Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain General Electric Company (GE) GE90 series turbofan engines. This proposal would reduce the cyclic life limits for certain mid fan shafts with undesirable microstructure, and remove from service those mid fan shafts prior to exceeding the new limits and replace with serviceable parts. Reports of magnetic particle inspections conducted by the manufacturer identifying segregation in the raw material, resulting in lower fatigue life properties, prompted this proposal. The actions specified by the proposed AD are intended to prevent mid fan shaft failure, which could result in an uncontained engine failure and damage to the aircraft.