Thorp Air Command - T18.net

The guys that have the wings tanks would have the right answer "behind door number 2 !" My guess would be when the main tank fuel level goes from "Full" toward "MT ?" Another option if you want a light to make the arse dry is a Low Fuel Level Sensor from www.aircraftextras.com .

RB

Easier than that. We use a float switch that turns on a light when the tank is empty. Get em from Aircraft Spruce. My main tank is rigged with another float switch to cut the relay off to the pumps so it won't overfill. My relay is set with a 3 second delay so it won't cycle in rough air. In practice, I climb to altitude on the main, level off, switch on the aux pumps, and run 'til the lights come on, then turn off the pumps and continue on the main. When the wings run dry, I have two hours plus reserve remaining. My aux wing tanks feed into the top of the main to prevent syphoning back into the wings.

_________________
Bob Highley
N711SH
SN 835
KLAL

I like easy .

RB

I second Bob on his fuel pumps ,lights ,float switches. I don't have the delay type relay, its been working for 25 years.

I had the same question a few years ago about the wing tanks in my flying plane. Bob and Bill's system is the way to go, but I didn't want to cut into anything in order to install the parts. So, I went with this method:

I have a "red cube" installed which tells my Dynon D120 about fuel flow and fuel level in the main tank. There is also a fuel float sender in my main tank that tells my Dynon D120 about the fuel level in my main tank. When my main tank gets to 10 gallons (according to red cube reading), I turn on my wing tank pump which pumps at the rate of 0.5 gallons per minute. So, I set my primary flight display timer for 32 minutes (16 gallons of wing aux fuel). Once the timer goes off, I turn off my aux fuel pump. I verify the fuel made it to the main tank by reference to the fuel level as indicated by the fuel float sender (not the fuel level as calculated by the red cube). When I fill up my main tank, its never more than 1 gallon off from what my "red cube" fuel level reads, even after filling the main tanks with the aux wing fuel.

Like I said Bob/Bills system is the way to go, but you can do it with a watch.