Characterizing the Impact of Control Surfaces Free-Play on Flutter

Free-play nonlinearity of the control surfaces has a direct impact on aircraft’s dynamic stability characteristics. . It is impossible to design and manufacture a control surface with zero free-play. As control surface free-play increases, tighter limits must be imposed on the aircraft mission capability. Typically, researchers have utilized an oversimplified piecewise-linear torque-rotation relationship to assess the impact of control surface free-play on flutter. This simplistic approach fails to consider the effects of complex dynamic phenomena, such as intermittent contact and friction between surfaces, that occur as control surface moves from free-play region to non-free-play region and vice versa. Materials Technologies Corporation and Georgia Tech propose an advanced structural analysis tool for characterizing the impact of control surfaces free-play on flutter based on the nonlinear multibody dynamics analysis concept. In our approach, the complete hardware of the wing structure, including the mechanism that results in free-play, are modeled as individual dynamic elements; capturing the complex dynamic phenomena occurring at the transition region of free-play. Phase I concept feasibility of our multibody dynamics based approach will be demonstrated through comparisons between the numerical predictions and subsonic wind tunnel test results for horizontal tails. Proposed approach will be further refined and validated in Phase II with transonic and supersonic wind tunnel tests. Once developed, our innovative tool will provide a quick construction of the structural model, and accurate prediction of the stability behavior of control surfaces with free-play.