blueline wrote:
nobody knows anything about them, nobody can fix them, nobody has spares
Exactly what we found
I have received some old installation and maintenance manuals for a Badin-Crouzet autopilot, as installed on an early 1970s Robin. I intend to scan it in for my avionics manuals library (which lives on a private site) but in the meantime if anyone needs to know something specific, drop me an email and I will see if it is in there.
Even by GA standards, it is really old stuff. Basically mid-1960s, all hand-drawn, and would have cost a fortune in labour to even draw it up let alone manufacture it.
A competent electronics person could fix this stuff, given the circuit diagrams and a lot of time spent setting up a bench text fixture. However the same comment applies to any autopilot testing.
I have the same situation with my old King H-14. There are maybe one or two places left in the US that can work on them. They’re also pneumatic. Same era autopilots.
Pneumatic servos, with electronic control, presumably?
IIRC, some WW2 stuff was wholly pneumatic, with pneumatic error amplifiers, etc.
If your find a working one anywhere, I’d be interested for my Rallye.
I’m unable to find a more modern autopilot with STC for my plane.
I doubt you will find a “definitely working” one anywhere, unless somebody has just scrapped their Robin, because what will they replace it with?
The best way forward is to find an “electronics boffin” and fix it “off the books”. It would have to be somebody who is “nobody”, in case he gets sued 
Have you tried Electronic Maintenance Aviation
Aka EMA – Aeromecanic
Tel +33 4 42 77 05 77
[email protected]
Don’t know how old the information is, it comes from an 75yr old Jodel 120 owner here
I think I have written this before but I think Badin Crouzet became part of Sextant Avionique which is now part of Thales Group.
I think the part of Crouzet Peter is writing about went into switches and things for airlines.
This might be of interest
Probably cost a fortune but it doesn’t hurt to do some further research does it?
