Accident Sequence
The accident flight was the first flight after maintenance personnel replaced the forward elevator trim cable. Shortly after takeoff, the flightcrew reported a runway trim and manually selected nose-up trim. However, the elevator trim then traveled to the full nose-down position. Control column forces subsequently increased to 250 pounds, and the flightcrew was unable to maintain control of the airplane.
Maintenance Actions
During the replacement of the cable, maintenance personnel skipped a step in the manufacturer's airliner maintenance manual (AMM). They did not use a lead wire to assist with cable orientation. Additionally, the AMM incorrectly depicted the elevator trim drum, and the orientation of the cable around the drum was ambiguous. Despite these issues, the maintenance personnel stated that they had completed an operational check of the airplane after maintenance.
Investigation Findings
The Safety Board performed a mis-rigging demonstration on an exemplar airplane, which reversed the elevator trim system. An operational check on that airplane revealed that when the electric trim motor was activated in one direction, the elevator trim tabs moved in the correct direction, but the trim wheel moved opposite of the corresponding correct direction. When the manual trim wheel was moved in one direction, the elevator trim tabs moved opposite of the corresponding correct direction. Additionally, the captain did not address the recent cable change noted on his maintenance release and did not perform a first flight of the day checklist, which included an elevator trim check.