Summary
The Federal Aviation Administration (FAA) proposes to adopt a new airworthiness directive (AD) that is applicable to certain Rolls-Royce Corporation (formerly Allison Engine Company) 250-C28 series engines. This proposal would require removal of third stage turbine wheels, part number (P/N) 6899383, with certain serial numbers (SN's), from service before exceeding new, reduced life limits. This proposal would also establish a drawdown program to require the removal of those turbine wheels that exceed the new lower limit. This proposal is prompted by five reports of uncommanded shutdown caused by third stage turbine blade tip fractures, and turbine shroud fractures. The actions specified by the proposed AD are intended to prevent uncommanded shutdown of the engine due to fractures of third stage turbine blade tips and third stage turbine shrouds.