Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan Engines

This amendment adopts a new airworthiness directive (AD), applicable to certain Pratt & Whitney PW4000 series turbofan engines, that reduces life limits of certain 4th stage low pressure turbine (LPT) disks. It also allows the original life limits of the disks to be restored if reoperation is performed to incorporate the original slotted cooling hole configuration. This amendment is prompted by reports that a change of a cooling hole geometry, which was introduced in the design of certain 4th stage LPT disks, inadvertently caused a reduction on the cooling air flow to the disk and an increased level of stress. The actions specified by this AD are intended to prevent an uncontained disk failure and damage to the aircraft.