In-Flight Investigation of Landing Approach Flying Qualities of Transport Aircraft with Relaxed Static Stability

摘要

An in-flight simulator was used to investigate the influence of longitudinal static stability reduction on the landing approach flying qualities of transport aircraft. The static margin was varied from 14% MAC to -10% MAC by rearward center of gravity translation. No clear tendency of Cooper-Harper pilot ratings to deteriorate with decreasing stability is detectable until inherent instability, corresponding to 6 sec time-to-double amplitude, is reached. Mean Cooper-Harper ratings for all pilots show a slight improvement when the static margin is changed from 14% to 5% MAC. The effect of turbulence on the configuration is relatively low until time-to-double amplitude reaches 6 sec. For configurations with a time-to-double amplitude of 6 sec, turbulence intensity becomes greater and determines the gradient of deterioration. Pilot effort ratings and comments confirm the Cooper-Harper rating tendency. After an initial drop their effort to fulfill the task with the same accuracy in all cases increases with increasing instability.