IMHO-The FAA has a very odd methodology when it comes to adding airplanes to an AML. The Dynon Skyview has been in a lot of Certified and experimental aircraft by now and it seems like the EFIS software pretty much stays the same. All the servos in all the existing autopilots from various manufacturers use arms pushing rods or capstans moving yoke cables. The only outlier I know of is Brittian with their pneumatic bellows. It's been that way for 6 centuries. By now any airplane type that isn't brand new has had an autopilot applied to it. It seems like the FAA refuses to accept the historic record as a fact. They want to start at square one and reverify everything. "One definition of insanity is repeatedly doing the same things again, expecting a different outcome."
Yes there's a lot of brackets to design, but that can be outsourced pretty easily and get a DER stamp. An IA has to pass judgement on the installation before the airplane is returned to service. The IA has the last word with regard to applicability because every airplane that isn't fresh off the assembly line has probably had other STCs applied to it and any conflicts have to be resolved.
Flight testing? What?! Do Dynon's arms or capstans do something magically different than Garmin's or S-Tec's or anybody's? Does the manufacturer sticker on the servo change the flight characteristics of an airplane with an autopilot attached? Once you can test the servo on a bench and determine that it behaves like everyone else's, you make that part of the PMA specification not, something you have to test on every new addition to the AML.
So, how are Dynon servos different? The shear pin that's used as a fail safe against the servo jamming. I think everyone else is using spring washers and clutches that connect the output of the servo gearbox to the shaft that drives the arm or capstan. I actually like the shear pin better because, if the servo jams, I have to overpower it once and break the pin. Then I can carry on hand flying the airplane to my destination the same way I fly the airplane with the autopilot off. And, I can even leave that fuel stop and continue my trip with the arm or capstan merrily spinning on the servo output shaft. If I have a servo with washers and clutches, I have to fight that all the way to the ground. Essentially learning a new way to fly the airplane in mid air with passengers and weather to contend with until the wheels are on the ground. Then, do I really want to take off again and continue doing that? I probably wait for an avionics shop to open and send someone to where I am to remove/replace the servo, if they have a spare on hand that's been setup for my airplane. Less fun than finishing my flying and taking my airplane home to call a mechanic to do the remove/replace on a more leisurely schedule.
So what's the hold up? Yeah, pins are different than clutches. So, pins have been proven to work on a dozen types/models already on the AML. Is that going to change if you put the same servo in a different type/model? With the exception of brackets and rods/cables, which haven't changed in 60 years or more, what is the agency struggling to establish? The cynic in me suspects that there is something other than safety and scientific method at work here.
