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.

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.

Fixed side curtains between upper and lower wing tips helped to control sideways airflow and provided additional directional (yaw) stability.

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.

[4] The D.8's water-cooled 4-cylinder, 60 hp (45 kW) Green engine directly drove a single pusher propeller, saving weight compared with the D.5's chain drive.

[5] 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.

Nieuport had obtained a licence to build the D.8 and Felix gave a series of demonstration flights in France on their behalf.

It combined the double upper wing elevons into a single surface and had very rounded rear wingtips.

[3] 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.