The FV4211 Aluminium Chieftain Tank Background
The two principal threats to a tank prior to the new millennium were from Kinetic Energy penetrators aka Armour Piercing Fin-Stabilised Discarding Sabot (APFSDS) and shaped charged HEAT rounds. Armoured technology had struggled in trying to develop a universal armour capable of defeating both these threats.
Rolled Homogeneous Armoured steel must be hard yet impervious to shock in order to defeat APFSDS. Steel with these characteristics is produced by processing cast steel billets of appropriate size and then rolling them into plates of required thickness.
In order to defeat threats, the greater the thickness RHA needs to be, which makes the tank heavier and increases the negative effect on its mobility.
The FV4211 Aluminium Chieftain Tank Development
In 1963 a project to develop a new armour that was lighter than RHA but capable of offering twice the effectiveness in defeating all threats whilst having an equal thickness, was started by the Fighting Vehicles Research and Development Establishment (FVRDE) based in Chobham, Surrey.
By the mid-60’s they had developed a new bonding process and a matrix, which secured the tiles & kept them under a constant compression. This compression of the tiles hugely increased the hardness and resistance of the tiles, thus increasing the number of times the armour can be repeatedly hit before failing, compared to that of other composite armour. The exact tile composition is a British state secret.
This new armour was known as Burlington armour, however it was soon called Chobham, which was the location of FVRDE. The armour was successfully tested several times in ‘loose plate’ trials, that is a box containing the new armour was fired at on a range.
The real test would come in fitting this across the frontal arc (turret and hull) of a tank. It was planned that this would be completed by 1975 as the British Army Chieftain was due to be replaced 10 years later.
It was decided to build a new tank, but use a lot of the automotive components of the existing Chieftain. The new tank was to be called Chieftain Mk5/2, however this was later changed to FV4211 and nick named the Aluminium Chieftain, as it was to be constructed of aluminium instead of steel.
FVRDE completed the construction of the first aluminium hull with its armoured skirts within 13 months. A ballasted (filled with sand bags) Windsor turret was added to represent a fully weighted turret yet to be built, so the vehicle could complete its 12000 mile automotive trials and development. These presented some cracks from stress which were rectified.
This vehicle was designated MTR-1 and demonstrated the vehicle could support the new turret. MTR-1 was chopped up for further testing while a second hull was built at the Leeds Royal Ordnance Factory and fitted with the new turret.
The turret was designed to use No21 cupola and Advanced Integrated Fire Control System. Trials of the vehicle proved successful and it was decided to build a further 9 prototypes for trials by selected Regiments of the RAC. When the project was cancelled, the 9 prototypes were in various state of completion.
Chobham Armour and its influence on the Abram’s and Leopard 2
Only the first prototype TV-A was completed and fully loaded with Chobham armour. The vehicle was sent to FVRDE in Chobham where it was used as a static display to show visiting dignitaries such as the US Military M1 Abram’s project manager and those from the Anglo-German FMBT studies which had been going on at the same time as the Leopard 2 development in the 1970’s (this was not the MBT80 project).
In a fairly recent article written by Richard Rawlins, who is a Former Department Manager and Technical Manager for the MoD for some 30 years on Chieftain and Challenger 2. His work had included the managing of various research program’s and he reported that that it was revealed in the 1976 that the Leopard 2’s armour was also based on Chobham Armour rather than the believed spaced type armour, following the Germans being briefed on Chobham during the FMBT studies, however only the US signed a Memorandum Of Understanding with the UK in 1972 and they were given all the research to date on Chobham for the M1 Abram’s.
FV4211 prototype TV-A is now on display at the Bovington Tank Museum in the UK.