A variable airfoil camber proposes to reduce loads of lifting surfaces. The system stability is investigated in an incompressible flow using a two-dimensional four degree of freedom model on pitch, plunge, slat and flap angles, in which the kinematic of slat and flap are coupled by a linear relationship. Concentrated cubic structural restoring forces as effect of nonlinearities are considered. The aeroelastic governing equations are written and integrated numerically using a fourth order Runge-Kutta scheme for the time domain evaluations. The identification and stability analysis of limit cycle oscillations are presented for a range of the system parameters. Evaluations of the Duhamel and the quasi-steady approximations; and a method in the frequency domain using describing functions combined with the Sherman-Morrison formula are compared. Double period, quasi-periodic and chaos phenomenon were identified, being strictly dependent to initial boundary conditions.