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G3X - How many interconnects is enough?

R

Raiz

Well Known Member
The Garmin installation manuals contain lots of interconnect drawings but, as every system is a little different, they can't provide a complete diagram for every system. So, how do you know where to stop adding redundant and backup interconnections?

The attached image shows a possible system for discussion purposes.
  • Green depicts ARINC connections
  • Blue is for CAN bus
  • Purple is the RS-232 connections that seem (to me) to be essential; and
  • Red shows RS-232 connections that seem to be optional.

As an example, take the MapMX link between the GNX 375 and the G5. The Garmin manual says that will allow you to shoot a fully coupled approach if the PFD dies. That's impressive, and probably the best option if you don't have an MFD. On the other hand, if there is an MFD, I'd rather use that because the approach will be the same as normal. Would it be better to send that MapMX link to the MFD instead of the G5?

It's not really a question about this specific case. It's more a question about where to find the information to make an informed decision. Can anyone help me?
 

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And how many ports are there? The gnx375 has 5 serial ports. One goes to the ELT. A couple for the PFD. So choices need made for sure. I wonder if the 375 connects to the PFD by Bluetooth the way the 45r remote transponder does. Good diagram by the way.
 
Just me

Lots of connections.
But i did not have to use bluetooth for any connections. The gnx375 is fully utilized to provide data to elt, and the other garmin boxes. A schematic is a must. I had my schematic reviewed and blessed by a Garmin rep at Oshkosh before I started soldering.
 
PilotjohnS said:
Lots of connections.
I had my schematic reviewed and blessed by a Garmin rep at Oshkosh before I started soldering.
Click to expand...

Most of the guys at the Garmin tent are salespeople and even if you did get a hold of a real tech guy I doubt he would have time to do a full review.

Soldering? The only things I solder are CAN bus wires and headset jacks.
 
Walt said:
Most of the guys at the Garmin tent are salespeople and even if you did get a hold of a real tech guy I doubt he would have time to do a full review.

Soldering? The only things I solder are CAN bus wires and headset jacks.
Click to expand...
I agree with Walt again, solder is not the connection of choice in a high vibration environment. Get a quality crimper.
 
Refering to the image in Raiz post, it's my understanding that only one AHRS
is required in a standard G3X system. AHRS2 is optional.
The G5 is capable of operating as a standalone flight display or a fully integrated backup instrument for G3X systems.

Good luck
 
Interconnect Drawings

Raiz said:
The Garmin installation manuals contain lots of interconnect drawings but, as every system is a little different, they can't provide a complete diagram for every system. So, how do you know where to stop adding redundant and backup interconnections?

The attached image shows a possible system for discussion purposes.
  • Green depicts ARINC connections
  • Blue is for CAN bus
  • Purple is the RS-232 connections that seem (to me) to be essential; and
  • Red shows RS-232 connections that seem to be optional.

As an example, take the MapMX link between the GNX 375 and the G5. The Garmin manual says that will allow you to shoot a fully coupled approach if the PFD dies. That's impressive, and probably the best option if you don't have an MFD. On the other hand, if there is an MFD, I'd rather use that because the approach will be the same as normal. Would it be better to send that MapMX link to the MFD instead of the G5?

It's not really a question about this specific case. It's more a question about where to find the information to make an informed decision. Can anyone help me?
Click to expand...

The MAPMX connection to the G5 provides GPS data to the G5 for the purposes of AHRS aiding. While it will also provides a very limited set of navigation data to the G5 (unscaled lateral deviation), the full set of both lateral and vertical (scaled for IFR navigation) deviation is provided via CAN. The GNX 375 sends that information via ARINC 429 to the GAD 29, from there the GAD 29 forwards that information to all displays on the CAN bus.

The G5 can be provided with GPS data from various sources. The ideal GPS source for the G5 is the GPS receiver internal to the G5. When using the internal GPS, you are not relying on an external box to be functioning for the backup indicator (G5) to function properly. It makes that unit more of a standalone unit. With its own GPS source, and a backup battery attached, it is very resilient to any external failures such as an electrical system failure. A glareshield mounted antenna is an economical solution to ensure the G5 GPS receiver has a solid GPS fix at all times, and does not require you to mount an additional antenna externally on the aircraft.

If you do use the MAPMX datapath from the GNX 375, you do have the option of paralleling the output line from the GNX 375 to both the MFD and G5.

Thanks,

Justin
 
Thanks Justin, that explanation is perfect.

In the illustrated system with a PFD, MFD and 2xADAHARS, I'd prefer the more independent resilient G5 that is essentially just a backup flight instrument (albeit a very capable one) and I'm happy to add a glareshield mounted GPS antenna to support it.

If it were in a system with a PFD and 1xADAHRS but still with the intention of IFR flight, I'd probably go the other way because failure of the PFD would leave you wanting all the capability you can get from the G5.
 
One thought for you, we did our own wiring but we purchased an interconnect diagram from Stein. Took much of the guesswork out of the process.
 
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