Human factors in maintenance: impact on aircraft mishap frequency and severity.

INTRODUCTION: Aviation mishaps caused by maintenance factors vary in severity, but can cost untold sums in lives and equipment lost. This study proposes to demonstrate that certain specific maintenance-related human factors are significantly correlated with both mishap frequency and severity. METHODS: Using information from the Maintenance Error Information Management System (MEIMS), 1,016 aircraft mishaps caused by human factors in maintenance were examined. These mishaps were previously categorized using the Human Factors Analysis and Classification System-Maintenance Extension (HFACS-ME). Frequency analysis was used to determine the most common HFACS-ME factors seen in aircraft mishaps. Logistic regression techniques were used to describe the relationship between the dichotomized outcome of mishap severity and the human factors found in the HFACS-ME. RESULTS: Inadequate supervision, attention/memory errors, and judgment/decision errors were the factors found most often in aircraft mishaps. The factors of inadequate design, inadequate adaptability/flexibility, inadequate lighting/light, confining workspace, and attention/memory error increased odds of being associated with a higher severity mishap. DISCUSSION: Emphasis in training and education placed in the first three factors mentioned may reduce overall number of mishaps. Concentrating resources on the final five factors may decrease the number of severe mishaps.