Sump Tank Modifications v3

The fuel selector valve will select which fuel tank (or aux tank) delivers fuel to the sump tank. I decided to add a 1/2″ inlet to the sump tank, level with the fuel selector valve, which will now be the fuel inlet. This required cutting a hole in the back of the sump tank and adding a new hard point. The rear cutout was glued back in place with floxxy-poxy and leak-checked.

I will use one of the existing fittings in the upper corners of the sump tank for fuel return from the engine fuel servo, and simply cap the other one. I added an emergency shutoff ball valve on the fuel feed line to the engine.

Fuel Selector Valve and Linkage

Based on the results of the previous fuel selector valve tests, I made the decision to put the fuel selector valve between the whale tail and the landing gear bulkhead, just above the MLG pulleys and between the right and left brake hydraulic lines.

The Andair valve I purchased (Right, Left, Off, and Aux) has four 1/2″ ports, and orientation is important for the fuel lines and for the shaft linkage. I fabricated an aluminum sheet metal mount that will mount to the landing gear bulkhead. The valve position is slightly right of center because the shaft runs in the right side of the keel.

I calculated that even a steel 1/4″ diameter shaft of the required length would have too much torsional deflection, so I opted to make the shaft from 3/8″ aluminum. The estimated torsional deflection is about 3 degrees. The tank selector is mounted just below the instrument panel, accessible by both pilot and copilot. From there, a shaft runs down to a 90 degree gearbox, and then the shaft runs aft all the way the the whale tail, supported by oillite bushings. A u-joint directs the shaft up to the selector valve.

It is pretty busy in this area with the battery and solenoids, hydraulic pump, brake lines, MLG retraction cables, and fuel selector valve. I still have to route the landing gear hydraulic lines and a cable conduit in the keel, so it will get even tighter.