Koolhoven F.K.51

infobox Aircraft
name = F.K.51
type = Trainer, Reconnaissance Aircraft
logo =
manufacturer = Koolhoven


caption =
designer =
first flight = 1935
introduction =
retired =
status =
primary user = Royal Dutch Air Force
more users = Spanish Republicans
produced =
number built = 142
unit cost =
developed from =
variants with their own articles =

The Koolhoven F.K.51 was a 1930s Dutch two-seat basic training biplane built by the Koolhoven Company.

Design and development

The Koolhoven F.K.51 was the winning design in a 1935 Dutch government contest for a new trainer. Designed by Frederick Koolhoven the prototype biplane trainer first flew on 25 May 1935. The aircraft was an equal-span biplane designed to use a variety of engines between 250hp (186kW) and 500hp (373kW). It was a two-seater and had a tailwheel undercarriage. The Royal Dutch air force (LVA) ordered 25 aircraft in 1936 and 1937, powered by a 270hp (201kW) Armstrong Siddeley Cheetah V radial engine. A further 29 aircraft were later bought with 350hp (261kW) Armstrong Siddelet Cheetah IX engine. The Dutch Naval Aviation Service ordered 29 aircraft each powered by a 450hp (335kW) Pratt & Whitney radials. The Royal Dutch East Indies Army bought 38 aircraft between 1936 and 1938 each powered by a 420hp (313kW) Wright Whirlwind. The Spanish Republican government ordered 28 F.K.51s, 11 with 400hp (298kW) Armstrong Siddeley Jaguar IVa radials and 17 aircraft (designated F.K.51bis) each powered by a 450hp (335kW) Wright Whirlwind R-975E radials. Production totalled at least 142 aircraft.

Operational history

While the majority of F.K.51s were employed as elementary trainers within the Netherlands or in reconnaissance roles by the Royal Dutch Air Force in the Dutch East Indies, twenty-eight were clandestinely sold to the Republican government during the Spanish Civil War, all despite a Dutch embargo on the sale of arms to either side of that conflict. Some of those arriving in Spain were used as light bombers by the Republicans in the Cantabrian region of Spain. The F.K.51s were in active use in Royal Dutch Flight Schools during the first months of World War II in the training of young Dutch pilots, but with the German invasion of the Netherlands in May 1940, the F.K.51s were deemed obsolete and most never took to the air being too slow and vulnerable. The majority of F.K.51s were destroyed on the ground by attacking Luftwaffe aircraft.

Operators

;NLD:
*Dutch Naval Aviation Service
*Royal Dutch Air Force
*Royal Dutch East Indies Army;flagicon|Spain|1931 Spanish Republicans

pecifications

aircraft specifications
plane or copter?=plane
jet or prop?=prop
ref=
crew= 2 (one student, one instructor)
capacity=
payload main=
payload alt=
length main= 7.80 m
length alt=25 feet 7 inches
span main= 9.00 m
span alt=25 feet 6 inches
height main= 2.80 m
height alt=9 feet 2 inches
area main=
area alt=
airfoil=
empty weight main= 1,000 kg
empty weight alt= 2,205 pounds
loaded weight main= 1,600 kg
loaded weight alt= 3,527 pounds
useful load main=
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engine (jet)=
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thrust main=
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thrust original=
afterburning thrust main=
afterburning thrust alt=
engine (prop)= Armstrong Siddeley Cheetah IX, 9-cylinder, air-cooled radial piston engine
type of prop=
number of props= 1
power main= 261 kW
power alt= 350 hp
power original=
propeller or rotor?=
propellers=
number of propellers per engine=
propeller diameter main=
propeller diameter alt=
max speed main= 235 km/h at 2,280 m
max speed alt= 146 mph at 7,480 feet
cruise speed main=
cruise speed alt=
stall speed main=
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never exceed speed main=
never exceed speed alt=
range main= 850 km
range alt=528 miles
ceiling main= 5,000 m
ceiling alt= 18,370 feet
climb rate main=
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guns= One fixed forward-firing 7.7 mm (0.303 inch) machine gun in fuselage cowling, one similar weapon in a flexible mount in the rear cockpit
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hardpoint capacity=
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ee also

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References

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