Compared with other mechanical products, aircraft structures have more rigorous requirements on flying performance, safety, reliability and service life. Based on the finite element method (FEM), the key component of the wing box model is explored in this paper, which provides a reference for the structure design and manufacture of aircraft wing box. The three-dimensional point cloud data of components are obtained by optical measurement systems, the deviation analysis between the point cloud model and the nominal model is carried out as a prerequisite, and then the natural characteristics of the model is analyzed. The results show that 99.15 % of the measured points have deviations within 0.38 mm, which verifies the accuracy of the nominal model. The first six modes are all bending modal shape, and the larger amplitude region mainly occurs in the wing ribs, which means its bending strength should be improved for structure design. Besides, the sixth-mode simultaneously result in front spar, stringer and rib bending vibration.

A thin, low cambered aerofoil with a tab at the trailing edge in inviscid, incompressible, two-dimensional, unstalled flow with varying freestream velocity and arbitrary, different motions for both aerofoil and tab is considered. The general expressions for unsteady lift and aerodynamic moment on aerofoil and tab are derived within the assumptions of potential theory.To verify the approach proposed in this paper, the classical Theodorsen case of an oscillating aerofoil is adopted. For this case, aerofoil loads are calculated in the time domain by applying an inverse Laplace transformation to the approximation of the lift deficiency function in the frequency domain.The comparison of the results calculated by this method with those obtained by other methods and experiments shows good agreement, which validates the general formulation. The loads on an aerofoil having different frequencies for main aerofoil pitch and tab deflection are calculated.