THE CAPTAIN'S FAILURE TO MAINTAIN PROFESSIONAL COCKPIT DISCIPLINE, HIS CONSEQUENT INATTENTION TO FLIGHT INSTRUMENTS AND ICE ACCRETION, AND HIS SELECTION OF AN IMPROPER AUTOFLIGHT VERTICAL MODE, ALL OF WHICH LED TO AN AERODYNAMIC STALL, LOSS OF CONTROL, AND A FORCED LANDING. FACTORS CONTIBUTING TO THE ACCIDENT WERE: POOR CREW DISCIPLINE, INCLUDING FLIGHTCREW COORDINATION BEFORE THE STALL AND THE FLIGHTCREW'S INAPPROPRIATE ACTIONS TO RECOVER FROM THE LOSS OF CONTROL. ALSO CONTRIBUTING TO THE ACCIDENT WAS FATIGUE INDUCED BY THE FLIGHTCREW'S FAILURE TO PROPERLY MANAGE PROVIDED REST PERIODS.