Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan Engines

This document supersedes 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 AD will reduce the allowable crack length, reduce the inspection intervals, and introduce an improved inspection method. This AD is prompted by continued reports of diffuser case ruptures, and improved understanding of crack propagation rates. The actions specified by this AD are intended to prevent diffuser case rupture, uncontained engine failure, and damage to the aircraft.