keeping the header full

I’d like to get some opinions regarding a safe, simple, and user friendly fuel system. I have an aerobatic plane with three tanks, a header and two wing tanks. I would like to design the system such that the engine only draws from the header. During cross-country flight I’ll need to use a transfer pump to fill the header from the wing tanks. Ideally, I’d like to flip a switch and have the pump cycle automatically at the appropriate time to keep the header within a certain range. I could figure this out easily enough with a float type switch in the header, but I’d like to eliminate all moving parts from the header. Can I use a capacitive level sensor to do the job?

Thanks,

Aaron

I am assuming you have a low wing.The Aircupe has an engine driven fuel pump that continuously fills the header tank. The header tank overflows back into the wing tanks. The header tank gravity feeds the engine. The header tank has a float and wire fuel gauge that tells the pilot when fuel pump is not working.
Joe

I think you still will need a fuel selector of some sort. The aerobatic fuel pickup in the header is a flop tube. Even when working properly the flop tube cannot reach all the fuel in the tank thus leaving you with a fairly large amount of unusable fuel for cross country work. And flop tubes have a nasty habit of breaking off from time to time. When that happens you may only be able to use half the fuel in the header. My Stephen's has a fuel selector to to switch between the aerobatic pickup in the header that is built into the tank and a pickup at the very bottom of the tank. If you use a transfer pump, especially in combination with an electronic fuel level sensor, I'd recommend plumbing for a direct feed from the wing tanks as a backup.

I like the idea of the selector for the bottom of the header, it’s something that I’ve already incorporated into my design.

Can anyone tell me the best way to allow a capacitance fuel probe to control a fuel pump?

A capacitance fuel probe would not be a very good sensor to control a fuel pump. The fuel will be sloshing around and you will get wild readings. Of course, you could filter the readings and go from there but that's a lot of work and expense for the circuitry. There are infra-red detectors used as low fuel detectors that are useful to flash a light when a certain fuel state is reached. You might want to adapt one of these.

But Joe Fisher's suggestion up top is the best; just keep the pump running to keep the header tank full with overflow returning to the wings.... Simple is always better!

Blue skies,

Tom

I agree with the simplicity of just keeping the pump running, and letting it overflow into the wing tank. It’s really so simple that I’m embarrassed to have not thought of it.

It’s probably the route I’ll go, but just to educate myself I’d like to look into other options. If an infra red detector can trigger a light, it can also be made to control a relay and a pump. Do you have a brand or source that you could point me to?

Also, I don’t think that slosh will be a huge deal, as the pump will only be on during cross countries. The wing tanks will be empty for serious acro.

Aaron

Here is one type (although I did not use it).

http://www.aircraftspruce.com/pdf/20...l/Cat09433.pdf