Prediction of Early Fatigue Crack Growth in PSE Lower Wing Skin of N-2XX Aircraft using DCRACK

Aircraft structural reliability is strongly influenced by fatigue crack propagation in critical wing components subjected to cyclic loading. This study predicts and compares fatigue crack growth at two Principal Structural Element (PSE) locations on the N-2XX aircraft at PT Dirgantara Indonesia using DCRACK simulation: Skin A containing a 164.86 mm access hole and Skin B without geometric discontinuities. Crack growth behaviour was analysed using exponential regression modelling and interpreted within a fracture mechanics framework based on the stress intensity factor range (ΔK). The results show that Skin A exhibits a two-stage crack growth response. Stable Paris-regime propagation occurs during flight cycles 1–600, followed by accelerated exponential growth due to increased stress concentration around the access hole, with crack growth rate rising from 1.642% to 20.33%. In contrast, Skin B maintains predominantly stable crack propagation up to 1200 cycles with an average growth of 6.566 mm and a low growth rate of 1.18%, indicating greater fatigue tolerance. Overall, the findings confirm that geometric discontinuities amplify local stress intensity and accelerate fatigue damage. These results highlight the importance of geometry-sensitive inspection scheduling and support the application of fracture-mechanics-based damage tolerance principles in aircraft structural maintenance planning.