An AirAsia X flight crew facing an engine oil pressure problem failed to follow procedures by increasing thrust when they should have shut down the engine down and then tried to restart it after it failed.
The pilots then chose to divert to Melbourne when both Adelaide and Alice Springs, which was just 445km away when the incident occurred, were closer.
The errors are outlined in an Australian Transport Safety Bureau final report into the engine failure in 2016 on a flight from Sydney to Kuala Lumpur with 234 passengers and 10 crew on board.
AirAsia X has since restated flight crew operational requirements for engine restarts and diversion decision making.
It is also using the incident as the basis of a training package on diversions and engine failures.
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The AirAsia X pilots received an “engine 2 oil low-pressure alert’ alert message which investigators later determined was due to shaft failure in the Rolls Royce Trent 700’s oil pressure pump.
The alert required the crew to immediately reduce thrust to idle and then follow an Airbus procedure to shut down the engine if the warning persists.
However, investigators acknowledged there was some ambiguity in the checklist language and believe the crew misinterpreted the term “persists” to mean that they wait to see if the condition persisted.
They instead attempted to trouble-shoot the engine and formed the view that the warning was the result of a gauge failure.
“With the intent of further troubleshooting, the crew then increased the engine’s thrust. This led to the engine stalling and ultimately failing,’’ the ATSB said in the report.
“Despite available guidance and cumulative evidence to the contrary, the flight crew determined that the right engine was not damaged and could be restarted.
“Consequently, and contrary to the operator’s procedures, the flight crew made two attempts to restart this engine. Both restart attempts failed.
“Also contrary to the operator’s procedures, the flight crew elected to divert to Melbourne following the engine failure, bypassing closer suitable aerodromes.”
Among other things, the flight crew decided to divert to Melbourne because they believed the emergency was controlled, they were more familiar with Melbourne, they didn’t believe the other two airports had the relevant emergency services and it had the best maintenance options.
But the ATSB said the decision to fly to Melbourne instead of the closer airports increased the time the aircraft was operating “in an elevated risk environment of single-engine operations”.
ATSB director transport safety Dr Stuart Godley said the incident demonstrated the importance of flight crews adhering to standard operating procedures when responding to alerts.
It also demonstrated the importance as well as the need to design those procedures with clarity, he said.
“Further, the investigation report identifies that where there is not a need for an immediate response, that flight crews look at the full contextural and available information before deciding on a plan of action,” he said.
AirAsia said in a statement that safety always underpinned its operations and it had fully cooperated with the ATSB throughout the review process.
“AirAisa reviewed its internal policies and procedures and corrective action was taken immediately,” it said.
“AirAsia X has achieved IATA’s IOSA certification since 2014 – the global benchmark for upholding the world’s highest safety standards.
“AirAsia operates within the same strict safety guidelines as every airline operating in Australia and we work hard to ensure the highest standards of safety and operational integrity are maintained at all times.
“Safety is about continual improvement and we welcome the findings from the ATSB report, as well as any updates from the manufacturer or feedback that we receive from any regulator that we have ongoing dialogue with, to review any areas to improve.”
