On 21 April 1940, at the French test centre at Orléans-Bricy, a slim French fighter went up against a captured Messerschmitt Bf 109E. The German machine was faster in a straight line. But in a turning fight, the French aircraft could stay with it, and for the first time in the war France had a fighter that could meet the Luftwaffe’s best on something close to equal terms.

That fighter was the Dewoitine D.520. It was elegant, well armed and genuinely good, and it arrived just too late. When Germany attacked in the west on 10 May 1940, only one French fighter group was flying it. Six weeks later France had fallen, and the best fighter it built in 1940 went on to serve almost everyone except the side it was built for.

A fighter named after its target speed

In June 1936 the French Air Ministry asked for a fast, modern single-seat fighter. Émile Dewoitine set up a new design office, and his chief engineer Robert Castello began work on what became the D.520. The ministry, impressed by Britain’s new Hurricane and Spitfire, raised the bar to a top speed of 520 km/h. According to the French aviation historian Raymond Danel, the D.520 name was a deliberate nod to that number.

Official interest went first to the rival Morane-Saulnier MS.406, and Dewoitine’s company was swallowed by the new state-owned SNCAM in the 1936-37 nationalisation of French industry. Dewoitine, now its deputy managing director, kept the project alive as a private venture. On 3 April 1938 the ministry finally ordered two prototypes, and on 2 October 1938 the first D.520 flew.

The first prototype was a disappointment, reaching only about 480 km/h and overheating badly. A new radiator under the fuselage, ejector exhausts and a three-bladed variable-pitch propeller fixed most of that. By spring 1939 the D.520 had passed its design speed, and the first production order for 200 aircraft followed. As war approached, orders grew into the thousands.

Small engine, big punch

The D.520 was built around the Hispano-Suiza 12Y-45, a liquid-cooled V-12 of well under 1,000 hp. It was lighter than the Rolls-Royce Merlin but noticeably less powerful than the engines in the latest German and British fighters, and the D.520 topped out at about 530 km/h.

Where it shone was firepower. A 20 mm Hispano-Suiza HS.404 cannon fired through the propeller hub with 60 rounds, backed by four MAC 1934 machine guns of 7.5 mm in the wings with 675 rounds each. Older French fighters such as the MS.406 carried only two machine guns alongside the cannon. When a D.520 pilot ran out of cannon shells, he still had four fast-firing guns and plenty of ammunition left.

The pilot sat well back in the fuselage, behind the trailing edge of the wing, under a sliding canopy with armour plate behind the seat. That gave a good view downwards in flight, but on the ground the long nose in front of him was a real drawback when taxiing. Despite its modern design, the D.520 was considered more difficult to fly than the older MS.406. Fuel load mattered too: with full wing tanks, directional control suffered, especially in a dive.

Footage of the Dewoitine D.520, France’s most modern fighter of 1940.

The first production D.520 flew in November 1939, but early aircraft failed their acceptance tests on speed and cooling and had to be modified. The type was not declared combat ready until April 1940. Groupe de Chasse I/3 received its first, unarmed examples in January and only became fully equipped in the first days of May.

Six weeks in May and June 1940

On 10 May 1940, SNCAM had built 246 D.520s, but the air force had accepted only 79 of them. GC I/3 was the only operational group on the type. Over the following weeks four more Groupes de Chasse converted, along with naval fighter units, and production climbed fast. By the armistice in late June, 437 D.520s had been built.

In combat the D.520 did everything its designers had hoped. Against the Bf 109E it was slightly slower but more manoeuvrable, and the Musée de l’Air et de l’Espace at Le Bourget credits it with 108 confirmed and 39 probable victories in the Battle of France. Wikipedia’s figure is a little higher. Either way, a few hundred fighters had made a real mark in just six weeks.

Its most famous pilot was Pierre Le Gloan of GC III/6, whose group flew on the Italian front in June 1940. He went on to score 18 confirmed victories, almost all of them in the D.520. His aircraft, number 277, is the scheme carried today by the D.520 displayed at Le Bourget.

French historian David Méchin on how the D.520 was designed and built (in French).

Fighting for everyone

The armistice did not end the D.520’s career; it scattered it. Many of the surviving aircraft were flown to North Africa to avoid capture, helped by a fuel capacity that gave the D.520 more range than most contemporary single-seaters. In 1941 the Vichy government was allowed to resume production for its own air force.

Vichy D.520s fought British and Australian fighters over Syria and Lebanon in the summer of 1941, where Le Gloan added British aircraft to his tally. In November 1942 they fought again when the Allies landed in North Africa. After the Germans occupied the rest of France, captured D.520s became Luftwaffe trainers and were passed on to Axis allies.

The story came full circle in 1944. After the liberation of south-western France, Free French Forces of the Interior assembled a fighter group of recaptured D.520s under the former test pilot Marcel Doret, and flew them against the German pockets around Royan and Bordeaux until Spitfires replaced them in March 1945.

Aircraft Files traces the D.520 from its design to its service on both sides of the war.

The last D.520s left French service as trainers in 1953. Today a handful survive, the best known in the World War II hall at Le Bourget. They are a reminder of an uncomfortable what-if. France did build a fighter that could stand up to the Bf 109 in 1940. It simply did not build enough of them in time.

Sources: Wikipedia (Dewoitine D.520), History of War (J. Rickard), Musée de l’Air et de l’Espace via Seine-Saint-Denis Tourisme, HistoryNet, Wikimedia Commons