Abstract: The aerodynamic derivatives and flight loads of an aircraft are calculated using nonlinear experimental aerodynamic forces and linear theoretical aerodynamic forces separately. The impact of aerodynamic type, dynamic pressure, and angle of attack on the control surfaces’ efficiency is analyzed, and the emphasis is placed on the relationships between the two factors of control surface efficiency and aileron reversal, and the three factors of the elastic loads of the wing surface, elastic pressure differential distribution, and the elastic aerodynamic pressure center of wings. The analytical results indicate that the control surface efficiency analyzed based on nonlinear experimental aerodynamic forces and linear theoretical aerodynamic forces are different. Due to the influence of the elastic deformation of flexible structures, the efficiency drops constantly with the increase of the dynamic pressure, which even causes aileron reversal. The analysis based on nonlinear experimental aerodynamic forces also reveals that the control surface efficiency is affected to a great extent by the angle of attack, which can not be considered in the analysis based on linear theoretical aerodynamic forces.

Key words: efficiency analysis, aileron reversal, flexible structures, aeroelasticity, control surface, flight dynamics, dynamic load, nonlinear aerodynamic forces