ECU Backup switch - How does it work?

[Will]

Hello All! I recently asked on the Rotax Owners Form Page https://www.rotax-owner.com/en/915is-te ... 1-failure about the 915si engine about this question.

And the question is this. I know for instance that in the POH of the Sling Tsi that it says to switch off the ECU backup after priming the pumps and switch it off before the engine starts. But I want to understand this.

If the ECU Backup switch is on all the time, will the EFIS warning you first off that the Alternators 1 & 2 have died if they ever do. Or will nothing happen and you will keep flying the plane without knowing anything is wrong until the battery dies and you fall out the sky.

So my question to the form to make it easier to understand, is this. Is it 100% necessary to make sure that ECU backup is switched off. And if it is left on, will the EFIS warn the pilot about the alternators breaking if they ever do.

Thanks All!!

[Will]

Trying to make more sense of this question....

I am basically asking what and how does the ECU Backup switch in the Sling TSI work.

Will the plane alert you if both gen1 and gen2 fail if the ECU switch is on.

and is it bad to have it on all the time?

Thanks Guys!

[Heftiger]

I think this video will answer your question:

[ibgarrett]

I happened to show this video to my wife last night... if you watch it you may see hippie Jean in the video...