learning from incidents. 'Loss of situation awareness' has appeared quite frequently in recent incident reports, brought about by factors ranging from loss of channel lights to the use of a mobile phone whilst on watch.
Johnson (Ref 4) concludes 'Most human factors' research is concerned with improving our understanding of human error. Very little of it can be directly applied to reduce the impact or frequency of those errors'. From the point of view of encouraging corrective or improvement actions, it is desirable to link the analysis to models of good practice. In the case of the 'sharp end', this would be a model of Crew Resource Management. Other models are appropriate to design offices, manufacturing facilities, and other places.
Information presentation
Any incident investigation will result in a large volume of data, some of which has little relevance to the conclusions. Many incident reports are very detailed, lengthy and written for the expert professional. The need for a full narrative is not questioned, but for maximum benefit the incident and its precursors need to be interpreted for a wide audience.
The use of some diagrammatic formats such as fault trees should be regarded as for the specialist only. The lessons learned must be presented so that the competent reader can draw conclusions of value.
Learning from incidents can only be effective if the learning outcomes are communicated effectively to the widest possible audience. It follows that there are benefits in adopting a format which is clear, logical and standard. The logical approach to organising the information is user-centred, ie, by stakeholders. The understanding of the reader is significantly enhanced if he understands why things did happen that way; reconstructing the evolving mindset would appear to offer considerable value in this regard.
The importance of clear presentation is crucial when there are a number of links between systems and people. Of significance is identification of opportunities that were, for some reason, missed. This may be that information was not understood by the people involved or too much data was available and the interpretation placed on this was incorrect. Neither necessarily infers a lack of competence. If the benefits of learning from incidents are to be achieved, then the information to be presented increases in scope considerably, to accommodate those shortfalls where there are lessons to be learned but which were deemed not to be among the causes or contributing factors.
Non-proximate causes
It sometimes appears that investigations take a long time and publication of the final report appears to be far after the event. In reality, investigators have to work quickly, before the evidence fades, and work patiently through the collected data. They need to consult with a large number of interested parties. They then have to reach conclusions which are robust and make recommendations which will have a significant impact if implemented effectively. Since the focus is inevitably on a single incident, it is not surprising that it is rare to find
62 THE NAVALARCHITECT FEBRUARY 2006
investigators making recommendations based on other than the proximate causes, which means that some information which could provide a learning opportunity is discarded as not relevant. Where prosecution is being pursued, it is also the case that investigators can do sufficient to achieve that aim but no more (of particular importance in relation to human error as a cause).
The consequence of various pressures on investigators to achieve a quick result is that some of the less obvious but nevertheless important lessons are lost. The authors, in conducting some paper studies, have found a number of cases where opportunities for learning have been missed.
This happens also in informal investigations where the pressure is to find a solution to the problem and not to investigate, for instance, how the circumstances arose in the first place. As an example, Fig 1 shows a broken section of shaft, with a keyway and a classic fretting fatigue fracture. The shaft mounted a flexible coupling, fitted on a taper and secured by a threaded retaining nut.
Investigation identified that the cone angle of the taper was unusually large and this demanded a carefully controlled fitting procedure, which was not apparently followed.
So the proximate cause of the failure is identified, but why did the designer choose the form employed and why was the fitting procedure not followed? In terms of avoiding recurrences, these lessons might be important. It has become apparent that 'drawing office rule of thumb' values have fallen into disuse and a number of cases where failure has resulted from details which would not satisfy these practices, with designers relying on calculations and analysis.
The authors believe that a great deal can be learned from studying the underlying factors in determining why things were done in a particular way. When a combination of factors is involved in an incident, this can make it more difficult to establish why decisions were made but, with an industry reliant on subcontracting and increasingly complex systems, understanding
the issues involved can help the regulator to decide where the most appropriate risk control measures can be targeted.
Structured analysis using a systems approach Asmall literature has been identified that takes a systems approach to accident causation and analysis. It is not homogeneous. The authors have taken a systems approach in the following respects:
• relevant systems have been identified (see Annex A) and treated as systems
• a systems (rather than mechanistic) approach to causation is taken (see Annex B).
The approach to incident analysis adopted by the authors makes use of a spray diagram (Ref 5) or 'mind-mapping' format. This presents the data in an informal but structured form that is very compact. It also allows links to be drawn between the various elementary causal factors and for links to be brought together in standard groups.
This particular incident analysis activity does not need to identify the specific causal sequences or logic, enabling the use of simpler diagrams. It is recognised that this format may not suit all phases of incident analysis.
The format bears some similarities to accepted methods such as TRIPOD (Ref 6), event trees, and fault trees. The reasons for adopting this particular format were:
• simplicity and ease of understanding • it draws out the multi-agent nature of accident causation and identifies the main groups of agents through the life cycle
• by focusing on the main groups of agents, the format is user-centred and allows the reader to concentrate on their particular area of interest
• it enables cause and contributory factors to be related to models of good practice, such as the approach developed under the EU funded ATOMOS project (rather than
Fig 1. A failed coupling shaft.
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