On December 28, 1989, a Beech A24R (registration N37329) operated by 37329 Inc. was involved in an aviation accident near Merrill, WI. Investigators recorded the probable cause as: FLIGHT INTO KNOWN ADVERSE WEATHER BY THE PILOT, AND STRUCTURAL/WING ICE. FACTORS RELATED TO THE ACCIDENT WERE: THE ICING CONDITIONS AND TREES IN THE AREA OF THE ACCIDENT. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An aircraft collided with trees and terrain after the pilot reported structural ice accumulation and inability to maintain altitude. The wreckage was found three days later.
Accident
During a flight, the aircraft collided with trees and terrain as the pilot was attempting to reach an airport. The pilot had informed air traffic control personnel that structural ice was accumulating on the aircraft and that he was unable to maintain altitude. Subsequently, the aircraft descended below an altitude where radar contact could not be maintained. Air and ground search procedures were initiated after all contact with the aircraft was lost. Three days later, the aircraft was found by ground searchers.
Investigation
Layered pieces of ice were found in the wreckage area, measuring 3/4 to 1-1/4 inches thick. These pieces of ice contained inner surfaces that matched the shape of airfoils. The weather along the route consisted of low overcast skies, below freezing temperatures, and fog. Weather in the area was influenced by a warm front, with low overcast skies, freezing temperatures, and fog to the north of the front. Before the flight, the pilot was advised of occasional moderate rime icing along his route.