I'm doing some housekeeping on my RV-8A - the weight and balance hasn't been physically checked since the aircraft was built in 2008 - although previous owners did a rough job of adding/subtracting weight when components were changed, I'd like a more accurate measurement. Coupled with the need to replace some corroded fuel drains, this gives me the opportunity to check my fuel gauge calibration as well.
To determine the unusable fuel, I did it two different ways. First, I flew the aircraft down to about 5 gallons of fuel total (3 left, 2 right). Then, I uncowled it and routed the fuel line into some 5-gallon gas cans instead of the fuel injector servo. I drained the fuel from both sides using the electric fuel boost pump. I measured the remaining fuel by removing the fuel drains, and catching the remainder in measuring cups. In my right tank (normal fuel pickup) I only got about two tablespoons of fuel. In my left tank (flop tube), I got 4 ounces. I thought this seemed low, and wanted to be certain, so I put a liter of fuel in each tank, cranked the engine, and ran it until it quit (or at least, until it started to quit, I didn't let it continue to cough). Removed the fuel drains again, and the same result 2 TBSP and 4 ounces.
The RV-8A sits at/very near level flight attitude on its gear, so I think that was a good representation of a flight attitude. Reading through this forum, the amount sounds similar, but on the low side of average for what others have measured.
So, when I do my weight and balance, I'll use those small amounts as unusable fuel.
Here's my question!
I have resistive float fuel senders coupled to a Dynon system with a FloScan 201B. The senders are pretty good, but not accurate enough to measure fuel to the accuracy of my unusable fuel amounts. Should I add a small amount (1 liter maybe?) of fuel to each tank to set the "zero" for my fuel calibration, to account for gauge inaccuracy? Or should I trust that "zero is zero" and the gauge will let me know if I'm there accurately enough?
My next step is to do several calibration flights to ensure the Dynon fuel rate calculation is correct, and to calibrate the flowmeter setting.
To determine the unusable fuel, I did it two different ways. First, I flew the aircraft down to about 5 gallons of fuel total (3 left, 2 right). Then, I uncowled it and routed the fuel line into some 5-gallon gas cans instead of the fuel injector servo. I drained the fuel from both sides using the electric fuel boost pump. I measured the remaining fuel by removing the fuel drains, and catching the remainder in measuring cups. In my right tank (normal fuel pickup) I only got about two tablespoons of fuel. In my left tank (flop tube), I got 4 ounces. I thought this seemed low, and wanted to be certain, so I put a liter of fuel in each tank, cranked the engine, and ran it until it quit (or at least, until it started to quit, I didn't let it continue to cough). Removed the fuel drains again, and the same result 2 TBSP and 4 ounces.
The RV-8A sits at/very near level flight attitude on its gear, so I think that was a good representation of a flight attitude. Reading through this forum, the amount sounds similar, but on the low side of average for what others have measured.
So, when I do my weight and balance, I'll use those small amounts as unusable fuel.
Here's my question!
I have resistive float fuel senders coupled to a Dynon system with a FloScan 201B. The senders are pretty good, but not accurate enough to measure fuel to the accuracy of my unusable fuel amounts. Should I add a small amount (1 liter maybe?) of fuel to each tank to set the "zero" for my fuel calibration, to account for gauge inaccuracy? Or should I trust that "zero is zero" and the gauge will let me know if I'm there accurately enough?
My next step is to do several calibration flights to ensure the Dynon fuel rate calculation is correct, and to calibrate the flowmeter setting.
