The pilot stated that after taking two other passengers on an hour-long sightseeing flight he made an approach and landing to the helipad. He was not satisfied with the landing and he lifted off the helipad to reposition and re land the helicopter. Once airborne the helicopter started spinning to the right, rising to about 50 feet, and pitching up. He rotated the throttle off, lowered the collective, and as the helicopter approached the ground, he pulled up on the collective. The low rotor rpm horn was sounding as they descended. The helicopter impacted the ground in a 30-degree left angle of bank, collapsing the left skid, and rolled over on its left side. All occupants egressed through the right cabin door. The pilot said that he may have pulled up too aggressively when attempting to reposition the helicopter, precipitating the loss of control. A Federal Aviation Administration inspector examined the helicopter and found no preaccident mechanical malfunctions or failures that would have precluded normal operations.