The balloon was launched in a south-westerly wind of about 10 knots. About 20 minutes after take-off the windspeed had increased to about 15 knots, and the pilot decided to land in the grounds of the Aspley High School. As the balloon passed over a small hill it climbed to about 400 feet above ground level. It had then descended to about 150 feet, when the pilot noticed telegraph lines ahead. He ignited both burners for 12 seconds and it became evident that the basket would only just clear the lines. At the same instant he noticed powerlines some five metres above the telegraph lines. With impact imminent, the pilot instructed the passengers to crouch down and hold on to the handholds. Both burners were turned off and he began deflating the balloon. Following the collision with the powerlines, the lines and seven of the twelve flying wires of the balloon melted. This resulted in the basket hanging at a 45 degree angle to the horizontal. The basket and balloon struck the ground some 250 metres from the lines, bounced, and finally came to rest after sliding a further 40 metres.

Circumstances:

The pilot had purchased the aircraft some time prior to the accident and did not fly it until he had completed a full training course on gyroplanes of some 7-8 hours. Since completing the training, the pilot had flown about ten hours on type, mainly on windmill inspections on the property. The witnesses to the accident reported that the pilot had taken off on a windmill inspection and they had seen him return about 15 minutes later. As they watched from about one kilometre away, they saw the pilot approach the landing area at about 400 feet above ground level and commence a turn. The aircraft was then seen to nose over and continue in a dive until it struck the ground and exploded on impact. The South Australia Rotor Club was co-opted to assist with the investigation and through their assistance it was learned that this type of gyroplane was fitted with a large pilot cabin that extended some two feet in front of the rudder pedals. Other pilots have reported that this fitment induced severe pitch down in flight and/or severe yawing due to the imbalance of the air loads on the cabin compared to the correctional force available from the moments of an unmodified empennage. In effect, the anti-yaw moment from the rudder and fin is insufficient and the aircraft is without an effective horizontal stabiliser for effective anti-pitch control. A reduction of power at the onset of any perceived instability would be instinctive and would also reduce a pilot's ability to control the yaw due to the reduced propeller wash over the rudder and fin. The conclusions drawn from the investigation were that the pilot experienced a pitch down and/or yaw in flight that resulted in the imposition of negative g forces. These forces caused the retreating main rotor blades to dip and strike the fin and rudder. At the same time, the propeller would have disintegrated on contact with the rotor blades as they dipped into its arc. The blade strikes were such as to stop the main rotor and put the aircraft beyond the control of the pilot.

Significant Factors:

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

1. Faulty design. The aircraft was unstable when fitted with a large forward cabin.

2. An uncommanded DEPARTURE from controlled flight caused the main rotor blades to strike the propeller and empennage.

3. The rotor blades were stopped in flight rendering the aircraft uncontrollable.

Recommendations:

1. That the Civil Aviation Authority, in conjunction with the Australian Sports Rotorcraft Association (ASRA), advise all gyroplane operators of the design instability of the Wasp Air Buggy II when fitted with a large cabin.

2. That the CAA, in conjunction with the ASRA, devise and/or approve a suitable modification to the empennage of gyroplanes in conjunction with the fitment of large cabins.

3. That the short period oscillation of gyroplanes operated in Australia be examined. i.e. fit or replace the horizontal tailplane. A number of accidents in Australia can be attributed to DEPARTURE from controlled flight as a result of excessive pitching, (porpoising).

After taxiing trials and several low level hops 5 to 10 feet above the ground, the pilot commenced the takeoff for the aircraft's first test flight. He subsequently advised that the aircraft was slow to accelerate after lifting off at 45 knots. He maintained 10 to 15 feet above the runway and waited for the airspeed to build up before attempting to climb. During this period, the aircraft was buffetted by a gust of wind which caused loss of airspeed. The pilot lowered the nose of the aircraft, descended slightly, and managed to stabilize the aircraft at 47 knots with full throttle selected. Engine RPM appeared normal. The airspeed slowly increased to 57 knots and the pilot managed to climb the aircraft over the end of the runway. Video coverage of the flight suggests a maximum height of about 75 feet was attained. The pilot considered that either the engine was not delivering full power or that there was extraordinary drag associated with lateral gusts of wind. He turned towards the only suitable forced landing area, but the engine progressively lost power. The pilot manipulated the throttle, but power was not regained. Control of the aircraft was lost at a height of about 20 feet and it struck the ground with about 40 degrees of right bank and in a steep nose down attitude. The pilot later advised that as the engine failed, the aircraft's pitch stability decreased to almost neutral. He recalled a lack of elevator response seconds before ground impact. This is consistent with an occurrence during the low level hops when the pilot had been flying 5 to 10 feet above the runway with full power and had closed the throttle. The nose dropped despite the pilot's counteracting elevator input. Examination of the engine revealed that there was some binding in the Bowden cable to the enrichment valve resulting in a strong possibility that the valve was off its seat. This would have prevented the engine from achieving full power. In addition, a brass vacuum pipe insert to the crankcase was found to be loose. This pipe has a flexible hose attached which delivers low pulsation pressures from the crankcase to one side of the diaphragm within the mechanical fuel pump. With the crankcase pressures being able to escape past the threads of the loose pipe there was the potential for the engine to fail because of fuel starvation as the pump became inefficient, especially after the pilot closed the throttle.

The pilot had recently finished modifying his Benson style Rotorcraft and he was attempting to have it ready to participate in the annual Sports Aircraft Association of Australia fly-in at Serpentine which was planned for the weekend following the accident. The pilot had not flown since he commenced work on the modifications over twelve months prior to the accident. The Technical Committee from the Rotorcraft Club of WA Inc. inspected the aircraft and its modifications on the day before the accident and they required some changes to be made before the aircraft was flown. Some of the committee members also advised the pilot that he should have an experienced, current pilot with him when he test flew the aircraft. A friend, who was not a Rotorcraft pilot, accompanied the pilot to the Club's flying area on the afternoon of the accident and helped prepare the aircraft for flight. The aircraft became airborne after spending some time taxying around on the ground. The pilot carried out a number of turns. In one turn, the aircraft was also seen to climb and descend, before entering what appeared to be a controlled, steep descent. The aircraft did not completely recover from the descent before it collided with the ground and the pilot was killed. The accident occurred after sunset and just prior to official last light on the dry bed of a salt lake. An inspection of the wreckage did not disclose any faults with the aircraft that may have contributed to the accident. The engine was delivering power at the time of impact.

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.

The aerodrome caretaker had been requested to inflate a tyre on one of the operator's aircraft. The engines of VH-IGT were operating when the pilot observed the caretaker approaching, carrying a battery which powered an air pump. The caretaker walked around the tail of the aircraft, placed the battery near the right wheel, moved to the wing tip and proceeded towards another aircraft. He then realised he had taken the battery to the wrong aircraft and returned, walking directly towards the right engine. The pilot attempted to shutdown the engines but the caretaker continued forward and was struck by the rotating propeller.

Following a normal flight the aircraft was established on final approach for landing. At about 140 feet above the ground the approach angle flattened and the nose pitched up. The co-pilot who was flying the aircraft believed that a windshear situation had been encountered and he initiated a go around. As full power was applied the nose pitched up violently. The crew did not observe any cockpit indications as to the reason for this reaction. The pilot in command took control of the aircraft and initiated a rolling turn. This had the effect of reducing the pitch angle and by manipulating power levers and rolling the pilot was able to regain control of the aircraft at about 6500 feet. A safe landing was subsequently carried out. Witnesses later reported that they observed that the aircraft had reached pitch and bank angles of 60 and 80 degrees respectively. The investigation did not reveal any fault with the aircraft or its systems which might have accounted for the incident. An analysis of the Flight Data and Cockpit Voice recorders indicated that the stabiliser trim had been operated 11 times in the two minutes of flight leading to the call for full power. The trim had been operated in bursts of about one second except that just before full power was applied the trim was operated for almost 10 seconds. The co-pilot had indicated that he had used the trim to reduce the aircraft speed during the approach. It was considered likely that he had either inadvertently kept the trim switch depressed or had experienced a brief electrical relay fault which resulted in full nose-up trim being applied. Shortly after the pilot in command had assumed control the trim was operated for a further 12 seconds presumably as nose down-trim was applied. Neither crew member recalled hearing the trim "clacker" operating. The audio level of this was low and it was likely that the device may not have been heard above the ambient noise level. Because there had been no indication of the cause of the initial pitch-up the crew had difficulty in determining the appropriate course of action. Although the investigation revealed that the initiating factor was probably a full nose-up trim situation the crew believed the problem was caused by a structural failure or a thrust reverser malfunction.

The pilot was carrying out solo circuit training. On this landing the aircraft was reportedly affected by a strong crosswind gust and collided with the airfield boundary fence.

During the later stages of the approach the aircraft developed a higher rate of descent than desired. The right main gear subsequently struck a sand filled drum which was located just short of the threshold lip. The impact resulted in the right wing being buckled and one of the right engine mounts fracturing. The pilot reported that he did not believe that the landing was heavy and as a consequence did not discover the damage on a subsequent superficial inspection before continuing the flight. The approach was flatter than normal and into a 20 to 30 knot wind. On late final the aircraft encountered a downdraught and the pilot did not arrest the rate of descent, resulting in the touchdown occurring prior to the threshold.

The glider was winch launched to a height of 900 feet above the ground. The pilot was unable to find any strong lift, and when the glider had descended to 600 feet the pilot rejoined the circuit for landing. Some sink was experienced on the downwind leg and the glider was only about 200 feet above the ground when the base turn was made. During the turn onto final approach, the right wing of the glider struck the ground. The aircraft swung sharply to the right and subsequently landed heavily. There was no other traffic in the area and the pilot could have modified his circuit and landed on a cross-strip. It was likely that he had attempted to land the aircraft close to the winch launch cable to facilitate the next flight.