Because of the geometry of the fuel tanks and dihedral of the wings, a
single float type sender can not read accurately at both full and
empty. The important thing is that the gauges be accurate at the low
end in order to indicate when you are getting short on fuel. The "fix"
is to make a calibrated dipstick to tell you how much fuel you start
out with for fuel planning purposes. The gauges will give you a
reality check on your fuel planning. Once you get your fuel totalizer
function calibrated, that will most likely become your primary fuel
monitoring device with your dip stick to verify the starting point and
the gauges as a reality check.
I have the 12 gallon tanks on my Zodiac. My fuel gauges can only read
the last nine gallons or so in the tanks and my dip stick can only
read the first nine gallons. If I have less than three gallons in the
tank, the bottom of the tank directly below the filler cap is dry.
With the 15 gallon tanks, you will probably have the same situation,
the float will hit the top of the inboard end of the tank with about
nine gallons in the tank and the bottom of the tank below the filler
cap will be dry after about nine gallons are used.
On Oct 10, 2008, at 9:25 PM, Dr. Andrew Elliott wrote:
> I very carefully bent the fuel level sender arms in accordance with
> the instructions before fitting them to the factory fuel tanks on my
> 601XL with 15G tanks. I (duh?) did not calibrate the senders before
> putting the wings on the plane. I did check the resistance and both
> went from 73 to 10 ohms.
>
> Unfortunately, I found today, when calibrating the senders for my
> EFIS, that the right tank sender doesn't register the 1st gallon and
> then maxes out at 8.5 gallons. The left tank starts right away, but
> maxes out at 6 gallons.
>
> I am really not looking forward to trying to extract and adjust the
> bends in the float wires through the access hole, but I really don't
> want to have displays that only register 1/2 the fuel in the plane.
> (Even though it will be OK at low fuel levels.) I do have a fuel
> flow and totalizer function.
>
> Anyway, I am looking to hear if anyone else has had this problem,
> and what the fix was? Maybe I installed them upside down?
>
>
--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
