The Koolhoven F.K.51 was a 1930s

Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () Dutch may also refer to: Places * Dutch, West Virginia, a community in the United States * Pennsylvania Dutch Country People E ...

two-seat basic training biplane built by the Koolhoven Company.

Design and development

The Koolhoven F.K.51 was the winning design in a 1935 Dutch government contest for a new trainer. Designed by

Frederick Koolhoven Frederick (Frits) Koolhoven (11 January 1886 – 1 July 1946) was an aircraft designer in Britain and his native Netherlands. Koolhoven was born in Bloemendaal, Netherlands. After training as an engineer in Liège and Antwerp, he worked from 19 ...

the prototype biplane trainer first flew on 25 May 1935. The aircraft was an equal-span biplane designed to use a variety of engines of . It was a two-seater and had a fixed tailwheel undercarriage. The Royal Netherlands Air Force (LVA) ordered 25 aircraft in 1936 and 1937, powered by a Armstrong Siddeley Cheetah V radial engine. A further 29 aircraft were later ordered with

Armstrong Siddeley Cheetah IX The Armstrong Siddeley Cheetah is a seven-cylinder British air-cooled aircraft radial engine of 834 cu in (13.65 L) capacity introduced in 1935 and produced until 1948. Early variants of the Cheetah were initially known as the Lynx Major.Lums ...

engine. The

Dutch Naval Aviation Service The Netherlands Naval Aviation Service ( nl, Marineluchtvaartdienst, shortened to MLD) is the naval aviation branch of the Royal Netherlands Navy. History World War I Although the MLD was formed in 1914, with the building of a seaplane base ...

ordered 29 aircraft each powered by a

Pratt & Whitney Pratt & Whitney is an American aerospace manufacturer with global service operations. It is a subsidiary of Raytheon Technologies. Pratt & Whitney's aircraft engines are widely used in both civil aviation (especially airlines) and military aviat ...

radials. The

Royal Dutch East Indies Army The Royal Netherlands East Indies Army ( nl, Koninklijk Nederlands Indisch Leger; KNIL, ) was the military force maintained by the Kingdom of the Netherlands in its colony of the Dutch East Indies, in areas that are now part of Indonesia. The ...

bought 38 aircraft between 1936 and 1938 each powered by a

Wright Whirlwind The Wright Whirlwind was a family of air-cooled radial aircraft engines built by Wright Aeronautical (originally an independent company, later a division of Curtiss-Wright). The family began with nine-cylinder engines, and later expanded to incl ...

. The Spanish Republican government ordered 28 F.K.51s, 11 with Armstrong Siddeley Jaguar IVa radials and 17 aircraft (designated F.K.51bis) each powered by a Wright R-975E Whirlwind radials. Production totaled at least 142 aircraft. Twenty-four fuselages of the F.K.51 were assembled at

Aviolanda Aviolanda was a Dutch aircraft manufacturer. The company was established in December 1926 by H. Adolph Burgerhout. Aviolanda mainly produced licensed-built aircraft, such as the Curtiss P-6 Hawk, the Dornier Wal and Do 24 flying boats, and the ...

Operational history

While the majority of F.K.51s were employed as elementary trainers within the Netherlands or in reconnaissance roles by the

Royal Netherlands Air Force , colours = , colours_label = , march = ''Parade March of the Royal Netherlands Air Force'' , mascot = , anniversaries = , equipment ...

in the

Dutch East Indies The Dutch East Indies, also known as the Netherlands East Indies ( nl, Nederlands(ch)-Indië; ), was a Dutch colony consisting of what is now Indonesia. It was formed from the nationalised trading posts of the Dutch East India Company, which ...

, twenty-eight were clandestinely sold to the Republican government during the Spanish Civil War, all despite a Dutch embargo on the sale of arms to either side of that conflict. Some of those arriving in Spain were used as light bombers by the Republicans in the

Cantabria Cantabria (, also , , Cantabrian: ) is an autonomous community in northern Spain with Santander as its capital city. It is called a ''comunidad histórica'', a historic community, in its current Statute of Autonomy. It is bordered on the east ...

n region of Spain. The F.K.51s were in active use in Royal Dutch Flight Schools during 1939–1940 in the training of young Dutch pilots. Some LVA F.K.51s were briefly used for reconnaissance duties following the

German invasion of the Netherlands The German invasion of the Netherlands ( nl, Duitse aanval op Nederland), otherwise known as the Battle of the Netherlands ( nl, Slag om Nederland), was a military campaign part of Case Yellow (german: Fall Gelb), the Nazi German invasion of t ...

in May 1940, with several F.K.51s being destroyed on the ground by attacking

Luftwaffe The ''Luftwaffe'' () was the aerial-warfare branch of the German ''Wehrmacht'' before and during World War II. Germany's military air arms during World War I, the ''Luftstreitkräfte'' of the Imperial Army and the '' Marine-Fliegerabtei ...

aircraft. The Dutch Naval Aviation Service's F.K.51s were used to carry neutrality patrols from January 1940, with most being damaged or destroyed during an attack on

De Kooy Airfield De Kooy Airfield ( nl, Vliegveld De Kooy) is an airfield south of Den Helder, Netherlands, named after the nearby hamlet De Kooy. It serves as both a civilian airport under the name Den Helder Airport and a naval airport under the name ''Mari ...

on 10 May. In December 1941, the Royal Dutch East Indies Army had 27 F.K.51s available for service, and on 5 December 1941, its flying schools were shut down, allowing the F.K.51s to form two reconnaissance squadrons based on

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...

.Shores, Cull and Izawa, 1992, pp. 59–60

Operators

;: *

Royal Netherlands Air Force , colours = , colours_label = , march = ''Parade March of the Royal Netherlands Air Force'' , mascot = , anniversaries = , equipment ...

; *

Spanish Republican Air Force The Spanish Republican Air Force was the air arm of the Armed Forces of the Second Spanish Republic, the legally established government of Spain between 1931 and 1939. Initially divided into two branches: Military Aeronautics ('' Aeronáutica M ...

; *

Spanish Air Force , colours = , colours_label = , march = Spanish Air and Space Force Anthem , mascot = , anniversaries = 10 December , equipment ...

Specifications

References

Bibliography