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What type of capacitance fuel sender is this?

P

Peter M

Member
Hello aviators

I purchased an RV6 almost 12 months ago and haven't stopped grinning since. The fuel gauges have never worked and the previous owner told me they were disconnected due to BNC sealing issues. In the end he gave up and gummed the whole lot up and relied on the fuel totaliser which does work well. I'd like to resolve those issues and plan to remove the tanks, replace the inspection plates with a hermetically sealed BNC connector and do the job properly. However, I'm not sure about the fuel sender that's installed in the tanks. I know from the builders log its a capacitance type but other than that I have no information about it. A photo of the sender is below. Does anyone recognise it and point me to a web site where I can find out more about it? All help and comments would be appreciated.

http://www.circle-consulting.co.nz/images/rv2c_013.jpg
 
Peter, I don't recognize that sender, looks like a capacitance probe type, but as long as you're taking the fuel tank apart, why don't you consider installing Van's capacitance system. I've had it in my RV-6 going on 12 years now without a hiccup. It's very accurate, it's got no moving parts, and not much can go wrong with it if properly installed. You will need to purchase a couple of transducers that convert farads to Mhz, depending on the type gauge you have, but these will be installed on the outside of the tank near the wing root area.

Good luck. :)
 
Pat Hatch said:
Peter, I don't recognize that sender, looks like a capacitance probe type, but as long as you're taking the fuel tank apart, why don't you consider installing Van's capacitance system. I've had it in my RV-6 going on 12 years now without a hiccup. It's very accurate, it's got no moving parts, and not much can go wrong with it if properly installed. You will need to purchase a couple of transducers that convert farads to Mhz, depending on the type gauge you have, but these will be installed on the outside of the tank near the wing root area.

Good luck. :)
Click to expand...

I agree with Pat, the Van's capacitance system is outstanding. In fact it is much more accurate than my fuel flow will ever be.

Dynon sells the converters Pat mentioned for a very reasonable price.
 
That is actually the most common type of capacitance fuel quantity probe. When you open up the tank and take a closer look at the probe, there will be a part number printed on the outer plate, but before you open the tank and condemn the probe, I would take a closer look at the reference capacitor as I dont think there is anything wrong with the probe. If the totalizer works fine, but the indicator gauge doesnt, it is usually the reference capacitor in the gauge, not the probe. The reference capacitor in the gauge is adjustable and sometimes that is all you need to do. I can tell you how to troubleshoot it without opening anything, but you would be better off by reading page 14-43 and 14-44 of the AMT airframe manual found here to familiarize yourself with how it works:
AMT Airframe
 
Thanks to those for replying to my question so promptly especially Randle. That document you provided the link for is a great reference. Everything you wanted to know about fuel and fuel systems but were afraid to ask!

Just to clarify: I have no reason to doubt that my capacitance fuel senders work and shouldn't need to replace them. When I purchased the aircraft and the reason for the fuel gauges not working was explained to me I was told that the senders and gauges did work but there were sealing issues around the BNC connectors. In the end they gave up, disconnected the gauges, gummed up the connectors and used the fuel totaliser to manage the fuel.

Before I go pulling the tanks out and replacing the inspection plates with plates that have new good quality and hermetically sealed BNC connectors mounted on them I wanted to gather as much information as possible about the tank system. What I'm looking for is someone who recognises the fuel probe and can give me a brand name or web site link that I can use to find out a bit about them, how they're wired, calibrated, etc. Thanks guys.
 
When I built my tanks I had the same sealing issue with the BNC. The solution was to GOOP on the proseal!

The center terminal leaked so on the inside of the tank, I covered the BNC connector and ran the proseal up the wires, so nothing would get past it. Five years and 500 hours and they still don't leak.
 
Peter M said:
That document you provided the link for is a great reference. Everything you wanted to know about fuel and fuel systems but were afraid to ask!
Click to expand...
If you think that chapter is good, you should download the whole book, then the other three that are meant to go with it. I posted all that info here:
http://www.vansairforce.com/community/showthread.php?t=101694

Peter M said:
What I'm looking for is someone who recognises the fuel probe and can give me a brand name or web site link that I can use to find out a bit about them, how they're wired, calibrated, etc. Thanks guys.
Click to expand...

As far as the a manufacturer, here in the states, they are usually manufactured by Honeywell, Simmonds Precision, or DBA Goodrich, I am not sure about your local manufacturers. How they are wired and calibrated depends on if it is a 3-wire or 2-wire probe. Your best bet would be to get the manufacturer and model number off of the indicator and go from there, the probe is usually matched with the gauge and not universal or a different manufacturer. If you could post more info on your setup it would help as well. There should be a couple adjustment screws or rheostats on the back of the gauge used to calibrate the system.
 
Thanks Randle. Those manufacturer's names is a good start.

From memory there's three wires going to the gauges. I'll be up at the hangar tomorrow so will take a gauge out of the panel, have a good look and take some photos.

How do you get three wires through a BNC connector???
 
You don't, usually it is through a cannon plug but have you pulled your wing root panel and looked to verify it is a BNC? The 3-wire has isolated redundant cicuits for the totalizer and gauge while the 2-wire probe runs the totalizer and gauge with the same sense value (picofarad) from the unit.
 
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