In early 1916, the British War Office drew up a specification for a multi-seat escort fighter to be powered by one of the new Rolls-Royce Eagle engines, with an endurance of at least seven hours, intended to protect formations of bombers from German fighters such as the Fokker E.I, with an additional role of destroying enemy airships.
Orders were placed for prototypes from Armstrong Whitworth, Sopwith and Vickers, all of which were of unconventional design owing to the need to give their gunners a good field of fire in the absence of an effective synchronisation gear to allow guns to be fired safely though the propeller disc.
The gunners were housed in two long nacelles mounted on top of the middle wing, allowing them to be seated ahead of the propeller disc, with the pilot's cockpit situated behind the wings in the slim central fuselage, giving a poor view.
[9][10] This design never flew, with the head of Armstrong Whitworth's Aircraft department, I. Fairbairn-Crawford, forbidding test flights.
[12] Four examples of the F.K.6 were ordered in April 1916,[12] two of which were intended for the Royal Naval Air Service,[5] but only one was built, this demonstrating poor performance when tested.