The Flared Folding Wingtip (FFWT) concept allows an aircraft’s wingspan to extend beyond airport gate limitations, while its freely moving wingtip can serve as a Gust Load Alleviation (GLA) device, potentially reducing the required structural weight of the wing.
To study the behavior of the FFWT in combination with a highly flexible wing, this project designed and manufactured a wind tunnel demonstrator, featuring ailerons on both the fixed wing section and the folding wingtip. The inboard aileron is sized to achieve a hypothetical roll rate of 15°/s, comparable to CS-25 certified aircraft, while the outboard aileron is designed to return the wingtip to its neutral position.
Sizing the wing spar of a highly flexible demonstrator while ensuring flutter occurs in the free hinge condition within the velocity range of the Open Jet Facility (OJF) at TU Delft proved to be a conflicting design requirement. This led to a predicted flutter speed of 20 m/s and a maximum wingtip deflection of 5.64%
A Ground Vibration Test (GVT) was conducted to validate the Finite Element Method (FEM) model. A comparison between the locked and free hinge conditions revealed that the locked hinge introduced unexpected flexibility into the structure, which suggests that the FEM representation should be refined to better capture the actual structural behavior.