Before the accident flight, the pilot asked for the weights of passengers, fueled the helicopter accordingly, and then flew to pick up the passengers. However, when the pilot arrived to pick up the passengers, they appeared to be heavier than the weights he had used for them in his preflight planning. The pilot reported that he was able to lift off and bring the helicopter to a hover, so the helicopter seemed to have sufficient power for takeoff. However, as the helicopter flew forward over a thicket, the main rotor rpm began to decrease. The pilot lowered the nose to increase rpm. The rpm did not increase, and the helicopter impacted terrain hard and sustained substantial damage when its tailboom separated. The pilot estimated that the helicopter’s weight at the time of the accident was inside the envelope for in-ground-effect operations, but was outside the envelope for out-of-ground-effect operations. The pilot reported that there were no mechanical malfunctions with the helicopter during the flight. The pilot stated that he should have requested that one person remain on the ground until more fuel was burned off.