As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD - FLT 1891 - BOS-ORD, STAB TRIM FAILED WHEN AUTO PILOT WAS DISCONNECTED DURING DESCENT. TRIM BEGAN TO RUN AWAY ON SHORT FINAL. TURNED OFF BOTH TRIM MOTORS. LANDED ORD WITHOUT INCIDENT. AFTER LANDING TURNED TRIM MOTORS BACK ON AND WAS UNABLE TO TURN TRIM WITH THE ELECTRIC FROM EITHER PILOT LOCATION. REPLACED ELECTRIC TRIM ACTUATOR. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)