Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan Engines

The FAA is adopting a new airworthiness directive (AD) for certain Pratt & Whitney PW4000 series turbofan engines. This AD requires initial and repetitive borescope inspections (BSI) or fluorescent penetrant inspections (FPI) for cracks in the anti-vortex tube (AVT) shelf slots on the 10th stage disk of the high-pressure compressor (HPC) drum rotor disk assembly. This AD results from 47 reports received since 2007 of HPC 10th stage disks found cracked in the AVT shelf slots during shop visit inspections. We are issuing this AD to prevent failure of the HPC 10th stage disk, uncontained engine failure, and damage to the airplane.