De Havilland DH 51
de Havilland found he could buy 80-horsepower V-8 Renault aero-engines for the equivalent of about $6 each. He built and sold three big Renault-powered biplanes, DH 51s, but the design was too large for popularity. DH had got an engine-design-er friend of his, Frank Halford, to improve a couple of these till they were producing 120 hp for the DH 51s.
The design was developed around the 67kW R.A.F.1A engine, of which war surplus supplies were available at knockdown prices. First flown in July 1924 by Geoffrey de Havilland, the D.H.51 proved to be satisfactory, but since the engine did not have dual ignition a Certificate of Airworthiness was refused. Ten hours of airborne testing would have been required with the single-ignition RAF1A, but de Havilland decided that the cost of this was not justified.
It was decided to re-engine the D.H.51 with an Airdisco engine and this move, although conferring considerably enhanced performance, took the aircraft well outside the economic operating bracket for which it was designed. As a result, only three were built; the first two enjoyed reasonably long and active lives, being written-off in 1931 and scrapped in 1933 respectively, but the third, built in 1925 and shipped to Kenya, became the first aircraft on that country's civil register. Dismantled during the war, it survived to fly again and now, after several rebuilds, is again back in the UK, maintained by the Shuttleworth Trust at Old Warden as the oldest airworthy design of the de Havilland Aircraft Company.
Engine:1 x Airdisco inline piston, 89kW
Take-off weight: 1016 kg / 2240 lb
Empty weight: 609 kg / 1343 lb
Wingspan: 11.28 m / 37 ft 0 in
Length: 8.08 m / 26 ft 6 in
Height: 2.97 m / 9 ft 9 in
Wing area: 30.19 sq.m / 324.96 sq ft
Max. speed: 174 km/h / 108 mph
Ceiling: 4570 m / 15000 ft