What happened
During cruise flight, the pilot experienced a sudden loss of engine power. As the aircraft descended in response to the emergency, the engine ceased producing power entirely. The pilot executed a forced landing on tundra terrain. Upon inspection, the airplane was found to be substantially damaged.
The investigation
A detailed teardown of the engine was conducted to determine the root cause of the failure. Examination revealed that the number 4 piston had its compression ring burned past. This condition pressurized the crankcase, which subsequently forced the oil out of the system. The loss of lubrication and internal pressure led to the engine seizing.
Findings
The mechanical failure was traced directly to the compromised state of the piston rings. The burned past compression ring on cylinder number 4 allowed combustion gases to bypass, creating excessive pressure within the crankcase. This pressure differential expelled the engine oil, resulting in a complete loss of lubrication and subsequent seizure of the engine components.
Safety message
Regular inspection of piston rings and monitoring of engine performance parameters can help identify early signs of ring failure or excessive blow-by, potentially preventing sudden power loss.