Test Rig Landing Gear Free-Fall System Model Simulation and Design Optimization Using Matlab

Abstract

In order to comply with the safety level demanded by civil certification requirements and military standards, alternative methods of extending retractable landing gear are provided in practically all airplanes of this type currently flying throughout the world. However, the emergency extension operation system design is not unique and architectures comprising simpler systems like free-fall or spring-assisted up to more complex systems like auxiliary hydraulics-assisted or pneumatics-assisted ones can be found in different airplanes. The airplane landing gear 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. This paper aims at describing the modeling and simulation of a general landing gear emergency extension system built in a test rig, for a non-assisted type system, applying only an extension by gravity. Due to the low associated cost, satisfactory results and capability of easily assessing the trade-offs between different systems configurations, modeling applying computational software has become a frequent practice in aeronautical industries with the purpose of reducing product development cycle. Therefore, a parametric model of the landing gear emergency extension system was created in MATLAB ® Simulink ® and the system performance at nominal and particular operational conditions could be predicted by running several model simulations. Afterwards, through the assistance of MATLAB ® tools, discrete and continuous optimization processes were accomplished to illustrate the benefits of applying these techniques to improve system operation response. An optimum damping condition permits 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.