A Flight Investigation Of An Automatic Gust Alleviation System In A Transport Airplane

A flight investigation has been conducted of an automatic gust-alleviation system designed primarily to improve riding comfort in rough air. The gusts were sensed by a vane located on a boom ahead of the airplane. The wing flags moved in response to the vane in such a way as to counteract the change in wing lift due to the gust and a portion of the elevator moved to counteract pitching moments due to flap deflection. In the final configurations, inboard portions of the wing flaps also moved in such a way as to counteract the change in angle of attack at the tail due to the gust. The result indicate alleviation of normal acceleration of up to about 60 percent at the natural frequency of the airplane (0.6 cycle per second) and about 40 percent at 2 cycles per second. A further increase in riding comfort was achieved by a simultaneous alleviation of pitching velocity. For this particular airplane, gusts having frequencies greater than 1.5 cycles per second at a speed of 130 knots had little effect on riding comfort. Brief tests were also made of a configuration intended for reducing structural loads and of a configuration utilizing an accelerometer as the gust sensor. The gust alleviation capabilities of these configurations were somewhat less than that of the optimum configuration with vane-type gust sensor.