S. I. Zhavoronok, A. A. Zagordan

The wheel-s rolling instability of rigidly fixed main landing gear on initial landing run-s stages when the nose wheel has no contact with runway-s surface has been observed in practice and has no theory based on traditional non-holonomic constraint model of deformable wheel. The yaw instability with progressive rising of the oscillation-s amplitude can be observed at the first stage of wheel-runaway contact, so that the non-holonomic constraint in the contact spot center is incorrect due to the finite angular acceleration of the wheel and the wheel-s slip, and the wheel deformations are small. The special software using deformable wheel model in this problem-s solution are also ineffective. V. F. Zhuravlev and D. M. Klimov have the new holonomic model for the approximately rigid wheel formulated using the multi-component dry friction model. It was supposed that the dry friction has main effect to the rolling stability. Using of this model for initial rolling stages can be more accurate than the classic models of deformable wheel. Some results of both theory and experimental study of main landing gear instability are presented. A new model of the main landing gear with both longitudinal and lateral overhang is constructed using the multi-component Contensou-Erismann dry friction theory and Zhuravlev-s solution for the wheel-runaway contact spot and nonlinear motion equations are derived. A pile driver stand test for the landing gear has been made physically and simulated numerically using the proposed model and the qualitative correspondence of theory and experiment has been shown. To achieve the quantitative correspondence the fictive damping factors of the mathematical model have been calibrated to have the plays approximated accounting. After the calibration based on special test the quantitative correspondence of stand test and theoretical solution has been shown. Using the theory and experimental data comparative analysis it has been proved that the new shimmy model based on the dry friction multicomponent model can quite adequately characterize the main landing gear wheel-s rolling instability and it can be used to model the initial stage of plane landing. Using the landing numerical simulation it was theoretically confirmed the observed effect of wheel hunting oscillations amplitude rising after its spinning.