In the final throes of this build... any opinions on leveling a taildragger for the fuel gauge calibration?
The fuel indications in the EFIS systems we are using now are so darn accurate if calibrated properly, I think it makes no sense to not do it in a level flight attitude.
Doing it in level flight and ground attitude (on systems that have the capability) is personal preference but for a tail dragger I think it is worth while.
What EFIS system are you referring to? I have dual AFS 4500?s. Calibrated my tanks two gallons at a time with the airplane in a level attitude and they are miserably inaccurate. So much that I don?t pay any attention to them. I use the gallons used from the red cube as my indication of fuel in the tanks. Finally tweaked that to where it is reliable.
Really curious on how much extra fuel goes in after the fuel floats hit the top of the tank.
(
I called the FBO and got a bored line guy to come out with the fuel truck. We added fuel two gallons at a time, calibrated in tail down attitude, then lifted the tail to flight attitude, took a calibration, dropped the tail, and repeated until the tanks were full.
I have what is likely one of the last capacitive fuel sender kits and dynon voltage converters feeding a garmin system. The setup is very accurate below 4/5th of a tank.
I wouldn't be too concerned about doing this calibration until you are on the gear, and even then it can wait until you are flying.
Not sure if there is a reg. but I waited until after completion and had a few hours of flight time. I’m a bit old school and made a fuel tank dip stick the first time we filled her up, 5 gallon increments.
I don’t care for the saw horse idea as being too narrow even with a cushion. I would be one angry hombre if I put a crease in my new pony. So, small 300# step platform, some shotgun ammo cases and firm foam cushions under the bar attach point got me to level to do the fuel and attitudes calibration.
Hanger floor reasonably level for the lateral leveling, nothing was needed there.
Be careful.
R
Then you must have done something wrong, because that doesn't match the experience of most RV builders.
Maybe I need to qualify the accuracy statement since some people haven't fully developed a good understanding of how the standard float level sensors work in an RV...
When you have a wing tank on a wing with dihedral like we have on RV's, and have the fuel level sensor installed in the inboard most rib bay of the tank, it will never be possible to have the gauge measure the fuel level from 100% full to totally empty. That is because the dihedral angle makes some of the fuel in the tank, located at a higher level than the float on the sensor is. So until the fuel level reduces within the sloped tank to a point that the float just begins to drop from its highest possible point, there will be no indication of fuel usage and when doing the calibration process, the last few gallons will not register a change.
None of this matters in the grand scheme of operating the airplanes because knowing whether the fuel level has reduced 2 gallons or 3 gallons below a full tank doesn't matter.
What matters is accuracy from 1/2 full to empty. In general, RV's are very accurate from in the neighborhood of 3/4 to 4/5 ths, down to empty.
In the case of the 25 gallon tank in the RV-14, use of the first 4 gallons or so will not register as a change on the gauge, but from 21 gallons down to empty it will be very accurate.
Any thoughts on why this is so?
Thanks
Getting a dipstick calibrated drove me nuts. I found two things. The fuel wicks up a lot more than you think. 1/2 gal on my 7. The second is that a little roll knocks off the measurements. So - set the jacks under the wings to level them had hold the position as one tank is filled. A small glass or plastic tube worked best to measure the level. I tried wood, metal ruler and a tube. The tube worked best.
I made a strip of .025 X .3" from aluminum. It is marked by drilling 1/16" holes (maybe smaller) to catch the fuel in 1/2 gal increments. Wicking can easily show more than a 1/2 gal higher but the hole is not filled with fuel. Unlevel ground conditions yield less accurate levels on a single tank, but the combination is well within a gallon, mostly a half.
I only calibrated the stick with the tail on the ground.
But did both for the electronics.