The Handley Page Heyford was a twin-engine biplane bomber designed and produced by the British aircraft manufacturer Handley Page. It holds the distinction of being the last biplane heavy bomber to be operated by the Royal Air Force (RAF). The Heyford was developed in response to Specification B.19/27 for a new heavy night bomber. Much of the design can be attributed to the work of George Volkert, Handley Page's lead designer. Unlike the company's preceding aircraft, the Heyford comprised metal construction instead of wood; it also had an unorthodox arrangement wherein the fuselage was joined to the upper wing rather than the lower one, which gave the aircraft a relatively nose-high orientation while on the ground. Considerable revision of the proposal occurred even after its submission, which was recognised as the Air Ministry's preferred option. A sole prototype, designated Handley Page HP.38, was produced, performing its maiden flight on 12 June 1930 and commencing service trials shortly thereafter. During November 1933, the first Heyfords entered service, being initially flown by No. 99 Squadron at RAF Upper Heyford; before the end of 1936, Bomber Command had a total of nine operational squadrons equipped with the Heyford. Despite forming a considerable portion of the RAF's bomber fleet during the mid-1930s, the Heyford had a relatively short service life as it was rapidly eclipsed by a new generation of monoplane bombers, such as the Armstrong Whitworth Whitley and the Vickers Wellington. The replacement of the type had commenced during 1937 as more capable bombers were introduced during a major rearmament push for the RAF; the Heyford was formally declared obsolete in July 1939, barely two months prior to the outbreak of the Second World War. Despite this, the type continued to be used in secondary roles, being used as glider tugs, experimental aircraft, and trainers, into the 1940s. The Handley Page Heyford was a twin-engine biplane bomber designed for nighttime operations. It featured a relatively novel configuration in which the fuselage was attached to the upper wing – somewhat resembling the 1914-designed German Gotha G.I. This arrangement provided a favourable field of fire for its defensive weapons, which were positioned on the nose and dorsal sections, along with the ventral retractable "dustbin" turret, each of which were armed with a single .303 in (7.7 mm) Lewis light machine gun. The wings of the Heyford were equal in both span and dihedral. The lower wing featured a thickened center section to accommodate the aircraft's single bomb bay. Automated wing tip slots improved the take-off performance considerably. Propulsion consisted of a pair of Rolls-Royce Kestrel engines, which each drove a set of fixed-pitch propellers. The Heyford featured a mixed construction; its wings were covered by fabric while the structure comprised a twin-bay metal frame, while the fuselage consisted of an aluminium monocoque forward section with a fabric-covered frame to the rear. It was operated by a crew of four, typically consisting of a pilot, a bomb aimer/navigator/gunner, a radio operator and a dorsal/ventral gunner. Open positions were provided for the pilot and both the nose and dorsal gunners. The Heyford was furnished with a fixed undercarriage that consisted of large, spat-covered wheels that were mounted at the leading edge of the lower wing. This arrangement enabled ground crews to safely attach bombs even as the engines were still running, but also had the consequence of positioning the pilot roughly 17 ft (5 m) above the ground. Another benefit of this nose-high angle was a relatively short and speedy take-off run. Variants H.P.38 Single prototype powered by two Rolls-Royce F.XIV engines and flown in June 1930. H.P.50 Heyford I Powered by 575 hp (429 kW) Rolls-Royce Kestrel III engines: 15 built, serial numbers K3489-K3902 (last aircraft built as Mk.II prototype). H.P.50 Heyford IA Engine support changes, power-driven generator, four-blade propellers: 23 built, serial numbers K4021-K4043. H.P.50 Heyford II Powered by 640 hp (480 kW) Kestrel IV engines: 16 built, serial numbers K4863-K4878. H.P.50 Heyford III Supercharged 695 hp (518 kW) Kestrel VI engines: 70 built in two batches, serial numbers K5180-K5199 and K6857-K6906. For a total of 125 (including the prototype, J9130)
