Engine Cylinder Head Separation Forces Emergency Landing in Corn Field (N9828)

Accident Narrative

Approximately 15 minutes after departure, the pilot noticed a loss of airspeed while the aircraft was flying between 300 and 500 feet above ground level en route to the assigned spray field. Despite applying full throttle, the airspeed continued to decrease. The pilot then observed oil on the right side of the engine cowling. To avoid an interstate highway, the pilot banked left. Just prior to landing, the pilot reported that the airplane 'quit flying.' The aircraft came to rest upright in a corn field. A post-impact fire consumed approximately half of the aircraft.

Investigation Findings

A post-accident inspection revealed that the number 3 engine cylinder head had separated into two sections. Examination of the fracture faces showed features consistent with a fatigue failure. The failure initiated at the root of the cylinder head thread engaged with the uppermost barrel thread. Engine maintenance records indicated that the engine had accumulated approximately 7,495 hours total time, with about 615 hours since overhaul.