MidEx216
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Fuel Dump - Environmentally Hazardous?

Wed Aug 05, 2009 6:09 am

Hi again

This past weekend, my girlfriend and I were at OSH, walking around the A380. At one point, I pointed out the black nozzle and the back of the wing, and told her about dumping fuel to land, etc... When I said that she looked at me skeptically saying it couldn't be very good for the environment. I did kinda blow it off, saying it evaporates easily, but I can't help but wonder really how insignificant it is. I mean, an airliner holds a lot of fuel. Sure, it would be much worse of the plane went down, but how much exactly are we dumping, and how much of an affect does it really have?

Thanks for your input,
Paul
 
Mir
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RE: Fuel Dump - Environmentally Hazardous?

Wed Aug 05, 2009 10:00 am

I don't know if I'd call it environmentally hazardous in the same way that an oil tanker spill (even a minor one) would be, but yes, it's not something you want to have happen if you can avoid it at all. And if you do have to dump fuel, then you want to do it high enough so that it has time to evaporate before it reaches the ground.

Of course, in a dire emergency, you do what you've got to do.

Quoting MidEx216 (Thread starter):
how much exactly are we dumping

A 747-400's MTOW is 875,000lbs. The MLW is 630,000lbs. So you'd have to get rid of 245,000 lbs of fuel (close to the weight of a 757 - that's quite something to think about), or 35,000 gallons at 7lbs per gallon (the weight of jet fuel changes with temperature). So it's no trifling amount. That's if the airplane is full, of course, if it isn't, then you won't have to dump as much to get to the 630,000.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
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Faro
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RE: Fuel Dump - Environmentally Hazardous?

Wed Aug 05, 2009 10:16 am

Definitely environmentally hazardous, yes. But then there's no choice; save your plane or take the risk of a heavy, fuel-laden overweight landing with all the post-landing structural checks. Question of priorities: endangered human lives are worth more than the immediate environment.

Faro
The chalice not my son
 
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afterburner
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RE: Fuel Dump - Environmentally Hazardous?

Wed Aug 05, 2009 2:32 pm

Quoting Mir (Reply 1):
the weight of jet fuel changes with temperature

According to my basic physics knowledge, if gravity stays the same, temperature change won't result in weight change. However, the volume tends to change.
I think what you wanted to say was the density of jet fuel changes with temperature.

[Edited 2009-08-05 07:36:36]
 
CanadianNorth
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RE: Fuel Dump - Environmentally Hazardous?

Wed Aug 05, 2009 6:48 pm



Quoting Afterburner (Reply 3):
the density of jet fuel changes with temperature.

I see what your saying, and it makes sense. However, for example, if the fuel got more dense, would that not mean a litre of said fuel would be heavier than when it was at the less dense temperature?



CanadianNorth
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zanl188
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RE: Fuel Dump - Environmentally Hazardous?

Wed Aug 05, 2009 6:52 pm



Quoting MidEx216 (Thread starter):
At one point, I pointed out the black nozzle and the back of the wing, and told her about dumping fuel to land, etc... When I said that she looked at me skeptically saying it couldn't be very good for the environment.

What difference does it make if you burn the fuel or dump it? Either way it ends up back in the environment.....
Legal considerations provided by: Dewey, Cheatum, and Howe
 
dragon6172
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RE: Fuel Dump - Environmentally Hazardous?

Wed Aug 05, 2009 7:37 pm

Just tell her it is less harmful (arguably?) than the plane crashing, all of the fuel burning, much of the structure, seats, interior plastics, composites, etc burning.

Quoting CanadianNorth (Reply 4):
I see what your saying, and it makes sense. However, for example, if the fuel got more dense, would that not mean a litre of said fuel would be heavier than when it was at the less dense temperature?

The volume is what is dependent on temperature. Density is mass/volume, so a change in volume means a change in density, but not a change in mass. So in your example you have a liter of fuel at a certain temperature and measure its mass, then you change the temperature to check again. But by changing the temperature you have changed the volume, so in order to check a liter of fuel at the new temperature you will have to either add or subtract fuel from your bucket. Adding or subtracting changes the amount (mass) of a substance you have. That is why the mass would be different at two temps with the same volume of fuel.

Not sure if that makes sense.... but that is my attempt.
Phrogs Phorever
 
Mir
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RE: Fuel Dump - Environmentally Hazardous?

Wed Aug 05, 2009 9:16 pm



Quoting ZANL188 (Reply 5):
What difference does it make if you burn the fuel or dump it? Either way it ends up back in the environment.....

True, but it's a matter of concentration. If you burn off 100,000lbs of fuel, you'll do so while flying a significant distance, so it's spread out over a wider area than if you dump it all at once (you dump quite a bit faster than you burn).

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
rwessel
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RE: Fuel Dump - Environmentally Hazardous?

Wed Aug 05, 2009 11:00 pm



Quoting ZANL188 (Reply 5):
What difference does it make if you burn the fuel or dump it? Either way it ends up back in the environment.....

If you burn it, it turns into (mostly*) water vapor and carbon dioxide, both of which are harmless**. If you dump it, you're dumping a bunch of medium chain hydrocarbons into the environment, all of which are toxic.


*Jet engines also emit quantities of volatile organics (mostly unburned hydrocarbons), nitrous oxides, carbon monoxide, sulfur dioxide and particulates, but the total quantities are small.

**Greenhouse effects or excessive concentrations of either excepted, of course.
 
jetplaner
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RE: Fuel Dump - Environmentally Hazardous?

Thu Aug 06, 2009 3:46 am

In my opinion, human lives greatly outweigh the environmental impact of dumping fuel. Maybe someone here also knows how often planes actually do dump fuel. I wouldn't imagine it would be all that often.

-Jetplaner
 
pwm2txlhopper
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RE: Fuel Dump - Environmentally Hazardous?

Thu Aug 06, 2009 5:36 am

I'd say at altitude, going hundreds of knots, the fuel would spread out and evaporate so much that anything that actually reached the ground would be in such trace amounts that it would be harmless?

One example to help picture this... Go dump a gallon of water off a 20 story building. One might imagine that someone standing below would get wet... But if you observe the fluid as it falls, it just spreads out and by the time it hits the ground, it's almost like it's a thin spray. Add several dozen thousands of feet to that, a few hundred knots, and winds aloft, and there's not going to be any significant concentration in one spot!

If somebody's going to be concerned about trace amounts of Jet-A scatted over God knows how many miles, and it's cumulative effects on the environment, then I'd say who cares? They're probably just tree huggers! The same nuts that freak out about their "carbon footprint" from their plane trips!
 
rwessel
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RE: Fuel Dump - Environmentally Hazardous?

Thu Aug 06, 2009 6:08 am



Quoting Jetplaner (Reply 9):
In my opinion, human lives greatly outweigh the environmental impact of dumping fuel. Maybe someone here also knows how often planes actually do dump fuel. I wouldn't imagine it would be all that often.

I came across this a while ago:

Citizen's Aviation Watch asked the (US) EPA that a few years again, and in the response letter, the EPA stated that the FAA reported that "fuel dumping occurs only about 127 times per year." I assume that's in the US, although the letter doesn't specify.

http://www.us-caw.org/pdf/Fueldump.pdf
 
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HAWK21M
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RE: Fuel Dump - Environmentally Hazardous?

Thu Aug 06, 2009 8:02 am

I guess its a choice between the better of the worst option.
Fuel dumping will def have its effects on the environment over a long duration of dumping.
But in an emergency where people have to be saved,it is called for.
regds
MEL.
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tdscanuck
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RE: Fuel Dump - Environmentally Hazardous?

Mon Aug 10, 2009 5:57 am



Quoting Jetplaner (Reply 9):
Maybe someone here also knows how often planes actually do dump fuel.

At 127 times per year, the hydrocarbon concentration due to fuel dumping from all airlines everywhere is going to be lower than the unburned hydrocarbon emissions of the world's car fleet in a few hours (probably less than that).

So it's "bad" in the sense that you'd rather not do it but, compared to the other sources of atmospheric hydrocarbons, airplane fuel dumping is basically invisible.

Tom.
 
prebennorholm
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RE: Fuel Dump - Environmentally Hazardous?

Mon Aug 10, 2009 9:54 pm

The polution from fuel dumps is totally negligible compared to what drying paint is emitting to the atmosphere. Or what gas vapors are emitted when we fill the car.

But it's all nothing to worry about. At least not as long as we accept the solid rocket boosters on the Shuttle.

And don't even try to compare all the world's fuel dumps to a healthy forest fire or a volcanic eruption, things which this planet has been suffering for billions of years before homo sapiens stepped on it for the first time.

Quoting Rwessel (Reply 8):
If you dump it, you're dumping a bunch of medium chain hydrocarbons into the environment, all of which are toxic.

"Toxic" is a big word here. Anyway I don't recommend that you drink a lot of kerosene, neither that you spend a long time breathing dense kerosene vapors. Same goes with salt. If we eat a pound of salt, we will be in trouble, but if we get no salt at all we will soon be in equally great trouble.

Airliner fueling people, who accidentally have taken a kerosene shower, will be suffering from a bad smell for some time, but that's all. Kerosene cannot be considered a poison.

I wonder what the figures would be if we made a scientific comparison between atmospheric polution caused by airliner fuel dumps and general use of perfumes on this planet. One difference will be that not all perfumes smell as bad as kerosene.

Most prominent difference will probably be that fuel dumps are mostly done outdoor where even smoking is allowed.
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HaveBlue
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RE: Fuel Dump - Environmentally Hazardous?

Tue Aug 11, 2009 12:46 am



Quoting Jetplaner (Reply 9):
Maybe someone here also knows how often planes actually do dump fuel. I wouldn't imagine it would be all that often.

I don't know the answer to that, but my roommate had to dump fuel from an almost completely full 747-200 shortly after take off... twice in the same day! It was over South Korea and I discussed it in the "A Day in the Life of a Pilot" thread also in Tech/Ops. #2 engine failed probably around 16 minutes or so into the flight and the fuel was dumped to get down the the MLW.

Quoting Mir (Reply 1):
A 747-400's MTOW is 875,000lbs. The MLW is 630,000lbs. So you'd have to get rid of 245,000 lbs of fuel (close to the weight of a 757 - that's quite something to think about), or 35,000 gallons at 7lbs per gallon (the weight of jet fuel changes with temperature). So it's no trifling amount. That's if the airplane is full, of course, if it isn't, then you won't have to dump as much to get to the 630,000.

Exactly!
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Mir
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RE: Fuel Dump - Environmentally Hazardous?

Tue Aug 11, 2009 1:13 am



Quoting Prebennorholm (Reply 14):
One difference will be that not all perfumes smell as bad as kerosene.

And not all smell as good.  Smile

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
rwessel
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RE: Fuel Dump - Environmentally Hazardous?

Tue Aug 11, 2009 3:11 am



Quoting Prebennorholm (Reply 14):
I wonder what the figures would be if we made a scientific comparison between atmospheric polution caused by airliner fuel dumps and general use of perfumes on this planet.

Hmmm... Fragrance appears to be about a $10B/yr industry. Assuming $25/oz, that's about 3.1 million gallons. Spread over 127 fuel dumps per year, that would be around 25,000 gallons, which is likely a bit higher than the actual average fuel dump - probably by a factor of three or so.

Hey - you asked!  duck 
 
prebennorholm
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RE: Fuel Dump - Environmentally Hazardous?

Wed Aug 12, 2009 7:42 pm



Quoting Rwessel (Reply 17):
Hmmm... Fragrance appears to be about a $10B/yr industry. Assuming $25/oz, that's about 3.1 million gallons. Spread over 127 fuel dumps per year, that would be around 25,000 gallons, which is likely a bit higher than the actual average fuel dump - probably by a factor of three or so.

Tnx for the calculations, Rwessel! Interesting.

Now I have absolutely no knowledge about Fragrance, saw that brand name first time one munite ago. Google tells me that it is a very American thing. And I have no idea about their market share.

Now Americans always seem to have a problem realizing that "the rest of the world" really exists outside CNN pictures  duck  even if 300 million Americans are merely 5%.

Anyway perfume consumption may not be equally spread around the globe. While NYC mostly has a smell of half burned hydrocarbons, then Paris smells in a somewhat more "expensive" way.

Quoting MidEx216 (Thread starter):
This past weekend, my girlfriend and I were at OSH, walking around the A380. At one point, I pointed out the black nozzle and the back of the wing, and told her about dumping fuel to land, etc... When I said that she looked at me skeptically saying it couldn't be very good for the environment.

At the end of the day I think it is fair to say that our highly unscientific calculations prove that atmospheric polution from perfumes is worse than all the world's airliner fuel dumps by a double digit factor.

Dear MidEx216, tell that to your gf - it may save you a fortune over the next fifty years.  Wink
Always keep your number of landings equal to your number of take-offs
 
rwessel
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RE: Fuel Dump - Environmentally Hazardous?

Wed Aug 12, 2009 10:09 pm



Quoting Prebennorholm (Reply 18):
Now I have absolutely no knowledge about Fragrance, saw that brand name first time one munite ago. Google tells me that it is a very American thing. And I have no idea about their market share.

Actually, "Fragrance" is the proper name for the entire perfume industry. I had no idea it was also a brand. And the $10B/yr appears to be the global number. In general I know nothing about any of that, except which box to buy for Christmas!  Wink
 
prebennorholm
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RE: Fuel Dump - Environmentally Hazardous?

Wed Aug 12, 2009 11:01 pm



Quoting Rwessel (Reply 19):
Actually, "Fragrance" is the proper name for the entire perfume industry.

Thanks again! I learned a new word of the English language today, one which isn't included in my 631 pages English - Danish dictionary.

But you are right, "fragrance" is included among 450,000 other words in the 2662 pages of my 9lb 9.4oz Webster's with so small letters that I had to find extra strong reading glasses.

So perfumes "only" polute three times more than airliner fuel dumps.
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