7.7.22 Capacitive Fuel Sender Plates & BNCs

I have decided I will be using the capacitive fuel sender system. The primary reason for this is the dihedral (angle) of the wings. Looking at the plans it appears that the bottom of the outboard end of the tanks is almost level with the top of the inboard end. For this reason a dipstick can only measure from full to half empty and a float style fuel gauge can only measure from half full to empty.

However, a capacitive fuel gauge measures the volume of fluid in the tank through capacitance. This gives a much wider range of measurement than either of the two above. The downsides are that changing fuel types requires re-calibration of the EFIS and servicing it is nearly impossible if it develops any problems. I don’t plan to change fuel types very often so problem #1 is not a big issue for me. If I have any problems with the capacitive system I will then fit a float sensor if need be.

The capacitive system uses two plates in the fuel tank that are connected together by wire and then connected to the BNC connector.  All this is isolated from the main tank structure by non-conductive washers. So the first step is to position and drill holes for BNC connector as well as the vent tube fitting in both inboard fuel tank ribs.

Once the holes were drilled I trial fitted the connector and elbow. I was very pleased at how close/tight that fitting turned out. Being a fuel tank it was important to keep cuts as close as possible to minimise possible leak points.

The next step was to find the capacitive plates and match drill them to the ribs in the correct locations using the prepunched holes in the plates. Once that was done I match drilled the nut plates and then dimpled the cap plates and nut plates. Finally I riveted on the nutplates and with that all 4 cap plates were done and ready to use.

That’s all for today’s session.

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