Airworthiness Directives; General Electric Company GE90 Series Turbofan Engines

This amendment adopts a new airworthiness directive (AD), applicable to certain General Electric Company (GE) GE90 series turbofan engines, that requires reducing the cyclic life limits for certain fan mid shafts with undesirable microstructure, and removing from service those mid fan shafts prior to exceeding the new limits and replacing with serviceable parts. This amendment is prompted by reports of magnetic particle inspections conducted by the manufacturer identifying segregation in the raw material, resulting in lower fatigue life properties. The actions specified by this AD are intended to prevent fan mid shaft failure, which could result in a total loss of thrust and inflight engine shutdown.