Robinson Helicopter R22 BETA accident near Corcoran, Minnesota, December 23, 2012

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

Before landing, the pilot hovered the helicopter about 10 feet above the ground to see if tarps covering the north half of the concrete helipad would move, and he then decided to continue the landing. The helicopter approached from the north, which placed the tail rotor over the tarps. The area south of the helipad was free of obstructions. While the pilot was shutting down the helicopter after landing, the helicopter made an uncommanded counterclockwise rotation of about 40 degrees. The pilot applied corrective pedal input with no response. The helicopter then rotated about three full revolutions before the tail boom and main rotors struck a nearby parked trailer, and a fire ensued. Postaccident examination of the helicopter did not reveal any preimpact anomalies; however, the examination was limited due to extensive impact and postimpact fire damage. Examination of the accident site revealed several cuts in the tarp in the area where the tail boom was positioned during landing. Although the pilot reported that the tarp did not impact the tail rotor, the evidence suggests that the tarp was lifted into the tail rotor during the shutdown, which likely caused damage to the tail rotor blades and resulted in a loss of tail rotor authority and the subsequent uncommanded rotation. Further, because the area south of the pad was free of obstructions and the reported wind was variable at 2 knots, the pilot could have landed the helicopter facing north, which would have placed the tail rotor over the unobstructed ground south of the helipad.

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.