Action
Final rule.
Summary
The FAA is superseding Airworthiness Directive (AD) 2021-05-16 for certain Pratt & Whitney Division (PW) PW4164, PW4164-1D, PW4168, PW4168-1D, PW4168A, PW4168A-1D, and PW4170 model turbofan engines. AD 2021-05-16 required 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 required 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. This AD was prompted by notification to the FAA of an inadvertent omission in the LPT 4th-stage air sealing ring segment assembly part numbers. This AD requires initial and repetitive replacements of the LPT 4th-stage air sealing ring segment assemblies with parts eligible for installation. This AD 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. The FAA is issuing this AD to address the unsafe condition on these products.