The Y-5 was on an agricultural application operation in Nengbei Farm, Heilongjiang Province, China. After takeoff on the 22nd sortie, the temperature of the oil rose sharply and the engine power dropped, making it impossible to maintain normal flight. After landing back the airstrip, the aircraft caught fire and the crew evacuated immediately. The captain was slightly injured and the co-pilot was slightly injured, and the aircraft partially burned out. Investigation Conclusion: The investigation determined that the main reason for the incident was: the aircraft engine piston ring broke off, damaging the internal structure of the engine, generating a large number of metal chips, blocking the engine oil supply line, resulting in insufficient oil supply, engine wear intensified, the temperature of the oil rose sharply. At the same time, the cylinder seal deteriorated as a result of the broken ring, causing the engine power to drop and unable to maintain normal flight. The captain, in handling the emergency, did not immediately execute the emergency landing as required by paragraph 8.1.3 of the Emergency Quick Checklist, and incorrectly decided to return to the field for landing. The engine was severely damaged and then caught fire.