Volcanic Ash Can Pose Hazards to Air Traffic

When volcanoes erupt, lava flows are what concern many people. But as air traffic increases, some scientists at agencies in the U.S. and abroad—including the National Oceanic and Atmospheric Administration (NOAA), U.S. Geological Survey (USGS), and NASA—also are focusing on how to avoid costly and potentially deadly problems that can arise from volcanic ash clouds. The clouds can rise into the cruise altitude of aircraft and can affect traffic thousands of kilometers away from a volcano, as wind car­ ries the ash. The ash can ruin planes, and cause loss of thrust and even flameouts. It also can slicken runways and damage planes on the ground. While awareness of the problem is grow­ ing, scientists soon will lose some key satel­ lite instrumentation for tracking ash (see above) . A global network of nine Volcanic Ash Ad­ visory Centers (VAACs)—organized through the World Meteorological Organization and International Civil Aviation Organization— works with local meteorological watch of­ fices and others to quickly identify and track plumes. The VAACs, which some scientists say vary in technical ability, also aim to com­ municate information rapidly so that pilots re­ ceive sufficient warning of ash clouds. The network relies on data from pilots, gov­ ernment agencies, onsite seismic stations, and remote sensing devices. Polar orbiting satel­ lites provide coverage of polar regions, includ­ ing Alaska, several times a day. GOES geostationary orbiting satellites can be used to pick out silicate particles by subtracting data on one channel from that on another, and can track plumes every 15 minutes. That time resolution is vital to protect air­ craft, said Terry Keith, scientist in charge at the Alaska Volcano Observatory (AVO) in An­ chorage, which is managed by the USGS and works closely with the VAACs. But the next series of three GOES satel­ lites—to be launched around the year 2 0 0 2 — will not have that split-channel capability. The Air Line Pilots Association (ALPA) and others are pushing to restore the capabil­ ity on subsequent GOES satellites, though it would still mean a 3-5 year data gap. That lack of satellite data "could cause an ash plume to go for a potentially dangerous distance in the air before anybody ca tches it," Keith said. "It will increase the risk of fly­ ing into a volcanic ash cloud." That gap in data also could mean more false alarms issued, as ash monitors react con­ servatively to volcanic events. Ash is "something that can be avoided" if it can be seen on imagery, said Grace Swanson, supervisory meteorologist with the Satellite Analysis Branch of NOAA's National Environ­ mental Satellite, Data, and Information Serv­ ice, who works at the Washington, D.C. VAAC. "Why walk through a known hazard," she said, "when you could go around some­ thing?" Some scientists are investigating stop gap measures to provide satellite detection of ash clouds. A team led by NASA Senior Research Scientist Arlin Krueger has proposed build­ ing a volcanic ash monitor, or Volcam. Two cameras, one infrared and one ultraviolet, could detect ash clouds and sulfur dioxide clouds, provide other s c i ence data, and ride piggyback on satellites that have available space. Three or four orbiting Volcams could monitor the entire disk of the Earth continu­ ously at 15-minute intervals, he said. Of the world's 550 or so active volcanoes, about 60 erupt each year, and about 10 raise ash clouds that can affect air traffic locally and possibly in distant regions. Volcanic ash is composed of microscopic silicate minerals and shards of glass. When a plane flies through ash, engines—particularly those on two-engine jets that are larger and more fuel-efficient than older engines, but that take in enormous amounts of air and operate at higher temperatures—ingest the ash. It then can melt and solidify, clog air flow, erode parts, and lead to engine flameout. It also can abrade leading edges of aircraft. Several c lose calls with ash clouds have occurred. In 1989, for instance, a KLM 747 flew into ash from Alaska's Mount Redoubt and lost engine power. The plane made an emergency landing, but suffered $80 million in damages. "For the first time, it made the problem real to us here in the United States," said USGS Acting Director Thomas Casadevall, an expert on volcanic ash hazards. The ash problem is compounded with more planes in the air, often traveling at night when clouds are less visible, and flying more flexible routes. More planes also are flying above potential volcanic hot spots, such as the Pacific "ring of fire" that includes active volcanoes in the Philippines, Indonesia, Ja­ pan, Russia, Central and South America, the Pacific Northwest, and Alaska. The Anchorage airport, for instance, is near about 70 active volcanoes in the Aleu­ tian Arc and Kamchatka, Russia. This air traf­ fic hub, through which 93% of all cargo flights from Asia to the United States are funneled, is "an amazing juxtaposition of volca­ noes and airplanes," said volcanologist Tom Miller, scientist in charge at AVO from 19881993. He said ash clouds are a concern in Alaska 4 days per year on average, with the 15,000-20,000 people flying in airplanes above Alaska on a typical day potentially at risk. With more people flying and more cargo being shipped by air, the c h a n c e of encoun­ tering ash clouds could increase, without ac­ curate warning systems. With uncertainty about what cloud density planes can safely fly through, scientists seem in agreement that the best strategy is to accurately track vol­ can ic ash and quickly communica te that data so that airplanes avoid ash clouds. Rerouting or cancell ing flights to avoid ash may be costly, due to using extra fuel and delays in delivering goods, but it is cheaper than losing planes and people. "If traffickers need to spend a little money to reroute traf­ fic," said William Phaneuf, ALPA staff engi­ neer, "that's the cost of doing business."— Randy Showstack