Dumping Fuel?
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For aircraft that can dump fuel, mainly longhaul, the fuel is dumped straight out of the tanks via a jettison pipe. The outlet is usually near the wing tip. The jettison fuel pipe situated in the fuel tanks is set at a certain position to prevent total emptying of the tanks. I think Air Traffic try and place the aircraft over the sea if nearby but otherwise overland.
Of course it all depends on the nature of the problem requiring the aircraft to land in the first place!!
Of course it all depends on the nature of the problem requiring the aircraft to land in the first place!!
Join Date: Oct 2003
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Ever seen a dump and burn from an F111?
Dump pipe is down the back between the tail pipes.
Start dumping and add a touch of afterburn and it all lights up.
Most spectacular.
Flame front never quite catches up with aircraft.
The afterburner fuel pump/s pump out the fuel at a very high rate cause you want to be rid of a lot of weight in a big hurry if you lose an engine after take off when heavily loaded.
Dump pipe is down the back between the tail pipes.
Start dumping and add a touch of afterburn and it all lights up.
Most spectacular.
Flame front never quite catches up with aircraft.
The afterburner fuel pump/s pump out the fuel at a very high rate cause you want to be rid of a lot of weight in a big hurry if you lose an engine after take off when heavily loaded.
Join Date: Dec 2003
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What happens on teh gorund?
I was on a Tristar once that dumped a lot of fuel after leaving ASI bound for MPA.
Wondered at the time what happened to the fuel on the ground - or in our case sea?
I guess aviation fuel is very light. Does it form a slick? If over land does a mist of fuel descend or is it dispersed before getting that far down?
Dan
PS Landed back on ASI - plane was well broken and we spent a nice few days in the sun drinking Castle Lager, looking at turtles and climbing Green Mountain.
Wondered at the time what happened to the fuel on the ground - or in our case sea?
I guess aviation fuel is very light. Does it form a slick? If over land does a mist of fuel descend or is it dispersed before getting that far down?
Dan
PS Landed back on ASI - plane was well broken and we spent a nice few days in the sun drinking Castle Lager, looking at turtles and climbing Green Mountain.
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UK Regs
In the UK we say that fuel dumping should be over 10,000' agl and over the sea if possible, so it all evaporates. In extremis, it can be dumped above 7,000'agl in winter and 4,000'agl in summer. The powers that be have decided that this is high enough that none of it reaches the ground.
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The Airbus books say that dumping can be performed in any config. and at any altitude but they recommend above 5,000 agl to give it a chance to evaporate/disperse before hitting the ground.
Prof. Airport Engineer
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Most of the Low Cost airlines with the NG Boeing 737 models have an in-tank pickup system connecting through to the rear galley. This is Boeing fitted option XLG4044 and is not available for after-market fit. In the floor below the galley and under the forward oven is located an actived carbon unit for filtration - the access hatch for carbon loading is just in front of the oven unit. For carriers with a polished floor in the rear galley, it is easily seen as the 300mm x 250mm access hatch. Other carriers have it below the carpet. The unit is pressurised and can filter the fuel under pressure at high flow rates. The unit separates the low aromatics from the high aromatic alcohols in the fuel, and the low aromatics (which are very watery after processing) are piped to the rear toilets which start to flush continuously. The airline then sells the high aromatic processed alcohols to the passengers on a user pays basis. In CAA trials, a high density 737-800 with 177 seats was filled with Scottish football supporters and flown at an altitude of 6,000 feet. The trial started and the system was able to process/dump 4,000 litres of Jet A1 fuel within 41 minutes. It took a further 18 minutes to complete serving the high aromatic alcohol to the passengers, and 9 minutes to run the low aromatic waste through the toilet flush systems. Although since the aircraft was below maximum emergency landing weight after the 41 minute mark, it was able to approach and land during the serving and toilet operation. The airline then discharged the 177 Scottish football supporters, each having drunk on average 6.7 litres of alcohol, into the British Airways lounge at Terminal 4, emptied the toilet tanks onto the apron, and then flew back to Australia.
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"I think Air Traffic try and place the aircraft over the sea if nearby but otherwise overland."
Hmmm... Just a quick thought. I wonder if it's the pilots who "...try and place the aircraft over the sea"?
Only, they are the people who are flying it aren't they, or has that fly-by-internet got ahead of me?
Hmmm... Just a quick thought. I wonder if it's the pilots who "...try and place the aircraft over the sea"?
Only, they are the people who are flying it aren't they, or has that fly-by-internet got ahead of me?
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And the phones at the airport still run hot on those nice cool humid days when aircraft are producing nice contrails in their vortices on final approach - "They're dumping fuel on approach again!"
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Fuel Dump
Maybe this should be on the F4 thread, but here goes - if you selected wing fuel dump on (about 4000lb, as I recall) and then pulled a large amount of AOA (no figures, that's incriminating), the fuel dump trail would wrap up forward over the upper surface of the wing and in front of the leading edge. Very pretty, but a little impractical.... 
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In a similar vein, I love the look of horror on peoples faces when an airliner on take off creates "lift vortices" around the engine - particularly prevalent in 777's and 737's. I heard one person on board once proclaim that we had a mass of smoke coming out of the wing! 
What is the correct term for lift-induced vortices? Especially those around engine pods etc where it seems most prevalent. I know the high AoA creates the lower pressure, forming the cloud etc, but why so prominant around the nacelles? is it more disrupted air? Or is it the engine nacelle strake forming a wake-turbulence type corkscrew vortex from it's tip?
What is the correct term for lift-induced vortices? Especially those around engine pods etc where it seems most prevalent. I know the high AoA creates the lower pressure, forming the cloud etc, but why so prominant around the nacelles? is it more disrupted air? Or is it the engine nacelle strake forming a wake-turbulence type corkscrew vortex from it's tip?
