When I was a kid I used to design medical diagnostic tech robotics.
I was admittedly, a weird kid.
The feedback tasks of any autopilot are really very simple.
This clever gadget would probably work just fine on a 337.
As a portable device, no FAA involvement.
'Clamp and go'
My Ye Olde Navomatic gets its course correction off the CDI.
I just upgraded my panel to Avidyne fantasy suite w new King CDI.
KI 209 I think?
The CDI gets signals from IFR GPS 550 AND and provides left right guidance to AP.
Including GPSSS, which is merely anticipating turns over a fix, instead of hard correction.
Doesn't drive AP elevator, but that's trivial anyway.
Trim for level flight, engage AP. Done.
Little AP head by right knee can climb / descend, hold heading, intercept/track, hold altitude, etc.
The portable AP looks like $3K.
https://www.portapilot.com/product-page/portapilot-vnav
Plus another $100 to supply power from 24 volts
https://www.portapilot.com/product-p...ng-power-cable
I four AP is dead and no longer supported,
and you really need one, to hold heading, altitude and track course,
for $3k I'd give the portable a try and see how it does.
If its terrible I'm sure they'd take it back.
My guess is it would work just fine.
It's just some some stable convergent (not divergent) feedback systems after all.
Report back to us if you do.