In 1938, the French Air Ministry noticed that domestic aircraft manufacturing capacity could not re-equip the ''
Armée de l'Air'' with modern fighters quickly enough. In order to win some contracts with the French, the Dutch manufacturer
Koolhoven quickly designed a single-seat fighter that would use French-supplied engines and other components. The Koolhoven fighter was intended primarily for fighter units based in the colony of
French Indochina. Design work on the new fighter began early in 1938.
Erich Schatzki, the designer of the
Fokker D.XXI, joined Koolhoven from Fokker in March 1938, but despite claims that Schatzki designed the F.K.58 as well, design work was well underway (60% complete) by the time Schatzki joined, although he was involved in the final design. The prototype, powered by a
Hispano-Suiza 14AA radial engine, flew for the first time on 17 July 1938. The structure of the fuselage consisted of welded steel tubing covered with sheet metal (front part) and
fabric (aft); the wing had 2 wooden box spar members and ribs, with a
bakelite stressed skin covering. Aerodynamically balanced split flaps on the wing trailing edges ensure a lower landing speed. The oleo-pneumatic undercarriage retracted inwards with the wheels housed in the lower fuselage faired into the lower engine cowling by small doors. The empennage is built up from wood and control surfaces are metal framed with fabric covering. In January 1939, the ''Armée de l'Air'' placed an order for 50 aircraft, to be powered by
Gnome-Rhône 14N engines, although the first four aircraft, which were already under construction, were completed with the Hispano-Suiza. When the Dutch order for FK.58s was placed, it was realised that Koolhoven did not have sufficient production capacity to support both orders, and the final 10 FK.58s of the French order were subcontracted to the Belgian company
SABCA. Due to the unavailability of Gnome-Rhône engines and French instruments, just 17 aircraft – six F.K.58s and 11 F.K.58As – were completed at the Koolhoven works, with Dutch-supplied engines and instruments – and delivered to the ''
Armée de l'Air''. The remaining 23 aircraft being built in the Netherlands, which were at different stages of completion, were transferred to
Nevers, where the aircraft were to be finished by personnel employed by Koolhoven. However, only one F.K.58 was completed before the factory was captured by the Germans, together with the remaining airframes. The ten aircraft being built by SABCA were complete with the exception of their engines, which had not been delivered by France, when
Germany invaded Belgium on 10 May 1940, and were placed on a train for delivery to France, but all ten aircraft were destroyed when the train was attacked by German aircraft. On 2 July 1939, the Dutch government placed an order on behalf of the
Luchtvaart Afdeling (Netherlands Army Aviation Corps) for 36 F.K.58s, to be powered by
Bristol Taurus engines. However, as the British government restricted exports of the Taurus, alternative engines were proposed, including the
Rolls-Royce Merlin and the
Daimler-Benz DB 600. Tests were carried out using the DB 600, but hopes to obtain a supply of the German engine via Switzerland failed and in the absence of better alternatives it was decided to use Dutch stocks of the
Bristol Mercury VIII (as used by the Dutch
Fokker D.21 and
Fokker G.1). The lower output of the Mercury, relative to the Taurus, would have reduced speed, with a maximum speed of at and a cruise speed of estimated. The F.K.58s comprising the Dutch order were in various stages of construction when they were destroyed by a German
air raid on the Koolhoven factory in May 1940. Had the ''Armée de l'Air'' received its full order of 50 aircraft, before for the
Battle of France, it is unlikely that they would have changed the outcome. Even though Koolhoven credited the F.K.58 prototype with high performance, French test centers recorded that the series aircraft were slower than what was claimed by the manufacturer. Additionally, the manoeuvrability was found to be poor by the French pilots. ==Operational history==