On April 21, 1988, a Cessna 150M (registration N9410U) operated by Southern Illinois University was involved in an aviation accident near Zeigler, IL. Investigators recorded the probable cause as: The engine ran rough and quit due to exhaust valve binding caused by carbon-like deposits on the valve stems. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 3 related events involving the same aircraft type or operator are linked below.
During practice emergency landing, engine ran rough and quit. Partial power regained but forced landing in plowed field resulted in aircraft nosing over. Post-crash inspection found exhaust valve binding due to carbon deposits.
Incident Details
During an instructional flight, after completing a practice emergency landing procedure, the engine began to run rough and subsequently quit. The instructor was able to regain partial power and performed a forced landing in a freshly plowed field. Just before the aircraft came to a complete stop, it nosed over.
Post-Inspection Findings
Following the incident, the engine was test-run on the airframe and exhibited very rough operation. A differential compression check revealed low compression on cylinders #2 and #4. Further investigation showed that the exhaust valves on cylinders #2 and #4 were binding when the valves were approximately 0.25 inches from their seats. Examination of the valve stems found a carbon-like deposit surrounding the stem, extending from the valve face to the area where the stem enters the valve guide.
Probable cause
The engine ran rough and quit due to exhaust valve binding caused by carbon-like deposits on the valve stems.
What happened in the 21 Apr 1988 Cessna 150M accident near Zeigler, IL?
During practice emergency landing, engine ran rough and quit. Partial power regained but forced landing in plowed field resulted in aircraft nosing over. Post-crash inspection found exhaust valve binding due to carbon deposits.
What aircraft was involved and where did it happen?
The accident on 21 Apr 1988 involved a Cessna 150M, registration N9410U, operated by Southern Illinois University, at Zeigler, IL.
What was the probable cause of the accident?
The engine ran rough and quit due to exhaust valve binding caused by carbon-like deposits on the valve stems.
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