Ash clouds threaten air traffic
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how much of the nasty stuff which coats turbine blades with glass and blocks pitot tubes
On the available published evidence (and ONLY that - I'm not privy to confidential info from engine manufacturers), ash at low levels is quite unlikely to coat blades permanently or block pitot tubes. OK - particles might melt and stick temporarily onto turbine blades BUT chances are (speculating a bit here!) it seems UNLIKELY that there'd be enough to form a continuous film on the blade, given the conditions inside the engine. Then, when the turbine's internal temperatures cycle (due to throttle up/down and especially shutdowns and restarts on the ground), differential expansion movement of the metal and ash particles MAY allow it to flake off, causing no further problem.
A key issue with small quantities of ash, ESPECIALLY if there are repeated ash encounters, is presumably going to be build-up of accumulations in confined spaces, such as inside blades, in the air galleries serving the cooling holes. Unless blade cooling fails, this ash presumably would NOT melt but seems to me there must be plenty of possibilities for lumps of it to build up. Of course, if the air-flow IS impeded, then the blade overheats, the ash melts and the blockage becomes permanent and potentially very damaging.
What I've not seen yet is any comment about possibilities of removing ash post-flight BEFORE it builds up and melts.... Engine washing (eg. P&W Eco Power) is already in use for other reasons - maybe it would also be relevant for ash.
Over to you, engine experts.
A key issue with small quantities of ash, ESPECIALLY if there are repeated ash encounters, is presumably going to be build-up of accumulations in confined spaces, such as inside blades, in the air galleries serving the cooling holes. Unless blade cooling fails, this ash presumably would NOT melt but seems to me there must be plenty of possibilities for lumps of it to build up. Of course, if the air-flow IS impeded, then the blade overheats, the ash melts and the blockage becomes permanent and potentially very damaging.
What I've not seen yet is any comment about possibilities of removing ash post-flight BEFORE it builds up and melts.... Engine washing (eg. P&W Eco Power) is already in use for other reasons - maybe it would also be relevant for ash.
What I've not seen yet is any comment about possibilities of removing ash post-flight BEFORE it builds up and melts.... Engine washing (eg. P&W Eco Power) is already in use for other reasons - maybe it would also be relevant for ash.
This is a suitable discussion for the Tech section
The only time that the ash is going to melt is when it's entrained in the compressor air as it passes through the stoichrometric heat of the burner. Once it reaches the cooler turbine it's either melted or not. Once you are out of the cloud the residual ash is expected to be only lodged in crevices where it can't get blown away.
How long it stays in those crevices is up to the operator and their maintenance procedures (detect and remove)
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I will be very surprised if anyone with appropriate knowledge is permitted to manage this issue, as recently on BBC television, an Austrian Green MEP, one Eva Lichtenberger proclaimed that the 'airlines and pilots would make decisions on commercial grounds and hence it needs to be left to the European Union to decide impartially'!
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If anyone (else! I probably don't get out enough! 
) wants to delve into the technicalities of ash in turbines in the Tech section, please start a suitable thread and I'll join in. I tried it already in the Engineers area and it failed to generate much traffic.
) wants to delve into the technicalities of ash in turbines in the Tech section, please start a suitable thread and I'll join in. I tried it already in the Engineers area and it failed to generate much traffic.
Per Ardua ad Astraeus
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- it's there waiting for you!
Loma - I think you misunderstood Brooksigs post?
You said
He said
Two different scenarios.
Yours: Ash in the combustion stream Brooksig and others: Compressor air fed THROUGH the blades for cooling and never combusted
Loma - I think you misunderstood Brooksigs post?
You said
The only time that the ash is going to melt
Unless blade cooling fails, this ash presumably would NOT melt but seems to me there must be plenty of possibilities for lumps of it to build up.
Yours: Ash in the combustion stream Brooksig and others: Compressor air fed THROUGH the blades for cooling and never combusted
I'm not a volcano expert.
But this is the first time I've seen a earthquake in Katla instead of Eyjafjallajökull (which I will refer by its name in English, Island Mountains Glacier) Volcano.
Earthquakes - Mýrdalsjökull
Two in the past 24hours.
But this is the first time I've seen a earthquake in Katla instead of Eyjafjallajökull (which I will refer by its name in English, Island Mountains Glacier) Volcano.
Earthquakes - Mýrdalsjökull
Two in the past 24hours.
Last edited by peter we; 30th Apr 2010 at 08:49.
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Self Loading Freight - Demanding To Fly Into Ash
What the f*ck don't people get
- volcanic ask shuts down jet turbines.
Yet, as always, we get the SLF who demand to fly during this period.
These same f*cks then would sue at the drop of a hat when their left with the APU as the only remaining operating turbine at altitude (if available).
Better not play bluff with volcanic ash - even if you miss out on your holiday to Ibiza.
(mind you, you probably only paid $10 for the seat...)
- volcanic ask shuts down jet turbines.Yet, as always, we get the SLF who demand to fly during this period.
These same f*cks then would sue at the drop of a hat when their left with the APU as the only remaining operating turbine at altitude (if available).
Better not play bluff with volcanic ash - even if you miss out on your holiday to Ibiza.
(mind you, you probably only paid $10 for the seat...)
I Have Control
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Fraud b737800capt06
Bit similar to Sunfish, eh? Why all the vitriol from Australia, which never gets volcanic ash? Bit bored, are we/you?
No self-respecting airline pilot refers to pax as you do.
No self-respecting airline pilot refers to pax as you do.
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This week's Flight international quotes a maximum allowable ash concentration of 10e-16g/cuM (That's ten to the minus seventeen). This was reduced to 10e-16 to allow flying to resume.
If - if that figure is correct - and Flight is generally pretty good with accuracy- this leads to some interesting numbers...
Mass flow thru a CFM56 approx 1000lb/sec or 454Kg/sec
Air density at FL200 approx 0.5Kg/cuM
Volume flow is 900cuM/sec
or 3.24Million cuM/hr - ie 3,2 x 10e6
Times the max allowable concentration and we have 3.2 x 10e6 times 10e-16
= 3.2 x 10e-10 grams per hour of ash. That's far too small to be a hazard, by a factor of ten or a hundred billion or so, surely? There is something gigantically wrong here!
Shurely shome mishtake?
(and I hope it isn't my maths)
Standing by to be corrected!
If - if that figure is correct - and Flight is generally pretty good with accuracy- this leads to some interesting numbers...
Mass flow thru a CFM56 approx 1000lb/sec or 454Kg/sec
Air density at FL200 approx 0.5Kg/cuM
Volume flow is 900cuM/sec
or 3.24Million cuM/hr - ie 3,2 x 10e6
Times the max allowable concentration and we have 3.2 x 10e6 times 10e-16
= 3.2 x 10e-10 grams per hour of ash. That's far too small to be a hazard, by a factor of ten or a hundred billion or so, surely? There is something gigantically wrong here!
Shurely shome mishtake?
(and I hope it isn't my maths)
Standing by to be corrected!
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This week's Flight international quotes a maximum allowable ash concentration of 10e-16g/cuM (That's ten to the minus seventeen). This was reduced to 10e-16 to allow flying to resume.
[...]
Shurely shome mishtake?
(and I hope it isn't my maths)
Standing by to be corrected!
[...]
Shurely shome mishtake?
(and I hope it isn't my maths)
Standing by to be corrected!
A link to the flight article, if it's online, would be good (my quick search hasn't turned it up).
A couple of things don't tally:
1. the "previous" limit has always been referred to as "zero" - not any particular density. Elsewhere in the world this is apparently treated as "zero visible", in Europe as "zero detectable / zero predicted by model" - the latter obviously being a moving target that doesn't make sense. 10e-17g may be the current limit of detectablity I guess.
2. other reports have the new limit at 2000 ug/cuM (micrograms / cubic metre), with no risk below 200, precautions between 200 and 2000 and no flight above 2000. Measured levels over the UK apparently never exceeded 100.
Those new levels are way off what you have quoted from Flight - I suspect they've just completely misprinted a number somewhere.
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Risk
Where is the empirical evidence from engine/airframe manufacturers to warrant anything but zero tolerance?
Firstly 'zero tolerance', as you put it, would presumably mean no flights at all in any areas with any quantity of ash in the air. Taking this to the logical extreme, a single particle of ash in the entire European airspace would be enough to ground everyone. That's 'zero tolerance'.
Secondly, would this approach also apply to other know risk factors, such as bird strikes and thunderstorms, such that all flights in any areas affected by birds and CB's would also be banned? 'Zero tolerance' again?
Flying involves some risk (everything does). Establishing an acceptable level of risk is what the airline industry does every day, and what most people do themselves every day. It's 'risky' to drive to work, but most of us accept the risk because we live too far away to walk. Would we drive after no sleep for 36 hours, or when drunk? Most of us would say no, because the risk is much higher, but we can't demand a 'zero tolerance' of risk on the roads or none of us would ever get in our cars.
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"zero tolerance"?
Originally Posted by infrequentflyer789
1. the "previous" limit has always been referred to as "zero" - not any particular density. Elsewhere in the world this is apparently treated as "zero visible", in Europe as "zero detectable / zero predicted by model" - the latter obviously being a moving target that doesn't make sense.
It amazes me that some pilots (if that's what they really are?) now claim they think getting back in the air was a dangerous decision forced by "reckless" airlines who allegedly put finance before safety?
As far as I know there is not one case known where an a/c sustained damage, while staying out of visible ash in VMC. I'd be interested in hearing about it, if there was such a case.
I can't wait for the National Geographic documentary to be made about this "blunder of the century"!
This article by the "Daily Mail" is spot on, I think.
NASA Encounter with Ash
I'm not sure if this has been posted but for anyone who is interested in the effect of volcanic ash, the NASA Airborne Sciences Platform aircraft (a converted DC-8 fitted with CFM-56-2 turbofans) inadvertently flew through a volcanic ash cloud in 2000. The full report is here: http://www.avweb.com/pdf/volcanic_as...sa_grindle.pdf
Vital reading I'd say. A proper scientific analysis. Total cost of engine refurbishment as a result of this encounter (which was 200 miles from the known ash plume) was $3.2million...
- GY
Vital reading I'd say. A proper scientific analysis. Total cost of engine refurbishment as a result of this encounter (which was 200 miles from the known ash plume) was $3.2million...
- GY
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to: b737800capt06
I'm a pilot who flies very often as a passenger. I hope not to hear such remark from you in person. I don't think you got enough spine. Close the door, drive me home and don't wake me up with your b*l*s**t "welcome aboard" pa announcement, will you? You bite the hand who feeds you... How pathetic!
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Already posted and the aircraft was in a 'visible' (in the sense it blocked out star light) ash cloud, although the cloud was not avoided due to it being at night.
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GarageYears
I read this report before but it is not a scientific study. All it basically says is that the aircraft was flying at NIGHT. That in itself is odd for a scientific flight? Why do the flight at night when the crew cannot see what they are flying into?
The only indication was the ash sensing equiptment on the aircraft which gave an ash indication.
The aircraft was checked on landing but with NO indications of an ash encounter on the initial inspections.
So much so that they continued for another 65 hrs of flight before the engines were stripped and damage discovered.
There is nothing to say that the ash encounter was the one they suspected. It may have occurred at a later time or an earlier time in a dense ash encounter.
This was a research aircraft which goes into these areas on purpose!
There are obvious cautions to take flying anywhere near a serious volcano.
One dont do it at night, make the areas no go at night.
Two I would imagine fly at very low engine settings in those zones.
There have never been any fatalities caused by ash encounters which is more than can be said for encounters with other weather phenomina or natural phenomina.
We dont ground aircraft in the bird migration seasons yet many aircraft have been downed by birds with fatalities caused by bird ingestion.
Thunderstorms, hail storms, severe turbulence etc have all downed aircraft with resultant fatalities but NOT ASH.
There are two types of threat in dispersed ash a threat to life which has not occurred yet in even dense ash encounters and a threat to the aircraft owners pockets.
The threat to the owners pockets is their choice? and not ours to judge over.
I see that Heathrow alone lost £29 million in the few days the airport closed. Who knows what the airlines lost but it was massive.
Yes have guidlines on how to operate near ash areas that is sensible but ground the whole of northern Europe???
As another poster said "life is a risk" otherwise we might as well stay in bed lock the doors and die of inactivity.
Pace
I read this report before but it is not a scientific study. All it basically says is that the aircraft was flying at NIGHT. That in itself is odd for a scientific flight? Why do the flight at night when the crew cannot see what they are flying into?
The only indication was the ash sensing equiptment on the aircraft which gave an ash indication.
The aircraft was checked on landing but with NO indications of an ash encounter on the initial inspections.
So much so that they continued for another 65 hrs of flight before the engines were stripped and damage discovered.
There is nothing to say that the ash encounter was the one they suspected. It may have occurred at a later time or an earlier time in a dense ash encounter.
This was a research aircraft which goes into these areas on purpose!
There are obvious cautions to take flying anywhere near a serious volcano.
One dont do it at night, make the areas no go at night.
Two I would imagine fly at very low engine settings in those zones.
There have never been any fatalities caused by ash encounters which is more than can be said for encounters with other weather phenomina or natural phenomina.
We dont ground aircraft in the bird migration seasons yet many aircraft have been downed by birds with fatalities caused by bird ingestion.
Thunderstorms, hail storms, severe turbulence etc have all downed aircraft with resultant fatalities but NOT ASH.
There are two types of threat in dispersed ash a threat to life which has not occurred yet in even dense ash encounters and a threat to the aircraft owners pockets.
The threat to the owners pockets is their choice? and not ours to judge over.
I see that Heathrow alone lost £29 million in the few days the airport closed. Who knows what the airlines lost but it was massive.
Yes have guidlines on how to operate near ash areas that is sensible but ground the whole of northern Europe???
As another poster said "life is a risk" otherwise we might as well stay in bed lock the doors and die of inactivity.
Pace
Last edited by Pace; 30th Apr 2010 at 17:08.
Distortions, distortions....
Pace, I suggest you re-read the report.
The flight was a positioning flight to allow the aircraft to conduct SOLVE missions (ozone loss and validation) within the Artic zone north of Sweden. So nothing odd there - just like my red eye to London or Amsterdam it is difficult to fly to Europe from the USA without hitting night at some point.
The fact they were running the instrumentation was standard practice.
The flight path of for the flight had been conservatively adjusted to put the track 200 miles North of the predicted ash cloud.
Immediately on landing the engine oil, oil filters and heat exchanger filters were removed and saved for analysis. Visual inspection did NOT reveal and damage, and since borescope inspection equipment was NOT available at the deployment airfield, and there was no apparent change in engine performance, the research flights continued.
There were seven SOLVE research flights and the report notes that ash was detected as traces during these, but at MUCH MORE DIFFUSE levels than in the first encounter - remember this is an instrumented aircraft, so they RECORD all this... there is no question where or not they flew through "a later dense ash encounter" - that is fantasy on your part.
As for your assessment that this is not a scientific study - well I leave that up to the reader to decide. I have yet to see any reports from any of the sampling flights over Europe that decided everything was suddenly perfectly safe.
My point - well, it seemed there was a lot of conjecture on the evidence that ash damages things or not. Here's evidence it does. The report includes measurements taken during the encounter of the sulfur dioxide concentration in parts per trillion by volume amongst other data, and it is clear when the encounter started and ended. The report also includes clear pictures of the disassembled engine parts.
My intent was to educate, not advocate - I'm not saying don't fly, neither am I suggesting fly.
Personally I have no intent of getting on an aircraft when I am aware there is a big cloud of ash floating in and around my flight path. My choice. Since most of my flights are for business and can be adjusted, I don't feel inclined to exposes myself to undue risk. I realize others do not have that luxury.
If you could let me know the next time a large flock of Canada Geese are in my flight path, then I will choose not to get on that aircraft also... for me it's all about risk management.
Oh, and let's see if there is a spike in engine maintenance over the next 6 months. Time to look at GE, PW and RR stocks.
- GY
The flight was a positioning flight to allow the aircraft to conduct SOLVE missions (ozone loss and validation) within the Artic zone north of Sweden. So nothing odd there - just like my red eye to London or Amsterdam it is difficult to fly to Europe from the USA without hitting night at some point.
The fact they were running the instrumentation was standard practice.
The flight path of for the flight had been conservatively adjusted to put the track 200 miles North of the predicted ash cloud.
Immediately on landing the engine oil, oil filters and heat exchanger filters were removed and saved for analysis. Visual inspection did NOT reveal and damage, and since borescope inspection equipment was NOT available at the deployment airfield, and there was no apparent change in engine performance, the research flights continued.
There were seven SOLVE research flights and the report notes that ash was detected as traces during these, but at MUCH MORE DIFFUSE levels than in the first encounter - remember this is an instrumented aircraft, so they RECORD all this... there is no question where or not they flew through "a later dense ash encounter" - that is fantasy on your part.
As for your assessment that this is not a scientific study - well I leave that up to the reader to decide. I have yet to see any reports from any of the sampling flights over Europe that decided everything was suddenly perfectly safe.
My point - well, it seemed there was a lot of conjecture on the evidence that ash damages things or not. Here's evidence it does. The report includes measurements taken during the encounter of the sulfur dioxide concentration in parts per trillion by volume amongst other data, and it is clear when the encounter started and ended. The report also includes clear pictures of the disassembled engine parts.
My intent was to educate, not advocate - I'm not saying don't fly, neither am I suggesting fly.
Personally I have no intent of getting on an aircraft when I am aware there is a big cloud of ash floating in and around my flight path. My choice. Since most of my flights are for business and can be adjusted, I don't feel inclined to exposes myself to undue risk. I realize others do not have that luxury.
If you could let me know the next time a large flock of Canada Geese are in my flight path, then I will choose not to get on that aircraft also... for me it's all about risk management.
Oh, and let's see if there is a spike in engine maintenance over the next 6 months. Time to look at GE, PW and RR stocks.
- GY