The Fokker D.XXI was developed in response to a request in May 1934 of the NEIAF (ML-KNIL) for a replacement for the Curtiss Hawk.
It was to be a relatively simple aircraft, given the circumstances in former Dutch East-Indies: a fixed undercarriage, mixed construction: partially steel tubes covered with linen: partially aluminium alloy and a wooden wing and a fixed 12 mm machine-gun in the fuselage plus two ( both in height and sideways ) adjustable 7.62 mm in the wings . Furthermore, the device had to be able to carry a light bomb load.
The design had to be read before the midst of September 1934
Fokker offered two designs: the D.XIX, which was developed from the Fokker D.XVII, and new design, no 112 with a single low wing. Both were to be equipped with the Rolls Royce Kestrel IV.
Design 112 could also be equipped with a radial engine.
In the end the NEIAF chose design 112, which had received the Fokker designation D.XXI in November 1934. As the engine the Bristol Mercury VIS radial engine was selected in April 1935.
The prototype, with fuselage number 541, was completed in February 1936 and made its first flight, with the NEI serial FD -322, on February 27, 1936.
Meanwhile, NEIAF had changed its mind and wanted a so called battle air force, consisting of fast twin-engined bombers . For this, the Martin Model 139 was purchased and there was no money for the purchase of fighter aircraft.
The Ministry of Colonies offered the Fokker D.XXI then to the Ministry of Defence, who initially was not interested in the aircraft.
In the autumn of 1936, partly due to the increased tension in the meantime, the LVA showed more interest in the Fokker D.XXI. In the spring 1936 Fokker had already received some export orders from Finland, which later also purchased license rights. The Finnish version was equipped with an neforced, thucker undercarriage, because of use with skis during the winter. The Finnish state factory built another 90 examples, equipped with Pratt & Whitney Wasp engine.
Denmark in 1938 ordered two examples and built another ten examples under license. These aircraft had also the Finnihs enforced and thicker undercarriage. Spain also signed a licensing agreement for 50 examples, of which was, however, only one built.
In 1937 - 1938 Fokker offered a further development, design 150 equipped with a Bristol Hercules engine of 1375 hp and design 151 with a Rolls-Royce Merlin II of 1050 hp or a Daimler Benz DB 600H rated 1090 hp. Neither of these designs was built.
|Length:||8,22 m||Wingspan:||11 m|
|Height:||2,95 m||Wing area:||16,2 m2|
|Empty weight:||1450 kg||Max. start weight:||2050 kg|
|Max. speed:||480 km/hr||Climbing speed:||- m/min|
|Cruising speed:||- km/hr|
|Range:||950 km||Service ceiling:||11 000 m|
|Engine type:||One Bristol Mercury VIII rated 830 hp .|
|Armament:||Four wing mounted Browning M-36 7,9 mm machine guns.|