Narrative:

While being vectored on an IFR flight from big bear city airport to long beach airport, I picked up an alarming amount of ice in a short period of time at 9000' MSL in IMC. The reported ice was higher and I felt I was safe. I asked the approach controller I was talking to for lower due to ice. I was told that I would be given lower in about 6 mi. I was given a descent to 8000' MSL. The window ice started to clear but the wings, struts and propeller were still iced. I was asked by approach what the status of the ice was. I told her that the ice seemed to be clearing...but that the wings and strut were still covered. I was then cleared to 7000' MSL. I descended to 7000' while still in IMC and moderate turbulence I looked outside at the now melting ice. I looked back at the instruments to discover that I was in a downdraft and was losing altitude. I stopped the descent at about 6700' MSL and was in the process of climbing back to 7000' when the controller reminded me that the assigned altitude was 7000' and gave me the current altimeter setting in the area. I had blown my assigned altitude due to my preoccupation and failure to react more rapidly. Flying IMC in mountain areas requires all of your attention even though one may have distrs.

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Original NASA ASRS Text

Title: SMA CRUISING IN IMC ICES UP, REQUESTS LOWER ALT, AND OVERSHOOTS NEW ALT IN DESCENT.

Narrative: WHILE BEING VECTORED ON AN IFR FLT FROM BIG BEAR CITY ARPT TO LONG BEACH ARPT, I PICKED UP AN ALARMING AMOUNT OF ICE IN A SHORT PERIOD OF TIME AT 9000' MSL IN IMC. THE RPTED ICE WAS HIGHER AND I FELT I WAS SAFE. I ASKED THE APCH CTLR I WAS TALKING TO FOR LOWER DUE TO ICE. I WAS TOLD THAT I WOULD BE GIVEN LOWER IN ABOUT 6 MI. I WAS GIVEN A DSNT TO 8000' MSL. THE WINDOW ICE STARTED TO CLR BUT THE WINGS, STRUTS AND PROP WERE STILL ICED. I WAS ASKED BY APCH WHAT THE STATUS OF THE ICE WAS. I TOLD HER THAT THE ICE SEEMED TO BE CLRING...BUT THAT THE WINGS AND STRUT WERE STILL COVERED. I WAS THEN CLRED TO 7000' MSL. I DSNDED TO 7000' WHILE STILL IN IMC AND MODERATE TURB I LOOKED OUTSIDE AT THE NOW MELTING ICE. I LOOKED BACK AT THE INSTRUMENTS TO DISCOVER THAT I WAS IN A DOWNDRAFT AND WAS LOSING ALT. I STOPPED THE DSNT AT ABOUT 6700' MSL AND WAS IN THE PROCESS OF CLBING BACK TO 7000' WHEN THE CTLR REMINDED ME THAT THE ASSIGNED ALT WAS 7000' AND GAVE ME THE CURRENT ALTIMETER SETTING IN THE AREA. I HAD BLOWN MY ASSIGNED ALT DUE TO MY PREOCCUPATION AND FAILURE TO REACT MORE RAPIDLY. FLYING IMC IN MOUNTAIN AREAS REQUIRES ALL OF YOUR ATTN EVEN THOUGH ONE MAY HAVE DISTRS.

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.