Action
Notice of proposed rulemaking (NPRM).
Summary
We propose to adopt a new airworthiness directive (AD) for all Pratt & Whitney Division (PW) turbofan engine models PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 with a certain 2nd-stage high-pressure turbine (HPT) air seal part number (P/N) installed. This proposed AD was prompted by discovery of cracks in the 2nd-stage HPT air seals. This proposed AD would require, for those air seals that meet certain cycles since new (CSN) criteria, inspection and removal from service of HPT air seals that fail inspection. We are proposing this AD to prevent failure of the 2nd-stage HPT air seal, which could lead to an uncontained engine failure and damage to the airplane.