Westland Whirlwind (fixed wing)

Whirlwind
Westland Whirlwind in a rare Second World War colour photograph
Role	Heavy fighter
National origin	United Kingdom
Manufacturer	Westland Aircraft Limited
First flight	11 October 1938
Introduction	June 1940
Retired	October 1943
Primary user	Royal Air Force
Produced	1940 – January 1942
Number built	116

The Westland Whirlwind was a British twin-engined heavy fighter developed by Westland Aircraft. A contemporary of the Supermarine Spitfire and Hawker Hurricane, it was the Royal Air Force's first single-seat, twin-engined, cannon-armed fighter.

When it first flew in 1938, the Whirlwind was one of the fastest and most heavily armed combat aircraft in the world. Protracted development problems with its Rolls-Royce Peregrine engines delayed the project, and only a relatively small number of Whirlwinds were built. During the Second World War, only three RAF squadrons were equipped with the Whirlwind, and, despite its successful use as a fighter and ground attack aircraft, it was withdrawn from service in 1943.

By the mid-1930s, aircraft designers around the world perceived that increased attack speeds were imposing shorter firing times on fighter pilots. This implied less ammunition hitting the target and ensuring destruction. Instead of two rifle-calibre machine guns, six or eight were required; studies had shown that eight machine guns could deliver 256 rounds per second. However, the eight machine guns installed in the Spitfire and the Hurricane fired rifle-calibre rounds, which did not deliver enough damage to quickly knock out an opponent. Cannon, such as the French 20 mm Hispano-Suiza HS.404, which could fire explosive ammunition, offered another type of heavy firepower, and attention turned to aircraft designs which could carry four cannon. While the most agile fighter aircraft were generally small and light, their limited fuel storage also limited their range and tended to restrict them to defensive and interception roles. The larger airframes and bigger fuel loads of twin-engined designs were therefore favoured for long-range, offensive roles.

The first British specification for a high-performance machine-gun monoplane was F.5/34, but the aircraft produced were overtaken by developments by Hawker and Supermarine. The RAF Air Staff thought that an experimental aircraft armed with the 20 mm cannon was needed urgently and Air Ministry specification F.37/35 was issued in 1935. The specification called for a single-seat day and night fighter armed with four cannon. The top speed had to be at least 40 mph (64 km/h) greater than that of contemporary bombers – at least 330 mph (530 km/h) at 15,000 ft (4,570 m).

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