One of the most vital assets on the modern battlefield is the capability of close air support in support of the ground commander. Specialized ground attack and support aircraft have been a deciding factor in battles throughout the twentieth century. Initially close air support originated in the form of grenades or small bombs being dropped over the sides of biplanes and small dirigibles during the First World War. These were used against opposing sides trench lines in support of artillery barrages and advances across the barren landscape of No Mans Land. Dedicated close support platforms were developed subsequently in the years following the armistice and the end of the First World War. Aircraft specifically designed to support the ground forces in the form of dive bombers anti tank platforms took on a new form when in 1936, a resurgent Luftwaffe under the guidance of Hermann Göring, himself a veteran of the First World War and the Nazi Party deployed its new Junkers Ju 87 airframe. The Ju 87 commonly referred to as the 'Stuka' taken from its official title of Sturzkampfflugzeug meaning 'dive bomber' was a twin seat, gull winged, fixed under carriage attack aircraft essentially a flying artillery piece able to provide sturdy, accurate and effective fire support against ground targets.
The Ju 87 proved successful in the 1936 Spanish Civil War and during the Blitzkrieg campaign against Poland in 1939. The type operated with limited successes during the 1940 Battle of Britain where the types slow nature, poor maneuverability and lack of defensive armament made it vulnerable to interception by Royal Air Force fighters. It would go on to serve in the Balkans campaigns as well as in North Africa and along the Eastern Front during Operation Barbarossa against the Soviet Union. In the Eastern Front campaigns, the Stuka found a new lease on life when it was armed with heavy cannons and employed as a 'tank buster' to destroy Soviet armored vehicles. Oberst Hans-Ulrich Rudel a Stuka pilot would become the most decorated German pilot during the Second World War including being the only person awarded the Knights Cross of the Iron Cross with Golden Oak Leaves, Swords and Diamonds. His kill count would total some 2000 vehicles destroyed including 800 vehicles, 519 tanks, 150 artillery pieces, 70 landing craft, 9 enemy aircraft, 4 armored trains, several bridges, a destroyer, two cruisers and a Soviet battleship the Marat.
The United States and the United Kingdom had their own dedicated close air support aircraft the Republic P-47 Thunderbolt and the Hawker Typhoon respectively. Both aircraft saw subsequent deployment against German forces in the latter years of the war when the Luftwaffe had been all but defeated on the western front. Following the initial landings on the beaches of Normandy codenamed Operation Overlord, American P-47s and British Typhoons provided close air support for advancing ground forces during the hedgerow campaigns employing effective firepower against well placed German tanks such as the Tiger and Panther. Using an assortment of heavy cannons, wing launched rockets or bombs the capability of these aircraft combined with their rugged construction and nature made them valuable assets to the advancing ground forces. Utilizing speed, maneuverability, armored construction designed to protect the pilot and capabilities for carrying a large amount of ordnance refined the way ground attack aircraft would be forever be developed.
The successes of ground attack aircraft during the Second World War would not be completely or correctly noted without mentioning one of the most effective ground attack platforms of the war, the Soviet Union's Ilyushin Il-2 Sturmovik. Known as the 'Hunchback', 'Flying Tank' or 'Flying Infantryman' by ground forces, the type was effectively employed against German forces during their invasion of the Soviet Union. The heavy armor of the aircraft made it exceptionally difficult for the Germans to shoot down the type and it was commonly nicknamed 'Schlächter' or Slaughterer or 'Der Schwarze Tod' the Black Death. German pilots referred to it as Eiserner Gustav 'Iron Gustav' or Zementbomber 'Concrete Bomber'. Even Soviet leader Josef Stalin was an admirer of the type and championed it, paying it a great tribute in his own unique way. It was said that when one production factory fell behind in producing the planes, Stalin sent an angry worded cable to the factory manager demanding more airplanes and stressing the vitality of the type to the war effort. He ended the cable with the words 'This is my final warning.'
After the end of the Second World War, dedicated close support aircraft were largely disregarded in favor of fast moving fighters and fighter bombers. In the United States, the most effective close support platform in the years after the war was the Douglas A-1 Skyraider. The piston powered, propellor driven aircraft known as the 'Spad' was effectively deployed in Korea and Vietnam. Fast jets nicknamed 'Fastmovers' by ground forces were largely ineffective in close air support operations because the high operating speeds didn't afford pilots the opportunity of time to accurately pinpoint targets on the ground as well as the drawback of lacking loiter time on target.
In 1966, the United States Air Force instituted the Attack Experimental (A-X) program office which was followed on 6 March 1967, by the request placed with 21 defense contractors for a low cost dedicated attack aircraft. Pierre Sprey, an aircraft designer and defense analyst partnered with the Secretary of the Air Force to outline the details of the requirements for the new aircraft. Interviews with Skyraider pilots resulted in the desire for the new type to have a long loiter time, good maneuverability at low speeds, extreme battlefield survivability and heavy cannon firepower. Design elements were taken from the earlier Soviet Ilyushin Il-2, German Henschel Hs 129 and the American Douglas A-1 Skyraider. Additional information was taken from accounts written by German Stuka ace Hans-Ulrich Rudel in his biography. The final proposal took shape in May of 1970. The threat of Soviet armored forces and the emphasis of the new type to be able to operate in an all weather environment concluded that the aircraft be designed specifically for a 30mm cannon, fly with a maximum speed of 460mph, have a takeoff distance of 4,000 feet, be able to carry an external combat load of 16,000lbs with a 285 mile mission radius and have a unit cost of US $1.4 million.
From this point on out the program began to develop in two phases, with the initial requirement for the aircraft developed, the requirement for the new aircraft's cannon armament was soon developed. The requirement for the cannon dictated that it be of 30mm in caliber with a requirement for a high rate of fire at 4,000 rounds per minute with high muzzle velocity.
Northrop and Fairchild Republic were selected by the United States Air Force to submit prototypes. Northrop would submit the YA-9A and Fairchild Republic would submit the YA-10A with General Electric and Philco-Ford being selected to submit prototypes for the cannon armament.
In develop separate from the aircraft, the 30mm cannon was not available for the initial aircraft trials and both aircraft were retrofitted with the smalled M61 Vulcan 20mm gatling gun. The Fairchild Republic YA-10A prototype built in Hagerstown, Maryland first flew on 10 May 1972. Following a trial and fly off competition, the YA-10A was selected over the YA-9A by the United States Air Force on 18 January 1973. General Electric was selected to manufacture the 30mm cannon designated GAU-8 in June 1973.
The first production aircraft were flown in October 1975 with the Air Force receiving its first deliveries of the type in March of 1976 with 715 airframes being built and delivered to the United States Air Force between 1976 and 1984. The aircraft would designated officially as the A-10 Thunderbolt II, inheriting it's name from the rugged World War II era Republic P-47 Thunderbolt.
The Thunderbolt II has superior maneuverability characteristics at low operational speeds attributed to its large wing area, high wing aspect ratio and large ailerons. The inclusion of the high wing aspect ratio permits the type to accomplish short takeoff and landing or STOL capability allowing it to operate from improvised airfields near the front lines of a conflict. The loiter time for the aircraft is great and the airplane can operate at altitudes under 1,000 feet with 1.5 mile visibility. Its slow operating speed of 330 knots or 350 miles per hour makes it a much more suitable attack platform than fast moving jet aircraft. The aircraft's infrared signature is lowered by passing engine exhaust over the types horizontal stabilizer and between the twin tail pylons. The placement of the engines high on the fuselage and behind the wings partially shields them from anti-aircraft fire as well as keeps them high out of the risk of the ingestion of foreign objects or debris.
Specially designed wing panels are resistant to combat damage and they bear no load so damaged panels can be quickly replaced in field environments. The ailerons are positioned near the far end of the wings to produce a greater rolling moment. The ailerons of the A-10 are almost 50% of the total wingspan of the aircraft improving control of the aircraft at slow speeds. The aircraft is ideal for field use, being designed to be maintained with minimal equipment. The Thunderbolt II was designed so that parts from both the right and left side of the aircraft are interchangeable including the aircraft's engines, main landing gear and vertical stabilizers. The A-10 was further designed with a sturdy landing gear, low pressure tires and large straight wings to allow for operation from short unprepared strips with a high ordnance load thus permitting operation from damaged sites. If an airfield's runaway is damaged, the A-10 can operate from short taxiways as well as straight sections of road such as the autobahns in West Germany.
The airframe was designed to be extremely tough, able to sustain direct hits from armored piercing and high explosive rounds fired from calibers up to the Soviet 23mm. Flight systems are triple redundant in design with mechanical systems to back up the double redundant hydraulic systems thus allowing the attack pilot to maintain flight and land the aircraft when hydraulics are lost or even if part of the wing is lost. It was also designed to continue operation with one engine, one tail, one elevator and with half of one wing missing. The aircraft utilizes self sealing fuel tanks, and landing gear that partially protrude from its wing nacelles to allow for belly landings in the event of an emergency with minimal damage to the aircrafts underside.
The pilot is protected by a 1,200lb titanium armored 'bathtub' which has been tested to withstand direct hits from 23mm as well as 57mm rounds from multiple trajectories and deflection angles. The armor protection makes up roughly six percent of the aircraft's empty weight although it does provide protection for the pilot against fragmentation as well. The canopy itself is resistant to small fire adding additional protection to the pilot.
Although capable of mounting a variety of weapons systems, the A-10s primary armament is the General Electric GAU-8 30mm Avenger cannon.The weapon system fires a depleted uranium armored piercing shell at a rate of 3,900 feet per minute. The cannon takes half a second to come up to speed with 50 rounds being fired during the first second, and roughly 70 rounds per second afterwards. The gun maintains a high accuracy of being able to place some 80% of its shots within a forty foot diameter circle from 4,000 feet while in forward flight. The GAU-8 is also optimzed fora slant range of 4,000 feet with the A-10 in a 30 degree dive. It is positioned off center in the nose of the aircraft with the front landing gear placed to the right of the center line so that the actively firing cannon is directly on the aircraft's center line. General combat load on the cannon is 1,174 rounds of 30mm ammunition although it can carry a maximum of 1,350 rounds.
A second common weapon utilized by A-10 pilots is the AGM-65 Maverick guided missile which allows the Thunderbolt II to engage targets at greater distances than engagements with the GAU-8 well out of the range of modern anti-aircraft systems. Other weapons include cluster munitions, Hydra rocket pods with the additional capability of being able to use laser guided bombs and the AIM-9 Sidewinder air to air missile for a defensive capability against enemy aircraft.
A-10s were initially deployed to RAF Bentwaters/RAF Woodbridge in England complete with the European I woodland paint scheme designed to minimize visibility from above in the low operating environment of the aircraft. It used dark green, medium green and dark grey to effectively blend in with the typical forest terrain of Europe. Another feature of the type was a false canopy painted on the underside of the aircraft behind the cannon to confuse enemy ground forces of the aircrafts attitude and maneuver direction. A-10 detachments rotated from RAF Bentwaters/RAF Woodbridge to four locations in West Germany known as Forward Operating Locations. These sites were Leipheim, Sembach Air Base, Nörvenich, and Ahlhorn.
A-10s were frequently painted with nose art such as sharks mouths and hog faces. It was initially unwelcomed by fighter pilots who generally favored speed and appearance. An additional role picked up by the aircraft was the forward air control role in which the aircraft would be redesignated as the OA-10 and utilize a load of Hydra smoke or white phosphorous rockets for marking ground targets.