NTSB Suspects Fan Mid-Shaft Failure In GEnx-1B Incident

U.S. National Transportation Safety Board (NTSB) investigators believe the failure of a General Electric GEnx-1B engine on a taxiing Boeing 787 July 28 stemmed from the failure of a fan mid-shaft. The fan shaft forms the low-pressure spool of the GEnx-1B engine and connects the fan stage with the low-pressure (LP) turbine. The shaft is made up of two main sections, and the failure is thought to have emanated in the torque-retaining nut connecting the two. The NTSB says the GEnx engine “fractured at the forward end of the shaft, rear of the threads where the retaining nut is installed.” It adds that the fan mid-shaft is “undergoing several detailed examinations, including dimensional and metallurgical inspections.” ...