fuel control valve

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Tom Gordon

Filing Flight Plan
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Tom
Hello - this might be a dumb question, but maybe not. In a 1973 Cessna 172, on the fuel control valve face, if the knob is pointing at 10 or 2 (imagine a clock face), will fuel still be flowing? If so, from both tanks? Thank you -
Cessna_172_OFF-LEFT-BOTH-RIGHT.jpg
 
Welcome Tom,

Check your photo, it has an error.
 
Have somebody hold your strainer open and move your valve selector around to find out. Checking the position of my fuel valve is a pre-takeoff priority so I've not concerned about it being positioned in-between.
 
Knowing how cheesy that valve is, I can bet fuel is flowing at 10 or 2 o'clock.
However, I'd be concerned that it could get the WOT fuel flow rates out of those positions. The detents are there for a reason.
 
do yourself a favor and leave it on both and never move it .mine was set that way for 30 years .m model same as yours .just check it before the takeoff roll.use your hand and check that it is in the detent. you have no need to know the answer to your original question as it should never be 10/2 as there is no detent there. and no there will not be proper fuel flow
 
hotprops said:
do yourself a favor and leave it on both and never move it .mine was set that way for 30 years .m model same as yours .just check it before the takeoff roll.use your hand and check that it is in the detent. you have no need to know the answer to your original question as it should never be 10/2 as there is no detent there. and no there will not be proper fuel flow
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Thanks to all
 
hotprops said:
do yourself a favor and leave it on both and never move it
Click to expand...

Is that an in-flight recommendation?

On the Cardinal we ALWAYS park it on left to avoid cross feeding. I start on Left. During taxi I switch it to Right. Then when getting to the run-up area I switch it to Both and it stays there until after shutdown.

Theory is I know it's feeding from both tanks.
 
Tom Gordon said:
Hello - this might be a dumb question, but maybe not. In a 1973 Cessna 172, on the fuel control valve face, if the knob is pointing at 10 or 2 (imagine a clock face), will fuel still be flowing? If so, from both tanks? Thank you -
Cessna_172_OFF-LEFT-BOTH-RIGHT.jpg
Click to expand...

Simply put, if you can not feel that the valve is in a detente position it may cause you trouble.
 
hotprops said:
do yourself a favor and leave it on both and never move it .mine was set that way for 30 years .m model same as yours .just check it before the takeoff roll.use your hand and check that it is in the detent. you have no need to know the answer to your original question as it should never be 10/2 as there is no detent there. and no there will not be proper fuel flow
Click to expand...

Yeah I wouldn't do that.

Everything in the plane should be functional and used, even when I lived someone super hot, I still put the carb heat and cabin heat on once per flight day, just to make sure everything was OK, and keep things from getting "sticky"

The fuel selector is a huge item,
set to one tank for storage and for fueling to prevent it from getting imbalanced. Also if you ever start flying larger cessnas, you'll find they don't exactly feed fuel in a perfect 50/50 manner set to "both".
Add to that if you ever have a issue with one tank, you're going to want to isolate that tank off, and I wouldn't want that to be the type of situation I decided to see if that lever still works :)
 
pasta man it is not a cardinal ,james o course I checked it on annual. and it went 39 years without a rebuild.
 
hotprops said:
pasta man it is not a cardinal
Click to expand...

That's okay, you can look at pictures and dream of when it will be.

But for working the valve on any "high wing, gravity driven fuel system" the advice holds.

Just like changing tanks on low wing aircraft generally is the same, even though they are no where as frickin' cool as an RV. :)
 
hotprops said:
do yourself a favor and leave it on both and never move it .mine was set that way for 30 years .m model same as yours .just check it before the takeoff roll.use your hand and check that it is in the detent. you have no need to know the answer to your original question as it should never be 10/2 as there is no detent there. and no there will not be proper fuel flow
Click to expand...
Isn't there an AD for some (quite a few of them) Cessna fuel selectors that reccomends against doing that above a certian altitude in cruise flight?
 
It was AD 72-07-02 and applies to models up (and including) the 172K. You should have a placard that reads: "SWITCH TO SINGLE TANK OPERATION IMMEDIATELY UPON REACHING CRUISE ALTITUDES ABOVE 5000 FEET. "

The AD says this is to reduce the possibility of power interruption at those altitudes caused by vapor formation. The problem is where the tubing passes down the door posts. Running one tank allows it to go through their faster and remain cooler than if you run it from both sides.

The AD is terminated by installing the kit that adds vent tubes to the door posts.
 
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I've always thought about that selector on Cessnas, the design of it with those visual tick marks suggest there is some ability to blend L, R, both. I would not try it, nor suggest it, but the OPs question is legit. I also have thought about going to R only in the Skyhawk at cruise to balance out the faster consumption in L but was afraid to touch it in the rentals to be frank. @Ravioli I like the idea of start, taxi, and run-up on L, R, and both to make sure all feed!
 
Ravioli said:
Is that an in-flight recommendation?

On the Cardinal we ALWAYS park it on left to avoid cross feeding. I start on Left. During taxi I switch it to Right. Then when getting to the run-up area I switch it to Both and it stays there until after shutdown.

Theory is I know it's feeding from both tanks.
Click to expand...

And on most 182s, you can try setting it to left or right not to crossfeed, and it'll crossfeed via the upper vent tube that runs between the tanks, anyway, any time the tanks are full far enough to put the fuel level above the tube. :)
 
denverpilot said:
And on most 182s, you can try setting it to left or right not to crossfeed, and it'll crossfeed via the upper vent tube that runs between the tanks, anyway, any time the tanks are full far enough to put the fuel level above the tube. :)
Click to expand...

Same for the 172's. If the tanks are more than 3/4 or so full, the fuel selector is only a suggestion as to what tank will drain down.
 
flyingron said:
the fuel selector is only a suggestion as to what tank will drain down
Click to expand...
This always kind of bothered me. Being able to have a "both" feed is great and one less thing to worry about with switching tanks.. but in the case of fuel contamination, etc., it would be nice to be able to directly pull off the intended tank
 
flyingron said:
It was AD 72-07-02 and applies to models up (and including) the 172K. You should have a placard that reads: "SWITCH TO SINGLE TANK OPERATION IMMEDIATELY UPON REACHING CRUISE ALTITUDES ABOVE 5000 FEET. "

The AD says this is to reduce the possibility of power interruption at those altitudes caused by vapor formation. The problem is where the tubing passes down the door posts. Running one tank allows it to go through their faster and remain cooler than if you run it from both sides.

The AD is terminated by installing the kit that adds vent tubes to the door posts.
Click to expand...

Not the cooling so much. If the fuel in the tank sloshes around enough an air bubble can get into the fuel line. It will try to travel back up the line to the tank, but the fuel flow will try to keep it from doing so, and with the bubble in the way, the fuel has to squeeze around it. The bubble becomes a restrictor. Single-tank operation speeds up the flow and pulls the bubble down and gets rid of it through the carb's float bowl vent.
 
hotprops said:
do yourself a favor and leave it on both and never move it .mine was set that way for 30 years .m model same as yours .just check it before the takeoff roll.use your hand and check that it is in the detent. you have no need to know the answer to your original question as it should never be 10/2 as there is no detent there. and no there will not be proper fuel flow
Click to expand...

So how do you shut the fuel off to check the gascolator fuel filter? o_O

Being able to shut off the fuel is a safety item and it has to work. It may seem trivial, until there are problems.
 
JAWS said:
So how do you shut the fuel off to check the gascolator fuel filter? o_O

Being able to shut off the fuel is a safety item and it has to work. It may seem trivial, until there are problems.
Click to expand...

All fuel selectors I am familiar with on certificated aircraft (the exception being Navions that haven't been modified) have an "OFF" position.
 
Norman said:
All fuel selectors I am familiar with on certificated aircraft (the exception being Navions that haven't been modified) have an "OFF" position.
Click to expand...

Navions have always had OFF positions from the factory. What they don't have is LEFT or RIGHT positions. Unless you have an aux tank, the thing is just OFF and ON. If you've got an underseat tank it's ON-AUX-OFF. The factory baggage compartment tank drains into the right main by another valve. If you've got tip tanks the valve varies, but I've never seen one without OFF.
 
guys go up a few posts and all your questions will be answered yes it was checked at every annual for full full function and not f...ed with during the year.got over 30 something years out of that fuel selector. what was funny I was replacing/repairing tons of selectors on ,m,n Skyhawks.and mine kept on playing nice. I became the guy to go to when your Skyhawk selector went tu. I found a way to repair it and test it for one third of time/cost of most everyone else around. if you go by the than available repair manual and even a well written cpa article floating around ,you sure as hell were going to go to hell,if you were not already living it with your cut and bleeding duct taped hands, screaming profanities, into the bilge of someone's fing Skyhawk. leave well enough alone. I do not like the smell of 100ll in the cabin at altitude knowing that the OFF position was the station were the selector was likely to leak the most.
 
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