Originally Posted by lomapaseo
Your arguments are tiresome and not borne out by fact but only by your own imagination.
I don't agree with any of this.
This is supposed to be a discussion of an important issue in commercial aviation. It would help if people accurately evaluated the contributions of the discussants.
In my previous post
http://www.pprune.org/rumours-news/4...ml#post5706296 I pointed out that for a risk evaluation, even a superficial one, four quantities were needed, which I labelled (a), the chance that current levels of ash posed no risk; (b) the damage which ensues if current levels pose no risk; (c) the chance that current levels of ash pose some risk; (d) the damage that thereby ensues. I pointed out that the risk is (a)x(b) + (c)x(d).
This is the way risk is assessed and has been for 299 years, and there is nothing anybody here can say that will change this.
Pace argues that (a) is 1 and (c) is 0. But he also agrees that, at some unknown level of concentration, (a) will no longer be (1) and (c) no longer 0.
Now, of course, the second term is not really a simple multiplication, but a sum: (c1)x(d1) + (c2)x(d2) +... + (cn)x(dn), where c1.....cn represent classes of concentration and d1,...,dn different levels of damage.
Sunfish's contribution to this assessment is to point out the various levels of damage that can ensue (the d's), and that many of those chances, the c's, are unknown, but that some of them can be estimated from history and science.
Mad(Flt)Scientist has pointed out inter alia that it is fruitless to expect those chances to be well-known in detail, by comparison with a case heshe considers broadly similar, that of SLD's.
I don't find any of this "tiresome". I find it essential to an appropriate risk assessment.
PBL