Koolhoven FK.51

from Wikipedia, the free encyclopedia
Koolhoven FK.51
Koolhoven FK 51 (7320943498) .jpg
FK.51 in the Militaire Luchtvaart Museum
Type: Trainer aircraft
Design country:

NetherlandsNetherlands Netherlands

Manufacturer:

Koolhoven

First flight:

May 25, 1935

Production time:

1936-1938

Number of pieces:

141 + 1 prototype

The Koolhoven FK.51 was a beginner's training aircraft from the 1930s and one of the most successful developments by the Dutch aircraft designer and industrialist Frits Koolhoven .

Development and use

The FK.51 was as biplane same span in composite construction designed and was for the use of aircraft engines provided in the power range from 250 to 500 hp. In the course of its operational history, the type was flown with different engines. A prototype was built that Z-1received the license plate and completed the flight test with H. M. Schmidt-Crans on May 25, 1935 from Waalhaven airfield . After successful completion, he received the civil registration number PH–AJVand was presented as a flight demonstrator to international interested parties. The Dutch Air Force (LVA) were convinced by the benefits and ordered a first series of 25 FK.51 that a British Cheetah V - radial engine received with 270 hp and were delivered in the period 1936 and the 1937th They turned out to be well-suited, robust aircraft for beginners' training, so the army decided to purchase another 29 pieces. This construction lot received more powerful Cheetah IX engines with 350 hp and was handed over to the LVA by 1938.

The Dutch Navy also decided to equip their Marine Luchtvaartdienst (MLD) with this type, opting for an even more powerful US Pratt & Whitney with 450 hp as a drive. Finally, the colonial forces in the Dutch East Indies also announced their needs and received 28 FK.51s, equipped with Whirlwind engines, between 1936 and 1938 , which were later followed by at least seven more for use in the East Indies .

Koolhoven received another order from the Spanish Republic , which ordered a total of 28 FK.51s for their Air Force (FARE). The series comprised 28 copies; 11 of these were fitted with 400 hp Jaguar IVa engines and the remaining 17 were fitted with R-975E Whirlwind engines. The government, which was in the middle of a civil war with the Spanish nationalists, did not only use these for schoolwork. Some aircraft were equipped with two 7.7 mm machine guns in the wings and a defense post in the rear cabin, in which a movable 7-7 mm machine gun for the rear gunner was, and were used as night fighters or reconnaissance aircraft . Others were used for night flight training.

construction

The FK.51 was a single-handled, braced and staggered biplane with an upper and lower wing of the same span and depth. The fuselage consisted of a tubular steel framework with a rectangular cross-section and an oval fabric covering. It contained the 280 l fuel tank and the lubricant tank with a 32 l capacity. The engine was covered with a NACA hood . The wing consisted of two rails , straps made of Spruce and Sperrholzbeplankung . Ailerons were only on the upper wing. The tail unit was formed by the horizontal and vertical fin as a plywood-covered wooden framework, as well as elevators and rudders made of fabric-covered metal frames, with the elevator in the flight and the rudder on the ground having adjustable trim tabs . The horizontal stabilizer was braced towards the fin and the lower edge of the fuselage. The landing gear consisted of the non-retractable main landing gear, equipped with wheel brakes and low-pressure tires, as well as the rear wheel that could be rotated through 360 °.

Technical specifications

Parameter Dates with "Cheetah IX"
crew 2
span 9.00 m
length 7.85 m
height 2.85 m
Wing area 27.00 m²
Wing loading 58.8 kg / m²
Power load 4.14 kg / hp
Area performance 13 hp / m²
Preparation mass 990 kg
Takeoff mass normal 1450 kg
maximum 1600 kg
drive an air-cooled seven - cylinder Armstrong Siddeley Cheetah IX radial engine
power 270 PS (199 kW) - 350 PS (257 kW) at an altitude of 2200 m
Fuel volume 280 l
Top speed 232 km / h near the ground
253 km / h at an altitude of 2200 m
Marching speed 206 km / h near the ground
229 km / h at an altitude of 2200 m
Landing speed 84 km / h
Rate of climb 420 m / min from the ground
Rise time 2.4 min at 1000 m altitude
5.2 min at 2000 m altitude
8.6 min at 3000 m altitude
Service ceiling 6300 m
Range 775 km
Armament a rigid 7.7 mm MG Lewis in the upper wing and
a movable 7.7 mm MG Lewis on a turntable

Users

NetherlandsNetherlands Netherlands
Luchtvaartafdeeling : 54 (tactical numbers 1 - 25 and 400 - 428)
Koninklijke Marine : 24 (tactical numbers E-1 - E-24)
Koninklijk Nederlandsch-Indian Leger : 35 (tactical numbers K-2 - K-29 and K-102 - K-108)
Spain Second RepublicSecond Spanish Republic Spain
Fuerzas Aéreas de la República Española : 28 (tactical numbers EK-001 - EK-028)

literature

  • Peter Alles-Fernandez (Ed.): Aircraft from A to Z. Volume 2. Bernard & Graefe, Koblenz 1988, 3-7637-5905-0, p. 432.

Web links

Commons : Koolhoven FK51  - Collection of pictures, videos and audio files

Individual evidence

  1. Werner von Langsdorff : Handbook of aviation. Year 1939 , 2nd, unchanged edition, J. F. Lehmann, Munich 1937, p. 327/328.