Bearing compartment module behind secondary Trent 900 oil leak

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Qantas Airways has specified the part it is replacing in some of its Rolls-Royce Trent 900 engines due to a secondary oil leak. That oil leak is unrelated to the stub pipe fault identified earlier this month as the cause behind the Qantas Airbus A380 uncontained engine failure on 4 November.

The part in question is the high pressure (HP)/intermediate pressure (IP) bearing compartment module in "A mod" and "B mod" Trent 900 variants, the spokesman says.

"The 'C mod' doesn't have the faulty bearing compartment," he says.

The HP/IP bearing structure is fed oil from the stub pipe, which had internal fatigue cracking in the A380 incident, leading to an oil leak and engine failure, investigations by the Australian Transport Safety Bureau (ATSB) have found.

Qantas has identified 16 engines with oil sediment in the HP/IP turbine. The engines do not have a stub pipe fault, the spokesman says.

The carrier says those engines "require either modification to the latest standard or full replacement". As of last week five engines had been changed.

According to a source familiar with the matter, the carrier's Trent 900 engines will be upgraded to "C mod" standard. All of Qantas' Trent 900 engines are "A mod" or "B mod" variants, the spokesman confirms.

"With the engines being replaced the expectation is they will be replaced with the 'C mod' [changes] in place or the 'C mod' [powerplant] will be installed in the first place," the source says.

The Qantas spokesman says the decision to modify or replace an engine is being made "based on advice from Rolls-Royce". Rolls-Royce manages Qantas' Trent 900 engines under the TotalCare programme.

Last week, sources said Singapore Airlines is in the process of bringing its "A mod" variants to "C mod" standard and would eventually modify "B mod" variants as well.

"The priority is to make sure you have no 'A mods'," a source has said.

Weakness in the "A mod" and "B mod" variants was raised again last week after the ATSB recommended one-off stub pipe inspections on "A mod" and "B mod" variants only.

"The suspected misaligned counter-boring [in the stub pipe] stopped at a certain point in the production process," a source says.

Rolls-Royce has said "there has been no design change relevant to this failure between A, B and C versions of the engine".

"It is not true that we knew about a problem in the A and B versions of the engine and went on to correct it in the C version," a Rolls-Royce spokeswoman has said.