Im running 4 tanks plus UAT in an aircraft im building and I was considering running a UAT to two tanks then those two tanks to another set of tanks and then running 2 vent lines out instead of a T with one vent line out. Would there be a problem with this and have you tried it? I thought 2 vent lines would alleviate the pressure of the 4 tanks. True or not? 4 tanks too much? Will the tanks still drain the same? Tell me how you set up your 4 tanks.
Thanks
Scott

That is pretty much how I would do it.........FWIW

25 ounces a minute is hell to move it'nt it?

On the P200 powered Lightning Roger has, we were able to get away with all fuel fitting being at least a 4mm diameter inside dimention.

I have not seen the tanks of a UB, but if they are using bv's insert type fuel fitting, those are .094 diameter, and therein lies probably all of your problems (I think). Air is so easy to move, but the pump is able to move fuel out of your UAT faster than your other tanks can feed it. (again, I'm guessing on the BV fuel fittings.

This site I use commonly for machining http://www.madison.k12.wi.us/toki/teched/codrills.htm indicates that .094 is 2.4 mm. A serious bottleneck, or in fluid talk "feet of head, differential pressure, etc".

Anyway, if I'm way off here, I apoligize, but certainly having dual inputs to the UAT is going to help keep it full, but if the small oriface for moving fuel is your problem, you also have to keep in mind head pressure to the pump to draw the additional lines, T's etc. Also have a harder chance of getting perfectly even draw through everything.

Anyway, the fitting was my first thought.

Two vent lines will work as far as vents go, however it's not practical if you use a taxi tank. You'd be replacing fuel in only half your tanks unless you use two taxi tanks.

One reason tanks balloon when filling is because the vent is too restrictive. Usually the most restriction is at the tee. A better idea is to use an oversized tee and an extra large line after the tee. The single line after the tee needs to be sized to flow twice as much as the individual tank lines.

I normally use 5/32" tygon to plumb my tanks. Get a 3/16" tee at your local auto parts store and force the lines onto it. After the tee use 3/16" tygon. Also if you have a fitting where it exits the fuse that also needs to be sized for 3/16" line.

Joe

seanreit:
Thanks for that link! I have been working on a Excel spread sheet with that data but was missing the lettered & numbered sizes!
Charlie

Charlie, you should know I only steel from the best of them

LOL!

Here's how I'd start. Plumb them with the biggest, smoothest bending, tubing possible. I'd say atleast 5/32", x large tygon and run them in series to the UAT. If your running a jet cat, I go to the test functions menu, up the pump voltage to 5V and completely drain the fuel system, through the fuel pump.

That JC pumps sucks, alot! If your UAT turns into a raisin and starts sucking bubbles through the filter element, then you are too restricted.

Why 5 volts? Because thats probably close to full throttle.