Aeroelastic trim analysis of flexible aircraft based on 3-D lifting-line theory

An effective and easy way to analyses the static aeroelastic trim problems of very flexible aircrafts with large aspect ratio wings has been established in this paper, considering the geometric nonlinearity of the structure and the nonplanar effects of aerodynamics. The deformation of flexible aircraft is so large that the traditional aeroelastic methods based on the small deformation hypothesis are no longer suitable, so a new analysis system is eagerly required. The new method in this paper based on the 3-D lifting-line theory is applied to compute the nonplanar steady aerodynamics. Surface spline interpolation method is responsible for the structure/aerodynamics coupling. Moreover, the nonlinear finite element method gives the final nonlinear deformation. By combing these creative methods above and using the iterative computation based on rigid aircraft trim, the results considering the geometric nonlinear effects have been obtained and compared with the linear results, which indicate the new method is much more effective and reliable to the facts and very suitable for rapid and efficient analysis in the preliminary stage of very flexible aircraft design.