What was found
AIRCRAFT WAS GROUNDED: ON TAXI DURING 90 DEGREE TURN ENCOUNTERED ADR 1 FAULT WHICH SELF CLEARED. ON CLIMB (FL200) AND AT CRUISE (FL330) ENCOUNTERED UN-COMMANDED YAW MOVEMENT WITH ACCOMPANYING ADR1 FAULT MOMENTARILY (1/2 SECOND) BEFORE CLEARING ITSELF. AP2 WAS ENGAGED. SWITCHING TO AP1 WAS A YAW UPON THE 4TH ADR1 FAULT. ON DECENT IN LIGHT TURBULENCE ADRS "ON BAT", IR1"FAULT" , ADR "FAULT" ILLUMINATED INTERMITTENTLY ABOUT 4 OR 5 TIMES.. REPLACED #1 AIR DATA AND INERTIAL REFERENCE UNIT (ADIRU) PER AMM 34-12-34.