A group of pilots had travelled from a property strip to a nearby dam in order to complete training exercises on a float-equipped Bell 47 helicopter. VH-SRE was not fitted with floats but had been used to ferry some of the pilots to the area. At the conclusion of the training operation the pilot arranged to ferry VH-SRE back to the property strip. After take-off a practice autorotation was conducted over the dam and was followed by some unauthorised low flying in the vicinity. On arrival at the strip low level runs were performed along the strip with torque turns at each end. Control of the aircraft was lost during the third of these turns and the aircraft struck the ground in a steep nose-down attitude. Fire broke out on impact and engulfed the wreckage. The subsequent investigation did not reveal any evidence of a pre-impact defect or malfunction of the aircraft which might have contributed to the accident. Several of the pilots who observed the flight reported that the final manoeuvres performed were outside the normal operating parameters of the helicopter, and were conducted at an unsafe height above the ground. It was, however, not possible to establish which of the pilots was flying the aircraft at the time of the accident.