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| HS.404 | |
|---|---|
| Name | HS.404 |
| Caption | Hispano-Suiza HS.404 20mm autocannon |
| Origin | France |
| Type | autocannon |
| Designer | Hispano-Suiza |
| Designed | 1935 |
| Manufacturer | Hispano-Suiza, SNECMA, British Alvis, Bristol Aircraft, Oerlikon |
| Production date | 1938–1950s |
| Weight | 43 kg (barrel and receiver; varies by mount) |
| Length | 1780 mm |
| Cartridge | 20×110mm Hispano |
| Caliber | 20 mm |
| Action | gas-operated short recoil |
| Rate | 700–850 rounds per minute (varies) |
| Velocity | 840–880 m/s |
| Feed | 60-round drum or belt (model dependent) |
HS.404 The HS.404 is a 20 mm autocannon developed by Hispano-Suiza in the late 1930s, widely used by many air forces and navies during World War II and beyond. Noted for its high muzzle velocity, compact profile, and adaptability, the cannon powered fighters and naval mounts from France to United Kingdom, United States, Spain, and beyond. Its design influenced later autocannon families and spawned licensed production, variants, and derivative weapons that saw extensive combat in conflicts from the Second World War to the postwar era.
Design work began at Hispano-Suiza under the technical direction of firm engineers responding to requirements from the French Air Force and export customers for a powerful 20 mm automatic armament. The HS.404 combined elements from earlier Hispano projects and contemporary developments at Oerlikon and Mauser, adopting a gas-operated, locking-breech mechanism with a barrel recoil buffer to control cyclic stresses. Early trials involved test beds at Istres and industry trials overseen by French ordnance authorities and led to production tooling shared with SNECMA and licensed firms. With the outbreak of World War II, displaced French tooling and engineers influenced licensed manufacture in the United Kingdom by Bristol Aircraft and by Alvis for aircraft installations, while captured examples and blueprints affected production decisions in Nazi Germany and neutral states.
The HS.404 fires the 20×110mm Hispano cartridge from a 60-round drum or belt feed adapted for wing-mount or turret installations. The weapon uses a gas-operated, swinging lock system with a short recoil and gas tappet to cycle at a nominal 700–850 rounds per minute; muzzle velocity ranges around 840–880 m/s depending on barrel length and ammunition type. Dimensions and mass vary by installation—fighter-mounted variants prioritized compact length and weight reductions for installations in Supermarine Spitfire and Hawker Hurricane wings, while naval mountings added water-cooled jackets and reinforced receivers for continuous fire in Royal Navy AA mounts. Ammunition types included high-explosive, high-explosive incendiary, and armor-piercing rounds developed by state arsenals such as Woolwich Arsenal, Atelier de St. Etienne, and later by American and Spanish manufacturers.
Licensed and improvised versions proliferated: British production produced the Hispano Mk.II, Mk.III and Mk.V adaptations for fighters including the Supermarine Spitfire, Hawker Typhoon, and de Havilland Hornet; American firms produced the T17 and designated HP/HT-series trials for installation in P-38 Lightning and P-39 Airacobra prototypes. Postwar derivatives include revisions by SNECMA and Spanish firms that led to the HS.820 line and influenced designs by Oerlikon and GIAT Industries. Naval and ground versions featured water-cooled barrels, power drives, and integration into systems like the Bofors mounting families and various twin and quad turrets fitted on HMS Ark Royal escorts and escort carriers.
Entering service in the late 1930s with the Armée de l'Air and exported to allied air arms, the HS.404 saw early combat in the Spanish Civil War and extensive action during World War II. After the Fall of France, surviving stocks and tooling supported Royal Air Force conversions and expedited British Mk.II and Mk.III production. The cannon equipped frontline fighters and naval close-range defenses throughout the conflict and was retained in many postwar inventories during conflicts in Korea and colonial theaters, being mounted on transport aircraft, jet trainers, and coastal batteries.
Operator states included France, United Kingdom, United States, Spain, Belgium, Netherlands, Portugal, Italy (postwar), Chile, Peru, Argentina, Egypt, Greece, Turkey, Sweden (licensed and imported), and numerous Commonwealth air forces such as Royal Australian Air Force and Royal Canadian Air Force. Many navies, including the Royal Navy, Spanish Navy, and various South American naval forces, adopted naval variants. Licensed and captured stocks also found their way into armed forces of Nazi Germany and neutral European states during the wartime period.
In aerial combat, the HS.404's high muzzle velocity and effective 20 mm explosive payload made it lethal against contemporary bomber and fighter designs such as Messerschmitt Bf 109, Junkers Ju 88, Heinkel He 111, and Focke-Wulf Fw 190. Pilots flying aircraft armed with the cannon, including those of RAF Fighter Command and USAAF units, reported improved destructive effect over rifle-caliber machine guns, though early reliability and feeding problems in certain installations—most notably in some Mk.I British production—required remedial engineering and gunnery training changes exemplified by reports circulated through Air Ministry and USAAF ordnance channels. Naval anti-aircraft installations benefited from the round’s explosive performance against low-flying attackers during convoy actions and carrier operations in the Atlantic and Mediterranean theaters.
Surviving HS.404 examples are preserved in collections and museums such as the Royal Air Force Museum, Imperial War Museum, Musée de l'Air et de l'Espace, National Museum of the United States Air Force, and maritime museums with restored escort carrier and destroyer exhibits. Restored fighters and naval mounts at airshows and naval heritage sites display functional and inert HS.404 units, while specialty restorers and private collections in United Kingdom, France, Spain, and United States maintain firing-capable and deactivated specimens. Many ordnance archives in national arsenals retain technical drawings, service manuals, and spare components used in restoration projects.
Category:Autocannon Category:20 mm artillery