Flying ash: a lesson in ignorance

[hairyears]

I think I should revise my opinion that the authorities over-reacted with the blanket ban: I suspect that much of Europe's airspace is safe for aviation, but there are absolutely no hard numbers on where, or how high, or how much as is safe. All we've got - and all that NATS have got - are anecdotes about aircraft flying into dense clouds of ash,

Comments

[oldbloke]

In possibly the best ep of Bang Goes The Theory EVAH, they had a demo of a jet turbine blade getting a coating of glass as ash entered the combustion chamber. And of it shattering off when the blade was rapidly cooled. But, as they said, not something you want to rely on with N hundred passengers aboard.
They also showed the plane NERC (iirc) are using to dip into the ash cloud for samples. Lots of science being done fast here!

[hairyears]

Yeah... I saw the pictures of that plane, it's the twin-prop that flew round London at the weekend.

I wonder what the engines are...

It might surprise you to learn that many sleek-looking light aircraft run on low-tuned side-valve engines that you'd recognise from a 1950's lawnmower. Light aviation's more about conservative engineering and reliability than power-to-weight ratios!

Of course, the big deal with piston engines in dusty conditions is that you can put dust filters on them. They need air for combustion, but not as a working fluid in the same way (and in the same volumes) required by turbines.

[katsmeat]

is that you can put dust filters on them.

Indeed, as any aviation geek would tell you. The fighters that got sent out to the North African desert by both sides during WW2 were specially modified "tropical" versions, with honking big air-filters fitted. This isn't novel technology.

[uitlander]

The Finnish air force engine tests are starting to appear in English.

Personally, I prefer to take read the results of air force tests in preference to the results presented by airlines desperate to start flying again for economic reasons.

While there is doubt I do not think planes should go back into the air.

[hairyears]

The Finnish 'Test' is just another anecdote: from what I hear, they flew through visible ash - far heavier than is considered (or hoped) to be safe for transit - and everyone's pantomiming surprise and shock at the damage.

I trust that they will be publishing continuous dust density readings from the flight... Otherwise it's just an expensive stunt.

[uitlander]

Try this then.

The economic interests of airline CEOs does little to set my mind at rest about airline safety in the current environment without independent confirmation based on a large number of tests.

[liadnan]

What the airlines themselves say and think ultimately matters rather less than what certain specialist underwriters at Lloyds think. Plus those to whom the planes are mortgaged or from whom they are leased. And they are going to be equally sceptical about the airlines' own results.

[nicnac]

The good news? Hopefully the ash-emitting phase of the Eyjafjallajoekull eruption is dying down.

You jinxed it!

[beingjdc]

I am interested in what, if anything, we can imply from this point (from Wikipedia)

Eyjafjallajökull lies just west of another subglacial volcano, Katla, which is much more active and known for its powerful subglacial eruptions and its large magma chamber. Each of the eruptions of Eyjafjallajökull in 920, 1612, and 1821-1823 has preceded an eruption of Katla

[jlms]

That has been one of the main discussion items in the news reporting here (in Sweden) ; the most recent article I can find right now is from the day before yesterday, when a seismologist stated that 1) Katla has tended to erupt with regular intervals with or without the influence of Eyjafjöll; the latest eruption was in 1918 and seismologists have been expecting an eruption since the 1960s, 2) there has been no increased seismic activity associated with Katla so far, and there would normally be signs at least a month beforehand (as there were in the case of Eyjafjöll), 3) three connected eruptions are, to say the least, statistically very shaky evidence.

So it could go either way.

[purplekaz]

Can anyone else add any facts?

Yes. The fact is that I want to be able to travel to Norway by boat, even when there isn't a volcano errupting.

BRING BACK THE FERRIES!

[purplekaz]

First I'd have to spend several hours getting to Aberdeen, then the ferry from Aberdeen to Shetland takes fourteen hours, then another ferry to Bergen. I did fly to Shetland a couple of years ago but it cost £300.

What I'd really like is a boat from Harwich to Oslo, but failing that, even bringing back to Newcastle to Bergen ferry would be a good start.

[robert_jones]

I suspect you already know this, but you can go from Harwich to Oslo in two boats and train via Esbjerg and Copenhagen.