Airworthiness Directives; Pratt & Whitney Turbofan Engines

We propose to adopt a new airworthiness directive (AD) for all Pratt & Whitney (PW) PW4164, PW4168, PW4168A, PW4164-1D, PW4168-1D, PW4168A-1D, and PW4170 turbofan engines. This proposed AD was prompted by crack finds in the 6th stage low-pressure turbine (LPT) disk. This proposed AD would require removal of affected 6th stage LPT disks. We are proposing this AD to prevent failure of the 6th stage LPT disk, which could lead to an uncontained disk release, damage to the engine, and damage to the airplane.