While returning to the airfield the glider experienced a deterioration of lift and the pilot decided to carry out a landing on the Stuart Highway. The pilot observed two vehicles on the road and attempted to warn them of his intention to land. The first vehicle stopped but a bus following, continued along the roadway. The pilot decided to land before reaching the bus. After touchdown the pilot moved the glider to the side of the road but the left wing struck a road sign then a tree. The glider slewed off the road and the landing gear was torn off. The pilot was forced to accept a collision with known obstructions in order to avoid the bus. The countryside in the vicinity of the highway was considered unsuitable for an outlanding.

The aircraft was observed to head in a northerly direction after take-off. About 20 minutes later, the witness saw the aircraft, which was flying at an altitude of about 80 feet, returning. As he watched, the aircraft appeared to turn to the right and roll inverted, before disappearing behind trees and buildings. The aircraft struck the ground in a steep nose down attitude. The aircraft impacted the ground at about the base turn position. An inspection of the aircraft did not reveal any fault which may have contributed to the occurrence.

The pilot was competing in the Hinkler Bi-Centennial Air Race. Earlier in the day the aircraft had made a forced landing near Roma due to a propeller oil seal failure. Following repairs by the owner/pilot the aircraft departed Roma for Charleville. At approximately 1740 hours the pilot made a PAN call and advised he was shutting the engine down due to another propeller oil seal failure. During the subsequent forced landing the pilot had to swing the aircraft left to avoid a tree. The aircraft hit an anthill, causing the landing gear to collapse. The pilot received facial lacerations. Investigation revealed that the moulded leather propeller seal had failed in the area of the moulding. It could not be determined if the second propeller seal failure was associated with the change of the seal following the first propeller seal failure. This accident was not the subject of an on-scene investigation.

At the time of the attempted take-off, the night was dark, with overcast cloud conditions and light rain falling. Wind conditions were light and variable. The pilot reported that initial acceleration was normal, and the aircraft became airborne at about 95 knots. A positive rate of climb was established and the landing gear was selected up. The pilot subsequently advised that the speed then decayed to 90 knots. At this time there was nothing unusual in the engine noise and the controls felt normal. Shortly afterwards the propellers struck the ground 116 metres beyond the end of the runway. The aircraft then struck an embankment and passed through a fence before coming to rest 247 metres from the initial ground strike. Although wind conditions were light and variable when the engines were started, shortly after the accident the wind was moderate from the west/south-west. A detailed analysis conducted by the Bureau of Meteorology indicated that while the pilot was preparing for take-off, a cold front with winds in excess of 20 knots had probably passed over the aerodrome. As the pilot had conducted the take-off on runway 08, there was probably a substantial tailwind component. Conditions were also assessed as suitable for the development of microbursts, but the lack of recording instruments in the area prevented confirmation that this type of phenomenon had in fact occurred. The pilot had been deprived of the opportunity to observe changing wind conditions at the aerodrome. The wind direction indicator adjacent to the threshold of runway 08 was not lit, and the illuminated wind direction indicator was not visible from the point where the aircraft was lined up for take-off.

The aircraft was being taxied to a parking bay at the completion of the flight. The pilot observed a fuel tanker parked near the edge of his taxi- path and moved the aircraft so that the nosewheel was tracking 4.6 metres to the right of the marked lead-in line. Just after this the marshaller assumed the responsibility for directing the aircraft to the parking bay. He directed the pilot to taxi straight ahead but the left wingtip struck the rear of the fuel tanker. The aircraft was stopped and the passengers and crew evacuated. The tank of the fuel tanker was damaged but not holed, and about two metres of the outboard section of the left wing of the aircraft was bent. The fuel tanker had been positioned to refuel an Australian Airlines Jetstream aircraft. The rear of the tanker encroached slightly on the taxiway. It was revealed during the investigation that groundstaff responsible for the positioning of the tanker were unaware of the correct meaning of the various taxiway markings. They had believed that the markings at the edge of the taxiway indicated the limit of the area on which servicing vehicles could be parked. The markings, in fact, indicated the limits of the full strength and low strength pavement. Both the marshaller and the pilot misjudged the clearance between the wingtip of the aircraft and the tanker.

The pilot was competing in the Australian National Gliding championships. An outlanding became necessary when thermal activity declined and an approach was made to a dry field which was used for irrigation. On the downwind leg of the circuit, the pilot noted that a ditch crossed the field, however this ditch was not visible to him when on final approach. During the landing roll the glider collided with the ditch. The pilot had overflown a more suitable landing area, with the intention of making the outlanding closer to the destination aerodrome. The paddock ultimately selected was the most suitable in the vicinity, but required an approach between clumps of trees and alongside a power line. During the latter stages of the approach the pilot's vision was affected by sun glare.

The student was receiving training in forced landing procedures. The first three exercises were completed without incident. At the end of the fourth approach to the selected paddock, the student applied full power and initiated a climb, intending to return to 3000 feet for a further exercise. However, when the aircraft had reached about 1700 feet, the engine lost power. The instructor took control, but was unable to gain any response from the engine. The aircraft was landed in a paddock, and collided with a fence some 200 metres from the point of touchdown. Examination of the aircraft revealed that one fuel tank was empty, while the other tank contained about 7 litres of usable fuel. The engine had lost power when the fuel in one tank was exhausted, and air evidently entered the system, preventing normal engine response when the instructor selected the opposite tank. No dipstick had been available and the instructor, who did not rely on the aircraft fuel gauges, had made an erroneous visual assessment of the fuel quantity prior to DEPARTURE. The aircraft had flown for more than 5 hours since the last refuelling.

During the return flight from the gas production platform, passing 2300 feet on descent into Karratha, the crew and passengers heard a muffled noise from the rear of the helicopter. The aircraft continued the descent in controlled flight for a short period of time before it yawed violently to the left and rolled to approximately 90 degrees of left bank. The co-pilot was flying the aircraft at the time and he lowered the collective lever and placed the aircraft into an autorotational descent. However, the aircraft continued to yaw to the left so the pilot took the controls and with the assistance of the co-pilot a controlled autorotational descent was resumed. The descent continued, during which time the co-pilot carried out a number of actions associated with the loss of some of the aircraft systems and armed the flotation bags. Shortly thereafter, the aircraft again rolled violently to the left to a bank angle of approximately 130 degrees. The pilot was able to regain some control and rolled the helicopter to an upright position, however the descent rate had increased. As a result of the violent yaws, the pilots' headsets were flung from their heads making communications between them extremely difficult. During the final stage of the descent the co-pilot was able to retrieve his headset and broadcast a MAYDAY call which was received by Karratha Control Tower. Just prior to impact with the sea, the pilot pulled on full collective to reduce the descent rate and cushion the landing. The helicopter impacted the surface with a low forward speed and yaw, slightly nose low and banked to the right. The time interval between the first indication of a problem and impact was 45 seconds. Following impact, the aircraft capsized and floated nose low with both the cockpit and cabin doors submerged. The crew and surviving passengers exited the fuselage via windows and doors in the cockpit and cabin areas. However, escape was hampered by the immediate influx of the cloudy seawater and bubbles created in the water. Obstructions in the form of dislodged internal panelling and headset attachment cords also had to be negotiated, and disorientation due to the aircraft's inverted attitude and its angle of rest, had to be resolved before escape was possible. The co-pilot made two attempts to rescue the two unaccounted for passengers, but the aircraft sank in 13 metres of water before he was able to do so. The recovery team advised that it appeared that the two victims had attempted to escape but failed to reach safety. The 15 survivors were rescued by a small fishing boat that was operating in the area of impact. The bodies of the deceased and the wreckage were recovered later on the day of the accident. Prior to impact with the sea the aircraft had suffered an inflight break up. The break up began when one tail rotor blade failed approximately one third of the way out from the blade attachment point. The loss of this section of the blade resulted in severe out of balance forces which caused extensive damage to the tail rotor, tail rotor gear box and mountings, horizontal stabilizer, vertical pylon, aft section of the tail boom and the tail rotor controls and systems. The blade leading edge spar and skin had suffered from fatigue cracking which significantly reduced the blade's load carrying capacity. The blade failed when the remaining unaffected metal in the leading edge spar and skin could no longer carry the inflight loads imposed on the blade. The fatigue cracking had originated from a small indentation in the rear face of the leading edge spar. The indentation was caused by a misaligned jig key used during the construction of the blade and the damage was not detected by the manufacturer's quality control inspection procedures. The subsequent fatigue cracking of the spar was not discovered by the operator although the inspection procedures used were in accordance with the manufacturer's recommendations. The losses of control during the descent were the result of inflight losses of essential aircraft structure and systems. There was no information available to the crew about the handling characteristics of the aircraft with significant sections of the rear stabilizers missing. The information on the aircraft handling characteristics, during autorotational descent with the flotation system inflated, was contradictory and inconclusive, therefore the pilot elected not to inflate the flotation bags during the descent. The co-pilot had intended inflating the bags just prior to impact, but because of cockpit workload insufficient time was available. The helicopter was not fitted with a system which would automatically activate the flotation bags upon entry into water.

The pilot was on the final leg of a competition gliding exercise, when deteriorating lift made an outlanding necessary. Final approach to the selected paddock was into a 10 to 15 knot wind, but was also towards the setting sun. The pilot had difficulty in seeing ahead because of the sun glare, which was exaggerated by a thin film of dust on the canopy. The pilot failed to see powerlines ahead of the aircraft. Following collision with the wires, the aircraft struck the ground heavily. This accident was not the subject of an on scene investigation.

The pilot was undertaking an outlanding after failing to complete an attempted 150 kilometre soaring flight. The selected landing area was large and flat and was sparsely covered by grass. After a normal touchdown the aircraft rolled for about 100 metres before the landing gear collapsed. The aircraft slid for a further 50 metres before coming to rest with substantial damage to the fuselage undersurfaces. The pilot reported the landing surface was very rough, probably due to the earlier movement of cattle during wet conditions. He was not sure that the roughness of the ground could be determined from the air. This accident was not the subject of a formal on scene investigation.