There is a common theme developing on this thread and outside - the lack of scientific information on the CONCENTRATION of ash
The Met office has obviously reacted to this by publishing this update at 12:36 titled "Science underpins ash cloud advice".
Met Office: Icelandic volcano eruption
Here is my comment emailed to their pressoffice
"I am increasingly concerned about postings on your website have a bias against aviation and contain 'bad science'
I refer to the article titled above Last updated: 1231 BST on Tuesday, 20 April 2010
Clearly this is in response to critiscms but it does not answer the key questions:
the first is for the Met Office
1) what are the actual and forecast
concentrations of ash at different location and altitudes (g/m3) and other data such as particle size distribution and composition.
the second is for the aviation industry and regulators
2) what is a safe concentration
there is no doubt there is a concentration which is damgaging but equally there will be a level where the risk of damage is statistically insignificant (not zero)
All the information at present states whether ash is present or not but gives no information on concentrations.
This has caused the present problem because ICAO have not defined an acceptable concentration for IFR flight
It is bad science to refer to absence of ash or zero concentration. This is a physical and mathematical impossibility.
Every aircraft flies in the presence of ash on every flight. The concentration may be below the limit of detection of the sensor but it is not zero.
The limit of detection needs to be stated.
The bias is in referring to damage to F16 aircraft while not referring to the very large number of General Aviation flights that have taken place over the past few days without any known damage and at various altitudes and some with turbine engines. Neither is a Met Office matter.
Lets have figures and proper scientific reporting please."