On Thursday, May 9, 2019 at 5:49:22 AM UTC-7, son_of_flubber wrote:
If you have a Trig transponder and install TABS or ADSB-out, why can't you use the Public ADSB Compliance report in place of Transponder Compliance test?

The ADSB COmpliance report seems superior because it tests the whole system in the air for several hours, whereas the Transponder Compliance test is an artificial test done in the hangar for 30 seconds.

https://adsbperformance.faa.gov/paprrequest.aspx

What tests exactly? There are two transponder tests, Part 43 appendix E (altitude encoder test) and Part 43 appendix F (Transponder RF test).

The encoder test (required when the static system is opened, etc) could not be achieved by the FAA Public ADS-B Performance Report, it relies on the encoder being correct.

The transponder RF test verifies the transponder replies correctly to a Mode A, C and S interrogations and checks for some corner cases of known possible issues, the FAA Public ADS-B Performance Report does not provide that information, there is no guarantee that an aircraft will experience all those different interrogations during a flight, etc. and the system may not be able to tell what is going on in a "live" non-test environment. Things that might be doable very roughly like infer transmitted power would be relatively inaccurate, better to measure those at the aircraft.

Now, two year checks made a lot more sense when transponders were powered by unreliable traveling wave tubes and had lots of components inside. Modern solid state transponders, with highly integrated digital components are much more reliable. So two years may be overkill, but I'd not hold my breath waiting for that to change.

The FAA Public ADS-B Performance Report are great for letting owners see that an ADS-B Out system is configured and working properly. Including being the *only* way for most glider pilots to know a 2020 Compliant or TABS ADS-B Out system is fully working... e.g. on a Trig transponder you can't just rely on seeing a lat/lon display on your transponder... the transponder can show you a lat/lon but you don't know the actual GPS reception is giving you a high enough NIC quality parameter, or that the SIL setup parameter is set correctly, ... things that can stop ATC or some airborne ADS-B In receivers being able to see your aircraft via ADS-B Out. And just asking ATC "can you see me" at times may not help, if you are within SSR coverage the controller can't tell if they are seeing you via SSR or ADS-B. And your buddy seeing you on a PowerFLARM also does not tell you if ATC or IFR/certified ADS-B In system can see your ADS-B position. ... so look at those performance reports. https://adsbperformance.faa.gov/paprrequest.aspx

Everybody flying with ADS-B Out should pull a report or two after installation to make sure things are OK, and maybe once a year or so after that. Those reports can be used by an A&P as part of a install in a type certified aircraft, or they can utilize ADS-B capable ground test equipment -- more $$$ than Mode-S transponder test gear -- which few folks working with gliders will have access to. For experimental aircraft installs there is no documentation needed of a test, but get one done yourself. And regardless of who installed and claimed to test or not what they did, pull your own report and check.

The FAA is looking at the equivalent of those reports as well. And they are likely to contact you eventually if there are glaring problems (and as I mentioned before they are likely to contact folks with TABS systems (which by definition are not 2020 Compliant)... the FAA has no way of knowing the install is not intended to be 2020 Compliant).

As always anybody with a Public ADS-B Performance Report and has questions about it can email the PDF report to me. I'm getting about one a week. GPS Antenna installation quality (affecting NIC), basic TT21/TT22 setup menu mistakes, flying on the edge of ADS-B ground coverage, or forgetting to get the transponder firmware updated, are the most likely causes of issues being flagged in those reports. I'm updating some of the Trig setup instructions (most folks have hopefully been using the notes that Richard and I wrote on the Craggy website) and will get those updated soon.