NTSB Identification: DEN00IA076.
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Incident occurred Saturday, April 08, 2000 in ENGLEWOOD, CO
Probable Cause Approval Date: 04/06/2001
Aircraft: Beech A60, registration: N928PT
Injuries: 3 Uninjured.

NTSB investigators used data provided by various sources and may have traveled in support of this investigation to prepare this aircraft incident report.

On departure, the left engine of the twin-engine airplane failed. Postincident examination of the left engine revealed a six-inch hole in the case, and that two connecting rod bolts on the number one cylinder had separated. Examination indicated that one of the rod bolt failed due to fatigue. An SEM examination of the outside surface adjacent to the fracture face revealed no indication of a manufacturing anomaly. Fretting damage was found on the arm of the connecting rod that was associated with this bolt. The physical evidence suggested that the bolt was improperly torqued. Maintenance records indicate that the left engine received a major overhaul 2.5 hours before the incident. A representative of the engine manufacturer said that the rod bolts on this engine are properly installed when the tightening of the nut stretches the bolt to a specified dimension.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

The failure of a number one cylinder connecting rod bolt due to under-torquing during engine major overhaul.

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