Airworthiness Directives; Pratt & Whitney JT9D-7R4 Series Turbofan Engines

This amendment adopts a new airworthiness directive (AD), applicable to Pratt & Whitney (PW) JT9D-7R4 series turbofan engines, that requires replacement of 3rd, 4th, and 5th stage low pressure turbine (LPT) vane retention bolts and nuts, the removal of the 5th stage vane configuration which includes an electro-discharge machined (EDM) slot and replacement with a cast slot configuration, and prohibits the use of uncured anti-gallant compound on vane retention hardware. This amendment is prompted by reports of LPT failures that resulted in uncontained engine failures. The actions specified by this AD are intended to prevent LPT vane failures, which can result in uncontained engine failure, fire, and possible damage to the aircraft.