ADS-B PAPR performance report failed on Kinematics...implications?

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bkspero

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bkspero
A friend flying in his plane behind me said that my traffic symbol disappeared from his screen for a few minutes on a short (25 minute) flight yesterday in the airspace between New York and Philadelphia. I checked my flight path and Track Log data on Flightaware and there was no gap in it (there were 2-4 entries every minute, and none of the positions seemed wildly divergent from the others). There was no mention of a problem from ATC who were providing flight following.

But to be complete, I requested a PAPR ADS-B performance report from the FAA website, and I was surprised to find that it showed a failure for Position Change in the Kinematics section (copy of that page attached). MCF was 3, resulting in a % Fail of 3%. I then requested a report for the flight home, and that one showed a MCF of 1 resulting in 1.54 % Fail...passing, but non-zero. Everything else in the report seemed reasonable and normal.

I have 5 PAPR reports from prior years starting in 2015 and going through June of 2023. None of those show any Kinematics errors. And even the failed report shows no problem with Navigation Accuracy Category for Position (NACp).

I've read the ADS-B PAPR User's Guide and am not clear on what I should do next. Neither the failed PAPR report nor the passing report for the subsequent flight indicate that my plane is now on the No Service Aircraft List (NSAL), so it doesn't seem like this failure grounds the plane. Any suggestions?

My shop has no experience with this situation.
 

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  • ADSB FAA airborne performance analysis report Aug 24 2024a Kinematics Page.pdf
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Temporary gap between ADSB stations?
 
What do you want to do about it?

I would not do anything. My ADSB drops targets regularly, happened yesterday for a few seconds.
 
Lndwarrior said:
Temporary gap between ADSB stations?
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Unless there is something I don't understand about ADS-B service, I don't think this is the issue. In this airspace my ADS-B in receiver typically shows reception from 5-6 stations, and never fewer than 4.
 
4RNB said:
What do you want to do about it?
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I want to do the right and legal thing...whatever that is. And I would like to keep flying the plane. But I can't find much online about what the requirements are. I recognize that aircraft with ADS-B out systems must operate those systems at all times in flight (unless they have prior permission to fly otherwise). My presumption that this requirement includes that the system be operating properly. But the failing report makes no mention of grounding my plane. And it doesn't even make note that my plane has been placed on the No Service list (where the PAPR instructions say that it would be listed on the report if that was the case). So I was hoping that someone more familiar with the application of this regulation would point me to regulatory guidance that covers this situation.

Second, I would like to identify and correct whatever has caused these Kinematics errors to develop after nine years of what seems to have been flawless operation. For this I was hoping that someone more familiar with this issue might identify possible causes other than the obvious one that the GPS is giving inaccurate position reports (as, based on its navigational performance, gps position seems to be rock solid).
 
bkspero said:
I want to do the right and legal thing...whatever that is. And I would like to keep flying the plane. But I can't find much online about what the requirements are. I recognize that aircraft with ADS-B out systems must operate those systems at all times in flight (unless they have prior permission to fly otherwise). My presumption that this requirement includes that the system be operating properly. But the failing report makes no mention of grounding my plane. And it doesn't even make note that my plane has been placed on the No Service list (where the PAPR instructions say that it would be listed on the report if that was the case). So I was hoping that someone more familiar with the application of this regulation would point me to regulatory guidance that covers this situation.

Second, I would like to identify and correct whatever has caused these Kinematics errors to develop after nine years of what seems to have been flawless operation. For this I was hoping that someone more familiar with this issue might identify possible causes other than the obvious one that the GPS is giving inaccurate position reports (as, based on its navigational performance, gps position seems to be rock solid).
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The only reason I ever got an ADSB report is when ATC kept asking me to confirm my altitude on an IFR day. If they do not worry you, I would not worry about it, particularly since this seems to happen sometimes.

Do you KNOW you had 9 years flawless? You have 9 years worth of reports?

What does this paper say about the numbers you got? https://adsbperformance.faa.gov/PAPRUsersGuide.pdf

Are you NPE? Have you received a LOF?
 
Kinematics delta position errors may be an ADS-B system issue, not an avionics issue.
That is, you are not alone in 'suddenly' noticing this error where none had been present before and no changes have been made to your equipment ... others, including myself, have experienced it in recent weeks.

There is a thread (or at least some posts in a thread) addressing this on the VansAirforce forum. https://vansairforce.net/threads/uavionix-status-update.223887/page-4
Of particular note is this post: https://vansairforce.net/threads/uavionix-status-update.223887/post-1786763
Aug 16, 2024

#174

Regarding the kinematic position failures, uAvionix support shared with me an unofficial statement from the FAA, below. They're expecting an official letter from the FAA that can be shared.

The Delta Position kinematics flags you’ve been seeing in some of the PAPRs is not an avionics problem.

This is a problem we’re having with the ADS-B Performance Monitor which our team is working tirelessly to correct.

Please don’t make any changes to any avionics due to these delta position flags.
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I ran a PAPR on my Bonanza for my 4:15 hour flight home from Oshkosh. I also got an MCF of 3 and 2.52% on Position delta. This is what the user guide says:

Kinematics: A reasonableness check is made of changes in Baro/Geo Altitude, Position, and Velocity. Items highlighted in red were identified with position changes outside the range expected for normal aircraft performance.
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My flight was IFR, at 11,000 and other than the flight over Lake Michigan was essentially direct to my destination, so no maneuvering at all and just one LPV approach. IMHO, the issue is with their reasonableness checks and not with the performance of my system. I see it on many of the PAPR checks that otherwise are perfect based on the other measurements. I would totally ignore it as being useless information. I see a new company is listed on the PAPR and am guessing there is an issue with their software or assumptions. I will ask my contacts at the FAA to see what is going on with the PAPR and will post a comment if I learn something.

Edit: My post was just made at the same time as the previous post from JoeSelch.
 
4RNB said:
Do you KNOW you had 9 years flawless? You have 9 years worth of reports?
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Yes, one a year. Not on each anniversary, though. I tried to collect data during different seasons and weather conditions to confirm that the system was operating properly under all normal flight conditions

4RNB said:
What does this paper say about the numbers you got? https://adsbperformance.faa.gov/PAPRUsersGuide.pdf

Are you NPE? Have you received a LOF?
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The PAPR users guide is pretty brief about Kinematics failures. Only saying that they result from position or altitude changes that are larger than expected. Does not specify how large a change triggers an exception, nor does it say what the consequences are of a failure in this area.

As I wrote, there was no mention of the plane being on the Non Service List on either the report with the failing entry or a report for a subsequent flight a few hours later. I have not gotten a letter of failure, either.
 
Thanks to all who responded. Particularly 4RNB, JoeSelch, and John Collins with your direct experiences. I will keep on flying, but will check PAPR reports periodically to see if the situation changes (for the better, or worse :) ).
 
FWIW, my avionics guy says don't worry about it. If there's a problem with your ADSB out the FAA will reach out to you.
 
I haven't looked at this stuff for a long time and I'm not about to do any research, but I'd check the part 91 requirements for ADS-B. IIR in addition to the TSO, there are specific requirements for NIC, NACp, NACv, and maybe SIL and SDA. Those are navigation integrity category, navigation accuracy category for position and velocity etc. You may be within limits.
 
kontiki said:
there are specific requirements for NIC, NACp, NACv, and maybe SIL and SDA. Those are navigation integrity category, navigation accuracy category for position and velocity etc. You may be within limits.
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All of those were within limits. I plan to keep flying it until either the plane's ADS-B performance is questioned by ATC, or I get an indication that the system either shows up as NPE on a PAPR report, or I get a letter of failure from the FAA.
 
bkspero said:
Thanks to all who responded. Particularly 4RNB, JoeSelch, and John Collins with your direct experiences. I will keep on flying, but will check PAPR reports periodically to see if the situation changes (for the better, or worse :) ).
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The FAA acknowledged that the PAPR report has an error in the Kinematics and they are working to resolve it.
 
Thanks, John. Did they publish this information somewhere, or was it a private communication? Seems to be something worth telling us about.
 
bkspero said:
Thanks, John. Did they publish this information somewhere, or was it a private communication? Seems to be something worth telling us about.
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I guess it was a private question forwarded to an FAA contact. This is her response when she checked into it.

I heard back pretty quickly…

They said the kinematic issue is a known problem and they are currently working on it. They asked if you could submit your questions to Flight Standards at “9-AWA-AFS-300-ADSB-AvionicsCheck@faa.gov”. They have a process in place for how to answers PAPR related questions, so you should be able to get an “official” reply that way.
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If you want an official response, send your query to the Flight Standards email address.
 
I sent a follow up question to the Flight Standards email address on another issue relating to whether or not the Garmin GTX 345D is using a single antenna or dual antennas. The PAPR reports I got for three aircraft indicate that they are broadcasting erroneously using a single antenna instead of a top and bottom dual antenna. They are investigating, but it is looking more like there is an issue with the Garmin GTX 345D. The D stands for diversity, which means a top and bottom antenna is being used. Some US pilots that frequent flying into Canada are interpreting the Canadian ADS-B Out mandate to require diversity to communicate with the satellite system. The Canadian mandate doesn't explicitly require diversity.
 
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