The volcanic eruption of [[Eyjafjallajökull]] in Iceland shut down flights across Europe. Is the restart of commercial flights wise?
Reuters interviewed experts who explained some of the main risks to aircraft flying through this volcanic ash (see http://www.reuters.com/article/idUSTRE63I3A320100419 ):
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The abrasive effect of the ash can strip off vital aerodynamic surfaces and paralyze an aircraft engine. Aircraft avionics and electronics can also be damaged. Pitot tubes, or speed sensors -- whose sensitivity to ice or foreign objects was highlighted during a probe into the loss of an Air France jet last year -- can get bunged up and fail. The cockpit windshield can turn opaque, scoured by ash. Ash can bring clouds of sulfuric and hydrochloric acid.
-- What happens inside the jet engine?
The awe-inspiring speeds and temperatures inside a modern jet engine are its own downfall when invaded by lava dust. "Volcanic ash fragments are just a few millimeters wide, very hard and very sharp. They can get inside the engine and other parts of the plane and wear away everything they come into contact with," says Jacques Renvier, technical director at French aero engine manufacturer Snecma. First, abrasive ash can damage compressors which squeeze air ready for combustion, making them less aerodynamically stable. From there, pressurized air is forced into the combustion chamber which is so hot -- 1,200-2,400 degrees Celsius at cruise altitude -- that the fragments melt, then meld. Then this liquid rock smashes into colder parts and solidifies like cooled glass. Nozzles designed to shoot air toward the engine's turbines, which turn the engine's moving parts, start to thicken with lava. As a result ventilation is blocked and the nozzles burn too hot. Finally clumps of lava cut the space for air to escape and can provoke an engine stall, shooting flames from the back. "You basically strangle the engine," Renvier says.
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Despite all this, with over $1 billion in losses, and mounting, the airline industry has pressured authorities, who have begun to allow limited flight operations (see http://www.msnbc.msn.com/id/36637380/ns/travel-news/ ).
Are we likely to see gradually increasing mechanical failures in planes that fly through volcanic ash zones that are not properly delineated? Will these planes fail during flights near the ash cloud, which is invisible to human eyes and weather radar, or is it possible that accumulated damage may cause earlier failures than those normally prevented by routine maintenance, even in flights nowhere near the ash, after flying through it earlier?
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M$3 Answers
In Germany, flights by Lufthansa were allowed again after much pressure by its national airliner, but their responsible minister, Ramsauer, has gotten much critique by pilots and other politicians, for giving in to commercial pressure at the expense of safety. Also, many flights have been allowed, as long as pilots can navigate on sight alone. This decision has been highly criticized by pilots, as they feel they are getting loaded with the responsibility of keeping the plane safe.
In The Netherlands, airspace as been opened, but with some restrictions, allowing airliners only to fly in certain 'corridors'.
France is divided, but Air France has announced it will resume transatlantic flights from the two Paris-area airports, Charles de Gaulle and Orly.
I've heard Dutch pilots explain they can avoid 'dense' areas on sight, as they appear when in flight as if driving through mist, and are easy to avoid by flying higher/lower, or taking a few turns. Also, they assured me flying through these ash banks would be harmless, as they could also fly at a lower speed, effectively making the engines stay cooler, and thereby sustaining less damage from the dust at high speeds.
Plus, even in the case of sustained damage, and an engine failure, bigger planes are equipped with enough engines to remain intact, and able to proceed without a problem.
With all these specialists not agreeing on whether flight is safe, my personal feeling is, that it's probably not entirely safe yet, and I would postpone any flight, if I had to travel now.
http://www.channel4.com/news/articles/uk/ash+flight+ban+to+remain+over+most...
http://www.etaiwannews.com/etn/news_content.php?id=1232532&lang=eng_new...
http://www.iii.co.uk/news/?type=afxnews&articleid=7848251&subject=m...
http://www1.voanews.com/english/news/europe/Limited-Flights-Resume-Across-E...
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M$
Thanks for the info
Quoting from the question does not provide an answer. Quantify the increase in engine wear and tear as a function of how dense the ash cloud a plane flies through and how long it is in the cloud. Quantify the impact on needed maintenance schedule changes. Quantify the increase in risk of e.g. engine failure if regular maintenance is followed, but not increased maintenance.
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M$
Would airlines not lose a lot more money if their planes started falling out of the sky, their customers staying away in fear, and the relatives of their dead passenger joining in calss-action lawsuits against them? This even assuming we accept the apparent premise of your answer that in business the financial aspect trumps everything else.
And, of course, finances should always come before safety.
I'm not sure I agree with your assertion that the engines are unlikely to fail at about the same time. According to Time (see http://www.time.com/time/health/article/0,8599,1982328,00.html ):
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in 1982, a British Airways flight from Kuala Lumpur to Perth, Australia, passed through an ash cloud that had just erupted out of a volcano in Indonesia. One by one, each of the engines on the jumbo jet shut down, and the plane began to dive toward the ground. Disaster was averted only when the pilot managed to glide below the ash cloud, clearing the engines; the flight was able to make an emergency landing in Jakarta.
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I'm actually more concerned about the potential for hidden accelerated wear and tear that the regular maintenance schedule would be insufficient to repair than I am of all the engines failing in mid-air on a flight through the ash. The pitot tubes for example could lead to an Air-France-like disaster.
Even at "lower speeds" with engines running cooler, wouldn't you expect temperatures high enough to melt glass? Would you expect increased abrasion of turbine blades, blockage of nozzles, etc.?
Even with multiple engines, since all the engines would be equally affected by the ash, wouldn't 4 engines quit at roughly the same time if any of them quit?
Well, I'm not an expert, but according to that pilot, the biggest problem is that the ash heats up, and becomes a glass deposit on the engine, thereby blocking the engine. At lower speeds, the engine doesn't get hot enough to turn the ash into glass, so that particular problem won't arise.
Also, according to him, the density of the ash was not high enough to cause blockage or severe 'streaking' damage to the wings and engines, as long as they avoided the thickest parts of the ash cloud.
Again, I'm not the expert here, this is what I understood from the man.
As for the four engines quit at the same time: No, that won't happen. Basic statistics and chaos theory leads to the conclusion that one engine would fail considerably earlier than the others, and the same applies to the third, etc.
Faillure is based on many factors, and the ash/glass is only one of them. You can compare this with fixing four newly bought light bulbs, and switching them on continuously. Not all four will fail at the same time, there will be a considerable amount of time in between failures. The same applies to engines of a plane, even with the added stress of the ash cloud.
I hope I explained it clearly enough, it's quite clear in my mind, but somewhat difficult to put in text.
I think you're right. In this (Dutch) news report, it is stated that an airplane of American airliner World Airways flying from Maastricht to Oostende-Brugge (less than half an hour flying), has ash deposit on the wings.
Guess it is indeed not yet safe to fly.
Good find! I'm not sure these events would be similar to planes flying into the ash clouds over Europe, as the story on TIME, nor the Wikipedia page about the incident, describe at what distance from the vulcano they flew into the plume. If they flew right into it, around the vulcano, the density of ash would be much higher than the planes would face right now.
Then again, maybe the same would indeed happen, and all engines would indeed fail.