What happened
During the cruise phase of flight, the flight crew experienced a flight control difficulty that prevented them from trimming the aircraft for level flight. The pilot initially reported that maintaining wings level required between 80 and 100 pounds of control wheel force. This requirement later decreased to an estimated 50 to 70 pounds. Due to these difficulties, the crew performed a precautionary landing. The aircraft remained undamaged following the landing.
The investigation
An examination of the aircraft's systems revealed that the trim switch was functioning intermittently. Investigators found that the switch had been contaminated with salt, dust, hair, and other organic materials. Additionally, the investigation confirmed the presence of corrosion on the switch contacts.