de Havilland DH.34
The de Havilland DH.34 was a single-engined biplane airliner built by the de Havilland Aircraft Company, first flown on 26 March 1922. It was designed around its operators' requirements: a Napier Lion engine, wooden two-bay wings and a cabin for nine passengers between them. Daimler Airway put it into service on the Croydon–Paris route a week after the first flight, and it was flown intensively by Daimler, Instone Air Line and, from 1924, Imperial Airways. Eleven were built, including one for the Soviet airline Dobrolyot. Six were lost in accidents in four years of service, and Imperial's fatal Purley crash of December 1924 prompted Britain's first public inquiry into a civil air accident. Imperial retired the type in March 1926, and no example survives.
Why It Mattered
The DH.34 was built for the first generation of British airline services, ordered in an initial batch of nine for operators who had concluded from their DH.18 work that air travel's economics demanded a more efficient aircraft. Century of Flight calls it de Havilland's most successful type of the early post-war years. Its Purley crash of 24 December 1924, though, gave the type a grimmer place in history: the Imperial Airways aircraft's loss, in which all eight people on board died, brought about Britain's first public inquiry into a civil aviation accident.
Design Notes
The DH.34 began as the DH.32, a biplane of similar capacity to the eight-passenger DH.18 but with a more economical Rolls-Royce Eagle engine; when operators were consulted, work on the DH.29 and the DH.32 stopped, and the airliner took a fuselage like the DH.29's, seating nine passengers. Construction was wooden: a plywood-clad fuselage and two-bay, fabric-covered wooden wings, the two pilots in an open cockpit ahead of the wing, the cabin between the wings. The single 450 hp Napier Lion was chosen because Instone and Daimler Hire already operated Lion-powered DH.18s, and it was fitted with an inertia starter, so the propeller never had to be swung by hand. Unusually, the cabin could carry a spare engine across its rear, loaded through a door shaped for the purpose; operators did not carry one routinely, but used the arrangement to fly an engine out to a stranded aircraft. Its weakness was the high stalling speed of 63 mph, blamed for a fatal crash in 1923; extensions added to the upper wings increased the span, and aircraft with the revised wing were designated DH.34B.
Operational History
The prototype flew on 26 March 1922, the first production aircraft was delivered to Daimler on 31 March, and Daimler put the type into service on its Croydon–Paris route on 2 April 1922. Daimler eventually operated six DH.34s, four of them leased from the Air Council; Instone Air Line operated four more, all leased; and one aircraft was built to the order of Dobrolyot, the Soviet airline. The fleet was worked hard on the cross-Channel routes, logging some 8,000 hours in its first nine months, with the second Daimler aircraft passing 100,000 miles without an overhaul. Beyond Paris, Daimler flew a daily Croydon–Manchester schedule from October 1922 and added routes from Croydon to Amsterdam, Hanover and Berlin in 1923. The accident record was heavy: six DH.34s were lost during the four years of operation, several fatally, including Daimler's aircraft which crashed at Ivinghoe in September 1923, killing all five on board. When Imperial Airways was created on 1 April 1924, merging Daimler, Instone and two other British airlines, the DH.34s it inherited stayed in service until March 1926, when it retired the type as it gave up single-engined aircraft in favour of multi-engined ones.
Afterlife
No DH.34 survives today; the British Aircraft Directory knows of none preserved in a British museum, and the last four aircraft in service in Britain were scrapped in 1926. The engines outlasted the airframes by a little: once the type was retired, its Napier Lions were removed and put to work in Imperial's fleet of Handley Page W.10s. What the type left behind was a precedent rather than an aeroplane: the public inquiry after Purley was the first held into a civil aviation accident in the United Kingdom, and Croydon Airport was expanded afterwards, absorbing most of Beddington Aerodrome.