GAU-8 Avenger
From Wikipedia, the free encyclopedia
| GAU-8 Avenger | |
|---|---|
 The GAU-8/A Avenger's barrel and breech assembly (ammunition drum off edge of photo). |
|
| Type | Autocannon |
| Place of origin |  United States |
| Service history | |
| In service | 1977–present |
| Used by | United States |
| Production history | |
| Manufacturer | General Dynamics |
| Number built | Approx. 715[1] |
| Variants | GAU-12/U Equalizer GAU-13/A |
| Specifications | |
| Weight | 619.5 lb (281 kg) |
| Length | 19 ft 10.5 in (6.06 m) (total system) |
| Barrel length | 90.5 in (2.30 m) |
|
|
|
| Cartridge | 30 × 173 mm |
| Caliber | 30 mm caliber |
| Barrels | 7 |
| Action | Electric-Motor, Hydraulic-Driven |
| Rate of fire | 3,900 rpm (rounds per minute) |
| Muzzle velocity | 3,500 ft/s (1,070 m/s) |
| Maximum range | Over 4,000 feet (1,220 m) |
| Feed system | Linkless feed system |
The General Electric GAU-8/A Avenger is a 30 mm, hydraulically-driven seven-barrel Gatling-type rotary cannon that is mounted on the United States Air Force's A-10 Thunderbolt II. It is among the largest, heaviest and most powerful aircraft cannon in the United States military, and when the entire cannon with its drum-style ammunition magazine is considered, one of the largest cannons ever fitted into an aircraft. Designed specifically for the anti-tank role, the Avenger delivers a very powerful round at a high rate of fire.
Contents |
[edit] History
The GAU-8 was created as a parallel program with the A-X competition that produced the A-10. The specification for the cannon was laid out in 1970, with General Electric and Philco-Ford offering competing designs. Both the A-X prototypes, the A-10 and the Northrop YA-9, were designed to incorporate the weapon, although it was not available during the initial competition, and the M61 Vulcan was used as a temporary replacement. Once completed, the GAU-8 represents some 16% of the A-10 aircraft's unladen weight. The gun is placed slightly off center in the nose of the plane with the front landing gear positioned to the side. In a similar class is the Russian Gryazev-Shipunov GSh-6-30, which is lighter and has a higher fire rate but has a lower muzzle velocity and overheats faster.
The A-10 and 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.
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.
[edit] 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 5½ in (5.93 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.[2] The magazine can hold 1,174 rounds, although 1,150 is the more normal load-out. Muzzle velocity when firing Armor-Piercing Incendiary rounds is 3,250 feet per second (990 m/s), almost the same as the substantially lighter M61 Vulcan's 20 mm round.
The standard ammunition mixture for anti-armor use is a four-to-one mix of PGU-14/B Armor Piercing Incendiary, with a projectile weight of about 15.0 oz (425 grams or 6,560 grains) and PGU-13/B High Explosive Incendiary (HEI) rounds, with a projectile weight of about 12.7 oz (360 grams). The PGU-14/B round incorporates a depleted uranium penetrating core. The Avenger is lethal against tanks and any other armored vehicles.
A very important innovation in the design of the GAU-8/A shells is the use of aluminum alloy cases in place of the traditional steel or brass. This alone adds 30% to ammunition capacity for a given weight. The shells also have plastic driving bands to improve barrel life. They are imposing to examine and handle, measuring 11.4 inches (290 mm) in length and weighing 1.53 lb (694 g) or more.[2]
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.[3] Later this was changed to a fixed rate of 3,900 rpm.[4] 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 life of at least 36,000 rounds for each set of barrels.[citation needed] It is also said that this is to deal with the substantial deceleration of the plane that results from firing (see below for details). Technically, however, there is no tech order limitation on the duration the gun may be continuously fired; therefore the pilot could, in theory, hold the trigger down and expend all rounds in the handling system with one burst, with no damage or ill effects. However, this constant rate of fire does shorten barrel life considerably, and imposes more barrel inspections at shorter cycle intervals.
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.[5] The barrels themselves are driven by the aircraft's dual hydraulic system.[6]
The GAU-8/A ammunition is linkless, reducing weight and avoiding a great deal of potential for jamming. The feed system is double-ended: the spent casings are not ejected from the aircraft (which takes a great deal of force if the possibility of severe airframe damage is to be eliminated) but are cycled back into the ammunition drum. The feed system is based on that developed for later M61 installations, but uses more advanced design techniques and materials throughout, to save weight.[2]
[edit] Variants
Some of the GAU-8/A technology has been transferred into the smaller 25 mm GAU-12/U Equalizer developed for the AV-8B Harrier II aircraft, which is about the same size as the M61 but is considerably more lethal. 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, and the Avenger forms the basis for the Dutch-developed Goalkeeper naval air-defence gun. No current or contemplated aircraft other than the A-10, however, carries the full-up Avenger system.[2]
[edit] Recoil
 |
This section needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (January 2009) |
 |
This section may contain original research or unverified claims. Please improve the article by adding references. See the talk page for details. (October 2007) |
A persistent urban legend is that the recoil force of the Avenger matches that of the A-10's engines and as such the plane would slow down, stall, and subsequently crash if the gun were to be fired for long periods of time (some even claim that the aircraft would begin to fly backwards). However, the GAU-8/A product homepage states the recoil force as 10,000 pounds-force, or about 45 kN, which is less than the maximum combined output of the A-10 engines (82.6 kN).[7] Hence the recoil force of the gun is slightly more than half of the total thrust of the engines. While this is quite significant and can noticeably slow the aircraft, it is not sufficient to stop the aircraft. During test firing of the gun in the A-10 in the early 1970s the USAF experimented with putting a muzzle brake on the end of the gun and extending the nose of the plane out around this muzzle brake to vent the gun gases backwards. It was decided during this testing that the effect of the gun was not significant enough to warrant the added expense and complexity of adding this to every plane in the inventory.
Each barrel fires when it reaches roughly the 9 O'clock position, when looking at the nose of the plane, resulting in off-center recoil forces. It was discovered during development that if the recoil forces were not transmitted down the exact centerline of the plane, they would push the entire plane off target during firing. As a result, the entire gun assembly itself had to be mounted off-center in the other direction—towards the 3 O'clock position—to compensate. It also lies below the aircraft's center of gravity, being boresighted along a line 2 degrees below the aircraft's line of flight. This arrangement accurately centers the recoil forces, preventing changes in pitch and/or yaw when firing. This configuration also provides space for the front landing gear, albeit mounted on the right side of the nose.[8]
According to 355th Fighter Wing Weapons and Tactics Chief at Davis-Monthan AFB in Tucson, AZ, there is no recoil problem with the GAU-8/A. 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. Gun exhaust is essentially oxygen-free, and is certainly capable of causing flame-outs of gas turbines. The A-10 engines have a self sustaining combustion section. When the gun is fired the igniters come on to ensure no flame out occurs.[9]
[edit] Accuracy specifications
- Accuracy: 80% of rounds fired at 4,000 feet (1,200 m) range hit within a 20 feet (6.1 m) radius
- PGU-14/B API Armor Piercing Incendiary (DU)
- PGU-13/B HEI High Explosive Incendiary
- PGU-15/B TP Target Practice
- Armor penetration:
- 69 mm at 500 meters
- 38 mm at 1000 meters
[edit] See also
[edit] References
- ^ A-10 history
- ^ a b c d Spick, 2000, p. 44.
- ^ Stephens 1995, p. 18.
- ^ TCTO 1A-10-1089, Flight manual TO 1A-10A-1 (20 February 2003, Change 8), page vi, 1-150A.
- ^ [1]
- ^ [2]
- ^ http://www.geae.com/engines/military/tf34/index.html
- ^ A-10 Described: GAU-8 Cannon / External Stores. Vectorsite.net, 1 October 2008.
- ^ Jenkins, Dennis R. Fairchild-Republic A/OA-10 Warthog. North Branch, Minnesota: Specialty Press, 1998. ISBN 1-58007-013-2.
- Spick, M. The Great Book of Modern Warplanes, Salamander Books, 2000. ISBN 1-84065-156-3
- GAU-8 Avenger, www.mindfully.org (retrieved 27 April 2005)
- 30 mm cannon GAU-8 Avenger, by Jirka Wagner (retrieved 27 April 2005)
[edit] External links
 |
Wikimedia Commons has media related to: GAU-8 Avenger |
- General Electric GAU-8/A Avenger on USAF National Museum site
- FAS.org: GAU-8 Avenger, Hill Aerospace Museum (retrieved 27 April 2005)
- Video of the GAU-8 Avenger test firing
|
||||||||||||||
