Cessna 152 fuel system question

[Steve]

Flew the 152 for the first time the other day. As I understand it, the 2 fuel tanks are interconnected at the tops of the tanks incase one of the vented fuel caps were to clog. The fuel valve's only settings are on and off. If I were to fill up a 152 with empty tanks, why doesn't the fuel flow over to the other tank? From what i've noticed its possible to have one tank full, and one empty. How is this possible?

 

[MauleSkinner]

Flew the 152 for the first time the other day. As I understand it, the 2 fuel tanks are interconnected at the tops of the tanks incase one of the vented fuel caps were to clog. The fuel valve's only settings are on and off. If I were to fill up a 152 with empty tanks, why doesn't the fuel flow over to the other tank? From what i've noticed its possible to have one tank full, and one empty. How is this possible?

It does flow over to the other side...that's why your POH says something like "fill one side, then fill the other, then go back to the first side and fill some more if you want it completely full". It's just not real fast

If you're getting massive fuel imbalances on a regular basis, you've probably got some issues with your vented caps in flight.

Fly safe!

David

 

[avbug]

Fuel imbalance may be a vent issue, but may also be flying with a slight bank or flying with the inclinometer (skid ball) out of center. Even though the fuel ports in each tank may be submersed, they may feed or draw unevenly if flown out of kilter.

 

[MauleSkinner]

Fuel imbalance may be a vent issue, but may also be flying with a slight bank or flying with the inclinometer (skid ball) out of center. Even though the fuel ports in each tank may be submersed, they may feed or draw unevenly if flown out of kilter.

Good point. I did a flight review in a PA-12 with a guy who always flew in a left-wing-low slip within 1000 feet of the ground (I suspect he was trying to look around the nose. Got interesting landing in right crosswinds). That's how I broached the subject with him..."Do you find that you usually land with more fuel in the left wing than in the right?" Sure enough, he did.

Fly safe!

David

 

[JimNtexas]

I haven't flown a 150 in decades, but my 1971 Cardinal RG has a similar on/off fuel selector. It is well documented by our owners orgainization that this system is prone to unbalanced fuel feeding. What happens on Cardinals is that when fuel gets into one of the vent lines (perhaps when you turn on the ground) it will cause a slight suction in that tank. The engine will then draw from the fuel tank with least resistance. I've seen one tank empty completely before the other starts to feed. The fuel pump is strong enough to overcome the suction in the full tank, so you won't lose the engine over it.

The recommended proceedure when this happens in the Cardinal is to cross control in level flight, sometimes this will clear the blocked vent. It works for me, but I don't do it if I have passengers.

 

[nosehair]

but I don't do it if I have passengers.

"Ladies and Gentlemen, this is your Captain speaking. Please ensure your seatbelts are securely fastened, as I think we will encounter some momentary turbulance in just a few moments."

...(wiggle the rudder...)

"Ahh, OK, everyone, I think we clear. You may relax and resume your slouched positions."