BENCH-TEST INVESTIGATION OF THE TRANSIENT-RESPONSE CHARACTERISTICS OF SEVERAL SIMULATED AIRPLANES INCORPORATING AN AUTOPILOT SENSITIVE TO YAWING ACCELERATIONS

摘要

An autopilot sensitive to yawing acceleration was used to control four simulated airplane (mass-spring) configurations and a series of bench tests were conducted to determine the response characteristics of the combinations. The occurrence of an unstable mode of motion was predicted in previous theoretical analyses, NACA TN 2006 and TN 2005, in which the autopilot was assumed to have a constant time lag and a constant amplitude ratio. The transient characteristics of the closed-loop system oscillating in yaw were measured and the results show that, with the actual autopilot, no unstable mode of motion was present throughout the frequency range investigated. Examination of the frequency-response characteristics of other existing autopilots indicates that this unstable mode of motion would probably not exist if these autopilots were used, because constant time lag and amplitude ratio do not satisfactorily approximate the frequency-response characteristics of such autopilots in the frequency range where the unstable mode is predicted.