SYDNEY — An oil leak was the most likely cause of the midair disintegration of a superjumbo engine last month, investigators confirmed Friday. They said a potentially dangerous manufacturing defect may still exist in Rolls-Royce engines used by 20 of the A380s.
The Australian Transport Safety Bureau released its preliminary report into the blowout that caused a Qantas A380 to make an emergency landing Nov. 4 in what was the most significant safety issue for the world's newest and largest jetliner.
The bureau confirmed earlier suggestions that oil leaking from tubes in a super-hot part of the engine caused a fire, than eventually caused a turbine disc to fly apart and send shrapnel slicing through a wing of the plane.
The ATSB says a manufacturing defect in the Rolls-Royce engine could cause such fires.
The ATSB said Thursday it had found a suspected manufacturing flaw in oil tubes in part of the Rolls-Royce Trent 900 engines and recommended new safety checks for A380s using those engines. The 20 superjumbos using the engines are flown by Qantas, Singapore Airlines and Germany's Lufthansa.
Earlier warnings blamed an oil leak for a fire and subsequent chain of failures that sent heavy parts flying off an engine on the Qantas A380 shortly after it took off from Singapore.
The ATSB, which is leading the international investigation into the Qantas' engine breakup, added some specifics, saying a section of an oil tube that connects the high-pressure and intermediate-pressure bearing structures of the engine was the danger area.
The problem could lead to "fatigue cracking, oil leakage and potential engine failure from an oil fire," the ATSB said.
It said Rolls-Royce, affected airlines and other safety regulators were responding to the finding with action to ensure the A380s involved were safe.
Planes using Trent 900 engines underwent extensive checks and modifications in compliance with a Nov. 11 directive from the European Aviation Safety Agency that warned of dangerous oil leaks following the Qantas incident.
On Thursday, the agency said it had no immediate plans to change that directive following the ATSB's recommendations.
"We believe the safety of the engines is ensured by our previous (Nov. 11) airworthiness directive, namely the engine inspections," spokesman Dominique Fouda said. "But if there are additional findings in the next several days, we reserve the right to change that directive."
Qantas, which grounded its six A380s for three weeks after the blowout, said Friday it had completed the new checks on one of the two A380s it has returned to service, and had found no problem.
Qantas replaced 16 Trent 900s before putting just two of its A380s back into the skies five days ago. The others are still undergoing tests.
Meanwhile, Qantas said Thursday it filed a statement of claim in an Australian court that will allow it to pursue possible legal action against Rolls-Royce if it isn't satisfied with a compensation offer from the engine manufacturer.
Singapore Airlines has 11 superjumbos which use Trent 900 engines and Lufthansa has three.
Singapore Airlines said Thursday it is conducting new checks of its engines. The airline "is complying with the recommendations and carrying out the new inspections, alongside other inspections recommended by Rolls-Royce and included in the directives from the European Aviation Safety Agency," it said in a statement.
Associated Press writers Rod McGuirk in Canberra, Australia, and Slobadan Lekic in Brussels contributed to this story.