Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to Pratt & Whitney (PW) JT9D-7R4 series turbofan engines. This proposal would require replacement of 3rd, 4th, and 5th stage low pressure turbine (LPT) vane retention bolts and nuts, and the removal of the 5th stage vane configuration which includes an electro-discharge machined (EDM) slot and replacement with a cast slot configuration. This proposal is prompted by reports of LPT failures that resulted in uncontained engine failures. The actions specified by the proposed AD are intended to prevent LPT vane failures, which can result in uncontained engine failure, fire, and possible damage to the aircraft.