The Light Tank Mark IA was the second light tank to be ordered by the British Army, and was a slightly improved version of the Mark I. The Mark IA had a larger turret and taller superstructure than the Mark I, with sloped armour on the new upper section of the superstructure. Four of the five Mark IAs used the same suspension as the Mark I, while on the E8 the leaf spring suspension of the Mark I was replaced with Horstmann suspension, which featured horizontally mounted coil springs attached to a ball and socket joint. This system gave an easy smooth ride at medium speeds on reasonable ground, but on rougher ground or at high speeds an almost uncontrollable level of bouncing could develop. Despite this problem the Horstmann suspension was retained on the Light Tank Mark II. Like the Mark I the IA was built with a separate chassis, with the armour and automotive components attacked to the framework.
Five Mark IAs were produced, with the designations A4E6 to A4E10. Like the Mark Is they were used for experimental purposes. The A4E10 was used to test a two-gun armament, with a .5in Vickers machine gun mounted above the .303in gun. Another was used to test the Ricardo 65hp engine, and a third to test a different suspension system that didn't require the rear idler wheel. Four of the five Mark IAs were sent to India in 1931 for tropical trials. These tanks were given square bevel sided non-rotating cupolas at the Base Workshops at Chaklala, and were also used to test different methods of reducing the temperature inside the tank. The most successful of these involved the use of an asbestos fabric lining. The Mark IA was followed by the Mark II, the first version to be produced in significant numbers.
Light Tank Mark 1A, A4E6-A4E10
Hull Length: 13ft 2in
Hull Width: 6ft 1in
Height: 5ft 7in
Weight: 4.8 tons
Engine: Meadows six cylinder, 58 bhp
Max Speed: 32mph
Max Range: 160 miles mission radius
Armament: One .303in Vickers machine gun