Optimization of the Passive Shock Absorber of a Military Aircraft

For a large military transport the potential is assessed to improve its behavior during touch down and ground run by optimization landing gear parameters. Four oleo force parameters were chosen for the optimzation: the damping coefficients at compression and expansion, the pre-load, and the lenght of the gas spring. With respect to feasibility the variation of the parameters is restricted to a band of 20% about the normal value. Aim of the optimization is the reduction of the vertical acceleration of touch down. During ground roll the ride index has to be minimized. Touch down and ground run were first treated separately. Thus a basis is provided to assess whether switching the damping can satisfy the requirements of both phases. In addition the complete cycle from touch down to roll out was investigated. Concerning the results: It is to be observed that the optimal performance is achieved with the parameters at their limits. The performance in terms of reduction of acceleration, respectively improvement of ride comfort is enhanced by an amount between 20% and 30%.