What happened
On the evening of 24 February 2020, a Sikorsky S-92A, registration LN-ONT, operated by Bristow Norway AS, experienced a serious loss of control following takeoff from the Maersk Invincible oil installation in the North Sea. The departure occurred at night under challenging weather conditions involving heavy rain and strong winds, which left the crew with no external visual horizon.
Shortly after departing the helideck, the aircraft lost altitude, airspeed, and heading. The helicopter entered an unstable flight profile, accelerating backward with a high nose attitude. For approximately 40 seconds, the aircraft was effectively out of control, drifting 210 meters north of the platform. The crew eventually regained control about one minute after takeoff, though they were at an altitude lower than the original helideck height before establishing a steady climb toward Stavanger Airport Sola.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the flight data, cockpit voice recordings, and crew interviews. The investigation focused on the transition from takeoff to instrument flight and the crew's ability to manage the aircraft during the period of instability. Investigators analyzed the aircraft's technical performance, weather conditions, and the crew's use of Threat and Error Management (TEM) and Crew Resource Management (CRM) procedures.
Findings
- The primary cause of the incident was spatial disorientation experienced by the pilot flying, likely triggered by a sensory illusion during the transition to instrument flight caused by head movements and simultaneous vertical and horizontal acceleration.
- The use of the cyclic trim release button to adjust the pitch-up attitude likely exacerbated the unstable flight conditions.
- The pilot monitoring also experienced a period of disorientation, and the crew's CRM was noted to be ineffective during the most critical phase of the incident.
- The crew had not conducted a specific briefing to address the particular threats posed by the demanding nighttime departure conditions.
- The operator's standard deviation calls lacked specific procedures for communicating abnormal pitch variations, which contributed to miscommunication during the recovery attempt.
Safety action
- The NSIA recommends that the Norwegian Civil Aviation Authority emphasize oversight of how offshore operators manage TEM training and daily operational routines.
- A safety recommendation was issued to the operator, Bristow, regarding the implementation of standard deviation calls for abnormal pitch variations to prevent future communication breakdowns.