GTX 345 Not Transmitting ADS-B "Out"

iamtheari

iamtheari

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My plane has a GTN 750 and a GTX 345. The ADS-B In and Out worked fine since I got the plane a couple years ago, but after I had the pitot/static/transponder checks done last month they seem to have quit working. The GTN shows that the GTX is alive and well, just waiting for data, so my guess is that the "In" side works but the "Out" side is not transmitting, which thus does not trigger the ground towers to send me the "In" data. Neither the GTN nor the GTX shows any errors, at least not that override the normal displays.

I've sent a message to the avionics shop that did the IFR checks, but while I await their response I thought I would tap the POA brain trust for ideas on things I can check to help narrow down the problem. Anyone have some experiments I can try while I play hooky tomorrow? Thanks!
 
Daleandee said:
Have you done a Public ADS-B Performance Report (PAPR)? https://adsbperformance.faa.gov/PAPRUsersGuide.pdf
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No, but I’m not sure what I’d gain there. My flight shows up on Flight Aware (and “In” products all worked) on the flight to the avionics shop that did the IFR checks, while the flight home and all other flights since then do not show up. I feel like they turned something off or bumped a loose wire while they were in there. I did check and it is squawking Alt, not Standby, so that shouldn’t be the problem.
 
iamtheari said:
No, but I’m not sure what I’d gain there.
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Do the PAPR report. It's FREE, it's easy, and there's some good data there that may help the avionics shop determine what the fault is. If you've had a recent flight you can plug that one in and see what the results are. Usually after sending a request you get a report back within 10-15 minutes. What you got to lose? :dunno:
 
Daleandee said:
Do the PAPR report. It's FREE, it's easy, and there's some good data there that may help the avionics shop determine what the fault is. If you've had a recent flight you can plug that one in and see what the results are. Usually after sending a request you get a report back within 10-15 minutes. What you got to lose? :dunno:
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They have no data from today’s flight (10/21/2022 UTC). So that’s a data point at any rate.
 
I just had this happen. Turn off your 345, hold ent and power on. You're in set up mode. Now press the func button until you see FIS-B processing. It should obviously be enabled. Mine was disabled for some reason after everything HAD been working fine. Quick easy check. And yes I still pass my performance reports when this was happening.

Edit I see you didn't get picked up for a PAR report. My issue was likely different than yours then.
 
Daleandee said:
Wouldn't that have been the 20th?
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In Greenwich, it was the 21st. I checked the 20th as well and got nothing.


simtech said:
I just had this happen. Turn off your 345, hold ent and power on. You're in set up mode. Now press the func button until you see FIS-B processing. It should obviously be enabled. Mine was disabled for some reason after everything HAD been working fine. Quick easy check. And yes I still pass my performance reports when this was happening.

Edit I see you didn't get picked up for a PAR report. My issue was likely different than yours then.
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Thanks for the tip. I went to the plane this morning to check and there didn’t seem to be any issues in the configuration, but at least I can find that out before I talk to the avionics shop since they’re not local.
 
iamtheari said:
My flight shows up on Flight Aware
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If you go to globe.adsbexchange.com and look up your tail number/flight, does it say that the source is ADS-B and give all the associated info?
 
asicer said:
If you go to globe.adsbexchange.com and look up your tail number/flight, does it say that the source is ADS-B and give all the associated info?
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Yes. The data source for the flight to the avionics shop last month is ADS-B. No data is available after that (which should include the flight home the next day and my flight last night).

One thing I should check is that the GTX shows a pressure altitude when in flight. I normally keep the flight timer up so I don't see that information. It's inconceivable that it would not be getting data from the encoder immediately after the IFR checks were signed off, but I keep using that word for conceivable things. :)
 
Please let us know what the answer is when you get it. I'm truly curious as to what you find out ...
 
Daleandee said:
Please let us know what the answer is when you get it. I'm truly curious as to what you find out ...
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If not for my obligation to POA, I wouldn’t even post the final answer. The pressure altitude was reading fine on my flight to the shop today. But there was an important clue: the “R” that flashes when ATC radar pings the transponder was noticeably absent for the whole flight, even though I was approaching a TRACON facility. It turns out to have been a tremendously simple problem: The coaxial antenna connector had worked its way off of the back of the transponder tray. No idea if it was disconnected or just bumped a few lucky times in the past few times the glare shield was removed to work behind the panel, but there you have it. Plug the antenna in.
 
iamtheari said:
If not for my obligation to POA, I wouldn’t even post the final answer. The pressure altitude was reading fine on my flight to the shop today. But there was an important clue: the “R” that flashes when ATC radar pings the transponder was noticeably absent for the whole flight, even though I was approaching a TRACON facility. It turns out to have been a tremendously simple problem: The coaxial antenna connector had worked its way off of the back of the transponder tray. No idea if it was disconnected or just bumped a few lucky times in the past few times the glare shield was removed to work behind the panel, but there you have it. Plug the antenna in.
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Glad it was a simple fix. Sounds like good diagnostic work - start with the basics and then move on to more complicated possible causes.
 
WDD said:
Glad it was a simple fix. Sounds like good diagnostic work - start with the basics and then move on to more complicated possible causes.
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I’d agree more readily had I not skipped work and flown 1.5 hours round trip to get it fixed. :)
 
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