Conceived in 1916 as a replacement for the F.E.2b in the fighter-reconnaissance role, the F.E.9 was of similar pusher configuration and therefore already obsolescent by the time it appeared in 1917. Emphasis was placed in the design upon providing the gunner with a good field of fire and the pilot a good all-round view. To this end, the nacelle was located close beneath the upper wing and was carried on struts above the shorter-span lower wing. The large overhang of the upper wing brought the F.E.9 almost into the sesquiplane category, and called for bracing wires from triangular kingposts above the interplane struts of the single-bay cellule. A cruciform tail unit was carried on four slender booms, as on the F.E.2, and the Vee-strutted undercarriage incorporated oleo legs. Construction was largely of wood, but pairs of steel tube N-struts linked the nacelle to the upper and lower wings. Power was provided by a 200hp Hispano-Suiza eight-cylinder V-type water-cooled engine and the planned armament comprised two 7.7mm Lewis guns on pillar mounts, ahead of and behind the front cockpit, and both fired by the observer - the latter rearwards over the pilot's head and the top wing. Installation of a third gun, on the side of the fuselage for use by the pilot, was planned.
Authority was given by the War Office for construction of three prototypes and a production batch of 24 in October 1916, and testing began in April 1917. Difficulties with control in flight and various modifications made in attempts to eradicate them delayed production, and in the event only three F.E.9s were built.
Testing of the prototypes continued, in the course of which two-bay wings were tried on the second aircraft, which was also flown for a time by No 78 Home Defence Squadron, RFC.
Engine: 1 x 200-h.p. Hispano-Suiza
Span: 11.5 m (37 ft 9.5in)
Length: 8.6 m (28 ft 3 in)
Height: 2.97 m / 10 ft 9 in
Wing area: 33.91 sq.m / 365.00 sq ft
Gross weight: 1125 kg (2480 lb)
Maximum speed: 169 kph (105 mph)
Ceiling: 4725 m / 15500 ft
Royal Aircraft Factory F.E.9