Excerpt. © Reprinted by permission. All rights reserved.
The following is the text entry for the Koolhoven FK.50 airliner of the mid 1930s. It is typical of the format of the 300 or so airliner entries in the book:
Koolhoven FK.50 Country of origin: Netherlands. Powerplants: Two 420hp (313kW) Pratt & Whitney Wasp Junior T1B nine cylinder radials; two bladed propellers. Performance: Cruising speed 140kt (260km/h); range 540nm (1000km). Weights: Empty 2505kg (5522lb); max takeoff 4100kg (9038lb). Dimensions: Wing span 18.00m (59ft 1in); length 14.00m (45ft 111/4in); height 3.70m (12ft 11/2in); wing area 44.7m2 (481sq ft). Accommodation: Two crew and eight passengers. Production: 3.
History: Frederick Koolhovens company was one of the leading Dutch aircraft manufacturers in the 1920s and 1930s, its more successful products including the FK.33 ten seat twin engined commercial transport which flew with Deutsche Luft Hansa, German Aero and KLM (on its Amsterdam to Paris, London and Malm services) and the FK.42/43 3-4 seat single engined monoplanes which found some favour with private and air taxi operators. The FK.41 was built under licence in Britain by Desoutter. Military training and general purpose types were also built (and a fighter later on) as was the one-off FK.48 six passenger commercial twin of 1935. This was used by KLM on its Rotterdam-Eindhoven route. The FK.50 was of similar high wing layout but larger and capable of carrying eight passengers. Construction comprised a wooden cantilever two spar wing and fabric covered metal fuselage and tail unit. The cockpit was enclosed and six of the eight passengers sat on individual chairs with the remaining pair on a bench seat at the rear. Only three were built, all powered by Pratt & Whitney Wasp Junior radials. The first was flown in September 1935 and delivered to Switzerlands Alpar Luftverkehrs later in the year. Two others joined the Alpar fleet, one in early 1936 and the other in 1938, this aircraft differing in having twin fins and rudders in place of the original single unit. The third FK.50 also featured a modified cockpit, larger wheels, increased maximum weight and smaller engine nacelles replacing the earlier rather bulbous NACA cowlings. Sometimes referred to as the FK.50A, this aircraft was ordered to replace the second example which had crashed in September 1937. The FK.50 displayed remarkable longevity despite its tiny production run and single operator. The two remaining aircraft survived the war and were operated on a Berne-London (Croydon) service during 1946. The first aircraft was broken up in 1947 but the third survived until 1962 when it crashed in Liberia and was destroyed. Koolhoven proposed a military version as the FK.50B with more powerful Bristol Mercury radials, a crew of four, defensive guns and a 1000kg (2205lb) bomb load accommodated in a largely redesigned and deepened fuselage, but this never progressed beyond the drawing board. Photo: The third Koolhoven FK.50 with twin fins.