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Quest for Performance: The Evolution of Modern Aircraft


Part II: THE JET AGE


Chapter 12: Jet Bomber and Attack Aircraft


Close-Air-Support Aircraft



[402] A need arose during the Vietnam conflict for a specialized aircraft capable of giving close air support to troops operating in the forward battle area. Needed was a heavily armed aircraft that could respond rapidly to a call for help and had the ability to destroy tanks, artillery batteries, and other types of enemy strongholds. Neither a fast aircraft nor one with long range was required; good maneuverability, extended loiter time in the battle area, and a lethal weapons load were needed. Low cost, easy maintenance with minimum turnaround time, and high survivability in the face of enemy ground fire were other characteristics desired. The aircraft was intended only for daytime operations in fair weather.

Detailed requirements for such a close-air- support aircraft were issued by the USAF in May 1970. Fairchild- Republic and Northrop were given contracts for the construction of prototypes to be used in a flyoff competition from which a winner would be selected for production. Fairchild-Republic with its A-10A was declared the winner in January 1973. First flight of the aircraft occurred in May 1972, and the first squadron to be equipped with the A-10A became operational in October 1977. The aircraft is still in production with a planned output of over 700 units.

[403] The A-10A, dubbed the Thunderbolt II, is shown in figures 12.28 and 12.29. Configuration of the Thunderbolt II is like that of no other modern aircraft and, in some respects, seems to be a throwback to an earlier aeronautical age. The unswept wing is tapered only slightly and is mounted near the bottom of the flat-sided fuselage, about midway between the nose and the tail. Airfoil sections vary in thickness ratio from 16 percent at the root to 13 percent at the tip. An aft-loaded camber line is used in the airfoil sections to improve turning performance at low speeds in the battle area. In effect, this camber line acts like a flap with a small permanent deflection. A single-slotted trailingedge flap is provided, and ailerons are used for lateral control. For aerodynamic braking, the upper and lower surfaces of the ailerons separate and deflect above and below the wing.

Two General Electric turbofan engines are contained in separate nacelles that are pylon mounted slightly above and to either side of the fuselage and behind the wing. The horizontal tail is below and to the rear of the engines; the vertical surfaces are at the tips of the horizontal tail outboard of the engines. Serious exhaust impingement on both the...




Figure 12.28 - Fairchild-Republic A-10A close-air-support aircraft. [USAF via Martin Copp]




[404] Figure 12.29 - In-flight view of Fairchild- Republic A-10A close-air-support aircraft. [USAF via Martin Copp]

....horizontal and vertical surfaces is avoided by this arrangement. Conventional elevators and rudders are provided for pitch and yaw control, respectively. Main-landing-gear units retract into fairings below the wing, and the single nose-wheel gear is offset to facilitate optimum location of the offensive cannon. The single pilot's cockpit is near the nose of the fuselage and is equipped with a zero-zero ejection seat. (A successful escape can be made at zero altitude and speed.) Protection of the cockpit area is provided by an armored "bathtub" constructed of titanium said to be able to withstand the impact of projectiles of up to 23 mm in size.

Primary armament of the A-10 is a large 30-mm seven-barrel rotary cannon. This impressive weapon can fire at a rate of either 2100 or 4200 rounds per minute. Equipped with 1950 rounds of ammunition, the gun weighs 4041 pounds; its empty weight is 1975 pounds. The gun is positioned in the nose so that the firing barrel is always located on the centerline of the aircraft. Muzzle of the cannon may be seen protruding from the nose in figures 12.28 and 12.29. In addition to the formidable 30-mm cannon, four store-mounting stations are [405] provided under each wing and three are located beneath the fuselage. A wide assortment of different stores can be carried on the aircraft. With full internal fuel tanks, the maximum external load is a remarkable 14 341 pounds.

The data in table VI show a maximum gross weight of 40 269 pounds for the Thunderbolt II. With a payload of 9540 pounds, mission radius is 288 miles, including a 2-hour loiter period on station. Ferry range with no payload and maximum external fuel is 3510 miles. At a cruising speed of 329 miles per hour, time required for the single pilot to fly this distance is a little over 10 hours. Certainly a fatiguing flight, but not a remarkably long one for a single pilot. Maximum speeds for the A-10A given in table VI are comparable to those achievable by the fastest propeller-driven fighters of World War II.

Certainly the Thunderbolt II (sometimes irreverently referred to by crew members as the Warthog) will never reap any honors for ascetic appeal. Yet, given its unique mission requirements, a more practical design is difficult to envision. Its ultimate usefulness in a combat situation, however, has yet to be proven.