Airworthiness Directives; Sikorsky Aircraft-manufactured Model CH-54A Helicopters

This amendment adopts a new airworthiness directive (AD), applicable to Sikorsky Aircraft-manufactured Model CH-54A helicopters, that requires an initial and recurring inspections and rework or replacement, if necessary, of the second stage lower planetary plate (plate). This amendment is prompted by cracked plates that have been found during overhaul and inspections. The actions specified by this 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.