Dewoitine D.520 — Notice Descriptive et d'Utilisation

Ministère de l'Air · Armée de l'Air — Primary-Source Archival Edition

France's most capable fighter at the outbreak of the Second World War, the Dewoitine D.520 represented the pinnacle of SNCAM engineering under Émile Dewoitine — a masterful balance of aerodynamic refinement, liquid-cooled V12 power, and exceptional handling stability. This archival edition presents the original Notice Descriptive et d'Utilisation de l'Avion de Chasse D.520 S, issued by the Ministère de l'Air / Armée de l'Air, together with the official Tableau des Caractéristiques data sheet.

Document Manifest

• Notice Descriptive et d'Utilisation — Avion de Chasse D.520 S, Moteur 12-Y45 — Ministère de l'Air / Armée de l'Air, original issue. Covers airframe description, systems utilisation, and operational procedures.
• Tableau des Caractéristiques — Avion D.520 S — Official characteristics data sheet. Covers: Forme, Spécifications et Emploi; Encombrement et Assiette de Garage (full dimensional data); undercarriage geometry; propeller ground clearance at all oleo coefficients.

Airframe Geometry — From the Tableau des Caractéristiques

• Envergure maximum: 10 m 200
• Longueur totale: 8 m 760
• Hauteur totale (ligne de vol, train sorti): 3 m 390
• Hauteur de l'axe hélice au-dessus du sol — Au repos, coefficient 1 (mi-course, ½ aplatiss.): 2,265 m | tout à plat: 2,030 m
• En ligne de vol, coefficient 1: 1,845 m | tout à plat: 1,615 m
• Garde de l'hélice — Au repos, coefficient 1: 0,74 m | tout à plat: 0,465 m
• En ligne de vol, coefficient 1: 0,32 m | tout à plat: 0,09 m
• Angle au sol (tangente à la roue / extrémité hélice, en ligne de vol, coefficient 1): 10°
• Type: Avion de chasse monoplace, monomoteur, refroidissement par liquide, monoplan cantilever à aile basse

Aerodynamic Design & Airframe Engineering

The SNCAM design team prioritised strict drag reduction to extract maximum velocity from a lower-horsepower engine. The wing adopted an all-metal, single-spar duralumin-skinned structure with a NACA 23012 airfoil profile on the vertical stabiliser to enhance tracking stability at high speeds.

The original prototype (D.520-01) suffered from severe engine overheating via dual underwing radiators. Aerodynamic revisions relocated the cooling apparatus into a single, aerodynamically clean under-fuselage bath, resolving boundary layer separation issues. Under the SNCASE design office in 1942, advanced aerodynamic modelling on D.520 No. 465 eliminated stray airframe drag trails — sealing manufacturing gaps and redesigning engine cowlings shaved 0.65 off the 100 Cx drag coefficient.

Engine Technical Notes — Hispano-Suiza 12Y-45

• Powerplant: Hispano-Suiza 12Y-45, 12-cylinder liquid-cooled V12 — 930 hp (697 kW) at take-off
• Supercharger: Mechanically driven, single-stage, single-speed
• Propeller: Three-blade variable-pitch pneumatic Ratier or Chauvière
• Moteur-canon configuration: Engine blocks cast with a central hollow axis between cylinder banks, allowing a 20 mm Hispano-Suiza HS-404 autocannon to fire through the propeller hub — a defining engineering characteristic of the type

Handling & Stability

Official CEMA (Centre d'Essais du Matériel Aérien) flight testing reported the D.520 as an exceptionally pleasant, stable, and highly manoeuvrable gun platform. Wide-track undercarriage retracted inward into the wing profile — unlike the narrow-track Bf 109 — giving excellent ground handling stability and minimising ground loop risk on unpaved airfields. Aerodynamic reports validated superb stall warning behaviour and predictable spin recovery, making the type significantly safer for low-hour pilots transitioning from biplanes.

• Flight controls: High-aspect-ratio fabric-covered ailerons; pneumatically actuated split trailing-edge flaps

Performance Data — CEMA Trials

Engineering Bulletins & Variants

• Bulletin D.520-S / No. 465 — Higher-pressure supercharger compressor wheel fitted to production lines to boost high-altitude performance under occupational restrictions
• Bulletin D.524 — Experimental installation of the 1,200 hp Hispano-Suiza 12Y-89; nose assembly lengthened to accommodate modified cooling plumbing
• Bulletin SE.520Z — Post-war structural conversion framework for the 1,600 hp Hispano-Suiza 12Z engine; all secondary machine guns relocated entirely inside the wing profile for a pure wing-cannon layout

This is an archival, static-copy edition fixed at its original publication date. Intended for historical reference, flight simulation, museum restoration, and educational use only. Not approved for active airworthiness maintenance under FAA 14 CFR § 43.13, EASA Part-M, or equivalent international regulations. Operators of active aircraft must use current, revision-controlled publications from the Type Certificate holder or an authorised distributor.

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