Van's Air Force
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Fuel sender
- Thread starter paulsmit
- Start date
Carl Froehlich
Well Known Member
Exactly the same on my RV-10 (also SkyView).
Take the time to properly calibrate the float senders and they will always be within a gallon of actual (when in the indicating range). I set mine up to read from empty up to full travel of the sender - so they just read "23+" when above 23 gallons in that tank. Make sure you level the plane during calibration.
Carl
I know people love their capacitive senders, but I've never used them so they're an unknown to me. I used the standard Van's floats in the RV-10 and RV-14 both and they work out well.
Additional comments:
On both planes, during the calibration stage, I had a float stick in the up position, despite making sure I had clearance. Interestingly, on BOTH planes, I just banged my hand on the wing, the float dropped, and then it never happened again. In flight, it's highly unlikely you'll have one stick due to the movement, if you build them properly. Don't be discouraged about them due to that comment....as I said, it was a one-time event within the calibration process. Not in flight.
Regarding Calibration:
Different EFIS's have different options for getting accurate calibrations. On my GRT Engine monitor, you can calibrate them but it gives a linear calibration scaling. So even when you run their calibration program so that it outputs more accurate serial data, there are periods within the calibration where they aren't as accurate due to the tank geometry. Specifically, the last couple gallons and anything above 22 gallons, are harder to count on with a linear calibration. It comes to be about spot on right about in the middle between 10 and 14 gallons or so. Most users won't end up with just a sloppy linear calibration....
After the linear calibration was done, I re-filled the tank, one gallon at a time, and verified how many REAL gallons, displayed on the gauge. (i.e. 3 real gallons shows as 4 gallons, etc)
On my Chelton, the way it works is that once you have the rough linear calibration done, there is a table that you enter the values at specific increments so that you have a column of actual gallons vs displayed gallons. This corrects the linear calibration so that it displays more accurately. Once you do this step, and most EFIS's have a way to do this sort of thing, you should end up with fairly accurate floats. Much more accurate than your car's gas gauge, at least.
This weekend I was flying some time off and got down to 6-7 gallons per side while flying to a fuel stop. I got there and the fuel pump wasn't working.
That got me a little excited because I didn't want to blindly trust my floats. I had to find an alternate airport for fuel that was nearby. Remember that I'm doing break-in so I'm pushing north of 13-14GPH a lot of time running higher power settings...sometimes 15-17GPH.
I flew on 20+ miles to the next airport and landed with 5gal showing on both floats. At this point I haven't calibrated my totalizer, only my floats, so I wasn't as comfortable with being this low. I've never landed my RV-10 with less than 10 gallons remaining. I don't like to play it that close.
I filled the tanks and sure enough, I put in just over 40 gallons of gas. Remember that if I fill my tanks I get just over 50 to fill them. So the floats were dead on. To make it even better, my uncalibrated flowmeter was also within 1 gallon. I don't want to calibrate that on short flights, but now I feel much better about doing some longer X/C flight to fine tune the flow cal later.
Once you have your flowmeter calibrated, you really will not care so much about how accurate your floats are. They are basically only a guideline to how full a specific tank is, to know which one you want to use for takeoff or landing. Your flowmeter will be what you really care about. That will tell you precisely how much fuel you have. That said, if your float is reading way low...suspect something. I had an IFR flight where I had to sump the tanks in heavy rain. I didn't notice that my sump stuck open. It was a 1.25hr flight. I noticed that my float was going down on a tank I wasn't actively using. That got my attention. What I SHOULD have done was switch to that tank asap to use up any fuel I could. When I landed at home, with no rain, I saw the leaking sump. It wasn't leaking fast enough to use all the fuel in that tank, but without float gauges I wouldn't have even known I'd had the problem. So while a flowmeter is what you really care about, the floats provide some function also.
The short answer is this: The floats will work fine for you and are easy to install. If you go capacitive, you have a learning curve and modification time to waste time with. But when all is said and done, any of them need proper calibration and then they should function just fine.
Additional comments:
On both planes, during the calibration stage, I had a float stick in the up position, despite making sure I had clearance. Interestingly, on BOTH planes, I just banged my hand on the wing, the float dropped, and then it never happened again. In flight, it's highly unlikely you'll have one stick due to the movement, if you build them properly. Don't be discouraged about them due to that comment....as I said, it was a one-time event within the calibration process. Not in flight.
Regarding Calibration:
Different EFIS's have different options for getting accurate calibrations. On my GRT Engine monitor, you can calibrate them but it gives a linear calibration scaling. So even when you run their calibration program so that it outputs more accurate serial data, there are periods within the calibration where they aren't as accurate due to the tank geometry. Specifically, the last couple gallons and anything above 22 gallons, are harder to count on with a linear calibration. It comes to be about spot on right about in the middle between 10 and 14 gallons or so. Most users won't end up with just a sloppy linear calibration....
After the linear calibration was done, I re-filled the tank, one gallon at a time, and verified how many REAL gallons, displayed on the gauge. (i.e. 3 real gallons shows as 4 gallons, etc)
On my Chelton, the way it works is that once you have the rough linear calibration done, there is a table that you enter the values at specific increments so that you have a column of actual gallons vs displayed gallons. This corrects the linear calibration so that it displays more accurately. Once you do this step, and most EFIS's have a way to do this sort of thing, you should end up with fairly accurate floats. Much more accurate than your car's gas gauge, at least.
This weekend I was flying some time off and got down to 6-7 gallons per side while flying to a fuel stop. I got there and the fuel pump wasn't working.
That got me a little excited because I didn't want to blindly trust my floats. I had to find an alternate airport for fuel that was nearby. Remember that I'm doing break-in so I'm pushing north of 13-14GPH a lot of time running higher power settings...sometimes 15-17GPH.
I flew on 20+ miles to the next airport and landed with 5gal showing on both floats. At this point I haven't calibrated my totalizer, only my floats, so I wasn't as comfortable with being this low. I've never landed my RV-10 with less than 10 gallons remaining. I don't like to play it that close.
I filled the tanks and sure enough, I put in just over 40 gallons of gas. Remember that if I fill my tanks I get just over 50 to fill them. So the floats were dead on. To make it even better, my uncalibrated flowmeter was also within 1 gallon. I don't want to calibrate that on short flights, but now I feel much better about doing some longer X/C flight to fine tune the flow cal later.
Once you have your flowmeter calibrated, you really will not care so much about how accurate your floats are. They are basically only a guideline to how full a specific tank is, to know which one you want to use for takeoff or landing. Your flowmeter will be what you really care about. That will tell you precisely how much fuel you have. That said, if your float is reading way low...suspect something. I had an IFR flight where I had to sump the tanks in heavy rain. I didn't notice that my sump stuck open. It was a 1.25hr flight. I noticed that my float was going down on a tank I wasn't actively using. That got my attention. What I SHOULD have done was switch to that tank asap to use up any fuel I could. When I landed at home, with no rain, I saw the leaking sump. It wasn't leaking fast enough to use all the fuel in that tank, but without float gauges I wouldn't have even known I'd had the problem. So while a flowmeter is what you really care about, the floats provide some function also.
The short answer is this: The floats will work fine for you and are easy to install. If you go capacitive, you have a learning curve and modification time to waste time with. But when all is said and done, any of them need proper calibration and then they should function just fine.
