On Saturday, February 18, 2017 at 2:15:12 AM UTC-8, wrote:

One wrinkle to be aware of is certified ADS-B In systems will *not* see your traffic at all if it is using a non-certified/non-compliant ADS-B source. They are as anal-retentive as the FAA ADS-B ground infrastructure (or rather last year the FAA made the ground infrastructure deliberately as anal-retentive as the airborne certified ADS-B In systems to discourage use of non-compliant GPS sources partially to help force better compatibility with those certified airborne ADS-B In systems).

So folks who have an experimental glider sure they can hook up any old GPS source say to a Trig transponder, and it will show up on PowerFLARM and non-certified ADS-B In systems. But really not a good idea, probably not a good idea to talk about without being clear on the limitations, especially now there is a Trig TN72 GPS is suitable for use in experimental gliders and does not have those limitations (Lots of discussion on the TN72 on other threads on r.a.s.). But if folks have an experiential glider with a Trig transponder and want ADS-B Out the TN72 is really now likely the minimum they should be thinking of.


Daryl, maybe I misunderstood....I had read that an adsb target using an uncertified gps would not be considered a 'client' by ATC, but I assumed the location of an uncertified-adsb target would still be included in data broadcast by ATC to client aircraft. I would have thought the transponder alone would have justified inclusion.


A transponder alone will make you a TIS-B target for client aircraft. As long as you are within both SSR and ADS-B ground system coverage. The SSR coverage there is the gotcha, e.g. no coverage at many gliderports and airport pattern areas or say down low on ridges where there might be lots of glider traffic. And TIS-B is so imprecise and has other issues it's of little use compared to Flarm for glider-glider traffic avoidance.

I believe non-compliant GPS (e.g. TSO-C145c or meets performance requirements of, or TSO-C199) will *not* make you a ADS-R target, and even TSO-C199 may not get you on ATC traffic displays (but again if within SSR coverage ATC will see you via that).

Also, would an uncertified-adsb target be detected by a certified-adsb receiver via direct (air-to-air) transmission, and at what approximate range?

Absolutely not. A *certified* ADS-B In receiver will not display non-complaint ADS-B Out equipped aircraft via ADS-B direct. It will run right into that target with no warning at all. If the aircraft is also equipped with TCAD/PCAS and the target aircraft has a transponder then that system would provide traffic display and TA and (for TCAS-II) RA alerts.

The bottom line is probably just don't mess with non-compliant GPS sources, they will not provide the results that most glider pilots will just expect.. The TN72 (esp. with a Trig transponder) should be the minimum goal to use in experimental gliders today if you want to do ADS-B Out. As folks actually get those systems installed it would be great to hear their experiences and costs. Unfortunately certified gliders currently require installation of a full TSO-C145c certified GPS source, with costs that are non-starters for most owners. I would be nice to see TSO-C199/TABS installation and use regulations that allowed for installation of a TN72 type ADS-B Out GPS sources in certified gliders.

All this mess is part of why PowerFLARM for glider-glider traffic awareness is a popular choice. And its PCAS and 1090ES In helps provide some inbound traffic coverage.

For awareness to other traffic and ATC, especially airliners and fast jets, the humble transponder (Mode-C or Mode-S) is very very effective. In busy traffic areas get a transponder like a Trig TT-22 that you will be able to upgrade to ADS-B Out in future, hopefully as costs fall and regulations improve. In really busy traffic areas please don't put off installing and using a transponder while waiting for ADS-B future toys.

Thanks for any help.

No problem.

As folks get ADS-B Out stuff installed and working, please share your experiences with others.