fs35 Electronics and Avionics

In principle, the fs35 contains a CD155 retrofit kit for the DA40D. However, since many cable harnesses are reused when converting a DA40, they are missing in the kit. We therefore decided to take over the entire electrical system from the Cessna172-CD155 installation, so we can be optimally supported by Technify Motors. In order to meet the requirements of a redundant FADEC power supply, the aircraft power supply from the CD155 Cessna conversion kit was also used. As can be seen in the picture, we have arranged the electrical components much more compactly than in the spacious Cessna, since our firewall compartment is much smaller.

The other side of the firewall was also a bit cramped. Here the FADEC (full authority digital engine control), generator control unit, engine wiring harness, backup batteries for engine controls and the Dynon system, transponder, radio, as well as the collision warning device and the entire wiring for the instrument panel are all accommodated.

After constructing brackets for all of the components, we started laying the cables. We realized that although many planes have been built in our workshop, we’ve done little electrical engineering. Therefore we had to first acquire the proper tools, cable lugs and crimp contacts for plugs.

It has proved to be extremely practical to label all cables with a shrink tubing labeling device during installation. These were then also documented in the circuit diagram. We used white plastic L-profiles, which are later removed, to help us lay the individual wires cleanly and construct the wiring harness.

After all the cables for the power supply and engine electronics had been laid and two days of testing and measuring, came the exciting moment. Connect the battery for the first time, plug in the fuses, switch on the main switch. Will it smoke? Is a fuse missing? No! The CED (Central-Engine-Display) and the AED (Auxillary-Engine-Display) started and began to light up. Then we did some tests on the engine electronics and started installing the avionics in the instrument panel. The central elements are two Dynon Skyview HDX displays. The Dynon system communicates via serial interfaces with the transponder, collision warning device and GPS module. The connections to radio, intercom, the sensor data box with IMU and between the displays are established via the Dynon SV-Net.

For most components of the Dynon system we used the supplied plugs and cables, which simplified the installation considerably. The audio cables of the Intercom, which is connected to the radio, headsets and collision warning device were routed through the canopy frame into the luggage compartment to the headset jacks. The coaxial cables to the radio, FLARM and ADSB antennas in the vertical fin and to the transponder antenna on the underside of the fuselage below the tank also run through the canopy frame.

After the first power on of the avionics the Dynon system was configured. Now both displays communicate with each other, as well as with transponder, radio and collision warning device. Collision warnings are also displayed on the AIR Traffic Display from AIR Avionics. During initial tests in the workshop, we were able to receive ADSB signals and radio messages from passing airliners.

The Dynon is equipped with a moving map and a primary flight display with artificial horizon, direction, and altitude display. Alternatively, these can be displayed as round instruments. The map and the PFD can be separately displayed on the two screens, as well as on a split screen. In addition, a towing camera is to be installed in the future.


In the near future we will continue with the production and installation of the control stick, replacement of the provisional instrument panel, installation of the electrical trim and lighting, the electrical heating control and wiring of the fuel pump and the propeller electronics.