Robinson R44 N74805 accident near Kailua/Kona, Hawaii

Probable cause

An on-ground upset for reasons that could not be determined because postaccident examination of the helicopter revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.

NTSB analysis

During aninstructional flight in the helicopter, the pilot under instruction set up for anapproach and landing to a flat and smooth gravel road. Once the skids were on the ground, the pilot under instruction lowered the collective toward the FULL DOWN position. The helicopter then began to rock in a fore and aft motion. The flight instructor took the controls as the intensity of the rocking increased; the helicopter then ascended in uncontrollable flight. The flight instructor subsequently landed the helicopter on the gravel road; it came to rest upright about 20 to 30 ft and at a little more than a 45° angle from the initial touchdown point. The helicopter sustained substantial damage to the fuselage. Postaccident examination of the helicopterrevealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. Thus, the reason for the reported on-ground upset could not be determined.

Text from the NTSB. Open the NTSB docket for WPR16LA168 for the full record.