Armstrong Whitworth FK.10
The Armstrong Whitworth F.K.10 was a British First World War quadruplane fighter developed as part of a brief period of experimental interest in multi-wing aircraft. Designed by the Dutch-born engineer Frederick Koolhoven, the F.K.10 aimed to improve lift and manoeuvrability by stacking four narrow-chord wings in a compact arrangement. Although the concept appeared promising on paper, it emerged late in 1916, just as biplane fighters were proving dominant in both performance and practicality.
Constructed primarily of wood and fabric, the F.K.10 featured a single-bay wing structure with balanced ailerons on the middle wings, a neatly faired fuselage, and a two-seat configuration intended for reconnaissance and fighting. Power came from a 130 hp Clerget rotary engine, which was common among Allied aircraft of the period. Despite the engine’s reliability, the aircraft struggled to match the speed and climb of contemporary fighters such as the Sopwith 1½ Strutter.
The British government placed an order for 50 aircraft, but testing quickly revealed limitations. The additional wings produced more drag than anticipated, reducing performance, while the expected advantages in lift and agility did not materialise. As aviation understanding progressed, designers recognised that the aerodynamic penalties of four-wing layouts outweighed any theoretical benefits. Only five were built of the RFC order, with a further three built for the RNAS. They were not used operationally and the design was not developed further.
