Fault-Tolerant Control on a UH-60 Black Hawk Helicopter using Horizontal Stabilator

The present study proposes an augmentation to the existing control mixing on the UH-60 Black Hawk to utilize the horizontal stabilator as a control effector in the feedback control to compensate for locked-in-place failure in the main-rotor swashplate actuators. Stabilator use has previously been shown to work in an adaptive sense, where the control mixing is remapped in flight once failure is detected. Now it is shown to perform well when the defined mixing utilizes the stabilator even on the undamaged aircraft, removing the need to detect and identify specific failures on the aircraft. Post-failure, the aircraft retains level 1 handling qualities ratings in pitch bandwidth and disturbance rejection. For forward actuator failure, the aircraft departs level 1 in the vertical rate response and pitch stability margin. There is a general improvement in handling qualities ratings as stabilator authority is increased. The aircraft is simulated flying a trajectory to a recoverable state post-failure, where the descent rate and forward speed are appropriate for a rolling landing. Stabilator hardover is also considered; the aircraft is shown to compensate for a stabilator hardover at a moderate flight speed, retaining level 1 handling qualities with only minor degradation relative to the undamaged aircraft except for failure at 80 knots showing level 3 stability margins.