Narrative:

I am filing this report since I deviated from assigned altitude due to icing (severe). I was flying at 4000 ft just above the clouds when I entered a cloud and before I could get the propeller heat to work we accumulated a great deal of ice which caused me to descend. Once I came out of the clouds the aircraft was under control. I went ahead and landed to check out the aircraft and everything was ok. Flight watch was only calling for light to moderate ice. There was another aircraft in area that verified ice conditions.

Google
 

Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION OCCURS WITH SMT DURING AN INFLT ENCOUNTER WITH SEVERE ICING CONDITIONS.

Narrative: I AM FILING THIS RPT SINCE I DEVIATED FROM ASSIGNED ALT DUE TO ICING (SEVERE). I WAS FLYING AT 4000 FT JUST ABOVE THE CLOUDS WHEN I ENTERED A CLOUD AND BEFORE I COULD GET THE PROP HEAT TO WORK WE ACCUMULATED A GREAT DEAL OF ICE WHICH CAUSED ME TO DSND. ONCE I CAME OUT OF THE CLOUDS THE ACFT WAS UNDER CTL. I WENT AHEAD AND LANDED TO CHK OUT THE ACFT AND EVERYTHING WAS OK. FLT WATCH WAS ONLY CALLING FOR LIGHT TO MODERATE ICE. THERE WAS ANOTHER ACFT IN AREA THAT VERIFIED ICE CONDITIONS.

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.