Rich wrote:

Yes, I do know more is sucked out than returned. But I'm sucking from
2 tanks that are T'd & returning to only one of those tanks. Both do
have their own vented caps.

In my experience with Cessna's the tanks rarely equalize
for some strange reason.

Does the fuel line friction have anything to do with it... outboard
tank being further away?

Rich

Why are you sucking from both Rich? If you do that you might want
to consider a header tank and return the fuel to the header tank.

Paul Lamar

Pumping from two tanks connected by a T will cause one tank to
run dry and the engine to quit while the other tank has a lot of fuel
still in it.  This is why all pumped multi-tank systems have a fuel
selector.  Think about it, do you think everybody is just switching
tanks for fun?  If you drain the fuel by gravity into a VENTED
sump and pump from the sump, it will work.  Recycling fuel to the
sump may cause vapor locking on a hot day with a long taxi (like
leaving an airshow).

Please review the CD, there was much discussion of this and this
sort of stuff will get you hurt.  Slavishly copy a certified A/C fuel
system which is configured like your A/C.

Be very careful with fuel systems, they demonstrably do NOT behave
like you might think they will and people have died verifying this.

Bill
Long EZ builder & pilot
mechanical engineer

Bill, 2 tanks are in each wing. Each wing is to be connected to the
Andair fuel selector with return. The left wing tanks will NOT be 'T'd
to the right wing tanks.

Attached is a sketch.

Rich

Now I understand. TWO tanks in each wing. This is dangerous Rich. 
If one tank in one wing has its line uncovered you risk not 
feeding from that wing at all.

The outer tank should feed to the inner tank and then only
feed from the inner tank to the selector valve. Usually this is done
with a large diameter pipe between the two and a one way flapper valve that
prevents fuel from flowing from the inner tank back out to the outer tank.
Also the outer tank should be vented. Return fuel can go to both
OUTER tanks in each wing.

When you are low on fuel don't slip the airplane as you might
slip with the selected tanks down. I usually keep my fuel selector
on both and if I have any fuel in the upper wing the engine keeps
running. Naturally! If you have to think about which way you are slipping
and which wing is selected there is of course  more chance for error.

High wing Cessna's have far fewer tank selection based accidents
than a low wing system like you describe. Probably because
of the both position on the selector valve.

What would be even better is two small tanks in both inner wing
tanks with one way valves so if you slip you will have enough fuel 
to keep the engine running for a few minutes.

Paul Lamar
 
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