Concept studies for Chieftain began 12 years before it entered service in 1965. The main types of tank introduced into British Army service since 1945 were the Charioteer, a tank destroyer introduced in 1953; the Conqueror, a heavy tank destroyer introduced in 1953; the Centurion, a Main Battle Ttank introduced in 1945, and the Chieftain Main Battle Tank introduced in 1966. The Chieftain succeeded the Centurion and was in turn replaced by the Challenger. It weighed less than the Centurion. It had an exceptionally powerful 120-millimeter gun [at a time when the the 105 mm. tank gun was standard in NATO], first-class armor and long endurance. It had fairly reliable armor protection for the time, although this resulted in increased combat mass. The upper frontal body plate has a great angle of slope. Characteristic of this tank is the fact that the driver-mechanic assumes a reclining position for the combat mode of operation.
The Army went very carefully into the questions of bridge classification before deciding to adopt this tank. Considering its performance and its fire-power, it was not a heavy tank. It combined much more devastating fire-power than that of the Conqueror heavy tank, with the weight and mobility of a medium tank of the Centurion class. It had an extremely powerful gun, far more powerful than the present tank armament, strong armor, and it had a multi-fuel engine which ran equally well on heavy diesel oil or high-grade petrol. It has good cross-country performance. It can even swim with a very small and easily erected adaptation which the crew themselves can erect. One of its most important qualities, most appreciated by its crews, is its silhouette. This is not simply an aesthetic appreciation (though nobody would be likely to deny that cavalry soldiers are of a more cultured, sensitive stamp than those in other arms) but it is directly related to the self-preservation interest. It determines the sort of target presented to an enemy. And in this context the Chieftain provided maximum comfort for its crew and the maximum frustration for the enemy seeking to destroy it.
The Chieftain tank underent trials in 1961, and entered British ground forces service in the 1960s. The White Paper for 1962 stated that the Chieftain was on order. But in 1962 Chieftain tank had some teething troubles. During trials with the engine running at full power the gearbox became overheated. The cause of the overheating is known, and modifications are now being tested; these put production back by about six months. The acceptance trials of the Chieftain tank began in early 1963, at which time it was hoped to place a production order then for delivery early in 1965. By 1963 Britain already had a very good tank in the up-gunned Centurion, but, if the outcome of the trials was satisfactory, the Chieftain would start to take its place in 1965.
In July 1963 the UK put on a demonstration on the range at Kirkcudbright to representatives of NATO and Commonwealth countries. The atmosphere was like the July sales at Newmarket. The British were confident they had a future winner, a real thoroughbred. The buyers stood around like buyers do, anxious to crab. Altogether, it was not the most impressionable of audiences. But when the tank's phenomenal gun destroyed a target at the first shot at a hitherto unheard of range, there was a spontaneous outburst of clapping. The day produced another and unexpected object-lesson. When the tank crews lined up afterwards—they were men of the R.A.C., not specially selected—someone asked them how long 1550 they had been serving. None had less than five years and some over nine. This too, in a gathering which included the commanders of many short-service conscript armies, was not without its effect. But there was considerable difficulty in persuading foreign buyers of arms from the United Kingdom to purchase Chieftain tanks.
Chieftain troop trials were satisfactory and by early 1964 two production lines were being set up. At that time it was planned that this tank would come into service in 1965, and most of B A.O.R. would be equipped with it in 1967–68. By early 1965 production of the Chieftain tank is under way. This was a most advanced and complex weapon system, possessing many new features, and it had its share of difficulties inherent in getting going the production line of a new and sophisticated equipment. By early 1966 delivery had started in the UK country and plans called for Chieftain to begin to come into service in B.A.O.R. towards the end of 1966. The Chieftain was the mainstay of the British Army of the 1960s and 1970s.
The Chieftain mounted a long barreled L11A2 120mm rifled cannon, guidance-stabilized in two planes. A 7.62-mm machine gun is coaxially mounted. The tank also has a 12.7-mm ranging machine gun and a7.62-mm anti-aircraft machine gun has been mountedon the commander's cupola. The Chieftain solved the problem of ranging the main gun by using a ranging machine gun with similar ballistic characteristics as the cannon. When the machine gun rounds hit the target, the gunner could be reasonably assured that his cannon round will hit. Early Chieftains and some later modified tanks mount the 50. Cal M2HB machinegun over the main gun as a ranging gun. Iran and Kuwait retained the .50 Cal MG. The HESH round is used for antitank chemical-energy (CE) antiarmor missions, and for HE effects against personnel and materiel. The combat load consists of 64 separately loaded rounds.
A six-cylinder multi-fuel engine and mechanical trans-mission are installed in the tank. The transmissionsystem is interconnected with the springs and shockabsorbers. The track has metal joints and rubber lining.The Chieftain tank has undergone several stages ofmodernization directed primarily towards increasingfire power through the use of more sophisticated firecontrol systems. It has been purchased by Iran (over 700), Kuwait and Oman. The Iranians claim to employ a snorkel system on Chieftain, for fording to 5 meters depth.
The fantastic story of the Chieftain tank engine is proof of the old adage that truth is stranger than fiction. It reveals a state of affairs in Ministry of Defence procurement that would have failed Marlborough and Wellington. The engine took 17 years — from 1957 to 1974 — to develop. At the beginning of the first sitting at which the Commons Public Accounts Committee considered the Chieftain, General Sir John Gibbon set out exactly what had happened. He said: ‘What happened in this case was that we placed two design studies, one with Rovers and one with Leylands, in 1955. That was all part of a co-ordinated plan for the design and development, and eventually the production of a new tank. We did it in that way because we wanted to exploit the previous experience in engine design of the Meteor petrol engine which had been used in the Centurion tank, the predecessor of the Chieftain tank, and a Leyland design which would be a multi-fuel engine based on the conventional diesel engines of that time.
Both those approaches failed, and, of course, all the time that they were failing the design of the tank hull was going ahead and the design of all the things that would have to go inside he tank hull was also going ahead. By the time we got to 1958, when it was decided to adopt the opposed piston two stroke engine, the shape of the Chieftain hull was becoming fairly firm. The space available for the engine, when everything else had been taken into account, pointed to a tall and a narrow engine, which in fact, very luckily, exactly suited the shape of the opposed piston type engine … I think that it is probably not quite fair to say that we had to make an engine that fitted into the tank. Of course, if the engine had not fitted in and we had had to re-design the tank and perhaps make it rather bigger, it would have been heavier and we should have had to take much longer over the design of the hull itself.’ It seems that the Ministry discovered project managers some time in 1967, though that sort of management expertise had been known to the rest of industry for several decades.
The problem facing a Committee examining that kind of case, where the project has gone on for such a long time, is the recurrence in the evidence of the phrase "I was not there at that time, I am afraid." The witnesses, however expert in their own right, often have to refer back—in the Chieftain case, as much as 15 or 16 years. Not surprisingly, they cannot directly account for what went adrift.
The amazing saga continues. An engine was chosen for the tank—one that had not been used in fighting vehicles before, and then, piling horror upon horror, a decision was made to go ahead before it had been proved in trials or there had been further examination. Sir John Gibbon was asked whether the decision in 1963 could be justified by the military prognostications at the time ‘vis-à-vis our relationship with the Warsaw Pact".’ He replied: ‘I believe that I should take exactly the same decision in those circumstances as somebody did in those days, in that the British Army needed a new tank and needed it as quickly as was reasonably possible.’ Any hon. Member, whether or not he had knowledge of military affairs, would also believe that it would be useful if the tank actually functioned. It is all very well asking for it quickly, but if the engine does not work it will not be a great deal of use, whatever may be the balance of armaments.
In the 1960s the production of Chieftain tanks was split between the Vickers factory and the Royal Ordnance factory in Leeds. The full re-equipment of B.A.O.R. with Chieftains was substantially completed by 1972. It had been the policy of successive Governments to look first to the Royal Ordnance Factories for heavy armoured fighting vehicles, and in lean times this means that tank production work must go to the Royal Ordnance Factory at Leeds. This was the most efficient procedure as far as defence votes are concerned, as it avoided the excessive overhead costs that would arise from maintaining two sources of supply. It was sensible that the production of these tanks should be concentrated at one factory, and it was concentrated at Leeds. The decision was taken in the light of a comparison in 1970 of the costs at the two potential sources of production.
By 1979 some 1,600 engineering workers in the defence division of Vickers were anxiously awaiting decisions by the Government on new armaments orders, including an order for 77 Chieftain tanks for Vickers at Elswick which negotiated the tender. At the beginning of 1979 the Army Board considered it a matter of urgency that 77 Chieftain tanks should be ordered to bring the war maintenance reserve for the British Army of the Rhine up to date. The board accepted the request and treated it as a matter of urgency. The Government pulled out all the stops. Vickers Limited tendered and the tender was found acceptable. Had it not been for the general election, the order would have been given to Vickers and the tanks would have been produced at the Elswick works in Newcastle upon Tyne. But by June 1980 the order still had not been placed with Vickers on Tyneside.
A variety of fire control systems and thermal sights were available for Chieftain. Some 324 Chieftains were upgraded with the Barr and Stroud TOGS thermal sight system. The 1R26 thermal camera can be used with the 1R18 thermal night sight. It has wide (13.6°) and narrow (4.75°) fields of view, and is compatible with TOGS format. GEC Sensors offers a long list of sights including: Multisensors Platform, Tank Thermal Sensor, and SS100/110 thermal night sight. Marconi, Nanoquest, and Pilkington offer day and night sights for the Chieftain.
Charm Armament upgrade program, with the 120-mm L30 gun incorporated in Challenger 1, was available for Chieftain modification programs. The work to consider a replacement fire control system for Chieftain started before the 1987 Canadian gunnery competition.
Chieftain entered service with the British Army in 1965. Although it continues to give excellent service, over time it advanced in years, and technology in this field moved ahead. It proved impracticable to organise an international collaborative tank project in an early time scale. Allied collaboration in tanks and their armament remains an important objective for the future; but by the late 1980s Chieftain must be replaced as soon as practicable by a tank developed nationally by the UK or an ally.
As of 1991 the Government's intention was to re-equip completely two regiments of Chieftains. It was believed that after the Options arrangements were fully in place, there would remain two regiments of Chieftains. They will be replaced with the new Challenger 2 tank. The numbers in this contract would be up to about 130, which is larger than required to equip two regiments but included tanks for training and logistical support.
- Mk 5: Final production variant, with a new engine and NBC system, modified auxiliary weapons and sights. Mk 6-11 are upgrades to earlier models, with addition of IFCS. Mk 12 added ROMOR (aka: Stillbrew) spaced armor boxes. Mk 11 and Mk 12 have Thermal Observation and Gunnery Sight (TOGS).
- A variety of support vehicles were developed from the tank. They include recovery vehicles, AVLB, dozer, mineclearer, air defense and 155-mm SP artillery systems.
- Khalid/Shir 1: Jordanian variant which has chassis, turret and weaponry of the Chieftain, but which incorporates engine and running gear upgrades of Challenger I. The fire control has seen a number of improvements, including a new ballistic computer.
- The Chieftain-900, built by the Vickers firm at the beginning of the 1980's, remained in its stage of experimental development. One of the most notable improvements to the Chieftain was the Chobham armored Chieftain 900 which featured a distinctive glacis plate.
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