unported flop tube

Does your flop tube have a weight on the end? (it should have)

Is it flexible enough? Was the tube that you used new when you put it
in? (if not, old tubes are stiffer than new ones) Stiff is NOT good.

Was it specified for Avgas? (Some rubber will harden and thus stiffen
when submerged in avgas, so you need to make sure that it is the
correct compound). Remember, Stiff is NOT good.

Was the flop tube the correct length as specified for your aircraft?
(if it is too short that will happen) Also too long is not a good idea
either. Does it reach all areas of the tank?

Is your flop tube and weight still properly attached?

Did you use sealer on the connections? Some times if you did not seal
the connections and the connections are not submerged, theoretically
at least, air could get into the fuel line this way and cause problems.
I have never heard of this happening however, but others may have more
information.

Another thought, is the fuel venting system in your airplane correct,
or plugged when inverted? It may not even be the flop tube. How is
your system vented when inverted? If not properly vented, this will
also cause starvation.

In my Eagle fuel quantity does matter, in vertical maneuvers at least,
For a Hammer head I need at least 6.5 gals of fuel, or it will
unport. In my airplane that is okay, because that is the fuel level I
should be heading for the airport anyway. Have you tried to determine
how much fuel you need to have to avoid this problem?

In inverted flight I have never had it unport.

See our website www.gut-works.com

Call if we can help.

Keep the dirty side up, and the clean side down.

Ron



jasonlee wrote:
A possible fix would be to keep the tube submerged at all times by,
making the tube mobile or attaching a float at its end to keep it
where it should,
another solution may be , and dont trust me here , test it first, to
make the tube double ended so one end would always be submerged.
a third solution may be to mount the end of the tube so that it
pivots and follows the fuel all this time being submerged.

This you will have to engineer yourself.