Editing Dewoitine D.520 (section)

===Specification and rivals===
On 12 January 1937, the A.23 technical programme was launched by the Air Ministry.<ref name="Danel 4"/> The specifications called for a maximum speed of {{cvt|520|km/h}} at {{cvt|4000|m}}, the ability to climb to {{cvt|8000|m}} in less than fifteen minutes, with takeoff and landing runs not exceeding {{cvt|400|m}}.<ref name="Danel 3 4"/> The armament was to be two {{cvt|7.5|mm|3}} [[machine gun]]s and one {{cvt|20|mm|3}} [[Oerlikon FF|Hispano-Suiza HS.9 cannon]], or two HS.9 cannons.<ref name="Dan30">Danel and Cuny 1966, p. 30.</ref>

Other aircraft designed to the same specification included the [[Morane-Saulnier M.S.406#M.SE0|Morane-Saulnier M.S.450]], the [[SNCAO 200|Loire-Nieuport 60 (later C.A.O 200)]], and the [[Caudron C.714|Caudron-Renault C.770]], none of which either left the drawing board or entered service. Two other concurrent French designs, the [[Bloch MB.150#Variants|Bloch MB.152.01 and Bloch MB.155.C1]] series and the [[Arsenal VG-33]] entered service in small numbers with the French Air Force during the Battle of France, but too late to play a significant role.<ref>Danel and Cuny 1966, pp. 28, 295.</ref>

In addition to the lack of a prototype order, Dewoitine was absorbed into the larger Société nationale des constructions aéronautiques du Midi ([[SNCAM]]) state-owned manufacturing consortium. As a result of this organisational restricting, along with continued alterations within the French Air Force's established manufacturing programmes, work on the design of the D.520 was suspended throughout much of 1937, and it was not until January 1938 that a small number of draughtsmen started work on the first detailed drawings for the [[prototype]].<ref>Danel and Cuny 1966, pp. 30, 296.</ref>

However, Émile Dewoitine, now the deputy managing director of SNCAM, was keen to proceed with the project and decided to proceed to the detail design drawing phase with the aim of producing a pair of prototypes and a single structural test frame, confident that official interest would be found for the type.<ref name="Danel 4"/> On 3 April 1938, this private initiative was rewarded with the issuing of Air Ministry contract No. 513/8, which regularised the programme; by this point, the first prototype had almost been completed.<ref name="Danel 4"/>