Improvements of some analysis methods for flight flutter test data using unsteady aerodynamic considerations

To date the analysis of data from ight utter tests is routinely carried out under the
assumption of steady or, at best, quasi-steady aerodynamics. This approach is favored mainly
because of its simplicity. In this paper it is shown that, even for some very simple simulated
aeroelastic systems, utter predictions that ignore the unsteadiness of aerodynamic loads can
be signi cantly inaccurate. Then, two simple system identi cation techniques are proposed that
can model both the steady and unsteady aerodynamic loads acting on an aeroelastic system in
incompressible ow. These methods can be used in order to obtain a complete description of an
aeroelastic system subject to unsteady aerodynamic forces, including its dependence on ight
conditions. Finally, the new methods are applied to a simple simulated unsteady aeroelastic
model. The resulting utter predictions are compared to those obtained from two standard
ight utter test data analysis approaches and are shown to be signi cantly more accurate.