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The Fairchild Republic A-10 Thunderbolt II is a single seat, twin-engine, straight wing jet aircraft developed by Fairchild-Republic for the United States Air Force. Its official name comes from the Republic P-47 Thunderbolt, a fighter particularly effective at close air support. The A-10 is more commonly known by its nicknames "Warthog" or "Hog". The A-10 was designed for close-in support of ground troops, close air support, providing quick-action support for troops against helicopters, vehicles, and ground troops. It entered service in 1976 and is the only production-built aircraft that has served in the USAF that was designed solely for CAS. Its secondary mission is to provide forward air controller - airborne (FAC-A) support, by directing other aircraft in attacks on ground targets. Aircraft used primarily in this role are designated OA-10.

The A-10 was intended to improve on the performance of the A-1 Skyraider and its poor firepower. The A-10 was designed around the 30 mm GAU-8 Avenger rotary cannon that is its primary armament. Its airframe was designed for durability, with measures such as 1,200 pounds (540 kg) of titanium armor to protect the cockpit and aircraft systems, enabling it to absorb a significant amount of damage and continue flying. Its short takeoff and landing capability permits operation from airstrips close to the front lines, and its simple design enables maintenance with minimal facilities. The A-10 served in Operation Desert Shield, and Operation Desert Storm, the American intervention against Iraq's invasion of Kuwait, where the A-10 distinguished itself. The A-10 also participated in other conflicts such as Operation Urgent Fury in Grenada, the Balkans, Afghanistan, Iraq, and against the Islamic State in the middle east.

The A-10A single-seat variant was the only version produced, though one pre-production airframe was modified to become the YA-10B twin-seat prototype to test an all-weather night capable version. In 2005, a program was begun to upgrade remaining A-10A aircraft to the A-10C configuration with modern avionics for use of precision weaponry. With a variety of upgrades and wing replacements, the A-10's service life may be extended to 2028.

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The Fairchild Republic A-10 Thunderbolt II is a single seat American twin-engine, straight wing jet aircraft developed by Fairchild-Republic. It entered service in 1976, and is the only United States Air Force production-built aircraft designed solely for (relatively) close quarters support of ground troops, close air support, providing quick-action support for troops against Helicopter, vehicles, and enemy foot-soldiers. The A-10 distinguished itself in Operation Desert Storm, the American intervention against Iraq's invasion of Kuwait. This validated both the concept of cheap, simple CAS aircraft, and the A-10 itself. The A-10 has gone on to serve as one of the cornerstones of the Air Force's operations since it's acceptance in 1975 in Grenada, Desert Storm, the Balkans, and in what is colloquially known as the Global War on Terror, including the 2001 invasion of Afghanistan, the 2003 invasion of Iraq, and in the war against Daesh/ISIS.

The role of tactical aircraft against vehicles became one of the most notable advances in warfare that came about during World War 2, a role which would be further developed in Korea and Vietnam. The A-10 was intended to improve on the performance of the A-1 Skyraider, and one of the Skyraider's biggest weaknesses was it's poor firepower. A separate program was launched to determine the best weapon to fit the A-10 with, the GAU-8 was the result of that program.. The A-10 was designed around the 30 mm GAU-8 Avenger rotary cannon that is its primary armament. The A-10's airframe was designed for durability, with measures such as 1,200 pounds (540 kg) of titanium armor to protect the cockpit and aircraft systems, enabling it to absorb a significant amount of damage and continue flying. Its short takeoff and landing capability permits operation from airstrips close to the front lines, while its simple design enables maintenance at forward bases with limited facilities. The A-10A single-seat variant was the only version built, though one A-10A was converted to an A-10B twin-seat version. In 2005, a program was begun to upgrade remaining A-10A aircraft to the A-10C configuration.

The A-10's official name comes from the Republic P-47 Thunderbolt of World War II, a fighter that was particularly effective at close air support. The A-10 is more commonly known by its nicknames "Warthog" or "Hog". Its secondary mission is to provide forward air controller - airborne (FAC-A) support, by directing other aircraft in attacks on ground targets. Aircraft used primarily in this role are designated OA-10. With a variety of upgrades and wing replacements, the A-10's service life may be extended to 2028.

Development

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The Fairchild Republic A-10 Thunderbolt II is a single seat twin-engine, straight wing jet aircraft developed by Fairchild-Republic for the United States Air Force. It was designed for close-in support of ground troops, close air support, providing quick-action support for troops against Helicopter, vehicles, and enemy foot-soldiers. It entered service in 1976 and is the only production-built aircraft that has ever served in the USAF that was designed solely for CAS. The A-10 distinguished itself in Operation Desert Storm, the American intervention against Iraq's invasion of Kuwait. The A-10 has gone on to serve as one of the cornerstones of the Air Force's operations since it's acceptance in 1975. The A-10 has participated in Urgent Fury in Grenada, Desert Storm/Shield, the Balkans, and in what is colloquially known as the Global War on Terror, including the 2001 invasion of Afghanistan, the 2003 invasion of Iraq, and in the war against Daesh/ISIS, among others.

Background

The role of aircraft in ground combat was maturing quickly in the 1930s and 1940s with the Spanish Civil War and World War 2. In the 1930s the German air force believed that this role would best be served by dive bombers attacking poorly defended supply forces; trucks, and supplies. The experience of the German Kondor Legion in the Spanish civil war confounded their expectations. Their successes mostly came from their guns in strafing runs. This led the German air force to develop an aircraft specifically designed for this role, the Henschel Hs 129. The Hs 129 was designed to be protected against ground gunfire, having a bathtub of armor protecting the pilot and nose of the plane. It also had large guns. Eventually the luftwaffe would strap a 75mm ground anti-tank gun under it's fuselage.

Criticism that the U.S. Air Force did not take close air support (CAS) seriously prompted a few service members to seek a specialized attack aircraft. In the Vietnam War, large numbers of ground-attack aircraft were shot down by small arms, surface-to-air missiles, and low-level anti-aircraft gunfire, prompting the development of an aircraft better able to survive such weapons. In addition, the UH-1 Iroquois and AH-1 Cobra helicopters of the day, which USAF commanders had said should handle close air support, were ill-suited for use against armor, carrying only anti-personnel machine guns and unguided rockets meant for soft targets. Fast jets such as the F-100 Super Sabre, F-105 Thunderchief and F-4 Phantom II proved for the most part to be ineffective for close air support because their high speed did not allow pilots enough time to get an accurate fix on ground targets and they lacked sufficient loiter time

The effective, but aging, Korean War era A-1 Skyraider was the USAF's primary close air support aircraft. A-1 losses were high, over 250, and it's guns were ineffective against armor. The A-37 was also used in the role, but it's payload was meager and it didn't have good loitering endurance. On June 7, 1961, Secretary of Defense McNamara ordered the air force to develop two tactical aircraft, and that one of them should be focused on the Combat Air Support mission. The Air Force undertook a broad review of it's tactical force structures and concluded that it should adopt a cheap aircraft to supplement the F-4 and F-111. The Air Force first focused on the F-5 because of it's air to air performance.

A 1965 cost effectiveness study shifted the focus from new F-5s to cheaper A-7Ds, and a contract was awarded. Further deliberation on the A-7 led to increases in requirements for the A-7, an engine, and avionics, which pushed doubled the cost estimate for the A-7, pushing it out of contention. A 1966 Air Force study on existing Air Force CAS capabilities revealed that the Air Force had gaps in the helicopter escort, and suppression fire roles, and that the Army was pursuing a new, high cost Army helicopter program to fill those gaps, but also posing a threat to Air Force tactical funding. The study concluded that the Air Force should acquire a simple, cheap, dedicated CAS aircraft at least as capable as the A-1, and that it should develop doctrine, tactics, and procedures for CAS aircraft to accomplish the missions for which the armed helicopters were provided. On September 8th, 1966, General McConnell ordered that a specialized CAS aircraft be designed, developed, and obtained, on December 22 a Requirements Action Directive (RAD) was issued for the A-X CAS plane.

A-X program

In 1966, the USAF formed the Attack Experimental (A-X) program office. On 6 March 1967, the Air Force released a request for information to 21 defense contractors for the A-X. The objective was to create a design study for a low-cost attack aircraft. In 1969, the Secretary of the Air Force asked Pierre Sprey to write the detailed specifications for the proposed A-X project; Sprey's initial involvement was kept secret due to his earlier controversial involvement in the F-X project. Sprey's discussions with Skyraider pilots operating in Vietnam and analysis of aircraft used in the role indicated the ideal aircraft should have long loiter time, low-speed maneuverability, massive cannon firepower, and extreme survivability; possessing the best elements of the Ilyushin Il-2, Henschel Hs 129, and Skyraider. The specifications also demanded that each aircraft cost less than $3 million. Sprey required that the biography of World War II Luftwaffe attack pilot Hans-Ulrich Rudel be read by people on the A-X program.

In May 1970, the USAF issued a modified, more detailed request for proposals (RFP) for the aircraft. The threat of Soviet armored forces and all-weather attack operations had become more serious. The requirements now included that the aircraft would be designed specifically for the 30 mm rotary cannon. The RFP also specified a maximum speed of 460 mph (400 kn; 740 km/h), takeoff distance of 4,000 feet (1,200 m), external load of 16,000 pounds (7,300 kg), 285-mile (460 km) mission radius, and a unit cost of US$1.4 million. The A-X would be the first USAF aircraft designed exclusively for close air support. During this time, a separate RFP was released for A-X's 30 mm cannon with requirements for a high rate of fire (4,000 round/minute) and a high muzzle velocity. Six companies submitted aircraft proposals, with Northrop and Fairchild Republic selected to build prototypes: the YA-9A and YA-10A, respectively. General Electric and Philco-Ford were selected to build and test GAU-8 cannon prototypes.

Two YA-10 prototypes were built in the Republic factory in Farmingdale, New York and first flew on 10 May 1972 by pilot Howard "Sam" Nelson. Production A-10's were built at Fairchild in Hagerstown, Maryland. After trials and a fly-off against the YA-9, on 18 January 1973, the USAF announced the YA-10's selection for production. General Electric was selected to build the GAU-8 cannon in June 1973. The YA-10 had an additional fly-off in 1974 against the Ling-Temco-Vought A-7D Corsair II, the principal USAF attack aircraft at the time, in order to prove the need for a new attack aircraft. The first production A-10 flew in October 1975, and deliveries commenced in March 1976.

One experimental two-seat A-10 Night Adverse Weather (N/AW) version was built by converting an A-10A. The N/AW 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 system officer responsible for electronic countermeasures (ECM), navigation and target acquisition. The N/AW version did not interest the USAF or export customers. The two-seat trainer version was ordered by the Air Force in 1981, but funding was canceled 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.\

Production

On February 10, 1976, Deputy Secretary of Defense Clements authorized full-rate production, with the first A-10 being accepted by the Air Force Tactical Air Command on March 30, 1976. Production continued at a rate of 15 aircraft per month, which was believed to be the best rate Fairchild could deliver. A total (including the two prototypes) 715 airplanes was delivered in 1984. When A-10 full rate production was first authorized the planned service life was 6,000 hours. A small reinforcement to the design was quickly adopted when the A-10 failed initial fatigue testing at 80% of testing, with the fix, the A-10 passed the fatigue tests.

8,000 flight hour service lives were becoming common at the time, so fatigue testing of the A-10 continued with a new 8,000 flight hour target. Fatigue testing for the new target quickly discovered serious cracks at WS. 23 where the outboard portions of the wings are joined to the fuselage. The first production change was to add cold working at WS. 23 to address this problem. Soon after that, the Air Force determined that the real world A-10 fleet fatigue was more harsh than estimated forcing them to change their fatigue testing, introducing "spectrum 3" equivalent flight hour testing.

Spectrum 3 fatigue testing started in 1979. This round of testing quickly determined that more drastic reinforcement would be needed. The second change in production, starting with aircraft #442 was to increase the thickness of the lower skin on the outer wing panels. A tech order was issued to retrofit the "thick skin" to the whole fleet, but the tech order was rescinded after roughly 242 planes leaving roughly 200 planes with the original "thin skin". Starting with aircraft #530 cold working at WS0 was performed, and this retrofit was performed on earlier aircraft. A fourth, even more drastic change was initiated with aircraft #582, again to address the problems discovered with spectrum 3 testing. This change increased the thickness on the lower skin on the center wing panel but it required modifications to the lower spar caps to accommodate the thicker skin. The Air Force determined that it was not economically feasible to retrofit earlier planes with this modification.

Upgrades

The A-10 pioneered the "design to cost" concept that placed a high emphasis on cost efficiency which contributed to the A-10's low purchase price, cost of maintenance, and cost of repair. This emphasis on low cost performance, as well as the A-10's low position on the Air Force totem pole lead to a very slow upgrade cycle. The Pave Penny pod, allowing the A-10 to detect targets designated by lasers, and launch laser guided weapons at the designated targets, was added to the A-10 late in the design stage. The A-10 began receiving an inertial navigation system in 1980. Starting in 1987 some A-10s received minor upgrades to add the forward air controller role to their portfolio, allowing them to replace OV-10 Broncos in that role. A-10s with this modification became OA-10s, and received minor avionics upgrades as well as minor modifications to their weapon pylons that enabled the OA-10 to launch illumination devices.

Development of the Low Altitude Safety and Targeting Enhancement (LASTE) upgrade program started in the 1980s, and in 1990 the Air Force started upgrading A-10s with LASTE. A-10s played a large role in operation Desert Storm started in August of the same year that the LASTE upgrades started but too few aircraft had been upgraded at that time for it to have a significant effect. The LASTE upgrade imparted significant improvements to the avionics including ground collision warnings that would almost completely reduce deadly training crashes, navigation improvements, and autopilot, as well as making the A-10 compatible with night vision goggles. The LASTE upgrade included the Ground Clearance Avoidance System (GCAS) which issued voice warnings triggered by a radar altimeter. It also included Enhanced Attitude Control (EAC) which stabilized the aircraft when the cannon was being fired. The Low Altitude Autopilot (LAAP) system gives an A-10 with the LASTE upgrade the ability to set altitude, or set both altitude and bearing. Finally the LASTE upgrade also includes a digital bombing computer with options for direct drop delivery as well as lobbed delivery allowing the A-10 to accurately hit a target at a greater distance.

In the 1990s the A-10s received the Color Airborne Video Tape Recorder(CAVTR) which would later be replaced by the Digital Video Airbone Data Recorder (DVADR). "Commencing in 1999, the A/OA-10 fleet was additionally upgraded with the installation of an Embedded Global Positioning System/Inertial Navigation System (EGI). In conjunction with this aircraft modification, a replacement Control Display Unit (CDU) [were] installed [along] with its own separate OFP (Operational Flight Program) software." The first A-10 with the EGI upgrade was received by the Air Force in the spring of 2000, and the entire fleet was upgraded by 2003. The EGI replaced the Litton LN-39 Inertial Navigation System (INS). "Integrated Flight & Fire Control Computer. Begun in FY01, this project was formerly known as the LASTE Upgrade Computer and will involve improvements to the aircraft’s digital datalink, digital terrain system, Common Missile Warning System, and MIL-STD 1760 databus/smart weapons." Also in 2001 the Air Force initiated a program to replace and combine the A-10s electronic, chaff, and flare defensive countermeasures with the ALQ-213.

On September 28th 2008 General North issued an urgent operational need request to AFCENT for a Head Mounted Cueing System (HMCS). A contract to respond to this request was issued in 2010 for the Scorpion HMCS which would allow the pilot to, among other things, designate a target by looking at it.

Hog-Up Service Life Extension and Wing Replacement Program

In 1987, Grumman Aerospace took over the A-10 program. Following from the 1992 decision to keep the A-10, Grumman developed a Force Structural Maintenance Plan and Damage Threat Assessment by 1993. On the military side, the A-10 Program Office didn't incorporate the updated procedures into the maintenance tech orders. Critically, the Analytical Condition Inspection implemented by the program office did not inspect every plane as specified in the FSMP, but, instead, employed statistical sampling, inspecting only a fraction of the fleet. A-10 maintenance suffered from budget constraints, and inspections were performed in the field rather than centralized with programmed depot maintenance. The A-10 program would see a large amount of upheaval on both the military and corporate side, with numerous changes in contractor along with large upheavals on the military side resulting from changes brought about by the base re-alignment and closure commission.

The first sign of trouble were two "near-critical" sized cracks found. Initially these were classified as minor, they would be reclassified as critical in 2001. Northrop Grumman was tasked with creating a plan to double the service life of the fleet in 1998, this would be used as the foundation for attempted service life extension programs. Unfortunately the Grumman plan was based on the assumption that the FSMP had been implemented and that subsequent testing had been uneventful, both these assumptions were wrong. The SPO began a repair program to implement Grumman's planned wing replacement program in 1999 as the "HOG UP" program. Classing it as a repair program bypassed the acquisition process, and allowed the SPO to use maintenance funding for the program. This also bypassed the Configuration Control Board, as well as strict evaluation of the proposed upgrade.

The SPO added center wing fuel bladder replacement, rework of the flight control system, nacelle fitting inspections, and other areas at the request of Air Combat Command. During this period the two near critical cracks previously uncovered received more scrutiny. The cracks previously classified as minor were classified as critical. This disrupted the HOG UP program, greatly increasing it's scope and more than quadrupling it's cost. An independent review of the HOG UP program at this point concluded that the data the wing upgrade relied on could no longer be trusted. This independent review was presented in September 2003. Shortly after that, fatigue testing on a test wing failed. There were also mounting problems with wings in service that were failing inspections at an increasing rate. The Air Force estimated that they would run out of wings by 2011. Three plans were explored, replacing all the wings with new ones was the cheapest, costing $741 to implement, and $1.72 billion over the life of the program. In June, 2007 Boeing was awarded a $2 Billion contract to produce as many as 242 replacement A-10 wing sets. The first new wing set was delivered in February 2011. Boeing is under contract to deliver 173 wing sets through 2017.

A-10C

Starting in 2005 A-10s that received the Precision Engagement upgrade are designated A-10Cs. The Precision Engagement upgrade is an almost complete overhaul of the A-10's avionics, it enables the A-10C to network with ground, air, and sea forces, it enables the A-10C to employ GPS guided weaponry, It upgrades the A-10C so that it can use state of the art sensor pods, and it upgrades the A-10C's logistics, communications, and defensive systems. The PE upgrade "[includes] an improved fire control system, electronic countermeasures, upgraded cockpit displays, the ability to deliver smart bombs, moving map display, hands on throttle and stick, digital stores management, LITENING and Sniper advanced targeting pod integration, situational awareness data link or SADL, variable message format, or VMF, GPS-guided weapons, and upgraded DC power. The entire A-10 fleet has been Precision Engagement modified and now carries the A-10C designation." "The upgraded A-10C reached initial operational capability in September 2007." The PE upgrade will also add all-weather combat capability to the A-10. The upgrade will also upgrade the A-10 with a Hand on Throttle and Stick configuration mixing the flight stick of the F-16 with the throttle of the F-15. Additionally the A-10 will receive a very modern communications suite including a Link-16 radio, and SATCOM.

The Precision Engagement upgrades "backbone is the central interface control unit, which replaces most of the old armament control system and also interfaces with other mission subsystems to provide an integrated solution for the pilot and maintenance technician. The CICU takes various sources of information from the aircraft's subsystems--such as targeting pods, radios, processors and displays--and integrates and displays the information in a manner that is meant to reduce pilot workload. The massive increase in data provided by the PE system can be complex and confusing, which is why Lockheed Martin engineers are working with A/OA-10 pilots to "look for ways to improve and add information that the pilot needs to see," says Il Grande." The PE also "[includes] with the CICU is the integrated flight and fire control computer (IFFCC). The IFFCC replaces the A/OA-10's current low-altitude safety and targeting enhancement (LASTE) system.

"The PE upgrade includes two new color multi-function displays, Hands on stick and throttle pilot controls, a new central interface control unit (CICU) that provides digital stores management and overall avionics systems integration, upgraded processors, Up front controller (UFC), a new instrument panel, upgraded power systems, and the interfaces necessary to accommodate the new gps guided smart weapons. The upgrade was expanded to incude digital mapping." The upgrade also includes "the situational awareness data link (SADL) which will provide both air-to-air and ground-to-air digital communications of target data." "SADL uses the enhanced position location reporting system (EPLRS) waveform, which will provide secure, jam-resistant data communications, such as friendly force data from Army units, in near real time."

"The two new 5-by-5-inch liquid crystal, multifunction color displays in the Thunderbolt II's PE kit replace analog switching devices and round dials, and require installation of a new instrument panel. The displays, supplied by Elbit Fort Worth, are interchangeable and provide various control menus that provide the pilot-vehicle interface. The displays also will present a digital map on the tactical awareness display (TAD), produced by Lockheed Martin. The data link information and other tactical data are automatically oriented and scaled in order to be correctly overlayed on the map. This will "show where the good guys are and where the bad guys are," Il Grande explains. Pilots thumb through the menus on the displays, using the surrounding bezel keys or the HOTAS (hands on throttle and stick). The PE kit will add the up front controller, which is positioned just below the HUD, so that Warthog pilots can keep eyes up while inputting data. The UFC has the same keyboard as on the CDU and typically would be used to input menu items, navigational information and weapons delivery data."

"The mission planning system (MPS) will allow the pilot to plan his route, the weapons employed and drop sequences, and target information on the ground. He then uses a cartridge to load the mission plan onto the aircraft. As part of the Precision Engagement EMD program, the Southwest Research Institute is upgrading the MPS. Warthog pilots also will be able to program the weapons and check the weapons' status, while in fight." "For the maintenance technician, the A/OA-10's CICU and an existing control display unit (CDU) have been fitted with upgraded software to improve the detection and isolation of avionics subsystem failures. Southwest Research Institute is providing an upgraded operational test system (OTS) with a diagnostic interface to the aircraft avionics and weapon systems. These enhancements are expected to improve the system's maintainability and, thus, its availability."

Proposed Upgrades

Proposed further upgrades included integrated combat search and rescue locator systems and improved early warning and anti-jam self-protection systems, and the Air Force recognized that the A-10's engine power was sub-optimal and had been planning to replace them with more powerful engines since at least 2001 at an estimated cost of $2 billion dollars.

Other uses

A-10 at RAF Fairford, 2005

On 25 March 2010, an A-10 conducted the first flight of an aircraft with all engines powered by a biofuel blend. The flight, performed at Eglin Air Force Base, used a 1:1 blend of JP-8 and Camelina-based fuel. On 28 June 2012, the A-10 became the first aircraft to fly using a new fuel blend derived from alcohol; known as ATJ (Alcohol-to-Jet), the fuel is cellulousic-based that can be derived using wood, paper, grass, or any cellulose based material, and are fermented into alcohols before being hydro-processed into aviation fuel. ATJ is the third alternative fuel to be evaluated by the Air Force as a replacement for petroleum-derived JP-8 fuel. Previous types were a synthetic paraffinic kerosene derived from coal and natural gas and a bio-mass fuel derived from plant-oils and animal fats known as Hydroprocessed Renewable Jet.

In 2011, the National Science Foundation granted $11 million to modify an A-10 for weather research for CIRPAS at the U.S. Naval Postgraduate School, replacing a retired North American T-28 Trojan. The A-10's armor is expected to allow it to survive the extreme meteorological conditions, such as 200 mph hailstorms, found in inclement high-altitude weather events.

In 2015, Boeing revealed that it was holding initial discussions on the prospects of selling retired or stored A-10s in near-flyaway condition to international customers. However, the Air Force subsequently stated that it will not permit the aircraft to be sold.

Design

Overview

A-10 inboard profile drawing

"The A-10 Thunderbolt 2 is a cantilever low-wing monoplane with wide chord, deep airfoil section. One-piece constant chord center wing section, tapered outer panels, cambered wing tips. Two-segment, three-position, trailing-edge slotted flaps, interchangeable right and left. Wide span ailerons, made up of upper and lower surfaces that separate to serve as airbrakes. Small leading-edge slat inboard each mainwheel fairing. Redundant, armor shielded flight control system. Semi-monocoque aluminum alloy fuselage with four main longerons, multiple frames, and lap-jointed, and riveted skin." It has "cantilever aluminum structure with twin fins and interchangeable rudders mounted at tips of constant chord tailplane. Interchangeable elevators, each with an electrically operated trim tab."

The A-10 has superior maneuverability at low speeds and altitude because of its large wing area, high 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 loiter for extended periods and operate under 1,000 ft (300 m) ceilings with 1.5 mi (2.4 km) visibility. It typically flies at a relatively low speed of 300 knots (350 mph; 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. The skin panels are integral with the stringers and are fabricated using computer-controlled machining, reducing production time and cost. 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 are larger than is typical, almost 50 percent of the wingspan, providing improved control even at slow speeds; the aileron is also split, making it a deceleron.

The A-10 is designed to be refueled, rearmed, and serviced with minimal equipment. Also, most repairs can be done in the field. 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.

Front view of an A-10 showing the 30 mm cannon and offset front landing gear

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. During ground taxi, the offset front landing gear causes the A-10 to have dissimilar turning radii. Turning to the right on the ground takes less distance than turning left. 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 are hinged toward the aircraft's rear; if hydraulic power is lost, a combination of gravity and wind resistance can open and lock the gear in place.

Durability

The A-10 is exceptionally tough, being able to survive direct hits from armor-piercing and high-explosive projectiles up to 23 mm. It has double-redundant hydraulic flight systems, and a mechanical system as a back up if hydraulics are 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 under favorable conditions to return to base, though control forces are greater than normal. The aircraft is designed to fly with one engine, one half of tail, one elevator, and half of a wing missing.

The cockpit and parts of the flight-control system are protected by 1,200 lb (540 kg) of titanium aircraft armor, referred to as a "bathtub". The armor 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 0.5 to 1.5 inches (13 to 38 mm) determined by a study of likely trajectories and deflection angles. The armor makes up almost 6 percent of the aircraft's empty weight. Any interior surface of the tub directly exposed to the pilot is covered by a multi-layer nylon spall shield to protect against shell fragmentation. The front windscreen and canopy are resistant to small arms fire.

This A-10 suffered extensive damage during Operation Iraqi Freedom in 2003

The A-10's durability was shown on 7 April 2003 when Captain Kim Campbell, while flying over Baghdad during the 2003 invasion of Iraq, suffered extensive flak damage. Iraqi fire damaged an engine and crippled the hydraulic system, requiring the aircraft's stabilizer and flight controls to be operated via the 'manual reversion mode'. Despite this damage, Campbell flew the aircraft for nearly an hour and landed safely.

The A-10 was envisioned 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 wings are also mounted closer to the ground, simplifying servicing and rearming operations. The heavy engines require strong supports, four bolts connect the engine pylons to the airframe. The engines' high 6:1 bypass ratio have 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 and their exhausts are angled upward by nine degrees to cancel out the nose-down pitching moment they would otherwise generate due to being mounted above the aircraft's center of gravity, avoiding the need to trim the control surfaces against the force.

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; projectiles would need to penetrate the aircraft's skin before reaching a tank's outer skin. Compromised fuel transfer lines self-seal; 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 refueling 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.

Weapons

A side-view drawing of the A-10's GAU-8/A Avenger gun and its approximate location in the fuselage

Although the A-10 can carry considerable disposable stores, its primary built-in weapon is the 30 mm GAU-8/A Avenger Gatling-type cannon. One of the most powerful aircraft cannon ever flown, it fires large depleted uranium armor-piercing shells. In the original design, the pilot could switch between two rates of fire: 2,100 or 4,200 rounds per minute; 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, 65 or 70 rounds per second thereafter. The gun is accurate enough to place 80 percent of its shots within a 40-foot (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 4,000 feet (1,220 m) with the A-10 in a 30-degree dive.

Another view of the A-10's GAU-8 installation

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 5-foot, 11.5-inch (1.816 m) ammunition drum can hold up to 1,350 rounds of 30 mm ammunition, but generally holds 1,174 rounds. To prevent enemy fire from causing the GAU-8/A rounds to fire prematurely, armor plates of differing thicknesses between the aircraft skin and the drum are designed to detonate incoming shells. A final armor layer around the drum 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.

The AGM-65 Maverick air-to-surface missile is a commonly used munition, 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. During Desert Storm, in the absence of dedicated forward-looking infrared (FLIR) cameras for night vision, the Maverick's infrared camera was used for night missions as a "poor man's FLIR". Other weapons include cluster bombs and Hydra rocket pods. The A-10 is equipped to carry laser-guided bombs. 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 wing for self-defense.

Modernization

A-10 Thunderbolt II, fully armed

The A-10 Precision Engagement Modification Program will update 356 A-10/OA-10s to the A-10C variant with a new flight computer, new glass cockpit displays and controls, two new 5.5-inch (140 mm) color displays with moving map function and an integrated digital stores management system.

Other funded improvements to the A-10 fleet include a new data link, the ability to employ smart weapons such as the Joint Direct Attack Munition (JDAM) and Wind Corrected Munitions Dispenser, and the ability to carry an integrated targeting pod such as the Northrop Grumman LITENING or the Lockheed Martin Sniper Advanced Targeting Pod (ATP). Also included is the Remotely Operated Video Enhanced Receiver (ROVER) to provide sensor data to personnel on the ground.

In 2016 the USAF announced a thick-skin urgent spares kitting (TUSK) wing assemblies program to extend the lifespan of the aircraft past 2040.

Colors and markings

An A-10 from the 343rd Tactical Fighter Wing prepares to drop Mark 82 bombs at the Yukon Command Training Site in 1988.

Since the A-10 flies low to the ground and at subsonic speed, aircraft camouflage is important to make the aircraft more difficult to see. Many different types of paint schemes have been tried. These have included a "peanut scheme" of sand, yellow and field drab; black and white colors for winter operations and a tan, green and brown mixed pattern. Many A-10s also featured a false canopy painted in dark gray on the underside of the aircraft, just behind the gun. This form of automimicry is an attempt to confuse the enemy as to aircraft attitude and maneuver direction. Many A-10s feature nose art, such as shark mouth or warthog head features.

The two most common markings applied to the A-10 have been the European I woodland camouflage scheme and a two-tone gray scheme. The European woodland scheme was designed to minimize visibility from above, as the threat from hostile fighter aircraft was felt to outweigh that from ground-fire. It uses dark green, medium green and dark gray in order to blend in with the typical European forest terrain and was used from the 1980s to the early 1990s. Following the end of the Cold War, and based on experience during the 1991 Gulf War, the air-to-air threat was no longer seen to be as important as that from ground fire, and a new color scheme known as "Compass Ghost" was chosen to minimize visibility from below. This two-tone gray scheme has darker gray color on top, with the lighter gray on the underside of the aircraft, and started to be applied from the early 1990s.

Notes

F-105 limitations: the F-105, was big and fast, but “the ability to fly closely and slowly enough to see the target, to work safely in poor weather, to carry sufficient ordnance, and to remain over the battle area were all limited.” The Air Force F-4C would not arrive in Vietnam until December 1964 and, although it carried a heavier bomb load than the F-105, it still did not have the low speed, low altitude and loiter capability needed in a CAS aircraft. The Air Force initially had to rely on ex-trainers and WWII-vintage attack planes such as the T-28D and the B-26. These were short-lived solutions, however, as the slow speed and lack of armor on the T-28D made it vulnerable to ground fire, and the aging B-26’s were eventually grounded due to structural problems. A better interim solution became available with the use of the semi-obsolete Navy A-1 Skyraider10 (see Figure 6). The A-1 had good lowspeed maneuverability, it could carry upwards of 8,000 lbs of bombs, and it was able to loiter around the battlefield and respond quickly to calls for support fires. “Even many of those who favored the supersonic jets conceded that the propeller-driven A-1 was the CAS star.”11 Limitations of the A-1 were the limited number of them available from the Navy (production had ended in 1957) and its inability to destroy more heavily armored targets. Losses of the A-1 continued to escalate in the mid 1960s; particularly due to the radar guided Anti-Aircraft Artillery (AAA) guns being employed by North Vietnam. The A-37A (Figure 6), an adaptation of the T-37v subsonic trainer, was developed as a counterinsurgency aircraft and deployed to Vietnam in 1967, but the A-37A had neither the payload capacity nor the loiter time of the A-1E

timeline

June 7 '61 - SoD McNamara orders 2 tactical jets, one CAS Jan 7 '65 - SoD orders requirements for CAS jet compiled Dec '65 - SoD approves order of A-7D for interim CAS - A-7 generally successful in cas wrt vietnam flap 22 dec '66 - RAD A-X Requirements Action Directive specialized CAS airplane. 19 Apr '67 - af completes A-X proposal 1 Mar '68 - af completes initial Concept Formulation Package for A-X 11 Dec '68 - DCP 23 Development Concept Paper for A-x complete 6 june '69 - TDP technical development plan complete Sep '69 - AF recommends 30mm gatling cannon as integral weapon 6 apr '70 - DCP 23a with parallel undocumented development competitive prototype accepted 27 apr '70 - A-X System Program Office SPO created 8 may '70 - RFP issued 16 nov '70 - GAU-8 RFP issued 18 dec '70 - YA-9A YA-10A chosen as winning proposals, prototypes ordered June '71 - Philco Ford, GE chosen for GAU prototypes/competitive development 17 June '73 - A-10 chosen 21 jun '73 - GE chosen for GAU-8 Jul '73 congress orders flyoff, reduces funding 10 feb '76 full rate production contract awarded

VDL (TGP VIDEO TO JTAC) ∎ LARS (UHF, ENCRYPTED DATABURST, DME INTERROGATIONS) ▪ The only system integrated CSEL HHR Tactical Awareness Display (TAD), Rover (VDL) ScorpionTM HMCS (Helmet Mounted Cueing System) ∎ AFCENT Urgent Operational Need • Issued 28 Sep 2008 (Signed by General North)

The A-10 was judged to have better ground handling capability – a result of the low wing design and more ordnance space on the larger wing. The Air Force also believed the A-10 to be closer to production, thus allowing for faster progress in the test program. 67 Other comments made at the DSARC review included Secretary Seamans statement to the effect that the simpler design of the A-10 was more likely to allow achievement of the $1.4M unit flyaway cost, and DDR&E Foster commented that the pilots who had flown both prototypes preferred the A-10 for combat operations.

Benefits of turbofan

The A-X Request for Proposal (RFP), including all attachments and “boiler plate”, was 104 pages, and it limited each contractor’s response to 585 pages. This represented a sizable reduction in the RFP for its time, and Deputy Secretary of Defense Packard considered it a “major breakthrough” made possible through the use of competitive prototyping, and indicated it was the direction he wanted the Defense Department to go.55 Two crucial goals in the RFP were achievement of weapon system effectiveness, and low costs. The RFP established a design-tocost goal of $1.4M unit flyaway cost (FY70$) for a 600 aircraft buy.

Simplicity of design. No propeller and no reduction gear, or, at least, a much smaller or simpler system; • Ease of maintenance, vital in the battlefield and for optimum sortie rates; Ease of installation, being modular in design, and ease of access; • The high-bypass turbo was relatively quiet compared with the propeller or conventional jet engine; • Affordability: cheap to purchase, cheap to run, cheap to replace; • Reduced IR signature; • High thrust at low speed, enhancing maneuverability.

Dr. Foster stated that “the proposed aircraft seems to be too large, and has too much range/payload at this early stage. It is so similar to A-7 that it is hard to justify when we already have A-7. A smaller, less costly, quick reaction aircraft seems more appropriate.”47 After reviewing the DCP, the Deputy Secretary of Defense approved $12M in the FY70 budget for Contract Definition, contingent on the Air Force’s completion of supplemental studies addressing the size and weight of the A-X, survivability of the A-X in the anticipated threat environment, and methods to improve the aircraft night and adverse weather capability.48

Historical analysis of ground fire attrition in World War II, Korea and Vietnam was used to determine which aircraft equipment was most vulnerable and/or likely to lead to loss of an aircraft due to ground fire. The known causes included engine, controls, structure, pilot and fire. The CFP identified design emphasis that could reduce the loss rates. These design features were:41 1. Fuel can be protected from fire and kept from ignition sources. 2. Manual controls can be made practically invulnerable. 3. Crew compartments can be sufficiently shielded and armored to make pilot losses insignificant. 4. Engines can be shielded, fire protected, and made almost fully redundant. Their oil supplies can be protected. Maneuverability was also identified as a component of survivability, and the effects of speed and maneuverability were analyzed against probability of aircraft loss for a range of delivery profiles and threat systems. The performance requirements most important for short range attack were low cruise speed with combat loads, and both high instantaneous and sustained g-limits for initiation and execution of short radius turns without losing altitude. Superior low speed maneuvering and dive capabilities were shown to enhance close-in fast re-attack tactics, allowing operation in visibility half or less than that required for high speed jet aircraft. The importance of this on the A-X availability due to weather conditions can be seen in Table 6. High speed jet aircraft required minimums of 2000 ft cloud ceiling and 3 mile visibility for safe operations, while the A-X was expected to operate with minimums of 1000 ft/1 mile.

Maintenance man-hours per flying hours (MMH/FH) emerged as a key metric and direct indicator of aircraft complexity and was plotted against peak and sustained sortie rates for a range of aircraft operating in SouthEast Asia (see Figure 11). Of note, there was an observed ratio of more than 3:1 in MMH/FH between the most complex and the simplest strike aircraft, with the F-4 and F-105 aircraft having actual MMH/FH values of 33.2 and 27.6, respectively, and A-1 and A-37 having values of 14.3 and 7.8, respectively.38 Sustained sortie rate was determined to be relatively insensitive to aircraft complexity, most likely due to lower than maximum sortie rates. Together with the higher allowable peak sortie rates, the most valuable aspect of simplicity was shown to be the ability to operate from austere forward bases, with the attendant improvement in response time.

"On 8 September 1966, General McConnell directed that the Air Force take immediate action to design, develop, and obtain a specialized close air support aircraft, and on 22 December 1966, Headquarters USAF issued a Requirements Action Directive (RAD) for a specialized aircraft designated the A-X - ioc was declared to be delivery of the first 18 into operational inventory.

"The avionics for the A-X were specified in terms of a “skeleton” package (below minimum requirements), a “lean” package (met only minimum requirements) and three add-on packages that would supplement the “lean” package.29 Table 5, reproduced from an AFSC Historical Publication, lists the A-X avionics equipment packages as well as their projected weights and costs. The “skeleton” avionics package included only communication and Visual Flight Rules (VFR) navigation aids. The “lean” package added Doppler Navigation for night and adverse weather, and a radar ranger and gun camera for improved weapons accuracy and post-attack effectiveness evaluation. The “lean” package met requirements for three of the four indicated missions, but was considered inadequate for armed reconnaissance in the immediate battlefield area. The first add-on option improved capabilities for finding targets and terrain avoidance – considered important when hunting for targets. The second add-on improved capabilities for locating vehicles by adding moving target indication (MTI) to the radar and inertial supplements to the Doppler navigation system to improve the over-all accuracy. The third add-on package provided increased strike capability with the addition of the Maverick missile.xiii According to the A-X Proposal, “the prime mission of the A-X and the Maverick are the same – air-to-surface close support, the Maverick should be one of the prime weapons of the A-X.”30 Incorporation of the Maverick missile required a cockpit television display for aligning the missile’s seeker on the target.

Addendum

Hog-Up, a service life extension program first starts in 1999.

'99 - Wing Outer Panel (WOP) Mid-Spar web re-work. Wing Center Panel (WCP) rework N/A for USAFE, Center fuselage fuel cell floor & boost pump flange repair, Wing station (WS) 90 repair, Center fuselage inspection, Fuselage station 365 bulkhead repair, ACI inspection

'03 - Forward/Aft fuel tank cavity Corrosion control/inspections, Leading edges inspections, Paint, Flight control re-work, Additional ACI inspections

$140 million '99 to $600 million in '03

PCAS

The LASTE system was upgraded with Integrated Flight & Fire Control Computers (IFFCC).Jensen, David. "All New Warthog." Avionics Magazine, 1 December 2005.</ref>

A-X SPO was redesignated the A-10 SPO, and two months after that it was re-designated the

Deputate for A-10 No major compatibility problems were noted, but a secondary gun gas ignition problem was noted. This caused a flame area in front of the aircraft, obstructing

pilot vision and causing fluctuations in the engine pressure. Initial attempts to correct the problem

by lengthening the gun barrels and using plastic bonded ammunition (as opposed to copper) failed to correct the problem (although the plastic bands were expected to extend the barrel life by cutting friction and corrosive blowby).80 A double-baffled deflector was added but still failed

to eliminate the engine perturbations. The final fix for the problem involved adding a potassium nitrate suppressant to the ammunition propellant. Follow-on tests with the new ammunition propellant mixture confirmed success in resolving the problem. Of note, the solution to the gun gas ignition problem created a second problem; excessive residue from the gun firing covered

the canopy and impaired vision.81 The solution to this turned out to be far easier; a windshield washer was installed on the front of the canopy and was found to be operationally acceptable. Procedures for washing the engine with water were also developed as the residue (potassium bicarbonate) was found to be water soluble. A second integration problem identified had to do with the gun pointing angle. Test pilots had reported that the gun angle was not right for low dive angle and low slant range strafing. Strafing at larger angles and slant ranges was satisfactory, but pilots were unable

to concentrate bursts under low dive angle/low slant range employment. Flight tests conducted in June 1974 demonstrated that a 2 degree change in gun alignment would correct the problem. The gun alignment problem, with the proposed fix, was briefed at the DSARC IIIAxxviii review in July 1974. The fix for the alignment problem was implemented, and subsequent flight test indicated optimum gun alignment for the A-10 attack profile. ammunition costs accounted for 90% of lifetime costs of gun Aggressive risk and cost reduction measures such as these (and others) reportedly allowed the program office to reduce the GAU-8/A round cost to $15 each, representing an 80% reduction from the original cost estimate! They set up a screened off “Tiger Works” to create a facsimile of Lockheed’s “Skunk Works”. fairchild/republic hadn't had a full scale production like for 9 years since the conclusion of

the f-105 line. Faced with initiating production, the AF was worried that F/R lacked the

capability to perform the production phase. establishing executive vice president control of all technical and production aspects of the A-10, and placing the Hagerstown plant under the authority of Farmingdale. Fairchild also undertook major capital investment, “replacing its overaged machinery and increasing its make/buy ratio for major machined parts for the A-10 from 23:77 to about 55:34. On 31 July 1974, Deputy Secretary of Defense Clemens authorized the Air Force to proceed with initial production using $39M for long lead funding. The Air Force was given approval to procure 52 aircraft providing that “contract options to procure a smaller quantity (that is, 28 aircraft) be kept open”97 pending completion of remaining tests and the Critical Design Review (CDR) for the armor piercing round. The DSARC met again in November 1974 to review closure of these issues. By then the GAU-8/A deficiencies with regards to the gun depression angle and secondary gun gas ignition had been resolved, and engine qualification tests for the TF-34 were completed on 31 October 1974. The CDR for the armor piercing round had not been completed, but was scheduled to be completed by Aerojet in December 1974.xxxi Based on this review, the Air Force was authorized to proceed with FY75 and FY76 production of 52 aircraft. The FY75 purchase of 30 mm ammunition was authorized pending successful completion of the CDR for the armor piercing round. A two month delay in the first flight of the DT&E aircraft caused a subsequent delay in the DSARC IIIB review from October 1975 to February 1976. Required tests prior to the fullrate

production decision included:98 • Freedom from flutter • Initial performance measurements • Flying qualities • GAU-8/A-10 accuracy • Ammunition performance (vs. tanks, trucks and APC’sxxxii) • Bombing accuracy • Laser spot seeker (PAVE PENNYxxxiii) integration • Aerial refueling • IOT&E. By the end of 1975, the one remaining issue was fatigue testing. The aircraft undergoing

fatigue testing developed cracks on the fuselage frame at about 80 per cent of the desired 6,000 hour mark. A reinforcement corrected the problem, and the 6,000 hour objective was achieved on 28 October 1975. The reinforcement was to be retrofitted to several existing and pre-production aircraft, and the amended production process was to be in place by mid-1976 to support aircraft

1. 14 and beyond.99 With this issue resolved, Deputy Secretary of Defense Clements authorized

full-rate production at a maximum rate of 15 aircraft per month. This was a reduction from the Air Force’s proposed rate of 20 per month based on the assessments of the contractor’s ability

to finance and produce efficiently.100 On 30 March 1976 the Commander of the Tactical Air Command accepted the first production A-10 from the Commander of Air Force Systems Command. Full rate production approval for the GAU-8/A gun system and ammunition was given in March 1976. As the threat focus changed to the European Battlefield some of the earlier considerations were being looked at again. The lack of “relaxed stability” in prolonged manual flying was putting a strain on pilots. An inertial navigation system, weapons delivery computer, built-in drag chute, upgraded avionics and Heads-Up Display (HUD) were added. A two seat variant, the YA-10B, was developed by Fairchild for Night/Adverse Weather (N/AW) and use as a trainer. Proposed changes for the N/AW variant, in addition to the two-place cockpit, included ground mapping radar, a Forward Looking Infrared (FLIR) pod, and larger vertical stabilizers. The only YA-10B actually built was a modified pre-production A-10A (see Figure 20). While the Air Force flight tested the YA-10B in 1979, they chose not to pursue further development of the two seat variant. In the 1980s the OA-10 Observation and Reconnaissance conversion was introduced. The alterations necessary were relatively minor and inexpensive to implement. These were mostly internal although there was modification in the pylon loading to allow phosphorus marker rockets to replace the Mavericks and bombs. the '82 army airland battle doctrine moved away from the traditional battle line and emphasized

maneuvering and swift attacks on enemy reserve troops placing a greater emphasis on the

battlefield air interdiction role of planes such as the A-10. The army's introduction of the

Ah-64 apache introduced a form of direct competition to the A-10 at the same time.

The 1985 report stated that it expected the A-10 would lose its effectiveness in mid to high intensity

conflicts by the mid 1990s. Specific concerns were survivability against new Surface-to-Air Missiles, the ability to perform air interdiction, and the ability to operate in night and adverse

weather.xxxiv A modification of an existing aircraft that could be fielded in the mid 1990s was considered necessary to avoid competition with the top new fighter development priority; the Advanced Tactical Fighter (precursor program for the F-22). By 1985 the Air Force completed the first of several studies which suggested that a modified variant of the F-16, labeled the A-16, would be a good choice for a CAS aircraft to support the AirLand Battle. Other authors have written that the idea for the A-16 actually originated about the time that the Army unveiled the AirLand Battle doctrine. OSD was critical of the Air Force proposal for not giving full consideration to other candidate aircraft, and disapproved the Air Force recommendation.xxxv An Air Force Scientific Advisory Board (SAB) report also raised concerns, concluding that CAS and BAI missions are sufficiently different for each to warrant a separate aircraft. The SAB recommended pursuing a new specialized CAS aircraft for the future, while modifying the A-10 with advanced avionics and more powerful engines for the short term. OSD directed the Air Force to perform a Close Air Support Aircraft Design Alternative (CASDA) study, and created the Close Air Support Mission Area Review Group (CASMARG) to ensure the Air Force considered other alternatives besides the A-16. In December 1987, the Air Force issued a request for concept proposals and received proposals from 9 manufacturers, including Fairchild Republic. Fairchild was not awarded a study contract due, in part, to their recent problems executing the T-46 program. OSD remained skeptical of the program, and Congress raised questions as well, requesting a GAO study on the status of the Air Force’s efforts to replace the A-10.103 The GAO report noted that the intended start of the A-10 replacement, 1993, occurred earlier than the service or structural life required. The Air Force had already started converting A-10s to OA-10 Forward In addition to flying CAS missions, it conducted BAI missions in Kuwait and Southern Iraq, combat air patrols looking for SCUD mobile missile launchers, armed reconnaissance, and armed escort for search and rescue missions. Despite a lack of avionics for night missions, A-10 pilots adapted by using the

display from their infrared Maverick missiles. The GAO reported that the A-10 had the highest sortie rate, with an average of 1.4 sorties per aircraft per day, and delivered more guided munitions (almost 5,000 Maverick missiles) than any other aircraft type.105 The GAO report also indicated that the number of A-10 sorties was likely undercounted, indicating an even higher achieved sortie rate was likely. While the gun was considered effective, the number of gun “kills” was unclear due to conservative rules for performing Bomb Damage Assessment during and after the war. An Iraqi regimental commander described the A-10 as “the single most recognizable and feared aircraft”, noting its ability to conduct multiple raids per day, loiter around the

battlefield, and attack with deadly accuracy.106 The A-10 survivability was also generally confirmed: “… the Hog’s redundant flight control system allowed crippled planes to fly home. Aircraft Battle Damage Repair (ABDR) crews repaired in-theater all but one of the estimated seventy damaged A-10s during this war – and of those, twenty suffered significant damage. These repairs were usually quick, and used cheap, accessible materials.” Post Desert Storm, the CAS roles and missions debate lived on. Air Force Chief of Staff General Merrill McPeak favored giving the CAS mission (and the A-10) to the Army, but he wanted the Army to give up the deep strike missions with the Army Tactical Missile System (ATACMS). He was outvoted by the other service chiefs and his sweeping recommendations for roles and missions realignment would not be implemented Part of what made General McPeak’s

recommendations more difficult to accept by the other services were the wide ranging impacts they would have had. Beyond the changes in CAS and deep strike roles, he

wanted the Army and the Navy out of the space and long range air defense business, and he recommended that the

Marine turn their fixed wing F/A-18’s over to the Navy. The Air Force made a decision to keep the A-10 in the active duty force, albeit in smaller numbers due to an overall

reduction in combat wings in the Air Force. Beginning in 1991, 183 A-10s produced from production orders prior to FY78 were placed in long term storage at Davis Monthan AFB, and several others were retired to museums or converted to battle damage repair or maintenance trainers. six A-10s lost DS “Wheels up, hard stick landing. Everyone said it couldn't be done, including the Flight

Manual's and Tech Orders... pilot Capt Rich Biley proved'm wrong on 22 Feb 1991! … Capt Biley was unhurt during the crash.” The A-10 was originally designed for 6,000 hours of use comprising a specified mix of operational weights, sortie types and maneuver loads. The original design spectrum was used for the initial full-scale fatigue testing performed from 1975-1977.111 The original test to two lifetimes (12,000 hours) was completed successfully with repairs in 1976. Noting that other current aircraft were being designed for 8,000 hours service life, the fatigue test was

continued with the intent of reaching two times the longer service life. In 1977, after 13,768 Effective Flight Hours (EFH), cracks were observed at Wing Station (WS) 23 where the wing is joined to the fuselage. The wing was repaired using extensive cold working of the lower wing center panel to improve the fatigue life. The test was to resume, but a new design load spectrum, referred to as Spectrum 3, was adopted based on a 3,000 hour Loads/Environment Spectra Survey (L/ESS). Spectrum 3, based on evidence of more severe fleet usage than originally predicted, was more severe than the original design spectrum. Wing testing resumed in 1979 under Spectrum 3, but was halted at 58% of Spectrum 3 service life due to several failures (and subsequent repairs) at both the left and right wing outer panels and finally the centerline WS

0. There were several design changes that resulted from the full-scale fatigue testing using Spectrum 3. The thickness of the lower skin on the wing outer panels was increased, and cold working was performed at the location of the fatigue test crack initiation. The effectivity of

this change was for production aircraft #442 and subsequent, but a tech order (TCTO-0952) was generated to inspect or reskin the lower wing outer panels of all previous production aircraft (production #’s 7-441). TCTO-0952 was rescinded in 1986 with approximately 200 aircraft not having received the modification. The wing center panel also underwent a redesign in order to withstand 8,000 hours of Spectrum 3 usage. The redesign consisted of increasing the lower skin panel thickness and modifying the lower spar caps to accommodate the thicker wing skins. The effectivity of the wing center panel redesign was production aircraft # 582 and subsequent. Due to the extent of the wing center panel modification, no retrofit to earlier aircraft was economically feasible. Cold working of the wing center panel at WS0 was also performed starting with production aircraft #530, and performed as a retrofit to earlier aircraft. These modifications resulted in several structural configurations as shown in Table 11. A wing-only fatigue test was conducted on a configuration consisting of a cold worked wing center panel, a production left outer panel, and a retrofit right outer panel. This wing

was successfully tested to 12,000 EFH of Spectrum 3 with repairs between 1980 and 1988. Having demonstrated two times the service life, the retrofit configuration wings were qualified for

6,000 hours of Spectrum 3 usage. The thick skin production wings were qualified for 8,000 hours. Fatigue testing of the forward fuselage and empennage was also conducted between 1980 and 1986, demonstrating 17,500 EFH of Spectrum 3 usage on the forward fuselage, and over 19,000 EFH of Spectrum 3 usage, with repairs, on the empennage. The DTA analyzed 52 control points in the wing, and comparison between the 1980 and 1993 DTAs indicated that service lives were reduced on 8 of these control points after the later assessment. The 1993 DTA and its associated Force

Structural Maintenance Plan (FSMP) took into account the three different structural configurations for the A-10 (see Table 11). Of greatest concern for the wing was the fuselage attachment joint at WS 23 for the retrofit configurations (especially those that had not received the thick wing outer panel retrofit prior to TCTO-0952 being rescinded). Generally following the guidelines in MIL-STD-1530A, the 1993 maintenance plan established inspection intervals based on service life and safety limits, and was intended to be accomplished as programmed inspections on all aircraft. The FSMP inspection requirements were not incorporated into the inspection and maintenance tech order (T.O. 1A-10A-6) and, therefore, not accomplished as intended.112xxxviii The A-10 program office, by then part of the Air Logistics Center at McClellan AFB, CA, chose to perform the inspections using sampling as opposed to monitoring all aircraft. The Analytical Condition Inspection (ACI) program contained some of the FSMP inspection locations, including the critical WS 23 location, but the inspections were conducted on relatively few aircraft as compared to the fleet wide inspections called out in the FSMP. There were several factors contributing to the breakdown in the FSMP implementation.113 The A-10 did not utilize Programmed Depot Maintenance, so inspections would have to have been conducted in the field, and severe budget constraints were also cited. Sometime in the mid 1990s the flight data recorder system, used to sample the fleet wide usage, became unsupportable and no longer yielded accurate data. In 1997, the SPO competed the prime contract and subsequently awarded Lockheed Martin Systems Integration (LMSI), formerly IBM Federal Systems Division in Owego, NY, an Indefinite Delivery/Indefinite Quantity (ID/IQ) contract to take over as the new prime for A-

10. It should be noted that LMSI was not an aircraft company and did not have the aircraft infrastructure available at Lockheed Martin’s Fort Worth, TX or Marietta, GA locations. At the time, the SPO expected that Northrop Grumman would be part of the prime team since Lockheed Martin and Northrop Grumman had proposed a merger in July of 1997. In March of 1998 the US Department of Justice moved to block the merger in federal district court, and the merger was subsequently called off in July of 1998. As a result, Northrop-Grumman was diminished to a supporting role, and became further marginalized by Lockheed Martin’s use of Southwest Research Institute to provide structural analysis as part of the prime contract team. For the

next six years, “the prime team consisted of organizations that had no direct experience or infrastructure developing, building, and supporting an entire aircraft.”115 In late 2004, the

Air Force “requested” that LMSI include Northrop Grumman as a member of the prime team, but Northrop’s participation would be limited to specific structures work for several more years. An Air Force Materiel Command Red Team in 2003 (see associated endnote) indicated “a systemic

neglect of the A-10 weapon system after the initial retirement started in 1988”. The Analytical Condition Inspections conducted in 1995-96 discovered cracks in several wing locations due to fatigue. Most of the cracks were consistent with the DTA crack growth curves updated in 1993, but two cracks at WS 23 were clearly under predicted by the low Initial Flaw Size (IFS) curve, and one of the cracks was of “near-critical” size (see Figure 24). For reasons not determined by the Red Team Investigation in 2003, the SPO classified the cracks as minor and did not reconsider their implementation of the FSMP.117 Suspected reasons for the classification decision include avoidance of the disruption and burden associated with field inspections by operational units. In 1998 Northrop Grumman was tasked to provide a cost effective structural enhancement program focusing on the most critical areas.119 In August 1998, they delivered a report entitled “A-10A Aircraft Wing Center Panel Rework-Fatigue Life Improvement”. The plan detailed structural changes required to support a 16,000 hour service life. The report recommended immediate implementation, and verification using a full-scale fatigue test on a modified wing. This report formed the basis of the subsequent HOG UP program to extend the structural life to the year 2028, but the report was based on the assumption that the 1993 FSMP had been implemented. Further, the report did not consider the impact of ACI crack data or new fatigue sensitive locations that had been identified by field inspections. The SPO initiated

the HOG UP program in 1999 as a repair program instead of a modification despite the fact that the majority of the parts for the repair were to be kitted, and the same configuration was to be applied to all thin-skinned wings.120 Managing HOG UP as a repair did not require acquisition approval, and maintenance funding could be used. Since it was a “repair”, the SPO held that Configuration Control Board (CCB) action was not required, and “appropriate configuration control concerns, such as technical analysis of service life, technical contents of the

program, and method to evaluate an organic or contractor prepared engineering change proposal did not occur.” The HOG UP program expanded from its initial beginnings. At the request of Air Combat Command, center wing fuel bladder replacement, rework of the flight control system, nacelle fitting inspections, and other areas were added to HOG UP. Figure 25 shows a comparison of the 1999 and 2003 program. All modifications were considered worthwhile, but the Red Team investigating the program in 2003 noted no composite estimate of the risk of structural failure had been generated and expressed concern that the repair might not result in

the intended life extension.122 A further complicating factor had to do with the problematic cracks

at WS 23. In 2001 the WS 23 crack was reclassified as critical, and a new tech order (TCTO 1438) was issued for inspection of the wing center panel and WS 23 fastener holes. Estimates in 2003 were that 35 aircraft would require refurbished wings associated with the WS 23 repair. Although not originally part of HOG UP, the WS 23 inspection and repair was subsequently scheduled to be conducted concurrently with the expanded HOG UP repairs.xxxix This touched off a series of problems due, in part, to longer than expected time to produce HOG UP wings, and higher number of unusable wings found as a result of the WS 23 inspection (they found 27 bad wings they had not expected). By the time the Red Team investigated the HOG UP program, it had grown from approximately $140M to over $600M, not including unprogrammed costs associated with the WS 23 wing refurbishment and associated remove and replace process. Further, the full-scale fatigue testxl to validate the HOG UP repair had not yet been done,

leaving the Red Team to conclude that the actual structural condition of the fleet remained unknown,

and the repair was “un-validated for extending the lives of A-10 wings to 2028 (~16,000 Hours).”123 Several alternative approaches were offered by the Red Team, including the replacement of

hightime production center wings with previously considered inviolate wings or newly manufactured thick wing versions of the center wing.

The fatigue-test was to be conducted over a three year time period, simulating 10 years of

operational use. xli Wings classified as inviolate were “thin” wings with generally low service life in storage at

Davis Monthan AFB. Subsequent to the Red Team report in February 2003, the wing undergoing full-scale fatigue testing failed short of the 16,000 hour life expectancy.125 In addition, thin-skin

wings coming into the depot were failing inspection at an increasingly higher rate, and it became

clear that the Air Force would run out of serviceable wings by about 2011.126 By 2005 the failure

rate of the thin center panel wings coming in for service life extension was averaging close to 30%. In 2005 the AF completed a business case analysis which considered three options for structural life extension.127 Option 1 consisted of organic sustainment of the thin skin wings. It

entailed salvaging and rebuilding WS 23 failures to eliminate shortfalls, and increasing the SLEP1 to extend the service life. The estimated Life Cycle Cost (LCC) for Option 1 was $4.6B. Option 2 entailed purchasing 135 wings to replace the WS 23 failures, and increasing SLEP1 for the remaining wings. The LCC for Option 2 was $3.16B. Option 3 was to buy 242 wings to replace WS 23 failures and avoid the high cost of adding to the SLEP1. The estimated LCC of Option 3 was $1.72B. A decision was made to pursue Option 3 based on clear cost avoidance associated with that option. In early 2006, the Air Force prepared a budget justification for production

of newly manufactured “thick skin” wings to re-wing the remaining “thin skin” A-10s in the inventory.128 The budget estimate was $741M for replacing up to 121 wings, with the intention that 242 wings would be replaced between 2012 and 2018. Also in the budget justification was approximately $5M to build a computer model capturing the most current configuration of the A-10 wing assembly to support future sustainment operations. This became necessary, in part, to duplicate the as-built configuration as opposed to the as-designed. This also allowed the SPO

to compete the contract for new wings, an important consideration due to the absence of an

Original Equipment Manufacturer (OEM). In the end, Aerospace Engineering Spectrum LLC would be awarded the contract to build a computer model for a wing that would be manufactured by Boeing (the winner of the new wing contract in 2007). The wing would be installed on an aircraft built by Fairchild Republic, for which Lockheed Martin was now the prime.xlii This was the new reality of sustainment for the A-10. 3.7.4 A Second Life for a Modern Day Hog Prior to, and coincident with the HOG UP program, several other upgrade programs were addressing other aspects of the A-10 weapon system. In the early 1990s, the aircraft was modified to incorporate the Low Altitude Safety and Targeting Enhancements (LASTE) system. This system added ground collision avoidance warnings, an Enhanced Attitude Control (EAC) function for aircraft stabilization during gunfire, a low altitude autopilot system, and

computed weapon delivery solutions for targeting improvements. The LASTE system also added an Operational Flight Program (OFP) to provide the computer control software necessary to perform the above functions. Starting in 1999, the A-10 was upgraded with the installation of

an Embedded Global Positioning System/Inertial Navigation System (EGI). The EGI system provides improved navigation and situational awareness. Perhaps the most significant upgrade was the Precision Engagement (PE) program awarded to Lockheed Martin in 2005. This program, which results in the modified aircraft being redesignated as A-10Cs (see Figure 26), includes enhanced precision target engagement capabilities. The A-10Cs are able to carry the INS/GPS guided Joint Direct Attack Munitions (JDAM) and the Wind Corrected Munitions Dispenser (WCMD). Other modifications in the PE upgrade include hands-on throttle and stick control, new multi-function cockpit displays, situational awareness data links, digital stores management, integrated flight and fire control computer, LITENING II and Sniper laser targeting pod carriage, and a new armament HUD control panel. Flight testing of an A-10C prototype began in 2005, and as of January 2008 the 100th A-10C conversion had been delivered.129 The PE upgrade is intended to evolve the A-10 from its origins as a cold-war tank killer, to an aircraft capable of performing a wide range of operations to support the Global

War on Terror and other contingencies. As of the date for this case study (2008), programs for replacement of the TF-34 engine with a higher thrust model have been formulated but not yet funded. With the combination of the PE upgrade and the re-winging of the thin skin production aircraft, the Air Force has committed itself to sustaining the A-10 for the foreseeable future. The LASTE system also added an Operational Flight Program (OFP) to provide the computer control software necessary to perform the above functions. At the request of the government, Northrop Grumman became part of the prime team with Lockheed

Martin in 2005. Close attention to key mission characteristics (lethality, survivability, responsiveness, and simplicity) allowed the concept formulation and subsequent system design to result in an effective CAS aircraft, and design-to-cost goals kept the government and contractor focused on meeting the critical requirements at an affordable cost. The A-10 did not meet all its cost goals, but it came much closer to them than most major defense development programs did in that time frame or since then. There were many aspects of the A-10 program that were unique for its day. It was a design-to-cost program when most other aircraft programs were clearly putting performance first. It was the first major defense program to embrace the newly favorable competitive prototyping approach to allow a source selection decision to be made on the basis of demonstrated performance and maturity of the design.

An A-10A of pre-glass cockpit design

In 2005, the entire A-10 fleet began receiving the Precision Engagement upgrades that include an improved fire control system (FCS), electronic countermeasures (ECM), and smart bomb targeting. Aircraft which received this upgrade are redesignated A-10C; work was to be completed in 2011. The Government Accounting Office in 2007 estimated the cost of upgrading, refurbishing, and service life extension plans for the A-10 force to total $2.25 billion through 2013. The Air Force Material Command's Ogden Air Logistics Center at Hill AFB, Utah completed work on its 100th A-10 precision engagement upgrade in January 2008.

In 2007, the A-10 was subject to a service life extension program (SLEP); Boeing was awarded a contract to build as many as 242 A-10 wing sets in June 2007. In November 2011, two A-10s flew with the new wings fitted. In September 2013, the USAF awarded Boeing a $212 million follow-on contract for 56 new wings, increasing the total ordered to 173. Re-winging improves mission readiness, decreases maintenance costs, and allows the A-10 to be operated up to 2035. In plans to retire the A-10, the USAF considered halting the wing replacement program, saving an additional $500 million on top of the total savings of retiring the fleet, coming to $4.2 billion. By May 2015, the re-winging program was too far into the contract to be financially efficient to cancel.

In 2012, Air Combat Command requested the testing of a 600-gallon external fuel tank which would extend the A-10's loitering time by 45–60 minutes; flight testing of such a tank was conducted in 1997, but did not involve combat evaluation. Over 30 flight tests were conducted by the 40th Flight Test Squadron to gather data on the aircraft's handling characteristics and performance across different load configurations. The tank slightly reduced stability in the yaw axis, however there is no decrease in aircraft tracking performance.

In July 2010, the USAF issued Raytheon a contract to integrate a Helmet Mounted Integrated Targeting (HMIT) system onto A-10Cs. The Gentex Corporation Scorpion Helmet Mounted Cueing System (HMCS) was also evaluated. In February 2014, Secretary of the Air Force Deborah Lee James ordered that development of Suite 8 software upgrade continue, in response to Congressional pressure. Software upgrades were originally to be ceased due to plans to retire the A-10. Suite 8 software includes IFF Mode 5, which modernizes the ability of friendly units to identify the A-10 as a friendly aircraft.

April fools joke by AF, replace A-10 with star wars X-wings

Including this agreement, the Air Force has ordered 173 wings. 2013

More than 250 A-10s were retired between 1991 and 1992. :In 2003, the Air Force studied cutting back on the life-extension programs due to increasing cost. This was widely interpreted as a proposal to eliminate the A-10 fleet itself. However, retirement was ruled out and the upgrade and life-extension programs continued. In 2007, the Air Force began a new program to replace the wings of 231 older A-10s. Although not dispositive, the continued investment in upgrades appears to indicate the Air Force did not then plan to divest A-10s. The re-winging program was ended in FY2013 at 145 aircraft.

"The aircraft has participated in operations Desert Storm, Southern Watch, Provide Comfort, Desert Fox, Noble Anvil, Deny Flight, Deliberate Guard, Allied Force, Enduring Freedom and Iraqi Freedom."

The A-10 Thunderbolt 2 is a cantilever low-wing monoplane with wide chord, deep airfoil section. One-piece constant chord center wing section, tapered outer panels, cambered wing tips. Two-segment, three-position, trailing-edge slotted flaps, interchangeable right and left. Wide span ailerons, made up of upper and lower surfaces that separate to serve as airbrakes. Small leading-edge slat inboard each mainwheel fairing. Redundant, armor shielded flight control system. Semi-monocoque aluminum alloy fuselage with four main longerons, multiple frames, and lap-jointed, and riveted skin. Cockpit is within a bathtub-shaped armor section inside airframe. Gun mounted below cockpit, ammunition drum and feeder mounted behind cockpit. Cantilever aluminum structure with twin fins and interchangeable rudders mounted at tips of constant chord tailplane. Interchangeable elevators, each with an electrically operated trim tab. Tricycle-type, hydraulic operation landing gear. Main gear retract forward, into housings near mid-wing. Pod-mounted, high-bypassratio turbofan engines mounted to the upper rear surface of fuselage, halfway between wing trailing edges and tail leading edges.

EGI. The Embedded Global Positioning and Inertial Nav System (EGI) is an all-weather nav system providing positioning, velocity, and acceleration data for the aircraft. The EGI will replace the original LN 39 system and provide savings of $18 million per year in maintenance costs. USAF is refitting 369 aircraft with the EGI in a $190.6 million project, with final installations taking place in late FY03. The first modified aircraft was redelivered to USAF in the spring of 2000. http://www.forecastinternational.com/archive/disp_old_pdf.cfm?ARC_ID=1003

LASTE - 1990, egi "commencing in '99" with complementary cdu and OFP block upgrade. http://fas.org/man/dod-101/sys/ac/a-10.htm oa-10 conversions start 1987 - http://www.gao.gov/assets/150/146941.pdf - http://www.militaryfactory.com/aircraft/detail-page-2.asp?aircraft_id=25 nvg upgrades complete 1997

"Moseley has said that he considers improving the A-10 engines a high priority, but the funding to update the engine had to be sacrificed to pay for the wing replacement. (See “Washing- ton Watch: Building Better Warthogs,” September 2006, p. 16.) The propulsion upgrade program, or PUP, envisioned by the service would allow the A-10’s TF34 engines to pro- vide up to 30 percent more thrust, Henry said. There’s no money to develop the change, but the requirement is carried as a high priority if funds do become available. “That program is suspended, ... on hold,” Henry said. “Any self-respecting fighter pilot wants to have more power, but it’s one of those tough decisions. ... What it comes down to [is] ‘bang for the buck.’ There are other things that would be more important to the A-10.” While an engine improvement would improve survivability of the airplane, the wing replacement is a more urgent “sustain- ment” issue, Henry said. The Air Force had to “mortgage the PUP,” Johns said, “but we still want to do that.”

Original spectrum 1-2 6,000 hour configuration. First modification, cold working and thick skin. Second modification, cold working ws 0? New testing for 8,000 hrs. OA-10 modification includes internal electronics and minor modifications like modifying hardpoints to accept flares. Hog Up (1999), Hog Up (2003), Hog Up problems. Hog Up generally to extend flying hours to 16,000 hrs and include long due improvements. 2001 ws 23 reclassified as critical. 2003 timeframe first batch thin skin wing failures lead to predicted crisis in 2011 timeframe. Air force explored 3 options, sustained maintenance, replacing the 135 first batch thin skin wings with newly manufactured replacements, or replacing all 242 wings. The third option, replacing all wings was judged to be the cheapest, and the AF chose that option, first ordering 121 replacement wings, planning to replace all 242 by 2018 at the latest. The AF also used 3d scanners to create a 3d model of batch 3 thick skin wings with ws 0 cold worked to create an as created baseline to account for any differences between the design and the real life factory output, as the current primary contractor, lockheed martin didn't have comprehensive manufacturing documentation from the original manufacturer, fairchild. LASTE 1990s. Operational Flight Program. Enhanced Attitude Control. EGI embedded gps/ins. Night Vision Goggle compatible instrumentation. PEU 2005, A-10C. JDAM, WCMD. HOTAS controls, MFDs, datalinks, digital stores management, integrated flight and fire control computer, litening II and SNIPER laser targeting pod support, new armament HUD control panel. "There were many aspects of the A-10 program that were unique for its day. It was a design-to-cost program when most other aircraft programs were clearly putting performance first. It was the first major defense program to embrace the newly favorable competitive prototyping approach to allow a source selection decision to be made on the basis of demonstrated performance and maturity of the design."

"Alas, no program is perfect, and the A-10 provides no exceptions to that observation. Overlooked problems associated with production readiness and contractor financial stability did not go away and had to be resolved far too late in the development program. More significantly, the original structural design proved inadequate for the design life, and even fixes during production were inadequate for all but the latest aircraft produced. This problem was compounded by loss of the Original Equipment Manufacturer (OEM), on-again/off-again decisions to retire the A-10, unstable funding for inspection and repair, and major personnel disruptions resulting from a BRAC decision. Critical “health of the fleet” structural inspections were not performed during sustainment, and a subsequent repair program failed to provide the desired level of life extension. Despite these problems, the A-10, with precision engagement upgrades and new wings in production, appears to be back on track for a life extension that will double its service life and keep it flying until 2028."

Northrop's A-X entrant looks a little like a manned predator drone. Grumman, boeing and McD Douglas, twin engine turboprop? Cessna over wing jet engines, similar to A-10 but single tail, worse (side?) IR signature.

A-10C ioc september 2007.

notes from case study.

A-10C

"In 2005, the entire A-10 fleet began receiving the Precision Engagement upgrades that include an improved fire control system, electronic countermeasures, upgraded cockpit displays, the ability to deliver smart bombs, moving map display, hands on throttle and stick, digital stores management, LITENING and Sniper advanced targeting pod integration, situational awareness data link or SADL, variable message format, or VMF, GPS-guided weapons, and upgraded DC power. The entire A-10 fleet has been Precision Engagement modified and now carries the A-10C designation." "The upgraded A-10C reached initial operational capability in September 2007."

The Precision Engagement (PE) upgrade would bring the A-10 fleet to the A-10C standard. The PE upgrade "will give A/OA-10 pilots all-weather combat capability with "smart" weapons, as well as greater situational awareness and an entry into the network centric warfare environment. These new capabilities derive from the updated hardware and avionics that employ existing technologies... The upgrade will allow the standoff delivery of precision-guided weapons, such as the Joint Direct Attack Munitions (JDAMs) and Wind Corrected Munitions Dispensers (WCMDs), both GPS-calibrated smart bombs in the Air Force inventory. With these weapons, plus a targeting pod and data link that delivers targeting data, A/OA-10 pilots will be able to engage targets in all weather and at safer distances and higher altitudes."

The PE upgrade includes two new color multifunction displays, Hands on stick and throttle pilot controls, a new central interface control unit (CICU) that provides digital stores management and overall avionics systems integration, upgraded processors, Up front controller (UFC), a new instrument panel, upgraded power systems, and the interfaces necessary to accommodate the new gps guided smart weapons. The upgrade was expanded to incude digital mapping, as well as the hardware and interface for the Northrop Grumman Litening and Lockheed Martin Sniper reconnaissance and targeting pods, which house optical sensors and laser designators, and the situational awareness data link (SADL) which will provide both air-to-air and ground-to-air digital communications of target data. "SADL uses the enhanced position location reporting system (EPLRS) waveform, which will provide secure, jam-resistant data communications, such as friendly force data from Army units, in near real time."

Proposed upgrades included integrated combat search and rescue locator systems and improved early warning and antijam self-protection systems.

"Launched in 2001, the Precision Engagement program rescues a tough combat aircraft that the Air Force probably would begin phasing out in about 2019. The A/OA-10's original service life was to be 8,000 hours, a milestone that many Warthogs are about to meet, if they haven't already done so. The modernization effort, however, is expected to extend the aircraft's service life to 2028."

The PE "backbone is the central interface control unit, which replaces most of the old armament control system and also interfaces with other mission subsystems to provide an integrated solution for the pilot and maintainance technician. The CICU takes various sources of information from the aircraft's subsystems--such as targeting pods, radios, processors and displays--and integrates and displays the information in a manner that is meant to reduce pilot workload. The massive increase in data provided by the PE system can be complex and confusing, which is why Lockheed Martin engineers are working with A/OA-10 pilots to "look for ways to improve and add information that the pilot needs to see," says Il Grande."

The PE "[includes] with the CICU is the integrated flight and fire control computer (IFFCC). The IFFCC replaces the A/OA-10's current low-altitude safety and targeting enhancement (LASTE) system.

"LASTE provides computer-aided capabilities for the low-flying Warthog, including ground collision avoidance, enhanced attitude control for aircraft stabilization during gunfire, and a low-altitude autopilot system, as well as ballistic weapons control and target detection and tracking. Hardware and software upgrades to LASTE resulted in IFFCC. And as part of the Precision Engagement program, BAE Systems is upgrading the IFFCC software to add HUD symbology in support of targeting pods, data link and smart weapons integration."

"The mission planning system (MPS) will allow the pilot to plan his route, the weapons employed and drop sequences, and target information on the ground. He then uses a cartridge to load the mission plan onto the aircraft. As part of the Precision Engagement EMD program, the Southwest Research Institute is upgrading the MPS. Warthog pilots also will be able to program the weapons and check the weapons' status, while in fight."

"For the maintenance technician, the A/OA-10's CICU and an existing control display unit (CDU) have been fitted with upgraded software to improve the detection and isolation of avionics subsystem failures. Southwest Research Institute is providing an upgraded operational test system (OTS) with a diagnostic interface to the aircraft avionics and weapon systems. These enhancements are expected to improve the system's maintainability and, thus, its availability."

"The two new 5-by-5-inch liquid crystal, multifunction color displays in the Thunderbolt II's PE kit replace analog switching devices and round dials, and require installation of a new instrument panel. The displays, supplied by Elbit Fort Worth, are interchangeable and provide various control menus that provide the pilot-vehicle interface. The displays also will present a digital map on the tactical awareness display (TAD), produced by Lockheed Martin. The data link information and other tactical data are automatically oriented and scaled in order to be correctly overlayed on the map. This will "show where the good guys are and where the bad guys are," Il Grande explains. Pilots thumb through the menus on the displays, using the surrounding bezel keys or the HOTAS (hands on throttle and stick). The PE kit will add the up front controller, which is positioned just below the HUD, so that Warthog pilots can keep eyes up while inputting data. The UFC has the same keyboard as on the CDU and typically would be used to input menu items, navigational information and weapons delivery data."