T-55M, T-55AM Model 1983
In 1983, the T-55 upgrade program entered a new phase, featuring a comprehensive rebuilding of the T-55. The upgraded T-55s were designated T-55M and upgraded T-55As were designated as T-55AM. This upgrade included passive applique armor, the Volna fire control upgrade, optional fitting of the new Bastion guided projectile, automotive upgrades and many small improvements.
The applique armor package was developed by NII Stali in Moscow, the main Russian research institute for metalurgical and armor research. The applique did not receive an official name, although some documents refer to it by the acronym "BDD." NII Stali unofficially called this applique armor "bra armor" because of the two rounded panels added on either side of the gun tube.
The glacis applique armor consists of a welded steel box formed from 30 millimeters steel sheet. Inside are six layers of 5 millimeters steel plate spaced 30 millimeters apart with the cavity between filled with penapolyurethane. The turret applique is a similar hollow construction, but the cast shell is thicker, about 60 millimeters on the outer side. The new turret armor increases the tank's protection from its basic 210 millimeters of steel to the equivalent of 380 millimeters against APFSDS and 450 millimeters against HEAT according to Russian sources. The hull applique raises the effective protection from 200 millimeters equivalent to 410 millimeters against APFSDS and 380 millimeters against HEAT. The total package adds about 2.2 metric tons to the weight of the tank.
During the 1991 Gulf War, a small number of Iraqi tanks appeared with an improvised armor applique which was a crude duplicate of this type of armor, which utilized alternating layers of rubber/steel and may have been based on Russian advice.
Side skirts were added to provide additional protection to the suspension and hull sides against shaped-charge warheads. This consists of a 10 millimeters-thick, steel-reinforced rubber material. There is an optional antimine package consisting of a 20 millimeters armored plate mounted on frames under the hull to protect the driver against antitank mines. For enhanced antiradiation protection, improved antiradiation lining was added to these tanks, and the crews were issued with IPZh-1 anti-radiation protective vests.
The Volna fire control system was based around a KTD-2 laser rangefinder, mounted externally on the gun mantlet in an armored box. The laser rangefinder has an effective envelope from 500 to 4,000 meters. The Volna system includes the BV-55 analog ballistic computer, the first time a ballistic computer was used on the T-54/T-55 series.
The gunner's normal TSh-2M-32P was replaced by the improved TShSM-32PB gunner's sight, which has a continuously stabilized field of view in the vertial axis. The previous Tsiklon two-axis stabilization system was replaced by the upgraded Tsiklon Ml gun stabilization system.
The T-55M/T-55AM were fitted with the new 9K116 Bastion 100mm guided projectile system developed by the Shipunov design bureau in Tula. This system consisted of a 3UBK10-1 100mm ammunition round which encases the 9M117 missile. This round resembled a conventional 100mm round and was handled and loaded in the same fashion. To guide this laser-beam riding projectile, the gunner's normal sight was replaced by the 1K13 sight in place of the normal TPN-1 sight. Other necessary additions were the 9S831 transformer, a control panel and a new electronic panel.
The missile was fired like a conventional round, with a rocket engine igniting l.S seconds after the round fired. The sustainer rocket engine in the missile would burn for 6 seconds. The missile has a flight time of 26 to 41 seconds, at which point it self- detonated if it had missed its target. The missile had an effective penetration of 1,000 millimeters against homogenous steel armor and an effective range of 4 kilometers against both helicopters and tanks. Generally, the tank would carry four to six of the missile rounds in addition to its usual combat load.
The T-55M upgrade also included automotive improvements. The V-55U engine was substituted for the previously standard V-55V. The V-55U offered an increase of 40 horsepower to 620 total horsepower with inertial supercharging and partitioned intake manifolds. Roadwheel dynamic travel was increased from 135 to 149 millimeters to 162 to 182 millimeters through the use of new torsion bars. These were produced using an electroslag process which also doubled their effective life. The T-55M and T-55AM were gradually refitted with the RShM track (developed for the T-72) which necessitated a different drive sprocket; this new track added a half tonne to overall vehicle weight.
Some T-55M and T-55AM also had other improvements, including a new side skirt made of metal reinforced rubber sheeting for protection against shaped-charge projectiles. The Type 902B Tucha smoke discharger system began to be introduced at this time, which fired the 3D6 81mm smoke grenade at ranges of 200 to 350 meters. The grenades supplemented the TDA smoke discharge system and their cloud lasts 60 to 130 seconds. Four 3D6 grenades create a smokescreen 100 to 120 meters wide and 8 meters high.
Other improvements on the T-55WT-55AM include the substitution of a R-173 radio for the older R-123, and incorporation of features to defend the tank against napalm attack.
While the T-55M modernization program was continuing, it was decided to incorporate the V-46 engine from the T-72 into the T-55 and T-62. The version used was designed V-46-5. Modified T-55s with this engine were designated with a "1" suffix, such as T-55M-1, T-55AM-1, T-55AD-1, andT-55MV-l,etc.
Both the Polish and Czechoslovak tank factories began a T-55 upgrade program paralleling the Soviet T-55M/T-55AM upgrade called the T-55AM2. However, not all of these upgrades included the 9K116 Bastion missile system. The basic T-55AM2 does not fire the Bastion missile. The version fitted with the 1K13 fire control system capable of guiding the 9K116 Bastion missile is designated T-55AM2B (Czechoslovak built) and T-55 AM2P (Polish built). The Czechoslovak equivalent of the Soviet Volna fire control upgrade uses the locally designed Kladivo laser rangefinder, mounted over the gun tube and a Czechoslovak wind sensor mounted centrally on the turret rear. The Polish equivalent uses the Polish Merida fire control system with the laser rangefinder integrated into the gunner's sight, and a hammer-head wind sensor forward on the turret.
In 1983, the NII Stali in conjunction with the NIIBT Research Institute of the Main Armor Directorate at Kubinka completed the development of the Kontakt explosive reactive armor for tanks. Reactive armor is generally called "dynamic protection" (dinamicheskaya zashchita) in Russian. Although the Soviets had examples of Israeli Blazer armor from examples captured by the Syrians in the 1982 Lebanon war, the Soviet type was of a different type according to Russian sources. This reactive armor has undergone several generational changes; this is not immediately apparent as the same external boxes have been used. In Russian service, the ERA bricks are called kostek (dice).
T-55M retrofitted with Kontakt explosive reactive armor are designated T-55MV, the "V" signifying vzryvnoi, or "explosive." The T-55 AM was designated T-55AMV when fitted with reactive armor. The use of dyanmic protection appears to have been less common on the T-55 series than the passive "bra" armor. The Soviet Naval Infantry is known to use dynamic armor on their T-55 tanks. In 1993, the Czech Republic showed its own local version of reactive armor on a T-55 tank at the EDET trade fair.
In 1994, NII Stali displayed a photograph of a T-55 tank fitted with its third generation of applique armor, Kontakt-5, originally developed for the T-80U. This is a combined passive/reactive armor package intended to provide enhanced protection against both APFSDS and HEAT. At the Niznhi-Novgorod arms show, a NII Stali placard compared the armor protection offered by the three generations of applique on the T-55 tank.