A study for Unsafe Act classification under crew interaction during procedure-driven operation

In this study, a method for UA (Unsafe Act) classification under a simulated procedure driven operation was proposed. To this end, a procedure driven operation was divided into four stages by considering the crew relations such as instructions and responses. Based on the four stages of a procedure driven operation, ten patterns of UA occurrence paths and the related operators per path were identified. From the ten types of UA occurrence paths including related operators, it is practicable to trace when and by whom a UA is initiated during a procedure driven operation, and the interaction or causality among the crew after the UA is initiated. Therefore, the types of UAs were classified into 'Instruction UA', 'Reporting UA', and 'Execution UA' by considering the initiation time and initiator of UA. A case study to implement the UA type classification and to define the related operators per UA was performed with the ISLOCA scenario simulator training data. The UA classification scheme proposed in this paper can be practical in that it does not require expertise relatively in a human performance analysis and it prevents bias by subjective judgment because it is based on an observation-based approach to exclude subjective judgment.