Summary
The FAA proposes to adopt 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 proposed AD would require operators to remove from service affected gas producer rotor assembly tie bolts. This proposed AD results from eleven reports of RRC tie bolt failure due to high cycle fatigue. We are proposing 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.