Introduction
On a night positioning flight to Squireship, approximately 20 NM (37 km) offshore Port Hedland, helicopter VH-ZGA descended into the ocean. The operator conducted marine pilot transfer flights under day/night VFR. The helicopter was an EC135 equipped for single-pilot IFR but operated under night VFR. This flight was the third night line training flight, during which a recently employed pilot acted as pilot in command under supervision of a company instructor pilot.
The accident helicopter was not equipped with a flight data recorder or cockpit voice recorder. The Australian Transport Safety Bureau (ATSB) analyzed ADS-B data and interviewed the surviving pilot. The ADS-B data indicated abnormal vertical flight path and airspeed during circling and before final approach. The surviving pilot could not recall specific details of the pre-accident sequence.
Local Operational Conditions
Night VFR operations required clear of cloud, in sight of ground or water with visibility greater than 5 km. CASA strongly recommended night VFR only when a natural visual horizon was discernible, or sufficient external cues for pitch and roll attitude, unless the helicopter had an autopilot/stabilization system or was a two-pilot operation.
On the night of the occurrence, there was no cloud or atmospheric reduction below minima, but visual cues were degraded due to dark night conditions (low celestial lighting) and scarcity of cultural lighting offshore. Squireship's external lighting provided local illumination greater than a single point light, useful as a visual reference for circuit and final approach profile, but insufficient to determine pitch and roll attitude throughout the circuit.
Squireship was underway at 12–13 kt, and its relationship to shipping channel markers was not constant, limiting their value. Other illuminated ships in the area provided little to no visual assistance.
Safety Factors
The ATSB identified eight safety factors that contributed to the occurrence and ten factors that increased operational risk but were not influential in the accident development. These included five safety issues related to helicopter equipment and operator processes, including fatigue management. Safety issues not related to fatigue management were addressed by the operator soon after the occurrence. Regulatory changes introduced later imposed additional requirements on marine pilot transfer operations.
Conclusion
The ATSB derived flight path data and contextual information such as environmental conditions, operator procedures, and operational capability were used to identify contributing factors. The degraded visual environment, dark night, and limited external lighting were key conditions present.