Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to CFM International CFM56-5 series turbofan engines. This proposal would reduce the low cycle fatigue (LCF) retirement lives for certain high pressure turbine rotor (HPTR) front air seals, and provide a drawdown schedule for those affected parts with reduced LCF retirement lives. This proposal is prompted by results of a refined life analysis performed by the manufacturer that revealed minimum calculated LCF lives significantly lower than the published LCF retirement lives. The actions specified by the proposed AD are intended to prevent a LCF failure of the HPTR front air seal, which could result in an uncontained engine failure and damage to the aircraft.