Airworthiness Directives; Bell Helicopter Textron, Inc.-Manufactured Model OH-13E, OH-13H, and OH-13S Helicopters

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This document proposes superseding an existing airworthiness directive (AD) for Model OH-13E, OH-13H, and OH-13S helicopters manufactured by Bell Helicopter Textron, Inc. (BHTI). That AD currently requires either recurring liquid penetrant or eddy current inspections of the main rotor blade grip (grip) threads for a crack. If a crack is detected, that AD requires, before further flight, replacing the cracked grip with an airworthy grip. That AD also establishes a retirement life of 1200 hours time-in-service (TIS) for each grip. This proposed AD would add two part numbers (P/N) to the applicability and requires only recurring eddy current inspections of the grip threads. This proposed AD would also require reporting any results of the grip inspections to the FAA Rotorcraft Certification Office. This proposal is prompted by the issuance of an AD for the civil BHTI Model 47 helicopters and the results of an accident investigation, an operator survey conducted by a trade association, various comments concerning the subject of the current AD, and a further analysis of field service data related to the BHTI Model 47 helicopters. The actions specified by this AD are intended to prevent f