Hiller UH-12E N5334V accident near Bovill, Idaho

Probable cause

A loss of helicopter control for undetermined reasons based on the available evidence for this accident.

NTSB analysis

The helicopter was performing an aerial application flight. While approaching the fertilizer service truck to refill the bucket, the pilot felt a “sudden jolt,” and the helicopter lost altitude. The pilot was unable to regain control, and the helicopter did not yaw after the jolt. The helicopter subsequently impacted the terrain below. The helicopter sustained substantial damage to its main rotor blades and fuselage. Before the pilot could exit the helicopter, “everything” on the helicopter, including the engine, automatically shut down.

Postaccident examination of the wreckage, including the engine, revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. Also, the examination yielded no evidence to explain why the engine automatically shut down after the accident. As a result, the reason for the pilot’s loss of helicopter control could not be determined based on the available evidence for this accident investigation.

Text from the NTSB. Open the NTSB docket for WPR21LA354 for the full record.