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".