Our Beautiful World

Aviation and Volcanic Ash

Millions of people fly by jet each year, but only a few knows the risk of flying near active volcanoes.
During the periode from 1980 to 1995 there have been 25 issues where turbin-aircrafts has flown through clouds of ash,
in some cases forced their engines to stop. In each case this has costed tens of thousands of million dollars, but luckily
no lives have been lost. (See the Redoubt and Galungung volcanoes.)

Wind carries volcanic ash and gas from the volcano toward the southeast, out over the Pacific Ocean directly toward some of the
busiest air routes between Asia and both Europe and the United States. One Boeing-747 aircraft reported encountering ash at about
11 km above sea level, but was able to get out of the eruption cloud by climbing up to 12 km.

During one flight a Boeing 747 use 150 tons of air each minute in each of its four engines. If there is ash in the air, tons af ash will be filtered through
the engines. This is so, even if an ash-cloud is just visible to the pilot's eye, and not visible on normal radar equipment.
Busy air-routes, like those passing Alaska from USA to the Far East, need constant monitoring, and special web-pages are dedicated such.

Even if volcano-eruptions are of short time, and often are in deserted parts of the earth, potentially dangerous ash-clouds may move very fast from
their origin to air-routes and inhabited areas, and the planes in such areas will be damaged.

In the northern part of Chile, on the 16th of September in 1986, an ashcloud emitted from the Lascar-volcano, to a height of 15.000 m. asl.
The ash moved with the wind in a two kilometer thick cloud, which stayd between 10 and 14 km asl. Normal height for aircrafts is about .10.000m.
This cloud passed over Salta in Argentine, just two hours after the eruption, where also ash fell to the ground. About 3 hours later, the cloud had
travevlled about 400 km, through an area of 100.000 km².

The Klyuchevskoy volcano in the deserted areas of the Kamchatka-penminsular in Eastern Russia, reaches 4725 m asl. It has eruptions every second year,
and are one of the most active non-island volcanoes in the world. Normally the wind blows toward Klyuchevskoy from west and north-west,
and those winds carries tons of ash down towards the air-routes in the northern Pacific. Under an eruptions on the 30th of September, 1994, there
were full stop in air-traffic for more than 60 hours. The cloud reached 18.600m asl and strong winds at 240 kj/hour blew the ash south.
There are more than 70 air-crafts passing through this area daily, carrying about 10.000 passengers.

More than 80 commercial aircraft have unexpectedly encountered volcanic ash in flight and at
airports in the past 15 years. Seven of these encounters caused in-flight loss of jet engine power,
which nearly resulted in the crash of the airplane. A range of damage may occur to airplanes that
fly through an eruption cloud depending on the concentration of volcanic ash and gas aerosols in
the cloud, the length of time the aircraft actually spends in the cloud, and the actions taken by
the pilots to exit the cloud.

Numerous instances of jet aircraft flying into volcanic ash clouds have demonstrated the serious
damage that can be sustained. Ash particles are angular fragments having the hardness of a pocket-
knife blade and, upon impact with aircraft traveling at speeds of several hundred knots, cause
abrasion damage to forward-facing surfaces, including windscreens, fuselage surfaces, and compressor fan blades. Moreover, the melting temperature of the glassy silicate rock material that
comprises an ash cloud is lower than the operating temperatures of modern jet engines;
consequently, ingested ash particles can melt and then accumulate as re-solidified deposits in the
engine. The overall result of an aircraft's flying into an ash cloud can be degraded engine
performance (including flame out), loss of visibility, and failure of critical navigational and
operational instruments.

See also the Spurr-volcano in Alaska. Click here.


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