SO FAR SO GOOD: No major incidents have been reported since European airspace restrictions were relaxed.
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Air travel in Europe inched back to normal Wednesday, as officials estimated that newly opened flight routes would permit air traffic to approach 75 percent of its normal capacity. Ash plumes from Iceland's Eyjafjallajökull volcano had all but extinguished flight operations across the U.K. and mainland Europe for the better part of a week.
Barring a tragic outcome, which is thought to be unlikely, it will be difficult to know the extent to which jet engines can tolerate mild to moderate intakes of ash. The damage might be cumulative and is tough to detect, says Michael Fabian, a professor of mechanical engineering at Embry-Riddle Aeronautical University in Prescott, Ariz.
In an effort to keep planes and passengers safe, officials broke the affected areas of airspace around Europe into three tiers: normal flight zones where ash no longer poses a risk, no-fly zones where ash remains in high concentrations, and intermediate, potentially hazardous zones where flights can proceed with caution, subject to route restrictions and other limitations. To draw those boundaries, flight controllers were forced to determine what constitutes an acceptable level of volcanic ash, despite a lack of data to inform their assessment.
The three-tiered approach is "designed to prevent airliner contact with levels of ash that are 10 times the normal levels," says Kyla Evans, a spokesperson for the Brussels-based intergovernmental air traffic agency EUROCONTROL. "In other areas, where there is possible ash contamination, but at lower concentrations, aircraft can fly."
Fabian says that jet engines' tolerance to ash is not well defined. "That's an unknown—that's the problem," Fabian says. "There really isn't much data about how much can you tolerate. It's going to vary tremendously by engine."
Volcanic ash is highly abrasive and can melt down to a glass in the extreme heat of a turbine engine; past encounters with volcanic clouds have produced near-catastrophic results. In 1989, for instance, a KLM airliner approaching Anchorage, Alaska, passed through an ash plume spewing from nearby Mount Redoubt. All four engines flamed out, and the plane glided to 4,000 meters in altitude before the pilots were able to restart them and land safely. According to a U.S. Geological Survey report on volcanic aviation hazards, the plane suffered $80 million in damage, including the cost of a new set of engines. So air operators pay close attention to volcanic ash, for both safety and economic reasons. "You know it's going to be bad on the engine, so you historically just avoid it," Fabian says.
If one of the flights now passing through European airspace suffers any detrimental effects from minor exposure to volcanic ash, those effects may not present themselves as suddenly as in the 1989 incident over Anchorage. "It's a cumulative thing," Fabian says. "Who knows if it happens on the first flight?"
Evans of EUROCONTROL adds that flights passing through potentially contaminated areas may be required to report back with the results of postlanding inspections, but Fabian says that such checkups do not reveal all potential damage. "I'm sure they'll borescope after flights—that's like a video camera with a snake—and they'll run it up the tail and look at the blades and the surface," he says. And indeed, that is precisely what engine manufacturer Pratt & Whitney advised its customers to do in the event of ash exposure. "But the trouble is they're not seeing the inside of the blades, and you won't get that until you do an overhaul or a flow test of the blades." Pulling the engine apart for that kind of testing simply is not possible for operators with a manifest of prescheduled flights, Fabian adds.
"I'm sure they're using their basic instrumentation to see if the temps look right in terms of thrust level and pressure levels, but there's a question mark out there in terms of how the turbines are surviving," he says. "It's going to be interesting to see how things play out. You hope that they don't push it too hard."
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23 Comments
Add Comment"... flight controllers were forced to determine what constitutes an acceptable level of volcanic ash, despite a lack of data to inform their assessment. " I hope that they have written authorization for making an assessment without data. Sounds like playing Russian roulette - as long as no-one gets hurt, it's a perfectly safe game.
Reply | Report Abuse | Link to this"How Much Volcanic Ash Is Too Much for a Jet Engine"
Reply | Report Abuse | Link to thisIf there is enough to make the engine stop, its too much. ;)
Like the old mechanics credo: Tighten it up until it becomes loose, then back off a 1/4 turn.
No expertise, just fear.
Reply | Report Abuse | Link to thisHow do turbines flame out when ash melts? How do they restart? Do you know how? If not, why opine here?
Reply | Report Abuse | Link to thisOne piece of information I never saw is how far away from the visible plume of ash did the plane off Anchorage go?
Reply | Report Abuse | Link to thisDid the pilot see they were going through a dffuse haze and thought it was water vapor? Put another way, would one of these ash clouds that can down a plane be invisible?
I wonder how one of the pilots that flies in an intermetiate-risk zone report how much ash was in the flight path (other than carrying a lidar)
I can see this has become a major pain in the ash ...
Reply | Report Abuse | Link to thisi find this article surprising. British Airways Flight 9 On 24 June 1982, a 747-236B. The aircraft flew into a cloud of volcanic ash thrown up by the eruption of Mount Galunggung (south-east of Jakarta, Indonesia), resulting in the failure of all four engines. not only that but the windshield turned opaque due to the 'sandblasting' nature of the ash. the ash entered the cabin via the engines appearing 'as smoke' but more harmful since it was ash causing painful breathing issues. [1]
Reply | Report Abuse | Link to thishow much evidence do you need for "How Much Volcanic Ash Is Too Much...?" ?
[1] http://en.wikipedia.org/wiki/British_Airways_Flight_9
There is plenty of technical information on the Web. The gist is that ash clouds of dangerous density are hard to find, with radar or visual. The general rule is to check with the aviation clearinghouse for ash clouds. However, a night-time eruption can still cause a cloud.
Reply | Report Abuse | Link to thisRe the current cloud: watch for the first flameout caused by corporate greed, with maximum finger-pointing all around.
Really interesting is Katla!
@jcvillarreal - "would one of these ash clouds that can down a plane be invisible?"
Reply | Report Abuse | Link to thisindeed yes. because ash clouds contain no water vapor (they are not clouds but rather collections of microscopic bits of rock) they are invisible to radar. that and night flying basically opens up new dangers for IFR and VFR.
http://en.wikipedia.org/wiki/British_Airways_Flight_9
[ormondotvos] "How do turbines flame out when ash melts? How do they restart? Do you know how? If not, why opine here?"
Reply | Report Abuse | Link to thisthis is explained here http://en.wikipedia.org/wiki/British_Airways_Flight_9 [1]
basically:
"As the ash entered the engines, it melted in the combustion chambers and adhered to the inside of the power-plant. As the engine cooled from not running and as the aircraft descended out of the ash cloud, the molten ash solidified and enough broke off to allow air to flow smoothly through the engine allowing a successful restart. The engines had enough electrical power to restart because one generator and the onboard batteries were still operative; generator or battery power is required for ignition of the engines" [1]
Well, as a too frequent flyer -- I would prefer that we apply the precautionary principle. Having for-profit corporations argue for resumed flights because they are losing $millions does not seem convincing (!) -- when KLM flew a "test flight" and said their plane was OK was that supposed to be scientifically convincing? Was their assumption that the volcanic ash is somehow evenly distributed over the entire European no-flight area at all altitudes? Seems a very doubtful proposition to me. What do vulcanologists and meteorologists say about that?
Reply | Report Abuse | Link to thisjcvillarreal brings up vital points. Will Sci Am answer them? Follow up to this kind of serious thought is essential. With the answers to his questions, obtained from the pilots if possible, a data base can be begun. It should be possible to put detectors on aircraft to analyse particulate levels and warn pilots to turn away from dangerous levels. These detectors could be attached to any plane that would be exposed, so ordinary flights would not need to carry them. This would reduce the cost of the equipment. A universal mount could be installed on all planes, and the information would be transmitted wirelessly to a portable instrument in the cockpit.
Reply | Report Abuse | Link to this
Reply | Report Abuse | Link to thisjcvillarreal brings up vital points. Will Sci Am answer them, or suggest the research to someone? Follow up to this kind of serious thought is essential. With the answers to his questions, obtained from the pilots if possible, a data base can be begun. I would suggest that it should be possible to put detectors on aircraft to analyse particulate levels and warn pilots to turn away from dangerous levels. These detectors could be attached to any plane that would be exposed, so ordinary flights would not need to carry them. This would reduce the cost of the equipment. A universal mount could be installed on all planes, and the information would be transmitted wirelessly to a portable instrument in the cockpit. A fail-safe self-check would be part of the equipment, periodically testing the link. Of course if the detectors can be made inexpensively enough, they would simply be required on all aircraft. Even a piston engine would be at risk if the air filters were not adequate. It appears to me that the information referenced by other comments is not being organized into a coherent data base that could be used to solve the problem. This is far too serious a problem to be ignored. If this instrumentation is made available, the confusions about where to restrict flights would be resolved. Each plane would test the level of contamination, and immediately report dangerous levels as detected. This would allow controllers to update their warnings continuously. It would allow pilots to seek a safe path to an airport, near to their destination, if not to the original airport itself. Although this would still be a difficult situation, it would be far better than the total chaos we have just experienced.
Reply | Report Abuse | Link to thisjcvillarreal brings up vital points. Will Sci Am answer them, or suggest the research to someone? Follow up to this kind of serious thought is essential. With the answers to his questions, obtained from the pilots if possible, a data base can be begun. I would suggest that it should be possible to put detectors on aircraft to analyse particulate levels and warn pilots to turn away from dangerous levels. These detectors could be attached to any plane that would be exposed, so ordinary flights would not need to carry them. This would reduce the cost of the equipment. A universal mount could be installed on all planes, and the information would be transmitted wirelessly to a portable instrument in the cockpit. A fail-safe self-check would be part of the equipment, periodically testing the link. Of course if the detectors can be made inexpensively enough, they would simply be required on all aircraft. Even a piston engine would be at risk if the air filters were not adequate. It appears to me that the information referenced by other comments is not being organized into a coherent data base that could be used to solve the problem. This is far too serious a problem to be ignored. If this instrumentation is made available, the confusions about where to restrict flights would be resolved. Each plane would test the level of contamination, and immediately report dangerous levels as detected. This would allow controllers to update their warnings continuously. It would allow pilots to seek a safe path to an airport, near to their destination, if not to the original airport itself. Although this would still be a difficult situation, it would be far better than the total chaos we have just experienced.
More volcanic eruptions appear to be in the offing.
Reply | Report Abuse | Link to thisIf one eruption is already causing so much disruption in air travel, can one imagine the scenario of 10 such volcanoes starting to bellow and spew out ashes simultaneously with equal forces?
With escalating frequency of earthquakes and eruptions in recent years, would anyone care to explain what on earth is happening to our earth? Global warming alone?
Actually they have been studying this for some time.
Reply | Report Abuse | Link to thisBesides the link in the article, there is also amongst others this one -
http://volcanoes.usgs.gov/ash/trans/aviation_threat.html
It's funny how no one is ever prepared for these things when they happen, yet are told about these things in advance. Complacency, it'll never happen (to me).
@tan boon tee
Reply | Report Abuse | Link to thisThere is no need for 10 volcanoes to erupt, if Yellowstone erupted again it would cover the entire earth with as creating a complete blackout of the sun.
This has nothing to do with global warming, the centre of the earth is hotter than the sun, and this comes from there.
Could some appropriate regulatory body please commission some testing, urgently, starting perhaps with pouring sand into a static engine running at full stick.
Reply | Report Abuse | Link to thisLimits seem to have been set based on the amount of dust in the air. That would allow the engine manufacturers to estimate how much would flow through the engines and the amount that could be deposited on the engine components. It that is low enough to ensure that the engine performance won't deteriorate too quickly all should be well. Prolonged flight under these conditions would be expected to reduce the engines' time between overhauls and that would be a significant cost to whoever picks up the bill.
Reply | Report Abuse | Link to thisAt the funeral
Reply | Report Abuse | Link to thisAshes to Ashes
Dust to Dust
If the Lord don't get you
The Volcano must!
I am an aerospace engineer, and have had the opportunity to visit a major engine manufacturer and look at engine parts that were subjected to the ash associated with Mt St Helen.
Reply | Report Abuse | Link to thisThe concern about flying into the dust cloud comes in two areas.
1. Safety- This is an issue, but really not as large of one as you may think. The dust has to be really heavy to actually effect engine operation.
2. Engine life/maintence- When the ash goes into the engine it melts and then coats the "blades/fins" within the engine when it cools down. This reduces the efficiency of the engine and greatly reduces engine life.
From the airlines perspective, it does not make sense to fly the planes through the dust and risk having to replace an engine that costs over $1M. It is probaly 90% a financial and 10% safety.
Why not go back to using piston engine aircraft during times of volcanic ash in the skies? These engines can be equipped with filters on the air intakes, to protect the engines from the abrasive action of ash. The air flow rate through turbine engines is too high to use filters. There are many DC-3s still in service, and WW2 aircraft can be taken out of museums and upgraded for commercial air transport.
Reply | Report Abuse | Link to thisWhat is considered to be too much (in milligrams per cubic meter)? I have heard that the original acceptable concentration was 20 micrograms per cubic meter, which is almost at clean room standards. The air we breathe is the same air that jet engines use, so what is acceptable?
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