I am hoping someone can help me out with this - I have a Garmin Aera 660 in my plane with a GDL 39 ADS-B receiver and the map on the 660 displays my own tail number as a traffic target. Unlike in foreflight, there is no setting to disable "ownship" detection, and I have scoured the internet for help on this with no luck. My transponder is ADS-B out (978) and it's broadcasting the proper tail number and the 660 has that matching tail number entered in the aircraft profile. My understanding is that it should filter out my traffic target based on that but it is not happening. Anyone have any ideas? Thanks!
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Aera 660 displaying ownship traffic target
- Thread starter acutl1001
- Start date
It is rare to see an Aera 660/760 with GDL 39/5X fail to properly identify ownship, so there must be something going on with your specific equipment.
The GDL 39/39R (and newer GDL 5X receivers) do an "ownship" determination for the purpose of filtering out received traffic packets from our own aircraft in one of 2 ways:
1. The first and best way is that the GDL is installed in an aircraft with a G3X or G3X Touch system and transponder. The system shares the transponder ICAO address (N number) of the aircraft with the GDL and the GDL will always perfectly filter out all traffic packets that have the ownship ICAO address.
2. The second method of ownship determination is for the GDL to compare the GPS position and GPS altitude it receives from the Aera 660, as well as the pressure altitude measured by the GDL (in non-pressurized aircraft) to the same data in each traffic packet to find itself and discover its ICAO address. This address, once known, is then used to filter out traffic packets originating from our own aircraft.
Portables like the Aera 660 with GDL 39/5X can be moved from plane-to-plane, so it was decided (right or wrong) that it is best that they not be given a fixed ICAO address (like your transponder does which never leaves your plane).
The aircraft identifier, if entered on the aircraft profile page of the Aera 660, identifies a specific aircraft profile, but this information is not shared with the GDL for the aforementioned reason.
One possible explanation for the method 2 ownship determination to fail is if the pressure altitude measured by the GDL is significantly different from the pressure altitude transmitted by your UAT. You might try telling your GDL that it is installed in a pressurized aircraft so it stops using its internal pressure altitude sensor. This is explained in the pilot guide. If making this change stops the display of ownship as a traffic target, then either the GDL or the UAT is likely using an incorrect pressure altitude.
You might also verify that your Aera 660 GPS fix is always 3D Differential. If you have the Aera 660 installed in a location where the internal antenna is not working as well as it should, this could also influence the ownship determination.
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