How does Mode S Enhanced Surveillance (GPS position) fit in with ADS-B OUT (and checking your ADS-B OUT using Foreflight)

Super. Many thanks. That’s exactly the info I was seeking.

Here is what you do with ForeFlight and a Stratus 2 receiver. Get your avionics up and running, good GPS position.. Connect to the Stratus 2. Verify on ForeFlight that you are connected to the Stratus 2. Go to More>Devices. Verify that you see the ADS-B listed as a capability on the Stratus Device. Tap the device box to get to the detail status. In the detail status, find own ship. It should have your registration number listed to the right as detected. Tap on the > to go to ownship detail view. What your ADS-B Out is broadcasting should be displayed. You can alternatively go to the Map view, and tap the gear settings icon, then the Stratus 2 Status and then ownship to display the detail being broadcast.

Note that the Stratus 2 or any portable receiver does not determine ownship, it simply receives ADS-B Out broadcasts, near and far. Your ownship broadcast is coming from near, very near, like 5 meters away?. ForeFlight determines that there is a target within a certain distance and altitude based on the GPS position from the Stratus or other GPS position information. After so many matches, it tags the closest one that fits the criteria as ownship and then decodes the information for the ownship detail display. Ground stations need not apply.

Here are some screenshots, a mixture of my airplane N7083N (I have UAT) and from a friend’s airplane N6331S who has 1090ES. I used my Stratus 2. I used the second method of selecting the gear settings icon on the map view and then the Stratus 2 settings and then ownship for details.

@NCYankee I understand about needing an ADS-B IN device that receives 1090 MHz, which I have. My question is related to viewing the data on FF outside the US where their report is not available …. per your comment on Aug 27:
NCYankee wrote:

I have everything I need to decode the ADS-B Out with my ForeFlight App. As we were testing ADS-B traffic, I requested that diagnostic information be easily accessible in the app. I used it once on a case that involved the FAA and Garmin to determine when the GTX 330ES was switching to ground mode.

I think I must have misunderstood you here. According to FF, diagnostic info isn’t accessible. I can only see the presence or absence of my aircraft on FF based on the data received from the ADS-B IN receiver. I understood your comment to mean you can see more than that, i.e. diagnostic data, and how you saw it was my question since I can’t find it in FF.

Of course, to have own-ship data sent to FF from the ADS-B IN receiver, I need to have the receiver configured without own-ship call sign. In normal operation, the ADS-B IN receiver is provided with own-ship so that it could be ignored.

All versions of FF will decode the data, but you need to have a dual frequency ADS-B receiver to receive the ADS-B Out ownship broadcasts. The Stratus 2 or 2S works best as it does not modify the data. A Scout may work as well. A Stratux might work, but does change the data. A GDL39/50/51/52 should work, but some of the data will be missing, but GP will fully decode the data. If you don’t have a receiver that receives the 1090 MHz broadcasts, then there is no way for FF or GP to display the data. If you fly in the US, you can get a compliance report from the FAA using their website. All you have to do is enter your tail number and a date of your flight, and the report will be emailed to you.

I asked FF about this, and they basically said “can’t do at this time”. Perhaps I phrased the question wrongly. Did you have a special version of FF, @NCYankee?

NCYankee wrote:

I have everything I need to decode the ADS-B Out with my ForeFlight App. As we were testing ADS-B traffic, I requested that diagnostic information be easily accessible in the app. I used it once on a case that involved the FAA and Garmin to determine when the GTX 330ES was switching to ground mode.

How does this work? I’d like to verify my IFD540/AXP340 ADS-B Out signal and have ForeFlight but see no such capability. As far as I can tell, the diagnostics logging in ForeFlight is just accessible/usable by ForeFlight staff.

Peter wrote:

Can you imagine getting this stuff installed, here in Europe? Most installers don’t even know about this, let alone have test kit enabling them to check what exactly is being emitted.

It is relatively simple if one follows the STC IM. Pick the right equipment, wire it, configure it and test it as described in the STC IM. There is expensive test equipment, but I have everything I need to decode the ADS-B Out with my ForeFlight App. As we were testing ADS-B traffic, I requested that diagnostic information be easily accessible in the app. I used it once on a case that involved the FAA and Garmin to determine when the GTX 330ES was switching to ground mode. Garmin saw what I was doing and added it to their app, Garmin Pilot. Avionics shops can use their expensive equipment or just use an iPad, a portable receiver, and either ForeFlight or GP. FreeFlight was selling a box for $5000 to test their UAT installs and I showed a sales person how I did that with ForeFlight at a trade show. He said something like that will kill sales of the tool. I used my ForeFlight and Stratus receiver on a flight to deliver an A36 over the weekend to its new home. The aircraft has dual GTN systems attached to a GTX330 (not ES) and a GDL88 (UAT ADS-B Out system). The N number had been changed about two years ago when the aircraft was painted, The N number appeared in the ADS-B Out message, but the wrong ICAO Aircraft ID showed in the message. I decoded it and it was for the previous N number, so my conclusion was that the GDL88 is installed with the new N number, but the GTX still has the old one. That will get flagged by the FAA and the new owner will need to get it fixed.

Peter wrote:

Getting back to my original Q, I guess that

The point is that ADS-B and ATCRBS radar are two independent surveillance systems with two separate theories of operation..

means that the two will work concurrently; one doesn’t disable the other. Presumably the software must be written so that the periodic ADS-B OUT emission is slightly delayed if the transponder is responding to SSR.

It is more likely to be first come, first served. If the transponder is responding to an interrogation, the ADS-B will probably be delayed, because timing of the ADS-B message has a built in jitter and is not precisely 1 second between squitters. The other way around, my guess is that any interrogation during the time the squitter is occurring will simply be ignored. There are multiple opportunities for a radar or TCAS/TAS system to repeat an interrogation if it is not responded to and the timing between interrogation and reply must be fixed for distance to be determined.

Peter wrote:

Can a GTX330 (year 2005) be upgraded to ADS-B OUT?

Yes, they need to be returned to Garmin because there is a hardware and firmware upgrade. Firmware can be upgraded in the field, but the hardware update can only be done at Garmin. Garmin charges about $1200 for the upgrade. It may be easier just to buy a used GTX330ES on eBay as many are being replaced by the GTX345. You could still sell your GTX330 non ES in Europe to someone that needs or wants mode S, but does not care about ES.

One of the big installation errors is that the GTX330 upgrade to GTX330ES is not a remove, return to Garmin for upgrade, slide back in operation, in that additional wiring may be required and the configuration needs to be updated on both the GTX and the position source such as the GNS. Interesting that even if the serial port is not interconnected, the GTX in the US is usually wired to the GNS via an ARINC port that includes latitude and longitude, so the system works, but as an NPE.

Peter wrote:

let alone have test kit enabling them to check what exactly is being emitted.

The PilotAware can be configured to show what’s being emitted for extended squitter. It’s not very expensive. When you put ADS-B into an LAA permit aircraft, the report from PAW is one of the things you submit with the form you send to the LAA.

NCYankee wrote:

There are several formats of RS232 from the Garmin units that will get the Trig to generate a position, but only one format is compliant and must be used if the Trig software is at the version that supports RTCA DO 260B. It must be configured for ADS-B Out + format.

Thanks!

There is an older version that is compliant with RTCA DO 260A and the early software versions of the Trig unit, it is named ADS-B Out. Aviation Data or ADS-B Out will make the combination with the Trig NPE.

The Trig IM does say that using Garmin GPSs with the ADS-B (non-plus) output format is compliant with EASA specifications (CS-ACNS), but not with FAA specs (91.227)! Do you have any idea why? EASA is usually more picky than the FAA…