Aviation safety investigations & reports

Collision with terrain involving AS350 VH-SZS, 60 km east of Woomera, South Australia, on 20 March 2019

Investigation number:
AO-2019-015
Status: Active
Investigation in progress

Preliminary report

Preliminary report published: 10 May 2019

What happened

On 20 March 2019, an Airbus Helicopters AS350, registered VH-SZS (SZS) was performing aerial work on Pernatty Station, South Australia, approximately 60 km east of Woomera Airfield. The helicopter operator had been contracted to conduct stringing operations on a new 132 kV electrical transmission line from the Mount Gunson South substation to the Carrapateena mine site. The task involved stringing draw wire[1] and optical ground wire and the total length of the stringing operations, 51 km, was divided into twelve stages that were identified with reference to numbered transmission poles. The stage being conducted on the morning of 20 March was from pole 159 to pole 179, a distance of 4.8 km. To facilitate stringing operations, the helicopter was fitted with a Mack Innovations (Australia) Pty Ltd (Mack Pull) bi‑directional line stringing system and a 30 ft sling.

At about 0900 Central Daylight Time[2], SZS departed from the nearby Carrapateena Airport and the pilot rendezvoused with the operator’s refueller and the stringing team near the work site for a pre-start briefing. Afterward, the stringing team proceeded to their assigned work positions. At about 1000 the pilot took off and proceeded to pole 179, the end of that stringing stage, for a radio check with the stringing team ground crew. The helicopter then proceeded to pole 159 to commence stringing operations.

In preparation for helicopter stringing operations, the draw wire had previously been strung to a pulley on pole 159 using an elevated work platform. Just after 1000, when SZS reached pole 159, ground crew attached the draw wire to a remote hook at the end of the 30 ft sling. SZS then pulled the draw wire out from a Tesmec S.p.A. (Tesmec)[3] stringing machine and proceeded to pole 160 to clip the draw wire into the pulley. Stringing operations continued normally for poles 161, 162 and 163. While approaching pole 164 at about 1017, witnesses reported seeing the helicopter collide with the pole and impact terrain near the base of the pole. The pilot, who was the sole occupant, received fatal injuries.

Wreckage examination

Examination of the accident site indicated that after impacting pole 164, the helicopter came to rest on its right side approximately 2 m from the base of the pole (Figure 1).

Figure 1: The accident site near pole 164 on Pernatty Station. Also visible are the previously strung poles. The direction of travel of the helicopter was from pole 163 to pole 164.

Figure 1: The accident site near pole 164 on Pernatty Station. Also visible are the                    previously strung poles. The direction of travel of the helicopter was from pole                  163 to pole 164. Source: ATSB

Source: ATSB

The cockpit and fuselage roof were substantially disrupted from impact forces. The tailboom had almost entirely detached at the fuselage junction and fractured forward of the horizontal stabiliser, due to ground impact. Two of the main rotor blades had separated from the rotor head and came to rest next to the fuselage. The third blade remained attached, and had become entangled around the main rotor gearbox. The sling, which had separated from the Mack Pull, was found a short distance away toward Pole 163. The draw wire was also found to have separated from the remote hook on the sling. Markings on pole 164 indicated that the helicopter collided with the pole about 17 m above the ground (Figure 2).

Figure 2: Impact marks and damage to pole 164

Figure 2: Impact marks and damage to pole 164. Source: ATSB

Source: ATSB

The ATSB recovered a number of components from the accident site for further examination. The helicopter was not equipped with a flight data recorder or cockpit voice recorder, nor was it required to be.

Further investigation

The investigation is continuing and will include consideration of the:

  • pilot’s qualifications, experience and medical history
  • maintenance documentation
  • recovered helicopter components
  • operational documentation
  • witness interviews
  • electronic devices recovered from the helicopter.

_____________

The information contained in this update is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this update. As such, no analysis or findings are included.

 

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  1. The draw wire is thinner (13mm) and lighter (0.55 kg/m) than the conductor wire (31.5mm, 1.96 kg/m). After the helicopter strings the draw wire, a groundbased winch is used to pull the conductor wire through.
  2. Central Daylight Time: Coordinated Universal Time (UTC) +10.5 hours.
  3. Tesmec S.p.A. are an Italian manufacturer of stringing machines. In this case, a dieselpowered hydraulic winch/brake, which provides tension while the helicopter is drawing wire out and then acts as a winch to pull the final conductor wire back though.
General details
Date: 20 March 2019   Investigation status: Active  
Time: 10:18 CDT   Investigation level: Defined - click for an explanation of investigation levels  
Location   (show map): Pernatty Station, 60 km east of Woomera Airfield (Carrapateena Mine)   Investigation phase: Evidence collection  
State: South Australia   Occurrence type: Collision with terrain  
Release date: 10 May 2019   Occurrence category: Accident  
Report status: Preliminary   Highest injury level: Fatal  
Anticipated completion: 1st Quarter 2020    

Aircraft details

Aircraft details
Aircraft manufacturer Airbus Helicopters  
Aircraft model AS350 B3  
Aircraft registration VH-SZS  
Serial number 7421  
Operator Aeropower Pty Ltd  
Type of operation Aerial Work  
Sector Helicopter  
Damage to aircraft Substantial  
Departure point Carrapateena Airport, South Australia  
Destination Carrapateena Airport, South Australia  
Last update 14 June 2019