Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan Engines

This amendment adopts a new airworthiness directive (AD), that is applicable to Pratt & Whitney (PW) PW4000 series turbofan engines with 2nd stage high pressure turbine (HPT) air seal assembly part number (P/N) 50L976 or P/N 50L960 installed. This amendment requires operators to recalculate 2nd stage HPT air seal assembly cycles-in- service, based on flight hour-to-cycle ratio usage. This amendment also requires upon recalculation, initial and repetitive on-wing borescope inspections of 2nd stage HPT air seal assemblies for cracks based on the newly calculated service life. This amendment also requires the removal from service of any cracked seal assemblies, and the removal of seal assemblies at or before newly calculated service life limits. This amendment is prompted by reports that thirteen 2nd stage HPT air seal assemblies have been found cracked in the rim area. Although these thirteen air seals were operating in the hottest configuration design, which is no longer in service, the current design 2nd stage HPT air seal assemblies are still operating in a temperature environment that is hotter than anticipated. The actions specified by this AD are intended to prevent 2nd stage HPT air seal assembly fracture that could result in an uncontained engine failure.