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Pratt and Whitney Wasp Major Aero-Engine. 28 cylinders. Output 3,500 hp on take off. This type of engine powered BOAC Stratocruisers between 1949 and 1959, and they were all tested and overhauled at the Treforest Engine Overhaul Plant.

The manufacture of aircraft and aircraft engines is not an activity traditionally associated with Wales but, in 1940, British Overseas Aircraft Corporation, latterly British Airways, established an aircraft engine overhaul plant at Treforest. Then, all aircraft were propeller-driven by piston engines burning aviation fuel and this engine was one of the most powerful engines of its type which was overhauled at Treforest.

It is a Pratt and Whitney Wasp Major, a type used in the Boeing Stratocruiser between 1949 and 1959, and it represents the ultimate stage in the development of the aircraft piston engine.

It could develop 35,000 HP on take-off and, with 28 cylinders, this represents about 125 HP per cylinder. The large number of fins on each cylinder show that the engine was aircooled and, because the cylinders are arranged in 4 rows of 7 cylinders, each row is slightly staggered from the row in front so that the cooling air strikes each row of cylinders in turn.

Source: Welsh Industrial & Maritime Museum Guidebook, 1984