Dunne D.8

J. W. Dunne's first swept biplane wing aircraft, designed to have automatic stability, dated from his employment at the Army Balloon Factory (later RAE Farnborough) during 1906–09. After leaving Farnborough, Dunne set up a private company, the Blair Atholl Aeroplane Syndicate Ltd. Its first aircraft was the Dunne D.5. When this crashed in 1911 it was rebuilt as the first D.8. The two models shared similar wings and the same engine, but the D.8 had a single pusher propeller instead of the chain-driven pair of the D.5. Their fuselages and undercarriages were also different. The D.8 was a tailless four bay unstaggered biplane with constant chord wings swept at 32°. The wings were built up around two spruce spars, the forward one forming the leading edge. To help achieve stability the incidence and interplane gap decreased outboard, the former becoming negative. This washout on tips well behind the centre of gravity provided longitudinal stability in the same way as a conventional tailplane set at lower incidence than the wings. Camber increased outwards. Simple, near parallel, pairs of interplane struts joined the spars. Fixed side curtains between upper and lower wing tips helped to control sideways airflow and provided additional directional (yaw) stability. Wing tip elevons were used for control, operated by a pair of levers, one either side of the pilot. The D.8 initially used just one pair of elevons, mounted on the upper wing, a rectangular cutout in the side curtains allowing for their movement as on the D.5. The D.8's water-cooled 4-cylinder, Green engine directly drove a single pusher propeller, saving weight compared with the D.5's chain drive. The Green engine was later replaced by an 7-cylinder Gnome rotary engine. This engine also powered the second aircraft, which was a two-seater with the pilot placed just ahead of the wing leading edge and the passenger (who had dual control) at the trailing edge. There were now control surfaces on both upper and lower wings, the side curtains having the rear corners cut off at an angle to allow them to move. Each of the upper wings carried a pair of elevons, nearly doubling the control surface area. ==History==

The maiden flight of the first D.8, fitted with a Green engine, took place at Eastchurch in June 1912. It was present at the Larkhill Military trial in August 1912, though it did not take part in the competition. In 1913 the D.8 was fitted with an 80 hp Gnome engine which greatly improved performance and reliability. The fuselage was modified and built around steel tubes rather than wood. The interplane struts were streamlined steel tubes. It also had a simplified undercarriage. Dunne obtained a War Office order for two D.8s, though one was cancelled because of late delivery. The other was delivered to Farnborough on 3 March 1914, where it was given the RFC number 366. It made several flights on 11 March piloted by N. S. Percival, who had flown the first D.8 many times at Eastchurch and was now an RFC officer. The general judgement was that in the search for balance between stability and controllability, the Dunne design overemphasised the former. ==Derived types==

• Nieuport-Dunne Derived from the D.8 and built under license by the French Nieuport company and exhibited at the Paris Salon in 1913. • Burgess-Dunne The Burgess Company based in Marblehead, Mass, USA gained the US manufacturing rights and built a series of aircraft derived from the D.8. They became known as Burgess-Dunne machines and were mostly single-float planes. The first flew in March 1914, piloted by Clifford Webster. Apart from wingtip floats the wings were identical to those of the D8, but the fuselage was revised with a distinct nacelle containing a more enclosed cockpit. The aircraft was a single-seater, with the heavier Curtiss OXX2 water-cooled engine moved forwards, shortening the fuselage and with its radiator placed between engine and pilot. The single float was long, shallow and flat bottomed viewed from in front, with a single step. The prototype behaved well in the air and on the water. The second machine was very similar to the first, but room was made for a second seat by replacing the single fuselage mounted radiator with a pair fixed to the rear float struts. The third machine, another two-seater but powered by a Salmson M-9 radial providing , was delivered to the US Signal Corps in either 1914 or 1915. Two were also delivered to the US Navy as type AH-7, fitted with a Curtiss engine :The Burgess-Dunne types were largely built by Barry D. MacKeracher. • D.10 A development built around 1912 with a modified wing, which proved a failure and was converted back to a D.8. ==Specifications (second aircraft)==