Summary
The FAA proposes to supersede an existing airworthiness directive (AD) for Rolls-Royce Corporation (formerly Allison Engine Company) (RRC) 501-D series turboprop engines. That AD currently requires removal from service of certain turbine rotor components at reduced life limits. This proposed AD would require the same actions but adds two new life limits. This proposed AD results from RRC reevaluating and revising component life limits for 501-D22 series turboprop engines. We are proposing this AD to prevent uncontained turbine rotor failure resulting in an in-flight engine shutdown and possible damage to the airplane.