On February 15, 2000, at 1530 central standard time, a Piper PA-23-250, N106RS, piloted by a commercial pilot, sustained substantial damage during a precautionary landing on runway 18 (4,001 feet by 75 feet snow/ice covered asphalt) at the Amery Municipal Airport (AHH), Amery, Wisconsin. The 14 CFR Part 135 domestic passenger flight was operating on an instrument flight rules flight plan. Instrument meteorological conditions prevailed at the time of the accident. There were no reported injuries to the pilot or the two passengers. The flight originated from the Roseau Municipal Airport, Roseau, Minnesota, at 1323, and was en route to the Watertown Municipal Airport, Watertown, Wisconsin. In a written statement, the pilot stated that he had received a full weather briefing the previous night and had received updated weather on the day of the flight. The pilot said that he checked weather on the weather computer at the departure airport and then called Flight Service about 30 minutes prior to the flight and received another weather update from a weather briefer. The pilot said that, after speaking with the weather briefer, he updated his flight plan to change his route of flight to avoid an area of heavy precipitation. The pilot said that the aircraft began to accumulate ice in cruise flight at 6,000 feet msl. The pilot said that he heard another aircraft request a descent from 6,000 feet msl to 4,000 feet msl due to icing. The pilot said that the other aircraft then requested a climb back to 6,000 feet msl because icing conditions at 4,000 feet msl were worse than at 6,000 feet msl. The pilot stated that he then asked air traffic control (ATC) if they had any reports from aircraft at higher altitudes along his route of flight. The pilot said that ATC told him that an aircraft had reported moderate mixed icing at 10,000 feet msl. The pilot said that he elected to stay at 6,000 feet msl because the "...accumulation at that time was not a threat...." The pilot said that the rate of accumulation of ice began to increase and that he contacted ATC and requested and received clearance to climb. The pilot said that he began to climb but was unable to climb higher than about 8,000 feet msl and that the ice accumulation rate was such that the heated windscreen would not keep the windscreen clear. The pilot stated that he then contacted ATC and requested immediate vectors to the nearest airport, which ATC provided. The pilot executed a precautionary landing at AHH. The pilot said that the runway at AHH was snow covered and that the windscreen was still iced over. A police report states that the runway was covered with 2-3 inches of snow and that beneath the snow cover, the asphalt was covered with a layer of ice. The report also states that the aircraft slid into a snowbank. A postaccident examination of the aircraft, by a Federal Aviation Administration Inspector, failed to reveal any anomalies that could be associated with a preexisting condition. No mechanical malfunction was reported by the pilot in his written report. The aircraft was found to be equipped and certified for flight into known icing conditions.