Ash clouds threaten air traffic
Brookes:
I'm sorry to say that until your ash forecasting becomes more accurate and operational issues regarding maintaining separation for a mass diversion are addressed, then grounding may remain the only available option.
Pace:
Please do not tell me you have not read the following report:
http://www.alpa.org/portals/alpa/vol...8AshDamage.pdf
1. There is plenty of evidence of what happens when a jet meets volcanic ash. This aircraft was fitted with CFM 56's so its reasonably representative of modern types.:
In other words, things will work just fine, right up until they don't.
That was one aircraft. You do not need to be a genius to understand what happens to engine logistics if Fifty or one hundred aircraft suffer this amount of damage, there is not enough engine overhaul capacity in the world to cope with such an event! How many times do I have to tell you this?
As for risks, of course there is risk, but the risk has to be managed. Currently the only method we have of managing the VA risk at present is to close airspace until a better method is found.
That's no excuse for pretending that zero VA is the only option, or is actually a viable option. We just need better forecasting.
Pace:
I do not question your arguement on risk! but if you read my previous posts you will see there are FAR greater demonstrated risks with a long history of fatal accidents which we do accept and think little of.
Ash todate has a couple of unfatal incidents in dense ash at night and no reported incidents in light ash in over 50 years and millions of flights.
The percieved threat and thats all it is does not warrant the restrictions and financial hits that light ash has caused.
If you want to avoid being killed in an aircraft then dont fly as there is always an element of risk.
Ash in low density is one of the tiniest risk situations and doesnt justify the reaction it has generated or the financial damage to the aviation industry it has created much of which has been media generated hype and scaremongering.
I can point you in many areas of aviation which do hold a far higher risk element and proven risk element if you want to improve safety but it aint ASH
Ash todate has a couple of unfatal incidents in dense ash at night and no reported incidents in light ash in over 50 years and millions of flights.
The percieved threat and thats all it is does not warrant the restrictions and financial hits that light ash has caused.
If you want to avoid being killed in an aircraft then dont fly as there is always an element of risk.
Ash in low density is one of the tiniest risk situations and doesnt justify the reaction it has generated or the financial damage to the aviation industry it has created much of which has been media generated hype and scaremongering.
I can point you in many areas of aviation which do hold a far higher risk element and proven risk element if you want to improve safety but it aint ASH
http://www.alpa.org/portals/alpa/vol...8AshDamage.pdf
1. There is plenty of evidence of what happens when a jet meets volcanic ash. This aircraft was fitted with CFM 56's so its reasonably representative of modern types.:
More than 100 commercial aircraft have unexpectedly encountered volcanic ash in flight and at airports in the past 20 years. Eight of these encounters caused varying degrees of in-flight loss of jet engine power (ref. 1). In some cases this nearly resulted in the crash of the airplane. Reference 5 explains that a range of damage may occur to aircraft that fly through an eruption cloud depending on the concentration of volcanic ash and gas aerosols in the cloud, the length of time the aircraft actually spends in the cloud, and the actions taken by the pilots to exit the cloud.
There were no indications to the flight crew, but sensitive onboard instruments detected the 35-hr-old ash plume. Upon landing there was no visible damage to the airplane or engine first-stage fan blades; later borescope inspection of the engines revealed clogged turbine cooling air passages. The engines were removed and overhauled at a cost of $3.2 million.
There was no evidence of engine damage in the engine trending results, but some of the turbine blades had been operating partially uncooled and may have had a remaining lifetime of as little as 100 hr.
That was one aircraft. You do not need to be a genius to understand what happens to engine logistics if Fifty or one hundred aircraft suffer this amount of damage, there is not enough engine overhaul capacity in the world to cope with such an event! How many times do I have to tell you this?
As for risks, of course there is risk, but the risk has to be managed. Currently the only method we have of managing the VA risk at present is to close airspace until a better method is found.
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Katla is NOT erupting and there are NO indications that Katla is about to erupt.
At least, that's what the Icelandic Met Office say, and if anyone should know, they should.
Órói á stöðvum við Eyjafjallajökul (see top of page)
At least, that's what the Icelandic Met Office say, and if anyone should know, they should.
Órói á stöðvum við Eyjafjallajökul (see top of page)
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Re: New Scientist report on VA in engines
Looks like someone at New Scientist has caught the Bureaucratic Disease causing mental 'tunnel vision'. Ex Cathedra view on testing engines: 'destructive testing across a range of them will be incredibly expensive'. Yes - it would. IF you took brand-new engines straight off the line, put them in a test cell and trashed them. But that wouldn't be a valid test anyway! What you need is a tired engine that's (presumably) most vulnerable to VA ingestion, due to the crud from other sources that's already in there! So if you start your testing programme using engines that are already due for scrap or major rebuilds, cost will start to unwind. Seems obvious to me.....
And why bother taking engines off the aircraft for testing? Now we have a higher floor-limit for ash concentration (4000 microgrammes) and a max dwell time, it would be a simple matter (very low actual risk and low cost) to take empty aircraft already due for engine-removal on a short tour round Iceland, having first borescoped the engines to re-confirm starting state of the HP turbine section. OK - maybe not ultra-precise and full of exhaustive scientific perfection and rigour - but at least enough 'first principles' data to guide next research steps, if any required. Why not?
And why bother taking engines off the aircraft for testing? Now we have a higher floor-limit for ash concentration (4000 microgrammes) and a max dwell time, it would be a simple matter (very low actual risk and low cost) to take empty aircraft already due for engine-removal on a short tour round Iceland, having first borescoped the engines to re-confirm starting state of the HP turbine section. OK - maybe not ultra-precise and full of exhaustive scientific perfection and rigour - but at least enough 'first principles' data to guide next research steps, if any required. Why not?
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Originally Posted by brooksjg
Looks like someone at New Scientist has caught the Bureaucratic Disease causing mental 'tunnel vision'. Ex Cathedra view on testing engines: 'destructive testing across a range of them will be incredibly expensive'.
PBL
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Given that not everyone here knows how to perform an elementary calculation of the risk due to flying through volcanic ash, I put a crude one up at http://www.abnormaldistribution.org/...cial-aviation/
It is part of what I presented in my Risk course this morning. I thought it would be cool to illustrate the things we had been talking about with a topical example.
PBL
It is part of what I presented in my Risk course this morning. I thought it would be cool to illustrate the things we had been talking about with a topical example.
PBL
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Please do not tell me you have not read the following report
You are not dragging that one up yet again as your supreme example
I dont think there is a soul here who has not read that report half a million times.
That was a dense ash encounter at night who here has ever suggested that you will not get a serious problem by flying into dense ash at night?
So whats your solution close down masses of airspace for long periods of time in response to mass hysteria and and a tiny un proven risk while there are far far greater risks you are prepared to take which are proven time and time again in aviation.
Oh well Sunfish with your approach there would not be a problem as there would not be an aviation industry! Get Real
Pace
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Methinks Sunfish is anti-aviation, and hence keeps up a repetitive diatribe on mass-grounding of flights. His/her earlier stuff contains vitriolic remarks about £10 flights to IBZ, etc. Perhaps a frustrated non-pilot or eco-warrior. Certainly not a professional pilot.
Sunfish is a PPL from Melbourne who hates Qantas, hates Commercial Pilots, and thinks he knows everything about aviation.
Pity the string of crashed aeroplanes in his wake speak otherwise.
He is on a tight leash in D&G and has not worked out what the P in pprune stands for yet, but for some reason can't stay away for more than a few days.
Pity the string of crashed aeroplanes in his wake speak otherwise.
He is on a tight leash in D&G and has not worked out what the P in pprune stands for yet, but for some reason can't stay away for more than a few days.
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It is part of what I presented in my Risk course this morning.
Doesn't matter - at least part of the audience must have lost focus, otherwise your comments would have been re-edited by now.
Estimating the total ticket-sale revenue for your example flight is one thing. Then using ALL of that revenue in a break-even calculation, taking into account the probability of whether the flight trashes the engines is something entirely different!
You seem to have have failed to account for OTHER costs associated with the flight, starting with the cost-of-ownership of the aircraft itself, excluding engines, crewing costs etc. OK - you dostate these are crude figures. But realities suggest that margins are already wafer-thin and it's quite surprising that airline operators at the budget end of the market even bother to get out of bed in the morning! Add on the risk of (at least 2) trashed engines during a VA alert, and it would be easy to understand a complete suspension of ops.
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GROUND EVERY AIRCRAFT IN EUROPE NOW! One of our planes took a bird down an engine last night, knocking off a couple of fan blades in the process.
How long will the authorities continue to allow this madness of commercial flights when birds are flying? Can we not close European airspace?
That one bird caused 100% more damage to an aircraft than I've personally ever seen volcanic ash do!!
How long will the authorities continue to allow this madness of commercial flights when birds are flying? Can we not close European airspace?
That one bird caused 100% more damage to an aircraft than I've personally ever seen volcanic ash do!!
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'Your' course? or a course you were at?
I remember reading his Usenet posts years ago as he attempted more formal analysis of the human-machine interface as computers became increasingly involved in aircraft control and navigation.
Since the aircraft accident rate continues to go down, we have fewer statistics to work with so the theoretical aspects of risk management perhaps guide us more on where to allocate our training, maintenance and operational resources. Of course, politics and economics probably have the last word in the real world as many have observed on this thread.
As a pilot, I just want to keep those engines turning and not have to fill out paperwork when I land...
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Given that not everyone here knows how to perform an elementary calculation of the risk due to flying through volcanic ash, I put a crude one up at http://www.abnormaldistribution.org/...cial-aviation/
It is part of what I presented in my Risk course this morning. I thought it would be cool to illustrate the things we had been talking about with a topical example.
PBL
It is part of what I presented in my Risk course this morning. I thought it would be cool to illustrate the things we had been talking about with a topical example.
PBL
On your item 4, you seem to have taken pCatastrophe = pIFSD - this isn't correct. Ok, you mention dead-stick landing, and lets say we accept that even with a Sully/Burkill you are still looking at a hull loss so catastrophe impact applies. Still it's not right though:
Firstly, you need all engines shutdown - and the documented incidents show asymmetric damage. Correlated, but not 100%.
Secondly, you need a failure to relight. We know that descending to clean air will cool, solidify and shatter the glass, typically allowing a relight (every time so far, I believe).
So, pCatastrophe = pIFSD * (correlationIFSD ^ no.engines) * (1 - pRelight). Couple of orders of magnitude there ?
Then on item (2) - you are probably going to have the increased inspection costs anyway as a regulatory cost of flying. Adjust your business model - or go bust.
On (3), your impact is probably going to vary much more widely. Engines have a limited life anyway, in some cases you will have effectively just lost some remaining hours use. Notably, the NASA report states that the most damaged engine was coming up for major work anyway - and it isn't clear if the 3m cost included that engine, or the work that was going to be done anyway. Conversely you could hit Sunfish's problem and have the cost of a fleet grounded due to lack of engine repair capacity. I think the impact range on (3) is more like 10^5 - 10^8 (Sunfish scenario, or bust).
But that's all minor nitpicking really.
Then we get to the cost of not flying.
You've used gross ticket revenue as the loss! Seriously, did no one in your audience call you on that ? [ Probably a good job I'm not on your course, I don't think I'd be a good quiet student these days
]In the EU, at least, the cost of not flying is very little to do with ticket price. Much as some airline bosses would love to say "flight cancelled, here's your 50p back (less £5 admin charge)", they can't.
The main cost of not flying is the cost of getting your pax back.
Options, roughly:
1. your pax agrees to take ticket refund
2. you pay for them to get on another airline
3. you put them on one of your flights later (+hotels/meals etc. for 50% who are on return leg)
Now, (1) you'd love, but you can't choose, (2) ain't going to happen with everyone grounded, so you are stuck with (3). Cost of putting pax on your own flights - zero (more or less) if you use your spare capacity. Unfortunately, if you are running daily at say 80% load factor, a 1 day shutdown means a four day backlog (5 days total, 3 days ave pax. delay). A six day shutdown would be a 24day backlog, 30 days total, 18 days ave pax delay. At, say, 100 per day per pax for hotels (who aren't exactly going to be handing out discounts...) etc., that's 1800 per 50% of pax, or approx 150k
(+ some for the outward pax) for your example flight. Reality is that it may be a bit less than that because you will give seats to these pax that you would normally have sold - but those will be last minute seats that would have gone for premium prices, so you still lose several times the average ticket price paid by the stranded pax. May be cheaper than the hotels though...And then of course if the shutdown is holiday season when your load factors are much higher than average...
Feed those numbers (150k) into your risk equation and (by day five or six) you need pMajorDamage around 1 in 5, and pIFSD about 1 in 20 (say pRelight is 0.95) to be worth not flying. Now, if you've done a few test flights looking for ash, and seen no sign of a (1) event let alone a (2) or more, I think you'd be legitimately screaming for airspace to be opened.
Same equation, even same risk events and impacts, ... very different results. All in the assumptions and inputs. [so who's right ? Well, I am not an aviation safety expert like PBL - but that isn't where we differ on our figures. Reality is that neither of us is an accountant for an airline. ]
Your regulators have done a very good job in a very short time. You should all be thankful.
And as a special favour, here is a couple of photos I just took of a scrapped first stage blade. There are well over 100 cooling channels in it, most thinner than a small needle. Many of them are not circular either.
It's about twice/ three times life size.
Pace and Brooksg will now explain how each of those little holes on each blade or vane in every affected engine is going to be cleaned and checked for volcanic glass.
Leprechauns? Little elves perhaps? The best I can think of is an alkaline cleaner, but of course I don't know what that will do to any ceramic coatings or the metallurgy, including hydrogen embrittlement etc.
Against stupidity the very gods
Themselves contend in vain. - Schiller
Themselves contend in vain. - Schiller
It's about twice/ three times life size.
Pace and Brooksg will now explain how each of those little holes on each blade or vane in every affected engine is going to be cleaned and checked for volcanic glass.
Leprechauns? Little elves perhaps? The best I can think of is an alkaline cleaner, but of course I don't know what that will do to any ceramic coatings or the metallurgy, including hydrogen embrittlement etc.
Last edited by Sunfish; 30th May 2010 at 00:33.
Nice photos of a turbine blade.
So air flows through those holes and comes out the other end.
So dust is light enough to float in the air at very high altitudes and manages to flow into the cooling channels and out the other end.
Too much dust and problems begin to develop oh so slowly at first.
It's a good thing that too much of a bad thing doesn't occur very often.
Now if we could only get birds down to the size of dust specs.
It's the melting of the dust and replating that's the problem, but fortunately that's pretty rare if you manage your flight path around the worst of the clouds.
So air flows through those holes and comes out the other end.
So dust is light enough to float in the air at very high altitudes and manages to flow into the cooling channels and out the other end.
Too much dust and problems begin to develop oh so slowly at first.
It's a good thing that too much of a bad thing doesn't occur very often.
Now if we could only get birds down to the size of dust specs.
It's the melting of the dust and replating that's the problem, but fortunately that's pretty rare if you manage your flight path around the worst of the clouds.
You've got it all in one paragraph there. If you talk to the sales team, who "sell" the engines, I am sure they licked their lips at the prospect of selling some additional units to a research study into the issue. "Yes, Mr Study-Leader, it is most unfortunate that what you want to study is Incredibly Expensive." Especially if it looks like a government-sponsored project, when the typical government-sponsored project approach of sales teams would apply (ie take your normal price to the commercial world and multiply by 10).
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lomapaseo
Not so. No cooling effect doing it your way. Cool air is taken through a bleed and exits from all the holes in the blade, thus keeping it cooler. The dust travels through the bleed system and can melt and block the exit holes... blade gets too hot and is damaged.
So air flows through those holes and comes out the other end.
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The dust travels through the bleed system and can melt and block the exit holes... blade gets too hot and is damaged
(Forget, for a moment, accurate detection of areas of HIGH VA concentration in bad visibility and especially at night, and the specific risks from this. Forget also the possibility of blocked pitot heads and other critical features of the aircraft that might be affected by LOW VA .)
A VA particle passing through a combustion chamber will probably be melted, so may solidify onto a turbine blade. Yup - Very Bad Thing, especially if the build-up of glassy material blocks the exit(s) of cooling duct(s).
VA particles going through the cooling bleed and then through the inside of a (hot) blade might also melt and would then presumably be more likely to re-solidify in a clump where the temperature was lower and block some ducts. Another Very Bad Thing.
BUT what is the temperature of the cooling air inside a blade or other potential hot-spot? As low as possible, obviously, so as to give maximum cooling effect - engine manufacturers have a design trade-off between larger volume of hotter air versus smaller, cooler volume to achieve a given cooling effect. So given that it costs thrust to divert air into the cooling bleeds, the air temperature is going to be minimised by design. The big question: can the turbine cooling air temperature ever exceed the melting point of VA? If so, under what circumstances and where?
Anyone know this? I don't know and can't find any reference myself....
The big question: can the turbine cooling air temperature ever exceed the melting point of VA? If so, under what circumstances and where?
Anyone know this? I don't know and can't find any reference myself....
Anyone know this? I don't know and can't find any reference myself....
But it hasn't happened yet because the probability of the if factor and a high ash concentration hasn't come together.
I wonder if the if factor includes a meteorite strike at the same time