Garmin GI-275 Install Question

[AerostarDriver]

I am trying to install a GI-275 MFD with a GNS-480 already hooked up to dual G5s. Does anyone know if it is possible for the GI-275 to work by splitting the ARNIC 429 NAV and GPS Outs that are also going to the GAD 29B while not using the ARNIC 429 return? I just want to use the GI-275 as an MFD but Garmin cannot seem to provide an answer, in fact they told me that the GI-275 does not support the GNS-480 which their own website and the install manual do not reflect their claim.

[Yetti]

In theory since I can't find an install manual.  If the 275 has a Canbus that would be how it talks to the GAD29   The GAD29 has both ARINC 429 inputs and outputs.

 

Canbus is a network where you can add many devices to it.  Same thing Garmin uses for Marine communications.    GAD29 install manual has a great description on the CANBUS network.  

 

Sorry not a Garmin guy.   But I have installed a Dynon Skyview.   Which uses a Serial network instead of Canbus.

[McMooney]

On 2/2/2021 at 10:03 PM, AerostarDriver said:

I am trying to install a GI-275 MFD with a GNS-480 already hooked up to dual G5s. Does anyone know if it is possible for the GI-275 to work by splitting the ARNIC 429 NAV and GPS Outs that are also going to the GAD 29B while not using the ARNIC 429 return? I just want to use the GI-275 as an MFD but Garmin cannot seem to provide an answer, in fact they told me that the GI-275 does not support the GNS-480 which their own website and the install manual do not reflect their claim.

what else is connected, the 480 has a good number of arinc 429's

[AerostarDriver]

13 hours ago, McMooney said:

what else is connected, the 480 has a good number of arinc 429's

I believe with my GAD29B I am using both available outputs with my GAD using one input and then my GTX-330ES using one input for traffic. This would leave me with 1 unconfigured input and the ability to split both the 429 outputs if the protocol was correct. After talking with Sarasota avionics it does not look like it is possible unless I give up traffic on the GNS 480 and have the GI-275 be the only traffic display. Another option that was raised by my A&P was to use a MX20 and MX200 MFD which would give me more ARNIC in and outs BUT would kind of defeat the point as I don't have the panel space and I am looking to use the GI-275 as the MFD.  Sarasota avionics recommended I call Garmin to see if the GI-275 would pass the traffic back to the GNS-480 but Garmin tells me, "The GI-275 is not listed for compatibility with the GNS-480 and that my installer can work with Garmin engineers to figure out if that is possible".  

[McMooney]

17 minutes ago, AerostarDriver said:

I believe with my GAD29B I am using both available outputs with my GAD using one input and then my GTX-330ES using one input for traffic. This would leave me with 1 unconfigured input and the ability to split both the 429 outputs if the protocol was correct. After talking with Sarasota avionics it does not look like it is possible unless I give up traffic on the GNS 480 and have the GI-275 be the only traffic display. Another option that was raised by my A&P was to use a MX20 and MX200 MFD which would give me more ARNIC in and outs BUT would kind of defeat the point as I don't have the panel space and I am looking to use the GI-275 as the MFD.  Sarasota avionics recommended I call Garmin to see if the GI-275 would pass the traffic back to the GNS-480 but Garmin tells me, "The GI-275 is not listed for compatibility with the GNS-480 and that my installer can work with Garmin engineers to figure out if that is possible".  

Just reread the installation manual  3tx 2rx

Not an avionics tech but the Arinc429 specification shows the ability to daisy chain up to 20 receivers per arinc429 tx.  

[Minivation]

Well, it appears I certainly got myself into a rabbit hole with this one.

I am referencing the following documents:

• Garmin GNS480 installation manual, 560-0982-01 Revision M
• Garmin G5 Part23 AML STC installation manual, 190-0112-10 Revision 24
• Garmin GI-275 Part23 AML STC installation manual, 190-02246-10 Revision 7

[quote]Does anyone know if it is possible for the GI-275 to work by splitting the ARNIC 429 NAV and GPS Outs that are also going to the GAD 29B[/quote]

TECHNICALLY speaking, this technically should work. The GNS480 features 3 A429 inputs and 2 A429 outputs. When connecting to an EFIS (including the G5 via GAD29) both of the outputs are occupied, one in GPS "GAMA429" format (GPS position, navigation waypoint info, etc.) and the other in Nav "VOR/ILS" format (lateral and vertical HSI deviation info). (I am not sure if the GI-275, when configured for MFD mode, would even make use of the VOR/ILS info, though) In addition, one input is used under "EFIS" format (selected course, airdata, etc.)

[quote]while not using the ARNIC 429 return?[/quote]

Since the EFIS input INTO the GNS480 pertains to information generated by an air data computer (see GNS480 IM Page 2-34, Table 2-9, Column 3) the GI-275 need not (and should not) need to provide a return to the GNS480. The G5 is sufficient.

Note that the flight plan info, including the proverbial magenta line, is communicated to the G5 / GI-275 separately via an RS232 channel in "MapMX" format. Whatever RS232 output from the GNS480 to the existing G5 HSI using this format will need to be spliced to run to the GI-275 as well.

As @McMooney mentioned, A429 specs call for enough current to drive up to 20 receivers. Of course, there is a wire run limitation of something like 150ft, but that's way beyond the scope of GA aircraft. As per a previous conversation I had with Garmin, each RS232 output can only reliably drive 2 devices, maybe 3.

Alternatively, the GI-275 has a built-in GPS receiver, so maybe installing a separate GPS antenna and running a coax cable to the GI-275 may be an easier solution, but surely less elegant.

== Other Considerations ==

That said, the LEGALS are what I'm not quite sure on. I can only reasonably assume the GNS480 and G5 (and its associated LRUs) were installed under STC, and so will the GI-275. The GI-275 install manual explicitly mentions the GNS480 as a "compatible GPS source" under Appendix C.4 Table C-5, but this table also explicitly mentions an ARINC429 output (i.e. GI-275 -> GNS480) in "GAMA429" format. Of course, technically speaking, this functionality is already covered by the G5 as mentioned above, and while I am personally inclined to consider this arrangement a minor deviation from the STC, but it is a well-established fact that different FSDOs have wildly varying temperaments when it comes to these kinds of matters.

Another point of consideration is how useful your GI-275 installation would be. If you're purely interested in a separate MFD through which you could view a nice moving map, this would be a suitable arrangement. However, other functions from ADS-B In (TIS-B traffic and FIS-B weather) won't work since, as far as I can collect, you do not have a compatible panel-mount ADS-B In device. (You may be able to display TIS-A traffic from the GTX330ES via an A429 line from the GTX330ES to the GI-275, but I can't confirm this as the Garmin Dealer Portal went inop while I was typing this reply).

I hope this info offers some help. I've attached scans of excerpts from the sources I mentioned above along with my annotations.

[carusoam]

Seeing if Greg is familiar... @Baker Avionics...

Best regards,

-a-

[AerostarDriver]

7 hours ago, Minivation said:

Well, it appears I certainly got myself into a rabbit hole with this one.

I am referencing the following documents:

• Garmin GNS480 installation manual, 560-0982-01 Revision M
• Garmin G5 Part23 AML STC installation manual, 190-0112-10 Revision 24
• Garmin GI-275 Part23 AML STC installation manual, 190-02246-10 Revision 7

[quote]Does anyone know if it is possible for the GI-275 to work by splitting the ARNIC 429 NAV and GPS Outs that are also going to the GAD 29B[/quote]

TECHNICALLY speaking, this technically should work. The GNS480 features 3 A429 inputs and 2 A429 outputs. When connecting to an EFIS (including the G5 via GAD29) both of the outputs are occupied, one in GPS "GAMA429" format (GPS position, navigation waypoint info, etc.) and the other in Nav "VOR/ILS" format (lateral and vertical HSI deviation info). (I am not sure if the GI-275, when configured for MFD mode, would even make use of the VOR/ILS info, though) In addition, one input is used under "EFIS" format (selected course, airdata, etc.)

[quote]while not using the ARNIC 429 return?[/quote]

Since the EFIS input INTO the GNS480 pertains to information generated by an air data computer (see GNS480 IM Page 2-34, Table 2-9, Column 3) the GI-275 need not (and should not) need to provide a return to the GNS480. The G5 is sufficient.

Note that the flight plan info, including the proverbial magenta line, is communicated to the G5 / GI-275 separately via an RS232 channel in "MapMX" format. Whatever RS232 output from the GNS480 to the existing G5 HSI using this format will need to be spliced to run to the GI-275 as well.

As @McMooney mentioned, A429 specs call for enough current to drive up to 20 receivers. Of course, there is a wire run limitation of something like 150ft, but that's way beyond the scope of GA aircraft. As per a previous conversation I had with Garmin, each RS232 output can only reliably drive 2 devices, maybe 3.

Alternatively, the GI-275 has a built-in GPS receiver, so maybe installing a separate GPS antenna and running a coax cable to the GI-275 may be an easier solution, but surely less elegant.

== Other Considerations ==

That said, the LEGALS are what I'm not quite sure on. I can only reasonably assume the GNS480 and G5 (and its associated LRUs) were installed under STC, and so will the GI-275. The GI-275 install manual explicitly mentions the GNS480 as a "compatible GPS source" under Appendix C.4 Table C-5, but this table also explicitly mentions an ARINC429 output (i.e. GI-275 -> GNS480) in "GAMA429" format. Of course, technically speaking, this functionality is already covered by the G5 as mentioned above, and while I am personally inclined to consider this arrangement a minor deviation from the STC, but it is a well-established fact that different FSDOs have wildly varying temperaments when it comes to these kinds of matters.

Another point of consideration is how useful your GI-275 installation would be. If you're purely interested in a separate MFD through which you could view a nice moving map, this would be a suitable arrangement. However, other functions from ADS-B In (TIS-B traffic and FIS-B weather) won't work since, as far as I can collect, you do not have a compatible panel-mount ADS-B In device. (You may be able to display TIS-A traffic from the GTX330ES via an A429 line from the GTX330ES to the GI-275, but I can't confirm this as the Garmin Dealer Portal went inop while I was typing this reply).

I hope this info offers some help. I've attached scans of excerpts from the sources I mentioned above along with my annotations.

@Minivation THANK YOU! This has been extremely helpful. So far this has been the only truly educated answer I have been able to get from anyone.

I am approaching this from the perspective of just wanting an MFD to augment my GNS-480 (specifically terrain and traffic). I also intend to use a second GI-275 for my engine monitor to be installed at a later date, thus this would also give me the ability to display multiple engine pages at once.

Legally, as far as I can tell, note 6 on the G5 install manual for dual G5s you cannot have an other device configured as an CDI attached to the navigator driving the G5. In my case I am just looking to get a moving map displaying the flight plan and Traffic from the 330ES which Garmin says works just fine.

The G5 manual makes reference to splicing the RS-232 with other devices that need it, when I asked two Garmin installers about splicing ARINC 429, they said they "did this all time". When I asked for example, they used G5s and the MX200 when paired with a GNS 480... I believed MX20/MX200 was mostly RS-232 based but I could be wrong.

I think I am going to try it, worse case I end up just configuring the unit as an EIS and needing to get a GEA 24. Thanks again.

[McMooney]

Just noticed, in the install doc above, there are examples of ARINC429 splices

[AerostarDriver]

Took about 5 hours to make the harness, do the splices and get everything mounted up. Now just need to add a hole for a circuit breaker and add two pins to the GTX-330 connector. Still a few weekends from flipping the master but this was quite easy to do while I had everything pulled apart for the dual G5's.

[AerostarDriver]

Everything is installed and working through some minor issues. All of the current issues require pulling the backplane on the GNS-480.

• ARINC 429 Port 1 has only one input option "ADC" which is not called out in the 480 Manual.
• For whatever reason RS-232 is not sending any information to any device.
• G5s need a software update as the HSI being at 4.21 and ADI being at 6.00 means they don't talk well to the rest of the canbus network.

[OR75]

23 hours ago, AerostarDriver said:

Everything is installed and working through some minor issues. All of the current issues require pulling the backplane on the GNS-480.

• ARINC 429 Port 1 has only one input option "ADC" which is not called out in the 480 Manual.
• For whatever reason RS-232 is not sending any information to any device.
• G5s need a software update as the HSI being at 4.21 and ADI being at 6.00 means they don't talk well to the rest of the canbus network.

Only part I understand is your 3rd point about the software not being the same in the 2 G5s (easy fix) 

no idea what pulling the backplane on the 480 means 

[AerostarDriver]

23 minutes ago, OR75 said:

Only part I understand is your 3rd point about the software not being the same in the 2 G5s (easy fix) 

no idea what pulling the backplane on the 480 means 

I am not sure what to call it but the 480 tray has a back plate that holds all of the Sub-D housings. The way the Garmin installer installed the tray makes it nearly impossible to pull the tray though the front side of the panel without removing the whole stack. The solution I came to was to use a very long screw driver and undo the back plate from the back of the tray from the front side of the panel. This allows me to maneuver the back plate out far enough to insert and remove pins which is exceptionally difficult. I can not imagine doing this in an airplane that has a 201 sloped windscreen.

On the other two points, the GNS480 has 3 Inputs and 2 Outputs for the ARINC ports depending on what manual you have and what section you look at the GNS 480 states usage of the ports. After spending much time on the internet the latest GNS 480 manual (560-0982-01 Rev L) I could find states the following:

Upon further investigation having the GI-275 feed data in to the GNS-480 meaningless. Looking at the labels their is nothing the GI-275 in the MFD only configuration is generating. In addition, the G5 STC prohibits another device from acting as a CDI with OBS so having it feedback data for that reason is also pointless.

My RS-232 issue was a case of a pin being in the RX rather then TX.  

Buttoned everything up today and had my IA signed off on it.  While not explicitly stated in either install manual that this configuration is supported, both liberally allow for splices in both the ARINC 429 lines and RS-232 lines as needed.