Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Pratt & Whitney (PW) JT9D series turbofan engines, that currently requires initial and repetitive in-shop or on-wing inspections of the diffuser case rear rail for cracking, and removal, if necessary, of the diffuser case. This action would reduce the allowable crack length, reduce the inspection intervals, and introduce an improved inspection method. This proposal is prompted by a report of an additional diffuser case rupture, and improved understanding of crack propagation rates. The actions specified by the proposed AD are intended to prevent diffuser case rupture, an uncontained engine failure, and damage to the aircraft.