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 (RRC) 250-B and 250-C series turboprop and turboshaft engines with certain part numbers (P/Ns) of compressor adaptor couplings manufactured by Alcor Engine Company (Alcor), EXTEX Ltd. (EXTEX), RRC, and Superior Air Parts (SAP) installed. This AD requires operators to remove from service affected compressor adaptor couplings. This AD results from nine reports of engine shutdown caused by coupling failure. We are issuing this AD to reduce the risk of failure of the compressor adaptor coupling and subsequent loss of all engine power.