Airborne Windsports "The Osprey", Belgrave South, Victoria, on 11 March 1989

Circumstances:

The pilot had not previously flown at the site and decided to make a short solo first, prior to taking a friend for a flight. Because of the strip slope he took off downhill and landed uphill. The wind conditions were light and variable. Satisfied with the site and the conditions he then strapped the passenger into the rear seat. The passenger wore a helmet and was briefed on avoiding contact with the foot throttle. Take off was made downhill again and the machine was flown around the area for a few minutes. A landing approach was then made but on descending to about 30 feet the pilot realised that he would be unable to stop before the fence at the far end of the strip. Full throttle was applied for a go around. The terrain beyond the end of the strip sloped uphill and the pilot realised he was going to have trouble clearing the trees ahead. A left turn was initiated, but the aircraft collided with trees before descending steeply to the ground. Examination of the engine revealed that the throttle cable assembly was incorrectly adjusted and because of this it was not possible to obtain full power. The two carburettors were each fitted with a foam air filter. These were aged and heavily contaminated with dust and oil, which further reduced the amount of engine power available. The filters were mounted at right angles to the air stream and had been permanently deformed. For aircraft of this type there are no standards in terms of strip length required or climb out gradient. The go around flight path required clearance of terrain that was steep, and tree covered. This type of machine, which has been built and sold in Australia for some time, was not approved for operation with two persons on board.

Significant Factors:

The following factors were considered relevant to the development of the accident:

1. Selection of an operating site which required clearance of trees and rising terrain in an overshoot situation.

2. Less than full engine power available because of an incorrectly adjusted throttle cable and the physical condition of the air filters.

3. The pilot misjudged the landing approach.

4. Insufficient aircraft performance available to clear terrain beyond the strip.

Recommendations:

1. Consideration be given by the Civil Aviation Authority and Australian Ultralight Federation to the issue of simple guidelines for strip standards for use in these class of machines. This should include standards for length and maximum slope for take-off/landing areas, as well as for approach and climb out clearance paths.