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

[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

 

[eman1200]

To start….

 

[hawkman]

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.

 

[hawkman]

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.

 

[Walboy]

My understanding is that the GTN requires a heading source to display ADSB traffic on the map.

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.

 

[hawkman]

I wonder if the X over the two icons here and here might indicate something amiss?

 

[hawkman]

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?

 

[Plano Pilot]

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.

 

[Ryan Klems]

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?

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.

 

[hawkman]

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?

 

[Ryan Klems]

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.

 

[hawkman]

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.

 

[Ryan Klems]

I presume you are asking about the picture? It is from the GTX installation manual.

 

[hawkman]

Thank you. That's very helpful. I'll let you know how it goes...

 

[hawkman]

Update. The avionics shop says that, in order to show the traffic correlated on the GTN 750, it requires a heading source:



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?

 

[John Collins]

It depends, the KI-525 needs to have bootstrap in order to generate the heading output. If it isn't already part of the KI-525, it is expensive to add.

 

[hawkman]

So the 750 does need a heading source in order to use both TAS and ADSB?

 

[Ryan Klems]

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.

 

[hawkman]

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.

 

[hawkman]

Follow up to this, I found this section of the installation manual that seems to indicate that this is a configurable option:



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

 

[hawkman]

Update: Avionics shop back at the hangar today. Apparently there is a way to wire up the analog heading source from the KI 525A system into the GTN 750. As usual, the technician isn't telling me exactly how but he swears up and down that this will work. Here's what I found in the GTN installation manual:



5.5.1.9 says this:


All of this is predicated on the need for a heading source in the first place, which I am still confused about since the WX-500 is providing one.

 

[Ryan Klems]

Update: Avionics shop back at the hangar today. Apparently there is a way to wire up the analog heading source from the KI 525A system into the GTN 750. As usual, the technician isn't telling me exactly how but he swears up and down that this will work. Here's what I found in the GTN installation manual:

Yeah, that's the XYZ synchro connection I was talking in about in post #18 above.

All of this is predicated on the need for a heading source in the first place, which I am still confused about since the WX-500 is providing one.

The WX-500 does not provide a heading source. It works best if it is given a heading source (it can receive heading either via XYZ synchro or over the serial connection, selected via configuration straps on the unit) It also can work without a heading source, but then the strikes do not remain tied to a heading so requires manual clearing of strikes every time you change heading to keep the data relevant, so definitely works better when it has a heading source.

 

[hawkman]

Just back from the airplane. KI-525A heading source now connected via one of the 750's analog inputs. This has the somewhat interesting effect of showing where the airplane is pointed while on the ground, something which wasn't possible before. However, this new heading source hasn't solved the map page issue, nor do I see any evidence of ADSB/TAS correlation taking place.

On the ground - and I haven't yet tested it in the air - you can pick one or the other of TAS or ADSB traffic. Not both. And neither show on the map page. I took photos which should show this situation pretty clearly.

Here's ADSB traffic on the traffic page:



And the same traffic with the map page enabled:



Here's TAS traffic on the traffic page:


and the same traffic with map page showing:



The GTN 650 also doesn't show the traffic on the map page, but I didn't take photos of it.

You cannot select both at the same time. Note that the traffic icon still shows as X-ed out:

You can even see a lightning strike so the WX-500 is working too - and also why I didn't flight test it today. (As an aside, the strike finder has always worked correctly with heading data and shows strikes correctly on the map when you change heading, so it must be getting that data from somewhere.)

At this point the GTN and GTX have all the data from all the hardware that's available within the airplane. So the software engineer in me says this has to be some kind of configuration issue.

Any ideas? The avionics guy seems stumped at this point; he's going to call Garmin. I feel like we're back at the beginning here again, except this time the GTN knows which heading to orient the map that its not showing the traffic on...

 

[Ryan Klems]

My guess is that they still haven't connected the 870 to the GTX, and that both the GTX and 870 are wired in to the GTN. The 870 should _only_ be connected to the GTX. Did they provide you any sort of wiring diagrams? Appendix A's from the Garmin ICA's showing the configuration values? Anything?

 

[hawkman]

Sadly no diagrams. I get the sense they're making this up on the fly. As an engineer I've been extremely frustrated by this process but I've held my tongue mostly because I don't have any other options here.

Would the presence of the soft buttons on the traffic page to select ADSB and/or TAS (which the 750 calls TCAS) on the 750 be proof that the 870 is still connected to the GTN? This is how it was before the GTX was installed, so it's not unreasonable to assume that this wasn't changed.

I just whipped this drawing up in powerpoint, is this what it should look like as a very rudimentary block diagram?



(edited)

 

[Ryan Klems]

The connection between the GTX and the GTN(s) should be over HSDB (Garmin's proprietary ethernet connection). The GTX could be connected to both GTNs directly, or connected just to one of them and then it would be relayed from one to the other. If you want the stormscope strikes to appear on both GTNs, the RS-232 Tx from the WX-500 would need to be spliced and sent to both units. The WX-500 Rx needs to be connected to only one unit's Tx (likely the 750) for control of the stormscope. The HSDB connection should also (I believe) forward the heading back to the GTX. It's been a while since I've used the XYZ synchro connection to a GTN, so I'm not 100% sure on that. If you want control of the 345 from the GTN, then there is additionally a RS-232 connection from the GTN to the GTX. From the pictures, I can see that you do have that control wired and configured, but it doesn't have to be if you wanted those fields back for something else. Also note that the GTX automatically controls the standby/operate on the TAS unit, which it does based on air/ground state. Once everything is confirmed to be wired as it's supposed to be, your installer could force the airborne state using a laptop and the install tool, which then should allow you to see all the combined traffic. I'm not sure there is another way to force the TAS to operate on the ground when it is interfaced to the GTX. When you go in to the menu on the traffic page, you are not able to have both "ADS-B Display" on and TCAS Status in "Operate". If you select one, the other turns off and vice-versa? Once you have confirmed the wiring is correct, I'd be curious how it behaves if the installer forces airborne mode on the GTX via the tool.

 

[hawkman]

Thanks for this. I've redrawn my diagram based on what you've said and what I think is set up based on how it is operating. Here's what I believe it looks like now - which I will verify with the installer today if I can.


A couple of questions:

1. How can I have the RS-232 control between the GTN and the GTX disabled? This was one of my initial issues with the install, I didn't want to lose the field where I had previously had my DTK shown to a redundant squawk code/button. I imagine it doesn't make sense to remove the cabling but I don't want or need that functionality.

2. The TAS seems to be operating on the ground. Is this another hint that it's not connected to the GTX?

3. And can you confirm that there must be no connection between the 870 and the GTN, only the GTX? Is it possible to simply disable this connection in the configuration rather than make cabling changes or must the cabling be disconnected?

Thanks again. All of this would be so much easier if the installer would simply show their work.

 

[hawkman]

One more question...

4. When the GTX has traffic input from both TAS (KTA 870) and ADS-B, will I see (non-ADSB) TAS targets on my iPad in Garmin Pilot via Bluetooth from the GTX?

 

[Ryan Klems]

1) You can just turn off the associated RS232 ports in the GTN and GTX configs and that will disable the control, you don't have to remove the wiring if you don't want to
2) I think so, my guess is the control of the 870 is wired to the GTN through the two discretes
3) Yeah, those all (ARINC and 2 discretes) need to be moved over to the GTX and not the GTN and the configurations updates
4) I believe so, I'm not 100% positive though... it's been around 3 years or so since I last did a 345+TAS install and I honestly just don't remember for sure

Your drawing looks correct, other than there is a missing control RS232 connection going from the GTN750 -> WX-500 and the two discretes that (test & standby) that would have been wired to the GTN that also need to move to the GTX

 

[hawkman]

Thanks again. Before I go back to the installer, can I confirm that "2 discretes" means the button and switch in the wiring diagram?

<- these, right? (plus the ARINC data bus)

Now it's pretty clear to me that all need to be connected to the GTX and only the GTX. Let's see what they say.

 

[Ryan Klems]

Yep, those two wires. They aren't button/switches per se, but that is their effect. The Garmin box pulls those low to effectively "press a button".

 

[hawkman]

Aha, ok that's why those are now blanked out on the TAS control panel. I wondered about that. Shows how much my avionics people have been explaining things to me...

 

[hawkman]

It's been a week since my last update and I remain completely in the dark with no response to anything. But all hell seems to be breaking loose at Garmin.

Garmin Support refuses to answer any question and says that only the dealer can answer the question. The dealer is asking Garmin, although about what, I am unclear. They've yet to respond to them.

And now it's turned into some internal Garmin argument with the dealer about how they went about installing the GTX unit which had been pulled, yellow-tagged, from another aircraft during an upgrade. Supposedly dealers aren't allowed to do this? Garmin is trying to get me to provide the serial number to somehow police their own dealer network?

None of this is helpful. I can't get a simple answer to a simple question: if I see these two traffic source buttons on the 750, does that mean that the KTA 870 is wired to the 750 directly instead of being wired to the 345?

This situation is really depressing. This is a relatively simple engineering problem and now every party is finding some way to blame the other instead of simply doing the (probably simple!) work to finish it.

 

[hawkman]

Update: FIXED.

I have to hand it to the avionics shop, they really stuck with this. Even if their original communications weren't ideal, they worked extraordinarily hard on getting this resolved.

They had all the wiring correct with one small but important problem that was overlooked. It turns out that the HSI's flux gate which provides heading has three axes of analog output and also one 27 VAC "clock" to synchronize things. If I understand this correctly, if that clock signal isn't provided, the GTN will understand the heading correctly but won't be able to sync with the map page and the transponder can't integrate the two sources. What had happened was that the pin to the GTN for this signal was bent, resulting in the wiring being right but the signal not getting through.

So, to recap: TAS must be connected as above to the GTX and analog heading info must be connected to the GTN, including the all-important "clock" AC line to sync things up.

Now I see both ADS-B and TCAS targets on the map page which is a huge relief. Again, shout out to the avionics shop.