Summary
This document proposes adopting a new airworthiness directive (AD) for Eurocopter France (ECF) Model EC120B helicopters. This proposal would require inspecting the attachment of the bolted assemblies of the cyclic pitch flight control torque tube (torque tube) for an appropriate locking device. If a bolted assembly is single-locked, the proposed AD would require, if necessary, tightening the self-locking nuts at certain intervals and modifying the torque tube after a certain time. This proposal is prompted by the discovery that some of the attachments of the torque tube were fastened with a single-locking device instead of the intended double-locking device. The actions specified by this proposed AD are intended to prevent separation of the cyclic pitch stick yokes from the torque tube, loss of cyclic control, and subsequent loss of control of the helicopter.