On June 23, 2004, about 1115 Pacific daylight time, a Bell 206B, N305FD, collided with terrain and rolled on its side near Lancaster, California. The Los Angeles City Fire Department was operating the helicopter under the provisions of 14 CFR Part 91, as a public-use flight. Both of the certified flight instructor rated pilots sustained minor injuries; the helicopter sustained substantial damage. The instructional cross-country flight departed Van Nuys Airport, Van Nuys, California, about 1045, destined for the General William J Fox Airfield, Lancaster. Visual meteorological conditions prevailed, and a company visual flight rules (VFR) flight plan had been filed. In a written statement, the pilot-undergoing-instruction (PUI) stated that prior to the flight, both he and the acting certified flight instructor (CFI) checked the weather, calculated performance limitations, and reviewed preflight information and training goals. Upon reaching Lancaster, they checked the wind direction and speed, and verified it with each other. While practicing a turning (180-degree) autorotation, the PUI established the helicopter on final from 400 feet above ground level (agl). The PUI stated, in a telephone interview, while on final he experienced a momentary decay in rotor rpm, which he attributed to a wind shift. He then made a slight altitude adjustment, as he was a little high. About 70 feet agl, he leveled the helicopter, rolled in throttle, and started his flare. About 50 feet agl, he leveled in the flare because the helicopter "did not feel like it was building energy" and was not as effective in the flare. The rotor rpm was at 100 percent. He noted that there seemed to be not enough engine power to recover. He leveled the aircraft to get out of the flare and raised the collective. The low rotor horn sounded shortly after. The helicopter landed hard, bounced, spun around, hit the ground again, and rolled over on its right side. Damage was incurred to the helicopter's main rotor and drive shaft, tail rotor and drive shaft, skids, transmission mount, and fuselage. Both pilots had their hands on the controls at the time of the accident. An engine teardown was conducted and no mechanical anomalies were discovered. The fuel control and governor bench tested to specifications. The Los Angeles City Fire Department "flare autorotations" procedure states "At approximately 75 feet from the ground, you begin your flare by applying a smooth pressure on the cyclic. Flaring the ship at the right altitude and leveling the ship from a flare require quick but smooth movement of the cyclic. You will lost some altitude coming out of the flare but the ship should be level by the time you reach 10 feet."