Robinson Helicopter Company R44 II accident near Ronan, Montana, July 6, 2017

The NTSB's narrative final · quoted from the NTSB record

The private pilot departed on a local, private flight in the helicopter with a family member onboard for a scenic tour of the area. The pilot reported that, about 45 minutes into the flight, he slowed the helicopter to 35 knots, descended it to about 300 ft above ground level (agl), and then entered a left orbiting turn to follow an animal. The helicopter then experienced an uncommanded yaw, which the pilot perceived as a loss of tail rotor authority, and it then began to spin clockwise and descend. The pilot immediately attempted to counteract the spin by lowering the collective control, reducing power, and applying left antitorque pedal, which he maintained for the rest of the descent. When the helicopter was about 5 ft agl, the pilot pulled the collective control, but he was unable to arrest the descent, likely because the descent rate was too high, and the helicopter subsequently impacted the ground hard, which resulted in substantial damage to the tail cone and tail rotor. Postaccident helicopter examination revealed no evidence of any preaccident mechanical malfunctions or failures that would have precluded normal operation. Further, the pilot reported that there were no problems with the engine and that it continued to run normally after the helicopter came to rest. It is likely that the pilot allowed the airspeed to drop below translational lift, which resulted in a loss of tail rotor effectiveness and a subsequent spin. Despite remedial actions to compensate for the spin, the descent rate was likely too high to arrest it, which resulted in the hard landing.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.