THE BRITISH jet-engine maker Rolls-Royce began making changes to the engines installed on A380 aircraft before last week's drama involving a Qantas superjumbo.

The revelations made by Airbus's chief operating officer, John Leahy, in Sydney yesterday came before an admission by Rolls-Royce last night that it was responsible for the engine failure last week.

Mr Leahy said design changes had been made to newer Rolls-Royce Trent 900 engines before last week's problems in Singapore, but he declined to say what had prompted the change or whether Airbus knew about engine problems previously. ''I don't know but I know they are constantly updating their manufacturing standard,'' he said.

The immediate availability of a redesigned engine raises questions about whether the manufacturer knew there was a problem before Qantas's near-disaster.

In a statement released last night, Rolls-Royce's chief executive, John Rose, said ''we regret the disruption we have caused'' and he signalled an impact on the company's profitability.

However, the statement provided no detail about why or when changes were made to engines for the A380s at production plants in Europe.

Sir John said the failure was confined to a ''specific component in the turbine engine area of the engine [that] … caused an oil fire'' which led to a turbine disc being blown out.

Rolls-Royce said it would replace the relevant part but did not say how long it would take or when Qantas's grounded A380 fleet could fly again. Singapore Airlines, which also uses the engines, has also grounded three A380s, while Lufthansa has replaced one engine.

''This will enable our customers … to bring the whole fleet back into service,'' Sir John said.

Shortly before the Rolls-Royce statement last night, the Airbus chief for the first time described the explosion as ''like a black swan [event with] parts going in all directions''.

Mr Leahy said Rolls-Royce had found a solution which involved installing computer software that would automatically shut down the engine before it exploded.

Mr Leahy conceded it would ''take some time'' to fix the problem as the changes meant the engines would have to be pulled apart.

''These are all electronically computer-controlled engines [so] you would see a failure mode starting and you would immediately shut down that engine so you don't let it get out of control,'' he said. ''They know how to do that and that software fix should be done in the next couple of weeks.''

Airbus will also ship to Australia from its production plants in Europe engines that have been built to a different design standard than those fitted to Qantas's first six A380s.

Rolls-Royce's investigation of the midair incident involving QF32 on November 4 has focused on an oil fire that caused the failure of the number two engine's intermediate turbine disc.

Neither Airbus or Qantas know how long it will take to make the changes to the engines, Mr Leahy said. But he described as ''ridiculous'' suggestions it would take as long as three months.

He said Qantas's chief executive, Alan Joyce, and its operations boss, Lyell Strambi, were ''more than a little upset by a lack of statements from Rolls'' when he met them in Sydney yesterday.