Partners in Freedom

		Fairchild Republic A-10 Thunderbolt II


Specifications Manufacturer Fairchild Republic Date in service March 1976 Type Close support and attack Crew One Engine General Electric TF34-GE-100A Users U.S. Air Force Dimensions Wingspan . . . . . . . . . . . .57.5 ft Length . . . . . . . . . . . . . . 53.3 ft Height . . . . . . . . . . . . . . 14.7 ft Wing area . . . . . . . . . . 506 sq ft Weight Empty . . . . . . . . . . 18,591.0 lb Typical combat . . . 23,498.0 lb Performance Max speed . . . . . Mach number of 0.56 Radius of action . . . . . 695 n mi

		Highlights of Research by Langley for the A-10 At the request of industry and the Department of Defense, Langley personnel participated in reviews and assessments during competitive stages of Attack Experimental (A-X) Program. Langley conducted wind-tunnel tests and provided data for all competing designs in A-X Program. Langley and Fairchild conducted joint tests of a powered A-10 model in the 7- by 10-Foot High-Speed Tunnel to determine the effects of engine exhaust on aerodynamic characteristics. Fairchild consulted with Langley personnel on A-10 wing airfoils, stall characteristics, high-lift aerodynamics for low-level maneuvers, and spin characteristics. Langley conducted extensive spin tunnel tests of the A-10 for a variety of external store configurations. The Fairchild Republic A-10 was the result of the Air Force’s A-X competition that began in 1967 for a close-support aircraft capable of withstanding the highly lethal environment near the front lines. During the A-X competition, the Department of Defense (DOD) requested that Langley participate in mission analyses, conduct supporting wind-tunnel tests, and provide analyses of the competing designs. During the summer of 1967, tests were conducted in the Langley 7- by 10-Foot High-Speed Tunnel on designs submitted by Grumman, Northrop, McDonnell, and General Dynamics. In 1970, the requirements for the A-X mission were changed, and the Air Force issued a new request for proposals (RFP). Six companies responded to the RFP, and designs by Fairchild and Northrop were selected for further development. In preparation for a competitive fly off under the “fly before buy” philosophy, Langley conducted performance and spin tunnel tests of the Fairchild Republic and Northrop configurations, known as the YA-10A and the YA-9A, respectively. After the Air Force selected the A-10 as its close-support aircraft in January 1973, Langley conducted extensive tests in the Langley 20-Foot Vertical Spin Tunnel of the production configuration with a large variety of external stores. Langley facilities used in support of the A-10 Program also included the 7- by 10-Foot High-Speed Tunnel.

		Langley Contributions to the A-10

The A-X Competition		In the Vietnam conflict concentrated small-arms fire, ground-to-air missiles, and other more sophisticated defenses were particularly lethal to aircraft flying close-support missions. This situation resulted in dramatic changes in philosophy for the capabilities of aircraft conducting these missions. Specialists at Langley were asked to identify technologies that could be applied to a hard-maneuvering aircraft with a relatively high degree of survivability. In March 1967, the Air Force released a request for proposals (RFP) for a new Attack Experimental (A-X) Program. In 1967, numerous wind-tunnel tests were conducted in the Langley 7- by 10-Foot High-Speed Tunnel to obtain analysis data for designs by Grumman, Northrop, McDonnell, and General Dynamics. The tests were led by William P. Henderson and Linwood W. McKinney, who conducted extensive briefings for the Department of Defense (DOD) and the industry competitors on the merits of each configuration. In the years following 1967, the A-X mission requirements began to change as the threat of Soviet armor and all-weather operations became embedded in military priorities. In 1970, a new A-X RFP was released by the Air Force and six companies responded. After a formal study, Northrop and Fairchild were named as final competitors for a fly off competition at Edwards Air Force Base. In 1971, tests of a powered model of the Fairchild A-10 were conducted in the 7- by 10-Foot High-Speed Tunnel by Vernon E. Lockwood. The principal objective of the tests was to determine the effects of engine exhaust flow on aerodynamic characteristics in high-power conditions. The tests were conducted with a special model installation in which the powered engine nacelles were not mounted directly to the airframe, but to a separate sting that included air supply lines for the simulation of power. Critical data were obtained on the impact of power on performance and stability of the configuration, including ground effects. Powered-model tests of the Fairchild A-10 with engines supported by an auxiliary upper sting in the Langley 7- by 10-Foot High-Speed Tunnel.
Spin Recovery		In 1972, tests were conducted in the Spin Tunnel by Stanley H. Scher for the competing Northrop (A-9) and Fairchild (A-10) A-X configurations. Results of these tests were used for evaluations and planning for the competitive fly off that occurred at Edwards Air Force Base later that year. In addition to providing information on advantages and disadvantages of each configuration, these results provided spin and recovery characteristics for pilots of the respective vehicles. The Fairchild aircraft was announced as the winner of the competition on January 18, 1973, and a formal request for tests in the Langley Spin Tunnel for the development program was received from the Air Force. A large number of tests were conducted because of the variety of external stores, tanks, and armament carried by the aircraft. High Reynolds number tests were performed with an A-10 model at spin attitudes in the NASA Ames Research Center 12-Foot Pressure Tunnel prior to the spin tunnel tests to determine whether the model would exhibit significant scale effects, and if so, what modifications might be made to correct for these effects. Results of the tests at Ames showed no appreciable scale effects for angles of attack below about 75 deg, but appreciable scale effects (more prospin yawing moments at low Reynolds numbers) for angles of attack above 75 deg. Nose strakes were sized to artificially compensate for the scale effects, but no flat spins (angle of attack greater than 75 deg) were evident and the strakes were not used. Spin tunnel tests of the A-10 configuration.

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October 17, 2003