Summary
The Federal Aviation Administration (FAA) proposes to adopt a new airworthiness directive (AD) that is applicable to CFM International (CFMI) CFM56-5B and -7B series turbofan engines. This proposal would require retirement of stage 2 LPT nozzle segments and stage 3 LPT nozzle segments, listed in Table 1 of this proposed AD, from service before accumulating 25,000 cycles-since-new (CSN), or by October 31, 2008, whichever occurs earlier. This proposal would also require installation of new design (either new or reworked) nozzle segments, that would aid in containment of the LPT rotor in the event of LPT shaft failure. This proposal is prompted by a report of an LPT shaft failure caused by a hydromechanical unit (HMU) malfunction that induced a higher than anticipated LPT rotor overspeed. The actions specified by the proposed AD are intended to aid in containment of the LPT rotor in the event of LPT shaft failure, which could result in uncontained engine failure and damage to theairplane.