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SCHEMATIC DRAWING OF THE FUEL TANK SELECTOR VALVES

One more thing is the fact that a mechanical fuel valve must be installed in the cockpit to be accessible, and that means that fuel and the potential for fuel leakage has been brought right into the living quarters. The compartment behind the seats is not that far away, but at least it is better than actually IN the cockpit.

MECHANICAL FUEL PUMP FITTINGS AND CLEARANCES
A special elbow is required to plumb the mechanical fuel pump on an 0-320 to the carburetor on a Glass Goose. The space available to route the line from the pump to the carburetor or anywhere else for that matter is very limited in that area. The outlet of the pump must be directed down along the back of the shear web of the wing and into the engine compartment. There is no other route available. A normal elbow is too short to reach to the aft side of the shear web, and the fitting on the fuel pump does not have normal pipe threads but special aircraft fitting threads, so a special elbow must be used.

The connector is an AN833 "bulkhead elbow" and it is used with an AN894 "nut". The nut fits the threads on the fitting. The AN833 elbow has a normal male aircraft flare fitting on one side but on the other side it has an "extended" flare fitting. That is, it is longer on that side and has twice as much thread area! Also, in the middle of those threads is groove cut all the way around the fitting.

 That groove is used to hold an O-ring which, is actually the part that seals the fitting so it doesn’t leak fuel. This fitting and the nut are pictured in the ACS catalog.

First, install the nut on the long side of the fitting. The nut will have a "land" or "groove" turned on one side. That side will need to be towards the end of the side of the fitting you are screwing it onto (the "outside"). Screw the nut all the way down on that side. As you do so, the nut will screw past the "groove" in the threads and the land on the nut will be toward the groove. Now slip the O-ring over the end of the AN833 fitting and down into the groove. Now, the fitting can be screwed into the fuel pump outlet. You will see that there is also a "land" to accept the O-ring around the perimeter (edge) of the fuel pump outlet. Screw the fitting in until the O-ring is just touching the land in the fuel pump. You should be able to screw the fitting so that it is pointing straight down as it will need to be without violating
GLASS GOOSE GAZETTE * ISSUE #18, April, 2001
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