ADS-B aircraft on scope

[Coty Smith]

I’ve had a Garmin GDL-39 for a while an would regularly see aircraft that didn’t show on ADS-B. I assumed it was because I didn’t have ADS-B out. I’ve installed a Garmin GTX 335 and have ADS-B out now. I still see aircraft that are not showing on the scope. One was an American Airlines at 10,000 ft coming in to DFW. Others were traffic called by ATC while I was at 7000 or 8000 ft. I expected the radar returns would have better coverage and show what ATC saw, that’s not been the case. Anyone else seeing something similar?

[Andy95W]

No, that has not been my experience.  I also have a GDL-39 but I have the FreeFlight ADS-B out.

I can think of 2 reasons this might be happening to you. The display for your AdS-B can be configured with filters to show or not show traffic, such as only showing traffic within 2000 feet of your altitude.  The other reason, and probably more likely, is the configuration of the GTX-335.  It should be configured to let the ground system know that you have ADS-B IN on a UAT receiver, otherwise the ground stations will not be broadcasting the band that you need to receive.

[Marauder]

1 hour ago, Andy95W said:

No, that has not been my experience.  I also have a GDL-39 but I have the FreeFlight ADS-B out.

I can think of 2 reasons this might be happening to you. The display for your AdS-B can be configured with filters to show or not show traffic, such as only showing traffic within 2000 feet of your altitude.  The other reason, and probably more likely, is the configuration of the GTX-335.  It should be configured to let the ground system know that you have ADS-B IN on a UAT receiver, otherwise the ground stations will not be broadcasting the band that you need to receive.

Andy is correct. I would check the settings on the filters. I have multiple screens that display my ADS-B in. I keep the one on the Aspen MFD as unfiltered which shows all aircraft regardless of altitude and the one on the L-3 9000+ for "NRM" which only displays planes that are +/- 2,700 of my altitude. 

[Raptor05121]

9 hours ago, Coty Smith said:

I’ve had a Garmin GDL-39 for a while an would regularly see aircraft that didn’t show on ADS-B. I assumed it was because I didn’t have ADS-B out. I’ve installed a Garmin GTX 335 and have ADS-B out now. I still see aircraft that are not showing on the scope. One was an American Airlines at 10,000 ft coming in to DFW. Others were traffic called by ATC while I was at 7000 or 8000 ft. I expected the radar returns would have better coverage and show what ATC saw, that’s not been the case. Anyone else seeing something similar?

This has been asked on the Stratuxforums. ADS-B out aircraft, for some reason, are still not getting the full picture. One member has tried to get in contact with the FAA for an answer and got no where, if I recall correctly. 

[Coty Smith]

In Foreflight I have filters turned off, to see all traffic. I also checked the Garmin 335, there does not seem to be a setting to show an alternate ADSB in. The Garmin Aera 560 nor ForeFlight showed the missing traffic. Of course they both had the GDL39 as input. ForeFlight  does recognize “own ship” and knows there is ADSB out. 

I’ll keep an eye on it and see if there is a pattern, but there is an occasional plane that doesn’t show.

[takair]

1 hour ago, Raptor05121 said:

This has been asked on the Stratuxforums. ADS-B out aircraft, for some reason, are still not getting the full picture. One member has tried to get in contact with the FAA for an answer and got no where, if I recall correctly. 

There is a common misconception that ADS-B out automatically gets you ADS-B in traffic.  It is Not automatic and must be intentionally set up.  The ADS-B out only systems have a setting to determine ADS-B IN capability.  Because most of our ADS-B IN units are portable, the installer of the ADS-B out unit will typically set the ADS-B IN capability to NO.  The GTX-335 has two settings for this.  One if you are capable of receiving UAT and one for 1090. To get the full traffic picture , these must be set for YES (or equivalent...can’t recall the nomenclature).  For those flying bigger birds with Rockwell Collins equipment, there is a strapping option for this.  The FAA does a poor job of advertising this and it leaves a safety gap since most assume they are now getting the big picture....in fact, they are missing a huge piece of it and are relying on aircraft that are appropriately strapped to request traffic.

[Andy95W]

2 hours ago, Coty Smith said:

In Foreflight I have filters turned off, to see all traffic. I also checked the Garmin 335, there does not seem to be a setting to show an alternate ADSB in. The Garmin Aera 560 nor ForeFlight showed the missing traffic. Of course they both had the GDL39 as input. ForeFlight  does recognize “own ship” and knows there is ADSB out. 

I’ll keep an eye on it and see if there is a pattern, but there is an occasional plane that doesn’t show.

The setting to enable your GDL-39 to see traffic would be in the GTX-335 installation manual, probably under how to configure your device.  It would normally only be accessed and programmed by your avionics shop.  

Perhaps someone here can look it up if they happen to have the actual installation manual, or if not you should call your installer.

[Raptor05121]

11 hours ago, takair said:

There is a common misconception that ADS-B out automatically gets you ADS-B in traffic.  It is Not automatic and must be intentionally set up.  The ADS-B out only systems have a setting to determine ADS-B IN capability.  Because most of our ADS-B IN units are portable, the installer of the ADS-B out unit will typically set the ADS-B IN capability to NO.  The GTX-335 has two settings for this.  One if you are capable of receiving UAT and one for 1090. To get the full traffic picture , these must be set for YES (or equivalent...can’t recall the nomenclature).  For those flying bigger birds with Rockwell Collins equipment, there is a strapping option for this.  The FAA does a poor job of advertising this and it leaves a safety gap since most assume they are now getting the big picture....in fact, they are missing a huge piece of it and are relying on aircraft that are appropriately strapped to request traffic.

In the instances of what I was referring to, is a complete ADS-B Out/In combo, setup accordingly. I'll try and find it again.

[bradp]

The only thing I have noted is that the ADS-B track on a target will disappear for a second or two and then be back in the next “sweep” regardless of whether it’s with my hide distant traffic filter on or off.  

uat and 1090 settings should both be set to “on” on your GTX-335.  If you feel comfortable doing this the installation manuals are out there and it’s an easy couple of pages in the config menu.  

Id also recommend getting an ads b compliance report - when I did my upgrade the compliance report was the tip off that I had an incorrect config setting.  Since then it’s been working well.  

[Coty Smith]

I have my ADS-B compliance report. It passed, but only shows 1090 out, no 1090 in or UAT in. Sounds like that could be the problem.

i pulled down the install manuals but the settings didn’t jump out at me. I may need to set in the airplane and step through it. I think I’ll give the avionics installer a call.

Coty

[takair]

4 hours ago, Coty Smith said:

I have my ADS-B compliance report. It passed, but only shows 1090 out, no 1090 in or UAT in. Sounds like that could be the problem.

i pulled down the install manuals but the settings didn’t jump out at me. I may need to set in the airplane and step through it. I think I’ll give the avionics installer a call.

Coty

Tell your avionics man that you want these set to yes...assuming you have a dual band ADS-B in unit.