What happened
During flight, the pilot reported experiencing severe vibration originating from the left engine. In response to the abnormal condition, he shut down the affected engine and proceeded to land the aircraft without further incident.
The investigation
Post-accident examination of the propeller assembly revealed significant mechanical failures. One propeller blade was found to be missing a portion of its structure. Detailed analysis of this failed component indicated evidence of high-cycle, low-stress fatigue with a surface origin for the crack initiation.
Additionally, inspection of the remaining two blades showed they were manufactured below minimum dimensional specifications. These blades also exhibited improperly polished and protected surfaces, suggesting manufacturing or maintenance deficiencies contributed to the premature failure.