Robinson R22 N22UH accident near Prescott, Arizona

Probable cause

The flight instructor’s delayed remedial action to address a low rotor rpm condition, which resulted in an excessive descent rate and a subsequent hard landing.

NTSB analysis

The flight instructor and student pilot were practicing straight-in autorotations in the helicopter. During the autorotative descent, about 400 ft above ground level with the student at the controls, the instructor noticed a high rate of descent and a decay in main rotor rpm. The instructor told the student that he had the controls and started applying collective and throttle to recover rpm. He felt the collective go up and again told the student that he had the controls. The instructor was unable to arrest the descent before the helicopter landed hard and rolled over. The instructor reported that there were no pre-impact mechanical malfunctions or failures with the airframe or engine that would have precluded normal operation. He further stated that the accident could have been prevented if he had stayed ahead of his student and the helicopter.

Text from the NTSB. Open the NTSB docket for WPR16LA156 for the full record.