Fuel Sight Tube Question

[PAgyropilot]

I've seen a few clear fuel site tubes with the orange floatee in them, on the masts of RAF 2000s with 130hp engines. Does anyone have any experience (or simply good input) on a similar type sight tube on an RAF 2000 (or any gyro) with a fuel injected engine? I was wondering if the little floatee, or air, may be sucked into the fuel system when the fuel level was low, because the fuel flow rate is a lot higher on a fuel injected engine, even though much of it is returned to the engine, and that higher fuel flow rate might create a suction from the sight tube. It may be a dumb question, but it never hurts to get experienced input. Thanks.
- Baron

 

[Vance]

I've seen a few clear fuel site tubes with the orange floatee in them, on the masts of RAF 2000s with 130hp engines. Does anyone have any experience (or simply good input) on a similar type sight tube on an RAF 2000 (or any gyro) with a fuel injected engine? I was wondering if the little floatee, or air, may be sucked into the fuel system when the fuel level was low, because the fuel flow rate is a lot higher on a fuel injected engine, even though much of it is returned to the engine, and that higher fuel flow rate might create a suction from the sight tube. It may be a dumb question, but it never hurts to get experienced input. Thanks.
- Baron

The sight tubes I have seen on RAFs were not connected to anything but the tank.

The fittings kept the floating ball from exiting the tube and the tube could be calibrated by filling the tank a gallon at a time.

In my experience some clear plastic tubing quickly turns brittle and yellow with some fuel additives so the selection of the tubing and maintenance is important.

 

[PAgyropilot]

The sight tubes I have seen on RAFs were not connected to anything but the tank.

The fittings kept the floating ball from exiting the tube and the tube could be calibrated by filling the tank a gallon at a time.

In my experience some clear plastic tubing quickly turns brittle and yellow with some fuel additives so the selection of the tubing and maintenance is important.

Thank you for your reply, Vance. I hadn't looked carefully, and I'm sure you are correct, that the tubes were connected directly to the tanks. That would preclude the problem that concerned me.

Baron

 

[wolfy]

A mates gyro has a fuel injected subaru and his fuel level in his sight tube gets sucked down I think about 2-3 inches (if my memory is right) when running. But I think his sight tube is on the suction line to the engine on a T piece under the tank.
If he sees this I am sure he will clarify.

wolfy