I just got N545PG flying. 25 hrs so far. We are trying to calibrate the fuel tanks. We followed the instructions exactly and the resistance numbers stay the same for 3/4 and full tank. Has anyone else run into this problem? Maybe put a different bend in the float wire? Thank you in advance!
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fuel sender calibration prob!
- Thread starter Hoss
- Start date
TomVal
Well Known Member
Fuel Tank Calibration
Hoss,
I am in the process of re-calibrating my fuel tanks. I was not the original builder of my aircraft, but as a result of having to pull the tanks to comply with the service bulletins, I am doing the calibration.
My resistive float readings are being input to a GRT 4000 EIS. The calibration instructions state that the float reading will bottom out (resistance level stops decreasing) well before the tank is empty. Note the fuel quantity remaining at that point. Although the fuel quantity gage is reading "empty", the difference between the fuel remaining minus the unusable fuel can be considered as a reserve fuel (not necessarily sufficient to meet VFR or IFR reserve requirements). Similar logic applies to your tank full indication.
As you fill the tank towards full, the resistive float reading will top out (stop increasing) before the tank is physically full. You should note how much fuel is in the tank at the point at which the resistive reading stops increasing.
For example, lets assume you have a 21 gallon tank. The resistive reading stops increasing at 18 gallons. At 18 gallons, the fuel quantity gage indicates full although there is still room in the tank for an additional 3 gallons. It is important to know at what point does the fuel quantity gage begins dropping off from the full indication. Therefore, if you top off the tank at 21 gallons, the fuel quantity gage will indicate full until the actual fuel remaining drops below 18 gallons.
I hope this explanation doesn't throw you off course. I will be in the process of re-calibration of my tanks in a few days...I'm still learning the process.
Regards,
Hoss,
I am in the process of re-calibrating my fuel tanks. I was not the original builder of my aircraft, but as a result of having to pull the tanks to comply with the service bulletins, I am doing the calibration.
My resistive float readings are being input to a GRT 4000 EIS. The calibration instructions state that the float reading will bottom out (resistance level stops decreasing) well before the tank is empty. Note the fuel quantity remaining at that point. Although the fuel quantity gage is reading "empty", the difference between the fuel remaining minus the unusable fuel can be considered as a reserve fuel (not necessarily sufficient to meet VFR or IFR reserve requirements). Similar logic applies to your tank full indication.
As you fill the tank towards full, the resistive float reading will top out (stop increasing) before the tank is physically full. You should note how much fuel is in the tank at the point at which the resistive reading stops increasing.
For example, lets assume you have a 21 gallon tank. The resistive reading stops increasing at 18 gallons. At 18 gallons, the fuel quantity gage indicates full although there is still room in the tank for an additional 3 gallons. It is important to know at what point does the fuel quantity gage begins dropping off from the full indication. Therefore, if you top off the tank at 21 gallons, the fuel quantity gage will indicate full until the actual fuel remaining drops below 18 gallons.
I hope this explanation doesn't throw you off course. I will be in the process of re-calibration of my tanks in a few days...I'm still learning the process.
Regards,
flion
Well Known Member
This is exactly why I'm looking into the capacitive senders. Due to the sloped geometry of the tank, a float sender will always be unable to indicate the last few gallons. If it were installed at the other end of the tank, it would read true full but then would read empty with a few gallons left. That might be a good safety feature but, as far as I know, no one has done this; I expect because the temptation to run on empty ("hey, there's a few gallons left") might be bad.
Anyway, when calibrating my -6A, I read the resistance values (easy with the BMA interface but a multimeter would do it) starting from empty and adding one gallon at a time. I found it maxed out at 18 gallons. BMA lets you set several data points and linearizes between them; I biased my calibration toward the bottom of the range so that it would be most accurate when the tanks are nearly empty. And then I usually rely on time and fuel burn anyway.
Anyway, when calibrating my -6A, I read the resistance values (easy with the BMA interface but a multimeter would do it) starting from empty and adding one gallon at a time. I found it maxed out at 18 gallons. BMA lets you set several data points and linearizes between them; I biased my calibration toward the bottom of the range so that it would be most accurate when the tanks are nearly empty. And then I usually rely on time and fuel burn anyway.
