Another Qantas A380 has finished its flight from Singapore to London on only three engines after a recurrence of a problem with an oil feed line on one of the Rolls-Royce Trent 900 engines fitted to the giant airliner.

This time (on February 24) the A380 flew for the last five hours with one engine reduced to idle (effectively delivering no power, but able to be called upon if needed).  In the earlier, similar incident on February 15 a different Qantas A380 flying the same route encountered reduced oil pressure in an engine while near New Delhi, however the crew didn’t need to reduce the power to idle until they were two hours from London.

Both incidents are being investigated by the ATSB, and in the case of the latest engine-to-idle incident, it happened near Ashgabat in Turkmenistan.

It should be emphasised neither of these incidents posed a significant threat to the safety of the flights, but they definitely pose a risk to Rolls-Royce, which has been caught in the spotlights of airline disfavor after the disintegration of the same engine type on a Qantas A380 just after it had departed from Singapore for Sydney on November 4.

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That incident seriously damaged the very first A380 Qantas put into service, ripping 27 holes in its wing, disabling one of two hydraulic control systems, and compromising the handling of the jet, which is still on the ground in Singapore pending extremely expensive but fully insured repairs.

Plane Talking can report that in each of the Qantas incidents affecting London flights an external high pressure/intermediate pressure oil line was found to have worked loose enough to compromise the oil feed. At least four similar incidents are understood to have occurred on the same engine type fitted to the Singapore Airlines fleet of A380s.

Each of the Qantas A380 flights to London to experience this problem were able to retain a normal cruising altitude, in the first case remaining at 38,000 feet until cleared to descend to Heathrow airport, and maintaining 36,000 feet after the second incident over Turkmenistan.  An A380 can cruise at 41,000 feet, however operational cruise levels over Europe are often reduced because of higher level headwinds or air traffic control directions.

Earlier airliner designs, like the Boeing 747 or big twins engined jets like the A330s or Boeing 777s cannot maintain similar altitudes to the A380 in these circumstances, and the twin engined designs take larger reductions in the form of single engine cruise speeds and altitudes than four engined designs. In a four engined jet the loss of one engine doesn’t necessarily require a landing at the nearest suitable airport, as is the case in twin engined jets, but the usual operating procedure is for the crew of the quad jet to plan for the loss of a second engine, which would require an immediate diversion on the remaining two engines.

The two London incidents should actually make travellers flying A380s between Los Angeles and Sydney or Melbourne more confident, because the five hours on three engines which the Qantas jet flew would have enabled the same jet to back track or divert to a range of airports in California, Hawaii, Tahiti, and Nadi (Fiji) or Noumea or Auckland within that same time at any stage of the 14-15 hours flight time for against headwinds to  Australia, or just over 13 hours when flying to the US.