As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT IS PITCHING UP AND DOWN UNCOMMANDED. REQUIRES EXCESSIVE FORCE ON CONTROL WHEEL TO MAINTAIN DESIRED PITCH, EVEN WITH ELECTRIC TRIM DISCONNECTED. REMOVED AND REPLACED ELECTRIC ELEVATOR TRIM TAB ACTUATOR IAW REPS AIRLINER 1900D M/M 27-30-07-201. PERFORMED ELEVATOR ELECTRIC TRIM TAB CABLE RIGGING IAW 27-30-07-201 PAGE 10. PERFORMED ELEVATOR ELECTRIC TRIM OPERATION CHECK PROCEDURE 27-30-09. ALL CHECKS GOOD.