Fokker D-XXI [D-21]
The Fokker D-XXI [D-21] was the first mono-wing fighter design from the Dutch Fokker factory. In fact the plane was designed  for use by the Dutch Colonial Air Force, but in the end they rejected the prototype.
Design and construction
In December 1937 the Dutch War Department ordered 36 off D-XXI's for the Dutch Air Force, intended to form two fighter squadrons [2 x 12 plus 6 spare each]. The plane was fitted with the same engine as the Fokker G-1, the Bristol Mercury VIII. This caused the fuselage to be wide bodied. The cockpit was situated quite far to the rear, nearly behind the root of the wings. Since the landing-gear was quite high, the pilot had virtually no vision in front of him during take-off. In practise this proved to be a minor problem. The firm expansion-fitted landing-gear was not retractable, which surprisingly proved to cause only insignificant drag. The two extended 'legs' did however remain a remarkable feature of this quite successful fighter.
The plane was originally fitted without a capable aiming-device for its four wing-based 7.9 mm FN machineguns. Pilots themselves developed a simple rod construction in front of the canopie. Although later an optical device had been made available, the pilots preferred the old rod to serve their aiming purposes, which proved to be a fine working solution.
Fitted with the Mercury engine the plane proved to be slightly under-speeded for a modern mono-wing fighter. Due to the fact that the plane was under-powered, it was not suitable for any high altitude interception role. However, its efficient aerodynamic profile, low wing pressure and high engine torque were features that provided the D-XXI with excellent dog-fighting capacities, which it would proof when outmatching the much faster Bf-109 during the many dog-fight engagements in May 1940. The result was a positive dog-fight score against its adversaries. The Finnish airforce - that had ordered the D-XXI as well - proved even more successful with this fighter. A handful of Finnish D-XXI fighters claimed almost two-hundred air-victories over the Russian airforce during both Finnish-Russo wars.
The Finnish airforce also experimented with the Fokker design. Some of their D-XXI's were equipped with slides [for snowy terrain] in stead of the standard landing-gear, and also 20 mm guns were tested. Tests with retractable gear failed to pay off.
The Fokker D-XXI was the prime Dutch fighter during the May War. The majority survived the first Luftwaffe strike. Many were able to perform al sorts of low altitude interception and escorting duties during the five days in May 1940.
The D-XXI proved a hard plane to fly, anxious especially in low speed manoeuvring. But the well skilled fighter pilots loved to fly it. When they pilots soon experienced that they were able to compete with the Bf-109 and Bf-110, confidence grew. Yet the pilots complaint about the poor performance of the four high-firing rate machinguns, that too often failed and required frequent adjustment.
After the capitulation the majority of the remaining D-XXI's were destroyed by the Dutch. Only a few were captured by the Germans, and - as far as we have been able to trace - none was actively used in German service.
|Number in service:||36|
|Engines:||Bristol Mercury VIII, 830 hp|
|Speed:||460 km/hr max.[17,000 feet]|
|Weight [in flight]:||2,050 kg|
|Flight time [max]:||2 hrs [930 km]|
|Armament:||4 x 7.9 mm FN machinegun in the wings|