RECONFIGURABLE FLIGHT CONTROL SYSTEMS FOR A TANDEM ROTOR HELICOPTER

This paper describes a study on control reconfiguration as applied to a tandem rotor helicopter. Two reconfiguration strategies are examined: on-line recalculation of the control gains, and a method to redistribute control power to compensate in the event of failure. The first approach is shown to be capable of completely recovering performance, the latter one is shown to be useful only when an additional control effector is available. The failures examined in the study result in degraded stability and response characteristics in roll and yaw in a way that is usually not severe and can be corrected through reconfiguration. On the other hand, for all forward flight conditions considered, the aircraft developed strong, divergence-type instabilities in pitch. Catastrophic loss of control appeared likely in these cases. Reconfiguration stabilizes the system and substantially improves the handling qualities characteristics. Control reconfiguration on rotorcraft appears viable but limited. Supplementing current rotorcraft with additional control effectors is highly desirable, if not necessary, if control reconfiguration is to be more applicable.