Pace:
Sorry cannot agree with you that its simple really You could quite easely have an area marked as below the accepted limits in Ash and have one cloud which is unique and solitary but of a much denser level than the remaining area.
Nothing is constant sadly in our atmosphere.
I can well remember flying a twin to Malaga single pilot ................
...............The best indicator with storms or otherwise is to use your eyes and your instincts and knowledge as relying on aids only whether aircraft based or land based will give you a shock you dont want.
That is why I dont hold with the science but do with pilots and good old see and avoid.The SCIENCE is an aid to the captain not the CAPTAIN and for me thats the whole basis of my arguement with this thread. Listen to the airlines and the pilots and thankfully that message seems to be proving correct.
The same goes with ASH which to date has not harmed anyone in I repeat over 50 years when there were no fancy gizmos to mislead anyone which sadly also now seems proved to be a costly mistake.
I'm afraid you just don't get it.
1. See and avoid doesn't work by day with fine ash clouds as has already been demonstrated. It certainly doesn't work at night.
2. With at least 1000 flights per day to and from Europe, we are talking about the
balance of probabilities of finding ash. It is irrelevant if one aircraft or ninety aircraft make it through without ash damage. Your personal experience is irrelevant.
This is about
managing risk for a fleet of 1000+ aircraft engaged in European travel at any given time. As I said many pages ago, the penalty for getting the ash forecasts wrong is hundreds and hundreds of damaged aircraft sitting on the ground for months as they wait for their engines to be rebuilt by overloaded maintenance facilities staffed by exhausted engineers.
To put it another way, there are not hundreds of spare engines sitting around in Europe or America for some mass engine change.
To put it yet another way, suppose the forecasters get it wrong, or the volcano decides not to cooperate and Forty B747's need engines changes as a result. Are you going to sit there and argue that Boeing/GE/RR or the airlines should have had 160 spare engines just sitting around unallocated against this possibility? I can tell you they don't.
There are relatively few spares around against birdstrikes etc. The engines are monitored on the wings and then scheduled to be removed (sometimes as modules) during heavy maintenance and from there scheduled into engine overhaul and from there scheduled either to sit as a spare for a while or back onto another aircraft. The idea with that is to ensure that engine "Life" is managed so that engine changes due to time expired components don't happen except at scheduled heavy maintenance. Spares (blades and vanes) are usually ordered as sets, or overhauled as sets to fit in with the engine maintenance schedule.
It is a complex process and if you throw in anything other than the ordinary level of unforeseen engine changes, you will quickly run out of serviceable engines in the resulting chaos as well as suffer massive cost overruns.