Few years later, I have met few problems with the GTX345, and I hope you can help.
First, the internal AHRS, which was exceptionally accurate in the beginning, lose precision (with instability in roll while the aircraft was flight straight), and finally failed (as reported by Garmin Pilot or Firelight). I had read some other reports before my purchase related to AHRS fragility.
Anyway, this is an extra feature, not critical.
More recently, another failure, more annoying.
I noticed that I had less ADSB(in) targets showing on the G1000.
I compared with a portable solution, and was able to confirm.
When zooming out the main map, I used to have a nebula of traffic (in unrestricted mode). I don’t see them anymore, with only few traffic remaining.
Two times, I had a « TRAFFIC FAILED » notification after starting the aircraft and avionics, while all needed inputs were available (HDG, attitude, GPS, air data…). I had to cycle the XPDER (breaker) to resume operations.
My set-up inclues a legacy G1000 (GDU 12.03), using GTX345 in emulated GTX33ES + GDL 90 mode.
My GTX345 has software 3.40 and I’ve seen a SB to upgrade 3.62, which will be done soon.
I have not been able to pull out the logs and check eventual errors yet.
Does reduced ADSBin sensitivity, suggests a type of failure for you ?
PS: ADSBin reduced sensitivity caused the ADSR gateway with ADL (GOLZE) failed – implying the loss of FLARM traffic report on the G1000
PetitCessnaVoyageur wrote:
Two things I have been taught: “the higher the frequencies, the longer the faces” and “it’s almost always in the cable”, and indeed, this has held true rather often. If you receive less targets, I’d check the antenna installation, that’s at least the common issue with FLARM. For that purpose, they have a nice program that cross checks the installation called CARP – maybe something like that is available for ADSB, too? It works by getting the data from all other planes around you and analysing the time, distance and direction when they detected you or vice versa, so you’d need a continuous data stream.Does reduced ADSBin sensitivity, suggests a type of failure for you ?
Please note that XPDER or ADSBout never failed so far.
Is the antenna used for ADSBin the same as the XPDER one ? We can check connectors, and easily try another one.
Same antenna
Few more notes.
A previous SB, ref 25006A (25006A_ASDN_Time1738864744284_pdf) was released February 5, 2025, addressing a problem that could be related to mine:
GTX 45R/GTX 345 Transponder Series ADS-B Software Version 3.61 corrects an issue that could result in
momentary loss of the ADS-B In function under specific, rare conditions including the presence of a
duplicate address aircraft track (1090 MHz) in a high-density traffic environment.
Then last SB, ref 25035A (25035a_pdf)
GTX 45R/GTX 345 Transponder Series ADS-B Software Version 3.62 contains the following changes:
• Improved Runway Occupancy Awareness (ROA) processing
• Improved traffic self-test applicable to Garmin Integrated Flight Decks
My actual revision is 3.40.
Several revisions were released: 3.41, 3.51, 3.60, 3.61, 3,62, with considerable improvement list.
Hard to say if it will solve my sensitivity problem, or create new ones :-D
Just sharing my experience with an NGT9000 which uses transponder antenna and a dedicated TAS directional antenna. Had intermittent traffic issues since installation 2 years ago. I found the following correlates, and fixing them each time have brought the traffic system back to life.
1. Clean the antenna. Seriously, not joking. The transponder antenna on the belly accumulates exhaust oil and dirt. The film interferes with transmission and reception. Cleaning it helps acquire ADSB targets.
2. The TAS directional antenna is very sensitive and relies on signal difference between cables. During the annual, engineers move the cables behind the panel – sometimes tightening, sometimes loosening. Found too much bend in one instance. Another time found the cables trapped by the defrost gate lever which yanked one of the BNC connectors.
3. Antenna re-calibration using software. If available for your installation, helps the TAS system correct for changing signal attenuation over time – e.g. cables degrading with age or after your cables have been messed around during the annual.
4. Interference from frequencies in the same band like DME. Also found Bluetooth from mobile phones and headsets like Zulu 3 interfere with traffic reception, although not on the same frequency band, turning them off brings the traffic system back to life. The directional antenna is installed above the cabin, only couple of cm above the pilot and co-pilot ’s head. Go figure.
So far the traffic system has been one of my best avionics investment, when all above precautions are taken into consideration.
@flyingelephant wrote:
1. Clean the antenna. Seriously, not joking. The transponder antenna on the belly accumulates exhaust oil and dirt. The film interferes with transmission and reception. Cleaning it helps acquire ADSB targets.
Thank you for your suggestions.
When I read this, I looked at my XPDR antenna and thought: that must be the problem. Unfortunately, cleaning the antenna didn’t solve it.
Regarding my efforts.
Upgrading the SW was not piece of cake. You have actually two SW, one for main, the other for ADSBin.
The SW (pair of) are evolving at two speeds, and at this moment, you have the more advanced TSO’d version (2.90/3.62) and the less advanced certified, STC’d version (2.85/3.51).
Before I knew that, I had upgraded the GTX345 to 2.90/3.62, to discover the G1000 would not recognize it
Upgrading requires two steps: one on the GTX side (with computer and USB cable), one on the G1000 side (with a SD loader / interface card).
If it does not recognize the SW, the G1000 would say “SW MISMATCH, COMMUNICATION HALT’d”, with the result of a grounded aircraft (no XPDR working anymore).
After some cold sweats, and requiring the help of Garmin (and a tech), we were able to downgrade, and tell the G1000 he could talk with the new revision (2.85).
Next flight was a deception, since in unrestricted mode, I could see a fair amount of TAS targets (max range is theoretically 40nm), and only one ADSB target, instead of the usual nebula you usually see (including all aircraft in flight level cruise).
I asked Garmin for help in troubleshooting.
We will try to swap the antenna, to be sure the problem is not there (please remind the fault developed progressively, with less and less target showing up).
The G1000 is probably not responsible for this, as when I connect my tablet to the GTX345, I don’t see more ADSB traffic with Foreflight.
Please also note another, new, symptom: on start up, I frequently get a TRAFFIC FAILED message, which was not the case before. This requires cycling the XPDR with its own breaker, and allows to clear the failure message, and get proper TAS information.
PetitCessnaVoyageur wrote:
(please remind the fault developed progressively, with less and less target showing up)
This could point to some defect popping up and worsening in time, such as a cable/connector going bad or some semiconductor/capacitor inside the transponder going bad.
PetitCessnaVoyageur wrote:
Please also note another, new, symptom: on start up, I frequently get a TRAFFIC FAILED message, which was not the case before. This requires cycling the XPDR with its own breaker, and allows to clear the failure message, and get proper TAS information.
I would say this might be an indication of either a software mismatch/incorrect initialization sequence during avionics bootup issue, or a developing problem inside the transponder that allows the unit to power up correctly only sometimes/the second time it is turned on. I imagine if there is a problem with the transponder, it would show an error message on the transponder screen. If the protocols/fw versions are incorrect, there would likely be no error message on the transponder screen, only on the G1000. Can’t be quite sure, as certified are sometimes a bit different from non-certified (where my little experience comes from).
Given your initial report of the « TRAFFIC FAILED » occasional occurrence that could be resolved by power cycling, it could be an incorrect initialization sequence during avionics bootup that comes up now more often after the fw update – maybe more mismatched boot times between the units. You could try powering up the transponder later, only after the G1000 has booted up and if the error no longer shows up, or if it initially shows up and then clears with transponder power-up, that would explain it.
I hope my last part is not too convoluted, but such is the process of troubleshooting. It helps if you have handy a sheet of paper and a pen and note down all combinations of powerup sequences and timing with the respective results.
Hi there,
Time for an update.
After SW update, the problems remained.
I tried a new XPDR antenna, but it didn’t change a thing (the same as the DME).
Also, I have been able to diagnose the GTX345 (with Garmin Configuration Tool on a PC) when the fault appears in the G1000.
This is what I got:
I also sent the diagnostic report and ADSB recordings to Garmin.
My unit probably failed.
My hypothesis is that the ADSB in (1090 RX) socket failed, which is disappointing for a low power part.
I asked Garmin for a gesture (being out of warranty), for a XPDR that worked for only 500h – that makes a very low MTBF, considering the previous GTX33 worked flawlessly for the previous 16 years.
The return enquiry can only be made by a Garmin reseller, which will happen after the holiday period.
I’ll let you know how it finishes !
