Garmin GI275 MFD un-sync CDI side-sync

T

turbosuper

Pre-takeoff checklist
Joined
Aug 3, 2021
Messages
130
Display Name
turbosuper
I have an experimental GI275 ADI, GI275 MFD, and a GTN750Xi. In order to have the GTN CDI button control the ADI so that ILS energize works on both, you must have CDI side-sync set to "Aways On" in the ADI config. The issue is, the CDI side-sync setting is pushed to both GI275s. I need CDI side-sync on for the ADI, but off for the MFD. This does not seem possible. The MFD is the CDI display for NAV2/GPS2.
 
Does anyone have a working similar setup where you have a GTN CDI button controlling the NAV source on a GI275 ADI and another GI275 as CDI for NAV2/GPS2?
 
What are you trying to accomplish?

FWIW, I have twin GI 275s and GTN 650xi. I control the CDI source from the GI 275, not from the GTN.
 
WDD said:
What are you trying to accomplish?
Click to expand...
I want to control CDI source on the 275 ADI with the CDI button on the GTN. What NAV indicator do you have for your nav2?
 
I’ll try take some pictures when I schlep out to the plane tomorrow.
 
After contacting Garmin support the short answer is, the Garmin system cannot do this. With one GI275 ADI, a GI275 MFD and a GTN, there is no way to isolate the CDI of the MFD 275 from the ADI and have the ADI be CDI synced to the GTN. The answer is to buy more Garmin.

One of the issues with my current setup is that the ADI has no dedicated CDI button (it is not quick or user friendly to go into the menu to change nav source) so the GTN CDI button really needs to control the ADI.

If a GI275 ADAHRS HSI was added to the system then the ADI and HSI would be CDI synced with both set as pilot units and the HSI CDI button would control the ADI source, but still not the GTN as that would require CDI side sync set to Always On thereby also syncing the MFD. The MFD could be set as a co-pilot unit and CDI side sync set to pilot control and off in the pilot config menu. This would allow the MFD to independently select its nav source. It seems the GI275s do not integrate fully with a GTN, at least with respect to CDI source selection.
 
Last edited:
Not sure if this helps, but I control the source (LNAV, GPS1, GPS2) from the GI275 HSI. See the “CDI” selector touch screen button center bottom of the HSI. This selects source for both GI 275s IMG_1264.png
 
Does the nav source displayed on your GTN also change when you use the HSI CDI button? Is GPS2 also a GTN? What if you select GPS2 on the HSI, what nav source is shown on GTN 1?
 
I have a GTN 650xi for GPS 1 and LNAV, and a GNC 375 for GPS 2.

I don’t have an indicator or selector for CDI source on my GTN 650xi.

My GTN and GNC are synced, and my GI 275s are synced as well. The GI 275 ADHR is backed up (required) by the GI 275 HSI, so sync is necessary.
 
Last edited:
Does ILS energize work when doing an ILS approach? If you load the LOC freq into active on the GTN does it auto switch to LOC prior to the FAF?
 
Yes, GI 275 HSI switched to ILS / VLOC when I had the ILS loaded and activated.
 
My dual GI275s are linked....and looks/functions just like WDDs....
 
I had the same issue (I think) when my 3rd 275 was installed. Side sync was on and the mfd and HSI would only show the same source. Configuring the mfd so bacically it though it was on the copilot side lets me select the CDI individually. I only select the CDI source on the 275 though. I don’t think I touch the CDI on my 750.
 
manac said:
I had the same issue (I think) when my 3rd 275 was installed. Side sync was on and the mfd and HSI would only show the same source. Configuring the mfd so bacically it though it was on the copilot side lets me select the CDI individually. I only select the CDI source on the 275 though. I don’t think I touch the CDI on my 750.
Click to expand...
Do you have a CDI key on your GTN750?
 
Trying to envision how you'd control two different instruments with different navigation sources within your GTN 750. The GTN 750 can control what navigation data it sends out (Nav radio or GPS), but how would it even "know" that a second navigation source exists let along control it? Would you envision your GTN 750 with two different CDI buttons, one labeled CDI 1 and the other CDI 2? Thus I believe this is why when you have multiple sources the CDI selection is controlled by the GI 275, as it can "see" the other sources.

turbosuper said:
The MFD is the CDI display for NAV2/GPS2.
Click to expand...

You mentioned you have a GTN 750, assume that is your Nav1 / GPS 1. What is your Nav2 / GPS2? You could always go "old school" and have an dedicated CDI, maybe a simple mechanical one, to the Nav2/GPS2. You'd then only send the GTN 750 navigation data to your GI 275.

All in all, probably the cleanest approach would be to replace your current DG with a GI 275 HSI, tie all of your navigators into it, and select CDI source from the GI 275 HSI. Yeah, I think you're looking at ....

turbosuper said:
The answer is to buy more Garmin.
Click to expand...
 
Last edited:
WDD said:
You mentioned you have a GTN 750, assume that is your Nav1 / GPS 1. What is your Nav2 / GPS2? You could always go "old school" and have an dedicated CDI, maybe a simple mechanical one, to the Nav2/GPS2. You'd then only send the GTN 750 navigation data to your GI 275.
Click to expand...
Nav2 / GPS2 is a KX165A and GPS 175
 
  • Like
Reactions: WDD
Are you syncing your G175 and GTN? Input on one changes and also shows on the other?
 
You must log in or register to reply here.
Back
Top