Incident Overview
During cruise flight, the flight crew encountered a flight control difficulty related to the aircraft's inability to be trimmed for level flight. The pilot initially reported that 80 to 100 pounds of control wheel force were required to maintain wings level. Later, the pilot estimated the required force as 50 to 70 pounds. The crew subsequently performed a precautionary landing, during which the airplane remained undamaged.
Investigation Findings
Examination following the incident revealed that the trim switch was intermittent. Further inspection confirmed contamination of the switch, which contained "salt, dust, hairs and other organic materials." Additionally, corrosion was found on the switch contacts. These factors were associated with the malfunctioning trim system that necessitated the precautionary landing.