On August 21, 1993, a Beech C23 (registration N6547R) operated by Bullion, Dena L. was involved in an aviation accident near Lakeview, OR. Investigators recorded the probable cause as: The number one exhaust valve head broke away at the neck, causing the engine to run rough and lose power. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During cruise flight, the engine ran rough, RPM dropped, and the airplane could not maintain altitude. The pilot performed a forced landing in a field, but the airplane hit rough terrain during the landing roll. Post-crash inspection revealed the number one exhaust valve head had broken away at the neck.
Incident Overview
During a cross-country flight, while the airplane was in cruise flight, the engine suddenly began to run rough. The engine RPM dropped, and the airplane was unable to maintain altitude. In response, the pilot initiated a forced landing to an open field. During the landing roll, the airplane collided with the rough terrain.
Post-Crash Inspection
After the accident, an inspection of the engine was conducted. It was found that the number one exhaust valve head had broken away at the neck. No other mechanical anomalies were noted in the source.
Sequence of Events
The engine roughness and RPM drop occurred without warning during cruise. The pilot executed a forced landing to the nearest suitable open field. The rough terrain during the landing roll resulted in a collision, ending the roll.
Probable cause
The number one exhaust valve head broke away at the neck, causing the engine to run rough and lose power.