Roll-performance criteria for high augmented aircraft

Highly augmented fly-by-wire aircraft have shown a degradation in roll performance during compensatory tasks such as tracking, similar to the ones observed for the pitch axis. Gibson's method, which involves a combination of time-domain and frequency-domain techniques, has been shown to provide excellent handlingqualities criteria for the pitch axis, especially in identifying pilot-induced oscillations. The present work extends Gibson's method to develop similar handling-qualities criteria for the roll-axis control system. The effects of parameters such as roll damping, transport delay, system gain, and corresponding pilot ratings are studied for developing handling-qualities criteria and to evaluate the flight-control system performance. Flying-qualities levels are obtained in both the time and the frequency domain. In addition, frequency-domain analysis is used to identify pilot-induced oscillation-prone configurations and the presence of roll ratcheting. The analysis is performed and validated using an existing experimental data base on lateral flying qualities of highly augmented class IV aircraft.