Narrative:

After flying into icing conditions, I requested a return to origin airport. I was given vectors and then cleared to descend to 2500 ft, until established on the ILS approach. I had picked up quite a bit of ice and was distraction during my initial descent by ice breaking off the airplane. During my distraction and looked out the window, as I started to enter VFR WX conditions, the controller asked my altitude and I noticed that I had inadvertently descended to 2100 ft. At that time I notified the controller that I was at 2100 ft and was canceling IFR. I also apologized for the deviation, explaining that I had become distraction by the ice build-up. To prevent a recurrence, altitude awareness should be maintained at all times, regardless of outside factors.

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Original NASA ASRS Text

Title: PLT OF A C210 OVERSHOT ALT DURING DSCNT DUE TO DISTR OF ICE BREAKING OFF THE ACFT AND ALSO BREAKING OUT IN VFR CONDITIONS. WHEN APCH CTLR INTERVENED ABOUT HIS ALT, RPTR CANCELED HIS IFR FLT PLAN.

Narrative: AFTER FLYING INTO ICING CONDITIONS, I REQUESTED A RETURN TO ORIGIN ARPT. I WAS GIVEN VECTORS AND THEN CLRED TO DSND TO 2500 FT, UNTIL ESTABLISHED ON THE ILS APCH. I HAD PICKED UP QUITE A BIT OF ICE AND WAS DISTR DURING MY INITIAL DSCNT BY ICE BREAKING OFF THE AIRPLANE. DURING MY DISTR AND LOOKED OUT THE WINDOW, AS I STARTED TO ENTER VFR WX CONDITIONS, THE CTLR ASKED MY ALT AND I NOTICED THAT I HAD INADVERTENTLY DSNDED TO 2100 FT. AT THAT TIME I NOTIFIED THE CTLR THAT I WAS AT 2100 FT AND WAS CANCELING IFR. I ALSO APOLOGIZED FOR THE DEV, EXPLAINING THAT I HAD BECOME DISTR BY THE ICE BUILD-UP. TO PREVENT A RECURRENCE, ALT AWARENESS SHOULD BE MAINTAINED AT ALL TIMES, REGARDLESS OF OUTSIDE FACTORS.

Data retrieved from NASA's ASRS site as of July 2007 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.