|Role||Basic training monoplane|
|First flight||30 June 1938|
|Primary user||Netherlands Army|
The F.K.56 was a low-wing monoplane powered by a 450 hp (336 kW) Wright Whirlind 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 an inverted gull wing. The second prototype had retractable landing gear while a third prototype was fitted with a straight wing and dual controls.
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.
Data from 
- Crew: 2
- Length: 7.85 m (25 ft 9 in)
- Wingspan: 11.50 m (37 ft 9 in)
- Height: 2.30 m (7 ft 7 in)
- Wing area: 20 m2 (220 sq ft)
- Empty weight: 1,058 kg (2,332 lb)
- Max takeoff weight: 1,600 kg (3,527 lb)
- Powerplant: 1 × Wright Whirlind R-975-E3 Radial piston engine, 336 kW (451 hp)
- Maximum speed: 300 km/h (186 mph; 162 kn) at a height of 500m (1640 ft)
- Range: 800 km (497 mi; 432 nmi)
- Service ceiling: 7,300 m (23,950 ft)
|Wikimedia Commons has media related to Koolhoven Aircraft.|
- Orbus 1985, p. 2272
- The Illustrated Encyclopedia of Aircraft (Part Work 1982-1985). Orbis Publishing.