The Hawker Hoopee was a radial powered naval fighter that despite undergoing a prolonged series of trials never entered service, being superseded by the inline-powered Hawker Nimrod. Although the Air Ministry had issued specification N.21/26, calling for a naval fighter, the Hoopee was built during 1927 as a private venture. Despite this it did conform to most requirements of the specification, including the use of a Bristol Mercury II radial engine (despite Hawkers wanting to use the Rolls Royce F.X inline engine).
The Hoopee was built as a two-bay biplane, with staggered wings. Compared to other Hawker aircraft of the period (including the F.20/27, Hornet and Fury) the main difference was in its size - the two-bay wings were five feet longer than the 30ft wings on the land fighters. The Hoopee underwent Service trials at Martlesham Heath during 1928, where it performed well enough to encourage the Air Ministry to ask Hawkers to continue developing the aircraft. In 1929 it was given twin floats, and at this point the Mercury II was found to be under-powered. It was replaced first with a Mercury VI and then with an Armstrong Siddeley Jaguar V with a Townend ring to reduce drag. At the same time new single-bay wings were installed. This version of the aircraft was judged to be more successful, and was more popular with the test pilots.
The Hoopee was modified again in 1930. This time it was given a 560hp Armstrong Siddeley Panther III 14-cylinder radial engine, the most powerful engine to be used on the Hoopee. Concentric Townend rings were used, as were wheel spats. In this configuration the Hoopee recorded a top speed of 196.5mph, but by now the Air Ministry had finally been convinced of the superior performance of the new inline engines, and the prototype Hawker Nimrod had already made its maiden flight.
450hp Bristol Mercury II 9-cylinder radial
520hp Bristol Mercury VI on seaplane version
400hp Armstrong Siddeley Jaguar V 14-cylinder radial engine
560hp Armstrong Siddeley Panther III 14-cylinder radial engine
Wing span: 35ft 6in (two bay), 33ft 2in (single bay)
Length: 25ft 4in (Mercury engine), 24ft 6in (Panther engine)
Empty Weights: 2,490lb (Mercury II), 2,505lb (Jaguar V), 2,785lb (Panther III)
Loaded Weights: 3,550lb (Mercury II), 3,600lb (Jaguar V), 3,910lb (Panther III)
Max Speed: 196.5mph (Panther III)
Climb to 10,000ft: 8min 10sec (Jaguar V), 6min 40sec (Panther III)
Service Ceiling: 23,600ft (Panther III)
Armament: Two forward firing Vickers guns
Bomb-load: Four Admiralty 3.5in flares or 20lb bombs under wings