Summary
We propose to adopt a new airworthiness directive (AD) for all Pratt & Whitney Division (PW) PW4074, PW4074D, PW4077, PW4077D, PW4084, PW4084D, PW4090, and PW4090-3 turbofan engines. This proposed AD was prompted by an uncontained failure of a high-pressure turbine (HPT) hub during takeoff. This proposed AD would require an inspection to measure the surface condition of the aft side web/rim fillet of HPT 1st stage hubs and removal from service of hubs that fail inspection. We are proposing this AD to prevent failure of the HPT 1st stage hub, uncontained hub release, damage to the engine, and damage to the airplane.