The effects of material variations on aircraft inspection schedules based on stochastic crack growth model

Based on stochastic crack growth model, the effects of material variations on aircraft inspection schedules are investigated in this paper. Fatigue tests are performed to obtain the log standard deviation of fatigue lives due to material variations. The test materials are 7475-T7351, 7050-T7451, 2024-T851 and 2124-T851. The effects of material variation on inspection schedule are significant. For a large material variation, the inspection schedule should be shortened for conservative consideration. The effects of sample size on the material variation under 50% and 95% confidence levels are investigated numerically. The results of this study provide a guideline to allocate resources of fleet planning more realistically by compromising between the cost (or time) of fatigue experiments and aircraft inspections.