Garmin GNC355 to GRT HX EFIS To Intercom

[PittsCondor]

I'm going to bite the bullet and buy the GNC 355 Nav/COM and remove my ICOM 200. Currently I have Garmin Area 796 sending a signal to the GRT HX and audio alarms to the FlightCom Intercom. I want to remove the 796 from the HX and drive it with the GNC 355. I'm hoping someone out there has the wiring pinouts I need to use for the GRT HX and the GNC 355. Also the Com outputs to the intercom they could share with me. Also any lessons learned would be appreciated.

If willing to share your pinouts please email them to me at: [email protected]

Thanks in advance.

 

[BobTurner]

You'll want to:
Download the 3 HX manuals off the GRT web site.
Get ahold of the installation manual for the Garmin 355.
Have your intercom manual available.
Aircraft grade wire, good dSub pin crimpers, both regular and high density, for both male and female pins. And a supply of those pins.
Run RS232 connections and ARINC connections between the gps and EFIS.
Look in the manuals to see how the connections have to be configured: baud rate, formats.
Run the analog com lines from the mike jack and PTT switch, and audio out to the intercom, etc. Best to use shielded wire, insulate the jacks from the airframe and run a dedicated ground wire to the intercom.
Use the manuals, figure out what hole the pins have to go in in the connectors.
It's not particularly hard - just one pin at a time - but a bit tedious. There's probably something I forgot. Just read the manuals.

Have you thought about ADSB-out? The 355 is an approved position source for ADSB-out. However, it's in Garmin's proprietary "ADSB+" or "ADSB++" format, so to use it you'll need a mode S-ES transponder or a 986 MHZ UAT ADSBout box that can read that format (GARMIN, Trig, transponders I think both work). Lots of ADSB-in receivers work with the HX to display the wx and traffic data except for Garmin ones, which again use proprietary software.

 

[PittsCondor]

Thanks Bob,

You helped me tremendously when I installed the dual GRT HX units. Since the ICOM 200 and intercom were already in the airplane I'm not really sure how its all wired up. I'll get the manuals and try to reverse engineer it.

I currently have the Appareo Stratus ESG transponder so I don't think I can send data to the GNC355 for traffic and weather. I also have a Garmin GDL39 which is supplying traffic and weather to the Aera 796. I have the SkyRadar sending traffic and weather to the GRT HX.

I never was able to get the hardwired connection from the GDL39 to 796 to work so I am connecting via Bluetooth. If I could get the hard wire connection to work I might be able to connect via bluetooth from the GNC355 to the GDL39 and get traffic and weather or maybe hardwire GDL39 to GNC355.


Your thoughts?

 

[BobTurner]

I think that's okay. Even the 6" HX with a split screen for traffic and wx is a lot bigger than all but the largest GPS screens. You want the traffic on the HX, not the GPS.

 

[h&jeuropa]

This thread covers it all pretty well:

https://vansairforce.net/community/showthread.php?t=200501&highlight=GRT+GPS175

There is the setup sheet from GRT and a wiring diagram from someone who has done this.

Your Appareo is strictly ADSB out. I have the same.

Skyradar is ADSB in and I'd suggest you continue to use it to display on your HX.

The screen on the GNC355 is pretty small for ADSB, your HX is much better.

You will want/need an ARINC connection from the GNC355 to HX so you can shoot approaches (display horizontal and vertical guidance info). Your HX may have it built in or you can purchase from GRT.

The bug I pointed out in Garmin's data stream is no longer a problem, GRT has implemented a fix in the EFIS software update that was released this past summer.

Jim Butcher

 

[lr172]

Aircraft grade wire, good dSub pin crimpers, both regular and high density, for both male and female pins. And a supply of those pins.

From my experience any HD pins used by Garmin and PS Eng are always Male, so I would check the manuals before ordering HD Females. Likely not cheap and hard to find.

Larry

 

[lr172]

I never was able to get the hardwired connection from the GDL39 to 796 to work so I am connecting via Bluetooth.

Your thoughts?

I bought a bare connector from someone here for my gdl39 and couldn't make it work. Took the shell of the connector and the tiny 26 gauge wires had corrossion and broke off the connector. You can find the connector at digikey, but requires good soldering skills in tight areas.

Larry

 

[PittsCondor]

I spent the day trying to reverse engineer the ICOM 200 wiring to the FlightCom403B. Looks like only 3 wires that are actually wires being used by the intercom (500 Ohm output, Com Mic Input, PTT) lots of grounds and power wires linked together. How confusing.

The GPS wiring to the HX is straight forward. ARNIC A,B, Serial Input, Serial Ground.

I'm buying the 355 from Stark Avionics. I'm going to have him make a wiring harness. I'm thinking about running new wires from the 355 to FlightCom and abandon the original wires that were from the ICOM to FlightCom. I should only have to pull the few pins out of the FlightCom and insert pins from the 355.

I will terminate the ends that go to the EFIS myself since those pins are easy to do.