PT-91 Twardy
The PT-91 Twardy is a Polish main battle tank. A development of the T-72M1, it entered service in 1995. The PT-91 was designed at the OBRUM and is produced by the Bumar Łabędy company, part of the Bumar Group, a Polish technical military consortium. Changes from the T-72M include a new dual-axis stabilized fire-control system, reactive armour, a more powerful engine, transmission and new automatic loader.
Unlike many other T-72 upgrades, Polish Army PT-91s feature elements created almost exclusively by domestic companies, including the new engine, fire control system, and all communication system elements. Many of the elements were used to upgrade existing fleets of T-72 tanks in countries including the Czech Republic, Georgia, and India. A total of 232 PT-91 tanks were delivered to the Polish Land Forces: 92 newly built vehicles and 140 from refurbished T-72M and T-72M1 tanks, designated PT-91MA and PT-91MA1, respectively.
History
In the late 1980s, the Polish Army modernized all of its obsolete T-55 tanks to the T-55AM Mérida standard. The successful conversion convinced the General Staff that similar modernization programs could be applied to other Soviet-designed tanks made in Poland and used by the Polish Armed Forces. In late 1988, the decision was made to prepare the modernization of the T-72M1, using experience gained from the production of licensed T-72M, T-72M1 and T-72M1K.The Gliwice-based OBRUM was chosen as the main design bureau. However, initially, the work progressed at a very slow pace, mainly because the Polish General Staff was also considering the purchase of a newer version of the T-72 or the modern T-80.
After the political upheaval of 1989 and dissolution of the Soviet bloc, Polish-Soviet talks on purchase of modern tanks came to a halt and support for designing a new Polish tank gained momentum. The first design proposed by the bureau was code-named Wilk, but the project was cancelled. Instead, priority was shifted to a different project named Twardy.
The basic aim of the T-72 conversion was to adapt it to the reality of modern warfare and fix its most visible deficiencies. Among those were low mobility, insufficient armour, lack of a fire control system and poor stabilisation of the main gun, which resulted in poor firing accuracy. An additional problem was the lack of passive night vision aiming systems.
Development
Starting in July 1991, T-72 modernization programs were implemented by the Bumar-Labedy factory, which had been producing T-72s under Soviet license. The modernized main battle tank was designated the PT-91 Twardy. Bumar-Labedy enhanced the tank's armour protection, fire control system and the engine. In 1993, the Polish Defense Ministry ordered 20 PT-91 tanks, to be used for field trials and armed forces tests.The new dynamic armour, developed by the Poland Military-Technical Institute, increased the main battle tank's protection from high-explosive anti-tank projectiles and missiles. The protection consisted of 394 tiles with explosives, which would detonate in case of a direct hit. The tiles cover 9 m2 of the tank: 108 are placed on the turret, 118 on the hull and 84 on each side's anti-HEAT screens. The Twardy uses steel anti-HEAT screens instead of the rubber one used on the T-72.
The ERAWA tiles fit together almost without gaps, unlike the gaps on the modernized Soviet T-72 which measure up to 15 mm, noticeably decreasing their defensive effectiveness. There are two ERAWA modifications: ERAWA-1 and -2, differing in weight of the explosives. Experiments showed that the ERAWA dynamic defense decreases the high-explosive jet impact depth by 50–70% and that of penetrator projectiles by 30–40%. Furthermore, ERAWA's explosive containers do not detonate when hit by a shot of up to 30 mm calibre or by shell or mine fragments, or when covered in burning napalm or petrol.
The Twardy is armed with the same 2A46 125 mm smoothbore gun used in the T-72, fitted with an automatic reloading mechanism which reduces the tank crew by one, as it replaces the gun loader, and gives a rate of fire of 8 to 10 rounds per minute. Additional armament comprises the 7.62 mm PKT coaxial general-purpose machine gun and 12.7 mm NSVT anti-aircraft heavy machine gun. The PT-91 has a thermosmoke device that generates smoke screens from fuel, and has 24 grenade launchers fitted with smoke, anti-personnel fragmentation, or tear gas grenades developed specifically to provide a non-lethal protection.
The modernization of the fire control system began with replacing the older Soviet 2Є28M two-plane stabilizer with a new stabilizer developed in Slovakia. The system has an electronic information block showing the tank's technical condition. Furthermore, it informs the commander when the sighted fire becomes ineffective from excessively high cross-country speed or other reasons.
The fire control system, developed by Polish engineers, contains the PCD gunner's day sight and the TES thermovision night sight developed by the Israeli company El-Op, the POD-72 commander's combined day-night passive observation and aiming sight, a ballistic computer, a laser rangefinder, and a data system processing information for the ballistic computer. The sighting of the ballistic computer depends on the target's speed, weather conditions, projectile temperature, and projectile type.
The driver uses the US-DK-1 control and diagnostic complex to control the tank's main systems, displaying information on a monitor. The driver's night sight was replaced by the Radomka passive night sight.
The modernized tank's increased weight led the developers to add a more powerful engine: a 12-cylinder S-12U diesel engine produced in Warsaw by PZL-Wola, generating 850 hp instead of 780. The main improvement is the modernized fuel and air injection system. This caused, however, a noticeable decrease in the tank's road endurance. The latest Twardy variants have the 1,000 hp S-1000 engine with a turbocharger.