12-Foot Free-Flight Tunnel 12 foot Free Flight Tunnel

Testing a 1/12th scale model of SBN-1 in the 12-Foot Free-Flight Tunnel: The 12-foot free-flight wind tunnel was constructed in 1939 to assist researchers studying the problems of stability and control. The desire was to allow researchers to "fly" dynamic scale models within the controlled conditions of a wind tunnel. This tunnel followed the success developing a 5-foot free-flight wind tunnel in 1937.>From TN 810: "Variation of any dimension of the model can be readily accomplished and the effect on the flying qualities can be determined. Models of proposed airplanes can also be inspected and undesirable stability and control characteristics can be discovered and corrected in the initial design stages." "The NACA free-flight tunnel is a simple open-return tunnel of octagonal cross section, 12 feet wide at the throat and 32 feet long. ... The tunnel is so arranged that its longitudinal axis, and thus the air stream, may be inclined at different angles to the horizontal. A hydraulic jack provides control over the tunnel angle. Suitable guide vanes and screens are installed in the entrance cone of the tunnel to insure uniform air-flow distribution. The housing is spherical; so the relation of the tunnel to the wall does not vary with tunnel angle. The tunnel is equipped with a voltage control for the propeller-drive motor that provides an extremely flexible air-speed regulation. " "A tunnel operator stationed at the side of the tunnel test chamber adjusts the air speed in the tunnel to the speed of the model and accommodates the tunnel angle to the flight-path angle of the model. The operator thus controls the longitudinal and the vertical location of the model in the tunnel. This operator also controls the power input to the model for powered flight." "The pilot is the principal observer because he has control of the model and can detect deficiencies in stability or control. The pilot's observations give a direct qualitative indication of the stability and control; records from three 35-millimeter moving-picture cameras mounted to photograph the motion of the model in three mutually perpendicular planes supply quantitative data on the stability characteristics of the model and its response to control displacements. Neon lamps in the common field of the three cameras indicate the control displacement." 12 foot Free Flight Tunnel: Testing a 1/12th scale dive-bomber model in Langley's 12 foot Free Flight Tunnel, 1940. The model's controls responded to remote control inputs from the operator. The tunnel replaced the 5 foot Free Flight Tunnel in 1939.

NASA Identifier: L21003