Fixing Rolls-Royce’s disposable A380 engines

Trent 900 side view.JPGA Rolls-Royce Trent 900 engine seen on Qantas A380 VH-OQC at Sydney on 6 November. Photo: Will Horton

Building the world’s largest passenger aircraft and the engines to power it was no easy feat. But now, fixing the beleaguered Rolls-Royce Trent 900 engines that power A380s from Qantas, amongst other carriers, will be a new challenge.

Qantas operates the Trent 972 engine, which delivers a maximum thrust of 72,000 lb. The only other current two Trent 900 operators, Lufthansa and Singapore Airlines, operate the Trent 970 with a maximum 70,000 lb of thrust.

That extra 2,000 lb on each engine is needed to get the A380 off LAX’s relatively short runways in a headwind with a full load for a 14 hour flight in light of Airbus adding structural weight to the A380 in 2007. Prior to that time Qantas planned to use the 70,000 lb Trent 900 variant.

However, the extra thrust exposes the engine to 540 psi at P30, which causes the engine to experience “high severity”, the affidavit says. Rolls-Royce’s interim suggestion to Qantas has to been to derate the engines in order to “reduce the engine pressure ratio in the ‘P30′ area of the engine and therefore increase the life of the oil transfer tubes within the HP/IP support structure”, the affidavit says.

The oil transfer tubes are the suspected cause of an oil leak that started a fire and then the uncontained engine failure. The derated thrust, however, reduces payload and makes the LAX-Australia route unprofitable.

The Trent 900 has had three modification standards: A, B, and C. Qantas and Rolls have agreed the carrier should not operate at all the “A mod”. The “B mod” and “C mod” can be used, even for maximum thrust–but only 75 times. After the 75th maximum thrust take-off, the engine needs to be replaced, Qantas’ head of engineering and maintenance told lawyers preparing the affidavit.

Rolls in 2000 quoted Qantas a list price of US$12.85 million per Trent 900. If four engines were only to be used 75 times their cost would be $685,333 per flight, or on a full flight with 450 passengers, an extra $1522.96 per passenger. Mind you, fares across the Pacific can easily be had for two-thirds that price.

That is, simply, uneconomical. At some point it would be cheaper for Rolls to extend LAX’s runways, including paying people to move out of houses and businesses in the way, than pay for new engines every 75 flights. (As part of the TotalCare agreement between Rolls and Qantas, Rolls looks after and repairs Qantas’ engines.)

The likely repair will be to figure out a way to reduce the engine pressure ratio and/or strengthen oil pipes. But how? That’s the $12.85 million dollar question.

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