The helicopter was being operated from a clearing in flat, tree covered terrain. It was heading into wind and had reached a height of about one metre after lift-off when it suddenly swung to the right and moved backwards. The tail skid and rotor struck the ground and the helicopter swung further right. The main rotor blades then contacted the ground and the helicopter rolled on to its side. The pilot reported that a local whirlwind had caught the helicopter just after lift-off. Overnight rain had prevented the tell-tale dust plume from developing. This accident was not the subject of an on-site investigation.