Transport Canada CF-2019-16

This emergency AD requires revision to the rotorcraft flight manual to ensure that control of the helicopter is maintained in all phases of operation. There have been three occurrences where pilots reported unexpected forces or uncommanded inputs to the directional (yaw) control system. Each of these occurrences took place during ground operations. Subsequent investigation has revealed that a yaw trim runaway can occur while the automatic pedal trim function is operating. Transport Canada found that the current version of the RFM is not adequate to reduce the risk of a trim runaway and ensure that control of the helicopter is maintained. In addition, the RFM does not contain specific procedures for responding to a trim runaway.