Aviation safety investigations & reports

Loss of control and near collision with terrain, Leonardo Helicopters AW139, VH-TJO 26 km east of Goulburn Airport, New South Wales, 24 July 2020

Investigation number:
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase


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[Download  PDF: 1017KB]

What happened

On 24 July 2020, the crew of a Leonardo Helicopters AW139, registered VH-TJO, departed Shellharbour Airport, near Wollongong, New South Wales, with four crew onboard (including a single pilot and aircrew officer). The flight was conducted under the night visual flight rules, with the assistance of night vision goggles, to recover two bushwalkers from the Bungonia National Park, New South Wales.

On arrival at the search and rescue location the helicopter was descended to approximately 240 ft above ground level and reduced speed. The aircraft was then tracked over high ground past the edge of an escarpment, where the terrain dropped away to the valley floor.

During this time an uncommanded, and increasing, rate of descent and lateral drift developed. This was identified by the aircrew officer, with corrective instructions provided to the pilot. During the recovery, the engine power output exceeded airframe limitations, rendering the helicopter temporarily unserviceable.

What the ATSB found

The ATSB identified that the pilot's likely fixation on locating the bushwalkers resulted in them not maintaining an effective scan on the cockpit instruments and outside visual references. This resulted in the loss of hover reference and development of an unintended descent and lateral drift.

In response to the loss of reference, the pilot unsuccessfully attempted to engage the helicopter’s auto hover rather than commence an overshoot. A subsequent focus on selecting the automated mode further delayed the resumption of the scan and recognition of the increasing descent rate.

During the event, air to ground communications between the onboard paramedic and ground party hindered communications between the pilot and aircrew officer.

It was also identified that the external aircraft white lighting was inadequate to clearly illuminate the area below and to the side of the aircraft. This delayed the identification and recovery from the unsafe aircraft state.

Finally, the pilot did not announce losing hover reference, delaying the aircrew officer’s awareness of the developing situation and support to the pilot. As a result, it was estimated the aircraft came within 20 ft of terrain before the descent and drift were arrested.

What has been done as a result

Following this incident, Helicorp Pty Ltd, trading as Toll Helicopters, made several changes to their procedures and equipment aiming to prevent reoccurrence:

  • Aircraft external lighting to be upgraded to include a dedicated high-powered search light.
  • Sterile cockpit procedures specific to emergency medical services flights, as well as a specific procedure in the event of a loss of hover references have been amended in the company operations manual.
  • Additional human factors training with a focus on spatial disorientation, confirmation bias and communication techniques for all flight and medical crew.
  • Pre-flight operational risk assessment approval process introduced specifically for all complex night vision imaging system winch activities.

Safety message

Operations at night in low light conditions can be challenging to even the most experienced crews. Low light conditions reduce available visual cues for maintaining aircraft position and undesired aircraft states can develop rapidly. To mitigate these risks, crews conducting night operations in such conditions should maintain adequate references, taking into account equipment limitations such as external lighting, and maintain an effective scan to ensure continual awareness of the position and movement of the helicopter.

This incident also illustrates the importance of an appropriate response if an undesired aircraft state occurs.

Download Final Report
[Download  PDF: 1017KB]

The occurrence


Safety analysis


Safety issues and actions


Sources and submissions

About the ATSB


The ATSB is investigating the near-collision with terrain involving Leonardo Helicopters AW139, VH-TJO, 25 km East of Goulburn, New South Wales, on 24 July 2020.

While conducting a single-pilot NVG EMS flight, the aircraft entered an uncommanded descent and drift. The aircraft was recovered in close proximity to obstacles and during the recovery, the helicopter sustained an over torque.

As part of the investigation, the ATSB will be gathering information from a range of sources for analysis. Investigation activities will include interviewing the crew of the helicopter, analysing flight data, and reviewing procedures and manuals.

A report will be released at the end of the investigation. Should a critical safety issue be identified during the course of the investigation, the ATSB will immediately notify relevant stakeholders so appropriate and timely safety action can be taken.

Safety Issue

Go to AO-2020-038-SI-01 -

External aircraft white lighting

The external aircraft white lighting was inadequate to illuminate the terrain below and to the side of the aircraft at the required operating height., This delayed the identification and recovery from the unsafe aircraft state resulting in the pilot not identifying the developing rate of descent during the incident, delaying the recovery from the descent.

Safety issue details
Issue number: AO-2020-038-SI-01
Status: Open – Safety action pending
General details
Date: 23 July 2020   Investigation status: Completed  
Time: 22:58 EST   Investigation level: Defined - click for an explanation of investigation levels  
Location   (show map): 26 km east of Goulburn Airport (Bungonia National Park) New South Wales   Investigation phase: Final report: Dissemination  
State: New South Wales   Occurrence type: Near collision  
Release date: 08 April 2022   Occurrence category: Serious Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Leonardo Helicopters  
Aircraft model AW139  
Aircraft registration VH-TJO  
Serial number 31740  
Operator Helicorp Pty. Ltd.  
Type of operation Aerial Work  
Sector Helicopter  
Damage to aircraft Nil  
Departure point Wollongong Airport, New South Wales  
Destination Wollongong Airport, New South Wales  
Last update 08 April 2022