A Rational Numerical Method for Simulation of Drop-Impact Dynamics of Oleo-Pneumatic Landing Gear

Abstract

Oleo-pneumatic landing gear is a complex mechanical system conceived to efficiently absorb and dissipate an aircraft’s kinetic energy at touchdown, thus reducing the impact load and acceleration transmitted to the airframe. Due to its significant influence on ground loads, this system is generally designed in parallel with the main structural components of the aircraft, such as the fuselage and wings. Robust numerical models for simulating landing gear impact dynamics are essential from the preliminary design stage in order to properly assess aircraft configuration and structural arrangements. Finite element (FE) analysis is a viable solution for supporting the design. However, regarding the oleo-pneumatic struts, FE-based simulation may become unpractical, since detailed models are required to obtain reliable results. Moreover, FE models could not be very versatile for accommodating the many design updates that usually occur at the beginning of the landing gear project or during the layout optimization process. In this work, a numerical method for simulating oleo-pneumatic landing gear drop dynamics is presented. To effectively support both the preliminary and advanced design of landing gear units, the proposed simulation approach rationally balances the level of sophistication of the adopted model with the need for accurate results. Although based on a formulation assuming only four state variables for the description of landing gear dynamics, the approach successfully accounts for all the relevant forces that arise during the drop and their influence on landing gear motion. A set of intercommunicating routines was implemented in MATLAB® environment to integrate the dynamic impact equations, starting from user-defined initial conditions and general parameters related to the geometric and structural configuration of the landing gear. The tool was then used to simulate a drop test of a reference landing gear, and the obtained results were successfully validated against available experimental data.

Variable Stroke Fatigue Test Technology for Aircraft Landing Gears

“…All of the above five loads need to be applied in the test. At the same time, to absorb the impact energy during the aircraft landing process, oil-gas mixture is used to fill between the shock-absorbing struts and main struts of the landing gear [21]. Therefore, under different load conditions, the shockabsorbing struts have different compression amounts.…”

Investigation on the Effect of Anti-Braking System on Nose Landing Gear Shimmy

“…Equation ( 10) is the balance equation describing the horizontal speed V of the aircraft, where C is the air resistance coefficient and μ is the coefficient of the adhesion force of the tire and the ground, which can be calculated by the following equation ( 12) [17], where R is the tire radius.…”

Editorial for the Special Issue “Aircraft Modeling and Simulation”

“…In the second group, focused on structural dynamics modeling area, two articles were published on an adaptive winglet finite element model (FEM) issue [3] and on the modeling of an oleo-pneumatic landing gear using MATLAB instead of FEM, which was considered as one of the originalities of this paper [4].…”

“…In [4], a new methodology is shown, in which four state variables are considered for the modeling and simulation of the oleo-pneumatic landing gear drop impact dynamics. The forces obtained during the drop were simulated on both horizontal and vertical axes.…”