Fuel Selector Off

[Chief]

When you park your plane in the hangar, do you turn your fuel selector "off", or do you leave it on a selected tank?

[aerofarm]

I always turn mine off. It became habit when I had a couple leaking tanks to help keep fuel smell out of cabin. Don't know if it helped, just always did it. Now with new tanks, I still do.

Nate

[Jay]

I leave mine on the main tanks. Yes, I check the fuel selectors when I start the engine and again before takeoff, but I've always felt that turning them off is setting myself up for a potential problem. If they start leaking, then the answer is to get them fixed.

Jay

[Chief]

Thanks, not sure my tanks are leaking, I see no visible leaks, but you get the smell for sure. May be my selector leaking a little. It's not a big deal. Just curious.

[Ray B]

You should be able to see the stain if the fuel selector is leaking. Remember the tanks usually go bad top side first, so fuel fumes can get to the cabin and no sign of a leak on the belly. That's what happened to my left main. (And it was only 35 years old!----I've got to look at that warranty policy again!) I leave mine on. Ray B

[Chief]

Good point, thanks Ray

[Ben Ayalon]

It is on 'Off' when the engine is not turning.

Ben

[Ray B]

Hi Ben, We're talking old singles, not you modern twin types. Engine or master SW on or off has no effect on our fuel selector. Ray B

[Ben Ayalon]

Hi Ray
I am also talking old singles. The fuel selector On or Off has a great effect on the engine running or not running .
I always turn the selector off after shutting down, a very simple and effective safety action that will stop the engine from firing up if someone plays with the engine. I will agree if you say that the O/IO-540 is a bit hard to swing but smaller engines are not. So since my airforce days I just made an habit of it.

All the best

Ben

[Ray B]

Ah, but then there's that float bowl full of gas if you left the mags hot. I did turn the fuel off in my old Stearman for two reasons, if the primer leaked it could puddle in an intake tube (#8 I think) and do bad things to the connecting rod on start up under just the right circumstances, and sometimes the carb dripped for no good reason (same thing on my old C-170). But the low wing tanks negate those problems. The military even turned the oil tank off at hight on many trainers. After many first morning flight engine freeze ups civilian registration required removal of the oil shut off. In the end I don't think it makes much difference as long as you remember to turn it back on! Ray B

[Ben Ayalon]

Yes, there is that small amount of fuel in the float chamber but the aircraft will not chase you if you were not killed when it fired up. I agree that there should be many "if's" for the engine to fire up just by turning the prop.
Nice aircraft the Stearman, I remember them as A.G aircraft flying at ~ 300' on their way to the fields.

Ben

[Richard Muller]

Hallo ICS friends

Before I stop my engine after flight I make a Mag-Check and my students learn it from the first flight.
When anything is wrong, you can go to maintenance and you stay not on ground when you will fly away next time.
When Mag-Check is ok after landing and wrong before the next take off, you can see it’s normally no mechanical frailer, it could be a frailer by humidity.
But the greatest safety Item is, that you can see, if a magneto is hot.
Normally you stop the engine wit the mixture, so the fuel system from the mixture valve and the carburettor bowl is empty.
When you start your fuel pump before starting engine and you have a digital fuel flow meter you can see the fuel flow will start to fill the carburettor bowl an goes to zero when all is full again.
When you leave the mixture pulled and the magnetos are not hot, it is normaly not possible that the engine fires when you turn the prop.
Remember, your key of the inition switch can only removed when the ignition is off.
So I see no real reason to cut off the fuel selector switch when my fuel system is ok and there are no leakes.

Richard G. Müller

[Ray B]

Hi Richard, Next time your in the shop have one of the mechs show you a carb. and how the mixture valve works. The carb. bowl is still full of gas after the engine is shut down with the mixture pulled lean. A bump or push on the throttle will still put some gas in the intake via the accelerator pump.-----Want to know how far your plane will chase you if it fires up on a prop start and the gas selector is off (carb type engine) and no chocks no tie down? Get out on the T/W set up for 1500RPM and start the engine, (mix. rich) it might surprise you. Ray B

[Richard Muller]

Hay Ray,

You are right, the mixture metering valve works to the main nozzle.
But when the Mixture is full pulled (lean), the throttle is closed, the fuel pressure is zero, the ignition is off and you have tested that no MAG is hot, it is nearly impossible that your engines start when you turn the propeller.
If you will be absolutely on the save side, don’t touch your propeller or step aside from your plan.

Richard G. Müller

[Ray B]

We better not go any further on the safest way to park our planes. OHSA may be watching and decide the very safest would be to mandate we all remove the prop after flight! Ray B