La Vita è Bella Life is Beautiful. La Vita es Bonita. 美麗人生　

242愛的鼓勵 7訂閱站台

 火山灰對噴射機的引擎影響至鉅。

1982年英航與新航在印尼上空，1989年荷航也在阿拉斯加上空，因飛過火山灰雲層而失去動力。

North Europe hit by volcanic ash

Air traffic has been severely disrupted across northern Europe by volcanic ash drifting
south and east from Iceland.

Airspace was closed or flights cancelled in countries including the UK, the Republic of Ireland,
Denmark, Norway, Sweden, Finland and France.

The ash, which could damage plane engines, came from a volcanic eruption in the south-west of
Iceland.

The volcano was still emitting ash on Thursday afternoon, and the flight problems could continue for 48 hours.

By Thursday afternoon, the UK had shut its airspace and other countries were in the process of
following suit.

"The extent is greater than we've ever seen before in the EU," said Brian Flynn, deputy head of
operations at Eurocontrol, the European air traffic control organisation.

"The meteorological situation is such that the volcanic ash is progressing very slowly eastwards but there is not a lot of wind... so it is very slow and very dense."

'Wait and see'

UK airspace was shut down to all but emergency flights from midday (1100 GMT) on Thursday, and will not reopen until 0700 BST (0600 GMT) on Friday at the earliest. It was also closed in the Republic of Ireland.

"Volcanic ash represents a significant safety threat to aircraft," said the UK's Air Traffic Control
Service (Nats).

Oslo airport, which is Norway's largest, was closed on Thursday morning, meaning Norwegian
airspace was completely closed.

"Flights will be cancelled probably all day with the current prognosis," said Jo Kobro, information
manager at Oslo Airport. "Then we have to wait and see what the new weather forecasts will say about the wind direction, and if we are lucky the volcano diminishes in strength."


Tim Farish, who had been planning to fly from Oslo to London on business, said he had been told by the airline SAS to stay at home and not bother calling for updates.

"We can actually smell sulphur in the air here now from the volcano cloud," he told the BBC from his home in the Norwegian capital. "This could last for a few days apparently, so all I can do, like anyone else, is sit and wait."

Belgium, Sweden and Denmark announced they would be shutting their entire airspace, while
northern Finland's airspace was closed and the Netherlands' was being closed progressively.

French aviation officials said on Thursday afternoon that the main airports in Paris and other airports in the north of the country were to be closed.

There was severe disruption in Germany and in Spain.

Road cut off

The last volcanic eruption beneath the Eyjafjallajoekull glacier in south-western Iceland was on 20 March, and it forced about 500 people in the sparsely populated area from their homes. Before that, the previous eruption started in 1821 - and lasted for two years.

Eyewitnesses and local officials said two flows of floodwater had started coming off the glacier on Wednesday, and that a road along the flooded Markarfljot river had been cut in several places.

As many as 800 people were evacuated from their homes.

On Thursday, the flooding was reported to have subsided, but the volcano was still producing ash that was being blown towards Europe.

"It is likely that the production of ash will continue at a comparable level for some days or weeks.  But where it disrupts travel, that depends on the weather," Einar Kjartansson, a geophysicist at the Icelandic Meteorological Office, told the Associated Press.

"It depends how the wind carries the ash."

Iceland lies on the Mid-Atlantic Ridge, the highly volatile boundary between the Eurasian and North American continental plates.

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/europe/8622978.stm
Published: 2010/04/15 16:58:04 GMT    © BBC MMX




Why Iceland volcano has grounded UK flights

ANALYSIS
By Victoria Gill
Science reporter, BBC News

More than 1,000km from the event itself, Iceland's second volcanic eruption in the space
of a month has caused flights in the UK to be grounded.

Scientists and aviation authorities are continuing to monitor a plume of volcanic ash that is moving southwards over the UK.

The entirety of UK airspace closed from noon on Thursday.

National Air Traffic Services said: "No flights will be permitted in UK controlled airspace other than emergency situations" until 0700 BST on Friday at the earliest.

The eruption ejected the plume, which is made up of fine rock particles, up to 11km into the
atmosphere.

 "This ash cloud is now drifting with the high altitude winds," said Dr David Rothery, a volcano
researcher from the UK's Open University.

"The main mass is over Scandinavia, but it is also over the north of Great Britain and is likely to
spread south over the whole island by the end of [Thursday]."

The plume is so high that it will neither be visible nor pose a threat to the health of humans on the ground, although Dr Rothery added that we may have a "spectacularly red sunset" on Thursday evening.

The major concern is that the ash could pose a very serious hazard to aircraft engines.

Dr Dougal Jerram, an earth scientist at the University of Durham, UK, explained: "Eruptions which
are charged with gas start to froth and expand as they reach the surface.

"This results in explosive eruptions and this fine ash being sent up into the atmosphere.

"If it is ejected high enough, the ash can reach the high winds and be dispersed around the globe, for example, from Iceland to Europe. These high winds are exactly where the aeroplanes cruise."



Emergency developments

Airports operator BAA confirmed that all flights at Heathrow, Stansted and Gatwick would be
suspended from midday.

"Air traffic restrictions have very properly been applied," said Dr Rothery. "If volcanic ash particles are ingested into a jet engine, they accumulate and clog the engines with molten glass."

In 1982, British Airways and Singapore Airways jumbo jets lost all their engines when they flew into an ash cloud over Indonesia.

Reports said that the ash sandblasted the windscreen and clogged the engines, which only restarted when enough of the molten ash solidified and broke off.

A KLM flight had a similar experience in 1989 over Alaska.

Stewart John, a fellow of the Royal Academy of Engineering and former president of the Royal
Aeronautical Society, explained that the ash can cause severe damage.

"This dust really is nasty stuff," he told BBC News. "It's extremely fine and if it gets into a jet engine, it blocks up all of the ventilation holes that bleed in cooling air.

"Jet engines operate at about 2,000C, and the metals can't take that. The engine will just shut
down."

In the case of the 1982 British Airways flight, Dr John explained, when the plane emerged from the cloud, the pilot repeatedly tried and failed to restart the engines.

"They were going down and down, and had just about accepted that they would have to ditch.
"But, at the last minute, one engine started. By repeatedly turning the engine over and having a
clean airflow going through, he managed to blow the ash out."

Dr Rothery explained that as a result of those incidents, emergency procedure manuals for pilots
were changed.

"Previously, when engines began to fail the standard practice had been to increase power. This just makes the ash problem worse," he said.

"Nowadays, a pilot will throttle back and lose height so as to drop below the ash cloud as soon as possible. The inrush of cold, clean air is usually enough to shatter the glass and unclog the engines.

"Even so, the forward windows may have become so badly abraded by ash that they are useless, and the plane has to land on instruments."

Dr John concluded: "We do not know how long this will last. "It's like a typhoon - because you can't fly through it, you can't directly monitor it, so we have rely on satellite images and to err on the side of extreme caution."

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/8621992.stm
Published: 2010/04/15 12:11:31 GMT    © BBC MMX