The Koolhoven FK.55 was a classic example of an aircraft concept over-promising on what it could deliver. The FK.55 started out as a sleek, mid-engine fighter that could push over 550 km/h in level flight, but it ended as nothing more than a disappointing failure.
Design of a Koolhoven high-performance aircraft first started late in 1937. The result, finished in early 1938 was the F.K.55, a single-seat fighter of radical design with contra-rotating propellers and an engine housed behind the pilot. It had initially been proposed to do away with ailerons on the wings, and replace them with “slot-spoilers” for lateral control, however this idea was abandoned early in the project.
Of mixed metal and wood construction with wooden wings, the F.K.55’s front fuselage was made of steel tube while wood formed the tail and rear fuselage. Its 640 kW (860 hp) Lorraine Pétrel engine afforded only just enough power to take off and to stay in flight. The production version would have used the more powerful 900 kW (1,200 hp) Lorraine 12R Sterna engine but this never happened.
Koolhoven FK 55 photo L’Aerophile December 1936
Operational history
The aircraft flew for the first time on 30 June 1938. It flew for two minutes then landed. Underpowered, the FK.55 was cancelled in the same year.
Sources: Wikipedia; YouTube