I calibrated the fuel tank senders today. I’m using the Princeton two-point capacitive senders which are pretty straightforward to calibrate. Here are the basic steps:
- Empty the tank (I had already done this when determining unusable fuel for the W&B).
- Power on the sender.
- Hit the set button to set the empty point.
- Fill the tank.
- Hit the set button again to set the full point.
The sender then puts out the full 0-5V range from empty to full. This is much better than the Dynon capacitive senders which can’t be calibrated and generally put out a small fraction of that voltage range across the whole tank capacity. The Princeton senders solve the dynamic range problem, but the voltage still doesn’t necessarily follow the fuel volume in a linear way. The SkyView system solves that by including a separate calibration mechanism where you add fuel 2 gallons at a time. Each time fuel is added, a button is hit on the SkyView to correlate that particular voltage reading from the sender with that fuel volume. Unfortunately, this means that I need to start over with an empty tank to do the SkyView calibration. Since I don’t have any interest in draining that much fuel out of the tanks, I’ll have to wait until I’m flying and can burn down the fuel.
I did this for the left tank by pouring fuel from gas cans into the tank, but it was very time consuming and I ended up spilling some gas. Since I hadn’t run the engine in a month, I taxied the plane down to the pump to calibrate the right tank. I used that as an opportunity to break in the brakes a bit more too.
Using the capacitive probes with the Princeton senders should result in a nearly perfectly linear fuel gauge reading across the entire tank capacity. This is quite a bit better than the resistive senders which read empty when there is still a fair amount of fuel in the tanks and reads full well below the full capacity of the tank…