Model based aircraft design : high angle of attack aerodynamics and weight estimation methods

University dissertation from Linköping : Linköpings universitet

Abstract: This thesis addresses modelling of high angle of attack aerodynamic characteristics and weight estimation for highly maneuverable aircraft during conceptual design. In order to allow configuration selection with sufficient confidence, especially with unconventional configurations, high angle of attack aerodynamic prediction and weight estimations methods need to be improved. In this thesis, a state-space variable approach is proposed for modelling high angle of attack aerodynamics including large angular rates. A new weight estimation based on a parametrical CAD model is also proposed.The aerodynamic model is intended for use in both conceptual design and in later design phases. In conceptual design, the parameters are defined from geometrical data. Good results have been obtained with slender delta wings and on in various full configurations. When test data or CFD data arc available, the parameters are obtained from identification. Various results are presented with high accuracy iu the model. The developed model has been implemented in flight simulation, and in a sizing example, where two different aerodynamic models were used in order to show the influences of large angular rates on the geometrical layout. The presented weight estimation method is based on parametrical CAD models, and the weight is extracted from the structure layout. This allows any type of a ircraft configuration to be investigated, without the use of empirical or statistical approaches. Comparison with known aircraft has shown good agreement.This thesis introduces a new aerodynamic model that includes large angular rates at any angle of attack, and a new weight prediction method. Both have shown good agreement with compared data and indicate that the models are suitable for conceptual design and that further studies should be conducted in order to extend the possibilities demonstrated here.

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