14.1.10 Calibrating Fuel Tanks

This entry is part 28 of 38 in the series 14 - Final Assembly / FInishing

This turned out to be a real pain.

I was expecting a relatively straight-forward process.  Something along the lines of add 5 gallons, press a button, repeat, etc.  That’s why I added the shut-off valves on the last trip.

Then I discovered that my fuel probes have five “setpoints” (Empty, 1/4, 1/2, 3/4 and Full). Which means that I have to fill the tanks to determine how much they hold, empty them, then refill while defining the setpoints.

So I removed the lines between the strake tanks and the sump, attached four feet of flexible line to the strake tank, ran the line out the main gear opening and attached the valve at the end. This way I can drain the tanks without too much fuss.

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I borrowed eight 5 gallon fuel cans and had them filled at the FBO (I’ve been hoping for 45 gallons per side, but I didn’t want to get more fuel than necessary so I started with 40 gallons) Then carted them over to the hangar.

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Then I started filling the tank and checking the level after each 5 gallons with my 12″ scale.

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And 40 gallons just barely fit.  A bit disappointing since I was hoping for more capacity.  So I drained the fuel out… Which took about 7 minutes per 5 gallon can (so about 45 minutes to drain a tank). And that’s when I realized that the plane wasn’t level.  I had neglected to tighten the collar on the right jack and it leaked down so that the right wing was low. I raised the jack until the plane was level and then moved over to the left side. After putting in all 40 gallons, I still had about 1/2″ left. So back to the factory to borrow another 5 gallon can, over to the FBO to get it filled, back to the hangar and poured it in the left tank. It didn’t take much before it was full but it looks like just shy of 42 gallons.

Then I drained out the fuel and refilled defining the fuel probe setpoints with “Empty” at 2 gallons, 1/4 at 10 gallons, 1/2 at 20 gallons, 3/4 at 30 gallons and “Full” at 41 gallons (although the probe looks at anything over about 35 or so as full).

Then I drained the left tank and refilled the right defining the setpoints the same as the left side. When I was finished, I determined the right tank holds just a little more than 41 gallons.  So I decided to call the fuel tanks at 41 gallons.

Then I drained the right tank (for the last time), reconnected the strake to sump fuel lines and dumped the fuel back in. After a short period the fuel equalized between the two tanks and I was done with th  at task.


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