Summary
The FAA proposes to adopt a new airworthiness directive (AD) for Rolls-Royce Corporation (formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison) (RRC) models 250-C30, 250-40, and 250-C47 series turboshaft engines. This proposed AD would add an additional life limit for third- and fourth-stage turbine wheels. This proposed AD results from analysis by RRC of failures of third- and fourth-stage turbine wheels. We are proposing this AD to prevent loss of power, possible engine shutdown, or uncontained failure.