Wirestrike

The pilot was assisting stockmen to move cattle through a gate when one animal broke away. While manoeuvring to cut off the escaping animal, the helicopter struck a single wire power line which traversed the area. The power line was approximately 11 metres above ground level at the point where the collision occurred. The impact caused the main rotor to sever the tailboom and the helicopter fell to the ground and caught fire. The pilot was aware of the location of the power line and had been working in close proximity to it prior to the accident. This occurrence was not the subject of an on-site investigation. The information was provided by witnesses to the accident.

At the conclusion of a mustering operation, the pilot flew to a neighboring property. He made an approach to a line of the houses at the property but no-one came out to meet the helicopter. He then decided to hover-taxy to a shed some 90 metres away and land. Whilst taxying the helicopter at about 10 knots, the pilot suddenly noticed a three phase power line immediately in front of him, angled at about 30` to his track. He attempted to avoid a collision by initiating a back-up but the mainrotor mast and tailrotor became entangled in the three wires. The bubble was smashed by a flailing wire as the helicopter descended out of control. The ensuing landing was heavy, resulting in a collapsed left skid gear. The helicopter remained substantially upright. The pilot later said that the power poles supporting the span were obscured by trees.

Circumstances:

The aircraft departed on a flight to the Lake Eildon area. Subsequently, witnesses observed an aircraft, fitting the description of VH-GGS, operating at heights up to 200 feet above the ground/water level. The aircraft was later sighted near Woodfield flying at about 150-200 feet above the ground, tracking approximately north towards high ground, where it appeared to fly very close to the top of a hill. There were no witnesses to the remainder of the flight. Country Fire Authority personnel, investigating a reported sighting of smoke, discovered the burning wreckage of VH-GGS, surrounded by a grass fire. The aircraft had struck a single wire powerline, the impact severing the outer 1.3 metres of the right wing before the aircraft struck the ground 135 metres beyond the initial impact point. The wire was about 10 metres above the ground at the point of contact and strung between widely spaced poles that were difficult to see. Wreckage examination was limited by the extreme fire damage, but no evidence was found of any defects which might have contributed to the accident. The passenger knew a family at Lake Eildon. He had told them that he might fly over their property to let them know he was in the area.

Significant Factors:

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

1. The aircraft was intentionally operated at low altitude.

2. The pilot apparently did not see the powerline in time to take avoiding action.

Circumstances:

Prior to landing in a large paddock, the pilot advised the passengers that the balloon would touch down after it passed a dead tree about halfway along. The passengers assumed the pre-briefed crouched position and braced themselves for the landing. Just after the balloon passed the dead tree one of the passengers observed two power cables running across the flight path five metres in front of the balloon. The pilot was alerted and almost simultaneously, the balloon's suspension cables struck the power line. After contact, the balloon slid along the conductors for approximately 30 metres, pulling them downwards, until the basket contacted the ground. One passenger reported receiving an electric shock causing the pilot to order an evacuation and he and two passengers left the basket. The pilot was later observed reaching towards the balloon from outside the basket. Both the pilot and the passenger, who had remained in the basket, were electrocuted. Fire subsequently destroyed the balloon. The power cables ran across the paddock in a single span with a distance between the poles of 366 metres. The supporting poles were in adjoining paddocks and hidden by trees. The type and layout of the cables made them very difficult to see. Evidence indicates the pilot was not aware of the location of the power line prior to the flight, and he did not see them until just prior to impact and at that point it was too late to avoid them. The retrieval crew were following the balloon and did not arrive at the landing site until after the accident. The power cables made contact with the uninsulated, inadequately bonded envelope suspension cables attached to the two forward corners of the basket. There was some evidence that a lack of bonding may have caused an electrical potential difference across the basket which in turn led to the shock reported by the passenger. It could not be determined which of the metal components the pilot and passenger were touching when they were electrocuted. Injuries received by the pilot and damage to the fabric covered metal parachute vent line, indicated that it was probable that the pilot touched the vent line allowing the current to flow to ground. The fabric cover on the vent line was insufficient insulation for the magnitude of the current involved. Each of the power cables was protected by a fuse and although both these fuses worked, the failure sequence did not prevent the two fatalities. Had both cables been earthed earlier in the sequence, it is probable that the fuses would have blown thus protecting the balloon's occupants. The actions of the pilot and passengers indicated a lack of knowledge of safety practices to be used when in the vicinity of high voltage power cables.

Significant Factors:

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

1. The pilot was unfamiliar with the area where he intended to land and he was not aware of all the potentially dangerous obstructions, such as power lines.

2. The pilot did not see the power cables until it was too late to avoid them.

3. Inadequately insulated and bonded balloon components which came into contact with live power cables and a lack of a suitable method of safely grounding the balloon after power line contact.

4. There was a lack of adequate knowledge of safety practices to be used when in the vicinity of high voltage power cables.

Recommendations:

It is recommended that the Civil Aviation Authority, in conjunction with the Australian Ballooning Federation and Commercial Balloon Operators, reassess existing requirements for commercial balloon operations and surveillance of standards and in particular give consideration to

1. Introducing a requirement that operators of fixed duration flights, be required to have adequately surveyed all proposed landing sites within its area of operations.

2. Ensuring as far as practicable, that at least one member of the retrieval crew is either present at the proposed landing site, or in such other position as to be able to brief the pilot on obstacles and assist with rapid deflations and evacuations as required.

3. Introducing a safety education program which provided pilots with advice on electrical contact safety procedures.

4. Redefining the Flight Manual Emergency Landing procedures concerning the briefing of passengers before ground contact, with particular emphasis on orderly basket evacuation and electrical contact safety procedures.

5. Initiating manufacturer approved methods, of reducing the amount of exposed metal and providing electrical bonding of all metal components, to achieve neutral electrical potential difference between any two components.

6. Initiating a research and development program into on-board, electronic, directional, power line detection devices.

7. Initiating a research program into whether or not a pre-touchdown electrical grounding device should be fitted to all balloons

On arrival at the property, the pilot landed the aircraft in front of the homestead. A short time later he departed with the property owner on board for a cattle spotting flight. On returning to land, again in front of the homestead, the aircraft hit a single powerline, pitched nose up and fell to the ground inverted. The pilot stated that he was not aware of the presence of the powerline prior to colliding with it.

Nearing the completion of the task the aircraft struck a single power line. The aircraft remained airborne but the pilot decided to land in a paddock and assess the damage. He found that the top 30 centimetres of the rudder had been torn off. Prior to spraying the paddock, the pilot had physically checked the position of the powerline. During the application he had flown under it at least 12 times but whilst considering the best method to complete the clean-up runs, he forgot about its presence. The front mounting of the wire deflector had been attached to the top of the fibreglass cockpit and not mounted onto the solid roll-cage framing. When the powerline contacted the wire deflector, the fibreglass failed and allowed the deflector wire to sag under the imposed load. This allowed the powerline to run a lower path and sever the rudder substantially below the rear deflector attach point.

The pilot was conducting spraying operations over an irregularly shaped paddock. Power lines were located along two sides of the paddock. At the end of a clean-up run conducted parallel to one set of the lines, the aircraft struck and severed two wires which crossed its path. It then yawed sharply and collided with the other wires, before impacting the ground in a steep nosedown attitude. During the ensuing short ground slide both the engine and the rubber fuel tank were torn out. The pilot later advised that he had been aware of the power lines, but had temporarily overlooked their presence.

The aircraft was to spray a paddock of rice with a non-toxic herbicide. The pilot carried out an aerial survey of the area prior to commencing the spraying. During the survey he noted that a spur powerline ran to a pole at the north-eastern corner of the paddock, and mistakenly assumed that the line ended at the pole. No other information about the area to be treated was obtained. As the aircraft approached from the north to commence the first spray run it struck the continuation of the powerline which was strung above the northern boundary of the paddock. The aircraft remained airborne, dragging between 200 and 300 metres of powerline, and was subsequently landed in a wheat stubble paddock.

At the end of each spray run to the east, the aircraft was flown under a power line before the turn to change direction was commenced. Several runs had been completed when the pilot climbed the aircraft to commence the turn and the aircraft collided with the power line. The pilot dumped the remainder of the load and the aircraft continued to fly, trailing the power line. After travelling a short distance the aircraft apparently stalled and struck the ground in a nose down attitude. A fire broke out and completely engulfed the wreckage. The pilot subsequently advised that he had temporarily overlooked the presence of the power line. It was probable that on this particular spray run a pole supporting the wire was no longer in the pilot's field of vision. The severed wire became entangled around the right wing and lift strut, resulting in bending of the strut and probably inducing stalling of the wing.

The pilot had arranged to meet his son at the Barooga airstrip. Although he had overflown the strip on several occasions he had never previously operated into the strip. After arrival, he was requested to take some friends for scenic flights over the local area. On final approach, on the second of these flights, the aircraft struck powerlines which were strung across the eastern end of the strip, about 85 metres prior to the threshold. The aircraft struck the ground in a nose down attitude 25 metres beyond the powerlines and came to rest inverted. The pilot was unaware of the existence of the powerlines and had not sought the owner's approval or ascertained the strip condition and dimensions before commencing the operation. The poles supporting the powerlines were adjacent to tall trees which resulted in them being difficult to see. Also, it was late afternoon and the approach was being conducted into the west.