An in-flight engine shutdown involving a Qantas Airbus A380 on 20 May 2017 has been traced back to cracking caused by corrosion resulting from cleaning chemical residues in one of its Rolls-Royce Trent 900 engines.
Around two hours after taking off from Los Angeles bound for Melbourne, the crew heard a loud bang and felt vibrations through the aircraft, registered VH-OQG. The first officer noticed that the N1 level of engine four was much lower than the other three, and two electronic centralised aircraft monitoring messages were flashed up in quick succession.
As the crew worked through procedures responding to the ECAM messages, they received a message indicating a fire in engine four. In response, they selected the master off switch for the engine and discharged one fire retardant into it, before diverting back to Los Angeles.
The aircraft landed safely at Los Angeles, and subsequently taxiied to its gate where all 484 passengers and 24 crew disembarked without injury.
Minor damage to the aircraft right flap and flap fairing was observed during an engineering inspection, which was attributed to debris exiting the rear of the engine, but no visible indication of fire.
The Australian Transport Safety Bureau states in its final report on the incident that the number four engine failed after corrosion led to fatigue cracking in the low-pressure turbine stage two blades, which separated and caused damage through the engine.
The corrosion was caused by chemical residues from the engine’s last service in July 2015, and R-R identified 12 other engines for removal owing to them having undergone a similar cleaning process.
Five of those engines had been removed at the time of publishing the report, the ATSB adds.
R-R subsequently changed its engine cleaning procedures to remove residual cleaning chemicals, and the European Aviation Safety Agency released an airworthiness directive in June 2018 mandating the replacement of blades that may have been affected by corrosion in accordance with a service bulletin from the manufacturer.
In its safety message, the ATSB commended the crew for their handling of the emergency, while also pointing out that the incident “highlights the importance of reviewing maintenance processes to ensure best practice is followed.”