Amateur-built RV-8 N391V accident near Wickenburg, Arizona

Probable cause

The fatigue failure of a propeller pitch change pin due to excessive shot peening of the pin’s surface during the manufacturing process.

NTSB analysis

The 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. The pilot made a forced landing to the desert, and the airplane came to rest on its nose, which caused substantial damage to the airplane. A postaccident engine run and subsequent engine examination revealed no mechanical anomalies that would have precluded normal operation. The 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 percent 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.

Text from the NTSB. Open the NTSB docket for WPR14LA046 for the full record.