Koolhoven F.K.58

https://en.wikipedia.org/wiki/Koolhoven_F.K.58

The Koolhoven F.K.58 was a single engine, interceptor-fighter aircraft designed
and mainly manufactured by N V Koolhoven in the Netherlands under contract by
France. Intended for Armée de l'Air use, the F.K.58 saw limited service in the
Battle of France.

In 1937, the French Conseil Supérieur de l'Air decided that domestic aircraft
manufacturing capacity could not, in the event of war, equip the Armée de l'Air
with fighters quickly enough. The Dutch manufacturer Koolhoven was contracted to
design a cheap, easily built, high-performance fighter, that could be built and
serviced with French-supplied engines and other components. According to some
sources, the Koolhoven fighter was intended primarily for fighter units based in
French colonies.

On 17 July 1938, the prototype Koolhoven Model 1166 (later renamed the F.K.58)
flew for the first time. Designed by Erich Schatzki – a Jewish refugee from
Germany – the F.K.58 may be seen as a development of his preceding fighter
design: the Fokker D.21. The F.K.58 used the same composite materials as the
D.21: the structure of the fuselage consisted of welded steel tubing covered
with sheet metal (front part) and fabric (aft); the wings had wooden members
with a plywood and fabric skin.

In January 1939, the Armée de l'Air placed an order for 50 aircraft, to be
powered by Gnome-Rhône 14N engines.

Due to the unavailability of Gnome-Rhône engines and French instruments, just 17
aircraft – six F.K.58s and 11 F.K.58As – were completed at the Koolhoven works,
with Dutch supplied engines and instruments – and delivered to the Armée de
l'Air. Production was transferred to Nevers, where the aircraft were re-built
with French components and the extraneous parts were returned to the
Netherlands. However, only one more F.K.58 was produced from scratch at Nevèrs.

In July 1939, the Dutch government placed an order on behalf of the Luchtvaart
Afdeling (Netherlands Army Aviation Corps) for 36 F.K.58 variants, powered by
Bristol Taurus engines. As the British government restricted exports of
Tauruses, they were to be replaced by Dutch stocks of the Bristol Mercury VIII
(as used by the Dutch Fokker D.21 and Fokker G.1A). The lower output of the
Mercury, relative to the Taurus, would have allowed a top speed to some 480
km/h.

The F.K.58s comprising the Dutch order were in various stages of construction
when they were destroyed by a German air raid on the Koolhoven factory in May
1940.


Role
Fighter

Manufacturer
Koolhoven

Designer
Erich Schatzki

First flight
17 July 1938

Introduction
1940

Retired
1940

Primary users
French Air Force
Polish Air Force

Produced
1939-1940

Number built
20

The F.K.58 was originally ordered to serve with AdA units based in French
overseas territories. Following the outbreak of war with Germany, however, the
type was assigned to an ad hoc, Free Polish air force unit commanded by Captain
Walerian Jasionowski. Roughly equivalent to a French escadrille, or Polish
eskadra, it was often known by the unofficial name "Eskadra Koolhoven". The
unit's official role was patrouille ("patrol") – as the AdA designated units
that defended rear areas against long-range bombers and other enemy aircraft, as
part of the Défense Aérienne du Territoire ("Territorial Air Defense"; DAT). The
unit operated from the Salon and Clermont-Aulnat air bases.

By May 1940, 13 aircraft were operational with Eskadra Koolhoven. As delivered,
however, the fighters were unarmed and the Poles had to acquire machine guns and
fit them. From 30 May 1940, they were in service, patrolling firstly in the
Avignon-Marseille area, and then over Clermont-Ferrand. At least 47 operational
sorties were recorded, but the Escadron did not encounter enemy aircraft.

The type's service life was short-lived, with ; the unit had no confirmed
victories, but at least one F.K.58 was lost. After the fall of France, all
surviving airframes were scrapped.

Specifications (F.K.58)

General characteristics
Crew: One
Length: 8.7 m (28 ft 6.75 in)
Wingspan: 11 m (36 ft 1.25 in)
Height: 3 m (9 ft 10 in)
Wing area: 17.3 m2 (186.2 ft2)
Empty weight: 1,930 kg (4,255 lb)
Loaded weight: 2,750 kg (6,063 lb)
Powerplant: 1 × Gnome-Rhône 14N-16 radial engine, 768 kW (1,030 hp)

Performance
Maximum speed: 505 km/h (314 mph)
Cruise speed: 450 km/h (280 mph)
Range: 750 km (466 mi)
Service ceiling: 10,000 m (32,810 ft)
Rate of climb: 11.6 m/s (1,130 ft/min)
Wing loading: 159 kg/m2 (32.6 lb/ft2)
Power/mass: 0.28kW/kg (0.17 hp/lb)

Armament

4 x 7.5 mm FN-Browning machine guns in underwing fairings




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