Influence of Geometric Coupling on the Whirl Flutter Stability in Tiltrotor Aircraft with Unsteady Aerodynamics
Publication: Journal of Aerospace Engineering
Volume 25, Issue 1
Abstract
A further improvement is attempted of an existing analytical model for an accurate prediction of the aeroelastic stability of a tiltrotor aircraft. A rigid-bladed rotor structural model with the natural frequencies selected appropriately in both the flapping and lagging motions is used. The geometric coupling between the wing vertical bending and torsion is also included. The pitch-flap and pitch-lag couplings are also added. Three different aerodynamic models are combined with the structural model: two quasi-steady models and one full unsteady aerodynamics model. Frequency domain analysis is conducted to predict the whirl flutter stability boundary. It was found that the geometric coupling must be included at an appropriate level to predict the whirl flutter boundary accurately. The addition of the wing bending/torsion coupling and the control system flexibility improves the prediction accuracy significantly. Unsteady aerodynamics influences the stability prediction. The whirl flutter boundary is predicted to be less when quasi-steady aerodynamic models are used as compared with that for unsteady aerodynamics. For these two cases, different behaviors regarding the intersection among the relevant structural modes, especially between the lower frequency rotor modes and the wing modes, are observed from the frequency and damping prediction.
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Acknowledgments
This work is supported by the Defense Acquisition Program Administration and Agency for Defense Development in Republic of Korea under the contract UNSPECIFIEDUD070041AD. It is also supported by the New and Renewable Energy Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea Government Ministry of Knowledge Economy (UNSPECIFIEDNo. 20104010100490) and by the Korea Aerospace Research Institute under the Korean Helicopter Dual-Use Component Development Program funded by the Ministry of Knowledge Economy.
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Information & Authors
Information
Published In
Journal of Aerospace Engineering
Volume 25 • Issue 1 • January 2012
Pages: 143 - 148
Copyright
© 2012 American Society of Civil Engineers.
History
Received: Feb 21, 2010
Accepted: Nov 29, 2010
Published online: Dec 4, 2010
Published in print: Jan 1, 2012
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