02/28/2010. Remarks by Johan Visschedijk: "In 1915, Frederik Koolhoven, the chief designer of Sir W.G. Armstrong Whitworth & Co. Ltd., initiated work on a highly unorthodox three-seat triplane powered by a 250 hp Rolls-Royce twelve-cylinder liquid-cooled engine. It was intended to accommodate two gunners each with a 0.303 in (7.7 mm) machine gun in shallow nacelles mounted above the center wing on each side of the fuselage, the gunners being seated ahead of the propeller plane of the tractor engine.

Although a prototype was completed and allegedly designated F.K.5, this was never flown, being extensively damaged as a result of a ground loop during its first take off attempt. The design was extensively revised early in 1916 to meet an RFC requirement for an airship interceptor and long-range escort fighter. The revised design is believed to have been designated F.K.6 (and certainly not F.K.12 as has sometimes been stated) and four examples were ordered, two of these being intended for the RNAS.

In the event, only one F.K.6 was built. The gunners' nacelles were under-slung on the central main wing, armament remained two 0.303 in (7.7 mm) Lewis guns and the 250 hp Rolls-Royce engine was retained. It is believed that relatively limited flight testing was undertaken."

Span: 62 ft 0 in (18.89 m)
Length: 37 ft 0.75 in (11.29 m)
Height: 17 ft 0 in (5.18 m)