A study on the influence of ground static pitch angle on ground-roll instability

Purpose – During high-speed ground-roll phases, fixed-wing aircrafts, particularly those with flying-wing configurations, may exhibit various ground-roll instability phenomena. This study aims to investigate this issue by analyzing how the ground static pitch angle affects directional stability during high-speed ground-roll phases. Design/methodology/approach – In this study, a generalized mathematical model for ground-roll dynamics is established based on simplified force analysis that considers the influence of landing gear configuration and aerodynamic moments. The model is implemented within a Matlab/Simulink simulation framework and validated through comparison with existing simulation results from previous studies. Additionally, root locus analysis is used to examine the effects of key parameters, particularly ground static pitch angle on system stability. Findings – The analysis indicates that exceeding a critical ground static pitch angle ([Formula presented]) compromises directional stability during ground-roll by increasing aerodynamic lift and pitching moment, which reduce landing gear friction and amplify destabilizing nose gear moments. This instability is further exacerbated in flying wing configurations due to the absence of vertical tail surfaces. These findings are reinforced by the results obtained from simulation. Originality/value – This study develops a generalized analytical model of ground-roll dynamics that explicitly incorporates pitch angle effects, a factor often neglected in previous research. In contrast to Song et al. (2015), which relied on simplified force analysis, and Yin et al. (2023), which focused on parameter sensitivity without linking to aircraft configuration, this study derives stability boundary evolution through root-locus analysis. The findings reveal a critical instability mechanism relevant to novel configurations such as flying wings, providing new insights for aircraft design and takeoff performance evaluation.