A flutter prediction method with low cost and low risk from test data

Abstract

The most common approach to flight flutter testing is to track estimated modal damping ratios of an aircraft over a number of fight conditions. However, the risk is inevitable when this method is utilized since the aircraft must fly near the flutter boundary. In this paper, a method with low cost and low risk for flutter boundary prediction is proposed. Based on structural modal parameters from the ground vibration test (GVT) and the structural response at the sub-critical speed, the generalized aerodynamic force coefficient vector can be solved. The generalized displacement vector is designed as the input and the generalized aerodynamic force coefficient vector as the output. System identification is used to construct the reduced-order aerodynamic model. The aeroelastic model based on experimental results can be constructed by coupling the structural motion equation and the aerodynamic equation in state space. Analyzing the characteristics of the fluid–structure coupling system changing with the dynamic pressure, the flutter onset behaviors can be solved by the eigenvalue method. Wind tunnel tests confirm that this method only needs one wind-on test at the sub-critical speed to predict the flutter onset with a certain precision even the reference dynamic pressure is far from the flutter critical point.