Investigation of the dynamics of passenger airplane landing
Company «Tupolev», 17, nab. Akademika Tupoleva, Moscow, 105005, Russia
The problem of landing dynamics investigation remains one of the most important tasks in airplane performance calculation. Its significance is especially emphasized by the fact that most aircraft accidents still occur during landings. It is necessary to take the following factors into account for the detailed investigation of the important physical aspects of the considered problem:
· the strongly nonlinear behavior of the landing gear shock absorbers,
· the Coulomb friction forces in tires and seals,
· the contact interactions between moving parts of shock absorbers,
· the contact between rotating deformable wheels and ground,
The developed mathematical model of the landing gear legs demonstrates all of the required functional parts of the real mechanism. Mass-stiffness beam based airplane model is linked to landing gear legs. The whole described system is solved by direct integration method with the usage of MSC Software products (MSC.Nastran or MSC.Marc). A specially developed program code for MSC.Patran preprocessor simplifies building and editing of both aircraft and landing gear legs models significantly. It also allows the designer to carry out the optimization.
To verify the accuracy of the developed aircraft model its calculated natural frequencies were compared with the results of the modal tests of the real structure. Drop tests were simulated to verify the operation of the shock absorbers of the main landing gear legs. Both of these verification checks showed good agreement between the data obtained from the model and during the experiments, which allows the researchers to use the developed methods for further practical research.
Both symmetric and asymmetric landing cases are investigated on the example of Tu-204SM passenger airplane. Calculation results are compared with the flight test data and information from several published works [2, 3] (the comparison was made, for example, according to the shape of the curves that describe the dependencies between the reaction forces, accelerations and time during the landing). The developed model was also used for calculating landing loads and investigating the operational efficiency of landing gear shock absorption.
Application of the Patran Common Language for the automatization of the model building process and usage of the widely employed MSC.Marc solver make the created methodology more clear and friendly to new users. The author expects that this feature would help to widen the scope of practical application of the developed methods and models. Besides the author considers solving the optimization problem aimed at attaining maximum operational efficiency of landing gear shock absorption as a very important practical task, the appropriate investigation of which is planned in the future.
Keywords:airplane, landing dynamics, mass-stiffness model, shock-absorbers, numerical methods
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- Snisarenco T.V., Chubni V.D. Uchenye zapiski TsAGI, 2008, vol. XXXIX, no. 3, pp. 63-76.