What was found
DECLARED EMER FOLLOWED NEW POLICY IN FOM. PROGRESSIVELY GOT WORSE INTO DUTCH ROLL. OSCILLATING BOTH DIRECTIONS, FOLLOWED QRH DISCONNECT YD. HARD PUSH ON RT RUDDER, NEEDED TO COUNTER WITH LT INPUT PRIMARILY, ONCE IT LEVELED DRIFTED TO LT FROM HAVING INPUT TO CORRECT THE PUSH ON RT. LANDED SAFELY & CONTACTED MOC. VERIFIED NR 1 YAW DAMPER ACTUATOR FAILS DURING OPERATIONAL CHECK INITIALLY, HARD FAIL WOULD NOT RESET. R & R NR 1 & 2 IAW MX CONTROL, YAW NR 1 DAMPER ACTUATOR WITH SERVICEABLE ACTUATOR IAW AMM 22-22-01 & SYS OPERATIONAL TEST GOOD IAW AMM 22-22-01.