Safety considerations for WCET evaluation methods in avionic equipment

Most safety-critical avionics systems are defined as “hard real time”. That means they must deliver their function within pre-defined deadlines. Missing a single deadline at system level is considered as a failure condition that may be catastrophic. At software level, this is a single failure that must be mitigated with appropriate means to prevent that failure condition. Real-time requirements are addressed in software components by Worst Case Execution Time (WCET) evaluations. Several methods have been explored in the literature, for which classifications have been proposed according to their techniques and precision of their results. However, these classifications do not consider the contribution of WCET evaluation techniques to safety processes. In this paper, we present a safety process that integrates WCET evaluation on embedded software. This process allows us to highlight the benefits and limits that WCET evaluation methods bring in industrial practices