PIC OF B777 RPTS CONSISTENT LOCALIZER VARIATIONS AT ORD ON THREE SEPARATE OCCASIONS DURING ILS RWY 22R APCHES IN VISUAL CONDITIONS.

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WE WERE SHOOTING THE RWY 22R ILS APCH AND RECEIVED A VERY LARGE DEV FROM CTRLINE. THE REASON I AM WRITING THIS IS THAT THIS IS THE 3RD TIME THAT THIS HAS OCCURRED TO ME. THE SCENARIO IS ORD IS LNDG RWY 14R AND RWY 22R AND DEP RWY 22L; RWY 27L; AND RWY 14L. WE HAD NUMEROUS INTERNATIONAL FLTS ON RWY 14L. CLRED FOR THE APCH OUTSIDE FNUCH TO DSND AND MAINTAIN 5000 FT BY NOLEN AND MAINTAIN 250 KTS UNTIL ADVISED. INTERCEPTED LOC AND JUST PRIOR TO NOLEN SLOWED TO 180 KTS. WHILE SLOWING; GOT ABOUT ½ TO 1 DOT HIGH ON GS. JUST INSIDE NOLEN GET A RAPID LOC DEV TO THE L AND AUTOPLT TURNS ACFT TO THE L THEN LOC GOES TO THE R ALMOST FULL DEFLECTION AND ACFT TURNS R TO CHASE LOC. THE AUTOPLT WAS DISCONNECTED AND A VISUAL APCH WAS MAINTAINED TO GET BACK TO THE LOC. AFTER RIDGE EVERYTHING IS NORMAL AGAIN. THE FIRST TIME THIS HAPPENED; THE PF WAS NEW AND I THOUGHT HE MIGHT HAVE BEEN OVER CORRECTING. THE SECOND TIME I WAS FLYING AND AGAIN I THOUGHT THAT I MIGHT HAVE BEEN OVER CORRECTING; BUT THIS TIME I COULD SEE THE RWYS AS THE DEV OCCURRED AND IT APPEARS THE FIRST L DEV IS ERRONEOUS AND SOME TYPE OF INTERFERENCE. ON A LOW VISIBILITY OR THUNDERSTORM DAY THIS COULD PRESENT A PROB. ALL 3 EVENTS STARTED WITH A RAPID L DEV ON THE LOC. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR ADVISED THAT EACH OF THE INSTANCES OCCURRED WHEN THE ARPT CONFIGURATION WAS SUCH THAT DEPS WERE BEING MADE ON RWY 14L; ALTERNATING WITH THE ARRS ON THE INTERSECTING RWY 22R. HE STATED THE DURATION OF EACH ANOMALY WAS CONSISTENT AND THE ENTIRE EPISODE; FROM NOMINAL LOCALIZER DISPLAY; TO HARD L; TO HARD R AND BACK TO NOMINAL; OCCURRED IN APPROX 1.5 TO TWO SECONDS. HE DID STATE THAT THE COUPLED AUTOPLT DID ATTEMPT TO FOLLOW SIGNAL AND; BECAUSE OF AUTOPLT DAMPING; THE AUTOMATIC RECOVERY TO A NOMINAL CONDITION WOULD LIKELY HAVE REQUIRED A DISTANCE OF TWO OR THREE MILES. THIS WAS AN ESTIMATE IN AS MUCH AS THE FLT CREW DISCONNECTED THE AUTOPLT IN EACH INSTANCE WHEN IT BEGAN TO FOLLOW THE INITIAL LOCALIZER DEFLECTION TO THE L OF THE COURSE.