On September 16, 1995, an Air Tractor AT-301 (registration N2362D) operated by Gosa's Aerial AG was involved in an aviation accident near Plains, GA. Investigators recorded the probable cause as: Fracture of the number four cylinder rocker arm housing due to overload, resulting in rocker arm pin failure, loss of exhaust valve continuity, and engine power loss. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During an aerial application flight, engine power loss occurred, resulting in a forced landing and nose-over that damaged the aircraft. Examination revealed a fractured rocker arm housing on cylinder number four.
Accident Overview
An agricultural aircraft experienced an engine power loss during the first spray run of an aerial application flight. The subsequent forced landing resulted in the aircraft nosing over and sustaining damage.
Engine Examination Findings
Post-accident examination of the engine identified a fracture of the number four cylinder rocker arm housing. The fracture surface exhibited a rough, granular, and irregular appearance, characteristic of an overload failure. Further investigation revealed that when the rocker arm housing separated from the cylinder, the rocker arm pin failed. This allowed the rocker arm to separate from the cylinder, leading to a loss of continuity to the exhaust valve. The exhaust valve subsequently remained closed, causing the engine to lose power.
Conclusion
The accident was caused by the failure of the number four cylinder rocker arm housing and associated components, leading to engine power loss and the forced landing.
Probable cause
Fracture of the number four cylinder rocker arm housing due to overload, resulting in rocker arm pin failure, loss of exhaust valve continuity, and engine power loss.