An experimental study on flared folding wingtips

Effects of wing stiffness, aeroelastic tailoring and hinge release threshold on gust load alleviation performance

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The flared folding wingtip (FFWT) is a concept presented by Airbus to increase the aerodynamic efficiency and provide a means of load alleviation. A gate-to-gate demonstration of this concept has already been presented with the AlbatrossONE, a scaled aircraft featuring the FFWT concept. In this demonstration, the aircraft fold the wingtips during taxiing to fulfil gate requirements and extends it before take-off for improved efficiency. In addition, they can be released during flight to provide load alleviation and reduce the roll rate reduction caused by the increase in the wingspan. The objective of this thesis is to further study the FFWT concept.

An aeroelastic wind tunnel experiment to identify the influence of the wing stiffness and hinge release threshold on the gust load alleviation performance of a folding wingtip design is presented in this study. Five models with different stiffness and tailoring properties are tested and the wing root bending moment at different conditions is compared to the response with locked hinge conditions to assess the impact on the gust load alleviation capabilities of the folding wingtip.

The results show that the structural properties do not have an important impact on the peak load alleviation but the hinge release threshold and timing do. Releasing with the correct timing can reduce significantly the peak loads. However, the dynamics of the system are affected by this release: the flutter speed is decreased and, although the performance can improve, load oscillations increase, which can be considered detrimental for reasons such as fatigue.