The NTSB has turned its attention to a fan mid-shaft in its investigation into the July 28 contained failure of a General Electric GEnx engine during a ground test run of an Air India Boeing 787 in Charleston, N.C. The Board confirmed today that the part fractured at the forward end of the shaft, rear of the threads where assembly calls for installation of a retaining nut. The NTSB said it has begun several detailed examinations of the fan mid-shaft, including dimensional and metallurgical inspections.
The GEnx engine uses a “dual shaft” design, meaning one shaft connects the compressor spool at one end to the high-pressure turbine spool at the other end. A longer “fan shaft” connects the fan and booster in the front of the engine to the low-pressure turbine in the back.
Officials have transported the 787’s combined cockpit voice recorder/flight data recorder unit to the agency’s recorders laboratory in Washington, D.C. for processing and readout. Both recordings captured the event and analysis continues.
Along with conducting detailed examination of the engine and metallurgical analysis of its components, investigators have also begun reviewing the engine manufacturing and assembly records, said the NTSB.
The failure in the “back end” of the engine sparked a grass fire at Charleston International Airport during a pre-flight test, forcing the airport to close its main runway for more than an hour.
The incident involved the second of three 787s that have rolled off Boeing’s new assembly line in Charleston, South Carolina. It came roughly a week after Japan’s All Nippon Airways had to ground its five Rolls-Royce Trent 1000-powered 787s following the manufacturer’s discovery of corrosion in a crown gear within an external gearbox during product development testing.
ANA has since returned all five of its airplanes to service.