During World War II, the German firm Mauser began development of a radically new 20 mm autocannon using a motorised firing mechanism in order to improve the rate of fire. By the late-war period the Mauser MG 213 was beginning to mature, but by this time the presence of large bombers like the Boeing B-17 and Avro Lancaster led to the rapid up-arming of Luftwaffe fighter aircraft. Mauser responded by adapting the MG 213 to fire the 30 mm round from the MK 108 cannon. This relatively small 30 mm round had a low muzzle velocity but included a large explosive charge that was useful against non-manoeuvering targets like bombers. Development of this MG 213C version was still ongoing when the war ended. In the post-war era, the MG 213 became well known in armament circles, and a number of companies took up development. This included the Armament Development Establishment in the UK and GIAT in France. A common 30×113mm round was developed that offered a dramatic improvement in muzzle velocity from the MK 108's 540 m/s to the new design's 790 m/s. This was only slightly lower than contemporary 20 mm cannon like the Hispano Mk. V's 840 m/s, making the new round suitable for use during dogfights as well as against larger targets. The mechanism improved the rate of fire from the Mk. V's 750 rpm to 1,300 rpm, a significant improvement. The new weapon was quickly developed and production was set up at the Royal Small Arms Factory in Enfield; the name was created by combining the ADE initials of the Armament Development Establishment with N for Enfield, producing ADEN. 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 last version to see production was the Mk. IV. An improved version, the Mk. 5, incorporates a multitude of small changes to improve reliability and increase rate of fire 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, 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 Sea Harriers and the Swedish FFV Aden, which is used on the BAE Hawk. The FFV Aden contains the weapon and 150 rounds of ammunition, is 151.57 in long, and weighs 802.5 lb fully loaded. GIAT also introduced their version of the design as the DEFA cannon. The two weapons are very similar and can use the same ammunition.
ADEN 25
The ADEN Mk 5 became the basis for the planned ADEN 25, which was to be a somewhat larger weapon firing the new range of NATO25 mm ammunition at a much higher muzzle velocity of. The lighter ammunition was also to produce a higher rate of fire, 1,650 to 1,850 rounds per minute. Severe development problems plagued the ADEN 25, which proved unable to meet its design weight target. It was finally cancelled in 1999. As a result, RAF Harrier GR.7 and GR.9 aircraft did not carry a cannon, no attempt apparently having been made to retrofit the older ADEN 30 mm pods. Fleet Air Arm Sea Harriers retained the 30 mm weapon until their retirement in 2006.
