The ADEN (named for the Armament Development Establishment, where it was designed, and Enfield, where it was produced) was developed in the late 1940s as a replacement for the older Hispano-Suiza HS.404 20 mm cannon used in British aircraft of World War II. It is based (as are the French DEFA cannon and American M39 cannon) on the mechanism of the German Mauser MG 213C, an experimental revolver cannon designed for the Luftwaffe, but never used in combat. The ADEN entered service on the Hawker Hunter in 1954, and subsequently used on every British gun-armed aircraft until the advent of the Panavia Tornado in the 1980s.
The current version is the ADEN Mk 4. Although its muzzle velocity of 2,592 ft/s (790 m/s) is lower than the Hispano's 2,789 ft/s (850 m/s), the substantially larger and heavier projectile makes the ADEN more lethal, and it has a higher rate of fire of about 1,300 rounds per minute.
An improved version, the ADEN Mk 5, incorporates a multitude of small changes to improve reliability and increase rate of fire slightly to 1,500–1,700 rounds per minute. No new Mk 5s were built, but many older weapons were converted, being redesignated Mk 5 Straden.
Aircraft using the ADEN 30 as in-built armament have included the A-4S Skyhawk, English Electric Lightning, Folland Gnat (and HAL Ajeet), Hawker Hunter, Gloster Javelin, Saab Lansen, Saab Draken, SEPECAT Jaguar, Supermarine Scimitar, and CAC Sabre. Several podded versions exist, including the installations scabbed below the fuselage of British Hawker Siddeley Harrier (and USMC AV-8A/Cs) and Sea Harriers and the Swedish FFV Aden, which is used (among others) on the BAE Hawk. The FFV Aden contains the weapon and 150 rounds of ammunition, is 151.57 in (3.85 m) long, and weighs 802.5 lb (364 kg) fully loaded.
The ADEN is very similar to the French DEFA cannon, and the two weapons use the same range of 30 mm ammunition.