Ash? What ash?

April 17, 2010 7:46 AM

Are the CAA and other European aviation bodies over-reacting to the current volcanic ash situation?

The reason I ask is that I'm right in the middle of England and in all directions I see nothing but glorious blue sky. This comes on the back of the satellite image from a few days ago showing a clearly defined and narrow strip of ash coming from Iceland, on track to pass the northern edge of Scotland. They've shut Gatwick and Heathrow, near London, for an ash cloud that was at the time more than 700 miles away, and even now does not appear to be showing its face.

I'm aware of what ash can do if you go through it (precedent of Speedbird 9).

posted by Biru to science & nature (17 answers total)

According to Slate, even a tiny bit of ash is very bad for the planes. So while they are probably being overly cautious, they are paid to be that way.
posted by mmascolino at 7:50 AM on April 17, 2010

They are over reacting to the extent that yes, most planes probably could complete their trips without crashing. But when you know there is danger, you can't send planes up.

And even though the plume is the main part of it, the ash is also dispersed to where you can't see it. Which just makes it take a little longer for the engines to shut down.
posted by gjc at 8:01 AM on April 17, 2010

The ash cloud is said to be 18,000 to 35,000 ft up in the sky. That's quite far away compared to most clouds. I'd imagine that it's far more dispersed than a cloud, too.

The most recent article I read indicates that a fine layer of ash has reached the ground in some parts of England. Run your finger over a parked car, maybe.

Finally, here is a picture of ash damage done to a Finnish aircraft. From the picture it's hard to understand the danger, but it's clearly, you know, present.
posted by acidic at 8:05 AM on April 17, 2010

The volcanic ash tends to be concentrated at the high altitudes where commercial airliners fly. But near the ground, it's dispersed, and doesn't have the same effect on cars, trains, or ship engines.
posted by proj at 8:06 AM on April 17, 2010

You know how a bit of drizzle can seem like intense rain on the windshield of your car at 100 km/h? Modern airliners fly at almost 1000 km/h. A light sprinkling of ash is, in effect, a sandblaster to aircraft.
posted by randomstriker at 8:25 AM on April 17, 2010

Another issue is that the great circle routes that airlines use to go from North America to Europe pass over or near Iceland, so it may be clear in central Britain, but cloudy along the path to central Britain. Especially for the 777 and other twin engine jets that can't go too far from land.
posted by allthegoodnamesweretaken at 8:35 AM on April 17, 2010

If you take a look at the most recent image from this page from the London Volcanic Ash Advisory Center, you can see that even when there isn't an advisory directly over the UK, it's often totally surrounded by advisory areas.

These graphics outline the areas where they think there's significant chance of volcanic ash drifting in, even if there isn't any there right this moment. The concern in any of these areas is that they could go from clear to ash-filled without sufficient advanced warning to avoid the ash clouds. The problem is especially bad at night, since ash doesn't show up on radar.

The different coloured lines show the altitude ranges where the ash might be found. FL is Flight Level, which is pressure altitude in 100's of feet--FL200 is 20,000 feet, roughly, give or take changes in barometric pressure.
posted by FishBike at 8:39 AM on April 17, 2010

"Risk" is normally quantified as likelihood of an adverse incident happening times the potential severity of the incident. However remote the likelihood may be that a plane catches two or four engines full of ash at the moment, the potential consequences are such that this rates as high risk. Or higher.

So - no flights.
posted by genesta at 8:43 AM on April 17, 2010 [2 favorites]

The volcanic ash acts like sandpaper or blasting media. It destroys jet engines.
posted by Gungho at 8:56 AM on April 17, 2010

Kottke just linked to this BBC article on what happened when a jet flew through an ash cloud around Indonesia a while back. It sounds like the kind of situation you'd want to avoid if you knew that even a fraction of planes in the air would encounter the same thing.
posted by adamrice at 9:03 AM on April 17, 2010

No, they are not overreacting. The ash cloud is not particularly dense and at high altitude, it's no surprise you can't see it from the ground.

Flying through an ash cloud at 600mph is like sandblasting the aircraft. Even if it didn't destroy the engines it would make it impossible to see out the cockpit.

If you think that the ash cloud has bypassed the UK you should check out the latest satellite imagery from NASA MODIS. Ash is being released in "bursts" at the moment and there's no concrete way of telling where each burst is going to go.
posted by alby at 9:26 AM on April 17, 2010

There was a piece on the BBC news explaining that aircraft are sold with a condition that they shouldn't be flown through clouds of volcanic ash. I would imagine the insurers would also specify the same thing. So they might be over-reacting, but they basically have no choice.
posted by BrokenEnglish at 9:42 AM on April 17, 2010

Interestingly, the engines on most commercial aircraft are leased, independent of the aircraft itself.
So, beyond the whole "not wanting to put our customers in peril" thing, I would suspect that ingesting even a small amount of volcanic ash just might void the lease/warranty on those very expensive engines.
posted by Thorzdad at 11:22 AM on April 17, 2010

Also, last time this particular volcano whose name I cannot type erupted (in 1821), it went off for months.

The longer it keeps pumping more ash into the atmo, the longer air travel is going to be messed up.
posted by DaveP at 9:34 PM on April 17, 2010

Yeah, as stated in the original post... I know all about Speedbird 9 and what ash does. It's just that I keep seeing end of the world reporting on news channels, and read yesterday in The Times that Britain was "Under a catastrophic ash cloud" and I could not reconcile what I see with these reports. I've seen no evidence of ash in the sky, I've seen no ashfall on the ground. Furthermore, despite the fact that Scotland lies between Iceland and Heathrow and that the volcano is still spewing out ash, I struggle to understand the logic in banning flights from Luton, Heathrow, Stansted and Gatwick, but allowing them from Glasgow, Prestwick and Edinburgh.

As for the great circle routes, it might take a little longer, cost a bit more in fuel, but there's no real reason why the flights can't be rerouted a few hundred miles to the south in order to avoid passing close to Iceland. To whomever mentioned the limitation of twin engined aircraft and flying over water... specifically the 767/777, those aircraft are covered under ETOPS regulations which are not specific to operating over water, merely to time from point of failure to alternate landing site, and it is possible to apply for an extension to regular ETOPS limitation allowing the aircraft to operate on routes where it may be up to four hours flying time from a safe place to land, thus making transatlantic flights possible using alternate routes.

Anyway, thanks for your answers.
posted by Biru at 6:10 AM on April 18, 2010

Several airlines have flown test flights and have reported no damage. Of course, it's in their financial interest to get flights started as soon as possible, but it does make you wonder whether the danger is not as high as has been reported.
posted by klausness at 10:47 AM on April 18, 2010

Further to klausness's comment, it now appears that the levels of ash measured in UK airspace may have been up to twenty times lower than would be required to cause engine damage.

Source: Dr Grant Allen from the Centre for Atmospheric Science at the University of Manchester.

Via BBC News.
posted by Biru at 9:57 AM on April 21, 2010