What happened
The incident occurred during an agricultural operation specifically identified as an aerial seeding flight. While performing this duty, the engine of the agricultural airplane experienced a sudden loss of power. Unable to maintain altitude or continue the mission, the pilot initiated a forced landing procedure.
The aircraft touched down in a rice field located near the operational area. Upon impact with the ground, the main landing gear assembly failed structurally and broke off from the airframe. The momentum of the aircraft caused it to flip forward, coming to rest in an inverted position on its roof. This sequence of events resulted in substantial physical damage to the lower fuselage and propulsion system.
The investigation
Post-accident examination of the wreckage revealed specific mechanical failures within the engine assembly. Investigators found that the bearing associated with the number 3 cylinder exhaust rocker-arm had frozen solid. This seizure locked the rocker-arm in place, preventing normal valve operation.
The excessive force generated by the locked component caused the rocker-box cover to rupture and break open. This internal engine failure is consistent with the reported loss of power during the flight phase.