What happened
On 18 February 2009, a Eurocopter EC225 LP Super Puma, registration G-REDU, was conducting a scheduled night flight from Aberdeen Airport to the Eastern Trough Area Project (ETAP) Central Production Facility Platform in the North Sea. During the final stages of the approach, the aircraft encountered reduced visibility caused by fog or low cloud.
As the helicopter approached the platform, the crew performed a series of descents and climbs. During the final approach, the aircraft entered a continuous descent that resulted in an impact with the sea surface approximately 300 metres southwest of the platform. Despite the impact, the helicopter remained upright due to the automatic inflation of its flotation equipment. All occupants successfully evacuated into liferafts and were rescued by search and rescue assets.
The investigation
The investigation examined the flight crew's actions, the aircraft's technical systems, and the environmental conditions. Investigators looked into why the crew did not recognize the descending flight path and why automated warning systems failed to alert them to the decreasing altitude. The investigation also reviewed the maintenance and certification status of the aircraft and the specific visual conditions present during the night approach.
Findings
- The crew's perception of the helicopter's position and orientation relative to the platform was incorrect.
- The pilots were subject to oculogravic and somatogravic illusions, which were likely intensified by the reflection of the platform lights on the sea surface.
- Both crew members were focused on visually acquiring the platform and were not monitoring the flight instruments.
- There was no established night visual approach profile or specified criteria for a stabilized approach.
- The 100 ft radio altimeter height alert failed to activate due to a likely malfunction of the Terrain Awareness Warning System (TAWS).
- The crew had suspended the 150 ft audio-voice alert, and they were unaware that the TAWS was inoperative.
- The aircraft was properly maintained, and the crew was appropriately licensed and rested.