NACA-TN-2948

Abstract

Flight tests were made with a typical light airplane to investigate possibilities for obtaining reliable control at low flight speeds. It was found that satisfactory lateral control occurred consistently, even under conditions simulating extremely gusty air, at angles of attack approximately 2&#176; below that for the maximum lift coefficient (or the stall of the wing as a whole). This 2&#176; margin was substantially the same both with full power and with the engine throttled and throughout the range of center-of-gravity locations tested. Supplementary tests were then made on the control at high angles of attack under actual gusty air conditions, on the possibility of entering spins, and on the amount of elevator control required for normal three-point landings. It was found that with the original plain untwisted wing obtaining the constant 2&#176; margin below the stall required widely different elevator deflections for the range of power and center-of-gravity locations tested. Also, none of these settings was high enough to produce a three-point landing. <br>An attempt was made to find a configuration that would provide sufficient elevator control for a three-point landing under the most critical condition (forward center of gravity) and that at the same time would have insufficient elevator control to exceed the angle of attack at which reliable lateral control is obtained in flight under all of the center-of-gravity and power conditions. The entire series of tests was repeated with the wing twisted to 4&#176; and to 8&#176; of washout and with five different lengths of leading-edge slots covering the outer 30, 50, 60, 70, and 90 percent of the wing span. With 8&#176; of washout the aileron control itself was satisfactory under all conditions tested, even at angles of attack well beyond that for the airplane maximum lift coefficient. Longitudinal fluctuations occurred, however, at all angles of attack above that for the initial stalling of the center of the wing. The results for the 30-percent slots were the same as those without slots. With all of the other slot configurations lateral control was maintained at high angles of attack, but severe longitudinal fluctuations occurred at angles of attack above that for the stall of the plain wing.