|D.1 and D.4|
|Manufacturer||Army Balloon Factory|
|Designer||John William Dunne|
|First flight||July 1907|
The Dunne D.1, was an experimental tailless aircraft built in the United Kingdom in 1907. It comprised a main unit which could be flown as a glider, to which a chassis unit with power train could be added. The glider achieved a short flight in 1907. The D.1 was later rebuilt as the powered D.4, which achieved short hops in 1908.
Design and development
Designed by Lieutenant J.W. Dunne at the Army Balloon Factory, Farnborough, the Dunne D.1 was a biplane glider whose design embodied Dunne's ideas about inherent stability in an aircraft, which he had developed during several years of experimentation with models. It was a tailless biplane with swept wings whose angle of incidence decreased towards the tips, a feature known as washout.
The wings were constructed as a self-contained glider of wire-braced wooden construction, designated the D.1-A. Its undercarriage consisted of a pair of skids underneath the lower wing. Take-off was achieved by launching the glider from a wheeled platform.
A separate, wheeled chassis unit incorporated twin Buchet engines on a common drive shaft, together with twin counter-rotating pusher propellers belt-driven from the shaft. The arrangement delivered only around 15 hp (11 kW) of power. When mounted on this platform the craft was designated the D.1-B. It took off from a flat guide track, reminiscent of the system used by the Wright brothers for some of their early flights.
The D.1 was assembled in great secrecy at the Army Balloon Factory. To maintain security for the flight trials, the craft was dismantled, taken to Blair Atholl in Scotland by a team of Royal Engineers in July 1907 and there reassembled. It was initially flown as a glider and the power unit was sent up later.
Piloted by the Commander of the Balloon Factory Colonel J. E. Capper, its only flight lasted 8 seconds and ended in a crash in which Capper was slightly injured. The flight had however convincingly demonstrated the automatic stability which was it chief design goal.
It was repaired on site and the powered chassis unit, now arrived from Farnborough, was fitted. During a test in October, the aircraft slipped sideways off the launching ramp and was severely damaged.
Over the winter of 1907-08 the aircraft was repaired and modified to become the D.4. The wing from the D.1 was modified with more conventional elevons, hinged parallel to the trailing edge. It was mounted direct to a new steel-frame chassis. A single 25 hp (19 kW) R.E.P. engine now drove the pair of pusher propellers. The framework projected forward of the wing and was partly covered in fabric, forming a streamlined nacelle to house the pilot. Vertical end plate fins were added between the ends of the biplane wings. In 1908 trials were again made at Blair Atholl, with Lt Lancelot D.L Gibbs at the controls. Engine power was not sufficient for the aircraft to take off, but several short hops were achieved during November and December 1908.
- Walker, 1974.
- Lacey, G. W. B. "History and Secrecy" (letter), Flight, 17 June 1955, p.852.
- Lewis, P.; British Aircraft 1806-1914. London: Putnam, 1962
- Taylor, Michael J. H.; Jane's Encyclopedia of Aviation. London: Studio Editions, 1989, pp. 347. ISBN 978-0-517-10316-6.
- Percy Walker, Early Aviation at Farnborough, Volume 2: The First Aeroplanes, Macdonald, 1974.
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