Dear Stoic, once again, allow me to quote hindsight. Nobody in 1982 was aware of the effects of a volcanic cloud even if they realized that it was a volcanic cloud. There were no Notams issued about volcanic eruptions affecting safety of flight in 1982 until the BA09 incident.

Sorry Stoic, I disagree. Forget Notams, there was no experienced aviation knowledge about operating in volcanic ash. The Icelandic volcano that caused the cloud erupted for the second time in memory after 200 hundred years ago. That is a 100 years after the first powered flight, which I am sure you are well aware of.
A somewhat off the present topic but I feel has a certain relevance is the previously unknown effects of mother nature on humble aircrew and aircraft.

BOAC Flight 911


BOAC Boeing 707 at London Heathrow in 1964
Accident summary
Date March 5, 1966
Type In-flight breakup
Site Mount Fuji, Japan
Passengers 113
Crew 11
Injuries 0
Fatalities 124 (all)
Survivors 0
Aircraft type Boeing 707-436
Operator BOAC
Tail number G-APFE
Flight origin Tokyo International Airport
Destination Kai Tak Airport
BOAC Flight 911 (Speedbird 911) was a round-the-world flight operated by British Overseas Airways Corporation.
On 5 March 1966, the Boeing 707-436 operating this flight was commanded by Captain Bernard Dobson, 45, from Dorset, an experienced 707 pilot who had been flying these aircraft since November 1960.
The aircraft, registered G-APFE, disintegrated and crashed near Mount Fuji, Japan shortly after departure from Tokyo International Airport, at the start of the Tokyo-Hong Kong segment. All 113 passengers and 11 crew members were killed in the disaster, including a group of 75 Americans associated with Thermo King Corporation of Minneapolis, Minnesota, on a 14-day company sponsored tour of Japan and Southeast Asia. There were 26 couples traveling together in the group, leaving a total of 63 children orphaned.
This was the third fatal passenger airline accident in Tokyo in a month. On February 4, the worst single plane crash in aviation history at the time occurred near the same airport when 133 persons died as a Boeing 727 belonging to All Nippon Airways, a Japanese domestic line, plunged into Tokyo Bay while preparing to land. Then, a day before the BOAC disaster, a Canadian Pacific Airlines Douglas DC-8 jet crashed on the runway while landing at the Tokyo International Airport, killing 64 of the 72 persons aboard.


One day after the tragedy, speculation was that fierce winds above Mount Fuji were responsible. The New York Times reported: "Despite these reports of a fire and explosion aviation experts said that adverse wind conditions around the volcanic cone about 40 miles south of Tokyo may have caused the crash. The vicinity of the 12,388-foot peak is notorious for tricky air currents. Technicians in New York said that a condition could exist where turbulent air could have caused the aircraft to undergo a drastic maneuver that might lead to a crash. Such violent forces, they said, might have caused an engine to disintegrate, possibly setting fire to the wing or fuselage."
The accident aircraft arrived in Tokyo at 12:40 hours on the day of the accident from Fukuoka Airport where it had diverted the previous day due to conditions on the ground in Tokyo. The weather there had since improved behind a cold front with a steep pressure gradient bringing cool dry air from the Asian mainland on a strong west-northwest flow, with crystal clear sky conditions. During their time on the ground, the crew received a weather briefing from a company representative, and filed an instrument flight rules (IFR) flight plan calling for a southbound departure via the island of Izu Ōshima, then on airway JG6 to Hong Kong at flight level 310 (31,000 feet).
At 13:42 hours the crew contacted air traffic control requesting permission to start engines, and amending their clearance request for a visual meteorological conditions (VMC) climb westbound via the Fuji-Rebel-Kushimoto waypoints, which would take them nearer to Mount Fuji, possibly to give the passengers a better view of the landmark. The aircraft began taxiing at 13:50 and took-off into the northwest wind at 13:58. After takeoff, the aircraft made a continuous climbing right turn over Tokyo Bay, and rolled out on a southwest heading, passing north of Odawara. It then turned right again toward the mountain, flying over Gotemba on a heading of approximately 298°, at an indicated airspeed of 320 to 370 knots, and an altitude of approximately 4,900 m (16,000 ft), well above the 3,776 m (12,388 ft) mountain peak.


Mount Fuji as seen from an airliner
While flying into the wind, approaching Mount Fuji from the downwind side, the aircraft encountered severe clear-air turbulence associated with lee waves, causing a sudden structural failure that initiated the in-flight breakup sequence. At the time of the accident, winds at the summit of Mount Fuji were measured at 60 to 70 knots from the northwest. Lenticular clouds associated with lee waves were observed on weather satellite photos taken 30 minutes before the accident some 240 km (150 mi) to the south, but were not visible in the vicinity of the accident where the skies were clear.
A U.S. Navy A-4 Skyhawk that was sent up shortly after the accident to search for the wreckage encountered extreme turbulence in the accident area. The cockpit accelerometer display registered peak acceleration values of +9 and -4 g-units, causing temporary loss of control, and leading the Navy pilot to believe his aircraft would also break-up in the turbulence. The pilot regained control and landed safely, but the aircraft was grounded for post-flight inspection by maintenance personnel. Many other aircraft that passed near Mount Fuji that day also reported moderate to severe turbulence.
The accident was photographed by Japan Self-Defense Forces personnel at the nearby East Fuji Maneuver Area, and an 8 mm film shot by one of the passengers during the flight had resisted the crash. Witnesses on the ground reported seeing the aircraft in a flat spin trailing white "smoke" prior to breaking up in flight. The white cloud was later determined to be atomized jet fuel escaping from the fuel tanks due to the breakup. The film shot on board was developed by investigators, and showed evidence that the aircraft experienced severe turbulence just prior to the accident. No evidence was recovered from the flight data recorder, which was destroyed by fire with the rest of the nose section which fell separately. The aircraft did not have a cockpit voice recorder, and no distress call was received from the flight.
The aircraft left a debris field 16 km (10 mi) long. Analysis of the location of wreckage allowed the accident investigators to determine that the vertical stabilizer attachment to the fuselage failed first. It left paint marks indicating that it broke off the port side horizontal stabilizer as it departed to the left and down. A short time later, the ventral fin and all four engine pylons failed due to a leftward over-stress, shortly followed by the remainder of the empennage. The aircraft then entered a flat spin, with the forward fuselage section and the outer starboard wing breaking off shortly before impact with the ground.
Although some stress cracking was found in the vertical stabilizer bolt holes, it was determined by subsequent testing that it did not contribute to this accident. Still, it was potentially a significant safety-of-flight issue. Subsequent inspections on Boeing 707 and similar Boeing 720 aircraft as a result of this discovery did reveal this was a common problem, and corrective maintenance actions on the fleet eventually followed.
The probable cause determination was: "The aircraft suddenly encountered abnormally severe turbulence over Gotemba City which imposed a gust load considerably in excess of the design limit."

Hot Dog
 

This is a bit difficult to follow because my posts are being disappeared.

You say: The reason being that we avoided flying in visible volcanic ash. Airmanship.

The BA009 1982 was an inadvertent encounter.

Regards

S

So if somebody flew into the Icelandic volcanic cloud at night, it would have been OK?:rolleyes:

Hot Dog
 

Who has suggested that?

The problem is that UK airspace was closed down for an ash cloud that could not be seen 1000 miles from the eruption.

Only on certain headings Stoic but I have no desire to continue this dialog any further. Cheers HD.:ok:

Mods,

Why is there a persistent removal of posts from anyone who comments that the ill effects of ash have always involved 'visible' ash clouds (sometimes not appreciated or seen due to night - but always sufficiently dense to by visible or obscure stars)?

I'm still amazed at the IMO totally unbalanced view so many are taking about this whole thing. I also accept that I am heavily leaning in a particular direction too and am at risk of being blind to the inaccuracies of my own logic. But, I have heard it stated more than a few times that previous ash encounters have not resulted in a single accident and even the ones that included engine flamouts, had engines sucessfully restarted and a safe landing completed.

Imagine a design fault which had caused over reported 100 incidents (and likely many more unreported) leading to damage and a combined total of hundreds of millions of dollars in reapir bills. One year alone had 23 incidents. 7 incidents involved engine failure including two with all engine loss but none resulted in accidents. The occurence of the issue could be loosely forecast but it was difficult to narrow down the exact conditions under which it would occur. The fact that 100 issues had occured at all suggests that inadvertent and unexpected recurrence was both possible and likely. Are you really telling me that the public and the industry would accept an amendment to the regulations to allow continued flight of affected aircraft as long as they don't enter flight conditions which were already known to guarantee the problem would arise? And all because the industry itself was compaining that they would lose money and risk collapse if they were not allowed fly?

Of course not. The authorities would be firm and insist that the manufacturer(s) involved do something about it immediately, and would only allow flight if they were sastified, using hard proof from tests and unquestionable technical confirmation that the issue had been resolved or at least could be guaranteed to not recur under all but the most rare and easily avoidable conditions.

Now, of course, that's a stupid comparison, but really if you think about it, it is effectively what this ash thing is about. Safe airspace was designated using a best guess method. Many aircraft, including some civilian machines continued (some yet to be confirmed) to have issues. Does that not say the best guess wasn't good enough? Nope. Cause it'd be too painful and difficult to say "Whoops. Got it wrong. Let's try again." And as always seems to happen, the problem quickly goes away by itself, nobody was hurt, no aircraft fell out of the sky (if I hear another pilot say "what's the problem? I don't see aircraft falling out the sky" I'll punch him.) and it can all be quietly put to bed, even though all the evidence suggests it didn't quite go as smoothly as was originally hoped.

I tell ya, sometimes this industry and the people in it make me dizzy, with all their declarations that they can not be shaken from accepting the lessons of the past and that commercial pressure shall never be allowed influence judgement when it comes to issues that can cause damage or affect safety regardless of the cost. But of course, that only applies when it suits them. A la carte professionalism I suppose you'd call it.

Hi,

The problem is the confusion and misuse of a principle does not apply to all situations ...
The confusion between the foresight principle and the precautionary principle.
The precautionary principle is often used for situations that require only a foresight principle ..
It's semantic .. but nevertheless the words have their importance given the different actions taken by the principle employed.
We are now living in a society driven by fear .... and this is not innocent ....

jcjeant

I cannot disagree with what you are saying but this has happened so many times now that many are questioning the science.

Even global warming which so many claim is created by man and with the same scare tactics is under a big ? Yet it will cost the UK £18 billion and no doubt crucify our industry even further.

I am sure in a few weeks this latest expensive exercise will disappear into a distant memory until the next HUGE scare arises generated by the science in whatever field.

Oh well maybe the Hadron Collider another media generated scare with backing by some scientists will have turned us all into a black hole so none of us will have to worry :ugh:

Pace

Interestingly, there is a phenomenon very much like you describe...

Bird strikes, we know broadly when and where they occur, they are estimated to cost aviation £1.2bn pa., have a recent history of causing complete and unrecoverable loss of power, and have caused fatal accidents and the loss of airframes in non-fatal accidents. (at least everyone so far involved with ash encounters has been able to get the engines going again!) Should we stop civil aviation during bird migration season? No of course not. We should take sensible mitigation steps. That is all people seem to suggesting - not that ash is not a problem - just the approach of closing down Europe was out of proportion to the risk.

Hi,

Indeed the approach was to apply the precautionary principle.(all grounded)
When the "corridors" were put in force it was the foresight principle applied.
This principle was to apply immediately .. and the costs and disturbances will not be what they are today ...

PJ2

We all know that flying in thick dense volcanic ash clouds as seen bellowing out of the volcano source would be a very serious encounter.

My instincts are that in VMC and daylight if the ash is so dispersed as to be invisible then there is no threat.

Many will demand on what scientific basis that comment is made but then NO ONE experts or otherwise seems to really know scientific or not!

We do know that the Alaska eruption circled the world 3 times before it fully dissipated.
What the eye doesnt see??? How many aircraft flew through low level density ash totally oblivious to the fact?

The new levels are a good starting point until practical experience proves otherwise.

I like MMs Comparison with bird strikes which have brought down aircraft unlike ash which to date hasnt.

We live with potential bird strike threats and dont close down masses of airspace in the migration season.
Until the science can come up with solid data or detection equiptment for aircraft practical experience and common sense are our best options.

Pace

How memories are short. I find it incredulous for anyone, let alone Sir Richard, to suggest that in the first two or three days of the ash reaching/covering the UK we could have continued operations in the face of an anti-cyclone dragging volcanic ash into our airspace. We would have had to put aside good airmanship, all of our knowledge of VA and its hazards, ignored the advice in our ops/airplane and engine manufacturers manuals- and that of the ICAO led VAAC. That was never going to happen. The fact that NATS prevented IFR flight in our airspace is in truth, secondary to the above; how many airline pilots would have been comfortable getting airborne or flying through this airspace given the information they had available to them at the time? How many Chief Engineers would have had the confidence to say, it's OK let's continue operations? Who had the confidence to risk the repair or replacements of leased engine's and airframes?

It was only after the risk was assessed by regulators and OEM's that it was established that it was safe and reasonable to start flying again. And by then the ash was much more widely dispersed. And to do that in the time they did was quite remarkable.

Of course, with hindsight, the airline industry should have had this issue sorted out long- However, to those not involved in the negotiations to set safe limits of ash- we thought we had- the rule was- we don't fly into VA!

Sure, there are many lessons to be learned and we'll all do it better next time, but it is disingenuous for anyone to say or suggest that we could have just kept flying as normal or been able to pick our way through corridors free from ash.

Not a bad discussion these last (few posts ....if they survive :))

The answer probably lies in the details.

On the surface it appears that the historical single-flight safety impact from volcanic ash (Eric Moody etal.) was the failure to look for a clear route around the (unknown to the pilot) volcanic ash cloud. The same might be said for the last weeks only the cloud patterns were known but no chance was ever given to search out a clear path.

Now that the decision to manage flights around various densities of volcanic ash has been shared, it has been shown that one can minimize the risk down to something like avoiding bird ingestions that knock you out of the sky.

The human does learn to adapt even though we may not fully understand.

I don't like the rhetoric that heaps distrust on the CEO,s They only take advice of the avaition safety experts (believe it or not).

I suppose we could always fill a room with aviation safety experts and listen to the discussions, but I suspect that this has already happened and we are just second guessing what they discussed :)


OTOH have we noticed many qualified aviation safety experts in the press that say the present course of action is unsafe?

To me the opinions of individuals is only that, unless you represent a larger contingent that has reviewed the issue and history.

Iceland warned of volcano danger to planes “for years” | IceNews - Daily News

I wasn't making the statement on belief. The FACTs as best as they are currently assembled say.

1. No aircraft has ever encountered a loss of power that could not be recovered at lower altitude - even while flying through significant densities of ash.
2. There appears not to be a single documented instance of an in flight abnormality attributable to ash with a density lower than that of visible haze - and most seem to have been in thin cloud or denser. (This is different from saying low levels of ash don't result in accelerated wear - which it quite likely does)
3. Operator's in areas of volcanic activity have SOPs that allow them to continue to operate - with limitation (which curiously didn't seem to apply to Europe when the skies where opened.)
4. There are risks that down aircraft every year and operators continue to operate exposed to these risks (because you couldn't operate a business if you didn't - and after all the only reason the airline industry exists is to make money serving its customers).

Well said Captainpaddy. Sort of reminds me of that old rubric that "everyone is safe until they are in a hurry" which in this case seems to be that the industry is safe until it is faced with a problem that might require a stand-down, some research, and heaven forbid--discomfiture! (and I say that in all repsect for the thousands of people who were genuinely discomfited by this eruption-disruption and had to doss down where they could for days on end)

We are safe Sir Richard seems to be saying however, but we are in an awful hurry to get things moving again...

I continue to be amazed that many professionals on this thread cannot see the possibility that very low levels of certain contaminants, entering the internal cooling system of HPT blades, could result in subsequent premature failure of those blades due to a reduction in the cooling available.

John Farley

Premature compared to what:confused:

What metric should alert us and when will they know? in one month? one year??

JF

You're so correct. The key word though, is 'could'.

We need to know if it 'will' cause the damage, or not.

At least this period of flying in low concentrations of ash will likely provide an answer.


Granted, with a little forethought, the answer to the 'how much is too much' question could easily (if at a cost) have been discovered.

We will now find out.

The cost to the airlines of the enforced stoppage must exceed by many times what the 'research', which was too dear to do, would have cost.

plus ca change.:rolleyes:


We make money (BA forecast £600m loss this year) or we fold.

Possibly - but only after a long delay!

As I understand CAA and EASA directives, and current airlines reaction to them, the initial basis of ALL investigation of potential ash encounters starts with EITHER in-flight observation of ash in the air or hitting the aircraft (St Elmo's Fire, ...?) OR the strong possibility that the route DID pass through an ash cloud. Then, specific ground inspection will be done, starting with Mark 1 Eyeball examination of the aircraft for 'traces of ash'.

As has already been discussed much earlier in this thread, there's a stack of good evidence that a flight CAN pass through quite dense ash with NO in-flight indication AT ALL and nothing found visually post-flight (in particular, the NASA DC-8 incident in 2000).

Seems to me that the key problem that remains completely unaddressed is any 'backstop' testing so that even in the absence of any other evidence, ash in turbine hot section cooling systems WILL be detected and appropriate maintenance done, ideally before major damage occurs. (Don't know whether any ash removal from inside blades is even theoretically possible without tearing the whole engine apart!) Filters on bleeds from the engines provide a DEFINITE indicator of ash ingestion but as far as I know there is no organised plan to test them post-flight.

Remember that a lot of aircraft tend to fly reciprocal routes (A to B, then B to A, maybe several times in the same day). Ash encountered on multiple flights will obviously become a CUMULATIVE problem, especially if low levels of ash are unexpectedly present on a busy route and not detected by any of the current means!

Everyone is wondering what happens when you fly through a widely dispersed ash cloud and its after effects.

Here is link to the USGS study on exactly that - the aftermath of Mt. Pinatubo in 1991 (bigger eruption than this one)Casadevall

Flying for CX at the time I remember Manila was closed for 2 weeks while the eruption was on and the ash scraped off the RWYs afterwards (55nm downwind from the Volcano).

Other than that there were various re-routes on HKG-AUS vv and in the (very busy) South China Sea.

There was some damage to aeroplanes but mostly very minor (see above report). One IFSD was reported in the 18 encounters during the aftermath.

To all the doom forecasters:

Have any of you actually been up there this last week? Are any of you actually airline pilots?
If so: have you refused to fly this week?

I have been to the UK, to various parts of Scandinavia and to Italy this week. All the AMT`s that I have spoken to have told me that they haven`t seen any evidence of ash on any of the aircaft this week.

Let`s just all be grateful for the experience our industry is gaining these days on the subject.

Off to fly now....

I'm not 'forecasting doom'!
Just the potential for massively-increased engine maintenance costs, which will inevitably and eventually hit YOU straight in the pay-cheque!

What difference does it make make whether you've flown through ash, flown in an EPZ or even just 'flown'?

I thought it was generally agreed that in many situations, even CAVOK, it was possible, even likely that flight-deck crew will see NOTHING on instruments or outside the aircraft that will give any clue AT ALL of the presence of ash! If you've got an instrument that images diffuse ash-clouds, you're sitting ona gold-mine!

Is it not a better idea to spend a relatively small amount of money on post-flight detection of an ash encounter than to risk millions on engine overhauls and spares that may not even be do-able on a reasonable timescale? (eg. repairs to all 4 engines on the NASA DC-8 after 8 MINUTES flying through ash at night: $3.2million)

PS
It's interesting that there WERE symposia and publications (eg. by USGS) after Pinatubo in the early 90s but not much got done about it! Much easier to justify activity and expenditure after a major event that cost LOTS of money. Much harder after the dust has settled :) Well - here we are again!

It is generally stated, although it does not appear to be true. It is clear that if the crew can not see out (eg. it is moonless night over ocean or they are in IMC) they can't see ash. However, in all of the documented encounters it was clear after the fact that the ash was visible (Eg. the stars become obscured but the crew couldn't tell if they were in or under cloud because it was night - the NASA DC-8).

To JFs point - the above applies to the immediate flight safety incidents that have been documented by USGC or ICAO. It is quite possible (even probable) that flying in invisible ash could significantly reduce the life of engine components and cause premature failure - I don't think anyone in this thread is arguing otherwise. However, that appears to be much more of an operational economic and maintenance inspection question than a flight safety issue.


There conclusion appears to have been don't carry on in an ash cloud - (determined by the cabin fills with haze, you smell sulphur, St Elmo's fire appears, your windshield gets sand blasted). Also, there appeared no evidence of any long term ill effects of operating in the general environment. How much more study should they have done?

Err - no. The (now very old) USGS report on Pinatubo includes several notes about aircraft damage found well AFTER flights that could have caused it! The authors commented that the reason that there's no location given for some of the tabulated incidents is that no-one knew where they happened!

And I was not suggesting more studies - there already seems to have been plenty of evidence, even from the early 90s. I meant real-world policies and procedures that actually MEASURED stuff (like ash in the air and collected on / in aircraft when there was likely to be a problem) and then ACTIONS to minimise risk and further cost. Ad hoc Mk 1 Eyeballing ain't it!

This really is the bit that gets my goat. I and most others I listen to or read are not claiming by any stretch of the imagination that an aircraft will fly tomorrow, suffer multiple engine failures and glide for a landing into Blackpool. We are not forecasting doom at all. In fact I am very aware of the possibility and indeed hoping for it to turn out to be the case that nothing comes of this at all. But the single point is WE DO NOT KNOW WHAT WILL HAPPEN.

How pathetic an answer is it to say "we'll find out what damage is done in due course". Or for someone to say they flew 6 flights over the last three days and did not have single problem - as if this gives any indication of general conditions to be expected across the whole European network. That's the same ridiculous logic that was used to open the airspace so quickly in the first place.

Damage can be done and in fact, damage has been done. I completely agree that there must be conditions under which it is safe to fly and it is extremely unlikely that sustained significant damage would be done to every aircraft on every route. But we have not had any proper examination of that possibilty whatsoever. Worse than that, some of the test flights which did occur did find potentially damage causing levels of ash. Although it seems this finding was too close to the agrrement on the regulations. The point of no return must have been reached. Most signifcantly though in my mind they found multiple varying layers of ash conecntrations when this new regulation is based an three zones of constant and evenly spread concentration - something that nature will never provide.

This isn't about simply whether an aircraft will fly and crash. This about so much more than that. It is about the heavily commercially orientated mindset of those tasked with being objective and non-commercially orientated.

If this was a scenario that was likely to continue for weeks or months then I would understand the need to find a way to save our entire industry. But our industry as a whole was never at risk because this was NEVER going to last that long. Our safety process has been influenced by shareholders. Plain and simple. That's my problem.

No proper system of analysis nor operational procedures have been employed. Let me ask all you airline guys out there that challenge those who did or didn't fly already since the clampdown: When you're up there, after having studied your ash charts before you left and you're pootling through swedish airspace and suddenly ATC advises you of a new VA sigmet for the area you are flying in or intending to land in what do you do? The same as the rest of us - tear it up and throw it away because the chart didn't show it in your area I imagine. How do you deal with a pirep? That's something completely different surely? And there has been pireps of ash encounters - whether they were valid or not is another question - but aircraft are ignoring them completely. We have been led by the bloody nose here!!!!

Can anyone explain how the AACC shows zone 1 and 2 limited to Iceland while Gothenburg is confirmed to be zone 2 by ATC?

Put your head back there so I can a good hold on your nostrils while I walk into this cave to see what's in it.............

mm_flynn

how can you say

but feel that it wouldn't be a flight safety issue?

That's just strange! So if an engine quits 20 hours before it planned overhaul that's a problem for the bean counters more than for us?

The logic for ash being such a signficant safety issue is that it is one of those common mode failure things. If you are in sufficient ash to fail one engine, the odds are pretty high that the rest of them are going to roll back in a few moments. I think everyone agrees that is a big problem.

However,

engine overhauls are not scheduled 1 hour before expected failure, they have quite a lot of safety margin and typically have some type of condition monitoring to detect accellerated wear. A failure due to Ash wear is likely to be at a random time, and therefore the redundancy logic works.

Just to be clear - I am not saying flying in invisible ash has no effect - just that the risks seem similar or lower to lots of other risk.

The figure is failure within 100-500hours after the encounter, according to NASA. So in a few weeks you could have thousands of wrecked engines and billions of dollars in repair bills, plus possibly years get replacement parts.

That would concern more than just the bean counters, wouldn't it?

Why are we wasting all this money over ETOPS procedures, IFSD rates, etc, when it is clear that most here are prepared to accept a higher level of risk. Have we ever lost an aircraft due to strictly ETOPS issues? Based on that the procedures are superfluous.

I think we should be looking at what we may have to do if (when?) Katla erupts as many claim is a highly likely event.
Eyjafjallajökull might just be the warm-up!
We dont have much time to think this thing out.

mm_flynn I understand your redundancy logic theory. Nice one! Never really cnosidered that. Although as you say, each engine is likely to be affected in a similar way and to a similar degree. So is it not cutting the redundancy logic a little fine? Can it not be considered possible that another engine may suffer similarly within a short period of time following an ash encounter?

Normal redundancy works because failures are much more random and occur from tiny differences in quality of manufacturing or unusual isolated interaction with other components and therefore the time scale for failure is very wide and varying.

But if what peter says is true then if you are likely to see problems within 100-500 hours then that is much too small a window to expect isolated and seperate issues. What I mean is that if one engine dies 105 hours after an ash encounter, there has been reasonably significant damage. It is therefore correct to assume another engine will suffer the same fate within a very short period.

Yes, engine monitoring should highlight longer term issues long before they become a problem, so I don't expect we will see engines failing spontaneously in 2 or 3 months time. I just hope we don't have repair bills which cripple the industry more than another couple of days of waiting for the ash to clear would have done. And an engine change takes a lot longer than 2 days....

CaptainPaddy

Although the Volcanic Eruptions have declined slightly the low ash levels have remained constant over the UK and are forecast to remain so for the remaining of this week.

Paddy on the previous zero tolerance levels you seem to support we would be in over two weeks of no fly! not a couple of days longer as you put it.
Taken from the metoffice

Pace

Are you sure about that? the UK has looked completely clear for some time according to the Met office.
The wind direction is also favourably predicted for the UK until Saturday or so.

lomapaseo

I was using the word premature in the sense of earlier than expected. Whether that is measured in simple engine running hours or cycles would depend on what is normal for the particular engine.

By 'certain' contaminants I was referring to those that at HPT blade temperatures change their nature to a 'glass' like material that has been known to flow and coat surfaces.

Sadly I think this whole situation is one of those 'where we know what we don't know'

I would not like to be thought of as a doom-monger just as somebody who does not know enough to make a flight safety based commercial decision on this topic - sometimes it is great being retired!

Is it just me or has anybody else noticed that the clouds have a brownish tinge to them? Just my observation whilst flying down T9 to the Canaries on Friday morning. It also may just be a coincidence but the whole of the cabin and flight deck stank very strongly of burning paper on engine shut down on stand.
The cabin crew senior reported the fumes to be like someone had just struck a box full of matches, all the passengers were very concerned. Duration of the fumes lasted about 7 to 8 minutes and I opened the DV to get fresh air into the flight deck. The engineer could not find anything obvious after a thorough inspection, neither could I during the walk round

The same thing happened the next day on the sane aircraft.

BR.

I still haven't seen a reply to what was different about this eruption compared to the thousands of others that have happened since the advent of turbine engines, which have had no ill effects reported beyond a few where the aircraft was actually close enough to be visual with the eruption, and which were avoided by all other aircraft by common sense rather than a continent-wide ban.

When Mount St. Helens blew in 1980, for example, the ash generated was so thick that snowploughs had to be deployed on roads well downwind, yet there were only local aviation closures and diversions, and no adverse effects were reported from the continuing use of other airports and airways beyond the immediate and obvious zone. Why was a different approach taken this time, and what was the basis for it ?

Unfortunately this thread has deteriorated into a series of hypothetical arguments between 3 or 4 protagonists on one side and most of the aviation society on the other. Some people do not seem to be able to differentiate between risk, safety, commercial decisions, personal choice and living life as a human being. Sorry to bring Capt. Moody up again, but since his encounter with volcanic ash, many people have unfortunately been killed in aircraft accidents of one sort or another, but none to my knowledge as a result of their jet being affected by said ash. Even though it, or ash like it has been present in the air ever since.
Engineering, and especially engine monitoring, has moved on leaps and bounds in the last 30 years and that leads directly to safer flying and also (believe it or not) better commercial decisions and therefore cost saving, which in turn is passed onto passengers.
From the moment you are born life is a risk and when you become old enough to make your own decisions then your risk assessment of a situation will determine the way you live that life. Unless you are a deportee, nobody will ever be forced to get on an aircraft. If you feel the aircraft is unsafe and don't want to travel that is a decision for the individual, but please leave commercial decisions about engine life etc. to the people who have the data in front of them and not a rumour forum.
Now mind how you drive home because in the last 25 years nobody has been killed in the air by volcanic ash, but 100 000 people have been killed on UK roads. What's the difference in risk involved in that?

When I last took a bird, it most definitely WAS centrifuged (and diced).