Modeling and analysis of tilt-rotor aeromechanical phenomena

The paper presents a recent effort to explore tilt-rotor aeromechanical phenomena with an emphasize on aeroelastic stability in forward flight (airplane mode). A general tilt-rotor model has been developed and implemented using a numerical technique that preserves symbolic exactness of the equations of motion. The stability study is based on an eigenvalue analysis about a nonlinear periodic trim solution. The present method enables both high resolution periodic response, and clear tracing of the instability drivers by providing the exact partial derivatives of the involved degrees of freedom in each one of the associated equations of motion. In addition to the common way of identifying trends and sensitivities by parametric study, the present approach supplies information about the effectiveness of possible mechanisms that are not included in the baseline model. The present results demonstrate the ability of the method to provide such unique insight into the aeromechanical phenomena in forward flight. Illustrative indications regarding required tilt-rotor design features that will postpone the instability phenomena are discussed.