SV ADS-B traffic anomally?

[kurtfly]

Dear Dynon,

Yesterday during an IFR flight from Tampa, Fl. to Fort Worth, TX I noticed two traffic displays anomalies at different times.

First, was "Displaced" labeled under the target. The second was a target's label toggling between "1200" and "VFR". Both of these occurred between FL panhandle and New Orleans area.

I have occasionally seen the squawk code but never "VFR". I have never seen the "Displaced" label before. Just wondering.

I have a SV 10T, with xpdr and ADS rcvr. SV ver. 14.2

 

[Dynon]

I think (but am not certain - a colleague may correct me) that both of those are the data labels that are being transmitted by the ATC system.

 

[dynonsupport]

Colleague here...

Any ID's seen beneath a target are sent by the aircraft itself over ADS-B. This means they are ADS-B out targets, not just targets with transponders. ATC doesn't control these, and can't input ones for aircraft that aren't ADS-B OUT.

The plane can send out whatever it wants and we display it. There are FAA rules on what you are supposed to put out of course. Different vendors of ADS-B implement things differently.

The one going VFR/1200 is telling you they are in "anonymous" mode and don't want you to see their tail number. You are allowed to show 1200 or VFR, and that vendor alternates between those every few seconds.

"Displaced" sounds like someone entered that for their flight ID (instead of N1234A or UA123). Not ADS-B legal or compliant, but again, all we do is show it.

 

[airguy]

That raises an additional question - can all ATC facilities see the tail number if it's broadcast by the airplane? Or only certain facilities?

 

[dynonsupport]

We're not experts on how the ATC system uses ADS-B right now, but our understanding is that some ATC facilities do have access to ADS-B data (and thus the N number) but most do not yet.

As a total guess, I've noticed that my local ATC never asks me for an IDENT while they do ask other aircraft, and I've wondered if this is because they can see my N number and thus don't need a secondary verification that a target is the correct one.