The pilots of a super-sized Qantas Airlines jet grappled with an extraordinary, cascading series of critical system failures after an engine disintegrated earlier this month, pilots and aviation safety experts familiar with details of the event say.
The pilots were inundated with 54 computer messages alerting them of system failures or impending failures during the two-hour airborne drama with more than 450 passengers aboard, said Richard Woodward, a vice president of the Australian and International Pilots Association who has spoken with all five pilots who were in the cockpit.
With only about eight to 10 messages able to fit on a computer screen, pilots watched as screens filled only to be replaced by new screenfuls of warnings, he said.
"I don't think any crew in the world would have been trained to deal with the amount of different issues this crew faced," Woodward said.
"The amount of failures is unprecedented," he said. "There is probably a one in 100 million chance to have all that go wrong."
Attention since the Nov. 4 incident has focused on one of the Airbus 380's four Rolls Royce engines, which experienced an unusual type of failure that blasted out shrapnel-like shards of metal, punching holes in the plane's left wing.
As many as half of the 80 Rolls-Royce engines that power A380s, the world's largest jetliners, may need to be replaced, Qantas CEO Alan Joyce said Thursday.
The 40 potentially faulty engines would need to be replaced with new engines while the fault is fixed, raising the specter of engine shortages that could delay future deliveries of the 7-story-tall superjumbo.
Qantas has grounded its fleet of six A380s, each powered by four of the giant Rolls-Royce Trent 900 engine.
But the picture emerging of the pilots' struggle to save the plane and its passengers has also raised questions about facets of the plane's design.
Airplanes are supposed to be designed with redundancy so that if one part or system fails, there is still another to perform the same function. That didn't always happen in this case, safety experts said.
"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 John Goglia, a former National Transportation Safety Board member and an expert on aircraft maintenance.
The shrapnel sliced electric cables and hydraulic lines in the wing. The wing's forward spar -- one of the beams that attaches the wing to the plane -- was damaged as well. And 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 plane, said and a Qantas A380 pilot.
The electrical power problems prevented pilots from pumping fuel from tanks in the tail to tanks farther forward, he said. Gradually the plane became tail heavy and the aircraft's center of gravity began to move, he said.
That may have posed the greatest risk, safety experts said. If a plane gets too far out of balance, it will stall and crash.
Among the messages pilots received was a warning that the ram air turbine -- a backup power supply -- was about to deploy, although that didn't happened, Woodward said. The message was especially worrisome because the system only deploys when main power systems are lost, he said. The smaller backup supply is only able to power vital aircraft systems.
Airbus planes -- especially newer, cutting-edge planes like the A380 -- rely more on electrical signals and less on hydraulics than earlier generations of airliners.
Qantas declined to comment on anything that occurred in the cockpit during the emergency, or on damage to the plane.
"An international investigation is continuing into the QF32 incident and Qantas is assisting in those investigations," Qantas spokesman Simon Rushton said. He said the airline retains confidence in the A380.
Airbus spokesman Justin Dubon, pointing to the investigation by Australian safety authorities of the incident, said, "We can't feed any speculation. We don't know the full facts. The A380s is certified to the latest and highest standards."
Woodward praised the plane, saying it was a testament to its strength that it was able to continue to fly relatively well despite all the problems that were occurring. But he also said it's likely new consideration will be given to the design and location of the plane's electrical wiring in the wings.
"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.
It was just luck that there happened to be five experienced pilots -- including three captains -- aboard the plane that day. The flight's captain, Richard de Crespigny, was being given his annual check ride -- a test of his piloting skills -- by another captain. That captain was himself being evaluated by a third captain. There were also first and second officers, part of the normal three-pilot team.
Even with five pilots working flat-out, it took 50 minutes to prioritize and work through each of the messages -- necessary steps to determine the status of the plane, Woodward said.
Contributing to this report were Rohan Sullivan and Greg Keller in Sydney and Joshua Freed in Minneapolis, Minn.,