FUEL PUMS - Boeing and Airbus. Is it working correctly?

1st Official Post

    Hi just little help to understand :)

    If I turn OFF all the fuel pumps, the engines, if they are already running, should turn off? But they still work.

    Or if I don't turn ON the fuel pumps at all. How is it possible that I can still start the engines? (Without the fuel pums ON)


    From my point of view the APU bleed works correctly. Without APU you can not really start the engines, but without FUEL PUMS ON you can?

    In X-plane, you can not start the engines without PUMS ON, or let the engines running, when you set PUMS OFF.


    Please explain :) Thank you

    • Official Post

    Fuel flows through gravity if the fuel pumps are off. Inside each engine and in the APU there is a separate high pressure fuel pump which can suck fuel as well to a certain extent. So it's realistic that engines can be started and keep running with the fuel pumps off in aircraft where the engines are hanging below the wing.

    Fuel pumps in the wings serve the purpose of delivering fuel under higher pressure so that there is no vacuum created in the fuel lines where air bubbles could form. This could cause cavitation and damages to important parts and could also impact a stable fuel supply. They are also very important to keep the engine running in turbulence as there may be periods of negative g-load where the engine might otherwise flame out due to temporary lack of fuel.

    Quote from PilotHaus

    Thank you so much for this. I keep in mind.

    I only have a small postscript. Do you have any idea why the x plane simulator has it so that you can't start the engines without FUEL PUMS ON?

    Anyway thank you so much! I appreciate your work:thumbup:

    At the moment in order to switch off engines on the aircraft,Take an Airbus A320 for example,are the engine 1 and 2 master switch or engine ignition switch set to off.

    • Official Post
    Quote from Max.M

    Would IPACS consider adding this feature? It sounds cool but I understand its too insignificant.

    By design the fuel pumps inside the wing can supply fuel even under negative g load for several seconds (I think it was 10 seconds). So it would be quite difficult to achieve during flight actually and thus it's very rare. But knowing our users it would not be unheard of to fly an airliner inverted...

    If we implement the fuel system and fuel mass like we plan to then the natural fuel flow under acceleration ("gravity flow" during normal flight) would be natively simulated.