sn26567 wrote:
By the way, why did Qantas order the Trent 972 engine that has a higher trust than the Trent 970 used by most other airlines?
"It uses the extra thrust for maximum weight take-offs on the long-haul routes between Los Angeles, Sydney and Melbourne.
The extra thrust is particularly important on the Melbourne route which, at more than 15 hours, is the longest in the Qantas network."
It comes from this article in "the australian" :
HIGH-POWER take-offs used by Qantas A380s on trans-Pacific routes could be responsible for potentially dangerous oil leaks now under scrutiny.
The leaks may be a possible factor in last week's engine explosion near Singapore.
Engineers believe the higher thrust levels at which the carrier operates its Rolls-Royce Trent 900 engines may result in resonating vibrations that cause oil lines to crack.
The theory has emerged after in-depth inspections uncovered oil in three A380 engines in areas where it should not be present.
All three engines are being replaced as the airline continues with its regime of rigorous checks in the wake of the near disaster on flight QF32 last Thursday.
The Qantas A380 involved, which came into service two years ago, was also used for the trans-Pacific story. The oil leaks in the three engines, found in the intermediate pressure turbine area housing a disc similar to the one that disintegrated in last week's spectacular mid-air drama, caused spotting and pooling that had the potential to spark damaging fires in the engine.
An August oil fire in the same area of a Trent 1000 engine, a derivative of the 900, is believed to be responsible for an uncontained failure on a test bed in Britain.
Qantas A380s have a maximum thrust setting of 72,000lbs, higher than fellow Trent 900 operators Lufthansa and Singapore Airlines but still 3000lbs below the design limit of 75,000lbs. It uses the extra thrust for maximum weight take-offs on the long-haul routes between Los Angeles, Sydney and Melbourne.
The extra thrust is particularly important on the Melbourne route which, at more than 15 hours, is the longest in the Qantas network.
Engineers from Qantas and Rolls-Royce had been looking for reasons the oil leaks had been found in Qantas planes but had not turned up in inspections performed by Singapore Airlines and Lufthansa. They were particularly concerned the engines were relatively new, with the damaged engine on QF32 having recorded just 900 landings and take-offs before it flew apart.
The engines on the three planes are identical except for a computer chip that defines the maximum power rating and the engine is certified to operate at the higher thrust level.
The engineers arrived at what is now the flying kangaroo's lead theory after considering whether the engines might be acting differently during operations from their performance in factory tests.
If the theory pans out, the hope is that Rolls-Royce can devise a way of operating the engine on take-offs and climbs that does not produce the damaging resonance.
The airline is continuing to inspect for other potential engine faults, but Qantas chief executive Alan Joyce said yesterday the focus of the investigation had narrowed in terms of the oil leaks and he was comfortable it was on the right track.
Mr Joyce said the leaks should not be occurring and were outside the normal specifications and design of the aircraft. He said it was too early to be definitive on what the issues causing the engines to perform outside normal parameters were, or how long they would take to be repaired.
"We are working very closely to get a speedy recovery on this, but I won't comment on how long it will take until that investigation is completed," he said.
Mr Joyce said the airline would not resume flying the A380s until it was 100 per cent sure its operations were safe. It has already replaced one of the three affected engines, has a second spare ready to go and is working with Rolls-Royce on finding a third.
