A300 CREW REPORTS AUTOPILOT ROLL OSCILLATIONS DURING INSTRUMENT APPROACH IN ICING CONDITIONS.

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AT CRUISE FROM ZZZY THE SAT INDICATED -60 DEGS C. THE WX AT DEST WAS WINDS 320 DEGS AT 15 KTS WITH LIGHT SNOW. WE ARRIVED ZZZX AT APPROX A GROSS WT 275000 LBS AND 26.6 ON FUEL WITH THE OUTBOARD FUEL TANKS NEAR FULL. DURING THE DSCNT TO ZZZX AT APPROX 10000 FT AND ABOUT 30 MI W WE ENTERED INTO THE FIRST CLOUD LAYER AND ICING CONDITIONS WITH A TAT -12 DEGS C. I TURNED ON THE ENG AND WING ANTI-ICE BEFORE ENTERING ICING CONDITIONS. ON THE DOWNWIND LEG ATC ASSIGNED 210 KIAS AND 6000 FT. AT 6000 FT I REMAINED IN A CLEAN CONFIGN IN LIGHT RAIN AT -10 DEGS TAT. ON AN EXTENDED DOWNWIND OF 18 MI; ATC ASSIGNED 180 KIAS AND 4000 FT AT WHICH TIME I CONFIGURED TO FLAPS 15 DEGS. AT 4000 FT WE BEGAN ENCOUNTERING LIGHT TO MODERATE SNOW AT ABOUT -8 DEGS TAT. ATC VECTORED AND CLRED US FOR THE RWY 35L ILS. AT GS INTERCEPT WE EXTENDED THE GEAR AND SELECTED FLAPS 20 DEGS AND REDUCE SPD TO 170 KIAS. AT 2000 FT AGL WE SELECTED FLAPS 40 DEGS AND SLOWED TO VAPP. WITH A VREF 128 PLUS 5 KTS FOR WING ANTI-ICE AND 5 KTS FOR WIND EQUALS VAPP OF 138 KTS. WHEN SETTING THE VAPP SPD IN THE MCP I NOTED THAT THIS SPD WOULD ONLY BE 3 KTS ABOVE VLS. SO; I SET 140 KTS IN THE MCP FOR THE APCH. AT THIS POINT WE HAD NO VISUAL CLUES FROM THE COCKPIT OF AIRFRAME ICING. BUT; AS YOU KNOW IT IS HARD TO DETECT AIRFRAME ICING VISUAL IN THE A300. AT ABOUT 1500 FT AGL AND -8 TAT THE AUTOPLT BEGAN CTL WHEEL ROLL OSCILLATIONS AND CONTINUE TO INCREASE IN INTENSITY UNTIL I DISCONNECTED THE AUTOPLT. ONCE THE AUTOPLT WAS DISCONNECTED THE ROLL OSCILLATION CEASED. THE ACFT SEEMED TO HANDLE OK; BUT ROLL CTL SEEMED A LOT MORE SENSITIVE THAN NORMAL. ON LNDG WE LEFT THE FLAPS DOWN AND INFORMED MAINT OF THE LOGBOOK ENTRY. AT MY REQUEST MAINT ACCOMPANIED ME FOR A POSTFLT INSPECTION. THE TRAILING EDGE FLAPS AND LEADING EDGE SLATS HAD NO SIGNS OF ICE ACCUMULATION. THERE WAS A TRACE OF ICE ON BOTH THE NOTCH AND KRUGER FLAPS. HOWEVER; THERE WAS HVY FROST ON THE BOTTOM OF THE OUTBOARD WINGS AND THE MECH NOTED THAT THE TOP OF THE OUTBOARD WINGS HAD A THIN LAYER OF ICE AND HVY FROST. IN CONCLUSION I HAVE NOTICED THAT ON THE A300 WITH A COLD SOAK WING FROM CRUISE; THAT WHEN DSNDING ON ARR INTO ICING CONDITIONS THAT HAVING FULL FUEL IN THE OUTBOARD WING TANKS SIGNIFICANTLY ACCELERATES THE FORMATION OF ICE ON THE UPPER OUTBOARD WINGS. IT APPEARS THAT A POSSIBLE PROC CHANGE; THAT WHEN LNDG WITH A TOTAL FUEL GREATER THAN 16000 LBS (OUTBOARDS FULL) AND ANTICIPATING AN ARR IN ICING CONDITIONS THAT BURNING A FEW 1000 LBS FROM EACH OUTBOARD WING AT CRUISE BEFORE DSCNT INTO ICING CONDITIONS COULD SIGNIFICANTLY REDUCE THE FORMATION OF ICE ON THE OUTBOARD WINGS; PROVIDED THAT THIS WOULD NOT REPRESENT A STRUCTURAL PROB. I HAVE HAD THE PRIVILEGE OF FLYING MANY DIFFERENT TYPE ACFT IN MY CAREER AND THE A300 IS THE FIRST I HAVE EXPERIENCED THIS TYPE OF ICING ACCUMULATION PHENOMENON. THIS JUST LEAVES ONE TO WONDER IF THIS TYPE OF ICE ACCUMULATION WAS CONSIDERED DURING ACFT CERTIFICATION AND AT WHAT POINT DOES THIS ICE ACCUMULATION PHENOMENON REPRESENT A SIGNIFICANT SAFETY CONCERN.