Researchers have no clear guidelines on air travel through ash-filled skies
The threat of volcanic ash to airplane engines has been known and monitored for several decades, but no clear standards have been set for when aircraft are allowed to fly through the ash and when they must stay put.
According to Richard Wunderman of the Smithsonian Institution's Global Volcanism Network, who is also part of a national working group that studies the issue, scientists and engineers simulated the effects of ash on grounded airplane engines in the early 1990s and found that it was significant.
A 1994 report by the U.S. Geological Survey described the problems -- and the fact that many busy aviation routes pass over areas with active volcanoes -- but progress has been limited in terms of providing instruments that would tell pilots that they've entered an ash cloud, filters that could protect the engines, or firm guidelines on how much ash is too much ash.
"Unfortunately, the rate of progress has been slow," Wunderman said. "We have a lot of science underway to understand volcanic ash and the threshold limits for safe flying, but where that line is we really don't know."
He said that although ash monitoring has improved significantly in recent years, it remains almost impossible to know where an ash cloud begins or ends.
Several near-catastrophic incidents involving volcanic ash alerted the world to the problem -- total engine losses over Indonesia in 1982 and Alaska in 1989 -- and a worldwide monitoring system was created as a result. The International Civil Aviation Organization, a U.N. agency, coordinates monitoring and preparedness training. One such event was scheduled to take place in Europe this year.
Wunderman said that as part of the USGS ash study, the KLM plane that almost crashed in Alaska was taken apart and examined.
In a preface to that study, principal author Thomas Casadevall wrote: "In the past 15 years, more than 80 jet airplanes have been damaged owing to unplanned encounters with drifting clouds of volcanic ash in air routes and at airports. Seven of these encounters caused in-flight loss of jet engine power, which nearly resulted in the crash of the airplane."
Wunderman said that planes have continued to enter ash clouds -- with more than 100 incidents since 1970, according to the USGS -- but that ramping up funding to defend against the hazards "has not been a high priority."
The dynamics of how ash harms engines are well understood. The ash is made up of, among other things, tiny glass shards formed when the volcano's magma hits the much-cooler atmosphere. Those shards rise and can enter passing engines, which reach temperatures above 4,000 degrees Fahrenheit at top cruising speeds. The glass once again gets heated to the point of melting, melds into larger chunks and globules of rock, and then hardens again as glass when it comes into contact with the cool outer metal of the engine mount.
The result is a harder and sharper material that can enter the fuel line or the nozzles that shoot air toward the engine's turbines. The engines can seize up from lack of fuel or ventilation, sending the plane into a steep decline.
Fortunately, the same dynamics of heating and cooling that make volcanic ash so hazardous can come to the rescue. The engines that went dead amid volcanic ash in Indonesia and Alaska were brought back to life after the planes descended to the point where the outer metal wasn't cold enough to keep the glassy lava from melting once more. That opened up essential passageways, and the engines could restart.
In the United States, the problem generally occurs in Alaska, Hawaii or the Pacific Northwest, said Federal Aviation Administration spokesman Les Dorr. Monitoring groups cooperating with and funded by the USGS, the National Oceanic and Atmospheric Administration, along with affected states, follow the ash clouds and alert organizations from the Department of Defense to the FAA when the ash appears to be threatening aircraft. Notices to airmen then go out to avoid specific areas, and a plane can be ordered to the ground if it inadvertently went through an ash cloud.