J

JDA_BTR

Well Known Member
If my only nav source in a G3X system is a GNX-375, is an ARINC box still required?
Another way to ask the question is "when exactly is an ARINC required in a G3X system?"
 
The short answer is that if you have a G3X system and any type of IFR GPS, then yes you do need both RS232 and ARINC 429 connections.
 
JDA_BTR said:
If my only nav source in a G3X system is a GNX-375, is an ARINC box still required?
Another way to ask the question is "when exactly is an ARINC required in a G3X system?"
Click to expand...
Enclosed is the system architecture of the G3Xt system taken from the installation manual.
Most of the components are optional however some are requierd.

Good luck
 

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To expand a bit...
I found this out when hooking up a Garmin 430 W to the Dynon D10a. Didn't think I needed ARINC, because the 430 outputs 'rs-232 serial', and the D10a directly accepts that. Yeah, well, BUT.

(1) The rs-232 serial DOES NOT output 'GPSS'. In other words, when doing a GPS approach, you'll typically have a T shape and you are allow to make the 90 degree turn before crossing the waypoint. GPSS provides the proper CDI (and autopilot) info to start the turn in advance. Otherwise it overflies and then wanders back onto the new heading.

(2) the rs-232 serial data doesn't provide the change in CDI deflection tolerance from en-route to approach. So you can be a mile off centerline, but the CDI isn't full deflection. This could bite a subsequent pilot/owner if they don't know this limitation.

Now, if you don't fly IFR, you probably won't care. Or if you only fly VOR/ILS approaches.
 
blaplante said:
I didn't know that. I know an SL30 (and several others) will work via rs-232.
Click to expand...
From the IM rev: AW.
The Garmin GNC® 355 radio, GNS™ 4XX/5XX receiver, GNX™ 375 IFR navigator, GPS 175, and GTN™ 6XX/7XX moving map navigators are supported by the G3X system, including WAAS approach capability. This integration requires the use of a GAD 29 ARINC 429 interface module. GPS navigation data is provided to the G3X system through one RS-232 input and one ARINC 429 input for each GNC 355, GNS 4XX/5XX, GNX 375, GPS 175, and GTN 6XX/7XX IFR GPS navigator unit. The G3X system sends flight data and selected course information back to the external GPS navigator through an ARINC 429 output.The G3X system uses an additional ARINC 429 input to receive VOR, localizer, and glideslope deviation information from a Garmin GTN 650/750 or GNS 430/480/530 IFR GPS/NAV receiver.VOR, localizer, and glideslope information from a Garmin GNC 255, GNC 215, or SL30 VHF NAV receiver is also supported. These radios connect to the G3X system using an RS-232 connection to a GDU display.

Good Luck
 
I've enjoyed seeing all the features wanted for the G3X over the years. But this is a feature I'd really like to see. It really makes no sense to me that we need an additional ARINC 429 box to connect a GNX375 to a G3X for approaches. I get it if there is a radio involved, or multiple devices from different vendors. But in an all-Garmin G3X setup it seems like something they could easily make happen with our modern electronics and data streams. It's #2 behind why can't the G3X or GTN take database updates via Wifi/bluetooth.
 
JDA_BTR said:
I've enjoyed seeing all the features wanted for the G3X over the years. But this is a feature I'd really like to see. It really makes no sense to me that we need an additional ARINC 429 box to connect a GNX375 to a G3X for approaches. I get it if there is a radio involved, or multiple devices from different vendors. But in an all-Garmin G3X setup it seems like something they could easily make happen with our modern electronics and data streams. It's #2 behind why can't the G3X or GTN take database updates via Wifi/bluetooth.
Click to expand...
I think the biggest reason why is the limitations placed on certified IFR navigators and how they interact with other instruments to properly display navigation and approach information. They probably don’t want to spend the extra money certifying it via an additional communication protocol.
 
Yes….having to have a separate ARINC module is a bit frustrating, but you have to know the back story about a small band of Garmin engineers (who were homebuilders) going rogue and developing one of the most popular EFIS systems around (so popular it is now available for certified aircraft) under the noses of the more snooty “certified crowd” at Garmin. The company isn’t as monolithic as you might think. (Heck….I can’t even get the Garmin bicycle computer guys to make their “Light Network” software to operate the same way twice on the same bike…..)

Not a Garmin unique problem (ARINC) either - I remember that I had to buy a unique ARINC module to make my GRT EFIS work with a Garmin navigator early on as well.

As pointed out above, you’d have thought the Apollo Program Office could have gotten North American and Grumman to at least look at each other’s drawings! 🤣
 
One more thing... The ARINC messages are an industry standard, so we can have Garmin equipment drive a Dynon system, etc.
The SL30 messages are openly documented in the Apollo (pre Garmin) manual, so anyone can figure that one out (and many radios emulate the SL30 for that reason).

The Garmin 330 ES traffic messages to the Garmin 430 series boxes... being all Garmin... they went proprietary. I have tried to figure it out since TIS-A traffic is now pretty useless. I'd like to take GDL-90 traffic messages (openly documented) and send it to the 430 like it was a TIS-A message. Hah. Looks like without an NDA with Garmin you don't get anywhere.

So when we ask for 'why can't Garmin just talk to Garmin without an ARINC box', careful what you ask for. You'll probably get another proprietary and secret protocol that won't work with anything else.
 
Memory is a funny thing. I see that picture and I remember the smell of the old electronics rooms. The equipment gave the rooms a certain smell.
 
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