Flight Testing with the Flutterometer

The utterometer is an on-line tool that indicates a measure of distance to utter in terms of a ight condition during a ight test. The measure of distance is computedasa robust utter margin by applying ¹-method analysis to consider the worst-case effects of modeling uncertainty. The approach is to update the robust utter margin at a series of test points by analyzing ight data. The utterometer was used during an envelope expansion of the Aerostructures Test Wing. This paper describes the results of that ight test. Algorithmand implementation details that are critical to the successful application of the tool are discussed. Also, ight data and analysis are presented to demonstrate the utterometer operation. The ight test demonstrated that the uttero meter is able to predict aconservative estimate of the utter speed.