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.