Incident Description
During cruise flight, the flight crew observed a rudder ratio warning light illumination. Shortly thereafter, the aircraft experienced uncommanded right rudder movement accompanied by left aileron input. The airplane remained under control, and the crew manually counteracted the rudder movement. The captain decided to abort the flight and performed a safe landing at the departure airport.
Subsequent Warnings
On two subsequent flights, the rudder ratio warning was again displayed, despite repeated maintenance attempts to resolve the discrepancy. Over a span of approximately two months, a total of four warnings occurred.
Examination and Resolution
After the fourth warning, an examination of the left yaw damper module was conducted. The inspection revealed a malfunction in the left hydraulic pressure switch within that module. The unit was removed and replaced. Following this replacement, no further incidents involving a rudder ratio warning were reported.