Last year, when the Mount Redoubt volcano blew up southwest of Anchorage, Alaska Airlines’s response was to ground its fleet, divert flights and wrap the engines in the parked planes in plastic.
That is how seriously airlines take volcanic ash. Of course, an ash cloud has never hovered over an airspace as congested and critical as Europe’s.
As airlines were forced to ground flights for five days in the wake of the eruption of a volcano in Iceland, some criticized the European authorities as having overreacted and needlessly stranding millions of passengers and tons of cargo. But with flights scheduled to slowly resume Tuesday, the industry’s record shows a very low level of tolerance for getting airplanes anywhere near volcanic ash.
“We’ve been flying for over 100 years, but volcanoes have been around for a lot longer and frankly, they win,” said Capt. Rory Kay, the head of air safety at the Air Line Pilots Association and a Boeing 757 and 767 pilot. “We have to treat them with the greatest respect.”
Guidelines say avoid ash
Even though volcanoes have always been a threat to aviation, there are no guidelines for dealing with volcanic ash clouds other than to avoid them — in contrast with the standards for dozens of other potentially hazardous situations like landing in low visibility.
Jet engines are vulnerable to ash, which can cause engines to stall, or shut down. The ash, which acts like millions of pieces of shredded glass, can also scrape the paint off the planes or sandblast the windshield. Ash clouds are also tricky to make out, since they can resemble vapor clouds.
“There is almost no day where there is no volcanic ash cloud somewhere in the world that people are tracking and trying to avoid,” said Tom Murray, the director of the Volcano Science Center, part of the United States Geological Survey, in Anchorage. “It is that frequent. There is a lot of activity you need to keep track of.”
In most cases, flights are rerouted or diverted, and people do not notice, said Robert W. Mann Jr., an aviation industry expert in Port Washington, N.Y.
“Ash clouds happen all the time, but thankfully they just don’t happen in one of the most densely populated, most densely traveled areas in the world,” Mr. Mann said. “If it happens in the middle of the Pacific, it’s like a tree falling in the middle of a forest. You don’t really notice it.”
From 1953 to 2008, just 89 planes were reported to have encountered an ash cloud, said Denis Chagnon, a spokesman for the International Civil Aviation Organization in Montreal.
But the real perils were demonstrated in June 1982, when a British Airways Boeing 747, flying to Australia from Malaysia, flew directly into an erupting volcano’s ash cloud.
One after the other, all four engines shut down within minutes, turning the aircraft into a overweight glider. After 15 harrowing minutes, the plane had dropped about 20,000 feet, enough for the plane to fly under the ash cloud and allow for clean air to feed the jet turbines. At that point, the crew was able to restart the engines, which allowed for an emergency landing.
‘You do not want to fly in an ash cloud’
Another Boeing 747, belonging to Singapore Airlines, lost power in three of its four engines when it hit ash from the same eruption. And in December 1989, all four engines of a three-month-old KLM Boeing 747 shut down when the plane encountered ash from Mount Redoubt. The plane descended to 12,000 feet from 25,000 feet before the crew was able to restart two of the engines.
The lessons are simple, said Bob Graves, director of operations at Alaska Airlines. “You do not want to fly in an ash cloud, and we did not see any data that would persuade us there would be safe level to fly through ash,” he said. The aviation authorities in Europe have been using computer models to predict the presence of ash. But those models are not precise enough to say where it is safe to fly.
“Ash cloud detection is very primitive,” said Paul Tronsor, the head of FedEx’s global operations control. He said that volcanoes affect a route flown by FedEx about once a month. FedEx flight operators, he said, always use a buffer zone of about 400 to 500 miles.
FedEx flew its first flight out of Paris on Monday, Mr. Tronsor said, and will resume partial operations from several European airports on Tuesday.
The three Boeing 747 episodes of the 1980s led to the creation of a system of global monitors of volcanic activity to warn pilots about the threat caused by ash clouds.
That is the system that shut down Europe’s airspace, after Norwegian air traffic controllers first sounded the alarm in the middle of last week.
‘Reviewing past engine experience’
Peggy Gilligan, the associate administrator for aviation safety at the F.A.A., said that General Electric Aircraft Engines has taken the lead in a government and industry program, which began this weekend, to assess the ability of jet engines to operate with ash. A spokeswoman for G.E., Deborah Case, said that the company was “reviewing past engine experiences with volcanic ash” to see how they performed and what level of damage was sustained. Ms. Case was not able to say when G.E. expected to have results from its review.
Setting a standard for ash may be possible, in theory. For the moment, the models tend to point to a black-and-white solution, “while in fact what we’re dealing with here are various shades of gray,” said Barry Humphreys, the chairman of the British Air Transport Association, the trade group of the British carriers.
“There’s no doubt at all that there are thick clouds of this stuff out there and it is dangerous to fly through thick clouds, but there’s areas around the edge where it’s much thinner, and areas where there’s no cloud.”
The article, "," first appeared in The New York Times.