page_title: PT-91 Twardy
section_title: Development
hierarchical_section_title: PT-91 Twardy / Development
caption_attribution_description: English: PT-91 Twardy tank Polski: Czołg PT-91, pulpit kierowcy US-DK-1
context_page_description: The PT-91 Twardy is a Polish main battle tank. A development of the T-72M1, it first entered service in 1995. The PT-91 was designed at the OBRUM and is produced by the Bumar Łabędy company, a part of the Bumar Group, a Polish technical military consortium. Changes from the T-72 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, the Polish Army PT-91s are upgraded using elements created almost exclusively by domestic companies, including a new engine, the fire control system and all communication system elements. Many of those elements were used to upgrade existing fleets of T-72 tanks in countries including the Czech Republic, Georgia, and India.
context_section_description: Starting from 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 PT-91 Twardy. From base modification, it differs in increased protection, fire control system and engine. In 1993 the Polish Defense Ministry ordered 20 PT-91 tanks to be used for field trials and Armed Forces tests.
  The main battle tank's protection from high-explosive anti-tank (HEAT) projectiles and missiles is increased by the new Erawa dynamic armor developed by the Poland Military-Technical Institute. This protection consists of 394 tiles with explosives, detonating in case of a direct hit. The tiles cover 9 m² on the tank. 108 tiles 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 used on the T-72. Erawa's main difference from the Soviet analogs is that Erawa's containers fit almost without gaps while on the Soviet modernized T-72 gaps reach 10–15 mm noticeably decreasing defense 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 penetrator (APFSDS) projectiles by 30–40%. Furthermore, 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 125 mm smoothbore gun 2A46 used in the T-72, fitted with an automatic reloading mechanism which reduced the tank crew by one as it replaced the gun loader, and gave 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 generating smoke screens from fuel and 24 grenade launchers fitted with smoke, anti-personnel frag or tear gas grenades developed specifically to provide a non-lethal protection against football hooliganism.
  The modernization of the fire control system started by replacing the earlier used Soviet two plane stabilizer 2Є28M with a new stabilizer developed in Slovakia. It has an electronic information block showing the tank's technical condition. Furthermore, it informs the commander when the effective sighted fire becomes ineffective because of an excessively high cross-country speed or other reasons.
  The Drawa fire control system, developed by Polish engineers, contains the gunner's day sight PCD and the TES thermovision night sight developed by the Israeli company El-Op, the commander's combined day-night passive observation and aiming sight POD-72, 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 control and diagnostic complex US-DK-1 controlling the tank's main systems and 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. It is a 12-cylinder S-12U diesel engine, a modernized version of the Soviet V-46-6 produced in Warsaw by PZL-Wola (850 hp instead of 780). The main improvement is the modernized fuel and air injection system. This caused a noticeable decrease in the tank's road endurance. The latest Twardy variants have the 1,000 hp S-1000 engine with a turbocharger.
caption: Driver's control panel US-DK-1.
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