- Associated Press - Thursday, December 2, 2010

SYDNEY, Australia (AP) — Australian investigators on Thursday identified the source of an oil leak that caused a superjumbo jet’s engine to blow apart in midair last month, and said a suspected manufacturing defect in the Rolls-Royce engine was to blame.

They warned airlines the potential flaw could cause engine failure.

The Australian Transport Safety Bureau recommended that the three airlines that use Rolls-Royce’s massive Trent 900 engines on their Airbus A380s go back and conduct more checks now that it had pinpointed the problem area. Three airlines fly a total of 20 the Airbus aircraft.

Earlier warnings blamed an oil leak for a fire and subsequent chain of failures that sent heavy parts flying off an engine on a Qantas A380 shortly after it took off from Singapore on Nov. 4, the most serious safety problem for the world’s largest and newest jetliner.

The ATSB, which is leading the international investigation into the Qantas breakup, added some specifics on Thursday, 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 relates to the potential for misaligned oil pipe counter-boring, which could lead to fatigue cracking, oil leakage and potential engine failure from an oil fire,” the ATSB said in a brief statement.

It called the problem “a potential manufacturing defect.”

Counterboring involves placing a larger hole over a smaller hole to make room for a seal. The ATSB said a misalignment of those holes had produced a thinning of the oil pipe wall and fatigue cracks. That could have led to oil leaking into a section of the engine containing extremely hot gas — a mixture of burned fuel and air. If oil comes into contact with the hot gas, it will burn.

“It is a design error, and obviously a major one,” said Peter Marosszeky, a jetliner maintenance expert at the University of New South Wales.

Rolls-Royce had no comment Thursday morning.

The ATSB recommended close inspections of all Trent 900 engines to look for signs of the problem. Any engines that display such signs should be removed from service, it said.

In response to that recommendation, Rolls-Royce, affected airlines and other safety regulators were taking action to ensure the A380s involved were safe, the ATSB statement said.

The three airlines — Qantas, Singapore Airlines and Germany’s Lufthansa — conducted extensive checks of their Trent 900 engines and modified some parts in compliance with a Nov. 11 directive from the European Aviation Safety Agency. That order was to look for oil leaks in the same section of the engine, but it did not mention a potential source.

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.”

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