Lack of supervision factor in fatal Squirrel powerline crash

written by Adam Thorn | March 16, 2021
The accident site near pole 164. The direction of travel of the helicopter was from pole 163 to pole 164 (ATSB)

An ATSB report into the fatal crash of a Squirrel helicopter that was stringing powerlines has concluded post-training supervision by the aircraft operator may have prevented the accident.

The unidentified person onboard died when the helicopter’s main rotor blade struck a pole around 60 kilometres east of Woomera Airfield, South Australia, on 20 March 2019.

However, the investigation revealed this collision was likely caused by the experienced pilot using an adapted technique that increased the uptake of dust, reducing visibility.

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“There were no requirements in the operator’s procedures to provide any post-training supervision for powerline operations,” said the ATSB’s director of transport safety, Stuart Macleod. “What supervision was provided was ineffective in identifying that a modified stringing method was being used by the pilot.”

In response, operator Aeropower has introduced a raft of new measures including the introduction of consolidation flight checks at key points for pilots newly authorised in specialist tasks.

The AS350B3e Squirrel helicopter, registered VH-SZS and operated by Aeropower, was stringing powerlines from the Mount Gunson South substation to the Carrapateena mine site, a total distance of 51 kilometres, approximately 60 kilometres east of Woomera Airfield on 20 March 2019.

While pulling the draw wire with a nose-high and rearward attitude, the helicopter’s main rotor blades struck the pole about 17 metres above the ground. The helicopter subsequently impacted the ground near the base of the pole.

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Several ground crew from the stringing team extinguished a small post-impact fire and removed the pilot from the aircraft to a safe distance. A short time later emergency services and paramedics from the mine site attended the scene and confirmed that the pilot, who was the sole occupant, had received fatal injuries. The helicopter was destroyed.

Shortly after being trained in powerline stringing operations, for unknown reasons, the pilot modified the stringing methodology. In addition to placing the helicopter at low level in the vicinity of the powerline poles, the modified methodology also exacerbated the uptake of dust. This, in combination with the position of the sun and the rearward attitude of the helicopter, likely reduced the pilots’ visibility of the pole and their situational awareness of it.

In November 2020, the ATSB was advised that Aeropower had taken a number of proactive safety actions specifically relating to the supervision and review of newly authorised pilots in specialist tasks.

“These actions taken by Aeropower address the key concern of the investigation’s identified safety issue, being the supervision of pilots recently trained or authorised in a new specialist task,” Macleod said.

“The mandated extension of command under supervision time, the introduction of periodic consolidation flight checks, and the mandated extension of mentoring time are all expected help better prepare newly trained pilots for solo operations and provide them with additional defences to the hazards associated with specialist flight tasks.”

The investigation also highlighted that experience alone will not always prevent a pilot from having an accident. In this case, the pilot was a very experienced deputy chief pilot with nearly 6,500 flight hours.

VH-SZS traversing between pole 163 and 164. Pole 163 is visible in the image, while pole 164 is out of the frame to the right. The direction of travel is from left to right in this image. (ATSB)

Research published by the ATSB in 2012 as part of its Avoidable Accidents series titled Experience won’t always save you, showed experience does not always provide a safeguard.

“Using pilot experience as mitigation for potential operational risks is inadvisable,” Macleod said.

“The ATSB has found that in some occurrences, very experienced pilots were undertaking flying that involved much higher risk. And as a consequence, we found that in those circumstances their flying experience alone was unable to help them avoid an accident.”

Australian Aviation has contacted Aerospace for comment.

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