On August 2, 1988, a Beech A36TC (registration N3707Z) was involved in an aviation accident near Vega, TX. Investigators recorded the probable cause as: Failure of the crankshaft initiated by a pre-existing fatigue crack. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During a night cross-country flight, engine oil appeared on windows. Oil pressure dropped to zero, engine vibrated, propeller separated. Pilot made forced landing on highway service road, impacting signs and reflectors. Investigation revealed pre-existing fatigue crack in crankshaft.
Incident Details
During a night cross-country flight, the pilot observed engine oil appearing on the windows. Unable to reach an airport before the oil pressure reached zero, the pilot experienced engine vibration and then the propeller separated from the engine. With forward visibility compromised and limited side visibility, the pilot executed a forced landing on a highway service road. During the landing roll, the airplane struck highway signs and reflectors. The pilot reported a fire on the highway behind the airplane, but it did not reach the aircraft.
Investigation Findings
A teardown examination of the engine revealed a failure of the crankshaft that was initiated by a pre-existing fatigue crack. Evidence indicated that the opening of this fatigue crack led to a gradual loss of lubricating oil, which subsequently resulted in the separation of the propeller.
Probable cause
Failure of the crankshaft initiated by a pre-existing fatigue crack.