The Hawker Hart was a British two-seater biplane light bomber aircraft of 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. Beyond Britain, the Hart would be operated by a number of 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 160 mph (258 km/h). Designs were tendered by Hawker, Avro and de Havilland. 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.
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 .303 in (7.7 mm) 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. Up to 520 pounds (240 kg) of bombs could be carried under the aircraft's wings.
J9052, the prototype Hart, 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 176 mph (283 km/h) in level flight and 282 miles per hour (454 km/h) in a vertical dive. 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.[N 1] 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.
The production Hart day bomber had a 525 hp (390 kW) Rolls-Royce Kestrel IB 12-cylinder V-type engine; a speed of 184 mph (296 km/h) and a range of 470 mi (757 km). It was faster than most contemporary fighters, an astonishing achievement considering it was a light bomber and had 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.
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 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. 1004 Harts were produced.
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.
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.
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 memoirs how his squadron developed dive-bombing techniques in the mid-1930s for their B4s.[N 2] 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.