G5 still the best option for G3X backup instrument

[PT20J]

The G3X, G5 and GFC 500 were designed to work in concert and they share resources seamlessly. Fail the G3X ADAHRS and it uses the G5 ADAHRS. Fail the entire G3X and the G5 will drive the GFC 500. 

When the GI 275 was introduced, Garmin allowed it to be used as a G3X standby, but it was dumbed down to the equivalent of a stand alone ADI. It didn't integrate with the G3X or share resources like the magnetometer, it couldn't connect to a GPS, and it wouldn't drive the GFC 500. Garmin has fixed most of that. But in reading the AFMS for the latest G3X software 9.15, I notice that a GI 275 still cannot drive the GFC 500 in a G3X installation. Maybe Garmin will eventually fix that. But right now, I would not install a GI 275 with a G3X because there is not backup for the autopilot.

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[blaine beaven]

Has this changed yet, and the GI 275 is able to drive an autopilot with a G3X? 
 

I’m going to order equipment next week for my avionics upgrade and wondering about GI 275 v G5. 
 

Thanks!

[ArtVandelay]

G5/G3X/GFC500 is developed by same group (experimental), 275 is from the certified team, so I have doubts about it being completely integrated.
But nothing prevents you from installing both. You can put G5 on the left side of the panel.

[PT20J]

Most of the capabilities are driven by software and Garmin has more software updates than Microsoft or Apple .

The only way to be sure is to get with your avionics shop and carefully review the frequently updated proprietary installation manuals which should describe the limitations. 

The current version 6 of the G3X AFMS still says that the GI 275 will not drive the GFC 500 If the G3X or GSU 25D fails  (the G5 will), and the G3X will not display comparison alerts from between the GSU 25D and the GI 275. 

The G5 is cheaper, better integrated with the G3X, and has a longer battery run time than the GI 275.  Personally, I would still choose it if I were designing a G3X panel today.