The Hazard of Flying Through an Ash Cloud

Mon, May 17, 2010 — David Evans


Volcanoes are huge glass factories. The ash spewed into the atmosphere by Icelandic volcano Eyjafjallokull is a glasslike substance that can wreak havoc on jet engines. Unfortunately, the ash is so fine and in such low concentrations it cannot be detected by radar but nevertheless poses a danger for any airplane flying through it.

The need for advanced warning is spurring development of a special version of an IR (infrared) camera and software for use as a warning device on commercial aircraft similar to weather radar. Certification of this technology is at least a year away, and retrofitting it onto today’s airliners could take one to three years after that. Meanwhile, Eyjafjallokull is erupting massively again. Disruption of flights is a certainty. Indeed, the current eruption could go on for a long time, and with the Azores high pressure area soon to establish itself, the wind direction could be unfavorable for quite lengthy periods.

Volcano Eyjafallokull produces a volume of microscopic glass in excess of the entire world's glass industry.

Volcano Eyjafallokull produces a volume of microscopic glass in excess of the entire world's glass industry.

The last eruption and resulting ash cloud was bad enough. The photographs below shows what volcanic ash can do to an engine. The aircraft is a Cessna Citation Jet flown out of Germany a few weeks ago. Notice how badly the titanium compressor and turbine blades are damaged. Fortunately, the other engine kept running, albeit sluggishly.




Eyjafjallokull’s specific recipe for glass grains that float in the air includes silica, alumina, iron oxide, and a half dozen other oxides, according to a chemical analysis by researchers at the University of Iceland’s Nordic Volcanological Center. During the last eruption, a molten mixture of these ingredients was shot through an ice-filled crater at the summit. That provided the rapid cooling to make glass. Then this nascent glass was pulverized into microscopic flecks by great blasts of steam and gas from the volcano.

In just three days of eruptions in April, 100 million tons of this glassy powder would bring air traffic to, from and over Europe to a halt. It would take the world’s entire glass industry years to produce that much glass.

Presently, plots of likely ash are based on IR photographs from space, which are processed through computer models to yield total ash quantity, concentration and size of particles.

As indicated, permitted ash levels have been raised. (See Aviation Safety Journal, ‘New Standard Permits Airlines to Fly Into Volcanic Ash’) This permission is all based on computer models. It seems that this could be complemented by assigning monitoring aircraft to each airport. These aircraft would be tasked to fly 20 mile circles around said airports. Equipped with sensors, real ash levels could be detected, and damage to aircraft and engines could be largely avoided.

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