ROBUST FLUTTER MARGIN OF A TYPICAL WING SECTION USING WIND TUNNEL EXPERIMENT DATA : A PRELIMINARY STUDY 1 Abstract Flutter prediction methods usually rely on tracking modal damping trends,estimated from flight/experimental data, which are not always accurate indicators of flutter onset. This methods is based on a finite element model of the aircraft and does not directly consider flight/experimental data from the physical model. A new approach to computing flutter instability boundaries based on the structured singular value is presented. This approach is developed that utilizes a theoretical model while directly accounts for the variations using the experimental data. The aeroelastic stability problem is formulated in a fremework suitable for well-developed robust stability theory by parameterizing around velocity and introducing uncertainty operators to account for modeling errors. Experimental data can be used to validate the robust system model and increase accuracy of the flutter margin estimate. Parameterization around velocity allows the generalized equation of motion to be a linear function of wind tunnel flow-speed so that perturbations to this parameter can be entered in the form of linear fractional transformation. The μ-analysis method will treat the perturbation as a system uncertainty. Two uncertainty operators are used to describe the modeling uncertainties in the linear aeroelastic model. The first uncertainty operator is associated with the state matrix of aeroelastic linear model. This uncertainty models variations in both the natural frequency and damping values for each mode. The second uncertainty operator is a multiplicative uncertainty on the force input to the linear model. This uncertainty is used to cover nonlinearities and unmodeled dynamics. The level of both uncertainty is determined from reasoning of the modeling process and analysis on the wind tunnel experiment data. Using this method on an aeroelastic wing section system gives a flutter prediction that is closer to the experimental result, which means it can give a better prediction from safety point of view. 1. Introduction Aeroelastic system is a combination of elastic structure and aerodynamics system. Aeroelastic is a critical system, since it can lead to an unstable condition. Several analysis techniques for predicting the behaviour and stability of an aeroelastic system have been developed. Most of those techniques based their analysis on mathematical representation of the system, whether analytical models or empirical ones. In other words, the analysis and investigations will entirely depend on the quality of the model representation and/or the technique in obtaining ROBUST FLUTTER MARGINS OF A TYPICAL WING SECTION USING WINDTUNNEL EXPERIMENT DATA : A PRELIMINARY STUDY H.Y.Sutarto, Rianto A.S., Zaki S., L.Gunawan Vibration And Control Laboratory Department of Aerospace Engineering Institute Of Technology Bandung Indonesia e-mail : sutarto@ae.itb.ac.id Keywords: Structured singular value, LFT, Flutter Margins. ICAS 2002 CONGRESS