Engine failure, 74 km south-east of Melbourne Airport, Victoria, de Havilland Canada Dash 8

At approximately 0725 Eastern Daylight-saving Time on 3 December 2005, during a scheduled passenger service from Wynyard, Tasmania to Melbourne, Victoria, the crew of the de Havilland Canada, Dash 8 aircraft, registered VH-TQW, heard a loud bang from the left side of the aircraft. The crew then observed the loss of the number one (left) engine's torque and oil pressure indication.

Following company procedures, the crew shut down the left engine, advised Melbourne Air Traffic Control of their situation, and continued the approach. A single engine landing was conducted at Melbourne.

A subsequent examination of the aircraft indicated that an internal failure of the left engine had occurred. The engine, a Pratt and Whitney Canada, PW121 model, serial number 120257, was removed from the aircraft and sent to the engine manufacturer's overhaul facility in Singapore for disassembly and examination. The examination was conducted under the supervision of the Air Accident Investigation Bureau of Singapore on behalf of the Australian Tranport Safety Bureau (ATSB).

The engine examination found that the engine accessory gearbox bevel gearshaft (towershaft) had failed, separating into three segments. The failed towershaft disrupted the supply of fuel and oil to the engine, resulting in the engine failure.

As a result of this and other, similar, towershaft failures in this engine type, the results of this occurrence and a broader investigation are included in ATSB Safety Investigation Report 200501912.