I’m working as an inspector now at a relatively large Part 145 repair station. We mostly work on turbine engine stuff. King Airs, Cessna Jets and Pilatus PC-12s. A lot of that stuff has or is converting to Garmin because it’s all integrated with the aircraft systems. Garmin provides all the 337 language citing an STC and they provide the AFMS. A lot of this is signed by one FAA person. My guess is that because of the kind of money involved and the fact that a lot of the aircraft involved are Part 135 carriers, Garmin has been assigned their own ACO people that don’t get shared with all the other requests that would normally pile up in the FAAs in basket.
Setting that aside, the FAAs does tend to be arcane and/or arbitrary. This makes working through a project tiresome unless you can have one to one discussions with them as you work through the process. Having your own assigned Agency people gives you that. The rest of us (Dynon included) are left to work up a package based on what you understand is a common sense application of the FARs, submitting that and waiting for a response from the Agency. This makes for a very long iterative process.
i kind of hoped at some point the FAA would apply some scientific method and logic to this process. Once you have established that the servos work as designed on a couple of dozen aircraft types. And, determined that the logic controlling them is sound and reliable. And, the aircraft in question are conditionally stable and amenable to A/P control. What remains should be sheet metal mounts and rigging. That should be easy work for a DER and after some test flights, the approval should be pro forma. But, as has been pointed out to me on multiple occasions, that’s not the way the Agency works. The follow on question of why doesn’t it work that way never elicits a satisfactory response.