Why volcanic ash is so dangerous

As many of us have discovered to our cost, volcanic ash, such as that spewed from Iceland’s Eyjafjallajoekull volcano, makes conditions too dangerous for flying. But what exactly are the dangers and have there been problems in the past which justify the blanket ban on air traffic?

The main risk is that an accumulation of volcanic ash particles in a jet engine can cause the engine to become clogged with molten glass resulting in an eventual shut down of the engines. The characteristics of the dust mean that when it reaches a very high temperature it will melt. Modern jet engines operate at a higher temperature (2000 degrees C) than the melting point of the dust, meaning that the system required to keep the engine cool enough to operate would melt as, in turn, would the engine.

The Finnish Air Force flew several fighter jets over Northern Finland last Thurs prior to air space being closed and reported substantial damage to engines resulting from the ingestion of volcanic ash.

In 1982, after the eruption of an Indonesian volcano, a BA plane got into trouble near Java. The pilot Eric Moody explained that all engines were lost for around 15 mins and the plane plummeted from 37,000 feet to 12,000 feet. Eventually his repeated attempts to restart the engines worked for one engine and he was able to avoid ditching the 747. A Singapore Airlines plane had a similar experience as a result of the same volcano and in 1989 a KLM plane flew into problems in Alaska following a volcanic eruption.

As a direct result of Mr Moody’s experience in 1982 the emergency protocols were changed for pilots.

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