On April 22, 1992, a Beech B36TC (registration N7252X) operated by Bodell, Michael J. was involved in an aviation accident near Mona, UT. Investigators recorded the probable cause as: Failure of the crankshaft due to non-metallic inclusions (oxides) that provided stress risers, leading to crack development under cyclic loading and subsequent propagation until failure. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During a cross-country flight, the pilot reported an engine power loss and declared an emergency. A forced landing was initiated, but the airplane collided with a ditch during the landing roll. Examination revealed a broken crankshaft due to non-metallic inclusions that caused stress risers and crack propagation.
Incident Overview
During a cross-country flight, the pilot reported a loss of engine power while in cruise flight. An emergency was declared, and the pilot initiated a forced landing to an open field. During the landing roll, the airplane collided with a ditch.
Engine Examination
An examination of the engine revealed that the crankshaft was broken between the number two main journal, extending to the number two main journal cheek and number two connecting rod journal.
Metallurgical Findings
A metallurgical examination identified occluded material within the crankshaft, which appeared to be oxides or other non-metallic inclusions produced during the manufacture of the metal prior to forging. The metallurgical report stated that these oxides most likely provided stress risers which concentrated stresses in the crankshaft to develop cracks under cyclic loading. The cracks propagated until failure occurred.
Probable cause
Failure of the crankshaft due to non-metallic inclusions (oxides) that provided stress risers, leading to crack development under cyclic loading and subsequent propagation until failure.
What happened in the 22 Apr 1992 Beech B36TC accident near Mona, UT?
During a cross-country flight, the pilot reported an engine power loss and declared an emergency. A forced landing was initiated, but the airplane collided with a ditch during the landing roll. Examination revealed a broken crankshaft due to non-metallic inclusions that caused stress risers and crack propagation.
What aircraft was involved and where did it happen?
The accident on 22 Apr 1992 involved a Beech B36TC, registration N7252X, operated by Bodell, Michael J., at Mona, UT.
What was the probable cause of the accident?
Failure of the crankshaft due to non-metallic inclusions (oxides) that provided stress risers, leading to crack development under cyclic loading and subsequent propagation until failure.
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