Application of Bayesian updating to the risk analysis of aircraft structures

For the continued safe operation of aircraft within and beyond the design lives, it is vital to quantify the risks involved. One of the risks is the probability of failure of critical structural components by sudden fracture following accumulated fatigue damage. The key factors that affect the risk of fracture are the distributions of the initial flaw sizes at the critical locations on the aircraft and their subsequent evolution under service load, both of which are difficult to determine to a desired accuracy and certainty. In this paper, a new method is proposed to improve the accuracy of the probabilistic risk analysis of aircraft structures by progressively updating the distribution of the initial flaws based on subsequent observations. Specifically, the current flight hours of an aircraft are used to update the initial assumption of the distribution of the initial flaw sizes, based on the Bayes' theorem. A specific case was used to demonstrate the capabilities of the method. This research contributes to the continued efforts by the Defence Science and Technology Organisation to improve and enhance structural integrity assessment of military aircraft, in support of the Australian Defence Force.