Flight Test Working Group Analyses in Support of the Third Aeroelastic Prediction Workshop

In this paper, collaborative aeroelastic analyses of the X-56A experimental aircraft are presented, which support the activities of the Flight Test Working Group, a subgroup of the third Aeroelastic Prediction Workshop (AePW3). The objective of the Flight Test Working Group was to study the application of flutter prediction tools to a complete aircraft and compare those predictions to flight-test data. The teams generated a total of six different predictions of the body freedom flutter exhibited by the X-56A. The computational predictions of frequency and damping are compared with the flight-test data. All the methods gave similar predictions of the flutter speed but were all about 10–20 knots higher than the measured flutter speed. Additionally, the different generalized aerodynamic forces and the aerodynamic work from the computational tools are compared to illustrate the differences in the methods. Analysis of the aerodynamic work done on the flutter mode by each mode is used to provide insight into the source of errors between flutter predictions. At the flutter speed, the total energy dissipated is equal to the total energy added by the flow. The computational models that best match the test data are dissipating less energy in the pitch mode. However, with only six different predictions, it was not possible to develop more definitive conclusions.