What is the volcanic cloud density that is 'safe' and when is it not safe to fly, and, should an encounter occur, what is the safest course of action?"
PJ2
We all know that flying in thick dense volcanic ash clouds as seen bellowing out of the volcano source would be a very serious encounter.
My instincts are that in VMC and daylight if the ash is so dispersed as to be invisible then there is no threat.
Many will demand on what scientific basis that comment is made but then NO ONE experts or otherwise seems to really know scientific or not!
We do know that the Alaska eruption circled the world 3 times before it fully dissipated.
What the eye doesnt see??? How many aircraft flew through low level density ash totally oblivious to the fact?
The new levels are a good starting point until practical experience proves otherwise.
I like MMs Comparison with bird strikes which have brought down aircraft unlike ash which to date hasnt.
Bird strikes, we know broadly when and where they occur, they are estimated to cost aviation £1.2bn pa., have a recent history of causing complete and unrecoverable loss of power, and have caused fatal accidents and the loss of airframes in non-fatal accidents. (at least everyone so far involved with ash encounters has been able to get the engines going again!) Should we stop civil aviation during bird migration season? No of course not. We should take sensible mitigation steps. That is all people seem to suggesting - not that ash is not a problem - just the approach of closing down Europe was out of proportion to the risk.
We live with potential bird strike threats and dont close down masses of airspace in the migration season.
Until the science can come up with solid data or detection equiptment for aircraft practical experience and common sense are our best options.
Pace