Redundant Fuel Systems

My Cozy Mk. IV has totally redundant fuel systems, not just two fuel tanks. Designed for safety and simplicity of operation in flight, the systems were designed to compliment the fuel injected, FADEC, UL Power UL520iS engine. Here's a no-frills description of how it works and why.

[@ScottsSynthStuff]

This is great, except...if you run a tank dry, your dual redundant fuel system now has multiple single points of failure: you're totally dependent on the remaining fuel pump, gate valve and filters all operating perfectly, with no option to revert to your redundant system. I think I would change this to utilize a common sump tank, then have the pump system selectable by the pilot. Fuel injection return could just go back to the sump, rather than a specific blister. The selector valve could select between which blister feeds the sump tank.

[@danah358]

Shouldn’t the recirculated fuel leaving the fuel injector spider or rail go to the fuel tank first for cooling, and not directly back to the fuel valve in cockpit?

[@GregoryACross]

Dana, it's necessary to first determine which tank to return the fuel to with the valve. (The valve does not determine which tank fuel comes from - the selected running fuel pump does). I have set my system up to return fuel to the blister of the side it came from. It cools in the one gallon header tank that the blister feeds.

[@danah9576]

Ok, that makes sense. One variation you could consider is making one combined 2 gal pump tank with the two feed lines to it each having a check valve. But then you lose the redundancy of bad fuel situation.

[@GregoryACross]

@@danah9576 Great minds think alike! It originally was one, two gallon tank, then I added an internal divider to make it two, one gallon tanks. One, two gallon tank would also do away with the redundancy goal of two sets of filters and pumps, too.