Airworthiness Directives; Schweizer Aircraft Corporation and Hughes Helicopters, Inc. Model 269A, 269A-1, 269B, 269C, and TH-55A Series Helicopters

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This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Schweizer Aircraft Corporation and Hughes Helicopters, Inc. Model 269A, 269A-1, 269B, 269C, and TH-55A series helicopters with certain main rotor (M/R) drive shafts installed, that currently requires a one-time radiographic inspection or a non-destructive inspection of certain M/R drive shafts for cracks, distortion, corrosion, or other surface damage, at specified time intervals or upon the occurrence of specified conditions. This action would require the same inspections as the previous AD, but would expand the applicability of certain inspections to additional models of the affected helicopters and would exclude certain M/R drive shafts from certain inspections. This proposal is prompted by a reevaluation of the previous AD as a result of a comment suggesting the need to expand the applicability of certain inspections to additional models of the affected helicopters and to exclude certain M/R drive shafts from certain inspections. The actions specified by the proposed AD are intended to prevent structural failure of the M/R drive shaft, separation of the M/R from the helicopter, and