GPS Loss and Terrain Warning

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   I had no problem on my long trip down to the Bahamas but coming back to the US today I had many with the top 540.  I am not sure if this is related to the GPS signal loss that someone else spoke of but I had many, many GPS signal losses with some lasting 5 min.  Each one was followed by a "Terrain Ahead, Pull up Warning" even though I was at 8000 ft over the ocean :).  At the same time ATC told me they lost my transponder code and asked me to recycle.  I noticed that at these times, the transponder said ADSB signal lost but it came back on when the GPS warning disappeared. The red alert for the terrain stayed on the whole flight.  I cycled the top 540 to see if that would correct the issue but after it rebooted, the GPS signal loss issue started again along with the "terrain warning, pull up" issue.   Any thoughts.   I still have a flight home from Florida in front of me and was hoping there was something I could do to correct this.

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teeth6 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 10 Mar 2014 Status: Offline Points: 741	Post Options Post Reply Quote teeth6 Report Post Thanks(0) Quote Reply Topic: GPS Loss and Terrain Warning Posted: 01 Jan 2015 at 1:16pm
	I had no problem on my long trip down to the Bahamas but coming back to the US today I had many with the top 540. I am not sure if this is related to the GPS signal loss that someone else spoke of but I had many, many GPS signal losses with some lasting 5 min. Each one was followed by a "Terrain Ahead, Pull up Warning" even though I was at 8000 ft over the ocean :). At the same time ATC told me they lost my transponder code and asked me to recycle. I noticed that at these times, the transponder said ADSB signal lost but it came back on when the GPS warning disappeared. The red alert for the terrain stayed on the whole flight. I cycled the top 540 to see if that would correct the issue but after it rebooted, the GPS signal loss issue started again along with the "terrain warning, pull up" issue. Any thoughts. I still have a flight home from Florida in front of me and was hoping there was something I could do to correct this.

AviJake Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 26 Mar 2009 Location: Lincoln MA Status: Offline Points: 2815	Post Options Post Reply Quote AviJake Report Post Thanks(0) Quote Reply Posted: 01 Jan 2015 at 1:27pm
	You've experienced the same GPS loss that several folks have seen on their units. We believe we've addressed those as part of Rel 10.0.3.0 that is going through final testing now. As for the terrain alerts, that is a natural, albeit undesired, behavior of the system recovering from a GPS loss and momentarily thinking it's got a low GPS altitude. The root cause of that (GPS loss) should go away in Rel 10.0.3.0 but we've also made a change in Rel 10.1 code that suppresses that terrain alert in the event of a GPS recovery. I definitely wouldn't expect to see the red terrain warning message stay on for the entire flight however. If you can, send me/us your datalogs and we'll take a quick peek at them to see if anything interesting shows up. (sjacobson@avidyne.com and I'll make sure the logs get passed along to others as well).
	Steve Jacobson sjacobson@avidyne.com

teeth6 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 10 Mar 2014 Status: Offline Points: 741	Post Options Post Reply Quote teeth6 Report Post Thanks(0) Quote Reply Posted: 01 Jan 2015 at 9:23pm
	Steve, I had some time to download the system log files when I stopped for the night enroute. Please let me know if you also need the other log files (engine, etc). I emailed the log file to you. The red terrain warning definitely did stay on for the whole flight and even came back on after I did a restart of the top unit but I figured that was cross feeding from the bottom unit which also displayed the red warning. Do you have any idea what triggers this GPS signal loss ...ie, is there some combination of actions I can avoid to not trigger it? It is strange it happened repeatedly on my top unit but not at all on the bottom unit. Also, weird it had not happened on the top unit thru many hours of use until this trip. Let me know if the log files give an hints or if you need other logs as well.

AviJake Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 26 Mar 2009 Location: Lincoln MA Status: Offline Points: 2815	Post Options Post Reply Quote AviJake Report Post Thanks(0) Quote Reply Posted: 03 Jan 2015 at 8:10am
	Looking. Will report back any findings.
	Steve Jacobson sjacobson@avidyne.com

teeth6 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 10 Mar 2014 Status: Offline Points: 741	Post Options Post Reply Quote teeth6 Report Post Thanks(0) Quote Reply Posted: 03 Jan 2015 at 8:26am
	Thank you will email you photos of the display also

AviJake Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 26 Mar 2009 Location: Lincoln MA Status: Offline Points: 2815	Post Options Post Reply Quote AviJake Report Post Thanks(0) Quote Reply Posted: 05 Jan 2015 at 4:18pm
	Got the datalogs and pix and we see something unusual with respect to the terrain alerts but we need more information. Specifically, we need: 1. Date of the occurrence. 2. Event logs from both IFDs. 3. Flight logs from both IFDs. 4. System log from the other IFD.
	Steve Jacobson sjacobson@avidyne.com

teeth6 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 10 Mar 2014 Status: Offline Points: 741	Post Options Post Reply Quote teeth6 Report Post Thanks(0) Quote Reply Posted: 05 Jan 2015 at 4:54pm
	Date of occurence is January 1, 2015. I will get the other logs asap.