Model of the XN2Y-1 for testing in 15-Foot Spin Tunnel. This was one of two balsa wood models (the other was a 1/12-scale model of the F4B-2) for initial testing and calibration of the new tunnel. Researchers were very concerned that the results they might achieve with models in the tunnel would not correlate with the spinning behavior of full-scale airplanes. They noted that: "comparisons between results from the N.A.C.A. spinning balance and full-scale flight tests have indicated considerable scale effect upon aerodynamic characteristics in spinning attitudes." Thus, these first two models were chosen for testing in the new tunnel because their full-scale spinning characteristics were already well known. These first tests proved encouraging to the researchers but they did not achieve the precise degree of reliability hoped for. The facility's opening however, does signify the advent of a serious and long term commitment to studying the problem of aircraft spinning. Charles Zimmerman wrote in NACA TR No. 557: "At the beginning of a test the model is mounted upon a launching spindle about the axis of which it is free to rotate. This spindle is on the end of a wooden rod and is held in the center of the tunnel by one of the operators standing in the observation chamber. With the spindle vertical the attitude of the model is such that the fuselage axis is approximately 35 to the horizontal, nose down, and the wings are 10 to the horizontal with the left wing tip the lower (for a right spin). When the model is in this attitude, air flowing upward through the tunnel causes it to rotate fairly rapidly. The air speed is increased by a second operator until the air force on the model is equal to its weight. The model then automatically disengages itself from the spindle and continues to float in the air stream entirely free of mechanical restraint. The launching spindle is immediately withdrawn from the tunnel. The air speed is adjusted until it just equals the rate of descent the model would have in still air and the model is at approximately eye level in the test section." (p. 267) The 15-foot spin tunnel was a new facility for testing spins, building on research begun in the mid-1920s which involved launching dynamic scale models from the top of the balloon shed at Langley field. There was a great deal of research on spinning going on in England that was being closely followed by engineers at Langley. British success with a vertical wind tunnel, triggered the construction of the 5-foot vertical wind tunnel at Langley. It also resulted in the construction of the 15-foot Spin Tunnel. Langley received authorization to begin construction in June 1933. The building was finished in September 1934 but final calibration tests were not completed until March 1935. Spin tests began in April 1935.
