Wirestrike

Earlier in the day the pilot had flown VH-MDI from a mining camp at Windy North to Broome. On arrival at Broome, at 0913 hours, the pilot was handed a completed flight plan by his Chief Pilot, and briefed for two flights to Koolan Island. The purpose of these flights was to convey nine or ten passengers from Koolan Island to Derby. The aircraft was subsequently refuelled to full tanks and departed Broome at 0956 hours arriving at Koolan Island at 1103 hours. After loading five passengers and their luggage, the pilot taxied the aircraft for take-off from runway 23. Runway 23 is 810 metres in length and has an overall uphill slope of 1.17 percent. The wind at the time was a direct crosswind of between 10 and 15 knots. The aircraft became airborne approximately 54 metres before the end of the runway. It was observed to descend into a small ravine off the end of the runway, then climb steeply and strike power lines before impacting the ground in a near vertical nose down attitude. Following the impact, the aircraft cartwheeled once and burst into flames. Investigation disclosed that the take-off had been commenced from a point approximately 50 metres in from the threshold of the runway. The all-up-weight at the commencement of the take-off exceeded the maximum permitted for the runway selected by about 320 kilograms, given the prevailing conditions. Examination of the wreckage did not reveal any evidence of mechanical defects which could have contributed to the accident. This was the first time the pilot had flown a Cessna 210 type aircraft into Koolan Island although he had been checked on island operations in a different aircraft type by the Chief Pilot.

Prior to the commencement of the spraying operation, the pilot carried out an aerial survey of the area noting the position of all wires. On the first run, the aircraft was flown under both sets of wires. When the run in the opposite direction was commenced, the pilot intended flying the helicopter over the first set of lines and under the second set of lines. However, the helicopter collided with the second set of lines and impacted the ground 70 metres beyond the wires. The pilot stated that he had forgotten about the second set of wires and was flying the aircraft higher above the crop than normal. The previous night the pilot had had a disturbed sleep and was probably suffering some fatigue.

Prior to the flight the pilot checked the strip details with the owner. These included advice that there was a powerline on the approach. On arrival the pilot located a powerline near the north-east end of the strip. He assumed that this was the one to which the owner had referred, and decided to land from the opposite direction. On final approach, he saw a single wire powerline ahead and attempted, unsuccessfully, to fly beneath it. The aircraft yawed violently to the left as it struck the wire, but the pilot was able to regain control and safely land the aircraft. Post-flight inspection revealed that a section of the fin and the complete rudder assembly had been torn from the aircraft. The point of impact with the wire was 262 metres short of the strip threshold and occurred when the aircraft was at a height of about 30 feet above the ground. The span between the poles supporting the wire was 333 metres, and the poles were difficult to see against the background.

In the pre-take-off briefing the instructor advised the student that during the flight they would conduct an inspection of the power lines crossing the Herbert River. The student subsequently flew the aircraft, in accordance with the instructor's directions, at about 100 feet above the river. The instructor was aware of four power line crossings. After passing the first, and when en-route to the second, the pilots heard a scraping sound and the aircraft slowed. Despite the attempts of the pilots the aircraft nosed down and subsequently struck the surface of the water at a shallow angle. Investigation revealed that the aircraft had collided with a power line, the presence of which was unknown to the instructor and had not been seen by either pilot. One of the supporting poles was obscured by trees, while the other pole was located approximately 350 metres across the river in a sugar cane plantations. All the wires were estimated to be 100 feet above water level.

Circumstances:

The pilot was involved with a group of Venturer Scouts on camp in Tasmania. At the time of the accident, about 20 members of the group were involved in water skiing activities at Meadowbank Lake. The pilot had earlier arranged to make two scenic flights to Cox Bight in the State's south-west for members of the group. He had also told one of the scouts that he would fly past them at the lake. The lake was on the planned track to the south-west and the flight on which the accident occurred was the first of the two planned flights. The lake is approximately 13 kilometres long and lies generally in a north-west/south-east direction. The aircraft was seen approaching from the north-west over the lake at low level. It flew past the group which was located on the south-west bank of the lake. The occupants could be seen waving to those on the shore. Shortly after passing the group, the aircraft hit the top wire of a three wire powerline that was suspended across the lake at a height of about 12 metres above the water. The wire first impacted the left main wheel and then slid up the wheel leg. The wire broke at the poles from which it was suspended either side of the lake. It was then dragged some distance by the aircraft. The two poles were approximately 300 metres apart. The aircraft continued for about 500 metres before diving into the water. The powerline would have been very difficult to see from the aircraft. There were no hazard markers of any description on the powerline, and it would have blended into the background of cliffs on the edge of the lake.

Significant Factors:

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

1. The aircraft was flown on a low altitude across the lake surface.

2. The powerline would have been difficult to see from the aircraft.

The pilot had been conducting spraying operations from the property during the day. Late in the afternoon he decided to position the helicopter to a new site located approximately 2 kilometres along the road to the south. He was joined by a passenger for the short positioning flight. There was no significant weather reported at the time of the flight and visibility was reported to be greater than 10 kilometres. The sun was setting and had descended below the hill tops to the west. The pilot stated that shortly after takeoff, glare from the setting sun obscured his vision. He descended until he was out of the line of sight of the sun and he then proceeded at that height until the helicopter struck power lines, which shattered the bubble and caused the nose of the helicopter to pitch up. The pilot was able to regain control sufficiently to carry out a run on landing. The pilot stated that there was no mechanical defect or malfunction which could have contributed to the accident. The investigation revealed that the bubble of the helicopter was slightly crazed but it was assessed as serviceable by the maintenance organisation and the pilot. The bubble was also found to be covered with a film of chemical spray. A witness who flew in the helicopter on the flight immediately preceding the accident flight stated that the condition of the bubble did not obscure vision through it. It is considered that the helicopter was being flown at an unsafe height and the pilot failed to see the power lines prior to impacting them. This accident was not the subject of an on scene investigation.

Circumstances:

The aircraft was carrying out a short familiarisation flight before beginning the day's powerline inspection program. On board were the pilot and the owner of the property being used as a temporary base for operations. The aircraft took off toward the east over a flat paddock, the pilot's intention being to turn north from a point near the centre of the paddock then to intercept an east-west powerline and to follow that line westwards. While still tracking east, at about 20 feet altitude, the aircraft struck and snapped a north-south powerline crossing the take-off path. The aircraft then continued forward for about 60 metres before impacting the ground and coming to rest five metres beyond the impact point. An eyewitness to the accident stated that he was 'almost certain' that he had informed the pilot of the existence of the north-south powerline when the aircraft had first arrived at the property, seven days before the accident. The pilot stated that he had no prior knowledge of the line. The aircraft had taken off from the pad at least three times and had landed at the pad at least four times since first arrival. All prior movements had been to the west of the pad, and the pilot had not been reminded about the line. Prior to take-off on the day of the accident, the pilot briefed the passenger about the proposed profile of the flight and asked the passenger for any comments. The passenger agreed with the proposed profile but did not mention the north-south powerline. The pilot looked to the east to note any obstructions but did not see the line which was very difficult to see from the take-off point. In addition, due to the relatively low position of the sun in the north-eastern sky, glare may have adversely affected his vision. Further, the flat, open terrain did not provide any visual cues to alert him to the requirement for obstruction clearance. However, the pilot did not closely inspect the take-off path from the ground. Examination of the wreckage did not reveal any defects in the aircraft which may have contributed to the accident. The performance capability of the aircraft was such that the climb gradient required to clear the powerline could have been easily achieved.

Significant Factors:

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

1. The pilot did not closely inspect the proposed DEPARTURE path for obstructions prior to take-off.

2. The line was very difficult to see from the take-off point. Glare may have aggravated this problem.

3. The flat, open terrain, without obvious obstructions along the take-off path, provided no cues alerting the pilot to the need for obstruction clearance.

Circumstances:

The pilot was operating from an agricultural airstrip which was aligned north-south. A powerline, approximately 6 m above ground level and located 220 m from the northern threshold, crossed the approach path at an angle of 60 degrees. The pilot elected to take off into the light northerly breeze, flying under the powerline, and to approach over the wires, landing into the south. He determined his descent point by sighting along the run of the power poles, the nearest of which was partially obscured by trees. During his third approach to land, the pilot had forgotten the powerline until sighting it as it was about to pass under the aircraft nose. He applied full throttle and raised the aircraft nose too late to prevent the main landing gear from contacting the powerline. The aircraft impacted the ground in a near-level attitude, 108 m from the point of contact with the powerline and travelled a further 29 m before coming to rest. Both cables of the powerline were dislodged from 9 poles, 1 of which was broken. One cable was broken but remained caught in the left main landing gear. The pilot vacated the aircraft as a fire quickly spread from the engine area to the wings and fuselage.

Significant Factors:

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

1. The pilot did not adopt an appropriate procedure for avoiding the powerline.

2. The pilot forgot the presence of the powerline. 3. The pilot saw the wires too late to avoid colliding with them.

During the approach, the aircraft gear struck a set of three power lines. The pilot said that he misjudged the clearance over the second set of power lines located at the north-western end of the strip.

Circumstances:

The aircraft had been delayed in servicing and repair and had only been released six weeks prior to the accident. This delay had caused the operator/pilot to fall behind in his commitments and, according to some witnesses, caused him to worry about the situation. On the day of the accident, the pilot had just completed spraying a 243 hectare paddock and had landed to reload. After take-off for the new task, the pilot was seen to make an aerial inspection of the paddock before entering the first swath run. At the end of this run, the aircraft collided with a Single Wire Earth Return (SWER) powerline and crashed. It was later shown that the aircraft was in a bank to the right of about 18 degrees. The SWER line ran across one end of the paddock at an angle and on the crop side of a windmill just inside the fence which bordered the road. The line contacted the right main gear and outboard spray boom attachment struts on the right wing. The wire broke after impact, but the aircraft hit the ground heavily on the right main gear. The gear detached from the aircraft, the propeller struck the ground and the aircraft slewed around as it came to rest after some 27 metres of ground travel. The front half of the aircraft was destroyed by fire which broke out almost immediately the aircraft stopped. Two main hypothesis were proposed. One was that the pilot was distracted from a less than demanding task by business worries. The other was that the pilot had perceived that the SWER line was on the right of the windmill and outside the fence and therefore did not present an obstacle to his procedure turn. Neither hypothesis could be substantiated. An additional concern was the fact that the pilot had died from impact injuries in an accident that, prima facie, was survivable. Concern focused on whether the pilot had secured his harness properly and/or whether the inertia reel had failed. Detailed engineering inspection of the inertia reel by the Bureau and the manufacturer could not positively determine the mode of operation of the inertia reel. However, the postmortem report showed that the nature of injuries to the pilot, while sufficient to cause death prior to the fire, were such as to indicate that the inertia reel had probably not failed.

Significant Factors:

The following factor was considered relevant to the development of the accident:

The pilot did not see the powerline in time to avoid a collision.