Rotax 912is/915is Installation

[VictorV]

Both of these engines have the same basic wiring so I'm interested in hearing from those that have either type of engine.

There are 5 cables that come from the engine lanes which interface with the ECU (3 of them) and the rest of the aircraft electronics (the 2 HIC connectors).
4 of them have a ground tab on them and I am trying to determine where the ground tab is supposed to be connected. The 2 options are EMS
ground (on the fusebox) and airframe ground. The EMS ground is connected to the airframe ground only during application of start power.
In the 915is installation manual there are 2 references to these grounds and they appear to contradict each other:

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Screen Shot 2023-08-21 at 6.15.52 PM.jpg

and

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Does anyone know which one I should follow?

Victor

[Redline]

Victor,
I hesitate giving much input because a) I'm not an expert at this, and b) we have yet to perform the first start-up and test of the engine (a few more weeks!). My dad and I spent hours reading both the Rotax and Kitfox installation manuals, and probably made a few dozen calls to confirm.

Section 77-00-00 has a good image showing some of what you're inquiring about. Section 24-00-00 has a wiring diagram (AE 5S_0160) that we stared at for hours. The small ring terminals ground to the M4 posts on regulator A. Regulator B is grounded to the airframe. The other larger ring terminals from the electromagnetic shielding wires can ground to the firewall.

Evan Brunye did a great video overview of the 915 when he was building his Sling (he's since built a Kitfox and won a builder award). This was very helpful: https://www.youtube.com/watch?v=2VaiBcHjzlA

Hope that helps. And if any of you 912is/915is veterans spot an error in what I'm saying, please let me know!

[VictorV]

Victor,
The other larger ring terminals from the electromagnetic shielding wires can ground to the firewall.

Those are the ground wires I was referring to. The grounds on the other end (engine side) go to their
respective Regulator A/B.

Anxious to hear what others say.

Victor