Fuel tank fails to feed

[astjp2]

Re: Fuel tank fails to feed

I guess my point is that there is less than 2 psi of differential pressure between the wing and header tank. Not much pressure and at most a 3/8" diameter line does not equal much ability to flow at a high rate of pressure or volume. If the header tank does not have sufficient outflow, the wing tank will find it harder to drain also at these low pressures. Tim

[Guest]

Re: Fuel tank fails to feed

No disagreement Tim, you just got me thinking about it :-)

Dave

[astjp2]

Re: Fuel tank fails to feed

No disagreement Tim, you just got me thinking about it :-)

Dave

[Hank Jarrett]

Re: Fuel tank fails to feed

If we show the fuel system is tight with no leaks around the wing cap and the vent tubes are open and clear the difference must be the pressure on top of the main fuel and on top of the wing fuel. If the pressure in the main tank is higher than the wing tank, fuel is NOT going to flow.

The way to test this is with a manometer. You run a piece of aquarium tube to the side of the main and wing fuel tank filler area with some colored water in a loop with a clamp on the tube. The orientation and direction of the tube ends is critical and needs to be normal to the local flow to work. When you open the clamp the water should flow immediately from the wing end and out the main end. If it happens fast you will know by the water on the windshield. If it flows from the main to the wing there is more pressure at the main cap and you have to overcome that pressure with the head pressure from the height of the fuel in the wing, which is NOT that much.

If you have a restriction in the fuel line anywhere or the tube is too small the condition will be worse. If you fill the wing and main and there is air in the line between them it will be hard to get the flow started regardless of the pressures.

Hank

[Forrest Barber]

Re: Fuel tank fails to feed

My brain is still catching up We will use this discussion at the fly-in this year....