RAS Post by Darryl Ramm.

ADS-B Glossary

1090ES: Mode S Extended Squitter Transponder. An ADS-B transceiver operating on one of two FAA-approved datalink frequencies. It operates on 1090 MHz, using a Mode S Extended Squitter transponder (1090ES for short, referring to the ADS-B information appended to the Mode S data). 1090ES is the international standard; in the United States, it is required for operations above 18,000 feet and for Part 135 operations. While the 1090 ES datalink provides traffic information, it does not receive weather data.

ADS-B: Automatic Dependent Surveillance-Broadcast. In this core technology behind the FAA’s Next-Generation Air Traffic Control System, a datalink transceiver automatically broadcasts the aircraft’s location and other data at regular intervals. The system doesn’t wait to be interrogated, like a transponder.

SSR: Secondary surveillance radar (SSR) is a radar system used in air traffic control (ATC), that not only detects and measures the position of aircraft, i.e. bearing and distance, but also requests additional information from the aircraft itself such as its identity and altitude. Unlike primary radar systems that measure the bearing and distance of targets using the detected reflections of radio signals, SSR relies on targets equipped with a radar transponder, that replies to each interrogation signal by transmitting a response containing encoded data. SSR is based on the military identification friend or foe (IFF) technology originally developed during World War II, therefore the two systems are still compatible.

ADS-R: Automatic Dependent Surveillance-Rebroadcast. ADS-B has two datalink systems, and because they use different frequencies, they can’t talk to each other. Enter ADS-R, a ground-based system which relays 978-MHz UAT traffic to 1090-MHz Mode S Extended Squitter traffic, and vice versa. In areas with radar service, information on non-ADS-B aircraft is broadcast to aircraft equipped with ADS-B In.

TIS-B: Traffic Information Service Broadcast. TIS-B is an uplink of radar-identified traffic from ground stations to ADS-B-equipped aircraft. This traffic can be displayed in panel-mounted avionics, or on a tablet or other electronic display, along with ADS-B traffic received directly or via ADS-R.

FIS-B: Fight Information Service-Broadcast. FAA ground stations transmit FIS-B—which includes no-fee weather, temporary flight restrictions, and other data—over the Universal Access Transceiver (UAT) datalink frequency. FIS-B is considered an advisory service and includes METARs and TAFs; Nexrad precipitation maps; airmets, sigmets, and convective sigmets; winds and temperatures aloft; pireps; TFRs; and status of special use airspace.

CDTI: Cockpit Display of Traffic Information. Traffic information received via ADS-B—whether directly, via ADS-R, or through TIS-B—is displayed on a multifunction display (MFD), other panel-mounted avionics, or on an iPad or other portable electronic device.

UAT: Universal Access Transceiver. An ADS-B transceiver operating on one of two FAA-approved datalink frequencies. A UAT operates on 978 MHz (978UAT). Equipment costs generally are lower than for 1090ES, and this frequency can receive free traffic and weather information (the UAT must also support the optional ADS-B In). The United States is the only country using the UAT standard.

Equipment TT21 or TT22 with undefined GPS Source Not recommended

0) SIL=0 (any old NMEA GPS source driving a TT21 or TT22 transponder) provides the following capabilities for your glider - (Not recommended, use one of the other options below instead).

Has all the standard transponder capabilities, including ATC SSR visibility and PCAS, TCAD and TCAS compatibility
Is visible to portable 1090ES In traffic displays (e.g. a Stratus or Stratux receiver driving EFB software)
Is visible to PowerFLARM (with ADS-B In Option)
Is NOT visible to certificated fixed install 1090ES In traffic displays in GA aircraft and above
Is NOT visible to UAT In equipped aircraft via ADS-R- no ADS-R rebroadcast by the ground infrastructure to those aircraft
Is shown as a TIS-B target to TIS-B client aircraft when within SSR coverage
Does NOT makes your glider a client of ADS-B ground based services so you cannot see other traffic vis ADS-R and TIS-B (and remember PowerFLARM does not display ADS-R or TIS-B anyhow)
Is *NOT* visible to ATC via ADS-B (ATC can still see you when within SSR coverage) - Does NOT provide flight privilege in airspace in 14 CFR 91.225 that requires ADS-B Out, remembering gliders already have some exemptions there.

Equipment TT21 or TT22 with TN72 GPS Source , Class Standard or Experimental Aircraft

1) SIL=1 (A TN72 GPS driving a Trig TT21 or TT22 transponder) this is the "TABS" install and provides the following capabilities for your glider.

Has all the standard transponder capabilities, including ATC SSR visibility and PCAS, TCAD and TCAS compatibility
Is visible to portable 1090ES In traffic displays (e.g. a Stratus or Stratux receiver driving EFB software)
Is visible to PowerFLARM (with ADS-B In Option)
Is visible to certificated fixed install 1090ES In traffic displays in GA aircraft and above
Is visible to UAT In equipped aircraft - via ADS-R rebroadcast by the ground infrastructure to suitably equipped client aircraft
Is NOT shown as a TIS-B target to client aircraft when within SSR coverage (since the system is using ADS-R to show you as a more precise target to those clients)
Does (if properly configured) make your glider a client of ADS-B ground based services so you can see other traffic vis ADS-R and TIS-B (but remember PowerFLARM does not display ADS-R or TIS-B traffic)
Is NOT visible to ATC via ADS-B (ATC can still see you when within SSR coverage)
Does NOT provide flight privilege in airspace in 14 CFR 91.225 that requires ADS-B Out, remembering gliders already have some exemptions there.

You would only do this install in a type certified glider where the TN70 option was too expensive or the slightly larger GPS case could not fit (I hope folks would work out how to make it fit).

Or in type certified or experimental glider if you had a TT21 and did not want to have it upgraded to a TT22.

In an experimental glider you can just use a TN72 GPS to do full 2020 Compliance/SIL=3 which you can't do in a type certified glider since the TN72 GPS is not TSO-C145 approved but the TN70 GPS is.

Equipment TT22 with TN72 or TN70 GPS, Class Standard or Experimental

3) SIL=3 (Trig TT22 (not TT21) with either a TN72 GPS in an experimental glider or TN70 GPS in a type certified glider). This is a fully 14 CFR 91.227 2020 ADS-B Out compliant system and provides the following capabilities for your glider.

Has all the standard transponder capabilities, including ATC SSR visibility and PCAS, TCAD and TCAS compatibility.
Is visible to portable 1090ES In traffic displays (e.g. a Stratus or Stratux receiver driving EFB software).
Is visible to PowerFLARM (with ADS-B In Option)
Is visible to certificated fixed install 1090ES In traffic displays in GA aircraft and above
Is visible to UAT In equipped aircraft - via ADS-R rebroadcast by the ground infrastructure to suitably equipped client aircraft
Is NOT shown as a TIS-B target to client aircraft when within SSR coverage (since the system is using ADS-R to show you as a more precise target to those clients)
Does (if properly configured) make your glider a client of ADS-B ground based services so you can see other traffic vis ADS-R and TIS-B (but remember PowerFLARM cannot display ADS-R or TIS-B traffic).
Is visible to ATC via ADS-B (including outside of SSR coverage)
Does provide flight privilege in airspace in 14 CFR 91.225 that requires ADS-B Out, remembering gliders already have some exemptions there

I'm still wondering if ... the TABS system will allow us to be seen by ATC and get clearances to transit restricted or CLASS B,C airspace. If not, I'd have to go for the more expensive TN-70 ... full compliant.

TABS is not 14 CFR 91.227 complaint so does not give you any flight privileges in airspace that requires ADS-B Out in 14 CFR 91.225. So TABS should not ever have been thought of as an option there. It's a system really "engineered" (technically and regulation wise) to provide aircraft-aircraft traffic awareness, not ATC surveillance.

And in practice, as far as I am aware (and noted in the lists above) the ATC systems are just not configured to allow ATC to see SIL=1 targets. They only display SIL=3. ATC will still see you via SSR when within SSR coverage. Lack of ATC visibility may make TABS not so appealing for many folks. For others TABS may be a nice easier option to provide visibility to GA aircraft in busy areas (especially where ATC can see you via SSR anyhow) and especially if you are combining with a traffic display that can show you ADS-R and TIS-B traffic.

If 2020 ADS-B Out airspace flight privileges is one of the things you want and you have a type certified glider then a TN70+TT22 is what you should be installing. A few of those install have happened and more are in progress. You or your A&P may want to talk to me before getting started, it's actually pretty easy, I mostly just want to make sure people don't make it more complex than it needs to be.

Regulatory :

It is important for A&Ps involved in any work to read that doc and just do the minimum paperwork described in that paper. No more, no less. If they ever start talking about using the STC for a major alteration approval run away. Specifically the answer to the question "After initial approval, can applicable ADS-B OUT systems be installed on aircraft not covered by that approval?" ... is what is being applied here, read it carefully, it talks about using an applicable AML STC... if there is one... here there is not as the AML does not apply to the glider, so OK you use the STC only to justify the pairing provided for in that answer. read it carefully. eg FAA is saying is if there *was* a different AML STC they want you to use that instead, and since there is not... you don't. That answer both explains the policy here and tells the installer all the paperwork bits they have to do in this case.
Under FAA Memo titled “Installation Approval for ADS-B OUT Systems,” the FAA explains that after an STC is achieved for ADS-B OUT equipment, additional installations can be accomplished on aircraft not listed under the AML STC by an A&P with Inspection Authorization (IA) so long as the installation does not require airframe modification. This process requires completion of a two page FAA form known as a 337. We are providing a mostly complete sample Form 337 . Once the form is completed your installer will mail it into the FAA office in Oklahoma City. The process is normal for many ADS-B installations and your installer is likely familiar with the process.