I designed the layout of the fuel system. I think it's pretty standard and straight forward.
I may not need check valves in the system if the pumps have this feature built in. Check valves (of some sort) are an important part of a two pump delivery system; because, without them, gas (may) be pumped around in a circle and not correctly pressurize the separate branches of fuel system.
I was wondering about fuel a “return” system, but Ellison fuel injection systems Inc DOES NOT recommend them for aircraft applications, except as a last resort for vapor lock prone systems. They do recommend insulating your lines and locating the fuel pump near the tank, away from the engine. This prevents about 95% of vaporizing problems. That will be easy to do in my gyro. My fuel pump will be under the seat, and under the fuel tanks.
In my design, I have my seat tanks with ¼ ID gas line, and my Aux tank has 3/8. So I will have to have a reducer before the fuel selector valve. I have a 3 position 4 port selector valve. This valve has all ¼ ports. ¼ ID gas line provides ample size for a 150 HP engine. It’s not uncommon to see dirt track racing cars (midgets) with 5/16” ID line with 250HP engines. I can easily flow 30GPH thru a ¼ ID line, and I am not going more than about 6 feet from tanks to engine.
In my system, the left and right tanks are full gravity feed through the selector valve, gascolator and to the fuel pump. The center Aux tank will have about a 1 foot rise from the tank outlet up to the selector valve, but then it’s downhill to the gascolator, and electric fuel pump. So even the aux tank will naturally siphon once gas is in the line… naturally siphon down to the fuel pump. From the fuel pump, it will be about 2 to 3 feet rise up to the engine.
Also somewhere in here, I will have a pressure gauge probably on the manifold at the engine, and also a fuel flow sensor that will send my GPH data to the instrument panel.
The fuel line will be 98% aluminum tubing, but will have very small sections of flexible gas tubing to allow for flex and vibration damping. The flex sections will literally be less than ¼ gaps between the aluminum sections, to prevent collapse under suction. Fuel line collapse under suction is probably not likely, but I just don’t want to take the chance.