A preliminary investigation has found a faulty oil pipe in the engine was the most likely cause of the incident that forced the Sydney-bound plane back to Singapore on November 4.

When the No.2 engine exploded at 7000 feet, fragments of the turbine disc and other engine parts tore through the wing and struck the fuselage, wrecking many critical flight systems and causing fuel to stream from the craft.

Australian Transport Safety Bureau chief commissioner Martin Dolan said if it had not been for the actions of the crew, the  flight would not have returned safely to Singapore.

"The aircraft would not have arrived safely in Singapore without the focused and effective action of the flight crew,'' he said.

The damage was extensive, leaving the plane severely disabled, according to the report released by the bureau this morning.

Investigators found pilots faced a barrage of warnings that alerted them to what was wrong, including damage to two independent hydraulic systems and electricity failure.

There were multiple brake system warnings and the wing slats were inoperative, the report said. "Reverse thrust was only available from the No.3 engine, no leading edge slats were available, there was limited aileron and spoiler control, anti-skid braking was restricted to the body landing gear only, there was limited nose wheel steering and that the nose was likely to pitch up on touchdown,'' investigators reported.

The flight computer indicated that they could not apply maximum braking until the nose wheel was on the runway.

That left pilots facing the prospect of being unable to stop the plane on the length of the runway at Singapore's Changi Airport, leading to the prospect of an aerodynamic stall if the plane came in to land too slowly, or a runway overrun if it came in too fast.

After the autopilot function faltered, the pilot in command, Richard de Crespigny, elected to fly the stricken craft in manually from 1000 feet.

He managed to get the main wheels down on the runway, the damaged front wheels six seconds later and threw the No.3 engine into maximum reverse thrust, pulling up the aircraft on the runway with just 150 metres to spare.

But the pilots could not shut down the No.1 engine using either the emergency shut-off or inbuilt fire extinguishers as fuel continued to leak out in the vicinity of hot brakes.

Firefighters on the ground drowned the engine in foam and managed to shut it off.

Passengers did not get off the plane for about an hour.

Much of the investigations then centred on the cause of the explosion.

A faulty oil stub pipe is the leading culprit, which, in a domino effect, is thought to have allowed oil to leak into the engine, catch fire and cause the heavy turbine disc to fracture and fly out of the engine, which along with other internal engine parts, struck the wing and fuselage.

The safety bureau has issued a new warning on the part, requiring operators of the Rolls-Royce Trent 900 engines to carry out immediate inspections of the component on engines fitted to the Airbus A380s, in addition to existing checks.

Those inspections are under way by Qantas, Singapore Airlines and Lufthansa.

Australian Transport Safety Bureau chief commissioner Martin Dolan told reporters in Canberra today if it had not been for the actions of the crew, the flight would not have returned safely to Singapore.

He said the incident was the result of "an uncontained engine failure", which saw a loose disc shear through the left wing and other parts of the aircraft.

"The initial assessment was that the most likely cause of the engine failure was problems with the release of oil into a particular part of the engine, leading to an oil fire and consequences finally in the liberation of the disc elements," he said.

"That was initially responded to by ensuring there were regular inspections for oil leakages in the ... engine in the Airbus 380.

"And on that basis with caution continued operations were seen as acceptable."

Mr Dolan said it was not absolutely certain the pipe was the cause of the problem but said the flaw in the pipe's manufacturing was "significant enough it needs to be dealt with".

Mr Dolan added that if it had not been for the actions of the crew, the flight would not have returned safely to Singapore.

The investigation also found the explosion of the Rolls-Royce Trent 900 engine caused significant damage to the left wing of the aircraft including severed wiring, which meant that the crew could not shut down a second engine.

Qantas today said it had completed the one-off Trent 900 oil feed stub pipe inspections on the first of the two aircraft that have resumed service.

"No issues as outlined by the ATSB were found, and the aircraft will operate to London via Singapore as scheduled this evening,'' the airline said.

Inspection of the second aircraft has commenced.