Fatal Wire Strike on Take Off from Communications Site
The Transportation Safety Board of Canada (TSB) have released their report on a helicopter that departed a microwave communication site and fatally struck one of the microwave tower guy wires. The lack of effective risk assessment and landing site data jumps out in their report as does a casual approach to some pre-flight preparation. There are key survivability lessons too.
…had been flown to [the Moliak] remote microwave tower site approximately 5 nautical miles west-southwest of Rigolet, Newfoundland and Labrador, with a pilot and 2 passengers on board. At about 1609 Atlantic Daylight Time, the helicopter lifted off from the helipad at the tower site and struck a tower guy wire with the main rotor.
The helicopter struck the ground and settled on its upper right side. One passenger sustained fatal injuries, the pilot sustained serious injuries, and the other passenger sustained minor injuries.
The Circumstances of the Accident
The TSB say:
The passengers were a Bell Aliant employee and a contractor. The pilot had flown with these passengers often and they had been working together at other tower sites on the previous 3 days.
The pilot had worked at CHL since 2005 and often flew to microwave tower sites, including the Moliak site. The pilot was familiar with its layout. The last time the pilot had flown to the Moliak site was 18 December 2014.
The flight departed from CHL’s base at the Happy Valley–Goose Bay Airport at 1333 [Local Time] and arrived at the Moliak site about an hour later. The helicopter was landed facing north on the site’s raised helipad. The passengers then carried out the site maintenance for about 1.5 hours while the pilot rested in the site radio building. Once the work was completed, the passengers advised the pilot, who began preparing for the return flight. The pilot noted that the wind was light and from the north.
The pilot helped the passengers load their tools and equipment onto the helicopter. Some cargo was placed on the cabin floor behind the left front seat; the left side of the rear split-bench seat had been folded up for this purpose [inconsistent with CAR 602.86(1) for stowage].
The pilot began the helicopter start-up procedure, completed the pre-takeoff checks, and confirmed that all doors were latched and that all occupants had their seatbelts fastened.
The standard safety briefing was not conducted on the day of the occurrence [inconsistent with CAR 703.39(1)].
The pilot visually scanned the area to the left of the helicopter, was interrupted briefly by a non-operational communication made by a passenger, and then continued to scan to the right of the helicopter to ensure that the area was clear for takeoff. The pilot did not note the outer guy wires and did not include them in his departure plan. At about 1609, the pilot lifted off and began intentionally moving forward.
The helicopter was just clear of the helipad and about 2 metres above downward-sloping terrain, when the contractor touched the pilot’s left shoulder. The pilot’s attention was drawn left and he then saw the tower guy wires in front and to the left of the helicopter.
As the pilot moved the cyclic control aft and to the right to avoid the wires, the helicopter’s main rotor struck a guy wire. The helicopter rolled rapidly to the right, struck the ground and settled on its upper right side directly below the outer guy wires.
The Moliak Microwave Communications Tower Site
Bell Aliant operates 27 microwave tower sites in Labrador, all of which are accessed by helicopter.
The helipad locations were collaboratively selected with CHL and Bell Aliant management personnel over 20 years ago, and at that time no formal risk assessments were conducted. Landing site diagrams were not available to the crew at the time of the occurrence.
The Bell Aliant Moliak site is on:
…the top of a hill at an elevation of 365 metres. The tower height is 67.1 metres above ground and is supported on 3 sides (120° azimuth spacing) by steel cable guy wires, arranged in inner and outer groups of wires. The inner group of 3 wires are anchored about 25 metres from the tower, and the outer group of 3 wires are anchored about 55 metres from the tower,
The 3 small buildings at the site contain communications and power generation equipment and are connected by raised walkways covered with wooden decking. One such walkway extends about 35 metres west of the tower to the helipad, which is a raised square wooden deck about 0.5 metre above ground level and about 6 metres square. The centre of the helipad is about 14 metres away from the closest guy wire.
The AS350 has a 13 metre D Value.
It is normal practice in a helicopter, as it is in any aircraft, to land and take off into the wind. To stay well clear of any obstructions, all company pilots flying to the Moliak microwave tower site approach and depart from the south or southwest. The pilot did not follow this normal departure practice on the occurrence flight.
Moliak is the only Bell Aliant site with the helipad located within the circumference of the outer guy wire anchor points.
The investigation determined that all of the guy wires were visible from an AS 350 helicopter when parked facing north on the helipad, but did not have high-visibility markings.
…the ELT’s acceleration switch axis of detection is angled 45° down in relation to the longitudinal axis of the helicopter in the direction of forward flight. [As] the helicopter struck the ground on its right side…the ELT did not automatically activate due to insufficient impact forces along the acceleration switch axis of detection.
The occurrence helicopter was equipped with a SkyTrac ISAT-100 system. The SkyTrac system records the time and GPS position for engine start-up, takeoff, landing, and engine shutdown. To record a takeoff, the SkyTrac system requires the collective lever to be raised, and the helicopter to indicate a speed of 5 knots for a minimum of 4 seconds.
The SkyTrac system did not send an overdue notification following the collision, because the requirements to record a takeoff were not met. After the accident, the pilot selected the helicopter master electrical switch off, then depressed the emergency button on the satellite flight following cockpit interface panel….[so] an emergency notification was not sent by the SkyTrac system because it was not powered…
The survivors telephoned for assistance.
The pilot was seated in the right front seat, the employee in the left-front seat, and the contractor in the forward-facing passenger seat located behind the pilot, on the outer right side of the helicopter.
A post-mortem medical examination was conducted on the contractor. The examination concluded that the contractor sustained fatal injuries when his upper body was crushed under the helicopter.
Both the pilot and the employee used the full 4-point [front seat] restraint system and remained restrained in their seats throughout the accident sequence. First responders found the contractor’s 3-point [rear seat] restraint system fastened and his upper body outside of the right cabin door. Following the accident, it was found that the contractor’s shoulder belt was misrouted under his left arm.
The TSB note the pilot was not wearing a flight helmet (nor is one required by regulation). They report that:
CHL strongly encourages their pilots to wear flight helmets, but does not require that they are worn unless the client mandates it.
However, pilots would have to pay 50 percent of the helmet purchase cost (CHL reimbursing the balance).
Organisational Factors and Safety Management
CHL is the largest helicopter operator in Canada. The company operates 184 helicopters from 26 bases across Canada, including 4 from the Happy Valley–Goose Bay base.
For over 30 years CHL had been contracted to provide helicopter transportation services to the Bell Aliant microwave tower sites in Labrador. This occurrence was the first wire strike for CHL at a microwave tower site.
CHL has a safety management system (SMS). The SMS is not required by regulation and its effectiveness has not been verified by Transport Canada. All employees are given initial training on SMS and recurrent training every 36 months.
CHL had completed general risk assessments for various flight operation types, including external load operations and VFR operations. [However] no specific risk assessments had been completed for flight operations into any of the microwave tower sites.
CHL did not provide any formal [single-pilot resource management] SRM training…
CHL uses a Flight Hazard Index card, which considers a series of human factors and flight operation conditions, to assess the level of risk associated with a particular flight.
The pilot calculated the risk score prior to the occurrence flight and assessed the total risk score to be low. The [TSB] investigation [also] assessed the level of risk using the Flight Hazard Index card; the total risk score was low. [However] the company Flight Hazard Index card does not include a flight operations condition for landing site hazards.
There was no indication of mechanical or system failure during the occurrence flight, and fatigue, incapacitation or physiological factors did not affect the pilot’s performance.
In relation to the wirestrike:
The pilot flew to microwave tower sites regularly and was accustomed to the presence of guy wires at these sites. The pilot had previously flown to the Moliak site and was aware of the proximity of the guy wires to the helipad. On the occurrence flight, the pilot did not note the outer guy wires and did not include them in the departure plan. The pilot performed a visual scan before departure; however, the visual scan was not effective in perceiving the outer guy wires. The pilot’s scan had been interrupted, which may have compromised the scan.
To be situationally aware, a pilot has to be aware of what is happening around them in order to understand how information, events, and the pilot’s own actions will impact their goals and objectives in the future—in this case, to achieve a successful takeoff. Both the routine scan and the interruption while performing the visual scan would reduce the level of the pilot’s attention, thereby contributing to degraded situational awareness. The pilot’s lower level of attention while conducting a routine flight led to an ineffective visual scan resulting in degraded situational awareness.
Company pilots depart the Moliak site to the south or southwest to remain clear of obstructions. However, on the occurrence flight, the pilot did not follow this practice and was not aware of the obstructions until being alerted by the contractor. It is also possible the pilot reverted to the normal practice of taking off directly into the wind. The helicopter struck the guy wires before evasive action could be taken, which caused the helicopter to roll rapidly and impact the ground.
During the pre-takeoff visual scan, the pilot was interrupted by a non-operational communication. This type of activity can be a distraction and can affect a pilot’s operational attentiveness during a critical phase of flight.
TSB Findings as to Causes and Contributing Factors
TSB Findings as to Risk
Other TSB Findings
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