Strange ADS-B out failure

[takair]

I’ve had a NavWorks UAT ADS-B system installed since before they went belly-up.  Never a problem with it.  Friday, I did a one hour leg, no problem.  On the way back, while picking up flight following, Philly approach asks me if I have ADS-B.  They ask me to recycle and then say they don’t show ADS-B, but transponder is fine.  There were no failure indications in the cockpit….it continued to provide traffic to the GNS-430.  Further questions to NY approach indicated the same.  Oddly, one controller said that they show my ADS-B as not installed, vs failed.  

Here is the odd thing, Upon returning home, I did a PAPR check.  Both flights indicate good ADS-B operation.  No failures, other than when I recycled.  This includes matching flight ID and 30 minutes in class B “rule airspace”.  The only other odd thing is that Foreflight showed a strange drop in altitude to 0 for much of the flight.  

Today I had similar experience.  However, ATC did not say anything and only said I didn’t have ADS-B after I questioned them.  Oddly, in both cases, ATC said standby….like they had to go look it up.  In all cases, FlightAware recorded the flights, including ADS-B hits.

I have a note to the FAA ADS-B folks, I’m generally familiar with ADS-B including certification, but this has me baffled.  Anybody run into this….good PAPR but ATC can’t see your ADS-B?

[carusoam]

Hey Rob!
 

Let’s see if @1980Mooney is around…

I believe… He has demonstrated really good skill with finding data from ADSB devices…

Best regards,

-a-

 

[1980Mooney]

OK just to make sure we are talking about N7125U on Friday and today.

When I look at FlightAware on the Friday return leg I don't see where you said it shows you at "0" altitude.  The data is complete with no gaps in time stamp.  It is all listed as UAT data except for 1 minute 46 seconds minutes at 3:12 PM however the data is still there.

[1980Mooney]

If you "fly" your route on ADSB-Exchange, which uses available ADSB as well as its own receiver network, it shows that you are UAT the entire route - both legs - there and return

https://globe.adsbexchange.com/?icao=a98695&lat=40.882&lon=-74.062&zoom=10.2&showTrace=2022-03-18&trackLabels&timestamp=1647635546

Your squawk going down was 4372

Your squawk on the return was 4261 

ADSB-Exchange had trouble with your track briefly at 3:18 11 seconds but it did not drop you to "0".  FLightAware picked you up fine at that point.

It seems like there may be some delay in the presentation of your location and speed data but it is all seems to be there  

 

let me know if I am looking at the same track that you were  

 

Edited March 21, 2022 by 1980Mooney

[carusoam]

Way Cool 1980!   

Lets see if Rob is back…
 

Hey Rob @takair!

Check out the details from 1980 above…

Best regards,

-a-

[takair]

6 hours ago, 1980Mooney said:

If you "fly" your route on ADSB-Exchange, which uses available ADSB as well as its own receiver network, it shows that you are UAT the entire route - both legs - there and return

https://globe.adsbexchange.com/?icao=a98695&lat=40.882&lon=-74.062&zoom=10.2&showTrace=2022-03-18&trackLabels&timestamp=1647635546

Your squawk going down was 4372

Your squawk on the return was 4261 

ADSB-Exchange had trouble with your track briefly at 3:18 11 seconds but it did not drop you to "0".  FLightAware picked you up fine at that point.

It seems like there may be some delay in the presentation of your location and speed data but it is all seems to be there  

 

let me know if I am looking at the same track that you were  

 

Hi yes, you got it. Thanks for the analysis!!!   I saw the same thing. I also got the FAA performance review which shows healthy. The drop out I likely when I recycled.  I pulled the breaker for a short time. The altitude issue is in my ForeFlight track logs. Never had an issue before, so an odd coincidence. The Sunday flights did not record at all. I’ve sent them error logs. Will see what the FAA says. I don’t know what ATC looked at when I questioned them after the first report.  It did take them a few minutes to reply tot he question, so it appears they are not monitoring all the time. 

[0TreeLemur]

4 hours ago, takair said:

Hi yes, you got it. Thanks for the analysis!!!   I saw the same thing. I also got the FAA performance review which shows healthy. The drop out I likely when I recycled.  I pulled the breaker for a short time. The altitude issue is in my ForeFlight track logs. Never had an issue before, so an odd coincidence. The Sunday flights did not record at all. I’ve sent them error logs. Will see what the FAA says. I don’t know what ATC looked at when I questioned them after the first report.  It did take them a few minutes to reply tot he question, so it appears they are not monitoring all the time. 

Yes, it seems that the ADS-B info is not fully integrated into the current system.  One example, controllers have a very hard time getting my tail number correct at first contact.  N2903L is often read back by controllers as N2093L, N3092L, or N2902L.   So, I started saying "N29 oh tree lima" and that helps a bit.  It seems that using "tree" instead of 3 really helps with cognition somehow.   But often I forget - another cognitive error. 

Sometimes even after I correct the controller after an incorrect readback, the next center replies with the original incorrect tail number.   It seems like whenever they put me in the system, the ADS-B info would allow identification of errors, and autocorrect.  As I understand it, controllers have to click on an airplane to pull up their ADS-B info and they usually don't. 

[takair]

Follow-up.  I contacted the FAA avionics check branch and got the following response:  “ATC can sometimes misreport ADS-B performance.  The PAPR report is the only true way to check ADS-B operation.  Suggest you check the system again after a few more flights.  You are good for now.”  
 

This is good news given the unsupported nature of my system.  I installed this system before the mandate and have really liked having it.  However, given the 2020 mandate, it is disappointing that ATC still does not use it routinely and the system can misreport performance.  
 

Long story short, This seems to confirm the the PAPR is the official measure of performance, even if ATC questions operation.