Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Pratt & Whitney JT8D series turbofan engines, that currently requires a determination of the utilization rate and coating type of the 7th, 8th, 9th, 10th, 11th, and 12th stage high pressure compressor (HPC) disks, and removal, inspection for corrosion, and recoating of those HPC disks based on utilization rate. This action would shorten the inspection interval for certain low utilization disks. This proposal is prompted by reports of an additional uncontained 9th stage HPC disk failure due to corrosion pitting. The actions specified by the proposed AD are intended to prevent fracture of the HPC disks, which can result in uncontained release of engine fragments, inflight engine shutdown, and airframe damage.