The pilot of a tour helicopter, which was forced to make a hard landing in a Maui cow pasture last month, told federal investigators that he was 10 minutes into his third scenic air flight of the day when he experienced mechanical problems.

According to a preliminary report by the National Transportation Safety Board, the Sunshine Helicopter pilot said the main rotor speed started to decrease and the low rotor warning alarm sounded during the flight on June 17.

The pilot said he lowered the collective pitch control to increase main rotor speed, but the helicopter started to descend. He raised the collective pitch control and the main rotor speed started to decrease again. At that point, the pilot entered an autorotation, disengaging the engine from the main rotor system, and landed the helicopter in the tall elephant grass.

During autorotation, the rotor blades move by the upward flow of air as the helicopter descends.

The helicopter landed hard on a grassy buff, structurally damaging the fuselage and tail boom, the NTSB report said.

The trip was arranged by the Make A Wish Foundation for Anne Marie Fraser, 17, who is battling Ewing’s Sarcoma, a rare bone cancer, the Associated Press reported.

“Her wish was to come to Hawaii,” her mother, Susanne Fraser said. “And she picked Maui as her island.”

Anne Marie Fraser was with her mother, father and sisters, who are ages 13, 15 and 18.

The family and the pilot were not injured when the Airbus AS 350 BA helicopter made the emergency descent from 2,500 feet.

“A horn went off in the helicopter, like a honking noise,” Susanne Fraser said. “Me and my husband kind of looked at each other like that was that.”

The helicopter was over water, she said.

The pilot told the passengers they were at an altitude where he could control the glide. He turned toward land and made an emergency landing on a grassy bluff.

The hard landing occurred in the Kapuna area north of Waihee Stream.

The NTSB said the helicopter’s engine was removed and has been shipped to the engine manufacturer’s facility for further examination.