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Wing tanks- capacitance probe installation http://t18.net/thorpforum/viewtopic.php?f=19&t=8657 |
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Author: | peterjaypriest [ Fri Nov 19, 2021 10:13 pm ] |
Post subject: | Wing tanks- capacitance probe installation |
So, my new-to-me T-18 has fuel tanks in the outer wings. Those are plumbed to refill the header via a Facet pump and a left-right toggle switch. But there's no fuel gauge for those wing tanks, and I'd really like to know, with some confidence, how much fuel is in them through a long flight. I've thought about adding a totalizer for each tank, but that won't really tell me how much fuel is in the tanks if there's a leak, etc. I'm contemplating adding a fuel capacitance sending unit to each side, and wonder if anyone has done this- especially to a flying airplane. It would involve drilling a hole through the ribs- but maybe that's workable. Anyone have any thoughts on the subject? Thanks, Peter |
Author: | fytrplt [ Sat Nov 20, 2021 7:52 am ] |
Post subject: | Re: Wing tanks- capacitance probe installation |
I just use a float switch in the wing tanks. It turns on a light on the panel when the tank goes dry. When wing tanks are dry, I have two hours plus reserves left in the main. I feed the wing tanks into the main from the top so there is no back flow. I also have a float switch in the main that cuts power to the transfer pumps so it will not overfill. I gage my fuel in hours, not gallons. I burn ten gallons per hour, so 5 in each side gives me an extra hour. |
Author: | Ryan Allen [ Sat Nov 20, 2021 9:05 am ] |
Post subject: | Re: Wing tanks- capacitance probe installation |
10 years ago, I too bought my T18 with wing tanks but no wing tank fuel gauges. Like yours, my tanks pump fuel to the main header tank. When I first bought my plane I had the same desire as you. In the end, I decided use a timer on my panel to tell me how much fuel has been pumped into my header tank. By testing over many iterations, I know my facet fuel pump sends .67 gallons per minute to the header. So I run mine pump in 3 gallon increments for 4 minutes and 30 seconds at a time. I then verify fuel has been added to the main tank by verifying that the digital fuel gauge in my header tank has increased. If I see no fuel is being added to my header tank (via the digital fuel gauge reading), I know I have a fuel transfer problem. |
Author: | peterjaypriest [ Sat Nov 20, 2021 9:20 am ] |
Post subject: | Re: Wing tanks- capacitance probe installation |
Thanks Bob and Ryan. I have read through lots of the posts, and see that some builders have installed float sending units in their wings. Others know the transfer rate of their pump, and use a clock. My wing tanks run from the inboard to the outboard rib on the front of each outer wing. Because of the dihedral, I don't know that a float gauge would measure the full capacity. If nothing else, I may install a liquid (fuel) detector in the fuel line for each wing tank- that will show when a tank is empty, at least. Many of the Glasair guys (I also have a Glasair) have installed the long capacitance probes in their wings and are very happy with the accuracy. Just not sure if a retrofit is feasible. The reality is that I won't be filling these tanks often so, like you, Ryan, I may just use the instruments I have now- a clock and a header fuel gauge. |
Author: | ljkrume [ Mon Nov 22, 2021 3:20 pm ] |
Post subject: | Re: Wing tanks- capacitance probe installation |
Hi fellas, I have the same setup like you and Bob for wing tanks. A Facet pump feeds he header; I simply open the valve from one wing or the other. I also bought a Dual LM394 Module, a small circuit board for about $8 online, and connected both channels to a wire from the main sender. One turns off the Facet pump when full, the other turns on a warning light when about only 6 gallons remain, before the engine goes quiet. For wings, I simply wanted to know when each one is empty so not to needlessly run the pump when dry. I plan on alternating each wing and timing each draw, as others mentioned. The sensor is simply a small Neodymium magnet in a float, captured in a vertical track on the most inboard rib (bottom end) of the tank. Outside the rib is a magnetic reed switch, which likewise can turn on the light. No holes to drill or feed-through wiring to worry about. Magnets conveniently work right through aluminum. If anyone would like to try the same thing I have a few extra reed switches. They’re really small and free for the asking. Les |
Author: | Ryan Allen [ Tue Nov 23, 2021 8:22 am ] |
Post subject: | Re: Wing tanks- capacitance probe installation |
thats cool Les. Nice idea! |
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