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Dewoitine D 520
D 520

Type: Single-Seat Fighter
Origin: Dewoitine
First Flight: October 2, 1938
Service Delivery: February 1, 1940
Final Delivery: N/A
Number Produced: N/A

Model: Hispano-Suiza 12Y-45
Type: V12 Liquid cooled
Number: One       Horsepower: 910 hp

Wing span: 33 ft. 5.75 in. (10.2m)
Length: 28 ft. 8.5 in. (8.75m)
Height: 11 ft. 3 in. (3.4m)
Wing Surface Area: 171.91 sq. ft. (15.97 m²)

Empty: 4,630 lbs. (2100 kg)
Max. Take-Off: 6,173 lbs. (2800 kg)

Maximum Speed: 329 mph (530 km/h)
Initial climb: 2,362 ft./min. (720 m/min)
Service Ceiling: 36,090 ft. (11,000m)
Range: 777 Miles (1240 km)

One 20mm Hispano-Suiza 404 cannon firing through spinner
    Ammunition: 60 Rounds
Four 7.5mm MAC 1934 machine guns in wings
    Ammunition: 500 Rounds per gun

Design and development - Source: Wikipedia
Design of the Dewoitine 520 started in November 1936 at the private design firm led by Emile Dewoitine. Trying to address problems in earlier designs, he created a fighter using only the latest techniques and engines. The new design was to be able to reach 520 km/h and became known as the "520". Only months later the firm was conglomerated into one of a number of design-and-manufacturing pools, in this case SNCAM. Still known as the D.520, work on the design continued at the new company.

The prototype D.520 flew on 2 October 1938, powered by the new 890 hp (660 kW) Hispano-Suiza 12Y-21 liquid-cooled engine. The plane managed to reach only 480 km/h in flight tests, much slower than expected. Most of the problem seemed to come from greater than expected drag from the underwing radiators, so these were merged into a single radiator under the fuselage. After minor damage in a landing accident, the engine was changed to a newer -29 and included exhaust ejectors for added thrust, along with an adjustable prop. These changes were enough to allow the aircraft to reach its design speed.

The prototype was followed in 1939 with two airframes with a new sliding canopy and a larger tail unit. These were armed with a 20 mm cannon firing through the propeller spinner (a feature later found on many German and Russian designs) and two 7.5 mm machine guns in small pods under the wing. The third also included a small tail-wheel instead of the original skid. Flight tests went fairly well and a contract for 200 production machines to be powered by the newer -31 engine (later replaced by the -45) was issued in March of 1939. A contract for an additional 600 planes was issued in June reduced to 510 in July.

With the outbreak of war, a new contract brought the total to 1280, with the production rate to be 200 machines per month from May 1940. The Aéronautique navale then ordered 120. Another Armée de l'air order in April 1940 brought the total to 2250 and increased quotas to 350 a month.

The first production D.520 flew in November, powered by the 830 hp (620 kW) 12Y-31 and armed with two 7.5 mm machine guns in housings underneath the wings. It had a curved, one-piece windshield and a sliding canopy. The rest of the production machines were delivered with the 930 hp (690 kW) 12Y-45 engine with a new supercharger and a Ratier 3-bladed propeller (a few had the -49 of 910 hp (680 kW)). They were armed with a Hispano-Suiza 404 20 mm cannon firing through the propeller hub and four MAC 1934 7.5 mm machine guns in the wings. The curved, one-piece windshield from the prototypes was replaced with one containing an optically flat panel.

As the first batch of machines rolled off the production lines, they failed acceptance tests due to insufficient top speed and troublesome cooling. Redesigned compressor intakes, a modified cooling circuit and propulsive exhaust pipes proved to be effective remedies for these shortcomings, but as early examples had to be retrofitted with those improvements, the type was not declared combat-worthy until April.

Operational history - Source: Wikipedia

Battle of France

The Groupe de Chasse I/3 was the first unit to get the D.520, receiving its first aircraft in January 1940. These were unarmed and used for pilot training. In April and May they received 34 production machines, which proved to be very popular with the pilots. In tests against a captured Bf 109E-3 (handicapped by an engine that didn't develop full power), the D.520 proved to be 20 km/h slower, but had better high speed manoeuvrability. The D.520 matched the turning circle of the Bf 109 but displayed nasty departure characteristics, spinning out of the turn repeatedly during the tests while the Bf 109, owing to its slats, could easily sustain the turn on the edge of the stall.

When Germany invaded France and the Low Countries on 10 May, 228 D.520s had been manufactured, but the Armée de l'Air had only accepted 75, as most others had been sent back to the factory to be retrofitted to the new standard. As a result, only GC I/3 was fully equipped with the D.520, with 36 planes. They met the Luftwaffe on 13 May, shooting down three Henschel Hs 126s and one Heinkel He 111 without loss. GC II/3, GC III/3, GC III/6 and GC II/7 later completed their conversion to the D.520 and all took part in the Battle of France. A naval unit, the 1st Flotille de Chasse, was also equipped with the D.520. GC II/6 and GC III/7 converted to the D.520 but too late to see action.

By the time of the armistice at the end of June, 437 D.520s had been built and 351 of these had been delivered. In that time they had 108 confirmed kills and 39 probables, losing 54 to enemy action. As French resistance collapsed in the middle of June, GC I/3, II/3, III/3, III/6 and II/7 flew their aircraft to Algeria. Three more, from GC III/7, escaped to Britain and 153 machines remained in France.

Under Vichy

In April 1941, production was started again and in June, 550 were ordered to replace all other single-seat fighters. The plan was to have the D.520 eventually equip a total of 17 Groupes with 442 aircraft, three Aéronavale escadrilles with 37 aircraft each plus three training units with 13 aircraft. As per terms of the Armistice with Germany, all improvements were prohibited and planes of the new batch were similar with the ones manufactured one year earlier.

D.520s of GC III/6, II/3 and naval escadrille 1AC faced the allies during the Syria-Lebanon campaign in 1941, where they claimed 31 kills over British and Australian planes, while losing 11 of their own in air combat and 24 to AA fire, accidents, and attacks on their airfields. However, No. 3 Squadron RAAF — which had just converted to the new P-40 Tomahawk I — claimed five D.520s destroyed, for the loss of one P-40 in air combat.

During Operation Torch, GC III/3 (who was really GC I/3 renamed, as the previous unit with this designation had been disbanded) opposed the Allies over Oran, while Flottile 1F saw some action versus the US Navy over Casablanca. Many D.520s were destroyed on the ground.

D 520

Late and postwar service - Source: Wikipedia
In December 1942, as French forces formerly under Vichy had sided with the Allies, there were 153 D.520s left in French hands in North Africa. They flew a few patrols during the Battle of Tunisia, but were considered obsolete, and their radio sets were incompatible with Allied equipment. From early 1943 on, they were relegated to training duties at the fighter school in Meknes, and progressively replaced by Spitfires and P-39s in combat units.

During the liberation of France, a few examples abandoned by the Germans were used by ad hoc units in ground attacks against the isolated German pockets of resistance on the Western coast.

Postwar, those that remained in France were used as trainers, serving in this role until 1953.

Foreign users - Source: Wikipedia
As the German forces invaded Vichy's so-called "free zone" in November 1942, they captured 246 D.520s; additionally, a new batch of 130 was built under German occupation. Some were used by the Luftwaffe for training purposes. The Germans also transferred 120 D.520s to Bulgaria and 60 to Italy.

Variants - Source: Wikipedia
D.520 - Main production version.

D.521 - Hispano-Suiza engine replaced by a Rolls-Royce Merlin, one example built, project cancelled.

D.523 - Version powered by engine upgraded to the 1,100 hp-12Y51. Prototype was on trials in June 1940 but development was halted by the armistice.

D.520 DC ("Double Commande" – dual control) - Postwar two-seater conversion used by France.