Incident Overview
During the takeoff initial climb, the flight crew of a transport category airplane encountered a jammed horizontal stabilizer trim actuator. Shortly after takeoff, while climbing out, the "STAB OUT OF TRIM" annunciator light illuminated in the cockpit. The crew immediately disengaged the autopilot and attempted to use the electric trim control, but found it inoperative at both the pilot and co-pilot positions. Subsequently, they tried the manual trim control, which was jammed and immovable.
Crew Actions
To manage the situation, the crew leveled the airplane at 13,000 feet and executed the "Stabilizer Out of Trim" and "Jammed Stabilizer" checklists. These procedures did not resolve the issue. The crew then declared an emergency with air traffic control and conducted an otherwise uneventful landing at Los Angeles. According to the pilot, the manual trim control remained jammed and immobile throughout the flight.
Post-Flight Examination
After landing, a post-flight examination revealed that the horizontal stabilizer trim actuator motor was seized. The actuator motor was subsequently replaced with a serviceable unit, and the aircraft was ferried to Seattle for further inspection. No other faults were found in the pitch trim system, and the airplane was returned to service. Further examination of the removed actuator motor confirmed that the motor was mechanically seized. According to a representative of Boeing Aircraft Company, with the motor seized, manual trimming of the stabilizer would have required the flight crew to exert sufficient force on the trim wheel to cause the motor clutch to slip, in addition to the force needed to overcome normal system friction.
Outcome
The aircraft was ferried to Seattle for inspection after replacement of the seized actuator motor. No additional defects were discovered in the pitch trim system, and the airplane was subsequently returned to service.