Sikorsky S-76C, G-XXEB
During approach and descent to Denham Aerodrome, with autopilot disengaged, the pilot became aware of the aircraft yawing right. The pilot made a corrective pedal input and felt a restriction in the left pedal which also appeared to have an effect on the neutral yaw pedal position. The pilot declared a PAN and conducted an uneventful running landing. The yaw control system abnormality remained until the aircraft was shut down. The fault was later traced to the Pedal Damper Trim Actuator (PDTA). A detailed examination of the PDTA found that a small metal sealing ball had split within the solenoid valve. This caused an internal leakage of hydraulic pressure resulting in a PDTA trim runaway input and restriction within the helicopter yaw control system.
Sikorsky S-76C G-XXEB 01-14.pdf (233.52 kb)