Airworthiness Directives; Rolls-Royce Corporation (Formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison) 250-B and 250-C Series Turboprop and Turboshaft Engines

The FAA is adopting a new airworthiness directive (AD) for Rolls-Royce Corporation 250-B and 250-C series turboprop and turboshaft engines with certain part numbers (P/Ns) of gas producer rotor assembly tie bolts manufactured by EXTEX Ltd., Pacific Sky Supply Inc., Rolls- Royce Corporation (RRC), and Superior Air Parts Inc. This AD requires operators to remove from service affected gas producer rotor assembly tie bolts, and install serviceable tie bolts. This AD results from eleven reports of RRC tie bolt failure due to high cycle fatigue. We are issuing this AD to prevent tie bolt failure that could cause loss of engine power, resulting in a first stage turbine wheel overspeed and an uncontained engine failure.