Airworthiness Directives; Pratt & Whitney PW4074, PW4074D, PW4077, PW4077D, PW4084, PW4084D, PW4090, PW4090D, PW4090-3, and PW4098 Turbofan Engines

摘要

The FAA is superseding an existing airworthiness directive (AD) for Pratt & Whitney PW4074, PW4074D, PW4077, PW4077D, PW4084, PW4084D, PW4090, PW4090D, PW4090-3, and PW4098 turbofan engines. That AD requires initial and repetitive visual and borescope inspections of the No. 3 bearing weep tube and turbine exhaust case (TEC), and removal of the high pressure turbine (HPT) assembly and replacement of any heat distressed HPT assembly hardware if oil wetting or staining is found. This ad requires the same actions. This AD results from the finding of a significant reference error in one of the borescope inspection compliance paragraphs. We are issuing this AD to prevent thermal distressed HPT assembly hardware from remaining in service, which could result in a cracked HPT stage 1 disk or HPT stage 1-2 air seal and an uncontained engine failure.