CEN24LA092

The total loss of engine power due to carburetor icing and the pilot’s failure to utilize carburetor heat in meteorological conditions conducive to the formation of carburetor icing.

The pilot reported that prior to descending during the cross-country flight, he activated the carburetor heat. As the pilot initiated the descent, the engine began “coughing” and was “progressively failing,” until a total loss of engine power occurred. The pilot switched fuel tanks, he adjusted the mixture, and he activated the carburetor heat to no avail. During the forced landing to a remote grass field covered with snow, the airplane came to rest inverted, and the pilot was able to egress from the airplane without further incident. The pilot reported to first responders that the carburetor had “iced up.” The airplane sustained substantial damage to the fuselage and both wings. When the temperature and the dewpoint near the time of the accident were plotted on a carburetor icing probability graph, it was revealed that the airplane was likely operating in meteorological conditions conducive to the formation of carburetor icing (for both glide and cruise power settings). The pilot reported there were no preimpact mechanical malfunctions or failures with the airframe or the engine that would have precluded normal operation. The Piper Aircraft PA-22-150 Tri-Pacer Owner’s Handbook discusses the use of carburetor heat during cruise operations and states, “unless icing conditions in the carburetor are severe, do not cruise with the carburetor heat on” and “apply full carburetor heat only for a few seconds at intervals determined by icing severity.”