Van's Air Force
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2 RV7A POH Questions
- Thread starter Tcheairs
- Start date
1. Incase the mechanical pump fails on takeoff, you may not have time to troubleshoot and restore power.. using the electrical pump means you have your backup already on. Note, for those that fly fuel injected Continental engines such as Bonanzas, the Lycoming can run both mechanical AND electric pumps together without flooding out.. Continentals don’t like both pumps on, as the mechanical combined with the electric pump are too much and have caused flooded out engines and even accidents.
2 some purple shut their fuel selector to prevent a leak from ending up on the hangar floor.. perhaps an older carb with a worn needle and seat or sunk float could leak fuel.. I personally don’t do it and never had a problem..
2 some purple shut their fuel selector to prevent a leak from ending up on the hangar floor.. perhaps an older carb with a worn needle and seat or sunk float could leak fuel.. I personally don’t do it and never had a problem..
Fuel selector off is for two reasons...
One, if the fuel system downstream has a leak, your fuel will leak out on the floor. Less of an issue on tailwheel models, more for a tricycle gear with full tanks i'd guess.
Two, if some looky-loo spins your prop when it's parked, and the mags happen to be left on by accident, if the fuel is "off" it can only run for so long before it stops. If it's on, it could run until the tank is empty or the plane hits something or someone.
Lots of "ifs" have to line up for Two to happen, but turning fuel off is easy and doesn't hurt anything.
One, if the fuel system downstream has a leak, your fuel will leak out on the floor. Less of an issue on tailwheel models, more for a tricycle gear with full tanks i'd guess.
Two, if some looky-loo spins your prop when it's parked, and the mags happen to be left on by accident, if the fuel is "off" it can only run for so long before it stops. If it's on, it could run until the tank is empty or the plane hits something or someone.
Lots of "ifs" have to line up for Two to happen, but turning fuel off is easy and doesn't hurt anything.
I vote NOT putting the Fuel Selector in the OFF position.
If there's a leak, I'd rather know about it than hide it. I think the idea of using it to limit the injuries and damage from an inadvertent engine start by a bystander is locking the barn door after the horse has bolted.
Leave it where it was when you shut down and move on.
If there's a leak, I'd rather know about it than hide it. I think the idea of using it to limit the injuries and damage from an inadvertent engine start by a bystander is locking the barn door after the horse has bolted.
Leave it where it was when you shut down and move on.
PilotjohnS
Well Known Member
fuel selector
I leave the fuel selector on for two reasons:
1) If I forget to select the tank during preflight/ runup, I wont die when the engine quits 50 feet up.
2) less wear on the orings. there is enough wear already switching tanks in flight, dont need to add to it. JMHO
I leave the fuel selector on for two reasons:
1) If I forget to select the tank during preflight/ runup, I wont die when the engine quits 50 feet up.
2) less wear on the orings. there is enough wear already switching tanks in flight, dont need to add to it. JMHO
Desert Rat
Well Known Member
It's pretty hard to imagine that you could run long enough to get in the air with the fuel turned off on an airplane without a header tank. If it's carbureted you just have what's in the float bowl, if it's fuel injected you have less than that.
I actually ran some calculations recently. At 8 GPH and a typical -6AN fuel line, I believe approx 7" of fuel is used per second. Given the length of tubing from tank selector to carb, that's an awful lot of seconds of run time. I definitely don't buy the idea that the purpose of OFF is to protect bystanders in case of an inadvertent engine start.
I actually wonder if the practice is a holdover from training in a Cessna, where the tanks can cross-feed. At my flight school, we parked the Cessna's on a hill, so we put the tank selector in any position other than BOTH to prevent that.
I actually wonder if the practice is a holdover from training in a Cessna, where the tanks can cross-feed. At my flight school, we parked the Cessna's on a hill, so we put the tank selector in any position other than BOTH to prevent that.
Desert Rat
Well Known Member
Yeah, Cessnas will do that for sure. The fuel injected ones will also gravity feed and start to drip if you have an oopsie and don't get the mixture 100% in idle cutoff. The carbureted ones are less prone to that unless the needle and seat are worn out.
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Of course. I hadn't thought about the suction that would get created if the selector was an off position and the engine was trying to run. Yeah my 7"/sec figure probably doesn't apply here.
Overall advice: Treat every propeller like it could start spinning at any moment. And if you don't have time to do a pre-takeoff checklist, then don't takeoff.
Overall advice: Treat every propeller like it could start spinning at any moment. And if you don't have time to do a pre-takeoff checklist, then don't takeoff.
