Summary
The FAA proposes to supersede Airworthiness Directive (AD) 2021-05-16, which applies to certain Pratt & Whitney Division (PW) PW4164, PW4164-1D, PW4168, PW4168-1D, PW4168A, PW4168A-1D, and PW4170 model turbofan engines. AD 2021-05-16 requires initial and repetitive replacements of the low-pressure turbine (LPT) 4th-stage air sealing ring segment assemblies with parts eligible for installation. AD 2021- 05-16 also requires initial and repetitive dimensional inspections of the LPT case for bulging and, depending on the results of the dimensional inspections, repair or replacement of the LPT case. Since the FAA issued AD 2021-05-16, the FAA was notified of an inadvertent omission in the LPT 4th-stage air sealing ring segment assembly part numbers. This proposed AD would correct this omission. The FAA is proposing this AD to address the unsafe condition on these products.