On June 30, 1999, at 2330 central daylight time, a McDonnell Douglas 500-E helicopter, N686F, owned and operated by the Oklahoma City Police Department, was substantially damaged during a night practice autorotational landing at the Downtown Airpark Airport, Oklahoma City, Oklahoma. The commercial pilot and observer were not injured, and the passenger received minor injuries. Dark night visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 public use flight. The local flight departed the Downtown Airpark Airport, about 40 minutes prior to the accident. The pilot reported that after completing patrol duties, the flight returned to the airport. He proceeded to practice some quick stop maneuvers, slope landings, and a hovering autorotation. The pilot further reported that he then entered the traffic pattern and "once [on] downwind ... entered a 180 degree autorotation" for the area east of runway 16 on the north end of the field. During the approach, and "after reapplying power, the flare was executed at too low of an altitude, and the tail boom made contact with the ground." The pilot added that "tail rotor use was lost," and the helicopter came to rest on its right side. The operator reported that an examination of the helicopter revealed that the tailboom was partially separated about three feet aft of its fuselage attaching point. The main drive shaft was damaged, the tail rotor drive shaft was separated at its aft flex coupling, and the right skid was separated.