On September 24, 1997, a Beech C23 (registration N1851Z) was involved in an aviation accident near Champaign, IL. Investigators recorded the probable cause as: All eight valve lifters were broken, with brittle fractures due to overload. Some areas on the lifter faces showed evidence of heavy loading from the camshaft. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A CFI reported engine roughness and rpm drop, followed by oil pressure loss. Despite troubleshooting, the engine lost power. Examination revealed all eight valve lifters broken due to overload.
Incident Overview
A certified flight instructor (CFI) was piloting an airplane approximately 4 miles from the airport, in radio contact with the control tower, when the engine began to run rough and the rpm dropped from 2500 to 2200. The CFI notified the tower and requested a closer runway. Troubleshooting efforts were unsuccessful; the rpm subsequently dropped to 2000. Oil began to cover the windscreen and oil pressure dropped to zero. The CFI believed seizure was imminent and pulled the mixture to lean, attempting to glide to the runway. However, the airplane was low in altitude. The CFI sidestepped to aim for the grass and avoid runway lighting and the localizer, but could not make the grass and landed in a cornfield.
Engine Examination
Post-incident examination of the engine revealed that all eight valve lifters were broken. Analysis of the lifters and lifter pieces showed brittle fractures due to overload. Some areas on the lifter faces exhibited evidence of heavy loading from the camshaft.
Probable cause
All eight valve lifters were broken, with brittle fractures due to overload. Some areas on the lifter faces showed evidence of heavy loading from the camshaft.