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  #1  
Old 11-06-2010, 02:56 AM
Chickenwrangler Chickenwrangler is offline
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What happens to the fuel dumped by aircraft?

When a plane has to dump fuel does it vaporize into nothing or actually reach the ground?

If it does reach the ground what kind of mess would it make and could it ignite, and if dumped over open water would it create a floating film of fuel?

That Airbus A380 out of Singapore dumped a lot of fuel before returning for landing, what happened to it all?

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  #2  
Old 11-06-2010, 03:36 AM
Kobal2 Kobal2 is online now
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Barring safety emergencies, fuel dumping is usually restricted by altitude (i.e. can't dump fuel below X thousand feet) and most modern planes use systems to vaporize the fuel stream as much as possible to help evaporation. ATC controllers also try to avoid populated areas when directing fuel dumping planes.

Within these parameters, the fuel turns to gas (or liquid particles not heavy enough to precipitates) and ends up in the atmosphere and on the clouds. I would guess it eventually mixes with the rain, in low enough concentrations that it's barely noticeable. Remember, planes fly very fast, so while they're dumping quite a bit of fuel, they do so over a very large area.

As for ignition, dumped fuel is certainly flammable and often set aflame on purpose via afterburners at air shows because it makes an impressive fire trail. Watch (low alt. dump 'n burn starts around 5:00). However that's only true at the point of dumping, once the gas has vaporated a bit the fuel/air concentration is too low for sustained combustion. As evidenced by the fact that when the pilot shuts the AB off, the flaming trail extinguishes immediately.

Last edited by Kobal2; 11-06-2010 at 03:38 AM..
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  #3  
Old 11-07-2010, 05:21 AM
Chickenwrangler Chickenwrangler is offline
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Thanks Kobal for interesting and comprehensive answer.

I learn something new every day

:-)
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  #4  
Old 11-07-2010, 08:03 AM
Airman Doors, USAF Airman Doors, USAF is offline
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As a point of interest, very few civilian aircraft have the ability to dump fuel, while virtually every military aircraft does. Remember when the JetBlue flight landed with the nose gear rotated 90 degrees? They had to circle the field for hours because they had too much fuel and they couldn't dump it.

Contrast that with a C-130. More than once we have lost an engine and had to dump almost all of our fuel to make safe landing weight. The Navy dumps fuel after virtually every flight and landing on an aircraft carrier for the same reason.
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  #5  
Old 11-07-2010, 11:27 AM
SeldomSeen SeldomSeen is offline
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Not fuel, but I once watched a crop duster make an emergency landing near my house after his engine conked out as he was making a tight low-altitude turn. He jettisoned his whole load of insecticide directly over a neighbor's garden. The gush of concentrated chemicals pretty much wiped out the garden as I recall (but it got rid of all the bugs), but no other damage was done. Don't recall whether the neighbor sued for damage, but I doubt it, as most were just glad to see the guy get out alive. Pitch dark, in the middle of farm country thick with canals, power lines, barns, houses & haystacks...and he managed to land right-side-up in a field and walk away.
SS
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  #6  
Old 11-07-2010, 04:56 PM
LSLGuy LSLGuy is offline
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Fuel dumping is common on airliners, but nowadays only on the large ones.

e.g. 747, 767, 777 & 787 yes. 717, 737, 757 no.

The old 707 & 727 could dump even though they're not that large, but that was 1950s design philosophy, not 1990s.

Airbus is similar. The 318/19/20/21 (like the LAX nose gear incident ) can't dump. The 330, 340, 350, & 380 can. Not sure about the 300 & 310 but I'd bet they can.

The fuel is dumped at a real high flow rate out a plain old pipe that projects into the airstream. No fancy vaporizing nozzle as Kobal2 suggests. But it is being shoved out into a 200+ mph hurricane, and that spreads it into small droplets pretty quickly.

We were supposed to not dump below 5000 above the ground as dumping at lower altitude could end up with a mist or drizzle of fuel landing on the ground. But if we needed to get lighter now and were at low altitude, well we re gonna dump; The choice was either dump the fuel and maybe get some on the ground, or have the airplane and all the fuel arrive on the ground in one big ball of fire & aluminum and people chunks.

The Airbus dumped (educated guess) about 300,000 lbs of fuel. Or very roughly 50,000 gallons. That's way short of enough to fill even one Olympic swimmming pool. Inside a flying machine that's a bunch of fuel. Dumped into an ocean or evaporated into an atmosphere, well that's a lot less than a drop in a buicket.

Last edited by LSLGuy; 11-07-2010 at 05:00 PM..
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  #7  
Old 11-07-2010, 06:51 PM
Cheshire Human Cheshire Human is offline
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Quote:
Originally Posted by Airman Doors, USAF View Post
As a point of interest, very few civilian aircraft have the ability to dump fuel, while virtually every military aircraft does. Remember when the JetBlue flight landed with the nose gear rotated 90 degrees? They had to circle the field for hours because they had too much fuel and they couldn't dump it.

Contrast that with a C-130. More than once we have lost an engine and had to dump almost all of our fuel to make safe landing weight. The Navy dumps fuel after virtually every flight and landing on an aircraft carrier for the same reason.
If by "civilian" you mean "general aviation", you would be correct. If you are including commercial passenger aircraft ("civil aviation") in that, then no. Commercial passenger aircraft are required to be able to dump fuel. They are only allowed to do it, however, under very tightly regulated circumstances.

The JetBlue incident you mention, for example, was not allowed to dump fuel, because they had a perfectly flyable aircraft. It's only problem was with the landing gear. So it's 'burn off fuel until you feel comfortable with trying the landing, the runway is yours when you are ready.'

Had the situation been "This pig's only going to fly a couple more minutes, where's the nearest runway!", the response would have been (making up directions and distances, here) "Fly 242, altitude at your discretion. Runway 27 is 33 miles, all traffic is clear. Wind is steady, 163 at 17. Dump fuel as needed. Crash trucks are standing by. Good luck and Godspeed."
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  #8  
Old 11-07-2010, 07:36 PM
Pork Rind Pork Rind is online now
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Quote:
Originally Posted by Cheshire Human View Post
Commercial passenger aircraft are required to be able to dump fuel. They are only allowed to do it, however, under very tightly regulated circumstances.
Wikipedia and my memory both disagree with this assertion...

Quote:
Since most twinjet airliners can meet these requirements, most aircraft of this type such as the Boeing 737 (all models), the DC-9/MD80 and Boeing 717, the A320 family and various regional jet ("RJ") aircraft do not have fuel dump systems installed. In the event of an emergency requiring a return to the departure airport, the aircraft circles nearby in order to consume fuel to get down to within the maximum structural landing weight limit, or if the situation demands it, simply lands overweight without delay.
Quote:
... the FAA changed the rules to delete the 105% requirement, and FAR 25.1001 was enacted stating a jettison system was not required if the climb requirements of FAR 25.119 (Landing Climb) and FAR 25.121 (Approach Climb) could be met, assuming a 15-minute flight. In other words, for a go-around with full landing flaps and all engines operating, and at approach flap setting and one engine inoperative, respectively.
Boeing's own documentation also disagrees.

Last edited by Pork Rind; 11-07-2010 at 07:39 PM..
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  #9  
Old 11-07-2010, 08:18 PM
Cheshire Human Cheshire Human is offline
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I don't even have to condense this, all I did was hit "quote", and there is nothing left to reply to. Here's Porky's argument. I just can't figure out what he/she's arguing for/against.
Direct quote follows:
Quote:
Originally Posted by Pork Rind View Post
Wikipedia and my memory both disagree with this assertion...





Boeing's own documentation also disagrees.
End of unaltered "quote" tags, here.

Do you think you could be just a little more specific about what I said, that you object to? I cannot answer an argument that was not made, and this is ALL I got when trying.
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  #10  
Old 11-07-2010, 08:37 PM
Lord Mondegreen Lord Mondegreen is offline
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The PDF from Boeing states which aircraft model do or do not have in-flight fuel jettison capability. A few which don't are:
  • All 737 models
  • Both 757 models
  • Some 767 models

I'm guessing Pork Rind's point is that Boeing's document calls into question the validity of your statement:

Quote:
Commercial passenger aircraft are required to be able to dump fuel.
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  #11  
Old 11-07-2010, 08:46 PM
Absolute Absolute is offline
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Quote:
Originally Posted by Cheshire Human View Post
I don't even have to condense this, all I did was hit "quote", and there is nothing left to reply to. Here's Porky's argument. I just can't figure out what he/she's arguing for/against.
Direct quote follows:

End of unaltered "quote" tags, here.

Do you think you could be just a little more specific about what I said, that you object to? I cannot answer an argument that was not made, and this is ALL I got when trying.
You know, being a smartass like that really looks stupid when you're clearly in the wrong.

He quoted a statement you made, said he disagrees with your statement, and provided evidence.
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  #12  
Old 11-07-2010, 09:01 PM
Richard Pearse Richard Pearse is online now
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Quote:
Originally Posted by Cheshire Human View Post
I don't even have to condense this, all I did was hit "quote", and there is nothing left to reply to. Here's Porky's argument. I just can't figure out what he/she's arguing for/against.
Direct quote follows:

End of unaltered "quote" tags, here.

Do you think you could be just a little more specific about what I said, that you object to? I cannot answer an argument that was not made, and this is ALL I got when trying.
Can you not see his quotes? Or maybe he added them on his edit (my edit: this can't be the case because there is well over 5 minutes between his post and yours.) Seems clear enough to me anyway.

Last edited by Richard Pearse; 11-07-2010 at 09:02 PM..
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  #13  
Old 11-07-2010, 09:08 PM
Cheshire Human Cheshire Human is offline
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OK, let's leave this 'til tomorrow. I was writing for/to the engineers I was discussing this with. Then you all showed up. I'm going to bed. I will look tomorrow, and see what the people I was discussing this with have to say, about my dumbass opinions. Yours are irrelevant to me. If you care, get back to me in 24 hrs., until then, Bon Soir....
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  #14  
Old 11-07-2010, 09:23 PM
Absolute Absolute is offline
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Quote:
Originally Posted by Cheshire Human View Post
OK, let's leave this 'til tomorrow. I was writing for/to the engineers I was discussing this with. Then you all showed up. I'm going to bed. I will look tomorrow, and see what the people I was discussing this with have to say, about my dumbass opinions. Yours are irrelevant to me. If you care, get back to me in 24 hrs., until then, Bon Soir....
It's okay, you've already demonstrated what kind of person you are: smugly confident in the accuracy of his own inaccurate statements and rude and evasive when confronted. Talk about irrelevant.
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  #15  
Old 11-07-2010, 10:04 PM
Pork Rind Pork Rind is online now
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Quote:
Originally Posted by Cheshire Human View Post
Do you think you could be just a little more specific about what I said, that you object to? I cannot answer an argument that was not made, and this is ALL I got when trying.
Undoubtedly my post was no literary masterpiece, but it had all the elements necessary to make the point. You claimed in your post that commercial passenger aircraft were required to be able to dump fuel. I quoted your relevant sentence, stated that I disagreed, then rather than rely on my sometimes faulty memory, I pasted in a key paragraph from Wikipedia, including the applicable FARs.

Then, just to be sure I pasted a link to Boeing's own documentation that counters your assertion. I suppose I could have described the link better, but I was worried the edit window was closing. Given that other posters understood what was intended just fine, I don't see what the problem is.

Last edited by Pork Rind; 11-07-2010 at 10:04 PM..
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  #16  
Old 11-08-2010, 01:05 AM
Richard Pearse Richard Pearse is online now
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Quote:
Originally Posted by Cheshire Human View Post
OK, let's leave this 'til tomorrow. I was writing for/to the engineers I was discussing this with. Then you all showed up. I'm going to bed. I will look tomorrow, and see what the people I was discussing this with have to say, about my dumbass opinions. Yours are irrelevant to me. If you care, get back to me in 24 hrs., until then, Bon Soir....
It's ok to say you are wrong.

Your Assertion: Commercial passenger carrying aircraft are required to have fuel dumping capability.

Fact: Many commercial passenger carrying aircraft do not have this capability. Aircraft without the ability to dump fuel includes the A320 and B737, two of the most common passenger jets in the world. That JetBlue flight was an A320 and could never have dumped fuel.

Conclusion: You are wrong.

It is actually a common source of amusement at an aviation forum I frequent when the media report an aircraft such as a B737 "dumping fuel prior to making an emergency landing" given that such a thing is not possible. It is a great demonstration of the lack of fact checking and general ignorance of specific subject matter that is rife in the media.

If you have an emergency after take-off you have two options, land over weight or burn/dump fuel and land under weight. For many scenarios an immediate landing isn't required but if it is, landing over weight is not a big deal. It requires a check by engineering afterward but there shouldn't be any structural problems if the landing was normal. There is normally performance data available for landings up to the max take-off weight and the crew should check this prior to take-off so they know what their options are.
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  #17  
Old 11-08-2010, 09:53 AM
Elendil's Heir Elendil's Heir is offline
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I was wondering about this when I heard about the Airbus incident. Thanks.
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  #18  
Old 11-08-2010, 10:21 AM
Colibri Colibri is offline
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Quote:
Originally Posted by Absolute View Post
You know, being a smartass like that really looks stupid when you're clearly in the wrong.
Quote:
Originally Posted by Absolute View Post
It's okay, you've already demonstrated what kind of person you are: smugly confident in the accuracy of his own inaccurate statements and rude and evasive when confronted. Talk about irrelevant.
[Moderator Note]

Let's dial back on the personal attacks. No warning issued, but make your points without getting personal about it.

Colibri
General Questions Moderator
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