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-   -   Float/Capacitance fuel sending units (https://vansairforce.net/community/showthread.php?t=127176)

cwharris 06-30-2015 07:23 AM

Float/Capacitance fuel sending units
 
I?m about to start on my tanks and so I was wondering if I can install BOTH the Float Style Sending Units that come with the Wing Kit and also install a Princeton Capacitance fuel probe sending unit. I would use the Probe units as my primary sending units that would get wired into my EFIS System and then I would wire the Float Style Units that come with the kit to a stand-alone back up fuel Gauge. Has anybody tried to install both types of sending units? Is this something that I should do or not do?

Tom023 06-30-2015 07:33 AM

Check E's blog:

http://rv-14a.blogspot.com/search/la...l%20Probes?m=0

Mike H 06-30-2015 08:00 AM

What advantage do the capacitive fuel probes give you over the standard float senders?

Icarus 06-30-2015 08:31 AM

...
 
In theory? Less susceptible to variance due to disturbance of the fuel in flight. No moving mechanism.

In practice? Having flown a mix of aircraft with both, I still seem to ignore gages and stick the tanks. If you're building now, why not. I would much rather prefer a good fuel totalizer. [Which reminds me...the D-10EMS is on the way ! ]

Now...if you could build in a cork sight gauge a la stearman/cub...:)

Mike H 06-30-2015 12:32 PM

I know the capacitive senders sound good in theory, and I know lots of builders go this route, I am just not sure if it is a better way of doing things in our application. Capacitive systems are the onLy way to go due to the design characteristics of some aircraft fuel cells, but not so much our small tanks. Capacitive fuel quantity systems require maintenance eventually. Even though there are no moving parts all it takes is some oxidation on the electrical connections to cause some wildly erratic or inaccurate indications. Capacative systems are not tolerant of imperfect connections, crimps, soldering of coax center conductor pins, shielding, FOD and many other variables. Eventually you will have to clean and re-tourque, or reterminate connections, and to be able to accomplish this you will need access to the inside of the tank. Access inside of the -14 and -10 tanks requires cutting and installing access panels in the rear tank wall.

rightrudder 06-30-2015 03:34 PM

Quote:

Originally Posted by Icarus (Post 994726)

In practice? Having flown a mix of aircraft with both, I still seem to ignore gages and stick the tanks.

Smart move. I have a healthy mistrust of fuel gauges too. Sticks don't lie! :)

N941WR 06-30-2015 08:10 PM

Go with the capacitance senders and use your fuel flow and watch as your backups.

I have the Dynon SkyView with their capacitance senders and am always amazed at how accurate they are!

rvbuilder2002 06-30-2015 09:10 PM

With the current technology we have in EFIS with the calibrated/mapped fuel levels, all the systems are very accurate when they are working.
Any of the different system types can fail.
Once we got rid of the wire wound resistor fuel level sensors the reliability seemed to go up.
I have maintained a large # of RV's for many years (currently 8 airplanes) and in that time I have replaced one mechanical fuel level sensor.
Of the problems I have heard of that others have had probably half of them are self induced (damaged during installation, etc.).

cwharris 06-30-2015 10:44 PM

Thanks for all the input. Looks like I'm sticking with the Float Sending Unit that comes with the kit. Thanks again.

Snowflake 06-30-2015 11:01 PM

Having now flown with a red cube measuring fuel flow, and having seen how accurate flow measurement can be, I don't think i'd put level senders in tanks at all if I could avoid it. One red cube in each wing root, dip the tanks before each flight, and you'll know fuel level more than accurately enough for VFR operations. The only downside is that it requires remembering to set the totals when you fill or top up the tanks.


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