Shortly after the aircraft departed the television station helipad, the pilot became concerned about a decay in the power available. He carried out a precautionary landing on a suburban road adjacent to, but on the opposite side of a fence from the helipad. One of the two passengers disembarked and the pilot carried out a power check which appeared normal. The pilot elected to reposition the helicopter back on to the helipad. Shortly after lift off the power again decayed and the pilot attempted a precautionary landing back onto the road. The main rotor blades made contact with the tail boom during the second landing. Although some minor faults were found in the engine fuel system none of them were significant enough to cause the loss of power reported by the pilot. No other faults were found which may have contributed to the accident. The reason for the loss of power was not determined. The pilot's decision to attempt a return to the pad was influenced by the apparently normal power check, following the first landing, and his concern about the possibility of a vehicle/aircraft collision if the aircraft remained on what was a major access road with visibility restricted by a curve.