Originally Posted by
Pace
Then that beggars the question isnt the pilot better placed with his/her experience on determining what is safe or not...
I would say... not necessarily.
Most pilots won't have any experience with flying in this kind of crud.
Most of the stuff, even in the 'black' zones, is diffuse enough not to be visible even in VMC conditions, so what about IMC and night-time?
What is safe? One flight, two flights, three flights without any
obvious engine-related problems? Then your colleague, who takes over the aircraft, hits a bit more ash, and together with the amount you've already unknowingly accumulated, sheds a few turbine blades?
Let's not oversimplify the issue.
CJ