The Dewoitine D.520 was slower than the Messerschmitt Bf.109E but clearly superior in manoeuvrability. A comparison was made on April 21, 1940, with an intact Bf.109E-3 that had been brought down in French territory. This comparison highlighted the fine qualities of the best French fighter of World War 11. Had France not surrendered in June 1940, the Dewoitine D.520's career might have been comparable to that of British and German fighters. Of the 775 D.520s built during the war, only 36 were on front-line duty on May 10, 1940, too few to have a significant effect.

The D.520 was born in 1936. It was a private undertaking of the famous French airplane builder Emile Dewoitine. But the military authorities did not officially accept the project until April 3, 1938. The French government had already ordered Morane Saulnier M.S.405s, and the development of still another fighter aircraft did not seem sensible. The first Dewoitine D.520 prototype took to the air on October 2, 1938, but it did not make a favourable impression. Because of the arrangement of the radiators, the engine overheated, and the plane failed to reach its expected speed of about 325 m.p.h. So the aircraft was altered. The radiators were moved from the wings to the belly of the aircraft, and the exhausts were redesigned, thus overcoming the main difficulties. A second prototype was built, and its rudder, cockpit, and landing gear were subsequently modified. During official test flights, this plane reached speeds up to 340 m.p.h. at 17,000 feet altitude. The plane reached a height of over 26,000 feet in 12 minutes and 53 seconds. When preliminary testing ended, in April 1939, a first order for 200 aircraft was placed, with delivery set between September and December. A second order was placed in June, for 510 planes. By April 1940, orders for the D.520 amounted to 2,320 aircraft, to be delivered at a rate of 350 per month.

5th Escadrille Groupe de Chasse III/6 Armee de l'Air de l'Armistice, Algeria 1941

Production was very slow because of difficulties in tuning the engine and putting finishing touches on the armament system. By January 1940, only 13 planes had come off the assembly line. Only in April, when the 139th aircraft was delivered, could the Dewoitine D.520 be considered fully operational. By June 25, when the armistice was signed, a total of 437 planes had been built. The Germans resumed production in the summer of 1941 and continued until December 1942. The Dewoitine D.520 was used by the Luftwaffe, Regia Aeronautica (60 aircraft in 1942-43), Bulgaria (120 aircraft from 1943), and Romania, as well as by Free French units when the Allies invaded Europe.

After the war a few dozen D.520s were equipped with double controls and used as training aircraft. The last D.520 fighters remained in service until September 1953, in a special non-combat unit, the Escadrille de Presentation of the Armee de l'Air.

Specifications (Dewoitine D.520)

Type: Single Seat Fighter

Design: Dewoitine

Manufacturer: SNCA du Midi

Powerplant: One 935 hp (698 kw) Hispano-Suiza 12Y 45 12-cylinder inline, liquid cooled, piston engine.

Performance: Maximum speed 332 mph (535 km/h) at 18,100 ft (5500 m); service ceiling 34,540 ft (10500 m).

Range: 552 miles (890 km) with internal fuel stores.

Weight: Empty 4,490 lbs (2036 kg) with a maximum take-off weight of 6,160 lbs (2790 kg).

Dimensions: Span 33 ft 6 in (10.20 m); length 28 ft 9 in (8.76 m); height 8 ft 5 in (2.57 m); wing area 171.84 sq ft (15.97 sq m).

Armament: One 20 mm Hispano-Suiza 404 cannon firing through the propeller hub, plus four 7.5 mm (0.295 in) MAC 34 M39 machine guns.

Variants: D.520 (prototype and production), D.521 (a single D.520 with a 1,030 hp (768 kw) Rolls Royce Merlin engine but this proved unsatisfactory), D.524 (the single D.521 with a 1,200 hp (895 kw) Hispano-Suiza 12Z engine), D.530 (planned upgrade using a 1,400 hp (1045 kw) Rolls-Royce or a 1,800 hp (1342 kw) Hispano-Suiza 12Y engine, but it was never built), D.550 (racing version of the D.520 with a more powerful engine and shorter wings), D.551/D.552 (military versions of the D.550 powered by the 12Y 51 or 12Z engines, respectively. Neither were never built due to the German occupation).