On March 26, 1989, a Beech 95-B-55 (registration N27WF) operated by Casebolt, Fon was involved in an aviation accident near Crothersville, IN. Investigators recorded the probable cause as: Failure of the right engine due to the pin retaining plate cutting through the crankshaft counterweight, which had not been surface-hardened (tufrided) as required for engines built or rebuilt after 1968 and 1973-74, respectively. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During a local pleasure flight, the right engine failed. The pilot reduced left engine power and performed a forced landing. During rollout, the nose gear collapsed in muddy terrain, causing the aircraft to nose over.
Accident Overview
During a local pleasure flight, while in normal cruise, the right engine experienced a complete failure. The pilot responded by reducing power on the left (operating) engine to curb violent vibration and executed a forced landing in an open field. As the aircraft rolled out after touchdown, it entered a muddy area. The nose gear became bogged down, then collapsed, and the aircraft nosed over.
Engine Examination
Post-accident examination of the right engine revealed that the pin retaining plate had cut through the crankshaft counterweight, releasing it. Further inspection showed that the counterweights had not undergone a surface hardening process known as 'tufriding'. This process prevents the pin retaining plate from cutting or wearing through the counterweight. Tufriding has been required on new engines since 1968 and on rebuilt engines since 1973-74.
Maintenance History
The accident engine was rebuilt by the manufacturer in 1971. The logbook and maintenance information provided by the pilot were incomplete.
Probable cause
Failure of the right engine due to the pin retaining plate cutting through the crankshaft counterweight, which had not been surface-hardened (tufrided) as required for engines built or rebuilt after 1968 and 1973-74, respectively.
What happened in the 26 Mar 1989 Beech 95-B-55 accident near Crothersville, IN?
During a local pleasure flight, the right engine failed. The pilot reduced left engine power and performed a forced landing. During rollout, the nose gear collapsed in muddy terrain, causing the aircraft to nose over.
What aircraft was involved and where did it happen?
The accident on 26 Mar 1989 involved a Beech 95-B-55, registration N27WF, operated by Casebolt, Fon, at Crothersville, IN.
What was the probable cause of the accident?
Failure of the right engine due to the pin retaining plate cutting through the crankshaft counterweight, which had not been surface-hardened (tufrided) as required for engines built or rebuilt after 1968 and 1973-74, respectively.
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