A-10 Thunderbolt II

The A-10 Thunderbolt II is a 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 CAS.

The A-10's official name comes from the 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.

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Development

The A-10 was developed in response to the increasing vulnerability of ground attack-planes to ground air defenses, as evidenced by the large number that were shot down by small arms fire, surface-to-air missiles, and low level anti-aircraft gunfire during the Vietnam War. This indicated the need for a specialized, heavily armored aircraft with long loiter time and large ordnance load, much like the Ilyushin Il-2 or A-1 Skyraider.

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". 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 first prototype YA-10A made its maiden flight on the 10th of May 1972, followed by the second prototype on the 21st of July 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 YA-10B two-seat version was built. The Night Adverse Weather aircraft was developed by Fairchild from the first Demonstration Testing and Evaluation (D T&E) A-10 prototype 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 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.

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 jets, and were determined to leave the dirty work of close air support to Army helicopters. 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.

The A-10 has received many upgrades over the years. Aircraft were upgraded with inertial navigation and a Pave Penny laser sensor (marked target seeker) pod that allowed the pilot to detect laser energy for PID (Positive Identification) of an illuminated target. The Pave Penny is a passive seeker and cannot self-designate a target for a Laser Guided Bomb (LGB). Later, the Low-Altitude Safety and Targeting Enhancement (LASTE) upgrade provided computerized weapon-aiming equipment, an autopilot, and ground-collision warning system. The A-10 is now compatible with night-vision goggles for low-light operation. In 1999, aircraft began to be given Global Positioning System navigation systems.

The A-10 is scheduled to stay in service with the USAF until 2028, when it may be replaced by the F-35 Lightning II. Beginning in 2005, the entire A-10 fleet is being upgraded to the "C" model that will include improved fire control system (FCS), electronic countermeasures (ECM), and the ability to carry smart bombs. The A-10 will be part of a service life extension program (SLEP) with many receiving new wings. As of April 2007, modifications to provide precision weapons capability were well underway. A contract to build 242 new A-10 wing sets was awarded to Boeing on June 29, 2007.

Design

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The A-10 has superior maneuverability at low speeds and altitude, thanks to straight, wide wings with downturned "droop" wing tips. These also allow short takeoffs and landings, permitting operations from rugged, forward airfields near front lines. The aircraft can loiter for extended periods of time and operate under 1,000 feet (300 m) ceilings with 1.5-mile (2.4 km) visibility. It typically flies at a relatively slow speed of 180 knots (200 mph or 320 km/h), which makes it a much better candidate for the ground-attack role than fast fighter-bombers, which often have difficulty targeting small and slow-moving targets.

Engine exhaust passes over the aircraft's Stabilizer and between the twin tails, decreasing the A-10's infrared signature and lowering the likelihood that the aircraft can be targeted by heatseeking missiles. The placement of the engines partially shields them from anti-aircraft fire behind the wings and tail.

The A-10 has integrally machined skin panels. Because the stringers are integral with the skin there are no join or seal problems. These panels, built using computer controlled machining, reduce the man-hours and hence the cost of manufacture. The tests of war have shown that this type of panel is more battle-hardy. Damaged panels can be replaced and cheaply riveted into place.

Most thin flat areas of the airframe are honeycomb panels. This is because thin honeycomb sandwich panels are less likely to deform in any direction than sheet metal panels even if part of the panel has been blown off or structurally compromised. Honeycomb panels of this type on the A-10 include the flap shrouds, the elevators, the rudders and other sections of the fins. The leading edge of the mainplane is honeycomb to provide strength with minimal weight compromise.

The ailerons are at the far ends of the wings to gain greater rolling moment as with most aircraft but there are two distinguishing features. First, the ailerons are larger than is typical, almost 50% of the chord, providing improved control even at slow speeds. The aileron is also split, allowing the halves to separate and function as [[[air brake|air brakes]].

The Thunderbolt II can be serviced and operated from bases with limited facilities near battle areas. An unusual feature is that many of the aircraft's parts are interchangeable between the left and right sides, including the engines, main landing gear, and vertical stabilizers. The sturdy landing gear, low-pressure tires and large, straight wings allow operation from short rough strips even with a heavy ordnance load, allowing the aircraft to operate from damaged airbases. The aircraft is designed to be refueled, rearmed, and serviced with minimal equipment. Operating from a forward area is both useful for close air support and necessary due to the A-10's relatively low cruise and top speeds.

Durability

The A-10 is exceptionally hardy, to the point that some service men refer to it as 'an airborne tank.' Its strong airframe can survive direct hits from armor-piercing and high-explosive projectiles up to 23 mm. The aircraft has triple redundancy in its flight systems, with mechanical systems to back up double-redundant hydraulic systems. This permits pilots to fly and land when hydraulic power or part of a wing is lost. Flight without hydraulic power uses the manual reversion flight control system; this engages automatically for pitch and yaw control, and under pilot control (manual reversion switch) for roll control. In manual reversion mode, the A-10 is sufficiently controllable under favorable conditions to return to base and land, though control forces are much higher than normal. The aircraft is designed to fly with one engine, one tail, one elevator and half a wing torn off. Self-sealing fuel tanks are protected by fire-retardant foam. Additionally, the main landing gear is designed so that the wheels semi-protrude from their nacelles when the gear is retracted so as to make gear-up landings (belly landing) easier to control and less damaging to the aircraft's underside.

The cockpit and parts of the flight-control system are protected by titanium armor, referred to as a "titanium bathtub". The tub has been tested to withstand multiple strikes from 20 mm cannon fire. The thickness of the titanium varies from ½ an inch to 1½ inches determined by a study of likely trajectories and deflection angles. This protection comes at a cost, though; the armor plating itself weighs almost 6% of the entire aircraft’s empty weight. To protect the pilot from the fragmentation likely to be created from impact of a shell any interior surface of the tub that is directly exposed to the pilot is covered by a multi-layer nylon spall shield. The protection for the pilot from above obviously comes second to the necessity for the pilot to have good all-round vision. The canopy cannot protect the pilot as well as the titanium, but the bullet-proof diffusion-bonded stretched-acrylic canopy can withstand small arms fire and is spall-resistant, although the canopy needs to be penetrable by the ejection seat. The front windscreen, however, offers shielding likewise resistant to 20mm cannon fire.

Recent proof of the durability of the A-10 was shown when USAF Captain Kim Campbell, flying a ground support mission over Baghdad during the 2003 invasion of Iraq suffered extensive flak damage to her A-10. The hit damaged one of the A-10's two engines and crippled its hydraulic system, forcing the back-up mechanical system to operate the aircraft's stabilizer and flight controls. Despite this, the pilot managed to fly it for an hour and landed it safely at the air base in manual reversion mode.

Propulsion

One of the characteristic features of this aircraft is the placement of the General Electric TF34-GE-100 turbofan engines. There are many reasons for the location of the engines on the Warthog. First, as this aircraft was expected to be operated from forward air bases, often with semi-prepared substandard runways, there would be a high risk of FOD (Foreign Object Damage). The height of the engines significantly lowers the chance of sand or stones damaging the complex parts of the jet engines. This also means engines can remain running, allowing for shorter servicing and rearming turn-around times by ground crew. Servicing and rearming are further helped by having wings closer to ground than would be possible if the engines were wing mounted. As mentioned above the position also reduces the IR signature which starts low anyway due to the high bypass ratio of the engines. The bypass ratio is 6:1 and so the engines are very quiet which reduces the risk of detection. Because of their high position, the engines are angled upward nine degrees to bring the combined thrust line closer to the aerodynamic center of the aircraft. This avoids trimming measures to counteract a nose-down pitching moment if the engines were parallel to the fuselage. The engines, being particularly heavy components, require strong supports. Accordingly, forged engine-mounting nacelle frames are pin jointed to machined support beams.

All four fuel tanks are near the center of the aircraft thus decreasing the likelihood of them being hit or being separated from the engines. There are several methods employed to protect the tanks themselves. The tanks are separate from the fuselage and so projectiles would need to penetrate the skin before reaching the tank. The refueling system is purged after use so that there is no fuel unprotected anywhere in the aircraft. All pipes self-seal if they are compromised. Most of the fuel system components are situated inside the tanks so that if a leak were to occur from the component the fuel would not be lost. If a tank does get damaged there are check valves that can ensure that fuel does not flow into the compromised tank. The most important fuel system protection aid is the reticulated polyurethane foam that is sprayed into the empty space in a tank holding debris and restricting fuel spillage in the event of damage. The other source of possible combustion, the engines, are shielded from the fuel system and the rest of the airframe by firewalls and fire extinguishing equipment.

Because of the close proximity of the front landing gear and the A-10's main cannon, the landing gear is offset to the aircraft's right and cannon slightly to the left. The offset front landing gear causes the A-10 to have dissimilar turning radii. Turning to the right on the ground takes less space than turning left.

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 at a rate of about 3,900 rounds per minute (50 rounds per second during the first second, 70 rounds per second thereafter). The massive shells and high muzzle velocity allow the Thunderbolt II to destroy heavily armored main battle tanks with as few as six direct hits. The gun is accurate as well, being capable of placing 80% of its shots within a 20-foot wide circle from a distance of 1 mile while the aircraft is in flight.

The fuselage of the aircraft is actually built around the gun. For example, the nosewheel is offset to starboard so that the gun's firing barrel is aligned on the aircraft's centerline. The early A-10s carried 1,350 rounds of 30 mm ammunition. It was replaced by the 1174 round drum. The helix in the 1350 drums were being damaged during loading. The 1174 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 30mm 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, 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 night vision goggles, the Maverick's infra-red camera was used for night missions. 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.

Operational history

The first unit to receive the A-10 Thunderbolt II was the 355th Tactical Training Wing, based at Davis-Monthan Air Force Base, Arizona in March 1976.

The A-10 saw combat for the first time during the Gulf War in 1991, destroying more than 1,000 Iraqi tanks, 2,000 military vehicles, and 1,200 artillery pieces. A-10s shot down two Iraqi helicopters with the GAU-8 gun. Seven A-10s were shot down during the war, far fewer than military planners expected. A-10s had a mission capable rate of 95.7%, flew 8,100 sorties, and launched 90% of the AGM-65 Maverick missiles fired in the conflict. Part of the reason for this success were the burning oil wells that provided Iraqi tanks some cover from advanced electronics and high-flying fighters like the F-15 and F-16, where the trained eye, longer gun range and stable gun platform of the A-10 proved its worth.

In the 1990s many A-10s were shifted to the forward air control (FAC) role and redesignated OA-10. In the FAC role the A-10 is typically equipped with up to six pods of 5 inch (127 mm) Zuni rockets, usually with smoke or white phosphorus warheads used for target marking. They remain fully combat capable despite the redesignation.

A-10s again saw service in the 1999 Kosovo War, in the later stages of the 2001 invasion of Afghanistan, in Operation Anaconda in Afghanistan in March 2002 and in the 2003 Iraq war. In Afghanistan the A-10 is based at Bagram.

A friendly fire incident occurred when two A-10 Thunderbolt II aircraft of the Idaho Air National Guard, 190th Fighter Squadron, nearing the end of an operational mission, attacked a four vehicle British reconnaissance patrol of Scimitar armoured vehicles. The vehicles were fired upon by the A10s' GAU-8 Avenger 30 mm cannon in a series of strafing runs. As a result of the attack Lance Corporal Matty Hull died and five colleagues were injured. One of the A-10 pilots who attacked the British patrol was subsequently confirmed as Lieutenant Colonel Gus Kohntopp. Hull was three days shy of his 27th birthday. This might have been accepted as just another accident except for the provocative statement broadcast by Eldon Anderson on the evening ITN news broadcast accusing Britsh World War II veterans of cowardice. The British public were outraged by this insult and Mr Anderson was forced to make a (rather unconvincing) apology on the following evening's broadcast. Again, the matter might have been laid to rest, except that at the official inquest into Matty Hull's death the United States refused to allow American witnesses to give evidence before the Court (a position that many Britains to this day interpret as a deliberate attack on the honour of their armed forces by the United States Government).

On April 30, 2003, USCENTAF issued Operation Iraqi Freedom: By the Numbers, a declassified report about the aerial campaign in the conflict. Sixty A-10s were deployed in Iraq; one was shot down near Baghdad International Airport by Iraqi fire late in the campaign. Of the A-10s deployed, 47 were Air National Guard Aircraft, and 12 were from the Air Force Reserve. The A-10 had a mission capable rate of 85% in the war, and fired 311,597 rounds of 30 mm ammunition. The A-10 also flew 32 missions in which the aircraft dropped propaganda leaflets over Iraq.

The A-10 is scheduled to stay in service with the USAF until 2028 , when it may be replaced by the F-35 Lightning II. The entire A-10 fleet is currently undergoing upgrades. The A-10 could stay in service longer due to its low cost and its unique capabilities which the F-35 simply cannot incorporate — such as its cannon, ruggedness and slow flying capabilities.

Nicknames

How the A-10 Thunderbolt II received the nickname "Warthog" (or simply "Hog"), dates back to Fairchild-Republic's initial deliveries. There are several rumors that the name was derived from the report of the main gun, which has a surprisingly low pitch and sounds much like the snorting or grunting of a hog. This, coupled with the A-10's lack of aesthetic appeal and thick skin, make the aircraft reminiscent of a warthog.

Another suggested reason for the "Warthog" nickname comes from the fuselage rivet heads. For production economy and simplicity, the fuselage used different types of rivets. Only those forward of the trailing edge of the wing are flush-head. Those aft of the wing are protruding-head, which makes the skin surface look and feel "bumpy". (This was done since the boundary layer separates at this point on the fuselage, and therefore the bumpiness does not affect the drag of the aircraft.) When the A-10 was first delivered to Davis-Monthan AFB, the crew chiefs thought the protruding rivet heads looked like warts, and dubbed the A-10 "the Warthog". The "Hog" nickname also dates back to its predecessors. The F-84 Thunderjet was front-heavy and would sometimes tip over, leaving its nose in the mud, leading to the "Hog" designation.

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.

Survivors on display

Operators

The A-10 has been flown exclusively by the United States Air Force and its Air Reserve Components, the Air Force Reserve and the Air National Guard. As of 30 September 2005, 17 squadrons operate the A-10 or its OA-10 variant (8 USAF, 6 ANG, and 3 AFR).

;United States Air Force

;Air National Guard

  • 103d Fighter Wing - Bradley ANGB, Connecticut (BRAC 2005 removed aircraft)
    • 118th Fighter Squadron
  • 104th Fighter Wing - Barnes ANGB, Massachusetts (BRAC 2005 saw unit transition to F-15A/B+)
    • 131st Fighter Squadron
  • 110th Fighter Wing - Battle Creek ANGB, Michigan (BRAC 2005 moves aircraft to 107 FS)
    • 172nd Fighter Squadron
  • 111th Fighter Wing - [Willow Grove ARS, Pennsylvania (BRAC 2005 sees unit losing aircraft in 2012)
    • 103rd Fighter Squadron
  • 124th Wing - Boise Air Terminal, Idaho
  • 175th Wing - Martin State Airport, Maryland
    • 104th Fighter Squadron
  • 188th Fighter Wing Fort Smith, Arkansas (Transitioned from F-16s to A-10s due to BRAC 2005)

;Air Force Reserve

References

  • Fitzsimmons, Bernard, ed. ''A-10 Thunderbolt II'' (Modern Fighting Aircraft Series). New York: Arco Publishing, Inc., 1984. ISBN 0-668-06070-0.
  • Winchester, Jim, ed. "Fairchild A-10 Thunderbolt II." Military Aircraft of the Cold War (The Aviation Factfile). Rochester, Kent, UK: The Grange plc., 2006. ISBN 1-84013-929-7.

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