Uuumm, you've obviously not read through the thread. IATA were invited to provide input to ICAO when the VA guidance was being written. They didn't turn up, so the guidance was zero tolerance. When it was published IATA still didn't respond. Responding after the event is too late.

BD

Yes, thanks for that perspective. I was thinking about immediately following the latest eruption and hours before they shut down most of the air routes. But I accept that if IATA had laid the groundwork earlier via ICAO this might have had a different outcome.


Perhaps I read the thread thoroughly as did many others but still don't get a passing grade, but what the heck that's what discussion forums are all about or we all flunk :)

Claire

I'n not a pilot. Of course in you view that makes anything I say invalid. So be it.

Just a few things you ought to know. You use the term empirical evidence. It means specifically evidence obtained via senses. Capt Moody has a lot of empirical evdience that flying through ash is bad for prolonged flight and engine function. As empirical evidence goes its very convincing. I'm sure Capt Moody had all the empirical evidence he needed when all four engines on his 747 went out. He wasnt the only pilot who experienced empirical evidence that volcanic ash and engines do not go well together. So empirical evidence means that flying into ash clouds can upset your afternoon somewhat. apologies for the sarcasm.


OK so what is needed is quantitiave analysis - we know that aircraft can do some very scary things in volcanic ash. If I have to nail home my point, that is empirical evidence. The next step from empirical evidence is that a problem is known, so how severe is the problem? Quantitive analysis means to evaluate how much of the nasty stuff which coats turbine blades with glass and blocks pitot tubes makes the aircraft unsafe and secondarily, makes the components of the aircraft liable to failure earlier than design specs. My concern is that the quanititive analysis should not have economic pressures applied on it. I'm all ears to hear construcitve quanititive analysis of the volcoanic ash problem.

one thing I wonder is if the silicates may alloy with the blade materials and create brittle points?

For a quantitative assessment you need to evaluate all the effects.

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.

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)

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'!

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.

- it's there waiting for you!

Loma - I think you misunderstood Brooksigs post?
You said He saidTwo different scenarios.
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.

deleted :bored:

Self Loading Freight - Demanding To Fly Into Ash
 

What the f*ck don't people get:confused: - volcanic ask shuts down jet turbines.:ugh:

Yet, as always, we get the SLF who demand to fly during this period.:rolleyes:

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).:ok:

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...)

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.

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!

Roy

There is nothing on his profile so the 06 prob the version of Microsoft flight sim he uses on his home PC.

Pace

Your math looks ok but i think the starting numbers are out. Could be a misprint in the exponent (eg. e-6 vs e-16) or units - cubic cm / cubic M / cubic mm would all make rather a lot of difference.

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.

Risk
 

Two points spring to mind.

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.

"zero tolerance"?
 

That's what I always thought: stay clear of any visible ash concentration and there will be no immediate danger. Amazing how a simple misinterpretation of "zero tolerance" could lead to such a huge overreaction.

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 :eek:

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!