As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT DEPARTED TEB EN ROUTE TO RST. IN CRUISE FLIGHT AUTOPILOT DISCONNECTED AND YAW DAMP FAIL MESSAGE ILLUMINATED. AIRCRAFT RETURNED TO TEB. LANDING WAS UNEVENTFUL. DEFERRED YAW DAMP CHANNEL "A" PER MEL 22-20-2. AIRCRAFT REPOSITIONED TEB-MKE. STERLING MAINTENANCE CURRENTLY INVESTIGATING FAILURE OF YAW DAMP CHANNEL "A".