Handley Page HP.50 Heyford
The Heyford was the RAFs last biplane heavy bomber, an unusual type with the fuselage attached to the undersurface of the upper wing and the centre section of the lower wing thickened for internal carriage of the bombload. The long main landing gear units were attached at their upper ends to the engine nacelles, while the wheel spats were attached at their rear to the lower-wing centre section. The Heyford prototype flew in June 1930, and production of 124 aircraft up to July 1936 comprised 38 Mk Is and Mk lAs, 16 Mk Is with de-rated 391.2kW Rolls-Royce Kestrel VI engines, and Mk IIs and 70 Mk IIIs with fully rated 428.5kW Kestrel VI engines and four-blade propellers.
The Heyford was an equal-span biplane with staggered wings: the upper wing centre-section rested on top of the fuselage, while the lower was positioned well below the fuselage, connected to the under-fuselage by N-type struts. The inner interplane struts supported the engine mountings.
Bombs of various sizes were carried inside the thickened centre-section of the lower wing, each bomb being carried in a separate cell closed by spring doors. The fixed landing gear comprised two large wheels faired into the lower wing.
The nose and dorsal gun positions of the Heyford were equipped with Scarff mountings for their 0.303-in (7,7-mm) Lewis or Vickers guns.
Of the three versions of the Heyford, the Mks I, II and III, the visible differences are primarily in detail, including such items as alternative wheel pants, three- and four-bladed propellers, and varying radiator intake designs. The main bomb load was housed in the thickened centre section of the lower wing. Additional bombs were carried on external racks.
A total of 124 Heyfords were built, made up of 38 Mk I and IA, 1 intermediate Mk IA/II, 16 Mk II and 71 Mk III - including changes made from the original production orders.
The type entered service in November 1933 with No 99 Sqn at Upper Heyford, and equipped a total of 11 squadrons before being phased out from 1937, removed from first-line service in 1939 and finally declared obsolete in July 1941.
Heyford Mk IA
Engines: 2 x Rolls-Royce Kestrel IIIS, 429kW/ 575 hp
Span: 22.86m / 75 ft
Length: 17.68m / 58 ft
Height: 5.3 m / 17 ft 5 in
Wing area: 136.6 sq.m / 1470.35 sq ft
Empty weight: 4580 kg / 10097 lb
Max T/O weight: 7666 kg / 16,900 lb
Max. speed: 229 km/h / 142 mph at 13,000 ft
Ceiling: 6400 m / 21000 ft
Range: 1480 km / 920 miles with 726-kg (1,600-lb) bombload
Armament: 3 x 7.7-mm (0.303-in) mg, 1588 kg (3,500 lb) bombs