On June 20, 1991, a Grumman G-164-A (registration N8842H) operated by James W. Wehrman was involved in an aviation accident near Edgar, NE. Investigators recorded the probable cause as: The partial blockage of the oil cooler by a rag, which caused excessive engine oil temperature. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
Following an excessive oil temperature warning ten minutes into flight, the pilot performed a precautionary landing on a roadway. The aircraft subsequently struck a post and entered a ditch during the rollout.
What happened
The pilot reported that approximately ten minutes after takeoff, he observed an excessive engine oil temperature indication. In response to this mechanical anomaly, he initiated a precautionary landing on a nearby road. During the landing roll, the left wing of the aircraft struck a post, causing the airplane to veer off the roadway and into a ditch.
The investigation
A post-accident examination of the aircraft revealed that the engine overheating was caused by a rag that had become lodged in the oil cooler assembly. This obstruction partially blocked airflow through the cooler, preventing proper heat dissipation and leading to the excessive temperature reading observed by the pilot during flight.
Findings
The primary factor contributing to the incident was the partial blockage of the oil cooler by foreign debris. The presence of the rag restricted cooling efficiency, resulting in abnormal engine temperatures. The pilot's decision to execute a precautionary landing on a road mitigated potential catastrophic failure but resulted in structural damage upon impact with ground obstacles.
Probable cause
The partial blockage of the oil cooler by a rag, which caused excessive engine oil temperature.