Dumping fuel over land

[Flankerman]

I was sitting at my modelling desk yesterday (10 October) - when I heard a jet noise.

My DNA kicked in and I ran to the window - to see a Boeing 787 flying fairly low in a wide arc a mile or so away around my house.

What made me look twice were the contrails - except they weren't !! :woot.gif:/>

It was dumping fuel - from vents about mid-span - and a lot of it as it described a 3-mile wide circle and headed back in the direction of Bristol - still streaming fuel.

I thought the marking were British Airways - but I have since discovered it was United Airlines flight #UA5 from Heathrow to Houston.

Apparently it had a lighting strike and orbited Bristol before returning to Heathrow for an emergency landing.

A couple of internet searches turned up these.....

http://inagist.com/all/520573769866571777/

https://twitter.com/airlivenet (scroll down the page).

Now, I know why they dump fuel - to reduce the landing weight - but my question is does the fuel completely disperse before it reaches the ground ??

How common is it to dump at such a low height ??

Surely it doesn't atomise completely ?? - what if I was directly under it - would I get a shower of fuel ??

What if I was smoking ?? - what about my washing on the line ?? - or my cars paint finish ??

It was fascinating to watch - and the flight landed safely - so no big deal in the grand scheme of things - but I have never witnessed such a thing before.

Any thoughts ???

Ken

Edited October 11, 2014 by Flankerman

[Andrew Maverick Taylor]

Hi Ken.

I am a little familiar with this situation. Many years ago, I used to work at the British Airways maintenance facility at Cardiff airport just on the other side of the Bristol Channel. Cardiff was also the main diversion airport for Concorde if it had any issues prior to crossing the Atlantic or if it couldn't make it to LHR.

We frequently had aircraft that would come into Cardiff that needed to dump fuel prior to landing. One such case was the union strike at Heathrow when the catering services refused to supply the airlines for some reason. For about a week, we had three 747-400s land daily fully loaded with passengers and cargo but due to the short runway at Cardiff, the 747s can land fully loaded as long as fuel is dumped, but they can't take off loaded.

I believe that the fuel dump area is over the Bristol channel and not directly over land. Despite the concerns about the flammability of jet fuel, it is actually quite hard to ignite. You could throw a cigarette butt into a pool of it and the likely hood of anything happening is quite slim. The biggest danger around atommised jet fuel is static electricity. If the concentration of fuel to air is right, a slight discharge of static could ignite it.

I wouldn't be too concerned because it is likely that the aircraft was discharging it's fuel over water but without seeing a specific tracking of the aircraft's movements, then clearly I can't say.

Hope this puts you at ease a little.

Andrew

[Flankerman]

Hi Andrew,

I wasn't concerned - just a little intrigued that it was happening definitely over land - not a mile away from where I am near Malmesbury.

I just wish I'd picked up my camera rather than my binoculars - as it first transitted my rear window, then my side and finally off towards Bristol seen from my front window.

It was very clearly dumping.

Ken

[huntermountain]

I guess they'll dump fuel wherever necessary, depending on how fast they need to land. I witnessed a b-707 dumping fuel some years back(1997 actually), when a nose wheel refused to lower. They dumped fuel over the sea, because the airport was less than a mile from the sea. But even if it was farther away, I think they would have flown to the sea. The situation wasn't going to get any worse by staying in the air longer.

I was fortunate to be able to head to the airport fast enough to see the pilot perform a perfect landing, keeping the nose pitched up only to let it touch the ground in a foam carpet. Nobody got hurt, and other than a few scratches on the belly and the loss of the landing gear doors, there was very little damage to the plane.

[11bee]

In a true emergency, pilots have the authority to dump at any altitude and over populated areas. For less pressing emergencies, they try to get out over the water or if that's not an option, they will try to get to a higher altitude so the fuel will completely vaporize prior to reaching the ground.

As noted above, it's very unlikely that the fuel would cause a fire risk. The fuel / air mixture has to perfect to support an explosion. However, there is an environmental issue. If the fuel hasn't vaporized before it hits the ground, it's no different than if a tanker rolled over and released it. You have cleanup issues and testing, reporting required.

Years ago, a DC-10 taking off from Logan Airport had an engine catastrophically fail and the crew had to immediately dump at very low altitude. A mist of fuel covered a populated area. A lot of complaints from residents about the odor and some small amount of residue on cars, etc. but no real damage or injuries. I think the airline even escaped being fined for the release given that it was a life or death emergency (in Massachusetts, that says a lot).

Edited October 11, 2014 by 11bee

[11bee]

Strange, I cannot find any articles about this incident. Google News is usually pretty good on vacuuming up stuff like this.

[shadoweng]

What do you consider low altitude? We would dump as long as we were above 5000ft.

[Fly-n-hi]

In a true emergency, pilots have the authority to dump at any altitude and over populated areas. For less pressing emergencies, they try to get out over the water or if that's not an option, they will try to get to a higher altitude so the fuel will completely vaporize prior to reaching the ground...

In a true emergency we don't have to dump fuel at all. We can land over weight. If the plane's on fire...I'm landing no matter what. Even in less pressing emergencies we aren't required to land under max landing weight.

Landing over weight is really only a problem if you land descending at a rate faster that 150 feet per minute (or something close to that). Landing at that rate or faster would be a very hard landing.

Edited October 11, 2014 by Fly-n-hi

[11bee]

In a true emergency we don't have to dump fuel at all. We can land over weight. If the plane's on fire...I'm landing no matter what. Even in less pressing emergencies we aren't required to land under max landing weight.

Landing over weight is really only a problem if you land descending at a rate faster that 150 feet per minute (or something close to that). Landing at that rate or faster would be a very hard landing.

Interesting, I had always thought that it was impossible to land over max weight, due to either stress on the airframe or being too fast to stop on the runway. Any idea if this only applies just to the modern jets that you are flying or to older aircraft? In the case of that DC-10 at Logan, I was told that they had to dump for quite some time despite having their number two engine disintegrating at takeoff and a fire warning light illuminated.

[habu2]

Max Landing weight is a function of descent rate at touchdown and available runway/braking length.

[Fly-n-hi]

Interesting, I had always thought that it was impossible to land over max weight, due to either stress on the airframe or being too fast to stop on the runway. Any idea if this only applies just to the modern jets that you are flying or to older aircraft? In the case of that DC-10 at Logan, I was told that they had to dump for quite some time despite having their number two engine disintegrating at takeoff and a fire warning light illuminated.

I'm not sure about DC-10s or L-1011s, etc. but I imagine its the same for all the passenger aircraft. If you make a smooth landing then weight isn't really a factor. But on the same token, if you make a hard landing maintenance will have to inspect the landing gear and some other things regardless of weight.

We have an overweight landing checklist that guides us and reminds us of certain considerations in case we have to do it.

Also, keep in mind that gas was cheap back in the 60's & 70's. So dumping 75,000+ lbs of fuel wasn't nearly as expensive as it is today.

Edited October 13, 2014 by Fly-n-hi

[TheFlyingDutchman]

A lot of people think of images of Canadair's dumping water over forest fires when they read about a fuel dump. It isn't even close to that. The fuel is jettisoned at such a high pressure that it atomizes and most likely vaporize before it reaches the ground. Also on low altitudes.

A few years back there had been an incident involving a Royal Air Maroc b737 suffering multiple bird strikes after T/O here at Schiphol, flaming out one of the engines. It made a VERY low (under 600 ft, as confirmed in the official investigation report) emergency turn over my town and landed safely. Some media reported that the plane dumped fuel after which people were complaining about fuel hitting their cars and gardens. A b737 can't even dump fuel. After every aviation related incident people come up with stories that are then copied by the media.

Not a single fish will die as a result of a fully tanked 747 dumping it all over the sea. It isn't a very environmental friendly solution either but keep in mind the speed of an airliner and the amount of dumped fuel compared to the amount of water in the sea below.

I had always thought that it was impossible to land over max weight, due to either stress on the airframe or being too fast to stop on the runway.

Does a higher landing mass actually result in a significantly longer brake distance?

Edited October 13, 2014 by TheFlyingDutchman

[ALF18]

A lot of people think of images of Canadair's dumping water over forest fires when they read about a fuel dump. It isn't even close to that. The fuel is jettisoned at such a high pressure that it atomizes and most likely vaporize before it reaches the ground. Also on low altitudes.

A few years back there had been an incident involving a Royal Air Maroc b737 suffering multiple bird strikes after T/O here at Schiphol, flaming out one of the engines. It made a VERY low (under 600 ft, as confirmed in the official investigation report) emergency turn over my town and landed safely. Some media reported that the plane dumped fuel after which people were complaining about fuel hitting their cars and gardens. A b737 can't even dump fuel. After every aviation related incident people come up with stories that are then copied by the media.

Not a single fish will die as a result of a fully tanked 747 dumping it all over the sea. It isn't a very environmental friendly solution either but keep in mind the speed of an airliner and the amount of dumped fuel compared to the amount of water in the sea below.

Does a higher landing mass actually result in a significantly longer brake distance?

I've dumped fuel at about 10,000 feet; ATC wanted me to be that high to ensure it was fully atomized. As to overweight landing, I have not seen anyone consider landing overweight unless they were on fire and about to explode... the risk of damage to the aircraft is high (imagine a tiny bit of turbulence when you're about to touch down), and braking distance is significantly longer when overweight. Kinetic energy needs to be dissipated, and weight makes it way worse. Abnormal (emergency) procedure checklists all say to dump fuel until below max landing weight. If you don't, you'd better have a darn good reason, or face tough questions from your chief pilot.

ALF

[Fly-n-hi]

I've dumped fuel at about 10,000 feet; ATC wanted me to be that high to ensure it was fully atomized. As to overweight landing, I have not seen anyone consider landing overweight unless they were on fire and about to explode... the risk of damage to the aircraft is high (imagine a tiny bit of turbulence when you're about to touch down), and braking distance is significantly longer when overweight. Kinetic energy needs to be dissipated, and weight makes it way worse. Abnormal (emergency) procedure checklists all say to dump fuel until below max landing weight. If you don't, you'd better have a darn good reason, or face tough questions from your chief pilot.

ALF

Its only a problem if you improperly plan on using a runway that is too short...and that would be a problem regardless of actual weight. I'd be interested to see what exactly your manual says about it. Plus, our 757/767s, 737s & A320s don't even have the ability to dump fuel. The only way to reduce the weight would be to fly in circles for 2+ hours. This is how that conversation would go here:

Our Chief Pilot would ask "I noticed you dumped $100,000 worth of gas when the manual says you can land overweight. Care to explain that?"

Me, "Well, I didn't want to damage the plane."

Chief Pilot: "Are your landings really that bad?"

Me, "Well, I didn't want to go off the end of the runway."

Chief Pilot: "You were over the US. There are about 1000 runways over 10,000 feet...and we fly to many of them regularly. How much runway do you need? The 767 can land at 351,000 lbs flaps 30 with poor braking action and still stop in 10,000 feet."

Me, "Uh..."

Here's an excerpt from our manual (which is basically the Boeing manual):

A pilot may consider making an overweight landing when a situation arrises that requires the airplane to return to the takeoff airport or divert to another airport soon after takeoff. Landing overweight is considered a safe procedure. FAR criteria require that landing grear design be based on:

• A sink rate of 10 feet per second (600 feet per minute) at the maximum designed landing weight and,
  
• A sink rate of 6 feet per second (360 feet per minute) at the maximum design take off weight
  
• Typical sink rates at touchdown are 2 to 3 feet per second (120-180 feet per minute) and even a "hard" landing rarely exceeds 6 feet per second (360 feet per minute).
  

There has been no adverse service experience with airplanes certificated under 14 CFR 25 involved in overweight landings. Furthermore, service experience indicates that damage due to an overweight landing is extremely rare. A normal touchdown of 200-300 feet per minute should impose no structural problems.

When in doubt read the manual. I could go on but I think you get the idea.

Edited October 14, 2014 by Fly-n-hi

[TheFlyingDutchman]

Well the question is because of an item I saw on Dutch TV a while back. They were showing that a van loaded above its legal weight (but with proper brakes) does not stop later than an empty van when making an emergency stop. I know, a van is not an airplane but I was wondering if this applied to both.

[Fly-n-hi]

Well the question is because of an item I saw on Dutch TV a while back. They were showing that a van loaded above its legal weight (but with proper brakes) does not stop later than an empty van when making an emergency stop. I know, a van is not an airplane but I was wondering if this applied to both.

That's interesting. I would think that an overloaded van would take more distance to stop. I'd like to see that video If they have an english version.

In our case more weight = increased landing distance. For example a 767 landing at 180,000 lbs, flaps 30, at sea level, with no wind can stop in 3440 feet. If it weighed 351,000 lbs it would take 6290 feet. So weight does make a significant impact on landing distance.

Edited October 14, 2014 by Fly-n-hi

[11bee]

So weight does make a significant impact on landing distance.

As well it should, that is basic physics. I don't understand how Flying Dutchman's van analogy was possible. If all things are equal (condition of brakes, road surface, tires, etc) and maximum breaking force is applied in both scenarios, I don't understand how it is possible that both vans stopped in the same distance.

[Fly-n-hi]

As well it should, that is basic physics. I don't understand how Flying Dutchman's van analogy was possible. If all things are equal (condition of brakes, road surface, tires, etc) and maximum breaking force is applied in both scenarios, I don't understand how it is possible that both vans stopped in the same distance.

Yeah, that's why I'd like to see the video. There has to be a catch to it.

[TheFlyingDutchman]

I have found the video. Unfortunately there are no English subtitles. You can select Dutch subs, just in case that helps But you should get the idea without text either.

They don't really give an explanation for the brake results, though.

From 17:27

http://www.npo.nl/blik-op-de-weg/17-05-2013/AVRO_1611867

Edited October 15, 2014 by TheFlyingDutchman

[T0M4ever]

As well it should, that is basic physics. I don't understand how Flying Dutchman's van analogy was possible. If all things are equal (condition of brakes, road surface, tires, etc) and maximum breaking force is applied in both scenarios, I don't understand how it is possible that both vans stopped in the same distance.

Perhaps the extra load over the rear of the van is increasing the grip of the rear tyres under braking, and thus increasing the effectiveness of the rear brakes in slowing the van down?

[ALF18]

Its only a problem if you improperly plan on using a runway that is too short...and that would be a problem regardless of actual weight. I'd be interested to see what exactly your manual says about it. Plus, our 757/767s, 737s & A320s don't even have the ability to dump fuel. The only way to reduce the weight would be to fly in circles for 2+ hours. This is how that conversation would go here:

Our Chief Pilot would ask "I noticed you dumped $100,000 worth of gas when the manual says you can land overweight. Care to explain that?"

Me, "Well, I didn't want to damage the plane."

Chief Pilot: "Are your landings really that bad?"

Me, "Well, I didn't want to go off the end of the runway."

Chief Pilot: "You were over the US. There are about 1000 runways over 10,000 feet...and we fly to many of them regularly. How much runway do you need? The 767 can land at 351,000 lbs flaps 30 with poor braking action and still stop in 10,000 feet."

Me, "Uh..."

Here's an excerpt from our manual (which is basically the Boeing manual):

A pilot may consider making an overweight landing when a situation arrises that requires the airplane to return to the takeoff airport or divert to another airport soon after takeoff. Landing overweight is considered a safe procedure. FAR criteria require that landing grear design be based on:

• A sink rate of 10 feet per second (600 feet per minute) at the maximum designed landing weight and,
  
• A sink rate of 6 feet per second (360 feet per minute) at the maximum design take off weight
  
• Typical sink rates at touchdown are 2 to 3 feet per second (120-180 feet per minute) and even a "hard" landing rarely exceeds 6 feet per second (360 feet per minute).
  

There has been no adverse service experience with airplanes certificated under 14 CFR 25 involved in overweight landings. Furthermore, service experience indicates that damage due to an overweight landing is extremely rare. A normal touchdown of 200-300 feet per minute should impose no structural problems.

When in doubt read the manual. I could go on but I think you get the idea.

You're right about the manual. If it is allowable under the AFM, then by all means, do it, and if you don't I agree the chief pilot will have some questions as to why you didn't.

I did some checking yesterday, and came up with the following:

-The CF-18 has virtually no restriction on landing weight (kind of). At max all-up weight (51,900 lb), it says not to exceed 600 fpm on landing. Between 39,000 lb and 44,000 lb, it gives the limit as 1,000 fpm, and below 39,000 lb it says "unrestricted".

-A friend flies Jetstreams. He says they have a published procedure for overweight landings, but then he said there was only about 400 lb gross weight difference between max T/O weight and max Landing weight, so that's kind of academic.

-The Challenger 604 AFM just mentions "max landing weight" of 38,000 lb (about 14,000 lb below max T/O weight), but does not mention anything about overweight landings; it doesn't say they are prohibited, nor does it explain how one might go about performing one or what maintenance actions might be required afterward.

We taught our clients in the simulator on the 604 to dump fuel to get down to 38,000 on landing if necessary, but also if there was a reason to get on the ground right away, to land overweight (i.e. uncontrollable fire or a dire medical emergency).

Second topic: I agree with 11bee's assessment that it is not possible to stop in the same distance with a higher weight aircraft. I can't speak for truck braking systems, especially when the weight distribution may come into it, but for an aircraft, the minimum stopping distance is predicated on the following:

-Very precise touch-down speed. Kinetic energy is proportional to the square of the velocity; 10 extra knots has a HUGE impact on stopping distance.

-Maximum braking with anti-skid, on an ideal surface. Braking effectiveness is optimal with about 10% slip of the wheels. Therefore, with a higher gross weight, there is no way with an aircraft anti-skid system functional that you can get more braking action with a higher weight.

ALF

[Fly-n-hi]

You're right about the manual. If it is allowable under the AFM, then by all means, do it, and if you don't I agree the chief pilot will have some questions as to why you didn't.

I did some checking yesterday, and came up with the following:

-The CF-18 has virtually no restriction on landing weight (kind of). At max all-up weight (51,900 lb), it says not to exceed 600 fpm on landing. Between 39,000 lb and 44,000 lb, it gives the limit as 1,000 fpm, and below 39,000 lb it says "unrestricted". :woot.gif:/>

-A friend flies Jetstreams. He says they have a published procedure for overweight landings, but then he said there was only about 400 lb gross weight difference between max T/O weight and max Landing weight, so that's kind of academic.

-The Challenger 604 AFM just mentions "max landing weight" of 38,000 lb (about 14,000 lb below max T/O weight), but does not mention anything about overweight landings; it doesn't say they are prohibited, nor does it explain how one might go about performing one or what maintenance actions might be required afterward.

We taught our clients in the simulator on the 604 to dump fuel to get down to 38,000 on landing if necessary, but also if there was a reason to get on the ground right away, to land overweight (i.e. uncontrollable fire or a dire medical emergency).

Second topic: I agree with 11bee's assessment that it is not possible to stop in the same distance with a higher weight aircraft. I can't speak for truck braking systems, especially when the weight distribution may come into it, but for an aircraft, the minimum stopping distance is predicated on the following:

-Very precise touch-down speed. Kinetic energy is proportional to the square of the velocity; 10 extra knots has a HUGE impact on stopping distance.

-Maximum braking with anti-skid, on an ideal surface. Braking effectiveness is optimal with about 10% slip of the wheels. Therefore, with a higher gross weight, there is no way with an aircraft anti-skid system functional that you can get more braking action with a higher weight.

ALF

I think the taboo about landing overweight probably comes from an "old school" way of doing things...and I don't mean that in a negative way. After all, if you land below the max landing weight then you theoretically won't have any issues with the structural integrity of the plane. Clearly it is better to error on the side of caution. But in this case its not really more cautious since the manufacturer (in my case, Boeing) has said its ok to do.

I know that the fact that fuel has become sooo expensive is what has caused our flight department to change it's stance on overweight landings. To be honest, we just recently changed our policy. It used to be our (company) policy to make attempts to land below max landing weight.

Bottom line: Don't slam it on the runway!

[Fly-n-hi]

And let me be clear that our normal policy is to land below max landing weight. What I've been talking about in the last few posts is an urgent situation or an emergency in which you aren't on fire or falling apart.

For example, let's say that you are flying out to Hawaii and you have a pressurization problem right after you reach cruise altitude. Well, in this case the plane isn't in any immediate danger but obviously you're not going to continue out over the water. You're going to return for landing...or land at an alternate. In a 757, in order to land below max landing weight, you'd have to fly around for about 3 to 3.5 hours to burn enough fuel to get down to you max landing weight since the 757 doesn't have the ability to dump fuel.

In this situation it would be ok to land overweight. This is the sort of situation I'm addressing.

Edited October 16, 2014 by Fly-n-hi

[82Whitey51]

"US Naval aircraft spotted dumping fuel over North Yorkshire town - but residents are assured it was safe"

http://www.darlingtonandstocktontimes.co.uk/news/11532573.US_Naval_aircraft_spotted_dumping_fuel_over_North_Yorkshire_town___but_residents_are_assured_it_was_safe/

[11bee]

"US Naval aircraft spotted dumping fuel over North Yorkshire town - but residents are assured it was safe"

http://www.darlingtonandstocktontimes.co.uk/news/11532573.US_Naval_aircraft_spotted_dumping_fuel_over_North_Yorkshire_town___but_residents_are_assured_it_was_safe/

Can't believe that the pilot decided to circle over the town's supermarket!!! What was he thinking? Heads need to role for this one.