FAILURE OF THE PILOT TO MAINTAIN CONTROL OF THE AIRCRAFT, HIS FAILURE TO PREVENT THE AIRCRAFT FROM EXCEEDING THE NEVER EXCEED SPEED (VNE), AND SUBSEQUENT EXCEEDING OF THE DESIGN STRESS LIMITS OF THE AIRCRAFT. FACTORS RELATED TO THE ACCIDENT WERE: WEATHER CONDITIONS (INCLUDING ICING CONDITIONS), IMPROPER AIRSPEED, AND LOSS OF ENGINE POWER FOR UNDETERMINED REASON(S).