Narrative:

We flew downwind at 8000 ft -8 degrees C for about 10 min then descended to 4000 ft still in the clouds but had some ground contact. Intercepted the localizer and glideslope at 4000 ft and started down; both autoplts were on. The aircraft started making very abrupt left and right aileron control inputs to the point I suspected something was wrong as it was also having trouble maintaining reference plus 5. I told my first officer I was adding speed to maintain reference plus 10 at least and took the autoplt off. The plane settled down a bit and I continued the approach. We had good ground contact and I had the runway 22R/left in sight but I was landing on runway 21L. The winds were 270/15 but we were getting bounced around pretty good. I know I had the runway in sight and thought about turning on the wing anti-ice but I did not want to take the chance of shedding just one wing of ice at 1000 ft; the engine anti-ice was on the whole time. Hand flying the aircraft was very roll sensitive but I learned to make small corrections and we made a normal landing. I had the flaps at 40 so maintenance could inspect them. I was told the top of the wing was covered with 1/4 inch of rime ice with clear on top. The right wing was worse than the left. From the crew door I could see the ice outside the slat leading edge by the navigation light. It started at the light and rolled back to the top of the wing. The PNF was a new hire in his first week of IOE. He performed all his duties and calls.

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Original NASA ASRS Text

Title: AN A300 WITH SLATS EXTENDED ON APCH; OAT -8 DEGS C IN IMC WITH ONLY ENG ANTI-ICE ON; BEGAN UNCOMMANDED ROLLING. RPTR SUSPECTS AIRFRAME ICING IS THE CAUSE.

Narrative: WE FLEW DOWNWIND AT 8000 FT -8 DEGS C FOR ABOUT 10 MIN THEN DSNDED TO 4000 FT STILL IN THE CLOUDS BUT HAD SOME GND CONTACT. INTERCEPTED THE LOC AND GLIDESLOPE AT 4000 FT AND STARTED DOWN; BOTH AUTOPLTS WERE ON. THE ACFT STARTED MAKING VERY ABRUPT L AND R AILERON CTL INPUTS TO THE POINT I SUSPECTED SOMETHING WAS WRONG AS IT WAS ALSO HAVING TROUBLE MAINTAINING REF PLUS 5. I TOLD MY FO I WAS ADDING SPD TO MAINTAIN REF PLUS 10 AT LEAST AND TOOK THE AUTOPLT OFF. THE PLANE SETTLED DOWN A BIT AND I CONTINUED THE APCH. WE HAD GOOD GND CONTACT AND I HAD THE RWY 22R/L IN SIGHT BUT I WAS LNDG ON RWY 21L. THE WINDS WERE 270/15 BUT WE WERE GETTING BOUNCED AROUND PRETTY GOOD. I KNOW I HAD THE RWY IN SIGHT AND THOUGHT ABOUT TURNING ON THE WING ANTI-ICE BUT I DID NOT WANT TO TAKE THE CHANCE OF SHEDDING JUST ONE WING OF ICE AT 1000 FT; THE ENG ANTI-ICE WAS ON THE WHOLE TIME. HAND FLYING THE ACFT WAS VERY ROLL SENSITIVE BUT I LEARNED TO MAKE SMALL CORRECTIONS AND WE MADE A NORMAL LNDG. I HAD THE FLAPS AT 40 SO MAINT COULD INSPECT THEM. I WAS TOLD THE TOP OF THE WING WAS COVERED WITH 1/4 INCH OF RIME ICE WITH CLEAR ON TOP. THE RIGHT WING WAS WORSE THAN THE LEFT. FROM THE CREW DOOR I COULD SEE THE ICE OUTSIDE THE SLAT LEADING EDGE BY THE NAV LIGHT. IT STARTED AT THE LIGHT AND ROLLED BACK TO THE TOP OF THE WING. THE PNF WAS A NEW HIRE IN HIS FIRST WEEK OF IOE. HE PERFORMED ALL HIS DUTIES AND CALLS.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.