A Dutchman in the British aircraft industry

Frits Koolhoven learned his trade abroad. Born in Bloemendaal in 1886, he trained as an engineer in Liège and Antwerp, worked for the Belgian car maker Minerva, and in 1911 built the Heidevogel, an improved Farman-type biplane. From 1912 he designed aircraft in England, first for British Deperdussin, then from 1914 for Armstrong Whitworth, where his initials gave the F.K. series its name, and from 1917 as chief designer of the British Aerial Transport Company. When BAT went bankrupt he went home in 1920, found the Dutch market dominated by Fokker, and took a job with the car maker Spyker.

Living in Fokker’s shadow

In 1921 a group of businessmen founded the Nationale Vliegtuig Industrie and hired Koolhoven as chief designer. Like BAT, it produced advanced designs that drew attention worldwide but almost no orders, and it failed in 1926. Koolhoven persuaded several of its shareholders that the business could work if he had complete control. He took over its hangar at Waalhaven airfield in Rotterdam and founded N.V. Koolhoven Vliegtuigen, carrying his design numbers with him: F.K.1 to F.K.28 had been drawn in England, F.K.29 to F.K.34 at NVI, and F.K.35 to F.K.59 would be Koolhoven’s own.

The FK-41 and the Desoutter

For its first years the company survived on one-off aircraft built to order, slowly working into private flying. The breakthrough came in 1930 with the F.K.41 high-wing cabin monoplane. Koolhoven built only seven himself, but it was built under licence in England by Desoutter as the Mk.I and Mk.II. The twin-engined F.K.48 airliner flew for KLM, and the more powerful F.K.50 for the Swiss operator Alpar. From 1933 military orders picked up: the F.K.51 biplane trainer, 142 built, served the Dutch army and the Royal Netherlands East Indies Army.

Fighters for France, trainers for Spain

The F.K.51 also went where it should not have. Despite a Dutch arms embargo, 28 were sold clandestinely to the Republican government in the Spanish Civil War, where some flew as light bombers in Cantabria. By 1938 air forces across Europe were competing for every aircraft Koolhoven could build, and the Waalhaven factory covered 8,000 square metres with 1,200 employees. Even France, whose own industry could not keep up, ordered 50 of the F.K.58 single-seat fighter, which first flew on 17 July 1938; a shortage of French engines meant only about 20 were finished, and a few flew in the Battle of France.

Rubble at Waalhaven

The end came on the morning of 10 May 1940. As Germany invaded the Netherlands, a mass of German bombers struck Waalhaven airfield and reduced the Koolhoven works to rubble, destroying every drawing, model and document. Koolhoven was convinced the raid had been aimed at him personally, in revenge for his British war work. He registered as a member of the Dutch Nazi party, the NSB, in 1940, was briefly detained after the war, and died of a stroke in Haarlem on 1 July 1946. The company lived on as a holding, built two prototype sailplanes, and was liquidated in 1956.

Fabrieken

• Waalhaven works · Waalhaven airfield, Rotterdam — Former NVI hangar; destroyed 10 May 1940

Mensen

• Frederick (Frits) Koolhoven · founder and designer (1886–1946) — Earlier designer for Armstrong Whitworth and BAT
• Robert B. C. Noorduyn · chief draughtsman at BAT alongside Koolhoven

Records en primeurs

• Second-largest Dutch aircraft manufacturer after Fokker, 1926–1940