Accident Description
A pilot reported that during a climb after takeoff, he engaged the autopilot. While making an entry on a trip sheet, he felt a bump and noticed the aircraft had started to descend. Disengaging the autopilot resulted in a violent pitch-down. Reducing power had an adverse effect, so he increased power again. He finally leveled the aircraft just prior to impacting in a field at cruise power. All eight occupants escaped with minor injuries.
Findings
Examination of the aircraft revealed that the elevator trim tab cables were crossed between the tab actuator and the pulley in the tail cone. The trim tab was found fully trimmed nose-down. The aircraft had just received an annual inspection during which the elevator trim actuator had been removed, inspected, and lubricated. This was the first flight since the inspection.
Probable Cause
The official probable cause attributes the loss of control to incorrect elevator trim/tab control due to improper installation by company maintenance personnel, combined with uncontrolled aircraft handling by the pilot.