Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to CFM International (CFMI) CFM56- 5C2/G, -5C3/G, and -5C4 series turbofan engines. This proposal would require a reduction of the low cycle fatigue (LCF) retirement lives for certain high pressure turbine rotor (HPTR) front shafts, HPTR front air seals, HPTR disks, booster spools, and low pressure turbine rotor (LPTR) stage 3 disks. This proposal is prompted by the results of a refined life analysis performed by the manufacturer which revealed minimum calculated LCF lives lower than published LCF retirement lives. The actions specified by the proposed AD are intended to prevent an LCF failure of the HPTR front shaft, HPTR front air seal, HPTR disk, booster spool, and LPTR stage 3 disk, which could result in an uncontained engine failure and damage to the aircraft.