LIMIT CYCLE FLUTTER CHARACTERISTICS RELATED TO CONTROL SURFACE OF LARGE AIRCRAFT¹⁾

The freeplay of the control surfaces is a cause of the structural nonlinearity, which will easily lead to the limit cycle flutter. According to the design requirements, considering the center freeplay of the control surface, rational function approximations of the unsteady aerodynamics in the frequency-domain are constructed based on the Minimum-State Approximation Formula, with the nonlinear stiffness caused by the center freeplay being described by the subsection function. Then the nonlinear response characteristics and the behaviors of the limit cycle flutter due to the freeplay on the control surface are studied. Results show that due to the influence of the central freeplay in the nonlinear system, the limit cycle oscillation is produced below the linear flutter speed, and the limit cycle amplitude increases with the increase of the flight speed or the center gap.