Garmin G5 or GI275 for backup AI?

[vfa192]

I'm in the process of upgrading the panel in my RV-8 and am trying to decide what to use for backup AI. In terms of Garmin products, what advantage would the G5 have over the GI275 with ADAHRS? It seems most people today go with the G5. I'm just not sure why?

I regularly fly the aircraft in light IFR (min 1,000' & 2SM) so I'm designing the panel to have some redundancy for GPS and COM. I'm planning on installing a G3X touch along with GTN750, GNC255, and GMC307 autopilot control. Here's what I had in mind?



Any opinions/recommendations on backup AI and panel layout would be appreciated.

---
Mark Ross
RV-8 N184MR "Drone Killer"

 

[kirkbauer]

The GI275 is only available as a certified product and therefore it is about twice the price. I like the looks of it better than the G5, though. Does the GI275 have backup battery and lightning protection options like the G5 has available?

 

[larryj]

I had a G5 in a previous airplane and now have a GI275 in my current airplane. The GI275 is more capable, higher resolution screen and I prefer it. Both units have back-up battery (if installed) and the GI275 integrates with my G3X Touch just fine. Caveat: I've read the G5 integrates with the G3X with more functionality than the GI275 although this has not been an issue for me; the GI275 with the latest software update and the proper wiring works pretty good with the G3X. I don't have an autopilot but the GI275 manual covers running an autopilot with it. All of my stuff is certified (just a data point).

 

[mburch]

One question I'd have is whether the GI275 works with the G3X Touch autopilot in the same way that the G5 does in the event that the G3X Touch PFD stops working,

No, it does not.

 

[Carl Froehlich]

Some thoughts:
- The G5 is a backup. The GI275 is a very expensive enhanced backup. In other words the cost to value ratio is not there.
- A full functional 7” display second EFIS to go with your 10” display is, in my opinion, a better way to go. This however will require you rethinking the GTN-750 to free up the needed panel space. The 750 is a good backup moving map but not a PDF. A 7” EFIS is both.
- The GTN-650 and 750 both provide the certified IFR capabilities you want. Both feed your EFIS displays so the larger 750 screen is redundant - and considering the panel space restrictions it is more problem than solution.
- Remote XPDR and remote COMM #2 are recommended. I assume Garmin offers these.
- Having the autopilot control low bucks the trend - but I consider this location superior to the standard of high on the panel. Keep the stuff you look at high. The autopilot control box should where you hand falls on it.
- Continue to keep the EFIS displays as high as possible. If you use the GTN-650 keep it high as well to fat finger in the ATC reroutes.
- At some point you will want to make changes. Plan on this. For example move the air vents off the panel. Easy enough to hang them below the panel, one on each side.

The photo is the SkyView version of all this. Note at some point I may change out the analog airspeed instrument for a G5. The center potion of the panel is fully removable in ~15 minutes - addressing the aspects of maintenance and future panel changes.

 

[georgemohr]

The G5 is a great backup option, its very simple, its inexpensive, and its very dissimilar in code and platform hardware from the rest of the avionics.

 

[Walt]

I'm a fan of the GI275, much nicer hi-res screen, sits flush, interfaces to the G3X is via 232 (vs CAN bus) which I like, less likely for CAN bus issues to affect the operation, 100% independant of the G3X in other words. Has multiple screens like: map, HSI/CDI, traffic, weather, terrain. Shares database with the GTN via HSDB. The only thing it lacks IMO is flight director/AP interface to the G3X (but it does show approach guidance info), fingers crossed that's on the someday list for FD/AP interface.



This was an older 2 screen install that I did in an RV8, (the touch and G5 wasn't out yet).
I think the 2 screen layout looks nice and adds redundancy.
I think I had to extend the panel for this setup but that's what he wanted.
I would arrange things a little differently normally.

 

[georgemohr]

Here's ours for ref:

 

[donoraz]

I'm a fan of the GI275, much nicer hi-res screen, sits flush, interfaces to the G3X is via 232 (vs CAN bus) which I like, less likely for CAN bus issues to affect the operation, 100% independant of the G3X in other words. Has multiple screens like: map, HSI/CDI, traffic, weather, terrain. Shares database with the GTN via HSDB. The only thing it lacks IMO is flight director/AP interface to the G3X (but it does show approach guidance info), fingers crossed that's on the someday list for FD/AP interface.

View attachment 73782

This was an older 2 screen install that I did in an RV8, (the touch and G5 wasn't out yet).
I think the 2 screen layout looks nice and adds redundancy.
I think I had to extend the panel for this setup but that's what he wanted.
I would arrange things a little differently normally.

View attachment 73783

Does anyone know if the GI275 will drive the GMC 507 autopilot in the event the Axis fails?