Tower shaft failures on PWC engines

On 28 April 2005, at approximately 0910 Western Standard Time, a EMB-120ER Brasilia aircraft, registered VH-XUD, was being operated on a chartered flight from Perth, Western Australia to Telfer, Western Australia when the left engine failed. The failure occurred approximately 100km NE of Meekatharra while the aircraft was cruising at 25,000 ft. A PAN alert was declared by the crew and the flight was then redirected by air traffic control to Meekatharra where the aircraft was landed without further incident.

On 3 December 2005, at approximately 0725 Eastern Summer Time, a De-Havilland Canada Dash 8 aircraft, registered VH-TQW, was being operated on a chartered flight from Wynyard, Tasmania to Melbourne, Victoria when the left engine failed. The failure occurred approximately 74 km from Melbourne aerodrome. The crew continued with their approach conducting a single engine landing without further incident.

Subsequent inspection revealed that the tower shaft within the turbomachinery section of the engines of both aircraft had failed. The ATSB received the failed components for examination and analysis. The investigation revealed that fracture of the tower shafts led to the loss of fuel pump operation and subsequent failure of the engines.

It was found that fatigue cracking of the tower shaft had initiated from surface damage that had been produced during the assembly process when the spiral bevel gear was pressed onto the tower shaft.