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hilli25

Flying without Fuelpumps on ?

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Hello, Yesterday i'm flying a short flight.I have forgotten to switch the fuelpumps on, but i have no problems with the engine.Normal Engine Start, normal Takeoff, normal Cruseflight (Level260) and normal landing.All Settings are tuned to realistic. Is this a bug or is it normaly that i can fly without switch the fuelpumps on? With best regards Stefan H.

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I think that the center tanks are on by default, did you have a full fuel load?

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the NG has an amazing feature called gravity fuel pumps..

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I'm not rated on the NG but I would think that their are 2 kind of pumps, the engine driven ones (mechanical) and electrical ones. Normally, the Engine driven ones are used in case of an electrical failures. Be careful to turn off the centre tank pumps when no more fuel in there to prevent overtemp and cavitation...and ultimately damages.

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It's not a bug, the fuel pumps are there to provide positive pressure in all situations but the engines can run on vacuum/gravity feed if they need to. One problem the FCOM mentions is the possibity of disolved air coming out from the fuel as the outside pressure reduces causing a stop of the vacuum draw of the fuel with pumps off. I tested this in FSX and they stayed running ok anyway (not sure if it is simulated)

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I think that the center tanks are on by default, did you have a full fuel load?
Hello, no i have only fuel in left and right wing tanks (2000kg each side)
It's not a bug, the fuel pumps are there to provide positive pressure in all situations but the engines can run on vacuum/gravity feed if they need to. One problem the FCOM mentions is the possibity of disolved air coming out from the fuel as the outside pressure reduces causing a stop of the vacuum draw of the fuel with pumps off. I tested this in FSX and they stayed running ok anyway (not sure if it is simulated)
OK, thanks for this information. with best regard Stefan H.

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But is there anyway to actually turn off the center tanks? So that the plane wont use fuel from center tanks.

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But is there anyway to actually turn off the center tanks? So that the plane wont use fuel from center tanks.
Turn off the centre pumps should do it but leave the other four on, the reason the centre tank usually depletes first is because the centre pumps are stronger than the main tank pumps, it was designed this way. With no serious pressure from the centre tank the main/wing tanks should deplete first, but that isn't how the aircraft is designed to be used.

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Don't wait until Center tanks are empty before you switch off Center Pumps, When the tanks get to 1,000 then turn center pumps off..

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By the way, PMDG has done this gravity feed future nicely simulated in the MD 11. When you turn off all the pumps all engines keep running. But after a short time engine number two shuts off, while 1&3 keep running. :(

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Don't wait until Center tanks are empty before you switch off Center Pumps, When the tanks get to 1,000 then turn center pumps off..
Yes, 1000 lbs, for us using metric loads that is ~454kg

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Turning off center pumps before fuel runs out doesn't work for me. Still uses center tank fuel even with pump off...

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