No, it's not like that at all. Just like with shoes, you expect engines to wear out from normal use, but no-one knows how accelerated any wear may be, if there is any increase at all, with varying levels of ash contamination. To use your analogy, it's like expecting a normal pair of shoes to stand up to walking across a rough lava field - they just won't last as long, but you can't predict how quickly they'll wear out.

What is certain is that the ash will build deposits that do more than just cause wear - they will cause hot spots and thermal stresses or melting of components as well as affect the internal thermodynamics of the engines. How rapidly these deposits form is unknown. What level of deposit is safe is unknown. How big these deposits can grow before detaching is unknown. the level of damage caused by deposits breaking off is unknown... Therein lies the problem; there are too many unknowns to determine if flying through this amount of predicted contamination is safe.

I thought this might be interesting. The previously grounded BAe146-301 from FAAM is currently airborne over Scotland at FL260. Let's hope it provides more answers.

http://www.faam.ac.uk/index.php/position

Someone posted that it was measured at over 2000ppm. The NASA aircraft that was damaged, flew through 600ppm I believe.

Correct me if I'm wrong, but if a an engine is producing 10,000lb of thrust, it would be consuming 0.01lb of dust per second ppm. Or 36lb per hour (16.36Kg).

600ppm would mean 9816kg per hour passing - and melting - through the engine.

That is correct. (If the aircraft is already cruising at its best level)

theoretical mathematical model
 

For everyone who is disgusted that the Met Office are using "theoretical mathematical models" to FORECAST the ash movement... wtf do you think they use for all their other FORECASTS? Little pixies? Oracles? You've got to start from something, and microscopic radioactive particles seams like a good enough starting point for me - seeing as it's only been running for a week.

Theoretical methemtatical models
 

Dusty B - Agree. But that is also why we need the physical empirical evidence to go with it. Now (and for the last 5 days) we've had the chance. May be too late to enact a solution based on the 2 observations - theory vs actual. But, it will bode well for the future if this scenario arises again. Sorry to bang on, but we need the evidence eventually and the level of 'test flights' thus far and how they've been executed does not appear to show the needed due diligence.

Funnily enough, the model is being verified by observed data...

And of course aircraft are transitting UK airspace - its open above FL200!

BoughtTheFarm, you're right - test flights need to be instrumented and done properly, covering the whole range of flight levels across all areas, rather than just a jolly around the eastern Atlantic at FL whatever which proves nothing. Even then, If you go fishing (test flight) you might not catch a fish (ash) , but it does not mean there are no fish (ash) in the sea. (air)

With the greatest respect guys, and I know it's not really 'any of my business' but the mods have repeatedly asked for the 'spotteresque' posts to be kept out of here. Can see their point, it clutters up interesting debate and they are working overtime keeping the thread tidy.

I'll shut up myself now.

BA planes ...
 

Just heard that the BA longhaul planes on the way to LHR have been told they are not landing there today ...

Unfortunately, it just seems that there is a sort of subculture of (usually) right-wing people in the UK who are obsessed with the idea that the Met Office is plotting against them. This thread has now reached the point where the same people who were yelling that Gordon Brown was at fault for closing the airspace and it wasn't really a problem - no link or citation has yet been produced to support the idea that it was Brown's decision rather than CAA, NATS, or VAAC - are now yelling that Brown should really intervene and have it reopened rather than "hiding behind NATS".

And, apparently, a volcano going off in Iceland is Harriet Harman's fault. Frankly, you could cry.

Also, with regard to the link to The Register: when I was a tech journalist (like Andrew Orlowski) we had a saying that if it was on the BBC it was probably out of date, if it was on ZDNet it might be right, if it was in Wired it was probably right but overhyped, and if it was in the Reg there was no way of telling whether it was right, wrong, or pure pub drivel. I am not aware that the former fanzine editor has any competence to say anything at all intelligent about modelling ash dispersal, and it would vastly improve his product if he were to shut up more often.

Dusty B:

Fair enough to use mathematical models for forecasting weather patterns and cloud movements. This is quite scientific and has years of proven ground.....BUT to use theoretical mathematical formulas that have never been tested to predict the levels of concentration of the volcanic ash that is dangerous to aircraft would appear to me to be verging on irresponsability.

On the other hand, one has to say in their favour, that if they are not provided with electric screwdrivers, then they are doing a very good job using a hammer for the screws......

NATS operate with a licence from HMG, and all other European ANSPs operate similarly with a licence from the state. NATS must operate within the terms of it's licence and all of the other rules, regulations and laws applicable to an ANSP. The 'law' governing flights in ash conditions is the ICAO document referenced in previous posts. Who exactly could be sued and for what reason? Who has done something wrong or likely to bring harm to others?

BD

Wippersnapper

So let me get this right. There is absolutely no danger in the BA aircraft approaching LHR in this lovely weather, but they are being refused permission because NATS is concerned about the long term damage to their engines. Is this correct?

Very wrong. You need to calculate the air flow through the engine. Nothing to do with thrust.

An example. Which I based upon figures from the Canadian VAAC, which seems to use a distinctly better model than the British one, with results divided in low, medium and high concentrations. Low goes from 10 to 100 micrograms per cubic meter of air. If you consider a plane flying at 180 m/s, an engine with a capture area of 3 square m, and a concentration corresponding to the upper limit of the "low" concentration, over ten minutes (an estimate of the time to cross a lower level cloud, after takeoff or before landing), you absorb roughly 0.3 grams of ash per engine.

@DjerbaDevil

There are a couple of points where you misunderstand:

1. The VAACS model is not predicting concentration. It explicitly stated in the earlier graphs (although appears to have stopped doing so) that density of the "cloud" is unknown. This is not to excuse the process, but merely to state a fact. Maybe the ICAO should alter their process to not consider such models where concentration is unknown, but the VAACS model is officially approved by the ICAO.

2. The VAACS model does not try to suggest at which concentration of ash engines might be damaged. That is for the engine manufacturers to decide. Since they do not know, they recommend concentrations of zero.

It looks like common sence is about to prevail. The Met Office model is about to be given the heave ho.

I don't know if the link was posted yet, I've not been following the thread assiduously, but here is the NASA technical report. I hope it is helpful. It seems to me to conclude that flying through a diffuse cloud can cause hard to see damage that nonetheless has a major impact on engine lifetime and hence safety.

http://www.alpa.org/portals/alpa/vol...8AshDamage.pdf

SUMMARY

In the early morning hours of February 28, 2000, the National Aeronautics and Space Administration (NASA) DC-8 Airborne Sciences research airplane inadvertently flew through a diffuse plume of volcanic ash from the Mt. Hekla volcano. 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. Satellite data analysis of the volcanic ash plume trajectory indicated the ash plume had been transported further north than predicted by atmospheric effects. Analysis of the ash particles collected in cabin air heat exchanger filters showed strong evidence of volcanic ash, most of which may have been ice-coated (and therefore less damaging to the airplane) at the time of the encounter. Engine operating temperatures at the time of the encounter were sufficiently high to cause melting and fusing of ash on and inside high-pressure turbine blade cooling passages. 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. There are currently no fully reliable methods available to flight crews to detect the presence of a diffuse, yet potentially damaging volcanic ash cloud.

Ok.

So (180m/s x 3m) *10microgram=5400microgram/second.

5400microgram * 10*60= 3.24grams in 10 minutes.

At a higher concentration (still low) of 100 micrograms per cubic meter of air it would be 32.4g per engine per transit through the layer.

This is assuming 10 minutes transit, I believe the cloud is now down to FL10 and below isn't it?

"It looks like common sence is about to prevail. The Met Office model is about to be given the heave ho."

So we are going to use common sense for future weather predictions as well are we?

200 years of science, some of the most powerful computers in the world and all we needed was common sense instead.

peter we
 

I have just been giving the NASA DC8 report a once over. There is no statement of the ash cloud's particulate parts per million during the 7 minute encounter but there are two graphs, 7a and 7b, of what happened. 7a shows the sulphur dioxide concentration against time which peaks at about 800,000 parts per trillion by volume. 7b shows the aerosol number density against time which peaks at about 28,000 per cubic centimeter. Can anybody explain how these figures translate to the concentration of particulates in parts per million (physics a bit rusty!).

One bit of good news for the brave souls flying the test flights is the following quote from page 13 of the NASA DC8 report:


Sounds like an on-the-wing de-coke!:)

Right. I made an algebraic error. 32 g is it.

You can easily adapt to different times and conditions.

Well, yes and no. ICAO EUR Doc 019, if that is what you are referring to, comprises guidance and recommendations for various bodies to follow if a volcano blows in the N Atlantic area, but is a very long way from being law in England and Wales or anywhere else in the UK.

Any other ICAO document would have a similar status.

IF the person or organisation who decided on the airspace restrictions got it wrong, or was not even empowered to do that in law even though he/she/it obviously can in practice, repeat IF, then that's where the airline lawyers will aim.

Reason? Don't be naive; money, and lots of it, in compensation at taxpayer expense.

From a political perspective this is all further proof that the lunatics are running the asylum.

Management is doing "things right", leadership is doing the "right thing".

If we had leaders with any backbone they would have the moral courage to open the airspace, albeit with some restrictions. Having those BA aircraft diverting away from LHR is utter nonsense.

What's the problem ???
 

David Learmount, on Flightglobal (q.v.) rightly says that "the" problem is twofold:
1) A volcano in Iceland is erupting vioently
2) A very stable High-pressure system is unusually far North and directing the plume south-eastwards.
#2 is unusual for this time of year.
This is an unprecedented situation, which is why none of the "risk assessment" or researchers have predicted it (for all their Ph(u)Ds from Llaregub U).
Because of the above, engine manufacturers have not spent time and money collecting samlpes of volcanic ash to throw at engines on test-beds (And probably won't in the future, for cost/benefit reasons, which is sensible).

OK, it causes chaos and hardship for passengers (and airlines), which insurance companies will no doubt still be disputing in years to come.
The situation will ease when the weather pattern changes - maybe a Low will send the stuff from this and any bigger bang northwards, over the Pole and into Nothern Canada or even Alaska - then what will Sarah Palin say ???


N.B. Tongue ever so slightly in cheek at times ...

Oh, but airline industry is conducting such a research on an Europeanwide basis right now. If things go pear shaped, at least historical LIDAR, wx baloons and research aircraft data will show what was the concentration that stopped the fun. If not we'll know what's the safe level.

I did participate in a "test" flight today, albeit on the fringes of the VA propagation forecast (as forecast by the Met Office, not Eurocontrol) and therefore I would be only too happy to wake up and discover that Finnish Hornet story was hoax, that data from Friday's met flight in UK are secret to hide the fact that closing the aerospace was overreaction and that avoiding VA by using Mk1 eyeball guarantees long and happy engine life.

What are my chances of waking up fat, dumb and happy?

Poor to nil, I'd estimate.

Parts per million
 

Just been trying to get a feeling for "parts per million" as this is discussed a lot on this thread - and what is apparently being measured.

1 part per million - by weight, what is it?

Well, the weight of the atmosphere causes pressure, and sea level pressure is about 1,000hPa = 100,000N/m2 so that means about 10tons of air above each square metre. (That makes sense because 1m3 of dry air weighs about 1.2kg at sea level, so without allowing for declining pressure, thats 8,000m - so if the air spreads up to 20-30km before "fading out" that makes sense). Thats 10million tons above each square kilometre.

The weight of air above the UK, surface area, 250,000km2 must therefore be 10million times 0.25million tons = 2.5 trillion tons. (2.5 thousand billion tons)

So, if the ash were 1 part per million, and were spread uniformly throughout the air above the UK, the ash in the UK air would weigh 2.5 million tons.


Similarly the whole of Europe is 10million km2, 40X UK so there is about 100trillion tons of air above Europe. 1ppm would be 100 million tons.

Some other points:

1 ton per second of ash generation means a million tons every 12 days

The first three days of the eruption on 14 April 2010 at Eyjafjallajökull. generated about 750 tonnes / second on average - so thats about 200 million tons errupted in total so far

If spread uniformly over (just) europe that would be 2ppm

Obviously its not spread uniformly, has also spread over the atlantic and russia.

Can anybody provide a number for the mass of air passing through a typical (e.g. A320) jet engine per hour of flight?

If anything is a display of backbone it's the fact that in the UK the restrictions still stand while the rest of Europe is out flying. I should say that somebody IS demonstrating moral courage, and a proper respect for safety.

Less ash, more lava: Eyjafjallajökull changing its style?
 

From a Volcanologists blog, a ray of hope maybe ?


Less ash, more lava: Eyjafjallajökull changing its style? The Volcanism Blog

Or the opposite view is saving face and trying not to get sued! My guess is we will be flying by Friday or Saturday, until the wind changes that is and then we will either have a different kind of ash or we will be using option 2 or 3 of the EASA plan. We are currently on option 1 according to the information being published by my company. So I am hopeful we will see sense returning to the situation shortly.

BBC News - Ash ban to remain for most of UK
Leaving aside the arguments about wise caution/over caution, what do we think the plans are for a decompression descent? OK, not probable but caution is still caution.

@ Tyres ... valuable input. There was always the hope that the eruption process would change; perhaps this is the "end of the beginning"?

@ Spotters various ... thank you for your inputs gleaned from the spotters websites. :ugh:

Having read every page of this thread over the last six days (up to page 99 which is when I started typing this offering) it is clear that there is a wide variety of argument and counter argument, much of it centering around conjecture.

Having been trained in the industry as an engineer 50 years ago! (though I never "practised) and as a PPL of 20 years, from what I can deduce there are some things we know, some we don't know and some which we ought to know for future episodes of a similar nature.
In summary I think these include -

What we know -
1 A volcano erupted and due to the high inflow of glacial meltwater it's output consisted of high level of fine particulate ash which is relatively unusual.

2 An unseasonal slow moving high over the UK caused a southerly flow which caused the plume to move south before splitting and moving both east and west. This dispersal pattern is generated by computer models rather than direct empirical observation.

3 Volcanic ash (VA) with high levels of silica CAN cause severe problems both short and longer term to jet engines, both immediately suppressing combustion and damaging turbine blades.

4 An ICAO "directive" or advisory, issued after a major emergency in 1982 laid down "rules" to be followed in the event of VA clouds impinging on airspace.

5 The subsequent shutdown of UK and European airspace has caused economic damage to the industry, other industries, national economies and considerable discomfort and worse to large numbers of passengers.

6 A small number - very limited - of "research flights" have launched in the later stages of this situation and the results, if clear, have not been widely published.

7 Airframe, engine manufacturers, operators and national and international regulators have failed to undertake or insist upon research which would increase knowledge on which to base actions regarding such situations.

What we don't know -
1 The degree of accuracy of the models and therefore the actual dispersal of dust, either laterally or vertically, and there is little information as to the vertical thickness of layers.

2 Precise data about particulate size, or chemical composition once the dust has reached altitude, and even if we did -

3 There appear to be few if any advisories from engine manufacturers as to the chemical composition of dust, the particulate size, or the density of cloud (ie likely throughput) which engines can "tolerate" without damage, or continue to operate in while maintaining power while suffering damage.

There are many, many more knowns and unknowns but these seem to be the key ones.

Therefore given that the regulators and "safety authorities" do not know what's going on, or what is a safe situation in the first place it is entirely predictable that they will take the NIL RISK route, assuming the worst case scenario and avoiding it by putting aircraft on the ground.

Far more important than what is happening at the moment is what WILL happen in the coming months. The industry must undertake detailed research to find out what its equipment will "tolerate", while national and international authorities MUST put in place systems to ensure that any computer models of future events can be checked in detail by actual sampling to ensure that a vital industry is operated on the basis of knowledge rather than computer guesstimation.

Had such work been done on a regular basis since 1982, we would have 28 years worth of useful information instead of very little.

Until that happens I suspect that the authorities will insist that we sit this out until it goes away…..

BA124 nearly made it to LHR but is presently turning back to AMS (now looks like Brussels)

This is not a spotters post. I'm wondering why it is safe to land at Brussels but it's not safe to land at Heathrow? The weather is the same at both, and they are both in the Met Office 'ash cloud'.

After reading much of this thread, along with some other research, I can only conclude that it's going to be difficult to define a "safe" concentration.

Any outpourings from a volcano, encountered by a turbine powered aircraft, are likely to pose some sort of long term risk.

From: http://www.caa.co.uk/docs/375/fsd_may93_p1-9.pdfFrom: http://www.nasa.gov/centers/dryden/p...ain_H-2511.pdf(Interesting photos on page 1).

Sounds like flying in any aeroplane that has ever been flown through volcanic ash and/or gas is going to be less safe than one that has not.

I realise that most things in life involve risk assessments - I'm just glad I'm not the one with the responsibility of making the decisions here. I think it may be a little unfair to be slating people for taking the safe(r) route of maintaining the airspace suspensions.

Just my point of view.

OC619

This is beginning to look like the blind leading the blind leading the blind.

If you study the six-hourly actual/predicted 'ash cloud' source map data from the London VAAC that is being published by the Met Office and allegedly being used by NATS to make its UK Controlled Airspace open/closed decisions, you can see from the predicted data yesterday exactly why they chose to open the Scottish FIR and nearby regions, albeit temporarily, today. However, the maps are all clearly marked "ASH CONCENTRATIONS UNKNOWN".

If the ash concentrations are unknown then how is it possible to define the edge of the contaminated area where presumably the ash concentration has supposedly fallen to some identifiably small but as stated "UNKNOWN" level in the first place? What is that level and how does the VAAC even know where to draw the line?

Further, this apparently unknown concentration region of ash extends throughout most of Europe where flying has been permitted today.

NATS is clearly basing its fly/no fly decisions precisely on these maps and the livelihoods of large numbers of people around the world are being substantially impacted by this extremely ill-defined and completely misleading information.

Someone needs to be brave enough to step up and stop this madness. Everyone is hiding behind data produced by a group of well-meaning technical staff at the London VAAC but not being prepared to make a common sense decision as the stakes of making that call are astronomically high if wrong!

It does appear that the Europeans have been prepared to stick their necks out well before our politicians/bureaucrats have.

Is UK signed up to ICAO? Yes. Is part of NATS licence to comply with ICAO etc? Yes.
Very big if and given that NATS has complied precisely within the terms and conditions of it's licence they're squeaky clean (and I do believe I've said this previously).
Compensation for what, following the guidance and recommendations of one of the governing bodies for Aviation? I would very firmly put the boot on the other foot and state that NATS should be prosecuted if it had FAILED to follow the ICAO guidance and recommendations.

BD

Those BA planes could be getting re-routed to Shannon Ireland. Some info here from the irish aviation authority:

Irish Aviation Authority - UPDATE ON AIRSPACE RESTRICTIONS

Looks like im going to be stuck in Paris until the end of the week.

there are too many unprofessional people out there. Nobody knows how to deal with a crisis and everybody just act to protect themself, not in the name of the safety of flight, but in the name of the "law" wich is far away from the environment we're all working in. no common sense:=:confused:

Perception of and attitudes to risk management I guess. What I still don't understand is why flights were allowed into Luton this afternoon, but none were allowed into LHR.

Anyone know why the flights from Canada to Luton were cleared through closed airspace ?

80/-

Colleague heard from a Klm pilot on his freq that KLM policy is that they are only allowed fly IFR in VMC conditions ??????..... seeing as they were the ones shouting about how safe it was to fly......why this policy????