As the eruption of Iceland’s volcano Eyjafjallajokull (a nightmare for both airlines and non-Icelandic newscasters) has shut down all of northern Europe’s air travel, the New Scientist presents a nice primer on why and how volcanic ash threatens aircraft:
Volcanic ash is composed of particles of glassy pulverised rock less than 2 millimetres in diameter. When an aircraft flies into it at its high cruising speed, the cockpit windows get a sandblasting, obscuring the pilots’ view. Crucially, though, the engines suck the dust in, where it melts in the hot combustion chamber and fuses to form globs on the turbine vanes that block the engine airflow. Only when it cools and solidifies – as the aircraft plummets engineless – can enough of the muck flake off to allow an engine restart.
A nightmare, indeed. So, if you’re lying on the floor of Heathrow or Charles De Gaulle, it’s a headache I’m sure–but nothing like the experience of losing engine power. NPR ran a fascinating interview with the Captain of a British Airways 747 that suffered all-engine failure because of a volcanic eruption off Jakarta in 1982 — only a reminder of the frailty of aircraft in the face of fine volcanic ash.