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Garmin GAD 29 Wiring Guidance Needed

P

Pilotjim77

Well Known Member
Hello Everyone,

I'm looking for some wiring guidance. My current setup is 430W, single G5, dual GRT WS Efis displays, and Trutrak ADI 2 autopilot. I am replacing the TT with an XCruze 100, and I am adding a GAD 29 to receive glideslope on the G5.

The attached is the 430W/G5/GAD 29 wiring diagram found in the G5 manual. I added in the wiring for my autopilot and GRT along with a selector switch. I have a few questions:

1. There are currently four 429 wires from the 430W which are connected to the GRT Efis (C connector). Can I splice into the 429 output wires from the 430W? I need two more wires, one to the GAD 29 and one to the autopilot switch.

2. If yes, where should the splices be located? Together? Close to any termination?

3. Does the GAD 29 require its own 5A circuit breaker?

Please critique my wiring diagram as appropriate. Thanks for any input.

Jim
 

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Disclaimer: I have never wired a GNS or the non-Garmin stuff in your panel.

Does the 430W not have bidirectional RS-232? I don’t know if the MapMX protocol requires it or not, but I would wire the full 3-wire RS-232 port if possible.

I don’t think you can connect two ARINC 429 outputs to one input as you show from the GRT and GAD 29 to the 430W. Does the 430W have another available ARINC 429 input?

I do believe that one ARINC 429 transmitter can feed multiple receivers, with a splice anywhere convenient. Hopefully someone more knowledgeable can advise on splicing rules to minimize data errors.

I think the GAD 29 can share a breaker with something else. In my G3X Touch system I think I wired it to share the GTN breaker since the GAD 29 doesn’t do anything but talk to the GTN. In your panel, I would say the GAD 29 is more linked to the G5 than anything else, so that would be the breaker to share if you don’t give it one of its own.
 
iamtheari said:
Disclaimer: I have never wired a GNS or the non-Garmin stuff in your panel.

Does the 430W not have bidirectional RS-232? I don’t know if the MapMX protocol requires it or not, but I would wire the full 3-wire RS-232 port if possible.

I don’t think you can connect two ARINC 429 outputs to one input as you show from the GRT and GAD 29 to the 430W. Does the 430W have another available ARINC 429 input?

I do believe that one ARINC 429 transmitter can feed multiple receivers, with a splice anywhere convenient. Hopefully someone more knowledgeable can advise on splicing rules to minimize data errors.

I think the GAD 29 can share a breaker with something else. In my G3X Touch system I think I wired it to share the GTN breaker since the GAD 29 doesn’t do anything but talk to the GTN. In your panel, I would say the GAD 29 is more linked to the G5 than anything else, so that would be the breaker to share if you don’t give it one of its own.
Click to expand...
Thanks, Ari,

Yes, regarding the RS232 wires, I believe these are pins 1,2, and 7 on the 4001 connector on the 430W. These are all wired to the GRT EFIS.

I think you are correct about the 429 data. I believe I do have additional 429 inputs available on the 430W at pins 50 and 51 that are not currently being used. Perhaps that's what I should do. Just wish I knew a little more about this stuff.
 
Any ARINC 429 stream has one talker and a number of listeners, so yes you can splice into the 429 lines, I've never done it but it is unlikely the matter where the splices are located.
Be careful with the 429 connecting the 29, 430, TT and GRT - it looks like you have 2 talkers on the same line.
For the power lines it doesn't really matter which c/b the 29 is on, it doesn't draw much current.
You may have to sit down with the manuals for each box to figure out what is possible.
I don't know enough about the TT with an 429 interface, but I don't think switching the input as you have shown will work. Is there another 429 output from the GRT that can go direct to the TT?
 
Arinc uses an RS-4xx style protocol similar to 232 in data transmission characteristics. The transmission control is similar to 232 and therefore when one device is a Tx and others are Rx, that is fine. HOWEVER, you cannot have a shared wire with two Tx devices and one Rx device, as there is no method for managing who gets to transmit and therefore will transmit simultaneously and data is contaminated. Cant remember how many Arinc ports the 430 has, but you will need to add another Rx port for the 429, as it cannot be shared with the one connected to the GRT. Something like a CANBUS or certain RS-4xx protocols, like the Dynon bus, is very different as it has controls (i.e. software referee) that manage transmissions from each device

Not having data sent from the 429 is of no concern if your only goal is getting data from the 430 to display CDI and/or navigation info. Only thing being transmited from the GRT or G5 is air data. You don't want the 430 getting that data from two different sources anyways. I don't believe that the 430 will even allow you to program two different sources of air data either.

Larry
 
Last edited:
Southern Pete said:
Any ARINC 429 stream has one talker and a number of listeners, so yes you can splice into the 429 lines, I've never done it but it is unlikely the matter where the splices are located.
Be careful with the 429 connecting the 29, 430, TT and GRT - it looks like you have 2 talkers on the same line.
For the power lines it doesn't really matter which c/b the 29 is on, it doesn't draw much current.
You may have to sit down with the manuals for each box to figure out what is possible.
I don't know enough about the TT with an 429 interface, but I don't think switching the input as you have shown will work. Is there another 429 output from the GRT that can go direct to the TT?
Click to expand...
Thanks, Pete. So there can only be one "talker" on a given line. That helps to make some sense of it.

lr172 said:
Arinc uses an RS-4xx style protocol similar to 232 in data transmission characteristics. The transmission control is similar to 232 and therefore when one device is a Tx and others are Rx, that is fine. HOWEVER, you cannot have a shared wire with two Tx devices and one Rx device, as there is no method for managing who gets to transmit and therefore will transmit simultaneously and data is contaminated. Cant remember how many Arinc ports the 430 has, but you will need to add another Rx port for the 429, as it cannot be shared with the one connected to the GRT. Something like a CANBUS or certain RS-4xx protocols, like the Dynon bus, is very different as it has controls (i.e. software referee) that manage transmissions from each device

Not having data sent from the 429 is of no concern if your only goal is getting data from the 430 to display CDI and/or navigation info. Only thing being transmited from the GRT or G5 is air data. You don't want the 430 getting that data from two different sources anyways. I don't believe that the 430 will even allow you to program two different sources of air data either.

Larry
Click to expand...

Thanks, Larry. I believe I'm getting air data from the GRT now, so I wouldn't need it from the G5 through the GAD 29. So, I could eliminate the 429 output connections from the GAD 29, correct?
 
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