Research On Binding Prevention Design Technique Of An Unmanned Aircraft Landing Gear Shock Absorber

Shock absorber is the key component of the landing gear in absorbing and dissipating thehorizontal kinetic energy during dropping and ground maneuvers of the aircraft, which works only ifthe relative motion occurs between the piston rod and the cylinder, so that the dynamic reaction forceswork to dissipate the energy. And once shock absorber binding problem occurs, there will be functionfailure, which may result in aircraft structure damage or posture unbalance. Since the strut withcamber angle used in the modern fighter landing gear, that problem has been getting attention. Thelanding gear shock strut binding problem occurred during an unmanned aircraft’s flying test, basingon that background this paper focuses on the mechanism behind binding, binding analysis model andbinding prevention optimal design of shock absorber structure. That makes much sense to thedevelopment of binding prevention design technique of shock absorber.In this paper, the main landing gear shock strut of an unmanned aircraft has been investigated asthe research object. At first, via comprehensive analysis and estimation of the configuration, frictionstructure, typical friction models, ground loads and geometry parameters of the landing gear of anunmanned aircraft, built up the force analysis model of the shock strut with friction force, especiallydeduced the calculation formula of the critical friction coefficient and accordingly analysed thebinding characteristic in both static and dynamic conditions. Later, as for the key factors influencingthe binding characteristic, the friction force was calculated considered of the shock strut flexibilityand the ideal planar slide constraint and compared with the results calculated in rigid shock strutcondition. And then the drop dynamics was modeled with taking friction force into account.Combined with the landing gear drop dynamic response curve, the physical meaning of traditionaldynamic binding analysis method was studied. Research shows that method does not hold and for theanalysis of binding problem in the whole process, just taking the static method is directiy. Finally,according to the model and conclusions above, improved the structure of the shock strut andeliminated the binding phenomenon.