ADEN cannon The Royal Small Arms Factory ADEN is a 30 mm revolver cannon used on many military aircraft , particularly those of the British Royal Air Force and Fleet Air Arm . Developed post - WWII primarily to meet British Air Ministry ' s requirement for increased lethality in aircraft armament , the cannon was fired electrically and is fully automatic once it is loaded . Design & development . 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 213 C , 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 , 430 ft / s ( 741 m / s ) is considerably 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 Harrier s 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 . ADEN 25 . The ADEN Mk 5 became the basis for the planned ADEN 25 , which was to be a somewhat larger weapon ( length : , weight : ) firing the new range of NATO 25 mm ammunition ( as in the American GAU - 12 Equalizer ) 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 . Unfortunately , 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 didn ' t 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 . Users . " Please note that this list is not exhaustive . "