THREE days after the Helios crash, which has prompted unprecedented interest from around the world, experts remain baffled as to what went wrong.
Experts who spoke to newspapers in the US and the UK said that if there was indeed a sudden decompression and temperatures and oxygen levels fell, the pilots and the flight attendants for some reason didn’t react in the way they were trained to.
“It’s odd,” said Terry McVenes, executive air safety chairman for the Airline Pilots’ Association, International. “It’s a very rare event to even have a pressurisation problem and in general crews are very well trained to deal with it.”
He said warnings should go off if an airliner suddenly loses pressure, and pilots are trained immediately to put their oxygen masks on and dive to 12,000 feet, where there’s enough oxygen for people to breathe. Another clue to a sudden pressure loss would have been frost on the windows, he said.
If the fighter pilots could see into the cockpit, the windows couldn’t have been iced over, as they were in the 1999 crash of a Learjet 35 that killed golfer Payne Stewart. Investigators blamed that crash on a sudden decompression.
Robert Benzon, who headed a probe by the US National Transportation Safety Board into Stewart’s death, is to join the Cyprus investigation.
Stewart’s Learjet flew halfway across the US on autopilot before crashing. That investigation found the crew were incapacitated because they didn’t get oxygen when the cabin lost pressure.
Experts told Reuters yesterday it was extremely rare for a plane, particularly a large passenger airliner, to lose oxygen, and emergency systems should have kicked in enabling the pilots to take the plane down to a safe altitude.
Paul Czysz, emeritus professor of aerospace engineering at St Louis University, told a newspaper in the US he could not understand why the co-pilot was slumped over. He said that if a cabin loses pressure suddenly, passengers and flight crew have only seconds to put on oxygen masks before losing consciousness. Death would follow quickly.
“He couldn’t have been unconscious for a small decompression at 34,000 feet,” Czysz said. “Something’s amiss.”
He said that the pilot and the co-pilot would have had five times as much oxygen as the passengers “Even if the pressurisation system was failing, it doesn’t fail instantaneously. Even if it goes fast, you can seal the cabin, you’ve got all the oxygen in the cabin to breathe, you’ve got the masks and you’ve got plenty of time to get to 12,000 feet,” Czysz said.
Jim Hall, former chairman of the National Transportation Safety Board, said it was possible the oxygen in the cockpit failed. “The accident did not have to occur,” Hall said. “It has to be either a training issue or an equipment issue.”
Another expert suggested that perhaps contamination or failure of the oxygen supply had occurred, which could explain why the Helios pilots did not follow normal depressurisation procedures.
“The concept that the oxygen may have somehow been contaminated is a very low-probability event,” he said. “But this is such a weird situation, that’s definitely something I would look at if I were investigating.”
