Abstract
In recent years, the development of lighter and more efficient transport aircraft has led to an increased focus on gust load alleviation. A recent strategy is based on the use of folding wingtip devices that increase the aspect ratio and therefore improve the aircraft performance. Moreover, numerical studies have suggested such a folding wingtip solution may incorporate spring devices in order to provide additional gust load alleviation ability in flight. It has been shown that wingtip mass, stiffness connection and hinge orientation are key parameters to avoid flutter and achieve load alleviation during gusts. The objective of this work is to show the effects of aeroelastic hinged wingtip on the problem of worst-case gust prediction and the parameterization and optimization of such a model for this particular problem, that is, worst-case gust load prediction. In this article, a simplified aeroelastic model of full symmetric aircraft with rigid movable wingtips is developed. The effects of hinge position, orientation and spring stiffness are considered in order to evaluate the performance of this technique for gust load alleviation. In addition, the longitudinal flight dynamics of a rigid aircraft with an elastic wing and folding wingtips is studied. Multi-objective optimizations are performed using a genetic algorithm to exploit the optimal combinations of the wingtip parameters that minimize the gust response for the whole flight envelope while keeping flutter speed within the safety margin. Two strategies to increase flutter speed based on the modification of the wingtip parameters are presented.
Highlights
Atmospheric gusts and turbulence can significantly affect aircraft ride quality and increase airframe loads
A possible solution to the second problem is to use a folding wing that can be employed on the ground. An example of this technique is the latest version of the Boeing B777X where, through the use of wingtips, the wingspan will be 7 m longer than that of the original B777.4 The folding wingtip capability will be used only on the ground during taxi to and from the gates allowing the aircraft to fit within the airport gate
The wingtip is considered as a rigid body of mass mwt with the centre of mass (CM) at Γ = (Γx, Γy) defined in a reference coordinate system with the origin at the leading edge of the elastic wing tip and with the x-axis parallel to the hinge axis, as shown in Figure 2 θ is the degree of freedom related to the wingtip rotation and it is defined such that a positive angle variation produces a downwards displacement
Summary
Atmospheric gusts and turbulence can significantly affect aircraft ride quality and increase airframe loads. The only deformable parts of the model are the wing, in bending and in torsion, and the wingtip These two elastic modes have been considered because, typically, they are the modes at lower frequencies.[3] Additional degrees of freedom could have secondary effects in the study of the gust load alleviation. The wingtip is considered as a rigid body of mass mwt with the CM at Γ = (Γx, Γy) defined in a reference coordinate system with the origin at the leading edge of the elastic wing tip and with the x-axis parallel to the hinge axis, as shown in Figure 2 θ is the degree of freedom related to the wingtip rotation and it is defined such that a positive angle variation produces a downwards displacement. The maximum peak of the bending moment is reduced by 62%–63%, the maximum peak of the torsional moment is reduced by 31%– 38% and the maximum peak of the shear force is reduced by 31%–33%
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
