wrote in message
ups.com...
Please tell me, Jim, what's wrong with insisting that the caps
aren't supposed to allow air out of the tank (except at high pressures
as a safety release) and thereby upset the pressure balance between
them and allow fuel to cross over in flight, which often leads to fuel
loss in flight?

Dan

I'm not Jim, but the point that he, Newps, and I are trying to make is that
the pressure imbalance is not so much caused by the caps as it is evidenced
by them. The under-wing vent tube is the primary culprit, a very large
percentage of the time. The fuel flow imbalance would exist even if it were
not able to vent out the right cap.

You are also ignoring the fact that the inter-tank vent tube contains fuel
for quite a while, due to the shape of the tanks and the dihedral of the
wings.