The Australian Transport Safety Bureau (ATSB) is investigating a second incident involving the engine oil quantity on a Qantas Airways Airbus A380, which had one of its engines reduced to idle thrust on a flight on 24 February.
This follows a similar incident on 15 February, which also involved another Qantas A380.
In the most recent incident, the aircraft, registration VH-OQG, was operating from Singapore to London Heathrow when its number three Rolls-Royce Trent 900 engine's oil quantity decreased while cruising near Ashgabat in Turkmenistan.
"The crew reduced its thrust to flight idle," says the ATSB, which has commenced investigations into the incident.
The aircraft involved in the incident was built in December 2010, according to Flightglobal's ACAS database.
This is the second such incident involving engine oil quantity on Qantas' A380s, which are all powered by Trent 900s.
On 15 February, the crew of a Qantas A380, registration VH-OQC, reduced the number four engine to idle after observing a gradual decrease in oil quantity. The aircraft was also operating on a Singapore-London Heathrow flight.
The ATSB had said that subsequent inspections into the earlier incident showed that the fitting of the engine's external high pressure / intermediate pressure oil line "had less than the required torque".
The Trent 900's HP/IP bearing module has been linked to last November's uncontained engine failure on a Qantas A380, which has yet to return to service.
In a report on that incident released last December, the ATSB says a manufacturing defect led to cracking within a stub pipe that feeds oil to the HP/IP structure, resulting in oil leakage and an engine failure.