Summary
The Federal Aviation Administration (FAA) proposes to supersede an existing airworthiness directive (AD), applicable to certain Rolls-Royce Corporation (formerly Allison Engine Company) AE 3007 series turbofan engines. That AD currently requires removal of certain compressor cone shafts from service before exceeding new cyclic life limits and replacement with serviceable parts. This proposal would require increasing the cyclic life limit for certain serial numbers of new compressor cone shafts, part number (P/N) 23070729, that are used on AE3007A1/3 and AE3007A1P engines. This proposal is prompted by recent approved changes in engineering and manufacturing processes for new compressor cone shafts P/N 23070729. The actions specified by the proposed AD are intended to prevent low-cycle fatigue (LCF) failure of cone shafts, which could result in an uncontained engine failure and damage to the airplane.