On May 31, 1998, at 1145 hours Pacific daylight time, a Fields Baby Belle experimental helicopter, N656VK, crashed approximately 5 miles northwest of Inyokern, California. The aircraft was destroyed and the private pilot/owner, the sole occupant, suffered serious injuries. The personal flight originated at the pilot's home and was en route to the Inyokern airport to refuel. Visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that during the preflight, he found a piece of the engine cooling shroud rubbing against the engine flywheel. He further stated that the first run-up was aborted due to metal chaffing sounds near the fan housing. The pilot estimated that he had approximately 10 gallons of fuel onboard prior to takeoff. He reported that the purpose of the flight was to fly to Inyokern airport to obtain fuel and to practice approaches and landings. The pilot reported that he took off and passed through translational lift. Approximately 40 mph and 60 feet agl, he felt a vibration, which began increasing. The pilot reported that the tachometer needle was in the green arc. He stated that he attempted to reduce the vibration by raising the collective. The pilot reported that he decided to land and as he applied aft cyclic and reduced the collective, the aircraft began yawing to the left and he ran out of right pedal. The aircraft then nosed over in an uncontrolled descent and impacted the ground at approximately a 45-degree nose-down attitude and 20-30 degree left roll. The helicopter came to rest on its right side. There were three eyewitnesses to the accident. They reported that just after takeoff, they saw the helicopter turn left, dip the nose down and to the left, and drop forward to the ground in about a 30-45 degree slope. Upon reaching the accident site, the witnesses noted that the cockpit bubble had burst outward and toward the passenger side. The cyclic stick was gone, with just wires left. One main rotor blade was bent along the ground. The transmission was torn out and tilted toward the pilot's side of the ship. One of the tail rotor blades was bent. The pilot reported that he built the kit helicopter, which has a total time of 67 hours. The kit does not include a low rpm warning system. According to the kit manufacturer, the main rotor blades rotate clockwise and the tail rotor rotates 5.5 revolutions for every single revolution of the main rotor. If a low main rotor rpm situation is encountered and anti-torque is not reduced through the pedals, the aircraft will yaw to the left. Power available from the engine is directly proportional to rpm. If the rpm drops 10 percent, there is 10 percent less power. With less power, the helicopter will start to settle, and if the collective is raised to stop it from settling, the rpm will be pulled down even lower, causing the ship to settle even faster. If rotor stall occurs, the blades will either "blow back" and cut off the tail cone or it will just stop flying, allowing the helicopter to fall at an extreme rate. The recovery from low rpm is to add throttle and lower collective. The pilot holds a private pilot certificate with a single engine land rating and has a helicopter solo endorsement dated August 22, 1997.