Scott suggested that a crossover valve allows the fuel in both wings
to be pumped to the header if one Facet pump fails. That's almost true.
When the crossover valve is open, the pump draws from both sides.
When one side sucks air, it provides the lower pressure drop in the line
and the pump sucks mostly air. The pumping rate of fuel goes way down.
This is the way my present fuel system works. It will be changed.


Having redundant pumps and plumbing doesn't give access to the
wing fuel in the event of an electrical failure. To answer that situation,
my fuel system has a valve to select either wings or header. When "wings"
is selected, the fuel is drawn from a small sump between the two wings.
There is one pump from there to the header which sucks air as described
above.

-bob

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