Airworthiness Directives; Pratt & Whitney PW4074, PW4074D, PW4077, PW4077D, PW4084, PW4084D, PW4090, PW4090D, PW4090-3, and PW4098 Turbofan Engines
The FAA is adopting a new airworthiness directive (AD) for Pratt & Whitney PW4074, PW4074D, PW4077, PW4077D, PW4084, PW4084D, PW4090, PW4090D, PW4090-3, and PW4098 turbofan engines. This AD requires borescope inspection of the No. 3 bearing weep tube, on engines with high oil consumption that troubleshooting procedures fail to determine the source of oil loss. This AD also requires for all engines, initial and repetitive visual inspections of the turbine exhaust case (TEC) in the vicinity of the No 3 bearing oil vent tube for evidence of oil wetting or staining. If the vent tube borescope inspection is unsuccessful due to tube blockage, this AD also requires borescope inspections of the high pressure turbine (HPT) assembly for oil wetting or staining. This AD also requires removal of the HPT assembly and replacement of any heat distressed HPT assembly hardware if oil wetting or staining is found. This AD is prompted by reports of engine HPT assembly hardware being damaged as a result of thermal distress from oil igniting after leaking from the No. 3 bearing compartment. 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.