GTN 750 + GTX 345 = no traffic on map page?

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hawkman

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Hawkman
Hi, I have the following avionics:

- Garmin GTN 750
- Garmin GTN 650
- Garmin GTX 345 ADSB in/out
- Honeywell KTA 870 TAS
- WX 500 stormscope
- Flight Stream 210
- KAP 140 + KI 525A
- iPad with Garmin Pilot, Bluetooth interfaced to FS210 + GTN345

I just had the GTX 345 installed. Before I was getting the traffic info from the TAS on the map page, but now it only appears on the traffic page of both the 750 and 650. The Stormscope is showing strikes correctly on the map and the iPad is showing ADSB traffic correctly.

My understanding is that the GTN requires a heading source to display ADSB traffic on the map. Both the stormscope and the TAS provide such heading data. As I mentioned, the iPad is showing the traffic correctly on the map.

Is there some setting I need to change myself or have the avionics shop change?

Thanks
 
To start….

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Thanks for this. I do have the "traffic" button enabled. Am I missing something else?

FYI this is what it looks like, you can see the traffic on the 650 below but not on the map of the 750.

1729362415638.jpeg
 
This one is a bit more informative because you can see a thunderstorm strike between MPMG and MPTO. Without a heading source, it wouldn't show this.


1729363142098.jpeg
 
hawkman said:
My understanding is that the GTN requires a heading source to display ADSB traffic on the map.
Click to expand...

I don’t think heading source is required. I operated my GTN with input from a GDL-88 for quite some time and never had a problem displaying traffic on the map page.
 
I wonder if the X over the two icons here 1729369171043.png and here 1729369189104.png might indicate something amiss?
 
I just met with the Garmin dealer. Apparently they didn’t take into consideration the existing TAS system in my Cessna 182T which came from the factory. They have serviced this plane for over a decade and were well aware of its configuration. When they did the GTX 345 install they must have encountered this issue, but didn't ask me to approve any additional work to resolve it. So they just closed everything up and pretended that it was all working, showed me the traffic page but neglected to show me the map page, and got me to sign off on the work. As you can see, I spotted the issue immediately.

Apparently the issue comes from the existing TAS unit having analog data. The dealer *thinks* they can connect it to the GTN 750 to resolve it, but of course this is more work involving removing all the seats again, taking the panel apart and rewiring. All of this would have been really easy had they just been up front about the issue.

In the short term they have disabled my TAS system in the configuration as an input to the 750 and now it paints ADSB targets just fine on the map. But the problem is that in this country, most people don’t have ADSB, that’s why an integrated ADSB/TAS solution was what I asked for.

Anyone else have a similar configuration?
 
Our Citation has 2 750's, a 345R and Skywatch 899. The 899 traffic will show on the 750's. I may be wrong but I believe the 899 is connected to the 345R.
 
hawkman said:
I just met with the Garmin dealer. Apparently they didn’t take into consideration the existing TAS system in my Cessna 182T which came from the factory. They have serviced this plane for over a decade and were well aware of its configuration. When they did the GTX 345 install they must have encountered this issue, but didn't ask me to approve any additional work to resolve it. So they just closed everything up and pretended that it was all working, showed me the traffic page but neglected to show me the map page, and got me to sign off on the work. As you can see, I spotted the issue immediately.

Apparently the issue comes from the existing TAS unit having analog data. The dealer *thinks* they can connect it to the GTN 750 to resolve it, but of course this is more work involving removing all the seats again, taking the panel apart and rewiring. All of this would have been really easy had they just been up front about the issue.

In the short term they have disabled my TAS system in the configuration as an input to the 750 and now it paints ADSB targets just fine on the map. But the problem is that in this country, most people don’t have ADSB, that’s why an integrated ADSB/TAS solution was what I asked for.

Anyone else have a similar configuration?
Click to expand...
The KTA 870 needs to be wired in to the 345 and nothing else. The 345 needs to correlate and concentrate the ADS-B + the TAS traffic and feed it to the other devices. This is a pretty common setup with various active traffic devices and the 345. Once this is done you will see all the traffic on the 750 & 650.
 
Thanks for this. The avionics tech says the 870 only has “analog” output. When you say wired to the 345, do you mean ARINC digital data?
 
The 870 (really the 810 traffic processor) has an ARINC 429 output. Not sure why they’d be calling that analog (I mean at the end of the day it is just voltages on some wires, so everything is essentially analog, but….) This and a few other things are what get wired to the 345. It’s the same signal that would have been the only way to wire it to the 750 in the first place. It just needs to be wired to the 345 only, where it will concentrate all the traffic and correlate it (don’t want to show two targets if it’s getting both active and ADS-B from a single ship) They also need to make sure only the audio from the 345 is going to the audio panel, the KTA should no longer be wired for sound, as all that will be handled by the 345.
 

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Thank you for this. If you don't mind my asking, where did this come from? I'm going to present this to my avionics guy.

Now that I see this, I realize what he did was leave the KTA870 wiring connected to the GTN750 where it had been before. He needed to move it to the GTX345. Either being clueless or lazy, not sure which.
 
Thank you. That's very helpful. I'll let you know how it goes...
 
Update. The avionics shop says that, in order to show the traffic correlated on the GTN 750, it requires a heading source:

1729888936453.png

They say:

"Currently, the GTN 750 does not have any heading connection, so it cannot present information on both types of traffic. However, the aircraft has a KI-525A that can provide heading information to the GTN 750. This connection was not contemplated because it was not part of the initial installation parameters. This is an additional connection to the system we are installing."

They didn't describe what that additional connection would be. Going on what I have read and seen in this thread, the GTX should handle all the correlation - the GTN 750 doesn't seem like it should be involved at all.

Does this seem right?
 
So the 750 does need a heading source in order to use both TAS and ADSB?
 
The traffic correlation should happen on the GTX, not the GTN, (and it's certainly best if the correlation is based on the same heading information, and it improves the correlation performance, see the IM screenshot, but the GTX will do still correlate the traffic without an ownship heading). Without a real heading source, the GTN will not show traffic until it's moving (thereby providing a GPS track based heading source). One could wire the 870 to receive heading over 429 from the GTX, (and the WX-500 could be strapped to received the heading over RS-232) which would forward the GPS based heading to the 870 (using Format 5 on the GTX ARINC output), that way at least they'd all be based on the same track based heading. It certainly is best if you have a real source of heading, however, and a real heading source will allow you to see traffic even while sitting still (which can be useful to see what's in the pattern for example while not moving). In which case wiring the XYZ synchro to the GTN should, if I recall correctly, then forward on to the GTX over HSDB (and to the WX-500 if strapped for serial heading ... and you could also then wire the the 870 for ARINC 429 heading using the GTX as the ARINC concentrator with a Format 5 ARINC 429 feed... this would then make things a bit more straightfoward if you ever ripped out the whole KCS-55A compass system and replaced it with a GI-275 for example). Things are certainly much more straightforward with a digital heading source, but should still be possible with what you have, even if you went the route of GPS track for heading.

Screenshot 2024-10-26 at 22.44.55.png
 
According to the avionics shop, they wired it up as shown in the first diagram in a prior message. But having flown with it in this configuration, it didn't show any traffic on the map so I don't think it was using the GPS heading info. I'm pretty sure it wasn't correlating the TAS data because I saw no diamonds (TAS targets, which has no heading info, just altitude and position), just arrows (ADSB targets), on the traffic page. Since we disabled the TAS data on the GTN, it shows the ADSB traffic on the map, including on the ground. But at no point did I see any TAS targets. I get the impression the GTX isn't processing the TAS data in either case.

I am very keen to have traffic data on the ground when I'm not moving because that's a very nice double check to my visual traffic check before I'm given a clearance onto the runway. I don't know what the plan is on Tuesday morning when the avionics shop plans to rectify this situation - they haven't told me - but there was talk of installing an "inexpensive analog-to-digital converter" to connect the KC-55A to the GTX using some apparently unused wires between the avionics bay and the panel. Or perhaps there is a configuration-only solution?

I'm sure at some point in the future, my KAP-140 will fail thus requiring an upgrade to GI 275 + Garmin autopilot. But that's a $15,000+ project and I'm not keen on it in the short term. Plus I already replaced my attitude indicator with a UAvionix AV-30 which I really like because it has AoA, so a GI 275 as AI isn't really an option.
 
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Follow up to this, I found this section of the installation manual that seems to indicate that this is a configurable option:

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[2] seems to indicate that this is possible. However I'm a bit concerned about [1]. The two seem to contradict each other.
 
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