Fokker D.XXI represented a complete breakaway from previous Fokker
biplane and high-wing monoplane designs, being a low-wing monoplane
with fixed, spatted landing gear. The Netherlands army air division
contracted for a prototype in 1935 to evaluate the type's potential for
use in the Netherlands East Indies, and although it was planned
originally to use a 650 hp (485 kW) Rolls-Royce Kestrel IV engine, the
prototype first flew on 27 February 1936 at Eindhoven (then called
Welschap) with a 645 hp (481 kW) Bristol Mercury VI-S radial with
Fokker test pilot Emil Meinecke at the controls. At this time the
Netherlands government was inclined more towards bombers than fighters
for home use, but a change in policy in the summer of 1937 led to an
order for 36 D.XXIs to be powered by Bristol Mercury VII or VIII radial
engines. There were many Fokker projects for developed D-XXI’s with
retractable landing gear and other engines, but the production aircraft
was generally similar to the prototype. In the seventh prototype (No.
217) test pilot H. Leegstra set a Dutch height record at 37,250 ft
In the same year seven
Mercury VIII powered D.XXIs were ordered for the Finnish air force, and
a licensed production arrangement was concluded under which the Finnish
State Aircraft Factory at Tampere built 93 D.XXIs between 1938 and
1944. Of these, the first 38 Mercury-powered aircraft were completed by
1938, but a further 50 built in 1941 were modified to take the 825 hp
(615 kW) Pratt & Whitney Twin Wasp Junior SB4-C/-G engine, 80 of which
had been bought in 1940. Finnish D.XXIs had all four guns mounted in
the wings, instead of two in the fuselage and two in the wings. A final
batch of five Bristol Pegasus-powered D.XXIs appeared in 1944.
were delivered to Denmark and a further 10 were built in the Royal Army
Aircraft Factory, Copenhagen. They had Mercury VI-S engines and one 20
mm Madsen cannon in a fairing beneath each wing. Licence production of
the D.XXI in Spain by the Republican government was begun, but the
assembly lines were captured by the Nationalists and it is thought that
no D.XXIs were completed. Meanwhile, in Holland the first D.XXI for the
Nether- lands air force flew on 20 July 1938, and the last of 36
production aircraft was handed over on 8 September 1939.
At the time of
Germany's invasion of the Netherlands on 10 May 1940 (totally the Dutch
Air Force had 36 Fokker D-XXI aircraft, registrations were 212 to 247
in white numbers on both sides of the fuselage). Unfortunately, when
the war started, only 28 28 D.XXIs were operational. The 28 operational
Fokker’s are divided in 1e JAVA (De kooy airfield, near Den Helder),
2nd JAVA (Schiphol, near Amsterdam) and the 1e Afdeling Jachtgroep
Veldleger (1st Division Fighter Group Field Army) at Ypenburg Airpark,
near Rotterdam. At De Kooy are 11 D-XXI’s. They are divided in in three
sections of 3 and one section of 2 aircraft. Only the aircraft of the
commanders are equipped with radio’s, so there is no communication
possible between the pilots in the aircraft. 2nd JAVA is posted at
Schipol and has nine operational D-XXI aircraft.
The manoeuvrability of
the Dutch fighters stood them in good stead during the five days before
the Netherlands capitulated, although eventually they were overwhelmed
by sheer weight of numbers (and limited ammunition supplies) and only
eight remained airworthy. Their greatest victory came on 10 May, when
D.XXIs destroyed 37 out of a formation of 55 Junkers Ju 52/3ms which
crossed the Dutch border in the early morning.
capitulated to the Russians, on 12 March 1940, 29 D.XXIs were still on
strength. It was decided subsequently to build another 50 aircraft, so
the Finnish air force had a number available when hostilities with the
USSR restarted in June 1941. Some of the D.XXIs began to be replaced by
the relatively unsuccessful IVL Myrsky in August that year, although a
few lingered on long after the end of the war until finally withdrawn
from service in 1948.
Most of the Finnish
D.XXIs operated with 'snowshoe' landing gear during the winter. One
Twin Wasp-powered aircraft was modified to have retractable landing
gear, but its performance was not improved sufficiently to warrant
conversion of the other in-service aircraft. A number of pre-war Dutch
D.XXIs served as test beds for engines such as the Rolls-Royce Kestrel
V and Hispano-Suiza 12Y, and projects were in hand for versions with
the Bristol Hercules (Project 150), Rolls-Royce Merlin (Project 151)
and Daimler-Benz DB 600H (Project 152), all with retractable landing
gear and aerodynamic improvements to the design.
At the present day,
there is only one Fokker D-XXI present in the Netherlands, this
aircraft is displayed in the Militaire Luchtvaart Museum (Military
Aviation Museum) at Soesterberg Airbase. It is a former Finnish
aircraft, painted in Dutch markings.
A 3D wire-frame of the Fokker D.XXI
D.XXI-1 - First
production aircraft, delivered to Denmark. They were powered by a
Mercury VIS radial, armed with two 7.92 mm (0.312 in) guns in the
fuselage and two 20 mm Madsen cannon in large underwing gondolas faired
into the undersurface of the wing just outboard of the main landing
gear units. Length was 23 ft 7.5 in (7.20 m). Empty weight was 2,701
lbs (1225 kg) with a maximum take-off weight of 3,858 lbs (1750 kg).
Maximum level speed was 245.5 mph (395 km/h) at optimum altitude,
cruising speed was 207 mph (333 km/h) at optimum altitude. Range was
559 miles (900 km) and service ceiling was 29,530 ft (9000 m). Number
D.XXI-2 - The first
D.XXI-2 of 36 was handed over in July 1938 to the Dutch air force, the
last in September 1939, one week after Germany invaded Poland. Number
D.XXI-3 - Finland
received 7 D.XXI-2's, and was licensed to build their own aircraft,
resulting in the D.XXI-3. 38 were built, and delivered in 1939, and
played an important role in the Winter War against the invading
USSR-forces. The D.XXI-3 was equal to the D.XXI-2 in all respects. The
powerplants were one PZL or Tampella (Bristol) Mercury VII radial
engine made in Poland or Finland respectively. Number built: 38.
D.XXI-4 - The D.XXI-4
was powered with a different engine as supplies of the Finnish-built
Mercury radial were earmarked for the VL license-built version of the
Bristol Blenheim. Finland had bought 80 Twin Wasp R-1535-SB4C-G Junior
engines, rated at 825 hp (615 kW), from the USA in 1940, and production
of the D.XXI-4 with this engine totalled 50 aircraft. This variant had
a slight degradation of performance and agility. Other major changes
from the D.XXI-3 standard were the armament of four 7.7 mm (0.303 in)
machine-guns in the wing leading edges, a larger vertical tail surface
for continued directional stability despite the larger engine, and the
rearward extension of the cockpit glazing to provide the pilot with
larger fields of vision.
The details of the
D.XXI-4 included a span of 36 ft 1 in (11.00 m), an aspect ratio of
7.47 and an area of 174.375 sq ft (16.20 sq m). Length was 27 ft 9 in
(8.46 m), and height was 9 ft 8 in (2.95 m). It had an empty weight of
3,384 lbs (1535 kg), with a maximum take-off weight of 4,817 lbs (2185
kg). Maximum level speed of 270 mph (435 km/h) at 9,020 ft (2750 m),
cruising speed of 220.5 mph (355 km/h) at 9,020 ft (2750 m), climb to
9,845 ft (3000 m) in 4 minutes 30 seconds, and a service ceiling of
31,990 ft (9.750 m). Number built: 50.
D.XXI-5 - Similar to
the Fokker D.XXI-4, but with a Bristol Pegasus radial, rated at 920 hp
(686 kW). Number built: 5.
Design: Ir. E.
Schatzki in 1935 (purely to meet the requirements of the Netherlands
East Indies Army Air Service)
V. (Nederlandsche Vliegtuitenfabriek) Fokker in Amsterdam.
License-built by Valtion Lentokonetehdas Finland, Haerens
Flyvertroppernes Vaerkstader Denmark and the Spanish Republic
(Dutch) One 830 hp (619 kW) Bristol Mercury VIII 9-cylinder radial
engine driving a Ratier propeller. (Danish) One 645 hp (481 kW) Mercury
VIS engine driving a Ratier propeller. (Finnish) One 825 hp (615 kW)
Pratt & Whitney R-1535-SB4-G or C Twin Wasp Junior 14-cylinder two-row
radial engine driving a Hamilton Standard propeller.
(Mercury VIII) Maximum speed 286 mph (480 km/h) at 14,500 ft (4420 m);
(P&W R-1535) Maximum speed 272 mph (439 km/h); service ceiling
(Mercury) 36,090 ft (11000 m), (P&W R-1535) 32,000 ft (9750 m).
77 Imperal gallon (92.47 US gal or 350 litres) internal fuel stores
plus provision for 2 wing tanks.
590 miles (950 km); (P&W R-1535) 559 miles (900 km).
) Empty 3,180 lbs (1422 kg) with a maximum take-off weight of 4,519 lbs
(2050 kg); (P&W R-1535) Empty 3,380 lbs (1534 kg) with a maximum
take-off weight of 4,820 lbs (2186 kg).
36 ft 1 in (11.00 m); length 26 ft 10 3/4 in (8.20 m); height 9 ft 8 in
(2.95 m); wing area 174.38 sq ft (16.20 sq m).
(Dutch) Four 7.9 mm (0.312 in) FN-Browning M.36 machine-guns, two in
the fuselage (500 rounds per gun) and two in the wings (300 rounds per
gun). (Danish) Two Madsen 7.9 mm (0.312 in) machine guns in the wings
and two Madsen 20 mm cannons in underwing blisters. (Finnish) Four 7.7
mm (0.303 in) Vickers machine guns in outer wings.
D.XXI-1, D.XXI-2, D.XXI-3, D.XXI-4, D.XXI-5.
optical tube-sight or the reflector sight Revi 3C or D.
flight 27 March 1936; service delivery (Dutch) January 1938; (Finnish
production) June 1938, (Danish production) 1939.
Netherlands, Finland, Denmark.