History of the flight
The pilot of the Bell 206 helicopter had been tasked to conduct a powerline inspection for the local electricity power supply company (power company). The helicopter took off from Jandakot Airport at 0500 Western Standard Time and arrived at Northam one hour later. Two personnel from the power company boarded the helicopter at Northam, one acting as observer and the other as the powerline inspector. The pilot occupied the front right seat, the observer the left front seat and the powerline inspector occupied the left rear seat. The helicopter then transited to the Bonnie Rock area to commence the inspection. The inspection progressed in a westerly direction from Bonnie Rock to Beacon with the helicopter flying parallel to, and on the northern side of, the main powerline.
At approximately 0800, the pilot discontinued the powerline inspections and flew the helicopter to Koorda for refuelling. After refuelling, the crew commenced the inspection of the powerline between Beacon and Bencubbin townships, flying south on the western side of the main powerline. At 1100 the pilot again discontinued the powerline inspection and flew the helicopter to Koorda for refuelling and lunch.
During the lunch break the work progress was discussed and, because less than 200 poles remained in the powerline inspection to Bencubbin, the crew decided to reverse the direction of the inspection and fly from Koorda to Bencubbin. At 1230 the helicopter departed Koorda and flew to Bencubbin, where they resumed the inspection at approximately 1300. The pilot then flew a parallel course on the eastern side of the main powerline from Bencubbin tracking north to where the earlier inspection had finished.
Approximately 3 kms north of Bencubbin, the observer saw what he thought to be an anomaly with a "beehive" structure (insulator device) atop one of the poles. The pilot then banked the helicopter to the left to conduct a 180-degree turn over the main powerline to return to the beehive. He then established the helicopter in a hover on a southerly heading on the western side of the main powerline. The inspection revealed that the anomaly was in fact bird droppings and nothing of concern.
Intending to resume the inspection, the pilot transitioned the helicopter from the hover to forward flight. The powerline inspector reported that he believed the pilot intended to complete another 180-degree left turn, again crossing the main powerline to resume the northerly track on the eastern side.
The inspector told investigators, that after the helicopter pitched nose down and accelerated into forward flight, "the helicopter's engine began sounding as though it was labouring, as if the helicopter was struggling under a heavy load". He then looked out of the left side of the helicopter and saw the first pole of the spur line. The helicopter then struck the ground and was destroyed by impact forces and the subsequent fire. The pilot and observer received fatal injuries, and the inspector received serious injuries.
Pilot information
The pilot gained a Private Pilot (Helicopter) Licence in February 1980, a Commercial Pilot (Helicopter) Licence in February 1981 and a Senior Commercial (Helicopter) Licence in April 1987. He then accrued many hours both in Australia and overseas on a variety of single and twin-engine helicopter types and gained experience in logging, low-level aerial survey, medical evacuation, fire fighting and external sling load work. He obtained a command multi-engine helicopter instrument rating in October 1991, having accrued a total of 4,495 hours as pilot in command at that time. He then accrued large helicopter experience, which included offshore oil rig crew transfer and operations in the North Sea, Canada and Mozambique. In July 1994 he qualified for, and was issued with, an Air Transport Pilot (Helicopter) Licence.
The pilot undertook low-level recurrency flight training 3 months prior to being employed by the operator. The pilot who conducted the recurrency training said that training was oriented to offshore operations and that the instruction given did not cover powerline inspections. When the pilot commenced casual flying for the operator, he successfully completed a check flight on the Bell 206 helicopter type with the operator's Chief Pilot. The flight did not include any specific training and checking regarding powerline survey or inspection operations. The Chief Pilot later stated that "he only hired pilots with low-level flying endorsements and he believed that, in accordance with the [Civil Aviation] regulations, that training qualified them for his company's operational requirements".
At the time of the accident, the pilot had accrued about 7,830 hours total helicopter flying experience of which 3,468 hours were on the Bell 206. The pilot had a Class 1 medical certificate. He was required to wear vision-correction spectacles while flying and was doing so at the time of the accident.
The pilot had not been on duty for the three days prior to the day of the accident. There was no indication that he was experiencing any personal or medical problems that may have adversely affected his performance.
Observer/Inspector information
The power company employee occupying the rear seat acted as the powerline inspector, and inspected the powerlines in consultation with the observer while referring to maps to assist in identifying the location of defects, as well as the location of known hazards. The employee in the front left seat acted as the observer, scanning for powerline anomalies, assisting the pilot in command by scanning for hazards in the intended flight path, as well as maintaining radio communications with the power company base at Northam. The observer required vision correction for reading only. At the time of the accident, the observer was not wearing spectacles and did not require them for distance sight. Neither employee had undergone any formal training to enable them to carry out their in flight roles in helicopter powerline inspections, despite there being a requirement to do so in the operator's operations manual. The operations manual stated that, "Operating crew means any person having duties on board an aircraft in connection with the flying or safety of the flight of that aircraft."
There was no indication that either power company employee was experiencing any personal or medical problems that may have adversely affected the performance of their respective duties.
Observer/Inspector training
The operations manual also provided guidance in the form of Special Instructions on the training required for non-operator personnel to permit them to conduct the role of operating crew for other operations such as aerial photography. However such training guidance was not provided for low-level powerline inspections.
The Network Service Division of the power company for whom the operator was working did not have a published requirement for such training. The power company reported that the two employees were selected as a consequence of their seniority within the company and their familiarity with the powerlines in the area. At least one of the employees had personally been involved in the construction of the powerline network being surveyed. The two employees had received a basic safety briefing from the helicopter operator, which included information on how to approach an operating helicopter and seat belt fastening and exit details.
Meteorological information
The temperature at the time of the accident was about 35 degrees C with surface winds being generally light from the west. It was also humid, with a band of cloud in the area having a base of between 4,000 to 6,000 feet. Some convective shower activity may have been developing in the area at the time. Rescuers said that due to the combination of the overcast conditions and the pale colour of the harvest stubble, there was little contrast between the powerlines and the surrounding background.
Flight following
The helicopter was fitted with VHF communications equipment, including dedicated air to ground radio for communications with non-aviation related ground parties. The power company routinely provided flight following from its Northam township base and, although no formal communication schedule was in place, the crew of the helicopter called the Northam base at irregular intervals. Those broadcasts were primarily to inform the power company of their intentions including when a section of a task was completed, an anomaly was found, or a task was discontinued for rest breaks or refuelling.
At the time of the accident, an employee at the Northam base noticed that the circuit breaker for the Bencubbin three-phase line had tripped and, considering that a helicopter operating in the area might be in trouble, isolated that breaker to prevent an automatic reset. After he had unsuccessfully attempted to contact the helicopter by radio, he raised the alarm within the company. The alarm was also raised in Bencubbin township by a passing motorist who was flagged down by the survivor waving from the field.
Wreckage and impact information
The helicopter had collided with a spur line running west, almost at right angles to the main powerline. The spur line consisted of two 12mm, three-strand, high-tensile steel wires. The force of the collision shifted the pole adjacent to the main line approximately 100mm in its foundation steel supports. The next three poles to the west of the accident site were pulled down. The wires of the spur line were strung between poles that were set 310m apart in the first span. Four spans of the spur line each approximately of 300m in length were downed. Under normal tension those wires were approximately 7.2m above the ground at mid-span rising to 9.9m at the poles. The downed support pole to the west of the spur "T" junction was set in the field adjacent to a fence. The poles and wires blended with a line of trees and some shrubbery extending in that direction.
Impact marks indicated that during the accident sequence the wires were trapped by the left skid, and pulled tight in the direction of flight until the tension caused the left skid tube assembly to fail at the forward and rear, cross-tube to skid-tube, attachment points. The left landing skid tube was then thrown rearward by the recoiling action of the conductor wire.
The helicopter appeared to have rolled to the left, probably due to the restraining force of the wire on the left skid, and became inverted before impacting the ground. Several strikes of the main rotor severed the tail boom immediately in front of, and immediately behind, the horizontal stabilisers. The main rotor mast failed below the static stops, liberating the main rotor. The fuselage impacted the ground inverted on a heading of about 215 degrees and came to rest 80 metres south of the spur line. The helicopter was not fitted with a wire strike protection system (WSPS) and there was no requirement that a WSPS be fitted for this type of work.There was no indication that the helicopter was incapable of operating normally before the collision with the powerline.
Survival
The helicopter cabin contained five seating positions; two single seats in the forward cockpit and three seats in a bench arrangement in the rear. The front seats were fitted with both lap and shoulder restraints. The rear bench seats were fitted with lap seat belts only. The inverted attitude of the helicopter just before it impacted the ground exposed the right front seat and its occupant to the full force of the impact. Consequently, the accident was considered to be non-survivable for the pilot. The results of the postmortem revealed that the front left seat occupant was fatally injured from a combination of impact forces and the ensuing fire.
The inspector occupying the rear left seat was thrown clear of the helicopter during the impact sequence. Lap seat belts for the rear seats were found in the wreckage trail with charred webbing and the buckles still fastened. Evidence indicated that an anchor point for the rear left seat belt failed during the ground impact and subsequent breakup sequence.
Emergency locator transmitter
The helicopter carried a fixed emergency locator transmitter (ELT) mounted in an approved manner within the forward cabin area. The inverted attitude of the helicopter at impact was outside the design mounting criteria for the ELT and most probably resulted in the failure of the ELT to transmit prior to being consumed by the post accident fire.
Organisation and management
The Electrical power supply company
The power company had two distinct divisions requiring helicopter support. The Transmission Division of the company was responsible for the maintenance of the high voltage transmission lines, usually carrying voltages in excess of 66 kilovolts. The Network Service Division was responsible for distribution lines carrying all voltages lower than 66 kilovolts.
a. Transmission Division
Due to the highly specialised requirements of helicopter powerline inspection work and the high voltages involved, the tender documents for helicopter support of activities for the Transmission Division were very detailed. The documents contained the requirements and scope of work required, general conditions, special conditions, quality control requirements and technical drawings of electrical transmission tower installations. In turn, the successful tenderer submitted to the power company, copies of Safety Management Plans, a Quality Plan, pertinent extracts from the helicopter company training manual, a computerised inspection and patrol software program and a Powerline Procedures Manual.
b. Network Service Division
The Network Service Division, for which the accident helicopter was operating, did not require a formal tender process for the helicopter line survey work, nor was the process formally aligned to any published criteria. Helicopter operators with whom the Network Service Division had established a relationship over several years were normally contracted to provide the service. The relationship was such that the subdivision was able to call upon those helicopter operators at very short notice if an urgent task arose.
The Network Service Division's principal engineer reported that they also assumed that, as the helicopter operator was approved to hold an Air Operator's Certificate for the type of work they required (low-level operations), their requirements and obligations to provide a safe environment for their employees had been met. The engineer also reported that they believed that the approved helicopter operator would bring the relevant expertise to the job and supply any specific training for the power company employees that might be required to meet the task.
The operator
The operator was permitted, under the Air Operator's Certificate (AOC) issued by the Civil Aviation Safety Authority (CASA), to conduct charter and aerial work operations including powerline inspections. The operator had been engaged in powerline inspection work for the Network Service Division of the power company for a period of approximately 10 years.
The Chief Pilot was also the operator's Managing Director and AOC holder. The line pilots, including the pilot involved in the accident, were employed by the operator, on a casual basis. The Chief Pilot did not conduct Check and Training because the operator was not approved by CASA to do so. When a requirement for Check and Training arose, the company would arrange a sub-contractor to carry out the work on its behalf by a CASA approved Check and Training pilot.
The operator's operations manual was a document using a modular design. It was co-authored by the Chief Pilot and an individual specialising in authoring regulatory documents. The manual had scope to tailor to any operator requirements as evidenced by "Reserved" sections within the separate modules. A section was reserved for a Flight Safety Program, but had not been activated at the time of the accident. Additionally, the operator said that a formal Flight Safety Program had not been instituted due to the company's small size. However, the Chief Pilot stated that training and risk assessment were verbally delivered to the pilot prior to each task and that he was debriefed after completion of the task. Several other stipulated Special Instruction requirements for activities listed in the AOC section of the operator's operations manual were also not activated at the time of the accident.
The operations manual detailed the requirements and instructions for specialised operations such as Aerial Photography, Aerial Spotting, Aerial Survey (including powerline inspections), Dropping and External (Underslung) Loads.
Operating Standards
The investigation found that the only published guidance and operating standard in Australia for any helicopter powerline work, was the Electricity Supply Association of Australia Ltd (ESAA) document "Guidelines for use of helicopters for live line work", August 1995. That publication was recommended by ESAA as a reference text for minimum industry standards for work in the vicinity of live power lines. Although the publication was not comprehensive, it was considered by some members of the electrical and aviation industries to be a good basis from which to develop standards, particularly for work on and in the vicinity of high voltage powerlines. While it was recognised that the guidelines were intended for working on, and in the vicinity of, energised powerlines, it was also considered that some of the general principles for helicopter operation, safety and training could easily be adapted and applied to operations and training manuals for low voltage line inspection of the type being conducted at the time of the accident.
The Transmission Division of the power company responsible for the high voltage distribution had knowledge of that publication and reference was made to it in the specialist tender documents issued to its prospective helicopter contractors. However, the helicopter operator and the Network Service Division responsible for the low-voltage network were not aware of the existence of the ESAA publication at the time of the accident and therefore did not consider it as a possible reference text.
Regulatory references and requirements associated with operating at low levels in the vicinity of powerlines were found in Civil Aviation Orders (CAOs). The CAOs addressed agricultural and mustering operations. All helicopter pilots engaging in agricultural and mustering operations were required to undergo training and testing in accordance with the CAOs, before gaining a rating. Similar references and requirements did not exist for pilots undertaking low-level powerline work.
The operator's Chief Pilot said that he told company pilots to maintain a minimum height of 5m above the power poles while they were engaged in powerline surveys. Although the minimum safe clearance figure of 5m was recommended in the ESAA document "Guidelines for use of helicopters for live line work", August 1995, the document was not a reference text for the operator at the time of the accident and the recommended safe distance was not promulgated in the operator's operations manual. In addition, the operations manual did not provide guidance on structured crew communications and phraseology, the responsibilities of each crewmember, and individual crew actions in the event of an emergency during powerline inspections. In addition, the manual did not provide guidance on turn-back techniques or the avoidance of many of the hazards unique to powerline inspections.
Hazard Identification
After comments by some pilots regarding the positioning of pole-marker numbering at the base of certain poles, the Transmission Division had commenced a program to position pole numbers at the top of poles. That was accompanied by marker ball placement on certain lines (over 80 kilovolts) to identify hazards to flight.
The Network Service Division had no such program in place to identify, by physical means, hazards to flight on any of the lower voltage networks. No other visual cues, such as yellow disc or orange ball markers at the spur line junction, were in place that would have assisted the pilot or his front seat observer conducting the aerial survey to recognise that they were in the vicinity of a hazard. In addition, the crew was only calling the pilot's attention to hazards that were on the flightpath side of the main line. A copy of the specific map identifying the powerline positions was on board, and was being referenced by the inspector on the day of the accident. During the investigation the Chief Pilot remarked that "the observer was known on occasion to rely on his memory in areas he knew well".
