What happened
On 23 August 2013, at approximately 1717 UTC, an AS332 L2 Super Puma, registration G-WNSB, crashed into the sea roughly 1.5 nautical miles west of Sumburgh Airport in the Shetland Islands. The aircraft was performing a commercial passenger flight, serving as the third leg of a four-leg rotation between a semi-submersible drilling platform at Borgsten Dolphin and the airport.
During the approach to Runway 09, the helicopter was following radar vectors for a non-precision LOC/DME approach. Flight data indicates that while the aircraft was three miles from the runway threshold, it was following the established horizontal and vertical profiles with the autopilot engaged. However, as the helicopter reached approximately two miles from the threshold, it was flying roughly 240 feet below the required vertical profile, descending at 5-00 feet per minute with an airspeed of 68 knots. As the airspeed dropped below 30 knots, the aircraft experienced an increasing nose-up pitch and a rapid increase in the rate of descent. The helicopter eventually struck the water in a near-level attitude with a slight right bank. Both engines were still producing power at the moment of impact. The accident resulted in 4 fatalities among the passengers and one serious injury to the crew.
The investigation
Following the accident, the AAIB deployed investigators to the Shetland Islands. The investigation involved international cooperation with the French BEA, the helicopter and engine manufacturers, and aviation authorities including EASA and the UK CAA.
Investigators recovered significant wreckage from the sea, including the main rotor gearbox, the main rotor head, both engines, and the tail boom. The tail boom contained the Combined Voice and Flight Data Recorder (CVFDR), which was recovered and processed after a 48-hour drying period. Analysis of the recorded data provided the primary insight into the aircraft's flight path and performance during the final moments of the flight.