Originally Posted by
Intruder
There will always be second-guessers. The fact that there were no ash incidents gives clear evidence that the Eurocontrol policy was successful. There is no way to tell how many incidents or mishaps there would have been without the policy.
Yes there is, because the policy was changed from "no fly" to "fly" while the ash cloud was still there. Apparently even on the previous "zero tolerance" measures the asirspace would be open now, but there were, depending on who you believe, two, three or several days of flying through it. Say it was two days of flying through it, and six days of not:
- Total commercial jets (or any jets actually) that fell out of the sky in the six days not flying through the ash: none.
- Total commercial jets that fell out of the sky in the two days flying through the ash: none.
- Calculate total commercial jets that would have fallen out of the sky if same threshold had been applied across the six days: six * zero / two = none.
If you think that is over-simplistic, you might want to consider that
allegedly (since it's the daily mail - although it appears a well written and researched article from what I do know) the measured ash concentration over the UK never got higher than 1/20 of the current "safe limit". See
The ash cloud that never was: How volcanic plume over UK was only a twentieth of safe-flying limit and blunders led to lock-down | Mail Online
We live in an imperfect random world that is inherently not perfectly mesurable - zero tolerance policies are inherently dumb. Find
any VA ? - have to close airspace.
That's the easy part.
Now how do you reopen it ? How do you
prove there is
zero VA ? How many test flights over how many days (remembering you've just grounded your test aircraft for repainting, after the eruption started...) have to come up clean ? What if you didn't cover the whole area and missed some ash, what if your instruments aren't sensitive enough,
how do you prove there is zero VA so you can re-open airspace ?
Answers on a postcard to the relevant authorities, they need your help because their previous plan looked like:
1. IF find VA THEN close airspace
2. Hope (1) never happens