Operational issues - have they Please read the manual?
HIGH-POWER take-offs used by Qantas A380s on trans-Pacific routes could be
responsible for potentially dangerous oil leaks now under scrutiny as 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 Continued on Page 2 Continued from Page 1 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.
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