In my experience, the capacitive fuel
level system calibrated to read full with auto fuel with no ethanol will read
about three-fourths full when the tanks are full of AvGas. So although there
is a difference between the conductivity of those two fuels, the difference is
not that extreme. The capacitance difference between either type of fuel
and ethanol is HUGE, however. Although I have avoided using fuel with
ethanol, I would expect that the capacitive system would make a good ethanol
detection system and be of little value as a fuel level indicator since the
indication would be of having much more fuel than is actually there. Unless
the capacitive system is recalibrated for the particular mix of fuel containing
ethanol at the time or referenced to a cell containing fuel of the same
composition, the level indications should probably be treated with a great deal
of skepticism.
It would be valuable to get feedback from
someone who has had firsthand experience with the effect of fuels containing
ethanol on capacitive sender calibration. I certainly would like to be
shown to be wrong about this.
Wishing I wouldn’t have had a choice…
Steve Boese
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bobby J. Hughes
Sent: Wednesday, April 22, 2009
11:39 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: fuel
senders
100LL and auto fuel have
different capacitance. Not sure about different blends of auto fuel. Bobby
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of n3773@comcast.net
Sent: Wednesday, April 22, 2009
10:35 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] fuel senders
i
wanted to comment that in the 12 years i have been flying my -6a i've noticed
many people installing capacitance fuel senders. i didn't have a choice
15 years ago. meanwhile i have read so many posts from people having
troubles with them. i have the old float/resistor type, as does my hangar
mate. we both have over 1000+ hrs on our planes and have had no problems.
we installed them, connnected the wire to the guage, done. the last
quarter tank seems to go a bit faster than the first, same as my truck.
the only fuel level problem i've had was from installing low-fuel level
switches which melted, despite specs that said they were for fuel usage, and
almost popped out of the tank. but, that ocurred early on, and i realize
that i watch the fuel level like a hawk when flying. kevin
[gadgets are fun when they work right. debugging isn't. try
fixing intermittent auto pilot/gps glitches for instance]