Development of the Envelope Function for Flight Flutter Testing

The Envelope Function is a non-parametric approach to determine the overall stability of flight flutter test data without the need for system identification. The approach can also be used to predict the speed at which flutter will occur. This paper describes two developments to enhance its use: firstly statistical confidence bounds of the predicted flutter speed are determined, and secondly an on-line implementation for real-time application is introduced. Both approaches are demonstrated using simulated flight flutter tests on aeroelastic models.