Design and Development
The Heyford was built to meet Air Ministry specification B.19/27 for a heavy night bomber to replace the Vickers Virginia, which required a twin-engined aircraft capable of carrying 1,546 lb (700 kg) of bombs and flying 920 miles at 115 mph (185 km/h). The specification resulted in a large number of proposals being submitted by the British aircraft industry, with designs by Fairey (the Fairey Hendon) and Vickers (the Type 150 and Type 163) being built as well as Handley Page's design. The prototype, the Handley Page HP.38, was designed by Handley Page's lead designer G. R. Volkert and first flew on 12 June 1930 at Handley Page's factory at Radlett, powered by two 525 hp (390 kW) Rolls-Royce Kestrel II engines driving two-blade propellers.
The aircraft was of mixed construction having fabric-covered, two-bay metal-frame wings, while the fuselage had an aluminium monocoque forward section with a fabric-covered frame to the rear, It had a crew of four, 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 had a novel configuration, with the fuselage attached to the upper wing and the bomb bay in the thickened centre lower wing. This provided a good defensive field of fire for the nose and dorsal guns as well as the ventral retractable "dustbin" turret, each equipped with a single .303 in (7.7 mm) Lewis Gun. The fixed undercarriage consisted of large, spat-covered wheels. The design allowed ground crews to safely attach bombs while the engines were running, but the result was that the pilot was some 17 ft (5 m) off the ground.
The HP.38 proved successful during service trials at Martlesham Heath and with No. 10 Squadron RAF and was chosen as the winner of the B19/27 competition, being ordered as the HP.50 Heyford. Production Heyford Is were fitted with 575 hp (429 kW) Kestrel III engines and retained the two-blade propellers, while the IAs had four-blade propellers. Engine variations marked the main Mk II and III differences; the former being equipped with 640 hp (480 kW) Kestrel IVs, supercharged to 695 hp (518 kW) in the Heyford III.
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