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Newps wrote:
G Farris wrote:



I have heard that the left tank becomes slightly pressurized, due to
the
forward-facing vent on that tank, which is why it drains faster than
the
other. I do not claim this to be a fact - just something I've heard.

The left tank becomes pressurized because the vent tube is slightly out
of rig. It's supposed to be directly behind the strut. If it gets a
clear view of the incoming slipstream it forces a lot more air into the
tank. That forces fuel from the left to the right tank via the vent
line above the headliner in the cockpit. You will never solve the
problem until the vent tube under the left wing is positioned correctly
and then you only mitigate the problem to a certain degree.

Seems to be a popular misconception as to how that fuel gets
across to the other side.

(Snip)

Dan, your explanation is theoretically correct, but Newps wrote from
experience. With an incorrectly located vent, and both tanks full, fuel is
forced from left to right. The right tank stays full, and usually dumps
fuel out through the cap, which has a vent that opens both positive and
negative (Monarch caps, at any rate). Ram air pressure continues to force
fuel to the right side, until the left tank empties. The indicator for this
is when the right fuel gauge stays put, and the left goes rapidly toward
empty. Fuel running off the right flap in flight is another hint.

That's how my 182 managed to "burn" 32 gallons/hr on one leg of a long
trip.

Cessna fixed the problem in later years by adding a vent behind the right
strut. For the single vent planes, the location is so critical that it is
specified to the hundredth of an inch. That precision is related to
airflow, not ice.