Whirl Flutter Analysis of a Tiltrotor Semi-Span Wind Tunnel Model for Test Results Correlation

Abstract

The Clean Sky 2 Advanced Testbed for TILtrotor Aeroelastics (ATTILA) project is aimed at whirl flutter testing of a semi-span wind tunnel model of a tiltrotor, and is intended to support the development of the Next Gener-ation Civil Tiltrotor (NGCTR) Technology Demonstrator. The wind tunnel model has been designed by targeting the main dynamic properties of the full scale demonstrator, and multiple analytical models were used and cross-validated to drive the design choices. The main model components were dynamically characterized after manufacturing with the double aim of checking the design and to correlate the numerical models. This paper provides an overview of the wind tunnel model and describes the numerical models used to predict its whirl flutter characteristics. It also presents the correlation of the numerical models based on the experimental data. Finally, sensitivity analyses are presented that allows both to identify the most relevant parameters affecting whirl flutter, and to quantify the impact that uncertainty on model parameters can introduce in the frequency and damping of the main whirl flutter modes.