windytoo, you're spot on. This is just hypothetical argument. I'm certainly one of the few who seem to have a problem with what happened, so I accept I may well be a protaganist. Unfortunately we keep bouncing back and forth about what the risk is or isn't. Yet, I maintain my probelm is not so much with whatever apparent risk may have been out there but with the manner in which it was handled and ultimately decicded to not exist.

I just get tired of people telling me no aircraft have crashed from ash in the past as if that means there is no risk. Then when the same people admit that ash does carry risk, they then say as long as you not within a few hundred miles of the eruption you're OK. Get your hands on one of the early satellite images from last Thursday and tell me you would have been happy flying over Scotland or Scandinavia. Yet we should be fine since we're so far away. And on and on the argument goes.

Cars and road deaths compared to ash encounters is just pathetic IMHO. If you are a pilot then you train twice a year for an engine failure at V1, brief for it every single day and plan for it on every single departure at HUGE COST to the industry in lost payload and excess engine wear. Yet how many engine failures at V1 have occured over the last 50 years. The one in MAN recently was the latest I know of and maybe a handful before that. That makes it much less likely than a car crash, so why bother worrying about it by your logic. Apples and Oranges mate.

I'm just frustrated that we seem to be happy with a completely rushed assessment of the danger which flies in the face of previous thinking without proper analysis, for a problem that would go away, at least for the short term, within a matter of days.

Talk all you like about risk only being in the immediate vicinity of an eruption. Research aircraft found visible and significant layers of ash in UK airspace. One of these aircraft was grounded to due the risk of possible damage sustained. Military jets suffered damage in various areas and were grounded. Civilian airliners have had suspected damage. Why oh why is that so easy to ignore? I suppose all involved were just drinking heavily the night before and don't really know what they're talking about. All the talk about visible ash being the only issue is all rubbish also. How many ash clouds have you seen from the air? How can you all be so sure you'd be able to recognise it? It's not some black gritty looking cloud for Christ's sake. What about embedded ash? On and on it goes. I tell ya my head is sore from banging it off this wall. :ugh:

Pace, check the latest London VAAC charts.

But, as I said you're right, this is a circular argument and maybe I'm just missing the point entirely. Maybe ini years to come I'll look back and say what a **** I was to have been so worried. Let's hope that's the case. So I at least will leave it there. Safe flying everyone.

We will continue to debate this til the cows come home. There will be no resolution until there is something in writing from both the manufacturer and the regulator that clearly states a policy.

For instance, unless the manual states "approved for flight in icing", would you launch into an area of forecast icing on the premise that it would be possible to see and avoid icing conditions, i.e. mk 1 eyeball style.

I was once faced with a dilemma that that set "legal" against common sense.
Location: tropical island
Temp 32C
Weather:3/8 Cu/SC
1 Pitot heat failed, spares 24 hrs away.
Sector: 50nm, not above 6,000'
Freezing lvl:15,000'
Mel: Pitot heat, No. fitted 2, No. reqd 2

I was a new Capt. raring to go, but as my C.P said, if you blew a tyre you would get nailed for the MEL infraction even if it had nothing to do with it.:rolleyes:

Yes.
Yes.
No, why should I? Current official party line is that unless one has flown through the cloud that has been positively identified as containing VA (through stench or ash deposits found postflight) there is no empirical evidence that anything untoward might have happened to engines and no thorough engines innards inspection is warranted. No one in aviation has been yet killed by the volcanic ash, anyway.

Guess If I'm extremely unlucky, new guidelines regarding the allowed VA contamination will ensure that my life coverage is paid in full to my dependents.

Slight downside is that I'm not a cargo pilot.

Oh good lord, I said I was done here! The air in a jet engine.....oh never mind. I just can't do it anymore. A bird and an ash particle are kind of difficult to compare don't ya think? Look at some bird ingestion test and tell me if you see the bird drifting towards the outside of the intake from centrifugal force before it hits anything.......

Some perspective on this. The only incident where there is no indication the crew knew about the ash at the time is

There is very little additional information on this flight (not even who the operator was) so unclear if this was CAVU damage, night or IMC.

USCG to make the point that for several years there were issues with window and paint degrading and sulphate build up in hot sections for aircraft effected by the gas cloud (which was across the whole of the Northern Hemisphere).

Looks like the debate is over, then. Boeing tells you not to fly into volcanic ash clouds. Eurocontrol and several member nations published a clear policy that prohibited IFR flight into areas they deemed unsafe due to the volcanic ash cloud. They assessed the risk and decided it was too high for continued IFR flight. That is the basis of sound risk management when it comes to aviation safety.

There will always be second-guessers. The fact that there were no ash incidents gives clear evidence that the Eurocontrol policy was successful. There is no way to tell how many incidents or mishaps there would have been without the policy.

Airlines now want the governments to pay them for the money they think they lost. What would have been the cost of even ONE crash due to ash injestion? I think the airlines may have saved money...

[quote] It's a law of physics. You start to give ANY MASS a rotational velocity around a point then its going to move outwards.

Sorry but even if the forces are tiny and the movement is small the effect is still there.

However i'm not in a position to state without facts or figures if there would be any difference in ash density into the non-bypass airflow. /quote]

:ok:

The bigger stuff gets thrown out further,

The stuff at the fan blade roots doesn't get much acceleration, same with birds. The spinner shape is also critical to particles heavier than air.

Pretty easy to model once you've defined the particle size.

claims-counter claims are just that unless you want to take it to the technical section :)

Oh windytoo..

I do agree that the experts in engineering and airframe design are the best people to assess the actual damage to aircraft there are some precedents which make your logic most uncomfortable.

Challenger space shuttle for a start. O rings which were stiff and amenable to bypass gas when cold. This knowledge was available prior to the flight but was not acted upon by political, managerial and financial pressure. Does that sound familiar? I strikes a definate chord with me in the volcanic eruption saga.

If you wish to compare flight safety in the way you do then you accept the lowest common denominator of safety. If 100,000 people died each year in the UK because of aircraft accident then no one would fly. Is flight safety paramount or something that can be degraded?

Of couse life is a risky thing since birth but risk evaluation depends on known factors or trust. In real life people evaluate risk against benefits. I am not forced to get on any aircraft but that is an absolute. If I do not get on an aircraft then me dying in an aircraft crash is minimal ( but not impossible- the aircraft may crsh into me on the ground). I choose to pay the fare and get on an aircraft because I want to go somewhere of benefit to me. Its not an absolute, its a spectrum of risk. Am I prepared to get on an aircraft not only with the risk of it crashing but me spending days or weeks at great cost not being able to get back to home?

In the past two weeks I have put a plain sheet of A4 paper on my patio table, and guess what - ash deposits. Not every day, but enough for me to wonder what is really up there. I'm no engineer and I have no idea if the accumulated dust on my little A4 amounts to a signficant engine-failing quantity but it makes me think.

The difference between "could " and "will" is easily quantified. Its Murphy's Law.

That assetertion is disingenuous.

The issue was not flight into volcanic ash cloud, the issue was flight in an airspace that could have had VA particlates.


argumentum ad ignorantiam.

So no burden of proof. Ergo, argumentum ad ignorantiam.

The airlines were financially damaged do to mis-management of a situation, as such yes they should be. They were damaged by the actions of another party out of their control, as such, they have scope for recompense of damages.

Brucewayne

If you can tell me the difference between a volcanic ash cloud and airspace that "could" have ash particulates in it then that would solve the huge multimillion quid probelm that airlines in Europe face.

I dont want to get hard-nosed on logic but you cannot use burden of proof on the fact that accidents have not occurred. Burden of proof can only be validly applied on an event that has actually happened. My Latin is a bit rusty but reductio ab absurdum is the term which fits. In this context it means that you would accept any risk because you do not recognise it as a problem.

I have to give Thompson Kudos for this approach...

Thomson Airways ... Personal Update! - Key Publishing Ltd Aviation Forums


Good on them :D:D:D

...

Can't believe we're quoting from the same document!!!

The one I'm looking at is
The 1991 Pinatubo Eruptions and Their Effects on Aircraft Operations by Thomas J. Casadevall,1 Perla J. Delos Reyes,2 and David J. Schneider3

In that report incident 91-09 is perhaps the best example of an undetected encounter with NO external evidence on the aircraft yet still severely trashed turbines. There are several others where no primary incident location is recorded, for several possible reasons. As the original authors state:
At this date, I doubt that anyone could say with any confidence which reason accounted for which piece of missing data in incidents in 1991!

BUT the key feature that is common to this AND the later NASA DC-8 incident north of Iceland AND probably some aspects of the Finnish F-16 Hornet ash incident two weeks ago is that there ARE many well-documented cases of significant turbine damage when the pilots were completely unaware of any ash encounter. You may not like these facts but unfortunately they are there in black and white, from multiple independent sources.

Concord:

You are forgetting that between each row of blades in both Compressor and turbine there are stator blades whose job is to ensure that precisely what you think will happen (rotational motion) does NOT happen.

To put it another way, rotational motion in both Compressor and Turbine gas streams is wasted (rotational) energy.

Hmmm - I wish I'd never mentioned centripetal forces acting on ash particles in the first place!

Suffice it that an ash particle entering a high-bypass engine near the cicumference of the fan will DEFINITELY go down the bypass duct and cause no problem, a particle near the hub will DEFINITELY go into the core and might not emerge at the other end! Other particles at other points between hub and circumference will have varying chances of going 'through' or 'round' the hot section.

The point that even with a high bypass ratio, the core must still eat tons of air to get enough power to turn the fan is well taken.

Bottom line: only engine manufacturers can offer definitive numbers for the max ash particle density per cubic metre of intake air, taking account of everything that might happen to the air and the particles going through their turbine.

Yes there is, because the policy was changed from "no fly" to "fly" while the ash cloud was still there. Apparently even on the previous "zero tolerance" measures the asirspace would be open now, but there were, depending on who you believe, two, three or several days of flying through it. Say it was two days of flying through it, and six days of not:

• Total commercial jets (or any jets actually) that fell out of the sky in the six days not flying through the ash: none.
• Total commercial jets that fell out of the sky in the two days flying through the ash: none.
• Calculate total commercial jets that would have fallen out of the sky if same threshold had been applied across the six days: six * zero / two = none.

If you think that is over-simplistic, you might want to consider that allegedly (since it's the daily mail - although it appears a well written and researched article from what I do know) the measured ash concentration over the UK never got higher than 1/20 of the current "safe limit". See The ash cloud that never was: How volcanic plume over UK was only a twentieth of safe-flying limit and blunders led to lock-down | Mail Online


We live in an imperfect random world that is inherently not perfectly mesurable - zero tolerance policies are inherently dumb. Find any VA ? - have to close airspace. That's the easy part.

Now how do you reopen it ? How do you prove there is zero VA ? How many test flights over how many days (remembering you've just grounded your test aircraft for repainting, after the eruption started...) have to come up clean ? What if you didn't cover the whole area and missed some ash, what if your instruments aren't sensitive enough, how do you prove there is zero VA so you can re-open airspace ?

Answers on a postcard to the relevant authorities, they need your help because their previous plan looked like:

1. IF find VA THEN close airspace
2. Hope (1) never happens

Partly correct.

The rotational motion only lasts between the aft side of the spinning blade and the entrance to a stator row. However it is within that distance that the heavier particles will deflect outward. Very significant between the back of a fan blade and the inlet to the core.

I believe that there are some patents filed on this very basis (GE, Boeing, etc.)

Since our world is so imperfect and random, we sometimes have to resort to the best information available when making decisions, even knowing that information is imperfect. The best information the government authorities had were the cloud models, which predicted significant ash over a wide area. When the lives of so many people and the reliability of so many engines is at stake, there is no sane choice but to be conservative IF, as is proclaimed by all the regulators AND the airlines, "Safety is Paramount" is indeed the truth. Personally, I applaud those regulators for deciding it is time to do more than pay lip service to safety concerns that happen to have significant cost and corporate and personal inconvenience.

How many of those airlines would have accepted strict liability for any damage and/or injury caused by ash ingestion? I suspect not one.

Intruder

I am glad you have the complete confidence in the "experts" The trouble with that is that everyone has their own interests their own backs to watch their own agenda.

Zero ash tolerance was abandoned in a matter of days for plucked out of the sky percentage ash? More like sock it and see?

Even the new limits are riddled and based on a fairly constant level of ash over a large distance. Where are those samples taken and what happens in the areas not taken? You may get a suitable level in one area which fits within the limits but half a mile away a much denser area which has been completely missed.

In the Alaskan eruption Ash circulated the globe three times before completely dissipating. 1000s of aircraft probably penetrated low density ash ridden air without even knowing about it. Maybe what the eye doesnt see the heart doesnt grieve?

The pilot as in any situation is best placed to determine whether a flight is safe or not. Not some politician or Quango leader who has no aviation experience whatsover and is more intent on watching his/ her back or lining his or her colleagues hands in gold.

As in any other atmosphere threat whether thunderstorms, bird strikes, strong winds, fog etc the pilot has the data but makes the decisions.
More aircraft have been downed by thunderstorms, More aircraft downed by fog, more aircraft downed by in flight turbulence and windshear, more aircraft downed by bird strikes, more downed by strong crosswinds, more by ice than ever in diffused ash.

Yes those pilots fly within minima and regulations but they fly.
Why is ash any different?
If we never flew because of a potentail threat albeit how small the skies would have been empty a long time ago.

Pace

I'd be interested in your attitude to the effects of VA on the medium term safety of the aircraft. That is, in a few weeks time when you are not aboard but the effect of your decision is going to affect the reliability of the aircraft.

Or the affect on profitability over the longer term that results in UK/European aircraft not being economical to run due to VA damage?

(Not that any of this seems to have surfaced so far and it's academic as we have taken the decision to run the experiment).

I'm pretty sure that was the St Helens volcano that did that. I'm also fairly sure that much of the ash that circled the globe was at altitudes >65,000 ft (see section on Plinian Column), which should have kept it out of reach of most planes.