915 (12V) Wiring Harness Question

Rotax don't waste any ink! And the labelling on the wiring is wanting as well. You really need to read and reread the installation manuals of the 915iS. Pictured is what I did for the HIC FRAME connectors as there are 2 earthing systems which can't be connected together.

Also be aware that you only have a minimal amount of times that  you can insert and remove those HIC plugs. Apparently the contact coatings degrade. Unbelievable.

Another trick when earthing is to use stainless steel hardware and star washers which bite into the connectors. Also dielectric grease. This is aviation not automotive wiring.

And incidentally I mounted the ECU inside the gyrocopter. Mounting electronics next to high temperatures is never a good idea. (maintain your fire rating through the fire wall with the correct hardware!)

Regards......Chook.

I understand the two earthing(ground) systems, and the insertion limited EMU connectors (Not HIC connectors).

The EMU electrically isolates the mounting hardware from the EMU itself. 

If you attached this to the Airframe (and consequently the Airframe ground) then the bolt with be tied to the Airframe ground. I am assumeing that the EMU ground is connected to the Regulator A ground through the EMU connector. The ring connector will be at aircraft ground potential.

From the install manual:

The casing of the ECU must not be connected to the airframe ground. The rubber vibration damping (insulation material) must not be removed. If the rubber dampers were removed, the engine ground and the aircraft ground would be short-circuited.

So in your picture if the mounting bolts for the EMU are mounted to aircraft ground ... then the ring connector will also be at airgraft ground potential.

In my case this is to a carbon fibre bulkhead. Not quite Aircraft ground, but not quite isolated either.

The other end (Near the HIC connector) , I am not sure where those wires are going to in your aircraft  ... can you elaborate ? Are you connecting the two ring connections, associated with the two HIC connector bundles to aircraft ground ? 

My only guess is that this has something to do with lightning protection ... having a small air-gap between the EMU and aircraft ground (via the rubber dampers) to disipate a strike.

Richard it has been 2 years since I wired this machine up and I promised myself that I would not do another. However it was wired it allowed isolation between the Engine and Frame earths until they are connected by the ECU as checked with a meter.

I would have to revisit this machine and ask the owner if I could remove the engine covers so probably not. 

I am heading up to my hangar Friday(tomorrow) and Saturday and if I find some of my notes on this job I will put them up here for you.

Regards.....Chook.