The Hawker Henley was a British two seat target tug derived from the Hawker Hurricane that was operated by the Royal Air Force during World War II.
In 1934 Air Ministry Specification P.4/34 was issued which called for a light bomber that could also be deployed in a close-support role as a dive-bomber.
Fairey, Gloster and Hawker attempted to fulfil this need and competition was tight to attain the highest performance possible.
As the aircraft required only a modest bomb load and with performance being paramount, the Hawker design team chose to focus its efforts on developing an aircraft similar in size to their Hurricane fighter.
The Hurricane was then in an advanced design stage and there would be economies of scale if some assemblies were common to both aircraft.
This resulted in the Henley, as it was to become known, sharing identical outer wing panel and tailplane jigs with the Hurricane.
Both were equipped with the Rolls-Royce Merlin engine as it offered the best power-weight ratio as well as a minimal frontal area.
The Henley’s cantilever fabric-covered monoplane wing was mid-set, a retractable tail wheel landing gear was selected, and accommodation provided for a pilot and observer/air gunner, which differed from the Hurricane’s single-seat cockpit.
Although construction of a Henley prototype began as early as mid-1935, with priority given to Hurricane development, it was not until 10 March 1937 that, powered by a Merlin “F” engine, it was first flown at Brooklands, shortly after the competing Fairey P.4/34.
Subsequently, the aircraft was refitted with light alloy stressed-skin wings and a Merlin I engine (production version of the F) and further test flights confirmed the excellence of its performance.
It could reach a top speed of 300 mph (480 km/h).
By this time the Air Ministry had, however, decided that it no longer required a light bomber (probably because it was felt that this role was adequately filled by the Fairey Battle).
Accordingly, the Henley, which in line with RAF policy had not been fitted with dive brakes; bomb crutches; or specialised bomb sights and thus limited to attack angles of no greater than 70° was relegated to target-towing duty.
The Air Ministry’s decision to abandon work on dive bombers in 1938 had much to do with the danger of engine overspeed in a dive.
This could be alleviated by the use of constant speed propellers, such as the Rotol, but these were not available in significant quantity until 1940 and they were then urgently needed to improve the performance of the Hurricane, which they successfully did.
Henley production was subcontracted to Gloster Aircraft and 200 were ordered into production.
The second prototype was fitted with a propeller-driven winch to haul in drogue cable after air-to-air firing sorties.
This was first flown on 26 May 1938.
Two-seat target tug aircraft for the RAF, 200 built.