Koolhoven (aircraft manufacturer)

N.V. Koolhoven was an aircraft manufacturer based in Rotterdam in the Netherlands. From its conception in 1926 to is destruction in the Blitzkrieg in May 1940, the company remained the Netherlands' second major aircraft manufacturer (After Fokker). Although many of its aircraft were as unsuccessful economically as they were brilliant from a design standpoint, the company managed to score several 'hits', amongst them the FK-58 single-seat monoplane fighter, the FK-50 twin-engine passenger transport and the FK-41 built in England under licence by the Desoutter.

History

In 1920, aircraft designer Frederick 'Frits' Koolhoven returned from England to his native Netherlands. The postwar years had not been good to him: The British Aerial Transport Company for which he was chief designer went bankrupt and all other manufacturers were struggling for survival themselves too hard to think of hiring. The Netherlands, Koolhoven hoped would be better. Yet, even there he found that while the Netherlands new airline KLM was a willing taker for all planes it could get, the market was almost completely owned by Fokker. Out of other options Koolhoven returned to his old job and worked as an automobile engineer for the Spyker automobile factory.

In 1922, his luck began to change when a group of businessmen founded the N.V. Nationale Vliegtuig Industrie (National Aircraft Industry, inc.), and selected him to be the chief designer. Still, the time was not yet ripe for a second Dutch aircraft manufacturer and, just like with BAT, N.V.I. continued to spew out technically advanced designs that attracted attention from all over the world... but virtually no orders. The company lasted only four years.

At the demise of N.V.I. Koolhoven was 40 years old and had spent the last 15 years building aircraft for others, following the technical and commercial whims of a number of bosses. At 40, he decided he could do better for himself and managed to convince several of the N.V.I. shareholders that the company would have been viable, if only he had the final say not only on technical matters, but also on day to day planning and marketing. Apparently enough of the shareholders agreed and even while N.V.I. was being dissolved, the new company, N.V. Koolhoven vliegtuigen (Koolhoven aircraft, inc.) moved into its first temporary hangar at Rotterdam's Waalhaven military airfield.

At first, the company managed to stay afloat by making one-off purpose-built airplanes on command, slowly branching out into the private plane sector and over and over again trying to break into the military market. Finally the company struck gold with the FK-41 high-wing tourist monoplane. Although N.V. Koolhoven itself only built 6 Fk-41's the airplane was built in license in England as the Desoutter Mk.I and later improved as the Mk.II . By that time also the military market picked up and Koolhoven increasingly built trainers and observation aircraft for the Dutch air force as well as for various other countries.

By 1938, the Koolhoven factory at Waalhaven covered 8000 square meters and boasted 1200 employees. While still no match for Fokker, Koolhoven had established itself firmly as the number 2 manufacturer in the Netherlands, and with a new war looming, its order books continued to fill as air forces from all over Europe were virtually fighting over each plane that rolled off the production line. Even France found itself buying Koolhoven FK-58 fighters as its own aircraft industry was unable to keep up with the demand from the Armée de l'Air

The end came on May 10th 1940. In the first hours of the Blitzkrieg, as a prelude to the invasion of the Netherlands, the Luftwaffe set out to destroy as much as possible of the Dutch air force on the ground. On the morning of that day, a massive armada of German bombers appeared over Waalhaven and almost completely destroyed the airfield with all it surrounding facilities. This also included the Koolhoven factory and within just a few hours, Koolhoven's company had been reduced to a pile of rubble. More important, with the factory also disappeared all drawings, models, documents of Koolhoven's projects. Even today, the only photographs remaining of Koolhoven's planes are newspaper clippings and private snapshots.

Frederick Koolhoven died of a stroke, July 1, 1946. His company, although without means of production, continued to exist as a holding. Over the next 10 years various attempts were made to start up new projects, but apart of the construction of two prototype sailplanes nothing happened and in 1956 N.V. Koolhoven Aeroplanes was finally closed and liquidated.

Aircraft

Apart from the Heidevogel of 1911, Koolhoven designed 59 aircraft, which he consecutively numbered FK-1 to FK-59. About half of this were design studies that were never built. Koolhoven designed projects FK-1 to FK-28 in England for Armstrong Whitworth and BAT, projects FK-29 to FK-34 for N.V.I. and projects FK-35 to FK-59 for his own company. The first 'true' Koolhoven airplane therefore would have been the FK-35. However on formation of the N.V. Koolhoven, Frits Koolhoven took with him the design of the FK-30 "Toerist" light sportsplane original designed for NVI, but not built. Several "Toerists" built by the new FK Koolhoven therefore constitute the earliest airplanes of that company, if not by production date, then at least by numbering.

The [http://www.koolhoven.com|website of the Koolhoven foundation] lists 26 Koolhoven designs, starting with the F.K.30 and then going from F.K.35 to F.K.59. It however also notes that the designs F.K.37, 38, 39 and 59 were never built, while only giving pictures of woden models for the designs F.K.35 and F.K.36. Jane's Encyclopedia of Aviation only lists the Koolhoven designs F.K.40, 41, 42, 43, 46, 48, 49, 51, 52, 53 and 58 but mentions a F.K.50-b bomber project, which the Koolhoven foundation site doesn't.

The best-known amongst those designs are the F.K.41 high-wing monoplane, which was built in license as the Desoutter Mk.II and the F.K.50 twin engine transport monoplane, two of which were used by the Swiss aircraft company alpar. Amongst the military designs, the most successful were the Koolhoven F.K.51 biplane reconnaissance aircraft, which saw service in extensive numbers in the Dutch air force from the mid-Thirties until the Second World War, the Koolhoven F.K.52 biplane which was used by the Finnish Air Force and the Koolhoven F.K.58 single-seat monoplane fighter. The latter was the plane ordered by France and flew in the Armée de l'Air during the Battle of France

A complete list of the Koolhoven aircraft and projects is given below:
* Koolhoven F.K.30 "Toerist" (Tourist) Light high-wing sports monoplane, 1927
* Koolhoven F.K.35 seaplane scout and fighter, available as low-wing monoplane or biplane, 1926
* Koolhoven F.K.36 larger biplane version of the F.K.35, 1926
* Koolhoven F.K.37 Design for a 3-engined airliner for the KLM (not built)
* Koolhoven F.K.39 Various design studies for a moonoplane two-seat fighter (not built)
* Koolhoven F.K.40 Airliner for 4 or 5 passengers, 1928
* Koolhoven F.K.41, high-wing monoplane cabin "sport coupe", built in licnence by Desoutter in England
* Koolhoven F.K.42 High-wing open cockpit Private plane, 1929
* Koolhoven F.K.43 Three passenger cabin sportsplane/air taxi resemblant of the F.K.41, 1930
* Koolhoven F.K.44 "Koolmees" (tomtit) Private plane resemblant of the F.K.41/F.K.43
* Koolhoven F.K.45 biplane Aerobatic plane, 1931
* Koolhoven F.K.46 biplane trainer, 1930
* Koolhoven F.K.47 biplane private plane/trainer, 1933
* Koolhoven F.K.48 six passenger twin-engined airliner used by the KLM, 1934
* Koolhoven F.K.49 twin-engine Photo- and cartography aircraft, purpose built for the Dutch air force 1935
* Koolhoven F.K.49A Multi purpose aircraft, 1937
* Koolhoven F.K.50 eight passenger twin-engined airliner, a more powerful F.K.48, used by Alpair 1935
* Koolhoven F.K.51 Military biplane trainer with open seating, 1935
* Koolhoven F.K.52 two-seat biplane scout and fighter with enclosed cabin, 1936
* Koolhoven F.K.53 "Junior" low/mid wing light touring plane, 1936
* Koolhoven F.K.55 high-wing monoplane cabin "Executive plane" with retractable gear, 1937
* Koolhoven F.K.55 Twin-engined experimental high performance fighter, 1936
* Koolhoven F.K.56 Low-wing monoplane two-seat advanced trainer and scout, 1937
* Koolhoven F.K.57 Twin-engined low-wing executive plane, 1938
* Koolhoven F.K.58 Modern monoplane high performance fighter, 1938
* Koolhoven F.K.59 Multi-purpose development of the F.K.52, no information available whether built, last Koolhoven design, 1940

Legacy

Founded in 1989 by aviation enthusiast Jan den Das, aviation historian Theo Wesselink and technical curator Harry van der Meer, the [http://www.koolhoven.com/ Koolhoven Aeroplanes Foundation] tries to keep the legacy of Fritz Koolhoven's aircraft alive by restoring or rebuilding some of his most famous aircraft. Its highlight is the restoration of the only remaining FK-21 BAT BANTAM, a Koolhoven design. Its site also has the most complete list of all Koolhoven designs.

References

"Koolhoven, Nederlands vliegtuigbouwer in de schaduw van Fokker", Theo Wesselink and Thijs Postma, Unieboek B.V., Bussum NL"Jane's encyclopedia of Aviation", various contributors, Portland house, New York 1980

External links

* [http://www.koolhoven.com/ Koolhoven Aeroplanes Foundation]