Ash clouds threaten air traffic
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My thanks to Airbubba for his encomium. I hope I deserve it!
This one.
Concerning my crude PRA, both brooksjg and infrequentflyer789 point out that identifying revenue with net income isn't realistic. I know that, indeed I thought I had pointed it out.
Do they have a better one which can be justified using publically-available figures?
My trivial calculation yields a low estimate for the risk; in other words, if you think net income is less than this revenue estimate, which it almost certainly is, then my crude estimate of risk is an underestimate. It still seems to me pretty high, rather higher indeed than Pace's estimate of zero risk. That's why I said it yields insight, because many discussants seem not yet to have seriously attempted to estimate the risk.
Infrequentflyer789 apparently wants to add another term:
Is it?
On the first day of the ban, I was in Delft, in the Netherlands, with people who had travelled from Vienna, Suffolk and Liverpool, all busy trying to rebook themselves by rail. None of those people have been permanently lost to their carrier of choice that day. As far as I know, Eurostar has not had a noticeable permanent slump in bookings since the debacle in mid-December 2009. And I doubt all those transatlantic passengers are going to start travelling by ship. (I do know of one set of colleagues who travelled back to Brunswick from Beijing on the Trans-Siberian railway! But they didn't all do it; my colleagues who took a chance on waiting for the next available flight managed to get back a few days earlier.)
So I am not sure about a claim that it is the main cost. But if you have a way of including some estimate of it in a risk analysis, please go ahead.
You also want to say that the severity of losing all engines is not necessarily catastrophic. Sure, as anyone who read about the Air Transat "save" of August 2001 knows, but it is usually taken to be catastrophic as far as certification and regulation goes. Some - indeed some would argue most - engineering definitions of risk classify an event category by worst-case outcome.
I am not sure what equation you mean – I didn't propose one.
I don't see off-hand how «feed[ing] those numbers» in to anything I wrote will give me something which I can interpret as a risk estimate, but as I said if you can indeed produce a modified risk analysis with it according to the De Moivre formula, and you can justify the approximations, more power to you. I'd like to see it.
PBL
Originally Posted by brooksjg
'Your' course? or a course you were at?
Concerning my crude PRA, both brooksjg and infrequentflyer789 point out that identifying revenue with net income isn't realistic. I know that, indeed I thought I had pointed it out.
Do they have a better one which can be justified using publically-available figures?
My trivial calculation yields a low estimate for the risk; in other words, if you think net income is less than this revenue estimate, which it almost certainly is, then my crude estimate of risk is an underestimate. It still seems to me pretty high, rather higher indeed than Pace's estimate of zero risk. That's why I said it yields insight, because many discussants seem not yet to have seriously attempted to estimate the risk.
Infrequentflyer789 apparently wants to add another term:
Originally Posted by infrequentflyer789
The main cost of not flying is the cost of getting your pax back.
On the first day of the ban, I was in Delft, in the Netherlands, with people who had travelled from Vienna, Suffolk and Liverpool, all busy trying to rebook themselves by rail. None of those people have been permanently lost to their carrier of choice that day. As far as I know, Eurostar has not had a noticeable permanent slump in bookings since the debacle in mid-December 2009. And I doubt all those transatlantic passengers are going to start travelling by ship. (I do know of one set of colleagues who travelled back to Brunswick from Beijing on the Trans-Siberian railway! But they didn't all do it; my colleagues who took a chance on waiting for the next available flight managed to get back a few days earlier.)
So I am not sure about a claim that it is the main cost. But if you have a way of including some estimate of it in a risk analysis, please go ahead.
You also want to say that the severity of losing all engines is not necessarily catastrophic. Sure, as anyone who read about the Air Transat "save" of August 2001 knows, but it is usually taken to be catastrophic as far as certification and regulation goes. Some - indeed some would argue most - engineering definitions of risk classify an event category by worst-case outcome.
Originally Posted by infrequentflyer789
Feed those numbers (150k) into your risk equation
I don't see off-hand how «feed[ing] those numbers» in to anything I wrote will give me something which I can interpret as a risk estimate, but as I said if you can indeed produce a modified risk analysis with it according to the De Moivre formula, and you can justify the approximations, more power to you. I'd like to see it.
PBL
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rather higher indeed than Pace's estimate of zero risk.
Where please have I indicated that there is Zero risk?
When you get up in the morning and cross the street there is not Zero risk that you will not be flattened by an out of control Lorry!
There are in my book two types of risk. Demonstrated risk where there is previous evidence of that risk causing real harm to life and if you like suspected risk where there is no evidence of a threat.
We all know that aircraft crash in strong winds and shear and do so on a continuing basis. We have wind limits as well as cross wind limits to work within but still the crashes happen.
What do you do? do you drop the acceptable wind strengths and make travel by aircraft less reliable. Do you train pilots better or give them better equiptment? But that is a demonstrated risk which is known and which we appear accept.
We know that flying into dense ash can stop engines that is a demonstrated risk with a couple of incidents to prove.
But light ash has a suspected risk only! does it warrant the massive cost and destruction to the aircraft industry that we have bestowed on it mainly demanded by media hype and scaremongering?
If you have evidence that light ash can stop engines in flight show it?
No one doubts dense ash. That can be seen and mapped but light ash cannot. For that reason we have computer generated mathematical forecasts of where it may or may not be.
But frankly until there is some evidence I personally have no fear of flying in clear air which may hold the equivalent of half a thimble full of talc in a five bedroom house to me thats paranoia.
Unless of course you practically prove otherwise and not by another load of mathematical calculations.
I totally support more inspections on aircraft flying in light ash as my only concern as a pilot is damage that can bring an aircraft down (and not increased maintenance cost) but to close huge blocks of airspace on an as yet ungrounded fear is overkill (excuse the pun)
Pace
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Originally Posted by Pace
Where please have I indicated that there is Zero risk?
Originally Posted by Pace
You are trying to do a risk analysis on something which to date statistically has shown NOT to be a risk.
Originally Posted by PBL
(a), the chance that current levels of ash posed no risk; (b) the damage which ensues if current levels pose no risk; (c) the chance that current levels of ash pose some risk; (d) the damage that thereby ensues. I pointed out that the risk is (a)x(b) + (c)x(d)........
Pace argues that (a) is 1 and (c) is 0.
Pace argues that (a) is 1 and (c) is 0.
Originally Posted by Pace
I do not question your arguement on risk!
PBL
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You are trying to do a risk analysis on something which to date statistically has shown NOT to be a risk.
Did I misunderstand? NO
The piece I placed above still does not use the word ZERO which is very different to a statement saying "has not shown to be a risk".low level ash has NOT shown itself to being a risk to life to date! that may change although I very, very, very, much doubt it.
It may shorten engine life and as such increase costs but I challenge you again to name one situation in the whole history of aviation where there has been a situation where entry into low levels of ash have caused a situation where life could have been threatened?
We are probably both being pedantic in our use of the word risk and probably both have differing interpretations of the word risk?
Mine is more differentiating between a known and proven risk and a feared percieved risk which is not yet proven.
Because the one is proven while the other is not it does NOT mean the other is zero risk (if you get what I mean
There is a much higher known risk of being downed by birds what are you doing to close down coastal based airports and chopping off huge blocks of airspace in the migration season as has happened over light ash?
There is a saying that no one ever built a statue to a committee yet there have been too many committees involved in all of this and all with their own agendas again if you understand what I mean
Pace
There is some miscommunication here concerning risk.
What is missing is the statistical term called "expectation" which is the product of the probability of an event multiplied by the cost if the event occurs.
That is why you still fly given the fact of bird strikes:
Probability of birdstrike times cost of birdstrike = expectation value.
Furthermore, we manage the birdstrike probability down as far as we can by removing food sources, using bird scarers etc. We also alert pilots to the proximity of wildlife (or at least Australian NOTAMS do)
We also manage the cost of a birdstrike down as far as we think it is economically viable. That is why we require engines to be able to deliver thrust for so many minutes after ingesting a standard bird.
Now take Volcanic ash.
We manage the probability of hitting it by having VAAC's, forecasts, closing airspace.
But at this time we cannot manage the costs down if ash of sufficient density is flown through.
To put it another way, we cannot build an ash proof aircraft or engine.
What is missing is the statistical term called "expectation" which is the product of the probability of an event multiplied by the cost if the event occurs.
That is why you still fly given the fact of bird strikes:
Probability of birdstrike times cost of birdstrike = expectation value.
Furthermore, we manage the birdstrike probability down as far as we can by removing food sources, using bird scarers etc. We also alert pilots to the proximity of wildlife (or at least Australian NOTAMS do)
We also manage the cost of a birdstrike down as far as we think it is economically viable. That is why we require engines to be able to deliver thrust for so many minutes after ingesting a standard bird.
Now take Volcanic ash.
We manage the probability of hitting it by having VAAC's, forecasts, closing airspace.
But at this time we cannot manage the costs down if ash of sufficient density is flown through.
To put it another way, we cannot build an ash proof aircraft or engine.
Rather, we cannot agree on what constitutes "standard ash" against which to test or regulate. There's no such thing as a bird-proof engine, either, if the ambient bird density is high enough...
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Citation CJ2 Volcanic ash encounter pictures
I've received these pictures and since I haven't found anything related to this event listed here, I'm posting the pictures.
It's a PDF file so I've shared it in this link:
http://db.tt/qz74EL
I don't have anymore info other than the pictures, sorry.
It's a PDF file so I've shared it in this link:
http://db.tt/qz74EL
I don't have anymore info other than the pictures, sorry.
A volcano in the Gulf Coast would get rid of that nasty oil spill. 
Why they think the oil leaving the "loop current" for the Gulf stream (which heads for England) is a good thing is not for me to reason why.
Why they think the oil leaving the "loop current" for the Gulf stream (which heads for England) is a good thing is not for me to reason why.
Pugachev Cobra
Nope, that has nothing at all to do with VA and the pix have been done to death. Not digging at you, just stating the fact.
All else Yes, it's those pix again.
Nope, that has nothing at all to do with VA and the pix have been done to death. Not digging at you, just stating the fact.
All else Yes, it's those pix again.
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Citation CJ2 Volcanic ash encounter pictures
Been there, already got the T-shirt.....
IT'S A HOAX!!! (Something else unpleasant happened to this engine, during MARCH ie. before VA became an issue).
Already been through this thread on 19th May. Didn't you even look at the 'properties' of the picture before wrapping it up and posting it. (I bet it had a date in it!!)
Do keep up!
Rather, we cannot agree on what constitutes "standard ash" against which to test or regulate. There's no such thing as a bird-proof engine, either, if the ambient bird density is high enough...
The environmental encounter regulations are based on probability of encounter. The probability of encounter considers historical experience. Thats why the Feds want all bird strikes reported so as to approximate the sizes, quanities per engine and results. The encounter stuff obviously contains all possibilities of avoidance (both by the birds as well as man). Additionally it keeps track of nature changing by virtue of things like the canada goose etc.
The results of the encounter also consider the good and bad point of changing technologies in the product (high-bypass, wide chord fan blades, FADECs etc. etc.)
When it comes to volcanic ash and super cooled droplets the data to base a standard test on need to consider how often you expect to encounter any given size and density per minute as well as available technolgy within the aircraft to withstand the encounter.
The prioritization for answering the questions about designing to a known standard would also consider what level of standard provides a freedom from risk of an serious result to something ten to 100 times better than the overall risk we are flying within today.
So it seems that since the average operations today in a volcanic ash enviornment have not exceeded the risk floor of 10 to 100 times better than the average risk from all causes, that maybe we should be chasing after some bigger fish like super-cooled droplets in both avoidance and capability.
BTW, cost doesn't enter into setting min safety standards but of course does enter into everything else in how to run a business.
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Originally Posted by lomapaseo
BTW, cost doesn't enter into setting min safety standards ...
The ALARP principle is also used in other jurisdictions.
Reducing risks ALARP means, roughly, that risks must be reduced until the cost of reducing them further becomes "grossly disproportionate" to the benefits.
PBL
Last edited by PBL; 31st May 2010 at 12:37.
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Turbine cooling system temperature
On 30th May I posted that I had been trying to discover the maximum temperature of air inside turbine blades and other parts of the cooling system.
I now have an answer for one type of (high bypass) engine: the air can be 650 to 700 C degrees. This vould be relevant to any discussion about VA going through the engine core, since this is quite close to the suggested melting point of the ash and therefore the ash could at least in theory block the cooling holes in a liquid state. This is presumably more problematic than considering blockages due to solid, very small particles.
The same source suggested that there are also concerns about melted VA hitting the outside of turbine blades after going through the combustor. Some surface chemistry possibilities that do the blade no good, apparently. Again, it's all a question of how much VA......?
I now have an answer for one type of (high bypass) engine: the air can be 650 to 700 C degrees. This vould be relevant to any discussion about VA going through the engine core, since this is quite close to the suggested melting point of the ash and therefore the ash could at least in theory block the cooling holes in a liquid state. This is presumably more problematic than considering blockages due to solid, very small particles.
The same source suggested that there are also concerns about melted VA hitting the outside of turbine blades after going through the combustor. Some surface chemistry possibilities that do the blade no good, apparently. Again, it's all a question of how much VA......?
brooksjg
Can you provde more support, link, personal experience, etc. that suggest that the melting point of VA is "quite close" to the cooling air temperature of 650-700 C degrees in a turbine blade?
I don't recall that there is any documented cases of melted VA inside a turbine blade
I now have an answer for one type of (high bypass) engine: the air can be 650 to 700 C degrees. This vould be relevant to any discussion about VA going through the engine core, since this is quite close to the suggested melting point of the ash and therefore the ash could at least in theory block the cooling holes in a liquid state. This is presumably more problematic than considering blockages due to solid, very small particles.
I don't recall that there is any documented cases of melted VA inside a turbine blade
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I don't recall that there is any documented cases of melted VA inside a turbine blade
I've seen various 'melting points' for VA mentioned, some early in this thread. However, since they were considerably lower than the figure I 've now been told for the max air temperature in the cooling ducts, I sort-of discounted most of these lower numbers as incorrect - otherwise, as you suggest, VA would have melted and evidence would surely have been produced from previous encounters. The other problem is that glassy materials with high silica content don't have a 'melting point' as such - they soften / liquefy over a range of temperatures.
But saying that such-&-such could not have happened is not the same as failing to find evidence that it ever did.....
I'm not in a position to clarify this and further speculation would not add value. But I, for one, would like to hear more from people who do know the correct answers. An information vacuum seems to have occurred!
I'm not in a position to clarify this and further speculation would not add value. But I, for one, would like to hear more from people who do know the correct answers. An information vacuum seems to have occurred!
The good and the bad about this vacumn of knowledge is that the really significant findindings get reported and leak out within the industry while the business as usual stuff remains burried in the logs. That was the way it has been with bird ingestions as well.
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Hey guys, there never was any vaccuum. Every profession has sufficient alpha animals amongst them to fill the void with whatever limited knowledge they have. It makes for boring reading, though. Here we have two groups: Those who got it, and those who will never get it. I am stunned that after decades of painful lessons and rules written with blood, so many still think that they, and only they, have the right answer. I've had it. Over 'n' out!
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Here we have two groups: Those who got it, and those who will never get it
There are at least three groups at the Sharp End!
- the certain (but possibly wrong) sceptics who are not supported by the current (or previous) rules about VA;
- the certain and uncertain 'conformists' who may prefer to go along with whatever's thrown at them rather than appear radical, non-conformist, awkward-squad, etc.;
- the other sceptics who go along with whatever rules are current but are uneasy about the 'certainties' as presented.
Then there are other players:
- regulatory bodies, including some people who seem uncomfortable with any form of risk management. Why such people ever end up working in regulatory organisations where the main activity is essentially risk management defeats me. Elimination of risk will never be an option - if it were, aircraft would never have been developed at all!
- businessmen, accountants and shareholders wanting to make money out of the industry;
- governments who suddenly realize that whole economies will go rapidly down the pan without aviation.
Complete certainty is not an option either - I doubt there ever will be any about VA and its risks.
Regulation based on 'Zero VA' was clearly never based on observational science. It was an easy decision until some VA actually loomed into view, then its weakness became self-evident (and proved by actual experience). The current permitted VA maxima are also a line-holding exercise in the continued absence of real research. The forecasting system is also evidently prone to errors, especially over-estimation of coverage, again presumably due to lack of real data collected by direct observation of the ash clouds.
Somehow or another, the industry must pull together and spend the money, on engine research and on atmospheric observation (not forecasting / prediction, if certainty about ash location and density is the requirement).
The only element entirely beyond control is the volcanoes.
I'm sick of this. Comments slagging off about regulators are just unfounded.
Here are the documents and research details to date.
ICAO volcanic ash contingency plan, edition 2 September 2009.
Documents
ICAO manual.
http://www2.icao.int/en/anb/met-aim/...Amend.%201.pdf
ICAO taskforce:
ICAO NEWS BRIEF ICAO News Centre
Here are the documents and research details to date.
ICAO volcanic ash contingency plan, edition 2 September 2009.
Documents
ICAO manual.
http://www2.icao.int/en/anb/met-aim/...Amend.%201.pdf
ICAO taskforce:
ICAO NEWS BRIEF ICAO News Centre
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Sandblast effect ...
From down the back the other day, noticed the painted RYANAIR logo on both my favorite airline's winglets had been significantly 'sandblasted' with the letters 30% obliterated. When I got off, I noted that the spinner spirals on the engines looked similarly beaten up.
Is this ash damage? I don't recall noticing such wear and tear previously. If so, are Europe's workhorse airlines now getting a better picture of what's it costing in extra maintenance ?
Is this ash damage? I don't recall noticing such wear and tear previously. If so, are Europe's workhorse airlines now getting a better picture of what's it costing in extra maintenance ?