What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) Pilot reported at 20,000 feet, the elevator trim dn annunciator illuminated. The pitch trim indicator was reading +1 degrees (full nose down). Crew disconnected autopilot (following abnormal procedure checklist), and aircraft pitched down with the control yoke in the full aft position. Crew was not able to maintain altitude (200-300 ft./min. Descent) initially. However, they were able to maintain altitude and control of the aircraft below approximately 9000 ft. Cessna aircraft, along with a Cessna service center have replaced a suspected faulty horizontal stabilizer actuator and autopilot controller. Cessna aircraft will conduct an evaluation of these parts with FAA aco oversight.
As the FAA filed it
(-23) PILOT REPORTED AT 20,000 FEET, THE ELEVATOR TRIM DN ANNUNCIATOR ILLUMINATED. THE PITCH TRIM INDICATOR WAS READING +1 DEGREES (FULL NOSE DOWN). CREW DISCONNECTED AUTOPILOT (FOLLOWING ABNORMAL PROCEDURE CHECKLIST), AND AIRCRAFT PITCHED DOWN WITH THE CONTROL YOKE IN THE FULL AFT POSITION. CREW WAS NOT ABLE TO MAINTAIN ALTITUDE (200-300 FT./MIN. DESCENT) INITIALLY. HOWEVER, THEY WERE ABLE TO MAINTAIN ALTITUDE AND CONTROL OF THE AIRCRAFT BELOW APPROXIMATELY 9000 FT. CESSNA AIRCRAFT, ALONG WITH A CESSNA SERVICE CENTER HAVE REPLACED A SUSPECTED FAULTY HORIZONTAL STABILIZER ACTUATOR AND AUTOPILOT CONTROLLER. CESSNA AIRCRAFT WILL CONDUCT AN EVALUATION OF THESE PARTS WITH FAA ACO OVERSIGHT.