DEVELOPMENT

At first sight, the Fairchild A-10 seems an unlikely combat aircraft for the 1980s. In size, this single-seat close-support aircraft rivals the World War II B-25 Mitchell bomber, while its top speed of 380kt (700km/h) could be comfortably exceeded by World War II piston-engined fighters such as the P-51 Mustang, Tempest and FW-109. Despite these apparently unam­bitious figures, the A-10 plays a major role in maintaining USAF ground-attack strength, and would be one of the major anti-armour weapons deployed against a present-day Westward thrust by the Warsaw Pact.

Although fielded as a specialised anti­tank/close support aircraft intended to operate in the European environment, the A-10 owes its origins to a late 1960s requirement for a low-cost aircraft to re­place the Douglas A-1 Skyraider. As was the case in Korea during the early 1950s, the USAF found itself fighting an infantry war without a suitable close-support air­craft. High-technology aircraft such as the A-6 Intruder and F-lll were designed to penetrate the best defensive systems which Soviet technology could create, de­livering heavy ordnance loads or even nuclear weapons onto fixed targets, but were hardly suitable for laying down heavy loads of iron bombs, cluster muni­tions, napalm and unguided rockets on near-invisible targets close to friendly troop positions. Toggling ordnance loads on to enemy bunkers and defensive pos­itions was seen as a prosaic task best left to older fighters such as the F-100.

Experience showed that one of the best aircraft for close-support work was the A-1 Skyraider. A veteran of the 1950s, this aircraft was cheap to operate, carried four 20mm cannon in the wings, had enough hardpoints to carry a heavy ordnance load, and was tough enough to take combat damage and still get home. Unfortunately, there were just not enough of these vet­erans left, and combat attrition was slowly thinning out the remaining examples.

At one point, the Pentagon even con­sidered returning the Skyraider to pro­duction, but cost studies suggested that the design could not economically be resurrected. Instead, USAF planners drew up a specification for an aircraft A-X. Studies were carried out in 1966 starting from a blank sheet of paper-no-one had any idea just how a dedicated close-sup­port aircraft should be configured, but the USAF was determined to find out. Key areas of the new requirement were man­oeuvrability, survivability, lethality, sim­plicity, long endurance, fast reaction time, and the ability to operate from unprepared airstrips.

In the late 1960s General Dynamics, Grumman, McDonnell Douglas and North­rop worked with the USAF to refine furth­er the A-X concept, and in May 1970 Northrop and Fairchild were asked to develop and test-fly rival designs desig­nated YA-9A and YA-10A respectively. The YA-10 flew for the first time on May 10, 1972, beating the YA-9A by 20 days, and two examples of both designs were in the hands of USAF evaluation pilots by October. Selection of the Fairchild design as the winner was announced on January 18, 1973, and the company was given a $159.2 million contract for the first 10 production aircraft.

Congress required some convincing that the A-X concept was valid, and insisted on a second fly-off, this time against the Vought A-7. This took place in April and May of 1974, with the A-10A being de­clared the winner on June 20.

Original planning assumed a total buy of 600, but this was soon increased. The target figure was to fluctuate between 707 and 825 during the life of the programme. Production was slowly built up to a peak of 144 aircraft per year, and by the early 1980s most had been delivered. President Carter's FY82 budget request allocated no funding to the A-10, but the new Reagan Administration restored money for 20 air­craft a year to keep the line rolling, but abandoned the planned A-10B two-seat Combat-Ready Trainer version.

Funding for the first 14 trainers had originally been planned in the FY82 budget. Broadly similar in appearance and performance to the single-seater, the A-10B would have carried a revised cockpit with an enlarged canopy, a second ejec­tion seat and systems for the second crew­man. These changes would have added less than 1,5001b (680kg) to the aircraft weight.

Another abortive two-seat development was the planned Night/Adverse Weather version. A two-seat A-10 was originally devised in 1976 as a possible FAC-X forward air control aircraft for the USAF.

This project never came to fruition, but Fairchild decided to press ahead with a private-venture two-seater in the hopes of selling the result to the USAF as a special­ised night/all-weather attack aircraft. The new variant would have a 94 per cent structural commonality and some 80 per cent equipment commonality with the basic A-10A, the company claimed, while new items of specialised nav/attack av­ionics would allow operation with cloud ceilings down to 300ft (90m) and in visi­bility of down to a mile (1.6km).

An experimental prototype using pod-mounted systems was flown for the first time on May 4, 1979. Following four months of company flight test, it was handed over to the USAF for 300 hours of flying at Eglin AFB, Florida. Despite suc­cessful night operations against moving targets such as armoured vehicles, the USAF declined to place an order, hoping to obtain much of the night/adverse weather capability it would need from the LANTIRN pod system being developed for both this aircraft and the F-16.

Fairchild tried hard to obtain export orders, but the fact remains that few air forces outside the superpowers can afford to deploy a specialised single-mission air­craft costing some $10 million a copy at early 1980s prices. Potentiar customers included Chile, Egypt, Morocco, Pakistan, Peru, Thailand, and Venezuela. At one time Peru seemed likely to be the first export customer, evaluating the type in late 1981 as a possible Canberra replace­ment, only to turn it down the following year.

As the line began to run down, Fairchild proposed a number of other variants of the A-10 in the hope of obtaining further orders, but none attracted an order. The 713th and final A-10A was delivered to the USAF in April 1984, ending the 11-year production run.

STRUCTURE

The shape of the A-10 looks distinctly odd by modern standards, almost as if the team which designed the Heinkel 162 Volks-jager in 1944 had returned to their draw­ing boards to create a modern twin-en­gined version. Form has been dictated by function, however, and the aircraft's shape is the result of careful design.

Best-known feature of the fuselage is the armoured "bathtub" which protects the cockpit area. Manufactured from titanium, it is designed to withstand direct hits from cannon shells of 23mm calibre-the type fired by the Soviet ZSU-23-4 Shilka self-propelled anti-aircraft gun. The remainder of the fuselage is of more orthodox design, and built from aluminium alloy.

The wing is of straight form and three-spar construction, and has 7 degrees of dihedral on the outer panels. Control sur­faces consist of two-section trailing-edge flaps, a small leading edge slat on the inboard wing sections, and ailerons which split into upper and lower sections to serve as airbrakes. Large fairings buried in the wing house the main legs of the undercarriage. Even when the latter is retracted, the tyres protrude slightly, a feature designed to allow the aircraft to carry out "wheels-up" landings with min­imal damage should the undercarriage fail to extend.

The novel rear-fuselage engine installa­tion keeps the powerplants well apart, minimising the risk that combat damage to one will also affect the other. The engines are in a good position to avoid ingesting gun gas or runway dirt (a good feature for an aircraft intended for deployment at temporary airstrips). They are also in a good position to ingest turbulent air should the wing stall, a problem dis­covered in early trials, but soon fixed.

The twin tails offer further aids to sur­vivability. If one is shot away or suffers rudder damage, the pilot can still maintain control with the other. In combat, the vertical and horizontal surfaces screen the hot aft section of the engines from the attention of simple man-portable heat-seeking missiles such as the SA-7.

Much attention was given at the design stage to survivability and maintainability. The fuel tanks-two tear-resistant, self-sealing tanks in the fuselage and two integral tanks in the wing centre section- are filled with reticulated foam to minim­ise the chance of fire following a hit, while all pipework external to the cells is fitted with a self-sealing cover. Total internal capacity is 10,700lb (4,850kg), and may be supplemented by up to three 600 gallon (2,270 litre) external tanks.

All control surfaces are hydraulically actuated, the control systems have built-in redundancy and being protected by armour. To minimise front-line spares holdings, right and left-hand flaps, control surfaces and their actuators, undercarriage legs, and engines are interchangeable be­tween right and left-hand sides.

The only significant structural modifica­tions which the aircraft has seen are the revised two-seat cockpit proposed for the abandoned trainer and night/all-weather attack versions. The sole prototype of the latter was the only aircraft to have an enlarged tail, whose vertical surfaces were increased in height by some 20in (50cm).

POWERPLANT

The General Electric TF34-GE-100 is a twin-spool, high bypass-ratio turbofan originally developed as the 9,275lb (4,207kg) thrust powerplant of the US Navy's S-3A Viking ASW aircraft. The slightly downrated TF34-100 selected for the A-10 is rated at 9,065lb (4,112kg), and has a specific fuel consumption of 0.3711b/ lb/hr. This is slightly higher than the 0.363lb/lb/hr figure of the Navy's -400A engine, but is good news for a pilot who intended to fly long sorties, loitering near the FEBA to await requests for close-support to be made by the troops on the ground.

The first TF34-GE-100 ran in July 1973,1 and completed its MQT trials in October of the following year, in good time to meet the February 1975 flight date of the first A- I 10 DT&E aircraft. Delivery of production engines started in June of the same year, and more than 1,700 examples of this variant have now been built.

The engine is 100 in (254cm) long, 49in (124cm) in diameter, and weighs l,439lb (653kg). A simple intake of annular form without inlet struts or guide vanes leads to a single-stage fan with 28 wide-chord titanium blades. This is followed by a 14-stage axial compressor whose first five 1 stators are variable-a common feature on GE engines. The early stages are manufac­tured from titanium, the remainder from nickel alloy. An annular combustor fitted with 18 burners and borescope ports for engine inspection passes hot gas to a two-stage high-pressure and four-stage low-pressure turbine.

AVIONICS

By modern avionics standards, the A-10 started life not so much austere as near-naked. The most complex items fitted to the basic aircraft were the RWR and the equipment associated with the AGM-65 Maverick missile, but an inertial naviga­tion system was soon added. Most of the remaining equipment was a versatile com­munications fit including VHF/AM, VHP/FM, UHF/AM and UHF/ADF radios, plus IFF and crypto equipment for secure voice communications.

Inevitably, this simple fit has since been supplemented. Normally carried on a short pylon on the lower right-hand side of the fuselage (just forward of the cock­pit), the 32lb (14.5kg) Westinghouse Pave Penny laser-designation pod detects targets marked by laser designators carried by ground troops or in other aircraft, passing data to the pilot's HUD and to the aircraft weapon-delivery system.

A complex suite of avionic systems was test-flown on the prototype Night/All-Weather version of the aircraft. This in­cluded a Westinghouse WX-50 terrain-following radar, Ferranti laser rangefinder, Texas Instruments AN/AAR-42 FLIR, and a Litton LN-39 inertial navigation set. The prototype installation was pod-mounted, but the definitive aircraft would have car­ried the new sensors internally.

In the long-term, the USAF hopes to retrofit the aircraft with the Martin Mariet­ta LANTIRN (Low Altitude Navigation Targeting Infrared for Night), a pod-mounted thermal imaging sight intended to provide a night low-altitude attack capability. Currently under engineering development for use on the A-10 and F-16, it consists of two externally-mounted pods. The navigation pod weighs about 4001b (180kg) and contains a Ku-band terrain-following radar plus a wide field-of-view FLIR whose output is displayed in the form of imagery on the pilot's raster-scanned HUD. The 5001b (225kg) targeting pod houses an optical stabilisation system which is shared by wide and narrow field-of-view FLIR, a laser designator/range-finder, plus dual-mode automatic trackers. Plans for the installation of an automatic target-recogniser facility within the target­ing pod have been postponed due to the degree of technological risk involved.

The USAF is pressing ahead with de­velopment of the system, despite the fact that LANTIRN has been heavily criticised by Congress. At one point, the cost of the programme almost led to cancellation, but the US Department of Defense finally ac­cepted the USAF's claim that the project was essential to its future plans. Flight tests are currently under way, and Con­gress has asked that the system be tested in competition with the AAS-38 FLIR pod being developed for use on the F-18.

Shortage of defense funds prevented this competitive evaluation from being carried out, and at the time this text was prepared the USAF had been allocated only sufficient LANTIRN money to con­tinue performance evaluation of the first development pods. Production or any preparations for production have been ruled out by Congress until alternatives to LANTIRN have been fully explored. At an estimated unit price of more than $5 million per aircraft, the system seems bound to attract further political con­troversy, and its future is far from secure.

ARMAMENT

Most important weapon carried by the A-10 is the General Electric GAU-8/A seven-barrel 30mm cannon. This is a rotary-barrelled weapon of the Gatling type able to fire its 1,170 rounds of ammunition at a rate of 70 rounds per second, some three times the rate possible with rotary-breech weapons such as the 30mm ADEN and DEFA. The weapon is intended to deal with enemy armour, so fires discarding-sabot projectiles (manufactured from de-pleted-uranium) at muzzle velocities 3,500ft/sec (l,066m/sec). A one second burst should be sufficient to deal with most main battle tanks, and the ammu­nition drum carried by the A-10 has enough ammunition for more than 15 such bursts. The gunsight has no air-to-air modes, but any pilots managing to get a MiG in the sight are unlikely to be deter­red from trying a quick burst.

Eleven hardpoints are fitted as stan­dard-four under each wing and three beneath the fuselage. In practice however, all three of the latter cannot be used at the same time. Ordnance must be fitted either to the centreline pylon, or to the flanking pylons. A maximum load of 16,000lb (7,260kg) may be carried, including Mk 82 or Mk 84 "iron" bombs or their laser-guided equivalents, BLU-1 or BLU-27/B incendiary bombs, CBU-52/71 or Rockeye cluster munitions, SUU-23 gun pods, or AGM-65 Maverick missiles. Counter-measures systems such as the ALQ-119 jamming pod and the ALE-40 chaff/flare dispenser may also be carried.

PERFORMANCE

Top speed of an A-10 at sea level and in clean condition is a mere 380kt (705km/h) while "never-exceed" speed is only 450kt (835km/h). By modern standards, these figures may seem unimpressive at first sight, but detailed reading of the A-10 specification shows that the aircraft is well matched to its intended role. Heavily loaded, few fighters will do much excess of 450kt under similar conditions, even if their top speed is Mach 2, but with two TF34s pushing, the A-10 driver knows that his maximum speed is available even when carrying a heavy warload. Flying at 5,000ft (1,500m) with a load of six Mk 82 bombs, the aircraft can still make its nomi­nal 380kt.

At maximum take-off weight, the air­craft can get airborne from 4,000ft (1,200m) strips and land in half that length. At a forward-airstrip weight of 32,770lb (14,865kg)-four Mk 82 bombs, 750 rounds of ammunition, plus 4,500lb (2,040kg) fuel load-the A-10 needs only 1,450ft (440m) of take-off run, and 1,300ft (395m) on landing. Assuming a 1.7hr loiter and a 20min fuel reserve, the aircraft has a range of 250nm (463km), rising to 540nm (1,000km) for a deep strike mission against a known target. Ferry range against a 50kt (90km/h) headwind is more than 2,100nm (3,950km).

Like the dedicated attack aircraft of yesteryear such as the Ju-87 Stuka, 11-2 Stormovik and Henschel Hs-129, the A-10 relies on air superiority having been won by its air force's fighters. Jumped by MiGs or other agile fighters, it could be badly mauled. But the job of the A-10 is not to play Red Baron but to get ordnance on target, come home, reload, and fly off to repeat the performance again and again until the battle is won.

Several years ago, the author discussed A-10 survivability with one of the first USAF pilots to be assigned to the type-a Vietnam veteran. The A-10 was no "bulletproof airplane" he insisted. "If a Shilka gets a good sight on you, it could saw the wing clean off with 23mm fire- no airplane can take a large number of hits and survive. But most of the aircraft downed in action just get a few rounds ... and we lost a lot of good guys in Vietnam to those 'few round' kills. Sure, you'd lose of lot of guys in a Central Front battle-but a large number of A-lOs and their pilots would be able to come home after hits which would have downed a lesser air­plane."