"Jay" wrote in message om...
For a low wing aircraft with dual wing tanks, what is the point of
having a fuel selector valve. It seems to be a source of some fuel
exhaustion caused accidents. Wouldn't it just be easier to feed off
both simultaniously?

Because there's a fuel pump involved. If one tank goes dry, the pump
sucks air. Easy experiment. Grab two straws. Stick one in a glass of
water and let the other one stay outside the glass and try to drink from
them.

There are a few low wing planes with "BOTH" positions on the selector, but
they drain to a common tank and the pump draws singly from there.