The Australian Transport Safety Bureau (ATSB) has found that fatigue cracking in the blade slots of a high-pressure turbine disk led directly to the uncontained failure of the left engine of a Boeing 767 aircraft that occurred near Brisbane on 8 December 2002.
The aircraft was operating a scheduled passenger service to Auckland, New Zealand and was forced to return to Brisbane airport after the failure. Damage to a wing leading-edge flap from engine debris and the weight of the fuel being carried for the trans-Tasman flight led the flight crew to perform a prepared emergency landing, during which the passengers were instructed to adopt the 'brace' position.
In its investigation report released today, the ATSB found that growth of the slot cracking resulted in the fracture and release of a large segment of the first-stage high-pressure turbine disk, puncturing the engine casing and nacelle, before striking the engine pylon and an adjacent leading edge flap panel. While the reasons for the disk cracking were not conclusively established, the ATSB found that several aspects of the disk manufacturing process or subsequent repair operations could have contributed to crack formation.
As a result of the investigation findings, the engine manufacturer has implemented changes to the disk manufacturing and repair processes and has revised the inspection requirements for the disks fitted to the affected engine model. Both the US Federal Aviation Administration and the Australian Civil Aviation Safety Authority have mandated the new inspection requirements.