Application of QFT to the problem of failed in-flight controllers during approach and landing of a B-720 aircraft

Previous studies by NASA Dryden have shown the use of throttles for emergency flight control to be extremely difficult, especially for landing. Flight control using only the throttles to achieve safe landing for a large jet transport airplane, the Boeing 720, is investigated using quantitative feedback theory. Results are compared to an augmented control developed in a previous study. The controller corrects unsatisfactory open-loop characteristics by increasing the system bandwidth and damping, but improvement of the control bandwidth remains very difficult. The pitch controller is robust when turbulence is absent or moderate. The roll controller performs well in the absence of turbulence, but is sensitive to moderate turbulence. Handling qualities of the augmented control for approach and landing were evaluated by piloted simulation flights