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.