Editing Dewoitine D.520 (section)

===Production===
In April 1939, the rate of production of fighter aircraft throughout France was far beneath official expectations.<ref name="Danel 5"/> With the outbreak of war, a new contract brought the total of D.520s on order to 1,280, with the production rate to be 200 aircraft per month from May 1940. During January 1940, the ''[[French Naval Aviation|Aéronautique Navale]]'' placed its own order for 120 aircraft.<ref name="Danel 5"/> Another French Air Force order in April 1940 brought the total to 2,250 and increased production quotas to 350 a month.<ref name="Car730">Caruana 1998, p. 730.</ref> In addition to domestic orders, [[Poland]] was interested in acquiring around 160 D.520s in order.<ref name="Danel 5"/>

On 2 November 1939, the first-production D.520 conducted its first flight.<ref name="Danel 5"/> On this and the other aircraft, the rear fuselage was extended by {{cvt|51|cm}}, the engine cowling panels were redesigned, the curved, one-piece windscreen was replaced by one containing an optically flat panel and armour plate was fitted behind the pilot's seat.<ref name="Car730"/> Most production examples were powered by the {{cvt|935|CV|kW hp}} [[Hispano-Suiza 12Y]]-45 with the new [[Joseph Szydlowski|Szydlowski]]-Planiol [[supercharger]], although later production versions used the {{cvt|960|CV|kW hp}} [[Hispano-Suiza 12Y]]-49.<ref name="Danel 5 6">Danel 1971, pp. 5–6.</ref> The production standard armament was a {{cvt|20|mm|3}} HS.404 cannon firing through the propeller hub and four belt-fed MAC 1934 M39 {{cvt|7.5|mm|3}} machine guns in the wings.<ref name="Danel and Cuny 1966, p. 249">Danel and Cuny 1966, p. 249.</ref>

[[File:D.520 Le Bourget Cckpit06.jpg|thumb|The D.520 on display at Le Bourget showing the pilot's seat and armour plate]]
As the first batch of D.520s rolled off the production line, they failed acceptance tests due to insufficient top speed and troublesome cooling.<ref name="Danel 6">Danel 1971, p. 6.</ref> Redesigned compressor intakes, a modified cooling circuit and propulsive exhaust pipes proved to be effective remedies of these shortcomings, but as early examples had to be retrofitted with these improvements, the type was not declared combat ready until April 1940, at which point the D.520's operational standards had been defined.<ref>Danel and Cuny 1966, p. 73.</ref> In order to speed up the redesign process, a total of four production aircraft were handed back to SNCAM to serve as special test machines.<ref name="Danel 6"/>

The manufacturing process was deliberately optimized, each aircraft consumed a reduced 7,000 man-hours each to produce, roughly half the time compared to the previous D.510 and MS.406, and far less than many other fighters of the time, such as the MC.200/202 (21,000 hours), but around 50% greater than a Bf 109E (4,500 hours). The French Air Ministry planned for over 300 aircraft a month to be built and managed to reach this goal, especially in June 1940, but it was too late to affect the tide of battle.<ref name="Gigli-Cervi"/><ref name="Danel 3"/> The armistice greatly curtailed production of D.520, which would have otherwise been a fighter aircraft produced in far greater numbers and with improved models.<ref name="Danel 3"/>

Additional plans had included another manufacturing line at [[Asnières-sur-Seine]], [[Paris]], for a lightened version of the aircraft, known as the ''D.521''. An initial batch of 18 pre-production D.521s had been produced at [[Bagnères-de-Bigorre]], [[Occitania (administrative region)|Occitanie]] and had been prepared for their maiden flight when the armistice came into effect.<ref name="Danel 3"/> During 1940, negotiations with American manufacturer [[Ford Motor Company|Ford]] had been underway with the aim of establishing the licensed production of an Americanised version of the type, designated as the ''D.522''. This model was anticipated to have been powered by an [[Allison V-1710]]-C15 engine, capable of generating {{cvt|1040|hp|order=flip}}, instead.<ref name="Danel 3"/>

In April 1941, during the aftermath of the armistice with Germany, a new programme was launched in which the production of 1,074 new aircraft were to be manufactured in the unoccupied zone of [[Vichy France]].<ref name="Danel 10"/> Of these, 550 were to be D.520s, which were confirmed as ordered under contract No. 157/41 on 8 August 1941. The intention was for the type to replace all other single-engine fighters that remained in service with the [[Vichy French Air Force]] and to eventually equip additional units that were to be reformed from September 1942 onwards.<ref name="Danel 10"/> An initial batch of 22 D.520s were delivered during August 1941. In total, a further 180 machines were constructed, bringing the production total to 905.<ref name="Jackson p. 17.">Jackson 2003, p. 17.</ref><ref name="Danel 10"/>