FLIGHT INTO KNOWN ADVERSE WEATHER CONDITIONS BY THE PILOT, WHICH RESULTED IN ICE ACCUMULATION ON THE AIRCRAFT AND SUBSEQUENT LOSS OF AIRCRAFT CONTROL (TAIL PLANE STALL) AS THE FLAPS WERE FULLY EXTENDED. FACTORS RELATED TO THE ACCIDENT WERE: THE PILOT'S INADEQUATE USE OF THE PREFLIGHT BRIEFING SERVICE, INADEQUATE TRAINING PROVIDED TO THE PILOTS BY COMPANY/MANAGEMENT PERSONNEL, INADEQUATE SURVEILLANCE BY THE FAA, AND ICING CONDITIONS.