On Wednesday, March 25, 2015 at 8:03:03 PM UTC-7, Bill T wrote:
Darryl, I've been looking and for most standard certificated aircraft, not experimental, it takes STC to install ADS-B equipment. A couple of STCs I have found do not list the Piper Pawnee, PA-25. Any Pawnee I have seen is registered under Restricted category. Any ideas?
BillT

Bill, it does not directly take an exact STC to install an ADS-B Out. But the FAA does wants an STC to act as the basis for a field approval. What I believe they mostly care about is the GPS, ADS-B Out device and required peripherals (e.g. control heads etc.) and wiring interconnect are known to work together/have been though a proper STC process. (and to see the horror involved there look at AC 20-165A).

The first FAA clarification that a field approval was acceptable was this http://download.aopa.org/aircraft/121105faa-ads-b.pdf

Bottom line is if you had to do this now for some reason, then I'd have a read of this stuff, but basically get out you check book and find a good avionics facility and talk with them and/or the manufacturer and/or and the local FSDO if needed (a good shop should really do all that for you), about what is possible/how exactly to get field approval. If they have not done a field approval based ADS-B Out installs of similar equipment I would *not* want to be the first customer lined up with my aircraft to have them do this.

A list of approved/STC'ed pairings of ADS-B Out and GPS sources is included in this newsletter https://www.faa.gov/nextgen/ga/media...stallation.pdf (may be slightly out of date).

But it is just way too early today, I would wait until manufactures are (hopefully) offering affordable transponder/1090ES Out with built in GPS (which AFAIK will still need to be fully TSO-ed for a restricted category aircraft, but the integrated install still will make things easier). And let the manufacturer of that help your avionics shop with how to get that install field approved.