Modeling aircraft braking performance on wet and snow/ice-contaminated runways

Abstract

The paper deals with the modeling of friction between aircraft tires and contaminated runway surfaces. Wet, snow- and ice-covered surfaces are considered. A tire Brush model developed for aircraft braking on dry runways is adapted to take into account the effect of contaminants. Compared with a dry surface, contaminants are assumed to affect the static and dynamic friction coefficients, the tire stiffness, the tire slip ratio, and the length of the contact patch. Linear relationship is established between static and dynamic friction coefficients. The dynamic friction coefficient is reduced using an empirical model for wet surfaces and experimental fitting for snow- and ice-covered surfaces. The tire stiffness is modified considering the frequency and temperature dependence of the tire mechanical properties. Values on snow and ice are lower than those on wet and dry surfaces. A physical model is developed to calculate the length of the wet contact patch. Finally, it is assumed that the aircraft effective slip ratio is surface-dependent, and values are determined for each of the studied contaminants. Theoretical friction–slip curves are realistic in terms of shape and differentiation between surface conditions. The model is applied to a Falcon 20 aircraft and a runway monitoring device called IMAG (Instrument de Mesure Automatique de Glissance). Friction–slip and friction–speed curves are calculated and compared to experimental data. It was found that the model can be used to relate ground friction to aircraft braking performance with enough reliability.