Today marks the tenth anniversary of the loss of Super Puma G-WNSB on the approach to Sumburgh (Shetland) with four fatalities. Although the Mountain Assurance blog is really about the mountains, this tragic incident is important for a couple of reasons.

  1. The human factors elements of the incident such as task management in challenging weather conditions, can sometimes be found in incidents in the mountains.
  2. The Air Accident Investigation Branch (AAIB) took two different approaches to modelling the human factors elements of the incident. Both of which reached similar conclusions.

The crew of Rescue Bond One, the industry rescue helicopter based on the Miller Platform, was also involved in the initial search and rescue effort. An interview with retired Search and Rescue pilot Graham Stein can be found here at: Mountain CRM: An interview with a Search and Rescue Helicopter Pilot.

Super Puma G-WNSB (c) CC BY-SA 2.0 Ronnie Robertson - Puma G-WNSB IMG_6151
Super Puma G-WNSB CC BY-SA 2.0 Ronnie Robertson – Puma G-WNSB IMG_6151

The Incident

The incident itself culminated with the impact of the AS332 L2 helicopter with the sea, during the approach to Sumburgh airport. The three sector flight involved a stop at Sumburgh to refuel. This followed a late change in the passenger manifest, and was made in poor weather conditions and low visibility despite being in summer.

A number of Non-technical Skills failures are noted leading up to, and immediately prior to impact. These include communication lapses, (with the ‘pilot monitoring’ failing to advise a level off or abort of the approach), Situational Awareness and task management. Notably a high workload option was chosen for the approach when alternatives existed.

AAIB Report and Human Factors Analysis

The AAIB produced a detailed report which can be found here at: AAIB Report – G-WNSB. Of particular interest to work in the mountains are the independent Human Factors (HF) reports under Appendix H and I. These consider the Human Factor elements using different approaches, but both describe high workload in the later stages of the flight, combined with ambiguity in standard operating procedures which may have contributed to the approach taken.

Appendix I uses an Accident Route Matrix (ARM) approach which is a systems developed by the Royal Air Force Centre for Aviation Medicine (RAFCAM). This provides an investigation methodology built on James Reason’s Swiss Cheese model of Latent and Active Failures combined with the Human Factors Analysis and Classification System (HFCAS).

For an excellent description of how James Reason’s Swiss Cheese model can be applied to the mountains or outdoor adventurous activity I can recommend Safety, Risk and Adventure in Outdoor Activities by IFMGA Mountain Guide Bob Barton.

In the RAFCAM analysis it is apparent in their view that the crew were subject to a number of factors prior to the incident. In outdoor sector speak they were probably operating in exactly the same way as their peers.

“The entry conditions describe HF aspects that were relevant to the G-WNSB accident and were present before the day of the incident. The majority of the entry conditions were not specific to the G-WNSB crew or to the day of the accident, but were common issues that could have influenced any crew.”

Aircraft Accident Report AAR 1/2016 – G-WNSB, 23 August 2013


There were two key threats relevant to this incident. The first issue was work preparation and the work environment, namely the relationship between pre-flight planning and deteriorating weather conditions. Two flight plans were initially prepared, before the co-pilot recommended routing directly to Aberdeen from the Borgsten Dolphin platform due to deteriorating weather conditions. The additional request to take an extra passenger, resulted in an additional leg to facilitate refuelling at Sumburgh.

The approach to Sumburgh was then made on instruments due to the reduced visibility. The second was that of procedure, and the ambiguity of Standard Operating Procedures (SOP’s) with regard to instrument approaches. The Aircraft Accident Report states a contributory cause as a lack of defined SOP’s for this type of approach (Aircraft Accident Report: 1/2016). This provided the pre-conditions for the selection of automation chosen, and ultimately what became an unstable approach prior to impact with the sea.

The operator’s 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.

Aircraft Accident Report AAR 1/2016 – G-WNSB, 23 August 2013

Non-technical Skills and the Mountain Environment

So what has this got to do with being in the mountains? Well, although the environment is different the same themes are frequently evident in human performance.

In this incident there is an obvious absence of communication on approach tactics, which is symptomatic of the lack of a shared mental model, and hence limited situational awareness. During the flight itself communication between the Pilot Flying (i.e. Commander) and Pilot Monitoring (Co-pilot) was conversational and non-standard. As a result, it could be argued that some information was unclear.

The full transcript can be seen in Appendix D of Aircraft Accident Report: 1/2016. A pivotal moment was the absence of any communication from the Co-pilot in the later stage of the approach, most notably he did not advise a level off or abort, when visual references could not be gained. This failure to level off or abort the approach represents a violation of procedure, and rendered the safety barriers ineffective.

Finally, these communication issues are also symptomatic of lapses in teamwork and Crew Resource Management (CRM). The Non-technical skills lapses identified above contributed to the crews failure to make effective use of all available resources to assure a safe and efficient operation.

In the Mountains

When working together in the mountains we can:

  • Make sure that everybody knows the plan and is effectively on the same page. Create a shared mental model.
  • At key decision points in our day remember that communication needs to be effective.
  • Remember that changes of plan can mean that risk assessment can be time pressured, and changes may not get the same level of scrutiny. Especially in challenging weather conditions.
  • Our brains capacity to cope with different tasks is finite. Off-load tasks e.g. by planning well.

For providers and users of standard operating procedures (SOP’s):

  • SOP’s should be revised frequently to prevent ambiguity. Ask the people that do the work if they help or hinder.

If you liked this article you may wish to read Attentional Narrowing: Why mountain guides and pilots know it can put you in harms way or Mountain CRM: An interview with a Search and Rescue Helicopter Pilot. Check out Assured Training or E-Learning.

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