What happened
Approximately 20 minutes into the flight, while operating at cruise power and an altitude of roughly 7,000 feet, the aircraft began to lose manifold pressure and the engine started to sputter. The pilot reported a simultaneous loss of power, airspeed, and altitude. Although the pilot applied full carburetor heat, the loss of engine power continued. Unable to locate a clearing, the pilot executed a forced landing into trees and terrain, resulting in substantial damage to the aircraft.
Prior to the event, the pilot had obtained a weather update indicating light snow and forecast icing conditions below 10,000 feet; however, the pilot determined that these potential conditions did not preclude safe flight. At the time of the accident, weather at the nearest airport included light snow, freezing fog, a temperature of -1 degree Celsius, and a dew point of -3 degrees Celsius.
The investigation
Mechanical examination of the engine revealed that the right magneto failed to produce a spark. Upon disassembly, investigators found that the contact point would open and close when the magneto was rotated. Additionally, the spark plugs were found to be black and sooty. The air filter element was wet enough that water could be wrung from it, and water was also present within the filter housing. The carburetor heat control was found in the off position.