On 18 August 2011, an Aérospatiale AS355F2 (Twin Squirrel) helicopter, registered VH-NTV, was being operated under the visual flight rules (VFR) in an area east of Lake Eyre, South Australia. At about 1900 Central Standard Time, the pilot departed an island in the Cooper Creek inlet with two film crew on board for a 30-minute flight to a station for a planned overnight stay. It was after last light and, although there was no low cloud or rain, it was a dark night.
The helicopter levelled at 1,500 ft above mean sea level, and shortly after entered a gentle right turn and then began descending. The turn tightened and the descent rate increased until, 38 seconds after the descent began, the helicopter impacted terrain at high speed with a bank angle of about 90°. The pilot and the two passengers were fatally injured, and the helicopter was destroyed.
What the ATSB found
The ATSB found that the pilot probably selected an incorrect destination on one or both of the helicopter's global positioning system (GPS) units prior to departure. The ATSB concluded that, after initiating the right turn at 1,500 ft, the pilot probably became spatially disoriented. Factors contributing to the disorientation included dark night conditions, high pilot workload associated with establishing the helicopter in cruise flight and probably attempting to correct the fly-to point in a GPS unit, the pilot’s limited recent night flying and instrument flying experience, and the helicopter not being equipped with an autopilot.
Although some of the operator’s risk controls for the conduct of night VFR were in excess of the regulatory requirements, the operator did not effectively manage the risk associated with operations in dark night conditions. The ATSB also identified safety issues with the existing regulatory requirements in that flights for some types of operations were permitted under the VFR in dark night conditions that are effectively the same as instrument meteorological conditions, but without the same level of safety assurance that is provided by the requirements for flight under the instrument flight rules (IFR).
What's been done as a result
The Civil Aviation Safety Authority (CASA) has advised of safety actions in progress to clarify the nature of what is meant by the term ‘visibility’ in dark night conditions, provide enhanced guidance on night VFR flight planning, and provide enhanced guidance on other aspects of night VFR operations. The ATSB has issued a recommendation to CASA to prioritise its efforts in this area. In addition, CASA advised that it will require that helicopter air transport operations with passengers at night use either a helicopter fitted with an autopilot or a two-pilot crew.
The ATSB advises all operators and pilots considering night flights under the VFR to systematically assess the potential for the flight to encounter dark night conditions by reviewing weather conditions, celestial illumination and available terrain lighting. If there is a likelihood of dark night conditions, the flight should be conducted as an IFR operation, or conducted by a pilot who has an IFR-equivalent level of instrument flying proficiency and in an aircraft that is equipped to a standard similar to that required under the IFR.
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On 18 August 2011, an Aérospatiale Industries AS355F2 helicopter, registered VH-NTV, was operating in an area east of Lake Eyre, South Australia (SA). On board were the pilot and two passengers. The helicopter landed on an island in the Cooper Creek inlet, about 145 km north of Marree, SA, at about 1715 Central Standard Time.
At about 1900, the helicopter departed the island, and soon after takeoff it collided with terrain. The pilot and the two passengers were fatally injured, and the helicopter was destroyed by the impact forces and a fuel-fed fire.
Updated 19 July 2013
The Australian Transport Safety Bureau (ATSB) received the results of the flight simulations and modelling that were previously advised as being conducted by external specialists in June 2012. The ATSB is now finalising its draft report, which will be sent to directly involved parties and other parties with an interest in July/August 2013. Feedback from those parties on the factual accuracy of the draft report over the 28-day DIP period will be considered for inclusion in the final report, which is anticipated to be released to the public in September/October 2013.
Updated 9 July 2013
The Australian Transport Safety Bureau (ATSB) received the results of simulations and modelling conducted by external specialists in June 2012. The ATSB is now finalising its draft report, which will be sent to directly involved parties and other parties with an interest in July/August 2013. The final report will be publicly released in September/October 2013.
Update 26 November 2012
The Global Positioning System (GPS) data that was recovered from the accident site indicates that the helicopter took off normally, before being established on a heading of 035 °M at 1,500 ft above mean sea level (AMSL). After maintaining 1,500 ft for 17 seconds, the helicopter commenced a gradual turn to the right and started to descend. The descending right turn continued for about 35 seconds until the last GPS plot at an altitude of about 728 ft, or about 725 ft above the elevation of the accident site. The location of the accident site was consistent with a continuation of the recorded flight path.
The Australian Transport Safety Bureau (ATSB) is examining various scenarios to explain the helicopter’s flight path, including spatial disorientation and pilot incapacitation. As part of these activities, the ATSB has arranged for simulations to be conducted of the flight by external agencies. Given the time required to conduct and analyse these simulations, the final report is now not expected to be released until the first quarter of 2013.
Although the reasons for the flight path have not yet been determined, the ATSB is concerned about the conduct of visual flight rules (VFR) flights in dark night conditions – that is, conditions with minimal celestial illumination, terrestrial lighting cues or visible horizon. The ATSB is reviewing the regulatory requirements and guidance for the conduct of night VFR flights, and the training and ongoing assessment of pilot skills to conduct such flights. The ATSB is also preparing an ‘Avoidable Accidents’ educational report focussing on night VFR accidents.
The information contained in this web update is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from 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 occurrence as outlined in the web update. As such, no analysis or findings are included in this update.
Update 15 August 2012
Since the Preliminary Report was issued on 16 September 2011, the ATSB investigation has:
- examined the helicopter's maintenance and airworthiness records
- examined the helicopter's engines, instruments and other recovered components
- tested fuel samples from the drums that were used to refuel the helicopter
- recovered and analysed data from a GPS device on board the helicopter
- reviewed the pilot's experience and medical status
- analysed witness statements and conducted further witness interviews as required.
The download and analysis of the GPS data required an extensive period of time, as well as input from overseas investigation agencies.
Overall, the analysis of the circumstances of the accident has been difficult due to the limited evidence available.
The ATSB has completed its data collection activities and is preparing its draft final report, which will be issued to Directly Involved Parties for their comments.
Although some of the operator’s risk controls for the conduct of night visual flight rules flights were in excess of the regulatory requirements, the operator did not effectively manage the risk associated with operations in dark night conditions.
|Who it affects:||The operator’s flight crew|
|Status:||No longer relevant|
Aerial work and private flights were permitted under the visual flight rules in dark night conditions, which are effectively the same as instrument meteorological conditions, but without sufficient requirements for proficiency checks and recent experience to enable flight solely by reference to the flight instruments.
|Who it affects:||All aircraft operating under the night visual flight rules (VFR)|
|Status:||Safety action pending|
Helicopter flights were permitted under the visual flight rules in dark night conditions, which are effectively the same as instrument meteorological conditions, but without the same requirements for autopilots and similar systems that are in place for conducting flights under the instrument flight rules.
|Who it affects:||All helicopters operating under the night VFR|
|Date:||18 August 2011||Investigation status:||Completed|
|Time:||1902 CST||Investigation level:||Complex - click for an explanation of investigation levels|
|Location:||145 km north of Marree (near Lake Eyre)|
|State:||South Australia||Occurrence type:||Loss of control|
|Release date:||14 November 2013||Occurrence category:||Accident|
|Report status:||Final||Highest injury level:||Fatal|
|Aircraft manufacturer||Aerospatiale Industries|
|Type of operation||Aerial Work|
|Damage to aircraft||Destroyed|