170A uneven fuel consumption on “both”

[jonathoncopland]

Afternoon All,
New 170A owner here, having a issue with fuel evenly moving on the both selection. In the first 15 hours since picking up I have had two flights that were not in a row that resulted in uneven fuel consumption. The aircraft has a recently rebuilt fuel selector, two brand new vented fuel caps. Any suggestions?

Both occurrences resulted in a 50% different between fuel usage between tanks.

[Bruce Fenstermacher]

This is typical of the 170 model not just the A model. When I cared about it I'd run off of left or right to keep them even or to even them out.

[cessna170bdriver]

Agreed. This past Saturday I did a 3-hour round trip to Troy, Ohio, and on return, the right tank (the one with the vented cap) took 9.5 gallons, and the left tank took 14 gallons. And that was after being parked level at Troy for 4 hours with the selector on both. If I refuel after the airplane has sat for a while with the selector in both, the tanks take close to the same amount of fuel within a gallon or so. For legs longer than about 2 hours I switch to the fullest tank until they more or less even out, then switch to both for landing.

[GAHorn]

Afternoon All,
New 170A owner here, having a issue with fuel evenly moving on the both selection. In the first 15 hours since picking up I have had two flights that were not in a row that resulted in uneven fuel consumption. The aircraft has a recently rebuilt fuel selector, two brand new vented fuel caps. Any suggestions?

Both occurrences resulted in a 50% different between fuel usage between tanks.

Uneven fuel useage has been discussed previously at:

http://www.cessna170.org/forums/viewtop ... uel#p24083

and at:

http://www.cessna170.org/forums/viewtop ... fuel#p9094

Basically, one of your tanks is crossfeeding the other via the vent-line. In other words.... BOTH tanks are feeding your engine,...but one tank is replenishing the other and keeping it fuller until gravity and head-pressure breaks the siphon-action and they return to both feeding individually. Bottom line: Don't worry about it. If the selector is in BOTH....any tank with fuel will feed the engine.

Personally, I place the selector in “Both” and leave it there, eventually they even-out with each other again, as explained in the links provided.

[counsellj]

As I have seen with many clients that I have flown with, they simply have lazy feet or haven't developed a good feel with their backside for flying slightly uncoordinated. After a couple hours, this will present exactly what you are experiencing. Make sure your T/B is actually level to the airplane. Then go fly an concentrate on keeping it coordinated and see if that changes anything.

Jughead

[daedaluscan]

I think Jughead is spot on. I get very different fuel usage from the different tanks depending on how the plane is loaded. And I think I need to mess with my rudder trim tab, when I fly alone I rest my right foot lightly on the pedal, but with two in the plane I don't need to. I fly on both all the time, and I am very conservative with leg length. Three hours is plenty for me.