Originally Posted by
Bleve
Not necessarily. I'm not familiar with the RJ fuel system, but on just about every aircraft I've flown fuel is normally drawn from the top of a standpipe with sits above the bottom of the tank. When the fuel level drops below the standpipe, fuel is then drawn from the bottom of the tank.
I don't believe this is EVER true. When the fuel level drops below the level of the "standpipe", the fuel STOPS FLOWING! There is no switch-over to another, lower feed. That's the definition of "unusable fuel".