MAINTENANCE ITEM 11

*** FUEL TANK SELECTION ***

By Lee Beery

Although -this is not a maintenance item it was a concern that several people expressed at our last meetinq. — Will the engine continue to run when all fuel is gone from let's say the right tank (both fuel shut off valves are open) and the left tank is still 1/4 full? The concern was that the engine driven fuel pump would just pull air from the right tank rather than fuel from the left tank. At that time, I could not say for certain that would not be the case, so I did a test of this condition and here are my findings.

With one gallon of fuel in the right tank and ten gallons in the left tank, I flew around our airport at 5,500 AGL, closed the left tank S/O valve and very shortly the engine power went to -0- as did the fuel pressure. I opened the left tank S/O valve and within 15 seconds fuel pressure was normal and the engine power returned. Again I turned off the left tank and in 30 seconds the engine lost power. I opened the left tank and the power returned. Then I repeated this procedure while in a left turn and the power return took about 45 seconds. At no time did I close the S/O valve to the empty tank nor did I switch on the fuel emergency pump. Based on what I experienced, if I was not sure which tank was supplying the fuel, I would be inclined to leave both valves open.