Roger wrote:
On 28 Nov 2006 08:18:32 -0800, wrote:

Even with a certified gravity fed system I understand you can get
cross flow. Didn't the 210s have this problem when parked on an
uneven surface?

All the Cessna singles do it, both the simple 150 system that
has a tee between the two lines before the fuel enters the shutoff
valve, and the other systems that use the left-right-both-off selector
valve. They'll crossfeed in the "both" position, which is where most of
them stay most of the time. Placing the selector in the left or right
or off position will stop the crossfeeding. Shutting off a 150's valve
won't stop crossfeed.
The tanks on the Cessnas are vented together to keep pressures
as equal as possible. A cracked fuel cap gasket or broken valve vent
check valve will upset the pressure balance, especially on the right
wing tank, causing the left tank to drain sooner.
Having vents at the tips aggravates the spillage by increasing
the head pressure at the vent opening. Cessna keeps them close to the
tank's outboard wall.

Dan