On May 25, 1999, a Grumman-schweizer G-164B (registration N6524K) operated by Central Valley Aviation was involved in an aviation accident near Buxton, ND. Investigators recorded the probable cause as: the number one cylinder's separation, the pilot's visual lookout not possible through the oil given off by the number one cylinder, and the embankment. A factor in the accident was the oil. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 1 related events involving the same aircraft type or operator are linked below.
During cruise, the engine ran rough and emitted smoke and oil, covering the windshield. The pilot diverted and performed a forced landing, during which the aircraft departed the road leading to the runway and struck an embankment, coming to rest inverted. Examination of the separated cylinder head revealed no preexisting cracks but contact marks consistent with piston ring or crown.
Incident Narrative
During cruise flight, the pilot reported that the engine began to run rough. Subsequently, the engine blew smoke and oil, and the windshield became covered with oil, obscuring the pilot's forward visibility. The pilot maneuvered the airplane toward the airport. On approach to runway 09, the pilot had no visibility through the oil-covered windshield. During the forced landing, the airplane ran off a road that leads to the runway's centerline and struck an embankment located in the safety area before the approach end of runway 09. The airplane came to rest inverted next to the embankment.
Examination Findings
Examination of the number one cylinder head, which was found separated from its cylinder, revealed no indications of preexisting cracks. The separation occurred in the combustion dome between the cylinder head and the screw-on cylinder barrel. The cylinder head exhibited marks and dents consistent with contact from the piston ring or piston crown.