THE PILOT'S FAILURE TO ACTIVATE THE PITOT HEAT BEFORE ASCENDING ABOVE THE FREEZING LEVEL IN INSTRUMENT METEOROLOGICAL CONDITIONS (IMC), FOLLOWED BY HIS IMPROPER RESPONSE TO ERRONEOUS AIRSPEED INDICATIONS THAT RESULTED FROM BLOCKAGE OF THE PITOT TUBE BY ATMOSPHERIC ICING. CONTRIBUTING TO THE ACCIDENT WAS: THE PILOT'S LACK OF CURRENCY IN FLYING IN IMC.