On September 24, 2012, about 1600 Pacific daylight time, a McDonnell Douglas 369FF helicopter, N911BL, sustained substantial damage during a hard landing following a practice autorotation at North Las Vegas Airport, Las Vegas, Nevada. The two pilots, who both held flight instructor certificates, sustained minor injuries. The helicopter was registered to the Las Vegas Metropolitan Police Department, and the flight was a public aircraft operation. Visual meteorological conditions prevailed for the local training flight, which had originated from North Las Vegas Airport approximately 30 minutes before the accident. A flight plan had not been filed. The pilot-in-command (PIC)/pilot-giving-instruction stated that he and the pilot receiving instruction were alternately practicing autorotations. He decided to demonstrate a 270-degree autorotation to the touchdown point on taxiway Zulu. He began the maneuver on a 180-degree heading, 800 feet above the ground and an airspeed of 85 knots. As he crossed his intended touchdown point, he rolled the throttle back to begin the autorotation. He thought the wind was about 180 to 230 degrees at 15 knots gusting to 26 knots. He entered a left turn. While in the turn, he reported that because of a tailwind he increased his bank angle to maintain his ground reference to the touchdown point. The pilot receiving instruction reported that moments later, the helicopter was in a high rate of descent and its airspeed was decreasing. The helicopter impacted terrain in a tail low attitude. Subsequently the tail boom separated from the fuselage, the helicopter rolled onto its right side, and the right landing skid support structure folded under the fuselage. At 1605, the reported wind at North Las Vegas Airport, elevation 2,205 feet, was 270 degrees at 13 knots gusting to 22 knots. The calculated density altitude, using the barometric pressure of 29.77 inches of mercury, was 5,116 feet.