Landing Gear Free-Fall Simulation and Kinetic Energy Optimization 2010-36-0139

The free-fall operation comprises a redundant, dissimilar and independent mechanically operated method of extending airplane landing gear due to a main hydraulic system failure or an electrical system malfunction. However, the emergency extension operation system design is not unique and spring-assisted, auxiliary hydraulics-assisted or even pneumatics-assisted landing gear free-fall design can be found in different airplanes. This paper aims at describing the model simulation and the optimization of certain parameters related to the associated hydraulic system, for emergency operation condition, in a non-assisted system configuration comprising simple extension by gravity. Since the free-fall modeling involves different subjects like landing gear extension dynamics, hydraulic actuator kinematics, fluid mechanics and even aerodynamic drag, which illustrates the complexity behind its simulation and optimization, a deep literature review was accomplished in order to support all the formulation necessary to make the modeling feasible. For this purpose, a parametric model was created in MATLAB Simulink, which, by means of an iterative process, allowed the determination of specific parameters values that optimized the damping for that operation. Parameters like restrictor orifices and hydraulic actuator piston areas were evaluated for a chosen landing gear configuration and system performance optimized through the assistance of MATLAB optimization tools. Finally, the purpose of the optimum damping comprised the attenuation of the impact effects suffered by aircraft structure when landing gear falls by gravity in an emergency operation, as well as the assurance of sufficient energy for landing gear locking at the end of its downward movement.