In my mind this seems like a bad idea for a lot of reasons, like the dumped fuel lighting on fire itself, or perhaps leaving fuel vapor in the wing tanks (which may be even worse than regular liquid fuel) or even just because if you do put the fire out you would now have a new emergency.

But, I've been wrong before. Perhaps it would actually help put out the fire and being forced to glide would be an improvement over an engine fire, right?

So I thought I'd simply ask the experts. Might a large commercial jet (like a B747, A380, etc) dump it's fuel if an engine caught on fire in order to starve the fire of fuel?

PS- For the sake of this thought experiment, pretend the fire had robbed the engine of the ability to cease fuel flow to it... Unless that really makes no sense, in which case please feel free to call me on it and that can be the answer.

  • $\begingroup$ Your PS makes no sense; fuel shutoffs, like practically everything on a plane, have redundant backups, so even if the fire has damaged the fuel pump to the point it's leaking fuel into the engine to sustain the fire, you can cut off the fuel further back, even if that means cutting the fuel to the other engine on that wing in a four-engine config. If there's no way left to shut off the fuel, you likely have bigger problems as it would mean the damage causing the engine fire has also severely damaged the wings and fuselage. $\endgroup$
    – KeithS
    Aug 20 '15 at 2:59
  • $\begingroup$ @KeithS My PS makes sense! But mostly because my PS specifically says that if my idea doesn't make sense please correct me ;), so, overall, as a post script, it makes sense. Even though my idea on fuel cut offs is quite clearly wrong -_-;; $\endgroup$
    – Jay Carr
    Aug 20 '15 at 4:23
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    $\begingroup$ It is unlikely that dumped fuel will ignite, unless it is sprayed in the direction of the actual fire. And if it ignites, it is unlikely to increase hazard to the plane, since the plane will be moving hundreds of knots faster than the dumped fuel. $\endgroup$
    – WGroleau
    Oct 3 '15 at 16:59
  • $\begingroup$ RELATED: aviation.stackexchange.com/questions/71905/… $\endgroup$
    – Fattie
    Nov 24 '19 at 18:03

An airliner experiencing an engine fire might dump fuel, but not to starve the engine. That is much more easily accomplished by simply shutting down the fuel pumps to that engine, which would be a first-line firefighting technique as it's the most economical and the most likely to allow for a restart (less maintenance is required on an engine that's simply shut down versus one that's been doused with chemical suppressors, and those same chemical suppressors might extinguish the fire but would also inhibit relighting it).

There are several redundant fuel shutoff systems in most airliners, from the fuel pumps themselves to actual shutoff valves in the fuel lines in case the pumps themselves are the failure point. Any failure that would completely prevent the crew shutting off the fuel supply to a damaged engine would likely create much more immediate problems, like severe structural damage to the wing or fuselage of the aircraft. All of these shutoffs in addition to active fire suppression systems such as chemical extinguishers are under the flight crew's manual control; an engine on fire is usually still producing at least some thrust, which may be more important than extinguishing the fire in certain critical phases of flight.

The plane is more likely to dump fuel if it's close to its departure airport when the emergency occurs. In such a scenario, the aircraft is likely above its maximum landing weight (which is less than the max takeoff weight as the forces on the landing gear and the runway are less on takeoff than for landing and the plane is expected to burn most of its fuel weight by the time it gets where it's going), and therefore the fuel dump is simply to reduce the aircraft's weight for an emergency landing, so the landing gear doesn't collapse on touchdown. Additionally, if anything else goes wrong during the landing, dumping fuel would leave the plane with as little fuel as possible to minimize the spread or intensity of a fire on the ground, which can impede or prevent escape from the plane. However, fuel dumps from commercial aircraft are rare, used in situations where the necessity of dumping fuel to land safely and spare the passengers outweighs the financial costs of losing the fuel and the environmental costs of cleaning up the spill.

  • 10
    $\begingroup$ Good answer and I up-voted it. However, I slightly disagree with: " However, fuel dumps from commercial aircraft are rare and used only in dire emergencies when the aircraft has to get back on the ground ASAP." If it's a dire emergency, something like a bomb scenario immediately after takeoff, we were trained to make an overweight landing. Dumping fuel takes time, which is fine if it's not a dire (severe?) emergency, at least in a 747. The one time I did it was for an engine fire and shutdown on departure. We used 20 minutes or so necessary to fly to a dump area and then dump 150000 lbs.. $\endgroup$
    – Terry
    Aug 20 '15 at 4:30
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    $\begingroup$ My understanding is that fuel dumped from an airliner evaporates, or at least stays suspended in the atmosphere until it does; it doesn't typically reach the ground. In that case there isn't really any "cleaning up" that can be done, and in particular no monetary cleanup costs incurred (there is of course the intangible environmental cost of the pollution). Is that not correct? $\endgroup$ Sep 4 '15 at 18:05
  • $\begingroup$ @NateEldredge I seem to remember being told in ground school that Jet-A evaporates within 2,000 vertical feet. $\endgroup$
    – Terry
    Sep 4 '15 at 18:32
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    $\begingroup$ ... Where it would contribute a significant fraction of the smog-producing VOCs in the air for miles around. No liquid may hit the ground (and even if it did it would vaporize fairly quickly) but it's an uncontrolled release of atmospheric pollutants which the airline usually has to answer for if the dump was performed within a national jurisdiction (it's possible a jet could fly out to international waters, dump, then circle around). $\endgroup$
    – KeithS
    Sep 8 '15 at 14:25
  • $\begingroup$ @KeithS - "it's possible a jet could fly out to international waters, dump, then circle around" ...and then you get SwissAir 111 $\endgroup$
    – TLW
    Nov 24 '19 at 19:18

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