The Hawker Hart is a British two-seater biplane light bomber aircraft that saw service with the Royal Air Force (RAF). It was designed during the 1920s by Sydney Camm and manufactured by Hawker Aircraft. The Hart was a prominent British aircraft in the inter-war period, but was obsolete and already side-lined for newer monoplane aircraft designs by the start of the Second World War, playing only minor roles in the conflict before being retired.
Several major variants of the Hart were developed, including a navalised version for the Royal Navy's aircraft carriers. The Hart was also operated by foreign nations, including Sweden, Yugoslavia, Estonia, South Africa, and Canada.
Design and development In 1926, the Air Ministry stated a requirement for a two-seat high-performance light day-bomber, to be of all-metal construction and with a maximum speed of . Designs were tendered by Hawker, Avro and de Havilland.Lewis 1974, p. 146. Fairey, who had sold a squadron's worth of its wooden Fox bomber in 1925, was not at first invited to tender to the specification, and was sent a copy of the specification only after protesting to the Chief of the Air Staff, Hugh Trenchard.Jarrett Aeroplane Monthly May 1995, p. 13.Taylor 1974, p. 196.
Hawker's design was a single-bay biplane powered by a Rolls-Royce F.XI water-cooled V12 engine (the engine that later became known as the Rolls-Royce Kestrel). It had, as the specification required, a metal structure, with a fuselage structure of steel-tube covered by aluminium panels and fabric, with the wings having steel spars and duralumin ribs, covered in fabric. The crew of two sat in individual tandem cockpits, with the pilot sitting under the wing trailing edge, and operating a single Vickers machine gun mounted on the port side of the cockpit. The observer sat behind the pilot, and was armed with a single Lewis gun on a ring mount, while for bomb-aiming, he lay prone under the pilot's seat.Jarrett Aeroplane Monthly June 1995, pp. 30–32. Up to of bombs could be carried under the aircraft's wings.Mason 1991, p. 170.
The prototype Hart, serial J9052, first flew in June 1928, being delivered to the Aeroplane and Armament Experimental Establishment at RAF Martlesham Heath on 8 September. It demonstrated good performance and handling, reaching in level flight and in a vertical dive.Jarrett Aeroplane Monthly May 1995, p. 14.Mason 1994, p. 205. The competition culminated in the choice of the Hawker Hart in April 1929. The de Havilland Hound was rejected due to handling problems during landing and because of its part-wooden primary structure. While the Avro Antelope demonstrated similar performance and good handling, the Hart was preferred as it was far cheaper to maintain, a vital aspect to a programme during defence budget constraints that the British armed forces faced during the 1920s. The Fairey Fox IIM (which despite the name was a new aircraft), delayed by Fairey's late start on the design compared to the other competitors, only flew for the first time on 25 October 1929, long after the Hart had been selected.
A total of 992 aircraft were built as Harts. It became the most widely used light bomber of its time and the design would prove to be a successful one with a number of derivatives, including the Hawker Hind and Hector. There were a number of Hart variants, though only slight alterations were made to the design. The Hart India was a tropical version, the Hart Special was a tropical Hawker Audax, a Hart variant with desert equipment; a specialised Hart Trainer was also built which dispensed with the gunner's ring. Vickers built 114 of the latter model at Weybridge between 1931 and June 1936.Lewis 1974, pp. 176, 233.
The production Hart day bomber had a Rolls-Royce Kestrel IB 12-cylinder V-type engine; a speed of and a range of . It was faster than most contemporary fighters, an astonishing achievement considering it was a light bomber. It also enjoyed excellent manoeuvrability, making the Hart one of the most effective biplane bombers ever produced for the Royal Air Force. In particular, it was faster than the Bristol Bulldog, which had recently entered service as the RAF's front line fighter. This disparity in performance led the RAF to gradually replace the Bulldog with the Hawker Fury.Lewis 1974, p. 176.
Demand was such that production was spread out among a wide selection of aircraft companies. Of the 962 built in the United Kingdom, Hawker produced 234, Armstrong Whitworth 456, Gloster 46, Vickers 226 and 65 aircraft built under licence by South African Air Force Roberts Heights Depot, Pretoria, in South Africa, and 42 were produced in Sweden under licence by ASJA who built 18, Götaverken who built three and the Central Workshops of the Air Force (CVM) who built 21."Hawker Hart." aeroflight.co. Retrieved: 4 December 2012. 1004 Harts were produced.
Operational history The Hart entered service with No. 33 Squadron RAF in February 1930, replacing the larger and slower Hawker Horsley. No. 12 Squadron replaced its Foxes with Harts in January 1931, with a further two British-based Hart light bomber squadrons forming during 1931.Thetford Aeroplane Monthly July 1995, p. 51.
Harts were deployed to the Middle East during the Abyssinia Crisis of 1935–1936. The Hart saw extensive and successful service on the North-West Frontier, British India during the inter-war period. Four Hawker Harts from the Swedish Air Force saw action as dive bombers during the 1939–1940 Winter War as part of a Swedish volunteer squadron, designated F19, fighting on the Finnish side. Though obsolete compared to the United Kingdom's opposition at the start of the Second World War, the Hart continued in service, mainly performing in the communications and training roles until being declared obsolete in 1943.Lewis 1974, p. 233.
The Hart proved to be a successful export, seeing service with the Royal Egyptian Air Force, Royal Indian Air Force, South African Air Force, Estonian Air Force, Southern Rhodesia, Sweden (where it was designated B4) and the Kingdom of Yugoslavia. The Rhodesian Hardys saw service on the Allied side during the opening moves of the East African theatre of World War II.
Swedish Air Force General Björn Bjuggren wrote in his memoirsBjuggren, Björn (1965). Attack: minnen från trettiofem års flygtjänst (in Swedish). Stockholm: Norstedt. how his squadron developed dive-bombing techniques in the mid-1930s for their B4s. When the Hawker engineers found out, they issued a formal objection, saying that the aircraft had not been designed for that purpose. However, the Swedish pilots proved that the aircraft was up to the task and dispelled their concerns.Lewis 1974, p. 224.
Variants
Hart Hart I Two-seat light bomber aircraft for the RAF. 525 hp Kestrel IB engine.Mason 1991, p. 488. Hart SEDB 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.Mason 1991, p. 492. Hart (India) Tropicalised version for the RAF, used by RAF in the North West Frontier of India, with larger radiator and extra equipment.Jarrett Aeroplane Monthly May 1995, p. 15. Hart (C) Two-seat unarmed communications aircraft for the RAF, a small number were used by No. 24 Squadron RAF; eight built.Mason 1991, pp. 490, 494. Hart Trainer (Interim) Hart light bombers converted into training aircraft. Two built.Mason 1991, p. 160. Hart Trainer Two-seat dual-control trainer aircraft, with reduced sweepback on top wings to compensate for movement in center of gravity caused by removal of military equipment.Mason 1991, p. 161. 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.Mason 1991, p. 489. Hart (Special) Tropicalised version for the RAF, used by the RAF in the Middle East. Based on Audax airframe with desert equipment, and de-rated Kestrel X engine.Wixey Air Enthusiast January/February 2002, pp. 57–58.Mason 1991, p. 159. Hart (Testbeds) Several Harts were used as engine testbeds, including G-ABMR and G-ABTN which were used to test several variants of Kestrel engines. K2434 was used by Napier to test the Napier Dagger I, II and III. K3036 was used by Rolls-Royce to test the Merlin C and E, complete with a ventral radiator.Mason 1991, pp. 166–170. Estonian Hart Export version for Estonia, equipped with an interchangeable wheel or float undercarriage; eight built.Mason 1991, p. 165.Wixey Air Enthusiast November/December 2001, pp. 28–29.
Hawker Hartbees Hawker-built pattern aircraft; 4 built and exported to South Africa. Hartbees Mk.I Two-seat general-purpose, ground support aircraft for the South African Air Force, powered by a 608 hp (453 kW) Rolls-Royce Kestrel VFP piston engine; 4 aircraft built by Hawker Aircraft in the UK, 65 aircraft built under licence by SAAF Roberts Heights Depot, Pretoria, in South Africa. Swedish Hart Light bomber for Swedish Air Force. Four Hawker-built pattern aircraft, powered by a Bristol Pegasus IM2 radial piston engine were delivered in 1934. Following successful evaluation, 42 were built under licence in Sweden by AB Götaverken of Göteborg, powered by a Swedish-built NOHAB Pegasus IU2.
Audax
The Hawker Audax was a Hart variant, designed for army cooperation, seeing much service in the British Empire. The first Audax flew in late 1931 and over 700 Audaxes were produced (including export). The Audax was similar to the Hart, though had some modifications, including a hook to pick up messages. It was armed with a single Scarff ring-mounted .303 in (7.7 mm) Lewis gun and a fixed forward-firing .303 in (7.7 mm) Vickers machine gun and was powered by a version of the Kestrel engine and had a maximum speed of . A number of variants of the Audax were produced, including the Audax India, a tropicalised version of the Audax for service in India and the Audax Singapore for service there."Hawker Audax and Hawker Hind." 211squadron.org. Retrieved: 13 July 2013.
Other air forces which also used the Audax included the Royal Canadian Air Force, the Royal Indian Air Force, the South African Air Force, the Royal Egyptian Air Force, the Royal Iraqi Air Force, the Imperial Iranian Air Force, the Straits Settlements and the Southern Rhodesian Air Force. During the Second World War the Audax saw limited service in Africa on the Kenya–Abyssinia border during the Second Italo-Ethiopian War. The Audax also saw service in Iraq, at RAF Habbaniya, west of Baghdad, after the uprising there, during the Anglo-Iraqi War. In the days leading up to that battle crews began to upgrade the Audaxes stationed there, despite having received orders forbidding such actions. They fitted some to carry bombs instead of bombs.
The Audax ended its service by 1945. A derivative of the Audax, the Hawker Hartebeest, a light bomber, was built for the South African Air Force with modifications made from the Audax. Sixty-nine of these aircraft were built, the majority in South Africa. The aircraft saw action in East Africa during clashes against Italy who occupied Abyssinia.Arthur, Max. Lost Voices of the RAF. London: Hodder & Stoughton, 20055. .
A.V. Roe built 287 Audaxes as part of the RAF expansion scheme during 1935–1937. These did not warrant an Avro type number but between 1937 and 1938, Avro built 24 modernised Audaxes for the Egyptian government, powered by Armstrong Siddeley Panther VIA radials. Acknowledging the amount of redesign work done, these were designated the Avro Type 674.
Audax I Two-seat army cooperation aircraft for the RAF, powered by a 530 hp (395 kW) Rolls-Royce Kestrel IB, or 580 hp Kestrel X piston engine. Audax (India) Tropicalised version for the RAF, used by the RAF in India. Audax (Singapore) Tropicalised version for the RAF, powered by a Rolls-Royce Kestrel V piston engine, used by the RAF in Singapore and British Malaya. Canadian Audax