Australian investigators are reviewing Rolls-Royce's quality control procedures as a probe into last November's uncontained Trent 900 engine failure on a Qantas Airways Airbus A380 continues.
The Australian Transport Safety Bureau (ATSB), in an update on the 4 November 2010 incident released on 18 May, said it is studying how the engine manufacturer could have missed a defect in an oil feed tube, which had been identified as the cause behind an oil fire and the subsequent engine failure.
Investigations into the incident so far have showed that the defect had caused a section of the oil tube to thin out and crack, leading to an internal engine oil fire which weakened the intermediate pressure (IP) turbine disc. The disc then separated from the turbine shaft, puncturing the engine case and wing structure.
Together with the United Kingdom's Air Accident Investigation Branch and Rolls-Royce, the ATSB is "examining the circumstances and missed opportunities with the potential to have detected the reduced wall thickness and offset counter bore of the oil feed tube" before, during and after the manufacturing of the IP turbine module case.
The bureau is also reviewing the quality audits and quality assurance system as part of the manufacturing process and assessing how effective they are in detecting defects, it added.
Following the uncontained engine failure, Rolls-Royce initiated the removal of 53 Trent 900 engines from service due to concerns over the wall thickness of the oil feed tube.
As part of the probe into the incident, investigators and Airbus are also studying the A380 and the system damage that occurred as a result of the engine failure.
Tests using a flight simulator programme developed by Airbus have taken place at the Airbus facility in Toulouse, said the ATSB. "Those tests sought to establish the aircraft's handling capabilities with the simulated damaged fuel transfer system, damaged flight controls and lift augmentation devices, and damaged electrics and electronic systems having effect," it added.
"The simulation found that the aircraft had operated in 'normal control law', in which, regardless of a flight crew's input, computers prevent the exceedance of a predefined safe flight envelope," said the ATSB.
The bureau expects to finish the gathering of information for the investigation by end-July. It aims to complete analysis of that information by May 2012.
The A380 involved in the incident, registration VH-OQA, remains in Singapore "where repair schemes were being developed by Airbus and relevant components were being manufactured to facilitate that repair".