The Hawker Hart was designed against Specification 12/26, which called for a high performance two seat light day bomber of all-metal construction.
Arguably, the requirement arose following Fairey’s development of the Private Venture Fairey Fox, flown in January 1925, exploiting the Curtiss D-12 engine and Curtiss-Reed propeller to achieve a day bomber that was some 50 mph faster than contemporary RAF fighters.
The Fox was of wooden construction and only 28 were purchased by the RAF. Nevertheless, the design effectively forced the modernisation of Air Ministry thinking and indirectly led to both the monobloc Rolls-Royce Kestrel engine, and the Hawker Hart family of aircraft.
Specification 12/26 was demanding for its day and resulted, in the Hart, in a single bay biplane with all-metal primary structure married to a cleanly-cowled 12-cylinder Rolls-Royce Kestrel engine. The first prototype J9052 was flown for the first time in June 1928.
The pilot sat ahead of a rear gunner / bomb aimer, equipped with a Lewis gun for self-defence, mounted on a gun-ring of Hawker design. The swept upper wings featured a deep cut-out in the centre-section to improve the pilot’s upward view. Splayed-out N-type interplane struts were used and the lower wing was unswept.
Selected following competition, production followed against Specification 9/29. In the event, 1,004 Hart aircraft were built, of which Hawker constructed 234.
Contract production was undertaken from 1931 by Gloster Aircraft Co Ltd (46), Sir WG Armstrong Whitworth Aircraft Ltd (456), Vickers (Aviation) Ltd (226), together with 42 aircraft under licence at Trollhäten, Sweden.
The Hart was an outstanding design, which gave rise to many variants. Developments included the Demon, Audax, Osprey, Nimrod, Hind, Hardy, Hartbees, Hector and Fury. These types are discussed separately.
The RAF used the Hart in both its original light bomber role and as the Hart Trainer, fitted with dual control and with all armament deleted. The Hart Trainer also featured reduced sweep of the upper wing to compensate for changes in centre of gravity when the military equipment was removed.
In addition, the Hart was used in a number of roles, with variants for communications, operation in India and tropical regions.
The type was also used by Canada (1), Estonia (8), South Africa (320+ ex-RAF), Southern Rhodesia (ex-RAF aircraft), Sweden, Yugoslavia (4 loan aircraft) and Egypt (14 ex-RAF). Swedish aircraft were powered by the 580hp Bristol Pegasus radial engine, four aircraft being built by Hawker, followed by 42 constructed locally.
The Hart was also extensively used for engine testing, various examples being host to various versions of the Rolls-Royce Kestrel, Napier Dagger, Bristol Perseus, Mercury, Pegasus and Jupiter, and the Rolls-Royce PV12 and Merlin.
Variants & Numbers
|Hart I||Two-seat light bomber aircraft for the RAF. 525 hp Kestrel IB engine.|
|Hart SEDB (Single Engine Day Bomber)||Two-seat single-engined light bomber aircraft for the RAF, powered by a 525 hp Rolls-Royce Kestrel IB, or a 510 hp Kestrel X (DR) piston engine.[|
|Hart (India)||Tropicalised version for the RAF, used by RAF in the North West Frontier of India, with larger radiator and extra equipment, 57 built.|
|Hart (C)||Two-seat unarmed communications aircraft for the RAF, a small number were used by No. 24 Squadron RAF; eight built|
|Hart Trainer (Interim)||Hart light bombers converted into training aircraft. Prototype from Audax K1996, plus two built Kingston (K2474, K2475).|
|Hart Trainer||Two-seat dual-control trainer aircraft, with reduced sweepback on top wings to compensate for movement in centre of gravity caused by removal of military equipment. 54 Hawker, 114 Vickers Ltd, 303 Armstrong Whitworth.|
|Hart Fighter||Two-seat fighter version for the RAF used by No. 23 Squadron RAF, with Kestrel IIS. Later redesignated as the Demon; six built|
|Hart (Special)||Tropicalised version for the RAF, used by the RAF in the Middle East. Based on Audax airframe with desert equipment, low pressure tyres and de-rated Kestrel X engine|
|Estonian Hart||Export version for Estonia, equipped with an interchangeable wheel or float undercarriage; eight built.|
|Swedish Hart||580hp Bristol Pegasus IM2 radial engine. Four built in UK 42 in Sweden.|
|Hart test aircraft||Four built as test and demonstration aircraft including G-ABMR, G-ABTN and K1102 (RR evaporative cooling). Additional aircraft also converted for engine test purposes including K2434 (Napier), K3036 (RR PV12, Merlin), and K3020 Bristol Pegasus, Mercury..|
|Total production||1,004 aircraft, 474 of which were Hart Trainers|
|Specification||Hawker Hart I|
|Powerplant||One 525hp Rolls-Royce Kestrel IB or 510hp Kestrel X (DR)|
|Span||37 ft 3 in|
|Maximum Weight||4,554 lb (Hart Trainer 4,150 lb)|
|Capacity & Armament||Pilot and gunner, one forward-firing Vickers machine gun plus one Lewis gun fired from rear cockpit; bomb load up to 520 lb|
|Maximum Speed||184 mph at 5,000ft|
|Endurance / Range||2hr 45min / 470 miles|
|Royal Air Force Museum, Hendon. First flown in 1931 and used by Hawker in various roles, including testbed, demonstration aircraft and a camera aircraft. It flew throughout the Second World War and continued flying until 1971. It was then transferred to the RAF Museum, where it is displayed painted to represent RAF Hart serial number J9941|
|Displayed at the Royal Air Force Museum, Hendon. Built in 1935 by Armstrong Whitworth, it flew as a training aircraft before being used as an instructional airframe.|
|Swedish Air Force Museum. Linköping. Displayed in Finnish markings.|