Military Factory logo

Koolhoven F.K.55 - Netherlands, 1938


Detailing the development and operational history of the Koolhoven F.K.55 Fighter Prototype.


 Entry last updated on 5/26/2016; Authored by Staff Writer; Content ¬©www.MilitaryFactory.com



Only one example of the Dutch Koolhoven F.K.55 fighter was ever completed before the program was cancelled in full prior to World War 2.







Prior to World War 2 (1939-1945) the Dutch held a respectable aero industry that produced a few notable types of local design. The Koolhoven F.K.55 was a prototype developed along the lines of a high-speed fighter and appeared during the latter half of the 1930s. The line ended with a sole example being built, its first flight held on June 30th, 1938, and the program terminated before the end of the year.

Its design, begun in 1937, was one of a sleek all-modern fighter with the cockpit set forward of the wing mainplanes and the mainplanes shifted just ahead of midships (and shoulder-mounted). Wingtips were rounded and the appendages straight in appearance. The tail unit was conventional with a single fin and a pair of horizontal planes. Construction was mixed, composed of metal and wood. A "tail dragger" undercarriage was featured. The engine of choice became a Lorraine 12Hrs "Petrel" V-12 of 860 horsepower driving a pair of two-bladed propeller assemblies at the nose in contra-rotating fashion. Due to the placement of the cockpit, well forward in the fuselage, the engine was installed aft of the pilot (as in the famous Bell P-39 "AiraCobra" fighter detailed elsewhere on this site).

The completed aircraft was made ready for its first flight in the early part of 1938 and has all of the appearance required of a high-performance aircraft. A fixed undercarriage greeted this monumental moment for the design with the intention that a retractable system be instituted later in development. However, in practice, the design proved lacking in the power necessary for the role - the 860 horsepower produced for the engine was just take-off power. Underpowered and costly to revise, this aircraft endeavor was eventually abandoned by Koolhoven and fell to the pages of military aviation history. Engineers pushed for the installation of a Lorraine "Sterna" supercharged engine of 1,200 horsepower to no avail.

As designed, the F.K.55 sported an maximum speed of 317 miles per hour, a cruising speed nearing 280 miles per hour, a range out to 530 miles and a rate-of-climb of 2,580 feet-per-minute (all figures estimated by Koolhoven). Its proposed armament scheme was to fit a 20mm cannon firing through the propeller hub and 4 x .303 machines guns, two installed in each wing. The P-39 fielded similar armament though a more potent 37mm autocannon in the nose. Its performance was much better as well: a maximum speed of 375 mph was seen in the Q-models. Like the F.K.55, it first flew in 1938 and went on to have a strong war record in the subsequent global conflict.










Koolhoven F.K.55 Specifications



Service Year: 1938
Type: Fighter Prototype
National Origin: Netherlands
Manufacturer(s): Koolhoven - Netherlands
Total Production: 1


Structural (Crew, Dimensions, Weights)



Operating Crew (Typical): 1
Overall Length: 30.35 feet (9.25 meters)
Overall Width: 31.50 feet (9.60 meters)
Overall Height: 8.53 feet (2.60 meters)

Weight (Empty): 3,527 lb (1,600 kg)
Weight (MTOW): 4,850 lb (2,200 kg)

Power / Performance (Engine Type, Top Speed)



Engine: 1 x Lorraine Petrel 12Hrs 12-cylinder Vee engine developing 860 horsepower.

Maximum Speed: 275 knots (317 mph; 510 kph)
Maximum Range: 459 nautical miles (528 miles; 850 km)
Rate-of-Climb: 2,580 feet-per-minute (786 m/min)

Armament / Mission Payload



PROPOSED:
1 x 20mm cannon firing through propeller hub
4 x 7.7mm (0.303) machine guns in wings

Global Operators (Customers, Users)



Netherlands (cancelled)

Model Variants



F.K.55 - Base Series Designation; single prototype completed in 1938.