Incident Description
During cruise flight at Flight Level 230, the airplane abruptly pitched upward, causing the autopilot to disengage. The pilot was unable to control the airplane using the control yoke. By adjusting engine power and trim, the pilot eventually regained control and performed an emergency landing at Sacramento without further incident.
Investigation Findings
Post-incident examination revealed that the threaded portion of the rod end bearing, part number 49261-02, had separated at the point where the threads are inserted into the aft end of the elevator control tube assembly, part number 40847-07. The elevator control tube connects to the elevator pitch horn. Metallurgical analysis determined that the separation resulted from a fatigue failure.
Maintenance Background
The aircraft had undergone inspections at 37 hours and 134 hours before the incident, conducted in accordance with an approved aircraft inspection program. However, neither inspection specifically required an examination of the elevator control tube assembly.