Nonplanar aerodynamic computation and trim analysis under large deflection of flexible aircraft

Due to large structural elastic deflection and the accompanying geometrically nonlinear aeroelasticity, flexible aircraft make the traditional planar aerodynamic computation inaccurate and obsolete. Spatial curved lifting surfaces call for nonplanar aerodynamic computation to describe their real load conditions and structural aeroelastic response. In this paper, two effective nonplanar (spatial curved) aerodynamic computation methods (3-D lifting-line method and nonplanar vortex lattice method) were established and combined with surface spline interpolation to accomplish geometrically nonlinear aeroelastic trim analysis. The 3-D lifting-line method is simple and effective, as is the nonplanar vortex lattice method, which can consider the warp effect and is capable of complicated model and repetitious computations. Rigid and linear trim results were compared with nonlinear analysis results. The nonlinear trim analysis results from those two aerodynamic methods are consistent with one another and both are quite different from the linear analysis results when deformation is large, which indicates the importance of nonplanar aerodynamic computation and nonlinear aeroelastic analysis.