jonlaury(at)impulse.net Guest
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Posted: Tue Sep 12, 2006 8:48 am Post subject: Fuel Pump Switch(es)Fuel Pump Switch(es)Fuel Pump Switch(es) |
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My $.02.
Electrically dependent planes with two pumps need a dedicated switch for each pump drawing from independent power sources.
FWIW, I am using an EFI on my 6cyl Franklin in a Glasair TD and have spent a lot of hours thinking about my fuel system. As fuel starvation seems to be the most common cause of engine stoppage, and that my 58 year old ADD noggin sometimes trys to kill me, I wanted a system that was as idiot proof as possible. That meant not having to remember to switch tanks, that all fuel in the system goes to the intake of the pumps no matter what I do. All I have to remember is to turn on the pump(s) when I start the engine. I have a fool proof reminder to do that, when the engine won't start.
Fuel from my split tanks flows through one way umbrella valves to a common sump,on the bottom of the wing and at the low point of the fuel system. A header tank is also plumbed to the sump. All recirculated fuel goes back to the header with an internal overflow well that will dump the overflow back to the mains. Both pumps, (separate switches, to two batteries), pointed aft, draw from the common sump. There is no R-L selector valve, no shut off valve, as the Bosch aerotor pumps, each with a built in check valve, do not flow fuel without power and the fuel filter on the FW is higher than the sump . If I don't want fuel to flow to the engine, I turn off a switch. There is an on-off valve for the header tank so that I can allow the header to be refilled from recirculated fuel to use for landings and TO's (more head on the pump intakes), however if I forget to turn this on, and the tank fills, it will overflow back to the mains.
As long as their is fuel on board, it will flow to the pump intakes, mental incapacitation of the pilot notwithstanding.
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