Image above: Free-flight test of a model blended-wing-body transport. Credit: NASA
The 30- by 60-Foot Tunnel at Langley Research Center in Hampton, Virginia, is a subsonic wind tunnel originally designed for static tests of full-scale models and actual aircraft at operational flight speeds. Such ground-based tests eliminated scale effects and provided basic information prior to and during flight tests. Scale effects are the corrections applied to measurements of a test model so that they correspond to flight conditions. More recent studies in the tunnel often focus on stability and control characteristics and high-lift capability for both civil and military aircraft.
Image to left: This production Vought F4U-1 was tested to verify drag reduction recommendations. Credit: NASA
Originally known as the Full Scale Tunnel (FST), it was the largest wind tunnel in the world until 1945 and in 1985 was named a National Historic Landmark. The tunnel has been used to test World War II fighters, submarines, the Mercury space capsule, concepts for a supersonic transport, a replica of the Wright Brothers' 1903 flyer, racecars, and a blended-wing-body transport aircraft concept. When early aircraft designs were found to have high drag measurements, many aircraft were sent to this tunnel for "drag clean-up."
The building housing the tunnel is 434 feet long and 222 feet wide, with a maximum height of 97 feet. The actual test section is open, and measures 30 feet high, 60 feet wide, and 56 feet long. Two four-bladed wood (originally cast aluminum alloy) fans, each 35.5 feet in diameter and powered by a 4,000-horsepower motor, produce the air stream. During normal operation, the two motors use approximately 3 megawatts of electricity. The tunnel is a closed-loop design, with two return passages that allow for continuous airflow at speeds from 25 to 120 miles per hour. A closed-loop tunnel has ductwork with interior vanes and screens to direct and calm the airflow through the test section.
Constructed During the Depression
Image to right: Langley woodworkers shape the twin fan blades. At right, blades are shaped from laminated blanks. At left, a set of blades is given a final sanding. Credit: NASA
In early 1928, Dr. Joseph S. Ames, then chairman of the National Advisory Committee for Aeronautics (NACA, NASA's predecessor), wrote the U. S. Director of the Budget explaining the need for a full-scale wind tunnel. The larger tunnel would complement existing tunnels and allow for closer examination of external struts, surface gaps, air leaks, and other surface irregularities. After convincing Congress that the tunnel would be worth the cost of almost a million dollars, the NACA asked for a two-year appropriation of $900,000 to construct the tunnel. This request was granted in February 1929. Smith J. DeFrance, who had previously worked with Langley's Variable Density Tunnel (VDT), led the planning for the tunnel. Because the 30- by 60-Foot Tunnel was designed and built during the Depression, DeFrance's team was able to take advantage of inexpensive materials and a large pool of unemployed engineers. Before construction, the team built a 20-percent scaled model to study the airflow, as the tunnel was the first with an elliptic throat. The throat is the smallest cross section of a wind tunnel -- in this case, it is at the entrance to the test section and has two fans mounted side by side to generate airflow.
In February 1930, a contract was signed with the J. A. Jones Construction Company and construction of the tunnel began. The completed tunnel was dedicated on May 27, 1931, during the Sixth Annual Aircraft Engineering Conference. DeFrance's team did not spend all the appropriated funds; the excess money was returned to the U. S. Treasury.
Image to right: The Mercury space capsule undergoing tests in January 1959. Credit: NASAThe 30- by 60-Foot Tunnel has provided research information on many military, commercial, and general aviation configurations. Its many contributions include fundamental aerodynamic tests of full-scale aircraft during the 1930s; drag reduction or "clean up" studies of full-scale military aircraft during World War II; tests of the Albacore, the fastest submarine in the world in 1950; tests of the nation's first spacecraft, the Mercury capsule; tests of full-scale general aviation aircraft; free-flight tests of models of vertical takeoff and landing (VTOL) aircraft; and tests of lifting body, supersonic transport, and present-day military aircraft configurations. Over the years the interior of the tunnel has been modified several times to adapt to changing needs. In the 1960s and 1970s, the tunnel underwent renovation and was equipped for free-flight dynamic model tests. This technique is unique to the facility. In free-flight tests, remotely piloted 10- to 20-percent scaled models are flown in the tunnel air stream. A tether is attached to the model for instrumentation and control. Such tests allow researchers to assess flight characteristics and evaluate control options without risking the life of a pilot or an aircraft.
Training New Engineers
Image to right: A replica of the 1903 Wright Flyer was tested in 2003 to learn more about its flight characteristics. Credit: NASA
Today, the 30- by 60-Foot Tunnel continues to contribute to the future of aerospace. The tunnel is operated by Old Dominion University's Batten College of Engineering and Technology. Professors and students use the tunnel to conduct aerodynamic tests of ground, air, and sea-vessel structures. It is the largest university-operated wind tunnel in the world. NASA Langley is a federal custodian of historic properties, including this tunnel, and conforms with the provisions of the National Historic Preservation Act. More information about the 30- by 60-Foot Tunnel is available at:
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