Airworthiness Directives; Sikorsky Aircraft Corporation Model S-76A Helicopters

This amendment revises an existing airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-76A helicopters. That AD currently requires a one-time inspection of the tail rotor blade (blade) spar elliptical centering plug (centering plug) for disbonding and the addition of a retaining pad on the pitch change shaft between the output tail rotor gearbox flange and the inboard tail rotor spar. This amendment contains the same requirements as the existing AD but clarifies that the 500-hour time-in-service (TIS) repetitive inspections, which could cause inadvertent damage, are not required. This AD also incorporates by reference a revised alert service bulletin (ASB) that does not include the 500-hour TIS repetitive inspections. This amendment is prompted by operator confusion about whether the current AD continues to require the 500- hour TIS repetitive inspections. The actions specified by this AD are intended to verify that the FAA has determined that the 500-hour TIS repetitive inspections are not required to prevent the centering plug from disbonding and moving out of position, loss of tail rotor control, and subsequent loss of control of the helicopter.