'Human ingenuity prevented Qantas crash'

2010-11-19 16:32
Washington - Even in a cockpit jammed with the most advanced computers, sometimes only a human being will do.

Like when your super-sized airliner is climbing thousands of meters over Indonesia and one of its four engines explodes, shooting flames and blasting shrapnel holes in the wing. And then computer warnings of impending failures of systems across the aircraft start flooding onto cockpit screens.

That was the position five pilots found themselves in two weeks ago when their Qantas jetliner suffered an extraordinary engine breakdown that set off a cascade of other events, each of which by itself would have represented a serious safety problem on an ordinary day.

The Airbus A380, which was carrying more than 450 passengers and crew, is on the leading edge of a new generation of smarter, more highly automated airliners, planes so sophisticated they can sometimes even override a pilot to prevent a critical error. Faced with a crisis, however, it was creative thinking, not computer programming, that landed the plane safely.

"These conditions were a step beyond what the airplane was designed for, and it was the pilots who sorted it out so that it resulted in a safe landing," aviation safety consultant John Cox of St Petersburg, Florida, said in an interview on Thursday.

Richard Woodward, a fellow Qantas A380 pilot who has spoken to the pilots and vice-president of the Australian and International Pilots Association, said the number of failures faced by the pilots was unprecedented.

Growing imbalances

"There is probably a one in 100 million chance to have all that go wrong," Woodward said in an interview.

But it did.

Engine pieces sliced electric cables and hydraulic lines in the wing. Would the pilots still be able to fly the seven-story-tall aircraft?

The wing's forward spar, a beam that attaches it to the aircraft, was damaged as well. Also the wing's two fuel tanks were punctured. As fuel leaked out, a growing imbalance was created between the left and right sides of the aircraft, Woodward said.

The electrical power problems prevented the pilots from pumping fuel forward from tanks in the tail. The aircraft became tail heavy.

That may have posed the greatest risk, safety experts said. If the aircraft had become too far out of balance, the Singapore-to-Sydney jetliner would lose lift, stall and crash.

Two extra pilots

And then there was that incredible stream of computer messages, 54 in all, alerting the pilots to system failures or warning of impending failures.

One warned that a ram air turbine, a backup power supply, was about to deploy, although that never happened, Woodward said. The message was especially worrisome because the system deploys only when main power systems are lost. The smaller backup supply is able only to power vital aircraft systems.

That is "the last thing you need in that kind of situation", he said.

As luck would have it, there were two extra pilots, both captains, aboard on November 4. The flight's captain, Richard de Crespigny, was being given his annual check ride, a test of his piloting skills, by another captain. That man was himself being evaluated by a third captain. There were also first and second officers, part of the normal three-pilot team.

In all, the crew had more than 100 years of flying experience.

"The computer can only do what it knows how to do. They don't get creative very well," Cox said. "These extreme catastrophic conditions, very rare as they may be, point to the need for very high quality training and high calibre individuals flying the plane."

Prioritising problems

De Crespigny concentrated on handling the controls, while the others dealt with the computer alarms and made announcements to the giant planeload of passengers, some of whom said they were frantically pointing to flames streaming from the engine. Working flat out, it took 50 minutes for the pilots to work through all the messages.

When pilots receive safety warnings, they are supposed to check the airline's operating manual and implement specific procedures. But with so many warnings, the Qantas pilots had to sort through and prioritise the most serious problems first.

It is likely that for some of the problems there were no procedures, because no airline anticipates so many things going wrong at once, said John Goglia, a former US National Transportation Safety Board member.

Attention since the November 4 incident has focused on the Airbus 380's damaged Rolls Royce engine. As many as half of the 80 engines that power A380s, the world's largest jetliners, may need to be replaced, Qantas CEO Alan Joyce said on Thursday. That raises the possibility of shortages that could delay future deliveries of the superjumbo.

Qantas has grounded its fleet of six A380s.

Designed with redundancy

Actually, Woodward praised the aircraft, saying it was a testament to its strength that it was able to continue to fly relatively well despite all the problems. But he also said it is likely that the design and location of electrical wiring in the wings might be reconsidered.

Airplanes are supposed to be designed with redundancy so that if one part or system fails, there remains another to perform the same function. That did not always happen in this case, safety experts say.

"The circumstances around this accident will certainly cause the regulatory authorities to take a long and hard look at a number of certification issues," said Goglia, the former National Transportation Safety Board member and an expert on aircraft maintenance.

"What we have got to ensure is that systems are separated so that no single point of failure can damage a system completely," Woodward said. "In this situation the wiring in the leading edge of the wing was cut. That lost multiple systems."

However, Michael Barr, who teaches aviation safety at the University of Southern California, said a commercial aircraft cannot be designed with certainty to withstand a spray of shrapnel, which can inflict damage anywhere. The proper focus, he said, should be on determining what caused the engine to fail and fixing that problem.

All the experts were agreed on one point.

"It must have been an exciting time on that flight deck," Barr said dryly. "It's not something you'd ever want to try again."

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