On the Fine-Tuning of the Stick-Beam Wing Dynamic Model of a Tiltrotor: A Case Study

The T-WING project, a CS2-CPW (Clean Sky 2 call for core partner waves) research initiative within FRC IADP (Fast Rotor-Craft Innovative Aircraft Demonstrator Platform), focuses on developing, qualifying and testing the new wing of the Next-Generation Civil Tilt-Rotor (NGCTR). This paper introduces a case study about a methodology for refining the stick-beam model for the NGCTR wing, aligning it with the GFEM (Global Finite Element Model) wing's dynamic characteristics in terms of modal frequencies and mode shapes. The initial stick-beam model was generated through the static condensation of the GFEM wing. The tuning process was formulated as an optimization problem, adjusting beam properties to minimize the sum of weighted quadratic errors in modal frequencies and Modal Assurance Criterion (MAC) values. Throughout the optimization, the MAC analysis ensured that the target modes were tracked, and, at each iteration, a new set of variable estimates were determined based on the gradient vector and Hessian matrix of the objective function. This methodology effectively fine-tunes the stick-beam model for various mass cases, such as maximum take-off weight (MTOW) and maximum zero-fuel weight (MZFW).