On May 13, 2002, about 1040 mountain standard time, a Schweizer 269C, N577TA, impacted the ground during an autorotation near the Phoenix Deer Valley Airport (DVT) Phoenix, Arizona. The helicopter, operated by Scottsdale Helicopters as an instructional flight under the provisions of 14 CFR Part 91, sustained substantial damage. The certified flight instructor (CFI) was not injured, and the helicopter rated private pilot sustained minor injuries. Visual meteorological conditions prevailed for the local area flight that departed the Scottsdale Airport (SDL), Scottsdale, Arizona, about 0945. No flight plan had been filed. In a written statement submitted by the CFI, he stated that he entered a training autorotation at altitude. He initiated a deceleration and brought the rotor rpm to "the top of the green." Then, he turned the helicopter into the wind and was gaining the "required airspeed for the end of the maneuver." The CFI stated that everything was as he expected until the helicopter reached approximately 200 feet above ground level (agl). The helicopter dropped quickly, and the CFI felt that this was the result of a change in wind direction. The engine could not provide enough performance to abort the maneuver; as a result, the CFI attempted to cushion the landing. As the helicopter contacted the ground, the left skid caught on desert terrain and it rolled onto its left side. The CFI stated in a phone interview that he noted no mechanical anomalies with the helicopter or engine. In a written statement, the student stated that he had approximately 1,400 hours of flight time in helicopters. The majority of it had been flown in turbine powered rotorcraft. The student contracted with the operator to prepare him for his commercial check ride. He had flown with the CFI approximately six to seven times prior to the accident. After departing SDL, they flew directly to a helicopter practice area north of DVT. After a series of autorotations and simulated pinnacle approaches, the CFI informed the student that they needed to return to SDL. The student climbed to 2,000 feet mean sea level (msl) and noted that the airspeed was 60 knots. The student recalled that the CFI stated, "Let me have the controls." The student acknowledged the request and said, "You have the controls." The student stated that as soon as the CFI took the controls he conducted a "quick stop" (no forward airspeed). The student noted that the altitude increased to about 2,020 to 2,030 msl. The CFI initiated a right-hand turn, and dropped the collective. The student heard the CFI state, "Watch this." Several days after the incident the CFI told the student that he had said, "Watch the disk." The CFI had an accent and English was his second language; the student could not say which statement was accurate. As the CFI began the right turning autorotation, the helicopter began to descend rapidly, and the student felt that there was no forward airspeed. The altitude was approximately 400 feet agl. About 200 feet agl the rate of descent increased. The student reached for the collective to slow the rate of descent, but found that it was in its full up position. The airspeed indicator indicated no forward airspeed; the rotor and rpm needles were joined at the 2 o'clock position. The helicopter impacted the ground at a high descent rate, and had turned almost 360 degrees since beginning the maneuver. A witness to the accident saw the helicopter flying southbound in level flight. The helicopter then stopped and made a turn to the right. The witness stated that it appeared that it was a decelerating right turn. He saw the rate of descent increase and the helicopter was still turning. He lost sight of it behind the Cave Creek Dam. The Safety Board investigator determined that the density altitude was approximately 4,000 feet at the time of the accident.