One of the more interesting post-World War Two tank designs was the British FV4401 Contentious. The intent of the FV4401 was to provide a light (up to 20-tons), easily transportable armored fighting vehicle (AFV) that could be air dropped and provide armored support for airborne and rapid deployment forces. There were two designs put forward under the FV4401 designation. The first was a one man, thinly armored vehicle fitted with two 120mm L6 WOMBAT recoilless rifles, the latter being used due to their light weight. Each L6 was equipped with a autoloader fed from a seven-round rotary magazine. This first design was more of a tank destroyer, akin to the Japanese Type 60 tank destroyer developed from 1956 to 1960. The second design is the focus here.
Work commenced on the two-man FV4401 (sometimes called the Contentious II) in the mid-1950s and the design had a number of novel features. For armament, the Ordnance QF 20-pounder (84mm) gun was initially selected as, at the time, it was a excellent gun and was also used in the British Centurion main battle tank (MBT). Rather than put the gun in a true turret from the outset, the gun was fitted into the hull of the prototype in a very limited traverse mounting. This kept the height of the FV4401 low and also saved weight. The gun was provided with an autoloader which could effectively fire twelve rounds per minute. To elevate and depress the gun, the FV4401 was fitted with suspension that could be raised and lowered and to provide additional traverse, the tank was turned in place. To speed aiming, the gun had an optical light pulse sight which was tied into a servo that allowed for automatic adjustment of the gun and monitored the alignment of the gun as a whole. This was akin to an early implementation of a Movement Reporting System (MRS). Both the commander and the gunner had complete driving and gunnery controls. For armor protection, the front glacis was to feature horizontal rows of metal ridges. The purpose was to break up incoming projectiles before they struck the armor proper. Behind this was a four foot empty space that was filled with diesel fuel. When full, the fuel provided the equivalent of twenty-four inches of armor and behind that was a 40mm thick back plate which separated the fuel compartment from the crew compartment. Components for the initial prototype, namely the lower chassis, were taken from a British FV4101 Charioteer medium tank, the road wheels from the FV300 series (a project for lightweight armored fighting vehicles), and for an engine, a Rolls-Royce B Range diesel engine was used. This engine series, topping out at 187 horsepower for the B81 model (as used in the FV430 AFV series), wasn't to be the final engine fit as the Contentious II was to use an engine developing between 300 to 500 horsepower. The FV4401 was envisioned that at the sacrifice of added weight, a turret could be fitted as well as be fully Nuclear, Biological, and Chemical (NBC) sealed. The proposed turret was to be low in profile so as not to add significant height to the Contentious II.
Sometime in the late 1950s, the FV4401 Contentious II prototype was completed. It was far more of a test vehicle for the adjustable suspension, gun mounting, and fire controls as the prototype was unarmored and the fuel tanks were situated outside the tank, secured to the track guards. The armor concept had been tested and showed that ignition of the diesel fuel following penetration did not occur. If a fire was started, the crew compartment offered some protection and it was planned to house the fuel within the space in armored tanks which would be able to contain any explosion. The explosion risk came more from the tank being penetrated when the fuel level was low and fumes were more in abundance within. To minimize fuel loss, the fuel in the front part of the hull were to be inside compartmentalized tanks. This novel armor, however, was not fitted to the prototype but would have had the Contentious II program continued and more refined prototypes produced. The 20-pounder gun was sighted to 2,000 yards and at that range, the Armor-Piercing Discarding Sabot (APDS) ammunition could penetrate 290mm of rolled homogeneous armor and at 1,000 yards, it could punch through 330mm of armor. This was more than enough to deal with two of the most common Soviet tanks, the T-54 and T-55. Ranging was accomplished by a pulse radar (seen here on the bracket above the gun). Despite the good performance of the 20-pounder gun, work was done on up-gunning the Contentious II with either a 120mm gun, a 155mm gun, or even a larger caliber gun.
As for being air dropped, tests were done using steel constructed replicas in the general shape of the turreted Contentious II design starting in November 1956. They were deployed from a Blackburn Beverley heavy transport, the replicas fitted directly with skids and air bags as a form of impact cushioning. However, these tests were not overly successful, the steel showing significant damage from the landing forces despite the parachute braking and air bags. At least one of the damaged replicas ended up as a range target after impacting the ground, the test personnel seeing no worthwhile reason to recover it.
The FV4401 Contentious II prototype was also tested at Lulworth Range in Dorset, England, against a 6X6 vehicle, the TV1000 Rhino, which was envisioned in a similar role as the FV4401 but using wheels. The TV1000 had stability problems, the rubber on the wheels wore out at an alarming rate, and the TV1000 used skid steering, much like a tank does, and thus offered little over the FV4401 which was deemed superior.
Despite the novel features and relative success during testing, the FV4401 was not put into production nor were further prototypes completed (some sources say at least two more were built) in the FV4401's final form. Had the FV4401 entered service, it would have given British airborne forces a significantly more advanced weapon in comparison to the U.S. M56 Scorpion which entered service in 1957 and would have also been superior to the Soviet ASU-57 airborne assault gun that began service in 1951.
Today, the prototype shown in the photograph at Kirkcudbright Training Area survives to this day, able to be seen at the Tank Museum at Bovington in Dorset, England. Unlike the photograph, the FV4401 at Bovington is armed with a Royal Ordnance L7 105mm gun which was added for display purposes.
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