GAU-8 Avenger

Last updated
GAU-8/A Avenger
GAU-8 Avenger contrast.jpg
The GAU-8/A Avenger's barrel and breech assembly
(ammunition drum off right edge of photo)
Type Gatling-style autocannon
Place of originUnited States
Service history
In servicesince 1977
Used by United States Air Force (Avenger)
Various navies (Goalkeeper)
Production history
Designer General Electric
ManufacturerGeneral Electric
General Dynamics
Producedsince 1977
Variants GAU-12/U Equalizer
GAU-13/A
Specifications
Mass619.5 lb (281 kg)
Length19 ft 10.5 in (6.06 m) (total system)
112.28 in (2.85 m) (gun only)
Barrel  length90.5 in (2.30 m)
Width17.2 in (0.437 m) (barrels only)

Cartridge 30×173 mm
Caliber 30 mm
Barrels7-barrel (progressive RH parabolic twist, 24 grooves) [1]
Action Electrically controlled, hydraulic-driven
Rate of fire 3,900 rpm (variable) [2] [3]
Muzzle velocity 3,324 ft/s (1,010 m/s) (API)
Effective firing range4,000 feet (1,220 m)
Maximum firing rangeOver 12,000 feet (3,660 m)
Feed systemLinkless feed system

The General Electric GAU-8/A Avenger is a 30 mm hydraulically driven seven-barrel Gatling-style autocannon that is primarily mounted in the United States Air Force's Fairchild Republic A-10 Thunderbolt II. Designed to destroy a wide variety of ground targets, the Avenger delivers very powerful rounds at a high rate of fire. The GAU-8/A is also used in the Goalkeeper CIWS ship weapon system, which provides defense against short-range threats such as highly maneuverable missiles, aircraft, and fast maneuvering surface vessels. The GAU-8/A is produced by General Dynamics.

Contents

History

The GAU-8 was created as a parallel program with the A-X (or Attack Experimental) competition that produced the A-10. The specification for the cannon was laid out in 1970, [4] with General Electric and Philco-Ford offering competing designs. Both of the A-X prototypes, the YA-10 and the Northrop YA-9, were designed to incorporate the weapon, although it was not available during the initial competition; the M61 Vulcan was used as a temporary replacement. Once completed, the entire GAU-8 assembly (correctly referred to as the A/A 49E-6 Gun System) [5] represents about 16% of the A-10 aircraft's unladen weight. Because the gun plays a significant role in maintaining the A-10's balance and center of gravity, a jack must be installed beneath the airplane's tail whenever the gun is removed for inspection in order to prevent the aircraft from tipping rearwards.

GAU-8 closeup A10gun1.jpg
GAU-8 closeup
GAU-8 with barrel shroud visible A-10A SN 75-0270 GAU-8.jpg
GAU-8 with barrel shroud visible

The gun is mounted slightly to the port side with the active firing cannon barrel on the starboard side at the 9 o'clock position and on the aircraft's center line. The front landing gear is positioned to the starboard side. [6] The gun is loaded using Syn-Tech's linked tube carrier GFU-8/E 30 mm Ammunition Loading Assembly cart. This vehicle is unique to the A-10 and the GAU-8. [7]

The A-10 with its GAU-8/A gun entered service in 1977. It was produced by General Electric, though General Dynamics Armament and Technical Products has been responsible for production and support since 1997 when the division was sold by Lockheed Martin to General Dynamics. [5]

Design

The GAU-8 itself weighs 620 pounds (280 kg), but the complete weapon, with feed system and drum, weighs 4,029 pounds (1,828 kg) with a maximum ammunition load. It measures 19 ft 5+12 in (5.931 m) from the muzzle to the rearmost point of the ammunition system, and the ammunition drum alone is 34.5 inches (88 cm) in diameter and 71.5 inches (1.82 m) long. [8] Power for operating the gun is provided by twin hydraulic motors pressurized from two independent hydraulic systems. The magazine can hold 1,174 rounds, although 1,150 is the typical load-out. Muzzle velocity when firing armor-piercing incendiary rounds is 1,013 m/s, almost the same as the substantially lighter M61 Vulcan's 20 mm round, giving the gun a muzzle energy of just over 200 kilojoules. [9]

30x173mm round next to a .30-06 Springfield for comparison 30mm GAU-8 Avenger round.jpg
30x173mm round next to a .30-06 Springfield for comparison

The standard ammunition mixture for anti-armor use is a five-to-one mix of PGU-14/B Armor Piercing Incendiary, with a projectile weight of about 14.0 oz (395 grams or 6,096 grains) and PGU-13/B High Explosive Incendiary (HEI) rounds, with a projectile weight of about 13.3 oz (378 grams or 5,833 grains). [10] The PGU-14/B's projectile incorporates a lightweight aluminum body, cast around a smaller caliber depleted uranium penetrating core. [11] In 1979, the Avenger was tested against M47 Patton tanks and caused "severe damage". [12]

An innovation in the design of the GAU-8/A ammunition is the use of aluminum alloy cases in place of the traditional steel or brass. [13] This alone adds 30% to ammunition capacity for a given weight. The projectiles incorporate a plastic driving band to improve barrel life. The cartridges measure 11.4 inches (290 mm) in length and weigh 1.53 pounds (0.69 kg) or more. [8] [13]

GAU-8 mounted in A-10 GAU-8 in A-10.jpg
GAU-8 mounted in A-10

The Avenger's rate of fire was originally selectable, 2,100 rounds per minute (rpm) in the low setting, or 4,200 rpm in the high setting. [2] This rate was later changed to a fixed rate of 3,900 rpm. [3] At this speed it would take 18 seconds of sustained fire to empty the magazine. In practice, the cannon is limited to one and two-second bursts to avoid overheating and conserve ammunition; barrel life is also a factor, since the USAF has specified a minimum life of at least 20,000 rounds for each set of barrels. [14] There is no technical limitation on the duration the gun may be continuously fired, and a pilot could potentially expend the entire ammunition load in a single burst with no damage or ill effects to the weapons system itself. However, this constant rate of fire would shorten the barrel life considerably and require added barrel inspections and result in shorter intervals between replacement.

Each barrel is a very simple non-automatic design having its own breech and bolt. Like the original Gatling gun, the entire firing cycle is actuated by cams and powered by the rotation of the barrels. [13] The seven-barrel carriage assembly itself is driven by the aircraft's dual hydraulic system. [14]

The GAU-8/A ammunition feed is linkless, reducing weight and avoiding a great deal of potential for jamming. The feed system is double-ended, allowing the spent casings to be returned to the ammunition drum. [15] Additionally, returning empty cases to the drum has less effect on the aircraft's center of gravity than ejecting them. The feed system is based on that developed for later M61 installations, but uses more advanced design techniques and materials throughout, to save weight. [8]

Firing system

Accuracy

The GAU-8/A is extremely accurate and can fire up to 3,900 rounds per minute without complications. The 30-mm shell has twice the range, half the time to target, and three times the mass of projectiles fired by guns mounted in comparable close air support aircraft. [16]

The GAU-8/A Avenger Gatling gun next to a Volkswagen Beetle. Removing an installed GAU-8 from an A-10 requires first installing a jack under the aircraft's tail to prevent it from tipping, as the cannon makes up most of the aircraft's forward weight. GAU-8 meets VW Type 1.jpg
The GAU-8/A Avenger Gatling gun next to a Volkswagen Beetle. Removing an installed GAU-8 from an A-10 requires first installing a jack under the aircraft's tail to prevent it from tipping, as the cannon makes up most of the aircraft's forward weight.

While the GAU-8/A has a muzzle velocity that is comparable to that of the M61 Vulcan, it uses heavier ammunition and has superior ballistics. The time of flight of its projectile to 4,000 feet (1,200 m) is 30 percent less than that of an M61 round; the GAU-8/A projectile decelerates much less after leaving the barrel, and it drops a negligible amount, about 10 feet (3.0 m) over the distance. [17] The GAU-8/A precision when installed in the A-10 is rated at "5 mil, 80 percent", meaning that 80 percent of rounds fired will hit within a cone with an angle of five milliradians; this equates to a 40-foot (12-meter) diameter circle at the weapon's design range of 4,000 feet (1,200 m). [18] By comparison, the M61 has an 8-milliradian dispersion. [13]

Recoil

Because the gun's recoil forces could push the entire plane off target during firing, the weapon is mounted laterally off-center, slightly to the port side of the fuselage centerline, with the active firing barrel lying directly on the aircraft's centerline. [6] The firing barrel also lies just below the aircraft's center of gravity, being bore-sighted along a line 2 degrees below the aircraft's line of flight. This arrangement accurately centers the recoil forces, preventing changes in aircraft pitch or yaw when fired. This configuration also leaves space for the front landing gear, which is mounted slightly off-center on the starboard side of the nose. [19]

The GAU-8/A utilizes recoil adapters. They are the interface between the gun housing and the gun mount. By absorbing (in compression) the recoil forces, they spread the time of the recoil impulse and counter recoil energy transmitted to the supporting structure when the gun is fired.

The A-10 engines were initially susceptible to flameout when subjected to gases generated in the firing of the gun. When the GAU-8 is being fired, the smoke from the gun can make the engines stop, and this did occur during initial flight testing. [4] Gun exhaust is essentially oxygen-free, and is capable of causing flameouts of gas turbines. The A-10 engines now have a self-sustaining combustion section. When the gun is fired, the igniters come on to reduce the possibility of a flameout. [20]

The average recoil force of the GAU-8/A is 10,000 pounds-force (45 kN), [5] [21] which is slightly more than the output of each of the A-10's two TF34 engines of 9,065 lbf (40.3 kN). [22] While this recoil force is significant, in practice a cannon-fire burst slows the aircraft by only a few miles per hour in level flight. [20]

Variants

Some of the GAU-8/A technology has been transferred into the smaller 25 mm GAU-12/U Equalizer, which was developed for the AV-8B Harrier II aircraft. The GAU-12 is about the same size as the 20 mm M61. GE has also developed the GAU-13/A, a four-barreled weapon using GAU-8/A components, which has been tested in podded form as the GPU-5/A. The Avenger also forms the basis for the Dutch-developed Goalkeeper CIWS naval air-defense gun. No current or contemplated aircraft other than the A-10 carries the full-up Avenger system. [8]

Specifications

A side-view drawing of the GAU-8/A Avenger's mounting location in the A-10's forward fuselage GAU-10 Drawing.jpg
A side-view drawing of the GAU-8/A Avenger's mounting location in the A-10's forward fuselage

See also

Related Research Articles

<span class="mw-page-title-main">M61 Vulcan</span> 20 mm Gatling-type rotary cannon

The M61 Vulcan is a hydraulically, electrically, or pneumatically driven, six-barrel, air-cooled, electrically fired Gatling-style rotary cannon which fires 20 mm × 102 mm rounds at an extremely high rate. The M61 and its derivatives have been the principal cannon armament of United States military fixed-wing aircraft for over sixty years.

<span class="mw-page-title-main">Recoilless rifle</span> Type of light artillery gun

A recoilless rifle (rifled), recoilless launcher (smoothbore), or simply recoilless gun, sometimes abbreviated to "RR" or "RCL" is a type of lightweight artillery system or man-portable launcher that is designed to eject some form of countermass such as propellant gas from the rear of the weapon at the moment of firing, creating forward thrust that counteracts most of the weapon's recoil. This allows for the elimination of much of the heavy and bulky recoil-counteracting equipment of a conventional cannon as well as a thinner-walled barrel, and thus the launch of a relatively large projectile from a platform that would not be capable of handling the weight or recoil of a conventional gun of the same size. Technically, only devices that use spin-stabilized projectiles fired from a rifled barrel are recoilless rifles, while smoothbore variants are recoilless guns. This distinction is often lost, and both are often called recoilless rifles.

<span class="mw-page-title-main">M2 Browning</span> .50 calibre heavy machine gun

The M2 machine gun or Browning .50 caliber machine gun is a heavy machine gun that was designed near the end of World War I by John Browning. While similar to Browning's M1919 Browning machine gun, which was chambered for the .30-06 cartridge, the M2 uses Browning's larger and more powerful .50 BMG cartridge. The design has had many designations; the official U.S. military designation for the infantry type is Browning Machine Gun, Cal. .50, M2, HB, Flexible. It has been used against infantry, lightly armored vehicles and boats, light fortifications, and low-flying aircraft.

<span class="mw-page-title-main">Autocannon</span> Rapid-fire projectile weapon that fires armour-piercing or explosive shells

An autocannon, automatic cannon or machine cannon is a fully automatic gun that is capable of rapid-firing large-caliber armour-piercing, explosive or incendiary shells, as opposed to the smaller-caliber kinetic projectiles (bullets) fired by a machine gun. Autocannons have a longer effective range and greater terminal performance than machine guns, due to the use of larger/heavier munitions, but are usually smaller than tank guns, howitzers, field guns, or other artillery. When used on its own, the word "autocannon" typically indicates a non-rotary weapon with a single barrel. When multiple rotating barrels are involved, such a weapon is referred to as a "rotary autocannon" or occasionally "rotary cannon", for short.

<span class="mw-page-title-main">MG 151 cannon</span> Aircraft cannon

The Maschinengewehr MG 151 is a low caliber, belt fed autocannon for aircraft use, developed in Nazi Germany from 1934 to 1940 and produced by Waffenfabrik Mauser during World War II. It was originally produced in 15.1 mm caliber from 1940, chambered for a 15×96mm cartridge, but due to demand for higher effect against aircraft, especially with the introduction of mine shells for the 20 mm MG-FF/M aircraft cannon, the design was rechambered to 20 mm caliber in 1941, using a newly developed 20×82mm cartridge. The initial 15 mm variant then became known as the MG 151/15, with the new 20 mm variant becoming the MG 151/20.

<span class="mw-page-title-main">M197 electric cannon</span> 20 mm Gatling-type rotary cannon

The M197 electric cannon is a 20 mm three-barreled electric Gatling-type rotary cannon used by the United States military.

The General Dynamics GAU-12/U Equalizer is a five-barrel 25 mm Gatling-type rotary cannon. 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 gunships 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 fighter jets.

The M134 Minigun is an American 7.62×51mm NATO six-barrel rotary machine gun with a high rate of fire. It features a Gatling-style rotating barrel assembly with an external power source, normally an electric motor. The "Mini" in the name is in comparison to larger-caliber designs that use a rotary barrel design, such as General Electric's earlier 20 mm M61 Vulcan, and "gun" for the use of rifle ammunition as opposed to autocannon shells.

The Gryazev-Shipunov GSh-23 is a twin-barreled 23 mm autocannon developed in the Soviet Union, primarily for military aircraft use. It entered service in 1965, replacing the earlier Nudelman-Rikhter NR-23 and Rikhter R-23.

<span class="mw-page-title-main">M39 cannon</span> Single-barrel autocannon

The M39 cannon is a 20 mm caliber single-barreled revolver cannon developed for the United States Air Force in the late 1940s. It was used on a number of fighter aircraft from the early 1950s through the 1980s.

<span class="mw-page-title-main">GAU-13</span> Gatling-style autocannon

The General Electric GAU-13/A is a 30 mm electric Gatling-type rotary cannon derived from the GAU-8 Avenger cannon.

<span class="mw-page-title-main">Hispano-Suiza HS.404</span> 20 mm autocannon

The HS.404 is an autocannon originally designed by and produced by the Swiss arm of the Spanish/Swiss company Hispano-Suiza in the mid-1930s. Production was later moved to the French arm of Hispano Suiza.

<span class="mw-page-title-main">MG FF cannon</span> 20 mm autocannon aircraft armament

The MG FF was a drum-fed, blowback-operated, 20 mm aircraft autocannon, developed in 1936 by Ikaria Werke Berlin of Germany. It was a derivative of the Swiss Oerlikon FF F cannon, with the Oerlikon FF design itself a development of the Imperial German World War I Becker 20 mm cannon, and was designed to be used in space-limited, fixed mountings such as inside aircraft wings, although it saw use as both an offensive and a defensive weapon, in both fixed and flexible format. It saw widespread use in those roles by the German Luftwaffe, particularly during the early stages of World War II, although from 1941 onwards it was gradually replaced by the Mauser firm's 20 mm MG 151/20, which was lighter, and had both a higher rate of fire and muzzle velocity.

<span class="mw-page-title-main">Rotary cannon</span> Multiple barreled automatic firearm

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 rates of fire than single-barreled autocannons of the same caliber. The loading, firing and ejection functions are performed simultaneously in different barrels as the whole assembly rotates, and the rotation also permits the barrels some time to cool. The rotating barrels on nearly all modern Gatling-type guns are powered by an external force such as an electric motor, although internally powered gas-operated versions have also been developed.

20 mm caliber is a specific size of popular autocannon ammunition. The dividing line between smaller-caliber weapons, commonly called "guns", from larger-caliber "cannons", is conventionally taken to be the 20 mm round, the smallest caliber of autocannon. All 20 mm cartridges have an outside projectile (bullet) diameter and barrel bore diameter of approximately 0.787 inches (20.0 mm). These projectiles are typically 75 to 127 mm (3–5 in) long, cartridge cases are typically 75 to 152 mm (3–6 in) long, and most are shells, with an explosive payload and detonating fuze.

<span class="mw-page-title-main">Mk44 Bushmaster II</span> 30 mm chain gun

The Mk44 Bushmaster II is a 30 mm chain gun manufactured by Northrop Grumman. It is a derivative of the 25 mm M242 Bushmaster, and uses 70% of the same parts as the M242 while increasing the firepower by as much as 50% with the 20% increase in caliber size. The barrel is chromium-plated for extended life. The gun uses standard GAU-8 Avenger ammunition that is available in API, HEI and APFSDS-T variants.

<span class="mw-page-title-main">GAU-19</span> Electrically-driven heavy machine gun

The GAU-19/A is an electrically driven, three-barrel rotary heavy machine gun that fires the .50 BMG (12.7×99mm) cartridge.

<span class="mw-page-title-main">Mine shell</span> Type of shell construction

A mine shell or high-explosive, high-capacity (HEHC) in British military nomenclature, is a military explosive shell type characterized by thin shell walls and a correspondingly high quantity of explosives, much higher than the traditional high explosive shell type per caliber, meaning that mine shells trade fragmentation effect for a higher pressure wave effect when comparing to traditional high explosive shells.

<span class="mw-page-title-main">Afanasev Makarov AM-23</span> Double-barrel Autocannon

The Afanasev Makarov AM-23 is a Soviet designed aircraft autocannon that has been used in a number of aircraft in the Soviet Air Force. Its GRAU index was 9-A-036. It was often used in place of the earlier and slower-firing Nudelman-Rikhter NR-23.

<span class="mw-page-title-main">Gryazev-Shipunov GSh-30-1</span> 1980s Soviet 30mm aircraft autocannon

The Gryazev-Shipunov GSh-30-1 is a 30 mm autocannon designed for use on Soviet and later Russian military aircraft, entering service in the early 1980s. Its current manufacturer is the Russian company JSC Izhmash. The name GSH-30-1 is formed from the surnames of the designers Gryazev (Грязев) and Shipunov (Шипунов), the caliber of 30 mm and the single-barrel design of the gun itself.

References

  1. (PDF) https://apps.dtic.mil/sti/pdfs/ADB028651.pdf. Archived (PDF) from the original on February 16, 2022.{{cite web}}: Missing or empty |title= (help)
  2. 1 2 Stephens, Rick (1995). A-10 Thunderbolt II. World Air Power Journal. p. 18. ISBN   1-874023-54-9.
  3. 1 2 Time Compliance Technical Order 1A-10-1089, Flight manual TO 1A-10A-1. Vol. 1-150A (Change 8 ed.). United States Air Force. 20 February 2003. p. vi.
  4. 1 2 "GAU-8/A Avenger". National Museum of the USAF. Archived from the original on 2010-04-16. Retrieved 2009-09-14.
  5. 1 2 3 Goebel, Greg (October 1, 2008). "A-10: Development & Description". Archived from the original on 2009-09-25. Retrieved 2009-09-14.
  6. 1 2 Donald, David and Daniel J. March, eds. "A-10 Fighting Warthog", p. 20. Modern Battlefield Warplanes. Norwalk, Connecticut: AIRtime, 2004. ISBN   1-880588-76-5.
  7. "Turrets & Mounted Weaponry". Zombie survival wiki. Archived from the original on 2009-03-27. Retrieved 2009-09-14.[ verification needed ]
  8. 1 2 3 4 Spick 2000, p. 44.
  9. "30 mm GAU-8/A Ammunition" (PDF), Defense Systems, Orbital ATK, p. 2, November 2002, archived (PDF) from the original on 2017-02-07, retrieved 2016-05-18
  10. "GAU-8/A Ammunition (30 mm)". ATK. Archived from the original on 2014-01-09. Retrieved 2014-01-09.
  11. Stravonski. "Firepower of the A-10". Archived from the original on 2003-04-15. Retrieved 2009-09-14.
  12. "A-1O/GAU-8 Low Angle Firing versus Simulated Soviet Tank Company" (PDF). DTIC. June 1980. Archived (PDF) from the original on 2016-03-04. Retrieved 2016-01-25.
  13. 1 2 3 4 Wagner, Jirka. "30mm cannon GAU-8 Avenger". Archived from the original on 2013-01-05.
  14. 1 2 "Fact Sheet: General Electric GAU-8/A "Avenger" 30mm Cannon". Hill Air Force Base. Archived from the original on 2011-06-04.
  15. "GAU-8 Avenger". Archived from the original on 2005-02-19. Retrieved 2005-04-27.
  16. "A-10/OA-10 Thunderbolt II history". Military systems. Global Security. Archived from the original on 2008-05-16. Retrieved 2008-05-26.
  17. Jenkins 1998, pp. 64–73.
  18. "GAU-8 Avenger". FAS. Archived from the original on 2009-07-14. Retrieved 2009-09-14.
  19. "A-10 Described: GAU-8 Cannon / External Stores". Vectorsite. Archived from the original on 2008-12-25. Retrieved 2008-10-01.
  20. 1 2 Jenkins, Dennis R (1998). Fairchild-Republic A/OA-10 Warthog. North Branch, Minnesota: Specialty Press. ISBN   1-58007-013-2.
  21. "Armament Systems: Aircraft Gun Systems". General Dynamics Armament and Technical Products. Archived from the original on 6 March 2014. Retrieved 6 March 2014.
  22. "TF34 Engine". Global Security. Archived from the original on 2009-09-06. Retrieved 2009-09-14.
  23. dtic.mil(PDF) http://apps.dtic.mil/dtic/tr/fulltext/u2/a522397.pdf. Archived (PDF) from the original on 4 March 2016. Retrieved 2022-04-03.{{cite web}}: Missing or empty |title= (help)
  24. Zecevic, Berko; Terzic, Jasmin; Catovic, Alan; Serdarevic-Kadic, Sabina (April 21, 2010), Dispersion of PGU-14 ammunition during air strikes by combat aircraft A-10 near urban areas, Sarajevo, Bosnia and Herzegovina: University of Sarajevo, Mechanical Engineering Faculty, p. 80.
  1. 52% accuracy on rounds fired at a tank sized target from an A-10 using standard attack setups during one series on tests. [23]

Bibliography