On July 8, 2005, about 1400 Alaska daylight time, a high skid-equipped Hughes 500D helicopter, C-GLHQ, operated by Prism Helicopter, Inc., as an on-demand Title 14, CFR Part 135 flight, sustained substantial damage when the main rotor blades collided with a tree while landing at a remote site, about 5 miles east of Ambler, Alaska. The airline transport certificated pilot and the two passenger were not injured. The local flight operated in visual meteorological conditions, and a company VFR flight plan was in effect. The flight departed Ambler about 1330. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on July 9, the pilot reported that he had been ferrying survey crews between remote sites in a sparsely forested area throughout the morning and afternoon. He said that while landing in an area that contained trees, the passenger that was seated in the right front seat told the pilot that he getting too close to a spruce tree on the right side of the helicopter, so he discontinued the approach and selected another landing site. After the two passengers disembarked, the pilot continued to the next stop. He reported that while en route, site, he noticed a slight vibration that he had not noticed previously, and he elected to fly to the Ambler Airport so his mechanic could inspect the helicopter. After landing, the pilot reported he noticed damage to three of the five main rotor blades. He said he was uncertain of when the damage occurred, but noted it likely happened on his last landing, and it appeared that the blades struck a tree. The pilot indicated there were no preimpact mechanical problems with the helicopter. On August 6, it was determined by a repair station that all three damaged main rotor blades were unairworthy, and could not be repaired.