Saving Ash from a Volcanic Eruption: A Geologist's Perspective

[Matterwave]

Why can't planes fly lower ?

(years ago, a plane flew through an ash cloud, all its engines stopped, it plummeted thousands of feet, and the engines restarted when it reached clear air again)

From my very limited knowledge of planes, I think the air-altitudes are all split up for different purposes. The commercial flights have a specific range of altitudes they fly at, it may not be easy to allow them to fly at different altitudes.

Furthermore, there could be sound pollution from airplanes flying too low...or other safety hazards...

I'm not sure myself haha.

 

[Borek]

Other things ignored - low flight means high fuel consumption, shorter range and higher costs.

 

[Andre]

Optimum flight level is the tropopause. The jets I flew would use typically 2500 lbs/per hour at the tropopause versus maybe 6-7000 lbs/hr at low level to maintain 480 knots true airspeed.

Best cruising speed is a complex function of air density and air temperature. An important parameter for the engines is combination of temperature and the mach number which are directly related and making it perform best at lowest temperature. This is at the tropopause and above, which is typically at some 33,000 feet, however with big variations.

Going higher means less dense air at rougly the same temperature, however the reduction in drag is offset by reduced engine performance due to the lack of oxygen.

So the ash is below the best altitude for cruise flight, however I have no idea about the effects of low concentration ash during climb or descent in those layers.

 

[tomkeus]

I'm watching this entire situation and I'm amazed at incompetence bureaucrats across Europe demonstrated handling this situation.

Apparently, flight bans all over Europe were issued based on computer simulations run by UK Met Office. Although I understand that, because it is better to be safe than sorry I cannot understand why hasn't anyone in Europe took actual measurements or test flights after that. It took initiative of KLM and Lufthansa to get actual planes in the air for people to start talking that ban should be partially lifted based on real and not computer generated data.

Lack of action of flight regulating bodies and meteorological organizations to deploy balloons or flying labs or other measurements across Europe may prove to have cost Europe billions of euros.

Now, office eggheads probably realized that they've dropped the ball handling post-ban situation so they will probably stick with the total ban for some time yet in order to save their public face.

 

[cristo]

Apparently, flight bans all over Europe were issued based on computer simulations run by UK Met Office. Although I understand that, because it is better to be safe than sorry I cannot understand why hasn't anyone in Europe took actual measurements or test flights after that.

Err.. firstly the simulations were not just done by the Met Office in the UK; simulations have been done by many other European equivalents. In fact, once professor whom I saw interviewed yesterday say that there was a remarkable level of agreement between the different simulations. Secondly, planes have been up there collecting data, and test flights continue to be done. However, it makes sense that such flights are done by suitable aircraft to try and gauge the situation, and not by just seeing whether a commercial airliner can fly through the ash.

It took initiative of KLM and Lufthansa to get actual planes in the air for people to start talking that ban should be partially lifted based on real and not computer generated data.

The problem here is that off the back of these flights one can only show that a plane can fly through the ash. However, the KLM test flight was once flight for around one hour. This is not really good enough to say that the European airspace should be opened and service resumed as normal. Aircraft make many journeys in a day, and so will be flying through this ash over and over again, which will presumably bear a toll on the engines. Then there's the issue of how often should the engines be checked: after every flight like with the test flights, or at the end of every day?

Alternatively, you could just stick two fingers up like the Russians and Ukrainians but, well, that's not really too sensible, is it?

 

[sophiecentaur]

Other things ignored - low flight means high fuel consumption, shorter range and higher costs.

That doesn't seem too much of a hardship compared with the Total Loss at the moment. Plenty of people would be prepared to pay a 'low altitude surcharge' in order to get home on time.
It would mean that priority transport could still get through. If long haul were not possible at low altitude, the majority of long haul flights could still be made a full altitude.

It would need the Air Lanes to be temporarily re-planned in the affected area as well but that problem would not be as great if the total number of flights were a lot less during an emergency.
I wonder if this event has prompted anyone to think of devising an emergency low-altitude plan for the eventuality of this happening again - somewhere in the World.

 

[Frame Dragger]

That doesn't seem too much of a hardship compared with the Total Loss at the moment. Plenty of people would be prepared to pay a 'low altitude surcharge' in order to get home on time.
It would mean that priority transport could still get through. If long haul were not possible at low altitude, the majority of long haul flights could still be made a full altitude.

It would need the Air Lanes to be temporarily re-planned in the affected area as well but that problem would not be as great if the total number of flights were a lot less during an emergency.
I wonder if this event has prompted anyone to think of devising an emergency low-altitude plan for the eventuality of this happening again - somewhere in the World.

Did you not read Andre's post? We're not talking about a little boost in fuel, we're talking about a HUGE increase, and a subsequent DECREASE in range. It's cheaper and easier to fly around an ash cloud than below it, not to mention that ANY crash at this point would be instantly blamed on negligence by the airlines.

The difference in fuel is the difference between a profit, and a loss. When you add the HUGE decrease in range, there is no way for it to be feasible. Keep in mind also that people don't want jets roaring overhead at 10-12,000 feet, nor would any government's military allow that.

This has happened, it will happen again, and there is no contingency other than boats. That's real life.

 

[Borek]

I wonder if this event has prompted anyone to think of devising an emergency low-altitude plan for the eventuality of this happening again - somewhere in the World.

1821 eruption of Eyjafjallajökull lasted over half a year.

 

[sophiecentaur]

Did you not read Andre's post? We're not talking about a little boost in fuel, we're talking about a HUGE increase, and a subsequent DECREASE in range. It's cheaper and easier to fly around an ash cloud than below it, not to mention that ANY crash at this point would be instantly blamed on negligence by the airlines.

The difference in fuel is the difference between a profit, and a loss. When you add the HUGE decrease in range, there is no way for it to be feasible. Keep in mind also that people don't want jets roaring overhead at 10-12,000 feet, nor would any government's military allow that.

This has happened, it will happen again, and there is no contingency other than boats. That's real life.

Interesting. I have taken in all you have written. I'm not sure the military would have a say in the matter if the GBP insisted. . . . (LOL).
I searched and scanned through the thread but could find no actual figures and it is the actual number that count in a problem like this. Which number is the post, so I can look at it?

 

[Frame Dragger]

Interesting. I have taken in all you have written. I'm not sure the military would have a say in the matter if the GBP insisted. . . . (LOL).
I searched and scanned through the thread but could find no actual figures and it is the actual number that count in a problem like this. Which number is the post, so I can look at it?

Never underestimate the efficacy of SAMs...

Optimum flight level is thetropopause. The jets I flew would use typically 2500 lbs/per hour at the tropopause versus maybe 6-7000 lbs/hr at low level to maintain 480 knots true airspeed.

Best cruising speed is a complex function of air density and air temperature. An important parameter for the engines is combination of temperature and the mach number which are directly related and making it perform best at lowest temperature. This is at the tropopause and above, which is typically at some 33,000 feet, however with big variations.

Going higher means less dense air at rougly the same temperature, however the reduction in drag is offset by reduced engine performance due to the lack of oxygen.

So the ash is below the best altitude for cruise flight, however I have no idea about the effects of low concentration ash during climb or descent in those layers.

EDIT: For the record, the effect of ascent and descent to form a measure of glass on the engines, and while it may or may not be fatal or damaging (it usually takes quite some time for engines to fail from volcanic ash, and you can get out if it if you're lucky) it would certainly be terrible for the engines in the long run, and any crash would be hailed as grossly negligent. Outrage over a plane crash due to a desire to travel... I can see the news stories, lawsuits, and criminal case now.

 

[ViewsofMars]

I'm adding on to my previous message which I think was extremely important!

I also want to share a wonderful website to explore by John Seach. He has a very impressive bio. I wouldn’t mind going on a trek with him.
http://www.volcanolive.com/john.html

On his website today, Sunday 18th April 2010:

Eyjafjallajokull volcano, Iceland
Ash emissions are continuing from Eyjafjallajokull volcano in Iceland. Winds are blowing the ash over Europe, causing flights to remain grounded. All flights to and from Britain have been canceled until at least 7pm today. Ashfall has been reported in Britain. Five million travelers are stranded, waiting for flights to resume. Some may be waiting for more than a week to find available seats. If flight disruptions continue into this week there will be a shortage of some food products in Britain, which normally come in by air from east Asia and Africa. The grounding of flights has already cost the British economy about £1 billion, with £230m losses for every day of further disruption. The initial eruption of Eyjafjallajokull volcano last month was basalt, while the new eruption under the glacier last week involved andesite.
http://www.volcanolive.com/news.html

An article on BBC from today which brings added concern:

Ash cloud puts lives of bone marrow patients at risk
The ban on air travel in much of Europe is putting the lives of people waiting for bone marrow transplants at risk.
[Read on . . .]
http://news.bbc.co.uk/2/hi/uk_news/8628078.stm

More links :
http://www.nytimes.com/2010/04/18/world/europe/18ash.html
http://news.bbc.co.uk/2/hi/europe/8627720.stm
http://news.bbc.co.uk/2/hi/uk_news/politics/8628253.stm
http://news.bbc.co.uk/2/hi/europe/8627720.stm

They seem to be comparing this event worse than 911 as far as closing
down air space.

 

[Frame Dragger]

I'm adding on to my previous message which I think was extremely important!

I also want to share a wonderful website to explore by John Seach. He has a very impressive bio. I wouldn’t mind going on a trek with him.
http://www.volcanolive.com/john.html

On his website today, Sunday 18th April 2010:



An article on BBC from today which brings added concern:



More links :
http://www.nytimes.com/2010/04/18/world/europe/18ash.html
http://news.bbc.co.uk/2/hi/europe/8627720.stm
http://news.bbc.co.uk/2/hi/uk_news/politics/8628253.stm
http://news.bbc.co.uk/2/hi/europe/8627720.stm

They seem to be comparing this event worse than 911 as far as closing
down air space.

Oh yeah, nature always wins in those situations. Frankly, this is pretty impressive and clearly medical services have a lot of work to do. Perhaps ground-effect (on water) airplanes can be a viable solution for these kinds of emergencies, but not for mass transit.

 

[sophiecentaur]

@Framedragger

I read that post but the info is very sparse and doesn't really prove anything about low altitude, low speed flight economics. Clearly it's not what modern jets were designed for and their economics are on a bit of a knife edge.
Andre may well know what he's talking about but we normally expect more info or a reference rather than just accepting an 'assurance'.

I can't help thinking that planes stack for an hour or more around Heathrow and Gatwick and that is all accounted for in the flight plan. Is that so very different from a slow trip to Paris or Brussels?
It would be nice to see just how 'unthinkable' it is. The present situation is far from 'thinkable' too.
Is there a knowledgeable Engineer on the forum who can give information (without hyperbole) about this? I'd love to know the real situation.
After all, we wouldn't rely on what the Press have to say about anything else in our lives.

 

[ViewsofMars]

"

After all, we wouldn't rely on what the Press have to say about anything else in our lives.

"

Well sophiecentaur, I'm not Framedagger, but your comment is merely *your* opinion. Many press releases are made by scientists. And, public officials do consult with scientists and engineers as well as with news reporters.

I surely wouldn't wish to dismiss the fact that it wasn't a fabricated story just so the press could impress the public with lies. If planes aren't being flown it's for a darn good reason. Please remember that public safety comes first.

 

[Andre]

About aircraft range and altitude. Maybe this http://selair.selkirk.ca/Training/Aerodynamics/range_jet.htm helps a bit, especially this sixth graph.

[PLAIN]http://selair.selkirk.ca/Training/Aerodynamics/graphics/altitude-jet1.gif

Notice that a fuel flow of 540 lbs/hr generates a max range speed of 200 knots true airspeed (KTAS) at sea level and 440 KTAS at 45,000 feet. Notice also that the sea level curve is much steeper, so flying faster than best range is at a greater penalty than at high altitude.

Also I expect this graph to be based on air density only since -as said- the temperature and related mach number play a big role for engine performance/efficiency and these are not linear in that altutide range due to the tropopause.

The exact numbers are not very relevant but it gives an impression of the rate of changes in range versus altitude.

 

[Frame Dragger]

Thanks Andre, ViewsofMars... I didn't realize that this wasn't very common knowledge re: prop vs. jet engines. *shrug*

 

[ViewsofMars]

"

So the ash is below the best altitude for cruise flight, however I have no idea about the effects of low concentration ash during climb or descent in those layers.

"

Andre, you aren't a pilot are you? A simple yes or no will do. Honestly, I've known a few pilots. They wouldn't risk their life or passengers if there was risk. Have you read any articles where airline pilots are protesting the closure of air space in Europe? I haven't.

"

Thanks Andre, ViewsofMars... I didn't realize that this wasn't very common knowledge re: prop vs. jet engines. *shrug*

"

*Shrug* all you want FrameDragger! I said airline pilots!

 

[Andre]

""

Andre, you aren't a pilot are you? A simple yes or no will do. Honestly, I've known a few pilots. They wouldn't risk their life or passengers if there was risk. Have you read any articles where airline pilots are protesting the closure of air space in Europe? I haven't.

I used to be pilot but it's not a simple yes-no at all.

Obviously there is a lowest concentration at which harm is negliglible and concentrations at which major damage is inevitable. For instance, how many times have aircraft landed in dusty hazy conditions near big cities and that is clearly visible?

So it's rather impossible to say something useful here, but just suppose for arguing that the actual concentration is only 5% or 10% or 30% of the damage threshold in the regions where it counts, why the fuss then?

It's just that these things have probably never been tested because it used to be a non factor in the past, so probably nobody has a clue what the best decision is.

 

[Frame Dragger]

""

Andre, you aren't a pilot are you? A simple yes or no will do. Honestly, I've known a few pilots. They wouldn't risk their life or passengers if there was risk. Have you read any articles where airline pilots are protesting the closure of air space in Europe? I haven't.

I can't speak for Andre, but I'm no pilot, yet I know that volcanic ash is TRICKY. I've been trying to find a citation online, but I recall a NatGeo or Discovery program which described a plane that had flown into volcanic ash. The pilots had no CLUE what was happening, other than intermittant engine failure. They finally figured out that it was the ash vitrifying in the engines, but only once they landed. The pilots were simply bright and lucky enough to realize that they couldn't fly at their normal cruising altitude.

To be blunt, what information do you expect? It takes tiime for the glass to form, it's almost impossible to detect, and then BOOM, your engine can fail. Ascent and Descent are relatively brief compared to the time spend at altitude, and no one is willing to take that kind of risk. You don't crash test passenger jets in volcanic ash, and isolating the effect to a particular period of ascent or descent is pointless outside of a lab.

You don't fly air-breathing engines in ash, period.

@ViewsofMars: *shrug*
@Andre: Sorry if I stepped on your toes with this simul-post. I'll delete it if you prefer.

 

[lisab]

""

Andre, you aren't a pilot are you? A simple yes or no will do. Honestly, I've known a few pilots. They wouldn't risk their life or passengers if there was risk. Have you read any articles where airline pilots are protesting the closure of air space in Europe? I haven't.

""

*Shrug* all you want FrameDragger! I said airline pilots!

Haven't heard of protests, but the pilots who made http://www.cnn.com/2010/TRAVEL/04/18/volcano.ash.test.flights/index.html?hpt=T1" must not have felt they were in danger, otherwise they would not have flown. The test flights, btw, apparently showed no ill effects from the concentrations of ash through which they flew (which I presume were quite low).

I think it's a good bet that there is a concentration of ash which is safe to fly through; what that level is isn't known. Which raises the question: is there a way to measure concentration of airborne ash? Because before we can determine what level is safe to fly through, we need a way to measure it.

 

[ViewsofMars]

"

You don't fly air-breathing engines in ash, period.

@ViewsofMars: *shrug*

"

Duh, FrameDragger! You don't fly airplane(s) into air space that has volcanic ash. You can locate that information in several articles via link that I have provided on this page and the previous one.
---
"

Haven't heard of protests, but the pilots who made http://www.cnn.com/2010/TRAVEL/04/18/volcano.ash.test.flights/index.html?hpt=T1" must not have felt they were in danger, otherwise they would not have flown. The test flights, btw, apparently showed no ill effects from the concentrations of ash through which they flew (which I presume were quite low).

I think it's a good bet that there is a concentration of ash which is safe to fly through; what that level is isn't known. Which raises the question: is there a way to measure concentration of airborne ash? Because before we can determine what level is safe to fly through, we need a way to measure it.

"

Hi lisab. :) Since pilots are inside the plane, I doubt there would be volcanic ash in the air they breathe. Volcanic ash clogs up the engine of a plane. Perhaps a very short span of time in air space with ash might not cause a plane's engine to die. Of course, measuring what level is safe could result in the pilot's death. Of course, they would have to get an *ok* by the control center of an airport and present the route. Has that happened yet?

Quite frankly, I haven't located the instrument used for measuring in air space the amount of volcanic ash. Perhaps, we should go digging for that information. I'm sure it's out there in cyberspace.
---

"

@ViewsofMars: "Duh"? I don't know if you're angry or amused, but you're absolutely making me laugh in real life (with, not at). Maybe a bit of a softer touch would be helpful however? Everyone doesn't feel as rough-and-tumble online as I do.

"

FrameDragger, I'm a serious contender with a gentle manner. And I don't mind you
rolling on the floor laughing. Also, as you can see, I like to condense cyberspace and free it up for others. I personally think a person should enjoy particpating in discussions. I may not always agree with everything someone has to say, but I do appreciate knowing that people are having a wee bit of fun.

 

[Frame Dragger]

Haven't heard of protests, but the pilots who made http://www.cnn.com/2010/TRAVEL/04/18/volcano.ash.test.flights/index.html?hpt=T1" must not have felt they were in danger, otherwise they would not have flown. The test flights, btw, apparently showed no ill effects from the concentrations of ash through which they flew (which I presume were quite low).

I think it's a good bet that there is a concentration of ash which is safe to fly through; what that level is isn't known. Which raises the question: is there a way to measure concentration of airborne ash? Because before we can determine what level is safe to fly through, we need a way to measure it.

Sure, you could probably do these tests at JPL...I believe they had a setup to test the effect of static discharge caused by particulate matter.

The problem is: Volcanic ash is not homogenous, and just hasn't been well studied. It takes some time for glass to choke an engine, and frankly... who will take that risk with a full cabin? There is the issue I raised earlier as well, which is that there could be cumulative damage.

I would also add that pilots do things such as fly into Hurricanes, not because they feel they are in no danger, but for the same reasons they fly into Anti Aircraft Fire. They have to: it's a job they love, and there is no other way right now (that people are willing to pay for). I doubt those same pilots would do this with a 747 and a full crew-cabin.

Finally, what is a safe concentration? You could determine an average, and still run into a sticky patch, which probably means that you and all souls will be lost. Airplanes just don't have much of a fail-safe at high altitudes if the engines are glassed.

@ViewsofMars: "Duh"? I don't know if you're angry or amused, but you're absolutely making me laugh in real life (with, not at). Maybe a bit of a softer touch would be helpful however? Everyone doesn't feel as rough-and-tumble online as I do.

 

[Borek]

I recall a NatGeo or Discovery program which described a plane that had flown into volcanic ash. The pilots had no CLUE what was happening, other than intermittant engine failure. They finally figured out that it was the ash vitrifying in the engines, but only once they landed. The pilots were simply bright and lucky enough to realize that they couldn't fly at their normal cruising altitude.

http://en.wikipedia.org/wiki/British_Airways_Flight_9

 

[Frame Dragger]

http://en.wikipedia.org/wiki/British_Airways_Flight_9

Borek you wigged genius, THANK you!

 

[lisab]

Sure, you could probably do these tests at JPL...I believe they had a setup to test the effect of static discharge caused by particulate matter.

The problem is: Volcanic ash is not homogenous, and just hasn't been well studied. It takes some time for glass to choke an engine, and frankly... who will take that risk with a full cabin? There is the issue I raised earlier as well, which is that there could be cumulative damage.

I would also add that pilots do things such as fly into Hurricanes, not because they feel they are in no danger, but for the same reasons they fly into Anti Aircraft Fire. They have to: it's a job they love, and there is no other way right now (that people are willing to pay for). I doubt those same pilots would do this with a 747 and a full crew-cabin.

Finally, what is a safe concentration? You could determine an average, and still run into a sticky patch, which probably means that you and all souls will be lost. Airplanes just don't have much of a fail-safe at high altitudes if the engines are glassed.

@ViewsofMars: "Duh"? I don't know if you're angry or amused, but you're absolutely making me laugh in real life (with, not at). Maybe a bit of a softer touch would be helpful however? Everyone doesn't feel as rough-and-tumble online as I do.

Yes, good points. I would expect the ash concentration to vary some, but I wonder how much the ash itself varies? Are some types of ash more likely to glassify than others? I really don't know.

 

[Galteeth]

Is this eruption likely to have any short term effects on the climate?

 

[Frame Dragger]

Yes, good points. I would expect the ash concentration to vary some, but I wonder how much the ash itself varies? Are some types of ash more likely to glassify than others? I really don't know.

The answer is "yes". Some ash is organic or composed of non-silicates, but a LOT of it is very fine pumice, which vitrifies like *snaps fingers*. There is also glass ALREADY suspended in the ash, which rapidly melt and then fuse, forming nucelation sites for more growth.

This might be useful: http://volcanoes.usgs.gov/ash/properties.html

 

[Frame Dragger]

Is this eruption likely to have any short term effects on the climate?

The ash is unlikely to have much of an effect, but if this volcano released a lot of SOx, then it could have an effect for 2 or 3 years.

 

[tomkeus]

http://en.wikipedia.org/wiki/British_Airways_Flight_9

I'm really getting tired of people quoting BA Flight 9. It went into ash plume 150km downwind of the volcano. I don't see that this case is any argument to close down airspace 2000 or 3000km away from the Iceland.

Even after that, Indonesian authorities have closed down just the area adjacent to the volcano. They didn't proceed and shut down entire South East Asia.

I mean, we had large eruptions, even larger recently but not one caused shutdown on such large scale as in Europe. This is plain and simple irrational paranoia.

For example, engine flameouts did occur while flying through heavy rains. Does this mean we have to ground all air traffic if we have some rain sipping somewhere?

 

[ViewsofMars]

"

The problem is: Volcanic ash is not homogenous, and just hasn't been well studied. It takes some time for glass to choke an engine, and frankly... who will take that risk with a full cabin? There is the issue I raised earlier as well, which is that there could be cumulative damage.

"

Frame Dragger, do you have a link (url) to substantiate your claim?

"

I would also add that pilots do things such as fly into Hurricanes, not because they feel they are in no danger, but for the same reasons they fly into Anti Aircraft Fire. They have to: it's a job they love, and there is no other way right now (that people are willing to pay for). I doubt those same pilots would do this with a 747 and a full crew-cabin.

"

Frame Dragger, do you have a link (url) to substantiate your claim?

"

Finally, what is a safe concentration? You could determine an average, and still run into a sticky patch, which probably means that you and all souls will be lost. Airplanes just don't have much of a fail-safe at high altitudes if the engines are glassed.

"

Frame Dragger, do you have a link (url) to substantiate your claim?

FrameDragger, I'm strickly asking for references for my own on-line library collection. (Please note that I have on the last two previous pages to this topic provided links (url's).) Thanks in advance for your help FrameDragger.

 

[Frame Dragger]

""

Frame Dragger, do you have a link (url) to substantiate your claim?

""

Frame Dragger, do you have a link (url) to substantiate your claim?

""

Frame Dragger, do you have a link (url) to substantiate your claim?

FrameDragger, I'm strickly asking for references for my own on-line library collection. (Please note that I have on the last two previous pages to this topic provided links (url's).) Thanks in advance for your help FrameDragger.

Please don't take this the wrong way, but this is something you can do with google and search terms such as "hurricane flight plane" or "composition volcanic ash". From there, you whittle down the info to something more specific, such as: "Volcanic ash troposphere remain" or "concentrations". Here is a simple search: "Composition volcanic ash"... and look at what it yields: http://www.google.com/search?hl=en&rlz=1T4DKUS_enUS306US306&q=composition+volcanic+ash&aq=f&aqi=g-m1&aql=&oq=&gs_rfai=

When it comes to something like QM or Relativity, I can understand wanting citations, but in this case it's probably good to do independant research, if for no better reason than having that skill at hand.

@tomkeus: Good luck selling that to your insurance company and investors if you own an airline.

 

[mheslep]

About aircraft range and altitude. Maybe this http://selair.selkirk.ca/Training/Aerodynamics/range_jet.htm helps a bit, especially this sixth graph.

Notice that a fuel flow of 540 lbs/hr generates a max range speed of 200 knots true airspeed (KTAS) at sea level and 440 KTAS at 45,000 feet. Notice also that the sea level curve is much steeper, so flying faster than best range is at a greater penalty than at high altitude.

Also I expect this graph to be based on air density only since -as said- the temperature and related mach number play a big role for engine performance/efficiency and these are not linear in that altutide range due to the tropopause.

The exact numbers are not very relevant but it gives an impression of the rate of changes in range versus altitude.

I was generally aware of these penalties, and they suggest to me a reason for temporarily raising the ticket prices to pay for more fuel and for reducing the number of flights. It doesn't explain to me, by itself, why the airspace should be completely shut down.

 

[ViewsofMars]

Please don't take this the wrong way, but this is something you can do with google and search terms such as "hurricane flight plane" or "composition volcanic ash". From there, you whittle down the info to something more specific, such as: "Volcanic ash troposphere remain" or "concentrations". Here is a simple search: "Composition volcanic ash"... and look at what it yields: http://www.google.com/search?hl=en&rlz=1T4DKUS_enUS306US306&q=composition+volcanic+ash&aq=f&aqi=g-m1&aql=&oq=&gs_rfai=

Why would I use Google? I am a science researcher. I go to either peer-reviewed articles or use U.S. Government-Science website for scientific information, or a scientist's website, etc. By the way, I already had reviewed http://volcanoes.usgs.gov/ash/properties.html
I was basically asking you for a website to confirm your comments. Please don't through it back on me. Why? Because it is insulting. I'm especially still waiting on your comment, "Finally, what is a safe concentration? You could determine an average, and still run into a sticky patch, which probably means that you and all souls will be lost. Airplanes just don't have much of a fail-safe at high altitudes if the engines are glassed." That isn't a scientific statement.

 

[tomkeus]

@tomkeus: Good luck selling that to your insurance company and investors if you own an airline.

You don't have to sell anything. Just wait for a few more days for losses to accumulate and they will be begging you get those planes airborne.

 

[sophiecentaur]

About aircraft range and altitude. Maybe this http://selair.selkirk.ca/Training/Aerodynamics/range_jet.htm helps a bit, especially this sixth graph.

[PLAIN]http://selair.selkirk.ca/Training/Aerodynamics/graphics/altitude-jet1.gif

Notice that a fuel flow of 540 lbs/hr generates a max range speed of 200 knots true airspeed (KTAS) at sea level and 440 KTAS at 45,000 feet. Notice also that the sea level curve is much steeper, so flying faster than best range is at a greater penalty than at high altitude.

Also I expect this graph to be based on air density only since -as said- the temperature and related mach number play a big role for engine performance/efficiency and these are not linear in that altutide range due to the tropopause.

The exact numbers are not very relevant but it gives an impression of the rate of changes in range versus altitude.

Thanks for the info on those graphs Andre. Looking at the minima on those two red curves it seems to me that the 'fuel consumption' (mpg, in motorcar terms, ignoring winds) at 45k is about twice that at sea level. (i.e. same fuel flow at just over twice the air speed) Presumably it wouldn't be quite so bad at 10k as at ground level. That would imply that the cost of flying low would only be about twice that of flying at normal altitudes. Sounds a lot more attractive than spending hundreds of pounds on hire cars, extended stays in hotels and missed business deals.

So why aren't they considering at least some flights (high priority, perhaps) at lower, safe, altitudes? Is it just an admin (ATC) problem?

I feel that this thread should be split into two - one to deal with the safety issue and the other to discuss possible (non-hazardous) solutions.