Koolhoven F.K. 58, the short lived Dutch fighter for the French

Would you like to see the Koolhoven F.K. 58 ingame for the French techtree?
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Hello everyone! Today I’m going to suggest the Koolhoven F.K. 58 that was operated by the French!

A F.K. 58 with a French camouflage. The original civilian registration letters can still be seen through the paint
Source: Koolhoven F.K.58 - Destination's Journey



At the end of the 1930’s the French government was desperate for more fighter aircraft. And so then started looking towards both domestic and foreign options to fill this demand, but on the foreign market things were not as easy. The Curtiss-Wright Hawk’s the French had ordered were very expensive and the British air industry had their hands full with RAF orders. And Germany was seen as a potential future enemy, so no requests were made towards them.

The only option that remained was the Netherlands. But even here the biggest company, Fokker, also had their hands full with orders for the Dutch Airforce. And so the next best option was the Dutch company Koolhoven.

The founder of Koolhoven, Frits Koolhoven, was certainly an interesting man. And when the French contacted him about their problem, mister Koolhoven simply replied with: “So you need fast and excellent fighter aircraft. Well let’s just built one for you.” And so works immediately started on this new aircraft, given the design number (Ontwerp) 1166, and when the design reached a futher stage, the name F.K. 58.

Two Prototypes were made and tested by Koolhoven, and also handed over to the French for a short time so they too could test fly them. Overall the results were very good, and in Januari of 1939 the French government made an order of 50 F.K. 58’s. But unlike the Prototypes which were fitted with Hispano-Suiza 14AA engines, the French models had to be fitted with the Gnome-Rhône 14N39.

The aircraft fitted with the Hispano-Suiza engine were called F.K. 58.
The aircraft fitted with the Gnome-Rhône engine were called F.K. 58A.

But Frits Koolhoven was so certain that the F.K. 58 would sell, that he had already started production of the aircraft before the proper French order was made. And so the first four that were already under construction were already being fitted with the Hispano-Suiza 14AA engine.
After a little discussing the French agreed to accept these four even if they had the wrong engine.

These four F.K. 58’s were given Dutch civilian registration names. These were PH-AVB, PH-AVE, PH-AVG and PH-AVH. When they arrived in France these names were removed and they were given French registration numbers. Those being C-016, C-017, C-018 and C-019.

The four aircraft were test flown by French pilots shortly after they arrived, and the results were not good. It turned out that a 100 kg counter weight was installed in the aircraft. The Hispano-Suiza 14AA engine was still very experimental and it turned out to be heavier then advertised, so the counter weight was added to fix the center of gravity.

This ended up hurting the performance of the aircraft, and so all four were denied for the French Air Force. The aircraft ended up being given to the training squadron. Two of them later ended up with a Mechanics training school.

The remaining two planes that were still with the training squadron ended up getting bombed by the Luftwaffe when they attacked France.

The wing of a F.K. 58
Source: Foto's



The Koolhoven F.K. 58 was a small lightweight fighter with a retractable landing gear. The base model of the F.K. 58 was powered by a 1,063 hp Hispano-Suiza 14AA engine which gave it very good performance due to the planes small size. Although it turned out that the four aircraft given to France with this engine were a bit overweight due to the engine being heavier then advertised.

The straight line speed at an altitude of 5,300 meters was around 475 km/h. And the max dive speed recorded was a staggering 890 km/h! Keep in mind the aircraft did this in 1938, which lead to people calling this the fastest aircraft in the world at the time.

The weaponry planned for the French F.K. 58’s was four 7.5 mm FN-Browning mle 38 machine guns. As can be seen in the proto below, the machine guns were added in underwing pods that had two machine guns each.

A drawing of the landing gear and machine gun pod under the wing
Source: Koolhoven FK-58



A drawing of the F.K. 58
Source: Koolhoven F.K.58 - Destination's Journey

Crew: 1 Pilot
Length: 8.71 m
Wingspan: 11.02 m
Wing area: 17.23 m2
Height: 3 m
Empty weight: 1,800 kg
Full weight: 2,550 kg
Powerplant: Hispano-Suiza 14AA (1,063 hp)

Maximum straight line speed: ~475 km/h at 5,300 meters
Maximum recorded dive speed: 890 km/h
Service ceiling: 10,500 m

4 × 7.5 mm FN-Browning mle 38 machine guns



I think this plane could be a nice addition to France. It could be added to Rank 1, right after the H-75’s. The plane is very similar to the H-75, only it’s a little lighter.

Since the Netherlands has been added to the French techtree with the introduction of the BeNeLux, it might also be nice to add some more Dutch aircraft models that France has operated themselves.

So there you have it! Please make sure to vote in the poll above, and let me know what you think of this little fighter aircraft!



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Why is this one 8 km/h slower than the prototype?

The French models were reported to have a 100 kg counter weight added to the aircraft to offset some inconsistencies in the engine weight.

This weight is not mentioned in any information for the Prototype models. And online I saw different top speeds listed by different sources. So I decided to pick the lowet mentioned top speed for this model with the extra weight.