Amateur-built RV-8 N838RV accident near Clermont, Florida

Probable cause

The pilot's exceedance of the airplane's critical angle of attack while maneuvering for a forced landing; which resulted in an aerodynamic stall and loss of control. Contributing to the accident was the fatigue failure of the crankshaft for reasons that could not be determined based on the available information.

NTSB analysis

The private pilot was in cruise flight in the experimental, amateur-built airplane. The pilot transmitted a mayday call via radio, stating that he had "lost an engine." Witnesses saw the airplane before impact and stated that the airplane was not making any sound. One witness saw the airplane enter a sharp turn before entering a nose-low descent. The airplane then impacted an open field; the sharp turn followed by the nose-low descent is consistent with an aerodynamic stall.

Examination of the experimental, kit-built engine revealed that the crankshaft had fractured forward of the No. 2 connecting rod journal. Further testing of the crankshaft revealed that the fracture was the result of fatigue cracking. There were no chemical variations or foreign material present in the metallurgical testing. The crankshaft only had 20 hours total time in service, suggesting that initiation of the cracking and the subsequent failure of the crankshaft was almost immediate. As there were no apparent metallurgical mechanical deficiencies with the crankshaft, the fatigue failure was likely the result of unusual stresses; however, there was insufficient information about the engine operation in the final 17 minutes of flight to determine the reason for the failure.

Although the pilot's toxicology results tested positive for Zolpidem, a prescription medication for the treatment of insomnia, the values were below the normal therapeutic range and there was no evidence that impairment contributed to the accident.

Text from the NTSB. Open the NTSB docket for ERA16FA127 for the full record.