BeechNut
Has anybody bothered to study the similarities between the eruption of Mt St Helens in 1980 in N.America? Google isn't turning much up on the subject
Although the visible plume was well defined, the ash from Mt St Helens reached the US east coast in three days and spread around the world in fifteen days. There are plenty of referenced to this, such as
Keep Your Eye On Mt. St. Helens' Ash, Alaska Science Forum
At the time, maps were available showing the location of the visible plume, and we planned around this area.
In 1991, the ash from Mt Pinatubo extended around the globe, and is often credited with reducing world temperatures. Once again, aircraft were warned of the location of the visible plume, and avoided it. There were some spectacular sunsets that year.
When Mt Redoubt erupted in 1989/90, we continued operating into Anchorage (daylight only), visually avoiding the plume. This often meant a longer route in, due to the closeness of Mt Redoubt to Anchorage.
If there are any engineers who were around at the time then perhaps they could comment as to whether there was any damage to the aircraft during these times.
Perhaps it's time for the engine manufacturers to determine if there is a safe level of ash. Do we know how the present level compares with past eruptions?
Dave