The pilot of a tour helicopter, forced to make a hard landing in a Maui cow pasture last month, said he was 10 minutes into his third scenic air flight of the day when he experienced mechanical problems. The National Transportation Safety Board released a preliminary report on the incident. The Sunshine Helicopter pilot says the low rotor warning alarm sounded and he lowered the collective pitch control to increase main rotor speed, but the helicopter started to descend. At that point, he entered an autorotation, in which the rotor blades move by the upward flow of air as the helicopter descends. The aircraft landed hard on a grassy bluff. The helicopter was damaged, but no one was injured. The NTSB says the helicopter's engine was removed and has been shipped to the engine manufacturer's facility for further examination.