HISTORY OF FLIGHT On December 11, 2004, at 1013 Pacific standard time, a Robinson R22B, N145RJ, made a hard landing and collided with obstacles while attempting to execute an emergency autorotation onto the rooftop heliport on the Wells Fargo Bank Building, downtown Los Angeles, California. Rainbow Air Academy, Inc., was operating the helicopter under the provisions of 14 CFR Part 91. The private pilot and the one passenger were not injured; the helicopter sustained substantial damage. The personal local flight departed Long Beach, California, about 0915. Day visual meteorological conditions prevailed, and no flight plan had been filed. The primary wreckage was at 34 degrees 3.182 minutes north latitude and 118 degrees 15.099 minutes west longitude. The renter pilot reported that while flying over downtown Los Angeles, about 1,200 feet mean sea level (msl), he observed the low rotor speed warning light illuminate followed by the low rotor speed warning horn activating. He entered an autorotation and attempted to land on top of the Wells Fargo Bank Building, which is a 56-story office building. During the landing phase the helicopter overshot the landing pad, and the main rotor blades came in contact with window washing equipment. The helicopter missed the helipad, and came to rest below the helipad on the roof. The helicopter sustained damage to the main rotor blades and tail boom. The helicopter was recovered from the rooftop and transported to storage for further examination. Investigators from the National Transporatio Safety Board, the Federal Aviation Administration, Robinson Helicopter Company, and Textron Lycoming were parties to the investigation. The wreckage was examined at Robinson Helicopter Company, Torrance, California, on January 6, 2005. Investigators established control continuity for the throttle and mixture controls. Both controls moved freely from stop to stop. The bottom spark plugs were removed from each cylinder. The spark plug electrodes were gray in color, which corresponded to normal operation according to the Champion Aviation Check-A-Plug AV-27 Chart. Fuel samples were taken from the main and auxiliary fuel tanks and the gascolator. All three samples were blue in color with no water present. The vent lines were disconnected from the fuel tanks, which appeared to be a result of contact with push/pull tubes at ground impact. The vent lines were clear. Without using any extraneous or substitute equipment, the engine was started, warmed up and run at 104 percent for approximately 10 minutes with no anomalies. The governor was switched on, and it functioned properly. A magneto ground check was performed with the following results: When switched to the "L" position, the rpm dropped (approximately 15 percent). When switched to the "R" position, there was no rpm drop. When switched to the "OFF" position, the rpm dropped, but the engine continued to run. Examination of the wires on the left magneto revealed the "P" lead was attached to the "Retard" terminal, and the "Retard" lead was attached to the "Print" terminal. The leads were removed and reinstalled properly. The engine was again run, and a magneto ground check was performed. Both magnetos responded properly. ADDITIONAL INFORMATION The Safety Board investigator released the wreckage to the owner's representative.