Summary
We propose to adopt a new airworthiness directive (AD) for Airbus Helicopters Model MBB-BK 117 C-2 helicopters with certain duplex trim actuators installed. This proposed AD would require repetitively inspecting the lateral and longitudinal trim actuator output levers for correct torque of the nuts. This proposed AD is prompted by a design review that the attachment screws can become lost under certain circumstances. The proposed actions are intended to prevent the loss of an attachment screw, which could result in movement of the output lever in an axial direction, contact of a bolt connecting the control rod to an output lever with the actuator housing, and subsequent loss of helicopter control.