AS-90

The AS-90 (acronym for: Artillery System for the 1990s, known officially as: Gun Equipment 155 mm L131) is a lightly armoured self-propelled artillery piece used by the British Army.

The AS-90 was first deployed by the British Army in 1993,. 179 were acquired to re-equip six of the eight self-propelled field artillery regiments (each 24 guns) in the 1 (BR) Corps, replacing the 105 mm FV433 Abbot SPG and older M109 155 mm Self Propelled Gun. It remains in UK service and will equip three field regiments supporting armoured infantry brigades for the forseeable future.

AS-90 was designed and built by the Armaments division of Vickers Shipbuilding and Engineering (VSEL), whose parent company became BAE Systems in 1999. VSEL provided 179 vehicles between 1992 and 1995 at a cost of £300 million ($480 million USD).

The AS-90 underwent a capability enhancement program in 2008 and 2009, primarily relating to upgrades of the AS-90's electronic system.

In 1999, Marconi Electronic Systems was contracted to upgrade British Army AS-90s to include a 52 calibre gun in order to increase the range of the artillery. Critical to the program was a bi-modular charge system from Somchem of South Africa (selected after extensive trials of ammunition from many suppliers), which offered greatly reduced barrel wear. However, this ammunition failed to meet the requirement for insensitive munitions and the project was terminated.

Development
AS-90 started in the mid-1980s as a private venture on the 'gamble' that the tri-national SP70 would fail. When this duly occurred, the Ministry of Defence (MoD) issued a cardinal point specification on one page for a new 155 mm SPG. Four tenders were submitted, and AS-90 was the only offer that was not 'brochureware'. The MoD was also required to consider the US "Paladin", an upgraded M109 howitzer.

The MoD has undertaken studies in 2006-09 to "up gun" the Royal Navy's main shipboard gun armament, the 4.5 inch Mark 8 naval gun, to accept the 155 mm ordnance from the AS-90. This would introduce a common gun calibre for the British Army and Royal Navy, helping with ammunition logistics, and encouraging joint Army-Navy development of extended range and precision guided shells.

Design
In 1963 certain NATO nations, including the UK, agreed a Ballistics Memorandum of Understanding for a 155 mm 39 calibre ordnance and a baseline projectile with the shape used for the US M549 rocket-assisted shell. The AS-90 uses a conforming 39 calibre barrel which fires the L15 unassisted projectile out to a range of 24.7 km. However, this was a new design of ordnance and uses a split sliding block breech with Crossley obturation, instead of the more usual screw breech, to permit bagged charges (no metal cartridge cases). The breech mechanism has a primer magazine holding 18 primers.

It is fitted with an auxiliary power unit to eliminate the need to run the main engine to keep the batteries charged while stationary; electrical servos drive the automated elevation, traverse, magazine, shell transfer arm and loader as well as power for electronics and communications.

The vehicle is fitted with an autonomous navigation and gun laying dynamic reference unit (DRU) mounted on the trunnion. All main turret functions are controlled by a Turret Control Computer (TCC) with control and display units for the No 1 (Detachment Commander), No 2 (loader) and No 3 (layer). The combination of the DRU, TCC and powered laying controls provide autolaying. Every gun is fitted with a radar Muzzle Velocity Measuring Device. Reversionary mode laying uses deflection laying via the direct fire sight.

The gun can be brought into action fully closed down, the barrel can be clamped and unclamped from within the vehicle. Into and out of action times are less than 1 minute.

Characteristics

 * Crew: 5, on board when moving (driver plus 4 gun detachment), full gun detachment 10 including driver, 4 detachment members in the turret.
 * Length: 9.07 m
 * Width: 3.3 m
 * Height: 3.0 m
 * Armour: 17 mm (maximum, steel)
 * Weight: 45 tons
 * Calibre: 155 mm
 * Range: 24.9 km (39 cal), 30 km (52 cal) standard charges
 * Rate of fire: 3 rounds in 10 seconds (burst), 6 rounds per minute for 3 minutes (intense), 2 rounds per minute for 60 minutes (sustained)
 * Secondary armament: 7.62 mm L7 GPMG
 * Ammunition carried: 48 projectiles and charges (31 turret and 17 hull), 1000 MG rounds
 * Main Engine: Cummins VTA903T 660 bhp 90 degree, v8, 4 stroke, liquid cooled, turbo diesel,
 * Max Speed: 55 km/h (Road)
 * Range: 370 km or 231 mi (Road)
 * Ground clearance: 0.41 m; Gradient: 60°; Vertical obstacle: 0.75 m; Trench crossing: 110 inches; Fording depth: 1.5 m

Variants
AS-90D - Modified for desert use. Thermal protection for crew and extra cooling for engine and machinery. Tracks adapted for reduced wear in sandy conditions.

AS-90 "Braveheart" - Basically the AS-90, but fitted with the 52 calibre length gun. This project was terminated due to non-compliant propellant charges.

Haubicoarmata "Krab" - (eng. Howitzer-cannon Crab) Licensed "Braveheart" turret on a Polish chassis UPG, with modern "Azalia" BMS. Designed and integrated in Poland, by Huta Stalowa Wola and WB Electronics. , two Krab ("Crab") prototypes were built, and successfully completed all required evaluations and state acceptance trials. Initial serial production started in 2008, 24 units are planned before 2015 of 72 projected for Polish Land Forces with 8 in testing phase as of 2012.