Incident Overview
During a flight about 40 minutes after departure, a pilot and passenger heard the pneumatic door seal give way. The pilot recycled the switch but noted no change. A few minutes later, a faint smell of electrical burn was detected. The pilot turned off the heater, and the smell subsided. Upon reactivating the heater, the smell returned immediately, stronger than before. Black smoke then began entering the cabin from above and beneath the instrument panel. The pilot observed orange sparks and flames under the panel.
Emergency Descent and Landing
The pilot initiated a steep descent and searched for a landing site. Spotting a north-south oriented dirt road, the pilot executed a 180-degree turn to land. However, the aircraft overshot the road, and the pilot determined insufficient altitude and airspeed to maneuver back. The pilot leveled the airplane and landed in a field. During the landing roll, the aircraft encountered uneven rising terrain and trees.
Post-Incident Examination
An examination of the aircraft revealed that the door seal inflation pump was heavily charred. Inspection of the cabin showed the door inflation seal around the cabin door was missing. Both forward air vents were found in the open position. Plastic insulation surrounding electrical wiring in front of the right air vent was melted. Melted plastic was observed on the floor beneath the right side air vent. No other anomalies were identified.