Airworthiness Directives; Sikorsky Aircraft Corporation-Manufactured (Sikorsky) Model Helicopters (Type Certificate Currently Held by Erickson Air-Crane Incorporated)

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We are superseding Airworthiness Directive (AD) 97-19-10 for Sikorsky Aircraft Corporation-manufactured Model S-64E helicopters (type certificate currently held by Erickson Air-Crane Incorporated (Erickson)). AD 97-19-10 required inspecting and reworking the main gearbox (MGB) assembly second stage lower planetary plate (plate). This action establishes or reduces the life limits for certain flight- critical components, removes from service various parts, requires repetitive inspections and other corrective actions, and requires replacing any cracked part discovered during an inspection. This AD is prompted by further analysis performed by the current type certificate holder and the service history of certain parts. The actions specified in this AD are intended to prevent a crack in a flight critical component, failure of a critical part, and subsequent loss of control of the helicopter.