Theoretical Study of the Effect of Wind Velocity Gradients on Longitudinal Stability and Control in Climbing and Level Flight

摘要

A change in the wind vector over a short distance along the flight path (wind gradient) has caused several severe airplane accidents during take-off and land¬ing. Results of a previous study (NASA TN D-8496) showed that, in descending flight, a positive wind gradient (decreasing head wind) caused severe divergent motion and a negative wind gradient (decreasing tail wind) caused oscillatory motion which should not create a control problem. This paper reports the results obtained when the same method of analysis was applied to climbing and to straight and level flight. In straight and level flight, a wind gradient was found to cause effects similar to those found in descending flight. In climbing flight, it was found that a negative wind gradient caused a slightly divergent oscillation that presented no control problems and a positive wind gradient caused oscillatory divergence. Results of motion studies indicated that adequate control of the air¬plane motions can be provided by automatic control systems.