Hughes 369 N721RP accident near Jamestown, North Dakota

Probable cause

The pilot's excessive descent rate while flaring during a practice autorotation with a power recovery, which resulted in an impact with terrain.

NTSB analysis

The pilot reported that he was performing a practice autorotation with a power recovery, and was the sole occupant in the helicopter. He reported that the power was introduced at 200 feet above ground level (AGL) and he entered the flare at too low of an altitude. The tail rotor system impacted the soft ground adjacent to the planned landing area. The helicopter sustained substantial damage to the tailboom, the tail rotor driveshaft assembly, and the tail rotor system.

The pilot verified that there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.

The Federal Aviation Administration has published Advisory Circular (AC) 61-140 Autorotation Training (2013). This AC discusses the flare portion for autorotation training and states in part:

Every autorotational flare will be different depending on the existing wind conditions, airspeed, density altitude, and the aircraft gross weight.

This AC also discusses common errors during autorotation training and states in part:

Improper flare (too much or not enough).

Flaring too low or too high (AGL).

Text from the NTSB. Open the NTSB docket for GAA16CA168 for the full record.