops transports with more firepower than before. From 1988 to 1991, the production of the BMP-2 ran in parallel with the BMP-3, and in the 1990's, most of the production capacity of the KMZ plant had been redirected towards producing the BMP-3 to fulfill export contracts. Small orders of BMP-2s and BMP-3s were delivered to the Russian Army, but the volume of deliveries was small due to the economic situation of the Russian Federation at the time. In 2005-2006, the Russian Army received its last batch of approximately 40 new-built BMP-2s. Since then, no new BMP-2s have been supplied to the Russian Army, but KMZ still engages in the production of spares and routinely carries out overhaul and modernization work for existing vehicles.<br />
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<h3>
<span style="font-size: large;">TABLE OF CONTENTS</span></h3>
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<ol>
<li><a href="#comstat">Commander's Station</a></li>
<li><a href="#tkn-3">TKN-3B</a></li>
<li><a href="#tkn-ai">TKN-AI</a></li>
<li><a href="#1pz-3">1PZ-3</a></li>
<li><a href="#comm">Communications</a></li>
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<li><a href="#gunstat">Gunner's Station</a></li>
<li><a href="#sights">Sighting Complexes</a></li>
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<li><a href="#stabs">Stabilizers</a></li>
<li><a href="#2a42">2A42 Cannon</a></li>
<li><a href="#ammunition">Ammunition</a></li>
<li><a href="#second">Secondary Weapon</a></li>
<li><a href="#firingports">Supplementary Weapons</a></li>
<li><a href="#missiles">Missiles</a></li>
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<li><a href="#prot">Protection</a></li>
<li><a href="#bmp-2d">Applique Armour</a></li>
<li><a href="#fueldoors">Fuel Tank Doors</a></li>
<li><a href="#smoke">Smokescreen</a></li>
<li><a href="#nbc">NBC Protection</a></li>
<li><a href="#fire">Fire Fighting</a></li>
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<li><a href="#pass">Passengers</a></li>
<li><a href="#driver">Driver Station</a></li>
<li><a href="#mob">Mobility</a></li>
<li><a href="#fuel">Fuel Endurance</a></li>
<li><a href="#water">Water Obstacles</a></li>
<li><a href="#dist">Distribution</a></li>
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<h3>
<span style="font-size: large;">COMMANDER'S STATION</span></h3>
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The commander of a BMP-2 is the squad leader of the Soviet motor rifle squad, the same as in a BMP-1. While he has been moved from the hull to the turret, the squad leader fulfills the same role as the commander of a BMP-1. He dismounts along with the passengers when required, leaving the gunner to do double duty in his absence.<br />
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The commander has his own hatch, which has an unusual clam shell shape to grant enough space to accommodate the extremely sparse array of periscopes.<br />
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The commander of the BMP-2 is only given a miserly <b><i>two (!)</i></b> general vision periscopes to supplement his ubiquitous TKN-3B. Not only is that less than what the gunner gets, it's also much less than what the commander's NATO counterparts get. The commander of the Marder 1, for instance, is furnished with a generous array of five periscopes covering 160 degrees frontally. However, it must be mentioned that the cupola rotates, so unlike the gunner seated beside him and the commander of a Marder 1, the commander of a BMP-2 can spin the cupola around to see all 360 degrees around him. It is not as convenient as being able to glance in whichever direction at leisure, but the overall effect is similar, and at least the commander of a BMP-2 has a greater field of view than a 160 degree frontal arc. It would, of course, be much better to have two more periscopes like on the cupolas of T-54 and T-62 tanks. To top it all off, there is a TNPT-1 rear view periscope mounted in the hatch to give the commander immediate rearward awareness. It is useful for directing the driver when buttoned up. In non-combat situations the commander may opt to peek out of his hatch instead.<br />
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As usual, all of the periscopes are heated with the RTS-27 heating system to prevent fogging. RTS stands for "<i>Регулятор Tемпературы Стекла</i>" (Regulyator Temperatur' Stekla), which literally means "Glass Temperature Regulator".<br />
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Unfortunately, it seems that this system is a common source of complaints, according to forum posts on the Russian internet. The RTS periscope heating system is installed in nearly all Soviet vehicles, including the T-72, T-64, BTR-80, and many, many more. However, none of them have had any complaints about periscopes fogging up, except for the BMP-2 and its predecessor. Based on anecdotal evidence collected from several BMP-2 crew members, both current and former, it seems that the RTS heating system doesn't always work on the BMP-2 for some reason. It has been the source of much grief during the winter, as the periscopes usually fog up so badly that it becomes impossible to see through them. It is possible that this is simply due to the poor condition of training vehicles, but this is only speculation. It seems strange that such a simple system went wrong here when it could function fine in everything else.<br />
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<a href="https://www.blogger.com/null" id="tkn-3b"></a>
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<h3>
<span style="font-size: large;">TKN-3B</span></h3>
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One considerable advantage to the BMP-2 in overall fighting efficiency over its contemporaries is that the commander has the TKN-3B combined active/passive pseudo-binocular periscope at his disposal. Pseudo-binocular meaning that although the device has two eyepieces, the two optic feeds are combined to one aperture, which the viewer sees out of. The TKN-3B has a fixed 5x magnification in the day channel with an angular field of view of 10°, and a fixed 3x magnification in the night channel with an angular field of view of 8°. The periscope can be manipulated up and down for elevation, but the commander's cupola must be manually spun for horizontal viewing.<br />
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For tanks like the T-72, the TKN-3B might be a somewhat mediocre tool compared to the PERI-R17 panoramic sight with television feed for the Leopard 2, but for an IFV like the BMP-2, it was rather remarkable. It wasn't stabilised, and featured only rudimentary rangefinding capabilities, and its nightvision capabilities were not competitive by 1980 (the TKN-3 first entered service in 1963), but it at least <i style="font-weight: bold;">had</i> nightvision capabilities, and it had a decently high magnification. Night vision came in two flavours; passive light intensification or active infrared. In the passive mode of operation, the TKN-3B uses its light intensification module to amplify ambient light to produce a legible image. This mode is useful down to ambient lighting conditions of at least 0.005 lux, which would be equivalent to an overcast, moonless and starless night. In these conditions, the TKN-3B can be used to identify a tank-type target at a nominal maximum distance of only 400 m due to the resolution limit, but as the amount of ambient light increases such as on starlit or moonlit nights, the distance at which a tank-sized target is discernible can be extended. In dark twilight hours, the TKN-3M may be able to make out the silhouette of a tank at a distance of up to 800 m or more, but the sight is hamstrung again, this time not by the absence of light, but by the low magnification. Any brighter than dawn or dusk, and the image will be oversaturated and unintelligible.<br />
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The active mode requires the use of the OU-3GA2, an IR spotlight operating on 110W, connected directly to the BMP-2's 27V electrical system. With active infrared imaging, the commander can reliably spot large objects from a distance of more than a kilometer depending on meteorological conditions, but identifying targets as tanks or trucks or APCs can only be done at around 800 m, but potentially more if the opposing side is also using IR spotlights, in which case, the TKN-3 can be set to the active mode but without turning on the IR spotlight. This is possible because the switch for activating the spotlight is the right thumb button while the operating channel selector is on the TKN-3 itself, meaning that they can be turned on separately.<br />
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The problem with IR spotlights as a whole is that although the user can use them to spot for targets, the targets can use them to spot the user too, but from much further away. Because of the diffraction of light waves, anybody observing the user won't just see a dot of light. If you observe a tank with its IR spotlight on, most of the tank would be brightly illuminated from miles away. The diffracted light does have the benefit of lighting up the ground better for the driver to see, though, so the common issue of speed control due to short visibility distance with the complementary IR periscope for the driver is slightly alleviated in battle conditions. If you look at the photo above, you can clearly see what I mean by this. The spotlight (running on a small pocket battery in this case) illuminates the apartment building, but also the most of the ground. If you had an infrared filter on your gunsight or rifle scope, like the PSO-1 for the SVD rifle, you could very easily see the source of light and call out its position.<br />
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Shortcomings in the night vision capabilities of the TKN-3B may be solved by the use of illumination rounds fired over enemy positions. This doesn't solve all of its problems, of course, because the low resolution may complicate the quick and proper identification of enemy vehicle types at long distances, and overhead lighting doesn't penetrate dense forest canopies. More recently, IR illumination rounds similar to the British L58A1 have been developed and put into service, which may benefit the TKN-3B greatly. Needless to say, this new type of ammunition is a godsend for the ageing BMP-2s of today..<br />
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Rangefinding is accomplished through the use of a stadiametric scale sighted for a target with a height of 2.7 m, which was the average size of the average NATO tank or IFV. The TKN-3B is unstabilized, making it exceedingly difficult to properly identify enemy tanks or other vehicles at extended distances while the BMP-2 is travelling over rough terrain, let alone determine the range. The left thumb button initiated turret traverse for target cuing. The range of elevation is +10° to -5°. The OU-3GA2 spotlight is also directly mechanically linked to the periscope to enable it to elevate with the TKN-3B.<br />
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<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-k6BsJIWkjFE/VmWGhoLaVfI/AAAAAAAAEtY/FyrdOec9Fqs/s1600/tkn-3.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="375" src="https://3.bp.blogspot.com/-k6BsJIWkjFE/VmWGhoLaVfI/AAAAAAAAEtY/FyrdOec9Fqs/s400/tkn-3.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">TKN-3 viewfinder</td></tr>
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The TKN-3B gave the BMP-2 a true hunter-killer capability, something totally foreign to NATO IFVs of the era. By simply placing the crosshairs on the target and pressing left thumb button, whereupon the turret will spin to meet the target. The cupola lacks a contra-rotating motor, but it is light enough and the ball bearings of the cupola are smooth enough that it does not have enough inertia to not spin away with the turret, making it easy for the commander to keep the cupola aimed at the target while the turret spins around to meet it. This was not so easy in the T-62, which gave the commander a steel rung for the commander to hold on to. The fact that this hunter-killer feature exists is of huge importance, as the commander is elevated from a simple observer to an active participant. He could participate even further if required, using his 1PZ-3 multipurpose sight.<br />
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<a href="https://www.blogger.com/null" id="tkn-ai"></a>
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<h3>
<span style="font-size: large;">TKN-AI</span></h3>
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The TKN-AI is a descendant of the TKN-3 family. It has improved nightvision capabilities, but offers little else. Like the all members of the TKN-3 family, TKN-AI is unstabilized and controlled manually. The magnification in the daytime channel is 4.75x and the magnification in the night channel is 5x.<br />
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TKN-AI features a pulsed laser spotlight, but evidence shows that it can be replaced with a PL-1-01 laser beamer, presumably to increase the range of vision. The laser spotlight superficially resembles an OU-3 spotlight from a distance, but as you can see in the photo above, the aperture for the IR laser is much, much smaller than the external diameter of the spotlight itself. Both the spotlight and the PL-1-01 beamer can switch from active illumination to pulsed illumination, whereby the IR laser beam is modulated and pulsed to an operating frequency is 5.2 kHz with an illumination pulse duration of 130 ns. This is meant to reduce laser backscatter when viewing through haze or fog. The identification distance for a tank-type target is 1000 meters in the active mode, but it might be possible to increase the detection range by installing the PL-1-01 instead of the spotlight.. The device is also capable of rangefinding using timed laser pulses controlled by the TKN-AI. The claimed accuracy of ranging is 20 m within a range of distances between 200 m and 3000 m.<br />
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Besides active infrared imaging, the TKN-AI features a passive mode with a 2+ generation image intensifier module. It is possible to identify a tank-type target at 600 meters in the passive mode, which is slightly better than the 500 m range of the TKN-3B.<br />
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Modernized BMP-2s using the TKN-AI are known to have participated in exercises, like the one in the photo below. It can be seen with the characteristic PL-1-01 pulsed laser beamer where the old OU-3 IR spotlight should be.<br />
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<div><br /></div><div><br /></div>An additional incentive for the replacement of incandescent and xenon IR lamps with a laser beamer was the end of xenon lamp production at the Riga Electric Lamp Plant in 1991, thus constraining the sustainability of the continued use of Soviet legacy spotlights.<br />
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However, this upgraded device still retains some drawbacks of older IR nightvision devices. Being a rather powerful IR laser projector, an illuminated PL-1-01 can be spotted from great distance with a simple helmet-mounted nightvision monocular or goggles by the target of observation, though the IR beam is also likely to blind the observer at the same time. <div><br /></div><div>The IR beam itself may also be visible if there is smoke or fog around the battlefield as it will diffuse the light of the laser beam and make it visible to anyone equipped with nightvision equipment. If that occurs, then it would be extremely simple for any observer to trace the beam back to its originator, thus revealing the location of the BMP-2, leaving it open to artillery or air attack. The object of the commander's attention will also be alerted as long as he has nightvision equipment, since he would be able to see himself or the area around him illuminated by the laser.<br />
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<a href="https://www.blogger.com/null" id="1pz-3"></a>
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<h3>
<span style="font-size: large;">1PZ-3</span></h3>
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Besides manning the periscopes and managing the vehicle, the commander is also in charge of fending off air attacks. To do this, he is provided with a 1PZ-3 anti-aircraft sight mounted on the turret ceiling in front of his cupola. It can also be used as a backup sight for ground targets if the need arises. When not in use, the aperture window is covered by an armoured hood.<br />
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The 1PZ-3 sight is monocular with a very large range of elevation. It features internal electric heating and has two special light filters. The sight can be used without a filter when firing upon ground targets, but if necessary, a "Special" filter or a "Neutral" filter can be applied by turning a lever. The "Special" filter is simply a laser protection filter that protects the operator from being blinded by direct laser illumination, and the "Neutral" filter is a neutral density filter that reduces the amount of light that is transmitted to the operator's eyepiece, thus darkening the image. This makes it easier for the operator to detect and track aircraft in the sky during bright daylight hours, but it can also be used when engaging ground targets if necessary.<br />
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The sight lacks independent stabilization, but because of its direct mechanical connection to the stabilized 2A42 cannon in the turret, the sight is stabilized in the vertical plane. However, due to the coarse nature of this type of stabilization, the stabilization precision is not high and the viewfinder image may vibrate when the vehicle is moving on rough ground. The sight can elevate and depress as far as the cannon can, which would be from -5 degrees to +75 degrees in elevation.<br />
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The sight has two magnification settings; 1.2x and 4x. The field of view through the sight is 49 degrees in the 1.2x setting and 14 degrees in the 4x setting. The lower magnification was only suitable for engaging aircraft. Shooting at air targets flying at subsonic speeds is theoretically possible at ranges up to 2,500 m and at altitudes up to 2,000 m. In practice, the effective range is much less.<br />
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The two images below show the sight under the 1.2x and 4.0x magnification settings.<br />
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As far as anti-aircraft sights go, the 1PZ-3 had no outstanding characteristics and contained only the essential markings for leading moving aircraft. The sight also has the secondary purpose of serving as the commander's only optic for ground targets and being the BMP-2's backup gun sight as well, and to that end, its viewfinder provides graduated range scales and simple deflection markings, as shown in the images above. To aim, the operator turns a knob to raise and lower a horizontal line until it matches the desired mark on the fixed range scales. The horizontal line forms a crosshair with the fixed vertical line running down the center of the viewfinder. The operator elevates the autocannon or coaxial machine gun of the BMP-2 until the crosshair is superimposed on the target, and then he can open fire.<br />
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The commander may override turret and weapons control at the press of a button and take over using the control handles that he is furnished with.<br />
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Here is a screenshot of the reticle of a 1PZ-3, taken from a video of a BMP-2 firing its cannon:<br />
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These tools, taken as a whole, mean much more than the sum of their parts. The independent surveillance equipment, target designation, duplicated gunnery controls and independent sighting systems give the commander a level of dominance over his own machine that many of his NATO counterparts did not have. While the commander of an M2 Bradley did have a gunsight extension to see what the gunner sees and a set of gunnery controls to use them with, he did not have a sight of his own, as there was no backup sight, and he did not have his own cupola and he did not have a magnified optic with a stadia rangefinder. The BMP-2 had all of these, and the BMP-2 had a fully matured hunter-killer capability to go with it.<br />
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<a href="https://www.blogger.com/null" id="comm"></a>
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<h3>
<span style="font-size: large;">COMMUNICATIONS</span></h3>
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From the introduction of the BMP-2 in 1980 until 1984, the commander was in charge of the R-123M radio, installed at the very rear of the turret shelf (the turret is wider than the turret ring, so there is a wide shelf at the base). Voice transmissions are done using the throat microphone integrated into his tanker's helmet. The throat microphone is reportedly of good quality and much more useful than an open microphone. The commander can listen to both extra-vehicular transmissions or communications from his own crew from the headphones of his tanker helmet.<br />
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<br />R-123M</h3>
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The R-123 radio had a frequency range of between 20 MHZ to 51.5 MHZ. It could be tuned to any frequency within those limits via a knob, or the commander could switch between four preset frequencies for communications within a platoon. The switching process takes 3 seconds to complete. The radio has a transmitting and receiving range of between 16km to 50km, depending on the antenna used and the type of terrain. The R-123M had a novel glass prism window at the top of the apparatus that displayed the operating frequency. An internal bulb illuminated a dial, imposing it onto the prism where it is displayed. The R-123M had an advanced modular design that enabled it to be repaired quickly by simply swapping out individual modules.<br />
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The dismounted squad leader will have an R-392 or R-126 radio to communicate with the commander of the BMP-2 at shorter distances. The squad should be operating 800 meters away from its BMP at the most, though this obviously is dependent on the tactical situation as well.<br />
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R-173</h3>
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In 1984, the now-outdated R-123 radio was replaced by the R-173 radio, which had a frequency range of between 30 MHZ to 75.999MHZ. It has 10 preset frequencies. It had an electronic keypad for entering the desired frequency, and an LED display. Its main improvement over older radios is the ability to send encrypted analogue and digital signals.<br />
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<h3>
<br />R-168-2UE-2</h3>
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Sometime in the late 2000's, most BMP-2s had a new and advanced R-168-2UE-2 frequency-hopping encypted radio installed to replace the obsolete R-173, which was found to be susceptible to eavesdropping and jamming during the first Chechen campaign/invasion.<br />
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The R-168 family of radios is now standard throughout the Russian ground forces, from infantry platoons to tank companies. It can produce frequency hops 100 times a second, and the data is encrypted as well. It can also send and receive digital data.<br />
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The commander can exit the vehicle by two means - the hatch above him, or by spinning the turret to face the rear, and then going out through the passenger compartment. In the latter case, he must swing open the turret basket perimeter shield (shown below) to exit the turret. The last two photos are provided courtesy of Mr. Tim Gow from the excellent megablitzandmore blog for modelers.<br />
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Besides the necessary tools and spare parts, there isn't much space inside the vehicle for stowing long term supplies. The turret doesn't have external bins or baskets either, but it does have numerous loops around its rear perimeter, as you can see below.<br />
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The loops are meant for securing foliage and camouflage netting on the turret, but the crew can strap their personal effects onto them too.<br />
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<a href="https://www.blogger.com/null" id="gunstat"></a>
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<h3>
<span style="font-size: large;">GUNNER'S STATION</span></h3>
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The gunner's station is relatively sparse. All of the weapon controls are placed directly in front of the gunner, and most of the accessories, including the intercom control box, dome light and the turret traverse lock are arranged around the turret wall. The gunner has three fixed general vision periscopes, two on each side of his primary sight and another aimed to the left. The gunner is also provided with a TNPT-1 rear view periscope in his hatch. This periscope lets him see directly behind the turret. All in all, the gunner has the same number of general vision periscopes as a BMP-1 gunner but<br />
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This gives him relatively good visibility and he can take over the vehicle from the commander if the commander dismounts with the passengers. The gunner's has no periscope aimed to the right of the turret, and it was not really possible to provide a view to the right at all because the ATGM launcher already occupied that part of the turret roof. Compared to its direct foreign counterparts, the BMP-2 accommodated its gunner quite well in this respect. The gunner in an M2 Bradley, for instance, has two general vision periscopes flanking the ISU (Integrated Sight Unit) covering the 11 o'clock and 1 o'clock sectors like in the BMP-2, but half of the view from both periscopes is blocked by the large housing for the sight and the view from the left periscope is completely blocked when the TOW launch pod is raised. A Marder 1 gunner had three periscopes, but they only covered the left side of the turret and were evidently only meant to compensate for the commander's inability to see to the left as the view was completely blocked by the external autocannon installation and the gunner's sight.<br />
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<a href="https://www.blogger.com/null" id="sights"></a>
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<h3>
<span style="font-size: large;">SIGHTING COMPLEXES</span></h3>
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<span style="font-size: large;">BPK-1-42</span></h3>
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<br />The BPK-1-42 combined day-night sight was the primary sight for a BMP-2 gunner. It has a fixed magnification of 5.6x in the day channel, and a fixed 5x magnification in the night channel. Rangefinding is accomplished with a stadiametric scale in the lower right corner of the sight view finder. The BPK-1-42 sight has dependent stabilization in the horizontal and vertical planes. The elevation limits of the mirror head of the sight ranges from -8 degrees to +30 degrees. The stabilization system of the weapons provides dependent stabilization to the sight via a simple connection rod.<br />
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There are two eyepieces on the sight. The one on the left is the optic for the nightvision channel. Observation and target engagement at night is achieved in either the passive or active modes. The passive mode uses an image intensifier tube to amplify ambient light to a visible level. It is possible to identify tank-type target at distances of up to 600 or 700 meters on a cloudless, starry night with ambient light levels of at least 0.005 lux.<br />
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The active mode requires the use of the co-axially mounted OU-5G infrared spotlight for illumination. Although the OU-5G spotlight is only approximately the same size as the OU-3 spotlight used for the commander's TKN-3B periscope and is only rated for a somewhat power of 180 W, its illumination capability is greatly superior as it uses a xenon lamp instead of an incandescent lamp. It has a white light output of 15 million Candelas - half that of the L-4A spotlight used on tanks, which also used a xenon arc lamp but ran on 600 W. <div><br /></div><div>Using the IR spotlight, the nominal maximum detection range for a tank-type target is 650-900 meters. The main issue is that by the time the BMP-2 entered service in the early 1980's, active infrared illumination was entirely anachronistic as NATO ground forces had already shifted completely to passive systems including image intensifier technology and thermal imaging technology. On the BPK-1-42, the passive mode has the obvious advantage of not emitting any radiation which might be picked up by the surveillance equipment of enemy forces.<br />
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The nightvision optic is equipped with an electric shutter linked to the trigger on the gunner's handgrip, which is in turn linked to the BU-25-2S control console (we will examine this later under the 2A42 section). Every time the cannon fires, the shutter activates and protects the aperture from the blinding flash. This is because the light intensification tube operates on extremely high voltages to amplify ambient light to visible levels. If a bright flash was captured, the intensification tubes would burn out from the huge power surge, or even explode. This would happen behind the thick aluminium casing of the sight casing, but he gunner is not entirely safe. Although the image intensification tube would be destroyed, it would still put the amplified image of the flash on the eyepiece for a split second, potentially blinding him.<br />
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<a href="http://3.bp.blogspot.com/-DK7OI2W_UNE/VlNYTiR4P_I/AAAAAAAAEdI/C2I31m8wyco/s1600/bpk-2-42.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="293" src="https://3.bp.blogspot.com/-DK7OI2W_UNE/VlNYTiR4P_I/AAAAAAAAEdI/C2I31m8wyco/s400/bpk-2-42.jpg" width="400" /></a></div>
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The right eyepiece is for daytime use. First, the gunner finds the range to the target using the stadiametric rangefinder. Then, he inputs the range into the sight using a dial located on the right side of the sight housing. The chevron aiming point and the range scales will then drop until the fixed range indicator markings align with the desired range on the range scales. Then, the gunner uses the handgrips and elevates the cannon until the dropped chevron is placed squarely on the target, thus obtaining a ballistic solution. This video is recommended if the written description is insufficiently clear <a href="https://www.youtube.com/watch?v=niq1_RK2fjA">(link)</a>. The viewfinder markings may be illuminated by an internal light bulb to facilitate aiming at twilight hours.<br />
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Both the active and passive night channels use the same viewfinder, but due to the constricted field of view through the night channel, the range adjustment scales and stadia rangefinder scales were blocked out, leaving only the reticle in the center of the viewfinder. This was permissible because the viewing range of the sight was only 800 meters, so fire correction can be done by using the burst-on-target gunnery method. However, the gunner could still shoot further than 800 meters if the conditions allow it. When using the BPK-1-42 sight at night, the range is set to a battlesight of 800 meters. In this setting, the tip of the center chevron and the upper tip of the windage marks are calibrated for a distance of 800 meters and the bottom end is calibrated for 1,200 meters. Rangefinding can be done knowing the angular values of the chevron and lead lines. By comparing the height and width of the target to these markings, the gunner could then estimate the distance using a formula. However, the probability of achieving a hit with a short burst from the autocannon using only the battlesight technique is quite high due to the short distances involved.<br />
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The viewfinder of the sight is shown below. Note the small field of view in the night channel (represented by the small circle around the reticle) compared to the day channel.<br />
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The sighting range against ground targets with BT (AP-T) shells is 2,000 meters. With OFZ (HE-I) and OT (F-T) shells, the range is 4,000 m. Obviously, the lack of any serious rangefinding equipment is an serious detriment to the ability of the gunner to quickly and efficiently dispatch armoured threats. Still, it is some consolation that this shortcoming is not something exclusive to the BMP-2, and that all of its chief rivals, namely the Marder 1 and Bradley, are similarly neglected in this department. The Bradley, for example, did not receive a laser rangefinder until the M2A2 ODS modification in 1991, by which time the BMP-2s of the Soviet Army could hardly be considered a threat for obvious reasons.<br />
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Nevertheless, the BMP-2 was somewhat disadvantaged in that its 30mm AP-T shells had a much lower muzzle velocity compared to the 20mm and 25mm APDS rounds that the Marder 1 and M2 Bradley used. It would be easier for a Bradley gunner to obtain a first round hit using his stadia rangefinder or by using the gunnery techniques such as battlesight and bracketing thanks to this advantage. The advantage held by the BMP-2 gunner is the high rate of fire of the 2A42. He can use the battlesight technique to fire off a burst without delay after seeing a target, and then rely on the dispersion of the shells to obtain at least one hit. The disadvantage, of course, is the high expenditure of ammunition for a relatively small effect on the target.<br />
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The sight aperture is protected by a pane of ballistic glass, but there
is also a retractable steel cover that could be opened and closed from
the inside of the turret. The steel cover only covers the nightvision
channel aperture. This helps to prevent accidental exposure of the
nightvision system to bright light in daytime. The decision to not have
any protection for the daytime sight aperture is very strange.<br />
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<span style="font-size: large;">BPK-2-42</span></h3>
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In March 1986, the BMP-2 was modernized into the BMP-2 obr. 1986. One of the upgrades was the replacement of the BPK-1-42 with the BPK-2-42. The most noticeable difference is the revision aiming reticl. The daytime sight channel was slightly improved with a fixed 6x magnification to extend the engagement envelope, and the nighttime channel was also slightly improved with a 5.5x magnification. The sight provides an angular field of view of 10° in the daytime channel and the 6°40′ in the night channel. The increased field of view was partly due to the expansion of the windage markings.<br />
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<span style="font-size: large;">SOZh</span></h3>
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All of the BMP-2s used in the Suvorov Attack challenge during the International Army Games 2016 and 2017 were equipped with the PL-1-01 laser beamer instead of IR spotlights. The PL-1-01 is a pulsed laser beamer that can be used for illumination, replacing the previous infrared spotlight. The BPK-2-42 sight is not compatible with the PL-1-01, so it must follow that the original sights have been swapped out for the newer TKN-4GA-01, or TKN-4GA-02, or SOZh. The photo below (Credit to Vitaly Kuzmin) shows the PL-1-01 on the right hand side of the cannon.<br />
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The new sight housing lacks the hinged steel cover of the BPK-2-42. The sight housing limits the sight to a frontal view only, which would be strange if the TKN-4GA-01/02 sight was installed, as it has an integrated auxiliary high elevation sight for anti-aircraft purposes. This is evidence that the SOZh may have been installed instead of a TKN-4GA series model sight. Another indication that SOZh has been installed instead of a TKN-4GA model lies in the fact that the 1PZ-3 anti-aircraft sight remains intact.<br />
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<a href="https://www.blogger.com/null" id="stabs"></a>
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<h3>
<span style="font-size: large;">STABILIZERS, GUNNER'S CONTROLS</span></h3>
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<a href="http://3.bp.blogspot.com/-git2pQl9aic/VlBzSYL8MbI/AAAAAAAAEOY/Xa9chORrkqQ/s1600/bmp-2%2Bgun%2Belevation.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-git2pQl9aic/VlBzSYL8MbI/AAAAAAAAEOY/Xa9chORrkqQ/s1600/bmp-2%2Bgun%2Belevation.jpg" /></a></div>
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The BMP-2 uses the 2E36 stabilizer complex. The stabilizer was continually upgraded throughout its military service life, evolving into the 2E36-1, and later into the 2E36-4. The BMD-3, which uses the same turret as the BMP-2, is equipped with the 2E36-5. The BMD-2, which does not share the same turret as the BMP-2 or the BMD-3, has the same fire control system as the BMP-2 and is equipped with the 2E36-1 stabilizer variant. The relatively recent BMD-2M upgrade is equipped with the most modern iteration of the series - the 2E36-6, and the similarly recent BMP-2M is probably equipped with a similar type.<br />
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The layout of the components of the stabilizer inside the turret is shown in the drawing below.<br />
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The 2E36 complex has two modes of operation; automatic and semi-automatic. In the automatic mode, the stabilizer operates in the traditional sense, obeying prompts from the gunner and keeping the turret and gun stabilized at a point determined by the gunner. The gun elevation limit is -4 degrees to +30 degrees in this mode.
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The semi-automatic mode, on the other hand, is primarily meant for anti-aircraft purposes where the maximum gun elevation angle of +75 degrees may be needed. The gun cannot be elevated by the gunner to more than the maximum elevation limit of the BPK-1/2-42 sight of +30 degrees, so the commander must take over. Using the commander's override, full control of the horizontal and vertical drives are handed over to the commander, who is then relieved from his regular duties and instead must take over as gunner, while the gunner does his best to take the place of the commander. The stabilization accuracy is reduced and the precision of the weapon elevation drive is sacrificed but is overcharged to increase the rate of elevation, enabling the commander to track speedy maneuvering aircraft at low altitudes and close range more easily. This includes ground attack aircraft passing overhead or at closer ranges, where the
relative speed of the aircraft in question is higher than if it was many
hundreds of meters away. At longer distances, the elevation angle
necessary to engage an aircraft at a certain altitude is less than if the
aircraft is closer and the relative speed of the aircraft is also lower, so turret rotation speed is less important but more precision is required. In that case the gunner may
continue to make use of the stabilizer in the automatic mode, as the maximum elevation of the BPK sight is more than sufficient for engaging low-flying aircraft at relatively close range.<br />
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At a cruising speed of 25 km/h to 35 km/h, the stabilizer is reportedly capable of maintaining its orientation with an average stabilization accuracy of less than 1 mil, meaning that the angular deviation of the gun from the point of aim does not exceed 1 mil.<br />
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Automatic Mode</h3>
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Maximum Traversal Speed: 30°/sec<br />
Minimum Traversal Speed: 0.07°/sec<br />
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Maximum Elevation Speed: 30°/sec<br />
Minimum Elevation Speed: 0.07°/sec<br />
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Semi-Automatic Mode</h3>
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Maximum Traversal Speed: 30°/sec</div>
Minimum Traversal Speed: 0.1°/sec<br />
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Maximum Elevation Speed: 35°/sec</div>
Minimum Elevation Speed: 0.1°/sec<br />
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The turret traverse motor is the EDM-20. It is shown in the photo below. It runs on 400W. The elevation motor is the EDM-14, and it runs on 180W.<br />
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There are two gyroscopic tachometers installed. One for the horizontal plane and another for the vertical. They measure any changes in the orientation of the turret and weapons and sends commands to the stabilizer motors to apply the necessary corrections to keep the weapons oriented in the same direction as before the turret turns.<br />
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The gunner uses the same make and type of control handles that the commander is furnished with. The stabilizer is turned on via the control handles.<br />
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If the stabilizers fail or if the power supply is cut off, there is a set of manual controls in the form of a pair of flywheels familiar to all Soviet AFVs. The turret rotation flywheel is located on the turret ring to the left of the gunner, for his left hand. The weapons elevation flywheel is located behind the BPK sight, used with his right hand. The handle for the elevation flywheel has two electric solenoid triggers, one for the co-axial machine gun, and the other for the cannon. In order to use the manual controls, the stabilizer must be off or set to the "manual" mode of operation and the manual controls must be engaged. In the manual mode, the elevation limits of the gun are -5 degrees to +75 degrees.<br />
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<h3>
<b><span style="font-size: large;">ARMAMENT</span></b></h3>
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<a href="http://2.bp.blogspot.com/-4b8kMLPtTUw/VlHxazH6dyI/AAAAAAAAEY8/xdjU4gVam6A/s1600/bmp-2%2Bturret.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://2.bp.blogspot.com/-4b8kMLPtTUw/VlHxazH6dyI/AAAAAAAAEY8/xdjU4gVam6A/s640/bmp-2%2Bturret.jpg" width="468" /></a></div>
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The armament of the BMP-2 is installed in the large steel turret. It is composed of a 2A42 automatic autocannon and a PKTM coaxial machine gun. It was necessary to widen the turret ring to 1,740mm in order to accommodate the two-man turret. Interestingly enough, the turret ring diameter of the BMP-2 is larger than the M2 Bradley which has a turret ring diameter of 1,500mm. The turret weighs 1,370 kg empty and the weight of the turret when fully loaded is 2,561 kg. The turret has an external diameter of 2,155mm.<br />
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<span style="font-size: large;">2A42</span></h3>
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The BMP-2 is armed with the 2A42 dual-feed open-bolt gas-operated autocannon chambered for the Soviet 30x165mm cartridge. The cannon features a forward ejection system to eject spent shell casings and a quick-detach barrel assembly for ease of replacement in field conditions. The cannon weighs a total of 115 kg and is 3,027mm in length, not including the metal box surrounding the receiver inside the turret of the BMP-2. The barrel weighs 38.5 kg and measures 2,416mm in length, or 80.5 calibers.<br />
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According to its technical manual and <a href="http://www.tulamash.ru/catalog/14">the website of the manufacturer</a>, the 2A42 generates a recoil force of 40 to 50 kN. Despite its larger caliber and greater muzzle energy, this recoil force is directly comparable to the M242 Bushmaster chain gun which generates a recoil force of 40 kN. This is due to a combination of a larger and more effective muzzle brake combined with the more developed short-stroke recoiling barrel mechanism. The M242 has the same features, but they are not as developed. Case in point - upon firing, the barrel of the 2A42 recoils backwards by 30mm (35mm maximum), and although the M242 barrel also recoils backwards, its recoil stroke is only 14mm (18mm maximum). In both autocannons, the bolt only unlocks at the end of the short recoil stroke of the barrel, at which point the gas pressure has fallen sufficiently that it is safe for the chamber to be unsealed by the bolt. The increased delay is created by the rearward velocity of the barrel, which begins moving immediately upon firing, decreasing the relative velocity of the bolt carrier, which beings moving only after the projectile has traveled past the gas port. For a more direct comparison, the 30mm RARDEN autocannon produces a recoil force of 13.34 kN - less than half that of the 2A42. This is, of course, due to the long-stroke recoil operating mechanism of the RARDEN wherein the barrel and bolt recoil together as a single unit for a distance of around 300mm, thus greatly damping the recoil force.<br />
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As it is an open-bolt autocannon, the bolt assembly has to be retracted until it engages with the sear before firing can commence. This is done by hand with a special cocking ratchet before engaging in combat, but in combat conditions, the gunner can instead activate a pyrotechnic squib that will cycle the action instantaneously. Three squibs are available.<br />
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The use of an open-bolt operating mechanism means that the barrel is left open on both ends so that there is airflow into the chamber when the cannon is not being fired, which is an important safety feature because a cartridge left in the chamber after intensive firing can cook off. It is also a minor performance factor because the additional cooling helps prevent the barrel from overheating and warping. It also ensures that the next shot is strictly dependent on the gunner's choice because the cannon only loads the next round available in the feed mechanism when the trigger is pulled and the bolt goes into battery.<br />
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The barrel of the 2A42 is rather unusual as there is a triangular segment just ahead of the first few inches of the tube, which is noticeable in the photo above and especially clear in the picture below. On the left side of the barrel is the gas tube, which is concealed under a rigid retangular box.<br />
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This triangular segment is a part of the gas system for the long stroke gas piston situated inside a gas tube installed next to the barrel. Unlike most modern autocannons of Western origin, the 2A42 works on a gas operating principle to cycle rounds and operate the linked ammunition feeding system, which is partly visible in the photo below. Upon firing, the barrel has a recoil stroke of <a href="http://www.ztsspecial.sk/en/special-production/30-mm-automatic-gun-2a42">between 30mm and 35mm</a>. This helps to delay the opening of the bolt until the pressure is low enough while simultaneously damping the recoil forces on the mounting cradle. The flat part of the triangular portion of the barrel interfaces with tracks on the rigid rectangular box so that the barrel assembly can reciprocate predictably and precisely with each recoil stroke.<br />
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From the diagram below and on the right, the bolt assembly of the 2A42 seems to resemble the rotating bolt assembly of a PK or PKM machine gun, and this is not too far off from the truth. The bolt has two locking lugs and is rotated via an angled trough cut into the bolt carrier, as you can see in the diagram on the right. Inside the hollow gas piston is a captive recoil spring, which provides the necessary energy to return the bolt assembly into battery after each shot. The bolt carrier is fundamentally the same as in any Kalashnikov rifle, with the only exceptions being the additional mechanisms for the ratchet cocking mechanism (the gunner must use a ratchet lever to manually operate the bolt assembly due to the extremely strong recoil spring), and the electrical firing system, along with a spring-loaded deflector to push spent shell casings to the side and into the ejection chute. The spring-loaded deflector can be seen in the diagram on the left below. It is in front of the bolt breech face, so that after the bolt extracts a spent shell casing and the bolt assembly travels back by the required distance, the deflector springs out and pushes the empty casing away.<br />
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The empty casing is then pushed forward by the bolt when it goes into battery for the next shot. This supplies enough momentum to the empty casing for it to travel the rest of the way down the ejection chute and out the ejection port, seen in the drawing below.<br />
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It is possible to conduct field disassembly of the 2A42 from inside the turret of the BMP-2 without special tools. This allows the crew to replace broken parts or troubleshoot the cannon without taking it out of its mounting cradle, which can only be done with special machinery. A video of the cannon being disassembled from inside a BMP-2 is available here (<a href="https://vk.com/video223963867_170633880">link</a>). A second video from the same uploader shows the removal of the barrel assembly by hand (<a href="https://vk.com/video223963867_170633889">link</a>). The way the barrel assembly is extricated shows that the rectangular box around the gas tube is indeed a rigid structure to support the recoiling action of the barrel, and you can see how the gas tube and spent casing ejection port come out along with the barrel, hence the term "barrel assembly". Of course, in order to carry out a field disassembly of the cannon, it must be removed from its mount in the turret. The photo below shows the 2A42 after a field disassembly.<br />
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<br />The feed system is mechanical, and resembles a Degtyarev-style machine gun belt feed mechanism. After initially traveling a short distance in its recoil stroke, a lug on the bolt carrier connects with a prong-shaped feed lever and cranks it rearward, driving one of the feed pawls to advance an ammunition belt by one step. As the bolt carrier reverses direction and begins its return stroke, the lug cranks the prong forward and drives the feed pawl back to its initial position, readying it for the next round, and one of the locking lugs on the bolt pushes on the base of the leading round in the belt, chambering it. The switching of the belt feed is done mechanically by turning a lever on the back of the receiver, switching the feed lever to drive one feed pawl instead of the other, while also mechanically blocking the electronic round count sensor for the de-selected belt. The belt feed switch lever must be turned by hand by one of the two turret crew members in the BMP-2. When loading the BMP-2, one of the belts is selected with the switch lever before the bolt carrier is cocked back, so that the belt will be advanced into the feeding position and the gun will be ready to chamber a round. If the gun is switched to feed from the opposite belt, the gun will chamber a round from the current belt before advancing the opposite belt, and only then will it begin to chamber rounds from the opposite belt.</div><div style="text-align: left;"><br /></div><div style="text-align: left;">The 2A42 has variable rate of fire settings for either semi automatic, 'low' for 250 rounds per minute or 'high' for about 550 rounds per minute, although the cannon can in fact achieve a rate of fire of 800 rounds per minute on the 'high' setting if it gets hot enough. Whether this is deliberate or not is hazy, since KBP, the manufacturer of the cannon, specifically lists the rate of fire in the 'high' setting to be "550 to 800 RPM". According to the BMP-2 manual, the main rate of fire setting for engaging ground targets is the low setting. In order to save ammunition when firing in the low rate of fire setting on ground targets, the following burst lengths are recommended:<br />
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<blockquote class="tr_bq">
At a range of up to 500 m - 2-3 shots<br />
At a range of up to 1,000 m - 4-5 shots<br />
At a range of up to 1,500 m - 8-10 shots</blockquote>
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The main rate of fire setting for engaging air targets is the high setting, and the recommended burst length is 17-50 shots.<br />
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Setting the rate of fire can be done electronically via the BU-25-2S control box or manually via a lever on the receiver of the cannon itself. The relatively high rate of fire of 2A42 is very useful during engagements with anything from aircraft to large concentrations of infantry, or even when attacking a well-fortified position, as the cannon would be very effective at suppressing enemy troops. The 2A42 is irreplaceable during engagements with irregular forces operating under unconventional tactics, as was the case in both Afghanistan and Chechnya, where the BMP-2 was quite consistently rated more highly than the BMP-1 in usefulness. Under such difficult circumstances, the ability to rapidly suppress likely hiding spots and areas of interest with powerful cannon shells is absolutely invaluable for preserving the vehicle itself as well as the lives of the dismounts.<br />
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The 2A42 cannon was the subject of a rivalry between the GRAU and Kurganmashzavod. In short, GRAU insisted on keeping a 73mm cannon, and favoured the 2A41 presented by the ChTZ (Chelyabinsk Tractor Plant). Kurganmashzavod insisted on the 2A42 developed by the KBP design bureau. In one attempt to persuade military officials to adopt the Object 681 with the 2A41 73mm smoothbore cannon, a comparison trial was organized. The target was a T-72 tank, and the distance was 1,200 meters. The Object 681 opened fire first (on the side of the tank), and not one single round penetrated the tank. One went over, one fell short, and the other successfully impacted the side skirt, but the reinforced plastic side skirt flexed in such a way that the round did nothing. Then, the Object 675 - the BMP-2 prototype - stepped up. It let off three bursts of 8 rounds in the high rate of fire mode. All external equipment including periscopes and the gunsights were completely destroyed, and the roof mounted anti-aircraft machine gun was rent from its mount, landing 15 m away from the tank.<br />
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Later on during its acceptance trials, the BMP-2 fired on a combat loaded T-55 (modernized) and T-72 from the side, again with 3 x 8 round bursts on the high rate of fire mode. The T-55 had its anti-aircraft mount, IR searchlight, and externally mounted laser rangefinder shredded away. The 100mm cannon was hit and penetrated in two places. The external fuel tanks mounted on the overtrack fenders ignited and burned outside the tank, but the gunsight was unharmed and tank was in a drivable state. A total firepower kill was achieved due to the damaged cannon. The T-72 also had its anti-aircraft machine gun ripped off, and its optical devices were damaged. The fender fuel tanks were hit and the inferno damaged the turret seals (compromised the sealing of the NBC system) and some of the burning fuel leaked to engine compartment and damaged the engine, though the automatic fire suppression system worked. It was counted as a mobility and firepower kill. These results were published in Sergey Suvorov's volumes on the BMP-1 and BMP-2.<br />
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This is only an anecdote, of course, not a scientific study on the ammunition expenditure required to disable a tank. From these demonstrations, it appears that a BMP-2 may mission-kill a tank at a distance of 1,200 meters using only 24 rounds out of its combat reserve of 500. According to the official results of the effectiveness of the 2A42 cannons from the state trials of the BMPT, an average of 24 rounds are needed to eliminate a generic IFV-type target at a distance of 2,000 meters or more using AP ammunition, while 24 rounds of HE ammunition are needed to eliminate an ATGM team in a trench at 1,500 meters or more and 29 rounds are needed to eliminate a full infantry squad in a trench at the same distance.<br />
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The maximum number of shots that the gunner is allowed to fire continuously on full auto in the high rate of fire mode is 50 shots, equivalent to around five full seconds of continuous shooting. Another 50 rounds of short bursts in the high rate of fire mode is allowed after that, after which the barrel must be left to cool completely to prevent any lasting damage. Firing on the low rate of fire mode, if done in short bursts, can be done until the entire ammunition supply is depleted.<br />
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<span style="font-size: large;">ACCURACY</span></h3>
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The accuracy of the 2A42 cannon is typical for a weapon of its class. The technical dispersion of AP-T (BT) rounds fired from the 2A42 is 0.4 mils in both the horizontal and vertical axes, and the technical dispersion of HE-I and HE-T (OFZ, OT) rounds is 0.5 mils in both axes. For comparison, it is stated in <a href="http://www.alternatewars.com/BBOW/Weapons/AFV_Guns/OATK_25x137mm_Ammo.pdf">an official Orbital ATK marketing brochure</a> that the 25mm M791 APDS round fired from the M242 chain gun has a dispersion of 0.3 mils in both axes while the M792 HE-T round has a dispersion of 0.55 mils in both axes. As for the 30mm RARDEN cannon, it is stated on page 278 of Jane's Ammunition Handbook 2009 that its dispersion is 0.5 mils.<br />
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Accuracy degrades as the cannon heats up, and as the cannon can fire so quickly, it also heats up more rapidly than other cannons. Stresses will also be very high on the barrel if the gunner habitually fires in the highest rate of fire in long bursts, leading to a short barrel life. <a href="http://www.tulamash.ru/catalog/22">According to the manufacturer</a> and <a href="https://ebooks.grsu.by/voen_podgotovka/tema-12-30-mm-pushka-2a42.htm">a Belorussian military textbook</a>, the guaranteed service life of the 2A42 is 6,000 shots. A simple upgrade involving the replacement of 10% of the parts in the 2A42 can increase the service life by 50% to 9,000 shots. This upgrade took place in 1995 and is now the new performance standard for the 2A42 cannons in the Russian Army. As mentioned before, the cannon is equipped with a barrel swap-out system to enable quick replacement of worn barrels in the field without special tools or heavy machinery, so this feature is obviously quite useful to the crew and technicians maintaining the vehicle.<br />
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In addition to the high effectiveness of the gun on ground targets, the high elevation of 75 degrees enables the gunner to effortlessly engage targets located on elevated positions and fast, low flying aircraft, even if they are flying almost directly overhead. The high anti-aircraft potential should not be underestimated; the air forces of NATO nations played a critical role in ground operations and still do, and the surge of interest in the concept and technology of attack helicopters in the late 60's and 70's had led to the birth of an entirely new class of air power that was exceptionally lethal to ground assets. Even though its own development was plagued with challenge after challenge and delay after delay, the BMP-2 was introduced just in time to become a sufficiently relevant part of the BMP fleet of the Soviet Army by the time the vaunted AH-64 Apache and A-10 Warthogs arrived on the scene in the mid-80's, even if it was only by a lucky coincidence.<br />
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<a href="http://4.bp.blogspot.com/-skRvDKSIzvo/VlM5TzS0V7I/AAAAAAAAEcI/FW1NAW6YRHw/s1600/bmp-2%2Bnight%2Bfiring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="424" src="https://4.bp.blogspot.com/-skRvDKSIzvo/VlM5TzS0V7I/AAAAAAAAEcI/FW1NAW6YRHw/s640/bmp-2%2Bnight%2Bfiring.png" width="640" /></a></div>
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<a href="http://eng.mil.ru/en/news_page/country/more.htm?id=12006254@egNews">As of 2015</a>, BMP-2 gunners in motorized rifle units in the Western Military District had target distances for gunnery training extended to 1.9 km. New targets representing armoured vehicles were also introduced and new tactics were practiced. The new exercise was reportedly established due to the introduction of newer weapons, presumably referring to modernized BMP-2s equipped with the new fire control system.<br />
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<a href="https://4.bp.blogspot.com/-OFXaGCmFIuY/V1NjY9SubfI/AAAAAAAAGk0/cYgPRilCyHwcsw_hYkDSl7tIZdvgcJzrACLcB/s1600/bmp-2-m1403_30-mm-pushka-2a42.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-OFXaGCmFIuY/V1NjY9SubfI/AAAAAAAAGk0/cYgPRilCyHwcsw_hYkDSl7tIZdvgcJzrACLcB/s1600/bmp-2-m1403_30-mm-pushka-2a42.jpg" /></a></div>
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Due to the recoil forces generated when firing the cannon, early prototypes of the BMP-2 had problems with the stabilization system. Special modifications were successfully applied to allow the stabilizer to properly realign the cannon after each shot.<br />
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All said and done, the accuracy of the 2A42 is at least on par with the Rh202, which had a long but disproportionately thin barrel, and wasn't very accurate on full auto either. Overall, the 2A42 is best compared not to the Rh202 but to the Oerlikon KCB. The calibers are the same, and the rates of fire are the same. However, the KCB has an L/75 barrel, while the 2A42 has an L/80 barrel. The weight of 2A42 is 115 kg, while KCB weighs 138 kg.<br />
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The vehicle's entire ammunition load of 500 rounds is stowed in curving containers affixed to the turret floor, on which the seats for the gunner and commander are mounted. Of those 500 rounds, there are 340 HEI and HEI-T rounds in one compartment of the container and 160 AP-T rounds in the other. The ratio between these two ammunition types was designed based on the expected frequency of use.<br />
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A ready supply of 500 rounds is considered to be quite large, especially for a 30mm autocannon. For comparison, the M2 Bradley carries just 70 rounds of APDS and 230 rounds of HE in its ammunition containers, making it vastly inferior to the BMP-2. However, it is necessary to mention that the Bradley also carries a reserve supply of another 600 rounds whereas the BMP-2 does not have any reserve ammunition. The caveat is that the reserve ammunition is packed into individual containers and stowed loosely and because of this, the reserve supply is effectively useless during combat because it is not possible to transfer it into the M242 autocannon feed system in a reasonable time even with the help of the passengers, so the main advantage it brings for the Bradley is a reduced reliance on ammunition resupplies.<br />
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Another comparable example is the original Marder 1 which carried 420 rounds of 20mm ammunition divided into 345 rounds of HE and 75 rounds of APCR, which was fed to the Rh202 autocannon in a single belt in the original Marder 1 or fed via a dual-feed system beginning with the Marder 1A1 model. Another 830 rounds were carried as a reserve supply and because they were stowed in loose containers, it was also not useful during combat.<br />
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However, when the BMP-2 is compared to the British FV510 "Warrior", the BMP-2 has a very clear advantage. The FV510 only provides 45 ready rounds for its RARDEN autocannon with another 205 rounds in reserve stowage. The distribution of ammunition types is unknown, but assuming that half or more than half of the ammunition is of the HE variety and the remainder is APDS, then the FV510 may only have 20 or fewer APDS rounds available in its ready racks. Needless to say, this severely restricts the firepower of the vehicle and limits its ability to act as a force multiplier compared to the BMP-2.<br />
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The feed system of the 2A42 is very strong as it is designed to pull a belt of 30mm rounds from the bottom of the turret up to the level of the cannon receiver. The feed mechanism includes a gearbox which consists of a worm gear (a worm and a worm wheel), a delivery clutch and spur gears. When switching between the low and high rates of fire, the gearbox changes the gear ratio of the pulling mechanism to adjust its speed.</div>
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<a href="http://3.bp.blogspot.com/-hCIgaEg1MdM/VlH9bp4UwwI/AAAAAAAAEaE/cf9hLgz2gT8/s1600/iutxkw38u2pk.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="235" src="https://3.bp.blogspot.com/-hCIgaEg1MdM/VlH9bp4UwwI/AAAAAAAAEaE/cf9hLgz2gT8/s320/iutxkw38u2pk.jpg" width="320" /></a></div>
As you can see in the photo above, the conformal ammunition container forms a cresent shape on the turret basket floor. Ammunition from the parallel containers are fed into separate spiraling guides that lead to the autocannon. The guides twist and turn so that the ammunition is oriented properly to load into the cannon. When replenishing the containers, the ammunition belts are pulled up to the receiver of the 2A42 by an MU-431 electric motor. Then, the belts are loaded into the feed system by hand and secured with a stopper in each feed channel. From there, the belt feed is entirely self-driven by the action of the bolt carrier as the autocannon is fired.<br />
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The top covers of the containers are clipped on with tension latches. They must be removed to load belts into the containers.<br />
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Empty links are collected in a metal bin underneath the cannon. Shell casings are ejected out of the turret.<br />
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Although it may be a very useful weapon, the 2A42 is still far from perfect. The gas-based operating system of the cannon has a rather negative influence on the accumulation of fumes in the receiver, and as the receiver is mounted in a flame-proof box that isn't particularly air-tight, the result is that the turret is usually flooded with almost comical volumes of smoke after firing off a few dozen or so rounds. Throwing open the hatches normally solves this problem, but as the crew can hardly be expected to do that in combat, there is a powerful ventilator fan installed in the turret roof on the gunner's side. The ventilator is connected to the flame-proof box containing the 2A42, and was designed to work together with the crew compartment ventilation blower to suppress the release of fumes into the fighting compartment as much as possible. The exhaust vent is located just beside the BPK-2-42 sight aperture and in front of one of the TNPO-170A periscopes, as you can see in the photo below.<br />
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The ventilator fan is connected to the box enveloping the receiver of the cannon via a flexible hose, so that the fumes are sucked out as efficiently as possible and with minimal disruption to air pressure in the fighting compartment. Like all of the other weapons-related equipment in the turret, the ventilator is controlled from the BU-25-2S control box. When a toggle switch on the control box for the ventilator is flipped to the "СНАРЯЖ" position, the system is turned on and the fan is automatically activated to extract fumes. Depending on the selected rate of fire, the ventilator will work in the normal mode or the "forced" mode. The ventilator is activated whenever the trigger button on the gunner's handgrips is pressed and runs for another 0.65 seconds after the trigger is released. Using the cannon in the 'low' setting is the least taxing on the ventilator system.<br />
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<tr><td style="text-align: center;"><a href="https://3.bp.blogspot.com/-YJdm4vejv5Q/Wj5SlmORIWI/AAAAAAAAKVY/hTsBKB69H4EQ2r6EucXfadYeLHi8AGwhACLcBGAs/s1600/ventilator.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="393" data-original-width="543" src="https://3.bp.blogspot.com/-YJdm4vejv5Q/Wj5SlmORIWI/AAAAAAAAKVY/hTsBKB69H4EQ2r6EucXfadYeLHi8AGwhACLcBGAs/s1600/ventilator.JPG" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Ventilator</td></tr>
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The ventilator is sufficient when firing the cannon in the low rate of fire mode, but it cannot extract fumes at the rate that they are produced when multiple bursts are fired in the high rate of fire mode. In order to reduce the concentration of fumes in the fighting compartment, the electronic firing system is programmed to limit a burst to 8 rounds in the 'high' setting, and 48 rounds in the 'low' setting. Fumes can exit the flameproof box through the imperfect seals around the edges of the access doors (which are for maintenance purposes, e.g. lubrication). It is possible to bypass the burst fire limitation by using the manual trigger.<br />
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The photo on the left shows the gap for the vent, which is on the right side of the flameproof box. The photo on the right shows the rear door of the box opened, with the seal and its spring visible.<br />
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But despite the powerful ventilator, and despite disciplined control of ammunition expenditure, the fighting compartment just always gets flooded with fumes. One early attempt in the history of the BMP-2 to bypass this problem entirely was to mount the cannon externally, in the style of the Marder 1.<br />
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<a href="https://3.bp.blogspot.com/-MUgr35I2SUs/V3N2QW5DQBI/AAAAAAAAG7Y/1AUR0eFhiDwruj3xT93YBfV7uZYtBlqqgCKgB/s1600/345_800_ice18.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-MUgr35I2SUs/V3N2QW5DQBI/AAAAAAAAG7Y/1AUR0eFhiDwruj3xT93YBfV7uZYtBlqqgCKgB/s1600/345_800_ice18.jpg" /></a></div>
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Besides completely eliminating the ingress of fumes, this type of turret had a smaller profile and also reduced the height of the occupied space. So why was this vastly superior design rejected in the end? Apparently, the turret was not airtight enough, so it was not safe in an NBC environment. The final production turret design itself had some initial issues with the fume ventilator not being airtight enough as well, although that was eventually solved when the vehicle entered mass production.<br />
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<a href="https://www.blogger.com/null" id="ammunition"></a>
<span style="font-size: large;">30mm AMMUNITION</span></h3>
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The maximum range of a 30x165mm projectile of any type is a little over 10 km, but this does not matter in combat as the maximum effective range of the armour-piercing shells is not more than 2,000 meters against lightly armoured targets, and the high explosive shells cannot be used effectively against targets further than 4,000 meters because the self-destruct fuze is designed to detonate at that range. The firing table below is for 30mm HE-I shells.<br />
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<a href="https://thesovietarmourblog.blogspot.com/p/30x165mm-cartridges.html">This page</a> contains a detailed examination of each 30mm cartridge available to the BMP-2 during its service in the Soviet Army, and later, in the Russian Army.<br />
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The graphs below, taken from "<i>The Soviet Light Armored Vehicle Threat To The AAAV</i>", shows the estimated penetration power of Soviet 30mm AP, APDS and APFSDS shells. The estimate for the penetration power of the AP round is essentially correct, but the estimate for the APDS round is slightly above the actual capabilities of the Soviet 3UBR8 round.<br />
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<span style="font-size: large;">AMMUNITION MANAGEMENT</span></h3>
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A pyrotechnic charge is used to instantaneously cock the cannon and ready it for firing. However, if a pyrotechnic charge is not loaded, then the gunner can still manually cock the gun by repeatedly working a lever attached to the cannon receiver. The process is laborious and time consuming (due to the heavy recoil springs necessary to withstand the tremendous recoil forces), but it does have its own advantages. Although such eccentricities would not be necessary in an electrically operated chaingun, a chaingun requires external power to fire. If the power source was interrupted, a chaingun would be rendered useless. Due to its gas-powered nature, the 2A42 can still be fired with the vehicle operating in "degraded mode", meaning to have a knocked out engine and no battery power, with all operations reverted to manual control. The advantage is that if the BMP-2 were to be hit by an RPG in the engine compartment, or if it ran over a large mine, the surviving gunner could still aid the squad of passengers in holding off the ambushing enemy until help arrives using entirely manual controls. However, one wonders if the trade offs are really worth this extra feature.</div>
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Selecting the ammunition type and checking the ammunition reserve is done from the BU-25-2S control box located between the commander's and gunner's seats, to the right of the PKTM ammunition container. Ammunition reserves for both the 2A42 cannon and the PKTM machine gun is shown on a small digital display, along with the ammunition type currently selected for the 2A42. Switching between ammo types is done by flicking a toggle switch. The commander may use the console if he is taking over from the gunner.<br />
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<a href="http://3.bp.blogspot.com/-Vf0A6s2A04U/VlHAn_bV0GI/AAAAAAAAEWs/9vjIfbn9DX0/s1600/bmp-2%2Bbu-25-2s.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="444" src="https://3.bp.blogspot.com/-Vf0A6s2A04U/VlHAn_bV0GI/AAAAAAAAEWs/9vjIfbn9DX0/s640/bmp-2%2Bbu-25-2s.jpg" width="640" /></a></div>
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The BU-25-2S control box is actually the weapons management complex of the BMP-2. It checks the ready to fire status of the 2A42 and displays it (a ready light is illuminated), and allows the gunner to select the desired rate of fire. It is also used to index ammunition types and quantity during the loading procedure.<br />
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Famous YouTube person msylvain59 has acquired a BU-25-2S control box for his own personal collection. You can see his disassembly video here: <a href="https://www.youtube.com/watch?v=TRVbJYMeUD4">msylvain59 video</a>. His video is extremely informative, even though he did not know what it was. As was pointed out in his video, the hinged cover of the control box has two built-in light bulbs pointed inward. There is a brightness adjustment dial (a potentiometer) to increase or decrease the brightness of the bulbs. The presence of a light source to illuminate the control box is extremely useful at night. <br />
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Loading small sections of ammo belts can be done by hand, but loading the full load of 500 rounds requires the help of mechanical advantage, which is provided by a special loading rig.<br />
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<h3>
<span style="font-size: large;">PKTM COAXIAL MACHINE GUN</span></h3>
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<a href="https://4.bp.blogspot.com/-R6yIjRHQ9X0/V1cnuz56HxI/AAAAAAAAGuk/TzbHb_b4bbY_0JMijZH1-8PJJC0pmyqOQCLcB/s1600/pktm.png"><img border="0" src="https://4.bp.blogspot.com/-R6yIjRHQ9X0/V1cnuz56HxI/AAAAAAAAGuk/TzbHb_b4bbY_0JMijZH1-8PJJC0pmyqOQCLcB/s1600/pktm.png" /></a></div>
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The PKTM is fed from a single belt of 2,000 rounds in the same manner as the BMP-1. The container for this very long belt is mounted on the floor of the turret to the right of the gunner's seat, as shown below.<br />
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<tr><td style="text-align: center;"><a href="https://3.bp.blogspot.com/-5O_cFYktwQQ/V1ICy_hyTiI/AAAAAAAAGd8/p_5kPKZf5EA7t7NQ-hVgSJLWZXtlprasQCLcB/s1600/PKT%2Bammo%2Bbox%2Bbmp-2.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="358" src="https://3.bp.blogspot.com/-5O_cFYktwQQ/V1ICy_hyTiI/AAAAAAAAGd8/p_5kPKZf5EA7t7NQ-hVgSJLWZXtlprasQCLcB/s640/PKT%2Bammo%2Bbox%2Bbmp-2.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Not the thing he has his finger on. It's the big long box to its left that, coincidentally, looks about wide enough for 7.62x54mm bullets</td></tr>
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The PKTM fires the 7.62x54mm cartridge. 7BZ-3 API (armour-piercing incendiary) rounds with the B-32 bullet and 7T2 API-T (armour-piercing incendiary tracer) rounds with the T-46 bullet are linked in a 4:1 ratio in the belt. The machine gun has a cyclic rate of fire of 700 to 800 rounds per minute. A 250-round box of 7.62x54mmR ammunition is provided in a continuous belt. The co-axial machine gun can be fired either by depressing the trigger button on the gunner's handgrips, or by pressing the emergecy manual trigger button located on the trigger unit installed at the back the receiver of the machine gun. Since the gunner has the 30mm cannon to play with, the PKTM is mostly used in situations where the firepower of the cannon might be overkill.<br />
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<h3>
<span style="font-size: large;">SUPPLEMENTARY WEAPONS</span></h3>
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<a href="https://2.bp.blogspot.com/-u-61sPuUp5w/V1cclSkkavI/AAAAAAAAGt8/6XL8WLFmG3UpjrZ4RORCXCapoX_I6d7ywCLcB/s1600/bmp-2%2Bfiring%2Bports.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://2.bp.blogspot.com/-u-61sPuUp5w/V1cclSkkavI/AAAAAAAAGt8/6XL8WLFmG3UpjrZ4RORCXCapoX_I6d7ywCLcB/s640/bmp-2%2Bfiring%2Bports.jpg" width="640" /></a></div>
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There is a firing port for each passenger. In total, there are six ports on the sides of the hull along the passenger compartment, and another near the driver's station for the seventh passenger.<br />
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There are two types of firing port. Squared ones, and teardrop-shaped ones. The square ports are aimed aggressively forward to take better advantage of the firepower of the PKM machine gun, and the teardrop ports are aimed more to the sides. These are meant for AK rifles. The AK firing ports are much simpler and even foreign rifles like the G3 and M16 can fit inside. However, the clip-on cuff designed to fit around the barrel and gas tube of Kalashnikov rifles will not be able to fit other types of weapons, so they will have to be removed. <br />
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<a href="http://3.bp.blogspot.com/-yfjkwhcfwOM/VlFpj7rjKvI/AAAAAAAAEVY/SIlS_PkOHS8/s1600/bmp%2Bfiring%2Bport.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="300" src="https://3.bp.blogspot.com/-yfjkwhcfwOM/VlFpj7rjKvI/AAAAAAAAEVY/SIlS_PkOHS8/s400/bmp%2Bfiring%2Bport.jpg" width="400" /></a></div>
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Firing ports may be useful in some very specific situations, but modern conflicts show us that anything running on wheels or tracks is subject to an RPG attack, so the moment that enemy contact is imminent, the best course of action - as proven through decades of unconventional warfare experience - is for the passengers to dismount and eliminate any attackers while the IFV lays down suppressive fire of its own. Although the passengers could theoretically suppress ambushers from their firing ports, nobody wants to be inside when an RPG hits, and the limited field of view from the firing ports makes the job too difficult to guarantee that this won't happen. However, if there was a need to use them, and the situation is appropriate, they can be quite useful. See this video (<a href="https://www.youtube.com/watch?v=LJ4bfxO7yQA&feature=youtu.be">link</a>) to see some soldiers fire out of the firing ports of their bulletproof BTR-80 at an unseen enemy.<br />
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There is a fume evacuation system compatible with AK-type weapons, Once installed in the firing port, the operator is to clap the sheet steel casing deflector (the AK spits spent brass out with extreme violence) on the top cover before firing. There is an air hose on the deflector, and once the evacuation system - powered by a moderately powerful (164W) MBP-3N suction fan, one per each side of the hull - is turned on, gunpowder fumes will be sucked out and vented off outside via a small outlet on the side of the hull, one on each side.<br />
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A single RPG-7 may be carried aboard the BMP-2 in the passenger compartment. There is also a special rack for a "Strela" or "Igla" MANPADS launcher for self defence from aerial attack. One of the passengers can stick himself out of one of the roof hatchs and use it against an imminent threat, but crew members can also use the MANPADS launcher if the passengers have dismounted. This is shown in the photo below. <br />
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<a href="https://1.bp.blogspot.com/-28SsTm8HnGk/Xb3Q54CGheI/AAAAAAAAPk0/c_qOpTovKw4DTs62mOqLiyCQmabYBKZPgCLcBGAsYHQ/s1600/bmp-2%2Bself%2Bair%2Bdefence.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="876" data-original-width="1123" height="249" src="https://1.bp.blogspot.com/-28SsTm8HnGk/Xb3Q54CGheI/AAAAAAAAPk0/c_qOpTovKw4DTs62mOqLiyCQmabYBKZPgCLcBGAsYHQ/s320/bmp-2%2Bself%2Bair%2Bdefence.png" width="320" /></a><a href="https://4.bp.blogspot.com/-0ipBqDDhqiY/V0xNdUNofUI/AAAAAAAAGY0/tK356PPUDFclTw4ugMrXF_V79W2Wzj_9ACLcB/s1600/bmp-2%2BMANPADS.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="256" src="https://4.bp.blogspot.com/-0ipBqDDhqiY/V0xNdUNofUI/AAAAAAAAGY0/tK356PPUDFclTw4ugMrXF_V79W2Wzj_9ACLcB/s400/bmp-2%2BMANPADS.jpg" width="400" /></a></div>
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The photos below show the roof hatches of BMP-1s being used for air defence:<br />
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It is also possible to fire an RPG from a hatch:<br />
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<h3>
<span style="font-size: large;">MISSILES</span></h3>
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In a Soviet BMP-2, the "Konkurs" missile was issued as it was the primary vehicular ATGM system. "Fagot" missiles could also be used from the BMP-2 missile launcher, but they were not standard issue. Due to advances in missile technology, the original 500 meter deadzone of the "Malyutka" missiles integrated into the original BMP-1 was eliminated, and this also indirectly meant that the BMP-2 possessed the same short range tank killer capability as the BMP-1 had with its 73mm cannon. The BMP-1 received its own drop-in 9P135M missile launcher late in 1979 as part of the BMP-1P modernization that allowed it to use "Konkurs" and "Fagot" missiles, but subsequently lost the ability to fire missiles from under armour.<br />
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<span style="font-size: large;">9P56M MISSILE LAUNCHER</span></h3>
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<a href="https://1.bp.blogspot.com/-vTvaQYpNXC0/XqaRAW4JWrI/AAAAAAAAQq0/SMRh-_5Kk_sb0ZtKiGVRGE1Q1arHt-ZFQCLcBGAsYHQ/s1600/bmp-2%2Batgm%2Bkonkurs.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="766" data-original-width="1200" height="255" src="https://1.bp.blogspot.com/-vTvaQYpNXC0/XqaRAW4JWrI/AAAAAAAAQq0/SMRh-_5Kk_sb0ZtKiGVRGE1Q1arHt-ZFQCLcBGAsYHQ/s400/bmp-2%2Batgm%2Bkonkurs.png" width="400" /></a><a href="https://3.bp.blogspot.com/-VP62bsngsRk/V1NM99i4GiI/AAAAAAAAGj4/3PUt3FqYpU4Uu5kKMrUlxEFYTFN-kWR5QCLcB/s1600/f0205060_54040f99848e3.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://3.bp.blogspot.com/-VP62bsngsRk/V1NM99i4GiI/AAAAAAAAGj4/3PUt3FqYpU4Uu5kKMrUlxEFYTFN-kWR5QCLcB/s400/f0205060_54040f99848e3.jpg" width="400" /></a></div>
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Launching the missiles is done from the proprietary 9P56M launcher unit contained inside the armoured box on the turret roof. The gunner is equipped with the 9Sh119M1 sighting unit taken from the more familiar 9P135M man-portable missile launcher complex. Because the missile guidance principle is semi-automatic, all the gunner has to do is lay the sights on the target. The sight has a 9.5x magnification and a field of view of 4.75 degrees. With a 7-8 power optic, a gunner is not only able to spot tanks, armoured personnel carriers and trucks from 4 km but also discern minute details to differentiate between different models. As such, the 9.5x magnification power of the 9Sh119M1 sight was sufficient for the 4 km maximum range of the "Konkurs" missile. Moreover, because the 9Sh119M1 on the turret roof was installed on an independently rotating launcher, the gunner had access to a higher magnification optic than the primary sight (5.6x) in a convenient position for reconnaissance in a turret defilade position, thus effectively extending the viewing range of the BMP-2.<br />
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The images below show the launcher, the 9Sh119M1 sighting system, and the flywheels for aiming the launcher, and the connection between the launcher and the flywheels.<br />
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The 9Sh119M1 sighting unit is pictured below, shown from the gunner's perspective. Beside the 9Sh119M1 is the 9S474 control mechanism. Essentially, it is a set of flywheels to control the elevation and rotation of the launcher complex, plus a launch button.<br />
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<a href="https://1.bp.blogspot.com/-PEZzBIj0I4U/XbW1QFVYuuI/AAAAAAAAPes/UepKkth7An0WaZDM-Jx4a94p-uss8cUQwCLcBGAsYHQ/s1600/gunner.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="767" data-original-width="1329" height="230" src="https://1.bp.blogspot.com/-PEZzBIj0I4U/XbW1QFVYuuI/AAAAAAAAPes/UepKkth7An0WaZDM-Jx4a94p-uss8cUQwCLcBGAsYHQ/s400/gunner.png" width="400" /></a><a href="https://4.bp.blogspot.com/-N3_rhSv9U_w/V1IBrltr9gI/AAAAAAAAGd0/4a4sl9VadtUU5P34gqsixN0VzV2_kH6FgCLcB/s1600/9sh119m1%2Bmissile%2Blauncher.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="223" src="https://4.bp.blogspot.com/-N3_rhSv9U_w/V1IBrltr9gI/AAAAAAAAGd0/4a4sl9VadtUU5P34gqsixN0VzV2_kH6FgCLcB/s400/9sh119m1%2Bmissile%2Blauncher.png" width="400" /></a></div>
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The periscopic aperture windows of the 9Sh119M1 sight are housed in the armoured box atop the turret as the photo below shows. The bottom eye of the sight is the gunner's viewing window, and the upper eye is the automatic missile tracking optic. To select between day and night operating modes, the gunner must reach out and manually flip a switch on the left side of the armoured housing connected to the corresponding switch on the 9Sh119M1 sight head. The same must be done if the gunner wishes to apply a high-contrast light filter on the aperture window of the sight.<br />
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The viewfinder for the 9Sh119M1 sighting unit is pictured below. It has a stadiametric rangefinder calibrated for a target with a height of 2.5 meters, marked for targets up to distance of 4 km. This was intended for the gunner to determine if the target was within the maximum range of the "Konkurs" missile. If it wasn't, the gunner could avoid wasting a shot on a faraway target. If the gunner is using this sight for turret defilade reconnaissance, it is also useful for measuring the range to the target before the BMP-2 drives up into a hull defilade position to open fire.<br />
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The traverse and elevation flywheels are used to lay the crosshairs of the viewfinder on the target. When used, the launcher rotates and the periscopic head of the sight is moved up and down inside its armoured housing. The sight depression limit is -5 degrees and the elevation limit is +15 degrees. When loading the launcher, the mechanical clutch for the traverse system is disengaged and the launcher can be rotated freely by hand. The practical firing arc of the missile launcher is 60 degrees, or 30 degrees to either side. The launcher can be rotated in an arc of 185 degrees, though this is practically never necessary as the turret is first oriented towards the target before the gunner begins to engage it with the ATGM.<br />
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<a href="https://1.bp.blogspot.com/-tRXS1sm7wwo/XqaO1pQnHEI/AAAAAAAAQqg/CypBfWYVOisKcxayzTbwRooqY-XeBUZOwCLcBGAsYHQ/s1600/atgm%2Bsighting%2B2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1366" height="223" src="https://1.bp.blogspot.com/-tRXS1sm7wwo/XqaO1pQnHEI/AAAAAAAAQqg/CypBfWYVOisKcxayzTbwRooqY-XeBUZOwCLcBGAsYHQ/s400/atgm%2Bsighting%2B2.png" width="400" /></a><a href="https://1.bp.blogspot.com/-9PwceLWzajU/XqaO1nTHHJI/AAAAAAAAQqk/Z6xOdhfM7JkOZpam9v2_ifWj0ZTDnJGOACLcBGAsYHQ/s1600/atgm%2Bsighting.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1366" height="223" src="https://1.bp.blogspot.com/-9PwceLWzajU/XqaO1nTHHJI/AAAAAAAAQqk/Z6xOdhfM7JkOZpam9v2_ifWj0ZTDnJGOACLcBGAsYHQ/s400/atgm%2Bsighting.png" width="400" /></a></div>
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The decision to use the sight of the 9P135M missile launcher inside the turret was quite ingenious, though not a new one, as the 9P148 tank destroyer also had the same design feature. Unlike the BMP-1P, FV510 "Warrior" and Marder 1 series, all of which used the more expedient solution of mounting a standard portable missile launcher externally on the turret roof, this unique arrangement allowed the BMP-2 to have a lower profile without requiring the dismounting of the missile launcher and also ensure that the launcher was protected from gunfire and shell fragments. Most importantly, it also allowed missiles to be fired from under armour in a turret defilade position, thus ensuring the full protection of the gunner and the vehicle itself from return fire. Moreover, the 9P56M launcher was created using existing components from the 9P135M, and as such, some cost savings were realized. All that said, the disadvantage of this arrangement is that the gunner guides the ATGMs with manual geared controls, which are precise, but not as convenient as having powered controls. <br />
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The 9P56M launcher includes a jamming detection and warning system, in addition to an emergency MCLOS backup control mode in case the automatic missile tracking system is jammed or loses visual contact with the missile for some other reason. In the MCLOS backup mode, the launcher is locked in place and The lack of powered electrical control systems is not a disadvantage, as the entire turret can be turned to aim the launcher, whereby only fine adjustments are made to the launcher using the flywheels, so that the effect is much the same as being able to control the missile launcher using the BMP's electric handgrips. The manpack-based 9P135M launcher is capable of aiming -20 degrees down and +20 degrees up, but due to the constricted opening of the armour box of the 9Sh119M1, the range of vertical elevation is reduced by an unknown amount.<br />
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The BMP-2 carries an extra tripod, which can be assembled with the dismounted sight to form a complete 9P135M launcher. This provided the dismounted infantry with the possibility of setting up an ATGM position in a more favourable location, separate from the BMP-2. This could be done if, for example, a good firing position is identified, but it can only be accessed by foot, or if the squad wishes to increase the depth of a defensive belt by placing the ATGM position far behind the rest of the squad. The 9P135M launcher is stowed separate from its tripod behind the commander's seat. The tripod is stowed in the passenger compartment, usually propped up against the wall. The 9P135M folds up into a very compact package, and it weighs only 22.5 kg total with the tripod. The commander can easily dismount the missile launcher from behind his seat and hand it over to someone sitting in the passenger compartment. <br />
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This is what a Konkurs missile looks like:<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://3.bp.blogspot.com/-tdEsNkCubjc/V0n2u1aBMBI/AAAAAAAAGWA/f33DqldzUAMPaEbDshNaQ9qsnLrzMts0gCLcB/s1600/03-45-09-konkurs_l3.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="426" src="https://3.bp.blogspot.com/-tdEsNkCubjc/V0n2u1aBMBI/AAAAAAAAGWA/f33DqldzUAMPaEbDshNaQ9qsnLrzMts0gCLcB/s640/03-45-09-konkurs_l3.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Photo credit to Military-Today</td></tr>
</tbody></table>
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Before the missile leaves the tube, the 9B61 gyroscope must be given about half a second to power up to its operating speed of 10,000 revs/min. This is the source of the whirring sound you might hear just before the missile speeds away with a bang.<br />
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Launching the missile is accomplished along the lines of a typical recoiless rifle design with an expulsion charge (a "gas generator") installed in the very rear of the missile tube to provide the initial push. The charge is contained inside a metal housing of a smaller diameter than the missile tube. About half a second after the launch operator presses the trigger to fire, the missile is ejected from a restraining cup attached to its rear (you can see it in the photo above). Then, a substantial charge of stick powder burns inside the gas generator and releases the gasses into the empty chamber between the missile and the gas generator, and the thrust from the rear turns the gas generator into a rocket nozzle and propels the missile forwards. Residual pressure within the gas generator is vented out from the rear of the missile tube via twelve small vent holes.<br />
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The gas generator kicks the missile out of the tube at a speed of 60 m/s. The rocket engine is not ignited until the missile has left the container and traveled about 15 meters. First, the 9Ch237-1 electric ignition cartridge for the main engine ignites the black powder ignition booster charge for the sustainer motor. This ignites the 9Ch179-1 solid fuel in the main engine, packed in a green rubber heat resistant pouch which accelerates the missile, already travelling at 60 m/s, to a speed of 250 m/s and maintains it at around 208 m/s throughout the rest of the flight. The Fagot and Faktoria missiles are ejected at about the same speed, and accelerate to a slightly lower maximum speed of 240 m/s before falling to a cruising speed of 186 m/s.<br />
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The "Fagot" missile, which we do not really want to examine in too much detail, is ejected out in the same fashion, though with a proportionately smaller gas generator. As you can see in the photo below, the gas generator for the Fagot missile tube has just six vent holes.<br />
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<h3>
<span style="font-size: large;">LOADING THE MISSILES</span></h3>
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A standard combat load consists of four missiles. There is a stowage rack for three missiles on the starboard side hull wall next to the turret basket. To facilitate quick loading, there is a missile ready rack in the middle of the turret next to the commander's seat, directly behind the BU-25-2S control panel. When the first missile is loaded onto the launcher by either the gunner or commander, the commander immediately replenishes this ready rack from the reserve rack on the hull wall to the right of the turret basket. This allows the following reload process to be carried out as quickly as possible regardless of the turret orientation by either the gunner or commander.<br />
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If an additional missile is mounted on the launcher before combat, a total number of five missiles can be carried, but this is prohibited under Army regulations as it can be dangerous to drive with a live missile loaded on the launcher, since the launch tube is only a fiberglass container that offers no ballistic protection. Air bursting artillery shells and concentrated machine gun fire can damage the missile, set the rocket fuel alight and render it unsafe to handle. Generally speaking, a missile is only loaded when combat is imminent or a target has already been spotted.<br />
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Depending on whether the commander is present in the turret, reloading the missile launcher can be done by the gunner alone, or it can be a cooperative effort between the gunner and the commander. The passengers are not involved in the reloading process. The process of loading the missile itself can be done under armour from either the gunner's hatch or the commander's hatch.<br />
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If the commander is present in the turret, the loading process can be faster. Firstly, the commander must then order the gunner to rotate the 9P56M launcher to the 9 o'clock position, and then he must open his hatch, tilt the empty missile container upwards to a vertical orientation and then release it from the launcher by pressing the red button on the underside of the launch tube. He can then throw the container off the side of the turret. Then, he will have to reach down to the missile stowage rack beside him to obtain one. The new missile is installed by pushing it up the vacated missile launch rail. Once that is done, the launcher is turned to its original orientation by the gunner. If the commander is absent from the turret, the gunner must turn the turret to the 3 o'clock or 6 o'clock positions in order to reach the missile rack, but other than that, the process is the same. These steps cannot be carried out if the flywheels are not disengaged as the traverse and elevation gears block external forces from moving the launcher, but because the 9Sh119M1 sight is placed direct in the middle of the turret between the gunner and commander, it is possible for either crew member to carry out the entire loading process independently of one another.<br />
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The need to open at least one of the turret hatches to reload the missile launcher was unavoidable, so it is not possible to carry out the process while also maintaining an NBC protection seal. However, this reloading method is still quite good as it provides almost complete protection to the crew members and it can be done without the assistance of the passengers.<br />
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Each missile tube being a full 1.26 meters in length, maneuvering one around the inside of the BMP-2 turret is no mean feat. As such, the minimum rate of fire - that is, the speed of reload plus the time taken when firing on a target at the maximum range of 4,000 m - is about three shots per two minutes, or 1.5 RPM. The maximum firing rate can be as high as 3 RPM using the "Konkurs" under the most optimal conditions (short range, highly proficient crew). It should be understood that these rate of fire figures include firing a missile that has already been loaded beforehand.<br />
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Overall, it can be considered quite fast compared to the Marder 1, but not compared to the M2 Bradley with its two-shot missile pod. However, the missile launcher on the Bradley cannot be reloaded if all passengers have dismounted, and the Marder 1's MILAN missile launcher cannot be loaded under armour. The BMP-2 allows both. The "Fagot" missile and its small size and low weight make it a more attractive option than the "Konkurs" in this context, but the reduced firing range and lethality make it an unreasonable choice.<br />
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<h3>
<span style="font-size: large;">9M113 "Konkurs"</span></h3>
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<a href="https://3.bp.blogspot.com/-gVuAYj5ZQ54/V1MTLuDnP8I/AAAAAAAAGhw/hL9h7pLcdjABWtozmhjUB3Gkmv6-HZHDwCLcB/s1600/konkurs.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="480" src="https://3.bp.blogspot.com/-gVuAYj5ZQ54/V1MTLuDnP8I/AAAAAAAAGhw/hL9h7pLcdjABWtozmhjUB3Gkmv6-HZHDwCLcB/s640/konkurs.jpg" width="640" /></a><br />
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The original Konkurs missile entered service in the Soviet Army in 1974. The maximum range of this missile is 4 km, and the minimum range is 75 meters, as dictated by the distance-armed fuse. The missile features the 9N131 shaped charge warhead with a wave shaper. Weighing in at 2.75 kg, the 112mm warhead creates a shaped charge jet with a velocity of 11 km/s.<br />
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An infrared lamp is installed in the tail of the missile to act as a tracking point for the optronics system of the launcher. Throughout its 4-kilometer long maximum firing range, guidance commands are transmitted through a very fine wire. The spool fits around the tail of the missile and gradually unravels as the missile speeds off. The spool weighs 740 grams. The missile stays steady in flight thanks to a 9B61 gyroscope unit which detects course deviations and sends corrections to the four small steering fins at the nose of the missile.<br />
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Mass of Missile: 14.6 kg<br />
Mass of Missile and Launch Container: 25.3 kg<br />
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Missile Diameter: 135mm<br />
Warhead Diameter 112mm
Warhead Mass: 2.75 kg<br />
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Minimum Penetration: 560mm RHA<br />
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Average Penetration: 600-650mm RHA<br />
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Missile Cruising Speed: 208 m/s<br />
Rate of Spin: 5 - 7 RPM<br />
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The missile has a maximum diameter of 135mm, but tapers down to a smaller diameter, which is why the warhead has a diameter of only 112mm. The taper is between the warhead and the rocket motor, and the tapered portion is just an aerodynamic fairing as you can see in the drawing below.<br />
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In many ways, the Konkurs was superior to other missile systems of the first half of the 70's like the MILAN, and its performance was still highly competitive by the time the ITOW appeared eight years after it. In fact, the Konkurs was directly comparable to the ITOW in performance, only that it was slower, but this was balanced out by a much lighter overall weight and a slightly better maximum flight range. However, even if the Konkurs could be rightly held in high esteem as an extremely effective system throughout the 70's, the appearance of the next generation of NATO tanks in the early 1980's had a great impact on the value of the missile on the modern battlefield. For instance, the M1 Abrams was designed with protection from 127mm anti-tank missiles in a frontal arc of 50 degrees. On the hull and turret, its armour reached 750mm RHA in effective thickness in this frontal arc. The Konkurs missile would not have been an effective weapon against a tank with this level of protection.<br />
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<h3>
<span style="font-size: large;">9M113M "Konkurs-M"</span></h3>
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Tandem warhead descendant of the original Konkurs. Due to internal disagreements and repeated delays, the Konkurs-M only entered service in the late 80's. Ignoring the precursor warhead, the greatly increased penetration power of the missile was achieved with the increased diameter of the shaped charge (the missile is essentially a cylinder with blunt ends) and the increased standoff distance.<br />
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Mass of Missile: 16.5 kg<br />
Mass of Missile and Launch Container: 26.5 kg<br />
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Missile Diameter: 135mm<br />
Warhead Diameter: 135mm<br />
Warhead Mass: 4.75 kg<br />
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Diameter of Precursor Warhead: 60mm<br />
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Minimum Penetration: 750mm RHA behind ERA<br />
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Average Penetration: 800-900mm RHA behind ERA<br />
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Missile Cruising Speed: 206 m/s<br />
Rate of Spin: 5 - 7 RPM<br />
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The new warhead of the Konkurs-M did not only incorporate an additional precursor in front of the original 9N113 warhead, but was an entirely new design. The shaped charge was revised and is much heavier, and together with the precursor warhead, this raised the mass of the missile to 16.5 kg.<br />
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<h3>
<span style="font-size: large;">9M111 "Fagot"</span></h3>
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The Fagot missile entered service before the Konkurs and was originally meant only as a man-portable missile system, but as the missile launcher in the BMP-2 is almost identical to the universal 9P135M launcher, the BMP-2 may fire Fagot missiles as well. The minimum firing distance is 70 meters, and the maximum guided distance is 2,000 meters. Although quite capable of defeating any tank armour from the era in which it was introduced, it became somewhat obsolete like the Konkurs in the early 80's. Nevertheless, it would still be capable of defeating the new generation of NATO main battle tanks from the sides and rear.<br />
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Total Weight (With Missile Tube): 12.9kg<br />
Missile Weight: 7.7 kg<br />
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Missile Diameter: 119mm<br />
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Minimum Penetration: 400mm RHA<br />
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Average Penetration: 460-500mm RHA<br />
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Average Flight Velocity: 186 m/s<br />
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As usual, the missile was steered with four small steering fins, but unlike some other missiles developed in the USSR, the "Fagot" used a electromechanical control system to move the steering fins. The main advantage of an electromechanical control system over a pneumatic system is that the responsiveness of the missile during flight is uniform until the battery is fully expended, whereas the power of a pneumatic system declines with use until the air pressure drops below the usable level. This is not as pertinent of an issue with a SACLOS missile like the Fagot as it is for an MCLOS missile where the gunner must manually control the missile, but it still makes some difference. The steering system is shown in the drawing below.<br />
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<a href="https://4.bp.blogspot.com/-1y6D7U8VyBU/WpboGqHjbdI/AAAAAAAALEA/YiWQmsaZ4ak3uXuIvIoz1k8KBHJtHAWXwCLcBGAs/s1600/steering%2Bfins.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="315" data-original-width="312" src="https://4.bp.blogspot.com/-1y6D7U8VyBU/WpboGqHjbdI/AAAAAAAALEA/YiWQmsaZ4ak3uXuIvIoz1k8KBHJtHAWXwCLcBGAs/s1600/steering%2Bfins.png" /></a></div>
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<h3>
<span style="font-size: large;">9M111M "Faktoria"</span></h3>
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The Faktoria, sometimes referred to as the "Fagot-M" is an updated Fagot missile, introduced in 1980. The maximum firing range was increased to 2,500 meters, and the armour penetration capability was raised to at least 460mm RHA, while simultaneously cutting down the weight of the missile by a small amount to 12.9 kg. The cruising speed was very slightly reduced to 180 m/s.<br />
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Total Weight (With Missile Tube): 13.2kg<br />
Missile Weight: 8.0 kg<br />
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Missile Diameter: 120mm<br />
Warhead Mass: 1.76 kg<br />
Explosive Charge Mass: 1.0 kg<br />
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Penetration: 550mm RHA<br />
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Average Flight Velocity: 180 m/s<br />
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<h3>
<span style="font-size: large;">PROTECTION</span></h3>
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Alhough the steel hull appears to be outwardly identical to the hull of the BMP-1, the BMP-2 uses a more advanced Cr-Ni-Mo steel alloy designated BT-70Sh. This new steel was used for the two-man turret as well. BT-70Sh is almost exactly equivalent to ATI 500-MIL steel as indicated by the material properties described in <a href="http://www.findpatent.ru/patent/246/2460823.html">this patent for BT-70Sh</a>. BT-70Sh steel has a hardness of 534 BHN when processed to the type of thin plates used on the BMP-2. It becomes exponentially more difficult to treat steel to a high hardness past a certain thickness while maintaining the other mechanical characteristics of the metal using the available thermomechanical techniques at the time, and thinner plates are typically much easier to process.<br />
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The use of the new steel allowed the designers to compensate for the increased overall weight of the vehicle compared to the BMP-1 while maintaining the same level of protection by decreasing the thickness of the sides of the hull by a few millimeters. The sides of the hull remained proofed against 7.62mm armour-piercing bullets and the frontal arc remained proofed against 23mm armour-piercing shells from 500 meters. Furthermore, the frontal arc of 120 degrees was also immune to 12.7mm armour-piercing bullets.<br />
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The research paper <a href="http://www.dtic.mil/docs/citations/ADA516824">here (link)</a> is important in understanding value of the BMP-2's armour protection, as there is little direct information on the armour of the BMP-2 from original Soviet sources. Reading this document in its entirety is recommended, but an understanding of V50 is needed to correctly interpret the results. The contents of this document pertains to the testing of ATI 500-MIL high strength steel plate of the ATI brand name using three different caliber of common machine gun ammunition: .308 cal M2 AP, .50 cal M2 AP, 14.5mm B-32 AP, and 14.5mm BS-41 AP (WC core). Range is a factor of velocity, and since the V50 figures in the document are velocity values and not ones for range, we must find out the range for ourselves with this range-velocity chart <a href="http://www.sniperforums.com/forum/cartridges-calibers/6836-14-5x114mm-russian.html">here (link)</a>. There are charts for .50 cal M2 AP and 14.5mm M-44 Ball (ballistically equivalent to B-32).<br />
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The front of the hull was split into two halves. The lower glacis is totally devoid of anything of inerest, but the upper glacis was dominated by the peculiar armoured aluminium engine access panel. This panel is made from armour-grade aluminium alloy, but as nobody ever mentioned what alloy it is, we can assume that it is most likely made from the same ABT-101 aluminium alloy used in the BMD-1 and BMD-2 airborne IFVs. ABT-101 has a hardness of 145 BHN, and it is much stronger than aluminium alloy 5083 used in armoured vehicles like the M113 and the M2 Bradley. But besides the strangeness of having aluminium in a predominantly steel hull, the most noteworthy feature pf the engine access panel is the seven ribs running across it laterally. If viewed head-on, they line up such that they form a seamless virtual "wall", as shown in the photo below.<br />
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<a href="http://3.bp.blogspot.com/-8eBFRZ1hiWI/VlQ_lRLHVgI/AAAAAAAAEdk/K3NiWhyClmk/s1600/bmp2%2Bfront.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="438" src="https://3.bp.blogspot.com/-8eBFRZ1hiWI/VlQ_lRLHVgI/AAAAAAAAEdk/K3NiWhyClmk/s640/bmp2%2Bfront.jpg" width="640" /></a></div>
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These ribs are a crucial component of the protective qualities of the engine access panel. It achieves this with a combination of its own innately unique properties and the benefit of increasing the stiffness of the plate, which is accomplished without significantly increasing the mass of the plate. Original research on the usefulness of protruding ribs as a way to defeat ballistic threats was done parallel to Swedish efforts in the same vein during the mid-60's. The Russians applied the concept to the BMP in 1966, and the Swedes to the Stridsvagn 103.</div><div><br /></div><div>At very high armour obliquity, the predominant factor in protection lies in the prevention of back surface failure. To capitalize on this, aluminium or titanium can be used, enabling a plate of greater thickness to be used as compared to steel. <br /><br /></div><div>The image below, taken from the NII Stali website, shows a simulator of the BMP-2 upper glacis plate after a test with a 23mm BZT round (API-T). The rib is destroyed at the point of impact, but the shell ricocheted after passing through the rib and it merely clipped the second rib on its edge.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-YaKO3eYJKcs/X2km3ME0RNI/AAAAAAAARoQ/k_ah3J05QfQo_5dd7UqfLKNhMYip5AmdQCLcBGAsYHQ/s1023/Detail%2BAl.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1023" height="300" src="https://1.bp.blogspot.com/-YaKO3eYJKcs/X2km3ME0RNI/AAAAAAAARoQ/k_ah3J05QfQo_5dd7UqfLKNhMYip5AmdQCLcBGAsYHQ/w400-h300/Detail%2BAl.jpg" width="400" /></a></div><br /><div><br />
The ribs on the BMP-2 (and BMP-1) measured 25mm in height, 12mm in thickness, and were spaced 200mm apart, but due to the steep angle of the slope of the BMP's engine access panel, the difference in spacing is nullified. One important detail is that the ribs are not exactly vertical, but perpendicular to the engine access panel, so they are sloped inwards at 12 degrees. These measurements and the photos below were provided by Chris Conners, proprietor of the excellent American Fighting Vehicle Database website (<a href="http://afvdb.50megs.com/">afvdb.50megs</a>).<br />
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The shape and orientation of the ribs on the engine access panel can be seen in the image below.<br />
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The geometry of the access panel itself is surprisingly complex. It is thinnest immediately behind each rib, and gradually thickens as it approaches the next one. The thinnest part of the panel is 10mm and the thickest part is 15.5mm. The effectiveness of the panel against gunfire is unclear, but there can be no doubt that it is at least proofed against 7.62mm bullets of all varieties as well as 12.7mm armour-piercing bullets as well. <br />
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<a href="https://1.bp.blogspot.com/-_BpLVx5pa_I/V3v7Y-9LO4I/AAAAAAAAHAk/7mYCYUSvhRIx7Bmw9BE0C-XBTxgmL-v9ACLcB/s1600/aluminium%2Bplate.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-_BpLVx5pa_I/V3v7Y-9LO4I/AAAAAAAAHAk/7mYCYUSvhRIx7Bmw9BE0C-XBTxgmL-v9ACLcB/s1600/aluminium%2Bplate.png" /></a></div>
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This phase diagram taken from "<i>Armour: Materials, Theory, and Design</i>" illustrates the importance of steep sloping to the engine access panel. In this case, a 6.35 mm aluminium alloy plate was used as a target and 6.35 mm-diameter steel-cored bullets as projectiles. A 6.35 mm projectile like this is representative of the steel armour-piercing core of the average 7.62mm rifle bullet. The AP core of a 7.62x54mm Russian B-32 bullet, for instance, has a diameter of 6.1 mm with a weight of 5.39 grams. It has a nominal muzzle velocity of 830 m/s. The AP core of a .30 caliber M2 AP bullet has a diameter of 6.2 mm and weighs 5.17 grams. It has a muzzle velocity of 855 m/s. The AP core of a 7.62x51mm M61 bullet has a diameter of 6.3 mm and weighs 3.8 grams. It has a muzzle velocity of 838 m/s.<br />
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Even with such a thin aluminium alloy plate, the armour piercing core simply ricochets without achieving perforation. Depending on the impact velocity, the end result may vary. At 700 m/s, the bullet will ricochet intact, but above that, it will fracture on impact and the fragments ricochet off the plate. As the aluminium plate used in the experiment is highly likely to be 5083 aluminium alloy, inferior to ABT-101 alloy.</div><div>
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The lower glacis is probably the stronger half of the front hull. It is a 15mm plate sloped at 56 degrees - thinner than same plate on the BMP-1 which was 19mm thick sloped at 57 degrees. The reduced thickness was compensated by the increased hardness and strength of the new BT-70Sh steel which raised the effective thickness of the 15mm plate on the BMP-2 to the same level as the BMP-1. In practical terms, this compares favourably to the 32mm plate sloped at 24 degrees that forms lower glacis of the Marder 1, A1 and A2 when attacked with small arms and some autocannons, including the ordnance from the Marder 1. For instance, German DM43 APCR ammunition of the 20x139mm caliber fired from the Marder 1's Rh202 autocannon is able to penetrate 32mm of RHA armour at 0 degrees at 1,000 meters, but its performance drops sharply down to just 8mm of penetration on armour sloped at 60 degrees at the same distance. For the better half of its life during the Cold War, this part of the BMP-2 was therefore frontally immune to 12.7mm machine gun bullets and to 20mm shells and anything in between from close range. The vastly more effective DM63 APDS was introduced sometime in the mid-80's, and that would have been able to defeat the frontal armour of the BMP-2 out to 1,000 meters and more.<br />
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Like the BMP-1, the side armour of the BMP-2 is good for a vehicle of its weight if the Marder 1 is used as a reference point. The armour on the sponsons and the firing ports is 13mm thick and vertically sloped at 15 degrees. The armour on the lower side of the hull is 15mm thick and flat. The flotation aids mounted on the sponsons as side skirts are filled with foam and are equivalent to 10mm of steel. The flotation aids protect the tracks and provide additional spaced armour for the hull, but they only cover a third of the area of the hull profile. The sides provide reliable protection from 7.62mm machinegun fire, and resist .50 caliber AP ammunition only from above 200 meters. The field manual FM 7-8 "Rifle Platoon And Squad" from 1980 notes that a .50 caliber machine gun will penetrate the side of a BMP from 200 meters or less.<br />
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Besides the physical thickness of armour, the passenger compartment of the vehicle has an extra 7 to 8 degrees of horizontal slope. Combined with the minor vertical sloping on the sponsons, this additional horizontal slope increases the protection for both the passengers and the internal fuel tanks from attacks in the frontal arc of the BMP.<br />
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This design quirk lends evidence to the intention of the designers to afford extra protection to the most sensitive assets of the vehicle. It would be extremely incorrect to say that the BMP-2 (and by extension its predecessor) was a "deathtrap" for being designed without consideration for combat survivability. The extra 8 degrees of horizontal slope will do absolutely nothing if the vehicle is struck by an RPG, or if it runs over a large IED, but it will be significant when the BMP is advancing towards a hail of heavy machine gun fire.<br />
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<a href="https://3.bp.blogspot.com/-O_gKkD4-Q8M/V0wlCiZEpkI/AAAAAAAAGYE/GbT7Fagc6mUDgQuRuG8wFFpOMS_Me6GfgCLcB/s1600/bmp-2_tank_at_the_open_landmachtdagen_2010.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://3.bp.blogspot.com/-O_gKkD4-Q8M/V0wlCiZEpkI/AAAAAAAAGYE/GbT7Fagc6mUDgQuRuG8wFFpOMS_Me6GfgCLcB/s640/bmp-2_tank_at_the_open_landmachtdagen_2010.jpg" width="640" /></a></div>
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The thin strip of sloped armour (above) at the very top of the hull sponsons is no better nor worse than the rest of the side armour. The photo below, courtesy of Mr. Conners once again, gives us an idea of how thick it really is. Knowing that the sponsons are 16mm thick, we can compare that (the straight bit) to the bent flap of steel, which is bent directly from the sloped strip of the overtrack hull. Using pixel scaling, the thickness comes out at 7.13mm. Not very thick, but with its slope of 60 degrees, it is more than enough to deflect 7.62x51mm AP bullets from any distance.<br />
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<h3>
<span style="font-size: large;">TURRET</span></h3>
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The thickest sections of armour are found at the center of the turret surrounding the gun mantlet. The physical armour thickness reaches its peak at the base of the turret underneath the gun mantlet as the drawing below shows.<br />
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The thickness of this part of the turret is unknown, but based on the thickness of the turret roof depicted in the drawing, it is much thicker than the turret cheeks. The turret cheeks form the front half of the circular turret and it has a thickness of 20mm. It is sloped 43 degrees at the front of the turret, declining to 36 degrees at the sides. Ignoring the horizontal slope component from the circular shape of the turret, the cheek armour has a line-of-sight (LOS) thickness of 27.3mm with only its vertical slope of 43 degrees. This is a close equivalent to the turret of the BMP-1, but the BMP-2 turret is slightly tougher as it is built from BT-70Sh steel with a higher hardness and higher yield strength than the 2P high hardness steel of the BMP-1.<br />
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Like the hull, the turret armour offers complete immunity from .50 caliber and 14.5mm armour-piercing bullets in its frontal arc and can resist 23mm BZT shells (API-T) from 500 meters.<br />
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The rear half of the turret is weaker, having a thickness of just 10mm and sloped at 28 to 20 degrees, with the smallest slope angle at the rearmost point of the turret. From the side, the turret has enough armour to resist 7.62mm armour-piercing bullets at point blank range.<br />
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Once opened, the turret hatches serve as armoured shields. As they are about as thick as the turret roof armour is, which is about 13.6mm, they are fully proof against anything less than a 12.7mm bullet. The shield gives the commander full body and arm protection once he is outside, making him a very tricky target for any potential snipers. If the commander would prefer not to have his head above the hatch so conspicuously, he can rotate the cupola a bit to the side to poke his field binoculars out so that everything except his eyes can be sheltered behind the shield-hatch. <br />
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The conflict in Ukraine has proven that artillery is still an incredibly important asset, even in an unconventional war. Apparently, the majority of armoured vehicle losses were due to artillery fire. Among the many victims was the BMP-2 below. As you can see, the roof armour was no match for a 122mm high explosive shell.<br />
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<h3>
PERFORMANCE AGAINST MACHINE GUNS</h3>
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If you haven't read the bullet penetration test document presented <a href="http://www.dtic.mil/docs/citations/ADA516824">here (link)</a>. I have condensed the relevant information to a usable format:<br />
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Muzzle Velocity of M2 AP: 876 m/s<br />
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V50 of <b><u>7.7mm</u></b> ATI 500-MIL plate at 30°: 627 m/s<br />
V50 of <b><u>9.7mm</u></b> ATI 500-MIL plate at 30°: 723 m/s<br />
V50 of <b><u>3.1mm</u></b> ATI 500-MIL plate at 30°: 787 m/s<br />
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This means that at 960 m, .50 cal AP will go through 7.7mm of 534 BHN steel angled at 30 degrees to the vertical. At 600 m, it will go through 9.7mm of the same steel angled at 30 degrees. At 400 meters, the bullet is defeated by 3.1mm of AT 500-MIL plate, indicating the possibility of a catastrophic failure of the steel core by shattering.<br />
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Here is the graph generated as part of the test conclusion and discussion.<br />
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Keeping in mind that the muzzle velocity of a .50 caliber AP bullet is 2910 ft/s, we can see that the only velocity at which the penetration of the bullet will exceed 13mm (0.51 inches) is just under 2,600 ft/s. Referring to our ballistic chart here (<a href="http://www.sniperforums.com/forum/cartridges-calibers/6836-14-5x114mm-russian.html">link</a>), we can see that the velocity of 2,450 ft/s corresponds with the distance of around 400 meters. Therefore, the upper side hull armour of the BMP-2 can resist a .50 caliber AP bullet from 400 meters given that the hull is angled slightly by a few degrees. The lower side hull armour is 15mm thick but completely flat, so it is actually slightly weaker. Conversely, the middle of the hull where the flotation aid is present would be immune to .50 cal AP even from point blank range due to the high combined thickness of armour and the spacing of the flotation aid from the hull sponson.<br />
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The turret is vertically sloped at 28.5 to 35 degrees and has additional horizontal slope due to its rounded shape, so it is able to resist .50 caliber AP bullet from closer distances. However, the rear of the turret is only 10mm thick and is flatter, so it is only capable of resisting .30 caliber bullets.<br />
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<h3>
14.5mm B-32 Steel Cored Armour Piercing bullets</h3>
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Muzzle Velocity of 14.5 B-32: 988 m/s<br />
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V50 of <b><u>15.6mm</u></b> of ATI 500-MIL plate at 30 deg: 730 m/s<br />
V50 of <b><u>15.4mm</u></b> of ATI 500-MIL plate at 30 deg: 739 m/s<br />
V50 of <b><u>18.8mm</u></b> of ATI 500-MIL plate at 30 deg: 841 m/s<br />
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This means that at 980 m, a 14.5mm B-32 bullet will go through 15.6mm of ATI 500-MIL plate angled at 30 degrees to the vertical. This is almost exactly double the performance of the .50 M2 round for a very small increase in caliber and small increase in overall dimensions. At 915 meters, the 14.5mm B-32 bullet will go through 15.4mm of the same steel at the same slope. At 525 m, the 14.5mm B-32 bullet will go through 18.8mm of the same steel at the same slope.<br />
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Here is the graph of thickness against V50:<br />
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As you can see, the side hull will be defeated from any distance within 600 meters.<br />
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<h3>
14.5mm BS-41 Tungsten-Carbide (WC) Armour Piercing bullets</h3>
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Muzzle Velocity of 14.5mm BS-41 bullet: 1005 m/s<br />
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V50 of <b><u>24.5mm</u></b> of ATI 500-MIL plate at 30 deg: 869 m/s<br />
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The inherent suitability of a WC (Wolfram-Carbide, or Tungsten Carbide) core for anti-armour purposes is very apparent here. At 435 meters, the BS-41 bullet can perforate 24.5mm of ATI 500-MIL plate steel angled at 30 degrees.<br />
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Reading the graph tells us what we already know. The sides of the BMP-2 cannot defend from this type of bullet from a reasonable distance, but the frontal armour of the hull and turret will have no problems even at close range.<br />
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<a href="https://www.blogger.com/null" id="fueldoors"></a>
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<h3>
<span style="font-size: large;">FUEL TANK DOORS</span></h3>
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Contrary to popular belief, the infamous fuel-filled rear doors were far from being a hazard to the crew. To the contrary, there is evidence that much more thought was put into the design of these doors than commonly believed. The walls of the fuel tank are pressed from rolled sheets of medium hardness steel. According to Victor Malginov, the outer plate of the door is 13mm thick and the inner plate is around 5mm thick. The thickness of the outer plate is the same as the thickness of the rear hull armour, and the doors are slightly sloped at the same angle as the reset of the rear hull armour: 13.5 degrees. This is enough to stop ball ammunition from small arms at point blank range, grenade fragmentation from any distance, and splinters from small mortars. When taken together with the fuel and the inner ~5mm plate, it is clear that the ballistic protection offered by these doors is not worse than the side armour of the vehicle and may even be slightly better. <br />
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There is a prevailing myth that the fuel tanks could be set afire if the fuel tanks were hit by incendiary ammunition. The biggest issue with this is that incendiary ammunition simply was not common. Incendiary 7.62x51mm ammunition is rare, and so is incendiary 5.56mm ammunition, and in the latter case, it would not be able to defeat the outer 13mm plate of the fuel tank door in the first place. Even .50 caliber AP-I ammunition is rare compared to ball rounds and the standard APM2 armour piercing round. The standard .30 caliber APM2 armour piercing round also lacks an incendiary filler.<br />
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<a href="https://3.bp.blogspot.com/-2KD66cHaKFI/W6anea69eRI/AAAAAAAAMS0/Vf-QAbPnuKEZ9f1EpU412raxAfD68D8lwCLcBGAs/s1600/7.62%2Band%2B12.7%2Bapm2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="488" data-original-width="824" height="378" src="https://3.bp.blogspot.com/-2KD66cHaKFI/W6anea69eRI/AAAAAAAAMS0/Vf-QAbPnuKEZ9f1EpU412raxAfD68D8lwCLcBGAs/s640/7.62%2Band%2B12.7%2Bapm2.png" width="640" /></a></div>
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In the event of a penetration from an API bullet, the incendiary element will only ignite fuel just behind the exterior wall, because fuel needs to be oxidized in order to burn, and the only source of oxygen for the fuel that is exposed to the incendiary blast is the fuel just around the entry hole of the bullet, since fuel will leak out from that hole into open air. However, in such a case, the entire tank is completely safe from ignition. Burning fuel will simply leak out of the tank in harmless rivulets. If the interior wall of the fuel tank is perforated as well, the fuel will not be ignited due to a lack of heat, since the incendiary blast is on the <i>other</i> side of the fuel tank. This is because the incendiary element is located in front of the armour piercing core, and the external wall of the door-tank is more than enough to initiate ignition, and the incendiary blast will be partially outside the fuel tank, and partially inside, but due to the spaced effect and the presence of fuel, the blast will not be able to reach the interior side of the fuel tank.<br />
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So we know that if fuel is to be ignited, it will only be ignited outside the fuel tank. But what of the steel penetrator core that's still flying straight through the fuel tank? Fluids, including diesel fuel, are more than capable of slowing down or even outright defeating ballistic projectiles given sufficient volumes of it. How much is needed to stop specific bullets is not known, but with two thick armoured walls on either side, it's not hard to imagine that the rear doors could probably resist 7.62x51mm AP rounds without much effort. Large caliber artillery splinters would find themselves quickly stopped due to their irregular shape, but not before punching large holes into the outer walls. The parts of the rear doors cut out for firing ports do not hold fuel, but are compensated with an additional layer of armour welded on top of the door as shown below:<br />
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<a href="https://3.bp.blogspot.com/-by9Y2jvWWKc/V0yTjo6H4tI/AAAAAAAAGZ8/6Hc1cOdehdcDKt7JhLdIg615OdgUYal6ACLcB/s1600/bmp-2_031_of_104.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://3.bp.blogspot.com/-by9Y2jvWWKc/V0yTjo6H4tI/AAAAAAAAGZ8/6Hc1cOdehdcDKt7JhLdIg615OdgUYal6ACLcB/s400/bmp-2_031_of_104.jpg" width="400" /></a></div>
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These add-on plates reportedly have a thickness of 6-8mm. As such, the total thickness of steel at this zone would be between 24-26mm, and the protection value is increased by the curvature of the pressed steel door.<br />
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Given these facts, it's easy to see how the designers approached the task of increasing protection without increasing weight, as that was critical to the vehicle's amphibious qualities. The outer plate is thick enough to prevent punctures from most threats and the rear doors as a complete unit can resist most shell splinters from large caliber artillery and most small arms fire. The only credible threat within the context of the role of the BMP-2 would be heavy machine guns firing armour piercing ammunition, but in reality, the chances of a BMP-2 exposing its rear end to a heavy machine gun emplacement or a vehicle armed with one is exceedingly low that it may as well be a non-issue.<br />
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But for all that, the crew's initiative still plays the most important role. It is important to remember that both rear doors only hold a combined total of 122 liters of fuel out of a net total of 460 liters. In other words, the crew could easily make do without having them filled when in combat. It was never an issue in the first place, since Soviet vehicles have always carried more fuel than most, and even without the contents of the rear doors, the BMP-2 would still carry nearly the same amount as the M113. The rear doors may be filled with water, or soil, or sand to totally nullify the chance of fire and further boost its resilience. The website "Box O' Truth" did their own tests on the effectiveness of sand as a bullet stopping obstacle in their article "The Sands of Truth", which can be found <a href="http://www.theboxotruth.com/the-box-o-truth-7-the-sands-o-truth/">here (link)</a>. As it turns out, 7.62x51mm ball ammo won't go through 5 1/2 inches of sand (139.7mm) of sand, nor will 5.56mm SS109 rounds. But what are the dimensions of the rear doors?<br />
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Well, they measure about 275mm wide at the widest at the top, tapering down to 172mm wide at the thinnest at the bottom. This site <a href="http://www.inetres.com/gp/military/infantry/mg/50_ammo.html">(link)</a> states that a single .50 cal M2 AP round fired from the barrel of an M2 machine gun is capable of penetrating:<br />
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<blockquote class="tr_bq">
<b><i>Sand</i></b> </blockquote>
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355.6mm at 200m<br />
304.8mm at 600m<br />
152.4mm at 1500m</blockquote>
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Taking 275 to 172 milimeters of sand together with the ~5mm and 13mm steel walls of the rear doors, it appears that the doors have a reasonable chance of shrugging off .50 cal AP bullets at short range. If not, then the occupants are at least fully shielded from 7.62x51mm AP bullets, though they probably wouldn't need the sand for that. Even if the fuel doors were empty, they would still be as good as what some other IFVs have for armour. Take the CV90 as an example:<br />
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<a href="https://4.bp.blogspot.com/-FH74T_E2dMU/V1TfWPW_zMI/AAAAAAAAGnA/u--7tm0I6y0TZKE7pPxfixDJtjgqNotfgCLcB/s1600/cv90%2Brear%2Bhatch%2Barmour.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="478" src="https://4.bp.blogspot.com/-FH74T_E2dMU/V1TfWPW_zMI/AAAAAAAAGnA/u--7tm0I6y0TZKE7pPxfixDJtjgqNotfgCLcB/s640/cv90%2Brear%2Bhatch%2Barmour.JPG" width="640" /></a></div>
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In conclusion, there is more than enough evidence indicating that the armour on the BMP-2 was far from "paper thin". While it is true that its contemporary the M2 Bradley had greatly superior side armour with its double spaced armour configuration over its one inch thick 5083 aluminium hull, some context is needed before direct comparisons can be drawn. The M2 Bradley had to contend with powerful Soviet 14.5mm machine guns which could be found on the majority of BTR-60 and BTR-70 armoured personnel carriers as well as BRDM armoured cars, whereas the BMP-2 only had to face off against .50 caliber machine guns. Hunnicutt says that the Bradley's side armour is resistant to 14.5mm AP rounds from 200 meters, and it has been shown that the BMP-2's side armour is theoretically resistant to .50 cal AP rounds from around 400 meters. In practical terms, the fact that the side armour of the BMP-2 is nominally weaker is a minor detail. When seen in the appropriate context, the BMP-2 was not worse than its contemporaries in armour protection.<br />
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<h3>
<span style="font-size: large;">BMP-2D APPLIQUE ARMOUR</span></h3>
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Immediately as the Afghan campaign began in earnest during the turn of the decade, chinks in the BMP-2's armour began to show. Although the vanilla BMP-2 was more than good enough when faced with Kalashnikov fire, it was almost immediately apparent that heavy machine gun fire from Mujahideen ambushes (usually from a DShK) could easily perforate the 16 - 18mm side armour at very close distances. To counter this development, the BMP-2D, also known as the "Afghan BMP" variant was created. It introduced an array of armoured spaced plates mounted over the upper sides of the hull and a steel side skirt draping down from the overtrack sponsons to protect the bottom half of the hull. The top strip on the upper side was also reinforced with an extra sheet of 6mm steel welded on top of it. Contrary to some claims, the front hull armour was not reinforced, only the belly.<br />
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<a href="http://4.bp.blogspot.com/-1IiPBYG3NWM/VlG-B37e-LI/AAAAAAAAEWY/PRSuW1De4QE/s1600/bmp-2%2Bnormal.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="243" src="https://4.bp.blogspot.com/-1IiPBYG3NWM/VlG-B37e-LI/AAAAAAAAEWY/PRSuW1De4QE/s400/bmp-2%2Bnormal.jpg" width="400" /></a><a href="http://3.bp.blogspot.com/-6fCE304iwXc/VlG9iVR4EmI/AAAAAAAAEWQ/Dd0LqRTX8Vg/s1600/50.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="251" src="https://3.bp.blogspot.com/-6fCE304iwXc/VlG9iVR4EmI/AAAAAAAAEWQ/Dd0LqRTX8Vg/s400/50.jpg" width="400" /></a></div>
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The decision to only add protection to the sides and rear of the vehicle and not the front was informed by actual data gathered during the conflict. Ignoring the fact that the front of the vehicle was immune to 12.7mm machine gun fire, real combat damage reports showed that the front was almost never targeted by enemy forces throughout the duration of the war. According to the study "<i><a href="http://btvt.info/5library/vbtt_1991_afgan.htm">Исследование Боевых Повреждндений Образцов Отечественной БТТ</a></i>" (<i>Study of Combat Damages To Samples of Domestic BTT</i>), the distribution of hits sustained by BMPs from armour-piercing bullets was 33% to the sides of the hull, 50% to the rear of the hull and 17% to the roof of the hull. The turret did not receive any damage or received a statistically negligible proportion of damage. Thus, additional spaced armour plating was allocated to the side and rear projections of the BMP-2D.<br />
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<a href="http://1.bp.blogspot.com/-0Ztc15C9Njw/VlG-SsXusyI/AAAAAAAAEWg/7egdEVnnmV4/s1600/bmp-2d%2Bspaced%2Barmour.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-0Ztc15C9Njw/VlG-SsXusyI/AAAAAAAAEWg/7egdEVnnmV4/s1600/bmp-2d%2Bspaced%2Barmour.jpg" /></a></div>
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The steel side skirts are 6mm thick, and so are the steel panels on the hull sponsons that were mounted about two inches away from the base armour. The protective mechanism was twofold - it forced the incendiary element of an API bullet to deflagrate early and expend itself in the spaced gap, and it also chips off part of the penetrator core and creates fractures so that when it impacts the high hardness steel armour plate of the hull, the bullet shatters completely. If the bullet impacts at a higher obliquity, the armour piercing core can be shattered completely, thus completely neutralizing it as a threat.<br />
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<a href="https://2.bp.blogspot.com/-8KH6VDlAdk0/W6B-Y4FpSrI/AAAAAAAAMSc/xMpboyxViDAup1CR9zuQSZs7KRNK45WcwCLcBGAs/s1600/bullet%2Bhigh%2Bhardness%2Bplate%2B.50%2Bcaliber.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="522" data-original-width="354" height="640" src="https://2.bp.blogspot.com/-8KH6VDlAdk0/W6B-Y4FpSrI/AAAAAAAAMSc/xMpboyxViDAup1CR9zuQSZs7KRNK45WcwCLcBGAs/s640/bullet%2Bhigh%2Bhardness%2Bplate%2B.50%2Bcaliber.gif" width="433" /></a></div>
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Those two factors, in addition to the thickness of the panels themselves, entirely neutered the threat of 12.7mm and 14.5mm shots across the side of the hull even from close range. Extensive research on the effects of spaced armour with hard but thin sheets on high caliber armour piercing bullets has shown that even sheets as thin as 4.4mm are capable of shattering 12.7mm B-32 steel cored API bullets at shallow angles beginning from 20°, and that the same can be done with 5mm sheets on 14.5mm B-32 steel cored API bullets, or even tungsten carbide-cored BS-41 bullets. Indeed, that was precisely what the famous "bazooka plate" spaced armour on Pz. IV tanks was actually meant for, and not for defence from bazookas. The original double-spaced side hull armour configuration on the M2 Bradley was implemented for the same reason: protection from 14.5mm machine guns at distances as close as 200 meters, although the Bradley's side armour required two layers of spaced steel plates because bullets do not shatter easily on the soft and thin aluminium hull.<br />
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In addition to ballistic protection, the new side hull armour contributed to the vehicle's increased survivability from roadside IEDs, which were often composed of a cluster of partially buried artillery shells rigged to explode all at once. The extra steel side skirts would be extremely useful for defeating such shrapnel as artillery shell splinters lack an efficient ballistic shape and would break apart much more readily on non-homogeneous armour than the core of an armour-piercing bullet.<br />
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The floor of the hull is 8mm thick in all incarnations of the BMP-1 and BMP-2. It is stamped with reinforcing ribs for added stiffness, both for structural reasons as well as to reduce deflection from the influence of an explosive blast. A small 1.5 kg track-breaking mine exploding under the track would easily rend the track and blow off a roadwheel, but it would not pierce the belly. Heavier anti-tank mines were a much more serious challenge to overcome.<br />
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<a href="https://www.blogger.com/null" id="smoke"></a>
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<span style="font-size: large;">SMOKESCREEN</span></h3>
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The BMP-2 can either lay its own smokescreen by injecting a fine mist of diesel fuel into the exhaust manifold outlet, or make use of its smoke grenade launchers. The former option is an an ingenious, inexpensive, extremely useful and near-inexhaustible source of anti-IR smoke cover - a little-known fact is that since the smoke generated from this method will be the same temperature as the exhaust, it is hot enough to mask the vehicle's thermal signature. The only shortcoming of this system is the time taken to envelop the vehicle, but it is often used in platoon formations, so that a single tank or BMP can produce enough smoke to cover the entire platoon and its surroundings. A large number of battlefield maneuvers revolve around the use of this method of smoke generation for concealment. However, the exhaust manifold outlet will eventually cool when enough heat is absorbed by the diesel fuel, so there is a limit to how long the driver is allowed to use this feature. One potential hazard is that residual fuel particles in the exhaust manifold may catch fire when it gets heated up again after cooling.</div>
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But aside from this, the BMP-2 was equipped with the 902V Tucha smoke grenade system. </div></div></div></div></h3><h3><div style="text-align: left;"><div style="font-weight: normal;">
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<a href="https://www.blogger.com/null" id="nbc"></a>
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<h3>
<span style="font-size: large;">NBC PROTECTION</span></h3>
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The BMP-2 features a collective NBC protection suite, collective meaning that the interior of the vehicle is fully sealed from the outside environment, so that the crew and passengers do not need to don hazard suits. Beginning in 1984, the BMP-2 received a lining and cladding of anti-radiation pads. The BMP-2 obr. 1986 had the cladding fitted since the beginning of its production.<br />
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The turret cladding is called "Nadboi". It is about an inch thick, and most likely made of laminated borated polyethylene fiber sheets. If you look closely at frayed edges (photo below), you can see that it is distinctly fiber-like.<br />
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<a href="http://2.bp.blogspot.com/-l1wDVmvpPgc/VlNXlVietmI/AAAAAAAAEc4/NUkCZ90DoV0/s1600/bpk-2-42%2B%25282%2529.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="468" src="https://2.bp.blogspot.com/-l1wDVmvpPgc/VlNXlVietmI/AAAAAAAAEc4/NUkCZ90DoV0/s640/bpk-2-42%2B%25282%2529.jpg" width="640" /></a></div>
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The walls of the turret are entirely covered with it, and so is the roof. "Podboi" is designed to absorb neutrons from a nuclear explosion.<br />
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The interior walls of all of the occupied compartments of the vehicle is lined with an anti-radiation lining. It is effective at capturing neutrons, but more importantly, it has the secondary purpose of providing some much needed insulation. This is especially important if the vehicle is coated in burning napalm, seeing as the steel for the roof is only a little more than half an inch thick.<br />
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<a href="http://2.bp.blogspot.com/-8DP0aEC9ldg/VlFsPGT9n4I/AAAAAAAAEVk/Nw4uADae26s/s1600/bmp2%2Banti%2Bradiation%2Blining.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://2.bp.blogspot.com/-8DP0aEC9ldg/VlFsPGT9n4I/AAAAAAAAEVk/Nw4uADae26s/s640/bmp2%2Banti%2Bradiation%2Blining.JPG" width="640" /></a></div>
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Swedish tests on purchased ex-East German T-72s found that its lining of borated polyethylene was extremely effective at capturing spall, so it should be no different for the BMP-2, although the lining in the BMP-2 is much thinner. The external cladding should also give some small bonuses towards the overall effectiveness of the turret armour. The anti-radiation lining is notably absent from the the rear fuel doors, but this is not a problem. Water is surprisingly effective at absorbing radiation. Presumably diesel fuel is, too.<br />
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The protruding bow of the hull is crammed chock full of equipment, including a GO-27 gamma radiation detector. You can see it mounted to the starboard side hull in the photo below, to the left of the steering column.<br />
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<a href="http://2.bp.blogspot.com/-dRcRYwasxKI/VnKLoLe3M1I/AAAAAAAAFIk/g6my-tJX11M/s1600/bmp%2Bnbc%2Bsuite.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://2.bp.blogspot.com/-dRcRYwasxKI/VnKLoLe3M1I/AAAAAAAAFIk/g6my-tJX11M/s640/bmp%2Bnbc%2Bsuite.jpg" width="434" /></a> <span id="goog_1808794569"></span></div>
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The GO-27 sensor and automatic sealing system is responsible for detecting nuclear and chemical particles and for initiating the lockdown protocol. Every gap and port exposing the interior of the tank to the outside environment will be sealed, and the ventilation system will be put into supercharge mode.<br />
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<a href="https://www.blogger.com/null" id="fire"></a>
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<h3>
<span style="font-size: large;">FIREFIGHTING</span></h3>
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The automatic fire extinguishing system is only installed in the engine compartment. It operates on four TD-1 thermal sensors placed strategically around the engine to ensure a higher chance of prompt detection. On paper, at least. There are two five-liter fire extinguishers containing halocarbon agent 114B connected to the automatic fire extinguishing system. The fire extinguishers and a single TD-1 thermal sensor can be seen in the photo below (TD-1 is on the left side of the frame, above the green tube)<br />
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<a href="http://4.bp.blogspot.com/-jC1qdKFV-z4/VnFDL1DSF8I/AAAAAAAAFHk/idCzM09npig/s1600/bmp%2Bpowerpack.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://4.bp.blogspot.com/-jC1qdKFV-z4/VnFDL1DSF8I/AAAAAAAAFHk/idCzM09npig/s640/bmp%2Bpowerpack.jpg" width="640" /></a></div>
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In addition to that, there is a single handheld OU-5 five liter carbon dioxide fire extinguisher placed in the passenger compartment. Not very effective, to be honest. If the vehicle was hit and the interior was on fire, the first thing to do would be to bail out and run, because any fire would probably escalate into a blaze, because of the centerline fuel tank. Although the BMP-2 is just as well armoured as any other IFV, it is distinctly worse off if the armour <i>were</i><i style="font-weight: bold;"> </i>penetrated.<br />
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<h3>
<span style="font-size: large;">PASSENGERS</span></h3>
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The BMP-2 is the communal steed for the nine men (including the crew) that comprise a typical Soviet motor rifle squad. On paper, the BMP-2 is designed to fit a maximum of ten people, but when employed as per doctrine, there will be one seat left empty. For dismounts, six men would be seated in the passenger compartment behind the turret, and the seventh - the squad leader - sits in the turret as the commander of the vehicle. The seat behind the driver is left empty unless a ten-man squad is deployed. The BMP occupied by the Platoon Leader is the so-called "Platoon Headquarters". This vehicle carries only two passengers, the Platoon Leader and the Assistant Platoon Leader.<br />
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The eighth man in a ten-man squad may be a MANPADS gunner attached to the vehicle from company assets, or some other specialist. One rifleman in one of the squads of the platoon may be a designated marksman, and issued an SVD instead of an AK-74. If a ten-man squad is deployed, it is possible to run the BMP-2 with a full three-man crew and have seven dismounts.<br />
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The composition of a typical dismount squad is as follows:<br />
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<blockquote class="tr_bq">
1 x Squad leader, BMP-2 Commander (Sergeant) (AK-74)<br />
1 x Grenadier (Private) (RPG-7, PM)<br />
1 x Assistant Grenadier (Private) (AK-74)<br />
1 x Machinegunner (Private) (RPK-74 or PKM)<br />
1 x Senior Rifleman (Corporal) (AK-74 with grenade launcher)<br />
1 x Rifleman/Designated Marksman (Private) (AK-74/SVD<br />
1 x Rifleman/Medic (Private) (AK-74)</blockquote>
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The maximum number of troops carried per vehicle is less than the eight passengers carried by the BMP-1 (shown below) by one, but this is not too bad as both the BMP-1 and BMP-2 carry a squad of the same size. The missing seat will result in a BMP-2 platoon carrying fewer specialist personnel like medics. However, this can be remedied by removing one of the riflemen and replacing him with a specialist. Overall, the fighting efficiency of a BMP-2-based Soviet motor rifle platoon increased substantially over one based on the BMP-1, mostly thanks to the higher power of the 2A42 cannon.<br />
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The firepower of a Soviet motor rifle platoon is quite similar to a U.S Army mechanized infantry platoon in most regards. The M2 Bradley could seat nine men; six of them being dismounts. As the commander of a Bradley Fighting Vehicle (BFV) does not dismount, a BFV platoon would be numerically inferior to a BMP platoon, but the IFV would be more potent due to having a full crew. However, this can be countered by deploying a ten-man BMP squad. If ten-man squads are deployed in the BMP platoon, the disparity would be even larger, and the BMP platoon would gain additional capabilities due to having a full crew.<br />
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A BFV squad should be slightly superior in issuing lead, since they have a belt-fed squad automatic weapon (M249) rather than a magazine-fed one (RPK), but this is offset by the extra rifleman in a BMP squad. With regards to anti-armour and anti-air firepower, a BMP platoon is significantly superior. As you may recall, there is a 9P135M missile launcher mounted at the back of the turret basket of the BMP-2. This 9P135M launcher can be used alongside the missile launcher on the BMP-2 and the RPG-7 carried by the grenadier to seriously increase the anti-armour and anti-bunker capabilities of the squad. In addition to that, the BMP-2 has a means of defence against air attack, as there is an extra seat that may be occupied by a dedicated MANPADS operator. Otherwise, the seat can be used to store extra supplies. The introduction of the M2A1 Bradley equalized the difference in manpower, as it carried seven dismounts as opposed to six, but the BMP squad's advantages in anti-armour and anti-air firepower remain. It was not until much later that the BFV platoon gained a decisive advantage with the introduction of the Javelin and the wide proliferation of the M240B.<br />
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The height of the hull is 1,210mm, the width of the hull (not including the sponsons) is 2,250mm and the bench on which three people are supposed to sit on is only around 1,400mm long. After subtracting the thickness of the roof and belly armour, the internal height of the hull at the passenger compartment is 1,197mm. The height of the hull would be considered good in a tank but only because the seats are typically mounted close to the floor and the occupants are provided with a certain amount of legroom. In the case of the BMP-2 (and BMP-1), the low height of the hull forced the seats to be mounted close to the floor but the hull is too narrow to permit the passengers to stretch their legs.<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-XoXfVWXNl6A/XzQCyqnIreI/AAAAAAAARdU/E1aBcm4zh6girCQ63oF_zplKIdaMAyxCACLcBGAsYHQ/s1280/afghan%2Bbmp-2%2Band%2Bm113.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="862" data-original-width="1280" src="https://1.bp.blogspot.com/-XoXfVWXNl6A/XzQCyqnIreI/AAAAAAAARdU/E1aBcm4zh6girCQ63oF_zplKIdaMAyxCACLcBGAsYHQ/s640/afghan%2Bbmp-2%2Band%2Bm113.jpg" width="640" /></a></div>
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With bulky body armour, personal firearms, hundreds of rounds of ammo or even winter clothing, a ride in the BMP-2 can be very oppressive indeed. For a short trip of half an hour or so, a seasoned soldier should have very little to complain about as it is certainly much better than walking, and on long marches in unattractive weather, it may even be luxurious, but the total lack of stretching room and the shoulder-to-shoulder arrangement becomes incredibly uncomfortable as time drags on. However, according to military historian Kenneth Estes, the BMP-1 actually met all U.S Army ergonomics requirements after evaluations were conducted on captured examples. It could be surmised that the designers sought to provide an acceptable level of comfort without compromising the mass and silhouette of the vehicle and succeeded.<br />
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The benches are well padded with thick cushions. The benches are mounted to the floor with a clearance of only about 20 cm, so passengers have to draw their knees up almost to chest level when seated, which is rather disconcerting, truth be told.<br />
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The real estate underneath the port side half-bench is perfectly sized for two "spam cans" of 5.45x39mm or 7.62x39mm ammo, or a crate of hand grenades, or a crate of 40mm grenades. The other half of the bench is a fuel tank with a cushion on it, so nothing can be stowed under it. The starboard side half-bench has the fuel pump underneath it, so no luck there.<br />
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The back of the seats nearest to the door are shelves. Stored inside is a fuse box, and some relay boxes. The bottom shelf is usually empty. "Spam cans" of ammunition can be stowed here. The photo below shows such a shelf in a BMP-1.<br />
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The squad leader is seated behind the driver, where the commander in a BMP-1 would be seated. The squad leader's seat is accessible through the rectangular hatch above it. The squad leader has the "privilege" of being provided with two periscopes. One aimed forward, and one aimed to the forward-left. The (low quality photo) view from the forward periscope is pictured below.<br />
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There is nothing else of interest in his station. It's worth noting, however, that being forced to use the hatch the exit the vehicle and not doors like the rest of the passengers makes the squad leader's station a poor place to be, as you'd not only take longer to dismount, you'd be exposed to all and sundry while you are on the hull roof, and you'd have to jump down from quite a height. It's also a lot harder to get out if you are wearing body armour or winter clothing. All this has made the squad leader's seat a rather unpopular one, so unsurprisingly, some BMP-2 operators have opted to cut the squad down to six men and omit the seventh passenger. Instead, his spot is used by the crew to stow their personal effects, plus extra ammunition and first aid kits and anything else that might be needed.<br />
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The passengers get one fixed TNPO-170A periscope each, aimed to the side and slightly forwards. The visibility from these periscopes is adequate for providing the passengers with a sense of their surroundings and can help them find targets to fire at from their firing ports.<br />
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Both of the rear doors have a single TNPO-170A periscope in them as well. (photo below is of Czech OT-90, but is identical)<br />
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The ventilation system of the BMP-2 is composed of four small air inlets located on the edges of the hull roof. Filtration of chemical and biological particles is accomplished by fabric-type filters inside. These ventilators are also responsible for generating an overpressure inside the vehicle when entering NBC-contaminated areas.<br />
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This ventilation system also has a heating system and directed air outlets for every passenger (<span style="color: #b6d7a8;">Green</span>) in front of the fume evacuation inlets (<span style="color: red;">Red</span>). The pipes for these systems can be seen here:<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-XLLk6VGKuDw/V1UDh82EB3I/AAAAAAAAGos/QngLbxkwctkwDNIvxZp3bOzzGcDRQr0lQCLcB/s1600/fume%2Bevacuator%2Bpipe%2Band%2Bventilation%2Bpipe%2Bbmp-2.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://1.bp.blogspot.com/-XLLk6VGKuDw/V1UDh82EB3I/AAAAAAAAGos/QngLbxkwctkwDNIvxZp3bOzzGcDRQr0lQCLcB/s640/fume%2Bevacuator%2Bpipe%2Band%2Bventilation%2Bpipe%2Bbmp-2.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">This is the interior of a BMP-2 "Berezhok". It lacks firing ports, so the fume evacuator hose for the passenger's weapon is missing </td></tr>
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As you can see, the air outlets are placed just next to a periscopes. This is approximately eye level, so each passenger gets a weak stream of cool air blown in his face. Heat for the heating system is not generated electrically, but by the circulation of water around the engine. It would get hotter when the vehicle is in motion, and less so when idling.<br />
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There is a narrow corridor between the driver's station and the passenger compartment. A similar corridor exists in the BMP-1, but that one is larger due to the smaller turret. Although it is incredibly narrow, it is still possible to pass through this corridor in the BMP-2. The corridor is useful when doing work in the vehicle, as it allows tools and parts to be transferred from the cramped driver's station to the passenger compartment, but otherwise, it is not to be used in normal operations. During combat, it should only be used in case of an emergency where exiting via the driver's hatch or the squad leader's hatch is not possible.<br />
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A similar corridor is present in the M2 Bradley.<br />
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A simple perimeter shield separates the turret from the passenger compartment, lest any accidents happen to the person sitting closest to the turret.<br />
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For the passengers in the passenger compartment, there are two entry and exit paths to choose from: the roof hatches, or the rear doors. The former option admits only one person at a time, and jumping down from almost six feet up isn't the most appealing idea when the vehicle is in motion, and even if the vehicle was static, the roof hatches are mostly used only under unusual circumsmtances, like if the vehicle is sinking in water. They are far more suitable for other things like getting fresh air, shooting at airplanes, and so on. The roof hatches are spring-loaded with torsion bar springs and locked in place with a simple lever. When a passenger turns the locking lever, the hatch springs open and it can be locked in the open position by pushing it further until it is held under spring tension. The less interesting option for dismounting the BMP-2 is, of course, the rear doors.<div><br />
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The infantry was perceived to be most effective if they disembarked at a range where they could use their weapons most effectively. Soviet strategists estimated the ideal disembarking distance to be between 200 and 400 meters. Stopping the vehicle to allow the infantry dismount at such a close distance to the enemy was simply not an option. The only way to stay alive in the absence of adequate cover was to keep moving, and keep shooting, so the infantry must disembark while the vehicle is doing this at a reduced speed. The current accepted convention of a ramp with a single door would not suffice, as the door would be suitable on the move, but would be (and it usually is, even in modern vehicles) too small too allow for the rapid exit of all of the passengers at a reasonable pace, and the wide ramp cannot be deployed on the move. The most optimal configuration for the expected role of the BMP as it was envisioned was a pair of wide doors. <div><br /></div><div>In <a href="https://arsenalen.se/katalog/pansarbandvagn-pbv-302/">the entry on the Pbv 302 armoured personnel carrier</a> in the official website of the Swedish Arsenalen museum and in <a href="https://www.ointres.se/pbv_302.htm">the Pbv 302 article on the Ointres website</a> by Rickard Lindstrom, it is stated that Swedish trials found that the passengers could dismount faster with two rear doors instead of a powered ramp like on the M113. Initially, an early prototype of the Pbv 302 had been fitted with a powered ramp inspired by the M113, but they were abandoned shortly afterward. The serial Pbv 302 had two rear doors, like the Soviet BMP and MT-LB.<br /><div><br /></div><div>In terms of size, the doors are comparable to commercial automobiles. They measure 0.865 meters tall and 0.8 meters wide, almost as tall and almost as wide as the doors of a Lada Riva, and almost as tall as the doors on a Volkswagen Golf.<br /><br />
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The interior volume of the BMP-2 is small, so the amount of space relegated to stowage is also small. There is practical no surplus at all. All available spaces are used efficiently. The backrest of the seat closest to the door is designed with a shelf inside it. Here, a predetermined quantity of ammunition and grenades can be stowed. These are twelve F-1 defensive hand grenades, 700 rounds of 7.62x39mm rounds, a single 200-round box for a PKM machine gun and a single container of loose 440 rounds of 7.62x54mm rounds. There is also a hook to hang a bag of rocket grenades for the RPG-7, and as mentioned in earlier, there are racks for a single RPG-7 and a single Strela or Igla MANPADS launcher. <br />
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<h3>
<span style="font-size: large;">DRIVER'S STATION</span></h3>
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The driver's seat is well-cushioned and it can be adjusted in height to enable the driver to remain below the hatch or to drive with his head out. The backrest is adjustable in the angle of inclination and it can be folded out flat so that it does not obstruct the driver's path to the passenger's station behind him.<br />
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<div><br /></div><div><br /></div>Overall, the dimensions of the driver's station are adequate, though it may feel narrow depending on the bulkiness of the driver's clothing. The length and height of the station are more than adequate, and the layout of the controls is convenient.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-a4GRtd9bsBY/XyeO5Q5Tn8I/AAAAAAAARao/ttJFEbwvRiMSNNYjgZAIexebv3iq7ulcQCLcBGAsYHQ/s1440/training%2Bstation%2B2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1079" data-original-width="1440" height="300" src="https://1.bp.blogspot.com/-a4GRtd9bsBY/XyeO5Q5Tn8I/AAAAAAAARao/ttJFEbwvRiMSNNYjgZAIexebv3iq7ulcQCLcBGAsYHQ/w400-h300/training%2Bstation%2B2.png" width="400" /></a><a href="https://1.bp.blogspot.com/-ibDeIgtNIjo/XyeO-duAMkI/AAAAAAAARas/h4vhNOXgt88Ple8t0gWTbczzbmvwWfO0wCLcBGAsYHQ/s1440/training%2Bstation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1440" height="300" src="https://1.bp.blogspot.com/-ibDeIgtNIjo/XyeO-duAMkI/AAAAAAAARas/h4vhNOXgt88Ple8t0gWTbczzbmvwWfO0wCLcBGAsYHQ/w400-h300/training%2Bstation.png" width="400" /></a></div><div><br />
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<a href="https://2.bp.blogspot.com/-CZ2Blp6d2yQ/VrdPQWYWy7I/AAAAAAAAFuU/2fkR_jDSz-M/s1600/bmp_driver.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em; text-align: center;"><img border="0" height="400" src="https://2.bp.blogspot.com/-CZ2Blp6d2yQ/VrdPQWYWy7I/AAAAAAAAFuU/2fkR_jDSz-M/s400/bmp_driver.jpg" width="270" /></a>Driving the BMP-2 was much easier than driving Soviet tanks of the era. This is because of the motorcycle bar-style steering wheel, which is reportedly extremely responsive thanks to a very good power steering system, making it is very easy to control the BMP-2 over rough terrain.<br />
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As befitting the high speed of the BMP-2, the driver was given four TNPO-170 periscopes in order to safely control the vehicle. Three of the periscopes cover a 120 degree frontal arc and another is aimed to the left. This gives the driver a sufficiently large field of view to maneuver the vehicle confidently in densely forested areas. The one downside of the vehicle's design is that the sloped upper glacis is at such an angle for the sake of protection and hydrodynamic stability that it also creates a rather large blind spot directly in front of the vehicle for the driver. The center periscope can be removed from inside the vehicle and replaced with an nightvision periscope. The TNPO-170 periscopes offer a rather small field of vertical vision compared to what the driver of, say, an M2 Bradley gets, but the width of the periscopes is sufficient.<br />
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Oddly enough, they didn't seem to think that wipers or screen blowers were necessary. The geometry of the front slope has some positive influence on the amount of dirt and grime that ends up on the periscopes while driving, but some former BMP-2 drivers have complained of the inconvenience of not being able to wipe it off when buttoned up.<br />
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The driver can replace his TNPO-170A periscope with a TVNE-1PA infrared periscope for night driving. Used in tandem with the small infrared headlamp, the driver can see as far as 60 meters using this periscope. Not far enough to drive at 60 km/h, perhaps, but far enough that he has enough time to avoid obstacles while driving at around a crawl. The field of view from the periscope is very narrow, and the dependence on infrared light for illumination is a major weakness.<br />
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The TNP-350B periscope is used while swimming. It is 350mm tall which is tall enough to look above the trim vane when it is extended for swimming. The field of view from the TNP-350B is very limited due to the height of the periscope, so the driver cannot navigate by himself when negotiating larger bodies of water. The commander must help from his vantage point in the turret. However, the TNPO-170A periscope to the driver's left can still be used when swimming so the driver is not entirely confined to the single TNP-350B in front of him.<br />
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In terms of comfort, the driver's station is satisfactory. His station is widest at the top and narrowest at the feet because of the left hull sponson.<br />
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The driver is also supplied with a GPK-59 gyrocompass to help him navigate at night.<br />
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<a href="https://www.blogger.com/null" id="mob"></a>
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<h3>
<span style="font-size: large;">ENGINE, TRANSMISSION, SUSPENSION, MAINTENANCE</span></h3>
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Some accusations have been leveled at the BMP-2 concerning its armament, its armour, and its (lack of) amenities, but its mobility has never been in question, and for very good reason.<br />
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Contrary to what some sites may claim, the BMP-2 mounts the very same UTD-20 diesel engine that powered the BMP-1, not a more powerful one. The UTD-20 or UTD-20S1 produces 300 hp at 2,600 rpm, with a maximum torque output of 981 N.m at 1,500 rpm to 1,600 rpm which is very good for the weight of the vehicle. The high torque output grants the BMP-2 excellent acceleration characteristics on challenging terrain and together with the relatively narrow tracks, allows the vehicle to steer with ease. The engine alone weighs 665 kg dry. It has a specific fuel consumption rate of around 175 g/hp.h to 178 g/hp.h. The dynamic characteristics of the UTD-20 are shown in the chart below, taken from a BMP-1 manual. The top left of the chart shows the gross power output in horsepower, the middle right of the chart shows the gross torque output in kg.f, and the bottom right of the chart shows the specific fuel consumption rate.<br />
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There are two ways to start the engine. The standard method is, of course, the electric ignition switch, but that tends to be useless in extremely cold weather. To start the engine in such conditions, the BMP-2 gets the traditional compressed air tanks commonly found on tanks since the T-34. These air tanks blast air into the combustion chambers to get the pistons working and burning diesel once more.<br />
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The engine air intake is shared with the ventilation air intake, with the common intake being located behind the turret. The air cleaner itself is in the engine compartment, below the ejector cooling system duct. The intake housing can be raised when swimming, to ensure that water does not enter the air intake ducts. Coarse and fine air filtration is accomplished by a single-stage multi-cyclone air cleaner, which ensures that the engine receives air with a purity of 99.5%. The dust collected by the multi-cyclone filters is collected in a pan, where it is blown into the exhaust stream of the engine exhaust due to the negative pressure.<br />
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<div><br /></div><div><br /></div><div>The ejector duct is where the air flow through the radiators, the exhaust, and the dusty air from the filters will mix together and flow out. The exhaust manifolds from the engine, represented by the mark (12) in the diagram below, provide a flow of high-velocity, hot exhaust, which generates a strong negative pressure in the duct. This draws atmospheric air through the radiators placed above the exhaust. From there, the mixture is expelled through a specially shaped duct. Due to the shape of the duct, the angle of the exhaust vents, and the constant supply of exhaust from a running engine, there is effectively no danger of engine flooding from natural sources of water ingress, including rain and waves (when the BMP is swimming). Water is not allowed to pool at the bottom of the duct, as the flow of air will rapidly blow it out. Similarly, flaming liquids, such as burning fuel, do not have any entrypoint to the drivetrain. If the engine stops and the flow of exhaust gasses cease, the engine is protected by exhaust manifold valves.</div><div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhEkTHsguQE2JqXian9pGq92W3Ah1l847Tggc7PCRAsnkjljr3zYOidiGpLTDy7AFWGss-CDHlGoRPs5wXa5oQ9EKdQVmDg5remjiB9msfDMloMUBeZPDPNVYSGXcn_TFtSRViCFNKkWXHDU81YmYJ9owcG5OUNVWgkaw-7BKOEiDx4wXrKZr8yZFv7Bw/s1478/ejector%20cooling%20duct%20diagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="946" data-original-width="1478" height="205" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhEkTHsguQE2JqXian9pGq92W3Ah1l847Tggc7PCRAsnkjljr3zYOidiGpLTDy7AFWGss-CDHlGoRPs5wXa5oQ9EKdQVmDg5remjiB9msfDMloMUBeZPDPNVYSGXcn_TFtSRViCFNKkWXHDU81YmYJ9owcG5OUNVWgkaw-7BKOEiDx4wXrKZr8yZFv7Bw/s320/ejector%20cooling%20duct%20diagram.png" width="320" /></a></div>
<div><br /></div><div>When the BMP has been parked in the rain without a radiator and exhaust cover, water can pool up inside the ejector duct. Before starting the engine, the water must be drained from the duct using the drainage port, marked (32) in the image above.</div><br />
The picture below shows the transmission. There is power steering. Braking is hydraulic. The transmission and the engine are built together as a single powerpack unit, thus simplifying replacements in the field.<br />
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Much has been said about the excellent speed and agility of the BMP-2, and every private owner of one would agree, but according to enlisted crewmen, there are some points about it that make the situation a little bit greyer. The main issue is that the suspension is not exactly top-notch. Due to the increased weight from the new turret, it was deemed necessary to reinforce the torsion bars for the frontmost pair of roadwheels as well as the rearmost pair, as these would experience the majority of the strain when driving into dips and dives. However, it is still too light, and the stinginess with the shock absorbers mean that the vehicle tends to oscillate more than expected from this type of vehicle. Later production model BMP-2s received an extra shock absorber on the second roadwheel, but most of them only had two; one on the last roadwheel and another on the first. The transmission isn't world class either. It's good enough, but the vehicle tends to lurch when starting off and the clutch is not very responsive. An experienced driver may find these to be very minor problems, but coupled with the substandard suspension and the common practice of slowing down to a crawl to engage targets before speeding off again, the BMP-2 is highly unsuitable for anyone prone to seasickness.<br />
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However, it's definitely not all bad news. The torque output and low speed characteristics are marvellous, so the BMP-2 has superb passability over rough terrain at average cross country speeds of 20 km/h to 35 km/h. According to private owners, the BMP-2 is also extremely agile. Its obstacle crossing capabilities are quite standard. It can climb a vertical slope of 35 degrees, traverse a side slope of 20 degrees, and climb a vertical wall 0.7 m in height, but not more, due to the overhang of the nose of the hull. The BMP-2 can cross a trench 2 .5m in width by driving over it at low speed, but it can cross much wider tranches by literally jumping over them, which isn't very difficult for it to do.<br />
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Still, keep in mind that nothing is infallible. The BMP-2 can still get stuck, just like any other vehicle, though it is definitely not anywhere close to being overweight. Its thin tracks might be a liability for some other platform, but thanks to the compressed design of the BMP-2, it only exerts a ground pressure of 0.65 kg/sq.cm when combat loaded. The Marder 1, with its much wider tracks, still cannot escape the fact that it is about 2 times heavier than the BMP-2. The Marder 1 exerts 0.83 kg/sq.cm of ground pressure.<br />
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The tracks, torsion bars and drive sprockets were not carried over from the BMP-1, despite being almost indistinguishable from one other aesthetically. Besides the frontmost and rearmost torsion bars being reinforced, the tracks are of a different type. Unlike the old type, the BMP-2's tracks can accept rubber track pads for driving on asphalt, and they have contact needles for better grounding of the radio, thus apparently reducing radio interference. Not too sure how this works, though. The roadwheels were also replaced with sturdier ones that could better handle the stress from the greater weight of the BMP-2. It should also be mentioned that the this combination of three upgrades gave the vehicle an extra 50mm of ground clearance over the BMP-1, so that the BMP-2 has a ground clearance of 420mm. This means that the vehicle can be driven with more authority over rocky or lumpy terrain, as there is less chance of the hull floor scraping against the ground.<br />
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If the BMP is stuck fast in some soft sand or in sticky mud, which is rare, it is possible for it to extricate itself with the use of the famous log. The video below demonstrates how it is done. You can see for yourself how invaluable the log can be.<br />
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<a href="https://www.blogger.com/null" id="maintenance"></a>
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<h3>
<span style="font-size: large;">MAINTENANCE</span></h3>
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More than 90% of all maintenance can be done by simply lifting the engine access panel on the upper glacis. Its lightweight aluminium construction and hinged mounting makes it into sort of an oversized bonnet. Two men could hinge it open easily. The photo below shows NVA personnel having a look under the hood of their BMP-1s.<br />
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The radiator is slightly less convenient to access. The access hatches are bolted and hinged like the engine access panel, but the size of the hatches are somewhat smaller. The entire radiator deck will have to be unbolted and lifted with a small crane in orer to replace a broken radiator.<br />
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Most would opt to lift the engine access panel to do regular scheduled maintenance, but doing that is not the only way of getting to the engine. Inspections and oil top-ups may be done without leaving the vehicle by opening the insulated bulkheads separating the engine compartment from the inhabited compartments. The small one-man turret of the BMP-1 made accessing the rear engine bulkhead hatch from the passenger compartment relatively easy, but the wider turret and the missile stowage racks made this impossible, but this is no big loss. You could still get to it just as easily from the commander's station, where it would be right in front of you, as you can see below. This hatch allows you to see the rear part of the engine, the radiator pack, and the air compressor used to fill up the compressed air tanks used for starting the engine.<br />
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<a href="https://1.bp.blogspot.com/-JGhQFAPZjPE/V1IODxQJ5cI/AAAAAAAAGeQ/tQ_gic_6p-U3UV2vrbSpy9x6fx9W53cKQCLcB/s1600/bmp-2%2Bengine%2Bbulkhead.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="358" src="https://1.bp.blogspot.com/-JGhQFAPZjPE/V1IODxQJ5cI/AAAAAAAAGeQ/tQ_gic_6p-U3UV2vrbSpy9x6fx9W53cKQCLcB/s640/bmp-2%2Bengine%2Bbulkhead.png" width="640" /></a></div>
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The hatches on the driver's station fireproofed bulkhead allows him to inspect the engine itself. An experienced driver-mechanic can diagnose and troubleshoot a faulty powertrain directly from his station. An opened bulkhead hatch can be seen in the "Driver's Station" section.<br />
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Electricity in the vehicle is supplied by two 6STEN-140M or 6ST-140R accumulator batteries connected in series, with a combined capacity of 140 Ah. Each battery weighs 62kg.<br />
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The BMP-2 is considered an extremely dependable vehicle, despite early concerns with the BMP-1 of over complexity due to the steering system. Private owners of de-militarized BMPs have spoken of their satisfaction on hobby forums, and the BMP-2 has a very good reputation in military service.<br />
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<a href="https://www.blogger.com/null" id="fuel"></a>
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<h3>
<span style="font-size: large;">FUEL ENDURANCE</span></h3>
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The BMP-2 has five fuel tanks; three internal tanks and two rather infamous exterior ones - the rear doors, which we have already talked about quite a bit. The port side rear door holds 55 liters and the starboard side door holds 67 liters (the port side door has less as it has a firing port embedded in it). The main tank in the passenger compartment - which forms half of the partition splitting the passenger compartment into halves - holds 225 liters.<br />
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The D-100 fuel pump is located underneath the seat of the starboard side bench closest to the door. It is a reasonably sized pump, running on 150W. The vehicle in the photo below is a Czech OT-90, but the pump is the same model and in the same location. The fuel pump has yellow tubes running out of it.<br />
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<a href="https://2.bp.blogspot.com/-PVZx0xtW0I0/V1U0em0f8LI/AAAAAAAAGrA/a1uN8eavPUwIT8LrwP8OLYYO8fjPko_oACLcB/s1600/100_0109-1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://2.bp.blogspot.com/-PVZx0xtW0I0/V1U0em0f8LI/AAAAAAAAGrA/a1uN8eavPUwIT8LrwP8OLYYO8fjPko_oACLcB/s640/100_0109-1.jpg" width="480" /></a></div>
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Because the bench was shortened to seat only three passengers as opposed to four as in the BMP-1, it became necessary to add an additional two fuel tanks to compensate for the reduced main tank capacity. In some hilariously misguided attempt to store as much fuel as possible in the passenger compartment, these two tanks are made to be half of the bench on either side of the passenger space, meaning that one passenger on either bench will be seated on a fuel tank. The port side tank can be seen below:<br />
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<a href="http://2.bp.blogspot.com/-7ZiPw3etEpk/VlMRMQs1slI/AAAAAAAAEbA/O3I-PhVnPBU/s1600/bmp-2%2Bpassenger%2Bspace.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://2.bp.blogspot.com/-7ZiPw3etEpk/VlMRMQs1slI/AAAAAAAAEbA/O3I-PhVnPBU/s640/bmp-2%2Bpassenger%2Bspace.png" width="640" /></a></div>
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The port side tank holds 55 liters and the starboard side tank holds 58 liters.<br />
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With all fuel tanks filled, the BMP-2 has a maximum cruising range of 600 km on paved roads. That means that if the highways were clear, you could drive from Berlin to Cologne on a single tank! But no one really expects that to happen. Indeed, armoured vehicles on the frontline don't really get to drive around much once they reach contested territory, so why carry around so much fuel? Well, a generous cargo of fuel means that a BMP-2 could fight for two to three days in a continuous, unstoppable offensive push on a single fill of fuel, giving it a great deal of independence and autonomy in the field. It becomes possible to conduct a deep penetration offensive or counterattack with minimal supporting assets like fuel trucks and bridgelayers, though obviously these assets are still very necessary, but among all the other little details and idiosyncrasies of its construction, this one is perhaps the best proof that BMP-2 was designed with just that one, single objective in mind - continental domination. One of the other details designed with the same intent in mind, as many should already know, is its amphibious capabilities.<br />
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<a href="https://www.blogger.com/null" id="water"></a>
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<h3>
<span style="font-size: large;">WATER OBSTACLES</span></h3>
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The BMP-2 is almost as adept in the water as it is on land. In fact, several compromises had to be made to the structure of the hull for the sole purpose of improving its performance in the water, including the slight tapering of the passenger compartment <a href="http://www.military-today.com/apc/bmp2_l2.jpg">(see here)</a>, which reduced the amount of stowage space for the person sitting closest to the rear doors, but also reduced drag. The short and stubby bow of the original BMP from 1966 gave the driver a good view of what was in front of the vehicle when driving, but the bow was too short to properly enter rivers from a steep bank, as the bow would tip too deeply into the water, so the bow was lengthened. This created a large blindspot in front of the BMP, but made it possible to enter bodies of water from any angle. Suffice to say, they took this requirement quite seriously.<br />
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<a href="http://2.bp.blogspot.com/-rZNJwUqbujg/VlMPOUJ2jyI/AAAAAAAAEa0/ydoX_BR-NIg/s1600/bmp-2%2Bcrossing%2Bwater.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-rZNJwUqbujg/VlMPOUJ2jyI/AAAAAAAAEa0/ydoX_BR-NIg/s1600/bmp-2%2Bcrossing%2Bwater.jpg" /></a></div>
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Propulsion in water is produced by the flowing of water around the tracks being channeled rearwards with the use of a special aluminium alloy hydrodynamic grille which is placed where the rear fenders usually are. The rearwards stream of water produces forwards thrust. The faster the tracks move, the more the water that flows through the hydrodynamic grilles. This system is the same as in the M113 in principle - movement of the tracks in water - only better optimized thanks to the addition of the grilles and the more hydrodynamic shape of the hull.<br />
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As one might expect, one of the biggest dangers while swimming is that cannonfire punctures the hull and springs a leak. This is not normally possible, since the only parts of the vehicle that are liable to get hit are above water, and since they are above water, the only way water could get in is if the waves are tall enough to wash over the hull, and even then the rate of the inflow of water isn't really worth worrying about if the holes are nickel-sized, which would be how big of a hole you'd get if hit by a shaped charge grenade. Still, these are other, distinct hazards, like large caliber artillery shells exploding right next to the vehicle and rupturing weld seams. In the unlikely event of something like that occurring, the vehicle is insured by a pair of MBP-2 bilge pumps located underneath the squad leader's seat. The bilge pumps are electrically powered and run on 300W each. It is powerful enough to suck in water from the floor of the hull and eject it out through a small valve on the belly of the hull. If it is not enough to keep the vehicle afloat until it reaches the shore, the bilge pumps can at least buy the passengers and crew enough time to bail out through the various hatches on the roof of the vehicle and swim to safety.<br />
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Just as with the BMP-1, the ventilator must be erected and the trim vane must be extended before entering water. The ventilator is telescopic, allowing it to be taller than the turret when fully extended while keeping deck penetration at a minimum.<br />
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<a href="https://2.bp.blogspot.com/-uc30IRv_6lE/WLjpSUwGHBI/AAAAAAAAIds/WCqR6JUITZwc9bqH_4asn2XEGvwGOWUHwCLcB/s1600/snowy%2Bbmp-2.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" src="https://2.bp.blogspot.com/-uc30IRv_6lE/WLjpSUwGHBI/AAAAAAAAIds/WCqR6JUITZwc9bqH_4asn2XEGvwGOWUHwCLcB/s1600/snowy%2Bbmp-2.jpg" /></a></div>
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The ventilator tube is tall enough that the air inlet will remain dry even in rough seas.<br />
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<a href="http://1.bp.blogspot.com/-CCLDznfFruU/VlHGwVc5DHI/AAAAAAAAEW8/psYD8pBVsgE/s1600/bmp-2%2Bswimming.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="403" src="https://1.bp.blogspot.com/-CCLDznfFruU/VlHGwVc5DHI/AAAAAAAAEW8/psYD8pBVsgE/s640/bmp-2%2Bswimming.jpg" width="640" /></a></div>
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Because the hull design of the BMP-2 was not altered despite the weight gain, it became necessary to revise the fenders and sideskirts to add foam filled flotation aids to boost the vehicle's buoyancy.<br />
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<a href="https://4.bp.blogspot.com/-E1velZh8vWY/V0yudm23sqI/AAAAAAAAGaw/Qqw7iyblyqQMJfujZk6TAEggJEefnlBmACLcB/s1600/BMP-2_img_2315.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="396" src="https://4.bp.blogspot.com/-E1velZh8vWY/V0yudm23sqI/AAAAAAAAGaw/Qqw7iyblyqQMJfujZk6TAEggJEefnlBmACLcB/s640/BMP-2_img_2315.jpg" width="640" /></a></div>
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Here is proof that the fenders and skirts are in fact solid:<br />
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<a href="https://2.bp.blogspot.com/-RVomOWvLGnw/V1TshZI_SLI/AAAAAAAAGn0/R542tncthRsCMdmhKokKxGRqkDHqpTqsQCLcB/s1600/berlin-3-0042.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://2.bp.blogspot.com/-RVomOWvLGnw/V1TshZI_SLI/AAAAAAAAGn0/R542tncthRsCMdmhKokKxGRqkDHqpTqsQCLcB/s400/berlin-3-0042.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-2BMs7TUmg7w/V1XhMygKUjI/AAAAAAAAGtU/b4EOyijEr8UgHKkj_nu-j0tb--mbkuI4gCKgB/s1600/image0002.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://3.bp.blogspot.com/-2BMs7TUmg7w/V1XhMygKUjI/AAAAAAAAGtU/b4EOyijEr8UgHKkj_nu-j0tb--mbkuI4gCKgB/s400/image0002.jpg" width="300" /></a></div>
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Thanks to full two-plane stabilization for the 2A42 cannon and its inherent adeptness at providing suppressive fire, the BMP-2 can launch an accurate and relentless attack on coastal or riverbank targets with all weapons (including the ATGM) while swimming, which may contribute to ensuring a successful landing operation. It is also possible for the passengers to fire out of their firing ports, which is somewhat more effective in water than on land since the vehicle really can't possibly go much faster than 7 km/h, and if the water is not still enough to use the firing ports, it is not safe for the BMP-2 to swim in that water.<br />
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<a href="http://4.bp.blogspot.com/-pgChT8P_qQc/VlNDfvoOVjI/AAAAAAAAEcY/KN-OUE80gRc/s1600/bmp-2%2Bamphibious.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://4.bp.blogspot.com/-pgChT8P_qQc/VlNDfvoOVjI/AAAAAAAAEcY/KN-OUE80gRc/s400/bmp-2%2Bamphibious.jpg" width="400" /></a></div>
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Testing of the speed at which the BMP-1 could cross water obstacles was brutal. There was an incident where during a high speed water entry, the BMP flew into the water, bellyflopped, and burst the floor. Water rushed into the vehicle and sank it. After that, the floor was reinforced with additional ribs to improve structural strength. This is why the BMP can safely do this (skip to 1:36):<br />
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<iframe allowfullscreen="" class="YOUTUBE-iframe-video" data-thumbnail-src="https://i.ytimg.com/vi/FjYbmIzMfJk/0.jpg" frameborder="0" height="266" src="https://www.youtube.com/embed/FjYbmIzMfJk?feature=player_embedded" width="320"></iframe></div>
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<a href="https://www.blogger.com/null" id="dist"></a>
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<h3>
<span style="font-size: large;">DISTRIBUTION</span></h3>
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<a href="https://2.bp.blogspot.com/-TpIQR9pEXJ4/V0y18zDmYiI/AAAAAAAAGbI/d6ur40kAGYQqeDo1mbxKriooEUx2gl7xACLcB/s1600/bmp-2%2Bon%2Bthe%2Bproduction%2Bline.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-TpIQR9pEXJ4/V0y18zDmYiI/AAAAAAAAGbI/d6ur40kAGYQqeDo1mbxKriooEUx2gl7xACLcB/s1600/bmp-2%2Bon%2Bthe%2Bproduction%2Bline.jpg" /></a></div>
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Thanks to bureaucratic depravity, the BMP-2 was introduced far later than it could have, and should have been, and that impacted the number of units the USSR managed to churn out prior to its disintegration. Still, as I've already said in the introduction, Kurganmashzavod produced about 14,000 BMP-2s in the space of 9 years, that is, from 1980 to 1989. At the peak of production in 1989, between 1,800 to 2,000 units exited factory gates, three times higher than the highest ever annual rate of production of the M2 Bradley. This information comes courtesy of a declassified CIA report available here (<a href="https://www.cia.gov/library/readingroom/docs/DOC_0000498688.pdf">link</a>). <a href="https://www.forecastinternational.com/archive/disp_pdf.cfm?DACH_RECNO=453">According to Forecast International</a>, serial production of the BMP-2 was wrapped up in the Russian Federation and in Slovakia in 2008. No new units have been produced by any major contractor since then, but modernization efforts have been ongoing in India and other operator nations for years. Forecast International estimates that a sum total of 33,939 BMP-2 and BMP-2 variants have been produced since its inception in 1980. According to them, a new-production Russian BMP-2 costs $404,000 in 2007 U.S Dollars, and used Russian BMP-2s are available at the jaw-dropping price of $78,000. India's domestically produced "Sarath" costs $398,000 apiece.<br />
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In some ways, the BMP-2 can be considered the "T-72 of IFVs". They are a close second to the most mass-produced vehicle of its type (the BMP-1), just like the T-72, and just like the T-72, the BMP-2 is obsolete, but still very, very capable even in this day and age, and even more so if upgraded and evolved a la T-90A. Speaking of the BMP-1, it should be mentioned that although the production of the BMP-2 was deliberately curtailed by internal strife, it still managed to end up to compete closely with its predecessor in numerical strength within the ranks of the Red Army, though came as close as it is only in recent years. Production of the BMP-1 ended very soon after the introduction of the BMP-2 - a development catalyzed by the superior combat performance of the latter in Afghanistan.<br />
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The fact that a whopping 34 nations are operators of the BMP-2 says something about its desirability, and also the eagerness of the Soviet Union to sell to whomever they could. These sales were often for political reasons, sometimes with trade agreements on the side and promises of "enduring friendship", but discounts and package promotions are simply not the only reason for the popularity of the BMP-2. If this is not evident to you after reading this article, feel free to talk about it in the comments section below.</div></div></div></div></div><div><br /></div>Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com25tag:blogger.com,1999:blog-3103574899092646031.post-60192062745923900642016-02-23T04:46:00.005-08:002022-05-02T10:20:52.336-07:00T-80<head>
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<a href="http://3.bp.blogspot.com/-rwviacnJLUQ/VqJmEoyRSmI/AAAAAAAAFbA/1l7SoSRdvtI/s1600/t-80%2Btankograd.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="282" src="https://3.bp.blogspot.com/-rwviacnJLUQ/VqJmEoyRSmI/AAAAAAAAFbA/1l7SoSRdvtI/s640/t-80%2Btankograd.png" width="640" /></a></div>
<h2 style="text-align: center;">
</h2>
<div style="text-align: center;">
<span style="font-size: xx-small;"><i>With contributions by Mike Ennamorato, including this introduction.</i></span></div>
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Although the T-80 is mostly remembered in the Western world for its lackluster performance during the invasion of Grozny, there was once a time when it was one of the most highly regarded assets in the vast Soviet tank fleet. In terms of technological novelty and sophistication, the T-80 was the top of the line and primarily distinguished itself from the T-64 and T-72 by having a gas turbine engine. Thus, by the end of the 1970's, the Soviet Army was the only army in the world to simultaneously operate three different main battle tanks with three different engines: an opposed piston diesel multifuel engine, a traditional V-shaped diesel multifuel engine, and a gas turbine multifuel engine.<br />
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As one should come to expect from anything on the other side of the Iron Curtain, the inception of the T-80 is rather intriguing story. While the Kharkov engineers were still ironing out issues with the 5TDF opposed-piston engine for the T-64, experiments on mounting a turboshaft engine were already in full swing. It was requested that production expand from just Kharkov (KMDB) to Kirov (LKZ) and Nizhny Tagil (UKBTM) as well. Both of the latter plants struggled to produce some of the more complex parts for the T-64 - namely the engine - due to a lack of personnel familiar with the intricacies of the fundamentally different engine, and hence, created their own variations of the basic T-64. UKBTM and LKZ split design elements and ended off designing what came to be known as the T-72 and T-80 respectively. LKZ's progeny were defined by their signature turbine engines and more robust suspension as well as a revised hull in order to accommodate the larger engine compartment and new suspension. The new hull was hybridized with the turret of the T-64A, thus forming the original model T-80. The early Object 219 sp.1 prototypes (of which few were produced) bore an even closer resemblance to the T-64A, as it was practically the same tank with the exception of the enlarged engine compartment and the different engine.<br />
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Upon entering service after extensive testing alongside its cousins the T-64A and T-72 in various climates, it was clear that this new vehicle was far more extravagant and expensive than the ones preceding it, making the T-80 much less common than its counterparts. It also came off as being a more ambitious project than T-72 (evidenced by a far longer development span). However, the final production model T-80 (Object 219 sp.2) came too late for its own good. The instant it entered low-rate production in 1976, it was already surpassed in capability by both the T-64B and T-72A: a troubling situation for a vehicle meant to replace and supplement them, made worse by its excessive price tag. As a result, the T-80B was quickly ushered into service a mere two years after the T-80, boasting the ability to fire ATGMs from the cannon while on the move with the Kobra system, and an updated armour layout that had better prospects against the latest and future anti-tank munitions. Beginning in 1980, a more powerful 1100 hp GTD-1000TF engine was installed in all new-production tanks. These upgrades along with the addition of Kontakt-1 explosive reactive armour and a further enhanced composite armour package formed the basis of the T-80BV, which arrived in 1985. The most advanced direct T-80 variant - the T-80U, arrived in 1986, and came with the revolutionary but flawed Kontakt-5 heavy reactive armour package. This new model presented improvements to just about everything; a new digital fire control system, engine, explosive reactive armour, and some other tidbits. Some late model T-80BV tanks had the T-80U turret installed but retained the familiar coat of Kontakt-1.<br />
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So without any further ado, let us dive deep into the intricacies of the T-80.<br />
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<h3>
<span style="font-size: large;">Table of Contents</span></h3>
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<hr />
<ol>
<li><a href="#comstat">Commander's Station</a></li>
<li><a href="#gunstat">Gunner's Station</a></li>
<li><a href="#tpd">T-80 Fire Control System</a></li>
<li><a href="#1a40">T-80B Fire Control System</a></li>
<li><a href="#1a45">T-80U Fire Control System</a></li>
<hr />
<li><a href="#stabs">Stabilizers</a></li>
<li><a href="#2e28m2">2E28M2 "Sireneviy"</a></li>
<li><a href="#2e42m1">2E42M1</a></li>
<li><a href="#autoloader">Autoloader</a></li>
<li><a href="#loose">Loose Stowage</a></li>
<li><a href="#cannon">Cannon</a></li>
<li><a href="#missiles">Missiles</a></li>
<li><a href="#pkt">PKT Co-axial Machine Gun</a></li>
<li><a href="#aa">NSVT Anti-Aircraft Machine Gun</a></li>
<hr />
<li><a href="#prot">Protection</a></li>
<li><a href="#t-80">T-80</a></li>
<li><a href="#t-80b">T-80B</a></li>
<li><a href="#t-80bv">T-80BV</a></li>
<li><a href="#k1">Kontakt-1</a></li>
<li><a href="#k5">Kontakt-5</a></li>
<li><a href="#smoke">Smoke Screen</a></li>
<li><a href="#firefighting">Firefighting</a></li>
<li><a href="#nbc">NBC Protection</a></li>
<hr />
<li><a href="#driver">Driver's Station</a></li>
<li><a href="#trans">Transmission, Suspension</a></li>
<li><a href="#engines">Engines</a></li>
<li><a href="#water">Water Obstacles</a></li>
<li><a href="#fuel">Road Endurance</a></li>
</ol>
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<h3>
<b><br /></b><b>As of 23 February 2019, this article is still undergoing minor renovations. If there are any errors or inconsistencies, feel free to write them down in the comments section</b></h3>
<h3>
<b>The section on the armour protection of the T-80 and its variants - specifically the T-80U - can only be considered a rough guideline as of February 2019. It is still being renovated pending further research.</b></h3>
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<a href="https://www.blogger.com/null" id="comstat"></a>
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<h3>
<span style="font-size: large;">COMMANDER'S STATION</span></h3>
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<a href="http://1.bp.blogspot.com/-0qS8Y74-o80/VqScY_QaVSI/AAAAAAAAFdQ/1m856SjXz0g/s1600/t-80b%2Bcommander%2527s%2Bhole.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="302" src="https://1.bp.blogspot.com/-0qS8Y74-o80/VqScY_QaVSI/AAAAAAAAFdQ/1m856SjXz0g/s640/t-80b%2Bcommander%2527s%2Bhole.png" width="640" /></a></div>
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The commander is seated on the right hand side of the turret and enters through a relatively tight clamshell-shaped hatch. The hatch is sprung with a torsion spring to make it easier for the commander to open the heavy armoured hatch, and the hatch offers protection from bullets when locked in the open position. If the commander wants to fight outside the hatch or simply take in the his surroundings with his head out and a pair of binoculars, he is almost fully shielded from sniper fire from the front, and the hatch can be spun around along with the cupola to face any direction.<br />
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Just like with the T-64 before it, accommodations for the commander are relatively spartan but still objectively superior to the T-54 and T-62 medium tanks. The commander's seat is well padded and adjustable in height and legroom is not in short supply, but there are not many concessions for width below waist level. This is due to the layout of the MZ autoloader which stowed ammunition in a ring around the turret ring. This reduced the internal diameter of the crew compartment in the hull which was already not particularly wide. However, this is not necessarily a problem as the amount of room for the commander's upper body is more than adequate.<br />
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In summertime, the roominess of the commander's station is acceptable for the average Soviet tanker, but in winter, the commander's bulky clothing cuts down on the already modest volume of habitable space. Taller people will not find it perfectly habitable as there is plenty of headroom. For ventilation, there is a small DV-3 plastic fan mounted on a ball joint just in front of him. It is enough for European summers considering the international standards for tank ventilation of the time (there were none), but not the high heat of Northern Africa and the Middle East. Because the commander is seated inside the turret cabin, he is isolated from the hull where the NBC filtration and ventilation system is installed. As such, there is virtually no airflow inside the turret cabin besides the breeze from the DV-3 plastic fan.<br />
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Like with the T-72 and T-64, the commander of the T-80 is supplied with four general vision periscopes, but the designers managed to remedy the rearwards blind spot with the inclusion of a TPNT-1 rear view prism block embedded into the center of the hatch. It is useful for directing the driver while buttoned up. In non-combat situations, the commander could just open his hatch and peek out, of course. The TKN-3 observation device directly in front of the commander is supplemented by two TNPO-160 periscopes embedded in the fixed cupola roof pointing in the 10 o'clock and 2 o'clock sectors and another two TNPO-165 periscopes embedded into the hatch pointing in the 8 o'clock and 4 o'clock sectors, thus giving him a generous field of view around the turret. With the inclusion of the TNPT-1 rear view prism, the commander theoretically has a full 360-degree view around the turret from six observation devices. While not as comprehensive as many NATO tanks in terms of the number of observation devices, the cupola of the T-80 is rotatable, so the dead zones between the periscopes are easily eliminated by simply rotating the cupola. In broader terms, general vision periscopes are useful for directing the driver, checking the positions of the commander's platoon mates and getting a sense of the surrounding environment.<br />
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However, the commander's responsibilities are not limited to simply monitoring the situation outside. In case the autoloader malfunctions, the commander is also responsible for manually operating the autoloader carousel. The ammunition type indexer memory unit (<span style="color: yellow;">YELLOW</span>) performs the double function of an indicator unit with LEDs in it to show what type of ammunition is currently aligned with the elevator and ramming mechanism so that the commander knows when he has reached the desired ammo type -<br />
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- and the silver-gray object (<span style="color: red;">RED</span>) underneath it is the hydroelectric carousel rotation drive motor. If all electrical power is cut to the tank, rotating the carousel is achieved by working the hand crank attached to the side of the motor.<br />
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The commander also has a control dial to operate the autoloader in the semi-automatic loading mode where he can control the loading process step by step to use the remaining functional parts of the system in the event of an autoloader failure or troubleshoot issues with the autoloader. From this dial, the commander can hydrolock the cannon in the loading position, raise the ammunition cassette to the loading position, ram the ammunition into the cannon breech, return the ammunition cassette to the carousel, and return the cannon to the stabilized mode whereby it is ready to fire. The commander is provided with an ammunition type selection dial (<span style="color: blue;">BLUE</span>) to allow him to select the type of ammunition that is to be loaded when operating the autoloader in the semi-automatic mode.<br />
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Besides all that, the commander is provided a control box (<span style="color: lime;">GREEN</span>) to control the autoloader replenishing procedure. The autoloader replenishing procedure can be described as the normal loading procedure except run in reverse, and without the ramming step.<br />
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Besides having his general vision periscopes and controls, the commander also gets to play around with a multifunctional pseudo-binocular TKN-3M sight. This is his primary means of observation.<br />
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<h3>
<span style="font-size: large;">TKN-3M "Kristal"</span></h3>
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The original T-80 from 1976 was equipped with the TKN-3M pseudo-binocular combined periscope, similar to the T-64 and T-72 before it. Pseudo-binocular meaning that although the device has two eyepieces, the two optic feeds are combined to one aperture, which the viewer sees out of. It has a fixed 5x magnification in the day channel with an angular field of view of 10°, and a fixed 3x magnification in the night channel with an angular field of view of 8°. The periscope can be manipulated up and down for elevation, and the commander's cupola must be manually spun for horizontal viewing.<br />
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By 1976, the TKN-3M was already somewhat obsolete. It featured target cuing and was very compact, but it wasn't stabilized, and featured only rudimentary rangefinding capabilities and its night vision capabilities were only borderline acceptable for 1976. Night vision came in two flavours; passive light intensification or active infrared. In the passive mode of operation, the TKN-3M intensifies ambient light to produce a more legible image. This mode is useful down to ambient lighting conditions of at least 0.005 lux, which would be equivalent to an overcast, moonless and starless night. In these conditions, the TKN-3M can be used to identify a tank-type target at a nominal maximum distance of 400 m due to the resolution limit, but as the amount of ambient light increases such as on starlit or moonlit nights, the distance at which a tank-sized target is discernible can be extended. In dark twilight hours, the TKN-3M may be able to make out the silhouette of a tank at a distance of up to 800 m or more, but the sight is hamstrung again, this time not by the absence of light, but by the low magnification. Any brighter than dawn or dusk, and the image will be oversaturated and unintelligible.<br />
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The active mode requires the use of the OU-3GA2 or OU-3GKU IR spotlight, which connects directly to the tank's 27V electrical system. With active infrared imaging, the commander can identify tank-type targets from a distance of around 400 m, or potentially more if the opposing side is also using IR spotlights. In that case, the TKN-3M can be set to the active mode but without turning on the IR spotlight. The switch for activating the spotlight is the right thumb button while the operating channel selector is on the TKN-3M itself. The problem with spotlights as a whole is that while the user can use them to spot for targets, the targets can use them to spot the user too, but from much further away. However, the OU-3 design is particularly flawed in this respect because it lacks an occluder. The lack of an occluder means that around half of the light from the spotlight is projected directly forward instead of into the parabolic reflector. As such, an enemy observer will not only see a circular patch of light. When observing a Soviet tank with its IR spotlight on, a large portion of the tank will be brightly illuminated. The additional illumination brings the minor benefit of lighting up the ground for the driver to see more clearly, so the common issue of speed control due to short visibility distance with the complementary IR periscope for the driver is slightly alleviated in battle conditions.<br />
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The maximum distance at which a tank-sized target can be identified in the active mode is stated to be 400 to 450 meters, although the spotlight can illuminate objects further away than that. The main issue is the low resolution of the image and the low magnification factor of the TKN-3M. The OU-3GA2 and OU-3GKU spotlights are not particularly powerful. Both use an incandescent lamp that consumes just 110 watts and the spotlights have an aperture diameter of only 215 mm. The only difference between the two spotlights is the shape of the hinges on which the spotlight lamp is mounted.<br />
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Without the infrared filter, the spotlight emits white light <a href="http://gaz66avto.ru/data/documents/Rec_34741.PDF">at 240 candelas</a>. The infrared filter prevents all but approximately 0.001% of the light in the visible spectrum (360-760 nm) to pass through, and the light that passes through is at the higher end of the visible spectrum. As such, the spotlight emits a very faint red light with an intensity of around 0.24 candelas that can be perceived by the naked eye at close range when the OU-3 spotlight is activated in low light conditions. The intensity of near infrared light is much higher, of course. This light can be detected by the photosensor of a digital camera without an infrared blocking filter. The photosensor displays this infrared light - which is otherwise invisible - as pink light. This can be seen in the photos below, showing the OU-3 of a BRDM-2 (pictures from kmshik from the <a href="http://www.gaz69.ru/ipb/topic/124887-%D0%B1%D1%80%D0%B4%D0%BC-2/?page=5">Gaz 69 forum</a>).<br />
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When the OU-3 spotlight is used without the infrared filter, the TKN-3M can be used at night in the daylight mode possible and the viewing distance can be increased at the cost of exposing the exact location of the tank to everyone. This is permissible in certain circumstances, but it is not common.<br />
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Overall, the TKN-3M offers very poor night viewing capabilities compared to modern thermal imaging sights, but it was an improvement over the original TKN-3 model from 1964 due to the inclusion of image intensification technology, which was appropriately advanced for the time. However, by the late 1970's, the system was outstripped by more advanced Western passive image intensifying optics.<br />
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The OU-3GA2 spotlight is mounted coaxially to the TKN-3M periscope via a connecting rod, visible in the photo below to the left hand side of the spotlight. Due to the vertical offset in the mounting position of the spotlight, some parallax error is to be expected.<br />
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Rangefinding is accomplished through the use of a stadiametric scale sighted for a target with a height of 2.7 m, which is the average size of the average NATO tank. The TKN-3 is not stabilized, making it difficult to reliably identify enemy tanks or other vehicles at extended distances while the tank is travelling over rough terrain, let alone determine the range. The left thumb button initiated turret traverse for target cuing. The range of elevation of the periscope is +10° to -5°. Because the OU-3GA2 spotlight is directly mechanically linked to the periscope, the elevation angles remain the same when using the TKN-3M in the night vision mode.<br />
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Target designation is done by placing the crosshair reticle in the periscope's viewfinder over the intended target and pressing the cue button. The system relies on the use of a single direction sensor installed on the cupola ring, so the system can only account for the cupola's orientation and not the elevation of the TKN-3M, so the cannon will not elevate to meet the target. This was not a serious issue because the gunner should be able to see the target quite easily from his sight once the turret has slewed on target.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-k6BsJIWkjFE/VmWGhoLaVfI/AAAAAAAAEtY/FyrdOec9Fqs/s1600/tkn-3.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="375" src="https://3.bp.blogspot.com/-k6BsJIWkjFE/VmWGhoLaVfI/AAAAAAAAEtY/FyrdOec9Fqs/s400/tkn-3.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">TKN-3 viewfinder</td></tr>
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<h3>
<span style="font-size: large;">PNK-4S Universal Sighting Complex</span></h3>
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<a href="http://1.bp.blogspot.com/-a6Ajcwvmolc/VqScuTGyYQI/AAAAAAAAFdY/I3xPbbK_ugg/s1600/T-80U_tank_interior_-04.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="253" src="https://1.bp.blogspot.com/-a6Ajcwvmolc/VqScuTGyYQI/AAAAAAAAFdY/I3xPbbK_ugg/s400/T-80U_tank_interior_-04.jpg" width="400" /></a><a href="http://3.bp.blogspot.com/-tiJLagZCymI/VqPc9BHjjTI/AAAAAAAAFcw/3gZLpoHQMZQ/s1600/pic_62_large.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://3.bp.blogspot.com/-tiJLagZCymI/VqPc9BHjjTI/AAAAAAAAFcw/3gZLpoHQMZQ/s400/pic_62_large.jpg" width="266" /></a></div>
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For the Soviet optronics industry at the time, the PNK-4S was only a small technical innovation, but the device placed the T-80 on the same level as the best NATO tank at the time, namely the Leopard 2 with its revolutionary PERI-R17 independent panoramic sight. Like the PERI, the PNK-4S complex combines the functionality of an auxiliary gunnery complex with that of a comprehensive surveillance unit, giving the commander full authority with regards to the fire control system including the ability to directly override the gunner, which can be useful in some situations, such as to immediately engage a standout threat at the very instant it is spotted. All this is done with a simple thumbstick on the control module located to the right of the TKN-4S pseudo-binocular surveillance device around which the PNK-4S system revolves.<br />
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The decision to use a thumbstick was probably because a full joystick could not be easily manipulated with precision while the operator's body and arm was rocking around if the tank were going over rough terrain, while the thumb would be completely stationary if the hand was securely gripping the handgrip. The index finger rests on the trigger button at the back of the handgrip.<br />
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The PNK-4 system is a part of the 1A45 fire control system, as it connects directly to the tank's ballistic computer and fully duplicates the control scheme of the gunner. It can also be used independently from the fire control system in case of an emergency as explained further in the TKN-4S section. When used in the gunnery mode, the PNK-4 module is locked facing forwards. Horizontal cupola rotation control then becomes horizontal turret control, and vertical sight movement then becomes gun elevation. Independent vertical stabilization is still present, so that the sight does not elevate when the gun does to load.<br />
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The control module has all the necessary controls for the use of the main gun, including ammunition selection vis-à-vis the autoloader. Late T-80U variants with a remotely controlled anti-aircraft on the cupola would also make use of this control module for aiming and firing. With all this and the TKN-4S sighting complex, the T-80U could boast of having one of the most sophisticated hunter-killer systems in the world at the time.<br />
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<span style="font-size: large;">TKN-4S</span></h3>
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The foremost improvement of the TKN-4S over the TKN-3M is the addition of an independent stabilizer with its own gyroscopic sensor and compensator motor, visible on the left side of the main periscope housing as the large bulging module. The stabilizer is designated as the 1ETs29-4s. The stabilization accuracy on the vertical plane is at least 0.30 mils, while the stabilization accuracy on the horizontal plane is much lower at 0.88 mils, because of the much greater burden of the cupola compared to the mirror in the sight aperture. This means that the maximum deviation from the original point of aim is 0.30 m vertically and 0.88 m horizontally at a distance of 1000 m. The sight can maintain this level of performance while the cupola is rotating at speeds of up to 35 degrees per second. The vertical range of elevation is quite reasonable, spanning from -10° to +20°, granting the commander an uninterrupted line of sight on any given target while the tank is on the move over terrain of any degree of impassibility (within reason).<br />
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<a href="http://1.bp.blogspot.com/-PTFD1kfhA6I/VqPdPwX4qcI/AAAAAAAAFc4/Sp2ol7CafnU/s1600/t55agmr14l.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em; text-align: center;"><img border="0" height="640" src="https://1.bp.blogspot.com/-PTFD1kfhA6I/VqPdPwX4qcI/AAAAAAAAFc4/Sp2ol7CafnU/s640/t55agmr14l.jpg" width="483" /></a>Another major improvement over the TKN-3M came in the form of a higher maximum magnification factor of 7.6x in the day channel in the high magnification setting, along with the option to switch to a low magnification setting of 1.0x. The night channel has a fixed 5.2x magnification. The principal advantage of the increased magnification in daytime is that it enables the commander to see and designate targets at ranges suitable only for missiles and beyond what was determined to be the maximum effectiveness threshold for ballistic munitions. The field of view under x1 magnification is 47° for the day channel and 7° under maximum magnification, or 7°40' under maximum magnification in the night channel, owing to the relatively low effective viewing distance at night. The night vision module uses newer third generation light intensification technology; better than what the old TKN-3MK had, but still not competitive against first-gen thermal imagers. Like the TKN-3, the TKN-4S can operate under active IR imaging or passive light intensification. In the latter case, the TKN-4S facilitates the identification of a tank-type target at a distance of at least 700 meters under ambient lighting conditions no brighter than 0.003 lux. This is a major improvement over the TKN-3MK, which only allowed the user to identify a tank type target at 400 meters under 0.005 lux of ambient light. The viewing distance for the TKN-4S can be improved by the presence of moonlight, which can increase the viewing distance by several hundred meters.<br />
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Because the TKN-4S is designed to use the same OU-3GA2 spotlight as the TKN-3, the active mode option does not present any improvements, only just enabling the commander to identify a tank-type target at a distance of 800 m. This is a significant improvement, but still vastly inferior in general effectiveness compare to 1st Gen thermal imaging systems.<br />
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The difference between the active and passive modes of operation is that in the active mode, the maximum practical viewing distance changes minimally across a wide range of ambient lighting conditions and weather conditions. Passive light intensification is more sensitive in this respect. If not for mortar and artillery-delivered IR illumination flares which could be aimed and shot over enemy positions, active infrared imaging would be completely obsolete. In such a scenario, however, the IR spotlight is rendered totally redundant.<br />
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In hindsight, it is quite clear that pursuing light intensification technology instead of investing in prospective thermal imaging technology was a huge mistake, one that ended up setting back the Soviet Union by nearly a decade in this particular field. Up until quite recently, modern day Russia had still been playing catch-up with Western tanks by assimilating French sighting technology through technological cooperation. However, that doesn't change the fact that the TKN-4S still had a fairly modern nightvision feature, when the day-only PERI-R17 didn't. All in all, the TKN-4S was arguably one of the most advanced and most versatile device of its type available to any modern tank in the world, until that title was usurped after the fall of the USSR when the new CITV was introduced on the M1A2 Abrams in 1992 along with the new PERI-R17A2 in 1998. Both had thermal imaging technology, and were generally better in every possible way.<br />
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Unlike the TKN-3, which had only a simple lead measuring scale and a stadia rangefinder scale, the TKN-4S has markings for all ammunition types and all the necessary range and lead scales, plus the stadiametric rangefinder. Because the PNK-4 system lacks a ballistic computer and laser rangefinder, the targeting procedure is devolved into manual mode. The commander must manually find the range to the target using the stadia scale, of which there are two. The one on top is for a target 2.5 meters in height, for a modern tank-type target like the Leopard 2 and Abrams, which are shorter than their predecessors. The one below it is for a target 2.0 meters in height, for APC-type targets like the M113.<br />
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<a href="https://2.bp.blogspot.com/-WKAwpOjoPrU/V546EUxkTXI/AAAAAAAAHKE/R2TrdkeqSyQ_57b2d7Ax_IfkX86PmzbUwCLcB/s1600/pnk-4.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-WKAwpOjoPrU/V546EUxkTXI/AAAAAAAAHKE/R2TrdkeqSyQ_57b2d7Ax_IfkX86PmzbUwCLcB/s1600/pnk-4.jpg" /></a></div>
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Besides all that, the TKN-4S has a handy 1x periscope installed just under the rubber forehead pad for wider forward vision, supplementing the two TNPO-160 periscopes flanking the device. It's not much, but it does grant the commander an almost totally uninterrupted field of vision around the frontal 180-degree arc of the cupola.<br />
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<a href="http://2.bp.blogspot.com/-tYmMZ_pmmg4/Vqz5miU3iBI/AAAAAAAAFko/ZOhBmhGx5pY/s1600/2016%2B-%2B5.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="478" src="https://2.bp.blogspot.com/-tYmMZ_pmmg4/Vqz5miU3iBI/AAAAAAAAFko/ZOhBmhGx5pY/s640/2016%2B-%2B5.jpg" width="640" /></a></div>
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The PNK-4S system uses a different cupola counterrotation motor from the one used for the TKN-3. Instead of a motor mounted at the turret ring that was joined to the cupola by a cardan shaft, the cupola rotation motor for the new cupola was installed on the turret roof and connected to the cupola via a drive sprocket. The motor is powerful enough to spin the cupola at a maximum speed of 40 degrees per second, easily outstripping the turret, so there is no danger of the commander losing visual contact of his target. The electronic components for the control of the cupola rotation motor are contained inside an armoured box mounted externally above the housing for the TKN-4S sight, as shown in the photo above.<br />
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<a href="http://1.bp.blogspot.com/-m_Zazq9Vufc/Vq4kehR-hZI/AAAAAAAAFoQ/dHgZgGqqtLM/s1600/t-80%2Bcupola%2Bmotor.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="390" src="https://1.bp.blogspot.com/-m_Zazq9Vufc/Vq4kehR-hZI/AAAAAAAAFoQ/dHgZgGqqtLM/s400/t-80%2Bcupola%2Bmotor.png" width="400" /></a></div>
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Strangely enough, the PKN-4 complex does not include a laser rangefinder, despite the availability of quite compact models already in the late 70's. To determine the distance to a tank-type target, the commander must still rely on a stadiametric ranging scale similar to the type found on the TKN-3, although the precision of the operation may have increased marginally thanks to the higher magnification factor. Still, this isn't that big of a problem, because the gunner can quickly and painlessly conduct ranging himself anyway, and the gunner should be putting more time in observing the target than the commander anyway, who is supposed to be spending his time looking for other things to shoot at.<br />
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<h3>
<span style="font-size: large;">GUNNER'S STATION</span></h3>
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<a href="http://3.bp.blogspot.com/-TzLgafMJw14/VqScECFjGfI/AAAAAAAAFdI/EKtSm_ufi-M/s1600/gunner%2527s%2Bhatch%2Bt-80b.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="282" src="https://3.bp.blogspot.com/-TzLgafMJw14/VqScECFjGfI/AAAAAAAAFdI/EKtSm_ufi-M/s640/gunner%2527s%2Bhatch%2Bt-80b.png" width="640" /></a></div>
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The original T-80 turret was essentially identical in form and in function to the one from the T-64A, the T-80 itself being a derivative of it. Just like the turret of the T-64A, the gunner in the T-80 was provided with nothing but a single front-facing periscope for general vision. Later on, both the T-80B and T-80U turrets gave the gunner's station two TNPO-165 general vision periscopes facing forward and one TNPO-160 periscope aimed to the left, giving the gunner a good view of his surroundings in addition to helping to improve the lighting condition of his station, which is pretty neat as well.<br />
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<a href="http://3.bp.blogspot.com/-jS4sLlOtaHQ/VrByeBt1YfI/AAAAAAAAFqY/vijHX2_9j04/s1600/t-80%2Bgunner%2527s%2Bperiscopes.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="273" src="https://3.bp.blogspot.com/-jS4sLlOtaHQ/VrByeBt1YfI/AAAAAAAAFqY/vijHX2_9j04/s400/t-80%2Bgunner%2527s%2Bperiscopes.jpg" width="400" /></a><a href="http://4.bp.blogspot.com/-IySD4WDEEao/VrByfsu82xI/AAAAAAAAFqg/y-sskjXwgao/s1600/gunner%2527s%2Bside%2Bperiscope.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="271" src="https://4.bp.blogspot.com/-IySD4WDEEao/VrByfsu82xI/AAAAAAAAFqg/y-sskjXwgao/s400/gunner%2527s%2Bside%2Bperiscope.jpg" width="400" /></a></div>
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Keep in mind that in most NATO tanks, the gunner is not provided with any general vision devices at all, but inversely, the station in the T-80 is slightly more cramped and amenities are few are far in between. Wider tankers will find it very difficult fitting into the station due to the narrow hatch, but lankier people will find the tank more accommodating, especially since there is plenty of room to stretch his legs. If the gunner is short <i>and</i> slim, all the better.<br />
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Besides the controls for gunnery related things, the gunner also has access to a multitude of toggle switches for a variety of things around his station. Among them are switches for the ventilation system (just below his hatch), switches for the dome light, switches for the intercom system, and others.<br />
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The new and more spacious turret of the T-80U also enabled the crew to carry a small number of additional cartridges. It certainly was not the most reassuring design feature, but more importantly, the ammunition somewhat reduced the available space, so removing them was quite normal.<br />
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<a href="http://2.bp.blogspot.com/-Ds72qhxs3oU/VqOFjh_rXjI/AAAAAAAAFcQ/JAO8aCY1XWU/s1600/russian-t-80ue-tank-interior-.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-Ds72qhxs3oU/VqOFjh_rXjI/AAAAAAAAFcQ/JAO8aCY1XWU/s1600/russian-t-80ue-tank-interior-.jpg" /></a></div>
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<h3>
<span style="font-size: large;">Fire Control</span></h3>
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Being the best tank in the Soviet Union meant a few things. One of them was having the best optics and compact computer technology money could buy. One of the few interesting and unique traits of Soviet-style sighting complexes was the control handles. Instead of a thumbstick like on the Chieftain or a pair "steering wheel" style hand grips where turret slewing was done by turning the handles like, well, a steering wheel (z-axis), spinning the turret was done by rotating the grips on the y-axis. The hand grips have two buttons each. The left trigger button is for firing the coaxial machine gun and the left thumb button is resetting the laser rangefinder. The right trigger button is for firing the main cannon, and the right thumb button is for firing off the laser rangefinder.<br />
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<h3>
<span style="font-size: large;">T-80 obr. 1976</span></h3>
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<span style="font-size: large;">TPD-2-49</span></h3>
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<a href="https://3.bp.blogspot.com/-DBojiBEz2iQ/Vsh90ZYTAhI/AAAAAAAAF_M/Y949XTSWq1I/s1600/t-80%2Bmodernized%2B2006.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="271" src="https://3.bp.blogspot.com/-DBojiBEz2iQ/Vsh90ZYTAhI/AAAAAAAAF_M/Y949XTSWq1I/s400/t-80%2Bmodernized%2B2006.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-22Cp0SjNhus/Vsh906AKBEI/AAAAAAAAF_Q/t7-f_iCbKEg/s1600/t-80%2Bmodded%2B206.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="271" src="https://3.bp.blogspot.com/-22Cp0SjNhus/Vsh906AKBEI/AAAAAAAAF_Q/t7-f_iCbKEg/s400/t-80%2Bmodded%2B206.jpg" width="400" /></a></div>
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The earliest T-80s were essentially modified T-64As, and as such, they had a great many things in common. Among these commonalities was the use of the TPD-2-49 optical coincidence rangefinder.<br />
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<a href="http://3.bp.blogspot.com/-JOZfJDyhdCI/VojdIHzyddI/AAAAAAAAGI0/RcWY_1a-9cs/s1600/1G42_Frontplatte.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://3.bp.blogspot.com/-JOZfJDyhdCI/VojdIHzyddI/AAAAAAAAGI0/RcWY_1a-9cs/s640/1G42_Frontplatte.jpg" width="456" /></a></div>
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By 1976 standards, the TPD-2-49 was already incredibly outdated. It was first used on the original T-64 introduced in 1966, but since then, the TPD-K1 laser rangefinding sight had been invented and was already in use on the T-64B and T-72A, both introduced in 1976.<br />
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The optic aperture is split into two halves, top and bottom. The two input lenses see different parts of the same target, and the gunner must use the adjustment dial near his hand grips to line up both halves and obtain a seamless picture.<br />
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<a href="https://4.bp.blogspot.com/-F00Gp8572kk/Vr7xfw8sUrI/AAAAAAAAF88/XzE7VrY0Ab0/s1600/tpd-2-49%2Bcoincidence%2Brangefinder.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://4.bp.blogspot.com/-F00Gp8572kk/Vr7xfw8sUrI/AAAAAAAAF88/XzE7VrY0Ab0/s640/tpd-2-49%2Bcoincidence%2Brangefinder.gif" width="640" /></a></div>
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This process was cumbersome and somewhat inaccurate - the error margin was 3 to 5%, which meant that the range could be off by up to a shocking ±200m at 4000m, or a much less serious ±30m at 1000m range. However, it's worth considering that the average tank engagement distance expected in Europe was estimated to be 1500m, relieving the TPD-2-49 somewhat. Plus, the use of hypersonic APFSDS ammunition meant that the error margin could usually be ignored since the ballistic trajectory was so flat that amount of drop was completely negligible at out to 1500m or more. The problem was much more pronounced with HEAT and HE-Frag ammunition, which were heavier, had a worse ballistic coefficient and traveled at much lower velocities. With the advent of long range ATGM systems mounted on jeeps, scout cars, IFVs and even light tanks, accurate long-distance fire with HEAT and HE-Frag shells was imperative.<br />
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One downside of optical coincidence rangefinders is that they tend to have reduced accuracy on camouflaged targets. Tanks or other targets concealed with camouflage netting and bushes can be difficult to accurately range because the outlines of the tank may not be very clear to the gunner, and determining the silhouette through other visual cues is time consuming, not to mention that it requires at least a fairly experienced gunner. Other methods of breaking up the silhouette of the tank can be effective. As such, the T-64A turret and fire control system could be considered practically obsolete by the time it was integrated as part of the T-80, so only a few hundred of the original 1976 production variant were ever manufactured and some were subsequently brought back up to current technological standards with the retrofitting of the TPD-K1 sight during the early 1980's.<br />
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<span style="font-size: large;">TPN-1-49-23</span></h3>
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<a href="http://1.bp.blogspot.com/-inZdgjY-0c0/VS0-MyVD71I/AAAAAAAABwA/EqXWtpOFIVg/s1600/tpn-1-49-23.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://1.bp.blogspot.com/-inZdgjY-0c0/VS0-MyVD71I/AAAAAAAABwA/EqXWtpOFIVg/s1600/tpn-1-49-23.png" width="179" /></a><a href="http://3.bp.blogspot.com/--Xoy02Tj9Is/VS09zWhM4zI/AAAAAAAABv4/VPxFlqUOjto/s1600/a884699ced588889.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://3.bp.blogspot.com/--Xoy02Tj9Is/VS09zWhM4zI/AAAAAAAABv4/VPxFlqUOjto/s1600/a884699ced588889.jpg" width="193" /></a></div>
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The TPN-1-49-23 was the gunner's night vision sight for the original T-80, but it was relatively short-lived and it was replaced soon after by the more advanced TPN-3-49. The TPN-1-49-23 can either use ambient light intensification or use infrared light conversion and intensification by relying on the L-4A "Luna-2" IR spotlight for illumination. The Luna-2 spotlight is mounted coaxially to the main gun. Unlike the commander's OU-3GA2 or OU-3GKU spotlight, the L-4A spotlight uses a xenon arc lamp with an IR filter instead of an incandescent lamp. It draws power from the tank's 27V electrical system and consumes 600 W of power. Removing the IR filter transforms the IR spotlight into a regular white light spotlight, but this can only be done in a non-combat situation.<br />
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<a href="https://3.bp.blogspot.com/-g_FDhRfNv2s/VtF61LCktdI/AAAAAAAAGDY/fF9bgdu6_04/s1600/image.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="450" src="https://3.bp.blogspot.com/-g_FDhRfNv2s/VtF61LCktdI/AAAAAAAAGDY/fF9bgdu6_04/s640/image.jpg" width="640" /></a></div>
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Take a look at this video <a href="http://yandex.ru/video/search?text=l-4%20%D0%9B%D1%83%D0%BD%D0%B0%20%D0%BF%D1%80%D0%BE%D0%B6%D0%B5%D0%BA%D1%82%D0%BE%D1%80&path=wizard&parent-reqid=1456566049149585-13446269744592605324153114-sas1-2005&filmId=QpMB4nhXUXI&redircnt=1456566086.1">here</a> to see the L-4A spotlight in action.<br />
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The L-4A spotlight has an aperture diameter of 305 mm, smaller than the spotlights for the M60A1 and the Chieftain. The Chieftain's spotlight, for instance, has an aperture diameter of a staggering 570 mm, and consumes 2 kW of power. This is admittedly quite beneficial for searching for targets, because although the beam itself is only about 570 mm in diameter, dust, water vapor and smoke in the air help dissipate the light and increases ambient light levels, and illuminating a reflective object such as the ground will generate a bigger lit up spot. But despite the huge size and power of the spotlight, the nightsight on the Chieftain has an identification distance of just 1000 m. Despite using a much, much less powerful spotlight, the performance of the TPN-1-43-29 is quite close, with the ability to identify tank-type targets at around 800 m. The passive setting allows the same target to be spotted at ranges of up to 800 m if the ambient light is no less than 0.005 lux, which is the typical brightness of a moonless, starlit night with clear skies. Clarity and spotting distance improves with increasing brightness. The identification distance is expanded to around 1,000m on moonlit nights, and it is possible to spot tanks at distances of more than 1,300 m during dark twilight hours, although low magnification and mediocre resolution complicates viewing beyond that range. This level of performance is on par with the best Western equivalents of the mid to late 60's, but for 1976, the TPN-1-49-23 was simply no longer competitive. It did, however, have light intensification technology, which tanks like the M60 did not have until 1977.<br />
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If used as a backup sight, it can be used to identify tank-type targets at up to 3,000m in daylight or more, if the geography and weather permits it. It has a field of view of 6 degrees at 5.5x maximum magnification. Variable zoom allows reduction of magnification to 1x to give the gunner much better general visibility for spotting targets.<br />
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The sight has dependent stabilization in the vertical plane with 20 degrees of elevation and 5 degrees of depression. Dependent stabilization means that the sight is <i>technically</i> stabilized, but it piggybacks on the vertical stabilizer for the cannon. Since the cannon has to elevate by +3 degrees for the loading cycle, the gunner will usually lose sight of his target immediately after firing, so he will be unable to observe the "splash" so that he knows how much elevation correction he needs to apply. The commander can see, of course, but that's not a very convenient way of doing things.<br />
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Though the cover can be removed and the sight used during daytime, the light intensification channel must never be activated, because excessive light input will overload the sight unit and possibly damage it. In accordance with this, the aperture has shutters linked to the trigger unit. Upon firing, the shutters automatically close to shield the unit from the intense flash of cannon fire at night. These shutter may also be manually opened and closed via a handle.<br />
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<h3>
<span style="font-size: large;">TPN-3-49</span></h3>
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<a href="https://1.bp.blogspot.com/-psPxGmei1c4/Vr7Nbd16LgI/AAAAAAAAF8c/pp9ENlHii9U/s1600/TPN-3-49.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-psPxGmei1c4/Vr7Nbd16LgI/AAAAAAAAF8c/pp9ENlHii9U/s1600/TPN-3-49.jpg" /></a></div>
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Complementing the primary sighting complex from the original T-80 all the way to the T-80U is the obligatory nightvision sighting system, which also functions as the backup sight in the event of the destruction of the main sighting unit.<br />
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Although it still only features a 1st Generation IR imaging module, the TPN-3-49 boasts a more advanced (and also bulkier) design than the earlier TPN-1-49-23. More specifically, it features a more sensitive IR receiver module, enabling it to see farther using the same L-4A "Luna" IR spotlight as its predecessors. The spotlight is mounted coaxially with the cannon and follows it in elevation and depression via simple mechanical linkages.<br />
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There are three selectable reticle settings for the viewfinder, one for each ammunition type; APFSDS, HEAT, and HEF. Each reticle different ranging scales for the gunner to input range data onto. Gunnery is reduced to its most basic level when using the TPN-3-49. Determining the range to the target is done by comparing the size of its profile with the size of the chevron, which is a rudimentary and rather imprecise method of rangefinding that is still implemented in the most modern sighting systems as a fallback option for when everything else fails. Unfortunately, this is the only way for the gunner to conduct rangefinding. However, it was determined that since the viewing distance was so short, it didn't really matter anyway.<br />
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<a href="https://3.bp.blogspot.com/-7oGC0ilSdcU/Vr7EiMc-GTI/AAAAAAAAF8A/XBnz9T4HdVY/s1600/TPN-3_Strichbild.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="400" src="https://3.bp.blogspot.com/-7oGC0ilSdcU/Vr7EiMc-GTI/AAAAAAAAF8A/XBnz9T4HdVY/s400/TPN-3_Strichbild.jpg" width="400" /></a><br />
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The sight is not connected with the 1V517 ballistic computer. Laying the gun onto the target is done by lining up an adjustable horizontal line to an appropriate graduation on the range scale, which also moves the chevron up and down. So for instance, if a tank-type target is located 900 m away, the gunner places the horizontal line between the "8" mark and the long mark, which drops the chevron slightly. By using the handgrips to lay the dropped chevron up and back on target, the cannon is given proper supraelevation and a ballistic solution is formed.<br />
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The maximum identification distance of a tank-type target is 1,300 meters in the active channel, and 850 meters in the passive channel under lighting conditions no brighter than 0.003 lux. This figure will increase as ambient light gets brighter, but an important point to take is that the amount of ambient light needed to achieve the 850 m identification distance - 0.003 lux - is lower than the 0.005 lux standard by which the performance of the TKN-3 is measured by. This essentially means that on the same night, the gunner will be able to see about a half kilometer further than the commander. Although the TPN-3-49 appears to be less capable than the gunner's IR sight on the British Chieftain with its 1000-meter nominal identification range, it's worth noting that that system uses a 2 kW spotlight that has a diameter of around 570 mm.<br />
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In accordance with its function as a night sight, TPN-3-49 features an automatic internal shutter that blocks off the light intensifier device via an electric signal from the trigger on the gunner's handgrips. This is to protect it from burning out from the flash of the cannon firing, as the device is extremely sensitive and a bright flash of light so close to the sight will generate a sudden spike in voltage large enough to fry the vacuum tubes. Of course, the image produced may also be bright enough to cause eye damage to the gunner. The light amplification channel must never be activated during daytime, because daylight is already bright enough to permanently damage the sight.<br />
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The armoured housing for the sight head of the TPN-3-49 can be distinguished by its small and squarish front profile, and the small bolt at each corner of the armoured cover. It is taller than the housing for the TPN-1-49-23.<br />
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<a href="http://2.bp.blogspot.com/-7WOWf3xnWLU/Vqz_uEwCoGI/AAAAAAAAFlI/DfvwmSD57M4/s1600/tpn3-49%2Bsight%2Baperture%2Bhousing.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="268" src="https://2.bp.blogspot.com/-7WOWf3xnWLU/Vqz_uEwCoGI/AAAAAAAAFlI/DfvwmSD57M4/s400/tpn3-49%2Bsight%2Baperture%2Bhousing.jpg" width="400" /></a><br />
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<h3>
<span style="color: black; font-size: x-large;">T-80B (1978)</span></h3>
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<span style="font-size: large;">1A33 Fire Control System</span></h3>
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<span style="font-size: large;">1G42 Sight</span></h3>
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<a href="http://1.bp.blogspot.com/-mPNt-L6Gu4g/Vq4g8zc8-hI/AAAAAAAAFns/AiXMTjY76h4/s1600/t-80%2Bgunner%2527s%2Bstation.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="432" src="https://1.bp.blogspot.com/-mPNt-L6Gu4g/Vq4g8zc8-hI/AAAAAAAAFns/AiXMTjY76h4/s640/t-80%2Bgunner%2527s%2Bstation.jpg" width="640" /></a></div>
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The T-80B was equipped with the more advanced 1A33 fire control system featuring the 1G42 primary sight with the associated fire control sensors and computers together with the Kobra missile system. The 1G42 sight has an accelerometer and an independent gyroscopic sensor enforcing an independent 2-axis stabilization system. Supplementing all that is the 1V517 digital ballistic computer, the 1B11 crosswind sensor and the 1B14 ambient temperature sensor. Atmospheric data from the sensors is fed to the ballistic computer together with range data to form a firing solution. The system also includes a Delta-D sensor which records the distance traveled by the tank after the lasing of a target. This allows the tank to accurately engage a target without re-lasing it even if the tank has approached or receded from the target.<br />
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Unlike the rather outdated 1A40-1 fire control system used in the T-72B, the 1G43 features fully automatic lead calculation and automatic gun superelevation. What this means is that the aiming chevron at the center of the sight picture remains static as the FCS adjusts the elevation to account for ballistic drop and adjusts the orientation of the turret to account for lead. The sight is not displaced sideways as the gun is adjusted for lead, thanks to the 2-axis stabilizer in the 1G42 - the horizontal stabilizer rotates the sight aperture to compensate for the shifted orientation of the turret, thus allowing the gunner to maintain an unchanged view of the target.<br />
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The diagram below shows the markings and indicators in the sight picture. The digital readouts at the bottom of the sight picture show the type of ammunition currently loaded and the distance to the target. Beside the digital readouts are two LED light bulbs. The one on the left lights up to indicate that the cannon is ready to fire, and the one on the right lights up when the commander designates a target.<br />
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<a href="https://4.bp.blogspot.com/-YQAR5cBlbts/VtFazpGU_HI/AAAAAAAAGCU/Zg1p76qRBDI/s1600/1g42.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="366" src="https://4.bp.blogspot.com/-YQAR5cBlbts/VtFazpGU_HI/AAAAAAAAGCU/Zg1p76qRBDI/s640/1g42.jpg" width="640" /></a></div>
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Besides the digital component of the targeting system, there is a range scale at the top meant for manual gunlaying in an emergency. It works just like in earlier gunsights like the TSh2B-32 for the T-54; the gunner turns a dial and the range scales move up and down while the horizontal line running across it stays fixed. The only difference between the old TSh2B-32 and the 1G42 is the range scale for APFSDS ammunition - marked "Б" in the diagram above - is not vertical, but split into a diagonal line instead. This is because the ballistic drop of 125mm APFSDS is too small to be represented on a vertical range scale - the scale would appear as a solid black bar with indiscernible markings and range values.<br />
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The horizontal sliding line lying on the vertical range line (labeled as "<i>Шкала Боковых Поправок</i>") moves up and down together with the range scale as the dial is turned. When the dial is turned for a farther distance, the sliding line slides down, and vice versa. The intersection point between the horizontal and vertical line forms the crosshair when firing in manual mode.<br />
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The crosswind sensor is shown in the photos below. It uses a rather old-fashioned windmill-type anemometer to measure windspeed and not a digital hot wire anemometer in later designs with a meteorological mast. Since the 1B11 anemometer can only be affected by crosswinds, the device cannot measure headwinds and tailwinds. It device is heated to prevent failure by icing and to enable windspeed measurements in low temperature environments.<br />
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<a href="https://3.bp.blogspot.com/-17IYL75gxsA/VtFa0GYav7I/AAAAAAAAGCY/WkrEDnTJ1bY/s1600/1b11%2Bcrosswind%2Bsensor%2Bcloseup.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://3.bp.blogspot.com/-17IYL75gxsA/VtFa0GYav7I/AAAAAAAAGCY/WkrEDnTJ1bY/s400/1b11%2Bcrosswind%2Bsensor%2Bcloseup.jpg" width="400" /></a><a href="https://2.bp.blogspot.com/-Yh1C2QD2Tls/VtFa0Y5jJMI/AAAAAAAAGCc/a1u8YNkc5Yg/s1600/1b11%2Bcrosswind%2Bsensor.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="268" src="https://2.bp.blogspot.com/-Yh1C2QD2Tls/VtFa0Y5jJMI/AAAAAAAAGCc/a1u8YNkc5Yg/s400/1b11%2Bcrosswind%2Bsensor.jpg" width="400" /></a></div>
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<span style="font-size: large;">GTN-12</span></h3>
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The Kobra gun-launched guided missile is guided to its target via a radio command link, and the radio signal is transmitted by the GTN-12 antenna unit located directly in front of the commander's cupola. The transmitter is linked to the sighting system using the 9S416-1 control system, which translates the shifting of the point of aim in the 1G42 sight to generate a command signal for the missile, thus forming a SACLOS guidance regime.<br />
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<a href="https://4.bp.blogspot.com/-bfP0d-OxH8I/Vr6R02WlfqI/AAAAAAAAF7A/O2qv1WbED4c/s1600/gtn-12%2Bkobra%2Bguidance%2Bunit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://4.bp.blogspot.com/-bfP0d-OxH8I/Vr6R02WlfqI/AAAAAAAAF7A/O2qv1WbED4c/s640/gtn-12%2Bkobra%2Bguidance%2Bunit.png" width="640" /></a></div>
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The infrared bulb at the tail of the 9K112 missile is detected and tracked by the 1G42 sight. Due to the use of radio guidance, it is possible to jam the 9K112 missile during its flight. However, it does not appear that such equipment was developed or fielded by the expected enemy so this appears to be a very minor drawback.<br />
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<a href="https://www.blogger.com/null" id="1a45"></a>
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<span style="color: black; font-size: x-large;">T-80U</span></h3>
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<span style="font-size: large;">1A45 Fire Control System</span></h3>
<span style="font-size: large;"><b>1G46 Sight</b></span></div>
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The 1G46 sight is rather large and bulky, weighing in at 115 kg. The sight has independent two-plane stabilization with a range of elevation of -15 to +20 degrees, and a range of traverse of 8 degrees to either side. According to <a href="http://uoe.com.ua/products/en/?id=0&pid=catalogue&language=eng&catalogue_id=934&type=content">Ukroboronexport</a>, the minimum laying speed in both axes is 0.05 degrees per second, which equates to the ability to lay the chevron with a maximum error of 0.88 meters at a distance of 1,000 meters in both the vertical and horizontal planes. The sight has two magnification settings to choose from: 2.7x or 12x.</div>
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The layout of the sight is almost exactly the same as the 1G42. The only differences are in the shape of the stadia rangefinder, the size of the horizontal sliding line for manual aim, and the shape of the digital readouts and the indicator lights at the bottom of the sight picture. A photo of the reticle can be seen below (credit to Stefan Kotsch).</div>
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<span style="font-family: arial; font-size: 43.3038px; vertical-align: baseline;"><a href="http://1.bp.blogspot.com/--8oO-lGpUmg/VoXcWh4pgjI/AAAAAAAAGHk/qB6u9nCdPBc/s1600/1G46_010.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="622" src="https://1.bp.blogspot.com/--8oO-lGpUmg/VoXcWh4pgjI/AAAAAAAAGHk/qB6u9nCdPBc/s640/1G46_010.jpg" width="640" /></a></span></div>
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The 1G46 sighting complex also comes with a liquid cooled laser beam encoding and transmitting unit attached to the right hand side, unlike the T-72B, which used its 1K13-49 auxiliary sight for this purpose. This probably explains the heavier weight of 1G46 compared to other Soviet sighting complexes. The missile control unit is pictured below.</div>
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Other than the inclusion of the encoded laser projection unit, there is not much difference between the 1G46 and the 1G42. The independent stabilization system for the sight head has a good accuracy by Soviet standards, but the sighting line drift can be problematic. If the tank is moving at a high speed of around 25 km/h, the sight may drift away from the original point of aim at a rate of 0.2 mrads per second, so in the space of five seconds, the chevron will have moved 1.1 meters off target. This can be easily corrected by twitching the hand grips just slightly, but this does mean that the gunner has to be mindful. It is not known if there is automatic drift compensation.<br />
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<span style="font-size: large;">T01-P02-01 "Agava-2"</span></h3>
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<a href="http://3.bp.blogspot.com/-MLHOf6mGK3M/Vq4ggKCt0lI/AAAAAAAAFnk/7yxr_pOSgwk/s1600/agava.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://3.bp.blogspot.com/-MLHOf6mGK3M/Vq4ggKCt0lI/AAAAAAAAFnk/7yxr_pOSgwk/s640/agava.jpg" width="376" /></a><a href="http://3.bp.blogspot.com/-KZHMsfj7lAA/VqyFi4WNXHI/AAAAAAAAFfo/5z2v7f0ie0w/s1600/t-80u%2Bgunner%2527s%2Bstation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-KZHMsfj7lAA/VqyFi4WNXHI/AAAAAAAAFfo/5z2v7f0ie0w/s1600/t-80u%2Bgunner%2527s%2Bstation.png" /></a></div>
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The revelation that new Western developments in thermal imaging technology was producing compact thermal imaging sights that were rapidly outstripping the capabilities of light intensifying night vision sights resulted in new research on creating analogous devices to up the ante. Thermal imaging was not an unknown scientific field for the Soviet military industry during the 1980's as prototype imaging systems for tanks had already been developed by the early 80's and installed on a small number of T-80 tanks on a trials basis. Working prototypes were already available for testing purposes by the early 80's, but problems with establishing mass production held up the development of thermal sights in the Soviet Union for a long time. In this sense, Soviet tank technology was behind the West by almost a decade, in both technological achievement as well as industrial know-how.<br />
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Only the command variant models of the T-80U, the T-80UK, had the Agava-2 installed due to their prohibitively high cost. The widespread introduction of this technology was not only a manufacturing challenge, but it would have bloated the already incredibly high price of the T-80 tank series. Due to the lack of widespread service compared to the basic T-80U, it was not common to find T-80UK tanks during the 1990's, but still, the Agava-2 had a few interesting quirks that are worth investigating.<br />
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Instead of an optical eyepiece or a "fishbowl" lens like the type found on the Abrams, the viewfinder on the Agava-2 was a 384x288p CRT monitor screen similar what the PZB-200 used. The sight itself is only capable of limited optical zoom, from 1.8x to 4.5x. To attain a greater degree of magnification, electronic interpolation (digital enhancement) is used to generate 18x zoom.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://2.bp.blogspot.com/-XgZ6MmQ4R70/VrmuezoLTZI/AAAAAAAAFvQ/IAAEWimLIVI/s1600/agava-2%2Bviewfinder.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-XgZ6MmQ4R70/VrmuezoLTZI/AAAAAAAAFvQ/IAAEWimLIVI/s1600/agava-2%2Bviewfinder.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">(Not actual resolution of viewfinder screen)</td></tr>
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Under the highest magnification setting, the sight facilitates the identification of a tank-type target at a distance of around 2500 m under clear weather conditions. While the sight itself may be more than serviceable enough at combat distances, the low resolution and small size of the monitor makes it difficult to distinguish targets from one another at longer distances.<br />
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<a href="https://4.bp.blogspot.com/-zcEyKuUIS24/Vrmvua3J05I/AAAAAAAAFvY/Xt6azpXSprA/s1600/T-80UM1%2Bgunner%2527s%2Bscreen%2Bagava-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://4.bp.blogspot.com/-zcEyKuUIS24/Vrmvua3J05I/AAAAAAAAFvY/Xt6azpXSprA/s640/T-80UM1%2Bgunner%2527s%2Bscreen%2Bagava-2.jpg" width="640" /></a></div>
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The commander is also provided with a 4.33" CRT monitor which feeds from the Agava-2, giving the commander a duplicate image of what the gunner is seeing.<br />
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<a href="https://3.bp.blogspot.com/-DxdEZMTFld4/VrmvvjBsf_I/AAAAAAAAFvc/MyJo3_40-M4/s1600/T-80UM1%2Bcommander%2527s%2Bscreen%2Bagava-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://3.bp.blogspot.com/-DxdEZMTFld4/VrmvvjBsf_I/AAAAAAAAFvc/MyJo3_40-M4/s640/T-80UM1%2Bcommander%2527s%2Bscreen%2Bagava-2.jpg" width="640" /></a></div>
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The armoured housing that protects the sight aperture can be distinguished from the one for the TPN-3-49 by a hinge on the left of the armoured window cover. The window can be opened from within the tank via a simple pullstring, as you can see below. This particular T-80 is an experimental T-80B equipped with the Agava-2. The armoured housing is identical between all models.<br />
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<a href="https://2.bp.blogspot.com/-dICfRyg1CN0/Vrm3IpKgjlI/AAAAAAAAFvs/pzUQUPrjZiM/s1600/agava-2%2Bhousing.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-dICfRyg1CN0/Vrm3IpKgjlI/AAAAAAAAFvs/pzUQUPrjZiM/s1600/agava-2%2Bhousing.jpg" /></a><a href="https://4.bp.blogspot.com/--tuA2oxwmaM/VrxjpL4-FyI/AAAAAAAAF2M/tEBPIBODh_g/s1600/agava-2%2Bt-80b%2Bexperimental.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="297" src="https://4.bp.blogspot.com/--tuA2oxwmaM/VrxjpL4-FyI/AAAAAAAAF2M/tEBPIBODh_g/s400/agava-2%2Bt-80b%2Bexperimental.jpg" width="400" /></a></div>
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<span style="font-size: large;">STABILIZERS</span></h3>
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<span style="font-size: small;">By 1976, it would have been unimaginable to not include full two-axis weapons stabilization as a prerequisite for the T-80. Being a developmental offshoot of the T-64A, the original T-80 came with the same two-axis stabilizer system. The layout of the stabilizer components remained the same as the T-64A, which was also true when the 2E42 was introduced, as shown in the drawing below.</span><br />
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<a href="https://4.bp.blogspot.com/-QVbu0UovJZo/XDnE5M0aUhI/AAAAAAAAM4k/m69QhrXHw6Aa0c0a3B33uXFQWAtU3kw5gCLcBGAs/s1600/stabilizer%2Bcomponents.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1209" data-original-width="1255" height="385" src="https://4.bp.blogspot.com/-QVbu0UovJZo/XDnE5M0aUhI/AAAAAAAAM4k/m69QhrXHw6Aa0c0a3B33uXFQWAtU3kw5gCLcBGAs/s400/stabilizer%2Bcomponents.png" width="400" /></a></div>
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<span style="font-size: large;">2E28M, 2E28M2</span></h3>
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The 2E28M two axis stabilizer is used in the original model T-80 being the newest stabilizer at the time of its development, while the 2E28M2 was used for modernized T-80 models with the TPD-K1. The stabilization system is precise enough to guarantee hits on tank-sized targets at distances of up to 1.6 kilometers while the tank is travelling cross country, as indicated by Soviet tank gunnery exercise norms.<br />
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The hydroelectric generator for the hydraulic gun elevation mechanism is pictured below.<br />
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<a href="https://4.bp.blogspot.com/-WvQXkHbd9aE/VruCfaPeSOI/AAAAAAAAF08/UIuxmPCJqSI/s1600/2e38m2%2Bhydroelectric%2Bpump.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="365" src="https://4.bp.blogspot.com/-WvQXkHbd9aE/VruCfaPeSOI/AAAAAAAAF08/UIuxmPCJqSI/s640/2e38m2%2Bhydroelectric%2Bpump.png" width="640" /></a></div>
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The maximum turret rotation speed is 18° per second. It would take it a minimum of 20 seconds to do a complete 360° revolution. An inherent shortcoming of hydraulic stabilizers is their risk factor in case of turret penetration. Hydraulic fluid is highly flammable, and it would most likely cause and spread an internal fire very quickly. This is an especially serious concern to the T-80, since the layout of its autoloader does not shelter the ammunition from burning fluids. 2E38M2 uses MGE-10A, a type of mineral hydraulic oil with very low temperature sensitivity, having an operating range of between -65°C to 75°C. The entire system operates at 7.25 psi. This is quite dangerous, as with all hydraulic systems, because hydraulic oil may spurt out from burst tubes at high speeds, spraying large portions of the interior with the flammable liquid.<br />
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The entire stabilization complex is centered around the use of a gyrostabilizer meant for measuring angular velocities in order to enforce corrections. The weight of the sum of all the components is 320 kg.<br />
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<b>Vertical Stabilizer:</b><br />
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Maximum elevating speed: 3.5° per second<br />
Minimum elevating speed: 0.05° per second<br />
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<b>Horizontal Stabilizer:</b><br />
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Maximum turret slew speed: 18° per second<br />
Minimum turret slew speed: 0.07° per second<br />
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The hydraulic fluid reservoir for both the 2E28 is mounted to the roof of the turret, just adjacent to the commander's head. It has a clear window with replenishing indicators. Maintaining the stabilizer and its associated subsystems is the gunner's responsibility. <br />
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<a href="http://3.bp.blogspot.com/-wYmD_FZCW3k/VqybEZje9iI/AAAAAAAAFgI/Q-Vs-pTEEaY/s1600/t-80b%2Bcupola%2Bcounterrotation%2Bmotor.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="185" src="https://3.bp.blogspot.com/-wYmD_FZCW3k/VqybEZje9iI/AAAAAAAAFgI/Q-Vs-pTEEaY/s400/t-80b%2Bcupola%2Bcounterrotation%2Bmotor.png" width="400" /></a></div>
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<span style="font-size: large;"><br />2E42M1</span></h3>
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The components shown in the photo above are the amplidyne generator for the turret traverse motor, the hydraulic arm for the vertical stabilizer with its attached hydraulic pump, and the turret traverse motor itself, from left to right.<br />
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The photo below shows all of the components for the turret rotation mechanism. From left to right: Amplidyne generator, relay control box (to control rate of rotation), and the electric motor for turret traverse.<br />
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<a href="http://4.bp.blogspot.com/-yA4fxetiQN4/VgIpkr7v_zI/AAAAAAAADp0/ktmBBWL1tbY/s1600/305035-2E42%25D0%259C1.jpg"><img border="0" height="424" src="https://4.bp.blogspot.com/-yA4fxetiQN4/VgIpkr7v_zI/AAAAAAAADp0/ktmBBWL1tbY/s640/305035-2E42%25D0%259C1.jpg" width="640" /></a></div>
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<span style="font-size: small;">The 2E42M1 combines a hydroelectric turret rotation and stabilization drive with a hydroelectric cannon elevation and stabilization drive.</span></div>
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<span style="font-size: small;"> </span><br />
<span style="font-size: small;">The hydroelectric pump for powering the cannon elevation system is located under the cannon's breech, and the hydroelectric pump for turret traverse is installed in front of the gunner, behind his sight unit.</span><br />
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<a href="http://4.bp.blogspot.com/-_3c0_fMSIqE/VgIo7eoDzJI/AAAAAAAADpg/zw3e4Gsmizc/s1600/t-80%2Bhull%2Bfloor.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://4.bp.blogspot.com/-_3c0_fMSIqE/VgIo7eoDzJI/AAAAAAAADpg/zw3e4Gsmizc/s640/t-80%2Bhull%2Bfloor.jpg" width="640" /></a></div>
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<tr><td class="tr-caption" style="font-size: 12.8px;">Amplidyne generator for 2E42M1 visible in the upper left corner of the photo<br />
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<span style="font-size: small;">Besides being more precise than the 2E28M-2, the horizontal stabilizer motor is also more powerful, giving the turret on the T-80U a quicker rate of rotation.</span><br />
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<span style="font-size: small;"><b>Vertical Stabilizer:</b></span></div>
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<span style="font-size: small;">Maximum elevating speed: 3.5° per second</span></div>
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<span style="font-size: small;">Minimum elevating speed: 0.05° per second</span></div>
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<span style="font-size: small;"><b>Horizontal Stabilizer: </b></span></div>
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<span style="font-size: small;">Maximum turret slew speed: 24° per second</span></div>
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<span style="font-size: small;">Minimum turret slew speed: 0.054° per second</span></div>
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<span style="font-size: small;">The sum total of the components belonging to the stabilization system weighs 320 kg.</span></div>
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<a href="https://www.blogger.com/null" id="autoloader"></a>
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<h3>
<span style="font-size: large;">AUTOLOADER</span></h3>
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<a href="http://1.bp.blogspot.com/-4-IQfkPGncA/VmT1ZqH1jGI/AAAAAAAAFUI/m08Q0UC-Ax0/s1600/giphy%2B%25281%2529.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-4-IQfkPGncA/VmT1ZqH1jGI/AAAAAAAAFUI/m08Q0UC-Ax0/s1600/giphy%2B%25281%2529.gif" /></a></div>
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Being a direct offshoot off of the T-64 family, the T-80 inherited its autoloader directly from its parent design. The official designation of the autoloader is the MZ ("Механизмом Заряжания") which directly translates to "Loading Mechanism", identical to the T-64A, but an updated version with new radio-guided gun-launched missile compatibility rapidly supplanted the original variant when the T-80B entered service shortly after the original T-80. Another updated version with an improved electronic system was used in the T-80U. In all of its variations, the MZ autoloader is of a hydroelectric type, utilizing hydraulic actuators to drive almost all of its moving parts. Between it and the AZ autoloader used on the T-72 series of tanks, it is quicker to load and has a considerably larger capacity, but it also has its own peculiarities and drawbacks. As usual, the gun needs to be lifted to a fixed angle to line it up properly for the loading mechanism to ram fresh rounds into the chamber, and this is done by the hydraulic vertical stabilizer piston of the cannon. To hold it in place, the gun is hydrolocked.<br />
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The autoloader carousel rotation mechanism is hydraulic, as is the lifting arm that brings the ammunition cassettes up to the ramming position behind the gun breech. The hydraulic lifting arm for the ammunition cassettes is located on the false floor of the turret crew cabin, as you can see in the photo below. A total of 2.2 liters of MGE-10A hydraulic fluid is used in the autoloader.<br />
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<a href="https://3.bp.blogspot.com/-FIiSRvflqYk/Wdjn_pcq46I/AAAAAAAAJzc/v_-IeorV3Vcg5vVo-Ckiwn2XNUvDfsKxQCLcBGAs/s1600/hydraulic%2Bcomponents.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="589" data-original-width="785" height="480" src="https://3.bp.blogspot.com/-FIiSRvflqYk/Wdjn_pcq46I/AAAAAAAAJzc/v_-IeorV3Vcg5vVo-Ckiwn2XNUvDfsKxQCLcBGAs/s640/hydraulic%2Bcomponents.jpg" width="640" /></a></div>
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The ammunition cassette lifting arm can be seen in action in this <a href="https://www.youtube.com/watch?v=p050CWtnZ0U">video of the autoloader of the T-64</a>.<br />
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Both the gunner and commander are provided with controls to the autoloader. The gunner's autoloader controls can be seen below. Photo credit to "<a href="http://photo.qip.ru/users/coast70/150430735//#mainImageLink">coast70</a>" from the QIP.ru photo sharing platform. The dial on the left allows him to select his desired ammunition type, and the big black button on top initiates the loading sequence. The white display panel on the right indicates the status of the autoloader.<br />
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<a href="https://1.bp.blogspot.com/-ldheRV_yOlA/WdjawN_EJfI/AAAAAAAAJyg/AWTxDefL_u8gZ9R1PstQX1rZf5yg00DMACLcBGAs/s1600/t-64%2Bautoloader%2Bcontrol.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="1280" height="480" src="https://1.bp.blogspot.com/-ldheRV_yOlA/WdjawN_EJfI/AAAAAAAAJyg/AWTxDefL_u8gZ9R1PstQX1rZf5yg00DMACLcBGAs/s640/t-64%2Bautoloader%2Bcontrol.jpg" width="640" /></a></div>
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The two-part cartridges are stowed in an 'L' position in the autoloader carousel, thus forming a basket around the turret ring. The basket carousel is mounted directly to the turret ring and moves with the turret, but it rotates independently of the turret when cycling for new ammunition. The turret ring of all T-80 turrets are designed with two ball bearing race rings: one between the turret and the hull and one between the turret and the autoloader carousel. This can be seen in the drawings below.<br />
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<a href="https://3.bp.blogspot.com/-479KKYO9hy8/W_b5_gUN2AI/AAAAAAAAMj4/UtUGgakPI1Q6-_Azd70wTIYOQ4RxzeGPACLcBGAs/s1600/t-80b%2Bturret%2Bring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1372" data-original-width="1299" height="400" src="https://3.bp.blogspot.com/-479KKYO9hy8/W_b5_gUN2AI/AAAAAAAAMj4/UtUGgakPI1Q6-_Azd70wTIYOQ4RxzeGPACLcBGAs/s400/t-80b%2Bturret%2Bring.png" width="377" /></a></div>
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The autoloader carousel rotates at a rate of 26 degrees per second, and some additional fractions of a second are needed for the system to brake when the desired ammunition type is reached. When loading ammunition into the autoloader, the ammunition type is indexed by setting the appropriate type in the autoloader loading control box located next to the commander. Turning the carousel by one step takes up 12-15% of the total loading time, and turning it by three steps takes up 17-22%<br />
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<a href="https://1.bp.blogspot.com/-J8PYWFbFuh8/W_by7gw4BnI/AAAAAAAAMjA/A6pRrlq-hQ4tTbksMbREh5RLyHgAYhLegCLcBGAs/s1600/T-84%2BOplot%2Bproduction_19%2B.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1000" data-original-width="666" height="400" src="https://1.bp.blogspot.com/-J8PYWFbFuh8/W_by7gw4BnI/AAAAAAAAMjA/A6pRrlq-hQ4tTbksMbREh5RLyHgAYhLegCLcBGAs/s400/T-84%2BOplot%2Bproduction_19%2B.jpg" width="266" /></a><a href="https://3.bp.blogspot.com/-dFnjiYTml2g/W2u5Djo1TxI/AAAAAAAAMLQ/PvbDrYJjl5UMrfU1_b0YaMs259o3m3M7ACLcBGAs/s1600/pic_20.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="399" data-original-width="127" src="https://3.bp.blogspot.com/-dFnjiYTml2g/W2u5Djo1TxI/AAAAAAAAMLQ/PvbDrYJjl5UMrfU1_b0YaMs259o3m3M7ACLcBGAs/s1600/pic_20.jpg" /></a></div>
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The propellant charges are held vertically and the projectiles are held horizontally. This arrangement exposes the vulnerable propellant charges vertically, and without any armour protection to speak of (the aluminium cassettes are too thin), this layout increases the probability of ammo deflagration in the event that the armour of the tank is perforated from the front, sides and rear. The propellant charges are the most volatile half of the two-part ammunition, and storing them in such close proximity to the turret ring area of the tank where the majority of shots land would not bode well for the tank if the armour was perforated. Indeed, the thought of being surrounded by a ring of volatile propellant is hardly comforting for the crew in the turret. However, the layout of the autoloader carousel also allows the maximum possible quantity of ammunition to be stored within the geometric constraints of the turret ring diameter. The layout of the autoloader also gives the crew slightly more vertical space compared to the AZ autoloader of the T-72.<br />
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<a href="https://4.bp.blogspot.com/-CwoeruvGADs/W_bzy8MG4bI/AAAAAAAAMjM/YnSeZVRSD-Y--JgnGGX4ioTOeOv3PsxOgCLcBGAs/s1600/T-84%2BOplot%2Bproduction_6%2B.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1000" data-original-width="666" height="320" src="https://4.bp.blogspot.com/-CwoeruvGADs/W_bzy8MG4bI/AAAAAAAAMjM/YnSeZVRSD-Y--JgnGGX4ioTOeOv3PsxOgCLcBGAs/s320/T-84%2BOplot%2Bproduction_6%2B.jpg" width="212" /></a><a href="https://2.bp.blogspot.com/-QRzlTY4uTsA/WdjguzT4puI/AAAAAAAAJy4/OaOU-JKdhpcxgMsdBeZtZzTS1RlsFTGeACLcBGAs/s1600/korzina%2Bring%2Bof%2Bammo.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="589" data-original-width="785" height="300" src="https://2.bp.blogspot.com/-QRzlTY4uTsA/WdjguzT4puI/AAAAAAAAJy4/OaOU-JKdhpcxgMsdBeZtZzTS1RlsFTGeACLcBGAs/s400/korzina%2Bring%2Bof%2Bammo.jpg" width="400" /></a></div>
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The cartridge cassette is composed of two lightweight aluminium trays connected by a hinge.<br />
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<a href="http://3.bp.blogspot.com/-UKoZmGMM8bo/VqSz31lmQSI/AAAAAAAAFdw/QVjUeLHMlzY/s1600/t-80%2Bautoloader%2Btrays.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="288" src="https://3.bp.blogspot.com/-UKoZmGMM8bo/VqSz31lmQSI/AAAAAAAAFdw/QVjUeLHMlzY/s640/t-80%2Bautoloader%2Btrays.png" width="640" /></a></div>
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The second half of the cassette is raised by the hydraulic elevator mechanism acting upon an angled lug in front of its hinge point. The same elevator supplies most of the force propelling the cassette upwards, and it also helps support the weight of the cassette when it is unfurled. The first half of the cassette has an eccentric mounting point for the system of levers of the alignment mechanism to act upon.<br />
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<a href="https://2.bp.blogspot.com/-gGarQuwkRk8/VryxYegJGwI/AAAAAAAAF3Q/jz5YVMy_-SI/s1600/6ets-15%2Bautoloader%2Bdiagram.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="362" src="https://2.bp.blogspot.com/-gGarQuwkRk8/VryxYegJGwI/AAAAAAAAF3Q/jz5YVMy_-SI/s400/6ets-15%2Bautoloader%2Bdiagram.jpg" width="400" /></a><a href="http://1.bp.blogspot.com/-HcSauVXSeuM/VmT0acBzbQI/AAAAAAAAFUA/ivp-BI-CAjw/s1600/giphy.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://1.bp.blogspot.com/-HcSauVXSeuM/VmT0acBzbQI/AAAAAAAAFUA/ivp-BI-CAjw/s400/giphy.gif" width="400" /></a></div>
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As you can see in the GIF above, the two halves of the cassette split apart and release the cartridge from its bonds just a moment before the ramming cycle begins.<br />
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One drawback of the MZ autoloader is that it takes up some horizontal space because the ring of ammunition is installed within the diameter of the turret ring so the crew stations are narrower than the turret ring diameter would suggest. According to factory drawings of the T-64 (Object 432), the diameter of the crew cabin in the turret is 1590mm, although it may be worth noting that the Object 432 is armed with a 115mm D-68 gun and not a 125mm D-81 gun, and that the autoloader carousel holds 30 rounds of the slightly more compact 115mm cartridges instead of 28 rounds of 125mm cartridges. However, the difference is very small. The internal diameter of the turret crew cabin is less than the width of the hull and much less than the tank's turret ring which is 2,162mm in diameter. The photo below shows how the autoloader carousel occupies a significant amount of space and reduces the internal diameter of the crew compartment. The backrest visible in the lower half of the photo is the gunner's seat, and the gun is to the right.<br />
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<a href="https://3.bp.blogspot.com/-AfmEtwGsoj4/WdjgaN7IB7I/AAAAAAAAJy0/KIm_sID8HoUPfHdUcLx_4lTKRyZ58f7dQCLcBGAs/s1600/159939118.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="589" data-original-width="785" height="480" src="https://3.bp.blogspot.com/-AfmEtwGsoj4/WdjgaN7IB7I/AAAAAAAAJy0/KIm_sID8HoUPfHdUcLx_4lTKRyZ58f7dQCLcBGAs/s640/159939118.jpg" width="640" /></a></div>
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One of the distinguishing features of the MZ autoloader is its ammunition capacity - it holds a remarkable 28 rounds of ammo, more than the 22 rounds carried on the T-72, more than the 22 rounds in the ready racks in the bustle of an M1 Abrams (105mm), much more than the 17 or 16 rounds in the M1A1 Abrams (120mm), and nearly double that of the 15 rounds on the Leopard 2. The average loading speed of the MZ autoloader is easily on par with an average human loaders, and even outpaces the AZ autoloader of the T-72 by around one second under ideal circumstances. According to a T-80 technical manual, the combat rate of fire is 7-8 rounds per minute. This is corroborated by the T-64A and T-64B/B1 manuals, which give a combat rate of fire of 8 rounds per minute from the same autoloader and the same fire control system. However, the autoloader itself is capable of loading a round and returning the gun to aim on a target of the gunner's choosing in only 6 seconds if the gunner chooses not to change ammunition types, so the maximum technical rate of fire is actually 10 rounds per minute. A translated cyclogram of the steps in the loading cycle is presented below:<br />
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<a href="https://4.bp.blogspot.com/-EzNEXvH7CIM/WpTz5_cRmdI/AAAAAAAALCA/Tx5QsLyJqpM8sHscSmbIaNCHSUnECvJRwCLcBGAs/s1600/mz%2Bcyclogram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1520" data-original-width="1200" height="640" src="https://4.bp.blogspot.com/-EzNEXvH7CIM/WpTz5_cRmdI/AAAAAAAALCA/Tx5QsLyJqpM8sHscSmbIaNCHSUnECvJRwCLcBGAs/s640/mz%2Bcyclogram.png" width="504" /></a></div>
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This cyclogram comes from the document "<i>Автоматические Системы Заряжания Вооружения Бронетанковой Техники</i>" (Automatic Gun Loading Systems of Tanks) published by the Russian Ministry of Defence, 2011.<br />
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The average time between shots is 7.1 seconds to 19.5 seconds, but the 19.5 second loading time is only true if the gunner is switching from one ammunition type to another and the desired ammo type happens to be the last one in the carousel. Since the autoloader carousel can only rotate in one direction, this forces the carousel to rotate over 26 other rounds (347 degree rotation) at a rotational speed of 26 degrees per second to reach the last one in the carousel. By dividing 347 degrees by 26 degrees per second, we find that the rotation of the autoloader carousel takes up 13.5 seconds, plus a few fractions of a second to account for the initial acceleration period and the braking time. The loading of the cartridge itself takes just under 6 seconds to complete and the total time taken adds up to 19.5 seconds. However, 19.5 seconds is not realistic with a standard combat load of ammunition during real combat, as the autoloader will choose the first round of ammunition of the type specified by the gunner. If, for instance, the tank carried a 3:3:3 ratio of APFSDS, HEAT and HE-Frag (which it does not), the autoloader carousel would have 9 shots of each type loaded plus one extra round. Assuming that the gunner began with APFSDS and decided to switch to HEAT, the carousel would need to rotate over 8 other APFSDS shells to reach the first HEAT shell. If he began with APFSDS and decided to switch to HE-Frag, the carousel would need to rotate over 17 other shells to reach the first HE-Frag shell. This is not quick, but the time needed to rotate over 17 rounds is still much less than 26 rounds. If the gunner switches from HE-Frag back to APFSDS, the carousel will need to rotate over 8 rounds to reach the first APFSDS round. Unless the ammunition is loaded in an unusual order and autoloader is operating under the most unusual circumstances, it would be impossible for a loading cycle to take as long as 19.5 seconds to complete.<br />
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Tankers often came up with their own solutions on how to solve these problems, and one of the solutions was to load ammunition in a repeating pattern, as detailed by Major Mikhail Chobitok in this excerpt from <i>"<a href="https://www.libfox.ru/307354-20-m-saenko-t-64-osnovnoy-boevoy-tank.html#book">T-64: Main Battle Tank</a>"</i> by M. Saenko:<br />
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"<i>Затолкать артвыстрелы в конвеер МЗ можно в любой последовательности. Но в бою, время на заряжание пушки – дороже золота.</i><br />
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<i>Поэтому, если при загрузке равномерно чередовать боеприпасы по типам, то и поиск (а соответственно и заряжание) их будет быстрее.</i><br />
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<i>Конвеер МЗ при заряжании вращается только в одну сторону. Если загрузить сначала все бронебойные, потом все кумулятивные, потом все осколочные, то, выбрав на заряжание любой тип, будешь ждать, пока конвейер прокрутит все и доберется до нужного. А для эффективной стрельбы вероятность нахождения боеприпаса в конвейере должна быть одинаковой! Вот и думай танкист, как тебе быть… Пришлось повозиться.</i>"<br />
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Translated:<br />
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"<i>Loading the rounds into the MZ autoloader conveyor can be in any order. But in battle, the time to load the gun - more expensive than gold.</i><br />
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<i>Therefore, if the ammunition is evenly arranged in alternate ammo types, then the search for the ammunition (and therefore loading) will be faster.</i><br />
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<i>The conveyor when loading the MZ autoloader rotates in one direction only. If you load at first all armor-piercing, then all HEAT, then all HE-Frag, then, having chosen on loading any type, you will wait until the conveyor scrolls everything and gets to the correct one. But to effectively fire the probability of finding ammunition in the conveyor should be the same! Think as if you were a tanker... you have to tinker.</i>"<br />
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In other words, the ammunition was arranged thusly:<br />
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<b><i>APFSDS</i></b> - <i>HEAT</i> - HE-Frag - <b><i>APFSDS</i></b> - <i>HEAT</i> - HE-Frag - <b><i>APFSDS</i></b> - <i>HEAT</i> - HE-Frag<br />
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This makes it quicker for the gunner to switch from one ammunition type to the other, but when the ammunition is arranged in such a way, the carousel must rotate over two shells to get to the same ammo type for every loading cycle. So if the gunner needed to fire at the same target with the same type of ammunition twice in a row (such as if he were engaging a tank with APFSDS, for example), the loading cycle would take 7.5 seconds. This matches the claimed 7.5 second reload speed implied by the combat rate of fire according to the manual. This is not a coincidence. The average minimum time between shots of 7.1 seconds is achieved under the assumption that the autoloader always loads the next round in the carousel (6 seconds) and another 1.1 seconds is taken to aim the gun. This may be how the 8 RPM rate of fire figure is obtained. However, Chobitok does not explain how he or his compatriots accounted for the fact that the combat load of T-64 tanks did not contain an equal ratio of the three ammunition types, which was further complicated by the advent of gun-launched "Kobra" missiles in 1976.<br />
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Of course, this was not necessarily how all T-64 crews did it. It is reasonable to expect that this became a technique that was later passed down by word of mouth to fresh arrivals at specific tank companies, but it may not be institutional knowledge that was taught nationally to all recruits in tank schools.<br />
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Either way, it should be quite obvious by now that the rate of fire may not be the same in all situations, even if all tank crews adhered strictly to the same method of loading ammunition into the carousel. One must not forget that it is often the skill of the crew that determines how much time passes between each shot. Both the gunner and commander do their part to seek out potential threats through their respective vision devices, but the commander must also identify the target upon discovery and he must convey this information to the gunner. The gunner must then verify that he is seeing the same object as the commander, and then proceed determine the range to the target. On the original T-80 with the TPD-2-49 optical coincidence sight, rangefinding can take four seconds or more, depending on the skill of the gunner, but the average time needed to find a target using the tank's vision devices is rather more hazy. As such, the actual time needed to take the first shot is invariably longer than 7.1 seconds, and only subsequent shots on the same target - so the time needed to find and range the target is eliminated - can occur at the theoretical maximum speed of 6 seconds.<br />
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The autoloader is insensitive to scorching heat, freezing cold, nor does it care how fast the turret is spinning, thanks to its impeccable sense of balance. It does not matter if the tank is rocking around like a bucking bronco at 50 km/h over the most gutted dirt paths. The autoloader will still load a shell in the specified time, every time. The common argument that the autoloader can be "knocked out" by hard impact or a hit on the tank's armour is fallacious - a hit on the tank's armour that does not fully penetrate yet is powerful enough to disable the autoloader would also be powerful enough to concuss the people inside the turret and effectively disable the gunner and commander as well as the loader. From an economics standpoint, an autoloader makes sense too. Manufacturing an autoloader on an assembly line costs a certain amount, but training a loader would take at least around 3 months and cost more, and a shoddily trained candidate will not be able to perform "up to spec". Of course, it can be pointed out that depending on unskilled labourers to assemble the autoloaders would also produce the same effect, but really, but shoddy craftsmanship would most likely manifest as reduced reliability, not as reduced loading speed.<br />
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<h3>
<span style="font-size: large;">REPLENISHMENT </span></h3>
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When reloading the cassettes, these halves must be locked together with a special key before the cassette can be indexed and lowered back into the autoloader. This is shown in the photo below.<br />
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<a href="https://2.bp.blogspot.com/-OZsVsV6U9vw/Vrxw1iKDgVI/AAAAAAAAF2w/pL73O1b2Fhk/s1600/Untitled.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-OZsVsV6U9vw/Vrxw1iKDgVI/AAAAAAAAF2w/pL73O1b2Fhk/s1600/Untitled.png" /></a></div>
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Ramming is conducted by a rigid chain actuator located at the back of the turret, directly behind the breech of the gun. The rammer passes through the open back end of the cassette, shoving the propellant and the projectile assembly into the gun chamber in one swift motion and immediately retracting so that the spent shell stub of the previous round can be placed into the cassette before it is folded up back into the autoloader carousel.<br />
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<a href="https://1.bp.blogspot.com/-e3caGC6as6Y/VrytSGE0tvI/AAAAAAAAF3E/s1Gi-1JOhsU/s1600/az%2Bautoloader%2Brammer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://1.bp.blogspot.com/-e3caGC6as6Y/VrytSGE0tvI/AAAAAAAAF3E/s1Gi-1JOhsU/s320/az%2Bautoloader%2Brammer.png" width="142" /></a></div>
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According to the manual, the process of restocking the entire combat load of ammunition including non-autoloader stowage can take between 25 and 30 minutes to complete, while replenishing the ammunition reserves of the autoloader carousel takes between 13 to 15 minutes. Reloading the autoloader is a simple process. All that happens is that the normal loading cycle is reversed, so instead of shells being rammed into the breech of the cannon, the cassettes are raised into position, where they are loaded with a fresh round, then lowered back into the autoloader.<br />
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One of the peculiarities of the autoloader is that the entire row of cartridges stowed around the perimeter of the turret ring completely isolates the driver from the rest of the crew. This makes it practically impossible for the commander to communicate with him without using the intercom system or for the driver to evacuate the tank through the turret. The latter requirement is quite a serious one because the driver cannot exit through his own hatch if the tank cannon is directly above it. However, the designers were kind enough to create provisions for creating a passage between the driver's station and the turret.<br />
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<a href="http://1.bp.blogspot.com/-iGzZP1nzLbk/VgIo5UigrgI/AAAAAAAADpU/uMu7UQKG30Q/s1600/t-80%2Bturret.jpg"><img border="0" height="342" src="https://1.bp.blogspot.com/-iGzZP1nzLbk/VgIo5UigrgI/AAAAAAAADpU/uMu7UQKG30Q/s640/t-80%2Bturret.jpg" width="640" /></a></div>
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However, even this small provision is extremely flawed. The driver can only enter the turret via a small cutout in the turret cabin, but in order to get through the ring of ammunition, he must first remove two cassettes from the ring. This is done using a special lever, which the driver must secure to a protruding lug at the base of the ammunition cassette and then lift it off its mounting point on the carousel ring. This is quite easy if the cassette is empty but extremely difficult if it is not, considering that the tank's two-part ammunition weighed as much as 33.0 kg in the case of standard HE-Frag cartridges and the driver must perform his task from within the confines of the tank, not to mention that the cassettes themselves add some weight as well. The driver would need to deposit the two dismounted cassettes onto the turret cabin floor, preferably with assistance from the two crewmen in the turret.<br />
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<a href="https://1.bp.blogspot.com/--O6dniZQS6o/W2vAGqXN_1I/AAAAAAAAMLc/K-S7AlpIyPE9_lvHMzqOPcvnhXR6eUxnwCLcBGAs/s1600/cassette%2Bremoval%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1236" height="640" src="https://1.bp.blogspot.com/--O6dniZQS6o/W2vAGqXN_1I/AAAAAAAAMLc/K-S7AlpIyPE9_lvHMzqOPcvnhXR6eUxnwCLcBGAs/s640/cassette%2Bremoval%2Bsystem.png" width="494" /></a></div>
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<a href="https://www.blogger.com/null" id="loose"></a>
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<h3>
<span style="font-size: large;">LOOSE STOWAGE</span></h3>
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Whereupon the entire load of ammunition in the autoloader has been expended, the crew has the option of replenishing it with extra cartridges from racks placed here and there all around the interior of the fighting compartment of the tank. The original T-80 and the T-80B had a rather small reserve capacity of just 7 cartridges, stowed in the hull in a conformal fuel tank-cum-ammo rack located on the port side of the hull, just behind the driver's seat.<br />
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<a href="http://2.bp.blogspot.com/-xpYKUBfnOI4/VrBvQqmPWgI/AAAAAAAAFqE/clf_TqN5riU/s1600/t-80%2Bhull%2Bammo%2Brack.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://2.bp.blogspot.com/-xpYKUBfnOI4/VrBvQqmPWgI/AAAAAAAAFqE/clf_TqN5riU/s640/t-80%2Bhull%2Bammo%2Brack.png" width="640" /></a></div>
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Five shells of any type and seven propellant charges can be stowed in the racks, and another two shells may be strapped onto the exterior of the rack to complete the set. These two extraneous shells each have a metal cup bolted to the floor of the hull to hold them in place.<br />
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<a href="https://3.bp.blogspot.com/-ebQQqk-a1pc/VrnkTQAp0_I/AAAAAAAAFwg/6TOHbLPoCOg/s1600/t-80%2Bloose%2Bstowage.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://3.bp.blogspot.com/-ebQQqk-a1pc/VrnkTQAp0_I/AAAAAAAAFwg/6TOHbLPoCOg/s640/t-80%2Bloose%2Bstowage.png" width="640" /></a></div>
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The new T-80U and its turret had space to store 10 extra cartridges. Stowing extra ammunition in the turret was a substantial security risk with the chance of catastrophic ammo detonation jumping up by two times, since now the turret and not just the hull was potential cause for a popped turret. So as mentioned before in the "Gunner's Station" segment, the crew could, and would have opted not to make use of the racks in the turret.<br />
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<a href="https://www.blogger.com/null" id="cannon"></a>
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<h3>
<span style="font-size: large;">CANNON</span></h3>
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-xOtTEuU2mDA/VqJuZDnJoZI/AAAAAAAAFcA/n37ShCUKeEY/s1600/t-80%2Bshooting.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="312" src="https://3.bp.blogspot.com/-xOtTEuU2mDA/VqJuZDnJoZI/AAAAAAAAFcA/n37ShCUKeEY/s640/t-80%2Bshooting.png" width="640" /></a></div>
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There only ever were a few things in common between the members of the Soviet "tank triad", and the cannon was one of them. Like its brothers, the T-80 mounted the 2A46 125mm smoothbore cannon, but along with the T-64, the T-80 was consistently ahead of the T-72 in implementing the latest and most advanced 125mm gun variants.<br />
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<u><br /></u>
The initial T-80 was equipped with the 2A46-1 cannon (D-81TM) which was an improved variant of the original 2A26 (D-81T). The T-80B was equipped with the 2A46-2 cannon which featured the necessary electronic equipment to fire guided missiles.<br />
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<a href="http://3.bp.blogspot.com/-SnuqTRQGhh8/Vq0Gt2N6s1I/AAAAAAAAFmU/7KIUEYfwfpo/s1600/flying%2Btank.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-SnuqTRQGhh8/Vq0Gt2N6s1I/AAAAAAAAFmU/7KIUEYfwfpo/s1600/flying%2Btank.jpg" /></a></div>
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<h3>
<span style="font-size: large;">AMMUNITION</span></h3>
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This section will only contain details on the missiles compatible with T-80, as the basic types of ammunition available to the T-80 are identical to what was available to the T-72. Therefore, if you wish to read about APFSDS, HEAT and HE-Frag ammunition, please head over to <a href="https://thesovietarmourblog.blogspot.com/2015/05/t-72-soviet-progeny.html">the T-72 article</a>.<br />
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<a href="https://www.blogger.com/null" id="missiles"></a>
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<h3>
<span style="font-size: large;">MISSILES</span></h3>
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The relevance of gun-launched guided missiles designed for tank cannons of a limited bore diameter is arguable, to put it mildly, but what is most certainly true is that they were prohibitively expensive and their value against new NATO composite armour arrays was questionable at best until the new tandem charge Refleks-M missile arrived. Besides, the tank would have had very few chances to exploit the incredible range offered by its arsenal of missiles due to the infrequency of encountering large expanses in Central and Western Europe. The huge flatland fields of the Ukraine were optimal, but the Red Army was certainly not planning on being on the defensive.<br />
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However, missiles are not used just for shooting at ground targets. Airborne targets are fair game as well. In fact, besides the Germans, Soviet tank crews are the only tankers that are trained to engage low-flying aircraft as part of their curriculum. The only difference was that West Germans were taught to attempt to use APDS shells to do the job. With speedier 125mm APFSDS ammunition, the T-80 was capable of this too, as mentioned before, but the likelihood of scoring a hit isn't very high.<br />
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<a href="http://4.bp.blogspot.com/-BywXw29AvXM/Vq4jEaKnR7I/AAAAAAAAFoI/WQ1Mej9ZHRE/s1600/kobra%2Bmissile%2Bin%2Bautoloader%2Btray.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="570" src="https://4.bp.blogspot.com/-BywXw29AvXM/Vq4jEaKnR7I/AAAAAAAAFoI/WQ1Mej9ZHRE/s640/kobra%2Bmissile%2Bin%2Bautoloader%2Btray.jpg" width="640" /></a></div>
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The missiles used for the T-80 are split into two halves; rocket motor and fuse for the front half, and warhead plus guidance receiver for the back. The two halves are snapped together by the straightening motion of the loading cassette as it is moved into the ramming position.<br />
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<h3>
<span style="font-size: large;">9M112 "Kobra"</span></h3>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://2.bp.blogspot.com/-xAYy_3AjnTU/WHq9UUzju0I/AAAAAAAAIJw/kYaucXRQAEMrleqTZsz0NyGgwLwF0CGYwCLcB/s1600/9M112_Kobra.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-xAYy_3AjnTU/WHq9UUzju0I/AAAAAAAAIJw/kYaucXRQAEMrleqTZsz0NyGgwLwF0CGYwCLcB/s1600/9M112_Kobra.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">From Stefan Kotsch's website</td></tr>
</tbody></table>
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The 9M112 missile had only a single charge warhead placed at the front half of the missile. The shaped charge liner was possibly made of aluminium. An improved version with a copper warhead was also in use, designated 9M112M. The basic 9M112 version was introduced in 1976, while the improved 9M112M was introduced in 1979. The main improvement of the 9M112M over the basic 9M112 was the use of the new 9N129 warhead with a 20% higher penetration. 9M112M entered service in 1978 and began mass production in 1979. The 9N129 warhead uses OKFOL for a more powerful blast effect and for a more energetic cumulative jet.<br />
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<a href="https://4.bp.blogspot.com/-XNk5RtYUH8k/WHq9waSDIVI/AAAAAAAAIJ0/Ou5OnjFPuYoSh2Vb60g-NO5O3oxPIVS9wCLcB/s1600/11%25D0%25BA%25D0%25BE%25D0%25B1%25D1%2580%25D0%25B0.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://4.bp.blogspot.com/-XNk5RtYUH8k/WHq9waSDIVI/AAAAAAAAIJ0/Ou5OnjFPuYoSh2Vb60g-NO5O3oxPIVS9wCLcB/s640/11%25D0%25BA%25D0%25BE%25D0%25B1%25D1%2580%25D0%25B0.jpg" width="640" /></a></div>
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The placement of the shaped charge warhead at the front of the missile severely limits the standoff distance. This has a negative effect on its penetration power, and renders the missile no more powerful than the typical 125mm HEAT shell.<br />
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Penetration:<br />
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9M112: 250mm at 60°<br />
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9M112M: 300mm at 60°<br />
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The missile is soft-launched out of the gun barrel by the 9D129 propellant charge.<br />
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The 9M112 missile is guided by radio command and directed by the GTN-12 radio antenna. The "Kobra" system is fully integrated into the 1A33 fire control system and works together with the 1G42 sight, which the gunner uses to designate the aiming point. The integral laser rangefinder in the 1G42 sight is also used to determine the distance to the target in order to determine the appropriate mode of guidance. At engagement distances of 4 km, the missile does not fly at a level altitude. Kobra climbs to 3 to 5 meters above the bore axis of the tank and cruises at this elevated altitude until it reaches within 600 to 800 meters of the target, whereupon it descends back to cannon level and continues until it hits the target. The system uses range data from the 1G42 sight in order to plan a flight path and guide the missile toward the target when it enters the final phase of its flight. This enables it to avoid striking bushes, low hills and other natural obstacles throughout its long journey to the target. Together with the low firing signature of the missile, this feature may also decrease the reaction time of the target, as the elevated cruising altitude of the missile puts it above the direct line of sight of a potential target and the missile is also more difficult to see when framed against the backdrop of the sky.<br />
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In the direct fire more, the missile travels at a level altitude and reaches the target in this manner. This direct fire mode is generally intended for use against helicopters, but it is also intended as an emergency mode for shooting high priority targets that appear suddenly at close range if the tank already has a missile loaded.<br />
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<h3>
<span style="font-size: large;">3UBK20 </span></h3>
<h3>
<span style="font-size: large;"><span style="font-size: small;">9M119</span><span style="font-size: medium;"> </span>"Refleks"</span></h3>
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<a href="http://4.bp.blogspot.com/-zwO5SODROVk/VqyivaH3FCI/AAAAAAAAFg8/n9pNt3Tqv1Y/s1600/refleks%2Bmissile.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="252" src="https://4.bp.blogspot.com/-zwO5SODROVk/VqyivaH3FCI/AAAAAAAAFg8/n9pNt3Tqv1Y/s640/refleks%2Bmissile.png" width="640" /></a></div>
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The 9M119 "Refleks" laser beam-riding missile is similar to the 9M119 "Svir" used in the T-72B, but with an increased range of 5,000 meters instead of 4,000 meters. Guidance is accomplished by the integrated 9S517 laser beam unit on the 1G43 sighting complex.<br />
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The missile is soft-launched by a 9Kh949 reduced load piston-plugged ejection charge, giving the missile some momentum before the rocket motor kicks into action. The piston plug is designed to properly seat the missile in the chamber, but its primary purpose is to protect the laser beam receiver at the base of the missile from propellant gasses. The total weight of the 9Kh949 charge is 7.1 kg.<br />
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<a href="https://2.bp.blogspot.com/-GKe2-PlNby4/Vr4_xHEAoLI/AAAAAAAAF6w/gaAI6nCy-O0/s1600/9kh949oooasoidaso.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://2.bp.blogspot.com/-GKe2-PlNby4/Vr4_xHEAoLI/AAAAAAAAF6w/gaAI6nCy-O0/s320/9kh949oooasoidaso.jpg" width="129" /></a></div>
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The missile itself has an efficient layout with the rocket motor placed in the middle, the warhead at the very rear, and the control surfaces and mechanism at the front along with the fuse at the tip. The large distance between the tip of the missile and the warhead means that the warhead is given a large standoff distance without the need for a special standoff probe. The layout enables the 125mm missile to have a comparable flight range as the 127mm ITOW missile, and superior armour penetration performance, but in a much more compact package. With 700mm of penetration, "Refleks" is a much more serious weapon with a much better chance of defeating the new generation (at the time) of NATO tanks like the Leopard 2 and M1 Abrams, albeit from the side. The chances of defeating such tanks from the front with this missile are rather slim.<br />
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The missile uses a solid fuel motor, with four nozzles arranged radially. Flight stabilization is maintained via five pop-out tail fins with curved and angled surfaces to impart a slow spin onto the missile, while steering is accomplished by the two canard fins at the front. These are operated pneumatically, so the more corrections the gunner makes while the missile is mid flight, the less responsive the missile will be over time, though the gunner will have to be tracking a very difficult target like a moving helicopter for this to become noticeable.<br />
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Missile Diameter: 125mm<br />
Wingspan (Stabilizer Fins): 250mm<br />
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Shaped Charge Diameter: 105mm<br />
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Maximum Engaging Distance: 5000 m<br />
Minimum Engaging Distance: 100 m<br />
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Penetration: 700mm RHA<br />
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Hit Probability On Tank-Type Target Cruising Sideways At 30 km/h:<br />
100 m to 4000 m = >90%<br />
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Flight Distance Time:<br />
4000 m - 11.7 s<br />
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<h3>
<span style="font-size: large;">3UBK14M</span></h3>
<h3>
<span style="font-size: large;">9M119M</span><span style="font-size: large;"> </span><span style="font-size: large;">"Refleks-M"</span></h3>
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The appearance of "Refleks-M" gave the T-80 the newfound ability to more confidently destroy newer NATO tanks like the M1 Abrams and Leopard 2, given that their protection requirements for the frontal arc were limited to single charge missiles equivalent to the Milan. With its tandem charge warhead, "Refleks-M"<br />
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The precursor warhead has a cone diameter of 64mm, essentially just as large as a 66mm LAW warhead, and almost equally as powerful. Unlike some tandem warhead designs where a shallow shaped charge of low power is used as the precursor to create a hole in an ERA panel through which the primary charge can pass, the precursor warhead on the "Refleks-M" is large and powerful enough to initiate an ERA panel prior to the detonation of the primary warhead, thus considerably limiting its effects on the primary warhead. However, the downside is that the flier plates of the ERA panel can still fly into the path of the shaped charge jet from the primary warhead, so the effects of ERA may not be fully eliminated. One advantage in having a powerful precursor shaped charge is that it is also effective in compromising armour other than ERA due to its high penetration power. For a precursor charge built for breaching a hole into an ERA panel rather than initiating it, the shaped charge is too weak to have any significant effect on complex multilayered armour as it would fail to perforate even the front plate of the armour array. On the other hand, a large 64mm shaped charge can penetrate the initial layers of a multilayer array and leave the back layers of the armour vulnerable to the primary charge.<br />
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Overall, the combination of features found on the "Refleks-M" missile makes it a suitable weapon against legacy tanks uparmoured with ERA including a number of M60A3 and AMX-30B2 tanks as well as the new standard NATO tanks of the second half of the 1980's, namely the M1A1 Abrams and Leopard 2A4.<br />
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Penetration:<br />
700 - 750mm RHA (Without ERA)<br />
650 - 700mm RHA (Behind ERA)<br />
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<a href="https://www.blogger.com/null" id="pkt"></a>
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<h3>
<span style="font-size: large;">COAXIAL MACHINE GUN</span></h3>
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The T-80 is equipped with the ubiquitous PKTM general purpose machine gun as a supplementary coaxial weapon.<br />
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The PKTM is mainly distinguished from the earlier PKT by the smooth barrel as opposed to the fluted barrel of the PKT. Internally, the PKTM and the PKT differ in the same way that the basic PK and PKM models differ. When the PKM replaced the PK on the production lines in 1969, the production of the original PKT also halted. As such, the T-80 was only officially equipped with the PKTM as the tank only entered service in 1976. The machine gun is fed with 250-round boxes of ammunition with an additional four boxes carried inside the turret cabin next to the commander's feet for total ammunition capacity of 1,250 rounds. The commander is responsible for reloading the machine gun.< br/>
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7BZ-3 API (armour-piercing incendiary) rounds with the B-32 bullet and 7T2 API-T (armour-piercing incendiary tracer) rounds with the T-46 bullet are linked in a 4:1 ratio. The machine gun has a cyclic rate of fire of 700 to 800 rounds per minute. The cartridges are held in 50-round belt segments which are linked together. The coaxial machine gun can be fired either by depressing the trigger button on the gunner's handgrips, or by pressing the emergecy manual trigger button located on the trigger unit installed at the back the receiver of the machine gun.<br />
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In the case of the T-80U, the trigger button on the PNK-4S control module can also be used to fire the machine gun.<br />
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The machine gun is mounted to the right of the main gun, and protrudes from a pill-shaped port which provides vertical space for gun elevation. Since it is mounted alongside the main gun, it receives all the benefits of the stabilization system.<br />
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<h3>
<span style="font-size: large;">ANTI-AIRCRAFT MACHINE GUN</span></h3>
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<a href="http://3.bp.blogspot.com/-JGkwgtxlp_g/VqJfS9JVDCI/AAAAAAAAFXc/hISugWgs2lw/s1600/NSVT%2Bt-80u.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="329" src="https://3.bp.blogspot.com/-JGkwgtxlp_g/VqJfS9JVDCI/AAAAAAAAFXc/hISugWgs2lw/s640/NSVT%2Bt-80u.png" width="640" /></a></div>
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It should be clear by now that the T-80 (Object 219 sp.2) has remarkably little in common with the T-64A despite the fact that it was descended from it. The anti-aircraft machine gun installation is just another one of the details that distinguish the two types from each other.<br />
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The ZU-64 closed-hatch type anti-aircraft installation was being tested from April 13 to September 10, 1971, and it started appearing on T-64 tanks beginning from the T-64A obr. 1972 onwards. However, the ZU-64 had a flawed design and several of the flaws were conceptual and not technical. As such, a new anti-aircraft installation designated the ZU-219 was designed for the Object 219 and it was later evaluated in comparative trials held in Cuba, from February 1 to September 1, 1973. It was tested alongside the already established ZU-72 open-hatch type installation of the T-72, as well as the experimental ZTPU-2 and experimental ZU-62. At the end of the trials, it was recommended that all three Soviet main battle tanks should standardize on the ZU-219. However, the same questionable political factors that led to the creation and adoption of the infamous trio of main battle tanks prevailed here, and the T-72 retained its flawed ZU-72 installation while the T-64A retained its ZU-64 installation and the ZU-219 was shelved.<br />
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Following these developments, the vastly inferior ZU-80 anti-aircraft installation somehow became the final product that ended up being used on mass-production model of the T-80. The ZU-80 is an open-hatch type installation much like the ZU-72, but it is a unique and rather flawed design.<br />
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Unlike the ZU-72, the anti-aircraft installation is mounted directly onto the commander's cupola and not on a separate race ring or skate ring, but unlike the ZU-64, the cupola is not motorized so aiming must be done manually. The location of the machine gun mount had the rather unfortunate effect of completely disrupting the balance of the cupola, forcing the commander to put in more effort when rotating the cupola especially since he does this using the handlebars of his TKN-3 periscope. This issue is compounded if the tank is in motion, and especially so if the tank is moving over rough terrain. Due to the height and length of the machine gun, the tilting and swaying of the tank creates moments of force which the commander must fight when attempting to turn the cupola. The unbalanced loading of the cupola also makes it very difficult to rotate when the tank is on a slope. The ZU-64 would have the same issue, but it has a motorized horizontal drive which eliminates this problem entirely and give the commander a much more pleasant overall experience.<br />
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<a href="https://1.bp.blogspot.com/-q1_NvxRKJ0A/W1Nv6GMm-ZI/AAAAAAAALys/a8xdoKSN5MYQWe5e4yHTCTATplI3TPj2ACLcBGAs/s1600/zu.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="828" data-original-width="1600" height="330" src="https://1.bp.blogspot.com/-q1_NvxRKJ0A/W1Nv6GMm-ZI/AAAAAAAALys/a8xdoKSN5MYQWe5e4yHTCTATplI3TPj2ACLcBGAs/s640/zu.png" width="640" /></a></div>
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Firing the machine gun is done by pressing a trigger paddle located on a handlebar to the left of the gun mount. Elevation is done using a flywheel located on the right of the gun mount. The range of elevation is from -5 degrees to +75 degrees. Traverse is done by simply shifting the entire cupola manually. Although the design of the gun mount is clearly not ideal, to put it mildly, it should not be a serious issue when the commander is outside the hatch and using the machine gun. From outside the hatch, the imbalance of the installation would not be any different from a machine gun on a skate ring mount since the center of gravity of the machine gun itself is actually over the cupola ring even though the machine gun has a cantilever mount.<br />
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<a href="http://3.bp.blogspot.com/-6B8gBAv-MQw/Vqzz-XD_3bI/AAAAAAAAFkI/utp4s7gN0sY/s1600/nsvt.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-6B8gBAv-MQw/Vqzz-XD_3bI/AAAAAAAAFkI/utp4s7gN0sY/s1600/nsvt.png" /></a><a href="http://2.bp.blogspot.com/-GqH2B521gxw/Vqz0J_aIvfI/AAAAAAAAFkQ/GaNEQtfT9rI/s1600/nsv%2Brear%2Bsight.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="198" src="https://2.bp.blogspot.com/-GqH2B521gxw/Vqz0J_aIvfI/AAAAAAAAFkQ/GaNEQtfT9rI/s320/nsv%2Brear%2Bsight.png" width="320" /></a></div>
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The NSVT is a respectably accurate, rapid-firing heavy machine gun chambered in the 12.7x108mm cartridge. It fires at a cyclic rate of 700 to 800 rounds per minute. Against slow-moving or hovering helicopters, the NSVT may occasionally prove marginally useful in theory, especially if the helicopter in question has poor or no cockpit and fuselage protection, although firing at attack helicopters with a machine gun is generally an exercise in futility except under unusual circumstances. Firing at aerial threats is facilitated by a K-10T collimator sight attached to the machine gun cradle. Firing at ground targets can also be done with the K-10T by using the burst-on-target (BOT) method, but using the machine gun's original iron sights are more appropriate for the job. The NSVT operator is trained to fire in 10-round bursts.<br />
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<a href="http://4.bp.blogspot.com/-CfgM5ozebfc/Vqz7uYDtbyI/AAAAAAAAFk0/VWjHAUwtIaU/s1600/collimator-k10-t_front.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://4.bp.blogspot.com/-CfgM5ozebfc/Vqz7uYDtbyI/AAAAAAAAFk0/VWjHAUwtIaU/s320/collimator-k10-t_front.jpg" width="203" /></a></div>
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The K-10T collimator sight projects crosshairs onto the angled glass pane. A tinted glass block is placed in front of it to allow the operator to fire more effectively when facing the sun. When not in use, the sight is turned off and the protective cover is closed. The protective cover must also be closed when fording rivers to prevent water damage.</div>
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<a href="http://4.bp.blogspot.com/-HgiPzRfC9pE/Vqz7wSzqd2I/AAAAAAAAFk8/E9p6V1zYkHw/s1600/k10-t%2Bcollimator%2Breticle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="161" src="https://4.bp.blogspot.com/-HgiPzRfC9pE/Vqz7wSzqd2I/AAAAAAAAFk8/E9p6V1zYkHw/s640/k10-t%2Bcollimator%2Breticle.png" width="640" /></a></div>
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The relatively high cyclic rate of the NSVT compared to its peers like the DShKM and M2HB is useful when dealing aerial threats as the increased density of fire is useful when attempting to hit fast-moving aerial targets or at least deter the pilot from approaching the tank. Unlike the DShKM, the NSVT lacks a muzzle brake but has a flash hider instead which makes it distinctly more pleasant to shoot, especially in low light conditions. The operator is not only much less likely to be blinded by the muzzle flash, but he is also spared from the concussive effect of muzzle blasts.<br />
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The machine gun is fed with 100-round boxes. One box is placed on the machine gun mount and another two boxes are stowed outside the turret next to the commander's cupola for easy access. Three hundred rounds of 12.7mm ammunition is carried in total. The 100-round boxes are heavier and bulkier compared to the more familiar 60-round ammunition boxes provided for the NSVT of the T-72, making it slightly more time-consuming to reload, although this is compensated by the simple fact that the increased ammunition capacity reduces the need to frequently reload. However, by stowing the ammunition boxes externally, it is possible for them to be damaged by gunfire and artillery splinters. This is a drawback shared by all previous Soviet main battle tanks and medium tanks with an anti-aircraft machine gun, including the T-54, T-62, T-64, and T-72. In this case, there was no alternative as the commander's hatch is far too small for the commander to retrieve such large ammo boxes from inside the tank, transfer it through the hatch opening and onto the machine gun mount.<br />
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<a href="https://3.bp.blogspot.com/-yhGXLXT8-_Q/W1Nv4balTeI/AAAAAAAALyo/D0dkQEZRb2ERXhu5tQCxDlWgwBDB0cUQACLcBGAs/s1600/ammo%2Bboxes.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://3.bp.blogspot.com/-yhGXLXT8-_Q/W1Nv4balTeI/AAAAAAAALyo/D0dkQEZRb2ERXhu5tQCxDlWgwBDB0cUQACLcBGAs/s400/ammo%2Bboxes.jpg" width="400" /></a><a href="https://3.bp.blogspot.com/-mNI08BqHRYo/W1W5KyP3DnI/AAAAAAAAL0E/jELljgnZ_ZspSYPMS2SB9HJUEQoZQYpJwCLcBGAs/s1600/ammo.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="1280" height="300" src="https://3.bp.blogspot.com/-mNI08BqHRYo/W1W5KyP3DnI/AAAAAAAAL0E/jELljgnZ_ZspSYPMS2SB9HJUEQoZQYpJwCLcBGAs/s400/ammo.jpg" width="400" /></a></div>
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A mixture of B-32 (steel-core AP-I), B-30 (steel core AP) and BZT-44 (steel-cored API-T) is carried with the non-tracer and tracer rounds linked in a 4:1 ratio.<br />
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The ZU-80 anti-aircraft installation has been an integral part of the T-80B tank and can currently be found even on the latest T-80BVM tank models, as seen in the photo below.<br />
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<a href="https://2.bp.blogspot.com/-jUy4Y6wQw7o/W2Xsp6mbujI/AAAAAAAAL9M/YTAgxI8USyA95YtcasAUP68M7LkL3mXoQCLcBGAs/s1600/t-80bvm%2Bzu.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="533" data-original-width="800" height="426" src="https://2.bp.blogspot.com/-jUy4Y6wQw7o/W2Xsp6mbujI/AAAAAAAAL9M/YTAgxI8USyA95YtcasAUP68M7LkL3mXoQCLcBGAs/s640/t-80bvm%2Bzu.png" width="640" /></a></div>
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T-80 tanks have been observed with a strange metal loop with track links affixed to the back of the cupola. This is apparently a solution to the imbalance of the cupola, though it is clear that this solution does nothing to address the root cause of this problem. Although it seems to be reasonably successful as a counterweight, it also adds more weight to the cupola which partly offsets its primary benefit.<br />
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<a href="https://2.bp.blogspot.com/-uf-NB4Ye27c/W1Nv_pEcUCI/AAAAAAAALyw/nVyiu3B7YBszMP2cFKsJF--lTUtphNCdgCLcBGAs/s1600/8f68c6bdbbe7d5657b6eb0f37ce3e4d1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://2.bp.blogspot.com/-uf-NB4Ye27c/W1Nv_pEcUCI/AAAAAAAALyw/nVyiu3B7YBszMP2cFKsJF--lTUtphNCdgCLcBGAs/s400/8f68c6bdbbe7d5657b6eb0f37ce3e4d1.jpg" width="400" /></a></div>
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The T-80U continues to feature an anti-aircraft machine gun, but the method of mounting the NSVT is rather bizarre. Instead of a conventional ring or skate mount or perhaps a direct installation onto the rotating cupola like on the ZU-80, the NSVT on the T-80U is mounted on any one of three pedestals welded to the turret roof. This can be seen clearly in the photo below (credit to Vitaly Kuzmin).<br />
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<a href="https://4.bp.blogspot.com/-0Oan2XrvXs4/W1W42aBKUnI/AAAAAAAALz8/WK2NqWJcZqsjTPWJPob7CGhidXx7ahXrwCLcBGAs/s1600/kuzmin%2Bt80u.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="426" src="https://4.bp.blogspot.com/-0Oan2XrvXs4/W1W42aBKUnI/AAAAAAAALz8/WK2NqWJcZqsjTPWJPob7CGhidXx7ahXrwCLcBGAs/s640/kuzmin%2Bt80u.jpg" width="640" /></a></div>
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There is one forward and to the right of the commander's cupola (as shown in the photo above), one forward and to the left, and another directly behind the cupola. Alternatively, there is another pedestal behind the gunner's hatch. Elevation is done using a flywheel and traverse is done purely by physical force. The machine gun is still fed from large 100-round boxes and the stowage location of the reserve ammunition boxes remains the same.<br />
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<a href="http://2.bp.blogspot.com/-c_5SsIu6yMI/VqJhd-pq30I/AAAAAAAAFZw/TkDilSdbVVE/s1600/t-80u%2BAAMG%2Bpedestals%2Bturret%2Broof.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="460" src="https://2.bp.blogspot.com/-c_5SsIu6yMI/VqJhd-pq30I/AAAAAAAAFZw/TkDilSdbVVE/s640/t-80u%2BAAMG%2Bpedestals%2Bturret%2Broof.png" width="640" /></a></div>
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This unusual scheme has its own small advantages, but for the most part, this system is a detriment to the usefulness of the machine gun. For one, the fixed installation of the machine gun limits the aiming sector to only about 90 degrees forward and slightly to the right, and that's with the commander leaning out of the hatch. To aim sideways, the commander must exit his hatch and sit out on the turret roof, open to all and sundry. Aiming backwards is not possible unless the machine gun is installed on the rearmost pedestal, which is not feasible when already in combat, as the machine gun itself already weighs 25 kg. The photo below shows the machine gun mount being demonstrated.<br />
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<a href="https://3.bp.blogspot.com/-4BCOxEKJwzw/W2nz29fqM_I/AAAAAAAAMHc/xThwgIvAmfUSsotb0WwcSeGJ8KSmZkSLwCLcBGAs/s1600/t-80u%2Bnsvt.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="720" data-original-width="1080" height="426" src="https://3.bp.blogspot.com/-4BCOxEKJwzw/W2nz29fqM_I/AAAAAAAAMHc/xThwgIvAmfUSsotb0WwcSeGJ8KSmZkSLwCLcBGAs/s640/t-80u%2Bnsvt.jpg" width="640" /></a></div>
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The NSVT mount also includes a canvas belt catcher to prevent sections of belt from landing in front of the commander's pericopes and obstructing them.<br />
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<h3>
<span style="font-size: large;">1ETs29 Remote Weapons Station</span></h3>
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<a href="http://3.bp.blogspot.com/-StLqrU5EjnU/VqzpvCfYdqI/AAAAAAAAFjI/Mfd5m7Tbkkw/s1600/t-80%2Btkn-4s.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="480" src="https://3.bp.blogspot.com/-StLqrU5EjnU/VqzpvCfYdqI/AAAAAAAAFjI/Mfd5m7Tbkkw/s640/t-80%2Btkn-4s.jpg" width="640" /></a><br />
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In 1987, the all-new T-80UD received a new remotely controlled, electrically assisted machine gun mount integrated into a redesigned commander's cupola. It is independently vertically stabilized, and derives horizontal stabilization from the counterrotation mechanism of the cupola. The range of elevation permitted by the mount is extremely generous, spanning from -15° to +85°.<br />
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Aimed fire on ground targets is conducted using the PNK-4 combined sighting system through the eyepieces of the TNK-4S. The commander can shift from observation to shooting at the flick of a toggle switch, whereupon the reticle of the TKN-4S changes to a graduated one with suitable markings and the stabilizer for the NSVT mount is slaved to the sight. The commander is then able to use the sight elevation handgrip to operate the machine gun up and down by +20° and -4° down respectively.<br />
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If the commander wishes to fire at a target situated higher than the tank, he may use the PZU-7 anti-aircraft sight installed at the front left quadrant of the cupola. Using it disengages the machine gun from the TKN-4S, but the use of the thumbswitch is retained for aiming and firing. The sight has a maximum elevation of +70° and maximum depression of -5°.<br />
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<a href="http://1.bp.blogspot.com/-8SHbO8-TAX8/VqyXtt8F9sI/AAAAAAAAFf8/mA9NbtucKPA/s1600/t-80u%2Bpzu-5.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-8SHbO8-TAX8/VqyXtt8F9sI/AAAAAAAAFf8/mA9NbtucKPA/s1600/t-80u%2Bpzu-5.jpg" /></a></div>
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<a href="http://1.bp.blogspot.com/-a9UhXWkGlO4/Vqzw9ILZxOI/AAAAAAAAFjg/IXYdThV7iW0/s1600/pzu-5%2Bsight.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://1.bp.blogspot.com/-a9UhXWkGlO4/Vqzw9ILZxOI/AAAAAAAAFjg/IXYdThV7iW0/s640/pzu-5%2Bsight.jpg" width="640" /></a></div>
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Thanks to vertical stabilization, the commander has the ability to engage targets while on the move.<br />
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<a href="http://2.bp.blogspot.com/-JIebnJeGLuo/VqHjK-fJIUI/AAAAAAAAFXM/ajrBsXNfye4/s1600/utjos001.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-JIebnJeGLuo/VqHjK-fJIUI/AAAAAAAAFXM/ajrBsXNfye4/s1600/utjos001.jpg" /></a></div>
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The main merit of the new weapon system is of course the fact that the commander does not need to expose himself to fire the machine gun, thus isolating him from harm, but unfortunately, the new design is fundamentally not different from the much older ZU-64 installation. Unlike the ZU-219 design, 1ETs29 remote weapon system does not allow the commander to fire the machine gun manually from an open-hatch, thus constricting his ability to react to air attack in the same manner as the ZU-64.<br />
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<a href="https://www.blogger.com/null" id="prot"></a>
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<h3>
<span style="font-size: large;">PROTECTION</span></h3>
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<a href="http://3.bp.blogspot.com/-eDqNErqS6Jk/Vq4hD5uJKbI/AAAAAAAAFn8/XhRPiEUoPJc/s1600/t-80u%2Bhull%2Bon%2Bthe%2Bassembly%2Bline.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-eDqNErqS6Jk/Vq4hD5uJKbI/AAAAAAAAFn8/XhRPiEUoPJc/s1600/t-80u%2Bhull%2Bon%2Bthe%2Bassembly%2Bline.jpg" /></a></div>
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There is no doubt that it was the T-80 series that had the most sophisticated sighting systems and the best firepower, and the T-80s were one of the fastest tanks on Earth to boot, but nothing is perfect. For the T-80, the crux of the matter is the lackluster effort made in utilizing the best glacis armour available at the time, and the turret armour was surpassed by the T-72B in 1983. Regardless, the members of the T-80 family still had a warranty of virtual invulnerability to the vast majority of weapons deployed by NATO with a superiority margin of several years' worth of technology.<br />
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And let's not forget to mention that the secret to not blowing up is to not get seen. The T-80 was equally as short as its big brother the T-64 and its cousin the T-72, though it did get a little taller when the new Object 476 turret was fitted in 1985. Otherwise, the T-80 and T-80B from 1976 and 1978 respectively were both nearly as short as the novel Stridsvagn 103 by a margin of just a few centimeters. And one of the features that made the Strv. 103 so attractive to the Swedes was, of course, its low silhouette.<br />
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<a href="https://1.bp.blogspot.com/-nOVT7BxpwqM/VrpB5nrO0sI/AAAAAAAAFyw/1HS0e1GHMZ0/s1600/t-80u%2Bheight%2Bcomparison%2Bwith%2Bstrv103.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="174" src="https://1.bp.blogspot.com/-nOVT7BxpwqM/VrpB5nrO0sI/AAAAAAAAFyw/1HS0e1GHMZ0/s640/t-80u%2Bheight%2Bcomparison%2Bwith%2Bstrv103.png" width="640" /></a></div>
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Still, getting seen might be inevitable even at the best of times, and not getting seen might not even be possible sometimes, so when the tank <i style="font-weight: bold;">does</i> get hit, the only thing that's worth anything is the steel between the crew and certain death.<br />
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<h3>
<span style="font-size: large;">T-80 (Object 219 sp.2)</span></h3>
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The steel grade used for the construction of T-80 hulls was BTK-1. In 1976, this was the new standard steel grade. T-64 and T-72 tanks transitioned from 42 SM medium hardness steel to BTK-1 during that year.<br />
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Not only was the very first T-80 model from 1976 often visually indistinguishable from the earlier T-64A, they also shared many components and even had identical glacis armour geometry and configurations, although they also differed greatly. The entire upper glacis armour array measures 205 mm in actual physical thickness, but the 68° slope multiplies this figure to 547 mm in line-of-sight (LOS) thickness. The configuration is as follows:<br />
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<span style="font-family: inherit;"><span style="font-family: inherit;"><b>80 mm </b></span></span><b>H</b><b style="font-family: inherit;">HA</b><span style="font-family: inherit;"> > 105 mm Glass Textolite > </span><b style="font-family: inherit;">20 mm HHA</b></div>
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<span style="font-family: inherit;">The areal density of this armour array at the constructional angle of 68 degrees is 2,616 kg/sq.m, so the mass of the armour array is equivalent to a solid steel plate with a thickness of 333mm. Of that, 520 kg/sq.m is from the glass textolite interlayer and the remainder is from the steel plating. </span>A highly detailed examination of this composite armour design is available on the T-72 article. You can view it <a href="http://thesovietarmourblog.blogspot.com/2017/12/t-72-part-2-protection-good-indication.html">here</a>. The main difference between this armour and the armour of the T-72 ural is that BTK-1 high strength, high hardness steel is used as opposed to the medium hardness 42 SM steel, which is equivalent to normal HHA grade steel. As such, the protective value of the T-80 armour is higher by an undetermined amount. In all likelihood, it is somewhere between the older 80-105-20 armour with RHA steel and the 60-105-50 armour array of the T-72 Ural-1 and T-72A.<br />
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One of the distinguishing features of the T-80 armour that separates it from the T-64A is related to the implementation of three medium-sized periscopes installed in the upper glacis for the driver as opposed to a single large periscope in the upper glacis and two smaller ones embedded in the hatch. The visibility from the new scheme was good, but to accommodate the three periscopes, the cutout in the upper glacis armour had to be widened considerably. Since this cutout was a weakened zone, the increase in its size was not profitable, to put it mildly. The large cutout can be seen in the photo below (credit to VoLLanD).<br />
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<a href="https://2.bp.blogspot.com/-gXQn0H1hLxA/W1OxXP_vPPI/AAAAAAAALzk/FDJFwbMFy_0Asneui4k29-ki7mPwI7P2wCLcBGAs/s1600/1215632573_t_80_53.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="493" data-original-width="726" height="434" src="https://2.bp.blogspot.com/-gXQn0H1hLxA/W1OxXP_vPPI/AAAAAAAALzk/FDJFwbMFy_0Asneui4k29-ki7mPwI7P2wCLcBGAs/s640/1215632573_t_80_53.jpg" width="640" /></a></div>
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<span style="font-family: inherit;">This design flaw continued to plague the T-80 series to this day. It is not possible to eliminate this weakened zone without a fundamental overhaul to the armour geometry and the driver's station.<br /><br />In 1979, the original T-80 underwent a modernization program to bring it up to the level of the T-80B, which sported a revised design that was better optimized against emerging Western long rod penetrators.</span><span style="font-family: inherit;"> As a result, it was decided to weld a high hardness steel appliqué plate to supplement the base armour. </span>The pre-fabricated plates were sent to depots where they could be installed as part of regular scheduled maintenance, along with a few other minor things added as part of the modernization program.<br />
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<a href="https://2.bp.blogspot.com/-2UDbNhOhBDM/VtF8soN7fkI/AAAAAAAAGDk/pWF8eYWNC1I/s1600/t-80%2Bapplique%2Barmour.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="424" src="https://2.bp.blogspot.com/-2UDbNhOhBDM/VtF8soN7fkI/AAAAAAAAGDk/pWF8eYWNC1I/s640/t-80%2Bapplique%2Barmour.jpg" width="640" /></a></div>
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<a href="https://www.blogger.com/null" id="t-80b"></a>
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<span style="font-family: inherit; font-size: large;">T-80B (Object 219R)</span></h3>
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While the original glacis armour configuration was more than enough to contend with perhaps all 105mm ammunition of the APDS variety found on the other side of the Iron Curtain, by 1976, the design was already teetering on the brink of obsolescence. By that point, only the T-64B and T-80 were still using the older upper glacis armour design which was first used in the original T-64 (Obj. 432) that had been mass produced since 1964. Keeping in step with these developments, the new T-80B obr. 1978 (Object 219R) used a more optimized armour design with improved performance against long rod APFSDS rounds. According to Alexey Khlopotov (known online as "Gur Khan"), the configuration is as follows:<br />
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<b>60mm HHA</b> -> 100mm Glass Textolite -> <b>45mm HHA</b></div>
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This new array was based on the design developed for the T-72 Ural-1 and T-72A and was nominally equivalent in overall thickness and in the distribution of layers. This armour layout is also considerably more resilient compared to the 80-105-20 design retained in the T-64B. According to Andrei Tarasenko, the upper glacis armour of the T-80B was equivalent to 380mm RHA whereas the armour of the T-72A was equal to 360mm RHA. It is worth noting that many of his numbers lack an internal consistency and sometimes contradict each other, so it is inadvisable to take these numbers at face value. For an in-depth examination of the 60-105-50 armour, please refer to Tankograd's T-72 article, Part 2. In short, the use of BTK-1 instead of normal RHA steel for the front plate and back plate of the armour increases the effectiveness of the armour by not only offering greater resistance due to its increased toughness, but also by increasing the transverse loading experienced by a long rod penetrator passing through the plate. This increases the stresses experienced by the rod, making it more effective at breaking apart long rod penetrators. An indirect effect of this phenomenon is that the glass textolite interlayer sandwiched between the two steel plates will have an increased efficiency.<br />
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In 1980, the steel grade used for the production of T-80 hulls was upgraded to BTK-1Sh. BTK-1Sh is a grade of high hardness, high strength steel produced by electroslag remelting (ESR), giving it higher hardness without sacrificing ductility. Further confirmation of the use of BTK-1Sh rolled steel plates in T-80 tanks comes from a <a href="https://andrei-bt.livejournal.com/454554.html">Soviet study on the weldability of this steel</a>. In general, BTK-1Sh is recognized as a general purpose high strength steel, suitable for welding and for manufacture in thick plates of up to 85mm, or perhaps more. Depending on the thickness of the plate, the hardness of the steel ranges from 400 to 450 BHN.<br />
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In<span style="font-family: inherit;"> 1983, the </span><span style="font-family: inherit;"><span style="font-family: inherit;">recent revelations on newly emerging 105mm APFSDS technology - embodied by the Israeli M111 Hetz - prompted the need to add additional armour in order to proof the hull against the M111 round at shorter range. As such, a 16mm appliqué plate was welded directly onto the upper glacis. The plate was cut in such a way that it could be fitted directly onto the surface of the upper glacis and not interfere with the mine plough mounting points and the tow hooks. Steven J. Zaloga claims in page 23 of "<i>T-80 Standard Tank: The Soviet Army's Last Armored Champion</i>" that the appliqué armour plate is 20mm thick, but this is not corroborated by any Russian or Soviet sources.</span></span><br />
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<span style="font-family: inherit;">During this time, a new 5-layer glacis armour array was under development as a response to the growing threat posed by the new West German 120mm smoothbore cannon. When the T-80BV arrived in 1985 with the improved armour array</span><span style="font-family: inherit;">, the obsolescent T-80B could not be left behind, so there was a need to bring its standard of protection up to the level of the new T-80BV without changing the armour layout entirely as that was not possible without dismantling the tank hull. Once again, the solution was to weld additional armour onto the existing array, but this time, the new</span><span style="font-family: inherit;"> appliqué armour plate was</span><span style="font-family: inherit;"> 30mm thick. The thick 30mm plate has the same cutout shape as the earlier 16mm plate, so the only way to distinguish them is to simply check the thickness by eye. The photo below shows one example of a T-80B modernized to T-80BV standards. Notice the much thicker weld seams joining the appliqué plate to the upper glacis.</span></div>
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As a result of this modernization, the total thickness of steel in the upper glacis armour array was increased to 135mm while the thickness of glass textolite remained the same at 100mm. The areal density increased to 3,347 kg/sq.m of which 2,829 kg/sq.m was steel. The mass of the armour became equivalent to 426mm of solid steel. It is interesting to note that the five layered armour design of the T-64BV was developed using the 60-100-45 layout as the basis. The same 30mm high hardness plate was used, but instead of welding the high hardness plate to the surface of the 60mm front plate, the 30mm plate relocated to the interlayer. The thickness of the original 100mm glass textolite interlayer was reduced accordingly to 70mm, and it was divided into two layers, thus forming the now-familiar 60-35-30-35-45 design. Due to the increased efficiency of the five layer armour design, the upper glacis armour of the T-64BV is more resilient than the upper glacis of a modernized T-80B.<br />
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The T-64B was modernized to T-64BV standards with an appliqué plate of the same thickness, but it still retained the old 80-105-20 array and thus lagged behind the T-80B in this aspect. Due to the low efficiency of the thin 20mm steel back plate of the older design, the overall efficiency of the upgraded armour was not high. For the most part, the burden of eroding a long rod penetrator would be largely taken up by the thickened front steel plates (30mm + 80mm) as opposed to a pair of plates with an optimal distribution of thickness. As such, the modernized T-80B armour had a non-trivial edge over both the T-64B and the T-72A while differing very little in weight.<br />
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The turret of the T-80B is very similar to the turret of the T-72A, but is very slightly thicker (by around an inch or so) in certain areas. The transition from the turret of the T-64A to the "Kvartz" turret which was originally developed for the T-72A seems surprising given that the T-80 is descended from the T-64 and not the T-72, and especially since the turret appears somewhat crude compared to the enigmatic "Combination K" ceramic armour of the T-64B, made from two rows of sintered silicon carbide balls suspended in solid cast steel. However, the level of protection offered by the "Kvartz" composite turret was not worse and the production process was very simple and cheap compared to the "Combination K" design.<br />
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The gradient of the decline in armour thickness at the sides of the turret is also slightly less steep than the T-72A turret. The "Kvartz" insert also reaches slightly further back along the side of the turret. However, this turret design is not necessarily better protected than the T-72A turret across a wide frontal arc, since the curvature of the T-80B turret is more rounded as opposed to the teardrop shape of the T-72A turret. Because of this, more of the sides and less of the frontal cheek armour will be exposed when the turret is viewed from a side angle of 30 degrees or more. By compensating for the curvature with thickened armour, both turret designs offer a very similar level of protection across the frontal 70 degree arc.<br />
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<a href="https://1.bp.blogspot.com/-vy_r0N_oNIw/W_b4zScFWmI/AAAAAAAAMjs/4uALYT4jx60QMUL_IGabK2mbSPgEzhuVACLcBGAs/s1600/t-80b%2Bfront.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="772" data-original-width="1600" height="308" src="https://1.bp.blogspot.com/-vy_r0N_oNIw/W_b4zScFWmI/AAAAAAAAMjs/4uALYT4jx60QMUL_IGabK2mbSPgEzhuVACLcBGAs/s640/t-80b%2Bfront.png" width="640" /></a></div>
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The "Kvartz" turret design was carried over to the T-80BV (Object 219RV) but it was eventually replaced by the more advanced T-80U (Object 219AS) turret which incorporated NERA elements. In 2017, the T-80BVM model was unveiled. The modernization program makes use of Soviet-era stocks of ageing T-80B and T-80BV and gives them a new purpose as specialized cold weather tanks. One of the improvements from the modernization was the installation of Relikt explosive reactive armour on the frontal arc of the turret and on the upper glacis. Due to the use of the "Kvartz" filler as an integral component in the casting process for the composite armour in the turret, it is not possible to upgrade the armour of the T-80B and T-80BV. The hull armour also cannot be upgraded for a similar reason. As such, the only increase in protection is derived from Relikt ERA.<br />
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<span style="font-family: inherit; font-size: large;">T-80BV (Object 219RV)</span></h3>
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<a href="https://1.bp.blogspot.com/-x10-yok9T9Y/WJQ6hvX1KLI/AAAAAAAAIT4/2AstO93IJhEsKUiCBV1vEbpsMAcIZkc5gCLcB/s1600/T-80_MBT_reactive_armour.JPEG" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="432" src="https://1.bp.blogspot.com/-x10-yok9T9Y/WJQ6hvX1KLI/AAAAAAAAIT4/2AstO93IJhEsKUiCBV1vEbpsMAcIZkc5gCLcB/s640/T-80_MBT_reactive_armour.JPEG" width="640" /></a></div>
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<span style="font-family: inherit;"><br /></span><span style="font-family: inherit;">In 1985, the newly introduced T-80BV came endowed with a heavier, but more effective double sandwiched laminate array design for the upper glacis. Instead of a single layer of glass textolite between two steel plates, the new array is composed of two thinner layers of glass textolite sandwiched between three 50mm steel plates. The steel plates are made from BTK-1 high strength, high hardness steel like before. This new array has a physical thickness of 220mm and a LOS thickness of 587mm at the constructional angle of 68 degrees. The areal density of this array is 3,490 kg/sq.m, which is equivalent to a solid steel plate with a thickness of 444.6mm. The turret of the T-80BV was the same as the T-80B, which was itself very similar to the turret of the T-72A and featured a similar "Kvartz" filler. The turret was not improved except for the installation of Kontakt-1. As such, the principal difference between the T-80BV and the T-80B is in the upper glacis armour and in the installation of reactive armour. The new upper glacis armour array is as follows:</span><br />
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<span style="font-family: inherit;"><b>50 mm RHA</b> - 35 mm <span style="text-align: start;">Glass Textolite</span> - <b>50 mm RHA</b> -> 35 mm <span style="text-align: start;">Glass Textolite</span> - <b>50 mm RHA</b></span></div>
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The additional protection against KE attack was achieved with the addition of a center steel layer and in the revised distribution of layer thicknesses. At a slope of 68 degrees, the LOS thickness of the steel alone is 400mm. The two glass textolite layers are not as thick as in the previous models, but the increased thickness of steel led to an increase in protection against shaped charges all the same. Compared to the similar 5-layer array of the T-64BV, the armour of the T-80BV is thicker and heavier, having a total thickness of 150mm of steel distributed equally in three layers as opposed to 135mm of steel distributed in the order of 60-30-45. It is known that the optimal thickness of a steel front plate is 1-2 rod diameters, and considering that the diameter of the latest 105mm and 120mm APFSDS rounds were all less than 30mm, the 50mm front plate of the T-80BV armour array lies squarely within the range of optimal plate thicknesses, and so does the 60mm front plate of the T-64BV, so the T-80BV does not have an advantage or disadvantage in this respect. The only advantage of the T-80BV armour lies in the thicker 50mm center and back plates inside the armour array, which are thicker than the 30mm and 45mm center and back plates of the T-64BV by a non-trivial amount.<br />
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It is likely that the 50-35-50-35-50 armour array of the T-80BV is more efficient than the 60-35-30-35-45 array of the T-64BV. Conceptually, the design of the T-64BV armour array is only an evolution of the simpler three-layer array of the T-80B. On the T-64BV, the option of creating an entirely new configuration with a new distribution of steel layer thicknesses was not pursued. Rather, a 30mm plate of high hardness steel was simply added to the existing 60-100-45 design created for the T-80B as the center layer - it was mentioned by <a href="http://btvt.info/3attackdefensemobility/armor.htm">Andrei Tarasenko in an article</a> that the central steel plate in the five layer armour of the T-64BV had an increased hardness which increased the efficiency of the armour array. It is not known if the 50mm center layer of the armour of the T-80BV is made from a special grade of high hardness steel as well, or if all three steel layers are made from BTK-1. Based on Soviet and Russian studies on the topic, it is highly desirable to maximize the hardness of the center layer and increase the thickness of the steel back plate as this increases the efficiency of the armour array against long rod penetrators.<br />
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On page 297 of "<i>Particular Questions of Terminal Ballistics</i>" 2006 (<i>Частные Вопросы Конечной Баллистики</i>), an analysis of a five-layer composite armour arrays with steel and textolite reveals the inner workings of this type of armour and the methods of optimizing it. Analysis of experimental test results reveals that the penetrator rod experiences transverse loads in an oscillating pattern as it travels through a five-layer armour array. This is caused by the large differences in the physical characteristics of glass textolite and steel. The large oscillating amplitude of the lateral forces and torque generates strong bending stresses in the rod, thus weakening the rod and reducing its penetration power. The rod also experiences strong shock loads during each impact with the front surface of the steel plates. For a five layer design with three steel plates, three shock events are experienced by the rod. Deformation of the rod tip is observed throughout the penetration process, as the tip is deflected upwards by strong lateral forces when it impacts the front surface of the steel plates (impact phase) and then it is deflected downwards when it emerges from the back surface of the steel plates (breakout phase). The deformation of the tip during the breakout phase is caused by the asymmetry of material thickness above and below the rod. The asymmetry of material thickness generates an asymmetric load on the rod, causing the tip of the rod to deflect towards the path of least resistance.<br />
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Figure 5.27 (below) illustrates the physical changes experienced by the penetrator rod as it travels through an experimental five-layered steel and glass textolite armour array sloped at 65 degrees. The impact velocity of the rod is 1,450 m/s. As you can see in the first graph on the upper left corner, the transverse force imparted onto the long rod penetrator (F<span style="font-size: xx-small;">y</span>) is in the upwards direction when it travels through the front steel plate (1) and center steel plate (3) and then normalizes at the end of its travel through the steel back plate (5). Note that the rod is heavily deflected downward when it exits the back of the center steel plate. The upwards transverse force imparted during the penetration of the steel back plate (5) is only just enough to counteract this deflection. As you can see in the first graph, the direction of the transverse force on the rod shifts drastically as it enters the breakout phase on the center plate, plateaus for a short while, and then shifts further as the rod penetrates the second glass textolite layer (4). The sudden shift in transverse loading is amplified by the large forces involved, which creates huge stresses in the rod. The magnitude of forces is especially huge compared to the forces experienced by the rod as it travels through the front steel plate and first glass textolite layer. Furthermore, it can be seen that the resistive force along the axis of the penetrator (F<span style="font-size: xx-small;">x</span>) constantly increases as the penetrator progresses through the armour array, reaching its peak at the center layer, then fluctuates until the projectile reaches the steel back plate where the resistive force decreases until the penetration stops. Note that resistive force is proportional and opposite to the force imparted by the penetrator rod and is dependent on the mechanical properties of the target material.<br />
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From these results, it can be surmised that increasing the hardness of the center steel plate (for any given thickness) will maximize the stress on the rod and increase its deflection. Allocating more armour mass towards the center layer will also be advantageous. Increasing the thickness of the steel back plate is also desirable in order to better absorb the remainder of the penetrator and to further deflect its trajectory upwards, thus increasing the effective thickness of the back plate and imparting greater stress on the rod.<br />
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Breakout effects will indirectly generate additional losses in the penetration power of a long rod penetrator: during the period immediately after the rod emerges from the back of a steel plate, the tip of the rod has a low velocity relative to the rest of the rod and the tip will be deflected due to asymmetric loading. The tip will also continue to erode (read: lose mass) due to the release of accumulated stresses. When the tip of the rod impacts the next steel plate, the combination of low velocity and non-optimal shaping causes the tip to ricochet off the surface of the plate. This is a source of additional losses in rod material and structural integrity.<br />
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The glass textolite layers have a relatively minor effect compared to the steel layers, but the breakout effects also enhances the efficiency of the glass textolite: the penetration efficiency of a eroded penetrator rod with a deformed tip is reduced, and conversely, the efficiency of the glass textolite layer is increased.Still, it was identified that the protection value offered by a multilayered steel-glass textolite array is mainly derived from the spacing of the steel plates into multiple layers, but extensive testing on tank armour as well as special targets reveals that the efficiency of the glass textolite layers can be equal to steel of its own weight (mass efficiency coefficient of 1.0) when incorporated in an optimal multilayer design sloped at 65 degrees, and even exceed the mass efficiency of steel by 3-5% in some cases. The high obliquity of the upper glacis of the T-80BV (68 degrees) implies that the glass textolite layers in the armour have a mass efficiency coefficient of not less than 1.0.<br />
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This can be seen in the second graph on the right column. The bottom curve in the graph (u/V<span style="font-size: xx-small;">0</span>) shows the velocity of the rod tip at the point of contact with the armour. The long rod penetrator travels at a lower velocity in the steel layers than in the glass textolite layers, but a constant deceleration can be observed.<br />
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On a side note, it is stated in the book that a homogeneous glass textolite block can have a mass efficiency exceeding homogeneous steel armour by 1.3 to 1.5 times when impacted at a flat angle (by an unspecified type of projectile). However, the arrangement of glass fibers in the glass textolite gives it anisotropic properties, such that the efficiency of the material is vastly degraded when it is sloped. Furthermore, the enhanced strength and ductility of modern tungsten alloy and depleted uranium long rod penetrators makes them much tougher which inhibits the erosion of the rod as it penetrates glass textolite, thus rendering glass textolite largely ineffective as a barrier against modern APFSDS threats if not incorporated into a heavy multilayered array. Conversely, the low toughness of tungsten carbide increases the efficiency of glass textolite, which provides a justification for the high thickness of glass textolite used in the previous armour designs for the T-64, T-72 and T-80.<br />
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In pages 410-427 of "<i>Particular Questions of Terminal Ballistics</i>", a multitude of different array layouts with different ratios of layer thicknesses were tested against tungsten alloy long rod penetrators of differing aspect ratios to find the optimal distribution of thicknesses and the optimal obliquity. The results are particularly interesting as they can be compared to the five-layer design of the T-80BV.<br />
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The three-layer array shown below has a 1.2:2.12:1.0 ratio of layer thicknesses with steel front and back plates with a glass textolite interlayer. The ratio of thicknesses is equivalent to the 60-105-50 armour layout. This layout was placed at an angle of 68 degrees and was tested against two types of tungsten alloy long rod penetrators with equal lengths but different diameters (aspect ratios: UPE-3 = 11.0, UPE-4 = 12.0) and compared to other layouts. The calculated magnitude of force imparted on the penetrator in the vertical plane and along the axis of the rod is shown in the first two graphs, and the change in velocity of the penetrator at the tip and at the tail (in separate curves) is shown in the third graph.<br />
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<a href="https://2.bp.blogspot.com/-0c7zkfPakgA/WsOft8DCg5I/AAAAAAAALTo/PG5Jl7SUu9sCSu8gzqNoqurPdArMd7aUgCLcBGAs/s1600/60-105-50.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1276" data-original-width="774" height="640" src="https://2.bp.blogspot.com/-0c7zkfPakgA/WsOft8DCg5I/AAAAAAAALTo/PG5Jl7SUu9sCSu8gzqNoqurPdArMd7aUgCLcBGAs/s640/60-105-50.png" width="388" /></a><a href="https://2.bp.blogspot.com/-KisItILy9sU/Wu2xNPM8E2I/AAAAAAAALg8/b4enjFEzcao1vH-swMWbNtNWYppiZwTBgCEwYBhgL/s1600/seven%2Blayer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1105" data-original-width="600" height="640" src="https://2.bp.blogspot.com/-KisItILy9sU/Wu2xNPM8E2I/AAAAAAAALg8/b4enjFEzcao1vH-swMWbNtNWYppiZwTBgCEwYBhgL/s640/seven%2Blayer.png" width="346" /></a></div>
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As you can see for the 60-105-50 armour layout, the penetrator experiences large destabilizing effects inside the steel front plate, but remains almost completely steady inside the glass textolite interlayer, and then experiences a downward deflection as it impacts the steel back plate before becoming deflected upward. More specifically, it can be observed that the long rod penetrator is strongly deflected upward during the initial phase of its impact with the front plate, and then the rod is strongly deflected downward during the breakout phase before equalizing as it travels through the glass textolite interlayer. The large forces involved and the violence of the shift in vertical deflection shows that the long rod penetrator experiences huge transverse loading during its penetration of the steel front plate, but there is practically no transverse loading as it penetrates the glass textolite interlayer. Furthermore, the velocity of the penetrator rod tip drops sharply as it penetrates the front steel plate but barely changes as it travels through the glass textolite layer and the resistive force along the axis of the penetrator (F<span style="font-size: xx-small;">x</span>) is very small - up to 20 times less than the resistive force from the steel plate. This is in marked contrast to the constant deceleration of the rod tip and the high resistive force that was observed in the five-layer armour.<br />
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The interaction between the rod and the steel back plate is also interesting, as the gradient of the deflection curve implies that the rod would continue to be deflected upward as it penetrates deeper into the plate. Conversely, a back plate of low thickness (such as the 20mm back plate found in the T-80 obr. 1976, in some T-72 models and in all T-64 models prior to the T-64BV) is clearly inefficient because the downward deflection of the rod would reduce its effective thickness. This observation is supported by other studies confirming that the 20mm back plate of the older 80-105-20 armour design was inefficient against long rod penetrators, which was the original incentive for the shift to the 60-105-50 design on the T-72 in 1976 and for the shift to the 60-100-45 design on the T-80B in 1978.<br />
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Overall, the performance of the simpler three-layered armour is clearly worse compared to a seven layer armour which was able to obtain much better results by simply redistributing the same materials into more layers. Two different long rod penetrators were fired at the seven-layer target: UPE-3 and UPE-4 with aspect ratios of 10.0 and 12.0 respectively. As shown in the graphs, the transverse loading on the rod oscillates violently in direction and magnitude, imparting huge stress on the penetrator. Furthermore, the velocity of the penetrator is constantly reduced as it travels through the armour array, which implies that the efficiency of the glass textolite layers is much better as they have a much greater contribution to the erosion of the long rod penetrator.<br />
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These experimental armour designs used only normal RHA steel plates, but it is well known that increasing the hardness of the front plate leads to a corresponding decrease in the performance of a long rod penetrator attacking the armour. The effects of increasing the hardness of the other steel plates in the armour array also tend to be positive. Considering all the available information, it is understood that the upper glacis armour of the T-80BV is of an efficient layout and its mass efficiency greatly exceeds that of a monolithic steel plate of equivalent mass, and based on the information gathered so far, it is obvious that the low mass efficiency coefficient implied by the low numbers attributed to the upper glacis armour of the T-80BV like "430mm RHA" are simply impossible as the efficiency of the five-layer armour is obviously higher than the simpler three-layered armour used in preceding tank models.<br />
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Adding on to that, the drawing below, shared by <a href="http://forum.militarium.net/viewtopic.php?f=3&t=6917&start=150#p246383">Militarysta (Jaroslaw Wolski) on the Polish militarium.net forum</a>, details the formation of "lips" at the edges of the perforated plates due to the asymmetrical distribution of forces on the back surface of the plate during the penetration process. The "lips" are pushed into the path of the shaped charge jet or the long rod penetrator by a shock wave travelling through the non-metallic filler and rebounding off the neighbouring steel plate. The drawing are from MBB, a German company where the illustrious Dr. Manfred Held worked during the 70's and developed his first explosive reactive armour.<br />
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<a href="https://4.bp.blogspot.com/-qi4y3K1nyOs/WdjXwZlRTdI/AAAAAAAAJyQ/rudQ87vQdvc1JXXdDz1NHuHaJ3cZOWpRwCLcBGAs/s1600/Ko%2Bpozytowy%2Bvol%2B1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="492" data-original-width="800" height="392" src="https://4.bp.blogspot.com/-qi4y3K1nyOs/WdjXwZlRTdI/AAAAAAAAJyQ/rudQ87vQdvc1JXXdDz1NHuHaJ3cZOWpRwCLcBGAs/s640/Ko%2Bpozytowy%2Bvol%2B1.jpg" width="640" /></a></div>
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However, this appears to be a secondary effect at best. The contribution of the "lip" effect is reportedly quite low.<br />
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Because of the increased thickness of steel, the armour of the T-80BV is undoubtedly more resilient than the T-64BV design but the difference in mass efficiency is less clear as there are very few sources of information on how this affects the overall function of the armour array. According to Andrei Tarasenko in <a href="http://www.btvt.narod.ru/4/t-80.html">an article</a>, the upper glacis of the T-80BV was equivalent to 430mm RHA and the upper glacis of the T-64BV is equivalent to 410mm RHA.<br />
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Having a mass of 444mm in terms of thickness of solid steel, the calculated mass efficiency coefficient of the T-80BV armor according to Tarasenko's figure is 0.97. On the other hand, the mass of the T-64BV armour is equivalent to 404mm of solid steel so the calculated mass efficiency coefficient of the array is 1.01. Perhaps the ratio of layer thicknesses in the T-64BV design is better, but the low mass efficiency of both designs compared to monolithic homogeneous steel is highly dubious. Indeed, if these numbers are correct, then a single monolithic steel plate (mass efficiency coefficient of 1.0) would be more efficient than the multilayered composite of the T-80BV which obviously cannot be true. Furthermore, Tarasenko also claims that the armour of the T-72A modernized with a 16mm appliqué plate is equivalent to 405mm RHA, but the T-72A armour is equivalent to 403mm of steel in weight so the mass efficiency of the armour would ostensibly be 1.0. Needless to say, it is extremely unlikely that the 5-layer array of the T-80BV would perform worse than the appliqué armour stop-gap solution used on the older and simpler 3-layer design of the T-72, especially since <a href="http://btvt.info/3attackdefensemobility/armor.htm">Tarasenko states in another article</a> that the new 5-layer armour of the T-64BV was superior to the modernized T-64B armour with a 30mm appliqué plate. It is even less likely considering that the T-80BV uses an improved BTK-1 steel and not normal RHA steel like the T-72. In general, the low efficiency implied by Tarasenko's numbers is contradicted by the simple fact that simple two-layered design with a normal RHA steel front plate (not improved BTK-1 steel) and glass textolite back plate already has a mass efficiency coefficient of 1.0 against long rod tungsten penetrators with an aspect ratio of 10.0 and 12.5. A simple three-layer 80-105-20 design would be unquestionably better if not at least approximately equivalent, and a five-layer design such as the T-80BV array with a more optimized distribution of steel plate thicknesses simply cannot have a mass efficiency coefficient of less than 1.0.<br />
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Therefore, these numbers must be grossly underestimated by some amount. It is much more likely that the equivalent armour protection value of both the T-80BV and T-64BV is worth around 500mm RHA or more against a long rod penetrator, with the T-80BV being the more resilient of the two due to the higher steel thickness and better distribution of steel. At the very least, the higher thickness of the center layer in the upper glacis array of the T-80BV compared to the T-64BV begets a higher mass efficiency. Under the assumption that the T-80BV armour must be more efficient than the 60-105-50 armour of the T-72 (ME coefficient of 1.12 established earlier in this article), then the effective thickness must be equivalent to 497mm RHA against long rod heavy metal alloy APFSDS rounds at the very minimum. A mass efficiency coefficient of 1.25 to 1.3 would constitute a reasonable estimation given all available information. It is somewhat more difficult to predict the durability of the armour against shaped charges, but it must be worth more than 600mm RHA based on the 1.35 mass efficiency coefficient of the original 80-105-20 armour array. By multiplying 444mm with the reciprocal of 1.35, we get 600mm. Due to the improvements made over the old design, the real value of the armour should be somewhere between 600-700mm RHA but not higher.<br />
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On its own, this level of protection was sufficient for the anti-tank missiles and grenades of the 1970's, but more powerful weapons were being fielded rapidly in large quantities on the other side of the Iron Curtain. By 1985, the largest threats were the MILAN 2 and the TOW-2 which would have been enough to defeat the basic upper hull armour. The installation of Kontakt-1 was absolutely mandatory for the tank to withstand such powerful attacks. The 5-layer design was carried over to the T-80U which used Kontakt-5 instead of Kontakt-1.<br />
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<h3>
<span style="font-size: large;">Kontakt-1</span></h3>
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The addition of Kontakt-1 ERA armour added just under 1.2 tons to the original weight of the tank. The layout of the blocks was not optimal, to put it mildly.<br />
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<a href="http://2.bp.blogspot.com/-hFgcWDKuzKw/Vqzb4cRxZ7I/AAAAAAAAFiA/o8vAhPUyZSk/s1600/t-80b%2Bkontakt-1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-hFgcWDKuzKw/Vqzb4cRxZ7I/AAAAAAAAFiA/o8vAhPUyZSk/s1600/t-80b%2Bkontakt-1.jpg" /></a></div>
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Installing Kontakt-1 on the tank is easy but tedious. Each reactive armour block is attached to the surface of the hull, turret and sideskirts using a pair of bolts. The ease of installing and replacing the blocks meant that the entire modification could be done as part of regular scheduled maintenance. However, simplicity comes at a price in this case. The rubberized side skirts are rather fragile, and can be quite easily knocked off when the tank is travelling through densely wooded areas, or perhaps traversing obstacles in urban sprawl. With the added burden of a few dozen Kontakt-1 blocks mounted onto it, it only gets easier to accidentally knock the side skirts off. The photo below shows a "naked" T-80BV with the necessary provisions for mounting Kontakt-1.<br />
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<a href="https://2.bp.blogspot.com/-glU3GqI-rWY/Vrob6dH4zFI/AAAAAAAAFyM/m1-zojPFcoE/s1600/t-80bv%2Bsans%2Bk-1.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" src="https://2.bp.blogspot.com/-glU3GqI-rWY/Vrob6dH4zFI/AAAAAAAAFyM/m1-zojPFcoE/s1600/t-80bv%2Bsans%2Bk-1.jpg" /></a></div>
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A detailed examination of Kontakt-1 is available on the T-72 article. Please access it <a href="https://thesovietarmourblog.blogspot.com/2015/05/t-72-soviet-progeny.html">here</a>.<br />
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<span style="font-size: large;">T-80U (Object 219AS)</span></h3>
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The T-80U carried over the 5-layer glacis array from the T-80BV but differed by having built-in Kontakt-5 reactive armour instead of the less versatile Kontakt-1, although a few early T-80U samples had Kontakt-1 installed. Because the protection level of the underlying composite armour was not changed, the overall armour system was rendered obsolescent in short order by the appearance and later standardization of tandem warheads on many anti-tank weapons in the early 90's, although it is worth noting that these developments were directly influenced by extensive examinations of ex-Soviet and ex-East German tanks so the task of creating countermeasures to these tanks was made much simpler. The T-80U itself was notably examined in Sweden, where exact replicas of its turret and hull armour were made along with its complementary suite of Kontakt-5 armour. As a result, weapons like the Panzerfaust 3-IT (900mm RHA penetration behind ERA) could be created specifically to defeat its armour.
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The new cast turret installed on the T-80U (Obj. 219AS) is generally quite similar to the previous turret designs of the T-64 and T-80, but differs in the design of the armour insert cavities. Rather than casting the steel turret structure around the non-metallic inserts ("Kvartz" in the case of the T-80B), hollow armour cavities in the T-80U turret are formed during the casting process and the cavities are filled later down the production line, after which a steel cover plate is welded on top to seal the cavity. This was probably done mainly because the inserts could not be used as casting moulds unlike the sintered quartz filler of the T-80B turret, but this feature could also make it much easier to replace spent inserts and mend holes in the cast steel armour.<br />
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Another difference is the elimination of the turret roof weakened zones by increasing the height of the turret cheeks, thus increasing the slope of the turret roof to an angle too high for modern long rod APFSDS rounds to defeat. The thickness of cast steel at the gun mantlet zone was also increased, but the zone remained weak compared to the turret cheeks as it was still made from homogeneous steel. The thickness of some parts of the gun mantlet zone was increased to over 500mm, but the armour around the machine gun port (the other side of the turret is also cut in the same way) and the armour in front of the gun mounting trunnions were still quite thin. The drawing below (taken from the btvt.narod website) shows the shape of the armour cavities and the general armour layout of the turret. Note that although the sides of the turret are not sloped back as much as the T-72B turret, it is thicker, so a similar level of protection is maintained.<br />
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Externally, the turret appears to be much less rounded than previous Soviet tanks. The vertical slope on the turret face is only 15 degrees - much less than the 25-30 degree slope of earlier turrets. Furthermore, the joint between the roof of the turret and the turret facings is almost at a right angle as opposed to the gradual steep curve commonly observed on earlier turret designs. This reduces the number of weakened zones by some amount and gives the turret a more flattened shape.<br />
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The turret cheeks have a total physical thickness of 548mm. The thickness of the armour insert cavity is 260mm and the cast steel front wall is 98mm thick while the rear cast steel wall is 190mm thick. From a 35 degree side angle, the LOS thickness of the turret cheeks is around 600mm, and when viewed directly from the front, the LOS thickness increases to more than 800mm. The armour cavities are sealed with a heavy cover plate that forms the ceiling of the cavity once welded in place. This feature facilitates quick repairs at depots and enables the composite armour inserts to be upgraded over time if desired, unlike previous Soviet main battle tank turrets where the steel structure was cast around the non-metallic inserts. In the case of serial T-64A tanks, the cast steel shell was formed around prearranged sintered silicon carbide balls, and in the case of the T-72A and T-80B, the cast steel shell was formed around the "Kvartz" filler. In these instances, repair or replacement of the composite elements is not possible, and indeed, the older turret design of the T-80B could not be upgraded in the recent T-80BVM modernization beyond simply adding Relikt ERA panels. The T-80U turret does not suffer from the same drawback and can be readily modernized if the situation calls for it.<br />
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<a href="https://4.bp.blogspot.com/-J-6NATO4Oc8/W0tDLY3hZZI/AAAAAAAALwc/TluUzTk6EOMBu4Qf_3KLveS3SVeqa0oUQCLcBGAs/s1600/t-80u.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="132" data-original-width="252" src="https://4.bp.blogspot.com/-J-6NATO4Oc8/W0tDLY3hZZI/AAAAAAAALwc/TluUzTk6EOMBu4Qf_3KLveS3SVeqa0oUQCLcBGAs/s1600/t-80u.jpg" /></a></div>
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The armour inserts utilized in the T-80U series evolved over time, but it is known that most turrets excluding later variants used a type of NERA known as cellular polymer armour. Unlike the more common "bulging plate" type of NERA which was used in the T-72B turret as well as foreign tanks like the M1 Abrams and Leopard 2, the cellular armour in the T-80U lacks air gaps, making it somewhat thinner while offering a similar level of protection. At the moment, the author has not yet accumulated enough information on the specific details of these NERA inserts to write an adequately detailed description meeting normal Tankograd standards.<br />
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<a href="https://4.bp.blogspot.com/-PaXGDjIxfSA/VsnOTbDNtYI/AAAAAAAAF_s/Z7XEXu3GG6Y/s1600/Y08z2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-PaXGDjIxfSA/VsnOTbDNtYI/AAAAAAAAF_s/Z7XEXu3GG6Y/s1600/Y08z2.jpg" /></a></div>
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The outline of the cover plates on the turret cheek armour cavities is visible in the photos below.<br />
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<a href="https://3.bp.blogspot.com/-FZ2mF0FO4R4/VtFZ0YMlSJI/AAAAAAAAGCI/LqayWzM5kJE/s1600/1349674173_5.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://3.bp.blogspot.com/-FZ2mF0FO4R4/VtFZ0YMlSJI/AAAAAAAAGCI/LqayWzM5kJE/s400/1349674173_5.jpg" width="400" /></a><a href="https://4.bp.blogspot.com/-UTFoC5MYO7c/VtFZ0js-ROI/AAAAAAAAGCM/ALSXDyvkF6Q/s1600/c6AgY.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://4.bp.blogspot.com/-UTFoC5MYO7c/VtFZ0js-ROI/AAAAAAAAGCM/ALSXDyvkF6Q/s400/c6AgY.jpg" width="400" /></a></div>
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<h3>
<span style="font-size: large;">Kontakt-5</span></h3>
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<a href="https://1.bp.blogspot.com/-rQRXagzytHc/V2Jtnt2Q6jI/AAAAAAAAGyw/kWrRdF2m98YIJkqlUws3cuOhSS-4rDd5QCLcB/s1600/t-80%2Bera.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="376" src="https://1.bp.blogspot.com/-rQRXagzytHc/V2Jtnt2Q6jI/AAAAAAAAGyw/kWrRdF2m98YIJkqlUws3cuOhSS-4rDd5QCLcB/s640/t-80%2Bera.png" width="640" /></a></div>
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Although even the best 105mm APFSDS shells and the most powerful guided missiles had already been successfully nullified by the introduction of new composite armour and Kontakt-1 explosive reactive armour, there was still the 120mm threat to consider. 120mm ammunition of the early 80's were not a very serious threat in the short term for a variety of reasons, but it was clear that the new weapon had great potential, so serious countermeasures had to be devised. While the M1 Abrams was not armed with the M256 cannon for which it was famous for until the M1A1 upgrade in 1986, the Leopard 2 had achieved IOC in 1979 and had already grown into a thousand-strong contingent by late 1984. The folks at NII Stali did not twiddle their thumbs idly while news of the new NATO tanks trickled in, and thus, Kontakt-5 was introduced in 1985 as an integral component of the new T-80U.<br />
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Coverage on the glacis is good, but not for the turret, which is totally unprotected on either side of the gun mantlet. This was done in the interest of the driver's convenience in entering and exiting his station.<br />
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<a href="https://1.bp.blogspot.com/-IiKSTbla2yc/Vr8BgoSGq6I/AAAAAAAAF9w/0bESNFBDrSg/s1600/kontakt-5%2Bcoverage.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://1.bp.blogspot.com/-IiKSTbla2yc/Vr8BgoSGq6I/AAAAAAAAF9w/0bESNFBDrSg/s640/kontakt-5%2Bcoverage.jpg" width="640" /></a></div>
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British trialing had long ago concluded that it is the turret that sustains the majority of hits when engaging in tank-on-tank combat, a fact corroborated by independent Soviet tank loss analyses during WWII. This is because the lower third of the tank is usually not visible to the enemy due to tall grass and undergrowth, making the turret ring of the tank the perceived center of the tank.<br />
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<h3>
<span style="font-size: large;">How Kontakt-5 Works</span></h3>
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<a href="https://2.bp.blogspot.com/-m3NbZuWqNME/WtHQK_qPknI/AAAAAAAALbs/ukVza9q3r6Q5CZo6k0iTRlcpMMK0QpDEACLcBGAs/s1600/kontakt-5%2Bt-80.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="541" data-original-width="594" height="363" src="https://2.bp.blogspot.com/-m3NbZuWqNME/WtHQK_qPknI/AAAAAAAALbs/ukVza9q3r6Q5CZo6k0iTRlcpMMK0QpDEACLcBGAs/s400/kontakt-5%2Bt-80.png" width="400" /></a></div>
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Kontakt-5 was first implemented on a Soviet tank in 1985 on the T-80U. In 1989, Kontakt-5 was integrated into the T-72B as well, but in a different form. The design of the reactive armour differed between the two models, even though they shared the same name and are generally considered interchangeable.<br />
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The 4S22 explosive elements in the upper glacis armour blocks are angled in a V-shape similar to the way 4S20 elements are arranged in Kontakt-1 blocks. By having one of the elements angled at a different angle, and air gap is created, allowing the rear flyer plate to be propelled backwards, thus acting on a penetrating shaped charge jet in the in-pursuit regime which is more effective than a head-on regime Furthermore, there is a small air gap between the flat 4S22 element and the base armour, producing the same effects albeit more weakly. Overall, this design should be more effective against shaped charges than normal Kontakt-1 and also more effective than the Kontakt-5 used on the T-72.<br />
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An extensive analysis of the mechanism of Kontakt-5 is available on Tankograd's T-72 article. You can view it here: (<a href="https://thesovietarmourblog.blogspot.com/2017/12/t-72-part-2-protection-good-indication.html">Link</a>). </div>
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<span style="font-weight: normal;">There are two variants of Kontakt-5 employed on the T-80. The upper glacis panels are set at 68 degrees to the vertical plane, and that fact alone makes them extremely potent. However, the turret panels are set at only 50 degrees to the vertical plane. To compensate for this, the panels on the turret are of a bidirectional design. But first, let us examine the upper glacis of a T-80U.</span></div>
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<span style="font-size: large;">GLACIS</span></h3>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
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<a href="http://1.bp.blogspot.com/-1Ajdd0EO5K0/VgIxvPra2zI/AAAAAAAADq4/bkxUUrwM9DM/s1600/t-80%2Bera.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="236" src="https://1.bp.blogspot.com/-1Ajdd0EO5K0/VgIxvPra2zI/AAAAAAAADq4/bkxUUrwM9DM/s640/t-80%2Bera.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Flyer plates removed<br />
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To reduce the likelihood of a chain detonation, each module is separated by a 20mm heavy duty steel partition permanently welded onto the surface of the upper glacis.<br />
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Loading and reloading the reactive armour panels is an extremely simple affair, as long as you have a wrench at hand. Each module is filled with eight 4S20 explosive cells, arranged in a pattern of four, stacked two layers deep with the top layer angled using a special bracket as described earlier.<br />
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<a href="http://2.bp.blogspot.com/-CRfurH4r8PM/VqJkzB1RWaI/AAAAAAAAFak/fDuc2bOrYTo/s1600/t-80%2Bkontakt-5%2Binstallation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="297" src="https://2.bp.blogspot.com/-CRfurH4r8PM/VqJkzB1RWaI/AAAAAAAAFak/fDuc2bOrYTo/s400/t-80%2Bkontakt-5%2Binstallation.png" width="400" /></a><a href="http://1.bp.blogspot.com/-L8teLN1rqWo/VqJlQ7g-HZI/AAAAAAAAFaw/757YNZlKjRA/s1600/t-80%2Bkontakt-5%2Bthickness.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="297" src="https://1.bp.blogspot.com/-L8teLN1rqWo/VqJlQ7g-HZI/AAAAAAAAFaw/757YNZlKjRA/s400/t-80%2Bkontakt-5%2Bthickness.png" width="400" /></a></div>
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<h3>
<span style="font-size: large;">TURRET</span></h3>
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<a href="https://4.bp.blogspot.com/-Fp-kf7V_lwc/VrxBIlfz68I/AAAAAAAAF1w/ZNX3d-seGrg/s1600/t-80ud%2Bkontakt-5.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="291" src="https://4.bp.blogspot.com/-Fp-kf7V_lwc/VrxBIlfz68I/AAAAAAAAF1w/ZNX3d-seGrg/s640/t-80ud%2Bkontakt-5.jpg" width="640" /></a></div>
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Loading the turret panels is as simple as on the upper glacis. However, the flyer plates for the turret panels are not bolted onto a fixed housing. Rather, they are welded to the walls of the support structure frame. As such, replacing the turret blocks flyer plates is less straightforward than replacing the ones on the glacis, as doing so requires welding equipment and subsequently results in a longer turnaround time.<br />
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<a href="https://1.bp.blogspot.com/-C5jiYjAtxbY/VroQAaEQRdI/AAAAAAAAFxw/U8wSeOGyteM/s1600/kontakt-5%2Bt-80u.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="265" src="https://1.bp.blogspot.com/-C5jiYjAtxbY/VroQAaEQRdI/AAAAAAAAFxw/U8wSeOGyteM/s400/kontakt-5%2Bt-80u.png" width="400" /></a><a href="https://4.bp.blogspot.com/-D96jtNaTJXM/VroR00pPaAI/AAAAAAAAFx8/M9yzhlQ1MZA/s1600/t-80u%2Bkontakt-5.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://4.bp.blogspot.com/-D96jtNaTJXM/VroR00pPaAI/AAAAAAAAFx8/M9yzhlQ1MZA/s400/t-80u%2Bkontakt-5.png" width="400" /></a></div>
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<span style="font-family: inherit; font-size: x-small;">Click to enlarge</span></div>
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<a href="https://2.bp.blogspot.com/-B0aJtUYLTug/Vsn44Kxk6NI/AAAAAAAAGAw/QtBJkxdbRmk/s1600/dsc_0303.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-B0aJtUYLTug/Vsn44Kxk6NI/AAAAAAAAGAw/QtBJkxdbRmk/s1600/dsc_0303.jpg" /></a></div>
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<span style="font-family: inherit;"><span style="font-family: inherit;">Each turret module is composed of a single head-on flyer plate with a thickness of 15mm, with a robust 9mm steel box welded to it to contain four 4S22 explosive cells - two cells side by side, stacked two layers deep. The 9mm rear wall of the steel boxes act as an in-pursuit flyer plate.</span></span><br />
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<a href="http://4.bp.blogspot.com/-z-vs8aUkwXs/VqJqomJ8-5I/AAAAAAAAFbc/AG84TQ0RFb0/s1600/T-80%2Bk-5%2Bturret%2Binstallation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="297" src="https://4.bp.blogspot.com/-z-vs8aUkwXs/VqJqomJ8-5I/AAAAAAAAFbc/AG84TQ0RFb0/s400/T-80%2Bk-5%2Bturret%2Binstallation.png" width="400" /></a></div>
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<span style="font-family: inherit;">While the turret panels on the T-72B obr. 1989 are set at a slope of 68 degrees on both halves, the panels on the T-80U are only sloped at 50 degrees and 55 degrees for the upper and lower halves respectively. The sole advantage to the Kontakt-5 design on the T-80U is that less of the turret ring area is exposed, so the vertical coverage is somewhat better. In terms of horizontal coverage, it is not significantly better than the T-72B even though the individual armour panels on the turret appear to be seamlessly joined whereas the Kontakt-5 panels on the T-72B are clearly separated by gaps. This is because there are null zones between the pockets containing the 4S22 explosive elements, so a projectile impacting the joints between the 15mm front plates will not be able to detonate the 4S22 elements. The only effect is that the projectile must penetrate the 15mm front plate (equal to around 40mm of steel due to the slope) before impacting the base turret armour.</span><br />
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<a href="https://3.bp.blogspot.com/-zWHJHt5smlU/Vrw_CiEAzBI/AAAAAAAAF1c/WvOVf61ATcU/s1600/t-80.14143.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://3.bp.blogspot.com/-zWHJHt5smlU/Vrw_CiEAzBI/AAAAAAAAF1c/WvOVf61ATcU/s400/t-80.14143.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-EwiiaXNnxyk/VrxkeOGuN3I/AAAAAAAAF2U/9-620jbY6pU/s1600/t-72b%2Bkontakt-5%2Bslope.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://1.bp.blogspot.com/-EwiiaXNnxyk/VrxkeOGuN3I/AAAAAAAAF2U/9-620jbY6pU/s400/t-72b%2Bkontakt-5%2Bslope.jpg" width="400" /></a></div>
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<span style="font-size: small;"><br /></span></div>
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<span style="font-size: small;">The excellent protective properties of Kontakt-5 implies a very high mass efficiency, as the armour itself weighs very little compared to the amount of protection they provide in terms of steel thickness. For instance, the top and bottom halves of the turret panels have an areal density of 450 kg/sq.m and 500 kg/sq.m respectively according to Swedish data published by Rickard O. Lindström. This is equivalent to 57.3mm and 63.7mm of steel, which is very minor compared to the claimed penetration reduction of 20% claimed by NII Stali, and especially compared to an old NII Stali claim that attributes Kontakt-5 with an armour equivalency of 250mm RHA. In the latter case, the mass efficiency of Kontakt-5 would be nearly 5 times greater than normal steel, and in the former case, the mass efficiency would be 2.3 if the penetration of the APFSDS round was reduced by 140mm (for an APFSDS round with 700mm of penetration).</span><br />
<span style="font-size: small;"><br /></span>
<span style="font-size: small;">However, all things come at a cost. In the case of Kontakt-5, its high explosive content and power is also its biggest drawback, as it is perfectly possible for the activation of one module to set off another. The photo below doesn't actually show the aftermath of this phenomenon. It's just for illustration.</span></div>
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<a href="https://2.bp.blogspot.com/-7PJnHhVhmMg/VrxwsYOhh9I/AAAAAAAAF2s/2M5nW3nlGfk/s1600/reactive-T-80-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="423" src="https://2.bp.blogspot.com/-7PJnHhVhmMg/VrxwsYOhh9I/AAAAAAAAF2s/2M5nW3nlGfk/s640/reactive-T-80-2.jpg" width="640" /></a></div>
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<h3>
<span style="font-size: large;">SIDE HULL</span></h3>
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<a href="https://4.bp.blogspot.com/--Wy7DUkStd0/Vr8AJK5FnZI/AAAAAAAAF9o/LkzHG779Ue0/s1600/t-80u%2Bside%2Bhull%2Bkontakt-5.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://4.bp.blogspot.com/--Wy7DUkStd0/Vr8AJK5FnZI/AAAAAAAAF9o/LkzHG779Ue0/s640/t-80u%2Bside%2Bhull%2Bkontakt-5.jpg" width="640" /></a></div>
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Without effective measures for protecting the sides of the hull, the tank's speed and agility will be for nothing. 80 mm of steel, even angled at 70 degrees, isn't really worth much against quasi-modern shaped charges or long-rod penetrators. With Kontakt-5 and about a meter and a half of air space, though (depending on the incidence angle), the odds of survival suddenly doesn't seem that bad. With these side hull panels, the T-80 should be immune to hits from most 105mm APFSDS shells within a 70° frontal arc, but this probably goes down to a much narrower 40° arc for 120mm APFSDS. This should include the DM13, DM23, and M829.<br />
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<a href="https://3.bp.blogspot.com/-o0hvgSUPKuY/VrxvhdaoIWI/AAAAAAAAF2k/Zwq513-TTME/s1600/reactive-T-80-1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="444" src="https://3.bp.blogspot.com/-o0hvgSUPKuY/VrxvhdaoIWI/AAAAAAAAF2k/Zwq513-TTME/s640/reactive-T-80-1.jpg" width="640" /></a></div>
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<h3>
<span style="font-size: large;">ROOF</span></h3>
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Besides front facings of the turret, the upper glacis and the side hull, the roof of the turret is also partially protected by proprietary Kontakt-5 blocks.<br />
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<a href="http://3.bp.blogspot.com/-OnOoyUWNmlI/VqSdSnr8XgI/AAAAAAAAFdg/XcVUBpHFJo0/s1600/t-80%2Broof%2Bkontakt-5.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="450" src="https://3.bp.blogspot.com/-OnOoyUWNmlI/VqSdSnr8XgI/AAAAAAAAFdg/XcVUBpHFJo0/s640/t-80%2Broof%2Bkontakt-5.png" width="640" /></a></div>
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<h3>
<span style="font-family: inherit; font-size: large;">EFFECTIVENESS</span></h3>
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<span style="font-family: inherit;"><br /></span>
APFSDS ammunition was advancing rapidly, now that the 120mm cannon and the tanks that hosted them were in play. In 1989, the M829A1 was introduced - the best of its type so far. Measuring in at just a hair under 700mm in length, it was the lengthiest and thinnest long rod monobloc shell in the world. It could penetrate around 350mm RHA at 60 degrees at 2 kilometers' distance. Nothing came near it in performance. The M829A2 introduced in 1992 retained the construction of its predecessor except for a modified tip, and it flew faster thanks to better, more powerful propellant. In 1994, they discovered that M829A1 was unable to penetrate the front of the T-80U and T-72B obr. 1989. It was stopped by...<br />
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Kontakt-5.<br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><span style="font-family: inherit;">And on that bombshell, let's take a look at what sort of measures are in place to preserve the tank in case it </span><i style="font-family: inherit; font-weight: bold;">does </i><span style="font-family: inherit;">get penetrated.</span></span><br />
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<a href="https://www.blogger.com/null" id="firefighting"></a>
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<span style="font-family: inherit; font-size: large;">FIREFIGHTING</span></h3>
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<span style="font-family: inherit; font-size: large;">3ETs11-2 "Iney" Firefighting System</span></h3>
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To prevent the spreading of internal fires in the engine and crew compartments, the 3ETs11-2 "Iney" halon gas quick-acting firefighting system was installed, with the driver-mechanic as the primary operator. The system can operate in two modes; automatic and semi-automatic. In the automatic mode, the system reacts immediately to a fire in either the crew compartment or the engine compartment and acts upon the flame regionally, meaning that the system activates specific fire extinguisher nozzles to put out the flame, as opposed to just flooding the entire compartment. In the semi-automatic mode, the system can still automatically detect a fire but instead of immediately activating the fire extinguishers, the driver-mechanic is alerted via the P11-5 control and signal unit placed just in front of him. The decision as to what the next course of action should be is deferred to him.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://2.bp.blogspot.com/-gJe0TPFeJ6Q/Vr0Jsl0QtdI/AAAAAAAAF5o/fgfnG5bMbPU/s1600/iney%2Bfirefighting%2Bsystem%2Bindicator%2Bpanel.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-gJe0TPFeJ6Q/Vr0Jsl0QtdI/AAAAAAAAF5o/fgfnG5bMbPU/s1600/iney%2Bfirefighting%2Bsystem%2Bindicator%2Bpanel.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">P11-5</td></tr>
</tbody></table>
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There are 12 TD-1 thermal sensors strategically placed in the engine compartment and crew compartment. The ones in the crew compartment are attached just above the floor of the hull, and aimed mostly at the floor. You can see one of them in the picture below, just right of the three fire extinguishers attached to the 3ETs11-2 system.<br />
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<a href="https://2.bp.blogspot.com/-UYH3KvJuunA/VrzsWaAR_rI/AAAAAAAAF4Q/9Cr-1QDSz1Y/s1600/t-80korp2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://2.bp.blogspot.com/-UYH3KvJuunA/VrzsWaAR_rI/AAAAAAAAF4Q/9Cr-1QDSz1Y/s640/t-80korp2.jpg" width="640" /></a></div>
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The firefighting system reacts regionally when a rise of temperature to 150°C is detected in the crew compartments and engine compartments. The three PPZ fire extinguishers are fitted with electrically triggered quick release valves. The PPZ extinguishers use R-114B2, also known under the designation Halon 2402. It is very effective against any class of fire, but the tradeoff is that inhaling large quantities of it in a confined space (the inside of a tank, for example) is a huge health risk. It is advised to immediately throw open all hatches and exit the tank upon activation of the PPZ fire extinguishers. In the event of a penetrating hit, the tank and crew may be saved, but it cannot be manned until the gas has dispersed adequately. As such, the tank can be considered to be temporarily out of action.<br />
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<a href="https://1.bp.blogspot.com/-_zqdkHxaJfk/VrzuJ5hYV8I/AAAAAAAAF4c/CgOQDBFoD2k/s1600/ppz%2Bfire%2Bextinguisher%2Bt-72.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-_zqdkHxaJfk/VrzuJ5hYV8I/AAAAAAAAF4c/CgOQDBFoD2k/s1600/ppz%2Bfire%2Bextinguisher%2Bt-72.jpg" /></a><a href="https://3.bp.blogspot.com/-HTRzCUXuVnA/VrzuKITMTiI/AAAAAAAAF4g/yywGK-Q3jbs/s1600/td-1%2Bfire%2Bsensor.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="282" src="https://3.bp.blogspot.com/-HTRzCUXuVnA/VrzuKITMTiI/AAAAAAAAF4g/yywGK-Q3jbs/s320/td-1%2Bfire%2Bsensor.jpg" width="320" /></a></div>
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Two handheld OU-2 carbon dioxide fire extinguishers are also provided to supplement the automatic fire extinguisher system. If the TD-1 fire detectors fail to respond (usually in the case of small flames), then these will be the only firefighting tools available to the crew, aside from manually activating the PPZ fire extinguishers via the driver's control box. Carbon dioxide fire extinguishers are suitable on Class B and C (fuel and electrical fires), so they are right at home inside a tank. CO2 fire extinguishers are also more directional that halon extinguishers, so the user can starve a fire of oxygen quite effectively within the confines of the tank. Using the OU-2 extinguishers might be a more appealing option to activating the 3ETs11-2 system, since your chances of asphyxiating is somewhat lower.<br />
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<a href="https://1.bp.blogspot.com/-QiE0cvYW_Lc/Vrzx2dGshYI/AAAAAAAAF4s/aP9IjtotVyo/s1600/1399400020_1398604206_ou2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-QiE0cvYW_Lc/Vrzx2dGshYI/AAAAAAAAF4s/aP9IjtotVyo/s1600/1399400020_1398604206_ou2.jpg" /></a></div>
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<h3>
<span style="font-family: inherit; font-size: large;">SELF ENTRENCHMENT</span></h3>
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<a href="https://2.bp.blogspot.com/-Cxe9H5NJcto/W1cf5zuZXaI/AAAAAAAAL1A/h10apaThsyosEkIrxd6Bnm_KuPYgosjHwCLcBGAs/s1600/t-80%2Bdozer.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="980" data-original-width="1074" height="363" src="https://2.bp.blogspot.com/-Cxe9H5NJcto/W1cf5zuZXaI/AAAAAAAAL1A/h10apaThsyosEkIrxd6Bnm_KuPYgosjHwCLcBGAs/s400/t-80%2Bdozer.png" width="400" /></a></div>
<span style="font-family: inherit;"><span style="font-family: inherit;"><br /></span></span>
<span style="font-family: inherit;"><span style="font-family: inherit;"><br /></span><span style="font-family: inherit;">If a company of T-80s were to be called upon to defend a certain sector out of the blue, and there isn't any time to create proper fortifications, the crew may create their own cover using the dozer blade installed on the lower glacis.</span></span><br />
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<span style="font-family: inherit;"><a href="http://2.bp.blogspot.com/-MZ-J_tzOuto/VqS5rp2g_PI/AAAAAAAAFeI/07FC9TOm49Y/s1600/t-80%2Bself%2Bentrenchment.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-MZ-J_tzOuto/VqS5rp2g_PI/AAAAAAAAFeI/07FC9TOm49Y/s1600/t-80%2Bself%2Bentrenchment.jpg" /></a></span></div>
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<span style="font-family: inherit;"><br /></span><span style="font-family: inherit;">On flat, dry terrain, it can take up to 20 minutes to dig a tank-sized dugout. For maximum stealthiness, camouflage netting and some improvisation is usually necessary for a proper disguise, but such preparations require more effort and time. </span><br />
<span style="font-family: inherit;"><span style="font-family: inherit;"><br /></span></span>
<span style="font-family: inherit;"><span style="font-family: inherit;">However, because of the T-80's turbine engine, it is extremely ill-suited for static defence, seeing how the engine guzzles nearly as much fuel while the tank is immobile as when it is going at full speed. Because of this, it may not be able to sustain a counterattack when the moment comes.</span> <span style="font-family: inherit;"><br /></span></span><span style="font-family: inherit;"><br /></span><br />
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<a href="http://4.bp.blogspot.com/-X_1TFoHxmqI/VmceNbsEYBI/AAAAAAAAE0s/F4sLXAEpP_k/s1600/t-80.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-X_1TFoHxmqI/VmceNbsEYBI/AAAAAAAAE0s/F4sLXAEpP_k/s1600/t-80.jpg" /></a></div>
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<a href="https://www.blogger.com/null" id="smoke"></a>
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<h3>
<span style="font-family: inherit; font-size: large;">SMOKESCREEN</span></h3>
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The secret to not getting blown up is to not get hit, and the secret to not getting hit is to not be seen. To that end, the T-80 is equipped with a smoke grenade system to shield it from prying eyes, but unlike prior Soviet tanks, the T-80 is unable to generate a fuel-based smokescreen from its engine, for fear of a potentially explosive result. </div>
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<h3>
<span style="font-family: inherit; font-size: large;">902V Tucha</span></h3>
<span style="font-family: inherit;"><br /></span><span style="font-family: inherit;">The "Tucha" smoke grenade dispersal system was universal between all Soviet armoured vehicles invented during the 70's, and was subsequently retrofitted to vehicles made before that. For some strange reason, the gunner - and not the commander - has access to the sole control panel for firing the grenades.</span><br />
<span style="font-family: inherit;"><br /></span><span style="font-family: inherit;">There are three variations of grenade layouts featured on the T-80 series. The T-80, T-80B and T-80U had their smoke grenades arranged on the front turret cheeks, which appears paradoxical: if the tank was hit in the front and the commander wishes to withdraw to a safer location, he may or may not be able to deploy a smoke screen owing to the damage received to the smoke grenade launchers. The damage may not necessarily have to be from a turret strike; a hit on the upper glacis with a HEAT round or an APDS round will invariably produce a large amount of secondary fragments, which will tend to be deflected into the turret face by the high slope of the upper glacis.</span><br />
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<span style="font-family: inherit;">The T-80 and T-80B had a bank of five launcher tubes on the left hand side turret cheek, and only three launcher tubes on the right hand side due to the L-4 spotlight being in the way. Strangely enough, fewer smoke grenade launchers were provided compared to a T-72A without any good justification. The frontal part of the T-80B turret is virtually identical to the T-72A, and indeed, the left part of the turret has more than enough space to accommodate more smoke grenade launchers.</span><br />
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For the T-80BV, it was necessary to cluster the launcher tubes at the sides of the turret in order to not obstruct the placement of Kontakt-1 blocks over the turret cheeks. The earlier T-80BV with the T-80B turret and the late model T-80BV with the T-80U turret share the same configuration.<br />
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<a href="https://3.bp.blogspot.com/-miyEVqPnLq0/Vsn4Srl7cyI/AAAAAAAAGAk/oh3mpS7pt7o/s1600/w02003_5771564.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://3.bp.blogspot.com/-miyEVqPnLq0/Vsn4Srl7cyI/AAAAAAAAGAk/oh3mpS7pt7o/s400/w02003_5771564.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-JfbCv6PN9ZI/Vsn4lMCLusI/AAAAAAAAGAs/YGY7ps5dtIY/s1600/w02003_1977595.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://1.bp.blogspot.com/-JfbCv6PN9ZI/Vsn4lMCLusI/AAAAAAAAGAs/YGY7ps5dtIY/s400/w02003_1977595.jpg" width="400" /></a></div>
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<span style="font-family: inherit;">The launcher tubes on the T-80U are equally distributed, four per turret cheek. Since they are installed directly atop the Kontakt-5 panels, it's not hard to imagine what would happen to them if they got hit. Needless to say, many of the design decisions implemented on the T-80 series were highly suspect, to put it mildly.</span><br />
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<a href="https://4.bp.blogspot.com/-gI8R4gNWW_o/Vsnxh7ozv7I/AAAAAAAAGAI/R_zV-X1a1rQ/s1600/4thTankBrigade_-_T-80U_-10.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="170" src="https://4.bp.blogspot.com/-gI8R4gNWW_o/Vsnxh7ozv7I/AAAAAAAAGAI/R_zV-X1a1rQ/s640/4thTankBrigade_-_T-80U_-10.jpg" width="640" /></a></div>
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<a href="http://3.bp.blogspot.com/-5crlCZdnH_w/Vq0HLubv_iI/AAAAAAAAFmc/LF1xgAzJzH0/s1600/tucha-1%2Bsmoke%2Bgrenades.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="255" src="https://3.bp.blogspot.com/-5crlCZdnH_w/Vq0HLubv_iI/AAAAAAAAFmc/LF1xgAzJzH0/s400/tucha-1%2Bsmoke%2Bgrenades.jpg" width="400" /></a></div>
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<span style="font-size: large;">NBC PROTECTION</span></h3>
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Nuclear annihilation was a very real existential threat during the Cold War, and even more so during the 70's and early 80's; a period widely regarded as the peak of hostilities. Facilitating the crew's survival in the event of a nearby atomic blast or after one is the GO-17 NBC protection suite. The GO-17 system relied on a dosimeter installed inside the tank to detect and measure the dose rate of gamma radiation, and used a small air intake on the hull roof to detect the presence of biological or chemical contaminants in the air. The air intake was installed next to the driver's hatch, and is pictured below.<br />
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<a href="https://1.bp.blogspot.com/-Z27l1THHowQ/WdjjSIXiSyI/AAAAAAAAJzQ/uvZyc-Mbb_czDb8SHLhKjYW6ehaBm4X5QCLcBGAs/s1600/nbc%2Bsystem%2Bair%2Btester.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="453" data-original-width="350" src="https://1.bp.blogspot.com/-Z27l1THHowQ/WdjjSIXiSyI/AAAAAAAAJzQ/uvZyc-Mbb_czDb8SHLhKjYW6ehaBm4X5QCLcBGAs/s1600/nbc%2Bsystem%2Bair%2Btester.jpg" /></a></div>
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More details on the GO-17 NBC protection suite can be found on the T-72 article.<br />
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Under normal operating conditions, the crew was ventilated by a normal fan system with an integrated dust blower to ensure a clean supply of air. In case of NBC contamination, the system could operate on overpressure mode. The air intake for the crew compartment is located at the rear of the hull roof, next to the engine air intake. As you can see in the photo below, the air intake dome is protected from bullets by a heavy steel shield to the right.<br />
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<a href="https://1.bp.blogspot.com/-8Fiz0RjcEoM/WdjjNtrb_2I/AAAAAAAAJzM/yHfMym5V4QIXDz0PZtoEjsKk96WlQstNACLcBGAs/s1600/air%2Bintake.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="350" data-original-width="500" src="https://1.bp.blogspot.com/-8Fiz0RjcEoM/WdjjNtrb_2I/AAAAAAAAJzM/yHfMym5V4QIXDz0PZtoEjsKk96WlQstNACLcBGAs/s1600/air%2Bintake.jpg" /></a></div>
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The photo below shows the internal components of the ventilation system. The circular air outlet for normal, unfiltered air can be seen on the silver portion of the ventilator. The drum-shaped part is a filter designed to destroy biological and chemical particles contaminating the air. When the overpressure mode is activated, the circular air outlet is closed by a servomotor and the air is diverted into the drum filter.<br />
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<a href="https://1.bp.blogspot.com/-mRMEvPFiJr8/VswxSD7b5hI/AAAAAAAAGBE/FCUpNiYuEc8/s1600/korpus5.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://1.bp.blogspot.com/-mRMEvPFiJr8/VswxSD7b5hI/AAAAAAAAGBE/FCUpNiYuEc8/s640/korpus5.jpg" width="640" /></a></div>
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Besides the more active part of the tank's anti-contamination system, the interior walls are lined with an anti-radiation material. The liner is composed of borated polyethylene - a type of high-density polyethylene infused with boron - woven into fibers and made into sheets, which are then laminated and bound by a resin. Boron is known to be extremely effective at capturing neutrons thanks to its large absorption cross section, making it suitable for use as radiation shielding. The fibrous construction of the sheets and the lamination process also makes it a suitable spall liner not dissimilar to early flak vests that used woven nylon plates.<br />
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<span style="font-family: inherit; font-size: large;">MINE CLEARANCE</span></h3>
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<a href="https://1.bp.blogspot.com/-8BgHM0G30nU/VrzZvdcLK8I/AAAAAAAAF3w/dRe_pikoj9Q/s1600/t-80.14032.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-8BgHM0G30nU/VrzZvdcLK8I/AAAAAAAAF3w/dRe_pikoj9Q/s1600/t-80.14032.jpg" /></a></div>
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The mounting brackets on the upper glacis glacis are compatible with the KMT-6 mine plow. Th indiscriminately scoop up any mines, buried or unburied, anti-tank or anti-personnel, and shoves it to the side, creating a narrow mineless path for the tracks. This is fine... for the tank with the plow, which would be leading the crossing of the minefield as the only one of two in its company. For everyone else following behind, they can follow by driving on the track marks of the lead tank, but this is not possible in marshy and swampy ground, as doing so will lead to the tracks overpenetrating the soil, losing traction and getting stuck.<br />
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The ploughs can't reach anti-tank mines buried deeper than 8 or so inches, but this is fine, since the pressure exerted by the tracks probably won't be enough to set them off anymore at such depths.<br />
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<a href="http://2.bp.blogspot.com/-qp3vdNGgsLw/VqzmSXTrP3I/AAAAAAAAFik/m2bONTurjkE/s1600/mine%2Bplow%2Bplowing%2Bmine.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="446" src="https://2.bp.blogspot.com/-qp3vdNGgsLw/VqzmSXTrP3I/AAAAAAAAFik/m2bONTurjkE/s640/mine%2Bplow%2Bplowing%2Bmine.jpg" width="640" /></a></div>
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<span style="font-size: large;">DRIVER'S STATION</span></h3>
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<a href="https://4.bp.blogspot.com/-XL91ajVwhww/VreNNCfP1qI/AAAAAAAAFvA/cKCfj8iV0BA/s1600/t-80u%2Bdriver%2527s%2Bstation%2Bcenter%2Bkubinka.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://4.bp.blogspot.com/-XL91ajVwhww/VreNNCfP1qI/AAAAAAAAFvA/cKCfj8iV0BA/s640/t-80u%2Bdriver%2527s%2Bstation%2Bcenter%2Bkubinka.jpg" width="640" /></a></div>
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The left side of the cabin is dominated by the instrument panel. Just behind it is the front left hull fuel cell, and behind that is a stack of four accumulators.<br />
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<a href="https://4.bp.blogspot.com/-ALuCGYpAY0E/VreKMpqtQSI/AAAAAAAAFuw/5RB18Y_JtKk/s1600/t-80u%2Bdriver%2527s%2Bstation%2Bleft.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://4.bp.blogspot.com/-ALuCGYpAY0E/VreKMpqtQSI/AAAAAAAAFuw/5RB18Y_JtKk/s640/t-80u%2Bdriver%2527s%2Bstation%2Bleft.jpg" width="640" /></a></div>
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On the right side of the driver's compartment, the hatch opening and closing mechanism is installed on the roof and behind it is the GO-27 gamma radiation detection unit system with its control board direction under it. The red boxes at the front of the hull are the fire location and warning indicator box (left) and fire extinguisher activation boxes (right), previously mentioned in the "Firefighting" section of this article.<br />
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<a href="https://3.bp.blogspot.com/-4Fi4EmFcU98/VreKPkmU3gI/AAAAAAAAFu0/7t5yRhFQn1g/s1600/t-80u%2Bdriver%2527s%2Bstation%2Bright.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://3.bp.blogspot.com/-4Fi4EmFcU98/VreKPkmU3gI/AAAAAAAAFu0/7t5yRhFQn1g/s640/t-80u%2Bdriver%2527s%2Bstation%2Bright.jpg" width="640" /></a></div>
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Lighting for the driver is provided by a single dome light affixed to the ceiling of the station, just behind the driver's hatch and behind the driver's head, which is a rather poor idea since most of the light would be blocked by the driver, so finding the buttons on some of the control boards is harder than it should be. Just like the gunner and commander, the driver gets a DV-3 plastic fan right under his nose to help cool him down. The driver's seat is of the bucket type and is adjustable in height to allow him to drive under armour or with his head out of the hatch. The angle of the backrest can also be adjusted by a wide range of angles to ensure that the driver remains comfortable while performing his duties. The seat is shown in the drawing below<br />
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<a href="https://4.bp.blogspot.com/-4E1OWA4lbj4/W_b2a1z4C-I/AAAAAAAAMjg/KaUPZaWKJUEuV7OTwc-J8roNzhi23_S-ACLcBGAs/s1600/t-80%2Bdrivers%2Bseat.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1013" height="640" src="https://4.bp.blogspot.com/-4E1OWA4lbj4/W_b2a1z4C-I/AAAAAAAAMjg/KaUPZaWKJUEuV7OTwc-J8roNzhi23_S-ACLcBGAs/s640/t-80%2Bdrivers%2Bseat.png" width="404" /></a></div>
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The driver is furnished with a GPK-59 gyrocompasss. It is particularly useful when driving underwater since there's no scenery to refer to. To use it underwater, the driver memorizes the figure indicated on the gyrocompasss dial while on land. This tells him about the orientation of the tank. Once the tank enters water, the driver can refer to how much the dial deflects whenever he steers left and right to know how much and how long he must steer in the opposite direction in order to reorient the tank back towards its original travelling direction.<br />
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<a href="https://3.bp.blogspot.com/-N-BVGsxW5CU/VshbSw84CSI/AAAAAAAAF-Q/PqHmrxz12go/s1600/gpk.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://3.bp.blogspot.com/-N-BVGsxW5CU/VshbSw84CSI/AAAAAAAAF-Q/PqHmrxz12go/s320/gpk.jpg" width="262" /></a></div>
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The use of gyrocompasses can perhaps be labeled as a less sophisticated form of an Inertial Navigation System (INS), advanced versions of which are often present in modern combat vehicles due to their independence from outside input contrary to a GPS-based navigation system. You can see how the GPK-59 works on this video <a href="https://youtu.be/k1iwkd0A5rA">here</a>.<br />
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The T-80 is speedy compared to most other tanks but unfortunately, the full potential of the powertrain is not exploited and the tank is not as nimble as it could be. While certainly able to turn fast, it isn't too graceful, and this can be blamed on the rather antiquated lever-type steering system. The steering levers have power assist and can be handled smoothly by an experienced driver, but it is not as easy to handle compared to contemporary German and American tanks that had long transitioned to motorcycle-style handlebars and steering wheel-type configurations.<br />
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As seen in the previous photos, the driver has a bank of three periscopes arranged in an arc to give a better panorama of where the tank is going, which, in the T-80's case, is sort of a mix between necessity and luxury. The relatively high cruising speed of the T-80 demands better-than-usual situation awareness on the driver's part as a safety measure, and compared with the earlier T-64 and T-72 with their single wide angle periscope, the T-80's three facilitates quicker turning as the driver can see the corners of the tank. There are two variants of the same basic periscope layout; the original version where the periscopes are largely exposed, and the modified version introduced on the T-80U where a protective roof was added above the periscopes. The roof has a high thickness of steel and its purpose appears to be to protect the periscopes from the blast and fragmentation of explosive munitions impacting the turret. It probably also helps keep rainwater from obscuring the periscopes too badly.<br />
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The visibility from these three periscopes is demonstrated in this video (<a href="https://youtu.be/y_PXHAXI0cs">link</a>), taken by a T-80U driver.<br />
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At night, the driver suffers rather like all of his Soviet tanker brethren, only a bit worse. He is supplied with a single TNP IR imaging periscope. It facilitates a viewing distance of no less than 30 meters, within which he is guaranteed to be able to discern terrain features and obstacles, but because only the center periscope can be swapped out, the driver's field of view is rather narrow compared to the TNPO-160V used in the T-64 and T-72, which has a much wider aperture. With a view distance of only 30 meters and a bad case of tunnel vision at night, all the merits of the T-80's speed become irrelevant.<br />
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The driver is supplied with a face shield. It can be installed just behind the periscope, and it hooks up directly to the tank's electrical system. The face shield is mainly used when driving in convoys, serving to protect the driver's face from the dirt, insects and smoke (and in the T-80's case, hot exhaust plumes) of the leading tank as he drives with his head outside his hatch. It is only used when enemy contact is not a concern, as the shield prevents the cannon from depressing.<br />
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<span style="font-size: large;">TRANSMISSION, SUSPENSION</span></h3>
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<a href="http://4.bp.blogspot.com/-si0dGnRDQqU/VqzXfsohe_I/AAAAAAAAFh0/zvps-b-0APU/s1600/t-80%2Bflying%2Btank.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-si0dGnRDQqU/VqzXfsohe_I/AAAAAAAAFh0/zvps-b-0APU/s1600/t-80%2Bflying%2Btank.jpg" /></a></div>
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<span style="font-family: inherit;"></span>The radically higher forces following the implementation of a gas turbine engine wore out the T-64's small diameter lightweight roadwheels and suspension at an alarming rate. Hence, the T-80 received an all-new reinforced torsion bar suspension system paired with larger and sturdier forged aluminium roadwheels with a diameter of 640 mm, and because of the much higher rolling speed of the tracks, it became necessary to have five return rollers instead of three (T-72) or four (T-64) in order to provide more dynamic support, and the RMSh tracks inherited from the T-64 required some modifications as well. Because of the extremely high spinning speed of the roadwheels, even the thick rubber rims were not enough to handle the stress, so the tracks needed to be outfitted with thick internal rubber pads which also helped reduce vibration when driving over uneven surfaces, and thus helped improve crew comfort and shooting accuracy when travelling at lower speeds.<br />
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<a href="http://2.bp.blogspot.com/-rInDm9cardw/VqyvmoZ5sMI/AAAAAAAAFhk/FI8TcDnyNgI/s1600/t-80%2Bdust%2Btrail.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-rInDm9cardw/VqyvmoZ5sMI/AAAAAAAAFhk/FI8TcDnyNgI/s1600/t-80%2Bdust%2Btrail.jpg" /></a></div>
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<span style="font-size: small; font-weight: bold;"><span style="font-weight: normal;">The T-80 uses a hydraulically assisted mechanical transmission with dual planetary gearboxes and dual final drives. There are four forward gears and one reverse gear.</span></span><span style="font-size: small; font-weight: normal;"> </span><span style="font-size: small; font-weight: bold;"><span style="font-weight: normal;">The brakes are of a disk type, hydraulically operated. The T-80 turns on a pivot, meaning that to turn the tank on the spot, one of the two the tracks are locked in place while the other drives the tank around it. This system of neutral steering is mechanically simple, but vastly inferior to a pivot-type steering system where one of the tracks is run at the desired speed while the other is run slightly slower in the opposite direction. Besides being slower, false pivot steering creates a huge amount of friction and places more strain on the inactive track, leading to a quicker gradual weakening of the track and a shorter lifespan. To counteract this issue, the driver may "wiggle" the tank when turning so that the tension in the inactive track is released.</span></span></div>
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The transmission uses <a href="http://en.rustorgoil.ru/catalog/aviation_oils_and_lubricant/synthetic_oils_for_jet_engines/oil_synthetic_turbine_engines_b_3v/">B-3V synthetic oil</a>, of which 60 liters is needed. The same class of oil is used in helicopters like the Mi-17.</div>
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Because of the front-heaviness and high speed of the tank, nose diving into ditches and ruts would be particularly harsh on both the suspension and the crew. To alleviate the stresses of rough driving, the front two roadwheels and rearmost wheel are outfitted with hydropneumatic shock absorbers borrowed from the T-64. These aided recovery as the tank traversed natural obstacles.<br />
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<a href="http://1.bp.blogspot.com/-ObjWwcXluik/VqOTwJHcUZI/AAAAAAAAFcg/inBnJKjPDNU/s1600/t-80.gif" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="300" src="https://1.bp.blogspot.com/-ObjWwcXluik/VqOTwJHcUZI/AAAAAAAAFcg/inBnJKjPDNU/s400/t-80.gif" width="400" /></a><a href="http://3.bp.blogspot.com/-J6yxhNqIPgY/VrClpfjcTsI/AAAAAAAAFsc/BKyt9Mi3L2I/s1600/t-80%2Bshock%2Babsorbers.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="280" src="https://3.bp.blogspot.com/-J6yxhNqIPgY/VrClpfjcTsI/AAAAAAAAFsc/BKyt9Mi3L2I/s400/t-80%2Bshock%2Babsorbers.png" width="400" /></a></div>
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The T-80 and T-80B have the same type of transmission. There are 5 forward gears and 1 reverse gear. The T-80U has a modified transmission with 4 forward gears and 1 reverse gear. Here's a video (<a href="https://www.youtube.com/watch?v=lzOx-1g262Y">link</a>) of a T-80 driver showing off. The smooth transition to reverse and the high acceleration of the tank is demonstrated in the video. The T-80B weighs 42 tons. The T-80U weighs 46 tons. Stripped of additional armour, the T-80, T-80B and T-80U exert a ground pressure of 0.83 kg/sq.cm, 0.864 kg/sq.cm and 0.93 kg/sq.cm respectively.<br />
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<a href="https://www.blogger.com/null" id="engines"></a>
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<h3>
<span style="font-size: large;">ENGINES</span></h3>
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With the sole exception of the T-80UD, the T-80 series featured a gas turbine engine. Contrary to popular belief, the T-80 was not the first tank in the world to mount this type of engine, only the first in the Soviet Union. The first serially produced tank to have a gas turbine engine was the Swedish Stridsvagn 103 which formally entered service in 1967 - almost a full decade before the T-80. However, the Strv 103 had a dual engine setup with an opposed piston engine supplementing its gas turbine engine, whereas the T-80 was propelled solely by a gas turbine engine. It was the first in the world to have this feature, followed shortly by the M1 Abrams which entered service four years later.<br />
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Unlike the T-64 and T-72, the gearbox of the T-80 was coupled to the engine together with the air intake system in a single powerpack assembly. It was the first Soviet tank to feature this, but it was by no means the first in the world. The photo below shows the powerpack of a T-80 with the GTD-1000T at its core. The large size of the air intakes is evident in this photo.<br />
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<a href="https://1.bp.blogspot.com/-kcVQR_exDo4/XgzLYuM7ZVI/AAAAAAAAP2w/OdXklNJNg9YykYEPGgzhwmc3oRJuquBcQCLcBGAsYHQ/s1600/gtd-1000t.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="836" data-original-width="1099" height="486" src="https://1.bp.blogspot.com/-kcVQR_exDo4/XgzLYuM7ZVI/AAAAAAAAP2w/OdXklNJNg9YykYEPGgzhwmc3oRJuquBcQCLcBGAsYHQ/s640/gtd-1000t.png" width="640" /></a></div>
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Compared to the T-72, the running gear of the T-80 is lighter by a small amount but it is still heavier than the running gear of the T-64 despite being a direct offshoot of the T-64A. The running gear of the T-80 weighed 8.28 tons, as opposed to the 8.47 tons of the T-72 and the 6.2 tons of the T-64. Although the T-80 uses a compact gas turbine engine, the weight of the engine is not less than the 5TDF of the T-64 and is even slightly heavier than the V-46 of the T-72, and besides that, the auxiliary systems accompanying the engine itself are heavier. For instance, large air intakes were necessary for the engine to develop its full power, and the large size of the intakes necessitated an engine compartment of larger volume.<br />
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The tracks and roadwheels of the T-80 are also heavier than the ones used for the T-64. As such, the tank weighed somewhat more than the T-64A despite having the same weight of armour and similar internal equipment, including the gun.<br />
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The turbine blades and turboshaft spins at 26,650 rpm, but the gearbox lowers this figure down to a maximum of 3,554 rpm on the seventh gear at the drive shaft. The final drives further reduce the rotational speed before the power is finally transferred to the drive sprockets.<br />
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<a href="http://3.bp.blogspot.com/-_XbW8vd1oOw/VrB5CJ1C73I/AAAAAAAAFrA/UhkKjNtljtY/s1600/gtd%2Bengine.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="272" src="https://3.bp.blogspot.com/-_XbW8vd1oOw/VrB5CJ1C73I/AAAAAAAAFrA/UhkKjNtljtY/s400/gtd%2Bengine.jpg" width="400" /></a><a href="http://1.bp.blogspot.com/-aL3Fy3YXjEo/VrB5EoaCm9I/AAAAAAAAFrI/BFW_O81244o/s1600/gtd%2Bengine%2Bcutaway.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="277" src="https://1.bp.blogspot.com/-aL3Fy3YXjEo/VrB5EoaCm9I/AAAAAAAAFrI/BFW_O81244o/s400/gtd%2Bengine%2Bcutaway.jpg" width="400" /></a><a href="http://3.bp.blogspot.com/-FNwAQ7dbflI/VrB5FQ_PbNI/AAAAAAAAFrM/zYzQzDTBlQ0/s1600/gtd%2Bengine%2Bcutaway%2Bcloseup.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="276" src="https://3.bp.blogspot.com/-FNwAQ7dbflI/VrB5FQ_PbNI/AAAAAAAAFrM/zYzQzDTBlQ0/s400/gtd%2Bengine%2Bcutaway%2Bcloseup.jpg" width="400" /></a></div>
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<a href="http://1.bp.blogspot.com/-KJzS_6PgiDM/Vq0Ch4LQLBI/AAAAAAAAFlo/qA-O_BChuWU/s1600/t-80%2Bengine%2Bdeck.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="263" src="https://1.bp.blogspot.com/-KJzS_6PgiDM/Vq0Ch4LQLBI/AAAAAAAAFlo/qA-O_BChuWU/s400/t-80%2Bengine%2Bdeck.jpg" width="400" /></a><a href="http://1.bp.blogspot.com/-2MNMV36U01c/Vq3-nH89SSI/AAAAAAAAFnU/FMvpcEj3Bd0/s1600/gtd%2Bgas%2Bturbine%2Bengine.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="364" src="https://1.bp.blogspot.com/-2MNMV36U01c/Vq3-nH89SSI/AAAAAAAAFnU/FMvpcEj3Bd0/s400/gtd%2Bgas%2Bturbine%2Bengine.jpg" width="400" /></a></div>
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It is well known that the biggest nemesis to any jet engine is the ingestion of foreign objects. The cyclone air cleaners built into the rear of the engine shoulder most of the burden of filtration but since they can only ensure an air purity of 98.5%, the engine will still ingest a small portion of pollutants, but contrary to popular belief, the dust consumption tolerance of gas turbine engines is reasonably high. To counteract the buildup of residue on the turbine blades, the designers implemented an ingenious solution whereby the blades would be shaken by high frequency vibrations produced by a system of motorized hammers. The hammers were tuned to vibrate the turbine blades at resonant frequencies, causing any particles on the surface of the blades to become dislodged and fall off. These particles are then blown out by blasts of compressed air. This purging process occurs during the startup procedure and during the deactivation procedure. This system is not dissimilar to ultrasonic polishing for jewelry, and the sum of all of the individual engineering solutions was so effective that the T-80U surpassed the T-90S in endurance during comparative endurance trials in India. The original T-80 performed exceptionally during its initial military tests as well, passing its hot climate trials in the Karakum desert in Turkmenistan with flying colours.<br />
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A portion of the engine's many essential life support systems can be accessed by simply opening up the engine compartment access hatch. Scheduled maintenance and regular check-ups can be done from outside, but to do any serious repairs on the engine or any of the drivetrain components, the entire powerpack often needs to be lifted out with a crane.<br />
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<a href="https://1.bp.blogspot.com/-JAcVhBj4Mds/Vrm-bErNlpI/AAAAAAAAFwQ/cWVJINj_eY8/s1600/t80takbiv-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://1.bp.blogspot.com/-JAcVhBj4Mds/Vrm-bErNlpI/AAAAAAAAFwQ/cWVJINj_eY8/s640/t80takbiv-2.jpg" width="640" /></a></div>
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Th engine compartment cover has two filler ports for fuel and oil and two lifting points. The engine deck of a T-80B is shown in the drawing below.<br />
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<a href="https://1.bp.blogspot.com/-4HTkm3ZHxrU/W_b1zZwxiRI/AAAAAAAAMjY/f-xaAyPXADYf2z3h2bsga8ndIFKvIHB_QCLcBGAs/s1600/engine%2Bdeck.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1401" data-original-width="1237" height="640" src="https://1.bp.blogspot.com/-4HTkm3ZHxrU/W_b1zZwxiRI/AAAAAAAAMjY/f-xaAyPXADYf2z3h2bsga8ndIFKvIHB_QCLcBGAs/s640/engine%2Bdeck.png" width="564" /></a></div>
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There's no denying that the use of gas turbine engines in tanks have had more than their share of controversy, and for the most part, the controversy is not far off the mark. The most sanguine property is the excellent acceleration potential thanks to the high torque output of gas turbines at low revs, but the price for such performance is steep. From a defensive standpoint, the act of simply sitting idle to ambush or in wait of attack drains the tank's fuel reserves as prodigiously as when the tank is on the move, and if the tank were to be involved in a breakthrough assault as it was designed to do, the same issue limits its ability to exploit a successful breach and penetrate deep behind enemy lines.<br />
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Aside from that, one will find no small number of online sources repeating the claim that compact dimensions and low mass compared to conventional diesel powerplants are main selling points of this type of engine. The GTD series for the T-80 are no lighter than most diesel tank engines at a hefty 1050 kg (dry). However, it is a little smaller than many diesels, measuring in at 1.494 x 1.042 x 0.888 m (L-W-H) in all of its incarnations, compared to 1.480 x 0.896 x 0.902 m for the V-46 engine for the T-72. All members of the GTD family are marginally lighter than the AGT-1500, which weighs 1134 kg, and all of them are somewhat smaller, as the AGT-1500 measures 1.68x0.99x0.80.<br />
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An advantage to the use of jet fuels is that it will not gel up unless the ambient temperature is Arctic low, unlike raw diesel which will in fact gain viscosity in deep sub-zero temperatures if not mixed with some sort of antifreeze. The engines themselves can operate in ambient temperatures of down to -40°C and up to +40°C, but the true heat limit is significantly higher at +55°C, though running the engine at those sorts of conditions entails an extreme reduction of power. In addition to that, the GTD series of engines take no more than just 3 minutes to start up at temperatures of -40°C. That is more than 10 times shorter than the time it takes for a T-72 to get moving. This gives the T-80 a huge advantage in response time, which means that reinforcements can arrive around 40 minutes sooner, but the price of this blessing was very, very steep indeed. The price of the GTD-1000T was 10 times higher.<br />
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<span style="font-family: inherit;"><span face="arial, helvetica, sans-serif"><span style="font-family: "times new roman"; font-size: large;">GTD-1000T</span></span></span></h3>
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<span style="font-family: inherit;"><span face="arial, helvetica, sans-serif"><span style="font-family: "times new roman";">The GTD-1000T powered the original T-80. It would be later modified (minimally) to increase its output to match the ever increasing mass of future T-80 models. </span></span></span><span style="font-family: inherit;"><span face="arial, helvetica, sans-serif"><span style="font-family: "times new roman";">To the layman, the lower power output would ostensibly mean that the T-80 is less agile than something like the M1 Abrams (1980 original), but one must remember that the T-80 was nearly 36% lighter. The greatest bottleneck to the performance of the T-80 family was the manual transmission, which limited the acceleration of the tank in rough terrain and required more skilled drivers compared to a tank with an automatic transmission. The top speed of the tank on paved highways does not matter nearly as much, as the speed of tank convoys often depends on the optimum cruising speed (not top speed) of the tank where vibration and engine fatigue is minimal.</span></span></span><br />
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<span style="font-family: "times new roman";">Power - 1000 hp (745 kW)</span><br />
Rate of Rotation: 3554 RPM<br />
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<span style="font-size: large;">GTD-1000TF</span></h3>
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The newer GTD-1000TF for the advanced T-80B introduced in 1978 brought small but essential incremental improvements in both power output and fuel economy, which were achieved with the addition of a supercharger. Now, the engine is capable of developing 1100 hp, thanks to more oxygen fueling its fire, and the specific fuel consumption rate at full power was decreased slightly from 240 g/hph of the GTD-1000T to 235 g/hph (319 g/kWh). The GTD-1000TF is also used in the T-80BV. The photos below show the engine in the engine compartment of a T-80BV.</div>
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The photo below gives us a good view of location of the four accumulators, the oil and fuel tanks, and the air intakes (at the bottom corners of the photo). Note the little red TD-1 thermal sensor at the top left corner of the photo. Its location enables it to detect an electrical fire near the accumulators.</div>
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<span style="font-size: large;">GTD-1250</span></h3>
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To compensate for the added weight of Kontakt-5 armour on the new T-80U (1986), it was necessary to take another step forward and increase the power of the engine yet again. As its name suggests, the GTD-1250 can put out 1250 hp. The fuel efficiency of the GTD line-up reached its peak so far at 225 g/hph (306 g/hph).<br />
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Though still less economic from a design standpoint, the actual fuel consumption rate was nevertheless lower and the new engine gave the T-80U a small, but practically negligible edge in agility over the M1A1 and its descendants.<br />
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<a href="http://1.bp.blogspot.com/-rFK_UPgZh-E/VqJrT4mQAHI/AAAAAAAAFbs/Oooy5TscZ5Q/s1600/t-80u%2Brear%2Bend.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="318" src="https://1.bp.blogspot.com/-rFK_UPgZh-E/VqJrT4mQAHI/AAAAAAAAFbs/Oooy5TscZ5Q/s320/t-80u%2Brear%2Bend.png" width="640" /></a></div>
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The GTD-1250 uses a modified exhaust port with an interrupted rectangular grille pattern instead of squares like on the GTD-1000T.<br />
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Net Power Output: 1250 hp<br />
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Max Torque Output: 4395 Nm<br />
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Rated Speed: 3,000 RPM<br />
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Supplementing the engine is the GTA-18 auxiliary power unit (APU). It is a small 30 hp generator outputting 18 kW. Only the command variants are equipped with an APU.<br />
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<a href="https://www.blogger.com/null" id="water"></a>
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<span style="font-size: large;">WATER OBSTACLES</span></h3>
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<a href="http://3.bp.blogspot.com/-zgIsHYXqZTY/VqTpjkuYumI/AAAAAAAAFeY/NScw2HRJR88/s1600/t-80%2Bsloshing%2Bthrough%2Bmud.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="398" src="https://3.bp.blogspot.com/-zgIsHYXqZTY/VqTpjkuYumI/AAAAAAAAFeY/NScw2HRJR88/s640/t-80%2Bsloshing%2Bthrough%2Bmud.jpg" width="640" /></a></div>
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For all the sacrifices that needed to be made to gain the extraordinary speed of the turbine engine, the ability to cross rivers was not one of them. The T-80 was equipped with the OPVT underwater driving system, containing the same elements as the T-72 but differing in the type of snorkeling equipment. The tank is able to cross a river with a depth of 5.0 meters with preparation and ford a stream with a depth of 1.8 meters with minor preparation.
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Late model T-80 tanks may be provided with a proprietary "Brod" or "Brod-M" underwater driving system, allowing to drive into and across rivers as deep as 5.5 meters or even 12 meters in the case of the "Brod-M", and ford streams with a depth of up to 1.8 meters with minor preparations. Only the T-80UK and T-80UM models have this modification, and the T-80UD may have it as well. The snorkel configuration of the "Bord" kit is outwardly similar to the one used on the T-64, but the only real similarity is the implementation of a snorkel-mast where the commander can sit and direct the driver. However, the time needed to install the snorkels for the "Brod" system is much longer than for the OPVT system.<br />
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<a href="http://4.bp.blogspot.com/-h0oQJkT6CtA/VqyvGDhuUcI/AAAAAAAAFhU/x0L2z68xPbg/s1600/snorkel%2B2.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="319" src="https://4.bp.blogspot.com/-h0oQJkT6CtA/VqyvGDhuUcI/AAAAAAAAFhU/x0L2z68xPbg/s400/snorkel%2B2.jpg" width="400" /></a><a href="http://2.bp.blogspot.com/-ixQLgXur9LU/VqyvH5WwdLI/AAAAAAAAFhc/GKpZO7LchLw/s1600/t-80bv%2Bready%2Bto%2Bswim.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="292" src="https://2.bp.blogspot.com/-ixQLgXur9LU/VqyvH5WwdLI/AAAAAAAAFhc/GKpZO7LchLw/s400/t-80bv%2Bready%2Bto%2Bswim.jpg" width="400" /></a></div>
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<span style="font-size: x-small;"><i>Photo Credit (Left): Maxim Volkonovsky</i></span></div>
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Ventilation for the crew is provided by the snorkel for both the "Brod" and "Brod-M" systems. For the "Brod-M", the large snorkel-mast is installed by locking it onto the commander's hatch. An internal ladder allows the commander to climb in and out of his station, and if necessary, the entire crew can escape a drowned tank through the snorkel. This is a safer way of escaping the tank as compared to the T-72 which had a simpler OPVT snorkel system that forced the crew to flood the tank by opening the hatches in order to leave. However, the <br />
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<a href="https://3.bp.blogspot.com/-lVNvS6RlDuA/Vrn9iY3Q_zI/AAAAAAAAFww/Uoq9XADTsac/s1600/bord-m%2Bsnorkel.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="307" src="https://3.bp.blogspot.com/-lVNvS6RlDuA/Vrn9iY3Q_zI/AAAAAAAAFww/Uoq9XADTsac/s400/bord-m%2Bsnorkel.jpg" width="400" /></a><a href="http://1.bp.blogspot.com/-BrjHRwC5sr8/VrCeswJr3nI/AAAAAAAAFsE/pMSq1p9Z6Oo/s1600/t-80%2Bwith%2Bsnorkel.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="278" src="https://1.bp.blogspot.com/-BrjHRwC5sr8/VrCeswJr3nI/AAAAAAAAFsE/pMSq1p9Z6Oo/s400/t-80%2Bwith%2Bsnorkel.jpg" width="400" /></a></div>
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<i><span style="font-size: x-small;">Photo Credit: Maxim Volkonovsky</span></i></div>
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The tank is provided with a snorkel adapter for the engine air intakes. The adapter is a simple, totally hollow shell made with thin sheet steel, encompassing both air intakes and curving to form a pill-shaped inlet duct. It is stowed in a special container mounted at the rear of the turret. Alternatively, it can be left attached to the air intakes for convenience, like in the picture below. In that case, though, the range of traverse of the turret is severely restricted.<br />
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<a href="http://2.bp.blogspot.com/-Vl3cPVG-ZSs/VrCRLyM45lI/AAAAAAAAFr0/6ncAKdYX788/s1600/engine%2Bair%2Bintake%2Bfor%2Bsnorkel.jpg"><img border="0" height="426" src="https://2.bp.blogspot.com/-Vl3cPVG-ZSs/VrCRLyM45lI/AAAAAAAAFr0/6ncAKdYX788/s640/engine%2Bair%2Bintake%2Bfor%2Bsnorkel.jpg" width="640" /></a></div>
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The adapter also serves the secondary but equally important function of keeping the air intake grilles from being submerged or splashed with the water blown up by the exhaust. The clip below shows an early T-80 prototype using a pair of crude ventilation ducts as an interim solution.<br />
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While the pressure of the exhaust gasses is enough to eliminate backflow into the exhaust port in shallow water, it is not powerful enough to do so in deep water, making it impossible to use a valved exhaust cover like on the T-55, T-62 and T-72 for deep water driving. Instead, an exhaust tube is used to vent the exhaust gasses out and above water. Installing the exhaust tube requires the removal of the regular exhaust port, which can be hinged away and locked in place, as you can see in the photo below.<br />
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The exhaust port adapter is stowed away in a metal bin mounted on the rear of the turret.<br />
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Because of the large size and mass of all of the snorkeling equipment, it can take upwards of an hour to prepare for a river crossing. Fording a stream can be done without the crew ventilation tube and the exhaust tube, but the engine air intake snorkel must be installed, which can cost up to 20 minutes of the crew's time.<br />
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<span style="font-weight: normal;"><span style="font-size: small;">Crew members are each given a closed-circuit IP-5 rebreather for emergency use. It comprises a watertight, form fitting gas mask, a chemical respirator chamber containing potassium superoxide (</span></span><span style="font-weight: normal;"><span style="font-size: small;">KO<sub>2</sub>), and a flotation collar. The rebreather uses the chemical reaction between potassium superoxide and carbon dioxide, activated by water from the user's breath reduce the former two to oxygen and potassium carbonate. The freshly produced oxygen gas is mixed into the previously exhaled breath to replenish its oxygen concentration for rebreathing. The crew usually puts the IP-5 on before entering water as a precautionary measure.</span></span></div>
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<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-nS3nzD9aHNU/VT3zpPsnsSI/AAAAAAAACGA/62LOZN0f2a0/s1600/ip5.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://2.bp.blogspot.com/-nS3nzD9aHNU/VT3zpPsnsSI/AAAAAAAACGA/62LOZN0f2a0/s1600/ip5.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">IP-5<br />
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<a href="https://www.blogger.com/null" id="fuel"></a>
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<h3>
<span style="font-size: large;">ROAD ENDURANCE</span></h3>
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In terms of fuel efficiency, the GTD-1000T was ostensibly unremarkable, guzzling jet fuel at the incredible rate of 240 g/hph (326 g/kWh), while its American cousin the AGT-1500 had a specific fuel consumption of just 213 g/hph (290 g/kWh) while simultaneously offering higher power. However, we must not forget to take the "hp" in g/hph into account. Multiplying 1000 hp with 240 g/hph yields 240,000 grams per hour, which translates to 192 liters of TS-1 per hour at full power. In real number terms, this is lower than the consumption rate of the AGT-1500 by 25%, while outputting 50% less power.<br />
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For an engine of about the same size and weight, this is perfectly reasonable performance. However, it is always necessary to strike a balance between striking speed and striking distance, and while the raw performance of the GTD-1000T may not be as optimal as desired, its dimensions and foundations enabled it to be easily uprated whenever the need arises. The best example of this is the GTD-1250, having a much higher power output of 1250 hp, while at the same time offering lower specific fuel consumption rates of 225 g/hph. In real number terms of efficiency, the GTD-1250 gave more power for every liter it took by 6.9% than the GTD-1000T, while the GTD-1000TF offered 2.3% better efficiency. The GTD series of gas turbine engines was not let down by poor Soviet engineering.<br />
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However, all of that is academic. Actual mileage testing has yielded some very interesting tangible results for the GTD-1000T engine. The engine consumes between 430 liters to 500 liters of standard TS-1 jet fuel for every 100 kilometers (62 miles) traveled on paved roads, or 450 liters to 790 liters for the same distance but on dirt roads, depending on the severity of the terrain. Assuming that the tank does not stop even once during its journey, the T-80 can travel between 233 kilometers to 409 kilometers on a full tank of fuel when driving cross country. The efficiency of a gas turbine engine will be lower for a smaller engine compared to a larger engine. This is one reason why the GTD series is less efficient than the AGT-1500.<br />
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<a href="http://turbotrain.net/en/whatsgasturbine.htm">This article</a> is compulsory reading for all those meaning to understand the idiosyncrasies of gas turbine engines; strengths, weaknesses, and all. When operating with light loading, the power of the engine is not fully utilized. A large part of the fuel being consumed is burned up without doing any work, ending up as waste heat instead of useful mechanical energy. This is especially true for smaller engines like the GTD series. At full power, a gas turbine may be as efficient as, or more efficient than a diesel engine of the same power, but it is often not possible to travel place maximum load on the engine when travelling on most terrain. When idling, gas turbine engines are incredibly inefficient as they must guzzle fuel to compress enough air to feed its own fire.<br />
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Comparative testing of the T-80U against the Leopard 2A5 showed that the Leopard 2A5 could cruise around on gravelly mountain roads for a distance of 370 km, while the T-80U could go a similar distance of 350 km on the same track. As the Soviet doctrine of tank warfare involved a great deal of tactical maneuvering as opposed to static defence, it is conceivable that the constant motion of Soviet tank armies will result in a reduced rate of fuel wastage. However, it is clear that improved engine efficiency and the installation of an auxiliary power unit are still greatly desirable.<br />
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<span style="font-size: large;">DISTRIBUTION</span></h3>
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The best tank in the Soviet Union was also arguably the best tank in the world for a good long while. This, however, had the unfortunate side effect of ballooning the cost of each T-80 to up to three times as much as its cousins. In fact, a single T-80 cost nearly as much as an M60A3! What a nightmare. Although more advanced by an appreciable margin, the usefulness to cost ratio for a T-80 was not favourable compared to a T-72 or a T-64.<br />
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<a href="http://4.bp.blogspot.com/-JIERqgvZevI/VqyuPVNpt0I/AAAAAAAAFhM/yrPd4a1G3BQ/s1600/t-80s%2Bdock.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="413" src="https://4.bp.blogspot.com/-JIERqgvZevI/VqyuPVNpt0I/AAAAAAAAFhM/yrPd4a1G3BQ/s640/t-80s%2Bdock.jpg" width="640" /></a></div>
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With the fall of the Soviet Union and the subsequent economic collapse, the competition between the tank producing factories rose to a fever pitch. Today, only Uralvagonzavod remains. The Omsk factory in Saint Petersburg still refurbishes GTD gas turbine engines for T-80s still serving in the Russian Armed Forces, but no new examples are being produced. The production of the T-80 ended over a decade ago, and its fate has been sealed with the appearance of the T-90M and T-14.<br />
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Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com66tag:blogger.com,1999:blog-3103574899092646031.post-2187385600736553192016-01-15T06:50:00.003-08:002022-05-02T10:21:10.654-07:00T-10<head>
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<h2 style="text-align: center;">
<span style="font-size: x-large;">INVADER</span></h2>
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<span style="font-size: x-small;">By Miguel Miranda</span></div>
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With the Red Army victorious in Berlin the rest of the world drew its breath as the Allies readied the blows that would smite Imperial Japan. History often remembers the horrors of the battle for Okinawa and towering mushroom clouds over Hiroshima and Nagasaki—events that brought Japan to its knees and compelled its surrender.</div>
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Often unmentioned is a massive Soviet pincer that literally quashed the Imperial Japanese Army’s foothold in Manchuria. The offensive involved 1.5 million troops along with thousands of tanks, artillery and aircraft pouring from Siberia and Mongolia. Its devastating success effectively crippled Japan and robbed it of Manchuria’s vast natural resources.<br />
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It was proof—albeit an uncomfortable one for the exhausted Allies—that mechanized warfare was now a realm dominated by Stalin’s divisions. The very same Red Army succored by generous Lend-Lease and the goodwill of Washington, DC and London had learned from its humiliations in 1941 and ended the war equipped with the deadliest tanks in the world.<br />
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It wasn't just the T-34 that was hailed as consummate exemplar for its tracked brethren but the heavy armored fists of the SU-100 and SU-152 tank destroyers. The tank and the tank destroyer complemented each other on the battlefield in majestic synergy, each being used when appropriate for the sake of destruction.<br />
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And then there were Stalin’s own.<br />
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During the final years of the Great Patriotic War the Red Army’s generals had perfected combined arms operations utilizing withering artillery fire and the devastating salvos from Shturmoviks to create decisive combined arms attacks that smashed through enemy lines.<br />
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The weapon of choice for these assaults was the Joseph Stalin 2 or JS-2, an impregnable tank that marked a complete departure from its predecessors. It also foreshadowed the possible terrors of the next Great War when the Soviets had to duke it out against the Allies in Central Europe using main battle tanks on battlefields sown with radiation.<br />
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The Joseph Stalins were the antithesis of the earlier T-34’s. Despite the latter’s fame they suffered greatly from German tanks, aircraft, and anti-tank guns, not to mention their own mechanical and ergonomic faults.<br />
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The Joseph Stalin had better armor than the heaviest German tanks, had a larger main armament, larger dimensions, greater range, and better everything. Its only shortcomings were an uncomfortable interior and a 600 horsepower diesel engine whose mobility issues Soviet engineers never completely solved. This is why succeeding iterations like the Joseph Stalin-3 and 4 were never popular with the Red Army.<br />
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A spectacular success on the battlefield, more than 6,000 JS-2, 3, and 4’s were built and kept as the Red Army’s most lethal tanks during the early Cold War years. Clearly a favorite of their bloodthirsty namesake, when he passed away in 1953 the most recent and last iteration of this near-invincible lineage became the T-10.<br />
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Spacious and extremely heavily armed, it was the most atypical tank ever made in the Soviet Union. Yet it never enjoyed the same success as its cost-efficient (and weaker) replacements the T-55 and the T-62.<br />
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Why?<br />
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<h3>
<span style="font-size: large;">FROM THE OUTSIDE</span></h3>
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The T-10 that entered production in 1952 was certainly impressive to look at. Its nomenclature, which marked a return to the familiar Russian naming system for tanks, was given after Joseph Stalin passed away in 1953. Hence what could’ve been the Joseph Stalin-8 became the T-10 instead.<br />
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The T-10 was menacing to behold. As a latter-day heavy tank its dimensions were enormous, being 8 feet tall from its treads to its turret and 12 feet wide across with a length of 32 feet—measurements comparable to third-generation Main Battle Tanks today. It qualifies as the largest Cold War tank ever fielded by the Red Army, but by no means was it even remotely comparable to heavy tanks fielded on the other side of the Iron Curtain.<br />
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It also looked distinctively Soviet thanks to its chief designer, Joseph Kotin, whose long career involved the notorious KV-1 and the subsequent Joseph Stalin-2, 3 , and 4. Although Kotin is largely forgotten his impact on Russia’s armored heritage can’t be ignored. His influence, stubbornness, and political clout were the unseen forces that shaped the T-10’s career.<br />
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The T-10 retained the familiar rounded turret of Soviet tanks but had its own unique features. It utilized a hull based on the short-lived JS-3, a problematic model with serious mobility issues, but had a distinctive piked nose glacis with the patented glacis splash guard on top, which functioned as a simple wave breaker for when the tank falls into a ditch full of mud.<br />
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It was the only Cold War-era Soviet tank with seven road wheels—small ones at that. The T-10’s sheer size left ample space for infantrymen to latch onto the tank even when its role on the battlefield didn’t allow this. There were a pair of steel boxes on either side of the glacis and another pair at the back where extra fuel drums can be installed.<br />
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Along with steel towing cables, the logs for dragging the tracks through mud had their own latches on the left side of the hull above the tracks. Internally, the T-10’s layout allowed for generous storage space for weapons and ammunition. This included at least 1,000 rounds for the turret machine guns and an additional 600 rounds for the crew’s personal weapons—AKMS'.<br />
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True to its ancestry as a breakthrough tank, the T-10’s steel hide was truly formidable for its era. The thickness of the front of the hull’s reached 120mm on the upper glacis and 100mm on the lower glacis. Because of the steep piked nose, the actual thickness of the upper glacis actually reached a jaw-dropping 320mm!<br />
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According to military historians this protection level made it impervious to direct hits from 76mm and 90mm NATO guns at any conceivable distance, and based on calculations done with knowledge on the penetration performance of 120mm AP supplied by military historians like Ken Estes (who was himself an M103 crew member), the T-10 would have been totally immune to both the Conqueror and M103, and still resistant to 120mm APDS at ranges of 2000 meters and above.<br />
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One interesting thing to take note of is that the glacis armour on the T-10 was constructed of rolled homogeneous steel plates, whereas the Conqueror and M103 had an all-cast hull with a cast steel glacis of inferior hardness and strength. <br />
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The superb ballistic shaping of the turret gave it near-total invulnerability to contemporary tank cannons below a hundred and twenty millimeters in caliber. Horizontally, the curved and pointed sides of the turret converged at the mantlet at such a steep angle that any APBC or APDS shot would most likely simply glance off, and a hit close to the mantlet might not do much either. That area features a steep, curving slope of 50 degrees, curving to up to 70 degrees as we go farther up the turret, as you can see in the photo below:<br />
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The T-10’s relative obscurity meant the thickness of its turret armor is difficult to ascertain. A broader reading of open sources reveals the front "cheeks" on either side of the gun barrel was 250mm thick and reached 115mm on its sides.<br />
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This meant that for all intents and purposes, the mantlet area measured as much as an astounding 390mm! Being made of cast steel, though, the actual strength is slightly lower, and because the steel is softer than the rolled steel on the upper glacis, the front of the turret and the upper glacis can be thought of as having essentially identical protection properties.<br />
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The designers obviously concentrated all of the steel to the front, because the rear of the turret only had 60mm of armor while the roof had 40mm.<br />
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The mantlet was pretty thick in its own right, but obviously not as great as the rest of the turret.<br />
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Even the vulnerable flanks or sides had a thickness of 90mm. Not surprisingly, the engine compartment in the rear just had 30mm of armor, though it is sloped at 45 degrees for an actual thickness of 42mm - more than enough for machine gun and autocannon fire.<br />
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The intimidating protection levels, engine size, and armaments did come at a price. A combat ready T-10 weighed a little over 50 tons, which ran against a 1949 directive to tank design bureaus for a maximum threshold for weight not exceeding 50 tons. The T-64A, by comparison, only weighed a modest 38 tons while having objectively superior armour protection and a superior cannon with equal or better mobility.<br />
<h3>
<span style="color: white; font-size: large;">THE CREW</span></h3>
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<a href="http://3.bp.blogspot.com/-xeNg5IM4P2c/Vpj_nJSwYdI/AAAAAAAAFVo/BJiqMwBrJfc/s1600/Russian%2BT-10%2Bheavy%2Btank%2B09.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-xeNg5IM4P2c/Vpj_nJSwYdI/AAAAAAAAFVo/BJiqMwBrJfc/s1600/Russian%2BT-10%2Bheavy%2Btank%2B09.jpg" /></a></div>
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The T-10 had a typical crew of four. That’s the commander, gunner, loader, and driver who was seated underneath the v-shaped hatch atop the T-10’s upper glacis.<br />
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The commander’s station was left of the main gun. He has superb all-round vision thanks to a whopping seven general vision periscopes installed around the perimeter of his rotatable cupola, besides the usual primary periscope facing forwards. The primary periscope has night vision capabilities and a rudimentary stadiametric rangefinder. He has an IR spotlight attached to his primary periscope at the front of the cupola. The gunner was ensconced opposite him. When not buttoned up the gunner could use the turret’s secondary armament to scare off pesky low-flying aircraft. (A DShKT on the T-10/A/B and a KPVT on the T-10M). The large caliber of the co-ax helped conserve ammo, as the gunner could use the machine gun to disable and destroy trucks and APCs, and save more main gun ammo for tanks.<br />
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The loader on the T-10 is located on the right hand side of the cannon, adjacent to the commander and gunner. Contrary to popular belief, being the loader in a T-10 was a luxury cruise compared to the M103 and Conqueror. Thanks to Nicholas "The Chieftain" Moran of Wargaming, we have a good idea of how the loader (or loaders, in the case of the M103) in these tanks operate, as you can see in the "Inside the Tanks" video series on YouTube. Here is a segment on the loader's station in the Conqueror <a href="https://www.youtube.com/watch?v=8d_pxGcPwyU">here</a>, and a segment on the loaders' station in the M103 <a href="https://www.youtube.com/watch?v=VAI5qg2ZZiU">here</a>, featuring Ken Estes. Watching the videos, it's no exaggeration that the loader's duty isn't something that most people are physically qualified for, which is compounded by a poorly laid-out station in the case of the Conqueror. For instance, in the Conqueror, the loader must lift the two-part ammo above a guard rail and insert it into the breech from above, putting his body into a mechanically disadvantaged position. Despite having only one loader, the T-10 could achieve a higher rate of fire without fatiguing the loader whatsoever through a more rational design and the implementation of a powered rigid chain rammer.<br />
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There is a handy tray placed at hip level. The loader's only responsibility is to lay down the projectile on the tray, and then shove it into position behind the gun breech. A microswitch will be tripped by this action, and the powered chain rammer will ram the projectile into the chamber. Next, the propellant charge is placed on the tray, and the loader's safety button is pressed, initiating the chain rammer to load the propellant charge and automatically swing the tray off to the side while simultaneously readying the cannon to fire. The presence of the powered chain rammer and tray system enables the T-10 to bypass what is usually the most physically demanding part of a loader's job. Keep in mind - the combined weight of a propellant charge and a HE shell is 70 pounds (31.82 kg), and around 80 pounds in the case of the 120mm ammo used in the L11. Ramming it into the breech by hand is no mean feat. The rammer mechanism enabled the T-10 to fire faster than its NATO counterparts and continue to fire faster for a much, much longer period of time. It is possible for the T-10 to attain a rate of fire of up to 5 rounds per minute and maintain that rate, whereas a Conqueror would be limited to around 3, falling off rapidly over the course of battle. If you must know, this 5 RPM rate of fire figure did not come out of my ass. It is inferred that the T-10 could most likely achieve this rate of fire based on "5 RPM burst fire" figure quoted for the 2S1 Gvozdika artillery system, which had a similar 122mm gun and a very similar loading system (<a href="https://youtu.be/6qzrdRyXjFY?t=6m17s">video</a>).<br />
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The tray system also enabled the loader to lapload. In between shots, the loader can place a shell on the tray and have a propellant charge in his hands ready. The loader is not fatigued as the propellant charge is extremely lightweight (only 6.82 kg) compared to a generic 122mm projectile. The moment the cannon is discharged, the loader can immediately shove the tray into position, wait for the chain rammer to finish, place the propellant charge on the tray, and then complete the procedure. All this is done with very minimal physical effort on the loader's part.<br />
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The driver is stuffed into the front of the tank. Steering is done with tiller levers (like a tractor). His only window to the outside world is a single - but unusually wide - periscope.<br />
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Besides all that, there's not much else.<br />
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<h3>
<span style="color: white; font-size: large;">WEAPONRY</span></h3>
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As a breakthrough tank the T-10 was supposed to be better armed and better armored than anything else on the battlefield. Joseph Kotin and his team fulfilled either requirement and the original variant of the T-10 had a 122mm D-25TA main gun—the largest in the world during the 1950s.<br />
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The D-25TA was a rifled tank gun based on the favorite field artillery piece of the Red Army, besides the lighter ZiS-3 and medium-caliber D-44. It was recognizable by its length and bulbous muzzle brake. Even if it proved itself on the successful JS-2, retaining the D-25TA on the T-10 during the 1950s did pose problems.<br />
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Since it was based on a field artillery gun, the D-25TA did not have a bore evacuator. This inconvenienced the crew since noxious propellant fumes would pollute the fighting compartment with each shot. Despite the constant improvements to the Joseph Stalin tank family its 122mm rounds were of the separate charge type so rounds could be better stored in the T-10's interior.<br />
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Most of the projectiles were stowed around the turret ring and in the bustle of the turret, while all of the propellant charges were stowed on racks around the sides of the hull, with a large reserve of charges located in the starboard side front hull, directly in front of the loader for convenience.<br />
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While it has been argued that the two-piece ammo that came with the D-25 was a drag on the cannon's potential rate of fire, Soviet trialing of single-piece 122mm ammo yielded incomparably worse results. It's easy to see why, too. First and foremost, the ammo was split into two parts to divide the very substantial weight of the cartridge, and having compact halves of ammo was hugely helpful in the cramped confines of the tank.<br />
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The D-25TA’s effective range was rather dicey. On paper it could hit a tank-type target 2 km away, but the likelihood of achieving a hit within the first shot was not stellar, at least in practical terms. The cannon itself was no slacker in the accuracy department, of course, but the mediocre sighting system and manual gun laying devices severely affects the gunner's ability to aim it properly in a short time. As a rule, the crew must be well coordinated to execute shots in between short halts, if firing on the move, which would be frequent, seeing as the T-10 was meant for breakthroughs, after all.<br />
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In 1956 a much needed vertical stabilizer (codenamed "Hurricane") was added in the updated T-10A to enable the gunner to keep his sights on target while moving directly towards it, thus drastically improving the speed of shooting while driving straight into the enemy. The updated D-25TS with stabilization compatibility was installed. It features a prominent bore evacuator, which spared the crew from choking on noxious fumes.<br />
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Just one year later, in 1957, the T-10B with a dual plane stabilizer (codenamed "Thunder") was introduced, thus cutting short the time needed by the gunner for target acquisition while the tank is mobile and simultaneously giving even better precision.<br />
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<a href="http://3.bp.blogspot.com/-6wX_H_LYMXc/Vpj11xTe4WI/AAAAAAAAFU0/koNJkTrAqHQ/s1600/Russian%2BT-10%2Bheavy%2Btank%2BM62T2%2B122mm%2Bmain%2Bgun.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="480" src="https://3.bp.blogspot.com/-6wX_H_LYMXc/Vpj11xTe4WI/AAAAAAAAFU0/koNJkTrAqHQ/s640/Russian%2BT-10%2Bheavy%2Btank%2BM62T2%2B122mm%2Bmain%2Bgun.jpg" width="640" /></a><br />
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In the same year of the introduction of the T-10B, the D-25TS was superseded by the 122mm M62T2, which was introduced on the T-10M. It had a new ribbed muzzle brake, which helped to minimize the dust kicked up by the muzzle blast compared to the more conventional double baffle muzzle brake on the D-25TA while still retaining much of the recoil reducing action. The M62 gun was stabilized in two planes as well, but the T-10M did not use the "Thunder" stabilizer of the T-10B. Instead, it used the more advanced 2E12 "Downpour" stabilizer.<br />
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The separate charge ammunition was kept until the final T-10M variant was deployed. By that time the T-62 proved that cost-effective production methods coupled with superb design produced better tanks. Poor old tank designer Kotin had to contend with working with 1940s technology while other design bureaus were creating modern tanks like the T-64 armed with new guns that had extreme range and accuracy.<br />
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<h3>
<span style="color: white; font-size: large;">THE ENGINE</span></h3>
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The first three variants of the T-10 (T-10, T-10A, T-10B) ran on the 700 horsepower V-12-5 diesel engine that gave it a 42 kilometer per hour top speed and a 250 km range. As you'd expect, the engine is located in the ass of the tank.<br />
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Given its weaponry and robust armor, the sum total of the T-10 was a potential headache for NATO generals, but the initial hundred odd T-10’s manufactured in Chelyabinsk Kirov didn’t exactly fulfill expectations. The problem was, according to the latest intelligence at the time on NATO tanks like the M60 Patton and the Chieftain, the T-10 was awfully slow in comparison and its 250 km range was dismal. Even if a breakthrough was successful, the T-10 could not be relied upon to hold the momentum and continue penetrating into the enemy's rear.<br />
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For a so-called breakthrough tank the T-10’s mobility was only half as good as that of a 50-ton second-generation Western tank and its cruising speed is best described as… sluggish. Add the T-10A’s underwhelming TP-2-27 stabilized gun sights whose effective sighting range was less than 2 km and the result was a battlefield mediocrity. Slow to move and slow to fire.<br />
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To overcome this embarrassing flaw the T-10M used a better V-12-6 diesel engine that gave it a boost of 750 hp and a greater 50 km/h speed. Its original eight speed transmission was also changed to a convenient six speed. This improved the T-10M’s mobility by a small, but appreciable margin.<br />
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By the time the T-62 and the T-64 mesmerized the Soviet leadership during the 1960s the future of the lumbering T-10 was in doubt.<br />
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<h3>
<span style="color: white; font-size: large;">THE MYTHS</span></h3>
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Did its flaws make the T-10 a subpar tank? This and other questions form a growing mythology surrounding the T-10—an obscure development locked away in the recesses of the Cold War.<br />
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The T-10 is so neglected it’s usually unexamined in most literature that surveys Soviet armor during the 1950s and 60s. The pitifully small circles who do revisit the T-10’s brief career are Russophilic military enthusiasts (here’s looking at you, Tiles), webmasters of online modern armored vehicle databases, and World of Tanks fans.<br />
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For the sake of great writing, let this be judgment for those who passed judgment on the T-10. This is where the myths surrounding the last Soviet heavy tank come to die!<br />
<h3>
<span style="color: #f9cb9c;">Myth 1: It was too heavy for Russian bridges</span></h3>
Multiple profiles of the T-10 cite its weight as the single factor that led to its withdrawal from service and obsolescence. Apparently a tank weighing above 50 tons endangered Soviet roads and bridges.<br />
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This is untrue and is an issue that actually ruined the Joseph Stalin-4 or JS-4 in the 1940s. As previously mentioned, many of the T-10’s characteristics are present in modern MBTs. Note that by the 1960s NATO tanks like the M60 Patton and the Chieftain weighed as much as the T-10.<br />
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Even during the 1950s, when the US and the UK fielded their own heavy tanks based on leftover World War Two designs—the M103 and the FV104 Conqueror—these models were heavier than the T-10 but were sent to Europe and Southeast Asia. No, the truth is that the Soviets depended heavily on rails to haul heavy cargo across the USSR's vast expanses. Railcar weight limitations were the main issue. Even today, the requirement still stands, which is why the T-14 Armata weighs only 48 tons.<br />
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On the matter of the T-10's obsolescence - it was the writer Stephen Sewell who finally set matters straight with the article '<b><i>Red Star—White Elephant</i></b>' published in the July 2002 issue of Armor magazine. After an exhaustive reading of various declassified Soviet papers and documents on Red Army heavy tanks he realized it was Nikita Khrushchev who was the biggest hater of the T-10.<br />
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In 1960, Sewell wrote, Khrushchev was shown the T-10M, the prototype T-62, and the prototype T-64. Each tank represented the best of the Soviet Union’s armor design bureaus. Smitten by the concept of anti-tank missiles, Khrushchev was impressed the most by the T-64 and its promise. But he insisted the Red Army needed anti-tank missiles and medium tanks with carousel autoloaders instead of many different tanks.<br />
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The T-10M? No more heavy tanks, Khrushchev demanded.<br />
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In short, the T-10 was doomed because it didn’t fit with the prevailing Soviet ideas on modern tanks and anti-tank weapons. According to Sewell’s research when Leonid Brehznev’s replaced Khrushchev the tank designer Kotin managed to lobby for continued T-10M production until 1966.<br />
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<span style="color: #f9cb9c;">Myth 2: The T-10 never saw combat!</span></h3>
Not true! There are sources that claim the T-10 was exported in small numbers to Egypt and Syria. Meanwhile, alternate sources claim it was never exported at all.<br />
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The truth is, after studying the evolution of Kotin’s various Joseph Stalin tanks, the T-10 was kept by the Red Army for its (Group of Soviet Forces Germany) GSFG divisions and never shared with its allies.<br />
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The T-10 was a no-show during the invasion of Hungary because that year the improved T-10A just rolled out. It wasn’t in North Vietnam, the Sinai, or the 38th Parallel either.<br />
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The T-10M did play a critical role in the 1968 invasion of Czechoslovakia. By the time the Soviets did the same to Afghanistan in 1979 the T-10 was pulled from service and mothballed.<br />
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So the T-10 did see combat, albeit in a limited role.<br />
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<span style="color: #f9cb9c;">Myth 3: Oh wait. It did see combat in the Middle East</span></h3>
Nope. A lot of writers made this claim when they mistook the T-10 for the Joseph Stalin-3’s or JS-3’s delivered to Syria and Egypt in the 1950s.<br />
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Israeli Shermans and Chieftains did have a hard time fighting these Soviet monsters but surviving photographic evidence suggests a decent number of JS-3’s were destroyed in the Six Day War. (The JS-4 was only built in small numbers and shipped to the Far East.)<br />
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The best way to tell a T-10 from a Joseph Stalin is to look at the glacis, the tracks, and the gun.<br />
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A T-10 has a distinctive steel “V” on its glacis as well as a V-shaped driver’s hatch underneath the gun. The JS-3 carries two separate spare treads on its glacis beneath the driver’s hatch instead.<br />
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A T-10 runs on seven road wheels. The JS-3 runs on six.<br />
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A T-10, specifically the T-10M built in greater numbers, was armed with a 122mm M62T2 gun that had a bore evacuator and a ribbed muzzle brake. The JS-3 was armed with the older D-25TA that spewed foul propellant gas on the crew whenever it fired.<br />
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<span style="color: #f9cb9c;">Myth 4: It was a lousy tank</span></h3>
Nuh-uh. When it first rolled out of its Chelyabinsk Kirov factory no other tank in the world had as much armor or firepower. At worst, it was a slow poke.<br />
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Consider this. If the T-10 had to fight a NATO tank in the late 1950s, when the T-10 underwent upgrades to reach it’s A and B variants, it would’ve faced an American M47 or M48 with their puny M41 90mm guns. The T-10’s ridiculous level of armor on its glacis and turret could absorb direct hits from these calibers. Even the Centurion, British classic that it was, couldn’t take on the T-10 where it mattered—firepower and armor. What did the Germans have? Leftover Tiger II’s? HEAT ammunition was a contentious equalizer, but because of poorer accuracy and slower flight velocities, hitting a moving tank was more difficult at long distances, and the T-10 was not a particularly large example of a heavy tank, too, measuring in at only 2.43 meters in height and 3.56 meters in width. NATO tanks of the same class like the Conqueror stood tall and wide at 3.18 m and 3.99 m respectively.<br />
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But to be fair, NATO tank guns at the time had impressive range and optics. Their interiors were also more conducive to combat performance. Despite the T-10’s size and spaciousness the placement of its main gun ammunition and Soviet ergonomics (or lack thereof) made it an unsurprisingly miserable Russian tank to drive and fight in.<br />
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The T-10’s armor was better than a T-54/55’s and impervious to anti-tank weapons in the 1950s. What if it were hit by a TOW missile? Well, since that never happened, we can only envision how it plays out. (Yes, there’ll be an explosion.) More relevant were the Nord manually-guided anti-tank missiles of the late 1950s, but such devices were slow and fiddly and it was possible to distract the guidance operator by firing in his general direction, as American forces did to Malyutka missile operators in Vietnam.<br />
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While the T-10 had its flaws, its capabilities were no laughing matter.<br />
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<span style="color: #f9cb9c;">Myth 5: It was the ultimate tank</span></h3>
Not really. Sure, it looked evil and packed a huge main gun. But the T-10 had its limitations.<br />
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Its choice for armament and the problems this caused for the crew have been discussed in detail. Yes, the same impressive rifled main gun had poor range, infuriating ammunition storage, and lousy sights that needed to be changed on every variant. Yes, it was slow.<br />
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The original T-10/A/B didn’t have NBC protection.<br />
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Unlike the T-55 and its successors it couldn’t even cross rivers with a snorkel until this feature was added in the 1960s.<br />
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<span style="color: #f9cb9c;">Myth 6: Only a few were built</span></h3>
It was said that during the last years of the Soviet Union even Gorbachev and his Politburo had no idea how large the USSR’s annual defense budget was or how much of national GDP it consumed. The Soviets ran a police state fueled by secrets and propaganda. Statistics were as susceptible to obfuscation and censorship just like official press releases.<br />
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This is why it’s difficult to find accurate figures for any type of arms production during the Soviet era. The same applies to the short-lived T-10, whose career lasted from 1955 till 1968. Just 12 years.<br />
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Based on Sewell’s own research on the T-10, its flaws made for an erratic production schedule during the 1950s and its total numbers could be in the low hundreds. Profiles of the T-10 found on the Russian web even reveal how in 1957 two incompatible T-10M production lines were running.<br />
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However, there are those who make the bold claim 8,000 were produced and kept mothballed until 1993. That’s a staggering number of T-10M’s considering how only 6,000 Joseph Stalin-type tanks were built until 1948 while Western tanks like the Centurion (4,000+) or the M47 (estimated 8,000) had shorter production runs and weren’t that numerous.<br />
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The figure is even harder to ascertain when surviving T-10M’s are no longer accounted for. There could be either dozens or hundreds rusting away in Russian scrap yards. Maybe the bulk of them have been stripped down, decommissioned, and recycled. So who knows? Either way, it's safe to assume that more than a thousand were built.<br />
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<span style="color: #f9cb9c;">Myth 7: It was over-complicated and expensive to manufacture</span></h3>
Well, tanks are complicated machines.<br />
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They carry huge main guns, engines, and substantial amounts of munitions along with various mechanical and electronic instruments. By the 1960s autoloaders, rangefinders, night vision optics, comms, and other appendages were lopped onto tanks.<br />
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To dismiss the T-10 as over-complicated arises from an interpretation of available open sources. If the T-10 did burden its crew with its operation and maintenance this comes from glaring design flaws (recall its messy ammunition storage) rather than a deliberate level of complicated-ness.<br />
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Besides, from the T-55 onwards the Soviets built and developed tanks that were susceptible to constant upgrading and improvement. They did get more complicated over time. This is a condition familiar to modern tanks.<br />
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The cost of manufacturing T-10’s in the hundreds is as difficult to find out as its production numbers. Sewell argues having to maintain and upgrade the existing fleet of T-10’s during the 1960s was a main reason why its production stopped. It was too damn expensive when thousands of T-55’s could be built instead.<br />
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Perhaps the T-10’s greatest weakness wasn’t in any of its parts or features, but with its designer: Kotin.<br />
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Since working on the original KV-series in the late 1930s Kotin was a rabid and adamant partisan for the heavy tanks that won the Great Patriotic War. The problem was the success of the JS-2 left a familiar template that favored absurd tank design, i.e. the forgotten Object 260 or JS-7 that weighed 60 tons or the Object 279 with its four sets of tracks.<br />
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As long as Kotin’s design bureau preserved the JS-2’s DNA in their future projects the tanks would end up with incredible capabilities but lack fundamentals like a proper engine or safe ammunition storage. At one point in the early 1960s Kotin reportedly developed a prototype anti-tank missile carrier on a heavy tank hull and chassis, but like with all purebred missile tank prototypes of that era, it never saw the light of day.<br />
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<span style="color: #f9cb9c;">Myth 8: The Soviets hated it</span></h3>
Now this is a matter of pure speculation. For at least a decade the T-10 was, technically speaking, the most powerful tank in the Red Army. Unless excerpts from a tanker’s diary surface online describing the T-10 as a worthless pile of junk, it was a war machine built in a particular era that had its own strengths and weaknesses.<br />
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For the record, there were Soviet generals and politicians who believed in its role as a dedicated breakthrough tank. There were also figures like Khrushchev who considered the T-10M an anachronism. It was a sentiment shared by others, engineers and tankers alike, in the vast Soviet military-industrial complex.<br />
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<span style="color: #f9cb9c;">Myth 9: The Chinese built their own T-10’s</span> </h3>
<span style="font-weight: normal;">False! The T-10, like the T-64 and T-80, was never exported outside the Soviet Union. The only heavy tanks the People’s Liberation Army (PLA) could get their hands on were a small pool of JS-2’s inherited from their Soviet benefactors in the late 1940s and early 1950s.</span><br />
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The Chinese never built heavy tanks either. Technology transfers gave state-owned factories the capability to build copies of the T-54 but the Cultural Revolution and its consequences on the national economy set the Chinese back decades in military tech. This left the PLA stuck with their T-54 clones and its derivatives until the 1990s. To this day the bulk of the PLA tank armada are Type 59’s and Type 69’s.<br />
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It was only in the 2000s when the PLA got its hands on legit third-generation MBTs.<br />
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<h3>
<span style="color: #f9cb9c;">Myth 10: NATO’s own heavy tanks were superior</span></h3>
Now this is interesting, The threat posed by post-war Soviet heavy tanks, namely the IS-3, convinced the US and Britain to develop their own analogs for defeating these monsters. The UK eventually fielded the FV214 Conqueror, a 59-ton brute with a 120mm rifled gun. It was the Conqueror that was literally the closest a Western heavy tank got to facing off against its Soviet nemesis. Why? Just 159 Conquerors were ever made, and only a portion of those were sent to bolster NATO in West Germany.<br />
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The problem was it had all sorts of its own problems. Just like the T-10 its speed, reliability, and weight weren’t as superb as the tank appeared. Admittedly, it did implement a more sophisticated hunter-killer regime, but it also had a similarly cramped loader's station, a huge profile and an insufficiently powerful engine. Case in point: The T-10 had a power-to-weight ratio of 13 hp/t, while the Conqueror was a few points under at 10 hp/t! By 1966 the Conquerors were withdrawn and never seen again. The same happened to the 56-ton M103 that was designed and fielded in the same time span as the Conqueror. Just 300 were built from 1957 to 1974, nearly all of them under the umbrella of the Marine Corps.<br />
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…Right. The M103 never faced off against the T-10A/B/M. The design of the M103 was just as mediocre, and it had a 120mm main gun that needed two loaders plus the gunner and commander. Its enormous turret was hilarious to behold and made the M103 into a cartoon version of its siblings the M48 and M60. The Marines eventually got rid of the M103 in 1974. The problem with heavy tanks was the technology of the Cold War erased their reason for being. The T-10, Conqueror, and M103 were sort of evenly matched on paper. Being heavy tanks, their flaws were mutual. A single distinct advantage of the T-10 was that a lot more of them were made, and going by the data presented above, the T-10 would come out the winner in a tank duel at a mile's distance.<br />
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But there was never an occasion or incident that pitted the T-10 vs. M103 vs. Conqueror. Now what if? Well, boys and girls, that belongs to the realm of fiction. Tankograd doesn’t peddle fiction.<br />
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Here are the T-10’s variants.<br />
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<span style="font-size: large;"><b>T-10</b></span>: Original production model that entered service in 1955. It was armed with the 122mm D-25TA main gun used on the JS-2. Secondary armaments were a coaxial 12.7mm DShK M and another pivoting DShK M above the loader’s hatch.<br />
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<span style="font-size: large;"><b>T-10A</b></span>: A slightly improved T-10 that arrived in 1956 with a vertical plane stabilized main gun that also had a bore evacuator. New telescopic sights were installed for the commander and gunner as well as night vision optics for the driver. The numbers built weren’t significant.<br />
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<span style="font-size: large;"><b>T-10B</b></span>: A further improvement of the T-10A built from 1957 onward featuring a new gunner’s sight and a distinctive Red Army infrared search light beside the main gun.<br />
<br />
<span style="font-size: large;"><b>T-10M</b></span>: Introduced later in 1957 and the final variant with “modern” bells and whistles, including an NBC protection system. It was armed with the new M62T2 and ran on a 750 horsepower V-12-6 diesel engine. The secondary armament was changed as well. The T-10M had a coaxial 14.5mm KPV machine gun and another KPV on the loader’s hatch. It was the most heavily armed tank of its era and in 1963 T-10M’s were outfitted with wading snorkels. It was only in 1967 when the T-10M received APDS rounds like the 3BM11 that could defeat 320mm of rolled steel armor at 2 kilometers (or 110mm at 60 degrees at the same range), and HEAT rounds that could penetrate 400mm of armor at any range.<br />
<br />
<br />
The T-10M’s production lasted until 1966 and the tank was withdrawn from service in 1968. Most surviving T-10 tanks found in the occasional Red Army memorials are of the “M” variant.<br />
<br />
<h3>
<span style="color: white; font-size: large;">CONCLUSION</span></h3>
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-T7sB83F-s7w/VpkGB0AWtfI/AAAAAAAAFWk/gt267c_1D1M/s1600/Russian%2BT-10%2Bheavy%2Btank%2B12.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://3.bp.blogspot.com/-T7sB83F-s7w/VpkGB0AWtfI/AAAAAAAAFWk/gt267c_1D1M/s640/Russian%2BT-10%2Bheavy%2Btank%2B12.jpg" width="640" /></a></div>
<br />
<br />
If you’re reading this you’ve probably acquired a newfound appreciation for the T-10. (If not, then it’s possible you skipped the chunks of text above to spare yourself from a tedious pseudo-dissertation on Soviet militaria.)<br />
<br />
It’s apparent the T-10 and its better variants couldn’t have remained in the Soviet arsenal since the prevailing doctrine on mechanized warfare had changed by the late 1950s. The Red Army preferred the smaller medium tanks like the T-54/55’s for their belated would-be showdown with NATO. The advent of high tech MBTs like the T-64 and T-72 consigned the T-10 to obsolescence anyway.<br />
<br />
Radical approaches to tank design also marginalized what the T-10 represented. Why go full heavy tank when a low profile, a small turret, a three-man crew and amphibious capabilities were more important?<br />
<br />
It’s funny to think how the Soviet approach to tank design would’ve been changed forever if Kotin’s emphasis on size and firepower prevailed. Unfortunately, an impossible set of circumstances surrounding the T-10’s existence is needed for this to happen. Doing so creates alternate history and ignores historical reality.<br />
<br />
With what I now understand about the T-10 I’d like to imagine what if it was deployed in East Germany during the 1970s and 1980s. Then upgrades were in order! A larger engine and transmission, along with a better chassis, would have kept the T-10 a formidable adversary against second and third-generation NATO tanks. (In some aspects it had more in common with Western MBTs than the Soviet ones that replaced it.)<br />
<br />
The size of its turret was sufficient for a 125mm smoothbore gun, a laser rangefinder, and perhaps ERA blocks like on a T-72M. The autoloader might not be a good idea since the T-10’s interior favored a magazine and manually loaded guns. Indeed, given its dimensions, the T-10’s hull and chassis could function as a decent carrier for a self-propelled howitzer like the 2S19 Msta-B. Yet none of this ever was.<br />
<br />
In many ways the T-10 heavy tank was akin to the mullet, disco, and Soviet Communism. It was awesome in its heyday but now it’s almost forgotten and perceived as an egregious example of bad taste. Still, every now and then it's fun to throw a themed party.<br />
<br />
<br />
<br />
<h3>
<span style="color: white;"><b><span lang="EN-US"><span style="font-size: large;">ABOUT
THE AUTHOR</span></span></b></span></h3>
<div class="MsoNormal">
<span lang="EN-US">Miguel Miranda is a writer based in the Philippines.
He harbors a smoldering passion for Cold War militaria that contrasts his
shameful background as a recovering ex-journalist.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">His other interests span writing for
magazines, massage therapy, heavy metal, collecting old paperback novels, and
admiring good industrial design.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Miguel is the founder of 21<sup>st</sup>
Century Asian Arms Race (<a href="http://21stcenturyasianarmsrace.com/">21AAR</a>),
a website about modern weapon systems and their impact on ongoing wars and
crises across Eurasia.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The
website was founded because Miguel got the impression that China was
buying and reverse-engineering far too many advanced weapons for
everybody else's comfort. Now he realizes a handful of powerful
countries have made perpetual war a matter of business-as-usual and this
is why the 21st century is going to be really something else. So he
writes about this phenomenon instead.<span lang="EN-US"> </span>Some of 21AAR’s content also takes on a
historical and (gulp!) geopolitical perspective too, which means he’s got
variety down pat.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">In his spare time Miguel likes to be
affectionate toward living things. He’s currently working on an erotic spy
thriller.</span></div>
<br />
<h3>
<span style="color: white; font-size: large;">REFERENCES</span></h3>
<a href="http://all-tanks.ru/content/tyazhelyi-tank-t-10-8">http://all-tanks.ru/content/tyazhelyi-tank-t-10-8</a><br />
<br />
<a href="http://kubinkamuseum.ru/index.php?option=com_content&view=article&id=17&Itemid=213">http://kubinkamuseum.ru/index.php?option=com_content&view=article&id=17&Itemid=213</a><br />
<br />
<a href="http://english.battlefield.ru/en/tank-development/30-armored-cars/21-ba64.html">http://english.battlefield.ru/en/tank-development/30-armored-cars/21-ba64.html</a><br />
<br />
<a href="http://www.militaryfactory.com/armor/detail.asp?armor_id=260">http://www.militaryfactory.com/armor/detail.asp?armor_id=260</a><br />
<br />
<a href="http://www.militarymodelling.com/news/article/soviet-t10m-heavy-tank-in-1-35/22517">http://www.militarymodelling.com/news/article/soviet-t10m-heavy-tank-in-1-35/22517</a><br />
<br />
<a href="http://militariorgucoz.ru/military-news/22664-kak_vimirali_dinozavri_-_poslednie_tjazhelie_tanki_chast_4_6413.html">http://militariorgucoz.ru/military-news/22664-kak_vimirali_dinozavri_-_poslednie_tjazhelie_tanki_chast_4_6413.html</a><br />
<br />
<a href="http://xn----7sbb5ahj4aiadq2m.xn--p1ai/guide/army/ta/t10.shtml">http://русская-сила.рф/guide/army/ta/t10.shtml</a><br />
<br />
<a href="http://tankandafvnews.com/tag/t-10/">http://tankandafvnews.com/tag/t-10/</a><br />
<br />
<a href="http://tankarchives.blogspot.ca/2015/11/the-last-soviet-heavyweight.html">http://tankarchives.blogspot.ca/2015/11/the-last-soviet-heavyweight.html</a><br />
<br />
<a href="http://tanki-tut.ru/ussr-russia/is-8_t-10/">http://tanki-tut.ru/ussr-russia/is-8_t-10/</a><br />
<br />
<a href="http://www.tankovedia.ru/catalog/sssr/tank_t-10">http://www.tankovedia.ru/catalog/sssr/tank_t-10</a><br />
<br />
<a href="http://tanksim.org.ru/references/stk/T-10M/t10mstk.php">http://tanksim.org.ru/references/stk/T-10M/t10mstk.php</a><br />
<br />
<a href="http://www.tanks.net/early-cold-war-tanks/t-10-heavy-tank.html">http://www.tanks.net/early-cold-war-tanks/t-10-heavy-tank.html</a><br />
<br />
<a href="http://techarms.narod.ru/army/technics/04heavytank/t10/t10.html">http://techarms.narod.ru/army/technics/04heavytank/t10/t10.html</a><br />
<br />
<a href="http://www.tmuseum.ru/posmotrite-na-sajte/galereya-eksponatov/boennaya-tekhnika/tank-t-10">http://www.tmuseum.ru/posmotrite-na-sajte/galereya-eksponatov/boennaya-tekhnika/tank-t-10</a><br />
<br />
<a href="https://en.wikipedia.org/wiki/122_mm_gun_M1931/37_%28A-19%29">https://en.wikipedia.org/wiki/122_mm_gun_M1931/37_%28A-19%29</a><br />
<a href="https://www.blogger.com/goog_1878372059"><br /></a>
<a href="http://wowar.ru/tank-t-10">http://wowar.ru/tank-t-10</a><br />
<br />
<a href="http://www.net-maquettes.com/pictures/t-10-heavy-tank/?afg301_page_id=1#afg-301">http://www.net-maquettes.com/pictures/t-10-heavy-tank/?afg301_page_id=1#afg-301</a><br />
<br />
<br />
<br />
<br />Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com17tag:blogger.com,1999:blog-3103574899092646031.post-74333794304168448652015-12-15T08:03:00.001-08:002022-05-02T10:21:25.403-07:00BTR-152<head>
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<div class="Section1">
<h2 style="text-align: center;">
<b><span lang="EN-US"><span style="font-size: x-large;">GUN TRUCK</span></span></b></h2>
<div class="MsoNormal">
<div style="text-align: center;">
<span style="font-size: x-small;">By Miguel Miranda</span></div>
<br /></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<b><span lang="EN-US"><!--[if gte vml 1]><v:shapetype id="_x0000_t75"
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o:title="Soviet BTR-152 20"/>
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-yR511XhOowQ/VnAgcDGwPxI/AAAAAAAAFAw/GNjuXbCo0aQ/s1600/Soviet%2BBTR-152%2B20.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-yR511XhOowQ/VnAgcDGwPxI/AAAAAAAAFAw/GNjuXbCo0aQ/s1600/Soviet%2BBTR-152%2B20.jpg" /></a></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<br />
<div style="text-align: left;">
<span lang="EN-US">The former <st1:place w:st="on">Soviet
Union</st1:place> built the most dangerous APC’s in the world. Whether wheeled
or tracked these machines always packed a punch and had incredible speed. By
comparison, until the advent of the IFV, NATO’s only successful response to the
Soviet’s superb APC development was the American M113—a remarkable, albeit
utilitarian, vehicle in its own right.</span></div>
</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">To think the whole concept of the personnel
carrier, armed and armored for combat, didn’t catch on for some years after
World War Two and it was still the Soviets who led the way with an impressive
range of vehicles. Including a very peculiar truck.</span></div>
<div class="MsoNormal">
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-0_0fGeQgBQI/VnAgt6enfYI/AAAAAAAAFA4/3_AdN0AdBJ0/s1600/Soviet%2BBTR-152%2B01.jpg" style="margin-left: auto; margin-right: auto;"><img alt="The BTR-152 was one of the first Soviet vehicles to proliferate across the Middle East and Africa. Pictured are BTR-152B’s armed with quad-mounted DShK’s and a lone Goryunov. Because Arab armies sucked at waging war the Israelis ended up collecting a sizable fleet of their own BTRs" border="0" src="https://4.bp.blogspot.com/-0_0fGeQgBQI/VnAgt6enfYI/AAAAAAAAFA4/3_AdN0AdBJ0/s1600/Soviet%2BBTR-152%2B01.jpg" title="" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><div class="MsoNormal" style="text-align: center;">
<span lang="EN-US">The BTR-152 was one of the first
Soviet vehicles to proliferate across the Middle East and Africa.
Pictured are BTR-152B’s armed with quad-mounted DShK’s and a lone Goryunov. Because
Arab armies sucked at waging war the Israelis ended up collecting a sizable fleet of
their own BTRs...</span></div>
<div class="MsoNormal">
<br /></div>
</td></tr>
</tbody></table>
<span lang="EN-US">As a matter of fact, the Soviets
inadvertently arrived at the concept in 1950 after using their 6x6 ZiS-151
truck as the basis for an armored troop transporter whose exterior vaguely
resembled a US Army half track.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">This hybrid vehicle was designed by a team
of engineers led by B.M. Fitterman and staffed by K.M. Androsov, V.F. Rodionov,
A.P. Petrenko, P.P. Tchernayev, and N.I. Orlov.</span></div>
<div class="MsoNormal">
<br /></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1025" type="#_x0000_t75" style='width:333pt;height:246pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image003.jpg"
o:title="Soviet BTR-152 01"/>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-SuRepdNCiJo/VnAhM5S5v2I/AAAAAAAAFBA/fJ5dwTaf0jY/s1600/Soviet%2BBTR-152%2BHispano%2BSuiza%2B02.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="408" src="https://1.bp.blogspot.com/-SuRepdNCiJo/VnAhM5S5v2I/AAAAAAAAFBA/fJ5dwTaf0jY/s640/Soviet%2BBTR-152%2BHispano%2BSuiza%2B02.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">...which they gladly turned on their former masters. See this IDF BTR-152 mounted with a French Hispano Suiza .404 20mm anti-aircraft gun. Fun fact: France was actually Israel’s biggest arms dealer in the 1960s.</td></tr>
</tbody></table>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The final result was the <i>Bronetransporter</i>-152 or BTR-152. It was
ugly, to be honest. But it promised to shield a dozen infantrymen from harm and
mount the kind of heavy weapons that would make NATO troopers’ toes curl. (It
wasn’t actually the first BTR, a distinction reserved for the 4x4 BTR-40.) </span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The BTR-152 was hardly a far cry from its
ancestors, trucks and half-tracks alike, and even performed like these
vehicles. It ran on a 110 horsepower ZiS-123 gasoline engine and managed a top
speed of 68 kilometers per hour. Unlike the 8x8 BTR’s that succeeded it, the
152 wasn’t amphibious and could only manage fording across 30 inches of water.</span></div>
<div class="MsoNormal">
<br /></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
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<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image007.jpg"
o:title="Soviet BTR-152 parking lot"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-ztKJe5RSKr8/VnAh-lPeS0I/AAAAAAAAFBM/nK9VZTuVGak/s1600/Soviet%2BBTR-152%2Bparking%2Blot.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="446" src="https://3.bp.blogspot.com/-ztKJe5RSKr8/VnAh-lPeS0I/AAAAAAAAFBM/nK9VZTuVGak/s640/Soviet%2BBTR-152%2Bparking%2Blot.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span lang="EN-US">From 1950 until 1962 the BTR-152 enjoyed
levels of unprecedented success as the primary heavy troop transport and
workhorse for Red Army and Warsaw Pact forces. Manufactured in untold thousands
(exact production figures are conflicting, but are in the five digit range) and
exported to dozens of countries, the BTR-152 was the truck that could fight
back and do a lot of other things besides.</span></td></tr>
</tbody></table>
<div class="MsoNormal">
<span lang="EN-US">This despite the fact that its welded steel
armor wasn’t really as tough as it appeared—more on this later. </span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<st1:place w:st="on"><st1:country-region w:st="on"><span lang="EN-US">China</span></st1:country-region></st1:place><span lang="EN-US">
allegedly built its own copies of the BTR-152 but a lack of photographic
evidence puts this claim in doubt.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">What is beyond question, however, is the
BTR-152 was an inelegant marvel that was tough, reliable, and provided a
fighting chance for every poor man’s army in a dozen forgotten wars.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">It’s still being driven around today, for
eff’s sake.</span></div>
<div class="MsoNormal">
<br /></div>
<h3>
<b><span lang="EN-US"><span style="font-size: large;">THE
PERSONNEL CARRIER</span></span></b></h3>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The BTR-152 was a project of the <i>Zavod Imeni Stalina</i> plant or ZiS in <st1:place w:st="on"><st1:city w:st="on">Moscow</st1:city></st1:place> and irony of
ironies before World War Two its truck production line was modernized by an
American firm.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">This meant that American DNA permeated the
modern lineage of Soviet truck manufacturing. Undeniable proof of another
bizarre twist in the Cold War’s technological showdown. It deserves mention
that substantial quantities of US Army M2 half tracks were transported to the <st1:place w:st="on"><st1:country-region w:st="on">USSR</st1:country-region></st1:place>
as Lend Lease.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Initial production was carried out at the
ZiS’ Automotive Factory No.2 from 1950 until 1956. It was then shifted to the
Zavod imeni Likhacheva or ZiL until production ceased in 1962.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-SznLOPg2SvM/VnAiWYHiyTI/AAAAAAAAFBU/5A4bhxeBilM/s1600/US%2BArmy%2BHalf%2BTrack%2B105mm.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="468" src="https://2.bp.blogspot.com/-SznLOPg2SvM/VnAiWYHiyTI/AAAAAAAAFBU/5A4bhxeBilM/s640/US%2BArmy%2BHalf%2BTrack%2B105mm.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The M2 half track was a genuine multirole platform that could be equipped for various tasks. That front grille looks familiar though. Hmmm...</td></tr>
</tbody></table>
<div class="MsoNormal">
<span lang="EN-US">The influences that shaped the BTR-152 gave
it its best asset: spaciousness. Compared to all the other Soviet APCs that
followed the BTR-152 never lacked for space in its passenger compartment. On
paper the Soviets figured out 15 troopers could fit at the back plus a driver
and co-driver in the cab. Fifteen!</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">This is what an empty BTR-152B looks like. Troops enter from a rear swing door and parallel rows of seats can fit seven each. The 15th trooper mans the missing Goryunov machine gun. But ideally there should be a machine gun up front.</span></div>
<div class="MsoNormal">
<span lang="EN-US"><br /></span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-aw4IoD4ZN14/VnAilP5mGyI/AAAAAAAAFBc/LjgyuCLJn30/s1600/Soviet%2BBTR-152%2B04.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://4.bp.blogspot.com/-aw4IoD4ZN14/VnAilP5mGyI/AAAAAAAAFBc/LjgyuCLJn30/s400/Soviet%2BBTR-152%2B04.jpg" width="398" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"> For a wheeled APC driving the BTR-152
wasn’t a chore. That is, so long as no hostile fire was directed at it.</span></div>
</td></tr>
</tbody></table>
<div class="MsoNormal">
<span lang="EN-US"><br /></span></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-kD0TERi7-OE/VnAixPkaj1I/AAAAAAAAFBk/EH6wnl7nczU/s1600/Soviet%2BBTR-152%2Bbeing%2Bdriven.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="https://1.bp.blogspot.com/-kD0TERi7-OE/VnAixPkaj1I/AAAAAAAAFBk/EH6wnl7nczU/s400/Soviet%2BBTR-152%2Bbeing%2Bdriven.jpg" width="400" /></a></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Its design patterned after the M2 half
track, the BTR-152’s windshield was separated into two panels. When buttoned up
the driver just had to lower the hatches and reduce his vision to those classic
Soviet viewing slits. (That’s a fuel tank behind the driver’s seat, by the
way.)</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The side doors were just as interesting.
The upper panels could be lowered for better visibility and/or ventilation.</span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1035" type="#_x0000_t75" style='width:306pt;height:243.75pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image015.jpg"
o:title="Soviet BTR-152 09"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-AlfR-4BCEMs/VnAjBdcsGEI/AAAAAAAAFBs/nl6-i4t74fY/s1600/Soviet%2BBTR-152%2B09.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="317" src="https://4.bp.blogspot.com/-AlfR-4BCEMs/VnAjBdcsGEI/AAAAAAAAFBs/nl6-i4t74fY/s400/Soviet%2BBTR-152%2B09.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Check out the vacant driver’s seat</td></tr>
</tbody></table>
</span></div>
<div class="MsoNormal">
<span lang="EN-US"><br /></span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-9JSM_okZ5AE/VnAjM6uzbKI/AAAAAAAAFB0/mDla6upZ68o/s1600/Soviet%2BBTR-152%2Bsteering%2Bwheel.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://3.bp.blogspot.com/-9JSM_okZ5AE/VnAjM6uzbKI/AAAAAAAAFB0/mDla6upZ68o/s1600/Soviet%2BBTR-152%2Bsteering%2Bwheel.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">From a different angle in a better preserved vehicle.</td></tr>
</tbody></table>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">In case you ever need to drive a BTR-152
here’s a handy guide to what’s what.</span></div>
<div class="MsoNormal">
<br /></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1031" type="#_x0000_t75" style='width:331.5pt;height:248.25pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image019.jpg"
o:title="Soviet BTR-152 diagram 01"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-L9A5cn6TRbo/VnAjbigpkXI/AAAAAAAAFB8/sA2S5cxNxbI/s1600/Soviet%2BBTR-152%2Bdiagram%2B01.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-L9A5cn6TRbo/VnAjbigpkXI/AAAAAAAAFB8/sA2S5cxNxbI/s1600/Soviet%2BBTR-152%2Bdiagram%2B01.jpg" /></a></div>
<br />
<div class="MsoNormal">
<br /></div>
</div>
<span lang="EN-US" style="font-family: "times new roman" , "serif"; font-size: 12.0pt;"><br clear="all" style="mso-break-type: section-break; page-break-before: auto;" />
</span>
<br />
<div class="Section2">
<ol start="1" style="margin-top: 0cm;" type="1">
<li class="MsoNormal"><span lang="EN-US">Throttle pedal carburetor</span></li>
<li class="MsoNormal"><span lang="EN-US">Brake pedal</span></li>
<li class="MsoNormal"><span lang="EN-US">Clutch pedal</span></li>
<li class="MsoNormal"><span lang="EN-US">Control panel</span></li>
<li class="MsoNormal"><span lang="EN-US">Signal button</span></li>
<li class="MsoNormal"><span lang="EN-US">Tire air control</span></li>
<li class="MsoNormal"><span lang="EN-US">Gear lever transfer</span></li>
<li class="MsoNormal"><span lang="EN-US">Air vents and windscreens</span></li>
<li class="MsoNormal"><span lang="EN-US">Wiper</span></li>
<li class="MsoNormal"><span lang="EN-US">Front axle lever</span></li>
<li class="MsoNormal"><span lang="EN-US">Handbrake lever</span></li>
<li class="MsoNormal"><span lang="EN-US">???</span></li>
<li class="MsoNormal"><span lang="EN-US">???</span></li>
<li class="MsoNormal"><span lang="EN-US">???</span></li>
<li class="MsoNormal"><span lang="EN-US">Tire valve block</span></li>
<li class="MsoNormal"><span lang="EN-US">Gearbox shift</span></li>
<li class="MsoNormal"><span lang="EN-US">Heater</span></li>
<li class="MsoNormal"><span lang="EN-US">Lever for radiator shutters</span></li>
</ol>
</div>
<div class="Section3">
<div class="MsoNormal">
<span lang="EN-US">And if you want to ace a quiz on the parts
of a BTR-152K—a later variant with an armored roof—this might come in handy.</span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1037" type="#_x0000_t75" style='width:327pt;height:339pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image020.jpg"
o:title="Soviet BTR-152 diagram 02"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-syuHlFLm2lE/VnAjuL1P01I/AAAAAAAAFCE/M3pHutFB4bU/s1600/Soviet%2BBTR-152%2Bdiagram%2B02.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-syuHlFLm2lE/VnAjuL1P01I/AAAAAAAAFCE/M3pHutFB4bU/s1600/Soviet%2BBTR-152%2Bdiagram%2B02.jpg" /></a></div>
<br />
<div class="MsoNormal">
<br /></div>
</div>
<span lang="EN-US" style="font-family: "times new roman" , "serif"; font-size: 12.0pt;"><br clear="all" style="mso-break-type: section-break; page-break-before: auto;" />
</span>
<br />
<div class="Section4">
<ol start="1" style="margin-top: 0cm;" type="1">
<li class="MsoNormal"><span lang="EN-US">Ax</span></li>
<li class="MsoNormal"><span lang="EN-US">Compartment for RPG launcher</span></li>
<li class="MsoNormal"><span lang="EN-US">Headset bag</span></li>
<li class="MsoNormal"><span lang="EN-US">Container for RPG rockets</span></li>
<li class="MsoNormal"><span lang="EN-US">Compartment for driver/co-driver personal effects</span></li>
<li class="MsoNormal"><span lang="EN-US">Compartment for spare radio parts</span></li>
<li class="MsoNormal"><span lang="EN-US">Gun rack</span></li>
<li class="MsoNormal"><span lang="EN-US">Compartment for spare parts</span></li>
<li class="MsoNormal"><span lang="EN-US">Compartment for ammunition</span></li>
<li class="MsoNormal"><span lang="EN-US">Starting lamp</span></li>
<li class="MsoNormal"><span lang="EN-US">Oil tank</span></li>
<li class="MsoNormal"><span lang="EN-US">Compartment for spare parts</span></li>
<li class="MsoNormal"><span lang="EN-US">Block winch</span></li>
<li class="MsoNormal"><span lang="EN-US">Spare tire</span></li>
<li class="MsoNormal"><span lang="EN-US">Ammunition box</span></li>
<li class="MsoNormal"><span lang="EN-US">Shovel</span></li>
<li class="MsoNormal"><span lang="EN-US">Canvass bucket</span></li>
<li class="MsoNormal"><span lang="EN-US">Spare box</span></li>
<li class="MsoNormal"><span lang="EN-US">Mounting kit</span></li>
<li class="MsoNormal"><span lang="EN-US">Antenna</span></li>
<li class="MsoNormal"><span lang="EN-US">First aid kit</span></li>
<li class="MsoNormal"><span lang="EN-US">Tool kit</span></li>
<li class="MsoNormal"><span lang="EN-US">Compartment for spare parts</span></li>
<li class="MsoNormal"><span lang="EN-US">Saw</span></li>
<li class="MsoNormal"><span lang="EN-US">Extinguisher</span></li>
<li class="MsoNormal"><span lang="EN-US">“Document bag”</span></li>
<li class="MsoNormal"><span lang="EN-US">Jack </span></li>
<li class="MsoNormal"><span lang="EN-US">Starting handle</span></li>
<li class="MsoNormal"><span lang="EN-US">Tow rope</span></li>
</ol>
</div>
<div class="MsoNormal">
<span lang="EN-US">Indeed, the BTR-152 had a lot of neat
features that are a bit scarce in modern APCs.</span></div>
<div class="MsoNormal">
<br /></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1038" type="#_x0000_t75" style='width:311.25pt;height:231.75pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image021.jpg"
o:title="Soviet BTR-152 rear view 02"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-ntM7jrOCYpY/VnAkBVQ28ZI/AAAAAAAAFCM/veBwjdRnT6c/s1600/Soviet%2BBTR-152%2Brear%2Bview%2B02.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://2.bp.blogspot.com/-ntM7jrOCYpY/VnAkBVQ28ZI/AAAAAAAAFCM/veBwjdRnT6c/s400/Soviet%2BBTR-152%2Brear%2Bview%2B02.jpg" width="400" /></a></div>
<span lang="EN-US">The vehicle’s exterior was furnished with a
complete set of entrenching tools. These included a shovel at the back and
opposite it was a crowbar, a two-handed saw clipped to the vehicle’s side, an
ax attached behind the frontal left tire, and a pick axe attached behind the
frontal right tire.</span><br />
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Sometimes a lug wrench was affixed beneath
the driver’s door.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Don’t forget the spare tire attached to the
rear swing door!</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">You’d think these tools were enough for
dismounted infantry to build a log cabin. But such implements were needed to
ready a prepared position if the situation arose.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Also notice the tarpaulin spread over the
BTR-152. This was a common half-measure to protect the BTR’s interior from snow
and rain. The arrival of the BTR-152K with three roof hatches rectified this
glaring fault.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Unlike the emerging generation of NATO
APCs, the BTR-152 was designed to allow its passengers to fight from within the
vehicle. Hence the three circular firing ports on either side of the hull and
two additional firing ports next to the rear swing door. </span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">This meant infantry could fight at
360-degrees within the BTR-152. </span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1039" type="#_x0000_t75" style='width:333pt;height:249.75pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image023.jpg"
o:title="Soviet BTR-152 front grille 01"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-Y7H4hvVuBFo/VnAkKjDB8fI/AAAAAAAAFCU/BGbcBTxXUo0/s1600/Soviet%2BBTR-152%2Bfront%2Bgrille%2B01.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://1.bp.blogspot.com/-Y7H4hvVuBFo/VnAkKjDB8fI/AAAAAAAAFCU/BGbcBTxXUo0/s320/Soviet%2BBTR-152%2Bfront%2Bgrille%2B01.jpg" width="320" /></a></div>
<br />
<span lang="EN-US">The BTR-152’s armored grilles could be
opened and closed at the push of a dashboard button. This was to protect the
radiator from gunfire. Some analysts claim this safety feature made the BTR-52
prone to overheating.</span><br />
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">But take note of the BTR-152’s headlights
in the photo above. The original BTR-152 only had a single pair and so did
succeeding variants. However, by the time the BTR-152V1 rolled out an
additional pair of infrared lights were installed along with improvements to
the chassis and transmission. See below.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://4.bp.blogspot.com/-i3N9h9YWg1w/VnAkVdu2sTI/AAAAAAAAFCc/YsgfRmZwdEU/s1600/Soviet%2BBTR-152%2B03.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://4.bp.blogspot.com/-i3N9h9YWg1w/VnAkVdu2sTI/AAAAAAAAFCc/YsgfRmZwdEU/s400/Soviet%2BBTR-152%2B03.jpg" width="400" /></a></div>
<div class="MsoNormal">
<span lang="EN-US">The bulge on the bumper, by the way, was
the housing for the mechanical winch. The original BTR-152 and BTR-152A only
had flat bumpers with a length of wire rope (for towing) wrapped around it. The
winch first appeared on the BTR-152B and succeeding variants and was encased in
a special container with a round flip top.</span></div>
<div class="MsoNormal">
<span lang="EN-US"><br /></span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1032" type="#_x0000_t75" style='width:168pt;height:112.5pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image027.jpg"
o:title="Soviet BTR-152B mechanical winch"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://4.bp.blogspot.com/-Qg4TLQZp7ok/VnAki4Csv_I/AAAAAAAAFCk/9_XPXUYCm3c/s1600/Soviet%2BBTR-152B%2Bmechanical%2Bwinch.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-Qg4TLQZp7ok/VnAki4Csv_I/AAAAAAAAFCk/9_XPXUYCm3c/s1600/Soviet%2BBTR-152B%2Bmechanical%2Bwinch.jpg" /></a></div>
<br />
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The BTR-152 also had a few worrisome quirks
like…</span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1041" type="#_x0000_t75" style='width:4in;height:3in'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image028.jpg"
o:title="Soviet BTR-152 28 fuel tank"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-UP1Uf-0faJc/VnAkwa00UrI/AAAAAAAAFCs/yykKGlZTWq4/s1600/Soviet%2BBTR-152%2B28%2Bfuel%2Btank.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://1.bp.blogspot.com/-UP1Uf-0faJc/VnAkwa00UrI/AAAAAAAAFCs/yykKGlZTWq4/s400/Soviet%2BBTR-152%2B28%2Bfuel%2Btank.jpg" width="400" /></a></div>
<div style="text-align: left;">
<br /></div>
<div class="MsoNormal" style="text-align: left;">
<span lang="EN-US">Every time the Soviets built an APC their
engineers would place the fuel tank in the most awkward position imaginable.
This applied to the BTR-152, where separate fuel tanks were located behind the
driver and co-driver’s seats. The photo above captures the tank behind the
co-driver.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The BTR-152’s fuel tanks were identifiable
from the outside via the round caps behind the driver and co-driver’s doors. </span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">It might have been the vulnerability posed
by these tanks that explains the large number of BTR-152’s abandoned in combat.
This phenomenon was quite common during the Six Day War when captured or
salvaged BTR-152’s resulted in the IDF having to maintain a whole fleet of
these APCs.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Maybe the driver and crew, being aware of
the BTR-152’s thin armor and the proximity of the fuel tanks, always found it
sensible to vacate the vehicle one it was crippled. </span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Since it was based on a proven truck
chassis, the BTR-152 was adaptable for multiple roles. It could also tow stuff,
like artillery or a ZU-23-2 anti-aircraft gun. </span></div>
<div class="MsoNormal">
<br /></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1042" type="#_x0000_t75" style='width:324pt;height:243pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image030.jpg"
o:title="Soviet BTR-152 21"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-_g_GErjoQJk/VnAk7LkNkkI/AAAAAAAAFC0/tnN9hrz6_3Y/s1600/Soviet%2BBTR-152%2B21.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://3.bp.blogspot.com/-_g_GErjoQJk/VnAk7LkNkkI/AAAAAAAAFC0/tnN9hrz6_3Y/s320/Soviet%2BBTR-152%2B21.jpg" width="320" /></a></div>
<span lang="EN-US">Here it is towing a ZU-23-2,
a.k.a. everybody’s favorite cheap AA gun.</span><br />
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">There were reportedly several BTR-152
variants. But thanks to the wonders of online research it has come to light
that not only were there more different types of BTR-152’s—the Soviets
classified them alphabetically! This makes it easier to identify them.</span><br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://4.bp.blogspot.com/-Nnpii8low9A/V0dS0ut2PmI/AAAAAAAAAMM/0lDVDtC1AR07WGHAKszlc6tLE455OrcSwCLcB/s1600/Soviet%2BBTR-152%2BEast%2BGermany%2B02.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="424" src="https://4.bp.blogspot.com/-Nnpii8low9A/V0dS0ut2PmI/AAAAAAAAAMM/0lDVDtC1AR07WGHAKszlc6tLE455OrcSwCLcB/s640/Soviet%2BBTR-152%2BEast%2BGermany%2B02.jpg" width="640" /></a></div>
<br />
<span lang="EN-US">For the record, the ZiS and ZiL factories
recognized 14 BTR-152 variants. Their combined production numbers reached 12,
421 units while the highest estimate for BTR-152’s built is a rounded figure of
15,000. </span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Here’s the breakdown.</span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"></span></div>
<br />
<div class="MsoNormal">
<span lang="EN-US">BTR-152 – Original open top production
variant armed with a Goryunov machine gun. (See above.)</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">BTR-152A – The first genuine an
anti-aircraft variant although the type of gun used wasn’t specified.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">BTR-152B/1 – A mechanical winch drum was
installed on the bumper beneath the grille.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">BTR-152D – A BTR-152V mounting a 14.5mm
ZPU-2 </span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">BTR-152E – A BTR-152V1 with a ZPU-2.</span><br />
<br />
<span lang="EN-US"><span lang="EN-US">BTR-152S – A so-called “communication
variant” with a large radio antennae near the windshield.</span></span><br />
<br />
<span lang="EN-US"><span lang="EN-US">BTR-152U - The passenger compartment is enclosed and enlarged. This is the BTR-152 converted into a mobile command post.</span> </span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">BTR-152V1 – Infrared headlights installed
for driver visibility along with crew compartment heater and a blower for
windshield.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">BTR-152V – The heavily upgraded variant
produced by ZiL from 1956 onward. Had equidistant tires and axels, increased
performance, and an enclosed passenger compartment.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">BTR-152K – An armored roof with three
hatches installed on a BTR-152V.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">BTR-152 HS.404 – An Israeli variant mounted
with an HS.404 anti-aircraft gun.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">BTR-152B ZU-23-2 – A technical used by Arab
militias in the <st1:place w:st="on">Levant</st1:place> armed with twin 23mm
anti-aircraft guns.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">This is the BTR-152K converted into an
ambulance.</span></div>
<div class="MsoNormal">
<br /></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1046" type="#_x0000_t75" style='width:297pt;height:177pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image038.jpg"
o:title="Soviet BTR-152 32"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-L3uUdHogyUs/VnAlQHrneKI/AAAAAAAAFDE/VU8fuKVDKW0/s1600/Soviet%2BBTR-152%2B32.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-L3uUdHogyUs/VnAlQHrneKI/AAAAAAAAFDE/VU8fuKVDKW0/s1600/Soviet%2BBTR-152%2B32.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span lang="EN-US">Arab forces were among the
BTR-152’s most prolific users. This modified BTR-152 captured by the IDF was
converted into a tow truck/recovery vehicle by a Lebanese militia.</span></td></tr>
</tbody></table>
<div class="MsoNormal">
<span lang="EN-US"><br /></span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-CfQ9lKB0hJc/VnAldlcZoJI/AAAAAAAAFDM/m9tJVogjDhY/s1600/Soviet%2BBTR-152%2B25%2Bcommand%2Bvehicle.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="276" src="https://3.bp.blogspot.com/-CfQ9lKB0hJc/VnAldlcZoJI/AAAAAAAAFDM/m9tJVogjDhY/s320/Soviet%2BBTR-152%2B25%2Bcommand%2Bvehicle.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span lang="EN-US">Here’s the rare and completely weird
BTR-152U, a command vehicle. It looks like a house built on a truck.</span></td></tr>
</tbody></table>
<h3>
<b><span lang="EN-US"><span style="font-size: large;">WEAPONRY</span></span></b></h3>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">This profile dubs the BTR-152 a “Gun
Truck.” The term itself conjures visions of a mean-looking rig with bulging
tires and serious firepower on its bed.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">This is precisely where the BTR-152
excelled. The Soviets knew it and produced a dazzling selection of variants
that carried almost all their large caliber machine guns in the 1950s. Ditto
every other army that found a use for the BTR-152, be they Palestinian freedom
fighters, the Vietnamese, the Israelis, and many others.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Although to call the BTR-152 “modular”
won’t cut it, different types of weapons were fitted into its spacious
passenger compartment. This converted the BTR-152 into a fighting vehicle that
could participate in mechanized combat (the 1967 Six-Day War) or vicious street
battles in the streets of <st1:city w:st="on">Budapest</st1:city> or <st1:place w:st="on"><st1:city w:st="on">Beirut</st1:city></st1:place>.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">According to open sources the BTR-152’s
first public outing was a <st1:place w:st="on">Red Square</st1:place> military
parade on November 7, 1951.</span></div>
<div class="MsoNormal">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-D26dxGByiSw/VnAmBUtj4iI/AAAAAAAAFDU/Be46plziesA/s1600/Soviet%2BBTR-152%2B11.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="384" src="https://4.bp.blogspot.com/-D26dxGByiSw/VnAmBUtj4iI/AAAAAAAAFDU/Be46plziesA/s640/Soviet%2BBTR-152%2B11.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span lang="EN-US">The photo above could </span>be the very first one of the BTR-152 in its original open top configuration. It was a moderately spacious
vehicle - those are five motorized infantrymen seated in three rows, totaling 15
diehard Commies - and was armed with a single machine gun.</td></tr>
</tbody></table>
<div align="center" class="MsoNormal" style="text-align: center;">
<br /></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1048" type="#_x0000_t75" style='width:130.5pt;height:62.25pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image044.jpg"
o:title="Soviet BTR-152 16"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-V7QfLjWWHfk/VnAmHoYRrbI/AAAAAAAAFDc/vj962sHu9kw/s1600/Soviet%2BBTR-152%2B16.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-V7QfLjWWHfk/VnAmHoYRrbI/AAAAAAAAFDc/vj962sHu9kw/s1600/Soviet%2BBTR-152%2B16.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"> Meanwhile, in East Germany, the BTR-152 sat nine Germans and their machine gunner. That’s 10 people and still a lot more than the mech infantry squads crammed into APCs today.</td></tr>
</tbody></table>
<div class="MsoNormal">
<span lang="EN-US">The original BTR-152’s sole armament was
the dependable 7.62x54mm Goryunov SG-43 mounted behind the enclosed cab.
Although a leftover from World War Two, it still uses a powerful round and has an awesome
rate of fire (500 rounds per minute), you couldn't really tell from the business end.</span></div>
<div class="MsoNormal">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-VNX-ST3C-Jw/VnAmZY7J5uI/AAAAAAAAFDk/mN8V028FKYQ/s1600/Soviet%2BSG-43%2BGoryunov%2Bmachine%2Bgun.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://1.bp.blogspot.com/-VNX-ST3C-Jw/VnAmZY7J5uI/AAAAAAAAFDk/mN8V028FKYQ/s1600/Soviet%2BSG-43%2BGoryunov%2Bmachine%2Bgun.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The Goryunov in action. Fun fact: The Chinese PLA actually converted it into a squad automatic weapon called the Type 67 by adding a pistol grip and a fixed wooden butt stock.</td></tr>
</tbody></table>
<div class="MsoNormal">
<span lang="EN-US">It didn’t take long before the BTR-152’s
role shifted from an APC to a self-propelled anti-aircraft gun. As previously
mentioned, the first iteration of this variant was the BTR-152A, whose main
armament was the 14.5mm ZTPU-2/ZPU-2. Basically a pair of the notorious KPV
anti-tank machine guns that would become the BTR-series’ perpetual main
armament.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The 14.5x114mm KPV is no laughing matter.
It’s still the world’s most powerful machine gun that can penetrate the armor
of most APCs and military vehicles in use today. The KPV’s 1,000 meter range
made it just as lethal against low-flying aircraft.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><!--[if gte vml 1]><v:shape id="_x0000_i1050"
type="#_x0000_t75" style='width:6in;height:230.25pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image048.jpg"
o:title="Soviet BTR-152 19"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-ZGFy8MsuXUU/VnAmzjGL5mI/AAAAAAAAFDs/tDHQxkAj90E/s1600/Soviet%2BBTR-152%2B19.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-ZGFy8MsuXUU/VnAmzjGL5mI/AAAAAAAAFDs/tDHQxkAj90E/s1600/Soviet%2BBTR-152%2B19.jpg" /></a></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Other sources suggest the BTR-152A also had
quad mounted 12.7x108mm DShK’s behind the Goryunov. Another variant, the
BTR-152D, was allegedly the one that mounted the ZPU-2’s. When Russian sources
are consulted this was revealed to be the BTR-152E. Confusing? Blame the
conflicting uncorrected “facts” of neglected open sources.</span></div>
<div class="MsoNormal">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-YJKEJHOewrQ/VnAm9LHTycI/AAAAAAAAFD0/pNi_9jGsZ5M/s1600/Soviet%2BBTR-152%2B06.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://4.bp.blogspot.com/-YJKEJHOewrQ/VnAm9LHTycI/AAAAAAAAFD0/pNi_9jGsZ5M/s640/Soviet%2BBTR-152%2B06.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><div class="MsoNormal">
<span lang="EN-US">Judging by the image above it appears the
BTR-152A/D/E was developed into a complete system. Take note of the P-12 mobile
radar array in the background. Did it serve to relay targeting information to
the BTR-152? Or was the BTR deployed as a mobile escort to protect the P-12? What are those levers stuck on the wheels?
(This was the external tire deflation system.)</span></div>
</td></tr>
</tbody></table>
<div class="MsoNormal">
<span lang="EN-US">The configuration of the BTR-152A/D/E is
also interesting. The ZPU-2 is fixed behind the cab and seats a gunner. The
remaining space at the rear of the vehicle is for the spotter…who stands gazing
at the sky with his binoculars.</span></div>
<div class="MsoNormal">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-DSOQ2xFKdm4/VnAnIskaoYI/AAAAAAAAFD8/44_oF70lngM/s1600/Soviet%2BBTR-152%2B01.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://3.bp.blogspot.com/-DSOQ2xFKdm4/VnAnIskaoYI/AAAAAAAAFD8/44_oF70lngM/s1600/Soviet%2BBTR-152%2B01.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Here’s
another grainy picture of the
BTR-152 A/D from behind. It appears the ZPU-2 was installed on a
retrofitted ring mount whose exact designation has been lost to history.</span></div>
</td></tr>
</tbody></table>
<div class="MsoNormal">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-dikPnnipf74/VnAncY1J23I/AAAAAAAAFEE/OqRQNbfu4Qo/s1600/Soviet%2BBTR-152%2B27.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://3.bp.blogspot.com/-dikPnnipf74/VnAncY1J23I/AAAAAAAAFEE/OqRQNbfu4Qo/s640/Soviet%2BBTR-152%2B27.jpg" width="422" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">It appears eight (yes, EIGHT) people can fit in a BTR-152 even with a 14.5mm ZPU-2 installed. Wow!</td></tr>
</tbody></table>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1054" type="#_x0000_t75" style='width:270pt;height:180pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image056.jpg"
o:title="Soviet BTR-152 08"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-LPI6htSlcRo/VnAn2HLuimI/AAAAAAAAFEM/aGePoHHAdsQ/s1600/Soviet%2BBTR-152%2B08.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="426" src="https://4.bp.blogspot.com/-LPI6htSlcRo/VnAn2HLuimI/AAAAAAAAFEM/aGePoHHAdsQ/s640/Soviet%2BBTR-152%2B08.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><br /></td></tr>
</tbody></table>
<div class="MsoNormal">
<span lang="EN-US">The photo above is of a BTR-152A/D during the invasion of Czechoslovakia.
Come to think of it, the superb elevation of the ZPU-2 made it quite useful in
suppressing hostiles taking pot shots from windows during urban combat. But a
well-aimed Molotov cocktail can still completely crisp the BTR-152’s exposed
interior.</span></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://4.bp.blogspot.com/-PtCydyZDB0M/VnAoHo66DzI/AAAAAAAAFEU/bFMCzafu8r8/s1600/Soviet%2BBTR-152%2BKPV-4.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="438" src="https://4.bp.blogspot.com/-PtCydyZDB0M/VnAoHo66DzI/AAAAAAAAFEU/bFMCzafu8r8/s640/Soviet%2BBTR-152%2BKPV-4.jpg" width="640" /></a></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The Soviets later developed an
anti-aircraft BTR-152 that could mount a ZPU-4 in a different setup. Given how
the armor of the BTR-152 enclosed the entire vehicle, the ZPU was reconfigured
to have two KPV’s above the cab and two KPV’s behind them whose elevation could
be raised. Peculiar but sensible. The same from another angle:</span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1056" type="#_x0000_t75" style='width:164.25pt;height:108.75pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image060.jpg"
o:title="Soviet BTR-152 KPV-4 02"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-syQgSIdYvbQ/VnAoNrUODYI/AAAAAAAAFEc/5xXw5SGmaC4/s1600/Soviet%2BBTR-152%2BKPV-4%2B02.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="422" src="https://1.bp.blogspot.com/-syQgSIdYvbQ/VnAoNrUODYI/AAAAAAAAFEc/5xXw5SGmaC4/s640/Soviet%2BBTR-152%2BKPV-4%2B02.jpg" width="640" /></a></div>
<span lang="EN-US">Since the BTR-152 was a vehicle of the
1950s whose production ceased soon after, the Soviets never developed the
platform to remain in step with advancing technology. It turns out it was the
client states and customers left with stocks of the BTR-152 who kept installing
larger and larger weapons.</span><br />
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">It was the storm and stress of the
Palestinian struggle against <st1:place w:st="on"><st1:country-region w:st="on">Israel</st1:country-region></st1:place>
that brought the BTR-152 to its lethal apogee. During the 1970s the PLO were
able to mount a ZU-23-2 anti-aircraft gun on a BTR-152. The result was
impressive in light of all the crappy Hilux technicals roving <st1:place w:st="on">Third
World</st1:place> war zones today.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><!--[if gte vml 1]><v:shape id="_x0000_i1057"
type="#_x0000_t75" style='width:6in;height:192.75pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image062.jpg"
o:title="Soviet BTR-152 17"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://4.bp.blogspot.com/-DCLxKh0c-tQ/VnAoWSkhbRI/AAAAAAAAFEk/fz6u2t7rk-g/s1600/Soviet%2BBTR-152%2B17.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="285" src="https://4.bp.blogspot.com/-DCLxKh0c-tQ/VnAoWSkhbRI/AAAAAAAAFEk/fz6u2t7rk-g/s640/Soviet%2BBTR-152%2B17.jpg" width="640" /></a></div>
<span lang="EN-US"><br /></span>
<span lang="EN-US"><br /></span>
<span lang="EN-US">Keep in mind the original BTR-152 weighed a
little over 8 tons. The ZU-23-2 added about 950 kilograms. Throw in a driver,
gunner, and loader and the BTR-152 is somewhat encumbered and rather top heavy. Ergo this
modification hampered the vehicle’s mobility.</span><br />
<span lang="EN-US"><br /></span>
<br />
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1058" type="#_x0000_t75" style='width:270pt;height:157.5pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image064.png"
o:title="Soviet BTR-152 07"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-4DLn3XRmhJA/VnAo9n4gB2I/AAAAAAAAFE0/lRlcW6iVHDU/s1600/Soviet%2BBTR-152%2B07.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="373" src="https://4.bp.blogspot.com/-4DLn3XRmhJA/VnAo9n4gB2I/AAAAAAAAFE0/lRlcW6iVHDU/s640/Soviet%2BBTR-152%2B07.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">A BTR-152mounted with a ZU-23 in action. Notice the helmets of the soldiers—they’re Israelis!</td></tr>
</tbody></table>
</span></div>
<div class="MsoNormal">
<span lang="EN-US">The Israelis began seizing abandoned
BTR-152’s as early as the 1956 Sinai War. No doubt aware of the vehicle’s
potential (look at all that room at the back!) they soon figured out a 20mm
Hispano Suiza .404 anti-aircraft gun could fit inside it. <st1:place w:st="on"><st1:country-region w:st="on">Israel</st1:country-region></st1:place>’s first genuine SPAAG was
born and served with distinction during the Six Day War and the Yom Kippur War.</span></div>
<div class="MsoNormal">
<br /></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1059" type="#_x0000_t75" style='width:342pt;height:190.5pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image066.png"
o:title="Soviet BTR-152 with Vulcan AAA"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-ZfVJ0r34qrc/VnAozCSHNII/AAAAAAAAFEs/aw4EvEC4H-M/s1600/Soviet%2BBTR-152%2Bwith%2BVulcan%2BAAA.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="222" src="https://4.bp.blogspot.com/-ZfVJ0r34qrc/VnAozCSHNII/AAAAAAAAFEs/aw4EvEC4H-M/s400/Soviet%2BBTR-152%2Bwith%2BVulcan%2BAAA.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><div class="MsoNormal">
<span lang="EN-US">This rare low-quality and date
unknown photo reveals a bizarre mating of a US-made M61 Vulcan anti-aircraft
gun with a BTR-152. Was it effective?</span></div>
<div class="MsoNormal">
<br /></div>
</td></tr>
</tbody></table>
<span lang="EN-US">The BTR-152’s peak was still a time where
anti-tank or anti-aircraft missiles and automatic grenade launchers were absent
from the battlefield. It would have been interesting to witness the additional
variants developed if it stayed in production.</span><br />
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<st1:place w:st="on"><st1:country-region w:st="on"><span lang="EN-US">Egypt</span></st1:country-region></st1:place><span lang="EN-US">
actually took the initiative in this regard. If imitation is the sincerest form
of flattery the BTR-152’s welded steel body was copied and mounted on a German
4x4 truck chassis and engine.</span></div>
<div class="MsoNormal">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-yx13WljhgNs/VnApIfv0TuI/AAAAAAAAFE8/c4ecGgmOSfY/s1600/Egyptian%2BWalid%2BAPC%2B4x4%2B02.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="458" src="https://3.bp.blogspot.com/-yx13WljhgNs/VnApIfv0TuI/AAAAAAAAFE8/c4ecGgmOSfY/s640/Egyptian%2BWalid%2BAPC%2B4x4%2B02.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span lang="EN-US">Spot the differences!</span></td></tr>
</tbody></table>
<div class="MsoNormal">
<span lang="EN-US">The vehicle was designated Walid and it
begat several variants, including a short-lived 122mm multi-rocket launcher
that saw extensive use in the Yom Kippur War. Several hundred Walid’s were
manufactured and select numbers were sold to <st1:country-region w:st="on">Iraq</st1:country-region>
and <st1:place w:st="on"><st1:country-region w:st="on">Sudan</st1:country-region></st1:place>
as well as a few other African countries. The Egyptian Army still maintains a
small fleet of its Walid APCs today.</span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1060" type="#_x0000_t75" style='width:189pt;height:135.75pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image068.jpg"
o:title="Egyptian Walid APC 4x4 02"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<h2>
<b><span lang="EN-US">PROTECTION<o:p></o:p></span></b></h2>
</div>
<div class="MsoNormal">
<span lang="EN-US">An armored vehicle’s absolute survival in
brutal combat is never a sure thing.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">When facing modern anti-tank weapons, RPGs,
and autocannons, the long and short of it is the BTR-152’s “armor” is exactly
that. Armor in quotation marks. Almost as if there weren’t any to speak of.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Consider that the BTR-152 was
conceptualized in the fires of the Great Patriotic War, prototyped in the late
1940s, and built in the 1950s. This meant it was an extremely simple design, even
crude, and the fineries that are taken for granted in today’s personnel
carriers were non-existent.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Based on available open source
specifications of the BTR-152’s armor, the protection levels were distributed
in a familiar pattern. The cab and engine compartment were best protected,
followed by the sides, and then almost nothing at the bottom. </span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1061" type="#_x0000_t75" style='width:324pt;height:215.25pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image070.jpg"
o:title="Soviet BTR-152 23"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://4.bp.blogspot.com/-9S2JV4r79xs/VnApWetdMoI/AAAAAAAAFFE/4yMm332_HHs/s1600/Soviet%2BBTR-152%2B23.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="425" src="https://4.bp.blogspot.com/-9S2JV4r79xs/VnApWetdMoI/AAAAAAAAFFE/4yMm332_HHs/s640/Soviet%2BBTR-152%2B23.jpg" width="640" /></a></div>
<br />
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><br /></span></div>
<div class="MsoNormal">
<span lang="EN-US">The annotated photo above of a BTR-152K
reveals its frontal armor around the cab was an impressive 15mm. This made it
impervious to sustained small arms fire.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The sides and rear were enclosed in welded
steel with a thickness of 9mm. A bit dicey, as NATO 7.62x51mm rounds, rifle grenades, and rockets
like the M72 LAW could’ve blown right through it.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The armor on the steel roof was little
better at 10mm. At least this could preserve any passengers from fragments and
flying shrapnel. A direct hit from rooftop RPG-7 would have turned the BTR-152K
into a fiery coffin.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The bottom, with its 300mm ground clearance,
had just 4mm. </span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Examining available photos of wrecked BTR-152’s
does reveal an interesting pattern. Few of these photos reveal any penetration
from small arms. It appears that shaped charges and explosions were the biggest
risks for BTR-152 crews.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Did somebody mention land mines?</span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1062" type="#_x0000_t75" style='width:163.5pt;height:121.5pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image072.jpg"
o:title="Soviet BTR-152 destroyed 01"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-jfZXiVtKEpU/VnApjEuVa8I/AAAAAAAAFFM/AuFTgUtuOQM/s1600/Soviet%2BBTR-152%2Bdestroyed%2B01.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="297" src="https://3.bp.blogspot.com/-jfZXiVtKEpU/VnApjEuVa8I/AAAAAAAAFFM/AuFTgUtuOQM/s400/Soviet%2BBTR-152%2Bdestroyed%2B01.jpg" width="400" /></a></div>
<span lang="EN-US">The above wonderfully illustrates the
BTR-152’s strengths and weaknesses. Knocked out by a land mine and ambushed by
Rhodesian/South African troops (those skimpy khaki shorts are a dead giveaway),
the passenger compartment is charred black and smoking. The tires have melted
and the escaping crew were probably gunned down as they burned alive.</span><br />
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">But the cab is 100% intact. Now imagine if
a BTR-152 bore the brunt of an IED, i.e. a booby-trapped 155mm shell. If fragments tore through the bottom and hit
the gas tanks situated behind the driver’s seat the resulting inferno would
incinerate everything inside.</span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1063" type="#_x0000_t75" style='width:57.75pt;height:81pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image074.jpg"
o:title="Soviet BTR-152 destroyed 04"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-sIe9Olq5tM4/VnAqEdGcKDI/AAAAAAAAFFU/zo11TzK0nM8/s1600/Soviet%2BBTR-152%2Bdestroyed%2B04.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://3.bp.blogspot.com/-sIe9Olq5tM4/VnAqEdGcKDI/AAAAAAAAFFU/zo11TzK0nM8/s640/Soviet%2BBTR-152%2Bdestroyed%2B04.jpg" width="452" /></a></div>
<span lang="EN-US">Like this unfortunate BTR-152 armed with a
single 14.5mm KPV. Notice how the armor is intact but the insides are charred. </span><br />
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Another glaring weakness of the BTR-152 was
its open top. Until the BTR-152K arrived in limited numbers, the open top was a
juicy target for all kinds of mischief. See this, circa Hungarian revolt:</span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1064" type="#_x0000_t75" style='width:297pt;height:197.25pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image076.jpg"
o:title="Soviet BTR-152 Hungarian Rising"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/--I90bxe2Myo/VnAqNGmX_BI/AAAAAAAAFFc/LUlWmpzmZ-Q/s1600/Soviet%2BBTR-152%2BHungarian%2BRising.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="425" src="https://2.bp.blogspot.com/--I90bxe2Myo/VnAqNGmX_BI/AAAAAAAAFFc/LUlWmpzmZ-Q/s640/Soviet%2BBTR-152%2BHungarian%2BRising.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span lang="EN-US">Take note of the different set of
tires it uses—these are indicative of the ZiS-151.</span></td></tr>
</tbody></table>
<br />
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1065" type="#_x0000_t75" style='width:185.25pt;height:123.75pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image078.jpg"
o:title="Soviet BTR-152 destroyed 02"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/--0B0aF5hUr8/VnAqi6f-tMI/AAAAAAAAFFk/yE27ztbINxU/s1600/Soviet%2BBTR-152%2Bdestroyed%2B02.jpeg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://3.bp.blogspot.com/--0B0aF5hUr8/VnAqi6f-tMI/AAAAAAAAFFk/yE27ztbINxU/s640/Soviet%2BBTR-152%2Bdestroyed%2B02.jpeg" width="640" /></a></div>
<span lang="EN-US"><br /></span>
<span lang="EN-US"><br /></span>
<span lang="EN-US">Throughout history people have
been mesmerized by wreckage of any sort. Anyway, the warped side armor and the
gaping hole suggest a shaped charge knocked out this BTR-152 and sent it
careening into a wall where it burned to oblivion.</span><span lang="EN-US"><br /></span><br />
<span lang="EN-US"><br /></span>
<br />
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-lO7VvuSgDmE/VnAqy4NJIdI/AAAAAAAAFFs/CkhnIUcxka0/s1600/Soviet%2BBTR-152%2Bdestroyed%2B03.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://3.bp.blogspot.com/-lO7VvuSgDmE/VnAqy4NJIdI/AAAAAAAAFFs/CkhnIUcxka0/s640/Soviet%2BBTR-152%2Bdestroyed%2B03.jpg" width="640" /></a></div>
<br />
<div class="MsoNormal">
<span lang="EN-US">Though relatively intact, the mangled BTR-152 above suggests its fuel tank was detonated. It set fire to the engine
and blew the separate panels that serve as a hood and the burning fuel pooling up underneath the truck then melted the tires.
The remarkable part is the rest of the vehicle is intact.</span><br />
<span lang="EN-US"><br /></span>
<span lang="EN-US"><br /></span></div>
<h3>
<b><span lang="EN-US"><span style="font-size: large;">MOBILITY</span></span></b></h3>
<div class="MsoNormal">
<span lang="EN-US"><br /></span>
<span lang="EN-US">The BTR-152 originally ran on the 110 hp
six cylinder ZiS-123 gasoline engine. This gave it a modest top speed of 65
km/h and a 650 km range.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">From 1956 onwards it ran on the 107 hp six
cylinder ZiL-137K in-line gasoline engine.</span></div>
<div class="MsoNormal">
<br /></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1067" type="#_x0000_t75" style='width:150pt;height:225pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image082.jpg"
o:title="Soviet BTR-152 engine compartment"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-mOLReULfraA/VnArZLdJ8MI/AAAAAAAAFF0/0F1gOCPJ4u0/s1600/Soviet%2BBTR-152%2Bengine%2Bcompartment.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://3.bp.blogspot.com/-mOLReULfraA/VnArZLdJ8MI/AAAAAAAAFF0/0F1gOCPJ4u0/s640/Soviet%2BBTR-152%2Bengine%2Bcompartment.jpg" width="424" /></a></div>
<br />
<div class="MsoNormal">
<span lang="EN-US">For lack of a credible photograph
let this suffice as a glimpse into a BTR-152V’s engine. Note the radio antennae
and the windshield wiper underneath the polycarbonate windscreen. Also note the thickness of the armour plating sheltering the engine and its associated supporting elements.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">It’s easy to dismiss the BTR-152 as a
primeval wheeled APC with questionable mobility on rough terrain. Like many
Soviet war machines the BTR-152 was also accused of being unreliable. </span>Hindsight proves the first criticism
irrelevant and since no vehicle can run perfectly in all conditions it’s worth
mentioning the BTR-152 managed to honorably soldier on like a Cossack's horse in the snow, in the
tundra, in the desert, and in the tropics during its 65-year career.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The second barb - unreliability - is a
perplexing one given how long the BTR-152 remained in distinguished service for more than half a century, starting in 1951
with the Soviet Red Army until the present with various militaries. Furthermore,
the Vietnamese army remains the BTR-152’s most eager user. They most certainly know it’s an
old vehicle and modern alternatives can be imported from their suppliers, i.e. <st1:country-region w:st="on">Russia</st1:country-region>, <st1:country-region w:st="on">Israel</st1:country-region>,
<st1:country-region w:st="on">China</st1:country-region>, and <st1:country-region w:st="on"><st1:place w:st="on">South Korea</st1:place></st1:country-region>,
yet they’ve managed to keep it running and even upgraded it with a diesel
engine as recently as 2012.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-MW67H3Gf_5c/VnAroMf_y5I/AAAAAAAAFF8/PdfMX5Y2NYg/s1600/Soviet%2BBTR-152%2Bengine%2Binspection.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://3.bp.blogspot.com/-MW67H3Gf_5c/VnAroMf_y5I/AAAAAAAAFF8/PdfMX5Y2NYg/s400/Soviet%2BBTR-152%2Bengine%2Binspection.jpg" width="400" /></a></div>
<div class="MsoNormal">
<span lang="EN-US">The model above is a Vietnamese BTR-152B—notice the
mechanical winch beneath the grille as well as the addition of wing mirrors.</span></div>
<div class="MsoNormal">
<br /></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1069" type="#_x0000_t75" style='width:252pt;height:189pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image085.jpg"
o:title="Soviet BTR-152 18 Afghanistan"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-ezbELrRrafw/VnArvF0vibI/AAAAAAAAFGE/J3ehPUXMS94/s1600/Soviet%2BBTR-152%2B18%2BAfghanistan.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-ezbELrRrafw/VnArvF0vibI/AAAAAAAAFGE/J3ehPUXMS94/s1600/Soviet%2BBTR-152%2B18%2BAfghanistan.jpg" /></a></div>
<span lang="EN-US">The BTR-152B above was photographed in <st1:country-region w:st="on"><st1:place w:st="on">Afghanistan</st1:place></st1:country-region>
where it functioned well despite freezing weather, thin air, abysmal roads, and
the persistent threat of land mines. Count the soldiers in the photo and this
reveals the BTR-152B also carried its full complement of 17. History sure
rhymes because NATO forces would later take their own armored trucks, the
heavier 15-ton MRAPs, and see these get bogged down in the Afghan highlands.</span><br />
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">But the BTR-152 did have its shortcomings
that manifested as early as 1953 and its designers spent years grappling with
these. For a Soviet APC weighing between 8 to 10 tons (depending on the
variant) it had low permeability when running through snow or sand.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The tires were also completely exposed,
thereby risking getting punctured by multiple gunshots. This compelled the
installation of a central tire inflation system. To further improve its
mobility in the snow a separate externally mounted tire deflation system was
devised.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-whiG6FcXv_M/VnAr8IFPIII/AAAAAAAAFGM/feX-T1LlL2Y/s1600/Soviet%2BBTR-152%2B10.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="402" src="https://2.bp.blogspot.com/-whiG6FcXv_M/VnAr8IFPIII/AAAAAAAAFGM/feX-T1LlL2Y/s640/Soviet%2BBTR-152%2B10.jpg" width="640" /></a></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The BTR-152 above is running in snow with
each of its ZiS tires wrapped in snow chains.</span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1071" type="#_x0000_t75" style='width:123pt;height:78.75pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image089.jpg"
o:title="Soviet BTR-152 24"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-w2nIMTeDjM8/VnAsC73uqsI/AAAAAAAAFGU/ZlGFlUCBkdA/s1600/Soviet%2BBTR-152%2B24.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="408" src="https://1.bp.blogspot.com/-w2nIMTeDjM8/VnAsC73uqsI/AAAAAAAAFGU/ZlGFlUCBkdA/s640/Soviet%2BBTR-152%2B24.jpg" width="640" /></a></div>
<span lang="EN-US">To improve its mobility in the
snow engineers installed a tire deflation system on the BTR-152. This is a rare
upgrade and isn’t seen on Middle Eastern or Asian BTR-152’s.</span><br />
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">But the BTR-152 did have a single glaring
weakness that its Soviet designers never completely overcame. Its 6x6 chassis
and the suspension and transmission that supported it wasn’t very capable running
over obstacles.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The BTR-152’s wheels, two at the front and
four at the back, used torsion bar suspension. But only the front had hydraulic
shock absorbers mated with leaf springs. The four wheels at the back had leaf
spring suspension too and no shock absorbers until 1957, a year after
production was moved to the ZiL factory.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">In the mid-1950s a test involving the
upgraded ZiL BTR-152V and two earlier ZiS BTR-152B’s exposed this glaring
weakness. The BTR-152V successfully crossed a 2.5 meter wide trench that was
1.5 meters deep. Its rivals, BTR-152B’s, struggled to accomplish the same.</span></div>
<div class="MsoNormal">
<span lang="EN-US"> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-3kB6puYyUlE/VnAsJXV4iTI/AAAAAAAAFGc/tc3hbItHxD4/s1600/Soviet%2BBTR-152%2B31.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-3kB6puYyUlE/VnAsJXV4iTI/AAAAAAAAFGc/tc3hbItHxD4/s1600/Soviet%2BBTR-152%2B31.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">A BTR-152V caught in a moment of weakness. If you can’t exactly stop it with bullets a wide enough ditch can ruin its day.</td></tr>
</tbody></table>
The original BTR-152’s turning radius of 12
to 14 meters was another problem for an APC that had to run on city
streets—imagine how it manages tight corners and alleys—and the best efforts by
ZiL engineers were able to reduce this by half.
</span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1072" type="#_x0000_t75" style='width:327pt;height:172.5pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image091.jpg"
o:title="Soviet BTR-152 31"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">When BTR-152 production ceased in 1962 the
consensus on the 6x6 chassis was clear. Its suspension system was inadequate
for the rigors of cross-country movement against obstacles and even less
effective when amphibious crossings are required.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">This led to the remaining BTR-152’s
“retirement” to rear echelon motor pools and security units once the BTR-60’s
long reign commenced. </span><br />
<span lang="EN-US"><br /></span>
<span lang="EN-US"><br /></span></div>
<h3>
<b><span lang="EN-US"><span style="font-size: large;">CURRENT
STATUS</span></span></b></h3>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">For a vehicle with questionable protection
levels and mobility issues the BTR-152 proved an indomitable war machine. Based
on archival footage and photographs it had a sterling combat record in the <st1:place w:st="on">Middle East</st1:place> where it fought in almost every Arab-Israeli
war from 1956 until the 1980s.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">The BTR-152 had a very prominent role in
the Lebanese Civil War (1975-1990) where it functioned as a poor man’s fighting
vehicle for the Palestinian Liberation Organization (PLO) and other factions. The
Rhodesian Bush War (1964-1979) was another theater where it saw extensive use
by Soviet-backed forces. </span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">At the same time the Soviets deployed the
BTR-152 and its brethren in <st1:country-region w:st="on"><st1:place w:st="on">Afghanistan</st1:place></st1:country-region>—a
country littered with the charred hulks of wrecked BTR-series APCs.</span></div>
<div class="MsoNormal">
<br /></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1073" type="#_x0000_t75" style='width:5in;height:190.5pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image092.jpg"
o:title="Soviet BTR-152 02"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-ZXB8nXE7Z_4/VnAsRUeVTuI/AAAAAAAAFGk/AbFCsbpR_Pw/s1600/Soviet%2BBTR-152%2B02.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://4.bp.blogspot.com/-ZXB8nXE7Z_4/VnAsRUeVTuI/AAAAAAAAFGk/AbFCsbpR_Pw/s1600/Soviet%2BBTR-152%2B02.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span lang="EN-US">Check out these Pashtun <i>mujahideen</i> posing in front of a wrecked
BTR-152. Capturing the quad-DshK should have been quite a windfall.</span></td></tr>
</tbody></table>
<span lang="EN-US">The civil wars in <st1:country-region w:st="on">Somalia</st1:country-region> and <st1:place w:st="on"><st1:country-region w:st="on">Yemen</st1:country-region></st1:place> during the 1990s also revived
it. In a strange twist the BTR-152 has resurfaced in the ongoing Syrian Civil
War (2011-?). The irony is quite painful because the present conflict involves
so many anti-tank weapons ranged against the aging second-generation Soviet-era
armor deployed by the Syrian Arab Army.</span><br />
<div class="MsoNormal">
<span lang="EN-US"><!--[if gte vml 1]><v:shape id="_x0000_i1074"
type="#_x0000_t75" style='width:6in;height:286.5pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image093.jpg"
o:title="Soviet BTR-152 22"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-w0aupL4sqZI/VnAsYFlsE4I/AAAAAAAAFGs/mgMPeO6L-LI/s1600/Soviet%2BBTR-152%2B22.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="265" src="https://3.bp.blogspot.com/-w0aupL4sqZI/VnAsYFlsE4I/AAAAAAAAFGs/mgMPeO6L-LI/s400/Soviet%2BBTR-152%2B22.jpg" width="400" /></a></div>
<br />
<div class="MsoNormal">
<span lang="EN-US">The image above portrays the BTR-152 in its
glory. Sure it can take abuse but don’t expect it to withstand direct hits
from shaped projectiles and calibers above 14.5mm. Notice the gaping hole
behind the driver’s seat? If it hit any lower it would’ve struck the fuel tank
and kaboom!</span></div>
<div class="MsoNormal">
<span lang="EN-US"><br /></span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-loJscnSaQWY/VnAshdakTaI/AAAAAAAAFGw/P4IxHvJdaDI/s1600/Soviet%2BBTR-152%2B14.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-loJscnSaQWY/VnAshdakTaI/AAAAAAAAFGw/P4IxHvJdaDI/s1600/Soviet%2BBTR-152%2B14.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span lang="EN-US">This is the state of most
BTR-152’s today. It appears old fighting vehicles never die. They just collect
rust and turn ugly. Notice the T-10M next to the ISU-122 at the back?</span></td></tr>
</tbody></table>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1075" type="#_x0000_t75" style='width:257.25pt;height:171.75pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image095.jpg"
o:title="Soviet BTR-152 14"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1076" type="#_x0000_t75" style='width:431.25pt;height:175.5pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image097.jpg"
o:title="Soviet BTR-152 26 upgraded"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div class="MsoNormal">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-mKTM2k2ClLk/VnAsuAXh2QI/AAAAAAAAFG8/RE4TK-IGafY/s1600/Soviet%2BBTR-152%2B26%2Bupgraded.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://3.bp.blogspot.com/-mKTM2k2ClLk/VnAsuAXh2QI/AAAAAAAAFG8/RE4TK-IGafY/s1600/Soviet%2BBTR-152%2B26%2Bupgraded.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span lang="EN-US">Rare footage of an up-gunned
BTR-152K fitted with a 14.5mm turret mounted on a custom roof. Take note of the
viewing slits installed above the firing ports.</span></td></tr>
</tbody></table>
<span lang="EN-US"><br /></span>
<span lang="EN-US">Except for grim war zones the BTR-152 is no
longer fielded by any national army even though its proliferation reached 40
countries across Europe, Asia, Africa, and <st1:place w:st="on">Latin America</st1:place>.
Even when its production ceased in 1962, the BTR-152 was still deployed by the
Red Army and the Warsaw Pact until the fall of the Berlin Wall. Based on open
sources by 1993 BTR-152’s could still be found in the Russian Army’s motor
pool.</span><br />
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">It survived the Cold War. Imagine that.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Yet its legacy lives on in the most
surprising way possible. In this day and age where roadside bombs loom large in
the minds of strategists and commanders armored trucks are once again in vogue.
There are a hundred different kinds of “tactical” and “mine-resistant” wheeled
vehicles peddled by at least a dozen countries today.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">They’re easy to produce—India’s state-owned
factories had no trouble developing an indigenous MRAP based on a common truck
chassis—and can take on different roles, from battle taxis to command vehicles
to ambulances. Just like the BTR-152. </span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">If one could imagine renewed production of
the BTR-152 with all of today’s bells and whistles the resulting platform could
be interesting. It won’t look pretty but it won’t be a pushover either. It’s
also perfectly suited for carrying big guns.</span><br />
<span lang="EN-US"><br /></span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span lang="EN-US"><!--[if gte vml 1]><v:shape
id="_x0000_i1077" type="#_x0000_t75" style='width:6in;height:258.75pt'>
<v:imagedata src="file:///C:\Users\User\AppData\Local\Temp\msohtmlclip1\01\clip_image098.jpg"
o:title="Russian BPM-97 6x6 01"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]--></span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-7KWPqabd_5k/VnAs1CRprWI/AAAAAAAAFHE/kvL3lhtW3is/s1600/Russian%2BBPM-97%2B6x6%2B01.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-7KWPqabd_5k/VnAs1CRprWI/AAAAAAAAFHE/kvL3lhtW3is/s1600/Russian%2BBPM-97%2B6x6%2B01.jpg" /></a></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<br />
<div style="text-align: left;">
<span lang="EN-US">But fear not. Because the spirit of the
BTR-152 lives on…in the BPM-97*!</span><br />
<span lang="EN-US"><br /></span></div>
</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<i><span lang="EN-US">*You
can bet its armor is "inadequate" too since destroyed “separatist” BPM’s have
been spotted in <st1:place w:st="on"><st1:country-region w:st="on">Ukraine</st1:country-region></st1:place>.<o:p></o:p></span></i></div>
<div class="MsoNormal">
<br />
<br />
<br />
<br /></div>
<h3>
<b><span lang="EN-US"><span style="font-size: large;">ABOUT
THE AUTHOR</span></span></b></h3>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><br /></span>
<span lang="EN-US">Miguel Miranda is a writer based in the <st1:place w:st="on"><st1:country-region w:st="on">Philippines</st1:country-region></st1:place>.
He harbors a smoldering passion for Cold War militaria that contrasts his
shameful background as a recovering ex-journalist.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">His other interests span writing for
magazines, massage therapy, heavy metal, collecting old paperback novels, and
admiring good industrial design.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">Miguel is the founder of 21<sup>st</sup>
Century Asian Arms Race (<a href="http://21stcenturyasianarmsrace.com/">21AAR</a>),
a website about modern weapon systems and their impact on ongoing wars and
crises across <st1:place w:st="on">Eurasia</st1:place>.</span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The website was founded because Miguel got the impression that China was buying and reverse-engineering far too many advanced weapons for everybody else's comfort. Now he realizes a handful of powerful countries have made perpetual war a matter of business-as-usual and this is why the 21st century is going to be really something else. So he writes about this phenomenon instead.</div>
<div class="MsoNormal">
<span lang="EN-US"> </span><br />
Some of 21AAR’s content also takes on a
historical and (gulp!) geopolitical perspective too, which means he’s got
variety down pat.</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US">In his spare time Miguel likes to be
affectionate toward living things. He’s currently working on an erotic spy
thriller.</span></div>
<div class="MsoNormal">
<br />
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<h2>
<b><span lang="EN-US">REFERENCES<o:p></o:p></span></b></h2>
</div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://en.academic.ru/dic.nsf/enwiki/463388">http://en.academic.ru/dic.nsf/enwiki/463388</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="https://en.wikipedia.org/wiki/ZiS-151">https://en.wikipedia.org/wiki/ZiS-151</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://bukvoed.livejournal.com/243418.html?thread=1893338">http://bukvoed.livejournal.com/243418.html?thread=1893338</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://gvtm.ru/btr-152">http://gvtm.ru/btr-152</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://www.globalsecurity.org/military/world/russia/btr-152.htm">http://www.globalsecurity.org/military/world/russia/btr-152.htm</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://www.kpopov.ru/travel/avtovaz_armor_12.htm">http://www.kpopov.ru/travel/avtovaz_armor_12.htm</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://kubinkamuseum.ru/index.php?option=com_content&view=article&id=72&Itemid=202">http://kubinkamuseum.ru/index.php?option=com_content&view=article&id=72&Itemid=202</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://www.nnre.ru/transport_i_aviacija/bronetransportery_i_bronemashiny_rossii/p70.php">http://www.nnre.ru/transport_i_aviacija/bronetransportery_i_bronemashiny_rossii/p70.php</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://fas.org/man/dod-101/sys/land/row/btr-152.htm">http://fas.org/man/dod-101/sys/land/row/btr-152.htm</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://www.razlib.ru/transport_i_aviacija/tehnika_i_vooruzhenie_1999_04/p2.php">http://www.razlib.ru/transport_i_aviacija/tehnika_i_vooruzhenie_1999_04/p2.php</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://www.rwd-mb3.de/ftechnik/pages/spw152k_san.htm">http://www.rwd-mb3.de/ftechnik/pages/spw152k_san.htm</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://tanki-su.narod.ru/btr-152.html">http://tanki-su.narod.ru/btr-152.html</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://www.thefullwiki.org/BTR-152">http://www.thefullwiki.org/BTR-152</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span lang="EN-US"><a href="http://www.tinlib.ru/tehnicheskie_nauki/bronetankovaja_tehnika_fotoalbom_chast_2/p18.php">http://www.tinlib.ru/tehnicheskie_nauki/bronetankovaja_tehnika_fotoalbom_chast_2/p18.php</a></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<h4 style="text-align: center;">
<b><span style="font-size: large;"><a href="http://thesovietarmourblog.blogspot.com/2014/10/the-soviet-armour-blog-this-blog-was.html" target="_blank">Check with the main page for the latest updates on new posts!</a></span></b></h4>
Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com14tag:blogger.com,1999:blog-3103574899092646031.post-63733752368110174572015-12-09T03:14:00.838-08:002023-09-03T06:34:29.550-07:00T-62 <div style="text-align: center;">
<div class="separator" style="clear: both; text-align: center;">
<a href="https://1.bp.blogspot.com/-Janw0X9mQzo/XOW3gZaAk0I/AAAAAAAAOAg/CXVSNalBIKYhOEdDVJ8vmADJgThsgGeEgCLcBGAs/s1600/driving.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="676" data-original-width="1024" height="422" src="https://1.bp.blogspot.com/-Janw0X9mQzo/XOW3gZaAk0I/AAAAAAAAOAg/CXVSNalBIKYhOEdDVJ8vmADJgThsgGeEgCLcBGAs/s640/driving.jpg" width="640" /></a></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
</div>
<br />
<br />
The T-62 medium tank, known under the factory product code of Object 166, formally entered service in the Soviet Army on the 12th of August 1961. The tank was designed by the OKB-520 design bureau headed by Leonid Kartsev and built at the No. 183 factory at Nizhny Tagil (now Uralvagonzavod). The tank was accepted into service as an interim countermeasure against the new American M60 tank. The M60 itself was not the tank most desired by the U.S Army as it was merely an interim solution to the slow progress of the T95 tank programme that went ahead on the basis of new information regarding the capabilities of the T-54, and it was perceived to be a dangerous new threat with overmatching capabilities by Soviet intelligence chiefly due to its 105mm M68 gun. Interestingly enough, the adoption of the 105mm L7 on Centurion tanks some years prior to the appearance of the M60 was not considered a significant development by the Soviet high command due to the small military presence of the British Army relative to the U.S Army and the Bundeswehr, which was supplied with American tanks. The priority was thus focused on assessing the American tank threat above all other potential adversaries.<div><br /></div><div>Although the T-62 was considered a new tank as it was taken into service, most of its parts were standardized with the T-55 and crew training for these two tanks were so similar that practically no transitional training was required for a T-55 crew member to transfer to a T-62. In this respect, the relationship between the T-62 and the T-55 was quite similar to the relationship between the M48 Patton and the M60(A1). </div><div><br /></div><div>To counter the M60, the main developmental effort was directed towards putting a new tank with the powerful 100mm T-12 smoothbore anti-tank gun in service. The 115mm U-5TS gun of the T-62 was created as a result of this effort, as it was able to to provide a level of armour-piercing performance matching the 100mm T-12 gun (in actuality, exceeding it) while avoiding the issue of excessive cartridge length. Were it not for the extreme length of its cartridges, the T-12 gun could have been fitted in a medium tank after modifications to the recoil system. </div><div>
<br />
The first prototypes were built in 1960 for factory testing, and in the following year, a batch of 25 tanks was manufactured for troop trials. Mass production began on the 1st of July 1962 and lasted until 1973, when it was replaced by the T-72. The T-62 began active service extremely swiftly; by 1963 it was already operational in the Group of Soviet Forces in Germany (GSFG) and it began supplanting the T-54 and T-55 in the Soviet Army. Production of the T-62 accelerated extremely rapidly, with 270 tanks produced in 1962 alone despite the late start in July as the first half of the year was occupied by extensive retooling efforts in preparation for mass production. This included the retooling of the automated welding processing line and the replacement of the rotary machines for turret ring production, among other things. </div><div><br /></div><div>According to data published in the book "<i><a href="https://ic.pics.livejournal.com/bmpd/38024980/5318604/5318604_original.jpg">Уральский вагоностроительный завод. 80 лет</a></i>", already by 1965, the total number of T-62 tanks delivered to the Soviet Army was 4,475 tanks, exceeding the cumulative total of 3,721 M60 and M60A1 tanks delivered to the U.S Army and the difference continued to grow over the years owing to the fact that the delivery rate of T-62 tanks averaged 1.5 thousand units per year whereas the annual production rate of M60A1 tanks (the M60 was discontinued in 1963) never exceeded 300 tanks until 1975. By 1973, the T-62 had almost entirely replaced the T-10M heavy tank and it had largely supplanted the T-54/55 in the GSFG, but even so, it was not considered a main battle tank. <div> </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-rl_nBuUcpCM/XzXfBvQf3OI/AAAAAAAARdo/8-HfQpDTQjgZx3z3Lo9fX1IHg97fkqzEwCLcBGAsYHQ/s1103/red%2Bsquare%2Bt-62%2Bparade.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="656" data-original-width="1103" src="https://1.bp.blogspot.com/-rl_nBuUcpCM/XzXfBvQf3OI/AAAAAAAARdo/8-HfQpDTQjgZx3z3Lo9fX1IHg97fkqzEwCLcBGAsYHQ/s640/red%2Bsquare%2Bt-62%2Bparade.jpg" width="640" /></a></div><div><br /></div><div>
<br />
However, main battle tank or not, available information shows that the T-62 not only managed to achieve parity with NATO main battle tanks like the M60A1, Chieftain and Leopard 1 but could even hold a minor advantage in several critical areas which enabled it to gain an advantage in kill probability over its adversaries.<div><br /></div><div>Bearing in mind that the T-62 was an unpretentious tank by design, the high velocity APFSDS ammunition fired from its smoothbore 115mm gun allowed it to achieve a level of anti-tank performance that outmatched the M60A1 despite the absence of an optical rangefinder and a ballistic computer as found on American tanks - in the 1977 edition of the field manual FM71-2, it is stated that the T-62 holds a 5-10% advantage of killing an M60A1 with the first shot at a range of between 600 to 1,400 meters with its APFSDS round (3BM4) compared to the M60A1's chance of killing a T-62 with its APDS round (M728) on the first shot. The M60A1 gained the upper hand at distances exceeding 2,000 meters, but this mattered little in a major European war given that the maximum expected tank combat distance did not exceed 1,500 meters in Central and Western Europe. In Germany, during the course of the Hunfeld II study that was carried out in the early 1970's in the Hünfeld region of Fulda, Germany, it was found that the average engagement range for M60A1 tanks was just 1,130 meters. At the infamous Fulda Gap itself, the maximum expected combat distance was just 800 meters.<br />
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In terms of mobility, the T-62 still held its own against the new generation of NATO main battle tanks partly because the M60A1 and Chieftain were both only slightly more mobile than its medium tank predecessors or not more mobile at all, while the Leopard 1 sacrificed a large amount of armour to achieve its mobility advantage. This sacrifice came at the cost of a higher probability of destruction - according to West German calculations derived from examinations of captured T-62 tanks delivered from Israel after the 1973 war, the Leopard 1 could achieve a slightly higher probability of a hit with the first shot against a T-62 (57% vs 52% at 1.5 km) but it was considered to be outgunned because the APFSDS round fired from the T-62 greatly overmatched the Leopard's armour and gave the T-62 the advantage of a higher probability of scoring a kill with the first shot. The Leopard 1 also lacked a gun stabilizer, so it could not leverage its superior mobility to increase its survivability by firing on the move. On the other hand, the T-62 had a good stabilizer system and it could fire on the move or quickly open fire on a short halt at ranges of 1.0 to 1.5 kilometers. <div><br /></div><div>All taken together, the T-62 was quite a formidable fighter on its own merits, not to mention that it was largely a necessity because it brought the necessary firepower to counter the M60A1 and Chieftain, but its attractiveness was further augmented by the fact that it was cheap (only 15% more expensive than a T-55), was highly cost-efficient, easy to produce in great quantities, simple to operate, and easy to train on due to its very high degree of commonality with the T-54 and T-55, whereas the NATO main battle tanks of the 1960's were expensive and complex - and in the case of the Chieftain, very troublesome to maintain - yet failed to bring a corresponding qualitative advantage over their Soviet counterpart.<br />
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A decade after it entered service, the T-62 was replaced by the T-64 and T-72 main battle tanks and it slowly began to be shifted to a secondary role. However, it was clear that the total replacement of the T-62 (and the T-54 series) would not be quick due to the immense size of the Soviet Army. As such, the T-62 continued to serve until the dissolution of the USSR. It remained a valuable wartime asset throughout the 1970's partly thanks to the solidity of its basic design, but it was enhanced by a number of low-level upgrades. The cost of such upgrades was low and they were performed during routine repairs at a predetermined point in the life cycle of each tank. Such upgrades included the refitting of new RMSh tracks and the addition of a KDT-1 laser rangefinder. </div><div><br /></div><div>With a total of around 14,000 tanks produced for the Soviet Army, it was only natural that the T-62 formed a major part of its arsenal even by the 1980's. However, by the end of the 1970's, a new generation of NATO tanks had appeared and a significant portion of the tank fleets of the major NATO military powers had undergone upgrades of some kind. Despite a constant escalation in the production rate of the newest main battle tanks such as the T-64B and T-72A, more than a quarter of the tanks in active service were still T-62s of various types. In order to fill the gap, a comprehensive modernization package developed at Nizhny Tagil was approved in 1981 and a programme was initiated to bring the T-62M and its sister, the T-55(A)M, into service. This upgrade focused on improving the armour protection and the fire control system to the standards of a baseline Soviet main battle tank from the early 1970's, equivalent to a basic T-64A or a T-72 "Ural", while improvements to the suspension and powertrain allowed the mobility characteristics to be remain positive. Firepower was improved thanks to new 115mm APFSDS ammunition and "Sheksna" gun-launched ATGMs, which a large portion of the modernized tanks could fire. Overall, these improvements made the T-62M a much more credible threat in the modern battlefield of the time. A large number of variants were derived from the basic "M" model of the modernization package.</div><div>
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The tanks that were modernized to the "M" standard officially entered service in 1983. According to the scope of the modernization programme, a total of 2,985 T-55AM and T-62M tanks would be upgraded from 1981 to 1985. Of that number, there would be 2,200 upgraded T-55 tanks and 785 upgraded T-62 tanks. The first ten tanks upgraded to the T-62M standard were delivered in 1981, and in 1982, forty tanks were delivered. In 1983, the model was officially accepted into service and fifty tanks were delivered in the same year. In 1984, the number of deliveries doubled to a hundred tanks, and in 1985, the full preparation of the necessary facilities and equipment enabled a whopping six hundred tanks to be delivered, thus fulfilling the objective of the programme. The production of T-72 tanks also peaked in 1985, coinciding with the entry of the T-72B into the service of the Soviet Army. All together, the tank fleet of the front line forces of the Soviet Army was successfully modernized. </div><div><br /></div><div>Moreover, the number of tanks that were upgraded along the lines of the T-62M were actually much higher as a result of the war in Afghanistan. The relatively large quantity of basic T-54/55 and T-62 tanks present in the theater of operations found themselves vulnerable to handheld anti-tank weapons elements such as captured RPG-7s, so some troops took the additional composite armour from the T-62M modernization package and fitted them to their own tanks at local depots without incorporating the other components of the package.<br />
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Slat armour screens - which were not a part of the original T-62M modernization package - also made their debut in Afghanistan. Such screens were installed at local bases and were highly valued because of the proliferation of handheld grenade launchers among Mujahideen fighters.<br />
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The details of such tanks will be explored later in this article.<br />
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Today, the T-62 is perhaps the least remembered among large number of tanks deployed by the Soviet Union during the Cold War. Its predecessor, the T-54/55, is known for being the so-called "Kalashnikov of tanks", having seen action in virtually every major military conflict on the planet during the past half century. Its successor, the T-72, has a similar level of fame for having participated in almost as many conflicts and in being the most mass-produced main battle tank. The T-62, on the other hand, lies in an indeterminate gray area. It is usually sidelined as an oddity, sometimes accused of being a failure, and sometimes (bizarrely) criticized for having a smoothbore gun. In the West, the T-62 is best remembered by those who served in NATO armies in the 1973-1980 time frame, especially those stationed in West Germany. Publicly available TRADOC documents and training films show that the U.S Army emphasized the T-62 as a foil to their own M60A1, which was apt considering that that was the political motivation behind the creation of the T-62. When more information on the T-64 and T-72 became available in the early to mid 1980's, all attention was shifted towards these two models and lesson plans focused on training soldiers to defeat an enemy tank that had composite armour.<br />
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Tactically speaking, there was practically no difference between it and its predecessor the T-55 in the mobility and armour protection departments, and the T-62 also shared most of its internal equipment with the T-55, thus simplifying both production and logistics to a certain extent. Even many of the newer devices were functionally similar, making the transition from a T-54 or T-55 to the T-62 wonderfully seamless for the crew. In fact, it is stated in a 1981 Soviet essay titled "<a href="http://btvt.info/5library/vbtt_1_1981_t_54_62.htm"><i>Из Опыта Совершенствования Основных Танков В Ходе Серийного Производства</i></a>" that 65% of the parts and assemblies in the T-62 were standardized with the T-55 tank. Most interestingly, the transmission, chassis, engine assembly, viewing devices and communication systems were completely interchangeable between the two contemporary tanks. Operationally, this made it extremely simple to supply spare parts and carry out repairs in the field. The non-interchangeable components such as the turret and hull are irrelevant as these items would never require a replacement. Rather, if a tank were knocked out by having its armour breached, it is much more likely to be salvaged for spare parts to support other tanks rather than be repaired, as that is much more expedient in actual wartime conditions.<br />
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That said, the high degree of commonality was not entirely positive, because this meant that the T-62 was only an evolutionary improvement that still remained at the same technological level as its predecessors. This affected its export success as clients were not too keen on adopting a new tank that only surpassed the T-54 in terms of firepower without a clear advantage in armour protection and no difference in mobility. It was generally considered to be no more than a stopgap solution until a new and radically superior tank arrived on the scene, but despite this, the T-62 was also one of the most powerful medium tanks fielded by the Soviet Army, the other being the T-64 (Object 432) that had a D-68 gun that fired the same ammunition as the U-5TS but in a two-piece form. The T-62 was also one of the last medium tanks fielded by the Soviet Army, as this class of tank was later replaced by the next generation of tanks known as the main battle tank. Although the replacement of medium tanks with a bona fide main battle tank did not occur until the T-64A entered service in 1967, the rate of progress in the advancement of tank technology in the USSR was still quite reasonable if compared to the state of affairs in the United States where total stagnation could be found with the M60A1 (itself an evolutionary step with only a marginally higher combat effectiveness than its predecessor the M48 owing to the failure of the siliceous core composite armour project) being the de facto main battle tank for two decades until the M1 Abrams supplanted it in the early 1980's.<br />
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Being a mere evolutionary stepping stone, we can observe the way Soviet school of thought on mechanized warfare evolved with it. In the early 60's, tank riding infantry was still considered a core part of mechanized warfare. The armoured APC had arrived on the scene in the form of the wheeled BTR-152 and tracked BTR-50, but infantry were sometimes obliged to move and fight as one with a tank as they could effectively provide protection from enemy anti-tank teams equipped with grenade launchers, and so to that end, the T-62 had handrails over the circumference of the turret for tank riders to hold on to. When the BMP-1 was introduced in 1966, it drove a major revision of contemporary tank tactics, and the shift in paradigm can be very well seen in the T-62's successors. The T-64A did not have any handrails, nor did the T-72, and the T-62M introduced in the 80's abolished them too.<br />
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The changes to the T-62 dutifully followed international trends as well, most notably the global shift to jet power in the aviation industry. Too fast to be harmed by machine gun fire, the ground attack jet rendered the normally obligatory 12.7mm anti-aircraft machine gun obsolete. During the late 1950's and early 1960's, anti-aircraft machine guns were thus omitted from medium tanks but remained on heavy tanks like the T-10M, partly because the KPVT on the T-10M offered more firepower than the smaller caliber DShKM on medium tanks. Even the usefulness of a 12.7mm machine gun on ground targets was not persuasive enough to justify the retention of anti-aircraft machine guns to Soviet specialists at the GBTU (Main Directorate of Armoured Forces). The T-55, T-55A and T-62 were all affected by this new policy. The heavy use of helicopters for fire support and landing missions during the American war in Vietnam created a need for tanks to be armed with a large caliber anti-aircraft machine gun, and this was further emphasized by the appearance of dedicated attack helicopters or gunships like the AH-1 "Huey Cobra". The first T-62 tanks armed with a DShKM in an anti-aircraft mount appeared in 1969, and this modification became standard for new-production tanks beginning in May 1970. Older tanks were also retrofitted at the factory when they were brought in for their scheduled overhauls.<br />
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The first pre-production models of the T-62 appeared in 1961. In the Soviet Union, the T-62 was mass-produced from 1962 to 1975, making it the direct contemporary of NATO tanks like the M60A1, Leopard 1 and Chieftain which appeared in 1962, 1965 and 1966 respectively. After 1975, all "new" T-62s are actually simply upgraded, modified, or otherwise overhauled versions from the original production run. By then, production at the No. 183 factory had irreversibly shifted to T-72 production.<br />
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Like the M60A1, Leopard 1 and Chieftain, the T-62 was a completely different tank than its predecessor, but unlike these three foreign tanks, it did not represent a major change in mobility or protection. Technically speaking, the only difference was in its firepower. Nevertheless, the inherently good tactical-technical characteristics of the basic T-54 were so good and the original design was so solid that the T-62 could still be considered an equal among these main battle tanks.<br />
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<h3>
Table of Contents</h3>
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<ol>
<li><a href="#erg">Ergonomics</a></li><li>Ventilation</li>
<li><a href="#comstat">Commander's Station</a></li>
<li><a href="#tkn-2">TKN-2 "Karmin"</a></li>
<li><a href="#tkn-3">TKN-3 "Kristal"</a></li>
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<li><a href="#gunstat">Gunner's Station</a></li>
<li><a href="#tsh">TSh2B-41, TSh2B-41U</a></li>
<li><a href="#tshs">TShS-41U</a></li>
<li><a href="#tshsd">TShSD-41U</a></li>
<li><a href="#tpn">TPN1-41-11</a></li>
<li><a href="#volna">Volna Fire Control System</a></li>
<li><a href="#tshsm">TShSM-41U</a></li>
<li><a href="#1k13">1K13-2 Sight</a></li>
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<li><a href="#loaderstat">Loader's Station</a></li>
<li><a href="#ammo">Ammunition Stowage</a></li>
<li><a href="#rof">Rate of Fire</a></li>
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<li><a href="#cannon">U-5TS (2A20) Gun</a></li>
<li><a href="#stabs">Stabilizer</a></li>
<li><a href="#autoejector">Auto-ejector</a></li>
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<li><a href="#ammu">Ammunition</a></li>
<li><a href="#hef">HE-Frag</a></li>
<li><a href="#ap">APFSDS</a></li>
<li><a href="#heat">HEAT</a></li>
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<li><a href="#second">Secondary Weapon</a></li>
<li><a href="#tertiary">Tertiary Weapon</a></li>
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<li><a href="#prot">Protection</a></li>
<li><a href="#sideskirts">Side Skirts</a></li>
<li><a href="#yom">Yom Kippur</a></li>
<li><a href="#brow">Ilyich's Eyebrows</a></li>
<li><a href="#belly">Belly Armour</a></li>
<li><a href="#slat">Slat Armour</a></li>
<li><a href="#k1">Kontakt-1</a></li>
<li><a href="#mineclearance">Mine Clearance</a></li>
<li><a href="#nbc">NBC Protection (PAZ)</a></li>
<li><a href="#smoke">Smokescreen</a></li>
<li><a href="#fire">Fire Fighting</a></li>
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<li><a href="#driver">Driver-Mechanic's Station</a></li>
<li><a href="#mobility">Mobility</a></li>
<li><a href="#suspension">Suspension</a></li>
<li><a href="#deck">Engine Deck</a></li>
<li><a href="#road">Road Endurance</a></li>
<li><a href="#water">Water Obstacles</a></li>
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<h3>
<span style="font-size: large;">ERGONOMICS</span></h3>
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The topic of differentiating the T-62 from the T-54/55 can be addressed quite easily as there were a myriad of differences that distinguished the T-62 from the T-54. The enlarged turret, now completely round, is the most major external difference between the two tanks, but the hull was also changed. Internally, the hull has a width of 1,850mm as shown in the drawing below, taken from the book "<i>Боевые Машины Уралвагонзавода: Танки 1960-х</i>" by Uralvagonzavod corporation. This is wider than the AMX-30 (1,780mm) but narrower than the Leopard 1 (1,980mm), both tanks of comparable silhouette size. The length of the fighting compartment increased by 386mm while the length of the engine compartment increased by 84mm. In total, the length of the hull increased by 470mm. The width across the hull extensions for the turret ring is not given in the book, but would be 2,760mm according to a technical description.<br />
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<div><br /></div><div><br /></div>The height of the hull was slightly increased from the T-55 as well. At the center of the hull where the fighting compartment is located, the internal height increased from 937mm to 1006mm. At the front of the hull, the internal height increased from 927mm to 939mm. At the fighting compartment, the useful internal height is just over 950mm due to the need for floor panels atop the torsion bars of the suspension. <br />
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The widened turret ring did not directly affect the width of the hull, but the length of the fighting compartment had to be increased by a small amount (386mm) in order to accommodate its increased diameter. The arrangement of the roadwheels and the torsion bar suspension was also revised in accordance with the redistribution of weight towards the nose of the hull, thus removing the distinctive gap between the first and second roadwheels on the T-54 and T-55 that is often used as an identification feature. Instead, the T-62 suspension has its three front roadwheels densely packed together, with larger gaps between the last two roadwheels. The combat weight of the tank was increased by one ton to 37 tons, but of this weight, less than 400 kg can be attributed to the weight difference between the 115mm U-5TS and the D10-T2S. The remainder is from the new hull and turret. Contrary to expectations, the T-62 was actually slightly lighter than the T-55A, which weighed 37.5 tons combat loaded.<br />
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However, that was not the entire extent of the changes made to the hull and chassis. Compared to the T-54/55, the maximum height of the hull was increased from 977mm to 1,036mm and the maximum internal height of the fighting compartment (from the rotating turret floor to the turret ceiling) went up very slightly from 1,600mm to 1,610mm. Due to the mildly sloping roof of the hull, the actual internal height differs at varying points across its length. Moreover, the suspension of the T-62 was fundamentally identical to the T-54 suspension, but it incorporated small improvements such as an increased ground clearance of 471.5mm instead of 440mm and it provided a somewhat smoother ride. Externally, at first glance, it seems that the T-62 is both wider and taller the T-54/55 by a few inches but surprisingly, the height of the T-62 up to its turret roof almost did not change at all compared to the T-54 - it increased only negligibly from 2,235mm to 2,248mm. Like the T-54, the total height of the tank up to the top of the commander's cupola is 2,400mm.<br />
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The internal volume of a T-62 was larger compared to a T-54 or T-55 chiefly due to the need to accommodate the bigger gun, but due to the increase in the turret ring diameter and the rearrangement of the internal equipment in the tank, it was possible to allocate more room to the crew. Although the T-62 superficially resembles the T-54 from many angles, the dome-shaped turret was larger and noticeably more spacious, even with the larger cannon. This can be largely attributed to the 2,245mm diameter turret ring, which was not only a big improvement over the 1,825mm ring of the T-54, but it was even quite cavernous compared to foreign tanks. The photo below, provided courtesy of Chris "Toadman" Hughes, shows a stripped-out T-62 hull.<div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9dQGviB8JD4/X0H87sNtfNI/AAAAAAAARfw/XrqQYj9Hj1EkqfxWcDANmxgM9F8duKBVgCLcBGAsYHQ/s2048/118191521_3325431290825546_126672690296737731_o.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1360" data-original-width="2048" src="https://1.bp.blogspot.com/-9dQGviB8JD4/X0H87sNtfNI/AAAAAAAARfw/XrqQYj9Hj1EkqfxWcDANmxgM9F8duKBVgCLcBGAsYHQ/s640/118191521_3325431290825546_126672690296737731_o.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The turret ring of the T-62 was much wider than the one on the Leopard 1 (1,980mm) and still somewhat wider than that of the M48 and M60 which had the widest turret ring (2,160mm) among all Western tanks in service at the time, later shared by the Chieftain. This was only partially offset by the larger cannon breech housing of the U-5TS gun compared to the 90mm medium velocity guns of most M48 models, but when measured across the recoil guards, the U-5TS was actually narrower than the 20 pdr. and the L7. </div><div><br /></div><div>Technically, the immense diameter of the T-62 turret ring was far in excess of the necessary size to handle the recoil of the 115mm gun. For example, the T-10M heavy tank which had a considerably more powerful 122mm gun could manage with a smaller turret ring of 2,160mm and even the later main battle tanks such as the T-64A and T-72 had a smaller 1,934mm turret ring despite having an even more powerful 125mm gun, thanks to the use of a two-man turret. While certainly beneficial in terms of reducing the intensity of stresses induced by the moment of force from the recoil of the gun, the large size of the T-62 turret ring was primarily designed for ergonomic purposes. It was a carryover from the earlier Object 140 medium tank project which featured the 100mm D-54TS gun, as the large working space granted by the large turret ring was necessary to allow the long and unwieldy 100mm cartridges to be handled by the loader, according to a description given by Chief Designer Leonid Kartsev in his memoirs. The turret ring diameter was left unchanged after the 115mm gun was created and fitted, leaving the tank with a surplus of space.</div><div><br /></div><div>The large turret ring provided some additional working space for the crew along the axis of the hull, though this was still limited by the ammunition racks placed at the front and back of the hull. Because of this, the effective increase in fighting compartment length was less than the difference in turret ring diameter between the T-62 and the T-54/55 (420mm). Rather, it merely corresponded to the increase in the hull length of 386mm. This can be seen in the photo below, taken from a West German report on a captured T-62 tank delivered by Israel. Additionally, it is important to note that it was not possible for the increased turret ring diameter to translate directly into an increase in seating space between the commander and gunner, because in virtually all turreted tanks, the need for the turret to rotate in a full circle means that the maximum seating space is governed by the clearance provided in the hull. This is not only evident from the hull width being smaller than the turret ring diameter, but it can also be seen in the fact that both the front and rear hull ammunition racks intrude into the turret ring perimeter. As such, the commander and gunner seats in a T-62 turret only gained a modest amount of space apart from each other, not as large as the turret ring alone suggests. The added width directly provided by the turret ring only begins at hip level for a standing crew member, considering that useful internal height of the hull at the fighting compartment is just over 950mm. </div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-pa5iRRAZ5Hc/XxliGl9e7GI/AAAAAAAART4/3NCwiETZKvsUxz-ti7Yf_-cR0MkLBDeawCLcBGAsYHQ/s1500/hull.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1000" data-original-width="1500" height="426" src="https://1.bp.blogspot.com/-pa5iRRAZ5Hc/XxliGl9e7GI/AAAAAAAART4/3NCwiETZKvsUxz-ti7Yf_-cR0MkLBDeawCLcBGAsYHQ/w640-h426/hull.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The wide turret ring granted the possibility of upgunning the T-62 without requiring serious turret modifications and without bringing repercussions to the working conditions of the crew, unlike the T-54 which was unsuitable for a gun larger than the D10T. In fact, this possibility was demonstrated by the Object 167 experimental tank which was built using the Object 166 turret and featured a 125mm D-81T gun complete with an assisted (semi-automatic) loading system. </div><div><br /></div><div>In terms of shape, the turret of the T-62 dispensed with the egg-shaped curvature of the T-54 turret in favour of an ostensibly simpler yet more sophisticated hemispherical turret. This contributed to a modest increase in the amount of habitable room inside the turret, mainly for the loader. The difference in the turret shapes can be seen in the two drawings below, with the T-62 on the left and the T-54 on the right.<br />
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<div><br /></div><div><br /></div>Interestingly enough, the T-62 turret is among the few conventional tank turret designs with its gun bore axis aligned with its centerline while having all crew members seated within the turret ring perimeter, giving both halves of the turret a symmetrical amount of space. Due to its enormous width, there was no need to have the gun installed with an offset toward the loader's station to free up more room for the gunner, commander and their equipment. Virtually all other turret designs with this layout solved the issue of insufficient space for the commander and gunner by providing the commander with a protruding cupola and seating him above the level of the turret ring, rather than within it. Other solutions include the omission of a third crew member, or the relocation of the commander from a tandem seating space with the gunner to an isolated seat behind the main gun. In general, alignment of the gun bore axis to the centerline of the turret is beneficial to the recoil reaction dynamics of the weapon system, as the recoil axis is aligned to the center of rotation of the turret. Thus, no excess torque is generated during the firing of a shot to turn the turret. This reduces the stress on the turret traverse mechanism and marginally reduces the total horizontal error in the point of aim.<br />
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One factor that partially counterbalances the overwhelmingly larger size of the T-62's turret ring compared to the T-54 or T-55 is the design of the turret ring itself. On the T-62, the walls of the turret rest on top of the ball bearing race ring of the turret ring in the same way as the turret of the Centurion tank whereas on the T-54/55, the walls of the turret are in front of the turret ring. The implications of this design decision on the protection level of the turret will be explored later in the "Protection" section of this article, but for now, the impact on the actual space available inside the turret is a more interesting topic to examine.<br />
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Because of the difference in the turret ring design, the T-54/55 turret has a relatively deep shelf between the turret ring and the wall of the turret along the rear half of its circumference. This creates additional space for internal equipment such as the radio transceiver and its power supply unit, the communications control boxes of both the commander and gunner, and so on. The T-62 turret has a much more shallow shelf that is only deep enough for smaller pieces of equipment like the communications control box. The radio transceiver had to be installed next to the gunner's seat, making the gunner's station narrower than the turret ring diameter implies, and a new turret traverse lock mechanism that protruded inwards of the turret ring was used. However, the overwhelmingly larger turret ring diameter of the T-62 still provides a net positive to the amount of crew space available.<br />
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Having a larger turret ring than the M48 and M60 did not mean that the T-62 was comparatively more spacious, as the hulls of the two aforementioned tanks were still wider. The M48 and M60 both had turret baskets which were mounted to the turret ring, thus giving a direct correlation between turret ring diameter and crew compartment diameter. For both the <a href="http://i.imgur.com/IoyYXtV.jpg">Leopard 1</a> and <a href="https://forum.warthunder.com/uploads/monthly_2016_08/24CutawayTank2.jpg.a317e253db6331b7bf6721d2954a260a.jpg">M48</a> or M60, the turret basket mount occupies some space and reduces the diameter of the crew compartment by a few centimeters. It would be safe to assume that the diameter of the crew compartment is approximately 1,900mm for the Leopard 1 and approximately 2,040mm for the M48 and M60 (due to hull width constraints). On the other hand, the T-62 lacks a turret basket so the width of the crew compartment is determined entirely by the internal width of the hull, which is 1,850mm. This is almost the same as a Leopard 1 but significantly less than the M48 and M60. On the other hand, the exceptionally large turret ring and correspondingly wide turret grants more room above the waistline. The length of the crew compartment is also larger, but even so, the commander and gunner in the T-62 are still seated rather closely, albeit much further apart than in a T-54 or T-55. This can be seen not only in the physical gap between the seats, but also in the position of the commander's footrest; in a T-54 or T-55, the commander's footrest was beneath the gunner's seat cushion, not behind it. The main improvement is seen in the loader's station, who also benefited from the relocation of several pieces of equipment. The seating arrangement in the T-62 turret is shown in the drawing below.<br />
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<div><br /></div><div><br /></div><div>Although the gain in space between the commander and gunner compared to a T-54 or T-55 was fundamentally constrained by the hull width, the greatly increased diameter of the turret ring still made a large difference as it permitted the commander to sit with his legs straight forward when his feet were placed on the footrest, and no longer straddling the gunner's back. The gunner could use the commander's knees as a backrest or choose to use his leather backrest which would be stretched from the recoil guard on the gunner's right and hooked to the turret ring on his left. The details of the gunner's seating station will be discussed at a later point. The seating situation can be seen in the image below.</div><div><br /></div><div><br /></div><div style="text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-aYGuODuMLjo/X1V9PoAqirI/AAAAAAAARjg/HXnv0JE8KzsO6-BZzEN1SdzNcGqqSM-6QCLcBGAsYHQ/s910/t-62m%2Binterior%2Bgunner%2Band%2Bcommander.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="609" data-original-width="910" height="320" src="https://1.bp.blogspot.com/-aYGuODuMLjo/X1V9PoAqirI/AAAAAAAARjg/HXnv0JE8KzsO6-BZzEN1SdzNcGqqSM-6QCLcBGAsYHQ/w400-h268/t-62m%2Binterior%2Bgunner%2Band%2Bcommander.png" width="477" /></a></div></div></div><div><br /></div><div><br /></div><div>In this aspect, the T-62 is on par with the Leopard 1, which is far from surprising given that they share almost the same hull width. The photo on the left below shows the interior of a Leopard 1, demonstrating the close similarity in working space in both tanks with the commander's recoil guards removed in both images. Even the Chieftain, shown on the right below, does not provide significantly more space between the gunner and commander despite the large size of the tank.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-f-h8JS0-ucY/X1V8C1hWrII/AAAAAAAARjY/UDNo-GodA1wDl6_7NLOTQAU7ez_t0SJTACLcBGAsYHQ/s761/leopard%2B1%2Binterior%2Bcommander%2Band%2Bgunner.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="761" data-original-width="735" height="320" src="https://1.bp.blogspot.com/-f-h8JS0-ucY/X1V8C1hWrII/AAAAAAAARjY/UDNo-GodA1wDl6_7NLOTQAU7ez_t0SJTACLcBGAsYHQ/w309-h320/leopard%2B1%2Binterior%2Bcommander%2Band%2Bgunner.png" width="309" /></a><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xuaOrxjmtVY/YA0dfPWuxII/AAAAAAAASmM/EDqmNLS75j8D8wdA0gBRyY22h2am0PvcACLcBGAsYHQ/s2048/chieftain%2Bcommander%2Band%2Bgunner.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1214" data-original-width="2048" height="238" src="https://1.bp.blogspot.com/-xuaOrxjmtVY/YA0dfPWuxII/AAAAAAAASmM/EDqmNLS75j8D8wdA0gBRyY22h2am0PvcACLcBGAsYHQ/w400-h238/chieftain%2Bcommander%2Band%2Bgunner.png" width="400" /></a></div><br /></div><br /><div>For comparison, the gunner in a T-54 had to have his back straddled by the commander when leaning into his backrest or sit in a slouching posture, which eventually leads to back aches if continued over a prolonged period. The alternative of having the commander place his knees around the gunner's back is also not ideal, because of the lack of space to move freely. In actual operational terms, this has tangible downsides, such as restricting movement when both crewmen are wearing winter clothing, or more seriously, hindering the commander and gunner while they are donning NBC protection equipment during a sudden chemical attack (which cannot be handled by the anti-nuclear protection system). The latter was not a consideration in legacy tank design concepts during WWII, which was inherited by the T-54. In this sense, the additional space provided in the T-62 was not merely a luxury, but had real tactical merits.</div><div><br /></div><div><br /></div><div><div style="text-align: center;"><a href="https://2.bp.blogspot.com/-jKyXEG9b4Go/W_P7TUsD0aI/AAAAAAAAMfc/ZdTtZL2pEnocqJPE4rkZIoQHU4uT1ctYwCLcBGAs/s1600/obj%2B167%2Bgunner%2Band%2Bcommander.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="335" data-original-width="417" height="321" src="https://2.bp.blogspot.com/-jKyXEG9b4Go/W_P7TUsD0aI/AAAAAAAAMfc/ZdTtZL2pEnocqJPE4rkZIoQHU4uT1ctYwCLcBGAs/s400/obj%2B167%2Bgunner%2Band%2Bcommander.png" width="400" /></a></div><div><br /></div><br />
The total internal volume of the T-54/55 is 11.4 cubic meters whereas the total internal volume of a T-62 is 12.5 cubic meters. Of that, the volume of the crew compartment is 8.05 cubic meters and 9.23 cubic meters for the T-54/55 and the T-62 respectively. After taking the internal equipment into consideration, the T-62 is the roomier of the two models by a small margin. In the third edition of the “<i>Отечественные Бронированные Машины 1945–1965 ГГ.</i>” series of articles authored by M.V Pavlov and I.V Pavlov, published in the July 2008 edition of the “<i>Техника и вооружение</i>” magazine, it is stated that the internal volume of the T-62 is 11.95 cubic meters, with 9.75 cubic meters from the hull and 2.2 cubic meters from the turret. For comparison, it is also stated that the T-55 has an internal volume of 11.1 cubic meters with 8.6 cubic meters from the hull and 2.5 cubic meters from the turret.</div><div><br /></div><div><br /></div><div>The engine compartment of the T-62 is also slightly larger, but only by an insignificant amount compared to the increase in the volume of the crew compartment. For comparison, the massive M60A1 had a total internal volume of 18 cubic meters and the volume of its crew compartment was 11.17 cubic meters. This is offset to some extent by the considerably larger 63-round main gun ammunition capacity of the M60A1, but even so, it is clear that the T-62 does not match the M60A1 in the amount of space allocated for the crew.<br />
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In terms of crew space, the T-62 is much closer to the "Patton" tank models that came before the M60A1 such as the M46, M47 and M48. For reference, the crew compartment of the M47 had a volume of 9.06 cubic meters and the M48 had a crew compartment volume of 10.48 cubic meters. After taking the internal equipment into account, the T-62 is on par or marginally superior to the M47 but slightly inferior to later models. In terms of proportions, the crew compartment of a T-54/55 occupies 71.25% of the total volume of the tank and the crew compartment of the T-62 occupies 73.8% of the total volume of the tank, making the T-62 a more volumetrically efficient design. The share of the crew compartment volume of both the T-54/55 and the T-62 is much higher than the 60.4% of the M47 Patton, 59.2% of the M48 Patton and 60.7% of the M60A1 thanks to the uniquely compact engine compartment design pioneered by the T-54. Like the T-54, each crew member in the T-62 was allotted some space for personal equipment and each crew member was provided with a <a href="https://cache3.youla.io/files/images/780_780/5b/ef/5bef001680e08e4de669c642.jpg">two-liter aluminium canteen</a> which would be stowed in a special holder near their respective stations. Rations would be stowed in the hull away from the crew stations.<br />
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Two hatches were installed on the roof of the turret, one for the commander as a part of his cupola assembly and one for the loader. Later on, the loader received his own cupola and the size of his hatch was reduced. The gunner was forced to exit through the commander's hatch if the crew is ordered to bail out which affected the speed of a hasty escape, but this imperfect arrangement was normal for manually loaded tanks around the world.<br />
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<div><br /></div><div><br /></div><div>For internal lighting, the T-62 is fitted with two PMV-61 dome lights for space illumination and five KLST-64 lamps for local illumination of displays and gauges. One dome light is placed on the turret roof next to the commander's station, and one is in the driver's compartment. The PMV-61 dome lights are part of the auxiliary electrical system of the tank, being wired to both the electrical network of the tank and to the power loop of the batteries through redundant connections. To turn on the dome lights, it is only necessary to switch on the master power relay, located behind the driver's station, which connects the batteries of the tank to the electrical network of the tank. To switch on the KLST-64 lamps, the engine has to be running to drive the generator. Additionally, the T-62 is furnished with three ShR-51 power sockets connected to the auxiliary electrical network. One is located on the driver's instrument panel, to supply power to the driver's heated weather hood during head-out driving in the rain or snow, or for night vision goggles, although the driver does not need a pair as he is equipped with the TVN-2 night vision periscope. Another is located in the engine compartment, for the portable PLT-50 lamp when carrying out repairs at night. The third is on the wall of the loader's side of the turret, and it can be used for a portable lamp for map reading purposes, for a portable DP-5 series dosimeter, or to power on the FG-125 infrared lamp mounted beneath the L-2G infrared spotlight for additional illumination during night driving, supplementing the single FG-125 mounted on the upper glacis.</div><div><br /></div>
<br /><h3 style="text-align: left;"><span style="font-size: large;">VENTILATION</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgknS0cJmfXv01kYUbfOzbOnwW-tNeMmLoNTucqUMqdJR-zUmJdOkkeVPT7OO7gQZFL-WdwpVDH4K2S04osMkoCFJTIa7X5MlDKgt5HUpvDfiMLJQ5hyg3snAnAe8gbk7XA0CjVlP3OIYnzkhR7qifARbqLaHh7DcvfZjY7gICtR7xv95FmQKFfEwKUsA/s549/ventilator.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="310" data-original-width="549" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgknS0cJmfXv01kYUbfOzbOnwW-tNeMmLoNTucqUMqdJR-zUmJdOkkeVPT7OO7gQZFL-WdwpVDH4K2S04osMkoCFJTIa7X5MlDKgt5HUpvDfiMLJQ5hyg3snAnAe8gbk7XA0CjVlP3OIYnzkhR7qifARbqLaHh7DcvfZjY7gICtR7xv95FmQKFfEwKUsA/s16000/ventilator.jpg" /></a></div><div><br /></div>
For ventilation, the T-62 featured a supercharged ventilator with an air intake on the rear of the turret as well as an ventilation exhaust fan in the bulkhead between the fighting compartment and engine compartment. To read more on the supercharger ventilator used in Soviet armoured fighting vehicles of the period, visit this <a href="https://thesovietarmourblog.blogspot.com/p/supercharger-ventilator.html">Tankograd article</a>.</div><div><br /></div><div>The ventilator has two modes, normal and supercharger. In the normal mode, the ventilator functions as a simple blower. This mode works in conjunction with the ventilation exhaust fan in the engine compartment bulkhead, whereby air enters the crew compartment via the ventilator and exits via the exhaust fan. The exhaust fan ensures good air circulation inside the tank even when the tank is idle, but when the cooling fan is running, a negative pressure is produced inside the engine compartment due to the powerful radiator cooling fan, which further increases the airflow rate inside the crew compartment. This method of operation is largely the same as the basic ventilation system of earlier tanks, with the exception that the ventilator ensures a higher air flow rate than the simple ventilator fans used in the past. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhygrbxWAx4bJ9X8NWkGbLpewRyHCf6aBvsvb__pxn5A5d0QsEp9j1hOvRHLsTS-nyu6PcacU87E74qhlfni-099s9wIx-aFidCcxkP-W5hAuqHx0F824x-cCUdg_nKLMa7v8o2D-39_uI3mZm1VnpEv7LHNYiHCElL3u2UL-dpU6fo1Be4vvfB4Xapmw/s1731/ventilation%20system.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1359" data-original-width="1731" height="314" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhygrbxWAx4bJ9X8NWkGbLpewRyHCf6aBvsvb__pxn5A5d0QsEp9j1hOvRHLsTS-nyu6PcacU87E74qhlfni-099s9wIx-aFidCcxkP-W5hAuqHx0F824x-cCUdg_nKLMa7v8o2D-39_uI3mZm1VnpEv7LHNYiHCElL3u2UL-dpU6fo1Be4vvfB4Xapmw/w400-h314/ventilation%20system.png" width="400" /></a></div><div>
<br />The ventilation exhaust fan can be turned on to draw air into the engine compartment via the crew compartment even if the ventilation blower is not used. In this case, air enters the crew compartment mainly via small gaps and through airways such as the signal pistol port in the commander's hatch. The location of the ventilation exhaust fan is shown in the drawing on the left below, marked (5), and the fan itself is shown on the right below. Heated air from the engine compartment does not permeate into the crew compartment through the ventilation exhaust duct even when the tank is idling because the exhaust fan ensures a constant air flow into the engine compartment.</div><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-HBX1e_WUytc/XVESNeTwa-I/AAAAAAAAO2Y/rVN9G0j7-1AjHE7hZ17XRnEceYJr2tv5ACLcBGAs/s1600/fighting%2Bcompartment%2Brear.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1035" data-original-width="1449" height="285" src="https://1.bp.blogspot.com/-HBX1e_WUytc/XVESNeTwa-I/AAAAAAAAO2Y/rVN9G0j7-1AjHE7hZ17XRnEceYJr2tv5ACLcBGAs/s400/fighting%2Bcompartment%2Brear.png" width="400" /></a><a href="https://1.bp.blogspot.com/-h4LiavIQ9_k/XVESHPO0PRI/AAAAAAAAO2U/z2Sk_u7PkJM-z8Vx-OjywS1X0YbmjHWSQCLcBGAs/s1600/ventilator%2Bexhaust%2Bfan.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1170" data-original-width="1600" height="292" src="https://1.bp.blogspot.com/-h4LiavIQ9_k/XVESHPO0PRI/AAAAAAAAO2U/z2Sk_u7PkJM-z8Vx-OjywS1X0YbmjHWSQCLcBGAs/s400/ventilator%2Bexhaust%2Bfan.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The second mode is the supercharged mode for generating an internal overpressure. In this mode, the supercharger produces an intense inflow of air, enough to generate an overpressure inside the crew compartment of the tank when all of the main airways are sealed. The second stage is a part of the PAZ (anti-nuclear) protection system. When an overpressure is needed, the individual crew hatches are closed and the rotary shutters of the ventilation exhaust fan port are sealed, so air can only enter or exit the crew compartment through small gaps such as the periscope mountings. The tank is not hermetically sealed, but these gaps were small enough that an overpressure could be maintained with a slow controlled outflow, given the inflow of 110 liters per second (233 CFM) from the supercharged ventilator blower. Note that 233 CFM is by no means high, even for a space as small as a tank interior, as a typical household desk fan will produce over 2,000 CFM in the 'high' setting. Alone, the supercharger cannot be relied upon to ventilate the entire crew compartment.</div><div><br /></div><div>If used in the supercharger mode in conjunction with the crew compartment exhaust fan, the airflow rate is considerably increased. Compared to the older ventilation system of the T-54, using the ventilation system in this way allowed the concentration of propellant fumes in the fighting compartment during combat to be reduced by a further 20-40%. Crew comfort was therefore considerably raised in hot weather. An overpressure is not produced in the crew compartment because of the exhaust fan.</div><div><br /></div><div>In cold weather conditions, a high airflow is undesirable as it would cool down the crew compartment even more by wind chill. In this case, only the ventilation blower would be activated to ensure a constant supply of fresh air, or turned off entirely, while the ventilation exhaust fan shutters would be left open without turning on the fan itself, thus allowing heat from the engine to enter the crew compartment. At the same time, the engine air intake from the radiator louvres is also closed, which allows heated air from the radiator pack to permeate into the engine compartment where they can pass into the crew compartment. </div><div><br />
<br />For personal ventilation, the gunner, loader and driver were each provided with a <a href="http://batcom.ru/products/zapchasti-dlya-spetstekhniki/ventilyatory/dv-3/">DV-3 fan</a>, as shown in the diagrams below. Only the commander lacked a fan, but considering that his seat is directly adjacent to the vent for the ventilation blower, there was probably no need for one. In the diagram on the left below (click to enlarge), the gunner's personal fan is marked (13) and the loader's personal fan is marked (20). In the diagram on the right below, the driver's personal fan is marked (44). The DV-3 is a simple 5.2W fan running on the 27 V electrical network of the tank. The commander does not have a personal fan, but he presumably does not need one, because the air outlet for the ventilator is just behind him. When not in use, the personal fans are folded away. The gunner's personal fan is behind the control handles to blow directly on the gunner's face, the loader's personal fan is on the turret ring next to his seat, and the driver's personal fan is next to the instrument panel, also aimed to blow directly on the driver's face. These fans are normally found to be missing in interior photos of existing tanks, probably because they have been stolen.<br /><br /><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-3PqFIPhd94Y/YRZVwMuq36I/AAAAAAAAUFc/eG8y4WC9lL8ZVmhiR7nyJ9rbWGeI7ghFgCLcBGAsYHQ/s2048/electrical%2Bcomponents%2Bin%2Bturret.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1194" data-original-width="2048" height="234" src="https://1.bp.blogspot.com/-3PqFIPhd94Y/YRZVwMuq36I/AAAAAAAAUFc/eG8y4WC9lL8ZVmhiR7nyJ9rbWGeI7ghFgCLcBGAsYHQ/w400-h234/electrical%2Bcomponents%2Bin%2Bturret.png" width="400" /></a><a href="https://1.bp.blogspot.com/-dnomlQ1ls-0/YRZ6X-RXldI/AAAAAAAAUFk/Vopi1irxYEYGfLo0qM1BNqGkr8iXzuXiwCLcBGAsYHQ/s2048/electrical%2Bcomponents%2Bin%2Bhull.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1396" data-original-width="2048" height="272" src="https://1.bp.blogspot.com/-dnomlQ1ls-0/YRZ6X-RXldI/AAAAAAAAUFk/Vopi1irxYEYGfLo0qM1BNqGkr8iXzuXiwCLcBGAsYHQ/w400-h272/electrical%2Bcomponents%2Bin%2Bhull.png" width="400" /></a><br /></div>
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<span style="font-size: large;">COMMANDER'S STATION</span></h3>
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<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--VzivRG8mVc/Xxlrk8MrTxI/AAAAAAAARUM/RZBNUFD0oNg64iwOEEbW-jeMI9OhtjHPgCLcBGAsYHQ/s1500/breech%2Bleft.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1440" data-original-width="1500" height="614" src="https://1.bp.blogspot.com/--VzivRG8mVc/Xxlrk8MrTxI/AAAAAAAARUM/RZBNUFD0oNg64iwOEEbW-jeMI9OhtjHPgCLcBGAsYHQ/w640-h614/breech%2Bleft.png" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div>
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The commander is seated on the left side of the turret, directly behind the gunner. The commander is responsible for observing the tank's surroundings, searching for targets during combat, coordinating the crew or coordinating other tanks in the platoon or company, operating the R-113 radio transceiver set, and more. Unlike the rest of the dome-shaped turret of the T-62, the casting around the commander's station was shaped in such a way that it is devoid of any vertical sloping or curving whatsoever besides maintaining the circular shape of the turret. This was necessary to enable the commander's rotating cupola to be installed. This also meant that any debilitating effects of the shaping of turret (lack of headroom, for instance) do not directly apply to him as the cupola is raised slightly above the level of the turret roof and the hatch is dome-shaped to further increase the available headroom.</div><br /><div><br />The commander's cupola superstructure is secured to the turret with screws rather than bolts like on the T-54, but <a href="http://data3.primeportal.net/tanks/till_sunderman/t-62/images/t-62_06_of_28.jpg">a new bolted cupola superstructure was implemented in the T-62 obr. 1972 model</a>. The cupola is mounted on a race ring. The fixed part constitutes just under half of the total size of the cupola, while the other half is occupied by the semicircular hatch. The hatch opens forward, which is quite convenient for when the commander wants to survey the landscape from outside - perhaps with a pair of binoculars - because the considerable thickness of the hatch makes it a bulletproof shield to protect the commander from sniper fire. The hatch has a thickness of 30mm and is curved.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-EDaUxhTC5Do/XUsJNStq6QI/AAAAAAAAOvY/SU16VVR8hf0EPQpYVJHwL1LBkgcas33CACLcBGAs/s1600/cupola.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="438" data-original-width="664" height="263" src="https://1.bp.blogspot.com/-EDaUxhTC5Do/XUsJNStq6QI/AAAAAAAAOvY/SU16VVR8hf0EPQpYVJHwL1LBkgcas33CACLcBGAs/s400/cupola.jpg" width="400" /></a><a href="http://4.bp.blogspot.com/-BR07jONtWPQ/VmMwHeavRII/AAAAAAAAEpM/stRmj2Y4xao/s1600/t-62%2Bcommander%2527s%2Bcupola.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://4.bp.blogspot.com/-BR07jONtWPQ/VmMwHeavRII/AAAAAAAAEpM/stRmj2Y4xao/s400/t-62%2Bcommander%2527s%2Bcupola.jpg" width="400" /></a></div></div><div><br /></div><div><br /></div><div>The commander's hatch is semicircular in shape and features a small port. Officially, it is known as the signalling port, as it is mainly used as a small opening for the commander to fire his 26mm flare pistol without opening the hatch. Its secondary purpose is to function as a secondary air intake point for the engine, if the engine is switched from its standard intake mode to using air drawn from the crew compartment. This can be done when additional ventilation is desired by the crew, but it is mainly used when wading through water obstacles that are deep enough to cover the hull but not the turret. It is necessary to open the port when doing this as otherwise, the engine will deplete the air inside the crew compartment faster than air can enter through the various small gaps in the tank, thus suffocating the crew until the engine stalls. Having the gun breech opened is not a viable alternate solution to providing a source of airflow, because the tank may need to open fire while wading. This feature was inherited from the T-54 family. </div><div>
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<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xvbADT6wge0/XSX5PFkWCsI/AAAAAAAAOkU/JMtpStzO5CE1sGNKPsWBkO-FJ69EuJ0nwCLcBGAs/s1600/t-62%2Bcupola.png" style="margin-left: 1em; margin-right: 1em;"></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhxBd6zZs-YR-70ua5xR66MIQDRBYrzRgPqLVoiYz2h75oj6zBQJEXVBuWgkY4aOw_h-0mtxjBNM3NpyxUQG10aIHAUzyc6s2wPenD8Zmkh25sHou4thI1d0jRr5Hth3DbO2NXkhOeeWVqY2OrgaE0VlDq7BO9KNIyKL1FP_M60Z6SX42aLZH8FgH5P-g/s1000/rianovosti.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1000" data-original-width="664" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhxBd6zZs-YR-70ua5xR66MIQDRBYrzRgPqLVoiYz2h75oj6zBQJEXVBuWgkY4aOw_h-0mtxjBNM3NpyxUQG10aIHAUzyc6s2wPenD8Zmkh25sHou4thI1d0jRr5Hth3DbO2NXkhOeeWVqY2OrgaE0VlDq7BO9KNIyKL1FP_M60Z6SX42aLZH8FgH5P-g/w265-h400/rianovosti.png" width="265" /></a><a href="https://1.bp.blogspot.com/-xvbADT6wge0/XSX5PFkWCsI/AAAAAAAAOkU/JMtpStzO5CE1sGNKPsWBkO-FJ69EuJ0nwCLcBGAs/s1600/t-62%2Bcupola.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1262" height="400" src="https://1.bp.blogspot.com/-xvbADT6wge0/XSX5PFkWCsI/AAAAAAAAOkU/JMtpStzO5CE1sGNKPsWBkO-FJ69EuJ0nwCLcBGAs/w315-h400/t-62%2Bcupola.png" width="315" /></a><br /></div>
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The commander's seat is thickly padded and he has a backrest as well as a footrest. On his immediate left is the A-1 communications control box of the R-114 intercome system. It is the master control box, serving as a connector hub for all other control boxes at each crew station. It enables the commander to switch between the radio(s) and the intercom for his headset. There are a few metal loops for strapping on personal effects, his binoculars (in its pouch), his personal sidearm (in its holster), a documents case and anything else that might need to be secured. He also has access to the turret traverse lock. Underneath his seat on the hull floor is the tank's heater unit. The commander's two-liter aluminium bottle can be seen secured to its holder. Unlike in the T-54, the radio is installed below the turret ring and next to the gunner which frees up a lot of horizontal space for the commander above the level of his midriff at the expense of the gunner. On the T-54/55, there is a padded knee rest attached to the turret ring where the radio is located in the T-62. All of this can be seen in the two photos below.<br />
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<a href="http://2.bp.blogspot.com/-xuLTXVijUOA/Vl2v91QI5VI/AAAAAAAAEhg/5sJN39_NUkU/s1600/T-62%2Bcommander%2527s%2Bstation%2Band%2Bhydraulic%2Bpump.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="256" src="https://2.bp.blogspot.com/-xuLTXVijUOA/Vl2v91QI5VI/AAAAAAAAEhg/5sJN39_NUkU/s400/T-62%2Bcommander%2527s%2Bstation%2Band%2Bhydraulic%2Bpump.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-bn-t0dm6xSs/XzJE3kVQzPI/AAAAAAAARcw/kj98IPxPRzsF3A3yxrCV-mhzssSDQFkxQCLcBGAsYHQ/s1920/t-62m%2Bcommanders%2Bseat.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="225" src="https://1.bp.blogspot.com/-bn-t0dm6xSs/XzJE3kVQzPI/AAAAAAAARcw/kj98IPxPRzsF3A3yxrCV-mhzssSDQFkxQCLcBGAsYHQ/w400-h225/t-62m%2Bcommanders%2Bseat.png" width="400" /></a></div>
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The photo on the right (from <a href="http://walkarounds.scalemodels.ru/v/walkarounds/afv/after_1950/T-62_interior_UVZ_Shinji/?g2_page=1">Aleksey Kotov</a>) shows the backrest of his seat and a few pieces of equipment. The turret traverse lock is just underneath the communications relay box. Besides these two components, there is very little else, and thanks to this, the commander has much more elbow room than a T-54/55 commander who is practically squeezed between the recoil guard on his right and the radio set on his left with enough space to only operate the radio and rotate the cupola with his hands on the handles. Overall, the amount of space for the T-62 commander is noticeably larger compared to the T-54/55 and it is entirely due to the very large turret diameter of 2,245mm. The screenshot below, taken from the video "<a href="https://youtu.be/f2TRMeQXlTs">The Beasts of Kabul: Inside the Afghan Army's Soviet Tanks</a>" by the Stars and Stripes news organization, gives a relatively good perspective of this space.<br />
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<a href="https://1.bp.blogspot.com/-gHaQ2ePj_sY/XPugbuq5dpI/AAAAAAAAOPU/bmkJ-0AIFRsf3cRT_AxNKmaIzV5cXt4lwCLcBGAs/s1600/afghan%2Bt-62.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1366" height="358" src="https://1.bp.blogspot.com/-gHaQ2ePj_sY/XPugbuq5dpI/AAAAAAAAOPU/bmkJ-0AIFRsf3cRT_AxNKmaIzV5cXt4lwCLcBGAs/s640/afghan%2Bt-62.png" width="640" /></a></div>
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Still, it's worth noting that in all of the images shown so far, the recoil guard between the commander and the U-5TS gun on his right has been removed. When installed, the recoil guard ensures that the commander's shoulder and arms do not enter the recoil path of the gun or get caught by any of its moving parts but allows him to see over its edge to communicate with the loader.<br />
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<a href="https://1.bp.blogspot.com/-eWqutXOF2As/XPuj5M058-I/AAAAAAAAOPc/PV72mUlfG9ksz6q1pSVXw9aM1YGRYWHAACLcBGAs/s1600/commanders%2Bstation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="967" data-original-width="1554" height="398" src="https://1.bp.blogspot.com/-eWqutXOF2As/XPuj5M058-I/AAAAAAAAOPc/PV72mUlfG9ksz6q1pSVXw9aM1YGRYWHAACLcBGAs/s640/commanders%2Bstation.png" width="640" /></a></div>
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However, the larger turret ring diameter of the T-62 had much less effect on the space between the commander and gunner. This can be seen in the drawing above. The commander sits directly underneath his cupola and his footrest is just behind the gunner's seat, so unless the commander keeps his legs spread, his knees will be pushing into the gunner's back. The close proximity between the two crew members makes the internal climate hotter and more humid, contributing to the overall discomfort in summer. It may not be as bad in the winter, but still, this is not a positive trait of the tank. The small space between the two men is compounded by the fact that the crew isn't provided with directional ventilation devices such as blowers, fans or directed air vents, so it can get quite stuffy inside. However, both the commander and loader are seated next to the PAZ ventilator blower air outlet in the turret, which is installed underneath the spent shell casing ejection port at the back of the turret. Besides the roomy loader's station, the commander's seat is one of the better places to be in the very spartan T-62.<br />
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<h3>
<span style="font-size: large;">COMMUNICATIONS</span></h3>
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXk3YvpFN8jg585oGKp1UBx08vxLsqSh-T8WwDC9vg_us8CKUCKaawUb_xHFpGS2mahbF-u-cgrMLGVggvPuz4v5MVIj-NdSzi0r-lz6y3HjKUQqTHrMy-itc_Dw4tOuK4N1-uISFa___w0CyqAQU0p3qJzg0gU_X2gvVAQOm37cI0HskeZTUxHSnDMQ/s938/r-113%20radio%20set.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="545" data-original-width="938" height="233" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXk3YvpFN8jg585oGKp1UBx08vxLsqSh-T8WwDC9vg_us8CKUCKaawUb_xHFpGS2mahbF-u-cgrMLGVggvPuz4v5MVIj-NdSzi0r-lz6y3HjKUQqTHrMy-itc_Dw4tOuK4N1-uISFa___w0CyqAQU0p3qJzg0gU_X2gvVAQOm37cI0HskeZTUxHSnDMQ/w400-h233/r-113%20radio%20set.png" width="400" /></a></div><div><br /></div><div>Throughout the service of the T-62 in the Soviet Army, it saw all three tank radio models fitted at various points. First beginning its service with the R-113, new production T-62 tanks switched to the R-123 when it became the new standard tank radio in 1965. With the T-62M modernization, the latest R-173 radio was fitted to tanks receiving the upgrade as part of their scheduled overhaul. </div><div><br /></div><div>Standard practice was for individual tanks to be fitted with a single radio transceiver, which would either be the R-113 or R-123, except in the case of the R-173 which came with an additional R-173P receiver as standard. Unit leader tanks, including platoon and company leaders, were equipped with an additional radio transceiver, fitted on the turret wall at the loader's station. For example, a tank with an R-123 would have an additional R-123 fitted on a frame at this location, and a tank equipped with the R-173 would have an additional R-173 (without additional R-173P receiver). The mounting frame for the additional radio can be seen in the image below, and further below that, an R-173 fitted on the mount in a T-62M can be seen. Because all three tank radios share identical dimensions, it can be assumed that the frame was not modified throughout the service life of the T-62.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEg7CuGO5EDfMFcVO-reWzVKM9BYLqlP75rcli84fsIKmb3Em7_RAFkO9u50R_F5m9pMkIIZIRkslHJVMST62pjPzkgc9Wqd3Mn6TTELbHnAs2VLsmwuDOoVoFRirG9u8-bsZoRDt_9KuG1VQpA4XqqrbimJaxFhsAvRiDlOseVDFT7j_mLoRWMDRLLHgA=s1920" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="360" src="https://blogger.googleusercontent.com/img/a/AVvXsEg7CuGO5EDfMFcVO-reWzVKM9BYLqlP75rcli84fsIKmb3Em7_RAFkO9u50R_F5m9pMkIIZIRkslHJVMST62pjPzkgc9Wqd3Mn6TTELbHnAs2VLsmwuDOoVoFRirG9u8-bsZoRDt_9KuG1VQpA4XqqrbimJaxFhsAvRiDlOseVDFT7j_mLoRWMDRLLHgA=w640-h360" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgAvwb_Keo9STBd84_CFv9ZBg0rKK2S14ABrwGWc6szBoIZj97-tV40U71a1shrqiLKERsfVj_Lt7GvBe_2eu0gc1CxNyGRzBQr5cT6U67CLOxEbQ4sTO6gxPYPGWGmTioD0Df5TmzMzU_qIWiysL3b0NKqRGNMDpL39_bUljS5ZJhURfs450al70LKjw=s1364" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="609" data-original-width="1364" height="286" src="https://blogger.googleusercontent.com/img/a/AVvXsEgAvwb_Keo9STBd84_CFv9ZBg0rKK2S14ABrwGWc6szBoIZj97-tV40U71a1shrqiLKERsfVj_Lt7GvBe_2eu0gc1CxNyGRzBQr5cT6U67CLOxEbQ4sTO6gxPYPGWGmTioD0Df5TmzMzU_qIWiysL3b0NKqRGNMDpL39_bUljS5ZJhURfs450al70LKjw=w640-h286" width="640" /></a></div><div><br /></div><div><br /></div><div>The additional radio in unit leader tanks was used to keep the tank commander, who was the unit leader, tuned to the communications network of the unit subordinated under his command on one radio and tuned to the network of his counterparts on the other radio. In this way, a tank company commander could issue orders to the leaders of tank platoons on radio, while monitoring communications on the company leader network to remain updated on events reported by other company leaders, receive orders from the battalion headquarters, and report on his own situation and actions. Because the tank commander can only listen on one channel at a time through his headset, he must either use the loudspeaker on one of the radios to listen on two channels at once, or instruct either the gunner or the loader to take over responsibility on the subordinate network to relay instructions.</div><div><br /></div><div><div>Command tanks, denoted by a "K" suffix, include the T-62K and T-62MK. The additional radio in both tanks was installed in the place of the two rounds of ammunition stowed on the turret wall, on the loader's side. As a result, the ammunition capacity was reduced by two rounds, which was a smaller loss compared to command versions of the T-54 and T-55 which placed the additional radio in the turret bustle behind the gun, in the place of an ammunition rack holding five rounds. The additional radio, which could be an R-112 or an R-130M, had a common connection with the commander's primary radio to the single whip antenna on the turret, made possible by the radio frequency filter. In T-62K command tanks, the additional radio was an R-112. In the T-62MK, it was an R-130M. To provide the possibility of continuous radio operation without needing to keep the engine running, command tanks were also fitted with an AB-1 auxilliary power unit.</div><div><br /></div><div>In command tanks, the loader was responsible for being the radio operator for the additional radio, and more importantly, helping the commander (who would also be the battalion commander) to handle the flow of information from the division headquarters and the companies organized under the battalion.</div></div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">R-113</span></h3>
<div style="text-align: center;"><a href="http://4.bp.blogspot.com/-3nuUMnv_3Uk/Vm8mgho1i0I/AAAAAAAAFAY/yv_1fXSbD3w/s1600/r-113%2Bradio.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="224" src="https://4.bp.blogspot.com/-3nuUMnv_3Uk/Vm8mgho1i0I/AAAAAAAAFAY/yv_1fXSbD3w/w400-h224/r-113%2Bradio.jpg" width="400" /></a></div><div><br /></div>As with other Soviet tanks operated since 1954, the T-62 was fitted with an R-113 radio at the time it was introduced into service. The R-113 radio operates in the 20.00 to 22.375 MHz range and has a range of 10 to 20 km with its 4 m-long antenna. It could be tuned into 96 frequencies within the limits of its frequency range. The transmission power of the R-113 is 16 Watts. The narrow operating range of the radio is sufficient for tactical communications, but being so narrow, it is easy for NATO forces to earmark the 20-22.375 MHz frequency range as the known communications band of Soviet tanks and thereby jam the entire range, while NATO forces could still operate with minimal noise at completely different frequencies. The transceiver unit measures 428x239x222 mm, and the power supply unit is 210x166x220 mm.</div><div><br /></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">R-123</span></h3><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-uUzs3iGE9rg/V1XFc9DKijI/AAAAAAAAGrY/qsnp1jfGG2sXXzz23gNQwnVieZcCrVD7ACLcB/s700/r123m.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="417" data-original-width="700" height="239" src="https://3.bp.blogspot.com/-uUzs3iGE9rg/V1XFc9DKijI/AAAAAAAAGrY/qsnp1jfGG2sXXzz23gNQwnVieZcCrVD7ACLcB/w400-h239/r123m.jpg" width="400" /></a></div><div><br /></div><div>In 1965, the radio was swapped out for a newer and much more advanced R-123 radio, as the R-123 was newly standardized for armoured vehicles in the Soviet army. The R-123 radio station was made to match the dimensions of the earlier R-113, allowing a direct swap to the new radio without needing new mounts or a new wiring harness. The R-123 radio had a frequency range of between 20 MHz to 51.5 MHz. It could be tuned to any frequency within those limits via a knob, or the commander could instantly switch between four preset frequencies for communications within a platoon. Communication is possible with low level infantry radio sets, including the R-105M, R-108M, R-109M, R-114 and R-126. It had a nominal range of between 16 km to 50 km depending on the terrain, weather and noise levels, but according to the manual, the communication range with other tanks when the tank is moving at 40 km/h is limited to 20 km with the noise suppressor turned off and 13 km with the noise suppressor turned on. </div><div><br /></div><div><br /></div><div><br /></div><div>The R-123 was designed with two deliberate features for increased jamming and noise immunity, which were its increased transmission power of 20 Watts, and its choice of operating frequencies. The increased transmission power was responsible for the increased range of the R-123 and it improved signal reception for receivers, but the increased power also improved the resistance to interference, as more powerful jamming would be required to suppress its signals. Compared to the standard SEM-25 tank radio used in the Bundeswehr which had a transmitting power of up to 15 W, and the AN/VRC-12 tank radio used in the U.S military since 1965 which had a transmission power of 30 W, the power of the R-123 is moderate. Moreover, the choice of the operating frequency range had a significant overlap with the operating frequency range of foreign radio systems. In the US Army, the AN/VRC-12 tank radio operated in the 30-75.95 MHz frequency range, the British used the VRC 353 with a 30-75.975 MHz frequency range, while German tanks were equipped with the SEM-25 radio station, which had a 20-69 MHz frequency range. This made it infeasible for enemy forces to utilize indiscriminate or barrage jamming - which was previously possible against the R-113 due to its narrow 20.00-22.375 MHz frequency range - as the range of possible frequencies was too large, and even if it were attempted, indiscriminate jamming would impair their own radio communications.</div><div><br /></div><div>The R-123 had frosted glass prism window at the top of the apparatus that displayed the operating frequency. An internal bulb illuminated a dial, imposing it onto the prism where it is displayed. The R-123 had a modular design that enabled it to be repaired quickly by simply swapping out individual modules.<br />
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<div><br /></div><div><br /></div><div>When transmitting, the radio station requires no more than 250 W, and when receiving in the simplex mode, it requires no more than 130 W. When set to the standby reception mode, only 80 W of power is needed. As the four 6-STEN-140 batteries of the T-62 have a total capacity of 7,280 Wh, the tank is theoretically capable of carrying out a silent watch, also known as a radio watch, for over a full day without depleting the batteries below the recommended minimum level. Even so, unlike foreign tanks, less care needs to be taken with the batteries because the T-62 can always start its engine with its pneumatic starting system. </div><div><br /></div></div><div><br /></div><div><h3 style="text-align: left;"><span style="font-size: large;">VISION</span></h3>
<br />The commander's primary periscope is either a TKN-2 or TKN-3 combined day-night periscope. It is boresighted to the main gun for a distance of no less than 1,000 meters, permitting accurate target designation. As befitting his tactical role, the commander's general visibility is facilitated by two TNPO-170 periscopes on either side of the primary surveillance periscope in the fixed forward half of the cupola, further augmented by two more periscopes embedded in the hatch, aimed to either side for additional situational awareness. Overall, this scheme could be considered more than adequate.<br />
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The TNPO-170 periscope has a total range of vision of 94 degrees in the horizontal plane (with head motion) and 23 degrees in the vertical plane. The four periscopes in addition to the TKN-2 or TKN-3 periscope aimed directly forward gives the commander a good view of the battlefield in an arc spanning the 4 o'clock position to the 8 o'clock position. There is no rearward-facing periscope, but the commander can look backward by simply turning the cupola to one side and looking back through one of the periscopes in the hatch.</div>
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The drawing below, taken from the U.S Army Operator's Manual for the T-62, shows the target acquisition sectors for the three crew members in the turret. The commander's sector of responsibility is the largest by far, and he also has the most suitable equipment for the task. By rotating his cupola, the commander of a T-62 can use his TKN-2 or TKN-3 periscope to scan in a full circle, or if the cupola is fixed facing forward as depicted in the drawing, the commander scans sector spanning the 5 o'clock position to the 7 o'clock positions. It is possible for the commander to look backwards through any of his periscopes by simply rotating the cupola, so in practice, the dead space marked in the drawing is not applicable in practice. As the drawing shows, even with the cupola fixed facing forward, the commander in a T-62 has effectively the same range of vision as in any other tank. </div>
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<span style="font-size: large;">TKN-2 "Karmin"</span></h3>
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<br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-fxw2Vifhc-I/YUlD7Gd3K2I/AAAAAAAAUMs/_JPGjgF4aVYzFRT6Kc5KGNA2z8bGGEQawCLcBGAsYHQ/s1507/tkn-2%2Bperiscope.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="835" data-original-width="1507" height="354" src="https://1.bp.blogspot.com/-fxw2Vifhc-I/YUlD7Gd3K2I/AAAAAAAAUMs/_JPGjgF4aVYzFRT6Kc5KGNA2z8bGGEQawCLcBGAsYHQ/w640-h354/tkn-2%2Bperiscope.png" width="640" /></a></div><div><br /></div><div>The original 1961 model of the T-62 featured the TKN-2 surveillance device mounted in the rotating cupola. The TKN-2 was the successor to the TKN-1S monocular night vision periscope, differing in that it provided a combined day-night capability rather than a night-only vision capability. Work on "Karmin" began in 1956 at the Zagorsk Optical and Mechanical Plant. In 1957, the TKN-2 was tested in an experimental T-55 test bed at the testing grounds of factory no. 183 (Uralvagonzavod). TKN-2 later went on to be installed on the original T-62 upon its introduction in 1961, thus becoming the first combined day-night periscope to be installed in a Soviet tank. The TKN-2 was a sufficiently modern surveillance device for its time. It had a target cuing feature, was compact, and had a relatively advanced passive light intensification system supplemented by an IR spotlight. On the other hand, it wasn't stabilized and featured only rudimentary rangefinding capabilities.<br /></div><div><br /></div><div>The TKN-2 has a fixed 5x magnification with an angular field of view of 10 degrees in the daytime channel, allowing a nominal maximum detection range of a tank-sized target of approximately 3 km, though this was greatly dependent on geography as well as weather and lighting conditions. The 5x magnification was carried over from earlier periscopes. When the target is situated in more open environments, the detection range tends to increase, and in a forested environment, the detection range tends to decrease. In one Soviet study, it was found that when observing stationary tanks and APCs with the naked eye, the identification range limit was 1.2-1.5 km for a ~100% target identification criteria, given an unlimited observation time. With a TKN-3, the average identification range was 3.5 km in the summer, and with a TSh2B, the identification range increased to only 3.6 km in the same conditions and under the same criteria. It was deemed that an increase in magnification from 1x to 5x could give a 2.5-times increase in identification range, but further increases in sight magnification yielded only marginal gains.</div><div><br /></div><div><br /></div><div>It has a fixed 4.2x magnification in the night channel with an angular field of view of 8 degrees. The periscope could be manually elevated upwards by <complete id="goog_658813447">+10°</complete> and downwards by -5°, and the cupola would have to be manually spun to scan horizontally.</div><div><br /></div><div>To switch from daytime to nighttime view, the commander must first retrieve the BT-5-26 power supply unit from its stowage box, remove the TNPO-170 periscope on the right of the TKN-2, install the BT-5-26 unit in the periscope slot, and connect it to the TKN-2. This links it to the electrical network of the tank via the cupola ring, allowing the night vision system in the TKN-2 to be powered up. In this condition, the commander can switch between the daytime viewing mode or nighttime viewing mode at will. The use of the periscope slot for the power supply unit was carried over from the TKN-1. The downside to this system is that vision is reduced as the right TNPO-170 periscope is absent, but the commander's work is made more convenient by not being obligated to switch swap out a TPKU-2B daytime periscope for a TKN-1 nighttime periscope as in a T-54 or T-55 tank. The photo below shows an example of the TKN-2 set up for night use, with a BT-5-26 power supply unit mounted into the slot for the TNPO-170 periscope to its right.</div><div class="separator" style="clear: both; text-align: left;"><br /></div>
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEheH91-3G5YmeVAe-ph-fUJNTkcU6S7Fv820h96wWfUPD9s6pDsIwyLEWK6yT2p2a76e3bc0H6S6FEGoD77gM8-p4f2r6Z3OwN8xmhPN7Cr6uOEF0kjj_XMSYZAJh83ggmuW57ckjY94nyRhM_ij7i37cprgDJ7QxEilFHV51P3acdV4xmgH3jqmi-N4w/s1304/tkn-2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1044" data-original-width="1304" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEheH91-3G5YmeVAe-ph-fUJNTkcU6S7Fv820h96wWfUPD9s6pDsIwyLEWK6yT2p2a76e3bc0H6S6FEGoD77gM8-p4f2r6Z3OwN8xmhPN7Cr6uOEF0kjj_XMSYZAJh83ggmuW57ckjY94nyRhM_ij7i37cprgDJ7QxEilFHV51P3acdV4xmgH3jqmi-N4w/w400-h320/tkn-2.png" width="400" /></a></div></div><div><br /></div><div>Night vision is provided via a single image intensifier tube with the image split between the two eyepieces. Daytime vision is binocular, with the two eyepieces connected to separate apertures. Switching from one mode to the other is done by turning an internal mirror. The TKN-2 had an active infrared night channel relying on the infrared light emitted from the OU-3 IR spotlight attached to the periscope aperture to provide a limited degree of night vision to the commander. With a nominal viewing range of only about 300 to 400 m, the TKN-2 was all but useless for serious target acquisition at night, providing effectively the same night fighting utility as the TKN-1S periscope for the T-54 and T-55 series. Performance could be improved with mortar-delivered IR flares, of course, but that is not an intrinsic merit of the device itself.<br />
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Due to the fact that the periscope is unstabilized, identifying a tank type target at a distance is very difficult while on the move over very rough terrain. However, the commander is meant to bear down and brace against the handles of the periscope for a modicum of improvised stabilization, which is adequate for when cruising at a moderate speed (about 20 km/h to 30 km/h) over a dirt road, but not when traversing over rougher ground.<br />
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The left handle has a thumb button for activating the OU-3 spotlight. The thumb button must be held to keep the light on. This allows the commander to illuminate his target intermittently or to flash friendly forces. To toggle the spotlight on or off, the commander must flip a toggle switch on the cupola race ring.<br />
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The OU-3 has an incandescent lamp with a removable IR filter. The filter is not totally opaque to visible light, allowing less than 1% to pass through, so the spotlight will glow faintly red when activated. It is linked to the periscope by mechanical linkages so that it elevates together with the TKN-2.<br />
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The OU-3 spotlight operates on 110 W of power. This is not much compared to the L-2 "Luna" spotlight used for the TPN1-41-11 night sight, and it is extremely weak compared to most Western IR spotlights. Considering that the Chieftain tank was introduced only six years after the T-62 and came equipped with a higher powered IR spotlight for its commander, the low power of the OU-3 spotlight may have made it a liability in real combat. In a scenario where both sides are actively searching for targets using IR spotlights but fail to find each other by seeing the light sources, the longer-ranged spotlight on the Chieftain enables it to spot a T-62 more quickly. Despite this, the fact that the commander has his own IR spotlight and a night vision sight of his own is still useful, so the commander of a T-62 cannot be considered too deficient in this department. Even if he cannot rely on his own OU-3 spotlight at long distances, the TKN-2 still gives him the ability to survey the battlefield under the light of artillery-launched illumination flares and find enemy light sources without using his own illumination sources.<br />
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<span style="font-size: large;">TKN-3 "Kristal"</span></h3>
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In 1964, new batches of T-62 tanks began to be equipped with the new TKN-3 combined day-night periscope, a modification of the TKN-2. The main design change introduced in the TKN-3 was the integration of the BT-5-26 night vision power supply unit into the periscope itself, rather than having a separate power supply box that required preparation to set up before night combat. The power supply is fitted below the eyepieces, increasing the height of the periscope compared to the TKN-2. Otherwise, in terms of design, the TKN-3 was visually identical to the TKN-2. By having the power supply integrated into the periscope itself, it ensured that the right TNPO-170 periscope would not be obstructed for any reason, and it completely eliminated the need for any preperation when switching from day to night combat. From this, a clear design goal in improving user convenience can be traced from the TKN-1S, to the TKN-2, to the TKN-3. Each successive design iteration eased the setup demands on the tank commander to prepare for night combat, to the point where on the TKN-3, there were virtually no setup requirements whatsoever.</div><div><br /></div><div>Technologically, the biggest improvement of the TKN-3 over the TKN-2 was the use of coated lenses for the daytime optical channel. This reportedly improved the light transmittance by a factor of two, thus substantially improving the brightness and contrast of the image and consequently increasing the commander's practical viewing range and also improving his ability to see camouflaged objects at long distances. Like the TKN-2, the TKN-3 has a fixed 5x magnification in the day channel with an angular field of view of 10 degrees and a fixed 4.2x magnification in the night channel with an angular field of view of 8 degrees. <br />
<br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-7hHy_hBpArc/YRZFJX90jXI/AAAAAAAAUE8/zRTG43CmNSkQZsuxSRb4XIB2R07DEanfwCLcBGAsYHQ/s411/TKN-3%2Bsight%2Bpicture.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="393" data-original-width="411" height="306" src="https://1.bp.blogspot.com/-7hHy_hBpArc/YRZFJX90jXI/AAAAAAAAUE8/zRTG43CmNSkQZsuxSRb4XIB2R07DEanfwCLcBGAsYHQ/s320/TKN-3%2Bsight%2Bpicture.png" width="320" /></a></div>
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TKN-3 provided night vision in the form of passive light intensification or active infrared illumination. In the passive mode of operation, the TKN-3 intensifies ambient light to produce a more legible image. This mode is useful down to ambient lighting conditions of at least 0.005 lux, which would be equivalent to a clear moonless, starlit night. In these conditions, the TKN-3 can be used to identify a tank-type target at a nominal distance of 400 m, but as the amount of ambient light increases such as on clear moonlit nights, the distance at which a tank-sized target is discernible can be extended by around twice the normal range, but the viewing distance is still limited by the low resolution image. Using the image intensifier under increasingly bright conditions may not be so beneficial since the image will have a low resolution.</div><br /><div>
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The active mode requires the use of the OU-3GK IR spotlight. Activating the OU-3GK is done the same way as with the TKN-2. With active infrared imaging, the commander can identify a tank at around 400 m or potentially more if the opposing side is also using IR spotlights, in which case, the TKN-3 can be set to the active mode but without turning on the IR spotlight. This way, the commander can see enemy tanks from many kilometers away at night, or at least three times further than the viewing range of the enemy tank relying on the spotlight. Without the infrared filter, the spotlight emits white light <a href="http://gaz66avto.ru/data/documents/Rec_34741.PDF">at 240 candlepower</a>.<br /><br />
Like the TKN-2, the TKN-3 had separate optical channels for the night and day viewing modes. In the daytime channel, the two eyepieces lead to separate apertures to provide stereoscopic vision, thus providing depth perception. For the night channel, the optical channel from the two eyepieces were merged to view from a single aperture lens.<br />
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To switch between the day and night channels, the user simply rotates a dial on the right side of the periscope housing by 90 degrees. This flips an internal mirror by 90 degrees, thus changing the optical path between the night vision unit and the regular daytime optical channel. The diagram below shows the two choices. Diagram (a) on the left shows the path of the light from the aperture through the night vision system and into the eyepiece, while diagram (b) on the right shows the mirror flipped 90 degrees and the light from the aperture passing through the normal optical channel for daytime use.<br />
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Rangefinding is accomplished through the use of a stadiametric scale calibrated for a target with a height of 2.7 m, which is the average height of the average NATO tank. The ranging error margin is negligible at distances of around a kilometer, but at distances exceeding approximately 1.6 km, it becomes difficult to accurately find the range of the target due to a multitude of factors, including weather conditions, limited magnification power, mirages (a big problem in deserts), and obstruction of parts of the tank (tall grass can hide the lower part of the hull). At long distances, contrast between the target tank and the background is also often very poor, since there is usually some modicum of camouflage to conceal the tank.<br />
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It is also possible to find the distance to the target tank by using the windage and elevation scales beside and above the central reticle in the TKN-3 viewfinder. Knowing the width of any Patton tank to be around 3.6 meters, the commander will know that the distance to the tank is exactly 900 meters if the tank can be bracketing it exactly between any two vertical lines on the windage scale (4 mils). If the commander sees a Patton tank presenting its profile, he can assume that its length is 7 meters, and he can place estimate the range to the tank by bracketing it between two of the long vertical lines on the windage scale (8 mils). If it fits perfectly, then the distance is just slightly under 900 meters, but can be rounded up to 900 meters with a negligible margin of error.<br />
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<tr><td class="tr-caption" style="text-align: center;">TKN-3 viewfinder</td></tr>
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Like the TKN-2 and other previous binocular sights for the commander, the TKN-3 is not stabilized, making it exceedingly difficult to reliably identify enemy tanks or other vehicles at extended distances while the tank is travelling over rough terrain, let alone determine the range. On a related note, the lack of stabilization would have made it equally difficult to operate an optical coincidence or stereoscopic rangefinder, especially one with a high magnification. The M17 rangefinder used in M60A1, for example, would have been next to useless if the tank was in motion over rough terrain since the rangefinder had a fixed 10x magnification, so the oscillations from the movement of the tank could cause too much jolting for the commander to keep the target focused. This means that the rangefinder is only useful when the tank is static, which may have been perfectly fine for the M60A1 and its contemporaries if the situation consistently permitted the tank to remain static. The T-62, on the other hand, is an offensive tank designed to fulfill specific tactical-technical requirements while remaining affordable, and high-precision optical instruments did not necessarily fit into this plan.<br />
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Optical rangefinders were therefore understandably absent from Soviet medium and heavy tanks, but not from Soviet tank destroyers and assault guns. Case in point: the SU-122-54 and experimental Object 268 both had stereoscopic rangefinders installed on the commander's cupola as a technical requirement. However, Object 268 was deemed superfluous and the need for the SU-122-54 evaporated fairly quickly after it was accepted into service, not least because problems were encountered with the rangefinder. Optical rangefinders only found their way into Soviet tanks on a large scale with the advent of the T-64; the first tank to have an independently stabilized primary gunsight, and also the first tank to have an integrated optical coincidence rangefinder installed in said gunsight.<br />
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The left thumb button initiates turret traverse for target cuing, and the right thumb button turns the OU-3GK spotlight on or off, but the button must be held to keep the spotlight on. The spotlight should not be turned on for more than 20 seconds, as it will overheat without periodic cooling. A toggle switch on the race ring of the cupola enables the commander to keep the spotlight on or off. The range of elevation is +10° to -5°. The OU-3GK spotlight is mechanically linked to the TKN-3 by a pushrod to enable it to elevate and depress with the periscope.<br />
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Target designating is done by placing the crosshair in the viewfinder of the TKN-2 or TKN-3 over the intended target and pressing the left thumb button, holding it until the turret is aligned with the periscope. It is theoretically possible to guide the turret if the commander keeps the left thumb button, hereby known as the target designator button, held down while turning his cupola. The system only accounts for the cupola's orientation, and not the periscope's elevation, so the the turret will traverse to meet the target, but the gun will not elevate to meet the commander's point of aim. This was not an issue, since the gunner needs to conduct the final lay on the target anyway. The wide field of view offered by the gunner's sight makes it practically impossible for the gunner to miss a target even if the turret was imperfectly aligned with the commander's periscope.<br />
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The target designation system is practically the same as the one used in the T-54. A direction sensor is installed at around the 3 o'clock position of the cupola, and has the function of determining the deflection of the TKN-3 relative to the longitudinal axis of the turret. The direction sensor consists of a roller placed in permanent contact with the cupola race ring, a cam attached to the roller and two switches. The roller is recessed into a notch in the cupola race ring when the cupola is turned to the 0 o'clock position relative to the turret - refer to the diagram in the middle.<br />
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When the cupola is turned to the right (see diagram on the right), the motion of the cupola race ring dislodges the roller from the notch and causes the roller to be deflected to the left by friction. The cam attached to the roller also rotates left, causing it to touch the switch on the right, but no action is taken until the target designator button is pressed. When the target designator button is pressed, an electric signal is sent from the button to the direction sensor via a conductor track on the cupola race ring. The depression of the right switch by the cam then triggers the turret rotation motor to turn the turret to the right until the roller returns to the notch, whereby the cam is no longer in contact with the right switch and no action is taken even if the commander keeps his thumb on the target designator button. The same mechanism is repeated in reverse when the cupola turns to the left. Since the direction sensor is composed of two switches which can only be either on or off, the command to initiate turret rotation is binary. This means that the turret is either turning, or it is not. For that reason, the turret always rotates at maximum speed when the target designation system is activated. This ensures that the gunner is cued to the target as quickly as possible. The the gun-laying precision of the turret at its maximum traverse speed is low, but that is irrelevant as the final lay is conducted by the gunner.<br />
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Because the cupola does not counter rotate as turret traverse is initiated, it may spin along with the turret as it rotates to meet the target cued by the commander, potentially causing him to lose his bearings. To prevent this, there is a simple U-shaped steel rung for him to brace with his right arm as he uses his left hand to designate the target. This wasn't as convenient as a counter rotating motor, of course, but it was better than nothing. The photo below shows the steel rung, as well as the toggle switch for the cupola's electrical systems (turns on power to TKN-3 and OU-3GK) next to the right part of the steel rung. The direction sensor is visible next to the left part of the steel ring.<br /><br />
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Overall, the commander's observation equipment and facilities saw a minor improvement over the T-54B and T-55, but overall it was not better than on tanks like the Leopard 1 or Chieftain. The target detection capabilities of a T-62 commander were significantly worse at very long ranges (exceeding 3 km) owing to the limitations of the 5x magnification of the TKN-2 or TKN-3, compared to the 6-20x magnification of the TRP-5 of the Leopard 1 or the 10x magnification of the No.37 periscope of the Chieftain. However, it is important to keep in mind that independent American, German and Polish studies and field exercises have shown that in Central Europe, there is hardly any open terrain wide enough for a line of sight to extend further than 2 km. In Western Europe, the maximum line of sight permitted by the terrain is even shorter.
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Sometime during the 1970's, a select number of tanks received a dust shield over the commander's hatch. It is a sheet steel face shield with a canvas skirt draping down. Being so thin, the dust shield is <i style="font-weight: bold;">not</i> bulletproof.<br />
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Nnot many T-62s received the addition though almost all T-72s did. The reason for this is unclear.<br />
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<h3>
<a href="https://www.blogger.com/null" id="gunstat"></a>
<span style="font-size: large;">GUNNER'S STATION</span></h3>
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A T-55 gunner will find himself in familiar territory upon sitting on the gunner's seat in a T-62. The gunner's thickly padded seat is not adjustable in height but it can be folded flush against the U-5TS gun recoil guard to enable both the gunner and commander to move to the driver's compartment or exit through the escape hatch in the tank belly, which is behind the driver's seat. The turret of the T-62 does not have a turret basket with a safety cage to isolate the turret crew from the hull, but the gunner has a footrest. As an alternative, the gunner could simply rest his feet on the the rotating floor, which may have to be done to free up space for the gunner to use the manual elevation and traverse handwheels without bumping his hands on his knees. In general, the gunner is in little danger of getting his feet caught on something in the hull as he is normally in control of turret traverse. Overall, the gunner's station is quite spartan - other than these features, there is no other furniture.</div><div><br /></div><div>As was, and still is common among manually loaded tanks, the gunner does not have a hatch of his own. Instead, he must ingress and egress through the commander's hatch. The biggest flaw with this layout is that if the commander is unconscious, incapacitated or killed, then the gunner will suddenly find it extremely difficult to leave the tank, especially under stress. The main advantage of the T-62 was that if the turret is facing forwards, the gunner may fold up his seat and crawl to the driver's station quite easily to exit through the driver's hatch. This is often impossible or extremely impractical in tanks with a turret basket.<br />
<br />The mounting frame for the gunner's seat, gunner's footrest, commander's footrest and the recoil guard is shown in the drawing on the right below. From the close proximity between the commander's footrest and the gunner's seat, it can be seen that the commander's knees would reach the gunner's back when both crew members are seated normally. On the one hand, the gunner is seated close to the lateral axis of the turret ring and as such, he gets to enjoy the full width of the turret ring, but on the other hand, the placement of the radio set below the turret ring (as opposed to the turret shelf next to the commander like in the T-54/55) takes up a large amount of horizontal space, although it is not intrusive. This can be seen in the drawing below.<br />
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<div><br /></div><div><br /></div>This detail is worth mentioning, because most NATO tanks had their radios located in the turret bustle and thus freed up space. It was for this reason that the gunners and commanders of T-62 tanks do not enjoy more space than their foreign counterparts despite the large difference in turret ring diameter. However, a T-62 gunner was better off in some other regards - because there is no turret basket, a T-62 gunner had satisfactory legroom and he could even stretch his legs in the empty space behind the driver's seat if the turret traverse was locked. This was not only impossible to do in a tank with a turret basket, but also problematic for certain tanks like the Leopard 1 as that had the large hydraulic reservoir and pump of its turret control system installed <a href="https://pp.userapi.com/c633919/v633919704/211b6/N721DeLhsDU.jpg">just in front of the gunner</a> which obstructed his right leg if he were to sit facing forwards, forcing him to sit twisted to the left. </div><div><br /></div><div>Unlike the T-55, the gunner in a T-62 has no backrest, but a leather backrest can be attached to a special loop on the turret ring to be stretched behind the gunner's back. Based on its design, it is clearly not as comfortable as a real backrest, but it would at least easier be to remove than the backrest of the seat in a T-55. If the leather backrest is not used, the gunner may simply use the commander's knees as his backrest, which is not particularly comfortable, but is also not unusual as this is also the case with several other tanks like the Leopard 1. The lack of a comfortable backrest for T-62 gunners is not a unique situation, and even in the M60(A1) which provides a bona fide backrest for the gunner, it was noted that there was insufficient back support.</div><div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-VWi6wdsnKGY/Xxl2qUIF6VI/AAAAAAAARUY/35wqjvw5tNwOUbJu0BqSjjPXzjX5jbu6ACLcBGAsYHQ/s1506/gunners%2Bseat.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1500" data-original-width="1506" height="399" src="https://1.bp.blogspot.com/-VWi6wdsnKGY/Xxl2qUIF6VI/AAAAAAAARUY/35wqjvw5tNwOUbJu0BqSjjPXzjX5jbu6ACLcBGAsYHQ/w400-h399/gunners%2Bseat.png" width="400" /></a><a href="https://1.bp.blogspot.com/-lYr_ngIcF-s/Xx_MoG7ahWI/AAAAAAAARXI/jTquOY9bx-AClhLncKufFdg_V1U44v_JwCLcBGAsYHQ/s752/gunners%2Bback%2Brest.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="723" data-original-width="752" height="385" src="https://1.bp.blogspot.com/-lYr_ngIcF-s/Xx_MoG7ahWI/AAAAAAAARXI/jTquOY9bx-AClhLncKufFdg_V1U44v_JwCLcBGAsYHQ/w400-h385/gunners%2Bback%2Brest.png" width="400" /></a></div><div><br /></div><div>
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Overall, the gunner's station is very well laid out and quite satisfactory in terms of ergonomics. Although it is still somewhat confining, it was not inferior to tanks like the Centurion and M60(A1) which had uncomfortable gunners' stations with small dimensions despite the tanks dwarfing the T-62 in external dimensions. In the report "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/627820.pdf">Human Factors Engineering Evaluation of the M60 Main Battle Tank</a>", it was detailed that "<i>The gunner's working area ... is very restrictive and extremely uncomfortable even for a short period of time</i>". Moreover, it was recommended in the report that "<i>The seat could be suspended from the side of the basket and designed to fold down and out of the way for easy access to and from the gunner's position</i>" - a feature that the M60(A1) lacked but was present in the T-62.</div><div><br />
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For extra visibility, the gunner has a single TNP-165 periscope pointed forward. The field of view from the periscope is 70 degrees. This periscope gives the gunner some additional awareness of the immediate area in front of the turret which can be important as the gunner is responsible for preventing the gun barrel from knocking into obstacles or digging into the ground. However, the TNP-165 for the gunner is more of a bonus than a necessity since the gunner's telescopic sight is installed on the same level as the axis of the gun barrel, so it is not difficult for him to see and control the gun to avoid damage. Rather, the TNP-165 periscope may be more useful for allowing the tank to be used more effectively in a turret-down position thanks to its high location on the turret roof. Having a telescopic primary sight mounted on the same level as the gun barrel means that the gunner cannot aim over the crest of a berm or hill when the tank is parked behind it, but by having a periscope on the turret roof just in front of the commander's cupola, the gunner is essentially given the same elevated view as the commander when the tank is in a turret-down position. The commander can use the target designation function of his TKN-3 optic when he sees a target, and the turret will be automatically traversed to face it and the gunner will be able to see it through the forward-facing TNP-165. After the gunner confirms visual contact with the target, he can look through his telescopic sight and wait until the commander gives the order for the driver to move forward. When the muzzle of the gun clears the crest of the berm or hill in front of the tank, the gunner can immediately acquire the target through his sight and open fire.<br />
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The periscope is also useful when the tank is not in combat as it gives the gunner some spatial awareness. Considering that the gunner does not have a hatch of his own, he is essentially stuck in his corner of the turret for the duration of any march which can quickly become tiresome.<br />
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In addition to all of the necessary switches and toggle buttons to activate this and that, there are also some other odds and ends at his station, including a turret azimuth indicator, which is used to orient the turret for indirect fire. It is akin to a clock, having two hands - the hour hand for general indication measured in 6000 mils, and the minute hand in 100 mil increments for precise turret traverse. Combined with the gunner's quadrant, the T-62 can conduct indirect fire.<br />
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<a href="http://3.bp.blogspot.com/-Tm-oFvb13z4/Vl2rvs36OLI/AAAAAAAAEhU/QxNw4AGH0l8/s1600/turret%2Bazimuth%2Bindicator.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="255" src="https://3.bp.blogspot.com/-Tm-oFvb13z4/Vl2rvs36OLI/AAAAAAAAEhU/QxNw4AGH0l8/s320/turret%2Bazimuth%2Bindicator.jpg" width="320" /></a></div>
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The azimuth indicator has an internal bulb that can be turned on to allow the gunner to read it at night.<br />
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<h3>
<span style="font-size: large;">SIGHTS</span></h3>
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<a href="https://www.blogger.com/null" id="tsh2b"></a><br />
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<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-hR1kC469EVA/VlAw2uGnoPI/AAAAAAAAEMs/Ja5BgAJD6gM/s1600/t-62%2Btsh2b-41u%2Bsight%2Baperture.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://3.bp.blogspot.com/-hR1kC469EVA/VlAw2uGnoPI/AAAAAAAAEMs/Ja5BgAJD6gM/s640/t-62%2Btsh2b-41u%2Bsight%2Baperture.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Telescopic sight aperture port, with nuclear attack seal in place</td></tr>
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The gunner is provided with either a monocular TSh2B-41 articulated telescopic primary sight and a TPN1-41-11 night sight. Because the sight aperture is just left of the gun barrel, there is a very high likelihood that it will be rendered inoperable if the turret takes a hit around the cutout for the sight aperture. A non-perforating hit on the cutout may create a big enough shock to knock the sight out of alignment or even crack the lenses, not to mention the disastrous effects of a direct hit on the aperture itself.<br />
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In terms of technological sophistication, the fire control system of the T-62 was fundamentally equivalent to the T-54B which was a tank from 1957. The fact that the TSh2B-41 sight itself was essentially a product belonging in the late 1940's was entirely inconsequential because there was no real advancement in this field anywhere in the world. On its own, the TSh2B series of articulated telescopic sights was excellent in terms of quality and interfaced well with the "Meteor" stabilizer of the T-62. Rather, the main issue that should be focused on is that the T-62 lacked an optical rangefinder of high accuracy such as those found on American tanks like the M48A2C (1956) and M60 (1959), which was the main shortcoming of earlier Soviet tanks. This is one shortcoming that it shared with tanks like the Centurion. The emphasis that is often placed on American tanks having a ballistic computer is rather misguided as the focus should really be on the lack of an optical rangefinder rather than the lack of a ballistic computer.<br />
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On the M48A2 and M60A1, the M13A1D ballistic computer was necessary to interpret the data from the optical rangefinder into a useful form. When the fire control system is operating normally, the range data from the measurement made by the commander is entered into the computer by the turning of the rangefinder coincidence adjustment dial to generate a firing solution based on the ammunition type entered by the gunner. If the rangefinder is not used or it is not working, another method of entering range data is to use a small manual range crank on the side of the computer housing, and if the gunner notices that the shots are missing the target, he can input small range corrections by turning a toothed knob next to the range indicator dial.<br />
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The main point in understanding this is so that it becomes completely clear that the M13A1D ballistic computer only accepts two inputs and generates one output: it accepts range and ammunition type data and generates sight superelevation data. It is not at the same level as a modern ballistic computer that generates a nuanced output using a much larger number of variables including crosswind speed, ambient temperature, atmospheric pressure, propellant charge temperature, gun bore wear level, and so on. In other words, the M13A1D ballistic computer fundamentally fulfills the same function as the range scales in any day sight. The only advantage of having the ballistic computer was that it handled range data more precisely than a human gunner could achieve by scrolling a range scale up and down against a fixed horizontal line, but due to the law of diminishing returns, the actual effect that this advantage had on the accuracy of fire was very limited when put in the context of the high velocity ammunition that had become standard by the 1960's.<br />
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In practice, the lack of an optical rangefinder in the T-62 did not stop it from outmatching M60A1 tanks largely thanks to the use of high velocity APFSDS ammunition, but also partly because of the large size of the M60A1 itself. Furthermore, a T-62 gunner could be expected to have a quicker target acquisition and reaction speed thanks to the presence of a gun stabilizer and the dependent stabilization of the TSh2B sight. Without a stabilizer of any sort, it was impossible for an M60A1 gunner to effectively scan the tank's surroundings when in motion and the time needed to prepare the first shot when firing on a short halt was much slower than a T-62. A detailed examination of this topic will be provided later in the section on the "Meteor" series of stabilizer of the T-62. For now, the gun sights and their relationship with the fire control system of the T-62 will be explored.<br />
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<h3>
<span style="font-size: large;">TSh2B-41, TSh2B-41U </span></h3>
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The TSh2B-41 is a monocular telescopic sight that functions as the gunner's primary sight for direct fire purposes. It has two magnification settings, 3.5x or 7x, and an angular field of view of 18° in the former setting and 9° in the latter setting. The magnification switch is located on top of the telescope housing. The TSh2B-41 also comes with a small wiper on the aperture window to clean off moisture and dust, and it comes with an integrated heater for defrosting. The sight has an internal light bulb that when turned on, illuminates the reticle for easier aiming in poor lighting conditions such as during twilight hours or dawn. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-BHq8a0Sgo6k/XxlfM0JngCI/AAAAAAAARTw/fPdw4yvqHuc_yQ7itprOGOIzm-6YPsaOQCLcBGAsYHQ/s3277/tsh2b-41.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="802" data-original-width="3277" height="156" src="https://1.bp.blogspot.com/-BHq8a0Sgo6k/XxlfM0JngCI/AAAAAAAARTw/fPdw4yvqHuc_yQ7itprOGOIzm-6YPsaOQCLcBGAsYHQ/w640-h156/tsh2b-41.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The glass was reportedly of superb quality and the insulation and shockproofing of the sight unit was sturdy enough to survive the blast wave of a nuclear explosion and ambient temperatures of over 200° C. There is an anti-glare filter inside the sight that can be applied or removed by toggling a switch on the side of the telescope housing. The anti-glare filter should only be used when looking directly at the sun, otherwise the filter washes out most of the colour and contrast, and darkens the image considerably, making it much harder to make out the shape of a camouflaged tank at long distance. The range adjustment wheel is located on the underside of the telescope housing. Turning the wheel turns a cardan shaft that leads to the articulated head of the sight which contains an elevating mechanism for the glass plate containing the viewfinder markings.<div><br /></div><div><br /></div><div>
<br />The design of the sight viewfinder was functionally identical to all other sights in the TSh2B series, with only the range scales being different to account for the unique ballistics of 115mm ammunition. It had all the prerequisite features of an early postwar sight, permitting both battlesight and precision gunnery with the use of the stadiametric ranging scale drawn in the sight viewfinder. </div><div><br /></div><div>For most engagements, where battlesight gunnery would be used, the gunner could aim at the roof of the target and open fire without requiring a range estimate, and have a fairly high probability of hit on account of the flat trajectory of 115mm APFSDS rounds. This method of battlesight gunnery does not take shot dispersion into account, which means that at the extremes of the shot trajectory, namely at the apogee and the end, the probability of hit is not more than 50% because there is a 50% probability that the shot will land short or go over the target.<br /></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-atJCPS2S_C8/YC3w6p25j1I/AAAAAAAASvQ/8h5dc5NEPpcqp7r3PFM8uPHnxcq-6xjCQCLcBGAsYHQ/s1671/direct%2Bshot%2Brange%2Bdefinition.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="555" data-original-width="1671" height="133" src="https://1.bp.blogspot.com/-atJCPS2S_C8/YC3w6p25j1I/AAAAAAAASvQ/8h5dc5NEPpcqp7r3PFM8uPHnxcq-6xjCQCLcBGAsYHQ/w400-h133/direct%2Bshot%2Brange%2Bdefinition.png" width="400" /></a></div><div><br /></div><div><br /></div><div>Against an M47, M48 or M60 series tank, all of which have a structural height of 2.3 meters (excluding the large cupolas), the point blank range of 115mm APFSDS is 2,000 meters. For comparison, the battlesight range taught to M60A1 gunners for their 105mm APDS rounds was 1,600 meters, based on the same concept of not having the apogee (maximum ordinate) exceed the height of the target. </div><div><br /></div><div>In the event of a miss, the design of the sight and its viewfinder permits the easy application of the burst-on-target gunnery technique, as the gunner is provided with ample lead markings to adopt new aiming points in deflection for misses due to wind, and he can lower the reticle by adjusting the range dial until the aiming chevrons meet the point of impact of the missed shot. By doing this, the gunner not only corrects in both deflection and elevation for a subsequent shot, but he also obtains range data as lowering the reticle will show him the range at which impact occurred on the range scales.</div><div><br /></div><div>
Below is the viewfinder of the TSh2B-41 sight:<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-51om5Tm1UX0/Vk8EuuG0ESI/AAAAAAAAEHA/a9iTkydIM6w/s1600/TSh2B-41%2Bsight%2Billustration.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="619" src="https://3.bp.blogspot.com/-51om5Tm1UX0/Vk8EuuG0ESI/AAAAAAAAEHA/a9iTkydIM6w/s640/TSh2B-41%2Bsight%2Billustration.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Range scales from left to right: APFSDS, HEAT, HE-Frag, Co-Axial Machine Gun</td></tr>
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<br /><br />When the gunner has obtained range data, he manually enters the necessary correction into the sighting system by turning a dial. The dial lowers the viewfinder glass plate, thus lowering the reticle in the gunner's view until the desired range lies on the fixed horizontal line. For instance, if the target is 1.6 km away, and the gunner wishes to engage it with high explosive shells, then he must turn the dial so that the notch marked "16" on the range scale for "OF" lines up with the fixed horizontal line. The aiming chevrons will drop by the same amount as the range scale, so that the gunner can then lay the center chevron on the target and open fire. <br /><br />
During the late 1960's, the glass plate containing the viewfinder markings were swapped out to include a separate range scale for the new and improved 3OF-18 HE-Frag shell. These sights were designated as the TSh2B-41U. The maximum direct fire distance of HEAT ammunition was increased to 3.7 km and the maximum direct fire distance for OF-18 and OF-11 shells were listed as 4.8 km and 3.6 km respectively.<br />
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<div><br /></div><div><br /></div><div>Compared to a good optical coincidence rangefinder with a wide optical base length, stadia rangefinding was rather imprecise, especially when used on partially obscured targets. <a href="https://pp.userapi.com/c844321/v844321705/107716/nRIn-UJ4UxM.jpg">British testing on the stadia rangefinder in the TLS (Tank Laser Sight)</a> installed in Chieftain tanks, identical in form and function to the Soviet type, showed that the average error, taken from three different sets of measurements, reached only 13.7%. The study included three series of tests on partially obscured targets. The average range measurement error for these targets reached 22-37%. When the measurements on the partially obscured targets are omitted from the data set, the average error plummets to merely 5.73%, 9.25% and 7.16%. The mean error across all three sets is 7.38%.</div><div><br /></div><div>Additionally, <a href="https://tankandafvnews.files.wordpress.com/2016/02/064.jpg">a British-Israeli report</a> covering the TSh2B-32 sight gives another valuable data set on the precision of stadia rangefinders. From the table in page 121 of the report (page 64 of the photo album), it is shown that the mean error in ranging tank-shaped screens, broadside tanks, oblique tanks and head-on tanks is 12.77% in the 7x magnification setting, degrading to 14.01% in the 3.5x magnification setting. The results of an analysis of the data were somewhat counter-intuitive. Page 122 of the report (page 65 of the photo album) mentions that the precision of rangefinding against hull-down tanks was surprisingly unaffected by the fact that half of the target was out of sight.</div>
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It is more difficult hitting targets with lower velocity ammunition like HE-Frag and HEAT shells, and even harder for moving targets. However, the inclusion of near-hypersonic APFSDS ammunition in the loadout of the T-62 greatly helped counterbalance this issue, making it markedly easier for the gunner to hit both stationary and moving tank-type targets, while most targets requiring HE-Frag shells like machine gun nests and pillboxes and other fortifications would be stationary anyway, thus making pinpoint accuracy on the first shot much less of a priority. On account of the extremely high speed of the APFSDS rounds fired from the 2A20 gun, the sight can be battlesighted at a very generous 1,000 m, allowing the gunner to confidently hit a tank of NATO-type dimensions in the open at any distance between 200 to 1,600 m by aiming at center mass without needing to ascertain the range beforehand. If the target is closer to 200 meters, the shot will land above center mass, i.e the turret. If the target is closer to 1,600 meters, the shot will land below center mass, i.e the lower hull.<br />
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Due to the "autoblocker" function of the "Meteor" stabilizer, the articulated aperture of the sight will raise along with the cannon when the loading procedure is underway. Depending on the location of the target, this can cause the gunner to (very annoyingly) lose sight of anything he is aiming at at the moment, thereby making the commander's the only pair of eyes to observe the 'splash' and give corrections or search for new targets. However, this can be bypassed if the gunner switched to the 3.5x magnification mode, whereby he will still be able to observe the 'splash' at the bottom part of the sight picture. He might also be able to get a glimpse at the bottom edge of his sight at 7x magnification, but this depends on the elevation of the cannon.<br />
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When on flat ground, the field of view of the sight on 7x magnification is almost always sufficient to maintain visual contact with a target even when the main gun is elevated by +2°30' (2.5 degrees) after each shot. This is immediately apparent if we split the 9-degree field of view of the sight into two halves: 4.5° degrees above the center point (the horizon), and 4.5° below. Raising the sight by 2.5 degrees leaves a 2-degree section between the horizon and the bottom of the viewfinder, where the target is visible. If the field of view is too small, the gunner can simply switch to the 3.5x setting with its 18-degree field of view. The raising of the sight together with the gun by 2.5 degrees will have a minimal effect on the gunner's ability to see the target after a shot.<br />
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Nevertheless, maintaining visual contact with the target through the sight would not possible if the T-62 is peeking over a reverse slope, and it would be very difficult if not practically impossible to do so if the tank is moving over rough ground. The "Meteor" stabilizer provided the loader with the option of turning off the autoblocker so that this would not become an issue, but turning off the autoblocker was not a real solution because the feature was designed as a safety measure for the loader. These complications led to the development of the independently stabilized TShS-41U.<br />
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<a href="https://www.blogger.com/null" id="tshs"></a>
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<h3>
<span style="font-size: large;">TShS-41U</span></h3>
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In the 1972 modification of the T-62, it was given the upgraded TShS-41U sight with electronic independent vertical stabilization of the sight by replacing the original mirror-based optical joint with a synchro-controlled prism. The sight entered mass production in 1971 and effectively replaced the older TSh2B-41, but because the mass production of the T-62 in the Soviet Union ceased in 1972, the T-62 obr. 1972 was the first and last T-62 model to have the TShS-41U installed from the factory.</div><div>
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In conjunction with the increased complexity of the sight compared to the basic TSh2B model, the control switches were made more accessible by grouping them onto a control panel behind the eyepiece of the sight. There are three toggle switches arranged in a row: one to turn on the independent stabilizer, one to turn on the sight heating system, and one to turn on the internal lamp to illuminate the viewfinder markings. The activation status of the independent stabilizer is signaled by a green indicator light above its switch. All of this can be seen in the two photos below.<br />
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The magnification switch, the lever for the light filter, and the aperture window wiper lever were all placed in the same locations as before. Underneath the control panel is the range adjustment wheel.<br />
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Unlike a true independent stabilizer, the synchro in the sight received angular input directly from the gyroscope of the "Meteor-M" stabilizer and allowed the prism to be moved independently relative to the gun. The synchro mechansim had a very poor mean vertical stabilization accuracy of 3 mils, but it only needed to be sufficiently accurate to maintain visual contact with a target as that was the design objective of the sight. When the "Meteor-M" stabilizer is set to the semi-automatic mode (powered controls without gun stabilization), the articulated head of the sight can elevate and depress by 15 degrees in each direction for a total range of vertical motion of 30 degrees, but due to the limited height of the cutout in the turret, the usable range of elevation is unchanged. The range of motion of the articulated head merely allows the eyepiece to be adjusted in height on its mount.<br />
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During normal operation with the gun stabilizer active, the TShS-41U sight remains stabilized by "Meteor-M" via the sight-follows-gun stabilization regime. The independent stabilizer is only activated under the condition that the gun autoblocker activates after a shot is fired (gun is hydrolocked at a fixed angle, turret rotation is locked). When the independent vertical stabilizer is active, the sight can independently elevate and depress by 5 degrees in each direction. The sight is elevated or depressed by the gunner using his control handles and the gunner can continue to observe through the sight within its own range of vertical motion of 10 degrees. This means that the T-62 gunner should be able to maintain visual contact with a target in the high magnification setting regardless of the orientation of the main gun while the tank is in motion over mildly undulating terrain. If the tank is travelling across rough terrain and oscillation of the tank exceeds a 10-degree vertical arc, the gunner can switch the sight to the low magnification setting and he may still be able to see the target. The stabilization of the sight returns to the normal regime once the gun autoblocker is turned off. Turning off "Meteor-M" also turns off the independent stabilizer of the TShS-41U because the gyroscopic sensor is powered down.</div><div><br /></div><div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhBgA5z0NU0SJ-mgx3F5aEU752Tm7FzT8cmxo16-vEt57wCXerqch8ZG8jBTwaQqLXJjubEYZhSHw_Fhq0ffZ_20Y_2TLuhDFqit9FAt1u3V18OuMjlaa4n6F6pUW3Rf2zdsCpNapgrLKkre1qyuevNUyp79pLN8cYD8RIhQns-wL3D4dwHOyDMA-NsOg/s3284/tshs-41u.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3284" data-original-width="2956" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhBgA5z0NU0SJ-mgx3F5aEU752Tm7FzT8cmxo16-vEt57wCXerqch8ZG8jBTwaQqLXJjubEYZhSHw_Fhq0ffZ_20Y_2TLuhDFqit9FAt1u3V18OuMjlaa4n6F6pUW3Rf2zdsCpNapgrLKkre1qyuevNUyp79pLN8cYD8RIhQns-wL3D4dwHOyDMA-NsOg/w576-h640/tshs-41u.png" width="576" /></a></div>
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Another improvement of the TShS-41U sight was the new rotary dial containing the range scales for all of the ammunition types as shown in the image below. This system was previously used on the TPS1 sight of the T-10A heavy tank in 1955. Instead of the ladder-type graduated range scales of the TSh2B-41, the scales are printed around the circumference of a rotating circular glass plate. This system indirectly improved the gunner's field of view by greatly reducing the amount of clutter in the upper half of the viewfinder, but more importantly, there were larger gaps between each graduation of the range scales and it became much easier to input an exact range setting. This was not difficult when HEAT and HE-Frag rounds were used, but due to the very flat trajectory of APFSDS rounds, the range scales would almost appear to be a solid black blob when the sight was used in the low magnification setting and the scales would appear very densely packed in the high magnification setting even though the markings were graduated by very large increments of 400 meters.</div><div><br /><br />
<a href="https://www.blogger.com/null" id="tshsd"></a>
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<span style="font-size: large;">TShSD-41U</span></h3>
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In conjunction with the development of the KDT-1 in 1974-75, the TShS-41U sight was modified with an internal digital readout linked to the laser rangefinder and a fixed crosshair for aiming the laser rangefinder, placed at the zero range position of the center chevron. This modification of the sight received the "D" suffix, becoming the TShSD-41U. There were two digital displays located in the lower edge of the sight viewfinder, one on top of the other. The top digital display displayed the range, and below it, a single-digit digital display indicated the number of returns received after ranging. Next to it was an illuminated indicator dot that signals when the laser rangefinder is ready to lase. </div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-wAePC9AYM2s/WD86xrQKa7I/AAAAAAAAHtQ/R0TUE3P7q509NECwVTKP66R6sbSr1lhcQCLcB/s1600/7cpTB.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="376" src="https://1.bp.blogspot.com/-wAePC9AYM2s/WD86xrQKa7I/AAAAAAAAHtQ/R0TUE3P7q509NECwVTKP66R6sbSr1lhcQCLcB/s640/7cpTB.jpg" width="640" /></a></div><div><br /></div><div>The sight did not automatically adjust the reticle or elevate the gun after lasing, so this integrated display was important for allowing the gunner to quickly read the measured range and then manually apply the correct ballistic solution without needing to break visual contact with the target. For comparison, the Chieftain Tank Laser Sight (TLS) No.1 Mk.1 and No.1 Mk.2 that appeared from 1976-1979 both had a separate digital readout in a special left eyepiece instead of being integrated into the sighting viewfinder of the right eyepiece. All together, this was even faster than using the stadia rangefinder. The mass production of this sight began in 1974 and it began deliveries to the troops alongside the KDT-1 on a wide scale.</div><div>
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<h3>
<span style="font-size: large;">KDT-1 LASER RANGEFINDER</span></h3>
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As part of the overall effort to bring the T-62 series up to modern levels of technology, the T-62 began to be fitted with the KDT-1 laser rangefinder in 1974 to 1975, coinciding with the decision to replace optical coincidence sights on the T-72 Ural with a laser rangefinder in the T-72 Ural-1 modernization project. The exact date of the beginning of the modernization programme is unclear, but Mikhail Baryatinsky writes in "<i>Т-62: Убийца «Центурионов» и «Олифантов»</i>" ("<i>T-62: Killer of Centurions and Olifants</i>") that the installation of the KDT-1 on some tanks began in 1975. </div><div><br /></div><div><br /></div><div>The rangefinder was mounted on top of the gun shield and was therefore parallel to the bore axis. Some tanks like the Chieftain, which also did not originally have a laser rangefinder and had one retrofitted at a later date, had it installed under armour. Having the rangefinder exposed outside the turret is no doubt a minor drawback, since it then becomes vulnerable to airbursting artillery shells or even the blast and fragmentation of a direct hit on the tank. The rangefinder is housed in an armoured box, and the armoured box offers protection against artillery and mortar splinters and small arms fire, but nothing more.<br />
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There is a control panel for the rangefinder system installed in its own special corner and the original control handles for the gunner were replaced with a new type from the "Meteor-M" stabilizer that had an additional trigger button for firing off the laser rangefinder. The KDT-1 and KDT-1-1 permit the gunner to obtain a range measurement almost instantaneously upon pressing the lasing button, on the right thumb handle of his control handles. The rangefinder will function only when its ready light is illuminated in the gunner's TShSD-41U sight, and the light goes out when the gunner releases the lase button. Only one measurement is made with each button press, regardless of how long the gunner holds the button. After each measurement, the laser rangefinder is ready for another lasing only after a delay of 3-5 seconds.<br />
<br />Under normal conditions, the rangefinder is started by turning on the power supply and then pressing the lase button after 1 minute (or up to 6 minutes at an ambient temperature of +50°C). The rangefinder ready light will illuminate in the TShSD-41U sight after 3-5 seconds to indicate that the rangefinder is ready to make a measurement. If, after readying the rangefinder, the gunner does not make any measurements for 3 minutes, the rangefinder is automatically turned off. The gunner must restart it by pressing the lase button again, and it will be ready after a 3-5 second delay.<br />
<br />The KDT-1 rangefinder features a Q-switched ruby laser (694 nm). The rangefinder had a maximum measuring distance of 4,000 meters and a minimum of 400 meters. The maximum margin of error in the measurement was 20 m and the average error was 10 meters. According to a 1981 Soviet essay titled "<a href="http://btvt.info/5library/vbtt_1_1981_t_54_62.htm"><i>Из Опыта Совершенствования Основных Танков В Ходе Серийного Производства</i></a>", the installation of the KDT-1 on the T-55A obr. 1975 resulted in an increase in the effective range of subcaliber and HEAT rounds by 10% and 15% respectively. Also, the time needed to fire the first shot was decreased by 10%, or in other words, the reaction time of the tank was shortened by 10%. The same level of quantitative improvement should be expected for the T-62 as its fire control system is functionally the same as that of a T-55A.<br />
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Having a laser rangefinder in 1974 was a significant advancement for the time. The best that the Leopard 1 series had at the time was the EMES 12A1 with a stereoscopic rangefinder which could be found on the Leopard 1A4 model built in 1974, while the laser rangefinder of the TLS sight that began being installed in some Chieftain was not combat-ready, requiring reliability improvements in the late 1970's to become viable. Only the M60A2 had a fully functional laser rangefinder, being the first serial tank to receive one. However, the M60A2 itself was a failure.</div><div><br /></div><div>The presence of the rangefinder is most helpful when firing on non-tank targets like bunkers and fixed fortifications including machine gun nests and anti-tank weapon emplacements, as these targets cannot be ranged with a stadiametric rangefinder, yet they comprise the majority of the targets that a tank would be called upon to eliminate. </div><div><br /></div><div>Additionally, the high velocity of 115mm APFSDS ammunition makes up for the lack of rangefinder in the fire control system at short to medium ranges, but not so much at longer ranges. The presence of a laser rangefinder further improves the accuracy of the tank at medium ranges, and greatly fortifies long range accuracy, making it possible to more confidently engage tank-type targets with less time. Consequently, a T-62 equipped with a laser rangefinder is considerably more likely to win a duel against a contemporary foreign tank.</div><div><br />
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<a href="https://www.blogger.com/null" id="tpn"></a>
<span style="font-size: large;">TPN1-41-11</span></h3>
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The TPN1-41-11 is a monocular periscopic night vision sight located on the turret roof just in front of the commander's cupola. It is a TPN1 sight adapted for the T-62, for which it received the 41-11 suffix. The sight has a fixed magnification of 5.5x and a field of view of 6°. It could operate in the active infrared imaging mode or the passive mode, but in either case it must be powered on to be used at night as the night vision system for both modes rely on an image intensification system. </div><div><br /></div><div>The separation of the night sight from the day sight is an important feature of the T-62 sighting system. If the tank is denied its night fighting advantage by the enemy's use of illumination rounds to blind friendly forces, it is possible for the gunner to immediately switch to the day sight. Similarly, the commander can switch to the daylight mode on his TKN-3 by simply flipping a switch. </div><div><br /></div><div>Powering on the sight is done by flipping a toggle switch on the BT-6-26 power supply unit on the turret wall, above the manual traverse handwheel. The TPN1 utilizes a single S-1 photocathode held at 18 kV. The large aperture window of the sight is instrumental in ensuring a long viewing distance as it collects a large amount of light to be reflected into the converter tube before it is magnified by the eyepiece optical group, and then finally displayed to the gunner. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-gKe-mXYOQb8/XzwgqGpv1TI/AAAAAAAARfM/Sjw2mvoAMMc78Q-ItNmPecOE6Cc_1ADywCLcBGAsYHQ/s1455/tpn1%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1455" data-original-width="1431" height="400" src="https://1.bp.blogspot.com/-gKe-mXYOQb8/XzwgqGpv1TI/AAAAAAAARfM/Sjw2mvoAMMc78Q-ItNmPecOE6Cc_1ADywCLcBGAsYHQ/w393-h400/tpn1%2Bcross%2Bsection.png" width="393" /></a><a href="https://1.bp.blogspot.com/-LtJPaGqS5Ko/XzwgqFok75I/AAAAAAAARfQ/xx31gO0rlMsUDfiUNt2t_U5YHLmopXqRwCLcBGAsYHQ/s1340/tpn1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1340" data-original-width="1339" height="400" src="https://1.bp.blogspot.com/-LtJPaGqS5Ko/XzwgqFok75I/AAAAAAAARfQ/xx31gO0rlMsUDfiUNt2t_U5YHLmopXqRwCLcBGAsYHQ/w400-h400/tpn1.png" width="400" /></a></div><div><br /></div><div><br /></div><div>In the active mode, the TPN1 works in tandem with the L-2G "Luna" IR spotlight which is coaxially linked to the cannon via a mechanical linkage. When the spotlight is turned on, a dim red lamp on the turret ceiling is also turned on to alert the crew that the tank is emitting light to remind them of the unmasking factor. The infrared light supplied by the spotlight is converted by the sight and amplified by the image intensifier tube, allowing the gunner to identify a tank-type target at distance of around 800 meters, which is not outstanding, but not worse than its immediate counterparts. This figure is corroborated by the U.S Department of the Army Operator's Manual for the T-62, which notes on page 3-12 that the L-2G spotlight provides the gunner with ability to successfully engage targets at a range of 800 m.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-j7PeG4zGHz4/XzwejwvJqbI/AAAAAAAARfE/A0I3bQD_bSU63cu-ryq4KFgEinHReAnTgCLcBGAsYHQ/s1438/spotlights%2Bon.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1048" data-original-width="1438" height="291" src="https://1.bp.blogspot.com/-j7PeG4zGHz4/XzwejwvJqbI/AAAAAAAARfE/A0I3bQD_bSU63cu-ryq4KFgEinHReAnTgCLcBGAsYHQ/w400-h291/spotlights%2Bon.png" width="400" /></a><a href="https://2.bp.blogspot.com/-vAsQWyj218Y/VtFn4DbmIpI/AAAAAAAAGCs/By58bfjldv0/s1600/132.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="244" src="https://2.bp.blogspot.com/-vAsQWyj218Y/VtFn4DbmIpI/AAAAAAAAGCs/By58bfjldv0/w400-h244/132.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>In the passive mode, its image intensification system achieves a nominal maximum identification distance of no less than 400 meters for a tank-type target under lighting conditions of no less than 0.005 lux, corresponding to a cloudless, starlit night. This level of performance was only matched almost two decades later in 1977 by the M60A1 RISE Passive with the M32E1 passive sight, which allowed tanks to be identified from a distance of not less than 500 meters in starlight conditions without illumination, as stated in the report "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a141935.pdf"><i>M60A1, M60AI RISE, and M60A1 RISE (Passive) Series Tanks, Combat, Full-Tracked 105-MM Gun - Update System Assessment</i></a>". This is despite the use of a newer <a href="https://tubedata.wernull.com/sheets/132/t/TH9655.pdf">S-20ER</a> multialkali photocathode (ER - extended red response) instead of the older 6914 series S-1 of the M32 sight. The very minor advantage of the M32E1 sight can be attributed to the shortcomings of the S-20ER photocathode, as it is still a Gen 1 photocathode and is very similar to older photocathodes in terms of resolution degradation at the edges of the image (4-5 times worse than at the center) despite the presence of an MCP, and the gain is not better than that of the S-1 photocathode in a TPN-1. The resolution of the S-20ER photocathode is 32-35 lp/mm, no higher than an S-1 photocathode.</div><div><br /></div><div>The intensity of the image can be adjusted by changing the voltage, which can be done by turning a dial on the sight. When in use, the gunner turns the dial until the image he sees has maximum contrast. As with the TKN-3, and indeed any optronics using light intensification, the viewing distance and resolution increases as ambient light intensity increases, but only up to a certain point before the sight is oversaturated and can no longer produce a legible image.<br />
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The diagram below, taken from the U.S Department of the Army Operator's Manual for the T-62, shows the reticle for TPN1-41-11. Note that the tip of the top vertical bar is calibrated for 800 meters for APFSDS (marked 'APDS' in the diagram) This is the nominal maximum viewing distance afforded by the sight in the active infrared mode, and is also a convenient battlesight distance. The gunner can use this aiming point to engage any target he sees through this sight in the active infrared mode and be assured that the shot will definitely hit.<br />
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Turning on the L-2 IR spotlight will also turn on a red tinted light bulb near the roof of the turret. This gives the gunner's station an ominous red glow and informs him of the activation of the spotlight. The sight has an internal lightbulb which facilitates aiming at night.</div><div><br /></div><div><br />
The spotlight is installed on a raised bracket with a hinged base, connected to the main gun to maintain coaxiality with the night sight. Besides having the spotlight beam level with the night sight aperture window, the rationale for having the spotlight on a raised mount appears to have been to allow the gunner to use the spotlight for illumination when scanning for targets in a turret defilade position, with both the spotlight and the night sight head peeking over cover. This is illustrated in the drawing on the right below. Vision in a turret defilade position is not necessarily the only situation where a raised spotlight would be beneficial, as having a raised spotlight may also help ensure that the beam is not blocked by bushes and other short obstructions. At the same time, because the commander is seated behind the gunner, his forward view is not obstructed by the spotlight. The spotlight does, however, still obstruct the commander's vision in the 2 o'clock sector to some extent. This is a side effect of the low profile of the commander's cupola, shared by other tanks with a low profile commander's cupola such as the Leopard 1 and the Centurion variants with night vision equipment. These two examples have the same sight and spotlight layout as the T-62, but mirrored left to right.</div><div>
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<div><br /></div><div><br /></div>Tanks that have the spotlight installed at the same level as the main gun, such as the T-64, T-72, Chieftain and AMX-30, do not possess the ability to use their spotlights from a turret defilade position. <br />
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The mounting frame for the L-2 spotlight for a Tiran 6 is shown in the photo on the left below (courtesy of Carl Dennis from Prime Portal). The spotlight is affixed to the frame at the four corners with bolts, and the large hole in the middle of the frame is for the power cable for the spotlight. The back of a partially dismantled L-2 spotlight can be seen in the photo on the right below.<br />
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TPN1-41-11 is mechanically linked to the TSh2B-41 and does not have independent stabilization. As such, just like the TSh2B-41, its range of vertical motion is limited and depends on the range of elevation afforded by the cannon, which is -6° to +16°.<br />
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One of the tactical advantages granted by the TPN1 sight compared to the infrared night vision sights that came later for the Chieftain and M60A1 was the fact that the TPN1 had a fixed installation at a permanent position in the turret. The sight could be boresighted once and it did not need to be calibrated again unless it was uninstalled, but that would be a rare contingency in field conditions as the sight would never need to be replaced even after suffering damage to its head assembly. The armoured hood could be simply unbolted and the head replaced without disturbing the sight itself, thus retaining its calibration with the main gun.<br />
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On the Chieftain and M60A1, it was somewhat different. As dusk approached, the tank had to be in a safe location away from any possible enemy forces and the gunner had to dismount the periscopic primary sight, stow it, and replace it with the L1A1 or L4A1 (in the Chieftain) or M32 (in the M60A1) infrared night sight which would need to be boresighted. This process was time-consuming and additionally caused the primary sight to lose its calibration, so when the gunner had to replace the night sight with the primary sight after dawn, he needed to spend more time calibrating the primary sight before the tank can begin a daytime operation.<br />
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<h3>
<a href="https://www.blogger.com/null" id="volna"></a><span style="font-size: large;">"VOLNA" FIRE CONTROL SYSTEM (T-62M)</span></h3>
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The T-62M introduced in 1983 came with an entirely new "Volna" fire control system. "Volna" is a comprehensive fire control system overhaul. All of the original components of the T-62's fire control system have been replaced, and some new technology has been added, including the KDT-2 laser rangefinder, the BV-62 analog ballistic computer, the new TShSM-41U sight, and all of the necessary electrical equipment like the 9S831 transformer to adapt the new technology to the tank's electrical system.<br />
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The addition of the BV-62 ballistic computer vastly reduces the amount of guesswork involved in the gunnery process. The gunner can manually input five ballistic variables, which are: the gun chamber temperature, ambient temperature, crosswind speed, atmospheric pressure, and the amount of barrel wear. These variables are not normally changed during combat. Information on the ammunition type is entered via a dial switch on the TShSM-41U sight. This makes the switch easily accessible to allow this routine task to be carried out conveniently.</div><div><br /></div><div><br /></div><div>
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<div><br /></div><div><br /></div>The gunner may set the ballistic computer to operate in either the automatic mode or the semi-automatic mode. BV-62 operates in the automatic mode by default. In this mode, it uses range information from the laser rangefinder and combines it with the other five variables to calculate a ballistic solution in the form of a servo control command to lower the aiming mark in the TShSM-41U sight by the appropriate amount. To switch the ballistic computer to the semi-automatic mode, the gunner turns the dial switch (marked '5' in the drawing below) from the "AVT" position to any of the other positions. This manually sets the range in 1000-meter increments from 0 meters to 3000 meters, and the potentiometer (marked '4') sets the range in 100-meter increments up to 1000 m. The ballistic computer does not accept data on the ambient temperature and atmospheric pressure when operating in the semi-automatic mode. The semi-automatic mode is only used in emergencies, such as if the laser rangefinder stops working.<br />
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The limitations of the system are numerous, the most obvious one being the need to manual input all of the aforementioned ballistic variables. The T-62M was not equipped with wind, temperature and atmospheric pressure sensors, nor was it equipped with sensors to determine gun chamber temperature or an electronic recording system to automatically calculate barrel wear. In order to enter the proper inputs into the ballistic computer, the gunner or commander must first calculate the correct values using a nomogram printed on the recoil guard. The amount of barrel wear can be estimated by meticulously recording the number of shots fired through the barrel, but exact information can only be known when the barrel is serviced using special instrumentation that is not carried in the tank.<br />
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Overall, "Volna" cannot be considered a cutting edge product for the 80's. Rather, it could be considered a cost effective modernization to raise the fighting capabilities of an old and outdated tank up to the level of the T-72B, although this is not entirely accurate either as some of its systems were developed in parallel with the 1A40-1 FCS. For instance, the "Svir" missile system installed in the 1A40-1 FCS of the T-72B was developed alongside the "Bastion" system for the T-55 and T-62 and shares the same technology as well as the same guidance equipment in the form of the 1K13 sight. The night fighting capabilities of a T-62M would also be on par with a T-72B thanks to the inclusion of the 1K13 sight.<br />
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<a href="https://www.blogger.com/null" id="tshsm"></a>
<span style="font-size: large;">TShSM-41U</span></h3>
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TShSM-41U is a further improvement over the TShSD-41U that brings up the sighting system of the T-62 up to the level of a baseline main battle tank like the T-64A or T-72, as per the design goal of the T-62M modernization. Externally, the TShSM-41U sight can be distinguished from the earlier TShS and TShSD models by the relocation of the control switches to a rectangular panel that is much closer to the eyepiece. Like the TShS sight, there are three toggle switches arranged in a row: one to turn on the independent stabilizer, one to turn on the sight heating system, and one to turn on the internal lamp to illuminate the viewfinder markings. The activation status of the independent stabilizer is signaled by a green indicator light next to the eyepiece.<br />
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One of the primary improvements was the possibility of automatically forming a ballistic solution in conjunction with a ballistic computer immediately after lasing a target. Moreover, the sight featured a new vertical stabilizer with a maximum stabilization error not exceeding 0.6 mils. The sight has two magnification settings, 3.5x or 6.9x, with an angular field of view of 18° in the former setting and 9° in the latter setting. Moreover, the sight communicates with the "Meteor-M1" stabilizer to determine if the point of aim is within the range of vertical motion of the main gun. If not, the electric firing circuit of the U-5TS cannon is disconnected and the gun readiness indicator light in the viewfinder of the sight is switched off.<div><br /></div><div>The photo below, published by the Padikovo museum in Russia, shows the view of a TShSM-32PV from the gunner's perspective. The TShSM-32PV is used to represent a TShSM-41U, as the two are almost indistinguishable externally. The control panel on the sight, located just under the eyepiece, features toggle switches to turn on the independent stabilizer, one to turn on the sight heating system, and one to turn on the internal lamp to illuminate the viewfinder markings. There is also a dial switch on the right of these toggle switches to select between APFSDS, HEAT and HE-Frag in the ballistic computer. The other controls of the sight remain the same as in the preceding models.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-b3hubleyzLU/Xr4zFkG30jI/AAAAAAAAQus/iKG71fO6HFkcWZ2wUMAezNK0gqrNbGTAgCK4BGAsYHg/tshsm-32pv%2Bin%2Bt-62m.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1365" data-original-width="2048" height="266" src="https://1.bp.blogspot.com/-b3hubleyzLU/Xr4zFkG30jI/AAAAAAAAQus/iKG71fO6HFkcWZ2wUMAezNK0gqrNbGTAgCK4BGAsYHg/w400-h266/tshsm-32pv%2Bin%2Bt-62m.jpg" width="400" /></a></div><div><br />
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Like the preceding models, TShSM-41U had dependent stabilization with a sight-follows-gun stabilization regime. The sight worked in conjunction with the "Meteor-M1" stabilizer. When the vertical stabilization is active, the sight can move by 15 degrees in both elevation and depression for a total range of vertical motion of 30 degrees. This was a major upgrade over the TShS series of sights. The independent stabilizer of the sight activates under two conditions: like the TShS-41U, it will activate if the gun autoblocker activates after a shot is fired, and it will also activate if the gun reaches the limits of its elevation and depression. For example, if the T-62 crests a hill with a slope of 15 degrees, the gun stabilizer will not be able to keep the gun aimed at the target due to its depression limit of -6 degrees but the TShSM-41U sight will enable the gunner to maintain a line of sight to the target. In this condition, the electric firing circuit of the main gun is disconnected as the line of sight of the TShSM-41U has exited the depression limit of the main gun. If the "Meteor-M1" stabilizer is switched to the semi-automatic mode (powered controls without stabilization), then the TShSM-41U sight can be aimed beyond the limits of the main gun in both elevation and depression using the control handles.<br />
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<div><br /></div><div><br />The viewfinder markings in the sight were identical to the TShSD-41U in layout with the exception that the digital range readout was changed to a target lead readout, and an additional indicator light for the integrated semi-automatic target leading system was added, marked (15) in the drawing below. The main gun readiness indicator light is marked (14), the laser rangefinder indicator light is marked (16), the digital lead readout is marked (18) and the readout for the number of laser returns is marked (17). The readout for the number of detected returns goes up to 3, and the three digital readouts of the lead display show a 2-digit mil value, preceded by a positive (+) or negative (-) prefix to indicate the direction that the gunner must lead the target. The number of detected returns indicates the number of discrete returns detected by the laser rangefinder during a single lase. Normally, these would be bushes, trees, mounds, rocks and other natural objects located behind or in front of the intended target.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Cb-PdM0sKG8/XTq2py7wm7I/AAAAAAAAOmU/hzMvi-sR4KEjY2drsXMZXCi9saysTb0nwCLcBGAs/s1600/tshsm-41u.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="343" data-original-width="398" src="https://1.bp.blogspot.com/-Cb-PdM0sKG8/XTq2py7wm7I/AAAAAAAAOmU/hzMvi-sR4KEjY2drsXMZXCi9saysTb0nwCLcBGAs/s1600/tshsm-41u.png" /></a></div></div><div><br /></div><br />
The gun laying system is semi-automatic, meaning that the aiming chevron drops vertically when a ballistic solution is obtained and the gunner must manually raise the chevron onto the target to apply the correct superelevation angle to the main gun. The ballistic solution is calculated by the BV-62 ballistic computer with input from the KDT-2 laser rangefinder. The ammunition type is selected by the gunner via a selector dial on the BV-62 control panel, and the selection will influence the amount of drop for the chevron to match the ballistic profile of the ammunition selected. After the range data has been acquired, the BV-62 computer can also calculate the necessary amount of lead for moving targets with two possible ammunition types - APFSDS or HEAT - at any distance from 800 to 1,800 meters. </div><div><br /></div><div>To calculate lead, the gunner first lase the target and then he must press the right thumb trigger and begin to track the target using either the crosshair or the center chevron. The lead indicator light turns on and the BV-62 computer begins to calculate the required lead according to the ammunition type selected, the range to the target determined by the laser rangefinder, and the angular speed of the target as determined by the sustained traverse rate of the turret. When the system has computed a lead solution, it is displayed in the digital display and the gunner can proceed to carry out a final lay. </div><div>
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Needless to say, although it is markedly better than manual lead estimation, this process is rather unrefined compared to the fully automatic lead calculation system implemented in the M60A3 fire control system, making it is easier for the gunner to make mistakes and thus skew the lead calculation. This restricts the usefulness of the feature, which is reflected in its relatively short maximum range of 1,800 m. Nevertheless, as long as the range to the target does not exceed this range limit, the acceptable margin of error is naturally quite high when firing at moving targets due to the very high velocity of 115mm APFSDS ammunition. The narrow range limit of 800-1,800 meters for lead calculation is generous enough for typical tank engagement ranges in a European theater, but not more. At 800 meters or less, lead calculation is simply unnecessary. </div><div><br />
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<span style="font-size: large;">KDT-2</span></h3>
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<a href="http://4.bp.blogspot.com/-yjgE7c4-npU/Vm8ZwAfw_BI/AAAAAAAAFAI/TgoBa9oOzuM/s1600/ktd-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://4.bp.blogspot.com/-yjgE7c4-npU/Vm8ZwAfw_BI/AAAAAAAAFAI/TgoBa9oOzuM/s400/ktd-2.jpg" width="400" /></a><a href="http://2.bp.blogspot.com/-ZuKE-dSwa_I/VmRLV01P3II/AAAAAAAAEtI/1GfikKSLiMQ/s1600/ktd-2%2Blaser%2Brangefinder.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="263" src="https://2.bp.blogspot.com/-ZuKE-dSwa_I/VmRLV01P3II/AAAAAAAAEtI/1GfikKSLiMQ/s400/ktd-2%2Blaser%2Brangefinder.jpg" width="400" /></a></div>
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The KDT-2 laser rangefinder utilizes an Nd:YAG laser in the 1,064 nm wavelength. This grants it better performance in poor weather conditions and reduces the probability of false returns compared to KDT-1 and KDT-1-1. The KDT-2 has a minimum measuring distance of between 500 to 4000 meters under clear meteorological conditions. The armoured cover on the aperture of the rangefinder is opened automatically when the gunner presses the trigger button to lase his first target. The cover remains open until manually closed. </div><div><br /></div><div>For sustained use, KDT-2 requires around 6 seconds between each lasing to prevent overheating, but it is not harmful to trigger the laser rangefinder in intervals of 3 seconds for short periods. The rangefinder is rated for 240 laser firings in a 4 hour period. Range data is displayed inside the TShSM-41U sight, but there is a separate digital display on the rangefinder control panel, as seen in the screenshot below (taken from this <a href="https://www.youtube.com/watch?v=kAP1vSOu9Ak">video</a> by RedcarUSSR channel).<br />
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Besides showing the range measurement, the control panel also has a target selector and a display to indicate the selected target on its left side. As mentioned before, the KDT-2 rangefinder has a range filter. It can receive up to three separate returns and record their range data with each lasing within the internal memory of its control unit, and the gunner can choose one of the three returns using the control panel. The number of detected targets varies because the single laser beam pulse from the rangefinder may reflect off of multiple objects behind or in front of the intended target. </div><div><br /></div><div>On the right side of the control panel, there is a system readiness indicator light in the upper right corner and a range filter display in the lower right corner. The drawing below is taken from <a href="http://www.kotsch88.de/f_t-55am.htm">the website of Stefan Kotsch</a>.<br />
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<br />Additionally, the KDT-2 also features a range filter. By selecting between the '1400' or '2400' settings, the rangefinder computer will filter out all range measurements of less than 1,400 meters or 2,400 meters. In normal operation, the rangefinder automatically filters out measurements below 500 meters, which constitutes the minimum range of the system. This is a necessary contingency because there may be circumstances where environmental factors strongly influence the range reading, and if the gunner notices that the range data received from the rangefinder is obviously incorrect based on his own visual range estimate, then he can switch on the range filter to discard bad measurements and thus obtain a more accurate reading.<br />
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The drawing below shows the interior of the armoured box for the laser rangefinder.<br />
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<span style="font-size: large;">AUXILIARY SIGHTS</span></h3>
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All T-62M tanks received the 1K13-2 to replace the TPN1-41-11 except the variants built without a missile launching capability. These variants are known as T-62M1 tanks.<br />
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<a href="https://www.blogger.com/null" id="1k13"></a>
<span style="font-size: large;">1K13-2</span></h3>
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The 1K13-2 is a combined day/night monocular periscopic sight which introduced the ability to guide new gun-launched anti-tank guided missiles like the 9K116-1 "Sheksna". It is one of several components integral to the 9K116-1 anti-tank guided missile complex. Besides the sight itself, the 9K116-1 complex also includes the missile control computer, the 9S831 transformer, and a power supply unit. The locations of these four components are shown in the drawing below. 1K13-2 also serves as the night vision sight for the T-62M and can also serve as an auxiliary daytime sight.<br />
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The sight is claimed to provide a maximum identification range of 5,000 m on a tank-type target in the daytime mode under its 8x magnification, but of course, the actual distance depends on meteorological and geographical conditions more than anything. Like the TPN1 sight, the night vision system of the 1K13-2 sight can operate in the passive or active modes. The range of vision in the active night vision mode is improved over the TPN1 thanks to the replacement of the old L-2G incandescent IR spotlight with the new L-4 xenon arc lamp IR spotlight. The night vision channel of the sight has a 5x magnification in either of the two modes. The sight enables the gunner to detect a tank-type target at nominal maximum range of 800 meters in the passive mode under lighting conditions of no less than 0.005 lux. Alternatively, the identification distance can be as high as 1,100 m in the active mode under illumination from the new L-4 IR spotlight. The sight has an internal light bulb that illuminates the reticle to facilitate aiming at night.<br />
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In contrast to all of the previous sighting complexes, the 1K13-2 sight has two-plane stabilization. The accuracy of stabilization while the tank is on the move at 15 km/h is 0.15 mrad in the vertical plane and 0.2 mrad in the horizontal plane. The presence of independent stabilization means that the gunner maintains control of the elevation of the sight while the gun is elevated by +2°30' during the loading process.<br />
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The sight can only be used to guide GLATGMs in the daytime mode, though it is possible to use the daytime mode during both day and night. At night, effective use of the GLATGMs necessitates target area illumination by external means, such as artillery-delivered illumination shells.<br />
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Overall, the "Volna" fire control system offers greatly improved combat performance compared to the basic fire control system of the basic T-62 model, but the abilities of "Volna" inherently do not exceed the capabilities of the TPD-K1 sight installed on the T-72A, but the design goal of bringing the capabilities of the T-62 up to the level of a baseline main battle tank such as the T-64A or T-72 was fully achieved. However, even with "Volna", one cannot seriously consider the fire control system of the T-62M to be superior to the Leopard 1A4 (built from August 1974 to March 1976) or any contemporary tank from the early 1980's. Again, it should be reiterated that the T-62M modernization was only a cost effective measure to bring the fighting capabilities of an obsolescent tank up to a useful level, and it is a complete success in that regard.<br />
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<span style="font-size: large;">LOADER'S STATION</span></h3>
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From 1961 to 1970, the loader's hatch built into the T-62 turret was large and circular in shape. It was slanted so that it followed the curving contours of the turret roof, so as not to obstruct the commander's view to the right, and to maintain the protective form of the turret. Beginning in May 1970, a DShKM anti-aircraft machine gun began to be installed on the loader's hatch. This required a level circular ring mount to operate, so the loader's part of the turret was renovated and a rotatable cupola was added. The area of the turret around the loader's station lost its dome shape to accommodate this new cupola. The thickness of the loader's hatch was 25mm on the original T-62 turret and remained the same thickness when the cupola was added. The loader's new hatch became an irregular semicircle of around half the size of the old type, roughly equivalent to the commander's hatch, making it around half as easy for the loader to enter or exit the tank, especially with bulky clothing. This design is a compromise, balancing the hatch size for a guarantee of usability, as it ensured the possibility of opening the hatch with the anti-aircraft machine gun present on its mount regardless of elevation angle. An alternate compromise was used in the original T-54 loader's cupola, featuring a full diameter hatch with the machine gun mount shifted forward, outboard of the cupola ring. With this design, the loader's hatch could not be opened or closed if the machine gun is positioned normally because the elevation mechanism overhangs the hatch, which complicates the procedure of its use. The machine gun mount must either be traversed away in the transport position, increasing the time needed to ready the weapon to fire, or fully elevated so that the elevation mechanism and spade grips on the machine gun clear the hatch, which raises the silhouette of the tank and greatly increases the danger of getting the machine gun caught on tree branches and overhead bridges. Both options have their own set of merits and demerits, with no clear advantage over the other. </div><div>
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There are two variations of the same loader's cupola on the T-62. Existing T-62 tanks had the loader's hatch area cut off and replaced by a new cast cupola by welding as an add-on structure, whereas T-62 tanks built from May 1970 and onward had a modified one-piece turret with a structurally integral cupola for the loader. Older tanks without the loader's cupola would also receive it when modernized to the T-62M standard. An example of a T-62 with an integral cupola can be seen in the photo on the left below, and the photo on the right below shows a modernized T-62 with a weld-on cupola. <br />
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To conserve space inside the tank, the ammunition boxes for the external DShKM machine gun are stowed externally on the side of the turret with clips. This also makes it easier for the loader to reload the machine gun as he can simply reach down to retrieve a fresh box instead of going back inside the tank and it is not easy to come out of the hatch with a large box of 12.7mm rounds (which weigh 11 kg each) as the hatch is rather small. The disadvantage is that the boxes can be damaged by artillery splinters and gunfire.
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For general observation purposes, the loader is provided with a single MK-4S periscope with a rear view feature. It can be elevated and depressed or rotated 360 degrees for all-round vision, although the geometry of the turret and position of the L-2 spotlight blocks out a large portion of the loader's field of vision. Officially, the total field of view from the MK-4S periscope is 250 degrees measured from the 9 o'clock position to the 5 o'clock position, which is quite good. However, granting forward vision to the loader is often considered superfluous given that both the gunner and commander would be looking forward and observing the target anyway. As such, the loader should be focused on scanning the right side of the turret instead. Even so, a periscope is generally not very useful in combat as the loader must concentrate on his loading duties, and in the case of the T-62 as well as all other Soviet tanks, the loader must also occasionally reload the coaxial machine gun as it is fed from individual 250-round boxes instead of a large container with a continuous belt. The loader would generally be much more useful if he spent his spare time to rearrange the ammunition supply of the tank into the ready racks instead. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-k0WFbaMjo_c/X2q3l_xXbPI/AAAAAAAARpo/_Zx75mxsDIojkRuQUTi_N7FfKHJEG3KDACLcBGAsYHQ/s914/mk-4%2Bperiscope.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="914" data-original-width="877" height="400" src="https://1.bp.blogspot.com/-k0WFbaMjo_c/X2q3l_xXbPI/AAAAAAAARpo/_Zx75mxsDIojkRuQUTi_N7FfKHJEG3KDACLcBGAsYHQ/w384-h400/mk-4%2Bperiscope.png" width="384" /></a></div><br /><div><br /></div><div>The loader's spring-loaded seat can be installed on one of two possible positions on the turret ring. It is adjustable for height in three positions and the spring-loaded hinge automatically folds up the seat when the loader is not sitting on it. Furthermore, the entire seat frame can be folded up and fixed to the turret wall with a wing bolt. If it is still in the way, the loader can simply remove the seat and stow it away somewhere non-intrusive. The seat provided for the loader is meant for marches only as he performs his duties standing. The loader can choose to be seated facing forward or facing the cannon breech. The former option is the most comfortable as the loader can stretch his legs for long journeys and the loader can stand on his seat to peek out of his hatch or use the external anti-aircraft machine gun, and the latter option allows him to load the cannon with the two rounds stowed in the turret or service the cannon while seated but prevents him from exiting his hatch as the seat is not underneath the loader's hatch. </div><div><br /></div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-8FJpH3kwbCA/XxwXUDwrYkI/AAAAAAAARVY/1q4flMfqdwkiGuIqsZCw8I2W8Wau-RtNgCLcBGAsYHQ/s1920/t-62m%2Bloader%2Binterior.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="360" src="https://1.bp.blogspot.com/-8FJpH3kwbCA/XxwXUDwrYkI/AAAAAAAARVY/1q4flMfqdwkiGuIqsZCw8I2W8Wau-RtNgCLcBGAsYHQ/w640-h360/t-62m%2Bloader%2Binterior.png" width="640" /></a></div><div><br /></div><div><br /></div>Unlike in a T-54 or T-55 where the crew compartment ventilation system air intake was positioned at the loader's station, either as an intake fan on the turret ceiling or as a blower on the turret shelf next to the coaxial machine gun, the T-62 has its ventilator installed under the shell casing ejection port. It is uncertain if this relocation had a positive or negative effect on the loader's working conditions other than the removal of a potential obstruction in his work space. With regards to ventilation, the reduced airflow around the coaxial machine gun is a marginal downside, but it is exchanged for better airflow behind the main gun where some fumes are expelled after firing along with the spent cases. </div><div> <br />
<br />The drawing below shows the design of the loader's seat and how it appears when the seat and its frame are folded against the turret wall. The loader is also provided with a fixed handgrip on the turret wall to hold himself steady as the vehicle is traveling, or as the gun is firing.
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When not seated, the loader stands on the rotating floor which has a diameter of 1,450mm, just slightly larger than the 1,370mm floor in the T-54B and T-55 series. The rotating floor is rather narrow since it does not reach the sides of the hull. Practically speaking, the loader may not always be standing on the rotating floor while carrying out his duties since the "Meteor" stabilizer blocks the rotation of the turret after every shot from the main gun until the loader arms the system by pressing on an arming lever. Thanks to this feature, the loader does not need to ensure that his feet are strictly planted on the rotating floor itself when taking ammunition from the hull racks.<br />
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<div><br /></div><div><br /></div><div><div>The design of the rotating floor was largely the same as the floor used in T-55 tanks built from 1960 onward. Power is delivered from the hull to the turret via a VKU-27 rotating power unit placed at the center of the rotating floor, and the power cables pass through a steel tube which joins up with the mounting frame for the gunner’s seat, passing through it and connecting to various devices in the turret via multi-pin sockets, or terminal leads, in the case of the turret switchboard and a few devices like the radio power supply unit. There was also an additional tube to convey the audio wires for the intercom system, connecting the driver to the intercom circuit in the turret without electrical interference from the power supply cables.</div><div> </div><div>This design allowed the rotation of the turret to move the rotating floor while at the same time keeping the cables tucked away discreetly, and without using additional space. An important feature of the rotating floor is that the rotating floor is not rigidly connected to the rotating contact, but through a simple spring-loaded clutch. If the rotating floor is impeded from rotating for any reason, the turret drives will have sufficient torque to overcome the clutch, and it will be able to turn without damaging the VKU-27 unit.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEji24SXSkjP5tAwSkcMdfVHqy8CKxyLL_QlZyuwNeRk87W9PxC-12P_PRiRsQtMTRZrRoDwx9Y1ehm60n8JnesnTL8wjxYIfYDAz83gOsi-uR6PmwkU9Qb--km3VDRmUaWhRWu-i3KqYlBMGKwIgG43bDoUznaI7_TAeI4xxB0rZzBqCUFH4WR-aalToQ/s3969/rotating%20slip%20ring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2913" data-original-width="3969" height="294" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEji24SXSkjP5tAwSkcMdfVHqy8CKxyLL_QlZyuwNeRk87W9PxC-12P_PRiRsQtMTRZrRoDwx9Y1ehm60n8JnesnTL8wjxYIfYDAz83gOsi-uR6PmwkU9Qb--km3VDRmUaWhRWu-i3KqYlBMGKwIgG43bDoUznaI7_TAeI4xxB0rZzBqCUFH4WR-aalToQ/w400-h294/rotating%20slip%20ring.png" width="400" /></a></div><div><br /></div><div> </div><div>In 1965, a new wiring harness scheme was introduced as the new standard in the ground vehicles of the Soviet Army, and accompanying it was the VKU-330-1 rotating power unit, which became standard for tanks, infantry fighting vehicles, and other turreted combat vehicles in anticipation of the growing sophistication of vehicle electrics and electronics. Connections at the rotating power unit were now made with a set of three multi-pin sockets with low and high current pins, in addition to one very high current socket, making it more convenient to disconnect the turret electrics from the hull during various field repair operations and expanding the number of devices that could be accommodated. The very high current socket was dedicated to the gun stabilizer power supply, rated for 360 A, but capable of withstanding 500 A for 5 minutes at a time with 30-minute intervals. The VKU-330-1 had enough pins to connect up to 47 circuits, of which only 33 were utilized in the T-62, but the remainder became useful later as additional electrical devices were added in the T-62M modernization.</div></div><div><br /></div>
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The main drawback of the dome-shaped turret is that the loader hardly has any headroom while standing compared to a contemporary Western tank like the M60A1 or the Chieftain. The loader's station in the T-62 has 1,600mm (5'4") of vertical space from the rotating turret floor to the turret ceiling, slightly more under his hatch, but less near the turret walls due to the hemispherical shape of the turret. For comparison, in the M60A1, the internal height of the fighting compartment measured from the turret basket floor to the turret ceiling is 1,950mm, and in the Chieftain, it is 1,730mm. In the Chieftain, this was enough to allow a man of average or below average height to stand completely upright inside the tank, whereas the M60A1 allowed a 95th percentile adult male to do so. The amount of vertical room in the T-62 is merely comparable to tanks like the M46 and M47. It is also comparable to the Abrams series, which provides 1,638mm (64.5") of vertical height at the loader's station from the floor of the turret basket to the turret ceiling (measured). The specific figure of 1,600mm was tied to the industry practice of setting requirements according to 50th percentile anthropomorphic data, and the minimum for effective work was deemed to be 1,600mm. This was around 90-100mm shorter than the average stature of the general male army population at the time (with helmet and boots). Relative to the modest height of its crew, the vertical space allocated for the loader in the T-62 could be considered adequate. In this context, it should be noted that for the Abrams, the loader's station height of 1,638mm is relatively inadequate from a design standpoint because the Army imposes a height limit of 1.85 meters for crew members, which represented the 95th percentile male serving in ground forces of the U.S military as of 1966.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GXG-cuwahDM/Xxlp5xwGncI/AAAAAAAARUA/QIwWtA-0WEQJwbTteXBjgp98jHfX-9NpwCLcBGAsYHQ/s1500/breech%2Bright.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1408" data-original-width="1500" height="375" src="https://1.bp.blogspot.com/-GXG-cuwahDM/Xxlp5xwGncI/AAAAAAAARUA/QIwWtA-0WEQJwbTteXBjgp98jHfX-9NpwCLcBGAsYHQ/w400-h375/breech%2Bright.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The vertical space was increased in the 1972 model of the T-62 by slightly raising the ceiling and by adding a new cupola to the loader's side of the turret. Now, a loader of average height could stand up straighter when ramming shells into the breech. The available height in the loader's station is still functionally the same as before, not exceeding the ceiling height of the turret itself by more than an inch or so, but the new shape increased the available room in some circumstances.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-M-f2JfNfVng/X-2jMvDg9VI/AAAAAAAASkk/_o8rLf4e_NYqT_S-CeHgfeCVbUtbxKrTgCLcBGAsYHQ/s728/Loading.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="546" data-original-width="728" height="300" src="https://1.bp.blogspot.com/-M-f2JfNfVng/X-2jMvDg9VI/AAAAAAAASkk/_o8rLf4e_NYqT_S-CeHgfeCVbUtbxKrTgCLcBGAsYHQ/w400-h300/Loading.gif" width="400" /></a></div><div><br />
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On the whole, the loader does not have very much room to work with compared to capacious tanks like the M60A1, but he has much more shoulder room than the loader of a T-54 and even the loader of a Leopard 1 or a Centurion as the width of the T-62 turret is immense. The two images below show the loader's station in a Leopard 1. The photo on the left, taken from a Canadian Army safety presentation, shows the emptied vertical ammunition racks in a Leopard C2. The image on the right, a screenshot from the video <a href="https://youtu.be/oxnLl9t5q-M">Inside the Chieftain's Hatch. Snapshots: Leopard 1</a>, shows the same racks fully stocked with ammunition in a Leopard 1A1.</div><div>
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<div><br /></div><div><br /></div>When the racks are empty, the turret is barely wide enough to accommodate the shoulders of the woman in the photo, and if they are stocked one or two rows deep, there is not enough space at this part of the turret to stand. As the photo on the left shows, the only remaining space for the loader is the small corner at the edge of the turret basket floor. Even when the maximum space is created by emptying these racks, the protruding "teeth" of the racks still somewhat restrict the width of the station and pose a tripping and injury hazard. These racks can be used with any ammunition type but if smoke shells (WP) are carried, then the racks are reserved for them as WP shells need to be stowed vertically. In combat, these ready racks mostly hold HESH or WP rounds, and if the loader must access KE rounds instead, then aside from the limited number on hand, he must squeeze between these racks to access the front hull racks.<br /><br /></div><div>The photo on the left below (source unknown) shows the loader's station of a Danish Centurion tank with a partial load of six 105mm training rounds in its turret ready rack. When carrying a full load of nine rounds, the loader is squeezed between the ammunition and the recoil guard on the L7 gun. He has barely any room to stand and as he is not even provided with a seat. Compared to a Centurion, the loader's station in a T-62 is very comfortable.</div><div><br /></div><div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-eLcko7-5AqA/Xtw3-2dbVVI/AAAAAAAAQ54/UyAdHGYOOBEzdrLKOayXoL-r2EWphYFCwCK4BGAsYHg/s960/ammo%2Bstowage.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="720" height="400" src="https://1.bp.blogspot.com/-eLcko7-5AqA/Xtw3-2dbVVI/AAAAAAAAQ54/UyAdHGYOOBEzdrLKOayXoL-r2EWphYFCwCK4BGAsYHg/w300-h400/ammo%2Bstowage.png" width="300" /></a><a href="https://1.bp.blogspot.com/-rSvcte6ZoeA/Xtw4UD7eNBI/AAAAAAAAQ6Q/YdG_e-RRCGoDv6wJVb3V215sklTYql1dwCK4BGAsYHg/s1709/centurion%2Bammo%2Bstowage%2Bscheme.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1709" data-original-width="1097" height="400" src="https://1.bp.blogspot.com/-rSvcte6ZoeA/Xtw4UD7eNBI/AAAAAAAAQ6Q/YdG_e-RRCGoDv6wJVb3V215sklTYql1dwCK4BGAsYHg/w256-h400/centurion%2Bammo%2Bstowage%2Bscheme.jpg" width="256" /></a></div></div><div><br /></div><div><br /></div><div>These issues do not exist in a T-62 because it does not stow ammunition in vertical racks that intrude into the loader's space, but instead provides the loader with a large open space to carry out his duties. Moreover, due to the large turret ring, there is enough elbow room for the loader to handle the ammunition. The T-62 has a turret ring diameter of 2,245mm and the gun breech housing of the U-5TS gun has a width of 495mm, with a total width of just over 500mm when the recoil guards are included. The gun is installed inline with the longitudinal axis of the turret, so the loader's station has a maximum width of 865mm when measured from the gun to the turret ring. Below the waist, however, the width of the loader's station is only comparable to the T-54 because the width of the hull is practically identical. Width was not lost to the larger width of the 115mm gun compared to the 100mm of the T-54/55 because the gun mount in the T-54/55 turret is not centered, but rather, was offset towards the loader's side to make room to accomodate the gunner and commander. </div><div><br /></div><div>However, it should be noted that the T-62 only stows a single 115mm cartridge on the floor next to the loader's foot whereas the T-54 stows four rounds on the hull wall. When loading, the single cartridge on the floor can be quickly transferred to the front hull ready racks to free up space on the turret floor while a T-54 loader would need to transfer all four rounds to free up the same space. As such, the available width of the floor for the loader of a T-54 tends to be 147mm narrower (diameter of 100mm cartridge casing) compared to the T-62. Overall, the layout and ergonomics of the loader's station can be considered good.</div><div>
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Besides the size of the loader's station, it is also necessary to take the ammunition itself into consideration and not just the amount of working space, and having said that, it will be surprising to many to know that 115mm cartridges are surprisingly lightweight. The T-62 has taken a lot of flak for its lack of amenities, especially for the loader, and there is even an apocryphal story about an Israeli loader being hospitalized for spinal injuries while evaluating a captured T-62. However, the fact of the matter is that Soviet 115mm rounds were quite efficiently designed compared to previous artillery and tank gun rounds. 115mm APFSDS rounds weigh only around 22 kg, lighter than 100mm steel AP rounds by an entire 8 kg, and the 115mm 3UOF1 HE-Frag rounds are lighter than 100mm UOF-412 by 2 kg despite launching a projectile of similar mass at a similar velocity. The HEAT ammunition for both calibers weigh the same, but 115mm HEAT shells are much more powerful and possess significantly better armour penetration. Only 100mm APDS and APFSDS rounds are outright lighter than 115mm APFSDS ammunition, but they are correspondingly less powerful. On the whole, the T-62 had the advantage in the ease of handling its ammunition.<br />
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In terms of size, 115mm ammunition is not significantly larger or more difficult to handle than 100mm ammunition within the confines of a tank turret, despite being wider and more voluminous. 115mm caliber cartridge cases have a length of 727mm and a rim diameter of 165mm, while 100mm caliber cartridge cases are 695mm in length and have a rim diameter of 147.32mm. However, 100mm casings are 147mm in diameter for most of its length and only neck down near the very end of the case whereas 115mm cases are necked at the midpoint, so being wider does not necessarily make them harder to handle. Case in point:<br />
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Also, the fact that the cases of 115mm cartridges are longer does not really matter, because most 115mm cartridges are still shorter overall. The 3UBM5 APFSDS cartridge, for instance, has a total length of only 950mm. The 100mm UBR-412B cartridge with an APBC shell measures 962mm in length, and the 100mm 3UBM11 APFSDS cartridge is 978mm in length, so generic 115mm APFSDS ammunition is actually shorter than its generic 100mm counterparts. Only 100mm APDS is significantly shorter than any 115mm round due to the low elongation of its core. As for HEAT rounds, the 100mm UBK4 cartridge measures 1,094mm in length, and the 115mm UBK3 measures 1,052mm in length, so once again, the 115mm caliber shows its relative merit. The same relationship exists for the HE-Frag ammunition of the two calibers. Overall, 115mm ammunition is not only shorter than 100mm ammunition but also lighter, and the larger case diameter makes little difference.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-m7P-ZJZ1n80/YUlbaot9QPI/AAAAAAAAUM4/DStUQtZhLkYM7btKsDEmliu2JnuFeuNHwCLcBGAsYHQ/s752/holding%2B115mm%2Bhe-frag%2Bround.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="752" data-original-width="552" height="400" src="https://1.bp.blogspot.com/-m7P-ZJZ1n80/YUlbaot9QPI/AAAAAAAAUM4/DStUQtZhLkYM7btKsDEmliu2JnuFeuNHwCLcBGAsYHQ/w294-h400/holding%2B115mm%2Bhe-frag%2Bround.png" width="294" /></a></div><div><br />
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Compared to 105mm ammunition, however, a generic 115mm APFSDS round weighs about 4 kg more than a generic 105mm APDS or APFSDS round, and all 115mm ammunition types are longer and wider than their 105mm counterpats. Still, the 115mm rounds are more powerful than their 105mm counterparts, so there is at least a good excuse for the added bulk. In the same working space, a loader should find it most difficult to handle 100x695mm cartridges, easier to handle 115x727mm cartridges, and easiest to handle 105x617mm cartridges, with all else being equal.<br /><br />
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Loading the U-5TS is no different than loading any other tank gun. After a shot is fired with the stabilizer in the "automatic" mode, the loader assist function of the stabilizer (referred to as the "autoblock") breaks the firing circuit of the gun and brakes the turret traverse and gun elevation drives, the latter by hydraulically locking the gun (hydrolock). The gun is locked in elevation during recoil when the autoblocker senses the motion of the gun breech housing, and continues to be locked until the loader hits the arming switch. </div><div><br /></div><div>Beginning in 1965, an upgraded autoblocker system was introduced. The new autoblocker not only suspends the gunner's vertical and horizontal guidance controls, but if the gun is below an elevation angle of +2°30' (2.5 degrees) relative to the hull, the system directs the gun elevation drive to automatically elevate the gun to an elevation angle of 2.5 degrees. The gun is then fixed in place by hydrolock (hydraulic lock of the elevation drive). This feature was implemented to reduce the probability of the gun barrel sticking into the ground when the tank is driven across rough terrain, while also the loader's safety and convenience. The T-55A also received the same update to its stabilizer in 1965. Before that point, the gun will simply remain stabilized after every shot.<br />
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While the auto-ejector is ejecting the spent shell casing, the loader extracts a fresh cartridge from one of the tank's ammunition racks, brings it up behind the breech, and rams it in. The breech block automatically seals the breech, and the loader presses his arming lever to close the electrical firing circuit and return the weapons to a fully stabilized status under the gunner's control. The gun will be armed and ready to fire.<br />
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The autoblocking device is shown below. The arming lever is marked (1) in the photo on the left below. The bottom of the lever is hinged against the recoil guard on the side of the breech, and its center is connected to the arming mechanism rod. Pushing against the top of the lever pushes in the arming mechanism rod, arming the gun. <br />
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The autoblocking device senses the firing of the U-5TS gun via a recoil sensing roller (4) attached to a lever (5), as seen in the drawing on the right above. The roller is pressed against the gun breech housing by a spring. When the gun recoils, a bump on the gun breech housing deflects the roller and trips a switch (7) which breaks the firing circuit of the gun, stops the turret traverse and gun elevation drives and fixes the gun in place by hydrolock. To manually activate the autoblocking system - that is, to manually set it to the blocked state after a round is fired, the loader can press the large button (13) on the front panel of the autoblocker device. This manually engages the recoil sensing roller, and the autoblocker system will behave as if a shot was fired. As a safety precaution, the autoblocker must be manually activated by the loader before he reloads the coaxial machine gun, as it is not safe for the gun to be free to elevate while the loader opens the top cover of the machine gun, handles the ammunition and charges the machine gun.<br />
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The location of the autoblocker unit can be seen in the drawing below, marked (17).<br />
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The loader assist function allows the loader to load the cannon quicker when travelling on the move. This feature is almost always misunderstood and comes across as self-defeating, but it is a known method of improving the rate of fire. More modern tanks such as the Leopard 2 and Abrams have the same feature, as demonstrated in this video clip <a href="https://www.youtube.com/watch?v=TwXwrx_lkSg">(link</a>). In the video, you can clearly see the breech rising slightly after the loader presses the loader's safety button, which deactivates the safety measures and the loader's assist function, readies the gun to fire, and sends a signal to the gunner that the gun is ready to fire.<br />
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Having a loader's assist function is particularly important when firing on the move, because advancing tanks usually slow to a crawl or halt to fire in order to maximize accuracy, and then immediately accelerate to a high speed and perform evasive maneuvers before the next shots as a way to minimize vulnerability to counter fire. The stressful period between shots would be when the loader is obligated to perform, and the loader's assist function is meant to aid him. It is worth mentioning that the T-55A has the same feature, and should not be a factor when comparing the rates of fire between it and the T-62.<br />
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If the situation demands that the gunner retains full control of the turret and gun while the gun is being loaded, then he can simply inform the loader to disable the loader assist system. The technical manual for the T-62 gives these instructions in pages 97 and 98.<br />
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<blockquote class="tr_bq">
"<i>Заряжание пушки. Перед заряжанием пушки необходимо убедиться в том, что цепи стрельбы в приборе автоблокировки выключены.</i> </blockquote>
<blockquote class="tr_bq">
<i></i><i>Для заряжания пушки необходимо:</i><br />
<ul>
<li><i>открыть затвор вручную; вынуть поддон и положить его на пол боевого отделения или в свободное гнездо бака-стеллажа;</i></li>
</ul>
<ul>
<li><i>извлечь из боеукладки выстрел соответственно поданной команде о снаряде и установить взрыватель;</i></li>
</ul>
<ul>
<li><i>вложить выстрел в патронник и энергичным движением дслать его вперед, при этом затвор автоматически закроется;</i></li>
</ul>
<ul>
<li><i>разблокировать цепь электрической блокировки спуска (одновременно выключается механическая блокировка), для чего заряжающему нажать левой рукой на рычаг включения цепи спуска прибора автоблокировки и доложить о готовности.</i></li>
</ul>
<b><i>Если после выстрела до последующего заряжания пушка должна быть в стабилизированном положении, то по требованию наводчика заряжающий включает цепь электроспуска, нажав на рычаг включения цепей стрельбы прибора автоблокировки. При этом пушка, снятая с гидростопора, автоматически занимает стабилизированное положение.</i> </b></blockquote>
<blockquote class="tr_bq">
<i></i><i>Для последующего заряжания пушки необходимо снова разомкнуть цепь электроспуска (выключается механическая блокировка), нажав на кнопку выключения цепей стрельбы прибора автоблокировки.</i>"</blockquote>
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Translated:<br />
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<blockquote class="tr_bq">
"<i>Loading the gun. Before loading the gun it is necessary to make sure that the firing circuit in the automatic blocking device is turned off. </i></blockquote>
<blockquote class="tr_bq">
<i>To load the gun it is necessary to:</i><br />
<ul>
<li><i>open the breech block manually; remove the shell casing and place it on the floor of the fighting compartment or in an empty slot in a storage rack;</i></li>
<li><i>take from the ammo rack a round according to the command given on the shell type and set the fuse;</i></li>
<li><i>put the cartridge into the gun chamber and vigorously push it forward, with the breech block automatically closing;</i></li>
<li><i>unlock the gun firing circuit (at the same time the mechanical lock is turned off), which is done by the loader who presses the arming lever with his left hand to release the autoblock and reports on the readiness </i>[to fire]<i>.</i></li>
</ul>
<i><b>If, after firing, the gun must be in a stabilized position </b></i><i><b>before loading the next round</b></i><i><b>, then at the gunner's request, the loader switches on the electric firing circuit by pressing the lever for turning on the firing circuit of the autoblocker. In this case, the gun, removed from hydrolock, automatically enters a stabilized state.</b> </i></blockquote>
<blockquote class="tr_bq">
<i>For the subsequent loading of the gun, it is necessary to again open the electrical firing circuit (turns off the mechanical interlock) by pressing the button for turning off the firing circuits of the autoblocker.</i>"</blockquote>
<div><br /></div><div>If desired, it is possible to load the gun without turning on the autoblocker beforehand, but it is unsafe to do so, as the firing circuit is closed and the gunner may accidentally fire the gun before the loader is clear of the recoil path. After each shot is fired, the recoil will trip the autoblocker as normal.</div><br />
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<h3>
<a href="https://www.blogger.com/null" id="ammo"></a>
<span style="font-size: large;">AMMUNITION STOWAGE</span></h3>
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The T-62 can carry a total of 40 rounds of ammunition for the 115mm gun. The two sets of front hull stowage racks, both of which are conformal fuel tanks, are identical and hold 8 rounds each for a total of 16 rounds of ammunition. These racks are pictured below. Another 20 rounds are stowed in the very back of the hull on the partition between the engine compartment and the fighting compartment. The loader has 2 rounds clipped to the turret wall directly behind him, and a single round secured by clips on his side of the hull wall, near his feet. There is another round stowed in the same way on the opposite wall, near the commander's feet.</div><div><br /></div><div>
The two drawings below illustrate the locations of the ammunition more clearly.<br />
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<div><br /></div><div><br /></div>To provide the loader with the ability to load the gun regardless of the orientation of the turret, the T-62 has hull ammunition racks positioned in the front, rear and sides of the crew compartment. This was, in essence, the same basic concept applied in most WWII era tanks, including later types such as the Panther and various Sherman models. To solve the issue of supplying the loader with ammunition for all-round fire, postwar Western tanks were universally fitted with turret ammunition racks instead, leaving the hull racks as a reserve. This took the form of vertical racks on the turret basket floor (Patton series, Centurion, Leopard 1), bustle racks (M60A1), a small rack on the turret wall (Patton series, Leopard 1), and additional ammunition in boxes on the turret floor. Looking at these two options purely from the standpoint of the availability of ammunition type, the advantage of having ammunition in the turret is that the turret racks can hold several different types of ammunition, which will all be available to the loader regardless of how the turret is oriented relative to the hull. However, due to the need to accommodate all four ammunition types, which are APDS, HEAT, HESH and WP (Smoke), only a handful of each type will be available at any given time. In contrast to this, the advantage of having nearly all ammunition stowed in the hull is that the availability of all ammunition types can be maximized when the turret is oriented within a forward arc, at the expense of poorer access when the turret is rotated off to the side or rear.<br />
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The 16 rounds in the front hull racks are the most convenient for the loader along with the rack of two rounds on the turret. The rounds in the front hull racks are held in place by friction and secured with simple spring-loaded handles, which can be easily hinged up to let the loader pull the round out by its rim. The round stowed in the top left slot in both ammo racks are not secured with a hinged handle but by a spring-loaded tab. On the right front hull rack, all of the slots except the two top slots in the left column are tilted nose-down. The four slots on the bottom two rows on the left front hull rack are also tilted nose-down. This is so that the loader pulls the rounds out at an angle, which is easier than pulling them straight rearward. To clear up space for the nose of the rounds in these tilted slots, the slots have a floor plate extension, so that the rounds cannot be inserted as deeply as the ones in the other slots. These details are visible in both of the photos below. </div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">To the left of these front hull racks is a shelf containing five 250-round boxes of ammunition for the coaxial machine gun. They are conveniently placed for the loader to quickly reload the coaxial machine gun. The mount for the ammunition box feeding the coaxial machine gun is positioned just above the front ammunition racks so that it is not in the way when the loader retrieves the rounds in the top row of the racks. </div>
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The loader must squat or lean down to access these rounds. These racks are principally identical to the ones found on the T-55 but differ in that they are wider in order to accept 115mm rounds. Soviet tank crew training mandated that in a tank duel scenario, the driver should turn the front of the hull toward the target. Doing this will not only present the toughest armour of the tank to incoming fire but also maximize the accessibility of the front hull racks. To use the ammunition in these racks, the loader flicks open the hinged handle at the cartridge slot opening with his right hand and grasps the rim of the cartridge with his left hand. When the loader stands up, he will be holding the cartridge with its nose pointed forward so it is easy for him to immediately fit the nose of the cartridge into the opening of the gun chamber with his right hand and then ram the round into the chamber with his left arm. There is no need to manhandle the cartridge around to get it in the proper orientation which would be necessary with some of the other ammunition racks in the tank.<br />
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Because the speed of loading the gun from the front hull racks is the highest compared to all other ammunition racks in the tank, they are considered the ready racks and they are reserved for anti-tank ammunition. If the standard combat ammunition load of 12 APFSDS rounds, 6 HEAT rounds and 22 HE-Frag rounds is carried in a T-62, there would be 10 APFSDS rounds and 6 HEAT rounds stowed in the front hull racks. The remaining two APFSDS rounds would be stowed on the hull floor on clips. This stowage plan was practiced in the Soviet Army and in the NVA.</div><div><br /></div><div>The two rounds clipped to the hull sides near the floor are not ready rounds, but provide the loader with access to armour piercing rounds when the turret is turned to the 9 o'clock position, whereby the front hull rack is largely inacessible. Unlike the hull side rack on a T-54 or T-55, which contains a stack of four rounds, the hull side stowage in the T-62 was limited to only one round on each side to allow the gun to elevate fully when the turret is turned to the 3 o'clock and 9 o'clock positions. Otherwise, the end of the casing ejector mechanism would be caught on the side racks.<br />
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As mentioned before, there are 20 rounds stowed in the rear of the fighting compartment, just ahead of the fireproof bulkhead that separates the fighting compartment from the engine compartment, in the same position as in a T-55. These are the reserve racks. However, unlike in a T-55, the ammunition in these racks were not hidden below the hull roof as the T-62 turret ring was large enough to expose the top of these racks. The rounds stowed in these racks were interlocked in a crosswise pattern to make the most out of the limited space, which was made possible by the rather unusual shape of 115mm cartridges. This ammunition rack was generally reserved for HE-Frag rounds.<br />
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<br />Due to the immense size of the turret ring, there is a relatively large amount of room between it and the casing ejector mechanism attached to the 115mm gun. This, combined with the fact that the turret ring exposed the top of these racks, enables the loader to access the ammunition in these rear racks quite conveniently. The two photos below, taken from the article "<i><a href="https://en.topwar.ru/144248-rasskazy-ob-oruzhii-tank-t-62-snaruzhi-i-vnutri.html">T-62 Outside and Inside</a></i>" on the Topwar website, shows a view of the empty rear fighting compartment rack in relation to the gun and turret ring. <br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GrA7svRBDIc/XzI_NLY4ymI/AAAAAAAARcY/cwmBE1RKrMY1kt5TzTuqpxFeLTSiIFM1ACLcBGAsYHQ/s1280/1531317877_img_9675.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="266" src="https://1.bp.blogspot.com/-GrA7svRBDIc/XzI_NLY4ymI/AAAAAAAARcY/cwmBE1RKrMY1kt5TzTuqpxFeLTSiIFM1ACLcBGAsYHQ/w400-h266/1531317877_img_9675.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-OCe4zYbawgM/XzI_NO3kjgI/AAAAAAAARcU/tVhNWQ9qG-wWJ3BrjEL_-0iQW7eAfeWHwCLcBGAsYHQ/s1280/1531317824_img_9685.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="266" src="https://1.bp.blogspot.com/-OCe4zYbawgM/XzI_NO3kjgI/AAAAAAAARcU/tVhNWQ9qG-wWJ3BrjEL_-0iQW7eAfeWHwCLcBGAsYHQ/w400-h266/1531317824_img_9685.jpg" width="400" /></a></div><div><br /></div><br />
All 20 cartridges are held in position by rubber cups supporting the base of each round, but only the first two columns of cartridges have metal frames to prop up the midsection. The diagram on the left below from the T-62 technical manual gives a better idea of how the metal frames are supposed to look, but it does not show all of the frames that are present. The first column in the stack has two frames, but the next two columns have only one more frame, and the top round in the stack is unsecured once the frame of the preceding column is removed, staying in place only by laying between the next two cartridges below it. Because the rounds are stowed in a deep stack with multiple columns, it is only possible to access the rounds at the back after depleting the rounds in each sequential column from top to bottom and after removing the support frames present. A frame is removed by unhooking it from its ceiling bracket, and then sliding it off its floor bracket. The frame is stowed away wherever there is free space. The remaining rounds in the last column are secured by clips fixed to the engine compartment partition and to the floor.</div><div>
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The loader is not able to access the rear hull racks as easily as the ready racks in the hull front, and it is particularly difficult to access the ammunition stowed at the very back of the racks. For this reason, the tank's load of HE-Frag rounds are stowed in this rack as it is not particularly critical to load the gun as quickly as possible when firing at the types of targets that are most effectively engaged with HE-Frag shells such as fixed fortifications and soft-skinned vehicles. However, with that said, the very large turret ring diameter of the T-62 meant that the loader did not have to crouch down and reach beneath the hull roof to access these rounds as a T-55 loader would. Because the turret ring overhangs the rear hull racks, the loader can easily reach and extract ammunition from the top of these racks from a variety of postures.<br />
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Last but not least is the ready rack on the turret wall next to the loader, just behind his cupola. It holds two rounds, mounted crosswise. Being located directly behind the loader if he was facing the breech, these are the most easily accessible to him. To load, he must unlatch a round from a rack first, grab it and turn to face the cannon breech, then ram it in. This can be easily done even when the loader is seated. The ready rack can be seen in the photo below. According to the manual, these turret racks are intended for APFSDS rounds only, although other ammunition types will fit without issue. The space behind the turret racks are not wasted; there is a bracket to stow the internal gun travel lock, spare parts and two pouches with four magazines for the Kalashnikov rifle carried on board the tank. <br />
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<h3>
<a href="https://www.blogger.com/null" id="rof"></a>
<span style="font-size: large;">RATE OF FIRE</span></h3>
<div><br /></div>Official Soviet documentation of tank crew norms (battle drills) specifies that readying the gun on an Object 166 (a T-62) from the ready racks should take no more than 13 seconds. There is no specific norm for loading the gun itself, only readying it for the first shot. The weapon is in a ready status, but the stabilizer is turned off for the drill. According to the instructions for the firing preparation drill, the loader must first open the closed gun breech to begin the loading process, which takes a few seconds on its own. The ammunition is secured in the appropriate stowage points. The timer for the drill starts when the instructor issues the command "manually load" and ends when the trainee reports "ready". </div><br /><div><br /></div><div>The "minimum" grade, which is the minimal passing grade, is 13 seconds, and the "good" grade is 11 seconds, while the "excellent" grade is 10 seconds. The standards for loading speed from the reserve ammunition stores are more lax; when loading from any ammunition rack other than the ready racks, the "minimum" grade is 15 seconds, the "good" grade is 13 seconds, and the "excellent" grade is 12 seconds.<br />
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The theoretical maximum rate of fire permitted by the gun should be around 8 to 10 rounds per minute, but the realistic rate of fire will always be much lower than the technical maximum fire rate due to the many secondary factors that arise during real combat. A Soviet study found that the average time needed for a T-62 loader to load the gun using various ammunition types was 9.2 seconds when the tank was static and 9.5 second when the tank was in motion at 20-25 km/h. For comparison, <a href="http://btvt.info/1inservice/m60a1_israel/vop_m60a1_israel_engine_fcs.htm">a report from a Soviet evaluation of the M60A1 published in 1976</a> found that the loader could load in 7 seconds.<br />
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However, the incorrect perception that the loading speed of the T-62 was excruciatingly slow still persists, helped in part by <a href="https://www.youtube.com/watch?v=cJfvIOAs-2o">this TRADOC video</a>. The short clips below shows the loader of a T-62 demonstrating the loading process. In these particular instances, the video clip takes a total of only 6.5 seconds and 7 seconds respectively. In the latter case, the loader is using the turret ready rack, which is less convenient than the front hull ready rack. From this demonstration alone, it is abundantly clear that a loading speed of 15 seconds is completely divorced from reality, and that there is more nuance in the matter.<br />
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In reality, the actual time between shots tends to be much longer than the loading speed as the gunner typically takes longer to find a target and acquire a firing solution than it does for the loader to load. The T-62 might be able to achieve something close to its theoretical maximum rate of fire if the commander and gunner forego the rangefinding procedure altogether and instead engage using battlesighting as mentioned in an earlier section of this article. This is a notable advantage for the T-62 as the margin of error at closer ranges is negligible thanks to the high velocity of its APFSDS ammunition and it can still theoretically out-shoot a Leopard 1 or M60A1 at typical combat ranges.<br />
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The T-62 technical manual lists the aimed rate of fire of the tank from a stationary position as 4 rounds per minute and supplementary documents state that the rate of fire is 4-5 rounds per minute. These figures do not represent the loading speed or maximum rate of fire, and generally should not be taken at face value because it merely represents the aimed rate of fire in simulated conditions, used to provide a baseline for expected crew performance in real combat, and for combat simulations. Part of the discrepancy between the practical average sustained rate of fire and the actual maximum aimed rate of fire comes from the obligations of the commander and gunner to carry out the entire formalized firing procedure during such tests, whereas the crew of a tank in real combat conditions may choose to use faster methods or simply require less time because of experience. These technicalities are specifically mentioned in the <a href="http://www.moremhod.info/index.php/library-menu/34-strana-kotoroj-bolshe-net/245-neizvestnyj-tank-chast3?showall=&start=17">book "Tank"</a> published in 1954 by the Military Publishing House of the Ministry of Defense of the USSR:</div><div>
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"<i>Техническая скорострельность определяется числом снарядов, которое можно выпустить за единицу времени, если считать, что пушка наводится в цель и заряжается мгновенно. Практическая скорострельность, т. е. число прицельных выстрелов в единицу времени, зависит от весьма большого числа обстоятельств (многие из них уже упоминались выше) и всегда бывает во много раз меньше технической</i>."<br />
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The translation:<br />
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"<i>The technical rate of fire is determined by the number of shells which can be fired per unit of time, if we assume that the gun is aimed at the target and is loaded instantly. The practical rate of fire - that is, the number of aimed shots per unit of time - depends on a very large number of circumstances (many of them have already been mentioned previously) and are always many times less than the technical rate.</i>"<br />
<br /><br /></div><div>This is a well-documented fact that is often obscured or misunderstood due to the way reload speeds are represented in tank games and even in some simulators. This is exemplified by data from military trials of the Strv 103B conducted in the United States in 1976-1977, part of which is available in <a href="https://tanks.mod16.org/pdf/Strv%20103B%20in%20the%20US.pdf">this document shared by renhanxue, administrator of the tanks.mod16 website</a>. When averaging between 400 shots taken against different types of targets from between 500 to 2,000 meters under various simulated scenarios (page 11 of the PDF), the M60A1 took 12.7 seconds to fire the first shot and the Strv 103 took 13.1 seconds. This is particularly noteworthy because the Strv 103 has an autoloader that is capable of loading the gun in around 3 seconds (with the complete loading cycle taking 4 seconds). From this, the nominal aimed rate of fire of the M60A1 and Strv 103B would be only 5 rounds per minute despite the fact that both tanks can be loaded at a significantly quicker rate. This is further reinforced by an <a href="http://btvt.info/1inservice/m60a1_israel/vop_m60a1_israel_engine_fcs.htm">independent Soviet evaluation of an M60A1</a> where it was found that the average time taken to open fire while static was 14 seconds, even though an average loading time of 7 seconds was achieved during mock loading tests. </div><div>
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With that said, this also raises an important question; if 115mm ammunition is lighter than 100mm ammunition and both the T-62 and T-54/55 are Soviet tanks that were evaluated by the same standards, why does the T-55A manual state that the rate of fire of the T-55A is 7 rounds per minute when stationary? The T-55A has a dual-axis stabilizer with a "loader's assist" feature like the T-62, yet its average rate of fire is ostensibly higher. Aside from different testing conditions, there are a few other possible explanations. One important factor to consider is that the T-55A carries 25 ready rounds, out of a total capacity of 43 rounds. There are 18 ready rounds in the front hull racks, and 7 ready rounds in the turret. For the T-62, there are only 18 ready rounds - 2 in the turret and 16 in the front hull racks - out of a total capacity of 40 rounds. Expressed as a percentage, ready ammunition makes up 58% of the ammunition in a T-55A and 45% of the ammunition in a T-62. Additionally, the T-55A stores another 4 rounds on the side wall of the hull on the loader's side. These rounds may be easier to access than the ones in the racks at the back of the fighting compartment, next to the engine compartment bulkhead. Furthermore, the rate of fire figure of 4-5 rounds per minute given in the manual is a single figure unlike the T-55A manual which lists separate firing rates for a stationary and moving tank, so some discrepancies in the criteria seem to exist and may possibly account for the unexplained differences in the claimed firing rates.<br />
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A reasonable estimate of the T-62's average rate of fire in combat while firing on short halts or on a slow crawl should be around 4 rounds per minute, as the loader is inconvenienced whenever the turret needs to turn when the tank is moving because of the narrow turret floor and the potential loss of access to his most convenient store of ammunition. How long the loader can maintain his speed under the most optimal conditions (fatigue notwithstanding) is a different matter entirely, of course, although this is a universal issue with all manually loaded tanks. The T-62 loses out in pure loading speed compared to contemporaries that have a turret bustle and racks in the turret basket, as the ammunition is accessible regardless of whether the turret is spinning or not, unlike the ammunition in the T-62 hull. <br />
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In terms of ammunition sustainability, the T-62 cannot hold a candle to its NATO counterparts. The Leopard 1 must be considered excellent in that all of its ammunition is in convenient reach of the loader, although its front hull racks are not as convenient to reach due to the turret ring not reaching the front of the hull. The M60A1 is also quite good as the loader has access to up to 37 rounds in the turret. With only 18 ready rounds, the T-62 should not be able to stay in continuous combat for as long as these tanks. In some cases, stationary tanks used as defensive weapons are obligated to hold a position for long periods under intense attacks so a large amount of ready ammunition is essential. The best example would be the Israeli experience during the Yom Kippur war. However, the combat history of tanks under the European powers during WWII paints a different picture and provides some legitimacy to the more conservative path taken by Soviet engineers.<br /><br />
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<h3>
<a href="https://www.blogger.com/null" id="cannon"></a><span style="font-size: large;">U-5TS (2A20) GUN</span></h3>
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The chief justification for the existence of the T-62 was the U-5TS smoothbore cannon, which bears the GRAU designation of 2A20. Static firing trials of the gun took place in September 1959, and then from April to September 1960, live testing of the U-5TS with the first Object 166 prototypes took place. The U-5TS was a modification of the 100mm D-54TS cannon (U-8TS) and it differs only in the gun tube. When mounted in the T-62, the height of the bore axis of the U-5TS from ground level is very low - only 1,758mm.<br />
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The first U-5TS gun tubes were created by simply boring out existing D-54 gun tubes and removing the muzzle brake, but of course, this caused certain issues and was not the basis of the final design. One of the issues was that because a large amount of mass was removed from the gun tube due to the increase in caliber, the gun assembly lost its balance and became rear-heavy. This would have been exacerbated by the addition of the spent shell casing ejector. Also, increasing the caliber of the bore without increasing the diameter of the gun tube made its walls thinner, which strongly affected the rigidity of the barrel. This affected its vibration characteristics and its sensitivity to atmospheric conditions (thermal warping), which affected shot dispersion. As such, a new barrel with a bore diameter of 115mm had to be designed from scratch. However, the recoil dynamics of the gun did not differ from the D-54TS, so any turret designed for the D-54TS would also be compatible the U-5TS. Based on service manuals, the gun breech assembly, gun cradle, recoil system, and many other components are shared with the D-54TS. Among the components not shared with the D-54TS were the recoil guards installed on the gun cradle and the spent shell casing ejector mechanism.<br />
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The barrel is 49.5 calibers long, or 5,700 mm, and the total length of the gun (from muzzle to breech block) is 6,050 mm. The chamber is 723mm long. The gun measures 4,827mm long from the trunnion axis to the muzzle; only slightly longer than the D10, which was 4,460mm long from trunnion to muzzle. Having a length of only 1,222mm from the trunnions to the rear of the gun breech block, the U-5TS occupies relatively little space in depth. The breech housing is 495mm in width, 645mm in height and 651mm in length, making it quite compact for a gun of its power. The actual width occupied inside the turret is slightly greater, as the sheet steel recoil guard is spaced 6-14mm away from the breech on the left, and 13-20mm away from the breech on the right. The width across the recoil guards would therefore be around 540mm.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ogS0LweMZHY/YBQO0vMCCsI/AAAAAAAASrI/AY1ioy1eMjoEtxqvPWeOJ5_sbggImTSSQCLcBGAsYHQ/s1261/recoil%2Bguard.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="697" data-original-width="1261" height="354" src="https://1.bp.blogspot.com/-ogS0LweMZHY/YBQO0vMCCsI/AAAAAAAASrI/AY1ioy1eMjoEtxqvPWeOJ5_sbggImTSSQCLcBGAsYHQ/w640-h354/recoil%2Bguard.png" width="640" /></a></div><div><br /></div><div><br /></div><div>This is much wider than the 122mm D-25T gun which has a width maximum of 480mm when measured at the widest points across its recoil guard, but should not be surprising as the D-25T operated at a lower pressure and had straight-walled cases, being derived from a field gun rather than being designed to be a high velocity tank gun. When measuring along the breech housing alone, the width of the gun is substantial, placing it between the 120mm L11 and L30 (483mm wide) and the 120mm Rh120 (500mm wide). However, the width of the Rh 120 smoothbore gun measured across the recoil guards is 660mm, according to data given by Dipl-Ing Rolf Hilmes in a seminar. Even the relatively narrow L11/L30 series has no width advantage, as the actual half-width when measured across the left recoil guard is around 368mm, and the half-width on the right recoil guard is as little as around 251mm, giving a full width of no less than 619mm. </div><div><br /></div><div>The same consideration even applies to 105mm guns such as the M68 and L7, which would ostensibly have the advantage of compactness thanks to their smaller caliber. Based on a measurement of the M68 gun on display at the Museum of Polish Military Technology, the width of the round breech housing is merely 436mm, but due to the large diameter of the concentric recoil mechanism (a large spring) and the semi-automatic mechanism protruding from the side, the gun has widely spaced recoil guards measuring 672mm across. When the full size of the gun assembly is considered, the U-5TS is actually the most compact amongst all guns of a comparable class.</div><div><br /></div><div>To keep the recoiling mass of the gun centered during recoil, the gun cradle features a dorsal guide plate. The plate fits into a trough cut in the top surface of the breech housing. This design was later carried over to the 125mm D-81 gun. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ANRZ5nhCuWU/YRajcEn30ZI/AAAAAAAAUFs/ctjGTVPGm1UT4ov1xFwX2QOYK2aHYHqwwCLcBGAsYHQ/s1176/t-62%2Bgun%2Bcradle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="796" data-original-width="1176" height="271" src="https://1.bp.blogspot.com/-ANRZ5nhCuWU/YRajcEn30ZI/AAAAAAAAUFs/ctjGTVPGm1UT4ov1xFwX2QOYK2aHYHqwwCLcBGAsYHQ/w400-h271/t-62%2Bgun%2Bcradle.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The nominal operating pressure when firing an APFSDS round in standard conditions with a propellant temperature of 15°C is 359 MPa, approaching the level of the 122mm M62-T2 which fires its AP shells at a nominal operating pressure of 392 MPa. This was considerably higher than the 320 MPa operating pressure of the 120mm L11 rifled cannon of the Chieftain main battle tank when firing L15A5 APDS at a propellant temperature of 15°C, and much higher than the 294 MPa maximum operating pressure of the D10-T. The increased operating pressure of the U-5TS gun was achieved by using a fretted (jacketed) barrel. The barrel is manufactured with an internal diameter that is slightly larger than specified, and then a jacket is heated up, fitted over the barrel, and cooled to place the barrel under constant tension. On the U-5TS, the frettage was installed at the zone of highest stress (where the propellant develops its peak pressure), which was the chamber.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-bf4totCTKQU/Xx_b_abxSaI/AAAAAAAARXQ/l0sUnEpwCIY1pF5bR0r5h634M6JMZncRQCLcBGAsYHQ/s2206/fretted%2Bbarrel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="796" data-original-width="2206" height="230" src="https://1.bp.blogspot.com/-bf4totCTKQU/Xx_b_abxSaI/AAAAAAAARXQ/l0sUnEpwCIY1pF5bR0r5h634M6JMZncRQCLcBGAsYHQ/w640-h230/fretted%2Bbarrel.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The primary justification for a smoothbore gun is that the nature of barrel wear with a smoothbore barrel is more conducive to a high pressure, high velocity gun. In both cases, the extent of throat erosion is the primary factor that determines the condition of the barrel, but the nature of throat erosion differs. This is due to the fact that the limiting wear for a smoothbore barrel is the thickness of the eroded bore diameter, whereas for a rifled gun, the limiting wear is the longitudinal length of the throat, because the delayed engagement with the rifling lands severely impacts the dispersion characteristics of the ammunition. The limiting type of erosion is shown in the drawing below, taken from the 2004 textbook "<i>Учебник Сержанта Танковых Войск</i>". The throat erodes at a much higher rate than the rest of the bore (excluding the muzzle) regardless of whether the barrel is rifled or not, and in both cases, the throat diameter progressively expands along a certain length due to erosion, but the progression of the eroded length is much faster than the progression of the eroded thickness. For instance, if a given ammunition is capable of eroding 0.003mm of thickness from the surface of the throat, then the throat diameter will expand at a nominal rate, but the length of the throat affected by erosion can be very long, since the projectile and propellant gasses act on the surface for the entire length of the bore. Given this fundamental limitation, ideally, the service life of a barrel should be determined by the eroded diameter. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEijnlHtB8da32C1ULM6QUJtmxOvfsWkPolRiNkST2dV71Px8xtpoEIyzGBO15MEIChGQqjUphb_8QMcyeReOOrJYT9120EWE60riQyDt7J6HXnEmbHayd1xat_-aM3oNoH4SK-DWbZER3Pkhf1np1geXc7aMUivnWj2YcF0hTuSZdxQhVFLPPyEOENWMQ=s1688" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="771" data-original-width="1688" height="292" src="https://blogger.googleusercontent.com/img/a/AVvXsEijnlHtB8da32C1ULM6QUJtmxOvfsWkPolRiNkST2dV71Px8xtpoEIyzGBO15MEIChGQqjUphb_8QMcyeReOOrJYT9120EWE60riQyDt7J6HXnEmbHayd1xat_-aM3oNoH4SK-DWbZER3Pkhf1np1geXc7aMUivnWj2YcF0hTuSZdxQhVFLPPyEOENWMQ=w640-h292" width="640" /></a></div><div><br /></div><div>Because the length of the eroded throat has an overwhelming effect on the precision of a rifled gun, increasing the longevity of the barrel by increasing the resistance of the bore surface against erosion yields less of an improvement. As such, for guns of increased power, the presence of rifling results in the barrel not being able to fulfill its full service life potential. For a smoothbore, the length of the throat affected by erosion is no longer the primary issue, but rather the throat diameter. Because of this, when comparing two identical guns firing the same ammunition that differ only in one being rifled and the other being a smoothbore, the smoothbore will have a longer service life. </div><div><br />Based on the limited information available, the U-5TS appears to have had an acceptable level of durability. It has an average barrel life of 450 shots or 400-450 shots, depending on the source. This average barrel life figure is valid when a mixture of HE-Frag, HEAT and APFSDS are fired. For comparison, it is stated on page 33 of the book "<i>M60 Main Battle Tank 1960–91</i>" by John Macdonald and Richard Lathrop that the average lifespan of an M68 gun tube was 500 rounds. It is important to note that this figure is heavily skewed by a high proportion of HEP (HESH) rounds and a very low proportion of APDS and HEAT rounds.</div><div><br /></div><div>It is stated in the report "<i><a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a076177.pdf">Prediction of Erosion From Heat Transfer Measurements</a></i>" that the M68 barrel permits the firing of only 125 rounds of M456A1 HEAT or 100 rounds of M392A2 APDS, which are analogous to the British L28A1 APDS. According to the report "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a056368.pdf">Measurement of Heat Input Into the 105mm M68 Tank Cannon Firing Rounds Equipped With Wear-Reducing Additives</a>", the maximum lifespan is also 1,000 rounds of "standard rounds". By firing a mix of ammunition primarily comprised of HEP rounds with very few APDS and HEAT rounds, an average lifespan of 500 rounds can certainly be achieved with the L7 and M68.</div><div><br /></div><div><br /></div><div>When installed in the T-62, the U-5TS has a total system weight of 2,315 kg, including the barrel, breech assembly, recoil system and gun cradle, which is referred to as the oscillating weight of the gun. For comparison, the L11A5 weighed 2,650 kg in total. The gun alone, which consists of the barrel and breech assembly, weighs 1,810 kg. This is almost as heavy as the L11A5 gun which weighs 1,900 kg. </div><div>
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In terms of ballistic performance, the U-5TS was significantly more powerful than the 100mm D-10T and the 105mm L7, although it apparently had slightly poorer accuracy at very long ranges compared to the L7 depending on the ammunition. However, the difference was minor enough to be irrelevant at combat ranges and NATO tanks were relatively big targets. Compared to the D-10T on the T-55, it was a vastly superior product and provided significantly more firepower with a surplus of potential for combating future threats. Besides being optimized to fire APFSDS rounds from the onset, the U-5TS also offered more powerful HEAT ammunition thanks to its larger caliber - an advantage that the D-54TS would not have been able to replicate. It is also worth noting that due to the larger caliber of the U-5TS over the D-54TS, it fired larger and heavier HE-Frag shells at a muzzle velocity of 905 m/s, equal to the D10, meaning that despite its much higher operating pressures, the casing of the shells did not have to be thickened. The D-54 fired its HE-Frag shells at a muzzle velocity of 1,000 m/s so the shell casing had to be thickened in order to better withstand the stress, thus reducing the mass of the explosive payload as a consequence. In turn, this drove down the ratio between the explosive mass and the total mass of the shell and worsened the fragmentation characteristics of the shell, not to mention that the smaller explosive mass made it weaker against heavy fortifications. The downside of the smoothbore U-5TS was that its HE-Frag shells had to be fin-stabilized and proved to be somewhat less accurate than the spin-stabilized HE-Frag shells of the D-54 at long ranges.<br />
<br />The U-5TS features an electrical solenoid firing mechanism for its striker-operated primer ignition system. The electric firing mechanism was wholly transplanted from the D10-TG, but the mechanical portions of the firing mechanism are not completely interchangeable, though some parts of the breech mechanism are interchangeable. The function of the firing solenoid is simply to produce the necessary force to trip a sear, which releases the firing pin. The firing pin, which is not interchangeable with the D10 series, is functionally a spring-loaded striker. If the electrical systems fail, it is still possible to fire the gun manually by tripping the sear of the firing pin mechanism via a trigger lever. The mechanism can be manually recocked for multiple attempts to fire.<br />
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The recoil buffer in the U-5TS was installed asymmetrically from the breech, and the recoil recuperator was installed underneath the breech with a small offset to the left. The asymmetric placement of the recoil buffer lead to an uneven distribution of the recoil force as a fired shot traveled through the barrel, creating a larger moment of force during the recoil stroke of the cannon. Consequently, increased oscillations at the muzzle were generated while the projectile was still traveling down the barrel which result in an increase in shot dispersion compared to a cannon with symmetrically mounted recoil buffers. However, placing the recoil buffer in this location reduced the width of the cannon assembly and the height of the breech above the bore axis, which enabled the T-62 turret with the same height as the turret of the T-54 to accommodate a gun depression angle of -6 degrees instead of -5 degrees despite the increased caliber of the U-5TS compared to the D-10T. The drawback is that the increased height of the breech below the bore axis decreased the maximum gun elevation angle to 16.5 degrees.<br /><br />
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For comparison, the British 105mm L7 cannon had <a href="http://www.kotsch88.de/kanonen/105mml7/leopard-1-4-kl.jpg">a symmetric recoil buffer layout with one recoil buffer on the bottom left of the breech and one on the top right of the breech</a> with <a href="https://www.flickr.com/photos/yetdark/3642117238">a recuperator installed on the right of the breech just underneath the top right recoil buffer</a>. By not having any recoil buffers directly above or below the breech, this freed up the space directly above and below the gun breech and helped to facilitate larger vertical aiming angles, but the downside is that the width of the cannon was increased. This reduced the available width of space available to the crew in the turret and the design of the recoil mechanism itself forced tank designers to use a wide and more vulnerable gun mantlet as exemplified by the Centurion and Leopard 1 turrets. The M60 and M60A1 turrets avoided the use of such a gun mantlet design thanks to the more compact concentric recoil mechanism of the M68.<br />
<br />The gun has a normal recoil stroke of between 350 mm and 415 mm, depending on the power of the ammunition used, with a hard stop at 430 mm. The recoil mechanism of the U-5TS was never changed during its production run, and the asymmetric layout of the mechanism was carried over to the 125mm D-81T (2A26) cannon on the T-64A with a few minor modifications. Compared to the M68 gun with its 343mm maximum recoil stroke, the U-5TS ostensibly requires a larger swept volume in the turret, thus requiring a taller turret for an equivalent range of gun elevation. However, the actual difference is much smaller. By adding up the maximum recoil stroke with the internal length, defined as the distance between the trunnion and the rear surface of the breech (1,222mm), the total swept length of the gun is 1,652mm. </div><br /><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggmKLKTMHTcJh7v5XkqB0bG-H132MiLbefYOUJjvuAdvywjp19UgssPfFr2FRjuINfMKc5dHJ9hmm88XWr1C5apPpYr4618O7rNrCUIcX40RhC2EuHu9ISfxVz7RUIW7EpXwn0xP-jy1pwnU6Xka9151U4g2nbgGO37gfz1xa9UuWnMTBKBX1HomaksQ/s4437/u-5ts%20in%20t-62.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1121" data-original-width="4437" height="162" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggmKLKTMHTcJh7v5XkqB0bG-H132MiLbefYOUJjvuAdvywjp19UgssPfFr2FRjuINfMKc5dHJ9hmm88XWr1C5apPpYr4618O7rNrCUIcX40RhC2EuHu9ISfxVz7RUIW7EpXwn0xP-jy1pwnU6Xka9151U4g2nbgGO37gfz1xa9UuWnMTBKBX1HomaksQ/w640-h162/u-5ts%20in%20t-62.png" width="640" /></a></div><div><br /></div><div>For the M68 gun, the distance between the trunion and the breech end is 1,270mm, which results in a total swept length of 1,613mm. As such, despite being a physically massive gun, the U-5TS is only slightly larger than the M68 in the main dimension relevant to the gun elevation range. Surprisingly enough, it is even more compact than the 90mm M3 gun in this regard as that had <a href="https://cdn.discordapp.com/attachments/763462491119681540/809239458007482388/unknown.png">an internal length of 57 inches</a> and a maximum recoil of 14 inches, giving a total swept length of 1,803mm. As another point of comparison, the L11, with its long inboard length of 1,470mm from trunnion to breech face, and 370mm of recoil, has a swept length of 1,840mm.</div><div><br />
<br />When the stabilizer is activated, the gun depression limit of the T-62 is reduced to -5 degrees, due to the need to create a braking zone for the gun in order to prevent it from slamming into the hard stops at high velocity when the tank is moving at high speed over rough terrain. The dead zone of the main gun is therefore 20 meters. The use of braking zones is a common feature of tank gun stabilizers. For instance, when tanks like the M60A1 were equipped with a stabilizer in the M60A1 (AOS) model, the gun depression limit was reduced to -8 degrees. Despite the relatively poor gun depression of the T-62 compared to typical NATO tanks like the M60A1 or the Chieftain, a gun depression limit of -6 degrees is enough to allow the tank to aim and fire while on the move over uneven terrain and take up positions behind most forms of natural cover. The inability to fire from a hull-down position from the reverse slope of certain hills or ridges is only a partial drawback, because not all hills are shaped perfectly for tanks with a gun depression limit ranging from -8 to -10 degrees to exploit, and it is not desirable for a tank to park itself on the crest of a hill, as it becomes silhouetted against the sky and can be seen from a long distance.</div><div><br />
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There are three methods of firing the cannon - the electric button trigger on the right control handle, the solenoid button on the manual elevation handwheel, and the manual trigger on the breech itself. </div><div>The gun has no external travel lock, instead relying entirely on an internal travel lock to secure its movement in elevation. The internal travel lock is a perforated bar secured to a locking eye on the turret roof, which is welded into the roof via a plug, which forms a visible circle on the exterior of the turret. To lock the gun, the gun is manually elevated until the travel lock eye on the face of the breech housing is aligned with one of the holes in the travel lock, and a pin is inserted through them, as shown in the photo below. Additionally, the coil spring for the ejector levers is visible in the photo on the lower left corner of the breech housing.<br />
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The U-5TS was completely unchanged throughout the service career of the T-62 in the Soviet Army until 1983 in the T-62M modernization when the barrel received an aluminium thermal sleeve that featured a design shared with the 125mm 2A46 cannon. The sleeve was divided into four sections, enshrouding the entire barrel along its entire length with a gap at the base of the barrel in order to not interfere with the gun mask during the cannon's recoil stroke. Plastic was used in order to keep the sleeve as light as possible so as not to interfere too much with the delicate balancing of the cannon, but still, additional ballast plates had to be added to the breech to maintain equilibrium.<br />
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By adding a thermal sleeve, the accuracy and consistency of fire could be increased at minimal cost. Together with the "Volna" fire control system which included a laser rangefinder and the smoother ride with the improved suspension of the T-62M, the thermal sleeve helped to increase the first-round hit probability when firing at point targets, especially in rainy weather. According to the article "Barrel Distortion and First-Round Hits" by Lieutenant Colonel David Eshel published in <a href="https://www.benning.army.mil/armor/eARMOR/content/issues/1985/JAN_FEB/ArmorJanuaryFebruary1985web.pdf">the January-February 1985 issue of the Armor magazine</a>, firing in the rain has resulted in errors of up to 7 mils from barrel distortion, and by contrast, the maximum barrel distortion from solar heating occurs at 10 a.m in the morning and 4 p.m in the afternoon and the errors from heating and other external factors cumulatively induce an error of up to 1 mil. The installation of a thermal sleeve over the gun barrel will reduce the error when firing in the rain down to only 0.25 mils.<br />
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<h3>
<a href="https://www.blogger.com/null" id="stabs"></a>
<span style="font-size: large;">STABILIZER</span></h3>
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Even as the first pre-production T-62 tanks rolled off the factory gates in 1961, it was already fitted with the new 2E15 "Meteor" 2-plane stabilizer. This was not a common practice in the West at the time, not even in the U.S Army which was a pioneer in the large scale implementation of gun stabilizers before WWII. Among the many tanks fielded by the major NATO armies, only the British Centurion tank series featured a gun stabilizer. The Leopard 1 caught up to the T-62 in 1970 with the Leopard 1A1 upgrade when it received a new Cadillac-Gage two-plane stabilizer, which was a modification of a stabilizer designed for "Patton" tanks created in 1964-1965. Before this, it only had powered traverse and gun elevation, and most Leopard 1 tanks retained this gun laying system as the 1A1 model was only produced in limited numbers. The M60A1 - which was essentially the most closely comparable nemesis to the T-62 - had just powered traverse and gun elevation like the Leopard 1 and only received a serious two-plane stabilizer in 1972 in the form of the AOS (Add-On Stabilizer) system retrofit using a Cadillac-Gage two-plane stabilizer derived from the system developed for the Leopard 1. Even then, the stabilizer was not noticeably more useful; although it was technically more advanced on paper, it did not facilitate higher hit probabilities compared to the T-62 when M60A1 AOS tanks fired on the move.</div><div><br /></div><div>When the T-62 was new, "Meteor" gave it a quicker reaction time when firing on short halts and when firing on the move, granting it a necessary advantage over contemporary Western tanks in highly mobile meeting engagements as that was considered the main format of tank combat by Soviet and Western experts. This also meant that the T-62 was more flexible on the dynamic battlefield, being nearly equally adept on the defensive as on the offensive.<br />
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The presence of a stabilizer was important in a variety of combat situations. In a duel between two moving tanks in a meeting engagement at a range of between 1.0 and 1.5 km, "Meteor" allows the T-62 to fire first by being able to fire without stopping, and expect a probability of hit greater than 50%. In a less time-sensitive situation, the crew can utilize two methods to improve firing accuracy: short halts and slow crawls. These are processes that must be coordinated by the commander. For either methods, the process is as follows: The commander spots a target, designates it for the gunner and cues the loader to load an appropriate round, while either he or the gunner measures the range to the target using a stadia rangefinder. The gunner then inputs the range data, lays the gun on target, and announces that he is ready to fire. The driver is ordered to either stop or slow down the tank. If the gun is to be fired while the tank is cruising or moving at a slow crawl, it is important that the driver does not change gears as per the instructions given in the T-62 field manual. Once stopped or slowed down, the gunner fires. If moving, it is preferable for the tank to approach the target straight ahead just before and during the shot. This minimizes the stabilization error in the horizontal plane which tends to be relatively high. Immediately after the shot, the driver immediately speeds up the tank and performs evasive maneuvers until ordered to prepare for the next shot by the commander.<br />
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If the T-62 is instead faced with an enemy ATGM or anti-tank gun team, the stabilizer allows the gunner to suppress the enemy with fire from the machine gun or main gun while the driver performs evasive maneuvers. This combination of passive and active countermeasures considerably reduces the probability of hit on the T-62. Without a stabilizer, firing upon the enemy while performing evasive maneuvers is much less effective, especially at long range which is particularly relevant if the tank is targeted by an ATGM.<br /><br />
<div>Control of gun elevation and turret traverse is conducted using the control handles.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-pXLBJfS4ctE/VlCvD-2l2PI/AAAAAAAAERw/YCBFNJ3nuhU/s1600/t-55%2Bmeteor%2Bhandgrips.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://1.bp.blogspot.com/-pXLBJfS4ctE/VlCvD-2l2PI/AAAAAAAAERw/YCBFNJ3nuhU/s320/t-55%2Bmeteor%2Bhandgrips.jpg" width="246" /></a></div><br /><br />In case of a total failure of the electrical systems or some other malfunction, the gunner must use hand cranked handwheels located directly behind the handgrips. The gearbox on the manual elevation and traverse mechanisms both have buttons for disengaging the powered actuators and engaging the manual drive gears. <br /><br />The maximum effort needed to elevate or depress the gun using the elevation handwheel does not exceed 5 kgf. Despite having a larger 115mm gun, this was a substantial improvement over the manual elevation mechanism of the T-54, which was already exceptionally light, requiring no more than 8 kgf of effort on the handwheel. This was achieved thanks to the near-perfect balance of the gun, and likely helped by the increased distance between the trunnion and the toothed elevation arc where the gun interfaces with the elevation mechanism, which increased the mechanical advantage from leverage.<br /><br /><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-8EABV-MII3E/YDnFSLvPSfI/AAAAAAAAS0g/DEBsOUIPUJIswewUDH498Jt4JDIvnUKagCLcBGAsYHQ/s1996/turret%2Brotation%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1336" data-original-width="1996" height="268" src="https://1.bp.blogspot.com/-8EABV-MII3E/YDnFSLvPSfI/AAAAAAAAS0g/DEBsOUIPUJIswewUDH498Jt4JDIvnUKagCLcBGAsYHQ/w400-h268/turret%2Brotation%2Bmechanism.png" width="400" /></a><a href="https://1.bp.blogspot.com/-lk3r12AJvvg/YDnJJI-9MhI/AAAAAAAAS0o/LCDd0VAJXKg75SSDcv6rdWQ744y2vwzCACLcBGAsYHQ/s1253/elevation%2Bflywheel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1253" data-original-width="1210" height="320" src="https://1.bp.blogspot.com/-lk3r12AJvvg/YDnJJI-9MhI/AAAAAAAAS0o/LCDd0VAJXKg75SSDcv6rdWQ744y2vwzCACLcBGAsYHQ/s320/elevation%2Bflywheel.png" /></a><br /></div></div><div><br /></div>
<div><br /></div><div>The firing circuit for the tank's weapon system is shown in the diagram below. The right trigger button on the gunner's control handles (6) and the trigger button on the elevation handwheel (7) are used to fire the main gun electrically. The left trigger button on the gunner's control handles (4) and the trigger button on the turret traverse handwheel (5) are used to fire the coaxial machine gun electrically. Before firing can be commence, the gunner must close the firing circuit for the desired weapon by setting the selector switch to the "On" position. There are separate switches for the main gun (13) and the coaxial machine gun (2). If the loader's assist function is present, the main gun firing circuit passes through the autoblocker unit (9), which keeps the firing circuit open until the loader presses his ready switch. </div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-pMgdJN7J0-A/YRTIcsK8WQI/AAAAAAAAUE0/hVjP6X4elFgfjKDrwHRFvXjHwXAaS97ggCLcBGAsYHQ/s1310/firing%2Bcircuit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1310" data-original-width="1160" height="400" src="https://1.bp.blogspot.com/-pMgdJN7J0-A/YRTIcsK8WQI/AAAAAAAAUE0/hVjP6X4elFgfjKDrwHRFvXjHwXAaS97ggCLcBGAsYHQ/w354-h400/firing%2Bcircuit.png" width="354" /></a></div>
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<h3>
<span style="font-size: large;">2E15 "Meteor" Hydroelectric Stabilizer</span></h3>
<div><br /></div><div>"Meteor" was developed and tested very quickly thanks to the close relationship that it shared with existing stabilizers. It was assembled and adapted for the T-62 from two previous stabilizer projects that were already proven in operation: the STP-2 "Tsyklon" from the T-54B and 2E12 "Liven" from the T-10M. To be specific, "Meteor" used the gyroscopic sensors, horizontal tachometer, automatic gun blocking system, and the electric fittings of the STP-2 stabilizer, while it used the amplidyne amplifier, vertical tachometer and the electric turret rotation drive from the 2E12 stabilizer, upgraded with an additional cooling fan. The hydraulic gun elevation drive was closely modeled on the type used in the 2E12 stabilizer but modified for the new U-5TS gun. Physically and logically, "Meteor" has more in common with the STP-2, which is only natural given that both systems work on the rather straightforward sight-follows-gun stabilization regime and both have the same type of fire control system. However, the new system was greater than the sum of its parts, offering considerably better reliability compared to both systems. The warrantied service life was 375 hours instead of 250 hours, as was the case for STP-2 and 2E12.<br /><br />As the years went by, the T-62 received continuously updated versions of "Meteor". The "Meteor-M" stabilizer was installed beginning in 1972 in new production tanks and was retrofitted to some tanks. It was designed to work alongside the TShS-41U and TShSD-41U sights. The "Meteor-M1" was installed in the T-62M. It featured new electronics and was adapted to work with the new "Volna" fire control system which included a ballistic computer. Both "Meteor-M" and "Meteor-M1" incorporated transistor electronics, replacing the vacuum tubes in certain components.</div><div><br /><br />"Meteor" has two modes of operation: Automatic and Semi-automatic. In the automatic mode, the stabilizers operate at full capacity and work to keep the gun oriented at the point of aim set by the gunner using his sight. In the semi-automatic mode, the gyrostabilizer system suspends operation, but not the horizontal and vertical drives. In effect, the gunner is left with power traverse and elevation but no stabilization. The semi-automatic mode is used when the tank is used defensively in a fixed position and when travelling in anticipation of imminent combat, the reason being that keeping the system in the semi-automatic mode improves the lifespan of the stabilizer system by reducing the wear of sensitive devices. Switching from semi-automatic to automatic is almost instantaneous. The semi-automatic mode is also used as a backup if a failure of the stabilizer system occurs.<br /><br /></div>The elevation and traverse mechanisms are capable of braking the gun and turret, but the main purpose of these brakes is to ensure that the gunner's lay on a target does not change while the tank is in various positions, such as being on a slope. Travel locks are needed to secure the gun and turret during marches, as in any tank. As a Class 1 lever, disruptions in the orientation of a tank gun can be represented in terms of moments of force about its pivoting point. The sources of these moments is the motion of the tank over uneven ground and angular oscillations of the tank due to the suspension when driving over rough surfaces. The faster the tank travels and the rougher the terrain, the larger the moment of force that is applied to a gun, as more of the tank's forward momentum is converted into upwards and sideward angular momentum. It is for this reason that travel locks are used to secure a gun in elevation, along with turret locks to secure the turret in rotation, when travelling; the large moments of force generated in cross-country travel will impart great stress on the turret control mechanisms. </div><div><br /></div><div>To maintain a given point of aim when a tank is moving across uneven ground, the stabilizer must apply a moment of force to the gun that is equal in magnitude and opposite in direction to any external disturbing moments. This is known as the stabilizing moment. The maximum stabilizing moment of the "Meteor" on the gun is 1,860 Nm, which is twice as high as the maximum stabilizing moment of 931 Nm from the STP-2 Tsiklon" stabilizer. This more than compensated for the larger weight of the U-5TS compared to the D10-T2S, providing improved stabilization performance on rough terrain. The stabilization stiffness (rotational stiffness) of the gun is 637 Nm/mil, more than double the 245 Nm/mil stabilization stiffness from the "Tsiklon" stabilizer. This means that more than twice as much torque has to be transmitted through the trunnion pin through friction in order to produce the same angular deviation in the line of sight of the bore axis to its point of aim. Stabilization stiffness is also influenced by the moment of inertia of a gun; long and heavy guns tend to have a larger moment of inertia which positively affects their stabilization stiffness.</div><div><br /></div><div><br /></div><div>Officially, the turret traverse is somewhat slow. According to a T-62 technical manual, the turret rotation speed is not less than 16 degrees per second. The figure given in the manual is a minimum threshold which must be met during normal operation, otherwise the stabilizer is considered faulty and will be sent for repairs or replacement. Going by this figure, it would take 22.5 seconds for the turret to make a full revolution. However, the real turret traverse speed under normal conditions can be higher. In TRADOC Bulletin 10, published February 1979, it is stated that the T-62 turret requires 20 seconds to rotate 360 degrees, translating to a rotation speed of 18 degrees per second. This information is quite credible given that the U.S Army extensively tested captured T-62 tanks delivered by Israel after the 1973 Arab-Israeli war. West German testing also found that a full rotation took 20 seconds, or 22 seconds with the tank situated on a slope. Additionally, M.V Pavlov and I.V Pavlov report in the "<i>Техника и Вооружение</i>" magazine that the turret rotation speed ranges from 17 to 19.6 degrees per second. Differences in the turret rotation speed can be attributed to different environmental temperatures and the position of the tank, with 16 degrees per second likely being possible only in abnormal circumstances.</div><div><br /></div><div>With the "Meteor-M1" stabilizer, the turret rotation speed of the T-62M was slightly reduced to not less than 15 degrees per second, according to the manual. The real speed may range from 16-19 degrees per second. Some degradation in performance can be expected due to the additional weight of the add-on composite armour blocks on the turret, as well as the imbalance that they cause, owing to the lack of a counterweight on the rear of the turret.</div><br /><div><br /></div><div>The maximum turret traverse speed is only slightly slower than tanks like the M60A1, which provided a turret traverse speed of 22.5 degrees per second. In practical terms, this can mean that after a target is detected by the tank commander, it could take one or two seconds longer for a T-62 gunner to be cued to the target compared to an M60A1 gunner, though only in extreme situations such as when turning the turret from the 9 o'clock position to the 3 o'clock position (180-degree turn). In general, such a marginal difference can be considered inconsequential.<br />
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<b>T-62 Manual:</b><br />
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Minimum Traverse Speed: not more than 0.07 deg/s<br />
Maximum Traverse Speed: not less than 16 deg/s<br />
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Minimum Gun Elevation Speed: not more than 0.07 deg/s</div><div>
Maximum Gun Elevation Speed: not less than 4.5 deg/s<br />
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<b>"<i>Техника и Вооружение</i>" Magazine:</b><br />
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Automatic Mode:<br />
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Minimum Traverse Speed: 0.07 deg/s<br />
Maximum Traverse Speed: 17-19.6 deg/s<br />
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Minimum Gun Elevation Speed: 0.07 deg/s<br />
Maximum Gun Elevation Speed: 4.5 deg/s<br />
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Semi-Automatic Mode:<br />
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Minimum Traverse Speed: 0.07 deg/s<br />
Maximum Traverse Speed: 20-25.7 deg/s<br />
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Minimum Gun Elevation Speed: 0.07 deg/s<br />
Maximum Gun Elevation Speed: 4.5 deg/s<br />
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"Meteor" is generally not accurate enough to be used for engaging targets on the move at long distances, but it allows targets at short to medium ranges (up to 1.5 km) to be fired upon with a high probability of hit. According to the book "<i>Отечественные Бронированные Машины 1946-1965</i>" (<i>Domestic Armoured Vehicles 1946-1965</i>), the third volume in the series "<i>Отечественные Бронированные Машины - XX Век</i>", the probability of hit on a static tank profile silhouette (tank target No. 12A) at 1.2-1.5 km while on the move is 64%.</div><div><br /></div><div>Engaging targets at a longer range or a smaller target at the same range (a hull-down tank, for example) requires the tank to make a short halt. The stabilization precision in the vertical and horizontal planes is 1 mil and 3 mils respectively when the tank is in motion at a speed of 25 km/h. That is, the maximum angular deviation of the point of aim will not exceed these limits when the tank is in motion. The median stabilization accuracy is unknown.<br />
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A stationary T-62 achieves a greater than 70% hit rate at 1,000 meters on a tank-type target moving at 20 km/h at a relative angle of approach of 30°, according to a U.S TRADOC bulletin, pictured below.<br />
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Considering that the tank lacks an optical coincidence rangefinder, this result is remarkably similar to the M60A1 AOS. This can be seen in the data from military trials of the Strv 103 conducted in the United States in 1976-1977, as recorded in <a href="https://tanks.mod16.org/pdf/Strv%20103B%20in%20the%20US.pdf">this document shared by renhanxue, owner of the tanks.mod16 website</a>. When averaging between 400 shots taken against different types of tank targets (head-on silhouette, oblique silhouette, full side profile silhouette) from between 500 to 2,000 meters under various simulated scenarios (page 11 of the PDF), the M60A1 AOS has a hit rate of 72% and the Strv 103 has a hit rate of 77%. Bearing in mind that moving targets are the most difficult type of target to hit (especially for earlier Cold War era tanks that lacked automatic target leading systems), the "<i>better than 70 percent chance of scoring a first round hit at 1,000 meters</i>" achieved by the T-62 can be interpreted to mean that its accuracy is generally on par with its Swedish and American counterparts.<br />
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In field manual FM71-2 published in 1977, it is indicated that the T-62 has a better chance of killing an M60A1 with the first hit with its APFSDS round than the M60A1 has against a T-62 with its APDS round at combat ranges. At point blank range, there is no difference in the probability of kill if an M60A1 or a T-62 were to fire at each other - both will have a 100% chance of achieving a kill. However, as the distance increases, the probability of kill of the M60A1 diminishes whereas the T-62 gains a consistent 10% advantage up to a distance of 1,200 meters, beyond which the difference between the two tanks begins diminish. It is not until a distance of 1,800 meters is reached where the M60A1 fully catches up to the T-62 and both tanks have exactly the same chance of killing each other with the first shot. Beyond 1,800 meters, the M60A1 gains and retains an advantage of 10-15% while the T-62 eventually becomes completely ineffective at distances exceeding 2,500 meters.<br />
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The advantage in the probability of kill held by the M60A1 at extreme long ranges most likely stems from its optical coincidence rangefinder. At such ranges, a M60A1 gunner has a better chance of scoring a hit compared to a T-62, whose gunner relies on battlesight gunnery techniques and a stadia rangefinder for precision shooting.<br />
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Based on the indicated kill probability for the M60A1 using APDS against a T-62, it can be inferred that the ammunition must be the M728 round, a licence-produced localized variant of the British L52A1 round. The earlier M392 round (analogue of L28) is not capable of defeating the front turret armour of a T-62 from 800 meters and above, and is not capable of defeating the upper glacis from 1,800 meters and above. On the other hand, the kill probability for the T-62 using APFSDS against the M60A1 is likely to have been calculated using the 3BM4 rounds that were captured together with the tank. By 1977, the 3BM4 round had been replaced by two newer types with significantly enhanced power - the 3BM6 and 3BM21.<br />
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At the Fulda Gap, the terrain prohibits tank combat at distances exceeding 800 meters, and in Central and Western Europe, independent American, German and Polish studies showed that the maximum tank combat distance does not exceed 1,500 meters in over 90% of cases. Given that the M60A1 does not hold any advantage over the T-62 except at distances exceeding 1,800 meters, it is not relevant to a European battlefield. Both tanks have a less than 40% chance of killing the other at a distance of 1,500 meters. The chances of the M60A1 most likely degraded further in the 1970's with the introduction of the T-62 obr. 1972 model with an improved TShS-41U sight.<br />
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The addition of M735 APFSDS rounds to the Army arsenal in 1979 gave the M60A1 and M60A3 the theoretical capability to kill T-62s from over two kilometers, but once again, the distance constraints imposed by Central and Western European terrain limited the usefulness of this advantage. Still, using APFSDS rounds against a T-62 would yield an increased probability of kill at combat ranges, but by 1974, a variety of upgrades had been applied to the T-62 including a laser rangefinder and newer 115mm APFSDS rounds. The M60A1 still relied on an optical coincidence rangefinder which was slower to use and less precise and only the M60A3 received an AN/VVG-2 laser rangefinder in 1978, so again, the T-62 generally still held the advantage.<br />
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However, this is only an indication of the accuracy of the T-62 when firing from a standstill. The primary value of the stabilizer is derived from the ability to fire with reasonable accuracy while the tank is on the move or on short halts. Movement makes it considerably more difficult for an enemy tank to successfully score a hit, and even simple maneuvers performed by a novice driver can make it even more difficult to score a hit.<br />
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According to calculated data, the probability of achieving a hit (using APFSDS) on a static tank profile silhouette target with the dimensions of 2.8 x 6.9 meters while the T-62 is moving at a speed of 20-25 km/h is 65.5% at a distance of 1.0 km, 38.5% at a distance of 1.5 km, and 24.0% at a distance of 2.0 km. By comparison, the probability of hitting the same target under the same conditions but with the stabilizer disabled is 2.6%, 1.15% and 0.65% respectively. When firing at a tank front silhouette target while moving at 20-25 km/h, the probability of hit is 47% at 1.0 km, 25.8% at 1.5 km, and 15.7% at 2.0 km.<br />
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According to the May 2012 issue of the "<i>Техника и Вооружение</i>" magazine, the "effectiveness" of firing on a static "tank" type target in profile while on the move at a distance of 1,000-1,500 meters is 50%, and at 1,500-2,000 meters and 2,000-2,500 meters the "effectiveness" is 37.5% and 30% respectively. It is unclear what the author means by "effectiveness", but the basic criteria for evaluating the maximum effective range of a tank is the range at which a 50% probability of hit can be achieved. Based on these test results, the maximum effective range of the T-62 when firing on the move is between 1.0 and 1.5 kilometers when the target is in profile. When firing at the front of a tank-type target, the maximum effective range is just under a kilometer. Such results are unimpressive by modern standards, but for 1961, it was excellent. It was certainly sufficient for a European theater.<br />
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In terms of gun laying precision, "Meteor" was technically outclassed by the M60A1 stabilizer from the M60A1 AOS (Add-On Stabilizer) of 1972. According to <i><a href="https://books.google.com.my/books?id=k1oYAAAAYAAJ&pg=SA1-PA9&lpg=SA1-PA9&dq=m60a1+gun+traverse+minimum+speed&source=bl&ots=1gj2Bdfe-U&sig=cAOrqHZ-b8wc4QU5ph6d0DQwiEM&hl=en&sa=X&redir_esc=y#v=onepage&q=m60a1%20gun%20traverse%20minimum%20speed&f=false">Direct support and general support maintenance manual: turret for tank, combat, full-tracked, 105-mm gun, M60A1 (2350-00-756-8497) and M60A1 (AOS) (2350-01-058-9487)</a></i>, the AOS system offered better gun laying precision, having a minimum traverse speed of 0.5 mils per second or 0.028 degrees per second, and an equal minimum elevation speed. The horizontal drive of the AOS system also offered a vastly superior maximum turret traverse speed. However, the stabilization accuracy of the AOS system was not very high. According to MIL-HDBK-799, page 6-19, the stabilization accuracy of the M60A3 with the AOS system was 1 mil, which is the same as "Meteor" despite the AOS system being more than a decade newer. Furthermore, real test results do not appear to support the superiority of the AOS system - Hunnicutt reports in page 200 of "<i>Patton: A History of the American Main Battle Tank, volume 1</i>" that test results from Aberdeen showed that the hit probabilities from a moving M60A1 with a Cadillac-Gage add-on stabilizer were "better than 50%" at "short to medium ranges". On page 49 of the March-April 1972 issue of "ARMOR" Magazine, in the article "<i>Tank add-on stabilization</i>" by John G. Loridas, it is stated that:<br />
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"<i>Through use of the add-on stabilization kit, the moving vehicle has attained hit probabilities of greater than 50 per cent during TECOM tests on stationary targets. This hit probability figure compares favorable to a hit probability of approximately 70 per cent for the same range and ammunition when firing from a stationary vehicle at a stationary target.</i>"
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A hit probability of 70% against a stationary tank-sized target when firing from a static position with APDS is achieved at a distance of 1,000 meters. As such, the article implies that a "greater than 50%" probability of hit - probably somewhere between 50% to 55% - was achieved at 1,000 meters during TECOM tests on stationary targets. With this evidence, it appears that the M60A1 AOS either did not exceed the T-62 in first-round hit probability or falls significantly below the level of the T-62 which, again, is reported to achieve a first-round hit probability of 65.5% on a tank-sized target at 1.0 km while travelling at 20-25 km/h.
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Most interestingly, brigade commander Colonel Thomas E. Carpenter states on page 48 of the July-August 1977 issue of "ARMOR" Magazine that the M60A1 was considered by USAREUR to have a 70% chance of "winning an engagement" against a T-62 at 1,000 meters provided that the M60A1 fired first. As such, tank gunners were trained to engage a tank with the battlesight gunnery technique in 5 seconds after visual contact. Battlesight gunnery is used because the speed in firing the first shot is critical, but with this technique, the advantage of the M60A1 in having an optical rangefinder is irrelevant whereas the higher speed and flatter trajectory of the APFSDS ammunition of the T-62 gives it the advantage when using the battlesight gunnery technique, and the presence of gun stabilization on the T-62 gives it an overwhelming advantage when firing from the move or from short halts. The advantages of the T-62 were only partly negated by the M60A1 AOS modification as shown earlier.<br />
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Overall, "Meteor" was quite good for 1961 and it was certainly much better than the stabilizer of the Centurion Mk. 3 and its later variants. It was also unquestionably better than having no stabilization at all, which was the case for the entire line of "Patton" medium tanks and for early Leopard 1 tanks, although the Leopard 1 could still be used effectively if care is taken in tactical planning as it had a vastly more sophisticated fire control system. "Meteor" could still be considered adequate during the 1970's and the relevance of the T-62 during that decade was reinforced when it began to be retrofitted with the KDT-1 laser rangefinder beginning in 1974-75.<br />
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As mentioned before in the "Sighting complexes" section of this article, "Meteor" features a loader assist function where it raises the cannon to an elevation angle of +2.5 degrees and holds it in place by hydrolock. The system relies on an autoblocker unit attached to the recoil guard on the loader's side of the U-5TS gun. Raising the gun puts it at a more convenient position for the loader to perform his duties, and it also prevents the cannon from undulating while the tank is moving over uneven terrain. Turret traverse is automatically suspended by the system disengaging the friction clutch electronically. It was important for the turret traverse to be suspended as almost all of the ammunition in the T-62 is stored in the hull. If the turret suddenly started rotating at high speed while the loader was still in the midst of extricating a round from one of the hull ammunition racks, perhaps due to the driver turning the tank to evade an obstacle, the unsuspecting loader might be caught off balance or even hit by the moving cannon assembly. If the turret were rotating slowly, such as when tracking a moving target at long range, this would not be a serious hazard.<br />
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Pressing the arming lever on the autoblocker will arm the cannon and restore the stabilizer to the full control of the gunner. This system is integral to "Meteor" and is active in both the automatic and semi-automatic operating modes of the stabilizer. It does not function when the stabilizer is turned off entirely. The auto-ejector system is independent of this system, so turning off either one will not affect the other. The autoblocker system is primarily intended to help the loader carry out his duties while the tank is on the move, as keeping the breech of the gun steady and keeping the turret fixed is most important when the tank is in motion.<br />
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There is an EMU-12PM amplidyne amplifier for the stabilizer system located at the very rear of the turret, just behind the commander's backrest. It takes the electrical signals from the "Meteor" control handles and amplifies the voltage to direct the gun elevation and turret traverse drives, thus translating minute gun laying inputs from the gunner into the movement of the gun and turret.<br />
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There is a gyroscopic tachometer for measuring the angular velocity of the turret and tank in relation to the intended target. The tachometer is installed at the very front of the gunner's station, behind the sighting complexes. The gyro-tachometer was taken from the STP-2 two-plane stabilizer system for the T-54B.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-gAsrqLrTxPo/VmPfxwXC9nI/AAAAAAAAEqE/tdGFPj8c_0Y/s1600/meteor-m1%2Bstabilizer%2Bgyroscope%2Btachometer.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="296" src="https://2.bp.blogspot.com/-gAsrqLrTxPo/VmPfxwXC9nI/AAAAAAAAEqE/tdGFPj8c_0Y/s320/meteor-m1%2Bstabilizer%2Bgyroscope%2Btachometer.png" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Gyroscopic tachometer for Meteor-M1</td></tr>
</tbody></table>
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<h3>
<a href="https://www.blogger.com/null" id="autoejector"></a>
<span style="font-size: large;">AUTO-EJECTOR</span></h3>
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The T-62 has an automatic shell casing ejection system. The main impetus for the development of such a system was the insufficient maturity of fully-combustible propellant charges (caseless ammunition) and the greater expediency of incorporating such a device given the time constraints for putting a tank with a 115mm gun into production using existing cased ammunition. As mentioned before, the interior of the tank hull is quite cramped since only the turret ring was widened, so the floor space in the fighting compartment remains the same as in the T-54. Having a few spent shell casings rolling around the floor was not desirable, to put it mildly. Moreover, during early testing of the Object 166, propellant fumes accumulating in the fighting compartment were still twice higher than the acceptable standard even though the cannon had a fume extractor. The culprit was the spent shell casings. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-7h2NtUHJ5fQ/Xu0oXtARQGI/AAAAAAAARHE/aq4CAv4v9TEnsfjDRp_6D1f9Tcprnp3EgCK4BGAsYHg/s1225/T62M-firing-big-2.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="545" data-original-width="1225" height="284" src="https://1.bp.blogspot.com/-7h2NtUHJ5fQ/Xu0oXtARQGI/AAAAAAAARHE/aq4CAv4v9TEnsfjDRp_6D1f9Tcprnp3EgCK4BGAsYHg/w640-h284/T62M-firing-big-2.gif" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div><br /></div><div>The smoldering unburnt propellant residue lingering inside the spent casings was the source of these fumes, and as the number of shots increased, the number of spent casings accumulated and so did the concentration of fumes in the fighting compartment. When the spent casings were instead ejected from the tank immediately after firing, the concentration of fumes in the fighting compartment was reportedly slashed by half with the added bonus of the loader being saved the trouble of periodically removing the spent shell casings by hand. Combined with the fume extractor built into the U-5TS gun and the powerful ventilation blower for the crew compartment, the total concentration of propellant fumes in the T-62 was was reduced to nearly zero. This greatly improved the working conditions of the crew, particularly the loader whose job was much more physical in nature.</div><div><br /></div><div>
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The ejector mechanism can be switched between the automatic mode or the manual mode. The manual mode essentially deactivates the ejection system. In the manual mode, the gunner must manually pick up the spent shell casing from the lifting tray, open the ejection port by pressing the "open" button on the ejector system control box, and throw the casing out. The ejection port will be kept open until the loader presses the "close" button. He can also throw it out of his own hatch if he prefers.<br />
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The auto-ejector mechanism does not interfere with the loader in any way as it is installed far from the cannon breech and is in a slightly lower position (to compensate for gravity as shell casings are extracted after firing), so it is completely out of the way when the loader is ramming a shell into the chamber. The T-62 is greatly superior to the T-54 in this regard because there is much more space between the cannon breech and the rear wall of the turret thanks to the large turret ring diameter, so there was room for the auto-ejector. In addition to that, the unusually long neck of 115mm cartridges makes it easier for the loader to insert them into the cannon chamber, as it allows him to insert them with a sideways angle.<br />
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The auto-ejector functions independently from the loader's assist function because its components are not logically linked to anything other than its own control system. If the loader's assist function is turned off by the loader, the auto-ejector will continue to function. It can dynamically detect the position of the ejection port relative to the gun at any elevation angle since its control system works using the input of limit switches rather than relying on a fixed set of programmed commands. It will also not proceed with ejecting a shell casing if it does not detect that a shell casing is caught in its tray. As such, low-pressure rounds such as blanks can be fired without needing to turn off the auto-ejector.<br />
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Underneath the loader's handle is the ejection system control box. The ejection mechanism can be set to either the automatic mode or the manual mode by flipping a toggle switch. Two push-buttons on the control box are used to open and close the ejection port in a semi-automatic mode. The ejection port can be opened and closed independently of the rest of the ejection system and this may need to be done if the system experiences a failure. If the tank is fighting in a chemically or biologically contaminated environment, then the auto-ejection system should be set to manual mode, and the crew dons rebreather masks. The mechanism does not work without electrical power.<br />
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If the lifting frame of the ejection mechanism is jammed in at its maximum elevation, the loader can rectify the issue by disengaging the worm gear of the rack-and-pinion mechanism in the lifting motor installed underneath the gun breech and then manually ensuring that the motor is cleared of jams by actuating the piston by working a small handle. Once the cause of the jam is removed, the worm gear is reengaged. When the worm gear of the actuator motor is disengaged, the entire ejection mechanism will be able to freely move up and down within the limits of its range of elevation angles. The same procedure can be done with the ejection port motor.
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The diagram below shows the sequence of ejection. The order of the sequence goes clockwise from the top left. Viewing the diagram in its original size is recommended.<br />
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<a href="https://3.bp.blogspot.com/-H2UMliqiUnk/WW4ttmXnFrI/AAAAAAAAItk/ADKynOZQyC8DNPYX1pckZA1mvJlLuAlAgCLcBGAs/s1600/t-62%2Bcasing%2Bejector.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="1092" data-original-width="1600" height="436" src="https://3.bp.blogspot.com/-H2UMliqiUnk/WW4ttmXnFrI/AAAAAAAAItk/ADKynOZQyC8DNPYX1pckZA1mvJlLuAlAgCLcBGAs/s640/t-62%2Bcasing%2Bejector.png" width="640" /></a><br />
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When the shell casing is ejected from the breech from the recoiling cycle, it is caught by the lifting tray which is a short "U"-shaped tray affixed to the lifting mechanism. The tray is short so as to not obstruct the loader as he is ramming a round into the gun. A spent casing ejected from the gun breech lands in the tray, where it is held in place by its rim by two spring-loaded grippers on either side of the tray, which can be seen in the photo below next to the ejectors. The grippers, which resemble pinball paddles, prevent the spent casing from sliding forward. A rubber-padded plate on the arm guard placed just behind the lifting tray stops the casing from travelling rearwards, and helps to soften the noise when it is caught in the tray. The ejector mechanism is automatically triggered when the base of the spent cartridge case strikes a switch located above the rear plate behind the lifting tray. The act of ejection itself is done by a spring-loaded mechanism with two ejector hooks that slam onto rim of the shell casing (refer to picture below) to kick it out of the ejection port opening. The ejector mechanism is powered by two springs - a stiff torsion bar comprised of a stack of spring steel plates integrated into the hinge of the ejector, and a coil spring fitted beneath the tray. Both springs are cocked by the recoil force of the gun via the octant-shaped reciprocating levers shown in the drawing above, and the ejector is held in place by a locking pin actuated by a solenoid.<br />
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When the presence of a spent shell casing is detected by the switch, the ejection port automatically begins to open so that it is fully opened by the time the ejector mechanism has aligned the ejection tray with the port opening. The ejector mechanism is lifted up to the ejection port and the control system halts the mechanism when a cam comes into contact with the triangular contact plate on the left of the ejection port. The contact plate is shown in the photo on the right below. It is the sharp triangular plate bolted to a protrusion welded to the turret roof between the commander's cupola and the ejection port. It is separated from the commander when the recoil guard is installed. The triangular contact plate (yellow), the cam that contacts the triangular contact plate (red), and the ejector (orange) are shown in the drawing on the left below.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-oqUYe1vJa9k/XPv6t-yk1II/AAAAAAAAOVk/So0hbJcezVANx3FRtDMmAijmBIC120hTgCLcBGAs/s1600/ejector%2Bcoloured.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="713" data-original-width="700" height="320" src="https://1.bp.blogspot.com/-oqUYe1vJa9k/XPv6t-yk1II/AAAAAAAAOVk/So0hbJcezVANx3FRtDMmAijmBIC120hTgCLcBGAs/w314-h320/ejector%2Bcoloured.png" width="314" /></a><a href="http://4.bp.blogspot.com/-tjMel6d-P9g/VmbwlU0wxbI/AAAAAAAAEzY/sm6WKbQFkc0/s1600/t-62%2Bcommanders%2Bstation.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://4.bp.blogspot.com/-tjMel6d-P9g/VmbwlU0wxbI/AAAAAAAAEzY/sm6WKbQFkc0/s400/t-62%2Bcommanders%2Bstation.jpg" width="400" /></a></div>
<div><br /></div><div><br /></div><div>The image below shows the ejector lever assembly and its hinge.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-RZwmvnpe_5c/YRTH8DscrpI/AAAAAAAAUEs/BsCiIVjVMFMzlfYN_ziBpB3-daaOi2pkgCLcBGAsYHQ/s823/ejector.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="823" data-original-width="691" height="320" src="https://1.bp.blogspot.com/-RZwmvnpe_5c/YRTH8DscrpI/AAAAAAAAUEs/BsCiIVjVMFMzlfYN_ziBpB3-daaOi2pkgCLcBGAsYHQ/s320/ejector.png" width="269" /></a></div>
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Upon touching the contact plate, the cam closes a limit switch. This verifies that the ejection mechanism is aligned with the ejection port and it sends a signal to the ejector lock solenoid. The solenoid retracts, removing the locking pin and releasing the ejector arm and the shell casing is thrown out very forcefully by the force of its spring, whereupon the ejection port closes and the mechanism returns to its original position. The case will be thrown forcefully enough to fully clear the engine deck of the tank, if the turret is aimed forward. As the photo below shows, the ejection port is operated by a servo motor and there is a handle to lock it and unlock it manually.<br />
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The ejection process is explained in detail in the T-62 technical manual. These are the relevant paragraphs from the manual (pp. 89-90):<br />
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<blockquote class="tr_bq">
"<i>При ударе фланцем о заднюю стенку ограждения гильза включает кнопку запуска электрической схемы. Происходит открывание люка в башне и подъем рамки на линию выброса. При подъеме рамки створка выходит из зацепления с зацепом, который возвратиться в исходное положение.</i> </blockquote>
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<i>Подъем рамки с гильзой происходит до тех пор, пока кулачок не коснется плоскости копира и не включить переключатели ограничения подъема рамки. Переключатели включается в положении рамки с гильзой против люка в башне. С включением переключателя подается напряжение на электромагнит сброса, который пальцем освобождает захват с зацепами от удержания его защелкой. Силой взведенного торсиона и пружин гильза выбрасывается через люк наружу.</i> </blockquote>
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<i>После выброса гильзы рамка опускается в исходное положение и закрывается люк в башне. При опускании рамка воздействует на скос зацепа и входит с ним в зацепление. После опускания рамки и закрытия люка все механизма выброса занимают исходное положение. </i>"</blockquote>
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Translated into English:<br />
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"<i>When the base of the spent shell casing strikes against the rear wall of the lifting tray, the casing trips a start button for the electrical circuit. The ejection port is opened and the frame is lifted to the ejection position. When the frame is lifted, the leaf is disengaged from the hook, which returns to its original position.</i> </blockquote>
<blockquote class="tr_bq">
<i>The lifting frame with the spent casing rises until a cam touches the surface of the kopira* and presses the frame lifting limit switches. The switches are positioned so the shell casing is aligned with the ejection port in the turret. With the pressing of the switch, voltage is applied to the ejector solenoid, which frees the ejector from the hooks holding it. With the force of the cocked torsion bar spring, the ejector throws the shell casing out through the ejection port.</i></blockquote>
<blockquote class="tr_bq">
<i>After the ejection of the casing the lifting frame is lowered to its original position and the ejection port in the turret is closed. When the frame is lowered, it acts against the bevel of the hook and is locked in place. After the frame is lowered and the ejection hatch is closed, all of the ejection mechanism will be in its original position.</i>"</blockquote>
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<i>*"kopira" is the provisional term for the triangular contact plate used in the manual and in other documents</i><br />
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According to the 1963 report "<a href="http://btvt.info/5library/vbtt_1963_04_gilzi.htm"><i>Автоматизация Удаления Гильз Из Боевого Отделения Танка</i></a>" by Engineer-Colonel Kipnis-Kovalev et al., the entire ejection process takes 2-3 seconds in total. The exact time depends on the elevation angle of the gun - if the gun is fully elevated, the ejection mechanism must be lifted higher to reach the ejection port; if the gun is fully depressed, the ejection mechanism has to travel a much shorter distance. The time taken by the ejection process is verified by <a href="https://youtu.be/JjSniVMa8tw">this video of a Vietnamese T-62 with a working ejector</a>. Knowing the steps of the mechanism, it is known that the ejection cycle starts by the opening of the ejection port and ends when it is fully closed, and in the video, the time taken matches the 2-3 second range given in the 1963 report. The quick action of the ejector mechanism means that the loader will never have to wait for it to finish before loading the cannon, so the system does not interfere with the loading procedure in any way. In fact, the two or three seconds spent by the auto-ejector should be over before a loader has finished retrieving a round from any of the ammo racks in the tank. By the time the lifting frame has lowered back to its original position, the loader should not yet be ready to ram a fresh round into the cannon.<br />
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By ejecting spent shell casings from the tank automatically, the loader's working conditions are greatly improved. The large shell casings have no more uses other than to trip the loader after they have been fired, and the unburnt propellant residue inside the casings emit large volumes of noxious fumes. Without an automatic ejector, the carbon dioxide and carbon monoxide concentration inside an enclosed tank invariably accumulates to an unacceptable level after multiple rounds have been fired in a short period. A high concentration of fumes affects all the crew members, but the loader is the most adversely affected since his duties are much more physically demanding than the others. In this context, the primary benefit of the auto-ejector system is that the working conditions of the crew as a whole are improved, especially the loader's, so that the rate of fire may be improved in the long term.<br /><br /></div><div>
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The entire system is centered on the KV2 control box, which coordinates the timing and execution of all of the actions of the auto-ejector.<br />
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Inside the KV2 control box are five relays. One relay controls the raising of the auto-ejector to the ejection position, one controls the lowering of the auto-ejector to the original position, one controls the opening of the ejection port hatch, and one controls the closing of the hatch. These four relays are coordinated by a time delay relay.<br />
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Using the toggle switch labeled (6) on the diagram above, the loader can either set the system to the "Automatic" mode or the "hatch control" mode, which is essentially the manual mode. When the toggle switch is set to the "Automatic" mode, the auto-ejection system works automatically as we have already examined. When set to the "hatch control" mode, the loader can press the "Open" button to manually open the ejection port. Pressing the "Close" button closes the ejection port. As the opening and closing of the ejection port hatch is no longer controlled by the system, auto-ejection is therefore suspended. This mode can be used in contaminated combat zones to suspend the operation of the auto-ejector and thus ensure that absolutely no contaminated particles can enter through the ejection port despite the positive pressure inside the tank. The ability to open the ejection port hatch is sometimes exploited by leaving it open for for extra ventilation in non-combat conditions or to turn the ejection port into a convenient loading hatch if needed, as demonstrated in the two photos below.<br />
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<div><br />Contrary to popular belief, shell casings can practically never bounce off the back of the turret and injure crew members during normal operation. This myth arose from anecdotes told by U.S Army personnel based on their early impressions while working on a partially dismantled T-62 war trophy delivered by Israel after the 1973 Arab-Israeli war. Major-Colonel James Warford, armour historian, <a href="http://www.tank-net.com/forums/index.php?showtopic=19761&page=6">recounted the details in a forum post</a>.</div><div><br /></div><blockquote><i>I apologize for briefly telling this story again, but...when I first got on one of the US Army's T-62s in 1978, I was told the story of the odd and somewhat dangerous "trigger" for the spent shell ejection system. When the tank arrived from Israel, the system's trigger (a roughly cut triangular-shaped piece of metal) was laying loosely on the turret floor. When the tank was fired, the shell casings were ejected on to the closed ejection hatch or port...then bounced around the fighting compartment. It took awhile for someone to figure-out that the loose piece of metal was actully the trigger that operated the ejection hatch. Once it was put into place, the system worked well and reliably. To this day...I think it likely that someone in Israel may have removed the trigger as a practical joke for the Americans.</i></blockquote><div><br /></div><div>If, by chance, a lag in the electronics causes the opening of the ejection port to be mistimed, the crew remains safe because there is no space for a shell casing to go between the lifting tray and the ejection port, as the sides of the U-shaped ejector tray physically prevents the case from being deflected towards the crew members seated on the left and right of the gun; the casing can only rebound forward and drop to the floor. It is also important to note that the commander is physically shielded by a recoil guard and the gunner is seated next to the cannon breech, in front of the commander, giving them additional security. If the ejection mechanism were to fail this way, the loader can simply pick up the shell casing from the floor and throw it away by hand or retain it by placing it back in the ammunition rack slot he took it from. The latter method may be necessary if the tank is used in a contaminated environment.</div><div><br />This persistent myth seems to have originated or at least evolved from an article titled "<i>The Soviet Tank Mystique</i>" by Major Raphael A. Riccio published in the November-December 1982 edition of ARMOR magazine. The relevant paragraphs of the article from page 33 of the magazine are shown below.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-G2jabAZ1Qq4/XPjBElwObwI/AAAAAAAAONc/StMFNuJY-CoJ6ed-Ci0PONrTmvoTuEcjgCLcBGAs/s1600/t-62%2Bbogus%2Bclaims.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="418" data-original-width="467" height="356" src="https://1.bp.blogspot.com/-G2jabAZ1Qq4/XPjBElwObwI/AAAAAAAAONc/StMFNuJY-CoJ6ed-Ci0PONrTmvoTuEcjgCLcBGAs/s400/t-62%2Bbogus%2Bclaims.png" width="400" /></a></div><br /><br />In this case, it appears that Major Riccio incorrectly believed that the ejection of spent shell casings from the turret was accomplished purely with the built-in ejector in the cannon breech itself rather than with a special powered ejector mechanism placed behind the breech assembly of the cannon, but all of the usual criticisms of the ejection system are present, garnished with figments of a healthy imagination. Over time, it became more widely known that the casing ejection was carried out with a special mechanism instead of the built-in ejector of the gun itself, but the so-called "lunacy" associated with the system borne out of ignorance - even in 1982, almost a decade after the U.S Army acquired captured T-62 tanks and examined them in detail - still remained with the T-62. Furthermore, the ejection system did not depress the gun when beginning the ejection procedure, and it was never necessary anyway since the ejection mechanism could automatically detect if it was aligned with the ejection port regardless of the elevation angle of the gun. This myth seems to be connected with Major Riccio's belief that the gun had to depressed so that the breech opening would be elevated into alignment with the ejection port. Unfortunately, this falsehood is still frequently repeated, even in books published by highly respected authors like Steven Zaloga ("<i>T-62 Main Battle Tank 1965–2005</i>", published in 2011). As detailed earlier, the auto-ejector mechanism in the T-62 was designed to work at any gun elevation angle.<br /><br />Interestingly enough, the method of shell ejection described by Major Riccio was implemented only once, in the Object 430 medium tank prototype, and it was specifically rejected in the 1963 report "<a href="http://btvt.info/5library/vbtt_1963_04_gilzi.htm"><i>Автоматизация Удаления Гильз Из Боевого Отделения Танка</i></a>" because this system created too many issues, the most obvious of which was the inability to have the ejection mechanism work at all elevation angles. Another was that placing the ejection port in the turret rear rather than in the rear part of the turret roof significantly weakened the armour protection, and having the ejection mechanism depend on the elevation mechanism of the cannon would cause the gunner to lose visual contact of the target as he must relinquish control over the elevation of the gun. Also, the need to delay the ejection of the spent casing after each shot in order to raise the gun to the correct elevation for ejection would interfere with the fume extractor, thus allowing more fumes to enter the fighting compartment. In other words, such an ejection scheme proved to be too intrusive into the normal operation of the tank, hence the more complex but much more effective auto-ejector design implemented in the T-62.<br /><br /><br />Another misconception is that the autoejection system compromises the PAZ (anti-nuclear) protection system of the tank because the opening of the ejection port allows airborne contaminants to enter the tank. While this may be true to some extent, the amount of contaminants ingressing the tank would be extremely tiny because the ventilation system maintains an overpressure inside the tank when the PAZ system is activated. The opening of the ejection port would allow more air to rush out rather than into the tank, and indeed, it was found that the autoejection system had a very minimal effect on the amount of radiation exposure suffered by the crew. It was proven during testing that the radiation dosage measured in the fighting compartment increased after firing thirty shots from the main cannon, but the increase was negligible compared to the radiation dosage from background radiation from operating in a site contaminated by a recent nuclear detonation. The combined dosage from radioactive particles and background radiation was within safe margins. Nevertheless, it was necessary for the crew to don their rebreather masks to operate in an area known to be contaminated with chemical or biological weapons. The filtration system for the ventilator cannot cope with the filtration of aerosols or other finer particles, as it lacks a HEPA filtration system. As such, a closed-cycle respirator is needed for the crew to survive.</div>
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<a href="https://www.blogger.com/null" id="ammu"></a>
<span style="font-size: large;">AMMUNITION</span></h3>
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The two biggest assets of the U-5TS cannon were the 3UBM-3 shell - the first ever APFSDS tank shell to enter service - and the 3UBK3 shell, which was a conventional HEAT shell.<br />
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Shell casings had an atypical form that is readily identified by a greatly elongated bottlenecked front section, which was necessary for properly seating the APFSDS shells for which the casings were specially designed for. The 100mm T-12 gun used ammunition that had the same case design. There are two types of casings; steel 4G9 cases and brass 4G10A cases. Naturally, the steel 4G9 cases cost less to manufacture, while the brass 4G10A cases cost more. Steel cases were used for HE-Frag ammunition, for which accuracy was of less importance while the more ductile brass cases were used for APFSDS and HEAT-FS.</div><div><br /></div><div>The KV-5 or KV-5U percussion primer was fitted to all 115mm ammunition. The KV-5 series was made for ammunition with a maximum design pressure of 430 MPa.<br />
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The standard combat loadout for a Soviet T-62 during the 1960's was 12 APFSDS rounds, 6 HEAT rounds and 22 HE-Frag rounds. According to the September issue of the 2008 edition of the "<i>Техника и вооружение</i>" magazine, a Soviet T-62 carried 16 APFSDS rounds, 8 HEAT rounds and 16 HE-Frag rounds. As usual, the loadout changes based on necessity, but generally speaking, APFSDS was preferred over HEAT with the number of APFSDS rounds exceeding HEAT rounds by two times. The official regulations called for the armour piercing ammunition (APFSDS and HEAT) to be stowed in the front hull racks for maximum ease of access to minimize the reaction time of the T-62 to an enemy tank in a duel scenario.<br />
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<h3>
<a href="https://www.blogger.com/null" id="hef"></a>
<span style="font-size: large;">HE-Frag</span></h3>
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High-explosive fragmentation shells are arguably the most important ammunition type for the T-62, given the expected tactical contributions of a Soviet tank to combined arms combat. Though tanks are obviously a major threat, the vast majority of the vehicular targets that a tank would encounter on the battlefield are lightly armoured vehicles such as APCs and IFVs or thin-skinned vehicles like trucks, and the tank will always be called upon by infantry for fire support against bunkers, machine gun nests, and other garrisoned troops. HE-Frag shells may be used as a last resort against enemy tanks as well, serving to knock out various essential components for anything from a mobility kill to a firepower kill.<br />
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The HE-Frag ammunition for the U-5TS suffered somewhat due to the implementation of the smoothbore solution because spin stabilization was truly the optimal stabilization solution for ammunition of this type. Fin stabilization added unnecessary weight that had to be balanced out by a reduction in the muzzle velocity or a reduction in the warhead mass, both of which had negative effects on the effectiveness of the round. In a comparison between the U-5TS and the D-10 that it replaced, the rifled 100mm gun could still hold its own simply by the virtue of spin stabilization. For comparison, the OF-412 shell had a steel casing that weighed 13.7 kg and the OF-32 shell had a casing that weighed 13.3 kg, whereas the 115mm OF-11 shell had a steel casing that weighed just 8.875 kg and the casing of the OF-18 shell weighed 11.925 kg.<br />
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However, the difference in the weight of the warhead casings was counterbalanced by the much larger filler ratios achieved by the 115mm rounds. Naturally, thanks to the larger caliber of the U-5TS compared to the D-10, its HE-Frag shells carried a considerably larger explosive charge and were more effective overall despite the need for stabilizer fins that added dead weight to the projectile. For comparison, the basic OF-412 shell for the D-10 had a Trotyl filler weighing 1.46 kg, whereas the basic OF-11 shell had a Trotyl filler weighing 2.7 kg - almost 1.85 times heavier. The share of the explosive charge in the OF-11 round by weight was 30.4%, which was too high above the optimal value of around 25%. The OF-18 shell from 1966 presented a major improvement with an explosive filler weight of 23.4%. The OF-412 had a filler weight of just 10.3%. Because of this difference, the fragmentation characteristics of 115mm HE-Frag shells were much closer to the mathematical optimum and the T-62 could boast of having more effective HE-Frag ammunition compared to the T-54 series.<br />
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Like most of the earlier high explosive shells used in the Soviet Army, the explosive compound used in most 115mm HE-Frag shells was Trotyl with the exception of the OF-27 shell which used A-IX-2 instead. In the Soviet Union, "Trotyl" refers to a 70/30 tetrytol composed of a mixture of 70% Tetryl and 30% TNT. The use of this explosive compound was quite a conservative decision since A-IX-1 was clearly a superior choice as it is much more brisant and A-IX-2 would have been even better, albeit more expensive. Trotyl is more powerful than TNT and slightly less powerful than tetryl, but more sensitive than TNT. Cast Trotyl as found in bombs and shells has a density of 1.60 g/cu.cm, which is slightly more than the 1.58 g/cu.cm density of cast TNT. The explosive velocity of Trotyl is 7,000 m/s and the Trauzl value is 285-320 ml. For TNT, these values are 6,900 m/s and 285-305 ml respectively. According to page 8-122 of the U.S Army technical manual TM 9-1300-214 titled "<i>Military Explosives</i>", the brisance of cast 70/30 tetrytol is 111% that of TNT when compared with the sand test.<br />
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<span style="font-size: large;">3UOF-1</span></h3>
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<span style="font-size: large;">OF-11</span></h3>
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The OF-11 was the basic HE-Frag shell that was first available to the U-5TS cannon in 1961. The warhead has a somewhat polygonal shape and a characteristically thin casing. The six steel stabilizer fins were attached to a hollow steel tailboom which was threaded into the base of the steel casing of the warhead and secured with screws. The OF-11 was somewhat unusual in that it had a tracer, made possible by the presence of the stabilizer assembly. The stabilizer assembly and its tracer was standardized with the BK4 HEAT projectile together with the general design of the warhead casing. The total weight of the stabilizer assembly is around 2.7 kg. OF-11 uses a Trotyl explosive filler.<br />
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This shell was initially fitted with the V-429V fuse and then it was later replaced with the V-429E fuse. These two fuses are used instead of the V-429 because the V-429 was armed using the centrifugal forces of a shell fired from a rifled gun making it incompatible with ammunition fired from smoothbore cannons. The V-429V was armed using the momentary braking effect caused by the opening of stabilizer fins and as such, was suitable for ammunition developed for the U-5TS.<br />
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Muzzle Velocity: 905 m/s<br />
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Maximum Direct Fire Range: 3,600 meters<br />
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Mass of Complete Round: 28.1 kg<br />
Total Mass of Projectile: 14.86 kg<br />
Mass of Warhead Casing: 8.875 kg<br />
Mass of Explosive Charge: 2.7 kg<br />
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Total Length of Projectile: 635mm<br />
Wingspan of Stabilizer Fins: 325mm<br />
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Because the warhead casing has a mass of 8.875 kg while the explosive charge had a mass of 2.7 kg, the share of the explosive charge by mass reached 30.4%. Although it's generally good to have a larger weight of explosives, this was somewhat too high above the mathematical optimum value.<br />
<br />Compared to the basic 100mm spin-stabilized HE-Frag shell used in the U-8TS gun (D-54TS) of the T-62A tank, basic 115mm HE-Frag possessed a greatly inferior maximum range of just 8.5 km when fired at the same gun elevation angle of 14 degrees as compared to the 14.6 km maximum range boasted by its 100mm counterpart. 115mm HE-Frag also had a significantly larger dispersion, having a probable dispersion of 1/232 fractions of the firing range in range whereas 100mm HE-Frag had a probable deviation of just 1/350 in range. This means that when firing at 5 km, the probable dispersion of 100mm HE-Frag reaches just 14.2 meters while 115mm HE-Frag achieves just 21.5 meters.</div><div><br />
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<h3>
<span style="font-size: large;">3UOF-6</span></h3>
<h3>
<span style="font-size: large;">OF-18</span></h3>
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The OF-18 was an improved shell with an ogived nose and a thicker shell casing for greater fragmentation mass and volume as well as a better optimized spray pattern for increased casualties. It used a Trotyl explosive filler, and like the OF-11, the warhead casing is made from 45Kh1 steel. The mass of the explosive charge could be increased compared to the OF-11 despite the thicker casing because the shell was lengthened to 697mm and the ogive form of the warhead was slightly more voluminous. Moreover, the hollow steel tail boom of the OF-11 round was replaced with a solid aluminium tail boom that attached to the base of a warhead casing via a large threaded slot. The aluminium tailboom features a hollow fairing that adds a boat tail to the base of the projectile, giving the projectile excellent aerodynamic characteristics. It weighs 1.964 kg. Together with the steel stabilizer fins, the total weight of the stabilizer assembly is 2.744 kg. Due to its increased length, ogived form, larger weight and improved design of the stabilizer fin assembly, the sectional density of the OF-18 projectile was significantly higher than the OF-11 and thus, it was superior at overcoming air resistance.<br />
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The downside of the improved destructive effect of the shell was that its increased weight brought down the muzzle velocity to just 750 m/s, but thanks to the improved ballistic performance brought about by the numerous changes to the projectile design, the OF-18 design could achieve a significantly increased direct fire range and maximum range as its lower rate of velocity loss allowed it to retain more of its velocity at long range compared to OF-11. Unfortunately, the author does not currently possess firing tables for the two rounds, but the relationship between the two rounds can be seen clearly in the range markings of the TSh2B-41 sight, shown below. Initially, OF-11 has a flatter trajectory out to 2,200 meters, but the increasingly large gaps between each marking in the range scale shows that it loses velocity quite rapidly. By contrast, OF-18 has a densely packed range scale reflecting its good velocity retention characteristics and its flatter long-range ballistic trajectory allows it to reach a distance of 4,600 meters at around the same gun elevation angle required for OF-11 to reach its maximum direct fire range of 3,600 mters.<br />
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Unlike OF-11, a tracer was not included with the projectile.<br />
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The OF-18 shell was fitted with the V-429E fuse as the standard fuse.<br />
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Muzzle Velocity: 750 m/s<br />
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Maximum Direct Fire Range: 4,800 meters<br />
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Mass of Complete Round: 30.8 kg<br />
Total mass of Projectile: 17.86 kg<br />
Mass of Warhead Casing: 11.925 kg<br />
Mass of Explosive Charge: 2.79 kg<br />
Mass of Stabilizer Assembly: 2.744 kg<br />
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Total Length of Projectile: 697mm<br />
Wingspan of Stabilizer Fins: 325mm<br />
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Thanks to the increased mass of the warhead casing and a corresponding increase in the mass of the explosive charge, the share of the explosive content by weight was 23.4%.<br />
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<h3>
<span style="font-size: large;">3UOF-37</span></h3>
<h3>
<span style="font-size: large;">OF-27</span></h3>
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The OF-27 is a newer shell that appears externally identical to OF-18, but differes is that it features an A-IX-2 explosive charge instead of the Trotyl filler traditionally used in Soviet tank and artillery shells and the thickness of the warhead casing was reduced by less than half a millimeter. The stabilizer fin assembly of the OF-18 was carried over without modifications. The reason why the mass of the A-IX-2 explosive charge is greater than the mass of Trotyl available in previous shells despite the slightly thinner casing is because A-IX-2 is more dense.<br />
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By maintaining the same projectile shape and almost the same total mass, the muzzle velocity of OF-27 is the same as OF-18 and the ballistic characteristics of the two shells are also the same. As such, they can be fired interchangeably without the need for modified sights.<br />
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The V-429E fuse was provided as the standard fuse.<br />
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Muzzle Velocity: 750 m/s<br />
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Maximum Direct Fire Range: 4,800 meters<br />
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Mass of Complete Round: 30.75 kg<br />
Total mass of Projectile: 17.82 kg<br />
Mass of Explosive Charge: 3.13 kg<br />
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Total Length of Projectile: 697mm<br />
Wingspan of Stabilizer Fins: 325mm<br />
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<h3>
<a href="https://www.blogger.com/null" id="ap"></a>
<span style="font-size: large;">APFSDS</span></h3>
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Being widely considered to be a pioneer on the introduction APFSDS technology into widespread service, the T-62 essentially relies on it as its main selling point, and for good reason. In accordance with the original objectives of the 115mm U-5TS gun, the 115mm APFSDS rounds that were supplied to T-62 tanks during the early 1960's were sufficiently powerful to defeat the armour of its contemporaries in most areas. This was achieved despite the use of steel penetrators thanks to the high muzzle velocity that the U-5TS gun generated.<br />
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The velocity of 115mm APFSDS ammunition was exceptionally high even when compared to the most modern APDS rounds available at the time, meaning that the projectiles had a very flat trajectory and it was very forgiving with regards to ranging errors. The extremely high velocity also meant that engaging moving targets was much easier since it would take less time for the shot to reach its target. APFSDS shells would also be very useful against vehicles moving at irregular speeds because the gunner does not need to apply much lead. This greatly helped offset the retarded engagement time caused by limitations of the T-62 fire control system and increased first-round hit probability significantly.</div><div>
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Furthermore, the accuracy of 115mm APFSDS rounds was more than sufficient for typical combat distances and was higher than contemporary 105mm APDS rounds. According to the data provided by Mikhail Pavlov, the mean dispersion of 3BM3 rounds (the first APFSDS round available for the T-62) at 2,000 meters was 0.4 meters in the horizontal plane and 0.5 meters in the vertical plane. This can be expressed as an angular dispersion of 0.2 mils in the horizontal plane and 0.25 mils in the vertical plane. This is the zone where 50% of the shots land. For comparison, it is stated in the report "<i><a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a031639.pdf">Performance of Chrome-Plated 105mm M68 Gun Tubes with Discarding Sabot Ammunition</a></i>" that the data accumulated from 563 acceptance tests of M392A2 rounds showed horizontal and vertical standard deviation dispersions of 0.30 and 0.33 mils respectively, for a CEP of 0.37 mils. This figure, 0.37 mils, was used as the passing criteria for ammunition acceptance tests. Even so, it was also noted in the report that that circular error of the shots fired from the unmodified M68 gun tube was marginally higher than the acceptance criteria, reaching 0.38 mils. This is shown in the image below. Given that CEP is equivalent to mean dispersion, both being measurements of the 50% dispersion zone of shots, it can be clearly seen that the precision of 115mm APFSDS significantly surpassed 105mm APDS.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GJzwEbZkiWg/X6D_ShFGpJI/AAAAAAAASA0/jOWE7czb6sQKgXLVLRK3tSUBTC3qBigIQCLcBGAsYHQ/s1098/m392a2%2Bdispersion.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="523" data-original-width="1098" height="190" src="https://1.bp.blogspot.com/-GJzwEbZkiWg/X6D_ShFGpJI/AAAAAAAASA0/jOWE7czb6sQKgXLVLRK3tSUBTC3qBigIQCLcBGAsYHQ/w400-h190/m392a2%2Bdispersion.png" width="400" /></a></div><div><br />
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At the time the T-62 entered service, the only tank to use the L7 was the Centurion and the only tanks to use the M68 were the M60 and M60A1. Both of these tanks were massive in stature with a height of 2,123mm and 2,290mm respectively excluding their large cupolas which span half the width of their turrets and protrude by 180mm and 480mm respectively. Against such large targets, the lower shot dispersion of 115mm APFSDS rounds and their flat trajectory can be credited for the high probability of hit at long range.<br />
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Thanks to the good ballistic characteristics of 115mm APFSDS and its high performance against the modern tank armour of its time, it was the preferred ammunition type for anti-tank work. In Soviet and East German T-62 tanks, the quantity of APFSDS rounds in a standard combat loadout was twice that of the HEAT rounds, and during the Iran-Iraq war, 70% of the hits recorded on Iranian Chieftain main battle tanks were 115mm APFSDS rounds, proving that it was the preferred ammunition type.<br />
<br /><br /><div>One of the universal features of all 115mm APFSDS rounds was the inclusion of a phlegmatizer liner fitted between the propellant and the wall of the cartridge case. The liner is wax paper, impregnated with either paraffin or ceresin wax, based on a description given in the 1970 textbook book "<i>Современная артиллерия</i>" (Modern Artillery). The use of phlegmatizers, meant to reduce bore erosion, had been used in full charge rounds since the so-called Great Patriotic War.</div><div><br /></div><div>When fired, the propellant gasses vaporizes the phlegmatizer and carries its particles into the barrel where it solidifies as a deposit on the surface of the bore, in a process known as sublimation. The coating forms a protective layer between the bore surface and the hot gasses. Its main purpose is to insulate the bore surface, lowering the rate of heat transfer from the propellant gasses and thus reducing heat erosion. The wax coating deposited on the bore surface is easily scraped away by the driving band of the next shot fired from the gun, so fouling does not occur even with sustained firing. Because of this mechanism, phlegmatizing liners are sometimes referred to as coolant liners, most notably in technical documents from Picatinny Arsenal. </div><div><br /></div><div>Additionally, a known issue faced by munitions engineers when creating high-velocity fin-stabilized projectiles is fin ablation during launch caused by the extreme temperatures of the propellant gasses. This was solved by the presence of a phlegmatizer, also known as a coolant, into the propellant charge. The phlegmatizer forms a protective barrier between the fins and the propellant gasses. The phlegmatizer coating remains on the fins during flight, providing some insulation from aerodynamic heating. </div><br />Sticks of DG-4 14/1 nitroglycolic powder propellant was used for 3UBM3, 3UBM4 and 3UBM5. According to <a href="https://sci.house/bazyi-raket-arsenalyi-scibook/markirovka-porohov-tverdyih-raketnyih-topliv-72994.html">the classification index for this type of powder</a>, DG-4 propellant has a calorific value of 820 kCal/kg. </div><div><br /></div><div>At some point, either 1970 or prior (most likely 1967), DG-4 14/1 propellant could be replaced by a 12/7 with 18/1 tr. propellant mix. 12/7 is granulated pyroxylin propellant with seven-channel grains, and 18/1 tr. is tubular pyroxylin propellant in stick form. The shift to granulated seven-channel propellant enabled progressive combustion to occur, which permits a more efficient conversion of propellant energy to kinetic energy. For a given weight of propellant and projectile, the maximum muzzle velocity can be achieved at the lowest maximum gas pressure. 12/7 propellant has a calorific value of 775 kCal/kg, and a flame temperature of 2,808 K, which is very low. This greatly aids in reducing bore erosion, especially in conjunction with the presence of a phlegmatizer, thus increasing the barrel life. Due to the lower calorific value compared to DG-4, to generate the same internal ballistics as 7.85 kg of DG-4, a greater mass of 12/7 and 18/1 tr. propellant is required.</div><div>
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It must be noted that the large, bore-riding stabilizing fins at the tail end of the projectile produced a great deal of aerodynamic drag. According to V.A Grigoryan in "<i>Защита танков</i>", 115mm fin stabilized projectiles had a muzzle velocity of 1,615 m/s (referring to the 3BM3), and a velocity of 1,358 m/s at 2 kilometers. This translates to a rate of speed loss of up to 128.5 m/s per kilometer of travel. The 100mm BM8 APDS round, on the other hand, apparently decelerates at a rate of 106.5 m/s per kilometer.<br />
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<h3>
<span style="font-size: large;">3UBM3</span></h3>
<h3>
<span style="font-size: large;">3BM3</span></h3>
<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-aNX6bzOB6cY/YEnlB6fYu_I/AAAAAAAAS2A/9qMXvDBhWPMY5jILqWW1XXn67XtzOUpxACLcBGAsYHQ/s1289/arrow%2Bprojectile%2B3bm3.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1289" data-original-width="451" height="320" src="https://1.bp.blogspot.com/-aNX6bzOB6cY/YEnlB6fYu_I/AAAAAAAAS2A/9qMXvDBhWPMY5jILqWW1XXn67XtzOUpxACLcBGAsYHQ/s320/arrow%2Bprojectile%2B3bm3.png" /></a></div><br /><div><br /></div><div>Entering service in 1961 to accompany the T-62, 3UBM3 was the first APFSDS round in the 115mm caliber to enter service. The design of the 3BM3 projectile shares a close similarity with the 3BM1 projectile for the 100mm T-12 anti-tank gun, which entered service shortly before the T-62. The projectile is essentially a steel rod with a screw-on steel cap on the end containing a tungsten carbide core. The steel cap has a blunt nose, thus behaving as both a protective cap to prevent the core from shattering upon impact and to improve performance on sloped armour. During armour penetration, the steel rod serves to drive the tungsten carbide core through armour with its large momentum, thus allowing a projectile with just 300 grams of tungsten carbide to outperform contemporary APCR and APDS ammunition.</div><div><br /></div><br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://2.bp.blogspot.com/-0aZ5KI1NDN0/V7wGjqHjVrI/AAAAAAAAHOs/5NJ3BGVp4T8-Y1j1g-Q47W4l9JhL8uiUQCLcB/s1600/sebm3.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-0aZ5KI1NDN0/V7wGjqHjVrI/AAAAAAAAHOs/5NJ3BGVp4T8-Y1j1g-Q47W4l9JhL8uiUQCLcB/s1600/sebm3.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Photo Credit: Stefan Kotsch</td></tr>
</tbody></table>
<br /></div><div><br /></div><div>During its flight, the equilibrium spin of the 3BM3 projectile is not provided by canted fins, as with most fin-stabilized projectiles. Rather, spin is imparted during acceleration inside the barrel via gas action. Each sector of the sabot has two holes with a diameter 4mm, angled tangentially to the sabot by 50 degrees. The holes are plugged with an epoxy filler. When a round is fired and the projectile moves down the length of the barrel, the propellant gasses eventually punch out the epoxy filler from the holes and flow out. The tangential thrust from the oblique flow of gasses induces a rotation rate on sabot, which slides between the copper driving band and the projectile, providing the sabot with the necessary centrifugal force for its petals to separate once the projectile leaves the muzzle, and imparting a slow equilibrium spin to the projectile via friction to stabilize it in flight. Sabot petal separation is additionally aided by the concave shape of the forward surface of the sabot, shaped as such to function as air scoops.</div><div>
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<div><br /></div><div><br /></div>The core, being 32mm in diameter, creates a channel wider than itself when it penetrates a steel plate. The steel rod follows the core through the channel, as its diameter of 33mm fits without excessive scraping on the edges of the penetration channel.<br />
<br />The time of flight of the 3BM3 round at five range intervals is given in the table below.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-l2rXRz_thfE/X4Nr_mI8dfI/AAAAAAAARtQ/WrxUYaQXwtM3buQlNKxAHTbybBoSjjQjwCLcBGAsYHQ/s1295/time%2Bof%2Bflight.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="250" data-original-width="1295" height="78" src="https://1.bp.blogspot.com/-l2rXRz_thfE/X4Nr_mI8dfI/AAAAAAAARtQ/WrxUYaQXwtM3buQlNKxAHTbybBoSjjQjwCLcBGAsYHQ/w400-h78/time%2Bof%2Bflight.png" width="400" /></a></div><br /><br />The point blank range of the 3BM3 on a target with a height of 2.0, 2.7 and 3.0 meters is 1,870 meters, 2,100 meters and 2,260 meters respectively.<br /><br />
As an APFSDS round from 1961, its contemporary was the 105mm L28 APDS round and its American licence-produced clone the M392. Compared to these APDS rounds, 3BM3 had superior penetration power and facilitated a higher probability of hit thanks to its high muzzle velocity of 1,615 m/s. It falls short of the Chieftain's 120mm L15A3 APDS round from the late 1960's round in terms of penetration on both flat and sloped armour plate, but even so, 3BM3 could still be appraised highly because it achieved its high performance using only 0.27 kg of tungsten carbide whereas the 105mm and 120mm APDS rounds used in NATO armies had tungsten carbide or tungsten alloy cores weighing 3 to 5 kg. Furthermore, 3BM3 allowed the T-62 to outmatch the M60A1 and Leopard 1 in firepower, giving it favourable odds in a tank duel scenario at typical combat ranges between these opposing tanks. The Chieftain was also vulnerable to 3BM3, although the heavier emphasis on armour obliquity in its design made it a tougher target.<br />
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Muzzle Velocity: 1,615 m/s<br />
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Mass of Complete Round: 22 kg<br />
Projectile Mass (incl. sabot): 5.5 kg</div><div>Projectile Mass: 4.0 kg<br />
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<blockquote class="tr_bq">
Certified Penetration at 1,000 meters:<br />
300mm at 0°<br />
130mm at 60° </blockquote>
<blockquote class="tr_bq">
Certified Penetration at 2,000 meters:<br />
270mm at 0°<br />
100mm at 60°</blockquote>
<blockquote class="tr_bq">
Page 56 of "<i>Отечественные бронированные машины</i> 1945-1965", M.V. Pavlov and I.V Pavlov, Tekhnika i Vooruzheniye magazine, September 2008 issue </blockquote>
<div><br /></div></div><blockquote><div>Perforation limits:</div><div>130mm at 60° from 1,150-1,250 meters<br />
100mm at 60° from 2,360-2,390 meters<br /><br />Page 63 of "<i>Боевые Машины Уралвагонзавода: Танки 1960-х</i>" by Uralvagonzavod corporation</div></blockquote><div><br /><br />
With what we currently know about the armour of the M60A1, BM3 would have been more than sufficient at combat ranges. The cast upper glacis of the M60A1 measures 109mm in thickness at an angle of 65 degrees, making for a more formidable target than even the sloped turret cheeks, but even so, most parts of the M60A1 should be vulnerable to BM3 at combat ranges, and that is without taking into account the differences in ballistic standards. For one thing, the cast steel armour of the M60A1 had a hardness of just 220 BHN. This means that the armour was significantly less resilient against APFSDS rounds than the same thickness of medium hardness steel armour such as standard RHA.<br />
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Knowing the armour thickness of the Chieftain Mk.5 tank from ultrasound measurements, it can be reasonably surmised that the 3BM3 is capable of reliably perforating the turret at any point from 1,500 meters or more, because the armour of the Chieftain was constructed from cast steel and not rolled steel, and we are basing our estimations on Soviet penetration values based on Soviet penetration criteria. The weak lower front plate of the hull can be penetrated from any conceivable distance, but the highly sloped upper front plate is a tougher target than even the turret, since 3BM3 could not handle such high impact angles very well.<br />
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The innovation of the BM3 projectile was that the tungsten carbide core within only only weighed about 300 grams, but the penetrator could easily defeat more armour than the 2.82 kg tungsten carbide core in the 100mm BM8 APDS shell of the T-55 that appeared six years later in 1967. For every BM8 penetrator built, the same mass of tungsten could have been used for ten 3BM3 shells that were more powerful and more accurate. The modest amount of tungsten used in the design of the BM3 round allowed it to be conserved for other purposes, which would have been critical from a strategic point of view in the event of a major war.<br />
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<h3>
<span style="font-size: large;">3UBM4</span></h3>
<h3>
<span style="font-size: large;">3BM4</span></h3>
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<a href="https://1.bp.blogspot.com/-y9XHgwDgcko/XU5y2FDS5TI/AAAAAAAAOys/MCufq47N7Pw1abnJxUtXcEMa-W6YG8PdQCLcBGAs/s1600/1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="111" data-original-width="600" src="https://1.bp.blogspot.com/-y9XHgwDgcko/XU5y2FDS5TI/AAAAAAAAOys/MCufq47N7Pw1abnJxUtXcEMa-W6YG8PdQCLcBGAs/s1600/1.jpg" /></a></div>
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Introduced in 1961 alongside the 3BM3, 3BM4 was a simpler and cheaper round featuring a steel penetrator with a steel armour piercing cap. This projectile had an increased muzzle velocity of 1,650 m/s, just a fraction above a mile a second. The penetrator is made entirely of 60KhNM tool steel with high strength and toughness. The hardness at the tip is specified for a lower boundary of 560 BHN and an upper boundary of 653 BHN. At the tail, which only interacts with an armour plate at the very end of the penetration process, the rated hardness is 340-414 BHN. The projectile is fitted with 6 high-strength steel fins, which were of a bore riding type that worked alongside the sabot to stabilize the shell as it travels down the barrel. The ends of the fins have copper lugs embedded in them to minimize abrasive damage to the much barrel bore. The armour piercing cap is made of 35KhGSA steel, built with a flat tip to decrease the vulnerability to spaced armour, improve impact performance on sloped armour as well as to protect the projectile from shattering upon impact. The necessity of an armour piercing cap despite the relatively low hardness of the steel was due to use of high carbon steel instead of maraging steel, which would retain more ductility without compromising strength.</div><div><br /></div><div>Ballistically, 3BM4 matches 3BM3. The same sabot was used for both rounds.</div><div><br /></div><div>In various U.S Army TRADOC descriptions of the capabilities of T-62 tanks, the so-called "Hyper-velocity APFSDS" rounds used by the T-62 were described as having a muzzle velocity of 1,650 m/s. This indicates that 3BM4 was the standard ammunition used by the Soviet clients.<br />
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Nevertheless, the presence of the armour piercing cap protects the round from the effects of simple spaced armour such as the type present on upgraded Leopard 1 turrets. The spaced plate will successfully destroy the armour piercing cap, but the penetrator will be intact, and it will have a high chance of defeating the relatively thin turret armour with ease even at high angles of attack.<br />
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<a href="https://3.bp.blogspot.com/-VMaI5EM-Zk4/WIWYn_5ZE9I/AAAAAAAAIRI/7sQgduWReiQeangCqsoF4m_36aNRmrdFwCLcB/s1600/1451157357-jp2njby.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="278" src="https://3.bp.blogspot.com/-VMaI5EM-Zk4/WIWYn_5ZE9I/AAAAAAAAIRI/7sQgduWReiQeangCqsoF4m_36aNRmrdFwCLcB/s400/1451157357-jp2njby.jpg" width="400" /></a></div>
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The main factors contributing to the penetrating performance of the shell is the relatively high length-to-diameter ratio of 13:1 and the fantastic speed of the projectile, but because it lacked a tungsten carbide core in its nose, its performance falls short of the BM3 on flat targets.<br />
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Muzzle Velocity: 1,650 m/s<br />
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Cartridge Mass: 22 kg<br />
Projectile Total Mass: 5.5 kg<br />
Steel Penetrator Mass: 3.196 kg<br />
Mass of the Armour Piercing Cap: 0.187 kg</div><div><br /></div><div>Full projectile length: 559mm<br />
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<blockquote class="tr_bq">Rated Penetration at 1,000 meters:<br />
250mm RHA at 0°<br />
135mm RHA at 60° </blockquote>
<blockquote class="tr_bq">
Rated Penetration at 2,000 meters:<br />
220mm RHA at 0°<br />
110mm RHA at 60° </blockquote>
<blockquote class="tr_bq">
Page 56 of "<i>Отечественные бронированные машины</i> 1945-1965", M.V. Pavlov and I.V Pavlov, Tekhnika i Vooruzheniye magazine, September 2008 issue </blockquote>
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Despite the rather substandard mechanical characteristics of the steel penetrator, the performance of 3BM4 still managed to exceed the L28, M392 and DM13 APDS rounds for the L7 and M68 cannons on flat steel targets. It is known that DM13 is rated to defeat 250mm of flat RHA steel at 800 meters whereas 3BM4 manages to defeat the same thickness of steel at a slightly greater range of 1,000 meters. Moreover, 3BM4 had better or at least comparable penetration power on oblique targets owing to the fact that it behaved as a long rod penetrator.<br />
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<br />
<h3>
<span style="font-size: large;">3UBM5</span></h3>
<h3>
<span style="font-size: large;">3BM6</span></h3>
<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-SP8L8ny-zg8/YDzkM7OoPjI/AAAAAAAAS0w/u9Rc8RLDbJknH5kxGGL1qKS_RdbRS13dwCLcBGAsYHQ/s1383/ubm5%2Band%2Bubm6.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1383" data-original-width="1291" height="320" src="https://1.bp.blogspot.com/-SP8L8ny-zg8/YDzkM7OoPjI/AAAAAAAAS0w/u9Rc8RLDbJknH5kxGGL1qKS_RdbRS13dwCLcBGAsYHQ/s320/ubm5%2Band%2Bubm6.png" /></a></div><div><br /></div>
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Introduced in service in either 1964 or 1966, or some time in between, the 3UBM5 cartridge with the 3BM6 projectile was a slightly more advanced but similarly cheap alternative to the 3UBM4 round that could approach the flat penetration power of 3BM3 while offering equivalent penetration power on sloped armour. Like 3BM4, the 3BM6 projectile featured an armour-piercing cap. It officially replaced both the 3UBM3 and 3UBM4 rounds by the mid-1960's - a technical manual for the T-62, approved for distribution on the 14th of January 1967, only mentions 3UBM5 and an unknown 3UBM6. </div><div><br /></div><div>Between 1966-1968, a new model of 3BM6 projectile without an armour-piercing cap began replacing the older type. Knowing this, the 3UBM5 round must have entered service before 1966. </div><div><br /></div><div><div>Externally identical, the 3BM6 projectile can be distinguished from the 3BM4 by the presence of knurls on the rim of the "ring" type sabot which are absent from the one on the 3BM4 projectile. The presence of these knurls can be connected to the creation of the T-64 medium tank with a 115mm D-68 gun, which uses an autoloader. These knurls were needed to ensure the smooth loading of the projectile into the D-68 gun chamber by a mechanical powered rammer, which can only push the cartridge along the surface of the chamber where the possibility of the projectile getting stuck against the shoulder of the chamber neck may arise.</div><div><br /></div></div><div>For the manually loaded U-5TS gun, a human loader can insert a cartridge while taking care not to scrape the shoulder of the projectile against the chamber walls, which is why the sabot for 3BM3 and 3BM4 did not have knurls.</div><div><br /></div><div>Before the introduction of 3UBM5, a series of new two-part 115mm rounds was created in 1964 for the T-64, which had the new D-68 gun. Alongside the T-64 itself, a new set of ammunition entered service in 1966. Among them was the 3BM5 projectile, which was part of at least two cartridges in at least one form. It was a part of 3VBM1 from 1964, and 3VBM5 from 1970, where it had no armour-piercing cap. The 3BM5 was not used in the single-part ammunition for the U-5TS, but 3BM6 had an almost identical design. The knurled sabot used on 3BM6, with six interface grooves, was very similar and possibly the same as the sabot for <a href="http://www.russianarms.ru/forum/index.php?action=dlattach;topic=12009.0;attach=142847;image">the early 3BM5 projectile for 3VBM1</a>.</div><div><br /></div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-15FoM-YT7Vc/VmbONk0qEUI/AAAAAAAAEv8/dO2UdAVEhUA/s1600/3ubm5%2Bfor%2B3bm6.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-15FoM-YT7Vc/VmbONk0qEUI/AAAAAAAAEv8/dO2UdAVEhUA/s1600/3ubm5%2Bfor%2B3bm6.png" /></a> </div><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/--vXCrHHRSQM/VmbON3euFII/AAAAAAAAEwA/N9fGsQAf-Ak/s1600/3bm6.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/--vXCrHHRSQM/VmbON3euFII/AAAAAAAAEwA/N9fGsQAf-Ak/s1600/3bm6.png" /></a></div><br />
<br /></div><div>Internally, they are quite different.<br />
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<a href="http://2.bp.blogspot.com/-XvmdTMpde2g/VocCUhNNClI/AAAAAAAAFN4/68hS83hdd7Y/s1600/ubm5%2B115mm.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="123" src="https://2.bp.blogspot.com/-XvmdTMpde2g/VocCUhNNClI/AAAAAAAAFN4/68hS83hdd7Y/s640/ubm5%2B115mm.jpg" width="640" /></a></div>
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<a href="http://3.bp.blogspot.com/-1ECCIkEiA88/VocCgRYwcHI/AAAAAAAAFOA/j4-yRNvYCL0/s1600/115mm%2Bbm6.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="164" src="https://3.bp.blogspot.com/-1ECCIkEiA88/VocCgRYwcHI/AAAAAAAAFOA/j4-yRNvYCL0/s640/115mm%2Bbm6.jpg" width="640" /></a></div>
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The penetrator is made from 35Kh3NM steel with a hardness of around 600 BHN. The 35Kh3NM grade of steel had been in use in standard full-caliber armour-piercing shells like the 100mm BR-412B and 122mm BR-471B since their creation in the late stages of WWII. Naturally, the hardening of the steel to around 600 BHN is consistent with the hardening of the older full-caliber shells of postwar production. The 3BM6 penetrator had a rounded nose and it had an armour piercing cap made from softer 35KhGS steel with a hardness of 451-552 BHN. Although still made entirely of steel, this shell offered appreciably higher performance on oblique steel plate but was still not on par with the 3BM3 on flat targets. The stabilizing fins are made from 40KhFA steel alloy with high thermal resilience. The fin assembly weighs a total of 0.651 kg.<br />
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Here is what the penetrator without the armour piercing cap and the windscreen (ballistic cap) looks like:<br />
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<a href="https://4.bp.blogspot.com/-SqeHtZEGHJU/V7wNMPeS25I/AAAAAAAAHO8/eAMO6t63fxUvjv32RVlBsQua4l4kdKK9QCEw/s1600/6.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-SqeHtZEGHJU/V7wNMPeS25I/AAAAAAAAHO8/eAMO6t63fxUvjv32RVlBsQua4l4kdKK9QCEw/s1600/6.jpg" /></a></div>
<br /><br />The propellant charge consists of 8.1 kg of 12/7 granular and 18/1 tr. tubular propellant exclusively - DG-4 was not used with 3UBM5. Due to the lower calorific value of the new propellant mix, counterbalanced by its increased efficiency, the internal ballistics with the new propellant did not change. As such, although 3BM6 had a slightly increased muzzle velocity of 1,680 m/s, higher than both 3BM3 and 3BM4, this was merely due to its slightly lower projectile weight. <br /><br />
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Projectile Maximum Diameter: 42mm<br />
Diameter of Stabilization Fins: 114mm<br />
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Total Projectile Length: 550mm<br />
Total Cartridge Length: 950mm<br />
Penetrator Length: 436mm<br />
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Mass of Complete Round: 21.66 kg<br />
Total Projectile Mass: 5.34 kg<br />
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Mass of Subcaliber Projectile: 3.86 kg<br />
Mass of Steel Penetrator: 3.009 kg<br />
Mass of Armour Piercing Cap: 0.167 kg<br />
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Muzzle Velocity: 1,680 m/s<br />
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<blockquote class="tr_bq">
Penetration at 1,000 meters:<br />
280mm RHA at 0°<br />
135mm RHA at 60° </blockquote>
<blockquote class="tr_bq">
Penetration at 2,000 meters:<br />
240mm RHA at 0°<br />
110mm RHA at 60° </blockquote>
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<br />
The new armour piercing cap appears to have improved the performance of the projectile on sloped armour to the point where it is superior to the BM3, making this shell even more useful than its predecessor on the heavily sloped armour of contemporary NATO tanks like the Chieftain and the M60A1. The graphs below, taken from the book "<i>Частные Вопросы Конечной Баллистики</i>" from 2006 (<i>Particular Questions of Terminal Ballistics</i>) published by Bauman Moscow State Technical University on behalf of NII Stali, shows the penetration curve of three different subcaliber ammunition types, each representative of different classes. 3BM6 is represented as the dotted and dashed line. The impact velocity for all three ammunition types is 1,500 m/s, which corresponds to a distance of between 1,200 and 1,600 meters. The y-axis shows the thickness of armour defeated under the nominal defeat criteria.<br />
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<a href="https://1.bp.blogspot.com/-6yNomsLRzpM/XU6A8GiFNCI/AAAAAAAAOy0/sDGAVagqWLATrGri7Z1NNo4wJp_MlrN0QCLcBGAs/s1600/penetration%2Bcomparison.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="868" data-original-width="1600" height="346" src="https://1.bp.blogspot.com/-6yNomsLRzpM/XU6A8GiFNCI/AAAAAAAAOy0/sDGAVagqWLATrGri7Z1NNo4wJp_MlrN0QCLcBGAs/s640/penetration%2Bcomparison.png" width="640" /></a></div>
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At 0 degrees, 3BM6 defeats 250mm RHA but as the target obliquity increases, the LOS depth of the perforation path of 3BM6 increases until around 63 degrees where it begins falling, finally ending at 82 degrees. This is a characteristic behaviour of long rod penetrators. Most importantly, it is shown in the graph that 3BM6 can defeat 160mm of RHA at 60 degrees, translating to a LOS thickness of 320mm.<br />
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Combat experience in the 1973 Yom Kippur conflict revealed that the M392A1 round (functionally identical to the basic M392) could not perform reliably on heavily sloped armour. This was quickly solved with a tungsten alloy tilting cap on the L28A1 and M392A2 in 1974 based on the technical solutions developed for the L52A1 round in the late 1960's. Both L28A1 and M392A1 were functionally identical and both could defeat 110mm of RHA steel at 60 degrees at 2,000 meters.<br />
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The L52 round could defeat 120mm of RHA at 60 degrees from a range of 1,830 meters, while the improved L52A2 round could defeat the same thickness of armour at a slightly increased range of 2,000 meters. At 1,000 meters, L52A2 could defeat 130mm of RHA at 60 degrees.<br />
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Despite lacking any heavy metal component whatsoever, 3BM6 was already enough to defeat the Chieftain at typical combat distances. According to a Soviet analysis of an Iranian Chieftain captured by the Iraqi army during the early part of the Iran-Iraq war, available here on <a href="http://btvt.info/3attackdefensemobility/432armor_eng.htm">Andrei Tarasenko's website, btvt.info</a>, the upper glacis and frontal turret armour of the Chieftain Mk. 5 could be defeated at a distance of 1,600 meters. The frontal cheeks of the turret could be pierced at 1,600 m, and the base of the turret could be pierced at 2,300 m. The upper front plate, an 85mm cast armour plate sloped at 70 degrees, could be defeated at 1,600 m, while the lower front plate could be defeated at more than 3 km. The table says 3 kilometers, since they did not bother to conduct testing past that distance but the velocity limit is listed as 1,000 m/s which corresponds to a distance of 5 km. Needless to say, these are excellent results, especially considering that it is achieved without the use of any tungsten at all in the construction of the projectile.<br />
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The performance of 3BM-6 on spaced armour is detailed in the table below. In the table below, the first column from the left shows the impact angle and the next three columns from the left list the spaced armour configurations: b<span style="font-size: xx-small;">1</span> and b<span style="font-size: xx-small;">2</span> denote the thickness of the first and second plates in millimeters, and L denotes the size of the air gap in millimeters. The fourth column from the right lists the velocity limit of 3BM6 for the spaced described armour configuration, and the third column from the right lists the velocity limit for a monolithic plate of the same thickness in steel (b1 + b2). The difference in the velocity limit is listed in the second column from the right. The first column on the right shows the difference in the velocity limits between the spaced armour configuration and a monolithic plate in percentage points, and also represents the improvement in mass efficiency.<br />
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<a href="https://4.bp.blogspot.com/-C-HoBdc8GoU/WsKUydmB4NI/AAAAAAAALSg/WxwmGzV5GdwbgTyQ1cYafgoM_lCuDHwXACLcBGAs/s1600/3bm6.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="613" data-original-width="818" height="478" src="https://4.bp.blogspot.com/-C-HoBdc8GoU/WsKUydmB4NI/AAAAAAAALSg/WxwmGzV5GdwbgTyQ1cYafgoM_lCuDHwXACLcBGAs/s640/3bm6.png" width="640" /></a></div>
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As you can see, the maximum improvement in mass efficiency was attained using a 90-1000-100 configuration which was also the toughest target and showed an improvement of 9.1% compared to a monolithic plate of the same physical thickness (190mm). Needless to say, however, the 1.0-meter air gap of this configuration is completely impractical for tank armour, and the total thickness of the array considering its 45 degree angle is huge: 1,683mm thick. The improvement in mass efficiency from the other configurations are all less than around 6 percentage points, so from these results, it can be said that 3BM6 performs well for simple spaced armour with two steel layers within the range of angles of between 0 to 45 degrees. In practice, simple spaced armour such as the type implemented on the turrets of upgraded Leopard 1 tanks would be no challenge for 3BM6 at any plausible combat distance, nor would the spaced armour of the MBT-70 or KPz-70 (had they entered service).<br />
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This round made up the bulk of ammunition exported to client states, making it the most numerous type of APFSDS ammunition available to Egyptian and Syrian tank crews during the Yom Kippur war.<br />
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<h3>
<span style="font-size: large;">3UBM9</span></h3>
<h3>
<span style="font-size: large;">3BM21 "Zastup"</span></h3>
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<a href="http://4.bp.blogspot.com/-AtP0a2p5XdI/Vfm0M9kWsuI/AAAAAAAADkI/C5Irtxcd_vs/s1600/115mm%2Bapfsds.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="640" src="https://4.bp.blogspot.com/-AtP0a2p5XdI/Vfm0M9kWsuI/AAAAAAAADkI/C5Irtxcd_vs/s640/115mm%2Bapfsds.jpg" width="158" /></a></div>
The 3BM21 round features a slightly more progressive design derived from the 3BM15 made for the 2A46 125mm cannon. The projectile has a tungsten carbide core installed at the front of the penetrator like the original 3BM3, but has a more streamlined form instead of a bulbous tip. This design was developed as part of a unified programme, from which the 3BM25 "Izomer" and 3BM22 "Zakolka" was created together with "Zastup" in accordance with an order issued in 1972 for the general modernization of anti-tank munitions for anti-tank guns of 100mm to 125mm calibers. However, there designs did not present a major advance from previously established ammunition technology. Rather, it was merely an evolutionary improvement that further increased the probability of a first-round kill against existing NATO tanks such as the M60A1 and Chieftain, without necessarily bringing new capabilities. 3BM21 became available to the troops at around the same time as "Izomer" and "Zakolka", in the mid 1970's beginning in 1975-76.<br />
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Like previous designs, an armour piercing cap with a flat tip is present to both reduce the likelihood of a ricochet and to protect the tungsten core from shattering upon impact. The difference between 3BM21 and previous 115mm APFSDS designs is that its cap is made from VNZh-90 tungsten alloy, now much bigger and more elongated. The armour piercing cap and the tungsten carbide core are clearly visible in the photo on the left.<br />
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Mass of Complete Round: 23.50 kg<br />
Projectile Mass: 6.26 kg<br />
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<br /></div>
Propellant Charge Mass: 8.20 kg<br />
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Muzzle Velocity: 1,600 m/s<br />
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Certified Penetration at 1,000 m: (Extrapolated from values at 2 km)<br />
360mm RHA at 0°<br />
145mm RHA at 60°<br />
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Certified Penetration at 2,000 m:<br />
330mm RHA at 0° *</div><div>
133mm RHA at 60° (Inferred)<br />
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* From Andrei Tarasenko's site (<a href="http://btvt.narod.ru/4/t62weapon.htm">link</a>), MV Pavlov, IV Pavlov "Domestic armored vehicles 1945-1965". Tiv №9 2008.<br />
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<h3>
<span style="font-size: large;">3UBM13</span></h3>
<h3>
<span style="font-size: large;">3BM28</span></h3>
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<a href="https://4.bp.blogspot.com/-3CgvonWCTuI/WW3_hjo0BlI/AAAAAAAAItI/6Jhkm-wMkXU0Mp9ZwG-kGlsf-co6Lty1ACLcBGAs/s1600/3ubm13.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="124" data-original-width="600" height="132" src="https://4.bp.blogspot.com/-3CgvonWCTuI/WW3_hjo0BlI/AAAAAAAAItI/6Jhkm-wMkXU0Mp9ZwG-kGlsf-co6Lty1ACLcBGAs/s640/3ubm13.jpg" width="640" /></a></div>
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The 3BM-28 round was the last and most advanced 115mm APFSDS design of Soviet origin, and it was also the last APFSDS round developed for the T-62 before it was withdrawn from service. 3BM-28 has a sheathed monobloc depleted uranium penetrator with a flat AM6 light alloy armour piercing cap at the tip. The penetrator is made from UTsN uranium-zinc-nickel alloy.<br />
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Muzzle Velocity: 1650 m/s<br />
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Mass of Penetrator: 4.36 kg<br />
Mass of Armour Piercing Cap: 0.1 kg<br />
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<br />
<blockquote class="tr_bq">
Penetration at 2.0 km:<br />
380mm at 0°<br />
200mm at 60° (Inferred) </blockquote>
<blockquote class="tr_bq">
From Andrei Tarasenko's site (<a href="http://btvt.narod.ru/4/t62weapon.htm">link</a>), quoted from MV Pavlov, IV Pavlov "<i>Domestic armored vehicles 1945-1965</i>". TiV magazine September 2008.</blockquote>
<blockquote class="tr_bq">
Penetration at 2.0 km:<br />
350mm at 0° </blockquote>
<blockquote class="tr_bq">
From "<i>Боеприпасы: учебник для вузов</i>".</blockquote>
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<h3>
<a href="https://www.blogger.com/null" id="heat"></a>
<span style="font-size: large;">HEAT</span></h3>
<h3>
<span style="font-size: small;"><span style="font-weight: normal;"> </span></span></h3>
<span style="font-size: small;"><span style="font-weight: normal;">Between the mid-50's to late 60's, shaped charge warheads was widely appraised as being the "great equalizer" of tank warfare. Tube-launched HEAT warheads became popular, being tremendously useful in a variety of roles ranging from general tank-killing to bunker busting or simply as a more flexible alternative to HE-Frag or HESH shells, but because of the immaturity of shaped charge technology in those days, manufacturing a HEAT warhead tended to be costlier than manufacturing a steel full-caliber shell or a HESH shell. </span></span></div><div><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: normal;">HEAT shells also had a lower post-perforation effect on all targets compared to conventional ammunition types - they were not as effective at destroying bunkers compared to HE shells equipped with a delay fuze, and they were not as efficient at destroying lightly armoured vehicles compared to HE and HESH shells. This is due to the limited mass of particles that can be ejected through an armour plate due to the small mass of the shaped charge liner, and of that small mass,</span></span> 70% to 80% is propelled behind the shaped charge jet<span style="font-weight: normal;"> as a slug</span><span style="font-weight: normal;">. In many cases, a shaped charge warhead optimized to penetrate a maximum thickness of armour will only produce a slender penetration cavity through which a shaped charge slug cannot pass. If the slug cannot pass, it does not contribute towards the post-perforation effect and will actually plug the breach in the armour from the blast overpressure of the explosion from the detonation of the warhead. As a result, only a modest stream of hypervelocity particles will come out through the exit hole in the armour plate, supplemented by a smattering of armour fragments. </span>Unless the ammunition loadout of a tank was rationalized to the extent that it carried HEAT rounds exclusively, this type of ammunition is best suited to only occupy the niche of defeating exceptionally heavy armour.<br />
<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
<span style="font-size: small;"><span style="font-weight: normal;">The typical tank-fired HEAT shells developed on both sides of the Iron Curtain were so powerful that they rendered all contemporary tank armour essentially useless in the event of a direct hit. Unfortunately, the post-perforation effects of HEAT rounds do not hold a candle to the power of KE rounds. <a href="http://www.tank-net.com/forums/index.php?showtopic=37096&page=34#entry1313879">A report provided by internet user "Wiedzmin"</a> had this to say about the relationship between HEAT rounds and Iranian Chieftains:</span></span><br />
<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
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<div>
"<i>There had been forty four HEAT strikes from both 115mm T62 tank gun rounds and TOW [only one TOW strike was recorded]. All but five had achieved some penetration; two Sagger warheads had achieved penetration; seven RPG 7 had struck but none had penetrated. The internal diameter of the 115 and TOW penetration was normally 35mm; penetration led to much less damage than APDSFS and seldom led to fires</i>"</div>
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<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span>
The relevant pages of the report are shown <a href="https://pp.userapi.com/c837421/v837421491/4914c/k9qfl6rqb8E.jpg">here</a>, <a href="https://pp.userapi.com/c837421/v837421491/49155/dQ3DuOWoaQk.jpg">here</a> and <a href="https://pp.userapi.com/c837421/v837421491/4915d/FY-pgCk92E8.jpg">here</a>.<br />
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<div>
<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div>
<div>
<span style="font-size: small;"><span style="font-weight: normal;">So despite the comparatively high penetration power of HEAT ammunition and the high probability of defeating the armour of the Chieftain main battle tank (39 cases of armour perforation out of 43 hits), it was still not qualified to complete substitute a good KE round. Real combat experience showed that 115mm APFSDS was more lethal than 115mm HEAT when used against tanks that both types could perforate; the Chieftain, in this case. Even abroad, foreign tank crews generally preferred APDS or APFSDS over other ammunition types when targeting tanks. For instance, during the course of the Hunfeld II study that was carried out in the early 1970's in the Hünfeld region of Fulda, Germany, it was found that M60A1 gunners overwhelmingly preferred to use APDS during simulated combat.</span></span></div>
<div>
<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div><span style="font-size: small;"><span style="font-weight: normal;">115mm HEAT rounds used single-channel DG-3 13/1 propellant. The propellant is cut into sticks with a length of 290mm, and then packed into bundles. Not only were HEAT cartridges loaded with a reduced charge so as to not fire at the same pressure as APFSDS ammunition, but DG-3 itself is a nitrodiglycolic propellant with a low calorific value of 750 kCal/kg, lower than the 820 kCal/kg calorific value of DG-4 propellant.</span></span></div><div><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div>
<div>
<span style="font-size: small;"><span style="font-weight: normal;">There are numerous indicators that HEAT ammunition was loaded with a propellant charge that traded off muzzle velocity in favour of thinning the thin walls of the projectile, with the positive side effects being the reduced barrel wear and high penetration performance, and negative side effects being the steeper trajectory and poorer hit probability on moving targets. </span></span></div><div><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div>
<div>
<span style="font-size: small;"><br /></span></div>
<h3>
<span style="font-size: x-small;"><span style="font-size: large;">3UBK3, 3UBK3M</span></span></h3>
<h3>
<span style="font-size: large;">3BK4, 3BK4M</span></h3>
<div>
<span style="font-size: large;"><br /></span></div>
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<a href="http://2.bp.blogspot.com/-mQQwCBy6aKc/VmbTDBwFw3I/AAAAAAAAExI/TcqOqru29Hs/s1600/3bk4.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-mQQwCBy6aKc/VmbTDBwFw3I/AAAAAAAAExI/TcqOqru29Hs/s1600/3bk4.png" /></a> </div>
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BK4 was the basic HEAT shell that entered service alongside the T-62 in 1961. It had a steel casing with a conventional conical aerodynamic fairing that shared a close resemblance to the casing of the OF-11 HE-Frag shell, although the casings of the two shells were not interchangeable. Because the BK4(M) shell was lighter than the OF-11 shell by just under 2 kg, its muzzle velocity was higher by 45 m/s, so the ballistic properties of the BK4(M) shell were not entirely identical to the OF-11 shell. However, the lighter mass of the BK4(M) reduced its sectional density so it decelerated at a slightly more rapid rate than the OF-11, so in practice, the ballistic trajectory of the two rounds remain quite similar.</div>
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The warhead uses a conical steel shaped charge liner with a squared apex. The explosive compound used in the warhead is A-IX-1, a composition containing 96% RDX and 4% paraffin wax. The BK4M shell used the same casing as the basic BK4 but had a copper shaped charge liner of the same diameter. The built-in standoff distance as measured from the base of the shaped charge liner to the tip of the fuze is 238.8mm, which is equal to 2.07 charge diameters (CD) or around 2.35 cone diameters.</div>
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The Soviet approach to the creation of HEAT rounds can be considered quite rational as the focus was placed on maximizing the primary effect of the warhead by sacrificing the muzzle velocity. By having a modest muzzle velocity relative to the pressure of the U-5TS gun, the warhead casing of the BK4 and BK4M rounds could be reduced, and in turn, the diameter of the shaped charge liner could be increased. The 105mm M456A1 round had an exceptionally high muzzle velocity of 1,174 m/s, so it required a thick warhead casing to withstand the stresses of acceleration inside the gun tube. Case in point: the BK4M warhead casing has a thickness of 8.03mm at the base and a thickness of 5.31mm at the mounting point for the shaped charge liner. This enabled a shaped charge liner with a diameter of 101.6mm to be installed. On the M456 warhead, the casing has a thickness of 10mm at the base and a thickness of 8.3mm at the mounting point for the shaped charge liner, and because of this, the shaped charge liner has a diameter of only 88.4mm. The difference in shaped charge liner diameter between the 115mm BK4 and the 105mm M456 is therefore not 10mm as the difference in the warhead diameters implies, but actually 13.2mm.<br />
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By maximizing the penetration power of the HEAT ammunition at the expense of velocity, the role of HEAT in a mixed ammunition load was intrinsically constricted to the niche of defeating tanks that are too heavily armoured to be handled with APFSDS rounds alone.<br />
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The replacement of the steel liner with a copper one was not considered sensitive technology, as there is evidence that these shells were freely exported to the Syrians and Egyptians. It is difficult to imagine that the BK4M shell was less prolific in the Red Army.<br />
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In shells produced from 1961 to 1963, there was a small 20-25 gram charge of A-IX-2 inside the hollow steel tailboom of the stabilizer fins, between the tracer and the warhead. It has no fuze or detonator - it is detonated by the explosion of the main warhead. The purpose of the small A-IX-2 charge was to increase the total fragmentation effect of the shell, but after several cases of the tailboom rupturing in the cannon barrel when fired, this feature was deleted. All BK4 shells produced since 1964 lack the explosive charge.<br />
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According to a well-known TRADOC bulletin, the penetration of 3BK4 or 3BK4M is roughly equal to the 105mm M456A1 HEAT round with both having a penetration of 432mm despite the difference in caliber between the two rounds. This may be explained by the use of a steel liner in the BK4 warhead instead of a copper liner as found in the M456A1, but a more likely explanation is a difference in the criteria. According to a 1979 Soviet report titled <i>"<a href="http://btvt.info/5library/vbtt_1979_03_probivaemost.htm">Выбор Кумулятивных Снарядов Для Испытания Брони</a></i>" (<i>Selection of Cumulative Shells for the Evaluation of Armour</i>), the average penetration of BK4M in armour plate is 499mm with a maximum of 559mm and a minimum of 418mm. All of the penetration figures represent the performance at both 0 and 60 degrees. Officially, the penetration of 3BK4M is rated at 440mm RHA.</div><div><br /></div><div>For the sake of comparison, the average penetration of M456A1 in the same medium hardness armour steel was found to be 398mm, and the maximum and minimum penetration were 434mm and 355mm respectively. Most interestingly, these figures imply that the TRADOC bulletin and other U.S Army documents are reporting the maximum penetration of M456A1 instead of the average penetration wheras the official Soviet figures represent the maximum perforation limit including an allowance for post-perforation effects. This nuance can also be seen in French literature on the 105mm F1 HEAT shell (Obus-G) which report that the penetration figures are 360mm at 0 degrees and 150mm at 60 degrees, but the Soviet study credits the F1 shell with an average penetration of 388mm.<br />
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When all of these rounds are normalized according to their average penetration, the 105mm M456A1 round has the lowest performance with a penetration of 398mm. <a href="https://pp.userapi.com/c850236/v850236543/199ef4/YtLqB0f_3yk.jpg">Newly released information with a RARDE source</a> indicates that the penetration of M456 is actually less - only 380mm RHA. According to the same source, the 120mm DM12 HEAT round for the Rheinmetall L/44 and M256 cannons can penetrate 480mm of RHA, which is less than BK4M despite the larger shaped charge cone diameter of 109mm. This can be explained by several factors, one of which is the more acute angle of the BK4M shaped charge cone and the smaller standoff distance of 1.78 CD instead of the 2.07 CD of standoff enjoyed by the BK4M warhead.<br />
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Based on this information, BK4M provided the capability to defeat the most heavily armoured NATO tanks from the front until the emergence of the Leopard 2 and M1 Abrams in 1979. It also permitted the T-62 to defeat the frontal armour of a T-64 or T-72 before these main battle tanks even came into service. However, the armour penetration performance of BK4 was already enough to greatly overmatch any NATO armour that a T-62 was likely to meet and it was enough to defeat even the most well-protected heavy tanks of its time. The higher the level of overmatch, the more powerful the post-perforation effect will be. Of course, a catch existed - by its nature, the post-perforation effect on tanks protected by thick armour was modest compared to KE ammunition. Main battle tanks like the M60A1 and Chieftain cannot withstand an attack from BK4 or BK4M.<br />
<br />BK4 and BK4M would be particularly lethal against more thinly armoured tanks like the Leopard 1 and older tanks like the M48 and M47, which formed the bulk of the tank fleets of NATO armies. However, APFSDS would be preferred under all circumstances due to its superior first-shot hit probability, sufficient armour penetration performance and superior post-perforation effect. Both HEAT rounds can be used interchangeably in a T-62 as they share the same ballistic characteristics, and they are both capable of defeating the armour of any enemy tank.<br />
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Although this round is capable of knocking out an M60A1 or a similar type of tank from the front on the first hit, the chances of scoring a hit with the first shot at normal combat ranges are rather low. At 1,500 meters, the probability of hitting an M60A1-sized target is only 20%. The maximum effective range of the 3BK4 round is around 1,000 meters as the probability of hit is 48% at this distance. This is seen in the diagram below, taken from the TRADOC bulletin.<br />
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The main factor that determines the lower accuracy of 3BK4 in this comparison is the lack of precise rangefinding equipment on the T-62, and the lower velocity of the shell exacerbates this. The M60A1 is technically more capable of exploiting low and medium velocity ammunition at longer ranges because it has an optical coincidence rangefinder.<br />
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Both the BK4 and BK4M use the GPV-2 piezoelectric point-initiating base-detonating spitbackc fuse. It is the same fuse used in the 100mm 3BK5 HEAT round for the D-10T. Upon impacting a hard target, the piezoelectric element at the initiator at the nose of the shell is deformed, causing it to release an electric signal that triggers the detonation of a spitback charge. The detonation of the spitback charge ejects an EFP towards the detonator receptacle at the mouth of the shaped charge liner and into the booster charge at the detonator, thus detonating the primary explosive charge of the warhead.<br />
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<b>BK4 (BK4M)</b><br />
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Mass of Complete Round: 26.00 kg<br />
Projectile Mass: 12.97 kg<br />
Shaped Charge Liner Mass: 0.706 kg (0.804 kg)
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Diameter of Shaped Charge: 101.6mm<br />
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Mass of Explosive Charge: 1.55 kg (1.478 kg)</div>
Explosive Charge Type: A-IX-1<br />
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Muzzle Velocity: 950 m/s<br /><br />
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<h3>
<span style="font-size: large;">3UBK7</span></h3>
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<span style="font-size: large;">3BK15, 3BK15M "Zmeya"</span></h3>
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"Zmeya" was developed alongside the 100mm "Ikra" and 125mm "Nadezhda" as part of a modernization program to upgrade the firepower of the Army's cannons in the 100mm to 125mm caliber range. The most notable difference in the new shells was the use of spike tip technology, which was not a new technology by the time 3BK15 was introduced in 1975. The ballistic peculiarities of spike nosed projectiles were known and had already been used to create tank shells as early as 1962 in the form of the 125mm 3BK12 round. It is not clear why this technology did not immediately carry over to the ammunition for the 100mm D10-T, 115mm U-5TS and 115mm D-68 when it was first implemented.<br />
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Two variants of the new round with steel and copper shaped charge liners were created in accordance with the standard practice of the Soviet Army. The 3BK15 shell had the warhead using a steel shaped charge liner and the 3BK15M shell used a copper liner for improved penetration power. Both variants were ballistically matched.<br />
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The 3BK15 had an improved warhead design compared to its predecessors, doing away with the traditional conical or ogived aerodynamic fairings in exchange for a a flat-sided cylindrical body and a spike nose carried over from contemporary 125mm HEAT shells. "<i><a href="http://www.dtic.mil/dtic/tr/fulltext/u2/801509.pdf">The Engineer's Handbook - </a></i><span style="color: #0000ee;"><i><u>Design For Control of Projectile Flight Characteristics</u></i></span>" from the U.S Army Materiel Command provides us with a more esoteric examination of spike noses.</div><div>
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The pictures below, taken from page 4-11, show the different airflow characteristics with different lengths of the standoff probe (referred to as the "spike nose") and at different mach numbers.<br />
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<div><br /></div><br />Such projectiles have a higher drag coefficient compared to ogived projectiles, but the stabilizing effect enhances its shot dispersion characteristics. On 3BK15, the higher drag was compensated to some extent by an increased muzzle velocity compared to 3BK4. However, the use of a spike tip presented serious engineering challenges due to a phenomenon known as dual flow on spike tips.<br />
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"<i>Examination of spark photographs showed that the low drag coefficients were associated with rounds on which the airflow separated from the spike at its tip, while on the high-drag rounds the flow separated at a point about half-way down the spike. This phenomenon was called "dual flow"; its existence was a function of the geometry of the spike. In order to avoid the occurrence of dual flow, with its serious effect on accuracy, modern spike-nosed rounds arc furnished with a small ring near the tip of the nose which insures the early separation of the flow.</i>"<br />
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In other words, a mach cone forms at the tip of the spike, and sometimes separates down the middle of the spike to form a second cone. Projectiles with two mach cones; one at the tip of the spike and one down the middle of the spike experienced higher drag, whereas projectiles with a single mach cone at the tip experienced low drag. A projectile with a simple straight spike could experience both flow configurations, resulting in some shots experiencing higher drag and landing low on the target, while others experience lower drag and land high. The purpose of the ring is to ensure the separation of flow at the tip of the spike, thus ensuring that the second cone down the spike is consistently eliminated leaving a single mach cone at the tip of the spike.<br />
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The effects of dual flow on accuracy are further explained in a Ballistics Research Laboratory study on this topic in the paper "<a href="http://www.dtic.mil/dtic/tr/fulltext/u2/479828.pdf"><i>The Effect on Drag of Two Stable Flow Configurations Over The Nose Spike of the 90mm T316 Projectile</i></a>" from 1954. Here is an excerpt:<br />
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"<i>Since the occurrence of either type of flow appears to be of a statistical nature, caused by unknown conditions, a given group of rounds fired on a target might contain both species. With markedly different drag characteristics, the two groups will gradually separate, principally in a vertical plane, by as much as three mils at 2000 yards. The vertical target will then contain both high and low rounds thus jeopardizing what otherwise might be a good dispersion pattern. Clearly, it is desirable to fix the flow over the spike in such a way that only one type of flow occurred and preferably of a lower drag type.</i>"<br />
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The lack of a ring similar to the type present on Western spike noses might be because a truncated cone nose already had acceptably low drag, as suggested in the BRL paper. The study showed that a truncated cone spike nose could reliably achieve stable low drag flow with almost as low of a drag coefficient as that achieved by a ringed spike, with no dual flow. See the table graph below:<br />
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The research conducted by the BRL resulted in engineers settling on the now common Western-style spike, with a square spike nose and a small ring. The 90mm M431 shell, for example, has <a href="http://64.78.11.86/uxofiles/mulvaney/images/90mm-HEAT-T-M431.jpg">a flat-headed fuse</a> and a small protruding ring around the spike, as did the 105mm M456 shell. </div><div><br /></div><div>Unlike the flow separation ring used on ammunition produced in the U.S and in other Western nations, Soviet engineers applied a more elegant solution utilizing the tapered shape of the V-15 fuze for the same purpose. Though the flow separation ring was an adequate solution, it ceases to function at lower velocities and the projectile experiences major instabilities. This resulted in ammunition such as the 105mm M456 round and 120mm DM12 round have a drastically increased dispersion at ranges of 2 km and above. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-PJizv_hePGM/X5_jY0k3GFI/AAAAAAAAR8g/0wDmIbUo_AA1O3LWy29POp8zIupmjqetwCLcBGAsYHQ/s1420/bk9%2Bshock%2Bfront%2Bcone.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1054" data-original-width="1420" height="297" src="https://1.bp.blogspot.com/-PJizv_hePGM/X5_jY0k3GFI/AAAAAAAAR8g/0wDmIbUo_AA1O3LWy29POp8zIupmjqetwCLcBGAsYHQ/w400-h297/bk9%2Bshock%2Bfront%2Bcone.png" width="400" /></a></div><div><br />
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The spike nose of 3BK15 had a length of 1.4 calibers and a maximum diameter of 0.38 calibers. The warhead also implemented some new old technologies to improve jet formation characteristics, including the use of a slightly tapered cylindrical wave shaper to optimize the propagation directions of the blast waves from the explosive charge. 3BK15 also has a more precisely drawn shaped charge liner cone and used a compressed filler to increase the density of the explosive filling.<br />
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The use of more energetic 12/7 stick powder boosted the muzzle velocity of 3BK15 to 1,060 m/s, or Mach 3.11. However, this was only to offset the higher drag of the projectile compared to the conventional BK4 projectile.<br />
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<b>3BK15 (3BK15M)</b><br />
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Mass of Complete Round: 26.3 kg<br />
Total Projectile Mass: 12.2 kg<br />
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Muzzle Velocity: 1,060 m/s<br />
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Penetration: (Unknown, estimated)<br />
460mm at 0° (520mm)<br />
230mm at 60° (260mm)<br />
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For some reason, the tracer was not placed at the base of the shell assembly. Instead, it was embedded into the wall of the warhead at the very front. It is possible that this was intended to take advantage of the modest spin rate of the projectile to generate a more distinct tracer signature, which could potentially help the gunner and commander track the fall of the shot more easily in poor weather conditions.<br />
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<h3><span style="font-size: large;">COAXIAL MACHINE GUN</span></h3>
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<div><br /></div><div><br /></div><div>An SGMT or PKT machine gun was installed in the T-62 as the secondary weapon to the 115mm gun. The machine gun is fed from a 250-round box, one of which would be stowed on the ready mount next to the machine gun with another nine stowed inside the hull for a total combat load of 2,500 rounds of ammunition. This load is consistent with other Soviet armoured fighting vehicles, which universally maintained a combat load of around 2,000 rounds for their 7.62mm coaxial machine guns. There are four boxes stowed on the loader's side of the hull, and another five on the opposite side, allowing the machine gun to be loaded at any turret orientation angle.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhncSrqEY5JvGKUHM_pjlupZGqC5KXgAHF8mfBDtYzpAgqGFVrUDqFFZsSm55QC3s_jo2BnshFpWCt7woy6EQEx2TqZhK1WdfvPBMD3AWAwLwX7egk8L_YkNzKjAs7A7Bk7U7Yrh0fjyiYLYPXchaRU6iI5IKtiG3WRtTGB5vBl4oA7TkR2A-C86FoQyg/s3912/p0057.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2192" data-original-width="3912" height="224" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhncSrqEY5JvGKUHM_pjlupZGqC5KXgAHF8mfBDtYzpAgqGFVrUDqFFZsSm55QC3s_jo2BnshFpWCt7woy6EQEx2TqZhK1WdfvPBMD3AWAwLwX7egk8L_YkNzKjAs7A7Bk7U7Yrh0fjyiYLYPXchaRU6iI5IKtiG3WRtTGB5vBl4oA7TkR2A-C86FoQyg/w400-h224/p0057.png" width="400" /></a></div><div><br /></div><div>This feed system became the norm during WW2 and was still standard at the time the T-62 entered service; for instance, the MG3 coaxial machine gun of the Leopard 1 was loaded using individual 230-round boxes, and the L8A1 coaxial machine gun Chieftain was loaded with 200-round boxes. The only exception was the M48 and M60 series. These tanks had a continuous 2,200-round belt for the coaxial machine gun which would be reloaded using four smaller 925-round boxes stowed in reserve when needed (changed to two 1,250-round boxes and two 625-round boxes in reserve beginning with the M60A1). </div><div><br /></div><div>Both types of feed system are valid, with advantages and disadvantages to each. While a voluminous supply of ready ammunition in a single belt reduces the workload of the loader, it also introduces the possibility of feeding issues from the insufficient pull strength of the machine gun, and it tends to be difficult to make use of the sustained fire potential of the ammunition supply simply because the barrel of the machine gun overheats. This was ostensibly solved in the M60 series by the introduction of the infamous M73 machine gun with a quick-change barrel, but considering that the M73 suffered from chronic jamming issues, it is obvious that there is some challenge in objectively determining the superior feeding solution. </div><div><br /></div><div>Aside from the feed system, it is also important to point out that when compared to all of its NATO counterparts, the T-62 - like all other Soviet tanks - carried much less ammunition for its coaxial machine gun. A combat load of 2,500 rounds is just over half of the capacity of a Leopard 1 (4,600 rounds) and less than half the capacity of a Patton series tank (5,900-5,950 rounds), Chieftain (6,000 rounds) or an M60A1 (6,850 rounds). Though how much ammunition is actually needed is a matter of debate, a direct comparison shows that the T-62 carries a far lighter combat load for its coaxial machine gun. The machine gun could be fired from the trigger button on the gunner's control handles, the trigger button on the manual elevation wheel, or with the manual trigger on the back of the machine gun receiver during an emergency situation such as the total loss of electrical power in the tank. The spent casings and emptied links are collected in a metal bin to the left of the machine gun.</div><div><br /></div><div>The ball mount for the barrel of the machine gun is hermetically sealed, but it is not uncommon to see tanks with the ball mount removed for convenience, leaving the barrel unsupported. Removing the ball mount makes it easier to mount and dismount the machine gun, which is a routine task during peacetime. Generally speaking, this should not be done on tanks that are expected to take part in combat as the ball mount serves to stop bullet and fragment splash from entering the tank, but this drawback is counterbalanced by some benefits. The lack of a rigid barrel support presumably increases shot dispersion, which may be considered desirable for a tank coaxial machine gun. Additionally, the open machine gun port provides an airway for the air blown into the tank by the ventilation system to flow out, thus evacuating fumes from the machine gun and also helping to cool the barrel.</div><div><br /></div><div>From a design perspective, having a 7.62mm machine gun for a coaxial weapon was an entirely conventional decision, and the specific design of the machine gun installation was largely unremarkable. It is only worth noting that the ammunition box was mounted entirely above the turret ring and not below it, unlike the T-54 and T-55. With one less obstruction, the loader's access to items in the hull was improved.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-XPP93KOkRtM/X0VPTBUrOWI/AAAAAAAARhE/YLJ9aL_ncmA-4gXk29Lp44miwm13p-GegCLcBGAsYHQ/s445/coaxial%2Bmg%2Bammo%2Bbox%2Blocation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="196" data-original-width="445" src="https://1.bp.blogspot.com/-XPP93KOkRtM/X0VPTBUrOWI/AAAAAAAARhE/YLJ9aL_ncmA-4gXk29Lp44miwm13p-GegCLcBGAsYHQ/s0/coaxial%2Bmg%2Bammo%2Bbox%2Blocation.png" /></a></div><div><br /></div><div><br /></div>The original T-62 model was armed with the SGMT machine gun chambered for the 7.62x54mmR cartridge as the coaxial machine gun. It had a cyclic rate of fire of 600 rounds per minute.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="http://4.bp.blogspot.com/-SlTYFRQot9I/VmMSfW_VlcI/AAAAAAAAEn8/MDTmaJr_1iM/s1600/sgmt%2Bmachine%2Bgun.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="179" src="https://4.bp.blogspot.com/-SlTYFRQot9I/VmMSfW_VlcI/AAAAAAAAEn8/MDTmaJr_1iM/w400-h179/sgmt%2Bmachine%2Bgun.png" width="400" /></a></div><div><br /></div><div>
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Beginning in August 1964, the SGMT was replaced by the new <a href="https://thesovietarmourblog.blogspot.com/p/pktm.html">PKT machine gun</a>. The two machine guns were ballistically matched so that they were interchangeable, with no need to swap out the glass viewfinder insert in the gunner's sights. The primary impetus for the change was not to have a better machine gun, but to standardize the PK general purpose machine gun in the Soviet Army.<br />
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<img height="172" src="https://3.bp.blogspot.com/-BLDjSGKUdhA/VRgWHimMEpI/AAAAAAAABgw/0TNlLhqld8o/s640/pktm.png" width="640" /></div>
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The PKT machine gun was fed from the same 250-round ammunition boxes of which ten were stowed, exactly as with the SGMT. </div><div><br /></div><div>The nominal maximum effective range of both machine guns is around 1,500 m, while the effective range against a running target is reportedly around 650 meters. The effective range against a standing enemy soldier is 800 meters.<br />
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<h3>
<a href="https://www.blogger.com/null" id="tertiary"></a>
<span style="font-size: large;">ANTI-AIRCRAFT MACHINE GUN</span></h3>
<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ac-ovq7H_CM/X0VKOE-S4MI/AAAAAAAARg0/SvuCGjDXTf4D0BXERWcvFBsCaLmssHvDwCLcBGAsYHQ/s1280/T-62%2Bwith%2BAAMG%2BDShKM.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="712" data-original-width="1280" src="https://1.bp.blogspot.com/-ac-ovq7H_CM/X0VKOE-S4MI/AAAAAAAARg0/SvuCGjDXTf4D0BXERWcvFBsCaLmssHvDwCLcBGAsYHQ/s640/T-62%2Bwith%2BAAMG%2BDShKM.jpg" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div>
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In 1969, it was decided to install the DShKM anti-aircraft machine gun on T-55, T-55A, and T-62 tanks and their subsequent modifications beginning in May 1970. The photo below shows a T-62 built in 1969 with a new loader's cupola and a DShKM machine gun. Like other T-55, T-55A and T-62 tanks built in the late 1960's, this example is equipped with RMSh tracks.<br />
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<a href="https://1.bp.blogspot.com/-UE_-vMx35BI/XUsJPMPZ9YI/AAAAAAAAOvw/8CA683jTB-MhDOUPOKs_xp0T_ptTqjebQCLcBGAs/s1600/t-62%2B1969%2Bwith%2Bdshkmt.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="808" data-original-width="1600" height="322" src="https://1.bp.blogspot.com/-UE_-vMx35BI/XUsJPMPZ9YI/AAAAAAAAOvw/8CA683jTB-MhDOUPOKs_xp0T_ptTqjebQCLcBGAs/s640/t-62%2B1969%2Bwith%2Bdshkmt.png" width="640" /></a></div>
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The new requirement for an anti-aircraft machine gun meant that the loader was given his own cupola with a race ring and a mount to place the DShKM machine gun. The DShKM was a robust 12.7mm machine gun with a rate of fire of around 600 rounds per minute, but it is unclear why it was retained for the T-62 when the NSV had recently entered service and was replacing the DShKM in all other applications.<br />
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The design of the anti-aircraft machine gun mount is distinct from the typical pintle-mount types found on the T-54, T-10 and other armoured combat vehicles. On the T-62, the machine gun is mounted on a cradle that is fixed to the cupola in azimuth, so aiming the machine gun in azimuth is done by turning the entire cupola rather than traversing the machine gun itself by a pair of spade grips. The operator does this by holding on to the fixed handle on the left side of the machine gun cradle and simply turning the cupola with his bodily strength. The DShKM is on a cantilever mount, so the cupola will tend to be slightly front-heavy unless the machine gun is elevated even though the loader's hatch acts as a counterweight when it is opened. The imbalance of the cupola can be a problem if the tank is on a steep incline or a steep side slope, but it is not a major issue. The equilibrium of the DShKM itself is maintained by a pair of equilibrator springs installed underneath the machine gun receiver. These springs ensure that the machine gun can be aimed with a uniform effort throughout its entire range of elevation angles.</div><div><br /></div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-QPyLqqOyiZI/XUsJNYYvY2I/AAAAAAAAOvg/_8b3lPpogYgR1w_jJtoJVusCEo8sIlY-wCLcBGAs/s1600/13%253D5_908353.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="680" data-original-width="1000" height="271" src="https://1.bp.blogspot.com/-QPyLqqOyiZI/XUsJNYYvY2I/AAAAAAAAOvg/_8b3lPpogYgR1w_jJtoJVusCEo8sIlY-wCLcBGAs/s400/13%253D5_908353.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-2q4JPNEe9qk/XAva0FBuuSI/AAAAAAAAMqA/4gCZxy5cZnEog_K9__4LmycNnqXExDjBQCLcBGAs/s1600/13%253D6_908354.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="651" data-original-width="997" height="260" src="https://1.bp.blogspot.com/-2q4JPNEe9qk/XAva0FBuuSI/AAAAAAAAMqA/4gCZxy5cZnEog_K9__4LmycNnqXExDjBQCLcBGAs/s400/13%253D6_908354.jpg" width="400" /></a></div><div><br /></div>
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Elevation is accomplished by turning a hand wheel which acts on a toothed arc. The elevation hand wheel has a brake lever that releases a simple brake mechanism when grasped, allowing the machine gun operator to aim the gun freely. When firing at a fixed target, the operator can release his grip to activate the brake. This fixes the machine gun rigidly in place, making it more accurate when firing long bursts. The cupola can also be braked in traverse by pressing down on the left handle, which drives a wedge into a slot in a split cone ring between the cupola and the turret. The ring expands, because its circumference is increased by the width of the wedge, and in doing so, it contacts the turret surface along the ring mount along its entire circumference, like a band or drum brake. This keeps the cupola firmly secured in traverse, allowing a ground target or hovering helicopter to be engaged with better accuracy. <br />
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<a href="https://3.bp.blogspot.com/-5Qms0ApzD1E/XOXSj50HZmI/AAAAAAAAOB0/89m44gBQwrQ0iMqP8m66FPtSbVXqLVVkACLcBGAs/s1600/dshkm%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="430" data-original-width="1600" height="170" src="https://3.bp.blogspot.com/-5Qms0ApzD1E/XOXSj50HZmI/AAAAAAAAOB0/89m44gBQwrQ0iMqP8m66FPtSbVXqLVVkACLcBGAs/s640/dshkm%2Bdrawing.png" width="640" /></a></div>
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The machine gun cradle allows the gun to be depressed by -5 degrees and elevated by +85 degrees with ease, but there are two caveats: the "Luna" infrared spotlight installed above the coaxial machine gun port is tall enough to obstruct the machine gun from depressing to its full extent when it is aimed directly forward, and the commander's OU-3 spotlight does the same. This minor design flaw is not an issue when firing at aircraft or when firing at ground targets at long range (since superelevation has to be applied anyway), but it can be a nuisance when aiming the machine gun at low-profile targets at short range. The spotlight is positioned in such a way that the muzzle of the DShKM will be blocked when it is depressed instead of allowing it to get behind the spotlight, so there is no chance of the loader accidentally shooting off the spotlight.<br />
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<a href="https://3.bp.blogspot.com/-qe5dEns1-O0/XOW3h3LGLAI/AAAAAAAAOAo/P6CCNrmAm7gKwWnl1bpq8oR4QnhsnuZjQCLcBGAs/s1600/t-62%2Bwith%2Bdshkm.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="402" data-original-width="588" height="273" src="https://3.bp.blogspot.com/-qe5dEns1-O0/XOW3h3LGLAI/AAAAAAAAOAo/P6CCNrmAm7gKwWnl1bpq8oR4QnhsnuZjQCLcBGAs/s400/t-62%2Bwith%2Bdshkm.jpg" width="400" /></a></div>
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The firing mechanism is actuated by a trigger lever on the fixed left handle on the gun cradle. The lever is connected to the trigger of the machine gun via a pull cable.<br />
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The DShKM is fed with standard 50-round boxes. One box is stowed on the machine gun mount and another five boxes are stowed on the right side of the turret next to the loader's cupola for easy access. The loader only needs only to bend down to reach these boxes, but since the machine gun is fed from the left, it is easiest to reload it when the cupola is pointing to the rear. The five boxes were not simply placed on the outside of the turret for the sake of convenience when reloading, but also to save space inside the tank and because it would have been difficult for the loader to extract an ammunition box from inside the tank and exit through his hatch with a large box in his hands. The disadvantage to this solution is that the externally stowed ammunition can be easily damaged by bullets, artillery shell splinters, and high explosive rounds.<br />
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Aiming at targets can be done with either the K-10T anti-aircraft collimator sight kept in the raised stowage box mounted to the gun cradle or the leaf-type iron sights on the machine gun. The K-10T facilitates accurate aiming at both ground level and high altitude targets, although the leaf sights on the DShKM would be more appropriate for aiming at ground targets. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Mvlwkr0xS5I/X0VJvyFrCpI/AAAAAAAARgs/wgRxAS9LnvM-XA-RsHvytNeWS2CF5X6dQCLcBGAsYHQ/s1024/t-62m%2Bposing.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="658" data-original-width="1024" src="https://1.bp.blogspot.com/-Mvlwkr0xS5I/X0VJvyFrCpI/AAAAAAAARgs/wgRxAS9LnvM-XA-RsHvytNeWS2CF5X6dQCLcBGAsYHQ/s640/t-62m%2Bposing.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div><div>The reticle of the K-10T is illuminated via a light collecting lens, which receives environmental light from a front-facing lens and magnifies it to project an illuminated image onto the reflector, with which the operator aims. In low-light conditions, the operator must fit a special battery-powered lamp onto a purpose-built bracket in front of the light collector lens to provide an artificial source of light for the illuminated reticle. </div><div><br /></div><div>For anti-aircraft purposes, the collimator sight has an ideal design and location to provide the operator with a maximum field of view while allowing him to aim regardless of how he is positioned, which changes depending on the elevation angle of the machine gun, as the operator does not need to adjust his head to obtain a correct eye relief as with iron sights. The proper method of aiming with the sight is for the operator to keep both eyes open and look through the sight with his his right eye, allowing his brain to perceive the projected sight reticle in his vision through both eyes. Moreover, as long as the right eye is used to aim and there is 165-250mm of eye relief, the operator's field of view is not obstructed by the stowage box next to the sight.</div></div><div><br /></div><div>The K-10T sight has a tinted screen in front of the reflector to reduce glare when aiming towards a bright background such as a bright clear sky or in the direction of the sun. The screen can be flipped down and out of the way if it is not needed. When flipped up, the screen darkens the background enough that there is a high enough contrast for the projected reticle to appear clearly in the operator's vision, allowing him to engage air targets with both eyes open.<br />
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<a href="http://4.bp.blogspot.com/-TozVaKDF49Q/VmkwR6GKPBI/AAAAAAAAE7c/r9wOo73nVK0/s1600/k-10t%2Bcollimator%2Bsight.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="260" src="https://4.bp.blogspot.com/-TozVaKDF49Q/VmkwR6GKPBI/AAAAAAAAE7c/r9wOo73nVK0/s320/k-10t%2Bcollimator%2Bsight.jpg" width="320" /></a><a href="http://3.bp.blogspot.com/-vOnFfMqItUM/Vmkwe-LzC5I/AAAAAAAAE7k/ZXyNX5b5HaQ/s1600/collimator-k10-t_front.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://3.bp.blogspot.com/-vOnFfMqItUM/Vmkwe-LzC5I/AAAAAAAAE7k/ZXyNX5b5HaQ/s320/collimator-k10-t_front.jpg" width="202" /></a></div>
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<a href="http://3.bp.blogspot.com/-Y3g-a4LOq6c/Vmkv-wiWdWI/AAAAAAAAE7U/-_IZvIuilak/s1600/collimator-k10-t_grid.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://3.bp.blogspot.com/-Y3g-a4LOq6c/Vmkv-wiWdWI/AAAAAAAAE7U/-_IZvIuilak/s640/collimator-k10-t_grid.jpg" width="640" /></a></div>
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When not in use, the protective cover is closed over the K-10T, mainly to shelter it from the weather. <br />
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The DShKM was technically sufficient against helicopters and other low-flying aircraft given that common types like the AH-1 Cobra did not have enough cockpit armour to protect the pilot from 12.7mm shots, and the windscreen was only a thin polycarbonate sheet that did not even offer any protection from rifle rounds at hundreds of meters. The rest of the fuselage lacked any meaningful armour protection. The main challenge would be reliably scoring hits on the helicopter. This task becomes even more of an issue if the tank is coming under fire, so the machine gun would probably be more useful as a deterrent against enemy aircraft. Historically, the anti-aircraft machine guns on T-54 and T-62 tanks were hardly ever used against aircraft at all. If used, they were most often aimed at ground targets, and only when the operator had some assurance of safety from enemy snipers.<br />
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<h3>
<a href="https://www.blogger.com/null" id="prot"></a>
<span style="font-size: large;">PROTECTION</span></h3>
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<a href="http://3.bp.blogspot.com/-DvmKgrAVb40/Ve1LeKqzcYI/AAAAAAAADgA/bEy-nxPtcxY/s1600/front.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://3.bp.blogspot.com/-DvmKgrAVb40/Ve1LeKqzcYI/AAAAAAAADgA/bEy-nxPtcxY/s640/front.jpg" width="640" /></a></div>
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The T-62's hull retains the same general layout as the T-54 but differs in dimensions. The armour thickness remained largely unchanged from its predecessor which could be considered a perpetual liability for the T-62 since the beginning of its service life in contrast to the T-54 which enjoyed a high level of immunity from contemporary anti-tank guns when it achieved initial operating capability (IOC) in the early 1950's. Even so, the design of the T-62 allocates a large proportion of its mass to armour - almost 50%. For a tank weighing only 37 tons, 18.3 tons is from armour alone.<br />
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Like the T-55 before it, the upper glacis armour of the T-62 was essentially immune to American 90mm armour-piercing rounds (excluding HEAT to some extent) and somewhat resistant to 20 pdr. APDS (at ranges of 1 km or more). This was due to the original requirement of the T-54 for protection from the Pzgr. 39 round fired from the 8.8cm Pak 43 or KwK 43 at a muzzle velocity of 1,000 m/s. This requirement was created because it was expected that the Pak 43 and KwK 43 or an equivalent cannon would become the standard cannon for future German medium tanks while the existing Tiger II heavy tank would eventually be replaced with a new design equipped with a 10.5cm or 12.8cm cannon. Even though the war ended before this became a reality, the requirement was not reduced to the benefit of the future of Soviet medium tanks as a class.<br />
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The front hull armour is composed of an upper and a lower glacis plate. The upper glacis has a thickness of 100mm and is sloped at 60 degrees for a line-of-sight (LOS) thickness of 200mm, and the lower glacis is the same thickness but it is sloped at a shallower angle of 55 degrees for a LOS thickness of 178mm. Soviet testing showed that from a head-on attack, the upper glacis is immune to 100mm blunt-nosed armour piercing rounds (BR-412B) from point blank range but the lower glacis can be defeated by BR-412B from a distance of 900 meters. The lower glacis can be considered a weak point, although it is largely inconsequential since the lower glacis is only a third of the height of the upper glacis.<br />
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It must be noted that the glacis armour is stronger than the LOS thickness may suggest when attacked with AP and APDS rounds due to the slope of the armour as these two ammunition types have degraded penetration on sloped plate.<br />
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A German source indicates that the hull of the T-62 can be defeated by 105mm DM13 APDS (West German licence-produced version of the British L28A1 round) from a distance of 1,800 meters. In a separate set of tests, West German data showed that the safety limit of the 100mm upper glacis plate of the T-55 at its constructional obliquity of 60 degrees is 2,000 meters. Here, the safety limit is defined as the distance where it is not possible to defeat the armour. This is consistent with other German info saying that the distance limit of 105mm APDS against this armour is 1,800 meters, where the distance limit is defined as the maximum range at which it is possible to defeat the armour.</div><div><br />
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When the impact angle increases slightly to 61 degrees, the safety limit against DM13 increases to 1,500 meters. Based on this, the distance limit would be around 1,300 meters. It is possible for the T-62 upper glacis to achieve a compound angle of 61 degrees if the hull is turned sideways by 14 degrees, but the same effect can be obtained if the ground were only slightly inclined. At an impact angle of 63 degrees, the safety limit is 1,000 meters. From this, the distance limit would be around 800 meters. To achieve a compound angle of 63 degrees, the T-62 hull would have to be turned sideways by 25 degrees. At an impact angle of 65 degrees, the safety distance is 200 meters. To have a chance of defeating the upper glacis, DM13 would have to strike it at its muzzle velocity. It is possible for a T-62 to increase the relative obliquity of its upper glacis by being situated on a gentle reverse slope.<br />
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These results are valid for DM13 itself, L28A1, and M392A1 which is the L28A1 round licence-produced in the U.S with minor modifications. In the U.K, the L28A1 round was quickly replaced by L52 in the mid to late 1960's and the U.S Army began licence-producing the L52 as the M728 round in the early 1970's. However, even though the L52 round was available by at least 1966, it is important to note that for NATO nations outside of Britain and the U.S, the 105mm L7 itself did not become commonplace until the late 1960's when the Leopard 1 achieved an initial operating capability (IOC) in West Germany, Belgium, the Netherlands and Norway, and when the Dutch finished upgrading their Centurion tanks by retrofitting L7 guns. Dutch and Norwegian Leopard 1 tanks were supplied with L52 rounds whereas in West Germany, DM13 was the standard APDS round for the Bundeswehr's Leopard 1 tanks.<br />
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With this in mind, the protection offered by the T-62 hull armour was good when the tank initially entered service and could still be considered adequate throughout the 1960's. It remained somewhat acceptable up to the early to mid-1970's. By then, both the L7 gun and the L52 round had become the new standard for NATO armies with the notable exception of West Germany. <br />
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Moreover, it is interesting to note that the 500-meter plummet in the effective range of DM13 with such a small increase in the impact angle from 60 degrees to 61 degrees indicates that despite the enhanced performance of this APDS design compared to early types like the Mk. 3 round for the 20 pdr. gun, sloped homogeneous armour still posed a very serious challenge.<br />
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The hull side armour is 80mm thick. The rounded collars for mounting the turret are cast steel with a thickness of 45mm, angled at 60 degrees. The side armour of the hull is immune to 100mm blunt-tipped armour piercing rounds (BR-412B) at point blank range from a side angle of 22 degrees. The belly of the tank is a pressed 20mm steel plate that was bent up at the edges to join with the side and rear hull plates. The slope of the edges of the hull belly plate is only 33 degrees, creating a minor weakened zone at the bottom part of the side of the hull. From a profile view of the tank, this weakened zone is rather narrow as it is only around 230mm tall and it is additionally protected by the large roadwheels of the tank across most of its length.<br />
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Being only 45mm thick, the rear of the hull is weakly protected but well within the norm for medium tanks. The plate is not completely flat, having a slight tilt of 2 degrees to be set perpendicular to the cooling fan axle. This was because the cooling fan was mounted with a 2-degree tilt relative to the gearbox in the T-54/55, and when the transmission was carried over to the T-62, the fan had to be mounted with the same tilt angle. The rear protects only from 12.7mm armour-piercing bullets and 155mm artillery shell splinters. This thickness of armour is not enough to provide complete protection from 14.5mm armour-piercing bullets, steel-cored 20mm AP rounds (20x139mm) and 23mm AP rounds at point-blank range. However, it is vulnerable to 20mm AP rounds with a WC core such as DM43 or M601. <br />
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According to the "<a href="https://imgur.com/gallery/fd4sK"><i>A-10 Pilot's Colouring Book</i></a>", the lower side hull armour of the T-62 can be pierced by the A-10's GAU-8/A 30mm gattling gun at a distance of 2,133 meters, but if the roadwheels are factored in, the maximum range where the armour can be perforated is only 790 meters. Furthermore, the upper side hull armour can only be pierced from a range of 1,500 feet (460 meters) from a normal angle and attack and air speed. If the hull is not perfectly perpendicular to the approach angle of the plane, the chances of piercing the side hull armour drop even further due to the low performance of PGU-14/B AP-I rounds on sloped armour plate. Furthermore, attacking under such conditions forces an A-10 pilot to target individual tanks which greatly increases the number of strafing runs required to disable any given tank unit and vastly increases the chances of the A-10 being shot down itself. The only way to reliably knock out a T-62 with the GAU-8/A of the A-10 would be to approach from behind, but this places the plane in great danger of being shot down almost immediately by anti-aircraft weapon systems marching behind the tank unit.<br />
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Overall, the T-62 can be considered quite well protected from air attack from the side, especially compared to a tank like the M47 even though the M47 was considered to be close to the T-54 and T-62 in armour protection in the study "<i><a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a522446.pdf">A-10/GAU-8 Low Angle Firings</a><a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a522446.pdf"> Versus Simulated Soviet Tank Company</a></i>". Evidently, this is not true and M47 targets were only used for expediency, as the M47 targets were observed to have been pierced from the side through the turret and hull from distances as far as 3,528 feet (1,075 meters) whereas the side of the T-62 turret is fully immune to 30mm PGU-14/B AP-I rounds from any distance and the hull side armour is only vulnerable from 460 meters.<br />
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The steel used for the all-welded RHA hull is 42SM armour steel which has a hardness of 280-310 BHN. The thicker steel plates tend to be softer while thinner plates tend to be harder. The difference in hardness is partly due to the difficulty in applying heat treatment to thicker steel plates, but also partly because there are optimal hardness levels for plates depending on their thickness, slope and the expected type of anti-tank threat. Against AP and APC rounds, the hardness of the 100mm RHA plate grants the optimal level of protection. However, as the type of threat evolved throughout the course of the Cold War, an increase in the hardness of armour of all thicknesses became more desirable. A higher hardness results in increased penetration resistance from all APDS rounds - particularly early generation designs with less developed armour piercing caps - and from APFSDS rounds.<br />
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Although the upper glacis armour of the T-62 is nominally thinner than that of an M48 Patton (110mm at 60 degrees) or an M60 (93.2mm at 65 degrees) or an M60A1 (109mm at 65 degrees), the T-62 uses RHA steel instead of cast steel, and not only that, the hardness of its RHA steel was significantly harder than that of American cast steel at the time. The M60's cast glacis armour, for example, was quite soft at only 220 BHN, and because of the lower strength and toughness of cast steel, it was not as effective as the rolled steel on the T-62.<br />
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An excellent demonstration of this difference can be found in Yugoslavian testing of T-54A tanks and M47 Pattons. Both tanks had 100mm of steel glacis armour sloped at 60 degrees, the only difference being that the M47 had a cast steel hull whereas the T-54 had a welded hull with RHA plates. It was found that BR-412B blunt-tipped APBC rounds fired from a D-10TG could defeat the upper glacis of an M47 at 750 m, whereas the T-54A was fully immune from any distance down to point blank range. The immunity of the T-54 upper glacis to BR-412B is corroborated by independent Soviet testing. Based on the Yugoslavian test results, the cast armour used in American Patton tanks offered around 90% as much protection as the RHA of the T-54A against full caliber APBC shells, which translates to a mass and thickness efficiency coefficient of 0.9. The effective thickness of the American cast armour was therefore around 10% thinner than the LOS thickness suggests.<br />
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<h3>
<span style="font-size: large;">TURRET</span></h3>
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<div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-5liqJGrkQxI/XzXvk_HLmUI/AAAAAAAAReA/dYlOu5IYvr0SJX9F8DNE6LLW2qM6h9JogCLcBGAsYHQ/s2048/t-62%2Bturret%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1220" data-original-width="2048" src="https://1.bp.blogspot.com/-5liqJGrkQxI/XzXvk_HLmUI/AAAAAAAAReA/dYlOu5IYvr0SJX9F8DNE6LLW2qM6h9JogCLcBGAsYHQ/s640/t-62%2Bturret%2Bdrawing.png" width="640" /></a></div></div>
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The T-62 uses MBL-1 armour grade cast steel for the turret, which has a hardness of 270 to 290 BHN. Externally, the main difference between its turret and the turret of the T-54 was the new hemispherical shape. The armour thickness was also increased, and together with the <a href="https://military.wikireading.ru/54267">new casting techniques</a> that were used in the manufacture of the monolithic turret, the T-62 had increased resilience from all angles of attack. When the T-62 was offered for export to the Yugoslavians, its turret was judged to have better armour protection than the T-54 turret but it was not enough of an improvement to justify the purchase of an entirely new tank.<br />
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Of particular interest is the fact that the T-62 turret is a one-piece casting, unlike the T-54 turret which had a bolt-on barbette for the commander's cupola, and separate plates for its roof. These plates then had to be welded onto the walls of the turret to fome the roof. The use of a one-piece casting increased the structural rigidity of the turret and improved the resistance of the roof to direct hits. Unlike the turrets of the <a href="http://data3.primeportal.net/tanks/brent_sauer/m47_patton/images/m47_patton_05_of_16.jpg">M47</a>, <a href="http://afvdb.50megs.com/usa/pics/m60a1gunshield.jpg">M60A1</a> and <a href="http://data3.primeportal.net/tanks/robert_de_craecker/leopard_1a2_abl/images/leopard_1a2_abl_13_of_15.jpg">Leopard 1</a> - to name just a few - the T-62 turret is an entirely convex shape, i.e it lacks shot traps where impacting shells, bullets or fragments may ricochet down into the turret ring or into the hull roof. However, the turret ring of the T-62 turret was somewhat more vulnerable than the turret ring of the T-54 turret due to the change in the thickness of armour in front of the ball bearing race ring. This is shown in the drawings below. The drawing on the left shows the layout for the T-62 and the drawing on the right shows the layout for the T-54. Compared to the T-54, the T-62 race ring structure is of a much heavier construction.<br />
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By shifting the turret armour backwards such that it rested on top of the race ring, the turret walls would not overhang the driver's hatch when the turret is aimed within a forward arc. Also, the imbalance of the turret could be kept under control so that the stress on the ball bearings would not be excessive. This came at the expense of an increased probability of jamming from direct hits due to the reduced armour thickness. The height of the turret ring weakened zone of the T-62 turret is 58mm. The thickness of the armour in front of the turret ring is 90-100mm, and the race ring structure itself provides an additional 100mm of steel thickness.</div><div><br /></div><div>The merits of various turret ring protection methods are examined in the study "<i><a href="http://btvt.info/5library/vbtt_1968_03_04_barbet.htm">Некоторые Вопросы Проектирования Защиты Стыка Корпуса И Башни</a></i>" by O.I Alekseev et al. It was noted that turret ring designs that required a cutout in the lower part of the turret like the T-54 and T-62 turrets was a liability. Conversely, the solution implemented in the M48 Patton, M60 and M103 where the turret ring was installed in a raised flange cast together with the hull was also assessed to be non-ideal solution as it still fails to prevent the turret from being jammed by a hit to the joint between the turret and the hull. The low thickness of the flange also results in a low level of armour protection. The best solution was found on the IS-3, T-10, Chieftain, Leopard 1 and M46 Patton. These tanks had the ball bearing race ring recessed below the hull roof, and in the case of the T-10, M46 and Chieftain, the gap between the turret and the hull roof was covered by raised parts of the hull.<br />
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The turret ring of the T-62 is additionally protected by an armoured collar that prevents bullets from slipping into the gap between the turret and the hull roof. The collar is clearly visible in the closeup photo below (credit to <a href="http://www.primeportal.net/tanks/carl_dennis/t-62_model_1972/index.php?Page=2">Carl Dennis</a>).<br />
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Furthermore, the top edge of the upper glacis plate extends slightly above the hull roof to form a lip, as shown in the two photos below. This fulfills the same function as the turret ring collar.<br />
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In terms of technical sophistication, the turret ring layout of the T-62 is superior to the M60A1 but inferior to the Leopard 1 and greatly inferior to the Chieftain. However, the Leopard 1 is a unique case as it was so lightly armoured that the jamming of its turret ring from a direct hit was of secondary importance to the perforation of its armour.</div><div><br /></div><div><br /></div><div>The gun mask of the T-62 turret protects the gun embrasure from direct hits by autocannons, heavy artillery fragments, and heavy machine gun bullets. The mask extends far enough to protect the chamber of the U-5TS gun and its frettage, but no more. The image below shows a destroyed gun mask, exposing its thickness and also the frettage on the gun barrel.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-pshZ9u5ME_k/Xx_lhpYfLMI/AAAAAAAARXo/z4lXwBKErJk7XcccwN7K1j1eEQ8qZKPcwCLcBGAsYHQ/s1350/barrel%2Bhit%2Band%2Bbroken.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1350" height="266" src="https://1.bp.blogspot.com/-pshZ9u5ME_k/Xx_lhpYfLMI/AAAAAAAARXo/z4lXwBKErJk7XcccwN7K1j1eEQ8qZKPcwCLcBGAsYHQ/w400-h266/barrel%2Bhit%2Band%2Bbroken.png" width="400" /></a></div><div><br />
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The frontal arc of the turret had a nominal maximum armour thickness of 214mm at the base. This is measured at the cheek at a side angle of 30 degrees from the geometric center of the circular turret. Being a hemispherical turret, the surface of the cheek armour is formed as a sector from a circle with a circular radius of 450mm. The rest of the front turret wall thinned down to as little as 95mm as the front turret transitioned into the roof, but the armour effectiveness was maintained due to the higher impact angle granted by the rounded armour surface. The machine gun port and gunner's sight port are weakened zones, as the armour is cut to accommodate them.</div><div><br /></div><div>The turret reaches a maximum physical thickness of 242mm on either side of the gun embrasure at the cavity for the gun trunnion blocks, but the armour in front of the trunnion blocks itself has a reduced thickness. The armour noticeably bulges outward to compensate for this, but even so, the armour in front of the trunnion blocks is only around half of the maximum thickness (242mm). At the same point, <a href="https://upload.wikimedia.org/wikipedia/commons/d/d3/T54_Training_Parola_Tank_Museum_9.jpg">the T-54 turret has a thickness of 210mm</a>.</div><div><br />
<br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-6_s6wIlrdeQ/XzXfpydK_mI/AAAAAAAARdw/YSHTtNHS_qIpN6fa8rcFPCtlDPRjT-gXACLcBGAsYHQ/s1035/SuT54551197.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="599" data-original-width="1035" src="https://1.bp.blogspot.com/-6_s6wIlrdeQ/XzXfpydK_mI/AAAAAAAARdw/YSHTtNHS_qIpN6fa8rcFPCtlDPRjT-gXACLcBGAsYHQ/s640/SuT54551197.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>Within a 120-degree frontal arc of the turret, the curvature of the exterior surface of the turret cheek in the vertical axis is expressed as the perimeter of the sector of an R450 circle, while the interior surface is formed from an R750 circle. Outside of this frontal arc, the turret armour becomes asymmetrical. The right side of the turret, which houses the loader, has an external surface curve formed from an R625 circle and an internal surface curve formed from an R700 circle. The left side, which houses the commander and gunner, is formed from an R662.5 circle. </div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://3.bp.blogspot.com/-b7-BgGgVbsY/V7q7H6-297I/AAAAAAAAHNI/cr1TpBEj6N86RSNx8iAhux3Hf21gb7aeACLcB/s1600/t-62%2Bfront%2Bview%2Barmour%2Blayout.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="197" src="https://3.bp.blogspot.com/-b7-BgGgVbsY/V7q7H6-297I/AAAAAAAAHNI/cr1TpBEj6N86RSNx8iAhux3Hf21gb7aeACLcB/s320/t-62%2Bfront%2Bview%2Barmour%2Blayout.jpg" width="320" /></a></div><div><br /></div><div><br /></div><div>Due to the immense thickness and the curve of the turret side armour, it is proofed against virtually all autocannon fire from point blank range. which is unusual for a medium tank and very respectable for a tank weighing only 37 tons. For comparison, the side of the Leopard 1 turret was vulnerable to 20x139mm DM43 AP rounds from a distance of 300-500 meters. Protection against this threat at 100 meters was only achieved by the Leopard 1 when a heavier welded turret was introduced on the Leopard 1A3 or when appliqué spaced armour screens were retrofitted to the original cast turret, as found on Leopard 1A1 tanks.</div><div><br /></div><div><br /></div>The T-62 turret resists 100mm APBC (UBR-412B) fired from the D10 gun at a limit velocity of 830 m/s in a frontal arc of 90 degrees, corresponding to a range of around 600 meters. In this context, the limit velocity is the ballistic limit velocity of conditional defeat, where the maximum damage inflicted to the armour by the projectile is the structural disruption of the back surface. This can take the form of bulges or cracked bulges. For comparison, the T-55 turret was designed to resist this threat at a limit velocity of 810 m/s in a frontal arc of 60 degrees (including the direct front), corresponding to a range of 800 meters. In a frontal arc of 90 degrees, the T-54 turret can only resist 100mm APBC at a limit velocity of 723 m/s, corresponding to a range of 1,800 meters. Evidently, the improvement in armour protection over the T-55 turret was quite considerable despite the low increase in nominal thickness from 200mm to 214mm. The superb frontal arc protection of the T-62 turret can be credited to its hemispherical shape.</div><div><br /></div><div>Yugoslavian tests showed that BR-412B could only perforate a T-54A turret from the front at 500 meters when evaluated according to the U.S Navy ballistic limit criteria using the V50 standard. From this, it can be seen that the disparity in the effective thickness given by the U.S Navy ballistic criteria and the Soviet limit of conditional defeat (PKP) criteria amounts to a range difference of 300 meters, equivalent to a velocity difference of 34 m/s. Based on this information, it can be estimated that to perforate the T-62 turret with 100mm APBC within its 90-degree frontal arc, a firing range of 250-300 meters is required. </div><div><br /></div><div>For comparison, the Chieftain turret was designed to resist 100mm AP-T weighing 34 lb fired at 3,400 ft/s (1,035 m/s) from a distance of 700 yards (640 meters) in a frontal arc of 45 degrees, while a S<a href="http://btvt.info/1inservice/chieftain/vop_chieeftain_bronirovanie.htm">oviet evaluation of a captured Iranian Chieftain Mk. 5P tank</a> found that the turret was protected from 100mm BR-412B at a distance of 100 meters within a frontal arc of 70 degrees. In general, the Chieftain turret is tougher by some margin, mainly from the direct front where the sloping turret surfaces offer the maximum armour obliquity.<br /><br />
The sloped roof above the T-62 turret cheeks is quite resilient despite the much lower thickness, chiefly thanks to the steep angling of the roof. The area of the roof above the gun has a thickness of 58mm sloped at an angle of approximately 80 degrees at the edge of the roof, thinning down very slightly to 54mm at a larger angle as it goes further towards the back, and then transitions to 30mm sloped at 83° over the middle and rear portions of the turret roof. From British testing of captured D-10S guns, it is known that 60mm of RHA plate is only perforated by BR-412B at its muzzle velocity, and only if the muzzle velocity reaches 910-913 m/s by elevating the propellant charge temperature to 18.3°C as compared to the standard testing temperature of 15°C. Overall, the protection offered by the roof is equivalent or better than the turret cheeks, and does not constitute a weakening in the armour scheme like a T-54 or T-55 turret due to the weld seams as the T-62 turret is a one-piece casting.<br />
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From the area around the commander's cupola, the thickness of the armour sharply declines to only around 65mm at the lower half of the rear of the turret, and only about 55mm at the upper half where it just begins to form the roof, below the ejection port and ventilator housing. In West Germany, a number of tests were conducted on a captured T-62 in 1974 to determine its level of protection from a variety of weapons, including small caliber and medium caliber automatic cannons. Among these tests were live fire tests with 20x139mm DM43 AP rounds with a WC core. The base of the rear of the turret (underneath the cartridge casing ejection port) was shot six times. <a href="https://sun9-25.userapi.com/c852136/v852136080/122727/ZK0jDwjFz0I.jpg">Shots 1 and 2 failed to perforate the armour, shot 3 perforated the armour, and shots 4, 5 and 6 were at the velocity limit</a>. All shots were fired from a distance of 100 meters. According to <a href="https://pp.userapi.com/c849132/v849132080/196d80/tpCBTWtWJhM.jpg">the analytical breakdown of each shot</a>, the armour thickness at the sectors where shots 4, 5 and 6 landed ranged from 58mm at 17 degrees to 68mm at 15 degrees. The sole case of armour perforation by shot 2 was recorded at a sector where the armour was 72mm thick but sloped at only 7 degrees.<br />
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30mm AP rounds with a DU core fired from the GAU-8/A of an A-10 ground attack jet can perforate the rear of the turret from as far as 1.3 kilometers. As mentioned earlier in the article, the turret hatches themselves are respectably thick, with the commander's hatch being 30mm thick and the loader's hatch being 25mm thick. The roof armour is 30mm thick. This is better illustrated by the diagram below.<br />
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<img src="https://4.bp.blogspot.com/-V4TuX9Mpq74/V7q7EGCFc8I/AAAAAAAAHNE/kx63U56co6cNbY8YZmBWP0QgG0mcXZVWQCLcB/s1600/t-62%2Barmour%2Blayout.jpg" /><br />
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From the 17th of February to the 10th of March 1978, test firings of the GAU-8/A on an A-10 were carried out on two captured T-62 tanks. The report "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a085713.pdf">Combat Damage Assessment Team A-10/GAU-8 Low Angle Firings versus Individual Soviet Tanks</a>" contains most of the important details from this test. Five missions were flown with a total of seven passes at individual tanks. Mission 1 and the first pass of Mission 2 were directed at the rear of a T-62, and in both cases, the rear of the turret was perforated once behind the commander's station, both impacts being very close to each other. It is rather strange, however, that it was reported that ammunition was set off in both cases despite the fact that no ammunition was stowed behind the commander's station in the description of the simulated combat configuration of the target T-62 tank. This seems to indicate that the testers placed additional ammunition where the amplidyne amplifier would be located in a real T-62 as shown in the photo below, and not only that, they placed additional ammunition in the tank without documenting it in the report.<br />
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On the second pass of Mission 4, the tank was attacked from the rear offset clockwise by 25 degrees (or 155 degrees from the front), and the rear of the turret again proved vulnerable, with four perforations recorded at the base of the turret directly behind the loader's cupola. This is where two rounds of ready ammunition is stowed and may have caused an ammunition explosion.<br />
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If fired at by tanks, a T-62 would expect to face the new L7 105mm cannon given that it is a 1962 tank and was primarily used to counter the latest threats from NATO. 20 pdr. guns and 90mm guns were still very common at the turn of the decade, but the 20 pdr. guns mounted on the tanks of the British Army were being replaced by the L7 and the American "Pattons" were being replaced by the M60 and M60A1 main battle tanks armed with the M68 and supplied with the M392, a licence-produced clone of the L28A1 APDS round. Later, the Leopard 1 was also armed with an L7 cannon firing the DM13 APDS round, also a licence-produced clone of the L28A1.<br />
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A West German evaluation of the T-62 turret detailed in a January 15, 1974 report indicates a somewhat higher level of armour protection at its front compared to the T-55 turret. While the T-55 turret was rated as being vulnerable to 105mm APDS at 40% of its frontal projection from over 2,000 meters away and 60% of its frontal projection was vulnerable only from over 800 meters, the T-62 turret was only vulnerable to 105mm APDS from over 800 meters over its entire frontal projection. It was also completely immune to 90mm AP rounds which the T-55 turret was not, although the T-55 turret was still tough enough that any enemy 90mm gun would have to be at a suicidal distance in order to defeat its armour.<br />
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<br />As with 100mm APBC, the higher uniformity of protection provided by the T-62 turret against 105mm APDS can only be explained by the greater all-round thickness offered by its hemispherical shape, as the armour thickness only increased slightly compared to the T-55 turret.<br />
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The turret of the T-62 had a height of just 810mm, equal to the T-54 turret. For comparison, the Centurion Mk.10 turret had a height of 956mm, the Chieftain turret had a height of 975mm, the M60A1 turret had a height of 1,020mm. The difference is not as large as one might have expected from the difference in the total heights, but this is because the height of the commander's cupola is being ignored. With its cupola included, the total height of the T-62 turret is only 914mm, whereas the total heights of the Centurion Mk.10, Chieftain and M60A1 turrets are 1,295mm, 1,237mm and 1,375mm respectively. The advantage of the T-62 turret in terms of silhouette size is further enhanced by its dome shape, as opposed to the flat roofs of the Centurion, M60A1, Leopard 1 and Chieftain turrets. As such, the perceived height may be smaller than what the actual maximum height implies. When a T-62 is in a hull defilade position behind a hill, berm or a prepared firing position, it presents a smaller target than a contemporary NATO tank in both the height of its silhouette and the size of the area exposed to direct fire, despite the large diameter of the turret.<br />
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The T-62 turret design shows a particular advantage compared to its direct counterpart, the M60A1. This difference is illustrated in the drawing below, taken from the book "<i>Kampfpanzer: Die Entwicklungen der Nachkriegszeit</i>" by Rolf Hilmes.<br />
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Aside from the very large difference in the exposed silhouette (620mm compared to 1,140mm), it can be seen that the exposed surface area of the inhabited zone of the M60A1 turret amounts to 2.0 square meters whereas the surface area of the inhabited zone of the T-62 turret is only 1.4 square meters. In other words, the area of the silhouette of the T-62 turret where the crew is present and is exposed to direct fire is 30% smaller. Needless to say, one of the factors behind this advantage is the extremely large and conspicuous commander's cupola on the M60A1 turret. The extremely low silhouette of the T-62 turret gives it an edge over the M60A1 when both tanks are hull-down with only the gun exposed over the crest of the obstacle. Of course, both tanks are soundly beaten by the Strv 103 in this respect, but only in this respect. When the (uninhabited) hull sponsons of the Strv 103 are taken into account, the total exposed surface area of the tank is 1.85 sq.m which is significantly larger than the total exposed surface area of the T-62 turret.<br />
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The difference in the silhouette sizes of the T-62 and its NATO counterparts extends beyond the turret and includes the entire tank. The most striking difference in silhouette size can be found when the T-62 is compared to its direct counterparts, the M60A1.<br />
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<a href="http://2.bp.blogspot.com/-SV7Fd--4FoU/VmpcSdM2MTI/AAAAAAAAE8w/Xgwg_BPPltM/s1600/t-62%2Bheight%2Bcomparision%2Bm60.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="268" src="https://2.bp.blogspot.com/-SV7Fd--4FoU/VmpcSdM2MTI/AAAAAAAAE8w/Xgwg_BPPltM/w400-h268/t-62%2Bheight%2Bcomparision%2Bm60.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-h3RW4sdYKwg/XzJPrwz3h3I/AAAAAAAARdE/RWnI4u2zR00GdwOZE3Iq229StXB38qZ2gCLcBGAsYHQ/s1969/t-62%2Bchieftain%2Bchallenger%2B1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1320" data-original-width="1969" height="268" src="https://1.bp.blogspot.com/-h3RW4sdYKwg/XzJPrwz3h3I/AAAAAAAARdE/RWnI4u2zR00GdwOZE3Iq229StXB38qZ2gCLcBGAsYHQ/w400-h268/t-62%2Bchieftain%2Bchallenger%2B1.jpg" width="400" /></a></div>
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Although the T-62 was only negligibly narrower and shorter in length compared to its NATO counterparts, it was significantly shorter in height at just 2.40 meters tall, which is half a meter shorter than the Chieftain, 0.80 meters shorter than the M60A1, and even slightly shorter compared to the French AMX-30 and German Leopard 1, both of which were designed with a strong focus on a reduced silhouette size. This is an extremely important aspect to the survivability of the T-62, as the avoidance of incoming enemy fire is paramount to the ability of a tank to fulfill its combat mission, followed by armour protection.<br />
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<div><br /></div>Visual camouflage was provided by the so-called "protective colour" of the green base paint applied to the tank, which was NPF-10 infrared absorbent paint. NPF-10 was originally introduced in 1953 as the standard dull green paint for armoured vehicles to replace the 4BO paint used throughout the Great Patriotic War, which was also infrared absorbent. In the Soviet Army, the dull green colour would be used as the base colour for a variety of deforming camouflage patterns for desert, summer and winter environments. Additional colours painted onto the green base coat created a deforming pattern under both visual and near-IR observation. A low reflectivity of near-infrared light provided camouflage under aerial photography using infrared filters, and also granted the tank a major advantage in night concealability compared to its contemporaries. </div><div><br /></div><div>In the U.S Army, the standard paint was a conventional olive drab enamel, later superseded in the late 1960's by a solar heat reflecting enamel designed to reduce crew compartment temperatures. The reflectivity of this paint was the same as conventional olive drab paint throughout the visual spectrum, but from 800 nm and upward, it had a very high reflectivity, significantly exceeding that of conventional paint. This produced a measurable decrease in vehicle internal temperatures, as most of the sun's energy is conveyed through near-IR radiation, but the high reflectivity in this spectrum greatly increased the observability of armoured vehicles. </div><div><br /></div><div>The image below shows the effectiveness of NPF-10 in camouflaging a T-54 tank in a snowy field under IR illumination. The T-54 on the left is painted in a white enamel paint, while the right T-54 is painted in regular green NPF-10. Both are placed against a snowy background. The photo above (а) shows an image under IR illumination, and the photo below shows an image under passive light intensification (б).</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiK8mbc5in6fsSC3_q6QVNLbvIvf3aOzo8Z94X56Q6EGElnG3O51Jh7PxGXhos1xzxmxcPhmdQfvXPuhYrsXHKuhKvjZ1fs7_VhsEXq359K4Yw1cUmcpSPMZvfDWPLDY6wxL-ul1yNzWMdrJWRoQk6cjHeNJrSi4gvWJEH2dlslF1FuL0zq4ynMarZEfQ/s2071/tanks%20under%20ir%20illumination%20npf-10%20and%20white.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1606" data-original-width="2071" height="310" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiK8mbc5in6fsSC3_q6QVNLbvIvf3aOzo8Z94X56Q6EGElnG3O51Jh7PxGXhos1xzxmxcPhmdQfvXPuhYrsXHKuhKvjZ1fs7_VhsEXq359K4Yw1cUmcpSPMZvfDWPLDY6wxL-ul1yNzWMdrJWRoQk6cjHeNJrSi4gvWJEH2dlslF1FuL0zq4ynMarZEfQ/w400-h310/tanks%20under%20ir%20illumination%20npf-10%20and%20white.png" width="400" /></a></div><div><div><br /></div><div>The images demonstrate that the white paint works to camouflage the tank under visual and passive night vision observation, but due to its high reflectivity in the near-IR spectrum, especially relative to snow, it does not work at all under IR illumination. Conversely, the regular NPF-10 green paint clashes with the white background, so it does not work under visual and passive night vision observation, but it renders the tank almost invisible under IR illumination. </div>
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<h3>
<a href="https://www.blogger.com/null" id="sideskirts"></a>
<span style="font-size: large;">SIDE SKIRTS</span></h3>
<div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ij4AVZxqYAE/X0IUVDLFhEI/AAAAAAAARf4/KoYhI8tEIdgyfXN9poCEHz6_rvHEINLawCLcBGAsYHQ/s800/3100541_800.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="704" data-original-width="800" height="352" src="https://1.bp.blogspot.com/-ij4AVZxqYAE/X0IUVDLFhEI/AAAAAAAARf4/KoYhI8tEIdgyfXN9poCEHz6_rvHEINLawCLcBGAsYHQ/w400-h352/3100541_800.jpg" width="400" /></a></div><div><br /></div><br />
The T-62 was not originally equipped with side skirts, but many T-62 tanks were retrofitted with steel-reinforced plastic skirts (interwoven textile) similar to that of the T-72 beginning in the early 1980's as part of the T-62M modernization programme.<br />
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The main function of the side skirts was to reduce the amount of dust kicked up by the tracks while travelling, which was highly undesirable for a variety of reasons. Generally speaking, such skirts are most useful for controlling the volume of dust blown over the engine compartment to reduce the amount of dust ingested by the engine air intake. It also reduces the amount of dust blown into the commander and loader if they were standing at their hatches. The photo below, taken from the book "<i>T-62 Main Battle Tank 1965-2005</i>" by Steven Zaloga, shows a T-62 equipped with side skirts operated by the DRA.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ykp9aVM2P5M/X3ARH_zkQvI/AAAAAAAARqc/Ez5q9OpJEFEbLufnVc_yTxlmIPBEmLvPgCLcBGAsYHQ/s2048/afghan%2Bt-62%2Bside%2Bskirt.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1262" data-original-width="2048" height="394" src="https://1.bp.blogspot.com/-ykp9aVM2P5M/X3ARH_zkQvI/AAAAAAAARqc/Ez5q9OpJEFEbLufnVc_yTxlmIPBEmLvPgCLcBGAsYHQ/w640-h394/afghan%2Bt-62%2Bside%2Bskirt.png" width="640" /></a></div><br /><div><br /></div><div>The side skirts acted as spaced armour for the hull, but the use of thin skirting in this role is often counterproductive due to the peculiarities of shaped charges. The thickness of the skirts is 10mm and the stiffness is sufficient to ensure that an RPG grenade fuze activates reliably, but not thick enough or strong enough to be of much use against kinetic energy penetrators. The skirts were mounted 610mm away from the hull. Gamma and neutron protection was slightly enhanced by these skirts due to their high hydrogen content. </div><div><br /></div><div>Though they have little value against more potent shaped charge warheads, such skirts can be expected to enable the hull sides to stop 105mm HEAT shells within a frontal arc of at least 60 degrees.<br />
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As part of the objective to increase the level of protection of the T-62 up to the level of Soviet main battle tanks of the 1970's, the T-62M modernization also included the necessary fittings to mount "gill" armour panels. However, these are very seldom seen on the T-62M. Tests showed that this armour could protect the sides of the hull from 1-2 hits of 115mm HEAT rounds at an angel of attack of 23 degrees.</div><div><br /></div><div>
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<div><br /></div><br />After this type of armour underwent testing in 1963-1964, it was only fitted to the T-64 and T-64A as well as early T-72 models. Medium tanks of the previous generation could also be retrofitted with the "gill" armour, but the large scale upgrading of the medium tank fleet was only expected during the "threatened period, immediately before the start of hostilities" in a major conflict on the orders of the head of the GABTU. Essentially, the "gill" armour was the Soviet equivalent to the additional bar armour on Swedish Strv 103 tanks for defeating HEAT shells.</div><div><br /></div><div>For a more detailed examination of "gill" armour, please visit <a href="https://thesovietarmourblog.blogspot.com/2017/12/t-72-part-2-protection-good-indication.html#gill">part 2 of Tankograd's T-72 article</a>.<br />
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<a href="https://www.blogger.com/null" id="brow"></a>
<span style="font-size: large;">Ilyich's Eyebrows</span></h3>
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All T-62Ms were equipped with large composite armour blocks on the front of the hull and on the turret, sometimes referred to as "BDD" armour in the West after it was given this name from the late 1990's and early 2000's. It is more popularly known as "Ilyich's Eyebrows" in reference to Soviet Premier Leonid Ilyich Brezhnev:<br />
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<a href="http://3.bp.blogspot.com/-O1YXs6Ye_Nk/Vb0jSj10DKI/AAAAAAAADBY/8VaOyOvqWvA/s1600/t-62M%2Bilyich%2527s%2Beyebrows.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://3.bp.blogspot.com/-O1YXs6Ye_Nk/Vb0jSj10DKI/AAAAAAAADBY/8VaOyOvqWvA/s400/t-62M%2Bilyich%2527s%2Beyebrows.JPG" width="400" /></a><a href="http://3.bp.blogspot.com/-QETsaCP3RXM/Vb0lJVbhcOI/AAAAAAAADBs/GZLFq0kKva4/s1600/leonid%2Bbrezhnev.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://3.bp.blogspot.com/-QETsaCP3RXM/Vb0lJVbhcOI/AAAAAAAADBs/GZLFq0kKva4/s320/leonid%2Bbrezhnev.jpg" width="320" /></a></div>
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Officially, the name of the add-on armour is somewhat more descriptive: "metal-polymer block". The add-on armour covers the hull glacis and the turret cheeks, but did not offer any protection for the lower hull area or the turret roof. It is a form of NERA armour, composed of a laminate of alternating steel plates and a polyurethane filling. First entering inventories in 1980, the add-on armour boosted the protection of the T-62 to the level of the T-64A or T-72 Ural, giving it the ability to resist widespread 105mm APDS and APFSDS ammunition as well immunity from anti-tank grenades and even some ATGMs. The metal-polymer block armour was developed during the late 1970's as part of ongoing research into reactive armour with a focus on defeating shaped charge weapons.<br />
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Older T-62 models could be outfitted with the new armour in the field as long as rudimentary arc welding equipment was available, and indeed, there are multiple documented cases of older model T-62 tanks in Afghanistan with "Brows".<br />
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The "Brow" armour blocks only provided coverage for the turret cheeks, and even then, the edges of the blocks lack the metal-polymer composite armour to make room for the large mounting points. On the right side of the turret, the metal-polymer block covers an arc of just under 50 degrees over the turret cheek, while the remainder is covered by the front steel plate. On the left side, the metal-polymer block covers an arc of just under 46 degrees, and the front steel plate of the armour blocks covers the rest. Overall, the "Brow" armour blocks cover the frontal 140-degree arc of the turret with a gap at the gun embrasure. The diagram below shows the mounting points for the armour kit. Note the large size of the connecting bolt and the rubber bushing underneath the washer at the top of the bolt. These help to ensure that the armour blocks stay on the turret when subjected to a tremendous shock from the impact of a powerful projectile.<br />
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<div><br /></div><div><br /></div><div>The metal-polymer blocks cover the entire 60-degree frontal arc of the turret. From a 30-degree side angle, the entire turret profile is shielded by the block, and although the far edge of the block lacks a metal-polymer composite, the curvature of the turret generates a very formidable thickness of armour coupled with a large air gap which may provide the same effective protection or more. </div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-blR_vXHC_9Q/X0VCWvcEN6I/AAAAAAAARgk/uWdmqcNKTMIi8FCA94MZgxIQcxRCmNROwCLcBGAsYHQ/s1262/t-62m%2B30%2Bdegree%2Bside%2Bangle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="886" data-original-width="1262" src="https://1.bp.blogspot.com/-blR_vXHC_9Q/X0VCWvcEN6I/AAAAAAAARgk/uWdmqcNKTMIi8FCA94MZgxIQcxRCmNROwCLcBGAsYHQ/s640/t-62m%2B30%2Bdegree%2Bside%2Bangle.png" width="640" /></a></div><br />
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There are two distinct variants of "Brow" armour. One version provides simple spaced steel protection over the machine gun port and the port for the gunner's primary sight, as seen in the photo below. This version appears to be the most common type. Photo courtesy of Vitaly Kuzmin.<br />
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The second version omits the spaced steel plates and leaves most of the gun mantlet area completely exposed, similar to the "Brow" armour block design for T-55AM and their variants, but this version lacks the distinctive scallop on the left armour block to accommodate the driver's head, so it is clear that it is not simply a transplant from the armour kit for the T-55AM. This version is not rare, but it is not common either.<br />
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The metal-polymer armour block on the front of the hull spans the entire upper glacis in height, but leaves two narrow zones on the top edges of the upper glacis uncovered. This is to leave the mine plow mounting points untouched. This is a rather strange design decision, as the metal-polymer armour block is firmly welded to the upper glacis and has no issues bearing heavy loads, as evidenced by the relocation of the towing hooks to the front plate of the armour block. There should be no problems in mounting a mine plow directly on the armour block. Aside from this puzzling feature, the design of the armour is quite rational.
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<h3>
<span style="font-size: large;">Method Of Operation</span></h3>
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The single composite armour block on the upper glacis of the hull is 150mm thick, or 300mm thick when taking the 60° slope of the hull into account. Inside the armor, a pack of thin steel plates is suspended in a plastic filler. Each internal steel plate is just 5mm thick, and the plastic layer fills the gaps in between. The physical thickness of the front plate of the glacis array is 30mm and the LOS thickness is 60mm. The internal steel plates are angled at 65° and the perpendicular spacing between each plate is 30mm. Combined with the 102mm base armour of the upper glacis, the total physical thickness of the upper glacis is 252mm and the LOS thickness is 504mm, of which 264mm is rolled steel. This is close to the 547mm LOS thickness of the T-64A/T-72/T-80 upper glacis armour (of which 267mm is steel), but "Brow" armor is probably more efficient because it uses a newer and more effective composite filler as opposed to a simple glass textolite interlayer.<br />
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The turret blocks have a uniform maximum thickness of 296mm across its curved profile, but thickness of the blocks varies considerably in the vertical plane. The composite filler is thinnest near the turret ring and thickest at the top of the armour block, where it measures 210mm in thickness. The turret blocks follow the same layout as the upper glacis block but differs in having a small air gap between the surface of the turret and the metal-polymer block. The front plate is made from cast steel and is divided into top and bottom halves: it is 71mm thick at the top half and 85mm at the bottom half. The top half is angled at 30 degrees and the bottom half is angled at 15 degrees. The metal-polymer block behind the front plate is contained inside a thin steel box with a thickness of around 5mm.<br />
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The added thickness compared to the upper glacis plate is probably intended to compensate for the relative weakness of cast steel compared to rolled steel and to compensate for the positive influences of the high slope on the glacis on the breakup of APDS and APFSDS rounds. The internal steel sheets in the turret array are the same thickness as in the upper glacis (5mm) but they are angled horizontally at 50° instead of 65°. However, the direction of the angle is such that a shot fired at the turret from a side angle will meet the internal plates at a greater relative angle. If, for example, a missile was fired at one of the "Brow" blocks on the turret at a side angle of 30°, the internal steel sheets would have a relative angle of 80°. Strangely enough, the internal steel sheets are not angled in the vertical plane even though this would probably have improved the performance of the armour. The layout of both the hull and turret armour modules forces a penetrating projectile to intersect with at least three of the internal steel sheets.<br />
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Against shaped charge weapons, "Brow" armour most likely operates on the transfer of kinetic energy from impacting projectiles to the thermoplastic polyurethane (TPU) layer through the propagation of shockwaves from the impact of the attacking penetrator. The TPU itself has some erosive effect against a shaped charge jet, but it should also be violently displaced out of the penetrator's path. However, the function of the thin steel sheets embedded into the TPU layer is not so clear.<br />
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One possible mechanism would involve the reflection of shockwaves from the surface of the thin metal sheets at an oblique angle to the penetrator, thereby pushing a greater mass of TPU into the penetrator. This would be mostly useless against APDS or long rod penetrators, but it should be quite effective against shaped charge jets, as TPU is a low density material suitable as a barrier against shaped charge jets.<br />
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The use of a high density front plate paired with a low density filler is principally identical to the original upper glacis armour of the T-64A except that the armour includes internal steel sheets. The high density front plate has the function of not only eroding an attacking shaped charge jet, but also particulating it. A low density filler would perform effectively against a particulated jet, and reducing the density gives better results. For the upper glacis armour of the T-64A, the low density filler is glass textolite, with a density of 1.3 g/cc. TPU has a density of <a href="http://www.polyurethanes.basf.com/pu/solutions/en/function/conversions:/publish/content/group/News_und_Medien/Spezialelastomere/Thermoplastic_Polyurethane_Elastomers_Product_Range_EN.pdf">between 1.1 to 1.2 g/cc</a>, making it highly optimal for this application. Coupled with the reflection effect and the additional erosive effect of the steel sheets themselves, the armour kit should be quite effective against shaped charge warheads. However, low density fillers like glass textolite generally do not have much effect against KE penetrators and polyurethane would fare much more poorly than glass textolite due to its worse mechanical properties, so some of the protection from the armour blocks (outside of the thick steel front plate) is very minor or negligible.<br />
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Another possibility is that the displacement of the TPU causes the steel sheets to bulge away and downwards laterally against a penetrator. This lateral motion would have the effect of either disturbing the delicate flow of cumulative jets or damaging a kinetic energy penetrator by creating stresses in the body, which are suddenly released, causing the penetrator to fracture. However, the presence of TPU behind each steel sheet would reduce the bulging velocity of the sheets, making them less effective, so the effect of the movement of the plates is probably quite minor compared to its value as a simple spaced barrier. The thickness of the internal sheets (5mm) is very low - less than 0.4 rod diameters of any long rod penetrator ever fielded, so it does not reduce the kinetic energy of a long rod penetrator in any meaningful way on its own unless it works by dynamic movement. Otherwise, the 5mm sheets will be easily perforated and experience plastic failure in the form of petalling and contribute almost nothing to the protection capacity of the armour.<br />
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Interestingly enough, one variation of the so-called <a href="https://2.bp.blogspot.com/-BtUECaRRUeY/VuacGGszJ2I/AAAAAAAAADc/X5CxGUrLpcwfFl4wlvSiVnWU85j9L7PVg/s1600/Chobham%2BType%2B2.png">"Chobham" armour</a> is described as alternating panels made from a plastic plate glued to a steel plate. This type of armour is unequivocally a type of NERA that functions by lateral dynamic plate movement. Unlike the metal-polymer block, however, the "Burlington" armour array uses individual dual-layer panels separated by air gaps instead of steel sheets suspended in a single mass of polymer material. The air gaps behind the panels is likely to enable the steel plates to move backwards ("in pursuit") against a penetrating shaped charge jet, thus disrupting the jet and reducing its effectiveness. The lack of air gaps in the metal-polymer block suggests that this is not the primary operating principle of the armour design, or that it is a less efficient design. Nevertheless, the similarities were not lost on other authors: On page 23 of "<i>T-62 Main Battle Tank: 1965-2005</i>", Steven Zaloga notes that the armour is similar to early version of "Chobham" armour. He goes on to state that the armour protection is equivalent to 380mm RHA against KE attack including long rod projectiles and 450mm against shaped charges.<br />
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According to the article<i>“Ilich’s Eyebrows”: Soviet BDD Tank Armor and Its Impact on the Battlefield</i>" by James Warford in the May-June 2002 issue of ARMOR magazine, a marketing pamphlet by NII Stali claims that metal-polymer armour adds the equivalent of 120mm RHA of armour against KE threats and 200-250mm RHA against shaped charges. Depending on how these numbers are interpreted, the approximate level of protection described in both sources is essentially the same. The article appears to be referring to this excerpt from page 429 of a marketing booklet, possibly the very same "<i>Suggestions on Modernization of MBTs and IFVs</i>" mentioned by Warford, under Chapter 2 "<i>Защита</i>" (<i>Protection</i>).<br />
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Against kinetic energy projectiles, the low efficiency of the metal-polymer filler means that the majority (not all) of the burden lies on the heavy steel front plate of the armour block and its spacing from the turret. It may not be too unrealistic to treat the overall armour as a form of dual-layer spaced armour. The photo on the left (credit to Vyacheslav Demchenko) is a profile shot of the armour of a T-62M. The photo on the right (credit to Jarosław Wolski, also known as Militarysta) shows the armour of an a T-55AM2 with the metal-polymer filler removed, leaving only the steel front plate. Note the declining size of the gap between the front plate and the surface of the turret at the base of the turret.<br />
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<a href="http://1.bp.blogspot.com/-X7ZQSaz05-M/Vk9TVEhd6MI/AAAAAAAAEJs/Dp8ACw2E-uY/s1600/t-62%2Bbdd%2Barmour.jpg"><img border="0" height="280" src="https://1.bp.blogspot.com/-X7ZQSaz05-M/Vk9TVEhd6MI/AAAAAAAAEJs/Dp8ACw2E-uY/s400/t-62%2Bbdd%2Barmour.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-F4prmWnCvMM/WxWcOKO0DRI/AAAAAAAALrY/zdlYmxjczDIi91laxRXSPK-EQjR20LuygCLcBGAs/s1600/t55am2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://1.bp.blogspot.com/-F4prmWnCvMM/WxWcOKO0DRI/AAAAAAAALrY/zdlYmxjczDIi91laxRXSPK-EQjR20LuygCLcBGAs/s400/t55am2.jpg" width="400" /></a></div>
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The armour kit offers a good amount of coverage for the upper glacis, but as mentioned before, the turret front is only partially protected by the metal-polymer blocks. The two "Brows" weigh 1.8 tons together, and the upper glacis block alone weighs around 1.5 tons. The additional steel-reinforced plastic side skirts add another 100 kg to the total weight of the tank. Equipped with the additional armour, the weight of a combat-loaded T-62M bloated to 41.5 tons - more than 3 tons greater than the vanilla T-62, and about the same as a T-72A. One issue with this is that all of the additional mass is disproportionately concentrated on the front of the tank, making it nose-heavy. For the turret in particular, the addition of 1.8 tons was especially serious in relative terms, and it made the turret unbalanced. This increased the load on the turret rotation drive, especially if the tank is not on level ground.<br />
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Using the information we have gathered so far, it is possible to estimate the areal density of the metal-polymer armour and determine its mass efficiency:<br />
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It is known that that the total physical thickness of the armour is 252mm, with the first 30mm being a layer of RHA steel and the last layer being the original 100mm upper glacis armour of the tank. The cavity inside the metal-polymer block is 120mm thick. Inside the metal-polymer block, there are three steel sheets in the path of a penetrating projectile. With a thickness of 5mm each and an angle of 65 degrees, the LOS thickness is 35.5mm. Subtracting this from the cavity thickness, we find that the LOS thickness of the polyurethane filler is 204.5mm. Assuming that the density of the polyurethane used in the armour has a density of between 1,100 to 1,200 kg/m^3, the areal density of the polyurethane should range from 225-245 kg/sq.m, with an average of 235 kg/sq.m. The total LOS thickness of the steel elements of the armour array is calculated by simply adding up the LOS thickness of the three steel sheets at its structural obliquity together with the 30mm front plate and 100mm base armour, all angled at 60 degrees. All in all, it is 296mm thick. Using the known density of RHA steel (7,850 kg/m^3), we find that the areal density of the steel is 2,323 kg/sq.m. Adding up the steel and polyurethane layers, the total areal density is around 2,558 kg/sq.m. This is equivalent in mass to a 326mm homogeneous steel block, so it is lighter than the well-known 80-105-20 armour array by the equivalent mass of 9mm of steel while having an armour protection level of 450mm RHA against shaped charges.<br />
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To quantify this, we divide the equivalent thickness of steel against shaped charges (450mm) with the relative mass of armour (326mm) to find that the the armour has a mass efficiency coefficient of 1.38. This is only a fractional improvement over the basic 80-105-20 composite armour array of the T-64/72/80 with glass textolite and does not reach the 1.40 mass efficiency coefficient of the Soviet bulging plate NERA armour used in the T-72B turret. There is some margin of error, of course, but based on all available information, it is completely unsurprising that the efficiency of the metal-polymer block armour lies somewhere between a simple three-layer glass textolite-based composite armour and multilayered NERA armour. Against a KE threat, the claimed protection level of 320mm RHA implies that the mass efficiency coefficient is 0.98, which is less than a solid homogeneous steel plate (1.0) and less than the 80-105-20 armour array (1.0). This is extremely unusual considering that even long rod penetrators perform worse against multilayered targets compared to monolithic targets of the same mass which is reflected in the type of tank armour simulator targets used by NATO. For example, NATO Double Medium is considered a tougher target than NATO Single Medium. Both targets are intended to represent the same type of target (the frontal armour of a Soviet medium tank), but NATO Double Medium is an increased difficulty target despite having the same thickness of steel (130mm) and same slope (60°), differing only in that the armour is split into two layers with an air gap in between (40-150-90).<br />
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By having a very similar distribution of steel plates of the same general properties while also benefiting from a more complex construction including internal steel sheets, it seems to be beyond question that the metal-polymer block on the upper glacis should have a mass efficiency coefficient of more than 1.0. Needless to say, the fact that the 320mm RHA figure contradicts this basic understanding of spaced and composite armour is abnormal and indicates that Zaloga's claim that the armour offers a protection level of 380mm RHA against KE attack is probably closer to the truth. The claim that "metal-polymer block armour adds 120mm against KE attack" from the NII Stali marketing pamphlet can still be true if it is interpreted to refer only to the turret from a 30 degree side angle, so it represents the average protection level rather than the maximum.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-zlnFhH7pdLk/VenXVi_lBjI/AAAAAAAADco/HP71FpBCC0A/s1600/t-62m%2Bturret%2Bbdd%2Barmour.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="340" src="https://3.bp.blogspot.com/-zlnFhH7pdLk/VenXVi_lBjI/AAAAAAAADco/HP71FpBCC0A/s640/t-62m%2Bturret%2Bbdd%2Barmour.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Turret block</td></tr>
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On the 5th of February 2017, a video of an SAA T-62M being struck by an ATGM began circulating on Twitter. The T-62M was attacked from the right flank by either a Fagot or Konkurs missile (judging by the tracking flare and flight pattern of the missile). The missile hit the "Brow" armour block on the right side of the turret, but all three crew members survived and evacuated the tank immediately. Watch the video here (<a href="https://twitter.com/worldonalert/status/828311047945723905">Twitter link</a>).<br />
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The video cannot affirm or disprove anything, as the missile struck the turret approximately where the gun breech is. There is no way to know if the missile defeated the side armour or not, because even though the loader is fine, this could be because he was seated below his hatch, meaning that he would not have been in the line of fire had the missile perforated the base armour. If the missile did not manage to get through, it is still more than possible that the crew bailed as a matter of principle. In fact, there is a high probability that the armour was defeated by the missile as a very similar scenario was tested during Hungarian trials at the end of the Cold War, where it was revealed that the side of the turret of a T-54 equipped with "Brow" armour (taken from a modernized T-55) could not resist a "Fagot" missile from the side. The shaped charge defeated the turret armour and the jet was stopped by the gun breech. The results of the test are detailed on this <a href="http://www.tank-net.com/forums/index.php?showtopic=23315">Tank-Net post</a>. This effectively means that the "Brow" armour for the turret combined with thee T-54 turret side armour (140-150mm of cast steel sloped 23-40 degrees) cannot resist a shaped charge warhead with around 400mm of penetration. By subtracting the base armour of the T-54 turret side armour (160-180mm) from 400mm, we find that the "Brow" armour block added less than 220-240mm of additional protection in effective RHA thickness. This is quite consistent with the claims made by NII Stali considering that this is based on a worst case scenario test.<br />
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The main difference is that the T-62 turret is slightly thicker on the sides (150-160mm) and has a higher LOS thickness due to more favourable angles of slope created by its dome shape, so there is a greater chance of providing up to 400mm of protection or more. It should be noted that this should not be considered poor. On the contrary, even narrowly failing to stop a HEAT warhead with 400mm of penetration is a very respectable result given that the turret side armour of the M1 Abrams over the fighting compartment is only rated to provide 380mm RHA of effective thickness against 81mm grenades (representing a light shoulder-fired weapon like an RPG-7), and only from a 45-degree side angle. From a 45-degree side angle, the LOS thickness of the T-62 turret armour and metal-polymer block increases drastically, guaranteeing an effective thickness of more than 400mm.<br />
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As mentioned earlier, the armour only covers around half of the surface area of the tank from the front and of that covered area, some parts lack the metal-polymer component, making it nothing more than simple spaced armour at those specific zones. From the front, these parts are the machine gun port on the right side of the turret and the gunner's primary sight window on the left side. These areas can be considered to be weakened zones, especially to shaped charge weapons, but they are still resilient to APDS attack. The 71-85mm spaced steel plate can de-cap APDS projectiles and damage the core, whereby it is broken up in the air gap before it reaches the turret front. Even without the spacing, the added thickness of steel makes the LOS thickness of this area reach 300mm of steel, rendering it effectively immune to all 105mm APDS rounds.</div><div>
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Some degree of protection is also provided against APFSDS rounds. Working with the assumption that M735 penetrates 330mm RHA at a 1 km (based on a report by Jane's that M735A1 penetrates 370mm at 1 km), we can see that the thickness of the steel alone is nearing the limit of the capabilities of early 105mm APFSDS. Late ammunition such as M833 should be more than enough to defeat the turret armour from the front across most of its projected area, but common ammunition such as DM23 (105) and M735 or M774 were more relevant for a T-62M. <br />
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In terms of protection, the T-62M can be considered on par with the T-72A in a few respects, but vastly inferior to the T-72B in armour protection against both KE and CE threats. The largest disadvantage is that the "Brow" armour leaves the mantlet area of the turret uncovered by the metal-polymer armour array, but at least the thick steel front plate forms spaced armour over the machine gun and gunsight ports. With the applique armour, the maximum total thickness of the turret armour of the T-62M is 566mm (296mm armour block plus ~70mm air gap plus 200mm turret) over the areas covered by the metal-polymer armour, though the average thickness should be lower. The total thickness is comparable to the T-72A turret, but needless to say, it should be self evident that the combination of a metal-polymer block and an air gap is more effective than "Kvartz".<br />
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Even if the internal armour array is badly damaged by multiple hits, the thick steel front plate of the blocks can still perform as simple spaced armour. In effect, the armour still provides a respectable amount of protection even if it is hit in the same area twice in a row, certainly still enough to immunize the T-62 from the shaped charge warhead of the less advanced versions of LAW rockets to the frontal arc. Going by steel thickness alone, the main armour of the turret together with the front plate of the armour blocks will still be too thick to be defeated by an M72A3 LAW from 1977.<br />
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Overall, the "Brow" armour on the T-62M was not cutting edge technology. Portable threats such as the 105mm M40 recoilless rifle (400mm penetration), LAW, Carl Gustav (400mm penetration), and the anaemic M47 Dragon (450mm of penetration) were effectively neutered, and the add-on armour can be considered very successful in that regard. However, the ITOW was just around the corner by the time the T-62M was introduced, and it would have been able to defeat this new armour with relative ease from the front based on available information. "Brow" armour could not change the status quo of the T-62 against opposing tanks given the relatively recent introduction of 105mm APFSDS ammunition, so even if it could offer full protection from 105mm M456 HEAT and M392A2 APDS and possibly earlier APFSDS like the American M735, this was of little importance as the U.S Army had already moved on to the M774 and M833 while the Germans had already armed themselves with the 105mm DM23 and DM33. By achieving a level of protection only equal to the T-64A, the T-62M was only suitable against similarly obsolescent NATO tanks. This, combined with the general obsolescence of the chassis itself, meant that the further upgrading potential for the T-62 was effectively exhausted. Nevertheless, these obsolete tanks reigned supreme in Afghanistan in the absence of the threat of APFSDS rounds, and it was there that "brow" armour proved to be the difference between life and death.<br />
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"Brow" armour was not exclusive to Volna-equipped T-62Ms, or even to the T-62M in general. Many T-62s have been seen in Afghanistan with "Brow" armour and sideskirts, but no other upgrades. The lack of a laser rangefinder is a dead giveaway for the tanks below:<br />
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This is expected, as "Brow" armour is an applique armour kit that is intrinsically compatible with the T-62. There is nothing to limit the installation of the armour kit to older versions of the T-62. In fact, it was not uncommon to see a pre-1972 model T-62 equipped with "Brow" armour in Afghanistan, as field technicians did the best they could to armour up the army's valuable armoured assets with whatever they had. The photo below shows an early model T-62 (distinguished by the loader's hatch) equipped with "Brow" armour and side skirts leading what appears to be a tank platoon including fully fledged T-62M tanks. The second tank in the line is a T-62M, as we can see by the smoke launchers on the right side of the turret.<br />
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<a href="https://4.bp.blogspot.com/-eXmUfTkX7Q0/WMYh2UNNe4I/AAAAAAAAIjo/QGsG7wkqohowfdD7WIL-LWCt8d-p00IkQCLcB/s1600/t-62%2Bbrow.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://4.bp.blogspot.com/-eXmUfTkX7Q0/WMYh2UNNe4I/AAAAAAAAIjo/QGsG7wkqohowfdD7WIL-LWCt8d-p00IkQCLcB/s640/t-62%2Bbrow.jpg" width="525" /></a></div>
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The photo below shows another early model T-62 with "Brow" armour.<br />
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And the photo below shows another one in a partially hull-down position.<br />
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<h3><span style="font-size: large;">ADDITIONAL MINE PROTECTION ARMOUR</span></h3>
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<a href="http://1.bp.blogspot.com/-Xv6dVGMCB4w/VmfhKLbZkeI/AAAAAAAAE2k/RmaGtQYU76g/s1600/t-62m%2Bbelly%2Bprotection.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="424" src="https://1.bp.blogspot.com/-Xv6dVGMCB4w/VmfhKLbZkeI/AAAAAAAAE2k/RmaGtQYU76g/s640/t-62m%2Bbelly%2Bprotection.jpg" width="640" /></a></div>
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Besides the additional protection offered by the composite armour blocks, the T-62M modernization also came with appliqué belly armour for extra mine protection in light of the situation that the Soviet Army was facing in Afghanistan at the time. The applique belly armour is quite simple in construction: it was composed of a large spacer frame with a height of 80mm onto which six individual rectangular steel plates were welded, as you can see in the photo above. The armour only protects the belly as far as the second roadwheel as this was where most anti-tank mines would detonate, typically because of a tilt-rod fuze. The escape hatch (which is behind the second roadwheel) also received an appliqué spaced armour plate but with a much smaller air gap.<br />
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<a href="https://1.bp.blogspot.com/-YZDr4g9H39s/XT5eAwlby1I/AAAAAAAAOm4/QwpPseOQ8jEVHPOxoBUr9wU3b3L30qHGgCLcBGAs/s1600/t-62m%2Badditional%2Barmour.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="201" data-original-width="426" src="https://1.bp.blogspot.com/-YZDr4g9H39s/XT5eAwlby1I/AAAAAAAAOm4/QwpPseOQ8jEVHPOxoBUr9wU3b3L30qHGgCLcBGAs/s1600/t-62m%2Badditional%2Barmour.gif" /></a></div>
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The thickness of the welded steel plates is 20mm and together with the 80mm air gap between it and the base belly armour, the package has a total thickness of 100mm. But despite this large thickness, the additional belly armour only reduced the ground clearance of the T-62M to 397mm from the original 430mm of clearance thanks to the increased ground clearance afforded by the new torsion bar suspension. Thus, the negative effects on cross-country mobility were largely minimized. Besides the increased protection afforded by the spaced belly armour, the driver's station was reinforced by a tubular steel strut fitted to the right of the driver's backrest connecting the belly to the roof, marked (2) in the drawing below. The strut is a steel tube, with a diameter of 108mm and wall thickness of 10mm. This reinforcing strut is placed next to the battery rack, connecting the hull belly to the hull roof near the longitudinal axis of the hull, so that the deformation of the belly from mine attacks will be greatly limited.<br />
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<a href="https://3.bp.blogspot.com/-qSHdG7wpP9U/Wg5KE0n3SwI/AAAAAAAAKIQ/kQumbzbDyCghtJCFWmxBoiYwUax5SvCjACLcBGAs/s1600/mines.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="390" data-original-width="720" height="346" src="https://3.bp.blogspot.com/-qSHdG7wpP9U/Wg5KE0n3SwI/AAAAAAAAKIQ/kQumbzbDyCghtJCFWmxBoiYwUax5SvCjACLcBGAs/s640/mines.jpg" width="640" /></a></div>
<div><br /></div><div><br /></div><div>The reinforcing strut can be seen in the image of a T-62M below. The driver's working space was not affected as the strut is adjacent to the backrest of the driver's seat and hence, does not intrude into the driver's shoulder room or impede his use of the driving controls or the firefighting system.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-ZQpyVExiz3I/XzJB31j6eQI/AAAAAAAARco/4PbO8lk3cegAjpUbpG11H4qi4G8XKk1TwCLcBGAsYHQ/s1920/t-62m%2Binterior%2Breinforcing%2Bcolumn.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="1920" height="360" src="https://1.bp.blogspot.com/-ZQpyVExiz3I/XzJB31j6eQI/AAAAAAAARco/4PbO8lk3cegAjpUbpG11H4qi4G8XKk1TwCLcBGAsYHQ/w640-h360/t-62m%2Binterior%2Breinforcing%2Bcolumn.png" width="640" /></a></div>
<div><br /></div></div><div><br /></div><div>The driver's seat was also upgraded with a new mounting system, comprised of a special steel floor plate that lacks physical contact with the hull belly plate. Instead, the floor plate is mounted to the left hull wall on its left side, and on the wall of the battery rack on its right side. The steel floor plate is spaced from the hull belly by a 30mm gap, which slightly reduced the total vertical space available to the driver, but vastly decreased the likelihood of spinal injury from a shockwave transmitted via the tank belly and through the seat. Additionally, above the first pair of torsion bars for the first pair of roadwheels, a porous rubber mat with a thickness of 20mm was glued to protect the driver's feet from shock and vibration transmitted through the belly, in case his feet were not resting on the driving pedals.<br /><br />Overall, the mine protection kit provided comprehensive protection from mines and IEDs detonated under both the tracks and directly under the belly of the tank. The resistance of the tank to mine attacks was greatly improved and the casualty rate of tank drivers in Afghanistan was significantly reduced as a result.<br />
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<h3>
<a href="https://www.blogger.com/null" id="slat"></a>
<span style="font-size: large;">SLAT ARMOUR</span></h3>
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<a href="http://4.bp.blogspot.com/-mFPTfU0dRi8/Vem707k0qdI/AAAAAAAADcA/m_lGLgzdrkA/s1600/slat%2Barmour.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://4.bp.blogspot.com/-mFPTfU0dRi8/Vem707k0qdI/AAAAAAAADcA/m_lGLgzdrkA/s400/slat%2Barmour.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-rf4V2Ge9ylg/XVEfe4Y4ZBI/AAAAAAAAO3M/wgm2TV9_lpgVgW2K7X2osAD_JFxY6MmJwCLcBGAs/s1600/slat%2Barmour%2Bt-62.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1065" data-original-width="1600" height="265" src="https://1.bp.blogspot.com/-rf4V2Ge9ylg/XVEfe4Y4ZBI/AAAAAAAAO3M/wgm2TV9_lpgVgW2K7X2osAD_JFxY6MmJwCLcBGAs/s400/slat%2Barmour%2Bt-62.jpg" width="400" /></a></div>
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Slat armour screens were developed by NII Stali and fielded on a relatively large scale in Afghanistan. Slat armour screens were not included in the original T-62M modernization package and there was no large scale upgrade programme to outfit tanks with slat armour.<br />
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A full set of slat armour screens consisted of four types of screens of different dimensions. The each side of the hull would have five screens installed, the rear of the hull would have two screens, and the rear half of the turret would have four screens installed. The front of the hull and turret were left unprotected as these parts of the tank could be protected by other forms of armour. For the T-62M, this role would be fulfilled by the metal-polymer armour blocks, and for the T-62MV, Kontakt-1 reactive armour takes up the task. In reality, supply and resource constraints meant that the two types of armour could not always be fitted together and it was not uncommon to see tanks lacking one or the other. For instance, many of the T-62 tanks that participated in the 2008 war with Georgia had slat armour but the front of their hulls and turrets were bare.<br />
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A full slat armour set weighs 0.55 tons. The total weight gain for a tank that is already outfitted with rubberized side skirts is 0.45 tons because the slat armour screens on the sides of the hull replace the skirts. According to NII Stali, the probability of defeating a typical shaped charge warhead from a handheld grenade launcher, represented by a PG-9S grenade as fired from an SPG-9 recoilless gun, is 60%.<br />
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Although the armour could not guarantee protection against handheld grenade launchers, it was still vastly more useful than the basic rubber side skirts originally installed onto the T-62M which could only grant protection if it was hit at a steep angle.<br />
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<a href="https://1.bp.blogspot.com/-dawOBKjYnAg/XUBEO4Fjr6I/AAAAAAAAOrg/01ACpTuFf-oQeW512w3HN5x1RPW0QsFNgCLcBGAs/s1600/afghanistan%2Bt-62m.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="480" data-original-width="635" height="483" src="https://1.bp.blogspot.com/-dawOBKjYnAg/XUBEO4Fjr6I/AAAAAAAAOrg/01ACpTuFf-oQeW512w3HN5x1RPW0QsFNgCLcBGAs/s640/afghanistan%2Bt-62m.jpg" width="640" /></a></div>
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<h3>
<a href="https://www.blogger.com/null" id="k1"></a>
<span style="font-size: large;">Kontakt-1</span></h3>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-vcum52O6Mqc/Vm7pzJ6cDLI/AAAAAAAAE-Y/287p4hXXMfc/s1600/t-62%2Bkontakt-1.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://1.bp.blogspot.com/-vcum52O6Mqc/Vm7pzJ6cDLI/AAAAAAAAE-Y/287p4hXXMfc/s640/t-62%2Bkontakt-1.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Photo from Andrei Tarasenko's website</td></tr>
</tbody></table>
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When Kontakt-1 became available in the early 80's, some T-62s were formally equipped with the armour, but only on an evaluatory capacity. Instead of Kontakt-1, T-62s were usually given slat armour instead, which could not be often seen on tanks that used Kontakt-1 like the T-64 and T-72. They both had the same basic function, but slat armour was much cheaper and easier to install.<br />
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T-62 tanks that were modernized to the T-62MV standard contained all of the same features of the basic T-62M, but had Kontakt-1 blocks installed on the front and sides of the hull and turret instead of metal-polymer armour. The total weight of the package amounted to 1,320 kg.<br />
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<a href="http://4.bp.blogspot.com/-QJmx2EGFPQY/Vm7uPTBYKTI/AAAAAAAAE-g/IU3pb-UTMHY/s1600/t-62m%2Bwith%2Bk-1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="442" src="https://4.bp.blogspot.com/-QJmx2EGFPQY/Vm7uPTBYKTI/AAAAAAAAE-g/IU3pb-UTMHY/s640/t-62m%2Bwith%2Bk-1.jpg" width="640" /></a></div>
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<span>Mounting the blocks are easy. Each one is bolted onto a spacer bolted to the surface of the hull and turret. The ease of installing and replacing the blocks meant that the entire modification could be done as part of regular scheduled maintenance. However, simplicity comes at a price in this case. The ERA boxes are somewhat fragile, and can be quite easily knocked off when the tank is travelling through densely wooded areas, or perhaps traversing obstacles in urban sprawl. </span></div><div><span><br /></span>
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<span>Each Kontakt-1 block consists of two 4S20 explosive elements - plastic explosives packed into a flat steel plates. Each plate of plastic explosive weighs 260 grams, and have an explosive power equivalent to 280 grams of TNT. The plastic explosives have a very low sensitivity to ensure that they can survive being hit by machine gun fire and even autocannon fire without detonating. The weight of each block is 5.3 kg, and a full set covering the entire tank weighs approximately 1.2 tons, meaning that there are around 220 blocks of Kontakt-1.</span><br />
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<a href="http://2.bp.blogspot.com/-UMWKxni5Yx0/VSu9XFlZGuI/AAAAAAAABvY/vzdyowt1Y3Q/s1600/648eca599e74.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="169" src="https://2.bp.blogspot.com/-UMWKxni5Yx0/VSu9XFlZGuI/AAAAAAAABvY/vzdyowt1Y3Q/s1600/648eca599e74.jpg" width="320" /></a><a href="http://2.bp.blogspot.com/-BAE1xl0zNhU/VZeIbWgO81I/AAAAAAAACn0/joOMeG8uld0/s1600/2c20.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="166" src="https://2.bp.blogspot.com/-BAE1xl0zNhU/VZeIbWgO81I/AAAAAAAACn0/joOMeG8uld0/s400/2c20.jpg" width="400" /></a></div>
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<span style="font-weight: normal;"><b><span style="font-size: large;">Method of Operation</span></b></span></h3>
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A full examination of Kontakt-1 is available on the T-72 article. View it <a href="https://thesovietarmourblog.blogspot.com/2015/05/t-72-soviet-progeny.html">here</a>.<br />
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<span style="font-size: small;"> </span><br />
<span>The entire tank is covered in all areas except for the rear half of the side skirts, and rear of the hull and turret, and the turret ring is left exposed. </span><span>Each Kontakt-1 block can reportedly reduce the penetrating effects of cumulative jets by up to 55% at 0 degrees obliquity, and up to 80% when angled at 60 degrees</span><span>.</span><span style="font-size: small;"> </span>According to NII Stali, a T-62 outfitted with Kontakt-1 has a level of armour protection equivalent to 650mm RHA at the turret in a 70-degree frontal arc and at the hull in a 44-degree frontal arc. Protection from handheld grenade launchers is guaranteed on the side of the tank even when hit from a perpendicular angle. The reactive armour effectively provides an additional 450-500mm of RHA steel on top of the basic steel armour of the T-62. With Kontakt-1, the tank becomes immune to almost all anti-tank guided missiles from the 1970's to the early 1980's, but due to the lack of composite armour underneath the reactive armour blocks, a T-62MV simply cannot reach the level of protection offered by a main battle tank like the T-72AV. </div>
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<a href="https://www.blogger.com/null" id="mineclearance"></a>
<span style="font-size: large;">MINE CLEARANCE</span></h3>
Equipment for clearing a path through minefields was issued to tank platoons, one each. One tank in any given platoon would be a model appropriately modified from the factory to mount any mine clearance devices from the early PT-54 all the way up to the KMT-8.<br />
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<span style="font-size: large;">PT-55 Mine Rollers</span></h3>
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Mine rollers meant to detonate anti-tank mines before the tracks do. Main disadvantage of mine rollers is that it is not safe for the cannon barrel to be pointing forward, due to the negative effects of the blast on its integrity. They weigh in at a hefty 8.8 tons, and quickly wear out the front suspension of the tank.<br />
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<a href="http://4.bp.blogspot.com/-CUro0sF9fdc/VmMsyUtg-cI/AAAAAAAAEow/mWJhSicsNeY/s1600/t-62%2Bmine%2Brollers.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="403" src="https://4.bp.blogspot.com/-CUro0sF9fdc/VmMsyUtg-cI/AAAAAAAAEow/mWJhSicsNeY/s640/t-62%2Bmine%2Brollers.jpg" width="640" /></a></div>
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Later on, the improved and progressively lighter PT-54M and PT-55 could be mounted. They could not clear as wide a path as the original PT-54, but are more sustainable because of their weight.<br />
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<span style="font-size: large;">KMT-4 Mine Ploughs</span></h3>
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Mine ploughs that dig up and shove anti-tank mines out of the way, creating a path just wide enough for the tracks to pass through They weigh 1.2 tons, and are lowered with a hydraulic piston powered by the tank's electrical system. The tank can move at normal speeds with the plough raised, but must slow down to 12 km/h with the plough lowered. The plough is light enough that it will not affect the frontmost torsion bars, which is helped by the better optimized arrangement of roadwheels on the T-62. The large gap between the first and second pair of roadwheels in the T-54 and T-55 designs meant that they would have been placed under excessive strain, possibly breaking them. <br />
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<a href="http://1.bp.blogspot.com/-Rm3by16-dmg/Vmby2-qVeMI/AAAAAAAAEzs/eBppjjQP_Aw/s1600/t-62%2Bmine%2Bplough.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="424" src="https://1.bp.blogspot.com/-Rm3by16-dmg/Vmby2-qVeMI/AAAAAAAAEzs/eBppjjQP_Aw/s640/t-62%2Bmine%2Bplough.jpg" width="640" /></a></div>
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Neither of these devices could remove or safely detonate tilt-rod mines, but tank crews could tie a piece of steel wire or cable across the two plows or rollers for a makeshift standoff detonator. Later mine clearance devices like the KMT-5 combined rollers with a plough while weighing less than the original PT-54-type rollers. Later on, the T-62 could mount more sophisticated KMT-6, 7 and 8 devices capable of detonating both tilt-rod mines as well as electromagnetically fused ones. This is mostly thanks to the completely standardized mounting system used for all Soviet mine clearance devices.<br />
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<h3>
<a href="https://www.blogger.com/null" id="nbc"></a>
<span style="font-size: large;">NBC PROTECTION (PAZ)</span></h3>
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The T-62 was furnished with a PAZ protection suite that was unified with the system first used in the T-55. The PAZ (Противоатомной Защиты) system, as its name suggests, was an anti-nuclear protection system rather than a full NBC protection system. Such a system was needed to ensure that contaminants cannot slip through gaps in the tank's armour to incapacitate or even kill the crew, and also to minimize the various effects of a nuclear blast that may cause severe illnesses in the long run. It was not designed to handle chemical or biological aerosol contaminants, though contaminated particles from zones previously covered with aerosols may be sufficiently dealt with. When passing through contaminated zones previously reconnoitered by BRDM-RKh or BRDM-2RKh cars, the vehicles in a tank unit will have to don NBC protection equipment as needed.</div><div>
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Unlike the T-55A that came later, the T-62 lacked an anti-radiation lining or cladding to protect the crew, leaving them much more vulnerable to gamma and neutron radiation if the tank was caught in a nearby nuclear blast. Although the crew is protected from breathing irradiated dust particles by the filtering system, they are not protected from the burst of initial radiation during the nuclear explosion itself, nor are the protected from the radiation released from irradiated debris and soil, which may penetrate the thin belly of the tank. Although the steel shell of the tank shields the crew from penetrating radiation to some extent, the steel itself becomes radioactive due to induced radioactivity from neutrons. As such, the steel alone cannot offer comprehensive protection, hence the need for a lining or a cladding made from anti-radiation materials. The lack of a lining was due to its weight - the weight limit imposed on the T-62 by the Soviet Army during its development was extremely strict, and the liner would have added 500 kg of weight to a tank that was already encroaching on the mandated limit.</div><div><br /></div><div>There was no compensation for the lack of an anti-radiation liner until the early 1980's, when anti-radiation vests became available as part of additional protective measures against neutron bombs. Such vests, which were heavy and could attenuate gamma radiation around the torso and groin, were issued to tanks such as the T-62M which had been modernized with external anti-neutron cladding (Nadboy) as part of the standard kit. It is unknown if unmodernized T-62 tanks had access to these anti-radiation vests, but it is possible that they would have been issued them in case of a nuclear war.</div><div><br /></div><div>The T-62 was considered to be no worse than any other Soviet medium tank in terms of its permeability to background radiation, but worse than a T-55A when faced with penetrating radiation, having the same level of protection as the T-55, T-54B and T-54A. According to the 1981 Soviet essay titled "<a href="http://btvt.info/5library/vbtt_1_1981_t_54_62.htm"><i>Из Опыта Совершенствования Основных Танков В Ходе Серийного Производства</i></a>", the T-62 attenuates penetrating radiation (neutrons and gamma rays) by 2.8 times and attenuates background radiation from an irradiated environment by 14 times. In contrast, the T-55A could attenuate penetrating radiation by 9 times thanks to special anti-radiation fittings on the turret cupolas and on the driver's hatch.<br />
<br />This is a somewhat coarse metric, but unfortunately, more detailed data from Soviet testing is not available. However, according to U.S testing with captured T-62s obtained after the 1973 Arab-Israeli war, presented in “Nuclear Notes Number 8: Armored Vehicle Shielding Against Radiation”, the T-62 was credited with a penetrating radiation transmission factor (TF) of 0.6 against neutrons and 0.1 against gamma radiation. Testing was carried out on the assumption that the neutron and gamma ray burst from a nuclear detonation could arrive from any direction, so the TF figure is an average of measurements across all aspects of the tank. These figures are slightly worse (higher) than the T-55, which had a TF of 0.5 against neutrons and 0.07 against gamma radiation, which is somewhat unusual, but may be due to differences in turret thicknesses at specific angles of irradiation. As a point of comparison, the M60A1 has a TF of 0.5 against neutrons and 0.1 against gamma radiation. <br />
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Of course, there was a serious attempt to add the anti-radiation lining to the T-62. In December 1962, two experimental Object 166P (T-62P) tanks were built at the No. 183 Nizhny Tagil plant and subsequently tested at the NIIBT testing grounds in Kubinka from February to March of 1963. Unfortunately, the results of the tests were negative; the addition of thick anti-radiation lining in the driver's compartment significantly reduced the available work space and even interfered with his hands. The amount of work space in the turret was also affected, and the view from the periscopes deteriorated. Because of this, the installation of the anti-radiation lining was rejected, and the T-62 never had one for the entirety of its service in the USSR and abroad. However, the T-62M received an external anti-neutron cladding during the mid-80's as a response to President Reagan's authorization of the production of neutron bombs like the W70-3. Designated "Podboi", this anti-neutron cladding was also installed on the T-64, T-72 and T-80 during the early to mid 1980's. One such T-62M is shown in the photo below (photo credit to Vitaly Kuzmin).<br />
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Unfortunately, the coverage of "Podboi" cladding on the T-62 is rather limited. There are large gaps between some of the anti-neutron mats, and the commander's cupola only has cladding on the hatch and not the forward part where the periscopes are situated. It is also the same for the loader's hatch.<br />
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Like any other tank, the T-62 could be decontaminated swiftly by being blasted with jets of hot air to remove chemical and biological agents, which is what is happening to the T-62 below:<br />
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<a href="http://4.bp.blogspot.com/-nGCCzWmodhA/VmaXYzqfCiI/AAAAAAAAEvs/lsv4Ll4yxCs/s1600/decontamination%2Bof%2Bt-62.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="428" src="https://4.bp.blogspot.com/-nGCCzWmodhA/VmaXYzqfCiI/AAAAAAAAEvs/lsv4Ll4yxCs/s640/decontamination%2Bof%2Bt-62.jpg" width="640" /></a></div>
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The "Podboi" anti-neutron cladding had a heat-resistant outer layer that allowed it to be exposed to the streams of hot air during such decontamination procedures.<br />
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<h3>
<span style="font-size: large;">ERB-1M</span></h3>
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With the need for nuclear protection firmly established with the appearance of tube artillery-delivered tactical nukes, the requirement for such a system remained the same for the T-62 as it did for the T-55, which had the most advanced and comprehensive nuclear protection scheme for any medium tank in the world at the time. For simplicity's sake, the T-62 was equipped with the same ERB-1M system as the T-55. ERB-1M could detect a nuclear explosion through a gamma radiation sensor located in the middle of the hull, just beside the commander's seat (red box), and activate the tank's collective protection suite.<br />
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When gamma radiation was detected and determined to be at or above a dosage indicative of a nuclear explosion or leak, all portholes would be automatically sealed to prevent contamination, as the tank was not actually airtight. The seals were applied via small pyrotechnic squibs detonated through an electric impulse sent from the main control unit of the ERB-1M system. The engine would be immediately stopped and the radiator cooling fan suspended. The radiator louvers would be automatically shut closed, and to fully assure the impenetrability of the fighting compartment from radioactive particles, the compressor in the ventilator would be powered up to create an overpressure. The driver has manual switches for activating the defensive systems.<br />
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The sealing mechanism for the gunner's telescopic optic is illustrated in the diagram below. The diagram is taken from the T-62 technical manual, page 560. As you can see, the area around the gunner's telescopic sight is a weakened zone due to space concessions required for the fitting of the sight. Based on the diagram at the top left, the thickness of the turret around the optic port was reduced by around 60% at the area above the port, and around 20% below it. The aperture of the telescopic sight peers out from behind a small porthole, under which the seal is installed.<br />
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The optic port itself is thinly armoured compared to even the weakened region. By scaling it with the base of the turret wall as depicted in the diagram, it is apparent that the armour is only 67.4mm thick. Note that it is a separate piece of armour made from rolled plate rather than cast steel. This would be enough for virtually any machine gun or autocannon fire, but nothing more. While tall, it is some consolation that the weakened zone is rather narrow, based on the drawing at the lower left corner of the diagram above. <br />
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A sealed optic aperture is shown in the photo below. The red box indicates the location of the seal when retracted. The entirety of the weakened zone is shown by the yellow box.<br />
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Ventilation for the crew is facilitated by a ventilator-filter system. The air intake of the ventilator is identifiable on the rear of the turret as a large, overturned frying pan-shaped tumor on the rear of the turret. The "frying pan" is quite thick. The ventilator is the same system as used in the T-55, merely installed at a different point on the turret.<br />
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<div><br /></div><div><br /></div>For general ventilation purposes, the air intake fan of the ventilator is activated, drawing air from the external intake and then blowing it into the turret with no filtration. Due to its location behind the 115mm gun, the airflow helps to reduce the concentration of propellant fumes during combat, working in conjunction with the built-in fume extractor of the U-5TS and the casing ejection mechanism.<br />
<br />Filtration of contaminated air is done by a centrifugal supercharger fan inside the ventilator drum housing. The supercharger fan consists of an annular rotor consisting of 160 blades surrounding the drive motor in the center of the drum, forming a narrow annular channel through which the air is sucked in. The necessary volume of the inflow is ensured by the intake fan. The rotor is driven by an MB-67 motor with a power of 800 Watts, connected via a direct coupling; no step-down gear box. The supercharger fan rotates at 7,000-7,700 RPM when running on the electrical network of the tank at a nominal power of 26 V. The supercharger performs filtration on air by cyclonic separation, ejecting irradiated dust and other contaminated particles out of a small slit at the base of the housing (refer to photo above). The filtered air has a 98% purity, and is released into the crew compartment via an air outlet. A 98% purity level is enough to reduce the hazard from radioactive fallout to a safe level, but is not enough for biological or chemical weapons, for which HEPA filters will be needed. The supercharger produces a positive pressure inside the tank and thereby preventing unfiltered particles from entering the tank, as the tank is not hermetically sealed. The exhaust, containing the dust extracted from the inflow, is ejected from the system via a small slit in the base of the turret.<br />
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When the overpressure system is activated, whether automatically or manually by the driver, the system generates a slight overpressure of 0.0015 kg/sq.cm or 147 Pa above the atmospheric pressure. This is sufficient to prevent irradiated particles from entering the tank, if all hatches are closed. The blower puts out an airflow rate of 110 liters per second (233 CFM), which is more than enough for the internal volume of the T-62. It is more powerful than the 200 CFM standard established for large enclosed vehicles. For instance, the Modular Collective Protection Equipment (MCPE) system were built for an air flow rate of 200 CFM, according to the book "America's Struggle with Chemical-biological Warfare" by Albert J. Mauroni, director of the U.S. Air Force Center for Strategic Deterrence Studies. As an example, the M1 Abrams series, which has a larger crew compartment volume than the T-62 and is equipped with the MCPE, relies on a 200 CFM ventilation blower coupled to two 100 CFM filter units to generate an overpressure, as do other specialist vehicles equipped with the MCPE, including the AN/TSQ-73 air defence control and coordination van. The high airflow is presumably helpful for the T-62 when its automatic casing ejection system is active, in addition to being generally beneficial in ventilating the crew area. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xL_nV4oaTFs/YScZr7oo53I/AAAAAAAAUHg/FhbisS9TLR0lE6_1gFXE4TFo4zJrXGK2ACLcBGAsYHQ/s1094/nbc%2Bfilter%2Bsets.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="516" data-original-width="1094" height="302" src="https://1.bp.blogspot.com/-xL_nV4oaTFs/YScZr7oo53I/AAAAAAAAUHg/FhbisS9TLR0lE6_1gFXE4TFo4zJrXGK2ACLcBGAsYHQ/w640-h302/nbc%2Bfilter%2Bsets.png" width="640" /></a></div><div><br /></div><div><br />
The supercharged filter-ventilator can be manually activated from a control box near the shell casing ejection port. The control box is easily within the loader's reach (red box below in the photo below). </div><div>
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Compared to a plug-in system where crew members must plug in their gas masks into the tank's air filter unit (a system that is commonly found in American armoured vehicles) the collective-type protection suite of the T-62 is ergonomically superior. The crew does not need to wear masks that obturates their vision or obstructs it entirely with fog, and they can breath normally without restrictions. Their speech is also not impaired because of such a mask. This was not the case in tanks like the M48A2, which was the first American tank with a filtered ventilation system but lacked an overpressure generator.<br />
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<a href="https://www.blogger.com/null" id="smoke"></a>
<span style="font-size: large;">SMOKESCREEN</span></h3>
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Like the T-54, the T-62 has an on-board smokescreen generation system known as a TDA, which stands for "Thermal Smoke Apparatus". Diesel fuel is injected into the exhaust manifolds, vaporizing it with the heat and expelling the resultant mist out of the exhaust. Upon exiting the exhaust manifolds, the mist condenses immediately in the cold environment and condenses, turning into a dense cloud of white, opaque fog. The rate of fog production depends largely on the load on the engine, so the tank will produce more smoke when it is travelling over rough ground at high speed than when it is parked and idling. According to the manual, the driver should not shift gears when the TDA is in action if he wants to maintain a continuous curtain of fog, as the change in engine load will affect the volume of fog produced. The driver must drive with the accelerator pedal fully depressed to prevent engine fuel starvation, and the engine speed must be kept at 1,600 rpm or higher. <br />
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<div><br /></div><div><br /></div>It is not recommended to use the system for more than 10 minutes, and there must be an allowance of 3-5 minutes between each use. If the driver adheres to all of the guidelines, the system can theoretically be used indefinitely as long as there is sufficient fuel.</div><div><br />
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<span style="font-size: large;">902V "Tucha" Smoke Grenade System</span></h3>
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<a href="http://2.bp.blogspot.com/-lWkJJa2D90M/VmfqrO7bjtI/AAAAAAAAE3Y/PwynuFL5F-E/s1600/t-62m%2Btucha.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://2.bp.blogspot.com/-lWkJJa2D90M/VmfqrO7bjtI/AAAAAAAAE3Y/PwynuFL5F-E/s640/t-62m%2Btucha.jpg" width="640" /></a></div>
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The T-62M was outfitted with the "Tucha" smoke grenade system to supplement the built-in TDA exhaust smokescreening system included since the original T-62 model.<br />
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<a href="https://www.blogger.com/null" id="fire"></a>
<span style="font-size: large;">FIREFIGHTING</span></h3>
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The T-62 is furnished with the "Rosa-2" automatic firefighting system inherited from the T-55. "Rosa" employs a halocarbon fire extinguishing agent designated Composition "3.5"; a compound allegedly consisting of ethyl bromide and carbon dioxide, composed of 70% ethyl bromide and 30% carbon dioxide by weight, pressurized at 50 atm. It is very likely that the compound actually contains methyl bromide and not ethyl bromide, as ethyl bromide is highly flammable in both liquid and vapor form. Methyl bromide, on the other hand, is an effective industrial fire extinguishing agent that was relatively common in the 1950's and 1960's. It is particularly notable as a high performance fire extinguishing agent in the aviation industry.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The mixture is effective, with its name "3.5" referring to it having an effectiveness 3.5 times greater than carbon dioxide alone. However, it is also extremely toxic in large quantities, particularly in enclosed spaces without ventilation. The compound is heavier than air, which mitigates its toxicity danger to the crew, but nevertheless, if a fire extinguisher bottle has discharged in the crew compartment, it is important for the crew members to hold their breath until they have evacuated the tank or donned their gas masks. To evacuate the fire extinguishing compound from the crew compartment, the drainage ports or the escape hatch are opened. Engine compartment fires can be extinguished by the system without requiring any special safety precautions.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The "Rosa" system employs TD-1 temperature sensors strategically positioned around the inside of the engine compartment and crew compartment to give the best chance of detecting fuel, electrical and other types of fires. "Rosa-2" reacts to a rise in temperature to 130-160°C. As the layout diagram below shows, there were four TD-1 sensors and eight fire extinguisher nozzles installed in strategic locations around the crew compartment, and there were four TD-1 sensors and five fire extinguisher nozzles in the engine compartment.<br />
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The photo below shows a TD-1 temperature sensor.<br />
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The system can operate in either 'automatic' or 'semi-automatic' modes. In the 'automatic' mode, the system alerts the driver of the source of the fire and immediately closes all of the radiator louvers, shuts off the engine, and shuts the ventilation fan port to deprive the fire of air. Then, the fire extinguishers are activated and the entire compartment is flooded with the extinguishing agent. In the 'semi-automatic' mode, the system alerts the driver of the presence of a fire via an alarm and a signal light, but does not intervene on its own. The driver can then choose whatever action he deems most suitable at the moment. He can control the deployment of the fire extinguishers from his station. The commander has a master switch for deploying the fire extinguishers as well.<br />
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When the fire extinguishers discharge in the crew compartment of the tank, the crew must evacuate immediately to avoid being poisoned by the fire extinguishing agent. Depending on the situation, the crew may reenter the tank after it has been ventilated, or more likely, the crew will evacuate from the battlefield and the tank is recovered later.<br />
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The film still below, taken from a TRADOC training film, shows a T-62 driver pressing the button.<br />
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The drawing below on the right below shows one of the fire extinguisher bottles with its special release valve mechanism, and the drawing on the left below shows the piping layout for the three fire extinguisher bottles.<br />
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In addition to the automatic fire extinguishing system, the driver is supplied with a single manual OU-2 carbon dioxide fire extinguisher. Carbon dioxide is suitable against Class B and C fires, namely fuel and electrical fires, which are the predominant causes of fire in a tank. The OU-2 is the only means of extinguishing fires in the fighting compartment.<br />
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<h3>
<span style="font-size: large;">ESCAPE HATCH</span></h3>
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The T-62 features an escape hatch to enable the crew to exit the tank in the very worst of emergencies. It is located directly behind the driver's seat and in front of the gunner. All of the turret's inhabitants can (relatively) easily swing down and out, but for the driver to exit, he must first fold his seat backwards, enter the turret, and then fold his seat forwards (the driver must fold as well) before he can egress.<br />
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<div style="text-align: center;"><a href="http://3.bp.blogspot.com/-BmCXKqfLV5A/Vm17ZX8YtpI/AAAAAAAAE9Q/wQWD1tpv_q4/s1600/t-62%2Bescape%2Bhatch.jpg"><img border="0" height="480" src="https://3.bp.blogspot.com/-BmCXKqfLV5A/Vm17ZX8YtpI/AAAAAAAAE9Q/wQWD1tpv_q4/s640/t-62%2Bescape%2Bhatch.jpg" width="640" /></a></div>
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Though small as always, the hatch is distinguished from escape hatches found on most Western tanks in that is that it is opened inwards on a hinge as opposed to dropping out of the bottom of the tank. Not only does this practically eliminate any potential concerns of the hatch dropping out on its own accord from vibrations and shock, it also means that it can be opened if the tank is submerged. The main disadvantage is that this type of hatch is less resistant to mine attack.<br />
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<h3>
<a href="https://www.blogger.com/null" id="driver"></a>
<span style="font-size: large;">DRIVER-MECHANIC'S STATION</span></h3>
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<a href="http://3.bp.blogspot.com/-gyGJZitTfLo/Vk8hOs1u1DI/AAAAAAAAEHM/ZHMYPqlByO8/s1600/t-62%2Bdriver%2527s%2Bhatch.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://3.bp.blogspot.com/-gyGJZitTfLo/Vk8hOs1u1DI/AAAAAAAAEHM/ZHMYPqlByO8/s640/t-62%2Bdriver%2527s%2Bhatch.jpg" width="640" /></a></div>
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The driver's station is practically identical to the one in the T-55 with only very minor differences. It is located at the front left quadrant of the hull, and the driver is provided with an armoured overhead hatch of the lift-and-swing type. When the hatch is unlocked, the turret traverse system is automatically locked as a built-in safety mechanism for the driver. The mechanism for this feature is quite simple: when the hatch opening handle is moved to the horizontal position in order to lift the hatch, a protruding tab is rotated away from a switch, marked (20) in the drawing below, and this breaks the circuit, thus causing the turret traverse drive to automatically brake and lock the turret in position. If the turret needs to turn when the driver's hatch is open for whatever reason, the driver can simply press and hold on the switch until the turret is turned to where it needs to be. A small indicator light connected to the turret traverse system is installed next to the hatch to alert the driver if the gun is directly over the hatch.<br />
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Besides these safety features, the driver's protection is also ensured by the thick armour of the hatch itself. As the drawing above shows, the thickness of the hatch is not uniform. The rear part of the hatch that is bolted to the hatch opening mechanism has an equal thickness as the hull roof (30mm), but the actual thickness of the hatch that fits over the opening is 50mm. The increased thickness of the hatch compared to the hull roof ensures that the driver is well-protected from the blast and fragmentation of explosive shells impacting the surface of the turret as well as from the splinters of artillery shells airbursting over the tank. As the drawing above also shows, the hatch itself rests above the level of the hull roof. This means that the driver gets an additional 30mm of headroom. The underside of the hatch at the center is padded to protect the driver's head when he is jolted up and down from driving over rough ground, and the rim of the hatch opening is also lined with rubber, both to seal the hole from the outside environment and to protect the driver's head to a limited extent.<br />
<br /><br />The driver's seat was installed in the gap between the first and second torsion bar pairs of the tank's suspension. Despite the elimination of the distinctive gap between the first and second roadwheels of the T-55, there was still enough space between the torsion bars to fit the driver's seat in the same location. In terms of dimensions and the layout of the controls, particularly regarding the distance between the seat backrest and the accelerator pedal, the T-62 is the same as the T-54 and T-55 that preceded it. It is, however, worth noting that the absence of an anti-radiation liner in the T-62 afforded the driver a larger workstation relative to the T-54. A measurement of the driver's station showed that it has a width of 33 inches, or 838mm. Of all the crew stations in the tank, the driver's station is the most sensitive to height. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">One important metric is the distance between the seat and the clutch, brake and accelerator pedal, which had to be large enough to ensure that the driver not only had enough legroom but could operate the pedals with his legs bent at an ergonomically ideal range of angles. The drawing on the right below, showing a cross section of the driver's station in a T-54 (identical to a T-62), illustrates the seating posture of the driver.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-r0L4XaApRDI/XxnH78lbGDI/AAAAAAAARUw/8SX4_bncwtwV73291CPzv3qR_9X8E6nVACLcBGAsYHQ/s427/comfortable%2Bfor%2Bdriver%2Bin%2Bconfined%2Bspaces.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="427" data-original-width="383" height="400" src="https://1.bp.blogspot.com/-r0L4XaApRDI/XxnH78lbGDI/AAAAAAAARUw/8SX4_bncwtwV73291CPzv3qR_9X8E6nVACLcBGAsYHQ/w359-h400/comfortable%2Bfor%2Bdriver%2Bin%2Bconfined%2Bspaces.png" width="359" /></a><a href="https://1.bp.blogspot.com/-V7SNkggGKao/XxnIhoA50wI/AAAAAAAARU8/hOXgDepK3kMln0pPq9-KXFn8FRTDE7gkgCLcBGAsYHQ/s517/driver%2527s%2Bstation%2Bin%2Bt-54.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="504" data-original-width="517" height="390" src="https://1.bp.blogspot.com/-V7SNkggGKao/XxnIhoA50wI/AAAAAAAARU8/hOXgDepK3kMln0pPq9-KXFn8FRTDE7gkgCLcBGAsYHQ/w400-h390/driver%2527s%2Bstation%2Bin%2Bt-54.png" width="400" /></a></div>
<div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">When the tank is parked, it is even possible for the driver to stretch both his legs straight into the empty space at the junction of the two glacis plates. This was achieved by having the driver's seat placed far behind the glacis plates, which was possible because the upper glacis plate was disproportionately longer than the lower glacis plate, thus creating additional hull length in front of the driver. In contrast, the upper and lower glacis sections of the M60 and M60A1 were almost the same length so that they joined at the halfway point of the hull. This severely reduced the length of the hull at the driver's station and forced the driver's pedals to be installed on the lower glacis itself at an extremely close distance to the driver's seat. In the report "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/627820.pdf">Human Factors Engineering Evaluation of the M60 Main Battle Tank</a>", it was noted that this was uncomfortable as well as fatiguing, and the location of the brake pedal was such that when the driver's foot rested on it, the steering wheel interfered with the driver's leg. This issue was later resolved in the M60A1 by replacing the steering wheel with a T-bar. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9CSUwvqFOqw/XxmzWhRiv4I/AAAAAAAARUo/CceNcxgq-doC_vpkeiYO-qyKBtTuujJTACLcBGAsYHQ/s997/m60%2Bdriver%2Bposture.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="773" data-original-width="997" height="310" src="https://1.bp.blogspot.com/-9CSUwvqFOqw/XxmzWhRiv4I/AAAAAAAARUo/CceNcxgq-doC_vpkeiYO-qyKBtTuujJTACLcBGAsYHQ/w400-h310/m60%2Bdriver%2Bposture.png" width="400" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">Steering is accomplished using a pair of tiller levers. To increase the size of the driver's workspace, the instrument panel was moved to the right. The speedometer was placed on a pedestal to the driver's left, and the gear shift is placed to his right. The driver is also in charge of the tank's automatic firefighting system. The use of steering tillers instead of a steering wheel was a relatively antiquated feature of the T-62 as it was more fatiguing to use in the long term, but it was not totally inferior as it was a simpler, cheaper, more robust and also less intrusive steering mechanism. Unlike in an M60, a T-62 driver is unimpeded in his work when seated normally. The main advantage of the M60(A1) was that it had a taller internal height at the driver's station - 1,040-1,060mm (calculated) compared to 969mm, which would be a noticeable difference for drivers of a taller stature. </div><div style="font-weight: normal;"><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-UKsNe7UO-3k/Vm2HSUGLbqI/AAAAAAAAE9s/BS1MgKR1s5o/s1600/t-62%2Bdriver%2527s%2Bstation.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="432" src="https://4.bp.blogspot.com/-UKsNe7UO-3k/Vm2HSUGLbqI/AAAAAAAAE9s/BS1MgKR1s5o/s640/t-62%2Bdriver%2527s%2Bstation.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>However, if compared to the driver's station of a Chieftain with its semi-reclined seat and periscope embedded in the hatch, the driver of a T-62 is clearly worse off in terms of his seated posture.</div></div>
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For daytime driving, the driver is provided with two BMO-190 periscopes. One periscope is aimed directly forward and the other is offset by 15 degrees to the right. Without head movement, the horizontal field of view through both periscopes is 76 degrees and the vertical field of view is 22 degrees. The maximum horizontal viewing arc with head motion from a BMO-190 periscope is 72 degrees, and total field of view from both periscopes is 87 degrees. The maximum dead space in the driver's vision in front of the tank is 4 meters. This layout was designed so that the driver is able to see the corners of the hull in order to be able to maneuver without hitting objects in confined spaces and in dense forests, but that is the limit of the visibility offered by this periscope layout. To obtain the best possible view, it is necessary for the driver to stoop forwards, which strains his back as he drives the tank.<br />
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Although the driver has two forward-facing periscopes and is therefore theoretically capable of searching for targets on his own, the reality during combat is that tank drivers must focus on driving the tank and performing evasive maneuvers when necessary. In most cases, the driver should move from cover to cover and he must scan for a route that provides minimal exposure to fire coming from the sides, features some flat stretches of ground to allow the gunner to fire with maximum accuracy on the move, and avoid driving the tank into a ditch while doing so. As such, the driver simply cannot be expected to search for targets, let alone targets at the expected combat ranges of 1.0 km to 1.5 km.<br />
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If the tank is stationary, the driver could help scan for targets or at least alert the crew to the sudden appearance of enemy forces directly in front of the tank, but this assumes that the tank is in a fully exposed position on open terrain. If the crew is aware that combat is imminent and that enemy forces could appear at any time, remaining stationary and fully exposed on open terrain is the worst possible course of action for a tank. Rather, the tank should be in a hull defilade position, and in such a position, the driver is generally not able to see anything through his periscopes.<br /><br />
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Due to the design of the periscope slots and the use of glass prisms in the periscopes instead of simple mirrors, the driver is well-protected from directs hits on the periscope aperture window from bullets. A bullet that hits the aperture prism will not ricochet down into the driver's compartment, and even if a sufficiently powerful projectile impacts the periscope from a high angle and penetrates deeply into the periscope slot, the driver's eyes are further protected by an additional pane of glass installed behind the rubber padding around the viewing windows of the periscopes. This can be seen in the drawing above.<br />
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The periscopes are slightly wider than the periscopes on the T-34, but the field of vision offered by the BMO-190 periscope is similar. Naturally, one of the most noticeably differences is the vastly improved quality of the glass compared to T-34 periscopes produced during wartime. As he is provided with one fewer periscope, the driver of a T-62 has inferior visibility compared to the driver of any "Patton" tank or a Leopard 1. The GIF below shows the view from the left periscope. Unfortunately, the view to the right side is partially obscured by a canvas bag, possibly a sandbag.<br />
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To remove the periscopes, the driver unscrews a nut on the side (left side for the left periscope, right side for the right periscope) to retract the clamp that holds the periscope in place and then pulls the periscope straight down by its handle to remove it from its slot. This also causes spring-loaded armoured shutters to flip down and shut the periscope port from gunfire and irradiated particles, thus allowing a damaged periscope to be replaced in combat conditions without endangering the driver. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">To clean the aperture window of the periscope from dust, soot, or any other contaminants, the driver unscrews the periscope and then moves it up and down several times. This way, the window is rubbed against a piece of rubber attached to the inside of the periscope slot and it is cleaned. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">Additionally, there is an aerosol cleaning system fitted to the periscope shutters, able to spray either of the periscopes on demand by pressing the thumb button on the end of the right steering tiller. The system consists of a cleaning fluid reservoir, the piping system and a connection to the tank's compressed air bottles. The driver selects one of the periscopes to clean by turning a selector lever, then turns the air release valve which produces a jet of air that draws the cleaning fluid from the reservoir, thus producing an aerosol that is sprayed at high pressure down the selected periscope window. In the summer, water is used, and in the winter, water with antifreeze is used. The water reservoir is placed on the fender, tucked between the side of the hull and the first stowage bin.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DMY32kDjISo/YA0AGOSRgcI/AAAAAAAASmA/ka07LQwr5NMyV8rwXeaNfV6fMxMRvk3IQCLcBGAsYHQ/s1276/periscope%2Bcleaning%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1276" data-original-width="946" height="320" src="https://1.bp.blogspot.com/-DMY32kDjISo/YA0AGOSRgcI/AAAAAAAASmA/ka07LQwr5NMyV8rwXeaNfV6fMxMRvk3IQCLcBGAsYHQ/s320/periscope%2Bcleaning%2Bsystem.png" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">Considering that the air bottles are pressurized to 150 kgf/sq.cm (14.7 MPa or 2,133 psi), the aerosol cleaning system is extremely powerful, likely powerful enough to dislodge any mud on the periscopes. It is only limited by the quantity of cleaning fluid in the water reservoir, as the air pressure is continuously maintained by the integrated AK-150SV air compressor in the tank. That said, even without water, the air jets alone have a strong cleaning power. In effect, the periscope cleaning system can be considered equivalent to the washer-wiper system on the Chieftain, and is far superior to the M60A1 and Leopard 1, both of which had no periscope cleaning system whatsoever.</div><div style="font-weight: normal;">
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The glass in the periscopes is of the K-108 grade, which is glass doped with cerium. When glass is exposed to strong gamma radiation from a nuclear explosion, it turns brown and darkens, greatly decreasing light transmission and visual quality. With cerium-doped glass, the darkening is ameliorated, and the glass will return to its original undarkened state within several hours when continuously exposed to sunlight. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">Unlike the TNP and TNPO periscopes installed elsewhere in the tank, the BMO-190 periscopes are not heated through the RTS electrical heating system to prevent fogging.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">As an additional driving aid, the T-62 is equipped with a gun clearance indicator system, which warn the driver if the gun is traversed beyond the width of the tank hull. This is so that the driver is always aware if the gun could prevent the tank from moving in a narrow passageway, such as when maneuvering between two trees or down a narrow alley. The driver is alerted by means of two warning lights, one on the left side of his periscopes, and one on the right. When the gun is traversed over to the left beyond the projected width of the tank hull, the left warning light is illuminated, and when the gun is traversed to the right, the right light is illuminated.<br />
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For nighttime driving, the driver is equipped with the TVN-2 binocular infrared nightvision periscope. It has a fixed 1x magnification and a 30° field of view. The left periscope can be replaced with the TVN-2. The driver must then connect the TVN-2 to a special cable from BT-6-26 power supply box. Infrared light is sourced from the single IR headlamp on the hull glacis and another similar lamp on the turret, installed just underneath the L-2G Luna spotlight. The range of vision is limited to 60 meters and the field of view is rather constricted compared to the daytime periscope, so the speed of the tank must be carefully controlled when driving in unpaved or otherwise unfamiliar terrain. It is not possible to navigate at night using only the TVN-2, as the driver will be unable to see the landscape and recognize landmarks.<br />
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The photo on the right below - taken from the U.S Army Operator's Manual for the T-62 - shows the TVN-2 as it looks when installed in the T-62. The screenshot shown on the left below shows the TVN-2 installed in a T-54.<br />
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<div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div>Two 5-liter compressed air tanks for cold weather engine starting are located just behind the driver on the left wall. The compressed air is also used for the periscope window cleaning system; an air nozzle installed just next to the armoured hood of the driver's left periscope is aimed at the periscope window to blast away dirt and debris.<br />
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Navigation is facilitated by a simple GPK-48 gyrocompass located near the driver's feet. The main function of the gyrocompass is to allow the driver to set a predetermined direction of travel and then follow it by steering the tank to keep the gyrocompass aligns at its 0 position. This is very helpful when a tank has to travel from waypoint to waypoint, but it is particularly useful when driving underwater or when driving at night. With the GPK-48, it is possible for the driver to ensure that the tank is moving in the correct direction when driving underwater as there is no way to navigate with zero visibility, and at night, it proves useful because of the inability to navigate by referring to landmarks. It would also be helpful when driving in poor weather conditions for the same reason.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-IPnPwAm3_9c/Vm8BZhJOOtI/AAAAAAAAE_E/tIaeMqTRZgg/s1600/gpk-48.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="304" src="https://4.bp.blogspot.com/-IPnPwAm3_9c/Vm8BZhJOOtI/AAAAAAAAE_E/tIaeMqTRZgg/s320/gpk-48.png" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Photo credit: mashpriborintorg from flikr</td></tr>
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In 1966, the T-62 received the GPK-59 gyrocompass, which was more precise and had less mechanical drift over time. It was also designed to divide a full circle into 60 units of angle rather than 360 degrees like GPK-48.<br />
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The use of gyrocompasses can perhaps be labeled as a rudimentary form of an Inertial Navigation System (INS), advanced versions of which are often present in modern combat vehicles due to their independence from outside input contrary to a GPS-based navigation system.<br />
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<h3>
<a href="https://www.blogger.com/null" id="mobility"></a>
<span style="font-size: large;">MOBILITY</span></h3>
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The tactical mobility of the T-62 - that is, its ability to maneuver under its own initiative as opposed to being carried on transporters like by lorry, rail, by plane or by ship - was only average for a tank of its time. Its engine and transmission were unified with the T-55 tank but it had a slightly worse power to weight ratio compared to the T-55 because it is heavier by a ton. As such, it is reasonable to expect the mobility characteristics of the T-62 to be slightly worse, at least theoretically. However, the T-62 has a better suspension with an increased range of roadwheel travel and a slightly lower ground pressure, so in practice, the T-62 has favourable driving characteristics when driving off-road. Furthermore, the difference in the power to weight ratio was diminished when compared to the T-55A which had a similar weight of 36.5 tons such that the T-62 could surpass the T-55A in cross-country driving speed. The center of gravity of the T-62 remained low, at 960mm from ground level, or 42.7% the total height of the tank up to the turret roof. This is very favourable compared to tanks such as the M60A1, which have a center of gravity 1,384mm from ground level (50.3% of total tank height). However, the actual advantage is somewhat lessened by the fact that the M60A1 hull width - or rather, the width between roadwheels - is much larger. Nevertheless, the proportionately lower center of gravity has benefits in terms of stability when cornering, and helps lighten the roadwheel loading on the opposing ends of the suspension when driving cross-country, as the moment of inertia is lessened. In terms of the roll angle limit for toppling the tank over on its side, the limit of the T-62 is 55 degrees, the limit of the M60A1 is 46 degrees.</div><div>
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As such, the level of tactical mobility achieved by the T-62 was certainly the highest among all available Soviet medium tanks at the time, and it was still quite competitive when placed in the international arena. The maximum attainable speed on a highway is given as 50 km/h, while West German testing of a T-62 conducted in 1974 using a captured T-62 from the Yom Kippur war of 1973 found that its maximum speed was 52.6 km/h. A T-62 technical manual states that the average speed of the tank on a dirt road is 22 to 27 km/h, while the average speed on a paved road is 32 to 35 km/h. These simplified figures are by no means compatible with any available information for contemporary Western tanks due to the simple fact that the testing conditions tend to be different, sometimes vastly so. Only the figures given for the average speed of the T-62 on a paved road can be directly compared.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">In terms of operational and strategic mobility, the T-62 was at the same level as the T-55. Regarding operational mobility, the T-62 was unmatched by foreign tanks due to the high efficiency of its powertrain and the large internal fuel supply available to the tank, which allowed it to cross exceptionally large distances. According to West German testing, the driving range of the T-62 without additional fuel drums on a track with 40% paved roads and 60% off-road trail was 345 km, whereas the Leopard 1 achieved a driving range of 288 km on the same track. With additional fuel drums, the range of the T-62 is calculated to reach 489 km - a full 200 km more than a Leopard 1. Compared with less mobile tanks like the M60A1, Chieftain and AMX-30B, the advantage of the T-62 is even more pronounced.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div><div><div><div>There are two air intake points for the engine. The main intake is the radiator louvres, and the secondary intake is the crew compartment. There is no particular need for a directed air stream to supply the air cleaner with air, because the intake is distributed along the four sides of the air cleaner unit, along the cyclones. Because the air is taken in from the sides of the unit rather than from above, the system is immune to clogging from leaves, twigs, and so on. The sides of the multi-cyclone array are also covered with a wire mesh for additional protection from foreign object ingress. Because of this design, the engine simply draws air from the engine compartment itself, and the radiator louvres simply provide an inlet for air to enter the engine compartment at a sufficient rates to support the engine. This is mainly provided by the draft created by the cooling fan, which draws air via the radiator louvres, and air is drawn into the engine itself due to the mechanisms of natural aspiration. During operation in normal weather conditions, air is supplied via the radiator, with the possibility of additional air from the crew compartment via the ventilation exhaust fan. Alternatively, air is supplied purely via the ventilation exhaust fan from the crew compartment as a basic necessity when the radiator louvres are sealed for a snorkeling operation. </div><div><br /></div><div>During operation in winter conditions, an air seal on the radiator louvre is flipped around to seal the path between the louvres and the air cleaner unit, forcing the engine to draw the heated air that leave the radiator packs instead. Normal operation (summer) is shown in drawing (a) below, and winter operation is shown in drawing (b) below.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-oF3VYTXVJVw/YSYUpezm12I/AAAAAAAAUHY/OlDOm26QVCgLMoP5zv3MZC-X4SiTgPvkgCLcBGAsYHQ/s1088/summer%2Band%2Bwinter.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1088" data-original-width="1000" height="400" src="https://1.bp.blogspot.com/-oF3VYTXVJVw/YSYUpezm12I/AAAAAAAAUHY/OlDOm26QVCgLMoP5zv3MZC-X4SiTgPvkgCLcBGAsYHQ/w368-h400/summer%2Band%2Bwinter.png" width="368" /></a></div><div><br /></div><br />The air supply of the engine is processed by a VTI-4 two-stage air cleaner with automatic dust ejection, created as a continuation of the "multicyclone" air cleaner introduced in the second half of WWII. The VTI-4 was developed at the VNII-100 research institute for medium tanks, with its first use being in the T-54 from 1953 and onwards. It uses a multicyclone first stage to separate the majority of the dust in the ingested air, including the heaviest dust particles, and the oiled mesh second stage filters out the finest dust particles. The result is an exceptionally high air purity level in all operating environments. The work done by VNII-100 on combining the two cleaning stages and optimizing the operating parameters of the VTI series of air cleaners gave the VTI-4 a combination of very low maintenance, high air purity, compactness, and low air resistance. </div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-G1RO_UUlczQ/Vfm4mc41nmI/AAAAAAAADkc/Lo6OepNVpjc/s1600/t-62%2Bengine%2Bair%2Bfilter.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="317" src="https://1.bp.blogspot.com/-G1RO_UUlczQ/Vfm4mc41nmI/AAAAAAAADkc/Lo6OepNVpjc/s400/t-62%2Bengine%2Bair%2Bfilter.png" width="400" /></a><a href="http://1.bp.blogspot.com/-TOLJvGV6HJA/VlAuIl7OhiI/AAAAAAAAEMQ/RwMv_63QMeA/s1600/t-62%2Bengine%2Bair%2Bfilter%2Bopen.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="348" src="https://1.bp.blogspot.com/-TOLJvGV6HJA/VlAuIl7OhiI/AAAAAAAAEMQ/RwMv_63QMeA/s400/t-62%2Bengine%2Bair%2Bfilter%2Bopen.png" width="400" /></a></div></div><div><br /></div><div>A multi-cyclone cleaner is used as the first stage of the air filtration system, functioning as the main filtration unit. It consists of 96 micro-cyclones, with the collected dust falling into an ejection duct where it is carried away by the engine exhaust. Due to the lack of moving parts in cyclone filters, and the use of gas suction from the engine exhaust to continuously extract the collected dust, the cyclone system has very low maintenance demands. Even as a pre-filter, the cyclone system handles the bulk of the filtration workload, providing an air purity of at least 99.4% on its own. The second stage is a fine filtration system comprised of three steel mesh filter cassettes of progressively finer meshes. These cassettes are oil filters, with the meshes being coated with a thin layer of engine oil by soaking before being loaded into the air cleaner unit. After passing through the second filter stage, an air purity of no less than 99.9% is achieved. A dust concentration of 0.1% or less is needed to ensure a long engine lifespan. The dust transmission rate through the VTI-4 is 0.078%, with an airflow rate of 472 liters per second. After passing through the last filter cassette, the main flow of air enters the supercharger of the engine via a large outlet duct, and some air is diverted out via a secondary air hose into the AK-150 air compressor, where it is used to refill the pneumatic reservoirs of the tank.</div><div><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-zvnA_i2Dhik/YSYNFxXz5LI/AAAAAAAAUHI/Lcdt-jPIXtU4jOLAzT3X26CVg947_Yc7ACLcBGAsYHQ/s1215/air%2Bfilter.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="903" data-original-width="1215" height="476" src="https://1.bp.blogspot.com/-zvnA_i2Dhik/YSYNFxXz5LI/AAAAAAAAUHI/Lcdt-jPIXtU4jOLAzT3X26CVg947_Yc7ACLcBGAsYHQ/w640-h476/air%2Bfilter.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The dust collected from the multi-cyclone array is ejected under the air stream of the engine exhaust. The air intake for the dust ejection system is on the engine deck, shown in the two photos below. The photo on the left, courtesy of Alex Chung, shows a closer view of the ejection duct air intake without its mesh cover and the photo on the right, from the <a href="https://www.net-maquettes.com/pictures/t-62/">Net-Maquettes</a> website, shows a better view of where the intake is located on the engine deck.</div><div><br /></div><div style="text-align: center;"><a href="http://1.bp.blogspot.com/-zprLAq2a6aE/Vmflo4rGIkI/AAAAAAAAE2w/NRnUruLIjJE/s1600/alex%2Bchung%2Bt-62%2Bengine%2Bair%2Bintake.jpg"><img border="0" height="265" src="https://1.bp.blogspot.com/-zprLAq2a6aE/Vmflo4rGIkI/AAAAAAAAE2w/NRnUruLIjJE/s400/alex%2Bchung%2Bt-62%2Bengine%2Bair%2Bintake.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-SiAcw9BkVBk/YSh9jmtrv5I/AAAAAAAAUH4/d2nJ1TVs9Ic60M8Xz8S4YW3P-UrNKJW-wCLcBGAsYHQ/s800/48445311972_f5cc2cb52d_c.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://1.bp.blogspot.com/-SiAcw9BkVBk/YSh9jmtrv5I/AAAAAAAAUH4/d2nJ1TVs9Ic60M8Xz8S4YW3P-UrNKJW-wCLcBGAsYHQ/w400-h300/48445311972_f5cc2cb52d_c.jpg" width="400" /></a><br /><br /></div><div><br /></div><div>The VTI-4 air cleaner unit requires cleaning after every 56 hours of driving. Running the tank beyond this number of engine-hours results is permissible, but a gradual decline in engine power may be experienced due to excess inlet pressure and restricted airflow to the engine.</div><div><br /></div></div></div><br />
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<h3>
<span style="font-size: large;">V-55, V-55V</span></h3>
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<a href="http://1.bp.blogspot.com/-EXR7GwiVLaw/VlAqLUwg5VI/AAAAAAAAEME/Wq0OYC15-o0/s1600/v-55a.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="354" src="https://1.bp.blogspot.com/-EXR7GwiVLaw/VlAqLUwg5VI/AAAAAAAAEME/Wq0OYC15-o0/s400/v-55a.jpg" width="400" /></a></div>The V-55V, a 12-cylinder 4-stroke liquid cooled diesel engine, was the primary engine model used in the T-62 throughout its entire production run. It differed from the basic V-55 used in the T-55 only in the use of a 6.5 kW F-6.5 or G-6.5 generator is installed instead of the original 5 kW G-5 generator. The V-55V is a traditional V-12 engine with a displacement of 38.88 liters and weight of 920 kg. The compression ratio is 15, which is typical for an engine of its type. Compared to equivalent engines of its time, namely the Meteor Mk. 4 and AV-1790, both petrol engines, the main downside of the V-55 was that it was a larger displacement diesel engine, which meant that it was naturally inclined to consume more oil. For comparison, while the engine oil consumption rate of the Meteor series in the Centurion is 5.44 liters per 100km, the V-55 does so at a rate of 6-8 liters per 100 km. Nevertheless, maintenance intervals for the T-62 are shorter than foreign counterparts even in regards to oil changes, as the tank carries more engine oil. For instance, oil changes are done every 100 engine-hours, as opposed to 60 engine-hours as on the Centurion series.<br />
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The V-55V engine puts out a maximum power of 580 hp at 2,000 RPM with a maximum torque of 2,354 N.m at an engine speed of 1,200 to 1,250 RPM. It idles at 600 RPM. The idling speed can be controlled with the use of the hand accelerator, and it may be necessary to raise the idling speed when power-hungry devices need to be kept running, such as the weapons stabilizer. With a gross power output of 580 hp, the T-62 has a nominal power to weight ratio of 15.46 hp/ton.</div><div><br /></div><div>After accounting for air intake and exhaust backpressure losses when fitted in a T-55 or T-62, the net power developed by the V-55 engine is around 542 hp, or 462 hp when the cooling system is included. The full curve is shown in the chart below, where:</div><blockquote><div><ol style="text-align: left;"><li>Gross engine power</li><li>Net engine power accounting for losses to intake and exhaust</li><li>Net engine power accounting for losses to intake, exhaust and cooling</li><li>Gross engine torque </li><li>Net engine torque accounting for losses to intake, exhaust and cooling</li></ol></div></blockquote><div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhaQwKKTzrnjuHvfAnhG2u1SG_LsOndUnNZpVvhMdow1com8715fPeYFChvfq8db0TDWHR_L-K8TVxwQeWe4rStkL99V6qRgDBSaTwCN8iXdnp2roHVZbGxNsktAtzGWUGdJmlS-gkIdfi5bgOxixmbUzSzDtYmZM6u8AvZlYDmf6Vbnf_XVyPze2EMBw/s1450/gross%20and%20net%20v-55.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1450" data-original-width="934" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhaQwKKTzrnjuHvfAnhG2u1SG_LsOndUnNZpVvhMdow1com8715fPeYFChvfq8db0TDWHR_L-K8TVxwQeWe4rStkL99V6qRgDBSaTwCN8iXdnp2roHVZbGxNsktAtzGWUGdJmlS-gkIdfi5bgOxixmbUzSzDtYmZM6u8AvZlYDmf6Vbnf_XVyPze2EMBw/w412-h640/gross%20and%20net%20v-55.png" width="412" /></a></div><div><br /></div><div><br /></div><div>To quantify the engine dynamics, two metrics are used - engine flexibility (adaptability) and engine elasticity. Engine flexibility is the difference between the peak torque and the torque at the rated speed, which determines the ability of the engine to absorb overloads when driven at the rated speed, while engine elasticity is the size of the powerband. Needless to say, the wider the powerband, the better. The engine elasticity coefficient of the V-55V is 1.1558, which is good. When expressed as a percentage, it is known as the torque backup, torque reserve or torque rise. In this case it is 15.58%. The engine elasticity coefficient is 0.6, which is also good, as this means that the powerband occupies 40% of the operating engine speed range. This performance level is likely due to the fact that the engine is naturally aspirated. </div><div><br /></div><div>For comparison, the Meteor Mk. 4B engine used in the Centurion series, also naturally aspirated, generates a maximum torque of 2,101 Nm at 1,600 RPM, falling to 1,815 Nm at the rated speed of 2,550 RPM. The engine flexibility coefficient is 1.1575, and so the torque reserve is 15.75%. Its elasticity coefficient is 0.627. The torque output of the Meteor is considerably lower than the V-55V, which has some ramifications in terms of low-end power output, though it has a higher peak power owing to its higher rated engine speed of 2,550 RPM.</div><div><br /></div><div>Meanwhile, the supercharged AVDS-1790-2A engine used in the M60 series, M103A2 and the M48A3 (and following M48 models) has a maximum torque of 2,318 Nm at 1,800 RPM and a torque of 2,225 Nm at 2,400 RPM. This meant that the engine has a very poor flexibility coefficient of 1.04, and a poor elasticity coefficient of 0.75 (powerband occupies only 25% of the operating engine speed range). It does, however, have a much higher peak power of 750 hp - an advantage of 29.3% compared to the V-55 series. At the same time, the discrepancy in power is lessened by the higher losses experienced by the AVDS-1790-2A. With a net power of 643 hp due to intake and exhaust losses, and an additional loss of 107-136 hp to the cooling system, the actual net power available at the transmission of an M48 or an M60 is only 507 hp or 536 hp respectively. As such, the actual advantage in power would only be 9.7% for an M48A3, and 16% for an M60A1.</div><div><br /></div><div>With that in mind, the power to weight ratio of an M48A3 when calculated using the net engine power and combat weight is actually 10.4 hp/ton, or 11.3 hp/ton in the case of the M60A1. For the T-62, it is 12.3 hp/ton. This is in contrast to the gross power to weight ratios, which otherwise indicate that the M48A3 (15.46 hp/ton) and M60 (15.75 hp/ton) surpass the T-62 slightly, where a T-62 weighing 37.5 tons when combat loaded would have a nominal power to weight ratio of 15.46 hp/ton.</div><div><br /></div><div>Taking into consideration the large difference in tank weights, the T-62 has a proportionately more suitable tank engine, owing to its good dynamics, high fuel economy and adequate power output.</div><div><br /></div><div>Like the ancestral V-2 engine developed during the 1930's, the V-55V has a bore diameter of 150mm and a piston stroke length of 180mm. It has a specific fuel consumption of 180 g/hp.h, which is marginally worse than the V-54 engine (174 g/hp.h) but remains reasonable for an engine of its size. The average fuel consumption per 100 km of travel is 190-210 liters on paved roads, and 300-330 liters on dirt roads. This is confirmed by West German testing conducted in 1974 using a captured T-62 from the Yom Kippur war of 1973. According to the German results, the T-62 consumes 165 liters per 100 km on a paved road and 339 liters per 100 km when traveling on a "field", which appears to be roughly equivalent to what the Russians considered a "dirt road".<br />
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<a href="http://3.bp.blogspot.com/-VMIJMNsko5U/VmQaRNJBRhI/AAAAAAAAEsk/BFF7p3zjH4E/s1600/v-55A%2Bengine%2Bperformance.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="320" src="https://3.bp.blogspot.com/-VMIJMNsko5U/VmQaRNJBRhI/AAAAAAAAEsk/BFF7p3zjH4E/s320/v-55A%2Bengine%2Bperformance.png" width="271" /></a></div>
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When compared by the available net engine power rather than gross power, the T-62 can be placed firmly in the category of contemporary medium tanks like the M48 Patton and the Centurion, but slightly better than the then-brand new Chieftain Mk. 3, and only slightly better than the M60A1. The T-62 could attain a top speed of 50 km/h on paved roads, and the average speed when going cross country was around half of that at 25 km/h, which was more or less the same as the M60A1. The nominal reverse speed was 6.8 km/h, as calculated from the engine speed and the gearing ratios. The de facto reverse speed was effectively 7 km/h. This was an acceptable speed even by Western standards. For comparison, the M60A1 had a reverse speed of 8 km/h.<br />
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According to the Polish study "<i style="font-weight: normal;">Propozycja Poprawy Manewrowości Czołgu Twardy</i>" <i style="font-weight: normal;">(Proposal to Improve Maneuverability of the "Twardy" Tank</i>) from the University of Technology in Szczecin, the T-54 requires 18 seconds to reach 32 km/h on a paved road. As the T-62 uses the same tracks and transmission but has a marginally higher power to weight ratio than a T-54 along with a better suspension, the acceleration characteristics should be improved by some amount. According to West German testing from 1974, the Leopard 1 reaches 40 km/h in just 14.2 seconds whereas the T-62 takes 22.75 seconds to reach 40 km/h. Based on the West German test data, the time for a T-62 to accelerate to 32 km/h should be around 16 seconds. Paul-Werner Krapke, chief designer of the Leopard 2, states in his book "<i style="font-weight: normal;">Leopard 2: Sein Werden und seine Leistung</i>" that the Leopard 1 accelerates to 32 km/h in 10 seconds on a paved street. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">For comparison, according to Soviet tests and data sheets from various U.S sources, the M60A1 with the T97E2 track reaches 32 km/h in 15 seconds and reaches 40 km/h in 25 seconds. The M60A3 reaches 32 km/h in 16 seconds, presumably also with T97E2 tracks. With the heavier and more durable T142 tracks, which <a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a141935.pdf">began replacing the T97E2 in 1974</a>, the acceleration to 32 km/h and 40 km/h worsened to 17.5 seconds and 30 seconds respectively. When directly compared to an M60 series tank according to the acceleration times to 40 km/h, the T-62 has better acceleration by a small margin, depending on the tracks fitted to the M60 series tank. This is congruent with the advantage in the net power to weight ratio held by the T-62, before accounting for power losses in the transmission. With the installation of RMSh tracks, the advantage of the T-62 is likely to further increase. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The slowest tank in any comparison would be the Chieftain. According to a 1983 Soviet report on the Chieftain Mk. 5R (a trophy from the Iran-Iraq war), the Chieftain takes 19 seconds to accelerate to 32 km/h, which is practically the same as a basic T-54, but it requires a very long time of 34-35 seconds to reach a speed of 40 km/h. </div><div style="font-weight: normal;"><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-y6GucHaQ3To/XUKqxsnGg2I/AAAAAAAAOuM/D1KnfUDB2-cBy6hIlLxCNvuWC_VwOleRACLcBGAs/s1600/chieftain%2Bacceleration.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="345" data-original-width="410" height="335" src="https://1.bp.blogspot.com/-y6GucHaQ3To/XUKqxsnGg2I/AAAAAAAAOuM/D1KnfUDB2-cBy6hIlLxCNvuWC_VwOleRACLcBGAs/s400/chieftain%2Bacceleration.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">1 - acceleration 2 - distance traveled</td></tr>
</tbody></table>
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<br />Compared with the Chieftain Mk. 5, the T-62 is faster over short distances, sustains its higher acceleration over long distances and can achieve a higher top speed, thus giving it a clear advantage. The T-62 would come out looking even better if it were compared to the Chieftain Mk. 3 as that had a less powerful engine than the Mk. 5 variants. Indeed, the Chieftain was rejected in favour of the Leopard 1 by the Canadians due to its excessively slow speed and poor mobility <a href="http://www.journal.forces.gc.ca/vol16/no4/page16-eng.asp">according to the Canadian Military Journal</a>, the official professional journal of the Canadian Armed Forces and the Department of National Defence.<br />
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However, the T-62 is still second best compared to the Leopard 1 by a wide margin. The gap between the Leopard 1 and the T-62 is hardly surprising given that the T-62 retained much of the mobility characteristics of the T-54 - a classical medium tank design from late WWII. The main factor in this large difference is the much more powerful engine MB 838 engine (830 hp vs 580 hp), more than powerful enough to offset the fact that the Leopard 1 is actually somewhat heavier than the T-62 (41 tons vs 37 tons) due to its large size.<br />
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One positive aspect of the T-62 design is that its rolling resistance is good when compared to the Leopard 1, which begets a high fuel efficiency. German empirical testing found that the rolling resistance of the T-62 was 237 N/ton whereas the rolling resistance of the Leopard 1 was 313 N/ton. The rolling resistance coefficient of the T-62 at 20 km/h is 0.0245, as compared to the M48A2 which has a coefficient of 0.0397, or the Chieftain which has 0.046. The closest counterpart is the Leopard 1, which has a rolling resistance coefficient of 0.0264, illustrating at least one benefit to the large-diameter roadwheels and lack of return rollers inherited from the T-54 suspension. </div><div style="font-weight: normal;">
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The T-62 could traverse difficult terrain as well as any other tank.
It could climb vertical obstacles up to 0.8 meters tall, climb a 32° slope and drive on a side slope of 30°. With the mudguards removed, the tank can climb a taller vertical obstacle. The tank can cross trenches
2.85 meters wide at low speeds, but it is possible to jump the tank over wider trenches provided that it travels fast enough.<br />
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The engine could be started either electrically, pneumatically or by a combination of air pressure and electricity in extremely cold weather, as mentioned before. Electric starting is done with the ST-16M electric starter and the air for pneumatic starting is supplied by the compressed air tanks. When starting the engine pneumatically, the two 5-liter air tanks mounted in the driver's station inject air into the cylinders of the engine, forcing the pistons into motion. This method is somewhat harsh on the engine, but it is dependable. Starting the engine in the summer is usually done electrically, but in the wintertime, the electric starting system may not be reliable due to piston lockup, so having the pneumatic option gives the tank more flexibility. In the harshest weather conditions, with the most poorly maintained tanks, starting the engine may require a combination of both methods simultaneously. Of course, the engine and engine oil must be preheated during cold weather conditions.<br />
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Like in the T-55, the compressed air tanks are refilled during normal driving by an AK-150SV air compressor, powered by the engine. AK-150 is a two-stage V-shaped reciprocating compressor. It runs on the power supplied by a power takeoff drive from the engine and uses pistons (operating essentially like a reverse order piston engine) to compress air drawn from the engine compartment, which it then routes directly to the air tanks. It is automatically stopped by a regulator valve when the air tanks are filled to their maximum safe capacity. It takes about an hour to refill both air tanks using the AK-150SV air compressor if the tanks are empty.</div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9PWzhR0Yc1Y/YRZMURbvVrI/AAAAAAAAUFU/EDmfg1ZtXmMBzZlGfgnfJIgcHEo5xBciQCLcBGAsYHQ/s1741/pneumatic%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1327" data-original-width="1741" height="488" src="https://1.bp.blogspot.com/-9PWzhR0Yc1Y/YRZMURbvVrI/AAAAAAAAUFU/EDmfg1ZtXmMBzZlGfgnfJIgcHEo5xBciQCLcBGAsYHQ/w640-h488/pneumatic%2Bsystem.png" width="640" /></a></div><div><br />
<br />On the V-55V, the F-6.5 generator is attached to the engine and is supplied with power from the driveshaft by a hydraulic fluid coupling. The generator produces 6.5 kW of electricity for the tank's electrical system. This was replaced with the G-6.5 generator at some point. The generator has a forced air cooling system. The impellers of the cooling system are attached to the rotor shaft of the generator. Air for the cooling system is sourced from the crew compartment via a duct connecting the generator casing to an intake on the engine compartment firewall, but in case of a nuclear attack, the PAZ system automatically switches it to the engine compartment intake. This increases the dustiness of the air ingested by the generator, but preserves the overpressure in the crew compartment and seals it from radioactive particles in the engine compartment. The generator is shown in the image below. The front end (input shaft) where air inters the generator is on the right, and air exits out the left. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-gRED9YTMUEY/YWtNmQX1YkI/AAAAAAAAUR8/JsKMhASnQbYR8JABZV1-kVgOHyxEG5PJACLcBGAsYHQ/s2048/g-6.5.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1301" data-original-width="2048" height="254" src="https://1.bp.blogspot.com/-gRED9YTMUEY/YWtNmQX1YkI/AAAAAAAAUR8/JsKMhASnQbYR8JABZV1-kVgOHyxEG5PJACLcBGAsYHQ/w400-h254/g-6.5.png" width="400" /></a></div><br /><div>On the T-62, the engine exhaust manifolds lead directly to the exhaust port, with no muffler or any other sound damping device whatsoever to control sound levels other than the S-shaped curves of the exhaust ducting. On one hand, the near-total absence of flow restriction completely eliminates any exhaust backpressure which improves the power output of the engine, but on the other hand, the tank is loud.</div><div><br /></div><div>
<h3>
<span style="font-size: large;">V-55U</span></h3>
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This engine was fitted to the T-62M. Thanks to a more optimized direct fuel injection system, it had a slightly increased output of 620 hp to compensate for the added weight of "Brow" armour on the T-62M, but was identical to the V-55V in every other way. The small increase in power does not adequately balance out the gain in weight, so the T-62M has noticeably poorer acceleration.<br />
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<h3>
<span style="font-size: large;">V-46-5M</span></h3>
<div style="font-weight: normal;">
<span style="font-size: large;"><br /></span></div>
<div class="separator" style="clear: both; font-weight: normal; text-align: center;">
<a href="http://1.bp.blogspot.com/-hBItP-Iq7ZM/Vmk1lFwe6hI/AAAAAAAAE8E/GhcANGrWL7Y/s1600/v_46_5m.gif" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-hBItP-Iq7ZM/Vmk1lFwe6hI/AAAAAAAAE8E/GhcANGrWL7Y/s1600/v_46_5m.gif" /></a></div>
The V-46-5M engine was derived from the V-46-6 engine developed for the T-72 and was mechanically identical except for the various modifications made to the driveshaft, the exhaust manifolds and the air intake system. The installation of the V-46-5M was made possible by the fact that it has the same size as the V-55 series of engines, which is thanks to the shared lineage of the two engines, but the increased length posed an issue as it interfered with the air filtration system.</div><br /><div style="font-weight: normal;"><br />
<br /><br /><br /><br />Due to the increased length of the V-46-5M engine, chiefly due to its supercharger, the engine compartment was no longer wide enough to accommodate both the engine and the air filtration system of its air intake, side by side. This necessitated the creation of an external armoured sponson compartment on the fender, similar to the external armoured top-loading air cleaner unit on M60 series tanks, and a modified filter to fit into the new layout that this created. The first stage cyclone filter is installed in the sponson, and the second stage cassettes are installed in a horizontal stack instead of a vertical stack. Functionally, the air filter is identical to the original VTI-4 filter, differing only in the ducting layout. The roof air intake points remained the same, but air entering the engine compartment now had to flow into the sponson compartment before being routed through the filter meshes. <br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-JlMRSU-RRsc/YSYJA8CHoxI/AAAAAAAAUHA/-XKvyf4rd0ollLEUrfB03gIWtxvdqHHJwCLcBGAsYHQ/s2715/air%2Bfiltration%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1158" data-original-width="2715" height="272" src="https://1.bp.blogspot.com/-JlMRSU-RRsc/YSYJA8CHoxI/AAAAAAAAUHA/-XKvyf4rd0ollLEUrfB03gIWtxvdqHHJwCLcBGAsYHQ/w640-h272/air%2Bfiltration%2Bsystem.png" width="640" /></a></div>
<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-pGbhSePSNdk/YSh-Szmw8AI/AAAAAAAAUIE/kCBp-Vuw9co0lpj-hMF1Ww6yx29-7y82gCLcBGAsYHQ/s2048/t-62m-1%2Bengine%2Bair%2Bintake%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1097" data-original-width="2048" height="342" src="https://1.bp.blogspot.com/-pGbhSePSNdk/YSh-Szmw8AI/AAAAAAAAUIE/kCBp-Vuw9co0lpj-hMF1Ww6yx29-7y82gCLcBGAsYHQ/w640-h342/t-62m-1%2Bengine%2Bair%2Bintake%2Bsystem.png" width="640" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The sponson air filter compartment can be seen in the photo below. The main engine air intake was also modified from its original position on the edge of the side of the engine access panel to the edge between the engine access panel and the fighting compartment roof.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-cwib6tX1FDM/YSYR5zKn_mI/AAAAAAAAUHQ/uYN4stce1IMKJwbwSLNsuMi3BVY-2xgDgCLcBGAsYHQ/s960/t-62m-1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="640" data-original-width="960" height="266" src="https://1.bp.blogspot.com/-cwib6tX1FDM/YSYR5zKn_mI/AAAAAAAAUHQ/uYN4stce1IMKJwbwSLNsuMi3BVY-2xgDgCLcBGAsYHQ/w400-h266/t-62m-1.jpg" width="400" /></a></div><div style="font-weight: normal;"><br /></div><br />Thus, the conversion of a T-62 to the T-62M-1 standard required more work than a basic T-62M. The bore diameter and piston stroke length are also identical, but the running components were reinforced to deal with the higher power output. The V-46-5M was de-tuned from the V-46-6 to generate 690 hp at 2,000 RPM instead of the normal 780 hp when configured for the T-72. Keeping in mind the fact that the appliqué metal-polymer armour increased the combat weight of the T-62M to 42 tons which is very close to a T-72A, the installation of the V-46-5M gave the T-62M-1 a power to weight ratio of only 16.4 hp/ton - significantly less than any T-72 variant. The sole advantage is that the engine has a longer lifespan and has better fuel economy. The maximum torque output of the engine is 2,844 N.m at an engine speed of 1,200 to 1,400 RPM.<br /><br />The V-46-5M is equipped with the G-6.5 generator .</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div><h3 style="text-align: left;"><span style="font-size: large;">TRANSMISSION</span></h3><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5oVqP4T6PuMCDzfQ3T27T-Hqq4kJfRvYrlZPN1xEiqKAbmgCJMBJce6iX5ER9nH4nLbhMgg2Bpl2ryzOPQByDOcrWLzxRz4AFcvzgwqBGgSEaHZgTnMSk2UxtNQWdUSsjFrKYwNCxZeyKTRtwB3jI_4EVNCAebw-hrPFQqXradTSFyh8YfRHo81WUcw/s4228/transmission.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3148" data-original-width="4228" height="476" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5oVqP4T6PuMCDzfQ3T27T-Hqq4kJfRvYrlZPN1xEiqKAbmgCJMBJce6iX5ER9nH4nLbhMgg2Bpl2ryzOPQByDOcrWLzxRz4AFcvzgwqBGgSEaHZgTnMSk2UxtNQWdUSsjFrKYwNCxZeyKTRtwB3jI_4EVNCAebw-hrPFQqXradTSFyh8YfRHo81WUcw/w640-h476/transmission.png" width="640" /></a></div><div><br /></div><div>The transmission consists of a synchromesh gearbox connected to two planetary steering units, which are drum-shaped units with an integral clutch. Like in the T-54 and T-55, the clutch is on the gearbox rather than on the engine as this was a more volumetrically efficient layout, given the need to install the air cleaner next to the engine without exceeding the width of the engine compartment. Unlike the T-34, which had a direct connection between the engine and the gearbox via the clutch, the T-62 has an additional gearbox between the two, placed underneath the air cleaner. This is the intermediate gearbox, which was necessary due to the transverse engine layout. It has a step-up gearing ratio of 0.7 to increase the input speed to the gearboxes. According to M.V. Pavlov and I.V. Pavlov in "<i style="font-weight: normal;">Отечественные Бронированные Машины 1945–1965 </i><i>гг</i><i style="font-weight: normal;">.</i>", this was to reduce the size of the transmission units arranged sequentially behind it. A number of additional benefits were also obtained from this design solution, which will be discussedlater. Cooling of the intermediate gearbox is done by air, using the flow of air entering the engine compartment via the engine deck intake. To that end, the casing of the intermediate gearbox was made of aluminum alloy and vertically ribbed to maximize the cooling efficiency from the flow of air. Air enters through the intake from the suction of the large cooling fan and the engine, and some of it enters the air cleaner via the rarefaction of the engine pistons during the intake stroke, while the remainder flows past the intermediate gearbox and to the rear through the cooling fan.</div><div><br /></div><div style="text-align: center;"><img border="0" data-original-height="1147" data-original-width="1334" height="344" src="https://1.bp.blogspot.com/-uFGvMKDCrKs/YU168NmrdqI/AAAAAAAAUPA/uOHpZYMrD6gEwMOYAP8lqpIJ6YoZr5h0ACLcBGAsYHQ/w400-h344/alternator%2Bforced%2Bair%2Bcooling.png" style="color: #0000ee;" width="400" /></div><div><br /></div><div>Arriving at the gearbox after passing through the intermediate gearbox, the torque from the engine is reduced by 0.7 times. This made it possible to use smaller gears and power shafts in the gearbox, which in turn reduces the overall size of the unit, and by extension, its weight. Lessening the torque flowing in the gearbox has a positive effect on the durability of the gears, namely the gear teeth, and the reduction of the gear sizes also translates to reduced rotating mass, not just in the gearbox itself, but also in the steering units and in the final drives. This reduces the rotating inertia within the powertrain and improves the acceleration characteristics of the tank.</div><div><br /></div><div>The gearbox and the mechanical linkages linking it to the gear shift can be seen in the picture below, taken from the T-62 technical manual. A power take-off unit is mounted atop the gearbox, and provides the cooling fan with a step-up ratio of 0.952 and the air compressor with a step-up ratio of 0.769. An interesting detail of the power take-off unit is that the fan drive is connected via a spiral bevel gear - the only gear with a helical cut in the entire drivetrain. This was presumably done for strength reasons given the limited size of the power take-off. To ensure that the air compressor and cooling fan are continuously powered at a fixed rate regardless of the gear setting of the transmission and regardless of whether the clutch is engaged or not, the power shaft from the intermediate power transfer mechanism is actually two power shafts, one nested within the other. The smaller inner shaft is connected to the power take-off unit, while the outer shaft is connected to the gearbox itself via the clutch. </div><div style="font-weight: normal;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-SL2smjWlXUQ/WZMglYvaZ5I/AAAAAAAAI-g/BqAufd8-5rIqWTFp2WRm9CcRSStH96xBACLcBGAs/s1600/t-62%2Btransmission.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1060" data-original-width="1600" height="422" src="https://1.bp.blogspot.com/-SL2smjWlXUQ/WZMglYvaZ5I/AAAAAAAAI-g/BqAufd8-5rIqWTFp2WRm9CcRSStH96xBACLcBGAs/s640/t-62%2Btransmission.png" width="640" /></a></div></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The clutch is a multi-disc dry friction clutch of a straightforward design. It contains 19 friction elements in total, with 10 driven discs and 9 friction discs. They are held together by a pressure plate sprung with 18 coil springs, which was an orthodox design at the time, as diaphragm springs were not used in automobile clutches until much later. All of the discs are made from steel and no friction pads or liners are present. This by itself was not a serious issue, as steel-on-steel clutches can have a long service life, but this type of clutch poorly tolerates disc slip. As such, clutch life depends on skillful handling of gear shifts. To prolong clutch life, double-declutching is recommended, even though it is not strictly necessary for the normal operation of the tank given that the gearbox features synchronizers.</div><br /><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">Both the gearbox and the final drives were borrowed directly from the T-55. The gearbox has five forward gears and one reverse, with splash lubrication for all gears. It is a conventional two-shaft manual constant mesh gearbox with synchronization on the 2nd to 5th gears. The 1st gear and the reverse gear are not synchronized. The gear selectors were made in pairs, with the 1st and reverse gears sharing one selector, the 2nd and 3rd gears sharing a synchronized selector, and the 4th and 5th gears sharing another synchronized selector.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The lack of a synchromesh system on the 1st and reverse gear was typical of old synchromesh gearboxes but it was not a downside because the driver only engages the 1st or reverse gears while the tank is motionless, and when the vehicle is motionless, synchronization between the engine speed and the transmission speed is not necessary. The main issue is that shifting from 1st to 2nd gear is harder and requires more skill, but this can be avoided if the terrain is hard enough that the tank can start moving from a standstill in 2nd gear. Moreover, most of the driving time in medium tanks was spent in 3rd gear during both summer and winter conditions, on dirt roads and off-road. For this reason, the T-62 gearbox had a reinforced 3rd gear. According to the paper "<i>Из Опыта Совершенствования Основных Танков В Ходе Серийного Производства</i>" by M.V. Berkhovetskiy and V.V. Polikarpov, the power take-off mechanism for the cooling fan and air compressor was reinforced, and the 3rd gear of the gearbox was strengthened on the T-62.</div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-luHXDF_KQVA/YWtQONXgTiI/AAAAAAAAUSU/gYgGFD4BfVkc0AJ_J3UR_HRom9tVuPo6gCLcBGAsYHQ/s2048/gearbox.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1422" data-original-width="2048" height="444" src="https://1.bp.blogspot.com/-luHXDF_KQVA/YWtQONXgTiI/AAAAAAAAUSU/gYgGFD4BfVkc0AJ_J3UR_HRom9tVuPo6gCLcBGAsYHQ/w640-h444/gearbox.png" width="640" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div>Splash lubrication was used. Steel synchronizer rings are present on the 2nd, 3rd, 4th and 5th gears. Prior to the T-62, bronze synchronizer rings were used, as was the standard for automobiles along with brass rings. However, the conversion was made to steel by the time the T-62 was introduced, presumably due to wear issues. The image below shows one of the couplings in the gearbox and the hinged joint with which it is connected to the control lever protruding on top of the gearbox. When the gear shift is pushed into position, the control rods linking the gear shifter to the gearbox will either push or pulls on the control lever to force the coupling into position, joining one of the gears on the third power shaft (driven shaft) with the second power shaft (intermediate shaft). In the particular example shown below, the coupling is paired with a synchronizer, consisting of a synchronizer body (1) and a synchronizer ring (3). </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xTH6Yfy2_AU/YWtjVZ6qRKI/AAAAAAAAUSc/R1ImEYVBln8dHRIX3vySQWck_kTHxqGSACLcBGAsYHQ/s2048/coupling%2Bsleeve.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1412" height="400" src="https://1.bp.blogspot.com/-xTH6Yfy2_AU/YWtjVZ6qRKI/AAAAAAAAUSc/R1ImEYVBln8dHRIX3vySQWck_kTHxqGSACLcBGAsYHQ/w276-h400/coupling%2Bsleeve.png" width="276" /></a></div><div><br /></div><div>By the time the T-62 was introduced into service, the synchronizers in the gearbox inherited from the T-55 had been improved to have a hardness of no less than 54 HRC to withstand wear and thereby extend their service life, which is a particularly important consideration for a tank. Steel synchronizer rings are sometimes used for high-performance transmissions for these reasons instead of brass or bronze, which, as a rule, are used in light passenger transports. To prolong the life of both the gearbox and the clutch, it is recommended to practice double declutching when driving the T-62.</div><div><br /></div><div>The diagram below shows the power flow of the gearbox in various gears.</div><div style="font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-S6qJbw7V2Ek/YWtmA06XupI/AAAAAAAAUSk/jCCXlKMbZ3UcpUa-Ik2y6__zVfRCA10NQCLcBGAsYHQ/s2048/gears.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1480" data-original-width="2048" height="462" src="https://1.bp.blogspot.com/-S6qJbw7V2Ek/YWtmA06XupI/AAAAAAAAUSk/jCCXlKMbZ3UcpUa-Ik2y6__zVfRCA10NQCLcBGAsYHQ/w640-h462/gears.png" width="640" /></a></div><div><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The following table lists the gear ratios in each gear, and the overall gearing ratio including the final drives.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><table border="1"><tbody><tr><td style="text-align: center;"><b> Gear </b></td><td style="text-align: center;"><b>Gear ratio</b></td><td style="text-align: center;"><b>Overall gear ratio</b></td></tr><tr><td style="text-align: center;">1</td><td style="text-align: center;"><span style="font-size: small;">6.0</span></td><td style="text-align: center;"><span style="font-size: small;">28.17</span></td></tr><tr><td style="text-align: center;">2</td><td style="text-align: center;"><span style="font-size: small;">2.8</span></td><td style="text-align: center;"><span style="font-size: small;">13.15</span></td></tr><tr><td style="text-align: center;">3</td><td style="text-align: center;"><span style="font-size: small;">2.0</span></td><td style="text-align: center;">9.39</td></tr><tr><td style="text-align: center;">4</td><td style="text-align: center;">1.43</td><td style="text-align: center;">6.71</td></tr><tr><td style="text-align: center;">5</td><td style="text-align: center;">0.9</td><td style="text-align: center;">4.23</td></tr><tr><td style="text-align: center;">R</td><td style="text-align: center;"><span style="font-size: small;">6.0</span></td><td style="text-align: center;"><span style="font-size: small;">28.17</span></td></tr></tbody></table></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The overall gear ratio is quite modest, which is indicative of the good power to weight ratio of the tank. For comparison, the transmission of the Centurion Mk. 5 had an overall gearing ratio ranging from 86.99 in 1st gear to 10.04 in 5th gear (top gear). Its vastly more aggressive gearing ratio was needed to obtain sufficient torque multiplication to propel the tank, which was not only heavier, but experienced higher rolling resistances due to its suspension design. This resulted in a much lower top speed than the T-62, despite the Meteor Mk. 4 engine of the Centurion having a naturally higher rated engine speed of 2,550 RPM. At the rated engine speed, the Centurion was only capable of reaching 34.6 km/h. </div><div style="font-weight: normal;"><br /></div><div>In contrast to this, the speed of the T-62 for each gear at an engine speed of 1,800 RPM (according to the manual) and at 2,000 RPM (rated engine speed) is as follows:<br /><br /><br /><div style="font-weight: normal;"><table border="1"><tbody><tr><td style="text-align: center;"><b> Gear </b></td><td style="text-align: center;"><b>Tank speed at 1,800 RPM (km/h)</b></td><td style="text-align: center;"><b>Tank speed at 2,000 RPM (km/h)</b></td></tr><tr><td style="text-align: center;">1</td><td style="text-align: center;"><span style="font-size: small;">6.85</span></td><td style="text-align: center;"><span style="font-size: small;">7.61</span></td></tr><tr><td style="text-align: center;">2</td><td style="text-align: center;">14.66</td><td style="text-align: center;">16.31</td></tr><tr><td style="text-align: center;">3</td><td style="text-align: center;">20.21</td><td style="text-align: center;">22.84</td></tr><tr><td style="text-align: center;">4</td><td style="text-align: center;">28.99</td><td style="text-align: center;">31.94</td></tr><tr><td style="text-align: center;">5</td><td style="text-align: center;">45.48</td><td style="text-align: center;">50.75</td></tr><tr><td style="text-align: center;">R</td><td style="text-align: center;"><span style="font-size: small;">6.85</span></td><td style="text-align: center;"><span style="font-size: small;">7.61</span></td></tr></tbody></table></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">At an engine speed of 2,200 RPM, which is the maximum speed of the engine, the tank may reach an absolute top speed of 55.83 km/h in 5th gear.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">From the gear ratios available, it can be seen that the spacing of each gear was calculated so that when upshifting at a speed of 2,000 RPM from the 2nd gear to the 3rd gear, and from the 3rd gear to the 4th gear, the engine will not fall below a speed of 1,400 RPM. Given that the engine develops its peak torque at 1,200 RPM, this means that when accelerating within these gears, the gearbox ensures that the engine is working well within its powerband. The two exceptions are when shifting from the 1st gear to the 2nd gear, and when shifting from the 4th gear to the 5th gear, where the engine speed will drop significantly to 900-950 RPM and 1,260 RPM respectively. If maximum acceleration performance from a standstill is desired, it would be best to avoid the 1st gear and start in 2nd gear, with the help of the torque multiplication of the steering drives to start moving. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><div>The gearbox connects to the final drives, which have a gear ratio of 6.706. The final drives on each side of the hull are the same as on the T-55, and are also interchangeable with T-54 final drives. It has a two-stage compound gear design, with a spur gear pair to perform the first reduction, and a planetary gear set coaxial to the drive sprocket to perform the second reduction. The use of a high gear ratio of 6.706 is complementary with the use of spur gears in the final drives, as opposed to herringbone gears or a planetary gear set. This is because it allows the forces acting on the gear teeth to be minimized, as the torque flowing into the final drive from the engine was minimally multiplied by the powertrain, thanks to the overdrive gearing of the intermediate power transfer mechanism and the low ratios of the gearbox itself. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiYdqDGndpagNCiVCwIuLDIL9UW2G-5sKtG-KLy5g24Lp9N3okDO0hWtx9GUglc60xMovyeHw2udzl8dcO2LecTJyU3lwo59y9OjBeSjADS64KPm0T8MnHIL00_9PGZH2oeyC0ZSaAgh9ls2Jli-wTdjrnbWC2H3i7f2lorZ9s2rh7g9jbku-z6b3obhQ/s4265/final%20drive.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3581" data-original-width="4265" height="336" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiYdqDGndpagNCiVCwIuLDIL9UW2G-5sKtG-KLy5g24Lp9N3okDO0hWtx9GUglc60xMovyeHw2udzl8dcO2LecTJyU3lwo59y9OjBeSjADS64KPm0T8MnHIL00_9PGZH2oeyC0ZSaAgh9ls2Jli-wTdjrnbWC2H3i7f2lorZ9s2rh7g9jbku-z6b3obhQ/w400-h336/final%20drive.png" width="400" /></a></div><div><br /></div><div><br /></div><div>In fact, the torque flowing through the T-62 final drives can be multiplied by a factor of just 4.2 at the most, when the gearbox is in 1st gear. This design concept was also applied in tanks such as the Centurion (Mk. 3 and onward) and Chieftain, both of which also used simple spur gears in their final drives and had high final drive ratios. Conversely, tanks like the Sherman series used a much smaller final drive ratio of 2.48 but had high gearbox and differential gearing ratios, which meant that the torque flowing through its final drives could be multiplied by a factor of up to 26.6868 in 1st gear. This necessitated the use of very large herringbone gears to withstand the stress, adding complexity, bulkiness, and rotating mass to the powertrain.</div></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><div>Like the T-55, the clutch in the T-62 is mechanically actuated, with the additional feature of a hydropneumatic system that is operated by the clutch pedal. The system is connected to the pneumatic network of the built-in AK-150SV air compressor mounted to the gearbox, using compressed air to drive a hydraulic actuator which engages and disengages the clutch pack. The hydropneumatic system is turned on manually by turning on an EK-48 electro-pneumatic valve when the tank is already in motion in the 2nd gear or higher. When setting the tank in motion by either starting from the 2nd gear or when shifting up from the 1st gear, the clutch pedal is only assisted by a spring. Without the spring assist, the effort required on the clutch pedal is 55 kgf. With the hydropneumatic system activated, the driver only has to push the clutch pedal a short distance until an electric switch on the pedal hinge bar is closed. This sends an electric signal to the EK-48 electro-pneumatic valve, opening the valve and allowing pressurized air to flow into the hydropneumatic booster servo. The hydraulic piston of the servo, acting on the clutch pedal hinge bar, pushes the clutch pedal the rest of the way and operates the clutch, effectively removing almost all effort needed on the driver's part to depress the clutch pedal. The image on the left shows the overall scheme of the clutch actuating mechanism and the hydropneumatic mechanism. The button (6) is the switch that triggers the EK-48 valve, and the pedal operates the switch via the spring-loaded mechanism surrounding the button. The image on the right below shows the basic spring mechanism that reduces driver effort on the clutch pedal and returns the clutch pedal to its position when force is released.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-SGLe0Tyq9FM/YCwWoviDPWI/AAAAAAAASuk/lZBkS0GvPg8bA_4GHu1rze--5KSxlZO_gCLcBGAsYHQ/s2043/hydropneumatic%2Bclutch%2Bassist.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="983" data-original-width="2043" height="193" src="https://1.bp.blogspot.com/-SGLe0Tyq9FM/YCwWoviDPWI/AAAAAAAASuk/lZBkS0GvPg8bA_4GHu1rze--5KSxlZO_gCLcBGAsYHQ/w400-h193/hydropneumatic%2Bclutch%2Bassist.png" width="400" /></a><a href="https://1.bp.blogspot.com/-tmYNEmBOjhY/YCwWoqGm4dI/AAAAAAAASuc/_8lImQ8Xb_sj8LS3xJJXe6l7u69sGcbZACLcBGAsYHQ/s1370/servo%2Bassist%2Bmechanism%2Bfor%2Bclutch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="604" data-original-width="1370" height="176" src="https://1.bp.blogspot.com/-tmYNEmBOjhY/YCwWoqGm4dI/AAAAAAAASuc/_8lImQ8Xb_sj8LS3xJJXe6l7u69sGcbZACLcBGAsYHQ/w400-h176/servo%2Bassist%2Bmechanism%2Bfor%2Bclutch.png" width="400" /></a></div><div><br /></div><div><br /></div><div>With the use of air pressure as the energy source for the actuator, this system functions as an automatic clutching and declutching system rather than a power assist, since it has a bang-bang control scheme. Once the pedal is pressed far enough to trip the switch, the driver no longer needs to apply force on the pedal. This is different from a power assist, which multiplies the driver's effort and provides full control throughout the entire range of motion of the pedal. The hydropneumatic system ensures quick declutching (in 0.1-0.3 seconds) and smooth and firm clutch engagement (in 0.4-0.6 seconds), regardless of the driver's skill. When the hydropneumatic system is active, the force needed to depress the clutch pedal is approximately 2-2.5 times less than when it is only spring-assisted. The effort required on the clutch pedal is unknown.</div><div><div><br /></div><div>Overall, the combination of a hydropneumatic system and the synchromesh gearbox makes the entire process of accelerating the tank a much lighter task for the driver than it was on earlier T-54 series tanks, as both the declutching and gear shifting are made easier. The automated clutch system was particularly useful as it helped to prolong the life of the clutch pack by ensuring that clutching and declutching is done in an optimal fashion. In terms of acceleration performance, it is also somewhat helpful as it allows the driver to depress the pedal rapidly when shifting gears. Nevertheless, shifting gears is still generally slower than an equivalent tank automatic transmission.</div></div></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The driving tillers (or levers) each control the track on its side. Each tiller has three positions, the first (0) for a normal forward drive, the second (1) for engaging the planetary mechanism on the corresponding track, and the third (2) to de-clutch the corresponding track and engage the brake. Pulling the steering tiller to the (1) position releases the clutch on the steering unit and engages the planetary steering unit by tightening a brake band on the steering unit, and pulling it to the (2) position releases the brake band around the steering unit while simultaneously tightening the brake band around the braking unit. Steel brake pads and steel brake drums are used as the friction surfaces. Together with the gearbox, the brake bands are cooled by the airflow from the cooling fan, which is essential as the brake bands are heated by the steering and stopping of the tank.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal; text-align: center;"><a href="https://1.bp.blogspot.com/-vY6uLZV-fOM/YCwWorALEUI/AAAAAAAASug/w_QXDwrCTmkRi7xdZIKyOy20MzvbFeTywCLcBGAsYHQ/s1762/steering%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1762" data-original-width="1625" height="320" src="https://1.bp.blogspot.com/-vY6uLZV-fOM/YCwWorALEUI/AAAAAAAASug/w_QXDwrCTmkRi7xdZIKyOy20MzvbFeTywCLcBGAsYHQ/s320/steering%2Bmechanism.png" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEioKT92sC10AKBTfVRQ9oT4gPPOT1T3YePhAF7MPUUwI0xjWILY-TyVP0L4RM2v3ARfQxr9rLpYr2qKDoYXXcxsT2gxrtykpA58oMIzIJHH-lherohS30TrAw-e5LjOfE-CMF6BPWOdAo2QDVHM3nHSO64O2w-75hnhf1piuYAfq_piosJf-9r2GvHVGw/s3413/steering%20unit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3413" data-original-width="2893" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEioKT92sC10AKBTfVRQ9oT4gPPOT1T3YePhAF7MPUUwI0xjWILY-TyVP0L4RM2v3ARfQxr9rLpYr2qKDoYXXcxsT2gxrtykpA58oMIzIJHH-lherohS30TrAw-e5LjOfE-CMF6BPWOdAo2QDVHM3nHSO64O2w-75hnhf1piuYAfq_piosJf-9r2GvHVGw/s320/steering%20unit.png" width="271" /></a><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">Steering is accomplished by engaging a planetary reduction gear, reducing the output speed by 1.42 times. The power input arrives at the ring gear, and the planet carrier is output to the final drive. The steering brake engages with the sun gear, and the service brake engages with the planet carrier. The track with the reduced speed becomes the inner track in a turn. Because the reduction has a fixed ratio of 1.42 regardless of the gear setting, the transmission only provides a single turn radius of 8.91 meters regardless of the gear. This fixed turn radius of 8.91 meters is effectively the minimum turn radius, as wider turn radii are possible by allowing the reduction gear to slip and thus apply a reduction of less than 1.42, although this involves increasing brake fade. The first gear is an exception, as steering can only be done by clutch and brake. On all gear settings, turning by clutch-and-brake gives a fixed minimum turn radius of 2.64 meters, which is achieved by putting one steering lever to the "1" position and the other to the "2" position. Having a single turn radius with the option of a clutch and brake turn is a trait that the transmission shares with the CD-850-6A of the M60A1, which provides either a 10.67-meter turn radius in normal steering or a 2.93-meter pivot turn.</div><div style="font-weight: normal;"><br /></div><div>Steering the T-62 is simple but generally quite uncomfortable, because the brake band on the steering unit is designed to switch from being fully disengaged to fully engaged, in order to minimize brake fade and thus prolong the lifespan of the brake band. </div></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">Because there is only one turn radius, an inexperienced driver can make the ride in a T-62 very jerky by pulling the levers to the "1" position for minor steering corrections or when making a large radius turn, as an inexperienced driver may pick up the habit of pumping the lever corresponding to the inner track between the "0" and "1" positions. This accelerates the wear on the drive components, and jerks the tank with every pump of the steering lever. The proper way to make small steering adjustments is to pull the lever towards the "1" position, but stop before fully engaging it. This way, the band brake only partially constricts on the ring gear of the planetary mechanism and does not lock it to the case. The ring gear slips, so a reduction of less than 1.42 is applied. The difference in speed between the left and right track will also be smaller as a result, so the turn radius is consequently larger. To make a gentle transition to a turn, the driver can slowly pull the lever to the "1" position instead of forcefully pulling it back so that the band brake is gradually applied over a longer period of time, thus eliminating the jerking effect. It is inadvisable to keep the lever from barely engaging the "1" position for prolonged periods as this will burn the band brake. At moderate speeds (in 2nd and 3rd gear), the turn radius is large enough that the tank is capable of smoothly entering into a turn in this way. However, at high speeds, the turn radius is relatively small, which results in jerky steering corrections with a considerable loss of speed regardless of how smoothly the driver pulls the lever into the "1" position. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">An interesting feature of the steering system is that the planetary steering unit also acts as a low range system for gears ranging from the 2nd to 5th, as by pulling the steering tiller from the (0) position to the (1) position, the track speed is decreased by 1.42 times, which multiplies the torque delivered to the track by 1.42 times. This method of torque boosting is useful when carrying out difficult tasks such as climbing a hill or knocking over obstacles. It can also be used in combat to slow down the tank momentarily to fire on the move without downshifting.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">This method of torque boosting cannot be used for prolonged periods. According to the Polish army "Podręcznik czołgisty" (Tanker handbook), the driving distance should not be greater than 100-150 meters when using this method. <br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-OxjEr0cpjWQ/XUEhPVylQAI/AAAAAAAAOtw/Ip3CLLPIdJYC9jQqDASnas569FsuwH1tQCLcBGAs/s1600/engine%2Band%2Btransmission.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="492" height="400" src="https://1.bp.blogspot.com/-OxjEr0cpjWQ/XUEhPVylQAI/AAAAAAAAOtw/Ip3CLLPIdJYC9jQqDASnas569FsuwH1tQCLcBGAs/s400/engine%2Band%2Btransmission.jpg" width="245" /></a></div><br /><br />By the early 1960's, both the geared steering system and the synchromesh gearbox were thoroughly outdated on account of the low steering precision and the penalty to acceleration speeds brought by the need to double declutch when shifting gears. Many Western tanks already had double differential or triple differential transmissions that shifted gears more quickly, and were capable of true neutral steering and offered a discrete turning radius on each gear setting, so that the steering precision is higher for any given gear setting. <br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-pjwSumAd3mU/XVEJl27SgMI/AAAAAAAAO1w/3MS5kdez9n84vaPEwau_dF3Xa4-Ddo8CwCLcBGAs/s1600/%25D1%2582-62-4.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="459" data-original-width="640" height="458" src="https://1.bp.blogspot.com/-pjwSumAd3mU/XVEJl27SgMI/AAAAAAAAO1w/3MS5kdez9n84vaPEwau_dF3Xa4-Ddo8CwCLcBGAs/s640/%25D1%2582-62-4.jpeg" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"></div><div><br /></div><div><br /></div><div><br /></div></div></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">
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<span style="font-size: large;">SUSPENSION</span></h3>
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Like the T-55 before it, the T-62 had individual torsion bar suspension and five hollow die-cast aluminium alloy roadwheels with a thick rubber rim. The T-62's suspension is aesthetically similar to that of the T-54 and T-55, but it can be differentiated by the even spacing between the three roadwheels at the front of the tank and the wider space between the two at the rear. This was done due to the shifted center of gravity of the tank due to the new enlarged turret, making it more front heavy than the T-55, thus necessitating more suspension elements at the front to ensure better load distribution for a longer lasting suspension as well as a smoother ride across bumpy terrain. The diameter of the roadwheels is 810 mm. They have a standard layout with a central channel for guide horns on the tracks to pass through. The same 5-spoked wheel was kept throughout the T-62's service life. The tank had 450mm of ground clearance.<br />
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The frontmost and rearmost roadwheels were fitted with rotary shock absorbers, identical to the type installed in the T-55. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The overall vertical travel range of the suspension is 220-224mm, with the bump travel being 160mm to 162mm, and the rebound travel being 62-64mm. This performance was already an improvement over the torsion bars of the T-55 which had a vertical range of travel of only 142mm until upgrades were applied later in its life. For comparison, the M48 and M60(A1) suspension granted a larger overall vertical travel range of 320mm with 220mm of bump travel and 100mm of rebound travel. Compared to the 407mm of the Leopard 1, the obsolescence of the T-62 suspension was clearly evident.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">However, although the vertical motion is not on the same level as the "Patton" tanks, the vibration dampening capabilities of the T-62 suspension are likely to be noticeably better based on the performance of the T-54 suspension. According to the results of West German testing of a captured T-54, the frequency response of the suspension was found to be marginally superior to that of the M48/M60 suspension and the ride comfort was evaluated to be roughly equivalent or superior.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><div><br /></div><div>The oscillating amplitudes experienced by the T-54 was considerably larger than the M48 at all tested speeds, with the largest difference observed at a speed of 10 km/h. The T-54 oscillates with an amplitude of 230mm whereas the M48 oscillates with an amplitude of just 130mm. However, the vibrational amplitude of the T-54 suspension hardly increases as the speed increases to 30 km/h, such that the difference between the two tanks diminishes to just 10mm. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-DQAhSpS7AqY/X29D2KLXZPI/AAAAAAAARqQ/LNOb7XRXap881mvlK053j00ZEkXMjzGtwCLcBGAsYHQ/s798/patton%2Bwellenstrecke.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="324" data-original-width="798" height="163" src="https://1.bp.blogspot.com/-DQAhSpS7AqY/X29D2KLXZPI/AAAAAAAARqQ/LNOb7XRXap881mvlK053j00ZEkXMjzGtwCLcBGAsYHQ/w400-h163/patton%2Bwellenstrecke.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-nqMRryDVjoY/X29D2Ab3Z8I/AAAAAAAARqM/U2aOUH0m19M-xsRvwVVF44NZMSVsdjduwCLcBGAsYHQ/s750/t-54%2Bwellenstrecke.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="330" data-original-width="750" height="176" src="https://1.bp.blogspot.com/-nqMRryDVjoY/X29D2Ab3Z8I/AAAAAAAARqM/U2aOUH0m19M-xsRvwVVF44NZMSVsdjduwCLcBGAsYHQ/w400-h176/t-54%2Bwellenstrecke.png" width="400" /></a></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div>However, it is important to note that oscillation amplitude has a relatively minor effect on ride comfort compared to the vibration frequency. A suspension with low vibrational frequency, which is normally achieved using softer springs with low natural frequencies, grants the crew a more comfortable ride, reduces equipment wear rates, and helps to prolong the service life of the powertrain. From 10 km/h to 30 km/h, the measured frequency of the T-54 suspension was consistently lower than the M48 suspension at every compared speed interval. At a low speed of 10 km/h, the difference was not particularly large, with the M48 being measured at 0.37 Hz while the T-54 was measured at 0.34 Hz. However, at a high speed of 30 km/h, the M48 suspension was measured at a frequency of 1.24 Hz whereas the T-54 suspension was measured at a frequency of just 1.1 Hz, indicative of softer torsion bars and better vibrational damping. As such, it is unsurprsing that the test crews reported "strong discomfort" while riding in the M48 at this speed but experienced only "discomfort" in the T-54 at the same speed.<br /><div><br /></div></div><div>When driven over an undulating track, the T-54 and Patton (M48) were closely comparable in terms of ride comfort according to a survey of the test crews. When moving at 5 km/h, the T-54 was considered bearable. At 10-15 km/h (up to 20 km/h), the crews felt slightly uncomfortable. At 25-30 km/h, the ride of the tank was considered uncomfortable. On the same track, the M48 was considered bearable up to a speed of 10 km/h, and it only became slightly uncomfortable when the speed increased to 15 km/h. However, at 20 km/h the crews felt uncomfortable and at 30 km/h, they felt severe discomfort. Overall, the T-54 and M48 were both acceptable in terms of ride comfort at low speeds and both were considered uncomfortable at high speeds, but the M48 was particularly bad at high speeds.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">
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Originally, the T-62 used the same OMSh single pin tracks as the T-54 and T-55 series. A full set of 96 links weighs 1,386 kg for one side of the hull. The combined weight of both sets of tracks is 2,772 kg, which is equal to only 7.2% of the total weight of the tank. The tracks are of a simple hinged type with no inner rubber padding or rubber bushings, nor were there any rubber track pads available for this type of track during the T-62's years of service, so travelling on paved roads was not very good for the asphalt. The track pins were not held in place so they could wriggle out of their slots from the vibration of the tracks over time. To keep the pins in place, a steel ramp was welded to the side of the hull near the drive sprocket where it could knock the pins back into their slots once they began to worm their way out of their slots by a certain distance. The tracks are 580mm wide with centered guide horns.<br />
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The idler wheel is of a skeletal design with 10 spokes. The drive sprocket has 4 spokes and 13 teeth.<br />
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Despite the slight increase in weight compared to the T-55, the lengthened contact length of the tracks helped reduce the ground pressure to such an extent that it is actually marginally less than the T-55. For comparison, the specific ground pressure of the T-55 is 8.04 N/sq.cm whereas the specific ground pressure of the T-62 is 7.95 N/sq.cm. In fact, the ground pressure of the T-62 could be considered to be on the lower end of the spectrum for medium and main battle tanks.<br />
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Exerting a nominal ground pressure of only 7.95 N/sq.cm, the T-62 was identical to the M60A1 (7.95 N/sq.cm) which was heavier by 12 tons but also much wider and longer. The T-62 was certainly better than the common M48A1 or M48A2 (8.24 N/sq.cm), and it was rather light-footed compared to tanks like the Centurions (around 0.95 kg/sq.cm for Mk. 3 and above) and the Chieftain (9.12 N/sq.cm), both of which were rather heavy tanks. Surprisingly, the specific ground pressure of the T-62 is slightly less than the Leopard 1 (8.44 N/sq.cm) although this does not really make much of a difference when all the other mobility factors are considered. However, the T-62 turns out to be unfavourable in terms of the mean maximum pressure (MMP), as its weight is distributed over fewer roadwheels. According to calculations using an empirical formula presented in the textbook "Theory of Ground Vehicles (Third Edition)", With an MMP of 242 kPa, it lies in the middleground between the M60A1 (236 kPa) and the AMX-30 (249 kPa), and is much heavier than the Leopard 1 (198 kPa).<br />
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To improve the lifespan of medium tank tracks and enhance automotive performance, a new RMSh track design was developed by the Omsk Transport Engineering Plant with development concluding in 1962. Beginning in 1966, these new RMSh tracks were fitted to new-production T-62 tanks. The RMSh is a single-pin metal track with rubber bushings, a design known as live track. It was considerably more durable thanks to larger and tougher connecting pins and the internal rubber bushings around each pin.</div><div style="font-weight: normal;"><br /></div><div>A set of 97 links weighs 1,655 kg and the combined weight of two sets of tracks is 3,310 kg. A T-62 tank upgraded with these tracks would weigh 538 kg more than a basic tank with the original OMSh tracks. All T-62M variants were fitted with the RMSh tracks as a standard component of the modernization. The installation of RMSh tracks increased the ground pressure (it is not wider than OMSh tracks) owing to its greater weight and thus decreased the power-to-weight ratio of the tank to 15.4 hp/ton, but due to the torsional springing effect of the rubber bushings, the power losses to unsprung weight are considerably reduced. The reduction in power losses increases the effective power available to propel the tank, which is additionally enhanced by the increased traction of the new track design.<br />
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<a href="https://1.bp.blogspot.com/-w2aQ-RdlGF4/XT5gO0ciAfI/AAAAAAAAOnI/5EJTNqjpmSkxGmvwe8_5NicpHyKvk2dDQCLcBGAs/s1600/in%2Bsnow.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="807" data-original-width="1417" height="364" src="https://1.bp.blogspot.com/-w2aQ-RdlGF4/XT5gO0ciAfI/AAAAAAAAOnI/5EJTNqjpmSkxGmvwe8_5NicpHyKvk2dDQCLcBGAs/s640/in%2Bsnow.jpg" width="640" /></a></div>
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<div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div>By switching to the RMSh track, the top speed of the T-62 increased from its nominal 50 km/h to 54 km/h. The average cross-country driving speed also improved, but to an unknown extent.<br />
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The easiest way to tell apart an OMSh track from an RMSh track is to observe the ends of a track link. The older OMSh track has an open loop at the ends of the track links whereas an RMSh track doesn't.<br />
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<a href="http://3.bp.blogspot.com/-pRL0V9ckIqc/VlAyPcKyIDI/AAAAAAAAENQ/nfhr3kW4Xi0/s1600/t-62%2Bsprocket.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="266" src="https://3.bp.blogspot.com/-pRL0V9ckIqc/VlAyPcKyIDI/AAAAAAAAENQ/nfhr3kW4Xi0/s400/t-62%2Bsprocket.jpg" width="400" /></a></div>
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On concrete surfaces, steel tracks such as the OMSh or RMSh models give relatively poor traction owing to the low coefficient of friction between steel and concrete, and a low coefficient of sliding friction which makes it easy for the tracks to slip completely when the tank makes a turn. This is only slightly ameliorated by the penetration of the steel grousers into the concrete surface, but owing to the light weight of the T-62, surface penetration is quite limited, so there is nothing to prevent the tracks from slipping if too much torque is applied, an issue which is much less pronounced with much heavier tanks such as the M60A1 and Chieftain. However, given that the destruction of hard surfaces for the sake of traction is generally undesirable, NATO tanks, including the two aforementioned models, are fitted with rubber track pads as a semi-permanent fixture.<br />
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<h3 style="font-weight: normal;">
<a href="https://www.blogger.com/null" id="deck"></a>
<span style="font-size: large;">ENGINE DECK</span></h3>
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The original engine deck had maintenance hatches to allow easier inspection of the engine and air cleaner without removal of the engine deck. The engine hatch was only large enough to permit access to the items above the engine, and the air filter hatch permitted the VTI-4 air filter to be serviced or removed. The hatches are unlocked by turning the two locking levers on each corner opposite the hinges using a wrench, and then opened by the handles. For more serious maintenance and repair tasks, it would be necessary to remove the engine deck, which was a much more laborious task as it involved unbolting the numerous bolts holding the deck onto the hull.<br />
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<a href="http://4.bp.blogspot.com/-jw6EIOp1_d8/Vmf1POMWyNI/AAAAAAAAE38/46b0mcyZdXw/s1600/t-62%2Bobr%2B1961%2Bengine%2Bdeck.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://4.bp.blogspot.com/-jw6EIOp1_d8/Vmf1POMWyNI/AAAAAAAAE38/46b0mcyZdXw/s400/t-62%2Bobr%2B1961%2Bengine%2Bdeck.jpg" width="400" /></a><a href="http://4.bp.blogspot.com/-_YCup4r39b0/VmfxHvxj5kI/AAAAAAAAE3w/FD7HDKV-24c/s1600/t-62%2Bengine%2Baccess%2Bhatch.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://4.bp.blogspot.com/-_YCup4r39b0/VmfxHvxj5kI/AAAAAAAAE3w/FD7HDKV-24c/s400/t-62%2Bengine%2Baccess%2Bhatch.jpg" width="265" /></a></div>
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The T-62 obr. 1967 model revised the engine compartment deck design and gave it a single large engine access panel, giving a completely free, unobstructed view of the innards of the engine compartment by opening the panel. The panel was sprung on a large torsion bar that was shared with the radiator packs, so it was still relatively easy to open despite its much larger size. The stamped steel seal for the radiator inlets (for snorkeling operations) is placed on top of the engine access panel when it is not in use. It may provide a modicum of additional protection from artillery shell splinters and from HE charges thrown onto the engine deck.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="font-weight: normal; margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-YuSaD4dsUgI/Vm78FeKtr5I/AAAAAAAAE-w/wAbejA0MaWc/s1600/t-62%2B1983%2Bengine%2Bdeck.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://2.bp.blogspot.com/-YuSaD4dsUgI/Vm78FeKtr5I/AAAAAAAAE-w/wAbejA0MaWc/s640/t-62%2B1983%2Bengine%2Bdeck.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Photo credit: Andrei Tarasenko's website</td></tr>
</tbody></table>
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<h3 style="font-weight: normal;">
<span style="font-size: large;">COOLING AND HEATING SYSTEM</span></h3>
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<div class="separator" style="clear: both; font-weight: normal; text-align: center;">
<a href="https://4.bp.blogspot.com/-C1yVnIgDiqM/WsXKzuQHIWI/AAAAAAAALU0/YA31g00pz5QvGPsTtuyxmBH4sNbXZMqzgCLcBGAs/s1600/engine%2Bheating%2Band%2Bcooling%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="589" data-original-width="1118" height="336" src="https://4.bp.blogspot.com/-C1yVnIgDiqM/WsXKzuQHIWI/AAAAAAAALU0/YA31g00pz5QvGPsTtuyxmBH4sNbXZMqzgCLcBGAs/s640/engine%2Bheating%2Band%2Bcooling%2Bsystem.png" width="640" /></a></div>
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The cooling and heating system of the T-62 is largely the same as the T-55 tank. The engine pre-heater is also the fighting compartment heater, and is located underneath the commander's seat in the fighting compartment. The cooling system is identical to the T-55, featuring a radiator in the engine deck and a centrifugal fan to circulate air through the radiator and out the tank. The centrifugal cooling fan is driven by the engine via a power takeoff gearbox integral to the main gearbox of the powertrain. The use of a mechanical power shaft to transmit power, unlike fan belts as used in some other tanks, eliminates the issue of fan belts snapping under the high stress of driving such a fan.<br />
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The radiator can be accessed by lifting the hinged armoured radiator access panel. Directly underneath the radiator unit is the cooling pack into which coolant carries heat from the engine to be dissipated by air sucked in through the radiator unit and out the rear of the engine compartment via a centrifugal fan. Armoured louvers in the radiator access panel protect the cooling pack from damage.<br />
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<a href="http://3.bp.blogspot.com/-HYGUteLJcjM/Vfm4iUPctsI/AAAAAAAADkU/SeKQkD4D1-c/s1600/t-62%2Bradiator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="468" src="https://3.bp.blogspot.com/-HYGUteLJcjM/Vfm4iUPctsI/AAAAAAAADkU/SeKQkD4D1-c/s640/t-62%2Bradiator.png" width="640" /></a></div>
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The fan is powered by the engine via a drive shaft connected to the gearbox, thus allowing the fan to meet the engine's cooling needs following its power output which is proportional to its heat output. The fan housing has its own armoured cover. When closed, the rubber seals around the edges of the cover prevent water ingress, allowing the tank to drive under water.<br />
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<a href="http://4.bp.blogspot.com/-o5tsj7Ucedc/Vmf1a-UFmBI/AAAAAAAAE4E/NsFJjrb1YK0/s1600/t-62%2Bradiator%2Bfan%2Barmoured%2Bcover.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="266" src="https://4.bp.blogspot.com/-o5tsj7Ucedc/Vmf1a-UFmBI/AAAAAAAAE4E/NsFJjrb1YK0/s400/t-62%2Bradiator%2Bfan%2Barmoured%2Bcover.jpg" width="400" /></a><a href="http://1.bp.blogspot.com/-nQrc_lE7YPM/Vk9P-kFyZ-I/AAAAAAAAEJY/Pck6Jyljhyo/s1600/t-62%2Bmod.1972%2Bair%2Bcooler%2Bfan.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="257" src="https://1.bp.blogspot.com/-nQrc_lE7YPM/Vk9P-kFyZ-I/AAAAAAAAEJY/Pck6Jyljhyo/s400/t-62%2Bmod.1972%2Bair%2Bcooler%2Bfan.jpg" width="400" /></a></div>
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As mentioned before, the radiator access panel includes armoured louvers. These protect from air burst artillery and mortar shells or even molotov incendiary bombs, and they are further augmented by auxiliary armoured covers which must be manually closed, but can be sprung open with the press of a button in the driver's station. They add some protection from air attack but their main function is to seal the radiator from the ingress of water when fording deep rivers or snorkeling.<br />
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<div class="separator" style="clear: both; font-weight: normal; text-align: center;">
<a href="http://3.bp.blogspot.com/-atOmSgKzGMM/Vk9QAX-bqOI/AAAAAAAAEJg/ctx-aJcrWAA/s1600/t-62%2Bmod.1972%2Bradiator.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://3.bp.blogspot.com/-atOmSgKzGMM/Vk9QAX-bqOI/AAAAAAAAEJg/ctx-aJcrWAA/s640/t-62%2Bmod.1972%2Bradiator.jpg" width="640" /></a></div>
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When the engine and radiator air intake is sealed and the vehicle is underwater, the engine draws air from inside the hull via a respirator fan located just behind the commander's seat, on the partition between the engine compartment and fighting compartment. There is no filter in the respirator fan.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="font-weight: normal; margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-ONPEzZd_8jY/Vm1_ey_M1rI/AAAAAAAAE9c/fljnaIbY-CE/s1600/t-62%2Bengine%2Brespirator.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://3.bp.blogspot.com/-ONPEzZd_8jY/Vm1_ey_M1rI/AAAAAAAAE9c/fljnaIbY-CE/s400/t-62%2Bengine%2Brespirator.png" width="325" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">(Notice the fan duct at the top of the photo)</td></tr>
</tbody></table>
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There is an electric air heater just in front of the fan duct and under the commander's seat (cylindrical tank in photo below). It supplies hot air to warm up the engine during cold weather, and it also functions as the heater for the crew compartment.<br />
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<a href="http://2.bp.blogspot.com/-JMuHqAsISMY/VmPjvZNZbbI/AAAAAAAAEq8/iL8__lsasCA/s1600/t-62%2BGO-27.jpg" style="font-weight: normal; margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://2.bp.blogspot.com/-JMuHqAsISMY/VmPjvZNZbbI/AAAAAAAAEq8/iL8__lsasCA/s640/t-62%2BGO-27.jpg" width="640" /></a><br />
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The tank's electrical supply needs are handled by four 6-STEN-140 accumulators located at the front of the hull, adjacent to the driver's station. These are lead acid batteries with a voltage rating of 12 V and an amperage rating of 140 Ah during a 20-hour discharge cycle. The four batteries are divided into two pairs connected in series and the two pairs are connected in parallel to double the operating voltage and amperage rating to 24 V and 280 Ah respectively. The batteries supply 24 volts when the engine is turned off, and the G-6.5 electric generator supplies 28 volts when the engine is running.<br />
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<h3 style="font-weight: normal;"><span style="font-size: large;">FUEL SUPPLY</span></h3>
<div class="separator" style="clear: both; font-weight: normal; text-align: center;"><a href="https://1.bp.blogspot.com/-mKyg5E_uUmw/X2UdivMz-VI/AAAAAAAARm0/VEZLTU7mUuELEXk-xOUBWhpmAgMwypy-QCLcBGAsYHQ/s2048/t-62%2Bfuel%2Bsystem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1438" data-original-width="2048" height="450" src="https://1.bp.blogspot.com/-mKyg5E_uUmw/X2UdivMz-VI/AAAAAAAARm0/VEZLTU7mUuELEXk-xOUBWhpmAgMwypy-QCLcBGAsYHQ/w640-h450/t-62%2Bfuel%2Bsystem.png" width="640" /></a></div><br /><div style="font-weight: normal;"><br /></div>
Fuel storage is divided between four internal tanks and three external tanks for a sum total of 960 liters. The largest internal fuel tank is located in the nose of the hull, behind the junction of the two front glacis plates. It has a capacity of 280 liters. Behind it, there are two more fuel tanks at the front of the hull which also serve as ammunition stowage racks. The right tank holds 145 liters and the left tank holds 125 liters. These three fuel tanks are interconnected in such a way that they function as a group. The last fuel tank is located at the starboard side of the hull, at the very rear of the fighting compartment, right next to the partition between the engine compartment and the fighting one. It holds 125 liters, and it serves as a buffer tank connecting the external fuel tanks to the front fuel tank group.</div><div style="font-weight: normal;">
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Since all of the fuel tanks are interconnected, the driver-mechanic only has to top up the tank from one fuel filler port. There is one at the rear of the hull leading to the rear fuel tank:<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://4.bp.blogspot.com/-yqlB9COy1IM/Vmfm4xyO9sI/AAAAAAAAE24/v0FqVv_B4C4/s1600/1ae.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="217" src="https://4.bp.blogspot.com/-yqlB9COy1IM/Vmfm4xyO9sI/AAAAAAAAE24/v0FqVv_B4C4/s400/1ae.jpg" width="400" /></a><a href="http://1.bp.blogspot.com/-KZYCGmPSPD4/VmfnQ-3htPI/AAAAAAAAE3A/B1wMxZgse-Q/s1600/w00928_1786687.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://1.bp.blogspot.com/-KZYCGmPSPD4/VmfnQ-3htPI/AAAAAAAAE3A/B1wMxZgse-Q/s320/w00928_1786687.jpg" width="320" /></a></div>
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<span style="font-size: x-small;">(Photo credit: Evgeny Starobinets)</span></div>
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And another two for the pair of conformal front hull fuel tanks at the front of the hull:<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://4.bp.blogspot.com/-JJPq7y-Vt9g/VmftBikp83I/AAAAAAAAE3k/5QRKV1RUZpg/s1600/t-62%2Bobr%2B72%2Bfuel%2Bfiller%2Bcaps.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://4.bp.blogspot.com/-JJPq7y-Vt9g/VmftBikp83I/AAAAAAAAE3k/5QRKV1RUZpg/s640/t-62%2Bobr%2B72%2Bfuel%2Bfiller%2Bcaps.jpg" width="640" /></a></div>
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The three external fuel tanks are mounted atop the starboard fenders, each with their own fuel filler caps. These external fuel tanks are part of the fuel system. Each tank has a capacity of 95 liters.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-wn7hgG6C_dI/VfR7TrkEX8I/AAAAAAAADh0/eno6iWly9_Q/s1600/t-62_29.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://1.bp.blogspot.com/-wn7hgG6C_dI/VfR7TrkEX8I/AAAAAAAADh0/eno6iWly9_Q/s400/t-62_29.jpg" width="300" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Here you can see how the fuel tanks are connected</td></tr>
</tbody></table>
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Total internal fuel capacity is 675 liters, augmented by another 285 liters carried on the external sponson fuel tanks. An additional 400 liters of fuel can be carried in two 200-liter auxiliary fuel tanks mounted on brackets at the rear of the tank to augment the tank's operational range. With all fuel tanks filled, the tank carries a sum total of 1360 liters of fuel. With auxiliary fuel tanks, the T-62 has a highway cruising range of about 650 km, or 450 km without. The cruising range on dirt roads with auxiliary fuel tanks is 450 km, and 320 km without.<br />
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<a href="http://3.bp.blogspot.com/-bt1XkAVv2tg/VenYAjZUjzI/AAAAAAAADcw/xBoaUs_75z4/s1600/t-62%2Brear%2Bdrums.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="368" src="https://3.bp.blogspot.com/-bt1XkAVv2tg/VenYAjZUjzI/AAAAAAAADcw/xBoaUs_75z4/s640/t-62%2Brear%2Bdrums.jpg" width="640" /></a></div>
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As mentioned before, all of the fuel tanks are interconnected. Like in the T-55, sequential fuel draining was implemented. The driver has a control knob located beside the right steering lever to select which set of fuel tanks he wants to draw from, choosing between using all fuel tanks, using the internal fuel tanks only, or the driver may cut off all fuel flow entirely. If all fuel tanks are used, the external fender fuel tanks are drained first, then the rear starboard tank, and then finally the group of three front fuel tanks. Alternatively, if the driver switches to internal fuel only, then only the group of three front fuel tanks is drained. The rear starboard fuel tank is not drained, even if it is full.<br />
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<h3>
<a href="https://www.blogger.com/null" id="water"></a>
<span style="font-size: large;">WATER OBSTACLES</span></h3>
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<a href="http://1.bp.blogspot.com/-jHLtVDTyaGw/Vl2FHOoSGZI/AAAAAAAAEfs/jdnm7HWAymM/s1600/t-62%2Bsnorkelling.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="450" src="https://1.bp.blogspot.com/-jHLtVDTyaGw/Vl2FHOoSGZI/AAAAAAAAEfs/jdnm7HWAymM/s640/t-62%2Bsnorkelling.jpg" width="640" /></a></div>
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Like the T-55 preceding it, the T-62 was built with the OPVT system to overcome water obstacles. A bilge pump was fitted to the fighting compartment floor, under the heater, and it expels water via an outlet on the hull roof just behind the turret. The outlet is closed by a stiff one-way valve, to permit the bilge pump to work even when the tank is driving at a depth of 5 meters. The OPVT system allowed the tank to snorkel across large bodies of water down to 5 meters deep and 1 kilometer wide, or ford waters as deep as 1.8 meters with minor preparation. Water obstacles with a depth of 1.2 meters or below did not necessitate any preparation to cross as the water would not reach the exhaust port, let alone flood the intakes and radiators on the engine deck. The two photos below show T-62 tanks fording shallow waters.<br />
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<a href="https://1.bp.blogspot.com/-B0zPwbo27U8/XVEJibfphrI/AAAAAAAAO1o/QZAULG6NWWIRmtfDYyzT36NYlW5ql-S5ACLcBGAs/s1600/t-62%2Bfording%2Bwater.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="608" data-original-width="1000" height="242" src="https://1.bp.blogspot.com/-B0zPwbo27U8/XVEJibfphrI/AAAAAAAAO1o/QZAULG6NWWIRmtfDYyzT36NYlW5ql-S5ACLcBGAs/s400/t-62%2Bfording%2Bwater.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-gpV3VLvyRS0/WW39FZSbmiI/AAAAAAAAItA/WdaXkAntWGYx5lLV-rikEKR4CoOIV_NzQCLcBGAs/s1600/t-62%2Btraversing%2Briver.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="548" data-original-width="800" height="273" src="https://1.bp.blogspot.com/-gpV3VLvyRS0/WW39FZSbmiI/AAAAAAAAItA/WdaXkAntWGYx5lLV-rikEKR4CoOIV_NzQCLcBGAs/s400/t-62%2Btraversing%2Briver.jpg" width="400" /></a></div>
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There are certain procedures that need to be followed prior to snorkeling, however. In order to prevent water from entering the engine air intake and radiators, they must all be sealed by locking their armoured covers down, and the bilge pump should be activated, which can be done with a switch on the driver's instrument panel. It is only necessary to close the armoured louvers for both the radiators and the air intakes when fording. Once the engine air intake is shut off, however, the engine must draw air from inside the tank through a respirator fan located just behind the commander's seat.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-xydrSVTHgFc/VmfB_5PhRjI/AAAAAAAAE1k/lj-IhKTl7vo/s1600/t-62%2Bexhaust%2Bvalve%2Bbank.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="307" src="https://1.bp.blogspot.com/-xydrSVTHgFc/VmfB_5PhRjI/AAAAAAAAE1k/lj-IhKTl7vo/s640/t-62%2Bexhaust%2Bvalve%2Bbank.jpg" width="640" /></a></div>
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When snorkeling, it is also necessary for the exhaust outlet to be sealed with a valve bank, which is a bolt-on cover for the exhaust outlet equipped with four spring-loaded circular exhaust ports that prevents exhaust gasses from being released until they can build enough pressure to blow out forcefully enough that water will not have a chance to leak in.<br />
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If the tank is to be snorkeling deeper than three meters, the last step is to seal all of the hatch gaps with a waterproof paste, which has the consistency of clay. The entire preparation process takes around 30 minutes for snorkeling, but the tank can readily ford across any stream without any preparations whatsoever.<br />
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The air supply for both the crew and engine is provided by the single snorkel erected from the turret roof.<br />
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The snorkel is broken down into three parts and latched onto the rear of the turret and under the auxiliary fuel tanks for convenient stowage during road marches and combat. The snorkel must be assembled on site by the crew before it can be used, and it is possible to install only one or two of the three parts depending on the depth of the body of water to be crossed. The snorkel is installed by first dismounting the MK-4S periscope in front of the loader's hatch, and fitting the snorkel in its place. Once the tank resurfaces and drives off, it is not necessary to remove any of the snorkeling accessories except the snorkel (for obvious reasons), which can be simply cast away by pushing on it from the inside. The MK-4S periscope can then be reinstalled. A replacement snorkel is obtained at a later point, either by rear echelon units collecting the discarded snorkels or provided during a resupply of spares.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-CnTik6kk5Mc/Vk9JGHu7nGI/AAAAAAAAEIM/8h_-U1eGvFM/s1600/t-62%2Bsnorkel%2Bport.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://4.bp.blogspot.com/-CnTik6kk5Mc/Vk9JGHu7nGI/AAAAAAAAEIM/8h_-U1eGvFM/s400/t-62%2Bsnorkel%2Bport.jpg" width="400" /></a></div><br />
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A wider type of snorkel is used during training. This type of snorkel fits over the commander's hatch, and is large enough to allow crew members to escape from the tank via an internal ladder. This is to help ensure that the crew does not drown underwater. These snorkels are not used in combat.<br />
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Besides crossing rivers by snorkeling, a safer alternative was to cross pontoon bridges. The light weight of the T-62 made it particularly safe to carry out such operations, even allowing large numbers of tanks driving on the same bridge simultaneously.<br />
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<h2 style="text-align: center;">
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<span style="text-align: left;"> </span><a href="https://3.bp.blogspot.com/-zD7Vs4n1uSI/Wnbpzq8vkPI/AAAAAAAAKsA/XaARE3ycak0LAmWcNDkg-7FqQkaZVx9dQCLcBGAs/s1600/bmd-2.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="960" data-original-width="1280" height="480" src="https://3.bp.blogspot.com/-zD7Vs4n1uSI/Wnbpzq8vkPI/AAAAAAAAKsA/XaARE3ycak0LAmWcNDkg-7FqQkaZVx9dQCLcBGAs/s640/bmd-2.jpg" width="640" /></a><br />
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<a href="http://1.bp.blogspot.com/-kVtnF0cLEDQ/ValXuBbOfwI/AAAAAAAAC2s/FseTd1xmHLQ/s1600/bmd_2.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="254" src="https://1.bp.blogspot.com/-kVtnF0cLEDQ/ValXuBbOfwI/AAAAAAAAC2s/FseTd1xmHLQ/s400/bmd_2.jpg" width="400" /></a></div>
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<span style="text-align: left;">The BMD-2 is an airborne infantry fighting vehicle specially built for paradrop operations by the VDV - Russian airborne forces, first introduced in 1985. Its design is based on its predecessor, the BMD-1, which it is a modification of. Like the BMD-1, the BMD-2 belongs to a class of superlight IFVs designed with an emphasis on air transportability to increase the mechanized strength of airborne infantry. The turret had the same turret ring diameter of 1,380mm as the BMP-1 turret which was used on the BMD-1. As such, minimal modifications were needed to mount the new turret.</span></div>
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The BMD-2 never fully replaced the BMD-1, and it would seem that it was never intended to. The BMD-2's primary asset was its flexible 30mm autocannon, perfect for suppressive fire - and coupled with the high gun elevation made possible by the new turret and stabilizer system - a formidable threat to low-flying aircraft or infantry in elevated positions such as high rises or perhaps valley divides and mountains like in Afghanistan. However, there were things that the autocannon couldn't do that the 73mm cannon on the BMD-1 could. For instance, a single 73mm high-explosive shell is nearly <i>15 times</i> more powerful than a 30mm equivalent, making it that much more useful for demolition work. Instead of replacing the BMD-1, the BMD-2 merely supplemented it, producing a synergy of sorts within the elite VDV.<br />
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<h3>
<span style="font-size: large;">COMMANDER'S STATION</span></h3>
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The commander of the BMD-2 is situated in the front left hull. He is typically the squad leader or platoon leader of the infantry squad attached to the BMD, so he disembarks along with the rest of the passengers, leaving only the gunner and driver to operate alone. While operating from within the vehicle, he takes charge of one of the two bow machine guns. Unlike his neighbour bow machine gunner, though, he is supplied with an extra fixed periscope for additional situational awareness. But still, being located in the hull means that he is in a less elevated position than he would be had he been placed in the turret like on the BMP-2, the BMD-2's land-borne cousin. This, and the non-optimum observation devices means that he mostly concentrates on coordinating tactical maneuvers through his radio or relaying orders to the rest of the crew, but he doesn't spot or designate targets for the gunner as a tank commander usually does. The driver has better forward vision, so the commander doesn't need to navigate for the driver either. The value of the periscopes would be that they give the commander a sense of his surroundings to better understand where the vehicle is in relation to landmarks, platoon vehicles, etc.<br />
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Originally, the commander's station in the first BMD-2 models was exactly identical to the one from the BMD-1. He is provided with a single fixed TNPO-160 periscope aimed to the left and a single TNPP-220 rotatable sighting periscope, slaved to his bow machine gun.<br />
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<a href="http://4.bp.blogspot.com/-chPvwESLzyM/VgT-3cEf-qI/AAAAAAAADzA/XfF2iuPdoSc/s1600/tir4ZJ1SpMk.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://4.bp.blogspot.com/-chPvwESLzyM/VgT-3cEf-qI/AAAAAAAADzA/XfF2iuPdoSc/s400/tir4ZJ1SpMk.jpg" width="400" /></a></div>
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The TNPP-220 periscope can be rotated and elevated or depressed only as far as the bow machine gun's arc of traverse. The periscope itself has total range of vision of 20 degrees in the vertical plane and 76 degrees in the horizontal plane, not accounting for traversal.<br />
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With just two periscopes and limited coverage, the commander's ability to assess the tactical situation was very severely handicapped. Later on though, the commander's bow machine gun was removed, and the periscope sighting device was replaced with an MK-4 periscope in a fully rotatable protective housing for better vision.<br />
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<a href="http://4.bp.blogspot.com/-PghD819jgAk/VgefSkyRR-I/AAAAAAAAD1o/hwFr_02uhgk/s1600/w00261_1189236.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="478" src="https://4.bp.blogspot.com/-PghD819jgAk/VgefSkyRR-I/AAAAAAAAD1o/hwFr_02uhgk/s640/w00261_1189236.jpg" width="640" /></a></div>
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The MK-4S periscope can be rotated by a full 360 degrees, and elevated by +18 degrees and depressed by -12 degrees. The periscope grants him a net range of vision of 18 degrees in the vertical plane and 47 degrees in the horizontal plane. Unfortunately, the placement still hasn't changed. His vision will still be easily interfered with by tall grass, large rocks, shrubbery and other terrain features, and his vision suffers tremendously if the vehicle is on the move over rough ground. The commander can bear down on the handle of the periscope for some impromptu stabilization to partially relieve the problem.<br />
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<a href="http://4.bp.blogspot.com/-YIfY8mKd070/VgT1mWs6qkI/AAAAAAAADyw/c1Xq-VCnTOs/s1600/mk-4%2Bperiscope.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-YIfY8mKd070/VgT1mWs6qkI/AAAAAAAADyw/c1Xq-VCnTOs/s1600/mk-4%2Bperiscope.JPG" /></a> <a href="http://3.bp.blogspot.com/-928lgp7llrU/VgT_Eb62MjI/AAAAAAAADzM/1lbB99TFTjE/s1600/mk-4%2Bperiscope.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://3.bp.blogspot.com/-928lgp7llrU/VgT_Eb62MjI/AAAAAAAADzM/1lbB99TFTjE/s320/mk-4%2Bperiscope.png" width="173" /></a></div>
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The TNPO-160 periscope is a simple fixed periscope. It provides a total range of vision of 28 degrees in the vertical plane and 78 degrees in the horizontal plane. All periscopes are heated through the RTS electric heating system to prevent fogging in cold weather conditions, and the MK-4S periscope housing is also heated to prevent it from being frozen in place.<br />
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<span style="font-size: large;">COMMUNITCATIONS</span></h3>
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The R-123 FM radio station is located directly in front of the commander, beside the bow machine gun.<br />
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<a href="http://1.bp.blogspot.com/-zapedFQ5KlM/VgHAUsQTnlI/AAAAAAAADnw/PdngKMTokxY/s1600/r-123.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-zapedFQ5KlM/VgHAUsQTnlI/AAAAAAAADnw/PdngKMTokxY/s1600/r-123.png" /></a></div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-1dDrMmyXY4w/VgHA1uHcQTI/AAAAAAAADn8/Jyr-AdxuC5w/s1600/r-123%2Bbmd.png" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-1dDrMmyXY4w/VgHA1uHcQTI/AAAAAAAADn8/Jyr-AdxuC5w/s1600/r-123%2Bbmd.png" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Radio visible beside the driver's indicator panel</td></tr>
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The R-123 radio had a frequency range of between 20 MHZ to 51.5 MHZ. It could be tuned to any frequency within those limits via a knob, or the commander could switch between four preset frequencies for communications within a platoon (which takes 3 seconds). It had a range of between 16km to 50km. The R-123 had a novel glass prism window at the top of the apparatus that displayed the operating frequency. An internal bulb illuminated a dial, imposing it onto the prism where it is displayed. The R-123 had an advanced modular design that enabled it to be repaired quickly by simply swapping out individual modules.<br />
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In 1984, the now-outdated R-123 radio was replaced by the R-173 radio, which had a frequency range of between 30 MHZ to 75.999MHZ. <span style="line-height: 16px;">It has 10 preset frequencies. It had an electronic keypad for entering the desired frequency, and a digital display.</span><br />
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<tr><td><a href="http://4.bp.blogspot.com/-VvTRVZ3FCuU/VTKTKyvbv9I/AAAAAAAAB20/2rtoI_6_PS4/s1600/r-173m.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://4.bp.blogspot.com/-VvTRVZ3FCuU/VTKTKyvbv9I/AAAAAAAAB20/2rtoI_6_PS4/s1600/r-173m.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">R-173</td></tr>
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In the late 2000's, several hundred BMD-2s began a modernization program which included capital repairs and the installation of a new and advanced R-168-2UE-2 frequency-hopping encypted radio.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="http://3.bp.blogspot.com/-IOoEFOklyEQ/VTJ39YXst2I/AAAAAAAAB2k/5nPSTo_c7RI/s1600/R-168-25UE-2_4.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="198" src="https://3.bp.blogspot.com/-IOoEFOklyEQ/VTJ39YXst2I/AAAAAAAAB2k/5nPSTo_c7RI/s1600/R-168-25UE-2_4.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">R168-25UE-2</td></tr>
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The R-168 family of radios is now standard throughout the Russian ground forces, from infantry platoons to tank companies. It can produce frequency hops 100 times a second, and the data is encrypted as well.</div>
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<h3>
<span style="font-size: large;">GUNNER'S STATION</span></h3>
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The gunner is the sole occupant of the one-man turret. Because of the increased internal volume of the bigger turret, his station is less cramped than the one in a BMD-1, but it is still extremely cramped by any reasonable standard. In order to accommodate the gunner in the small turret, the 2A42 cannon was mounted slightly to the right of the turret while the gunner's seat was offset to the left.<br />
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<a href="https://3.bp.blogspot.com/-gwweUZi3zlg/Wnbp8ywX-OI/AAAAAAAAKsE/4jyCk0rEJxEmo6c4yIVgaCXfn25WEfYzgCLcBGAs/s1600/bmd-2%2Bgunner%2Bseat.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="450" data-original-width="600" height="480" src="https://3.bp.blogspot.com/-gwweUZi3zlg/Wnbp8ywX-OI/AAAAAAAAKsE/4jyCk0rEJxEmo6c4yIVgaCXfn25WEfYzgCLcBGAs/s640/bmd-2%2Bgunner%2Bseat.jpg" width="640" /></a></div>
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The gunner has good all-round visibility from his station, which compensates for the lack of a commander in the turret. More importantly, it allows the gunner to independently spot and engage targets if the commander has dismounted the vehicle together with the other passengers. He is provided with four TNPO-160 periscopes, two aimed to the left and another two aimed to the right. Directly in front of him, of course, is where the gunsights are mounted. This is shown in the photo below.<br />
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<a href="https://1.bp.blogspot.com/-nRP3L3uNKMc/WncBJqHPQ1I/AAAAAAAAKsU/8lfFZijHOlc1i5PCBIwsgfP94IGbgx30wCLcBGAs/s1600/bmd-2%2Bturret%2Btop.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="622" data-original-width="984" height="403" src="https://1.bp.blogspot.com/-nRP3L3uNKMc/WncBJqHPQ1I/AAAAAAAAKsU/8lfFZijHOlc1i5PCBIwsgfP94IGbgx30wCLcBGAs/s640/bmd-2%2Bturret%2Btop.jpg" width="640" /></a></div>
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In order to not interfere with the gunner's hatch, the two periscopes on the left side of the turret are installed in a special bulge. A cut was made into the round turret and a curved armour plate was welded on top of it, as shown in the photo below. The shape of the roof plate was designed with the bulge in mind, so the circular plate was stamped out with an irregular edge, as you can see in the photo above.<br />
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<a href="http://3.bp.blogspot.com/-iaXIJLYcSyQ/ValXS5TV4II/AAAAAAAAC2g/_p7jSsoyLDc/s1600/w00261_9664965.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="298" src="https://3.bp.blogspot.com/-iaXIJLYcSyQ/ValXS5TV4II/AAAAAAAAC2g/_p7jSsoyLDc/s400/w00261_9664965.jpg" width="400" /></a></div>
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As mentioned before, the TNPO-160 provides a total range of vision of 28 degrees in the vertical plane and 78 degrees in the horizontal plane. Combined with the<br />
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He is provided with two sights; a combined day/night primary sight and a special high-elevation anti-aircraft sight.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-wWmZCRPoveI/VX2ORFL0_hI/AAAAAAAACj0/zFCwUU71TI8/s1600/bmd-2%2Bsights.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://2.bp.blogspot.com/-wWmZCRPoveI/VX2ORFL0_hI/AAAAAAAACj0/zFCwUU71TI8/s640/bmd-2%2Bsights.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Note the larger combined primary sight on the turret roof and the smaller high elevation anti-aircraft sight to the right</td></tr>
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The weapons complex and fire control system is identical to the BMP-2. The weapons are controlled from a BU-25-2S control panel. The ammunition reserves for both the 2A42 cannon and the PKTM coax are shown on a small digital display, along with the ammunition type currently selected for the 2A42, and the gunner switches the ammunition type for the 2A42 by flicking a toggle switch.<br />
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<a href="https://4.bp.blogspot.com/-D8YHtgv7d0U/WhvsiajHYhI/AAAAAAAAKOk/mE49vVEEqtwYVwHYG90xvOKwvcHeBzBwACLcBGAs/s1600/weapons%2Bcontrol%2Bpanel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="585" data-original-width="1050" height="356" src="https://4.bp.blogspot.com/-D8YHtgv7d0U/WhvsiajHYhI/AAAAAAAAKOk/mE49vVEEqtwYVwHYG90xvOKwvcHeBzBwACLcBGAs/s640/weapons%2Bcontrol%2Bpanel.png" width="640" /></a></div>
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At the back of the turret, on the roof, there is a small ventilation port which can be opened and closed from inside by the gunner. The cover is attached to a threaded guide rod, which has a handle at the bottom. The gunner simply turns the handle to screw guide rod down, lowering the cover and sealing the port hole. When it is closed, a rubber gasket prevents the ingress of contaminated particles from outside the vehicle, but also prevents the egress of gunpowder fumes from firing the 30mm cannon.<br />
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<a href="https://1.bp.blogspot.com/-iIjFkXrM8Rk/WhvsyAXF9PI/AAAAAAAAKOs/iZurxD3_JnEG9F_eSEhUjI6MVgCgkBHBACLcBGAs/s1600/ventilation%2Bport%2Bcover%2Bhandle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="586" data-original-width="1049" height="356" src="https://1.bp.blogspot.com/-iIjFkXrM8Rk/WhvsyAXF9PI/AAAAAAAAKOs/iZurxD3_JnEG9F_eSEhUjI6MVgCgkBHBACLcBGAs/s640/ventilation%2Bport%2Bcover%2Bhandle.png" width="640" /></a></div>
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<h3>
<span style="font-size: large;">SIGHTING COMPLEXES</span></h3>
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The BMD-2 mounts two sighting units - a BPK-2-42-01 transplanted from the BPK-2-42 sight that the BMP-2 uses, and a PZU-8 anti-aircraft sight.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-R5NG56OHXmA/VhgxwrpdrzI/AAAAAAAAD5g/78VPYHKHVNM/s1600/bmd-2%2Bsights.png" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://3.bp.blogspot.com/-R5NG56OHXmA/VhgxwrpdrzI/AAAAAAAAD5g/78VPYHKHVNM/s1600/bmd-2%2Bsights.png" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">PZU-8 to the left, BPK-2-42-01 to the right</td></tr>
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<span style="font-size: large;">BPK-2-42-01</span></h3>
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The BPK-2-42-01 combined passive/active universal sight is the gunner's primary sight. It is a very slightly modified variant of the BMP-2's BPK-2-42 sight, practically identical in all respects. The sight is capable of passive light intensification or active imaging with the help of the L-2 Luna IR spotlight mounted coaxially to the gun and turret. The reticle may be illuminated by an internal light bulb to facilitate aiming at twilight hours if the night mode is not used. The nominal maximum range for identifying a tank-type target using active night vision is 800 meters.<br />
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The daytime sight channel has a fixed 6x magnification in the daytime channel and 5.5x in the nighttime channel, and a field of view of 10° in the daytime channel and the 6°40′ in the night channel.<br />
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<a href="http://3.bp.blogspot.com/-YtWgfgCwxYc/VagegiSOeEI/AAAAAAAACxY/LzEghygXSJw/s1600/dfe20c28b8ccc8d0b8787d690362258b.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://3.bp.blogspot.com/-YtWgfgCwxYc/VagegiSOeEI/AAAAAAAACxY/LzEghygXSJw/s400/dfe20c28b8ccc8d0b8787d690362258b.jpg" width="400" /></a></div>
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The sight aperture is protected by a layer of ballistic glass to protect it from bomb splinters, but there is an additional spring-loaded pane of ballistic glass that may be lowered for protection from small arms fire. However, the supplementary pane has worse image clarity and could make reconnaissance a little bit harder, so it is usually kept raised unless explicitly needed. The sight has a small wiper.<br />
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The sight is an unremarkable one, unfurnished with any accurate method of rangefinding. To do that, the gunner must rely on a simple stadiametric scale with a maximum measuring distance of 2.5 km. Once the range to the target has been determined, the gunner must manually enter the range data into the sight, which then prompts it to make the necessary adjustments to the position of the reticle, namely, by raising the reticle up and down. The gunner must then manually lay the gun on the target by lining up the target with the adjusted reticle (which would be lowered to compensate for distance, forcing the gunner to raise the gun so that the reticle meets the target). This crude system is more commonly found on tanks from the 50's and 60's.<br />
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Overall, the process was slow and clumsy. Users probably preferred to depend on battlesighting, and walking the rounds onto target. This means that the reticle is fixed at a predetermined range, usually about a kilometer or so, and the gunner makes corrections on the fly depending on whether the shell went high or low. This cannot be considered advanced by any criteria, but it is some consolation that contemporary IFVs such as the M2A1 Bradley had to depend on a similarly clumsy stadiametric choke reticle for range finding.<br />
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<h3>
<span style="font-size: large;">SOZh-M</span></h3>
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Recently modernized BMD-2 models have swapped out the BPK sight for the new and slightly more sophisticated SOZh accompanied by a new PL-1-01 laser beamer replacing the old IR spotlight.<br />
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<a href="https://4.bp.blogspot.com/-FFlNukiT3r8/V8xDCfW9beI/AAAAAAAAHQs/uJeZvZAtxR4pxJkva8qzkNp5IpkoKtHswCLcB/s1600/23-44-29-isp-bmd-4m_080814_2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://4.bp.blogspot.com/-FFlNukiT3r8/V8xDCfW9beI/AAAAAAAAHQs/uJeZvZAtxR4pxJkva8qzkNp5IpkoKtHswCLcB/s640/23-44-29-isp-bmd-4m_080814_2.jpg" width="640" /></a></div>
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By emitting a pulsed laser beam, the PL-1-01 can also double as a laser rangefinder. A pulsed beam also reduces backscatter in poor weather conditions, thus allowing the gunner to see farther.<br />
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At this point, only a limited number of BMD-2s have been confirmed to be modernized thusly. One example is known to have ended up in East Ukraine. The "silent modernization" of BMD-2s is likely to be ongoing as part of the general military modernization plan.<br />
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<h3>
<span style="font-size: large;">PZU-8</span></h3>
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The PZU-8 sight is mounted on the side of the turret. It performs primarily in the anti-aircraft role, thanks to its extremely high elevation of +85° and depression of -10°. Its very large field of view of 50° enables the gunner to effectively track fixed wing ground attack aircraft as well as fast-moving attack helicopters. The sight lacks independent stabilization. It is directly linked mechanically to the cannon, so that it elevates and depresses with it.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-w6kaJwzvtTE/Vaf0RbrrDUI/AAAAAAAACvY/ttWsG2Xx17Q/s1600/pzu-8.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="478" src="https://3.bp.blogspot.com/-w6kaJwzvtTE/Vaf0RbrrDUI/AAAAAAAACvY/ttWsG2Xx17Q/s640/pzu-8.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">PZU-8 high-elevation auxiliary anti-aircraft sight. Notice the thickness of the steel protrusion protecting the sight along its length</td></tr>
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<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-2foNQ2GRSfw/VagMh0bbhzI/AAAAAAAACwc/n8PV-Cofm2M/s1600/97595b2b365f03d77d13a39049377728.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="425" src="https://2.bp.blogspot.com/-2foNQ2GRSfw/VagMh0bbhzI/AAAAAAAACwc/n8PV-Cofm2M/s640/97595b2b365f03d77d13a39049377728.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Aperture</td></tr>
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The sight elevates and depresses in line with the autocannon.<br />
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<a href="http://1.bp.blogspot.com/-UOsuyBD2YmQ/ValqzE4UHkI/AAAAAAAAC34/ASUkfTZQHPY/s1600/bmd-2%2Banti-aircraft%2Bsight%2Blook%2B1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="235" src="https://1.bp.blogspot.com/-UOsuyBD2YmQ/ValqzE4UHkI/AAAAAAAAC34/ASUkfTZQHPY/s400/bmd-2%2Banti-aircraft%2Bsight%2Blook%2B1.png" width="400" /></a><a href="http://4.bp.blogspot.com/-zBnB-i3Qez4/Valq1UmvRrI/AAAAAAAAC4A/ilLt0-ldvHg/s1600/bmd-2%2Banti-aircraft%2Bsight%2Blook%2B2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="235" src="https://4.bp.blogspot.com/-zBnB-i3Qez4/Valq1UmvRrI/AAAAAAAAC4A/ilLt0-ldvHg/s400/bmd-2%2Banti-aircraft%2Bsight%2Blook%2B2.png" width="400" /></a></div>
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<h3>
<span style="font-size: large;">STABILIZERS</span></h3>
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<span style="font-size: large;">2E36-1</span></h3>
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The BMD-2 is provided with two-plane stabilization in the form of the 2E36-1 fully electromechanical stabilizer, including the EDM-30 electric motor for turret traverse and the DGN-3 electric motor drive for weapons elevation.<br />
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<a href="http://2.bp.blogspot.com/-ml4mDzWzn_A/VhJ5MK11dNI/AAAAAAAAD4s/dOyY7BjnpYQ/s1600/2e36-1%2Bstabilizer%2Bmotor.gif" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-ml4mDzWzn_A/VhJ5MK11dNI/AAAAAAAAD4s/dOyY7BjnpYQ/s1600/2e36-1%2Bstabilizer%2Bmotor.gif" /></a> <a href="http://3.bp.blogspot.com/-KDSY-HX5MBk/VlHoetXM-KI/AAAAAAAAEYo/yyLrAJKN3Wo/s1600/dgn-3%2Belectric%2Bmotor.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="179" src="https://3.bp.blogspot.com/-KDSY-HX5MBk/VlHoetXM-KI/AAAAAAAAEYo/yyLrAJKN3Wo/s200/dgn-3%2Belectric%2Bmotor.jpg" width="200" /></a></div>
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The 2E36-1 stabilization system uses electric motors for both horizontal and vertical drives. The preclusion of any hydraulic drives saves space and increases the safety factor enormously; the lack of flammable hydraulic fluid being pumped at high pressure greatly reduces the chance of a catastrophic internal fire in the event of a turret perforation.<br />
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<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-jAoE6UEvZFs/VhJwmswR4cI/AAAAAAAAD4M/h94WCtApNCQ/s1600/bmd-2%2Bstabilizers.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="425" src="https://3.bp.blogspot.com/-jAoE6UEvZFs/VhJwmswR4cI/AAAAAAAAD4M/h94WCtApNCQ/s640/bmd-2%2Bstabilizers.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="color: orange;">Vertical stabilizer motor</span> and <span style="color: #6fa8dc;">Horizontal stabilizer motor</span></td></tr>
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<a href="http://2.bp.blogspot.com/-56KKRtYiZLY/VhJuisqxBXI/AAAAAAAAD4A/WsZ6ukV7nnQ/s1600/bmd-2%2Bgunners%2Bhand%2Bgrips.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="356" src="https://2.bp.blogspot.com/-56KKRtYiZLY/VhJuisqxBXI/AAAAAAAAD4A/WsZ6ukV7nnQ/s640/bmd-2%2Bgunners%2Bhand%2Bgrips.png" width="640" /></a></div>
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The 2E36-1 stabilizer system has two modes of operation; automatic and semi-automatic. In the automatic mode, the stabilizer operates in the traditional sense, obeying prompts from the gunner and keeping the turret and cannon oriented with maximal accuracy at a point determined by the gunner. The semi-automatic mode, however, only meant for anti-aircraft use. Once the cannon is elevated more than +35 degrees, the stabilizer system shifts into semi-automatic on its own accord. In this mode, the stabilizer disconnects from the BPK-2-42-01 sight, which cannot be used to aim at angles of elevation of above +35 degrees, and interfaces with the PZU-8 anti-aircraft sight. The stabilizer then loses some of its precision, but gains speed. This is to help track and engage fast, highly maneuverable attack helicopters strafing at low altitudes and at closer ranges, where the relative speed of the aircraft in question is higher than if it was many hundreds of meters away. At longer distances, the elevation angle
necessary to engage an aircraft at a certain altitude is less than if
the
aircraft is closer and the relative speed of the aircraft is also lower,
so turret rotation speed is less important but more precision is
required. In that case the gunner may
continue to make use of the stabilizer in the automatic mode. <br />
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The stabilizer is good enough for the job, though the turret traverse speed has the potential to be much higher. Modernized BMD-2Ms (the variant with Kornet launchers) are apparently equipped with the latest 2E36-6 stabilizer complex. How much the new system differs from the old one is not known at this time.<br />
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<b><i>Automatic Mode</i></b></h3>
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Time for full turret rotation: 12 seconds<br />
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Maximum Traversal Speed: 30°/sec<br />
Minimum Traversal Speed: 0.07°/sec<br />
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Maximum Elevation Speed: 30°/sec<br />
Minimum Elevation Speed: 0.07°/sec<br />
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With a minimum traverse and elevation speed of 0.07 degrees per second, the average accuracy of stabilization would be able to achieve an aiming precision of no less than 1.24 mils, which is equivalent to 1.24 meters at 1 km. With the accuracy of the armament itself accounted for, that degree of accuracy would be more than enough to guarantee consistent hits on targets of the APC and IFV variety at typical combat ranges, though the degree of precision is still very lacking compared to Western technological equivalents of the time.</div>
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<i>Semi-Automatic Mode</i></h3>
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Time for full turret rotation: 10 seconds</div>
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Maximum Traversal Speed: 35°/sec<br />
Minimum Traversal Speed: 0.1°/sec<br />
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Maximum Elevation Speed: 35°/sec</div>
Minimum Elevation Speed: 0.1°/sec<br />
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At a cruising speed of 25 km/h to 35 km/h, the stabilizer is capable of maintaining its orientation at or close to its best performance. Drifting is noticeable at higher speeds. Needless to say, the precision increases linearly as the speed of the vehicle decreases.<br />
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<span style="font-size: large;">ARMAMENT</span></h3>
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<a href="http://4.bp.blogspot.com/-E37nmRHDczg/VX2Ho0RDXbI/AAAAAAAACjk/DjtU90RBHxM/s1600/bmd-2%2Bfiring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-E37nmRHDczg/VX2Ho0RDXbI/AAAAAAAACjk/DjtU90RBHxM/s1600/bmd-2%2Bfiring.png" /></a></div>
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The primary weapons of the BMD-2 were a single 2A42 autocannon and a PKTM coaxial machine gun. The turret has provisions for mounting a 9M111 Fagot or 9M113 Konkurs ATGM on the roof to be fired by the gunner, who had to be partially exposed on the turret roof.<br />
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<span style="font-size: large;">2A42</span></h3>
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<a href="http://3.bp.blogspot.com/-Lk3bM77oq2g/VXxbn852XAI/AAAAAAAACiY/2NS2K5qZ6jo/s1600/009_2a42.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-Lk3bM77oq2g/VXxbn852XAI/AAAAAAAACiY/2NS2K5qZ6jo/s1600/009_2a42.jpg" /></a></div>
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The 2A42 is a dual-feed autocannon chambered for the Soviet 30x165mm cartridge. It has a variable rate of fire of either 200 rounds per minute or 550 rounds per minute. However, it can go up to 800 rounds per minute once the cannon is heated up by a few seconds of firing on full auto. Its high rate of fire is invaluable during engagements with concentrations of infantry, or when attacking a well-fortified position, whereby extra demolition power may be necessary. In practice, the 2A42 is simply irreplaceable during engagements with stealthy adversaries. Even with thermal imaging sights, it may prove nigh impossible to spot and hit skilled and agile foot soldiers hidden in foliage and constantly on the move. Under such circumstances, the ability to saturate likely spots and areas of interest with high-explosive cannon shells is absolutely invaluable for preserving the vehicle itself as well act as in support of dismounted infantry. This was one of the reasons why the BMP-2 and BMD-2 was much more successful in Afghanistan and Chechnya than the BMP-1 and BMD-1.<br />
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The gun has +60 degrees of elevation and -5 degrees of depression. This gave the BMD-2 the ability to engage aircraft, as well as targets located in high rises and tall mountains, but the inability to adequately take advantage of reverse slopes remains constant. This is quite a blow to the overall survivability of the BMD-2, as its armour is far too thin to be able to sustain a head-on firefight, so it must always operate undercover. "Hull down" doesn't necessarily involve reverse slopes, of course. The BMD-2 can still take advantage of thick shrubbery, large rocks and other terrain features for concealment, but having one option denied to it is no small matter.<br />
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<a href="http://1.bp.blogspot.com/-AD_IvjdEkCs/VhhRCf7DNsI/AAAAAAAAD6U/kcaqddwkHgE/s1600/4c378688892d4ff42cb546d561cf46e2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://1.bp.blogspot.com/-AD_IvjdEkCs/VhhRCf7DNsI/AAAAAAAAD6U/kcaqddwkHgE/s640/4c378688892d4ff42cb546d561cf46e2.jpg" width="640" /></a></div>
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Maximum dispersion is 346.67mm at a distance of 100m. This figure can be expressed as 13.036 MOA (13.036 x 1.047 inches at 100 yards). This figure was calculated from an acceptance test video of the DVK-30 drop-in turret <a href="https://www.youtube.com/watch?v=tZw64RVPtg4">(link)</a>. By obtaining an MOA figure, which is an angular unit of dispersion, we can very easily find out what sort of dispersion we would get at different distances. At 1000 meters, the maximum dispersion (which I will define as the length of the distance between the two impacts that are furthest from each other), should be 3.467 meters, and all shots fire must invariably lie within that limit. Alternatively, a figure of ∼3 meters at a distance of 1000m can be expressed as a dispersion of 3 mils. This is congruent with claims floating around the internet of an accuracy of "2 - 4 mils". No doubt that this is pretty terrible performance for an autocannon firing at 200-300 rounds per minute, but that should be the <u><i>maximum</i></u> dispersion. The median dispersion should be much smaller. The second volley in the video shows a dispersion of just 8.12 MOA. That would be a dispersion of only 2.362 meters at a distance of 1000 m. Again, this fits into the "2 - 4 mils" claim neatly. The 2A42 cannon has a predisposition to create vertical shot groups. In both of the firing tests shown in the video, four rounds were arranged neatly in a vertical pattern, with one outlying shot skewing the results for the worst. As such, even though the cannon has an angular dispersion of 2 - 4 mils, 80% of the shots seem to tend to end up in an oval group of less than 2 meters.<br />
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This data should be valid for full caliber rounds like the 3BR6 and 3OF8. Subcaliber rounds like the 3BR8 will display superior accuracy and better consistency at all ranges, but the difference is only truly visible at longer ranges. 3BR8 APDS should have a maximum dispersion of 2 mils when fired from the 2A42, and just like with full caliber rounds, most of the shots will likely be located in an oval group less than 2 mils in size, as shot patterning depends more on the particular harmonic properties of the weapon system rather than the ammunition itself. However, it remains to be seen if the BMD-2 will have access to 3UBR8 rounds.<br />
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<a href="https://2.bp.blogspot.com/-YqpGxeSlDK8/V3dV-qYUefI/AAAAAAAAG-c/8LLks_jAG-UJOXtmN2Y3AxWX2yx5k9JwQCLcB/s1600/bmd-2%2Bfiring%2Bat%2Brange.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="358" src="https://2.bp.blogspot.com/-YqpGxeSlDK8/V3dV-qYUefI/AAAAAAAAG-c/8LLks_jAG-UJOXtmN2Y3AxWX2yx5k9JwQCLcB/s640/bmd-2%2Bfiring%2Bat%2Brange.png" width="640" /></a><br />
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Although much less accurate than its immediate counterparts, the 2A42 cannon is more than capable of engaging pinpoint targets, though not as efficiently as the British RARDEN or American Mk44, which are more accurate by nearly two times. The RARDEN is accurate by virtue of special dampening and a very tame rate of fire, while the Mk44 is accurate thanks to a 69.4 kg barrel. If the gunner went for the RARDEN route and switched to semi-automatic to fire the cannon only about twice every second, it should be possible to <i><b>approach</b></i> (not <b><i>meet</i></b>) the same level of accuracy. Keeping in mind the fact that the ammunition capacity for the BMD-2 is quite limited, this is the only way the gunner can effectively eliminate armoured targets at long range while still having enough ammunition to complete the rest of the objective. In situations where accuracy may only have supplementary value, such as when engaging large concentrations of manpower, the 2A42 is at a clear advantage.<br />
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By virtue of its high rate of fire and powerful ammunition, the 2A42 is effective even against main battle tanks of the modern era, not to mention more lightly armoured vehicles. Live fire testing confirmed that the 2A42 is not only able to produce a 'mission kill' on main battle tanks, but also do it very rapidly, which is an invaluable attribute, especially for a vehicle as light as the BMD-2. In the space of a few seconds, the gunner can let off around 20 to 30 shots with a few short bursts at medium ranges and reliably guarantee the destruction or disablement of various exterior devices such as tracks, periscopes, sensors, weapons, or perhaps large exterior laser rangefinders and IR spotlights as found on 60's and 70's era tanks. After a few seconds of action, the BMD-2 can immediately disappear behind terrain under the cover of a smokescreen.<br />
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Recoil is managed by the double-baffle muzzle brake.<br />
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<a href="http://2.bp.blogspot.com/-GlZi20TGByg/Vau4gf1EVqI/AAAAAAAAC7M/-8LIcPBn0sY/s1600/2a42%2Bmuzzle%2Bbrake.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="358" src="https://2.bp.blogspot.com/-GlZi20TGByg/Vau4gf1EVqI/AAAAAAAAC7M/-8LIcPBn0sY/s640/2a42%2Bmuzzle%2Bbrake.png" width="640" /></a></div>
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The autocannon is mounted slightly off to the right, which drives an unfortunate tendency for the turret to spin slightly to the right when the autocannon fires long bursts in full automatic. The effect is negligible at slower rates of fire, though, so this idiosyncrasy shouldn't affect accuracy too much when it matters. This problem possibly led to the use of the low-recoil 2A72 cannon in the BPPU-1 turret for the BTR-80A and the BTR-82A instead of the 2A42.<br />
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The ammunition load of 300 rounds is stowed in separate conformal containers on the right side of the turret, the space on the left side being reserved for the gunner. 180 rounds of HEI/-T ammunition and 120 rounds AP-T and APDS-T ammunition are available. Under certain mission conditions where encounters with armoured vehicles are not expected, both containers can be loaded purely with HEI/-T ammunition. This was not uncommonly done in low intensity conflicts such as in Chechnya or Afghanistan.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-w6MI2UfA3ZY/VX2Z3Izxc5I/AAAAAAAACkE/lKJEtRAxayk/s1600/bmd-2%2Bammunition.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="306" src="https://2.bp.blogspot.com/-w6MI2UfA3ZY/VX2Z3Izxc5I/AAAAAAAACkE/lKJEtRAxayk/s640/bmd-2%2Bammunition.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The red container contains ready ammunition</td></tr>
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<a href="http://3.bp.blogspot.com/-_aHyLHhwo0Y/VagMal8ZzlI/AAAAAAAACwU/X7q-SnIFgcM/s1600/8c62a2c99973ff1222a277eb2840d333.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://3.bp.blogspot.com/-_aHyLHhwo0Y/VagMal8ZzlI/AAAAAAAACwU/X7q-SnIFgcM/s640/8c62a2c99973ff1222a277eb2840d333.jpg" width="640" /></a></div>
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Although the autocannon is undoubtedly quite powerful, the small stock of ready ammunition carried in the BMD-2 severely limits the vehicle's ability to conduct sustained firefights, and the lack of internal space makes stowing additional ammunition troublesome. Compared to the German Marder 1A+ series, for example; those carry up to 1250 rounds of a much less lethal 20mm caliber, but that means that a Marder gunner has far more freedom in choosing his targets and a better ability to provide suppressive fire. Whether that suppressive fire actually has a chance of injuring anybody is a completely different question. 20x139mm HEI ammunition for the Marder's Rh202 autocannon packs a measly 5.8g of Hexal, and the projectile itself weighs 125g. Compare that to the 3UOF8, which presides in an entirely different category altogether:<br />
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There are three pyrotechnic charges that can be used to instantaneously cock the cannon and ready it for firing or to clear a malfunction during combat. Normally, the cannon is readied manually by the gunner by having its bolt mechanism puled back by using a ratcheted lever attached to the cannon receiver. The process is laborious and time consuming (due to the heavy recoil spring necessary to withstand the tremendous recoil forces), but it does have its own advantages. Although such eccentricities would not be necessary in an electrically operated chaingun, a chaingun requires external power to fire. If the power source was interrupted, a chaingun would be rendered useless. Due to its gas-powered nature, the 2A42 can still be fired with the BMD-2 operating in "degraded mode" where the engine is knocked out and battery power is cut off, so that all operations are reverted to manual control.<br />
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<a href="https://thesovietarmourblog.blogspot.com/p/30x165mm-cartridges.html">This page</a> contains a detailed examination of each 30mm cartridge available to the BMD-2 during its brief service in the Soviet Army.<br />
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<h3>
<span style="font-size: large;">SECONDARY</span></h3>
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<img src="https://3.bp.blogspot.com/-BLDjSGKUdhA/VRgWHimMEpI/AAAAAAAABgw/0TNlLhqld8o/s1600/pktm.png" /></div>
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A PKTM machine gun is mounted on the turret as a coaxial weapon, mainly for use in situations where the autocannon might be unnecessary or excessive for the task. Considering the relatively limited capacity of ammunition for the autocannon and the lack of a reserve supply, it may be sensible to use the PKTM for tasks such as engaging infantry behind light cover. As a rule, 7.62mm rifle rounds are not powerful enough to prove to be meaningful in any large capacity against entrenched manpower or infantry behind field fortifications. Ammunition is supplied in 250-round belts stored in individual boxes. This was a downgrade from the BMD-1 which held 2,000 rounds in a single box so the gunner would not be distracted by the need to reload the machine gun. The only advantage is that smaller boxes of 250 rounds tend to be less likely to cause stoppages, but since the one-man turret is only occupied by the gunner and he is responsible for everything inside it, giving him more responsibilities does not increase the combat effectiveness of the weapon system.<br />
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<h3>
<span style="font-size: large;">BOW MACHINE GUNS</span></h3>
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Two more PKB machine guns are mounted on either side of the forward hull to be used by the two passengers seated on either side of the driver. Late model BMD-2s had the port side bow machine gun removed to free up more space for the commander to perform his other duties (manning the radio station, observing, etc). The unused machine gun port would be covered with an armoured plug.<br />
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<a href="http://3.bp.blogspot.com/-KgxVqQ4dFG0/VbTyih4dK4I/AAAAAAAAC8w/crLvI--zuWk/s1600/pkb%2Bmachine%2Bgun.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="140" src="https://3.bp.blogspot.com/-KgxVqQ4dFG0/VbTyih4dK4I/AAAAAAAAC8w/crLvI--zuWk/s640/pkb%2Bmachine%2Bgun.png" width="640" /></a></div>
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The PKB machine gun was a modified PK machine gun with removable spade grips and modified trigger. The the rotating TNPP-220 periscope directly in front of the bow gunner(s) is mechanically slaved to the machine gun port. This meant that wherever the machine gun was pointed, the periscope would accurately face the same direction. Elevation as well as horizontal traverse were both fully accounted for. The bow gunner would aim using a small scope on the right side of the TNPP-220 periscope, visible below.<br />
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<a href="http://1.bp.blogspot.com/-oTmcuQLRcWA/VhkKGRLStTI/AAAAAAAAD8A/6gDCMxF6fZE/s1600/bmd%2Bbow%2Bgunner.png"><img border="0" height="356" src="https://1.bp.blogspot.com/-oTmcuQLRcWA/VhkKGRLStTI/AAAAAAAAD8A/6gDCMxF6fZE/s640/bmd%2Bbow%2Bgunner.png" width="640" /></a></div>
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A small internal 1.5x scope is installed inside the periscope and the eyepiece is viewed through the prismatic glass block of the periscope. Fire correction is done simply by using the fixed reticle markings and by observing the fall of the tracers from the machine gun to determine the correct distance and deflection.<br />
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<a href="https://1.bp.blogspot.com/-YQE5mOmjjC8/XJnvQi3cY9I/AAAAAAAANm4/hqYUd0Mhx8k-Z2d7rxZNvrrskJyk02j0QCLcBGAs/s1600/tnpp-220.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1380" height="400" src="https://1.bp.blogspot.com/-YQE5mOmjjC8/XJnvQi3cY9I/AAAAAAAANm4/hqYUd0Mhx8k-Z2d7rxZNvrrskJyk02j0QCLcBGAs/s400/tnpp-220.png" width="345" /></a></div>
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The aiming mechanism of the BMD-1 was carried over to the BMD-2. As you can see in the two pictures below, the TNPP-220 periscope was mechanically linked to the ball turret by a pair of hinges. Traversing and elevating the bow machine gun would translate into the movement of the periscope. Because the periscope is placed directly above the machine gun, the horizontal parallax is negligible when aiming forward. However, when the machine gun is traversed or elevated, parallax in both axes increases.<br />
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Ammunition for the PKBs is supplied in 250-round belts in individual boxes. Although the aiming system is somewhat rudimentary from an technical point of view, it was quite useful and certainly quite novel. The spade grips and periscope combination probably allowed the bow gunner to hold the machine gun somewhat steady and provide reasonably accurate fire even while the vehicle is on the move.<br />
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The bow gunner's periscope and the ball turret for the machine gun are both heated. Heating for the periscope prevents fogging, and heating for the ball turret prevents it from freezing in place in icy weather. The mounting cradle for the PKTM machine gun is seen below.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-itlP7jbklYY/Vg1VAoDmCCI/AAAAAAAAD3I/5qqMHwedXkc/s1600/bmd%2Bbow%2Bmachine%2Bgun.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="359" src="https://1.bp.blogspot.com/-itlP7jbklYY/Vg1VAoDmCCI/AAAAAAAAD3I/5qqMHwedXkc/s640/bmd%2Bbow%2Bmachine%2Bgun.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The periscope-to-machine gun connection has been dismantled in this example</td></tr>
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Additionally, there are two firing ports on either side of the hull.<br />
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<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-VVLm0byy1wg/ValVAlAj43I/AAAAAAAAC2Q/R_NWm1quNGc/s1600/bmd%2Bfiring%2Bports.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="355" src="https://2.bp.blogspot.com/-VVLm0byy1wg/ValVAlAj43I/AAAAAAAAC2Q/R_NWm1quNGc/s640/bmd%2Bfiring%2Bports.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Firing port on the starboard hull</td></tr>
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<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-gIyCMBzwuvs/Vau06RtmYII/AAAAAAAAC7A/RA7IwUUz6Bc/s1600/w00261_1993595.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="478" src="https://3.bp.blogspot.com/-gIyCMBzwuvs/Vau06RtmYII/AAAAAAAAC7A/RA7IwUUz6Bc/s640/w00261_1993595.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Firing port on the rear exit hatch</td></tr>
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The firing ports can fit any type of rifle.</div>
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<h3>
<span style="font-size: large;">TERTIARY</span></h3>
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<a href="https://2.bp.blogspot.com/-c6_0KvSkIOo/WLjvY3XxCNI/AAAAAAAAIeA/O2pgf7hL9wAfAs_Z6Iu8pYsgxs2-FQjwwCLcB/s1600/bmd-2%2Bparade.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="436" src="https://2.bp.blogspot.com/-c6_0KvSkIOo/WLjvY3XxCNI/AAAAAAAAIeA/O2pgf7hL9wAfAs_Z6Iu8pYsgxs2-FQjwwCLcB/s640/bmd-2%2Bparade.jpg" width="640" /></a></div>
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Like the BMD-1P preceding it, the BMD-2 features a small protruding post on the roof of the turret, on which the 9M111 Fagot or 9M113 Konkurs ATGM systems may be mounted. The BMD-2 was issued with 9P135 Konkurs missile launchers, which were backwards compatible with Fagot missiles.<br />
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It must be said outright that one of the biggest failings of the BMD-2 lies in the fact that this rooftop ATGM may only be fired by either a dismounted passenger manning it from behind the turret, or by the gunner, who must open his hatch. The whole process from aiming and firing the ATGM to guiding it to its target may take as much as 20 seconds, exposing the user to return fire all the while. Although the operator (usually the gunner) may not have much to fear from bullets coming from the front, as his 6mm-thick hatch offers some protection, he would be in danger from overhead threats like airbursting mortar shells and bomb splinters from all around him.<br />
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As mentioned earlier, the missile launcher itself is the standard 9P135 launch-and-control unit, sans tripod. The launcher is placed very high up relative to the turret, far above even the gunsights. A cunning crew could take advantage of this and park their BMD-2 behind a hill, exposing only the missile launcher. After hitting the target, the variable height suspension may be lowered to conceal the launcher for a reload, and raised for another shot.<br />
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Another distinct, if questionable advantage to this setup is that the missile launcher can be dismounted and used by the crew when fighting on foot, if perhaps the vehicle is disabled. This means that even if they are forced to abandon ship, the crew still has heavy weapons on hand and still can repel an attack, and perhaps even live to put the launcher back on its pedestal.<br />
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Both the Fagot and Konkurs missiles are wire-guided, utilizing an infrared bulb at the rear end of the rocket for the launcher to track, and both missiles are launched via a two-staged propulsion system. The first stage is a squib cartridge in the rear of the container which generates high-pressure gas that propels the missile out of the tube. Once the missile has cleared some distance, the rocket motor activates and sustains the missile's flight up until it has reached its target. The high magnification power of 10x offered by the 9P135 launcher enables the gunner to use the long range of the missile to its full extent.<br />
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Like with the BMP-2, the high placement of the missile launcher plus the height adjustment feature of the BMD-2 presents some unique tactical opportunities. For example, it is possible for the BMD-2 to be placed in complete defilade with the hull and turret behind a hill, rock or other type of cover or concealment, and have the ATGM fired over it. The vehicle can adapt to a variety of such pieces of cover expressly due to its height adjustment feature.<br />
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There can be a total of 3 missiles stored behind the gunner's seat. Reloading the missile launcher is slow and laborious due to the rather cramped nature of the turret, but the fact that the missiles are stowed inside the turret itself and not in the hull simplifies matters considerably. The average rate of fire should be around 2 rounds per minute with both the Fagot and Konkurs.<br />
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<h3 style="text-align: left;">
<span style="font-size: large;">
PROTECTION</span></h3>
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The aluminium hull of the BMD-2 is carried over from the BMD-1, and the turret is made of steel, just like with its predecessor. The vehicle is very light, but that is not to say that the vehicle has distinguishably poor protection <i>per se</i>; Although the BMD-2 is much lighter than most other IFVs, it is also much, much smaller than most other IFVs, which means that it retains <b><i>armour density</i></b><i> </i>roughly equal to that of a volumetrically larger and correspondingly heavier vehicle.<br />
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The hull is made of aluminium alloy, while the turret is made of steel. The frontal arc can withstand .50 caliber machine gun fire at point blank range but the side armour can only resist 7.62mm machine gun fire from several hundred meters - worse than the non-airborne BMP-2, but comparable to the M113, a similarly aluminium-cladded armour personnel carrier. The rolled aluminium alloy plates used in the BMD-2 is ABT-101, same as the BMD-1.<br />
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Contrary to the Wikipedia-perpetuated urban legend of the BMD-2 and BMD-1 having "cast magnesium armour" that "burned fiercely when hit by an RPG", neither the BMD-2 or the BMD-1 used cast magnesium armour. ABT-101 is an aluminium alloy for fabricating rolled plates, and both the BMD-1 and BMD-2 are built from welded plates. ABT-101 is an Al-Zn-Mg alloy containing 91% aluminium, while the other 9% is composed of zinc and magnesium, but mostly zinc. The rumours of "magnesium armour" being responsible for burning BMDs are likely based on burnt-out wrecks with melted hulls and wheels, but this has nothing to do with the magnesium content in the armour, but rather the low melting point of aluminium (only 591-638°C for 5083 alloy) which is almost a three times lower than armour grade steel, and low enough that ammunition and fuel fires can melt it when heated for prolonged periods. However, the aluminium itself does not burn so external heat must be applied constantly. The amount of heat measured in armour plating after penetration by a medium caliber shaped charge warhead (around 81mm) is only around 500°C. This is not only lower than the melting point of aluminium, but the heat is only applied in a few microseconds so it is too brief to actually melt the armour.<br />
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According to several research papers written on the subject, the effectiveness of the best aluminium armour and aluminium laminate armours may reach up to 50% of steel by thickness, but non-armour grade aluminium alloys are typically only around 40% as effective (or less). An example of this would be 5083 alloy, used in the M113. 5083 alloy was only 34% as effective as steel for the same thickness.<br />
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ABT-101 was specially developed to be used as armour, and because of that, it had more suitable properties, giving it significantly better performance - up to 45% as effective as steel armour per thickness. However, because of the generally worse hardness of aluminium, it is much less capable of deflecting ballistic threats than typical armour-grade steel for the same thickness, so aluminium armour does not gain as much protection from angling as hard, armour-grade steel would. ABT-101 has a hardness of approximately 145 BHN, harder than mild steel and harder than 7039 aluminium alloy, which is known to be used in American designs like the M551 Sheridan and M2 Bradley, and much, much harder than the 5083 alloy, which had a hardness of just 75 BHN. However, all of these aluminium alloys are much softer than typical RHA steel, which typically ranges from 220 BHN to 300 BHN in hardness. The comparatively greater hardness affords the BMD-2 better performance against bullets of all types compared to foreign aluminium armour, and certainly significantly greater potential as sloped armour.<br />
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The turret is made from welded hard steel plates. The front is uniformly 22mm thick, sloped at 37 degrees. This is enough for .50 caliber AP bullets at point blank range, but not much more. The rear of the turret is around 10mm thick.<br />
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The frontal hull aspect draws a great deal of its protection value from its pike-nosed geometry and heavy angling, best seen here:<br />
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The upper glacis is angled at 75 degrees on the vertical axis, and the lower glacis at 47 degrees. There is also an additional 20 degrees of horizontal sloping for both upper and lower glaces, creating a pike nose shape that is usually associated with Soviet heavy tanks. According to the compound angle table published in page 47 of <i>World War II Ballistics: Armor and Gunnery</i>, the compound angle of the upper and lower glacis plates will be 76 degrees and 50 degrees respectively. The upper glacis is 15mm thick while the lower glacis is 32mm thick. The line of sight (LOS) thickness of the upper glacis and lower glacis is therefore 62mm and 50mm respectively which is very impressive for such a light vehicle. The pure armour thickness is important, but not as important as the large compound angle which makes it very difficult for an uncapped ogive penetrator (as found in a typical Spitzer bullet) to not ricochet immediately without so much as denting the armour.<br />
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The sides are quite thin. The upper side plate is only 23mm thick, and the lower side plate is thinner at just 20mm. The roof of the hull is not enough to resist large caliber airbursting artillery shells. Based on testing with 7.62mm and 12.7mm steel-cored AP-I bullets, 23mm of ABT-101 is equivalent to 10.35mm of RHA. In terms of effective thickness, the side armour is nominally equivalent to the BTR-60 and MT-LB.<br />
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To better appreciate the protection offered by the angles of the frontal armour, we can take a look at the phase diagram below. This phase diagram, taken from <i>Armour: Materials, Theory, and Design</i>, illustrates the huge importance of slope. As you can see, the test used a 6.35 mm aluminium alloy plate - no doubt 5083 aluminium - as a target, and 6.35 mm-diameter solid steel bullets as projectiles. A 6.35 mm projectile like this is representative of the steel AP core of the average 7.62mm rifle bullet. The AP core of a 7.62x54mm Russian B-32 bullet, for instance, has a diameter of 6.1 mm, with a weight of 5.39 grams. It has a muzzle velocity of 830 m/s. The AP core of a .30-06 M2 AP bullet has a diameter of 6.2 mm, and weighs 5.17 grams. It has a muzzle velocity of 855 m/s. The AP core of a 7.62x51mm M61 bullet has a diameter of 6.3 mm, and weighs 3.8 grams. It has a muzzle velocity of 838 m/s.<br />
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As you can see in the diagram, the thin aluminium plate is not thick enough to deflect the bullet at point blank range (muzzle velocity: 830-855 m/s) unless it is sloped at an angle of at least 65 degrees, whereupon the bullet will shatter against the plate and ricochet off harmlessly. The aluminium armour of the BMD-2 is never as thin as 6.35mm and the armour is not made from 5083 alloy so the findings above cannot be applied directly to the armour scheme on the vehicle. But still, it is an interesting example of the importance of obliquity, as it demonstrates that a 75 BHN metal plate of rather low strength is capable of deflecting a bullet that matches it in thickness given that the angle of impact is sufficiently high. The test may or may not be scalable, but if it is, and we substitute the 7.62mm AP bullet with a .50 cal or 12.7mm one, we see that the upper glacis of the BMD-2 with its thickness of 15mm and compound slope of 76 is more than enough to deflect heavy machine gun fire at point blank range as the thickness of the plate is greater than the diameter of a .50 cal M2 AP bullet core and the obliquity is extremely high, while the 840 m/s muzzle velocity of the bullet from an M2 Browning is in the same range as typical 7.62mm rifle rounds. As it turns out, this speculation is confirmed by testing that found that the front of the BMD-1 is indeed immune to 12.7mm B-32 from point blank range. The lower glacis plate is not thicker than the upper glacis despite the greater physical thickness and the compound angle of the slope is also less at only 50 degrees, so in theory it is more vulnerable, but again, testing found that the front was immune to 12.7mm B-32 rounds.<br />
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NII Stali has released some documentation on the ballistic performance tests of ABT-101 alloy. The graph below, titled "<i>Comparative Characteristics of Aluminium Alloy Armour of the U.S.A and Russia</i>", shows the thickness of the armour plate required to stop each bullet, quantified in terms of bullet diameter.<br />
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Legend: <i>Bullet B-32 (Russian)</i>, <i>Caliber: 7.62, 12.7</i><br />
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y-axis: Velocity (V)<br />
x-axis: Armour thickness/Bullet caliber ratio<br />
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<a href="https://4.bp.blogspot.com/-JWRpS3v8oAQ/WIIEI8-8qeI/AAAAAAAAIMU/9fzxKL6oQNgzDv4mN2wTqxcN789gdN7MQCLcB/s1600/aluminium%2Barmor%2Bnii%2Bstali.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="382" src="https://4.bp.blogspot.com/-JWRpS3v8oAQ/WIIEI8-8qeI/AAAAAAAAIMU/9fzxKL6oQNgzDv4mN2wTqxcN789gdN7MQCLcB/s640/aluminium%2Barmor%2Bnii%2Bstali.png" width="640" /></a></div>
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For reference: a 12.7mm B-32 bullet has a muzzle velocity of around 850 m/s when fired out of an NSV heavy machine gun, and a 7.62mm B-32 bullet has a muzzle velocity of 855 m/s when fired out of a PKM general purpose machine gun. Keep in mind that information for both the 5083 and 7039 alloys indicates that they are more efficient against 12.7mm bullets than 7.62mm bullets by weight compared to RHA steel.<br />
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Reading this graph, it appears that to stop a 7.62x54mm B-32 armour piercing bullet at a distance of 100 meters or so, it would take an ABT-101 armour plate with a thickness of around 4.2 calibers, which is 32mm. To stop the same bullet at a distance of 460 meters, it would take a plate with a thickness of 3 calibers, which will be 22.9mm - the same as the thickness of the upper side plate of a BMD-2. However, this does not necessarily mean that the side of a BMD-2 is badly protected from machine gun fire because NATO standardized on the 7.62x51mm cartridge during the 50's. The standard M61 steel-cored armour piercing bullet in the 7.62x51mm caliber is much less potent than .30-06 M2 AP and 7.62x54mm B-32, so the side armour of the vehicle still provides comprehensive protection against machine guns fielded by contemporary NATO armies.<br />
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<a href="https://4.bp.blogspot.com/--0LsFHB7tcw/WLjmmkc1iEI/AAAAAAAAIdk/VmcWOo_xYUghViek7JrsCQLhEJ-BhPYwwCLcB/s1600/pic_61.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/--0LsFHB7tcw/WLjmmkc1iEI/AAAAAAAAIdk/VmcWOo_xYUghViek7JrsCQLhEJ-BhPYwwCLcB/s1600/pic_61.jpg" /></a><a href="https://4.bp.blogspot.com/-YoEkKOZoFz0/WLjmmM2_tkI/AAAAAAAAIdg/pMFybi6Cj0cQ-UTOQFoWctr1ET9U4z8zwCLcB/s1600/pic_62.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-YoEkKOZoFz0/WLjmmM2_tkI/AAAAAAAAIdg/pMFybi6Cj0cQ-UTOQFoWctr1ET9U4z8zwCLcB/s1600/pic_62.jpg" /></a></div>
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Ballistic tests were conducted on the BMD-1 throughout its developmental cycle, and continued even after it formally entered service. During tests undertaken from October 25 to December 25 in 1972, the BMD-1 was subjected to more ballistic tests involving weapons ranging from 7.62x39mm ball bullets to 23mm hardened steel core armour piercing rounds. The black and white photos above and below show the state of the BMD-1 after the tests. These photos were taken from the December issue of Tekhnika i Vooruzhenie 2009.<br />
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<a href="https://3.bp.blogspot.com/-nKcmUl4MZzg/WLjmlaRkKLI/AAAAAAAAIdc/vrttgpFZQH8I-FnNY0iEvDmGGm79cHPagCLcB/s1600/pic_63.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://3.bp.blogspot.com/-nKcmUl4MZzg/WLjmlaRkKLI/AAAAAAAAIdc/vrttgpFZQH8I-FnNY0iEvDmGGm79cHPagCLcB/s320/pic_63.jpg" width="248" /></a> </div>
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The upper part of the side hull is proofed against 7.62x39mm BZ rounds at a distance of 125 meters, and the lower part is proofed at 175 meters. The front hull and turret are totally immune to 23mm BZT rounds (API-T) from a distance of 500 meters when shot from a frontal arc. If the firing range for 23mm BZT is decreased to 100 meters, the protected frontal arc shrinks to 28 degrees. 23mm BZT penetrates 24mm of RHA plate at 0 degrees at 500 meters, 15mm at 30 degrees at 700 m, 19mm at 0 degrees at 1000 m, and 10mm at 30 degrees at 1200 m. The table below lists the angle of immunity from four different types of small arms ammunition at point blank range.<br />
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<table border="1" cellpadding="5" cellspacing="0">
<tbody>
<tr>
<td>Ammunition
</td>
<td>Angle of immunity (°), immunity arc (°)
</td>
</tr>
<tr>
<td>12.7x108mm B-32 (AP, hardened steel core)
</td>
<td>35, 70
</td>
</tr>
<tr>
<td>7.62x54mm B-32 (AP, hardened steel core)
</td>
<td>53, 106
</td>
</tr>
<tr>
<td>7.62x54mm Light Ball (FMJ, mild steel core)
</td>
<td>70, 140
</td>
</tr>
<tr>
<td>7.62x39mm BZ (AP-I, hardened steel core incendiary)
</td>
<td>68, 136
</td>
</tr>
</tbody></table>
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Based on the information that a frontal arc is immune to 23mm BZT rounds from 500 meters, the frontal arc of immunity from that distance should be 54 degrees. During the course of the testing, it was discovered that the amount of protection afforded to the radiator packs (the two humps on either side, above the rectangular exhaust ports) from gunfire was unsatisfactory, but the sloped engine cover panel (see photo below) was heavy enough to deflect 7.62x39mm BZ rounds fired from a distance of 125 meters.<br />
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<a href="http://4.bp.blogspot.com/-yUiKenUcE0U/VhhXEot7w0I/AAAAAAAAD60/q1Z-39N61N0/s1600/bmd-2%2Brear.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="264" src="https://4.bp.blogspot.com/-yUiKenUcE0U/VhhXEot7w0I/AAAAAAAAD60/q1Z-39N61N0/s400/bmd-2%2Brear.jpg" width="400" /></a></div>
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Generally speaking, standard rifle caliber threats like the FN FAL, G3, M60, M240, and others are ineffective against the sides and rear of the vehicle even for perfectly perpendicular shots at close range, so the BMD-2 can be described as having sufficient all-round protection from infantry weapons. A large part of the frontal arc of the vehicle is immune to heavy machine gun fire at close to medium ranges and some resistance is provided against small caliber autocannon fire from the front at medium range. The immunity distance of 500 meters guarantees the BMD-2 some standoff distance as it can outrange other APCs and IFVs with its own 30mm autocannon while remaining largely impenetrable to return fire. Its protection from mortar bomb splinters is fine, but its protection from air burst rounds is completely insufficient and larger artillery rounds (6" caliber) are particularly dangerous.<br />
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The diminutive size of the BMD-2 contributes greatly to its overall survivability. With maximum ground clearance, the BMD-2 is negligibly taller than the average Soviet male combatant at 1.905m, but only 1.585m tall with minimal ground clearance. The photo below perfectly illustrates the low height of the BMD-2 at the maximum suspension height.<br />
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<a href="https://1.bp.blogspot.com/-jFXrUbO_NKs/WLfugthHuuI/AAAAAAAAIcc/Y6_3UKjhN1wpleTDosBwTxetPqTKWfjdgCLcB/s1600/bmd-2%2Bukraine.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-jFXrUbO_NKs/WLfugthHuuI/AAAAAAAAIcc/Y6_3UKjhN1wpleTDosBwTxetPqTKWfjdgCLcB/s1600/bmd-2%2Bukraine.png" /></a></div>
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Because of its small profile, it is exceptionally difficult to reliably score hits on the vehicle at long distances with machine guns using only the iron sights. Attempting to visually identify a camouflaged BMD-2 from afar would also be a challenge, especially when plenty of shrubbery is present and the crew is properly taking advantage of terrain features with the help of the vehicle's variable ground clearance. Thus, although the armour of the BMD-2 is wholly insufficient against serious anti-armour weapons, its survivability would still be quite high.<br />
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However, the advantage of small size has been greatly diminished in the present. Current generation autocannons like the new Rheinmetall Mk30-2/ABM and Bushmaster Mk44 are so accurate when paired with modern fire control systems that they will have no trouble at all achieving a near-100% hit rate at long distances on the BMD-2, even while both the weapon platform and target are on the move. Modern thermal imaging sights will be able to see and track the BMD-2 as clear as day at any distance except when the BMD-2 is operating in a hull down position.</div>
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<h3>
<span style="font-size: large;">ERGONOMICS</span></h3>
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<a href="http://2.bp.blogspot.com/-v0rXdNucEnY/VhhWlge52bI/AAAAAAAAD6s/CWztSpNtPGY/s1600/image%2B%25281%2529.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="424" src="https://2.bp.blogspot.com/-v0rXdNucEnY/VhhWlge52bI/AAAAAAAAD6s/CWztSpNtPGY/s640/image%2B%25281%2529.jpg" width="640" /></a></div>
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It should come as no surprise that the small size of the BMD-2 entails cramped conditions inside the passenger compartment. There are three seats immediately behind the turret basket for dismounts, arranged around the circumference of the turret. Two are located on either corners of the compartment and the center seat is located directly underneath the large exit hatch, but there is so little distance between the turret basket and the engine compartment partition that the dismount must sit sideways on this center seat.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-g_3BDxM4vo0/Vg1WNlkIALI/AAAAAAAAD3Y/r04ydXNOVJo/s1600/bmd%2Binterior.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="358" src="https://2.bp.blogspot.com/-g_3BDxM4vo0/Vg1WNlkIALI/AAAAAAAAD3Y/r04ydXNOVJo/s640/bmd%2Binterior.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Port side passenger's seat</td></tr>
</tbody></table>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-IppC-5qbU04/Vg1WR-3HzTI/AAAAAAAAD3g/CK8XOYA-gBI/s1600/bmd%2Bpassenger%2527s%2Bseat.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="358" src="https://3.bp.blogspot.com/-IppC-5qbU04/Vg1WR-3HzTI/AAAAAAAAD3g/CK8XOYA-gBI/s640/bmd%2Bpassenger%2527s%2Bseat.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Center passenger's seat</td></tr>
</tbody></table>
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The interior is very cramped in general. There is barely enough room for the squad to haul along additional equipment other than a RPG-16 or RPG-7D. The fender shelves (empty space of the hull above the tracks) can be used to stow a MANPADS launcher.<br />
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Each seat is provided with a periscope to grant the occupants some situational awareness. The two passengers seated on either side of the hull are given a TNPO-160 periscope each, which are aimed slightly forward. There is another MK-4 rotatable periscope mounted in the rear hatch, which allows excellent coverage of the vehicle's rear and flanks. This periscope lets the passenger seated at the center seat to direct the driver when reversing.<br />
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Ventilation for all occupants is provided by a single dome-shaped ventilator located on the starboard side of the hull, adjacent to the turret.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-LhN_qRPEI1g/Vagm2pAQU8I/AAAAAAAACyI/kP5SzheVwGA/s1600/8642b2c48d56585f35d6d1d016f95c43.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://2.bp.blogspot.com/-LhN_qRPEI1g/Vagm2pAQU8I/AAAAAAAACyI/kP5SzheVwGA/s400/8642b2c48d56585f35d6d1d016f95c43.jpg" width="400" /></a><a href="http://2.bp.blogspot.com/-5BXs7OYmawo/VagnsycSegI/AAAAAAAACyU/9b-K2mWLEVQ/s1600/w00261_9961715.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="298" src="https://2.bp.blogspot.com/-5BXs7OYmawo/VagnsycSegI/AAAAAAAACyU/9b-K2mWLEVQ/s400/w00261_9961715.jpg" width="400" /></a></div>
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The ventilator sucks in air through a wire mesh-covered radial port. It has an internal filter for operation in highly dusty or chemically and biologically contaminated zones, and the filter additionally incorporates an integrated self-cleaning system, utilizing blasts of high pressure air to blow dust and other filtrates out through the evacuation port (protruding port on the dome, not covered by mesh, as seen above). This ventilator is responsible for creating an overpressure to prevent any such contaminants from entering the vehicle.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-gYp754vGPKY/Vg1WMJGJ5DI/AAAAAAAAD3Q/re3vKGCWuTs/s1600/bmd%2Bventilation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="355" src="https://2.bp.blogspot.com/-gYp754vGPKY/Vg1WMJGJ5DI/AAAAAAAAD3Q/re3vKGCWuTs/s640/bmd%2Bventilation.png" width="640" /></a></div>
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The ventilator has an electric heater installed for supplying the occupants with warm air during the winter. There are two storage bins located on top of the engine deck. They are meant for tools and spare parts. The location of the bins practically guarantees that they will be untouched during combat.<br />
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<a href="http://3.bp.blogspot.com/-ddO7kJJOnLI/VagKbXpbhYI/AAAAAAAACwA/kik_tV9aPP4/s1600/bmd-2%2Bfuel%2Btanks.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://3.bp.blogspot.com/-ddO7kJJOnLI/VagKbXpbhYI/AAAAAAAACwA/kik_tV9aPP4/s400/bmd-2%2Bfuel%2Btanks.jpg" width="400" /></a></div>
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<h3>
<span style="font-size: large;">
DRIVER-MECHANIC'S STATION</span></h3>
<h3>
</h3>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://4.bp.blogspot.com/-KUNjcpXUvjI/WLMV_COZ3-I/AAAAAAAAIbE/-LWif_dXz_cPxu5Uolsu9FJ5chcF2P93ACLcB/s1600/90letRVVDKU-56-L.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://4.bp.blogspot.com/-KUNjcpXUvjI/WLMV_COZ3-I/AAAAAAAAIbE/-LWif_dXz_cPxu5Uolsu9FJ5chcF2P93ACLcB/s640/90letRVVDKU-56-L.jpg" width="640" /></a></div>
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At the very front of the hull is the driver's station. The steering system is of a tiller-type, with dry friction clutches. The tillers also connected to a pulley system, which opens and closes the water jet covers depending on how far the tillers are pulled back. He has access to all the necessary driving-related controls as well as controls for all of the miscellaneous features of the vehicle, including interior heating, NBC activation, and the like. <span style="font-size: large;"><span style="font-size: small;">The instrument panel can be seen in the photo below. Note that the absolute maximum speed is 100 km/h.</span></span><br />
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<a href="http://3.bp.blogspot.com/-r2PJXWcvFrQ/VhuqZf5eGWI/AAAAAAAAD9M/8VWQ3VaNE3k/s1600/bmd%2Bdriver%2527s%2Bpanel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://3.bp.blogspot.com/-r2PJXWcvFrQ/VhuqZf5eGWI/AAAAAAAAD9M/8VWQ3VaNE3k/s1600/bmd%2Bdriver%2527s%2Bpanel.png" /></a></div>
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The driver has very good driving visibility from his bank of three TNPO-160A periscopes. They are heated through the RTC system to prevent fogging.<br />
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<a href="http://4.bp.blogspot.com/-eD_QQeLCEf4/VagskowQIrI/AAAAAAAACyk/ASFv-GgBCvo/s1600/bmd%2Bdriver%2527s%2Binstrument%2Bpanel%2Band%2Bperiscopes.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="358" src="https://4.bp.blogspot.com/-eD_QQeLCEf4/VagskowQIrI/AAAAAAAACyk/ASFv-GgBCvo/s640/bmd%2Bdriver%2527s%2Binstrument%2Bpanel%2Band%2Bperiscopes.png" width="640" /></a></div>
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The center periscope may be replaced with a binocular night vision periscope.<br />
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<a href="http://2.bp.blogspot.com/-_uxkvbeyQWA/ValnD_o_WCI/AAAAAAAAC3Y/7SvyS1PnMeY/s1600/driver%2527s%2Bperiscope.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="235" src="https://2.bp.blogspot.com/-_uxkvbeyQWA/ValnD_o_WCI/AAAAAAAAC3Y/7SvyS1PnMeY/s400/driver%2527s%2Bperiscope.png" width="400" /></a></div>
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Or a TNP-370A extended periscope for when the vehicle is swimming.<br />
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<a href="http://4.bp.blogspot.com/-byM-OZR-bGA/VgIKkEM2NkI/AAAAAAAADoM/iOTnJvQFv1I/s1600/bmd-1%2Bdriver%2527s%2Bswimming%2Bperiscope.png"><img border="0" height="298" src="https://4.bp.blogspot.com/-byM-OZR-bGA/VgIKkEM2NkI/AAAAAAAADoM/iOTnJvQFv1I/s400/bmd-1%2Bdriver%2527s%2Bswimming%2Bperiscope.png" width="400" /></a></div>
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The TNP-370A extended periscope has a total range of vision of 42 degrees in the horizontal plane, and 12 degrees in the vertical plane. The periscope allows the driver to peer over the trim vane and navigate in the water without assistance from the gunner, who might be busy bombarding targets on shore.<br />
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The BMD-2 has a single F-125 IR headlight on the starboard side and a single F-126 white light headlight on the port side. The F-127 IR periscope is used exclusively in tandem with the binocular night vision periscope for nighttime driving. The view range of the periscope is completely insufficient for any real navigation, but it is good enough for road marches and less intense maneuvering. The IR filter cap may be removed to revert the IR headlight into a regular driving light if needed.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-l-f-vICsAwU/VhkT_tBL9II/AAAAAAAAD8Q/ubCtyg4-Yoo/s1600/bmd%2Bhorn%2Band%2Bir%2Bdriving%2Blamp.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://1.bp.blogspot.com/-l-f-vICsAwU/VhkT_tBL9II/AAAAAAAAD8Q/ubCtyg4-Yoo/s640/bmd%2Bhorn%2Band%2Bir%2Bdriving%2Blamp.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Starboard side driving light and of course, the horn</td></tr>
</tbody></table>
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<div style="text-align: center;">
<img height="324" src="https://3.bp.blogspot.com/-yAct-Hel0qc/VT5d3mqRGFI/AAAAAAAACGw/nmGesm3dVJE/s400/Infra_Red_Headlamp.jpg" width="400" /><img height="317" src="https://3.bp.blogspot.com/-CYY3B9U4yW4/VRg6TUtvI-I/AAAAAAAABi8/nBGzX23ksdQ/s400/fg-125.jpeg" width="400" /></div>
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For convoy driving, the F-126 headlight/blackout light may be used. Blackout lights function by directing light forwards and downwards through small slits, minimizing the amount of light being transmitted off in other directions. This is to minimize the possibility of being seen, especially from afar. Because blackout lights only illuminate very small areas in front of the vehicle, the driver can't really see any further than a few meters. Depending on them for navigation is completely out of the question.<br />
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<div style="text-align: center;">
<img height="375" src="https://3.bp.blogspot.com/-54c8glQzxkw/VRg6VhglUzI/AAAAAAAABjE/uS9IcJx8M4s/s400/fg-126.jpeg" width="400" /><img src="https://4.bp.blogspot.com/-4ET1fxo1O_Q/VT5YZzskcvI/AAAAAAAACGg/v76YwENE01Y/s1600/headlight.png" /></div>
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<h3>
<span style="font-size: large;">
MOBILITY</span></h3>
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<a href="http://3.bp.blogspot.com/-mzESwHnJwVo/VhhEAELjJlI/AAAAAAAAD54/stOCkut1a-U/s1600/5d-20.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://3.bp.blogspot.com/-mzESwHnJwVo/VhhEAELjJlI/AAAAAAAAD54/stOCkut1a-U/s640/5d-20.jpg" width="640" /></a></div>
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Both the BMD-1 and the BMD-2 are powered by the low-profile 5D-20 V-shaped 6-cylinder diesel engine, located at the rear of the hull. It produces 240 hp at 2400 RPM. Originally, there were three methods to start the engine; electrically, pneumatically and combined. The pneumatic method involved using compressed air from a 10-liter compressed air tank to get the pistons moving, while the electric method required the use of the S-5 15 hp electric starter motor. The combined method is, obviously, a combination of the two. The combination method is most useful in cold weather. In 1973, the BMD-1 received the AK-150MKV air compressor. AK-150MKV was powered by the engine via a reduction gear through the gearbox. The introduction of this air compressor enabled the BMD to refill its 10-liter compressed air tank on the move, thus making it possible to rely entirely on the pneumatic starting system for every occasion. <br />
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The BMD-2 is heavier than the BMD-1, but it is still an extremely light combat vehicle at only 8 tons empty, and 8.225 tons fully combat loaded. The power to weight ratio is 29.2 hp/ton when combat loaded, and over 30 hp/ton when not. This is slightly lower than the BMD-1, but still good for its class of vehicle. For context, the BMD-1 is lighter, just 6.7 tons empty. According to the manual, the BMD-1P weighs <span style="font-size: small;">6.7</span> tons empty, 7.2 tons with fuel and oil, and 7.38 tons fully loaded for combat. The power to weight ratio is 32.5 hp/ton when fully loaded, and the average ground pressure exerted is 7.1 psi.<br />
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Both the BMD-1 and BMD-2 have a maximum driving speed of 61 km/h on a highway, and an average speed of 30 to 50 km/h when travelling cross country. It readily accelerates, and the amount of torque generated lets the vehicle traverse rough terrain speedily.<br />
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The engine is liquid-cooled. The radiator is located to the left side of the engine compartment. The photo below shows the engine air intake.</div>
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<a href="http://2.bp.blogspot.com/-VvVxfqdMB5M/VgIRnYY_XGI/AAAAAAAADoc/b4IdX6wOQws/s1600/engine%2Bcooling%2Bfan.png"><img border="0" src="https://2.bp.blogspot.com/-VvVxfqdMB5M/VgIRnYY_XGI/AAAAAAAADoc/b4IdX6wOQws/s1600/engine%2Bcooling%2Bfan.png" /></a></div>
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Located immediately behind the engine is the transmission. The drive shaft that spins the engine air intake fan is the same shaft that connects to the gearbox.<br />
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<a href="http://4.bp.blogspot.com/-vHJtOZbXSXo/VagkniaoghI/AAAAAAAACx0/WC5bvaNrupQ/s1600/8db8c39f9077035a16852d8f65eeaaf7.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="426" src="https://4.bp.blogspot.com/-vHJtOZbXSXo/VagkniaoghI/AAAAAAAACx0/WC5bvaNrupQ/s640/8db8c39f9077035a16852d8f65eeaaf7.jpg" width="640" /></a><br />
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The exhausts are located at the two rearmost corners of the hull. The radiators are located on the top of either side of the two "humps", above the exhaust ports, and above the fuel and oil tanks.<br />
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Take a look at the photo below. Notice the pipes from the manifolds of the engine leading out towards the exhausts.<br />
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<a href="http://2.bp.blogspot.com/-tbLCjZaIRZA/VaghrI47NdI/AAAAAAAACxo/kmitL8YKWyE/s1600/e9a36e05cbab.jpg"><img border="0" src="https://2.bp.blogspot.com/-tbLCjZaIRZA/VaghrI47NdI/AAAAAAAACxo/kmitL8YKWyE/s1600/e9a36e05cbab.jpg" /></a></div>
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As mentioned before, the radiators are protected by armoured louvers which can be remotely shut by the driver from his station. They are supposed to provide protection from airbursting shells, small arms fire from above and flame attacks, but seeing how thin the roof of the hull of the vehicle is, there is no real point in taking this step.<br />
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There is an integrated electric heater to heat up air before it enters the engine, to facilitate starting in cold weather.<br />
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<a href="http://4.bp.blogspot.com/-nTo7Nw5li7Y/VX6U3VZzM3I/AAAAAAAACl4/Rfd8oVdK0E4/s1600/bmd-2%2Bsmokey.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="358" src="https://4.bp.blogspot.com/-nTo7Nw5li7Y/VX6U3VZzM3I/AAAAAAAACl4/Rfd8oVdK0E4/s640/bmd-2%2Bsmokey.png" width="640" /></a></div>
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The port side "hump" in front of the radiator holds essential fluids for the engine, such as lubricant, coolant and transmission oil. The photo below shows the ubiquitous armoured plugs that allow access to these fluids.<br />
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<a href="http://2.bp.blogspot.com/-7zpY0ZYFDi4/Val02_dkdkI/AAAAAAAAC5Y/cmOT73jbjjw/s1600/bmd-2%2Bcoolant.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://1.bp.blogspot.com/-uBSUhujdr50/Vdwgt8nAZGI/AAAAAAAADM8/d7TjcvQru98/s400/2015%2B-%2B5.jpg" width="400" /><img border="0" height="241" src="https://2.bp.blogspot.com/-7zpY0ZYFDi4/Val02_dkdkI/AAAAAAAAC5Y/cmOT73jbjjw/s400/bmd-2%2Bcoolant.png" width="400" /></a></div>
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The BMD-2 can climb a vertical slope of 32 degrees, traverse a side slope of 18 degrees, and overcome a vertical obstacle 0.7m in height. It is able to cross trenches 2.5m in width, but is is capable of leaping over gaps as wide as 4m or more by running on a ramp or hitting a bump just before crossing. The BMD-2 can this do effortlessly and almost without risk thanks to its ability to get itself up to a very high speed.<br />
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The BMD-2 has five solid die-cast aluminium roadwheels with rubber rims on either side. Lightweight hollow roadwheels like the type used in the BMP-1 and BMP-2 helped increase buoyancy, but they would not have been able to withstand the force of an airdrop landing, thus necessitating roadwheels exclusive to the BMD-1 and BMD-2. Despite this, the lightness of the chassis and the relative softness of aluminium compared to steel means that the overall resilience of the suspension to high dynamic loads and hard impacts is quite low. A collision with a tree will result in a ripped-off idler wheel and roadwheel.<br />
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<a href="https://4.bp.blogspot.com/-XmHktm66I1I/WFJoAD6ryjI/AAAAAAAAH4Y/XqzAnejNUuwsQHLgr4QYw-TqZwRBIkbpACLcB/s1600/tumblr_ohv8hzDElL1rqpszmo1_500.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-XmHktm66I1I/WFJoAD6ryjI/AAAAAAAAH4Y/XqzAnejNUuwsQHLgr4QYw-TqZwRBIkbpACLcB/s1600/tumblr_ohv8hzDElL1rqpszmo1_500.jpg" /></a></div>
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The BMD-2 has a ground pressure of 7.1 psi fully loaded, which is rather high despite its low weight. This is because of its thin tracks, which are also unfortunately somewhat fragile. The thinness of the tracks means that there is less frictional force with the ground (not the same as traction) when turning. This gives it superb agility over paved roads as well as dirt ones, but the BMD-2 suffers when crossing swampy ground. In which case, it <i><b>must </b></i>make good use of the eponymous log. The BMD-2's performance is snowy terrain is excellent. The relatively high ground pressure enables the tracks to penetrate snow and reach the frozen soil underneath, thus granting the BMD-2 good traction.<br />
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The innovative hydropneumatic suspension on the BMD-2 carries over from the BMD-1. It is very compact. The unique suspension gives the BMD-2 the ability to adjust ground clearance on-the-fly. The ground clearance can be adjusted to either 0.1m or 0.45m, or anything in between. The default setting for driving is 0.42m. The lowest setting is used to properly load the BMD-2 onto a plane before an air drop to minimize impulsive forces on the suspension in order to prevent damage to the suspension upon landing, but it is also useful for reducing the total height of the vehicle to let it fit better into the confines of a cargo hold. This is contrary to counterparts like the Bradley, which must be lashed to a loading pallet with tremendous force to compress the torsion bar suspension so that the hull would be as low as possible for loading. With the BMD-2, all this is done at the flick of a switch by the driver. The vehicle may be driven in any configuration. Fully lowered, the roadwheels have almost no room to travel and therefore cannot absorb shocks from terrain irregularities.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="http://4.bp.blogspot.com/-471jwAlE674/ValszGSh9qI/AAAAAAAAC4c/4sZUSmRpITg/s1600/down.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="235" src="https://4.bp.blogspot.com/-471jwAlE674/ValszGSh9qI/AAAAAAAAC4c/4sZUSmRpITg/s400/down.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">Lowered, not tensioned</td></tr>
</tbody></table>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="http://3.bp.blogspot.com/-lPqUYD5bXiA/ValsxyJfO9I/AAAAAAAAC4U/bgjzVpfNmpA/s1600/up.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="235" src="https://3.bp.blogspot.com/-lPqUYD5bXiA/ValsxyJfO9I/AAAAAAAAC4U/bgjzVpfNmpA/s400/up.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">Raised<br />
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</td></tr>
</tbody></table>
The hydropneumatic suspension system uses a pneumatic cylinder as a spring. Adjusting the height of the roadwheels is done by adjusting the pressure in the pneumatic cylinders. The pneumatic cylinder is placed above the hydraulic piston, which is connected to the roadwheel. The pneumatic cylinder has a manual release valve to relieve pressure (at the top of the cylinder, seen below), and air is ported to the chamber behind the hydraulic piston, pushing it or pulling it depending on whether the air in the pneumatic cylinder is pressurized or depressurized. To keep the roadwheel in position, the pressure must be constant. The system is self contained - the pneumatic cylinder contains all the air necessary. Air is distributed by valve banks located under the seats of the port side and starboard side passenger seats in the passenger space.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-d8nuIaOhHBo/VagSQMrq5QI/AAAAAAAACw0/xjLnFY5NP1U/s1600/f0d82dac85bddb6363d1c55a572d9c40.jpg"><img border="0" height="426" src="https://1.bp.blogspot.com/-d8nuIaOhHBo/VagSQMrq5QI/AAAAAAAACw0/xjLnFY5NP1U/s640/f0d82dac85bddb6363d1c55a572d9c40.jpg" width="640" /></a></div>
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The hydropneumatic mechanism is visible in the photo above. It is currently disconnected from roadwheel arm (you can even see the locking pin on the floor). The BMD in the photo must be resting on the belly of the hull, judging from the position
of the roadwheel arm.<br />
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Air for the pneumatic springs is supplied by an air compressor powered by the engine. It is located directly forward of the engine, behind the partition between the engine compartment with the passenger compartment.<br />
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<a href="https://3.bp.blogspot.com/-o9VM7R3BEEo/WLMOBTV4GoI/AAAAAAAAIag/BaL7PlmV8tovR54bB4H-5msjVTf1ofRrQCLcB/s1600/suspension.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://3.bp.blogspot.com/-o9VM7R3BEEo/WLMOBTV4GoI/AAAAAAAAIag/BaL7PlmV8tovR54bB4H-5msjVTf1ofRrQCLcB/s320/suspension.jpg" width="276" /></a><a href="https://3.bp.blogspot.com/-0c7ZHT2vwJE/WLMLf1kjOyI/AAAAAAAAIaU/yXYI5RZOSqwqSlWaxGmaCJW-V6-PIxVPgCLcB/s1600/bmd%2Bsuspension.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="251" src="https://3.bp.blogspot.com/-0c7ZHT2vwJE/WLMLf1kjOyI/AAAAAAAAIaU/yXYI5RZOSqwqSlWaxGmaCJW-V6-PIxVPgCLcB/s320/bmd%2Bsuspension.jpg" width="320" /></a></div>
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<div class="separator" style="clear: both; text-align: left;">
And of course, the idler wheel and drive sprocket can be adjusted for track tension as well. This is done by a hydraulic piston.</div>
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<a href="http://1.bp.blogspot.com/-Aj1-01Ys3Eg/Vg1TOmRHdMI/AAAAAAAAD20/CDRPbLuaexU/s1600/bmd%2Btrack%2Btension%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-Aj1-01Ys3Eg/Vg1TOmRHdMI/AAAAAAAAD20/CDRPbLuaexU/s1600/bmd%2Btrack%2Btension%2Bmechanism.png" /></a><br />
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The tracks on the BMD-1 are of the single pin variety with rectangular inner guide horns, as you can see below:<br />
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<a href="https://1.bp.blogspot.com/-k-BLezRbclg/WLMP_hlQO7I/AAAAAAAAIas/OI8JnfCNDgEPO0kizhPRhk8pw_UHrYE7wCLcB/s1600/pic_99.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="144" src="https://1.bp.blogspot.com/-k-BLezRbclg/WLMP_hlQO7I/AAAAAAAAIas/OI8JnfCNDgEPO0kizhPRhk8pw_UHrYE7wCLcB/s200/pic_99.png" width="200" /></a></div>
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The BMD-1P introduced new tracks with "dog bone" guide horns. These tracks are thicker and sturdier, but also slightly heavier. They are harder to throw and are just a bit better overall.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://1.bp.blogspot.com/-a_XjDfHdvA4/WLMQlqmQ7NI/AAAAAAAAIa0/cawPbXFANMUlFNATPtXoZITm46BiwU_ZgCLcB/s1600/pic_100.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="168" src="https://1.bp.blogspot.com/-a_XjDfHdvA4/WLMQlqmQ7NI/AAAAAAAAIa0/cawPbXFANMUlFNATPtXoZITm46BiwU_ZgCLcB/s200/pic_100.jpg" width="200" /></a></div>
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The new BMD-1P tracks carried over to the BMD-2.<br />
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<h3>
<span style="font-size: large;">FUEL</span></h3>
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The BMD-2 holds a total of 280 liters of fuel in three separate tanks at the rear of the hull on either side of the engine compartment, giving it a maximum cruising range of 500 km on a highway on internal fuel alone. Because of the location of the fuel tanks, they will never pose a threat to the crew or the vehicle itself during combat. From the rear, they are hidden by the radiator and exhaust, completely precluding the possibility of them getting damaged by shrapnel or machine gun fire. If the sponsons were penetrated from the sides, fuel would simply leak out onto the ground harmlessly, away from the exit hatch at the engine deck. This gives the crew a chance to safely evacuate without being burnt.<br />
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According to the table below, the nominal fuel consumption of the 5D-20 engine is 0.8 liters per kilometer. The rate of fuel consumption is 72-85 liters per 100 km traveled on dirt roads, and 60 liters per 100 km traveled on paved roads, while the hourly fuel consumption rate is 25-30 liters on a dirt road and 23-25 liters on a paved road, or 40 liters per hour when swimming. With a full load of fuel, the BMD-2 can travel around 280-350 km on a dirt road or 450-500 km on a paved road. The vehicle swim continuously for 7 hours.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://2.bp.blogspot.com/-JyDg22boilc/WncJn39vlaI/AAAAAAAAKsg/13TqDX2YxRwl_1qD33vMs3WyZswnDHTqQCLcBGAs/s1600/bmd-2%2Bfuel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="592" data-original-width="816" height="464" src="https://2.bp.blogspot.com/-JyDg22boilc/WncJn39vlaI/AAAAAAAAKsg/13TqDX2YxRwl_1qD33vMs3WyZswnDHTqQCLcBGAs/s640/bmd-2%2Bfuel.png" width="640" /></a></div>
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The table is taken from "Эксплуатация Многоцелевых Машин Контроль Технического Состояния И Техническое Обслуживание Боевой Машины Десантной БМД (БТР-Д), 2015", or, "Operation of Multipurpose Machines Monitoring of Technical Condition And Technical Maintenance of Combat Vehicle Landing BMD (BTR-D)", published by the Ministry of Defence of Russia in 2015.<br />
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To increase the range and autonomy of the vehicle when operating far ahead of the main force, an additional fuel tank is often included as standard equipment.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://3.bp.blogspot.com/-M1FILRPQ550/WnfuvCGGXrI/AAAAAAAAKtQ/YsNNq4J4h8wTm_iNSEPFOEnNwt3XAsu0QCLcBGAs/s1600/DSC09885.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="533" data-original-width="800" height="426" src="https://3.bp.blogspot.com/-M1FILRPQ550/WnfuvCGGXrI/AAAAAAAAKtQ/YsNNq4J4h8wTm_iNSEPFOEnNwt3XAsu0QCLcBGAs/s640/DSC09885.JPG" width="640" /></a></div>
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It is a fender fuel tank from a T-54 with a capacity of 95 liters. It is not connected to the fuel system, so the crew must manually siphon diesel from the external tank into the internal fuel tanks, which isn't very difficult since the fuel filler port is just next to where the external fuel tank is typically mounted.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://3.bp.blogspot.com/-Pe9HSvmjSOg/Wnfu3yv5dyI/AAAAAAAAKtU/tLgZZ2VVBAQYBagPrEtWJTUahVfTgonugCLcBGAs/s1600/1013313841.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="340" data-original-width="600" src="https://3.bp.blogspot.com/-Pe9HSvmjSOg/Wnfu3yv5dyI/AAAAAAAAKtU/tLgZZ2VVBAQYBagPrEtWJTUahVfTgonugCLcBGAs/s1600/1013313841.jpg" /></a></div>
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<h3>
<span style="font-size: large;">WATER OBSTACLES</span></h3>
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<a href="https://4.bp.blogspot.com/-D7oivSDqlMg/WncOXQCT_lI/AAAAAAAAKss/ZGQ5ZYtcH3ALbEUOwGy8dSvg1zNvTMt_QCLcBGAs/s1600/bmd-2%2Bswimming.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="370" data-original-width="600" src="https://4.bp.blogspot.com/-D7oivSDqlMg/WncOXQCT_lI/AAAAAAAAKss/ZGQ5ZYtcH3ALbEUOwGy8dSvg1zNvTMt_QCLcBGAs/s1600/bmd-2%2Bswimming.jpg" /></a></div>
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The BMD-2 is fully amphibious, and can readily enter and cross large bodies of water. But first, the driver must activate the electric bilge pumps (which throw water out of the interior if it is flooded), erect the wave breaker, and shut off the engine air intakes. All this is done automatically by flicking toggle switches. Like the BMD-1, the BMD-2 is propelled by two waterjets (pictured) when in the water.<br />
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<a href="http://4.bp.blogspot.com/-yUiKenUcE0U/VhhXEot7w0I/AAAAAAAAD60/q1Z-39N61N0/s1600/bmd-2%2Brear.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-yUiKenUcE0U/VhhXEot7w0I/AAAAAAAAD60/q1Z-39N61N0/s1600/bmd-2%2Brear.jpg" /></a></div>
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<div class="separator" style="clear: both; text-align: center;">
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Water is sucked up through underbelly ports located at the very rear of the hull, as you can see:<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-xmXydvkTwGA/ValnBqFgbKI/AAAAAAAAC3Q/vFHFixUEBzA/s1600/bmd-2%2Bwater%2Bjets.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="235" src="https://2.bp.blogspot.com/-xmXydvkTwGA/ValnBqFgbKI/AAAAAAAAC3Q/vFHFixUEBzA/s400/bmd-2%2Bwater%2Bjets.png" width="400" /></a></div>
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To prevent water from sloshing up to the driver's hatch a trim vane must be erected. There is also a simple ribbed wave breaker attached to the hull glacis.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-c8Z-scyqXbo/Val20g2gDwI/AAAAAAAAC5w/mvD1U163P8M/s1600/bmd-2%2Bwave%2Bbreaker.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="376" src="https://1.bp.blogspot.com/-c8Z-scyqXbo/Val20g2gDwI/AAAAAAAAC5w/mvD1U163P8M/s640/bmd-2%2Bwave%2Bbreaker.png" width="640" /></a></div>
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It is pushed up to the 'open' position by a small rod and crossbar assembly, pictured below:<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-GUTumZKe3Qk/Val3cn4gi7I/AAAAAAAAC58/b2eblqNiHek/s1600/wave%2Bbreaker%2Berector.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="376" src="https://1.bp.blogspot.com/-GUTumZKe3Qk/Val3cn4gi7I/AAAAAAAAC58/b2eblqNiHek/s640/wave%2Bbreaker%2Berector.png" width="640" /></a></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-c_be2U1zlnw/VajjLmNk-EI/AAAAAAAACzQ/m4kfipiwCdw/s1600/bmd%2Bwithout%2Bgills.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="218" src="https://4.bp.blogspot.com/-c_be2U1zlnw/VajjLmNk-EI/AAAAAAAACzQ/m4kfipiwCdw/s400/bmd%2Bwithout%2Bgills.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Wave breaker and trim vane removed</td></tr>
</tbody></table>
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Because the exhaust ports will be totally submerged when the BMD-2 enters water, the exhaust gasses are blown out by compressed air generated by the bilge pumps. The bilge pumps also work to throw water out of the hull through the same exhaust ports. This is done strongly enough to blow water straight up in the air.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-5SG7yZsivJc/VbT1oY8s86I/AAAAAAAAC88/2T4Z9NzQnWk/s1600/bmd-1%2Bin%2Bthe%2Bwater.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="298" src="https://2.bp.blogspot.com/-5SG7yZsivJc/VbT1oY8s86I/AAAAAAAAC88/2T4Z9NzQnWk/s400/bmd-1%2Bin%2Bthe%2Bwater.png" width="400" /></a></div>
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When the vehicle exits water, the exhaust ports will spit any collected water back out with tremendous force as long as the bilge pumps are still on.<br />
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<a href="http://1.bp.blogspot.com/-JJOfOJAOPGw/ValornT71yI/AAAAAAAAC3s/e1MwoMcNGrs/s1600/bmd-2%2Bthrowing%2Bout%2Bwater.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="376" src="https://1.bp.blogspot.com/-JJOfOJAOPGw/ValornT71yI/AAAAAAAAC3s/e1MwoMcNGrs/s640/bmd-2%2Bthrowing%2Bout%2Bwater.png" width="640" /></a></div>
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(The radiator is smoking, which never happens when driving on land).<br />
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<a href="http://4.bp.blogspot.com/-matK1D4E5uk/ValriPSvlpI/AAAAAAAAC4I/DUtYee94IWo/s1600/smoking%2Bradiator.png"><img border="0" height="376" src="https://4.bp.blogspot.com/-matK1D4E5uk/ValriPSvlpI/AAAAAAAAC4I/DUtYee94IWo/s640/smoking%2Bradiator.png" width="640" /></a></div>
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The BMD-2 is heavier than the BMD-1, but uses the same hull, which means that it has a considerably worse buoyancy reserve.<br />
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<h3>
<span style="font-size: large;">STRATEGIC MOBILITY</span></h3>
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The BMD-2 is rather famous for being an air-droppable "tank", and rightly so. It can be air-dropped directly into the battlefield by appropriate cargo planes such as the Il-76, from an altitude ranging from 2000m to just 500m. It is worth noting that if the transport plane is not flying at low altitudes, it will most certainly be detected and tracked by enemy radars, and so will the parachuting BMD. Although an air insertion is very quick, it is not clandestine.<br />
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Besides air drops into enemy territory, the light weight of the BMD-2 makes it very easy to transport in large quantities by plane.<br />
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<a href="https://1.bp.blogspot.com/-7iMXplFyGwg/WZ69mQ3JjHI/AAAAAAAAJLM/2q6-UsJeYq0o8pWYKEu8-nD9-KBOb57WwCLcBGAs/s1600/VDV10-1200.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="799" data-original-width="1200" height="426" src="https://1.bp.blogspot.com/-7iMXplFyGwg/WZ69mQ3JjHI/AAAAAAAAJLM/2q6-UsJeYq0o8pWYKEu8-nD9-KBOb57WwCLcBGAs/s640/VDV10-1200.jpg" width="640" /></a></div>
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Using the PRSM-925 retro rocket parachute system, the vehicle may be dropped with the entire crew plus passengers from an altitude of 500m to 1500m. The PRSM-925 rocket system needs only one large main parachute. It's primary purpose is to align the retro rocket and the suspended vehicle perfectly perpendicular to the ground, and its secondary purpose is to control the speed of descent, which is still very high. Because there's only one parachute, there is not much clutter that can entangle the vehicle on landing, and because the speed of descent is relatively high up until the retro rockets activate, the amount of time the BMD-2 is visible in the air is significantly reduced. Before being loaded onto a plane, the BMD-2 must loaded onto a shock absorbing pallet beforehand. This is to prevent the vehicle from sinking if it lands in marshy soil.<br />
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<a href="http://3.bp.blogspot.com/-DbptacEQ-yM/Vak9xqtaMSI/AAAAAAAAC1E/vDmc1Ssuzuk/s1600/Image601.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="418" src="https://3.bp.blogspot.com/-DbptacEQ-yM/Vak9xqtaMSI/AAAAAAAAC1E/vDmc1Ssuzuk/s640/Image601.jpg" width="640" /></a></div>
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The rockets are activated by a contact probe deployed from underneath the pallet. They ensure that the rocket activates at the optimum altitude for the softest possible landing.<br />
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<a href="http://2.bp.blogspot.com/-xPWxaetEXQw/VkTrOyRewcI/AAAAAAAAECE/UU3NfbzVXVU/s1600/bmd%2Bretrorocket%2Bprobe.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-xPWxaetEXQw/VkTrOyRewcI/AAAAAAAAECE/UU3NfbzVXVU/s1600/bmd%2Bretrorocket%2Bprobe.png" /></a></div>
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Alternatively, the RKMS-165 multi-parachute system may be employed:<br />
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It involves the use of a bouquet of 9 large primary parachutes, and instead of a rocket booster to soften the landing, a simple air cushion is used instead. Landing through this method is rougher, and is less suitable for a crewed landing. Additionally, the crew needs to remove several straps securing the hull to the air cushion before the vehicle can be put into action. This is far too time consuming for combat insertions, so this method is only used for delivering the BMD-2 to remote areas quickly where an airstrip or a suitable landing zone is not present, but immediate combat is not expected. Air transport is faster than rail transport, and much faster than having the vehicle driven by itself. Air dropped vehicles like the BMD-2 are often the only force multiplier that soldiers may have until heavier equipment can arrive, and that may take days.<br />
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<a href="http://1.bp.blogspot.com/-PgNrbEQO4dE/VagNVKzr5mI/AAAAAAAACwk/8ePkdP41FYA/s1600/64fad3827466ac78eb5c31ebcf347590.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://1.bp.blogspot.com/-PgNrbEQO4dE/VagNVKzr5mI/AAAAAAAACwk/8ePkdP41FYA/s640/64fad3827466ac78eb5c31ebcf347590.jpg" width="640" /></a></div>
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Another option lies in the use of heavy transport helicopters. The BMD-2 may be carried the Mi-26 or Mi-10 in particular.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-Bnb5sn62Zoc/Vaf0SobrHiI/AAAAAAAACvs/9GtjdY3IjzQ/s1600/image.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://1.bp.blogspot.com/-Bnb5sn62Zoc/Vaf0SobrHiI/AAAAAAAACvs/9GtjdY3IjzQ/s640/image.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Two BMD-2s about to be loaded into an Mi-26</td></tr>
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The BMD-2 may also be flown by a Mi-6, but only in an underslung configuration. Two BMD-2s may be transported internally per sortie in an Mi-26, or one in an underslung configuration. The Mi-10 may transport one BMD-2 attached to the fuselage.<br />
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<span style="font-size: large;">References</span></h3>
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<div>
<span style="color: orange;"><a href="http://www.arms-expo.ru/news/armed_forces/ocherednaya_partiya_bmd_2_napravlena_v_chasti_vdv/">http://www.arms-expo.ru/news/armed_forces/ocherednaya_partiya_bmd_2_napravlena_v_chasti_vdv/</a></span><br />
<br /></div>
<div>
<span style="color: #f6b26b;"><a href="https://www.youtube.com/watch?v=xwibzJx7ns0">https://www.youtube.com/watch?v=xwibzJx7ns0</a></span><br />
<br /></div>
<div>
<span style="color: orange;"><a href="http://mreadz.com/new/index.php?id=132817&pages=10">http://mreadz.com/new/index.php?id=132817&pages=10</a></span><br />
<br />
<span style="color: #f6b26b;"><a href="http://yandex.ru/clck/jsredir?from=yandex.ru%3Bsearch%2F%3Bweb%3B%3B&text=&etext=751.c7UxXDEkcWEqCyEeSVuy1ERyukJJo45AOTHwZ5i1S38iic77DNz7GRWY6UL1KhhPFkE6-dOSAkJRYRUZKND1LgGRl_RCuZ3lKOwx06YeFK8.6d084032b2f307dd1e03bdb09e3bc1d701f25ade&uuid=&state=PEtFfuTeVD5kpHnK9lio9T6U0-imFY5IWwl6BSUGTYmikYZdjGg-UeT2y4Uf0ZlYF4BcFvzgb5M&data=UlNrNmk5WktYejR0eWJFYk1LdmtxaFVOQzZXemg4c2w2RkV2WlVuWTNHV3hDX25BOWRwMWk4MnRxNG1tRmhIcFZoa0R3WXBETmtMMHRWQzJzeXQxNm1HNXE1ZTRFR0tEVkVseTNkSW5FUkdnMHY3X0N0bG5lTVZiZ3pXMHk2cjhzWG1GZ0VSZVdFdE9rSU9yQXZHYzh3&b64e=2&sign=b5b8c98da45817ba8e8bd84bcc01661f&keyno=0&cst=AiuY0DBWFJ5fN_r-AEszk-WJk_AsBlDZIGmYT3pk0bY9mTlVfXfgmLTpoTfTgww3iGNyrv3OT3qa0MTitr9zZkXcp-aTePRINvp5zQiZ3VIFXqD4_zj5pGJRv_54lhzNg2SaV4WXCVjFuzJOEJh26MRzIuyifn63cQCtyEbT8vZaMuM1Um5so3KG5cCKqFsGX1RiiiGTGFs&ref=orjY4mGPRjk5boDnW0uvlrrd71vZw9kpVBUyA8nmgRGT7nGqYMoHxvJQMAVaIT2y5lU-ps7m-PJUbon27-q8hP0Mny20cJP1b7Oca8-nlpoESQgI3gj8NfHdx0yL2DJFw5sRh1rp47ImG9am0VOOiE41Cr6TcRLs8IIDz6xw_d56PXe-_xYJioP5qYHzv8REyRB0cn18i166SCCx9VqFfw&l10n=ru&cts=1437066383317&mc=4.348036690149728">NII Stali Fact Sheet on Aluminium Armour</a></span><br />
<br />
<span style="color: orange;"><a href="http://www.dishmodels.ru/wshow.htm?mode=P&vmode=T&p=261&id=4395&tp=w">http://www.dishmodels.ru/wshow.htm?mode=P&vmode=T&p=261&id=4395&tp=w</a></span><br />
<br />
<span style="color: #f6b26b;"><a href="http://vmk.tplants.com/ru/products/bmd2/">http://vmk.tplants.com/ru/products/bmd2/</a></span><br />
<br />
<span style="color: orange;"><a href="http://lzos.ru/en/index.php?option=com_content&task=view&id=72">http://lzos.ru/en/index.php?option=com_content&task=view&id=72</a></span><br />
<br />
<span style="color: #f6b26b;"><a href="http://lzos.ru/en/index.php?option=com_content&task=view&id=71">http://lzos.ru/en/index.php?option=com_content&task=view&id=71</a></span><br />
<br />
<span style="color: orange;"><a href="http://kbptula.ru/en/productions/small-arms-guns-grenade-launchers/guns-machine-guns/2a42">http://kbptula.ru/en/productions/small-arms-guns-grenade-launchers/guns-machine-guns/2a42</a></span><br />
<br />
<span style="color: #f6b26b;"><a href="http://kubinkamuseum.ru/index.php?option=com_content&view=article&id=76&Itemid=274">http://kubinkamuseum.ru/index.php?option=com_content&view=article&id=76&Itemid=274</a></span><br />
<br />
<span style="color: orange;"><a href="https://books.google.com.my/books?id=BNvfNYW6yisC&pg=PA24&lpg=PA24&dq=bmp+squad+leader&source=bl&ots=epAOthRskO&sig=HcU2bjIyxVHBPzUhSHydf0fmiWE&hl=en&sa=X&redir_esc=y#v=onepage&q=bmp%20squad%20leader&f=false">https://books.google.com.my/books?id=BNvfNYW6yisC&pg=PA24&lpg=PA24&dq=bmp+squad+leader&source=bl&ots=epAOthRskO&sig=HcU2bjIyxVHBPzUhSHydf0fmiWE&hl=en&sa=X&redir_esc=y#v=onepage&q=bmp%20squad%20leader&f=false</a></span><br />
<br />
<span style="color: #f6b26b;"><a href="http://www.wk2ammo.com/showthread.php?3203-20x139-shells-for-the-HS-820-(Oerlikon-KAD)-amp-Rh-202-gun">http://www.wk2ammo.com/showthread.php?3203-20x139-shells-for-the-HS-820-(Oerlikon-KAD)-amp-Rh-202-gun</a></span><br />
<br />
<span style="color: orange;"><a href="http://www.rheinmetall-defence.com/en/media/editor_media/rm_defence/publicrelations/pressemitteilungen/2013_1/2013_Rheinmetall_IDEX_Medium_Calibre_Ammunition.pdf">http://www.rheinmetall-defence.com/en/media/editor_media/rm_defence/publicrelations/pressemitteilungen/2013_1/2013_Rheinmetall_IDEX_Medium_Calibre_Ammunition.pdf</a></span><br />
<br />
<a href="http://coollib.com/b/237493/read">http://coollib.com/b/237493/read</a><br />
<br />
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<h3>
<span style="color: white; font-size: large;">Bibliography</span></h3>
<br />
<span style="color: black;"><a href="https://books.google.com.my/books?id=rz7smHCwhX4C&pg=PA10&lpg=PA10&dq=bmd+fuel+tanks&source=bl&ots=t_KBK9lg0a&sig=Clxdak1TAG3_8WJyOoaLJAzxQoU&hl=en&sa=X&redir_esc=y#v=onepage&q=bmd%20fuel%20tanks&f=false">Soviet Bloc Elite Forces By Steven J. Zaloga</a></span> (unreliable)</div>
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<h4 style="text-align: center;">
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Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com7tag:blogger.com,1999:blog-3103574899092646031.post-42071588423757336552015-05-01T17:31:00.908-07:002024-03-03T21:56:05.809-08:00T-72: Part 1<head>
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<a href="https://4.bp.blogspot.com/-Azo5JGyi0gw/XACl4t9QZVI/AAAAAAAAMlU/wT_0EeXpUx8PuoW1co2SrVPk43dJRKLdwCLcBGAs/s1600/66e42e7b593ed0e575a32ac2e2e79907.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="642" data-original-width="966" height="424" src="https://4.bp.blogspot.com/-Azo5JGyi0gw/XACl4t9QZVI/AAAAAAAAMlU/wT_0EeXpUx8PuoW1co2SrVPk43dJRKLdwCLcBGAs/s640/66e42e7b593ed0e575a32ac2e2e79907.jpg" width="640" /></a></div><div><br />
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<span style="font-family: inherit;">The T-72 is known as one of the most numerous tanks in the world today, and the tank is likely to remain in some form of service for the rest of the 21st Century, so before we examine the history of the T-72, let us see how many of these tanks were actually built. A few years ago, Uralvagonzavod (UVZ) made efforts to declassify much of the history of the T-72 tank, including the number of tanks built by the factory. The table below comes from the factory archives of UVZ, published in the book "<i>T-72/T-90: The Experience of Creating Domestic Main Battle Tanks</i>" authored by S. Ustmantsev and D. Komalkov (head designer of the UVZ transport engineering bureau).</span><br />
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<a href="https://3.bp.blogspot.com/-2wePjVcJ-ks/WcdHsRxkLUI/AAAAAAAAJkU/Rn2e1ehQHQ4tWvFOlfynlx3JERpcgajlQCLcBGAs/s1600/production%2Bstatistics%2Bby%2Buvz.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="393" data-original-width="368" src="https://3.bp.blogspot.com/-2wePjVcJ-ks/WcdHsRxkLUI/AAAAAAAAJkU/Rn2e1ehQHQ4tWvFOlfynlx3JERpcgajlQCLcBGAs/s1600/production%2Bstatistics%2Bby%2Buvz.jpg" /></a></div>
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From 1973 to 1990, a total of 18,373 T-72 tanks and T-72 derivatives were manufactured at the UVZ factory floor and another 1,600 tanks were manufactured from 1991 to 1996. The Chelyabinsk Tractor Factory also took part in the manufacture of the T-72 tank, producing 1,894 units themselves between 1978 and 1990. In total, 20,267 T-72 tanks were produced in Soviet Russia, making it the second most numerous tank ever produced in both the USSR and the world, outstripping the T-62 for that title by a slim margin. Of that total, 5,264 T-72A tanks were delivered to the Soviet Army. But how did it come about? <span style="font-family: inherit;">The 2010 book "<i>T-72 Ural armor versus NATO</i>" by noted military historian </span>Mikhail Baryatinsky details the history of the development of the tank, and is the source for many of the diagrams and pictures shared below.<br />
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<span style="font-family: inherit;">Firstly, it should be clear that the T-72 is indeed a "mobilization model" of a sort with slightly inferior performance compared to the later models of the T-64 series. The main factor that relegates the T-72 to this category during its service career in the Soviet Army was its role as the primary tank model for motorized infantry units and other mainline Army units whereas the T-64 and T-80 series tended to be supplied to Guards units. The T-72 was also widely exported during the Cold War, and as such, the T-72 could be rightfully considered the backbone of the Soviet Army and that of many other nations together with the T-55 and the T-62. With that said, some Internet sleuths found <a href="http://s60.radikal.ru/i170/1307/35/f0c75b444254.jpg">this chart</a> of procurement prices showing that the T-72A (1979) was significantly more expensive than the T-64A. The more expensive pricing of the T-72 does not change the fact that it was a less sophisticated product compared to the later models of the T-64 such as the T-64B, although it was not originally intended to be such by the chief designer of the UKBTM design bureau, Leonid Kartsev. In fact, the original T-72 outpaced the T-64A in some technical areas due to the implementation of certain technologies.</span><br />
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<span style="font-family: inherit;">Let us take a look at the Object 167M. It is a precursor to the T-72, but is better described as a T-62 taken to the extreme. </span><br />
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<a href="https://2.bp.blogspot.com/-pMvjqE-DD10/WXOjKADA2PI/AAAAAAAAI0I/6DoJSluOfBY8Z9GS2_R7Gzv36JksrPWbQCLcBGAs/s1600/obj%2B167m.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="640" data-original-width="866" height="472" src="https://2.bp.blogspot.com/-pMvjqE-DD10/WXOjKADA2PI/AAAAAAAAI0I/6DoJSluOfBY8Z9GS2_R7Gzv36JksrPWbQCLcBGAs/s640/obj%2B167m.jpg" width="640" /></a></div>
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The Object 167M featured the now-famous AZ autoloader, composite armour for the upper glacis and turret, a 125mm D-81T cannon, a V-26 engine which developed 700 HP, a reinforced transmission to deal with the increased power, hydraulically powered gear shifting systems, the new "Liveni" two-plane stabilizer system, and a new suspension composed of six roadwheels with three return rollers. The tank did not enter mass production because the Object 432 had already been ordered to enter production as the T-64 by a resolution from the Council of Ministers of the USSR and the Object 167M had numerous drawbacks of its own. In February 26, 1964, the scientific-technical council GKOT examined the Object 167M project and rejected it. This was the end of the road for the Object 167M, but it was destined to leave its mark on Soviet tank history, as we shall see later on.<br />
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<span style="font-family: inherit;">The Minister of Defence Industry S.A Zverev came to the experimental workshop of the Uralvagonzavod factory on October 26, 1967, the 50th anniversary of the October Revolution. After an invitation to enter and examine a modified T-62 with a 125mm gun (a special development in response to Kharkov's failure to begin mass production of the T-64 on schedule) by UKBTM design bureau chief Leonid Kartsev, the minister requested a demonstration. The designer E.E Krivosheya and researcher L.F Terlikov who were loitering around the tank quickly joined the two inside, started it up and activated the autoloader. The minister was impressed by the autoloader and was enthusiastic on the idea of putting it in the T-64, but rejected Kartsev's proposal to also replace the</span> 5TDF engine on the T-64A with a supercharged derivative of the V-2 engine (from the T-34) developed in Chelyabinsk.<span style="font-family: inherit;"> He only agreed on changing the engine on the next day after a private meeting with the head of the Military Industrial Commission I.V Okunev. It was agreed that six T-64A tanks were to be sent to UVZ to be given the modifications specified by Kartsev, but the minister also dictated that the suspension and chassis were to be untouched. </span>On 5 January, 1968, Zverev officially gave the order to begin the "modernization" of the T-64A by the Uralvagonzavod factory. Thus the life of the T-72 began, but f<span style="font-family: inherit;">or the next few years, all prototypes of Kartsev's new tanks would either be modifications of these six T-64A tanks or modified copies thereof.</span><br />
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<span style="font-family: inherit;">The first of these modifications, dubbed "Object 172", was completed in the summer of 1968, and the second was completed in September of that same year. The Object 172 differed from the T-64A obr. 196 in the fighting compartment which had to be rearranged to fit the new autoloader, and in the engine compartment which was completely reworked for the V-45K engine and T-54-style cooling system.</span><span style="font-family: inherit;"> </span><br />
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Because the modifications were focused only on internal components and the engine compartment, the Object 172 was practically indistinguishable from a typical T-64A obr. 1989 from the front, but from the rear, the turret was clearly modified for the autoloader's ramming and ejection system, while the engine deck was completely distinct from that of the T-64 series. The engine compartment itself was also lengthened to accommodate the new powertrain and cooling system, so the tank is not as compact as the T-64 in length. The left side of the hull gained an exhaust port just above the second rearmost roadwheel - a location reminiscent of the earlier T-54 and T-62.<br />
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Baryatinsky's book gives us the details of the late stages of gestation of the T-72. Here are a few translated paragraphs:<br />
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"<i>... in the Design Bureau of the UVZ, which since August 1969 was headed by V.N. Venediktov, it was decided to use the chassis of the Object 167 with rubberized roadwheels of increased diameter and more durable tracks with open metal track pins [author's note: OMSh] similar to those of the T-62 tank. The development of this tank was carried out under the designation "Object 172M". The engine, boosted to 780 hp, received the index of V-46. A two-stage air-cleaning cassette system was introduced, similar to that used on the T-62 tank. The weight of the Object 172M increased to 41 tons, but the mobility characteristics remained at the same level due to the increase in engine power by 80 hp, the capacity of fuel tanks by 100 liters and the width of the track by 40 mm.</i><br />
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<i>From November 1970 to April 1971, Object 172M passed a full cycle of factory tests and then on the 6th of May 1971, it was presented to the Minister of Defence A.A. Grechko and to the Minister of Defence Industry SA. Zverev. By the beginning of the summer, a test lot was created from 15 vehicles, which, together with the T-64A and T-80 tanks, passed many months of testing of an unprecedented scale. At the suggestion of Major-General Yuri M. Potapov, a battalion composed of three companies with tank platoons was formed. Each company was formed from tanks of the same type. The route of the traffic was chosen from Dnepropetrovsk through Ukraine to Belorussia to Slutsk and then back to Dnepropetrovsk, and then through the Donbass and the North Caucasus to Baku, across the sea by ferry to Krasnovodsk, through the Karakum desert and the Kopetdag mountain range. The tests were due to be completed at a range, 60 km from Ashgabat. During the march, live firing tests were conducted at various firing ranges, and platoon and company level exercises with live firing and maneuvering were carried out at various tankodroms [author's note: training grounds].</i><br />
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<i>After the end of the tests, a report with the title "<i>Report on the results of military trials of 15 tanks 172M, manufactured by Uralvagonzavod in 1972</i>" was submitted. The final part of the report contained these remarks:</i><br />
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<ol>
<li><i>Tanks have passed the tests, but the lifespan of the tracks of 4,500 - 5,000 km is insufficient and does not fulfill the requirement for tank travelling capability of a distance of 6,500 - 7,000 km without replacement of tracks.</i></li>
<li><i>Tank 172M (warranty period - 3,000 km) and engine V-46 (350 m / h (?)) worked reliably. In the course of further testing up to 10,000 - 11,000 km, most of the units and assemblies, including the V-46 engine, operated reliably, but a number of major units and assemblies showed insufficient lifespan and reliability.</i></li>
<li><i>The tank is recommended for adoption into the armed services and serial production, provided that the identified shortcomings are eliminated and the effectiveness of their elimination is checked before serial production. The scope and time frames for improvements and inspections should be agreed between the Ministry of Defense and the Ministry of Defense Industry.</i></li>
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<i>In accordance with the decision of the Central Committee of the CPSU and the Council of Ministers of the USSR of August 7, 1973, Object 172M was adopted by the Soviet Army under the name of T-72 "Ural". The official order of the Minister of Defense of the USSR was published on August 13, 1973. In the same year, a pilot batch of 30 tanks was produced at Uralvagonzavod.</i>"<br />
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And thus, the T-72 was born. An amalgamation of the T-64A and the Object 167M, the T-72 would go on to become the second most widely produced tank in the world, behind only the T-54.<br />
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<span style="font-family: inherit;">In the end, the T-72 was similar enough to the T-64 that it was not easy to tell them apart at first glance, yet different enough that there was virtually no commonality in parts between the two tank families. This was one of the many headaches caused by the rivalries in the Soviet tank building industry, but still, this did not change the fact that the T-72 was an extremely capable tank. When viewed in terms of cost efficiency, the T-72 was second to none during its heyday and still remains a relatively competitive product to this day if given sufficient upgrades.</span><br />
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Although many T-72 models could be considered technically inferior to a T-64 or T-80 counterpart from the same period, the difference in combat capabilities was generally quite small. According to captured Soviet documentation from 1977 presented in <a href="https://www.cia.gov/library/readingroom/docs/1980-08-25.pdf">this CIA report</a>, the combat potential coefficient of the T-64A is 1.50 and the T-72 is rated at 1.50. Thus, the T-72 was considered to be the equal of the T-64A during the earlier years of its life. However, the gap in capabilities appears to widen as the years go by: the combat potential of the T-64B is rated at 2.10 and the "T-72 with TPD-K1" is rated at only 1.70. However, the T-72A (1979) did not yet exist by the time the document was published (1977) whereas the T-64B (1976) was already in mass production, so it is not so easy to directly compare the T-64B with the closest T-72 counterpart. Generally speaking, however, the determining factor appears to be in the fire control system. Indeed, the inclusion of the TPD-K1 laser rangefinding sight alone apparently gave the T-72 a 0.2 point advantage over the basic model. The additional advantages enjoyed by the T-64B included the ability to fire guided missiles which the T-72 family lacked until 1985 when the T-72B began mass production. The T-72 series also retained the same TPD-K1 sight in one form or another throughout its career in the 80's and into modern times. On the other hand, the T-64A began with the TPD-2-49 sight in 1972 which the T-72 Ural shared, but the T-64 was upgraded to the T-64B variant and was equipped with the substantially more advanced 1A33 sighting complex with the 1G42 sight in 1976 and retained it until 1987 when the T-64 family was discontinued altogether. However, the cost efficiency of the T-72 was a different matter.<br />
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In the book "<i>Combat Vehicles of Uralvagonzavod: T-72 Tank</i>" published by the Information and PR department of Uralvagonzavod, it is claimed that the money spent on purchasing a single T-80U could otherwise be invested in three T-72Bs (with an additional 16,000 Rubles), so in other words, the funds required to purchase two T-80U tanks could cover the cost of a platoon of T-72B tanks as well as a moderate supply of spares. One may be reminded of the stereotype of the Soviet Army favouring hordes of inferior tanks instead of a numerically small collection of technically superior ones, but this is simply not the case. Having a large number of tanks is necessary to ensure that tank support is regularly available to the infantry and there must be enough tanks to fulfill certain operational and strategic objectives, including having enough reserves to support and consolidate territorial gains.<br />
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Referring to the theory of cost efficiency detailed in the book <a href="http://materiel.narod.ru/kostenko1.pdf">"<i>Tanks: Tactics, Technology, Armament</i>" by Yu.P Kostenko</a>, the Uralvagonzavod editors claim that the calculated cost efficiency coefficient of the T-72B is 3.38 whereas the calculated cost efficiency coefficient of the T-80U is only 1.25. Theoretically, the cost efficiency of the T-72B is 2.7 times higher. The method by which combat effectiveness is quantified is a complex affair so it is difficult to independently verify these numbers using third party (i.e non-UVZ) primary sources, but this is merely academic. <span style="font-family: inherit;">The high cost effectiveness of the T-72 undoubtedly had a large influence on the monumental export success of the tank, especially considering that the core customer base for Soviet and Russian arms are Second World or Third World nations that typically do not have a large procurement budget and want the maximum return on their investment.</span><br />
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Furthermore, Kostenko writes in his 2001 monograph "<i>Tank: Man, Environment, Machine</i>" that the time needed for maintenance after 350 km of operation in a T-72B corresponds to 200 km of operation for a T-64B and 100 km of operation for a T-80B. In other words, the amount of maintenance required for a T-72B for any given unit of distance is 3.5 times less than a T-80B and 1.75 times less than a T-64B.
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<span style="font-family: inherit;">But b</span><span style="font-family: inherit;">efore we take a look at the T-72 in earnest, we must first remember that the original Ural variant underwent several major upgrades throughout its lifetime, creating significant discrepancies between each successive model. To complicate matters, each model in itself may have subtle improvements implemented during overhauls. For example, the transition from the T-72 Ural to the T-72A was gradual, with many of the changes embodied by the so-called "Ural-1" model that contained a mixture of features from both the T-72 Ural and the T-72A. The T-72 Ural-1 entered service in 1975-1976, depending on the source. Russian historian A.V. Karpenko states that this modification was accepted into service in 1975.</span></div><div><br /></div><div>In essence, the T-72 Ural-1 was effectively the first serial model of T-72 tank to implement the features tested from 1970-75 on the Object 175 and from 1972-1974 on the Object 172-2M "<i>Буйвол</i>" (<i>Buffalo</i>) experimental series, with a significant degree of overlap between the two models. This manifested itself quite tangibly, as when viewing a parts catalogue for a T-72, it can be seen that a large proportion of the parts do not bear a 172 product code, but rather a 175 product code.<br />
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<span style="font-family: inherit;">The vast majority of the Soviet Army's T-72 tanks up until 1979 was a T-72 Ural-1 model of some type, and this is instantly obvious when we examine the production record of the T-72: the production volume at Nizhny Tagil in 1975 and 1976 alone was 700 units and 1,017 units respectively, whereas only 250 units were released during the entire production run of the original T-72 Ural model from 1973 to 1974.</span><br />
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<span style="font-family: inherit;">Since 1977, the T-72 Ural-1 already began to be produced with a new turret with a "Kvartz" non-metallic filler. This turret was standard for the T-72A (Object 172M-1) and became associated with it. As such, there were at least two types of T-72 Ural-1 tanks with major differences. The transition of the T-72A to the T-72B was similarly difficult to track. The T-72B was created out of the "<i>Improved T-72A</i>" project, and such tanks entered service as T-72A tanks years before the T-72B itself was officially adopted. According to Alexey Khlopotov, the 172.10.077SB turret commonly associated with the T-72B entered production in September 1982 and the T-72A began to receive these turrets in 1983 together with a new hull and a new upper glacis armour design. Other improvements such as the V-84 engine would be installed as late as 1984, further blurring the line between the latest T-72A models and the T-72B1. These late model T-72A tanks have the external appearance of a T-72B, but are not actual T-72B tanks (Object 184). Without going into very much detail, we can condense the evolution of the T-72 tank into a few main models.</span><br />
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<b>Object 172M (T-72 Ural) 1973-1974</b><br />
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The original T-72 model with a monolithic cast steel turret and optical coincidence rangefinder-based sighting system. The IR spotlight was originally located on the left side of the cannon like the T-64A, but it was relocated to the right side in 1974 in order to improve driver safety.<br />
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<b>Object 172M1 (T-72 Ural-1) 1975-1979</b><br />
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In this model, the "Gill" armour panels on the side of the hull from the T-72 Ural (originally from the T-64) were replaced with conventional side skirts sometime in the later half of its production run. The optical coincidence rangefinder-based sighting system was replaced by a laser rangefinder-based version sometime during the production run, at an unknown point. Modified turrets lacking the protrusion for the second optic port for the coincidence rangefinder were devised for these variants. The tank also began to receive a thermal shroud on the gun barrel in 1975.<br />
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<b>Object 172M-1 (T-72A) 1979-1983</b><br />
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In 1976, the UKBTM design bureau was instructed by the Ministry of Defence to carry out a comprehensive modernization of the T-72 in order to increase its combat and operational characteristics. This work concluded with the adoption of the T-72A into the Soviet Army in 1979. Almost everything was changed; the tank had a revised hull armour and a new turret with a composite filler was implemented, the D-81TM cannon was installed, the 902A "Tucha" smoke grenade system was added, a new convoy light with a numerical display was installed, and more.<br />
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<b>Object 184 (T-72B) 1985</b><br />
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Second serious upgrade of the T-72. The new tank featured completely revised hull and turret armour, a new autoloader, a guided missile firing capability, a new cannon, a new engine, new sighting systems, and more.<br />
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<b>Object 184-1 (T-72B1) 1985</b><br />
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Simplified T-72B variant without the missile firing capability and with the original Ural autoloader. This aspect of the T-72B1 is examined later on in the article, in the section on the autoloader.<br />
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<br />The T-72B itself was subject to a modernization project, initiated by the decree No. 741-208 of the USSR Council of Ministers on the 19th of June 1986. The "Improved T-72B" project, under the Object 188 index, entered service in 1992 as the T-90.<br />
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Again, it must be stressed that this is only a very basic list of variants. It is unwise to generalize with regards to the T-72, as the model designation sometimes does not reveal the full story.<br />
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<span style="font-size: large;">Table of Contents</span></h3>
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<li><a href="#erg">Ergonomics</a></li>
<li><a href="#comstat">Commander's Station</a></li>
<li><a href="#tkn-3m">TKN-3M</a></li>
<li><a href="#comfcs">Commander's Fire Controls</a></li>
<li><a href="#comms">Communications</a></li>
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<li><a href="#gunstat">Gunner's Station</a></li>
<li><a href="#sc">Sighting Complexes</a></li>
<li><a href="#tpd">TPD-2-49</a></li>
<li><a href="#1a40-1">1A40, 1A40-1</a></li>
<li><a href="#aux">Auxiliary Sights</a></li>
<li><a href="#tpn">TPN-1-49-23</a></li>
<li><a href="#tpn3">TPN3-49</a></li>
<li><a href="#1k13">1K13-49</a></li>
<li><a href="#1a40-4">1A40-4 Sosna-U</a></li>
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<li><a href="#stabs">Stabilizers</a></li>
<li><a href="#2e28m">2E28M "Sireneviy"</a></li>
<li><a href="#2e42-2">2E42-2 "Zhasmin"</a></li>
<li><a href="#2e42-4">2E42-4 </a></li>
<li><a href="#metmast">Meteorological Mast</a></li>
<li><a href="#d-81t">D-81T Cannon</a></li>
<li><a href="#2a26m-2">2A26M-2</a></li>
<li><a href="#2a46">2A46</a></li>
<li><a href="#2a46m">2A46M</a></li>
<li><a href="#2a46m-5">2A46M-5</a></li>
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<li><a href="#ammostow">Ammunition Stowage</a></li>
<li><a href="#auto">Autoloader</a></li>
<li><a href="#loose">Loose Stowage</a></li>
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<li><a href="#ammu">Ammunition</a></li>
<li><a href="#hef">HE-Frag</a></li>
<li><a href="#heat">HEAT</a></li>
<li><a href="#ap">APFSDS</a></li>
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<li><a href="#second">PKMT Coaxial Machine Gun</a></li>
<li><a href="#aa">NSVT Anti-Aircraft Machine Gun</a></li>
<li><a href="#storage">Storage</a></li>
<li><a href="#esc">Escape Hatch</a></li>
<li><a href="#driver">Driver's Station</a></li>
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Due to length restrictions, this article has been divided into two parts. Part two is <a href="https://thesovietarmourblog.blogspot.com/2017/12/t-72-part-2.html">available here</a>.</h3>
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<span style="font-size: large;">ERGONOMICS</span></h3>
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In terms of ergonomic design, the T-72 is similar to the T-64, greatly superior to the T-62 and T-55, and broadly on par with many contemporary tanks. This is despite the extremely low height of the tank even compared to the T-62 and T-55, and the simple reason is that the use of an autoloader eliminated the need to allocate enough vertical space for a human loader to stand inside the tank.
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The reduction to a three-man crew also enabled a more spacious turret crew layout to be implemented where the gunner and commander occupied their own halves of the turret, and the amount of space for the driver also increased. If we refer to <a href="http://3.bp.blogspot.com/-aBnfqllGDQI/VIZm9eldmDI/AAAAAAAADsg/2sGi3lKKxxo/s1600/human-factors-1.png">this diagram</a> from "<i>Human Factors and Scientific Progress in Tank Building</i>" by M.N. Tikhonov and I.D. Kudrin courtesy of Peter Samsonov, it is seen that the commander of a T-72 has 0.615 cubic meters of space, the gunner has 0.495 cubic meters of space and the driver has 0.864 cubic meters of space. However, the commander of a T-72 apparently has much less space compared to a T-55 commander (0.828 cubic meters), but this is obviously not possible. For one, the commander in a T-55 has to wrap his legs around the gunner seated in front of him because there is simply not enough legroom and the breech guard squeezes him against the turret wall where the radio is located. It is the exact opposite for the T-72. As the commander's station in the T-72 is completely separated from the gunner's station, there is nothing in front of him below chest level, and as a result, he has an abundance of legroom and sufficient headroom is guaranteed. It is perfectly possible for exceptionally tall people to command a T-72 without any ergonomic issues, and the commander can stretch his legs out as far as he desires even when the turret rotates. The difference of 0.1 cubic meters between the T-72 and the T-64A is also highly suspect, given that the two tanks are so similar.<br />
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According to the article "<i>Elements of Tank Design</i>" by Gerald A. Halbert published in the November-December 1983 issue of ARMOR magazine, a seated man needs 0.4 cubic meters of space while wearing an NBC suit, a loader needs 0.8 cubic meters of space, and a driver needs 0.6 cubic meters of space. Halbert states that an additional 10% of space is needed for habitability and essential movement, so in actuality, a seated man wearing an NBC suit requires 0.44 cubic meters, a loader needs 0.88 cubic meters, and a driver needs 0.66 cubic meters. From this, it can be seen that the internal space provided for the T-72 commander greatly exceeds the ergonomic requirements for a seated man and the space provided for the gunner is still comfortably in excess of the requirements. The space provided for the driver of the T-72 also greatly exceeds the requirements. Furthermore, the rational and efficient layout of the controls and equipment in the tank facilitate crew comfort and ease of operation to a degree that cannot be expressed plainly in terms of volume.</div><div><br /></div><div>In terms of dimensions, the hatches for all crew members would meet the minimum U.S Army human engineering requirements for a rectangular hatch size needed to accommodate a 95th percentile U.S male wearing light clothing, which is 13 x 23 inches (330 x 580 mm), as shown in the table below. These figures are sourced from the military standards document "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a281401.pdf">Military Standard Human Engineering Design Criteria For Military Systems, Equipment And Facilities</a>", MIL-STD-1472D.</div><div><br /></div><div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-BTBuLR1LYzM/YBbK9ZDZuvI/AAAAAAAASsY/5MaCqyS9mNo7VaRfuRKFJeDtMOZo9i_cwCLcBGAsYHQ/s1424/hatch%2Bdimensions%2Brequirements.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="409" data-original-width="1424" height="115" src="https://1.bp.blogspot.com/-BTBuLR1LYzM/YBbK9ZDZuvI/AAAAAAAASsY/5MaCqyS9mNo7VaRfuRKFJeDtMOZo9i_cwCLcBGAsYHQ/w400-h115/hatch%2Bdimensions%2Brequirements.png" width="400" /></a></div></div><div><br /></div><div><br /></div><div>However, given that none of the hatches are rectangular, but either have rounded corners (driver's hatch) or are semicircular, these requirements are not directly applicable. In fact, there is no standard for semicircular hatches, only oval and circular hatches, so there is no way to properly check the adequacy of the T-72 hatches. With that in mind, the hatches on the T-72 would probably not meet the minimum size for personnel wearing heavy clothing (NBC suit, winter clothes), but in fairness, virtually all tanks were designed only with light clothing in mind. On a Chieftain, the driver's rectangular hatch measures 381x540mm (15x21.25"), while the commander's oval hatch has a 508mm (20") maximum diameter, and the loader's rectangular hatch measures 508x432mm (20x17"). None of them meet U.S requirements for bulky clothing.</div><div><br /></div><div>This was also true of newer tanks such as the Abrams series. A 1992 report by the U.S Army Biomedical Research & Development Laboratory, "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a260089.pdf">Evaluation of Ventilation Inside Armored Vehicles</a>", states that the loader's hatch is 23 inches in diameter (actual diameter is 22.5 inches). This is far felow the minimum requirement for circular hatches of 30 inches. The commander's hatch was measured to be 21.5 inches wide and 18 inches in length. This also falls short of the required size of oval hatches.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-EkOD9KRMRkg/YDjomzqjxsI/AAAAAAAAS0I/z5G9oaz06KImZ7n8599ZxhBeItFPj22awCLcBGAsYHQ/s1194/round%2Bhatches.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="309" data-original-width="1194" height="104" src="https://1.bp.blogspot.com/-EkOD9KRMRkg/YDjomzqjxsI/AAAAAAAAS0I/z5G9oaz06KImZ7n8599ZxhBeItFPj22awCLcBGAsYHQ/w400-h104/round%2Bhatches.png" width="400" /></a></div><div><br /></div><div><br /></div><div>When taking into account the major differences in the anthropometric data between the conscription age men of the USSR and the enlisted personnel of fighting age in the U.S military, the hatches of the T-72 are of a favourable size. A 95th percentile American ground forces serviceman had a weight of 91.5 kg based on studies in 1966 and in 1977 with large sample sizes of USMC and U.S Army personnel, whereas the 95th percentile Soviet young adult male (conscription age) had a weight of 81.57 kg according to the USSR Anthropometric Atlas, 1977. U.S Army tankers were, and still are, recruited to a 95th percentile standard with a 183cm (6'1") official height limit. Soviet tank crews were recruited to a 50th percentile (average), standard, with a 175cm official height limit.</div><div><br /></div><div>Keeping in mind that the 95th percentile for Soviet men is not the same as the 95th percentile for U.S men, and that smaller men were usually recruited for tank crews, the hatches on the T-72 were not only of an ideal size for a Soviet tank crew in light clothing, but were even adequate for winter clothing, whereas the same could not be said for U.S tanks.</div>
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According to Sergey Suvorov, the use of an carousel-type autoloader in the T-72 as opposed to a basket-type autoloader as in the T-64 reduced the vertical space in the tank by around 25 cm. However, the height of the crew compartment in the turret was still more than sufficient, as the crew members are seated at all times when performing their duties. In the T-72, the seats for both the commander and gunner are only a short distance above the tallest point of the false floor of the turret so both crew members sit with their legs outstretched. The gunner's seat is fixed at a height of 150mm above the false floor, and the commander's seat has a variable height. This matched the minimum seat height figure of 150mm used as a reference in Soviet tank ergonomics design textbooks. Referring to the drawing below, it can be seen that the seated height of an average man wearing a tankers' uniform with a standard Soviet tankers' helmet is 1,050mm including a seat with a height of 150mm. The height of the hull and turret of the tank is 1,730mm (excluding ground clearance), and the maximum height of the AZ autoloader carousel is 450mm. Therefore, the internal height in the fighting compartment of the turret after subtracting the thickness of the turret roof and anti-radiation lining is up to 1,200mm. The commander's cupola extends above the turret roof, so in actuality, the vertical space allocated to the commander significantly exceeds this figure, but on the other hand, the turret roof over the gunner's station is sloped which reduces the gunner's headroom by a few inches. From this, it is clear that even a man of extremely tall stature would be able to fit in the commander's station and the gunner's station would still easily accommodate a man of average height.<br />
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<a href="https://1.bp.blogspot.com/-CKLB-FXOJeU/XDnIUDGqNxI/AAAAAAAAM4w/bDWjMP6IDicfCRkWA1HonFRkdmxN5feuwCEwYBhgL/s1600/average%2Bhuman%2Bdimensions.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="374" data-original-width="603" height="247" src="https://1.bp.blogspot.com/-CKLB-FXOJeU/XDnIUDGqNxI/AAAAAAAAM4w/bDWjMP6IDicfCRkWA1HonFRkdmxN5feuwCEwYBhgL/w400-h247/average%2Bhuman%2Bdimensions.png" width="400" /></a></div>
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Even though the commander in a T-72 does not have the abundance of space that an M60A1 commander may be accustomed to, it meets all ergonomic requirements and it is a sizable improvement over the T-54 and T-62 as much of the equipment attached to the wall of the commander's station (like the bulky radio) have been moved forward so as to free up more space for his shoulders, as shown in the many photos featured in this article. This additional space allows the commander to freely service the coaxial machine gun and operate the radio. The gunner of the T-72 has less space since the sights and gunnery controls occupy all of the room in front of him. Both crew members have more than enough legroom thanks to the seating arrangement where each man has his own half of the turret. Based on the diameter of the autoloader carousel (1,800mm) and the location of the seats, the length of both the commander's station and the gunner's station is 1,150mm (measured from the backrest of their seats) which is more than the 1,000mm figure shown in the drawing above.<br />
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Overall, the T-72 definitely offers more space for the commander than a T-55 and the gunner gets more legroom, despite the what the figures given in "<i>Human Factors and Scientific Progress in Tank Building</i>" imply. It is likely that such figures are calculated by using a simplified model of human dimensions and internal tank dimensions which would not accurately reflect the actual conditions of the crew. In fact, the drawing shown below clearly illustrates why it would be quite impossible for the commander's station in a T-55 to be more spacious than in a T-72.<br />
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<a href="https://1.bp.blogspot.com/-mhX2ECpP5Q4/XDNgtxtkjcI/AAAAAAAAMzo/xhyL5gQqHvcdO0K2G8SO0-uqTfQ2F2ilQCLcBGAs/s1600/obj%2B167%2Bgunner%2Band%2Bcommander.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="335" data-original-width="417" height="321" src="https://1.bp.blogspot.com/-mhX2ECpP5Q4/XDNgtxtkjcI/AAAAAAAAMzo/xhyL5gQqHvcdO0K2G8SO0-uqTfQ2F2ilQCLcBGAs/s400/obj%2B167%2Bgunner%2Band%2Bcommander.png" width="400" /></a></div>
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The internal volume and the distribution of volumes did not change throughout the entire evolution of the T-72 series from the original "Ural" to the T-72B. According to the book "<i>Боевые Машины Уралвагонзавода: Танк Т-72</i>" published by the Uralvagonzavod Production Association, the fighting compartment has a volume of 5.9 cubic meters, the driver's compartment has a volume of 2.0 cubic meters and the engine compartment has 3.1 cubic meters of volume, for a total internal volume of 11.0 cubic meters. This information is repeated in <a href="http://tank72.tass.ru/5/">a media presentation from the TASS news agency</a> and the engine compartment volume is corroborated by various journal articles regarding the volumetric efficiency of various powertrains. According to the journal article "<i>Объемно-Массовый Анализ Защиты Серийных Танков</i>", the volume of the T-72B turret above the turret ring is 1.7 cubic meters, the volume of the hull is 9.3 cubic meters, and the total is 11.0 cubic meters. From this, it can be seen that the fighting compartment can be divided into the 1.7 cubic meters in the turret (28.8%) and the 4.2 cubic meters in the hull (71.2%).</div><div><br /></div><div>Other figures published for the internal volume of the T-72 are incorrect, like in the article "<i>Основы теории и история развития компоновки танка</i>" ("<i>Fundamentals of the theory and history of the development of the tank layout</i>") by Vasily Chobitok where it is stated that total internal volume of the T-72 is 11.8 cubic meters.</div><div>
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For comparison, the fighting compartment volume of the T-54/55 is 8.05 cubic meters, the fighting compartment volume of a T-62 is 9.23 cubic meters, the fighting compartment of the M47 Patton has a volume of 9.06 cubic meters, the M48 Patton has a fighting compartment volume of 10.48 cubic meters, and the volume of the M60A1 fighting compartment is 11.17 cubic meters. An especially noteworthy subject for a comparison is the Leopard 2A4, which has a fighting compartment volume of 10.1 cubic meters - less than an M48, which also had a smaller 90mm gun that took up less space.<br /><br /></div><div><br /></div><div>The diameter of the turret ring hole cut into the hull roof is 2,162mm. The external diameter of the turret ring is 2,275mm, the bearing pitch diameter is 2,116mm, and the internal diameter of the turret ring is 1,934mm. All numbers given are from technical drawings.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-3PWtlee20oI/X4RJi2GP59I/AAAAAAAARtk/fAJ86UOZnlgU91mCyTfJ5a8FqzrVl2XkQCLcBGAsYHQ/s2048/t-72%2Bturre%2Bring.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1975" data-original-width="2048" height="386" src="https://1.bp.blogspot.com/-3PWtlee20oI/X4RJi2GP59I/AAAAAAAARtk/fAJ86UOZnlgU91mCyTfJ5a8FqzrVl2XkQCLcBGAsYHQ/w400-h386/t-72%2Bturre%2Bring.png" width="400" /></a></div><div><br /></div><div><br /></div><div>Internally, the width of the turret is approximately equal to the diameter of the turret ring, with the area over the crew seats being wider than the turret ring itself due to the thinner side and rear armour, thus forming a shelf which is lined with anti-radiation material. With the partial removal of the lining on the T-72B3, the free space is used to install some electronic equipment instead. </div><div><br /></div><div><br /></div><div>The width of the lower part of the fighting compartment is equal to the internal width of the hull, which is around 1,940mm wide as calculated by subtracting side hull armour (80mm) and anti-radiation lining (50mm) from the external width of hull (2,200mm). The actual width at the fighting compartment is larger, as the anti-radiation lining is thinned down to an inch (25mm) and curved to conform to the diameter of the autoloader carousel. Owing to the increased hull width, the internal width is 100mm larger than the T-54 and T-62, which did not have an anti-radiation lining, and it is 190mm larger than the T-55(A), which did. For comparison, the Leopard 2 turret basket has a diameter of 1,990mm. Taking into account the fact that the anti-radiation liner is curved following the contour of the carousel, the fighting compartment diameter of the T-72 is 1,990mm, identical to the Leopard 2. The true fighting compartment diameter, as measured according to the carousel top cover diameter and turret ring diameter, is 1,940mm. Taking the carousel top cover as the surrogate of a conventional rotating turret floor, it could be said that the T-72 has the widest turret floor among both domestic and foreign contemporaries. This is the main factor that made it possible for the turret crew to be seated with abundant legroom.</div><div><br /></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-mWCSDk5tiJo/X4RKu04tfOI/AAAAAAAARt0/ttO3PTWi1JY7g7N_1MwLFTwyw8lhyhv8ACLcBGAsYHQ/s713/172m%2Bhull%2Bwidth.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="411" data-original-width="713" height="230" src="https://1.bp.blogspot.com/-mWCSDk5tiJo/X4RKu04tfOI/AAAAAAAARt0/ttO3PTWi1JY7g7N_1MwLFTwyw8lhyhv8ACLcBGAsYHQ/w400-h230/172m%2Bhull%2Bwidth.png" width="400" /></a><a href="https://1.bp.blogspot.com/-St6DMGwp3Z0/YSg_nfyPPBI/AAAAAAAAUHw/prQjI_Tq6LMJDcvfeg2K_TQbAR7tMU9KQCLcBGAsYHQ/s2048/hull%2Bside%2Bliner%2Bcutout.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1512" data-original-width="2048" height="236" src="https://1.bp.blogspot.com/-St6DMGwp3Z0/YSg_nfyPPBI/AAAAAAAAUHw/prQjI_Tq6LMJDcvfeg2K_TQbAR7tMU9KQCLcBGAsYHQ/s320/hull%2Bside%2Bliner%2Bcutout.png" width="320" /></a><br /></div><div><br /></div><div><br /></div><div>The difference between the diameter of the carousel top cover and the diameter of hole in the turret roof, very close to the bearing pitch diameter of 2,116mm, is very large, as the image below shows.</div><div> </div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-qc--aYlxcEc/YSg9cx6IJsI/AAAAAAAAUHo/7kkT_OhKVfIS8gX3Kx71g6rqFAb0j64VwCLcBGAsYHQ/s445/without%2Bturret.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="301" data-original-width="445" src="https://1.bp.blogspot.com/-qc--aYlxcEc/YSg9cx6IJsI/AAAAAAAAUHo/7kkT_OhKVfIS8gX3Kx71g6rqFAb0j64VwCLcBGAsYHQ/s16000/without%2Bturret.png" /></a></div><div><br /></div><div>This is more than the T-64 and T-64A which has the crew seated in a turret cabin suspended from the turret ring, which separates the crew from the turret ring by a radius equivalent to the thickness of the ring of ammunition in the autoloader, reducing the diameter of the crew space to only 1,590mm or less. Maximizing the width of the lower part of the fighting compartment is considered less important than maximizing the width of the upper part because the legs of the crew occupy less space than their shoulders (average human shoulder width: 450mm, average hip width: 350mm), not to mention that some elbow room is needed for the crew to operate the equipment in their respective stations. Even so, the additional width provided by the design of the T-72 autoloader is still a noticeable benefit. One major reason is that the turret is low enough that the turret crew will have at least part of their torsos below the level of the turret ring, and the gunner has his elbows below the level of the turret ring practically at all times while carrying out his duties. </div><div><br /></div><div>For instance, it can be seen in the images below (T-80B left, T-80U right) that, while the width of the crew stations is the same as the T-72 aside from the constrained diameter imposed by the cabin, and is quite generous, the space taken up by the cabin limits the size of the seats, particularly in the case of the T-80U where the cuts make the width and length constraints apparent.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_xft-JPf8-lcZyeRQv_0xtGCGyI1PuVf4JZlhgnZ9mbdTtqdVGK4KasF-maQbbP6yYhfA2gdSzy_oH6wi4EuiKjQD8GsO0OGf8Pcqdplg7Bf0gpaqkI6lD6H3d4Eo5DyOXcCe-R4d87GBJtldbw9LIAtLoFq9ywqxu3GfbdRbUf-9zi0V782KOOmyJw/s425/t-80b%20turret.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="360" data-original-width="425" height="339" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_xft-JPf8-lcZyeRQv_0xtGCGyI1PuVf4JZlhgnZ9mbdTtqdVGK4KasF-maQbbP6yYhfA2gdSzy_oH6wi4EuiKjQD8GsO0OGf8Pcqdplg7Bf0gpaqkI6lD6H3d4Eo5DyOXcCe-R4d87GBJtldbw9LIAtLoFq9ywqxu3GfbdRbUf-9zi0V782KOOmyJw/w400-h339/t-80b%20turret.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiEH1D54GapsI4yqNGb9VxMXkWtYf9lXmVwyQP5O45yJU3lWAwgKh5cwTTV7TLUI3tinCYoTeEYBQjEEToHaXBZt-AxknJc0unlF8HwcuE9-YqB_TrYYnLrzw_UiaEnSvlcaafsHwu978tN6GlFcSRjvt4SAAGNS5-meuefzG4uB3tfL_ILGKDEzCM7cA/s952/80u.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="789" data-original-width="952" height="331" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiEH1D54GapsI4yqNGb9VxMXkWtYf9lXmVwyQP5O45yJU3lWAwgKh5cwTTV7TLUI3tinCYoTeEYBQjEEToHaXBZt-AxknJc0unlF8HwcuE9-YqB_TrYYnLrzw_UiaEnSvlcaafsHwu978tN6GlFcSRjvt4SAAGNS5-meuefzG4uB3tfL_ILGKDEzCM7cA/w400-h331/80u.jpg" width="400" /></a></div></div></div><div><br /></div><div>
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The turret ring diameter of the T-72 is smaller than the turret ring diameter of the Leopard 2 (1,980mm), the Chieftain (2,159mm) and the M1 Abrams (2,159mm). Another factor behind the smaller internal volume of the turret of the T-72 - aside from the fact that it is built to accommodate only two crewmen instead of three - is the teardrop geometry which maximizes the frontal protection of the turret with minimal armour mass.</div><div><br /></div><div>
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However, the actual available crew space inside the T-72 turret is increased thanks to the compactness of the 125mm D-81T gun. When measured at the widest point of its gun cradle and fixed recoil guard, the width of the gun is only 600mm. For comparison, the width of the Rh 120 smoothbore gun measured across the recoil guards is 660mm, according to data given by Dipl-Ing Rolf Hilmes in a seminar. Additionally, a measurement of the M68 gun on display at the Museum of Polish Military Technology showed that the width across the recoil guards is 672mm. The width disparity in favour of the T-72 translates to increased room for the crew in the turret. Coupled with the wide 1,934mm internal turret ring diameter of the T-72, it turns out that the maximum width of the gunner's and commander's stations is 667mm.</div><div><br /></div><div>For the Leopard 2, the turret ring diameter is not indicative of the internal turret width because the side armour over the crew compartment (310mm in thickness) overhangs the turret ring by a significant amount and takes up additional internal space. After subtracting the overhang, the internal width of the turret coincidentally turns out to be 1,934mm - the exact same as the T-72. After subtracting the width of the Rh 120 gun cradle, the maximum width of the two halves of the turret occupied by the crew members is around 637mm.<br />
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This difference is illustrated in the two drawings below. Note that in the T-72 cross section, the proportions of the various internal components and the turret walls are not accurate. The image is used only to demonstrate the points of measurement. <br />
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<div><br /></div><div><br /></div><div>It is important to keep in mind that the actual crew space width is slightly less, because there are additional safety guards in both tanks. Still, it can be seen that the T-72 is not inferior to more modern counterpart in critical dimensions for crew ergonomics. According to the REO-SV-80 guidelines (<i>Guidelines for the ergonomic provisions of the creation of military equipment for the ground forces</i>), the crew station width should be 580mm wide for a tank gunner and 600mm wide for a tank commander. The T-72 conforms to these guidelines.</div><div><br /></div><div>The AZ autoloader used in the T-72 permitted free movement between the fighting compartment and the driver's compartment as there is a gap of approximately 500mm between the carousel and the hull ceiling, creating a crawlspace of sufficient size for an average man. The crawlspace is only inaccessible if the turret is turned to face the direct rear, thus positioning the autoloader elevator mechanism over the gap. It is also blocked if the commander's seat adjustment mechanism is positioned directly over the gap. Crawling to and from the driver position is possible when the turret is facing forward, but very challenging because of the multitude of gun stabilizer components hanging below the 125mm gun, constricting the crawlspace size. When the tank has its turret turned to the travel position or has its turret oriented forwards or to the sides, which highly likely in combat, there is sufficient space that a wounded driver can be evacuated through the turret by either of the two other crew members, or conversely (and more importantly), the crew members in the fighting compartment can crawl into the hull to access the escape hatch in the belly.</div><div><br /></div><div>Moreover, if the tank is driven into a deep water-filled ditch, the crawlspace gives the driver an avenue of escape as the driver's compartment is filled with water or at least provides enough room for the driver to keep his head above water.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-oaM7Xc_rKOc/X2nDibs2ioI/AAAAAAAARpA/4PXgHAfvCYkcKQDI0U-ssYTZZKpYhdMOACLcBGAsYHQ/s2048/sectors%2Bof%2Bfree%2Bpassage.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1284" height="400" src="https://1.bp.blogspot.com/-oaM7Xc_rKOc/X2nDibs2ioI/AAAAAAAARpA/4PXgHAfvCYkcKQDI0U-ssYTZZKpYhdMOACLcBGAsYHQ/w251-h400/sectors%2Bof%2Bfree%2Bpassage.png" width="251" /></a></div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">VENTILATION</span></h3>
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Besides the space allocated to the crew, there are other factors affect the comfort of the crew such as thermal regulation and ventilation. For collective ventilation, the T-72 features an FVU (filter-ventilator unit) which serves as a regular blower for general ventilation of the crew compartment and a filtration unit with an overpressure generator, driven by a supercharger. As a filtration unit, the FVU performs both cyclonic separation of coarse particles and fine filtration via HEPA elements. The purified air is then accelerated by a supercharger to ensure a rapid flow of air, sufficient to generate an internal overpressure. As it is a filter element and not a mechanical separator like the supercharger fan, the FVU filter needs to be checked after every 6,600-7,000 km of use.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-aRoPRjtuQxQ/YUR7ymYIsQI/AAAAAAAAULU/Bx8hNVYY-0QTiHF4awPg0XHp-aYvg6zwgCLcBGAsYHQ/s2048/t-72%2Bfvu.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1318" data-original-width="2048" height="412" src="https://1.bp.blogspot.com/-aRoPRjtuQxQ/YUR7ymYIsQI/AAAAAAAAULU/Bx8hNVYY-0QTiHF4awPg0XHp-aYvg6zwgCLcBGAsYHQ/w640-h412/t-72%2Bfvu.png" width="640" /></a></div><div><br /></div><div><br /></div><div>Additionally, the supercharger of the ventilation unit can be used while bypassing the filtration system in an auxiliary mode by turning it on manually. This can be done to enhance airflow in the crew compartment in hot weather. The supercharger is also connected to the firing circuit of the main gun and coaxial machine gun. When either the main gun or the machine gun is fired, the supercharger turns on automatically to increase air circulation in the crew compartment, helping to evacuate the fumes from the weapons so that an excessive concentration of fumes does not accumulate during sustained fire. When operating the coaxial machine gun or main gun manually due to a failure in the electrical firing circuits, the technical manual for the T-72 recommends turning on the supercharger manually before firing. </div></div><div><br /></div><div>In recent tank models with a modernized autoloader, including the T-90A and T-72B3, the spent casing ejection port also briefly opens after a shot is fired from the main gun. Combined with the automatic activation of the supercharger, a reduction in the concentration of propellant fumes in the tank is achieved.</div><div><br /></div><div>For local ventilation, each crew member in the tank is provided with a <a href="http://batcom.ru/products/zapchasti-dlya-spetstekhniki/ventilyatory/dv-3/">DV-3 personal fan</a>, a simple 5.2W fan running on the tank's 27V electrical system.</div><div><br /></div><div>When the tank is driven in regions with a hot climate, ventilation for the crew is supplemented by opening the OPVT intake hole in the engine compartment bulkhead, allowing the engine to draw air from the crew compartment. The effect of doing so is that the ventilator is combined with the powerful draw of the radiator cooling fan to create a strong draft inside the crew compartment. At the same time, this can improve the purity of the air for the engine in dusty environments. When using this method of ventilation, the supercharger should be turned on, or at least one hatch should be ajar, or the snorkel mount hole in the gunner's hatch should be opened. The diagram below shows the OPVT intake hole and the pulley mechanism used to open it from the driver's compartment. When opened, air is drawn through the crew compartment into the engine compartment, past the rear end of the engine near its exhaust ducts, and out through the cooling fan outlet. Opening this intake hole does not come without its costs though, as doing so will slightly increase the pressure in the engine compartment, compromising the negative pressure inside the engine compartment which draws air through the radiators. In situations where cooling efficiency is critical, such as in extremely hot weather conditions, it is imperative that no loss of efficiency is introduced, to prevent the engine from overheating. In such circumstances, the crew is obliged to acquiesce to the needs of the tank rather than their own.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgPPwaJMD27IpAuBpf3DNfDAnNDFPcvfBh_ZzZ8rPcxXsAC5LHFshTdMpjge8mMeyh06ol1uBt9JNe4BsxhuOYsKnodUNG9xAJI4y-V3963vqtYC1elohuxMtiSXTOC9-kjiglhlebKqMPtfiRE8QH-GauboHqpPG7Fr8ienEtOEEUGJV2xF9ItzNfXIA/s4488/opvt%20valve.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="4488" data-original-width="2728" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgPPwaJMD27IpAuBpf3DNfDAnNDFPcvfBh_ZzZ8rPcxXsAC5LHFshTdMpjge8mMeyh06ol1uBt9JNe4BsxhuOYsKnodUNG9xAJI4y-V3963vqtYC1elohuxMtiSXTOC9-kjiglhlebKqMPtfiRE8QH-GauboHqpPG7Fr8ienEtOEEUGJV2xF9ItzNfXIA/w244-h400/opvt%20valve.png" width="244" /></a></div><div><br /><div>Besides a fairly good ventilation system, the T-72 also featured a heater, adapted from the heater in the T-64. The heater is a dual-purpose device designed to pre-heat the engine before starting it in ambient temperature conditions of 5°C or below when using diesel and kerosene fuel, or when operating at 20°C and below when using gasoline. It was also designed to provide heat to the fighting compartment of the tank via a built-in radiator when it is turned on during engine preheating. The heater is installed at the rear starboard corner of the fighting compartment, beneath the fighting compartment ventilator and next to the rear hull conformal fuel tank. The fuel consumption rate is no more than 9 liters per hour, and it can run continuously. The only limit on the duration of operation is the fuel supply.<br />
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The device generates heat by producing a jet of flame in a special boiler using any of the three fuel types specified for the T-72 - diesel, gasoline or kerosene. The boiler heats up the coolant (water), which is circulated around the engine and oil tanks in a closed loop by a boiler pump powered by an electric motor with a manual backup. The same electric motor also powers the air intake fan which supplies air to the boiler and powers the fuel pump which supplies fuel to the boiler. Exhaust gasses from the combustion chamber in the boiler are ejected out of the tank through an exhaust outlet on the side of the hull. </div><div><br /></div><div>Heating for the fighting compartment of the tank is providing by a small tube radiator marked (9) in the drawing below which is heated with hot water from the boiler or from the engine. A fan, marked (6) in the photo below, blows air through the radiator to ensure that heated air circulates around the enclosed space of the tank fighting compartment more quickly. The heater fan is quite powerful, being driven by an MV-42 motor operating at a power of 175 W and turning at 3,500 RPM. Fans with the same motor are used in the ventilation exhaust fans in the T-10 heavy tank series. When using the heater while preheating the engine, the boiler pump of the heater is used to circulate hot water through the small radiator and the engine simultaneously. When using the heater with the engine running, the running engine heats up the circulating water which is pumped through the mini radiator under pressure from the main coolant pump, and heat for the crew is generated without using either the boiler or the boiler pump. To better appreciate the usefulness of this feature, it should be noted that on some tanks, heating for the fighting compartment is only provided by opening a flap in the engine compartment bulkhead to allow engine heat to enter which is a simple and dependable heating method but may also allow various noxious fumes to pollute the crew compartment. Heaters that depend on a boiler or electric element also tend to have very low reliability. This solution of using the tank's coolant with a mini-radiator, was an ingenious solution to the issue of reliable heating, which can be credited entirely to the original T-64 design.</div><div><br /></div><div>When running, the boiler effectively turns the preheater into a hot plate, which can be used to heat ration tins and water. </div><div>
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<br />Since the heater is installed beneath the fighting compartment ventilator, the flow of air from the ventilator blower fan helps to circulate the hot air inside the tank. The heater unit is shown in the photo on the left below (<a href="http://btvt.narod.ru/5/t72b1/t72b1.htm">photo originally shared on btvt.narod</a>). The heater exhaust outlet is situated between the fourth and fifth roadwheels on the starboard side of the hull, as shown in the photo on the right below (<a href="http://www.primeportal.net/tanks/thomas_voigt/t-72m/index.php?Page=8">photo credit to Thomas Voigt</a>).<br />
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A serious design flaw of the heater was that dirt or snow could enter the exhaust outlet and cause a blockage despite the outgoing flow of exhaust gasses, and frequent cleaning is required as soot accumulates easily in the combustion chamber of the boiler. This was a chronic source of heater breakdowns, giving it the reputation of being high-maintenance and unreliable. On the other hand, the likelihood exists that much of the soot accumulation issue stems from the use of the heater with worn and discharged batteries, since the T-72 technical manual states that it is prohibited to use the heater when the master power is less than 22 V as this leads to rapid carbon formation on the walls of the heater.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-5e3hBiRaEW0/X4ROVZGlbEI/AAAAAAAARt8/Ho8a8ztjGTQP-e40_kPrHIJYmBc_pnPegCLcBGAsYHQ/s800/heater%2Bservicing.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://1.bp.blogspot.com/-5e3hBiRaEW0/X4ROVZGlbEI/AAAAAAAARt8/Ho8a8ztjGTQP-e40_kPrHIJYmBc_pnPegCLcBGAsYHQ/w400-h300/heater%2Bservicing.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>A major advantage of the heater design is that the boiler does not need to be running to provide heat for the crew, as heat is supplied by the engine with the added bonus of somewhat contributing to the cooling of the engine. However, the system does not feature a temperature regulator as the heating element is not electric and the radiator fan motor has no speed control, so the fighting compartment heating system can only be either on or off using the toggle switch on the driver's instrument panel. The crew compartment is heated up at an accelerated rate while preheating the engine due to the large heat output of the boiler, and once the engine is started, heat for the crew compartment is sourced from the engine. The main disadvantage of the system is that heated air is not dispensed from vents at the individual crew stations like in a T-80.<br />
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Furthermore, the T-72 had a thick internal anti-radiation lining on the surfaces of the turret and hull. On the frontal cheeks of the turret where the armour was thickest, the lining was only 10-20mm thick as the armour itself provided good shielding from penetrating radiation such as gamma rays and neutrons, but on other parts of the tank including the sides, rear, and ceiling of the turret, the sides of the hull, and on the autoloader carousel cover, the anti-radiation lining was 45-50mm thick to compensate for the low thickness of armour. This lining was known as "Podboi". Beginning in 1983, an external anti-neutron cladding with a thickness of 50mm was added on the turret and hull surrounding the inhabited parts of the tank as a response to an announcement by U.S president Ronald Reagan in 1981 that the production of neutron bombs would be restarted. This cladding was known as "Nadboi". Both the internal lining and external cladding were made from a laminate of hydrogen-rich polyethylene (UHMWPE) and polyisobutylene sheets impregnated with lead.<br />
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Besides offering excellent protection from harmful radiation and blast waves as detailed in <a href="https://thesovietarmourblog.blogspot.com/2017/12/t-72-part-2.html#nbc">Part 2 of this T-72 article</a>, the thick anti-radiation lining inside and outside the tank provides thermal insulation for the crew and internal equipment in hot and cold weather. In cold weather, the temperature of the steel shell of a tank eventually equalizes with the outside temperature so that the crew would essentially be sitting in an ice box, and when the temperature drops below 0 degrees Celsius, the steel surfaces of a tank become too cold to be touched safely with bare skin. The same is true in hot weather as the interior of a tank heated by direct sunlight will become hotter than the ambient air temperature, given enough time. The laminated polymer material (polyethylene and polyisobutylene) of the anti-radiation lining acts as an insulator and a physical barrier between the steel shell of the tank and the crew, thus ensuring that the crew cannot accidentally burn or freeze themselves on the bare steel surface while also helping to regulate the internal temperature of the tank; in winter, the lining helps retain heat inside the crew compartment, and in summer, the lining helps prevent the heated steel shell from raising the internal temperature. The additional "Nadboi" cladding found on newer tanks adds another layer of insulation that is particularly useful in summer as the turret roof is the most exposed to sunlight.<br />
<br />The only foreign tanks with a lining comparable to "Nadboi" in insulation characteristics were the Chieftain and Challenger 1, both of which had a thin foam-backed plastic liner on the majority of the turret and hull surfaces in the crew compartment. This lining, which is around an inch thick, is reported to provide insulation against solar heat, cold and noise in a 1966 edition of the Chieftain user manual.</div><div><br />
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It may seem trivial, but temperature regulation inside a tank is important. Having an internal heater and a layer of insulation on the walls of the tank is a basic necessity for cold winters - something which the T-72 has and some tanks do not. For instance, the personnel heater in the M60A1 and M60A3 was astonishingly unreliable. According to a 1983 TACOM report titled "<a href="http://www.dtic.mil/dtic/tr/fulltext/u2/a129882.pdf">M60 Tank Personnel Heater Comparison Test</a>", the original Model "B" heater in the M60A1 was atrociously unreliable and frequently caused the automatic fire extinguisher system in the tank to discharge accidentally. The problems were recognized and a newer Model "C" heater was installed in M60 tanks since May 1980, but these were still extremely unreliable and the issue of frequent accidental fire extinguisher discharges was still not solved. The Model "C" heater had a mean time before failure (MTBF) of just 70 hours and the mean starts before failure (MSBF) was only 25 starts. Without reliable heating, the efficiency of the crew in wintertime or even during rainy weather would have been reduced. </div><div><br /></div><div>Even worse, some tanks like the Chieftain had a lining but did not have a heater at all, forcing the crew to depend entirely on multiple layers of clothing and thick mittens. This omission was only remedied in the final four years of the Chieftain's service life with the Mk. 10 model, but even then, the system was beset by serious issues; according to Rob Griffin, turning on all three of the new heaters would shut down the tank's electrical system. With that in mind, the famous boiling vessel or "BV" commonly found in British armoured vehicles seems much less like a morale-boosting appliance mandated by the Ministry of Defence for the benefit of weary tankers, and more of a basic necessity to ensure a modicum of comfort. Only the Leopard 1 provided the crew with both a personnel heater and a hot plate from the very first production models, making it arguably one of the most habitable tank of its peers even though, much like the T-72, it was not the most spacious.<br />
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In a T-72, each crew member was provided with a <a href="https://i2.guns.ru/forums/icons/forum_pictures/002590/2590500.jpg">two-liter aluminium bottle</a> which was stowed in a special holder near their respective stations. Officially, the bottle is meant for drinking water, but it can be filled with anything that the individual crew member desires. There is no provision for heating rations other than to place the ration tin next to the boiler of the heater or place it in the engine compartment via a flap in the bulkhead. With that, practically all aspects of the ergonomic design of the T-72 have been discussed, and a detailed examination of the primary characteristics of the tank can begin.<br />
<br /></div><div>For internal lighting, a T-72 has three PMV-71 dome lights and eight KLST-64 cabin lights. Both types of lights have the same TN-28-10 incandescent light bulb, which operate at up to 28 V and consume 10 W. The dome lights serve as the main and emergency lights, as they are not connected to the power supply network of the tank but are instead wired in a separate circuit with the tank's batteries. One dome light is installed on the ceiling of the driver's station and two are on the ceiling of the commander's station for global illumination, and for the convenience of the commander when reloading the coaxial machine gun. The eight KLST-64 cabin lights serve as additional local lighting at all crew stations, mainly for illuminating specific control panels. They can be switched on or off and have sliding lids to adjust the light levels. </div><div><br /></div><div>Additionally, the tank has three ShR-51 power sockets, mainly to supply power to portable lamps but also for night vision devices such as the PNV-57. The power socket resembles the cigarette lighter in cars. There is a power socket on the ceiling of the driver's compartment and one in the turret behind the gunner's seat. The third socket is outside the tank, next to the rear left convoy marker light. Unlike the T-10 heavy tank series, there are no cabin lights inside the engine compartment for servicing at night, so a crew member or mechanic must use a portable lamp instead, and the external power socket is placed there for that purpose. Additionally, the external power socket is used to plug in the MZA-3 fuel filler unit, with which the tank crew can refuel the tank independently of a fuel filler truck or refill the engine oil reservoir. The MZA-3 unit is a powerful, compact device that can pump out diesel at 60 liters per minute. The MZA-3 is also used to clean the air filter elements for the engine air intake system, which is cleaned by washing it with a powerful flow of diesel.</div><div><br /></div><div>As is usual for tanks, the electrical network is a decentralized system, where the power source is connected to multiple independent electrical hubs, which all of the electrical devices are connected to. Only the dome lights and the electric motor of the bilge pump are not connected to the power distribution system, but are instead wired directly to the tank's batteries. Power transmission is done by single-wire connections. The use of a single-wire scheme for power transmission served to reduce the weight of the wiring harnesses in the tank, as substantial weight savings could be gained by omitting a return wire from each connection. The body of the tank itself serves as the ground.</div><div><br /></div><div>In total, the electrical and pneumatic equipment built into the T-72 provided it with a level of self-sustainability that could theoretically allow it to indefinitely maintain a combat-ready status in field conditions without the involvement of additional maintenance support, as long as the tank remains supplied with consumables, including fuel, oil, water, food and ammunition. </div>
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<b><a href="https://www.blogger.com/null" id="comstat"></a><span style="font-size: large;">COMMANDER'S STATION</span></b></h3>
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The commander's cupola follows the same layout that was first implemented for the cupola of the T-54 obr. 1949, but with some significant differences. The T-72 cupola has a more thickly armoured hatch, and the hatch has a clam shell shape rather than a simple semicircular shape. It is also slightly taller and has a more pronounced dome shape due to the large thickness of the anti-radiation lining on the hatch. In terms of width, the T-72 cupola is very similar to the older cupolas of the T-54, T-55 and T-62. Structurally, it differs in the shape of the hatch and fixed roof, but it also differs in that it lacks the ventilation hole which is used during deep fording and for enhanced ventilation. This role was taken over by the snorkel hole on the gunner's hatch. The race ring of the T-72 cupola extends below the turret roof, whereas the one in the T-54 cupola does not. This is because the T-72 cupola has an additional toothed ring that engages with the counter-rotating mechanism. This feature will explored further later on.<br />
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The cupola housing is secured to the cast steel turret roof by a ring of bolts around its circumference, but unlike the T-54 cupola, the bolts are sheltered against gunfire and the weather. The T-72 cupola is also more complex as its race ring is not directly connected to the fixed base bolted to the fixed cupola housing but to an intermediate metal band, and that connects to the cupola housing via a larger race ring. The intermediate metal band is between the inner cupola (which carries the optics and hatch) and the fixed base. It serves as the machine gun ring mount. By releasing a locking mechanism, the intermediate band can be freed from the fixed base, thus allowing it and the machine gun installed on it to be rotated degrees independently of the rest of the cupola, as you can see in the photo below (photo from Russian Ministry of Defence).<br />
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This is also apparent in the photo below showing that the cupola is completely independent from the machine gun mount. Both the cupola and the anti-aircraft machine gun can be rotated without being interrupted by each other.<br />
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The independence of the machine gun mount from the cupola is demonstrated in <a href="https://youtu.be/Zth7dzgb7mA?t=2m54s">this video</a>, and in <a href="https://www.youtube.com/watch?v=vsbRtsnAMDk">this video</a>. <a href="https://www.youtube.com/watch?v=WQryFo2yxGY">This video</a> from TV Zvezda shows a fully assembled turret with the machine gun cradle on its mount, traversed to a forward position. By separating the machine gun mount from the cupola, the commander does not have to bear the weight of the heavy NSVT machine gun (25 kilograms), the machine gun ammunition and the machine gun mount itself when he rotates the cupola which is especially important because the machine gun is mounted eccentrically to the axis of rotation of the cupola, so the center of gravity would be shifted and the cupola would become imbalanced. Overall, this design feature reduces the amount of physical effort required to rotate the cupola, especially if the tank is on a slope. This issue was solved in the T-64A obr. 1975 by using an electric cupola traverse system (part of the remotely controlled anti-aircraft machine gun complex) so that the commander is not required to rotate it manually, but the T-80 and T-80B had its machine gun mounted directly on the cupola and the T-80U skirted the problem by having its anti-aircraft machine gun installed on fixed posts welded to the turret roof at various points. This aspect of the commander's cupola is further discussed in the section on the anti-aircraft machine gun later on.<br />
<br />If the anti-aircraft NSVT machine gun ring is locked facing the rear, the cupola can only be rotated in a 320-degree arc, with a 40-degree dead zone directly behind it. This is due to the base of the machine gun pintle blocking the cupola along a sector with a width of 40 degrees. The cupola is stopped against the base of the pintle by a protruding lug, highlighted in red in the drawings below. As the drawing shows, this lug overhangs the machine gun race ring so that it will be blocked against either the base of the pintle if the cupola is turned to the right, or blocked against the machine gun race ring locking device if the cupola is turned to the left. This traverse limit was presumably put in place so that the spotlight would not collide against the machine gun. If the machine gun ring is unlocked from the turret and coupled to the cupola, the cupola can make a full rotation.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLT26---UNTf9X7TUyST8TK1pn4yC0clTZOu2OU_2OYVK0037iaHhYEr-DjMzUN4xhC9ra-eOLO_R_FWyMHSOIegiybKcH_IT1-DG6lvEqDinTz7cgvZnpaM5l7XQxs7XzOfvxtdpuV-Bbqm8BCO44XIb2fP0x8x0JUPki3oo6w_zZXt7Nvag2eJM6nQ/s1898/cupola%20lug%20side.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="959" data-original-width="1898" height="203" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLT26---UNTf9X7TUyST8TK1pn4yC0clTZOu2OU_2OYVK0037iaHhYEr-DjMzUN4xhC9ra-eOLO_R_FWyMHSOIegiybKcH_IT1-DG6lvEqDinTz7cgvZnpaM5l7XQxs7XzOfvxtdpuV-Bbqm8BCO44XIb2fP0x8x0JUPki3oo6w_zZXt7Nvag2eJM6nQ/w400-h203/cupola%20lug%20side.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidMrWLfV36NtwVJnvNVjvHSOT0L0uMSPsNOFQ7oGb85gKi6rmce-LUeQ9q2ay_LgLX8oBx_LjDlAj_Ei_U7T6EkfJEWvqPhXXogi_FYIt6_DaiW7u8K4VrpD12AAZhfIE9FiXsz9wKC_zSkl3u0pSZ8QLsXOryLjaF5vSmbJCkoAkE90vGOUlp8QGK-Q/s1819/cupola%20lug%20top.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1563" data-original-width="1819" height="275" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidMrWLfV36NtwVJnvNVjvHSOT0L0uMSPsNOFQ7oGb85gKi6rmce-LUeQ9q2ay_LgLX8oBx_LjDlAj_Ei_U7T6EkfJEWvqPhXXogi_FYIt6_DaiW7u8K4VrpD12AAZhfIE9FiXsz9wKC_zSkl3u0pSZ8QLsXOryLjaF5vSmbJCkoAkE90vGOUlp8QGK-Q/s320/cupola%20lug%20top.png" width="320" /></a></div><div><br /><br />
The commander's seat has a robust design with a large square cushion and a large square backrest attached to the seat frame. It can be adjusted in height by releasing a locking pin via a squeeze handle, allowing the seat to be pushed up by a spring and locked in a raised position or pushed down by the commander's body weight and locked in a lowered position. The backrest can be folded inward to allow the commander to access any ammunition stowed behind the seat or to allow the driver to enter the turret if the turret is oriented to the rear of the tank. The seat can be removed by rotating it upward by 45 degrees and pulling it straight out in the same direction. It can also be folded fully in the vertical position. With the seat raised, the commander is seated normally with his feet resting flat on the autoloader carousel cover and he is in the best position to look out through the vision devices in his cupola. With the seat lowered, the commander can sit with his legs outstretched. During combat, the commander does not sit with his legs outstretched because there is less legroom on the autoloader carousel cover than the gunner has on his side of the turret, and because the ammunition box and spent link collector for the coaxial machine gun hang well below the turret ring level, so there is not much clearance if the gun is elevated.<br />
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<a href="https://1.bp.blogspot.com/-0k6Q7t_gjVc/XJDGNx3zXYI/AAAAAAAANj0/Kzz8NCz5f4MC71x16Xz0oDe--08Zi7TrgCLcBGAs/s1600/commanders%2Bseat%2Bdrawing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="555" data-original-width="600" height="370" src="https://1.bp.blogspot.com/-0k6Q7t_gjVc/XJDGNx3zXYI/AAAAAAAANj0/Kzz8NCz5f4MC71x16Xz0oDe--08Zi7TrgCLcBGAs/s400/commanders%2Bseat%2Bdrawing.png" width="400" /></a><a href="https://1.bp.blogspot.com/-m0nR91_XWqA/YDTG3AI36_I/AAAAAAAASyI/1BqC4hSF8fcRrBEBMpZ9xWumJmqoUvbbQCLcBGAsYHQ/s2048/seated%2Bcommander%2Bt-72m.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="320" src="https://1.bp.blogspot.com/-m0nR91_XWqA/YDTG3AI36_I/AAAAAAAASyI/1BqC4hSF8fcRrBEBMpZ9xWumJmqoUvbbQCLcBGAsYHQ/s320/seated%2Bcommander%2Bt-72m.jpg" /></a><br /></div>
<div><br /></div><div><br /></div><div>A removable recoil guard is attached to the commander's seat to shield him from the recoil path of the main gun when it fires. The top part of the recoil guard can be folded away to permit freer access to the gun breech or to allow the commander to crawl to the gunner's station and vice versa, and the entire recoil guard can be folded or removed to grant access to certain parts of the autoloader, mainly to replenish it with fresh ammunition. It is also removed if it is necessary to reload the main gun manually. To maximize the space available to access the autoloader carousel, the seat would be folded up, the backrest will then be folded inward over the seat and the recoil guard would be removed. This removes all obstructions between the commander and the carousel. </div><div><br /></div><div>The width of the commander's station, as measured at the position of the commander's torso, is 635mm (25 inches). The height of the station is 890-914mm (35-36 inches) when measured from the seat cushion to the ceiling of the cupola, when adjusted by a 5'10" man to view from the vision devices. The seat can be lowered to accommodate a taller man.</div><div><br /></div>The commander's hatch is of a forward-opening type with a clam shell shape, mounted on the rotating cupola. The overall diameter of the cupola is 700mm based on drawings of the T-64A turret and other information. Measurements on a T-72M showed that the commander's hatch is 584mm (23 inches) wide and 330mm (15 inches) long, which meets the U.S Army human engineering requirements for a 95th percentile male in light clothing. Because the cupola has a dome shape, the actual size of the hatch opening is slightly larger than the length alone suggests, because the commander exits while leaning to the rear rather than climbing straight up. </div><div><div style="font-size: 19px; font-weight: bold;"><div style="font-size: medium; font-weight: normal;"><br /><br /><div style="text-align: center;"><img border="0" data-original-height="2048" data-original-width="1536" height="320" src="https://1.bp.blogspot.com/-lEBOHwXKAds/YDR_fAYMUeI/AAAAAAAASwo/h9eOe6hpwMwjPCXIL92h_JNjRYRY_SBtACLcBGAsYHQ/s320/IMG_1081.png" style="color: #0000ee;" /><img border="0" height="283" src="https://2.bp.blogspot.com/-xbUyNMQhvJI/VTPQOMpeTQI/AAAAAAAAB5o/fF5PXhJY4Hc/w400-h283/forward%2Bvisibility.jpeg" width="400" /></div><br /></div><div style="font-size: medium; font-weight: normal;"></div></div><div><br /></div><div>Since the mid-2010's, T-72 tank crews are issued with 6B15 "Cowboy" suits, and the added bulk of the fragmentation vest can be a hindrance to the commander when moving through the narrow hatch opening. However, it is important to keep in mind the difference between a 95th percentile U.S male and a typical Soviet or Russian tanker.</div><div><br />The hatch is spring-loaded with a plate torsion spring built into the hinge to assist the commander in opening the hatch, as it is quite heavy due to its thick armour and the thick anti-radiation lining on its underside. It weighs 125 kg. A simple rotating handle locks the hatch when closed, preventing it from bouncing up and down when the tank is in motion, and a smaller handle at the bottom of the hatch serves to lock the hatch in place when it is opened, which is useful when the commander wishes to view the battlefield from outside the hatch, or when he needs to use the complementary cupola-mounted machine gun.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-xTaebwXs15U/VTPQY8e0iiI/AAAAAAAAB5w/F_iQ6ziIk1g/s1600/commander%27s%2Bhatch.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://2.bp.blogspot.com/-xTaebwXs15U/VTPQY8e0iiI/AAAAAAAAB5w/F_iQ6ziIk1g/s1600/commander's%2Bhatch.jpeg" width="400" /></a><a href="http://4.bp.blogspot.com/-hBV_GF5gkJE/VQa3jk2HfoI/AAAAAAAABW0/Fw9ys-sqHso/s1600/kdt-luke%2Bt-72.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://4.bp.blogspot.com/-hBV_GF5gkJE/VQa3jk2HfoI/AAAAAAAABW0/Fw9ys-sqHso/s1600/kdt-luke%2Bt-72.jpg" width="288" /></a></div><div><br /><br />Because it opens forward, the thick hatch gives the commander full-body protection from machine gun fire whenever he wants to pop out to observe his environment. To look over the hatch, the commander raises his seat to the tallest setting and stands on the seat. This allows him to stand with just his eyes peeking above the edge of the hatch, depending on the height setting of the seat. The image shown below, taken from a DDR training film provided by the Bundesarchiv, shows the commander and gunner of a T-72M standing behind their respective hatches.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-mquDxxjxLEc/X2OgXQbCkdI/AAAAAAAARms/8hZkzA2PvXIveyzPGYd7Fr9NovG_fkq2wCLcBGAsYHQ/s1398/ddr%2Bpanzer%2Bt-72%2Bstanding.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1064" data-original-width="1398" height="305" src="https://1.bp.blogspot.com/-mquDxxjxLEc/X2OgXQbCkdI/AAAAAAAARms/8hZkzA2PvXIveyzPGYd7Fr9NovG_fkq2wCLcBGAsYHQ/w400-h305/ddr%2Bpanzer%2Bt-72%2Bstanding.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The commander may even stand on the recoil guard and the height adjustment mechanism of his seat to gain a taller vantage point without completely exiting the vehicle. This would often be done when signalling with flags.<br /><br /><br /><div style="text-align: center;"><a href="http://3.bp.blogspot.com/-NJ_bxPLjduY/VUHYmHLPCRI/AAAAAAAACIc/LE1L9TQclTk/s1600/commander%2Bt-72.png"><img border="0" height="254" src="https://3.bp.blogspot.com/-NJ_bxPLjduY/VUHYmHLPCRI/AAAAAAAACIc/LE1L9TQclTk/w400-h254/commander%2Bt-72.png" width="400" /></a><a href="https://1.bp.blogspot.com/-ukD0MFo7pmg/X1rUvXzAw9I/AAAAAAAARkc/lgQhWw3W-OsyEAW09kLj1-pXwwIbhohcACLcBGAsYHQ/s2000/marching.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1333" data-original-width="2000" height="266" src="https://1.bp.blogspot.com/-ukD0MFo7pmg/X1rUvXzAw9I/AAAAAAAARkc/lgQhWw3W-OsyEAW09kLj1-pXwwIbhohcACLcBGAsYHQ/w400-h266/marching.jpg" width="400" /></a><br /></div><br /></div><div><br /></div><div>It is possible for the commander to sit on the backrest of his seat, allowing him to expose himself from chest level above the rim of the cupola. His view forward is blocked by the hatch unless it the cupola is swiveled to one side. Alternatively, he can fold up the seat to stand on the autoloader carousel (if the machine gun ammunition box stowed under it is removed) and have the cupola locked facing the rear. Due to the limited vertical space inside the tank, the commander exposes himself up to chest level this way, or less if he ducks down.</div><div><br /></div><div>During long marches, the commander may opt to sit on the rim of his hatch. In this position, the commander still has front body protection from the hatch. It is important that the commander can sit outside the tank during long marches as he would otherwise need to stand on his seat for hours at a time with no movement. If a commander stands still in this way on maneuvers that last all day, he becomes extremely fatigued and his feet can become swollen.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both;"><a href="https://1.bp.blogspot.com/-taKDkEa7jBA/X1rcXbmdMrI/AAAAAAAARlA/hiIEUkee9XQOcQHcICidDnSIGEG_78E-QCLcBGAsYHQ/s931/sitting%2Boutside.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="520" data-original-width="931" height="224" src="https://1.bp.blogspot.com/-taKDkEa7jBA/X1rcXbmdMrI/AAAAAAAARlA/hiIEUkee9XQOcQHcICidDnSIGEG_78E-QCLcBGAsYHQ/w400-h224/sitting%2Boutside.png" width="400" /></a><a href="https://1.bp.blogspot.com/-41X_V9_Qsks/X1rciQsRUvI/AAAAAAAARlE/xRDJpy1TP-cvigV9as7Xx5m9WHmHUXIDwCLcBGAsYHQ/s705/t-72ba%2Bdriving%2Bin%2Bdusty%2Bconditions.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="423" data-original-width="705" height="240" src="https://1.bp.blogspot.com/-41X_V9_Qsks/X1rciQsRUvI/AAAAAAAARlE/xRDJpy1TP-cvigV9as7Xx5m9WHmHUXIDwCLcBGAsYHQ/w400-h240/t-72ba%2Bdriving%2Bin%2Bdusty%2Bconditions.png" width="400" /></a></div></div><div><br /></div><div><br /></div><div>Beginning in the mid-70's, the commander's cupola may also have dust shield installed forward of the hatch. This shield, which is part of the same set as the weather hood for the driver, is installed before long marches in convoys. It would be dismantled before combat.</div><div><br /><br /><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-VBqN48gIGYw/WXJeKOze3HI/AAAAAAAAIxc/3gGtJEAxlk8DrtaVe9TK8WdAVPhR3ePywCLcBGAs/s1600/face%2Bshield%2Bt-72.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="448" data-original-width="392" height="400" src="https://3.bp.blogspot.com/-VBqN48gIGYw/WXJeKOze3HI/AAAAAAAAIxc/3gGtJEAxlk8DrtaVe9TK8WdAVPhR3ePywCLcBGAs/s400/face%2Bshield%2Bt-72.jpg" width="350" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"></div><br />The lower part is a simple hanging fabric sheet, which covers the commander's hatch when it is opened. The upper part is just a face shield for the commander for if he were to sit outside on the turret. It protects the commander from having dust and bugs blown directly into his face when travelling in a typical single-column marching formation.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-pamD_rcM5y0/XQ70X0FUrQI/AAAAAAAAOfw/JDvoU5tVy_o_aAsHKWTA4e6U1lKFA4IcACLcBGAs/s1600/dust%2Bshield.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1365" height="225" src="https://1.bp.blogspot.com/-pamD_rcM5y0/XQ70X0FUrQI/AAAAAAAAOfw/JDvoU5tVy_o_aAsHKWTA4e6U1lKFA4IcACLcBGAs/s400/dust%2Bshield.png" width="400" /></a><a href="https://4.bp.blogspot.com/-NiuKyWrqpL8/XJi7kSqafcI/AAAAAAAANmA/HTyPhPC3fAscZmG0ZxvSI7MTTV0Pz7JSgCLcBGAs/s1600/uvz%2Bsite.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="704" data-original-width="1024" height="275" src="https://4.bp.blogspot.com/-NiuKyWrqpL8/XJi7kSqafcI/AAAAAAAANmA/HTyPhPC3fAscZmG0ZxvSI7MTTV0Pz7JSgCLcBGAs/s400/uvz%2Bsite.jpg" width="400" /></a></div><br /><br />The shield made of thin sheet steel with an equally thin polycarbonate or perspex window and is thus not bulletproof, splinter-proof or fragmentation-proof although the commander's hatch certainly is. Therefore, the protection afforded to the commander does not change.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xSOhagesvZ8/V8-2fVVV7TI/AAAAAAAAHQ8/3EYDLNEwcz4CNVWM55--TYrw2jZtQbEtwCLcB/s1600/t-72b3%2Bcommanders%2Bfaceshield.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="123" src="https://1.bp.blogspot.com/-xSOhagesvZ8/V8-2fVVV7TI/AAAAAAAAHQ8/3EYDLNEwcz4CNVWM55--TYrw2jZtQbEtwCLcB/s640/t-72b3%2Bcommanders%2Bfaceshield.png" width="640" /></a></div></div><div><br /></div><br />
Like in the other two crew stations, the commander is ventilated by a single adjustable <a href="http://batcom.ru/products/zapchasti-dlya-spetstekhniki/ventilyatory/dv-3/">DV-3 fan</a>, a simple 5.2W fan running on the tank's 27V electrical system. Although it may seem silly in its simplicity, it is an important feature for keeping the crew comfortable or at least functional in the summer heat. Foreign tanks such as the Leopard 1, M60A1 and Chieftain, as well as their replacements, all had a ducted ventilation system with air outlets at every crew station in the turret. The DV-3 is shown in the photo below.<br />
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<a href="https://1.bp.blogspot.com/-9dEkZsf7Rao/WXJXpBtJbSI/AAAAAAAAIw0/Mso-D2Hmeg4q6JLBoHoSsemW1h3efqdmQCLcBGAs/s1600/dv-3%2Bfan.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="700" data-original-width="525" height="320" src="https://1.bp.blogspot.com/-9dEkZsf7Rao/WXJXpBtJbSI/AAAAAAAAIw0/Mso-D2Hmeg4q6JLBoHoSsemW1h3efqdmQCLcBGAs/s320/dv-3%2Bfan.jpg" width="240" /></a></div>
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The DV-3 is closely related to the DV-302T, which is a very similar fan used in aircraft like the Mi-8 helicopter, Il-76 and many more. In other words, the DV-3 was essentially an off-the-shelf product at the time the T-72 began mass production.<br />
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Because the commander has his own hatch, he may opt to simply stick himself out of the hatch and ride on the turret roof if he feels uncomfortable inside the tank. For additional ventilation in the crew compartment, the air source for the engine can be switched from the external intake to the crew compartment intake. The crew compartment intake draws air from the crew compartment, which greatly increases the airflow inside the tank if the hatches are open. Normally, the crew compartment air intake is designed to provide an alternate air supply for the engine during fording and snorkeling maneuvers where the depth of the water obstacle is more than 1.8 meters. When fording streams, the hatches on the turret roof should be left open if the situation permits, but if combat is imminent, the crew must have the hatches closed and only the snorkel tube installation port in the gunner's hatch is opened. In both cases, a tremendous volume of air flows into the fighting compartment through the openings to aspirate the engine, thus cooling down the crew. This would undoubtedly be very welcomed in hot weather.<br />
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The commander's main means of surveying the battlefield is a forward-facing TKN-3M binocular periscope, augmented by two rectangular TNPO-160 periscopes on either side and two TNPA-65A periscopes embedded in his hatch. The TKN-3 periscope is aimed directly forward and is aligned with the centerline axis of the cupola. As there is no unity vision capability from the TKN-3, the commander is inconvenienced when he wants to have a wide, unmagnified forward view as he has to turn the cupola and use his other periscopes. The two TNPO-160 periscopes flanking the TKN-3 are oriented 45 degrees from the centerline of the cupola. The drawing below shows the TNPO-160 in a generic tank mount, the sheet metal rain hood above the periscope head, and the rubber seal around the periscope slot that prevents the ingress of water into the vehicle.<br />
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With just these two periscopes, the commander has vision in a 176-degree frontal arc with a blind spot of 22 degrees to the direct front which is filled by the TKN-3. Because the cupola can rotate, the five periscopes in the cupola provide the commander with an all-round view when he is in a closed-hatch condition. There is no periscope that allows the commander to see directly behind the turret. For that, he must spin the cupola to one side and look out of either one of his TNPO-160 or TNPA-65A periscopes, although the anti-aircraft machine gun would usually be in the way as it is stowed directly behind the cupola in the "travel" position when not in use. Due to the conformal slant of the gunner's hatch on the left side of the turret, the commander's view to the left of the turret is largely unimpeded. Even the gunner's night vision sight does not completely block the commander's view as the height of the sight housing does not exceed the maximum height of the turret roof.<br />
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However, the commander's view to the left of the turret in the 10 o'clock sector was obstructed when Kontakt-1 reactive armour blocks were installed on the roof of the turret beginning with the T-72AV modification in 1985. This problem persisted when Kontakt-5 blocks replaced the Kontakt-1 blocks in the T-72B obr. 1989 model and continues to plague the T-90A. For these later models, the burden of monitoring these sectors falls upon the gunner. The photo on the left below shows the cupola of a T-72B3, and the photo on the right below shows the view from the left-facing TNPO-160 in the cupola of a T-72B3 looking at the Kontakt-5 blocks on the turret roof.<br />
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The TKN-3M periscope window is slightly more elevated than the other periscopes in the cupola, giving it more clearance over the clutter on the turret roof. As such, its field of view was largely unaffected when reactive armour blocks were added to the turret roof in later T-72 models. The video clip below shows archival footage from a Czechoslovakian Army training film showing the cupola of a T-72M being used to scan the forward 180-degree sector of the tank. <a href="https://www.youtube.com/watch?v=EqYupAqiVro">Original video from the VHU channel</a>. Note that the anti-aircraft machine gun is locked in place behind the cupola.<br />
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For general vision, the commander is provided with four periscopes to supplement the TKN-3. In total, the field of view of the commander from the cupola (without head movement) is 288 degrees, with a 72-degree dead zone to the rear. Due to the use of periscopes instead of vision blocks (slits with glass blocks) and the thick turret armour around the base of the cupola, the commander is completely protected from concentrated machine gun fire directed at the periscopes. There is absolutely no chance that for his eyes to be injured by broken glass due to the nature of solid glass prism periscopes and because the periscope eyepiece is protected by an additional layer of ballistic glass, as shown in the photo on the left below.<br />
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The volume of fire expected to hit the periscopes directly changes drastically depending on the distance between enemy combatants. Aimed machine gun fire is very unlikely to knock out a periscope unless it is from very close range, but as a tank closes in to overrun an enemy position, it becomes quite easy to do so. During WWII, infantrymen were taught to fire at the observation devices of tanks as a last resort and in many cases, these observation devices were merely slits or slits with glass inserts that gave minimal ballistic protection for the crew member using them. The effectiveness of such tactics was amplified if an anti-tank rifle like the PTRD was available.<br />
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This was one of the most persuasive incentives to use periscopes, but the improvement in user safety did not remove the incentive for enemy infantrymen to concentrate fire on the observation devices and these experiences have been validated time and time again, most recently during the current conflict in Syria where much of the fighting takes place in densely populated urban areas. The video still below, taken from <a href="https://www.youtube.com/watch?v=SiRvWO69C_E">this video</a>, shows a Syrian T-72 with two of its periscopes destroyed.<br />
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The TNPO-160 has a total field of view of 78 degrees in the horizontal plane and 28 degrees in the vertical plane.</div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">The TNPA-65A periscopes embedded in the hatch have a particularly noteworthy design among tank periscopes in that the periscope was specficially designed for tank hatches. Due to the position of the viewing window, the lower prism has an offset angle of 45 degrees, so that it is best used by the observer looking up at 45 degrees. Because it is not intended for the user to press his face against the viewing window when using the periscope, the TNPA-65A is not protected by additional ballistic glass, thus allowing it to retain a high light transmission coefficient of 0.6.</div><div style="font-weight: normal;">
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The total field of view from a TNPA-65A is 140 degrees in the horizontal plane and 35 degrees in the vertical plane. This is somewhat more than the TNPO-160, despite having the same width and a narrower viewing window. This is due to the periscopic effect which restricts the size of the image proportionately with the distance between the viewfinder window and the objective window. The periscopicity of the TNPA-65A is only 65mm, whereas the periscopicity of the TNPO-160 is 160mm. Due to their location in the hatch and their small size, it is ergonomically unfavourable to use them compared to the conventional TNPO-160 periscopes, as it is not feasible to press his eyes up against the viewing window because it is too close to the surface of the hatch. The ergonomic limitations of the TNPA-65A are, however, counterbalanced by their excellent field of view, and the high brightness of the image due to the high light transmission coefficient. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">When seated with his eye level aligned to the TKN-3M eyepieces and the TNPO-160 periscope windows, the field of view through the TNPA-65A periscopes in the hatch can be estimated to be equivalent to the field of view through the TNPO-160 periscopes. When compared to the equivalent T-54/55 or T-62 commander's cupola, which had regular periscopes embedded in the hatch, the use of the TNPA-65A allowed the hatch to be free of large protrusions, making it more convenient when ingressing and egressing.</div>
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K-108 cerium-doped glass is used for all of the periscopes. This special grade of glass ameliorates the browning and darkening caused by gamma radiation exposure, and is able to regain its clarity after several hours of exposure to sunlight. With ordinary glass periscopes, gamma radiation causes permanent darkening. Several of the viewing devices in the tank are electrically heated using the RTS-27-4A system to prevent fogging in cold weather. RTS stands for "<i>Регулятор Tемпературы Стекла</i>", which means "Glass Temperature Regulator".</div><div><br /></div><div><br /></div>
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The commander's cupola of the T-64 lacked an anti-aircraft machine gun and was furnished with only one TKN-3M periscope and two TNPO-160 periscopes. The field of view (without head movement) was 144 degrees. This cupola was carried over to the T-64A. Given that a successful template for a periscope layout in a cupola of this design was already established since the T-54 obr. 1949, it is a mystery why the T-64 cupola had such constricted visibility. Needless to say, the T-72 was vastly superior in this particular aspect. In 1975, a new and much more technically advanced cupola with a ZU-64A remotely controlled anti-aircraft machine gun system was implemented on the T-64A obr. 1975. Two TNPA-65 periscopes were finally added to the hatch of the new cupola, but to accommodate the PZU-5 sight for the ZU-64A system, the TNPO-160 periscope on the left of the TKN-3 had to be removed. As a result, the commander's visibility was still not on par with his T-72 contemporary. In fact, the higher statistical weight of forward-facing periscopes compared to side or rear-view periscopes makes the new cupola a downgrade over the older version, despite the increase in the number of periscopes. These nuances are important when evaluating the validity of various cupola designs.
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<br /><div style="text-align: center;"><a href="https://2.bp.blogspot.com/-ZjP8mqLJnaI/XI6hMqM1tAI/AAAAAAAANjE/AAmZbRdKt34cz_EX94iFmrqVMN5KtBAkACLcBGAs/s1600/t-64a%2B1.jpg"><img border="0" data-original-height="532" data-original-width="800" height="266" src="https://2.bp.blogspot.com/-ZjP8mqLJnaI/XI6hMqM1tAI/AAAAAAAANjE/AAmZbRdKt34cz_EX94iFmrqVMN5KtBAkACLcBGAs/s400/t-64a%2B1.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-TxrfWvXDtFE/XI6hMmLwmgI/AAAAAAAANjA/lEa26TClW0oBVCZKWf10PFMwwyPq1-K8QCLcBGAs/s1600/t-64a%2B2.jpg"><img border="0" data-original-height="536" data-original-width="800" height="268" src="https://1.bp.blogspot.com/-TxrfWvXDtFE/XI6hMmLwmgI/AAAAAAAANjA/lEa26TClW0oBVCZKWf10PFMwwyPq1-K8QCLcBGAs/s400/t-64a%2B2.jpg" width="400" /></a>
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Compared to a typical Western tank cupola, the number of fixed periscopes in the T-72 model is clearly less, but the number alone is not necessarily indicative of actual utility. For example, the Leopard 1 provided its commander with eight periscopes arranged around his circular cupola, but only five are aimed in the forward 180-degree sector and two of them are partly obstructed by the loader's cupola, loader's machine gun skate mount and loader's hatch opening mechanism on the left side of the turret. It is also important to note that the commander's cupola on the Leopard 1 does not rotate and the forward-facing periscope has a very high periscopicity so that the field of view in inherently narrower. In other words, the number of vision devices providing a view towards the forward half of the turret is not more than in the T-72 commander's cupola and there are other secondary factors that affect the commander's visibility. A T-72 commander only loses out in convenience when directing the driver to reverse the tank as he must rotate his cupola in order to see behind the turret or have the turret aimed to the rear.
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To further expand our perspective, it should be noted that the commander of an M60A1 is furnished with eight M41 prismatic vision blocks arranged around his oblong M19 cupola, with one aimed forward to cover the 11 o'clock sector, two of them aimed in the forward arc to cover the 10 o'clock and 2 o'clock sectors, two of them aimed to the sides, and three of them aimed in a 7 o'clock to 5 o'clock arc. There is one wide-vision periscope installed just behind and above the M85 machine gun in the cupola and aimed directly forward. Adding on the fact that the M19 cupola can rotate, and it is clear that an M60A1 commander has much better visibility than a T-72 commander under practically all circumstances. However, none of the M41 vision blocks are heated, so fogging will tend to seriously degrade visibility in chilly weather. Also, the objectively poorer rearward visibility from the T-72 cupola compared to Western tanks does not necessarily translate into objectively poorer combat performance as the value of observation devices depends on the context in which they would be used. It is a perfectly valid observation that when the tank needs to reverse, it is often in a non-combat situation where it is safe for the commander to be outside his hatch. In combat, it may be necessary to reverse in order to change positions or to reverse into turret defilade after firing a shot. In both cases - and in general - the driver would have approached the firing position from behind in the first place so he already knows that the area behind the tank is clear of obstructions and that he can freely reverse without fear of running into obstacles. If it is truly necessary for the commander to direct the driver when reversing the tank, the commander can rotate the cupola and use one of his periscopes for the task or open his hatch and peer out.<br />
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Furthermore, the fundamental purpose of the fixed periscopes has to be understood in order to assign them with their proper value. In combat, such periscopes are generally only useful if the enemy is very close to the tank (500 meters or less). Otherwise, they are only good for viewing the surrounding environment in order for the commander to gain a sense of spatial control over the tank, and this is done by finding landmarks. When the tank is moving speedily across rough terrain, observation through fixed unmagnified periscopes becomes ineffective due to the oscillation of the tank and the restricted field of view. The commander only sees an oscillating flicker between the ground and the sky, with no possibility of reliably discerning camouflaged enemy forces let alone identifying them.<br />
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For a modern tank created and fielded during the mid to late Cold War era, it is only practical to see and identify targets using a magnified optic and some form of stabilization is mandatory to allow it to be used effectively in a moving tank, as the narrower field of view through a magnified optic will exacerbate the negative effects of the oscillation of the tank. The TKN-3 periscope for the commander of a T-72 fulfills this purpose as it has a reasonably high magnification with a reasonable field of view, and it has handles to allow the commander to hold it steady.<br />
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The characteristics of a tank commander's observation practices when buttoned-up in a fixed cupola with eight periscopes and one fixed forward-facing sight in the turret were examined in the 1974 study "<i><a href="http://btvt.info/5library/vbtt_1974_02_obzornost.htm">Некоторые Статистические Характеристики Процесса Наблюдения Командира Танка</a></i>" (<i>Some Statistical Characteristics of a Tank Commander's Observation Processes</i>) by G.G Golub et al. Three special cupolas were constructed to replace the original commander's cupola of a T-64 that was used as the experimental platform. The frequency and duration of usage of each of the viewing devices was recorded using a small forward-facing lamp on the commander's headset which would illuminate an array of photodiodes (light sensors) placed on top of each viewing device when the commander looks through the viewfinder. The first cupola design was a fixed type with eight fixed and equally spaced unmagnified periscopes arranged radially around the circumference of the cupola and one forward-facing TPD optic (modified periscopic sight with optical rangefinder removed). The second cupola design was the same as the first design but it had a stabilized electric drive for cupola rotation. The third cupola design was a manually-rotating type analogous to the T-72 cupola, having a total viewing arc of 206 degrees (± 103 degrees from the centerline axis of the cupola).
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These cupolas were tested in various simulated combat conditions. The simulations were carried out in field conditions with moderately hilly terrain partly covered with bushes and trees. The targets included four tanks showing their frontal projection, three tanks in hull-down positions, two armoured personnel carriers, three ATGM teams, five recoilless rifles, and five anti-tank guns. All of these were arranged in such a way as to ensure that they would be uniformly concealed from the tank commanders as the tanks traveled down the pre-planned routes from a full 360-degree arc and at distances of 0.5 to 1.5 kilometers. The positions of the targets were shuffled throughout the experiments.
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It was found that in general, 30% of all battlefield observations were carried out using the forward-facing unmagnified periscope and at most, 5% of observations were done using the magnified 8x optic with a stabilized field of view. However, it was also found that in tactical situations such as carrying out a breakthrough mission, the frequency of the use of a magnified optic to search for targets increases up to 50%. Overall, more than 70% of observations were made using only three periscopes at the front of the cupola covering a 100-degree frontal sector and over 95% of observations were made in a 200-degree frontal sector. Most interestingly, the experiments revealed that the highest recorded frequency of usage of the rear-view periscope was only 0.8%. It was also noted that the periscopes installed at more than 110 degrees off the centerline axis of the cupola (8 o'clock) were difficult to use due to neck strain when the tank was in motion. This was most likely why the commander's cupola of the T-80 used a rear-view prism embedded in the roof of the commander's hatch instead of a conventional periscope placed behind the commander's head.</div><div>
<br />Based on these results, it can be seen that in a fixed cupola with all-round visibility, five unmagnified periscopes covering the front 180-degree sector provide 95.3% of the total visibility needs of the commander under various combat conditions. The rear-facing periscopes are rarely used. A rotating cupola that provides vision in a 206-degree arc will fulfill 98.1% of the commander's visibility needs under the same combat conditions. In other words, the practicality of the T-72 cupola design can be considered to be experimentally validated. Even a T-64 cupola with just one TKN-3 and two TNPO-160 periscopes can theoretically fulfill 70% of the visibility needs of its commander, but on the other hand, the improved visibility from the two additional TNPA-65A periscopes in the T-64A obr. 1975 or T-64B cupola is offset by the loss of one TNPO-160 periscope.
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Of course, the configuration of observation devices in the T-72 commander's cupola is certainly not perfect. A panoramic sight is ergonomically superior as the user's head does not need to move when the sight head rotates. The Leopard 1 is exemplary in this regard as it provided its commander with the excellent TRP-2A panoramic sight featuring a variable magnification of 4x to 20x, and beginning with the Leopard 1A4 in 1974, the commander was provided with the advanced PERI-R12 stabilized panoramic sight with a variable magnification of 2x or 8x. Panoramic sights were developed in the USSR during the 1930's and the PT-1 sight was the first to enter service, being installed on the T-26. Later, the PT-K panoramic sights were used on various modifications of the KV-1 and T-34, and indeed, Soviet engineers in the prewar era saw much greater value in panoramic observation devices compared to cupolas with multiple vision slits or periscopes and favored devices like the MK-4 rotating periscope (Gundlach periscope) and PT-1 for all-round visibility, but for one reason or another, postwar Soviet tanks were no longer equipped with such devices. Instead, all postwar Soviet armoured vehicles built in the 1950's standardized on the binocular TPK and TPKU periscopes paired with the TKN-1 night vision periscope, and beginning in the early 1960's, the TKN-3 series of combined periscopes became the new standard.</div><div><br /></div><div><br /></div><div>
Besides the observation devices, the commander's station is furnished with a variety of equipment in a rational layout for him to carry out his tasks. There is also an assortment of accessories that are not directly related to his job, but are placed near him because it was the only available space in the squeezed turret.<br />
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In the photo above, we can see the R-123 radio transceiver (<span style="color: #6fa8dc;">BLUE</span>) at the very bottom. The silver-gray box above it is a switch box (<span style="color: red;">RED</span>) for the communications system to switch between radio and intercom communication, and the white box beside it is a master control panel (<span style="color: #6aa84f;">GREEN</span>) for most of the functions in the tank. This control panel (pictured below) gives the commander dominion over things like the lights and the ventilator, and behind the silver and milk-white metal flaps at the corners of the panel are the emergency engine stop button and the emergency fire extinguishing system engagement button (activates all the fire extinguishers connected to the automatic firefighting system in the fighting compartment), respectively.<br />
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<div><br /></div><div><br /></div>Additionally, the commander is responsible for setting the fuse on HE-Frag shells, and this control panel enables him to do so by interrupting the operation of the autoloader. The commander flips the "ram" switch ("дос") to the off position, to interrupt the loading cycle. When the gunner presses the "load" button, having previously selected the "HE-Frag" option on his ammunition selector dial, the autoloader will function in the automatic mode and work as normal until it reaches the point where it has raised the shell to the ramming position, directly behind the gun breech. At this point, the mechansim stops, because the power rammer has been turned off. The commander sets the fuze, and then turns the "ram" switch back to the "on" position. The loading cycle then proceeds as normal. <br />
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The silver box (<span style="color: #ffd966;">YELLOW</span>) to the right of the intercom switch enables the commander to control the autoloader for the purpose of unloading it, and controlling the autoloader functions when loading the gun semi-automatically or manually.<br />
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<a href="https://3.bp.blogspot.com/-th_mpJgZq6o/Wb1yiCGUO5I/AAAAAAAAJfg/ndhVFlr1FX4DWrW9I4PQgxUo73zsud11wCLcBGAs/s1600/autoloader%2Bcontrols.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1288" data-original-width="626" height="400" src="https://3.bp.blogspot.com/-th_mpJgZq6o/Wb1yiCGUO5I/AAAAAAAAJfg/ndhVFlr1FX4DWrW9I4PQgxUo73zsud11wCLcBGAs/s400/autoloader%2Bcontrols.jpg" width="193" /></a><a href="https://2.bp.blogspot.com/-TyBh3FT5T7s/W2JC0eOooAI/AAAAAAAAL5I/RZFwYyI-GcIsFH8E5k0esDynhMdeP62pQCLcBGAs/s1600/az%2Bcommanders%2Bcontrol%2Bbox.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1040" data-original-width="731" height="400" src="https://2.bp.blogspot.com/-TyBh3FT5T7s/W2JC0eOooAI/AAAAAAAAL5I/RZFwYyI-GcIsFH8E5k0esDynhMdeP62pQCLcBGAs/s400/az%2Bcommanders%2Bcontrol%2Bbox.png" width="280" /></a></div>
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The box flips open to reveal control toggles for operating the individual elements of the autoloader system, like raising and lowering the shell casing catcher, opening and closing the ejection port, activating or deactivating the power rammer, and so on. If the autoloader is only partially malfunctioning, the commander can use this control box to operate some parts of the loading procedure automatically, and operate other parts manually. If the autoloader carousel malfunctions, it is possible to rotate the carousel manually, and crank the autoloader elevator by hand to extract ammunition and use the electric chain rammer to ram the ammunition into the breech.</div><div>
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Above that is a PMV-71 dome light and the already-mentioned DV-3 fan. The dome light contains a TN-28-10 incandescent lamp that runs on a voltage of 28 volts and consumes 10 W of power. Each PMV-71 dome light has an output of 10 candelas. At the upper left corner is a wooden dowel with a rubber head. This is a ramming stick for the commander to use when manually loading the cannon. Beside the dome light is an accelerometer to sense the rotational acceleration of the turret, allowing the stabilizer system to dynamically compensate for overloads due to the inertial imbalance of the turret.<br />
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Besides the dome light in front of the commander, there is another dome light light directly above the gun breech, making it quite easy for him to perform his duties, including loading and unloading the autoloader and loading the coaxial machine gun. With the installation of the 1K13 sight and the "Svir" missile system, the 1K75 control unit was fitted to the turret ceiling above the radio transceiver.<br />
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Here is another view of the station, this time from below. Photo from <a href="https://www.kyivpost.com/ukraine-politics/tankmen-get-used-living-behind-lines-forest-camp.html">KyivPost</a>.<br />
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Toggle switches for turning on the external and internal lights and the periscope heating system are located around the cupola ring. Two such switches are shown below. The switch on the right is to turn on all of the forward facing lights on the tank, and the switch on the left is to turn on all of the rearward facing lights.<br />
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<a href="https://4.bp.blogspot.com/-Qe02MGGM23o/WXJZWpWF_QI/AAAAAAAAIxA/d53y0QXESXk-olba-DHZoOa5plCNTSccQCLcBGAs/s1600/t-72%2Blight%2Bswitches.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="253" data-original-width="337" src="https://4.bp.blogspot.com/-Qe02MGGM23o/WXJZWpWF_QI/AAAAAAAAIxA/d53y0QXESXk-olba-DHZoOa5plCNTSccQCLcBGAs/s1600/t-72%2Blight%2Bswitches.jpg" /></a></div>
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<h3>
<a href="https://www.blogger.com/null" id="tkn-3m"></a><span style="font-size: large;">TKN-3M, TKN-3MK</span></h3>
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<a href="https://1.bp.blogspot.com/-LivUjxydZgA/XqBIncMozHI/AAAAAAAAQnk/I_8kWyifzwAxp5dOeE8iifJJMDFJ3u_KwCLcBGAsYHQ/s1600/tkn-3m%2Bfor%2Bt-72%2Bcupola.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1213" data-original-width="855" height="400" src="https://1.bp.blogspot.com/-LivUjxydZgA/XqBIncMozHI/AAAAAAAAQnk/I_8kWyifzwAxp5dOeE8iifJJMDFJ3u_KwCLcBGAsYHQ/s400/tkn-3m%2Bfor%2Bt-72%2Bcupola.png" width="281" /></a><a href="http://2.bp.blogspot.com/-3UEJ_J9NBJI/VRgrKvLKdYI/AAAAAAAABhs/iaus34prQF8/s1600/tkn-3.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://2.bp.blogspot.com/-3UEJ_J9NBJI/VRgrKvLKdYI/AAAAAAAABhs/iaus34prQF8/s400/tkn-3.png" width="320" /></a></div>
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The TKN-3M is a combined day-night binocular periscope with night vision capability in two modes; passive and active. The passive night vision capability was provided by a pair of Gen 1 photocathodes placed in series, forming a two-stage image intensifier cascade tube. This distinguishes it from the basic TKN-3, which used a two-stage Gen 0 cascade tube, intended only to improve the viewing range with infrared illumination without providing a meaningful passive viewing capability.</div><div><br /></div><div>The TKN-3M has a fixed 5x magnification in the day channel and 4.2x magnification in the night channel. It has a fairly average angular field of view of 10 degrees in the day channel and a field of view 8 degrees in the night channel. Due to the combination of night vision equipment with regular daytime functionality, there had to be two separate optical channels in the periscope. In the daytime channel, the periscope is a binocular device as the two eyepieces lead to separate apertures to provide stereoscopic vision. For the night channel, the optical channel from the two eyepieces were merged to view the image from a single aperture lens. In the two photos below, the reflection of the three lenses of the periscope can be seen in the periscope head. As such, the night channel is pseudo-binocular.<br />
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<a href="https://1.bp.blogspot.com/-qb3K3OKuSfg/XQJzv0HifTI/AAAAAAAAOa4/rVa-LxMxRV0nzwpUmN317EfoBSppIDKuwCLcBGAs/s1600/tkn-3.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="324" data-original-width="432" height="300" src="https://1.bp.blogspot.com/-qb3K3OKuSfg/XQJzv0HifTI/AAAAAAAAOa4/rVa-LxMxRV0nzwpUmN317EfoBSppIDKuwCLcBGAs/s400/tkn-3.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-Y8G8kuF4JTc/WZgjj18ojZI/AAAAAAAAJEI/5Zz826Jm4xgtxzF-ITMUIe6TNGVFz6z5ACLcBGAs/s1600/tkn-3b.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1067" height="296" src="https://1.bp.blogspot.com/-Y8G8kuF4JTc/WZgjj18ojZI/AAAAAAAAJEI/5Zz826Jm4xgtxzF-ITMUIe6TNGVFz6z5ACLcBGAs/s400/tkn-3b.jpg" width="400" /></a></div>
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<br />The magnification factor of the periscope was the same as the TPKU-2B periscopes used since the T-54, and is limited compared to more modern surveillance systems and may potentially make long-distance observation relatively problematic, especially if the weather is unfavourable. However, it is nominally sufficient for almost all types of combat. According to Soviet and foreign research, an optical sight with 5x magnification allows a tank to be identified from a distance of 3.0 kilometers. For comparison, an optical sight with no magnification would allow a tank to be identified from a distance of 1.0-1.5 kilometers in clear weather conditions. An optical sight with 4x magnification increases this distance to 2.5 kilometers under clear weather conditions, and an optical sight with 7x to 8x magnification further increases this range to 4.0-5.0 kilometers. In other words, a 5x magnification was sufficient for finding and identifying targets from any practical distance in the context of a major war in Europe, and it is enough to allow the commander to correct fire for the gunner when conducting long range direct fire bombardments of large point targets such as individual buildings. The maximum tank combat range in most parts of Europe does not exceed 1.5-1.8 km, and even in the North German plains, it does not exceed 2.0 km.<br />
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To scan in elevation, the TKN-3M can be elevated by +12 degrees and depressed by -8 degrees. The full range of elevation is 20 degrees, and the total vertical field of view is 30 degrees. This was a noticeable improvement over preceding medium tanks, which had an elevation range of only -5 degrees to +10 degrees. Because the periscope is not vertically stabilized, it is difficult to effectively find and identify targets at a distance while on the move over rough terrain. The commander is meant to bear down and brace against the handles of the periscope to control his line of sight, and this can be adequate for keeping the target within view for the smoother parts of off-road driving, but the degree of accuracy is generally not enough for estimating range range or correcting fire in elevation if the tank is in motion, and the vibrations of the periscope can interfere with the commander's vision when the tank is driving over rough ground. However, thanks to the counter-rotating mechanism of the cupola, the commander's view is stabilized in azimuth, which permits him to observe and issue accurate fire corrections in azimuth when the tank is on the move. The periscope can be locked in elevation by turning the screw of a clamp. <br />
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<a href="https://1.bp.blogspot.com/-5nSx3aY_VME/XqAfN9cJ7pI/AAAAAAAAQnU/U_icmF4IqegGwENNGnPxpbkPeDWB2hiwACLcBGAsYHQ/s1600/viewing%2Bthrough%2Btkn-3m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="602" data-original-width="1366" height="282" src="https://1.bp.blogspot.com/-5nSx3aY_VME/XqAfN9cJ7pI/AAAAAAAAQnU/U_icmF4IqegGwENNGnPxpbkPeDWB2hiwACLcBGAsYHQ/s640/viewing%2Bthrough%2Btkn-3m.png" width="640" /></a></div>
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Scanning in azimuth with the TKN-3M is done by manually turning the cupola, just as in all earlier Soviet tanks. If the gunner is persistently turning the turret to search for targets, the commander is able to stabilize his view by pressing the button at the end of the right handle of the periscope. This applies an electromagnetic clutch to link the cupola to the turret ring via a step-down reversing gearbox, thus automatically counteracting the rotation of the turret in any direction. This allows the commander to have a steady, uninterrupted view of the target while the turret is turning. As the turret is stabilized, this feature essentially provides a form of independent horizontal stabilization for all vision devices in the cupola. If the periscope is switched to the night channel, the same button will activate the counter-rotation system and also briefly activate the infrared spotlight, then automatically deactivate the spotlight after a brief period. If the spotlight is manually switched on for long-term searching, then the button simply activates the counter-rotation motor as long as it is held.</div><div>
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At the end of the left handle of the TKN-3M is a button to designate a target for the gunner, in the same way as the hunter-killer system in the T-54B using the TPK-1 periscope. When pressed, the turret turns at its maximum speed until it reaches the same angular position as the cupola. When designating targets for the gunner, the commander presses and holds both the right and left handle buttons to keep the cupola fixed on the target via the counter-rotation mechanism. Once the turret is slewed towards the target, the gunner will see the target, lay the gun, and then fire upon it. It is worth noting that the target designation button can be held down to slave the turret to the commander. Wherever he aims the reticle, the turret will follow.</div><div>
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The photo below shows the direction sensor, painted red, in contact with the three metal bands on the cupola ring above the golden toothed band. These metal bands interface with a roller inside the direction sensor, and the sensor detects the angular position of the cupola relative to the turret by detecting the direction in which the roller is deflected. The counter-rotating system is installed at the turret ring and transmits rotational energy from the moving turret to the cupola via a cardan shaft. The cardan shaft ends in a drive gear in contact with the toothed band around the circumference of the cupola ring. The drawing on the right below shows the counter-rotation mechanism and its connection to the turret ring.<br />
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<a href="http://3.bp.blogspot.com/-vnl4nVV7888/VTDMBoxxSvI/AAAAAAAABzA/N-CHbJw2fm0/s1600/t-72.26916.jpg"><img border="0" height="281" src="https://3.bp.blogspot.com/-vnl4nVV7888/VTDMBoxxSvI/AAAAAAAABzA/N-CHbJw2fm0/s400/t-72.26916.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-ljsT6Wcnxv8/XqBInW4EAnI/AAAAAAAAQno/Rm8_bRkHJXsVqPneEyTCPgqXb7jqwc7ewCLcBGAsYHQ/s1600/cupola%2Bcounter-rotating%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1102" data-original-width="579" height="320" src="https://1.bp.blogspot.com/-ljsT6Wcnxv8/XqBInW4EAnI/AAAAAAAAQno/Rm8_bRkHJXsVqPneEyTCPgqXb7jqwc7ewCLcBGAsYHQ/s320/cupola%2Bcounter-rotating%2Bmechanism.png" width="168" /></a></div>
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<br />Technologically, the TKN-3M was outstripped as early as 1965 by the TRP 2A independent panoramic sight installed on the Leopard 1, and by the highly advanced PERI-R12 panoramic surveillance and sighting system installed in the Leopard 1A4 beginning in 1974. Both of these devices were capable of a wide range of smoothly variable magnification settings and had powered traverse, and the secondary function as the sighting complex for the commander when he used the gunnery override mode. Having this ability in an independent surveillance device was a breakthrough for the late 60's, and many tanks would not have a similar feature until the late 80's or 90's.<br />
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<a href="https://1.bp.blogspot.com/-qi3vMIVo1to/XJMS8YLaLVI/AAAAAAAANk4/nzMHK2UjXyM9e1ZfSHDCCoYA1WB89u69ACLcBGAs/s1600/b3%2B2016.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="666" data-original-width="1000" height="426" src="https://1.bp.blogspot.com/-qi3vMIVo1to/XJMS8YLaLVI/AAAAAAAANk4/nzMHK2UjXyM9e1ZfSHDCCoYA1WB89u69ACLcBGAs/s640/b3%2B2016.jpg" width="640" /></a></div>
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<div>The TKN-3M sight has a set of markings incremented in fixed angular mil values and a stadiametric rangefinder designed for the commander to measure the range to a typical NATO tank with a height of around 2.7 meters from a distance of 800 m to 3,000 m or 800 m to 3,200 m depending on the TKN-3 variant. For the T-72, these markings are not to be used as the primary method of rangefinding as the gunner has access to a much more precise optical or laser rangefinder, depending on the T-72 variant. Both of these are less sensitive to environmental factors. </div><div><br /></div><div>Using the TKN-3M or TKN-3MK, it is entirely possible for the commander to see tank-sized targets from more than 3.0 kilometers if weather conditions and the geography of the battlefield allows for it, but in reality, conditions are almost guaranteed to be degraded in some way. The most difficult scenario would involve camouflaged targets hiding in foliage with minimal exposure and without moving.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4_3bIaGMEZA/WZiAnAXrf7I/AAAAAAAAJGs/ANtnbRkAez0DqLYhDwhiMOznjRgfM-NZACLcBGAs/s1600/0_eba32_66e6d878_orig.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="453" data-original-width="604" src="https://1.bp.blogspot.com/-4_3bIaGMEZA/WZiAnAXrf7I/AAAAAAAAJGs/ANtnbRkAez0DqLYhDwhiMOznjRgfM-NZACLcBGAs/s1600/0_eba32_66e6d878_orig.jpg" /></a></div></div><div><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both;"><br /></div></div><div style="font-weight: bold;"><div style="font-size: 19px;"><span style="font-size: small; font-weight: normal;"><br /></span><span style="font-size: small; font-weight: normal;">The markings on the horizontal and vertical scales can be used to determine the angular distance between terrain features for creating range cards, to determine the necessary fire corrections for the gunner in elevation and azimuth, or to estimate the range to a target, among other uses. In the TKN-3M and TKN-3MK, the size of the increment between the long lines on both the vertical and horizontal scale is 8 mils, and the long lines are divided into two halves of 4 mils by a short line. The width and height of the cross hairs from the center to the nearest short line are 4 mils. In the drawing below, example (α) demonstrates the use of the vertical scale to obtain a reference measurement of a tree, which is 16 mils tall, and example (б) demonstrates the use of the horizontal scale to perform fire adjustment for the gunner. In this example, the shot landed 20 mils to the left of the target, and seeing this, the commander orders the gunner to adjust his point of aim to the right by 20 mils.</span><span style="font-size: small; font-weight: normal;"><br /></span><span style="font-size: small; font-weight: normal;"><br /><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-yjp3rWU_Zr8/YTgWAWhzlQI/AAAAAAAAUKs/i94z8d2DBSgvu8s_iwrh5n1A9kwqEbOQQCLcBGAsYHQ/s2048/tkn-3%2Bangular%2Bmeasurements.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1150" data-original-width="2048" height="360" src="https://1.bp.blogspot.com/-yjp3rWU_Zr8/YTgWAWhzlQI/AAAAAAAAUKs/i94z8d2DBSgvu8s_iwrh5n1A9kwqEbOQQCLcBGAsYHQ/w640-h360/tkn-3%2Bangular%2Bmeasurements.png" width="640" /></a></div><div style="font-size: 19px;"><br /></div><div style="font-size: 19px;"><br /></div><span style="font-size: small; font-weight: normal;">Using these markings, it is also possible to determine the range to an enemy tank if the stadia rangefinder scale is not suitable. T</span><span style="font-size: small; font-weight: 400;">he same principles of angular size and trigonometry are applied. Otherwise, the commander may use the stadia rangefinder scale to measure the range to a tank of known height. However, compared to the preceding tanks of the Soviet Army, the importance of the stadia rangefinder was greatly diminished as the gunner had access to a stabilized optical or laser rangefinder. </span><br /><br /><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-FWDr8AfJax4/YC8M3Gr2y0I/AAAAAAAASvs/9jFwoPXS5XQJUHgQsOuSpKb7Mvks3B4XQCLcBGAsYHQ/s474/stadia%2Brangefinding.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="474" data-original-width="434" height="320" src="https://1.bp.blogspot.com/-FWDr8AfJax4/YC8M3Gr2y0I/AAAAAAAASvs/9jFwoPXS5XQJUHgQsOuSpKb7Mvks3B4XQCLcBGAsYHQ/w293-h320/stadia%2Brangefinding.png" width="293" /></a><br /></div><span style="font-size: small; font-weight: normal;"><div style="font-size: 19px; font-weight: bold;"><span style="font-size: small; font-weight: normal;"><br /></span></div></span><br /></div></div><br /><h3 style="text-align: left;"><span style="font-size: large;">NIGHT VISION</span></h3><br />To use the TKN-3M in the night vision mode, the only preparation needed is for the commander to plug the sight to a power outlet on the cupola and then power up the night vision unit by flipping the power switch. Once powered up, the commander can switch from the night vision channel to the daylight channel instantaneously. Switching to the night vision mode in the periscope viewfinder is done by opening the protective shutter of the night vision input window by turning a lever above the eyepieces of the sight, then flipping a selector switch on the right side of the periscope from "Д" to "Н". This switches the view in the eyepieces by flipping an internal mirror by 90 degrees, thus changing the optical path between from the daylight channel to the night vision channel. The switch is shown in the image below. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Gyjg0aRU6DQ/YC8XtZO06uI/AAAAAAAASv0/YzBP2AptzeA2R3HC8dBkPfbLWx2rLj8aQCLcBGAsYHQ/s1035/tkn-3m%2Bswitching%2Bto%2Bnight%2Bvision.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="926" data-original-width="1035" src="https://1.bp.blogspot.com/-Gyjg0aRU6DQ/YC8XtZO06uI/AAAAAAAASv0/YzBP2AptzeA2R3HC8dBkPfbLWx2rLj8aQCLcBGAsYHQ/s320/tkn-3m%2Bswitching%2Bto%2Bnight%2Bvision.png" width="320" /></a></div><div><br /></div><div><br /></div>If a bright light is interfering with the commander's vision, he should switch to the daylight channel to continue observation without forgetting to also close the shutter of the night vision optic to protect it from burning out.<br /><div><br /></div><div>The diagram below shows the two choices. Diagram (a) on the left shows the path of the light from the aperture through the night vision system and into the eyepiece, while diagram (b) on the right shows the mirror flipped 90 degrees and the light from the aperture passing through the normal optical channel for daytime use.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-gEq9PQW1N4M/Wiu4aJ6yiMI/AAAAAAAAKSw/Ww1kBAKyNmQP7mbt2qmdiJPWxtof2FVGACLcBGAs/s1600/tkn-3.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1361" data-original-width="1396" height="388" src="https://2.bp.blogspot.com/-gEq9PQW1N4M/Wiu4aJ6yiMI/AAAAAAAAKSw/Ww1kBAKyNmQP7mbt2qmdiJPWxtof2FVGACLcBGAs/s400/tkn-3.png" width="400" /></a></div><div><br /></div><br />
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</div>In the passive mode of operation, the light intensifier tubes in the sight amplify the ambient light to create a legible image in lighting conditions as dark as a typical moonless, starlit night (0.005 lux). As the amount of light increases, the effective viewing distance increases. The image gain can be adjusted according to the brightness level to obtain the best possible image clarity. Officially, a tank-type target can be identified at up to 500 meters at 0.005 lux ambient light, but identifying the same tank should be entirely possible at slightly further distances in moonlit nights, though excess brightness cannot be tolerated as the image intensifier tube may be damaged from the power surge. To limit the intensity of the incoming light, the periscope features an internal diaphragm with a manual adjustment lever. The commander adjusts the lever to limit the amount of light entering the periscope when operating under high levels of illumination at night, as well as when checking the device in the daytime for calibration purposes. This allows the night vision channel to be used even during dawn and dusk lighting conditions.</div><div><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-0SRfqPigs0g/X7jjPmOlIPI/AAAAAAAASIE/ESUTQcWBXjcwPfUKkgw5FGa1bdE3jDT1QCLcBGAsYHQ/s318/tkn-3%2Bview.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="316" data-original-width="318" src="https://1.bp.blogspot.com/-0SRfqPigs0g/X7jjPmOlIPI/AAAAAAAASIE/ESUTQcWBXjcwPfUKkgw5FGa1bdE3jDT1QCLcBGAsYHQ/s0/tkn-3%2Bview.jpg" /></a></div><div><br /></div><br />The two most significant advantages of the passive imaging system is that no infrared light is emitted, unlike an active infrared imaging system, and the image intensifier system enables the commander to detect the minute amounts of visible light emitted from enemy IR spotlights and headlights from long distances.<br /><br />
The TKN-3MK is an updated variant with a Gen 2+ image intensifier system, producing an image of higher resolution and with no peripheral distortions, which was the main downside of the cascading tube system used in the TKN-3M. However, the passive viewing distance remained the same at 500 meters under the same lighting conditions stated before (moonless, starlit nights with ambient light levels of 0.005 lux), possibly due to being hamstrung by the 4.2x magnification of the optics. Gen 2+ image intensifiers differ from their 1st generation counterparts by the implementation of an MCP, a so-called "electron multiplier". The addition of an MCP substantially increases the amplification factor of the device compared to a 1st generation image intensifier, but the price of a 2nd generation image intensifier is also much higher. All T-72B tanks are equipped with the TKN-3MK. Sadly, even the latest modifications of the T-72B3 is also equipped with the TKN-3MK, which is entirely inappropriate for its time.</div><div>
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Besides the passive image intensification mode, the TKN-3M and TKN-3MK can be used in the active mode by turning on the OU-3GA2 or OU-3GK1 IR spotlight mounted on the rotating cupola. Inside the spotlight is a relatively low-powered incandescent lamp designed to run on 110 W when connected to the tank's electrical system.<br />
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<a href="https://1.bp.blogspot.com/-t_ajzSsrVYY/Wiu88S-e9lI/AAAAAAAAKS8/pSjTyv8JlNsRHAqAAxJ7YS_P0WlKA9D_gCLcBGAs/s1600/ou-3gk.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1482" data-original-width="1326" height="400" src="https://1.bp.blogspot.com/-t_ajzSsrVYY/Wiu88S-e9lI/AAAAAAAAKS8/pSjTyv8JlNsRHAqAAxJ7YS_P0WlKA9D_gCLcBGAs/s400/ou-3gk.png" width="357" /></a></div>
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The maximum distance at which a tank-sized target can be identified in the active mode is 400 meters, although the spotlight can illuminate objects much further away than that. This is an improvement compared to the 250-meter range provided by the older TKN-1S periscopes used on tanks like the T-54B, but by the 1970s, this level of performance was outdated. The main issue is the low resolution of the image. The active mode was to be used if observation was inadequate in the passive mode. Ideally, an entire engagement should be carried out without the use of the spotlight at all, as it is a very convenient unmasking signal revealing the location of the tank to enemy forces.<br />
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Without the infrared filter, the spotlight emits white light <a href="http://gaz66avto.ru/data/documents/Rec_34741.PDF">at 240 candelas</a>. The infrared filter prevents all but approximately 0.001% of the light in the visible spectrum (360-760 nm) to pass through, and the light that passes through is at the higher end of the visible spectrum. As such, the spotlight emits a very faint red light with an intensity of around 0.24 candelas that can be perceived by the naked eye at close range when the OU-3 spotlight is activated in low light conditions. The intensity of near infrared light is much higher, of course. This light can be detected by the photosensor of a digital camera without an infrared blocking filter. The photosensor displays this infrared light - which is otherwise invisible - as pink light. This can be seen in the photos below, showing the OU-3 of a BRDM-2 (pictures from kmshik from the <a href="http://www.gaz69.ru/ipb/topic/124887-%D0%B1%D1%80%D0%B4%D0%BC-2/?page=5">Gaz 69 forum</a>).<br />
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When the OU-3 spotlight is used without the infrared filter, the periscope can be used at night in the daylight mode and the viewing distance can be further increased at the cost of exposing the location of the tank to all enemy forces, including those without night vision devices. This is permissible in certain circumstances, but it is not common.<br />
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Overall, the TKN-3M offers very poor night viewing capabilities compared to modern thermal imaging sights, but it was at least equally advanced as other devices of its type built in the 60's (the TKN-3 first appeared in 1964 on the T-62), and the use of image intensification technology was a novel feature up until the 70's, when the TKN-3M/MK was outstripped by more advanced Western passive image intensifying optics. The TKN-3M/MK was not replaced or sufficiently upgraded as the T-72 entered the 1980's.<br />
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The periscope aperture has a small wiper to clear it of rain and debris, as the photo below shows.<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-0IlRSRtMM44/YDjfDEhZx0I/AAAAAAAAS0A/VLYEMH08dF8ZFapk63O2sKUvDvHILmylgCLcBGAsYHQ/s1280/1354124720-0580186-www.nevsepic.com.ua.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="1280" height="300" src="https://1.bp.blogspot.com/-0IlRSRtMM44/YDjfDEhZx0I/AAAAAAAAS0A/VLYEMH08dF8ZFapk63O2sKUvDvHILmylgCLcBGAsYHQ/w400-h300/1354124720-0580186-www.nevsepic.com.ua.jpg" width="400" /></a></div>
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<span style="font-size: small; font-weight: normal;"><br /></span><span style="font-size: small; font-weight: normal;">As mentioned before, the TKN-3M sight depends on an OU-3GA2 incandescent IR spotlight for illumination when operating in the active infrared imaging mode. An inherent shortcoming to the usage of IR spotlights is that opposing forces using a similar night vision system can also see the beam of light along with its source. The SVD sniper rifle, for example, was fitted with the PSO-1 scope with a solar-powered rechargeable IR filter that gave the designated marksman or sniper the ability to see sources of active infrared illumination without the need for a large image intensification tube and a power source. </span><span style="font-size: small; font-weight: normal;">Devices like this make it easy for the T-72 to be caught in an ambush at night by other tanks of the era like M48s, M60s, Leopard 1s, Chieftains, etc, although it must be said that the inverse also applies. </span><br />
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<span style="font-size: small; font-weight: normal;">However, the OU-3 design is particularly flawed in this respect because it lacks an occluder. The lack of an occluder means that around half of the light from the spotlight is projected directly forward instead of into the parabolic reflector. As such, an enemy observer will not only see a circular patch of light. When observing a Soviet tank with its IR spotlight on, a large portion of the tank will be brightly illuminated. The additional illumination brings the minor benefit of lighting up the ground for the driver to see more clearly, so the common issue of speed control due to short visibility distance with the complementary IR periscope for the driver is slightly alleviated in battle conditions.</span></div>
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<span style="font-size: large;"><span style="font-size: x-small; font-weight: normal;"><b><br /></b></span><span style="font-weight: normal;"><b>COMMANDER'S FIRE CONTROLS</b></span></span></h3>
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None of the Soviet era T-72 models featured a set of firing controls for the commander. This feature only came on the recent T-72B3 modernization, equipping the commander to override the gunner entirely. He has a flatscreen display linked to the Sosna-U sight and the necessary controls for firing the main gun and the coaxial machine gun at his disposal in the form of a control unit, which includes a fixed handle with a thumbstick, trigger, autoloader controls, and more. </div><div><br /></div><div><br /></div><div>This arrangement provides the commander with the option capability that is no different from what most Western tanks already had for decades. These fire controls are part of the 1A40-4 fire control system. The resolution of the flatscreen display is not known directly, but <a href="https://euobserver.com/investigations/129953">it is reported</a> that the Catherine-FC thermal imager has an image resolution of 754x576 so it should be safe to assume that the display is configured for this.<br />
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Control of turret traverse and gun elevation is accomplished using the thumbstick. The decision to use a thumbstick was presumably because a full joystick could not be easily manipulated with precision if the operator's body and arm were rocking around while the tank travelled over rough terrain. Under such circumstances, the thumb would remain completely stationary if the hand was securely gripping a fixed handle. The commander's index finger rests on the trigger button behind the handle. The control unit also allows the commander to activate the autoloader to load any ammunition type except guided missiles.<br />
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<a href="https://www.blogger.com/null" id="comms"></a><span style="font-size: large;">RADIO COMMUNICATION</span></h3>
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<div><br /></div><div>All T-72 tanks were equipped with a radio station. It would be installed on the turret ring next to the coaxial machine gun and quite conveniently in front of the commander's seat. To work with the radio, the commander could simply reach forward. The ease of access to the radio is characteristic of Soviet tanks, as in a number of foreign tanks with a radio fitted in the turret bustle, the commander has little direct interaction with the radio and instead uses a separate control panel which only permits him to switch between frequencies. </div><div><br /></div><div>Various radio stations were used across the different T-72 models operated by the Soviet, and then Russian armies as shown in the following timeframes. </div><div><br /></div><div><ul style="text-align: left;"><li>1973-1984: R-123M transceiver with R-124 intercom</li><li>1984-2012: R-173 transceiver, R-173P receier, R-174 intercom</li><li>2012-present: R-168-25UE-2 transceiver, R-168 AVSK-B intercom </li></ul></div><div><br /></div><div>Each crew member was connected to the intercom network of the tank, allowing half-duplex communications between all three crew members. The radio is also connected to the intercom system, so that all crew members may listen at the same time, or one crew member can broadcast at a time. Normally, only the tank commander uses the radio, while the other two men only listen and respond to orders from the commander via the intercom. Additionally, a tank rider can plug into an intercom connector socket located between the commander's cupola and the shell casing ejection port on the rear of the turret, whereby he can talk to the crew. An additional tanker helmet and connector set is included in the standard equipment of the tank, and can be left on the turret for tank riders to use.</div><div><br /></div><div>Both the radio and intercom systems were directly routed to the laryngophone of the headset and the control box.</div><div><br /></div><h3 style="text-align: left;"><span style="font-size: large;">R-123M TRANSCEIVER</span></h3><div>
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<span style="font-family: inherit;"><span style="line-height: normal;"><br /></span></span><span style="font-family: inherit;"><span style="line-height: normal;">The T-72 and T-72A were originally supplied with an R-123M analogue radio </span></span>transceiver station<span style="font-family: inherit;"><span style="line-height: normal;">. At the time the T-72 entered service, the R-123 was the standard radio system for all armoured vehicles since the 1960's, and the R-123M model was a modernized variant. It replaced the R-113. The R-123M has a total operating frequency range of between 20 MHZ to 51.5 MHZ, which is wider than the R-113. The operating frequency range was split into 2 sub-bands, 20-35.756 MHz and 35.75-51.5 MHz.</span></span> <span style="font-family: inherit;">It could be tuned to any frequency within those limits when set to the manual tuning mode, or the commander could quickly switch between four channels with preset frequencies for platoon-level communications. It takes several seconds for the mechanism to switch between frequencies, and the channel number is displayed on an illuminated display on the top right corner of the radio. </span><a href="https://youtu.be/aouc4esijLY" style="font-family: inherit;">This instructional video shows the R-123 in use</a><span style="font-family: inherit;">. </span>Communication is possible with low level infantry radio sets, including the R-105M, R-108M, R-109M, R-114 and R-126. </div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">The transceiver unit of the R-123M measures 428x239x222 mm, and the power supply unit is 210x166x220 mm.</div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">A whip antenna was installed together with the radio, adjustable to 4-meter, 3-meter, 2-meter and 1-meter increments. It had a nominal range of between 16 km to 50 km depending on the terrain, weather conditions and noise levels, but according to the manual, with the whip antenna fully deployed to its 4-meter length, a T-72 travelling at 40 km/h with the radio noise suppressor turned on can expect a broadcast and reception range of at least 13 km or at least 20 km without the noise suppressor. If the antenna is set to the 1-meter length, the range is drastically reduced.</div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">As there is only one transceiver, the radio is limited to half-duplex communication on one frequency at a time. This is a trait it shares with the majority of vehicle radios of the time, including models such as the AN/VRC-12 (or AN/VRC-64) radio used in American tanks up to the Abrams series during the Cold War. These were all conventional transceiver sets limited to half-duplex communications on one frequency at a time. Command tanks would have an additional R-442/VRC receiver to permit the commander to listen on one frequency (simplex) while communicating in half-duplex mode on another using the transceiver.</div><div style="line-height: 16px; margin-bottom: 0in;"><span><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">The R-123 was designed with two deliberate features for increased jamming and noise immunity, which were its increased transmission power of 20 Watts, and its choice of operating frequencies. The increased transmission power was responsible for the increased range of the R-123 and it improved signal reception for receivers, but the increased power also improved the resistance to interference, as more powerful jamming would be required to suppress its signals. Compared to the standard SEM-25 tank radio used in the Bundeswehr which had a transmitting power of up to 15 W, and the AN/VRC-12 tank radio used in the U.S military since 1965 which had a transmission power of 30 W, the power of the R-123 is moderate. Moreover, the choice of the operating frequency range had a significant overlap with the operating frequency range of foreign radio systems. In the US Army, the AN/VRC-12 tank radio operated in the 30-75.95 MHz frequency range, the British used the VRC 353 with a 30-75.975 MHz frequency range, while German tanks were equipped with the SEM-25 radio station, which had a 20-69 MHz frequency range. This made it infeasible for enemy forces to utilize indiscriminate or barrage jamming - which was previously possible against the R-113 due to its narrow 20.00-22.375 MHz frequency range - as the range of possible frequencies was too large, and even if it were attempted, indiscriminate jamming would impair their own radio communications.</div></span></div><div style="line-height: 16px; margin-bottom: 0in;"><span style="font-family: inherit;"><span style="line-height: normal;"><br /></span></span></div><div style="line-height: 16px; margin-bottom: 0in;"><span style="font-family: inherit;"><span style="line-height: normal;">The R-123 had a relatively novel glass prism window at the top of the apparatus that displayed the operating frequency by projecting figures from a rotating scale. It had 1,261 possible frequency settings within its operating range, with an increment of 25 kHz. By having illuminated frequency and channel displays, the design of the R-123 was ideal for the darkened interior of a tank. </span></span><span style="font-family: inherit;">Moreover, another merit of the R-123 was its modular design that enabled it to be repaired quickly by simply swapping out individual modules rather than working on individual components.</span></div><div style="line-height: 16px; margin-bottom: 0in;"><span style="font-family: inherit;"><br /></span></div><div style="line-height: 16px; margin-bottom: 0in;"><span style="font-family: inherit;">For T-72M and T-72M1 tanks exported outside of the Warsaw Pact, the R-123M was the most advanced option available. By the time T-72 export gained traction in the 1980's, the Soviet Army had switched to the R-173 digital radio with data encryption as this had become the norm for modern armies. </span></div><div style="line-height: 16px; margin-bottom: 0in;"><span style="font-family: inherit;"><br /></span></div><div style="line-height: 16px; margin-bottom: 0in;"><span style="font-family: inherit;"><br /></span></div><h3 style="line-height: 16px; margin-bottom: 0in; text-align: left;"><span style="font-family: inherit;"><span style="font-size: large;">R-130M RECEIVER</span></span></h3><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-WCDTPQejTEg/X8VP_AWNvvI/AAAAAAAASL0/gLnm-1WOAHo9hy8eEUy0DzgKJnbj9_5oACLcBGAsYHQ/s976/r-130m%2Bset%2Bnva.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="641" data-original-width="976" height="263" src="https://1.bp.blogspot.com/-WCDTPQejTEg/X8VP_AWNvvI/AAAAAAAASL0/gLnm-1WOAHo9hy8eEUy0DzgKJnbj9_5oACLcBGAsYHQ/w400-h263/r-130m%2Bset%2Bnva.png" width="400" /></a></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><div style="line-height: 16px; margin-bottom: 0in;"><span style="font-family: inherit;">T-72K and T-72AK command tanks, used on the battalion and regimental levels, had an additional R-130M radio receiver to permit long range one-way communication with the regimental or divisional headquarters. In this way, if the battalion or regiment commander could not set up a field command post, the command tank could provide the basic essentials needed for operational coordinations. </span></div><div style="line-height: 16px; margin-bottom: 0in;"><span style="font-family: inherit;"><br /></span></div><div style="line-height: 16px; margin-bottom: 0in;"><span style="font-family: inherit;">The R-130M was installed behind the commander's seat, with the commander being the radio operator, appropriately enough. </span>The operating frequency range of the radio is 1.5-10.99 MHz. It is split into 10 sub-bands, with 95 frequency settings per band. It has its own whip antenna, adjustable to 4-meter, 3-meter, 2-meter and 1-meter increments. Command tanks can therefore be identified by their two antennas. The image below, showing a Georgian T-72 SIM-1 with the two antennas characteristic of a command tank.</div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-A9Oz3HiuFyk/X8Vf1jdwbRI/AAAAAAAASME/pCtiFlw4ZAcmXGPgtG5X2-Q1fI1jHmRBgCLcBGAsYHQ/s1280/1280px-Georgian_T-72Sim1_03.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="266" src="https://1.bp.blogspot.com/-A9Oz3HiuFyk/X8Vf1jdwbRI/AAAAAAAASME/pCtiFlw4ZAcmXGPgtG5X2-Q1fI1jHmRBgCLcBGAsYHQ/w400-h266/1280px-Georgian_T-72Sim1_03.jpg" width="400" /></a></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">With the basic 4-meter whip antenna, the R-130M permits communications out to a range of up to 50 km, both stationary and on the move. If the 10-meter mast antenna is deployed, it is possible to increase the reception range out to 350 km, but the tank must be stationary as the mast antenna must be secured with guy wires.</div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-tNiX1ak5qZA/X8VWw4OGG_I/AAAAAAAASL8/oeKf1hHvEhoXJU2LW8WghjQcqUik2l79wCLcBGAsYHQ/s705/r-130m%2Bantenna%2Bmast%2Bdeployed.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="502" data-original-width="705" height="285" src="https://1.bp.blogspot.com/-tNiX1ak5qZA/X8VWw4OGG_I/AAAAAAAASL8/oeKf1hHvEhoXJU2LW8WghjQcqUik2l79wCLcBGAsYHQ/w400-h285/r-130m%2Bantenna%2Bmast%2Bdeployed.png" width="400" /></a></div><br /><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">When working with the mast antenna, the AB-1 petrol auxiliary power unit (APU) in the tank is used to supply power to the radios instead of the engine, or to recharge the batteries if needed. It is installed to the right of the driver. The starboard side conformal fuel tank and ammunition rack was modified to accommodate it, having a reduced capacity of petrol to supply the generator exclusively and lacking slots for ammunition. Because of this, the ammunition capacity of the tank is reduced by 7 shots.</div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">The APU was designed to allow the tank to operate its long range radio equipment for an extended duration (up to 4 hours continuously) without having the noise of the tank engine interfere with communications. The AB-1 was installed in the T-72K, T-72AK and T-72BK.</div></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><h3 style="line-height: 16px; margin-bottom: 0in; text-align: left;"><span style="font-family: inherit;"><span style="font-size: large;">R-173 TRANSCEIVER</span></span></h3><div style="line-height: 16px; margin-bottom: 0in;">
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<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-C-ghpiLZtGA/X8VGB7BoxNI/AAAAAAAASLY/reSMy8kK9Dsq7pXTQKGnkFl1c8Fc6qKAACLcBGAsYHQ/s1000/R173m-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="697" data-original-width="1000" height="279" src="https://1.bp.blogspot.com/-C-ghpiLZtGA/X8VGB7BoxNI/AAAAAAAASLY/reSMy8kK9Dsq7pXTQKGnkFl1c8Fc6qKAACLcBGAsYHQ/w400-h279/R173m-2.jpg" width="400" /></a></div>
<div style="line-height: 16px; margin-bottom: 0in;"><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">Beginning in 1984, the R-123M was replaced by the R-173 digital radio transceiver. The R-173 can be used to to transmit and receive voice signals for normal communications, or transmit and receive encrypted analogue and digital data. The radio operates in a frequency range of 30-75.999 MHz with a frequency increment of 1 kHz, providing a much wider frequency range than the R-123. It could be programmed to receive and broadcast in 10 programmable preset frequencies, with a frequency switching time of 3 seconds. According to the 1984 paper "<i>Развитие Танковой Радиосвязи В Послевоенный Период</i>" (<i>Development of Tank Radio Communications in the Postwar Period</i>), the expansion of the operating frequency range was driven by the desire to combine the operating frequency ranges of domestic radio stations with the frequency ranges of the radios of the hypothetical enemy.</div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">It had an electronic keypad for entering the desired frequency and a digital display to show the frequency value, and again, it is worth noting that an illuminated display is ideal for the dark interior of a tank. The dimensions of the R-173 transceiver unit are 428x240x222mm. Thanks to the use of integrated circuits in the transceiver, the volume of the device was drastically smaller than the previous radio transceivers, making it possible to integrate the power supply unit into the same casing as the transceiver, occupying the block to the right of the radio. Thus, the space previously allocated to the power supply unit was freed up, allowing an additional R-173P receiver to be fitted. All T-72B tanks are fitted with a set of both an R-173 and R-173P as part of the radio station. It is also possible for very late production T-72A tanks to also have the new radio station. At the time the R-173 was introduced, the radios used in NATO tanks were still of the previous generation - or in other words, analogue devices with no built-in encryption. That said, there was no real gap in favour of the Soviet Army, because in 1984, the same year the R-173 entered service, the standard SE-412 tank radio station used in the Bundeswehr received an add-on voice encryption unit. </div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><a href="https://www.youtube.com/watch?v=Ac0fRfnWrBI">This video</a> shows an R-173 in use by an amateur radio operator.</div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><h3 style="line-height: 16px; margin-bottom: 0in; text-align: left;"><span style="font-size: large;">R-173P RECEIVER</span></h3><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-avyYVMWC2Mo/X8VGVnIgh4I/AAAAAAAASLg/802WA53uEmUuLzQogiMWCcTjC9XdRpPXQCLcBGAsYHQ/s469/R173pm-2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="443" data-original-width="469" src="https://1.bp.blogspot.com/-avyYVMWC2Mo/X8VGVnIgh4I/AAAAAAAASLg/802WA53uEmUuLzQogiMWCcTjC9XdRpPXQCLcBGAsYHQ/s320/R173pm-2.jpg" width="320" /></a></div><br /><br /></div><div style="line-height: 16px; margin-bottom: 0in;">Encrypted voice data received by the R-173P can be decrypted, and it operated in a frequency range of between 30-75.999 MHz like the R-173 radio. It also has 10 programmable preset frequencies. The R-173P receiver and the R-173 transceiver can be used simultaneously so that the commander can transmit and receive on the R-173 on one frequency (in the half-duplex mode) while also receiving uninterrupted voice communications on another frequency (in the simplex mode) via the R-173P.</div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">This capability was previously only provided for command tanks, which would often use the standard tank radio for communications with subordinates and use the additional long range radio as a continuous link to the headquarters of the next higher level, through which the battalion or regiment commander could receive orders. By providing a transceiver-receiver set to every tank, it became possible for Soviet tank platoons and companies to set up better-coordinated tactical networks. For instance, a platoon leader could use his R-173P receiver to maintain constant communication with the company leader while also delegating tasks to the two subordinate tanks in his platoon, while the two subordinate tank commanders in the platoon could use their R-173 transceivers to talk with each other while using their R-173P receivers to receive orders from the platoon leader. If this configuration is unsuitable, different network structures could be arranged depending on the circumstances. This was a capability that was previously found on standard tanks with the German SEM-25 radio of the Leopard 1 and early Leopard 2 models, or in M60 unit leader tanks equipped with an additional receiver.</div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">Thanks to its compactness, the R-173P was installed just next to the R-173, in the space previously occupied by the power supply unit. The photo below of a T-90 interior shows the location of the R-173P. </div><div style="line-height: 16px; margin-bottom: 0in;"> </div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--fP65lTc1uU/X8VG8nITRkI/AAAAAAAASLs/1-Wu9UU0Zg4Cx-a4hlZ6ZGK66assXswGgCLcBGAsYHQ/s1280/1532286325_333_8.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="853" data-original-width="1280" height="426" src="https://1.bp.blogspot.com/--fP65lTc1uU/X8VG8nITRkI/AAAAAAAASLs/1-Wu9UU0Zg4Cx-a4hlZ6ZGK66assXswGgCLcBGAsYHQ/w640-h426/1532286325_333_8.jpg" width="640" /></a></div><br /><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><h3 style="line-height: 16px; margin-bottom: 0in; text-align: left;"><span style="font-size: large;">R-168-25UE-2 RADIO SET</span></h3><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div></div>
<div style="text-align: center;"><a href="http://3.bp.blogspot.com/-IOoEFOklyEQ/VTJ39YXst2I/AAAAAAAAB2k/5nPSTo_c7RI/s1600/R-168-25UE-2_4.jpg"><img border="0" height="248" src="https://3.bp.blogspot.com/-IOoEFOklyEQ/VTJ39YXst2I/AAAAAAAAB2k/5nPSTo_c7RI/w400-h248/R-168-25UE-2_4.jpg" width="400" /></a></div>
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<br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><div style="line-height: 16px; margin-bottom: 0in;">To keep up with the increasing sophistication of electronic warfare threats, a replacement for the R-173 was sought after, leading to the creation of a universal R-168 radio system to equip all levels of a division with a single standardized radio transceiver-transceiver set. It was launched into service in the 2000's, but has been slow to proliferate, with mass production starting only in 2005. The most recent large scale modernization drastically increased the share of R-168 radios in the Russian Army, with armoured vehicles receiving the new radio during scheduled repairs. Tanks and other armoured vehicles received the R-168-25UE-2 model. All T-72B3 tanks are equipped with this radio station, including unit leader tanks at the company, battalion and regiment levels. </div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><a href="http://elektrosignal.ru/wp-content/uploads/2018/06/R-168-25UE-2.pdf">The R-168-25UE-2</a> consists of two R-168-5UTE-2 transceivers plugged into a central hub which connects the two transceivers to the electrical and communications network of the tank. The radio station measures 428х248х239 mm. The entire radio station is a self-contained unit, so the complete station is the same size as a single R-173. Because of this, additional space was freed up in the commander's station by the omission of a separate receiver unit.</div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">With an operating frequency range of 30-107.975 MHz and a frequency step of 25 kHz, the R-168-25UE-2 has a much wider operating band than previous radio sets, but because the minimum frequency is 30 MHz, full interoperability is only possible with the R-173 series and not the R-123 series, which has a minimum frequency of 20 MHz. It is entirely impossible to communicate with R-130M radios, as those work in a narrow frequency band of 1.5-10.99 MHz. When using the basic BShDA whip antenna, the tank has a transmitting and receiving range of 30 km on the move, and when using the ShDAM mast antenna, the range is extended to 60 km, although the tank must be halted. This meant that the R-168 also had the capability to serve as a replacement for R-130M radios for battalion and regimental-level command tanks thanks to the 60 km range limit, thus removing the need for dedicated command tanks, increasing the available space in the battalion and regiment commanders' tanks, and simplifying production to a single T-72B3 model. The radio enabled the T-72B3 to operate in the new network-centric data sharing system currently implemented in some Russian units.</div></div><div style="line-height: 16px; margin-bottom: 0in;">
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Besides the updated communications hardware, the tank's intercom and radio control box was also augmented with new digital control panel shown below. The display is illuminated, and an optional backlight for the buttons can turned on.<br />
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<a href="https://4.bp.blogspot.com/-5uKY8TXwzJQ/Vrtp-gdS3cI/AAAAAAAAF0I/mYQFNYn_Oi4/s1600/t-72b3%2Bcontrol.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="357" src="https://4.bp.blogspot.com/-5uKY8TXwzJQ/Vrtp-gdS3cI/AAAAAAAAF0I/mYQFNYn_Oi4/s640/t-72b3%2Bcontrol.png" width="640" /></a></div>
<div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">The R-168 series not only had data encryption but also featured frequency hopping for noise immunity in the presence of radio interference. It can produce frequency hops 100 times a second, and can transmit or receive encrypted voice or data at 1.2-16 kb/s. The radio has several modes of operation: fixed frequency, pseudo-random tuning of the operating frequency, adaptive communication, scanning reception at 8 preselected frequencies, work with a noise suppressor, retransmission, manual and automated recording of radio data from the device input of radio data with an optical interface or from an external computer, emergency erasure of radio data, transmission and reception of circular, address and tone calls, network control from an external computer via a standard RS-232C socket, voice informant of operator actions, dialogue mode, automated performance monitoring, simplex or two-frequency simplex at one of 8 preselected frequencies, and simultaneous transmission of voice and data.</div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div>
<br /></div></div><div style="line-height: 16px; margin-bottom: 0in;"><div>For the defence of the tank and crew against enemy infantry in close-in combat, there is a single assault rifle, either an AKMS or AKS-74, stowed in the turret with 300 rounds in 10 magazines. It is accessible to the commander, who is normally responsible for using it if the need arises, but the magazines are stowed on both sides of the turret. There is also a box with 10 F-1 defensive hand grenades, also accessible from the turret. The PKT coaxial machine gun in the tank may also be used as an improvised infantry machine gun by dismounting it and firing it with the backup mechanical trigger.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-uIt72d82xn0/YDDBRyuXfQI/AAAAAAAASwE/yJAPI9D0Mvs9ctpGNix9YTVodh3UTMMbwCLcBGAsYHQ/s1221/AKM%2Bfrom%2Bcommanders%2Bhatch%2Bground%2Btargets.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="913" data-original-width="1221" height="299" src="https://1.bp.blogspot.com/-uIt72d82xn0/YDDBRyuXfQI/AAAAAAAASwE/yJAPI9D0Mvs9ctpGNix9YTVodh3UTMMbwCLcBGAsYHQ/w400-h299/AKM%2Bfrom%2Bcommanders%2Bhatch%2Bground%2Btargets.png" width="400" /></a><a href="https://1.bp.blogspot.com/-KN4grQoWpZI/YDDBR0sDWEI/AAAAAAAASwA/44NLfHqknOoxnGhnXBWtV4yWSWuaOUryQCLcBGAsYHQ/s1330/AKM%2Bfrom%2Bcommanders%2Bhatch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="933" data-original-width="1330" height="280" src="https://1.bp.blogspot.com/-KN4grQoWpZI/YDDBR0sDWEI/AAAAAAAASwA/44NLfHqknOoxnGhnXBWtV4yWSWuaOUryQCLcBGAsYHQ/w400-h280/AKM%2Bfrom%2Bcommanders%2Bhatch.png" width="400" /></a></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;"><br /></div><div style="line-height: 16px; margin-bottom: 0in;">If the commander wishes, he can hand over the assault rifle to the gunner, and the gunner can load it with the magazines stowed at his station.</div><br /><div><br /></div></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-n3zcY6CmU5s/YDDBkDxxMXI/AAAAAAAASwU/xdmuNPRKAFUC5vndgUl5YaXxGyNgZY9bQCLcBGAsYHQ/s1366/AKM%2Bfrom%2Bgunners%2Bhatch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="928" data-original-width="1366" height="271" src="https://1.bp.blogspot.com/-n3zcY6CmU5s/YDDBkDxxMXI/AAAAAAAASwU/xdmuNPRKAFUC5vndgUl5YaXxGyNgZY9bQCLcBGAsYHQ/w400-h271/AKM%2Bfrom%2Bgunners%2Bhatch.png" width="400" /></a><a href="https://1.bp.blogspot.com/-qDLZipDuWtU/YDDBkD6c7kI/AAAAAAAASwQ/i9wdC-6GOYEGRVPKYz-Y2_Ps9GO61SK8wCLcBGAsYHQ/s1189/AKM%2Bfrom%2Bgunners%2Bhatch%2Bground%2Btargets.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="883" data-original-width="1189" height="297" src="https://1.bp.blogspot.com/-qDLZipDuWtU/YDDBkD6c7kI/AAAAAAAASwQ/i9wdC-6GOYEGRVPKYz-Y2_Ps9GO61SK8wCLcBGAsYHQ/w400-h297/AKM%2Bfrom%2Bgunners%2Bhatch%2Bground%2Btargets.png" width="400" /></a></div><br />
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<a href="https://www.blogger.com/null" id="gunstat"></a>
<span style="font-size: large;">GUNNER'S STATION</span></h3>
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The gunner is seated on the left side of the turret. He is provided with a single forward-opening hatch. Its most distinctive feature is the smaller circular port hole at its center for the installation of a snorkel. The port hole can also be opened to increase the airflow in the tank in conjunction with the switching of the engine air intake system from the external intake to the crew compartment intake. The hatch is spring loaded to assist the gunner when opening it and can be locked in the forwards position, like the commander's hatch. It is locked in place with a simple rotating latch. There is a single TNPA-65 periscope embedded in the hatch, facing to the left.<br />
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<a href="https://4.bp.blogspot.com/-4vtOp25zsLw/WxGYp2iIwsI/AAAAAAAALqw/fKxduuYaiGoiFBVQXOeuM2Sib5ohsTOiQCLcBGAs/s1600/hatch.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="589" data-original-width="785" height="300" src="https://4.bp.blogspot.com/-4vtOp25zsLw/WxGYp2iIwsI/AAAAAAAALqw/fKxduuYaiGoiFBVQXOeuM2Sib5ohsTOiQCLcBGAs/s400/hatch.jpg" width="400" /></a></div>
<div style="margin-bottom: 0in;"><br /></div><div style="margin-bottom: 0in;"><br /></div><div style="margin-bottom: 0in;">Measurements on a T-72M showed that the gunner's hatch is 584mm (23 inches) wide and 354mm (16 inches) long in radius, so like the commander's hatch, it meets the U.S Army human engineering size requirements for a 95th percentile male in light clothing. For comparison, the loader's hatch on an M60 is 22.5 inches wide and 15 inches long in radius.</div><div style="margin-bottom: 0in;"><br /></div><div style="margin-bottom: 0in;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Qdj0rR7f7js/YDSAq5TKdOI/AAAAAAAASww/VebYloyBXisjDBC1BNgYqRcMoGiIdRpPACLcBGAsYHQ/s2048/gunners%2Bhatch%2Bwidth.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="320" src="https://1.bp.blogspot.com/-Qdj0rR7f7js/YDSAq5TKdOI/AAAAAAAASww/VebYloyBXisjDBC1BNgYqRcMoGiIdRpPACLcBGAsYHQ/s320/gunners%2Bhatch%2Bwidth.png" /></a><a href="https://1.bp.blogspot.com/-R_5G8YuajdE/YDSArHOWe7I/AAAAAAAASw0/ZS3WUL4D-1wr10ER-e1jlnx8IJ_SFItCQCLcBGAsYHQ/s2048/gunners%2Bhatch%2Blength.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="320" src="https://1.bp.blogspot.com/-R_5G8YuajdE/YDSArHOWe7I/AAAAAAAASw0/ZS3WUL4D-1wr10ER-e1jlnx8IJ_SFItCQCLcBGAsYHQ/s320/gunners%2Bhatch%2Blength.png" /></a></div><br />
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The gunner is responsible for all of the equipment in the tank related to its firepower, including the autoloader, stabilizer, cannon, the sighting devices and their associated instruments. The gunner's station is dominated by the massive GPS (Gunner's Primary Sight) which completely fills the space between the gunner and the front wall of the turret. The gunner's station is the most cramped position in the T-72, and even more so if he is wearing winter clothing. However, it would be a mistake to consider the cramped nature of the gunner's station as a unique and defining feature of the T-72 or to exaggerate it beyond what it really is. As a whole, the T-72's turret does indeed have a much smaller volume than most tanks, but the space delegated to the gunner is very much on par with its contemporaries.<br /><span style="line-height: 16px;"><br /></span>
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<a href="https://2.bp.blogspot.com/-n9vNwLX6dzs/W2tRtCVV0tI/AAAAAAAAMJ8/j-RL2nJgNO0R6hcNUYca58sFQAwqDA54gCLcBGAs/s1600/0_69f05_e7b84cc9_XXXL.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="1025" height="398" src="https://2.bp.blogspot.com/-n9vNwLX6dzs/W2tRtCVV0tI/AAAAAAAAMJ8/j-RL2nJgNO0R6hcNUYca58sFQAwqDA54gCLcBGAs/s400/0_69f05_e7b84cc9_XXXL.jpg" width="400" /></a></div>
</div><div><br /></div><div><br /></div><div>The gunner's seat, which consists of a cushion and a backrest attached to a base, is permanently fixed. Beginning with the T-72B, the seat had a semi-permanent fixed position. The seat can only be adjusted backwards or forwards by unbolting it from the mounting frame and then bolting it onto a set of two alternative holes provided on the frame, but this is to be done once by the gunner of the tank and then left alone. In all T-72s, the backrest can be swiveled between three different positions. The main reason for swiveling the backrest is so that the gunner doesn't sit with his lower body twisted to the right, if the gunner doesn't simply rest his left foot on the autoloader carousel cover for whatever reason, because the folding footrest is offset to the right. The gunner can sit in a normal posture with his feet resting flat on the autoloader carousel cover, or with his legs outstretched, resting on either thecarousel cover or his footrest. The seat can be folded up and to the right to be flush against the recoil guard, but this requires the backrest to be removed by lifting it from its socket on the seat base. Folding the seat away creates a space on top of the autoloader carousel for the guner to sleep, or simply to widen the driver's crawlspace if he were evacuating the tank through the turret, especially if the turret is turned to the right. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Z_esPZwq4xI/YDS4r2hxtTI/AAAAAAAASxg/ZumZZnVCL5U3Zh7Ip59Zs9YZ3XNvpgXIQCLcBGAsYHQ/s2048/seated%2Bgunner%2Blegs%2Boutstretched.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1152" data-original-width="2048" height="225" src="https://1.bp.blogspot.com/-Z_esPZwq4xI/YDS4r2hxtTI/AAAAAAAASxg/ZumZZnVCL5U3Zh7Ip59Zs9YZ3XNvpgXIQCLcBGAsYHQ/w400-h225/seated%2Bgunner%2Blegs%2Boutstretched.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-rW1R3FGtoyk/YDS4r56TV-I/AAAAAAAASxc/dYfUyzD5kuIrrk7436YtjURwJzsgwYyTACLcBGAsYHQ/s2048/seated%2Bgunner.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="200" src="https://1.bp.blogspot.com/-rW1R3FGtoyk/YDS4r56TV-I/AAAAAAAASxc/dYfUyzD5kuIrrk7436YtjURwJzsgwYyTACLcBGAsYHQ/w150-h200/seated%2Bgunner.jpg" width="150" /></a></div><div><br /></div></div><div><br /></div><div>According to an Indian pilot study of locally built T-90S tanks, titled "<i>Ergonomics analysis of gunner station of armoured combat vehicle (ACV)- Tank T 90S with special reference to seat, visual sighting system and musculoskeletal discomfort: A pilot study</i>", the height of the gunner's seat from the carousel cover is 150mm. However, the seat is of a local modification, lacking the foam cushion of the original seat, instead having a woven jute seat with a canvas cover for durability reasons. The thickness of this seat should be much less than the original type, so it is likely that in an original T-72, the height of the gunner's seat is more than 150mm above the carousel cover.</div><div><br /></div><div>The two images below show two versions of the seat mounting frame found in the T-72. Most are of the design shown on the right, with T-72B and T-72S tanks using a slightly modified variant. The rear end of the seat mounting frame is fixed to the rear base of the turret, near the turret ring.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-5v7pCbeI0QI/XuGS3T9GePI/AAAAAAAARAg/3gH9vP_2BicH_TFa52lu3ENZ49-OSOOWQCK4BGAsYHg/s4185/gunners%2Bseat.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3041" data-original-width="4185" height="291" src="https://1.bp.blogspot.com/-5v7pCbeI0QI/XuGS3T9GePI/AAAAAAAARAg/3gH9vP_2BicH_TFa52lu3ENZ49-OSOOWQCK4BGAsYHg/w400-h291/gunners%2Bseat.png" width="400" /></a><a href="https://1.bp.blogspot.com/-K36N35VpU70/XuGVoqPqx4I/AAAAAAAARA4/bUjyRs7lUDUoylynymT4I4FdNjGNUyx4QCK4BGAsYHg/s4010/gunners%2Bseat%2Band%2Bfootrest.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3133" data-original-width="4010" height="313" src="https://1.bp.blogspot.com/-K36N35VpU70/XuGVoqPqx4I/AAAAAAAARA4/bUjyRs7lUDUoylynymT4I4FdNjGNUyx4QCK4BGAsYHg/w400-h313/gunners%2Bseat%2Band%2Bfootrest.png" width="400" /></a></div><div><br /></div><div><div>The front end of the frame is secured to the front of the turret via the a heavy steel bracket, shared with a few electric components. The middle of the frame is supported by the gunner's fixed recoil guard, which is bolted to the turret ceiling. The gunner's fixed recoil guard has four gun elevation marks for visual reference. These are: 0°, 3.5° (labelled as the loading angle), 10° and 13°. By referring to these marks, the gunner can manually elevate the gun to specific angles for certain tasks.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRf_JclofyGGBns15aKu9jQqdWA2EWowHPDfDOyc7PUIsfrGaodxb8RwTRbU7L9Fh3_DNfiWpndH5Ox-noAX_MKexD4hxWzL2Px9b7fsGK_ipxSIXKNTYeIr3F4HweiKkSW4NaVbXPulyOWNKi6_wntQlQZF10GDdUGY9LQfhRlmZhDPotVfg9_N5gXQ/s1885/fixed%20recoil%20guard.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1885" data-original-width="1749" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRf_JclofyGGBns15aKu9jQqdWA2EWowHPDfDOyc7PUIsfrGaodxb8RwTRbU7L9Fh3_DNfiWpndH5Ox-noAX_MKexD4hxWzL2Px9b7fsGK_ipxSIXKNTYeIr3F4HweiKkSW4NaVbXPulyOWNKi6_wntQlQZF10GDdUGY9LQfhRlmZhDPotVfg9_N5gXQ/w371-h400/fixed%20recoil%20guard.png" width="371" /></a></div></div><div><br /></div><div><br /></div><div>The width of the gunner's station, as measured at the position of the gunner's torso, is 571mm (22.5 inches). Because the gunner's seat is slightly behind the widest point of the turret ring, he has less shoulder room than the commander when seated normally. When the gunner leans forward, as he would when using the sights, the shoulder room increases. The height of the station is 890-914mm (35-36 inches) when measured from the seat cushion to the ceiling of the gunner's hatch. The variation is due to the slant of the hatch, so that the height is less toward the left side and more toward the right side. This meets Soviet requirements for a driver's station (driver's station height must be 850-900mm), which is the appropriate point of reference due to the seated posture of the gunner. Otherwise, the standard for a gunner is 1,300mm, but this is because the gunner is assumed to be seated in a normal posture with a high popliteal height.</div><div><br /></div><div><div><br />Refering again at <a href="http://3.bp.blogspot.com/-aBnfqllGDQI/VIZm9eldmDI/AAAAAAAADsg/2sGi3lKKxxo/s1600/human-factors-1.png">this table</a> from "<i>Human Factors and Scientific Progress in Tank Building</i>" by M.N. Tikhonov and I.D. Kudrin, we can see that the space afforded to the gunner is 0.495 cubic meters - well above the minimum of 0.44 cubic meters for a seated man in an NBC suit to inhabit and work in his station. This was an improvement over the T-55 which gave its gunner only 0.395 cubic meters of space. As mentioned before in the "Commander's Station" section of this article, the slanting roof of the turret over the gunner's station has the opposite effect that the commander's cupola had on the internal height available for habitation. To counteract this, the height of the seat was reduced such that the gunner was practically seated directly on top of the autoloader carousel cover. However, his legroom remains the same as the commander's. The gunner's seat is mounted on a frame attached to the back of the turret. The original design of the frame is shown below in the drawing on the right, and it was changed in the T-72B, shown on the left. From the seat backrest to the footrest, the gunner's station has between 1.1 to 1.2 meters of space, exceeding the average figure of 1 meter for an average male with a height of 1.7 meters.</div><div><br /></div></div><div><br /></div><div>It can be seen in the drawing below that for a gunner of average height, his head would be pressed up to the turret ceiling if he is operating the night sight offset to the left of the primary sight. His feet would be resting on a fold-out footrest, but he can simply extend his legs completely in the turret due to the two-man layout.<br />
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In terms of space and comfort, the gunner's station in a T-72 is quite adequate for crew members of average height and size, though there could be problems for people of extreme height, as the clearance provided for the gunner's head is not large. On long marches, both turret occupants may simply sit on the turret roof instead of remaining inside the tank. In this respect, the T-72 has a notable ergonomic advantage over many tanks in that the gunner has his own hatch and he can exit whenever he likes to sit on the roof or to stand upright. The ability to do this makes a drastic difference to the gunner's health and comfort in hot weather conditions, because the internal temperature of the tank will be much greater than the ambient air temperature owing to additional heating from the steel walls of the turret and hull, exposed to direct sunlight. In tests with T-55 and T-62 tanks, for example, the internal air temperature in the fighting compartment would be 6-9 degrees higher than the ambient air temperature at 21°C and 28°C when forced ventilation is not used.</div><div><br /></div><div>In the event of an internal fire, the entire crew can bail out through their own hatches with no fuss. This is quite unlike tanks like the T-55, Leopard 1, Abrams, or indeed, any other manually-loaded tank except for a few oddball designs like the M60A2 as the gunner is usually not provided with his own hatch. On long marches, he might be forced to stay put in his decidedly cramped station for hours at a time. This is not the case for the gunner of a T-72.<br />
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Like in most tanks, the gunner's station in the T-72 is the most cramped, but it is important to note that in the vast majority of manually loaded tanks, the gunner is not provided with a hatch of his own and as such. If a T-72 gunner began to feel uncomfortable for any reason, he can open his hatch and sit on the roof, or just stand on his seat and stretch. Additionally, in a typical manually loaded tank, if the commander were incapacitated or killed, the gunner would have to squeeze through the commander's body or shift it aside in order to bail out through their shared roof hatch. This is also not a problem for the T-72.<br />
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Ventilation is provided by a DV-3 fan, like in the commander's station. It is more than enough in European climates where temperatures are usually around 20° C (68° F) or less as it is a relatively powerful 5.2 W fan, but the cooling capacity may not be enough for summer weather let alone in hot, desert regions averaging 30°C to 40°C. In summer conditions, the internal temperature is drastically higher than the ambient temperature due to the heating of the tank from the sun, making it necessary to blow great quantities of air through the crew compartment to cool down. In such weather, the fan is only useful for increasing air circulation to stave off heat strokes, and little else, as the bulk of the ventilating task is shouldered by the ventilation supercharger or the engine cooling fan, if the engine partition port is opened. Still, it is unquestionably better than tanks that do not provide any personal ventilation at all. Several tanks made during the 60's and 70's lacked this ostensibly minor amenity.<br />
<br />The gunner is provided with a master control panel, with which he can control some lights, the ventilation supercharger, the emergency firefighting discharge button, and other functions in the tank. It is very similar to the commander's master control panel, but has a few different controls and lacks the emergency engine stop button and the autoloader rammer control switch used for setting the fuse on HE-Frag shells, which is not done by the gunner.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8G7bFJZtubgrza3ooxDwUDLXFABqJcbks-QafEk-QiBmS7G7LctRspnCBHQbGVHLSNsVOKbRNIE1zZGWWcaIO0OVKITl95zn7ui5cVQeUKfPJI7g0Dn3QQGGleMZMLsLBa8E_m7oJq-mIiTF2-VnoZ3dj1gAzXGKzrH0bkBAXXmVyTHVrJqFctFxw2Q/s1364/gunners%20master%20control%20panel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1364" data-original-width="926" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8G7bFJZtubgrza3ooxDwUDLXFABqJcbks-QafEk-QiBmS7G7LctRspnCBHQbGVHLSNsVOKbRNIE1zZGWWcaIO0OVKITl95zn7ui5cVQeUKfPJI7g0Dn3QQGGleMZMLsLBa8E_m7oJq-mIiTF2-VnoZ3dj1gAzXGKzrH0bkBAXXmVyTHVrJqFctFxw2Q/w271-h400/gunners%20master%20control%20panel.png" width="271" /></a></div><div><br />
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For general visibility, the gunner is provided with a single forward-facing TNP-165A periscope and another TNPA-65A periscope embedded his hatch, facing to the left. The TNP-165A periscope provides 71 degrees of vision horizontally and 33 degrees of vision vertically, and as mentioned before, the TNP-65A provides 140 degrees of vision horizontally and 35 degrees of vision vertically.<br />
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The TNP-165A is placed facing forward for the gunner to gain a wide view of his surroundings with the help of the rotating turret, to check the orientation of the gun barrel, and to make sure that the gun barrel is elevated safely when the tank is entering a ditch or overcoming some obstacle. In the daytime, the periscopes are also sources of light. It provides a field of view of 74 degrees horizontally and 35 degrees vertically. The design of the TNP-165A periscope is particularly noteworthy because it was created specifically for the gunner's stations of tanks. Its lower prism is shaped with an offset angle of 20 degrees so that the angle of the viewing window is intended for an observer below the normal eye level. This is because the eyepiece for the gunner's primary sight is already placed at the eye level of the gunner and a forward-facing periscope must be above it. As such, the gunner would have to be looking up to use the periscope. <br />
<br />Because the gunner does not lean forward with his eyes close to the viewing window when using the TNP-165A periscope, the danger of harm to the gunner's eyes from powerful bullets or fragments penetrating the periscope was very low. Additionally, a layer ballistic glass was laminated to the eyepiece to prevent glass fragments from being released into the crew compartment.<br />
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Most importantly, having the forward-facing TNP-165A periscope allows the gunner to more effectively use the tank from a turret-down status. The TPD-2-49 or TPD-K1 primary sight is periscopic so the gunner will have no trouble looking over the crest of a hill or a berm when the tank is hiding in a turret-down position. When the commander spots a target, he can designate it using the TKN-3 optic and the turret will slew over to point at it. The gunner will be able to see the target through his primary sight, lase it, and prepare to fire. Once the commander gives the order for the driver to move forward, the gunner can immediately open fire once the muzzle of the cannon clears the crest of the hill or berm and the FCS confirms that the cannon and the sight are aligned. However, the primary sight has an 8x magnification, so the gunner cannot see if the muzzle has gone over the crest of an obstacle from that alone. This is where the TNP-165A is particularly useful as it allows the gunner to independently verify the position of the cannon barrel without the commander's assistance.
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The TNPA-65A periscope installed in the hatch provides the gunner with an additional outlet to view the outside world. One of the common issues in turreted tanks with a conventional seating arrangement is that the commander's station is offset from the centerline of the turret, so even if his cupola provides him with good all-round vision, the adjacent side of the turret will block his view and create a large dead zone. Tanks with human loaders usually provide the loader with a periscope to cover this dead zone, but since the T-72 only has the gunner sitting adjacent the commander, he is the one who has a periscope. A benefit of this arrangement is that the gunner can afford to be less dependent on the commander, and another benefit of having the TNPA-65A facing to the left is that the gunner can see for himself if there are any obstacles on the left side of the tank so that he can determine if it is safe to traverse the turret. This may be important when the tank is fighting in a densely forested area or in urban areas. The commander would be responsible for checking the right side of the turret, of course. Having a good view of the left side of the turret. The view from both the TNPA-65A and the TNP-165A can be seen in <a href="https://www.youtube.com/watch?v=wUrC6itYPMc">this video from the inside of a T-72B3</a>.</div><div>
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In a more general sense, the two periscopes are also useful in that the gunner gains a sense of spatial awareness. This gives the gunner a wide view of the terrain ahead of the turret which is important as the primary sight has a fixed 8x magnification with no reduced magnification setting like the earlier telescopic TSh2-22 of the T-54 and TSh2B-41 of the T-62 (3.5x or 7.0x). Having some spatial awareness may also help to prevent motion sickness.
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<tr><td class="tr-caption" style="text-align: center;">1A40-1 sighting complex and 1K13-49 night vision/auxiliary sight</td></tr>
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As you can see in the photo above, the gunner is supplied with a duplicate of the commander's master control panel. Besides being able to initiate the fire control system, control the ventilation, turn on the lighting system, and much more, having the master control panel gives the gunner complete control over most of the electrical equipment in the tank, and also enables the gunner to set the fuse on a HE-Frag shell in lieu of the commander if necessary. This means that the T-72 can theoretically be operated with only a 2-man crew with a minimal loss in combat capabilities. This may be useful when a tank company or battalion is understaffed and there are no sufficiently qualified substitutes for the tank commander's position, however unlikely that may be. Of course, this capability is also largely thanks to the omission of a human loader.<br />
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Beginning in 1979, the T-72A began to receive the 902A "Tucha" smoke grenade discharge system. The 902A is distinguished from the 902B and 902V variants in having 12 grenades rather than 8 and 6 respectively. Note that the suffix does not have any specific meaning, and is simply alphabetical ordering in the Cyrillic alphabet ("А, Б, В" is equivalent to "A, B, C"). The gunner is in charge of using the system, but usually follows the instructions of the commander when doing so. Referring to the photo above, the control box for the system is located to his immediate left, at the gunner's elbow. </div><div><br /></div><div>The control box splits the bank of 12 grenade launchers into 3 groups. Using this control box, he is able to deploy smoke grenades from one of three launcher groups individually or in a salvo of up to four grenades at once. The toggle switches marked (4) in the drawing below are to individually turn on the three grenade launcher groups, and with the selector dial marked (3), the gunner can select how many grenades to fire with each press of the button marked (1). According to the manual, the groups are to be selected individually, and when one group is switched on, the others should be switched off. If, for example, wide smokescreens are needed, then the selector dial can be preset to fire four grenades at once, and the gunner cycles from groups 1 to 3 with each salvo. The control box may be preset prior to combat, or the commander can make a decision to order the gunner to use a custom setting if the circumstances demand it, even firing grenades individually and traversing the turret to create distributed smokescreens.<br />
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<div><br /></div><div><br /></div>When the 902B system was implemented on the T-72AV and T-72B to replace the 902A, the number of grenades was reduced to 8, but the same control panel was used. The only difference is that the toggle switch for group '3' was disconnected. The grenades in the 902B system remained split into two groups of four grenades each. <br />
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The large dial on the L-shaped box seen between the TPD-K1 eyepiece and the gunner's control handles is the AZ-172 autoloader control box. The autoloader can be toggled between the manual or automatic operating modes and the ammunition type can be selected by the gunner. The gunner triggers the autoloader to load by flicking the toggle switch on the underside of the control box to the left. The switch is directly behind and slightly above the left thumb of the gunner when he is grasping the hand grips of his control handles, so after each shot, if the gunner desires to load another round of the same type, he can activate the autoloader by simply raising his left thumb without needing to take his eyes off the eyepiece of the sight. When the dial is switched to a different ammunition type, the mechanical ballistic computer in the sight is electronically set to the ballistic cam of the corresponding ammunition. As such, if the gunner wishes to switch to a different ammunition type but already has a shot loaded, he should fire the shot that is presently loaded before selecting the next type and pressing the load button, so as to retain the ballistic solution calculated by the sight.</div><div><br /></div><div>Two variants of the control box exist. The older model has a green signal lamp to indicate that a round has been loaded and a red signal lamp to indicate that there is a shell casing stub in the ejection mechanism. The newer model has a backlit display with with the same two messages: a red signal alerts the gunner that there is a shell casing stub in the ejection mechanism, and a green signal alerts the gunner that a round has been loaded.<br />
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This control box can be found on tanks that are equipped with the TPD-2-49 and the TPD-K1 sights. A L-shaped space was left empty on both sights at the same location for this control box and for a control box of the same function in the T-64. The earliest T-72 tanks leaving the factory in 1973 and 1974 had a different autoloader control box placed under the communications relay box and next to the autoloader ammunition indicator. This older control box was used to select the ammunition type and toggle between the manual and automatic operating modes, but was probably not as convenient for the gunner to use simply because it is physically further away from all the other controls in front of him. The 'load' button was on a separate box placed next to the TPD-2-49 sight, which required the gunner to take his right hand off the hand grip of his control handles to use. The photo on the left below shows the 'load' button and the photo on the right below shows the control box. Functionally, the gunner's controls were still the same, only that the L-shaped shaped was left unoccupied. The old control box was plugged into the same socket. It may have been only a limited edition release to fill out the orders until the final control box design could begin mass production.<br />
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All of the control boxes have the same dial settings. The first two settings from the left are "load" and "off", and the rest are settings to select HE-Frag, APFSDS, and HEAT. The "load" setting is used when replenishing the autoloader carousel and the "off" setting turns off the autoloader.<br />
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The T-72B uses a different autoloader, sometimes referred to as the AZ-184, and the control box is also different as a result. With the introduction of a new ammunition type, the new control box has an additional option on the ammunition selector dial: missiles. Externally, the only detail to differentiate the new control box from an older one is the addition of a new setting on the ammunition selector dial. The T-72B3 features a modification of the AZ-184 autoloader which accommodates new APFSDS ammunition, and it can be seen in the updated control box. The new control box retains a similar layout as the previous model and is functionally identical.<br />
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The autoloader control box can be used to set the autoloader to automatic operation or manual operation. Setting it to manual operation mode enables the crew to manually load the gun with partial assistance from individual components of the autoloader, such as the chain rammer, or to manually load the gun entirely by hand. If the crew intends to load the cannon manually, setting the autoloader to the manual mode is mandatory as it allows the sighting complex recognize the readiness of the cannon once a shell is loaded.<br />
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The gunner is also provided with an autoloader ammunition indicator. The indicator is rather crude, even for its time, as the indicator display is based on simple milliammeter technology. Due to the small size of the indicator pin, it may be difficult to easily see the indicated number in a high intensity situation. As usual, the indicator has an internal light so that it can be read when all of the tank's hatches are closed.<br />
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The indicator does not have any selectors or dials on its own housing. Rather, it works in conjunction with the autoloader control box. When the gunner selects an ammunition type on the dial on the autoloader control box, the ammunition indicator automatically displays the ammunition reserve for that ammunition type currently stowed in the autoloader carousel. The number of empty slots in the autoloader carousel is determined by setting the ammunition selector dial to the "Load" position. This is useful when determining if there is an imminent need to replenish the autoloader carousel. The ammunition indicator only goes up to eleven, so if the number of rounds for any ammunition type exceeds eleven, the exact number of rounds can only be determined by finding out the number of rounds of the other ammunition types and the number of empty slots in the carousel.<br />
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Besides the autoloader controls, there is also a turret azimuth indicator, installed just next to the manual turret traverse handwheel. It is a part of the horizontal turret drive mechanism.<br />
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The indicator is akin to a clock, with an hour hand and a minute hand. The hour hand is mainly a tool of convenience as it shows the direction the turret is pointing to, but it is also an important tool for laying the gun for indirect fire. The minute hand is read with the hour hand to obtain a precise reading of the orientation of the turret for indirect fire purposes.<br />
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<span style="font-size: large;">SIGHTING COMPLEXES</span></h3>
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Initially, the T-72 Ural was equipped with the same TPD-2-49 sighting complex as the T-64A obr. 1972 and as such, its technical-tactical characteristics were practically identical in this aspect. However, due to a combination of technical and bureaucratic issues, the T-72 did not receive the latest sighting equipment after its debut in the Soviet Army.
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<span style="font-size: large;">T-72 "Ural"</span></h3>
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<span style="font-size: large;"><b>TPD-2-49</b></span></h3>
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The T-72 first entered service in 1973 equipped with the TPD-2-49 sighting complex. This was the most modern sighting complex available in the USSR at the time having just entered service one year prior as one of the new elements of the T-64A obr. 1972. The TPD-2-49 was developed from the TPD-43B, being nothing more than an improved modification given a -2 suffix. The sight itself is quite large. It weighs 60.5 kg and has dimensions of 500 x 705 x 300mm (H x L x W). It is a periscopic sight with an integral optical coincidence rangefinder with an optical base length of 1,500mm. The periscopic height (distance from eyepiece to aperture window) is 155mm, and the vertical offset of the aperture window relative to the bore axis of the main gun is 306mm.</div><div><br /></div><div>The sight is independently stabilized in the vertical plane and it has a large independent vertical range of motion of -15 degrees to +25 degrees. The minimum speed of vertical laying is no more than 0.05 degrees per second and the maximum is no less than 3.5 degrees per second. The internal gyroscope is installed at the far end of the sight housing, in a protruding block underneath the sight aperture. The head mirror of the sight is mechanically coupled to the cage of the gyroscope rotor, and stabilization is achieved by the high rigidity of the gyroscope against disturbances. Control of the elevation angle of the sight is done by moving the cage of the gyroscope to adjust its frame of reference, against which it will maintain its stability. The vertical stabilizer of the main gun is slaved to the sight via a rotary sensor on the cage. The accuracy of stabilization, defined as the maximum amplitude of oscillations within the range of stabilized vertical motion, is nominally rated at 1' and 8 seconds, or 0.336 mils. Based on the accuracy of the 2E28M gun stabilizer being rated at a tank speed of 35 km/h on "medium" cross-country terrain, it is likely that this accuracy of stabilization was also rated at 35 km/h under the same terrain conditions.</div><div><br /></div><div>
The sight assembly is mounted to the roof of the turret by a single large bolt. The load-bearing suspension elements of the sight are protected by shock-dampening bushings. The armoured nut holding the sight assembly to the turret roof is behind the armoured housing for the sight aperture, as you can see in the two photos below (from <a href="https://www.facebook.com/media/set/?set=a.1652076908337757.1073741840.1441732669372183&type=3">T-72.org Facebook group</a>). The armoured nut has a diameter of 110mm.<br />
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Further protection is provided by a 50mm layer of anti-radiation lining known as "Podboi" attached to the turret ceiling, between the sight assembly and the turret roof. This thick lining acts as a spall liner.<br />
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<a href="http://2.bp.blogspot.com/-0Rml_KBr55s/VTaDg4D04jI/AAAAAAAACBc/Cs2SHXMr2tY/s1600/TPD-2-49%2Boptic%2Bport.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="262" src="https://2.bp.blogspot.com/-0Rml_KBr55s/VTaDg4D04jI/AAAAAAAACBc/Cs2SHXMr2tY/s400/TPD-2-49%2Boptic%2Bport.png" width="400" /></a></div>
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The sight has two eyepieces; left and right. The left eyepiece shows the viewfinder of the primary optic which is used as the service optic for target searching and aimed fire. The optic has a fixed 8x magnification with a field of view of 9 degrees. The exit pupil diameter of the eyepiece for the primary optic is 4mm. This is a common exit pupil diameter for daylight optical devices, and roughly corresponds to the pupil diameter of a young adult male in bright daylight conditions, but it is relatively small compared to the 5.5mm exit pupil diameter used in the standard telescopic day sights used on domestic towed artillery, which is a more ideal figure. The relatively small exit pupil diameter means that some loss of light can be expected in low light or bad weather conditions, where the pupil of the gunner would naturally expand to collect more light, creating a mismatch with the exit pupil diameter.</div><div><br /></div><div>An optical sight with an 8x magnification allows a tank-type target to be seen and identified from a range of 4.0-5.0 kilometers. This is shown in the table below from page 12 of the article "<i>Forging the Thunderbolt</i>" published in the January-February 1976 issue of Armor magazine. The range figures denote the range at which the respective targets are recognizable by the naked eye or when viewed through a magnified optic with 7-8 power magnification.<br />
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With an 8x optic, a T-72 gunner could theoretically see and identify tanks from beyond the maximum effective range of his main gun in optimal conditions, but this does not make much difference in practice. In theory, no magnification is needed because the human eye is good enough to see and identify a tank from 1.0-1.5 kilometers, but in reality, environmental factors tend to affect visibility and military targets are often covered by some form of camouflage. Tanks may also be in hull-down positions so that the size of their silhouettes may be half or less than half of their full size to an enemy observer. It is necessary to have a sufficiently high-powered optic so that even a hull-down tank can be identified from typical combat distances; an 8x magnification fulfills this requirement. Besides this, it is necessary to give the gunner the ability to exploit the full direct fire capability of the tank's main gun. For the 125mm gun of the T-72, the maximum direct fire range using HE-Frag shells is 5.0 kilometers. As seen in the table above, an 8x magnification allows a gunner to see various soft-skinned vehicles, armoured personnel carriers and wheeled vehicles from a distance of 5.0-6.0 kilometers, so this requirement is also fulfilled by the TPD-2-49.</div><div><br /></div><div>In terms of scanning capability, the TPD-2-49 offers an excellent field of view but is deficient relative to most sights that provide a low magnification view. In the context of field binoculars, which could be used for scanning a battlefield under the same circumstances, the TPD-2-49 sight has a wider field of view than most military field binoculars with an 8x magnification, providing an apparent field of view of 72 degrees, handily exceeding the internationally established 60-degree apparent field of view threshold to be considered a wide field of view device. With that in mind, the view through the sight is only negligibly more constrained than the view through the commander's TKN-3M device, which has a 10-degree field of view but only a 5x magnification for an apparent field of view of 50 degrees. It also exceeded the preceding TSh2 sight series, which had a 7x magnification and the same field of view of 9 degrees in the high magnification setting. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgriWBsOZVSaQnqqWaX3E2PvwoVnXeGhz6EH3CgLxYXp1oWiLnVhv7XvAUOrOKE2dKu7BygtaL3l8_YhWUC7LG3UQkh0ekOCvlIVfQpARREvzcMqkV9dWs8svbuSuR04RmuRT0g_pgN2YKVQ-J5frstEWTZfI3BA7tb2lNpK6DrL3WNvo_39YLq30r1xQ/s800/tpd%20drawing.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="651" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgriWBsOZVSaQnqqWaX3E2PvwoVnXeGhz6EH3CgLxYXp1oWiLnVhv7XvAUOrOKE2dKu7BygtaL3l8_YhWUC7LG3UQkh0ekOCvlIVfQpARREvzcMqkV9dWs8svbuSuR04RmuRT0g_pgN2YKVQ-J5frstEWTZfI3BA7tb2lNpK6DrL3WNvo_39YLq30r1xQ/w325-h400/tpd%20drawing.jpg" width="325" /></a></div><div><br />
<br />The ammunition type is automatically inputted into sighting system via the autoloader ammunition selection dial. As mentioned before, the dial was positioned on the turret wall on early T-72 Ural tanks, but otherwise, it is located below the eyepieces of the sight on all T-72 models. The sight has an integral electromechanical ballistic computer. Immediately upon selecting the desired ammunition type on the autoloader selector dial, the electric motors in the ballistic computer will engage the ballistic cam corresponding to the selected type and begin applying the ballistic solution. Alternatively, when operating in manual mode, the gunner can use the mechanical dial at the top of the sight housing to manually engage the ballistic cam of one of the three ammunition types, thus manually selecting the ammunition type in the sight but not in the autoloader. With the ballistic cam set, he can use the range adjustment wheel to perform range measurements and adjustments in an unpowered mode.</div><div><div><br /></div><div>Subsequent shots do not require the process to be repeated, even if the gunner changes ammunition types. All he must do is select a new ammunition type, and the sight will automatically adjust to the proper superelevation using the range information from the previous measurement by electromechanically selecting a different ballistic cam. </div>
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The primary viewfinder of the sight includes a ladder-type graduated scale for firing the PKT coaxial machine gun to a maximum range of 1,800 m, for firing HE-Frag shells to a maximum direct fire range of 5,000 m, and markings on either side of the center chevron for precise aiming in deflection (leading targets) and for simple rangefinding. The basic increment of the lateral mil scale (small dash) marks an angular width of 1 mil, while the space between a large dash and the closest chevron is 4 mils, and the space between two chevrons is 8 mils. Soviet mils are used. At the top of the viewfinder, there is a ready-to-fire signal lamp and two range wheels with separate range scales. The top range scale is for the coaxial machine gun and the bottom range scale is for the main gun, with automatic switching to match the selected ammunition type. A red light is illuminated above the dial when the fire control system is ready to fire.</div><div>
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<div><br /></div><div><br /></div>On the top of the viewfinder is the range indicator dial which displays the measured range to the target. The dial is limited to a maximum range of 4,000 m. Once the gunner has measured the range to the target, the range will be displayed here for the gunner's reference. </div><div><br /></div><div>Although the fire control system only functions out to a maximum direct fire range of 4,000 meters, aimed fire with HE-Frag shells can be done at 4,600 meters and 5,000 meters with the markings in the viewfinder. The range in the sight needs to be set to zero, and then the marks can be used to aim on the target. This may be used to engage targets at very long ranges, but only with the burst-on-target gunnery method, as HE-Frag shells lack a tracer. The reason for providing a partial ability to engage targets beyond 4,000 meters is unclear, particularly the rationale for providing only two range marks to do so. A maximum range of 4,000 m is sufficient for engaging all direct fire threats that the T-72 would likely face on the contemporary battlefield, including all ATGMs operated by the hypothetical enemy. Fire control systems of much later tanks also generally lack the ability to compute a ballistic solution beyond 4,000 m, for lack of a need. Prominent examples include the M1A2 Abrams, which has a laser rangefinder capable of ranging out to 8,000 m, but will not compute a ballistic solution for a range greater than 4,000 m.</div><div><br /></div><div>The second scale above the range scale is the range equivalence scale for the coaxial machine gun. It requires HEAT to be selected in the ballistic computer to function; there is no ballistic cam for the coaxial machine gun, so an existing cam is used as a surrogate and combined with the special range scale to obtain a ballistic solution. Indeed, the HEAT setting is actually referred to as the HEAT/MG setting in manuals for this reason, although it is not marked as such on the gunner's controls.</div><div><br /></div><div>The process is as follows: before or after measuring the range to the target, the gunner selects the HEAT setting (it does not matter if different ammunition is loaded in the gun, or if no ammunition is loaded at all), and then, noting the range figure displayed in the range scale, the gunner uses the manual range adjustment wheel to turn the range disc until the indicator needle rests on the same figure in the range equivalence scale. Because the trajectory of the PKT is much steeper than HEAT shells, this invariably means that the reticle is lowered much further for a given range. When done, the reticle would be lowered by the correct distance for the gunner to use the chevrons on the reticle to aim the coaxial machine gun. This method of aiming is much quicker than resetting the range to zero and using the ladder scale to aim if the gunner is also using or has the intent to use the main gun, because there is no way to quickly reset the range in the sight to zero in order to use the ladder scale. <br />
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In terms of the quality of the sight picture, the TPD-2-49 is excellent. It is quite similar to the M32 periscopic sight of the M60A1 in magnification, but it has a slightly larger field of view of 9 degrees instead of 8 degrees. The drawing on the left below shows the internal layout of the sight and the mechanical connections between it and the main gun, including the linkage between the optical base tube and the main gun. The drawing on the right shows the path of light entering the sight. The base tube of the rangefinder has a dependent stabilization system, but the image passes into the sight via the input window of the primary sight which is independently stabilized. According to the manual, the image from the secondary optic is exactly aligned with the primary optic, but mechanically, it is evident that the precision of alignment is dependent on the stabilization precision of the gun, which in turn is dependent on the speed of the tank and the roughness of the terrain. Moreover, because the base tube is stabilized via the gun and not the independent stabilizer of the sight, the gunner loses the ability to carry out rangefinding when the gun automatically elevates during a reloading cycle. As such, there are certain limitations to the number of opportunities available for the gunner to use the rangefinder. After a shot is fired, and a reload is initiated, corrections in elevation are best applied by the burst-on-target gunnery method rather than repeating the range measurement process.<br />
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The right eyepiece displays the rangefinder viewfinder that is split horizontally into two halves, incorporating the sight picture from both the primary optical channel and the secondary optical channel. This was accomplished by having the image from the rangefinder base tube enter the aperture mirror of the sight, after passing through two 90-degree reflector prisms to invert the reversed image. Like the primary optic, the secondary optic also has a fixed 8x magnification, but it has a much smaller field of view of only 2 degrees. The two optics each see the same target but with one half of the image blocked out by an internal shutter, and the gunner must use the range adjustment wheel above his control handles to line up both halves and obtain a seamless image.<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgj-ZcWuX3e7XrATdzwpyyRoC_i7wpV22MvXhNGcF36eOiF6WPhe6ghCE8gPZHenMq626d6HH9E2TN5HZ5D1sO9gCyUk4EabJOTqAJz1MFv1kVC2Fys2MpiIgGlwLHF1OC4CtN0ltAMYBziUXk0of6i2YILISpEgfwLg7zprfJR4kYvP8wUS3snBrdRyQ/s926/range%20adjustment%20wheel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="764" data-original-width="926" height="330" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgj-ZcWuX3e7XrATdzwpyyRoC_i7wpV22MvXhNGcF36eOiF6WPhe6ghCE8gPZHenMq626d6HH9E2TN5HZ5D1sO9gCyUk4EabJOTqAJz1MFv1kVC2Fys2MpiIgGlwLHF1OC4CtN0ltAMYBziUXk0of6i2YILISpEgfwLg7zprfJR4kYvP8wUS3snBrdRyQ/w400-h330/range%20adjustment%20wheel.png" width="400" /></a><a href="http://2.bp.blogspot.com/-ZpYh4GIvZQ4/VcBz8ZyJnLI/AAAAAAAADGU/qgWlHg-_KWk/s1600/t-72%2Bhand%2Bgrips%2Bknob.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="298" src="https://2.bp.blogspot.com/-ZpYh4GIvZQ4/VcBz8ZyJnLI/AAAAAAAADGU/qgWlHg-_KWk/s400/t-72%2Bhand%2Bgrips%2Bknob.png" width="400" /></a></div></div>
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Like all other optical coincidence rangefinders, this system determined the range to the target using trigonometry, as illustrated in the drawing below. The range information is converted to gun superelevation information using a mechanical ballistic computer. The cam for the ammunition type in the ballistic computer is changed by turning the rotary ammunition selector switch at the top of the sight, above the eyepiece.<br />
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The distance to the target, D, is calculated by dividing the base length of the rangefinder, B (1.5 meters), with the parallax angle, α.<br />
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For example, if the angle α is 0.05 degrees, then the range to the target is 1,719 meters. The larger the base length of the rangefinder, the more precise the measurement can be.<br />
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In practice, a trained gunner keeps both eyes open even when operating a monocular sight to reduce eye strain. As there are two eyepieces on the TPD-2 sight, both eyes may be used simultaneously during the entire engagement process, or if the gunner is right-eye dominant, he may begin by searching with his right eye on the left eyepiece and then put both eyes on both eyepieces when a target is acquired. Because both the primary and secondary optics have the same magnification and display the same image, the gunner is not disoriented when both images are superimposed. This is shown in the drawing below. Image (a) shows the view through the primary optic, image (б) shows the view through the right eyepiece, and image (в) shows the gunner's view when he uses both eyes to operate the sight.<br />
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To measure the range to a target, the two halves of the image must be aligned as shown in the drawing below.<br />
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The images below show the gunner's view when he is carrying out the rangefinding process with both eyes open. In the image on the left, the right drawing shows that the two halves of the tank target are not in alignment when the sight is set to a range of 1,500 meters (15). Because the image of the target from the secondary optic (top half) is offset to the right, the range to the target must be greater than 1,500 meters. When the range is adjusted to 1,800 meters (18), the two halves of the target are in alignment and the correct measurement is made. The image on the right shows the same, but with a tank in profile as the target.<br />
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<a href="https://1.bp.blogspot.com/-mp0s25xjGSE/XpO82xLuoGI/AAAAAAAAQlA/cWeb_X-a10o28Rx07jB1PyKfoClcmTAQQCLcBGAsYHQ/s1600/TPD-2-49_01.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="191" data-original-width="362" height="210" src="https://1.bp.blogspot.com/-mp0s25xjGSE/XpO82xLuoGI/AAAAAAAAQlA/cWeb_X-a10o28Rx07jB1PyKfoClcmTAQQCLcBGAsYHQ/s400/TPD-2-49_01.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-En9h_xnPWKM/XpO8Fy3BvDI/AAAAAAAAQk8/oRFAj7xNYjQZ3kVlNFLE7T9C4_Jy5JvlQCEwYBhgLKs0DAMBZVoBrhmC_uD9QzFXIwcFQBp4Xu437b9kwUeYJhDrxMdg7z_o8z31ohLSNRCtSHEPbGpioDmGodIr3IL9NGnY8CjUhoy5r5Oqrt3sK_MUpjZlQh8yEzaNvHwEHG2OPPvlYijjQzhs8iG2qYRTtFG_EBKX79IoNKa1TtxAEt6yPOpKXI9mhv6P_V4BD0gXepobE0Um-xFT-HXAy4rl-xm9ydDNr3yrR0bVukCl5m8YHf5iOzI-B6c0Wihi31UVYUDNWYRGGg1PRKEMKNOsPiH5J-N82RuYmpEMHz60jFQGUN1qbXfZvJxxIru1hpPvCzgkt2Wf3_ud-_QB_F6tLadmh25nS2tApiPGbfQOw9kwLdFHONdhWokuxHCyAsJDukmcHt0l1_MdrQC8Vwe2xjN5q1R3k-_HYMZZ7m7MAhJeqMx9Ac1JpLoaCMpO5H0D22kUVOcASjrHCXHnN1vuUhZ8OYphmK-C6tKV1yNftcCgsu_q5d0i5sBQFfxd6najEVlEc41CXRVeM_ANpGJ9nHhVNNSoIN0tkmOKR_dhbtsi8gwPPtVKFAjCpMOqNRUoqwirQ4276R1kENztOvuv_eBG-LCGJ48OytTOJIFgw0f3O9AU/s1600/rangefinding.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="342" data-original-width="652" height="208" src="https://1.bp.blogspot.com/-En9h_xnPWKM/XpO8Fy3BvDI/AAAAAAAAQk8/oRFAj7xNYjQZ3kVlNFLE7T9C4_Jy5JvlQCEwYBhgLKs0DAMBZVoBrhmC_uD9QzFXIwcFQBp4Xu437b9kwUeYJhDrxMdg7z_o8z31ohLSNRCtSHEPbGpioDmGodIr3IL9NGnY8CjUhoy5r5Oqrt3sK_MUpjZlQh8yEzaNvHwEHG2OPPvlYijjQzhs8iG2qYRTtFG_EBKX79IoNKa1TtxAEt6yPOpKXI9mhv6P_V4BD0gXepobE0Um-xFT-HXAy4rl-xm9ydDNr3yrR0bVukCl5m8YHf5iOzI-B6c0Wihi31UVYUDNWYRGGg1PRKEMKNOsPiH5J-N82RuYmpEMHz60jFQGUN1qbXfZvJxxIru1hpPvCzgkt2Wf3_ud-_QB_F6tLadmh25nS2tApiPGbfQOw9kwLdFHONdhWokuxHCyAsJDukmcHt0l1_MdrQC8Vwe2xjN5q1R3k-_HYMZZ7m7MAhJeqMx9Ac1JpLoaCMpO5H0D22kUVOcASjrHCXHnN1vuUhZ8OYphmK-C6tKV1yNftcCgsu_q5d0i5sBQFfxd6najEVlEc41CXRVeM_ANpGJ9nHhVNNSoIN0tkmOKR_dhbtsi8gwPPtVKFAjCpMOqNRUoqwirQ4276R1kENztOvuv_eBG-LCGJ48OytTOJIFgw0f3O9AU/s400/rangefinding.png" width="400" /></a></div>
<div><br /></div><div>The range to landmarks can also be measured in the same way.</div><div><br /></div><div style="text-align: center;"><a href="https://4.bp.blogspot.com/-jXYWUaeffa8/WoG-EtCMCMI/AAAAAAAAKzo/Bj-9i04UaeQBKHZMgwULYuFNodU3JtD6wCLcBGAs/s1600/rangefinding%2Btree%2Bstereo%2Brangefinder.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="545" data-original-width="1368" height="158" src="https://4.bp.blogspot.com/-jXYWUaeffa8/WoG-EtCMCMI/AAAAAAAAKzo/Bj-9i04UaeQBKHZMgwULYuFNodU3JtD6wCLcBGAs/s400/rangefinding%2Btree%2Bstereo%2Brangefinder.png" width="400" /></a></div>
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In case of low visibility from poor weather conditions or from enemy countermeasures, the rangefinder can be set to a secondary mode, where instead of splitting the target into two halves, two full images of the target are displayed on top of one another. There is a fixed vertical line at the left side of the viewfinder, and the gunner must lay the line on the edge of the target tank in the bottom image by using his control handles, then turn the range adjustment wheel until the same edge of the target tank in the top image touches the line. In other words, if the same part of the tanks in both images touch the vertical line, then the two images are aligned. This is shown in the diagram below.<br />
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This method tends to be less precise, but may be easier to use if the outline of the tank is not clear or if the target is not a tank but something with an irregular shape. Because the image of the target is not bifurcated, this method of coincidence rangefinding may also be preferable when ranging hull-down tanks, as the small height of a turret can impose great difficulty on the conventional method of ranging. Both techniques can be used to determine the range to terrain features like trees or man-made structures like telephone poles and buildings, thus enabling the tank to accurately engage infantry-type targets hiding in wooded areas and urban areas alike. Most importantly, this allows the tank to open fire at anti-tank missile teams at long range with reasonable accuracy. To switch the rangefinder to this mode of coincidence measurement, a lever on the right side of the sight housing is turned.</div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidyTq_77hz7qpqZTVAPescNlT7sdqQZgANMzzmKHjZY98yzJbZw3bVUIeon0MIapdCbAJ0IT6To0kPR1ppliY4XRKQS7cHYyDZrViu4VkYFvenIU88FbVsuBAyYHht1nZ2Yg9Trs0PGVIWl0a6DwKlkxQM8NMbq5y_Gxjtcr-z3AnmDV4kSJ0VTip06A/s949/select%20ranging%20method.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="949" data-original-width="874" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidyTq_77hz7qpqZTVAPescNlT7sdqQZgANMzzmKHjZY98yzJbZw3bVUIeon0MIapdCbAJ0IT6To0kPR1ppliY4XRKQS7cHYyDZrViu4VkYFvenIU88FbVsuBAyYHht1nZ2Yg9Trs0PGVIWl0a6DwKlkxQM8NMbq5y_Gxjtcr-z3AnmDV4kSJ0VTip06A/w369-h400/select%20ranging%20method.png" width="369" /></a></div><br />
In case of an emergency due to a breakdown of the coincidence ranging mechanism, it was possible to use the sight as a stereoscopic rangefinder where right eyepiece displayed the full image (without a split viewfinder) from the secondary optic and the gunner could measure the range by turning the range adjustment wheel until the image of the target in both the primary and secondary eyepieces were exactly superimposed. This feature was made a requirement during the development process of the sight as a compromise between the proponents of stereoscopic and coincidence rangefinders. The provision of the stereoscopic rangefinding mode may be the reason for the omission of a stadia rangefinder scale as a backup ranging option.<br />
<br />The rangefinder has an automatic range compensation mechanism for firing on the move known as a Delta-D system. The system is intended to subtract the distance covered by the tank after a range input when the tank is in motion relative to the target. The angular position of the target relative to the tank is determined by a cosine potentiometer. The speed of the tank is measured by a tachometer installed on the axle of the right idler wheel. The accuracy of the measurement can be degraded by track slip, which will vary depending on the terrain. From these inputs, the system subtracts from the range setting in the sight by rolling back the range dial and raising the sight reticle. The gunner must manually re-adjust his aim as the reticle moves.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xE8w37RB6s4/YDSmwquFVrI/AAAAAAAASxE/LVXxagzI1owI0_KecJvFb1rtf6s7D2vXwCLcBGAsYHQ/s742/delta%2Bd.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="742" data-original-width="660" height="320" src="https://1.bp.blogspot.com/-xE8w37RB6s4/YDSmwquFVrI/AAAAAAAASxE/LVXxagzI1owI0_KecJvFb1rtf6s7D2vXwCLcBGAsYHQ/s320/delta%2Bd.png" /></a></div><div><br />
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The technical manual for the TPD-2-49 sight states that the average range measurement error is 3% from 1,000 meters to 2,000 meters, 4% from 2,000 meters to 3,000 meters, and 5% from 3,000 meters to 4,000 meters. However, according to the document SW 82-10067 X titled "<i>The Soviet T-72 Tank Performance</i>" from the CIA, the rangefinding accuracy of the TPD-2-49 sight is actually slightly better than the Soviet figures suggest, although the figures in the table still align quite closely. It is possible that a difference exists due to slightly different measurement criteria.<br />
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This level of ranging precision was much higher than the M17 optical coincidence rangefinder of the M48 Patton. In page 121 of a British report WO 194-2946 with the title "<i><a href="https://tankandafvnews.com/wo-194-2946-a-technical-assessment-of-the-t-55/">A Technical Assessment of the T-55</a></i>", data from actual testing showed that for a "Patton coincidence rangefinder", the mean error in ranging tank-shaped screens, broadside tanks, oblique tanks, head-on tanks and hull-down tanks at distances of 970 meters to 2,520 meters is 6.65%. At the same distances against similar targets, the ranging errors from the TPD-2-49 would be 3-4% or 2.5-3.5% depending on the source. This is just half of the M17 rangefinder.<br />
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Compared to the M17A1 rangefinder in the M60A1, however, the TPD-2-49 has significantly lower ranging precision. According to a Soviet study of a captured Israeli M60A1, the median range error from 500 meters to 2,000 meters is only 1%. At 2,000 meters, the error margin is 1.25%, from 2,000 meters to 3,000 meters, the margin is only 2%, and at ranges above 3,000 meters (up to 4,400 meters), it is only 3%. This is 2 percentage points lower than the TPD-2-49 across all distances. The difference can be explained by the longer base length of the M17A1 rangefinder of 2,006mm, and the slightly higher 10x magnification might also have a small positive effect. M17A1 also has the advantage of having a shorter minimum measuring distance as well as a longer maximum measuring distance of 500 meters and 4,400 meters respectively due to the larger range of traverse of its objective prisms.<br />
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Although an error of a few percent seems small, it can make a significant difference when combined with the natural dispersion characteristics of the ammunition fired from the tank gun. If APFSDS rounds are fired, a ranging error of 2.5% is not a serious drawback when considering that the maximum tank engagement distance expected in Europe was only around 1,800 m, not to mention that the use of hypersonic APFSDS ammunition meant that the error margin was practically insignificant at closer ranges such as at the Fulda Gap where the maximum tank combat range did not exceed 800 meters since the ballistic trajectory was so flat. The problem was much more pronounced with HEAT and HE-Frag ammunition, which were heavier, experienced more aerodynamic drag and were launched out of the barrel at much lower velocities than APFSDS rounds. With the increasing proliferation of long range ATGM systems mounted on jeeps, scout cars, IFVs and even light tanks, the ability to deliver accurate long-distance fire with HEAT and HE-Frag shells was not a trivial matter.<br />
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An inherent shortcoming of optical coincidence rangefinders in general is that the accuracy of the measurement is noticeably degraded when the target is obscured by camouflage or inclement weather. To obtain the maximum image contrast, optical filters may be applied by the gunner. The main advantage of the TPD-2-49 over contemporary optical rangefinder sights is that it is stabilized. As long as the main gun is laid on the target, the gunner can carry out the rangefinding process while the tank is in motion.<br />
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Moreover, the independent stabilization of the sight worked in conjunction with the two-axis gun stabilizer to generate better accuracy. Like the advanced TPS1 sighting complex of the T-10A and T-10B heavy tanks and unlike the simpler "Meteor" stabilizer for the T-62, the vertical stabilizer of the cannon is slaved to the vertical stabilizer of the TPD-2-49, meaning that the vertical motion of the cannon is directly slaved to the stabilizer for the sight. Deviations in the angular position of the gun from the sight are detected with a resolver, which passes a feedback signal to the stabilizer which corrects the elevation angle of the gun until feedback is no longer received. On top of this, a fire gating system was implemented. This allows the system to achieve a higher accuracy as the system will only permit the gun to fire when the elevation angle of the gun is aligned with the sighting line, which has a more precise stabilizer than the gun and reflects the true point of aim dictated by the gunner. The much larger range of elevation of the independently stabilized sight also allows the gunner to maintain constant visual contact with the target as the tank and even engage it while the tank moves across undulating terrain, as the system will automatically fire the cannon when it is in the proper elevation angle as long as the gunner holds down the trigger button. </div><div><br /></div><div>This feature also allows the gunner to see a target from a turret-down position behind the crest of a hill or a specially prepared ditch, which can be useful in certain situations. The gunner can search for a target, acquire a ballistic solution, lay the reticle on the target and proceed to press and hold the trigger button. When the commander gives the order for the tank to move forward, the gun will eventually align with the point of aim of the sight as the tank crests the hill and the gun will automatically fire. This is the signal for the driver to immediately reverse the tank back into cover. This can reduce the time spent in a non-turret-down position, thus shortening the period of vulnerability.<br /></div><div><br /></div><div>When the stabilizer is turned off, the sight reverts to a dependent stabilization mode. The sighting line will raise and depress along with the gun via the parallelogram linkage.</div><div><br /><br />
TPD-2-49 placed the T-72 "Ural" on equal footing with the best NATO tanks at the time in terms of fire control sophistication, including the Leopard 1. Compared to the M60A1 and Chieftain, the T-72 fire control system was qualitatively superior by a large margin. As the optical coincidence rangefinder was integrated into the sight and the whole package was independently stabilized (which no other system could boast of at the time), the TPD-2-49 could be considered a rather advanced sighting complex, on par with the fire control system of the Leopard 1 and superior to the setup on the M60A1 which had a separate primary sight and M17A1 rangefinder. The commander of an M60A1 would search for a target through his M28C periscope with his seat raised by 4". When a target is spotted, the commander would have to lower his seat to the lowest position in order to conduct the rangefinding process through the eyepiece of the M17A1 and enter the range data, and only then would the gunner be able to use his primary sight to conduct final lay to engage the target. In a T-72, the gunner alone carried out the rangefinding process and the final lay with the TPD-2-49 sight, and the formation of the ballistic solution would be immediately presented in the viewfinder of his sight. This streamlined the entire process, so the reaction time of the tank between the moment of visual contact and the firing of the first shot was slashed accordingly.<br />
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However, as time went on, it became increasingly clear that optical rangefinders were no longer satisfactory, largely because it took a great deal of concentration from the gunner to operate, and in the case of the TPD-2-49, it was very expensive to manufacture an advanced independently stabilized sight with an integrated optical rangefinder. They were also relatively fragile despite extensive shockproofing and the use of anti-vibration bushings in the mounting points, mainly due to the immense transfer of energy involved when dealing with anti-tank weapons. Any misalignment as a result of shocks from tank shell impacts could cause some lens to be misaligned even slightly and that would be enough to put it out of commission for the duration of a battle, and this was a big problem with the T-72 (and indeed, every other tank with such a rangefinder) because an optical tube connecting the first aperture to the main sighting unit ran across the turret ceiling above the cannon breech block. A shell impacting the turret roof might bounce off and not penetrate the steeply sloped armour, but the strong shock of the impact and the shifting of the relatively soft and relatively thin cast steel roof could cause enough damage to the optical tube that it might no longer be usable. The thick rubber bushings on the optical tube can be seen in the photo below.<br />
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The location of the optical tube connecting the apertures of the two optics can be seen in the photos below (credit to <a href="http://t-72.de/alt/html/tpd-2-49.html">t-72.de</a>).<br />
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This, in addition to the issues mentioned above, meant that production of TPD-2-49 sighting complexes was summarily discontinued soon after the improved TPD-K1 sight was available and modernization programmes to refit T-72 "Ural"s with TPD-K1 laser rangefinding sights began after that. The TPD-2-49 continued to be installed on mass produced tanks until around 1977 and "Ural" turrets cast with the armoured protrusion for the aperture port of the coincidence rangefinder optic continued to be produced along side it. T-72 "Ural" tanks modernized with the TPD-K1 did not have the armoured protrusion removed, but the aperture port was blocked off and permanently welded shut. Some modernized T-72 "Ural" tanks had the armoured protrusion cut off the turret roof, such as the example in the two photos below. The weld seams for the armour blocks to seal off the gap in the roof from the missing armoured protrusion are visible.<br />
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<br />The sight is mounted to the turret at two points: the front of the sight housing is bolted to a bracket on the turret cheek with two bolts, damped with thick rubber bushings, and the top of the sight housing is suspended from the turret roof. The suspension point is damped with a rubber gasket and has a coil spring vibration damper. The image below shows the roof suspension assembly.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5KNTIAbwx181-J_zqrG3fasijAYkVt8bwVmKC64UWlMYVlWwnWb42K5ewkcvxJPFV1QCufV8M5xCZJYJauY_XyP3W12n0awwuXc4ugXByfrDYXJ42epZymcWR5Op7F32-fpzVXPYN7k1kAptDMs7x8YtzwgemGB-4u4g6VhsL-iESyLXcLn90MB0fCA/s2193/tpd-2-49%20roof%20mount.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2085" data-original-width="2193" height="304" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5KNTIAbwx181-J_zqrG3fasijAYkVt8bwVmKC64UWlMYVlWwnWb42K5ewkcvxJPFV1QCufV8M5xCZJYJauY_XyP3W12n0awwuXc4ugXByfrDYXJ42epZymcWR5Op7F32-fpzVXPYN7k1kAptDMs7x8YtzwgemGB-4u4g6VhsL-iESyLXcLn90MB0fCA/s320/tpd-2-49%20roof%20mount.png" width="320" /></a></div><div><br /><br />
The housing for the primary optic of the TPD-2-49 sight is armoured.<br />
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The thickness of the side, the top cover, the rear, and the front of the armoured housing is 30mm. Based on the thickness alone, the sight housing should have enough armour to guarantee protection from machine gun fire and airbursting artillery shells. A similar armoured housing was used on the T-72A and T-72B. However, due to the slope of the turret roof, the presence of a gap for the sight head creates a narrow weakened zone where there is minimal armour protection. This zone is highlighted in the drawing below. A projectile penetrating the sight head in this zone may potentially cause damage to the sight itself, which will require much more serious repairs. At best, the projectile may only penetrate into the 50mm anti-radiation lining for the turret roof directly behind the sight head. Of course, an anti-tank weapon with high penetration power will quite easily defeat the limited armour in this zone and potentially kill the gunner with a head wound, but due to the extremely short height of this weakened zone, there is a very low probability of hitting it. The most relevant threats for this particular weakened zone are armour-piercing bullets larger than the 12.7mm caliber.<br />
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The glass window of the sight aperture is protected by a layer of SET-5L ballistic glass (19mm thick) to protect the internal mirrors from bullets and shell splinters. The ballistic glass panel comes with an integral heating system to prevent fogging, and it is provided with a small external wiper to remove any debris or mud that might obstruct the gunner's vision. There is also a sheet steel hood over the sight housing window that shelters it rain and snow, or even mud thrown up during rough cross-country driving. The hood is shown below. Tank crews carry an extra sight head in internal stowage for quick field replacement. To replace a damaged sight head, the bolts on top of the armoured housing must be removed.<br />
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The glass windows of the sight housing and the housing of the rangefinder optic both feature aerosol and air jet cleaning systems. The sight housing window has both a high pressure aerosol cleaning system and a mechanical wiper that is manually actuated by the gunner via a small rod. The rangefinder optic window only has the aerosol cleaning system, lacking a wiper. The air bottle for this cleaning system is mounted to the autoloader carousel and is not connected to the pneumatic system of the tank, and is thus not automatically refilled by the air compressor. When depleted, it can be swapped with one of the two air bottles in the driver's compartment, which are refilled. The reservoir of cleaning fluid has a capacity of 2.2 liters.<br />
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The cleaning system has a bank of nozzles arrayed along the top of the window to blow away dirt and snow. The system sources its air from the tank's high pressure air bottles, which are also used for the driver's periscope cleaning system and for starting the engine.<br />
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<span style="font-size: large;">T-72 "Ural-1", T-72A (Early)</span></h3>
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<b style="font-size: x-large;">TPD-K1</b></h3>
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The TPD-K1 is a sighting system which consisted of the sight itself in addition to the internal electronic ballistic calculator and the sight-stabilizer interface, including the control handles which are integral to the sight. It was first installed as standard tank equipment in 1978 on the T-72 obr. 1978 (one of the models colloquially known under the "Ural-1" umbrella term) and was retrofitted on a large number of older "Ural" tanks as part of a modernization effort. The TPD-K1 was later carried over to the T-72A in 1979 and to the T-72B in 1985 in a modernized form. The TPD-K1 first appeared in a T-72 in early 1975 and ten tanks with the new sight rolled off the production line at the tail end of the same year.<br />
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Around the same time, the T-64B had already entered mass production in 1976 and featured a new and more advanced 1A33 fire control system along with a guided missile launching capability. The 1A33 paired with the "Kobra" missile system was tested in a single T-72 prototype in 1976-1977 but did not enter mass production. It is interesting to note that older models of the T-64A were later upgraded with the TPD-K1 only in 1981.
The Object 172M-1-E3 export variant of the T-72 is equivalent to the "Ural-1" model. This model is known simply as the T-72M and features a TPD-K1 paired with the cast monolithic steel turret of the original "Ural". It was used in various Warsaw Pact nations and in East Germany, as seen in the photo below.<br />
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The TPD-K1 sight is a modification of the TPD-2-49 and shares many components. The sight has a fixed 8x magnification and a <span class="st">field of view of 9 degrees, like the TPD-2-49. TPD-K1 placed the T-72 at the same level as its American nemesis the M60A1, which also received its own AN/VVG-2 laser rangefinder unit in 1978 as part of the M60A3 upgrade. German Leopard 1 tanks did not receive their own laser rangefinders until the 1980's rolled around.</span></div><div><br /></div><div>Without an optical coincidence rangefinder system installed, the optic tube that ran across the ceiling over the cannon breech block in the T-72 Ural is no longer present.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ZDOXUGBpV4I/Wbf6MU_DcYI/AAAAAAAAJYk/VUb8lc4cNfwURuBmDUC8kxgHLUxnRikgQCLcBGAs/s1600/t-72m1%2Btop%2Bof%2Bthe%2Bcannon%2Bbreech.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1366" height="358" src="https://1.bp.blogspot.com/-ZDOXUGBpV4I/Wbf6MU_DcYI/AAAAAAAAJYk/VUb8lc4cNfwURuBmDUC8kxgHLUxnRikgQCLcBGAs/s640/t-72m1%2Btop%2Bof%2Bthe%2Bcannon%2Bbreech.png" width="640" /></a></div><br />
<span class="st"><br /></span><span class="st">Being a modernization of the TPD-2-49 sighting complex, the 78% of the components of the TPD-K1 were unified with its predecessor. Features such as the Delta-D system were retained. The TPD-K1 is independently stabilized in the vertical plane and it has an internal gyroscope installed in the same location as the one in the TPD-2-49. The range of independent vertical elevation is from -15 to +25 degrees, and the vertical cannon stabilizer of the T-72 is slaved to the stabilizer of the TPD-K1 sight in the same way as discussed previously with the TPD-2-49.</span> Like its predecessor, the sight is not stabilized in the horizontal plane. This has implications that we will explore later. </div><div><br /></div><div><div>The accuracy of stabilization, defined as the maximum amplitude of oscillations of the line of sight, improved to 0.2 mils. Based on the accuracy of the 2E28M gun stabilizer being rated at a tank speed of 35 km/h on "medium" cross-country terrain, it is likely that this accuracy of stabilization was also rated at 35 km/h under the same terrain conditions. This enhanced the targeting and firing precision of the weapon system as well as the image quality available to the gunner when he is observing the battlefield from a moving tank. The image below shows the image resolution of a sight with a stabilization accuracy of 0.1, 0.2 and 0.3 mils when the observer is in motion. However, this is limited to showing the effect of the vibrational amplitude, which is what the accuracy of stabilization represents. The actual deterioration of image resolution with TPD-K1 may not directly correspond to the image below because vibrational frequency from the tank suspension also plays a large role. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-bIMobrup2XM/X83xMf2gy3I/AAAAAAAASQw/mHgSO8fEgfUCMP329emLsfjVmRQZUSs4wCLcBGAsYHQ/s1026/stabilization%2Bprecision%2B0.1%2B0.2%2B0.3%2Bmrad.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="514" data-original-width="1026" height="320" src="https://1.bp.blogspot.com/-bIMobrup2XM/X83xMf2gy3I/AAAAAAAASQw/mHgSO8fEgfUCMP329emLsfjVmRQZUSs4wCLcBGAsYHQ/w640-h320/stabilization%2Bprecision%2B0.1%2B0.2%2B0.3%2Bmrad.jpg" width="640" /></a></div><div><br /></div></div><div><br /></div><div>With the Johnson Resolution Criteria scale shown in the images as a reference, it can be determined that a stabilization accuracy of 0.2 mils is sufficient for level 1 (detection), level 2 (classification) and level 3 (recognition) observation of vehicles. Identification of the vehicle may only be possible when a distinct silhouette is presented.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-z1n5bMhu7BU/YBhKWMCVpBI/AAAAAAAASsg/qE0-H_gdcA0GDgHUoTbmsUzvymqRBjxpACLcBGAsYHQ/s1117/johnson%2Bresolution%2Bcriteria.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="700" data-original-width="1117" height="251" src="https://1.bp.blogspot.com/-z1n5bMhu7BU/YBhKWMCVpBI/AAAAAAAASsg/qE0-H_gdcA0GDgHUoTbmsUzvymqRBjxpACLcBGAsYHQ/w400-h251/johnson%2Bresolution%2Bcriteria.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The stabilizer system for the sight is connected to the cannon for angular referencing and to provide stabilization for the sight when the independent stabilization system of the sight is not used. The parallelogram-type mechanical linkages that connect the sight (left side) to the cannon (right side) can be seen in the photo below. This allows the sight to determine the orientation of the cannon relative to a reference point generated by its internal gyroscope (with three degrees of freedom) so that the fire control system only permits the gun to fire when the point of aim of the gun is aligned with the point of aim of the sight. This system is known as a firing gate. If the two systems were not in alignment, a firing inhibitor would be activated. This generated a level of firing accuracy proportional to the precision of the independent stabilization system of the sight instead of the precision of the much coarser weapons stabilizer. Furthermore, it is important to note that the use of parallelogram linkages resulted in a much higher level of precision in angular measurement compared to simpler push rods, reportedly 10-12 times more precise.<br />
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<br />According to the technical manual for the 2E28M stabilizer, the fire gating system requires the sight and gun to be aligned such that the divergence did not exceed ±0.5 mils, the same as the TPS1 sight with the "Uragan" stabilizer in a T-10A. Compared to more modern stabilizers, the fire gate of the TPD-K1 and the 2E28M stabilizer has rather large tolerances. For comparison, the later Cadillac Gage stabilizer of the M1 Abrams permitted firing only when the divergence did not exceed ±0.25 mils.</div><div><br /></div><div>Another advancement of the newer system, as present in the M1A2 Abrams, was the decreased divergence between the bore axis of the gun and the line of sight through the primary sight. In the T-72, equipped with a TPD-K1, the divergence is between 1.5' to 4.5', or 0.43-1.30 mils, whereas in the M1A2 Abrams <a href="https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2005/garm/wednesday/smith.pdf">it is only 0.75 mils</a>.</div><div><br /></div><div><br /></div><div><div>The ballistic computer in the TPD-2-49 and the TPD-K1 was calibrated to the standard conditions corresponding to the nominal values in the firing table. These conditions are:</div><div><ol><li>Barrel in a new condition with no wear</li><li>Propellant charge and ambient air temperature of 15°C;</li><li>Air pressure of 750 mmHg</li></ol><br />If the firing conditions differ from the normal ones given in the firing table, for which the sighting system is calibrated for at the factory, then the corresponding correction coefficient can be entered into the potentiometer of the ballistic computer. The correction coefficient is obtained using the two nomograms displayed on the side of the 125mm gun. The nomogram on the left calculates the correction coefficient with barrel wear and air temperature as variables. The nomogram on the right calculates the correction coefficient with air pressure and temperature as variables. </div><div><br /></div><div>The altitude of the tank above sea level is determined by the tank commander by referring to his map. The other variables require data to be relayed to the commander, obtained either by a meteorological survey unit or by measurements with personal devices. With this, the tank commander finds the correction coefficients on both nomograms and sums them up arithmetically. He then informs the gunner of the total correction coefficient, who can then enter it into the sight via the ballistic correction dial. The dial is a potentiometer, acting as a voltage regulator to the reticle superelevation signal generated by the mechanical ballistic computer of the sight. Effectively, the potentiometer acts as a dynamic analogue computer that calculates the virtual density from air pressure and temperature and the loss of projectile velocity from increased air resistance from colder air combined with gas leakage due to barrel wear.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-sU-b1IIXtYs/YD10atyRLEI/AAAAAAAAS08/nBdr2HfNKa0dpyF8uWDIkGQsLpD5roK1wCLcBGAsYHQ/s1929/barrel%2Bwear%2Band%2Btemperature%2Bnomogram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1929" data-original-width="1625" height="400" src="https://1.bp.blogspot.com/-sU-b1IIXtYs/YD10atyRLEI/AAAAAAAAS08/nBdr2HfNKa0dpyF8uWDIkGQsLpD5roK1wCLcBGAsYHQ/w338-h400/barrel%2Bwear%2Band%2Btemperature%2Bnomogram.png" width="338" /></a><a href="https://1.bp.blogspot.com/-e1IkckxFTxE/YD10al_S30I/AAAAAAAAS04/OVgNZbpZL7AIKF6Q0B8aZ9P8X7g8m_sogCLcBGAsYHQ/s1973/temperature%2Band%2Bpressure%2Bnomogram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1973" data-original-width="1421" height="400" src="https://1.bp.blogspot.com/-e1IkckxFTxE/YD10al_S30I/AAAAAAAAS04/OVgNZbpZL7AIKF6Q0B8aZ9P8X7g8m_sogCLcBGAsYHQ/w288-h400/temperature%2Band%2Bpressure%2Bnomogram.png" width="288" /></a></div><div><br /></div><div><br /></div><div>For example, using the nomogram on the left, an air temperature of -25°C and a barrel wear of 2.5mm corresponds to a correction of 3.4%. Using the nomogram on the right, an air temperature of -25°C and an pressure of 650 mmHg corresponds to a correction of -6.1%. Added together, the total correction coefficient is -2.7%. Positive corrections increase the required superelevation angle for a given ballistic solution, and vice versa. These corrections mainly affect the accuracy of HEAT and HE-Frag shells at long range, as they are much more sensitive to deviations from normal firing conditions.</div><div><br /></div><div>The same system of manual data entry for ballistic corrections is used on the M60A3 and M1 Abrams, as described in the Master Gunner's Corner of the May-June 1982 issue of ARMOR magazine. The only exception is that instead of a nomogram, separate pressure and temperature readings are entered. </div></div><div><br />
The armoured sight aperture housing on the turret roof is very similar to the one used on the TPD-2-49, but instead of a simple sheet steel hood, additional ballistic protected is afforded to the sight aperture by the presence of two armoured "ears". The armoured "ears" extend quite a long distance from the aperture itself and fulfill the same purpose as the armoured doors of modern sight housing designs. The TPD-2-49 lacks such doors, so the aperture is only protected by a layer of ballistic glass without the option to seal it with an armoured shield like the night vision sight on the tank. A sheet steel hood is bolted to the armoured "ears" to provide protection from the elements in the same way that the hood for the TPD-2-49 did, and to shield the sight window from air-dropped napalm. Beginning in 1984, the T-72A began to receive the "Nadboi" anti-radiation cladding on many of the external surfaces of the tank. The armoured housing of the sight also received a layer of "Nadboi" as did the sheet steel hood, as the photo below shows.<br />
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The thickness of the two armoured "ears" is 11mm and the thickness of the sheet steel hood is around 4mm, as shown in the photo below kindly supplied by Jarosław Wolski (measurement was done on a T-72M1). The same shroud from the TPD-2-49 housing to shelter the sight aperture from the elements. As you can see in the photo above (showing a T-72B), the armoured "ears" may help limit the damage done to the sight aperture if one of the Kontakt-1 explosive reactive armour boxes next to the sight housing are detonated. It is unclear if the hood is made from armour-grade steel or just simple mild steel.<br />
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The TPD-K1 alone is shown in the two photos below. Note the two distinct polarized halves of the sight aperture. The laser rangefinder emitter and receiver is installed in the right half (LHS in the photo) and the gunner's optical viewing channel is on the left half (RHS in the photo). Note that the TPD-K1 in the two photos below is being suspended from its top mounting point. The mounts for the TPD-K1 are the same as the TPD-2-49. <br />
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<a href="http://4.bp.blogspot.com/-isWPvlnzTL4/VRgvlhojNHI/AAAAAAAABiI/qNavhMA8jAg/s1600/tpd-k1_04_z4.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://4.bp.blogspot.com/-isWPvlnzTL4/VRgvlhojNHI/AAAAAAAABiI/qNavhMA8jAg/s1600/tpd-k1_04_z4.jpg" width="208" /></a> <a href="http://2.bp.blogspot.com/-9oCu_Cwsds4/VRgvkAyt4bI/AAAAAAAABiA/ybV1SW6_GCU/s1600/tpd-k1_01_z1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="311" src="https://2.bp.blogspot.com/-9oCu_Cwsds4/VRgvkAyt4bI/AAAAAAAABiA/ybV1SW6_GCU/s1600/tpd-k1_01_z1.jpg" width="320" /></a> </div>
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The TPD-K1 comes with an integral neodymium doped glass infrared laser rangefinder. The sight is slightly unusual in that the laser rangefinder is installed inside the sight itself on the right hand side of the housing, but the rangefinder computer is installed outside the sight. This is apparently due to the fact that the TPD-K1 is essentially a modified TPD-2-49 sight, so the laser computer is practically an add-on module. The range data is processed in the rangefinder computer as digital information, which is converted to an analogue signal before it is converted to mechanical gun superelevation information using the mechanical ballistic computer. The mechanical ballistic computer is the same as in the TPD-2-49. The rangefinder is activated by pressing the right thumb button on the gunner's control handles, while the left thumb button is used to dump the range data memory in the sight (reset sight to 0 distance). The rangefinder lases only once with each press of the rangefinder button, regardless of how long the button is held after it is initially pressed.<br />
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The two photos below show the detached rangefinder computer. It is a processing and readout unit, with a digital display on its control panel to indicate the range reading, rounded up to the nearest meter. When lasing a target, three laser pulses are emitted in quick succession. To process the range data, the laser rangefinder computer features the ability to filter out measurements by fixed range thresholds at the gunner's discretion.<br />
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The photo belows show the rangefinder computer attached to the right side of the TPD-K1 sight module. When fighting at night, it is possible to aim at targets using the night sight but lase the targets using the TPD-K1, and then manually read the range measurement on the digital display to apply a correction in the night sight. To use the range filter system of the rangefinder, there is a range filter toggle switch located at the bottom of the unit. It is used to filter out range measurements of less than 1,200 meters or 1,800 meters, and placing the toggle switch in the central position lets the system run normally. This is used suppress bad readings due to clutter or obstructions such as bushes and wooden fences. If the gunner suspects that the range data is incorrect based on his intuition or based on a quick measurement by the commander using his stadia rangefinder, then the gunner can either lase the target again or use the range filter to obtain a true reading.</div>
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According to the <a href="http://ofbindia.gov.in/products/data/optical/25.htm">Indian Ordnance Factories website</a>, the laser rangefinder uses an IR laser in the 1,060 nm wavelength.<br /></div><div><br /></div><div>The laser rangefinder has an RMS range error of 10 m at distances of 500 m to 3,000 m. This is equivalent to an error margin of 0.33%. From 3,000 m to 4,000 m, the RMS error is 15 m. The rangefinder may become unreliable at distances of more than 3,000 meters due to laser scattering, so it could be necessary for the gunner to manually dial in the range to the target by other methods. Combined with the natural dispersion of the ammunition, this limitation makes it infeasible to engage point targets at distances beyond 3,000 m, but firing HE-Frag shells at targets further than 3,000 m is not a serious issue.<br /><br />
The two photos below show a TPD-K1 with the mechanical linkages that connect the sight to the cannon. The photo on the right is partly dismantled, exposing the internal PCBs in the laser rangefinder computer. The large rear suspension point on the top of the sight housing is clearly visible in both photos, but the armoured cap is missing on the example in the photo on the right. The shock-damping bushing on the screw is visible in both photos. <br />
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The rangefinder computer has a digital display to show the measured distance, and range information is ported through to the range indicator dial on the top of the gunner's viewfinder, which is the main display method for the gunner, as he does not have to break visual contact with the target. However, reading the range is generally not necessary since the fire control system will automatically calculate a ballistic solution. To lase a target, the gunner must place the illuminated red circle over it and then press the lase button (the right thumb button on the control handles). Almost immediately, the digital readout on the rangefinder computer will display the range, and the electromechanical ballistic computer will begin to lower the reticle, producing the ballistic solution, while at the same time the range scale at the top spins to give a visual reference for the distance. A firing solution is generated within 1 to 3 seconds and the gunner can then proceed to lay the reticle on the target. If the target is mobile, it must be tracked within the boundaries of the red circle until the range is obtained. The rangefinder unit takes an average of 6 seconds to cool down between uses, but rapid lasing with an interval of 3 seconds is permitted for short periods.<br />
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Range information is automatically routed to the ballistic computer integral to the sight, and the sight adjusts the reticle accordingly via the ballistic cam corresponding to the setting on the ammunition selector dial. Aside from the electromechanical integration of the laser rangefinder, the TPD-K1 functions the same as the TPD-2-49 when engaging targets with the main gun. <br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj36bDmne8hqdd6ymS4bFUgEFVptALqToJIAXRfqne_Dd88SmCd12e_cUjOXKw5ikWXlZkYAgENoSU4w9ZQcyNzGhTi4IlvtgdRP1JXgo_MDAPAu08ag5zEe6pZm-AZx4_akQxrXT_1P31oWgeoUjc7ZIGsV9zyZ8Jmr3JtrOPqK1v_cEneEdvDpqGqVQ/s689/tpd-k1%20viewfinder.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="677" data-original-width="689" height="393" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj36bDmne8hqdd6ymS4bFUgEFVptALqToJIAXRfqne_Dd88SmCd12e_cUjOXKw5ikWXlZkYAgENoSU4w9ZQcyNzGhTi4IlvtgdRP1JXgo_MDAPAu08ag5zEe6pZm-AZx4_akQxrXT_1P31oWgeoUjc7ZIGsV9zyZ8Jmr3JtrOPqK1v_cEneEdvDpqGqVQ/w400-h393/tpd-k1%20viewfinder.png" width="400" /></a></div>
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The ranging procedure is quite normal in the realm of tank fire control systems, but one oversight is that the laser rangefinder is fixed to the sight housing and has its own aiming axis, rather than being merged into the same optical group for the visual system of the sight. The separation is on a structural level, with the sight head itself being divided into two halves, the right half for theemitter and receiver of the laser rangefinder, and the left half for the gunner's optical sight. This can be observed when boresighting, when the reticle is adjusted until coincidence is achieved with the point of aim of the gun bore, while the aim point of the laser rangefinder does not change. The reticle can be adjusted by ±9 mils horizontally and vertically for boresighting purposes.<br /><br />
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In case the laser rangefinder breaks down or is incapable of returning an accurate range measurement for whatever reason, the TPD-K1 has a backup stadiametric rangefinder with markings for distances of 500 meters to 4,000 meters. Together with the manual
gun laying mechanisms, this allows the gunner to continue engaging targets even if all fire control systems have completely lost power. The image on the right below shows an example of a range measurement with the stadia scale on a tank at arange of 1,500 meters. A stadia rangefinder was not needed as a backup in the TPD-2-49 because the optical rangefinder had no reliance on electrical power. </div>
<div class="separator" style="clear: both; text-align: left;"><a href="http://3.bp.blogspot.com/-gUvWvQI4d1w/VTPlSN_LXvI/AAAAAAAAB6o/8NUAuWW3qqI/s1600/tpd-k1.jpeg" style="margin-left: 1em; margin-right: 1em;"><br /></a><div style="text-align: center;"><a href="http://3.bp.blogspot.com/-gUvWvQI4d1w/VTPlSN_LXvI/AAAAAAAAB6o/8NUAuWW3qqI/s1600/tpd-k1.jpeg" style="margin-left: 1em; margin-right: 1em;"></a><a href="http://3.bp.blogspot.com/-gUvWvQI4d1w/VTPlSN_LXvI/AAAAAAAAB6o/8NUAuWW3qqI/s1600/tpd-k1.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://3.bp.blogspot.com/-gUvWvQI4d1w/VTPlSN_LXvI/AAAAAAAAB6o/8NUAuWW3qqI/w300-h400/tpd-k1.jpeg" width="300" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj2E6FNlMiDIbj5_qR40oSTGgYSlfzBHtS2k8mPVK0X1GFnxR6aVLegm6wyhTslYKNdPeJHSI-FPTOEAXTx2-5EGebTZeC1MqVv4T1OwHVXQqIx4nmEFsa7r17H657AThAcS9ZvWJ58O-iMN1vGKLmJnX36yknnlexXWlvGnCLnZhRZjuMLp1W6rVklLw/s1080/t-62%20through%20tpd-k1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1080" data-original-width="810" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj2E6FNlMiDIbj5_qR40oSTGgYSlfzBHtS2k8mPVK0X1GFnxR6aVLegm6wyhTslYKNdPeJHSI-FPTOEAXTx2-5EGebTZeC1MqVv4T1OwHVXQqIx4nmEFsa7r17H657AThAcS9ZvWJ58O-iMN1vGKLmJnX36yknnlexXWlvGnCLnZhRZjuMLp1W6rVklLw/w300-h400/t-62%20through%20tpd-k1.jpg" width="300" /></a><br /></div></div></div>
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The viewfinder markings can be illuminated by an internal lamp for cloudy weather or when fighting in low light conditions.<br />
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The reticle of the sight includes a ladder-type graduated scale for firing the PKT coaxial machine gun to a maximum range of 1,800 m, for firing HE-Frag shells to a maximum direct fire range of 5,000 m, and markings on either side of the center chevron for manually applying lead on moving targets or for wind deflection corrections. On the top of the viewfinder is the range indicator dial which displays the measured range to the target. The dial is limited to a maximum range of 4,000 m. Once the gunner has lased the target, the range will be displayed here for the gunner's reference. </div><div><br /></div><div>Thanks to the use of digital data storage, it became possible to reset the range setting in the sight to zero at the press of the left thumb button on the gunner's control handles. With this feature, the range equivalence scale for the coaxial machine gun on the rotating range disc was removed, and the method for accurately engaging targets with the coaxial machine gun was somewhat simplified compared to the system used on the TPD-2-49. After measuring the range to the target, the gunner notes the range by either referring to the range disc or the digital display on the laser rangefinder computer, and then he resets the range to zero. Then, he uses the range ladder scale to lay onto target and fire. The advantage of this simplification is that the gunner does not have to use the range adjustment wheel to manually set the position of the reticle according to the machine gun range equivalence scale, or return it to the zero position. However, the downside is that if the gunner needs to keep the range setting in the sight for some reason, the machine gun would have to be aimed by observing the tracers. There are no markings for distances below 50 meters, so the gunner must aim entirely using tracers when engaging targets at very short ranges.<br />
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<a href="https://3.bp.blogspot.com/-80F8vewNE8o/WEvi8DntP4I/AAAAAAAAH0A/4D3iJL1u7gAj6ytnV3n6U8mwI87mLbw7gCLcB/s1600/tpd-k1%2Bsight.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="478" src="https://3.bp.blogspot.com/-80F8vewNE8o/WEvi8DntP4I/AAAAAAAAH0A/4D3iJL1u7gAj6ytnV3n6U8mwI87mLbw7gCLcB/s640/tpd-k1%2Bsight.jpg" width="640" /></a><br />
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As mentioned before, target leading is done manually by using the markings on either side of the center chevron. The gunner must estimate the lateral speed of the target by determining how long it takes for the target to move from the center chevron across the lead markings, and combine that information with the time of flight of the selected ammunition type to the measured range. Needless to say, this was not easy unless the gunner was experienced, and even so, the accuracy of manual lead estimation is invariably lower than an automatically computed lead solution. However, the significance of this deficiency against moving tank-type targets is counteracted by the immense speed (~1,800 m/s) of the APFSDS rounds fired by the T-72. At short ranges, the acceptable margin of error for lead with APFSDS rounds is very large, so it is quite forgiving to less experienced or less well-trained gunners.
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The inputted ammunition type is indicated by one of three coloured signal lamps at the top left corner of the sight. If the fire control system is being operated manually or in a degraded mode, the sight can be set to the desired ammunition type by turning the dial next to the signal lamps. Otherwise, the ammunition type is automatically inputted.<br />
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The ballistic computer in the sight is able to account for the ambient temperature, gun chamber or ammunition charge temperature, atmospheric pressure, and barrel wear. These values are calculated using a nomogram printed on the recoil guard on the commander's side and manually entered into the sight via a potentiometer dial on the upper right corner of the TPD-K1. Along with range data, this amounts to six variables. Due to the lack of sensor equipment to automatically detect environmental factors, this can only be done prior to a combat mission. It is not feasible to dynamically input corrections during combat.<br /><br /></div><div>As with the TPD-2-49, the TPD-K1 was also fitted with an aerosol periscope head window cleaner. The system differs in that the sight lacks a second optic port for the coincidence rangefinder, and as such, there is only one aerosol sprayer for the main sight. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-McHEzW8OxYY/YBOr-fMu-cI/AAAAAAAASpU/xtDA4zVetOASn604dpUy3BbUJUEOaLEiACLcBGAsYHQ/s2048/gunners%2Bsight%2Bcleaner.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1654" height="400" src="https://1.bp.blogspot.com/-McHEzW8OxYY/YBOr-fMu-cI/AAAAAAAASpU/xtDA4zVetOASn604dpUy3BbUJUEOaLEiACLcBGAsYHQ/w323-h400/gunners%2Bsight%2Bcleaner.png" width="323" /></a></div><br /><div><br /></div>
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<h3>
<span style="font-size: large;">T-72A, T-72B</span></h3>
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<a href="https://www.blogger.com/null" id="1a40-1"></a>
<span style="font-size: large;">1A40, 1A40-1 Sighting Complex</span></h3>
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The TPD-K1 sight, originally considered a piecemeal sighting unit, was later reclassified as the primary sight of the 1A40 sighting complex. The 1A40 sighting complex consists of the TPD-K1 sight and either the TPN1-49 or TPN3-49 night sight. If the 1K13-49 sight with the 9K120 "Svir" missile control system is installed, the fire control system is designated as the 1A40-1. In conjunction with this reclassification, the TPD-K1 received some small improvements related to the fire control system, the most notable of which is the new add-on lead calculator. The laser rangefinder was also improved in some way to permit shorter cooldown periods between lasings. According to Mikhail Baryatinsky, the T-72A received the 1A40 beginning in 1982, and the 1A40-1 came standard on the T-72B since its formal introduction in 1985. The T-72B1, lacking an ATGM capability, was fitted with the 1A40. 1A40 or 1A40-1 systems fitted to T-72BA tanks differ by the implementation of additional ballistic corrections using data collected by an external wind sensor and by a cant sensor. </div><div><br /></div><div>
It is important to note that the reclassification of the sight from TPD-K1 to 1A40-1 was not trivial. With the implementation of the ATGM guidance system, special changes were needed in the behaviour of the stabilizer, and as the gunner's control handles are integral to the TPD-K1 sight, the sight itself received a new electrical socket to connect to the missile control box. <br />
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The 1A40 sighting complex includes an additional eyepiece for the gunner's left eye for the UVBU lead calculation system. UVBU stands for "lateral lead generation device". The UVBU is an add-on system that brings the capabilities of the fire control system to a more modern level. The electronic calculator of the UVBU system is a separate unit that interfaces with the stabilizer, the gunner's control handles, the fire gating system, and the Delta-D mechanism.</div><div><br /></div><div>The primary function of the UVBU is to calculate the lead for a moving target based on the tracking rate of the turret, the selected ammunition type, meteorological corrections and barrel wear compensation entered manually by the gunner, and cant (roll angle). Cant calculation is only provided if the tank is stationary. The cant calculation functions up to a roll angle limit of 15 degrees. </div><div><br /></div><div>The input for the angular tracking rate is the control signal from the gunner's control handles, not the rotation of the turret itself. As such, the target leading function of the UVBU system can be used while the tank is on the move, as it is unaffected by the counter-rotation of the stabilized turret from changes in the orientation of the hull.</div><div><br /></div><div>If a meteorological sensor is fitted, the UVBU system also takes crosswind deflection into account in its lead calculation. When engaging a moving target, the UVBU system calculates the necessary amount of lead and displays it in figures which can be manually applied by the gunner on the lateral scale in the TPD-K1 sight viewfinder. For T-72BA tanks, when a stationary tank on a side slope lases a target, the required lateral correction to account for lead, cant and crosswind will be displayed. The indicator unit, shown below, is comprised of a clamp, the eyepiece, and the connector that is plugged into the TPD-K1.</div><div>
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The lead calculation system works by taking the tracking rate as the gunner is lasing the target, combining it with the ballistic data of the selected ammunition, and then translating that information into an angular deflection value in mils, which is displayed in the eyepiece as a virtual projection at infinity. The gunner will then know which marking on the lateral mil scale on the reticle he should adopt as the new aiming point. The system will display the mil figure as a positive or negative fraction to denote which the side that the gunner must use (negative for the scale on the left of the center chevron and vice versa). The display will remain in the indicator as long as the rangefinder button is held. The use of an eyepiece rather than a separate digital display ensures that the gunner does not need to break visual contact with the target. As the UVBU eyepiece displays a number on an empty background, the gunner can keep both eyes open while operating the sight to see the number floating in his vision, read the necessary deflection figure and then apply it.<br />
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<br />The lead calculation system functions across the entire working range of the fire control system, from 500-4,000 meters. The limit of the displayed lateral correction is 31.5 mils in either direction, almost fully spanning the entire deflection scale, which is marked for 32 mils in either direction. The maximum angular speed of the moving target is 1 degree per second, which is equivalent to a crossing target moving at a speed of 32 km/h at a range of 500 meters, or a crossing target moving at 251 km/h at a range of 4,000 meters. Thus, the leading system technically permits the gunner to engage relatively low speed, low-flying aircraft such as helicopters. The precision of the UVBU unit is not particularly high compared to the systems employed in more advanced fire control systems as it can only display a difference in the angular velocity of the target compared to the tank in increments of 0.5 mils (0.53 milliradians or 1.8 minutes of angle). This is partly because the graduated lateral correction scale in the sight viewfinder is in increments of 1 mil, and the gunner can only be expected to use the midpoint between increments as the aiming point, so smaller divisions are not feasible. The low precision of this method of lateral compensation has a negative effects on the hit probability at long ranges. Moreover, the semi-automatic nature of the system means that human error (primarily in the chosen point of aim) contributes more to the total error. The system is generally inferior to the lead compensation mechanisms of contemporary fire control systems for long range shooting against moving targets, especially with lower velocity ammunition like HEAT and HE-Frag. </div><div><br /></div><div>Other than that, the most serious drawback is the lack of automation. In the fire control system of an M60A3, for instance, lead for a moving target is calculated and automatically applied to the reticle by the ballistic computer after the target is lased, meaning that the reticle automatically adjusts horizontally so that the reticle has already compensated for lead. This allows the gunner of an M60A3 to press the trigger immediately after lasing as long as he continues to track the target with the reticle - no need to adjust the aiming point or use secondary markings to engage. This is faster than the system employed on the TPD-K1. This is an inherent flaw in the sight itself as it cannot automatically adjust the reticle for lead since it lacks independent horizontal stabilization and there is no provision for the horizontal displacement of the reticle in the viewfinder of the sight. While it may have been considered an innovative feature for a sighting complex from the late 1960's, the UVBU leading system was somewhat crude for 1982 and could already be considered technologically obsolete at the time that it was introduced. By the time the T-72B entered mass production in 1985, the 1A40-1 sighting complex itself could be considered outdated. The TPD-K1 is shown in the two photos below.<br />
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<div>Beginning in August 1989, the gun on T-72B tanks may be boresighted from inside the tank using the UVKV device, added to the 1A40 fire control system. The system requires that a 2A46M or 2A46M5 gun is installed. UVKV stands for "built alignment control device". It is a add-on device fitted to the armoured housing of the sight, just in front of the periscopic head of the TPD-K1 sight. It consists of an optical assembly containing a fixed lens group and a hinged, spring-loaded prism, with a pullcord to lower the prism over the aperture of the sight. </div><div><br /></div><div><div>The focal distance of the objective lens is 5,600mm, which is the distance between the sight and the muzzle of the gun. The boresighting notch will therefore be in focus, while the barrel and background will be out of focus. The view through the UVKV lens is restricted to 4.25 degrees. The gunner will therefore see the same viewfinder markings, but a much narrower image than normal. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhB0FdmVULqpO85Td00ss67tdsPycYucN-FMVAVh98yjHP89YZbS8Av54NPpZe7qRtN7MouJ9_0D7o30L6x4ENqu5zpbGoZPHmwt6p-V3J81IXMM1me4FHxx2zwe_3GKkMPh7DiQejKs_rpDToRZfMclHyC4zzgxAi2_JxsJdzV3Gd33xqRmMRpCFMckQ/s6265/uvkv.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1561" data-original-width="6265" height="160" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhB0FdmVULqpO85Td00ss67tdsPycYucN-FMVAVh98yjHP89YZbS8Av54NPpZe7qRtN7MouJ9_0D7o30L6x4ENqu5zpbGoZPHmwt6p-V3J81IXMM1me4FHxx2zwe_3GKkMPh7DiQejKs_rpDToRZfMclHyC4zzgxAi2_JxsJdzV3Gd33xqRmMRpCFMckQ/w640-h160/uvkv.png" width="640" /></a></div></div><div><br /></div><div>To carry out the boresighting process, the gun is elevated to a specific angle (ostensibly to maximum elevation), and then, the gunner lowers the UVKV unit over the aperture window of the sight by pulling on the pullcord. The view from the sight is thereby redirected through the lens of the UVKV unit via a prism so that the gunner will see the muzzle of the main gun rather than looking parallel to the axis of the gun. Using the TPD-K1, the gunner checks if the reticle markings are aligned with the notch. This is shown in the images below. If not, the sight is no longer correctly zeroed, and the gunner must calibrate the sight to the gun using the adjustment knobs. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCrRh_z3Q-_ALIaHTJKsSciK68qLUW35k8R23qfUzql4dGqA1kH_Yz0DOHHIs6QkdE2P1_buGpkhROqwTZKX6PN3kBjEUWit4jqvANsnmtjEH6qG55sGtTHmjjgavvXihd0R6GKL9HT5liyOTv8_Rr-D_pyYrn_eBDzpXgAzA7DBg5cDRu49b-zR3HYw/s1909/uvkv%20boresighting.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1909" data-original-width="1553" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCrRh_z3Q-_ALIaHTJKsSciK68qLUW35k8R23qfUzql4dGqA1kH_Yz0DOHHIs6QkdE2P1_buGpkhROqwTZKX6PN3kBjEUWit4jqvANsnmtjEH6qG55sGtTHmjjgavvXihd0R6GKL9HT5liyOTv8_Rr-D_pyYrn_eBDzpXgAzA7DBg5cDRu49b-zR3HYw/s320/uvkv%20boresighting.png" width="260" /></a><a href="https://1.bp.blogspot.com/-NVGG_DdPcHU/X2doZdA2S-I/AAAAAAAARnw/zV1QLpNEhsUEqdU_F6RchAAu8r79tOkYQCLcBGAsYHQ/s807/boresighting.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="807" data-original-width="605" height="320" src="https://1.bp.blogspot.com/-NVGG_DdPcHU/X2doZdA2S-I/AAAAAAAARnw/zV1QLpNEhsUEqdU_F6RchAAu8r79tOkYQCLcBGAsYHQ/w240-h320/boresighting.png" width="240" /></a></div><div><br /></div><div>The full process nominally requires 1 minute. The system is a static type, providing only a boresighting function. In practice, it can also be used to compensate for barrel bending, but because the process is not instantaneous, it may not be practical to do so in combat conditions. The maximum permissible alignment error is 0.15 mils. This may be higher than a conventional MRS that uses a mirror on the gun muzzle and light collimation. This visual boresighting method is fundamentally analogous to boresighting using an MRS (muzzle reference system), using special notches at the muzzle of the barrel which are used as reference points rather than collimated light. This feature is also integrated to the 1A40-1 and 1A40-1M sighting complexes.</div><div><br /></div><div>The images below roughly illustrate the boresighting concept.</div><div><br /></div><div style="text-align: center;"><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-CQXkQtZFXB0/YBJV0GIACII/AAAAAAAASoI/YnZnNCuIjk8COcU6FZSPXFw43Kb_BA-ogCLcBGAsYHQ/s773/boresighting.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="591" data-original-width="773" height="306" src="https://1.bp.blogspot.com/-CQXkQtZFXB0/YBJV0GIACII/AAAAAAAASoI/YnZnNCuIjk8COcU6FZSPXFw43Kb_BA-ogCLcBGAsYHQ/w400-h306/boresighting.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh2srZFd5rZ3PLYW0VOcMaZ8BRRe4Y6uEcvRN2wrds_74QyQ62bRHf4RO6Bn3EVRVPvQIWt2Mlgw1GhYKdeO1PzmDC69Lf65y1hhRE2qSKZV2oMUXCf3QDNHVmkha-hwHOsN0tBlkdgbSzTCqQjqjBlNxYVHzjccVM8aLEb-OjWTNkMwvyltqRwNsSXVw/s744/boresighting%20uvkv.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="669" data-original-width="744" height="360" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh2srZFd5rZ3PLYW0VOcMaZ8BRRe4Y6uEcvRN2wrds_74QyQ62bRHf4RO6Bn3EVRVPvQIWt2Mlgw1GhYKdeO1PzmDC69Lf65y1hhRE2qSKZV2oMUXCf3QDNHVmkha-hwHOsN0tBlkdgbSzTCqQjqjBlNxYVHzjccVM8aLEb-OjWTNkMwvyltqRwNsSXVw/w400-h360/boresighting%20uvkv.png" width="400" /></a></div><div><br /></div><div></div>
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The updated TPD-K1 sight of the 1A40 or 1A40-1 system also differs from the basic TPD-K1 in the viewfinder. The main difference is the presence of mil values printed on the lateral correction chevrons for the gunner's reference in conjunction with the UVBU leading system. Otherwise, the viewfinder is essentially identical.<br />
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The photo below (credit to: <a href="http://ru-armor.livejournal.com/298636.html?title=%26quot;%D0%9A%D0%BE%D0%BD%D1%81%D0%B5%D1%80%D0%B2%D0%B0%26quot;&hashtags=%D0%A272,%D0%A7%D0%B5%D1%85%D0%B8%D1%8F,%D1%84%D0%BE%D1%82%D0%BE&text=%D0%9E%D1%80%D0%B8%D0%B3%D0%B8%D0%BD%D0%B0%D0%BB%20%D0%B2%D0%B7%D1%8F%D1%82%20%D1%83%20477768%20%D0%B2%20%20%26quot;%D0%9A%D0%BE%D0%BD%D1%81%D0%B5%D1%80%D0%B2%D0%B0%26quot;%20%D0%A7%D0%B5%D1%88%D1%81%D0%BA%D0%B8%D0%B5%20%D1%82%D0%B0%D0%BD%D0%BA%D0%B8%20%D0%A2-72%20%D0%BD%D0%B0%20%D0%BA%D0%BE%D0%BD%D1%81%D0%B5%D1%80%D0%B2%D0%B0%D1%86%D0%B8%D0%B8:">ru-armor.livejournal</a>) shows the markings more closely.<br />
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It is possible to use different shell models by simply twisting a dial on the UVP control unit, pictured below. Eleven distinct types can be selected from this unit. The UVP control unit was first used on the T-72B. It is installed under the linear acceleration sensor, mounted to the turret roof, in front of the commander (behind the TKN-3 if the cupola is facing forward).<br />
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<div><br /></div><div><br /></div>The initial selection of ammunition models available in the UVP unit by default is: </div><div><ol style="text-align: left;"><li>AP: BM9, BM12, BM15</li><li>HEAT: BK12, BK18</li><li>HE-Frag: OF19</li></ol>
<div>Ammunition models other than this basic set are entered as additional entries.</div><br />
The UVP unit allows the gunner to instantly reset the sights for different types of each category of ammunition. It is also possible for the T-72 to use "exotic" ammunition this way. For example, one of the blank spaces on the indicator card for HE-Frag (labelled OF in the photo above) can be filled for flechette rounds. The gunner can then toggle the sight for the HE-Frag ammunition type, and then cycle the HE-Frag dial on the UVP panel to the flechette slot.<br />
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<a href="https://www.blogger.com/null" id="aux"></a>
<span style="font-size: large;">NIGHT SIGHTS</span></h3>
<div><br /></div><div>An important tactical nuance of the sighting system is that the night sight and the day sight are almost completely independent systems. If the tank is denied its night fighting advantage by the enemy's use of illumination rounds to blind friendly forces, it is possible for the gunner to immediately switch to the day sight. Similarly, the commander can switch to the daylight mode on his TKN-3M by simply flipping a switch. This is a capability that was carried over from preceding tanks, and is shared with certain foreign counterparts such as the M60A1 series. </div><div><br /></div><div>Other tanks, such as the Chieftain and Leopard 1, were not capable of switching between sights on the fly. The Leopard 1 permitted the commander to swap out his forward-facing periscope for an IR or passive night vision sight, but gave no sighting equipment for the gunner. The Chieftain allowed both the gunner and commander to swap out their day sights for an IR night vision sight, but according to historian and former Chieftain crewman Rob Griffin, this required a relatively lengthy boresighting and recalibration process, which would have to be repeated when swapping back the night sights for day sights. Needless to say, this is entirely unfeasible during combat.</div><div><br /></div><div><br /></div>
<a href="https://www.blogger.com/null" id="tpn"></a>
<h3>
<span style="font-size: large;">T-72, T-72A (Early)</span></h3>
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<span style="font-size: large;">TPN-1-49-23</span></h3>
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The TPN-1-49-23 is the gunner's night sight in the T-72 Ural and its variants, as well as almost all exported T-72 variants with the exception of the T-72S. It is a 1st generation night vision device that primarily relies on IR illumination, and has a secondary passive vision capability. The TPN-1 utilizes a single S-1 photocathode held at 18 kV.</div><div><br /></div><div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-gKe-mXYOQb8/XzwgqGpv1TI/AAAAAAAARfM/Sjw2mvoAMMc78Q-ItNmPecOE6Cc_1ADywCLcBGAsYHQ/s1455/tpn1%2Bcross%2Bsection.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1455" data-original-width="1431" height="400" src="https://1.bp.blogspot.com/-gKe-mXYOQb8/XzwgqGpv1TI/AAAAAAAARfM/Sjw2mvoAMMc78Q-ItNmPecOE6Cc_1ADywCLcBGAsYHQ/w393-h400/tpn1%2Bcross%2Bsection.png" width="393" /></a><a href="https://1.bp.blogspot.com/-LtJPaGqS5Ko/XzwgqFok75I/AAAAAAAARfQ/xx31gO0rlMsUDfiUNt2t_U5YHLmopXqRwCLcBGAsYHQ/s1340/tpn1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1340" data-original-width="1339" height="400" src="https://1.bp.blogspot.com/-LtJPaGqS5Ko/XzwgqFok75I/AAAAAAAARfQ/xx31gO0rlMsUDfiUNt2t_U5YHLmopXqRwCLcBGAsYHQ/w400-h400/tpn1.png" width="400" /></a></div><div><br /></div></div><div><br /></div><div>The sight has a fixed magnification of 5.5x and a field of view of 6 degrees. For comparison, the night sight of the Chieftain had a 3x magnification and a field of view of 14.3 degrees. The TPN-1-49-23 can be used in the passive image intensification mode, relying on ambient light in the nevironment, or in the active infrared imaging mode, whereby infrared light emitted from the L-2AG "Luna-2" IR spotlight is used to illuminate the target. The "Luna-2" spotlight is mounted coaxially to the main gun so that all three devices - sights, cannon and spotlight - are adequately aligned. Like the commander's OU-3GA2 spotlight, the "Luna-2" spotlight uses an incandescent lamp with a IR filter fitted in front of the bulb. Removing the filter transforms the IR spotlight into a regular white light spotlight. </div><div><br /></div><div>Unlike the L-2 spotlight on the T-54, T-55 and T-62 series, the spotlight on the T-72 was not installed on a raised bracket, being instead fitted well below the turret roof line. This was necessary because the commander was no longer seated on the same side of the turret as the gunner as on the preceding medium tank series, so it was no longer feasible to have the spotlight mounted at the same height as the night sight. Doing so would block the commander's forward vision, which would be completely unacceptable. It was of particular importance for the T-72 because the commander's TKN-3M periscope could depress by -8 degrees, more than what was possible in previous tanks. The only major implication of the new spotlight location is that the gunner cannot use the spotlight for illumination when scanning for targets in a turret defilade position with the TPN-1 sight peeking over cover, leaving only the commander with this capability. The image on the left below shows the bore axis offsets for all sights, spotlights and weapons on the turret relative to the main gun.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiLqLAZvN-1rp_R_qN0j730U15JIr14EuDw8P_sxxJsAzfWPrORcQ2BVOPRg86JYUP1eY4qppp9V64-EPDLHKKQFZOHPyEKKeY7swZ6qA9nP-FM0Whowmkj1WJ14nQAzH85ODpbZykjUsJN_fsIae9NVqOW-ISmSB4IDzbYspkR78bma5We53t6VxnLwQ/s1191/bore%20axis.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="664" data-original-width="1191" height="223" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiLqLAZvN-1rp_R_qN0j730U15JIr14EuDw8P_sxxJsAzfWPrORcQ2BVOPRg86JYUP1eY4qppp9V64-EPDLHKKQFZOHPyEKKeY7swZ6qA9nP-FM0Whowmkj1WJ14nQAzH85ODpbZykjUsJN_fsIae9NVqOW-ISmSB4IDzbYspkR78bma5We53t6VxnLwQ/w400-h223/bore%20axis.png" width="400" /></a><a href="https://1.bp.blogspot.com/-wn0UH5Kx3Bw/YTbB3fH_nmI/AAAAAAAAUKU/Eo7qSp5u5v0Od9Hmu_o7LAmNnMfduok8gCLcBGAsYHQ/s634/t-72%2B1976.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="449" data-original-width="634" height="227" src="https://1.bp.blogspot.com/-wn0UH5Kx3Bw/YTbB3fH_nmI/AAAAAAAAUKU/Eo7qSp5u5v0Od9Hmu_o7LAmNnMfduok8gCLcBGAsYHQ/s320/t-72%2B1976.png" width="320" /></a></div><div><br /></div><div><br /></div><div>As the gain from Cold War era S-1 photocathodes exceeded those of WWII vintage, Gen 0 devices were not completely blind without active illumination, although they still depended heavily upon infrared spotlights to obtain a useful viewing range. The degree of light amplification was sufficient for passive observation only under moonlight illumination or greater. </div><div>
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Like the main sight, the TPN-1-49-23 is protected by a square-shaped armoured housing, with a bolt-on steel cover for the aperture. Beside the aperture is a single fixed FG-125 infrared or white light headlight, which is used only as a driving light and not for the TPN-1-49-23.<br />
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The sight has a maximum viewing distance of 500-800 meters in the active mode using the "Luna-2" IR spotlight. The range of 800 meters is referring only to the detection range on a tank silhouette target, either a front-on view or a profile view.</div><div><br /></div><div>The maximum viewing distance of 800 meters is supported by the U.S Department of the Army Operator's Manual for the T-62, which notes on page 3-12 that the L-2G spotlight provides the gunner with ability to successfully engage targets at a range of 800 m. For comparison, the Chieftain had a maximum viewing range of 1,000 meters with its AFV No. 33 IR sight. This is likely due to its immensely powerful 2 kW spotlight with a large 570mm aperture, which should have greatly benefited the gunner in searching and engaging targets at longer ranges, compensating for the low 3x magnification of its sight.</div><div><br /></div><div>The M60A1 used the advanced AN/VSS-1 spotlight, featuring a motorized lens and occluder that enabled the gunner to remotely adjust beam width from 0.5-0.75 degrees in the narrow mode to 7 degrees in the wide mode as well as select between white light and infrared light on the fly. The AN/VSS-1 ran on 1 kW and had an output of 75 million candelas in the white light mode, or 25 million candelas in IR mode. Additionally, the M32 IR night sight installed in the M60A1 had an 8x magnification, giving the gunner better long range visibility.</div><div><br /></div><div>
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New passive night vision sight introduced in 1977 on the M60A1 Passive modernization offered better performance than the TPN-1 on the T-72, and towards the 1980's, large investments in thermal imaging technology in the U.S allowed them to completely leapfrog over the USSR in night fighting technology. This is best exemplified by the use of AN/VSG-2 thermal imaging sights in the M60A3 (TTS) in 1979. The T-72A was introduced in the same year, but most still had the same TPN-1-49-23 night sight, and only upgraded to the TPN-3-49 after some time into its production run, and only in small numbers.<br />
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Besides the general vulnerabilities associated with active infrared imaging systems, some countermeasures existed and were implemented on serial tanks, although these had rather limited success. One example is the infrared detector stalks used on Chieftain tanks, which was of extremely dubious utility. In the words of Rob Griffin on page 71 of his book "<i>Chieftain Main Battle Tank: Development And Active Service From Prototype To Mk.11 (Part 2)</i>" - In theory it was an excellent idea but in practice it was a dismal failure. False positives from ambient light were extremely frequent and as such, most troops would dismount the stalk and either leave it in a tool bin or back in the troop stores at the barracks unless the night combat exercise specifically focused on training crews in the use of the infrared detection equipment. It would be mounted on the tank for photo shoots and demonstrations to dignitaries and officials, of course.<br />
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Due to the short range of vision, the markings in the viewfinder of the TPN-1-49-23 are greatly simplified. All four ammunition types (including the coaxial machine gun) were represented on the markings, albeit not with complete exactness, but it was acceptable due to the short aiming distances expected. It's worth noting that the flat trajectory of subcaliber rounds like 3BM9 and 3BM15 made it infeasible to include them in the same set of markings as the other ammunition types, but their high muzzle velocity meant that it was fairly easy to hit a tank-sized target at short range anyway.<br />
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The end point of each line is an indicator for a certain distance for certain types of ammunition. A breakdown of the markings can be seen in the diagram below. This diagram is printed on an instruction panel on the sight itself, in case the gunner forgets the meaning of the markings in the heat of battle. As you can see in the diagram, the topmost point represents 100 meters for HE-Frag rounds, 200 meters for HEAT rounds and the coaxial machine gun, and 1,100 meters for subcaliber rounds. To fire subcaliber rounds at targets below 1,100 meters, the gunner would have to aim slightly above the topmost point. In practice, the topmost point serves as a battlesight mark, allowing the gunner to aim at the center of mass or the lower edge of a tank-sized target with a high probability of a hit at any range from 0 to 1,100 meters due to the flat trajectory of the shot.<br />
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<div><br /></div><div><br /></div>Engaging targets at long ranges is not fully supported by the sight, as the markings do not allow HEAT and HE-Frag to be fired accurately past 1,000 and 900 meters respectively. However, firing at extended ranges with APFSDS can be feasible using both battlesight gunnery techniques and precision gunnery. The latter is possible if the gunner uses the digital readout of the laser rangefinder of the TPD-K1 to obtain precise range readings. <br />
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It has been frequently noted in various websites that the T-72 can be distinguished from the T-64 by the change in position of the spotlight from the left side of the cannon to the right side. This change was not arbitrary; the spotlight was placed next to the coaxial machine gun port so that the driver was physically blocked from sticking his head out of the hatch and in front of the machine gun when driving the tank during road marches, and so that the driver does not have to be in front of the machine gun when entering and exiting his station.<br />
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The sight cannot be used in daytime, because sunlight will overload the sight unit and damage it, leading to premature failure. In accordance with this rule, the aperture has internal shutters linked to the firing trigger of the gunner's control handle. Upon firing, the shutters automatically close to shield the unit from the intense flash of cannon fire at night.<br />
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<a href="https://www.blogger.com/null" id="tpn3"></a>
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<h3>
<span style="font-size: large;">T-72A, T-72B1</span></h3>
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<span style="font-size: large;">TPN-3-49</span></h3>
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Officially, the T-72A obr. 1979 and all T-72B1 models were equipped with the TPN-3-49 night sight. The TPN-3-49 was used as a substitute for the 1K13-49 in the case of the T-72B1, and it exists as an upgrade over the TPN-1-49-23 for the T-72A. However, many T-72As and a few T-72B1 tanks still had the TPN-1-49-23 installed during the 1980's, presumably due to issues with the availability of the TPN-3-49. By that time, many of the tanks of the opposing forces were already equipped with thermal imaging sights, so attempting to use T-72 tanks stuck with the outdated TPN-1-49-23 in night combat against armoured units would probably be tantamount to suicide. Even infantry weapons like the TOW and Dragon had begun receiving the AN/TAS-4 and AN/TAS-5 thermal imaging sights respectively by 1978. In this context, the longer viewing range of the TPN-3-49 was not nearly enough for T-72 tanks to even approach parity in night fighting capabilities with the probable enemy.
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Like the TPN-1-49-23, the TPN-3-49 was mechanically linked to the main gun through a shaft passing through the TPD-K1 sight. The head mirror was thus vertically stabilized by the gun. The range of elevation of the sight was -6°13' degrees to +14°.</div><div><br /></div><div>
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The TPN-3-49 sight has a magnification of 5.5x and a field of view of 6°40'. TPN-3-49 is essentially a TPN-1 with a new photocathode. Structurally, the sight retained many of the key features and drawbacks of its predecessor, including a lack of independent stabilization. One of the improvements of the TPN-3-49 over the TPN-1-49-23 is the ability to switch between different viewfinder markings for different ammunition types, giving the gunner better aiming precision.<br />
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Instead of a single universal set of markings with predetermined aiming points, the TPN-3-49 features comprehensive range scales and a range dial for each type of ammunition.<br />
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The new night sight features a more sensitive electron-optical converter tube and amplifier system, giving the gunner a brighter and clearer image of higher resolution when using the sight in the active night vision mode. Another improvement came from the installation of the newer L-4A "Luna-4" spotlight, which is considerably more powerful than the older L-2AG "Luna-2" spotlight. The L-4 series uses a xenon arc lamp which is much brighter than the incandescent lamp of the L-2 series. The image intensifier in the TPN-3-49 is improved, but still belongs to the 1st Generation so the maximum viewing distance (identification of a tank) is only around 500-800 meters at an ambient light level of 0.005 to 0.01 lux. This is comparable to tthe M60A1 RISE Passive with the M32E1 passive sight, which allowed tanks to be identified from a distance of not less than 500 meters without illumination as stated in the report "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a141935.pdf"><i>M60A1, M60AI RISE, and M60A1 RISE (Passive) Series Tanks, Combat, Full-Tracked 105-MM Gun - Update System Assessment</i></a>". <br />
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The L-4A spotlight can be distinguished from the L-2AG by the location of the power supply cable socket. The socket on the L-2AG was located on the right side of the spotlight, but the socket on the L-4A is located at the back, as you can see in the photo on the right. The photo on the left shows an L-2AG.<br />
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Even without delving into thermal imaging technology, the night fighting capabilities of the T-72A were still rather limited. In terms of active infrared imaging, the T-72 was behind both the M60A1 and the Chieftain. </div><div><br /></div><div>The L-4A "Luna-4" spotlight is underwhelming in comparison to the AN/VSS-1, seeing as the spotlight ran on just 600 W and had an IR output of 30 million candelas - between three to five times less than the AN/VSS-1. Additionally, the beam width from "Luna" was fixed at around 1 degree horizontally and 0.8 degrees vertically, making it exceptionally difficult to search for targets across open terrain. Furthermore, the lack of an occluder, otherwise known as a blackout shield, in front of the xenon arc lamp in "Luna-4" meant that only a part of the light was directed from the concave reflector. The rest of the light was emitted in a forward arc, illuminating the tank itself as well as the ground in front of it, making the T-72 an extremely prominent target once the spotlight was activated.<br />
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Despite these drawbacks, the TPN-3-49 apparently allows a T-72A gunner to spot a target at a maximum range of 1,300 meters in the active infrared imaging mode. This is surprising when we consider the fact that the reported viewing distance for the gunner of a Chieftain Mark. 3 is only 1,000 meters, although that might be due to the relatively low 3x magnification of the Chieftain's No. 33 IR night sight.<br />
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<h3>
<a href="https://www.blogger.com/null" id="1k13"></a><span style="font-size: large;">T-72B</span></h3>
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<span style="font-size: large;">1K13-49</span></h3>
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<a href="http://3.bp.blogspot.com/-IeSkbEsrROY/Vl2eKYRrOqI/AAAAAAAAEhE/EtvG0IcnmfA/s1600/1k13-49.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="329" src="https://3.bp.blogspot.com/-IeSkbEsrROY/Vl2eKYRrOqI/AAAAAAAAEhE/EtvG0IcnmfA/s400/1k13-49.png" width="400" /></a></div>
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The 1K13-49 sight was created as the guidance control unit for the new 9K120 "Svir" laser-guided gun-launched missile system but continued fulfilling the function of a night vision sight, having improved night vision capabilities using technologies derived from the TPN-3-49. In 1984, a batch of 50 T-72A tanks were fitted with the sight and missile guidance system for troop trials. Within this batch, some were T-72AV tanks with the "Kvartz" turret and Kontakt-1 ERA, and some were T-72A tanks with an improved turret containing bulging plates (Object 184).</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-nmppoN2hu6A/Xx_wKDHl9PI/AAAAAAAARXw/l096MDeu3dYBWWcIwh8Rshw__MkslZsuwCLcBGAsYHQ/s1200/-72_113.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="854" data-original-width="1200" height="285" src="https://1.bp.blogspot.com/-nmppoN2hu6A/Xx_wKDHl9PI/AAAAAAAARXw/l096MDeu3dYBWWcIwh8Rshw__MkslZsuwCLcBGAsYHQ/w400-h285/-72_113.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-AYUN1wQPB9c/Xx_xML6CGQI/AAAAAAAARX4/zHJ4lJyx6r8_KsITt8adHRIptVFZdAjewCLcBGAsYHQ/s2048/t-72a.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1341" data-original-width="2048" height="263" src="https://1.bp.blogspot.com/-AYUN1wQPB9c/Xx_xML6CGQI/AAAAAAAARX4/zHJ4lJyx6r8_KsITt8adHRIptVFZdAjewCLcBGAsYHQ/w400-h263/t-72a.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>The electronic modulator and signal generator for the missile guidance system is in separate boxes located on other parts of the tank, but the laser emitter is installed inside the 1K13-49 sight itself. The system has an operating range of 100 m to 4,000 m. The 1K13-49 has the same functions as the 1G46 sighting complex and shares the same missile guidance technologies, but the 1K13-49 sight has lower magnification and has a reduced maximum range compared to the 5,000-meter range of the "Refleks" missile system used on the T-80U and later, the T-90. The first tanks that were assembled with the "Svir" missile system appeared in 1984 but the system only entered mass production in 1985 as an integral part of the T-72B tank. It was absent on the T-72B1 variant. The location of the "Svir" system components are shown in the drawing below.<br />
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<a href="https://1.bp.blogspot.com/-V4KRs5VKHmw/WwA3FIFJhZI/AAAAAAAALmI/ufu2AZjncmUIaIuEI9TWDpr11627W4hRwCLcBGAs/s1600/9k120%2Bsystem%2Bcomponents.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="865" data-original-width="1151" height="480" src="https://1.bp.blogspot.com/-V4KRs5VKHmw/WwA3FIFJhZI/AAAAAAAALmI/ufu2AZjncmUIaIuEI9TWDpr11627W4hRwCLcBGAs/s640/9k120%2Bsystem%2Bcomponents.png" width="640" /></a></div>
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The sight has a daytime channel that is normally used in conjunction with guided missiles, but having a daytime channel allows the 1K13-49 to be be used as a backup sight in case the TPD-K1 is non-functional. With a fixed 8x magnification in the daytime channel, the 1K13-49 can be an adequate replacement for the TPD-K1. According to the manual, the detection and identification range of static and moving targets with the 1K13-49 in the daytime channel is 5,000 meters. The relationship between the magnification power of an optical sight and the viewing distance has already been explored before, but it is worth repeating that a sight with an 8x magnification allows a tank-type target to be seen and identified from 4.0-5.0 kilometers. Based on this, it is obvious that an 8x magnification was not arbitrarily chosen. Rather, it was necessary to allow 9M119 guided missiles to be used effectively at their maximum range of 4.0 kilometers.<br />
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<a href="https://1.bp.blogspot.com/-KsejKDhh1lc/XhuAhR4YY3I/AAAAAAAAP4k/4NFIsegBPuc3aS8pO1nic_4vR7eCp48hwCLcBGAsYHQ/s1600/1k13%2Bhousing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1065" height="400" src="https://1.bp.blogspot.com/-KsejKDhh1lc/XhuAhR4YY3I/AAAAAAAAP4k/4NFIsegBPuc3aS8pO1nic_4vR7eCp48hwCLcBGAsYHQ/s400/1k13%2Bhousing.png" width="265" /></a></div>
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If the 1K13-49 sight is used as a backup to the TPD-K1, its drawbacks include a reduced field of view, the lack of a laser rangefinder and no proper range scales for different ammunition types. The gunner is forced to make the most of the simplified markings provided in the viewfinder, shown in the drawings below. An unusual feature of the sight is that the aiming mark is offset to the right of the viewfinder.<br />
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<a href="https://1.bp.blogspot.com/-cgQ_E3x_x4Q/XQ8LtnPNicI/AAAAAAAAOgM/41Y3m4RjJhwn9R-7-5TXFOGDQNgHRBiCQCLcBGAs/s1600/1k13%2Bdaytime%2Bchannel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="486" data-original-width="1600" height="194" src="https://1.bp.blogspot.com/-cgQ_E3x_x4Q/XQ8LtnPNicI/AAAAAAAAOgM/41Y3m4RjJhwn9R-7-5TXFOGDQNgHRBiCQCLcBGAs/s640/1k13%2Bdaytime%2Bchannel.png" width="640" /></a></div>
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The active infrared optoelectronic imaging system in the 1K13 sight is improved over the TPN-1 sight and is equivalent to the TPN-3. The target detection and identification range in the active mode with illumination from the L-4A spotlight is increased to 1,200 m. The passive mode has the same capabilities as the TPN-3, meaning that the 1K13-49 sight still only has an 500-800 m viewing distance under ambient lighting conditions of 0.005-0.01 lux. Like the TPN-1 night vision sight, the optical magnification power remains at 5.5x as this was still more than enough for the short viewing distances provided by the sight.<br />
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Like the TPN-3, comprehensive markings are provided for three ammunition types in the viewfinder of the night vision channel. The chevron and range indicator lines are adjusted up and down while the range scale remains static. To adjust for longer distances, the range indicator line is adjusted down until it lines up with the desired range, and the chevron will also drop down by the same amount. By laying the chevron onto the target, the gun is elevated by the necessary superelevation and the gunner can open fire.<br />
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<a href="https://3.bp.blogspot.com/-k9XdcG-Vv2I/WigJvzrdPMI/AAAAAAAAKQA/ov67EEgeApkKa7N2PkTp6RCcIgalK630ACLcBGAs/s1600/1k13%2Bviewfinder%2Bmarkings.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1527" height="640" src="https://3.bp.blogspot.com/-k9XdcG-Vv2I/WigJvzrdPMI/AAAAAAAAKQA/ov67EEgeApkKa7N2PkTp6RCcIgalK630ACLcBGAs/s640/1k13%2Bviewfinder%2Bmarkings.png" width="610" /></a></div>
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The sight has a field of view of 5 degrees in the daylight setting or 6°4' in the nighttime setting. It is independently stabilized in the vertical plane, with +20° elevation -7° depression.<br />
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<a href="http://2.bp.blogspot.com/-m67FJm8J77o/VUP7F0ufn_I/AAAAAAAACPw/v-7LubFCISU/s1600/26816.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://2.bp.blogspot.com/-m67FJm8J77o/VUP7F0ufn_I/AAAAAAAACPw/v-7LubFCISU/s1600/26816.jpg" width="400" /></a></div>
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As usual, the sight aperture has two protective housings; one enclosing the sensitive optical workings of the aperture itself with a glass window and a shock-proof shell, and another very heavy duty steel carapace covering that, along with a thick steel window shield.<br />
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<a href="http://3.bp.blogspot.com/-ic9VySHKOsM/Vl2c7sqdQiI/AAAAAAAAEg0/-6-ezBAxPoA/s1600/T-72%2Bsecondary%2Bsight%2Bunit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="330" src="https://3.bp.blogspot.com/-ic9VySHKOsM/Vl2c7sqdQiI/AAAAAAAAEg0/-6-ezBAxPoA/s400/T-72%2Bsecondary%2Bsight%2Bunit.png" width="400" /></a><a href="http://3.bp.blogspot.com/-AiwVq0YyhRc/Vl2c9Lqx1OI/AAAAAAAAEg8/TES2lmMtl2c/s1600/1K13%2Bprotective%2Bhousing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="330" src="https://3.bp.blogspot.com/-AiwVq0YyhRc/Vl2c9Lqx1OI/AAAAAAAAEg8/TES2lmMtl2c/s400/1K13%2Bprotective%2Bhousing.png" width="400" /></a></div>
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Externally, the key differences between the 1K13-49 and the other night sights lie in its distinctly larger armoured housing, complete with a remotely opened armoured shield.<br />
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<span style="font-size: large;">1A40-4 Sighting Complex </span></h3><div style="text-align: left;"><br /></div><div style="text-align: left;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jVk5hvKXxuk/X2OTYxRPccI/AAAAAAAARmk/t4GlzP-1ZLcFIWb3G6zS6vtVsuVVQnT9ACLcBGAsYHQ/s1600/t-72b3%2Bgunners%2Bstation.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="426" src="https://1.bp.blogspot.com/-jVk5hvKXxuk/X2OTYxRPccI/AAAAAAAARmk/t4GlzP-1ZLcFIWb3G6zS6vtVsuVVQnT9ACLcBGAsYHQ/w640-h426/t-72b3%2Bgunners%2Bstation.jpg" width="640" /></a></div><span><br /></span></div><div style="text-align: left;"><span><br /></span></div><div style="text-align: left;"><span>The 1A40-4 sighting complex is integrated with the autoloader and stabilizer of the T-72B3 tank. The complex includes includes the Sosna-U sight, TPD-K1 sight, a digital ballistic computer, and a wide variety of sensors for ballistic data. The control handles for the stabilizer and the autoloader control panel are integrated to the TPD-K1 sight </span>housing.</div><div style="text-align: left;"><br /></div><div style="text-align: left;"><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-p1u76Uk4uMs/WivRPBx1YVI/AAAAAAAAKTM/V_mKeE_JqakQOrY0sTr_1rzPeR35pCrDgCLcBGAs/s1600/t-72b3%2Bbiathlon.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1000" data-original-width="1500" height="266" src="https://1.bp.blogspot.com/-p1u76Uk4uMs/WivRPBx1YVI/AAAAAAAAKTM/V_mKeE_JqakQOrY0sTr_1rzPeR35pCrDgCLcBGAs/w400-h266/t-72b3%2Bbiathlon.jpeg" width="400" /></a></div><div style="text-align: left;"><br /></div><div style="text-align: left;"><span><br /></span></div><h3><span style="font-size: large;">Sosna-U</span></h3>
<div style="text-align: center;"><a href="https://2.bp.blogspot.com/-JIBnLgrPJIk/WMkago5DV0I/AAAAAAAAIk8/giIctIRkMDMAvdN_kUsLqvMuto7HPtVRQCLcB/s1600/sosna-u%2Bexhibition.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://2.bp.blogspot.com/-JIBnLgrPJIk/WMkago5DV0I/AAAAAAAAIk8/giIctIRkMDMAvdN_kUsLqvMuto7HPtVRQCLcB/s400/sosna-u%2Bexhibition.jpg" width="278" /></a></div>
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Sosna-U is a multi-channel sighting complex with a thermal imaging system utilizing the French-designed Catherine-FC produced under licence by VOMZ (Vologda Optical and Mechanical Plant) since 2010. It has a television channel for the thermal imaging system and a daylight optical channel. Additionally, it has an integrated laser rangefinder and a laser emitter for guided missiles. The thermal imaging camera is installed on the sight as a separate module, with all other sight components retaining the capability to function independently of the camera. The sight has independent two-plane stabilization. If configured to perform as the primary sight in lieu of the TPD-K1, as on T-72B3 tanks, a modified or entirely new stabilizer is needed to ensure that it is slaved to the sight in both planes.</div><div><br /></div><div>The design of the sight is compact enough that it can be fitted in the same position as the TPN-3 or 1K13 sight without modifications to the turret interior. However, the new sight head and its armoured housing are much larger, thus requiring the hole in the turret roof be enlarged to fit them.</div><div><br /></div><div>Integrated control panels above and below the sight eyepiece provide the essential controls for operating the sight.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Jmc8_2N3yHA/X1x0cd6YTcI/AAAAAAAARlo/PhCedQJo8EwlMqJLj8UNp6syN9FqvN9hgCLcBGAsYHQ/s2048/control%2Bpanel%2Band%2Bdisplay.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1539" data-original-width="2048" height="300" src="https://1.bp.blogspot.com/-Jmc8_2N3yHA/X1x0cd6YTcI/AAAAAAAARlo/PhCedQJo8EwlMqJLj8UNp6syN9FqvN9hgCLcBGAsYHQ/w400-h300/control%2Bpanel%2Band%2Bdisplay.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The right side of the sight housing contains the daylight sighting channel, the missile guidance beam emitter, and the laser rangefinder and all the necessary electrical system to support the operation of the sight.</div><div><br /></div><div>Like the earlier sights replaced by Sosna-U, it is suspended from the turret ceiling by the sight head mounting collar, which is affixed to the turret roof on a rubber bushing to isolate the sight from powerful impacts on the turret.</div><div><br /></div><div><br /></div><div>The Catherine-FC camera is mounted next to the daylight sight with the camera lens encased by the protective die-cast aluminium housing. The rest of the camera itself is already sealed within its own aluminium casing with internal shock dampeners.</div><div><br /></div><div>Behind the Catherine-FC camera is the laser encoding and modulating unit for the control of laser-beam riding missiles. The Sosna-U may have two different types of these laser control units, with no apparent difference in the name of the product.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://3.bp.blogspot.com/-C0PWBbskhfU/WMkGMnrCckI/AAAAAAAAIkw/qc_dLF4ggQcRmeM4qOboq_UZKqYwsNL2ACEw/s1600/sosna-u.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://3.bp.blogspot.com/-C0PWBbskhfU/WMkGMnrCckI/AAAAAAAAIkw/qc_dLF4ggQcRmeM4qOboq_UZKqYwsNL2ACEw/s400/sosna-u.jpg" width="245" /></a><a href="https://1.bp.blogspot.com/-Nb4__WwIRUU/X1QS-fc5BFI/AAAAAAAARi0/ZDcDPxqiXoQX6JBXcfovplyof_8g7NkJACLcBGAsYHQ/s2659/sonsna-u%2Brear.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2659" data-original-width="1183" height="400" src="https://1.bp.blogspot.com/-Nb4__WwIRUU/X1QS-fc5BFI/AAAAAAAARi0/ZDcDPxqiXoQX6JBXcfovplyof_8g7NkJACLcBGAsYHQ/w178-h400/sonsna-u%2Brear.png" width="178" /></a><br /><br /></div><div style="text-align: center;"><br /></div><div><br /></div><div>The window for the thermal camera on the sight head is not made from glass, which is opaque to most of the infrared spectrum, but from germanium. </div><div><br /></div><div><br /><br /><div>In the daylight mode, the sight provides a view through an optical channel for visible light (480-660 nm) which is accessed by the eyepiece on the sight housing. A tinted filter can be applied by turning a switch. For target scanning and precision shooting purposes, the gunner can switch between discrete low and high magnification settings. In the 4x magnification setting, the field of view is not less than 12 degrees. In the 12x magnification setting, the field of view is not less than 4 degrees. </div><div><br /></div><div>In the thermal imaging mode, the sight produces a digital image constructed by its optical thermographic scanning system. The camera scans in the 8-12 nm range of wavelengths which is within the LWIR (long wave infrared) spectrum. The gunner and commander can only utilize the thermal imaging channel via an external flatscreen display connected to the sight. There are low and high magnification settings. In the 3x optical magnification setting, the field of view is 9 x 6.75 degrees. In the 6x optical magnification setting, the field of view is 3 x 2.25 degrees. When digital magnification is used, the image is magnified to a maximum factor of 12x, with a field of view of 1.5 х 1.12.</div><div><br /></div><div>The thermal imaging system produces a high definition video output (625p) at a refresh rate of 50 Hz, with an image resolution of 754 x 576 px.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-HYkOtGsourA/X1x1YoGktgI/AAAAAAAARl0/wCFwOATxJAkbcsH5kSSf43lsbhjdXEGVACLcBGAsYHQ/s600/Sosna-U.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="450" data-original-width="600" height="300" src="https://1.bp.blogspot.com/-HYkOtGsourA/X1x1YoGktgI/AAAAAAAARl0/wCFwOATxJAkbcsH5kSSf43lsbhjdXEGVACLcBGAsYHQ/w400-h300/Sosna-U.jpg" width="400" /></a></div><div><br /></div><br />The two images below show the viewfinder of the sight in the daylight channel switched to the low magnification setting. The field of view through the high magnification setting is bracketed by four sets of marks in the four cardinal directions, so that the gunner may ensure that the visual contact with a target is not lost when he switches to the high magnification setting. <br /><br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GgzZJ3Pq-3o/X1P_D5iH7KI/AAAAAAAARig/4yfsRmjxnestYDSE4SSu9XhnG8sC5NFlgCLcBGAsYHQ/s2048/sosna-u%2Blow%2Bmagnification%2Bsetting.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="2039" height="320" src="https://1.bp.blogspot.com/-GgzZJ3Pq-3o/X1P_D5iH7KI/AAAAAAAARig/4yfsRmjxnestYDSE4SSu9XhnG8sC5NFlgCLcBGAsYHQ/s320/sosna-u%2Blow%2Bmagnification%2Bsetting.png" /></a><a href="https://1.bp.blogspot.com/-rxldp9ZnQ1k/X1P_eJm50-I/AAAAAAAARio/zNYyXqZ_64IzcY0KnLmYpbFSsNkc6LThQCLcBGAsYHQ/s2048/low%2Bmagnification%2Bsetting.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1891" height="320" src="https://1.bp.blogspot.com/-rxldp9ZnQ1k/X1P_eJm50-I/AAAAAAAARio/zNYyXqZ_64IzcY0KnLmYpbFSsNkc6LThQCLcBGAsYHQ/s320/low%2Bmagnification%2Bsetting.png" /></a></div>
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<br />The two images below show the view in the thermal imaging channel.<br /><br /><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-3zwY8YIzYvE/X1QopBPPEWI/AAAAAAAARjA/FXjjIeAE2TMYwQx7_NUa2FS5RNQki5N2QCLcBGAsYHQ/s1057/sosna%2Bview.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="793" data-original-width="1057" height="300" src="https://1.bp.blogspot.com/-3zwY8YIzYvE/X1QopBPPEWI/AAAAAAAARjA/FXjjIeAE2TMYwQx7_NUa2FS5RNQki5N2QCLcBGAsYHQ/w400-h300/sosna%2Bview.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-83ruR4_sloo/X1QpEl1vm2I/AAAAAAAARjI/FmCyfY5KeGkKTCP5iEOZgUf5EG5b-rx3QCLcBGAsYHQ/s2048/wide%2Bmode.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1438" data-original-width="2048" height="281" src="https://1.bp.blogspot.com/-83ruR4_sloo/X1QpEl1vm2I/AAAAAAAARjI/FmCyfY5KeGkKTCP5iEOZgUf5EG5b-rx3QCLcBGAsYHQ/w400-h281/wide%2Bmode.png" width="400" /></a></div><br /><div><br /></div>The maximum distance for detecting a tank-type target in the thermal imaging mode is 5 km. According to a <a href="https://www.thalesgroup.com/sites/default/files/database/d7/asset/document/catherinefc_uk_071005.pdf">Thales brochure for the Catherine-FC camera</a>, the maximum detection range for a tank target is around 10.5 km and the maximum recognition range is around 4.5 km. All figures were apparently obtained using real targets.<div><br /></div><div>Sosna-U also includes a target tracking system, demonstrated in <a href="https://youtu.be/G9uM3yKqKWg" target="_blank">this video</a>. As with practically all object tracking algorithms in use, the tracking system relies on the bounding box approach. The bounding box is set by laying the viewfinder reticle onto the target and pressing the button, whereupon the target is identified by image contrast.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-3YBRYaSEVQk/X1x0LuIjdKI/AAAAAAAARlY/l84a2EDPs8YoU8z2hvruDlXUSBrYmuV4QCLcBGAsYHQ/s2919/catherine%2Bfc%2Bcontrol%2Bpanel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1021" data-original-width="2919" height="224" src="https://1.bp.blogspot.com/-3YBRYaSEVQk/X1x0LuIjdKI/AAAAAAAARlY/l84a2EDPs8YoU8z2hvruDlXUSBrYmuV4QCLcBGAsYHQ/w640-h224/catherine%2Bfc%2Bcontrol%2Bpanel.png" width="640" /></a></div><div><br /><div>
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The 640 x 480 px (5.7 inch) multi-functional display (MFD) has three buttons for limited image display adjustments. The gunner can change the magnification settings with the "+" and "-" buttons, or switch between white-hot and black-hot display modes with the third button.<br />
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In addition to the sight itself, the T-72B3 upgrade also comes with a new digital ballistic computer. The sight itself cannot accept data from peripherals such as anemometers, thermometers, muzzle reference sensors, and so on. In order to make use of such data, a ballistic computer is necessary. </div><div><br /></div><div>The addition of the flatscreen display and the digital ballistic computer eliminates the possibility of stowing ammunition in the turret on the wall behind the gunner, as the gunner's master control panel is now moved to a spot behind his left shoulder, and the ballistic computer housing occupies quite a lot of space behind his seat.</div><div><br /></div><div><div>The sensor suite includes a meteorological mast constructed by combining a standard DVE-BS anemometer with an air temperature sensor. This is supplemented by an atmospheric pressure sensor installed inside the fighting compartment, on the autoloader carousel cover. There is also a thermometer on the carousel cover to measure the temperature of the propellant charges. A roll sensor was also installed.</div>
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<br />An unusual drawback of the Sosna-U is that the sight head cover has to be manually opened by unbolting it, which seems to be a step backwards from the 1K13-49.<br />
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<a href="https://3.bp.blogspot.com/-4qRsDd9EPsU/Vrtof_ag0gI/AAAAAAAAFz0/0ba9KDlLzU4/s1600/t-72b3%2Bsosna-u.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="224" src="https://3.bp.blogspot.com/-4qRsDd9EPsU/Vrtof_ag0gI/AAAAAAAAFz0/0ba9KDlLzU4/w400-h224/t-72b3%2Bsosna-u.png" width="400" /></a><a href="http://3.bp.blogspot.com/-byrTzBqpz78/VT3So0HVnVI/AAAAAAAACFk/9G62lM6KD_k/s1600/9e0d7831e40a.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://3.bp.blogspot.com/-byrTzBqpz78/VT3So0HVnVI/AAAAAAAACFk/9G62lM6KD_k/s1600/9e0d7831e40a.jpg" width="400" /></a></div>
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The IR lamp mounted next to the sight is used to replace the normal driving headlights if they are submerged under water or plastered with mud, which could happen if the tank is fording a stream or driving through a swamp. This lamp is turned on and off by the commander.<br />
<br /><br /><h3 style="text-align: left;">TPD-K1</h3>
<div><br /></div><div><br /></div><div>The TPD-K1 sight is retained as a backup to the Sosna-U. It is reduced to a standalone module as it was in the earliest versions of the T-72 - it is not connected to the ballistic computer and does not apply corrections based on sensor data. </div><div><br /></div>If the gunner chooses to use the TPD-K1 sight instead of the Sosna-U, his ability to engage moving targets is greatly limited by the lack of an independent horizontal stabilizer in the sight and the lack of a reticle displacement system like the primary sight of the M1 Abrams because the reticle is etched into a glass pane rather than a holographic projection, which is further hindered by the removal of its UVBU lead calculator unit.<br />
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<h3>
<a href="https://www.blogger.com/null" id="stabs"></a>
<span style="font-size: large;">STABILIZERS</span></h3>At the time the T-72 entered service, a gun stabilizer had been a standard feature of all tanks in the Soviet Army for almost two decades, and foreign tanks such as the M60A1 and Leopard 1 were also beginning to receive add-on stabilizers. In this context, the firepower advantage of the T-72 mainly manifested in the use of a more sohisticated stabilizer control system where the gun was slaved to the sight rather than the simple gun stabilizers used abroad. </div><div><br /></div><div><br /></div><div>
Turning on the stabilizer is done with the central toggle switch located just above the control handles on the TPD-K1 sight. The control handles integrated on the sight slightly differ depending on the stabilizer installed in the tank, but all share the same design.<br />
<br />Unlike the handles for the fire control systems of previous Soviet tanks, the handles are permanently attached to the TPD-K1 sight as an integral device. Potentiometers generate a signal from the vertical and horizontal deflection of the handles which are translated into the movement of the gun and turret via the stabilization system. The handles have a protruding ledge at the base for the gunner's hands to rest on, and the handles have two buttons each. The left trigger button is for firing the coaxial machine gun and the left thumb button is resetting the range in the sight (range memory dump). The right trigger button is for firing the main gun, and the right thumb button is for firing off the laser rangefinder. The firing circuit prevents the machine gun and main gun from firing at the same time.<br /><br />
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<h3>
<a href="https://www.blogger.com/null" id="2e28m"></a>
<span style="font-size: large;">
2E28M "Siren" ("Lilac") Hydromechanical Stabilizer</span></h3>
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The 2E28M dual-axis stabilizer is used in the T-72 Ural. Both the turret traverse and gun elevation drives are hydraulically powered. The stabilizer has two modes of operation: automatic and semi-automatic. The automatic mode is the primary mode for combat purposes; the stabilizer is at full operational capacity and will continuously attempt to align the gun with the aiming point of the gunner's primary sight with maximum precision. This mode is the default mode during combat and is used when firing from all positions - stationary, while moving, and during short halts. The semi-automatic mode is an auxiliary operating mode as well as an emergency mode in the event of stabilizer failure. In this mode, the elevation of the sight becomes directly slaved to the gun and the level of precision is reduced accordingly. The turret rotation speed is also slightly increased as the elevation mechanism no longer draws power. The semi-automatic mode is most suitable when the tank is stationary, or for firing during short halts, but it is not ideal for combat because the autoloader is consequently automatically set to the semi-automatic mode. Without the powered gun elevation system, the autoloader system cannot control the gun elevation angle to load rounds into the chamber, hence reverting to its semi-automatic mode. The slightly increased maximum turret traverse rate in the semi-automatic mode may help for tracking moving targets when the tank is in a stationary defensive position, but to fire upon targets, the automatic mode should be used.</div><div>
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Normally, the stabilizer is turned off entirely when combat is not expected, and the time needed to get the stabilizer to operational condition is two minutes. The stabilizer can remain in continuous use (turret traversing, braking, compensating for vibrations, gun moving) for a maximum period of four hours. Having the stabilizer in use for more than four hours can result in premature wear due to thermal stress in the amplifier and pump motors. Without continuous use, the stabilizer can remain turned on for as long as needed under normal conditions, including in dusty environments and while the tank is on the move.</div><br /><div><br /></div><div><div>Unlike the T-62, T-55 and T-54 series where turret rotation was actuated by an electric motor mounted on the turret ring, a hydraulic turret rotation motor was needed to cope with the high load of the unbalanced turret, especially if the tank was on an incline or a side slope. With the use of a hydraulic motor, an additional fire risk was introduced, because if the turret or turret ring was penetrated, the possibility of an explosion of aerosolized hydraulic fluid arose. </div><div><br /></div><div>To remedy this issue, the hydraulic turret rotation drive was located in the hull, behind the port side fuel tanks, and the hydraulic gun elevation booster was suspended under the 125mm gun alongside the gyro block. Only the replenisher fluid container (20) for the gun elevation drive is in the turret, behind the turret cheek armour. As such, there are no pressurized hydraulic fluids circulating in the turret exposed to a direct hit in case the turret is penetrated during combat. The diagram below, representing a T-72 turret with the original 2E28M stabilizer, shows the layout of all components linked to the stabilizer system. The components containing pressurized hydraulic fluid are the hydraulic booster for the gun elevation drive (2), the hydraulic turret rotation motor (13) and booster (11).</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-g9C445MYRUo/YBOz72iPPwI/AAAAAAAASpc/CdiqOf4vDi0Q_3GvWyMq7AL99rQa3Y-gACLcBGAsYHQ/s787/2e28m%2Bcomponents.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="500" data-original-width="787" height="406" src="https://1.bp.blogspot.com/-g9C445MYRUo/YBOz72iPPwI/AAAAAAAASpc/CdiqOf4vDi0Q_3GvWyMq7AL99rQa3Y-gACLcBGAsYHQ/w640-h406/2e28m%2Bcomponents.png" width="640" /></a></div><div><br /></div></div><div><br /></div><div>The photo below shows the turret rotation drive. To make use of the remaining space between the autoloader carousel and the battery rack, two rounds of ammunition are stowed next to the turret traverse drive.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-prCZCzC5c2M/YDShIImiuYI/AAAAAAAASw8/ouCkUPk3S3wyAyuARVxt_GFaoJ-mI3w2gCLcBGAsYHQ/s2048/turret%2Brotation%2Bdrive.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="400" src="https://1.bp.blogspot.com/-prCZCzC5c2M/YDShIImiuYI/AAAAAAAASw8/ouCkUPk3S3wyAyuARVxt_GFaoJ-mI3w2gCLcBGAsYHQ/w300-h400/turret%2Brotation%2Bdrive.png" width="300" /></a></div><div><br /></div><div><br /></div><div>As with any other 2-plane stabilizer system, the 2E28M revolves around the use of a pair of gyrostabilizers, housed inside a gyro block, for measuring angular velocities in order to enforce corrections. The "L"-shaped hydraulic booster and the gyro block fit together into a rectangular package that is suspended under the 125mm gun.</div><div><br /><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-qErfEzY82nU/YBO8zCr9RSI/AAAAAAAASpk/9V-628MimB8hgTz4UdKhB8fkRH9lintrwCLcBGAsYHQ/s656/hydrobooster.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="529" data-original-width="656" height="323" src="https://1.bp.blogspot.com/-qErfEzY82nU/YBO8zCr9RSI/AAAAAAAASpk/9V-628MimB8hgTz4UdKhB8fkRH9lintrwCLcBGAsYHQ/w400-h323/hydrobooster.png" width="400" /></a><a href="https://4.bp.blogspot.com/-3THfklWwn3I/Wb01valWheI/AAAAAAAAJdU/H8rmZT7qtfswlati_4nfEU1Qqwmxg--EgCLcBGAs/s1600/gyro%2Bblock.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="475" data-original-width="525" height="288" src="https://4.bp.blogspot.com/-3THfklWwn3I/Wb01valWheI/AAAAAAAAJdU/H8rmZT7qtfswlati_4nfEU1Qqwmxg--EgCLcBGAs/s320/gyro%2Bblock.jpg" width="320" /></a></div><div><br /></div>
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The screenshot below (screenshot taken from <a href="https://www.youtube.com/watch?v=LOGkkmQdvjU">this video</a>) shows the location of this gyro block and hydraulic booster pair. It is well below the turret ring. When the gun is fully elevated, these components fit into the empty space in the middle of the autoloader carousel.<br />
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<a href="https://4.bp.blogspot.com/-D_2_KJb0RX4/WbdBL3MdAYI/AAAAAAAAJV4/5JzAhG4fyyk7azLAJ4dMx8Yanzyb0M7cACLcBGAs/s1600/footspace.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="768" data-original-width="1366" height="358" src="https://4.bp.blogspot.com/-D_2_KJb0RX4/WbdBL3MdAYI/AAAAAAAAJV4/5JzAhG4fyyk7azLAJ4dMx8Yanzyb0M7cACLcBGAs/s640/footspace.png" width="640" /></a><br /><br /><br />Gun elevation is actuated by a hydraulic piston anchored to the left side of the gun breech on one end and to the turret roof on the other end. When directed with the control handles, the actuator is capable of smooth gun control at a speed of at least 3.5 degrees per second, but when the tank is in motion over uneven terrain, the gun is elevated and depressed at a speed of up to 8.5 degrees per second to counteract the pitching rate of the hull, in order to maintain a stable point of aim. </div><div><br /></div><div><div>If, during high-speed tank motion on uneven ground, the gun descends at a speed of 7.0-8.5 degrees per second or more, the elevation drive automatically brakes by hydrolock to prevent the gun from slamming into the ground. This is a necessary safety measure for travelling at high speeds on rough terrain, as the barrel of the 125mm is very long, and its overhang is quite pronounced due to the low height of the tank.</div></div><div><br /></div><div>
<br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-QsVHoNv6PnI/YBPC7I33ZeI/AAAAAAAASqE/2GBtmToIEXgrR76CfLefJV6O-hxkylkjwCLcBGAsYHQ/s1160/vertical%2Bstabilization%2Bscheme.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="839" data-original-width="1160" height="231" src="https://1.bp.blogspot.com/-QsVHoNv6PnI/YBPC7I33ZeI/AAAAAAAASqE/2GBtmToIEXgrR76CfLefJV6O-hxkylkjwCLcBGAsYHQ/w320-h231/vertical%2Bstabilization%2Bscheme.png" width="320" /></a><a href="https://1.bp.blogspot.com/-o6qBSZ4VYPY/YBUf6L_Jv9I/AAAAAAAASr0/T8Tmk8lF2tYwOMla_Z2gYekK_Dp2g08QQCLcBGAsYHQ/s1133/piston.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="603" data-original-width="1133" height="213" src="https://1.bp.blogspot.com/-o6qBSZ4VYPY/YBUf6L_Jv9I/AAAAAAAASr0/T8Tmk8lF2tYwOMla_Z2gYekK_Dp2g08QQCLcBGAsYHQ/w400-h213/piston.png" width="400" /></a><br /><br /></div><br />As mentioned earlier, the hydraulic motor for turret traverse is installed on the wall of the hull in a niche behind the front left fuel tank, which meant that the turret ring design differed considerably from other tanks. Instead of a fixed toothed ring affixed to the hull that the traverse gear pushes against, the hydraulic motor drives the turret via a toothed ring attached to the turret. Additionally, the T-72 turret ring still has a fixed toothed ring for the manual traverse mechanism. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEhp2ElEaWqPOWBNIfGQa2iJ5oww6RINB7fBHI9ehxuIxxUhiDyGL-zRB9LBTtTqullej3q0tTpd27cYsgJ31d-pS2bWUAwVv5VYFaRgw7GDCS1RnVW3jSrxTlpKzajK3YNSmPB3dE0uBOBxSjD-9TZDGLGUXZeox1iICtO7leqNh5W6sqxOODtAA1xipw=s505" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="485" data-original-width="505" height="307" src="https://blogger.googleusercontent.com/img/a/AVvXsEhp2ElEaWqPOWBNIfGQa2iJ5oww6RINB7fBHI9ehxuIxxUhiDyGL-zRB9LBTtTqullej3q0tTpd27cYsgJ31d-pS2bWUAwVv5VYFaRgw7GDCS1RnVW3jSrxTlpKzajK3YNSmPB3dE0uBOBxSjD-9TZDGLGUXZeox1iICtO7leqNh5W6sqxOODtAA1xipw=s320" width="320" /></a></div><div><br /></div><div><br /></div><div>The hydraulic motor provides two traversing modes: precise aiming and high speed. The precise aiming mode is controlled by the gunner's control handles and is used to set the point of aim on a target, to track moving targets, and to fire upon moving targets. The limit of this mode is 6 degrees per second, with a smooth stepless speed control from 0 to 6 degrees per second. The turret is always horizontally stabilized in this mode. The high speed mode is used when the commander designates a target with his TKN-3 periscope, when the driver activates the emergency turret turning system, and when the gunner wishes to turn the turret at its maximum speed. When turning at the high speed mode, the turret is horizontally unstabilized, regardless of which of the three crew members controls it. <br />
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The hydraulic pump for the gun elevation and turret traverse systems both operate continuously, i.e. without requiring a hydraulic accumulator to generate a stable pressure. The service life of the traverse motor is 600-1,000 hours. 10 liters of hydraulic fluid are used in the circuit of the turret traverse motor, and 17 liters are used in the circuit of the gun elevation system.<br />
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The hydraulic fluid used in the 2E28M stabilizer is MGE-10A, a mineral hydraulic oil with an exceptionally low temperature sensitivity, having an operating range of -65<span class="st">°C to 75</span><span class="st">°C with a minimal change in viscosity. According to GOST standards, the flash point of MGE-10A is 96°C, which is typical of other hydraulic oils. The OHT oil used in the hydraulic systems of Patton tanks had a flash point of 98.9°C, but it was replaced by FRH (fire resistant hydraulic) oil with a flash point of 204°C. While an oil like FRH is safer, it also brought the severe drawback of a significant loss in performance of hydraulic systems at temperatures below -25°C compared to OHT and continuously declines in performance as the temperature decreases. At a temperature of -54°C, the viscosity of FRH is 133,000 cSt. For comparison, OHT has a viscosity of 3,500 cSt at -54°C and MGE-10A has a viscosity of 1,500 cSt at -50°C, with a calculated viscosity of 1,560 cSt at -54°C. The large loss in performance brought by a fire resistant fluid like FRH would have been unacceptable for a Soviet tank, as it would violate the tactical-technical requirement for the T-72 to operate in a temperature range of -40°C to +50°C, as decreed by the government.<br />
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An inherent shortcoming of hydraulic components is the heightened risk of an internal fire in the event that fragments pierce a component carrying pressurized fluid and there is a heat source inside the tank. Hydraulic fluid is highly flammable, and it would most likely cause and spread an internal fire very quickly. In aerosol form, the fluid can be explosive. In the T-72, the placement of almost all hydraulic components below the level of the turret ring offers a level of security against this threat, as it is more likely for a shot to impact the turret and not the hull. An additional level of security is provided by the low quantity of hydraulic fluid used by the system - just 27-28 liters in total. It is slightly less than the 8 gallons (30.3 liters) of hydraulic fluid used in the M60A1 (AOS) and M60A3, and it is much less than the 75.7 liters of fluid used in the unified stabilization systems of the M1 and M1A1 Abrams.<br />
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The precision and overall operating characteristics of "Sireneviy" is notably higher than previous tank stabilizers and offers an improvement in fire-on-the-move capability compared to the T-55 and T-62 which had a simpler stabilization scheme where the sight was slaved to the gun. The aiming precision of the T-72 as a weapon system was quite high for the era thanks to the independent stabilization of the sights and the cannon to a high level of precision. This stabilization scheme was first implemented on the T-10M with the PUOT-2S stabilizer. According to the technical manual for the 2E28M stabilizer, the main gun and coaxial machine gun cannot be fired unless the bore axis of the gun and the line of sight of the gunner's primary sight (TPD-K1) do not diverge by more than 0.5 mils.<br />
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"Sireneviy" not only enables the T-72 to confidently engage tank-type targets at up to two kilometers in European climatic conditions when firing from a standstill and also engage tank-type targets when traveling at a 10-15 km/h cruising speed at distances of approximately 1.5 kilometers. However, the probability of hit decreases compared to firing from a standstill by 1.3-1.4 times when the speed of the tank is 15-18 km/h, and at speeds of 20-25 km/h, the accuracy of fire is reduced by 1.5-1.6 times.<br />
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According to the tactical-technical specifications listed in the technical manual for the 2E28M stabilizer, when the tank is moving on moderately rough terrain at a constant speed of up to 35 km/h, the minimum accuracy of stabilization does not fall below 0.8 mils in the vertical axis and 2.0 mils in the horizontal axis. If the accuracy falls below these thresholds, the stabilizer system must be sent for medium repairs or an overhaul. In actual use, the stabilization accuracy is much less than the minimum values given in the technical manual. According to the results of a long-term technical study published in the scientific journal article "<i><a href="http://btvt.info/5library/vbtt_1985_01_stabilizator.htm">Электромеханические Стабилизаторы Танкового Вооружения</a></i>" (<i>Electromechanical Stabilizers for Tank Weapons</i>), it was found that in 1977-1978 and in 1978-1979, the median stabilization error was recorded to be 0.777 and 1.01 mils respectively. By 1981, the median error improved to just 0.59 mils. The tank speeds reached during testing ranged from 22-33 km/h, approximately equivalent to the realistic speed of the tank when driving cross country. </span>For comparison, a Soviet study on a captured Chieftain Mk. 5R found that the median gun stabilization error was 0.75 mils in the horizontal axis and 0.35 mils in the vertical axis. </div><div><span class="st"><br /></span></div><div><span class="st">When firing, the vertical stabilization accuracy is dependent on the sight. For early T-72 tanks, the TPD-2-49 sight with a stabilization accuracy of 0.336 mils is used, decreased to 0.2 mils on the TPD-K1. The stabilizer has a drift rate of 16 mils per minutes in both axes.<br />
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In 1972, gunnery trials of fifteen Object 172M prototype tanks at a firing range against standard No. 12 "tank" targets (tank front silhouette) at distances of 1,600-1,800 meters showed that the probability of hit when firing on the move was 50.4%. From this, the maximum effective range could be considered 1,800 meters. By the same metric, the maximum effective range of the Chieftain Mk. 5R <a href="http://btvt.info/1inservice/chieftain/vop_chieeftain_opisanie.htm">when firing on the move</a> is 1,300 meters.<br />
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With a nominal traverse speed of no less than 18 degrees<span class="st"> per second in the automatic mode, the turret is relatively slow to turn compared to modern gun stabilizers. In the semi-automatic mode, the rate of rotation is increased to no less than 20 degrees per second. It would take a maximum of 18-20 seconds for the turret to complete a full 360-degree </span><span class="st">revolution. The figure given in the manual is a minimum threshold which must be met during normal operation, otherwise the stabilizer is considered faulty and will be sent for repairs or replacement. In practice, when the tank is operating under normal conditions, at a normal environment with a standard temperature of +15°C, the traverse speed can be higher. This difference was found in West German and U.S testing of the T-62, where the traverse speed turned out to be 18 degrees per second on level ground, rather than the minimum 16 degrees per second listed in the T-62 manual. West German tests found that when the turret was traversed on a 30% slope, the speed reached 16.4 degrees per second, closer to the Soviet figure. At the moment, foreign test data of the T-72 is unavailable, but according to <a href="https://findpatent.ru/patent/213/2138758.html">Russian patent No. 2138758</a>, the maximum turret traverse speed in the automatic mode is 20 degrees per second, and the maximum turret traverse speed in the semi-automatic mode is 22 degrees per second. From this, it can be seen that it would actually take 18 seconds for the turret to complete a full 360-degree revolution in the automatic mode, and 16.4 seconds in the semi-automatic mode. It is likely that the nominal traverse speed of 18 degrees per second of the 2E28M stabilizer will hold true if the turret is traversed when the tank is on a slope rather than on level ground, or in deep subzero temperatures where the increased viscosity of the hydraulic fluid will affect the speed of the hydraulic traverse motor.<br /><br /></span>The precise aiming traverse speed varies smoothly from the minimum speed up to a maximum of 6 degrees per second, whereupon there is a soft stop that resists the control handles from turning further. If the gunner twists the control handles harder, the rotation speed steps up from 6 degrees per second to 18 or 20 degrees per second with no smooth transition. The maximum speed of controlled gun elevation is 3.5 degrees per second. This figure is exceeded if the gunner twists the control handles to the maximum deflection, but the limit is not documented. It is possibly 7.0-8.5 degrees per second. When moving over undulating terrain that pitches the tank at a rate greater than the vertical aiming speed of the gun (3.5 degrees per second), the gun will continue to be stabilized on the chosen point of aim by elevating or depressing at a rate equal to the pitching of the tank, up to a limit of 7.0-8.5 degrees per second. When the hull rotates during a turn at a rate that exceeds the provided aiming speed limit of the gunner's control handles (6 degrees per second), the turret will also maintain its point of aim on the target, if the hull rotating speed does not exceed at least 18-20 degrees per second.<span class="st"><br /></span>
<br />
</span><br />
<h3>
<span class="st">
<span class="st"><b>Automatic mode</b></span></span></h3>
<span class="st">
<h3>
Vertical</h3>
<br />
<br />
Maximum Gun Elevating Speed: 3.5<span class="st">° per second </span>(not less than)<br />
<span class="st">Minimum Gun Elevating Speed: 0.05° per second</span><br />
<br />
<br />
<h3>
Horizontal</h3>
Maximum Turret Traverse Speed: 18° per second (not less than)<br />
Maximum Stabilized Turret Traverse Speed: 6<span class="st">° per second</span><br />
Minimum Precise Turret Traverse Speed: 0.07° per second<br />
<br />
<br />
<h3>
<b>Semi-automatic mode</b></h3>
<h3>
Horizontal</h3>
Maximum Turret Traverse Speed: 20<span class="st">° per second (not less than)</span><br />
<span class="st">Maximum Precise Turret Traverse Speed: 6<span class="st">° per second</span></span><br />
Minimum Precise Turret Traverse Speed: 0.3° per second<br />
<br />
<br />
<br />
Maximum time taken for complete rotation: 20 seconds<br />
<br />
<br />
The speed of turret rotation is quite fast by Soviet standards, considering that earlier tanks like the T-55 were not particularly fast. The turret of a T-55 with a "Tsyklon" stabilizer could spin around at no less than 15 degrees per second, and the turret of a T-62 could spin at </span>no less than 16 degrees per second. "Siren" is an improvement over earlier stabilizers in every possible way, including long term reliability.</div><div><span class="st">
<br />
Combined, all of the components belonging to the stabilization system weigh a sum total of 319 kg, including the working fluid (hydraulic fluid). On average, the stabilizer system consumes 3.5 kW of power.<br />
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<a href="https://www.blogger.com/null" id="2e42-2"></a>
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<h3>
<a href="https://www.blogger.com/null" id="2e42-2"></a>
<span style="font-size: large;">
2E42-2 "Zhasmin" Hydroelectric Stabilizer</span></h3>
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<a href="http://2.bp.blogspot.com/-U3DI_IpUnt4/VUQSdqLK5zI/AAAAAAAACRQ/K0sj3lbsKnk/s1600/2e42.jpeg"><img border="0" height="265" src="https://2.bp.blogspot.com/-U3DI_IpUnt4/VUQSdqLK5zI/AAAAAAAACRQ/K0sj3lbsKnk/s1600/2e42.jpeg" width="400" /></a></div>
<br />
<br />
The 2E42-2 is a stabilizer system with an electric turret traverse motor combined with a hydraulic gun elevation drive. Prototyping of the 2E42 began in the early 1970's, with tests beginning as early as 1974 on the Object 172-2M "<i>Buyvol</i>" experimental tank. This stabilizer began low rate production for field testing in 1983 and only began to be installed in mass produced T-72 tanks since 1984. Naturally, the T-72B, which officially entered service in 1985, came with this stabilizer as standard. The T-72 series received the 2E42 much later than the T-64 series, which first began to be installed on T-64B tanks starting in 1979.<br /><br />Due to the replacement of the hydraulic turret traverse drive of the 2E28M stabilizer system with an electric drive, additional internal volume (14 liters) in the tank was freed up, permitting more ammunition to be stowed in the niche behind the front left hull fuel tank. Additionally, the advantages of an electric motor were the lower labour costs for their manufacture as well as a longer service life, higher reliability and lower maintenance requirements, not just in terms of the frequency of checkups but also the ease of maintenance, as the hassle of pumping out the air from a hydraulic system after reassembly and the unpleasantness of hydraulic fluid leakages are both eliminated. The power consumption of the system was raised to 9 kW, but thanks to the implementation of regenerative braking, such that on average, the stabilizer system consumes 3.5 kW of power - the same as the 2E28M.</span></div><div><span class="st"><br /></span></div><div><span class="st">The turret traverse is provided by an EDM-16U motor. </span><a href="https://www.npoelm.ru/product/spetsproduktsiya/elektrodvigateli/elektrodvigatel-edm-16u/">EDM-16U</a> is a low-inertia 4-pole DC brushless electric motor, with an output of 1,500 W and a rated speed of 2,200 RPM. It features forced air cooling with a EVTs-4 electric blower fan. The motor features regenerative braking, allowing it to recover electric energy while braking by converting the momentum of the turning turret, thus reducing the power consumption of the stabilizer. The braking time for a moving turret was also diminished to as little as a third of that from the 2E28M stabilizer. This drastically improved the responsiveness of the turret. </div><div><span class="st"><br /></span></div><div><span class="st"><br /></span></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-mrccdtNrVF4/YBUGacWzkaI/AAAAAAAASrc/n_YuNGWwDtQ-QSgrlyhKa_QFwWK3DmEAQCLcBGAsYHQ/s800/edm-16u.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://1.bp.blogspot.com/-mrccdtNrVF4/YBUGacWzkaI/AAAAAAAASrc/n_YuNGWwDtQ-QSgrlyhKa_QFwWK3DmEAQCLcBGAsYHQ/w400-h300/edm-16u.png" width="400" /></a></div><div><br /></div><div><br /></div>For compactness and to simplify the turret ring design, the turret traverse motor was integrated with the manual traverse mechanism in a single unit, similar to the designs used in earlier Soviet medium tank stabilizers. It is not, however, directly linked to the same gearing mechanism as the manual handwheel as they are separated by a clutch, and the manual system has a coarse and fine gearing ratio selector whereas the electric motor has a fixed gearing ratio between it and the turret ring.</div><div><span class="st"><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-xlgvCmoAJWY/W2mYGgPcS-I/AAAAAAAAMCo/V_nsoQ-yL-AKY4kNiTobGy8MqSn6MlJ8ACLcBGAs/s1600/t-72%2Bhorizontal%2Bdrive.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="294" data-original-width="616" height="190" src="https://3.bp.blogspot.com/-xlgvCmoAJWY/W2mYGgPcS-I/AAAAAAAAMCo/V_nsoQ-yL-AKY4kNiTobGy8MqSn6MlJ8ACLcBGAs/s400/t-72%2Bhorizontal%2Bdrive.jpg" width="400" /></a></div><div><br /></div><div><br /></div><div>Turret traverse control signals are transmitted from the gunner's control handles to the motor via the EMU-12PMB amplidyne amplifier.</div><div><br /></div><div>It was reported in the scientific journal article "<i><a href="http://btvt.info/5library/vbtt_1985_01_stabilizator.htm">Электромеханические Стабилизаторы Танкового Вооружения</a></i>" that in 1981 and 1982, the recorded median stabilization error for the prototype of the 2E42 on T-72 testbeds was 0.4 mils and 0.377 mils respectively. The stabilization accuracy may have improved further by the time the 2E42 entered service and began serial deliveries in 1984. On average, in different weather conditions and at different times of the year, the recorded stabilization accuracy was 0.28 mils on 42 sample tanks tested in Ukraine and 0.34 mils on 73 sample tanks tested in the Urals, under somewhat more difficult conditions.</div><div><br /></div><div>The hydraulic booster is of a new, compact design. A new gyro block is also included in the 2E42-2 stabilizer.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-RcsoykrUJE0/YBUcvNrxHmI/AAAAAAAASrs/uYiBgdDFQxw-UhGvsGFLQOhCWtcpirmYgCLcBGAsYHQ/s960/elevation%2Bdrive%2Bhydraulic%2Bbooster.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="720" data-original-width="960" height="240" src="https://1.bp.blogspot.com/-RcsoykrUJE0/YBUcvNrxHmI/AAAAAAAASrs/uYiBgdDFQxw-UhGvsGFLQOhCWtcpirmYgCLcBGAsYHQ/w320-h240/elevation%2Bdrive%2Bhydraulic%2Bbooster.png" width="320" /></a><a href="https://1.bp.blogspot.com/-xaa2FrsjVGg/YBUhScHTecI/AAAAAAAASr8/djqHmybBlk49Y_qnRMMRJi9nNYfJF5djACLcBGAsYHQ/s542/piston.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="322" data-original-width="542" height="238" src="https://1.bp.blogspot.com/-xaa2FrsjVGg/YBUhScHTecI/AAAAAAAASr8/djqHmybBlk49Y_qnRMMRJi9nNYfJF5djACLcBGAsYHQ/w400-h238/piston.png" width="400" /></a><br /></div><div><br /></div><div><br /></div><div>As the only hydraulic actuator in the tank, only 3 liters of hydraulic fluid is present in the fighting compartment in total, including 2.8 liters in the built-in reservoir on the hydraulic booster, all beneath the turret ring level - there is no longer a replenisher reservoir fitted on the turret cheek as with the 2E28M. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEi8IKzIQ04d9tjnUceaIiCNgZyHeeOXZLQILPchVOZRwtLyQ2aejNBGphIav7ss8gphn9ioK__cY9zeITKVIAEGHqFcqhV7EFZvLlIYBjAQyh1F-6Zxtp60rtQXNUO-bj-yq1y7w257r3EmXO2w0fLoaneMHDKMG52M8STqmh269z6IIARUPN1YUKEM0w=s2106" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2106" data-original-width="1896" height="400" src="https://blogger.googleusercontent.com/img/a/AVvXsEi8IKzIQ04d9tjnUceaIiCNgZyHeeOXZLQILPchVOZRwtLyQ2aejNBGphIav7ss8gphn9ioK__cY9zeITKVIAEGHqFcqhV7EFZvLlIYBjAQyh1F-6Zxtp60rtQXNUO-bj-yq1y7w257r3EmXO2w0fLoaneMHDKMG52M8STqmh269z6IIARUPN1YUKEM0w=w360-h400" width="360" /></a></div>
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The T-72B obr. 1989 manual states that the maximum turret traverse speed is 16-24 </span>degreesper second, and mentions that the traverse speed when the target designation function is used by the commander is 16 degrees per second. A rate of rotation of 24 degrees per second is achieved by the gunner turning his control handles until it cannot turn any further. Thanks to the use of regenerative braking in the power traverse drive, the average power consumption of the stabilizer system was the same as the 2E28M at 3.5 kW despite the increased load of the uparmoured T-72B turret, especially considering that it is even more unbalanced than preceding T-72 turrets. The 2E42-2 has the same two operating modes as the 2E28M and previous Soviet tank gun stabilizers: automatic and semi-automatic.</div><div><span class="st">
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<br />
<h3>
<b>Automatic mode:</b></h3>
<h3>
Vertical</h3>
Maximum elevating speed: 3.5<span class="st">° per second</span><br />
<span class="st">Minimum elevating speed: </span></span>0.03° per second (not more than <span class="st">0.05</span><span class="st">° per second)</span></div><div><span class="st">
<span class="st"><br /></span>
<span class="st"><br /></span>
<br />
<h3>
<span class="st">Horizontal</span></h3>
<br />
Maximum Turret Traverse Speed: 16-24<span class="st">° per second</span><br />
<span class="st">Maximum Precise Turret Traverse Speed: 3° per second</span><br />
Minimum Precise Turret Traverse Speed: </span>0.05° per second (not more than 0.07° per second)</div><div><span class="st">
<br />
<br />
<h3>
<b>Semi-automatic mode</b></h3>
<h3>
Horizontal</h3>
Maximum Turret Traverse Speed: 16<span class="st">° per second</span><br />
<span class="st">Maximum Precise Turret Traverse Speed: 6° per second</span><br />
Minimum Precise Turret Traverse Speed: 0.3° per second<br />
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<br />
The turret traverse speed is improved to 24 degrees per second, enabling the turret to complete a full 360° rotation in just 15 seconds.<br />
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<br />
<h3>
<a href="https://www.blogger.com/null" id="2e42-4"></a>
<span style="font-size: large;">
2E42-4 "<i>Zhasmin</i>" Hydro-electromechanical Stabilizer</span></h3>
<br />
The 2E42-4 two-axis stabilizer is an improved modification of the 2E42-2 first used in the T-90. The 2E42-4 is installed in the T-72B3 and includes a more powerful horizontal drive for faster turret rotation. According to Sergey Suvorov in "<i>T-90: First Serial Tank of Russia</i>", the 2E42-4 for the T-90 has an average stabilization accuracy of 0.4 mils in the vertical plane and 0.6 mils in the horizontal plane. These are, indeed, the printed accuracy figures in a promotional export data sheet for the T-90S, with the additional information that when used in the commander's override mode (the so-called "double" mode), the stabilization accuracy in the vertical plane degrades slightly to 0.45 mils. It is unclear if the degradation also occurs in the T-72B3, as its override feature is not based on the TKN-4S sight, but on a digital sight extension for the SOSNA-U system.<br />
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<br />
The 2E42-4 stabilizer offers a huge weight reduction of 120 kg over the 2E42-2 stabilizer, for a total weight of 200 kg. This is mainly thanks to the design simplification of the hydraulic gun elevation drive, the improved turret traverse motor, and the usage of solid state electronics in the digitized control systems. The screenshot below gives us a good view of the hydraulic pump for the gun elevation drive. The pump is mounted below the breech, and connects to the hydraulic elevator piston seen in the upper right corner of the picture.<br />
<br />
<br />
<a href="https://3.bp.blogspot.com/-XAF5zh9SvQc/WYm__LcdMII/AAAAAAAAI5s/tJkjbzrWXgcskDdEzYOcsA86wA0Tf4WFwCLcBGAs/s1600/stabilizer.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="768" data-original-width="1366" height="358" src="https://3.bp.blogspot.com/-XAF5zh9SvQc/WYm__LcdMII/AAAAAAAAI5s/tJkjbzrWXgcskDdEzYOcsA86wA0Tf4WFwCLcBGAs/s640/stabilizer.png" width="640" /></a><br />
<br />
<br />
Screenshot taken from the RT Documentary show "Tanks Born in Russia (E5) Kirill’s girlfriend reveals her biggest secret" (<a href="https://youtu.be/Ft1f2MXkCDk?t=10m26s">link</a>).<br />
<div>
<br /></div>
<br />
<br />
<h3>
Vertical</h3>
Maximum elevating speed: 3.5<span class="st">° per second</span><br />
<span class="st">Minimum elevating speed: 0.05</span><span class="st">° per second</span><br />
<span class="st"><br /></span>
<span class="st"><br /></span>
<br />
<h3>
<span class="st">Horizontal:</span></h3>
<br />
Maximum turret rotation speed: 40<span class="st">° per second</span><br />
Minimum turret rotation speed: 0.054<span class="st">°</span> per second<br />
<br />
<br />
The much faster turret traverse speed enables the turret to complete a full 360° rotation in 9 seconds.<br />
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<br />
<br />
<h3>
<span style="font-size: large;">MANUAL</span></h3>
<br />
<br />
Manual traverse and elevation is possible with all T-72 turrets through the use of two handwheels located behind the hand grips. There are two gear settings; "coarse" and "fine". The former allows the turret to turn as fast as the gunner can work the handwheel, whereas the latter allows the gunner to produce minute changes to the lay of the turret and gun. </span><div><span class="st"><br /></span></div><div><span class="st"><br /></span></div><div><span class="st"><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-KpvnGTCewx8/XAS8awNpgyI/AAAAAAAAMos/xQUSAaIGsnovccfJ7r7iMg7sRjbCIvCHgCLcBGAs/s1600/t72-197.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="340" data-original-width="490" height="278" src="https://2.bp.blogspot.com/-KpvnGTCewx8/XAS8awNpgyI/AAAAAAAAMos/xQUSAaIGsnovccfJ7r7iMg7sRjbCIvCHgCLcBGAs/w400-h278/t72-197.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-wr_MfzM60WQ/Xxb75Dz0SfI/AAAAAAAARTg/rGYt9Hi9esgxvw-TtHa3B3-V80QU3KCMQCLcBGAsYHQ/s599/elevation%2Bwheel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="443" data-original-width="599" height="296" src="https://1.bp.blogspot.com/-wr_MfzM60WQ/Xxb75Dz0SfI/AAAAAAAARTg/rGYt9Hi9esgxvw-TtHa3B3-V80QU3KCMQCLcBGAsYHQ/w400-h296/elevation%2Bwheel.png" width="400" /></a></div></span></div><div><span class="st"><br /></span></div><div><span class="st"><br /></span></div><div><span class="st">Gun laying with the manual traverse can be just as accurate as with stabilizers if not more so, though obviously much, much slower and nearly impossible to achieve on the move. The high level of accuracy is due to the extremely large gear ratio in the "fine" setting. In this setting, multiple cycles of the handwheel will shift the turret by only a few fractions of a degree, allowing the gunner to conduct extremely fine adjustments to the lay of the gun. The gun elevation handwheel has a solenoid button for firing the main gun, and the gun itself houses a manual trigger mechanism that can be used in the event of an electrical failure.<br />
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-A-pTDpi_aQM/VUOy7C4C7RI/AAAAAAAACMs/NkIEhb9qWO4/s1600/hand%2Bgrips%2Band%2Bcrank%2Bwheels.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="362" src="https://2.bp.blogspot.com/-A-pTDpi_aQM/VUOy7C4C7RI/AAAAAAAACMs/NkIEhb9qWO4/s1600/hand%2Bgrips%2Band%2Bcrank%2Bwheels.png" width="640" /></a></div>
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<br />
In many early tanks with powered turret traverse, the gun elevation drive still tended to be manually driven because a well-balanced gun could be elevated and depressed at sufficient speed with a handwheel and there was little need to quickly shift the gun more quickly. However, quick turret traverse with a manual drive became impossible when the mass of tank turrets grew sharply during and after WWII.<br />
<br />
According to the proposal <a href="http://btvt.info/5library/vbtt_1985_06_avtomat.htm">"<i>Один Из Путей Повышения Надежности Комплекса Танкового Вооружения</i>"</a> ("<i>One of the Ways of Improving the Reliability of the Tank Armament Complex</i>") by A. I. Mazurenko and E. A. Morozov, the extremely low speed of turret rotation for a generic modern tank using manual controls makes it impossible to find and engage targets in combat conditions. Using the manual turret traverse handwheel, the speed of turret rotation on flat ground is 0.6-0.8 degrees per second and the speed of turret rotation when the tank is on a side slope of 15 degrees is halved to only 0.3-0.4 degrees per second. The amount of force required to work the handwheel is 1.6 kgf (15.7 N) when the tank is on flat ground and 20.0 kgf (196 N) when the tank is on a side slope of 15 degrees. The colossal increase in effort required to turn the turret when the tank is on a slope betrays the fact that the turret is extremely front-heavy as a result of the exceptionally thick frontal armour, large gun, and lack of a turret bustle to act as a counterweight. Tracking a moving target is virtually impossible unless the target is far away, and scanning for targets with the primary sight becomes impractical. From this, it is understood that the loss of powered turret controls can effectively bring a tank out of commission in many situations even if all other systems are operating at normal levels.<br />
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<br />
<a href="https://www.blogger.com/null" id="metmast"></a>
<br />
<h3>
<span style="font-size: large;">METEOROLOGICAL MAST</span></h3>
<br />
<br />
The T-72
first received a meteorological sensor unit with the T-72BA sub-variant.
This manifested in the form of the DVE-BS unit, which can detect changes in wind speed and automatically register it in the ballistic
computer. The maximum calculable winds speed is 25 m/s, which is equivalent to a 10 on the Beaufort scale. Such wind speeds are capable of uprooting trees and are very rarely experienced inland. The information gathered is synchronized with the automatic lead calculation unit found in the 1A40-1 sighting complex. The T-72B3 is also equipped with a DVE-BS unit.<br />
<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-dWa-cSFDiaQ/VUOzbqbL_aI/AAAAAAAACM8/4a9mZVYAh-I/s1600/PEL-T-72BA-Astana-2014-0012-Org-M.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="266" src="https://3.bp.blogspot.com/-dWa-cSFDiaQ/VUOzbqbL_aI/AAAAAAAACM8/4a9mZVYAh-I/s1600/PEL-T-72BA-Astana-2014-0012-Org-M.jpg" width="400" /></a><a href="http://3.bp.blogspot.com/-s6O9jjFjfLI/VUOzppfW8lI/AAAAAAAACNE/u6feIBFWHJw/s1600/getBigImage.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="189" src="https://3.bp.blogspot.com/-s6O9jjFjfLI/VUOzppfW8lI/AAAAAAAACNE/u6feIBFWHJw/s1600/getBigImage.jpg" width="320" /></a></div>
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<div class="separator" style="clear: both; text-align: center;">
</div>
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<h3>
<a href="https://www.blogger.com/null" id="d-81t"></a>
<span style="font-size: large;">D-81T GUN </span>(2A26M2, 2A46, 2A46M, 2A46M-5)</h3>
<div>
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-PoWCO_y7Pyo/VTQKXO_mjvI/AAAAAAAAB8o/_sqaC4HlMfo/s1600/t-72.27027.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://2.bp.blogspot.com/-PoWCO_y7Pyo/VTQKXO_mjvI/AAAAAAAAB8o/_sqaC4HlMfo/s1600/t-72.27027.jpg" width="640" /></a></div>
<br />
<br /></div>
<div>All T-72 models were armed with a variant of the 125mm smoothbore D-81T gun. The gun can fire a wide range of shells including APFSDS, HEAT, Flechette, HE-Frag, and even guided missiles beginning from 1985 with the T-72B model. The gun is loaded with two-part ammunition. The height of the bore axis from ground level is 1,651mm.<br />
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The cannon is partially derived from the U-5TS 115mm smoothbore gun and the evidence of this heritage can be found in the construction of the breech upon close inspection. The recoiling mechanism follows the same compact layout as the U-5TS, which helps to reduce the volume of internal space taken up by the cannon in the small turret. The recoil buffer and the recuperator is located at the bottom of the breech block rather than on top of it, so despite the larger caliber and mass of the cannon, it was possible to create a very low turret with a very steeply sloped roof while still affording the cannon a reasonably range of vertical motion. The recuperator was installed on the same vertical axis as the bore and the recoil buffer was installed on the right hand side of the breech next to the recuperator. Stacks of steel ballast plates were placed behind the gun breech for the purpose of adjusting the balance of the gun assembly. A fresh gun with a new gun tube would have a full stack of ballast plates, and as the bore lining was progressively eroded from firing (APFSDS rounds in particular were extremely erosive), the plates would be removed incrementally to balance out the lightening of the barrel and thus maintain the perfect balance of the gun.<br />
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Like the D-10T and the U-5TS that preceded it, the D-81T cannon was designed to be installed in a tank turret without a gun mantlet. By not using a gun mantlet like the M60A1 or the Leopard 1 and using a lightweight gun mask instead, it was possible to reduce the weight of the cannon, reduce the interior penetration of the cannon breech, and reduce the load on the vertical gun laying drive. This is because an armoured gun mantlet is a large load that has to be counterbalanced in order for the gun to remain balanced on its fulcrum. The gun mask on a T-72 is shown in the photo below.<br />
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When a large and heavy gun mantlet is installed, the gun breech must be larger and heavier to properly counterbalance its weight. This increases the load on the vertical gun laying drive and the added bulk reduces the space inside the turret. Alternatively, the distance between the gun breech and the gun mounting cradle could be increased which would increase the torque generated by the breech without increasing its mass, but this still leads to a reduction of the internal space in the turret and does not significantly reduce the load on the vertical gun laying drive. For these reasons, all Soviet medium and main battle tanks since the 1949 model of the T-54 turret lacked a gun mantlet. The elimination of the gun mantlet was also actively pursued in Britain. Case in point, the Chieftain and the Challenger 1 main battle tanks were all designed without a gun mantlet and one modernization option for the Centurion tank proposed the installation of <a href="https://yuripasholok.livejournal.com/4840919.html">the "Action X" turret</a> which lacked a gun mantlet.<br />
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Furthermore, the hydraulic pump for the vertical gun laying drive for the D-81T was mounted underneath the mounting cradle and moved together with the gun. This allowed the pump and associated components to be used as a counterweight. This allowed the engineers to curb the mass of the cannon breech assembly even further. These design features can all be seen in the drawing below, taken from a T-72A manual.<br />
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The gun can elevate +14 degrees and depress -6.21 degrees when facing the front, but elevate +15.25 degrees and depress only -3 degrees when facing the rear, over the engine compartment. When the stabilizer (2E28M, 2E42) is activated, the gun depression limit is marginally reduced to -5.34 degrees and the gun elevation limit is reduced to +13.78 degrees. This is a common feature of vertical gun stabilization systems intended to prevent damage to the elevation drive during normal operation. If the gun is allowed to move its entire range of motion up to the hard stops, it is possible for the breech housing to slam into the stops when the tank experiences a sudden jolt by going over a bump or falling into a rut. This results in an undesirable pressure overload in the hydraulic elevation drive. Due to the forward structural tilt of the hull roof of 1 degree, the actual gun elevation limits are 1 degree lower relative to ground level, giving lower gun elevation but better gun depression. <br />
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All earlier Soviet tank gun stabilizers also have this feature, and it can be found in foreign tanks as well. For example, the gun elevation of the M1 Abrams (105mm gun) is limited to +20 degrees in elevation and -10 degrees in depression by hard stops, but when the stabilizer is turned on, this is reduced to +19 degrees and -8 degrees. Similarly, the Challenger 1 tank is limited to +20 degrees in elevation and -10 degrees in depression by hard stops, but this can only be achieved using manual cranks. When the turret controls are powered on, the range of gun motion is reduced to +18 degrees and -8 degrees.<br />
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This is generally sufficient for cross-country driving with lots of dips, dives and bumps, but the T-72 is unable to fully exploit the reverse slope of steeper hills to enter a hull-down position. This was not seen as a drawback because pre-prepared dug-in defensive positions were preferred for defensive operations. The lackluster gun depression compared to most NATO tanks has the potential to become an issue in highly irregular terrain when firing on the move, but it was considered to be not significant enough to warrant the corresponding changes to the turret height, and indeed, the ground would have to be extremely uneven for a gun depression limit of -6 degrees to be problematic. Compared to previous Soviet tanks, the gun depression of the T-72 is slightly better than the typical -5 to -4 degrees.</div><div><br /></div><div>It is worth noting that despite the AZ autoloader decreasing the vertical space of the fighting compartment by 250mm compared to the MZ autoloader of the T-64A, there was still enough room to permit the same maximum elevation angle of +15.25 degrees with the 125mm gun. When raised to this angle, the recoil guard built into the gun will almost touch the autoloader carousel cover. </div><div><br /></div><div>
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The D-81T gun and its modifications are all quite compact. As mentioned before, its maximum width of only 600mm is substantially less than its closest counterpart, the Rh 120 smoothbore gun, which has a width of 585mm and a maximum width of 728mm when measured across its cradle. The total volume required to accommodate the D-81T in the T-72 turret (swept volume) is 0.83 cubic meters. This includes the space needed for the gun to elevate and depress through its entire range of motion and to recoil at all elevation angles. The compactness of the cannon was enhanced by the short maximum recoil stroke length of only 340mm which reduced the height of the turret needed to accommodate the cannon at the limit of its depression angle. For comparison, the maximum recoil stroke of the 122mm M62-T2S cannon of the T-10M heavy tank was 560mm.</div><div>
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Contrary to common perception, it is possible to extract loaded rounds from the chamber of the cannon despite the fact that the T-72 uses an autoloader, and in fact it is a basic necessity on all tank cannons. The cannon has a manual breech block opening mechanism and an extractor. The propellant charges are automatically extracted and ejected when the breech is manually opened, and the loaded projectile can be extracted by hand. Unlike a rifled gun that uses two-part ammunition, extraction of a loaded projectile does not require ramming it out from the muzzle with a long ramming staff because the driving band does not engage with any rifling when it is loaded. In combat, the universal method used to extract a round is to fire it.</div><div><br /></div><div>Spent casing stubs from the semi-combustible propellant charges are ejected from the chamber at a speed of 14-18 m/s after each shot.<br />
<br /><br /></div><div>For boresighting, the muzzle of the barrel has four shallow cuts in the shape of a cross. This is for the gunner to align and tie two pieces of string to form a crosshair over the barrel muzzle for the purpose of zeroing the gun in the field. According to the manual, the gun and sights are zeroed by aiming the gun barrel at a landmark at a distance of no less than 1,600 meters and then calibrating the sight until the center chevron aligns with the point of aim of the gun barrel. This ensures that horizontal parallax does not contribute to the dispersion of shots at long range. Horizontal parallax is not a problem if the gunsight has independent horizontal stabilization, but the TPD-2-49 and the TPD-K1 sights lack this feature. This feature was only incorporated with the installation of the Sosna-U sight.<br />
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The photos below show a crew member affixing the cross on the muzzle.<br />
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<div><br /></div><div><br /></div><div><div><br /></div><div>The condition of barrels are divided into the following categories depending on the percentage consumption of their service life. Bore erosion is measured 850-1100mm from the breech, which is the throat region of the barrel where maximum erosion occurs.</div><div><br /></div><div></div><blockquote><div>Category 1: New, as well as those that are in operation, and those that were in operation with a service life consumption of up to 25%, or with a level of bore erosion that does not exceed the value set for transfer to the 2nd category. Category 2 is reached when 250 shots with 1 EFC are fired or erosion reaches 0.9mm (25%).</div><div><br /></div><div>Category 2: Barrels that are in operation and those that were in operation, suitable for combat firing with a service life consumption of 25 to 80%, or with a level of bore erosion that does not exceed the value set for transfer to the 3nd category. Category 3 is reached when 800 shots with 1 EFC are fired orerosion reaches 2.6mm (80%).</div><div><br /></div><div>Category 3: Barrels that are in operation and those that were in operation, suitable for combat firing with a service life consumption from 80% to 100%, or with a level of bore erosion that does not exceed the value set for transfer to the 3nd category. Category 5 is reached when 1,000 shots with 1 EFC are fired or erosion reaches 3.3mm.</div><div><br /></div><div>Category 4: Uninstalled.</div><div><br /></div><div>Category 5: Disposal.</div></blockquote><div></div><div><br /></div></div>
Worn out barrels tend to exhibit worse accuracy and usually reduce the muzzle velocity of the projectile due to the incrementally increased diameter of the bore. This was especially noticeable during the first Gulf War, where Iraqi T-72s often urgently needed barrel replacements because they had been used since the Iran-Iraq war. Because of the embargo on military equipment, they continued to use barrels that had exceeded their condemnation limit as they had no access to new barrels and they lacked the sensitive technology to ensure a steady supply from local production facilities.<br />
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The reason that firing rounds out of a worn-out barrel is dangerous is because the bore has been eroded enough that there may be gaps between the driving band on the projectile and the surface of the bore. This permits propellant gasses to blow past the projectile, causing dangerous pressure fluctuations in the barrel. As the photo below shows, this can be very dangerous. Fracturing of the barrel is possible, but thankfully, the fuses of explosive ammunition like HE-Frag and HEAT shells exclude the possibility of premature detonation. Still, disintegrated fragments may potentially harm people and equipment in the vicinity.<br />
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<span style="font-size: large;">2A26M2</span></h3>
<div><br /></div></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-LpzQ7jzB2nk/XxWZpiCM8gI/AAAAAAAARTA/z3Xs5W4-WoYBed4udbgAE7Rw5sonX5-8gCLcBGAsYHQ/s1413/2a26m2%2Bbreech.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="737" data-original-width="1413" height="209" src="https://1.bp.blogspot.com/-LpzQ7jzB2nk/XxWZpiCM8gI/AAAAAAAARTA/z3Xs5W4-WoYBed4udbgAE7Rw5sonX5-8gCLcBGAsYHQ/w400-h209/2a26m2%2Bbreech.png" width="400" /></a></div><div><br /></div><div><br /></div><div>In June 1961, before the 115mm U-5TS gun even entered service with the T-62, the State Committee for Defense Technology (GKOT) of the USSR released requirements for a new tank gun that was capable of achieving a muzzle velocity of 1,800 m/s and had a point blank range of 2,100 m. The OKB-9 design bureau proposed a draft for a 125mm gun in July, and in the August of the following year, work on designing the new gun began under the orders of the Ministry of Defence and the GKOT. The resultant product was the D-81, which was adopted into service under the GRAU designation of 2A26. It is shown in the photo below.</div><div> </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-yEsyh_0JHtM/XxdA21_mlWI/AAAAAAAARTo/zCE9SYJ0uMQPSVugViuV_0cwEAU9_hbeQCLcBGAsYHQ/s1674/2a26%2Bgun.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="272" data-original-width="1674" height="104" src="https://1.bp.blogspot.com/-yEsyh_0JHtM/XxdA21_mlWI/AAAAAAAARTo/zCE9SYJ0uMQPSVugViuV_0cwEAU9_hbeQCLcBGAsYHQ/w640-h104/2a26%2Bgun.png" width="640" /></a></div><div><br /></div><div><br /></div><div>After initial troop testing in 1968 in early Object 434 tanks, a number of defects were discovered which led to the development of the 2A26M model in 1969. One of the complaints was the low service life of its barrel which purportedly amounted to just 350 shots of standard full caliber ammunition or 150 shots of subcaliber rounds only (3BM9). However, this information is unconfirmed and is somewhat suspect, as 3BM9 is known to erode a barrel at a rate 4 times higher than standard full caliber rounds. The original Object 172 and Object 172M prototypes used the 2A26M2 variant with adaptations for the AZ autoloader, and earlier T-72 Ural tanks were armed with the 2A26M2 as well. </div><div><br /></div><div>The gun has an electrical firing mechanism for the elctric primer on 125mm cartridges, with an additional firing pin and mechanical trigger for emergencies where there is either a malfunction in the electrical system or a fault with the primer.</div><div><br /></div><div>The full length of the gun alone is 6,350mm, and the length of the barrel is 6,000mm or 48 calibers, making the 2A26M2 an L/48 gun. This is somewhat less than the length of its closest counterpart, the British 120mm L11A5 gun, which had a barrel length of 6,600mm (L/55). However, due to some peculiarities of the chamber designs of these two guns, the practical difference in barrel length is much less than 600mm. The length of the rifled section of the L11 barrel where projectile acceleration occurs is 5,640mm, and for the 2A26M2, it is 5,200mm or 5,290mm, depending on the type of shell loaded.</div><div><br /></div><div>The flexural rigidity of the barrel was 3,285 N/cm (335 kgf/cm). This is considerably higher than the L11A5 gun, which had a barrel rigidity of just 2,820 N/cm.</div><div><br /></div><div>The necked chamber of the 2A26M2 barrel has a volume of 12.27 liters and a total length of 840mm. Of that, only 800mm of its length can be occupied by a two-part cartridge. When loaded, a propellant charge (with a nominal length of 408mm) is housed in the base of the chamber up to the neck, and the space ahead of it houses the projectile. The necking of the chamber allows a projectile to be smoothly guided through during the ramming process, and for this purpose, Soviet 125mm HEAT and APFSDS rounds had protruding knurls or raised lips on the rims of their bodies or sabots in order to ensure that there were no sharp angles that could damage either the round itself or the barrel. The remaining 40mm of length in the chamber is a forcing cone which necks down from 130mm to 125mm, thus obstructing the obturator of the projectile and preventing further forward motion. The drawing below, taken from the report "<i>Technical Diagnostics of Tank Cannon Smooth Barrel Bore and Ramming Device</i>" by J. Balla et al., shows a cross section of the chamber.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-LEoBxGYbnvY/XxXfJf-E6XI/AAAAAAAARTQ/p76q3zo7uNc6TJpnZovnMPODsLma3sl1gCLcBGAsYHQ/s782/2a46%2Bchamber.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="432" data-original-width="782" height="221" src="https://1.bp.blogspot.com/-LEoBxGYbnvY/XxXfJf-E6XI/AAAAAAAARTQ/p76q3zo7uNc6TJpnZovnMPODsLma3sl1gCLcBGAsYHQ/w400-h221/2a46%2Bchamber.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The obturator ring on a projectile, which has a diameter of 129mm, is radially compressed by the forcing cone until it fits within the bore diameter of 125mm as the projectile moves down the chamber after the propellant is fired. For a Soviet-era APFSDS round where there is only one obturator ring on the sabot, the projectile travels no more than 5,200mm down the barrel before exiting the muzzle. It is not the same with a HEAT or HE-Frag shell, as those have two obturator rings and a total of three points of contact with the barrel bore during acceleration (the other point being the stabilizer fin retention ring). When loaded, the second obturator ring is pressed against the forcing cone, and during the initial propulsion of the shell as it is fired, the gas seal is primarily ensured by the first obturator ring which is 90mm behind the second obturator. Thus, there is effectively an additional 90mm of barrel length available to these shells.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-OmNHgCPBfCM/X33hTkGjhNI/AAAAAAAARrU/iRLuHU47OsMXiLPvarEu1NUdwE2MZzJzQCLcBGAsYHQ/s549/he-frag%2Bloaded.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="231" data-original-width="549" src="https://1.bp.blogspot.com/-OmNHgCPBfCM/X33hTkGjhNI/AAAAAAAARrU/iRLuHU47OsMXiLPvarEu1NUdwE2MZzJzQCLcBGAsYHQ/s16000/he-frag%2Bloaded.png" /></a></div><div><br /></div><div><br /></div><div>When loaded, the projectile is kept from falling out of the chamber through the muzzle end by the forcing cone, and friction prevents it from sliding out the breech end. To unload, the standard procedure is to fire the gun in a safe direction. If the gun must be unloaded without firing it, the ejector lever will eject the propellant charge, but the projectile must be pulled out by hand.</div><div><br /></div><div>The size of the 2A26M2 breech housing is not known, but based on technical drawings, it is approximately 500mm wide. In terms of chamber diameter, the 2A26M2 was wider than an L11 series gun as that used straight cylindrical propellant charges, but it was narrower than an Rh120 which used aggressively necked cartridges. The single advantage of the narrow chamber of the L11 was that in combination with a vertically sliding breech block, the entire breech housing could become quite narrow - only 485mm, equivalent to the 122mm D-25T gun (480mm) and 115mm U-5TS gun (495mm).</div><div><br /></div><div><br /></div><div>The lack of a thermal shroud on the barrel of the 2A26M2 was a trait that it shared with tank guns from the late 1950's, namely the domestic U-5TS, British L7 series, and American M68. At the time the original 2A26 entered service (1968), the newest tank guns fitted on NATO tanks were the 120mm L11 gun of the Chieftain Mk. 2 (1967), and the 105mm CN-105-F1 gun of the AMX-30B (1967). Both had thermal shrouds - a canvas type for the L11 series and a magnesium alloy type for the CN-105-F1. An aluminium thermal shroud only became available for fitting onto existing 2A26M2 guns by the mid-1970's (at least as early as 1975). It was interchangeable with the shroud used on 2A46 gun barrels. The reason for the belated introduction of this simple technology is unclear.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-yPbP4GCPAkI/XxWHKgGDb7I/AAAAAAAARS4/iRsuM5mD27U-ksyjAF8YjrjNfeP9RI_zgCLcBGAsYHQ/s1750/2a26m2%2Bbarrel%2Bwith%2Bthermal%2Bjacket.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="397" data-original-width="1750" height="146" src="https://1.bp.blogspot.com/-yPbP4GCPAkI/XxWHKgGDb7I/AAAAAAAARS4/iRsuM5mD27U-ksyjAF8YjrjNfeP9RI_zgCLcBGAsYHQ/w640-h146/2a26m2%2Bbarrel%2Bwith%2Bthermal%2Bjacket.png" width="640" /></a></div><div><br /></div><div><br /></div><div>In one case, during testing of the Object 172-2M "Buivol" with the 2A46M gun in 1974, it was recorded that when the gun barrel without a thermal shroud was exposed to rain, the deviation of the midpoint of impact in height at a distance of 1 km was 3.6 meters, whereas with a thermal shroud, it was only 15 cm.</div><div><br /></div><div>The 2A26M2 weighed 2,350 kg without the stabilizer components attached beneath its gun cradle. It is lighter than the British 120mm L11A5 gun, which weighs 2,650 kg. The recoiling assembly, which consists of the barrel, breech housing and breech, all weigh 1,850 kg in total, which is very similar to the L11A5 (1,900 kg). The gun is slightly muzzle-heavy so that when a round is loaded, it becomes perfectly balanced. All 125mm guns were configured this way.</div><div><br /></div><div>The maximum operating pressure when firing a standard APFSDS round is 500 MPa. This pressure limit is reached with standard APFSDS ammunition (3BM9) when the propellant temperature is 50°C. In standard conditions where the propellant temperature is 15°C, the nominal operating pressure is 400 MPa. When firing HE-Frag shells, the nominal operating pressure at 15°C is 294 MPa and the maximum operating pressure is 363 MPa at 50°C, whereas for HEAT shells, the nominal operating pressure is just 232 MPa. At the same temperature, the British 120mm L11A5 gun reaches an operating pressure of only 320 MPa when firing its standard APDS ammunition, and it can reach a maximum of 420 MPa. The 120mm M58 gun which armed the M103 heavy tank had a maximum pressure of 330 MPa when firing its standard AP-T rounds. With this large difference in mind, it is evident that the 2A26M series set a new standard for tank gun performance at the time it entered service. This high performance was achieved by a combination of a high yield strength forged steel alloy and a frettage around the chamber of the barrel. The frettage is a jacket which is bound to the barrel by expanding it with heat, then cooling it so that it fits tightly and compresses the barrel, thus raising its maximum pressure limit. On the 2A26M2, the frettage was installed at the zone of highest stress, which was the chamber and the throat of the barrel.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-_t8ylS70ytg/Xx_hc1L66xI/AAAAAAAARXY/40vDVXYzLbwpd06qkLEhaH_TAxmk3dYAgCLcBGAsYHQ/s2094/frettage.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="794" data-original-width="2094" height="242" src="https://1.bp.blogspot.com/-_t8ylS70ytg/Xx_hc1L66xI/AAAAAAAARXY/40vDVXYzLbwpd06qkLEhaH_TAxmk3dYAgCLcBGAsYHQ/w640-h242/frettage.png" width="640" /></a></div><div><br /></div><div><br /></div><div>Naturally, the high operating pressure of the gun was achieved with a large amount of highly energetic propellant. A standard APFSDS round had 10.52 kg of propellant, and a standard HEAT or HE-Frag round had 5.66 kg of propellant.</div><div><br /></div><div><br /></div><div>The hydraulic recoil buffer is installed asymmetrically to the bore axis at the bottom right hand corner of the breech, and the recuperator is installed directly underneath the breech block. The asymmetric installation of the recoil buffer resulted in the unbalanced motion of the cannon during its recoiling cycle while the shell is still in the barrel, and the unbalanced motion generated somewhat more intense oscillations at the muzzle compared to a symmetric recoil system, resulting in larger shot dispersion.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Y38vd0VFQck/XxV3OqGwRbI/AAAAAAAARSs/yYEarfbrb6U5j8jYC7yRo0PzIzAro8SsQCLcBGAsYHQ/s504/2a26%2Bbreech.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="504" data-original-width="377" height="400" src="https://1.bp.blogspot.com/-Y38vd0VFQck/XxV3OqGwRbI/AAAAAAAARSs/yYEarfbrb6U5j8jYC7yRo0PzIzAro8SsQCLcBGAsYHQ/w299-h400/2a26%2Bbreech.png" width="299" /></a></div><div><br /></div><div><br /></div><div>This configuration was carried over from the U-5TS gun. The normal range of recoil stroke distances is 270mm to 320mm, and the maximum is 340mm with a hard stop. The hydraulic recoil buffer was specified to have 4.6-4.8 liters of oil, and operated at an initial pressure of 63-65 kg.f/sq.cm. The hydropneumatic recuperator contained 8.45 liters of oil. The recoil system reduces the recoil force of the gun by 10-15 times, but is physically constrained by the need to limit the recoil stroke distance to below 340mm. The recoil force when firing APFSDS rounds is 3,400 kN.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ulQA53kWsik/XxYHBNMsSfI/AAAAAAAARTY/w1lXLs15LjweC551tbH4FZ62R4W6aQq2QCLcBGAsYHQ/s3241/recoil%2Bmechanism.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="753" data-original-width="3241" height="148" src="https://1.bp.blogspot.com/-ulQA53kWsik/XxYHBNMsSfI/AAAAAAAARTY/w1lXLs15LjweC551tbH4FZ62R4W6aQq2QCLcBGAsYHQ/w640-h148/recoil%2Bmechanism.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The accuracy of the 2A26M2 was hampered by the use of 400 ml of air inside the recoil buffer in order to account for the thermal expansion of the hydraulic fluid. The heating of the hydraulic fluid is caused during the compression of the buffer which causes the fluid to expand. Without a compensating mechanism, the expansion of the fluid would increase the pressure of the buffer and interfere with the recoil dynamics of the cannon. The mixing of air with the hydraulic fluid solves this problem, but the presence of air also causes the recoil stroke to be uneven prior to the sufficient heating of the fluid-air mixture. As such, the accuracy of the gun was affected.<br /><br />
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The guns manufactured in the USSR and in Warsaw Pact nations had a steel bore surface and a level of durability equivalent to other steel bored tank gun barrels. It is alleged that early 2A26 guns produced and used in 1968 for troop trials had bore erosion issues which were subsequently solved with the 2A26M model. The full service life of the barrel is 1,000 shots with full caliber shells (HEAT or HE-Frag), but the accuracy life is 800 shots. The average service life of 2A26M guns, including the 2A26M2, is 600 rounds. This figure is achieved with a mixture of APFSDS, HEAT and HE-Frag. Less than three hundred rounds of APFSDS ammunition could be fired through the barrel. </div><div><br /></div><div>Replacing it was not an easy task. The turret had to be lifted by a crane and positioned so that the gun assembly could be removed through the rear. This was a highly time consuming process that required specialized equipment. In the field, the crane would have been provided by recovery vehicles. In this regard, the Soviet tank gun design was very much behind their Western counterparts. For example, the 90mm gun on the M48 Patton (a 1950's tank) already featured a quick change barrel.</div><div><br /></div><div>
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A fume extractor is installed approximately 3/5 down the length of the barrel. It is a concentric type, and of a conventional design with angled vent holes. The casing of the fume extractor on the 2A26M2 and all of its derivatives is made from steel. The length of the fume extractor is 840mm. Unlike the fume extractors used previously on the U-5TS and D10-T, there are no additional intake holes with check valves to increase the fill rate of the fume extractor chamber. When a shot is fired, the propellant gasses enter the fume extractor chamber through the vent holes, and during the rapid pressure equalization inside the barrel (to ~1 atm) after the projectile leaves the muzzle, the pressurized gas accumulated in the fume extractor is forced to exit into the barrel through the angled vent holes. The exiting gasses are regulated by built-in nozzles. The angled vent holes direct the gasses forward at a speed of around 500 m/s for a duration of 1-1.5 seconds, creating a jet that reduces the pressure inside the barrel by 3-5% compared to atmospheric pressure. The jet discharge induces a flow of air into the bore through the open breech and out through the muzzle, thus removing virtually all propellant fumes from the barrel. After a shot is fired, the muzzle blast is immediately followed by a puff of evacuated propellant gasses, pulled out of the barrel by the jet from the fume extractor.</div><div>
<br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5HWXq82MXD5_lyQrT6dEyG--3g_DvEchX2GLeJjej1g04eCFriQF-Tnr_hff9y7nHyWwnSvEILZzRhpTnCFCksB58ElUsXStQw1POkHsyuz6RoO4-OJuXjwPshb98pHu_WON1urLFzkH-j7IAyjf6EAkacDB2X54FdH2-VHomAVOm-XgvfYG4M0FOFA/s2851/2a26m2%20fume%20extractor.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1989" data-original-width="2851" height="446" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5HWXq82MXD5_lyQrT6dEyG--3g_DvEchX2GLeJjej1g04eCFriQF-Tnr_hff9y7nHyWwnSvEILZzRhpTnCFCksB58ElUsXStQw1POkHsyuz6RoO4-OJuXjwPshb98pHu_WON1urLFzkH-j7IAyjf6EAkacDB2X54FdH2-VHomAVOm-XgvfYG4M0FOFA/w640-h446/2a26m2%20fume%20extractor.png" width="640" /></a></div><div><br /></div>The use of checked valves in the fume extractors of earlier guns was to ensure that the extractor accumulates the minimum specified gas pressure within the extremely short time between the moment the projectile clears the intake channels until the exit of the projectile from the muzzle. The lack of such valves in the 2A26 series indicates that sufficient pressure could be obtained for other reasons, possibly related to the ammunition. To facilitate the operation of the fume extractor and maximize the rate of fire, the gun opens its breech and ejects the spent obturator stub before the gun returns to battery. The opening of the breech opens a path for air to flow into the barrel, thus avoiding the problem of generating negative pressure in the barrel upwind of the fume extractor, which impedes the exit of the fumes. Instead, a strong draft is created, blowing the fumes out of the barrel more effectively. This also helps in removing the fumes emanating from the obturator stub, which is retained in the stub catcher, just behind the breech.<br /><br />Because the breech opens and the stub is ejected before the gun has returned to battery, the gun is always ready to load immediately after firing a shot; there was no need to wait for the ejection system before loading a follow-up shot.</div><div><br /></div><div>There is a drainage plug at the bottom of the fume extractor. Its purpose is to allow the fume extractor to be drained of water. Doing so is crucial to prevent the destruction of the fume extractor if the gun is fired after it has accidentally taken in water. Incidentally, an improperly secured drainage plug is the usual culprit for the leakage of gas pressure when the gun is fired. This leads to the inability of the fume extractor to retain gasses, rendering it ineffective. The improper sealing of the drainage plug is indicated by a jet of propellant gasses shooting downward from the fume extractor when the gun is fired, and is normally followed by the conspicuous lack of the puff of evacuated propellant gasses after the muzzle blast. <br />
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<span style="font-size: large;">2A46</span></h3>
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In 1970, the 2A46 was created as a modernization of the 2A26M to rectify its issues. It was first fitted to the T-64A in 1970 as the 2A46-1 model. The T-72 Ural-1 (1975) was the first T-72 model to have the 2A46 installed. New technologies were mainly applied to the design and manufacturing of the barrel, but the rest of the cannon was not neglected. One of the most serious modifications was the implementation of a hydraulic recoil buffer fluid expansion compensator mechanism which abandoned the use of a fluid-air mixture like the 2A26. This gave the gun a more even recoil stroke which improved the dynamic motion of the shell inside the gun barrel, which in turn improved firing accuracy.</div><div> </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-GXoGfJxIVLs/XyVIsvEan1I/AAAAAAAARaA/OCLeTzz1x-YVib2AFJVl2LgfhtlL4tJOQCLcBGAsYHQ/s844/2a46%2Bbarrel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="266" data-original-width="844" height="202" src="https://1.bp.blogspot.com/-GXoGfJxIVLs/XyVIsvEan1I/AAAAAAAARaA/OCLeTzz1x-YVib2AFJVl2LgfhtlL4tJOQCLcBGAsYHQ/w640-h202/2a46%2Bbarrel.png" width="640" /></a></div><div><br /></div><div><br /></div><div>According to Soviet Army regulations, the condemnation limit of 2A46 barrels in terms of eroded bore diameter is 3.3mm. This is because ammunition fired through a bore that is eroded to a diameter of more than 128.3mm will lose gas pressure and may cause a barrel rupture due to the fact that the obturator and driving band does not exceed 129mm in diameter. The condemnation limit is reached upon firing 1,000 standard full caliber rounds, which are HE-Frag and HEAT. Alternatively, each barrel can be used to fire a maximum of 250 standard APFSDS rounds (3BM9) or 200 rounds of newer types (3BM15, 3BM22). </div><div><br /></div><div>According to <a href="http://www.kotsch88.de/g_2a46.htm">Stefan Kotsch</a>, citing 1986 data, the service life of a 2A46 barrel is 900 rounds. Based on available NVA documents regarding the lifespan of various tank components, the service life is considered to be 90% of the total lifespan. As such, the NVA data supports the official Soviet barrel life figure. Additionally, it is stated in the study "<a href="http://b-dig.iie.org.mx/BibDig2/P11-0358/CUTAFLUP-11.pdf">Wear of cannon 2A46 barrel bore</a>" by Robert Jankovych and Stanislav Beer, that one 2A46 barrel was used to make 830 shots with HE-Frag and HEAT rounds. </div><div><br /></div><div><br /></div><div>The design pressure was not increased from the 2A26M2. The recoiling system remained largely the same as the 2A26M2, with modifications to correct some design flaws. The normal range of recoil stroke distances is 270mm to 320mm, and the maximum is 340mm with a hard stop. Recoil distance is measured up to 340mm using a conventional recoil indicator.</div><div><br /></div><div>Only a few years after the 2A46 became the new standard tank gun, the 120mm Rh120 gun entered service as the main gun of the Leopard 2. Although it was short, being only an L/44 gun, it operated at a considerably higher pressure yet did not suffer from an excessive bore erosion rate due to the inclusion of a HC (High Contraction) chrome lining. The M256 and Rh120 guns, firing the M829 and DM13 rounds respectively, both had an operating pressure of 510 MPa at a temperature of 21°C. At a lower temperature of 15°C, the pressure can be extrapolated to be around 500 MPa, which was the maximum for a round like 3BM9 and close to the maximum for 3BM15 and 3BM22. The maximum operating pressure reached 630 MPa, achieved with a propellant temperature of 54°C. </div><div><br /></div><div>With this in mind, it is fair to say that the nominal operating pressure of the Rh120 and standard 120x570mm APFSDS cartridges was another class above the 2A46. This was possible thanks to the use of barrels processed by autofrettage. If the Rh120 were compared directly to the 2A46, the much higher pressure developed by the more energetic propellant of its cartridges evidently allowed it to overcome the limitations of its much shorter barrel and marginally smaller caliber (smaller by 9%) and match the 2A46 in ballistic performance, as the M829 and DM13 APFSDS rounds had muzzle energies of 10 MJ and 9.8 MJ respectively while the 3BM22 round had a muzzle energy of 10.1 MJ. Later 120mm rounds exceeded the muzzle energy of 125mm APFSDS rounds.</div><div><br /></div><div>Despite the high operating pressure and high temperature of the propellant used to achieve it, the barrel life of the M256 and Rh120 guns reaches 700 rounds when firing their respective standard APFSDS rounds; M829 and DM13.</div><div><br /></div><div>Compared to the 2A26M2, the full weight of the gun was slightly increased to 2,400 kg. The addition of the thermal shroud on the barrel together with the accompanying counterweight ballast plates accounts for the difference in weight. The weight of the recoiling assembly is 1,820 kg. For comparison, the recoiling assembly of the Rh 120 smoothbore gun weighs 1,905 kg. The barrel of the 2A46 weighs 1,156 kg on its own.</div><div>
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To manually open the breech, the commander has to pull on the breech opening handle in a single stroke, which is not easy in the confines of the tank as the pull weight of the handle is 245 N.<br />
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According to the Slovakian study "<a href="http://www.aijcrnet.com/journals/Vol_2_No_9_September_2012/17.pdf">Increasing Firing Accuracy of 2A46 Tank Cannon Built-in T-72 MBT</a>", it was calculated that the probability of hitting a T-72 tank target with the 2A46 at a distance of 2 km with the first round is 57%. Keep in mind that this represents the accuracy of a basic T-72 including its original fire control system. Errors from range measurements will translate into increased vertical dispersion which would have a negative impact on the probability of hit, especially since the dispersion of shots in the vertical axis is much higher than in the horizontal axis. The higher vertical dispersion is due to the asymmetric recoil system inherited from the 2A26M2. However, the mechanical dispersion of shots fired from the 2A46 were not inferior to foreign guns with symmetrical recoil systems such as the 120mm L11A5 despite the use of an asymmetrical recoil system. This is because in the L11A5, the hydraulic recoil buffers (one on the top right in front of the breech housing, one on the bottom left) were not pressurized to the same amount. During recoil when firing both APDS and HESH, the top buffer would be pressurized to 32.5 MPa while the bottom buffer would be pressurized to 26.6 MPa. This resulted in the symmetric recoil system behaving like an asymmetric type.</div><div><br /></div><div><br /></div><div>The accuracy of the 2A46 can be considered quite high from a practical standpoint as the targets would be taller NATO tanks like the Leopard 1 and M60A1. The Slovakian study on the modernization of the 2A46 mentions that a 23% improvement in the probability of hit was achieved with the new 2A46MS (YA1) cannon with the remark that the improvements could also be attributed to new fire control system components.</div><div>
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The barrel of the 2A46 cannon was enveloped by a thin aluminium thermal shroud in order to minimize barrel warping from the asymmetric thermal expansion of the barrel due to meteorological conditions. For example, the heating of the barrel from sunlight only occurs on the surfaces around the top of the tube, so the metal on the top part expands whereas the metal on the bottom part does not. This causes the barrel to bend downwards. Bending may also occur when the barrel is cooled unevenly, such as by rain or by a crosswind. It was found that barrel bend from environmental conditions could increase shot dispersion by up to 1.5-2.0 mils. A thermal shroud solves this issue by insulating the barrel from sudden external temperature changes.</div><div><br /></div><div>The thermal shroud is comprised of four segments, almost covering the entire length of the barrel except for the muzzle and a section of the base of the barrel in front of the armoured gun mask where the barrel is thickest. The lack of a shroud on the base of the barrel is mainly because of the need to account for the recoil stroke of the cannon, as the clearance between the gun mask and the gun barrel is very narrow. The length of the uncovered section at the base of the barrel is 540mm. The length of each thermal shroud segment is not the same: counting from from the base and ending at the muzzle, the first two sections are 836mm in length and the remaining two sections are 632mm in length.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-VcMQY1a8pok/X03cBImShbI/AAAAAAAARh8/g3SGBjbgCxsUIwBFWXMV8M6QPygSoJgWwCLcBGAsYHQ/s1243/thermal%2Bshroud.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="821" data-original-width="1243" src="https://1.bp.blogspot.com/-VcMQY1a8pok/X03cBImShbI/AAAAAAAARh8/g3SGBjbgCxsUIwBFWXMV8M6QPygSoJgWwCLcBGAsYHQ/s640/thermal%2Bshroud.png" width="640" /></a></div><div><br /></div><div><br /></div><div>Like the magnesium alloy shroud used on French 105mm F1 gun, the aluminium alloy shroud on 125mm guns functions by conductive dissipation with a highly conductive shroud and an air gap. When heated on one side by external heat sources or cooled by wind or rain, the temperature of the shroud quickly equalizes across its entire body due to its high thermal conductivity, whereas at the same time, the barrel is barely heated due to the air gap acting as an insulator. This ensures that the barrel is uniformly heated at a slow rate, which eliminates the temperature disparity across the barrel and thus suppresses thermal warping. Similarly, a concentric steel fume extractor naturally behaves as a thermal shroud. Aluminium alloys are particularly well-suited for this type of thermal shroud because aluminium is readily available and has exceptionally high thermal conductivity. </div><div><br /></div><div>The main alternative to a conductive dissipation shroud is an insulating shroud wrapped tightly around the barrel, as found on the British L7 and L11 guns. This type of thermal shroud functions by acting as a simple insulator from external heating by slowing the rate of heat transfer between the gun barrel and the outer shroud surface. It does not equalize temperature differences at different sides of the barrel, because the relative thickness of insulating material between two opposite ends of the shroud is much greater than the thickness between the sleeve surface and the barrel surface. This is the simplest and least effective type of thermal shroud for minimizing barrel warping, but it is more effective for decreasing the thermal signature of the barrel.</div><div><br /></div><div><br /></div><div>Each segment of the thermal shroud has two drainage holes at the bottom, as shown in the photos below (<a href="http://www.primeportal.net/tanks/azrael_raven/t-72_raac_museum/index.php?Page=7">courtesy of Azrael Raven from primeportal.net</a> and Plebola). Their primary purpose is to ensure that the shroud can be drained of water after a snorkeling operation across a deep river; it is futile to completely waterproof the shroud at such depths. It is reasonable to assume that each shroud segment has two holes, one at each end, to ensure that water can be drained regardless of the elevation angle of the gun. Additionally, if water from rain or melted snow enters the shroud through a worn seal or by holes caused by battle damage, the drainage holes ensure that the shroud does not accumulate water.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-aWvimzYi9I4/X02_6hw8vgI/AAAAAAAARho/2A_mTC-3xqQIMG5YPukqrL3YynLdO855ACLcBGAsYHQ/s800/thermal%2Bshroud.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="600" height="400" src="https://1.bp.blogspot.com/-aWvimzYi9I4/X02_6hw8vgI/AAAAAAAARho/2A_mTC-3xqQIMG5YPukqrL3YynLdO855ACLcBGAsYHQ/w300-h400/thermal%2Bshroud.jpg" width="300" /></a><a href="https://1.bp.blogspot.com/-RBgp5B_MR24/X02__MDRVkI/AAAAAAAARhs/1NDwcwazWVsTRxg5T1YnNa_8KbrQGwWJACLcBGAsYHQ/s2048/20200801_144720.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="400" src="https://1.bp.blogspot.com/-RBgp5B_MR24/X02__MDRVkI/AAAAAAAARhs/1NDwcwazWVsTRxg5T1YnNa_8KbrQGwWJACLcBGAsYHQ/w300-h400/20200801_144720.jpg" width="300" /></a></div><div><br /></div><div><br /></div><div>Due to the use of aluminium, the shroud is resistant to wear and tear from harsh environments, does not rust, and does not rot, unlike canvas thermal sleeves. Moreover, the addition of an insulating camouflage sleeve over the thermal shroud does not interfere with the thermal dissipation between the shroud and the gun barrel. The same is true if the barrel is covered with branches and netting for camouflaging purposes.</div><div>
<br />The addition of the thermal shroud is a source of increased accuracy, although it tends to be only noticeable in real world conditions and not during controlled bench testing where environmental conditions tend to be kept constant. In order to counterbalance out the weight of the thermal shroud, additional steel ballast plates were added to the stack behind the gun breech.<br />
<br />The fume extractor is the same as on the 2A26M2.<br />
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The T-72A began its service life in 1979 with the 2A46 and the T-72M (Obj. 172-E2) export model also used the 2A46. Several years later, the 2A46 was replaced by the newer and more accurate 2A46M, but its service life did not end there. The 2A46 was reverse engineered by the Chinese and an improved copy of the gun called the ZPT-98 is currently in production to equip the current generation of Chinese main battle tanks, including the Type 96, Type 99 and even the latest VT-4. A video of the assembly of a Chinese 2A46 is <a href="https://youtu.be/hPXkV2vXT3k?t=11m10s">available on YouTube</a> as part of a documentary on the VT-4. The screenshots below are taken from the video and show a disassembled ZPT-98 cannon.<br />
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One of the differences between the ZPT-98 and the 2A46 is the gun cradle. The cradle on the ZPT-98 closely resembles the one on the 2A46, but the trunnion on the cradle is derived from the D-10T gun mounted on the Type 59 tank. Other than that, the ZPT-98 is built with features derived from the 2A46M including a quick-change barrel and various other maintenance-oriented amenities.<br />
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<a href="https://www.blogger.com/null" id="2a46m"></a>
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<h3>
<span style="font-size: large;">2A46M</span></h3>
<div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-S0jw4LjUK84/XxWt_XHkuLI/AAAAAAAARTI/H9soai5qrHkgXC6Q3deZGD620AASYugXwCLcBGAsYHQ/s2666/2a46m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="525" data-original-width="2666" height="126" src="https://1.bp.blogspot.com/-S0jw4LjUK84/XxWt_XHkuLI/AAAAAAAARTI/H9soai5qrHkgXC6Q3deZGD620AASYugXwCLcBGAsYHQ/w640-h126/2a46m.png" width="640" /></a></div><div><br /></div><div><br /></div><div>The 2A46M featured a new breech block, gun cradle, recoil system and a new barrel with an interrupted screw mounting jacket which permitted quick swapping in field conditions. It was almost an entirely new gun, with very little parts commonality with the 2A46 and 2A26. At this late stage of evolution, only a handful of components from the 2A26 still remained, like a vestigial tail. The axle of the breech opening handle and most of the breech itself was carried over from the 2A26, with three out of seven breech components still retained from the old gun. A small number of minor components such as fasteners and bearings were from the 2A20. The only major component that is not indexed under the 2A46M item code is the toothed arc for the gears of the manual elevation mechanism (2A46.Sb.21).</div><div><br /></div><div>The length of the gun was slightly increased to 6,383mm due to the new breech housing, but the barrel remained 6,000mm long. It retained full compatibility with all 125mm ammunition. Other than the total length of the gun, its dimensions decreased at the breech area due to the new recoil mechanism layout, with the hydropneumatic buffers and recuperator all embedded into the breech housing itself. The 2A46M does not have a cutout in the breech housing along the side for a loader's hand. Instead, there is merely a small gap which allows a wooden ramrod to be pushed aside by the breech when it closes. This presumably served as additional mass to ensure that both sides of the breech housing were symmetrical in weight when the breech was in the closed position.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-2H-FRy-w-qw/XyVJw0APcRI/AAAAAAAARaI/fY7Q2K1Fk1kLhcdDtOrHeK97q13_HcSagCLcBGAsYHQ/s515/2a46%2Band%2B2a46M.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="270" data-original-width="515" src="https://1.bp.blogspot.com/-2H-FRy-w-qw/XyVJw0APcRI/AAAAAAAARaI/fY7Q2K1Fk1kLhcdDtOrHeK97q13_HcSagCLcBGAsYHQ/s0/2a46%2Band%2B2a46M.png" /></a></div><div><br /></div><div><br /></div><div>When the decision to modernize 125mm tank guns was made in the late 1970's, a number of new technologies such as autofretting had to be implemented to accommodate the greatly increased ballistics of new ammunition. The 2A46M barrel was not only produced by autofrettage, but also had an additional frettage installed around its chamber like the barrels of the 2A26M2 and 2A46 guns, as shown in the drawing below. An optional chrome lining can be applied to mitigate the increased bore erosion rate of the aforementioned new ammunition, but serially produced barrels for the Soviet and Russian Army do not have a chrome lining.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-cg1pZ0xmCLY/Xx_jSYe7WGI/AAAAAAAARXg/mNjDBAIKKds0qcOlM2x_Szu76Hg3_2PeQCLcBGAsYHQ/s454/fretted%2Bbarrel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="173" data-original-width="454" src="https://1.bp.blogspot.com/-cg1pZ0xmCLY/Xx_jSYe7WGI/AAAAAAAARXg/mNjDBAIKKds0qcOlM2x_Szu76Hg3_2PeQCLcBGAsYHQ/d/fretted%2Bbarrel.png" /></a></div><div><br /></div><div><br /></div><div>It is written in "<i>Combat Vehicles of Uralvagonzavod: T-72 Tank</i>" that the T-72 with the 2A46M cannon passed acceptance tests in 1978. According to Mikhail Baryatinsky, new T-72A tanks from 1981 onward were produced with the 2A46M, three years after the acceptance tests were passed. The 2A46M was installed with the T-72B since its introduction in 1985. The 2A46M is also noteworthy for having the necessary electronic components for launching guided anti-tank missiles.</div>
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The aforementioned technologies which applied in the design and manufacture of the 2A46M gun barrel allowed a reduction in shot dispersion to be obtained. The rigidity of the barrel was increased to 3,775 N/cm (385 kgf/cm). Accuracy was reportedly improved by 50% thanks to the new barrel itself and its mounting system, in addition to the completely revised recoil system of the gun. </div><div><br /></div><div>By manufacturing barrels using an autofrettage process, the maximum operating pressure could be substantially increased while also reducing fatigue. This solution was necessary to ensure the viability of high energy APFSDS shells such as 3BM26, 3BM32 and 3BM42. The design pressure or maximum safe pressure is not known. According to the study "<i><a href="http://irbis-nbuv.gov.ua/cgi-bin/irbis_nbuv/cgiirbis_64.exe?C21COM=2&I21DBN=UJRN&P21DBN=UJRN&IMAGE_FILE_DOWNLOAD=1&Image_file_name=PDF/znpsnu_2013_3_22.pdf">Применение Лазерных Технологий Для Повышения Срока Службы Изделия КБА-3</a></i>" ("<i>The use of laser technologies to increase the service life of the product KBA-3</i>") which deals with the Ukrainian KBA-3 gun (rebranded 2A46M-1 gun), the nominal operating pressure of 3BM42 "Mango" is 555 MPa at a propellant temperature of 15°C and it has a maximum pressure of 637 MPa at 50°C, exceeding the M829 and DM13 rounds which both had an operating pressure of 510 MPa at a propellant temperature of 21°C and could reach a maximum pressure of 630 MPa at 54°C. Ballistically, 3BM42 most closely corresponds to M829A1, which develops a maximum pressure of 570MPa at 21°C. As a rule, the design pressure of the gun is not less than the pressure of a standard APFSDS round at 50°C, implying that for the 2A46M, it is in excess of 637 MPa.</div><div><br /></div><div>The KBA-3 gun - which corresponds to the 2A46M-1 - lacked a chrome lining and as such, had a barrel life of just 200 rounds when firing standard APFSDS ammunition (3BM42). The barrel life of the 2A46M is greatly inferior to that of the M256 and Rh120, as the former has a useful life of 600 M829A1 rounds and the latter has a useful life of 700 DM13 rounds, or <a href="https://1.bp.blogspot.com/-AAwK0XZMFgg/XqWPMlxvVDI/AAAAAAAAAQI/ZhgBPjvaz0UgY3S_tNT1g_WSRe4CLN_WACLcBGAsYHQ/s1600/5fa357789d62f759a6e1461ba0aae7d94bd7c27.jpg">400-600 DM33 rounds</a>. It is advertised that with a chrome lining, the barrel lifespan of the 2A46M is 1,200 EFC and the number of standard APFSDS ammunition (3BM42) that could be fired is 450 rounds.</div><div><br /></div><div>
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The photo below (<a href="https://www.dishmodels.ru/wshow.htm?mode=P&vmode=T&p=2321&id=108366&tp=w">courtesy of Dmitry Derevyankin</a>) shows the symmetric installation of two recoil buffers at the top right and bottom left corners of the breech face, and the retention of the recuperator at its original position directly underneath the breech. The symmetrical installation of two smaller recoil buffers greatly reduces the moment (the turning effect of a force) experienced by the cannon during the recoiling cycle, and thus reduces the oscillations at the muzzle while the shell is still in the barrel. Both the vertical and horizontal dispersion could be reduced by this new layout, but the largest improvement would be in the vertical dispersion. The 2A46M has a normal recoil stroke of 260mm to 300mm and a maximum recoil stroke of 310mm with a hard stop. The main advantage of limiting the recoiling distance is the reduction in the volume needed in the turret to accommodate the gun over its entire range of elevation angles, and for the the 2A46M, the slight reduction was important because the breech assembly was lengthened slightly compared to the 2A46.<br />
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The gun in the photo below is actually a 2A46M-1 for the T-64BV and T-80BV, but the breech is otherwise identical to the 2A46M. The only differences are in the shape of the breech guards and in the presence of an electric motor for raising and lowering the shell casing stub ejection mechanism.<br />
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<div><br /></div><div><br /></div>The gun cradle was redesigned, with the most notable changes being the interface between the barrel and the cradle, and the guide rails for the breech assembly. Instead of a single dorsal guide plate that rides in a trough cut into the top of the breech, the 2A46M breech slides along two thick rails when recoiling.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-e1suPMCbo1A/XxU_DlaeKaI/AAAAAAAARSc/sFAZm_lVa8Uzv2ggDLWUbLRiOnQMabJTwCLcBGAsYHQ/s1265/2a46m%2Bgun%2Bcradle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="826" data-original-width="1265" height="261" src="https://1.bp.blogspot.com/-e1suPMCbo1A/XxU_DlaeKaI/AAAAAAAARSc/sFAZm_lVa8Uzv2ggDLWUbLRiOnQMabJTwCLcBGAsYHQ/w400-h261/2a46m%2Bgun%2Bcradle.png" width="400" /><br /></a></div><div><br /></div><div>
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The method of seating the barrel to the gun cradle was improved. According to a <a href="http://computerland-spb.ru/images/pdf_uvz/Guns_spreads.pdf">marketing presentation by UVZ</a>, the seating of the barrel was changed from the combination of the breech ring and support from a single contact point with the cradle to purely cradle support with two contact points. The small gap between the cradle support and the barrel (less than 1mm) in all D-81T pattern guns is a free expansion zone to minimize the impact on the ballistics of the barrel from thermal expansion after multiple shots are fired. By having the free expansion zone, the number of contact points between the cradle support never changes and the performance of the gun is more consistent.<br />
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Assuming that the increase in the mechanical accuracy of the 2A46M over the 2A46 is indeed 50%, then the probability of a 3BM-15 round fired from the 2A46M hitting a T-72 tank at 2 km would be 85.5% instead of 57% for the 2A46, if all other conditions are equal. This is quite a large improvement. The likelihood of hitting a taller target would be higher and could approach unity if newer ammunition with lower dispersion than the old 3BM-15 round with the outdated "ring"-type steel sabot was used.<br />
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The 2A46M was also a milestone product in another way: the new mounting system for the barrel enabled quick replacement in the field from the outside of the turret by pulling it out from the front, without needing to remove or shift the turret. The procedure reportedly takes around 2 hours, but it is not clear if this is for an operation done in a depot or in the field.</div><div><br /></div><div>Moreover, the oil level in the recoil buffers and recuperator could be checked without the opening of the stopper caps, making it much simpler and quicker to perform routine maintenance on the cannon. Previously, tank crews referred to a schedule to record and determine if the buffer and recuperator in the 2A46 required a top up. If that information was not available, then the cannon would need to be retrieved from the turret and it would have to be inspected on a testing mount and tested with a pullback winch.</div><div>
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The overhaul of the design of the cannon also brought improvements to some of its less major components. Most notably, the manual breech opening mechanism at the top left corner of the receiver had to be redesigned because of the location of the new recoil buffers. The new mechanism has a ratchet so that two tugs on the lever are needed instead of one, and the pull weight for the lever was decreased considerably. This makes it much easier to manually open the breech within the confines of the tank. The first pull on the handle opens the breech block halfway, and the second opens it fully. To close the breech, the breech block release lever on the left side (gunner's side) of the gun is released. If, for instance, there is a misfire, one possible course of action is to open the breech halfway and reseal it, hopefully reseating the cartridge and realigning the primer with the breech block.</div><div><br /></div><div>Another modification introduced in the 2A46M was a change to the fume extractor design. It is functionally the same, but greatly differs in some structural details. It could be speculated that the change was brought on by the increased maximum pressure permitted from the ammunition fired from the 2A46M.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxaoBhpIutlJ33ew-7bZZ-5G4zqzTJTcfm1YvimZnW6QQb9_R8e-eMSRyjD_gv_MpEir29pDHkzGJK7_K9o5uCkiConRt1gccLgSdYHi0j72bZLZex2Fq78kMMnfQCS_rFgGrrmRl4EYtoI8x9gwk_vIGw8SandVnKzWMfJcDf1xjNvv_LpphFrYhabw/s5221/fume%20extractor.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3097" data-original-width="5221" height="380" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxaoBhpIutlJ33ew-7bZZ-5G4zqzTJTcfm1YvimZnW6QQb9_R8e-eMSRyjD_gv_MpEir29pDHkzGJK7_K9o5uCkiConRt1gccLgSdYHi0j72bZLZex2Fq78kMMnfQCS_rFgGrrmRl4EYtoI8x9gwk_vIGw8SandVnKzWMfJcDf1xjNvv_LpphFrYhabw/w640-h380/fume%20extractor.png" width="640" /></a></div><div><br /></div><div><br /></div><div>Altogether, all of the modifications increased the mass of the cannon to 2.5 tons.<br />
<br />Beginning with the 2A46M, the gun may be boresighted with special notches at the muzzle of the barrel which are used as reference points.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Th4Moe1F_QM/X4770nvNwpI/AAAAAAAARxs/S_Pz45RPU68A8tTa9yKHlbDZMpcQ_Vh8gCLcBGAsYHQ/s1104/2a46m%2Bmuzzle%2Breference%2Bnotch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="813" data-original-width="1104" height="472" src="https://1.bp.blogspot.com/-Th4Moe1F_QM/X4770nvNwpI/AAAAAAAARxs/S_Pz45RPU68A8tTa9yKHlbDZMpcQ_Vh8gCLcBGAsYHQ/w640-h472/2a46m%2Bmuzzle%2Breference%2Bnotch.png" width="640" /></a></div><div><br /></div><div><br /></div><div>If the system malfunctions, it is always possible to revert to the conventional boresighting method using a cross. This feature fulfills the same function as a muzzle reference sensing system with the advantage of inherent robustness, as the calibration notches are cut into the bell of the barrel itself and not affixed like an MRS. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Mks_QtIxw58/X2dvWxl06-I/AAAAAAAARn4/tTBSTqSv4AQOnm-C53dvB4dIx5UTyBMmgCLcBGAsYHQ/s673/calibration%2Bnotch%2Bon%2B2a46m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="605" data-original-width="673" height="360" src="https://1.bp.blogspot.com/-Mks_QtIxw58/X2dvWxl06-I/AAAAAAAARn4/tTBSTqSv4AQOnm-C53dvB4dIx5UTyBMmgCLcBGAsYHQ/w400-h360/calibration%2Bnotch%2Bon%2B2a46m.png" width="400" /></a><br /></div><div><br />
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<span style="font-size: large;">2A46M-5, 2A46M-5-01</span></h3>
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<a href="http://3.bp.blogspot.com/-SC3iq-wUGiQ/VmkKpoh9iHI/AAAAAAAAE5g/sWyNPX6zFAU/s1600/2A46M-5.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="353" src="https://3.bp.blogspot.com/-SC3iq-wUGiQ/VmkKpoh9iHI/AAAAAAAAE5g/sWyNPX6zFAU/s640/2A46M-5.jpg" width="640" /></a></div>
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The T-72B3 builds upon the T-72B
with the inclusion of the 2A46M-5 gun (D-81TM-5), which was first introduced in 2005 and used in the T-90A. The 2A46M-5-01 can be considered to be the most sophisticated model of the entire
series thus far, but the improvements applied to this model are not known.<br />
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The dynamic balancing of the barrel during the firing procedure (while the shell is still in the barrel) was better tuned, thus minimizing oscillations at the muzzle. The barrel itself was improved with an increased rigidity of 4,118 N/cm (420 kgf/cm), which is 10.5% times greater than the 2A46M barrel. This serves to reduce oscillations transmitted through the suspension of the tank when it is driven over rough ground, thus improving the dispersion characteristics of the gun when fired on the move. Moreover, the maximum rated chamber pressure was increased to 608 MPa to permit the use of new APFSDS ammunition. According to <a href="http://www.zavod9.com/en/?pid=18">the manufacturer</a>, dispersion of all shell types by
an average of 15% to 20%, and the accuracy when firing on the move has been increased 1.7 times, thanks to the greatly decreased vibration of the gun the tank is in motion over rough ground. Overall, the estimated probability of hit in combat was increased by 20-29% for APFSDS ammunition, 4-12% for HEAT ammunition, and 21-38% for HE-Frag ammunition.</div><div><br /></div><div>The 2A46M-5 barrel features a chrome lining. It is not known if the lining spans the entire length of the chamber and bore or if it was merely applied to the chamber and the throat of the bore, 850-1,100mm from the breech, as that is the zone of maximum bore erosion when firing APFSDS rounds.<br />
<br />The 2A46M-5 features a quick-replacement mechanism for its barrel that is almost identifcal to the 2A46M gun. The barrel is released from the housing assembly by twisting it by 45 degrees, done by fitting a special wrench on a hexagonal part of the barrel. The threads that lock the barrel to the receiver are seen in the screenshot below, taken from a news tour on the No. 9 Factory which builds these guns.<br />
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<div><br /></div><div><br /></div>The improvements implemented in the 2A46M-5-01 gun, installed in T-72B3 UBKh tanks, are not known. In all likelihood, the guns are modified according to a <a href="http://btvtinfo.blogspot.com/2018/09/246-4-246-5.html">patent filed by the No. 9 artillery factory</a> describing changes to improve the service life of barrels by thickening the barrel at the gas ports for the fume extractor. </div><div>
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As you can see in the photo below, the location of the recoiling mechanism elements remained unchanged from the 2A46M. The main differences were not so obvious. More photos of the 2A46M-5 are available <a href="http://www.kotsch88.de/g_2a46m.htm">on Stefan Kotsch's website</a>.<br />
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The drawing below (<a href="http://army-news.ru/2014/09/tankovye-pushki-2a46m-5-i-2a46m-4/">from here</a>) showcases the location of the recoil buffers and the recuperator in relation to the axis of the cannon barrel. The drawing is probably valid for the 2A46M as well.<br />
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<h3>
<span style="font-size: large;">AMMUNITION STOWAGE</span></h3>
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A basic T-72 including the T-72 Ural and T-72 Ural-1 models can carry a maximum ammunition load of 39 rounds. This was increased to 44 rounds in the T-72A, and increased again to 45 rounds in the T-72B. In all T-72 models, 22 rounds were carried in the autoloader carousel as the ready supply, while all of the remaining ammunition was kept as a reserve supply. The reserve ammunition would be loaded into the autoloader carousel whenever it is necessary, but only when local security has been established. Replenishment of the autoloader from the reserve supply during combat is not practiced - it is much more expedient and much quicker to directly load the main gun manually.
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<span style="font-size: large;"> AUTOLOADER</span></h3>
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<span style="font-family: inherit;">The T-72 uses an "AZ" type </span><span style="font-family: inherit;"><span style="font-family: inherit;">electro</span>mechanical carousel-type autoloader with a 22-round capacity. All 22 rounds are stored in individual cassettes arranged radially around a central hub which houses the carousel rotation motor and drive as well as the power supply for the turret. The autoloader was modernized in the T-72B to missiles to be carried. The new autoloader had higher reliability, and could also store longer projectiles. We will first examine the original Ural autoloader (known as the AZ-172), and then examine the newer T-72B autoloader (known as the AZ-184) in the context of the improvements that were introduced to the original model. The patent for the T-72B autoloader (Russian Patent No. 2204776) is available <a href="http://russianpatents.com/patent/220/2204776.html">here</a>. </span>As mentioned earlier in this article, the gunner controls the autoloader from a control unit located on the TPD-K1 sight, and the commander has his own set of controls.<br />
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According to the memoirs of Leonid Kartsev, the AZ-style autoloader was developed independently by the UKBTM design bureau after Kartsev inspected a T-64 during its trials and felt "trapped" by the ring of ammunition surrounding the turret ring, noting that the crew in the turret had no form of contact with the driver besides the intercom system. Upon his return to Nizhny Tagil, he ordered the creation of an autoloader system with a different scheme of ammunition stowage with the intent of surpassing the MZ autoloader, resulting in the AZ autoloader. This new autoloader was first fitted to the Object 167M before being implemented in the Object 172 and then finalized in the T-72 Ural as the AZ-172. The AZ autoloader traded the larger 28-round capacity of the MZ autoloader for an all-electric motorized system, a slightly reduced 22-round capacity and a lower profile. The nuances of this autoloader will be the topic of discussion.</div><div><br /></div><div>The autoloader consists of three major assemblies: </div><div><ol style="text-align: left;"><li>The power rammer</li><li>The carousel</li><li>The elevator</li></ol></div><div><br /></div><div>Ammunition is stored in the carousel, which surrounds the slip ring power distribution box at the base of the turret. The carousel is merely a rotating frame containing cassettes that stores the ammunition. The cassettes are held on mainly by gravity, and spaced apart from one another by protruding supports. From the broader perspective of the overall layout of the tank, this method of storing ammunition is directly analogous to floor ammunition racks as found in a wide range of tanks from the WW2 era, including Cold War era tanks that inherited WW2 era design features, the most prominent of which are the M46, M47, and the Centurion series. The skeletal frame of the carousel and its hub on the slip ring power distribution box can be clearly seen in the photo below, taken from <a href="https://www.msmls.sk/en/services/repairs">MSM Land Systems</a>. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQ0EAOZXevAg4TASEpC_Q_wKzAzNFQlKqz9VrcM4hiwBNXKdgaXSjCsX3Wi5Xl0KfTImHEvxCklR8PHgK9xvAkRI-Q4UYfAlOKxgFUPCrRK_5LYznJstSsJ7-IV3D2COHqpnptoqxt6-W9qj1ihNWdIQFQIYcOmUsHGzHwUzas5QXVkyLuDPEGvB0LLxDG/s1280/contents_gallery_horizontal_zoom_97.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="1280" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQ0EAOZXevAg4TASEpC_Q_wKzAzNFQlKqz9VrcM4hiwBNXKdgaXSjCsX3Wi5Xl0KfTImHEvxCklR8PHgK9xvAkRI-Q4UYfAlOKxgFUPCrRK_5LYznJstSsJ7-IV3D2COHqpnptoqxt6-W9qj1ihNWdIQFQIYcOmUsHGzHwUzas5QXVkyLuDPEGvB0LLxDG/w640-h480/contents_gallery_horizontal_zoom_97.jpg" width="640" /></a></div><div><br /></div><div>The elevator is a chain pulley mechanism that raises a cassette to the loading position behind the gun breech, where it is rammed into the gun by the power rammer.</div><div><br />During an engagement, the following occurs:</div><div><ol style="text-align: left;"><li>The gunner selects an ammunition type on his selector dial, and presses the "load" button</li><li>Gun raises to the loading angle, while at the same time, the stub catcher is raised to eject the stub casing from the previous shot (raises but does not eject if no stub casing present)</li><li>Carousel spins until it reaches a cassette containing a cartridge of the selected ammunition type</li><li>Carousel stops when the cassette is directly under the elevator</li><li>Elevator lifts the cassette to ramming position No. 1, positioning the projectile behind the breech</li><li>Power rammer extends to ram the projectile and retracts</li><li>Elevator lowers the cassette to ramming position No. 2, positioning the propellant behind the breech</li><li>Power rammer extends to ram the propellant and retracts </li><li>Elevator lowers the cassette back into the carousel. Memory unit marks cassette as empty.</li></ol></div><div>There is overlap between some of these steps in the loading cycle, but otherwise, this fully describes the chronological progression of the loading cycle.</div><div><br />It is claimed in the memoirs of Leonid Kartsev that this was superior to the T-64A as the spent shell stub was a significant source of propellant fumes from smoldering residue inside the stub, and that disposing of the stub reduced the concentration of fumes in the fighting compartment. There is truth to this claim, as video evidence has shown that even when there is virtually no escape of fumes from the cannon breech after firing (indicating that the fume extractor is working well), the spent shell stub may still pollute the fighting compartment until the smouldering propellant residue is completely burnt. <a href="https://www.youtube.com/watch?v=6okDotojj58">This video</a> is a good example of this. We can also see from <a href="https://www.youtube.com/watch?v=l2d8JbBO5H4">videos of artillery crews</a> that this is also true for fully cased unitary ammunition, so the immediate ejection of the spent shell stub from the turret of the T-72 is beneficial to the working environment of the crew. However, the opening of the ejection port exposes the crew compartment to unpurified air in an NBC contaminated environment, which was avoided with the stub return mechanism of the T-64 autoloader. Nevertheless, the contamination from the ingress of irradiated dust particles was considered to be at acceptable levels, which was satisfactory for the Soviet Army as the prevailing concern was to be able to operate in a nuclear-contaminated battlefield, with chemicaland biological contaminants being of secondary importance.<br /><br />It is important to note that the creation of 125mm semi-combustible cartridges was tied to the development of semi-combustible ammunition for the 115mm D-68 gun for the T-64, and the core rationale for the use of this type of ammunition instead of conventional metal-cased ammunition was to facilitate the operation of the autoloader by eliminating the inconvenience of handling a large empty spent case, as well as the inconvenience of wasting the space it took up if it was simply ejected onto the floor of the fighting compartment. For the T-72 autoloader, these benefits only manifested in a very minor capacity, because the stub is ejected. The small size of the stub is helpful in that it is not obstructive to the cassette when it is lifted up to the ramming position, because the ejection mechanism has limited clearance with the cassette. The small size is also beneficial in case the stub catcher mechanism fails to catch the stub, and it falls onto the carousel cover. If this occurs, there is no interference with the loading cycle.<br />
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Each shell and propellant charge stored within the carousel is housed within a two-tiered steel ammunition cassette with extended bills to properly line up the shell or propellant charge with the
gun chamber. The diameter of the carousel spans the width of the hull. Below, you can see the ammunition cassettes being dropped in place on a T-72B3 autoloader carousel frame. The carousel rotates independently of the turret and the cover on top of it during both normal and manual operation. Rollers are installed on the carousel frame to ensure that it rotates smoothly along the cover.<br />
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The notch on the edge of the central hub marks where the tray lines up flush with the trapdoor on the carousel cover. The notch allows projectiles that are physically longer than the ammo cassette to pass through the trapdoor. As shown in the two photos below, the carousel itself is a simple skeleton frame made from welded steel tubing and pressed sheet steel and is relatively lightweight. The central hub of the carousel fits around the power distribution unit which supplies power to the turret.<br />
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The diameter of the autoloader carousel is around 1,800mm and the height of the carousel is around 450mm. The reason for the smaller capacity of the AZ autoloader compared to the MZ series used in the T-64 and T-80 series is structural in nature; both autoloaders array the projectiles in a circle, but the AZ carousel also arrays the propellant charges. Having a larger diameter, the size of the circle that can be arranged is therefore smaller, so fewer rounds can be stowed. Because of this, the AZ autoloader has a smaller capacity despite having the same diameter as the MZ autoloader. </div><div><br /></div><div>There is also a certain loss of volumetric efficiency as well, because both autoloaders are provisioned with a cylindrical space in the tank. With ammunition arranged in a circle, they form a multi-sided polygon, with the diameter of the ammunition being one side of the polygon. The more sides in the polygon, the closer it approximates a true circle. Having 28 cartridges, the MZ autoloader fills a cylindrical space with a 28-sided polygon, whereas the AZ autoloader fills its cylindrical space with a 22-sided polygon. The difference in volumetric efficiency is apparent from observing the fact that the gaps between the projectiles in an AZ autoloader are much larger than the gaps in an MZ autoloader.</div><div><br /></div><div>That said, however, the MZ autoloader series is considerably less volumetrically efficient in practice due to the large swept volume occupied by the cassette raising arm suspended below the carousel. This arm is needed to raise the cassette to the ramming position behind the gun breech. As the image on the left below shows, a very large empty volume is left underneath the carousel to allow the cassette raising arm to rotate together with the cabin. For comparison, the AZ carousel (right, below) is almost directly on top of the torsion bars. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCcngyWx4bvv5h-mpRZeNH6j_TBCF6iyhywvzlkTOgFswzz5b98zVcRYjGbV5Dj_8iKgiZb4uRhE_cTq17MShNz4846V4DGjVKXABVo2Wwn1q4T4TXyTOV1i9kGf82PBPFmJ5zS__Kf5KwqkKjIJ7AF3q6ZCbwBUM5L-KcTHH6g6MQ37OUkF8ZLqlpZQ/s728/mz%20autoloader%20floor%20clearance.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="571" data-original-width="728" height="251" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCcngyWx4bvv5h-mpRZeNH6j_TBCF6iyhywvzlkTOgFswzz5b98zVcRYjGbV5Dj_8iKgiZb4uRhE_cTq17MShNz4846V4DGjVKXABVo2Wwn1q4T4TXyTOV1i9kGf82PBPFmJ5zS__Kf5KwqkKjIJ7AF3q6ZCbwBUM5L-KcTHH6g6MQ37OUkF8ZLqlpZQ/s320/mz%20autoloader%20floor%20clearance.png" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgLe75joM4mF94DcB_bypXI81UmOiK0tZHPvhWLvHVO1WpuNcqmgAMw0XfM0Ki_vmQ1pfMgTe4LFxh9KH99ynYy3EuX6pM8WZVfPaT6p8jBXhjmAyT5MMGYKUPe8nvuaJHx39RWEv2ZCehaC8Hna7gZAaGvdJSw4UOb6-w_Z1mHQPOxxIPol-G5dtDd9g/s891/az%20clearance.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="718" data-original-width="891" height="258" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgLe75joM4mF94DcB_bypXI81UmOiK0tZHPvhWLvHVO1WpuNcqmgAMw0XfM0Ki_vmQ1pfMgTe4LFxh9KH99ynYy3EuX6pM8WZVfPaT6p8jBXhjmAyT5MMGYKUPe8nvuaJHx39RWEv2ZCehaC8Hna7gZAaGvdJSw4UOb6-w_Z1mHQPOxxIPol-G5dtDd9g/s320/az%20clearance.gif" width="320" /></a></div><div><br /></div><div>For a fighting compartment of a given volume, the AZ carousel design approach reduces the ammunition in the carousel itself, but provides a net increase in the usable volume, which is to the crew's benefit, and can be used to stow additional ammunition in reserve racks.</div><div><br /></div><div>Inside the carousel, the cartridges are held in metal cassettes. Each cassette consists of pair of a welded steel-walled cylinders with built-in locking mechanisms to hold the ammunition firmly in place. The weight of a full cassette is 14.2 kg. The top half of the cassette is 6.9 kg and the bottom half is 7.3 kg. The cassette in the autoloader of a former NVA-operated T-72M was measured to have a wall thickness of 2.54mm. According to GOST specifications, the closest thickness to 2.54mm for steel sheets is 2.5mm, and it is likely that the true thickness of the cassette walls is 2.5mm. The additional thickness measured on the real specimen is probably the paint on top of the metal. The cassettes could be considered a surrogate to a metal case for the semi-combustible cartridges, which are otherwise more fragile to mechanical influences and fragmentation.</div><div>
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The maximum length of each cassette is 680mm, which is just 2mm longer than the HEAT projectiles carried by the T-72 like the BK-14 and BK-18, and only 5mm longer than HE-Frag shells like the OF-19. The APFSDS ammunition supplied to tanks during the Cold War was the shortest among the three main ammunition types, and even the 3BM-46 "Svinets" projectile fits easily into the ammo cassette.<br />
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Modified cassettes are used in the T-72B carousel in order to accommodate guided missiles. The modified cassettes have special latches on both sides accommodate guided missiles and to prevent the stabilizing fins of the missile from accidentally deploying when the missile is rammed into the cannon.<br />
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Although the new cassettes are designed to accommodate guided missiles, the length of the cassettes remain at 680mm, so the 9M119 guided missiles (695mm long) supplied to T-72B tanks will overhang the cassette by 15mm. The main factor enabling guided missiles to be carried in the autoloader carousel was not the modified cassettes, but the reduction of the diameter of the hub of the carousel. Thanks to the provisions for accommodating anti-tank missiles, APFSDS rounds of higher elongation are compatible with the AZ-184 autoloader.<br /><br />
<br />The well-known author Steven J. Zaloga claims that there were some problems with zeroing the sighting system and the cannon because the sight was independently stabilized, and the vertical stabilizer for the cannon would sometimes fail to synchronize with the stabilizer unit in the sight as the cannon resets to its original position when finishing its loading cycle. However, it is doubtful if this issue truly exists, because the stabilizer for the cannon is slaved to the independently stabilized TPD-K1 sight and the fire control system features electronic fire gating via a resolver on the gun trunnion, so the stabilizer will always attempt to lay the cannon as close as possible to the aiming point of the sight and permit firing only when there is coincidence between the sight and the gun within a margin of 0.5 mils. The alignment will never be perfect, because the weapons stabilizer is less precise than the stabilizer for the sight. Zaloga may have mistakenly labelled the small alignment error between the two cross-linked systems as a design flaw.<br />
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The autoloading cycle requires the gun to be locked at a pre-programmed elevation of +3°30' (+3.5 degrees) which is done so automatically as the cycle begins. During the reload cycle, a cassette is elevated to the ramming position by an electric chain-driven elevator, and the two-part ammunition is rammed into the gun breech. First the shell is loaded, and the propellant charge follows. Because the cannon automatically elevates by +3.5 degrees at the beginning of the reload cycle, the top half of the autoloader elevator is slightly tilted by the same angle to bring the cassette into alignment with the breech. The slight tilt is visible in the diagram below. The diagram shows a T-72 Ural type autoloader. The T-72B has a modified carousel, but the autoloader is otherwise identical.<br />
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The electric carousel rotation motor is shown in the cutaway drawing below. The motor is installed on top of the carousel top cover and the ZU-172 memory unit that records the position of each round stored in the autoloader (among other things) is mounted on top of the motor.<br />
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The electric motor for the ammunition cassette elevation mechanism is installed on the ceiling of the turret. The use of an electric ammunition cassette elevation mechanism instead of the hydraulic system of the MZ autoloader enables the volume of flammable hydraulic fluid located close to the ammunition to be reduced, thus indirectly increasing the survivability of the tank.<br />
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Propellant charge casing stubs are automatically ejected by a stub catcher through a small port at the rear of the turret, visible below:<br />
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The stub catcher mechanism registers the presence of a casing via a switch installed in a paddle-shaped arm located behind the stub catcher, shown in the drawing on the right. The paddle-shaped arm also keeps the stub from falling out the back of the stub catcher. When a casing stub is ejected from the cannon, it hits a pin (4) at the back of the paddle-shaped arm which lifts a conductive flat spring (5) off an electrical contact (6), breaking the circuit and prompting the system to register the presence of a propellant charge casing stub in the stub catcher mechanism.<br />
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When the gunner activates the autoloader to load the cannon, the stub catcher mechanism is lifted to the ejection port in the turret roof by a linear actuator installed underneath the breech housing of the gun, and the stub is ejected by a pair of ejector levers, powered by a torsion bar. As the ejector mechanism is lowered back into its position behind the breech, the torsion bar for the ejectors is rewound. The paddle-shaped arm is swung away to the side (in the direction of the gunner) by the ammunition cassette elevator to make way for the ramming mechanism.<br />
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<div><br /></div><div><br /></div>If the ejection port does not open or opens with improper timing due to an electric or mechanical issue, the ejected case stub may only fall back into the tank without the possibility of harming either the commander or gunner.<br />
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When loading the cannon manually in the total absence of electrical power, the spent casing stub held in the stub catcher mechanism is removed by manually pulling the paddle-shaped arm away. After that, the casing stub can just be pushed out the back of the stub catcher and thrown away or stowed away somewhere in the tank. The spent casing stub shold be removed after every shot when firing the gun manually. If not, the casing stub from the next shot would hit the previous stub and fall down onto the carousel cover. Firing without removing the case stub is permissible in emergencies but should be avoided. The photo below shows a case stub being removed manually.</div><div><br />
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Unlike what most people assume, it is completely possible to unload the cannon after a shot is already loaded. Although not always necessary, this may be useful when two different threats appear one after another. For instance, enemy infantry may appear after the T-72 has finished dealing with an enemy tank, so switching to HE-Frag will be necessary. If an APFSDS round is still loaded in the cannon, it will have to be unloaded either by returning it to the autoloader or firing it off, perhaps into the previously knocked-out enemy tank to ensure that it is truly disabled. If it is desirable to conserve APFSDS ammunition, then the loaded round should be unloaded from the back end of the cannon rather than the front. This can be done by simply using the commander's autoloader control box. The empty ammunition cassette is raised from the carousel, whereby the commander can open the breech manually using the breech operating handle. The ejection of the propellant charge is done automatically by an ejector built into the cannon. The action of pulling the breech operating handle opens the breech and returning the breech operating handle to its stowed position manually activates the ejector to push the propellant charge out of the chamber. The chambered projectile is not ejected; it must be extracted by hand. The propellant charge and projectile are inserted into the empty cassette and returned to the autoloader carousel. After this, the gunner can continue the target engagement process as normal. The amount of time needed to complete this operation is non-trivial, but it is absolutely possible if the situation calls for it.</div>
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<span style="font-size: large;">MEMORY UNIT</span></h3>
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The autoloader is able to recognize the position of each round stored in the carousel using the carousel storage memory unit, as shown below (ZU-172 model for the AZ-172 autoloader). Three ammunition types can be indexed into the carousel in this model. This device is mounted next to the trapdoor of the carousel cover, at a position where the commander can access it easily when replenishing the carousel.<br />
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<span style="font-family: inherit;">To load ammunition into the autoloader, the commander must use his control box to cycle between cassettes. After loading a cassette, he must input the ammunition type into the memory unit by pushing one of three buttons, one for each type of shell: HEAT (К), APFSDS (б), or HE-Frag (O). When any one of the three buttons is pushed, the memory unit records the corresponding ammunition type and returns the cassette to the carousel, then the carousel spins to the next empty cassette.</span><br />
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The memory unit indexes the type of ammunition on a data disc stored inside the circular housing. The type of ammunition is identified using a binary system on the data disc. There are four magnetic rings on the surface of the disc. The rings are divided into a total of twenty two groups; one group for each round stowed in the autoloader carousel. Each group consists of three sets of four ring sectors. In each group, four of the sectors are for recording the type of ammunition (ammo set), four are used to determine when to brake the carousel rotation motor (braking set), and four are used to determine where to stop the carousel in order to line up the ammunition to the trapdoor (stopping set). Each sector stores one bit of data. As there are twenty two groups with twelve data recording elements capable of storing one bit each, the data disc is considered to have a storage capacity of 264 bits. </div><div><br /></div><div style="text-align: center;"><a href="https://4.bp.blogspot.com/-EN9CwuGacMg/WpaR0vREefI/AAAAAAAALCg/6tXnmGtfjS0PVuQPMqF0af0KkXzF9MjigCLcBGAs/s1600/ural%2Bmemory%2Bunit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1075" data-original-width="1179" height="363" src="https://4.bp.blogspot.com/-EN9CwuGacMg/WpaR0vREefI/AAAAAAAALCg/6tXnmGtfjS0PVuQPMqF0af0KkXzF9MjigCLcBGAs/w400-h363/ural%2Bmemory%2Bunit.png" width="400" /></a></div><div><br /></div><div>Within each group, the sectors are divided into the following sets: <br /><blockquote>ПК3, ПК6, ПК9, ПК12 - to record ammunition type<br />ПК2, ПК5, ПК8, ПК11 - to initiate braking<br />ПК1, ПК4, ПК7, ПК10 - to stop the carousel</blockquote></div><div>The ammunition recording set will record one ammunition type in each sector. </div><div></div><blockquote><div>ПК3 - Empty</div><div>ПК6 - HE-Frag<br />
ПК9 - APFSDS</div><div>ПК12 - HEAT</div></blockquote><div>As the data reader contacts turn around the fixed disc, the first set that will be read by the system is the ammunition type record set. Then, as the carousel continues to spin, the reader contacts will run over the braking set, causing the carousel rotation motor to begin braking. Once the reader contacts reach the stopping set, the motor brakes the carousel hard to fix it in place, positioning it on the cassette elevator. If the ammunition type read by the system does not correspond to the type chosen by the gunner on his selector dial, the braking and stopping sets are ignored.</div><div><br /></div><div>When the autoloader loading cycle is activated by the gunner, the carousel motor receives the command to rotate, but it does not know when to stop until the memory unit reaches the appropriate ammunition type, so if the gunner selects HEAT rounds, the carousel will rotate until the system reads the appropriate binary code on the data disc whereupon the command to brake and stop the carousel motor is read and processed by the autoloader.<br /><br />In other words, the system does not know what the shortest route to the selected ammunition type is. This system limits the carousel to rotating in only one direction even though the motor is actually capable of rotating in both directions. Due to the system limitations, the reverse rotation is only activated when braking the rotation of the carousel. This is unlike the MZ autoloader of the T-64A and T-80 which has an autoloader memory system that is able to dynamically read the positions of all ammunition stored inside the carousel and display it digitally on a special circular device. However, the MZ autoloader is also not capable of rotating in both directions. Instead, the MZ autoloader has a "sequence" loading mode where the carousel will automatically spin to the next round of the type selected by the gunner immediately after loading. <br /><br />After the round is loaded and the ammo cassette returns to the carousel, the memory unit instantaneously rewrites the data to a zero value to represent the empty status of the cassette so that the autoloader will ignore empty cassettes when loading. Conversely, the system is reversed when the autoloader is set to the replenishment mode, so that the carousel will only stop at empty cassettes when replenishing the carousel, ignoring filled cassettes.</div><div><br />When replenishing the carousel, recording the ammunition information is done by three current carrying pins connected to the magnetic rings via electrical contacts.
Data storage is done by changing the polarity of the sector groups to either positive or negative using the electrical contacts. The electrical contacts are spring loaded to keep them in contact with the magnetic rings to ensure that reading and writing the data is still possible even while the device is experiencing strong vibrations such as when the tank is on the move over rough ground or after the tank is hit with the shockwave of an explosive blast. However, the constant pressure wears out both the magnetic ring and the electrical contact over time as the disc rotates, leading to a loss in the ability to record and read data, and the conductive metallic dust produced by the rubbing of the contact on the ring surfaces can contaminate other parts of the unit, causing reading errors. Such errors could prevent the autoloader from accepting new ammunition when loading it, or cause the autoloader to lose track of where ammunition is stored or even to "forget" when to stop rotating the carousel if it is already in motion, so that it rotates indefinitely. Even if the recording surfaces are not worn out, it is also possible for the device to fail from the accumulation of dust and grime over time. At this point, it is possible to either replace the electrical contacts on the hard disc, or replace the entire memory unit. This is an easy task that can be done in the field as long as a spare memory unit is available, as the replacement of the unit only requires that the old one has its electrical cable unplugged.<br />
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The rotation of the reader contacts around the fixed data disc is not powered by an internal motor, but rather, is driven by the carousel rotation motor via a gearbox leading to shaft passing through the bottom of the memory unit. <br />
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The design of the data disc is clearly an extremely simple and archaic form of hard disc storage with an extremely low storage capacity. The lack of sophistication, however, is completely justified by the lack of a need to store a large volume of data and the high robustness required of the system. The simple design of the memory unit grants high resistance to shock and mechanical damage, and its self contained housing facilitates quick replacement if it is damaged. Apparently, one of the most common source of autoloader malfunctions is the memory unit.<br />
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<span style="font-family: inherit;">Due to the limit of three ammunition types, this memory unit is not used in the T-72B, as there is a new type of ammunition: guided missiles. According to t</span>he patent for the T-72B autoloader (Russian Patent No. 2204776)<span style="font-family: inherit;">, the memory storage was upgraded to accept a fourth ammunition type; missiles. The upgraded memory storage unit was also improved for better reliability.</span><br />
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<a href="https://3.bp.blogspot.com/-mREMFD75qn0/WpaQZowKhpI/AAAAAAAALCU/2DSv4-zYcXoL9e-84mDkxr5eMbIrmNklwCLcBGAs/s1600/t-72b%2Bautoloader%2Bmemory.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="500" data-original-width="951" height="336" src="https://3.bp.blogspot.com/-mREMFD75qn0/WpaQZowKhpI/AAAAAAAALCU/2DSv4-zYcXoL9e-84mDkxr5eMbIrmNklwCLcBGAs/s640/t-72b%2Bautoloader%2Bmemory.png" width="640" /></a></div>
<span style="font-family: inherit;"><br /></span><span style="font-family: inherit;">To record a fourth ammunition type, the data disc features five magnetic rings instead of four. The first sector in the ammo set records an empty cassette, while the other four record ATGM, APFSDS, HEAT and HE-Frag. The storage capacity increased to 330 bits. Additionally, this new memory storage unit features a new input mechanism with a rotary dial instead of three buttons. </span>The method of reading and recording data is functionally the same, differing only in how the mechanism functions. <span style="font-family: inherit;">The dial has four positions for the four ammunition types. To select and index an ammunition type, the dial is turned to one of the four positions, and then pressed. The position of the dial serves to position a mechanical stop, to limit how far the writer contact can travel along the disc. When the dial is pressed, a servomotor is activated to move the writer contact until it hits the stop, and then a current passes through the writer contact. Whichever sector the contact is laid upon will be energized. In this way, one of the five sectors will be switched to a one value while the others remain with a zero value, thus recording one ammunition type.</span></div><div><span style="font-family: inherit;"><br /></span></div><div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggdyd-ZGb-LWWIPdjXrFlaHx0Nj2Ttk8HQKuuj4VZLr1Z0IMJ4TdPSWf-73we77trzYUsWdMeY5oPmp-gGh0-zSeVliBHq0_LE2yzv2FE2Oe_e6YGeglHVyqFRorjPQxl03LCkJZu1ilcujJtKxaVGJ5OhX1IXRTVjBSrIUUiWzkq56mTTep2QffCwZQ/s4725/t-72b%20memory%20unit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3181" data-original-width="4725" height="269" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggdyd-ZGb-LWWIPdjXrFlaHx0Nj2Ttk8HQKuuj4VZLr1Z0IMJ4TdPSWf-73we77trzYUsWdMeY5oPmp-gGh0-zSeVliBHq0_LE2yzv2FE2Oe_e6YGeglHVyqFRorjPQxl03LCkJZu1ilcujJtKxaVGJ5OhX1IXRTVjBSrIUUiWzkq56mTTep2QffCwZQ/w400-h269/t-72b%20memory%20unit.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgKe6qgilmAHowzrUKUzmJlM4XloqEDoxZel4nQsknkLmYGWyWkXIENfmeiwVei9_3l9NmXl_gP98qwq8EBL4A9bB8Ts3_I0pBXCYy-v-MtA-0ZHb7g5D3qldM42x92xu6DZwpGWbFXe7wPEvEUo3na5XzDu6_iuppRCqTP2dPz_Aol9WexEY3_2KfHIg/s6121/new%20memory%20unit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="5315" data-original-width="6121" height="348" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgKe6qgilmAHowzrUKUzmJlM4XloqEDoxZel4nQsknkLmYGWyWkXIENfmeiwVei9_3l9NmXl_gP98qwq8EBL4A9bB8Ts3_I0pBXCYy-v-MtA-0ZHb7g5D3qldM42x92xu6DZwpGWbFXe7wPEvEUo3na5XzDu6_iuppRCqTP2dPz_Aol9WexEY3_2KfHIg/w400-h348/new%20memory%20unit.png" width="400" /></a></div></div><span style="font-family: inherit;"><br /></span></div><div><span style="font-family: inherit;"><br /></span></div><div><span style="font-family: inherit;">A closer look at the dial is available in </span><a href="https://youtu.be/BymLH03oIJs?t=3m7s" style="font-family: inherit;">this video</a><span style="font-family: inherit;"> at (3:08). The new memory unit can be seen in the screenshot below.</span><span style="font-family: inherit;"><br /></span>
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<span style="font-family: inherit;"><br /></span>The photo below shows a T-72 Ural or T-72A, as evidenced by the welded appliqué armour plate on the upper glacis. Note the T-shaped power distribution unit at the center of the hull where the carousel would be fitted.<br />
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<span style="font-family: inherit;"><br /></span><span style="font-family: inherit;">The model of the unit is the VKU-330-4, as shown below.</span><br />
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<span style="font-family: inherit;"><br /></span><span style="font-family: inherit;">The permissible length of projectiles in the T-72B autoloader carousel was increased by reducing the size of the central hub. This was done by redesigning the hub which was accompanied by a switch from the VKU-330-4 power distribution unit to the VKU-1 unit. The photo below shows a T-72B3 with a VKU-1. Note the three protruding arms instead of a T-shape.</span><br />
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This modification enabled the 695mm-long 9M119 guided missile to be used with the autoloader carousel. The T-72B1 uses the AZ-172 autoloader and memory system since it is a low cost version of the T-72B without the missile firing capability, so the upgraded autoloader is not necessary.<br />
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<span style="font-family: inherit;">In the T-90A autoloader, the system was revised and digitized. The information on the type and location of the ammunition in the carousel is stored digitally in a separate device, and the shortest distance to reach the ammunition is determined by an algorithm. The absence of the old disc-type memory unit is confirmed in the photo below, although the crankshaft housing from the carousel that would have rotated the hard disc is still present as a "vestigial tail" of sorts. This is evidence that although the control system was overhauled, the T-72B carousel was retained. The issue of two-way rotation is resolved by the implementation of a sufficiently sophisticated control system. The carousel rotation motor itself is reversible and has always been capable of both clockwise and anti-clockwise rotation since the original version in the T-72 Ural, but due to the rather crude ammunition retrieval system, the reverse function of the motor had only been used for braking until then.</span><br />
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<span style="font-family: inherit;"><a href="https://3.bp.blogspot.com/-4w09QlVqJl4/WblxDoNKAPI/AAAAAAAAJaE/g539CQeIWews8rQrSN61YwV0LhyLb_zOwCLcBGAs/s1600/t-90-44.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1022" data-original-width="1600" height="408" src="https://3.bp.blogspot.com/-4w09QlVqJl4/WblxDoNKAPI/AAAAAAAAJaE/g539CQeIWews8rQrSN61YwV0LhyLb_zOwCLcBGAs/s640/t-90-44.jpg" width="640" /></a></span></div>
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<span style="font-family: inherit;">There are some claims that the T-72B3 uses the autoloader from the T-90A, and that this allows the T-72B3 to use more elongated APFSDS rounds. Currently available evidence shows that this is not the complete truth. A T-72B3 with the old T-72B memory unit (<span style="color: red;">Red</span>) and commander's control box (<span style="color: #ffd966;">Yellow</span>) can be see in the photo below.</span><br />
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<span style="font-family: inherit;">This shows that the ammunition indexing and retrieval system is still based on the older T-72B, so the carousel must also be from the T-72B. However, it is clear that the system has been revised. Note that the old ammunition selector dial has been replaced with a new one. The photo below - this time showing the T-72B memory unit </span>(<span style="color: red;">Red</span>)<span style="font-family: inherit;"> in a T-72B3 obr. 2016 - supports this theory. Even in 2016, the T-72B3 is evidently still using the old T-72B carousel, and even the same control box </span>(<span style="color: #ffd966;">Yellow</span>)<span style="font-family: inherit;"> is used.</span><br />
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The T-72B3 obr. 2016 is indeed modified to accept longer APFSDS rounds. More specifically, it is designed to accommodate Svinets-1 and Svinets-2. This is according to a saved copy of <a href="http://zakupki.gov.ru/223/purchase/public/purchase/info/documents.html?lotId=4498123&purchaseId=3264240&purchaseMethodType=EP">order document No. 31603190542 by Uralvagonzavod corporation</a> in a government registry of purchase documentation which contains two mentions of modernizing the autoloader to enable the use of products designated as "S-1" and "S-2".<br />
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One similarity between the T-72B3 and the T-90 autoloaders is in the sequence of actions of the stub ejection port hatch which is observed to momentarily open and close immediately after firing without actually ejecting a shell casing stub, presumably to evacuate the fumes. This feature was first seen in the T-90 as displayed in <a href="https://youtu.be/kjC0a5kN-oI?t=3m15s">this video</a>, <a href="https://youtu.be/OcUFYyo20eg?t=1m34s">this video</a> and <a href="https://youtu.be/LiYmSxwUV-c?t=10m9s">this video</a> and many others. The fact that the T-72B3 also has this feature indicates that it shares something in common with the T-90 autoloader. As we have seen, there is evidence to show that the T-72B autoloader can load longer projectiles than the Ural autoloader, but there is nothing concrete that indicates that there were any further upgrades to projectile length after the T-72B. It is often assumed that the carousel is to blame for the limited projectile length, there is evidence that other factors are to blame for this limitation.<br />
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In June 2005, a patent (<a href="http://www.freepatent.ru/patents/2300722">Patent No. 2300722</a>) filed by UKBTM for a method of increasing the permissible length of projectiles usable in the autoloader was filed. The patent describes a modified autoloader elevator design wherein the ammo cassette is pulled backward to avoid the cannon breech as it is elevated to the ramming position. It is hinted in the patent that the main restriction on the projectile length is not the carousel, but the cannon. To be more specific, the patent states that a possible method of increasing the permissible length of projectiles involves moving the cannon forward, and that this would require significant reworking of the turret, and it would disrupt the balancing of the cannon. The carousel is not mentioned at all. It is not clear if this patented system was actually implemented in new production tanks or implemented at all, but since the carousel is not the main limiting factor, it is absolutely possible that the T-72B3 can simultaneously have the old T-72B carousel installed and still be able to fire the same shells as the T-90A.<br />
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<span style="font-family: inherit;">The photo below shows the location of the memory unit for the T-72 Ural and the carousel trapdoor through which the two-piece ammunition passes through. The drawings on the right show the carousel itself and the carousel frame.</span><br />
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This scan comes from the book "T-72/72M/72M1 in detail", from preview pictures available on super-hobby.com (<a href="https://www.super-hobby.com/products/T-72-72M-72M1-in-detail.html">link</a>).<br />
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<span style="font-family: inherit;"><br /></span><span style="font-family: inherit;">The time taken per shot is around 7 seconds. This enables the tank to achieve a maximum rate of fire of 7 to 8 rounds per minute. The cyclogram below shows the chronological order of the steps in the autoloading process.</span><br />
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The cyclogram gives a total loading time of around 7.7 seconds, but this is because the cyclogram includes the rotation of the carousel over two ammunition cassettes instead of transferring directly to the next one to represent a specific ordered arrangement of ammunition in the carousel or to represent a the time taken when switching ammunition types. The cyclogram also includes the firing and recoil of the cannon after the loading cycle, so the total time taken represents the time taken between shots rather than the time taken by a reload cycle. With a time between shots of 7.7 seconds, the AZ autoloader is on par with the MZ autoloader which achieves a speed of 7.5 seconds under the same circumstances (loading the third round in the sequence). The difference of 0.2 seconds is simply imperceptible.<br />
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As you can see in the cyclogram, the last second of the loading cycle is taken up by the release of the cannon from hydrolock and by the automatic laying of the cannon back into the last previous aiming position and then onto the new aiming point, so the gunner can open fire immediately, which is represented by the tag "Recoil of the cannon" that represents the firing of the cannon immediately after loading is concluded. This is possible because of the independent vertical stabilization of the gunner's primary sight and the separation of the turret traverse system from the rotation system of the autoloader carousel, so he can conduct ranging and aim at a new target during the loading cycle. This is no different from any other modern fire control system. The biggest drawback of the AZ autoloader is that it requires two ramming cycles instead of ramming the entire two-part cartridge in one go, like the MZ autoloader of the T-64.<br />
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The AZ autoloader carousel is very compact, as you can see in the photo below. Based on <a href="http://bastion-karpenko.ru/VVT/T-72_07.jpg">this official UKBTM drawing</a> of the cross-section of a T-72, the carousel occupies around half of the internal height of the hull, so its height is around 450mm, including the top cover. Excluding the top cover, the carousel has a height equivalent to a standing propellant charge (408mm), including the struts that mount the carousel to the belly of the tank. Note that the carousel in the photo below has a cylinder attached to the central hub, indicating that this carousel is for a T-72B.<br />
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There is some additional equipment installed on top of the carousel cover. The silver box you see near the center of the carousel cover is a KR-175 relay box. It connects to the VKU-330-4 power distribution unit and supplies power to the turret.<br />
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<span style="font-family: inherit;"><span style="font-family: inherit;">The T-72 does not have a significant disadvantage when compared to human loaded counterparts, which include the majority of NATO tanks. Most examples can achieve a 4 to 5 second loading time - when their tank is immobile. However, it's a whole different story on rough terrain.</span> </span>An
advantage to the autoloader is that a bumpy ride, change of direction
or slope traversal will never affect the autoloader's
operation in any way. It can maintain its normal cyclic loading rate in
whatever
condition or orientation the tank is in. In manually-loaded tanks, the whole vehicle will pitch and dive as it drives over ruts and mounds while the gun - <a href="https://books.google.com.my/books?id=M1P6jT8_yrgC&pg=PA48&lpg=PA48&dq=abrams+ready+rack&source=bl&ots=U7yXYt-ARV&sig=9b-J3wDZOQ5baxRN4Om7Sv6iEhg&hl=en&sa=X&redir_esc=y#v=onepage&q=abrams%20ready%20rack&f=false">which would be disconnected from the stabilization system in tanks like the Abrams when the loader drops the safety lever</a> - will move up and down on its own volition, making it less straightforward for the loader to get the shell aligned with the chamber to ram it in.<br />
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Firing on the move is usually done at a low cruising speed or at a crawl in order to maximize accuracy, but a tank speeds up and performs evasive maneuvers in between shots in order to avoid enemy fire, before slowing down again to return fire. The stressful time between shots is when the loader must perform his duties, and it would generally be harder to load the cannon during that time. <a href="https://www.youtube.com/watch?v=GzOLRj4iNPg">This video</a> illustrates this point perfectly. At 1:08 and 1:31 in the video, the movement of the gun delays the loader by around a second, extending his loading time to 7.9 seconds and 8.2 seconds respectively (loading time is defined as the time between dropping the loader's safety lever and moving back to a position away from the path of recoil). This would not be an issue for a tank furnished with an autoloader, but to be fair, this is also not an issue for tanks installed with a loader's assist system where the gun automatically raises by a few degrees and fixes the breech in detente, placing it at the optimum loading angle for the loader. The earliest tank to have this feature was the T-54B, followed by the T-62. Later on, tanks like the Leopard 2 and the Merkava 4 featured similar loader's assist systems.<br />
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The autoloader can maintain its cyclic loading speed throughout an extended engagement until the carousel is exhausted. On the other hand, the speed of a human loader is affected by the location of the ammunition and the orientation of the turret as well as the motion of the tank. For example, a Leopard 2 tank stows only fifteen rounds in the ammunition compartment in its turret bustle, but <a href="http://www.kotsch88.de/kanonen/120mmrh/leopard2-munkammer.jpg">only six rounds are available to the loader at any time</a> due to the small size of the blast door and the design of the collapsible ammunition racks, so he must manually rearrange the racks after the six rounds are expended. He cannot do this in between shots because the blast door must remain closed until the loader opens it to load the cannon or the purpose of the compartmentalized ammunition would be completely defeated. Furthermore, a human loader may become fatigued long before the ammunition is exhausted or even before combat even commences, whether it be due to excessive heat, excessive cold, shortage of food, shortage of water, or any other imaginable fact of life for a soldier fighting on the front lines. For instance, it was mentioned earlier in this article the personnel heater in the M60A1 and M60A3 was astonishingly unreliable and frequently caused the fire extinguisher system to discharge accidentally, and some tanks like the Chieftain did not have a heater at all. The efficiency of a human loader would be affected by this, whereas an autoloader would not.<br />
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All in all, the T-72's autoloader is entirely satisfactory for generating a sustainable rate of fire for realistic encounters.<br />
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<h3>
<span style="font-size: large;">CAROUSEL PROTECTION</span></h3>
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The overhead cover on top of the carousel acts as a false floor for the occupants in the turret. The entire carousel with all attached equipment weighs 460.1 kg, but the carousel with the cover alone (excluding the ammunition trays) weighs 293.72 kg, while the cover itself weighs 130.8 kg.<br />
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<a href="http://1.bp.blogspot.com/-FuHnv2zk8fc/VK1Qnd6vMuI/AAAAAAAABDY/CLCCxK9Vzq0/s1600/carousel%2Bautoloader.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="424" src="https://1.bp.blogspot.com/-FuHnv2zk8fc/VK1Qnd6vMuI/AAAAAAAABDY/CLCCxK9Vzq0/s1600/carousel%2Bautoloader.png" width="640" /></a></div>
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The autoloader carousel cover itself is a welded structure built from 2.54mm (0.1") steel plates. The sheet steel cover is bent down at the edges for structural stiffness. Additionally, the sheet steel guard behind the driver's station has a thickness of 3.1mm (0.123"). The closest thicknesses for sheet steel in GOST specifications is 2.5mm and 3.0mm respectively, so any additional thickness can be attributed to the paint on top of the metal. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-xrdzC5UkAvg/YDUsp8M_-hI/AAAAAAAASyo/O9p357CRCL8gk4NegAfXgwr0wzYlVBkJwCLcBGAsYHQ/s2048/carousel%2Bcover%2Bthickness.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="400" src="https://1.bp.blogspot.com/-xrdzC5UkAvg/YDUsp8M_-hI/AAAAAAAASyo/O9p357CRCL8gk4NegAfXgwr0wzYlVBkJwCLcBGAsYHQ/w300-h400/carousel%2Bcover%2Bthickness.png" width="300" /></a><a href="https://1.bp.blogspot.com/-qu-KqJ-BjdQ/YDUsp5ghgKI/AAAAAAAASyk/tTzEB843OlEPWXkUBzkJC1FCtxsf1tAwgCLcBGAsYHQ/s2048/carousel%2Bguard%2Bthickness.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="400" src="https://1.bp.blogspot.com/-qu-KqJ-BjdQ/YDUsp5ghgKI/AAAAAAAASyk/tTzEB843OlEPWXkUBzkJC1FCtxsf1tAwgCLcBGAsYHQ/w300-h400/carousel%2Bguard%2Bthickness.png" width="300" /></a></div><div><br /></div><div><br /></div><div>The cover is additionally covered in up to two layers of "Podboi" anti-radiation lining with a thickness of around 13mm each. "Podboi" is known to be an effective spall liner, so it serves as additional protection for the ammunition inside the carousel. The anti-radiation lining carried over from the T-72 Ural to the T-72A, T-72B and the T-72B3, but was removed in the T-90 and compensated by thickening the cover. Most zones of the carousel cover have two layers of the lining, so that the thickness is more than 13mm in the majority of zones, up to a total of 26mm. This not only gives the turret occupants a layer of security from penetrating radiation entering the tank from below via irradiated soil, but also improves the protection of the ammunition inside the carousel.<br />
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<br />Outside of the small sector behind the driver's seat, the perimeter of the carousel intersects with either the hull walls or the conformal fuel tanks. The thickness of the guards was increased for the T-72B autoloader. One of the original perimeter guards can be seen in the photo below (open image in new tab and zoom in). Note the two reinforcement ribs pressed in to the plate - this indicates that the plate is quite thin and flimsy.<br />
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This photo gives us a closer look at the guard. The sheet is quite thin - only a few milimeters thick - so it is more likely that its main function is to help prevent unintentional interactions between the driver and the carousel and not to protect the ammunition from spall and fragmentation, although it is worth noting that the guard fully covers the ammunition. A small gap exists between the carousel cover and the guard, but nothing of importance is behind it.<br />
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The sheet steel guard can also be seen on the left of the picture below. Screenshot taken from TV Zvezda series "<i>Made In the USSR</i>", episode "<a href="https://www.youtube.com/watch?v=uIA6sTp5HDs&t=407s">T-72 Main Battle Tank</a>".<br />
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In the T-72B, these ribbed steel guards were replaced with thicker solid aluminium plates, as seen in the photo below of a late model T-72B undergoing repairs at the 103rd Armoured Repair Plant in the Far East (<a href="http://darkbear-ru.livejournal.com/58233.html">photo credit to darkbear-ru</a>). The upgrade to the new aluminium plating began in April 1986. It is very unlikely that the tank in the photos below is a T-72B3 model because the delivery of the very first T-72B3 tanks only began in 2013, whereas the photos below were uploaded to darkbear-ru's livejournal in December 2012. Also, the tank has clearly seen some use as shown by <a href="https://imgprx.livejournal.net/c6cfad7f9565bf76bcbd9c89548fe3eda56b4255/5p8aMss_fUqKPpr0wA_2mRu6smeTsqUVLjRpfrhAOBB6KI7h1jTGZGmUR6pQ5WkJuFbMhO7KS0GKS_8lbRQy4w">the worn rubber rims of the roadwheels</a>.<br />
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The locations of the armoured guards around the perimeter of the carousel did not change. One plate is located between the driver and the autoloader carousel and another plate is located between the air supply unit and the autoloader carousel. Thus, the carousel is protected in the 10 o'clock to 12 o'clock sector and in the 4 o'clock sector. The front right hull fuel tanks offer protection in the 1 o'clock sector and the rear conformal fuel tank offers protection in the 5 o'clock to 8 o'clock sector. The remainder is unprotected, as there is no equipment between the carousel and the sides of the hull.<br />
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The lower left corner of the screenshot below grants us a closer look at the guards for the T-72B3 carousel. It appears that the aluminium guard plate was not changed from the T-72B to the T-72B3.<br />
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<a href="http://1.bp.blogspot.com/-zweDiGimGOQ/VMNN6cQhD2I/AAAAAAAABHw/sQAsD9yJ_Wk/s1600/carousel.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="358" src="https://1.bp.blogspot.com/-zweDiGimGOQ/VMNN6cQhD2I/AAAAAAAABHw/sQAsD9yJ_Wk/s1600/carousel.png" width="640" /></a></div>
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The T-90A appears to have the same aluminium guards as the T-72B and T-72B3 as well as additional guards on the sides of the carousel. The sector of the armoured guard directly behind the driver is shown in the photo on the left below (<a href="http://twower.livejournal.com/555737.html">credit to twower</a>). Note that there are two fire extinguisher canisters clipped to the guard plate. The same clips are seen in both of the photos of the T-72B and T-72B3, likely indicating that all three tanks have the same plate installed in front of the carousel, but it is less clear if the additional guards for the sides of the carousel were fitted to any T-72B model. The rather large gap seen in the photo below is only due to the top-down perspective of the photographer. When viewed horizontally, the armoured plate almost fully covers the side of the carousel.<br />
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As T-72B1 uses the autoloader of the T-72 Ural, it also retains the old type of thin sheet steel guard rather than the aluminium guard.<br />
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The type of steel used for the perimeter guards are not known, but the thickness of the older T-72 Ural-style sheet steel guards would be insufficient for real ballistic protection. The thicker aluminium plate in the T-72B can be considered to be more serious protection against spall and fragments, and would probably have a positive effect on the survivability of the tank under some circumstances. The thickness of the aluminium guard plate is likely to be around one centimeter, so that the weight is the same as the original sheet steel guard. It is important to point out that it is known that the original guards are made from steel and not aluminium because rust is observed on the surface of the sheets, whereas the new thick guard is known to be aluminium because of oxidation.<br />
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<a href="http://tankarchives.blogspot.my/2015/03/beyond-armour-effects.html">This article</a> translated by Peter Samsonov details the post-penetration effects of 125mm APFSDS ammunition. The original pages of the Russian document were <a href="http://andrei-bt.livejournal.com/339370.html">first shared on Andrei Tarasenko's blog</a>. The document featured in the article pertains to a lethality analysis done on 3BM9, 3BM15, 3BM22 and 3BM26. These four rounds will all be examined more closely later on, but for now, it is only necessary to summarize that the 3BM-9 is an all-steel "torpedo" projectile, while the 3BM15 and 3BM-22 are composite shells with a a tungsten carbide core at the front of the projectile, and the 3BM26 has a tungsten carbide core in its tail. All of the shots were for a 60 degree obliquity impact, and the velocity of all of the shells corresponds to their velocities at 2 km.<br />
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According to the article, the vast majority of fragments expelled behind the armour plate are smaller particles that are capable of penetrating 3-6mm of aluminium sheet at a distance of 0.5 to 1 meters. Although they do not seem powerful, these particles are far from harmless. Particles with the ability to penetrate more than 3mm of aluminium include particles with a mass of 2 to 50 grams and a velocity of 300 to 1,700 m/s. To gain an appreciation of the threat posed by such particles, note that a typical .22LR bullet weighs 2.33 grams and travels at 390 m/s and a 5.56mm M193 Ball bullet weighs 3.56 grams and travels at 990 m/s. As such, each particle that was found to be able to penetrate 3-6mm of aluminium would also be capable of causing lethal wounds.<br />
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Keeping in mind that the overmatch factor used in the experiments was in the range of 100mm to 300mm, these figures simply cannot be considered realistic if the same or equivalent ammunition was fired at a T-72 tank, but assuming that a composite shell managed to overmatch the front hull armour of the T-72B by 100mm to 300mm, most of the fragments will definitely not be able to penetrate the steel guard around the perimeter of the carousel, especially not after passing through the anti-radiation lining (which doubles as a spall liner) lining the interior walls of the tank. This is important, because igniting or detonating ammunition requires a certain amount of energy. Very low energy fragments that can barely pierce a millimeter of steel would have no hope of igniting the ammunition, and more energetic fragments may lose enough energy from impacting the carousel perimeter guard that they may fail to ignite the ammunition. The thick armour plate in the T-72B may even be able to protect the carousel from fragments that are capable of penetrating 30mm of aluminium or more, of which there are comparatively few. It is not known what type of aluminium alloy was used for the plates in the post-perforation analysis, but is is likely to be structual aluminium and not armour-grade aluminium. This is because the equipment in Soviet tanks (radios, control boxes, relay boxes, sights, etc.) is encased in a thick die-cast aluminium housing. We can safely say that the armoured plate, which appears to be around a centimeter thick, is equivalent to around 30mm of structual aluminium or more.<br />
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It is worth mentioning that the inefficient composite construction of Soviet APFSDS rounds like the aforementioned four models makes them exceptionally prone to disintegration and fragmentation after passing through armour plates. Early 105mm APFSDS also relied on composite projectiles, but later on, more efficient long rod ammunition was deployed, and such ammunition would produce much fewer but much more powerful fragments given the same degree of overmatch. So unless the penetrator barely makes it through the armour of the tank, long rod ammunition has a much better chance of penetrating the armour plate around the carousel than composite penetrators, even if the composite penetrator achieves a greater degree of overmatch somehow. All in all, the chances of reaching - let alone igniting - the ammunition in the carousel is rather low, even in the event of a hull penetration. Fragments from a turret penetration would most likely fail to even reach the carousel.<br />
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In short, only the T-72 Ural and T-72A use the original autoloader and original carousel with minimal side protection. The T-72B used a different autoloader carousel with revised ammo cassettes in order to fit missiles, and the size of the central hub was reduced in order to fit projectiles that exceeded the length of the ammo cassettes. The armour protection for the carousel was also upgraded by installing a bona fide armoured plate in front of the carousel, behind the driver.<br />
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Now, having examined the protection of the autoloader carousel from the front and from above, it is worth examining its protection from the side. There is no additional armour between the carousel and the side armour of the hull, but the side hull armour is split between a thicker upper half and a thinner lower half, and the upper half is lined with a thick layer of "Podboi" anti-radiation lining whereas the lower half is not.<br />
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The two drawings below show that the shells in both autoloaders are behind the thinner "tub" armour, but the propellant charges is behind the thickest part of the side hull armour in both designs. The drawing on the left shows a T-64B and the drawing on the right shows a T-72.<br />
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The difference in armour protection is difficult to quantify because there are various factors at play. One of the factors is the height of the lower side armour "tub" which is only around 250mm from the floor of the belly to the top of the "tub" on both the T-64 and T-72. Simply put, the lower side armour is an exceptionally low target and the tank is not likely to be hit there. The lower side armour is afforded some additional protection by the large diameter roadwheels, but the lower side armour does not have a "Podboi" anti-radiation lining so there is nothing to stop spall.<br />
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<h3>
<span style="font-size: large;">AMMUNITION IN CAROUSEL</span></h3>
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The carousel rotates independently of the turret. It can rotate to line up new shells at a nominal speed of 70 degrees per second, but as mentioned before, it can only rotate in a counterclockwise direction. This needlessly prolonged the loading cycle in some circumstances, but it is entirely possible to avoid this issue by practicing smart ammo placement. If APFSDS ammunition is stowed to the right of HEAT ammunition, and HEAT ammunition is stowed to the right of HE-Frag ammunition, the time needed to load anti-armour rounds can be greatly reduced at the expense of greatly increasing the time taken to reach the HE-Frag rounds. This way, the gunner can start with APFSDS, and then switch to HEAT without delay when APFSDS is exhausted, or switch to HEAT quickly to deal with IFVs when the high priority tank targets have already been knocked out. Switching to HE-Frag from APFSDS takes longer, but if the target is supposed to be engaged with HE-Frag, then it can be assumed that it is a lower priority threat. In general, sorting the ammunition this way is simply logical, as the time taken to switch ammunition types only increases when switching to ammunition designed for less dangerous threats. In this case, the hierarchy of danger would be: Tank, IFV, and Infantry or other.<br />
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One of the techniques developed by a T-64A tank company commander during the 1970's was to load the ammunition in repeating sets of alternating groups so that the time needed for the carousel to reach each round would be equal, and that less time would be spent switching ammunition types. For example:<br />
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<b><i>APFSDS</i></b> - <i>HEAT</i> - HE-Frag - <b><i>APFSDS</i></b> - <i>HEAT</i> - HE-Frag - <b><i>APFSDS</i></b> - <i>HEAT</i> - HE-Frag<br />
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By doing this, switching from APFSDS to HEAT would take less time than loading the next APFSDS round. This solved the problem of increased loading time when switching ammunition types, but created the additional problem of increasing the time needed to load ammunition of the same type. However, this was considered an acceptable compromise due to the slow carousel rotation speed of the MZ autoloader of the T-64 and T-80 - only 26 degrees per second. It would take an unbearably long time to scroll through large parts of the carousel simply to reach the desired ammunition type. This technique became institutionalized and was a typical method of sorting ammunition among tankers. However, it is not known if T-72 tankers were taught this technique, as it would not have been very useful. The carousel of the AZ autoloader spins almost three times faster than the MZ autoloader, so this problem is much less serious and the flaws of this sorting technique become rather more pronounced. For one, neither the T-64 or the T-72 carry an equal distribution of all three ammunition types, especially not when missiles became a part of their repertoire.<br />
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For instance, the standard combat load of a East German T-72M (according to an ex-GDR tank commander) would have 9 APFSDS rounds, 2 HEAT rounds and 11 HE-Frag rounds in the autoloader carousel. It is not possible to arrange these rounds in such a way that the three ammunition types alternate in repeating sets, and it would not be desirable to do so. When engaging tanks, it is much quicker to have the APFSDS rounds grouped together so that the next round is loaded as quickly as possible, allowing the gunner to rapidly fire a potentially decisive second shot. Arranging the ammunition in alternating groups takes away this capability.<br />
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Here is a video of a demonstrator autoloader carousel spinning:<br />
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In the summer of 1969, a comprehensive test cycle conducted on a number of Object 172 tanks in Central Asia and in the South-Western regions of Russia revealed that the air purification system, engine cooling system, the autoloader and the T-64 suspension had insufficient reliability. These issues were partially eliminated on the subsequent batch of Object 172 tanks. Work on these tanks continued until February 1971, and by then, most of the subsystems in the tank were working within acceptable parameters. The reliability of the Object 172 autoloader at that point was excellent, having a loading failure rate of only 1 per 448 loading cycles where one loading cycle was defined as loading one round of ammunition into the autoloader or the autoloader loading one round into the cannon. Some improvement in the autoloader can be expected since the testing of the Object 172 prototype in February 1971, so the MTBF (Mean Time Before Failure) of the autoloader is likely to be above 448 rounds for a production model T-72 (Object 172M) and probably improved with time.</div><div><br /></div><div>Periodic inspections and testing would greatly benefit the longevity of the autoloader. The newer T-72B (Object 184) autoloader is claimed to have improved reliability in a government-held patent, but the magnitude of the improvement is not known. If troubleshooting is not successful or if individual components cannot be repaired from inside the tank, then the replacement of the entire carousel can be done in the field with the help of a crane. Replacing the rest of the autoloader requires the turret to be partially dismantled.<br /><br />
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<h3>
<span style="font-size: large;">REPLENISHING THE AUTOLOADER</span></h3>
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The gunner has a full set of autoloader controls for selecting ammunition to fire, or to replenish the autoloader. In order to fill up the autoloader carousel, the commander uses his autoloader control box to manipulate the autoloader and fill empty ammunition cassettes. According to the manual, reloading the carousel with a full stock of ammunition from an external supply takes 4 to 5 minutes. During the reloading process, the commander remains inside the tank while the driver and gunner pass rounds from outside the tank to the commander through the commander's hatch and the commander sequentially fills the ready ammunition cassettes, as shown in the photo below. The commander's recoil guard must be removed to allow him to place the cartridges into the carousel trays, of course.<br />
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As mentioned before in the "Commander's Station" segment of this article, the commander's seat can also be folded away to free up space when replenishing the autoloader carousel. To do this, the seat would be folded up and the backrest will then be folded inward over the seat and the recoil guard would be removed. This removes all obstructions between the commander and the carousel. This feature is particularly useful when large quantities of heavy HE-Frag rounds are to be loaded as there is quite a premium on space when large and heavy objects are to be manhandled.
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The autoloader carousel of the T-72 can be considered quite easy to load because the position of the ammunition cassettes from the autoloader carousel is always the same. Thus, the task of loading the carousel is repetitive and predictable so that the crew may easily develop a rhythm, unlike some tanks which have multiple ammunition racks in different positions and may require the turret to be turned to certain positions to access certain racks.<br />
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The ability to quickly replenish the ammunition of the T-72 was a contributing factor to the success of the "tank carousel" tactic used during the war in Chechnya. Indeed, the quick turnaround time of a T-72 is not a universal trait of all tanks with autoloaders but is actually a byproduct of the straightforward and rugged design of the AZ autoloader, seeing as the T-64A (and its successors) requires 13-15 minutes to replenish its MZ autoloader carousel according to the manual. Of course, the MZ autoloader carries 6 more rounds than the AZ autoloader, but this is not the culprit of the large difference between the two systems: it takes between 28 to 32 seconds to load each round in the MZ autoloader whereas it only takes 11 to 14 seconds for each round in the AZ autoloader; reloading each round in the T-64 takes 2.4 times longer than the T-72.<br />
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<h3>
<span style="font-size: large;">LOOSE STOWAGE</span></h3>
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Aside from the carousel itself, ammunition is stored in racks located throughout the interior of the tank in various nooks and crannies with varying degrees of accessibility. While much of the ammunition in stowed in fairly secure conformal fuel tanks, there are a few rounds of ammunition that are placed out in the open. For the T-72 Ural, 17 rounds are carried in loose stowage. The stowage layout was revised in the T-72A, leading to an increase in the number of shells carried in loose stowage to 22. This enabled the tank to carry two full complements of ammunition into battle and fully replenish the autoloader carousel in the absence of resupply trucks or other sources of ammunition. The stowage layout in the T-72B was slightly modified from the T-72A, allowing an additional cartridge to be carried. The abundance of ammunition stowed outside of the autoloader carousel allowed the T-72 to exceed the ammunition capacity of the T-64A and its successors (37 rounds) despite the lower capacity of the AZ autoloader.</div><div><br /></div><div>Special attention was paid in the design of the ammunition racks in that the ammunition racks holding HE-Frag and HEAT shells are designed to lay the shells horizontally, in order to avoid the possibility of the operational state of the fuzes being disrupted by an anti-tank mine detonating under the tank, which creates a strong vertical acceleration. If the shells were stowed vertically, the acceleration acts along the longitudinal axis of the shell and there is a small chance that accidental arming of the fuze might occur due to this acceleration. Because of this, the only vertical projectile stowage points in the tank are reserved for APFSDS rounds exclusively. All HE-Frag and HEAT shels must be loaded onto the racks on the walls of the hull and engine compartment firewall, or in the front right fuel tank rack. Owing to this regulation, there is always a limit to how many HE-Frag and HEAT shells permitted in loose stowage, which may be higher or lower depending on the specific model. </div><div>
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Restocking the T-72 with a full load of ammunition including both the autoloader and the rounds held in loose stowage reportedly takes 13 to 15 minutes. By comparison, the T-64A (and its successors) requires 25 to 27 minutes to do the same despite the much smaller complement of ammunition stowed outside of its autoloader, probably because the rounds are stowed outside the autoloader carousel "basket" and access to the hull from the turret cabin is extremely limited.</div><div><br /></div><div>The stowage layout for the T-72 Ural is presented in the diagram below (39 rounds in total). The diagram is from a T-72A manual. There are 13 projectiles stowed in the hull, and 4 projectiles in the turret, on top of the autoloader carousel. Of the 4 projectile racks in the turret, 3 are laid vertically and are reserved for APFSDS rounds. There are 12 propellant charges in the hull, and 5 in the turret, on top of the autoloader carousel. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-E-N4EVJ0RkM/YU8L3paUnUI/AAAAAAAAUP0/20w0WX5832YDeh_1pkzfjeOdhO1rkXvpQCLcBGAsYHQ/s2048/ural%2B39%2Brounds.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1105" data-original-width="2048" height="346" src="https://1.bp.blogspot.com/-E-N4EVJ0RkM/YU8L3paUnUI/AAAAAAAAUP0/20w0WX5832YDeh_1pkzfjeOdhO1rkXvpQCLcBGAsYHQ/w640-h346/ural%2B39%2Brounds.png" width="640" /></a></div><br /><div><br />
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The stowage layout for the T-72A is presented in the diagram below (44 rounds in total). The diagram is from a T-72 weapons handling manual. There are 16 projectiles stowed in the hull, and 6 projectiles in the turret, on top of the autoloader carousel. There are 17 propellant charges in the hull, and 5 in the turret, on top of the autoloader carousel. A total of 5 stowage points are laid vertically and are reserved for APFSDS rounds - 2 in the hull, and 3 in the turret. <br />
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The layout for the T-72B is shown in the diagram below (45 rounds in total). The diagram is taken from a T-72B manual. As you can see, the stowage layout is largely identical to the T-72A, with a few changes. A positive change in the T-72B ammunition layout is that the number of cartridges stowed in the turret was reduced, moving more ammunition into the hull instead. 18 projectiles are stowed in the hull, and 5 projectiles in the turret, on top of the autoloader carousel. 19 propellant charges are in the hull, and 4 are in the turret, on top of the autoloader carousel. 2 shells are stowed in racks on the turret wall, on the gunner's side. Only 3 stowage points in the tank are laid vertically and are reserved for APFSDS rounds. <br />
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Almost all of the propellant charges - the most vulnerable half of the two-part ammunition - are stowed in cylindrical slots inside the conformal fuel tanks. There are twelve slots in the large fuel tank behind the autoloader carousel for propellant charges. Due to the excellent location, the charges are almost completely safe - the carousel would always be in the way instead unless the tank was hit from behind, and it is extremely difficult to hit this fuel tank from above due to the location of the autoloader elevator mechanism and the crew seats. The drawing on the right below shows the propellant charge inside one of the slots. Note that the only the steel casing stub is exposed while the combustible charge casing is fully enclosed by the fuel tank. The drawing on the left shows the arrangement of slots in the fuel tank. The depression at the left hand corner of the fuel tank is made to help accommodate the shells clipped to the side of the hull.<br />
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The location of the fuel tank at the rear of the fighting compartment of a tank without the autoloader carousel is shown in the photo below. Note the small red TD-1 flame detection sensor at the lower left corner of the photo, next to the fuel tank.<br />
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This stowage method minimizes the risk of immediate deflagration from open flames inside the tank because only the non-flammable steel casing stub is exposed. Of course, this arrangement is not completely fireproof, but it may give the crew enough time to evacuate the tank or extinguish the fire before it becomes too serious. The commander can access the propellant charges stowed in the fuel tank by either swinging the backrest of his seat forward (in the T-72 Ural and T-72A) or by pivoting the backrest of his seat to the side (in the T-72B) as shown in the photo below. The newer pivot arm mechanism on the T-72B allows the commander to stay seated as he access the ammunition at the back of the tank and loads it into the cannon, thus reducing fatigue and possibly increasing the rate of fire of the tank when using manual loading.<br />
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<a href="https://4.bp.blogspot.com/-miQAcRZOxtc/W2mdZgx6J2I/AAAAAAAAMDE/LxqJGG96wQgKsS3bDlpYp5qOXLJpaXQCACLcBGAs/s1600/test-drayv-tanka-t-72b3-surovyy-biatlon-avtonovosti_5818.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1000" data-original-width="1500" height="426" src="https://4.bp.blogspot.com/-miQAcRZOxtc/W2mdZgx6J2I/AAAAAAAAMDE/LxqJGG96wQgKsS3bDlpYp5qOXLJpaXQCACLcBGAs/s640/test-drayv-tanka-t-72b3-surovyy-biatlon-avtonovosti_5818.jpeg" width="640" /></a></div>
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The right hull fuel tank on the right hand side of the driver has slots for three propellant charges and either four shells (Ural) or three shells (T-72A, B) plus a single exposed propellant charge stowed in a circular cup at the back of the fuel tank. The right hull fuel tank is shown in the photo on the left (rotated to represent the actual orientation of the fuel tank in the hull) and a cross-section of the propellant charge slot in the fuel tank is shown on the right side. Note that the rim of the propellant charge is not laid flush to the surface of the conformal fuel tank slot unlike the conformal fuel tank at the back of the fighting compartment. This is because the charges are held horizontally so there is very little danger of burning liquid flowing into the slot.<br />
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<a href="https://3.bp.blogspot.com/-FsB5BQFwhL8/W2JcTgDvVqI/AAAAAAAAL5U/RwtK8i62vxUGdxLPbw8UuNL71Q9-xGnWQCLcBGAs/s1600/hull%2Bconformal%2Btank.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="617" data-original-width="515" height="400" src="https://3.bp.blogspot.com/-FsB5BQFwhL8/W2JcTgDvVqI/AAAAAAAAL5U/RwtK8i62vxUGdxLPbw8UuNL71Q9-xGnWQCLcBGAs/s400/hull%2Bconformal%2Btank.png" width="333" /></a><a href="https://4.bp.blogspot.com/-ACPJQI5Y39Y/W2JdGN7y8nI/AAAAAAAAL5c/vuMJSUDm5iIChDZVZEdxyJe6WIFJvqJZwCLcBGAs/s1600/conformal%2Bfuel%2Btank%2Bstowage.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="681" data-original-width="701" height="387" src="https://4.bp.blogspot.com/-ACPJQI5Y39Y/W2JdGN7y8nI/AAAAAAAAL5c/vuMJSUDm5iIChDZVZEdxyJe6WIFJvqJZwCLcBGAs/s400/conformal%2Bfuel%2Btank%2Bstowage.png" width="400" /></a></div>
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Cross-sections of the slots for the shells in the front right hull conformal fuel tank are shown in the diagram below. Two versions of the rack exist - the original type with four slots, used on T-72 Ural tanks, and the new type with three slots, introduced on the T-72A in 1979 and used in all subsequent models. The slots were designed with the dimensions of HE-Frag and HEAT shells in mind and were built exclusively for them. Stowing any ammunition types other than HE-Frag and HEAT in these slots is prohibited. The projectiles are securely fixed in place and do not slide out forward, as a latch holds it by the fin retention band from the front, while a cresent-shaped rotating cover stops the projectiles from sliding rearward. As there are no folding fins and no retention band on APFSDS ammunition and guided ATGMs, they cannot be secured within these racks. <br />
<br /><br /><div style="text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-CdXeJoW8wT8/YU8Na3QY3GI/AAAAAAAAUP8/uktoR1Y1h7YHisprqG1Ilsihl0lii_XXwCLcBGAsYHQ/s1981/starboard%2Bprojectile%2Brack%2Bural.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1187" data-original-width="1981" height="384" src="https://1.bp.blogspot.com/-CdXeJoW8wT8/YU8Na3QY3GI/AAAAAAAAUP8/uktoR1Y1h7YHisprqG1Ilsihl0lii_XXwCLcBGAsYHQ/w640-h384/starboard%2Bprojectile%2Brack%2Bural.png" width="640" /></a></div><a href="https://1.bp.blogspot.com/-SpjliF2ac9Q/YU72PXSnO5I/AAAAAAAAUPg/cBAxFw-A8-cDqLT6TeKsCpxyY9nNpA_zwCLcBGAsYHQ/s2048/starboard%2Bprojectile%2Brack.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1141" data-original-width="2048" height="356" src="https://1.bp.blogspot.com/-SpjliF2ac9Q/YU72PXSnO5I/AAAAAAAAUPg/cBAxFw-A8-cDqLT6TeKsCpxyY9nNpA_zwCLcBGAsYHQ/w640-h356/starboard%2Bprojectile%2Brack.png" width="640" /></a></div>
<div><br /></div><div><br /></div>To load projectiles into these racks, the cresent-shaped cover is rotated so that it clears an opening into an empty slot. Then, the spring-loaded latch is held open, and the projectile is inserted up til the fins, and the latch is released so that as the projectile is inserted all the way forward, it stops against the latch. The crescent-shaped cover is then turned away. Extracting projectiles from these racks is simpler, as the crescent-shaped cover only needs to be turned to open, and the projectile can be pulled straight out. The taper on the base of the projectile body will push the latch aside as the projectile is pulled out by its tail.<br />
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The location of these racks makes it convenient for the commander when loading the cannon manually, assuming that the turret is oriented forward or to the left. As you can see in the two photos below, the height of the propellant and shell compartments is just above the autoloader carousel. To use these racks, the commander should turn his TKN-3M/MK periscope to the right, lean forward to pull out a shell, ram it in into the gun, and repeat the motion to load the propellant charge. The main ergonomic issue with the arrangement is that the large ammo box for the coaxial machine gun is in the way, so the commander has to lean underneath it unless the turret is turned to the left.<br />
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More shells and propellant charges are stowed on top of the carousel cover. Some of the propellant charges and shells are clipped to the cover, and others are placed vertically and clipped to the turret ring. There is one position at the 11 o'clock sector of the carousel cover where a single shell can be clipped onto the cover lying down. This shell may obstruct the driver from moving to the gunner's position, or the gunner from pulling the driver out of the tank through the turret.<br />
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<a href="http://1.bp.blogspot.com/-FuHnv2zk8fc/VK1Qnd6vMuI/AAAAAAAABDY/CLCCxK9Vzq0/s1600/carousel%2Bautoloader.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="424" src="https://1.bp.blogspot.com/-FuHnv2zk8fc/VK1Qnd6vMuI/AAAAAAAABDY/CLCCxK9Vzq0/s1600/carousel%2Bautoloader.png" width="640" /></a></div>
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The circular "ashtrays" at the back of the carousel at either side of the trapdoor are where the shells and propellant charges are placed upright. The shells are secured using clips attached to the turret ring. The "ashtrays" can be seen in the photo below, but the diagrams from the manuals are much more useful. It is shown that two pairs of shells and propellant charges are stowed to the left of the carousel trapdoor, behind the backrest of the commander's seat. Here is one "ashtray" between the autoloader cassette elevator mechanism and the gunner's cannon breech guard. This is the same one as seen in the photo above, to the right of the carousel cover trapdoor. The conformal fuel tank at the rear of the fighting compartment can be seen in the background.<br />
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<a href="https://2.bp.blogspot.com/-XrZlAB3d-hE/WtMK8wCczJI/AAAAAAAALcY/vGbPb9xEfFMgEPt7-6XehgVGpUzJzIEPgCLcBGAs/s1600/carousel%2Bloose%2Bstowage.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="720" data-original-width="960" height="480" src="https://2.bp.blogspot.com/-XrZlAB3d-hE/WtMK8wCczJI/AAAAAAAALcY/vGbPb9xEfFMgEPt7-6XehgVGpUzJzIEPgCLcBGAs/s640/carousel%2Bloose%2Bstowage.jpg" width="640" /></a></div>
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To access the ammunition behind the seats of the gunner and commander, they must scoot forward in their seats and swing the backrest forward. Only then can the shells be unclipped and extricated. Since there is ammunition on both sides of the turret, both the commander and gunner can manually load the cannon if the situation calls for it.<br />
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The two pairs of shells and propellant charges stowed on the racks on the carousel cover are located behind the commander's seat. The clips that secure them to the turret ring can be seen in <a href="https://youtu.be/krp2y88nNCo?t=8m49s">The Challenger's video review of a Czechoslovakian T-72M1 tank</a>. These rounds are very easy to access. The commander only needs to swing or pivot the backrest of his seat out of the way, and then he can directly load the cannon or replenish the autoloader carousel in short order.<br />
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<a href="https://1.bp.blogspot.com/-how1JWtCTkM/WEu5tY5nqeI/AAAAAAAAHzE/oBlQZSKi-MQvztkfQyuQ0uYl6JMisNdHACLcB/s1600/t-72b%2Bbehind%2Bgunners%2Bseat.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="358" src="https://1.bp.blogspot.com/-how1JWtCTkM/WEu5tY5nqeI/AAAAAAAAHzE/oBlQZSKi-MQvztkfQyuQ0uYl6JMisNdHACLcB/s640/t-72b%2Bbehind%2Bgunners%2Bseat.png" width="640" /></a></div>
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The degradation of the propellant charges stowed out in the open atop the carousel cover is reduced by the inclusion of a protective metal sleeve that fits over the exposed combustible nitrocellulose-impregnated cardboard charge casing just over the metal casing stub. The sleeves are meant to protect the combustible charge from environmental damage, but these sleeves also offer a modicum of protection from open flames.<br />
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<a href="https://3.bp.blogspot.com/-nhfiIvfEZ8s/Wbq01D7HbvI/AAAAAAAAJbM/6uDF8KauRy4B62g7Ij51O6RCfDsTHkRKQCLcBGAs/s1600/ammo%2Bon%2Btop%2Bof%2Bcarousel.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="695" height="640" src="https://3.bp.blogspot.com/-nhfiIvfEZ8s/Wbq01D7HbvI/AAAAAAAAJbM/6uDF8KauRy4B62g7Ij51O6RCfDsTHkRKQCLcBGAs/s640/ammo%2Bon%2Btop%2Bof%2Bcarousel.jpg" width="278" /></a></div>
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Eight shells can be stowed on the engine compartment bulkhead, on top of the conformal fuel tank behind the autoloader carousel. Three more shells are clipped to the wall on the side of the hull, on the gunner's side. The shells are secured to the ammunition racks using clips. All of the stowage spaces on the engine compartment bulkhead and on the side hull wall are visible in the screenshot below (T-72B type tank hull on display). The gunner can easily access the shells clipped to the side of the hull, but only if the turret is turned slightly to the left.<br />
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<a href="https://4.bp.blogspot.com/-DkFB5CJATqg/WXrS4PObvrI/AAAAAAAAI1k/fcZLHoaZhPoKxQZLRpRtFA84-ByxBF5gACLcBGAs/s1600/t-72%2Bautoloader.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="768" data-original-width="1366" height="359" src="https://4.bp.blogspot.com/-DkFB5CJATqg/WXrS4PObvrI/AAAAAAAAI1k/fcZLHoaZhPoKxQZLRpRtFA84-ByxBF5gACLcBGAs/s640/t-72%2Bautoloader.png" width="640" /></a></div>
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The drawing below shows the racks. These racks can accommodate all ammunition types, including missiles as the drawing on the right shows (taken from a T-72B manual).<br />
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<a href="https://1.bp.blogspot.com/-YqZponkFZAk/W2JdI1f7ZYI/AAAAAAAAL5k/XpjPkbArkCs62i1QCWlxWu7pfAPUMm5aQCLcBGAs/s1600/open%2Bracks.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1013" data-original-width="758" height="400" src="https://1.bp.blogspot.com/-YqZponkFZAk/W2JdI1f7ZYI/AAAAAAAAL5k/XpjPkbArkCs62i1QCWlxWu7pfAPUMm5aQCLcBGAs/s400/open%2Bracks.png" width="297" /></a><a href="https://2.bp.blogspot.com/-ixuOLAYmbFg/W2ROQRX5MEI/AAAAAAAAL6w/pbsMnkD1xhwe_tZMiNSmPG0Der78Y4kIgCLcBGAs/s1600/t-72b%2Bracks.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1053" data-original-width="1151" height="365" src="https://2.bp.blogspot.com/-ixuOLAYmbFg/W2ROQRX5MEI/AAAAAAAAL6w/pbsMnkD1xhwe_tZMiNSmPG0Der78Y4kIgCLcBGAs/s400/t-72b%2Bracks.png" width="400" /></a></div>
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The commander can freely access the shells clipped to the wall at the back of the fighting compartment. Thanks to the lack of a turret basket on the T-72 turret, the commander can simply swing the backrest of his seat out of the way, unclip one of the shells, and then bring it up to the cannon to ram it in. He can then lean down and extract one of the propellant charges from the conformal fuel tank behind the autoloader carousel. The ease of accessing the ammunition in loose stowage heavily contributes to the relatively high rate of fire when loading manually and also reduces the time needed to replenish the autoloader carousel.<br />
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It is also worth noting that the APFSDS rounds are protected by a metal sleeve when stowed on the clips, as they have an incremental propellant charge attached to the sabot and thus have some need for the additional layer of protection during stowage. The photo below seems to show one APFSDS round with a green sleeve.<br />
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<a href="https://4.bp.blogspot.com/-3iJyRI-NvvM/XEfsF5wAY_I/AAAAAAAANIs/Kp8EUAm89kscF9LOF6iu7kzmvWtUIxh1QCLcBGAs/s1600/protective%2Bstowage%2Bcase.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="953" data-original-width="1271" height="298" src="https://4.bp.blogspot.com/-3iJyRI-NvvM/XEfsF5wAY_I/AAAAAAAANIs/Kp8EUAm89kscF9LOF6iu7kzmvWtUIxh1QCLcBGAs/s400/protective%2Bstowage%2Bcase.jpg" width="400" /></a></div>
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The screenshot below gives us a good view of the ammunition from the driver's perspective, so while it may appear that a shell penetrating the hull armour would seriously jeopardize the ammo, this is not necessarily the case. Due to the highly cluttered fighting compartment and the very large distance from the upper glacis armour to the ammunition mounted to the wall (more than two meters), the ammunition has a very good chance of avoiding any damage whatsoever. The photo below, for example, is the same view taken from the same angle, but it is clear that the engine compartment bulkhead is completely obscured behind the stabilizer components underneath the cannon and behind the seats of the commander and gunner. If the tank hull is penetrated from the front, the tank will likely be knocked out by a firepower kill via damage to the stabilizer or some other component of the gun control system, but an immediate ammunition detonation may be avoided and the crew may survive.<br />
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<span style="font-weight: normal;"><br /></span>
Although the loose ammunition stowed in the turret and hull is quite vulnerable, it is important to recognize the fact that some attention was paid to their protection. Most of the vulnerable propellant charges are held inside the conformal fuel tanks and those that are stowed in the open are at least protected by a fire retardant sleeve. These measures offer some protection from open flames. The projectiles held in loose stowage are not protected by similar measures, but they are already fire resistant to a large extent with the exception of the APFSDS rounds.<br />
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Furthermore, it is also clear that the ease of access to the ammunition held in loose stowage was a major ergonomic consideration during the design of the tank. The location of these rounds and the amenities provided to access them facilitate the speedy loading of the cannon and replenishment of the autoloader carousel. In the event that the commander is incapacitated or dead, the ammunition on the gunner's side of the turret is laid out in such a way that he could also load the gun manually in an emergency, but with only a few cartridges at hand, this cannot be sustained for longer than just a few shots.<br />
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<h3>
<span style="font-size: large;">FINAL THOUGHTS</span></h3>
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<span style="font-weight: normal;"><br /></span>
<span style="font-weight: normal;">All in all, there can be between 17 to 23 additional cartridges stowed outside the carousel for a total of between 39 to 45 rounds of ammunition depending on the specific model of T-72. However, in practice, crews tend to ignore certain spaces such as the shell stowage rack on top of the carousel cover (as seen above), and some crews may decide not to have any ammunition in loose stowage at all, so the actual sum total of loosely stowed ammunition can be anywhere from 22 to none. For example, a tactic developed in the modern Russian Army called the "tank carousel" or the "merry-go-round" involves the use of a platoon-sized unit (three or four tanks) with fully loaded autoloader carousels to engage enemy forces from pre-planned positions until they run dry. Then, they withdraw a short distance to replenish their ammunition from waiting trucks and allow another platoon of three or four tanks to immediately replace them. No ammunition is carried outside of the autoloader carousel, and the tanks always fire from hull-down positions. </span><br />
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<span style="font-weight: normal;">Nevertheless, from a design standpoint, the fact that the T-72 can have a total ammunition capacity of 45 rounds when the older T-54/55 with a 100mm cannon had 43 and the T-62 with a 115mm cannon had just 40</span><span style="font-weight: normal;"> was a noteworthy achievement in tank design efficiency. Compared to the Leopard 2 (42 rounds) and M1A1 Abrams (40 rounds), the T-72 carries more ammunition overall for a cannon of a similar caliber and power. Considering that many amateur tank enthusiasts and even historians like to espouse the higher ammunition capacity of early Cold-War era NATO tanks as a decisive advantage over the Soviet T-54 and T-62, the fact that the T-72 carries more ammunition than its contemporaries is curiously ignored. </span><br />
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<span style="font-weight: normal;">Surprising as it may be, the T-72 also carries more ready ammunition than its two most modern NATO counterparts as it has 22 rounds in the carousel compared to 17 and 15 rounds in the bustle ready racks of the M1A1 Abrams and Leopard 2 respectively. Moreover, only 12 rounds are immediately accessible in the bustle ready racks of the M1A1 before the loader must start collapsing the racks to access the cartridges that are out of reach, while only 6 rounds are immediately accessible in the Leopard 2. The ammunition capacity of the autoloader carousel is the same as the autoloader bustle of the Leclerc, and the Challenger 2 carries a few more rounds in its ready racks (25). Generally speaking, this is not an issue for any of these tanks because it is rare for a tank to expend so much ammunition in a single engagement. There is typically a lull in the fighting, which is when the loader in any tank would take the time to replenish his ready racks from the less accessible reserve ammunition racks. In the case of the T-72, the commander and gunner will replenish the carousel using the loose ammunition stowed inside the tank in the turret and hull.
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In an Abrams, the commander will have to open the bustle door on his side of the turret and pass cartridges over to the loader who will then stow them in the ready racks in his side of the turret bustle. It's worth noting that the sliding door for the bustle reserve rack in all variants of the Abrams did not have a hydraulic mechanism like the loader's ready rack door. The commander must manually crank open the heavy armoured door in order to access the ammunition, making it impractical and dangerous to use this rack as a substitute ammunition supply during combat.
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In a Leopard 2, the loader will have to take ammunition from the front hull racks and stow them in the bustle ready racks, and this is only possible when the turret is oriented in a specific sector as the front hull racks would otherwise be inaccessible to the loader.</span><br />
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<span style="font-weight: normal;"><br /></span>
<span style="font-weight: normal;">However, ammunition carried in loose stowage can be a huge liability in battle as it has been proven to be the main cause of irrecoverable or catastrophic tank losses. Some of the loose ammunition stowed in the hull is still somewhat secure, but the ammunition in the turret constitutes a significant risk to the survival of the crew. As the diagram below shows (diagram taken from Tank-Net), only 2% of shots land at a height of one meter from the ground in the 60 degree frontal arc of a tank. This is good news for the carousel autoloader, but the diagram shows that 65% of shots hit the turret. As such, the benefits of the low placement of the carousel may be completely undone by loose ammunition stowed in the turret. </span><br /><span style="font-weight: normal;"><br /></span>
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<span style="font-weight: normal;"><br /></span><span style="font-weight: normal;"><br /></span><br />
<span style="font-weight: normal;">However, it should be understood that the distribution of hits fluctuated somewhat over the years in various conflicts. In the Second World War, the majority of hits sustained by tanks were on the hull. It is commonly thought that this was due to the fact that the hulls of the tanks of the era tended to be much larger than their turrets and also quite tall due to the placement of the transmission at the front such as on the Panther and M4 Sherman. Later on, combat in Korea and in the Middle East showed that the share of hits recorded on the turret increased, creating a more even distribution of hits between the turret and hull. It is worth noting that the average combat distance in Korea was very short - only a few hundred meters - due to the nature of the terrain. Later on, it was observed by Dr. Manfred Held that in Kuwait during Operation Desert Storm (ODS), the vast majority of shots landed on the turret. The diagram below, taken from "<i>The Main Battle Tank of Russia: A Frank Conversation About The Problem of Tank Building</i>", shows the distribution of hits in the vertical plane by percentage for the 1967 Six-day war, the 1983 Yom Kippur war and ODS in 1991.</span><br />
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The three black bars in the diagram indicate (from top to bottom) the bottom of the turret, the belly of the tank, and ground level. The bottom of the turret - the turret ring - is considered to be 1.5 meters above ground level, and the belly of the tank is considered to be around 0.5 meters from ground level. The hull is therefore considered to be around 1 meter tall. This is a representation of a Soviet main battle tank like the T-72, T-64 or T-80. All of these tanks have a ground clearance of 0.48 meters, a hull with a height of 1.0 meters, and a turret ring located 1.48 meters above ground level. Considering that the AZ autoloader carousel has a total height of 450mm (including the top cover), the total height of the carousel from ground level is 940mm.<br />
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As you can see, even though the distribution of hits was not entirely consistent across the three conflicts, the fact that the lower half of the hull (between 0.5 to 1.0 meters from the hull belly) statistically sustained the fewest hits was universally true for all cases, and therefore, the autoloader carousel would sustain very few direct hits. The turret ring zone sustained the greatest number of hits statistically, which makes sense as the turret ring is the center mass of any tank. These observations are further reinforced by statistics on the hit distribution on combat-damaged tanks during WWII on the Eastern Front, where 90% of hits on Red Army tanks were recorded at a height of one meter above the ground, as reported by Sergey Gryankin on pages 12-13 in his article "<i>T-54</i>", published in the "<i>Техника-молодёжи</i>" magazine (<i>Technology of the Youth</i>). Again, this shows that the lower half of the hull would receive the vast minority of hits under combat conditions. From this, it can be seen that the majority of damage inflicted to the autoloader carousel in the event that the armour of the T-72 is defeated would be from projectile fragments or secondary fragments coming from above, i.e from the upper sections of the upper glacis or from the turret. These fragments would be attenuated by the "Podboi" anti-radiation liner. The air gap between the surfaces of the upper glacis and the turret further reduces the energy of fragments, and the carousel itself provides protection for the ammunition contained within.<br />
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Furthermore, it can be inferred from the hit distribution figures that omitting some of the ammunition carried in the turret would be eminently beneficial to the survival of the tank and its crew in the event that the turret armour is pierced. And indeed, as mentioned before, this was widely practiced by Russian tank crews during the wars in Chechnya along with new tactics such as the "tank carousel", which was developed to maximize the firepower of a tank platoon while minimizing exposure to enemy fire and minimizing the possibility of a hit to the ammunition. The concept of removing all ammunition from the turret to improve crew survivability was validated after data was collected from the wars in the Middle East. This lesson was institutionalized in the U.S Army as expressed by Colonel Robert E. Butler, project manager of M60 tank development, in his article "<i>M60A3 Tank Program</i>" published in the July-August 1977 issue of "ARMOR" magazine. On page 43, he details that the wars in the Middle East showed that a large percentage of tank hits were above the turret ring, and that in an effort to lessen the vulnerability of the M60A1, a program was initiated to relocate all the 21 rounds of main gun ammunition located in the turret bustle to the hull and research was conducted on installing a nylon or kevlar spall lining for all of the main gun ammunition.<br />
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Another noteworthy aspect to consider is the mine resistance of the autoloader carousel. The carousel of the AZ autoloader is mounted to the floor whereas the carousel of the MZ autoloader of the T-64 and T-80 is suspended from the turret and the autoloader itself is housed in the turret cabin. Only the rotary power supply unit connects the turret cabin to the hull floor. The extent of the difference in durability is difficult to determine, but it seems unlikely that a mine blast underneath the tank will disable the autoloader as a conventional anti-tank mine with a tilt-rod fuse would detonate under the driver's station and an anti-tank mine with a simple pressure fuse would detonate under the tracks at the first roadwheel. The shock from the explosion may potentially be a source of failure, but it would only be fair to point out that the power supply unit (for any tank) may be damaged as well as it is mounted to the belly. In that case, the power supply to the turret would be cut off and the loss of autoloader function becomes a much less serious issue by comparison.<br />
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<span style="font-weight: normal;">If the autoloader elevator malfunctions, it is still possible to operate the elevator mechanism manually using a crank wheel (pictured). The commander and the gunner may have to take turns to load the cannon depending on the location of the ammunition in loose stowage. The commander would obviously load the cannon using ammunition close to him, and vice versa. Some of the ammunition requires the turret to be oriented in a specific direction to access. The T-72A manual has a full table detailing the locations of the ammunition, the orientation of the turret needed to access it, and whose responsibility it is to load that ammunition. The benchmark time for a complete manual loading cycle is 26 to 30 seconds. The corresponding time for a T-64A as dictated in a manual is 1 minutes 40 seconds for the first shot and 1 minute for subsequent shots. In other words, a T-72 is able to sustain a rate of fire of around 2 rounds per minute with manual loading whereas a T-64 would struggle to attain a rate of fire of 1 round per minute. However, according to official Soviet norms (battle drills), the minimum acceptable times for loading in a T-72, T-64, and T-80 are all the same. The "minimum" grade for manual loading using ammunition from the ammunition carousel is for 1 minute, the "good" grade is for 50 seconds and the "excellent" grade is for 45 seconds.</span><br />
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If the carousel fails, it is possible to manually crank the carousel and access the ammunition inside using a cranking lever located underneath the commander's seat. However, the commander would have no idea where the desired ammunition type is located in the carousel, so it may be more feasible to simply use the ammunition in loose stowage.<br />
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Both the gunner and commander have free access to the autoloader from their respective stations. As such, it is possible for the crew to troubleshoot the device without leaving the tank or requiring the separation of the turret from the hull. The old Soviet promotional image below shows a tanker in the gunner's seat with his hands on the autoloader elevator and the stub ejection mechanism.<br />
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<span style="font-weight: normal;">Manual loading is something to be done in emergencies only, not only because it is much slower than normal automated loading, but because it also forces one of the two crew members to abandon his usual duties. In reality, autoloader failures are exceedingly rare (but not non-existent), so there is little need to worry about manual loading. The propensity for autoloaders to malfunction either from wear and tear or from a knock on the turret tends to be greatly exaggerated.</span><br />
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<h3>
<span style="font-size: large;"><br />AMMUNITION</span></h3>
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There are four main
types of ammunition for the 125mm gun. A typical loadout for a general infantry support mission would see that
HE-Frag shells are loaded in large quantities, for example, while more
HEAT and APFSDS shells would be loaded for ambushes where armoured vehicles are expected. A standard ammunition load would comprise of an equal mix of high explosive rounds (HE-Frag) and anti-armour rounds (APFSDS, HEAT) with APFSDS rounds being much more numerous than HEAT rounds. A standard mixture for a T-72 Ural is detailed in the 1979 manual "<i>Crew Operations Manual for the Weapons of the T-72</i>", where out of a total of 39 rounds of ammunition, there should be 19 rounds of HE-Frag ammunition, 14 rounds of APFSDS ammunition, and 6 rounds of HEAT ammunition. As for the ratio of ammunition carried as the ready supply in the autoloader carousel, there should be 11 rounds of HE-Frag ammunition, 7 rounds of APFSDS ammunition, and 4 rounds of HEAT ammunition. </div><div><br /></div><div>A T-72A, having a total ammunition capacity of 44 rounds, carries 22 rounds of HE-Frag ammunition, 16 rounds of APFSDS ammunition, and 6 rounds of HEAT ammunition. The ratio of ammunition types in the autoloader carousel remained the same. There should be 11 rounds of HE-Frag, 7 rounds of APFSDS, and 4 rounds of HEAT. A standard load such as this would weigh around 564 kg in the autoloader carousel.</div><div><br /></div><div>In the T-72B, the slightly larger ammunition capacity of 45 rounds accommodates a different loadout which may or may not include 6 ATGMs. Of that, 4 would be in the carousel, and 2 would be stowed in loose stowage. This would be accompanied by an equivalent reduction in the number of HEAT rounds. If ATGMs are not carried, which would always be the case in a T-72B1, the combat load is identical to a T-72A but includes one more APFSDS round. Additional HEAT rounds are not favoured.<br />
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<h3>
<span style="font-size: large;">PROPELLANT CHARGES</span></h3>
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<a href="http://1.bp.blogspot.com/-jvJmQXQYk_Q/VTQZHh9041I/AAAAAAAAB90/olZpOIwrht0/s1600/125_mm_Munition_Pulver.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="154" src="https://1.bp.blogspot.com/-jvJmQXQYk_Q/VTQZHh9041I/AAAAAAAAB90/olZpOIwrht0/s1600/125_mm_Munition_Pulver.jpg" width="640" /></a></div>
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<span>125mm ammunition for the D-81 gun series is split into two parts: propellant and projectile.</span><span style="font-size: small;"> </span>Each propellant charge is contained within a thin combustible casing that is consumed upon firing, and the entire assembly is embedded into a steel obturator casing stub shaped like a cup, much like a shotgun cartridge. All of the propellant charges have a total length of 408mm. With the rim sealing the chamber from outside, the total length of a propellant charge resting in the chamber is 383mm.</div><div>
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All muzzle velocity data for the 125mm ammunition listed in this article was obtained with a propellant charge temperature of 15°C.<br />
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The steel obturator stub, made from BV-11 steel, is the only part of the cartridge assembly left intact after firing. The stub on 4Zh40 and 4Zh52 charges was designed to withstand a chamber pressure of up to 5,000 kgf/sq.cm, or 490 MPa. In the T-64 and T-80 series, this stub is returned to the autoloader mechanism by a mechanical arm, but in the T-72, this stub is ejected from the tank via a small hatch at the rear of the turret roof. The diameter of the rim is 172mm, the diameter of the opening is 160mm, and its total length is 140mm. It weighs 3.45 kg. The purpose of the casing stub is to contain the propellant and obturate the breech for ensuring a complete seal, so that no flashback occurs.</div><div>
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The use of a relatively large steel casing stub as opposed to a small primer unit like on the bagged charges of the L11 contributed to the relatively hefty ~10 kg weight of each complete propellant charge, but given that the 125mm gun is automatically loaded, this has no negative impact. On the other hand, the effect of the increased mass from the steel casing stub on the 120mm cartridges for the Rh 120 L/44 and M256 guns, which weigh around 3 kg, has a tangible effect since these guns are manually loaded. </div><div><br /></div><div>The combustible case of the charge, which has a diameter of 156mm, is is essentially a type of fiberboard tube made from nitrocellulose fibers impregnated with TNT, with the TNT forming a combustible non-porous barrier to prevent moisture from penetrating the charge and also to prevent the case from burning incompletely in the presence of moisture. The case must withstand the stresses of handling, particularly when it is energetically rammed into the gun during loading. Its combustible casing has a tensile strength of 16 MPa, comparable to high density fiberboard (HDF). Other than serving as a container for propellant, the case also acts as a phlegmatizer (coolant) to reduce bore erosion when it is burnt during firing. </div><div><br /></div><div>When fired, the combustible case is reduced to carbon products including CO, CO2 and carbon solids (soot) by the temperature of combustion. As the propellant burn rate increases, the pressure rises to a point where the soot particles experience a phase transition from a gaseous state to a solid state to form a deposit on the bore surface via a process known as sublimation, whereby they protect the bore surface from heat erosion by forming a protective layer between the surface and the hot gasses. In metal-cased cartridges, the phlegmatizer was a layered sheath of wax paper (wax is a hydrocarbon) placed around the propellant sticks, but according to the military university textbook "<i>Курсовая работа по огневой подготовке - Вооружение танков и БМП</i>" (<i>Coursework on fire training - Armament of tanks and BMPs</i>), in semi-combustible cartridges such as 125mm ammunition, the combustible casing itself serves as the phlegmatizer. A phlegmatizer increases the barrel life by 2-5 times. </div><div><br /></div><div>When the Rh120 L/44 120mm gun was introduced as a replacement for the 105mm L7, the absence of a phlegmatizer lining can also be observed. Semi-combustible cartridges lacking a phlegmatizer liner were used in the Rh120, whereas a titanium dioxide-wax phlegmatizer liner was present in standard brass-cased 105mm ammunition. Evidently, the same effect had been achieved with the combustible cases, made from nitrocellulose and wood pulp fibers, impregnated with polyurethane resin for waterproofing. Wood fibers are almost entirely composed of cellulose, which combusts to leave carbon products.</div><div><br /></div><div>The absence of a separate phlegmatizer liner was inherited from 115mm two-part ammunition, developed for the D-68 gun mounted on the T-62, but even before then, this feature had already been pioneered by the first Soviet 122mm semi-combustible cartridges for tank guns in 1957. </div><div><br /></div><div>
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The GUV-7 electric-percussion primer is used in all of the three propellant charges designed for the D-81, giving the option to either fire the shell normally using the electric trigger on the gunner's control handles, the electric trigger on the manual elevation handwheel, or using the manual lever-operated striker pin incorporated into the breech block of the cannon. The required initiation voltage and current is 20 V and 2 A respectively. Being a combined electric-percussion primer, the firing reliability is extremely high, as there is always a backup in case one initiation method fails for whatever reason. The possibility of percussion initiation is particularly useful as the mechanical firing mechanism built into all D-81 series guns is available even if the electrical systems in the tank are shut down.</div><div>
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<div><br /></div><div><br /></div>GUV-7 is rated to withstand a chamber pressure of up to 5,000 kgf/sq.cm, or 490 MPa. It can, however, be used with high-pressure rounds such as 3BM26 and 3BM42 without issues, as indicated by its continued use in the 4Zh63 propellant charge despite the much higher operating pressures generated. </div><div><br />
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<h3>
<span style="font-size: large;">4Zh40</span></h3>
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Original propellant charge designed for the D-81, used since the T-64A. It uses the 15/1 Tr V/A single-channel tubular propellant in uncut sticks and 12/7 V/A seven-channel grains. Both types of propellant have high nitration. The mass of the propellant charge itself is 5.66 kg, while the steel obturator stub weighs 3.45 kg. The remainder is taken up by the combustible nitrocellulose casing and the primer.</div><div><br /></div><div>The propellant includes a coil of fine lead wire as a decoppering agent, to strip the barrel bore of copper residue left by the projectile driving bands with every shot.<br />
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<div><br /></div><div><br /></div><div>4Zh40 lacks a primer tube because it was not necessary for a uniform burn. Propellant in the form of long sticks gives a very uniform burn when ignited with a base primer, because the hollow channels inside and between the sticks permit the flame from the primer to travel the entire length of the charge and thus ignite propellant evenly along the axis of the charge. Both ends of the propellant sticks are covered by a satchel of DRP-3 black powder to aid initiate combustion. The bottom satchel serves to help initiate the propellant in the charge itself, and the top satchel helps initiate the incremental charge of an APFSDS round, if loaded together with 4Zh40.</div>
<div><br /></div><div>A ring-shaped satchel of VTKh-20 flame arresting powder is placed at base of the steel obturator stub to ensure that flashback does not occur after firing. </div><br />
The autoignition temperature of the combustible casing of the 4Zh40 charge is 170°C.<br />
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Mass of Complete Assembly: 10 kg<br />
Propellant Charge mass: 5.66 kg<br />
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<h3>
<span style="font-size: large;">4Zh52</span></h3>
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Newer general-purpose propellant charge. It is entirely filled with grains of 12/7 V/A seven-channel propellant rather than a mixture of uncut sticks and grains, providing a fully progressive combustion rate. 4Zh52 also features a primer tube, which was absent in the 4Zh40. A primer tube functions by conveying the flame from the primer and venting it equally along its entire length. The jets of flame spread radially so that the combustion of all of the propellant grains is initiated nearly simultaneously, thus ensuring a uniform burn. Without the primer tube, a charge filled with loose grain propellant tends to burn erratically, and would result in inconsistent ammunition velocities and inconsistent barrel wear.</div><div><br /></div><div>A coil of lead wire is included in the charge, a satchel of DRP-3 black powder at the top of the charge helps initiate the incremental charge of an APFSDS round, and a ring-shaped satchel of VTKh-20 flame arresting powder is placed at base of the steel obturator stub to ensure that flashback does not occur after firing. </div><div><br /></div><div><br /></div><div>4Zh52 is completely interchangeable with 4Zh40, as it ensures identical internal ballistics with all ammunition types. Here is a video of the Zh52 propellant charge being opened up (<a href="http://www.liveleak.com/view?i=2a8_1410086864">link</a>).<br />
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Mass of Complete Assembly: 10 kg<br />
Propellant Charge mass: 5.786 kg<br />
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<h3>
<span style="font-size: large;">4Zh63</span></h3>
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4Zh63 is a high-energy propellant charge to launch APFSDS shells at a greater muzzle energy than possible with previous propellant charges. It uses a new highly calorific APTs-235P 16/1 and 16/1 tr V/A single-channel tubular pyroxylin propellant in sticks, arranged in a single bundle. The APTs-235P propellant occupies almost the entire volume of the charge, and it is surrounded by a single layer of 16/1 tr V/A tubes. Due to the exclusive use of uncut sticks, the charge is not fitted with a primer tube. </div><div><br /></div><div><div>The black colour of the APTs-235P 16/1 propellant tubes is due to the use of a phlegmatizer coating, also known as a "deterrent". The 16/1 tr V/A tubes are conventional, high-nitration pyroxylin propellant.</div><div><br /></div><div>Despite being tubular sticks, which are geometrically inclined to produce a neutral burn rate, progressive combustion of propellant was achieved by introducing phlegmatizers into the outer layers of the finished propellant tubes. According to A. G. Gorst in the 1972 textbook "<i>Пороха и взрывчатые вещества</i>" (<i>Propellant and explosive substances</i>), phlegmatization of propellant grains is carried out by placing the finished grains in rotating drums, and the phlegmatizer solution is introduced by spraying through nozzles at a pressure of 2-2.5 atm, whereby a uniform wetting of the grains with the phlegmatizer solution occurs. This generating a uniform distribution of the phlegmatizer along the surfaces of the grain.</div><div><br /></div><div>With this method of treatment, the phlegmatizer penetrates into the thickness of the tubes at a depth of up to 15% of the thickness of the arch (the wall of the tube), and the concentration of the phlegmatizer</div><div>gradually decreases from the outer layers to the interior of the arch. Accordingly, the combustion rate of the propellant increases as the combustion front moves from the outer layer into the interior of the arch. The table below shows the effect of phlegmatizing of rifle powder. The weight of the charge can be increased by 30% and the muzzle velocity by 8% without increasing the maximum pressure in the bore.</div></div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-SwxgdEBDsEc/YD5og3vxAhI/AAAAAAAAS1c/5AujK6ayOWMz21flJq8TyqlM3qXJePHQgCLcBGAsYHQ/s1207/phlegmatized%2Bpropellant.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="427" data-original-width="1207" height="141" src="https://1.bp.blogspot.com/-SwxgdEBDsEc/YD5og3vxAhI/AAAAAAAAS1c/5AujK6ayOWMz21flJq8TyqlM3qXJePHQgCLcBGAsYHQ/w400-h141/phlegmatized%2Bpropellant.png" width="400" /></a></div><div><br /></div><div><br /></div><div>Gorst states that phlegmatization is only done for small arms and small caliber artillery systems (autocannons), which was true at the time the book was published (1972), but the technology had since then been leveraged for increased performance in APTs-235P and other compounds for high-performance guns and rocket engines.</div><div><br /></div><div><br /></div><div>4Zh63 is used with newer APFSDS rounds which also contain the same propellant in the incremental charge, but it seems that there is nothing to stop it from being used with older APFSDS rounds. It would presumably propel older APFSDS at a muzzle velocity far in excess of 1,800 m/s, assuming that it is used in a gun with a higher design pressure such as the 2A46M.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Ja5UuUl4ido/X34iKHSZPCI/AAAAAAAARrs/RQhWTPhaXGQZF1-CT_X3P5OWrpH6TklbQCLcBGAsYHQ/s1501/zh63%2Bpropellant.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1257" data-original-width="1501" height="335" src="https://1.bp.blogspot.com/-Ja5UuUl4ido/X34iKHSZPCI/AAAAAAAARrs/RQhWTPhaXGQZF1-CT_X3P5OWrpH6TklbQCLcBGAsYHQ/w400-h335/zh63%2Bpropellant.jpg" width="400" /></a></div><br /><div><br /></div><div><br />
Like the standard charges, a coil of lead wire is included together with a satchel of DRP-3 black powder at the top of the charge, and a ring-shaped satchel of VTKh-20 flame arresting powder is placed at base of the steel obturator stub. </div><div><br />
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Mass of Complete Assembly: 10 kg<br />
Propellant Charge mass: 5.3 kg<br /><br />
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<a href="https://www.blogger.com/null" id="hef"></a>
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<h3>
<span style="font-size: large;">HE-Frag</span></h3>
<div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-IAyu-DeM0Eg/YCsr_0UNZyI/AAAAAAAASuU/lW9sKQYRV4oQ5yaIthsFStf1s7qU7C3xQCLcBGAsYHQ/s740/cad7f9fd10a5.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="554" data-original-width="740" height="299" src="https://1.bp.blogspot.com/-IAyu-DeM0Eg/YCsr_0UNZyI/AAAAAAAASuU/lW9sKQYRV4oQ5yaIthsFStf1s7qU7C3xQCLcBGAsYHQ/w400-h299/cad7f9fd10a5.jpg" width="400" /></a></div><div><br /></div><br />
The T-72 normally carries a 50% load of HE-Frag shells in the autoloader in a standard combat loadout, although this will almost certainly
vary by situation. Traditionally, this type of ammunition is predominant in
Soviet armoured shock tactics, where tanks were regarded as the tip of the
spear during breakthroughs and many other types of combat missions. This approach was supported by real data showing that combat with heavily armoured tanks was infrequent and that the most common targets tended to be military and civilian structures, infantry and soft-skinned vehicles. HE-Frag shells were therefore a critical part of the combat loadout of any T-72.<br />
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Together with HEAT, the HE-Frag ammunition used in 125mm guns is considered a full charge, full caliber round. It erodes the gun barrel at a rate of 0.0033mm per shot.</div><div><br />
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<div><br /></div><div><br /></div>All 125mm HE-Frag shells were fitted with the V-429E point-detonating fuze. It has two settings - superquick and delayed. The fuze is armed by inertia; setback forces from the acceleration inside the gun barrel trips the arming mechanism, and when the shell experiences a braking effect from the unfolding of the stabilizer fins at a distance of 5 to 7 meters from the muzzle, the fuze is armed.<br />
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The fuse gives 125mm HE-Frag shells a great deal of flexibility. There are two fuze settings and the fuze cap can be left on or taken off, giving a total of four fuzing combinations. Of these, three are used. Setting the fuze in a T-72 is done by the commander using a special key if he determines that a different fuzing mode is suitable for a particular target. The key turns a valve that connects the percussion cap of the impact mechanism to the detonator cap. There are two paths for a flame from the percussion cap to travel to the detonator cap: the direct path through the valve, and a parallel path where it ignites a retarder, which then combusts and emits a flame to the detonator cap after some delay.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZeZsBBWpkCqgaOsEwkJC2JblX6XIZrKnh7OfmDRqbi9E2KAMTdAMus9MB5lZElPg50oIUSB892Jg_u0WOeZMSyTWzrRcXGy53P_wFaYcGhD3CLiHC0r-Y80H3PPraLz7AX70GhN8iKYc9UKK4pnQQP5i4QtK-KTcAwqxjkDY6Vo_P2y0ytPXMoBALng/s2508/v-429e.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2480" data-original-width="2508" height="395" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZeZsBBWpkCqgaOsEwkJC2JblX6XIZrKnh7OfmDRqbi9E2KAMTdAMus9MB5lZElPg50oIUSB892Jg_u0WOeZMSyTWzrRcXGy53P_wFaYcGhD3CLiHC0r-Y80H3PPraLz7AX70GhN8iKYc9UKK4pnQQP5i4QtK-KTcAwqxjkDY6Vo_P2y0ytPXMoBALng/w400-h395/v-429e.png" width="400" /></a></div><div><br /></div><div>When issued, the fuze is configured in the "HE-Frag" mode by default; it is set to "O" (superquick) and has the fuze cap fitted. The deformation of the protective fuze cap causes the striker to be driven into the percussion cap, and the intensity of the deformation is dependent on the target. For a soft target such as a soil berm, deformation is low, so the resultant delay is long. For a hard target such as a concrete wall or an armoured surface, the delay is very short, as the fuze cap is destroyed almost immediately. The detonator cap is set off immediately following the percussion cap because the connecting valve is open. When attacking infantry in the open or in covered positions such as anti-tank teams (recoilless rifle or ATGM) or machine gun nests, the fuze should left in the "HE-Frag" mode which gives it a nominal delay of 0.027 seconds to ensure that the shell will detonate with a minimal delay upon meeting a solid obstacle such as soft ground like mud and snow to produce a combined high-explosive and fragmentation effect, yet not detonate prematurely on light obstructions in front of the intended target. Owing to the flexibility of this fuze mode, it is viable against most targets.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ngfXQAli35w/YCsl4EYVNSI/AAAAAAAASuI/GJgwS6jPfcQ8OPGJh9aAo0EN5Z68qUobwCLcBGAsYHQ/s1115/fuze%2Bsetting.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1115" data-original-width="731" height="400" src="https://1.bp.blogspot.com/-ngfXQAli35w/YCsl4EYVNSI/AAAAAAAASuI/GJgwS6jPfcQ8OPGJh9aAo0EN5Z68qUobwCLcBGAsYHQ/w263-h400/fuze%2Bsetting.png" width="263" /></a></div><div><br />
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To use the shell in the "Frag" mode, the fuze is left in the "O" (superquick) setting and the protective fuze cap is removed. With the fuze cap removed, the striker is protected only by a steel foil membrane, which is thick enough to prevent the striker from being blown back by the flow of air, but is too thin to survive a collision with anything substantial. Upon impacting any obstacle, the steel foil membrane, which has a thickness of just 0.12mm, is pierced and the striker is driven into a percussion cap, triggering the detonator. The shell detonates instantly upon impacting practically any surface or obstacle, which can be useful as the tank may fire at the canopy of a tree to produce an airburst over infantry taking cover beneath it. However, it is forbidden to use the "Frag" mode in heavy rain or hail because a collision of the steel foil membrane with big rain droplets is enough to trigger a detonation.</div><div><br /></div><div>If the fuze cap is left on but the fuze is set to the "З" (delayed) setting, a "HE" effect is produced. The fuze is detonated not by a strike upon the nose, but by the deceleration force from the shell impacting an obstacle, which allows the percussion cap in the fuze to overcome the small resistance of its creep spring, and impact the unmoved striker. Then, the flame from the percussion cap ignites the retarder, generating an additional delay before the detonator is finally initiated. The shell is detonated after a much longer delay of 0.063 seconds after impact. This enables the shell to explode after penetrating the earth down to an optimal depth, thus displacing the largest possible volume of soil and delivering the maximum shock effect to enemy fortifications which tend to be below ground level by nature. In this way, a trench can be destroyed by firing a HE shell at a point just in front of the trench. The shell penetrates the earth at an oblique angle and explodes just next to the wall of the trench (a lucky shot may even explode inside the trench itself), thus demolishing it and possibly injuring or killing anyone in the way. </div><div><br /></div><div>If the fuze is set to the "З" (delayed) setting but the fuze cap is removed, the fuze is in the so-called "ricochet" mode. In this state, the fuze is reliably initiated upon impact with the surface of the ground, even on soft marshy ground or snow, but the delay ensures that the shell does not detonate until well after it has ricocheted off the ground, hopefully producing an airburst effect. </div><div><br /></div><div>
When used in the delayed HE mode against non-hardened structures like houses, the shell could pass through reinforced concrete, cinder block, adobe or brick walls and explode on the other side. The destruction of the tip of the fuze does not necessarily disable it, because only the retarder must be burning for detonation to occur. <br />
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<br />
With that in mind, HE-Frag rounds should not be mistaken as a purely anti-infantry or anti-structure munition as they may even be used as a substitute to
more specialized anti-armour shells like APFSDS and HEAT against heavy armour under certain circumstances, such as when all other ammunition has run out, or if effective destruction cannot
be achieved by other means. A direct hit with the fuse set to the superquick setting will likely result in the debilitating disability of the
cannon or the destruction of aiming devices, the destruction of the driver's vision blocks or the destruction of the tank suspension (although probably not all at the same time), producing a
firepower or mobility kill.</div><div><br />
When set in the HE mode, 125mm shells are extremely deadly to lightly armoured vehicles. For example, 76mm HE shells fired from the F-34 cannon of a T-34 were also found to be able to perforate the armour of tanks like the Pz.III. There is comparatively little information available on the internet on this topic, but Peter Samsonov's translation of a <a href="http://tankarchives.blogspot.my/2016/12/76-mm-he.html">report on the effects of 76mm HE-Frag shells at tanks with a variable fuse</a> is especially enlightening. Here is a fascinating paragraph from that report:<br />
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"<i>When firing [76mm] HE shells from mod. 1931 guns consider that they can penetrate 45 mm of armour at 30 degrees from 500 meters, and 50 mm of armour under the same conditions can be penetrated from 300 meters or closer.</i>"<br />
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Like any other anti-aircraft gun intended for engaging high altitude targets, the mod. 1931 gun fired relatively high velocity rounds (~800 m/s), but such velocities are pedestrian for modern guns like the 2A46. It is also worth noting that the shape of HE shells is ogived, so the efficiency of such shells on sloped armour is very low compared to a blunt-nosed APBC shell like the 100mm BR-412B. If 76mm HE shells are capable of defeating 45mm of armour plate angled at 30 degrees at 500 meters, a much larger 125mm HE-Frag shell travelling at the same velocity would be able to penetrate much more or at least achieve a more destructive effect. Indeed, Hungarian testing of 125mm HE rounds on T-34-85 tanks showed that frontal hits could perforate the upper glacis armour and detonate inside the tank with catastrophic effects as shown in the photos below.<br />
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Interestingly enough, the 0.063-second delay of the V-429E fuse is identical to the delay of other post-War fuses like the RGM-6 point-detonating fuse for 100mm HE-Frag shells, and this delay is longer than what WWII and pre-war fuses for artillery rounds provided, which was 0.03-0.05 seconds. This was most likely related to the increased standards of bunker fortifications and the disappearance of concrete piercing rounds from the arsenal of the Red Army shortly after WWII.<br />
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The side armour of some NATO tanks like the Chieftain and the Leopard 1 are probably vulnerable to 125mm HE shells from combat distances (1.5 km or more) given that their side armour is only 38mm thick, and it is likely that the thicker side hull armour of an M60A1 may not be enough to resist 125mm HE at closer distances. Thin side skirts may offer too little resistance to set off the V-429E fuse, even steel skirts which are found on tanks like the Centurion and Chieftain. The Leopard 1 is noteworthy as the armour on the side of its turret is only 40mm thick (angled at 30 degrees), so even the aforementioned 76mm HE shell fired from the 1931 anti-aircraft gun may potentially defeat the Leopard 1 from 500 meters. The addition of a 30mm spaced appliqué plate on the turret in later Leopard 1 variants might still not be enough to defend it from a 125mm HE shell, and even if the shell was successfully stopped, the explosion might still be powerful enough to split open the base armour plate. Against a heavily armoured IFV such as the M2A2 or M2A3 Bradley, the 38mm layer of steel appliqué armour on the hull will be entirely insufficient to stop such a shell even at long distances. Modern IFVs designed with relatively heavy armour to combat the ubiquitous RPG are probably still extremely vulnerable to 125mm HE.<br />
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As such, even though the T-72 carries more HE-Frag shells than anti-armour shells, it can be seen that this is not a problem as HE-Frag shells have a very substantial multi-role capability. It is not wrong to say that the combat value of an individual HE-Frag round easily exceeds that of an APFSDS round or a HEAT round. Nevertheless, it would be misleading to paint HE-Frag rounds as an ultimate weapon when in fact, the 125mm gun of the T-72 was chosen for the high armour penetration of its APFSDS ammunition. Indeed, during testing in the early 60's, it was found that the range and accuracy of HE-Frag rounds fired from the rifled 122mm D-83 gun was superior to the range and accuracy provided by the smoothbore D-81. However, the armour penetration of the sub-caliber ammunition fired from the D-81 was somewhat better which proved to be the determining factor in the comparative trials. The D-81 was given the GRAU index of 2A26 and the D-83 was given the index of 2A27, but only the 2A26 went on to see service in the USSR's new line of advanced MBTs.<br />
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Due to the high muzzle velocity of 125mm HE-Frag shells, the ballistic trajectory is relatively flat. This reduces its sensitivity to rangefinding errors and increases its range, but conversely, the low angle of impact of the shell when fired at the ground greatly limits the effectiveness of its fragmentation against infantry in the open, particularly if they are lying prone or in a trench. To maximize the anti-personnel effect, the tank should begin firing at infantry targets at a longer range to maximize the angle of descent and ensure that the shells impact the ground at a relatively low velocity. The gunner may also use ricochet fire to generate air bursts, which is drastically more efficient against infantry than ground bursts. The dispersion of 125mm HE-Frag shells is low enough (considering its purpose) to engage point targets and area targets alike. Combating ATGM systems - both man-portable and vehicle-mounted - occurs at long standoff ranges to prevent return fire. Naturally, this permits the angle of impact to be quite high and the impact velocity to be quite low; the official firing table for the OF-19 shell shows that the angle of descent and impact velocity at 4,000 meters is 3.6 degrees and 454 m/s respectively.
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Shot for shot, conventional 125mm HE-Frag ammunition was considerably more effective in a direct comparison with NATO tanks armed with 105mm and 120mm guns excluding the ammunition developed in the post-Cold War era. As a rule, the HEP or HESH rounds found on rifled 105mm and 120mm guns are effective on armoured targets (with homogeneous armour) and reinforced structures, but are ineffective when firing at targets in open ground due to the inertia-based fuzing system and poor fragmentation characteristics of the thin steel warhead casing. Some NATO nations like France used 105mm HE shells, but the large difference in caliber naturally makes them less effective than 125mm shells on a shot for shot basis. The smoothbore Rh120 L/44 and M256 guns were the worst in this regard as HEAT rounds were intended for everything that was not a tank. Given that the Soviet Army was completely mechanized by the 1980's, there was clearly a valid doctrinal reason for the simplification of the combat loadout to only two types of ammunition, but HEAT rounds are still extremely poor against infantry in the open and infantry sheltered in structures or behind cover. Recently, the need for HE-Frag ammunition in tanks armed with a smoothbore 120mm gun was recognized and its role was fulfilled by the DM11 round in German service. DM11 is also used by the U.S Marine Corp as the Mk. 324. <br />
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<h3>
<span style="font-size: large;">3VOF22<br />
3OF19</span></h3>
<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-LQ224mB63bY/YCsgvXfIRKI/AAAAAAAASuA/1xzd9zBIeDgXau_IeQk6HNU4NzKDpqybwCLcBGAsYHQ/s2048/3of19.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1761" data-original-width="2048" height="344" src="https://1.bp.blogspot.com/-LQ224mB63bY/YCsgvXfIRKI/AAAAAAAASuA/1xzd9zBIeDgXau_IeQk6HNU4NzKDpqybwCLcBGAsYHQ/w400-h344/3of19.png" width="400" /></a></div><div><br /></div><br />
The OF19 shell is a conventional HE-Frag shell with copper driving bands. The casing of the projectile has the shape of an ogive. It is interesting to note that this shell has a length of 675mm, making it the longest projectile among the three ammunition types carried by a basic T-72. This only changed with the inclusion of guided missiles in the T-72B and high elongation long rod projectiles later on.<br />
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A stabilizing fin assembly made from B-95 aluminium alloy is used. The forged steel casing of the warhead is made from S-60 structural carbon steel, a standard steel grade for this purpose with a carbon content of 0.60%, hence the -60 index. Although heat-treated S-60 steel can have a relatively high strength, artillery shell casings built using S-60 steel are not heat treated after forging. This greatly reduced the time and demands on skilled labour required in the manufacturing process, and the resultant low strength yields better fragmentation characteristics. The casing alone weighs 15.7 kg. </div><div><br /></div><div>In terms of total weight and the weight of its explosive payload, OF19 is nominally inferior to the 122mm OF-471N shell, the standard HE-Frag shell used in IS-3 and T-10 heavy tanks. However, the share of the explosive filler weight is at least comparable, as the weight of the steel casing is 15.7 kg, giving a high ratio of explosive filler to casing weight of 20% which gives good fragmentation characteristics for the given weight of the shell.</div><div><br /></div><div>In terms of the design characteristics relevant for HE-Frag shells, 3OF19 was exceptional. The closest Western analogue is the much more modern <a href="https://www.gd-ots.com/munitions/large-caliber-ammunition/120mm-imhet/">120mm IM HE-T round</a> which features the same conventional ogived shape and the same fuzing functions, but has a projectile weight of just 16 kg, just two thirds the weight of 3OF19. Its <a href="https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2009/insensitive/2Againes.pdf">formidable capabilities</a> against field fortifications, structures and light vehicles serve as a surrogate demonstrator for the much heavier 3OF19 shell. </div><div>
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Complete Shell Mass: 23 kg<br />
Complete Shell Length: 675mm<br />
Wingspan (deployed): 356mm<br />
Muzzle velocity: 850 m/s<br />
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Explosive mass: 3.148 kg<br />
Explosive composition: TNT<br /><br /><br /><div>According to <a href="https://dnr-sckk.ru/1068-2/">at least one source</a>, an organization for representing the so-called DNR under the implementation of the Minsk ceasefire agreements in Eastern Ukraine, the high-explosive (cratering) effect of the OF19 shell with the fuze set for fragmentation action is a crater with a depth of 0.3-0.4 m and a diameter of 1.5-1.7 m. With the fuze set for high-explosive action, a crater with a depth of 0.4-0.6 m and a diameter of 1.7-2.0 m is produced. This is somewhat worse than the nominal HE effects of 122mm artillery shells, which is a crater 0.7 m deep and 3 m in diameter according to artillery textbooks, but this may be due to the differences in local conditions relative to the formal Soviet criterion used in the creation of official texts. According to the textbook "<i>Основания Устройства И Конструкция Орудий И Боеприпасов Наземной Артиллерии</i>" (<i>Basic Artillery and Ammunition Structure and Design for Ground Artillery</i>), on average, a kilogram of explosive filler (TNT) accounts for 1.2-1.5 cubic meters of medium density soil. OF19 can therefore be expected to displace 3.8-4.7 cubic meters of soil in te HE mode. </div><div><br /></div><div>The crater dimensions for an OF19 shell set to the delayed HE mode is unknown, as is the crater volume.</div>
<br />In terms of fragmentation effects against targets in the open, the size of the nominal kill zone generated by OF19 is 370 square meters. In this zone, the statistical probability of a man lying prone being injured or killed from being hit by at least five shell splinters is 50%. For comparison, the nominal kill zone of the 100mm OF32 HE-Frag shell supplied to T-54/55 tanks in the 1970's is only 160 square meters. Moreover, 122mm HE-Frag shells are considered to have a nominal kill zone of 310 square meters. Shot for shot, a T-72 firing the OF19 shell is 2.3 times more effective than a T-55 firing the OF32 shell against personnel in the open, and also around 20% more effective than 122mm HE-Frag.</div><div><br />
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<h3>
<span style="font-size: large;">3VOF36<br />
3OF26</span></h3>
<h3>
</h3>
<div class="separator" style="clear: both; text-align: center;"><br /></div>
The OF26 is an improved variant of the 3OF19 shell, replacing the TNT charge with an A-IX-2 charge for increased fragmentation, incendiary and blasting power. Originally, the OF26 shell used copper driving bands, but a relatively recent modernization effort has replaced these with plastic driving bands to reduce barrel wear. The fuze, steel casing and stabilizing fin assembly remained the same as 3OF19.</div><div><br /></div><div>Despite the shell casing having the same internal volume, the filler weighs 3.4 kg due to its greater density compared to TNT; in their cast forms, A-IX-2 has a density of 1.76 g/cc while TNT is 1.60 g/cc. This raised the weight of the projectile to 23.3 kg. The share of explosive filler mass increased accordingly to 21%. However, this simple metric alone does not allow an accurate evaluation of the true relative effectiveness of the OF26 because a comparison of the weights of explosive charges can only be done if the explosive compound is the same. Rather, the effective weight of A-IX-2 in terms of TNT is much higher than the physical weight of the charge implies. A-IX-2 has 1.86 times more explosiveness than crystalline TNT as determined by the Trauzl test (530 ml compared to 285 ml), which is the most relevant metric for cased explosives, much more so than the calorific values alone. While a simple comparison of their calorific values shows that A-IX-2 has 1.54 times more heat energy, with a specific heat of explosion of 6.44 MJ/kg compared to a specific heat of explosion of 4.184 MJ/kg for TNT, the amount of explosive heat energy by itself says nothing about the ability of the explosive compound to do work; to transfer its explosive heat energy into the shell casing as kinetic energy. By using explosiveness as a reference point rather than the calorific value alone, a much more meaningful estimation of the blasting and fragmenting capability of an explosive can be made.</div><div><br /></div><div>For a fragmenting warhead, this translates to stronger blasting effect and a higher fragment energy for a given fragmenting efficiency. According to a study, a large improvement to the mass distribution of fragments is obtained in empirical testing with cylinders of different grades of steel. When a cylinder of S-60 steel was tested with TNT and then A-IX-2, it was found that the proportion of small fragments increased from 15% to 18%, the proportion of medium fragments increased from 26% to 35%, and the proportion of large fragments decreased from 59% to 47%. In this case, small fragments (µм) were defined as weighing less than 1 gram. Medium fragments (µс) weigh between 1-4 grams, and large fragments (µк) weigh more than 4 grams. With a larger quantity of small and medium fragments, the probability of hitting targets is increased, thus improving the lethality radius.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-XPTBdLuSDZM/YLCRDlECWoI/AAAAAAAATMg/cUnRwA36y5kzm_dzLKYRsVeReser6IlOwCLcBGAsYHQ/s1366/fragmentation%2Bperformance%2Bof%2Bdifferent%2Bsteels%2Bwith%2BTNT%2Band%2BA-IX-2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="690" data-original-width="1366" height="203" src="https://1.bp.blogspot.com/-XPTBdLuSDZM/YLCRDlECWoI/AAAAAAAATMg/cUnRwA36y5kzm_dzLKYRsVeReser6IlOwCLcBGAsYHQ/w400-h203/fragmentation%2Bperformance%2Bof%2Bdifferent%2Bsteels%2Bwith%2BTNT%2Band%2BA-IX-2.png" width="400" /></a></div><div><br /></div><div><br />
<br />
Total Length: 676mm<br />
Total Shell Mass: 23.3 kg<br />
Muzzle velocity: 850 m/s<br />
<br />
Explosive mass: 3.4 kg<br />
Explosive composition: A-IX-2<br />
<br /><br /><br />It is reported that due to the use of A-IX-2 instead of TNT, the casualty area of a 125mm HE-Frag shell increased by 25%. As such, the nominal kill zone can be considered to have increased to 462 square meters, although there is no source that explicitly gives this figure.<br />
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<br />
<br />
<h3>
<span style="font-size: large;">Practice HE-Frag</span></h3>
<br />
<br />
Practice HE-Frag shell that emulates the ballistic characteristics of live HE-Frag shells. Contains a 200-gram TNT charge to produce a bright flash that acts as a visual hit marker for the trainee gunner.<br />
<br />
<br />
Maximum Chamber Pressure: 3,432 bar<br />
<br />
Total Length: 676mm<br />
<br />
Total Shell Mass: 23.3 kg<br />
Muzzle velocity: 850 m/s<br />
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<br />
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<a href="https://www.blogger.com/null" id="heat"></a>
<br />
<h3>
<span style="font-size: large;">HEAT</span></h3>
<br />Although APFSDS was considered the primary anti-tank round and HE-Frag was preferred for all other targets, T-72 tanks carried a few HEAT rounds in their combat load as it was a flexible alternative option. Unlike older tanks like the T-54 which had a smaller and less powerful gun, this type of anti-tank ammunition was not reserved for heavy tanks because APFSDS rounds were the first choice for fighting tanks of all types owing to their higher probability of kill. Instead, the HEAT rounds of the T-72 were considered to be multipurpose.</div><div><br /></div><div>
<br />
The 125mm HEAT shells of the T-72 were powerful enough to pierce contemporary
armour in most cases and the explosive charge allowed them to be used
against lightly armoured vehicles with a much better result than APFSDS shells. HEAT shells may also be used against hardened concrete
bunkers or simple earthen fortifications with good results, and it is
entirely feasible to engage personnel or soft-skinned vehicles owing to the very thick steel case containing the charge even if it is not as effective as HE-Frag shells in this role. Given that actual combat experiences showed that tanks only occasionally fought other tanks but routinely had to deal with lightly armoured and unarmoured targets, buildings and field fortifications, HEAT rounds served as an alternative to HE-Frag rounds for the T-72.<br />
<br />
Against thickly armoured targets, HEAT shells produce deep but relatively small holes. The destruction of armoured and unarmoured targets is effected by several mechanisms. Aside from the direct impact of the residual shaped charge jet on equipment and enemy personnel, the secondary means of destruction include the blast of the explosive charge, the expanding gasses rushing through the hole in the armour (if not plugged by the shaped charge slug), the flash of heat energy inside the target (capable of causing flash burns) and most importantly, the spray of high velocity armour and jet fragments ejected behind the armour plate which can set internal equipment alight and injure the crew. All of the other mechanisms are less destructive and play a correspondingly smaller role.<br />
<br />
Inside an armoured target, the overpressure generated by the perforation of the armour is sometimes not powerful enough to reliably injure the crew or knock out essential equipment even if the tank is completely sealed. It is possible for the blast to injure crew members if the shell lands close to an open hatch, but this is merely circumstantial as it is not the primary function of the shaped charge warhead. There are recorded cases where tank commanders were injured or outright killed by grenades that would otherwise have failed to defeat the armour of the tank simply because the hatch was not sealed, which allowed the blast wave to enter the tank.<br />
<br />
Needless to say, the blast and shrapnel produced from the explosive charge and thick steel casing of a tank-fired HEAT shell can kill or injure dismounted infantry and external equipment, including periscopes, gun sights and other optical instruments without necessarily piercing the tank's armour. This can force the tank to operate in a degraded mode and render it more vulnerable to a follow-up shot or knock it out, but the success of this type of attack strongly depends on the location of the hit.<br />
<br />
According to <a href="http://www.kotsch88.de/tafeln/st_125mm-heat.htm">firing tables for 3BK-14M</a> provided by Stefan Kotsch, the HEAT shell has a horizontal deviation of 0.19 m and a vertical deviation of 0.19 m. On the other hand, the <a href="http://www.kotsch88.de/tafeln/st_125mm-ke-2A46M.htm">firing tables for 3BM-15</a>, also provided by Kotsch show, that the APFSDS shell has a horizontal dispersion of 0.20 m and a vertical dispersion of 0.20 m - the difference in dispersion is only a centimeter. The gap in probable deviations remains minor even at 2 km. At that distance, 3BK-14M has a horizontal dispersion of 0.38 m and a vertical dispersion of 0.39 m, whereas 3BM-15 has a horizontal dispersion of 0.4 m and a vertical dispersion of 0.4 m. The difference was only a centimeter or two.<br />
<br />
In practical real world conditions, the expected hit probability of HEAT ammunition is vastly lower than that of APFSDS ammunition for a variety of factors. This has been confirmed by Soviet studies on the hit probabilities for T-64A and T-72 tanks during live firing exercises. The primary factor in the advantage held by APFSDS rounds is the high velocity of APFSDS ammunition (3BM-15 has twice the muzzle velocity of 3BK-14M) that makes it much easier to score hits on moving targets at any distance. Case in point - the point blank range of 125mm HEAT ammunition is 1,000 meters whereas the point blank range of 125mm APFSDS ammunition from the 1970's is 2,120 meters. HEAT shells were also more susceptible to the interference of crosswinds and head or tail winds because their stabilizer fins had a much larger diameter than those of an APFSDS round. Another factor to consider is ranging errors, particularly at longer distances. Furthermore, the minor dispersion advantage of HEAT ammunition inevitably declined when sabots made with tighter tolerances and more reliable petal separation became available. The post-perforation damage of APFSDS shells can also be considerably more serious than HEAT shells of the same caliber.<br />
<br />
For these reasons, APFSDS was the primary anti-tank round and not HEAT, and this was reflected in the standard ammunition loadout for Soviet T-72 tanks as well as the T-72 tanks operated by Warsaw Pact armies. This also indirectly disproves the claim that the motivation behind the development of a 125mm gun was so that a larger diameter - and thus more powerful - HEAT shell than the available 100mm and 115mm caliber shells could be used against future NATO armour.<br /><br />
<div>
<br /></div>
Mechanically, the dispersion of 125mm HEAT rounds was less than their 120mm counterparts due to tighter tolerances. This can be seen in the fact that a significant difference exists even at the short range of 500 meters, where DM12 has a dispersion (50% zone) of 0.13 meters in both axes whereas 3BK14M has a dispersion (50% zone) of 0.09 meters in both axes. Additional factors in the difference can be attributed to the large span of the folding fins of the Soviet pattern of HEAT shells, which may provide a larger static margin of stability. According to a memorandum on the results of <a href="https://cdn.discordapp.com/attachments/638345814955130890/761126215985135666/unknown.png">trilateral trials of tank ammunitioon in 1977</a>, DM12 suffers from excessive widening of its angular dispersion at ranges above 2 km, such that at 3.5 km, its dispersion reaches 0.54 mils. At the same range of 3.5 km, the dispersion of 3BK14M is 0.81 meters vertically and 0.66 meters horizontally, which represents a deviation of 0.23x0.19 mils. In a comparison between a typical 125mm HEAT shell and a typical 120mm HEAT shell, the approach taken by the Soviet designers differed in that the muzzle velocity was reduced in favour of delivering a heavier, more potent warhead with a more powerful shaped charge.<br />
<br />Conversely, the high muzzle velocity of 1,140 m/s achieved by the 120mm M830 or DM12 HEAT round significantly shortened the flight time to a target, with a sizeable difference of 0.13 seconds even at a range as short as 500 meters, increasing to 0.20 seconds at 1,000 meters, and to 0.60 seconds at 2,000 meters. That said, this does not necessarily manifest as a drastic difference in the permissible lead error margin in practice, as 125mm HEAT is afforded a larger margin of error by the longer hulls and turrets of NATO tanks. Given a flight time of 2.9 seconds to 2 km for 125mm HEAT and 2.3 seconds to 2 km for 120mm HEAT, then at 2 km, a Leopard 2 moving at 10 km/h will travel just slightly over its own hull length (7.57 m), and at 20 km/h, it will travel just slightly over twice its hull length (15.2 m) in the time it takes for a 125mm HEAT shell to reach it. This is effectively the same as when the shooter and target are switched, as a T-72 moving at 10 km/h will travel exactly its own hull length (6.4 meters) in the time it takes for a 120mm HEAT shell to reach it, or twice its own hull length (12.8 meters) at 20 km/h.</div><div><br />The lack of a practical difference was not only limited to horizontal error, but vertical error as well. The flatter trajectory attained with the higher muzzle velocity of 120mm HEAT also gave no advantage against a typical Soviet main battle tank due to a height difference. The height of a T-72, measured from its hull belly to its turret roof, is 1.67 m - less than the height of an average man. The point blank range of M830 (DM12) against a target of this height is between 1,100 meters (1.52 m) and 1,200 meters (1.86 m). For comparison, the point blank range of 3BK14M against the Leopard 2 (1.98 meters from hull belly to turret roof) was 1,120 meters. In other words, they are practically the same. The same relationship exists if the APCs and IFVs of the two opposing sides are compared. Any difference in hit probability between 120mm and 125mm HEAT will primarily be as a result of the capabilities of the fire control system, rather than any ballistic factor.<br />
<br />
On the contrary, the high muzzle velocity brought with it the compromise of having a lighter projectile with a lighter warhead, and a much higher operating pressure of 485 MPa at a propellant temperature of 21°C. Moreover, given HEAT was the only ammunition type fielded alongside APFSDS for the Leopard 2 and M1A1 Abrams during the Cold War, it was the only viable option when dealing with lightly armoured vehicles, infantry in the open, field fortifications, and so on. For this purpose, the lighter warhead was a drawback.<br />
<br />
The trade-offs associated with achieving high muzzle velocities with high explosive shells are only acceptable if the tank has a simpler fire control system with a rangefinder of limited precision. This was the case for the T-55 and T-62. As such, it was a rational decision to supply these tanks with the 3BK17(M) and 3BK15(M) rounds with muzzle velocities of 1,085 m/s and 1,060 m/s respectively.<br />
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<br />
<br />
<h3>
<span style="font-size: large;">
3VBK-7(M)</span></h3>
<h3>
<span style="font-size: large;">3BK-12(M)</span></h3>
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://4.bp.blogspot.com/-7EziWWeZ188/WbfwSIpqvXI/AAAAAAAAJXs/CXqngIZE51g7npOLytWiSBoHvujDpLA_ACLcBGAs/s1600/3bk-12m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="233" data-original-width="477" height="311" src="https://4.bp.blogspot.com/-7EziWWeZ188/WbfwSIpqvXI/AAAAAAAAJXs/CXqngIZE51g7npOLytWiSBoHvujDpLA_ACLcBGAs/s640/3bk-12m.png" width="640" /></a></div>
<br />
<br />
The 3BK-12 was the first 125mm HEAT shell created for the D-81 series of guns. By the time the T-72 emerged, 3BK-12 had been replaced by the 3BK-14 but large quantities were probably stockpiled. The 3BK-12 was the basic variant with a steel shaped charge liner, and the 3BK-12M was the high performance variant with a copper liner. ("M" stands for "<i>med</i>", which means "copper" in Russian). The use of a copper liner grants improved penetration performance, but at a slightly higher price due to the cost of copper.<br />
<br />
The shell is characterized by the use of an aerodynamic spike which acts as a standoff probe and also serves to stabilize the airflow during supersonic flight in such a way that the projectile resists yawing and tumbling. The warhead of the shell has a trapezoidal wave liner, as seen in the drawing above. The shell uses the I-238 point-initiating base-detonating (PI-BD) spitback fuse which includes an initiator at the nose of the spike tip assembly and a detonator at the base of the warhead.<br />
<br />
The base of the casing had a threaded cup where the tail boom of the stabilizer fin assembly was affixed. The detonator of the I-238 fuze was sealed together with the rest of the payload inside the warhead casing. Like most fin-stabilized HEAT shells, the tracer was installed at the end of the tail boom of the stabilizer fin assembly.<br />
<br />
The casing of the shell is characterized by distinct knurls or "teeth" around the perimeter of casing surrounding the standoff probe, designed to ensure that the projectile is smoothly chambered when it is rammed into the gun breech, according to the textbook "<i>Устройство и действие боеприпасов артиллерии</i>". <br />
<br />
<br />
Projectile weight: 19 kg<br />
Total Projectile Length: 678mm<br />
<br />
Muzzle velocity: 905 m/s <br />
<br />
Explosive Charge: A-IX-1<br />
Explosive Charge Weight: 1.624 Kg<br />
<br />
Penetration (3BK-12):<br />
420mm RHA<br />
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<br />
<h3>
<span style="font-size: large;">
3VBK-10(M)</span></h3>
<h3>
<span style="font-size: large;">3BK-14M</span></h3>
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<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-DqcvUyf9vzE/VS_HWikrhAI/AAAAAAAABx8/eYXSmNZsbgk/s1600/14224706.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://1.bp.blogspot.com/-DqcvUyf9vzE/VS_HWikrhAI/AAAAAAAABx8/eYXSmNZsbgk/s1600/14224706.jpg" width="161" /></a><a href="http://2.bp.blogspot.com/-vBJmIh3wMls/VS_D38514CI/AAAAAAAABxo/CoesIFnf_hI/s1600/image012.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://2.bp.blogspot.com/-vBJmIh3wMls/VS_D38514CI/AAAAAAAABxo/CoesIFnf_hI/s400/image012.jpg" width="286" /></a></div>
<div>
<br /></div>
<br />
The 3BK-14 shell had a thoroughly updated design with the same external dimensions as the 3BK-12,
but with major internal differences. The most major improvement was the substitution of the A-IX-1 explosive compound used in the 3BK-12 with OKFOL. The higher explosive velocity of OKFOL increased the penetration power of the shaped charge jet without needing to increase the weight of the explosive charge. To accompany the new explosive compound, the shell used a new cylindrical wave shaper with a slight taper. The shell uses the V-15, a two part superquick piezoelectric point-initiating, base detonating fuze. It is rated for an impact angle of up to 70 degrees, which is excellent, but is not as good as a graze-sensitive shoulder fuze as found on some foreign designs such as the 105mm M456A2 shell from the early 1980's. It is armed inertially using the acceleration of launch. For 125mm HEAT shells, it is armed at a distance of 2.5 meters from the muzzle.</div><div><br /></div><div><br /></div><div>Due to the need for an electrical connection between the piezeoelectric initiator at the nose of the standoff probe and the detonator at the base of the warhead, a sheet metal contact funnel was installed inside the standoff probe. When the standoff probe was threaded into the warhead casing, the contact funnel would be in contact with the shaped charge liner, thus allowing the electrical firing signal to be delivered to the detonator.<br />
<br />
Also, the base of the warhead casing and the stabilizer fin assembly were both completely redesigned. Instead of a sealed base with a socket for the stabilizer fin tail boom, the warhead casing has a protruding threaded plug with a compartment for the detonator of the V-15 fuse. Now, the detonator could be installed more easily during production by simply inserting it into its compartment before securing the stabilizer fins onto the warhead. Moreover, the relocation of the bulk of the detonator to the protruding plug freed up space inside the casing itself, thus allowing a larger mass of explosives to be carried. Overall, the new shell design was an improvement over the 3BK-12 in every way.<br />
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<a href="http://2.bp.blogspot.com/-x4pub7k5zoo/VS_E6witRbI/AAAAAAAABxw/MhmqDGJc_CE/s1600/02%2B-%2B125mm%2BBK-14M%2BHEAT%2Bin%2Bflight.JPG" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="300" src="https://2.bp.blogspot.com/-x4pub7k5zoo/VS_E6witRbI/AAAAAAAABxw/MhmqDGJc_CE/s640/02%2B-%2B125mm%2BBK-14M%2BHEAT%2Bin%2Bflight.JPG" width="640" /></a></div>
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<br />
<br />
The use of a piezoelectric fuze instead of a spitback fuze decreased the delay between the impact and the detonation of the shell. This allowed the entire standoff distance offered by the projectile design to be maintained even when the shell impacts a hard target at a very high impact velocity, and this helped to improve the armour penetration of the shaped charge.<br />
<br />
3BK-14 and 3BK-14M are noteworthy for being the most advanced HEAT round supplied to client nations operating T-72 tanks as well, including East Germany. As such, it has proliferated more than any other HEAT round that entered service in the USSR.<br />
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<br />
<br />
Projectile Weight: 19 kg<br />
Total Projectile Length: 678mm<br />
Warhead Casing Length: 296mm<br />
<br />
Muzzle velocity: 905 m/s <br />
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Explosive Charge: OKFOL<br />
Explosive Charge Weight: 1.76 kg<br />
<br />
<br />
Based on the latest information available, the penetration power of 3BK-14 is equal to 3BK-18 as they do not differ in construction in any way that impacts their armour penetration performance. This is also true for the "M" variants of both shells. The two shells have a functionally identical projectile design, the same mass of explosives, the same shaped charge liner design, the same wave shaper, and the same V-15 fuze. Penetration figures credited to 3BK-14(M) that range from 450mm to 500mm RHA are plausible, but it must be noted that such values may not necessarily even represent the average penetration of the shells. Given that the 115mm BK-4M shell fired from the U-5TS gun of the T-62 has an average penetration of 499mm, a minimum penetration of 418mm and a maximum penetration of 559mm, the performance of BK-14M cannot be lower but should be significantly higher due to its larger larger caliber and its use of a piezoelectric fuzing system instead of a spitback fuze.<br />
<br />
<br />
Data on the fragmentation characteristics of BK-14M when impacting hard targets can be found in the study "<i>Осколочное Действие Кумулятивных И Осколочно-Фугасных Снарядов При Взрыве На Броне Танка</i>" ("<i>Fragmentation of Cumulative and High-explosive Explosive Shells during the Explosion on Tank Armour</i>") by Yu. A. Mikheev. Scans of the entire article as published in the "<i>Вестник Бронетанковой Техники</i>" ("<i>Bulletin of Armour Technology</i>") specialized magazine are available on <a href="https://andrei-bt.livejournal.com/403258.html">Andrei Tarasenko's blog</a>. The table below contains the relevant data:<br />
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<br />
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<a href="https://4.bp.blogspot.com/-e_7yoBmUPx4/W2aq50AbpwI/AAAAAAAAL_c/jbrP3ub4N7oXvob-mgQVDcVHH6pcnCm1wCLcBGAs/s1600/bk-14m%2Btable.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="204" data-original-width="289" height="282" src="https://4.bp.blogspot.com/-e_7yoBmUPx4/W2aq50AbpwI/AAAAAAAAL_c/jbrP3ub4N7oXvob-mgQVDcVHH6pcnCm1wCLcBGAs/s400/bk-14m%2Btable.png" width="400" /></a></div>
<br />
<br />
The detonation of the BK-14M warhead produces an average of 500 fragments in a forward cone of 38-47 degrees. 50% of the fragments are capable of perforating an aluminium sheet with a thickness of 5mm which is above the threshold of lethal injury (a shell fragment capable of piercing a 3mm aluminium sheet has more energy than a 5.56mm bullet), but it is not enough to perforate even the 6.4mm of side armour found on common armoured cars and half-tracks like the M3. 10% of the fragments are capable of perforating an aluminium plate with a thickness of 60mm, which translates to an average of around fifty fragments. The size of the shell fragments was determined by the maximum size of the holes in thin aluminium witness sheets. 4% of holes were recorded with maximum sizes from 50mm to 100 mm, 11% were recorded with sizes of 10mm to 50mm, and the remaining holes had a maximum size of less than 10 mm.<br />
<br />
With that said, it should be noted that the side armour of the aluminium-hull of an M113 tracked APC only has a thickness of 38mm and the frontal armour has the same thickness with a slope of 45 degrees. From this, it is clear that the use of a BK-14 shell on a typical APC or IFV target would not only guarantee the penetration of its armour by shaped charge attack with severe armour overmatch, but also inflict heavy internal damage by the spray of warhead casing fragments. This is aptly demonstrated by the damage inflicted to an M113 by a 105mm HEAT shell in the photo below. The fragmentation pattern of 105mm HEAT shells was similar to 125mm HEAT but the fragments are obviously less energetic and are lower in quantity due to the smaller caliber. A 125mm HEAT shell would inflict much more serious damage to the APC.<br />
<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://1.bp.blogspot.com/-RRpTVMe9m1Y/XAuXlZDKKqI/AAAAAAAAMp0/ykaXuK2PAmkCLaMZFYWQaLosW-9d-8HvwCLcBGAs/s1600/105mm%2BHEAT%2Bon%2BM113.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://1.bp.blogspot.com/-RRpTVMe9m1Y/XAuXlZDKKqI/AAAAAAAAMp0/ykaXuK2PAmkCLaMZFYWQaLosW-9d-8HvwCLcBGAs/s640/105mm%2BHEAT%2Bon%2BM113.jpg" width="640" /></a></div>
<br />
<br />
The fragmentation may also damage or destroy external components on tank-type targets which can cause a mission kill even if the shaped charge warhead fails to fully perforate the armour.<br />
<br />
<br />
<h3>
<span style="font-size: large;">
3VBK-16(M)</span></h3>
<h3>
<span style="font-size: large;">3BK-18(M)</span></h3>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://1.bp.blogspot.com/-XZXMxTpws2U/XYp470iXK6I/AAAAAAAAPOY/N5SWQWgH-IAH8Dv2RfsZiegg2_QUmOsRACLcBGAsYHQ/s1600/3bk-18m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1600" height="318" src="https://1.bp.blogspot.com/-XZXMxTpws2U/XYp470iXK6I/AAAAAAAAPOY/N5SWQWgH-IAH8Dv2RfsZiegg2_QUmOsRACLcBGAsYHQ/s640/3bk-18m.png" width="640" /></a></div>
<br />
<br />
The 3BK-18 was a modification of the 3BK-14 shell with only minor improvements related to the manufacturing process. The only noticeable difference was the redesign of the top part of the projectile to have a detachable standoff probe, as shown in the drawing above. All other parts were functionally identical to the 3BK-14.<br />
<br />
<br />
According to a 1979 Soviet report titled <i>"<a href="http://btvt.info/5library/vbtt_1979_03_probivaemost.htm">Выбор Кумулятивных Снарядов Для Испытания Брони</a></i>" (<i>Selection of Cumulative Shells for the Evaluation of Armour</i>), the average penetration of 3BK-18 in armour plate is 534mm, with a maximum penetration of 621mm and a minimum penetration of 421mm. Unfortunately, the performance of the 3BK-18M warhead is not stated, but based on the improvement gained by the substitution of the steel shaped charge liner for a copper liner, a 10% increase in penetration can expected. As such, 3BK-18M should penetrate between 580mm to 590mm of RHA steel.<br />
<br />
The armour piercing and fragmentation effect of the 3BK-18(M) shell is the same as 3BK-14(M).<br />
<br />
<br />
Muzzle velocity: 905 m/s<br />
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Projectile Weight: 19 kg<br />
Total Projectile Length: 678mm<br />
Warhead Casing Length: 296mm<br />
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Explosive Charge: OKFOL<br />
Explosive Charge Weight: 1.76 kg<br />
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<h3>
<b><span style="font-size: large;">APFSDS</span></b></h3><br />
Despite pioneering APFSDS shells with the introduction of the 2A20 115mm smoothbore gun, the Soviet Union never had the technology to mass produce true long rod tungsten or depleted uranium projectiles until the mid-80's, whereas the Americans had already fielded the M774 DU APFSDS round since the mid to late 70's. Even then, the long rod APFSDS rounds fielded by the Red Army had sheathed penetrators when American APFSDS rounds were already monobloc. Their best APFSDS rounds were composites composed of steel projectiles with small embedded cores. This type of composite shell was incredibly economical due to the very small quantity of tungsten used in each projectile, but it was limited in scope and growth potential. The last and most optimal composite APFSDS shell created on the basis of the subcaliber tungsten carbide core philosophy entered service in 1983. Long rod shells made with tungsten and depleted uranium alloys entered service just two years later after protracted development and troubleshooting as a direct response to intelligence on new Western multi-layered composite armour.<br />
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During the past few decades, modern Russia has fielded several long rod APFSDS rounds while retaining a large stock of older composite APFSDS ammunition. However, there was a serious deficit in truly modern examples of APFSDS ammunition due to a variety of factors. The requirement for the T-72B3 obr. 2016 to be able to use Svinets-1 and Svinets-2 ammunition was a belated attempt to remedy this problem.<br />
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In terms of armour penetration capability, the D-81T had great promise but the reliance on steel projectiles well into the 80's betrayed the fact that the Soviet munitions industry was not yet fully capable of producing heavy alloy long rod penetrators. Before 1985, all 125mm APFSDS ammunition followed the basic principle as the 3BM-3 introduced in 1961 in one form or another. The use of steel caps on steel long rod penetrators meant that the performance of these less-than-stellar APFSDS shells at high obliquities was somewhat lower than at lower obliquities, whereas it was the exact opposite with heavy alloy long rod rounds like the M111 "Hetz". Incremental improvements reduced the severity of the issue over time, but the problem was only truly solved when long rod tungsten alloy or depleted uranium shells were introduced in significant quantities in the late 80's. Producing high-quality weapons-grade tungsten carbide and other tungsten alloys in slug form was difficult and expensive, and manufacturing heavy metal alloy rods of sufficient strength for anti-armour purposes was not a trivial task. The equipment simply did not exist in the USSR.<br />
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The main defeat mechanism of APFSDS rounds against armoured targets is by damaging internal equipment and killing crew members with shards of broken armour (spall) and fragmentation from the body of the APFSDS projectile itself, but a secondary mechanism is setting internal equipment alight. The huge kinetic energy and extreme forces imparted during armour defeat results in some of that kinetic energy being converted to heat energy, which results in a flash of heat and a shower of high velocity sparks from particles of both armour material as well as penetrator material. This becomes an ignition source for flammable fuel and hydraulic fluid as well as the furniture in the tank.<br />
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Soviet steel and composite APFSDS rounds are highly lethal as they produce a large spray of fragmentation when armour perforation is successfully achieved. <a href="http://tankarchives.blogspot.my/2015/03/beyond-armour-effects.html">This article</a> translated by Peter Samsonov details the post-penetration effects of 125mm APFSDS ammunition. The original pages of the Russian document were <a href="http://andrei-bt.livejournal.com/339370.html">first shared on Andrei Tarasenko's blog</a>. The document featured in the article pertains to a lethality analysis done on 3BM-9, 3BM-15, 3BM-22 and 3BM-26. These four rounds will all be examined more closely later on, but for now, it is only necessary to summarize that the 3BM-9 has a steel long rod penetrator whereas the 3BM-15 and 3BM-22 are composite shells with a a tungsten carbide core at the front of the projectile, and 3BM-26 has a steel penetrator with a tungsten carbide core in the tail of the projectile tail. All of the shots were for a 60 degree obliquity impact, and the velocity of all of the shells corresponds to their velocities at 2 km.<br />
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According to the article, the vast majority of fragments expelled behind the armour plate are smaller particles that are capable of penetrating 3-6mm of aluminium sheet at a distance of 0.5 to 1 meters. Although they do not seem powerful, these particles are far from harmless. Particles with the ability to penetrate more than 3mm of aluminium include particles with a mass of 2 to 50 grams and a velocity of 300 to 1,700 m/s. To gain an appreciation of the threat posed by such particles, note that a typical .22LR bullet weighs 2.33 grams and travels at 390 m/s and a 5.56mm M193 Ball bullet weighs 3.56 grams and travels at 990 m/s. As such, each particle that was found to be able to penetrate 3-6mm of aluminium would also be capable of causing lethal wounds.<br />
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<h3>
<span style="font-size: large;">PRECISION, ACCURACY</span></h3>
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Besides the enhanced armour penetration capability compared to contemporary foreign APFSDS rounds, 125mm APFSDS was highly competitive in terms of precision. According to NVA firing tables for <a href="http://www.kotsch88.de/tafeln/st_125mm-ke-2A46M.htm">3BM15 shared by Stefan Kotsch</a>, the probable dispersion (probable error) of the shell when fired at 3,000 meters is 0.7 m in both the vertical and horizontal planes. At the same range, the probable dispersion of <a href="http://www.kotsch88.de/tafeln/st_120mm-ke.htm">the 120mm DM23 round (Pat 87)</a> is 0.6 meters and 0.5 meters in the vertical and horizontal planes respectively.</div><div><br /></div><div>Compared to APDS rounds, the precision of 125mm APFSDS was considerably higher. Information shared by the online user "Fu_Manchu" states that the spread of L15 APDS rounds at 3,000 meters is 1.925 m in the vertical plane and 1.375 m in the horizontal plane. The dispersion of 105mm APDS was similar. It is stated in the report "<i><a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a031639.pdf">Performance of Chrome-Plated 105mm M68 Gun Tubes with Discarding Sabot Ammunition</a></i>" that the data accumulated from 563 acceptance tests of M392A2 rounds showed horizontal and vertical standard deviation dispersions of 0.30 and 0.33 mils respectively, for a CEP radius of 0.37 mils. </div><div><br /></div><div><br /></div><div><br /></div><div>In any case, compared to Western 105mm and 120mm APFSDS models, Soviet projectiles suffer from very high drag - more than twice as high - but compensates for this with exceptionally high muzzle velocities. In general, a higher velocity projectile will have a higher probability of hit against any given target compared to a lower velocity projectile of identical characteristics. This is because the higher velocity projectile will have a shorter time of flight and will therefore be less affected by random factors such as meteorological variables.<br />
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The relationship between hit probability and projectile velocity is explored in "<i>Hit Probability of a High Velocity Tank Round</i>" by Fred Bunn. Computer simulations were done using data from the Armament Research Laboratory (ARL) and Army Systems Analysis Agency. It was found that for a "modern fire control system", there is a negligible increase in hit probability when the muzzle velocity of four different types of tank shells is increased from 1,600 m/s to 3,000 m/s when firing a static target from a stationary tank from distances of 1 to 4 kilometers. Four different projectile types were simulated: a conventional finned APFSDS round design, two flared cone-stabilized APFSDS round designs, and a HEAT round design. It was concluded that doubling the speed of an APFSDS round does not improve hit probability against a stationary target by any substantial amount.<br />
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Increasing the velocity of the projectiles had a much larger impact on the simulated probability of hit for moving targets. The three charts below show the different types of moving tank targets used in the simulations: the STAGS target, ATMT target and TEMAWS target. The STAGS target has a regular zigzagging movement pattern, the ATMT target has a randomized lateral movement pattern, and the TEMAWS target has an irregular zigzagging movement pattern. The TEMAWS target was considered the easiest and the STAGS target was considered the hardest.<br />
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The simulated probability of hit for all three targets at different projectile muzzle velocities is shown in the three graphs below (click to enlarge). It was found that doubling the speed of an APFSDS round increased the hit probability against a moving target by an average of 30% to 35% at a distance of 1 km and by 55% to 60% at a distance of 2 km.<br />
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<a href="https://1.bp.blogspot.com/-fljQC6niHnQ/W69gOTfo_nI/AAAAAAAAMWQ/juu97HDwT4U_PJ6bgHIzqxZMlm77PR8LACEwYBhgL/s1600/stags%2Btarget.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="740" data-original-width="1081" height="136" src="https://1.bp.blogspot.com/-fljQC6niHnQ/W69gOTfo_nI/AAAAAAAAMWQ/juu97HDwT4U_PJ6bgHIzqxZMlm77PR8LACEwYBhgL/s200/stags%2Btarget.png" width="200" /></a><a href="https://4.bp.blogspot.com/-RouFfRlV764/W69gOWeZd4I/AAAAAAAAMWY/HCcWtHWryBsOFsaSl0baGiqj98j28jV9ACEwYBhgL/s1600/atmt%2Btarget.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="748" data-original-width="1088" height="137" src="https://4.bp.blogspot.com/-RouFfRlV764/W69gOWeZd4I/AAAAAAAAMWY/HCcWtHWryBsOFsaSl0baGiqj98j28jV9ACEwYBhgL/s200/atmt%2Btarget.png" width="200" /></a><a href="https://3.bp.blogspot.com/-LVTNsJ9rfPU/W69gO9QxDiI/AAAAAAAAMWc/qGvXkxmD2d0Z1kY-a9w3_bQYLDiXFQcYQCEwYBhgL/s1600/temaws%2Btarget.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="716" data-original-width="1067" height="133" src="https://3.bp.blogspot.com/-LVTNsJ9rfPU/W69gO9QxDiI/AAAAAAAAMWc/qGvXkxmD2d0Z1kY-a9w3_bQYLDiXFQcYQCEwYBhgL/s200/temaws%2Btarget.png" width="200" /></a></div>
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From the results of the simulations, it can be seen that increasing the velocity of a finned APFSDS projectile from 1,600 m/s to 3,000 m/s will increase the probability of hit at all distances and that any increase in velocity will translate into an improvement in hit probability. The difference between a 1,400 m/s APFSDS round and a 1,800 m/s APFSDS round is not drastic, but still contributes toward a higher overall accuracy if all other factors are equal.<br />
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The selection of APFSDS ammunition available to the T-72 gave it the upper hand in any engagement with any of NATO's heaviest tanks until the new generation rolled out in the early 80's. Before the introduction of the Leopard 2 and M1 Abrams, the M60A1, M60A2 and Chieftain were the most heavily armoured tank designs used by NATO, but since it is well known that these tanks lack sufficient protection to resist 125mm APFSDS.<br />
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<h3>
<span style="font-size: large;">3VBM3</span></h3>
<h3>
<span style="font-size: large;">3BM10 (3BM9 Projectile)</span></h3>
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The 3VBM3 round was adopted in 1967 together with the 2A26 gun for the T-64A, and was considered a standard APFSDS round that formed the baseline for the ammunition designs that followed. 3BM9 is quite remarkable for being the first service munition to be fired at a hypersonic speed (Mach 5+). It was a cheaper alternative to the 3BM12 projectile, which featured a tungsten carbide core. Ballistically, the two projectiles are virtually identical. </div><div><br /></div><div>The 3BM9 projectile features a steel penetrator and a ballistic cap but does not have a soft steel armour piercing cap. The penetrator is made entirely of 60KhNM tool steel with high strength and toughness. The hardness at the tip is specified for a lower boundary of 560 BHN and an upper boundary of 653 BHN. At the tail, which only interacts with an armour plate at the very end of the penetration process, the rated hardness is 340-414 BHN. </div><div><br /></div><div>The high muzzle velocity of 3BM9 when firing at standard conditions is 1,800 m/s, and due to this remarkable speed, it had a point blank range of 2,120 meters when firing at a target with a height of 2 meters. When firing at a target with a height of 2.7 meters, the point blank range was 2,450 meters. When attacking a hull-down tank target, the target height can be considered to be 0.7-0.8 meters tall. The point blank range of 3BM9 against such a target is 1,300-1,400 meters, which is excellent.<br />
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<br />Though it was not more technologically advanced than contemporary domestic 100mm and 115mm APFSDS ammunition, 3BM9 was more than enough to deal with any NATO tank of the time, including the most heavily armoured such as the M60A1 and the Chieftain. According to a Soviet analysis of an Iranian Chieftain captured by the Iraqi army during the early part of the Iran-Iraq war, available here on <a href="http://btvt.info/3attackdefensemobility/432armor_eng.htm">Andrei Tarasenko's btvt.info website</a>, the Chieftain Mk.5 was considered to have totally insufficient protection even at its strongest points. The frontal part of the entire turret, hull upper front plate and lower front plate could all be defeated at 3 km or more. This essentially means that the T-72 Ural could defeat one of NATO's toughest tanks at any reasonable combat distance with zero expenditure of valuable tungsten - an extremely profitable situation for the Red Army in the event of a large scale war.<br /><br /></div><div><br /></div><div>3BM9 is supported by a three-section steel ring-type sabot with a copper driving band, identical in design to the sabots used for the 100mm T-12 anti-tank gun and the 115mm U-5TS tank gun, differing only in the presence of protruding knurls around its circumference. These knurls were needed to ensure the smooth loading of the projectile into the gun by a mechanical powered rammer, which can only push the cartridge along the surface of the chamber where the possibility of the projectile getting stuck against the shoulder of the chamber neck may arise.</div><div><br /></div><div>The sabot has six grooves to interface with the projectile, the same as on 115mm 3BM6. During its travel down the barrel, the projectile assembly gains a slow equilibrium spin via six angled vent holes drilled into the sabot, and the spin of the sabot is imparted to the projectile via friction. There are two 4.2mm holes per petal, angled 50 degrees tangentially along the projectile axis. They are filled with epoxy to seal the incremental propellant charge. Once fired, the expanding propellant gasses blow out the epoxy plugs. </div><div><br /></div><div>The centrifugal force from the spin of the sabot exerts a radial pressure on the copper driving band, which could help expand it to seal the barrel bore in case the bore was heavily eroded. It also served to break the eroded copper driving band once the projectile assembly leaves the muzzle, acting in conjunction with the force from the airflow acting on the scoop-shaped sabot petals to ensure consistent separation from the projectile. This solution provided </div><div><br /></div><div>
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<a href="https://2.bp.blogspot.com/-2wjNv41LOQc/WDu6IcFBu4I/AAAAAAAAHq4/tZ_VKzplxTUOb22SKw7VYPt012woVjf8wCLcB/s1600/steel%2Bring%2Bsabot.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="346" src="https://2.bp.blogspot.com/-2wjNv41LOQc/WDu6IcFBu4I/AAAAAAAAHq4/tZ_VKzplxTUOb22SKw7VYPt012woVjf8wCLcB/s400/steel%2Bring%2Bsabot.jpg" width="400" /></a></div>
<div><br /></div><div><br /></div>According to a firing table provided by Stefan Kotsch, 3BM9 suffers an average drop in velocity of 136 m/s per kilometer. This is slightly greater than the velocity drop suffered from 100mm and 115mm APFSDS, presumably as a result of the larger stabilizer fins.</div><div>
<br />The 3BM9 round erodes a barrel bore at 4 times the rate of standard full caliber shells (HE-Frag, HEAT). It erodes at a rate of 0.0132mm. <br />
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Muzzle velocity: 1,800 m/s<br />
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Mass of Projectile: 3.6 kg<br />
Mass of Sabot: 2.02 kg<br />
Total Mass: 5.67 kg<br />
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Total length of projectile: 518mm<br />
Length of steel penetrator only: 410mm<br />
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Projectile maximum diameter: 44mm<br />
Projectile minimum diameter: 30mm<br />
Average Diameter of Projectile: 36mm<br /><br />
<blockquote class="tr_bq">Penetration at 2.0 km:<br /><div>245mm at 0° </div><div>185mm at 45° </div><div>140mm/150mm at 60° </div><br /></blockquote>
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<span class="st">Penetration at 1.0 km:</span><span class="st"><br /></span>
300mm at 0°<br />
<span class="st">160mm at 60</span>° </blockquote>
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<span class="st">(According to a <a href="https://andrei-bt.livejournal.com/402448.html">Soviet GRAU document</a> and a <a href="http://i.imgur.com/GDzu52Z.png">comparison chart</a>)</span> </blockquote>
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<span class="st"><br /></span>Penetration at 2.0 km:<br />
290mm at 0<span class="st">°</span>140mm at 60<span class="st">°</span></blockquote>
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<h3>
<span style="font-size: large;">3VBM7</span></h3>
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<span style="font-size: large;"><b>3BM16 (3BM15 Projectile)</b></span></div>
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<div><br /></div><div><br /></div><div>At the time it entered service in 1972 (just one year before the T-72 Ural), 3BM15 was the most advanced APFSDS round available to Soviet Army tanks. This round developed a higher peak pressure compared to 3BM9 due to its greater weight, and because of this, it eroded a barrel bore at 5 times the rate of standard full caliber shells (HE-Frag, HEAT) and not 4 times like 3BM9. It erodes at a rate of 0.0165mm.</div><div><br /></div>Due to the use of an oversized propellant charge, the full length of a 125mm 3BM15 APFSDS cartridge when both halves are assembled is only 995mm compared to 1,018mm for an L15A5 APDS cartridge, despite the vastly greater length of the APFSDS projectile.<br />
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The 3BM15 projectile contains a steel penetrator made from 35KhZNM structural steel with a small VN-8 tungsten carbide core. The VN-8 core is a cemented tungsten carbide with an 8% nickel binder matrix. It is externally identical to the 3BM-9 projectile, but structurally, it bears a non-trivial similarity with Soviet APDS ammunition that entered service in the late 60's and even has connections to vintage APCR designs. Although decently hefty
and very speedy, the shell primarily relies on a small tungsten carbide subcaliber core for a large part of the penetration period. A ballistic windshield was crimped onto the soft 30KhGSA steel armour piercing cap. The purpose of the shock absorber cap was to improve the performance of the shell on sloped armour and to reduce the shock of the impact experienced by the brittle tungsten carbide core. The impact of the steel armour penetrating cap creates the distinct large entry cavities that were typical of Soviet tungsten-cored steel rounds. Tag number 5 in the photo below marks the impact of a 3BM-15 shell into the left turret cheek of a T-72M1 in Finland, Parola. Photo by Andrej Smirnov.<br />
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At this part of the T-72A turret, the total LOS thickness amounts to 560mm and of that thickness, there is 441mm of steel and 119mm of the "Kvartz" ceramic filling, all at an obliquity of 0 degrees. Unsurprisingly, 3BM-15 failed to defeat the armour.<br />
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The photo on the left shows the entry and exit of a 3BM-15 projectile into a 200mm steel armour plate at an impact angle of 0 degrees and an impact velocity of 1,280 m/s, corresponding to a distance of 4,000 meters. The photo on the right below shows the penetrated cavity inside a 200mm plate from a 300mm combined armour block (100mm + 200mm) after the penetration of a 3BM-15 round at an impact angle of 0 degrees at the impact velocity of 1,198 m/s, corresponding to a distance of 4,600 m. The velocities and corresponding distances were traced using a firing table for 3BM-15 made available to the public <a href="http://www.kotsch88.de/tafeln/st_125mm-ke-2A46M.htm">courtesy of Stefan Kotsch</a>.<br />
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The nature of the composite construction of 3BM-15 makes it immensely powerful against homogeneous steel targets, though only in the case of perpendicular or near-perpendicular impacts. The two graphs below show the penetration depth for three types of Soviet armour piercing ammunition on a 0 degree target at a fixed impact velocity of 1,500 m/s. The smooth line represents 122mm 3BM11 and 100mm 3BM8 (the two projectiles share the same core. The dashed and dotted line represents 3BM6 steel penetrator. The dashed line represents 3BM-15 steel and tungsten carbide core penetrator. The graph on the top (a) shows the penetration in physical plate thickness. The graph on the bottom (b) shows the penetration in line-of-sight (LOS) plate thickness after dividing by the cosine of the impact angle.<br />
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The impact velocity of 1,500 m/s corresponds to a distance of 2,100 meters for the 3BM-15, and as you can see, the penetration at 0 degrees is around 460-470mm RHA. The penetration falls dramatically at 15 degrees and falls to around 280mm between the angles of 30 degrees and 50 degrees, but rises to 300mm at the impact angle of 60 degrees. The penetration unexpectedly rises at an impact angle of more than 60 degrees and increases to a maximum around 360mm at an impact angle of 80 degrees before dropping off sharply, presumably due to projectile ricochet. The drop in penetration at the 15 degree critical angle was investigated and attributed to the location of the tungsten carbide core.<br />
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"<i>При взаимодействии с наборной (без зазора) или монолитной преградой лидирующий сердечник, сохраняющий благодаря всестороннему обжатию относительную целостность, снижает интенсивность расходования наседающей массы стального корпуса, экономить запас кинетической энергии снаряда и повышает его бронепробивное лействи в целом. Разрезы по поражениями в толстых наборных преградах показывают, что стальной корпус снаряда, разрушаясь путем трещинообразования, по расходуется мало; расходование его массы происходит экономно преимущественно за счет "стачывания" по боковой поверхности. По этой причине снаряды типа 3БМ-15 в диапазоне углов 0 ... 15 град, при которых сердечник функционирует нормально, обладают значительно более высоким бронебойным действием по монолитной броне, чем цельнокорпусные снаряды типа 3БМ-6.</i>"<br />
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Translated:<br />
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"<i>When interacting with a stack of plates (without gaps) or a monolithic target, the leading core, which preserves the relative integrity due to a uniform compression, reduces the intensity of the consumption of the mass of the steel casing, retains the kinetic energy of the projectile, and raises its armor-piercing capability as a whole. The cutaways of penetration channels in thick targets show that the steel shell of the projectile, being destroyed by fracturing, is consumed little; the expenditure of its mass occurs economically mainly due to "grinding" along the lateral surface. For this reason, projectiles of type 3BM-15 in the range of angles of 0-15 degrees at which the core functions normally have a much higher armor-piercing action on monolithic armor than solid-shell projectiles of the 3BM-6 type.</i>"<br />
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Being installed at the front of the projectile, the tungsten carbide core strikes the target plate first and creates an entry channel. For low obliquity impacts, the steel penetrator behind the core is able to follow the core into this entry channel and only the outer circumference of the steel penetrator rod is ground off due to the larger diameter of the steel penetrator compared to the diameter of the core. Thus, very little steel is eroded during the penetration of very thick blocks of armour. The high kinetic energy of the combined penetrator assembly (core + steel rod) is maintained due to the low erosion of the tungsten carbide slug and the high kinetic energy of the assembly, primarily from the mass of the steel penetrator. To put it another way, the projectile behaves like an arrow: the metal tip penetrates the flesh while the wooden shaft simply follows. The red zones in the drawing below shows the parts of the outer edges of the steel penetrator that are "ground off" during penetration:<br />
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The penetration channel created in an armour plate has a certain shape that is characteristic of the torpedo form of the 3BM-15 projectile. Referring to the photo below, it can be seen that the penetration channel at the surface of the plate is largest. This is due to the large 44mm diameter of the steel penetrator near the tip of the round. The taper of the projectile means that the diameter of the steel penetrator decreases throughout the penetration process, and as a result, the diameter of the penetration channel decreases accordingly.<br />
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This use of a steel rod behind a tungsten carbide core allows huge thicknesses of steel to be penetrated in an extremely efficient manner with minimal expenditure of valuable tungsten, but only if the alignment of the projectile can be preserved. If the tungsten carbide core is misaligned with the steel rod behind it during impact or during the initial stages of penetration, the task of defeating the armour plate falls entirely on the steel rod.<br />
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However, 3BM-15 is not the first example of this type of shell. There exists a variant of the BR-354P APCR round in the 76x385mm caliber that works on the same principle, shown below (right). In this variant, the tungsten carbide core is held in a soft metal "arrowhead" projectile with a steel plug placed behind it. This enabled deeper penetration into armour as well as greater beyond-armour damage without a large increase in the size of the tungsten carbide core of the basic BR-354P shell (left), which had a core of a similar size but no steel plug. This was an economical alternative to having a larger tungsten carbide core. Indeed, early Soviet APFSDS rounds like 3BM-15 share a surprising number of similarities with vintage APCR. <a href="https://thesovietarmourblog.blogspot.com/2018/02/pt-76.html">More information on BR-354P is available in Tankograd's PT-76 article.</a><br />
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At an angle of between 0 to 15 degrees, the projectile behaves in this manner and is able to penetrate a huge thickness of steel. At higher angles, the tungsten carbide core separates from the steel penetrator due to misalignment and the penetration of the armour plate is done by the steel rod alone. The graphical curves for penetration thicknesses achieved by 3BM-15 and 3BM-6 intercept at an angle of around 30 degrees. Due to this phenomenon, 3BM-15 can penetrate very high thicknesses of steel at flat angles but does not necessarily perform better on sloped plate compared to a steel long rod penetrator. At armour slopes of beyond 30 degrees, the 3BM-6 steel penetrator is able to perform better than 3BM-15 at the same impact velocity. The only advantage of 3BM-15 over 3BM-6 in this respect is that its muzzle velocity is much higher, so that the impact velocity of 3BM-15 will always be higher than 3BM-6 for any given distance.<br />
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The mechanisms at play on monolithic plates are complicated on their own, but the behaviour of 3BM-15 on multi-layered armour is even more complicated:<br />
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A stacked 300mm plate consisting of a 100mm plate and 200mm plate without an air gap in between was found to be 4.6% more resistant than a monolithic plate of the same thickness at an impact angle of 0 degrees. The introduction of an air gap between two plates proved to be an effective method of severely degrading the penetration of 3BM-15, but only for perpendicular impacts. In the table below, the first column from the left shows the impact angle and the next three columns from the left list the spaced armour configurations: b<span style="font-size: xx-small;">1</span> and b<span style="font-size: xx-small;">2</span> denote the thickness of the first and second plates in millimeters, and L denotes the size of the air gap in millimeters. The fourth column from the right lists the velocity limit of 3BM-15 for the spaced described armour configuration, and the third column from the right lists the velocity limit for a monolithic plate of the same thickness in steel (b1 + b2). The difference in the velocity limit is listed in the second column from the right. The first column on the right shows the difference in the velocity limits between the spaced armour configuration and a monolithic plate in percentage points, and also represents the improvement in mass efficiency.<br />
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The best performing spaced armour configuration was the 100-1000-200 array where a 48.1% improvement in mass efficiency was recorded. The velocity limit of 1,740 m/s corresponds to a distance of 300 meters. Of course, the large 1-meter air gap between the two spaced plates is rather large and impractical for tank armour purposes. The effectiveness of the spaced armour is dependent on the size of the air gap to a large extent as demonstrated by the increasing effectiveness of a spaced armour configuration with a 50mm front plate and a 200mm back plate as the size of the air gap is increased from 70mm to 300mm to to 1,000mm, but the optimal air gap size was 480mm. The improvement in mass efficiency was 46.4% for the optimal configuration - slightly higher than the array with the 1,000mm air gap. Of course, there are no examples of tank armour with completely vertical facings, so the results from the 15 degree and 30 degree impacts are much more interesting. The 30 degree impact cases are particularly interesting because the turret cheeks of the Abrams tank are known to be sloped at 21 and 30 degrees for each side, and the arrangement of plates likely follows the hull and mantlet armour modules where a pack of NERA panels is located behind a thin front plate, and an air gap is placed between the NERA pack and the thick back plate. The closest equivalent for this is the configuration described in the first row for 30 degree targets: a 50mm front plate and a 150mm back plate with a 330mm air gap. For the turret of an M1 Abrams, the air gap should be larger and some small effect from the NERA pack is expected, but overall, the mass improvement in efficiency from such a spaced armour configuration appears to be very small at only 2.4%. The distance corresponding to the velocity limit for the spaced array is 3,100 meters.<br />
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The table below shows the data for 3BM-15 on spaced armour at 60 to 65 degrees obliquity. The two new columns on the right lists the penetration depth into the second spaced plates (b2) using 4-6 test shots for the data, and the average penetration depth. The penetration depth is usually larger than the LOS thickness of the second spaced plates because the penetrator is heavily deflected as it travels through the air gap, so a relatively shallow penetration channel is gouged along the surface of the plate by the penetrator. Nevertheless, at the higher angles of 60 degrees and 65 degrees, spaced armour is not significantly more effective than a monolithic armour plate unless air gaps of more than 1 meter are used. For instance, the best result for spaced armour at 60 degrees was achieved with a 1,700mm air gap. Taking the 60 degree angle into consideration, the total size of the air gap is 3.4 meters. The best result for spaced armour at 65 degrees follows the same pattern. Even though 3BM-15 failed to fully defeat most of the targets (rows marked with "-" indicate full armour perforation), the impact velocities were extremely low, corresponding to a distance of around 6 km.<br />
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The 100-1430-50 spaced armour configuration at 60 degrees is very interesting because it broadly represents the toughest part of the side armour of the Leopard 2A0-A4, albeit with a much bigger air gap. According to the table, 3BM-15 is capable of defeating this target at an impact velocity of 1,590 m/s, corresponding to a distance of 1,450 m. The actual velocity limit for a more correct representation of the side armour should be lower than the listed value as the distance between the heavy 110mm ballistic plates and the 50mm side armour of the Leopard 2 should around 650mm, based on the <a href="http://tankarchives.blogspot.com/2017/05/leopard-tracks.html">known width of the D570F tracks</a> of the Leopard 2 (635mm). The difference between a ~650mm air gap and a 1,430mm air gap is not negligible, to put it mildly, so in other words, the 3BM-15 should be capable of defeating the most well-protected part of the side hull armour of the Leopard 2 at typical combat distances from a side angle of 30 degrees.<br />
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The photo below shows the defeat of a 100mm + 200mm RHA plate by 122mm 3BM11 tungsten-cored APDS at a 0 degree impact angle. The perforated plate on the left was achieved at an impact velocity of 1,272 m/s and the partial perforation on the right (you can see the remnants of the penetrator) was done at an impact velocity of 1,246 m/s (normal muzzle velocity from M-62 is 1,575 m/s).<br />
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From comparing the penetration paths of 3BM-15 and 3BM11, it can be seen that both projectiles create a relatively slender penetration channel through the plate but leave a large crater on the surface of the plate. However, the 3BM-15 projectile leaves an extremely deep crater. The 3BM11 projectile has a soft steel armour piercing cap of around 60mm in length in front of the heavy 50x120mm tungsten carbide core. From what we can see in the cross section of the plates, this soft steel cap is responsible for producing the shallow crater, but for the 3BM-15, the soft steel armour piercing cap over its 20mm tungsten carbide core is only 20mm in length so the source of the deep crater must be the steel penetrator behind the core.<br />
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3BM-15 was designed with adherence to the same design principle as the older 115mm 3BM-3 round, and 3BM-3 was intended to have armour penetration capabilities similar to or exceeding that of a contemporary APDS shell without incorporating as much tungsten carbide in its construction. 3BM-3 was highly successful in this regard, as it managed to achieve more penetration than BM-8 APDS for the 100mm D-10T using only a tenth of the amount of tungsten carbide in its core.<br />
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The fact that 3BM-15 is able to penetrate an astonishing thickness of ~470mm at 2,100 meters with a small 0.27 kg tungsten carbide slug when the large 2.78 kg core of the 3BM11 manages 400mm at the same velocity despite having more than ten times the mass is extremely interesting, to put it mildly. The difference in muzzle velocity between the two rounds should not be neglected, of course, and when we consider that the 3BM11 had a muzzle velocity of 1,575 m/s when fired out of an M-62 cannon whereas 3BM-15 had a muzzle velocity of 1,785 m/s, it is clear that the 3BM-15 APFSDS design was simply superior to an equivalent APDS round on low obliquity targets.<br />
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3BM-15 uses the same steel "ring" type sabot as the 3BM-9. The photo below is from a Rheinmetall brochure on PELE ammunition, demonstrating a modified 3BM-15 PELE round in flight and the airflow around the components of the round. The sabot was unmodified.<br />
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<br />In standard conditions where the propellant charge temperature is 15°C, the muzzle velocity of 3BM15 is 1,785 m/s. According to Yugoslavian data, the M88 (a copy of 3BM15) reaches a muzzle velocity of 1,800 m/s at a maximum operating pressure of 440 MPa. This is presumably obtained when the propellant charge temperature is 21°C.</div><div><br />
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Mass of Incremental Charge: 4.86 kg<br />
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Muzzle velocity: 1,785 m/s<br />
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Steel body maximum diameter: 44mm<br />
Steel body minimum diameter: 30mm<br />
Armour piercing cap diameter: 20mm<br />
Core diameter: 20mm<br />
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Total length of projectile: 548mm<br />
Length of steel penetrator only: 435mm<br />
Length of armour piercing cap: 20mm<br />
Length of core: 71mm<br />
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Mass of Steel body: 3.63 kg<br />
Mass of Core: 0.270 kg<br />
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Total Mass of Projectile: 3.83 kg<br />
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<blockquote class="tr_bq">
<span class="st">Penetration at 2.0 km:</span><br />
400mm at 0°<br />
200mm at 45°<br />
150mm at 60°</blockquote>
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These figures come from a <a href="https://andrei-bt.livejournal.com/402448.html">Soviet GRAU document</a> and are corroborated by the penetration data presented in "<i>Particular Questions of Terminal Ballistics</i>" 2006 (<i>Частные Вопросы Конечной Баллистики</i>) published by Bauman Moscow State Technical University on behalf of NII Stali, except for the penetration at 0 degrees which is much less than the 470mm obtained in the testing.</blockquote>
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Penetration at 2.0 km<br />
400mm at 0°<br />
180mm at 60°</blockquote>
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These figures come from page 587 of the "<i>Textbook of Means of Defeat and Ammunition</i>" 2008 (<i>Учебник Средства Поражения И Боеприпасы</i>) published by Bauman Moscow State Technical University.</blockquote>
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<span class="st">Penetration at 1.0 km</span><span class="st"><br /></span><span class="st">425mm at 0° </span></blockquote>
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<span class="st">This figure comes from "<i>Kampfpanzer: Die Entwicklungen der Nachkriegszeit</i>" by Rolf Hilmes.</span> </blockquote>
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Penetration at 2.0 km<br />
200mm at 38°<br />
150mm at 60°<br />
120mm at 67° </blockquote>
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These figures come from <a href="https://i.imgur.com/7v9h47C.jpg">a marketing brochure for the M88 round</a>, a Serbian (Yugoslavian) copy of 3BM-15. It is interesting to note that these figures align very closely with the experimental data presented in this article.</blockquote>
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<span class="st">It can be seen that if a source provides additional penetration figures for 3BM-15 at armour obliquity angles besides 0 degrees and 60 degrees, as shown in the GRAU document and the marketing brochure for the M88 round, then the figures also show that the behaviour of 3BM-15 is similar to a long rod penetrator with a characteristic increase in the LOS thickness of defeated armour plate if the obliquity increases beyond the critical angle of 15 degrees. For M88 the increase in LOS thickness is quite apparent: </span><br />
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<blockquote class="tr_bq">
Penetration at 2.0 km<br />
200mm at 38° = LOS thickness of 254mm<br />
150mm at 60° = LOS thickness of 300mm<br />
120mm at 67° = LOS thickness of 307mm</blockquote>
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It also appears that at angles larger than 60 degrees, there are diminishing returns in the LOS thickness of steel defeated by M88. This may be a limitation of a steel long rod penetrator that is not shared by tungsten alloy or depleted uranium alloy penetrators with higher strength characteristics. These figures are in agreement with the GRAU penetration figures, and the same increase in the LOS thickness of defeated armour plate is shown:<br />
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<blockquote class="tr_bq">
<span class="st">Penetration at 2.0 km:</span>400mm at 0° = LOS thickness of 400mm<br />
200mm at 45° = LOS thickness of 283mm<br />
150mm at 60° = LOS thickness of 300mm</blockquote>
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In other words, the penetration of 3BM-15 without its core can be calculated with a reasonable degree of accuracy using perforation equations designed for long rod penetrators such as the Lanz-Odermatt equation.<br />
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The steel "wedge" in front of the tungsten carbide slug is a soft steel armour piercing cap to protect it from shattering at the moment of impact with a steel target. Compared to the tungsten carbide core of 3BM-8 (far left), the core for 3BM-15 (far right) is incredibly tiny, and yet 3BM-15 penetrates far more armour.</div>
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(Credit for photos to PzGr40 from wk2ammo.com)</div>
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(Sourced from unisgroup.ba, wk2ammo.com)<br />
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A T-72 issued with 3BM-15 rounds could fire freely at any NATO tank during the 1970's and expect to defeat its armour, but it was particularly lethal to tanks like the AMX-30 and Leopard 1 which had particularly light armour that would not be enough to stop the round, yet offer too much resistance to prevent the steel projectile from fragmenting after perforating the armour plate. The only caveat is that the 3BM-9 round would perform even better against such armour configurations and it could do so at a lower cost. 3BM-9 would also perform better on high obliquity targets so it would be more effective against tanks with heavy sloped armour plating like the Chieftain and M60A1, essentially meaning that the high-performance 3BM-15 lacked a real niche during the 70's.<br />
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3BM-15 did not become more useful when the Leopard 2, M1 Abrams and Challenger 1 became the new standard NATO tanks in the early 1980's because its particular design was not conducive to defeating multilayered spaced NERA armour of that type. In fact, after the reunification of Germany, tests were conducted using the stocks of 3BM-15 rounds that accompanied the East German T-72M and T-72M1 tanks. It was found that the front armour of the Leopard 2A4 provided full protection against 3BM-15.<br />
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<h3>
<span style="font-size: large;"><b>3VBM-8</b></span></h3>
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<span style="font-size: large;"><b>3BM-18 (3BM-17 Projectile)</b></span></div>
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<a href="http://3.bp.blogspot.com/-AVsCXtHcr60/VToI_uM_jrI/AAAAAAAACEI/rdWrprso3sE/s1600/mod-34l.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://3.bp.blogspot.com/-AVsCXtHcr60/VToI_uM_jrI/AAAAAAAACEI/rdWrprso3sE/s1600/mod-34l.jpg" width="68" /></a></div>
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This 3BM-17 round is essentially identical to the 3BM-15 in appearance and in ballistics, but it lacked a tungsten carbide core and had a larger and much thicker armour piercing cap, making it a direct equivalent to earlier 115mm APFSDS rounds like the 3BM-4 and 3BM-6. The steel penetrator is made from 35KhZNM steel. In terms of barrel wear, it is equivalent to 3BM15 - that is, it erodes at 5 times the rate of standard full caliber rounds.<br />
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This round is ostensibly inferior to 3BM-15 in penetration power, but this may only be true on low obliquity targets. Given that the high penetration of 3BM-15 is only applicable when the obliquity of the target is low and that this is entirely due to the presence of a tungsten carbide core in its tip, an all-steel projectile with a long rod steel penetrator and a much larger armour-piercing cap would exhibit superior performance on sloped homogeneous armour plate and may also be more effective against non-homogeneous armour.<br />
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On one hand, the ostensibly simpler construction of the 3BM-17 projectile should result in better performance than 3BM-15 in practical terms, but on the other hand, this round is rarely listed among its peers like the 3BM-9, 3BM-15, 3BM-22, 3BM-26 and others. It was not designed as a training round since 3P-31 already existed and if anything, 3BM-9 was a more economical choice for this purpose. There is certainly still some mystery surrounding 3BM-17.<br />
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Muzzle velocity: 1,785 m/s<br />
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Armour piercing cap diameter: 30mm<br />
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Total length of projectile: 548mm<br />
Length of Projectile only: 435mm<br />
Length of armour piercing cap: 50mm<br />
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<h3>
<span style="font-size: large;">3VBM9 (Zakolka)</span></h3>
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<span style="font-size: large;"><b>3BM23 (3BM22 Projectile)</b></span></div>
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<a href="http://2.bp.blogspot.com/-x9spsif4uj8/VTLx0QFGqKI/AAAAAAAAB40/nkO2ANGVUrY/s1600/f93916fce942.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://2.bp.blogspot.com/-x9spsif4uj8/VTLx0QFGqKI/AAAAAAAAB40/nkO2ANGVUrY/s1600/f93916fce942.jpg" width="298" /></a><a href="https://2.bp.blogspot.com/-sCsw_dW6QHk/WDu5nN0FbeI/AAAAAAAAHq0/vogf8QsPqlsEnGXcYXAwyMjtt-YZuXkLQCLcB/s1600/3%25D0%2591%25D0%259C23.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://2.bp.blogspot.com/-sCsw_dW6QHk/WDu5nN0FbeI/AAAAAAAAHq0/vogf8QsPqlsEnGXcYXAwyMjtt-YZuXkLQCLcB/s400/3%25D0%2591%25D0%259C23.jpg" width="130" /></a></div>
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3BM22 began mass production in 1976, but only formally entered service in 1977. It features an enlarged and improved armour piercing cap in front of the tungsten carbide core to further improve performance on sloped armour plate. The projectile is shorter than the 3BM15, but it retains the steel ring-type sabot. The tungsten carbide core at the tip of the projectile is the same design as its predecessors and it is made from the same VN-8 tungsten carbide. The steel body is made with the same 35KhZNM steel as earlier APFSDS rounds. </div><div><br /></div><div>Like 3BM15 and 3BM17, it eroded a barrel bore at 5 times the rate of standard full caliber shells. However, due to a new projectile design, the ballistic characteristics of 3BM22 differ from all preceding rounds. According to Mikhail Rastopshin in the article "<i><a href="https://topwar.ru/1716-nashi-tanki-v-realnoj-vojne-obrecheny.html">Наши танки в реальной войне обречены?</a></i>" (<i>Are our tanks doomed in a real war?</i>), 3BM22 loses 105 m/s of velocity per kilometer of flight, which is significantly less than preceding rounds. </div><div><br /></div><div>The clearest difference between the 3BM-22 and the 3BM-15 is use of a tungsten alloy armour piercing cap made from VNZh-30MT alloy. Tungsten alloy has greater yield strength than tungsten carbide and has increased toughness, making it considerably more resilient compared to tungsten carbide, which is extremely hard but also very brittle. The long length of the tungsten alloy armour piercing cap secures the tungsten carbide slug more securely from deflection and enhances the impact performance of 3BM-22 on angled armour plate as the tip of the projectile is now much more resistant to deflection as compared to before. The tungsten alloy armour piercing cap has a larger diameter than the core and protrudes beyond the steel body, so that the armour piercing cap invariably strikes the target before the rest of the projectile even on a very high obliquity target. An additional benefit to the use of a large tungsten alloy armour piercing cap is that simple dual-layered spaced armour with a thin front plate should be substantially less effective against 3BM-22 as the cap is much more resilient than the steel caps of earlier designs, but in general, the penetrator shares most of the same drawbacks as the old 3BM-15 design because of the similar location of the tungsten carbide slug.
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3BM-22 is notable for its treatment as a surrogate for foreign APFSDS rounds during the 1970's by Soviet scientists and engineers when evaluating tank armour and in various related research topics. It was also used in the evaluation of prospective reactive armour designs.</div><div><br /></div><div><br /></div><div>
<br />Mass of complete projectile (incl. sabot): 6.55 kg</div><div>Projectile Mass: 4.485 kg<br />
Mass of Incremental Charge: 4.86 kg<br />
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Muzzle velocity: 1,760 m/s<br />
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Steel body maximum diameter: 44mm<br />
Steel body minimum diameter: 30mm<br />
Armour piercing cap maximum diameter: 30mm<br />
Armour piercing cap minimum diameter: 27mm<br />
Core diameter: 20mm<br />
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Total length of projectile: 558mm<br />
Total length of penetrating elements: 453mm<br />
Length of steel penetrator only: 400mm<br />
Total length of tungsten armour piercing cap: 88mm<br />
Length of tungsten armour piercing cap in front of steel penetrator: 35mm<br />
Length of tungsten carbide core: 71mm<br /><br />
Mass of core: 0.270 kg<br />
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<blockquote class="tr_bq">
Penetration at 2.0 km:<br />
470mm at 0°<br />
220mm at 60°</blockquote>
<blockquote class="tr_bq">From page 587 of the textbook "<i>Учебник Средства Поражения И Боеприпасы</i>" published by the Bauman Moscow State Technical University.</blockquote>
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<blockquote class="tr_bq">
Penetration at 2.0km:<br />
420mm at 0°<br />
170mm at 60°</blockquote>
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Guaranteed penetration according to the tactical-technical characteristics.</blockquote>
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Rickard Lindström reports in <a href="http://www.ointres.se/strv_103.htm">this article</a> that during a Swedish test in the early 90's involving an Strv 103 and a T-72 tank (purchased from the ex-GDR after the collapse of the USSR), 3BM22 rounds fired at the S-tank (at an unknown range) proved to be so powerful that it went all the way through the entire tank. This is hardly surprising given that 3BM22 or 3BM26 is capable of piercing the turret roof of the T-72B tank (45mm cast steel angled at 78 degrees) from a distance of 3,700 meters when the upper glacis armour of the Strv 103 is only equivalent to 50mm of RHA steel plate at 78 degrees.<br />
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It is hard to properly evaluate 3BM-22 given its year of introduction. It did not provide the T-72 with any capabilities that it did not already have, given that tanks like the M60A1 and Chieftain were still the most heavily armoured main battle tanks in NATO at the time and 3BM-9 was already enough to deal with these two tanks from beyond the maximum combat ranges expected in Central and Western Europe, but 3BM-22 would have been inadequate against the Leopard 2A0 and M1 Abrams even at short ranges. After the reunification of Germany, tests were conducted using the 3BM22 rounds that had been supplied to East German T-72M and T-72M1 tanks as the most advanced ammunition exported from the USSR. It was found that the front armour of the Leopard 2A4 provided full protection against 3BM22.<br />
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The enhanced penetration power of 3BM-22 on oblique homogeneous armour may make a difference at exceptionally long ranges and at highly unfavourable angles of attack, but such situations are not expected to be the norm. It is quite possible that 3BM-22 may have proven useful against a tank like the the Chieftain Mk.10 which received additional cast armour blocks on its turret that conformed to the constructional angles of its base turret armour of 50-60 degrees, but it was only one tank out of many tanks in the NATO repertoire of 1986.
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Existing reserve stocks of 3BM-22 are currently being expended in live-fire exercises, for which older projectiles are favoured since they are less harsh on the bore compared to newer high-pressure rounds.<br />
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<h3>
<span style="font-size: large;">3VBM-11 (Nadezhda)</span></h3>
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<span style="font-size: large;"><b>3BM-27 (3BM-26 Projectile)</b></span></div>
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Officially entering service in 1983, the 3BM-26 projectile was the most optimal Soviet APFSDS round for sloped and composite armour penetration that was still designed on the basis of a composite construction with a small tungsten slug placed in a steel projectile body. "Nadezhda" was the first APFSDS round to use the high-energy Zh63 propellant charge, allowing the heavier 3BM-26 projectile to reach the same muzzle velocity as previous models despite the increase in projectile mass at the cost of accelerated barrel wear due to the higher pressure.</div><div><br /></div><div>Unlike previous rounds that used the steel "ring" type sabot, the 3BM-26 projectile rides on a "bucket" type sabot made from a lightweight aluminium alloy. The new design of the "bucket" type sabot interfaced with the projectile via fine threads as opposed to six large threads as found on the "ring" type sabots, and this contributed to the improved accuracy of the round, although the magnitude of the improvement is not known. The sabot is made out of a light <a href="http://www.m-s-s.ru/mar/en/e_mat_start.php-name_id=1453.htm">V-96Ts1 aluminium alloy</a>, helping to decrease parasitic mass and thus increase firing efficiency Early versions of this round used a different projectile assembly with a steel "ring" type sabot that differed slightly from the design of previous APFSDS rounds. It appears that this type did not become the official production version of the 3BM-27 projectile assembly.<br />
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<a href="https://1.bp.blogspot.com/-6O_DpA3c6Bo/XPiO-5Nm5CI/AAAAAAAAONA/T-dpjCxb-swsOjbNdbaEZFRvhDO6VgXkgCLcBGAs/s1600/bm26%2Bnadezhda.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="122" data-original-width="511" src="https://1.bp.blogspot.com/-6O_DpA3c6Bo/XPiO-5Nm5CI/AAAAAAAAONA/T-dpjCxb-swsOjbNdbaEZFRvhDO6VgXkgCLcBGAs/s1600/bm26%2Bnadezhda.png" /></a></div>
<div><br /></div><div><br /></div>To mitigate the increased bore erosion rate of the more energetic projectile and propellant gasses, a polyamide driving band was used on the sabot instead of a copper one.<br />
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Unlike the 3BM-22 and 3BM-15 that preceded it, the core is located at the tail of the projectile body and not at the tip. This means that the core will only begin to come in contact with the target material only when the steel body in front has been completely eroded during penetration. Additionally, 3BM-26 differs from its predecessors in that it uses a VNTs (tungsten-nickel-zinc) tungsten alloy core instead of a tungsten carbide core. Direct information on the composition of this alloy is scarce, but nickel and zinc are commonly alloyed with metals to increase hardness. Thus, it is likely that the incentive behind the transition from a cemented carbide to an alloy was to eliminate the brittleness of cemented carbides while remaining as hard as possible. Of course, the tungsten alloy is also denser than tungsten carbide.<br />
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Behind the tungsten alloy core is a short steel rod with a length approximately equal to the core itself (71mm) and a diameter exactly equal to the core (20mm). This layout is exactly the same as a late variant of the BR-354P APCR round. The steel rod fulfills the same function as the steel rod behind cores of the earlier 3BM-15 and 3BM-22 projectiles - increasing the kinetic energy of the core with a minimal expenditure of tungsten. Behind the short steel rod is the tracer.<br />
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There is an air space forward of the core to give it room for forward travel under its own inertia as the rest of the body decelerates within the target material. This is to allow the core to retain the same impact velocity as the rest of the projectile at the moment of contact with the armour plate in spite of the erosion and deceleration of the steel penetrator in front of the core, so if, for example, the 3BM-26 projectile impacts a armour plate of infinite thickness at 1,520 m/s, the steel rod will penetrate the target until it is completely eroded inside the armour plate so that its final velocity is 0 m/s, but the core at the rear of the projectile retains the same impact velocity. Immediately after the steel rod is eroded, the core takes its turn and begins penetrating the target. The use of a tungsten alloy instead of a carbide vastly reduces the likelihood that the bare core will shatter when it impacts the plate after the steel rod is fully eroded.<br />
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At the very front of the projectile is the ballistic cap, crimped onto the armour piercing cap, which is slightly larger than the one in the 3BM-22 projectile. The increased length of the armour piercing cap did not significantly affect the performance of the 3BM-26 on oblique targets, as evidenced by the fact that the penetration of this round for a plate at 60 degrees is the same as the 3BM-22. To the contrary, the relative performance of the 3BM-26 projectile on sloped plate appears to be slightly worse seeing as the penetration on a perpendicular plate was increased but the penetration on sloped plate was not.<br />
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It is known that both 3BM-15 and 3BM-22 could not cope with even the modest "B-package" armour of the Leopard 2A0-A4 due to the placement of their tungsten carbide slugs at the front of the projectile, so out of all Soviet composite cored-steel APFSDS projectile designs, 3BM-26 has the best prospects against the new complex armour of the M1 Abrams and Leopard 2. The steel projectile is still as vulnerable to fracturing and disintegration when strong lateral forces are imparted onto the steel body by the bulging plates of a NERA array, but due to the location of the tungsten alloy slug, 3BM-26 can retain its most potent component upon reaching the back plate of the armour array. In previous designs, the tungsten carbide slug could be dislocated from the rest of the projectile after emerging from behind a spaced armour plate whereby it could yaw and shatter upon impact with the base armour - a consequence of the brittleness of tungsten carbide - while the steel rod behind the slug would be cracked and destroyed by the armour array.<br />
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Generally speaking, steel long rod projectiles will perform very badly against NERA armour or sloped spaced armour relative to monobloc tungsten alloy or depleted uranium alloy projectiles due to the comparatively low yield strength of steel. As explained in <a href="https://thesovietarmourblog.blogspot.com/2017/12/t-72-part-2-protection-good-indication.html">Part 2 of this T-72 article</a>, NERA plates and sloped space armour will defeat long rod projectiles via the destruction of the rod through the application of lateral stresses. In short, the lower yield strength of steel makes it more susceptible to structural failure when it experiences strong lateral stresses as it exits the back of a sloped spaced steel plate or as it passes through a NERA array. The tail usually survives the experience, but when the front part of the rod is broken up, the penetration of the tail may not be enough to defeat the back plate of the armour array. For a more holistic understanding of the concept, please visit Part 2.<br />
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In the M1 Abrams, the back plate is just 101mm thick. If we consider a scenario where an older round like the 3BM-15 were to penetrate the armour array of an M1 Abrams, the defeat of the back plate requires at least a third of the steel penetrator to survive the interaction with the NERA array and the front plate. The probability of succeeding is not very high. With a tungsten alloy core in the tail, the probability of success for the tail of the 3BM-26 penetrator is much higher, one reason being that tungsten alloy much tougher than tungsten carbide. The penetration of 3BM-26 is also higher on oblique targets compared to older rounds. This is because an older round like 3BM-15 is susceptible to losing its tungsten carbide slug if the projectile impacts an armour plate that is sloped at 17 degrees or above. 3BM-26 is able to retain its slug much more securely.<br />
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It must be observed that the use of a small tungsten alloy core instead of a more elongated penetrator like on the older American M735 was already an anachronism by foreign standards in 1983, but at least it was still a highly economical solution considering the lackluster technological capabilities of the Soviet munitions industry at the time. An additional economic advantage to 3BM-26 is that its core shares the same dimensions as the earlier pattern of tungsten carbide cores. It is possible to retrofit older stocks of ammunition with the more effective core.</div><div><br /></div><div>Due to the use of high energy propellant and increased muzzle energy, the bore erosion of 3BM26 was higher than all older rounds, increasing to 0.019mm on the 2A46, according to Rolf Hilmes in the book "<i>Kampfpanzer Heute und Morgen (2007 edition)</i>". When fired from 2A46, the calculated barrel life is only 157 shots, with a practical limit of 87 shots, beyond which an increase in dispersion occurs. When fired from 2A46M, which was designed for increased pressure ammunition, the barrel life is not adversely affected.<br />
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Muzzle Velocity: 1,720 m/s<br />
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Mass of the sabot: 2.2 kg<br />
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Mass of the projectile only: 4.8 kg<br />
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Total length of projectile: 558mm<br />
Length of (partly hollow) steel penetrator only: 395mm<br />
Length of armour piercing cap: 115mm<br />
Length of core: 71mm<br />
Diameter of core: 20mm<br />
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Maximum diameter of the projectile: 36mm<br />
Maximum diameter of armour-piercing cap: 36mm<br />
Minimum diameter of armour-piercing cap: 27mm<br />
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<blockquote class="tr_bq">
Penetration at 2.0 km:<br />
490mm at 0°<br />
230mm at 60<span class="st">°</span></blockquote>
<blockquote class="tr_bq">From page 587 of the textbook "<i>Учебник Средства Поражения И Боеприпасы</i>" published by Bauman Moscow State Technical University.</blockquote></div><div></div><blockquote><div><br /></div><div><div>Penetration at 2.0 km:</div><div>200mm at 60°</div><div><br /></div><div>Guaranteed penetration according to the tactical-technical characteristics.</div></div></blockquote><div><div></div><div><br /></div><div><br /></div>
There appears to be some discrepancy in the penetration data, as it is claimed in some Russian sources that 3BM26 "Nadezhda" has 18% more penetration than 3BM-22 "Zakolka". If the data of the certified penetration for 3BM-22 is used as a reference point (380mm at 2 km at 0° and 170mm at 2 km at 60° according to <a href="http://fofanov.armor.kiev.ua/Tanks/ARM/apfsds/ammo.html">Fofanov</a>), then the certified penetration of 3BM26 at 2 km must be 448mm at 0° and 200mm at 60°. Only the penetration figures at 60° matches the claimed 18% increase (200mm vs 170mm), but the penetration on flat plate does not show an 18% difference. This inconsistency may be explained if we take a closer look at the definition of certified penetration, which dictates that 80% of the projectile mass must be on the other side of the target plate with a consistency of 80% for a given velocity. Due to the requirements set out in the definition of this term, the minimum permissible penetration of 3BM-22 can never be lower than its certified penetration of 380mm at 2 km at 0°, so the only explanation is that the actual average penetration (410mm according to Fofanov) of 3BM26 must be much higher than its certified penetration would suggest. However, this requires us to make the assumption that Fofanov's figures are infallible and that the 18% figure is not directly based on Fofanov's own figures.<br />
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Despite total the obsolescence of this round as a front line anti-tank munition, "Nadezhda" is still used in reserve units in the Russian army to this day. Generally speaking, their fate is to be expended in live firing exercises.<br />
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<h3>
<span style="font-size: large;">3VBM-13 (Vant)</span></h3>
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<b><span style="font-family: "times new roman"; font-size: large;">3BM-33 (3BM-32 Projectile)</span></b></div>
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<a href="http://1.bp.blogspot.com/-ETAa2HN0-pQ/VTQh5r5DFnI/AAAAAAAAB-Q/7TY8u1qWGvc/s1600/bm-32.png" style="color: black; font-family: "times new roman"; font-size: medium; font-style: normal; font-weight: normal; letter-spacing: normal; margin-left: 1em; margin-right: 1em; text-transform: none; white-space: normal; word-spacing: 0px;"><img border="0" src="https://1.bp.blogspot.com/-ETAa2HN0-pQ/VTQh5r5DFnI/AAAAAAAAB-Q/7TY8u1qWGvc/s1600/bm-32.png" /></a></div>
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<font size="3"><span style="font-weight: normal;"><br /></span>
<span style="font-weight: normal;">Having been informed of new Western developments in composite armour technology, GRAU set forth new requirements to defeat future tank armour in the mid-70's. In 1977, work began on new APFSDS projectiles to accomplish this. The new ammunition would be based on totally new design concepts in order to avoid the limitations imposed by the previous composite rounds. The R&D project "Vant" entered service in 1985 as the 3VBM13 round with the 3BM32 projectile. It was made from depleted uranium, known in the USSR as "Material B". It was thought that the use of DU ammunition would be reserved for a major war, as the political leadership wanted to avoid the controversy surrounding the supposed health effects of DU. In a major war, the main advantage of "Vant" was that it cost 10-15% less than a comparable tungsten alloy round, and as such, could be procured in larger numbers.</span><br />
<span style="font-weight: normal;"><br /></span><span style="font-weight: normal;">The depleted uranium-nickel-zinc (UNTs) alloy penetrator rod has a monobloc construction, and the projectile is aesthetically similar to the 120mm DM13 APFSDS round, although it clearly does not have a maraging steel jacket like DM13 ("<i>Army</i>" magazine, volume 34, p. 450). The "bucket" style sabot design from the 3BM26 was carried over and modified, which meant that large bore-riding fins were still necessary. </span><span style="font-weight: 400;">The sabot is made out of a light </span><a href="http://www.m-s-s.ru/mar/en/e_mat_start.php-name_id=1453.htm" style="font-weight: 400;">V-96Ts1 aluminium alloy</a><span style="font-weight: 400;">. The driving bands are made from plastic and help reduce barrel wear, partially counteracting the higher operating pressure of the cartridge. The weight of the sabot is 2.1 kg.</span><br />
<span style="font-weight: 400;"><br /></span>
<span style="font-weight: 400;">The total weight of the in-flight projectile is 4.7 kg, including the stabilizer fins (0.435 kg), the tracer (0.03 kg), the penetrator and aluminium ballistic cap. The penetrator and ballistic cap weigh 4.32 kg together. The penetrator alone is estimated to weigh 4.3 kg. Interestingly enough, this is effectively the same weight as the DU penetrator of the 105mm M900 APFSDS round (4.246 kg).</span><br />
<span style="font-weight: 400;"><br /></span>
<span style="font-weight: normal;"><br /></span><span style="font-weight: normal;">According to Mikhail Rastopshin in his article "<i><a href="https://nvo.ng.ru/armament/2008-08-01/1_uran.html">Уран конструкторам не помог</a></i>" (Uranium designs don't help), "Vant" has an aspect ratio of 15. The long rod penetrator is somewhat longer than the 105mm M774 and M833 and it was also substantially thicker, but it was outclassed by the American 120mm M829 (1985). Rastopshin also stated that</span><span style="font-weight: 400;"> the drop in the velocity of 3BM32 at a distance of 2 km is 160 m/s, giving an average velocity loss of 80 m/s per kilometer.</span><br />
<span style="font-weight: normal;"><br /></span>
<span style="font-weight: normal;"><br /></span>
<span style="font-weight: normal;">Muzzle velocity: 1,700 m/s</span><br />
<span style="font-weight: normal;"><br /></span>
<span style="font-weight: normal;">Total projectile length: 480mm</span><br />
<span><span style="font-weight: 400;">Penetrator rod length: 380mm</span></span><br />
<span style="font-weight: 400;">Maximum diameter of the projectile rod: 34mm</span><br />
<span style="font-weight: 400;">Average diameter of the projectile rod: 30mm</span><br />
<span style="font-weight: normal;"><br /></span>
<br />
</font><blockquote class="tr_bq">
<font size="3"><span><span style="font-weight: 400;">Penetration at 2.0 km: </span></span><span><span style="font-weight: 400;">430mm RHA at 0° </span></span> </font></blockquote>
<blockquote class="tr_bq">
<span><span style="font-weight: 400;"><font size="3">From defence expo display plaque.</font></span></span></blockquote>
<blockquote class="tr_bq">
<font size="3"><span><span style="font-weight: 400;">Penetration at 2.0 km:</span></span><span><span style="font-weight: 400;">400mm </span></span><span style="font-weight: 400;">RHA at 0°</span><span><span style="font-weight: 400;">250mm RHA at 60°</span></span> </font></blockquote>
<blockquote class="tr_bq">
<font size="3"><span style="font-weight: 400;">According to Mikhail Rastopshin in </span><a href="http://nvo.ng.ru/armament/2008-08-01/1_uran.html" style="font-weight: 400;">this article</a><span style="font-weight: 400;"> and </span><span><span style="font-weight: 400;">in <a href="http://armor.kiev.ua/ptur/weapon/uran.html">another article</a>. </span></span><span> </span> </font></blockquote>
<blockquote class="tr_bq">
<span style="font-weight: 400;"><font size="3">Penetration at 2.0 km:</font></span></blockquote>
<div style="font-size: medium; font-weight: 400;">
<blockquote class="tr_bq">
560mm at 0°<br />
250mm at 60°</blockquote>
</div>
<div style="font-size: medium; font-weight: normal;">
<blockquote class="tr_bq">
These figures come from page 587 of the "<i>Textbook of Means of Defeat and Ammunition</i>" 2008 (<i>Учебник Средства Поражения И Боеприпасы</i>) published by Bauman Moscow State Technical University.</blockquote>
</div>
<blockquote class="tr_bq">
<span style="font-weight: 400;"><font size="3">Penetration into spaced targets: </font></span></blockquote>
<blockquote class="tr_bq">
<ul>
<li><span><span style="font-weight: 400;"><font size="3"><span><span style="font-weight: 400;">7-layer array at an angle of 60 degrees (630mm LOS) could be defeated at 3,200 m. </span></span> </font></span></span></li>
</ul>
</blockquote>
<blockquote class="tr_bq">
<ul>
<li><span><span style="font-weight: 400;"><font size="3"><span><span style="font-weight: 400;">7-layer array at an angle of 30 degrees (620mm LOS) could be defeated 3,200 m. </span></span> </font></span></span></li>
</ul>
</blockquote>
<blockquote class="tr_bq">
<ul>
<li><span><span style="font-weight: 400;"><span><span style="font-weight: 400;"><font size="3">3-layer spaced array at an angle of 65 degrees (1,830mm LOS) could be defeated at 5,000 m.</font></span></span></span></span></li>
</ul>
</blockquote>
<div style="margin: 0px;">
<font size="3"><span style="font-weight: normal;"><span><br /></span></span><span style="font-weight: normal;"><span>In terms of age, "Vant" is comparable to the American M829 round which began production in 1984 and entered service in the same year as "Vant" (1985) to equip the freshly inducted M1A1 Abrams tank. M829 is only 30 m/s slower than "Vant" at 1,670 m/s but it loses less velocity over distance due to its smaller low-drag fins, and the projectile had a longer 540mm monobloc DU penetrator capable of penetrating approximately 275mm RHA at 60 degrees at 2 km. The performance of M829 against multilayered composite armour is most probably superior to "Vant" due to the higher aspect ratio of its penetrator. In terms of penetration performance, all available evidence suggests that "Vant" is inferior to M829 but superior to the German DM23 (120) round which had a monobloc tungsten alloy penetrator with a lower aspect ratio of 11:1 and was launched at a slightly lower muzzle velocity.</span></span><br /></font>
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</h3>
<h3>
<span style="font-size: large;">3VBM-17 (Mango)</span></h3>
<h3>
<span style="font-size: large;"><b>3BM-44 (3BM-42 Projectile)</b></span></h3>
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<a href="http://2.bp.blogspot.com/-FjLkiKEIxOA/VU5s8v7_BNI/AAAAAAAACVo/ZP-fWtHJHfk/s1600/3bm-42.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://2.bp.blogspot.com/-FjLkiKEIxOA/VU5s8v7_BNI/AAAAAAAACVo/ZP-fWtHJHfk/s640/3bm-42.png" width="214" /></a><a href="https://4.bp.blogspot.com/-HYnT43-OEa8/WDvJ_abv0wI/AAAAAAAAHrM/fV_scQinkN4BsL86CZxXCG_xr01Nru0WQCLcB/s1600/%25D0%2591%25D0%259C42.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://4.bp.blogspot.com/-HYnT43-OEa8/WDvJ_abv0wI/AAAAAAAAHrM/fV_scQinkN4BsL86CZxXCG_xr01Nru0WQCLcB/s640/%25D0%2591%25D0%259C42.JPG" width="347" /></a></div>
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<br />
Developed in parallel with "Vant", "Mango" has a more complex construction using jacketed tungsten penetrators instead of a depleted uranium rod. The 3BM-42 projectile has a two-part tungsten alloy penetrator, but technically it is a three-part penetrator, as the rod supplemented by a 112mm tungsten alloy segment at the tip with a diameter of 22mm - greater than the diameter of the main penetrator. The penetrator is encased in a relatively thick steel jacket which holds the two long rod penetrators together.<br />
<br />
According to "<a href="https://www.sciencedirect.com/science/article/pii/S0734743X98000438">Numerical Analysis and Modelling of Jacketed Rod Penetration</a>", the common use of steel jackets on early long rod penetrators was due to the poor mechanical properties of the heavy metal alloys at the time. The most serious issue was the shearing of the threads that held the long rod penetrator to the sabot during acceleration inside the gun barrel when firing. If the projectile arrived at its target, the weakness of jacketed long rod penetrators is its reduced penetration power against homogeneous steel armour compared to a monobloc penetrator.<br />
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<a href="https://1.bp.blogspot.com/-eU1r5cI-nTM/WeuynEYZtQI/AAAAAAAAJ7M/r5LtxolxTpIutWhgXAmarqAU5skFD6v5wCLcBGAs/s1600/bm-42.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="144" data-original-width="516" src="https://1.bp.blogspot.com/-eU1r5cI-nTM/WeuynEYZtQI/AAAAAAAAJ7M/r5LtxolxTpIutWhgXAmarqAU5skFD6v5wCLcBGAs/s1600/bm-42.jpg" /></a></div>
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<br />
Since one of the long rod penetrators in "Mango" is shorter than the other, it is unclear why the shell is not longer than it is, as it should not be difficult to have two long rods instead of one long rod and one short rod. From various studies on the behaviour of long rod tungsten alloy penetrators on spaced armour and thin oblique plates, it is very likely that the shorter rod at the tip of the projectile will prevent the rest of the rod from breaking up after perforating a spaced armour plate at high obliquity, or at least control the damage in such a way that the rest of the rod will penetrate any further armour plating with greater efficiency.<br />
<br />
The tungsten alloy penetrator segment at the tip is only partially fitted into the jacket. As such, the damage sustained by the tip segment - hereafter referred to as the armour piercing cap - should be mostly isolated from the rest of the projectile. Theoretically, this should allow the integrity of the remainder of the projectile to be preserved against a spaced or composite armour array after passing through the initial armour elements. As the armour of both the M1 Abrams and Leopard 2 series are understood to rely on an array of oblique NERA panels and steel armour plates with air gaps, the effectiveness of "Mango" could be quite high. If used on a steeply sloped target, the relatively loose connection between the armour piercing cap and the rest of the projectile implies that it would be broken off on impact.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://2.bp.blogspot.com/-lsyJaXcEwWM/WhRIRutS-TI/AAAAAAAAKMg/LMkUOYIKsbUjxmQxvpREz4166xZ1gcJbwCLcBGAs/s1600/020%25D0%25A1%25D0%2591.png" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1562" data-original-width="538" height="640" src="https://2.bp.blogspot.com/-lsyJaXcEwWM/WhRIRutS-TI/AAAAAAAAKMg/LMkUOYIKsbUjxmQxvpREz4166xZ1gcJbwCLcBGAs/s640/020%25D0%25A1%25D0%2591.png" width="220" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Photo from <a href="http://soviet-ammo.ucoz.ru/index/125_3vbm17/0-94">soviet-ammo.ucoz.ru</a></td></tr>
</tbody></table>
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<br />
<span style="font-family: "times new roman";">The paper "</span><a href="https://www.sciencedirect.com/science/article/pii/S0734743X98000438" style="font-family: "times new roman";">Numerical Analysis and Modelling of Jacketed Rod Penetration</a><span style="font-family: "times new roman";">" reveals that decreasing the thickness of the steel jacket relative to the diameter of the (depleted uranium) rod to a ratio of 0.1 results in the smallest degradation of penetration against steel armour, but the steel jacket for 3BM-42 is rather thick - much thicker than on the 3BM-32. The total diameter of the projectile at the middle is 36mm, but the tungsten alloy penetrator rods have a consistent 18mm diameter throughout its entire length, meaning that the jacket is 9mm thick or 0.5 diameters. This hints at two possibilities: the jacket was intentionally designed for increased performance on composite armour at the expense of performance on monolithic steel armour, or they were simply not able to create an alloy that was strong enough to survive being propelled down a gun barrel. Quite frankly, the second possibility seems rather unlikely since the main issue with early tungsten alloys was the shearing of the threads joining the penetrator to the sabot, not the rod itself disintegrating. In fact, it is practically impossible for the rod itself to break apart during the acceleration stage. </span><br />
<span style="font-family: "times new roman";"><br /></span>
<span style="font-family: "times new roman";">The jacket can clearly differentiated from the tungsten rod in the photo below, taken from Andrei Tarasenko's website, btvt.narod. </span><br />
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<a href="https://2.bp.blogspot.com/-6DM2oADU0Fs/WhRNtnVEY-I/AAAAAAAAKMw/LvJv3CSqHEscgezOPYif1-0rb8mzbuCHACLcBGAs/s1600/3bm-42%2Bnozh.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="112" data-original-width="821" height="87" src="https://2.bp.blogspot.com/-6DM2oADU0Fs/WhRNtnVEY-I/AAAAAAAAKMw/LvJv3CSqHEscgezOPYif1-0rb8mzbuCHACLcBGAs/s640/3bm-42%2Bnozh.jpg" width="640" /></a></div>
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<span style="font-family: "times new roman";"><br /></span>
Having such a thick jacket, the cross sectional density of the projectile is much, much lower than a monobloc tungsten alloy rod, but this is compensated by the high overall mass of the projectile of 4.85 kg - identical to 3BM32 and compares favourably to the 4.6 kg mass of the 120mm DM33, which also had a slightly lower muzzle velocity of 1650 m/s.<br />
<br />
The study "<a href="http://ciar.org/shotmagnet/Armor%20and%20impactor%20studies/ISB_22_Comparison_of_Unitary_and_Jacketed_Rod_Penetrators.pdf">Comparisons of Unitary and Jacketed Rod Penetration into Semi-Infinite and Oblique Plate Targets at System Equivalent Velocities</a>" by J. Stubberfield et al provides further evidence to show that a jacketed penetrator such as the 3BM42 has enhanced performance against spaced armour. It was observed that the monobloc tungsten rod penetrated 12% more than the jacketed rod on the homogeneous RHA block, but the jacketed rod penetrated more than the monobloc rod by 17% on the spaced armour. According to the radiographs taken of the rods as they exited the spaced plates, the steel jacket on the jacketed rod was intact after the perforation and the jacketed rod itself appeared to be less fragmented compared the monobloc rod from the smaller quantity of debris. The spaced armour setup in the study was rather simple, consisting of only two oblique plates placed at an angle of 65 degrees, but even so, it is rather unlikely that a monobloc rod would perform better on an array with more spaced plates. Besides spaced armour targets, <a href="http://ciar.org/shotmagnet/Armor%20and%20impactor%20studies/ISB_21_Ballistic_Performance_of_Monoblock_and_Jacketed_Penetrators.pdf">it is known</a> that jacketed penetrators can perform substantially better against spaced NERA armour and may perform better against certain types of ceramic laminate armour.<br />
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<div style="font-size: medium; font-weight: normal;">
<br />
The 3BM42 projectile is generally similar to the 3BM32 in external layout due to the use of a similar "bucket" type sabot, but the projectile is significantly lengthier. The long-rod tungsten alloy penetrators are encased by a thin sheath made from <a href="http://lookpolymers.com/pdf/Crucible-Steel-S7-AISI-S7-Tool-Steel.pdf">S-7 impact-resistant tool steel</a>. It is known that jacketed or sheathed long rod penetrators have superior performance on composite armour arrays, because the sheath protects the rod from external perturbations and keeps it intact as the projectile passes through the array.<br />
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<a href="http://1.bp.blogspot.com/-72SnTx7WWM0/VgAUy1rmjjI/AAAAAAAADnc/wRGl0RhFHgw/s1600/mango.jpg"><img border="0" height="298" src="https://1.bp.blogspot.com/-72SnTx7WWM0/VgAUy1rmjjI/AAAAAAAADnc/wRGl0RhFHgw/s400/mango.jpg" width="400" /></a></div>
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As the photo above clearly shows, "Mango" still has bore riding fins with copper bearings on the apex of the fins that contact the barrel bore and keep the projectile centered as it is propelled. Larger fins create more drag, leading to a lower velocity downrange. However, the increased sectional density of the projectile compared to older rounds should have granted a significant improvent in the energy retention of 3BM42.<br />
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The dimensions of 3BM42 come from the table below. Unfortunately, the original source is not yet known.<br />
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<a href="https://4.bp.blogspot.com/-_nO58OUrU00/WhRhgCwbssI/AAAAAAAAKNQ/nuPJ0ewg8oU6jsHcAvozofBQrJGH6XMiACLcBGAs/s1600/3bm-42.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="297" data-original-width="691" height="275" src="https://4.bp.blogspot.com/-_nO58OUrU00/WhRhgCwbssI/AAAAAAAAKNQ/nuPJ0ewg8oU6jsHcAvozofBQrJGH6XMiACLcBGAs/s640/3bm-42.jpg" width="640" /></a></div>
<div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;">Normally, a muzzle velocity of 1,700 m/s is given for 3BM42. However, some other sources state that the muzzle velocity is 1,715 m/s. This discrepancy may be explained by a lightening modification made to the sabot in 1992, done by drilling two holes into each petal.</div><div style="font-size: medium; font-weight: normal;"><br /></div><br />
Muzzle velocity: 1,700 or 1,715 m/s</div>
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<div style="font-size: medium; font-weight: normal;">
Mass of Sabot: 2.2 kg</div>
<div style="font-size: medium; font-weight: normal;">
Mass of Projectile: 4.85 kg</div>
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<div style="font-size: medium; font-weight: normal;">
Length of projectile: 574mm</div>
<div style="font-size: medium; font-weight: normal;">
Diameter of projectile (maximum): 31mm</div>
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<div style="font-size: medium; font-weight: normal;">
Total length of two-part penetrator rods: 420mm<br />
Length of tungsten alloy armour piercing cap: 112mm</div>
<div style="font-size: medium; font-weight: normal;">
Diameter of two-part penetrator rods: 18mm</div>
<div style="font-size: medium; font-weight: normal;">
Diameter of tungsten alloy armour piercing cap: 22mm<br />
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<div style="font-size: medium; font-weight: normal;">
Penetrator L/D ratio: 20:1 (cumulative)</div>
<div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;">
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<div style="font-size: medium; font-weight: normal;">
EFC rating: 5</div>
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<blockquote class="tr_bq">
Penetration at 2.0 km:<br />
520mm at 0°<br />
230mm at 60°</blockquote>
</div>
<div style="font-size: medium; font-weight: normal;">
<blockquote class="tr_bq">
These figures come from page 587 of the "<i>Textbook of Means of Defeat and Ammunition</i>" 2008 (<i>Учебник Средства Поражения И Боеприпасы</i>) published by Bauman Moscow State Technical University.</blockquote>
<br />
<blockquote class="tr_bq">
Penetration at 2.0 km:<br />
210mm at 60° </blockquote>
<blockquote class="tr_bq">
Mentioned by Mikhail Rastopshin in <a href="https://vpk-news.ru/articles/4269#">an article</a>.</blockquote>
</div>
<div style="font-size: medium; font-weight: normal;">
<br />
<blockquote class="tr_bq">
Penetration into various targets:<br />
<ul>
<li>7-layer array at an angled of 60 degrees (630mm LOS) could be defeated at 3,300 m.</li>
<li>7-layer array at an angle of 30 degrees (620mm LOS) could be defeated 3,800 m.</li>
<li>3-layer array at an angle of 65 degrees (1,830mm LOS) could be defeated at 2,700 m.</li>
</ul>
</blockquote>
</div>
<div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;">According to a study on the feasibility of an APFSDS penetrator augmented by a small shaped charge, a live firing test showed that 3BM42 achieves conditional defeat (partial penetration) on a 350mm medium hardness armour steel plate when fired at a muzzle velocity of 1,350 m/s. The impact velocity is not known, but must be less than 1,350 m/s. This is characterized by back surface deformation and cracking, which can be observed in No. 3 in the the figure shown below.</div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4uQwsqFBjmY/X34m4fJot_I/AAAAAAAARr0/ciIYFWILkzI6pOwv32pMhhq_UNU3DDYIgCLcBGAsYHQ/s431/test.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="401" data-original-width="431" height="373" src="https://1.bp.blogspot.com/-4uQwsqFBjmY/X34m4fJot_I/AAAAAAAARr0/ciIYFWILkzI6pOwv32pMhhq_UNU3DDYIgCLcBGAsYHQ/w400-h373/test.jpg" width="400" /></a></div><br /><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;">Unfortunately, the velocity loss characteristics of 3BM42 are unknown, so it is not possible to accurately estimate the distance at which it achieves this result on 350mm of armour. Under the reasonable assumption that it is less than 3BM22 (105 m/s), the distance corresponding to an approximate impact velocity of less than 1,350 m/s may be around 4 km. </div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;"><br /></div><div style="font-size: medium; font-weight: normal;">
By comparing these penetration figures for "Mango" on the three spaced armour target arrays with "Vant" on the same targets, it can be seen that "Mango" has marginally better performance on the highly sloped 7-layer array and significantly better performance on the moderately sloped 7-layer array. However, the effectiveness of "Mango" plummets on the 3-layer array by a massive margin of 46% compared to "Vant", possibly indicating a higher sensitivity of the multi-part penetrator to large air gaps and the converse for the monobloc penetrator of "Vant". But in spite of this, these figures demonstrate the merits of "Mango" on complex sloped multilayer armour arrays, contradicting the notion that the unusual penetrator design had to be used owing to an inability to produce monobloc tungsten allow penetrators.</div>
<div style="font-size: medium; font-weight: normal;">
<br /></div>
<div style="font-weight: normal;">
However, without knowing more specific details regarding these armour arrays, it is not possible to determine how correctly they represent NATO armour, although it is clear that these targets are more challenging than the standard NATO Double Heavy and Triple Heavy targets on the basis of the number of layers alone.<br />
<br />
<span style="font-weight: 700;"><span style="font-weight: 400;">The effectiveness of a high elongation jacketed long rod penetrator on two variations of ceramic armour targets and a type of spaced NERA armour was investigated in the study "<a href="http://ciar.org/shotmagnet/Armor%20and%20impactor%20studies/ISB_21_Ballistic_Performance_of_Monoblock_and_Jacketed_Penetrators.pdf">Ballistic Performance Of Monobloc And Jacketed Medium-Caliber Penetrators Against Composite Armor And Spaced Targets</a>" by H. Kaufmann et al. For the spaced NERA armour target, t</span></span><span style="font-weight: normal;">he first layer is a NERA panel made from a sandwich of 7mm Armox plates with a 3mm center layer of rubber. Behind this is an 80mm medium hardness steel plate and the final layer is a 10-20mm hard steel plate. The entire array is sloped at 60 degrees. The mass efficiency of the armour against the jacketed rod was 0.8 and 1.1 for the two test shots. As stated in the paper, the jacketed rod was unaffected by the NERA panel and did not break apart.</span><br />
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<span style="font-weight: normal;"><br /></span></div>
<div style="font-weight: 700;">
<span style="font-weight: normal;">"</span><i><span><span style="font-weight: 400;">The spaced armor targets show relatively low stopping performance against the </span></span><span style="font-weight: 400;">jacketed rod. As x-ray pictures reveal, the tungsten cores pass the sandwich without </span><span style="font-weight: 400;">breaking which explains the low protection effect.</span></i><span style="font-weight: normal;">"</span></div>
<div style="font-weight: 700;">
<span style="font-weight: normal;"><br /></span></div>
<div style="font-weight: 700;">
<span style="font-weight: normal;">The relatively high effectiveness of the jacketed rod on a spaced armour target is reinforced by other studies and probably explains the long ranges at which "Mango" was able to penetrate the multi-layered spaced targets. Monobloc tungsten penetrators were fired three times at the same spaced target but the details were not divulged. The jacketed rods also demonstrated superior performance against one type of ceramic composite armour and performed at least as well as the monobloc rod against another type. This hints that "Mango" is probably effective at defeating the spaced NERA armour known to be foundation of the special armour used in the M1 Abrams and Leopard 2 series of main battle tanks.</span></div>
<div style="font-weight: 700;">
<span><span style="font-weight: 400;"><br /></span></span><span><span style="font-weight: 400;">With that in mind, it is important to note that the use of a jacket was still primarily a method to maintain the integrity of the rod during acceleration in the gun barrel and during flight, which was commonly done for early long rod heavy alloy projectiles. In the case of "Mango", the steel jacket is thickest around the middle of the rod where the threads connect the projectile to the sabot.</span></span></div>
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<br />
Operating under the assumption that the armour protection values of the M1 Abrams and Leopard 2 provided by various sources are in reference to a generic monobloc penetrator, a reasonable inference is that the lower performance of "Mango" on RHA targets compared to "Vant" is irrelevant since "Mango" has better performance on relevant threat armour. As such, a simple comparison of the penetration values claimed for "Mango" on RHA plate with the armour values of various tanks protected by composite armour is not only invalid, but is the opposite of the truth. It is very likely that the armour of the M1 Abrams will be defeated effortlessly by "Mango" beyond normal combat distances, since we now know the layout of the armour and some details of the steel plates it uses. It is also very likely that the thicker armour of the M1A1 can be still defeated by 3BM-42 at combat distances. Based on the limited information currently available, the Leopard 2A0-A3 is definitely more resilient than the M1 Abrams, but still vulnerable. All available evidence suggests that the turret of a Leopard 2A4 with the "C-Pakete" armour would not be vulnerable to "Mango" from the front even at a few hundred meters or less, but protection in a 60-degree frontal arc (including the turret cheeks and the side turret armour, excluding the side bustle armour) would not be provided and the front of the hull would probably still be a valid target at normal combat distances.</div>
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<h3>
<span style="font-size: large;">ATGM</span></h3>
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<h3>
<span style="font-size: large;">3UBK14 </span></h3>
<h3>
<span style="font-size: large;">9M119 "Refleks"</span></h3>
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<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jYiTr8jotko/W2S2eo73lqI/AAAAAAAAL7w/zwrLToO5AX8b9CIRhwhglmKhuCdcYqwmACLcBGAs/s1600/svir.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="492" data-original-width="1600" height="122" src="https://1.bp.blogspot.com/-jYiTr8jotko/W2S2eo73lqI/AAAAAAAAL7w/zwrLToO5AX8b9CIRhwhglmKhuCdcYqwmACLcBGAs/w400-h122/svir.png" width="400" /></a><a href="https://1.bp.blogspot.com/-5q594nImLsQ/Xzg8RaswJuI/AAAAAAAARe0/3BwZJwJibOQoqxgdjHerUrsnk5fog_o_wCLcBGAsYHQ/s2944/9m119.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1068" data-original-width="2944" height="145" src="https://1.bp.blogspot.com/-5q594nImLsQ/Xzg8RaswJuI/AAAAAAAARe0/3BwZJwJibOQoqxgdjHerUrsnk5fog_o_wCLcBGAsYHQ/w400-h145/9m119.png" width="400" /></a></div>
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The 3UBK14 cartridge contains the 9M119 "Refleks" guided missile and the 9Kh949 ejection charge. The "Refleks" missile was designed to be used in the 9K120 "Svir" missile system installed in T-72 tanks as well as the 9K118 "Razryv" system for the Sprut-B anti-tank gun and 9K119 "Refleks" system for the T-80U and T-90. </span></div><div><span class="st"><br /></span></div><div>The missile itself has a range of 5,000 meters, but due to the limited laser emission energy of the 1K13 sight, the maximum guided range of the missile is limited to 4,000 meters. For the T-72 series, the newer Sosna-U sight was necessary to exploit the full range of the missile. The maximum target speed is 70 km/h, allowing a T-72 gunner to engage an enemy tank in virtually all circumstances and also engage low-flying helicopters maneuvering at low speeds out to its maximum range. This was possible owing to the good kinematic performance of the missile even at long ranges, thanks to its sustainer motor.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Q5zw_DO9_rM/X4f_myzyCxI/AAAAAAAARuw/lbrC5u89eCkzh_fJ0AeaQOhoZLJvfQe4wCLcBGAsYHQ/s597/img_136.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="146" data-original-width="597" src="https://1.bp.blogspot.com/-Q5zw_DO9_rM/X4f_myzyCxI/AAAAAAAARuw/lbrC5u89eCkzh_fJ0AeaQOhoZLJvfQe4wCLcBGAsYHQ/s16000/img_136.jpg" /></a></div><div><span class="st"><br /></span></div><div><span class="st"><br /></span></div><div><span class="st">The missile has a single 4.2 kg shaped charge warhead designated 9N142. </span>The missile achieves excellent armour penetration for its caliber despite the limited overall length of the missile mainly because of the placement of the warhead at the rear of the missile, thus creating a large amount of standoff distance without the need for a special standoff probe. Because of this, a relatively high penetration of 700mm RHA was obtained from the 125mm caliber warhead as opposed to the typical 550mm RHA of penetration achieved by the 3BK-18M round. Another factor in the improved penetration is due to the increased caliber of the shaped charge cone as compared to a normal 125mm HEAT shell, which in turn was only possible because the body of the missile has a very thin casing. The missile self-destructs if the impact fuze is not activated within 28 seconds after launch.</div><div><br /></div><div><br /></div><div style="text-align: center;"><a href="https://3.bp.blogspot.com/-dZrss_2tlrQ/WHSeVKxOyLI/AAAAAAAAIFs/EdRmHhvWWt4DIsnLflS6uVcjMjgBFrFoQCLcB/s1600/refleks.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="357" src="https://3.bp.blogspot.com/-dZrss_2tlrQ/WHSeVKxOyLI/AAAAAAAAIFs/EdRmHhvWWt4DIsnLflS6uVcjMjgBFrFoQCLcB/w640-h357/refleks.jpg" width="640" /></a></div><div><br /></div><div><span class="st">
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The missile is launched using a 9Kh949 ejection charge. The piston plug is designed to properly seat the missile in the gun chamber as well as to transfer an electric signal to the internal battery and command system of the missile during launch. The total weight of the 9Kh949 charge is 7.1 kg. It is notably shorter than a standard 4Zh40, 4Zh52 or 4Zh63 propellant charge and does not reach the neck in the gun chamber, but it does not exceed standard charges in diameter. This allows 9Kh949 charges to be stowed in any ammunition rack in a T-72. Due to the low pressure developed by the reduced charge, the bore evacuator on the 125mm gun does not extract propellant fumes after the missile and the push rod has left the muzzle. Instead, the 9Kh949 charge features a small quantity of pressurized liquid carbon dioxide in a doughnut-shaped vessel. When the charge is fired, the propellant gas pressure causes a piston to pierce the vessel, and once the pressure in the barrel plummets after the missile has left the muzzle, the liquid carbon dioxide rushes out into the hot gun chamber, whereupon it rapidly vaporizes into carbon dioxide gas. The jet of carbon dioxide gas flushes the barrel of toxic propellant fumes before the breech opens. </span></div><div><span class="st"><br /></span></div><div><span class="st">The missile is launched at a relatively high muzzle velocity. The muzzle velocity of 9M119M is reported to be 400 m/s in the April 2012 issue of "<i>Мир Оружие</i>" magazine. It is stated in the textbook "<i>Конструкция Средств Поражения, Боеприпасов, Взрывателей И Систем Управления Средствами Поражения: Конструкция И Функционирование ПТУР</i>" (<i>Design of Destructive Devices, Ammunition, Fuses And Destructive Device Control Systems: Design And Function Of ATGMs</i>) that the muzzle velocity of 9M119 and 9M119M are 422-455 m/s. The velocity of the 9M119 missile may reach a maximum of 800 m/s according to Russian historian Aleksandr V. Karpenko in his book "<i>Ракетные танки</i>" published in the "Т<i>ехника молодежи</i>" magazine, issue No. 1, "<i>Броня</i>". This could refer to its velocity at the muzzle or its velocity just after the sustainer motor has burned out. The average velocity is 350-360 m/s, making the 9M119 series a completely supersonic type of missile.<br />
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<a href="https://4.bp.blogspot.com/-fb9y3GpPWyw/WivcliE04dI/AAAAAAAAKUE/3_pxCdPTGq0VxzqlYTZdvFP6KhQQhTOZgCLcBGAs/s1600/9kh949.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="996" data-original-width="1570" height="253" src="https://4.bp.blogspot.com/-fb9y3GpPWyw/WivcliE04dI/AAAAAAAAKUE/3_pxCdPTGq0VxzqlYTZdvFP6KhQQhTOZgCLcBGAs/s400/9kh949.png" width="400" /></a><a href="https://2.bp.blogspot.com/-GKe2-PlNby4/Vr4_xHEAoLI/AAAAAAAAF6w/gaAI6nCy-O0/s1600/9kh949oooasoidaso.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://2.bp.blogspot.com/-GKe2-PlNby4/Vr4_xHEAoLI/AAAAAAAAF6w/gaAI6nCy-O0/s320/9kh949oooasoidaso.jpg" width="129" /></a></div>
<div><br /></div><div><br /></div>
The missile has an volumetrically efficient layout with the rocket motor placed in the middle, the warhead at the rear, and the control surfaces and mechanism at the front along with the fuse at the tip with the laser receiver and stabilizing fins at the base of the missile. The stabilizing fins and laser receiver unit are covered by a protective cup that breaks away after the missile is ejected from the gun barrel. The cup protects the laser receiver unit from damage when the missile is rammed into the gun chamber (the chain rammer moves at a speed of 2 m/s) and also when the missile is launched out of the gun barrel. It also serves to contain the spring-loaded stabilizing fins until the missile has passed the muzzle of the gun barrel, whereupon the opening of the stabilizing fins breaks apart the protective cup. The cup also contains three electrical sockets which interface with three corresponding electrical contact pins located at the center of the 9Kh949 ejection charge, which can be seen in the drawing on the left, above. This is a datalink that transmits several firing procedure subroutines to the on-board guidance system of the missile immediately before it is launched.</span></div><div><span class="st"><br /></span></div><div><span class="st">Moreover, the placement of the sustainer motor at the center ensures that the center of gravity of the missile does not change as the motor burns out.</span></div><div><span class="st"><br /></span></div><div><span class="st"><div>To ensure that the missile can survive the acceleration forces of a high-velocity launch from a gun barrel, the obturator ring on the missile is not on missile body itself, but on the protective cap that covers the tail section of the missile. For the obligatory second point of contact, a guide ring is present on the missile body. It is located around the focusing cone of the shaped charge warhead. This region of the missile body has a reinforced structure. </div><div><span class="st"><br /></span></div><div><span class="st"><br /></span></div><div style="text-align: center;"><span class="st"><a href="http://4.bp.blogspot.com/-zwO5SODROVk/VqyivaH3FCI/AAAAAAAAFg8/n9pNt3Tqv1Y/s1600/refleks%2Bmissile.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-zwO5SODROVk/VqyivaH3FCI/AAAAAAAAFg8/n9pNt3Tqv1Y/s1600/refleks%2Bmissile.png" /></a></span></div><div><span class="st"><br /></span></div></span></div><div><span class="st"><br /></span></div><div>The unusual layout of the 9M119 missile, pioneered by Tula KBP Instrument Design Burau, was a necessary innovation to allow the missile to achieve the required range and armour penetration while remaining compact enough to be handled and loaded as two-part ammunition without autoloader modifications unlike the earlier 9M112 missile for the "Kobra" system. An additional factor in the long range of the missile was its high muzzle velocity relative to containerized missiles. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-IMCm4SDu2II/XzgeYid1SWI/AAAAAAAARek/bXsIJb6BbOggYw8TkVEm7-HZgE_xBLM2wCLcBGAsYHQ/s800/9m119.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="532" data-original-width="800" height="266" src="https://1.bp.blogspot.com/-IMCm4SDu2II/XzgeYid1SWI/AAAAAAAARek/bXsIJb6BbOggYw8TkVEm7-HZgE_xBLM2wCLcBGAsYHQ/w400-h266/9m119.jpg" width="400" /></a></div><div><br /></div><div><span class="st">
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The large distance between the fuse at the tip of the missile and the warhead gives the warhead a good standoff distance without the need for a special standoff probe. The layout enables the 125mm missile to have a superior flight range to the 127mm ITOW missile and superior armour penetration performance, but in a much more compact package. With 700mm of penetration, the 9M119 missile is a much more serious weapon with a much better chance of defeating the new generation (at the time) of NATO tanks like the Leopard 2 and M1 Abrams from their frontal arcs, although the chances of defeating such tanks from the direct front with this missile are rather slim.<br />
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The missile uses a solid fuel sustainer motor, with four nozzles arranged radially. The motor is tubular in shape, leaving the center hollow to permit the shaped charge jet to form properly and maintain its cohesiveness when it reaches the target. After the missile leaves the muzzle of the gun, its flight is unpowered but it maintains a relatively flat trajectory due to its high velocity. Some time after launch, the rocket motor is activated and burns for 6 seconds, after which the missile glides to the target under its own inertia. This can be seen in <a href="https://youtu.be/qTMbvqpXvz4">videos of the 9M119 being fired in exercises</a>. The average flight speed is 340-350 m/s when measured based on a maximum range of 5 km.</span></div><div><span class="st"><br /></span></div><div><span class="st">Flight stabilization is maintained via five pop-out tail fins with curved and angled surfaces to impart a slow spin onto the missile, while steering is accomplished by the two canard fins at the front. These are operated pneumatically. Pop-out inlets at the nose of the missile draw in air which is directed to the internal control surfaces of the fins by a special electronically-controlled valve system. <br /><br /><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-CfZ4hmUIGJ8/Xzg5L6PfTFI/AAAAAAAARes/uDuGhn6YX-MIrDXW9gwL-ITO1jViTKnygCLcBGAsYHQ/s1221/control%2Bsystem.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1015" data-original-width="1221" src="https://1.bp.blogspot.com/-CfZ4hmUIGJ8/Xzg5L6PfTFI/AAAAAAAARes/uDuGhn6YX-MIrDXW9gwL-ITO1jViTKnygCLcBGAsYHQ/s640/control%2Bsystem.jpg" width="640" /></a></div><div><br /></div><div><br /></div>Guidance is accomplished by the integrated 9S517 modulated laser beam unit on the 1K13-49 sighting complex. The guidance system was unified with other laser beam-riding systems like the 9K116 "Kastet" for the MT-12 anti-tank gun, 9K116-1 "Bastion" system for the T-55M and T-55AM, 9K116-2 "Sheksna" system for the T-62M and 9K116-3 "Basnya" for the BMP-3. The guidance commands are sent by modulated lasers divided into four sectors along the horizontal and vertical axis. This is illustrated in the drawing below.</div><div><span class="st">
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<a href="https://4.bp.blogspot.com/-Q4J2RnLp-4o/W2S1eaCHYwI/AAAAAAAAL7k/KD83eUJ6d5MxiREespFye6YyFquPeHEVQCLcBGAs/s1600/missile%2Bguidance%2Bscheme.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="569" data-original-width="755" height="482" src="https://4.bp.blogspot.com/-Q4J2RnLp-4o/W2S1eaCHYwI/AAAAAAAAL7k/KD83eUJ6d5MxiREespFye6YyFquPeHEVQCLcBGAs/s640/missile%2Bguidance%2Bscheme.png" width="640" /></a></div>
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This type of guidance is virtually impossible to jam. There are various guidance modes programmed into the 1K13-49 sighting complex, but the missile is always controlled in a SACLOS guidance regime. In the normal operating mode, the gunner must lase the target first to determine the range. Then, the gun is automatically elevated to a predetermined angle and the missile is fired. The guidance system directs the missile to fly at an altitude of 2-4 meters above the line of sight of the 1K13-49 sight, which is done partly to ensure that the missile does not come into contact with terrain features or other obstructions that may cause a premature detonation. At a distance of 600 to 800 meters from the target, the missile is lowered to the same level as the line of sight and guided directly toward the target, leaving it no time to react. This mode risks the chance that the target detects that it has been lased, but prevents it from detecting that it is being painted by a laser which would indicate that it is being targeted by a laser-guided bomb or missile. As such, this system prevents the target from realizing that it is being targeted by a laser-guided anti-tank missile. Also, it is possible to lase some other structure close to the target and not the target itself in order to prevent it from detecting any laser signature at all.</span></div><div><span class="st"><br /></span></div><div><span class="st">The probability of hitting a tank-sized target moving at 30 km/h with the 9M119 missile at its maximum guided range (4 km) is not less than 0.8, or 80%.<br />
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The alternate guidance mode is the direct fire mode which is akin to a simple SACLOS guidance regime. In this mode, the missile is launched out of the elevated barrel and immediately descends to the same level as the line of sight of the 1K13-49 sight. The missile is guided in a level trajectory in a straight line toward the target by the laser emitter which is slaved directly to the optical channel of the gunner's viewfinder. This mode is used when engaging helicopters and also when engaging targets that appear suddenly at short range, as this reduces the reaction time by 3 seconds because the gunner does not need to lase the target. This mode requires the modulated laser emitter to be aimed directly at the target until the missile arrives, thus allowing the target around 11 seconds to react if it is 4 kilometers away. There is also an emergency mode that is used when the laser rangefinder fails. This mode is essentially the same as the direct fire mode.<br />
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Missile Diameter: 125mm<br />
Missile Length: 695mm<br />
Wingspan (Stabilizer Fins): 250mm<br />
<br />Flight Range: 75 - 5,000 m<br />
Flight Time to Maximum Guided Distance (4 km): 11.7 s<br />Average Speed During Flight: 340 m/s<br />
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Penetration: 700-750mm RHA<br />
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Minimum Hit Probability: 0.8<br />
Hit Probability On Tank-Type Target Cruising Sideways At 30 km/h:<br />
100 m to 4,000 m = >0.9<br />
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The 9M119 missile was the longest type of ammunition available to the T-72 before the end of the Cold War. This fact is illustrated by the photo below (the missile shown in the photo is a 9M119M "Invar" with identical dimensions).<br />
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<a href="https://2.bp.blogspot.com/-edaMhRwdXfo/WcdtPnOoXgI/AAAAAAAAJlk/QhVVz8DwMbgahhM2BOpogvmslXiSmAqkQCLcBGAs/s1600/ammo%2Btypes.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1117" data-original-width="1249" height="572" src="https://2.bp.blogspot.com/-edaMhRwdXfo/WcdtPnOoXgI/AAAAAAAAJlk/QhVVz8DwMbgahhM2BOpogvmslXiSmAqkQCLcBGAs/s640/ammo%2Btypes.jpg" width="640" /></a></div>
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<h3>
<span style="font-size: large;">3UBK20 "Invar"</span></h3>
<h3>
<span style="font-size: large;">9M119M</span></h3>
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<a href="https://1.bp.blogspot.com/-LaNTQT8Yt1s/W2S8uBwpVtI/AAAAAAAAL78/M0yqj6cHKaw-fkoZKrMIXnMIBaDWuosWACLcBGAs/s1600/invar.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="744" height="400" src="https://1.bp.blogspot.com/-LaNTQT8Yt1s/W2S8uBwpVtI/AAAAAAAAL78/M0yqj6cHKaw-fkoZKrMIXnMIBaDWuosWACLcBGAs/s400/invar.jpg" width="330" /></a></div>
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The 9M119M "Invar" was a modification of the 9M119 missile featuring a precursor shaped charge, making it a tandem warhead. The tandem warhead is designated 9N142M. The missile was developed in response to the perceived threat of ERA becoming a standard fixture on modern NATO tanks. </span>"Invar" entered service in 1989 and currently remains in service in the Russian ground forces. The rocket motor was improved, giving the "Invar" missile a slightly increased speed. Externally, it is identical to its predecessor.</div><div><br /></div><div>The precursor is 42mm in diameter. Alone, it has a penetration of 110-150mm, according to the research paper "<i>Совершенствование оценки эффективности тандемных кумулятивных боевых частей</i>" (<i>Improving the assessment of the effectiveness of tandem cumulative warheads</i>) by Lieutenant Colonel R. S. Davliev. The precursor detonates instantaneously upon impact with a target, and the main charge is only detonated after a built-in delay of 300 microseconds elapses.</div><div><br /></div><div>According to <a href="http://www.promweekly.ru/archive/hpw/High_Precision_Wepons_1_2019.pdf">High-Precision Weapons newspaper, edition No. 1 2019</a>, the 9M119M missile is modular in design, allowing the front (control and motor), middle (warhead), and tail (communications unit) sections to be swapped out.</div><div><span class="st">
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Missile Diameter: 125mm<br />
Missile Length: 695mm<br />
Wingspan (Stabilizer Fins): 250mm<br />
<br />Flight Range: 75 - 5,000 m<br />
Flight Time to Maximum Distance (5 km): 17.6 seconds<br />
Average Speed During Flight: 350 m/s<br />
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Mass of missile: 17.2 kg<br />
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Primary Charge Caliber: 125mm<br />
Secondary Charge Caliber: 46mm<br />
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Armour Penetration:<br />
700mm RHA (Main charge only)<br />
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(<a href="http://roe.ru/catalog/sukhoputnye-vosyka/boepripasy/3ubk20/">Rosoboronexport</a>)<br />
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It appears that the primary charge of the missile is the same as the 9N142 warhead, and the only difference between the 9N142 and 9N142N is the addition of the precursor charge. The precursor warhead defeats ERA by fully perforating the ERA panels without initiating the explosive charge contained within, creating a relatively large channel for the shaped charge jet of the primary warhead to pass through unmolested. The primary warhead is timed to detonate 300 microseconds after the precursor.<br />
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The only issue is that the sights of the fire control system on Soviet tanks of that period did not have a high optical magnification, so seeing and targeting a tank-type target may prove difficult, especially in non-optimal weather conditions. The visibility issue of Soviet-era tanks was mostly solved by the replacement of the 1K13 sight with the Sosna-U thermal imaging sight in the T-72B3 modernization. However, the poor digital magnification capabilities of the sight makes it impossible to identify targets at long range so it will not be possible to distinguish a distant tank from other vehicles.<br />
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<h3>
<span style="font-size: large;">
PKMT Coaxial Machine Gun</span></h3>
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<a href="https://1.bp.blogspot.com/-bO64SDYwLLM/XlLDQKt1_GI/AAAAAAAAQEg/nTtWFCByD2U-2xRQNUHPGkYS2AMMz4XyQCLcBGAsYHQ/s1600/PKT%2Binstallation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="907" data-original-width="1600" height="361" src="https://1.bp.blogspot.com/-bO64SDYwLLM/XlLDQKt1_GI/AAAAAAAAQEg/nTtWFCByD2U-2xRQNUHPGkYS2AMMz4XyQCLcBGAsYHQ/s640/PKT%2Binstallation.png" width="640" /></a></div>
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The PKMT is mounted as a coaxial machine gun in the T-72. It is a specialized variant of the PKM general-purpose machine gun. <a href="https://thesovietarmourblog.blogspot.com/p/pktm.html">This page contains further information on the PKT(M) and the ammunition it fires</a>. If a PKT or PKMT is not available, it is possible to substitute it with an SGMT machine gun, as these guns are fully interchangeable. A spare barrel is carried in the spare parts and accessories kit of the tank, but it is only intended as a service replacement for a worn-out or damaged barrel, rather than as a quick-swap barrel for combat use.</div><div><br /></div><div>The machine gun is electrically fired by either pressing the left trigger button on the gunner's control handles, or the trigger button on the manual traverse handwheel. The trigger buttons transmit electrical pulses to a solenoid mechanism affixed to the rear of the machine gun receiver, operating the sear and thus firing the weapon. Alternatively, the PKMT can be fired without electrical power by having the commander push the backup trigger lever on top of the solenoid mechanism. When fired electrically, the supercharger of the ventilation unit, responsible for developing an internal overpressure in the tank, is turned on for as long as the trigger is held. This helps prevent excessive fumes from accumulating during sustained fire.</div><div><br /></div><div>
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In the T-72, the PKMT is mounted to the right of the main gun and protrudes from a pill-shaped port which provides vertical space for gun elevation. The mount fixes the machine gun firmly in place with two points of contact, and the mount itself has a shock absorbing mechanism that allows the machine gun to recoil backwards by a short distance with each shot. This prevents the weapon from vibrating under its own recoil force by allowing the net reaction forces arising in the machine gun to consolidate in a single direction; that is, rearwards.</div><div>
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<a href="http://4.bp.blogspot.com/-9s10LCVsq8s/VHdFDU3DXPI/AAAAAAAAA10/HdNTe_zFSXc/s1600/t-72_int_09_of_32.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://4.bp.blogspot.com/-9s10LCVsq8s/VHdFDU3DXPI/AAAAAAAAA10/HdNTe_zFSXc/s640/t-72_int_09_of_32.JPG" width="640" /></a></div>
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The machine gun is fed from the right and ejects to the left. Spent casings and belt segments fall into a collection box positioned directly underneath the machine gun, on which a frame for the machine gun's ammunition box is affixed. Just outside the ejection ports of the PKMT is a duct that is attached to the machine gun mount. The duct can be seen in the photo above, but it has its opening sealed with a cover. The duct serves to direct the spent casings and belt segments to the collection box. The collection box has a capacity of 500 spent casings and 20 belt segments (25-round segments), and another hundred or so casings and belt segments can be temporarily stored in the ejection duct itself if there is no time to empty to collection box. The drawing below shows the ejection duct, the collection box, and the ammunition box held on its frame.<br />
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<a href="https://1.bp.blogspot.com/--tOE98LcNcU/XlLQd7ZWxeI/AAAAAAAAQFo/oYc5n8VmTd0vlDbQFVj2M78db2_lM7Q3gCLcBGAsYHQ/s1600/pkt%2Bmount%2Brear.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1193" height="400" src="https://1.bp.blogspot.com/--tOE98LcNcU/XlLQd7ZWxeI/AAAAAAAAQFo/oYc5n8VmTd0vlDbQFVj2M78db2_lM7Q3gCLcBGAsYHQ/s400/pkt%2Bmount%2Brear.png" width="297" /></a></div>
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The collection box can be removed from its mount on the gun cradle so that the commander can empty it out of his hatch. <a href="https://youtu.be/uTGM1n8CYyQ?t=128">This video</a> shows the PKMT being fired in a T-72B and the ejection of the casings and belt segments into the collection box.<br />
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A full combat load of ammunition for the PKMT is 2,000 rounds. It is fed using 250-round boxes of belted ammunition linked in 25-round segments. This was a conventional configuration, standard for all postwar Soviet armoured fighting vehicles. Compared to all of its NATO counterparts, the T-72 carried a far smaller ammunition load. A combat load of 2,000 rounds is less than half of the capacity of a Leopard 1 (4,600 rounds) and around a third of the capacity of a Patton series tank (5,900-5,950 rounds), Chieftain (6,000 rounds) or an M60A1 (6,850 rounds). At the more extreme end of the spectrum, it should be noted that the Abrams series carries 10,000 rounds for its M240 coaxial machine gun - five times more than a T-72. </div><div><br /></div><div>Besides the ammunition box that comes prepared on the coaxial machine gun mount, there are seven additional boxes stowed in various parts of the fighting compartment in the T-72. Four of the boxes are stowed on the cover of the autoloader carousel near the commander (two next to his feet, two under his seat), one box is placed on the hull floor next to the driver's seat on the left, and another two boxes are stowed between the front right internal fuel tank and the autoloader carousel. Out of the total ammunition load of 2,000 cartridges, there are 1,200 ball (LPS) rounds, 200 armour-piercing incendiary (B-32) rounds and 600 tracer (T-46) rounds. The high concentration of tracer and AP-I bullets permits easy fire correction, which is convenient as coaxial machine gun fire is generally carried out with the burst-on-target gunnery technique.<br />
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Due to the use of individual boxes instead of a single large container, the commander must periodically reload the machine gun. This was likely the most major flaw of the T-72 design as it forced the commander to periodically shift his attention from his crucial observation, communication and command duties to perform a menial task. Needless to say, the frequency of reloads is entirely dependent on the number of targets that must be engaged, but based on the official practical fire rate of 250 rounds per minute, the 250-round supply of ammunition in each box allows a full minute of continuous burst fire. Realistically, the ammunition supply of the tank is unlikely to be exhausted in a single engagement or even a battle, particularly when the heat limit of the machine gun barrel is taken into account.</div><div><br /></div><div><div>The use of individual high-capacity boxes was the most common feeding method for tank coaxial machine guns at the time, with the MG3 coaxial machine gun of the Leopard 1 also being fed from individual 230-round boxes, while the L8A1 coaxial machine gun Chieftain was fed from 200-round boxes. The only exception to this convention was the M48 and M60 series. These tanks had a continuous 2,200-round belt for the coaxial machine gun which would be reloaded using four smaller 925-round boxes stowed in reserve when needed (changed to two 1,250-round boxes and two 625-round boxes in reserve beginning with the M60A1).</div>
<br />Continuing on from the Patton series, the M1 and M1IP tanks both have 3,300 rounds of ready rounds in a single belt, while the Abrams models armed with a 120mm gun have 2,000 rounds in a single belt. However, whether these tanks actually hold a tangible advantage over the T-72 in this regard is another matter, as the M240 is still fundamentally limited by the heat limit of its barrel. Unlike the M73 or M219 machine guns of the M60 series, it was not possible to replace the barrel of an M240 while it is on its mount. Replacing the barrel requires the weapon to be dismounted by the gunner, which is totally infeasible during combat and is highly inconvenient even outside of combat. Moreover, loading the bin to capacity is not often practiced as it tends to jam the machine gun as it is not able to reliably cope with the weight of a hanging belt when the ready bin is partially depleted, and the belt tends to coil around itself.</div><div><br /></div><div>Given that the T-72 relies on its commander to service the coaxial machine gun, the advantages of a large, voluminous ready supply of ammunition are particularly significant. However, even with this in mind, it is difficult to definitively conclude that this would have been the ideal option for the T-72, as although the feeding issues likely would not apply to the PKT or PKMT given their strong belt pull strength, the lack of provisions for barrel swaps still makes it doubtful if a significant improvement in performance could be gained, even assuming that all space and layout drawbacks were solved.</div><div><br /></div>
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ANTI-AIRCRAFT MACHINE GUN</span></h3>
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<div>T-72 tanks are equipped with the ZU-72 anti-aircraft installation with an NSVT heavy machine gun. Beginning in the 2010's, the 6P49 "Kord" machine gun has been observed on some T-72 tanks, mainly on the T-72B3 model. The "Kord" is standard for the T-72B3 UBKh. </div><div>
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<a href="https://2.bp.blogspot.com/-2qv7Z9hAkyo/Wb2XFOS1olI/AAAAAAAAJhI/gNv5yNq6UbE6m8-rmK2CAif1w5O_cgWagCLcBGAs/s1600/nsvt.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1140" data-original-width="1600" height="285" src="https://2.bp.blogspot.com/-2qv7Z9hAkyo/Wb2XFOS1olI/AAAAAAAAJhI/gNv5yNq6UbE6m8-rmK2CAif1w5O_cgWagCLcBGAs/w400-h285/nsvt.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-XnEEeQqajbg/XzQFstl7C3I/AAAAAAAARdg/BDB3myfykFwSzVAogodL9p9RkaE_wdqdgCLcBGAsYHQ/s1200/t-72b3%2Baamg.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="267" src="https://1.bp.blogspot.com/-XnEEeQqajbg/XzQFstl7C3I/AAAAAAAARdg/BDB3myfykFwSzVAogodL9p9RkaE_wdqdgCLcBGAsYHQ/w400-h267/t-72b3%2Baamg.jpg" width="400" /></a></div>
<div><br /></div><div><br /></div>The machine gun is primarily intended for the anti-aircraft role, though it may be used to shoot at ground targets as well. The machine gun mount is furnished with a K10-T reflector sight, or collimator sight, to facilitate more accurate fire at aerial targets, and aiming at ground targets is accomplished using the iron sights. The ZU-72 has a range of elevation of -5° to +75°. The cantilever mounting of the machine gun is made possible by a pair of spring equilibrators affixed to the mount. This makes it much less physically taxing on the commander to control the elevation of the machine gun, which is done by working a handwheel on the right of the machine gun mount as shown in the photo below. It has been reported to the author that the elevation mechanism is extremely smooth and light.</div><div><br /></div><div>By using a cantilever mount, the height of the machine gun system was reduced, and it was possible for precise aiming and firing to be carried out against both ground and air targets. Against air targets, the mount permitted the commander to drop down below the cupola for protection and still have the K10-T collimator sight positioned properly in front of him. This gave the commander some degree of safety against fragments from ground bursts of rockets and bombs delivered by aircraft, or any other form of return fire other than overhead munitions.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Hsc4JCfj61M/YD5tFMpaNEI/AAAAAAAAS1k/k2Qu4WIfBBQ_RBeWED4EriZcIoUB9ZpJwCLcBGAsYHQ/s1100/anti-aircraft%2Bfire.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="584" data-original-width="1100" height="340" src="https://1.bp.blogspot.com/-Hsc4JCfj61M/YD5tFMpaNEI/AAAAAAAAS1k/k2Qu4WIfBBQ_RBeWED4EriZcIoUB9ZpJwCLcBGAsYHQ/w640-h340/anti-aircraft%2Bfire.jpg" width="640" /></a></div><div><br />
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Due to the lack of a powered traverse mechanism, the ring mount must be rotated manually by the commander to aim the machine gun in the horizontal axis. Rotating the machine gun race ring is easy, but it takes a bit more effort if the tank is on a slope. Rotating the entire cupola instead of the race ring is more difficult due to its weight, but when the hatch is locked open, the cupola balances out the weight of the anti-aircraft machine gun. Normally, however, the cupola is locked facing the rear in the so-called "combat" position, leaving the machine gun free to rotate in an arc approximately equal to a half-circle. </div><div><br /></div><div>Firing is done by squeezing a trigger paddle on the left handle. The commander has to
stand on his seat in order to reach the machine gun. The machine gun mount was designed so that the sights of the machine gun would be at the eye level of a man of average height (1.7 meters). For a shorter commander, there may be issues with using the anti-aircraft sight even if his seat is raised as the photo below illustrates (taken from <a href="https://youtu.be/x0_NGmu7e4g">this video</a>). In such cases, he can stand with his left foot on the recoil guard and his right foot on the seat height adjuster mechanism.</div><div>
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<a href="https://3.bp.blogspot.com/-xMyYcwVFGho/XJCjthVFUmI/AAAAAAAANjg/EhtmcskXbgUX7NOF1271occElWwytfZQQCLcBGAs/s1600/nsvt%2Bt-72a%2Bmongolian.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1366" height="358" src="https://3.bp.blogspot.com/-xMyYcwVFGho/XJCjthVFUmI/AAAAAAAANjg/EhtmcskXbgUX7NOF1271occElWwytfZQQCLcBGAs/s640/nsvt%2Bt-72a%2Bmongolian.png" width="640" /></a></div>
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The elevation handwheel has a braking lever to hold the machine gun at a fixed elevation while shooting to facilitate better precision and to suppress the natural inclination of the machine gun to climb from recoil due to the cantilever mount. The commander activates the brake by grasping the lever like the handlebar brake of a bicycle. If the brake is not activated while shooting, the machine gun may experience overwhelming muzzle rise. Additionally, the machine gun can also be braked in azimuth by pressing down on the commander's left handle. Pressing the handle downwards causes the handle arm to push a braking pin inside the ring mount on the cupola, which drives a wedge into a slot in a split cone ring between the turret and the ring mount. The ring expands, because its circumference is increased by the width of the wedge, and in doing so, it contacts the turret surface along the ring mount along its entire circumference, like a band or drum brake. This locks the ring mount firmly on the turret. Braking the machine gun in both elevation and azimuth ensures that the maximum accuracy potential of the weapon is achieved when firing upon stationary targets, such as ground vehicles on a standstill or hovering helicopters.</div><div><br /></div><div>As mentioned before in the "Commander's Station" section of this article, the machine gun is mounted on a race ring that can spin independently from the rest of the cupola, ostensibly allowing him to fire the machine gun with a modicum of frontal protection from the hatch. However, this is impractical in real world conditions.<br />
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<a href="https://4.bp.blogspot.com/-coPXJl78bc4/WbAoiHUIogI/AAAAAAAAJTE/S7cI6fLsXM4WExkBf_kTamPyJsqmatOsQCLcBGAs/s1600/t-72%2Bmachine%2Bgun%2Bforward.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1024" height="300" src="https://4.bp.blogspot.com/-coPXJl78bc4/WbAoiHUIogI/AAAAAAAAJTE/S7cI6fLsXM4WExkBf_kTamPyJsqmatOsQCLcBGAs/w400-h300/t-72%2Bmachine%2Bgun%2Bforward.jpg" width="400" /></a></div>
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The photo above is an excellent example of this feature being demonstrated. In this position, the commander cannot reach the trigger on the other side of the machine gun mount. This is only possible if the hatch is on the right side of the machine gun like on the T-72 in the photo below. However, this prevents the commander from reaching the elevation handwheel so he cannot adjust the machine gun to correct his aim, so firing with the hatch in front of him is generally impractical.<br />
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<a href="https://3.bp.blogspot.com/-ZbgUKvO1tcY/Wv0VHu_xZqI/AAAAAAAALlY/9oRqht-wE8Egufv8X1B2X0AXDLi_oBl1ACLcBGAs/s1600/t-72%2Bparked.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1600" height="360" src="https://3.bp.blogspot.com/-ZbgUKvO1tcY/Wv0VHu_xZqI/AAAAAAAALlY/9oRqht-wE8Egufv8X1B2X0AXDLi_oBl1ACLcBGAs/s640/t-72%2Bparked.jpg" width="640" /></a></div>
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Unfortunately, the IR spotlight prevents the machine gun from being aimed when it is traversed to directly in front of the cupola, although it is possible to traverse the machine gun 360 degrees by elevating it to its maximum elevation to clear it from the IR spotlight. In the travelling position, the race ring for the machine gun mount is locked facing rearward by a spring loaded plunger, marked (18) in the diagram below. The inner cupola - which carries the commander's optics and hatch - runs on a smaller race ring along the intermediate band.<br />
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<a href="https://1.bp.blogspot.com/-0lIg_awObAw/WbBUbkmohmI/AAAAAAAAJTw/ty6VwzO8lFk5hq9-oFd0Xw-mAvYaGQlHQCLcBGAs/s1600/ball%2Bbearings.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="529" data-original-width="937" height="360" src="https://1.bp.blogspot.com/-0lIg_awObAw/WbBUbkmohmI/AAAAAAAAJTw/ty6VwzO8lFk5hq9-oFd0Xw-mAvYaGQlHQCLcBGAs/s640/ball%2Bbearings.png" width="640" /></a></div>
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When not in use, the machine gun is kept in the travel position, meaning that the inner cupola rotates without bringing the machine gun along, making it lighter and easier to spin around when the commander is surveying his surroundings. The cupola is therefore "free", though it cannot spin in full rotations, being limited to a 320-degree frontal arc. When the plunger locking the intermediate band to the fixed base is released, the machine gun is allowed to traverse freely along the race ring between it and the fixed base. The inner cupola may be locked to the intermediate band or left free. In the former case, the cupola rotates with the machine gun, so spinning the machine gun to face the front would spin the cupola to face the rear. This is the normal combat procedure, because it gives the commander complete access to the machine gun and allows him to reload it more easily. In the latter case, the position of the machine gun relative to the cupola can be changed as the commander wishes. It is possible for him to open fire on either side of the turret (at strafing aircraft, for instance) while keeping the cupola facing where bullets are expected to come from. The video clip below shows archival footage from a Czechoslovakian Army training film demonstrating a quick transition from free cupola rotation to a combat status. <a href="https://www.youtube.com/watch?v=EqYupAqiVro">Original video from the VHU channel</a>.<br />
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<a href="https://3.bp.blogspot.com/-3_WOsV99F_c/XGvUU_UHS6I/AAAAAAAANao/4BI4nLNaIMU8EUcFv3Y9Ipq6mBHH3wxxQCLcBGAs/s1600/zu-72.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="408" data-original-width="728" height="358" src="https://3.bp.blogspot.com/-3_WOsV99F_c/XGvUU_UHS6I/AAAAAAAANao/4BI4nLNaIMU8EUcFv3Y9Ipq6mBHH3wxxQCLcBGAs/s640/zu-72.gif" width="640" /></a></div>
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For engaging aerial targets, a T-72 commander would rely on a K-10T collimator sight. It was the standard anti-aircraft sight for anti-aircraft machine guns with a 12.7mm caliber. The reticle of the K-10T is illuminated via a light collecting lens, which receives environmental light from a front-facing lens and magnifies it to project an illuminated image onto the reflector, with which the operator aims. In low-light conditions, the operator must fit a special battery-powered lamp onto a purpose-built bracket in front of the light collector lens to provide an artificial source of light for the illuminated reticle. </div><div><br /></div><div>For anti-aircraft purposes, the collimator sight has an ideal design and location to provide the operator with a maximum field of view while allowing him to aim regardless of how he is positioned, which changes depending on the elevation angle of the machine gun, as the operator does not need to adjust his head to obtain a correct eye relief as with iron sights. The proper method of aiming with the sight is for the operator to keep both eyes open and look through the sight with his his right eye, allowing his brain to perceive the projected sight reticle in his vision through both eyes. Moreover, as long as the right eye is used to aim and there is 165-250mm of eye relief, the full reticle will be visible and the operator's field of view is not obstructed by the stowage box next to the sight (although his peripheral vision is). As it is a reflector sight, the reticle will be clearly visible on the target regardless of the eye relief, but the specified eye relief should not be exceeded as the outer lead rings of the reticle will begin to disappear. This makes it easier to use the reticle lead markings properly, unlike a conventional anti-aircraft spider sight where the operator focuses on the sight and the target is blurred against the background.<br />
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<a href="http://2.bp.blogspot.com/-jAVHznFTm0E/VO7XwJBYCpI/AAAAAAAABRM/IXZiHAJEEao/s1600/collimator-k10-t_front.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" src="https://2.bp.blogspot.com/-jAVHznFTm0E/VO7XwJBYCpI/AAAAAAAABRM/IXZiHAJEEao/s200/collimator-k10-t_front.jpg" width="126" /></a><a href="http://4.bp.blogspot.com/-4ij4R5yUifw/VOxfx_CWJAI/AAAAAAAABPs/HCJJs-jxpgA/s1600/collimator.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="216" src="https://4.bp.blogspot.com/-4ij4R5yUifw/VOxfx_CWJAI/AAAAAAAABPs/HCJJs-jxpgA/s400/collimator.png" width="400" /></a></div>
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<br /></div><div class="separator" style="clear: both; text-align: left;">Collimator sights were used on anti-aircraft machine guns on tanks since WWII, when the DShK began to be mounted onto some tanks in the Red Army near the end of the war. The K-10T is functionally identical to the K-8T collimator sight used at the time, but the K-10T differs in that it features a tinted screen to reduce glare when aiming in the direction of the sun. When flipped up, the screen darkens the background enough that there is a high enough contrast for the projected reticle to appear clearly in the operator's vision, allowing him to engage air targets with both eyes open. </div>
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Using the collimator sight is not compulsory. If it is damaged or unsuitable, the iron sights on the machine gun may still be readily relied upon. Using the iron sights is preferable when using the machine gun on ground targets, as the collimator has its own zero due to its offset from the bore axis of the machine gun, and it does not permit fine range adjustments. </div>
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<a href="http://3.bp.blogspot.com/-upoGiqyBimE/VOCaIBSjKtI/AAAAAAAABMo/_tVZM3t1Ibc/s1600/T-72_NSzVT_6936690648707590384_o.jpg"><img border="0" height="368" src="https://3.bp.blogspot.com/-upoGiqyBimE/VOCaIBSjKtI/AAAAAAAABMo/_tVZM3t1Ibc/s1600/T-72_NSzVT_6936690648707590384_o.jpg" width="640" /></a></div>
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<br />The K-10T is marked to engage targets flying at 400 km/h at a distance of 400 meters as a baseline reference, with the lead rings and graduated lines calculated accordingly. The sight is horizontally and vertically tilted for a battle zero of 400 meters when the NSVT is properly zeroed according to the T-72 manual, so that when firing with the sight leveled, the point of impact will coincide with the crosshair of the sight. This is mainly to facilitate firing at low-flying aircraft, but it is also convenient when firing at ground targets at close range as an alternative to the iron sights. The minimum sighting range available on the tangent sight of the NSVT is also 400 meters.<br /><br />
By equipping the machine gun with a separate collimator sight together with the foldable iron sights, the operator is given the option to use whichever aiming device he chooses for the occasion.<br />
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<div style="text-align: center;"><a href="http://2.bp.blogspot.com/-jf5T3VsUn_A/VQxgKgJOVzI/AAAAAAAABZo/8jtFWIXYc-U/s1600/k10-t_and_post.png"><img border="0" height="225" src="https://2.bp.blogspot.com/-jf5T3VsUn_A/VQxgKgJOVzI/AAAAAAAABZo/8jtFWIXYc-U/w400-h225/k10-t_and_post.png" width="400" /></a><a href="https://1.bp.blogspot.com/-Cu-9OS2m1pM/X83wpY2n7hI/AAAAAAAASQk/Rc8KPFv4oHgA8AcuvaEyYf10ldbzSp0VgCLcBGAsYHQ/s1280/k-10t.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1063" data-original-width="1280" src="https://1.bp.blogspot.com/-Cu-9OS2m1pM/X83wpY2n7hI/AAAAAAAASQk/Rc8KPFv4oHgA8AcuvaEyYf10ldbzSp0VgCLcBGAsYHQ/s320/k-10t.jpg" width="320" /></a></div>
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The height from the base of the machine gun mount to the top of the protective box for the K-10T sight is 550mm. The height of the K-10T sight matches the eye level of the operator when he is standing at such a height that he can comfortably reach his arms around the rim of the hatch to reach the controls, while the iron sights on the NSVT itself require the operator to lean down. <br />
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<a href="https://1.bp.blogspot.com/-FlwI_q4Sf1k/XhuDcBzbvjI/AAAAAAAAP44/lYWn8WP_q5IhmVADp9GKDeyNxYeVejoGQCLcBGAsYHQ/s1600/nsvt%2Bmount%2Bheight.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="832" data-original-width="1600" height="208" src="https://1.bp.blogspot.com/-FlwI_q4Sf1k/XhuDcBzbvjI/AAAAAAAAP44/lYWn8WP_q5IhmVADp9GKDeyNxYeVejoGQCLcBGAsYHQ/w400-h208/nsvt%2Bmount%2Bheight.png" width="400" /></a></div>
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The NSVT has a rate of fire of between 700-800 rounds per minute - somewhat faster than the M2HB, M85 or the earlier DShKM installed on the T-54 and T-62. The higher rate of fire improves the chances of hitting a fast-moving aerial target and the substitution of the prominent muzzle brake of the DShKM for a conical flash suppressor undoubtedly improved the commander's shooting experience, not to mention improving his vision when firing the machine gun in low light conditions and reducing the likelihood of being detected by aircraft. The nominal maximum effective range of the NSVT is approximately 800 meters against aerial
targets, but this is circumstantial. Obviously, the probability of hitting a
hovering helicopter would be much higher than hitting a moving
fixed-wing aircraft.<br />
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<a href="https://2.bp.blogspot.com/-rLFOxLeBVM4/WXJk1OBI8-I/AAAAAAAAIyc/djrNpzk-IiQxyQDj0AKLtGsrx2fiha_-QCLcBGAs/s1600/nsvt.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="359" data-original-width="537" height="267" src="https://2.bp.blogspot.com/-rLFOxLeBVM4/WXJk1OBI8-I/AAAAAAAAIyc/djrNpzk-IiQxyQDj0AKLtGsrx2fiha_-QCLcBGAs/s400/nsvt.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-RNki1ny9Mtc/Wr6qqv78hiI/AAAAAAAALPI/ycsX58FeHsU2aUPn07J0Br_HYPgu1AZ4ACLcBGAs/s1600/dO8_LO88iOk.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="369" data-original-width="604" height="243" src="https://1.bp.blogspot.com/-RNki1ny9Mtc/Wr6qqv78hiI/AAAAAAAALPI/ycsX58FeHsU2aUPn07J0Br_HYPgu1AZ4ACLcBGAs/s400/dO8_LO88iOk.jpg" width="400" /></a></div>
<div><br /></div><div><br /></div>As a rule, anti-aircraft machine guns can cause some amount of damage to low flying aircraft but are more or less useless for shooting down aircraft. Although it isn't difficult penetrating some of the more obvious weak areas such as the plexiglass windscreen on a helicopter even with a light ball round from an infantryman's rifle, the chances of actually hitting a fast moving target are rather slim. On the contrary, the role
of an AAMG is to be a deterrent: its objective is to deter the enemy pilot into pulling back from an attack, or perhaps even make him miss
his shot. Serious anti-aircraft work is to be carried out only by the
SHORADS (Short Range Air Defence Sytems) accompanying the T-72. In real world conditions, the NSVT on the T-72 has probably never been used against aircraft at all but has been occasionally used to target infantry, but even so, such occasions are relatively rare as the commander is always aware of the danger posed by snipers as he must be exposed to use the machine gun. </div>
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The machine gun is fed from a 60-round box secured to the ZU-72 mount on the right of the NSVT. The ammunition is held in six ten-round belt segments rather than a single fifty-round belt which was standard for the DShKM. Two boxes of ammunition
are stored in the rear external turret stowage bin and two more are strapped to the side of the turret just next to the commander's cupola. These two boxes are the easiest to access from outside the hatch as the
commander can reach down and place a box straight on the machine gun mount if he is facing forward. Including the box of ready ammunition mounted on the ZU-72 anti-aircraft installation itself, the total ammunition load carried by the T-72 is 300 rounds. </div><div><br /></div><div>Since he must manipulate the top cover of the NSVT and the ammunition boxes, the commander becomes more exposed while reloading, not to mention that he can become too preoccupied to notice threats around him.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-OPPUG7oRniU/X2n9K1ShtSI/AAAAAAAARpY/LOaRSSZWQuI16OpjN-5fyYZztv0uWH46ACLcBGAsYHQ/s900/0005-_MG_8368.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="900" height="266" src="https://1.bp.blogspot.com/-OPPUG7oRniU/X2n9K1ShtSI/AAAAAAAARpY/LOaRSSZWQuI16OpjN-5fyYZztv0uWH46ACLcBGAsYHQ/w400-h266/0005-_MG_8368.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-S_frYVCNd4A/X2n9LrX95sI/AAAAAAAARpc/gojDp73Bxts-DAgZNkPGlnsN-k5fArShwCLcBGAsYHQ/s922/reloading%2Bnsvt.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="590" data-original-width="922" height="256" src="https://1.bp.blogspot.com/-S_frYVCNd4A/X2n9LrX95sI/AAAAAAAARpc/gojDp73Bxts-DAgZNkPGlnsN-k5fArShwCLcBGAsYHQ/w400-h256/reloading%2Bnsvt.png" width="400" /></a></div><br /><div><br />
For firing at ground targets, two boxes of ammunition with a standardized mix of B-32 (API), BS (API with tungsten carbide core) and BZT (API-T) ammunition are provided, with the non-tracer and tracer rounds are loaded in a 5:3 ratio. For firing at air targets, three boxes of ammunition with a standardized mix of MDZ-M (HEI) and BZT (API-T) ammunition are provided, with a 5:1 ratio of non-tracer to tracer rounds. A total of 75 BZT rounds, 45 B-32 rounds, 30 BS rounds and 150 MDZ-M rounds are carried. All of these bullets can be used for fire correction as they are all capable of producing a visible flash and smoke on impact.</div><div><br /></div><div>For the anti-aircraft belt, the very high proportion of HEI rounds provided is consistent with the official stated purpose of downing enemy helicopters, particularly hovering ones, rather than simply fending off jet aircraft with the tracers acting as a deterrent as was the case for other tanks. Nevertheless, if deterrence is desired, the commander may load the machine gun with a ground targets belt. The higher proportion of tracer bullets in the ground targets belt is not as detrimental to the effective penetration power of each fired burst, as unlike the American practice of using tracer ball rounds (M17 has a mild steel core), BZT rounds are armour-piercing in nature, having a hardened steel core. </div><div><br /><br />
At a range of 500 meters, B-32 armour-piercing bullets have a penetration of 16mm at 0 degrees and 10mm at 30 degrees. This is enough to pierce the side armour of any armoured personnel carrier from practical engagement distances and eviscerate thin-skinned vehicles including trucks and jeeps. The penetration of BS-41 bullets is unclear but based on the difference between 14.5mm B-32 and BS-41 bullets (they are of a different caliber but have identical designs), it appears that 12.7mm BS bullets should have a penetration of 21mm at 0 degrees and 13mm at 30 degrees. BZT bullets have significantly reduced penetration power but they are exceptionally useful for fire correction as these bullets contain a tracer as well as an incendiary charge for a combined effect of tracing its own trajectory and signalling hits with a flash and a puff of smoke. The higher penetration of 12.7mm rounds compared to the coaxial 7.62mm machine gun makes the NSVT useful for shooting at troops hidden behind the cover of concrete walls, thick tree trunks or other types of obstructions.<br />
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MDZ-M bullets have no real armour piercing capability but can easily perforate the thin skin of aircraft and set internal equipment alight due to the use of an explosive-incendiary filler. They are rated to perforate duralumin sheets with a thickness of 2-3mm by high explosion blast, and create 30-40cm holes. The bullet easily penetrates the walls of steel drums (0.9mm) and can destroy light cover. The flash of the explosion also makes it very useful for fire correction purposes. Naturally, MDZ-M bullets are extremely effective against thin-skinned vehicles like trucks and jeeps, but it cannot defeat most physical barriers or at least cause damage behind these barriers, although it can certainly split wooden logs and set them alight or even shatter cinder block walls. The two images below show a Russian tanker in Chechnya firing MDZ bullets at rebel positions during the Battle of Grozny.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-d52kqgyZP9M/X2nOZK7U-xI/AAAAAAAARpI/bba4EME2KPkDdXm0uczC55XAydXGowAXQCLcBGAsYHQ/s1439/firing%2Bnsvt%2Bchechnya.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="892" data-original-width="1439" height="248" src="https://1.bp.blogspot.com/-d52kqgyZP9M/X2nOZK7U-xI/AAAAAAAARpI/bba4EME2KPkDdXm0uczC55XAydXGowAXQCLcBGAsYHQ/w400-h248/firing%2Bnsvt%2Bchechnya.png" width="400" /></a><a href="https://1.bp.blogspot.com/-cBMnaYjZ0KM/X2nQb4x-jMI/AAAAAAAARpQ/30F1Ca0M0QQ2R7X3yF1gKyK3DDl2dx15QCLcBGAsYHQ/s1442/loading%2Bmdz-m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="955" data-original-width="1442" height="265" src="https://1.bp.blogspot.com/-cBMnaYjZ0KM/X2nQb4x-jMI/AAAAAAAARpQ/30F1Ca0M0QQ2R7X3yF1gKyK3DDl2dx15QCLcBGAsYHQ/w400-h265/loading%2Bmdz-m.png" width="400" /></a><br /></div><div><br /></div><div><br /></div><div>
For firing at air targets, the BZT bullets aid in fire correction with its tracer and also provide some necessary armour-piercing capability so that aircraft with light armour will not be spared from damage. The combination of MDZ-M and BZT bullets in the anti-aircraft ammunition mix will maximize the probability of hit and maximize the probability of causing damage since both types of bullets are useful for fire correction and both are uniquely useful against aircraft in their own ways.<br />
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The commander has to pull a large charging lever to cycle the gun (pictured below). This was a unique design feature of the ZU-72 mount to provide the necessary leverage to comfortably retract the bolt carrier group in the NSVT, a role that was accomplished with a pulley mechanism in the NSV. The same mechanism is compatible with the "Kord" machine gun. Spent casings are ejected forward where they will roll down the sloped turret roof and off the tank. A canvas spent belt segment catcher is secured to the left side of the ZU-72.<br />
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<a href="http://2.bp.blogspot.com/-rL2dGOciJL0/VHdPsFCKUpI/AAAAAAAAA2E/klKpXfb6djk/s1600/Charging%2Blever.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="171" src="https://2.bp.blogspot.com/-rL2dGOciJL0/VHdPsFCKUpI/AAAAAAAAA2E/klKpXfb6djk/s1600/Charging%2Blever.png" width="640" /></a></div>
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According to a <a href="http://ans2.vm.stuba.sk/ANSYS2010/prednasky/Ansys%20Mechanical/Hub_Some_aspects_of_machine_gun_bullet_penetration_of_the_aluminium_sheet-metal_plate_using_ansys_autodyn.pdf">Czech study concerning the effect of typical machine gun bullets on the aluminium skin of common aircraft and the modeling of these effects</a>, the thin fuselage skin of helicopters like the Mi-8 and other Czech aircraft presents no challenge to 7.62x54mm and 12.7x108mm B-32 bullets.<br />
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According to the table below taken from the study, the velocity limit for 12.7mm B-32 API bullets for the skin of an Mi-8 is just 40-58 m/s. The corresponding distance for this speed is the maximum firing distance of 6 kilometers, so technically, the NSVT is capable of piercing the skin of a utility helicopter at any practical range. The thickest parts are the flanges at the two ends of the fuselage, measuring 3.7-4.7mm thick including the skin and flange itself, but this only represents a fraction of a percent of the surface area of the helicopter. It should hardly be a surprise that both the NSVT and KORD are easily capable of penetrating the thin skin of utility helicopters and common fixed-wing aircraft at distances far beyond the abilities of the commander to reliably engage them, but even so, the small incendiary content makes the B-32 bullet a second-rate option against aircraft. Owing to the lack of any meaningful armour and the very low thickness of structural elements, the <a href="http://www.thefirearmblog.com/blog/wp-content/uploads/2011/09/soviet_cannon-tfb.jpg">MDZ-M bullet</a> would be a much better option against aircraft as its explosive-incendiary action has a much better target effect and it provides a much brighter flash for more convenient impact sensing.<br />
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<a href="https://4.bp.blogspot.com/-jDLa-vYPEJ0/Wr_JJqDC7eI/AAAAAAAALP0/T27s0bCV8BUlj3CdRLa5CSZqAH8sIPS6gCLcBGAs/s1600/bullet%2Blimits.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="306" data-original-width="961" height="202" src="https://4.bp.blogspot.com/-jDLa-vYPEJ0/Wr_JJqDC7eI/AAAAAAAALP0/T27s0bCV8BUlj3CdRLa5CSZqAH8sIPS6gCLcBGAs/s640/bullet%2Blimits.png" width="640" /></a></div><br />
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The lack of a remote aiming and firing system for the machine gun like on the T-64 has been said to be one of the greatest drawbacks of the T-72. Former Russian tank crews who served in Chechnya mentioned that it was suicidal to man the machine gun when in combat in urban environments, so despite its high power and high rate of fire, the NSVT was not suitable for suppressing enemy positions in rubble or behind concrete walls. Tank crews in Syria have also never been observed to use the machine gun during urban combat, for the same reasons. It is interesting to note that Leonid Kartsev defended this design decision in his memoirs, stating that it helped to have an unobstructed field of view when firing at aircraft, but this is a rather weak argument since the commander of a T-64A could fire his NSVT from outside of his hatch as well if he desired. It was no coincidence that the ZU-72 anti-aircraft machine gun mount was replaced with a remote control system in the T-90 almost identical to the remote control installation of the T-64A.</span></div><div><span class="st"><br /></span></div><div><span class="st"><br /></span></div><div><div style="text-align: center;"><a href="https://4.bp.blogspot.com/-Xsyozeg9Uqc/Wr6qonabA3I/AAAAAAAALPE/N1kKGRDWt1UJu0hRkevShrfBlQe9645bQCLcBGAs/s1600/110919_armeyskoe3.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="390" data-original-width="550" height="452" src="https://4.bp.blogspot.com/-Xsyozeg9Uqc/Wr6qonabA3I/AAAAAAAALPE/N1kKGRDWt1UJu0hRkevShrfBlQe9645bQCLcBGAs/s640/110919_armeyskoe3.jpg" width="640" /></a></div><span class="st">
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However, if used against ground targets in open environments, the lack of a shield for the anti-aircraft machine gun is a much less serious problem and could be considered quite acceptable. A large number of tanks have a 7.62mm machine gun on a skate or pintle mount, including the Leopard 1, Leopard 2, and various Abrams models. On the M1A2 Abrams, a gun shield was only added to the loader's machine gun with the installation of TUSK, an urban combat kit.</span></div><div><span class="st"><br />
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<h3>
<span style="font-size: large;">STOWAGE</span></h3>
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<a href="https://1.bp.blogspot.com/-Q34kVaZ-73s/Xh1t2VdA4KI/AAAAAAAAP50/siFZML-JMTUusZ5byMXQAWmnJEwPPFyyACLcBGAsYHQ/s1600/stowage%2Band%2Bspare%2Bparts.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="932" data-original-width="1600" height="372" src="https://1.bp.blogspot.com/-Q34kVaZ-73s/Xh1t2VdA4KI/AAAAAAAAP50/siFZML-JMTUusZ5byMXQAWmnJEwPPFyyACLcBGAsYHQ/s640/stowage%2Band%2Bspare%2Bparts.png" width="640" /></a></div>
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The T-72 is furnished with a plethora of stowage bins. The most prominent ones are the two or three large bins located around the rear arc of the turret. These are used for storing machine gun ammunition, the crews' personal effects, and other accessories. The edges of the lids are lined with rubber and the lids are locked tightly by tension latches. This seals the contents of the bins from NBC contaminants and it also is effective at keeping water from entering the bins even when the tank is snorkeling across deep rivers. On another note, it is interesting to observe that although the turret of the T-72 lacks handrails for tank riders like preceding Soviet tanks, the practice of hitching a ride was still occasionally taught and exercised.</div>
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This is quite the improvement over the T-55 and T-62, as these older tanks were not equipped with external stowage bins on the turret but instead had loops from which bags could be suspended. As a result, the number of locations to stow day to day necessities was rather limited and could be lost if not secured properly to the stowage loops on the surface of the turret. The Israelis gave their Tiran tanks with Centurian-esque external stowage bins on the turret for this very reason.</div>
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The photo below shows the stowage bin at the very rear of the turret. There are two isolated stowage compartments in the bin. One on the right hand side (the left side in the photo) for smaller things, and the central compartment, which is large enough to contain practically anything. The bin is hinged to the turret, as you can see in the photo below.<br />
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The photos below shows the bin swung up and locked in place to allow easier access to the engine access panel. Photo on the right below from <a href="https://szextant.blogspot.com/2014/08/125-72-t-72-mbt-kozepes-alap-harckocsi.html">the Szextant blog</a>.</div>
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Besides the rearmost bin, there is also a stowage bin on the right side of the turret. It also has two isolated compartments. The smaller compartment stores 12.7mm ammunition.<br />
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On the T-72 Ural and most T-72A tanks and the export modifications thereof, the left side of the turret is unoccupied except for a snorkel tube segment. However, metal loops were provided so that this space could be used to secure a tarp. Finnish T-72M1 tanks were delivered without a stowage bin on the left side of the turret as was usual for the type, but <a href="http://www.inetres.com/gp/military/cv/tank/T-72/T-72M1_00.jpg">a proprietary conformal bin was added</a>.<br />
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A stowage bin was added to the left side of the turret of the T-72A obr. 1983 and the snorkel tube segment was moved to a new mounting point on the rear stowage bin. The bin is identical to the bin on the right side of the turret. Late production T-72A tanks and all T-72B models have the left turret stowage bin. The tarp which was previously stowed on the left side of the turret is instead lashed to any one of the stowage bins.<br />
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The walls of the stowage bins around the turret are constructed from sheet aluminium. They are not capable of resisting bullets or shell fragments, which is not ideal, but also quite normal for stowage bins.<br />
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There is also bank of 4 storage bins on the port side of the hull, directly above the tracks.<br />
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The port side storage bins are usually used to store maintenance equipment and spare parts.</div>
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<a href="http://1.bp.blogspot.com/-176N3k38sqE/Vf_7QXM3rZI/AAAAAAAADmQ/wj4X10B4IJ0/s1600/t-72%2Bfender%2Bstorage.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://1.bp.blogspot.com/-176N3k38sqE/Vf_7QXM3rZI/AAAAAAAADmQ/wj4X10B4IJ0/s640/t-72%2Bfender%2Bstorage.jpg" width="640" /></a></div>
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The installation of additional ERA boxes on the sides of the turret of the T-72B3 obr. 2016 necessitated the removal of the two side turret stowage bins. Only the rear turret stowage bin remains. The snorkel tube segment also had to be moved from behind the rear stowage bin to above it, in order to accommodate the slat armour screens surrounding the rear of the turret. The colossal improvement in armour protection did not come at no cost.<br />
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<h3>
<span style="font-size: large;">ESCAPE HATCH</span></h3>
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<a href="https://2.bp.blogspot.com/-NUxZxpFLmxU/Ww5NpuQW1aI/AAAAAAAALo8/RmtRYVU9Xa8LsLhBZnGvZFoi9LOysf41ACLcBGAs/s1600/escape%2Bhatch.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="995" data-original-width="613" height="640" src="https://2.bp.blogspot.com/-NUxZxpFLmxU/Ww5NpuQW1aI/AAAAAAAALo8/RmtRYVU9Xa8LsLhBZnGvZFoi9LOysf41ACLcBGAs/s640/escape%2Bhatch.png" width="394" /></a></div>
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Like many tanks of the era, the T-72 has an escape hatch, but unlike most escape hatch designs, the types used on the T-72 are hinged. The hatch is located directly behind the driver's seat, and can be accessed by all of the crew members. To exit through the escape hatch, the driver must remove the backrest of his seat. The gunner and commander can get to the hatch as well, but they have to be quite flexible in order to do so as they must crawl down from the turret. However, exiting through the hatch is not particularly difficult as it is of a very reasonable size, measuring 532mm in length and 387mm in width. This is roughly compliant with the optimal U.S Army human engineering requirements for an overhead hatch needed to accommodate a 95th percentile U.S male wearing light clothing, which is 13 x 23 inches (330 x 580 mm).<br />
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Although the three-man crew can exit the tank much more quickly by going through their own overhead hatches, an escape hatch in the hull belly can be indispensable in certain situations where it may allow crew members to escape the tank if it is flipped over or if the tank is disabled and under concentrated machine gun fire.<br />
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Two types of hatches were used on the T-72 series of tanks. The first type is shown in the drawing above. This type was used since the beginning of mass production in 1973 up until the T-72A ended production in 1984. This hatch is hinged to open inward and to the right side, and is locked in place by attaching a carabiner to a metal loop on the hatch. When closed, it is held in place by four locking levers on each of its corner. The hatch and its locking mechanism is strong enough that it does not compromise the integrity of the hull against a 6 kg to 10 kg anti-tank blast mine detonated under the tracks, but because the hatch opens inwards, it is naturally weaker than an outward-opening type or a drop-down type. This made it a potential weak point if an anti-tank mine or an IED detonated directly underneath the belly of the tank. However, the inward hinged design of the hatch makes it extremely easy to close and reseal it from inside the tank after opening it whereas a drop-out style hatch is usually inconvenient to reseal from inside. The primary advantage to the hinged hatch design is that it is possible for the crew to use the open hole as a toilet or to dispose of garbage and then simply close the hatch. Other than that, the inward-opening configuration may also make it easier to open the hatch when the tank is overturned thanks to the help of gravity.</div>
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The second type of hatch is shown in the drawing below. It was first implemented on the T-72B. This design is hinged as well, but it opens outward and is more resilient against underbelly blasts due to the interlocking of the hatch with the belly armour. The thickness of the hatch was also increased, as evident in the cross sectional drawing below. By comparing it to the hull belly which is 20mm thick, the hatch appears to be 30mm thick. It also appears to be quicker to open as it only has two locking levers instead of four. It is somewhat unusual in that the hatch opens outward and forward so that it dangles from the belly of the tank when left open, but it appears to be of sound design as it should combine the superior blast resistance of a drop-out type hatch with the flexibility of a hinged hatch. Strangely enough, the T-34 already had a hinged outward and forward-opening escape hatch since the 1940 model except that it had four locking levers and an oval shape.</div>
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<span>Considering its location, it is probably too small for anyone wearing bulky winter clothes to egress quickly, and more rotund tankers will obviously find it extremely difficult to exit through it. Both types of hatch are fully air-tight when secured properly. To unlock either type of hatch, a few taps from a hammer or mallet on each of the locking levers are needed, and the levers must be tapped into place to lock the hatch when closing it. The tight tolerances of the locking mechanism ensures that the hatch is pressed firmly onto the tank belly such that the rubber seals can form a complete seal. The locking levers are safety wired together (small holes are visible in the photo above) to prevent strong vibrations from accidentally jarring the hatch open. A short spade is clipped onto the hatch, and some equipment is usually placed on top of the hatch for a lack of better storage space inside the tank.</span></div>
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DRIVER-MECHANIC'S STATION</span></h3>
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<span><span style="font-weight: normal;">In a T-72, the driver is located centrally at the front of the hull instead of the left front corner as was the case for</span></span> the previous generation of Soviet medium tanks like the T-55 and T-62<span><span style="font-weight: normal;">. The decision to place the driver's station in a central position was influenced by positive results in navigation tests and became a more attractive option when a human loader was excluded. In tanks like the T-54, Leopard 1, Leopard 2, Centurion, and many others, the space next to the driver at the front of the hull was a convenient location for a set of ready racks for main gun ammunition as it would be easily within reach of the loader and it would be less likely to be hit during combat compared to ammunition racks in the turret. With the implementation of an autoloader, there was no longer any tangible benefit in having the driver offset to one side of the hull. The single drawback is that the driver would not be able to drive with his head out of the hatch if the gun was aimed directly forward.</span></span></div>
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<span><span style="font-weight: normal;">When driving, the driver must lean forward in order to operate the steering levers, step on the pedals and look through the periscope at the same time. Anecdotes from people who have sat in the driver's seat have reported that the station is spacious enough to let someone more than six feet tall to operate the pedals with a comfortable allotment of legroom, and it is a notable improvement over earlier Soviet medium tanks. Besides anecdotal sources, we can</span></span><span style="font-weight: normal;"> once again refer to </span><a href="http://3.bp.blogspot.com/-aBnfqllGDQI/VIZm9eldmDI/AAAAAAAADsg/2sGi3lKKxxo/s1600/human-factors-1.png" style="font-weight: normal;">this diagram</a><span style="font-weight: normal;"> from "<i>Human Factors and Scientific Progress in Tank Building</i>" by M.N. Tikhonov and I.D. Kudrin. From the diagram, it can be seen that the driver of a T-72 gets 0.864 cubic meters of space. This is more than the 0.621 cubic meters afforded to the driver of a T-55. </span></div><div style="font-weight: normal;"><span style="font-weight: normal;"><br /></span></div><div style="font-weight: normal;"><span style="font-weight: normal;">As mentioned before, the belly of the hull is a stamped steel plate with a special tub-like protrusion stamped to accommodate the driver. The height of the hull is 1,000mm while the height at the driver's station is 1,070mm due to the driver's "tub". The internal height of the driver's station when measured from the floor to the hull ceiling is around 1,020-1,030mm. Some small variance exists because the anti-radiation lining under the driver's hatch is not flat, but curved. This height is equivalent to the driver's station of a Leopard 2 which has an internal height of 1,045mm. The driver's station of the T-72 was an improvement over that of the T-54 in terms of height, as the T-54 hull has a hull height of 977mm and an internal height of 927mm. It was also taller than in a Leopard 1, where the maximum internal height at the driver's station is 1,065mm, reduced to 992mm where the driver's periscopes are fitted, at the junction between the sloping roof plate and the upper glacis plate. The closest equivalent was the M48 and M60 series, which have a hull height of 1,160mm when measured from the escape hatch under the driver's seat to the driver's hatch, but provided a maximum of 1,033mm of internal vertical height from the top of the escape hatch to the underside of the driver's hatch, decreasing slightly towards the front because the driver's hatch is tilted. </span></div><div style="font-weight: normal;"><span style="font-weight: normal;"><br /></span></div><div style="font-weight: normal;"><span style="font-weight: normal;">In terms of width, the driver's station is the largest in the tank, measuring 660mm (26 inches) wide at the backrest area. Due to the cutout in the front right fuel tank for the control cluster, the width of the station is noticeably larger in the area occupied by the driver's body, providing additional space for the convenience of using the gear shift and the control panels. </span></div>
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<span style="font-weight: normal;">When seated normally, the positioning of the driver's lower body is comfortable. His feet are at a slightly lower level as his hips when operating the foot pedals, and he can stretch out his legs quite easily as there is an abundance of room in front of and behind the pedals. Based on the length of several reference points on the hull, the length of the driver's station is approximately 1,200mm (measured from the backrest to the nose of the hull), but can vary depending on how the seat is adjusted. </span></div>
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The driver's seating arrangement is of a conventional design and is ergonomically inferior to that of the Leopard 2, M1 Abrams, Chieftain, and Challenger when the driver is working with a closed hatch. All of these tanks have the driver's periscopes installed in his hatch or on the hull roof behind the hatch which allows the driver to operate his controls with a more natural posture. The most comfortable seats are found in the M1 Abrams, Chieftain and Challenger, as the driver is furnished with a semi-reclined seat that has cushions for head support. In a T-72, the driver can sit in an upright posture with back support from the backrest of his seat, and there is enough legroom to operate the pedals comfortably. However, this seating arrangement has a drawback in that adjusting the seat rearward to increase the legroom leads to either worsened visibility or more discomfort for the driver, as he is now further from the periscopes. A tall driver who needs the additional legroom would be forced to lean far forward and press his eyes up against his periscope to get the most visibility out of the primary forward-facing periscope, which leads to back pain in the long term, or he must simply accept the reduced field of vision from a longer eye relief. This situation is illustrated in the drawing on the left below, albeit with a somewhat exaggerated depiction of a driver. In such a position, the driver would have enough legroom to stretch his legs to the pedals, as the screenshot on the right below shows. </div>
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<br /></div><div>With that said, it is worth noting that even the drivers seated in a supine seating position in all three of the aforementioned NATO tanks cannot exploit the full visibility potential of their periscopes without leaning forward, which they cannot do without incredible strain because of the supine posture. In general, there tends to be a compromise of some kind when vision devices are used, as unlike windshields, the viewing window is many times smaller, creating the issue of eye relief and thereby complicating the task of the tank designer in laying out the driver's controls. Ideally, if the driver is someone of average or less-than-average height, he will be able to sit upright, have his head positioned for a reasonable amount of eye relief, and still enjoy good legroom. </div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgAlnSImaJpwOfBxbn51QjIlSCAxzOyfNUPhT_duVAB5OO8TgP0FPSmw0oFsLDaUZDCcKk8KeJSn-Pd9dUVaDPKJQx5FJhRDKS53KEpneMqYUrDsX7PK1axH5HuF8k1URpbQKxS-sCjz1qei7Jqy_LoEbbqG8efP1OwG1W2WAA1YcMc9dJhTlQlH7mlRw/s1348/t-72%20driver%20trainer%206.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1078" data-original-width="1348" height="256" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgAlnSImaJpwOfBxbn51QjIlSCAxzOyfNUPhT_duVAB5OO8TgP0FPSmw0oFsLDaUZDCcKk8KeJSn-Pd9dUVaDPKJQx5FJhRDKS53KEpneMqYUrDsX7PK1axH5HuF8k1URpbQKxS-sCjz1qei7Jqy_LoEbbqG8efP1OwG1W2WAA1YcMc9dJhTlQlH7mlRw/s320/t-72%20driver%20trainer%206.png" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8fjM5Yx8e5h9aB_ZLKvfz5WSImnyhuCivchSKBCdd1tWzYovy7J6AKvjlrk2PYIYMW69dblGiyvwuFeB2uVU9HGShE9F1I4YkMbp6SRZWhYzcv2_gEKO-MLIidvF1nuvOQXIvI_eZF59xmJqnLdiLtW2o3mKhEDz_8JBdOPBdHmOg2jgq2j4bj1Yuhw/s1475/t-72%20driver%20trainer%207.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="934" data-original-width="1475" height="254" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8fjM5Yx8e5h9aB_ZLKvfz5WSImnyhuCivchSKBCdd1tWzYovy7J6AKvjlrk2PYIYMW69dblGiyvwuFeB2uVU9HGShE9F1I4YkMbp6SRZWhYzcv2_gEKO-MLIidvF1nuvOQXIvI_eZF59xmJqnLdiLtW2o3mKhEDz_8JBdOPBdHmOg2jgq2j4bj1Yuhw/w400-h254/t-72%20driver%20trainer%207.png" width="400" /></a></div><div><br /></div></div>
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However, although the driver's station is ergonomically inferior to a number of more modern Western tanks, it must still be considered satisfactory as it facilitated the work of the driver, with the only exception being that the location of the instrument panel was less convenient for the driver than if it were placed directly underneath and behind the front-facing periscope. Even so, this was not uncommon for many tanks, particularly tanks with steering wheels instead of tillers. In many regards, the T-72 driver's station was superior to a number of other tanks. </div><div style="font-weight: normal;"><br /></div>
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In terms of comfort, judged by the dimensions and layout of the station, the driver's station of a T-72 can be rated more highly than the Leopard 1, T-54, T-62, and M60A1. The main improvement of the T-72 driver's station over other tanks with the same seating layout is the increased legroom. When compared to an M60(A1), for example, the driver's station of a T-72 is more conducive to driver comfort, particularly over longer periods of time, due to the pedals being located on a slightly lower level than the driver's seat. The image on the left below is taken from the report "Human Factors Evaluation of the Tank, Combat Full Tracked: 105mm Gun, M60". Similarly, the Leopard 1 suffers from the same issue with the pedals being located on a higher level than the seat, although there is much more legroom than in the M60(A1). This can be seen in the image on the right below, taken from the report "<a href="https://www.researchgate.net/publication/277857649_Counter-IED_Initiative_PPE_Horizon_0_Phase_1_Protection_Versus_Performance_Preliminary_Trade-off_Analysis_Behavioural_Task_Analysis_Initiative_d'epi_pour_la_Lutte_aux_IED_-_Horizon_0_Phase_1_-_Analyse">Counter-Ied Initiative Ppe Horizon 0: Phase 1 Protection Versus Performance Preliminary Trade-off Analysis</a>", and in <a href="https://www.defencetalk.com/military/photos/cutaway-of-a-leopard-1tank.11245/full">various cutaways</a>. </div>
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<span style="font-weight: normal;"><span style="font-weight: 400;">The driver enters and exits his station via an oval hatch located centrally on the hull axis, underneath the cannon. When seated, the hatch would be directly above the driver's head. The hatch is 530mm in width (21 inches) and 390mm long (15 inches). This roughly meets the U.S Army human engineering requirements for an overhead hatch, as it is 2 inches narrower than mandated but it is also longer by 2 inches, so while it might not meet the requirements to the letter, the area of the opening is the same. In terms of the maximum dimensions, the hatch has effectively the same length as an M60 driver's hatch (394mm) but it is significantly narrower (734mm), although it is necessary to note that the M60 driver's hatch is a semicircular shape and not rectangular, so a direct comparison of maximum width is not necessarily meaningful. </span></span></div>
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<span style="font-weight: normal;"><span style="font-weight: 400;">The driver's hatch of a T-72 is around 50mm thick as shown in the photo below provided by Jarosław Wolski, and there is a 50mm-thick layer of "Podboi" anti-radiation lining underneath it. Overall, this level of protection for the driver is quite exceptional, although not infallible. At the time, there were no other tanks that provided their drivers with an equivalent amount of overhead protection.</span></span></div>
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<span style="font-weight: 400;">Although it is not particularly soft, the layer of "Podboi" has the secondary function of protecting the driver's head. A hard knock on a stiff plastic pad would not be comfortable, it would certainly be preferable to a knock on bare steel. The rubber seals of the hatch make it watertight to rain and for certain depths of water such that fording will usually not drench the driver. Unfortunately, the seals on the TNPO-168V periscope are not nearly as dependable. Being mostly</span> watertight, the tank can ford streams as deep as 1.2 meters or deeper without the danger of excessive water ingress. However, waterproofing clay must to be applied before driving the tank underwater as the seals are simply not that strong.</div>
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<span style="font-weight: normal;">Unless he is a contortionist, the driver can only enter or exit through his hatch when the cannon is elevated or if the turret is turned to one side so that the cannon barrel is not directly above it. As part of the safety measures incorporated in the turret rotation control system, the turret rotation drive is electronically blocked when the driver's hatch is open in order to prevent accidents when the driver is driving with his head out of the hatch or when he is entering or exiting his station. For T-72 models equipped with the "Tucha" smokescreen system, the launching of smoke grenades is also automatically blocked when the hatch is open, as the opening of the hatch also opens the electric firing circuit. </span></div><div style="font-weight: normal;"><span style="font-weight: normal;"><br /></span></div><div style="font-weight: normal;"><span style="font-weight: normal;">Furthermore, there is an emergency turret traverse switch on the left of the driver's periscope that, when pressed and held, will control the turret traverse drive to move the turret to the left (counter-clockwise) at the maximum speed</span>. The driver observes if the gun has passed over the top of the hatch or through the periscopes, whereby he stops the turret rotation and then exits the tank. This feature is integrated on all stabilizer models implemented in the T-72, including the 2E28M, 2E42-2 and 2E42-4. It is important to note that this feature can be used as long as there is power to the turret, and is independent of whether the stabilizer is on or off. To bring power to the turret, the driver can simply turn on the master power switch next to the battery pack to his left. This allows the driver to exit without relying on anyone in the turret. Moreover, there is no danger of the turret being locked with the gun over the driver's hatch, because the turret traverse lock has only two specific locking positions, with either the gun offset to the right or pointed to the rear.</div>
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<span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;">Additionally, the tank has a warning system integrated with the turret stabilizer that detects if the 125mm gun is overhanging the width of the hull, which increases the virtual width of the tank. This is important for avoiding collisions with obstacles, especially in narrow paths. The system indicates which side the gun overhangs the hull by two warning lights on the lower left and right corners of the driver's periscope cutout.</span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;">Overall, the number of safety features provided for a T-72 driver was unmatched by any foreign tank at the time it entered service.</span></span></div><div style="font-weight: normal;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></div>
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<span style="font-size: large;">PERISCOPES</span></h3>
<span style="font-weight: normal;"><span style="font-weight: normal;"><br /></span></span><span style="font-weight: normal;"><span style="font-weight: normal;">The driver is provided with a single forward-facing TNPO-168V periscope to facilitate driving. It is
a very wide periscope measuring 267mm across - much wider than the driver's head - with</span></span><span style="font-weight: normal;"><span style="font-weight: normal;"> a total field of view of 138 degrees in the horizontal plane and 31 degrees in the vertical plane. Naturally, there is a great propensity for water to wash over the driver's periscope when the tank s driven into a mudhole or if it is fording deep water obstacles, hence the presence of a V-shaped splash guard on the upper glacis. </span></span>The large mudguards on the fenders also help in this regard, as well as helping to reduce the amount of dust blown up from the tracks and into the periscopes or the driver's face. To prevent the ingress of water into the driver's compartment, the slot for the TNPO-168V is double-sealed with two rubber gaskets.</div>
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<span><span style="font-weight: normal;">The single large TNPO-168V periscope provides the driver with an uninterrupted view of the landscape and allows him to see both corners of the hull. It is one of two possible design solutions for a centrally-seated driver. The alternative is to have three smaller periscopes, one to see forwards and two to see each corner. This was used in tanks like the M48 Patton, T-80, early versions of the T-64 (Object 432), and many others. If the driver's station is offset to the left or right, only two small periscopes are needed. One to see forward and the adjacent corner of the hull, and the other to see the opposite corner of the hull. This was the layout used in the T-54 and T-62 series.</span></span><br />
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<span><span style="font-weight: normal;">A Hungarian contact with extensive experience driving demilitarized tanks remarked to the author in an email conversation that the TNPO-168V periscope was so wide that it was "<i>like a small window from inside</i>". <a href="https://www.youtube.com/watch?v=GjcVK6vc3wg">This video</a> showing the view through the TNPO-168V from inside the tank gives a good idea of the wide view of view provided by the periscope. </span></span>Another good example of the good visibility from the TNPO-168V periscope is demonstrated in this video (<a href="https://www.youtube.com/watch?v=DDe2aEsPN8U">link</a>).</div>
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<br /></div><div style="font-weight: normal;"><br /></div><div style="font-weight: normal;">A spare TNPO-168V is stowed in a bin next to the driver's seat for quick replacements in case the installed periscope is knocked out by fragments or gunfire during combat. To replace the periscope, the clamping nut securing it to the mount is loosened, and then it can simply be pulled out. </div>
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<span>Other than the TNPO-168V, two TNPA-65A periscopes are embedded in the driver's hatch, one looking in the 10 o'clock direction (50 degrees left) and the other in the 1 o'clock direction (15 degrees right).</span><span> To use them, the driver needs to look upwards. This feature was inherited from the T-64A. obr. 1972. Both periscopes increase the field of view of the driver, but the periscope on the right also serves as a convenient backup in case the main TNPO-168V periscope is destroyed by gunfire or fragments, and there is not enough time to swap it out with a spare.</span></div>
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<span>Because these supplementary periscopes are located in the hatch rather than the edge of the upper glacis like the TNPO-168V, they allow the driver to see over the sides of the hull, not just the corners. As they allow the driver to see obstacles next to the tank, they are useful when negotiating tight spaces such as a narrow street or when driving through a forest. In such circumstances, the tank does not move at high speed so it is permissible for the driver to momentarily take his eyes off the main periscope.</span><br />
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<span><br /></span><span>The total field of view from a TNPA-65A is 140 degrees in the horizontal plane and 35 degrees in the vertical plane. This is very slightly larger than the field of view from the TNPO-168V, despite the smaller physical size of the TNPA-65A. This is due to its very short height, and thus, its low periscopicity. The short height of the periscope allows it to be embedded entirely inside the hatch which has a total thickness of around 100mm including its anti-radiation lining.</span></div>
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With these three periscopes, the total horizontal field of view of the driver is 205 degrees, consisting of an arc spanning 85 degrees to the right and 120 degrees to the left. The driver's visibility greatly increased compared to the T-55 and T-62 and the practical driving speed of the tank increased accordingly. Driving with the hatches closed also became safer, and the driver could more easily navigate difficult terrain without the help of the commander.</div>
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<span><span style="font-weight: normal;">Like most of the other periscopes on the T-72, the TNPO-168V is heated through the RTS-27-4A heater system. The four ribs on the upper glacis between the periscope and the V-shaped splash guard are designed to prevent bullets from ricocheting into the TNPO-168V aperture window.</span></span></div>
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<h3 style="margin-left: 1em; margin-right: 1em; text-align: center;">
<img border="0" height="478" src="https://1.bp.blogspot.com/-HK-lAZh8G7w/VRgMEFpRsRI/AAAAAAAABgU/4MmA2akY5hU/s640/tnpo-168.png" width="640" /></h3>
<div style="text-align: left;"><span><span style="font-weight: normal;"><br /></span></span></div><div style="text-align: left;"><span><span style="font-weight: normal;">Like several Soviet tanks preceding it, the T-72 features two signal lamps on each side of the periscope viewing window, designed to inform the driver when the tank gun is traversed over the front corners of the hull on either side. This is so that the driver is aware of the position of the gun, and that he should not drive the tank through a narrow obstacle that the tank would normally be able to pass through without first informing the gunner.</span></span></div><div style="text-align: left;">
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<span><span style="font-weight: normal;">There is a horizontal handlebar below the periscope, used as part of the locking mechanism to secure the periscope in place.</span></span> The position of the periscope in the driver's station can be better appreciated by looking at the demonstration models shown in the photos below (photos from <a href="https://worldoftanks.ru/ru/news/common/voennaya_akademia_part2/">Wargaming</a> and <a href="http://itinerantdispatches.tumblr.com/post/132688356330/cutaway-t-72">Itinerant Dispatches</a>).</div><div style="text-align: left;">
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<span style="font-weight: normal;"><br /></span><span style="font-weight: normal;">When not in use, the TNPO-168V periscope is stowed away in its aluminium container.</span><br />
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<span>An aerosol periscope window blower is installed to ensure that the exterior window of the periscope is free of debris. The system consists of a cleaning fluid reservoir, the piping system and a connection to the tank's compressed air bottles. </span><span>The mechanism for this system is shown in the drawings below. </span>As the air bottles are pressurized to 150 kgf/sq.cm (14.7 MPa or 2,133 psi), the aerosol cleaning system is extremely powerful. To use it, the driver presses the lever button for an air release valve, marked (7) in the drawing shown below on the air distributor unit, which produces a jet of air that draws the cleaning fluid from the reservoir that is ducted to an outlet at the periscope window, thus producing an aerosol that is sprayed at high pressure down the selected periscope window. </div><div style="text-align: left;">
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<div class="separator" style="clear: both; text-align: left;">In the summer, water is used, and in the winter, water with antifreeze is used. The reservoir of cleaning fluid is a container installed in the nose of the glacis, behind the driver's pedals, making efficient use of the otherwise wasted volume. 7 liters of fluid are carried, and the reservoir can be topped up via a refilling pipe with a filler neck next to the driver's periscope. In the summer, when water is used as the cleaning fluid, the reservoir can serve as a source of drinking water for the crew. There is no tap, but there is a drainage plug on the bottom edge of the reservoir allowing the water to be drained into a flask. </div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">Alternatively, the system can be used as an air jet cleaner when washing the periscope with an aerosol spray is undesirable. In particular, dust and snow should only be cleaned by air. It can also used to blow off rain droplets since the periscope does not have a conventional mechanical windscreen wiper. Because of this, the constant supply of air from the internal air compressor in the engine compartment is invaluable in certain weather. The driver activates an air jet by twisting a valve on the air distributor unit. </div>
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<span><span><div style="font-weight: normal; text-align: left;"><span><span style="font-weight: normal;"><br /></span></span></div><h3 style="text-align: left;"><span><span style="font-size: large;">NIGHT VISION PERISCOPE</span></span></h3><br /></span></span><span style="font-weight: normal;"><span>For night time driving, the driver is provided with a TVNE-4B passive-active binocular periscope with a pair of Gen 2 light intensifier module</span></span><span><span style="font-weight: normal;">. </span></span><span style="font-weight: normal;">The periscope runs on the tank's 27 V power supply system, and can run continuously for eight hours. </span><span style="font-weight: normal;">It is typically kept in its proprietary aluminium box and stowed away by the driver until it is needed.</span><br />
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<span><span style="font-weight: normal;">The periscope is much narrower than the TNPO-168V, but the TVNE-4B still provides a decent field of vision as well as an acceptable viewing distance. TVNE-4B stands for "Tank Driver's Passive Night Vision Optic, model 4 with built-in power supply". According to the book "<i>Optical Night Vision Devices For Armoured Vehicles</i>" by S.A. Belyakov and published by the Russian Ministry of Defence, TVNE-4B provides a viewing distance of up to 60 meters in the passive mode under ambient light conditions of 0.005 lux (moonless, starlit night), and 100 meters in the active mode using the FG-125 IR headlight. </span></span></div><div style="text-align: left;"><span><span style="font-weight: normal;"><br /></span></span></div><div style="text-align: left;"><span><span style="font-weight: normal;">The active infrared mode of vision is very similar to both the earlier standard TVN-2 active IR periscope and the American M24 active IR periscope, but the passive mode offers inferior range compared to the contemporary AN/VVS-2 passive periscope, which offers a <a href="https://www.globalsecurity.org/military/library/policy/army/fm/44-43/Appg.htm">viewing distance of 150 m</a>. In terms of overall quality and functionality, the TVNE-4B is closer to the obsolete M24 than the AN/VVS-2. The <a href="https://upload.wikimedia.org/wikipedia/commons/4/40/%D0%A2%D0%92%D0%9D-5.jpg">TVN-5</a> closely mimicked the AN/VVS-2 and offered better performance, but came much later and is used only in limited numbers, so we will not be examining it in this article.</span></span><br />
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<span><span style="font-weight: normal;"><br /></span></span><span><span style="font-weight: normal;">The periscope can be directly inserted into the periscope slot for the TNPO-168V without any modifications, but a plastic spacer is slipped on top of the aperture head to give it a proper fit and to prevent water and mud from ingressing through the gaps. </span></span><span><span style="font-weight: normal;"><br /></span></span>
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<span><span style="font-weight: normal;">The plastic spacer can be seen at the very top of the exploded diagram below. The periscope only has a horizontal field of view of 36 degrees and a vertical field of view of 33 degrees. This is a minor improvement over the standard TVN-2 periscope of earlier Soviet medium and heavy tanks from the 1950's to 1960's, and adding on to that, the driver also has depth perception. Most night vision periscopes have two eyepieces that are merged into a single objective lens, so the user lacks stereoscopic vision and thus lacks depth perception. This makes it more difficult for a driver to judge the distance between his tank and an obstacle in front of him, and to judge the size of the obstacle to determine whether it is surmountable. By providing stereoscopic vision and a good viewing range, the TVNE-4B improves the overall safety of driving at night.</span></span><br />
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<span><span style="font-weight: normal;">Like previous night vision periscopes for Soviet medium and heavy tanks, the TVNE-4B can be installed in a special external frame outside of the tank to provide the driver with a means of vision at night when driving outside his hatch. The frame is mounted on three pegs on the hull roof between the TNPO-168V periscope hood and the driver's hatch and the periscope is placed inside. The mounting pegs can be seen in any photo of the T-72 driver's hatch.</span></span><br />
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<span><span style="font-weight: normal;">By being able to use the night vision periscope outside of the hatch, the driver has better overall situational awareness without sacrificing his ability to see far ahead of the tank. This improves the average speed of a unit during long marches and vastly reduces the chance of a road accident, as the driver would be able to see the marker lights of tanks that are not directly in front of his own.</span></span>
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<span><span style="font-weight: normal;">Although TVNE-4B technically only has a single small IR headlight for illumination, it may also pick up infrared light from the turret's three IR spotlights. The single FG-125 IR light located just beside the auxiliary/night sight on the turret is actually meant to augment the driver's viewing distance when operating in the active imaging mode and also to provide a source of light when the tank is wading across water obstacles. The periscope has 1.12x magnification. </span></span><span style="font-weight: normal;">Compared to the <a href="http://www.dtic.mil/dtic/tr/fulltext/u2/a018187.pdf">AN/VVS-2 passive driver's periscope</a>, the TVNE-4B appears to have poorer performance in most respects, with one notable exception being that it provides stereoscopic vision.</span><br />
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<span style="font-weight: normal;">The FG-125 IR headlight and FG-127 blackout headlight on the upper glacis of the tank are protected by a simple brushguard, and there are two sheet metal mudguards attached to the primary track mudguard to help prevent mud and dust thrown up from the tracks from befouling the headlights. These mudguards seem to be rather flimsy and are often observed to be absent. When the mudguard was changed to a T-80-style rubberized design on the T-72B (Object 184), the mudguards were modified as well. </span><span style="font-weight: normal;"><br /></span>
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<span><span style="font-weight: normal;">There is an accessory driving dome with a detachable windshield that may be installed to the outside of the hatch. Its main purpose is to protect the driver from bugs and dust while driving in non combat conditions. When driving in rain or snow, the hood of the dome covers the driver. The windshield is kept from misting by a heating system.</span></span></div><div style="text-align: left;"><span><span style="font-weight: normal;"><br /></span></span>
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<span><span style="font-weight: normal;">The driver of a T-72 Ural and T-72A sits on a bucket-type seat with removable bolsters on each side. </span></span>To adjust the seat in height, a lever on the left of the seat is squeezed and the handle is pulled back. This releases the locking mechanism holding the seat on a pair of toothed racks, and a built-in torsion spring raises the seat, or the driver may sit on the seat to lower it. When lowered, the seat is not a flat surface, but is instead tilted rearward like a car seat to support the thighs of the driver. To adjust the seat forwards or backwards, a lever under the seat cushion can be pulled to release the locking mechanism and allow the driver to shift the seat. This allows it to accommodate persons of a wider range of height, and also to raise the driver high enough to peek over the hatch. The mechanism slightly pivots the driver forwards when the seat is raised so that when the seat is raised to its maximum setting, the driver is in a more convenient position to put his head out of the opening of his hatch and the positioning of the driver's legs to reach the pedals remains largely unchanged, as the increase in height is offset by the seat being moved forward. The pivoting mechanism of the seat also adjusts its angle, eliminating its tilt and making it flat, which is more convenient for the driver with the raised seat. Depending on his height, the driver can adjust his seat forwards or backwards and up or down to best suit his bodily proportions. When the seat is set to its lowest setting, the driver is positioned as far back as possible from the pedals so that his legroom is maximized, thus allowing even tall drivers to drive the T-72 comfortably.</div><div style="text-align: left;"><span><span style="font-weight: normal;">
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The backrest of the seat can be reclined to three different angles or folded forward or backward. Folding the backrest backward gives the driver more room to crawl into the turret or may be used to give a more comfortable reclined position to sleep in. A cushion is issued as part of the T-72 parts kit, and it can be used to pad the seat or used as the driver's pillow. To use the escape hatch, the backrest may be removed and placed aside. The driver of a T-72 gets quite a lot of legroom, even more than the commander's and gunner's stations.</span></span><br />
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<span style="font-weight: normal;"><span>The seat for the driver of a T-72B is slightly modified from the original type. The bolsters of the bucket type seat were removed to allow the driver to wear an I-1 radiation vest more comfortably, but aside from that, the frame, backrest angle adjustment mechanism and seat elevation mechanism were left unchanged. To further enhance the radiation protection for the driver, anti-radiation panels were added on the back surface of the backrest, as shown in the drawing below.</span></span><br /><span style="font-weight: normal;"><span style="font-size: small;"><br /></span></span>
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<span><span style="font-weight: 400;">After experiences in Chechnya showed the vulnerability of tanks to large IEDs, some T-72BA tanks featured additional driver safety features. A new seat was installed and a strut was installed between the floor and the ceiling to prevent the hull belly from deflecting upwards and crushing the driver. There were also additional stiffening structures for the hull floor underneath the driver's seat to increase its rigidity. There was also the option of installing additional spaced armour for the hull underneath the front part of the hull that extends from the end of the lower glacis to behind the escape hatch behind the driver's seat. </span></span><br />
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<span style="font-weight: normal;">In 1987, a new suspended driver's seat was implemented in T-72B tanks as a response to combat experiences of the Soviet Army in Afghanistan, where the threat of IEDs revealed the inadequate mine protection of tank drivers. The new seat is shown in the drawing below. It is suspended from the hull ceiling by two heavy pressed steel plates. The seat itself is the same as an ordinary T-72B driver's seat, only that it is mounted to a special frame attached to the suspenders. According to the specifications of the T-72B3, tanks which did not have the suspended seat are upgraded with the seat during the modernization process.</span><br />
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<span style="font-weight: normal;">By suspending the driver's seat from the ceiling, not only is the driver protected from the shock of an explosion underneath the tank and the subsequent deflection of the hull belly, but he is also isolated from the vibrations of the hull belly from the engine and the suspension. This grants him a more comfortable driving experience. However, the seat is not completely isolated from the hull floor as there are still two bolts securing the front end of the seat mounting frame to the hull floor.</span><br />
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<span style="font-weight: normal;">The suspended seat can be seen in the two photos below.</span><br /><span style="font-weight: normal;"><br /></span>
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<span style="font-weight: normal;">The driver's <a href="http://img.allzip.org/g/227/orig/11976964.jpg">two-liter aluminium bottle</a> can be seen in the photo on the right, behind the B-3 power supply unit.</span><span style="font-size: small; font-weight: normal;"> </span>Like the commander and gunner, the driver's "air conditioning" comes in the form of a DV-3 fan.<br />
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<span style="font-weight: normal;">All of the driving-related indicator gauges and many driving-related switches are placed on an instrument panel to the driver's left, like in previous tanks like the T-62, T-54 and T-34. The placement isn't exactly convenient, but looking at them while driving (in any tank) isn't really very necessary anyway. Looking at the instrument panel is generally only necessary for tasks that are normally unneeded when the tank is moving, such as when the driver is troubleshooting some issue. Furthermore, there was a green light on the side of the ceiling that would light up when the turret rotates. Another green light would light up if the engine air filter became clogged. Another light would light up if the intercom got disconnected. The location of these lights are all in the driver's peripheral vision. The location of these lights are all in the driver's peripheral vision, so the driver would be informed without him needing to manually check the instrument panel.</span><br />
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<span style="font-weight: normal;">Behind the instrument panel is the front left hull fuel tank. The fire extinguishers are for the hull's
automated firefighting system is located next to it, and four 6STEN-140M lead-acid batteries are placed behind the front left hull fuel tank. The location of the batteries is shown in the drawing below. The </span>6STEN-140M is a 12 V battery comprised of six lead-acid cells held in a wooden box, with connector plates built into the lid to link the cells and provide connection terminals. The battery contains a total of 8 liters of electrolyte. <br />
<br /><br /><div style="text-align: center;"><img border="0" data-original-height="1089" data-original-width="1600" height="271" src="https://1.bp.blogspot.com/-iYoOmUjmQ-g/XhuDbAb0NfI/AAAAAAAAP40/XCAWQPKvDEYp-KkCYWl7dnMqIcOMsKzUACLcBGAsYHQ/w400-h271/accumulators%2Bin%2Ba%2Bt-72.png" style="color: #0000ee;" width="400" /></div><div style="text-align: left;"><br /></div><div style="text-align: left;"><br /></div><div style="text-align: left;">The batteries are mounted in a simple rack. The overall dimensions of each battery are 587 x 238 x 239mm, and so overall, a volume of around 0.134 cubic meters had to be allocated for the battery rack. Above it is a number of fittings for the power distribution box and various connectors, linking the batteries to the alternator on the engine. In the event that the front armour of the tank is perforated, the batteries may serve as an additional barrier to protect the ammunition behind it from fragments, in addition to the front left fuel tank.</div><div style="text-align: left;"><br /></div>The four 6STEN-140M batteries are split into two pairs which are wired together in series, and these two pairs are wired in parallel, thus supplying a nominal 24 V operating voltage. The nominal charge capacity of each battery is 140 Ah in a 20-hour discharge mode, or 126 Ah in a 10-hour discharge mode. The total charge capacity of the four batteries is 252-280 Ah. The total power capacity is 7.56 kWh. </div><div style="text-align: left;"><br /></div><div style="text-align: left;">The T-72B uses four improved 12ST-85R lead-acid batteries in a different wiring scheme, where all four batteries are wired in parallel because the 12ST-85R has an operating voltage of 24 V. It has an improved design comprised of 12 lead-acid cells in a fiberglass box, with a total electrolyte content of 10 liters. It has a nominal charge of 85 Ah in a 20-hour discharge mode, or 80 Ah in a 10-hour discharge mode. The total charge capacity increased to 320-340 Ah. The total power capacity is 9.18 kWh. With any battery, the sustainable capacity is less than the nominal capacity, as the manual specifies that the batteries should not be discharged more than 50% in summer conditions and they should not be discharged more than 25% in winter conditions. This guideline is specified to limit premature battery degradation as much as possible.</div><div style="text-align: left;"><br /></div><div style="text-align: left;"><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-iYoOmUjmQ-g/XhuDbAb0NfI/AAAAAAAAP40/XCAWQPKvDEYp-KkCYWl7dnMqIcOMsKzUACLcBGAsYHQ/s1600/accumulators%2Bin%2Ba%2Bt-72.png" style="margin-left: 1em; margin-right: 1em;"></a><a href="https://1.bp.blogspot.com/-Zf32tMv6UI8/YDargnbe6pI/AAAAAAAASy0/bBNL3yoJKBIKMtw6CnMJio_8Sjus3E3ggCLcBGAsYHQ/s2048/battery%2Brack.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="400" src="https://1.bp.blogspot.com/-Zf32tMv6UI8/YDargnbe6pI/AAAAAAAASy0/bBNL3yoJKBIKMtw6CnMJio_8Sjus3E3ggCLcBGAsYHQ/w300-h400/battery%2Brack.png" width="300" /></a><a href="https://1.bp.blogspot.com/-hHwIlmnFrL8/YDar_nmujwI/AAAAAAAASy8/hUWwkWdS5oIIbV3O-aF36VQ0fipZ5DEWwCLcBGAsYHQ/s2048/accumulator%2Brack%2Bcover.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1632" height="400" src="https://1.bp.blogspot.com/-hHwIlmnFrL8/YDar_nmujwI/AAAAAAAASy8/hUWwkWdS5oIIbV3O-aF36VQ0fipZ5DEWwCLcBGAsYHQ/w319-h400/accumulator%2Brack%2Bcover.png" width="319" /></a></div>
<span style="font-size: small; font-weight: normal;"><br /></span><br /><span style="font-weight: normal;">The mass of each battery is 62 kg for the 6STEN-140M model and 72 kg for the 12ST-85R model, and both are 10 kg less if not filled with electrolyte. Due to the enormous mass, it is extremely laborious to replace them through the driver's hatch. It is most convenient to undertake such a task if the turret is lifted from the hull, but otherwise, using the escape hatch is often considered the best option. When using the driver's hatch to replace all four batteries, the process nominally takes 40 minutes.</span><br />
<span style="font-weight: normal;"><br /></span><span style="font-weight: normal;">It is not known how long the tank can fight on battery power alone. For example, the two 12-volt batteries in the Challenger 1 turret have a total charge capacity of 100 Ah and allow the tank to operate in a silent watch mode for a nominal duration of 8 hours. Full discharge of the batteries is not needed to achieve this. The turret of a T-72 requires less power than a Challenger 1 and there is a larger battery charge capacity available. The proportions indicate that a T-72 should be able to carry out a silent watch operation for 24 hours or more without fully discharging the batteries (which would induce premature wear). As it is possible to start the engine pneumatically, the batteries can be discharged to their minimum limit with no real consequences other than the shortening of the battery lifespan. Once the engine is started, the air reserve is replenished by a compressor and the batteries are recharged. It is calculated that the 10 kW generator of a T-72 will take between half an hour to an hour to fully recharge the batteries.</span><br /><br />
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<span><span style="font-weight: normal;">There is a GPK-59 gyroscopic compass for directional navigation located next to the clutch pedal. It is particularly useful when driving underwater as there are no landmarks for the crew to navigate by. The use of gyrocompasses can perhaps be labeled as a rudimentary form of an Inertial Navigation System (INS), advanced versions of which are often present in modern combat vehicles due to their independence from outside input contrary to a GPS-based navigation system. </span></span><br />
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Due to length restrictions, this article has been divided into two parts. Part two is <a href="http://thesovietarmourblog.blogspot.com/2017/12/t-72-part-2.html">available here</a>.</h3>
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<h2 style="text-align: center;">
BTR-80</h2>
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<span style="font-size: medium;">T</span>he BTR-80 is an amphibious armoured personnel carrier, and is the successor to the BTR-70 and BTR-60 designs. Its inception was closely connected to the events unfolding in Afghanistan at the time, but the design of the vehicle had minimal innovation. The BTR-80 follows the traditional BTR layout; three sections of the vehicle, divided into the driver and commander's section at the front, passengers' and gunner's section in the middle, and the compartmentalized powerplant section at the rear. All the vehicle's occupants share a common space within the vehicle, and exit via side doors - a huge improvement over the side hatches of the BTR-70.</div>
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<span style="font-size: large;">COMMANDER'S STATION</span></h3>
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The commander in a BTR-80 would be the squad leader of a motorized infantry squad consisting of 8 men, including himself. While in the BTR-80, his job is to scan for possible threats and determine the next course of action.<br />
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The commander has a TKN-3M day/night binocular periscope with an accompanying OU-5-1 IR spotlight at his disposal, along with three TNPO-115 periscopes. Two of the periscopes flank the TKN-3M aperture and one is aimed to the right of the commander. The commander does not have a cupola, but the TKN-3 is is mounted in a ball joint housing to enable viewing in elevation and azimuth. The OU-5-1 IR spotlight is directly attached to the TKN-3M and will move with it. The photo below (from ambbrescia.com website) shows a TKN-3M with a heavy layer of cosmoline in its ball mount in a preserved BTR-80.<br />
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The TKN-3M has a fixed 5x magnification in the day channel, and a field of view of 10 degrees. The maximum target identification range is around 3000 m at daytime. The night channel has a 3x maximum magnification and a field of view of 8 degrees. The active mode requires the use of the OU-5-1 IR spotlight which supplies infrared light needed to illuminate the target.<br />
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<tr><td class="tr-caption" style="font-size: 13px;">TKN-3 periscope aperture with OU-5-1 IR spotlight attached to the same rotating block</td></tr>
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Due to the simple lack of an electronic fire control system for the weapons in the BPU-1 turret, the BTR-80 does not provide the possibility of target designation with the TKN-3.<br />
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<tr><td class="tr-caption" style="font-size: 13px;">TKN-3 in ball joint housing</td></tr>
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The commander has access to the R-123 radio. As of today, it is woefully obsolete. Enemy troops could easily listen in to any and all communications sent through these radio sets, which proved to be a fatal weakness during the Chechen campaign. The R-123 radio had a frequency range of between 20 MHZ to 51.5 MHZ. It could be tuned to any frequency within those limits via a knob, or the commander could instantly switch between four preset frequencies for communications within a platoon. It had a range of between 16km to 50km. The R-123 had a novel glass prism window at the top of the apparatus that displayed the operating frequency. An internal bulb illuminated a dial, imposing it onto the prism where it is displayed. The R-123 had a relatively advanced modular design that enabled it to be repaired quickly by simply swapping out individual modules.<br />
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<tr><td class="tr-caption" style="font-size: 13px;">Commander's workstation. Note the conveniently placed firing port.</td></tr>
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GUNNER'S STATION</span></h3>
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The gunner is seated inside the small one-man turret. The turret reaches the same level of armour protection as the hull and weighs 540 kg when fully loaded with all of its standard equipment. The turret race ring diameter is 1,075mm. The size of the turret is such that only a small part of the gunner's head is physically inside it, and the KPVT machine gun occupies the entire length of the turret, as shown in the drawing above. Due to the location of the eyepiece of the gunner's sight, his eyes are level with the turret ring and only the top part of his head intrudes into the space inside the turret. As such, the small size of the turret itself does not imply that the gunner's station is particularly cramped, especially considering that there is no turret basket around the gunner's seat.</div>
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<a href="https://2.bp.blogspot.com/-w_IHr26Qd1g/XLDEzW0pKkI/AAAAAAAANqM/K_YQsIIf89cCEsQfdAkGDMPtywhyYXlEwCLcBGAs/s1600/turret%2Btop%2Btop%2Bview.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1133" data-original-width="1600" height="452" src="https://2.bp.blogspot.com/-w_IHr26Qd1g/XLDEzW0pKkI/AAAAAAAANqM/K_YQsIIf89cCEsQfdAkGDMPtywhyYXlEwCLcBGAs/s640/turret%2Btop%2Btop%2Bview.png" width="640" /></a></div>
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For general visibility, the gunner is furnished with only two periscopes in addition to his periscopic sight to view the outside world. There is a single TNP-205 general vision periscope placed next to the 1PZ-2 sight, and one TNPT-1 rear-view prism directly above him on the turret ceiling. This pitiful combination means that the gunner has very little independence in detecting targets at short to medium distances, and even less in detecting targets located above the vehicle. This was somewhat offset by the abundance of observation devices in the passenger's compartment and the good visibility from the commander's station, but the height of the turret makes it a better vantage point than the hull for surveillance purposes. Even so, this arrangement was already enough to make the fully-enclosed turret a much better alternative to a pintle-mounted machine gun with a gunshield.</div>
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The photo on the left below (credit to Vitaly Kuzmin) shows the gunner's station of a modernized BTR-80, as indicated by the TKN-4GA-01 sight. The photo on the right shows an original BTR-80 turret with the old 1PZ-2 sight. Note the TNPT-1 rear-view prism on the turret ceiling and the dome light placed conveniently above the ammunition boxes of the KPVT and PKTM, making it easy for the gunner to load and service the machine guns in darkness.</div>
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The gunner is seated on a simple suspended seat with an oblong cushion. The backrest can be adjusted in height, the seat can be adjusted forwards and backwards, and the entire seat frame can be raised or lowered from its mounting point at the turret ring as shown in the drawing on the left below. The seat is not very comfortable for long periods as it has no padding, and there is no footrest nor any form of shielding to protect the gunner's legs as he spins around when the turret is rotated. Being seated on a seat that is suspended above the floor of the hull, the gunner has a better chance of surviving a landmine blast underneath the vehicle, which is also aided by his central location in the BTR. The travel lock for the turret is located near the gunner's left shoulder, and BTR-80s that are equipped with the 902V smoke grenade system have a control box located next to the turret travel lock. The mechanism for opening and closing the protective shield for the 1PZ-2 gunsight is located near the roof of the turret, directly above and to the left of the 1PZ-2 sight housing.<br />
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It is worth noting that the KPVT and PKT machine guns installed in the turret are well balanced at their center of gravity, but when the ammunition boxes are loaded onto the cradle, the entire assembly becomes somewhat rear-heavy. To counteract this, a balancing spring was installed, connecting the top of the gun cradle to the ceiling of the turret. With this, the gunner is able to smoothly elevate the weapons with only a light effort.<br />
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Gun elevation and turret traverse are done manually with the use of two manually-operated handwheels. The turret traverse handwheel also has the solenoid triggers for the KPVT and PKTM machine guns. The electrical system for the firing of the weapons are located underneath the weapon mounts.<br />
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A motivated gunner can slew the turret at a very quick speed, but the lack of powered traverse and stabilization is a drawback nonetheless. As an armoured personnel carrier that is still in service in the present, the lack of powered traverse was a noted grievance of BTR-80 gunners according to a TV Zvezda interview. Still, one could argue that the protection of a full turret like the turret makes it inherently superior to having an exposed pintle-mounted machine gun on the roof of the vehicle, as in the case of the M113 and earlier versions of the BTR-60.<br />
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<h3>
<span style="font-size: large;">SIGHTING COMPLEX</span></h3>
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The gunner is provided with a periscopic monocular 1PZ-2 day/night dual purpose sight. This sight has variable magnification settings of either 1.2x or 4x magnification. In the 1.2x magnification setting, the field of view is 49 degrees, and 14 degrees in the 4x magnification setting. The sight has no independent stabilization system. The aperture mirror of the sight has a maximum elevation limit of +81 degrees and a maximum depression limit of -10 degrees, but the weapons themselves can only elevate to +60 degrees and depress to -4 degrees due to the design of the turret and gun mount. The periscopic mirror in the sight aperture is vertically aligned with the weapons complex with mechanical linkages, and as such, the range of elevation of the sight is the same as the weapons.</div>
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This is more than enough to allow the gunner to fire at aircraft and input range corrections for ground targets located at high elevations, but the sight has no ability to track moving aircraft other than the simple concentric lead rings in the viewfinder of the sight. The same viewfinder is used against all target types, but the reticle markings for ground targets are too small to be used in the 1.2x magnification setting and the reticle markings for anti-aircraft work are not visible in the 4x magnification setting. In practice, the 1.2x magnification setting is mainly used for firing at aircraft or for non-precision fire at ground targets, and the 4x magnification setting is used exclusively for firing at ground targets.</div>
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The 1PZ-2 is used for aiming both the KPVT and PKTM coaxial machine gun. Both machine guns are sighted to a maximum range of 2,000 meters, but the maximum ranges for precise direct fire with these two weapons is mainly determined by the tracer burn-out distances of their tracer rounds. Fire correction is difficult without the help of tracers because the impact of the bullets is imperceptible at long ranges. As a rule, the maximum effective range of a 7.62mm machine gun on troops in open terrain does not exceed a kilometer and it is not effective against aircraft. Officially, the maximum effective range of the KPVT on lightly armoured vehicles is stated to be 1,000 meters and the maximum effective range on unarmoured targets or infantry is 2,000 meters. Against slow low-flying aircraft, the maximum effective range of the KPVT is 1,500 meters.<br />
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The sight has a simple reticle with fairly basic accommodations for range estimation and fire correction. A vertical line runs down the entire height of the viewfinder and a movable horizontal line runs across the entire length of the viewfinder. To adjust the sights for different ranges, the horizontal line in the viewfinder is lowered until it matches the corresponding number marked in the range scales. The intersection point between the vertical line and the horizontal line is the aiming point.<br />
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The drawings below show the reticle when it is adjusted to engage two types of targets. The first drawing (5.23) shows the reticle when it is calibrated for the KPVT to a distance of 1,400 meters and aimed at the center mass of an APC-type target. The second drawing (5.24) shows the reticle when it is calibrated for the PKT to a distance of 900 meters and aimed at the center mass of a car.<br />
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<a href="https://2.bp.blogspot.com/-1ga9rzuexGA/XLDEV8GdH0I/AAAAAAAANqE/RqHmndGxA2EYbx45On0TTROaq_PbHFBzgCLcBGAs/s1600/1pz-2%2Bviewfinder.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1279" data-original-width="1538" height="532" src="https://2.bp.blogspot.com/-1ga9rzuexGA/XLDEV8GdH0I/AAAAAAAANqE/RqHmndGxA2EYbx45On0TTROaq_PbHFBzgCLcBGAs/s640/1pz-2%2Bviewfinder.png" width="640" /></a></div>
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Lead and windage is adjusted using the horizontal deflection scale in the center of the reticle. A short horizontal bar above the horizontal deflection scale is calibrated to mark a distance of 500 meters for the KPVT. It aligns with the fixed horizontal line of the anti-aircraft rings. The horizontal deflection scale is also used for range estimations, but for more precise measurements, the gunner will have to rely on the commander as he has access to a stadiametric rangefinder in his TKN-3 periscope.<br />
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As usual, an internal bulb in the sight can be turned on to illuminate the reticle when fighting in low light conditions. To adjust the contrast of the image seen through the sight, the gunner can switch between two filters in the sight by turning a knob. For firing at ground targets, a neutral filter is used. For firing at air targets or for firing in the direction of the sun, a tinted filter is used.<br />
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The photo below shows the view through through the 1PZ-2 under 1.4x magnification. The tinted filter is in place.<br />
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<a href="https://2.bp.blogspot.com/-AVxmEH6GROU/WWtm4qyV5dI/AAAAAAAAIqw/L5pSi2HJi1IPBmAuDfLBUKfVmeWNPmnpQCLcBGAs/s1600/800px-1pz-7_1.2x.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="480" src="https://2.bp.blogspot.com/-AVxmEH6GROU/WWtm4qyV5dI/AAAAAAAAIqw/L5pSi2HJi1IPBmAuDfLBUKfVmeWNPmnpQCLcBGAs/s640/800px-1pz-7_1.2x.jpg" width="640" /></a></div>
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The photo below shows the view through through the 1PZ-2 under 4x magnification. The neutral filter is in place, so the actual color of the target can be clearly seen.<br />
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<a href="https://4.bp.blogspot.com/-_OzZkrOF_sA/WWtnCdUFbkI/AAAAAAAAIq0/fwn5neK8r2UEZ5ScTcgrs7MCAlvghTZpgCLcBGAs/s1600/800px-1pz-7_4x.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="480" src="https://4.bp.blogspot.com/-_OzZkrOF_sA/WWtnCdUFbkI/AAAAAAAAIq0/fwn5neK8r2UEZ5ScTcgrs7MCAlvghTZpgCLcBGAs/s640/800px-1pz-7_4x.jpg" width="640" /></a></div>
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The sight has a basic nightvision module. It is of the active infrared type, and it works in tandem the OU-3GA2M IR spotlight. The power of the 110 W spotlight is enough to allow the gunner to see and identify tank-sized targets up to 400 meters away, but seeing smaller vehicles such as armoured personnel carriers would be more difficult. The same reticle from the daytime channel is used in the night vision channel but with illumination provided by a green light bulb inside the sight. The illuminated reticle may also be used in the daytime channel when fighting during twilight hours.<br />
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<a href="http://1.bp.blogspot.com/-XYIEsBMve_w/VGlYhEyW9zI/AAAAAAAAAos/_6DGyCaMVNk/s1600/35271.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://1.bp.blogspot.com/-XYIEsBMve_w/VGlYhEyW9zI/AAAAAAAAAos/_6DGyCaMVNk/s1600/35271.jpg" width="320" /></a><a href="http://4.bp.blogspot.com/-K-3k21mPviA/VGlYk9dEsdI/AAAAAAAAAo0/5ZpCfJoN1VE/s1600/35270.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://4.bp.blogspot.com/-K-3k21mPviA/VGlYk9dEsdI/AAAAAAAAAo0/5ZpCfJoN1VE/s1600/35270.jpg" width="320" /></a></div>
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Overall, the night vision capabilities of the sight are extremely lackluster. It is not a serious contender in the world of night vision devices, and turning on the infrared spotlight would probably reveal the vehicle's position faster to enemy observers.<br />
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The 1PZ-2 is a utilitarian tool that fulfills all of the basic criteria for its purpose, but no more. In technological terms, it belongs firmly in the 1950's. Nevertheless, the 1PZ-2 is already more advanced than the PP-61AM periscopic sight that was standard for the BTR family of troop carriers since the BTR-60PB.<br />
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<span style="font-size: large;">TKN-4GA-01</span></h3>
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<a href="https://3.bp.blogspot.com/-uf_krCBBP3c/WtHcJEyBz7I/AAAAAAAALcI/VXUHdsOBVMADt3otdD-cKkt7_JJQ7FVSQCLcBGAs/s1600/tkn-4ga-01.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="514" height="400" src="https://3.bp.blogspot.com/-uf_krCBBP3c/WtHcJEyBz7I/AAAAAAAALcI/VXUHdsOBVMADt3otdD-cKkt7_JJQ7FVSQCLcBGAs/s400/tkn-4ga-01.jpg" width="256" /></a></div>
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Recently modernized BTR-80 units have had the new TKN-4GA-01 sighting complex installed. This is the same sight used in the BTR-82A, but unlike the BTR-82A, the gun on the BTR-80 remains unstabilized so the weapons still cannot be fired accurately on the move on rough terrain.<br />
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The turret was slightly modified to accommodate the larger and more modern sight and the mechanical linkages connecting the sight to the elevation mechanism of the weapons. Control of the turret and weapon elevation was still manually effected using hand cranks, but the elevation mechanism was modified to integrate with the new TKN-4GA-01 sight.<br />
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<a href="https://3.bp.blogspot.com/--z2ytS8KsIs/XMmtsjdyi2I/AAAAAAAAN1Y/SKpKRYlP4ds27rUtzub0Q6lnc3yADoJxACLcBGAs/s1600/front%2Bview.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="802" data-original-width="900" height="284" src="https://3.bp.blogspot.com/--z2ytS8KsIs/XMmtsjdyi2I/AAAAAAAAN1Y/SKpKRYlP4ds27rUtzub0Q6lnc3yADoJxACLcBGAs/s320/front%2Bview.jpg" width="320" /></a><a href="https://2.bp.blogspot.com/-DbRI2iyJ9c0/XMmtsQJlzVI/AAAAAAAAN1U/Hx1XCeHX1IIAc0JR_MbLCA7TRF_EFsMKwCLcBGAs/s1600/side%2Bview.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="542" data-original-width="900" height="240" src="https://2.bp.blogspot.com/-DbRI2iyJ9c0/XMmtsQJlzVI/AAAAAAAAN1U/Hx1XCeHX1IIAc0JR_MbLCA7TRF_EFsMKwCLcBGAs/s400/side%2Bview.jpg" width="400" /></a></div>
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The patent of the modernized BPU-1 turret with PL-1-01 laser beamer and TKN-4GA sight can be viewed via this (<a href="http://www.freepatent.ru/patents/2321815">link</a>). The patent was filed jointly by the Arzamas plant and GAZ in 2006.<br />
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<a href="https://3.bp.blogspot.com/-pOzMWgv83bo/XMmt-Fo6-lI/AAAAAAAAN1k/aI88ePpB39UAO7vR99fOcmnKfO8wftSTQCLcBGAs/s1600/tkn-4ga%2Bmount.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="580" height="400" src="https://3.bp.blogspot.com/-pOzMWgv83bo/XMmt-Fo6-lI/AAAAAAAAN1k/aI88ePpB39UAO7vR99fOcmnKfO8wftSTQCLcBGAs/s400/tkn-4ga%2Bmount.jpg" width="257" /></a><a href="https://4.bp.blogspot.com/-qiuOAqXzI_k/XMW6eZsRKBI/AAAAAAAANyQ/8SXa_r_CXBoUDDyx7-v2HtCmWfr49H2BwCLcBGAs/s1600/btr-80%2Btkn-4ga-01.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="535" data-original-width="354" height="400" src="https://4.bp.blogspot.com/-qiuOAqXzI_k/XMW6eZsRKBI/AAAAAAAANyQ/8SXa_r_CXBoUDDyx7-v2HtCmWfr49H2BwCLcBGAs/s400/btr-80%2Btkn-4ga-01.png" width="263" /></a></div>
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In the observation mode, the magnification of the daytime channel is fixed at 1x with an angular field of view of 49 degrees. In this mode, the magnification of the main optic is the same as the anti-aircraft optic, so the sight essentially becomes a stabilized binocular periscope and the gunner can spot targets with greater ease while the vehicle is moving. Once the gunner identifies a target and is ready to engage, he can switch to the higher magnification mode and use the monocular day sight to engage. In the daytime gunnery mode, the sight is monocular and only the right eyepiece is used. In the day setting, the sight offers a fixed 8.2x magnification and an angular field of view of 7 degrees. In the night setting, the sight has 8x magnification and an angular field of view of 7 degrees.<br />
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The simple anti-aircraft optic included in the TKN-4GA-01 is not improved over the 1PZ-2 but the greater magnification in the daytime channel compared to the 1PZ-2 enables the gunner to see and engage targets at longer ranges with more confidence than before, making the BTR-80 more effective overall. Another important upgrade lies in the inclusion of the PL-1-01 laser beamer, which not only has a greatly superior range compared to the earlier OU-3 IR spotlight but also features pulse modulation allowing its IR laser to penetrate more deeply into mist and fog, making it much more effective than the hopelessly outdated incandescent IR lamp used in the OU-3 during poor weather conditions. The PL-1-01 can also be used as a laser rangefinder in conjunction with sights of the TKN-4GA series, having an error margin of ±20 meters at a measuring distance of 200 meters to 3,000 meters. Combined with the 8.2x magnification in the daytime channel and the additional observation features implemented in the sight, this increased the effective firing range of the KPVT against lightly armoured targets, reduced the reaction time of the gunner to new threats, decreased the ammunition consumption rate per engagement, and vastly improved the combat effectiveness of the BTR-80 at night.<br />
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<h3>
<span style="font-size: large;">
KPVT</span></h3>
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The KPVT is an open-bolt single-feed heavy machine gun, fed with 50-round belts held in individual boxes. It is a modification of the original KPV infantry heavy machine gun, adapted into a coaxial machine gun for tanks. It fires the 14.5x114mm cartridge at a cyclic rate of 600 rounds per minute out of a 1.346 m barrel. The barrel is shrouded in an air-cooling jacket and supported with a metal frame on its mount in the BTR-80 turret. At the muzzle of the barrel is a conical flash hider and booster assembly. The booster is connected to the air-cooling jacket, and allows the propellant gasses escaping from the barrel to push the barrel against the end of the jacket, causing it to recoil backwards a short distance. The short-recoil action reduces the recoil impulse and more importantly, reduces the shot dispersion by dampening the vibrations of the machine gun. The machine gun cradle itself also contains a pair of recoil buffers to further enhance the accuracy of the weapon.<br />
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Ten ammunition boxes with a belt of 50 cartridges each are provided for a total of 500 rounds of ammunition. The boxes much be manually loaded by the gunner. First, the empty ammunition box is removed by pressing on the locking lever on the side of the box holder. The box will drop to the floor, and the gunner can retrieve a fresh box from the hull and load it into the box holder by pushing it in from below. If the turret is aimed forward, the closest ammunition rack to the gunner is to his immediate left and right. More boxes are stowed at the two rear corners of the hull and to the right of the commander's station.<br />
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Once a fresh box has been loaded, the next task is to put the ammunition belt into the feed system of the machine gun. To do this, the weapons complex must be elevated to the maximum limit as the KPVT occupies the entire length of the turret and it would not be possible for the gunner to reach the feed system. Raising the weapons complex also allows the top cover of the KPVT to be opened and for the gunner to find the feed lips and slot the belt of cartridges into the machine gun. After this, the charging cable is pulled to cock the gun and ready it to fire. The two pictures below show this process. The photo on the left shows a gunner straightening out a belt of rounds and the screenshot on the right shows a gunner preparing the cock the machine gun (screenshot from <a href="https://youtu.be/mmeOWMsMIEo">this video</a>).<br />
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<a href="https://2.bp.blogspot.com/-wWxBv4OmOr4/W1OmErM8XcI/AAAAAAAALzY/6gYLVFuZSOQMeBUu6UHzgUmcOG4vvMhZwCLcBGAs/s1600/kpvt%2Bbtr-80.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="240" src="https://2.bp.blogspot.com/-wWxBv4OmOr4/W1OmErM8XcI/AAAAAAAALzY/6gYLVFuZSOQMeBUu6UHzgUmcOG4vvMhZwCLcBGAs/s320/kpvt%2Bbtr-80.jpg" width="320" /></a><a href="https://3.bp.blogspot.com/-eOfQelsaYrw/XJ8rPHHFxZI/AAAAAAAANn8/5KALCOGJ2rABeFEvMXs1cWMGHRbGNsxrwCLcBGAs/s1600/charging%2Bkpvt.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1366" height="223" src="https://3.bp.blogspot.com/-eOfQelsaYrw/XJ8rPHHFxZI/AAAAAAAANn8/5KALCOGJ2rABeFEvMXs1cWMGHRbGNsxrwCLcBGAs/s400/charging%2Bkpvt.png" width="400" /></a></div>
<div><br /></div><div><br /></div><div>The feeding system is a two-stage type like the PK series of machine guns, despite the rimless design of the 14.5x114mm cartridge. In the first stage, a cartridge is pulled out of the belt, and in the second stage it is placed into a slot cut in the breech face. The spent case from the previous round is pushed down and out of this slot by the new cartridge, previously extracted from its belt. The spent case is then pushed out of the slot and into an ejection chute by a special ejector lever.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-T_kvcIjscAg/XvUpDjy5qrI/AAAAAAAARJU/crFIYOaJKVERbp_XaDeMFpQEDGyJdSQGACK4BGAsYHg/s1200/KPVT%2Bejection%2Bport.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="565" data-original-width="1200" height="302" src="https://1.bp.blogspot.com/-T_kvcIjscAg/XvUpDjy5qrI/AAAAAAAARJU/crFIYOaJKVERbp_XaDeMFpQEDGyJdSQGACK4BGAsYHg/w640-h302/KPVT%2Bejection%2Bport.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The forward-ejection mechanism for spent cases is one of the main features of the KPVT that differentiates it from the standard KPV infantry machine gun, which was considered mandatory for machine guns adapted for tank usage (typically as a coaxial machine gun). The gun mantlet of the BPU-1 turret has a special duct for ejected cases underneath the barrel clamp of the machine gun for this purpose. The ejection mechanism of the KPVT propels the spent cases forcefully enough to enable the system to function normally even when the machine gun is fully elevated, as the short video clip below shows (taken from an show about the BTR-80 from the Russian NTV channel). </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-YX4p5OKxqY4/XvUeaEmxXwI/AAAAAAAARI8/h3lJx7o6SPogEeeXA6DypcMnhcHyPGSfACK4BGAsYHg/s728/Forward%2Bejection.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="522" data-original-width="728" height="286" src="https://1.bp.blogspot.com/-YX4p5OKxqY4/XvUeaEmxXwI/AAAAAAAARI8/h3lJx7o6SPogEeeXA6DypcMnhcHyPGSfACK4BGAsYHg/w400-h286/Forward%2Bejection.gif" width="400" /></a></div><div><br /></div><div><br /></div><div>The drawing on the left below depicts the gun mantlet of the BPU-1 turret, showing the opening for the spent case ejection port underneath the opening for the KPVT barrel. The base of the turret has a cutout below the ejection port opening to ensure that the spent cases can clear the port even when the machine gun is fully depressed. The photo on the right below (courtesy of <a href="https://www.scalenews.de/btr-80-walkaround-87/">Sergey Sinitsyn</a>) shows the ejection duct underneath the barrel clamp for the KPVT and the spring-loaded lid on the duct, which is necessary to help ensure that the turret remains sealed from NBC contaminants when cases are not being ejected.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-PW42lEwIjTI/XvUtK9hrkkI/AAAAAAAARJs/qzp70kCgWcwPYhr64W1PDCpm0Ub-atdVACK4BGAsYHg/s1851/mantlet.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1288" data-original-width="1851" height="279" src="https://1.bp.blogspot.com/-PW42lEwIjTI/XvUtK9hrkkI/AAAAAAAARJs/qzp70kCgWcwPYhr64W1PDCpm0Ub-atdVACK4BGAsYHg/w400-h279/mantlet.png" width="400" /></a><a href="https://1.bp.blogspot.com/-shA1WSUQjXI/XvUtylvJYeI/AAAAAAAARKQ/078JkEkkkYomt9VT-MZkyBXm9FeG1JtKQCK4BGAsYHg/s2000/btr-80-walkaround-87-5.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1500" data-original-width="2000" height="300" src="https://1.bp.blogspot.com/-shA1WSUQjXI/XvUtylvJYeI/AAAAAAAARKQ/078JkEkkkYomt9VT-MZkyBXm9FeG1JtKQCK4BGAsYHg/w400-h300/btr-80-walkaround-87-5.jpg" width="400" /></a><div class="separator" style="clear: both; text-align: center;"><br /></div></div>
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Additional boxes of ammunition may be stowed inside the vehicle if the crew chooses to. They could simply be placed on the floor, on the seats, or anywhere that does not interfere with the general function of the vehicle.</div><div><br /></div><div>Although the cyclic rate of fire is 550-600 rounds per minute, the practical rate of fire is officially listed as 70-80 rounds per minute in the manual for the KPVT. The practical rate is achieved by limiting fire to short bursts of 2-5 rounds. When necessary, long bursts of up to 20 rounds against ground targets may be used, and when engaging aerial targets, the machine gun is fired in long bursts exclusively. Continuous full automatic fire is permitted up to 150 rounds for each barrel, after which it is necessary to let the barrel cool or replace it. <br />
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A spare barrel for the KPVT is carried in the vehicle. The KPVT has a heavy barrel and it is sufficiently cooled by air alone as long as it is fired in bursts, so it does not require barrel changes during combat. As usual, the machine gun is fired in bursts to ensure an efficient rate of ammunition consumption, and the subsequent reduction in the practical rate of fire also ensures that the barrel does not overheat. Furthermore, the presence of a coaxial 7.62mm machine gun to supplement the KPVT allows the gunner to conserve 14.5mm rounds when engaging soft-skinned targets and enemy infantry in the open. However, if the barrel is worn out or damaged during combat, having a spare barrel on board allows the vehicle to continue fighting after a quick barrel swap. <br />
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The available bullet types are the B-32, BS-41, BZT, BZT-M, MDZ, and MDZ-M which are armour-piercing incendiary (API), armour-piercing incendiary tracer (API-T) and instantaneous incendiary-high-explosive (HEI) respectively.<br />
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B-32 is an AP round made from tool steel, while the BS-41 is an AP round made from tungsten carbide. BS-41 is superior to the B-32, but the latter is still the most numerous type due to its economy. The BZT and BZT-M rounds are the tracer counterparts to the B-32 and BS-41 respectively. Both of these rounds have similar, and very modest penetration capabilities, and only serve to duplicate the flight trajectories of their counterparts. The also BZT-M differs from the BZT by having a slightly more powerful propellant to match its speed to that of the BS-41. The MDZ and MDZ-M rounds fulfill a niche requirement as anti-helicopter ammunition. This type of bullet has a limited advantage in the anti-personnel role in that it produces a small amount of splinters upon detonation, and it can set field fortifications alight.<br />
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<b>B-32 (AP-I)</b></div>
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<a href="http://2.bp.blogspot.com/-j1-dxsQ3mfE/VGjSX72nyHI/AAAAAAAAAmc/I8IYbubzTqg/s1600/14_5x114_B-32.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="103" src="https://2.bp.blogspot.com/-j1-dxsQ3mfE/VGjSX72nyHI/AAAAAAAAAmc/I8IYbubzTqg/s1600/14_5x114_B-32.jpg" width="320" /></a></div>
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<a href="http://4.bp.blogspot.com/-tB2Fwrd4bq4/VGjSZR5UmEI/AAAAAAAAAmk/NtPaPWylR1I/s1600/14_5x114_B-32_2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="230" src="https://4.bp.blogspot.com/-tB2Fwrd4bq4/VGjSZR5UmEI/AAAAAAAAAmk/NtPaPWylR1I/s320/14_5x114_B-32_2.jpg" width="320" /></a></div>
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The B-32 bullet is composed of a hardened steel core with 1.8 grams of volatile incendiary mixture packed at the tip. The steel core is to defeat light armour, and the incendiary mixture is useful for injuring the occupants or setting internal equipment alight. The normal operating pressure of the cartridge is 326.6 MPa, and it reaches a maximum pressure of 343.2 MPa.<br />
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One interesting aspect about the B-32 bullet is that it shares the exact same external and internal design as the 12.7mm B-32 and 7.62mm B-32, differing only in scale. The B-32 bullet design was originally made for the 7.62x54mm cartridge, but was later adopted in larger calibers due to its very good ballistic shaping.</div><div style="text-align: left;"><br /></div><div style="text-align: left;">The B-32 bullet contained 1.3 grams of aluminium-magnesium-barium nitrate incendiary compound in the tip and the BZT bullet contained 1.56 grams of the same incendiary compound, which is substantially more than the 0.84 grams of magnesium-barium incendiary compound in .50 caliber spotting rounds. The tracer of the BZT bullet burns out at 2,000 meters. These characteristics made the KPVT an excellent ranging machine gun as the flash of the impact would be more visible at long distances and in poor weather conditions.<br />
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Muzzle velocity: 1,021 m/s</div>
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Core: Heat-treated tool steel<br />
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The velocity limits of B-32 for various thicknesses of steel are listed as follows:<br />
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Muzzle Velocity of 14.5 B32: 988 m/s<br />
V50 of <b><u>15.6mm</u></b> of ATI 500-MIL plate at 30 deg: 730 m/s<br />
V50 of <b><u>15.4mm</u></b> of ATI 500-MIL plate at 30 deg: 739 m/s<br />
V50 of <b><u>18.8mm</u></b> of ATI 500-MIL plate at 30 deg: 841 m/s<br />
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This means that 980 m, a 14.5mm B-32 bullet will go through 15.6mm of ATI 500-MIL plate angled at 30 degrees to the vertical. This is almost exactly double the performance of the .50 M2 round for a very small increase in caliber and small increase in overall dimensions. At 915 meters, the 14.5mm B-32 bullet will go through 15.4mm of the same steel at the same slope. Odd, but not a big deal. A 0.2mm error margin is easily explained away by quality issues. At 525 m, the 14.5mm B-32 bullet will go through 18.8mm of the same steel at the same slope.<br />
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Here is the graph of thickness against V50:<br />
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The B-32 bullet has limited effect against an M2 Bradley IFV, as the core will be defeated by the two spaced steel plates that protect the aluminium armour underneath. The spaced side armour of the M2 Bradley reportedly provides all-round protection from 14.5mm armour-piercing rounds from a range of 300 meters.<br />
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<b>BS-41 (AP-I)</b></div>
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<a href="http://4.bp.blogspot.com/-j1-dxsQ3mfE/VGjSX72nyHI/AAAAAAAAAmg/fGRyWEvNkHU/s1600/14_5x114_B-32.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="103" src="https://4.bp.blogspot.com/-j1-dxsQ3mfE/VGjSX72nyHI/AAAAAAAAAmg/fGRyWEvNkHU/s1600/14_5x114_B-32.jpg" width="320" /></a></div>
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A souped-up armour-piercing cartridge first introduced for anti-tank purposes in 1941. It is very useful against lightly armoured vehicles like armoured cars and bullet-proofed utility and transport vehicles like M113s, Humvees and LAVs. Armoured attack helicopters are fair game as well. The extra penetration ability granted by the tungsten carbide core enables the the BS-41 to be useful against modern utility trucks and cars, but with the emergence of new and more advanced ceramic armour technology, the BS-41 cartridge will find its usefulness diminishing rapidly.<br />
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The bullet also has an incendiary compound packed at the tip of the bullet, just like the B-32. The bullet contained 1.3 grams of aluminium-magnesium-barium nitrate incendiary compound in the tip. <br />
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<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-g8UNk02WqTc/VlRaZ6dor8I/AAAAAAAAEd8/MupjEEapYYo/s1600/14.5mm%2BBS-41%2Bpenetration%2Binto%2Bmild%2Bsteel.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto; text-align: center;"><img border="0" src="https://3.bp.blogspot.com/-g8UNk02WqTc/VlRaZ6dor8I/AAAAAAAAEd8/MupjEEapYYo/s1600/14.5mm%2BBS-41%2Bpenetration%2Binto%2Bmild%2Bsteel.png" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Penetration of BS-41 into mild steel</td></tr>
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Muzzle velocity: 1005m/s</div>
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Core: Tungsten carbide<br />
Bullet Mass: 64.2 g<br />
Bullet Length: 51.2mm<br />
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Core Diameter: 11.72mm<br />
Core Length: 38.72mm<br />
Core Mass: 38.72 g<br />
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Incendiary Compound Mass: 0.97 g<br />
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Penetration: </div>
40mm RHA @ 100m<br />
35mm RHA @ 350m<br />
32mm RHA @ 500m<br />
20mm RHA @ 1000m<br />
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80.5mm Mild Steel @ Muzzle<br />
125mm 5083 Aluminium Armour @ 100m<br />
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Testing was conducted on the BS-41 against ATI 500-MIL plate, a high strength type of steel with a hardness of 500 BHN. This is much harder than normal RHA, which tends to have a hardness of around 300 BHN. The average hardness of mild steel is 145 BHN.<br />
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Muzzle Velocity of 14.5mm BS41 bullet: 1,005 m/s<br />
V50 of <b><u>24.5mm</u></b> of ATI 500-MIL plate at 30 deg: 869 m/s<br />
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At 435 meters, the BS41 bullet can perforate 24.5mm of ATI 500-MIL plate steel angled at 30 degrees. According to widespread claims on various websites and old Army documents, the 14.5mm BS-41 bullet is apparently also capable of perforating 40mm of steel armour (the properties of which are not specified, but assumed to be around RHA steel) at 100 meters at 0 degrees, and 32mm of the same steel at 0 degrees at 500 meters.<br />
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<b>BZT, BZT-M (APT-I)</b></div>
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<a href="http://3.bp.blogspot.com/-xzda_94pmKE/VGjTA8-ZNGI/AAAAAAAAAms/v1rz_YbZ5Yk/s1600/14_5x114_BZT.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="103" src="https://3.bp.blogspot.com/-xzda_94pmKE/VGjTA8-ZNGI/AAAAAAAAAms/v1rz_YbZ5Yk/s1600/14_5x114_BZT.jpg" width="320" /></a></div>
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The BZT and BZT-M have armour-piercing cores and incendiary tips like their armour-piercing-only counterparts, but these have an additional tracer element at the rear. The BZT has a steel core, and the BZT-M has a tungsten carbide core, both of equal dimensions. The tracer can burn until at least 2000m. These bullets are linked in a belt of AP ammunition in a 1:4 ratio.<br />
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<a href="http://4.bp.blogspot.com/-FbPzGW7hczw/VGjTC-uvo4I/AAAAAAAAAm0/6QulQsWlNX0/s1600/14_5x114_BZT_2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="233" src="https://4.bp.blogspot.com/-FbPzGW7hczw/VGjTC-uvo4I/AAAAAAAAAm0/6QulQsWlNX0/s320/14_5x114_BZT_2.jpg" width="320" /></a></div>
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Muzzle velocity: 995m/s (BZT) - 1005m/s (BZT-M)</div>
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Core: Heat-strengthened steel</div>
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Penetration: 20mm RHA @ 100m (BZT)</div>
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Tracer ignition distance: 50m - 120m from muzzle<br />
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As you can see in the pictures above, the BZT class of bullets have a shortened armour piercing core, with the addition of a volatile incendiary mixture packed in front of it at the tip of the bullet.</div>
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<b>MDZ, MDZ-M</b></div>
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<a href="http://4.bp.blogspot.com/-93XsgG6M918/VGjTgLhEnnI/AAAAAAAAAm8/IbNGaI9HTxo/s1600/14_5x114_MDZ.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="103" src="https://4.bp.blogspot.com/-93XsgG6M918/VGjTgLhEnnI/AAAAAAAAAm8/IbNGaI9HTxo/s1600/14_5x114_MDZ.jpg" width="320" /></a></div>
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<a href="http://3.bp.blogspot.com/-plmcM6P1xn0/VGjTiaDQ5LI/AAAAAAAAAnE/BSpPBD0n58o/s1600/14_5x114_MDZ_2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="171" src="https://3.bp.blogspot.com/-plmcM6P1xn0/VGjTiaDQ5LI/AAAAAAAAAnE/BSpPBD0n58o/s320/14_5x114_MDZ_2.jpg" width="320" /></a></div>
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<br />The MDZ is a high explosive incendiary (HE-I) bullet designed primarily for anti-aircraft work, but it is also suitable for soft skinned vehicles vehicles such as trucks, jeeps, and cars. The bullet has a bimetallic jacket containing an explosive filler. A detonator cap is installed at the nose of the bullet. It is extremely lightweight and occupies much less space compared to a mechanical fuze.</div><div style="text-align: left;"><br /></div><div style="text-align: left;">The filler of the MDZ bullet consists of ~5 grams of phlegmatized PETN. The phlegmatizer content is unknown, but the explosiveness of PETN (as determined by a Trauzl test) is 523 ml, while the A-IX-2 explosive-incendiary compound has an explosiveness of 530 ml, the same as pure hexogen. The explosiveness of the phlegmatized PETN charge is likely to be between A-IX-1 and A-IX-2. In terms of explosive payload, the MDZ bullet is similar to the 20x99mm OZ (HE-I) shell for the the ShVAK aircraft cannon, which contained 5.6 grams of A-IX-2. </div><div style="text-align: left;"><br /></div><div style="text-align: left;">The MDZ bullet is specified to blast a hole with a diameter of 20-30cm into a 1mm duralumin sheet at a distance of 1,500 meters. This is superior to a 20mm OZ round for the ShVAK, which is only capable of creating a 150x160mm breach in a 0.9-1.5mm duralumin sheet simulating the skin of aircraft.</div><div style="text-align: left;"><br /></div><div style="text-align: left;">Overall, the useful payload of the MDZ bullet is similar to the 20mm ShVAK OZ shell, despite the considerable difference in total projectile weight of 31 grams. The forged steel body of the OZ shell may be heavier and more effective at fragmenting compared to the jacket of the MDZ bullet, but at least in terms of weight, the difference is not as large as the total projectile weight suggests due to the fact that the OZ shell has a large mechanical fuze whereas the MDZ bullet does not.</div><div style="text-align: left;"><br />The MDZ-M bullet entered service in 2002. It was very similar to the original MDZ bullet from 1955, but with a slightly reduced explosive power and increased incendiary effect. As a result of the changes made to the filler, the weight of the bullet decreased slightly to 58.5 grams. The front is occupied by the explosive-incendiary charge, and the rear is occupied by the incendiary charge.<br /><br />The relatively thick steel wall of the bullet allows it to punch through the thin aluminium skin of transport helicopters like the Mi-8 and the Huey and explode inside with great fragmentation and incendiary effects. For example, the aluminium skin on the fuselage of an Mi-8 utility helicopter is made from D16AT aviation aluminium alloy with a thickness of <a href="http://ans2.vm.stuba.sk/ANSYS2010/prednasky/Ansys%20Mechanical/Hub_Some_aspects_of_machine_gun_bullet_penetration_of_the_aluminium_sheet-metal_plate_using_ansys_autodyn.pdf">only 0.8-1.0mm</a>, and the fuselage skin for many Western military and commercial helicopters is usually made from 7075 aviation aluminium alloy with an average thickness in the vicinity of 0.025 inches (0.635mm). This includes gunships like the AH-1 Cobra. The effect of an MDZM bullet on a sheet of aluminium is shown in the promotional display shown below.<br /><br />
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<a href="https://3.bp.blogspot.com/-PgdcpADT5Ko/Wr_V_hy3waI/AAAAAAAALQE/eEaZQaUQyoYGExL1Si10Y6xvIYnult6AQCLcBGAs/s1600/punched.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="358" data-original-width="500" height="286" src="https://3.bp.blogspot.com/-PgdcpADT5Ko/Wr_V_hy3waI/AAAAAAAALQE/eEaZQaUQyoYGExL1Si10Y6xvIYnult6AQCLcBGAs/s400/punched.jpg" width="400" /></a><a href="https://4.bp.blogspot.com/-5RvKGEfJ6j0/Wr_WCZlOWSI/AAAAAAAALQI/gP9APM6ZK3YLQLHmu01Qb64dL26ekKxrACLcBGAs/s1600/mdzm.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="413" data-original-width="550" height="300" src="https://4.bp.blogspot.com/-5RvKGEfJ6j0/Wr_WCZlOWSI/AAAAAAAALQI/gP9APM6ZK3YLQLHmu01Qb64dL26ekKxrACLcBGAs/s400/mdzm.jpg" width="400" /></a></div><div style="text-align: left;"><br /></div><div style="text-align: left;"><br /></div><div style="text-align: left;">The explosive-incendiary charge is composed of a 50/50 mixture of barium nitrate and PETN. The incendiary charge is No.7 Incendiary Compound, which is composed of a 50/50 ratio of barium nitrate and a mixture of aluminium and magnesium powder. In total, the explosive-incendiary charge weighs 2.9 grams and the incendiary charge weighs 1.55 grams. This payload is comparable to the total 4.6-gram payload of the 20mm OFZ (HEF-I) round for the ShVAK aircraft cannon, but due to the more energetic filler, it may have a stronger explosive and incendiary effect. </div></div><div style="text-align: left;"> </div><div style="text-align: left;">The MDZ-M bullet is advertised to be capable of blasting holes with a diameter of 20-40 cm in aluminium sheets with a thickness of 1-1.5mm.</div><div style="text-align: left;"><br /></div><div style="text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-6OqMWyWFtNk/XvV0oGyrupI/AAAAAAAARLg/OZSWFLtygv0eNPBcO4x6AMbJ2K6K13IFQCK4BGAsYHg/s1332/mdz-m.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1332" data-original-width="1200" height="400" src="https://1.bp.blogspot.com/-6OqMWyWFtNk/XvV0oGyrupI/AAAAAAAARLg/OZSWFLtygv0eNPBcO4x6AMbJ2K6K13IFQCK4BGAsYHg/w360-h400/mdz-m.jpeg" width="360" /></a></div>
<div style="text-align: left;"><br /></div><div style="text-align: left;">MDZ (MDZ-M)</div><div style="text-align: left;"><br /></div><div style="text-align: left;">Muzzle velocity: 1,000-1,008 m/s (1,000-1,015 m/s)</div><div style="text-align: left;">Bullet weight: 58.5 g (58.0 g)</div>
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The 14.5mm cartridge is no longer a reliable means of dealing with light AFVs in the present day due to the universal up-armouring of this class of vehicle, thereby leaving the 14.5mm caliber with only of limited use against certain targets. Surprisingly though, even with the KPVT machine gun, the BTR-80 is still much better armed than modern competitors, which are usually armed with only .50 caliber machine guns. The KPVT grants the BTR-80 superior anti-masonry capabilities and superb anti-personnel performance thanks to its ability to penetrate straight through sandbag, wood and cement fortifications in addition to a substantial demoralizing factor. In a direct comparison to some NATO armoured scout cars and APCs armed with 20mm autocannons - usually the excellent Rh202 - like the Spähpanzer Luchs, the BTR-80 comes off much worse in every way, without a doubt. Thus, we can classify the KPVT as something in between a .50 caliber machine gun and a 20mm autocannon.<br />
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As mentioned before, the KPVT is not stabilized. The gunner is only able to fire accurate if the vehicle is stopped or moving at a very relaxed speed over even ground. This has the effect of limiting the usefulness of the BTR-80 as a fire support vehicle.<br />
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SECONDARY</span></h3>
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Unlike a typical armoured personnel carrier, the BTR-80 has a coaxial machine gun. The machine gun is fed with 250-round boxes. Eight boxes are carried inside the BTR for a total ammunition load of 2,000 rounds. All boxes are within reach of the gunner who is responsible for reloading the machine gun. The machine gun has a cyclic rate of fire of 700 to 800 rounds per minute. The co-axial machine gun can be fired either by depressing the trigger button on the gunner's handgrips, or by pressing the emergency manual trigger button located on the trigger unit installed at the back the receiver of the machine gun.<br /></div><div><br /></div><div><a href="https://thesovietarmourblog.blogspot.com/p/pktm.html">This page contains a complete breakdown of the PKT and PKTM machine guns.</a><br />
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<span style="font-size: large;">FIRING PORTS</span></h3>
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<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-o4LjgTKBBi0/XuA4hRdf_WI/AAAAAAAAQ8M/MQwMFBruFLMdbBeg7-4UVw7eQwLdDa79gCK4BGAsYHg/s2049/passengers%2Bfiring%2Bports.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2049" data-original-width="1573" height="400" src="https://1.bp.blogspot.com/-o4LjgTKBBi0/XuA4hRdf_WI/AAAAAAAAQ8M/MQwMFBruFLMdbBeg7-4UVw7eQwLdDa79gCK4BGAsYHg/w308-h400/passengers%2Bfiring%2Bports.png" width="308" /></a></div><div><br /></div><br />There are eight firing ports on the BTR-80. Of this, there are three firing ports on the port side and four on the starboard side, all of which are canted forward to allow troops to fire to the front of the vehicle. The commander is also provided with his own firing port. Six of the firing ports are designed for a Kalashnikov rifle (AK-47, AKM or AK-74) and the other two are designed to mount a PKM machine gun. Depending on the specific firing port, the horizontal range of motion varies from 30 degrees to 50 degrees. The drawing above, taken from a BTR-80 technical manual, shows the range of motion of each firing port.<br /><br /><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-6iOg04ldIzk/XuBBjYn8BfI/AAAAAAAAQ9g/eAwYAL1u5u4mVc2D4xI5lP6IRtCvdySMACK4BGAsYHg/s1318/kalashnikov%2Bfiring%2Bport.png" style="text-align: center;"><img border="0" data-original-height="966" data-original-width="1318" height="294" src="https://1.bp.blogspot.com/-6iOg04ldIzk/XuBBjYn8BfI/AAAAAAAAQ9g/eAwYAL1u5u4mVc2D4xI5lP6IRtCvdySMACK4BGAsYHg/w400-h294/kalashnikov%2Bfiring%2Bport.png" width="400" /></a></div><div><br /></div><div><br /></div><div>The firing ports for PKM machine guns feature a special frame designed to help support the weight of the weapon, which can also be secured by a travel lock when not in combat.</div><div><br /></div><div><br /></div><div><div style="text-align: center;"><a href="https://1.bp.blogspot.com/-MZMegYy-JuM/XuBDYEZcUgI/AAAAAAAAQ94/V5JXaf_V3tMQC04cFIYso9qRnkiltDNmQCK4BGAsYHg/s1463/pkm%2Bfiring%2Bport.png" style="text-align: center;"><img border="0" data-original-height="1281" data-original-width="1463" src="https://1.bp.blogspot.com/-MZMegYy-JuM/XuBDYEZcUgI/AAAAAAAAQ94/V5JXaf_V3tMQC04cFIYso9qRnkiltDNmQCK4BGAsYHg/s320/pkm%2Bfiring%2Bport.png" width="320" /></a></div></div><br /><br />
The firing port itself and the armoured plug provides the same protection as the hull armour, and the triple-layered armoured glass window in each firing port offers protection from grenade and shell fragments. When not needed, each firing port can be sealed with an armoured lid which is operated from inside the vehicle.<br />
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<div style="text-align: center;"><a href="https://1.bp.blogspot.com/-QjQfJrhQsoY/XuBSv4VidBI/AAAAAAAARAE/CBBBrNo7B-MiDO5pb3rPI14iYp0t27u5ACK4BGAsYHg/s1877/firing%2Bports.png" style="text-align: center;"><img border="0" data-original-height="971" data-original-width="1877" height="332" src="https://1.bp.blogspot.com/-QjQfJrhQsoY/XuBSv4VidBI/AAAAAAAARAE/CBBBrNo7B-MiDO5pb3rPI14iYp0t27u5ACK4BGAsYHg/w640-h332/firing%2Bports.png" width="640" /></a></div><div><br /></div><div><br /></div> If a larger opening is needed, the firing port ball mount itself may be unlocked and swung open inwards, leaving an open circular porthole for the passenger to look out from or fire from.<br />
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There are two square roof hatches over the troop compartment, which allow dismounts to aim their personal weapons, RPGs, or MANPADs from the vehicle whilst affording some cover for the dismount. This feature is most useful for MANPADs. Unlike RPGs or automatic weapons, the accuracy of a MANPADS is not significantly affected by motion.</div>
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Each of the roof hatches also feature firing ports, although these are only simple round port holes that allow any type of weapon to be fired at targets above the vehicle. The main use of these ports would be to allow troops to fire at targets in tall buildings or cliffs flanking the vehicle while under the relative safety of bullet-resistant armour. Firing at aircraft would be not only be totally futile, but also rather counterproductive since there are MANPADS launchers available.<br />
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The commander's firing port is aimed directly forward and can traverse in a 50° horizontal arc and 50° in a vertical arc. The addition of this firing port required the commander's windshield to be shifted closer to the driver's windshield.<br />
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The firing port attendees were provided with sheet steel cartridge casing deflectors that would snap onto the receiver of their Kalashnikovs, since AK-type rifles ejected spent casings with quite a bit of force, so the user would otherwise pelt hot brass at his neighbour's face when he opened fire. The casing deflectors prevent this by redirecting spent casings downwards. Aside from that, the firing port stations were also fitted with a fume extractor system. Air hoses were attached to the sheet steel cartridge casing deflectors and were positioned just in front of the rifle's ejection port to suck in the powder gasses that escape from the ejection port as the rifle fired. Without this system, the BTR would be flooded with powder fumes, especially if all eight passengers have been firing continuously for extended periods of time without permission to open any of the hatches. This system is similar to the one installed in the BMP-1 and BMP-2.<br />
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In addition to the weapons organic to the BTR-80, the vehicle can also carry grenades, grenade launchers, assault flamethrowers, additional small arms ammunition, and MANPADS launchers, machine guns - both light and heavy - and even AGS grenade launchers or other equipment. The BTR-80 can transport almost anything that its occupants need for short missions.<br />
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<h3>
<span style="font-size: large;">
PROTECTION</span></h3>
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In accordance with its intended role, the BTR-80 was designed as a lightly-armoured vehicle. According to the specifications for the basic tactical-technical characteristics of the BTR-80, its requirements for protection did not change from its predecessors - its frontal armour had to resist 12.7mm armour-piercing bullets and it had to offer complete protection from 7.62mm armour-piercing bullets from all angles of fire. The basic requirements were already fulfilled by the BTR-60PB and BTR-70, but the BTR-80 achieved a higher level of security by having slightly thickened plating on the front and sides of the hull. The previous BTR models required more standoff distance in order to provide the required protection. Together with the revised powertrain, the added armour increased the weight of the BTR-80 by 18% compared to the BTR-70. The increased armour protection further decreased the chances of a successful armour perforation from small arms down to point blank range, although it should be noted that bullets tend to require some standoff distance to fully stabilize and that a yawing bullet has drastically less penetration power than a stabilized one.<br />
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The turret and hull are monocoque structures constructedt from welded <a href="http://masters.donntu.org/2008/mech/trifonov/library/s13.htm">2P high hardness, high strength armour steel</a> plates of two thicknesses: 7mm and 9mm. The 2P grade is a manganese-molybdenum steel with a carbon content of 0.23-0.29%. 2P grade plates with thicknesses of 8mm to 14mm have a tensile strength of 1450 MPa and a hardness of 388 – 495 BHN, while plates with thicknesses of 4mm to 7mm have a hardness of 444 – 514 BHN. For a lack of more specific information, the 2P plates used to construct the BTR-80 are assumed to have a hardness of 500 BHN.</div><div>
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For comparison, MIL-A-12560 specifies that RHA steel for a plate with a thickness of 6.35mm to 12.7mm should have a hardness of 341 BHN to 388 BHN. The direct foreign equivalent of 2P grade steel in specification is MIL-DTL-46100 high hardness armour steel for combat vehicles, so for any evaluation of the armour of the BTR-80 to be valid, the armour penetration of threat munitions should be in terms of the MIL-DTL-46100 standard and not in terms of RHA.<br />
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The use of high hardness steel (HHS) armour has been the norm for Soviet armoured personnel carriers since 2P steel was developed in the 1950's, but the higher efficiency of 2P grade steel compared to armour steels of lower hardnesses is only true for certain types of projectiles. Bullets from small arms are more readily defeated with high hardness plates set at an oblique angle, but fragmentation and splinters from grenades, shells and bombs are more efficient at piercing high hardness armour plate as their blunt shapes change the mechanism of penetration from ductile hole formation or fracturing to adiabatic shear plugging. This is shown in the graph below.<br />
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As the graph illustrates, the ballistic limit for .30 caliber M2 armour piercing bullets steadily increases until it plateaus when the hardness of 450 BHN is reached, but for .50 caliber fragment simulating projectiles, the highest ballistic limit (within the scope of the study) is achieved at a moderate hardness of 300 BHN. The efficiency of the 10mm plate drops drastically with increasing hardness and it reaches its lowest point at a hardness of 450 BHN. As the hardness decreases, the efficiency of armour against fragments and splinters increases, making aluminium armour plate a better choice than high hardness steel.<br />
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The upper frontal plate measures 9mm thick at an angle of 64 degrees and the lower frontal plate is 9mm thick at 45 degrees. The bow deck between the upper glacis and the lower glacis is 7mm thick and it is sloped at 84 degrees with the trim vane laid on top of it. The interstitial plate joining the two plates measures 7mm thick at an angle of 87 degrees. The angled corners are the same thickness as the upper and lower front plates beside them. The sides of the hull are 9mm thick on both the upper and lower sides. Besides a relatively high thickness and an optimal hardness for protection from small caliber fire, the side armour of the hull has the additional benefit of between 20 to 30 degrees of vertical slope on both the upper and lower halves. Like the rest of the side hull armour, the side doors have a thickness of 9mm. The rear of the hull, and the roof and the floor all measure in at 7mm thick. This is enough against 7.62x39mm BZ rounds and various 7.62mm ball rounds, but 7.62mm M61 AP rounds would be enough to defeat this armour.<br />
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The table below from the 1992 publicly disclosed paper "<a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/a257674.pdf">LAV Armor Plate Study</a>" shows the ballistic limit of three thicknesses of high hardness steel armour plates in the MIL-DTL-46100 standard against 12.7mm B-32 armour-piercing bullets at an obliquity of 45 degrees. The third row lists an extra-hardened plate (XH) that does not represent the armour standard and it should be ignored. From the table, it can be seen that the velocity limit of 12.7mm B-32 on a 9.71mm plate at 45 degrees is 2,528 ft/s. This is equivalent to a distance of 150 meters.<br />
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According to a variety of sources, the mass efficiency of high hardness armour is 1.3 times the mass efficiency of RHA steel against armour piercing bullets. The .30 caliber M2 armour-piercing bullet can perforate 0.45 inches of RHA steel set at 30 degrees at muzzle velocity according to the Navy Criterion. With the 1.3 mass efficiency coefficient of 2P steel, the 9mm of side armour on the BTR-80 hull is more than enough to offer comprehensive protection from this bullet. The less potent M61 armour-piercing bullet is even less likely to puncture the armour plate.<br />
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However, the thickness of the side armour of the hull is not nearly enough to provide any meaningful amount of protection from 12.7mm-caliber threats except ball rounds, and only if the bullet impacts the armour at a considerable angle. NII Stali states that without additional armour, the upper side of the BTR-80 hull can be defeated by the 12.7mm B-32 armour-piercing bullet from a distance of 1,500 meters.</div>
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The video below shows a BTR-80A sustaining hits to the side from an SVD rifle at point blank range. The bullets used are 7.62mm B-32 bullets which are equivalent to .30-06 M2 AP rounds. The BTR-80A does not have increased protection compared to a basic BTR-80 as the BTR-80A model is not designed for newly built vehicles but is instead a modernization package for existing vehicles.<br />
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<iframe allowfullscreen="" class="YOUTUBE-iframe-video" data-thumbnail-src="https://i.ytimg.com/vi/xK2gwLNBPxw/0.jpg" frameborder="0" height="266" src="https://www.youtube.com/embed/xK2gwLNBPxw?feature=player_embedded" width="320"></iframe></div>
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The roof of the BTR-80 is resistant to some small arms fire, but only from a limited range of angles. When fired upon at an angle, the roof would be able to resist .30 caliber M2 AP rounds, but if the vehicle is somehow attacked directly from above, its modest thickness indicates that it would only be resistant to 7.62mm ball rounds and 7.62x39mm BZ (AP-I) rounds. Regardless, battle damage research indicates that hits from machine guns to the hull roof in Afghanistan were rare compared to hits to the sides and rear of the hull, and the roof is not necessarily a vulnerable zone in the vehicle's armour. Even in a worse case scenario where a BTR-80 is ambushed from above while travelling along a mountain pass or down a street flanked by tall buildings, it is very difficult to fire upon the roof at a perpendicular angle. Instead, firing on the BTR-80 from a high elevation would reduce the obliquity of the upper side hull armour plate (while simultaneously increasing the obliquity of the lower side hull plate), making it relatively more vulnerable. If, for example, the vehicle was fired from a height corresponding to the maximum elevation angle of the KPVT in the BPU-1 turret (60 degrees), the bullets would impact the roof at an angle of at least 30 degrees and this is already enough to resist a 7.62mm armour-piercing bullet.<br />
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The turret walls are 9mm thick angled at 45 degrees at the front and sides, thinning down to 7mm at the rear but maintaining the same vertical slope angle throughout. As such, the front armour of the turret shares a similar level of protection as the front of the hull but the sides and rear of the turret have a somewhat higher level of protection than the sides and rear of the hull, primarily due to the increased slope obliquity. Furthermore, the circular shape of the turret adds an additional horizontal slope component that enhances its protection from small arms fire. The semi-cylindrical gun mantlet shares the same thickness as the front of the turret and mainly depends on its curved surface for its protective value. Like the hull, the roof of the turret is 7mm thick.<br />
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Overall, the level of protection offered by the BTR-80 was sufficient for the role of this class of troop transport for a conventional war. This is a very basic level of protection, so generally speaking, the BTR-80 only viable as a "battle taxi". It offers sufficient protection to go up against the organic firepower of a typical American mechanized rifle platoon, not counting any anti-tank weapons carried by the platoon, like the LAW, for example. If attacked by anti-tank grenades, the armour of the BTR-80 is not only incapable of resisting a complete perforation, but the welds that join the plates may burst with a direct hit as demonstrated by the BTR-80 in the photo below. This particular example was lost to an RPG attack in Ukraine.<br />
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However, the blast of an RPG grenade is usually not enough to breach the armour plates themselves even if it can be pierced easily by the shaped charge jet.<br />
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Needless to say, it is dangerous for a BTR-80 to directly confront enemy vehicles armed with autocannons as its armour is simply inadequate against such threats while returning fire with the KPVT may not be enough to eliminate the threat. In general, proper reconnaissance and planning should ensure that motorized infantry riding in BTRs do not face resistance armed with more than small arms. Against such forces, the BTR-80 is well-armed and well-protected enough for the task.</div>
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If the BTR-80 is acting as a battle taxi against a lightly-armed enemy force, there is no sense for the passengers to not be inside the armoured hull as the vehicle performs adequate as a shield from bullets and splinters. However, in situations where heavy weapons and mines are expected, soldiers often prefer to ride on top of the vehicle rather than in them, as this helps improve the chance of surviving a mine blast but also allows them to quickly dismount and spread out because such incidents are often followed up with an enemy ambush from hidden positions. Being outside the vehicle has many more disadvantages on its own, obviously, the primary one being that this practice makes the soldiers vulnerable to claymore mines, jumping mines, and to the most basic IEDs. If the BTR-80 is driven over an anti-tank mine with a tilt-rod fuze or a large IED, the chances of survival for the driver and commander would tend to be lower than the soldiers riding on top of the vehicle.<br />
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One important factor in the survivability of the BTR-80 to enemy fire is its relatively small size and low silhouette. The total height of the vehicle up to the infrared spotlight on the turret is 2.41 meters, but the height from ground level to the hull roof is only 1.91 meters. The average Soviet military-age male was considered to have a height of 1.7 meters, but a 95th percentile male is 1.83 meters. As such, the hull itself is only barely taller than a male soldier of above-average height and the small turret is a very small target to begin with. The low profile gives the BTR-80 good concealment potential in densely vegetated environments and it is a more difficult target to hit, especially when its speed is utilized properly. Being quite low to the ground, terrain features like rocks, mounds, shrubs and even tall grass can hide the BTR-80, and the tiny turret can be easily camouflaged.<br />
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The graph below from the study "<i>Simple Physical Models in Support of Vulnerability and Lethality Data for Wargaming and Simulation Environments</i>" shows the importance of a small silhouette. It shows the simulated probability of kill with a stationary vehicle firing a single 25mm APDS shot against a fully exposed stationary BTR-80, taking into account the known empirical data for the penetration of 25mm APDS and the armour protection of the BTR-80.<br />
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From the graph, it can be seen that the probability of a first round kill reaches 85% at point blank range and the probability of some combination of all mission kill types including a mobility kill, firepower kill, or a mobility plus firepower kill is at 100% until the distance exceeds 100 meters. This bodes ill for the BTR-80, but the chance of surviving the first hit increases drastically with the increase in distance such that at 1,000 meters, the probability of a first round kill has dropped to just 28%. At a distance of 2,000 meters, this drops even further to only 6%. Going by the general military criteria of "combat effectiveness", firing single shots ceases to be a combat effective gunnery technique at distances beyond 500 meters as the probability of a kill is below 51%. Firing in bursts is necessary to ensure a kill, and firing in bursts is absolutely necessary if the BTR-80 is maneuvering. At a distance of two kilometers, a moving BTR-80 has a very good chance of avoiding destruction even in the face of persistent enemy fire. The mobility of the BTR-80 makes a large difference and it is the main asset of the vehicle when it is so heavily outgunned, so it is also quite fortunate that the probability of achieving only a mobility kill on a BTR-80 with 25mm APDS is extremely low at all ranges - the blue line in the graph barely touches 1%.<br />
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SMOKE GRENADES</span></h3>
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The BTR-80 is provided with the 902V "Tucha" smoke grenade launching system which includes six 3D6 smoke grenade launchers arranged at the rear of the turret, aimed forward. The grenades are aimed by the gunner using his 1PZ-2 sights.<br />
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NBC PROTECTION</span></h3>
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The BTR-80 has a overpressure NBC protection suite similar to its predecessors. The higher pressure within the hull prevents particulate contaminants from entering the vehicle, and the occupants are supplied with purified air from an air filtration system. The air outlets for purified air are the only form of ventilation that the passengers are given when the vehicle is fully sealed.<br />
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FIREFIGHTING</span></h3>
<div><br /></div><div>The BTR-80 features an automatic fire extinguishing system, which works in the engine compartment. There are four TD-1 thermal sensors arranged in the engine compartment at strategic positions to sense a fire. Two Freon 114B2 fire extinguisher bottles are provided, allowing for two discharges. Once a fire is detected, the system floods the entire engine compartment with the extinguishing agent, and seals all ventilation points to starve the fire of fresh air, and to limit the escape of the extinguishing agent to the atmosphere. The system functions automatically by default, but it can be manually activated if the crew notices the fire before it is registered by the sensors.<br />
<br /></div><div>Additionally, the occupants are provided with OU-2 hand-held 1-liter fire extinguishers filled with the Freon 114B2 halocarbon extinguishing agent. Since 1985, an OP-10A powder fire extinguisher was included, mainly for extinguishing external fires. </div>
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ADDITIONAL ARMOUR</span></h3>
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BTR-80s have been seen with slat armour sets in various conflict zones as a response to the presence of RPG threats. These slat armour kits are only provided in small numbers to the Southern Military District and most often seen in the North Caucasus. BTR-80s mounted with slat armour screens are very commonly seen during anti-terrorist operations in Chechnya. The Ukrainian army has mounted slat armour on most of their BTR-type vehicles in light of the recent conflict in the Donbas region. Their availability on short notice is quite noteworthy as it indicates the ease of which they can be deployed. Slat armour is a cheap and convenient solution that provides a reasonable level of protection from common anti-tank threats that is compatible with the thin base armour of the vehicle.<br />
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The BTR-80 below is equipped with a slat armour kit developed by NII Stali. The slat armour screens cover the entire length and height of the hull sides and most of the front, with gaps left in the bottom edge of the lower glacis and the top edge of the upper glacis (presumably to not interfere with the view from the periscopes). The side doors in the hull are not protected by slat armour. In the example below, the lower half of the slat armour screens on the sides of the hull have been folded up. This feature is designed to permit free access to the wheels. The armour kit includes a layer of spaced armour plating underneath the slat armour screens made from ST-44 high-hardness steel to act as a dampener for shaped charge warheads as well as to provide additional protection from small arms fire. Note that the windscreens are also shielded by spaced armour panels, and that the panels on the lower glacis of the hull are divided into multiple longitudinal strips. These particulars can be used to differentiate it from other appliqué armour kits developed for the BTR-80.<br />
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The addition of the spaced armour plating underneath the slat armour panels helps to mitigate the damage caused by the blast of shaped charge grenades that successfully detonate despite the presence of the slat armour, and NII Stali advertises that the armour kit provides the upper side of the hull with protection from 12.7mm B-32 armour-piercing bullets from a distance of 325 meters. The claimed success rate of defeating anti-tank grenade threats such as the PG-9S grenade (fired from the SPG-9 recoilless gun) is 50% and the overall probability of the armour being breached by a PG-9S grenade is claimed to be 20%.<br />
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According to NII Stali, the entire armour kit weighs 1,000 kg. When installed on a BTR-80, the resulting gain in weight can be considered quite modest as the coverage offered by the additional armour is very generous. On the hull, the armour kit covers 90% of the front, 80% of the side and 90% of the rear. On the turret, the armour kit covers 60% of the front, 80% of the side and 100% of the rear. The slat armour screens work at any angle of attack.<br />
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The photo below shows a Russian BTR-80 with NII Stali slat armour kit in the Donbas region of Ukraine. The slat armour screens on the sides of the hull have been unfolded but the screens at the front of the hull have been removed for some reason.<br />
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<span style="font-size: large;">PASSENGER ERGONOMICS</span></h3>
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The vehicle can transport 8 troops, although it is quite cramped at full capacity. Fortunately, due to the open space accommodation, soldiers can arrange their equipment and themselves wherever they want and in whatever position they find most comfortable. During marches, there are three crew members - the gunner, the commander and the driver. However, the commander is the squad leader of the motorized infantry squad and he dismounts with the 7 other squad members of the BTR-80, so the vehicle is left without a commander and nobody is left to use the radio other than the driver. The BTR-80 will continue to provide local fire support with only the driver and gunner manning the vehicle.<br />
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A reasonable amount of attention is given to passenger comfort, although it is still surprisingly cramped inside. The vehicle is deceptively small.<br />
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When speaking of internal space, one of the many important factors to consider is the internal height of the vehicle. As mentioned before, the total height of the vehicle including the turret is 2.41 meters, but the height from ground level to the hull roof is only 1.91 meters. With a ground clearance of 475mm, the internal height of the BTR-80 hull is only 1.435 meters - less when the height of the false floor is accounted for. The total height of a seated 95th percentile USSR male is 1.345 meters, so a male soldier of above-average height should be able to sit inside the passenger compartment of the BTR-80 with his combat gear (including helmet), but the dimensions of the vehicle are best suited for a man of average height.<br />
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Departing from other designs, troops must dismount from side doors instead of a typical rear door or ramp. This has its own advantages and shortcomings. Frankly speaking, exiting from these narrow doors in full gear is more inconvenient than it should be, but the choice of two doors means that if one side of the vehicle comes under fire, troops can disembark from the other side. This means that in an ambush scenario, the occupants have a good chance to escape unless surrounded from both sides. The doors are split into two portions - the upper half which swings sideways and outwards, and the bottom half, which drops down and forms a step, which is useful if the vehicle is on the move.<br />
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The upper half of the door is hinged on the side so it is easy to open and close with the built-in handle, but to close the lower half, there is a pullstring with a handle and a simple pulley to help fight against gravity when lifting the door. The string is spring-loaded so it will coil itself up once the door is closed.<br />
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<div><br /></div><div>Additionally, the passengers may also exit the vehicle via top hatches. These are the main points of exit when the BTR is afloat on a body of water. As shown in the diagram below, the rim of the hatch opening on the hull roof is upturned, forming a lip, and the hatch closes over the lip. The rim of the hatch is downturned, and a rubber lining under the rim of the hatch is pressed against the lip to form a seal. Due to the presence of the hatch and the lip of the hatch opening, there is a measure of leak protection against water or flammable fluids even if the rubber lining has worn out, or burnt away in the case of a flame attack. To flow into the vehicle, fluid would first have to flow under the small gap between the rim of the hatch and the hull roof, which is the first barrier against thickened fuels such as napalm or improvised mixtures used in molotov cocktails. The fluid would then need to overcome the rubber seal and then flow up and over the lip, which is the second barrier. </div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdQVYTKar-1yTueWiJbhXX-DM3IOY6jsnNSz2jpEKzGK3x59e5EwwfozZKZP_tAjI2Mq60bJtGdrTFOjJ9B_dx1YoXWNHMwAIaQQTRwQaYug_QddGwDcopsNG9QncYthwAoWY12fLqX4mF6T8XTA1H8LuGT8xDdb-yiViNAC5KHE5MhC6hsnik4UNUAg/s2241/p0013.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1325" data-original-width="2241" height="378" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdQVYTKar-1yTueWiJbhXX-DM3IOY6jsnNSz2jpEKzGK3x59e5EwwfozZKZP_tAjI2Mq60bJtGdrTFOjJ9B_dx1YoXWNHMwAIaQQTRwQaYug_QddGwDcopsNG9QncYthwAoWY12fLqX4mF6T8XTA1H8LuGT8xDdb-yiViNAC5KHE5MhC6hsnik4UNUAg/w640-h378/p0013.png" width="640" /></a></div> </div>
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The accommodations for the passengers include two benches facing away from each other and periscopes for the passengers to monitor the situation outside the vehicle. The benches are designed this way due to the presence of the transmission, which is a byproduct of the rear engine layout of the BTR-80. Six people can be seated on the benches, three on each side. All six passengers are provided with their own firing ports and their own periscopes. There are stowage clips and bins for various essential provisions located between the benches and the engine compartment partition.<br />
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There are two more individual seats at the front of the vehicle, behind the driver's and commander's seats. The seats are placed facing inward towards each other. The passengers seated here are in an ideal position to help the gunner load the machine guns in the small one-man turret.<br />
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There two periscopes for the two passengers seated at the front of the hull, one facing the 11 o'clock direction and one facing the 1 o'clock direction. The passengers at the back of the hull have seven periscopes of which four are TNPO-115 periscopes aimed to the side, two are TNP-165A periscopes aimed towards the 11 o'clock and 1 o'clock directions, and one is a TNPO-115 facing the rear. All of the periscopes are heated to prevent fogging except for the TNP-165A model. The drawing below shows the layout of periscopes with black lines showing the wires for the heating system.<br />
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<a href="https://3.bp.blogspot.com/-usxlJS3Nuo8/XMxNQ5PU6hI/AAAAAAAAN3g/WiSpebjJUPQV1Fll_3qualel551csyKVwCLcBGAs/s1600/heated%2Bperiscopes.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="335" data-original-width="507" src="https://3.bp.blogspot.com/-usxlJS3Nuo8/XMxNQ5PU6hI/AAAAAAAAN3g/WiSpebjJUPQV1Fll_3qualel551csyKVwCLcBGAs/s1600/heated%2Bperiscopes.png" /></a></div>
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<h3>
<span style="font-size: large;">DRIVER'S STATION</span></h3>
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When driving in a non-combat situation, the driver relies on one of the two windscreens at the front of the vehicle for most of his driving work. In this condition, the armour panels for the windscreens are locked in a horizontal position to act as a visor, which helps to reduce glare from the sun and shelters the windscreens from snow and rain, thus helping to improve driving visibility. When combat becomes imminent, the driver must switch to an array of three TNPO-115 periscopes mounted to the ceiling, supplemented by another TNPO-115 periscope on the side of the hull. Sometime during the production run of the BTR-80, a fourth TNPO-115 periscope was added to the hull ceiling to further improve the driver's visibility towards the left, which makes sense given that the USSR and most of the world drove on the right side of the road. Like all other Soviet wheeled armoured vehicles since the early 1960's, the windshields of the BTR-80 omitted the vision blocks that were standard for early BTR-60 models and the BRDM-1 armoured car in the interest of improving ballistic protection. Still, five periscopes is enough to allow the driver to maneuver the BTR-80 safely , but visibility is still somewhat hampered compared to a heads-out driving status or when driving with the windshield.<br />
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At night, driving visibility is seriously affected as the driver must rely on a single forward-facing TVNE-4B night vision periscope. One of the TNPO-115 periscopes is swapped out for the TNVE-4B. The night vision periscope has a viewing distance of 120 meters. Due to the limited field of view and viewing distance, it is not safe for the BTR-80 to be driven at normal daytime speeds, so the average speed of the vehicle has to be severely restricted. When driving at night in a non-combat condition, the driver may drive with the help of a pair of night vision goggles.</div>
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<h3>
<span style="font-size: large;">
MOBILITY</span></h3>
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Despite its ungainly appearance, the BTR-80 is a very assertive cross-country vehicle. The weight of the vehicle is 13.6 tons plus 3% for a full combat load, adding up to a total of 14 tons in a combat configuration. This is somewhat heavier than the BTR-70 which weighed 11.5 tons, but the increased weight of the BTR-80 is compensated by the major improvement in performance gained from switching from a pair of petrol engines to a single diesel engine.<br />
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Early versions were originally powered by a single KamAZ-7403 diesel engine. The KamAZ-7403 produces 260 hp at an engine speed of 2,400 RPM and has a specific fuel consumption rate of 0.5 liters per kilometer. All BTR-80s manufactured only in 1993 have a YaMZ-238M2 diesel engine instead of the KamAZ-7403. This engine produces 240 hp at the same engine speed. Very few vehicles have the YaMZ-238M2 engine as its use was only a temporary measure due to the burning down of the Kamaz engine plant in 1993.<br />
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When installed in the BTR-80, the engine is slightly tilted forward. This was mainly done to leave enough room for the water jet duct installed on the floor of the engine compartment.<br />
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The BTR-80 has a power-to-weight ratio of 19.1 hp/ton. The vehicle can cross a two meter-wide trench and scale a vertical obstacle with a height of 0.5 meters. The chassis has a generous 475mm of ground clearance, allowing the BTR-80 to drive right over tree stumps, rocks, and the like. The maximum speed on paved roads is 100 km/h, although drivers are never allowed to exceed 90 km/h during peacetime and the official top speed on paved roads is 80 km/h. The average cross-country speed is between 20 km/h to 40 km/h.<br /><br />
The air intakes for the engine are located on the hull roof, just in front of the engine access panel and behind the starboard and portside passenger roof hatchs. The inlet is covered by a dome to prevent accidental water intake from rain and from waves when the vehicle is swimming in a body of water. This design also inherently protects from flame attack. The drawing on the left below shows the air cleaner and air heater and how it connects to the air inlet. The photo on the right below shows the air supply tube leading from the air cleaner to the engine.<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-BLnYlObW55Y/VgbeF7XC5OI/AAAAAAAAD1E/PmnmuqwelqY/s1600/image%2B%252845%2529.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://4.bp.blogspot.com/-BLnYlObW55Y/VgbeF7XC5OI/AAAAAAAAD1E/PmnmuqwelqY/s400/image%2B%252845%2529.jpg" width="400" /></a></div>
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<div>The cooling system of the BTR-80 has an open-type ventilation scheme, where the radiator is placed inside the engine compartment and the intake fan draws air through the radiator via the engine compartment itself. As such, any open port that leads to the engine compartment can serve as a radiator intake vent. The main intake is on the engine deck, directly atop the engine.</div><div><br /></div><div>The radiator intakes have a distinct design, similar to the engine air intake. The intake is divided into three panels, each with two elongated slots. The slots have high walls, and are covered with caps. During normal operation, air entering the engine compartment flows in an S-shaped path: air flows under the rim of the cap, makes a turn and flows over the wall of the slot, and then makes another turn and flows down, into the engine compartment. When the engine compartment needs to be sealed, the cap on each slot can be closed so that the rim rests on the surface of the panel and the inner surface of the cap presses against the rubberized rim of the wall of the slot, forming a tight seal, as shown in section A-A in the diagram on the left below. </div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgdPNGTp1QXGZlLyawOKmRb1-J3xl7FrSLVRp7s-2WMERTjwkaCXgXjbq8V_-ozHlZJlBbPUPDTeDepwvBtWk72ThEKruCBapI-I9vK_3RJ9aR1FvZ_IZE_Ev3dExJpElnzAMvmxVHrFrPoy6HEv9mqEdWkLBfry4Nk6V3Fhz3FgKR9WVp2wt0lllBi6A/s2084/radiator%20intakes.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1010" data-original-width="2084" height="194" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgdPNGTp1QXGZlLyawOKmRb1-J3xl7FrSLVRp7s-2WMERTjwkaCXgXjbq8V_-ozHlZJlBbPUPDTeDepwvBtWk72ThEKruCBapI-I9vK_3RJ9aR1FvZ_IZE_Ev3dExJpElnzAMvmxVHrFrPoy6HEv9mqEdWkLBfry4Nk6V3Fhz3FgKR9WVp2wt0lllBi6A/w400-h194/radiator%20intakes.png" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8p-UsLaUZNADV_nxHjGsmrsRdopX3QPLAFJfrCJrC5ROBiBv-_DHv7gGjgbw6qRSYcbQPzHaFXDauvu0LVVgfuxdEtidOeCn0UyfYRjYB-gmMSl0Gn0j-AfssZrtDD5OzP16my_yj0BLCxowqCzxNTVUjg5HRS51utgwOOe7J_EHpw96GmLZAVcRFbg/s530/top%20view.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="207" data-original-width="530" height="156" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8p-UsLaUZNADV_nxHjGsmrsRdopX3QPLAFJfrCJrC5ROBiBv-_DHv7gGjgbw6qRSYcbQPzHaFXDauvu0LVVgfuxdEtidOeCn0UyfYRjYB-gmMSl0Gn0j-AfssZrtDD5OzP16my_yj0BLCxowqCzxNTVUjg5HRS51utgwOOe7J_EHpw96GmLZAVcRFbg/w400-h156/top%20view.jpg" width="400" /></a><br /><br /></div><div><br /></div><div>Upon entering the engine compartment, the air flows around the engine and towards the rear of the compartment, reaching the radiator. Air passes through it, entering the centrifugal fan, and is ejected from the compartment via an outlet vent on the rear portside corner of the engine compartment. The radiator and radiator fan are shown in the image below.</div><div><br /></div><div style="text-align: center;"><a href="https://2.bp.blogspot.com/-8Bag3ka0pr0/XLcNdZyYbzI/AAAAAAAANsA/imiUGTfgiSQyK9L7JxHGXhyh63B8WoLzwCLcBGAs/s1600/radiator.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="478" data-original-width="634" height="301" src="https://2.bp.blogspot.com/-8Bag3ka0pr0/XLcNdZyYbzI/AAAAAAAANsA/imiUGTfgiSQyK9L7JxHGXhyh63B8WoLzwCLcBGAs/s400/radiator.png" width="400" /></a></div><div>
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Exhaust fumes are collected from the exhaust manifolds on either side of the engine and routed to a pair of mufflers mounted externally on the rear corners of the hull. Each of the two mufflers are encased in a sheet steel shroud and covered from the front with a thin armoured shield. These also function as exhaust cooling shrouds, using the differential pressure of the hot, high-velocity exhaust gasses flowing to the rear to draw cool atmospheric air into the shroud from the front. The induced flow of atmospheric air by exhaust gasses is also used to as the mechanism for extracting dust collected in the filters of the engine air cleaners.<br />
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The BTR-80 carries fuel in two 150-liter fuel tanks at the very back of the hull, located on the flanks of the engine cooling system. The fuel tanks feature internal anti-slosh partitions. The fuel filler ports are next to the brake lights. With a full load of 300 liters of diesel, the maximum driving distance of the BTR-80 is 600 km on a paved road and between 223 km to 480 km on cross-country trips. The fuel tanks are installed on either side of the radiator.<br />
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The transmission is of a hydromechanical planetary type with five forward gears and one reverse gear. All eight wheels are powered, but only the two front pairs of wheels are steering wheels with lateral deflection control. The vehicle has a minimum external turning radius of about 13.2 meters. Besides supplying power to the wheels, the transmission also includes a power takeoff system for the self-recovery winch installed in the bow of the vehicle and another power takeoff system for the water jet propeller. Due to the need for a watertight hull for amphibious operations, the entire powertrain - excluding the axles - is installed on top of the floor of the monocoque armoured hull, and a false floor is placed on top so that the occupants of the vehicle do not walk on the exposed chassis. In effect, the BTR-80 has a double floor, albeit a thin one.<br />
<br />The winch (1) is at the very front of the hull. It is connected to the transmission (3) by a transfer case (2). The water jet propeller (7) at the very rear of the hull is connected to the transmission by a power takeoff mechanism (6). <br /><br />
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The suspension of the vehicle is of an individual torsion bar type, typical of wheeled designs. Each wheel has a telescopic double action shock absorber to improve driving comfort. The BTR-80 may mount either KI-80 or KI-126 tubeless tyres with detachable armoured rims, both of which are bullet-resistant and semi-mine resistant. The latter is a later issue (mid 90's) which is superior in all of the characteristics previously described. An example of a mine that the wheels could reliably resist would be the BLU-43 anti-personnel mine, and mines like it. This affords the vehicle some dependability in regions saturated with area-denial mines, and grants the vehicle good survivability characteristics. Of special interest is the BTR-80's ability to drive even with two of its wheels completely destroyed. In fact, this feature enables the BTR-80 to continue moving even <i>after </i>being detonating an anti-tank mine, which, as a rule, would destroy at least one wheel. The tyres have an operating pressure ranging from 50 kPa to 300 kPa. The BTR-80 can endure travel for several hundred kilometers even with <i>all</i> its tyres punctured.<br />
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The BTR-80 has a centralized tyre pressure control system, enabling the driver to control tyre pressure while on the move in accordance with the type of terrain that the vehicle has to traverse.<br />
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The photo on the left shows a BTR-80 in Kosovo with KI-80 tyres. The large wheel hubs are the tell-tale sign that KI-80 tyres are in use. The photo on the right shows a BTR-80 with KI-126 tyres which have smaller wheel hubs.<br />
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The KI-126 tyre is currently standard among all BTR-80s.<br />
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<h3>
<span style="font-size: large;">WATER OBSTACLES</span></h3>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="http://3.bp.blogspot.com/-z43_YIjXKR4/VG0M_CaoobI/AAAAAAAAAtA/AIzKHr5oe88/s1600/4f627536d733.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://3.bp.blogspot.com/-z43_YIjXKR4/VG0M_CaoobI/AAAAAAAAAtA/AIzKHr5oe88/s1600/4f627536d733.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">Swimming BTR-80s. Note the raised tubes.<br />
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The BTR-80 is fully amphibious. It is propelled by two water jets, and can attain a maximum speed of 9km/h in the water. The driving endurance in the water is 12 hours. Turning in the water is achieved by closing off one of the water jet nozzles; closing the right nozzle turns the vehicle right, and closing the left nozzle turns the vehicle left. If both jets are malfunctioning, the vehicle may still move in the water by the turning of the wheels. The speed is reduced to a measly 4km/h, although the occupants would be saved from being stranded in the middle of whatever body of water they were trying to cross.<br />
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The wave deflector has to be erected before entering the water to ensure that driving visibility is not affected.<br />
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There are two ventilation tubes which must be raised when the vehicle is in the water. They provide air to the engine and allow exhaust gasses to be vented.</div>
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<h3>
ELECTRICAL SYSTEMS</h3>
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The BTR-80 can have two 12ST-85R1 batteries connected in parallel, or two 6ST-190TR batteries connected in series with a dual G290V three-phase synchronous generator set.<br />
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All crew members are provided with the R-124 intercom system.<br />
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<h3>
SELF-RECOVERY WINCH</h3>
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There is a winch installed inside the bow of the BTR-80. The winch is driven by a power takeoff shaft connected to the transmission and has a maximum pulling force of 4.6 tons, enough to let the BTR pull itself out of a bog or a ditch or perhaps rescue another stuck vehicle. The winch cable is 50 meters long.<br />
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The cable and hook can be accessed at the very front of the hull, through a small square port (shown above).<br />
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<span style="font-size: large;">CURRENT STATUS</span></h3>
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The original BTR-80 is no longer being procured by the Russian military, having being temporarily supplanted by the BTR-82A. However, export sales are an entirely different matter. The BTR-80 is still displaying a strong standing among international clients.<br />
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Surplus units from the late 90's cost approximately $400,000, and relatively new units should cost no more than that. Some civilian BTR-80s (new as well) are sometimes sold for as little as $50,000.<br />
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Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com21tag:blogger.com,1999:blog-3103574899092646031.post-63274434169319686612014-10-22T14:47:00.046-07:002023-04-20T01:49:07.759-07:00BMP-3<head>
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The BMP-3 is a modern IFV currently serving in the Russian Army and in a number of foreign militaries. It is the successor to the BMP-2 and has found great popularity outside of its native country due to its outstanding tactical-technical characteristics which include exceptional firepower, excellent frontal armour protection, high mobility, comfortable accommodations and a large upgrade potential. Throughout the years, the BMP-3 has proven to be an exemplary vehicle of its class while in the service of several nations across the globe. During its brief service life in the Soviet Army, it was only mass produced from 1988 to 1991 and only 250 vehicles were delivered to the Soviet Army. The production of the new BMP was carried out in parallel with the BMP-2.<br />
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Compared to the Soviet tank-building projects that were launched in the immediate postwar era, the <a href="http://armor.kiev.ua/Tanks/Modern/BMP3/bmp3_5.php">history</a> of the BMP-3 is short and straightforward. The Soviet Army was aware of the multitudes of shortcomings of the BMP-2, as revealed in the hot climate of Afghanistan. As such, the request was made for a new IFV design with improved characteristics. Two drafts were submitted, one of them by Kurganmashzavod. The Object 688 prototype created in Kurganmashzavod used a hull adapted from the Object 685 amphibious light tank, which resulted in less than optimal provisions for passenger dismounting, but otherwise had excellent potential as an amphibious troop carrier. It was necessary to raise the hull, change the shape of the front hull armour, change the turret ring construction and create a passenger space, among other things. Interestingly, the weapons of the Object 688 were placed in a low profile turret with a remotely controlled external weapons mount similar to the Object 680 prototype of the BMP-2. The photo on the left below, <a href="https://worldoftanks.com/en/news/chieftain/chieftains-hatch-kubinka/">taken by Nick "The Chieftain" Moran</a>, shows the Object 688 prototype housed at the Kubinka Tank Museum from its left quadrant and the photo on the right below shows it from the right quadrant.<br />
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Armed with a powerful 2A42 cannon (600 rounds), a coaxial 30mm AGS-17 grenade launcher (500 rounds), three PKTM machine guns (6,000 rounds) and a pair of ready-to-fire Konkurs anti-tank missiles in an external armoured pod similar to the M2 Bradley, the Object 688 could already be considered as the most well-armed IFV in the world had it entered service in the mid-1980's. However, the new low profile turret and its armament was deemed to be an insufficient upgrade over the BMP-2 to warrant the adoption of a completely new IFV with no commonality with the earlier BMP designs, and indeed, the BMP-1 and BMP-2 could also have an AGS-17 grenade launcher added to augment their primary weapons, and it had been done for a number of vehicles in Afghanistan where a low-velocity grenade launcher was ideal against light infantry protected by the terrain.<br />
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As such, the new turret had no significant advantages over the BMP-2 so the rationale for this rejection was clear and quite justified. The requirement for a new IFV to replace the existing BMP-2 was because the possibility of modernization had been almost entirely exhausted, and it had become impossible to deeply modernize the armament without using novel technologies or sacrificing the other tactical-technical characteristics of the vehicle such as its amphibious capability or its armour protection. The BMP-2 itself already represented the limit of the BMP-1 design from which it was derived, as it had to switch to a new armour steel grade with a lower thickness in order to control the weight gain from the new two-man turret to an acceptable level while retaining the same protection as the BMP-1.<br />
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To enhance the firepower of the prospective new IFV to a satisfactory level, the 2K23 armament complex was developed by Chief Designer Arkady Shipunov of the KBP design bureau. The new 2A72 and 2A70 cannons were designed specifically for the new IFV and the two weapons were combined into a single common gun cradle together with a PKTM coaxial machine gun. Both of the new weapons were designed to be highly compact with a very low weight in order to fit in such an arrangement. This combination of weapons gave the new IFV a unique set of capabilities with several advantages over previous models, and the 2K23 armament complex proved to be enough of a justification to adopt the new combat vehicle as a replacement for the BMP-1 and BMP-2.<br />
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In January 1985, the state tests of the BMP-3 began with four participating vehicles. The tests were conducted in Kubinka, Smoline, Kelayta and Alageze, which the vehicles passed, but as expected for any vehicle in this stage of development, a number of defects were revealed. Because the state tests were passed, the BMP-3 was accepted for service on the 1st of September, 1987, and put into low rate serial production by the Kurganmashzavod factory for refinement and future trials at the end of 1987.<br />
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A final cycle of tests took place from March 1988 to May 1989 where a BMP-3 unit of 10 vehicles from the Belorussian Military District participated in an experimental field operation with the new vehicles integrated into a mechanized rifle company. These tests were aimed at determining how quick soldiers could master the new vehicle, estimating the effectiveness of the recently improved BMP-3 and determining the quality of the serial production samples for further refinement. The experimental field operation demonstrated the superiority of the BMP-3 over the BMP-1 and BMP-2 in terms of tactical and firepower characteristics. It was first shown to the world at the Moscow parade in honor of the 45th Victory Day celebration on May 9, 1990. Shortly thereafter, the Soviet Union collapsed, leaving the BMP-3 in the hands of the newly formed Russian Army.<br />
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Due to its age, this article is currently undergoing renovations. It is regularly updated and may be taken down temporarily for revisions.</h3>
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<span style="font-size: large;">COMMANDER'S STATION</span></h4>
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The commander is seated on the right side of the turret, just like in a BMP-2 turret. He is responsible for observing the battlefield and designating targets for the gunner to subsequently engage, while also communicating with other vehicles in his unit via radio. The commander's seat is thickly padded and is adjustable in height. A dome light is installed on the turret well behind the commander's right shoulder. The 1V539 ballistic computer for the BMP-3's fire control system is installed on a partition between the seats of the commander and gunner.<br />
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The commander's cupola follows the same layout as the cupola of his counterpart in the earlier BMP-2, but differs in a number of details. Interestingly enough, the cupola was made from steel rather than aluminium like the rest of the vehicle. The underside of the commander's hatch had an anti-radiation lining that also acted as padding for the commander's head.<br />
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For battlefield surveillance and target designation, the commander was equipped with a TKN-3MB periscope and an array of general vision periscopes.<br />
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There are two fixed TNPO-170A periscopes mounted into the fixed half of the cupola at his disposal, and two additional TNPA-65 periscopes were embedded in the hatch facing the sides. The TNPO-170A offers a total horizontal field of view of 94 degrees and a total vertical field of view of 11-12 degrees while the TNPA-65 periscope offers a wide total horizontal field of view of 140 degrees and a total vertical field of view of 35 degrees. These figures represent the field of view with head movement. There is also a TNPT-1 rear-viewing prism with a total field of view of 80 degrees in the vertical plane and a total field of view of 140 degrees in the horizontal plane. The TNPT-3 is primarily used by the commander to help direct the driver when reversing the vehicle if the turret is pointed straight forward, as there are few other situations where the commander must look behind the turret. Except for the TNPA-65 periscopes, all of the vision devices in the commander's cupola are heated by the RTS heating system to prevent fogging in cold weather.<br />
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Compared to the BMP-2, the addition of two side-facing periscopes in the hatch of the cupola gave the commander of the BMP-3 a much better range field of view. Based on Soviet testing, over 95% of the observations made by tank commanders in various simulated combat scenarios were done in a 200-degree frontal sector. A rear-view periscope is only used in 0.8% of all cases. The cupola of the BMP-2 would only have fulfilled approximately 70% of the observational needs of its commander, so the increased visibility from the BMP-3 cupola represents an improvement of over 25%.<br />
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<span style="font-size: large;">TKN-3MB</span></h3>
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On most variants of the BMP-3, the commander is provided with the TKN-3MB. It can operate in two modes - active infrared imaging, or passive light intensification. When operating at night in the active mode, the OU-3GA2 IR spotlight must be used. The TKN-3MB sight has fixed 5x magnification in the day channel and an angular field of view of 10° in that setting. In the night channel, the sight has 4.2x magnification and an angular field of view of 8°. In the daytime, the nominal maximum identification distance for a tank is around 3,000 m, although this depends on meteorological conditions more than anything else. In the passive light intensification mode, the sight enables the commander to identify a tank-type target at a nominal maximum distance of 400 m, given that the ambient light is no darker than 0.005 lux, which is equivalent to a typical starless and moonless night. For an IFV that entered service at the very end of the Cold War, the night vision capabilities of the TKN-3MB was simply not competitive against the thermal imaging systems that had become standard for the Western counterparts of the BMP-3. Instead of being used to search for targets in a combat situation at night, the device would be most useful as a navigational tool in the passive night vision mode.<br />
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The TKN-3MB has<span style="font-size: small;"> a stadiametric rangefinding scale intended for approximate manual range estimations of tank-sized targets with a height of 2.7 meters at distances of up to 3.2 km, although this might be rather optimistic for most situations.</span><br />
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Like in all other Soviet tanks and IFVs prior to the BMP-3, the commander of the vehicle can designate targets by pressing the thumb button on the right handle on the TKN-3MB periscope. The cupola is equipped with a counter-rotating motor to keep the cupola facing the target as the turret spins to meet the target. The maximum error is 10 mils, which makes the target designation feature infeasible for actually laying the gun on target. Rather, this feature is only to put the gunner in visual contact with the target - the rest is entirely up to the gunner once he has the target in his sights.<br />
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<span style="font-size: large;">TKN-AI</span></h3>
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Later production models of the BMP-3 (these would also be equipped with the SOZh gunner's sight) will be instead equipped with the TKN-AI pseudo-binocular day/night passive-active observation device, which replaces the TKN-3MB. The TKN-AI enables day and night observation using natural light and also using a IR laser pulse-spotlight. When the TKN-AI is used in the pulse mode, it can detect a tank-type target at a distance of 1000 m. Pulsing the laser prevents backscatter when viewing through thick fog or haze. Reduction of backscatter increases the light penetration through the atmosphere, which has the effect of improving the viewing distance under poor weather conditions.<br />
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Additionally, the laser spotlight can be used as a rangefinder with the TKN-AI at a distance of between 200 m and 3000 m. The accuracy of the rangefinding function is 20 m. Using the Gen 2+ image intensifier module, the target identification range achievable using the TKN-AI for a tank-sized target is 600 m. The sight has a fixed magnification of 4.75x in day channel and 5x in the night channel. At night, the commander can detect enemy optronics (IR radiation emitters) at distances up to 3 km.<br />
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<span style="font-size: large;">COMMUNICATIONS</span></h3>
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The commander is provided with an R-173 radio for inter-vehicle communications. The R-173 radio is an FM radio that can operate in 10 preset frequency modes, with the ability to mechanically switch frequencies in 3 seconds. It is currently outdated and has been replaced with the R-168 frequency-hopping radio set with the ability to send encrypted data and switch frequencies 100 times per second. The commander is provided with a P-174 intercom device to communicate with the rest of the crew.<br />
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Like the BMP-2, the commander of the BMP-3 has a complete set of duplicated gunnery controls at his disposal. The upper right corner of the picture below (screenshot taken from the "<i>Poligon</i>" show aired on the Rossiya 2 channel) shows the commander's PP-088 weapons management console. The silver box to the left of it is a KR-80 relay box, and the gray box to the left of that is a power supply box.<br />
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The PP-088 console is a part of the 6ETs088 weapons control complex that is used to manage and weapons integrated into the vehicle as well as to select and fire smoke grenades from the 902B smokescreen system. The drawing below shows the PP-088 console in greater detail.<br />
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The weapons management console displays the ammunition reserve of the specified weapon type, readiness state of the weapons, and allows the commander to select the desired ammunition types for both the 30mm and 100mm cannons as well as control the operating mode of the autoloader and activate the autoloader to load the 100mm cannon. The console also enables the commander to select the rate of fire of the 2A72 30mm cannon. The PP-088 weapons management console must be switched on before the weapons can be used from the commander's station. The commander cannot fire guided missiles since his 1PZ-10 sight lacks the necessary provisions. He controls the weapons using a set of control handles identical to the gunner's. The photo below, taken from the twower livejournal blog, show's the commander's 1PZ-10 sight and his control handles. Behind it is the metal link feed chute that channels the 30mm ammunition belts from the containers underneath the crew seats up to the 2A72 autocannon.<br />
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<span style="font-size: large;">1PZ-10</span></h3>
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For daytime combat, the commander is equipped with the 1PZ-10 monocular dual-purpose sight with dependent stabilization in the vertical plane. The sight is broadly similar to the 1PZ-3 sight used in the BMP-2 but features modifications to enable 100mm rounds to be used.<br />
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The 1PZ-10 sight has 1.2x to 4x magnification. In the 1.2x magnification setting, the field of view is 49 degrees, narrowing down to 14 degrees in the 4x magnification setting. Like the gunner's PPB-2 sight, the 1PZ-10 is very flexible. It can elevate by +81 degrees and depress by -10 degrees, enabling it to target both aircraft and ground targets. It cannot, however, automatically track its targets, nor can the commander fire guided missiles using the 1PZ-10 sight as it has no guidance channel.<br />
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The sight is stabilized in the vertical plane by piggybacking on the weapons stabilization via a pair of mechanical rods. Since the stabilization mechanism interfaces with lenses and prisms inside the sight housing, the housing itself remains static as the stabilizer does its work, so the commander does not need to adjust his head backwards and forwards as his face is pressed up against the eyepiece.</div>
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1PZ-10 features a simple range adjustment system that is standard for sights in the 1PZ series. A horizontal line runs center of the sight viewfinder to form a crosshair with the fixed vertical line that runs down perpendicular to it. Ladder-type range scales for both cannons are provided. </div>
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The photo below shows the sight under 1.2x magnification. You can see the aforementioned range scales and horizontal bar.</div>
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To use this sight, the commander first estimates the range to the target by eye and then he turns the range adjustment dial to move the horizontal line until it intersects with the desired range marking for the desired ammunition type. For example, if the commander wishes to open fire with the 2A72 cannon at a congregation of enemy infantry at 1.6 kilometers, he simply twists the range adjustment dial until the horizontal line intersects with the range scale increment marked "16" for "30 OF". The horizontal and vertical lines in the viewfinder form a crosshair at the correct distance, and all the must do now is raise the weapons until the crosshair is placed directly on the target, thus giving the autocannon the correct superelevation, and open fire.<br />
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<h3>
<span style="font-size: large;">GUNNER'S STATION</span></h3>
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<a href="https://1.bp.blogspot.com/--gs_XVgN0n8/XbjaMHkEZmI/AAAAAAAAPiU/cvPZ7VnKIXcsxFktAdn1P70j_cNDzb4RgCLcBGAsYHQ/s1600/gunners%2Bstation.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1296" data-original-width="972" height="640" src="https://1.bp.blogspot.com/--gs_XVgN0n8/XbjaMHkEZmI/AAAAAAAAPiU/cvPZ7VnKIXcsxFktAdn1P70j_cNDzb4RgCLcBGAsYHQ/s640/gunners%2Bstation.jpg" width="480" /></a></div>
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The gunner of a BMP-3 was seated on the left side of the turret and he was provided with his own oval hatch. The hatch was sprung with a torsion bar for the convenience of the gunner when it is opened. For vision, the gunner is provided with two sighting systems and two TNPO-170A general vision periscopes, one aimed forward and the other aimed to the left. These two periscopes enhance his situational awareness and allow the gunner to cover the commander's blind spot to the left of the turret from the obstructive periscopic sights on the gunner's side of the turret. Compared to the BMP-2, the number of vision devices provided to the gunner was downgraded as the BMP-2 provided its gunner with three TNPO-170A periscopes that provided him with good forward and leftward vision, and he even had a rear view TNPT-1 prism in his hatch. The BMP-1 also provided its gunner with good vision as it had four periscopes aimed to the front and both sides of the turret, but lacked a rear view device.<br />
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However, it should be understood that in the BMP-1 and BMP-2, the commander of the vehicle was also the squad leader, and he was sometimes obliged to dismount with the passengers depending on the situation. Under such circumstances, the gunner had to command the vehicle from his station and he needed good visibility to do so effectively. With the BMP-3, it was different. The commander no longer dismounted with the passengers except perhaps under special circumstances, and as such, the BMP-3 retained its commander during combat at all times so the gunner could focus entirely on his tasks.<br />
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To protect the gunner from a bouncing shell casing in case the ejection mechanism fails, there is a curved aluminium shield installed on the turret ceiling next to the ejection port.<br />
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The gunner was also provided with a clock-type turret
azimuth indicator that was connected to the manual turret traverse mechanism. Unlike the gunner of a BMP-2, a BMP-3 gunner was capable of fighting air targets independently from the commander as he was provided with his own PPB-2 anti-aircraft sight. For communications, the gunner was provided with a standard P-174 intercom control box and nothing more.<br />
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<a href="https://1.bp.blogspot.com/-4FaVUxHRflA/XbjiGnPbB6I/AAAAAAAAPiw/TxHU5VMPIr0ZTCAjJdNC_Qt5wK7RDL9zACLcBGAsYHQ/s1600/turret%2Bazimuth%2Bcompass.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="640" data-original-width="960" height="426" src="https://1.bp.blogspot.com/-4FaVUxHRflA/XbjiGnPbB6I/AAAAAAAAPiw/TxHU5VMPIr0ZTCAjJdNC_Qt5wK7RDL9zACLcBGAsYHQ/s640/turret%2Bazimuth%2Bcompass.jpg" width="640" /></a></div>
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The gunner was provided with a PL-088 weapons management console, which performs the same functions as the PP-088 installed on the turret wall of the commander's station. As the picture below shows (screenshot taken from the "<i>Poligon</i>" show aired on the Rossiya 2 channel), the console is installed on the turret wall just next to the front-facing TNPO-170A periscope and below it is the intercom control box.<br />
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<a href="https://2.bp.blogspot.com/-NnSgOiTTwh0/WZ6odZA1UEI/AAAAAAAAJKw/SVxB0X2-Nd86fm3GYco8L9X1rjHHnjJcQCLcBGAs/s1600/gunners%2Bweapon%2Bstation.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="594" data-original-width="1366" height="278" src="https://2.bp.blogspot.com/-NnSgOiTTwh0/WZ6odZA1UEI/AAAAAAAAJKw/SVxB0X2-Nd86fm3GYco8L9X1rjHHnjJcQCLcBGAs/s640/gunners%2Bweapon%2Bstation.png" width="640" /></a></div>
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The drawing below shows the purposes of the many buttons and switches on the PL-088 console. Using this single console, the gunner can control the rate of fire of the 2A72, see the amount of ammunition left for both cannons, ready the weapons to fire, control the operating mode of the autoloader, activate the autoloader, and more.<br />
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The gunner is responsible for the fire control system and the stabilizer. He is provided with a set of control handles (shown below) installed directly underneath his primary sight, with which he can control the turret and the stabilizer system and apply corrections for stabilizer drift.<br />
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<a href="https://4.bp.blogspot.com/-QCga4kJTOCI/WZ6ob-6CdBI/AAAAAAAAJKo/PLtU739IlIIyGjD71MymHtZwAelR73dUwCLcBGAs/s1600/bmp-3%2Bhandgrips.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="768" data-original-width="1366" height="359" src="https://4.bp.blogspot.com/-QCga4kJTOCI/WZ6ob-6CdBI/AAAAAAAAJKo/PLtU739IlIIyGjD71MymHtZwAelR73dUwCLcBGAs/s640/bmp-3%2Bhandgrips.png" width="640" /></a></div>
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<h3>
<span style="font-size: large;">SIGHTING COMPLEXES</span></h3>
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<span style="font-size: large;">1K13-2</span></h3>
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<a href="http://3.bp.blogspot.com/-2xIB2UVfl8E/VEdBBwXkVvI/AAAAAAAAAa8/5rx97bDmmLI/s1600/bmp-3.31158.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="290" src="https://3.bp.blogspot.com/-2xIB2UVfl8E/VEdBBwXkVvI/AAAAAAAAAa8/5rx97bDmmLI/s400/bmp-3.31158.jpg" width="400" /></a></div>
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In a basic BMP-3, the gunner is provided with the 1K13-2 sighting system as his primary sight. It is used for the aiming and guidance of all weapons organic to the turret. Due to its integrated night vision system, the 1K13-2 can be used for observation both in the daytime and at night, with independent stabilization of the visual field in two planes. The presence of independent two-plane stabilization instead of single-plane stabilization is the primary distinguishing factor between the 1K13-2 and 1K13 sights, used on a large number of Soviet tanks since the early 1980's. </div><div><br /></div><div>The sight has a digital range display in the viewfinder. In the day channel, the sight has a fixed 8x maximum magnification, and 5.5x in the night channel. The field of view is 5 degrees at the 8x magnification in the day channel, and 6 degrees and 10 minutes in the fixed 5.5x magnification in the night channel. In the passive mode, the sight enables a tank-type target to be identified at a range of 800 meters at night with with ambient light of 0.005 lux, corresponding to a typical moonless, starlit night. The viewing distance is expanded in the active mode to 1,100 m with the use of the OU-5-1 IR spotlight.<br />
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<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-rrigMkn79r4/VTF7bV1e0_I/AAAAAAAAB1w/PtDigC1fHTM/s1600/1k13.jpeg" style="margin-left: auto; margin-right: auto;"><img border="0" height="482" src="https://4.bp.blogspot.com/-rrigMkn79r4/VTF7bV1e0_I/AAAAAAAAB1w/PtDigC1fHTM/s640/1k13.jpeg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Actually a view through the 1K13-49 sight, but it's close enough</td></tr>
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<br /><br />The baseline BMP-3's fire control system includes the 1V539 ballistic computer, a crosswind sensor, ambient air temperature sensor and a 1D16-3 laser rangefinder. Cant, speed and vehicle course angle sensors are included to register and compensate for any changes in the movement of the vehicle. The nominal range of the 1D16-3 rangefinder is between 500 m to 4,000 m with a measuring precision of ±10 meters. If necessary, the gunner can manually enter range data measured using the stadiametric ranging scales in the 1K13-2 sight viewfinder into the ballistic computer in the event of rangefinder malfunction.<br /><br />
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<a href="https://1.bp.blogspot.com/-qZHktwO0zEI/XbxSMCh8jGI/AAAAAAAAPkE/eb_hCmUrnY4czoJRvx5AWm3bcrj4nUL2gCLcBGAsYHQ/s1600/bmp-3%2Bfire%2Bcontrol%2Bsystem%2B1k13-2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="669" data-original-width="999" height="267" src="https://1.bp.blogspot.com/-qZHktwO0zEI/XbxSMCh8jGI/AAAAAAAAPkE/eb_hCmUrnY4czoJRvx5AWm3bcrj4nUL2gCLcBGAsYHQ/s400/bmp-3%2Bfire%2Bcontrol%2Bsystem%2B1k13-2.png" width="400" /></a></div>
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The 1D16-3 laser rangefinder was initially unreliable. Reportedly, it began to refuse to operate past 2,000 cycles, but this was soon rectified, and the TBF (time before failure) increased to 15000 cycles. The 1K13-2 sight, like the 1D16-3, originally had low reliability as well. In initial tests, it began experienced failures past just 500 cycles of operation. This was later resolved, and time before failure (TBF) was raised to 5600 cycles. The operating time limit of the sight was originally a measly 60.9 hours, but it was raised to 210 hours.<br />
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<a href="https://1.bp.blogspot.com/-m1_ocYk2ERw/XbjhauNVVqI/AAAAAAAAPio/Q-DI4Kbz8OgTcxTWFdQjzYe-LvlcSR46QCLcBGAsYHQ/s1600/pravda%2Bphoto%2B1.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="454" data-original-width="680" height="266" src="https://1.bp.blogspot.com/-m1_ocYk2ERw/XbjhauNVVqI/AAAAAAAAPio/Q-DI4Kbz8OgTcxTWFdQjzYe-LvlcSR46QCLcBGAsYHQ/s400/pravda%2Bphoto%2B1.jpeg" width="400" /></a><a href="http://3.bp.blogspot.com/-oE2fmK3itDM/VEC6-Qd5GrI/AAAAAAAAAHU/IFNOmElg_js/s1600/BMP-3%2C%2Blaser%2Brangefinder.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://3.bp.blogspot.com/-oE2fmK3itDM/VEC6-Qd5GrI/AAAAAAAAAHU/IFNOmElg_js/s400/BMP-3%2C%2Blaser%2Brangefinder.jpg" width="400" /></a></div>
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<a href="http://2.bp.blogspot.com/-d97jfLrCHd0/VEKJAj9Gr_I/AAAAAAAAALg/KwLgi3ixeFM/s1600/5.jpg"><img border="0" height="200" src="https://2.bp.blogspot.com/-d97jfLrCHd0/VEKJAj9Gr_I/AAAAAAAAALg/KwLgi3ixeFM/w400-h200/5.jpg" width="400" /></a><a href="http://2.bp.blogspot.com/-lTqUVJvf72g/VEKJBhPFGTI/AAAAAAAAALo/1TSVoGI6-UY/s1600/4.jpg"><img border="0" height="202" src="https://2.bp.blogspot.com/-lTqUVJvf72g/VEKJBhPFGTI/AAAAAAAAALo/1TSVoGI6-UY/w320-h202/4.jpg" width="320" /></a></div>
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<h3>
<span style="font-size: large;"><b>PPN-D SOZh</b></span></h3>
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<a href="https://1.bp.blogspot.com/-7HzCN1bJMOk/XbnInndArgI/AAAAAAAAPjY/TKiL8cBu6LsRBXEJE5FBPdWXb6TspgWDgCLcBGAsYHQ/s1600/sozh%2Bsight.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="296" data-original-width="448" height="263" src="https://1.bp.blogspot.com/-7HzCN1bJMOk/XbnInndArgI/AAAAAAAAPjY/TKiL8cBu6LsRBXEJE5FBPdWXb6TspgWDgCLcBGAsYHQ/s400/sozh%2Bsight.jpg" width="400" /></a><a href="http://2.bp.blogspot.com/-xZPwuyzpTp0/VESIT-Ve6mI/AAAAAAAAARs/2lHRLYFXIy4/s1600/-Sozh.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://2.bp.blogspot.com/-xZPwuyzpTp0/VESIT-Ve6mI/AAAAAAAAARs/2lHRLYFXIy4/s1600/-Sozh.jpg" /></a></div>
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Beginning in 1998, the PPN-D SOZh sight designed and manufactured by the Belorussian Peleng open joint-stock company began to be installed in the BMP-3. The sight had day and night channels with either passive light intensification or active IR illumination. It was independently stabilized in two planes and had an integrated laser rangefinder as well as a coded laser emitter for missile guidance. The laser rangefinder has a measuring range of 500 meters to 7,000 meters with range filtering to eliminate false returns. The measuring precision of the rangefinder is ±10 meters. The SOZh sight also features an internal periscopic vision block with a viewing window above the eyepiece and brow pad of the sight, as shown in the photos above and below.<br />
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<a href="https://1.bp.blogspot.com/-h-1G1nYeQpc/XcEAvTxv9yI/AAAAAAAAPmA/q9FmNchFB8ovB-9y-YMv8MnpMuLKjVS0gCLcBGAsYHQ/s1600/sozh%2Bsight%2Bexhibition.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="740" data-original-width="624" height="400" src="https://1.bp.blogspot.com/-h-1G1nYeQpc/XcEAvTxv9yI/AAAAAAAAPmA/q9FmNchFB8ovB-9y-YMv8MnpMuLKjVS0gCLcBGAsYHQ/s400/sozh%2Bsight%2Bexhibition.png" width="336" /></a><a href="https://1.bp.blogspot.com/-iibtkeQZMek/XbnFp1tCW4I/AAAAAAAAPjI/Jc4WxrNdCg4QI4hbDEyXPm-L2vnbxchxACLcBGAsYHQ/s1600/PPN-D_SOZH_1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="231" height="400" src="https://1.bp.blogspot.com/-iibtkeQZMek/XbnFp1tCW4I/AAAAAAAAPjI/Jc4WxrNdCg4QI4hbDEyXPm-L2vnbxchxACLcBGAsYHQ/s400/PPN-D_SOZH_1.jpg" width="153" /></a></div>
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The daytime channel has 5x and 14x magnification settings. The general vision periscope has a field of view of 20x5 degrees. The field of view is 6.66 degrees in the 5x setting, and 3.5 degrees in the 14x setting. The greatly increased maximum magnification gives the sight a necessary advantage over older sighting systems like the 1K13 and the BPK-1-42 (in the BMP-2) in terms of target identification clarity at longer distances, which was necessary to fully exploit the 5,500-meter range of the 9M117M-1 guided missile as well as the increased range of the 100mm 3UOF19 HE-Frag shells.<br />
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The viewfinder of the SOZh sight displays the ammunition type selected, the range to the target and a ready-to-fire signal. </div><div>
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The a nominal maximum range for identifying a tank-type target in daytime is 7,000 meters. The accuracy of the stabilization of the field of view is 0.1 mils.<br />
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Nighttime identification range for a tank-sized target is 800 meters in the passive mode, and 1,100 meters in the active mode, whereby the PL-1 IR laser pulse beamer mounted coaxially to the guns (see above) is used. The <a href="http://www.led-e.ru/assets/files/pdf/2012_1_45.pdf">PL-1 is a programmable IR laser pulse beamer</a> that can emit modulated laser signals at an operating frequency of 5.2 kHz with an illumination pulse duration of 130 ns. It can also function as a laser rangefinder. However, it is not used in that capacity on the BMP-3 since the SOZh sighting system has an integrated rangefinder with greater accuracy than the PL-1 is capable of. The PPN-D integrated laser rangefinder has a ranging error margin of around 10 m. PL-1 is only used as a source of infrared light for active infrared imaging night vision.<br />
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The PL-1 laser beamer was developed by the BelOMO optical and mechanical company. The device runs on 50 volts, and connects directly to the 27A electrical system of the vehicle. The OU-6 laser beamer is functionally equivalent to the PL-1, so the two of them can be used interchangeably. PL-1 projects a much more coherent and more intense beam of infrared light than a regular xenon IR spotlight, making it much easier to see faraway objects even in the presence of interference. The projector itself is contained inside a lightly armoured protective housing, which you can see in the photo below (a destroyed BMD-2).<br />
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The passive mode requires lighting conditions of at least 0.005 lux in order to achieve the aforementioned identification range, like the earlier 1K13-2.<br />
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<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-7C27UrCi1R8/VEY0yGZhEfI/AAAAAAAAAVc/ZmhPnnmA52U/s1600/bmp-3f-turret-500x375.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://3.bp.blogspot.com/-7C27UrCi1R8/VEY0yGZhEfI/AAAAAAAAAVc/ZmhPnnmA52U/s1600/bmp-3f-turret-500x375.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">PL-1 IR laser beamer<br />
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The guidance range limit of the SOZh sight for ATGMs is 5,500 meters, matching the maximum range of the 9M117M1 "Arkan" missile. The maximum divergence of launched ATGMs from alignment to the guidance channel and sighting system is 0.5 meters. In other words, the maximum distance the missile will stray from the line of sight of the guidance channel is 0.5 meters.<br />
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Currently, the SOZh sight is the standard gunner's sight on almost all Russian BMP-3s except for the earliest ones. Since the beginning, the BMP-3 was equipped with a 1V539 digital ballistic computer. 1V539 can process five programmable ballistic factors and calculate ballistic solutions for ranges up to 5,000 meters. The ballistic computer takes 10 seconds to boot up when the power supply is connected, and it can run continuously for 6 hours. Ballistic calculations are done instantaneously.<br />
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<h3>
<span style="font-size: large;">Vesna-K</span></h3>
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The Vesna-K was a newer main sight, first seen in the 1990's. It features thermal imaging, an integrated laser rangefinder, and an AST-B automatic target tracking unit. The nominal maximum detection range of a target is 6500 m, and the identification range of a tank-type target is 4500 m. The Vesna-K sight has a temperature sensitivity of 0.1 degrees Celsius, and can switch between either wide or narrow field of view settings. The field of view in the wide setting is 9 x 6 degrees, and 3 x 2 degrees in the narrow setting. Under maximum electronic magnification, the field of view is 1.5x1 degrees.<br />
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The AST-B tracking device has a tracking accuracy of 0.17 mils. It can track anything from people to low flying aircraft, though the anti-aircraft sight will have to be used to engage high flying aircraft or aircraft flying overhead.<br />
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It must be noted that Vesna-K is not a fire control system, just a sight. It is installed next to the Sozh, and acts as the de-facto night sight. A BMP-3 equipped with Vesna-K will still have the 1K537 ballistic computer.<br />
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To identify what sighting system a BMP-3 is equipped with, look whether the indicated (<span style="color: red;"><---</span>) device is a single-window or double-windowed one. Single-windowed ones are invariably either 1K13-2 sights or SOZh sights, and BMP-3s with 1K13-2 sights invariably come with the 1D16-3 laser rangefinder. Double-windowed ones have a Vesna-K.<br />
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The Russian Army has been refitting their BMP-3s with SOZh sights since at least 2008, but the Vesna-K has not proliferated due to financial reasons.<br />
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<h3>
<span style="font-size: large;">PPB-2</span></h3>
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The PPB-2 weapons sight is a monocular dual-purpose sight mounted to the right of the gunner's primary sight. The primary purpose of the sight is to provide the gunner with an anti-aircraft sighting instrument for high angle fire which is necessary for firing upon fast-moving low altitude aircraft flying at close range or even flying over the vehicle itself. The secondary purpose of the sight is to provide the gunner with a backup option in case the primary sight experiences a failure. To facilitate aiming at high altitude targets, the articulating periscopic head can look upwards by 81 degrees, and down by 10 degrees. However, because the sight is mechanically linked to the gun cradle, it is limited in its range of elevation by the vehicle's weapons. It has a field of view of 25-28 degrees at a fixed 2.47-2.6x magnification. It is marked with range scales for all onboard weapons as well as lead markers for leading aerial targets travelling at speeds not more than 250 m/s.<br />
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<a href="http://4.bp.blogspot.com/-K3TnPwpUGxU/VHQCcy3PI8I/AAAAAAAAAyo/mMMEf16eluw/s1600/PPB-2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="220" src="https://4.bp.blogspot.com/-K3TnPwpUGxU/VHQCcy3PI8I/AAAAAAAAAyo/mMMEf16eluw/s1600/PPB-2.png" width="400" /></a></div>
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Due to the limited magnification and lack of an integrated range adjustment system, the gunner's target finding capabilities are severely constrained. However, this is not a significant obstacle when targeting aircraft due to the nature of the task. As it is a greatly simplified sight with only the most essential working components inside it, the combat effectiveness of the BMP-3 against ground targets would be noticeably reduced if the gunner was forced to use the PPB-2 instead of the primary sight. As the photo above shows, the sight is surrounded by exposed nuts and screws and the sight itself has no dials, buttons or switches, indicating that there are no adjustments that can be made by the gunner in the field without a tool. It is interesting to note that PPB-2 only weighs 3.42 kg, compared to the more serious 1PZ-10 which weighs 18 kg.</div><div><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-jGlLMeWGQSo/VlBY_aLracI/AAAAAAAAENg/3jRwIIdd-PE/s1600/BMP-3%2Bgunner%2Bsight%252C%2BNorth%2BOssetia..jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://2.bp.blogspot.com/-jGlLMeWGQSo/VlBY_aLracI/AAAAAAAAENg/3jRwIIdd-PE/s400/BMP-3%2Bgunner%2Bsight%252C%2BNorth%2BOssetia..jpg" width="297" /></a><a href="https://4.bp.blogspot.com/-_wzp7HPA5j8/WZiDQWpoDCI/AAAAAAAAJG4/uZGMHxPgjB8E_2dmROJjJY1msJC-UvVlQCLcBGAs/s1600/0_edb40_4519f6ab_orig.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="625" data-original-width="347" height="400" src="https://4.bp.blogspot.com/-_wzp7HPA5j8/WZiDQWpoDCI/AAAAAAAAJG4/uZGMHxPgjB8E_2dmROJjJY1msJC-UvVlQCLcBGAs/s400/0_edb40_4519f6ab_orig.jpg" width="221" /></a></div><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both;"><br /></div><div class="separator" style="clear: both;"><br /></div><div class="separator" style="clear: both;">A closer view of the reticle can be seen below, taken from a screenshot from the "Poligon" show aired on the Rossiya 2 channel.</div><div class="separator" style="clear: both;"><br /></div><div class="separator" style="clear: both;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-5sWlLf9O_V0/VHQUdalyvyI/AAAAAAAAAz0/MW8eh_atCb0/s1600/SOZh%2BAperture.png" style="clear: right; margin-bottom: 1em;"><img border="0" height="356" src="https://2.bp.blogspot.com/-5sWlLf9O_V0/VHQUdalyvyI/AAAAAAAAAz0/MW8eh_atCb0/s1600/SOZh%2BAperture.png" width="640" /></a></div><div><br /></div>
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To conserve the service life of the primary sight, the PPB-2 was apparently used as the gunner's de facto primary sight during training as it is extremely simple and practically unbreakable, according to one anecdote.<br />
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<span style="font-size: x-small;"><span style="font-size: large;">STABILIZERS</span></span></h3>
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<span style="font-size: small;">The BMP-3 is equipped with the 2E52-2 electro-mechanical stabilizer. The factory designation of the 2E52-2 is ITsKR.461314.001.</span> This stabilizer enables very high accuracy firing through the use of two EDM-20M electric motors. The two motors are identical in performance and precision; one drives the gun elevation mechanism and one drives the turret traverse mechanism. A significant advantage of the all-electric nature of the stabilization system is that there is no dangerous flammable hydraulic fluid being pumped at high pressure around the turret, so that if the armour is perforated, the chances of the vehicle catching fire is greatly reduced. Not having any plumbing inside the turret also makes it easier to maintain the vehicle. Furthermore, hydraulic pumps are bulky, noisy and consume a lot of power, so omitting one from the BMP-3 gives it better fuel economy and adds comfort for the crew. Another important advantage is that the electrical endurance of the BMP-3 while laying in ambush with engines off is better, though still rather limited as the vehicle lacks an APU. <br />
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The stabilizer complex includes the 1B14 gyroscopic roll sensor. This gyroscopic sensor takes two minutes to power up to its operating speed, which is done when starting the vehicle. The warranty period is 1500 hours of operation. Besides that, there is also the PT115ks-1G angular position sensor and the TGP-5 accelerometer.<br />
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The 2E52-2 system operates in three possible modes; automatic, semi-automatic and guiding. The automatic and semi-automatic modes are similar to the modes of the same name featured in the 2E36 stabilizer complex for the BMP-2. In the automatic mode, the operation of the stabilizer is simplified and easily understood: the stabilizer keeps the weapons stable and aimed at the target with maximum precision as the vehicle moves. This is a general purpose mode meant for shooting at land targets and at hovering or slow-moving air targets. The technical manual for the BMP-3 lists these figures for the automatic mode:<br />
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Automatic Mode</h3>
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Maximum Gun Elevation Speed: 6 °/s<br />
Minimum Gun Elevation Speed: 0.02 °/s<br />
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Maximum Turret Traverse Speed: 30-35 °/s<br />
Minimum Turret Traverse Speed: 0.02 °/s<br />
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The manual vaguely mentions that the speed of turret traverse in the "overcharge" condition is 35 °/s, but it does not mention the maximum traverse speed for the automatic mode without "overcharge". I interpret this to mean that the turret traverse speed has a hard limit of 35 °/s that can be reached by simply turning the control handles left or right to the furthest possible position.<br />
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The median stabilization error of the 2E52-2 system in the automatic mode when the vehicle is in motion at a speed of 25 km/h is not more than 0.05 mils. This means that the BMP-3 can engage point targets from a distance of more than a kilometer while moving at typical cross-country driving speeds with essentially the same effectiveness as when it is immobile. The quality of the stabilizer can be considered on par with its contemporary analogues in this regard.<br />
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The semi-automatic mode is meant only for engaging air targets flying by or over the vehicle at high speeds at closer ranges. The acceleration and top speeds of the motors for both the traverse and elevation motors are boosted, at the cost of a great reduction in aiming precision. As it operates, the stabilizer will experience drift at a rate of 25 mils/min, meaning that the stabilizer will drift off target by 1.4 MOA as each second passes when left in continuous operation maintaining its aim at a single point as the vehicle moves sideways. This is not good performance, especially since this figure is already adjusted to include periodic drift compensation by the stabilizer complex. Nevertheless, it is mostly irrelevant since this stabilizer mode is only intended for a rather niche role.<br />
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Semi-Automatic Mode</h3>
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Maximum Gun Elevation Speed: 35 °/s<br />
Minimum Gun Traverse Speed: 0.1 °/s<br />
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Maximum Turret Traverse Speed: 35 °/s<br />
Minimum Turret Traverse Speed: 0.1 °/s<br />
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Besides the two standard operating modes, there was also the missile guidance mode. It is only used for guiding the BMP-3's gun-launched anti-tank guided missiles. The maximum speed of turret rotation in the guided mode is electronically limited to only 2.5 /s in order to prevent the gunner from accidentally breaking laser contact with the missile while tracking a target. The minimum gun laying speed is the same as in the automatic mode.<br />
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Maximum Gun Elevation Speed: 2.5 °/s<br />
Minimum Gun Elevation Speed: 0.02 °/s<br />
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Maximum Turret Traverse Speed: 2.5 °/s<br />
Minimum Turret Traverse Speed: 0.02 °/s<br />
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As usual, the gunner's control handles follow the traditional "Cheburashka" configuration. In fact, the control handles are the same ones used in the BMP-2. The commander gets his own pair to take control of the weapons when in commander override mode. Turret rotation is done by twisting the control handles around its vertical axis like a turntable, as opposed to a steering wheel style as is common on NATO tanks and IFVs.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-HIvj1fUyrk8/VRamT8L2QSI/AAAAAAAABeI/bJS9Vg_T2lo/s1600/control.jpeg" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://4.bp.blogspot.com/-HIvj1fUyrk8/VRamT8L2QSI/AAAAAAAABeI/bJS9Vg_T2lo/s1600/control.jpeg" width="217" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Gunner's handgrips</td></tr>
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The stabilizer complex needs two minutes to fully activate. When not in battle, the stabilizer should be set to the standby mode in order to prevent excessive wear. Upon entering combat, the stabilizer can be switched on from the standby mode, whereby it only requires a second or two to achieve full functionality.<br />
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In order to prevent injuries to crew members and passengers and to prevent damage to the stabilizer, the 2E52-2 stabilizer is automatically locked when the hatches of the driver or any of the passenger hatches are unlocked. The stabilizer also automatically shuts down and locks the turret in place when the GO-27 radiation sensor detects a strong influx of radiation. This prevents the turret from being damaged by strong winds.<br />
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<span style="font-size: large;">
ARMAMENT</span></h3>
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The 2K23 armament complex is housed in a fully traversable turret, consisting of a 100mm 2A70 low-pressure rifled gun, a 30mm 2A72 autocannon, and a 7.62x54mm PKTM co-axial machine gun. All three weapon systems are located on the same mount, which provides +60 degrees maximum elevation and -6 degrees maximum depression when the turret is facing the front, and +64 degrees elevation and -2 degrees depression when facing the rear. The cradle is in turn installed in the 5-ton turret (when combat loaded), which is fitted into a 1,982mm diameter turret ring. The turret has a low height of only 540mm and a width of 2,266mm, making it a relatively small target when a BMP-3 is in a hull-down position.<br />
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The weapons are managed using the 6ETs088 weapons control complex which contains the BU-088 control unit, the PP-088 and PL-088 consoles, the KZ-088 protection box, and the DNL-088 carousel tray sensor. All together, the system is able to track the ammunition left for both cannons and allows the commander and gunner to independently manage the weapons from their own stations.<br />
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<h2>
<span style="color: black; font-size: x-large;">2A72</span></h2>
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<a href="http://3.bp.blogspot.com/-7L8nTXFRXNQ/VPFzxHEIddI/AAAAAAAABRg/jMjBewtyBs8/s1600/bmp-3firing.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="339" src="https://3.bp.blogspot.com/-7L8nTXFRXNQ/VPFzxHEIddI/AAAAAAAABRg/jMjBewtyBs8/s1600/bmp-3firing.png" width="640" /></a></div>
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A 2A72 long-recoil, dual-feed autocannon is mounted beside the 2A70. Depending on the source, the 2A72 has a maximum rate of fire of 350-400 rounds per minute (KBP Tula) or 350-390 rounds per minute (Soviet Autocannon, Christian Koll). In the BMP-3, the fire rate is electronically limited to not less than 300 rounds per minute by the fire control system, so the technical maximum fire rate can only be achieved by firing the gun manually with the backup trigger. The technical maximum fire rate of the 2A72 is far lower than the fire rate of the 2A42 (550-800 rounds per minute) but still double that of its immediate counterparts, and comparable to the rate of fire of the 2A42 when used in the 'low' setting (200-300 rounds per minute). </div><div><br /></div><div>The relatively high rate of fire enables this cannon to be used in an anti-aircraft role to a limited extent when paired with the anti-aircraft sight on the BMP-3, but its viability is rather questionable as it does not fire quickly enough for this task. Either the gunner or commander can use their the PL-088 or PP-088 weapons control panel to set the cannon to fire in the single shot mode (1), in the "short" mode (КОР) which produces controlled 10-round bursts, or in the "long" mode (ДЛ) which is fully automatic fire. Two to three 10-round bursts are typically needed to destroy an IFV-type target at the maximum effective range of the 2A72.</div><div>
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The cannon has an extremely compact and lightweight receiver, making it ideal for the BMP-3 as the 100mm 2A70 occupies a significant amount of space on its own. The forward ejection system and long-recoil operation ensures that minimal propellant fumes enter the fighting compartment. Although not all of the fumes can be eliminated, the long-recoil operating system allows the propellant to burn more completely inside the chamber before chamber is unlocked and the casing is extracted. Like the 2A42 cannon that preceded it, the forward casing ejection system of the 2A72 prevents the unburnt propellant residue inside the casings from becoming an additional source of fumes inside the fighting compartment. The entire cannon has a total weight of only 84 kg, nearly half that of the Mk44 (156 kg), and even lighter than the RARDEN (113 kg), a similar long-recoil operated 30mm cannon. Considering the fact that the 2A72 is belt-fed and has selectable feeding, it is rather remarkable that the 2A72 is smaller and lighter than the clip-fed RARDEN, although it is beyond a doubt that the 2A72 sorely lacks the accuracy of its British counterpart if it is fired without the support sleeve attached to the 2A70 cannon.<br />
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The barrel and bolt assembly is designed to be pushed back under recoil after the shell leaves the barrel. After travelling for 270mm only under the resistance of the recoil spring for the bolt, the barrel comes into contact with the shock absorber tube at the end of the receiver and is stopped within 60-65mm by the shock absorber spring. When the barrel stops, the bolt will be at the back of the receiver and the recoil spring will be fully compressed. The bolt is held in place by an automatic sear that is engaged at the instant that the bolt reaches the back of the receiver. The barrel is returned to battery by the strong shock absorber spring, and when it is in battery, the barrel trips the auto-sear and the bolt is released. The bolt travels forward, chambers a fresh cartridge and is locked to the barrel, ending the recoil cycle and readying the gun to fire.<br />
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To prepare the 2A72 for loading and to chamber the first round or to clear misfires, the cannon can be cycled using an automatic electricmechanical system or with a manual crank. The electromechanical system works using a small electric motor coupled to a worm gear affixed to the barrel assembly in a very high gear ratio, because a very large amount of force is needed to pull the barrel and bolt against the recoil and shock absorber springs. Using the electromechanical cycling system, it takes 18-20 seconds to prepare the autocannon for combat. To use it, the gunner or commander simply presses a button on their PL-088 or PP-088 panel. If the cannon must be cycled manually, the commander will have to do it as he is seated closest to the cannon. Instead of an electric motor to retract the barrel and bolt assembly, the commander uses a crank handle and his physical strength. Of course, this takes much longer and it should only be done in emergencies.<br />
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The barrel weighs 36 kg and measures 2,416mm in length, or 80.5 calibers. The entire cannon measures 3,006mm in length. The light weight and thinness of the barrel can prove to be something of an issue if firing for prolonged periods due to barrel warping and elongation, which can interfere with the ballistic properties of fired projectiles. This is somewhat offset by the guide tube affixed to the end of the 100mm cannon, but the elongation of the cannon when sufficiently heated can lead to changes in the pattern of the rifling, resulting in deviations in projectile rotation speed, which in turn results in less-than-predictable shot patterning over very long distances. Nevertheless, the cannon configuration enables it to attain a more than reasonable standard of accuracy. The barrel of the 2A72 is considerably heavier than that of the RARDEN, which had a 24.5 kg barrel of around the same length (2.44 m). The heavier barrel of the 2A72 enables it to fire multiple bursts at a sustained rate without overheating, whereas the barrel of the RARDEN is only sufficient for the low rate of fire attainable by the cannon. Nevertheless, the service life of the 2A72 is not high compare to foreign counterparts. According to the manufacturer, the 2A72 is rated for only 6,000 shots, with the option to improve to 9,000 shots when upgraded as part of a modernization programme.<br />
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The 2A72 barrel can be replaced quickly in field conditions. It can be unscrewed and removed from the front using hand tools.<br />
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The accuracy of the 2A72 installed in the BMP-3 is significantly higher compared to an independently mounted one (such as on the BTR-82A, for example), due to a support sleeve at the muzzle end of the barrel, which is attached to the rigid barrel of the 2A70 cannon. Oversized rings on the barrel act as guides to stabilize the autocannon as it recoils within the support sleeve. Thanks to the support sleeve, barrel oscillations are kept mostly under control. This is a major contributing factor to achieving an acceptable accuracy standard despite the light weight of the barrel and the nature of the long-recoil action, which traditionally does not lend itself to good accuracy.<br />
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The 2A72 features a forward casing ejection system and can be fired in either the single shot mode or in the full automatic mode. If pin-point accuracy is needed, all that is necessary is to fire fewer rounds with more time in between each shot. Keeping the autocannon in the semi-auto mode guarantees workable accuracy if firing on full-auto is not appropriate for the task.<br />
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Loading the first round, or clearing a misfired round from the breech of the 2A72 can be done manually or with a pyrotechnic charge in the case of a misfire. Three replaceable charges are installed in special slots in the cannon for this purpose. To load the autocannon, the ammunition containers under the crew seats are first filled to the brim by passing long belt segments or a single continuous belt through the turret hatches and then manually feeding it into the container. When passing a single continuous belt, a special rig with a hand crank to feed the belt into the turret is used for expediency. Then, the metal feed chute connecting the 2A72 autocannon feed mechanism to the ammunition containers on the floor of the turret must be disconnected. This is done from the commander's station. Then, a long belt segment is inserted into the feed chute until its tail appears from the other end. The tail of the belt segment is linked up with the rest of the belt already in the container, and then the first cartridge of the belt is inserted into the feed mechanism of the autocannon. This process is repeated for the other belt containing an alternate ammunition type, and once that is done, the metal feed chute is reconnected to the autocannon feed mechanism once again.<br />
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During live fire gunnery training, a large ammunition supply is not needed. The crew is provided with a short belt segment, only enough for several bursts of fire in the fully automatic mode, and it is only necessary to load the belt directly into the feed mechanism of the autocannon. Since there is no ammunition in the floor containers, the feed chute is redundant. The BMP-3 manual states that it takes 35 minutes to load a full complement of 30mm autocannon rounds into the vehicle.<br />
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The ammunition storage comprises of two separate compartments, each dedicated to a specific type of shell. The right compartment, which is located under the commander's seat, houses AP shells, whereas the left compartment, which is located under the gunner's seat, houses HE shells. Like the BMP-2, the 2A72 of the BMP-3 is supplied with 500 ready rounds, split between 305 HE-I and HEI-T rounds and 195 AP-T rounds in separate belts. This is a 3:2 ratio.<br />
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Generally speaking, the ready supply of ammunition is more than enough to last an IFV like the BMP-3 through a typical battle. When running low on ammunition, there is a reserve supply of 250 rounds held in the passenger compartment. The composition of this reserve stock of autocannon ammunition is not specified and it is assumed that the same 3:2 ratio between HE and AP rounds is maintained, so there would be 150 HE shells and 100 AP shells. However, it is interesting to note that when the BMP-3 is compared to the BMP-2, the number of armour-piercing rounds increased (195 vs 160) while the number of high explosive rounds decreased (305 vs 340). This is probably due to the addition of the 100mm 2A70 cannon which overtook the autocannon in many of the niche roles that its 30mm high explosive shells previously filled, and naturally, the increased number of armour-piercing rounds for the autocannon implies that its purpose was more focused towards combat against lightly armoured vehicles.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://3.bp.blogspot.com/-D653p0aGNkA/VGTai_GkylI/AAAAAAAAAlU/3mK2wA3SIYM/s1600/30mm%2Bammunition.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="314" src="https://3.bp.blogspot.com/-D653p0aGNkA/VGTai_GkylI/AAAAAAAAAlU/3mK2wA3SIYM/s400/30mm%2Bammunition.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">From left to right; HE-I, HEI-T, AP-T, APDS</td></tr>
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The technical accuracy of the 2A72 is high, and it is equal to the 2A42 mounted in the BMP-2 turret. The dispersion of AP-T shells fired from the 2A72 is 0.4 mils in both vertical and horizontal axes. The dispersion of HE shells fired from the 2A72 is 0.5 mils in both vertical and horizontal axes.<br />
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During a "free range" firing accuracy test for the UAE trials in 1991, the 2A72 autocannon (firing an unknown round, but probably AP or HE) displayed a high efficiency (or so they say). Out of 18 oil barrels acting as targets, 15 were hit. It is not known at what range these shots occurred, and how many rounds were needed per barrel, but it is assumed that it was more than a few hundred meters' distance, or else the test would be a rather unproductive one. In a consecutive test, the autocannon displayed a high degree of accuracy at a range of 2600 m, probably against area targets, on the same day. Again, the criteria for what is considered "high" should be understood first, but those details were not divulged.<br />
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There is not much information on the firing accuracy of the 2A72 mounted on the BMP-3, but there is some data on the 2A72 as part of the "Kliver" drop-in turret for the BMP-1. The four graphs below, taken from "БМП-1 (1964-2000): Боевая машина пехоты" by Sergey Malyshev, show the effectiveness of the weapons complex of the "Kliver" system on various targets compared to the armament of an original BMP-1. The 2A72 cannon mounted on the "Kliver" turret is similar to the 2A72 on the BMP-3 in that both have supported barrels and the fire control system is functionally identical, so the accuracy should be similar if not identical, so the information on the performance of the 2A72 presented in the graphs should be directly applicable to the BMP-3 as well. The first pair of graphs, shown below, detail the probability of destruction of an M1A2 using a "Kornet" missile compared to the old "Malyutka" missile of the BMP-1 and the probability of destruction of an APC-type target using the 2A72 cannon compared to the 73mm gun of the BMP-1. The effectiveness of the "Kornet" missile is not relevant for the BMP-3, so we will focus on the graph on the right instead. As you can see from the first line (30-мм АП, с места), the probability of destroying an APC-type target with 16 rounds of ammunition while firing from a static position is around 50% at around 1.75 km, going up to 80% at 1.2 km and 90% at 1.0 km. The probability of destruction decreases with increasing distance according to an inverted logistical S-curve, and the probability decreases more rapidly with distance when firing on the move, as shown by the line in the middle (30-мм АП, с ходу). When firing on the move, the probability of destroying an APC with 16 rounds is 80% at a distance of 1 km, but falls to only 20% at 2 km. At such distances, a very large portion of the ammunition supply would be required to guarantee a kill, so it may be more economical to expend an ATGM.<br />
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The second pair of graphs is interesting as well. The graph on the right shows the probability of eliminating an ATGM team, usually defined as a team of two to three people with one portable ATGM launcher. The graph on the left shows the probability of destroying an AH-64 helicopter. From the graph on the left, we can see that the probability of eliminating an ATGM team with 16 rounds of ammunition is at least 60% from a distance of 2 km, falling to around 40% at around 3.5 km. Firing on the move against an area target like this has a small negative effect on accuracy even for a stabilized gun, resulting in a slightly reduced probability of elimination, down to 50% at 2 km. The graph on the right does not differentiate between firing in a static position and firing on the move, but overall, it seems as if the chances of shooting down an AH-64 is almost trivial. With 16 rounds, the probability of destroying an AH-64 is around 60% at 2 km, falling to 40% at 3 km. Helicopters are large targets, but they are not so easy to hit when moving around at speeds of 100-200 km/h or more, so it is quite likely that the calculations for the graph only considered a static hovering AH-64 and not a moving one.<br />
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<h3>
<span style="font-size: large;">30MM AMMUNITION</span></h3>
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The 2A72 autocannon uses 30x165mm cartridges. The propellant charge used for all shell types is designated as the 6/7P-5BPfl, a type of high-energy stick powder. Zinc-plated steel cases are used. This provides a small weight saving compared to brass cases.<br />
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<a href="https://thesovietarmourblog.blogspot.com/p/30x165mm-cartridges.html">This page</a> contains a detailed examination of each 30mm cartridge available to the BMP-3 during its brief service in the Soviet Army, and later, in the Russian Army.<br />
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Initially, the BMP-3 was only supplied with the standard AP-T, HE-I and HEI-T rounds that were also available to the BMP-2. The HE ammunition was very powerful and outperformed contemporary 30mm HE rounds, but the AP-T ammunition could no longer be considered potent for the late 1980's and early 1990's. During this time, existing NATO IFVs with additional armour had entered service. For example, the M2A2 Bradley entered service in 1988 and it featured heavy steel appliqué armour plating over its front and side armour that was thick enough to reliably resist 30mm AP-T rounds across a frontal arc of 60 degrees even at point blank range.<br />
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As such, there was a serious need for improved ammunition for the 2A72 autocannon to be justified in its role as an anti-vehicle weapon. This need was not fulfilled for many years until the 3UBR8 "Kerner" APDS round became available.<br />
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<h3 style="text-align: left;">
<span style="font-size: large;">2A70</span></h3>
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The 2A70 is a low-pressure rifled cannon with a caliber of 100mm. It can fire both HE-Frag shells and guided anti-tank missiles. It has a vertically sliding breech block. The 2A70 was a rather unusual choice of armament for an IFV due to its large caliber, but the capabilities offered by the weapon have apparently made it an attractive choice for the Russian military as well as the many foreign operators of the BMP-3. Its size and mass of 332 kg is excellent for a gun of its caliber.<br />
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The recoil mechanism of the 2A70 is wrapped around the base of the gun tube in the same configuration as the 2A28 "Grom" smoothbore cannon of the BMP-1. The mechanism consists of a hydraulic recoil buffer and a coiled return spring. To increase the precision of the cannon, the recoil mechanism features progressive braking with a low brake force and thus a low recoiling velocity at the initial stages of the recoil stroke, before the projectile leaves the barrel. This was due to the light weight and relatively low rigidity of the turret compared to a tank turret. By minimizing the brake force until the fired projectile leaves the barrel, the amount of force imparted to the turret is also minimized, and this reduces the influence of turret vibrations on the precision of shots. Moreover, the recoil stroke of the cannon was quite long as it was necessary to ensure that the turret could withstand the recoil of the low-pressure 100mm rounds.<br />
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Besides that, it is important to note that because the recoil mechanism is wrapped around the barrel, it is concentric to the bore axis. A symmetric or concentric recoil system greatly reduces the moment (the turning effect of a force) experienced by the cannon during the recoiling cycle as there is no pivot point upon which the barrel can oscillate. The reduction of the oscillations at the barrel muzzle while the shell is still travelling down the barrel results in a reduction in the vertical and horizontal dispersion of shots. The dispersion in the vertical axis is 0.4 mils and the dispersion in the horizontal axis is <0.5 mils. It is somewhat abnormal for the horizontal dispersion of a gun to be higher than the vertical dispersion, but in this case, it is explained by the fact that the bore axis of the 2A70 is not inline with the longitudinal axis of the turret; it is offset to the left to accommodate the coaxial 2A72 autocannon. This is shown in the drawing below.<br />
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When attacking area targets in the indirect fire mode, the direct fire dispersion characteristics are not directly applicable. While a circular or elliptical dispersion pattern is maintained, the area of the impact zone increases enormously because of the additional factor of distance, which is absent when firing at an upright target placed perpendicular to the ground. Vertical dispersion becomes dispersion in depth, and horizontal dispersion becomes dispersion in width, but the impact area is only elongated in depth and not in width because of distance. According to <a href="http://www.kbptula.ru/en/productions/armament-for-light-and-hard-armour/3uof19">the KBP website</a> and an official technical description book on the BMP-3 issued in 1988, the dispersion of HE-Frag shells fired from the 2A70 is equal to a 1/200 fraction of the firing range. For instance, at a range of 2,000 meters, the dispersion in depth will be 10 meters. The newer 3UOF19 round boasted of higher precision and had a dispersion of 1/250 in distance, or in other words, the dispersion radius was decreased by 20%.<br />
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The recoil guard of the 2A70 was affixed to the gun cradle and had a V-shaped cutout above the breech block of the cannon. Its purpose is unclear. The right side of the recoil guard was longer than the left side.<br />
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Due to the low muzzle velocity of the low-pressure 100mm shells, the rifling twist of the 2A70 had to be adjusted to ensure the proper stabilization of the 3OF32 shell which was originally designed for the D-10 gun as part of the 3UOF11 round. The original 2A70 barrel had 1 twist in 30 calibers. With the introduction of 3UOF19 rounds, the rifling twist rate was increased to 1 per 22 calibers.<br />
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<h3>
<span style="font-size: large;">AUTOLOADER</span></h3>
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The 2A70 is loaded automatically from an autoloader. The autoloader is all-electric, thereby avoiding the fire hazard of a hydraulic system, and it has a simple and robust construction. Ammunition is held in a carousel mechanism on the turret floor which has a capacity of 22 rounds. The autoloader has the same layout as the autoloader used in the T-72 series of tanks and as such, the loading procedure is largely the same as in the T-72, but it is simplified because the ammunition is unitary. Normally, the autoloader is used in the automatic mode, but a semi-automatic mode is available in case individual components fail. The loading mechanism also may be operated manually with the use of hand cranks in emergency situations.</div><div><br /></div><div>
The PL-088 console allows the BMP-3 gunner to operate the autoloader in 6 different modes. The four main modes are «АВТ», «СЕРИЯ», «ЗАГР», and «РАЗГР». These are "automatic" for normal operations, "series" for series loading, "loading", for replenishing the carousel, and "unloading", for unloading it. </div><div><br /></div><div><div>In the "automatic" mode, the autoloader begins loading the gun only after the gunner presses the "load" button on the PL-088 console after every shot. In the "series" mode, the autoloader works in the same way as in the "automatic" mode. It prompts the autoloader to automatically load the gun after every shot without gunner input until the switch is moved to a different position or until the ammunition load is depleted. </div></div><div><br /></div><div>Two additional modes, «ИСХ» and «АВАР», are only used in unusual circumstances. The «ИСХ» (Исходный - Initial) mode resets all autoloader components to their initial positions. This mode is useful in the event that the loading process is interrupted by a malfunction of some kind, as it allows immediate troubleshooting or switching to either semi-automatic or manual loading. The «АВАР» (Аварийный - Emergency) mode switches the autoloader to the semi-automatic mode, whereby each step of the loading process is only carried out if prompted by the gunner from the PL-088 console. </div><div>
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The autoloader carousel enclosed from the top and bottom and each cartridge held inside the carousel rests inside individual slots, but the circumference of the carousel is uncovered so that the base of the cartridges are exposed. A spring-loaded catch at the mouth of each slot allows cartridges to be loaded into the slot from behind and prevents them from sliding out. The hub of the carousel is a hollow cylinder that fits over the rotary power distribution unit that transfers electrical power from the hull to the turret. The rotation of the carousel is driven by an electric motor installed on the carousel top cover, which also serves as the false floor for the gunner and commander.<br />
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The drawing on the left below shows the elevator mechanism that transfers cartridges from the ammunition carousel to the loading position where it is rammed into the cannon, and the drawing on the right shows a general layout of the autoloader.<br />
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To put it simply, the elevator mechanism consists of an elevator rail and a clamp mechanism that slides along the rail. The clamp mechanism is designed to pick up a cartridge from the autoloader carousel by clamping it securely so that it can be brought up to the loading position by the elevator mechanism. Besides that, there is also a rigid chain rammer installed in the rear of the turret.<br />
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The kinematic components of the autoloader mechanism are shown in the drawing below. Note that the carousel top cover has a large thickness above the ammunition while the bottom of the slots for each cartridge are much thinner. This implies that the carousel provides a noticeable amount of overhead protection from spall and fragment damage.<br />
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When the loading process starts, the cannon is automatically locked at a 0 degree elevation angle and the elevator mechanism descends to pick up a cartridge from the autoloader carousel using its clamps, raising it to a predetermined position where it is aligned with the bore axis of the cannon at the front and the rubber pad of the chain rammer at the rear. The chain rammer then rams the clamped cartridge forward until the clamp mechanism touches the breech housing of the 2A70 cannon, whereby the clamps are opened by their internal spring. This releases the cartridge, which is already partly inside the barrel, and the cartridge is rammed into battery by the chain rammer. The rammer recedes and the elevator rail is lowered back to the standby position just above the carousel. The cannon is then automatically returned to the aiming point of the gunner. Because the gunner's primary sight is independently stabilized, the gunner can freely scan for more targets or begin laying the sights on a target before the loading process is complete.<br /><br />If an individual component in the autoloader system fails, it is possible to use the system in the semi-automatic mode. The gunner <br /><br />
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The GIF below shows most of the loading process, excluding the lowering of the elevator rail back to its standby position. The mechanism in the video clip appears to be moving rather slowly and more deliberately than in reality, most likely because it is set up for demonstration purposes and is probably running on the vehicle's batteries only.<br />
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A normal loading cycle takes 4 to 5 seconds to complete, putting the theoretical maximum rate of fire for HE-Frag shells at 12 to 15 rounds per minute. However, this figure is based entirely on the loading speed of the autoloader mechanism and not the actual achievable rate of fire. In reality, the maximum rate of fire is only 10 to 12 rounds per minute because the ejection process takes some time to complete, adding a short delay between each loading cycle. When loading the 2A70 manually, the BMP-3 manual states that it takes 15-20 seconds to load each round. The maximum rate of fire when loading the cannon manually would therefore be approximately 3-4 rounds per minute.<br />
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After the first shot is fired, the cannon must eject the casing of the previous cartridge before the loading process for the next shot can begin. After a shot is fired and the 2A70 has reached the end of its recoil stroke, it is locked in its recoiled position and it is automatically depressed to a predetermined angle while the ejection chute is lowered from the ceiling and the ejection port hatch is opened. Once all of these components are in their proper positions, the spent shell casing is ejected from the 2A70. The spent shell casing is thrown into the ejection chute and its trajectory is diverted upwards and out of the ejection port. The ejection chute is retracted and the ejection port is sealed, and then the cannon is returned to battery by the recoil mechanism. The cannon automatically returns to the previous point of aim.<br />
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The propellant is quite smoky and the 2A70 gun lacks a fume extractor, but discarding the casing of each round immediately after it is fired has the effect of reducing the volume of propellant fumes that linger in the turret. This is because the unburnt propellant residue inside the casing is a source of fumes and because the momentary opening of the ejection port provides an exit path for the fumes that flow out of the barrel when the breech block is opened. This was important as it allowed a high rate of fire to be achieved. If the 2A70 was fired at its maximum rate of 12 rounds per minute, the lack of any fume extraction measures would cause the concentration of fumes in the vehicle to build up at an unacceptable rate, forcing the rate of fire to be reduced.<br />
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<h3>
<span style="font-size: large;">RESERVE AMMUNITION</span></h3>
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Aside from the 22 rounds held in the autoloader carousel, an additional 18 rounds are stowed in a reserve ammunition rack behind the turret just under the three rear passenger seats. To retrieve the ammunition in these racks, the retaining clip resting on the base of the casing is depressed and the round is pulled straight out. The passenger seats do not have to be folded away to access them.<br />
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According to an official technical description book on the BMP-3 issued in 1988, the 18 rounds carried in the reserve ammunition rack can be substituted with 250 rounds of 30mm ammunition. As a rule, the choice between the two types of ammunition carried into combat will depend entirely on the circumstances.</div>
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The process of replenishing the autoloader is very straightforward. The unitary 100mm rounds are simply pushed into the rear opening of the autoloader carousel trays and they are held in place by a simple spring-loaded tab. To make it easier to reload, the autoloader carousel can be manually rotated so that empty trays are continually brought to face the rear for a passenger or a crew member to transfer ammunition into the carousel from the reserve racks or from outside the vehicle.<br />
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Once the ammunition held in the autoloader carousel has been fully expended, the crew can withdraw from combat to replenish the autoloader from this reserve supply. The process can be sped up by enlisting the help of the passengers. According to a BMP-3 manual, the time taken to fully replenish the autoloader carousel does not take more than 20 minutes. </div>
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<h3>
<span style="font-size: large;">ATGM LOADING</span></h3>
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One of the firepower advantages that the BMP-3 held over its predecessors was its larger quantity of ATGMs and the increased ease of loading them. In a BMP-2, the commander or gunner had to open their hatches to manually remove an expended missile container from the external launcher and replace it with a new one. This could be done under armour protection thanks to an innovative missile mounting system, but it still forced either the gunner or commander to lose overhead protection with the opening of their hatch and also depressurize the vehicle and breach its hermetic seal, thus exposing all of the occupants to an NBC-contaminated environment. The American M2 Bradley was unique, but not more sophisticated in this regard even though it had two ATGMs ready to be fired in its launch pod rather than just one. This is because it still had to be loaded manually by a passenger, and it could only be done from the roof hatch of the passenger's compartment. Still, the BMP-2 and M2 Bradley were certainly more sophisticated than the BMP-1P as the gunner had to exit his hatch in order to fire as well as to reload the ATGM launcher. This shortcoming was shared by foreign IFVs like the German Marder 1, the British FV510 Warrior and the French AMX-10P, and it was brought about by the use of the least costly and most expedient solution of simply mounting an existing man-portable launcher on the turret roof.<br />
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In the BMP-3, the use of a gun-launched ATGM system instead an external launcher gave it the ability to maintain its pressurization and thus remain sealed from an NBC-contaminated environment during the reloading process while having a larger supply of ATGMs than a comparable vehicle with external launchers. The loading of ATGMs was primarily the responsibility of the gunner but depending on the BMP-3 model, it may be done using an assisted manual loading system with the participation of the commander and a passenger, or it may be done by a full autoloader system.<br />
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All BMP-3 models with the original turret had three missiles stowed in the turret basket behind the gunner's seat backrest. Besides that, all BMP-3 models carried five additional missiles stowed in a rack on the port side of the vehicle hull as a reserve supply.<br />
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In practice, the turret ready racks are generally replenished from these hull racks by the passengers, although the gunner can do this independently of the passengers as well. Needless to say, the abundance of ammunition stowed in the open is somewhat troubling, although it is by no means unique to the BMP-3.<br />
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<h3>
<span style="font-size: large;">RAMMING MECHANISM</span></h3>
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In the original BMP-3 model, known internally under the product code of Object 688-sb.6, the loading of ATGMs was done manually but the convenience of the process was enhanced by a special loading mechanism. It is described as such in practically all publicly available sources but with varying levels of specificity. In page 30 of the book "<i>Боевые машины пехоты БМП-1, БМП-2 и БМП-3</i>" (<i>Infantry Fighting Vehicles BMP-1, BMP-2 and BMP-3</i>), Sergey Suvorov writes that the loading of missiles was carried out manually with a ramming mechanism. Aleksandr Kurochkin simply writes in "<i><a href="http://4.bp.blogspot.com/-4VgXFehreYU/UlW0ptTZSxI/AAAAAAAAB1I/YpiDBmVamE8/s1600/bmp-3+art3.jpg">Famous BMP-3: New Capabilities</a></i>" that prior to the introduction of an autoloader, a passenger assisted the gunner to load the ATGMs quickly.<br />
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The most detailed description is given in the study "<i>Soviet/Russian Armor and Artillery Design Practices: 1945-1995</i>", published in September 1996, where it is written in page 111-50 that the three ready rounds stowed in the turret basket are lifted to face the gun breech by a special rammer, but this rammer does not push the round entirely into the breech and the gunner or commander must push it in the remainder of the way. The study was sponsored by the Marine Corps Intelligence Activity (MCIA) and was written using unclassified and other public domain sources available at the time.<br />
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In the report "<i><a href="http://btvt.info/5library/vbtt_1991_bmp-3_100.htm">Комплекс Вооружения БМП-3</a></i>" (<i>Weapons Complex of the BMP-3</i>) by S. M. Berezin et al., published in the May 1991 issue of "<i>Вестник бронетанковой техники</i>", a manual ramming mechanism from the stowage racks is mentioned as part of the weapons complex and a mechanical ATGM rammer is listed in the weapons complex structure diagram, shown below. The ammunition rack is marked (<i>УП</i>) and the ramming mechanism is marked as (<i>МДП</i>). In the diagram, the components of electrically powered systems in the weapons complex are placed inside boxes with dotted borders, whereas unpowered systems are not. As the diagram shows, the ramming mechanism for ATGMs is not powered.<br />
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The training poster on the left contains a small graphic in a yellow box showing the loading steps of the ATGM loading mechanism. In the training poster on the right, the ramming mechanism is marked as (76) and the turret ready racks are marked as (77). This is a basic BMP-3 and not a BMP-3M model with an autoloader, as the vehicle depicted in the poster is stated to have a 1V539 ballistic computer, a UTD-29T engine, a 1K13-2 sight, and many other features that are characteristic of a basic BMP-3.<br />
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As mentioned before, there were three missiles stowed behind the gunner's seat in a special ready rack. Of the three, two of these missile were stowed with their bases fitted into cups on the turret floor and the tips were secured with tension straps at the turret ring. The first missile in sequence is not placed in a cup but on the ramming mechanism. The image below shows the missile tray of the ramming mechanism in clear view.<br />
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Before a missile is loaded, the gunner selects the ATGM loading mode on his PL-088 console. This prompts the autoloader to raise the elevator mechanism up to the turret ceiling to clear the space behind the 2A70 cannon. It also causes the cannon to elevate to a predetermined elevation angle in order to facilitate the loading process. The independent stabilization of the 1K13-2 sight allows the gunner to maintain visual contact with a target or even continue to guide a missile towards a target if one had been fired beforehand.<br />
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The loading process itself is illustrated in the diagram below. From left to right, it is shown that the first missile in the loading mechanism is held in the missile tray and when the loading process begins, the tray is swung around until it is behind the 2A70 cannon. The tray is then tilted forwards until the missile is aligned with the bore axis of the cannon, and then the tray itself is rammed forward by a passenger standing behind the turret until the front end of the tray reaches up to the breech housing of the 2A70 cannon. At this point, the base of the missile is within the reach of the turret occupants, so either the gunner or commander can take over from the passenger to ram the missile all the way into the cannon. If the gunner is busy guiding the previous ATGM, then it will be done by the commander. Once loaded, the ramming mechanism is returned to its original position by carrying out the process in reverse.<br />
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Due to the lack of powered actuators in this mechanism, all of the actions must be done manually. The GIF below shows the loading process, albeit with somewhat disjointed editing.<br />
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Once the first missile is loaded, a passenger has to manually transfer another missile from the ready rack to the tray so that it can be loaded immediately after the first missile is fired. Overall, the gunner does not need to exert himself during the loading process at all. The extent of his involvement can be easily limited to simply pressing a button to start the loading process. However, it is possible for the gunner to carry out the entire loading process independently from his seat although it is not convenient and quite fatiguing as it is quite awkward for him to reach behind his seat backrest. Nevertheless, it could be considered a point of redundancy that may prove useful if the BMP-3 must fire missiles after the passengers have dismounted. As a rule, however, the passengers should still be inside the vehicle if the missiles are being used at normal engagement ranges which can vary from anywhere between 1 km to 4 km. At such ranges, the passengers do not contribute any combat value to a battle because their weapons lack sufficient range.<br />
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It is not possible to estimate the loading speed based on video footage, but even so, it is understood that the mechanism makes it relatively easy to load the ATGMs as there was no need to manhandle each 22 kg missile. The combat rate of fire of ATGMs in the original BMP-3 is reported to be 2-3 shots per minute. Given that the ready rack holds only three missiles, it is evidently possible for the BMP-3 to empty out the ready racks within a minute.<br />
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It was possible to load a new missile into the 2A70 even while the previous missile was still airborne thanks to the laser beam-riding guidance system. Wire-guided missile systems usually have the wire spool stored inside the missile container itself, and as such, it would not be possible for these systems to have the previous container replaced before the missile reached its target. The rate of fire was therefore determined by the loading speed in addition to the time taken for the missile to reach its target. This technological handicap affected practically all wire-guided missile systems. Thanks to the ability of the BMP-3 to load a new missile before the previous missile reaches its target, the rate of fire was increased compared to other single-shot ATGM systems.<br />
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<h3>
<span style="font-size: large;">SIMPLIFIED CONFIGURATION</span></h3>
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In some examples, the BMP-3 may not have a ramming mechanism installed. They can be only be identified as such from inside, where it is possible to visually determine if the mechanism is present or not. It is unclear why these vehicles lack the ramming mechanism and the loading process is not documented in any documents available in the public domain.<br />
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In such vehicles, all three missiles in the ready racks are placed on a base cup and secured by a tension strap at the turret ring. The autoloader carousel lock mechanism is installed next to the base cup closest to the autoloader elevator.<br />
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The two image below show different perspectives on the turret basket with this ready rack configuration. The image on the right gives a closer look at the base cups.<br />
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The image below, taken from <a href="https://www.youtube.com/watch?v=LETIu3ZVM0w&t=12s">this video</a> uploaded by the TV Zvezda channel, shows a BMP-3 turret loaded with three missile mock ups in the ready racks. This particular example is a modernized BMP-3 with a Sodema thermal imaging sight undergoing factory tests at a firing range before delivery to the troops.<br />
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<h3>
<span style="font-size: large;">ATGM AUTOLOADER</span></h3>
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Suvorov writes in his article "<i>Королева Пехоты в Аравийской Пустыне</i>", published in the January 2001 issue of Tankomaster magazine, and in his book "<i>Боевые машины пехоты БМП-1, БМП-2 и БМП-3</i>", that Former Deputy Director General of Kurganmashzavod Vladimir Mikhailovich Aksentiev was developing a loading mechanism for ATGMs for the BMP-3 in 1990-1991. A prototype autoloader was made, but its shortcomings did not allow it to be implemented in serially produced vehicles. Nevertheless, it galvanized further efforts at Kurganmashzavod, leading to the implementation an ATGM autoloader for the BMP-3 in the late 1990's. According to Suvorov, the first public reveal of this system was in 1999 in the IDEX '99 arms expo at Abu Dhabi. It was advertised as part of the BMP-3M modernization package and one of the main advantages of this system was that it could be retrofitted to existing turrets as it did not occupy any additional space and required no major modifications.<br />
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Like the earlier system, the autoloader has a capacity of three missiles but they are held in the conveyor rather than in fixed racks. The loading process was fully automatic, requiring the gunner to do nothing more than to press a button.<br />
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The first missile in the conveyor is held by the loading mechanism which consists of a long tray with an integrated electric rammer. The motor for the ramming mechanism is located at the tip of the tray. The entire system is rather elegant as it functions using only two electric motors to carry out the entire loading process. The rammer uses one motor in its compact mechanism, and it pushes the missile into the breech of the 2A70 cannon in two strokes, presumably due to space constraints. The other motor is installed near the turret ceiling and it is used to pivot the loading tray into position behind the 2A70 and to lower it until it aligns with the bore axis of the cannon.<br />
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<a href="https://1.bp.blogspot.com/-PgW7-Eg48-w/Xkg-WOZdqlI/AAAAAAAAQAg/tCNUzKCi5kwZLuhhP9ZC6eadT-dVYpKgACLcBGAsYHQ/s1600/BMP-3M%2Bautoloader.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="607" data-original-width="531" height="400" src="https://1.bp.blogspot.com/-PgW7-Eg48-w/Xkg-WOZdqlI/AAAAAAAAQAg/tCNUzKCi5kwZLuhhP9ZC6eadT-dVYpKgACLcBGAsYHQ/s400/BMP-3M%2Bautoloader.png" width="348" /></a></div>
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When loading, the autoloader elevator for the conventional rounds is raised to the turret roof and the 2A70 cannon is automatically elevated to a fixed angle. Then, the loading mechanism is swung into alignment with the longitudinal axis of the 2A70 by its electric motor. The mechanism lowers the loading tray into position behind the breech via a cam, and the missile is rammed into battery by the integrated rammer. The missile conveyor automatically shifts the remaining two missiles forward during this part of the process. Once the missile is loaded, the loading tray is raised to its original position by the reverse drive of the loading mechanism motor and the mechanism is swung back towards the missile conveyor, latching onto the next missile in sequence. The two videos below show the loading process from two vantage points.<br />
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<iframe allowfullscreen="" class="YOUTUBE-iframe-video" data-thumbnail-src="https://i.ytimg.com/vi/4oe1_iQERK0/0.jpg" frameborder="0" height="266" src="https://www.youtube.com/embed/4oe1_iQERK0?feature=player_embedded" width="320"></iframe><iframe allowfullscreen="" class="YOUTUBE-iframe-video" data-thumbnail-src="https://i.ytimg.com/vi/sXnqEddTN5k/0.jpg" frameborder="0" height="266" src="https://www.youtube.com/embed/sXnqEddTN5k?feature=player_embedded" width="320"></iframe></div>
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As there are no official figures for the loading speed of this autoloader, it can only be determined using these two videos but only the video on the right shows the complete loading cycle. From that video, it appears that the loading cycle takes 13 seconds to complete. The official maximum rate of fire is 4 shots per minute and the practical rate of fire is 2 to 3 shots per minute.<br />
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Only one missile may be airborne at any one time as the gunner's sight only has a single guidance channel, but since there is no restriction on loading a new missile while the previous missile is still en route to the target, a new missile can be loaded as soon as the last one has been fired. Given that the flight time of a 9M117 missile to its maximum distance of 5 km is 16.8 seconds, the loading time does not exceed the flight time in long range engagements. At short to medium ranges, however, the missile can reach its target in less than 13 seconds, in which case the autoloader limits the rate of fire to no more than 4 rounds per minute, or rather, 4 rounds in the first 52 seconds. With one missile already loaded in the 2A70, it is possible to fire five missiles in one minute at medium ranges. This requires the participation of the passengers who must replenish the autoloader conveyor with missiles from the reserve rack. Because the passengers do not dismount until the enemy forces are within range of their weapons, it is quite practical for the BMP-3 to rely on the passengers for this task.<br />
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This theoretical rate of fire exceeds that of the BMP-2 and BMP-1P by a large margin as those can only fire two missiles per minute at the most. It rivals the M2 Bradley and can exceed it by a considerable margin when firing at targets from their respective maximum ranges, assuming that the BMP-3 begins with a missile already loaded in the 2A70 gun to match the Bradley having two missiles ready to fire in its launch pod. This is partly due to the wire-guided nature of the TOW missile system and partly due to the longer time of flight of all TOW missile models, despite their much shorter maximum ranges. The TOW-2A, for example, has a maximum range of just 3.75 km and it reaches this distance in 20.1 seconds, so the firing of both missiles in the Bradley's launch pod against a target at this maximum range already consumes a little more than 40 seconds. Moreover, the loading drill for the TOW launch pod on the Bradley takes around 90 seconds, during which the turret must be in the proper loading position with the launcher elevated by 500 mils (28.125 degrees). The 25mm autocannon is unusable during this time as it is also fixed at the same elevation angle. Being able to achieve four shots a minute when firing at a maximum range of 5 km, the BMP-3 has more than twice the rate of fire of the Bradley in the first minute and the difference only expands as the engagement period increases. The Bradley takes 6 minutes (360 seconds) to expend its entire load of 7 missiles when firing at its maximum range, whereas the BMP-3 takes just over 2 minutes (134 seconds) to expend its load of 8 missiles when firing at its maximum range.<br />
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The sole advantage of the Bradley is when only a single target has to be engaged at short range. This is because having two ready-to-fire missiles in a launch pod gives the Bradley the capability to fire two missiles at a target in quick succession to ensure a higher probability of kill. For instance, at a range of 1 km, the flight time of an I-TOW or a TOW-2A is only 5 seconds so it is possible for two missiles to hit a tank at this distance in 10 seconds. During this time, the first missile from a BMP-3 will have hit its target as well but the second would not be ready to fire yet. After firing its two missiles, the Bradley can be reversed to a turret defilade position for the long reload that follows.<br />
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<div style="text-align: center;">
<h3 style="text-align: left;">
<span style="color: black; font-size: large;"><b>100mm Ammunition</b></span></h3>
<h3 style="text-align: left;">
<span style="color: black; font-size: large;"><b>3UOF17 </b></span></h3>
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<div style="text-align: left;">
<span style="color: black; font-size: large;"><b>3OF32</b></span></div>
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<span style="color: black; font-size: large;"><b><br /></b></span></div>
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<a href="https://4.bp.blogspot.com/-AE2nvN7_1Po/VGTVruZyLVI/AAAAAAAAAk0/hOwBIb93rQE/s1600/602007-100MM_ROUND_3UOF17.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://4.bp.blogspot.com/-AE2nvN7_1Po/VGTVruZyLVI/AAAAAAAAAk0/hOwBIb93rQE/s320/602007-100MM_ROUND_3UOF17.jpg" width="110" /></a><a href="https://1.bp.blogspot.com/-9qtlLljnaN8/V542RKDlK5I/AAAAAAAAHJs/stCeZ1m1BwkxrkmqAPXR-g_FzV9Vym5ZQCLcB/s1600/100-3uof17.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://1.bp.blogspot.com/-9qtlLljnaN8/V542RKDlK5I/AAAAAAAAHJs/stCeZ1m1BwkxrkmqAPXR-g_FzV9Vym5ZQCLcB/s320/100-3uof17.jpg" width="153" /></a><a href="https://3.bp.blogspot.com/-BC6n5jsvHBA/WG5wZ7UjKaI/AAAAAAAAH_8/E3gOjEzmVd0mutf-PRxqn7p4MJwy1sb0gCLcB/s1600/7814016.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://3.bp.blogspot.com/-BC6n5jsvHBA/WG5wZ7UjKaI/AAAAAAAAH_8/E3gOjEzmVd0mutf-PRxqn7p4MJwy1sb0gCLcB/s320/7814016.jpg" width="167" /></a></div>
<div style="text-align: left;">
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The first 100mm round available to the original BMP-3. The cartridge includes a 3OF32 HE-Frag shell directly transplanted from the 100mm 3UOF11 cartridge, which was used in the D-10T cannon on the T-54 series of tanks beginning from 1970's. As such, the BMP-3 can be said to possess the firepower of a tank to some degree.<br />
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<b><br /></b></div>
Muzzle velocity: 250 m/s<br />
Firing range: 4,000 m (Direct)<br />
Maximum firing distance: 8,000 m (Indirect)<br />
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Chamber Pressure:<br />
At 15 degrees (C) ambient Temperature: 1870 kgf/sq.cm<br />
At 50 degrees (C) ambient Temperature: 2200 kgf/sq.cm<br />
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Fuze: 3B35 Impact Fuze<br />
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Complete round mass: 18.1 kg<br />
Shell mass: 15.6 kg<br />
Explosive mass: 1.7 kg <br />
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Number of Preformed Fragments and Their Mass:<br />
With a mass of not less than 0.5 g: 1,993<br />
With a mass of 0.5 g to 2 g: 814<br />
With a mass of 2 g to 15 g: 928<br />
With a mass exceeding 15 g: 251<br />
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Statistical Average Mass of Fragmentation: 6.2 g<br />
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Velocity of Fragments and Ratio of Fragment Velocities:<br />
100% - 1,040 m/s<br />
90% - 1,060 m/s<br />
80% - 1,080 m/s<br />
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Nominal kill zone: 200 sq.m <br />
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<a href="https://2.bp.blogspot.com/-pr3HEBO2JZA/WG5h3A1oK5I/AAAAAAAAH_Q/KBKNI9Iq1hoG3XgaBRIgg7eiNGWtNo-JQCLcB/s1600/of32.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://2.bp.blogspot.com/-pr3HEBO2JZA/WG5h3A1oK5I/AAAAAAAAH_Q/KBKNI9Iq1hoG3XgaBRIgg7eiNGWtNo-JQCLcB/s400/of32.jpg" width="187" /></a><a href="https://3.bp.blogspot.com/-BNrqD_LKFsw/WG5h3AafoRI/AAAAAAAAH_U/XmQ6bgZZBtAfiiNS0FzFnTEDtD68ZjAegCLcB/s1600/100mm%2Bof32.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://3.bp.blogspot.com/-BNrqD_LKFsw/WG5h3AafoRI/AAAAAAAAH_U/XmQ6bgZZBtAfiiNS0FzFnTEDtD68ZjAegCLcB/s400/100mm%2Bof32.jpg" width="115" /></a></div>
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<br />3OF32 was the heaviest shell available for the BMP-3, but it was not necessarily the most effective. The design of the shell body, especially the tail, does not produce an optimal fragmentation pattern, and the ratio of explosive charge to steel body mass (0.11) is not optimal as the high thickness of the shell walls was needed to withstand launch from the high velocity D10 and BS-3 guns.<br />
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<div style="text-align: center;">
<h3 style="text-align: center;">
<span style="color: black; font-size: large;"><b>3UOF19</b></span></h3>
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<a href="https://2.bp.blogspot.com/-F0VTATKgZHs/VGTLppy9hMI/AAAAAAAAAkI/6f2YgF_qBJw/s1600/3UOF19.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://2.bp.blogspot.com/-F0VTATKgZHs/VGTLppy9hMI/AAAAAAAAAkI/6f2YgF_qBJw/s320/3UOF19.png" width="85" /></a></div>
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<div style="text-align: left;">
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Muzzle velocity: 355 m/s</div>
<div style="text-align: left;">
Effective firing range: 6,500 m (Direct)</div>
<div style="text-align: left;">
Maximum firing distance: 8,000 m (Indirect)</div>
<div style="text-align: left;">
Fuze: 3B35 Impact Fuze</div>
<div style="text-align: left;">
Complete round mass: 15.8 kg</div>
<div style="text-align: left;">
Shell mass: 13.41 kg</div>
<div style="text-align: left;">
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<div style="text-align: left;">
Number of preformed fragments (mass of not less than 0.5 g): 3,393</div>
<div style="text-align: left;">
Average velocity of fragments: 1,420 m/s</div>
<div style="text-align: left;">
Average mass of fragments: 2.73 g</div>
<div style="text-align: left;">
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<div style="text-align: left;">
Nominal kill area: 360 sq.m</div>
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<div style="text-align: left;">
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This shell was launched at a higher muzzle velocity than its predecessor and has a greatly improved design, enabling it to produce more fragments.<br />
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<div style="text-align: center;">
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://3.bp.blogspot.com/-_WPiqkXj26o/VGTQjyLUA_I/AAAAAAAAAkk/2vDipkCgN80/s1600/3UOF19%2Bcasualty%2Bzone%2C%2BKBP.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="327" src="https://3.bp.blogspot.com/-_WPiqkXj26o/VGTQjyLUA_I/AAAAAAAAAkk/2vDipkCgN80/s400/3UOF19%2Bcasualty%2Bzone%2C%2BKBP.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Butterfly fragmentation pattern. N=number of fragments, S=area</td></tr>
</tbody></table>
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<span style="color: black;"><br /></span></div>
<h3 style="clear: both; text-align: center;">
<span style="color: black; font-size: large;"><b>3UOF19-1</b></span></h3>
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<a href="https://2.bp.blogspot.com/-LjG5O5nijIk/VGTLrM80n1I/AAAAAAAAAkQ/l4EU3v3bpiw/s1600/3UOF19-1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://2.bp.blogspot.com/-LjG5O5nijIk/VGTLrM80n1I/AAAAAAAAAkQ/l4EU3v3bpiw/s320/3UOF19-1.png" width="90" /></a></div>
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3UOF19-1 replaces the conventional point-detonating fuse of the 3UOF19 with a proximity fuse. The new 9E154 fuse is designed to detonate the shell at an altitude of around 3 meters above the ground, enabling it to defeat targets located behind cover or entrenched in foxholes or reinforced trenches. Thanks to the large casualty area produced by the airbursting effect, it is particularly useful when engaging hidden problematic targets such as ATGM teams or snipers. It becomes somewhat useless against IFVs, however, as the fragments are not nearly heavy enough to defeat even the thinnest roof armour, seeing as most IFVs are designed to withstand 155mm artillery air burst fragments. The proximity fuse also gives this shell the ability to engage moving aerial targets, as a direct hit is no longer necessary to achieve the desired effect.<br />
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Muzzle velocity: 355 m/s<br />
Firing range: 6,500m (Direct)<br />
Maximum firing distance: 8,000 m (Indirect)<br />
Fuze: 9E154 Proximity Fuze<br />
Complete round mass: 15.7 kg<br />
Shell mass: 13.31 kg<br />
Detonation altitude: 3 m ± 1.5 m<br />
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Number of preformed fragments (mass of not less than 0.5 g): 3,393<br />
Average velocity of fragments: 1,420 m/s<br />
Average mass of fragments: 2.73 g<br />
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Casualty area: 600 sq.m<br />
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Depending on the exact angle of firing, the shell doesn't always detonate 3 meters from the ground. It depends on the angle of incidence, which changes if the target is nearby or far away. At long distances, the shell may detonate 1.5 meters above the ground, since the side-looking optical sensors cannot see the ground because of the high angle of attack. A short distances, when the shell is essentially flying parallel to the ground, it may detonate at an altitude of 4.5 meters.<br />
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<div style="text-align: center;">
<b><span style="font-size: large;">Propellant charge</span> (All the above shells use this charge)</b></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://3.bp.blogspot.com/-IkBKn52ysmQ/VGTVycHYgEI/AAAAAAAAAk8/XtQVRrRjilA/s1600/Propellant%2BCharge%2C%2B100mm%2B2A70%2Bcannon.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="200" src="https://3.bp.blogspot.com/-IkBKn52ysmQ/VGTVycHYgEI/AAAAAAAAAk8/XtQVRrRjilA/s200/Propellant%2BCharge%2C%2B100mm%2B2A70%2Bcannon.png" width="191" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><br /></td></tr>
</tbody></table>
<br />
<h3>
<span style="font-size: large;">ACCURACY</span></h3>
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According to results from the BMP-3 trial in Turkmenistan for the UAE, the 3UOF17 shell has an average CEP (circular error probability) of 25m at a range of 4000m, meaning that 50% of fired shells will hit in an area with a circular diameter of 50 m at that range. Therefore, 3UOF19/-1 shells should have a CEP of 22.36m at 4,000 m, though this is probably lower than the real values, as 3OF19 has slightly different aerodynamic characteristics and a higher velocity.<br />
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For a low-velocity cannon, the 2A70 can achieve reasonably good results at long distances. Unfortunately, the low velocity nature of the 100mm shells means that they are quite susceptible to being blown off course by crosswinds or blown too far forward or too far back by head and tail winds. This invalidates any attempts to extrapolate the firing accuracy at 4 kilometers' distance to ascertain the firing accuracy at closer distances. Try it. You will find that it should be impossible for the 2A70 to hit a tank-sized target at even a few hundred meters' distance, when all of the evidence points to the opposite. Without much wind, or without prolonged exposure to wind, the accuracy of the 2A70 gun is much better than stated.<br />
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<h3>
<span style="font-size: large;">ANALYSIS</span></h3>
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An important thing to note is that although the 3UOF19(-1) shells can be shot to an absolute maximum of 8000m, the practical range will be limited to 4000m due to target identification range and ballistic computer limitations unless the newer SOZh gunner's sight (replacing the 1K13-2) and 1V539M ballistic computer is installed. Shooting at ranges more than 4,000 m requires switching to indirect fire mode. Unlike a true gun-mortar system like the Nona-S, the 2A70 cannon does not have access to mortar shells, making it impossible to hit targets at a high angle of attack at short distances. This is because conventional ogived shells like the 3OF32 lack the special shape and fins that enable mortar shells to consistently land always almost vertically like a shuttlecock. This means that the BMP-3 cannot attack the weaker top armour of enemy tanks and IFVs at short distances. It could do that at long range, but the low chance of scoring a hit makes this impractical.<br />
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With the 2A70 gun, the BMP-3 is able to engage soft targets more effectively than its autocannon, and engage both soft targets and light armour at greater ranges than possible with a 30mm cannon. The gun may also prove useful against lightly armoured targets that the autocannon cannot destroy, such as the German Puma and uparmoured CV90 IFVs, both of which are heavily armoured and are able to reliably resist 30mm APDS shells. Additionally, the 2A70 gun is much more effective at destroying structures and earth-and-log bunkers, and is much more efficient in dealing with ATGM teams.<br />
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Furthermore, as a result of the 2A70's indirect fire capability, the BMP-3 has unique opportunities to engage soft targets as well as lightly armoured vehicles at a variety of ranges, and in situations where air power and artillery support is not available. For instance, a tank could easily hit a target at two kilometers using its high power and high velocity HE-Frag ammunition, but it cannot do this over a tall hill, or over tall buildings. The high velocity of tank gun ammunition and the limited elevation of tank guns means that while it is possible to land a shell on top of a target at long distances, it is not possible at shorter distances. The low velocity of the ammunition fired from the 2A70 enables it to lob payloads across villages, small towns, hills, and other natural obstacles at short ranges to provide fire support for nearby troops, as opposed to troops from the neighbouring division. This feature substantially increases a mechanized division's overall combat effectiveness, and enables the BMP-3 to perform many of the same duties as the Nona-S, but not as extensively, as the Nona-S is inherently more powerful due to its larger caliber and it has access to a much wider variety of munitions. The development of the 2S31 Vena (which uses the BMP-3 hull, no less) aims to endow the ground forces with a Nona-S-like weapon system. Another outstanding feature is the excellent gun elevation, which enables targets in high-rise buildings to be blasted with a level of effectiveness that an autocannon simply cannot match.<br />
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It is evident that the popularity of large caliber autocannons in the 40mm to 57mm range is due to the need to accomplish the same tasks. All design choices have to compromise something, and in the case of the 30-100 combination, the compromise is that the anti-armour capabilities of the 30mm autocannon are very limited compared to a 57mm one. In the case of 57mm autocannons, the compromise lays in the limited explosive power of the shell compared to a 100mm solution. However, one could argue that this quandary has already been solved by the use of advanced technology. A programmable fuse can make a 40mm to 57mm HE-Frag shell highly effective against soft targets in the open and in field fortifications by employing an airburst mode, and even give it valuable bunker-busting capabilities by employing a delayed fuse. Another issue is that direct fire is more rapid and responsive than indirect fire, but the lack of indirect fire capability means that an autocannon-only IFV is perpetually at risk of return fire, usually from hidden ATGM teams. At least the BMP-3 has the option of engaging such dangerous targets at equally long range from the safety of terrain features.<br />
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<span style="font-size: large;"><b>ATGM</b></span><br />
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<div class="separator" style="clear: both; text-align: center;">
</div>
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Like all preceding BMPs of the Soviet Army, the BMP-3 had the capability to launch anti-tank guided missiles, but instead of having an external launcher with self-container missile containers, the vehicle capitalized on the 100mm caliber of the 2A70 cannon to incorporate the existing 9M117 missile that had previously been successfully used in 100mm and 115mm bore guns. The missile system works on the principle of laser beam riding guidance. This guidance principle has merits of its own, but one of the most important features is that it did not require a wire to transmit flight commands as that was incompatible with the gun-launcher concept. The three ATGMs available for the BMP-3 are:</div><div><br /></div><div><ol style="text-align: left;"><li>3UBK10-3 "Basnya" cartridge with the 9M117 missile</li><li>3UBK10M-3 "Kan" cartridge with the 9M117M missile</li><li>3UBK23-3 "Arkan" cartridge with the 9M117M1 missile</li></ol></div><div>
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The fire control system of the BMP-3 permits the gunner to fire and guide missiles while on the move at speeds of up to 25 km/h without any degradation in the probability of hit on tank-sized targets at all ranges. The BMP-3 can fire its missiles at an elevation angle of 28 degrees and a depression angle of -6 degrees when the turret is facing the front or sides, or at an elevation angle of 32 degrees to 2 degrees when the turret is over the rear of the hull. This range of elevation is sufficient to allow the vehicle to engage ground targets located at a higher elevation or even engage hovering and slow-moving aircraft such as helicopters. <br />
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The missiles are soft-launched out of the gun barrel, whereby the rocket motor activates and sustains a transonic speed (~330 m/s) until detonation. All missiles have a claimed probability of hit of 80% at their maximum ranges.<br />
<br />All three missiles have an optical laser beam receiver at the rear. Flight control is achieved using four canard fins.<br />
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<a href="http://1.bp.blogspot.com/-7YyO5FHyfYM/VEctLAkbQPI/AAAAAAAAAYs/L5jmFGXs0A4/s1600/Bastion-a.jpg"><img border="0" height="282" src="https://1.bp.blogspot.com/-7YyO5FHyfYM/VEctLAkbQPI/AAAAAAAAAYs/L5jmFGXs0A4/s1600/Bastion-a.jpg" width="320" /></a></div>
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The missile will fly at least 3.5 meters over the ground, give or take 0.35 meters, and descend to target level immediately before contact. This is primarily to keep the gunner's line of sight to the target clear, but it also helps minimize the possibility of the missile colliding with bushes or other terrain features, which may disturb the missile's flight or even prematurely detonate it.<br />
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<br />
<h3>
<span style="font-size: large;">3UBK10-3 "Basnya"</span></h3>
<h3>
<span style="font-size: large;">9M117</span></h3>
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The missile has an impressive maximum range of 4,000 meters and a rather high cruising speed. This enabled the BMP-3 to retain the same maximum range as the BMP-2 despite the smaller caliber of the 9M117 missile compared to the 9M113 "Konkurs".<br />
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The 9M117 missile has a single-charge warhead. It employs a hemispherical wave shaper, which
improves the integrity of the cumulative jet by focusing the explosive power of the warhead charge more efficiently. The diameter of the shaped charge warhead is slightly less than 100mm. It is smaller than the 112mm shaped charge of the 9M113 missile and cannot achieve a similar penetration performance. Nevertheless, the large standoff distance built into the missile design enabled the 100mm missile to achieve a much higher penetration power than conventional high velocity HEAT shells of the same caliber like the 3BK17M fired from the D-10T.<br /><br />
The missile uses the 9E256 graze-sensitive fuse. <br />
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Explosive Charge: OKFOL<br />
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Penetration: 550mm RHA<br />
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With a penetration power of 550mm RHA, this missile was essentially outdated when was introduced for the BMP-3 because of the widespread adoption of composite and reactive armour on NATO tanks at the time. This practically ensured their immunity to single shaped charge warheads of this caliber in a standard frontal arc of 60 degrees. Based on recent data on the performance of Abrams and Leopard 2 tanks in Syria, it can be surmised that the 9M117 would have been effective against earlier models (M1 to M1A1, and 2A0 to 2A4) of the aforementioned tanks in side engagements, but only in side engagements. Proliferation of this missile is unknown, but it has probably already been completely phased out in favour of "Arkan" due to its complete obsolescence.<br />
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<h3>
<span style="font-size: large;">3UBK10M-3 "Kan"</span></h3>
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<span style="font-size: large;">9M117M</span></h3>
<div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-cIvbbZwYsEg/Xzf7n-8iuNI/AAAAAAAAReM/OPVp63bj1so-_ZYeGFbj6NlSQWlfeUezwCLcBGAsYHQ/s800/9m117m.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="281" data-original-width="800" src="https://1.bp.blogspot.com/-cIvbbZwYsEg/Xzf7n-8iuNI/AAAAAAAAReM/OPVp63bj1so-_ZYeGFbj6NlSQWlfeUezwCLcBGAsYHQ/s640/9m117m.jpg" width="640" /></a></div><div><br /></div><div><br /></div><div>The 9M117M "Kan" missile was developed in response to the anticipated appearance of ERA on foreign tanks at the very end of the 1980's, at the turn of the decade. It has a tandem warhead that functions by detonating the ERA before the main charge is initiated, which also makes it more suitable for defeating composite armour. The 9M117M was developed by adding a precursor warhead to the nose of the 9M117 missile, with the accompanying modifications to the fuzing system and canard control fins to accommodate it. "Kan" successfully passed state trials and entered service only in 1993.</div><div><br /></div><br />
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<div><br /></div><br />The missile is currently useful against the side profile of modern tanks and against modern IFVs protected by ERA, such as the BUSK package for the M2A3 Bradley.</div><div>
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Explosive Charge: OKFOL</div>
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Primary Charge Penetration (after ERA): 550mm RHA</div><div>
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<h3>
<span style="font-size: large;">PKTM</span></h3>
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<a href="http://2.bp.blogspot.com/-4US4t2musfc/Vl8fjmRu5VI/AAAAAAAAEkw/Zmr4HETl3sg/s1600/bmp-3%2Bco-axial%2Bmachine%2Bgun.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="353" src="https://2.bp.blogspot.com/-4US4t2musfc/Vl8fjmRu5VI/AAAAAAAAEkw/Zmr4HETl3sg/s640/bmp-3%2Bco-axial%2Bmachine%2Bgun.jpg" width="640" /></a></div>
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The coaxial PKTM machine gun is sighted through the gunner's sights or the commander's anti-aircraft sight. The PKTM is mainly distinguished from the earlier PKT by the smooth barrel as opposed to the fluted barrel of the PKT. Internally, the PKTM and the PKT differ in the same way that the basic PK and PKM models differ. When the PKM replaced the PK on the production lines in 1969, the production of the original PKT also halted. By the time the BMP-3 entered service at the end of the Cold War, the PKTM had been established as the standard model. 7BZ-3 API (armour-piercing incendiary) rounds with the B-32 bullet and 7T2 API-T (armour-piercing incendiary tracer) rounds with the T-46 bullet are linked in a 4:1 ratio. The machine gun has a cyclic rate of fire of 700 to 800 rounds per minute. A 250-round box of 7.62x54mmR ammunition is provided in a continuous belt. The co-axial machine gun can be fired either by depressing the trigger button on the gunner's handgrips, or by pressing the emergecy manual trigger button located on the trigger unit installed at the back the receiver of the machine gun.<br />
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Aside from the main armament and the co-axial machine gun, the BMP-3 also mounts two PKTM<b> </b>bow machine guns, each with 2,000 rounds in a continuous belt. The machine guns are aimed through a single TNPZVE01-01 periscope-aiming device which has a collimator reticle projected on the viewing aperture through a fiber optic cable. The periscope itself thus becomes a gunsight, with a moving luminous reticle which moves as the PKT moves.<br />
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The periscope has a field of vision of 17.5 degrees in the horizontal plane and 10 degrees in the vertical plane. It has a magnification of 1x.<br />
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The machine guns are mounted in ball mounts and can be elevated by 15 degrees and depressed by 5 degrees. They can be swiveled 5 degrees inwards and 30 degrees outward, horizontally. The bow machine guns have an average maximum practical range of 600m, but much, much less if the vehicle is on the move over rough terrain. As far as bow machine guns go, this is as good as it gets. The TNPZVE01-01 periscope combines the good visibility of a periscope with the higher accuracy of an aiming device. Here, I would like to use the Sherman and T-34 as examples. The Sherman's bow machine gunner had an adjustable periscope to see the outside world, but no way to aim his machine gun. What he must do is fire in the general direction of the enemy, and adjust according to the tracers. In the T-34, the bow machine gunner has no periscope, but there is a small hole in the bow machine gun turret for him to look through the sights of his DT machine gun. This meant that he had an incredibly bad case of tunnel vision, but if he could see his target, he could make his shots count. The bow machine gunner concept in the BMP-3 takes the best of both and leaves all of the negatives behind. However, this does not mean that having bow machine guns are still viable in this day and age.<br />
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Interestingly, the driver can remotely fire the two bow machine guns. He has two button-triggers in thumb's reach on the steering bar, but he cannot aim the machine guns. This feature enables the driver to suppress enemy troops in front of him without the assistance of the crew in the fighting compartment, though the bow machine guns are still of questionable value. In fact, this is probably far more practical for self-defence, rather than to have dismounts operating them. Dismounted infantry can give more protection to a vehicle when outside it, rather than inside it. It's more a case of not letting the machine guns go to waste once the bow machine gunners have vacated the vehicle.<br />
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Aside from the bow machine guns, there are firing ports on either side of the vehicle - two on the port side and one on the starboard side, with a maximum 30 degrees horizontal swivel each. The ports may fit either AKs or PK machine guns, through the installation of adaptors which conform to the barrels to fit them in a universal slot in the ball turret. The occupants are provided with a TNPZVE01-01 periscope-aiming device just like the bow machine gunners.<br />
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<tr><td style="text-align: center;"><img border="0" height="293" src="https://2.bp.blogspot.com/-buq-WQp02f8/VEDN-0Jn0-I/AAAAAAAAAIQ/vGd__1evR5A/s1600/MANPADS%2Bracks%2C%2BBMP-3%2Binterior.png" width="400" /></td></tr>
<tr><td class="tr-caption" style="text-align: center;">One of two portside firing ports, interior view</td></tr>
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There is an aft firing port as well, located on the left rear hatch. A soldier must lie down over the engine deck cover to operate his rifle for this firing port. This firing port does not use a periscope for aiming. The soldier must aim through a transparent window.<br />
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<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-9j22cjuE24w/VGveSW3u6oI/AAAAAAAAAq4/EPV8PlUHMW4/s1600/BMP-3%2Brear%2Bfiring%2Bport.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="213" src="https://2.bp.blogspot.com/-9j22cjuE24w/VGveSW3u6oI/AAAAAAAAAq4/EPV8PlUHMW4/s400/BMP-3%2Brear%2Bfiring%2Bport.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Rear firing port</td></tr>
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<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-WDPS1SJQ1wE/VEc1trO4I6I/AAAAAAAAAZI/4HvzVzD8n3s/s1600/bmp-3.31340%2B(1).jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://3.bp.blogspot.com/-WDPS1SJQ1wE/VEc1trO4I6I/AAAAAAAAAZI/4HvzVzD8n3s/s400/bmp-3.31340%2B(1).jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Passenger periscopes</td></tr>
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The firing ports are intended to allow the passengers to suppress or neutralize threats like ATGM teams or scattered infantry while on the move, which will almost certainly be encountered if a breakthrough is achieved. The firing ports also help maximize the BMP's combat potential if the environment outside the vehicle is simply too hazardous, which was a perfectly possible scenario taking into account the commonness of tactical nuclear artillery shells. With the firing ports, the passengers can still contribute to the fight. <br />
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Regardless, the practicality of firing ports has been called into question in the modern age. Without the serious threat of nuclear war looming over us, it may seem to some that they are no longer necessary. Despite being primarily rooted in offensive tactics, the implementation of the firing ports gives the BMP-3 the critical ability to defend itself from deadly rocket grenade attacks from all directions, even at the rear. This is in contrast to "modern" designs which leave the flanks and rear completely vulnerable to ambushing RPG-wielding agents, leaving the burden of mutual protection to accompanying assets. The firing ports will, without a doubt, prove useful in the hairiest of situations. But then again, the likelyhood of being in a situation where the firing ports become useful are so slim that in many cases, it's not worth compromising the protection scheme.<br />
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Loading all ammunition in the BMP-3, including 100mm, 30mm, and 7.62mm ammunition, takes an average of 45 minutes with the participation of only the entire 3-man crew. The 100mm ammunition is loaded by reversing the gun loading procedure, the 30mm ammunition is loaded by inserting belts of it into a small hatch at the front of the vehicle, the missiles are secured on storage racks manually, and the co-axial machine gun ammunition is loaded manually in the turret.<br />
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<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-bEkRXZoZUpA/VEdAhiROkMI/AAAAAAAAAas/iCBudw6t-cQ/s1600/bmp-3.31154.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="409" src="https://3.bp.blogspot.com/-bEkRXZoZUpA/VEdAhiROkMI/AAAAAAAAAas/iCBudw6t-cQ/s1600/bmp-3.31154.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Photo by Sergey Suvorov</td></tr>
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In the course of the early testing phases of the BMP-3, several components were found to be particularly unreliable, among them were the main weapon systems. These issues were solved before March 1988. Of particular interest was the 2A70 gun loading system, which had a failure rate of 1.5 malfunctions per 1,000 rounds fired, which was reduced to 1.3, then to 1.12. The 2A72 had a failure rate of 1 failure per 1000 rounds fired, was reduced to 0.62, then to 0.5. The issues with the 2A72 were also related to the loading mechanisms.<br />
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During seaworthiness testing of the BMP-3 in 1985 off the coast of Sevastopol, the BMP-3 demonstrated the ability to fire accurately while afloat. With a T-55 (which was pulled out of storage) as a target, the 30mm autocannon, firing HE shells, managed to completely destroy all exterior sighting systems from a distance of 1,500 m. When fired at with the 100mm HE-Frag shells (unknown number of shots), close inspection revealed that the 100mm gun of the T-55 was broken in four places, and the hull front plate had visible external fractures, with cracks appearing in several places.<br />
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Such a demonstration provides a good justification for the belief that a 100mm HE-Frag round would be lethal even to most of the late Cold War era IFVs, which have far less protection than a tank. In a promotional video produced by KBP of Tula (the manufacturers of the 2A70 gun and its ammunition) showcasing the BMP-3M, it is claimed that the 100mm HE-Frag shell fired from a BMP-3 can destroy a lightly armoured vehicle with a high probability on the first shot, or with an absolute guarantee on the second shot.<br />
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Live-fire exercises confirmed the high precision characteristics of the BMP-3's armament system with regards to long range area targets. For instance, it was proven that 70% of shells will land in an area of 60x30 meters, simulating an enemy infantry platoon, from a distance of 3,500 meters. It was revealed in such exercises that the training of BMP-3 gunners did not correspond to the true potential of the armament of the BMP-3. For the full realization of the potential of the IFV during target practice, it was proposed to increase the firing range by an additional 1,800-2,500 meters during 2A70 gunnery training, and by 1,500-2,000 meters during 2A72 gunnery training. A new platoon firing exercise was also formulated whereby BMP-3 gunners had to fire at targets from 3,000-3,500m. The decision to do so was probably taken in the mid 90's.<br />
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This is a good indication that the potential of the 2K23 armament system is not being ignored. With the ammunition improvement in the form of new 100mm HE-Frag shells with increased range, it is more likely than not that BMP-3 gunners are now thoroughly trained to engage targets at very long distances. In fact, it is probably safe to say that the engagement envelope in which BMP-3 gunners are trained for is larger than that of any other IFV crew in the world.<br />
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<h3>
<span style="font-size: large;">
PROTECTION</span></h3>
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<a href="http://4.bp.blogspot.com/-huRKGNOrByE/Vhu5m8ogqkI/AAAAAAAAD-M/Rbkdau0RuCg/s1600/bmp-3%2Bassembly%2Bline.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="424" src="https://4.bp.blogspot.com/-huRKGNOrByE/Vhu5m8ogqkI/AAAAAAAAD-M/Rbkdau0RuCg/s640/bmp-3%2Bassembly%2Bline.jpg" width="640" /></a></div>
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<a href="http://1.bp.blogspot.com/-iLv-LEcNzvs/VRJvWeI0fdI/AAAAAAAABaw/aYEWAeJYnOw/s1600/bmp3.png" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em; text-align: left;"><img border="0" src="https://1.bp.blogspot.com/-iLv-LEcNzvs/VRJvWeI0fdI/AAAAAAAABaw/aYEWAeJYnOw/s1600/bmp3.png" /></a>The BMP-3 reaches the same level of all-round protection as its predecessors but distinguishes itself with its improved protection from artillery splinters along its side and rear projections, and also by its greatly enhanced frontal protection thanks to the use of spaced armour and the inclusion of a self-sealing fuel tank at the nose of its hull as part of the protection scheme. Thanks to this combination of technical solutions, the front armour of the BMP-3 was arguably the best out of all vehicles in its weight class, achieving a level of protection that is only reached by vehicles weighing up to 30 tons. For a brief period, the BMP-3 also had superior protection compared to the Bradley and Marder 1 series, as the base armour of both IFVs were functionally equivalent to the BMP-1. It should be noted that during the selection process for the successor to the BMP-2, the existence of 20mm and 25mm APDS ammunition was acknowledged as a crucial factor. This factor directly led to Kurganmashzavod suggesting to base the new IFV on the light tank chassis of Objekt 685 for its high protection during the development of the successor to the BMP-2 in the early 1980's.<br />
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The aluminium used for the BMP-3 hull and turret structures is ABT-102. The "ABT" (АБТ) designation is an acronym for "Алюминиевой Брони Танк", or "Aluminium Tank Armour". It was used for experimental light tanks, including the Object 685 which was used as the basis for the BMP-3 hull. ABT-102 is an Al-Zn-Mg alloy with a maximum strength of 450-500 MPa and a density of 2,850 kg/cu.m. Due to the high alloying, the density of ABT-102 exceeds the density of common alloys like the ubiquitous 5083 alloy which reaches 2,660 kg/cu.m. According to several research papers written on the subject, the thickness efficiency of aluminium armour may reach up to 50% of steel against steel-cored large caliber armour-piercing bullets such as .50 caliber M2 AP or the Soviet 12.7mm B-32, and ABT-102 was found to outperform RHA steel against APDS shells with tungsten carbide cores and APDS shells with tungsten alloy cores at high obliquity impacts.<br />
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ABT-102 aluminium alloy was originally formulated in the 70's for higher performance against ballistic threats compared to structural aluminium like 5083 alloy (used in the M113) and existing armour-grade aluminium like ABT-101, which is used in the BMD-1 airborne IFV and the BMP-1 in certain parts of the vehicle. ABT-102 is superior to ABT-101, which in turn is slightly superior to 7039 alloy, which is used in some areas of the M2 Bradley IFV. The belly of the BMP-3 is made from AMG-6, which is a structural aluminium alloy similar to 5083 alloy. The graph below, taken from an NII Stali booklet, shows a comparison of 5083 alloy, AMG-6 alloy, 7039 alloy, ABT-101 and ABT-102 in terms of their effectiveness at resisting armour-piercing bullets. ABT-102 is classified as not only being a bullet-resisting alloy, but also a shell-resisting alloy in reference to autocannon fire.<br />
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The creation of ABT-102 was accomplished on the basis of the ABT-101 alloy that was developed from 1962 to 1965. ABT-101 was used to construct the hulls of light IFVs like the BMD-1 and BMD-2, and it was also used for the engine access panel of the BMP-1 and BMP-2 that were otherwise entirely built from high hardness steel. A research paper by NII Stali has indicated that the thickness efficiency of the ABT-101 alloy can reach up to 45% of steel against large caliber armour-piercing bullets. The improved ABT-102 alloy should have a better thickness efficiency, but the magnitude of the improvement is still largely unknown.<br />
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The steel used in the spaced and applique armour over the front of the vehicle is BT-70Sh high hardness steel manufactured using electroslag remelting (ESR) technology. It has a hardness of 534 BHN and a maximum strength of around 1,900 to 2,000 MPa when processed to the thickness of the plates used on the BMP-3. The density of BT-70Sh is 7,850 kg/cu.m.<br />
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With a combat weight of 18.7 tons, the BMP-3 was heavier than the BMP-2 but it was considerably lighter than the M2A1 Bradley which weighed 22.8 tons combat loaded and much lighter than the Marder 1A2 which weighed 29 tons combat loaded, but it achieved a level of frontal protection similar to the M2A2 Bradley (1988) that weighed 27 tons and the Marder 1A3 (1988) that weighed 35 tons, losing out only in side protection. The Marder 1A3 was built to withstand 30mm APDS shells as a response to the appearance of the 30mm 2A42 autocannon on the BMP-2, and used spaced armour to achieve this.<br />
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However, its vastly greater weight does not necessary imply an equally vastly superior level of frontal protection. The protection scheme of the basic Marder 1 was only equivalent to the BMP-1, and in fact, its side armour was actually weaker than that of the BMP-1. However, even the basic model weighed 29 tons combat loaded. Moreover, some of the surplus weight of the Marder 1 comes not from thicker armour, but from its steel construction. The BMP-3 and Bradley were both built from aluminium rather than steel, and because of the large thicknesses of the plates used to construct the hull, it was possible to omit the structural supports that are necessary for a typical thinly armoured steel hull and instead use a monocoque design. This can reduce the weight of the hull by up to 20%. In practice, the BMP-3 managed to achieve a weight reduction of only 10% because reinforcement were still needed for the thin belly of the hull and support beams were needed to support the weight of the turret.<br />
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The front of the BMP-3 hull can be divided into three sections. There is a highly oblique upper glacis, a midsection, and a lower glacis. The upper glacis occupies a quarter of the total height of the hull, the midsection occupies another quarter, and the remaining half is occupied by the lower glacis. The upper glacis is a homogeneous aluminium plate. The midsection of the hull is composed of a thick aluminium base reinforced with a high hardness steel appliqué plate and augmented with a spaced high hardness steel wave breaker plate. The lower glacis armour consists of the same thick aluminium base armour as the midsection and is reinforced with a spaced dozer blade made from high hardness steel, but lacks the appliqué plate found on the midsection. The lower edge of the wave breaker overlaps with the upper edge of the dozer blade, so it is only possible to deploy the dozer blade after the wave breaker is extended.<br />
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Behind the entire front hull armour is the BMP-3's self-sealing fuel tank which is not only the vehicle's sole fuel container, but also acts as a spall liner or even as additional armour. Overall, the protection of the BMP-3 is 1.7 times higher compared to the BMP-2 and BMP-1 and it also achieves a higher weight efficiency.<br />
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According to the article "<i><a href="http://btvt.narod.ru/raznoe/vbtt_1991_bmp31.htm">Особенности Корпуса и Башни БМП-3</a></i>" (<i>Features of the BMP-3 hull and turret</i>) by O. A. Gomyrin and A. Ya. Shumilov, published in the May 1991 issue of "<i>Вестник бронетанковой техники</i>", the armour thickness of the BMP-3 are as follows:<br />
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<blockquote class="tr_bq">
1. Upper glacis, 18mm of ABT-102<br />
2. Hull cheeks, 60mm of ABT-102<br />
3. Turret front, 16mm BT-70Sh, 70mm air space, 50mm ABT-102<br />
4. Turret roof, 18mm of ABT-102<br />
5. Turret rear, 43mm of ABT-102<br />
6. Rear hatch, 15mm of ABT-102<br />
7. Rear sponsons, 13mm of ABT-102 (actual thickness: 43mm)<br />
8. Hull belly, 10mm of AMG-6<br />
9. Hull sponsons, 43mm of ABT-102<br />
10. Underside of sponsons, 15mm of ABT-102<br />
11. Lower hull sides, 43mm of ABT-102<br />
12. Lower glacis, 10mm BT-70Sh, 70mm air space, 60mm ABT-102<br />
13. Front hull midsection, 10mm BT-70Sh, 70mm air space, 12mm BT-70Sh, 60mm ABT-102</blockquote>
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The frontal armour of the BMP-3 is reportedly proofed against 30mm armour-piercing shells from a distance of 200 meters in its frontal arc. The criteria is not given, but as proofing refers to the total absence of structural defeat, it is very likely that the armour resists a perforation even at point blank range. It is assumed that the 3UBR6 steel AP-T rounds was used as the reference threat, but APDS rounds of a smaller caliber can be defeated as well. Based on an examination of the armour of the BMP-3, it is clear that even though the front armour of the hull reaches a high standard of protection, the hull does not have a uniform level of protection across its frontal arc of 60 degrees due to the relatively thin side armour which is borderline vulnerable to 23mm BZT shells (API-T) from 100 meters from a side angle of 30 degrees. Only the turret can guarantee protection from not only 23mm API-T but also 30mm AP-T shells in a frontal arc of such size.<br />
<br />In terms of its design, the armour scheme was created to achieve a higher level of protection than the preceding BMP-1 and BMP-2 without requiring an excessive amount of weight. The study "<i><a href="http://btvt.info/5library/vbtt_1983_04_abt-101.htm">Исследование Броневых Преград Для Легкой БТТ</a></i>" by Yu. I. Belkin et al., published in the April 1983 issue of "<i>Вестник бронетанковой техники</i>", shows that the efficiency of the multilayered spaced armour of the BMP-3 greatly exceeded that of homogeneous medium hardness steel (RHA) against tungsten-cored APDS shells. The relevant passage is shown below:<br /><blockquote>
"<i>В результате совместных исследований НИИ и КБ были разработаны оптимальные структуры комбинированной брони. При разработке этих схем были учтены особенности воздействия имитаторов зарубежных бронебойных подкалиберных снарядов. Обстрел образцов такой брони показал, что в сравнении с монолитной стальной броней средней твердости они дают уменьшение массы преграды на 20…50 %.</i>"</blockquote>
Translation:<br /><blockquote>
"<i>As a result of joint research by research institutes and design bureaus, optimal composite armour structures were developed. When developing these schemes, the characteristic effects of simulators of foreign armour-piercing subcaliber shells were taken into account. The shelling of samples of such armour showed that, in comparison with monolithic steel armor of medium hardness, they reduce the mass of the armour by 20-50%.</i>"</blockquote>
In other words, the mass efficiency of the spaced armour is 20-50% higher than rolled homogeneous armour against APDS shells of autocannons. This will be useful for evaluating the effectiveness of the vehicle's armour against APDS shells as it is easy to determine the areal density of the various armoured zones of the BMP-3.<br />
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Alone, ABT-102 aluminium plates have a higher mass efficiency coefficient than 2P high hardness steel at all angles against armour-piercing shells for autocannons. This is illustrated in the graph below, taken from the study "<i>Разработка Комбинированных Титан-Алюминиевых Башен</i>", which shows the necessary thickness to guarantee invulnerability from 23mm BZT shells (AP-I) from a distance of 100 meters. The thicknesses of the materials shown in the graph are normalized along the x-axis to have an equivalent weight. For example, 2P high hardness steel has a density of 7.85 g/cc, and a thickness of 23.2mm has an equivalent weight to 40mm of VT6 titanium alloy (density of 4.55 g/cc) and to 64mm of ABT-101 or ABT-102 aluminium alloy (density of 2.85 g/cc).</div><div>
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It is obvious from the curves that both VT6 titanium alloy and ABT-101/102 aluminium alloy outperform 2P high hardness steel at all angles of attack, although the difference is not shown for angles smaller than 28 degrees. When the armour obliquity increases to around 50-65 degrees, there is a minor - almost negligible - difference in mass efficiency between VT6 and ABT-101/102 in favour of VT6. At an obliquity of 30 degrees, around 29.7mm of high hardness steel is required to stop a 23mm BZT shell at a distance of 100 meters, but 73mm of ABT-101/102 aluminium alloy is required. This thickness of aluminium alloy plate is only equivalent in weight to a 26.5mm plate of steel armour, so it is able to achieve the same level of protection with only 89.2% of the mass, meaning that it has a mass efficiency coefficient of 1.12. In other words, it has 12% higher mass efficiency than 2P high hardness steel.<br />
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As the armour obliquity increases, the mass efficiency of aluminium alloy armour gradually increases as well. At 50 degrees, 24.75mm of high hardness steel is required to stop the 23mm BZT shell and 59mm of ABT-101/102 is required. This translates to a mass efficiency coefficient of 1.155, so the aluminium alloy armour has a 15.5% higher mass efficiency.<br />
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These results against 23mm BZT shells are also representative of 30mm BT (AP-T) shells as the design is very similar.<br />
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<span style="font-size: large;">HULL</span></h3>
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The midsection of the hull occupies a quarter of the total height of the hull structure. It is sloped at 30 degrees, which greatly enhances its protection as compared to a flat armour array, but not as much as compared to a more oblique armour array. This made it necessary to add a 12mm high hardness steel plate on top of the aluminium base armour. This appliqué armour plate is shown in the photos below:<br />
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Knowing the densities of ABT-102 and BT-70Sh and the known thicknesses of armour, calculating the areal density of this zone is very straightforward. The steel components of the armour array add up to a total thickness of 22mm and are equivalent in weight to 22mm of RHA steel, whereas the 60mm of aluminium alloy armour is equivalent to only 21.8mm of RHA steel. All together, the armour is equivalent to a 43.8mm RHA steel plate in weight. Taking into account the armour slope of 30 degrees, the effective weight of the armour is equivalent to 50.6mm of steel. The areal density is 397 kg/sq.m. This is somewhat heavier than the armour of the BMP-1, which had a maximum LOS thickness of 35mm on its lower glacis, giving an areal density of 274 kg/sq.m. Given a 1.5 mass efficiency coefficient, a high end estimate of the protection value of the steel-aluminium spaced array indicates that this part of the BMP-3 hull has an effective thickness equal to 75.9mm of RHA. Using a 1.2 mass efficiency coefficient indicates that the effective thickness is only equivalent to 60.7mm of RHA.<br />
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Interestingly, the front hull protection may be increased further by simply extending the wave breaker, creating even more spaced distance. The wave breaker is extended 480mm away and slightly raised when activated, thus increasing the air gap in front of the hull to 550mm with an effective air gap size of 635mm. Because the wave breaker is slightly taller than the midsection of the front hull, it does not leave gaps in the front armour when it is extended. The main disadvantage of leaving the wave breaker extended when not swimming is the increased overhang of the hull and the reduced driver visibility because of the large dead zone it creates.<br />
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Like the midsection plate, the lower glacis features the same base aluminium armour thickness of 60mm but it is set at a higher obliquity of 50 degrees. There is no wave breaker here, but there is a dozer blade of the same thickness made from the same high hardness, high strength BT-70Sh steel as the wave breaker. The dozer blade is spaced from the main armour by 70mm. The additional slope of the lower glacis enhances its protection from ballistic threats, so it did not require an steel appliqué armour plate on top of its aluminium base. A BMP-3 belonging to the 3rd Armor Brigade of the ROK is seen in the photo below with the dozer blade deployed and the wave breaker extended. To deploy the dozer blade, the wave breaker must first be extended.<br />
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As before, the areal density of the lower glacis is easily calculated. Adding up the aluminium base armour with the dozer blade, it turns out that the weight of the armour is equivalent to just 31.8mm of RHA steel plate. However, the greater angle of slope increases the effective weight of the armour is equivalent to 49.4mm of RHA steel. In other words, it is only negligibly lighter than the hull midsection armour. A high end estimate of its protection value using a 1.5 mass efficiency coefficient indicates that this part of the hull has an effective thickness equal to 74.1mm of RHA. Using a 1.2 mass efficiency coefficient indicates that the effective thickness is only equivalent to 59.3mm of RHA.<br />
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Alone, the 60mm plate of ABT-102 armour is already sufficient to guarantee total invulnerability from 23mm BZT shells fired from a distance of 100 meters. Moreover, the aluminium plate is equivalent to 33.9mm of armour steel by mass, but because it is 15.5% more mass efficient than high hardness steel against armour-piercing shells at its structural obliquity of 50 degrees, it is actually equivalent to a line-of-sight thickness of 39.1mm of 2P high hardness steel. This is already superior to the lower glacis of the BMP-1 which was constructed from a 19mm plate of 2P steel armour set at 57 degrees, giving an line-of-sight thickness of 34.9mm of 2P high hardness steel.<br />
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When the contribution of the high hardness steel dozer blade is taken into consideration, the gap between the BMP-3 and its predecessor in armour protection at this part of the hull expands even further.<br />
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The upper glacis is sloped at 80 degrees, and thanks to its high obliquity, practically all autocannon shells will either ricochet or fail to defeat the armour due to extreme deflection. With a physical thickness of 18mm, the obliquity of 80 degrees raises the LOS thickness of the upper glacis to 103.6mm. In terms of weight, the upper glacis is equivalent to a 6.5mm RHA steel plate sloped at 80 degrees.<br />
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Only long rod projectiles with a heavy metal penetrator can defeat this part of the hull, but even this type of ammunition may have issues on account of the high LOS thickness of armour present. Soviet studies determined that when the armour requires an obliquity of 70 degrees and above, homogeneous ABT-102 plate was more efficient than both homogeneous RHA steel plate and spaced steel armour of the same areal density.<br />
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All together, the entire front of the hull is uniformly armoured. However, due to the shape of the fuel tank behind the front hull armour, the actual protection value differs across the height of the hull, peaking at the midsection where the fuel tank reaches its maximum thickness. The contribution of the fuel tank towards the protection of the vehicle is examined later.<br />
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The turret ring is recessed into the hull and is additionally protected by thick armoured collars. The first collar surrounds the entire turret ring and the front half of the turret ring is protected by another armoured collar, as shown in the photo below. The first collar surrounds the base of the aluminium turret and the second collar is hidden behind the spaced steel turret shields. When attacking the turret ring of the BMP-3 in its frontal arc, projectiles must first pierce the spaced steel shield of the turret before contending with the double collars, and behind that is the base aluminium armour of the turret itself. As such, the possibility of the turret ring being hit and subsequently being jammed is very small as the combined thickness of the steel shield, collars, and base turret armour is extremely high.<br />
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The entire rear armour of the hull, including the doors, has a thickness of 43mm. The sponsons on either side of the doors hold the accumulator batteries and coolant for the engine.<br />
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The side armour has a uniform thickness of 43mm across the entire length of the vehicle. This is sufficient for steel-cored armour-piercing 7.62mm machine gun fire at all distances from any angle and it is resistant to artillery fragments. The 43mm side armour weighs the same as a 15.6mm plate of BT-70Sh high hardness steel. By weight, this would make the side armour identical to the BMP-2, but due to the greater thickness efficiency of ABT-102 aluminium alloy, the armour is actually more effective.<br />
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The cheeks of the front hull projection underneath the bow machine guns join the side of the hull with the front. Like the upper glacis, they are sloped at 80 degrees or 10 degrees relative to the longitudinal axis of the hull, but they are much thicker. This is because they are not only exposed to fire from the direct front and their obliquity is reduced relative to the side hull armour against attacks from a side angle. As the drawing below shows, an attack from a side angle of 30 degrees would impact the side hull armour at an angle of 60 degrees, but the same projectile would impact the cheek armour at 50 degrees.<br />
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At a side angle of 30 degrees, the side hull armour reaches a line-of-sight (LOS) thickness of 86mm and the cheek armour reaches a LOS thickness of 93mm. The increased thickness of the cheek not only compensates for the reduction in line-of-sight (LOS) thickness that comes with a reduced impact angle, but also for the improved performance of AP and APDS shells at lower obliquity.<br />
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Referring again to the study "<i>Разработка Комбинированных Титан-Алюминиевых Башен</i>", the side armour of the BMP-3 was not entirely sufficient to stop 23mm BZT shells from a distance of 100 meters when the side angle of hull is 30 degrees. At this side angle, the impact angle of the shell is 60 degrees and 48mm of ABT-101/102 aluminium alloy plate is required to ensure total invulnerability (prevention of conditional defeat). However, the cheek armour with its higher thickness of 60mm and lower obliquity of 50 degrees is capable of doing so. For the side armour to ensure invulnerability from 23mm BZT shells at 100 meters, the impact angle must be 63-64 degrees.<br />
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The side armour provides protection against 30mm BT shells (3UBR6) from a range 300 meters at an impact angle of 68 degrees, or a side angle of 22 degrees. Thus, the frontal arc of protection is 44 degrees. Against steel armour piercing shells, a 43mm plate of ABT-102 is equivalent to a BT-70Sh plate with a thickness of 21mm, so in other words, it has a mass efficiency coefficient of around 1.35 against this type of threat. As mentioned before, the mass efficiency advantage of ABT-102 declines as the impact angle approaches normal.<br />
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From a 20-degree side angle relative to the axis of the hull, the side armour should be capable of resisting 25mm APDS rounds owing to the high angle of the side armour and the high LOS thickness (126mm). This means that the BMP-3 does not have very much maneuvering freedom if engaged by an autocannon since only 40 degrees of its frontal arc is immune, and only at extended distances.<br />
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The use of very thick aluminium plates (60mm and 43mm) for the hull allowed a monocoque construction to be implemented because the armour itself has sufficient rigidity to act as load bearing structures, but the large weight of the turret necessitated the use of support columns around the turret ring. These columns can be seen in the two photos below. There are five in total. They connect the hull roof to longitudinal stiffening beams on the floor.<br />
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<a href="https://4.bp.blogspot.com/-RnyR_VhZGq0/WnWCw1FsyfI/AAAAAAAAKq4/BGUBY9fyBtUx-_BGhLrbHr2KRTp9D800ACLcBGAs/s1600/bmp-3%2Bwelding.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="533" data-original-width="800" height="266" src="https://4.bp.blogspot.com/-RnyR_VhZGq0/WnWCw1FsyfI/AAAAAAAAKq4/BGUBY9fyBtUx-_BGhLrbHr2KRTp9D800ACLcBGAs/s400/bmp-3%2Bwelding.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-3eyQb_zPj3Q/WnWCqgJc5sI/AAAAAAAAKq0/a7cAinYaQ-kD51aD2MQcIslExtcMLBOCgCLcBGAs/s1600/front%2Bhull.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://1.bp.blogspot.com/-3eyQb_zPj3Q/WnWCqgJc5sI/AAAAAAAAKq0/a7cAinYaQ-kD51aD2MQcIslExtcMLBOCgCLcBGAs/s400/front%2Bhull.jpg" width="400" /></a></div>
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Nevertheless, the weight savings from the omission of structural supports inside the hull reportedly amounts to 10%.<br />
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<span style="font-size: large;">TURRET</span></h3>
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The turret is also fabricated from welded ABT-102 aluminium alloy plates. The shape of the turret is identical to the BMP-2 turret. The aluminium roof is then welded onto the walls. The steel shield on the turret's frontal arc is made from BT-70Sh steel like the wave breaker, but it is thicker than the wave breaker for extra protection, which is needed due to the lack of a self-sealing fuel tank underneath the armour like on the hull. The spaced steel and aluminium combination should effectively render the turret virtually invulnerable against 20mm and 25mm APDS shells in a frontal attack, which comes naturally from the spaced plate due to the lack of an armour piercing cap on such shells, making it vulnerable to fracturing and fragmenting after passing through a high hardness, high strength spaced plate. The photos below show the naked turret, without any steel shields or bolt-on steel sheets on the roof.<br />
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<a href="http://1.bp.blogspot.com/-3ioYbRRKPKw/VD5upTkULcI/AAAAAAAAACs/8B3FJ-0V1uM/s1600/BMP-3%2C%2Bnaked%2Bturret.png" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="293" src="https://1.bp.blogspot.com/-3ioYbRRKPKw/VD5upTkULcI/AAAAAAAAACs/8B3FJ-0V1uM/s1600/BMP-3%2C%2Bnaked%2Bturret.png" width="400" /></a><a href="https://2.bp.blogspot.com/-HYE5V6bUVqQ/Wm9jU0bjDTI/AAAAAAAAKqM/Yz5xYd2MFHEUFgVoW1MO-MtIdN1S7OhPwCLcBGAs/s1600/068.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="450" data-original-width="470" height="382" src="https://2.bp.blogspot.com/-HYE5V6bUVqQ/Wm9jU0bjDTI/AAAAAAAAKqM/Yz5xYd2MFHEUFgVoW1MO-MtIdN1S7OhPwCLcBGAs/s400/068.jpg" width="400" /></a></div>
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The walls of the circular turret are constructed from four plates. The front half of the turret is composed of two curved 50mm aluminium plates that form the cheeks and a flat plate of the same thickness which forms the frame of the gun mantlet. The rear half of the turret is formed by a single 43mm aluminium plate curved into a semicircle. The front of the turret is vertically sloped at 45 degrees. If the turret is fired upon from the direct front, the circular shape of the turret introduces additional horizontal slope which improves the effectiveness of the spaced armour. However, when considering the frontal arc protection of the turret rather than its protection from the direct front, the circular shape of the turret means that projectiles from a side angle towards the center of the turret will impact the frontal turret armour at a perpendicular angle, leaving only the vertical slope to contribute towards the protection value of the armour.<br />
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The areal density of the turret cheeks with the spaced steel shields can be calculated. Adding up the aluminium base armour with the shield, the weight of the armour is equivalent to just 34.1mm of RHA steel plate. Together with the 45 degree obliquity of the armour, the effective weight is equivalent to 48.3mm of RHA steel. A high end estimate of its protection value using a 1.5 mass efficiency coefficient indicates that this part of the hull has an effective thickness equal to 72.5mm of RHA. Using a 1.2 mass efficiency coefficient indicates that the effective thickness is only equivalent to 58mm of RHA. If the low end estimate is used, the armour is equivalent to a 41mm RHA plate sloped at 45 degrees, making it dangerously vulnerable to the 30mm L14A2 shell for the RARDEN cannon as the penetration of that shell reportedly reaches 40mm RHA at 45 degrees at 1,500 meters. If the high end estimate is used, the armour is equivalent to a 51.1mm plate sloped at 45 degrees, in which case the L14A2 shell would struggle against the armour even at ranges of less than 500 meters.<br />
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Besides the shielded cheeks of the turret, a large part of the front turret projection is occupied by the gun mantlet which is quite wide as it also serves as the gun cradle that accommodates the BMP-3's unique combination of three coaxial weapons. The gun mantlet lacks the spaced armour shields of the frontal turret armour. As the photo below shows, the gun mantlet is a cylindrical structure of unknown composition that is designed to allow the weapons to reach a high elevation angle without exposing gaps in the turret. As it is cylindrical, it is reasonable to assume that it offers the same amount of armour protection regardless of the elevation angle of the weapons.<br />
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The armour protection value of the gun mantlet is unknown, but it should be noted that the diameter of the gun mantlet is very large. It easily exceeds the line-of-sight thickness of the spaced turret armour neighboring it. Whether it is a solid aluminium cylinder or a hollow tube is unknown, but due to its size, it is most likely hollow as it would otherwise be rather heavy. Even so, this implies that the mantlet itself can reach the same protection level as the rest of the frontal turret armour.<br />
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Besides the front, sides and rear armour of the turret, the roof is also exposed to direct fire and must be evaluated separately as it is not flat, but actually forms a shallow cone. The forward section of the roof ending behind the crew hatches is angled at 8 degrees from the horizontal plane, peaking at the center of the roof. The rear of the roof is canted back at 13 degrees. The transition between the two sections can be seen in the photo below. This was designed to provide room for gun depression and also to allow 100mm shell casings to be ejected out of the ejection port on the roof. Because the turret roof has a thickness of 18mm, the forward section is more resilient than the upper glacis of the hull due to its greater slope of 82 degrees (from the vertical axis).<br />
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Altogether, the frontal arc of the turret should be immune to 30mm AP-T shells from a distance of 300 meters, and the armour should also be resistant to 20mm and 25mm APDS rounds of the 1980's albeit at a greater distance. Like the front hull, a 30mm cannon with APFSDS ammunition is needed to reliably defeat the armour. The rear of the turret is as thick as the sides and rear of the hull so it is ostensibly only as resilient as those zones, but the rear of the turret gains additional protection from its curvature.<br />
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Early BMP-3s are often observed with a smooth hull and turret roof. Later on, additional high hardness steel armour plates were attached to the roof to augment protection from overhead fire. This kit was derived from a comprehensive armour modernization package offered for the BMP-3 by NII Stali during the 1990's. This package included a suit of ERA for the vehicle. The package was not accepted for service, but the additional roof armour was implemented to existing vehicles and all newly produced samples. The main purpose of this additional armour was to increase the protection of the BMP-3 from air bursting artillery shells, specifically 155mm shells which produces fragments that are capable of defeating a relatively large thickness of armour. However, it is clear that this additional armour also improves the protection of the vehicle from small arms fire coming from above, and there are a number of surfaces that are exposed to direct fire from the ground as well. This includes the roof of the hull sponsons, the upper glacis of the hull, and the roof of the turret.<br />
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<span style="font-size: large;">ADDITIONAL ARMOUR</span></h3>
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Additional slat armour and applique spaced side armour may also be installed, as seen here:<br />
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The addition of the hard steel spaced panel is most probably intended to immunize the sides against .50 caliber SLAP ammunition. .50 caliber SLAP has very high nominal penetration, but it is not very sophisticated. It is merely a tungsten carbide slug driven at high velocity. It does not have an armour piercing cap or any other buffers. This makes it very easy to defeat by spaced armour, as the strong but brittle tungsten carbide slug will shatter against the spaced plate, leaving only fragments to harmlessly impact the main armour.<br />
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New production BMP-3s will probably have this armour installed as standard. Thanks to the high buoyancy characteristics of the BMP-3, the additional weight had only a negligible effect on its swimming abilities. It is still able to travel at around 10 km/h in the water, and the vehicle's top speed remains unchanged to boot, though the change in weight should be somewhat noticeable for the driver. All BMP-3s will be retrofitted with the new armour as part of a low-cost modernization program to maintain fighting capabilities while waiting for sufficient numbers of new generation IFVs to accumulate.<br />
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It's worth noting that the slat armour and thin spaced steel panel combination isn't particularly high-tech, and that the BMP-3 could have been given them as an ad-hoc modification by technicians in the field anyway.<br />
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<span style="font-size: large;">FUEL TANK AS ARMOUR</span></h3>
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The fuel tank located immediately behind the front hull armour not only serves as the vehicle's only fuel container but also as an integral part of the protection scheme. It gives the BMP-3 the ability to resist larger autocannon rounds even if the front armour of the hull is perforated. Spalling from the frontal hull armour also becomes a non-issue to the crew. Most importantly, these benefits comes at no penalty to the overall weight of the vehicle, making the BMP-3 one of the best protected vehicles of its class. Thanks to the self-sealing nature of the fuel tank, fuel leakage is minimized.<br />
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However, the shape of the hull itself and the need to account for the needs of the crew meant that the shape of the fuel tank was not uniform, and as such, the amount of protection it offers is also not uniform. To accommodate the driver's instruments, the fuel tank has a cutout in the middle and there is no fuel tank in front of the driver's pedals at all although there is an anti-radiation liner in front of the driver's pedals which acts as a spall liner. This gives the driver a larger amount of space to work but reduces his protection somewhat compared to the bow gunners. Moreover, there are also gaps along the sides of the fuel tanks left for the suspension adjustment mechanisms connected to the idler wheels on both sides of the hull.<br />
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Because of the shape of the front hull, the fuel tank reaches its maximum thickness directly behind the midsection of the hull. Its thickness reduces towards the bottom of the hull following the slope of the lower glacis armour.<br />
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The fuel tank is filled with open-cell polyurethane foam and can store 700 liters of diesel. The placement of the fuel tanks to the front means that hydrodynamic effects due to the fuel stores will dissipate the energy of cumulative jets from shaped charge warheads as well as defeat kinetic penetrators.<br />
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An additional note is that the main armour has no anti-radiation liner, but the rear backing of the fuel tank does, and the backing is not partitioned from the driver. The driver would see the fuel tank if he peers behind his instrument panels. This is a good indication that the designers intended the fuel tank to be used specifically as additional armour, if further proof is required at all.<br />
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</div><div><br /></div><h3 style="text-align: left;">MINE PROTECTION</h3><div><br /></div><div>The hull belly plate is made from AMG-6 aluminium alloy, 10mm thick. AMG-6 is the equivalent of 5083 aluminium alloy. To maximize its rigidity, longitudinal beams were welded to the plate between the torsion bar housings, and the plate itself had stamped ribs for additional stiffness as the photo below shows. The front section of the belly between the firsts and second torsion bar pairs has a double bottom integrated integrated into its construction. This region is much more heavily reinforced against mine blasts compared to the rest of the belly. Between the two layers, there is an additional lateral beam and six longitudinal beams welded together and with the layers, forming a "waffle" pattern.</div><div><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-jX5bNoBQUWE/XbSqKfC0IeI/AAAAAAAAPec/PfwE7gjcBxEw4AXdrSsIP66JA4T8G6aeACLcBGAsYHQ/s1600/bmp-3%2Bfloor.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://1.bp.blogspot.com/-jX5bNoBQUWE/XbSqKfC0IeI/AAAAAAAAPec/PfwE7gjcBxEw4AXdrSsIP66JA4T8G6aeACLcBGAsYHQ/s640/bmp-3%2Bfloor.jpg" width="640" /></a></div></div><div><br /></div><div><br /></div><div>In the book "<i>Теория И Конструкция Танка: Т. 10. Кн. 2. Комплексная защита</i>" (<i>Tank Theory and Construction - Vol. 10, Book 2: Comprehensive protection</i>), a "waffle" pattern construction of this type is given as an example of BMP belly armour reinforced against mine blasts.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-hCFEQZDZRAw/Xs71cShNdrI/AAAAAAAAQ0g/vLgudmOvnRsJtF0xwcV6rnf7m_LAxBE3ACK4BGAsYHg/bmp%2Bdouble%2Bbottom%2Bconcept.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="617" data-original-width="983" height="402" src="https://1.bp.blogspot.com/-hCFEQZDZRAw/Xs71cShNdrI/AAAAAAAAQ0g/vLgudmOvnRsJtF0xwcV6rnf7m_LAxBE3ACK4BGAsYHg/w640-h402/bmp%2Bdouble%2Bbottom%2Bconcept.png" width="640" /></a></div><div><br /></div><div><br /></div>
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During the Soviet military intervention in Afghanistan, the issue of mine protection in asymmetric warfare became an important topic in light of the poor performance of BMP-1 and BMP-2 when faced with IEDs and anti-tank mines due to their thin belly armour. Although a typical small track-breaker mine with a payload of 1.5 kg TNT would not be able to significantly damage the hull when detonated under the track, BMPs often ran over much more powerful explosive devices. The driver was the most vulnerable member of the crew due to his location at the front of the hull, and the person seated behind him was the next most vulnerable. To improve the survivability of these vehicles, an additional spaced armour kit was developed to increase the rigidity of the hull belly, reduce the probability of a breach in the armour, and dampen the shock effect from the blast. The driver also received a new seat suspended from the hull ceiling. The same solutions were implemented in the BMP-3.<br />
<br /><br />In the BMP-3, the double bottom is only present underneath the stations of the driver and the two bow gunners so the rest of the occupants are ostensibly more vulnerable, but due to the layout of the vehicle, this is not true. The turret, which is behind the driver and bow gunners, is suspended from the ceiling at the turret ring, and only the passengers at the rear of the hull have to contend with just the single hull belly plate for protection. This was the most rational layout as the front half of the hull is the most affected by mine or IED blasts.</div><div><br /></div><div>Furthermore, rather than having the driver and bow gunners' seats and equipment installed onto the belly, they are installed on the sides of the hull or onto special support beams. The turret itself is physically isolated from the hull belly and is only connected to a false floor via a rotary electrical power distribution hub. The support columns connecting the hull roof at the turret ring to the hull belly (to support the weight of the turret) also serve as additional reinforcement to prevent an underbelly blast from deflecting the belly plate. In total, the hull structure is strongly reinforced against mine blasts.<br />
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All the seats - both for the crew and passengers - are not directly attached to the floor. The seats for the crew in the turret are suspended from the turret. One notable exception is the driver's seat, which is connected to the double bottom armour on the floor. The seat has integrated shock absorbers and layered foam padding. The passenger seats are mounted to the sides of the hull or to the engine compartment bulkhead.</div><div><br />
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<span style="font-size: large;">
EXPERIENCE IN CHECHNYA</span></h3>
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The first combat deployment of the BMP-3 was on the 1st and 2nd of January 1995 in Grozy, on the assault for the Grozny hospital complex. On a column heading for said hospital complex and around the complex itself, a total of 11 BMP-3s were destroyed (ammo detonated) by mines, buried explosive caches and mortar fire. Those same mines also knocked out several tanks. The total figure in the first six months of fighting is quite likely in the range of 20 to 30 vehicles, on the basis of the fact that the vast majority of the 163 destroyed IFVs were undoubtedly BMP-1/2s and BMD-1/2s. Generally, most BMP-3s were destroyed either by mines or by RPG fire. Against such threats, the BMP-3 has no advantages over its predecessors.<br />
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The BMP-3 did experience somewhat higher survival rates thanks to the placement of the fuel tank. Even if the armour was perforated by an RPG, it could not set fire to the vehicle, which meant that ammunition could not be detonated without a direct hit to the ammunition, unlike the BMP-1 and BMP-2.<br />
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Chechnya proves that the BMP-3 is as backwards as all Soviet era equipment when it comes to asymmetrical warfare. Large mines and IEDs are the largest threat, a threat which the BMP-3 is not designed to handle. The BMP-3 was designed for a European conflict, and if such a conflict were to ignite, it would have been unbeatable, but alas, those days are over. </div>
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<h3>
<span style="font-size: large;">ARMOUR UPGRADE KIT</span></h3>
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<div><br /></div><div><br /></div>There is an add-on armour kit available for the BMP-3, which is mounted over the upper sides of the hull. Each section of the armour has a foothold on its underside and there are additional footholds between each section. The additional armour obstructs the firing ports, rendering them unusable. </div><div><br /></div><div>The kit reportedly provides the hull side armour with total protection from 12.7mm armour-piercing bullets. The kit compensates for its own weight by including air pockets in the design, acting both as spacing and as flotation aids. The amphibious qualities of the vehicle are therefore completely unaffected.</div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-TBP24uuuHKY/XswpjuythFI/AAAAAAAAQyI/8v9z9w6CeQ05RYynedKZ3ONJxV8so5WqwCK4BGAsYHg/swimming%2Bwith%2Badd-on%2Barmour.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="960" data-original-width="1280" height="480" src="https://1.bp.blogspot.com/-TBP24uuuHKY/XswpjuythFI/AAAAAAAAQyI/8v9z9w6CeQ05RYynedKZ3ONJxV8so5WqwCK4BGAsYHg/w640-h480/swimming%2Bwith%2Badd-on%2Barmour.jpg" width="640" /></a></div><div><br />
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It appears that the Russian Naval Infantry are the only branch of the Russian military that uses this armour kit. Their BMP-3F vehicles can sometimes be seen with the kit installed. The photo on the left below shows a BMP-3F belonging to the Naval Infantry undergoing scheduled repairs and the photo on the right below shows a special BMP-3F with the "Bakhcha-U" turret and the armour kit.<br />
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<a href="https://1.bp.blogspot.com/-VSQluhGpMHI/XalQOg0mdoI/AAAAAAAAPcI/a8Lpibwrz6cJGYKMWmTPcYtv6nmZfzCcgCLcBGAsYHQ/s1600/bmp-3f%2Bwith%2Badditional%2Barmour.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="300" src="https://1.bp.blogspot.com/-VSQluhGpMHI/XalQOg0mdoI/AAAAAAAAPcI/a8Lpibwrz6cJGYKMWmTPcYtv6nmZfzCcgCLcBGAsYHQ/s400/bmp-3f%2Bwith%2Badditional%2Barmour.jpg" width="400" /></a><a href="http://4.bp.blogspot.com/-gIXU_F9U-co/VEYwRCxL7fI/AAAAAAAAAU0/2Tp28N9-bPg/s1600/bmp31pe0.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="253" src="https://4.bp.blogspot.com/-gIXU_F9U-co/VEYwRCxL7fI/AAAAAAAAAU0/2Tp28N9-bPg/s400/bmp31pe0.jpg" width="400" /></a></div>
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This kit has also been seen in use by BMP-3s belonging to the UAE.<br />
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<h4>
<span style="font-size: large;">"BAKHCHA-U" TURRET</span></h4>
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<a href="http://3.bp.blogspot.com/-5aDvpt1yahs/VgOTbx1UhQI/AAAAAAAADvc/jSnBfYEvToU/s1600/bakcha-u.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://3.bp.blogspot.com/-5aDvpt1yahs/VgOTbx1UhQI/AAAAAAAADvc/jSnBfYEvToU/s320/bakcha-u.png" width="315" /></a></div>
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The "Bakhcha-U" turret was originally intended to be equipped on the BMD-3, but has become an option for the BMP-3 as well. The new turret had a new armour protection scheme and features a new autoloader with a revised ammunition carousel and new sighting systems for both the commander and gunner. The new turret is claimed to have superior armour protection, though its exact qualities are unknown<br />
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<a href="http://1.bp.blogspot.com/-qm9RmIFlLbA/VEYzO3ghT3I/AAAAAAAAAVA/tWL0fbu72F0/s1600/Bmp%2B3ifv.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-qm9RmIFlLbA/VEYzO3ghT3I/AAAAAAAAAVA/tWL0fbu72F0/s1600/Bmp%2B3ifv.jpg" /></a></div>
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The turret also includes a new dual-channel gunner's sight and a new commander's panoramic thermal imaging device.<br />
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The gunner's new thermal imaging sight can acquire targets at day or night at ranges of up to 4,000 meters. The automatic target tracking system is sophisticated enough to automatically engage low-flying aircraft without gunner input save for the need for him to press the trigger.<br />
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The commander's panoramic sight:<br />
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The new autoloader carries 34 HE-Frag rounds stored vertically in a carousel. To load, the gun is automatically elevated beforehand and a round from the autoloader is dropped onto a tilted tray, where it is rammed upwards into the chamber.<br />
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A total of 500 rounds of autocannon ammunition is carried in steel bins, like the original turret. There are 255 rounds of armour-piercing ammunition and there are 245 rounds of high-explosive ammunition. The feed system for the 2A72 was not significantly modified.<br />
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The new autoloader stores 4 ATGMs in a vertical rack behind the commander. To load, a mechanical arm places a missile onto the independent ammunition carousel, which spins a short distance to line up the missile with the cannon breech, whereby it is rammed in. Like the loading procedure for HE-Frag shells, the gun must be elevated to load. The amount of time per loading cycle is not known. Although KBP released a promotional video showing the process, the autoloader was deliberately paused multiple times for the demonstration. Without the pauses, it takes just over 3 seconds to load each missile.<br />
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A BMP-3 with the "Bakhcha-U" turret passed all factory and state tests in 1999.<br />
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<h3>
<span style="font-size: large;">ERA</span></h3>
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<a href="http://1.bp.blogspot.com/-RPxmG7A6Hh0/Vhu04pAvywI/AAAAAAAAD9o/MQ5sJndGPWs/s1600/bmp-3%2BERA.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://1.bp.blogspot.com/-RPxmG7A6Hh0/Vhu04pAvywI/AAAAAAAAD9o/MQ5sJndGPWs/s640/bmp-3%2BERA.jpg" width="640" /></a></div>
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There are at least two known ERA kits available for the BMP-3, both of which were developed as a direct response to the vehicle's vulnerability to RPGs in Chechnya.<br />
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<b><span style="font-size: large;">Unknown ERA Kit (4S20)</span></b></h3>
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This is one of three ERA configurations developed for the BMP-3. It was first displayed in early 2001 in Omsk. It employs ERA boxes utilizing 4S20 explosive elements, which are able to protect the host vehicle from rocket strikes of the single-charge warhead variety.<br />
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This ERA-protected BMP-3 was developed during the First Chechen conflict where the vehicle proved vulnerable to not only HEAT warhead but also to heavy-caliber machine gun fire to the sides. This ERA package ensures greatly increased protection from single-charge warheads on all sides except the immediate rear, although it cannot by any means provide absolute protection from these shaped-charges.<br />
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<a href="http://1.bp.blogspot.com/-CAoMRidfzJU/VEKUbuxx_dI/AAAAAAAAAMk/tCFYIq_TNPs/s1600/bmp3d_03.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-CAoMRidfzJU/VEKUbuxx_dI/AAAAAAAAAMk/tCFYIq_TNPs/s1600/bmp3d_03.jpg" /></a></div>
Interestingly, the ERA-equipped BMP-3 formed the basis for later upgrades. For instance, the bolt-on armour overlays were in fact first introduced as part of the "improved protection kit" which included the ERA package. The overlays then crossed over and became a standard feature of all BMP-3s. Other features were never implemented, however, such as the beefed-up road wheels (necessary for supporting the increased weight) and applique steel side armour screens, which were necessary for supporting the ERA blocks and consisted of seven sections on each side of the hull. The boxes are completely resistant to both armour piercing and incendiary of the 7.62mm and 12.7 calibres and are also unaffected by burning napalm. The steel side screens also acted as applique armour and granted the side aspect complete immunity from 12.7mm AP and SLAP fire.<br />
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<a href="http://1.bp.blogspot.com/-6Fn6h6uvi6c/VEKUe5_5NQI/AAAAAAAAAM8/z08ONJvFCJo/s1600/bmp3d_073.jpg" style="clear: left; display: inline; margin-bottom: 1em; margin-right: 1em; text-align: center;"><img border="0" src="https://1.bp.blogspot.com/-6Fn6h6uvi6c/VEKUe5_5NQI/AAAAAAAAAM8/z08ONJvFCJo/s1600/bmp3d_073.jpg" /></a> They will be completely destroyed if struck and activated by a shaped charge warhead.<br />
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In this photo, you can see the turret armour ERA boxes' vulcanized rubber flaps lifted up. The rubber flaps are intended to detonate warheads ahead of the ERA, further increasing their potency.<br />
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50 sets of these ERA box-sets were procured by the UAE for testing and evaluation. No details on further acquisition have been reported. Recent videos of UAE operations in Yemen with BMP-3s show that they are not outfitted with ERA.<br />
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Each box weighs just 1.37kg, and the explosive charges contained within weigh a total of 0.28kg. There have been concerns that the thin walls of the boxes and the relatively large explosive charge will cause collateral damage to nearby personnel. The concussive effects (more than double of that of an RGD-5 grenade) can cause blast-related injuries to not only dismounted infantry, but also to soldiers <i>within</i> the vehicle. But then again, if an RPG is detonated outside the vehicle, this hardly matters anyway. </div>
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The introduction of the newer 4S24 package have made the 4S20 package completely obsolete. It is not supplied to any Russian army units.</div>
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<h3>
<span style="font-size: large;">NII Stali ERA for lightly armoured vehicles</span></h3>
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<a href="http://3.bp.blogspot.com/-bhjhx7SNeO0/VHd-I_jS5wI/AAAAAAAAA2s/DeeOi59-FJU/s1600/bm3_2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="236" src="https://3.bp.blogspot.com/-bhjhx7SNeO0/VHd-I_jS5wI/AAAAAAAAA2s/DeeOi59-FJU/s1600/bm3_2.jpg" width="400" /></a><a href="http://1.bp.blogspot.com/-wObsla3mSWQ/VHd-LB-IieI/AAAAAAAAA28/NAXH8pBfsIY/s1600/bm3_4.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-wObsla3mSWQ/VHd-LB-IieI/AAAAAAAAA28/NAXH8pBfsIY/s1600/bm3_4.jpg" /></a></div>
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The new ERA kit is very much similar to the earlier ERA kit containing 4S20 elements, but offers a greatly increased level of protection. Visually, the distinguishing element of the new kit is by the bevel on the top edge of the side boxes. The boxes are completely resistant to armour piercing and incendiary bullets of the 7.62mm, 12.7mm and 14.5mm calibers, and are also immune to a napalm attack, like its predecessor. More specifically, the boxes can resist 14.5mm B-32 armour-piercing bullets from a distance of 50m, and resist all armour piercing bullets of calibres smaller than that, from any distance.<br />
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The ERA kit is rated to protect the vehicle from RPG attacks with PG-7V, PG-7VL, PG-9V and PG-9S grenades with a probability of 95%. Additionally, the kit is also capable of defeating tandem HEAT warheads. Video evidence has shown that it is capable of defeating the PG-29V warhead from an RPG-29. The backing plate installed over the sides of the hull not only provides a mounting point for the ERA boxes but also serves as an additional layer of protection from machine gun fire and autocannon shells. With the ERA kit installed, the side of the BMP-3 hull is protected from 23mm APDS shells at a side angle of 60 degrees from a distance of 550 meters, and from 30mm AP shells at a side angle of 60 degrees from point-blank range. </div>
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The total mass of the package is 4,150 kg.<br />
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Despite the gain in weight, the BMP-3 is still completely amphibious. This is thanks to the large air spaces within the ERA boxes, which become flotation aids and balance out their own weight.<br />
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<h4>
<span style="font-size: large;">
Arena</span></h4>
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The Arena-E hard-kill defence system may be installed on the BMP-3. There are no reports of any BMP-3s in service in this configuration. The most likely reason is that the Arena can cost up to one-third of the BMP-3's price.<br />
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Arena can intercept anything in a collision course with its host vehicle that is traveling at anywhere between 70 m/s to 700 m/s. Its reaction time is no more than 0.05 seconds and no less than 0.03 seconds. Its integrated computer can differentiate between rocket grenades with trajectories that will result in an imminent miss with actual threats. Tracking begins as the target flies within 50m of the vehicle. Arena only protects the vehicle from grenades and missiles coming from within 15 degrees of elevation and 5 degrees of depression relative to the vehicle, so Arena <i style="font-weight: bold;">cannot</i> protect the BMP-3 from diving top-attack weapons nor rocket attacks from above. It can, however, protect from non-diving top attack weapons like the TOW 2B or the BILL-2. Arena only protects within a frontal arc of 110 degrees relative to the orientation of the turret, so it cannot protect the vehicle from the rear.<br />
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The radar mast has 6 individual arrays that can function independently, but coordinate and share data to provide a seamless picture for the ballistic computer.<br />
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One of the more obvious drawbacks is the highly exposed multi-faceted radar mast. Although it is modestly protected from fragmentation and shell splinters, it is very vulnerable to machine gun fire and large caliber snipers. Disabling this radar will prove costly for the operator, while the BMP-3 itself then becomes as vulnerable as before. Statistically speaking, mounting Arena may be very costly in the long run.<br />
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The entire Arena complex weighs 900 kg.<br />
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<h3>
<span style="font-size: large;"><b>SMOKESCREEN</b></span></h3>
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We should note that armour is not the only protective element of an armoured fighting vehicle, and that concealment plays a critical role. The BMP-3 is also provided with six 81mm 3D17 "Tucha" smoke launchers armed exclusively with 3D, the smoke from which can conceal the vehicle in the visual and IR ranges. The grenades are fired ahead of the vehicle, where ever the turret is pointing. The bloom time for these grenades is 3 seconds, with an average lingering time of 20 seconds, but it may be shorter or longer, depending on environmental conditions such as heat, wind, humidity, altitude, and so on.<br />
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Alternatively, the BMP-3 can produce its own smokescreen, just like most of the Soviet armoured vehicles preceding it.<br />
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<span style="font-size: large;"><b>NBC PROTECTION</b></span></h3>
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The BMP-3 has an NBC protection suite that hermetically seals the entire vehicle and supplies clean air to the occupants. The nuclear protection system incorporates the GO-27 radiation sensor, which detects harmful particles and immediately seals the vehicle to prevent the ingress of contaminants or radioactive particles, but certain ports must be closed manually. For example - the bow machine gun seals. The NBC system generates an internal overpressure of 490 Pa. The occupants are supplied with fresh air, which may be heated by the system. The ventilation system is fully filtered and includes an intake blower with a simple metal grid in the first stage, the SFT-200 cassette-type pre-filter for the second stage, and the FTS-200K filter-absorber for the third stage, ensuring that air distribution is constant and free from both radioactive dust and chemical contaminants<br />
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<span style="font-size: large;">FIREFIGHTING</span></h3>
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The BMP-3 uses the "Iney" automated fire detection and extinguishing system with coverage in the engine compartment and the crew compartment. </div>
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The engine compartment fire detection system includes four TD-1 temperature sensors, the relay/control box KR 40-2S, and two 1-liter fire extinguishers employing 114B-2 halocarbon extinguishing agents. Manual activation by the driver or the passengers is possible.</div>
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The crew compartment system is composed of eight optical thermal sensors with a high sensitivity and quick reaction time. Two 2-liter fire extinguishers are included, which have integrated pressure sensors and nozzles that limit the speed of spraying to not more than 150 m/s (for safety reasons). The activating force for these extinguishers are provided by single-use pyrotechnic charges. The sensors will react to a flame of 0.45m x 0.45m in size at 1.5 meter distance. The firefighting system is turned on automatic when someone steps into the vehicle via pressure sensors on rocker panels integrated into the hull floor. The system must be turned off manually to ensure that it is only deactivated with conscious effort. This minimizes the possibility of accidents from negligence.</div>
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Two OU-2 hand-held fire extinguishers are located in the front left section for easy access by the bow gunners and driver, and two OP-2A fire extinguishers are located in the starboard side of the passenger's section. The OP-2A fire extinguishers are intended for retarding various substances, including napalm.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-vt41PgBykxk/VEp8jT2qatI/AAAAAAAAAd8/sX4Tg8lhRfQ/s1600/fire2-1398238408.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-vt41PgBykxk/VEp8jT2qatI/AAAAAAAAAd8/sX4Tg8lhRfQ/s1600/fire2-1398238408.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The smaller one is OU-2.</td></tr>
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<h3>
<span style="font-size: large;">PASSENGER ERGONOMICS</span></h3>
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<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9nnEg1Yk2vs/XsxKfmj945I/AAAAAAAAQ0E/_CaOUj7eKREo_3KlBpw8P4_O6oshXkjhACK4BGAsYHg/passengers.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="453" data-original-width="680" height="266" src="https://1.bp.blogspot.com/-9nnEg1Yk2vs/XsxKfmj945I/AAAAAAAAQ0E/_CaOUj7eKREo_3KlBpw8P4_O6oshXkjhACK4BGAsYHg/w400-h266/passengers.jpeg" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div>
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The ergonomic qualities of the BMP-3 are far superior to its predecessors, and even quite favourable to many foreign designs in seating comfort and cargo capacity. The seating arrangement is conceptually similar to the BMD-1, but far more spacious. The unusual layout of the vehicle is extremely efficient in its use of space, allowing up to seven seated dismounts on four seats and a bench with the option of accommodating two additional passengers on the bench. The two bow machine gunners are considered passengers. The normal capacity of seven passengers is the size of a normal motorized infantry squad. The seating configuration is shown in the drawing below.<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Ca7cFdsJIxs/Xswtd8qXhpI/AAAAAAAAQy0/O2jSfHU7Z_AwJymBd3z1h0azpEOaASZ1QCK4BGAsYHg/layout%2Bview.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="795" data-original-width="1540" height="330" src="https://1.bp.blogspot.com/-Ca7cFdsJIxs/Xswtd8qXhpI/AAAAAAAAQy0/O2jSfHU7Z_AwJymBd3z1h0azpEOaASZ1QCK4BGAsYHg/w640-h330/layout%2Bview.jpg" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div>
<br />The bench just in front of the engine compartment has five padded seats, but normally, it is used by only three dismounts. The three bench seats have backrests. The two extra seats are usually folded down and used as a step when exiting through the rear. </div><div><br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-K61Zg4d_iIg/Xswv2lTtGLI/AAAAAAAAQzQ/l6nCA4tkvEER3eZso3OTUiWNjUqgpNzLQCK4BGAsYHg/interior%2Boriginal%2Bbmp-3.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="500" data-original-width="800" height="250" src="https://1.bp.blogspot.com/-K61Zg4d_iIg/Xswv2lTtGLI/AAAAAAAAQzQ/l6nCA4tkvEER3eZso3OTUiWNjUqgpNzLQCK4BGAsYHg/w400-h250/interior%2Boriginal%2Bbmp-3.jpg" width="400" /></a><a href="http://4.bp.blogspot.com/-iQfXTsfNmww/VgOiueUeWII/AAAAAAAADwY/093H5VExpE8/s1600/257.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://4.bp.blogspot.com/-iQfXTsfNmww/VgOiueUeWII/AAAAAAAADwY/093H5VExpE8/w242-h320/257.jpg" width="242" /></a></div><div><br /></div><div><br /></div><div>There is an integrated toilet built into the far left seat of the bench.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/--YVsxj_-s_U/Wmy8WSpeC3I/AAAAAAAAKpI/h1mUvxnZsikmawC0zgZ8CaTKFm_0ZWYzwCLcBGAs/s1600/toilet%2Bbmp-3.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1000" data-original-width="1500" height="266" src="https://1.bp.blogspot.com/--YVsxj_-s_U/Wmy8WSpeC3I/AAAAAAAAKpI/h1mUvxnZsikmawC0zgZ8CaTKFm_0ZWYzwCLcBGAs/w400-h266/toilet%2Bbmp-3.jpg" width="400" /></a><a href="https://1.bp.blogspot.com/-qwXcXi4chVE/Xswx_8wQcII/AAAAAAAAQzo/D7a-30cl5wUEzd7pjLsPgb9X5gQCEaQaACK4BGAsYHg/original%2Bbmp-3%2Btoilet.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="540" height="320" src="https://1.bp.blogspot.com/-qwXcXi4chVE/Xswx_8wQcII/AAAAAAAAQzo/D7a-30cl5wUEzd7pjLsPgb9X5gQCEaQaACK4BGAsYHg/w216-h320/original%2Bbmp-3%2Btoilet.jpg" width="216" /></a></div></div><div><br /></div><div><br /></div><div>According to the article "<i><a href="http://btvt.info/5library/vbtt_1991_bmp3_comp.htm">Особенности Компоновки БМП-3</a></i>" by S. F. Zakamaldin et al. and published in the May 1991 issue of "<i>Вестник бронетанковой техники</i>", the internal space for each passenger is 1.04 cubic meters. This is double that of the BMP-2, which allocated 0.52 cubic meters for each passenger. The volume allocated for each passenger in a BMP-1 was 0.54 cubic meters. The drastic increase in space was related to the standardization on the use of body armour for all infantrymen during the 1980's, coupled with the general upward trend in body weight and height of service age Soviet males since the early 1960's when the original BMP was created.</div><div><br /></div><div>The internal space provided for each passenger is not only much larger than that of earlier Soviet IFVs, but it is also unusually large compared to the BMP-3's foreign counterparts. The M2 Bradley, for example, provides 0.85 cubic meters of space for each passenger, and the CV90 is less spacious than the Bradley.<br />
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Despite the unorthodox layout hampering the traditional method of transporting wounded infantry on stretchers, the BMP-3 can still do so. Instead of lying in the middle of the passenger compartment like with the Bradley or CV90 or any other conventional IFV with an open passenger compartment, a stretcher-bound person would instead lie down over the engine deck. If the passenger compartment is in use, then one stretcher can be accommodated this way, as the stretcher would prevent passengers from dismounting. Otherwise, it is possible to transport two people on stretchers. The head or feet of the stretcher-bound person intrudes into the passenger compartment and overhangs the rear bench.</div><div>
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<div><br /></div><div><br /></div>If the vehicle is being used to transport injured soldiers from the front lines to an established checkpoint behind friendly lines, then there is no issue with transporting a full load of passengers in the passenger compartment plus two stretchers on the engine deck. Needless to say, the engine deck is not the most comfortable place to be, but this meant that a lot of people could be ferried per run. No other IFV in the world allows a full passenger load to be carried along with two stretchers. Normally, it is not possible to have any seated passengers at all if two stretchers are placed in the passenger compartment.<br />
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The number of accommodations offered to the passengers is excellent compared to other Soviet-era Russian combat vehicles, and compares favourably to many of the modern counterparts to the BMP-3. <br />
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When exiting the vehicle, the two extra seats are folded to allow dismounts to step over them and onto the engine deck. The roof hatches over the engine deck are tall enough to provide protection for the dismounts if they keep their heads down as they exit. With the turret providing frontal protection and the roof hatches providing side protection, the dismounts in a BMP-3 are not significantly more exposed to incoming fire compared to armoured personnel carriers with a rear hatch or ramp.<br />
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Due to the height of the engine deck, dismounting soldiers are at a risk of ankle injury if they jump off while the vehicle is in motion. To solve this problem, fold-out steps are placed just beneath the rear hatches.<br />
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The rear doors are sprung with torsion bars for the convenience of the passengers and are opened with a handle that is easily reached from inside the vehicle. Moreover, the doors have a special safety switch that is connected to the turret stabilizer system. When the door lock is closed, the lock handle maintains pressure on the safety switch and this allows the turret to rotate freely over the rear deck of the hull. When the door lock is opened, the switch is released and the turret is prevented from rotating over the rear deck of the hull. This ensures the safety of the passengers as they dismount.<br />
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There are two more man-sized stadium shaped personnel hatches on top of the rectangular roof hatches. These are spring-loaded with torsion bars and have the same thickness as the roof hatches. These hatches also feature a safety switch that prevents the turret from traversing over the rear deck of the hull when the lock is opened.<br />
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<a href="https://1.bp.blogspot.com/-CkyMHoLmwTs/XafVYJVYWlI/AAAAAAAAPa4/EOfKyFcHUiYD-lX1g_a9Amvzpzkw7QfNgCLcBGAsYHQ/s1600/rear%2Broof%2Bhatch.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="581" data-original-width="800" height="290" src="https://1.bp.blogspot.com/-CkyMHoLmwTs/XafVYJVYWlI/AAAAAAAAPa4/EOfKyFcHUiYD-lX1g_a9Amvzpzkw7QfNgCLcBGAsYHQ/s400/rear%2Broof%2Bhatch.jpg" width="400" /></a><a href="http://3.bp.blogspot.com/-ZGzCs7yQ4SU/VEc37RptOXI/AAAAAAAAAZc/rOo55Dhe06o/s1600/image.jpg"><img border="0" height="240" src="https://3.bp.blogspot.com/-ZGzCs7yQ4SU/VEc37RptOXI/AAAAAAAAAZc/rOo55Dhe06o/s320/image.jpg" width="320" /></a></div>
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The personnel hatches are designed to fulfill the same purpose as the roof hatches on conventional armoured personnel carriers. That is, they serve as an alternate exit to the main doors and they allow the passengers to pop out of the hull without exposing their entire body in order to fire heavy weapons such as an anti-tank grenade launcher or a MANPADS launcher. In a BMP-3, there are two MANPADS launchers stowed on the engine compartment deck for this purpose. Two passengers can open the hatches and stick themselves out to use these weapons. This gives the BMP-3 the same fire-on-the-move air defence capability as its predecessors, which would otherwise not be possible due to the unusual layout of the BMP-3.<br />
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The personnel hatches can also be used as emergency exit points if the need arises, but they are inconvenient for quick ingress and egress as they are not directly over the passenger compartment.<br />
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The BMP-3 provides far more space for personal storage when compared to its predecessors. The layout provides ample space for passengers to place their kits and if needed, their belongings may also be lashed onto the side of the hull, as shown below.<br />
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<a href="http://3.bp.blogspot.com/-kTiqHZkUz1s/VHW_O0gADKI/AAAAAAAAA1U/VFffuZ2eDCw/s1600/bmp-3.31224.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="425" src="https://3.bp.blogspot.com/-kTiqHZkUz1s/VHW_O0gADKI/AAAAAAAAA1U/VFffuZ2eDCw/s640/bmp-3.31224.jpg" width="640" /></a></div>
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Riding in the BMP-3 is very comfortable. This is in part due to the good suspension, but also due to the superb weight distribution of the vehicle. Placing the engine and transmission at the rear, all of the fuel in the front to counterbalance it, and all the passengers and crew in the middle along with the turret ensures that the weight is optimally distributed, and this in turn results in a very smooth ride and very quick recuperation from dips and dives with minimal oscillations.<br />
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Besides seating space, the BMP-3 can carry an enormous quantity of supplies and ammunition for its dismounts. See the diagram below.<br />
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<a href="https://4.bp.blogspot.com/-TgTtnsm7w20/WG6etudSHJI/AAAAAAAAIA8/8M3_xtb0M-E6vSY-eVXv1Cb3YI8Rz6HbgCLcB/s1600/bmp-3%2Binternal%2Bstowage.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="551" src="https://4.bp.blogspot.com/-TgTtnsm7w20/WG6etudSHJI/AAAAAAAAIA8/8M3_xtb0M-E6vSY-eVXv1Cb3YI8Rz6HbgCLcB/s640/bmp-3%2Binternal%2Bstowage.jpg" width="640" /></a></div>
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There are spaces for a plurality of AK-74 and AKM magazines, "spam cans" of ammo and wooden crates of grenades (hand grenades and underbarrel grenades) to be stowed, as well as dedicated racks for two MANPADS launchers, and a variety of disposable rocket launchers. At least five RPG-7 rocket grenades can be stowed, but there is space for much more. There is plenty of space on the sponson shelves for any additional supplies, which may be secured by straps attached to the walls. A standard 56-H-574 26mm flare gun with twenty flare cartridges is also stowed for emergencies and signalling purposes. This storage is <i>not</i> inclusive of whatever weapons and gear the dismounts carry personally, or any supplies which may be added. The 2,000-round boxes for the bow machine guns are better used by the dismounts, so one might consider that an additional source of ammunition.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="http://1.bp.blogspot.com/-wGnnwxaToQY/VEDN98Y6Y8I/AAAAAAAAAIM/62hoYKj9NMw/s1600/BMP-3%2C%2Binterior.png" style="margin-left: auto; margin-right: auto;"><img border="0" height="360" src="https://1.bp.blogspot.com/-wGnnwxaToQY/VEDN98Y6Y8I/AAAAAAAAAIM/62hoYKj9NMw/s1600/BMP-3%2C%2Binterior.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">In this film still, you can see the rear of the fighting compartment (turret), one of the seats beside the turret (mounted to the side, not to the floor), periscopes provided for the crews, and one of the seats arranged in a row opposing the engine compartment. Notice the "shelf" mentioned above</td></tr>
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<tr><td><a href="http://2.bp.blogspot.com/-slsCIRhwUfk/VEdB8yZToNI/AAAAAAAAAbU/4cO6_Q81jD0/s1600/bmp-3.263.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://2.bp.blogspot.com/-slsCIRhwUfk/VEdB8yZToNI/AAAAAAAAAbU/4cO6_Q81jD0/s1600/bmp-3.263.jpg" width="504" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">Seating arrangements, looking from the interior starboard side. All seats except the far side side seat are unfolded. You can also see a folded periscope on the ceiling.</td></tr>
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<tr><td><a href="http://4.bp.blogspot.com/-yCuOPF45ytU/VEdEVsBKWwI/AAAAAAAAAcI/n9spuiJ1TmM/s1600/bmp-3.258.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://4.bp.blogspot.com/-yCuOPF45ytU/VEdEVsBKWwI/AAAAAAAAAcI/n9spuiJ1TmM/s1600/bmp-3.258.jpg" width="412" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">Starboard side.</td></tr>
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The dismounts using the side firing ports may aim their rifles through the TNP3VE01-01 periscopes provided for them. They have moving reticles, pre-sighted for 600m for PKM machine guns, and are connected to the ball turrets by a fiber optic cable. The ball turrets are greatly recessed inward, to the point where the muzzle of a firing port weapon will not protrude from the hull side. There is a lid which closes on the exterior of the firing port, which is to seal the vehicle from radioactive and chemical contaminants.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="http://1.bp.blogspot.com/-y3cir6sz_W8/VEDhZGc-awI/AAAAAAAAAIk/waR5h9StpeQ/s1600/508_4.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://1.bp.blogspot.com/-y3cir6sz_W8/VEDhZGc-awI/AAAAAAAAAIk/waR5h9StpeQ/s640/508_4.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">In this photo, you can see an OU-2 manual fire extinguisher, the racks for storing ATGMs, the gunner's station, and a Greek man.<br />
Notice the fact that the space between the fighting compartment (turret) and the hull side has enough space for soldiers to shimmy through.<br />
This allows the bow machine gunners and driver to escape through the rear in an emergency.</td></tr>
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The three OU-2 manual fire extinguishers placed around the hull interior may be remotely activated by one of three buttons. One available to the driver, one for the commander and one for passengers in the passengers' section.<br />
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<tr><td><a href="http://2.bp.blogspot.com/-EnXV1-S_IKM/VEDk0tA4b1I/AAAAAAAAAIw/Tk-frg196TM/s1600/BMP-3_interior_20th_MRB.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://2.bp.blogspot.com/-EnXV1-S_IKM/VEDk0tA4b1I/AAAAAAAAAIw/Tk-frg196TM/s1600/BMP-3_interior_20th_MRB.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">You can see the firing port extensions, which are now half open (split-hinged). It is quite obvious from this picture that there is no other way to aim his rifle in the firing port except through the TNP3VE01-01 periscope-aiming device provided.</td></tr>
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<a href="http://1.bp.blogspot.com/-LxiEBBOF_cs/Vl8gltJGLwI/AAAAAAAAElA/kLhW7yncP8E/s1600/bmp-3%2Binterior.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://1.bp.blogspot.com/-LxiEBBOF_cs/Vl8gltJGLwI/AAAAAAAAElA/kLhW7yncP8E/s640/bmp-3%2Binterior.jpg" width="640" /></a></div>
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In the photo below, you can see the autoloader elevator,
which picks up rounds from the conveyor on the turret floor. You can
also see that the middle seat in the row of three is folded. If
unfolded, the BMP-3 can seat up to a true maximum of 7 passengers,
although they will have to squeeze very uncomfortably if they are fully
geared.<br />
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<a href="http://3.bp.blogspot.com/-_uu03_hSA_Q/VEDk2cygdEI/AAAAAAAAAI4/yELT8J8TF2Q/s1600/interior-21.jpg"><img border="0" height="480" src="https://3.bp.blogspot.com/-_uu03_hSA_Q/VEDk2cygdEI/AAAAAAAAAI4/yELT8J8TF2Q/s1600/interior-21.jpg" width="640" /></a></div>
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Provisions include a compressed air canister for starting the engine if the starter fails, compressed oxygen canisters for passengers in case the vehicle sinks, medical kits, and various other odds and ends.<br />
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<a href="http://3.bp.blogspot.com/-jragrTPIqoQ/VEZX4xaNjiI/AAAAAAAAAWk/tqDXI3TxLoU/s1600/image%2B(3).jpg"><img border="0" height="300" src="https://3.bp.blogspot.com/-jragrTPIqoQ/VEZX4xaNjiI/AAAAAAAAAWk/tqDXI3TxLoU/s1600/image%2B(3).jpg" width="400" /></a></div>
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On the topic of troops' opinion on it, it is true that the unusual method of exiting the vehicle is a source of regular bemoanings. The effort required to exit the vehicle is much more than that required for IFVs with large, powered rear hatches such as the M2 Bradley, Marder IFV, Warrior, etc. <a href="http://www.youtube.com/watch?v=_OMF7zehHxY">This video</a> shows that very clearly. The dismounts must heave the top hatches open, then swing the rear hatches open before finally jumping out, and that is in addition to the fact that stepping onto the engine deck from the passenger compartment is not an easy task already for fully geared troops. However, this issue is not serious enough to warrant a completely negative assessment from troops, although inconveniences in the heat of combat <i>does</i> give a trooper grievances and poor impressions on the vehicle. Fortunately, the lack of comfort when exiting the vehicle seems to be the only negative comment on the BMP-3 by the troops. There have been no other complaints mentioned so far, and the BMP-3 is definitely not regarded as a poor design overall.<br />
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To improve crew comfort, a KBM-3M2 air conditioning system may be installed, with or without a TBE auxiliary power unit. The time of continuous operation is not less than 8 hours. The air conditioner operates at 7 kW without the APU, or 8 kW with the APU. The air conditioner maintains a comfortable temperature of 25 to 29 degrees Celsius (adjustable), and can operate in ambient temperatures of up to 50 degrees Celsius, and with 45% relative humidity (to interior humidity). Cool air outlets are located at head level of each and every occupant in the vehicle, blowing cool, refreshing air in their faces. Ahhh.<br />
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<a href="http://2.bp.blogspot.com/-n2QBWtxaWOg/VELcusGeUPI/AAAAAAAAAPU/l-1nkv8mra4/s1600/BMP-3%2Bair%2Bconditioner%2B2.png"><img border="0" src="https://2.bp.blogspot.com/-n2QBWtxaWOg/VELcusGeUPI/AAAAAAAAAPU/l-1nkv8mra4/s1600/BMP-3%2Bair%2Bconditioner%2B2.png" /></a></div>
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The air conditioner occupies the empty dorsal space along the engine deck. It scarcely affects the ease of dismounting, and is more of a nuisance to anybody on a stretcher lying beside it more than anything.<br />
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The TBE auxiliary power unit is a miniature diesel engine, with an output of 2.5 kW.<br />
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<h3>
<span style="font-size: large;">DRIVER-MECHANIC'S STATION</span></h3>
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<a href="https://1.bp.blogspot.com/-pzXmu1j3W2M/XbjaMCuHnYI/AAAAAAAAPiQ/3HHB0TQBZQ0gTEjrMQ7N2OcWzWw2Em21QCLcBGAsYHQ/s1600/bmp-3%2Bdriver.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="433" data-original-width="650" height="426" src="https://1.bp.blogspot.com/-pzXmu1j3W2M/XbjaMCuHnYI/AAAAAAAAPiQ/3HHB0TQBZQ0gTEjrMQ7N2OcWzWw2Em21QCLcBGAsYHQ/s640/bmp-3%2Bdriver.jpg" width="640" /></a></div>
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The driver is seated centrally at the front of the hull and is provided with a conventional lift-and-swing type overhead hatch. The hatch is covered by external anti-radiation cladding. The hatch is slightly bulged to increase the driver's headroom and as a result, its front edge was slightly weaker than the upper glacis armour. To compensate for this, an additional armour plate was added.<br />
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The driver's seat is adjustable for height. To steer, the driver is provided with a motorcycle-style steering bar like in the BMP-1 and BMP-2.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-3WFdoaLXw9U/VEEcnRmhtuI/AAAAAAAAAJQ/oKAEqlxLmSs/s1600/0_6064d_84fb9212_XL.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://4.bp.blogspot.com/-3WFdoaLXw9U/VEEcnRmhtuI/AAAAAAAAAJQ/oKAEqlxLmSs/s1600/0_6064d_84fb9212_XL.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">(Old driver's instrument panel) On the steering bar , you can see two white buttons to control firing of the two bow machine guns. Left button for left gun and right button for right gun. The circular middle button is a horn.</td></tr>
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The driver has a healthy number of controls in front of him. He can control track tension, suspension height, all water-travelling related controls, driving lights, firefighting equipment, the smokescreen generator, the NBC protection suite and the bow machine guns, among the usual driving-related indicators and gauges. He is provided with a GPK-59 gyrocompass (pictured) for rudimentary directional navigation. The gyrocompass is useful when driving at night and for normal orienteering.<br />
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Driving visibility is provided by four TNPO-170A periscopes, three located right in front of him for forward viewing, and another one aimed towards the left. Unfortunately, the driver was not provided with a periscope aimed to the right because the hatch opening mechanism is in the way. For night driving, the center periscope can be replaced with TNPE-1B night vision periscope.<br />
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The new TSE-1 universal day-night driving periscope increases the viewing range of the driver at night. Plus, it does not use IR lamps, so that there are no longer any unmasking factors. Installation of the TSE-1 requires the newer driver's panel to be installed beforehand. It is a binocular passive sight with a 42x9 degrees field of view, and a 250m vision range during nighttime.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-lR_0YA58K80/VEdCpEqX5zI/AAAAAAAAAbk/A_KVCuZ7cjk/s1600/bmp-3.31156.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="472" src="https://3.bp.blogspot.com/-lR_0YA58K80/VEdCpEqX5zI/AAAAAAAAAbk/A_KVCuZ7cjk/s1600/bmp-3.31156.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Original driver's workstation.</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-8XUPeETF6y8/VESrM7nB3II/AAAAAAAAASo/2AP92_AQ8e8/s1600/_31.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-8XUPeETF6y8/VESrM7nB3II/AAAAAAAAASo/2AP92_AQ8e8/s1600/_31.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">New driver's instrument panel</td></tr>
</tbody></table>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-Xh0qa320BwI/VELZczzvh2I/AAAAAAAAAPI/ZQZbofJpZ6k/s1600/driver%27s%2Bworkstation%2C%2Bwith%2BTSE-1.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="211" src="https://2.bp.blogspot.com/-Xh0qa320BwI/VELZczzvh2I/AAAAAAAAAPI/ZQZbofJpZ6k/s1600/driver's%2Bworkstation%2C%2Bwith%2BTSE-1.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Latest driver's instrument panel, possibly Larisa</td></tr>
</tbody></table>
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An IUSSH-688 "Larisa" electronic chassis control system may be installed. "Larisa" serves to observe chassis conditions and inform the driver of abnormalities through displays and voice messages. It is unknown if this system has been implemented on any BMP-3s in service, although apparently it is a component of the BMP-3M. It is highly unlikely that "Larisa" is present in significant numbers in currently serving BMP-3s of the Russian armed forces.</div>
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<h3>
<span style="font-size: large;">MOBILITY</span></h3>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="http://1.bp.blogspot.com/-DGiGiA1JtnA/VD-PogBgDhI/AAAAAAAAAEI/YG_58geLicE/s1600/utd29ooaoskqwoek.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://1.bp.blogspot.com/-DGiGiA1JtnA/VD-PogBgDhI/AAAAAAAAAEI/YG_58geLicE/s1600/utd29ooaoskqwoek.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">UTD-29M Diesel. This engine has a fuel consumption not exceeding 250g/kWh<br />
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The BMP-3 is powered by a compact UTD-29M liquid-cooled diesel engine with an output of 500 hp, generating a power-to-weight ratio of 25 hp/ton. The engine is placed in the rear. The transmission is a four-speed, hydromechanical planetary type, with one reverse gear. The engine can operate up to no more than 3000 m altitude (high mountainous peaks). Above that, the air would be too thin for operation. There are 6 rubberized aluminium roadwheels with independent torsion bar suspension and 3 rubberized return rollers on either of the two tracks. The first two frontmost roadwheels and the rearmost roadwheel each have a telescopic hydraulic double-action shock absorber to improve ride smoothness. The maximum ground clearance of the vehicle is 510mm and the minimum is 190mm. The default clearance setting for normal driving sets the ground clearance to 450mm. Besides the benefits of having an adjustable suspension system, the increased ground clearance is an improvement over the BMP-2 which had a clearance of 420mm and an even bigger improvement over the BMP-1, which had just 390mm of clearance.</div>
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The nominal ground pressure with standard tracks is 0.61 kg/sq.cm, which is lower than the BMP-2's ground pressure of 0.63 kg/sq.cm despite the gain in weight. The 380 mm-wide tracks are of a dual-pin type with rubber pin bushings. The tracks have rubberized insoles and the option for asphalt-friendly rubber pads is available. The rubberized insoles reduce wear and tear and also reduce noise and vibrations, giving a more comfortable driving experience.<br /><br /></div>
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With the UTD-29M engine, the BMP-3 can reach a top speed of 72 km/h on paved roads, and travel cross-country at an average speed of 45 km/h (28 mph). Its maximum reverse speed is 20 km/h. The BMP-3 can climb a vertical wall with a maximum height of 0.8 meters, and cross a trench with a maximum width of 2.5 meters. It can climb a slope with an angle of 35 degrees and drive along a 20-degree side slope. Good traction allows the vehicle to stop halfway up a dry dirt slope of the aforementioned gradient, stop, and then climb up without slipping. Overall, the mobility characteristics of the BMP-3 match that of the BMP-2 in all of these parameters, but it surpasses the BMP-2 in its ability to climb vertical obstacles (it climbs a 0.7 meter wall). However, the BMP-3 is not the best in this regard as the overhang of the hull over the track idler imposes a stricter limit on the maximum obstacle height compared to some other hull designs. For example, the more conservative design of the M2 Bradley front hull allows it to climb a 0.91 meter wall. </div><div><br /></div><div>The BMP-3 weighs 18.7 tons combat loaded. The power-to-weight ratio with this engine is 26.7 hp/ton when combat loaded, which is notably better than all modern contemporaries. Officially, the power-to-weight ratio is stated to be no less than 25 hp/ton, accounting for the variable weight of the passengers. With 700 liters of fuel carried in the frontal internal fuel tank, the BMP-3 has an autonomous range of 600 km on paved roads. The range is reduced by 1.5 times when travelling cross country.<br /><br />
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It is interesting to note that the original UTD-29 engine was only installed on the very first batch of prototypes, used for testing. As of 1986, all serial BMP-3s have the slightly improved UTD-29M installed. Alternatively, the BMP-3 may instead have a UTD-32 installed, which has an output of 660 hp. The latest BMP-3 modification might also include the installation of a newer UTD-32T diesel engine, slightly improved over the UTD-32 from 1999. Specific improvements are not known.<br />
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Both the exhaust and radiator are located on the starboard side of the vehicle, one on top of the other. Exhaust gases are probably cooled by introducing air from the radiator before being expelled from the exhaust exit manifold. Both have internal louvers that must be closed before entering swimming.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="http://1.bp.blogspot.com/-TvF5CP6vSUE/VEc5WylmXzI/AAAAAAAAAZs/s_l0yB6pf5g/s1600/31335.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://1.bp.blogspot.com/-TvF5CP6vSUE/VEc5WylmXzI/AAAAAAAAAZs/s_l0yB6pf5g/s1600/31335.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">Radiator</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="http://1.bp.blogspot.com/-jz5mfMPayA4/VEc5S-6XRfI/AAAAAAAAAZk/XNT40kxZUbU/s1600/image%2B(3).jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://1.bp.blogspot.com/-jz5mfMPayA4/VEc5S-6XRfI/AAAAAAAAAZk/XNT40kxZUbU/s1600/image%2B(3).jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">Exhaust exit manifold, which is perforated.</td></tr>
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The engine is prone to overheating in extremely hot weather, as noted during the UAE trials. The cooling system is only adequate for its purposes in the hottest heat spells in a European climate, little else. A more efficient cooling system has existed since the trials' conclusion, and is currently installed on the BMP-3s operated by the UAE.</div><div><br />
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<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-uHjpFQ_k8tg/VD-WvhxOieI/AAAAAAAAAEs/K5eyk81FlSM/s1600/BMP-3%2C%2Bsuspension.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="360" src="https://3.bp.blogspot.com/-uHjpFQ_k8tg/VD-WvhxOieI/AAAAAAAAAEs/K5eyk81FlSM/s1600/BMP-3%2C%2Bsuspension.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px; text-align: center;">In this photo, you can see the rearmost roadwheel with its hydraulic shock absorber, the drive sprocket and its mud scraper.<br />
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<a href="http://2.bp.blogspot.com/-1rNwZJJmpVI/VEZaMhq0FAI/AAAAAAAAAW0/KyPzcGunhGo/s1600/image%2B(1).jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://2.bp.blogspot.com/-1rNwZJJmpVI/VEZaMhq0FAI/AAAAAAAAAW0/KyPzcGunhGo/s1600/image%2B(1).jpg" width="640" /></a></div>
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<a href="http://4.bp.blogspot.com/-NmlYB6Eorsw/VD-S7jM2mtI/AAAAAAAAAEU/-VoUQ8vheAE/s1600/BMP-3%2C%2Bengine%2Bdeck%2C%2Bexposed%2C%2BHD%2Bdetail.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="360" src="https://4.bp.blogspot.com/-NmlYB6Eorsw/VD-S7jM2mtI/AAAAAAAAAEU/-VoUQ8vheAE/s1600/BMP-3%2C%2Bengine%2Bdeck%2C%2Bexposed%2C%2BHD%2Bdetail.png" width="640" /></a></div>
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In the photo above, you can see the exposed engine with the engine deck panels and side panels removed. Servicing the engine is incredibly simple on the BMP-3 chiefly because of how easy it is to remove the engine deck panels. Removal of the engine is also a very relaxed affair. It is only necessary to remove the frame from the spine running down the engine deck, and that isn't very difficult since there's nothing there.<br />
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<a href="http://4.bp.blogspot.com/-G0h4AwFHp6Q/VlHjP33Mx4I/AAAAAAAAEYQ/On4cLQF9L-I/s1600/bmp-3%2Bengine%2Bdeck.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://4.bp.blogspot.com/-G0h4AwFHp6Q/VlHjP33Mx4I/AAAAAAAAEYQ/On4cLQF9L-I/s400/bmp-3%2Bengine%2Bdeck.png" width="400" /></a></div>
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Coolant is stored to the right-hand side, in the plum-coloured tank as seen in the photo above. Two 12ST-85R1 accumulators are located behind it. To the left-hand side is the exhaust and radiator. The exhaust outlet is at the starboard side of the hull while the radiator grille is on top.<br />
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<h3>
<span style="font-size: large;">WATER OBSTACLES</span></h3>
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<a href="http://2.bp.blogspot.com/-6CL_fX4QBbE/Vhu10xUn2EI/AAAAAAAAD94/hN9WCd0ZR6g/s1600/bmp-3%2Bswimming.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="368" src="https://2.bp.blogspot.com/-6CL_fX4QBbE/Vhu10xUn2EI/AAAAAAAAD94/hN9WCd0ZR6g/s640/bmp-3%2Bswimming.jpg" width="640" /></a></div>
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The vehicle is amphibious, more so than its predecessors. In the water, it is propelled by two waterjets which are powered by the engine in lieu of the tracks. Maximum speed in the water is 10 km/h. The waterjets are a single-stage, axial, auger type with guide vanes. Changing direction in the water is achieved by powered closing of either of the two flaps on the waterjet nozzles; closing the port side flap causes the vehicle to turn to the left, and closing the starboard side flap causes the vehicle to turn to the right. The minimum turning radius is 6 to 7 meters. The waterjets may be reversed, propelling the vehicle at a maximum of 2.5km/h. Turning is still possible in reverse. If the water jets malfunction while in the water, the vehicle may still propel itself using its tracks. The average speed in the water will reduced to a measly 4 km/h.<br />
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An especially seaworthy variant of the BMP-3, the BMP-3F, is pictured below.<br />
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<a href="http://3.bp.blogspot.com/-6EDK5U0DwCU/VgOi-uveP_I/AAAAAAAADwg/lmGa8V6edXU/s1600/bmp-3.31384.jpg" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="600" src="https://3.bp.blogspot.com/-6EDK5U0DwCU/VgOi-uveP_I/AAAAAAAADwg/lmGa8V6edXU/s640/bmp-3.31384.jpg" width="640" /></a><br />
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The BMP-3 sails very well in the water. It can endure conditions up to sea state 3, and fire accurately in sea state 2 - an admirable achievement. It is worth noting that unlike the previous BMPs, the BMP-3 driver does not need to swap his periscope for a special extendable one, which would be used to peek over the trim vane. With the BMP-3, the wave breaker works on a different principle, never extending above the glacis. Needless to say, this is entirely beneficial to the driver, and he does not need to rely on the commander to navigate while swimming.<br />
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An electric bilge pump is installed. Standard procedure calls for the driver to activate it before the vehicle enters water. This is insurance against accidental flooding of the hull, or flooding due to the hull being compromised from enemy fire. The bilge pump allows the BMP-3 to return to dry land safely without sinking, and at least give the occupants a fighting chance to survive catastrophic hull damage while in the water (hit by tank shell, for example).<br />
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<tr><td><a href="http://4.bp.blogspot.com/-xdAHflajUV4/VEdDVq3zBrI/AAAAAAAAAbw/BE2wHXA8bvk/s1600/bmp-3.31292.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://4.bp.blogspot.com/-xdAHflajUV4/VEdDVq3zBrI/AAAAAAAAAbw/BE2wHXA8bvk/s1600/bmp-3.31292.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">Water jet propeller.<br />
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Before entering the water, the vehicle must first erect a telescopic ventilation tube, which serves supply air to the engine. Since the tube opens up a new airway, it has its own air filter, substituting the ones on the hull top. The tube rises about 400mm above water level.<br />
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<tr><td><a href="http://3.bp.blogspot.com/-UE8yqWJ53qo/VEc5jL6AKaI/AAAAAAAAAZ0/hU0TtqSJJ1s/s1600/image%2B(2).jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://3.bp.blogspot.com/-UE8yqWJ53qo/VEc5jL6AKaI/AAAAAAAAAZ0/hU0TtqSJJ1s/s1600/image%2B(2).jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">The circular lid is the ventilation tube, which would protrude upon the driver's command.</td></tr>
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<tr><td><a href="http://4.bp.blogspot.com/-Yf84cenAJdA/VD-XneZ7JqI/AAAAAAAAAE0/hiYKeKrjay0/s1600/BMP-3%2C%2Bswimming.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="276" src="https://4.bp.blogspot.com/-Yf84cenAJdA/VD-XneZ7JqI/AAAAAAAAAE0/hiYKeKrjay0/s1600/BMP-3%2C%2Bswimming.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">Swimming BMP-3. The ventilation tube is raised.</td></tr>
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A more seaworthy minor variant of the BMP-3 designated the BMP-3F is available for Naval forces.<br />
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<tr><td><a href="http://2.bp.blogspot.com/-AHRWn_CmpxY/VESsf_AKr_I/AAAAAAAAAS0/L4RnQ4pweNw/s1600/bmp3f_1.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-AHRWn_CmpxY/VESsf_AKr_I/AAAAAAAAAS0/L4RnQ4pweNw/s1600/bmp3f_1.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 13px;">Notice the much taller ventilation tube, as compared to a basic BMP-3's.</td></tr>
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<span style="font-weight: normal;">This variant is touted as being capable of staying afloat for greatly extended period of time. The only exclusive difference between the BMP-3F and the BMP-3 is the ventilation tube, which is extended on the BMP-3F.</span></h4>
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<span style="font-size: large;">
BREM-L</span></h3>
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<a href="http://3.bp.blogspot.com/-5sv-i9wyz38/VELf9FjylsI/AAAAAAAAAP0/BPkdEgkolcg/s1600/brem_l_01.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="556" src="https://3.bp.blogspot.com/-5sv-i9wyz38/VELf9FjylsI/AAAAAAAAAP0/BPkdEgkolcg/s640/brem_l_01.jpg" width="640" /></a></div>
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Due to the BMP-3's significantly increased weight compared to the earlier BMPs, it could not be evacuated from awkward positions by a BREM-2 Armoured Recovery Vehicle. As a result, the BREM-L was developed. Because the BMP-3 hull and turret are constructed entirely of aluminium alloy with only supplementary steel shields instead of having an all-steel construction lkie its predecessors, argon arc welding equipment was needed to perform structural repairs in the field. This equipment is carried on the BREM-L, among other things. It is crewed by 3 men, with additional space for 2 auxiliary personnel.<br />
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<a href="http://2.bp.blogspot.com/-ARkKn1EZjWU/VlBf7EelypI/AAAAAAAAENw/9tbQQvPdFLE/s1600/brem-l%2Bwinching%2Bbmp-3.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="264" src="https://2.bp.blogspot.com/-ARkKn1EZjWU/VlBf7EelypI/AAAAAAAAENw/9tbQQvPdFLE/s400/brem-l%2Bwinching%2Bbmp-3.jpg" width="400" /></a><a href="http://1.bp.blogspot.com/-P1OH8nDHqQk/VlBf8Ddu2xI/AAAAAAAAEN4/CXTlhs_FJhc/s1600/brem-l%2Bremoving%2Bbmp-3%2Bengine.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="263" src="https://1.bp.blogspot.com/-P1OH8nDHqQk/VlBf8Ddu2xI/AAAAAAAAEN4/CXTlhs_FJhc/s400/brem-l%2Bremoving%2Bbmp-3%2Bengine.jpg" width="400" /></a></div>
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The BREM-L's crane is of a hydromechanical type with a maximum load capacity of 5 tons, or 11 tons if a double pulley block is used. It also has a hydraulic rescue winch with a pulling force of 140 to 160 kN. The winch cable is 150m long. </div>
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The BREM-L has a single PKTM in a rotating cupola for self defence, for which 1,000 rounds are provided in a single belt. Mobility characteristics are identical to that of the parent BMP-3, and also weighs about the same at 18.7 tons dry, or 19 tons fully loaded. Surprisingly, the BREM-L is also amphibious, which is very neat, because it means that it will be able to follow the BMP-3 anywhere it goes. It uses its built-in engineering dozer blade as a trim vane.<br />
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<a href="http://4.bp.blogspot.com/-WqC_CXw2-gs/VlBh2kscVFI/AAAAAAAAEOE/iMHnQgZ5nRI/s1600/brem-l%2Bswimming.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://4.bp.blogspot.com/-WqC_CXw2-gs/VlBh2kscVFI/AAAAAAAAEOE/iMHnQgZ5nRI/s1600/brem-l%2Bswimming.jpg" /></a></div>
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Servicing, maintenance</h3>
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There are some allegations that the BMP-3 is unreliable and disliked by troops due to its unreliability, but those allegations are completely untrue. It is true that the BMP-3 had teething problems - a common issue for many AFVs. Mechanical failures were present in relatively high rates. The average number of failures per 1000km travelled was as follows: 17.1 in 1986, 3.6 in 1988, 2.8 in 1990, and in 1992, less than 1 per 1000km. The problems were mostly related to parts quality, which resulted in Kurganmashzavod slightly modifying some components or improving the manufacturing process. The lack of experienced mechanics, tooling and equipment played their role as well; a lack of argon welders, for example. Also, the rear placement of the engine meant that the replacement of the engine with the three crew members only and under combat condition was a staggering 20 hours. However, teething problems are common and all of them are now completely rectified, although so far there have been no resolutions for simplifying the removal of the engine. Remember that the BMP-3 was not officially adopted into the Russian Army until 1990, and that the equipping of brigades with this vehicle beforehand was purely for trialing purposes. BMP-3 failures and malfunctions have never been mentioned as an issue by any armoured units in active service for more than two decades and counting.<br />
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<span style="font-size: medium;">
Service history, operators, future service</span></h3>
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It is an undeniable fact that the BMP-3 saw combat in Grozny, while the possibility that they were used in the second campaign and in Georgia during the South Ossetian war remains debated.<br />
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Regarding Chechnya:<br />
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The text states that the BMP-3 in the picture provided fire support due to the lack of tanks. The three people are not sitting on the vehicle. Rather, they are sticking out of their hatches.<br />
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There is photographic evidence of a<b> </b>BMP-3 destroyed in Grozny.<br />
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<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-EVM6RsHoDXs/VEpdtTpQC3I/AAAAAAAAAdw/n2T8rdaOXEE/s1600/image%2B(2).jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="384" src="https://3.bp.blogspot.com/-EVM6RsHoDXs/VEpdtTpQC3I/AAAAAAAAAdw/n2T8rdaOXEE/s1600/image%2B(2).jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">A BMP-3 turret husk being dragged. It had been blown off due to the detonation of interior munitions.</td></tr>
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There are no other significant photographic accounts of the BMP-3 being involved in any other conflicts other than the two mentioned above. It appears that only a small number was destroyed, which, in my opinion, is indicative of poor tactics more than poor engineering.<br />
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<b><span style="font-size: large;">EXPORT</span></b></h3>
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The BMP-3 is a successful export item. A famous example was the UAE open IFV tender, in which the BMP-3 soundly defeated the British MCV80 and American M2A1 Bradley and went on to sell in large quantities. <b>However</b>, it should be noted that the BMP-3s participating in this tender had Namut FLIR sights installed, due to the lack of suitable indigenous ones of such type available for the BMP-3 at the time (1993). Up until sometime around 2005, the UAE has been operating with 1K13-2 sights, which have now been replaced with SOZH sights. The BMP-3s that the UAE uses were superior to Russian BMP-3s at the time, and still are, in some ways, due to them having FLIR, allowing them a significant advantage in night fighting. And the BMP-3Ms that were more recently delivered (2005) are clearly superior to the current standard of Russian ones chiefly due to the presence of thermal sights.<br />
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<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-PTM236HXLxo/VEJ-vABI1MI/AAAAAAAAAK8/EGqIcZhhgAs/s1600/bmp3_08.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://4.bp.blogspot.com/-PTM236HXLxo/VEJ-vABI1MI/AAAAAAAAAK8/EGqIcZhhgAs/s1600/bmp3_08.jpg" width="513" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">BMP-3 belonging to the UAE</td></tr>
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Unfortunately, there have been reports of malfunctions related to desert operation during the BMP-3's testing phase for the UAE. Apparently, the cooling system for the engine was not effective enough, causing the engine to overheat too quickly. The particulate filtration system was not good enough to provide clean air during sandstorms and could not filter finely enough, which caused the engines to clog up after a long drive. Tracks falling off due to excessive sand was a problem as well. These problems were promptly resolved by modifying the filter and installing additional exterior rings around the drive sprocket and idler wheel. All UAE BMP-3s are modified thusly.<br />
The UAE has a total of 652 BMP-3s, and is the operator of the largest fleet of them.<br />
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In the Asian arena, the South Korean marines evidently value the BMP-3 (along with T-80Us) for their amphibious qualities. In 2005, they updated their BMP-3s to the standard of the Russian Army's. That is, they refitted their BMP-3s with SOZH sighting systems. Previously, the examples in their ownership had the 1K13-2 sight, which was the standard at the time when Russia traded 33 BMP-3s along with other military equipment as part of a debt reduction deal. Previously, South Korea had been unable to recreate the waterborne abilities of the BMP-3 their in their K21 IFVs (two of them sank, killing one crew member), thus securing the place of the BMP-3 in their supply chains. Contrary to what some believe, South Korea <i>does </i>employ the BMP-3 in active service, and not in the OPFOR (Opposing Force) role, which would be illogical anyway since North Korea doesn't have any BMP-3s. South Korea has a total of 70 BMP-3s, 33 of them were supplied under the debt reduction agreement and 37 with Vesna-K sighting systems of them were purchased under their own initiative . All South Korean BMP-3s are NATO-compliant.<br />
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<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-lRXHzLywGpc/VES-xVvHQnI/AAAAAAAAATg/rFOAwphfYe0/s1600/59339785.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://2.bp.blogspot.com/-lRXHzLywGpc/VES-xVvHQnI/AAAAAAAAATg/rFOAwphfYe0/s1600/59339785.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">South Korean BMP-3. Notice the radio antenna, which is similar to an American Bradley IFV's</td></tr>
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<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-6s9PB7u_oY0/VES_MHflYzI/AAAAAAAAATo/bcyU3rbSlGU/s1600/86250714.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://1.bp.blogspot.com/-6s9PB7u_oY0/VES_MHflYzI/AAAAAAAAATo/bcyU3rbSlGU/s1600/86250714.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">South Korean BMP-3s during a river crossing exercise</td></tr>
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The Indonesians possess 37 BMP-3Fs, and are in active service. The Indonesian Marines were reportedly extremely pleased with them. During an exercise shortly after the completion of the delivery, all participating BMP-3Fs hit all targets with its entire armament after landing on a coast.<br />
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<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-XKaBWWdX3V0/VEc8XYWFW_I/AAAAAAAAAaI/OiHor7ni-JM/s1600/bmp1.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://4.bp.blogspot.com/-XKaBWWdX3V0/VEc8XYWFW_I/AAAAAAAAAaI/OiHor7ni-JM/s1600/bmp1.JPG" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Indonesian BMP-3F, with Russian ambassador in plain clothes.</td></tr>
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The price for an individual BMP-3 is stated to be $800,000 to $950,000 during the late 90's. The price in the present day is not known, though there's no reason to believe that it exceeds $2,500,000 per unit.<br />
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Iron Drapeshttp://www.blogger.com/profile/07585842449654170007noreply@blogger.com23