7
$\begingroup$

During emergencies pilots are authorised to dump fuel, but is there any way or method to recover the fuel that has been jettisoned?

$\endgroup$
  • $\begingroup$ An airline will pay about $256,416 for a full load of fuel on an A380, but an alternative to jettisoning fuel will probably cost much more than that to put on every plane. $\endgroup$ – fooot Oct 1 '14 at 14:43
  • 3
    $\begingroup$ @fooot "about \$256,416". Are you sure it's not \$256,417.32? It's kinda silly to give six significant figures when you've said "about". $\endgroup$ – David Richerby Oct 1 '14 at 21:38
  • 3
    $\begingroup$ @DavidRicherby I realize it seems weird, I debated rounding it but decided it didn't matter much. Each person can decide how many significant figures to throw out based on how much they trust or agree with it. $\endgroup$ – fooot Oct 1 '14 at 22:25
  • 1
    $\begingroup$ @DavidRicherby I actually consider giving a too precise value as one means of sarcasm :D $\endgroup$ – yo' Oct 29 '14 at 16:15
8
$\begingroup$

In theory it could be done, you could rapidly dump fuel into empty tanks below the wings and drop them. At a certain height they deploy Parachutes and land. Just like the Space Shuttle ejects the side tanks.

But where?

Some fuel dumps are only authorized over water and it would cost more to rescue the tanks and bring them back to the airline.

Over land they'd probably smash into populated areas.

The cost for saving some thousands of $ of fuel is not fesable for the rescue.

Short answer yeah it could be possible, but dangerous and costly.

$\endgroup$
  • 2
    $\begingroup$ Use kevlar tanks, like in F1 $\endgroup$ – Firee Feb 26 '15 at 13:25
11
$\begingroup$

In practical terms, no. If you wanted to save/recover the dumped fuel then you would have only two basic options: dump the fuel as usual and then recover it somehow from the air; or, pump the fuel in a controlled way into a container outside the aircraft.

The first option is probably impossible: how could you capture a huge cloud of fuel and fuel vapor mixed with the air? That would be like gathering water from clouds.

The second is theoretically possible, but for civil aviation at least it probably requires too much equipment and risk. You could pump the fuel into a drop tank then jettison it with a parachute for a soft landing. Or you could pump the fuel into another aircraft via a tube, in a kind of reverse air-to-air refuelling. Or if you're dumping fuel from a helicopter (does that ever happen?) it could hover over a tank on the ground, pump out the fuel and then land.

But all of those suggestions are totally impractical (again, at least for civil aviation). Adding drop tanks or air-to-air hoses would add huge cost in materials and training and reduce the useful load of the aircraft significantly, all for a situation that rarely occurs. And for air-to-air pumping you would need an empty tanker aircraft to be available immediately, which is highly unlikely, plus there is the inherent danger of operating two aircraft very close together.

Since fuel dumping is an exceptional situation and many aircraft can't dump fuel anyway, it seems unlikely that investing in a recovery solution would be worthwhile.

$\endgroup$
  • $\begingroup$ I don't think helicopters need to dump fuel because max landing weight is equal to max takeoff (and you only need to be able to dump fuel if there is a 5% difference) $\endgroup$ – ratchet freak Oct 1 '14 at 14:53
  • 3
    $\begingroup$ Not to mention the fact that (unless the landing is required due to a medical emergency), air-to-air refuelling is the last thing you want to do with a stricken aircraft. Oh, and the cost of training all airliner pilots to execute it safely. $\endgroup$ – biziclop Oct 1 '14 at 15:34
  • 2
    $\begingroup$ I can't see why a helicopter would ever need to dump fuel for weight reasons - if you can hover above the tank, you can just hover above the landing zone, and then hover slightly lower....until you're hovering on the ground. Max landing weight isn't really applicable in the same way to a vertical landing $\endgroup$ – Jon Story Oct 29 '14 at 11:15
5
$\begingroup$

By conserve you mean collect for later use I am assuming. While it is technically feasible to do that it is extremely impractical. You'd have to either have another aircraft fly in formation in some sort of reverse in-air refueling system, or the pilots would need to fly over a system on the ground which would collect the fuel.

Any system to do this would require precision on the part of the aircraft needing to dump fuel, and in the kind of emergency where dumping fuel is required precision is one thing you aren't likely to get. Also, the cost of implementing a collection system far outweighs the cost of the fuel you'd save.

$\endgroup$
  • $\begingroup$ The dumped fuel does not usually reach the ground but instead evaporates in the air. It eventually will reach the ground, but extremely diluted as part of rain. $\endgroup$ – Jan Hudec Oct 1 '14 at 17:23
  • $\begingroup$ @JanHudec We should just train crews for an engine-out low pass so they can collect it off the runway. $\endgroup$ – fooot Oct 1 '14 at 18:17
  • $\begingroup$ @fooot: Whow, that wing is low. $\endgroup$ – Jörg W Mittag Oct 2 '14 at 0:02
4
$\begingroup$

I suppose the least expensive way to do it would be to reinforce the airplane structure so that it coud land at maximum takeoff weight. Then no dumping would ever need to occur.

Still not cheap enough to be practical, though. The weight of that extra structure would take fuel to carry around at all times, to save fuel only on the rare emergency.

$\endgroup$
  • 1
    $\begingroup$ Not all planes have the option of dumping fuel, but they just accept overweight landing and the possibility of inspections. $\endgroup$ – fooot Oct 2 '14 at 14:31
3
$\begingroup$

The pilot can either keep circling around to burn it off (doesn't conserve it) or just land overweight without jettisoning.

Burning it off is not an option if you want to get on the ground now to deal with the emergency. And landing overweight can create a new emergency if the gear collapses/too many tires blow.

$\endgroup$
  • $\begingroup$ Is there any way that we can develop a system that can conserve the fuel being dumped. $\endgroup$ – prakash Oct 1 '14 at 14:35
  • $\begingroup$ @prakash What do you mean by "conserve"? $\endgroup$ – Simon Oct 1 '14 at 14:38
  • $\begingroup$ We know that plenty of fuel being wasted during fuel jettisoning. Why don't we develop a mechanism or a system that helps to collect the fuel being dumped from the aeroplane... $\endgroup$ – prakash Oct 1 '14 at 14:42
  • 2
    $\begingroup$ @prakash Relative to total fuel used, there is very little fuel dumped. I'm sure that the amount of fuel dumped is far smaller than the additional fuel you would burn if you carried around the extra weight of whatever you could come up with to prevent the waste of dumping. In 12 years of flying aircraft that could dump fuel, I only had to dump fuel once. $\endgroup$ – Terry Oct 1 '14 at 16:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.