Koolhoven F.K.51 429 (replica) Royal Netherlands Air Force | Rob Vogelaar
The Koolhoven F.K.51 was the winning design in a 1935 Dutch government contest for a new trainer. Designed by Frederick Koolhoven the prototype biplane trainer first flew on 25 May 1935. The aircraft was an equal-span biplane designed to use a variety of engines between 250hp (186kW) and 500hp (373kW). It was a two-seater and had a tailwheel undercarriage. The Royal Dutch air force (LVA) ordered 25 aircraft in 1936 and 1937, powered by a 270hp (201kW) Armstrong Siddeley Cheetah V radial engine. A further 29 aircraft were later bought with 350hp (261kW) Armstrong Siddeley Cheetah IX engine. The Dutch Naval Aviation Service ordered 29 aircraft each powered by a 450hp (335kW) Pratt & Whitney radials. The Royal Dutch East Indies Army bought 38 aircraft between 1936 and 1938 each powered by a 420hp (313kW) Wright Whirlwind.