Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Pratt & Whitney JT9D series turbofan engines, that currently requires initial and repetitive eddy current inspection (ECI) or fluorescent penetrant inspection (FPI) for cracks in first stage high pressure turbine (HPT) disk cooling air holes. This action would require initial and repetitive FPI for cracks in cooling air holes of additional first stage HPT disks, and replacement with serviceable parts. In addition, this action would require initial and repetitive FPI for cracks in tie bolt holes of certain other affected second stage HPT disks installed in PW JT9D series turbofan engines. This proposal is prompted by reports of a cracked cooling air hole on one first stage HPT disk, and a cracked tie bolt hole on one second stage HPT disk. The actions specified by the proposed AD are intended to prevent turbine disk failure due to cooling air hole or tie bolt hole cracking, which could result in an uncontained engine failure and damage to the aircraft.