M551 Sheridan Light Tank (United States)
Channel: Main Battle Tank
Date: 18/01/2023

Development of the M551 Sheridan began in 1959. Its programme was known as the AR/AAV or Armored Reconnaissance / Airborne Assault Vehicle. First prototypes were built in 1962 and production commenced in 1966. Vehicle is named in honor to Civil War General Philip Sheridan. A total of 1 700 M551 Sheridan light tanks were built until 1970, when production ceased. The M551 Sheridan replaced the M41 tanks and M56 self-propelled guns in service with the US Army. Since 1978 the Sheridans were gradually phased out of service, however last operational vehicles were decommissioned only in 1996. Currently the US Army has no real replacement for this light airborne and amphibious tank.

   The Sheridan could be airdropped, including low altitude drops. The low altitude drops were made using LAPES extraction system. A special pallet absorbed most of the landing impact during landing. This maneuver allowed to deliver the tank when landing was not possible and enemy has a strong air defenses. In fact Sheridan was the only air-deployable tank in service with US Army.

   Hull of the M551 Sheridan is welded from aluminum alloys and turret is welded from steel. It was made in attempt to save weight. Front armor protects against 20 mm armor piercing rounds, while overall protection is against 14.5 mm bullets. Vehicle is fitted with NBC protection system.

   The M551 Sheridan light tank was armed with a rather unique fully-stabilized M48 152 mm gun-launcher capable of firing ordinary projectiles and MGM-51 Shillelagh anti-tank guided missiles. The ordinary munitions were short, fat, with combustible cases, and had to be carefully handled. These had a range of effective fire of 1.5 km. These ordinary rounds were sufficient for infantry support role and could even deal with most contemporary main battle tanks at short ranges, but had poor accuracy at longer ranges. The Shillelagh anti-tank guided missiles were intended to deal with hostile tanks at longer ranges. Missiles were stored in aluminum cases and had a range of up to 3 km. However due to the complicated electronics and and guidance system this missile ended up almost never being fired, except for crew training purposes. A similar gun-launcher, though in a slightly modified form, was later used on as the M60A2 main battle tank. Though operational experience of this unusual tank revealed that the 152 mm gun-launcher was inferior in terms of range and accuracy to 105 mm and 120 mm tank guns, firing ordinary munitions.

   Secondary armament consisted of 7.62 mm coaxial machine gun and 12.7 mm anti-aircraft machine gun.

   Vehicle had a crew of four, including commander, gunner, loader and driver.

   The M551 Sheridan was powered by the Detroit Diesel 6V53T diesel engine, developing 300 hp. Vehicle was fully amphibious after a preparation lasting two minutes. On water this light tank was propelled by its tracks.

   Approximately 200 of the Sheridans were used by the US Army during a Vietnam War. Its combat experience revealed a number of drawbacks. This light tank was very vulnerable to grenades and mines. Its gun-launcher had problems with cracks developing after repeated firing. The gun also had too much recoil for a light vehicle. Most field units were modified to help address the problems.

   The M551A1 Sheridan was an improved version of the base vehicle. It was developed in 1971 considering operational experience of the original M551. It had improved suspension and was fitted with a laser rangefinder.

   The M551 Sheridan  was a very innovative light tank design, however due to its numerous faults these tanks were phased out of service. The Sheridans had been replaced in reconnaissance role with the M60A1 main battle tanks and later with the M3 Bradley armored reconnaissance vehicles. In the 1980s a new M8 Buford air droppable light tank was developed in the United States, which was intended to replace the Sheridan. However the M8 programme was canceled in 1996, leaving the US airborne forces dangerously low on firepower.