Airworthiness Directives; Turbomeca S.A. Arriel -1B, -1D, and -1D1 Series Turboshaft Engines

This amendment adopts a new airworthiness directive (AD) that is applicable to Turbomeca S.A. Arriel -1B, -1D, and -1D1 series turboshaft engines. This amendment requires replacement of modules M03 modified to TU 204 standard with modules M03 not modified to TU 204 standard. This amendment is prompted by several reports of 2nd stage gas generator turbine blade failures. The actions specified by this AD are intended to prevent 2nd stage gas generator turbine blade failure resulting in uncommanded engine in-flight shutdown.