Transponder TT21 versus TT22 - Considerations

Also worth noting that "does it work" is not the same as "is it approved." ADS-B approved installations are by specific equipment for specific certified aircraft. At present, I'm not aware of any approved installations for specific gliders. Please correct me if I am wrong.

On Tuesday, January 20, 2015 at 5:29:06 PM UTC-8, wrote:
Also worth noting that "does it work" is not the same as "is it approved." ADS-B approved installations are by specific equipment for specific certified aircraft. At present, I'm not aware of any approved installations for specific gliders. Please correct me if I am wrong.

And "does it work" required careful definition of what exactly "work" means.. (e.g. would ATC see you at all? Would you receive ground based ADS-R and TIS-B service in the USA, etc.). Connecting two boxes together and transmitting something that is a flavor of ADS-B Out is a very low-bar, likely uselessly low.

And the corollary to "is it approved" is can I as a pilot or A&P get into trouble if I just go ahead and do it if it is not approved... and in the USA in a certified aircraft the answer to that question is very much yes.

USA ADS-B Out approvals are available now via FAA field approval, so in that sense they are based on specific instances of installs, as I already said the FAA wants that to be based on existing STCs, again all covered in AC 20-165A. The STCs that the FAA want to based that on were often AML (approved model list) STCs, so covering more than one specific aircraft type/install situation. No STCs/AML STCs exist for gliders that I am aware of, but solving that problem starts with a call to the friendly staff at your local FSDO, and being willing to write a large check for a suitable GPS and to pay the A&P/IA/shop to do the install and spend time dealing with the field approval. Where folks go into this with their eyes open and have good contacts at their local FSDO and involvement from the vendors I expect this to be quite doable in a certified glider. The willingness to spend $$$ and a reason to bother are all anybody need to get started...