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April 2010, in Iceland's Eyjafjallajokull volcanic eruption, volcanic ash spewed in plumes and clouds and spread across most of Europe. Many of us know someone who was impacted by the flight delays and cancellations due to volcanic ash. Billions were lost due to cancelled flights, delays and stranded travelers who had to be accommodated. And eventually, some people complained vehemently when the ash plumes could no longer be seen by the naked eye.
In May 2011, more ash was released in a new eruption by Grimsvotn, also located in Iceland. Again, planes are delayed and schedules disrupted. At the end of May 2011, volcanic ash is still affecting European airspace.
What you may not have realized was April 2010 was not the first time volcanic ash affected aviation. In 1991, the first International Symposium on Volcanic Ash and Aviation Safety was held.
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Airplanes and Volcanic Ash History
Engines may flame-out from the effects of the ash, and some planes have almost crashed. Two 747s, one in 1982 and one in 1989, lost power in all four engines due to volcanic ash. Neither occurrence caused any deaths, but the problem was taken very seriously, and the group of organizations now known as the Volcanic Ash Advisory Centers were created. These are the organizations that grounded the planes in April 2010. These volcanic ash flight safety foundations work with the United Nations International Aviation organization to keep airspace as safe as possible.
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Thomas J. Grindle and Frank W. Burcham, Jr. wrote a paper for NASA in 2003 on engine damage resulting from a NASA plane which flew through a high altitude and diffuse volcanic ash cloud in 2000. The ash cloud was not visible to the flight crew, and visual inspection after the flight didn’t show damage. However, an examination of the engines made when they were taken out and overhauled showed clogged turbine cooling passages. The NASA plane had not intended to fly through the ash plume, but it had a number of scientific instruments on board, allowing an unexpected analysis of the occurrence. The particles in volcanic ash are known as tephra.
The NASA plane flew through a cloud not visible to the naked eye. It also did not show up on radar. This eruption left very visible clouds, and NASA has some spectacular pictures of them. Even when volcanic ash is not visible, satellite photos will show the ash.
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One type of volcanic rock is obsidian – hard volcanic glass. Passage of volcanic ash through the extremely hot sections of the engine turbines melted some of the ash and deposited glass on the moving parts. This meant the engine parts could not perform efficiently.
As well, another volcanic rock is pumice – which is very abrasive. So the interior of engines in planes collect a layer of volcanic glass, and exterior surfaces were abraded as they moved through the ash cloud. This includes the windshields and leading edges of plane surfaces. Illustrations in the PDF published by NASA show both built-up ash glass inside the engines, and eroded leading edges on the plane. Windscreens abrade and there is loss of visibility.
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Jet turbines are hot. Turbines work on very precise tolerances – all of a jet engine does. Airbus had manufacturing issues with engines last fall because of engine misalignment. The problem was so serious, there was speculation Airbus might go out of business. Layers of glass accreting on the interior of the turbine blades meant that the turbines could not function properly – potentially not at all. Between the layers of glass melting and reforming and the abrasion of interior and exterior surfaces, the planes were not safe to fly.
Some volcanic ash particles are extremely small, and are carried high into the atmosphere. NASA imagery showed ash between two and four miles above the earth, and it still appeared in images of the atmosphere in the middle of May 2010.
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As well as governmental and UN organizations, aircraft companies have published material on Volcanic Ash Awareness. In 2006, Airbus released a 12 page Flight Operations Briefing note on Operating Environment Volcanic Ash Awareness. The Introduction starts out “Flying through an ash cloud should be avoided by all means due to the extreme hazard for the aircraft.”
Despite the frustration for travelers, the monetary damages for the airlines and the doubt on the part of citizens who could not see any ash, the safety of passengers demanded that cancelled flights due to volcanic ash were the only choice.
In the most recent eruption by Grimsvotn, even President Obama needed to adjust his flight schedule to the impact of volcanic ash nearing Irish airspace.
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NASA PDF on Engine Damage to a NASA DC-8-72 by Thomas J. Grindle and Frank W. Burcham, Jr. http://www.alpa.org/portals/alpa/volcanicash/03_NASADC8AshDamage.pdf
NASA monitors satellites for volcanic ash and other airborne hazards http://science.larc.nasa.gov/asap/research-ash.html
Images from MASA archive of Iceland volcano images http://www.nasa.gov/topics/earth/features/iceland-volcano-plume-archive1.html