Analysis of the ways of occurrence and prevention of critical combinations of events in man-machine systems

Models, methods and algorithms are proposed for analyzing the processes of development and preventing critical combinations of events of various kinds that lead to accidents and catastrophes in man-machine and organizational systems. Critical combinations are combinations of events that are individually relatively harmless, but in combination lead to an accident. In technogenic systems, such events are individual operator errors, equipment failures and adverse environmental effects. To investigate such combinations and identify measures to prevent them, the approaches of probabilistic safety analysis are used. Logical trees are constructed, the minimum sections of which are considered as models of critical combinations of events. For minimal sections, graphs of events and systems of differential equations are constructed, from the solutions of which one can determine the probability of realizing a particular minimum section, and also the intensity of measures to reduce these probabilities, which should be undertaken at different time intervals for the given system. As an example, situations associated with the emergence of critical combinations of events leading to fires in the engine of a twin-engine aircraft and its subsequent emergency landing are analyzed.