Incident Summary
During the takeoff roll, the pilot applied full power and heard a loud bang. Subsequently, the pilot observed that the right propeller had separated from the engine. The aircraft was on the ground at the time, and the takeoff was aborted.
Examination Findings
A metallurgical examination of the separated propeller hub was conducted. The examination revealed that the hub separated due to fatigue cracking that initiated from the holes for the studs used to attach the hub to the crankshaft flange. Additionally, a substantial amount of fretting was noted on the mounting face of the hub. This fretting indicates possible looseness between the hub and the crankshaft.
Conclusion
The observed fretting and fatigue cracking are likely the result of inadequate preload on the studs, which stemmed from inadequate assembly torque applied to the nuts. No other causal factors were identified in the investigation.