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    Koolhoven F.K.55 Fighter Prototype (1938)

    Koolhoven F.K.55 Fighter Prototype (1938)

    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.




    Staff Writer (5/26/2016): 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.





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    Technical Specifications:
    Koolhoven F.K.55
    Fighter Prototype


    PRIMARY

    Focus Model: Koolhoven F.K.55
    Origin: Netherlands
    Manufacturer: Koolhoven - Netherlands
    Service Entry: 1938
    Production Total: 1
    Crew: 1


    STRUCTURAL

    Length: 30.35 ft (9.25 m)
    Width: 31.50 ft (9.60 m)
    Height: 8.53ft (2.60 m)
    Weight (Empty): 3,527 lb (1,600 kg)
    Weight (MTOW): 4,850 lb (2,200 kg)


    POWER

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


    PERFORMANCE

    Maximum Speed: 317 mph (510 kmh; 275 kts)
    Maximum Range: 528 miles (850 km)
    Service Ceiling: 0 ft (0 m; 0.0 miles)
    Rate-of-Climb: 2,580 feet-per-minute (786 m/min)


    ARMAMENT

    Hardpoints: 0
    Armament Suite:
    PROPOSED:
    1 x 20mm cannon firing through propeller hub
    4 x 7.7mm (0.303) machine guns in wings


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


    OPERATORS
    Netherlands (cancelled)