What happened
During a flight toward the intended destination, the pilot activated the cabin heater, which led to a noticeable rise in ambient temperature and an unusual odor within the cabin. Upon turning the heater off, dark smoke began to fill the cabin, significantly reducing visibility for the occupants. During the attempt to perform an emergency landing in a field, the wing of the aircraft struck the ground, causing the plane to cartwheel.
Findings
Post-accident inspections of the heater unit revealed several leaks near the weld points of the combustion chamber. Maintenance records indicated that the heater had been flagged as inoperative during the most recent annual inspection. While a work order suggested repairs had been performed, there was no official logbook entry confirming the heater had been returned to service, nor were there records of recent testing or operational hours.
Evidence suggested the pilot may have been unaware of the heater's specific mechanical risks. A previous flight instructor noted that the pilot had used the heater on a prior occasion when an overheat warning light had activated. Although the instructor demonstrated how to reset the overheat circuit breaker, the pilot's decision to use the heater during the accident flight suggests a failure to follow the aircraft flight manual, which mandates a thorough inspection of the unit following an overheat event. Furthermore, there were no documented inspections of the aircraft by a mechanic prior to the flight, and no regulatory requirement existed to disable the heater or perform periodic inspections of this specific unit.