Koolhoven F.K.56
The Koolhoven F.K.56 was a 1930s Dutch basic training monoplane designed and built by Koolhoven.
Development
The F.K.56 was a low-wing monoplane powered by a 450 hp Wright Whirlwind R-975-E3 radial piston engine. Designed as a basic trainer, the F.K.56 had two seats in tandem for the instructor and pupil under a fully enclosed canopy. The first prototype flew on 30 June 1938 and had fixed conventional landing gear and a gull wing. The second prototype had retractable landing gear and was powered by a Armstrong Siddeley Cheetah X engine. Testing showed that the aircraft was too stable for use as a training aircraft, while the gull wing was too complex for mass production. A new, un-gulled, wing, based on that of the Koolhoven F.K.58 fighter was therefore designed, which was incorporated in a third prototype, which reverted to the Whirlwind engine and was fitted with dual controls. The third prototype flew on 5 December 1939.Ten aircraft were ordered by the Netherlands Army based on the design of the third prototype. These ten, including the re-worked first and third prototypes, were all delivered before the German invasion of the Netherlands in May 1940.
Earlier in February 1940 the Belgians had ordered twenty F.K.56 basic trainers and seven had been delivered before the rest were destroyed in an air raid on the Waalhaven factory.