Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Sikorsky Aircraft- manufactured Model CH-54A helicopters, that currently requires initial and recurring inspections and rework or replacement, if necessary, of the second stage lower planetary plate (plate). This action would require the same actions as the existing AD but would add two additional type certificate (TC) holders to the applicability of the AD and change one TC holder who has transferred ownership of the affected helicopters since the issuance of the existing AD. This proposal is prompted by the discovery that the applicability section of the existing AD is incomplete. The actions specified by the proposed AD are intended to prevent failure of the plate due to fatigue cracking which could result in failure of the main gearbox, failure of the drive system, and subsequent loss of control of the helicopter.