Overview
An engine failure occurred 37 operating hours after an overhaul. The failure was traced to the shearing of the locating dowel for the crankshaft gear. The shearing resulted from the use of an incorrect part in place of the specified attaching bolt.
Details
During the overhaul, a mechanic installed an incorrect part as the attaching bolt for the crankshaft gear. The mechanic was unaware of an airworthiness directive (AD) that applied to the affected parts and their installation. Consequently, the mechanic reused an apparently serviceable item that was not compliant with the AD.
An inspector involved in the process was aware of the AD but interpreted it as inapplicable to the parts in question. This misinterpretation allowed the installation to proceed without proper adherence to the directive.
Findings
- The locating dowel for the crankshaft gear sheared after 37 operating hours post-overhaul.
- The shearing was caused by the use of an incorrect attaching bolt instead of the specified part.
- The mechanic was unaware of the applicable airworthiness directive.
- The inspector was aware of the directive but interpreted it as inapplicable.
These facts were established from the investigation of the engine failure.