Action
Final rule.
Summary
We are superseding airworthiness directive (AD) 2013-15-09 for all Pratt & Whitney Division (PW) PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 turbofan engine models with certain second-stage high-pressure turbine (HPT) air seals installed. AD 2013- 15-09 required initial and repetitive inspections for cracks in second- stage HPT air seals. This new AD expands the applicability of AD 2013- 15-09 to include additional part numbers (P/Ns), requires removal of the mating hardware if the second-stage HPT air seal is found with a through-crack, and adds a mandatory terminating action. This AD was prompted by reports of cracking in the original location on two additional P/Ns and reports of through-cracks in a new location in the second-stage HPT air seal. We are issuing this AD to prevent failure of the second-stage HPT air seal, which could lead to uncontained engine failure and damage to the airplane.