Koolhoven F.K.51
in Nederlandse Militaire Dienst
Fred Bachofner
Review

Authors: Arnold van Gerwen, Rob Hamann, Luuk Boerman  
Publisher: Dutch Profile
ISBN: 9789490092511
Soft cover – Dutch/Engels language
publiced: 2024
Pages: 47
Price: 17,95 euro.


More or less a relatively unknown aircraft type that has more than proven its worth. It was a Military biplane designed as a trainer and scout. Specifications came from the LvA who were looking for a new transitional training aircraft in the thirties. Koolhoven (after the FK-49) finally received requests from the LvA and not only competitor Fokker. Frits Koolhoven got to work and looked closely at the performance of the Avro 626. The experience with the FK-46 and the construction methods were used in the design.  

The first prototype of the FK-51 flew in May 1935 from Waalhaven airfield where Frits Koolhoven's factory was located and was equipped with a Cheetah V engine with 275 hp. The aircraft had a fuselage of tubes covered with plywood and a wing of wood with plywood instead of the usual linen. After some tests, the LvA and also the MLD were enthusiastic, but they wanted some adjustments. The LA-KNIL was also interested, but for the tropics they had other wishes. Koolhoven therefore had to redesign quite a bit with other engine options. The LA-KNIL aircraft got a Wasp Junior engine and also a somewhat larger wing, but that did not have much effect on the performance.  

"The Koolhoven" as the aircraft is usually called in popular speech. The subject of this Dutch Profile, F.K.51 Koolhoven. There have been more Koolhoven types, but this was "THE". Frits Koolhoven developed the aircraft in record time in 1935 and with success.

The authors describe the history of this relatively unknown Koolhoven, in contrast to the Fokkers. The written word is supplemented with six pages of colour profiles by Luuk Boerman and more than fifty black and white photos and 1 single colour photo!
Briefly they also discuss the aircraft that were delivered to Spain via France and Switzerland (because of the arms embargo during the Spanish Civil War). The whole is concluded with a description of the life course of all Dutch Koolhovens.

Conclusion
A publication about a relatively unknown aircraft type, but has more than proven its value, especially in the Dutch East Indies.
This publication certainly belongs in the Dutch Profile series and it is certainly interesting to read about this piece of aviation history and to know that it was not only Fokker.

Thanks to Dutch Profile for making it available for a review.