11/15/2022. Remarks by Johan Visschedijk: "Designed by the Dutchman Frederik 'Frits' Koolhoven, the F.K.9 two-seat fighter-reconnaissance quadruplane was built by Sir W.G. Armstrong Whitworth & Co. Ltd. as a private venture and was initially flown in the summer of 1916. Initial trials dictated a number of modifications, new wings with enlarged ailerons, an enlarged fin, a redesigned engine cowling and increased undercarriage track being introduced.

Pictured in this form above, the F.K.9 was powered by a 110 hp Clerget 9Z rotary engine, and with a designed armament of one fixed 0.303 in (7.7 mm) Vickers gun and one free Lewis gun of the same caliber, the F.K.9 was officially tested in November-December 1916 at the Central Flying School, and a production contract for 50 examples of an improved version, the F.K.10, was awarded."

Span: 27 ft 9 in (8.46 m)
Length: 25 ft 10 in (7.87 m)
Height: 11 ft 4 in (3.45 m)
Wing area: 355 sq.ft (32.98 sq.m)
Empty weight: 1,226 lb (556 kg)
Loaded weight: 2,038 lb (924 kg)
Max speed: 100 mph (161 kmh) at sea level
Max speed: 94 mph (151 kmh) at 6,500 ft (1,980 m)
Max speed: 87 mph (140 kmh) at l0,000 ft (3,050 m)
Climb: to 6,000 ft (1,829 m) 12 min 30 sec
Climb: to 10,000 ft (3,048 m) 25 min
Service ceiling: 13,000 ft (3,962 m)
Endurance: 3 hr