Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to Pratt & Whitney JT8D series turbofan engines, that would have required a one-time visual and eddy current inspection of certain stage 3-4 low pressure compressor (LPC) disks and stage 7-12 high pressure compressor (HPC) disks identified by part number and serial number, for arc burns in tie rod, shielding, and pressure balance holes, and, if necessary, repair of tie rod holes. That proposal was prompted by reports of improper fixturing during the electrolytic cleaning process of certain compressor disks at a certified repair station, Avial or Greenwich Air Services, currently GE Engine Services Dallas LP, certificate number RA1R445K of Dallas, Texas, that can result in damage to the disks in the form of arc burns. This action revises the proposed rule by adding a drawdown schedule for removal of affected disks. The actions specified by this proposed AD are intended to prevent compressor disk cracking from arc burns in tie rod holes, shielding holes, or pressure balance holes, which could lead to a fracture of a compressor disk, resulting in uncontained release of engine fragments, inflight engine shutdown, and airframe damage.