Severe load spectrum development for transport aircraft from measured load data: A representative flight method: Representative Flight Method for Severe Load Spectrum

The development of severe load spectrum is essential for evaluating the durability and damage tolerance of transport aircraft structure to ensure safety and economic viability. However, traditional methods have lacked consensus on severity selection and often distort load sequences, which undermines reliability in full-scale fatigue testing. This study introduces a novel framework for developing high-fidelity severe Flight-by-Flight (F-B-F) spectrum from measured fleet load data. Statistical modelling of load variations within a specific transport aircraft fleet is used to establish severe damage criteria. Subsequently, flight data meeting these criteria are extracted to develop a severe load spectrum that accurately reproduces the actual severe load sequences. The accuracy and reliability of the spectrum developed are validated through fatigue tests on 2024-T3 aluminum alloy specimens with a centered hole. This approach bridges the gap between severe damage quantification and spectrum development, providing a robust method for generating reliable severe F-B-F spectrum.