Fractured fan shaft lead to 787 Dreamliner test failure

US federal aviation authorities probing an engine failure on a Boeing 787 Dreamliner during a pre-delivery test have found the plane, meant to be delivered to India, had a fractured fan shaft.

"A fan mid-shaft on the failed GEnx engine fractured at the forward end of the shaft, rear of the threads where the retaining nut is installed," the National Transportation Safety Board (NTSB) said in a statement, following its investigation on the Dreamliner, which encountered an accident during its recent test run.

Though NTSB continues with its investigation, it said this design failure does not pose immediate safety risk.

The incident happened on 28th July during a pre-delivery taxi test in Charleston, South Carolina.

A contained engine failure is a specific engine design feature in which components might separate inside the engine but either remain within the engine's cases or exit the engine through the tail pipe.

NTSB sent its team of experts on August 1.Officials from Federal Aviation Authority, Boeing and GE Aviation, along with those from NTSB specializing in engine systems and metallurgy travelled to a GE facility in Cincinnati, Ohio to disassemble and examine the failed GEnx engine.

GE is the manufacturer of the GEnx engine.According to NTSB the fan mid-shaft is undergoing several detailed examinations including dimensional and metallurgical inspections.

The GEnx engine is a newly designed aircraft engine, it said.It is a "dual shaft" engine, meaning that 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, NTSB explained.

The cockpit voice recorder and flight data recorder, which is a combined unit on the 787 Dreamliner, was transported to the agency's Recorders Laboratory in Washington, DC for processing and readout, NTSB said adding that both recordings captured the event and analysis is ongoing.

The investigations would continue, it said. 

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