Morane-Saulnier MS.406

The Morane-Saulnier MS.406 was the most numerous French fighter in service during the Battle of France in May-June 1940, and the first modern monoplane fighter to equip the Armee de l'Air in significant numbers. With its enclosed cockpit, retractable landing gear, and 20mm engine-mounted cannon, the MS.406 represented a dramatic modernization of French fighter aviation when it entered service in early 1939, but by the time Germany attacked in May 1940, it was already outclassed by the Messerschmitt Bf 109E in virtually every performance metric.

The MS.406 was not a bad aircraft. It was pleasant to fly, maneuverable at low and medium altitudes, and its 20mm Hispano-Suiza cannon gave it respectable firepower. But its Hispano-Suiza 12Y-31 engine produced a mere 860 horsepower, giving it a top speed of only 302 mph, roughly 50 mph slower than the Bf 109E. French pilots who flew the MS.406 against German fighters knew they were at a significant disadvantage and relied on teamwork, aggressive tactics, and the aircraft's tight turning radius to survive.

Despite its limitations, the MS.406 fought hard during the six weeks of the Battle of France. Equipped with the type, French fighter groups claimed 191 aerial victories against 89 combat losses, a creditable performance for an outclassed aircraft flown by determined pilots. After France's fall, the MS.406 continued to serve with several air forces, most notably Finland, where modified versions known as Morko-Moraani fought effectively against the Soviets.

The MS.406 traced its origins to a 1934 French Air Ministry requirement for a modern single-seat fighter capable of 400 km/h. Morane-Saulnier's response, the MS.405, first flew on August 8, 1935, making it one of the earliest low-wing, enclosed-cockpit monoplane fighters in Europe. The design was conventional but sound: a mixed wood-and-metal construction with fabric-covered control surfaces, a retractable main undercarriage, and the engine-mounted 20mm cannon that was becoming a French trademark.

The prototype showed promise but suffered from chronic engine cooling problems and structural issues that delayed development. The French aviation industry's nationalization in 1937 further complicated matters, as Morane-Saulnier's factory was reorganized under the SNCAO (Societe Nationale de Constructions Aeronautiques de l'Ouest). Despite these disruptions, the production version, designated MS.406, received its first orders in 1938, and deliveries began in earnest in early 1939.

By September 1939, approximately 600 MS.406s were in service, making it the backbone of the French fighter force. Production continued into 1940, eventually reaching 1,081 aircraft. However, the MS.406 was already being recognized as inadequate. The engine, which had seemed adequate in 1936, was hopelessly underpowered by 1940 standards. Attempts to install the more powerful Hispano-Suiza 12Y-45 or -51 engines were frustrated by supply shortages, those engines were allocated to the higher-priority D.520 program.

The Swiss Air Force purchased 82 MS.406s (designated D-3800) and license-built a further 207, designated D-3801 with a more powerful engine. Finland received 30 MS.406s and later modified them extensively, fitting captured Soviet Klimov VK-105 engines to create the Morko-Moraani ("Bogy Morane"), which achieved remarkable success against Soviet aircraft on the Finnish Front.