NTSB Probable Cause

THE PILOT'S FAILURE TO USE THE AIRPLANE'S ICE PROTECTION EQUIPMENT, WHICH RESULTED IN A PERFORMANCE LOSS DUE TO INDUCTION ICING, PROPELLER ICING, OR BOTH, WHILE FLYING IN CONVECTIVE INSTRUMENT METEOROLOGICAL CONDITIONS (IMC) AT AND ABOVE THE FREEZING LEVEL. THE PERFORMANCE LOSS LED TO A STALL, THE RECOVERY FROM WHICH PROBABLY WAS EXACERBATED BY THE PILOT'S IMPROPER RESPONSE TO ERRONEOUS AIRSPEED INDICATIONS THAT RESULTED FROM BLOCKAGE OF THE PITOT TUBE BY ATMOSPHERIC ICING.