On 11 April 2007, shortly after takeoff from Wagga Wagga Airport, NSW, the crew of a de Havilland Dash 8 aircraft registered VH-TQY, noticed an unusual popping sound, followed by a slight vibration through the power levers. On passing 3,800 ft there was a significant drop in torque on the left engine, with associated popping noise. The crew shut down the engine and returned to Wagga Wagga Airport. After initial inspection on the wing, the engine was removed and sent to the manufacturer for disassembly and examination.
The examination found that the engine's number-5 bearing, the high pressure (HP) turbine disc and stub-shaft had failed. These components were sent to the Australian Transport Safety Bureau for further examination. That examination determined the number-5 bearing had failed at its roller cage through fatigue cracking, the stub-shaft had failed under overload and the HP turbine disc had suffered blade tip rubbing.
The operator had experienced a previous number-5 bearing failure on another of its engines. That bearing displayed the same failure pattern of its roller cage and was consecutively serial numbered to the VH-TYQ engine's number-5 bearing.
As a result of this investigation, the engine manufacturer identified a batch of 15 bearings that required replacement and introduced procedures to minimise the risk of further number-5 bearing failures.
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