Ash clouds threaten air traffic

[Pace]

that can identify thick plumes of ash

John

This appears to be the biggest problem we have with the current methods of determing ash in the atmoshere.

If its dense it can be seen both by the pilot and by satellites. Setting any very low acceptable ash levels is going to cause a major problem of locating where they are by the simple fact that they cannot be seen.

As such we rely on computer and mathematical modelling which may hold X ash concentrations but may also hold X+Y or X-Y or infact no X at all.

Without analysing millions of test shots of air over huge areas we dont know.

Maybe the best way would be to scrap the minimal acceptable levels altogether and to use the satellite visible charts with a safety area around those visible dense ash concentrations.

On the basis that if you cannot see it its unlikely to hurt you aircraft flying in the computer generated low ash areas which are not visible and where ash may or may not be present should be monitored on a more regular basis until we do know more? but with NO meaningless limits

Pace

[PBL]

Your argument is based on an assumption that airlines are too stupid to recognise this, and therefore need civil servants to tell them what they can and cannot do.

I think Sunfish's argument is based on the fact that airlines sometimes do things which are not necessarily optimal for safety, for a number of reasons (in order to maintain market share, when everyone else is doing it, for example). It is appropriate for a regulator to step in when it judges that that is happening.

Indeed, that is still one of the most frequent comments about U.S. airline deregulation, that safety has suffered as a consequence (that is not necessarily my view; I am merely pointing out that some hold it).

In the current situation, it would be very hard for an airline not to fly, even if it judges that it is not wise to do so, if everyone else is flying. The airline would instantly lose all market share.

PBL

[Pace]

I think Sunfish's argument is based on the fact that airlines sometimes do things which are not necessarily optimal for safety,

What like flying in areas of thunderstorm activity, like flying approaches and departures with surface winds above 0, like flying in the bird migration seasons or into and out of coastal based airports etc etc etc :ugh:

Safety has to be based on a demonstrable threat there is no demonstrable threat from a light ash encounter only a percieved possible threat. There may be ??? a financial cost threat but as yet not even that is bearing up to scrutiny.

Pace

[brooksjg]

As far as I know we are not even close to regulations governing the general flight of UAVs in civil airspaceOh dear..... misinterpretation and sometimes misrepresentation are a bit of a safety hazard around here!

I NEVER suggested that any UAVs should fly in or near air routes.

If you want to run the line that UAVs will never be allowed in 'civil airspace' without defining what exactly you mean by that: ie. any bit of sky not specifically defined as 'military'? or what? Noting for a moment that Predators based at Bagram MUST pass over, under or through some 'civil' airspace in Afghanistan to get to where they need to go.....

I've no idea how this actually gets regulated inpractice but a knee-jerk 'Never until rules submitted in triplicate and signed off by God (or at least the Pope)' won't ever be helpful. I guess it depends what your 'medium term' is. But I assume you don't mean 'a month or two'. Believe me, if UK National Security was truly an issue and UAVs were the correct response, they would be whizzing round your ears by next week! I was tempted to add 'Get over it' but somehow resisted!

[infrequentflyer789]

In my opinion, the reaction of the regulators was measured, proportionate, prompt, cost efficient and minimised both risk and disruption to the public to a bare minimum.


Appreciate your knowledge on turbine blades, do you know how many there are on a Piper, or a microlight, or a glider ? Those folks running the regulator probably don't - in fact some are on record as stating "‘I know nothing about aeroplanes".

But you know, don't you ? So you must know what the other unspoken risk of VA is that grounded all these aircraft along with the jets ?

"measured" ? "proportionate" ? More like knee-jerk, incompetent, a**e covering. (unless you can enlighten us as to the VA risk to gliders ?).


<begin rant>
And as to the "minimised disruption" - you are having a laugh.

The regulators and governments meanwhile did absolutely **** all to help for several days until shamed into action by the media. Even then it was pathetic - over a week IIRC to get five or so coaches out of Madrid and a navy ship that they decided could take a whole 250 people from Santander (until the commander probably torpedoed the rest of his career by taking more). Tour operators were moving convoys of 30 coaches at a time inside a couple of days, and chartering ships for 2000 pax at a time.

Politicians talked out of one orifice about "dunkirk spirit" whilst effectively ordering the closing the channel ports to small boats trying to get people across (can't cross the channel on small private boats these days apparently - watch out GA, you'll be next). Immigration staff (presumably idle) at airports were not deployed to sea ports, resulting in queues hours long and broken onward transport arrangements. UK immigration at Calais was so well organised that our coach was sent through it twice (while ferry staff were counting down the minutes to departure).

"minimised disruption" ? Actively hindered anyone elses attempts to do so is more like it.

The whole affair was a classic example of our overstuffed EU/UK bureaucracy which has no plan, no clue, and no ability to respond other than by getting in the way.

<end rant>

[The SSK]

infrequentflyer789: The whole affair was a classic example of our overstuffed EU/UK bureaucracy which has no plan, no clue, and no ability to respond other than by getting in the way.

Entertaining rant but you're wrong about the EU. Initially they had no mandate to get involved, when they stepped in over the first weekend to clear up the mess that the national authorities were making of it (and a lot of highly placed bureaucrats racked up a lot of weekend overtime) things started to happen with some rapidity.

[crippen]

The British Health and Safety disease.

Belt, braces, AND DON"T STAND UP !:=

[Sunfish]

Infrequent:

Appreciate your knowledge on turbine blades, do you know how many there are on a Piper, or a microlight, or a glider ? Those folks running the regulator probably don't - in fact some are on record as stating "‘I know nothing about aeroplanes".

But you know, don't you ? So you must know what the other unspoken risk of VA is that grounded all these aircraft along with the jets ?

"measured" ? "proportionate" ? More like knee-jerk, incompetent, a**e covering. (unless you can enlighten us as to the VA risk to gliders ?).


You may have a point about piston engined aircraft and gliders. Last time I looked, the Piper I fly had an airfilter, but hey! the aircraft is hired so what do I care anyway? A little ash exposure might help the rings seal and save me a honing job.

When I studied risk management as an engineer and later when I had to apply it in an airline engineering department, we worked on facts. In the absence of facts regarding the likelihood of exposure to some quantity of ash by large numbers of aircraft, the regulator acted promptly and grounded the fleet until the available facts could be marshalled and discussed by people with the relevant expertise and experience. They did this promptly, efficiently and responsibly in a matter of weeks.

The fact that the regulators response didn't suit some of you is irrelevant.

As for comments about "commercial considerations" and individual airline decision making those are also way off the mark. Aircraft Insurance contracts and lease agreements would most definitely preclude doing anything not approved by a regulator, which is probably why Ryanair so promptly grounded its fleet in my opinion.

To put it another way: You would all be screaming about why the regulator didn't ground aircraft if half the fleet was now ash damaged and out of action for months.

[Mad (Flt) Scientist]

I'd like to offer an analogy to VA that I think is illuminating, because there are similarities. That analogy is SLD (Supercooled Liquid Water Droplets).

Unlike VA, SLD has been linked to actual hull losses.
Similarly to VA, there are NO accepted criteria for SLD.
The only advice any OEM gives anyone regarding SLD is the same as that for VA a month ago - avoid at all costs.
There is no reliable means today for detecting SLD, or VA, onboard an aircraft. In certain circumstances visual detection of either may be possible, but is assured in neither case.
Our ability to reliable predict SLD or VA is, in a word, unreliable, in both cases normally for lack of accurate data about the atmosphere.

To date the situation with SLD constitutes a (barely) acceptable risk - although it's been an issue of contention between FAA and NTSB for years. Industry and the regulators have been trying to come up with workable means to handle SLD since Roselawn, in earnest, and have got not very far. We've largely "got away with SLD" because it tends to be a localized event.

So, regarding the comparisons:

IF we've lost a number of aircraft to a known but rare phenomenon (SLD) and havent managed to significantly mitigate the risk, what chance was there really of anyone being any more prepared for the VA issue of the form it took last month? And, realistically, what chance is there of being any more prepared a decade hence?

AND, suppose some unusual weather pattern happened to generate large areas of likely or possible SLD. Would that really leave authorities any choice but to close the airspace which represented a significant risk of SLD?

Oh, and before someone cites the existing icing regs: the environmental data they ultimately rest on is OLD and geographically concentrated, and may be unrepresentative of world-wide conditions today....

[lomapaseo]

Sunfish

As for comments about "commercial considerations" and individual airline decision making those are also way off the mark. Aircraft Insurance contracts and lease agreements would most definitely preclude doing anything not approved by a regulator, which is probably why Ryanair so promptly grounded its fleet in my opinion.

To put it another way: You would all be screaming about why the regulator didn't ground aircraft if half the fleet was now ash damaged and out of action for months.

Your arguments are tiresome and not borne out by fact but only by your own imagination.

Your opinions have been registered, just like the rest of us. Hopefully you can't go on and on arguing to convince others by citing the same old "what ifs" that can not be backed by facts.

Regulations are codified, judgements are not.

[peter we]

Your arguments are tiresome and not borne out by fact but only by your own imagination.

Your opinions have been registered, just like the rest of us. Hopefully you can't go on and on arguing to convince others by citing the same old "what ifs" that can not be backed by facts.

His argument is the one followed by the authorities. He's right. Its not his imagination, its reality that VA shuts down airspace - he doesn't have to prove anything becuase he is simply explaining what is happening and will happen in future.

Refusing to accept the explanation of why its happening isn't an 'argument' or 'discussion', it simply a refusal to accept reality.

[Pace]

His argument is the one followed by the authorities. He's right. Its not his imagination, its reality that VA shuts down airspace - he doesn't have to prove anything becuase he is simply explaining what is happening and will happen in future.
Refusing to accept the explanation of why its happening isn't an 'argument' or 'discussion', it simply a refusal to accept reality.

Peter We

The above is not Sunfishes arguement at all neither have I seen one posting which disputes what you say above.

The arguement has been about HOW MUCH airspace is closed and what level of ash is acceptable to fly in?

That ranges from ZERO which some argue for up to the maximum dense stuff which billows out of the volcano mouth which no one but a fool would enter.

My own position is that if I can see and eye ball pollution clouds or dense mist and avoid then it will not harm me. It may harm the bank balance long term in clear air with low ash levels but to date there is ZERO evidence to back that up!!!

So really the arguement has been over low density levels of ash.

We have also argued about computer and mathematical ash movement forecasts which have also been innacurate infact some may even argue Dangerous as they give FALSE confidence of where ash may or may not be.

Sunfish has argued the doomsday scenario of 100s of engines all requiring rebuilds at the same time. He has absolutely NO evidence to back that up.

Neither has anyone any evidence whatsover through history that low levels of ash are any threat to safety.

Until that evidence raises its head any restrictions other than NOT to fly in visible ash clouds or mist will just ruin our industry and jobs which I have a sneaking feeling that some here want (not directed at you) especially when those restrictions are not based on a demonstrable safety threat.


Pace

[PBL]

Your arguments are tiresome and not borne out by fact but only by your own imagination.


I don't agree with any of this.

This is supposed to be a discussion of an important issue in commercial aviation. It would help if people accurately evaluated the contributions of the discussants.

In my previous post http://www.pprune.org/rumours-news/412103-ash-clouds-threaten-air-traffic-150.html#post5706296 I pointed out that for a risk evaluation, even a superficial one, four quantities were needed, which I labelled (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).

This is the way risk is assessed and has been for 299 years, and there is nothing anybody here can say that will change this.

Pace argues that (a) is 1 and (c) is 0. But he also agrees that, at some unknown level of concentration, (a) will no longer be (1) and (c) no longer 0.

Now, of course, the second term is not really a simple multiplication, but a sum: (c1)x(d1) + (c2)x(d2) +... + (cn)x(dn), where c1.....cn represent classes of concentration and d1,...,dn different levels of damage.

Sunfish's contribution to this assessment is to point out the various levels of damage that can ensue (the d's), and that many of those chances, the c's, are unknown, but that some of them can be estimated from history and science.

Mad(Flt)Scientist has pointed out inter alia that it is fruitless to expect those chances to be well-known in detail, by comparison with a case heshe considers broadly similar, that of SLD's.

I don't find any of this "tiresome". I find it essential to an appropriate risk assessment.

PBL

[Pace]

PBL

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

Pace

[PBL]

..... there are FAR greater demonstrated risks with a long history of fatal accidents which we do accept and think little of...........
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 ......


This is true. Indeed, it is well accepted as a general phenomenon.

Before he was appointed to the U.S. Supreme Court, Justice Stephen Breyer wrote a book "Breaking the Vicious Circle" (Harvard U.P., 1993), based on his Oliver Wendell Holmes lectures at Harvard, in which he includes in Table 5 (pp 24-27) the risks and cost-effectiveness of U.S. federal legislation selected from Fiscal Year 1992. The cost per premature death averted ranges from $100,000 in 1990 dollars (widely regarded by many to be a bargain) to $5,700,000,000,000 (yes, you read that right). About half the measures lie over $8,000,000 per premature death averted, which is regarded by almost everybody who deals with these issues as very expensive.

Cass Sunnstein has a similar, but shorter table in Chapter 2 of his study "Risk and Reason" (Cambridge U.P., 2002), in which he says "it is well-known that there is a great deal of variability in national expenditures per life saved."

Both Sunstein and Breyer deal with the question of how to approach this and other phenomena.

So now we are agreed on this phenomenon, what is your argument to get from the phenomenon of variability of response to risk (on which we agree) to the conclusion that flight should not have been restricted (on which we don't agree)?

PBL

[Pace]

PBL

Your response deserves a carefully though out reply which I will enjoy giving but sadly I have to do what I talk about too much see you couple of days ;)

Pace

[no sig]

Today, May 27th - Iceland Issues Second Warning on Katla, from:

2nd Iceland volcano issues ominous warning - Europe- msnbc.com (http://www.msnbc.msn.com/id/37371442/ns/world_news-europe/?Gt1=43001LONDON) -
A second, much larger volcano in Iceland is showing signs that it may be about to erupt, scientists have warned.

Since the start of the Eyjafjallajökull eruption, which caused cancellations of thousands of flights in Europe because of a giant ash cloud, there has been much speculation about neighboring Katla.

An initial research paper by the University College of London Institute for Risk and Disaster Reduction said: "Analysis of the seismic energy released around Katla over the last decade or so is interpreted as providing evidence of a rising ... intrusive magma body on the western flank of the volcano." "Earlier seismic energy release at Katla is associated with the inflation of the volcano, which indicates it is close to failure, although this does not appear to be linked to seismicity around Eyjafjallajökull," it added.

"We conclude that given the high frequency of Katla activity, an eruption in the short term is a strong possibility," the report said. "It is likely to be preceded by new earthquake activity. Presently there is no unusual seismicity under Katla."

Icelandic President Ólafur Grímsson has warned governments around Europe that a significant eruption at the volcano is close. "We [Iceland] have prepared ... it is high time for European governments and airline authorities all over Europe and the world to start planning for the eventual Katla eruption," he said.

The UCL scientists, engineers and statisticians also criticized the response to the earlier eruption."The impact of the eruption on regional airspace could have been predicted and better prepared for as the growing problem of aircraft-ash cloud encounters has been recognized for decades," the report added.

"Similarly, the potential for ash clouds, specifically from Icelandic volcanoes, to interfere with air traffic in UK, European and North Atlantic air-space was appreciated by the aviation industry well before the start of the Eyjafjallajökull eruption," it said.

"The response to the ash cloud’s arrival in UK and adjacent airspace was entirely reactive and therefore less effective than it should have been."

[brooksjg]

Don't expect a rational response anytime soon if those making decisions are politicians or people (ie. bureaucrats) controlled by politicians.

For a direct comparison, consider the risk of death or serious injury due to Carbon Monoxide poisoning. There are a number of deaths in UK every year caused by a 'combustion process' of some kind that's gone wrong (insufficient ventilation, broken flue, ..). The majority of the 10 to 20 annual deaths are caused by solid fuel burners or combustion of other than piped gas. However, a great deal on money is spent on CO awareness', fitting CO alarms which in the case of room-sealed, well-maintained appliances are almost entirely redundant, etc., a lot of it on piped-gas systems. The result is that maybe £15m is spent 'per death' on issues directly related to CO (omitting cost of training and certification of gas fitters) although it's perfectly obvious that a major part of this spend will make absolutely no difference to the annual death rate.

Politicians see votes in supporting CO Awareness, etc. but no votes in not supporting it, so that's where the money goes!

Similarly for everything involving safety issues: no benefit in reducing 'safety' and associated costs. Every political benefit from increasing it, even if from the outset it will make no difference to the safety outcome! (You will often see politicos doing their public grief acts, with a soundtrack along the lines of 'We tried and tried, and look, we increased safety budget by 50 % only last year. But sadly, despite all our efforts, Mrs Snoggins and her eleven chidlren all died in this freak accident'. It wasn't a 'freak accident', it was just 'an accident', and chances are the same result would have occurred if the budget had gone up 100%! People are dumb and screw up!

Aircraft, ATC and airlines' management of risk are highly developed and deliver excellent safety overall. However, you cannot entirely eliminate human failure and unquantifiable / unforeseeable risks such as SLD and VA. That's no excuse for pretending that zero VA is the only option, or is actually a viable option. We just need better forecasting.

[Agaricus bisporus]

those making decisions are politicians or people (ie. bureaucrats) controlled by politicians.


Sorry Brooksie, you've got that arse-backwards. In the UK it is the bureaucrats (ie the civil service) that control the politicians. Don't doubt it!

Have you never watched "Yes Minister?" It's far closer to the truth than most people imagine.

[brooksjg]

Of course you're right about who's really in control.
However...
The bureaucrat's natural instinct is the path of least resistance leading to no comebacks.
So if one of his political 'masters' requests, for example, a safety 'improvement' which costs the bureaucrat little or nothing and can attach no blame to him later - well, of course he'll indulge the MP and give him a nice ego-boost and a few cheap votes. Someone always ends up paying and it's always Us, one way or another, never Them.

[Sunfish]

Brookes:

That's no excuse for pretending that zero VA is the only option, or is actually a viable option. We just need better forecasting.

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:

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

Please do not tell me you have not read the following report:

http://www.alpa.org/portals/alpa/volcanicash/03_NASADC8AshDamage.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.

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.

[MarkerInbound]

Today, May 27th - Iceland Issues Second Warning on Katla

At least we can pronounce this one.

[peter we]

The newly defined safe limits of ash are ad hoc and arbitrary and cannot be scientifically justified. (http://www.newscientist.com/blogs/shortsharpscience/2010/05/ucl-report-calls-for-volcanic.html)

[The SSK]

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 (http://hraun.vedur.is/ja/Katla2009/gosplott.html) (see top of page)

[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'. 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?

[PBL]

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'.

Paul is a smart man and I am quite sure he is aware of what it would take to get accurate experimental data on damage to engines from volcanic ash, especially since he did talk to the people who make and sell them. I think he is right that it would be "incredibly expensive". I imagine the manufacturers said that as well.

PBL

[PBL]

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/2010/05/28/risk-assessment-of-volcanic-ash-to-commercial-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

[Pace]

Please do not tell me you have not read the following report

Sunfish

You are not dragging that one up yet again as your supreme example :ugh:
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 :ugh:

Pace

[RoyHudd]

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.

[The Green Goblin]

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. :ugh:

[brooksjg]

It is part of what I presented in my Risk course this morning.

'Your' course? or a course you were at?

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.

[itsresidualmate]

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!!

[Airbubba]

'Your' course? or a course you were at?

Professor 'L' is an authority in the field of risk management involving transportation and computer systems. I've had my differences with his analysis at times from my perspective as an operator but he has definitely influenced trends in training and accident investigation over the past couple of decades from what I can see.

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...:ok:

[infrequentflyer789]

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/2010/05/28/risk-assessment-of-volcanic-ash-to-commercial-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

The calculation may be elementary, but (as ever) the devil is in the inputs.


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... :eek:


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. ]

[Sunfish]

Your regulators have done a very good job in a very short time. You should all be thankful.

Against stupidity the very gods
Themselves contend in vain. - Schiller

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.

http://i8.photobucket.com/albums/a16/sunfish1/IMG_0447.jpg?t=1275178895

http://i8.photobucket.com/albums/a16/sunfish1/IMG_0453.jpg?t=1275179465

[lomapaseo]

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.

[WHBM]

.....especially since he did talk to the people who make and sell them. I think he is right that it would be "incredibly expensive". I imagine the manufacturers said that as well.
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).

[TyroPicard]

lomapaseo
So air flows through those holes and comes out the other end.
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.

[brooksjg]

The dust travels through the bleed system and can melt and block the exit holes... blade gets too hot and is damaged

This is the key to the whole set of issues around engine damage caused by LOW levels of VA.

(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....

[lomapaseo]

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....

No doubt the answer will probably be yes, if
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

[PBL]

My thanks to Airbubba for his encomium. I hope I deserve it!

'Your' course? or a course you were at?

This one. (http://www.rvs.uni-bielefeld.de/lectures/sommersemester.php#392155)

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:
The main cost of not flying is the cost of getting your pax back.

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.

Feed those numbers (150k) into your risk equation

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

[Pace]

rather higher indeed than Pace's estimate of zero risk.

PBL

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

[PBL]

Where please have I indicated that there is Zero risk?


For example, in this note (http://www.pprune.org/rumours-news/412103-ash-clouds-threaten-air-traffic-150.html#post5706492) you said
You are trying to do a risk analysis on something which to date statistically has shown NOT to be a risk.
and, when I said in this note (http://www.pprune.org/rumours-news/412103-ash-clouds-threaten-air-traffic-153.html#post5718042) that (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.
you replied that I do not question your arguement on risk!

I thought these statements seemed quite clear. Did I misunderstand?

PBL

[Pace]

You are trying to do a risk analysis on something which to date statistically has shown NOT to be a risk.

PBL

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 :E

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

[Sunfish]

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.

[Sepp]

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...

[Pugachev Cobra]

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.

[visibility3miles]

A volcano in the Gulf Coast would get rid of that nasty oil spill. :cool: :rolleyes:
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.

[Sepp]

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.

[brooksjg]

Citation CJ2 Volcanic ash encounter pictures

[YAWN]
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!

[lomapaseo]

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...

There is also no such thing as a standard bird either.

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.

[PBL]

BTW, cost doesn't enter into setting min safety standards ...

It does, sometimes quite centrally, depending on which jurisdiction you are in. There is a well established principle of English law called "ALARP", which is short for "as low as reasonably practicable", and in English law the providers of equipment and services which are safety-related are required to reduce risks ALARP.

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

[brooksjg]

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......?

[lomapaseo]

brooksjg

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.


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

[brooksjg]

I don't recall that there is any documented cases of melted VA inside a turbine blade

I'm glad you said that....

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!

[lomapaseo]

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!

That's the way it is sometimes when you always wished that you knew more about a subject.

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.

[heavy.airbourne]

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!

[brooksjg]

Here we have two groups: Those who got it, and those who will never get it
I wish it were that simple!
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.

[Sunfish]

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 (http://www.paris.icao.int/documents_open/show_file.php?id=274)

ICAO manual.

http://www2.icao.int/en/anb/met-aim/met/iavwopsg/Documents/Manual%20on%20Volcanic%20Ash,%20Radioactive%20Material%20and %20Toxic%20Chemical%20Clouds%20-%20Doc%209691%20-%20Draft%20incorporating%20Amend.%201.pdf


ICAO taskforce:

ICAO NEWS BRIEF ICAO News Centre (http://icaopressroom.wordpress.com/2010/04/29/icao-news-brief/)

[slip and turn]

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 ?

[TyroPicard]

lomapaseo
I don't recall that there is any documented cases of melted VA inside a turbine blade Not sure but I think a photo in this article (link below) shows that very thing... or if not melted then certainly able to clog the cooling holes?

Why Can't Planes Fly Through Volcanic Ash? NASA Found Out the Hard Way | Popular Science (http://www.popsci.com/science/article/2010-04/why-cant-planes-fly-through-volcanic-ash-because-nasa-tried-once)

[lomapaseo]

TyroPicard

Not sure but I think a photo in this article (link below) shows that very thing... or if not melted then certainly able to clog the cooling holes?


Yes those pictures have been posted many times within this thread. They closely match the known severe events affecting engines.

The discussion just above had to do with VA melting inside the turbine blades if the cooling air is hot enough.

as always follow you FCOMs, it's easier to change those than to convince all pilots of the finer points :)

[sabenaboy]

Well, you would have to be a fool or suicidal to go fly in such an ash cloud (http://images.huffingtonpost.com/gadgets/slideshows/6094/slide_6094_82102_large.jpg):

http://images.huffingtonpost.com/gadgets/slideshows/6094/slide_6094_82102_large.jpg

But it took a bunch of pen licking scientist and bureaucrats to stop me from flying in this kind of weather (http://www.thedailyparker.com/content/binary/Flight_3096.JPG): (And that's what the weather actually looked like over Belgium during the first NO-FLY weekend!) :ugh:

http://www.thedailyparker.com/content/binary/Flight_3096.JPG

Let's hope common sense will prevail if this or another volcano starts erupting again.

[BOAC]

Horses for courses, as they say. I reckon, however, there will be some little pink bottoms that will need levering off seat cushion buttons when one of the 2 engines goes POP mid-ocean with 120-180 minutes at MCT to nearest:)

[itsresidualmate]

You mean when a bird goes down the intake BOAC?! :)
Or the fuel calcs are wrong (or the wrong fuel gauge fitted!) and plane runs out of fuel?!
Or the water sed checks aren't done correctly and the donk flames out cos it's trying to burn water?!

Can't be anything to do with ash 'cos us engineer's can't find any damage from VA!

Somebody mentioned sand blasting on a Ruinair flight; Atmospheric sand, grit, pollen, small parachutists, what-have-you, is constantly eroding surfaces long before Erecckkkllannnoorrookkkfffic exploded. If you pilot chaps have a close look at your pitot probes and leading edges you'll see they're all eroded to some extent.

[BOAC]

You mean when a bird goes down the intake BOAC?! - erm, no, unless you have records of bird strikes at FL400 mid Atlantic?:ugh:Can't be anything to do with ash 'cos us engineer's can't find any damage from VA! - how many turbine blades do you actually section each day?

[itsresidualmate]

Not an attack on your post BOAC (difficult to express intonation in text!), simply pointing out there's a lot of stuff that'll bring an airliner down before VA does.

I have seen no evidence of VA damage. I know of no other engineer that has. Friends of mine work in engine bays as well as line stations, the grapevine would quickly flash up evidence of this nature, if it didn't Sunfish would!

You're right, I have no record of birdstrikes at FL400. Nor have I any evidence of volcanic ash damage.

[Sunfish]

residual:

Nor have I any evidence of volcanic ash damage.

That's because the regulators closed the airspace before evidence accumulated.

[itsresidualmate]

...and my elephant scaring crystal is working too, no elephants in my garden :ok:

[brooksjg]

Sunfish: I'm sick of this. Comments slagging off about regulators are just unfounded.

errr - what are you actually 'sick' about? Comments about inappropriate regulations? Inaction? Slow response?

I assume your ICAO reference is intended to reassure that ICAO is rushing about doing stuff and the results will be Real Soon. The meat (such as it is) of the press release says:
The multidisciplinary team of experts from States and industry facilitated by ICAO will prepare by 1 August a report on lessons learned from the crisis and identify guidance material and contingency plans which need to be updated. Building on the report, a roadmap for establishing globally-harmonized ash concentration thresholds, options for improved detection systems of volcanic ash, as well as recommendations to improve notification and warning systems, will be completed by May 2011.

Looks like a bit of 'Manana, but without the same sense of urgency' to me. Decide what report to write by 1st August and then spend the next 9 months writing it. But reports of any kind do not actually DO anything. On this timetable, there'd be no prospect of even getting the VA concentrations harmonized by mid-2011.

And 'options' are quite easy to write up. Selecting and implementing the right one (starting May 2011 at earliest) might take a bit longer. Slow? Inactive? Complacent? Pretty-much as useful as a Chocolate Teapot? You choose!

'Never mistake Activity for Effective Action'.

And meanwhile, in Another Part of the Forest, Easyjet is making PR capital (even if not actually gaining useful competitive advantage) by putting IR cameras on some of its aircraft at the cost, it says, of £1m. (see other posting). Well, at least it's action, even if uncoordinated and possibly not terribly useful.

[Juud]

Ground breaking volcanic ash detector
Following the Eyjafjallajoekull eruption, the travelling population of Europe may have become acutely aware of the fact that fine ash from the volcanoes is hazardous to jet aircraft and can remain in the atmosphere for a long time as it is transported by the winds.

Technology developed at NILU might in the near future enable aircraft to detect the ash from the eruption up to 100 km away.

Fred Prata, Senior scientist at NILU.
Senior scientist Fred Prata has developed the ground-breaking volcanic ash detector that allows the aircraft to see the microscopic ash particles and avoid it.

The specially developed camera will be able to give five minute warnings both day and night about ash ahead. Even better detection through the models is being developed at NILU at this very moment, ensuring that such crisis can be avoided in the future.

“Using the infrared camera, satellite data and algorithms that convert data from satellites, aircrafts will be able to get the necessary notifications every time they approach a volcanic ash cloud. The aircraft will then be able to steer clear of clouds and continue the journey instead of being put on the ground for an indefinite amount of time, as they do today," Prata says.

He believes it could save airlines enormous costs, and save the passengers from cancellations and delays.

Easyjet have announced that they are trialling a system to detect volcanic ash from their aircraft. (http://infrared100.********.com/2010/06/remote-ir-detection-of-volcanic-ash.html)

[peter we]

But it took a bunch of pen licking scientist and bureaucrats to stop me from flying in this kind of weather: (And that's what the weather actually looked like over Belgium during the first NO-FLY weekend!)

Stop blaming someone else, you know damn well its was the airline industry who set the standards and therefore its those who are responsible.

[lomapaseo]

Rather good perceptive posts above and in some cases sounding at odds with one another :ok:

The status quo takes a long time to change all the various opinions in our industry. Especially when it seemed to "get by" and more pressing problems du jour arise.

[brooksjg]

The specially developed camera will be able to give five minute warnings both day and night about ash ahead. Even better detection through the models is being developed at NILU at this very moment, ensuring that such crisis can be avoided in the future.

“Using the infrared camera, satellite data and algorithms that convert data from satellites, aircrafts will be able to get the necessary notifications every time they approach a volcanic ash cloud. (attrib above to Mr Prata)

Yeah - right. You get '5 minutes' (or less) warning of 'VA Ahead' - then you have to contact ATC, request a route / height change, wait for ATC to decide based on other traffic, etc. and action whatever change is advised. Err - not in 5 minutes, if everyone on your route and its reciprocal, at several different FLs, are all going through the same process!!!! Utter chaos would result. It's all very well arguing about 'Captain's Authority' deciding where the aircraft goes but in controlled airspace it's not a realistic scenario to actually exercise it as apparently proposed.

[green granite]

This might be worth watching:


Volcanic Ash: The Ticking Timebomb
Tuesday 08 June
8:00pm - 9:00pm
Five

Documentary exploring the likelihood and potential global effects of the eruption of Katla, a huge volcano lurking under the Icelandic ice. Katla is five times the size of its neighbour Eyjafjallajokull, which recently caused so much travel disruption when it blew clouds of volcanic ash into the atmosphere. Historically, every Eyjafjallajokull eruption has been followed by a flare-up at Katla. If such an eruption were to happen now, it is predicted that European airspace would be closed down for 18 months.

[Pace]

it is predicted that European airspace would be closed down for 18 months.

And what superb specimen of homo sapiens predicted that? Donald Duck?

It is unusual for airflows over Iceland to track towards the UK so how come 18 months? if that last load of scaremongering like the rest of the so called scientific scares from everything from BirdFlu to ash ever came true?

Oh well maybe one day they will actually get one right who knows? But that will probably be more luck than anything else or in that case bad luck :ugh:

Pace

[green granite]

I note they manage to work in global warming as a factor, although in a most unconvincing way.

[Pace]

really what should they have done??? Firstly talked to airlines who are used to dealing with ash in active volcano areas and use their operational advice.

Second use satellite real time visible ash plume monitoring. Stick a safety margin around those and make those dense ash areas NO GO.

Fly in daylight and if possible avoid flying in clouds especially pollution coloured clouds.

The mathematical computer generated low ash areas should have no ash limits at all ( better than choosing a number between one and ten) ;) but should have been purely precautionary areas. I say that because even with millions of tests you have no way of telling whether half a mile from the test spot you dont have denser areas.

Operate in those predicted low ash areas and be prepared for more inspections to monitor longer term ash damage if any.

Lastly eliminate all the expensive quangos and committees involved in the descision making process on the basis that committees can never agree about anything (No one ever built a statue to a committee :ugh: and have one body to make descisions

Thats it NO more NO less

Pace

[lomapaseo]

Lastly eliminate all the expensive quangos and committees involved in the descision making process on the basis that committees can never agree about anything (No one ever built a statue to a committee and have one body to make descisions

No and yes :)

Agree about the decsion making part of it not being dependant on committees and the need for a specific process tuned to daily info to make such decisions.

The committees are useful to evaluate the considerations that should be accounted for in the decision process. Hence in the regulatory sense we have codified rules and we have avisory material

[mike-wsm]

Katla is looking kinda busy, three quakes in the past four hours. Just thought y'all like to know.

[Lon More]

I hope the British Government is chartering some cattle boats to get the football hooligans (and that's just the players) back from RSA next week if it does kick off

[mike-wsm]

Yesterday's total was three quakes under Eyja-jokull and five under Myrda-jokull/Katla. We need to get those Strats, Connies and DC-3s back into production. Low level flying with piston engine power is the way to go.

[coalencanth]

The data from the earthquake monitors is pretty useless if we don't know how to analyse it. The tremor levels are very low, especially those closest to the Katla volcano. If you go and look at earthquake maps of other places in Iceland you'll see that minor quakes happen there all the time. Actually, the volcanic eruption probably obscured a lot of these quakes in the background tremor. What's more, these recent earthquakes around Katla have high error factors on them and are at very shallow depth. The Icelandics don't seem too concerned!

[mike-wsm]

Yes, these quakes are very small as compared with those occurring around the Pacific Rim on a daily basis but Katla tends to blow without warning, these small tremors are the only indicator we have. What worries me is that the quakes are so near the surface, indicative of something imminent.

I look forward to hearing Wright Turbo-Cyclones and Bristol Centaurus engines droning overhead.

[green granite]

I look forward to hearing Wright Turbo-Cyclones and Bristol Centaurus engines droning overhead.

Along with the smell of hot castor oil. :ok:

[sycamore]

G-G ,go to a Classic race day,it`s the smell of Castrol R you want.....

[Sir Richard]

Another explanation of some of the difficulties of predicting ash clouds.

Elegant Figures : Blogs (http://earthobservatory.nasa.gov/blogs/elegantfigures/?src=features-recent)

[brooksjg]

Beautiful imagery - but still fails to address the key problem: timeliness. I assume at least some of the satellites in use were in polar orbits, so there's a variable delay before the patch of atmosphere you want gets imaged. Geostationary sats are (maybe...) too far out to deliver the detail needed and anyway don't carry the relevant sensors. (I may be entirely wrong on this.)

[scotbill]

Apparently there is a conference in Keflavik next week with an assembly of assorted experts to consider the lessons of the great volcanic ash drama - and presumably to suggest future measures. Anybody going - or have any idea which way the wind might blow (sorry!) there?

SB

[infrequentflyer789]

Apparently there is a conference in Keflavik next week with an assembly of assorted experts to consider the lessons of the great volcanic ash drama - and presumably to suggest future measures. Anybody going - or have any idea which way the wind might blow (sorry!) there?

SB

Well I suppose we might get to know about the huge pile of damaged jet engines resulting from the decision to fly through non-zero levels of ash, reports of which remain absent from this site...

Or maybe not.

[WHBM]

Apparently there is a conference in Keflavik next week with an assembly of assorted experts
Would these be the same assorted experts who did such a ridiculous job of handling the situation in the first place ?

Have they invited anybody with a view other than their own one ?

[Nemrytter]

Beautiful imagery - but still fails to address the key problem: timeliness. I assume at least some of the satellites in use were in polar orbits, so there's a variable delay before the patch of atmosphere you want gets imaged. Geostationary sats are (maybe...) too far out to deliver the detail needed and anyway don't carry the relevant sensors. (I may be entirely wrong on this.)Geosats are very capable of delivering ash cloud information...but the problem for places like iceland is that the spatial resolution is quite poor (due to the angle between iceland and the equator):
EUMETSAT IPPS animation - Meteosat 0 degree Ash Iceland (http://oiswww.eumetsat.org/IPPS/html/MSG/RGB/ASH/ICELAND/index.htm)

Our geo satellites contain all the sensors needed for ash analysis. Although, as always, additional sensors would be an improvement (which will arrive in 2015).

On the plus side, because iceland is near the poles we gain a lot of high resolution polar data at high frequency - we can gain 5-6 images of iceland per day from polar sensors.

(edit) Oh, just noticed that the post was a month old. Apologies.

[ATC Watcher]

Before getting the Connies out in the air(*) I have been told that a US airline is suing an hollywood production firm for over a billion US$ for loss of revenue because this firm had placed high explosive charges near Eyjafjallajokull to start an eruption for film footage (for a mega production to come) a few days before the full eruption.
Could not find any confirmation of this on the web. Anyone heard something or is it just a wild story ?

(*) restauring a Connie to full flying status is extremely expensive and a very lenghty process as the Lufthansa staff in Berlin can tell you :They try since 2 years to get one in the air from 2 "good" airframes,but they are still years away .

[Nearly There]

Really? I doubt it though, if it did it would have to be a hell of a lot of 1.1 high explosives buried deep within the volcano a rather expensive do, surface explosions the gases are released upwards, with very little effect downwards.

[sabenaboy]

Good article in Flight international (http://www.flightglobal.com/articles/2010/09/16/347413/european-volcanic-upset-could-have-been-avoided.html)

[Analcyst]

Well Merapi has only be chuffing away for 12 days and QF has had two engines fail on climb out of Singapore so I guess a little respect for mother nature is probably overdue.
If ash forms a hard glaze on the hotsurfaces then I suppose the risk of blades being heavier than designed might stress an engine if the glaze is not dealt with.

[ggofpac]

Airlines stop Jakarta flights after volcano blast - Yahoo! News (http://news.yahoo.com/s/ap/as_indonesia_disasters)

here we go again....flights cancellations. :uhoh:

[mike-wsm]

A story has been making the rounds in the British press and elsewhere that an eruption is imminent in Bárdarbunga in Vatnajökull. The news seems to be based on a misunderstanding of a TV interview with a specialist at the Icelandic Met Office earlier this week.
http://www.icelandreview.com/icelandreview/daily_news/?cat_id=16567&ew_0_a_id=373779

[Lon More]

European volcanic upset could have been avoided


20/20 hindsight from Learmont

[Storminnorm]

Didn't I read somewhere, once upon a time, that there are
constant volcanic eruptions occuring all round the World?
Minor ones, admittedly, but most pumping loads of crap into
the atmosphere.

[beaufort1]

Interesting article from the BBC on how 'officials got it wrong on volcanic ash'.

BBC News - Officials 'wrong' on volcanic ash (http://www.bbc.co.uk/news/science-environment-12623089)

[lomapaseo]

Interesting article from the BBC on how 'officials got it wrong on volcanic ash'.



I believe this was covered a week ago in the Tech section.

[Nemrytter]

I'm not sure I agree with that article. A quick scan read gives the impression that the earth scientists were actively telling the UK govt/CAA about the threat of volcanos. I can't remember any such thing. I think the problem is more that one group of scientists doesn't talk to another group. Earth scientists don't really talk to aerospace scientists, and neither group talks to the government.

Also, a quick literature search doesn't show up much evidence that Vulcanologists were warning of an imminent eruption, the only papers I can find related to iceland are saying the opposite.

(edit) Rubbish spelling.

[stuckgear]

Simon,

I am surmising that your statement:


I'm not sure I agree with that article. A quick scan read gives the impression that the earth scientists were actively telling the UK govt/CAA about the threat of volcanos. I can't remember any such thing. I think the problem is more that one group of scientist isn't talking to another group. Earth scientists don't really talk to aerospace scientists, and neither group talks to the government.

Also, a quick literature search doesn't show up much evidence that Vulcanologists were warning of an imminent eruption, the only papers I can find realted to iceland are saying hte opposite.


is concluded from this statement in the article:


"The broader Earth science community had been predicting events around Iceland for some considerable time," Mr Miller said.

"That should have alerted the Civil Aviation Authority at a much, much earlier stage and we should have planned for that event."


As you will note from the article, Mr. Miller is Labour MP Andrew Miller, who's party was in administration during the farce. It can also be drawn from the quote above from Mr. Miller that he is attempting to direct responsibility to the CAA and away from the government failings.

However, this quote is rather telling :


Professor Beddington said: "We didn't expect volcanic ash - that wasn't on our risk assessment. It probably should have been when you look at the relative frequency of volcanic events in Iceland. We should have had that on the risk register".

When asked whether the the government had got it wrong over volcanic ash, Prof Beddington replied: "We failed to predict it was a likely event - absolutely."


The farce has been subject to thread discussions at length and there is not much point in rehashing the whole lot again and run around in circles. If you want to push an agenda then fine, thats up to you, but expect to be called on it.

[WHBM]

This latest news report is some completely self-seeking publicity by "scientists" for their own works. Possibly at a time when government financial support for various projects, scientific and otherwise, is being reduced, we should expect more such.

If the scientists were saying that the huge no-fly area was completely inaccurately calculated, and scientists should have identified what was done was a nonsense, fair enough. But they don't. This is about them playing a part in predicting volcanic eruptions in the first place and how likely this is. They are saying that they would have predicted the Iceland volcano as more likely than was believed.

What would be even more useful would be if they had predicted by scientific means that after 999 volcano eruptions in recent years which were handled fine, the 1,000th would result in ludicrous behaviour by civil servants who do not know one end of a volcano fromn the other.

Clever presentation of the press release allows a perception to be made to many that they are saying that if we had paid more attention to scientists, there wouldn't have been the disruption. It comes over like this in this morning's TV summaries which show a backdrop of thousands sat in departure lounges, the implication being that we would not have been sat there, delayed, if scientists had been listened to. Reading the report fully (which few will do) shows they don't say any such thing.

[stuckgear]

WHBM,

You're on the money there. One should always scratch beneath the surface for the reality, not take PR at face value. This situation is no different.


Flawed computer models may have exaggerated the effects of an Icelandic volcano eruption that has grounded tens of thousands of flights, stranded hundreds of thousands of passengers and cost businesses hundreds of millions of euros. The computer models that guided decisions to impose a no-fly zone across most of Europe in recent days are based on incomplete science and limited data, according to European officials. As a result, they may have over-stated the risks to the public, needlessly grounding flights and damaging businesses. "It is a black box in certain areas," Matthias Ruete, the EU's director-general for mobility and transport, said on Monday, noting that many of the assumptions in the computer models were not backed by scientific evidence. European authorities were not sure about scientific questions, such as what concentration of ash was hazardous for jet engines, or at what rate ash fell from the sky, Mr. Ruete said. "It's one of the elements where, as far as I know, we're not quite clear about it," he admitted. He also noted that early results of the 40-odd test flights conducted over the weekend by European airlines, such as KLM and Air France, suggested that the risk was less than the computer models had indicated. – Financial Times



The US is to slash all funding for the United Nations’ Intergovernmental Panel on Climate Change (IPCC) as the result of a proposed budget amendment by Republican Party Representative Blaine Luetkemeyer that was voted in on Saturday.
The US House of Representatives, which has a Republican majority, has agreed to remove $2.3m from the IPCC funding budget as part of $61bn in cuts that were voted through.
Luetkemeyer slammed the cross-governmental IPCC for engaging in ‘dubious’ scientific methods in what was dubbed the Climategate scandal.
The UN environmental body was accused of covering-up scientific results and arguments that opposed climate change theory, as its employees were asked to destroy certain emails.
Luetkemeyer reportedly wrote, ‘The IPCC is an entity that is fraught with waste and fraud, and engaged in dubious science, which is the last thing hard-working American taxpayers should be paying for.’

with income sources being limited, the 'scientific' community needs new sources of income?



Ash cloud models – overrated? A word on Post Normal Science by Dr. Jerome Ravetz | Watts Up With That? (http://wattsupwiththat.com/2010/04/19/ash-cloud-models-overrated-a-word-on-post-normal-science-by-dr-jerome-ravetz/)
Here is what Professor Jerom Ravetz of Oxford has to say about the issue (via email):
Interim contribution to the Post-Normal Science debate.
Considering the effects of the Icelandic volcano on air transport, we seem to have:

Facts Uncertain: how thin must the dust be, for it to be safe enough for flying?
Values in Dispute: Regulators wanting safety at all costs, others needing to get flying now.
Stakes High: Crippling costs to industry, versus big risks to aircraft and people.
Decisions Urgent: Every day the immediate costs mount, and the long-term costs grow.Is this analysis an invitation to scientists to cheat? Some of my critics would say so, and perhaps even some of my supporters as well!

[PBL]

WHBM, You're on the money there

If you are referring to this quote,

This latest news report is some completely self-seeking publicity by "scientists" for their own works.

then he most certainly is not.

This "latest news report" concerns the witness of the government's chief scientist before a Parliamentary Committee, which is currently holding hearings.

PBL

[NorthernKestrel]

Good couple of reports here from the Royal Aeronuatical Society on Ash Cloud lessons and implications for the aerospace sector...

Under the ash cloud | Aerospace Insight | The Royal Aeronautical Society (http://www.aerosocietychannel.com/aerospace-insight/2011/01/under-the-ash-cloud/)

and a more in-depth free specialist paper to d/l too...

http://www.aerosociety.com/cms/uploaded/files/Flying_Through_an_Era_of_Volcanic_Ash.pdf

[WHBM]

This "latest news report" concerns the witness of the government's chief scientist before a Parliamentary Committee, which is currently holding hearings.
That is exactly what I am referring to. Evidence to parliamentary committees is as thought-through by PR teams as anything that ends up in the media, and commonly press-released in parallel (with useful soundbite paragraphs at the bottom for news editors) the second after it has been said.

[Nemrytter]

The farce has been subject to thread discussions at length and there is not much point in rehashing the whole lot again and run around in circles. If you want to push an agenda then fine, thats up to you, but expect to be called on it.

What are you on about? I posted because someone else put the article up and it's a subject I'm interested in from a scientific perspective. I'm not British and don't live in the UK, so the politics behind it are of no interest to me.
Of course, you're more than welcome to disagree with my comments, but disagreeing with them on a political basis that I'm not even aware of is a bit much ;)

[ceedee]

New Scientist (http://www.newscientist.com/article/dn20410-europe-was-right-to-halt-flights-after-volcano.html) reports on the Proceedings of the US National Academy of Sciences (http://www.pnas.org/content/early/2011/04/22/1015053108):
The ash pumped out by the Icelandic volcano last year posed a serious risk to aircraft, a new analysis suggests, vindicating the decision to halt flights over Europe following the eruption.
...
[Fred Prata of the Norwegian Institute for Air Research] says the results show Europe was right to close its airspace. But, he adds, with better monitoring – including the sorts of real-time measurements Stipp carried out – it would be possible to keep some airspace open, with planes steered into corridors away from the worst of the ash.

[lomapaseo]

This press release is already running in the Tech section

[peter we]

The question is why airline executives have not been sued or even prosecuted for failing they duty to shareholders and having Business Impact Analysis (which they are supposed to act upon) and Business Continuity Plan for this event?

It is a legal requirement, after all, to do this and they were fully aware of the potential impact.

[SilsoeSid]

Why is it that my car is getting more crap on it now than when we were all scare mongered about the volcanic ash earlier?

Will we be having no fly zones to prevent a build up of pollen, and in turn honey, in jet engines clogging them up?

[BDiONU]

Tests on ash show volcano flight ban was right - Herald Scotland | News | Home News (http://www.heraldscotland.com/news/home-news/tests-on-ash-show-volcano-flight-ban-was-right-1.1097970)

"Some critics questioned whether it was justified, but now the new scientific report published in the journal Proceedings of the National Academy of Sciences concludes it was.

Researchers analysed samples of ash from the volcano and found they were capable of causing an air disaster.
The fragments remained sharp and abrasive even after attempts to blunt the particles by stirring them in water.
They would have sandblasted aircraft windows, making them impossible to see through, and could have stalled engines.
The report is at odds with claims made by airlines after European airspace was closed last year.
Some operators said that safety measures imposed by the semi-privatised air traffic control organisation, Nats, were an over-reaction."

The researchers, led by Dr Sigurdur Gislason from the University of Iceland, wrote: “The very sharp, hard particles put aircraft at risk from abrasion on windows and body and from melting in jet engines. In the lab, ash particles did not become less sharp during two weeks of stirring in water, so airborne particles would remain sharp even after days of interaction with each other and water in clouds. Thus, concerns for air transport were well-grounded.”

[The SSK]

The issue was never whether ash can cause damage to aircraft and engines, of course it can, the experiences of BA in Indonesia and KLM in Alaska are well enough documented.

The issue was with the critical density within the cloud and at its margins, how it was moving and how it was dissipating; I haven't read the report, but does it really make a convincing case that a sufficiently high risk necessitated the closure of airspace as far as the Adriatic coast within the first couple of days of the event? If so, how was it that this risk had suddenly disappeared by day 4, when almost all the affected airspace was reopened, leaving the 'danger area' where it had been all the time, a relatively limited region, at a relatively limited altitude, over the sea between Iceland, Scotland and Norway.