Only C145 is needed for a ADS-B out device. This is NOT a navigator, just a GPS position source. This is what GRT is advertising, and in our opinion, it is only usable for ADS-B out, not navigation. At $3K+, that's an expensive way to get just ADS-B out. We'd love to make one of our own at a more affordable price, but it's a huge challenge and not one of our priorities right now.
In an experimental, only two things need to be certified, your transponder, and your GPS if you want to file IFR. The AIM makes this clear:
1.[ch8194]Authorization to fly approaches under IFR using GPS avionics systems requires that:
(a)[ch8194]A pilot use GPS avionics with TSO- C129, or equivalent, authorization in class A1, B1, B3, C1, or C3; and
(b)[ch8194]All approach procedures to be flown must be retrievable from the current airborne navigation database supplied by the TSO-C129 equipment manufacturer or other FAA approved source. The system must be able to retrieve the procedure by name[ch8201]from the aircraft navigation database, not just as a manually entered series of waypoints.
and:
1.[ch8194]Authorization to conduct any GPS operation under IFR requires that:
(a)[ch8194]GPS navigation equipment used must be approved in accordance with the requirements specified in Technical Standard Order (TSO) TSO-C129, or equivalent, and the installation must be done in accordance with Advisory Circular AC[ch8201]20-138, Airworthiness Approval of Global Positioning System (GPS) Navigation Equipment for Use as a VFR and IFR Supplemental Navigation System, or Advisory Circular AC[ch8201]20-130A, Airworthiness Approval of Navigation or Flight Management Systems Integrating Multiple Navigation Sensors, or equivalent. Equipment approved in accordance with TSO-C115a does not meet the requirements of TSO-C129. Visual flight rules (VFR) and hand-held GPS systems are not authorized for IFR navigation, instrument approaches, or as a principal instrument flight reference. During IFR operations they may be considered only an aid to situational awareness.
It's our opinion that the AIM applies to all aircraft, and thus an experimental needs a certified GPS as well to file IFR. If you want to try and argue that your experimental meets all the TSO requirements for GPS without actually being TSO'd, that may work, but the TSO is 800 pages long for just C145, so that's going to be a lot of reading and even more testing.
LORAN, VOR, and other methods don't have this language in the AIM and thus you are able to put non-TSO'd units in an experimental and use them for primary navigation. In this case, it is up to the pilot to decide, but when it comes to GPS, the FAA has a written policy.
Again, this is all Dynon's opinion of the regulations, and you may have a different interpretation.
