Airworthiness Directives; Pratt & Whitney PW4164, PW4168, and PW4168A Series Turbofan Engines

Zusammenfassung

The Federal Aviation Administration (FAA) proposes to revise an existing airworthiness directive (AD), applicable to Pratt & Whitney PW4164, PW4168, and PW4168A series turbofan engines. That AD currently requires initial and repetitive torque checks for loose or broken front pylon mount bolts made from INCO 718 material and MP159 material. That AD also requires initial and repetitive visual inspections of the primary mount thrust load path. This proposal extends the cycles accumulated before performing the initial inspection, and reduces the frequency of repetitive inspections for MP159 material bolts, and adds a terminating action to the primary mount thrust load path inspections by introducing a new increased durability engine mount forward mount bearing housing. This proposed revision is prompted by component testing to assess the low cycle fatigue (LCF) life of the MP159 material bolts and the development of a new design forward engine mount bearing housing that meets the 8,000 flight cycle design intent for inspection. 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 an eng