Danger in the Stratosphere:
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During the past 14 years, there have been 23 incidents involving aircraft that
have inadvertently encountered eruption plumes. Apart from windshield pitting
resulting in loss of visibility, the most common result is engine damage that
occurs when volcanic ash enters the jet intakes; the volcanic ash melts and
coats turbine blades, often causing the engines to stall. Fortunately, in all
past cases, engines have restarted, but only after severe loss of altitude. Most
recently a Boeing 747 aircraft lost power in all four of its engines after
encountering the plume of the explosive eruption of Redoubt Volcano
on December 15, 1989; it glided without power from
8,534 meters (28,000 feet) until engines
were restarted at 4,267 meters (14,000 feet), only 1,219 meters (4,000
feet) above nearby mountain peaks. The airliner landed safely in Anchorage and
no one was hurt, but the damage to the aircraft has been estimated to exceed $80
million (Steenblik, 1990).
Personnel from the Volcano Hazards Program, particularly those at the Alaska Volcano Observatory, are working with officials of the Federal Aviation Administration (FAA) to develop automatic early warning systems for large ash clouds and to streamline communication for eruptions at U.S. volcanoes that might impact aircraft. Other countries have developed or are developing similar procedures, assisted in part by the World Organization of Volcano Observatories and coordinated through the International Civil Aviation Organization. |
