Mini-X versus G5 as backup for G3x

[BobTurner]

Just like rs232, one ‘out’ can power several ‘ins’, as long as both ins can read the format that’s sent.

[rapid_ascent]

Bob,

What about the other direction? To the navigator.

[BobTurner]

One ‘in’ can only see one ‘out’, or there will be gross confusion. Just hook up out from the main efis to the navigator’s ‘in’; nothing out of the standby efis to the navigator. If you lose the primary efis the navigator will continue to function without any efis data coming in; you’ll lose some things, like wind vectors on the gps.

[rapid_ascent]

The 430W has 2 ARINC inputs. Can those be wired one input to each EFIS and then selected via configuration or would this happen automatically or it doesn't work that way?

[BobTurner]

I don't know the answer. In an emergency you certainly don't want to have to go into the 430 set up menu! I'd have to read the manual (who does that?!!) to see what the 430 does if there is redundant data coming in on the 2 inputs. Or, as I said, just not hook up the standby EFIS.
I'd be curious to know what you find out.

[N49ex]

Originally Posted by BobTurner

You really mean "sort of independence". You're hoping no sort of crazy software error can propagate over the baro setting link. Or the software update link.

I went with RocketBob's approach: different brand for back up EFIS, absolutely no connections to main EFIS. Yes, I have to set baro settings in two places.

In that case, another option is to not connect the CAN bus to the G5 and add a GMU11 magnetometer. Then it is truly standalone. That way you still maintain the common look and feel and have a better battery life.

If you want to imagine "crazy software errors" transmitted over the CAN bus AND somehow causing the G5 to go crazy, that's a bit out there. BUT, quick story from commercial jet design - in the world of triplicated redundancy and voting, there have been approaches for ultimate independence by using separate development teams to generate the software and voting on checkpointed data, and lo and behold, they found that different teams could make the same mistakes based on common specifications, and the votes could pass, and there were still errors due to the common mistakes!

Goes to show you, there's always something!

[BobTurner]

Yep. I recall some years ago a major experimental avionics company got a new software upgrade thru beta test and distributed it. Everything was fine-until someone tried an alphanumeric airport ID (e.g., C83 vs KLVK). Every interconnected efis crashed.

[BobTurner]

Originally Posted by rapid_ascent

The 430W has 2 ARINC inputs. Can those be wired one input to each EFIS and then selected via configuration or would this happen automatically or it doesn't work that way?

Per the manual the 430 will look first at arinc inputs, then rs232, ... There is also a hierarchy for various arinc formats. But if they are both the same, I don’t know. Maybe you can send data efis to 430 via rs232 for the backup, that would definitely be the source only if the main arinc source failed.