Koolhoven F.K.50

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Koolhoven F.K.50
Koolhoven FK-50 photo L'Aerophile October 1938.jpg
Role Eight-passenger light transport monoplane
Manufacturer N.V.Koolhoven
Designer Frits Koolhoven
First flight 1935
Introduction 1935
Retired 1962
Primary user Swiss Alpar
Number built 3

The Koolhoven F.K.50 was a 1930s Dutch eight-passenger light transport monoplane designed and built by Koolhoven.


The F.K.50 was designed to meet a requirement from the Swiss airline Swiss Alpar for a light transport capable of operating in Switzerland. The F.K.50 was a cantilever high-wing cabin monoplane with a fixed wide track tailwheel landing gear. The fuselage was of welded steel tube construction, covered with fabric. The tailplane was of similar construction. The wings were wooden construction, covered with plywood. It was powered by two Pratt & Whitney Wasp Junior T1B engines and had a conventional single fin and rudder. The first of two aircraft first flew on the 18 September 1935 and the second flew in March 1936.[1]

A third aircraft, designated F.K.50A, was built in 1938 with a re-designed tail unit with twin vertical tail surfaces. It had a longer nose and larger mainwheels, with a higher all-up weight.[1]

Twp bomber variants, designated F.K.50B, were proposed but never built. The first was a straight conversion of the F.K.50; the second would have been powered by Template:Cnvert Bristol Mercury VIS radial engines. It would have been operated by a crew of four and carried a 2,200 pounds (1,000 kg) bomb load.[1]

Operational history[edit]

The three aircraft operated a regular service between Swiss destinations and onwards to Lyons and Marseilles and charter flights to Paris and London.



The first to be built, the aircraft entered service in October 1935. During World War II, the aircraft operated weekly between Berne and Croydon, United Kingdom. The aircraft was scrapped in 1947.[1]


The second to be built, the aircraft crashed on landing 25 kilometers from Basle Airport on 10 September 1937 with the loss of three lives.[1]



The sole F.K.50A, the aircraft was delivered in 1938. It also operated between Berne and Croydon during World War II. In 1947, it was sold to Liberian operator Maryland Flying Services and re-registered EL-ADV, operating with them until 6 July 1962 when it crashed near Monrovia.[1]


Two built, single vertical tail. The second aircraft had larger engine nacelles than the first.[1]
One built, twin tail, longer nose, bigger mainwheels, Higher all-up weight.[1]
Proposed Bomber variant, not built.[1]


  • Maryland Flying Services

Specifications (F.K.50)[edit]

Koolhoven FK-50 3-view drawing from L'Aerophile October 1938

Data from The Illustrated Encyclopedia of Aircraft (Part Work 1982-1985). Orbis Publishing. p. 2260.

General characteristics

  • Crew: 2
  • Capacity: eight passengers
  • Length: 14.30 m (46 ft 11 in)
  • Wingspan: 17.70 m (58 ft 0¾ in)
  • Gross weight: 4250 kg (9369 lb)
  • Powerplant: 2 × Pratt & Whitney Wasp Junior TB radial engines, 303 kW (406 hp) each


  • Maximum speed: 295 km/h (183 mph)



  1. ^ a b c d e f g h i "Koolhoven F.K.50". Aeroplane. No. March 2012. Cudham: Kelsey Publishing. pp. 32–33. ISSN 0143-7240.