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New eruption starting in Iceland? (merged)

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New eruption starting in Iceland? (merged)

Old 26th May 2011, 10:10
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And this lovely notion of " no-one has died from flying in Volcanic Ash" is typical Dead Body Economics. have you an acceptable number in your head ...would 200 be a good number or bad number?

'Dead Body Economics', as you call them, are the basis of all risk management calculations where that activity has the potential to be fatal. To be brutal the 'acceptable' number is the point where the costs associated with fatalities become unsustainable. For instance 2,500 road deaths a year is clearly 'acceptable' in the UK or we wouldn't be able to drive. This doesn't stop us from trying to lower the number though.

If the acceptable number was zero then we wouldn't allow people to drive cars, swim, ski or any number of potentially fatal activities.
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Old 26th May 2011, 10:14
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Quote:
The Met office have updated the long range forecast this evening and Friday now doesn't look so problematic. The forecasts I posted earlier are now out of date.
Surprise!!! surprise!!! and we are supposed to have confidence in this so called science

The press have been having a field day with charts printed of these predictions and doom and gloom of how passenegers holdays and flights will be ruined!!!


So you'd rather that the forecasts were left the same, despite the fact that the situation has now changed? Where is the sense in that?? What a ridiculous thing to say.
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Old 26th May 2011, 10:20
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And this lovely notion of " no-one has died from flying in Volcanic Ash" is typical Dead Body Economics. have you an acceptable number in your head ...would 200 be a good number or bad number?


About 100,000? That's roughly the number of people killed by civil aviation thus far... the entire industry spends it's time working out the acceptable level of risk of people dying.
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Old 26th May 2011, 10:52
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If I was an airline boss who wanted to minimise cancellation claims from passengers I would do everything possible to make darn sure they knew the cancellations wern't anything to do with my company. I'd want to be seen to be on the passengers side against anyone else I can find. Who cares if they are innocent. I'd also like to be seen as the only airline really trying to keep flying.
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Old 26th May 2011, 12:10
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So much for MOL's "mythical" ash. The following BBC article shows particles taken from a car windscreen in Aberdeen.

BBC News - Ash cloud particles examined by Aberdeen scientists
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Old 26th May 2011, 12:15
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Could the science be better? Yes - no doubt! Is anyone willing to pay for the science, and invest in the capability? That is the question... You'd like to think so - this is the second time in 2 years this has happened, but as Herman the navigator says, will the regulators just shrug their shoulders and say "nothing more for us to do"?

I guess we have moved on slightly from last year, but its clear that more can still be done, and we weren't quite ready for this eruption!
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Old 26th May 2011, 12:26
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Ah Herman:
think this conclusively shows that it's actually very straightforward to draw detailed contour plots (and that 1970s style arguments about computing power are a bit old hat).
If only the Met Office knew that all they had to do to deflect criticism was to to pretty up their charts and make them look more detailed......regardless of accuracy, and regardless of the ICAO/WMO/CAA stipulations of what they, as a VAAC, have to produce.

As an aside the Norwegian Met Service has nowhere near the computational power of the Met Office, so just because they have spangly charts doesn't mean they're better, though if that's all it takes to placate you, then I do worry.
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Old 26th May 2011, 14:59
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'dead body economics' - but unlike the effects of ash at least one can say the financial consequences of a loss are a known factor.

You can already see the raw data they are using as the basis for some forecast, decision or judgment is being tweaked. Collecting reliable data will take a long time and during this process of course you get a lot of garbage in, garbage out. Translated this comes out as fly above, fly below, don't fly at all. Getting this forecast accurate will take years. In the meantime let each company make their own decision rather than a third party making a blanket ban.
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Old 26th May 2011, 15:14
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Originally Posted by cuthere
Ah Herman:

If only the Met Office knew that all they had to do to deflect criticism was to to pretty up their charts and make them look more detailed......regardless of accuracy, and regardless of the ICAO/WMO/CAA stipulations of what they, as a VAAC, have to produce.

As an aside the Norwegian Met Service has nowhere near the computational power of the Met Office, so just because they have spangly charts doesn't mean they're better, though if that's all it takes to placate you, then I do worry.
cuthere, I'm quite well aware that the models have a significant degree of inaccuracy. And I wasn't suggesting that the Norwegian model is necessarily more accurate. It's more the fact that by provding something more than a big red blob, passengers, pilots and airlines can get a better idea of whether the 4mg liimit is close to, let's say, the 50 mg limit or whether that sort of much higher limit would provide much better flexibility (and on a personal note would avoided me being stuck in Helsinki at the moment - long story)...

If you or anyone else can give us the full story on how and why the 4 mg limit is as it is then I'm all ears. However, I will add that even a 50 mg limit would still be 40 times less than the 2g estimate for the KLM Redoubt incident.

Thoughts?
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Old 26th May 2011, 15:55
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Some insight into how the limits were developed can be found here
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Old 26th May 2011, 17:58
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Herman

This is the big question mark? are the limits set to ensure that jet engines run their full expected time ( An airline economic decision) or are they set at a level to ensure that an aircraft is not brought down on a particular flight?
The present limits are still a tiny fraction of the Ash density at the Volcanic cloud source and so low as to not be visible to the naked eye in mist or cloud form.

The Metoffice do a fantastic job limited by the data they have and the tools available to them as well as the mandate that is given to them.

The Friday predictions of dense ash over most of the uk had the media blazing those pictures with headlines of holidays to be ruined for millions of passengers!!!

As those computer predictions have been proved to be so inacurate then surely they should be backed up by round the clock testing of those airmasses to confirm the predictions?

No wonder the Airlines tear their hair out when the predictions change overnight.You cannot run any business with such uncertainty and its the Airlines and our industry who pay not the burocrats,regulators or backwatchers.

Pace

Last edited by Pace; 26th May 2011 at 18:27.
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Old 26th May 2011, 23:30
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http://www.caa.co.uk/docs/33/SafetyNotice201104.pdf

The CAA have issued new guidance:

"As a result of insufficient assurance for the accuracy of the vertical modelling, Volcanic Ash TDAs have previously extended from surface level to the upper limit of the modelled area of high ash concentration. Therefore, although procedures for the overflight of Volcanic Ash TDAs are in place, there has not previously been the ability for operations beneath areas of high ash concentration.

With immediate effect, Volcanic Ash TDAs will be promulgated by NOTAM with an associated upper and lower vertical extent. The publication of this information has been made possible due to improvements that have been made by the Met Office during 2011 to the dispersion model that predicts the movement of volcanic ash in the atmosphere. These included improvements to the way in which the ash concentrations in vertical layers are calculated. However, in order to mitigate an area of residual modelling uncertainty, the vertical extent of the Volcanic Ash TDA will include a lower vertical buffer zone beneath the level of the high contamination area depicted on Volcanic Ash Concentration Charts. This policy has been agreed on the basis of specialist scientific advice and accounts for the meteorological and eruption strength uncertainties that are inherent in this forecast."
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Old 27th May 2011, 01:16
  #293 (permalink)  
 
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Oh well maybe by version 20 we maybe somewhere close to reality? What can we expect with only 60 years experience to date ?anyone making a predictive model for the decline of our industry and job losses in all this ?
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Old 30th May 2011, 14:10
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Originally Posted by KBPsen
Some insight into how the limits were developed can be found here
Thanks KBPsen! This only covers the 2 mg limit though:

"The manufacturers were clear that although they were content that 2x10-3g/m3 represented a tolerable density level for their products, any further increase in this level would require more data on, and analysis of, the effects of ash contamination on airframes and engines" - 23 April 2010. The 4 mg limit (albeit with some riders) was introduced on 18 May 2010 - the data gathering and analysis process must have gone mighty quick in the intervening 3 weeks!

I also agree wholeheartedly with Pace in praising the Met Office's efforts. It's not the forecasting or data that I have a problem with; it's the use the data is put to and the fact that no one seems to have thought to figure out the result of making new rules until confronted with the practical consequences...

The referenced paper also says: "It would seem sensible to consider assessing the tolerability of ash and other particulates at densities of the order of 10^-2 g/m3". I hope that work is progressing as a matter of the utmost urgency, because the new "vertical" rules will be difficult to implement effectively and would be made completely redundant by lateral shrinkage, resulting from a higher density tolerance.
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Old 30th May 2011, 17:21
  #295 (permalink)  
 
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Maybe this time everybody could be involved in drawing up procedures. Several years ago, when the N Atlantic ash plan was drawn up, not one airline, engine or airframe manufacturer responded to invitations to contribute. They are quite happy complaining when it all goes t**ts up though!
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Old 30th May 2011, 18:49
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I also agree wholeheartedly with Pace in praising the Met Office's efforts. It's not the forecasting or data that I have a problem with; it's the use the data is put to and the fact that no one seems to have thought to figure out the result of making new rules until confronted with the practical consequences...
we're dealing with mother nature here, ala rain, hail, birds and now ash

The rules are not made up by throwing darts at a board to guess what is enough.

They are a balance between reasonable avoidance and a practical degree of capability in the product.

Let's start with what can be reasonably avoided versus what one in 10-100 million hours of operation will encouter.

Can somebody as a volcanologist, meteroloigist, flight dispatcher, big iron pilot tell what level of ash they expect to encounter over the lifetime of the fleet ??? e.g. no more than 1 in 10-100 million hours of operation ??

Then we can ask the new engine guys developing engines available sometime 10 years from now if any of those engine can withstand that specific level of ash.

Don't be surprised if the answer comes out yes but at a 10% decrease in fuel efficiency down to B727, DC-9 levels.

OK back to the meeting rooms, now how much ash are you willing to avoid to still meet the product advancements in fuel burn forecasted for 10 years from now ?

You see the answer does not rest alone with the regulator, nor the manufacturer. In fact without stastitically viable data (not tombstone) engineers have no where to start.

BTW, today's products are pretty much frozen regarding upgrade capability to tolerate ash, so you still have another 20 years of what you experienced in the last month in Europe to contend with even if you pour development and rule making resources into the pot in the meantime.

Those are the practical consequences.
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Old 30th May 2011, 19:22
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We had a volcanic ash encounter over the west of Ireland today. Shanwick informed us it might be there at multiple levels. We saw distinct thin but well defined bands of what looked like brown cirrus above and below us and then for two distinct threeish minute periods had a subtle but definitely present smell of rotten eggs in the flight deck. I asked my oppo and he denied responsibility.

There were no indications of any effect on the aircraft or engines, having just landed it is now undergoing detailed inspection.

So although the a/c is probably fine, there was definitely enough for the human nose to detect. I'd love to know the actual concentrations we encountered.

LD
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Old 30th May 2011, 21:23
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Locked door,

That sounds like an interesting event.

I just read this:
Originally Posted by VAAC Website
Latest information received from the Icelandic Meteorological Office indicate that the volcanic activity in Iceland has paused. As a result of this lower activity, UK airspace is not expected to be affected.

Volcanologists and Geologists term this quieter spell of volcanic activity as a ‘paused’ phase. However, it is typical for a volcano like this to have several ‘pauses’ as part of its overall eruption phase. Only when the volcano has been ‘paused’ for three months will it then be regarded as being dormant.

Although no ash is being emitted at the moment, while any volcanic activity continues the Met Office will continue to monitor the situation.
Therefore I wouldn't be amazed if what you encountered turned out to be something else? Pollution maybe?

Anyway, I'm sincerely interested! Please keep us updated!
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Old 30th May 2011, 21:43
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It definitely wasn't pollution, Shanwick passed us an ashtam, it was near where they said it would be. By the time we realised what we were looking at we were in it, and by the time we received climb clearance we were out the other side.
Ref the state of the eruption, my understanding is that the ash has been in the atmosphere for days so the current state of the volcano is not relevant.

The smell was definitely sulphur, and coincided with the discoloured layers we saw.

If I get feedback on the state of the aircraft I will pass it on.

LD
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Old 31st May 2011, 15:11
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It seems the regulators and forecasters have known that a problem was coming for quite some time. Found this paper last night:

Comparison of VAAC atmospheric dispersion models using the 1 November 2004 Grimsvotn eruption
METEOROLOGICAL APPLICATIONS, Meteorol. Appl. 14: 2738 (2007)
Comparison of VAAC atmospheric dispersion models using the 1 November 2004 Grimsv[]tn eruption - Witham - 2007 - Meteorological Applications - Wiley Online Library

Just one quote from the paper:

"One of the most important differences between the models used in this comparison is the technique used for defining the reported ash cloud. The results suggest that the criteria used by the London VAAC leads to a greater forecast extent of a plume than the concentration contours used by the other VAACs, whereas ash forecasts from Washington are the most constrained in aerial extent. Of note here, is that the London results are not based on a threshold chosen by an operator at the time, hence they are reproducible and errors cannot be directed to an individual. The use of one threshold, rather than contours of concentration, also clarifies the data for the forecaster. Given that the current ICAO guidance is to avoid all ash, it is unclear how a forecaster should deal with low concentration contours."
So the London VAAC model is known to be more pessimistic than all the others in use around the world. Aircraft are almost certainly flying elsewhere quite happily in what is known as the "Red Zone" in Europe, due to differences in the model output and interpretation. The paper also points out that the Washington VAAC uses the same intial criteria for defining the outer edge of the cloud as London VAAC. However, the Washington forecaster is allowed to use judgement and sattelite imagery to (apparently) go to levels that are 10, 100 or even 1000 times higher than the initial number. Not playing darts, as Lomapaseo suggest but very flexible nonetheless. I wonder what the London VAAC view on this is? Is the 2 mg limit effectively a 10x judgement call, for the specific case of the 2010 eruption?

Lomapaseo - I wouldn't personally want anyone to consider going back to JT8D type fuel efficiency, to guard against unexpected encounters with very high density ash (way above 4 mg per m3). I thought we were discussing the possibilities of raising the limits at the margins, to make everything a bit more flexible.... Incidentally, another paper (puff.images.alaska.edu/classes/pdf/Prata_2001.pdf) suggests (without reference) that the "US military consider mass loadings >50 mg/m3 a potential hazard to their aircraft operations".
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