What was found
AIRCRAFT WAS GROUNDED: IN FLT LEVEL 15000 WE FELT AND SAW AN ABRUPT YAW 2 TIMES. FIRST 6HR IN SMOOTH AIR THE AICRAFT ABRUPTLY YAWED LEFT.WE NOTICED L1.1 RUDDER TRIM AS WELL AS UNCOORDINATED FLIGHT AND BANK. APPROX 3MIN ELAPSED BEFORE RUDDER TRIM GRADUALLY RETURNED TO R0.3. THE SECOND WAS 1.5 HRS IN CONT LGT CHOP 15000.AIRCRAFT ABRUPTLY YAWED RIGHT. WE NOTICED 1.5 UNITS OF RUDDER TRIM AS WELL AS UNCOORDINATED FLIGHT AND BANK. APPROX 3MIN ELAPSED BEFORE RUDDER TRIM GRADUALLY RETURNED TO R0.2. MAINTENANCE REPLACED #1 FLIGHT AUGMENTATION COMPUTER AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK.