The UK Air Accident Investigation Branch (AAIB) has published a report into the fatal accident to Eurocopter AS332 L2 Super Puma, call-sign G-WNSB, on its approach to Sumburgh Airport in the Shetland Islands on 23 August 2013.
At 17:17 hrs UTC on 23 August 2013, an AS332 L2 Super Puma helicopter with 16 passengers and two crew on board crashed into the sea during an approach to land at Sumburgh Airport. Four of the passengers did not survive. The flight was transporting employees of the UK offshore oil and gas industry back to Aberdeen, and was calling at Sumburgh Airport to refuel.
The AAIB investigation identified the following causal factors in the accident:
- The helicopter’s flight instruments were not monitored effectively during the latter stages of the non-precision instrument approach. This allowed the helicopter to enter a critically low energy state, from which recovery was not possible;
- Visual references had not been acquired by the Minimum Descent Altitude (MDA) and no effective action was taken to level the helicopter, as required by the operator’s procedure for an instrument approach.
The following contributory factors were identified:
- The operator’s standard operating procedure (SOP) for this type of approach was not clearly defined and the pilots had not developed a shared, unambiguous understanding of how the approach was to be flown;
- The operator’s SOP at the time did not optimise the use of the helicopter’s automated systems during a Non-Precision Approach;
- The decision to fly a 3-axes with V/S mode, decelerating approach in marginal weather conditions did not make optimum use of the helicopter’s automated systems and required closer monitoring of the instruments by the crew;
- Despite the poorer than forecast weather conditions at Sumburgh Airport, the commander had not altered his expectation of being able to land from a Non-Precision Approach.
A comprehensive report is available at gov.uk/aaib-reports/aircraft-accident-report-aar-1-2016-g-wnsb-23-august-2013