The A-10 Thunderbolt II is an American single-seat, twin-engine jet aircraft developed by Fairchild-Republic for the United States Air Force to provide close air support (CAS) of ground forces by attacking tanks, armored vehicles, and other ground targets, also providing a limited air interdiction role. It is the first U.S. Air Force aircraft designed exclusively for close air support.
The A-10's official name comes from the Republic P-47 Thunderbolt of World War II, a fighter that was particularly effective at the CAS mission. However, the A-10 is more commonly known by its nickname "Warthog" or simply "Hog". As a secondary mission, it provides airborne forward air control, guiding other aircraft against ground targets. In the USAF inventory, the airframe is designated OA-10 when used primarily in a forward air control role.
There had been, over the years, some criticism of the U.S. Air Force not taking the role of close air support seriously enough which prompted a few members of the USAF hierarchy to desire a specialized close air support attack aircraft. In the Vietnam War large numbers of ground-attack aircraft were shot down by small arms fire, surface-to-air missiles, and low level anti-aircraft gunfire indicating that modern combat aircraft were still vulnerable to such defensive measures and prompted the development of an aircraft better able to survive such an environment. In addition, the UH-1 Huey and AH-1 Cobra helicopters of the day, which USAF commanders had said should handle the close air support role, were ill-suited for use against armor, carrying only anti-personnel machine guns and unguided rockets meant for soft targets. The F-4 Phantom was pressed into use as a CAS aircraft, but usually on an emergency basis, as its high cruising speed and fuel consumption rate hindered its ability to loiter, and the lack of an onboard gun on most F-4 variants coupled with the relative ineffectiveness of the standard 20mm Vulcan round against hard targets made strafing runs either ineffective or impossible.
On 6 March 1967, the U.S. Air Force released a request for information to 21 companies. Their objective was to create a design study for a low cost attack aircraft designated A-X, or "Attack Experimental". The officer in charge of the project was Col. Avery Kay. In 1969, the Secretary of the Air Force asked Pierre Sprey to write the detailed specifications for the proposed A-X project. However, his initial involvement was kept secret due to Sprey's earlier controversial involvement in the F-X project. Sprey's discussions with A-1 Skyraider pilots operating in Vietnam and analysis of the effectiveness of current aircraft used in the role indicated the ideal aircraft should have long loiter time, low-speed maneuverability, massive cannon firepower, and extreme survivability. Based upon this information Sprey felt the need to build an aircraft incorporating the best elements of the Ilyushin Il-2, Henschel Hs 129 and A-1 Skyraider. The specifications also demanded that the cost of the aircraft be less than 3 million dollars. In May 1970, the USAF issued a modified, and much more detailed request for proposals (RFP), as the threat of Soviet armored forces and all weather attack operations became more serious. Six companies submitted proposals to the USAF, with Northrop and Fairchild Republic selected to build prototypes: the YA-9A and YA-10A, respectively.
The YA-10A first flew on 10 May 1972. After trials and a fly-off against the YA-9A, the Air Force selected Fairchild-Republic's YA-10A on 10 January 1973 for production. (There was an additional fly-off against the A-7D Corsair II, the Air Force attack aircraft at the time, to prove the need to purchase a new aircraft) The first production A-10 flew in October 1975, and deliveries to the Air Force commenced in March 1976, to units at Davis-Monthan Air Force Base, Arizona. The first squadron to use the A-10 went operational in October 1977. In total, 715 airplanes were produced, the last in 1984.
One experimental two-seat A-10 Night Adverse Weather (N/AW) version was built by converting an A-10A. The Night Adverse Weather (N/AW) aircraft was developed by Fairchild from the first Demonstration Testing and Evaluation (DT&E) A-10 for consideration by the USAF. It included a second seat for a weapons officer responsible for ECM, navigation, and target acquisition. The variant was canceled and the only two-seat A-10 built now sits at Edwards Air Force Base awaiting a spot in the Flight Test Historical Foundation museum. The proposed two-seat A-10 trainer aircraft did not go into production, as it was felt that the A-10 was simple enough to fly that a trainer version would not be required.
The decision to make the 30 mm GAU-8 gun the main anti-tank weapon of the A-10 was influenced by Vietnam A-1 pilots and by Hans-Ulrich Rudel and his book, "Stuka Pilot". In World War II, Rudel flew the Ju 87G Stuka and destroyed many tanks using its two underwing 37 mm guns. His book was required reading for members on the A-X project. The JU-87G was an outmoded airframe with ersatz anti-tank weapons attached, yet still inflicted impressive casualties on Soviet tank forces.
A-10s were initially an unwelcome addition to the arsenal in the eyes of Air Force brass. The Air Force prized the high-flying, high-performance F-15 Eagle and F-16 Fighting Falcon air-superiority jets, and were determined to leave the dirty work of close air support to Army helicopters (the development of the AGM-114 Hellfire anti-armor missile and AH-64 Apache attack helicopter having since provided the Army with a viable anti-tank aircraft). Attempts to transfer the A-10 to the Army and the Marines were at first prevented by the 1948 Key West Agreement, and then by the A-10's impressive combat record during the Gulf War in 1991. Shortly after the war, the Air Force gave up on the idea of replacing the A-10 with a close air support version of the F-16.
Weapons Systems
Although the A-10 can carry a considerable weight of disposable stores, its primary built-in weapon is the 30 mm GAU-8/A Avenger Gatling gun. One of the most powerful aircraft cannons ever flown, it fires large depleted uranium armor-piercing shells. In the original design, the rate of fire was selectable, 2,100 rounds per minute in the low setting, or 4,200 in the high setting. Later this was changed to a fixed rate of 3,900 rounds per minute. The cannon takes about half a second to come up to speed, so 50 rounds are fired during the first second, 70 or 65 rounds per second thereafter. The gun is accurate as well, being capable of placing 80% of its shots within a 40-foot- (12.4 meter-) wide circle from a distance of 4,000 feet (1,800 meters) while the aircraft is in flight.[17] A two-second burst, therefore, will on average result in about 100 hits on a tank-sized target. The GAU-8 is optimized for slant range of 4,000 feet (1,800 m) with the A-10 in a 30 degree dive.
The fuselage of the aircraft is actually built around the gun. For example, the nosewheel is offset to the right so that the gun's firing barrel at the 9 o'clock position is aligned on the aircraft's centerline. The early A-10s carried 1,350 rounds of 30 mm ammunition. It was replaced by the 1,174 round drum. The helix in the 1,350 round drums were being damaged during loading. The 1,174 round drums were beefed up to accommodate real world conditions. The damage caused by a portion of those rounds firing prematurely due to impact of an explosive shell would be catastrophic. It is for this reason that a great deal of effort has been taken to protect the 5 ft (1.52 m) wide, 9 ft (2.74 m) long drum. There are many plates of differing thicknesses between the skin and the drum. These plates are called trigger plates because when an explosive shell hits a target it first penetrates its armor, then detonates. As the drum has many layers of thin armor, the shell's detonation is triggered before reaching the drum. A final layer of armor around the drum itself protects it from fragmentation damage. The gun is loaded by Syn-Tech's linked tube carrier GFU-7/E 30 mm ammunition loading assembly cart. This vehicle is unique to the A-10 and the GAU-8.
Another commonly used weapon is the AGM-65 Maverick air-to-surface missile, with different variations for either electro-optical (TV-guided) or infra-red targeting. The Maverick allows targets to be engaged at much greater ranges than the cannon, a safer proposition in the face of modern anti-aircraft systems. During Desert Storm, in the absence of dedicated forward-looking infrared cameras, the Maverick's infra-red camera was used for night missions as a "poor man's FLIR". Other weapons include cluster bombs and Hydra rocket pods. Although the A-10 is equipped to deliver laser-guided bombs, their use is relatively uncommon; at the low altitudes and speeds of typical A-10 operations, standard unguided bombs provide adequate accuracy at far lower cost. In any event, the guided weapons would provide little benefit, as there would be nearly no time for the weapons to steer onto a target. A-10s usually fly with an ALQ-131 ECM pod under one wing and two AIM-9 Sidewinder air-to-air missiles under the other for self-defense.
Variants
YA-10A
The first two prototypes.
A-10A
Single-seat close air support, ground-attack version.
OA-10A
Single-seat forward air control version.
YA-10B Night/Adverse Weather A-10
Two-seat experimental prototype, for night and adverse weather work. Later redesignated YA-10B. Only one example was built, which is now on static display.
A-10C
A-10As updated under the incremental Precision Engagement (PE) program featuring a new glass cockpit (including digital moving map displays), advanced datalink, and all-weather multi-mission precision weapons and laser targeting capability.
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