During the take-off roll, the crew of the Boeing 767 heard a loud bang sound so they immediately discontinued the takeoff. A runway inspection by the airport safety officer and fire crews found fuel and engine components on the runway. The aircraft was towed to the company maintenance facility and the runway was reopened after approximately 30 minutes.
Maintenance inspection found metal particles in the tailpipe of the engine. An engine change was carried out and the aircraft was returned to service.
Disassembly of the removed engine found that a blade in the second stage high-pressure turbine (HPT) had failed. The liberated blade then caused catastrophic secondary damage to components downstream during its passage through the engine. The manufacturer's design features for failure containment prevented damage to the aircraft or other systems by trapping high-velocity debris within the engine. Some low-velocity debris was ejected from the tailpipe.
The remaining segment of the blade firtree root in the HPT disc was retrieved and examined. The examination revealed the presence of a casting defect in a cooling-air channel web of the firtree root. This led to initiation of fatigue crack growth and eventual fracture of the turbine blade. Fatigue crack initiation was associated with a discontinuity created during casting. It was evident that the fatigue crack did not intersect the outer surface of the blade prior to failure.
After completion of the examination, the blade was returned to the engine manufacturer who has been requested to furnish a report on the metallographic sectioning examination of this component.
With the conclusion of the investigation into this occurrence, the following recommendations are made:
The Australian Transport Safety Bureau (formerly the Bureau of Air Safety Investigation) recommends that the engine manufacturer General Electric identify the source of the casting defect of the failed HPT blade.
The Australian Transport Safety Bureau (formerly the Bureau of Air Safety Investigation) recommends that the engine manufacturer General Electric review the adequacy of turbine blade manufacturing process controls to reduce the likelihood of blades containing casting defects being released into service.
The Federal Aviation Administration should note the safety deficiency identified in this document and take appropriate action.
|Date:||04 November 1999||Investigation status:||Completed|
|Time:||1006 hours ESuT|
|Release date:||07 March 2000||Occurrence category:||Incident|
|Report status:||Final||Highest injury level:||None|
|Aircraft manufacturer||The Boeing Company|
|Type of operation||Air Transport High Capacity|
|Damage to aircraft||Nil|
|Departure point||Melbourne, VIC|