"Koopas Ly" wrote:

With regards to fuel tanks in a C172, why does the takeoff and landing
checklists both call for the fuel selector handle to be in the "both
tanks" position?


Cessnas have the notorious characteristic of not drawing fuel evenly from
both tanks in the Both position. This can result in fuel imbalance. In a
Cessna 172 you might never notice any difference in the flight
characteristics, but in a 182 which has more fuel capacity in each wing than
the 172 has in total, you can develop an imbalance which becomes fairly
uncomfortable. By selecting one tank or the other, you can burn fuel
(mostly) from the full tank in order to reestablish lateral balance.

On longer XC flights in my 172N, my SOP is to depart with selector on
both & remain there 1/2 hour. Next 1/2 is on right only. Then, back to
both for next 1/2 hr, continuing that sequence with prelanding
checklist calling for both. The drawdown of fuel is much faster from
the left tank than the right when using both.

Also, why is the fuel selector set to one tank during refueling? Is
it to minimize crossfeeding?

I leave the selector on both when refueling. After topping the tanks,
I rock the wings before I go pay & pee. During the following
preflight, when I confirm the placement of the filler caps, the fuel
level is always topped off.
YMMV
John

If you're parked not quite level, and start refueling with the fuel selector
in the Both postion, if you start by topping off the high wing, some of that
fuel may crossfeed into the low wing while you switch sides and go about
filling the low wing. If you don't recheck the high wing, you might not
notice that the first tank is no longer full, and that you are a few gallons
short of the fuel load you planned for your trip.