Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Pratt & Whitney (PW) JT9D series turbofan engines. This proposal would require a fluorescent penetrant inspection (FPI) of the rear skirt of the diffuser case for cracks, and, if necessary, blending down to minimum wall thickness to remove cracks and subsequent FPI to determine if cracks have been removed, polishing, and shotpeening. If the cracks are shown by subsequent FPI not to have been removed, this proposed AD would require removing the diffuser case from service and replace with a serviceable part. This proposal is prompted by a report of a diffuser case rupture during takeoff roll that resulted in damage to the aircraft. The actions specified by the proposed AD are intended to prevent diffuser case rupture due to cracks, which can result in an uncontained engine failure and damage to the aircraft.