The RV-8 pilot reported that, during cruise flight, he felt a sustained vibration, which he thought was from the engine or propeller, and that the airplane then started to slow down.
He made a forced landing to the desert near Wickenburg, Ariz., and the plane came to rest on its nose, which caused substantial damage.
A post-accident propeller examination revealed that one of the propeller pitch change pins had broken. The pin’s fracture would have resulted in the sustained vibration and loss of speed reported by the pilot.
A metallurgical examination of the pin revealed that it had failed due to a fatigue crack that had progressed through about 70% of the pin. The fatigue crack initiated at dimples that had a depth and width consistent with excessive shot peening, which likely occurred during the manufacturing process.
The NTSB determined the probable cause as the fatigue failure of a propeller pitch change pin due to excessive shot peening of the pin’s surface during the manufacturing process.
NTSB Identification: WPR14LA046
This November 2013 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.