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Fuel Dump Question

Tue Dec 02, 2003 5:16 am

This question might sound a bit silly, but I'm curious anyway. When an emergency situation arises and a plane has to land, if it's overweight, the crew must dump some fuel. So far I understand. But where does the fuel go? I remember reading about SR111 when they were circling around water dumping fuel. Does that pose an ecological threat? Also, what would happen if the airplane dumps fuel above ground? Am I correct in understanding that airplanes don't dump fuel under normal operations? Looking forward to your replies.
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RE: Fuel Dump Question

Tue Dec 02, 2003 5:45 am

This topic is one of many that comes up regularly, so you might to do a search and catch the various past threads...
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RE: Fuel Dump Question

Tue Dec 02, 2003 7:15 am

The fuel is vented to the atmosphere where it dissipates rather quickly. The ability to dump fuel is a feature found on widebodies such as 777, 767, 747, MD-11, A330/340 etc. Narrow bodies like the 737, 757, MD-80 and A320 do not have the ability to dump fuel.
CX Flyboy
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RE: Fuel Dump Question

Tue Dec 02, 2003 12:54 pm

Under normal cirumstances aircraft don't dump fuel. It is only if you are faced with landing overweight because you have diverted, or had to return to the departure airport for some reason, then you will have to dump enough fuel to reduce tha landing weight.

In a severe emergency, like SR111, you should not be wasting time dumping fuel, especially if the integrity of the plane is in doubt. Most aircraft can physically land at max landing weight without damage to the airframe. Even if you have to write off the aircraft to save all the passengers, then so be it.

Fuel dumping is important, but especially after the SR111 incident, companies have been keen to tell their pilots, that getting the aircraft down below max landing weight is in no way the priority.
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RE: Fuel Dump Question

Tue Dec 02, 2003 1:10 pm

Actually, unless it is an option some other operators have ordered, B-767 and A-330 aircraft do not have fuel dump capability, even with ETOPS. Transport aircraft certificated under FAR Part 25 have a provision (25.1001) that states that if they can meet certain engine-out performance criteria at maximum takeoff gross weight, fuel dumping provisions are not required.

As the takeoff performance is predicated on the loss of one engine, and as that represents 50% of the thrust of a two-engine but only 25% of the thrust of a four-holer, most two-engine airliners have no trouble meeting 25.1001. Two-holers are [relatively] overpowered. Fuel dump is mostly a three and four engine thing.
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RE: Fuel Dump Question

Sun Dec 14, 2003 8:46 am

I have heard that overweight landings can be conducted to a certain extent, however, a mechanic has to check landing gear etc.
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RE: Fuel Dump Question

Sun Dec 14, 2003 9:40 am

You are correct.
All transport aircraft have been tested during certification for overweight landings.
The Lockheed TriStar (for example) during certification was tested at MTOW (-500 series, 510,000 pounds) with the landing conducted at a descent rate of 600feet/min.
However, for normal line ops, a max landing weight is established so that 'overweight landing inspections' do not have to be carried out, up to that listed weight.
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RE: Fuel Dump Question

Sun Dec 14, 2003 9:53 am

Fuel dump is necessary because of runway length (required landing speed) or because damage to the landing gear (weight) ?
Can pilots pitch the aircraft a little bit up for a smoother touch down ?

Jgore  Smile
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RE: Fuel Dump Question

Sun Dec 14, 2003 10:07 am


Not necessarily damage to the landing gear, but also damage to surrounding structure.
And yes, overweight landings require higher Vref speeds, so landing distance becomes a problem (with shorter runways).
And yes again, most pilots faced with overweight landings usually aim for the smoothest touchdown possible.
With generally good success.
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RE: Fuel Dump Question

Sun Dec 14, 2003 10:17 am

Thanks 411A
Appreciate it

Jgore  Smile
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RE: Fuel Dump Question

Sun Dec 14, 2003 3:00 pm


This past summer an MD-80 landed at STL over the max landing weight. Due to company policy they had to declare an emergency and the CFR equipment had to be on the ready. The aircraft came in at a much shallower decent that normal and touched down without incident.
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RE: Fuel Dump Question

Mon Dec 15, 2003 10:36 am

We dump fuel fairly often in that we blow TF-33s pretty regularly. The joke here is don't fish at Lake Draper, as that is normally where we dump fuel, but at altitudes where JP-8 dissipates into the atmosphere. Our fuel dump pogos are gravity fed, and dump around 3k pounds per minute to start and then it tapers off.

Ciao, and Hook 'em Horns,
Capt-AWACS, Yankee Air Pirate
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RE: Fuel Dump Question

Tue Dec 16, 2003 7:47 am

Our B767's do have fuel dump capabilities but our A300's do not.

An overweight/hard landing inspection is typically a phased inspection. initially you look for damage to the gear, pylons and the general fuselage area for buckling and fastener damage. If none is found, you're good to go. If damage is found then you dig deeper. You start opening panels and doing interior inspections.
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RE: Fuel Dump Question

Thu Dec 18, 2003 12:03 pm

The 727, and the DC8 are two narrow bodies with dump capability.

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RE: Fuel Dump Question

Fri Dec 19, 2003 3:54 am

A further note: Fuel dumping prior to an engine-out approach and landing is likely not based on runway length. You would just not believe how good the brakes are on any jet transport. The need to dump is probably based on engine-out approach CLIMB capability.

Simply put, under US FAR's you may not fly an airplane into a situation where you need all your engines to fly it out. Here's the situation. You've lost an engine and are landing. You begin an approach and plan your landing with less-than-full flaps. Why? Not because you want to increase your landing roll but because you want to be able to make a missed approach or a rejected landing if you need to. You will dump fuel with a target weight that is probably based on your ability to make a rejected landing with the engine inoperative.

If I remember, this is roughly what happened to the DHL B-727 at JFK a few years ago. They lost an engine, and were landing at JFK. The plane N722DH was a 727-200 with JT-8D-7 engines and therefore, somewhat underpowered. They had to go around and I'd bet that part of the flight was not fun. They dumped more fuel and came back around. On the landing, for unrelated reasons one landing gear failed.

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Photo © Michael F. McLaughlin

A few years ago I flew under a KAL 747 that was dumping fuel over the Sisquoc condor santuary just north of Los Angeles. I reported it and learned that they did not have an emergency. Never did hear the outcome.

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