Wirestrike

Before commencing operations, the pilot had carried out a detailed survey of the area and noted that a power line crossed the particular paddock to be treated. On the second spraying run the pilot temporarily forgot the presence of the power line, and the gear legs collided with the wires. The aircraft subsequently struck the ground in a steep nose-down attitude and cartwheeled for 30 metres before coming to rest with only the cockpit area still intact.

An early morning flight was arranged between the owners of the Gipsy Moth VH-UQV and the owner of a Tiger Moth VH-DDA with the intention of photographing the Gipsy Moth from the air. The owner of VH-DDA agreed to fly in the Gipsy Moth and occupy the rear seat whilst the pilot-in-command occupied the front seat. The Tiger Moth was flown by the other owner of the Gipsy Moth. The Gipsy Moth was flown by the rear seat pilot for the first part of the flight. At the completion of the photography, which was conducted in the circuit area at Maitland, the pilot-in-command took control of the aircraft. The aircraft was flown to the north-east of the aerodrome to the Hunter River where it was descended to fly at a low height over the river. With the pilot in-command still at the controls, the aircraft returned to the aerodrome at a height of about 500 feet. After passing the aerodrome southern boundary, the aircraft entered a steep turn to the left. The non-flying pilot in the rear seat reported the aircraft, whilst passing through a north westerly heading, was rolled to the right to avoid a tree. The right wing struck and severed a cable of an 11,000 volt power line causing the aircraft to cartwheel into the ground, within the aerodrome boundary. This accident was not the subject of a formal on scene investigation.

Circumstances:

Towards the completion of a scenic flight with five adult passengers on board, the pilot descended the balloon to a height of approximately 200 feet above ground level and commenced searching for a suitable landing site. His initial selection was subsequently abandoned to avoid frightening an injured horse. The balloon with limited fuel remaining continued at low level, passing over timbered country before commencing a deflated landing into a semi cleared area. The area was surrounded by tall trees to the left, right and rear of the flight path. A two-wire high voltage set of powerlines located just ahead of the pilot's proposed landing area, were not sighted by a ground retrieval crew member, who was in the vicinity of the landing site and in radio contact with the pilot, nor apparently by the pilot until late into the landing. The passengers had not been briefed to assist in observing for and reporting powerlines. The pilot then issued instructions which his passengers understood to mean that they prepare to exit the balloon basket. When approximately one metre above the ground, the first passenger evacuated the basket followed by the pilot, who had the fabric covered metal parachute vent line wrapped in a spiral around his forearm. With the load reduced the balloon began to ascend. One flying wire supporting the balloon basket at the lower section of the balloon envelope, contacted the powerlines before the balloon descended again. An electrical discharge was heard, and one powerline was severed. As the basket neared the ground a second and third passenger exited. The pilot was then observed lying on the ground fatally injured, apparently having received a high voltage discharge via the parachute vent line. The line had then detached from around his forearm. A fourth passenger then vacated the basket, leaving one passenger on board. With the release of the parachute vent line the exhaust vent closed and as there was still sufficient buoyancy retained within the envelope, the balloon slowly re-ascended. When at an estimated height of 10 metres above the ground, the remaining passenger was observed to fall from the balloon basket and receive fatal injuries. The balloon continued to drift for approximately two kilometres before settling to the ground in heavily timbered country. The pilot's technique of wrapping the parachute vent line around his wrist and forearm would have made rapid deflation difficult. His actions in preparing passengers to jump and his decision to exit the basket prior to landing, were totally alien to the normal and emergency modus operandi. It is believed that a previous similar type fatal accident involving a balloon colliding with a powerline, may have influenced his behaviour. Subsequent trials indicated that it is extremely difficult to evacuate all passengers from a basket in a short time frame without pre-warning, established drills, and orderly implementation. The weather conditions were calm and clear, but the early morning ambient light conditions would have made detection of the powerlines difficult. The area selected for the landing was the only alternative available considering the meteorological conditions and fuel remaining. The size of the area should have been within the capabilities of the pilot and balloon had there been no powerlines across the flight path. Stringent obstacle clear gradient requirements exist for the selection of take-off sites, but not for landing sites. Despite some instrumentation deficiencies, the balloon and all of its relevant equipment was serviceable and had been maintained in accordance with approved procedures. Electrical bonding and insulation properties of the balloon were considered to be inherent design deficiencies for this type of aircraft, thereby permitting differing electrical potentials to exist between individual components, particularly in the event of powerline contact.

Significant Factors:

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

1. The aborted landing to avoid injured stock placed the pilot in an emergency landing situation.

2. The lack of timely detection of powerlines deprived the pilot of vital pre-landing information.

3. The evacuation of the basket prior to touchdown made pilot control of the balloon buoyancy difficult.

4. The pilot could not deflate the envelope before the balloon ascended into the powerlines.

5. Lack of effective electrical insulation and bonding properties facilitated the conduct of the electrical discharge to earth.

6. The pilot received a fatal electrical high voltage charge through the parachute vent line which was wrapped around his forearm.

7. The balloon contained sufficient buoyancy to ascend after the parachute vent line became free and the parachute vent closed.

8. The pilot's actions may have been influenced by a similar previous accident.

Recommendations:

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

1. Initiating a research and development programme into an on-board, electronic, directional, powerline detection device.

2. Redefining the Flight Manual Emergency Landing procedures concerning the briefing of passengers before ground contact, with particular emphasis upon orderly basket evacuation methods.

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

4. Defining minimum obstacle clear approach parameters and gradients for commercial balloon landing sites consistent with balloon size and prevailing meteorological conditions.

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

The pilot had been conducting superphosphate spreading operations in the area two days prior to the accident and had completed approximately 60 trips during that operation. On the morning of the accident, he had just completed the sixth load when the outboard section of the right wing struck powerlines. The right wing was torn from its attachment points and separated from the aircraft. The aircraft then impacted the ground in a steep nose down attitude and came to rest 169 metres from the powerlines. A detailed examination of the aircraft and its systems failed to reveal any defect which could have contributed to the accident. The engine was operating at high power at the time of the impact. It is probable that the pilot forgot about the presence of the powerlines. It was noted that the pilot was not wearing a shoulder harness and that an unapproved modification had been made to the lap harness. The toggle fitted to the lap harness was a type approved for 9 to 12g applications only and therefore was not suitable for agricultural operations, which require equipment capable of withstanding 25g loads.

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.

The aircraft had been engaged in spraying cotton fields in generally turbulent flying conditions. Power lines crossed one end of the area at an angle of about 20 degrees to the direction of the swath runs. At their lowest point, these wires were about 10 metres above the ground. The pilot reported that as he approached the power lines, intending to fly underneath at the lowest point, the aircraft ballooned upwards in turbulence. Despite corrective action the cockpit mounted wire deflector struck the lines. The deflector was broken and much of the fin and rudder was torn from the aircraft, which subsequently impacted the ground about 800 metres from the power line.

Spraying runs were being conducted over a paddock which had power lines along one boundary. The pilot had been passing beneath the lines during each run, however after completing about two thirds of the task the wire deflector on the aircraft snagged and broke the powerline. The pilot carried out a precautionary landing and discovered that the rudder of the aircraft had been substantially damaged by the wire strike. At the point where the wire strike occurred there was less clearance between the wires and the ground than that available during previous swath runs. The pilot was aware of the situation, but had been subject to a visual illusion, which had led him to believe that there was sufficient clearance to allow the aircraft to pass beneath the wires. By the time he realised that the clearance was insufficient he was unable to take avoiding action, and had elected to allow the wire to strike the deflector, rather than risk the landing gear contacting the ground. The anti-snag deflector plate on top of the rudder had failed, allowing the wire to contact the rudder. The upper portion of this component had then been torn from the aircraft.

The company chief pilot, who holds an Agricultural 1 Rating, accompanied the pilot on the ferry flight. They surveyed the paddocks to be sprayed from the air before landing at a nearby agricultural strip where they discussed the order of work with the farmer and studied a local map. The pilot prepared a diagram of the paddocks and plotted wires and obstacles. The aircraft was then loaded with liquid chemicals and the pilot sprayed the first paddock while the chief pilot remained at the airstrip. Weather conditions were a light south westerly wind, with excellent visibility. After spraying the first paddock, the aircraft was reloaded. The pilot circled the second paddock before flying a spray run in a southerly direction between a highway and a railway line. During the run the pilot glanced at the boom pressure gauge and adjusted the setting. As he approached the railway line he commenced a pull-up during which the undercarriage struck a railways communications wire. The wire was about 4 metres above the ground and ran parallel to and just north of the railway line. Realizing that the aircraft had caught a wire, the pilot commenced a gentle, left turn starting at about 50 feet above the ground with the intention of landing as soon as possible in a safe area. During the turn, because of the drag of the wire, the aircraft vibrated and lost airspeed, despite the application of full power. After the turn the aircraft stalled from about 20 feet with wings level. The aircraft struck the ground in a slightly nose-low attitude and slid for 42 metres before coming to rest south of the railway line. Approximately 140 metres of wire was found trailing from part of the spray boom which had detached from the left wing and was located 5 metres behind the aircraft. The communication wires about 10 metres north of the railway tracks were the only significant obstruction near the crop. The steel poles supporting the wires were spaced reasonably close but the spray run was midspan such that the poles did not assist depth perception. The pilot could see the wires ahead at the end of the run. The wires were too low for the aircraft to fly beneath. It was the pilot's intention to fly over the wires. The pull-up was late and too shallow. The pilot had been given 17 hours flight training under close supervision by his employer immediately before commencing operational flying. At the time of the accident he was flying in a suitable area for an Agricultural 2 rated pilot with low experience.

Circumstances:

When nearing its destination after a flight of about three hours, the helicopter struck a set of power lines, eight metres above ground level, spanning a ridge line. Witnesses described flight path as "quite low and fast" compared to other helicopters they had observed approaching the Airport. Examination of the wreckage revealed wire strike damage to the upper surface of one blade, suggesting that the helicopter was in powered forward flight when it contacted the wires. A test run of the engine found it to be capable of normal operation.

Significant Factors:

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

1. The pilot crossed the ridgeline at low level.

2. The pilot did not see or avoid the power line. This accident was not the subject of an on-scene investigation.

Circumstances:

On the day before the accident, the pilot had been mustering cattle on Cukadoo Station which is the neighbouring property to Nithsdale. The owner of Cukadoo had accompanied the pilot during the mustering operation, which was close to the accident site. The pilot had flown over a single-wire powerline several times during the day and remarked that he would have to be careful of the powerlines. This was a spur line which joined the main line (which the helicopter struck) at right angles, approximately 1.4 km from the accident site. Late in the afternoon the pilot flew to Mt Isa, where he remained overnight, with the intention of returning to his own property in the Northern Territory the next day. During the evening, he had telephoned the owner of Mt Ryde Station west of Longreach, where he had cattle on agistment. The cattle were being driven to another property in the Northern Territory recently purchased by the pilot. The pilot was told that some of the cattle were still at Mt Ryde, and he became very concerned. The pilot said he would come down to Mt Ryde to resolve the matter. At about 0930 the next morning the sound of a helicopter was heard passing near Cukadoo homestead 200 km southeast of Mt Isa at very low altitude. Initially it appeared that the helicopter was going to land there, but the noise receded towards the southeast without the helicopter being sighted. About 5 minutes later the electricity supply to the homestead failed. Later in the day the wreckage of the helicopter was discovered by linesmen who were investigating the cause of the electrical supply failure. The helicopter had struck the Single Wire Earth Return (SWER) 19 Kilovolt line 9.5 km southeast of Cukadoo homestead. The wire was struck approximately mid-span between supporting poles 400 m apart, and about 7.5 m above ground level. The line was aligned approximately at right angles to the south-easterly flight path of the helicopter. The wire impacted the nose of the helicopter at about floor level, causing the helicopter to pitch nose-down, and the main rotor to sever the tail boom. The helicopter then impacted the ground and burned. Wreckage distribution indicated that the helicopter may have been at cruising speed at the time of impact with the wire. The location of the accident was approximately on track between Mt Isa and Mt Ryde. The powerline was in flat open grassland which could cause the poles to blend with the background. At the time of the accident the weather was fine, but there was a 10 to 15 knot south-easterly wind, and it appears that the pilot may have been flying at low level in an attempt to conserve fuel. There were no mechanical defects discovered which may have led to the development of the accident.

Significant Factors:

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

1. The helicopter was being flown at an extremely low height.

2. The pilot failed to see or avoid the powerline.