The following simulations have been executed using MATLAB R2016b. For the purpose of numerical simulations, the parameters $l1$, $l2,$ and $xA\u2212xC$ of the retraction system previously described have been chosen so that the constraint Eq. (1) is respected and that these parameters belong to the feasible region displayed in Fig. 6. Therefore, we have $l1$ = 0.6 m, $l2$= 0.4 m, and $xA\u2212xC$ = 0.4 m. Then, the material of the structure chosen is the Ti-6Al-6V-2Sn alloy, an alloy of titanium with 5–6 mass percent of aluminum, 1–2 mass percent of tin and 5–6 mass percent of vanadium. This material is frequently used for aircraft applications because it has a high yield stress of 1210 MPa but also has a low density of 4.54 g cm^{−3}. Moreover, that specific alloy can also be subject to heat treatments in order to strengthen it. The mass of link *AB* is $m1=6.4kg$, the mass of link *BC* is $m2=4.5kg$ and the mass of the strut and wheels is $m3=502kg$ with moments of inertias of *J*_{1} = 0.222 kg m^{2} and *J*_{2} = 0.065 kg m^{2}, individually. Finally, the viscous friction coefficients of moment of the revolute joints are identically equal to $c=c1=c2=c3=1Nms/rad$. From these data, the variations of the kinematic parameters are obtained in Fig. 9, and then, the variations of the reaction forces and actuation torques are deduced and displayed in Fig. 10 during two cycles of folding inside and unfolding outside the wheel wells. As shown with an increase of $\theta $ in Fig. 9, the landing gear strut is first folded. During the folding motion, i.e., while $\theta $ is increasing, $\phi $ decreases first, but then increases irrespective of the chosen shape for $\theta $ (here sinusoidal).