All pumps off but engines running at full power...This isn´t realistic or is it :-eek ?

Sorry Paul,this is realistic :-)In case of fuel pump pressure is lost, each engine is able to suction fuel from it

thx 4 the info quite amazing that it even works will full thrustbut are those pumps the same as the ones you can turn on /off on your overhead or are they seperate ones that cant be controlled by the flightcrew?

"It

The engines have engine driven fuel boost pumps too. As the description indicates, these pumps are bolted directly to the engine. Any time the engine is turning; these pumps turn too . . . and make pressure. You have no control here. The purpose of these pumps is to increase the fuel's pressure before it

Great explanation, Sam! Loved it. One question: in normal condition, all tanks are connected to all engines, right? So is this connection thtough the Tank Boost Pumps? And when they are OFF, the engine driven pump (+ gravity, I suppose) will allow head pressure to develop because other pumps are off and blocked? Obviously this will allow only 1 tank to be connected to the engine.- Neeraj

Excellent. We

wow I didnt want it that exactly but thx anywaynow I know much more about the fuel system.Much appreciated

Sam et al,My take on how to get the fuel pass the pumps.It's probably a rotodynamic pump, and if so there is really nothing to prevent the fuel to flow around the impeller. Think of a bow propeller on a big ship. If the propeller wasn't used, would the water flow around the blades or not?Only if the pump was of a displacement type would be have to have a bypass of some sort. But having a displacement pump on a modern jet does not make any sense.Hope it helps,

I've been told that some fuel will leak through the pumps (to be confirmed), but there are completely separate pick up points/plumbing for gravity/suction feed which bypass the tank pumps completely. Check valves keep the bypass system closed when the tank pumps are operating.Note that you don't want a vacuum being created in the tanks when the fuel is being sucked out of them. A small positive pressure is maintained in the tanks by the naca scoops underneath each wing and the vent system.Hope this helps.Cheers.Q>