Severe load spectrum development for transport aircraft from measured load data: A representative flight method

• A novel framework for high - fidelity severe flight-by-flight (F-B-F) spectrum development using measured fleet load data was proposed. • A novel modeling approach for fleet damage variation and its accompanying method for severe damage determination were proposed. • An improved load-sequence adjustment method tailored to a severe representative flight was proposed. • Test results from fatigue tests on 2024-T3 aluminum alloy specimens confirmed the validity of the severe spectrum development method. 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 was used to establish severe damage criteria. Subsequently, flight data meeting these criteria were extracted to develop a severe load spectrum that accurately reproduces the actual severe load sequences. The accuracy and reliability of the spectrum developed were 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.