Dutch single-seat fighter aircraft. The NV Koolhoven Vliegtuigen of Waalhaven, near Rotterdam, built the prototype F.K.58 within two months of completion of the design, and it flew for the first time on July 17, 1938, bearing the civil registration PH-ATO. Designed by Dr Erich Schatzki, formerly of Fokker, to meet a French requirement, the F.K.58 had plywood-covered wooden wings and fixed tail surfaces; a metal- and fabric-covered steel-tube fuselage; and metal -framed fabric-covered wing and tail control surfaces. A total of 450 litres (99 Imperial gallons) of fuel was carried internally, and the 1080-hp Hispano-Suiza 14Aa 14-cylinder two-row radial engine gave it a top speed of 483 km/h (300 mph).
This prototype was demonstrated to the French authorities at the Centre d'Essais du Materiel Aeden at Villacoublay on October 10, 1938, and an order for 50 aircraft followed in January 1939. Intended for use by the Armee de l'Air in French Indo-China, they were to be powered by, 1030-hp Gnome-Rhone 14N39 14-cylinder radials and designated F.K.58A. Deliveries began in mid-June 1939, and 17 were delivered within the next three months, of which the first four retained the Hispano-Suiza powerplant, the other 13 being F.K.58As. However, due to inadequate production facilities, the small Koolhoven factory was not able to complete the French order. The construction of 10 French F.K.58As was sub-contracted to SABCA in Belgium, but although the airframes had been completed when Germany invaded that country in 1940, their Gnome-Rhone engines had not been delivered from France.
Following the first flight of a second Hispano-powered prototype (PH-AVA) on February 14, 1939, the Netherlands government in the following month ordered 36 F.K.58s, to be powered by 1080-hp Bristol Taurus III engines; but here again engine supply problems intervened, and Koolhoven was unable to complete any of the order for the Luchtvaartafdeling (Dutch air force). The production line and the second prototype were destroyed in a Luftwaffe air attack, the first prototype having already been lost in a crash in January 1940.
Thus the only operational F.K.58s were those supplied to the Armee de l'Air. Armed with four 7.5-mm (0.29-in) FN-Browning machine-guns, in two underwing fairings out-board of the main undercarriage legs, most of them were deployed by patrouilles de protection in May 1940, in defence of such towns as Aulnat, Caen, Clermont-Ferrand, Cognac and La Rochelle. For a short time, they were among the Luftwaffe's most cosmopolitan opponents, for these Dutch fighters with French engines and Belgian guns were often flown by Polish pilots.
Span: 10.97 m (36 ft)
Length: 8.68 m (28 ft 51 in)
Gross weight: 2750 kg (6065 lb)
Maximum speed: 475 km/h (295 mph).