What happened
During a night-time operation departing from an offshore platform, a Eurocopter EC155B1, registration OY-HJJ, experienced a series of severe pitch excursions. Shortly after takeoff, the aircraft's airspeed dropped below 20 knots, triggering a subsequent descent. The helicopter's altitude decreased significantly, reaching a point approximately 50 feet above the sea surface. Despite the severity of the instability, the flight crew eventually managed to recover the aircraft to a stable flight condition.
The investigation
The investigation focused on the flight path and the crew's response to the aircraft's behavior. Analysis of the flight path indicated that the movements of the helicopter were consistent with inappropriate control inputs made by the crew. Investigators examined both technical elements of the aircraft and the organizational environment surrounding the flight.
Findings
It was determined that a combination of technical and organizational factors had created a situation where the flight crew believed the helicopter was malfunctioning. This perception led the crew to deviate from standard operating parameters. The resulting sequence of events caused the crew to become rapidly disoriented, which compromised their ability to maintain safe control of the aircraft during the excursion.