Flight Test Evaluation of Flutter Prediction Methods

Several methods have been formulated to predict the onset of  utter during  ight testing. These methods have been demonstrated using data from simulations; however, a rigorous evaluation that includes data from  ight testing must be performed. The ability of several methods to predict the onset of  utter by analyzing data from  ight tests of the aerostructures test wing is evaluated. The evaluated methods include data-based approaches that use damping extrapolation, an envelope function, the Zimmerman–Weissenburger  utter margin, and a discretetime autoregressive moving-average model. Also, a model-based approach that uses the 1-method  utterometer is evaluated. The data-based methods are demonstrated to be unable to predict  utter accurately using data from low-speed test points, but converge to the accurate solution as airspeed is increased. Conversely, the  utterometer is demonstrated to be immediatelyconservative using data from low-speed test points, but these predictions remain conservative and do not converge to the true  utter speed as the envelope is expanded. The operation of a  ight test should note the properties of each method to perhaps adjust test points based on the predicted  utter margins.