Designed by a team led by Dr-Ir Erich Schatzki and retaining traditional Fokker-type mixed construction, the D XXI was conceived in answer to a specification formulated by the KNIL (Koninklijk Nederlands Indisch Leger), the aviation element of the Royal Netherlands Indies Army, and was flown as a prototype on 27 February 1936. In the event, the initial production order was placed by the Finnish government, which acquired a manufacturing licence, a contract subsequently being issued in the Netherlands on behalf of the homebased LVA (Luchtvaartafdeling). The latter purchased 36 D XXIs powered by the 825hp Bristol Mercury VIII nine-cylinder radial engine and armed with four wing-mounted 7.9mm FN-Browning M.36 guns. Seven were acquired from the parent company by Finland, with delivery flights commencing 27 August 1937, and a further 35 were licence-built by VL (Valtion Lentokonetehdas), these being armed with four 7.7mm Brownings, two being fuselage mounted, and having PZL- or Tampella-built Mercury VII engines of 840hp. Two D XXIs were purchased by Denmark which subsequently licence-built a further 10, these mounting a pair of 20mm Madsen cannon and two 7.9mm machine guns, and licence manufacture was also initiated in Spain by Hispano Aviacion, assembly being undertaken at the SAF-15 factory at La Rabasa, Alicante. At least one D XXI was completed and flown in Spain with a Soviet M-25 engine taken from an I-16 before the production facility was overrun by Nationalist forces. At that time, 50 sets of wings, 25 fuselages and 25 undercarriages for D XXIs were discovered. The D XXI was offered by Fokker with various engines, including the Pratt & Whitney Twin Wasp Junior, and the basic D XXI was further developed with this engine in Finland by VL. The last Finnish-built Mercury-engined D XXI was fitted with a Finnish-designed retractable undercarriage after suffering a landing accident. It was test flown on 19 June 1941, the fixed gear being restored after another landing accident a month later.

3-View

A three-view drawing (1280 x 952)