The pilot was returning from a solo navigation exercise and had descended from 800 feet in the training area to 300 feet above ground level to comply with the height restrictions on ultralight aircraft. The engine began to run roughly and the aircraft lost height to about 200 feet. The pilot elected to carry out an immediate precautionary landing on the Stuart Highway as he was flying downwind and was uncertain of his ability to turn into wind for a landing if he lost any more height. A normal landing was made in the centre of the highway, but the aircraft diverged to the right and the pilot was unable to maintain directional control on the camber of the road. The aircraft then hit the roadside windrow and collided with bushes. No mechanical defects were found that could have contributed to the loss of engine power. Conditions were conducive to the formation of carburettor icing which would have been assisted by the use of Mogas fuel. Club officials stated that the limit on the altitude of ultralight operations prevented the pilot from flying at a greater height, and therefore denied him the opportunity of selecting another area for landing which was clear of obstructions.
