Annual General Assembly 2006 - Dalian

Project Session 1

Poor Monitoring Of The Navigation And Steering Equipment Increases The Reaction Time In Fault

Sauli Ahvenjarvi

ABSTRACT

Behaviour of the officer of the watch (OOW) in managing a failure in the automatic navigation and steering system has been studied by analysing five real accident cases. This paper describes the main results of the analysis. In all analysed cases the accident was partially caused by delayed operator action after a critical failure in the system. The situation is extremely difficult for the operator, when the system fails to give a direct alarm of the failure. The analysis revealed that the operator does not continuously monitor the performance of the equipment. The OOW concentrates on monitoring the overall situation and the movements of the ship rather than on finding out how the navigation and steering equipment is working. These two levels of monitoring are called 'the process level' and 'the equipment level'. Only if an abnormality is noticed on the process level the OOW pays attention to the equipment level. This can not be considered as a user error or an indication of fatigue, but a quite logical behaviour of the OOW. In all the five analysed accident cases the process level monitoring failed to give the OOW a reason to check the performance of the equipment until it was too late to avoid the grounding. This problem of delayed operator action is particularly dangerous in confined waters. It can not be solved by providing more visual information about the performance of the equipment, due to the behaviour of the operator. It can neither be solved by increasing the training of the users because the delayed operator action is not caused by lack of skills, knowledge or motivation. Some potential ways to solve the problem are discussed in the end of the paper.

Keywords: bridge systems; navigation; automatic steering; safety; human factor

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