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As seen in multiple pictures:

First, this one, it appears the aircraft is spraying copious amounts of fuel into the exhaust!

Surely this provides no thrust, not in the way an afterburner (which the F-111 has!) does.

Is it perhaps as an alternative to flares for anti IR missiles? It seems logical, but I don't think so, because I've seen it on takeoff too!

From this image, it looks like the aircraft is spraying COPIOUS amounts of fuel into the exhaust!

At any rate, it is QUITE badass!

enter image description here

EDIT: YouTube video!

EDIT: Can any other aircraft perform this?

Rodrigo de Azevedo
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Bassinator
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5 Answers5

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The F-111 has, like many aircraft, a fuel dump port so it can get rid of a lot of heavy fuel rather quickly. Most aircraft have the dump ports on the wings, the F-111 designers put it in the tail between the engines. End result is if you dump fuel and briefly light the afterburner you will ignite the liquid fuel in your wake creating a rather spectacular trail of fire.

Aerodynamically it's completely useless, financially it's very expensive, you'd only do it in combat if you were suicidal as it greatly increases your IR signature right where you don't want it, but at an airshow it does look totally badass, especially as the afterburner is adding a lot of noise at the same time.

I would expect any pilot who does a dump-and-burn outside of an airshow (or an emergency) will have his own tail set on fire by the air wing's commanding officer.

The SR-71 had a similar issue - it leaked like a sieve on the ground. Rotating for takeoff would occasionally set fire to the JP-7 on the runway leaving a burning trail behind it much like the Road Runner.

Reply to the video: watch the takeoff section carefully. You can clearly see the afterburners come on before the fuel dump starts.

Reply to about half the comments: Highly unlikely they designed it to do this. The F-111 was one of the earlier swing-wing planes, that meant that you can't put much on the wings. And as the bigger tank is in the fuselage anyway, someone would have looked at the space between the engines and thought it was just right for a dump pipe. The flame effect was probably discovered later.

paul
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    any links to pictures or videos of the SR-71 leaving a burning trail would be awesome. – BeowulfNode42 Oct 14 '14 at 05:57
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    I'm confused, if it's so useless, then why is it part of the design? Surely not only for airshows? – user50849 Oct 14 '14 at 12:21
  • @user50849 All aircraft have fuel dump ports. There are a variety of questions which cover the when, why, and how of fuel dumping, see http://aviation.stackexchange.com/search?q=fuel+dump – Adam Davis Oct 14 '14 at 13:09
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    @user50849 It also has uses in an emergency, where you might find yourself above an airfield about to land, but with too much heavy and flammable fuel: you want as little fuel as possible on a crash landing, but you don't want to fly in circles to burn fuel, so you can use a fuel dump port instead. – cpast Oct 14 '14 at 17:22
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    @user50849, it's not useless to dump fuel, and it's not useless to use the afterburners, but the only reason you'd do both in conjunction is for air shows :) – Jason Oct 14 '14 at 20:33
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    Suicidal in combat? Couldn't it be used to confuse a heat seeking missile that was already locked onto you and approaching from the front? (Admittedly you would have to time it just right.) – Loren Pechtel Oct 14 '14 at 22:01
  • @AdamDavis Many have fuel dump ports but certainly not all. – casey Oct 14 '14 at 22:38
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    @LorenPechtel How would that help? Seems to me it would just make you a brighter target for everything, and I don't think the fire trail behind is meaningfully further behind than the plane's usual exhaust to do anything but make your exhaust even brighter and easier to track. I can only see it helping if some missile controller decided it was too bright so it must be a flare and didn't detonate, but I doubt they do that. – Dronz Oct 15 '14 at 00:23
  • @Dronz I'm picturing it like a huge flare. Just like a flare can draw in a missile it could also. Since it's close to the engine it would only be of use if you could use it to draw the missile behind you--a missile coming from somewhere in front of you but not head on. – Loren Pechtel Oct 15 '14 at 01:17
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    @LorenPechtel Hmm. Unless I'm wrong, I think heat-seekers are already designed to target a plane in front of the engine heat, and I assume many explode when they get close. Flares are different in that the flare falls away (and the pilot generally changes direction after dropping the flare, to get as far away from the flare as possible before the IR missile arrives). There is also the hope that an IR missile will fail to keep seeing the plane's heat, especially from the front, so an ignited fuel dump would void that hope. – Dronz Oct 15 '14 at 01:36
  • @casey You're right, I should have said "most" – Adam Davis Oct 15 '14 at 02:13
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    @LorenPechtel only hypothetical case I can come up with is if the missile were to end up flying through the cloud of burning jet fuel and getting damaged as a result. But how likely is that (I'd guess missiles to be more sturdy than that, plus the chances of it happening would be miniscule). – jwenting Oct 15 '14 at 06:30
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    @jwenting Who cares if it's damaged? It can't turn around if it misses. In reality it's going to detonate once it's flown through the cloud but hopefully it's far enough away at that point that the plane isn't taken out. (And the fact that the plane & missile are moving apart at multiples of the speed of sound will rob the shrapnel of much of it's energy also.) – Loren Pechtel Oct 15 '14 at 22:40
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    "Dumping fuel" in emergencies is useful, but how is "dump-and-burn" useful in emergencies as you put it? – B Faley Oct 16 '14 at 07:58
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    @LorenPechtel, heat-seeking missiles home in on the exhaust plume and then, like all anti-aircraft missiles, explode in a shaped explosion designed to take out a nearby airplane. A dump-and-burn will just make the exhaust easier for the missile to track. – Mark Oct 16 '14 at 19:37
  • @Mark It depends on where the missile is coming from. If the missile is coming from the front and goes for the plume that leaves it behind the plane when it realizes it's not going to hit and self destructs. – Loren Pechtel Oct 16 '14 at 23:42
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    "The F-111 was one of the earlier swing-wing planes, that meant that you can't put much on the wings." The F-111 had four pylon store mounts on the wings, each capable of holding up to 5000lb of ordnance. – Romeo_4808N Dec 11 '16 at 04:39
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There was at least one occasion when the dump-and-burn was used in combat. During the 1986 attack on Libya

the U.S. pilots, desperate for fuel, jostling with one another in the air to get access to aerial refueling tankers. Unable to break radio silence, they could not locate the giant KC-10A Extenders and KC-135R Stratotankers that would keep them from crashing into the sea. An F-111 pilot finally solved the problem by doing a "little torching," as he dumped some fuel and ignited it with his afterburner, "creating a huge explosion that both lit up the sky and pointed the direction to the tanker"

Andrew Davidson
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    @reirab though technically it wasn't done IN combat. It was done post-combat during a combat mission. But maybe I'm splitting hairs here. – jwenting Oct 15 '14 at 06:32
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    For what it's worth, this use in combat is less suicidal than breaking radio silence. – corsiKa Oct 16 '14 at 20:18
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    @corsiKa out of interest, why do you say that? Does breaking radio silence make it easier to get some sort of lock? – cristobalito Jan 11 '16 at 21:38
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    Breaking radio silence might get you more in trouble with YOUR side, not the enemy. – Bassinator Feb 20 '16 at 00:41
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    Sorry to ask but how dump and burn help a fighter pilot find a tanker when they cannot break radio silence? – vasin1987 Oct 03 '16 at 18:54
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    @vasin1987: I assume this was during the night, so they couldn’t see the tanker. They briefly turned on the lights that way. – chirlu May 24 '17 at 18:54
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I used to be an F111 test engineer; the jet can hold about 19000 liters of fuel (without external tanks). At 0.81kg/Liter, that's 15390Kg (33,939 Lbs) of weight, which is substantial (the empty weight of the jet is 45200 Lbs / 20,500 Kg). Basically with a full load of fuel, the jet is 75% heavier.

Although the giant flame plume is cosmetic, the F111 can dump fuel like this in case you need to quickly reduce the weight of the aircraft; in-flight emergencies are one possible reason to reduce weight quickly. The fire is because the pilot lit the afterburners whilst dumping fuel. Assume you loose your flaps, or maybe you discover the brake lines are leaking... if you had to land on a short field (such as a small civilian airport), it makes sense to dump your fuel so you have a better chance of stopping quickly.

Mike Pennington
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    I am interested, how long can an aircraft sustain this? How long can he dump fuel before he doesn't have enough to land? – Bassinator Oct 14 '14 at 21:38
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    @HCBPshenanigans You can land an aircraft with no fuel, so I guess the answer to the question in your comment is "until the tanks are empty." – reirab Oct 14 '14 at 21:51
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    @reirab not really. There might be technical limits to the length of time the fuel dump valve can be opened. And the burning trail of fuel might possibly damage the aircraft, so there might be a time limit there as well to prevent flames from reaching back into the fuel dump system for example. – jwenting Oct 15 '14 at 06:34
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    @jwenting I was referring more to the 'How long can he dump fuel before he doesn't have enough to land?' question. Unless you're outside of glide range from somewhere to land, there's not really a minimum amount of fuel needed to land, since you can land with no power. That's not to say it's a good idea, but it is possible. Since this answer was more referring to conventional fuel dumping (as opposed to setting the dumped fuel on fire with afterburners,) I was answering more with that in mind. There might be a limit for actually setting the fuel on fire. – reirab Oct 15 '14 at 14:39
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We did have one "practical" application in "torching" as we used to call it: It was great way to find a Lead aircraft in a night formation to complete a night rejoin. Also we often considered it as a useful combat technique that if we got attacked by another fighter we would plan to start a dive towards the ground and we would do a short torch just before leveling off since the flash would clearly distract the attacker and make them think we hit the ground and break off the attack.

P Ghiron
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    This does not attempt to answer the question (although it is cool information that would be appropriate for a comment). – dalearn Dec 31 '18 at 01:11
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    Looks to me like this absolutely answers the "why" question as stated. – Ralph J Dec 31 '18 at 02:54
  • @RalphJ the way I see it, this answer provides lots of cool information but if every other answer was deleted, a viewer would not have their question of “what is it doing” answered. Since this is the case, it would be more appropriate as a comment because it helps improve the question. – dalearn Dec 31 '18 at 12:30
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The "Dump and Burn" as it was called here in Australia was used for 'effect' at air shows and for 'promoting' the Air Force as a great place to be.

The 'effect' was really quite spectacular. And frightening to those who saw it for the first time, like here in Brisbane, resulting in many phone calls to the police of a OFO sighting.

As used by some American pilots in SVN on missions to light up the area they were flying through too, for a better idea of just how close to the ground they were.

The Fuel Dump Atomizer Nozzle

A 'dump and burn' over Brisbane in the 80's, when the F-111's were 'active'.

T.J.L.
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Kerry COX
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    Welcome to Aviation.SE! If you have extra details, please improve your answer instead of leaving a comment which may be overlooked. – dalearn Dec 31 '18 at 01:13