Font Size: a A A

Research On Lang Gear Shock Absorber Design For A Flexible Airplane

Posted on:2007-08-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y J ShiFull Text:PDF
GTID:1102360215496988Subject:Mechanical design and theory
Abstract/Summary:PDF Full Text Request
With the development of modern airplanes, such as large transport airplanes and airplanes with thinner or large aspect ratio wings, the structures of the airplanes are becoming more flexible, which have a significant impact on the dynamic characteristics of shock-absorbing system of their landing gears. However, the consideration of the airplane flexibility in the design of a landing gear shock absorber has not been reported and the impact of airplane flexibility on the landing gear behavior needs to make a more detailed study. In addition, based on the fact that the modern weapon's capability of attacking runways is becoming increasingly powerful, to improve the capability of airplanes, where rigid or flexible, in taxing over rough repaired runways is an important factor in making the most of air force during wartime. So it is highly important to consider the flexibility of airplane structure and the capability of the plane in taxing over rough repaired runways in the design of gear shock absorber for modern military airplanes.Based on the extracted key factors to establish a simplified physical model to enlighten innovative idea of design, an equivalent multi-mass system for the flexible airplane is built as a theoretical basis for the landing gear shock strut parameters design, drop test design and rapid analysis of the performance of the airplane in landing or taxing. The landing gear shock strut parameters design iteration method is put forward on the basis of conventional design method with predicting landing energy distribution by using the equivalent multi-mass system for the flexible airplane. An example design and verification results show that this method is of prediction accuracy of the amount of energy stored in the fuselage with required accuracy, less iterations and high calculation efficiency, which have a theoretical and engineering value. The numerical results reveal that the absorption of energy by the airplane structure in landing impact can lower the landing gear loads, but reduce the efficiency in the of energy absorption and the dissipation the shock-absorbing system. Taking the fuselage of a flexible aircraft as a rigid one, the design of the landing gear may not have the anticipated performance, which needs to pay special attention.In this work, the dynamic equations of motion for the shock-absorbing system of a flexible airplane are formulated based on the equivalent multi-mass system for the flexible airplane, velocity-squared damping and poly-tropic air-compression spring for the oleo-pneumatic shock strut and exponential force-deflection for the tire. Numerical analysis of the response of the airplane taxing over a rough repaired runway shows that the introduction of dual chamber in a shock strut is simply to improve the elastic feature of the gas and play a certain role in improving the capability of taxing over a rough repaired runway, so the further improvements in the orifice hydraulic resistance are needed, which is of special interest in dealing with the improvements of the capability of an airplane in taxing over rough repaired runways.In the paper, we also make a study of the improvements in the structure of the shock absorber of existing airplanes and of the schemes for the control of orifice hydraulic resistance, including passive, active and intelligent controls. Numerical analysis shows that these schemes have remarkable effect on improving the capability of existing and conceptual airplanes in taxing over rough repaired runways, which gives the research direction of improving the landing gear shock absorber, and can be used for reference for related researchers.
Keywords/Search Tags:flexible airplane, landing gear shock absorber, parameter design, rough repaired bomb-damaged runway, landing response, taxi response
PDF Full Text Request
Related items