File:Variable Density Tunnel, Being Used by NASA Staff DVIDS718694.jpg

English: In 1922, at NASA Langley Research Center, the National Advisory Committee for Aeronautic (NACA), completed the Variable Density Tunnel (VDT), the world's first wind tunnel in which air pressures could be varied. Prior to the VDT, wind tunnels of substantial size operated at normal atmospheric pressure. Because test models were at a smaller scale, the aerodynamics effects did not coincide with the results obtained by actual flights of full scale aircraft. It was found that when air density could be altered, as in the VDT, test results using scale models coincided with the results obtained by using full-scale aircraft. The VDT made Langley a world leader in aerodynamic research. Information from the VDT was used in the designs of well known successful aircraft -- the DC-3 transport, the B-117 Flying Fortress and the famous twin-tailed P-38 that helped check the Japanese Zeros in World War II. In December 1985, the VDT chamber was designated a National Historic Landmark. In October 1989, almost exactly 67 years after the initial operation, it was moved from its original location to be permanently displayed beside the H.J.E. Reid Conference Center at NASA Langley in Hampton, VA. NASA Identifier: L3310