Secondary oil leak affecting Rolls-Royce Trent 900 engines

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Qantas Airways is modifying or replacing 16 of its Rolls-Royce Trent 900 engines due to a secondary oil leak besides the stub pipe fault, identified last week as the cause behind the Qantas A380 uncontained engine failure on 4 November.

These engines have oil sediment in the high pressure (HP)/intermediate pressure (IP) turbine, a Qantas spokesman says, unable to specify the exact area affected. The engines do not have a stub pipe fault, he says.

"The only stub pipe [fault] we have found is on [an] aircraft awaiting delivery," the spokesman says. On 8 November, the Australian Transport Safety Bureau said three Trent 900s, including one on an A380 to be delivered to Qantas, were found with the stub pipe defect.

The defect has been identified as the cause behind an oil leak and fire which resulted in the uncontained engine failure on the Qantas A380.

Sources familiar with the situation say the oil sediments were only on "A mod" versions of the Trent 900 engine. The Qantas spokesman could not confirm this.

The oil sediments were found after inspections required by an European Aviation Safety Agency airworthiness directive issued on 22 November, the spokesman says.

This directive required inspecting the air buffer cavity and "focusing on the oil service tubes within the HP/IP structure".

Rolls-Royce did not respond to requests for comment on the oil leaks found in Qantas' engines. The engine manufacturer has said it is addressing the stub pipe fault with a programme that involves "replacing the relevant module" although it has not specified what this module is.

"We're either modifying or replacing engines based on advice from Rolls-Royce," the Qantas spokesman says. The modifications require the engine to be brought to the "latest standard", but he declines to specify what changes that entails and if it means bringing the engine to "C mod" standard.

Meanwhile, Singapore Airlines (SIA) is in the process of modifying all the "A mod" variants of its Trent 900s to the "C mod" and will eventually modify the "B mod" variants as well, say sources familiar with the matter.

SIA's spokesman says the engines are covered under TotalCare agreements that the carrier has signed with Rolls-Royce, indicating that the modifications will be paid for by the engine manufacturer.

Asked if the carrier will seek compensation from Rolls-Royce for losses resulting from taking aircraft out of service for the changes, the spokesman says: "The priority at this point is managing the situation from an operational standpoint and ensuring that flights are not disrupted."

However, 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," says a Rolls-Royce spokeswoman. "The previously announced regime of inspection, maintenance and removal is ongoing."

Five of Qantas' 16 affected engines have been changed so far, says the carrier's spokesman. He adds the airline does not have an indication when it will complete the changes.

"It's clear Rolls needs to be able to provide replacement engines," the spokesman says.