THIS STORY HAS BEEN FORMATTED FOR EASY PRINTING

With economic pressure, ash risks even less clear

By Seth Borenstein
Associated Press / April 21, 2010

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WASHINGTON — Six days after volcanic ash shut down the skies over much of Europe, planes are back in the air, but science still can’t answer the question: Is it safe to fly again?

Mother Nature has given Europe a lesson in risk, aviation technology, scientific uncertainty, and economics. And how these fields intersect is messy.

Watching the same people who earlier said it was too dangerous to fly now say it’s safe “is just more proof that risk is a subjective idea,’’ said David Ropeik, a risk perception specialist at Harvard University.

When people turn to science for answers, they get a lot of equivocation.

“We really don’t have as good a handle as we should on the ash particle size, the ash concentration, and most important, just exactly how high the ash got up into the atmosphere,’’ said Gary Hufford, a US government volcano specialist based in Anchorage.

Would he get on a plane and fly into the ash cloud? “I would be cautious,’’ he said in a conference call yesterday afternoon.

Abrasive, gritty ash can damage jet engines, and even experts don’t know what density levels are safe. For that matter, they can’t say how much ash from the Icelandic volcano is floating in any one spot along the air traffic routes or where it is going next.

But airlines know what canceled flights can do to their bottom line. And passengers know when a canceled flight crosses the line from inconvenience to pain.

So Monday night and into yesterday, planes began flying across most of Europe — many for the first time since April 14. Safety officials called for closer inspections of planes for damage after they land.

As airports reopen, passengers may have to decide for themselves what risk is acceptable.

“With the amount of uncertainty, this now, I think, is a very hard decision,’’ said Paul Fischbeck, a risk analysis specialist at Carnegie Mellon University and a former military pilot. “How much risk are you willing to accept to reduce economic hardship and inconvenience?’’

At stake are billions of dollars and millions of stranded passengers, said Fischbeck. But if a plane goes down, the airline would be shut down by lawsuits, he said.

When the Eyjafjallajokull volcano first spewed, the answer was simple. Authorities usually shut down airspace when there’s volcanic ash.

“Standard safety procedure is: Don’t go there if you don’t know,’’ said Michael Fabian, a professor of mechanical engineering at Embry Riddle Aeronautical University in Prescott, Ariz.

But the days went on and the pain for airline companies and passengers increased and then people started questioning: How bad is it? How do you know?

“Hard questions reveal that the science isn’t as settled as first presented,’’ said George Gray, a specialist on risk at George Washington University and former science adviser to the US Environmental Protection agency.

Engineers worry about immediate, catastrophic damage that could occur if the ash dust congeals in an engine turbine, blocking air flow and shutting it down, Fabian said. In 1989, a Boeing 747 flew through volcanic ash over Alaska, all four engines failed, and the plane dropped more than 2 miles in five minutes before engines restarted. Ash can also cause long-term, damage to planes that could lead to later disasters if not dealt with.

Fabian said engineers know little about the risks from volcanic ash because it would take many hours and great expense to do repeated tests. And tests would be needed for the 20 different types of engines currently flown.

Beyond that, atmospheric scientists can’t say how much ash is in any one place or predict how or when it will disperse.