Garmin GI 275 question

[Llewtrah381]

Somewhere I thought I had seen that, for the AI version, the heading info at the bottom of the AI (circled in red) could be replaced with 3 or 4 boxes of other user-selectable data, if programmed as such at the time of installation. I think I even saw a screen shot of that. Now that I’m getting closer to actually getting them installed, I’ve looked all over and can’t find pictures or see a description in (older) install or current owner’s manuals. Does anyone know if this is a real option or did I maybe see it on an Aspen or something by mistake?



I know there’s an option to add a data box to the right of the one currently showing 350° in green. I’m hoping to swap out the heading stuff (available immediately below on the HSI) with wind speed, TAS, etc.

 

[Ryan Klems]

That picture is of the 4-in-1 config. You can switch to the 3-in-1 config (which drops the heading) to get the additional data fields. The 4-in-1 allows for one data field. See 8.7 on page 260 here: https://static.garmin.com/pumac/190-02246-01_l.pdf

 

[Llewtrah381]

That picture is of the 4-in-1 config. You can switch to the 3-in-1 config (which drops the heading) to get the additional data fields. The 4-in-1 allows for one data field. See 8.7 on page 260 here: https://static.garmin.com/pumac/190-02246-01_l.pdf

Thanks! I had seen that, as I mentioned below my pix but thought there was a way to eliminate the entire part I had circled and put boxes there.

And thanks for the link - that’s a newer version than what I had.

I may have seen what I’m asking for on an Aspen or something

 

[Ryan Klems]

Thanks! I had seen that, as I mentioned below my pix but thought there was a way to eliminate the entire part I had circled and put boxes there.

Yes, the picture you show is configured as a 4-in-1 instrument. If it were re-configured (installer configuration) as a 3-in-1, it would remove the entire heading section (the part you have circled). You can then fill that area in with the misc field boxes (GS, TAS, Winds). At least I think that's what you are asking about? I'd show a picture, but the 4-in-1 is the most popular config so that's pretty much all you find. Don't have an instrument handy or I'd take one for you.

edit: Actually, here is one from the install manual, 3-in-1 on left, 4-in-1 on the right, you can see the heading part removed. That then allows you to add more misc fields to the display (the boxes)... That I don't have a picture of.

 

[mr_happyland]

I grabbed this pic from the 275 FB user group. I'd like to do something similar if I end up installing them...

 

[Llewtrah381]

I grabbed this pic from the 275 FB user group. I'd like to do something similar if I end up installing them...
View attachment 114270

THIS!!! Exactly!

If that’s the 4-in-1 that Ryan mentions, that’s what I’ll ask my installer about. But thanks for the pix - it proves it’s possible

Add: I think it’s actually the 3-in-1 I’m after. But at least I know what to ask for!

 

[Ryan Klems]

THIS!!! Exactly!

If that’s the 4-in-1 that Ryan mentions, that’s what I’ll ask my installer about. But thanks for the pix - it proves it’s possible

Add: I think it’s actually the 3-in-1 I’m after. But at least I know what to ask for!

Yep, @mr_happyland's pic shows the 3-in-1 ADI configuration (install configuration) with 4 misc fields (TAS, GS, OAT and Winds) enabled (user config, as per 8.7 of the pilots guide).

 

[iamtheari]

Garmin is really selling themselves short with those “3-in-1” and “4-in-1” configurations. By my count, the 3-in-1 has:

1. Attitude
2. Airspeed
3. Altimeter
4. Vertical speed
5. Turn coordinator

 

[Ryan Klems]

Garmin is really selling themselves short with those “3-in-1” and “4-in-1” configurations. By my count, the 3-in-1 has:

1. Attitude
2. Airspeed
3. Altimeter
4. Vertical speed
5. Turn coordinator

Garmin considers the 3 functions of the 3-in-1 to be Attitude, Altitude and Airspeed. The 4-in-1 adds the Heading. But you are correct, (and also skid/slip) though the TC/rate of turn aspect requires the addition of the GTP59 (for TAS computation).

 

[Llewtrah381]

the TC/rate of turn aspect requires the addition of the GTP59 (for TAS computation).

Thanks for this. I double-checked and saw the probe is an option - a $560 option! I chatted w my installer and apparently the probe came with the setup he had ordered. Whew!

 

[WDD]

Can you have your Navigator / GTN send the signal to both the 275 AND a traditional CDI at the same time?

 

[Ryan Klems]

Can you have your Navigator / GTN send the signal to both the 275 AND a traditional CDI at the same time?

Unlike the G5, the GI-275 STC does allow that, with some caveats. Only one device can provide the selected course to the navigator, so if you have a secondary CDI, the GI-275 would be configured to not set the selected course and the mechanical CDI would have to provide that. It's a little different if using composite signal for the mechanical CDI, but different limitations would apply. I generally don't think it's a good idea to do it however.

 

[Randomskylane]

Unlike the G5, the GI-275 STC does allow that, with some caveats. Only one device can provide the selected course to the navigator, so if you have a secondary CDI, the GI-275 would be configured to not set the selected course and the mechanical CDI would have to provide that. It's a little different if using composite signal for the mechanical CDI, but different limitations would apply. I generally don't think it's a good idea to do it however.

I’m not following this. The garmin gps is sending info to the 275 and cdi, right? Are you talking about setting the heading bug, which I guess goes the other direction (for autopilot for example?)

 

[Ryan Klems]

I’m not following this. The garmin gps is sending info to the 275 and cdi, right? Are you talking about setting the heading bug, which I guess goes the other direction (for autopilot for example?)

No, not heading, the navigation course. This is true for GPS too, but might be easier to understand thinking of a VOR. You set the course to whatever radial you want to follow for the VOR, the navigator gets the selected course, and then drives the left/right needle the appropriate amount based on that selection. If the GI-275 was providing the selected course, then the OBS on the mechanical CDI wouldn't do anything, you could dial whatever course you wanted and the needle wouldn't move.

 

[WDD]

Interesting - thanks. The only reason I’m picturing this is to have the traditional large needles to use for approaches. I flew a few approaches using a G5 and found the small altitude dot to be difficult. Maybe for me it’s just different.

 

[iamtheari]

Can you have your Navigator / GTN send the signal to both the 275 AND a traditional CDI at the same time?

This came up in a different thread (one by @Salty) regarding having an Aspen and a CDI both sourced from the same navigator. I don't know if the GI 275 and/or G5 differ in that regard, but I recall that at least the navigator discussed there would tolerate an OBS input from the Aspen and, if the Aspen failed, from the CDI.

 

[Llewtrah381]

Unlike the G5, the GI-275 STC does allow that, with some caveats. Only one device can provide the selected course to the navigator, so if you have a secondary CDI, the GI-275 would be configured to not set the selected course and the mechanical CDI would have to provide that. It's a little different if using composite signal for the mechanical CDI, but different limitations would apply. I generally don't think it's a good idea to do it however.

I'm wrapping up an install of two 275s, with one an HSI, and am trying to have it display NAV from a KX-170B (technically, a MAC 1700). I'm also wanting to keep the existing CDI working. My Avionics installer believes this is doable but we're not having much luck. The NAV works fine on the old CDI and the 275 receives the test signal just fine in the Admin pages - but it won't show course deviation at all.

My question: as a non-Avionics guy, I had understood the CDI was doing most of the work rather than the MAC 1700. I thought the MAC sent out a "pulse" reference signal plus a variable azimuth signal and the CDI sorted it out (for VOR); I didn't think the radio actually did any of the math and didn't think the CDI provided "...the selected course to the navigator...", as you say. If true, it seems plausible more than one device could be connected and could display different radials (and their offset). Is that incorrect? Is there actually some feedback/input from the indicator to the radio itself to tell it which radial is dialed in? I've looked at a KX170B wiring in an install manual and don't see where it would feed back from the indicator to the radio, but I'm by no means knowledgeable on such things.

My installer has been on the phone with Garmin about this a few times with no success. I'm now wondering if the Garmin tech didn't know a second CDI was in the loop.

 

[Ryan Klems]

I'm wrapping up an install of two 275s, with one an HSI, and am trying to have it display NAV from a KX-170B (technically, a MAC 1700). I'm also wanting to keep the existing CDI working. My Avionics installer believes this is doable but we're not having much luck. The NAV works fine on the old CDI and the 275 receives the test signal just fine in the Admin pages - but it won't show course deviation at all.

My question: as a non-Avionics guy, I had understood the CDI was doing most of the work rather than the MAC 1700. I thought the MAC sent out a "pulse" reference signal plus a variable azimuth signal and the CDI sorted it out (for VOR); I didn't think the radio actually did any of the math and didn't think the CDI provided "...the selected course to the navigator...", as you say. If true, it seems plausible more than one device could be connected and could display different radials (and their offset). Is that incorrect? Is there actually some feedback/input from the indicator to the radio itself to tell it which radial is dialed in? I've looked at a KX170B wiring in an install manual and don't see where it would feed back from the indicator to the radio, but I'm by no means knowledgeable on such things.

My installer has been on the phone with Garmin about this a few times with no success. I'm now wondering if the Garmin tech didn't know a second CDI was in the loop.

Older nav receivers such as the 170's typically used a "composite" nav signal, and the CDI did all the resolving. They also didn't have the glideslope receiver built in, and used a separate glideslope receiver that was channeled by the nav unit (sometimes the glideslope receiver was built in to the CDI, such as the KI-212). Later units do the resolving inside the nav unit, via the OBS signals from the CDI. So in your case the CDI _is_ doing most of the work, essentially the raw nav signal is passed through to the CDI and it does all the interpretation. With regards to this setup in your install, has the composite nav calibration procedure been done on the GI-275?

 

[Llewtrah381]

Older nav receivers such as the 170's typically used a "composite" nav signal, and the CDI did all the resolving. They also didn't have the glideslope receiver built in, and used a separate glideslope receiver that was channeled by the nav unit (sometimes the glideslope receiver was built in to the CDI, such as the KI-212). Later units do the resolving inside the nav unit, via the OBS signals from the CDI. So in your case the CDI _is_ doing most of the work, essentially the raw nav signal is passed through to the CDI and it does all the interpretation. With regards to this setup in your install, has the composite nav calibration procedure been done on the GI-275?

View attachment 115546

Thanks for the reply and explanations.

He has it set on Composite and did do the calibration you noted. Interestingly, when doing that, there was the word “Active” at the top with an unchecked box and no apparent way to check it. This was while he had the calibrator working (my pix was just now and not with the calibrator). The Garmin rep had no idea what he was referring to and it’s not noted in the installation manual.

This feels like a configuration issue rather than a wiring one. That said, I’m checking with my installer to see if it’s worth trying to disconnect the CDI and see what happens; if that resolves it, maybe he could put in a toggle switch to enable me to pick the display.