| Chieftain (FV4201) | |
|---|---|
Chieftain Mk 10 or Mk 11 with Stillbrew Crew Protection Package. |
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| Type | Main battle tank |
| Place of origin | United Kingdom |
| Service history | |
| In service | 1966–1995 |
| Used by | UK, Iran, Iraq, Jordan, Kuwait, Oman |
| Wars | Iran–Iraq War, Iraq-Kuwait War |
| Production history | |
| Manufacturer | Leyland Motors |
| Specifications | |
| Weight | 55 long tons (62 ST; 56 t) |
| Length | 7.5 m (24 ft 7 in) - hull |
| Width | 3.5 m (11 ft 6 in) |
| Height | 2.9 m (9 ft 6 in) |
| Crew | 4 |
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| Armour | Glacis: 120 mm (72°)[1] Hull sides: 38 mm (10°) Turret: 195 mm (60°)[1] |
| Main armament |
L11A5 120 mm rifled gun |
| Secondary armament |
2 x L7 MG |
| Engine | Leyland L60 (multifuel compression-ignition) 750 hp (560 kW) |
| Suspension | Horstmann |
| Operational range |
500 km (310 miles) on roads |
| Speed | Road: 48 km/h (30 mph) Off road: 30 km/h (19 mph) |
The FV 4201 Chieftain was the main battle tank of the United Kingdom during the 1960s and 1970s. It was one of the most advanced tanks of its era, and at the time of its introduction in 1966 had the most powerful main gun and heaviest armour of any tank in the world.[2] The Chieftain also introduced a supine (lying backwards) driver position, enabling a heavily sloped hull with reduced height.
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The Chieftain was a radical evolutionary development of the successful Centurion line of tanks that had emerged at the end of the Second World War. The British had learned during the war that their tanks often lacked sufficient protection and firepower compared to those fielded by the enemy, and that this had led to high casualty levels when faced with the superior German tanks in World War II.
In the post war period, the British Army bolstered the Centurion with the 120 mm gun Conqueror heavy tank for long range anti-tank firepower against the Soviet IS-3.
Leyland, who had been involved in Centurion, had built their own prototypes of a new tank design in 1956, and these led to a War Office specification for a new tank. The design was accepted in the early 1960s. Chieftain was designed to be as well protected as possible and to be equipped with a powerful 120 mm rifled gun. The heavy armour came at the price of reduced mobility, chiefly due to engine power limitations, which was perhaps the Chieftain's main drawback. The engine selected took the multi-fuel route and as introduced gave less than the planned output; improvements to the engine did not increase power to the desired value.
The early BL Engine delivered around 450bhp to the sprocket which meant a top road speed of around 25mph and cross country performance was limited. Due to the cylinder linings being pressure fitted coolant leaks within the cylnder block were common, hence the familiar white smoke billowing from the exhaust. In the late 70's engine design changed with the introduction of Belzona which was used to improve the lining seals. Engine output also increased with later engines delivering some 850bhp to the sprocket. This meant better performance and an increased speed. However the engine was the main failing of this overly maligned vehicle, along with its rather uncomfortable coil spring suspension that made it a challenge to drive cross country and provide the crew with a comfortable ride.
The Chieftain design included a heavily sloped hull and turret which greatly increased the effective thickness of the frontal armour - 388 mm (15.3 in) on the glacis (from an actual thickness of 120 mm (4.7 in)), and 390 mm (15.4 in) on the turret (from 195 mm (7.7 in)).[1] It had a mantleless turret, in order to take full advantage of reclining the vehicle up to ten degrees in a hull-down position.
The driver lay semi-recumbent in the hull when his hatch was closed down, which helped to reduce overall height. The commander, gunner and loader were situated in the turret. To the left side of the turret was a large infra-red searchlight in an armoured housing.
The Leyland L60 engine is a two-stroke opposed piston design intended for multi-fuel use so that it could run on petrol or diesel or anything in between. In practice the engine did not deliver the expected power, and was unreliable, estimated to have a 90% breakdown rate, but improvements were introduced to address this. Primary problems included, cylinder liner failure, fan drive problems and perpetual leaks due to vibration and badly routed pipework. However, as the engine power improved the tank itself became heavier.
The tank was steered by conventional tillers hydraulically actuating onto external brake discs. The discs worked via the epicyclic gearbox providing "regenerative" steering. In reality the discs and pads became soaked in oil and diesel and the steering became difficult. The gearbox was operated motorcycle-style with a kick up/kick down "peg" on the left which actuated electro-hydraulic units in the gearbox; the accelerator was cable operated by the right foot. In the turret the loader was on the left and the gunner on the right of the gun with the commander behind the gunner. The suspension was of the Horstmann bogie type, with large side plates to protect the tracks and provide stand-off protection from hollow charge attack.
The main armament was the 120 mm L11A5 rifled gun. This differed from most contemporary main tank armament as it used projectiles and charges which were loaded separately, as opposed to a single fixed round. The charges were encased in combustible bags. Other tank guns, such as on the Conqueror, needed to store the spent shell cartridges or eject them outside. The combustible charges were stored in 36 recesses surrounded by a water/glycol mixture - so-called "wet-stowage". In the event of a hit which penetrated the fighting compartment, the jacket would rupture, soaking the charges and preventing a catastrophic propellant explosion[3].
The gun could fire a wide range of ammunition, but the most commonly loaded types were high explosive squash head (HESH), armour-piercing discarding sabot (APDS), or practice round equivalents for both types. The Chieftain could store up to 62 projectiles (though a maximum of 36 APDS, limited by the propellant stowage). The gun was fully stabilised with a fully computerized integrated control system. The secondary armament consisted of a coaxial L8A1 7.62 mm machine gun, and another 7.62 mm machine gun mounted on the commander's cupola.
The Chieftain had an NBC protection system, which the Centurion lacked.
The initial Fire-control system (FCS) was the Marconi FV/GCE Mk 4. A .50-cal (12.7 mm) ranging gun was mounted above the main gun (with 300 rounds available). This fired ranging shots out to a maximum of 2,600 yards (2,400 m), at which point the tracer in the ranging rounds burned out. The tank commander had a rotating cupola with nine vision blocks and a periscope, plus the 7.62 mm machine-gun and an infrared (IR) projector coaxial with the weapon. The aiming systems were provided for both gunner and tank commander; they had 1x or 8x selectable magnification power, and they were replaceable with IR vision systems for the night operations (3x magnification power). The left side of the turret had the big normal/ IR projector inside an armoured box. It had a relatively long range for this kind of system – up to 1–1.5 kilometres (0.62–0.93 mi).[4]
From the beginning of the '70s, the Mk 3/3 version replaced the ranging gun with a Barr and Stroud LF-2 laser rangefinder with a 10-kilometre (6.2 mi) range. This allowed engagements at much longer ranges, and also could be linked to the fire control system, allowing more rapid engagements and changes of target.
From the Mk 5 onwards, fire control was provided by the Marconi IFCS (Improved Fire Control System), using a digital ballistic computer. The upgrade was not finished until the end of 1980, when some examples (but not the majority) had the IR projector replaced with TOGS, the Termal image camera already fitted with the Challenger. Many examples had Stillbrew armour as well, meant to face Soviet 125 mm tank guns and heavy anti-tank missiles. These became the Mark 13 version. [4]
Like its European competitors, the Chieftain found a large export market in the Middle East, but unlike the earlier Centurion, it was not adopted by any other NATO or Commonwealth countries.
The Chieftain proved itself capable in combat and able to be upgraded with enhancements both for overall improvement and to meet local requirements. The Chieftain tanks were continuously upgraded until the early 1990s when they were replaced by the Challenger series of tanks whose design was influenced by that of Chieftain. The final Chieftain version used by the British Army until 1995, incorporated "Stillbrew" armour named after Colonel Still and John Brewer from the Military Vehicles and Engineering Establishment (MVEE), the Improved Fire Control System (IFCS) and the Thermal Observation Gunnery Sight (TOGS).
The first Chieftain model was introduced in 1967. Chieftains were supplied to at least six countries, including Iran, Kuwait, Oman and Jordan. An agreement for sale of Chieftains to Israel was cancelled by the British Government in 1969.[5] The largest foreign sale was to Iran, which took delivery of 707 Mk-3P and Mk-5P, 125–189 FV-4030-1, 41 ARV and 14 AVLB before the 1979 revolution.[6] Further planned deliveries of the more capable 4030 series were cancelled at that point. The tank's main combat experience was in the Iran–Iraq War of 1980-88.
Mark 1 and Mark 2 models had coaxial .50 cal. ranging machine guns prior to the introduction of the laser rangefinder.
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