Flights resume as ash fear recedes

Flights resume as ash fear recedes

The UK Met Office is still detecting an ash cloud above the UK, so how is it now safe to open up airspace?
The Civil Aviation Authority (CAA) confirmed that the guidelines regarding flying through volcanic ash have now changed, following six days of discussions between aviation engineers and experts to "find a way to tackle this immense challenge, unknown in the UK and Europe in living memory".
A spokeswoman from the CAA told BBC News: "Air manufacturers, both engine and airframe, were asked to look at the scientific evidence from test flights and at the Met office data, to understand how much volcanic ash in the atmosphere… jet engines could tolerate [without being] damaged."
Now, scientists and engineers have agreed a threshold concentration for ash of 0.002g per cubic metre of air. At or below this concentration, there is no damage to the engine.
So the CAA has opened airspace where the concentration of ash is the air is below this figure.
Does this mean the ban was never truly necessary?
The regulations before this event were set out by an international body called the International Civil Aviation Organisation (ICAO). It set a limit of "no tolerance" for any concentration of volcanic ash.
Dr Colin Brown, director of engineering at the UK's Institution of Mechanical Engineers, explained that previously, scientists were not able to detect and measure ash at the very low concentrations that modern analytical equipment is capable of measuring. So the best advice we had was to avoid it all together.
"Previous to this, the regulations were, if you see ash, you fly 100 miles away from it," he told BBC News.
"But now we have this blanket over the biggest airports in northern Europe. It's an unprecedented situation."
So over the past six days, the Met Office, the Natural Environment Research Council and some airlines have run several test flights. The research flights have used analytical instruments to measure the cloud, while commerical test flights have simply checked for engine damage.
The results from these test flights have now been translated into the new regulations.
The CAA spokeswoman said: "That figure has been fed into the Met office model to map the density of the ash cloud.
"Volcanic ash has not left UK airspace - it's still here, and it's a very fluid situation. There are still 'black blobs' where the ash is more dense, and the co-ordinates are being updated every 6 hours."
The CAA explained that for these new guidelines to be implemented, airlines would also be required to carry out "intensive maintenance ash damage inspection before and after each flight".
The government's chief scientific advisor, John Beddington, said that he was confident that the new regulations "guaranteed safety".
[link to news.bbc.co.uk]