Just to be clear, the current FARs for ifr gps, and ADSB gps, do not mention TSO. Instead, they say ?approved?. In FAR 1.1 (definitions) it says ?A TSO is one way, but not the only way, to (be approved)?. The FAA has approved a number of ADSB gps sources for EAB aircraft that are not TSO?d. To my knowledge, they have not approved any non TSO?d gps for IFR. But at least one avionics company - GRT - is quietly testing these waters. 5 years agoI?d have bet that this would never gain ifr approval. But now - with non-TSO?d D10?s and G5?s replacing the primary attitude indicator in nornally certified aircraft, I think there is some hope for a much lower cost approved ifr gps.