On Thursday, September 28, 2017 at 10:33:56 AM UTC-7, Darryl Ramm wrote:
On Thursday, September 28, 2017 at 9:12:56 AM UTC-7, jfitch wrote:
On Wednesday, September 27, 2017 at 10:24:48 AM UTC-7, son_of_flubber wrote:
I asked Trig support this question:

"Will a TT21 + TN72 transmit a non-zero quality indicator?"

Here is their reply:

"The TT21 is fully certified to the latest ADS-B Out cert TSO C166b – so it can output all the required data. It is true that if you wish to meet ADS-B Out compliance FAR 91.227, you should have a higher power TT22. However, there is no way for the radar to tell if you’re using a TT21 or TT22. Inspection of your aircraft would be the only way to tell.. As such I believe a number of experimental pilots have opted to ignore the requirement , but of course I cannot recommend this as it would be in violation of FAR 91.227 – the requirements for 2020 compliance.

The TN72 offers both a SIL =1 output, and also a SIL = 3 output. So this means that you can meet the FAA compliance check using your TN72 plus TT21. https://adsbperformance.faa.gov/PAPRRequest.aspx

If you so choose, you can opt to have your TT21 upgraded to a TT22. For more information on this please contact our US service centre below;

Trig Avionics Technical Support
9400 East 34th Street North
Wichita
KS 67226
United States

Tel: Toll Free 800 821 1212
Tel: +1 316 630 0101
Email:
Web: www.mcico.com
"

The response to my inquiry with is:

"The cost to update the TT21 to the TT22 is $950.00. Turn around time is 3-4 days in house."

That is some very useful information right there. Two questions:

Does the receiver (FAA) have any way to tell more information about the GPS source? If it is transmitting an SIL of 3 (required for carriage requirements), other than physical inspection can a receiver discriminate between a 70 and a 72?

There is no GPS Source vendor ID. No Mode-S transponder or UAT Out vendor ID, no serial numbers, no encryption signature, etc. allowed for in the design of ADS-B. The lack of signature is a much more serious shortcoming IMNSHO that any of the others. ADS-B Out systems do transmit SIL, NIC and NAC GPS quality parameters and interestingly CC (capability code) that describe if the aircraft has 1090ES In and/or UAT In.

What does Powerflarm do with a glider having both ADSB out and Flarm? Does it deambiguize?

Yes it deduplicates them, based in aircraft ICAO address. Presumably PowerFLARM gives priority to the FLARM signal but somebody like Dave would have to confirm that.

I believe FLARM also deduplicates Mode S PCAS alerts based on ICAO ID. It can't do that to Mode C PCAS alerts because there is no ICAO address broadcast on Mode C.

So hypothetically, an install of a TT21/TN72 in a certified glider is undetectable as such without a physical ground inspection? It looks to the receiver identical to a TT22/TN70 installation? (Ignoring here the regulatory consequences of such an inspection).