Airworthiness Directive · Amendment 39-21787 · Turbine section
Pratt & Whitney Division Turbofan Engines
This AD applies to Pratt & Whitney Division (PW) PW4164, PW4164-1D, PW4168, PW4168-1D, PW4168A, PW4168A-1D, and PW4170 model turbofan engines with low-pressure turbine (LPT) 4th-stage air sealing ring segment assemblies, part number (P/N) 50N463-01, P/N 50N526-01, or FAA-approved equivalent part numbers, installed.
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.
(1) For affected engines that have either the Talon IIA outer combustion chamber assembly, P/N 51J100 or P/N 51J382, or the Talon IIB outer combustion chamber assembly, P/N 51J381 or P/N 51J500, installed, at the next engine shop visit after the effective date of this AD, remove from service the LPT 4th-stage air sealing ring segment assemblies, P/N 50N463-01, P/N 50N526-01, or FAA-approved equivalent part numbers, and replace with parts eligible for installation.
(2) For affected engines not referenced in paragraph (g)(1) of this AD, at the next LPT overhaul after the effective date of this AD, remove from service the LPT 4th-stage air sealing ring segment assemblies, P/N 50N463-01, P/N 50N526-01, or FAA-approved equivalent part numbers, and replace with parts eligible for installation.
(3) For all affected engines, at each LPT overhaul after compliance with the required actions in paragraph (g)(1) or (2) of this AD, remove from service the LPT 4th-stage air sealing ring segment assemblies, P/N 50N526-01 or FAA-approved equivalent part numbers, and replace with parts eligible for installation.
(4) During each replacement of the LPT 4th-stage air sealing ring segment assemblies required by paragraphs (g)(1) through (3) of this AD, perform a dimensional inspection of the LPT case for bulging in accordance with the Accomplishment Instructions, paragraph 2, of PW Alert Service Bulletin No. PW4G-100-A72-262 Revision No. 1, dated September 3, 2020 (the ASB).
(5) If, during the dimensional inspection of the LPT case required by paragraph (g)(4) of this AD, any LPT case found to be outside the serviceable limits specified in Table 1: Serviceable Limits and Repairs of the ASB, repair or replace the LPT case before further flight.
For the purpose of this AD:
(1) An “engine shop visit” is the induction of an engine into the shop for maintenance involving the separation of pairs of major mating engine flanges H through P. The separation of engine flanges solely for the purpose of transportation without subsequent engine maintenance does not constitute an engine shop visit.
(2) An “LPT overhaul” is when the LPT rotor is removed from the engine, all four disks are removed from the LPT rotor, and all blades are removed from the disks.
(3) “Parts eligible for installation” are LPT 4th-stage air sealing ring segment assemblies, P/N 50N526-01, or FAA-approved equivalent part numbers, with zero flight cycles since new or with a P/N not mentioned in this AD.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
