Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Pratt & Whitney PW4164, PW4168, and PW4168A series turbofan engines. AD 98-04-14 currently requires initial and repetitive torque checks for loose or broken front pylon mount bolts, replacement, if necessary, with new bolts, and establishment of a new cyclic life limit. This action would add initial and repetitive torque checks of new material MP159 front pylon mount bolts. In addition, this action would add initial and repetitive visual inspections of the primary mount thrust load path. This proposal is prompted by the introduction into service of the new MP159 front pylon mount bolts and the determination through fatigue testing that the forward engine mount bearing housings have insufficient fatigue life expectancy. The actions specified by the proposed AD are intended to prevent front pylon mount bolt and primary mount thrust load path failure, which could result in engine separation from the aircraft.