Video: Qantas blames A330 incident on laptop computer use

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SEATTLE - It was a roller-coaster ride at 37,000 feet that sent passengers flying. Now some wonder if a laptop was to blame.

“Suddenly the floor wasn't there any more, and then I zipped up to the ceiling and then fell down again,” said one passenger.

And even for those who weren’t injured, it was a scary ride.

“Oh, it's been very awful, I'm just glad to be here,” said another passenger.

The incident happened almost a week ago, and at first looked like severe turbulence. Adults and even babies bounced around the cabin like dolls, breaking through overhead panels.

The big Airbus A330 suddenly went on a roller-coaster ride while cruising between Singapore and Australia, the plane at first climbing, then going into a sudden descent.

“The airplane went back to its cruising altitude and went through another dip, although it wasn't as severe as the first one,” said Todd Curtis, an aerospace engineer who runs the Seattle-based Web site, AirSafe.com, where the gyrations of Qantas Flight 72 are front and center.

The focus is on the plane's elevators, the A330 is a "fly by wire" airplane, meaning signals are sent to the flight control surfaces like elevators electronically. The Boeing 777 is also fly by wire.

While Australian safety authorities doubt consumer electronics used in the cabin caused the plane's flight computers to run wild, they are looking into it.

“There could be a unique perfect storm of events coming together that causes systems to behave in ways totally unanticipated,” said Curtis.

Curtis was part of a Boeing team investigating ways to prevent electrical interference. The issue took off in the early 1990s as people started bringing computers onto planes in large numbers.

The concern was mostly over interference with navigation. Experiments proved inconclusive, yet experts remain sharply divided over the growing influence of electronics on air safety.

One concern is that the advances in consumer electronics are moving faster than aviation engineers can test for potential impacts to a plane's electronics.

Update Oct. 14, 2008:

CANBERRA, Australia (AP) -- A faulty computer unit likely caused a Qantas jetliner to experience two terrifying midair plunges within minutes last week, an Australian investigator said Tuesday.

More than 40 people were injured when the Airbus A330-300 briefly nose-dived twice during a flight from Singapore to the western Australian city of Perth last Tuesday.

Julian Walsh, chief air investigator at the Australian Transport Safety Bureau, said an initial investigation indicated the cause was a computer unit that detects through sensors the angle of the plane against the airstream. He said one of the plane's three such units malfunctioned and sent the wrong data to the main flight computers.

The flight data recorder indicated the plane, carrying 303 passengers and 10 crew, climbed about 200 feet from its cruising level of 37,000 feet and then went into a nose-dive, dropping about 650 feet in 20 seconds, before returning to cruising level, the safety bureau said last week. The sharp drop was quickly followed by a second of about 400 feet in 16 seconds.

The problem is the latest in a series of malfunctions and near-misses for Australia's flagship carrier in recent weeks.

Australian authorities are still investigating an explosion aboard a Qantas 747-400 aircraft carrying 365 people over the South China Sea in July that ripped a hole in the fuselage. That explosion caused rapid loss of pressure in the passenger cabin but no one was injured.

Walsh said the French manufacturer Airbus had notified all operators of A330 and A340 aircraft, which are equipped with the same sensors, about how crews should respond to such a malfunction.

But aircraft are unlikely to be grounded over a malfunction that had never happened before, he said.

"It is probably unlikely that there will be a recurrence, but obviously we won't dismiss that," Walsh told reporters, saying they would investigate the problem further.

The faulty unit will be sent to the U.S. component manufacturer for testing, he said. A report on the accident is to be released next month.

Qantas said the preliminary findings showed that the fault lay with the manufacturer rather than the airline.

"This is clearly a manufacturer's issue and we will comply with the manufacturer's advice," the airline said in a statement.