Assessment of Advanced Flutter Flight-Test Techniques and Flutter Boundary Prediction Methods

Abstract

The paper presents an experimental study, conducted by the Israel Air Force, aimed at the assessment of several advanced flutter flight-test techniques that are designed to improve the efficiency and accuracy of flutter tests. These include the autoregressive moving-average and operational modal analysis system identification methods, the use of various system stability parameters, and the use of atmospheric turbulence versus prescribed flaperon motion as the source of structural response excitation. The methods are evaluated based on data from a dedicated transonic flight test of the F-16 platform. All of the tested methods are able to accurately predict the instability onset. The operational modal analysis method has the advantage that it does not require a priori knowledge of the instability mechanism, whereas the autoregressive moving-average method is easier to implement and straightforward to use in real time. Excitation by atmospheric turbulence is found to be adequate in the current test case, in which the modes are lightly damped and highly suitable for system identification methods that rely on stochastic inputs. The use of autoregressive moving-average and operational modal analysis methods based on responses to atmospheric turbulence appears to offer an accurate and cost-effective flutter testing methodology.