20000215018699A

(-23) Pilot experienced severe icing conditions, changed altitude but still experienced icing at various altitudes. Even though the aircraft was certified for known icing, it started to collect ice on the leading edge, the aircraft was not able to maintain a positive altitude. When the aircraft began to descend, pilot declared an emergency. Amery was nearest airport. Pilot said he had a hard time seeing the runway. The aircraft landed downwind on runway 18 and slid across runway. Aircraft came to rest several feet off runway in a snow bank. All three landing gear were sheared off. Bending in tips of both propellers indicates engines were in motion at time of impact. There were no injuries to pilot or passengers. (.4)the airplane sustained substantial damage during a precautionary landing after experiencing ice accumulation in cruise flight. The pilot received a full weather briefing the previous night and updated weather on the day of the flight. The pilot updated his flight plan to change his route of flight to avoid an area of heavy precipitation. The aircraft began to accumulate ice in cruise flight. Other aircraft along the route of flight reported I cing at altitudes above and below the accident aircraft's altitude. The rate of accumulation of ice began to increase and the pilot contacted air traffic control and requested and received clearance to climb. The airplane was unable to climb higher than about 8,000 feet MSL. The ice accumulation rate was such that the heated windscreen would not keep the windscreen clear. The pilot contacted ATC and requested immediate vectors to the nearest airport, where he executed a precautionary landing. The runway was snow covered with a coating of ice beneath the snow, and the windscreen was still iced over. The aircraft slid off the runway and struck a snowbank. Postaccident examination of the aircraft failed to reveal any anomalies. The aircraft was equipped and certified for flight into known icing conditions.