An single-seater, all-metal, closed-canopy monoplane fighter with retractable landing gear and a tail wheel. A prototype D.520-01 saw its first flight on October 2, 1938. The first production run was started in October of 1939, after World War II had already begun. In April of 1940, the French Air Force (Armée de l'Air) began using the D.520 in Groupe de Chasse 1/3, which was comprised of pilots who had already gained combat experience in the war.
The Dewoitne D.520 fighter was equipped with a V-12 liquid-cooled Hispano-Suiza HS12Y-45 engine with a takeoff power of 910 hp. Its armament included one Hispano-Suiza HS404 20mm cannon with 60 rounds and four belt-fed MAC 1934 M39 7.5mm machine guns in the wings with 675 rounds each.
The plane's design was new and somewhat raw, but it started production immediately as there was no time for the proposed improvements to be implemented. Instead, upgrades would be made during production, as time allowed. The production model had a redesigned carburetor air intake and a modified cooling system for the engine. Later Dewoitines featured jet exhaust pipes. The production model was sometimes referred to as the D.520S («serial») or the D.520C1 («chausser 1,» that is, single-seat fighter).
The Dewoitine D.520 flew for the first time in May of 1940 and a majority of its victories (18 confirmed kills) were won by one of the leading French aces, Adjudant-Chief (then Sous-Lieutenant) Pierre Le Gloan from GC III/6. Production of the D.520 was halted when France surrendered in the summer of 1940 and then restarted under German occupation in April of 1941.
Beginning in September 1942, the D.520 was the main fighter aircraft of the puppet government of Vichy. From April 1941 onward, the D.520s took part in clashes with British troops in Lebanon and Syria. In November of 1942, some D.520s joined la France Libre and fought for the Allies in North Africa. The D.520 also served with the Luftwaffe, and the Germans supplied the fighters to their allies in Italy, Bulgaria, and Romania.
The Dewoitine D.520 is rightly considered the best French fighter plane of World War II. Its initial competition included the Spitfire and the Messerschmitt. According to its characteristics, the Dewoitine was on about the same level as the rival German Bf-109E, though inferior in speed by 30 to 40 kph. Pilots who flew the D.520 reported excellent flight characteristics, good weaponry, and a comfortable and spacious cabin.
D.520 fighters were mass manufactured intermittently until June 1944, and in all, 610 were produced. The last planes, used as trainers, were retired by the French Air Force after the war, in September 1953.