Why is it OK for a jet to dump fuel?

Question

I can't figure any reason a jet would need to spread fuel over the habitants below. Besides, aren't most petroleum based products carcinogens?

Answer 1

Jets dump fuel very rarely, since fuel costs money.

The primary reason they dump fuel is because they are too heavy to land. Most jets have a maximum take-off weight which is higher than their maximum landing weight. If they don't estimate the fuel properly, they'll have to dump some before they land, which will usually get the pilots a reprimand, since airlines hate to waste money. On the other hand, in an emergency, the jets must dump fuel because they need to land before they planned.

Yes, there are some environmental issues with dumping fuel, but it's not spreading it on the inhabitants below. Planes don't dump fuel at very low altitude except in an extreme emergency, so the fuel vaporizes before it can fall to the ground as kerosene rain. Considering the normal level of pollutants in the air, some jet fuel dumped on rare occasions is not going to raise the level significantly.

Edit: Actually Thomas, there are many emergencies where they have plenty of time to dump fuel. A fire aboard, an engine or other system failure, and many other in-flight emergencies still leave the plane controllable, but the pilot's first job is to get the plane on the ground as soon as possible. In a catastrophic failure, then no, they usually don't have time to do anything but try to get the plane down, but these are rarer than a situation where the plane remains in control and the pilots have time to perform emergency procedures and a controlled landing at an airport.

Answer 2

This is an interesting question and answer series. You know that it can be dumped; that is an available function of an aircraft. You may also know the rules associated with performing that function. But, you do not have the ability to say that dropping of fuel is only done at certain times, only that it is expected to be done at those time. As in all activities, on the ground or in the sky, the human being has the option to follow rules and to not follow rules. As in all other avenues, too, random situations happen that may be organized or not organized, for any reason, and the dropping of fuel can be done for other reasons including illegal reasons. Just as aircraft has been used by terrorists, so can such aircraft be used for ulterior purposes. So, as the Chuck Norris' character ranger indicated on his show, with the price of fuel, if it's being used when it shouldn't be and in a large quantity, then something is up. Finding out why they might want to dump a lot maybe in certain areas, might be a good thing to look into. Also, this kerosene rain mentioned on here is something I didn't know about and now I do. You all have been informative but you should learn to never say never. Things can happen for all kinds of reasons.

Answer 3

I read through all these answers and not one touched on the primary reason aircraft dump fuel.
Almost the only reason we will dump fuel immediately is loss of an engine after take off or loss of engine that required a return to the departure airport. Situations that involve aircraft climb performance. The only time I have ever dumped fuel in my 38 years as an airline pilot, and that includes training scenarios, was associated with loss of engines. The main reason we dump is to get the plane light enough to fly and to climb either after take off or in the event of an engine out missed approach.
Diversions and landings at other airports where max landing wt. is an issue might be enough reason to dump fuel but those are considered controlled dumps and are very rare. They are done in an area that won't be impacted by the fuel dump. It takes about 3500' to dissipate jet fuel.
Many modern aircraft that have no problem meeting engine out climb performance requirements don't even have systems that enable dumping and are landed over weight from time to time. An entry in the logbook is all that is required. Sometimes it will require an inspection, but it is easier to hold and burn fuel down than dump.

Answer 4

Aircraft only dump fuel in the event of an emergency that requires an immediate landing. If the aircraft has enough fuel for a long haul trip, but must return for a landing shortly after take-off then it may be likely that the aircraft is going to be over the weight that the aircraft is approved for a safe landing.
The only alternative to dumping the fuel would be to keep flying around in circles until all of the necessary fuel is burned off, & in an emergency that would not be an option.

Now the Captain of an aircraft that intends to dump fuel can't just go ahead & dump fuel at his/her discretion either. 1st & foremost an emergency needs to be declared. Then the fuel can only be dumped at a location & altitude that is approved by the authority that has jurisdiction over the airspace that the dumping of fuel is to occur.
That way the environment over which the fuel may come raining down on will be adversely affected as little as possible, & people won't be as likely to be put in any danger.

Answer 5

Fuel is dumped in critical situations only. The action is NOT a normal event. To the contrary, operators of jets do all they can to conserve fuel, not dump it overboard. This holds true for civilian and military aircraft. Dumping fuel means there is an emergency of some sort going on. Additionally, that fuel is extremely unlikely to ever reach the ground. When dumped fuel hits the airstream, it vaporizes into very tiny particles that evaporate well before reaching ground level.

Answer 6

Jet fuel is also expensive.

The dumping is an emergency proceedure intended for the immediate saving of life and to reduce both the toxic and cacinogenic consequences of an uncontrolled burn-off in a crash. Raw fuel is not particularly hazardous by itself, and there is no evidence to think that it is any more carcinogenic raw than in the burned state, Remember if the fuel is not dumped, then it is burned in the engine, duh.

However in a crash it can cause other materials to burn, many of which are toxic, and can spread soot far beyond the runway location (assuming it comes to rest at the airport and not your backyard).

When possible, the dump is done over unpopulated areas to be sure.

Answer 7

not sure if most cause cancer but anyways imagine this a 747 if flying when suddenly the #3 engine and the front gear bay burst into flames the captain and fo will know but they will say UH-OH we are loaded with fuel we are all going to die this is why they don't tell you to smoke on a plane or at a gas station they dump it in the event of an emergency but there is another reason say someone fell very ill shortly after take off the plane becomes to heavy to land so the lighten the load by dumping

Hope that helps

Answer 8

I agree that jet fuel is not good for the environment, but keep in mind it is only used in emergency so that the plane can land at a safer weight. Having more fuel on-board during landing not only is a hazard during emergencies, but hinders the mobility and speed at which the plane must approach the runway.

Answer 9

Max. TOGW (max allowable take off gross weight) always exceeds MLW (max landing weight) on large transport category aircrafts, thereby the ability to dump fuel when the need arise, either due to emergency or flight crew discretion.
MZFW (max zero fuel weight) is constituted of the aircraft BOW
(basic operating weight) plus payload.
MZFW is the lesser of all weight limitations. All are manufacturer mandated structural weight limitations by design.
Having to dump to MLW after take off or climb out, very seldom occurs and is the environmental price we pay
to conveniently operate around the planet in relatively short time intervals.
Anything we humans undertake, generally presents some level of risk!

ie: early 100 series b747

MTW (max taxi weight) 738,000 lbs
Max TOGW 734,000 lbs
Max inflight weight with landing flaps selected 650,000 lbs
MLW 564,000 lbs
MZFW 526,500 lbs

Answer 10

Ahhhhh, not to worry weedhopper. If they need to have a plane dump fuel, they just send them out over the ocean or other large body of water, so as to not bother us land species. You won't be (directly) affected ;-)