Automatic Operational Modal Analysis of Flight Test Data Using a Modal Decomposition

This paper proposes a novel method for an automatic operational modal analysis. An available finite element structural model is used together with sensor data to derive a linear representation of the system, characterized by a set of mode shapes. The corresponding modal coordinates are used to formulate a criterion for the selection of the flight mode frequencies, which allows a reliable and automated flight mode detection. Furthermore, expanding the modal coordinates with high-resolution finite element modes allows the approximation of flight modes using a larger number of degrees of freedom than available from measurements at discrete locations. A verification case is presented using scaled flight test data of a PC-9/A trainer aircraft provided by the Defence Science and Technology Group.