The General Dynamics GAU-12/U Equalizer is a five-barrel 25 mm Gatling-type

rotary cannon A rotary cannon, rotary autocannon, rotary gun or Gatling cannon, is any large-caliber multiple-barreled automatic firearm that uses a Gatling-type rotating barrel assembly to deliver a sustained saturational direct fire at much greater ra ...

. The GAU-12/U is used by the United States, Italy and Spain, which mount the weapon in their attack jets such as the AV-8B Harrier II, airborne

gunship A gunship is a military aircraft armed with heavy aircraft guns, primarily intended for attacking ground targets either as airstrike or as close air support. In modern usage the term "gunship" refers to fixed-wing aircraft having laterally-mo ...

s such as the Lockheed AC-130, and land-based fighting vehicles. A lighter four-barrel version, designated GAU-22/A, is mounted on

F-35 Lightning II The Lockheed Martin F-35 Lightning II is an American family of single-seat, single-engine, supersonic Stealth aircraft, stealth strike fighters. A multirole combat aircraft designed for both Air superiority fighter, air superiority and att ...

fighter jets. Multiple-barrel firearms

Development

The five-barrel Equalizer cannon was developed in the late 1970s, based on the mechanism of the 30mm GAU-8/A Avenger cannon, but firing a new

NATO The North Atlantic Treaty Organization (NATO ; , OTAN), also called the North Atlantic Alliance, is an intergovernmental organization, intergovernmental Transnationalism, transnational military alliance of 32 Member states of NATO, member s ...

series of 25 mm ammunition. The GAU-12/U cannon is operated by an 11 kW (15 hp)

electric motor An electric motor is a machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a electromagnetic coil, wire winding to gene ...

, or in external mounts supplied by a

bleed air Bleed air in aerospace engineering is compressed air taken from the compressor stage of a gas turbine, upstream of its fuel-burning sections. Automatic air supply and cabin pressure controller (ASCPC) valves bleed air from low or high stage engine ...

driven pneumatic system. Its rate of fire is normally 3,600 rounds per minute, with a maximum of 4,200 rounds per minute. For use in the

AC-130 The Lockheed AC-130 gunship is a heavily armed, long-endurance, attack aircraft, ground-attack variant of the C-130 Hercules transport, fixed-wing aircraft. It carries a wide array of ground-attack weapons that are integrated with sensors, nav ...

gunship, the fire rate is limited to 1,800 rounds per minute in order to conserve ammunition and reduce barrel wear.

GAU-22/A

The GAU-22/A is a four-barrel version of the GAU-12/U designed for use on the

. The GAU-22/A's major difference is the use of four barrels, rather than the GAU-12/U's five barrels. The GAU-22/A is lighter and has a reduced rate of fire of 3,300 rounds per minute, but maintains the same, high accuracy of 5

milliradian A milliradian (International System of Units, SI-symbol mrad, sometimes also abbreviated mil) is an SI derived unit for angular measurement which is defined as a thousandth of a radian (0.001 radian). Milliradians are used in adjustment of ...

s, 80% circle of the GAU-12 and A-10's GAU-8. The weapon is produced by

General Dynamics General Dynamics Corporation (GD) is an American publicly traded aerospace and defense corporation headquartered in Reston, Virginia. As of 2020, it was the fifth largest defense contractor in the world by arms sales and fifth largest in the Unit ...

Ordnance and Tactical Systems. The

Nammo Nammo, short for Nordic Ammunition Company, is a Norwegian- Finnish aerospace and defence group specialized in production of ammunition, rocket engines and space applications. The company has subsidiaries in Finland, Germany, Norway, Sweden, Sw ...

25 mm PGU-47/U

APEX The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics) A-Bomb Abomination Absorbing Man Abraxas Abyss Abyss is the name of two characters appearing in Ameri ...

(Armor Piercing with Explosive) projectile has been developed for the GAU-22/A."Norway contracts for F-35 ammunition."
''UPI'', 29 November 2010. It features a tungsten carbide penetrator in the tip and an explosive fragmentation body, to be multi-purpose against both hardened and soft targets. Also, the presence of a clockworking inertia-driven mechanical

fuze In military munitions, a fuze (sometimes fuse) is the part of the device that initiates its function. In some applications, such as torpedoes, a fuze may be identified by function as the exploder. The relative complexity of even the earliest fu ...

in the mid-body, protects the round from shocks, misfires and cookoffs, making it safer to handle and fire.

Uses

The current principal application for the Equalizer is the AV-8 Harrier IIs of the

United States Marine Corps The United States Marine Corps (USMC), also referred to as the United States Marines or simply the Marines, is the maritime land force service branch of the United States Department of Defense. It is responsible for conducting expeditionar ...

Italian Navy The Italian Navy (; abbreviated as MM) is one of the four branches of Italian Armed Forces and was formed in 1946 from what remained of the ''Regia Marina'' (Royal Navy) after World War II. , the Italian Navy had a strength of 30,923 active per ...

and

Spanish Navy The Spanish Navy, officially the Armada, is the Navy, maritime branch of the Spanish Armed Forces and one of the oldest active naval forces in the world. The Spanish Navy was responsible for a number of major historic achievements in navigation ...

. The Harrier II carries the Equalizer system in a pair of detachable pods mounted on the fuselage underside, with the cannon in the port pod and 300 rounds of ammunition in the starboard pod, fed through a bridge at the aft ends of the pods that also contains the drive system for the gun (unlike previous Harriers which used dual cannons, with each pod containing a 30mm ADEN gun and its own ammunition supply). The complete installation, which includes a double-ended feed system that returns empty cartridges to the

magazine A magazine is a periodical literature, periodical publication, print or digital, produced on a regular schedule, that contains any of a variety of subject-oriented textual and visual content (media), content forms. Magazines are generally fin ...

, weighs 900 lb (410 kg) empty and 1,230 lb (560 kg) loaded. The detachable pods are located and shaped to be interchangeable with the usual ventral strakes or fences under the Harrier, both serving to help trap a cushion of high-pressure air under the aircraft to add lift while in hover mode. The strakes can easily be removed and the pods attached in their place, serving the same function while adding useful firepower. RAF and

Fleet Air Arm The Fleet Air Arm (FAA) is the naval aviation component of the United Kingdom's Royal Navy (RN). The FAA is one of five :Fighting Arms of the Royal Navy, RN fighting arms. it is a primarily helicopter force, though also operating the Lockhee ...

Harriers did not adopt the Equalizer for their Harrier GR7 and GR9s. The British had originally planned a pair of ADEN 25 guns (using the same ammunition as the GAU-12/U, but based on the 30 mm

ADEN cannon The Royal Small Arms Factory ADEN cannon (ADEN being an acronym for "Armament Development, Enfield") is a 30 mm revolver cannon used on many military aircraft, particularly those of the British Royal Air Force and Fleet Air Arm. Developed p ...

). That gun was canceled in

1999 1999 was designated as the International Year of Older Persons. Events January * January 1 – The euro currency is established and the European Central Bank assumes its full powers. * January 3 – The Mars Polar Lander is launc ...

after protracted development problems, and British Harrier GR7/9s were without gun armament until retirement. The Equalizer is also used in the AC-130U Spooky

, where one cannon is mounted on the port side, and the U.S. Marine Corps LAV-AD air-defense vehicle. Other applications have been planned for the GAU-12/U, including a mounting for the AH-1 Cobra

attack helicopter An attack helicopter is an armed helicopter with the primary role of an attack aircraft, with the offensive (military), offensive capability of engaging ground targets such as enemy infantry, military vehicles and fortifications. Due to their ...

. The Equalizer was also used as the basis for the ''Sea Vulcan 25'', a turret mounted gun for naval ship self-defense, although not as a

Close-In Weapon System A close-in weapon system (CIWS ) is a point-defense weapon system for detecting and destroying short-range incoming missiles and enemy aircraft which have penetrated the outer defenses, typically mounted on a naval ship. Nearly all classes of l ...

, as the gun was not automatic nor did it use radar tracking. Instead the gun was manually aimed using a digital gun sight and fire control. Sea Vulcan consisted of a 540-round helical drum magazine, a one-piece aluminum turret that can be opened with just a screwdriver, and the main gun. One unique advantage of the system was that it was capable of operating independently of ship's power; the gun and ammunition magazine were powered by a pneumatic drive and the turret motor by twin lead–acid batteries. Intended as a higher-firepower alternative to conventional deck-mounted machine guns and cannon, the weapon employs the Navy's Mk 24 target designator and laser range finder for enhanced accuracy. The gun was developed in the mid-1980s as a cost-effective protection for ships smaller than

frigate A frigate () is a type of warship. In different eras, the roles and capabilities of ships classified as frigates have varied. The name frigate in the 17th to early 18th centuries was given to any full-rigged ship built for speed and maneuvera ...

corvette A corvette is a small warship. It is traditionally the smallest class of vessel considered to be a proper (or " rated") warship. The warship class above the corvette is that of the frigate, while the class below was historically that of the sloo ...

or patrol boats, but did not enter this service. The GAU-12 was utilized as the principal armament for the Rutan ARES. The four-barrel GAU-22 is carried internally by the F-35A (the CTOL version of the F-35) on the port side of the fuselage, with 181 PGU-47/U APEX rounds. In contrast, the F-35B

STOVL A short take-off and vertical landing aircraft (STOVL aircraft) is a fixed-wing aircraft that is able to take off from a short runway (or take off vertically if it does not have a heavy payload) and land vertically (i.e. with no runway). The ...

and C CATOBAR aircraft mount the GAU-22 in a stealthy external gun pod under the fuselage, together with 220 rounds.

Specifications (GAU-12/U)

*Type: Five-barreled

*Caliber: 25 mm (0.98 in) *Operation:

electric Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwel ...

*Length: 83.2 in (2.11 m) *Weight (complete): 270 lb (122 kg) *Rate of fire: 3,600–4,200 rounds per minute *Muzzle velocity: (HEI) 3,400 ft/s (1,040 m/s); (API) 3,280 ft/s (1,000 m/s) *Projectile weight: (HEI) 6.5 oz (184 g); (API) 7.6 oz (215 g) *Muzzle energy: (HEI) 73,400 ft·lbf (99,500 joules); (API) 79,300 ft·lbf (107,500 joules)

Specifications (GAU-22/A)

*Type: Four-barreled rotary cannon *Caliber: 25 mm (0.98 in) *Operation: electric *Length: 83.2 in (2.11 m) *Weight (complete): 230 lb (104 kg) *Rate of fire: 3,300 rounds per minute *Muzzle velocity: (APEX) 3,200 ft/s (970 m/s) *Projectile weight: (APEX) 7.87 oz (223 g) *Muzzle energy: (APEX) 77,400 ft·lbf (104,900 joules)

Similar systems

Gryazev-Shipunov GSh-6-23 The Gryazev-Shipunov GSh-6-23 () (GRAU designation: 9A-620 for GSh-6-23, 9A-768 for GSh-6-23M modernized variant) is a six-barreled 23 mm rotary cannon used by some modern Soviet/Russian military aircraft. The GSh-6-23 differs from most Ame ...

Myriad CIWS Myriad CIWS was a twin 7 gun barrel, barrelled, 25 mm rotary cannon-style CIWS developed by a consortium including OTO Melara. The system's primary purpose, had it ever gone into production, would have been defense against anti-ship missiles, ...

References

External links

General Dynamics Ordnance and Tactical Systems GAU-12/U page

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Sea Vulcan archive Video
{{DEFAULTSORT:Gau-12 Equalizer Rotary cannon Multi-barrel machine guns Aircraft guns Articles containing video clips 25 mm artillery Military equipment introduced in the 1970s