The U.S. Geological Survey has issued a volcano advisory warning that increased seismic activity in and under Mt. St. Helens' lava dome may signal an impending eruption - and that has direct implications for pilots. Even a relatively minor eruption could spew volcanic ash thousands of feet into the air and drift tens of miles downwind.
"Volcanic ash is highly abrasive," said Kelvin Ampofo, manager of AOPA's Aviation Services department. "It can pit windscreens and landing lights so badly they're useless. In severe conditions, it can clog pitot-static systems and damage control surfaces. While piston engines are less likely to lose power than turbines if they ingest ash, the ash still can cause severe damage."
The best advice for pilots is to try to stay upwind of ash clouds and never try to fly through them. "If you enter an ash cloud inadvertently, reverse course," said Ampofo. "Don't try to fly through it or climb out of it. Volcanic ash clouds can be tens of thousands of feet high and extend hundreds or even thousands of miles from the volcano."
METARs will list obscurations due to volcanic ash as "VA."
October 1, 2004