A-10, the BRRRRRRTTTTT Machine...

A-10 history upgrades ammunition future
USAF A-10 Thunderbolt II.

The A-10 Thunderbolt II is the first U.S. Air Force aircraft designed for close air support of ground forces. The A-10 Thunderbolt II is an ugly beast (thus its nickname: Warthog or Hog), but it’s "hog drivers" think highly of it because of its ability to remain aloft after absorbing punishment from ground fire. Although it has received a lot of criticism in the past, this unique aircraft not only survives today but there are rumours that it will remain in service until 2040, becoming one of the oldest fighters of USAF!

The A-10 was born from the Attack-Experimental (A-X) program, which was launched in 1966 for the development of a ground-attack and close air support aircraft to replace the Douglas A-1 Skyraider. During the Vietnam War, the 1940s-vintage propeller-driven Skyraider was the only dedicated close air support aircraft in the USAF's inventory. While a capable aircraft for its era, with a relatively large payload and endurance, the propeller-driven design was on the other hand relatively slow and vulnerable to ground fire. The U.S. Air Force and Marine Corps lost 266 A-1s in action in Vietnam, largely from small arms fire.

In May 1970, USAF issued a modified, more detailed request for the specifications of this new aircraft. The threat of Soviet armoured forces and all-weather attack operations had become more serious. The new aircraft should have been capable of staying above the battlefield and engaging enemy targets at low altitude and speed, while providing extreme crew and aircraft survivability.

Later, the requirements were further specified including a maximum speed of 450 mph and a normal operating speed of 300 mph in combat to enable easier engagement of slow moving ground targets. Furthermore, the new aircraft was required to take off in less than 4,000 feet, enabling operations from small airfields close to the front lines, carry an external load of 16,000 pounds and have a mission radius of 285 miles, all for a final cost of $1.4 million per aircraft.

Of the six proposals submitted to the Air Force, Northrop and Fairchild Republic were selected to build their prototypes: the YA-9A and YA-10A, respectively. The entire design of the aircraft revolved around the new high-speed 30mm cannon. General Electric and Philco-Ford were also selected to build the new GAU-8 Avenger cannon in June 1973.

Two YA-10 prototypes were built in the Republic factory in Farmingdale, New York, and first flew on 10 May 1972 by test-pilot Howard "Sam" Nelson. Northrop built two YA-9A prototypes which were also used by the U.S. Air Force's Attack-Experimental Program. Unfortunately they didn't stand a chance against the ultimate design of the Fairchild Republic. In 1973, Fairchild Republic’s YA-10A was announced the winner for the new programme. The first production A-10 flew in October 1975. On 10 February 1976, Deputy Secretary of Defence, Bill Clements authorized full-rate production, with the first A-10 being accepted by the Air Force Tactical Air Command on 30 March 1976. Production continued and reached a peak rate of 13 aircraft per month. By 1984, 715 airplanes, including two prototypes and six development aircraft, had been delivered.

Fairchild Republic’s WWII fighter, P-47 Thunderbolt, had begun its service in Europe as fighter and bomber escort, but soon earned a reputation as a relentless and tough ground-attack aircraft. It was a natural choice for the company to name its new CAS-dedicated aircraft after its WWII-era forefather: “Thunderbolt II”.

Although developed initially to provide an aerial counterpunch to the mass of Soviet tanks, the A-10 did not see combat until the Gulf War in 1991. There the “Warthog” earned its nickname, getting pilots back to base despite heavy damage from ground fire, while destroying 900 Iraqi tanks, 2,000 armoured vehicles and trucks and over 1,200 artillery pieces. Just four A-10s were lost to Iraqi surface-to-air missiles in over 8,000 sorties. The A-10 gained its first air-to-air victory during the Gulf War when Capt. Robert Swain shot down an Iraqi helicopter with 30mm cannon fire. The A-10 next saw combat in the Balkans: in 1994, 1995 and again in 1999, before being deployed to Afghanistan in 2002 and participating in the entirety of Operation Iraqi Freedom.

The A-10A single-seat variant was the only version produced, though one pre-production airframe was modified into the YA-10B twin-seat prototype to test an all-weather night capable version. One experimental two-seat A-10 Night Adverse Weather (N/AW) version was built by converting an A-10A. It included a second seat for a weapons system officer responsible for electronic countermeasures (ECM), navigation and target acquisition. The two-seat trainer version was ordered by the Air Force in 1981, but funding was cancelled by U.S. Congress and the jet was not produced. The only two-seat A-10 built now resides at Edwards Air Force Base's Flight Test Center Museum.

The A-10 has superior manoeuvrability at low speeds and altitude because of its large wing area, low wing aspect ratio, and large ailerons. The wing also allows short takeoffs and landings, permitting operations from primitive forward airfields near front lines. The aircraft can fly for extended periods and operate under 1,000-foot (300 m) ceilings with 1.5-mile (2.4 km) visibility. It typically flies at a relatively low speed of 300 knots (560 km/h), which makes it a better platform for the ground-attack role than fast fighter-bombers, which often have difficulty targeting small, slow-moving targets.

The leading edge of the wing has a honeycomb structure panel construction, providing strength with minimal weight; similar panels cover the flap shrouds, elevators, rudders and sections of the fins. Combat experience has shown that this type of panel is more resistant to damage. The skin is not load-bearing, so damaged skin sections can be easily replaced in the field, with makeshift materials if necessary. The ailerons are at the far ends of the wings for greater rolling moment and have two distinguishing features: The ailerons cover almost 50 percent of the wingspan, providing improved control even at slow speeds and they are split, working also as speedbrakes.

The A-10 is designed to be refuelled, rearmed, and serviced with minimal equipment. Its simple design enables maintenance at forward bases with limited facilities. 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 aircraft ordnance load, allowing the aircraft to operate from damaged airbases, flying from taxiways, or even straight roadway sections.

The front landing gear is offset to the aircraft's right to allow placement of the 30 mm cannon with its firing barrel along the centerline of the aircraft. The wheels of the main landing gear partially protrude from their nacelles when retracted, making gear-up belly landings easier to control and less damaging. All landing gears retract forward, if hydraulic power is lost a combination of gravity and aerodynamic drag can lower and lock the gear in place.

The A-10 is exceptionally tough, being able to survive direct hits from armour-piercing and high-explosive projectiles up to 23 mm. It has double-redundant hydraulic flight system and a mechanical system as a back-up if the hydraulic power is lost. Flight without hydraulic power uses the manual reversion control system; pitch and yaw control engages automatically, roll control is pilot-selected. In manual reversion mode, the A-10 is sufficiently controllable to return to base, though control forces are greater than normal. The aircraft is designed to be able to fly with one engine, one half of the tail, one elevator, and half of a wing missing.

The cockpit and parts of the flight-control system are protected by 540 kg titanium armour, referred to as a "bathtub". This armour has been tested to withstand strikes from 23 mm cannon fire and some strikes from 57 mm rounds. It is made up of titanium plates with thicknesses from 13 to 38 mm determined by a study of likely trajectories and deflection angles. The armour makes up almost 6% of the aircraft's empty weight. The front windscreen and canopy are also resistant to small arms fire.

The A-10 was designed to fly from forward air bases and semi-prepared runways with high risk of foreign object damage to the engines. The unusual location of the General Electric TF34-GE-100 turbofan engines decreases ingestion risk, and allows the engines to run while the aircraft is serviced and rearmed by ground crews, reducing turn-around time. The engines' high bypass ratio (6:1) contributes to a relatively small infrared signature, and their position directs exhaust over the tailplanes further shielding it from detection by infrared homing surface-to-air missiles. The engines exhaust nozzles are angled nine degrees below the horizon to cancel out the nose-down pitching moment that would otherwise be generated from being mounted above the aircraft's center of gravity and avoid the need to trim the control surfaces to prevent pitching.

To reduce the likelihood of damage to the A-10's fuel system, all four fuel tanks are located near the aircraft's center and are separated from the fuselage, so projectiles would need to penetrate the aircraft's skin before reaching a tank's outer skin. Compromised fuel transfer lines are also self-sealed. If damage exceeds a tank's self-sealing capabilities, check valves prevent fuel flowing into a compromised tank. Most fuel system components are inside the tanks so that fuel will not be lost due to component failure. The refuelling system is also purged after use. Reticulated polyurethane foam lines both the inner and outer sides of the fuel tanks, retaining debris and restricting fuel spillage in the event of damage. The engines are shielded from the rest of the airframe by firewalls and fire extinguishing equipment. In the event of all four main tanks being lost, two self-sealing sump tanks contain fuel for 230 miles (370 km) of flight.

The A-10 has received many upgrades since entering service. In 1978, the A-10 received the Pave Penny laser receiver pod, which receives reflected laser radiation from laser designators to allow the aircraft to deliver laser guided bombs. The Pave Penny pod is carried on a pylon mounted below the right side of the cockpit and has a clear view of the ground. In 1980, the A-10 began receiving an inertial navigation system.

In the early 1990s, the A-10 began to receive the Low-Altitude Safety and Targeting Enhancement (LASTE) upgrade, which provided computerized weapon-aiming equipment, an autopilot, and a ground-collision warning system. In 1995, cracks were revealed on many aircraft, so a new plan was decided to address these issues and also increase the life span to 16,000 hours. This resulted in the "HOG UP" program, which commenced in 1999. Over time, additional aspects were added to HOG UP, including new fuel bladders, changes to the flight control system, and inspections of the engine nacelles.

In 2005, a program was started to upgrade the remaining A-10A aircraft to the A-10C configuration. The entire fleet of 356 A-10 aircraft began receiving the Precision Engagement upgrades including an improved fire control system (FCS), electronic countermeasures (ECM), and smart bomb targeting. The aircraft also received all-weather combat capability, with a new flight computer, new glass cockpit displays and controls, two new 5.5-inch (140 mm) colour displays with moving map function, and an integrated digital stores management system and a Hand-on-Throttle-and-Stick configuration mixing the F-16's flight stick with the F-15's throttle.

Other changes included two multifunction displays, a modern communications suite including a Link-16 datalink system and SATCOM. The LASTE system was replaced with the Integrated Flight & Fire Control Computers (IFFCC). The final aircraft that was upgraded to A-10C configuration left the factory in June 2011.

Although the A-10 can carry a considerable amount of ammunitions, its primary built-in weapon is the 30×173 mm GAU-8/A Avenger cannon. One of the most powerful aircraft cannons ever flown, it fires large depleted uranium armour-piercing shells. The GAU-8 is a hydraulically driven seven-barrel rotary cannon designed specifically for the anti-tank role with a high rate of fire of 3,900 rounds per minute. The cannon takes about half a second to reach top speed, so 50 rounds are fired during the first second, 65 or 70 rounds per second thereafter. The gun is accurate enough to place 80 percent of its shots within a 12.4 m diameter circle from 4,000 feet (1,220 m) while in flight. The GAU-8 is optimized for a slant range of 1,220 m with the A-10 in a 30-degree dive.

The fuselage of the aircraft is built around the cannon. The GAU-8/A is mounted slightly to the port side; the barrel in the firing location is on the starboard side at the 9 o'clock position so it is aligned with the aircraft's centerline. The gun's 1.8 m ammunition drum can hold up to 1,350 rounds of 30 mm ammunition, but generally holds 1,174 rounds. To protect the GAU-8/A rounds from enemy fire, armour plates of differing thicknesses between the aircraft skin and the drum are designed to detonate incoming shells.

The AGM-65 Maverick air-to-surface missile is a commonly used weapon for the A-10, targeted via electro-optical (TV-guided) or infrared. The Maverick allows target engagement at much greater ranges than the cannon, and thus less risk from anti-aircraft systems. Other weapons include cluster bombs and Hydra rocket pods. The A-10 is equipped to carry GPS and laser-guided bombs, such as GBU-39 Small Diameter Bomb, JDAM, WCMD and glide bomb AGM-154 Joint Standoff Weapon. The A-10s also fly most of their missions with an ALQ-131 ECM pod under one wing and two AIM-9 Sidewinder air-to-air missiles under the other wing for self-defence. 

The future of this old but highly capable platform remains the subject of debate. In 2007, USAF announced that the A-10 was going to remain in service until 2028, when it would likely be replaced by the Lockheed Martin F-35 Lightning II. However, critics have said that replacing the A-10 with the F-35 would be a "giant leap backwards" given the A-10's performance and the F-35's high costs. In 2012, the Air Force considered the F-35B STOVL variant as a replacement CAS aircraft, but concluded that the aircraft could not generate sufficient sorties.

Plans to develop a replacement aircraft were announced by the US Air Combat Command in August 2015. Early the following year, the Air Force began studying future CAS aircraft to succeed the A-10 in low-intensity "permissive conflicts" like counterterrorism and regional stability operations, admitting that the F-35 would be too expensive to operate in day-to-day roles. A wide range of platforms were under consideration, including everything from low-end AT-6 Wolverine and A-29 Super Tucano turboprops and the Textron AirLand Scorpion as more basic off-the-shelf options to more sophisticated clean-sheet attack aircraft or "AT-X" derivatives of the T-X next-generation trainer as entirely new attack platforms.

In January 2016, USAF was "indefinitely freezing" its plans to retire the A-10 for at least several years. In addition to Congressional opposition, its use in anti-ISIL operations, deployments to Eastern Europe as a response to Russia's military intervention in Ukraine, and re-evaluation of F-35 numbers necessitated its retention. In October 2016, the Air Force Material Command brought the depot maintenance line back to full capacity in preparation for re-winging the fleet. Then in June 2017 it was finally announced that the aircraft "...will be kept in the air force’s inventory for years to come until further notice!"

Long live the Warthog!

Text, Images: George Karavantos

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