SIMULATOR STUDY OF THE EFFECT OF CONTROL-SYSTEM TIME DELAYS ON THE OCCURRENCE OF PILOT-INDUCED OSCILLATIONS AND ON PILOT TRACKING PERFORMANCE WITH A SPACE-SHUTTLE-ORBITER CONFIGURATION.

An experimental study using a six-degree-of-freedom motion-base simulator has been made to determine the effect of control-system time delays on the occurrence of pilot-induced oscillations (PIO's) on the vehicle handling qualities and on pilot tracking performance for a landing-approach configuration of the Space-Shuttle orbiter. A linearized mathematical model was employed which represented a 300-knot orbiter with almost all time delays removed. Results showed that PIO's occurred when the amount of added time delay approximated that existing for the orbiter configuration flown in the approach and landing tests. Increasing the amount of delay increased PIO occurrences and resulted in degraded tracking performance. Decreasing the amount of time delay eliminated the PIO's.