A Boeing 747 jumbo jet approaching the Anchorage International Airport, Alaska, on December 15, 1989, lost power to all four engines and nearly crashed as a result of flying through volcanic ash erupted from Redoubt Volcano. In separate incidents in 1982, two commercial jumbo jets en route to Australia across Indonesia suffered loss of engine thrust from ingesting volcanic ash from the erupting Galunggung Volcano, Java, and descended more than 20,000 feet before the engines could be restarted. These are not the only incidents of this king. During the past 15 years, about 80 commercial jet aircraft have suffered damage from inadvertently flying into ash clouds that had drifted tens to hundreds of miles from erupting volcanoes.
The U. S. Geological Survey (USGS) has been involved in research on geologic hazards, such as volcanic eruptions and earthquakes, since its earliest days. With the Disaster Relief Act of 1974, the USGS was given formal responsibility "to provide technical assistance to State and local governments to ensure that timely and effective disaster warning is provided" for all geologic hazards. Addressing the threat of volcanic ash to aircraft safety, however, requires far more than the monitoring of volcanoes and warning of erupting ash clouds by the Survey. The ash must be traced and its likely trajectory must be forecast; aircraft must be alerted, and proper evasive actions must be taken by pilots. Agencies such as the National Weather Service and National Environmental Satellite Data and Information Service (both part of the National Oceanic and Atmospheric Administration), the National Aeronautics and Space Administration, and the Federal Aviation Administration are partners critical to the success of this mission. The International Civil Aviation Organization, various pilots' associations, air carriers, aircraft manufacturers, and many others are important as well.
The Redoubt encounter spurred government and university scientists, pilots, and representatives of the aviation industry to work together to reduce the hazards caused internationally by volcanic ash. As a result of the concern generated by the Redoubt eruptions and associated aircraft encounters, the First International Symposium on Volcanic Ash and Aviation Safety was held in Seattle, Washington, July 8-12, 1991. This volume contains the proceedings from that meeting.
Volcanologists and the subject of volcanic ash clouds are relatively new to discussions of aviation hazards. As a result, the various parties concerned with the hazard have had to set up new communication channels and to bridge substantial differences in organizational culture and professional language. The Seattle symposium in 1991 alerted and educated many about ash hazards to aviation. More importantly, it started a serious dialogue that resulted in a series of follow-up workshops, improvements in the detection and tracking of as clouds, and revised warning and response procedures. These are the actions that will be needed if the hazard of ash in the airways is truly to be mitigated.
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