In aircraft design, proper tailoring of composite anisotropic characteristics allows to achieve weight saving while maintaining good aeroelastic performance. To further improve the design, dynamic loads and manufacturing constraints should be integrated in the design process. The objective of this paper is to evaluate how the introduction of continuous blending constraints affects the optimum design and the retrieval of the final stacking sequence for a regional aircraft wing. The effect of the blending constraints on the optimum design (1) focuses on static and dynamic loading conditions and identifies the ones driving the optimization and (2) explores the potential weight saving due to the implementation of a manoeuvre load alleviation (MLA) strategy. Results show that while dynamic gust loads can be critical for wing design, in the case of a regional aircraft, their influence is minimal. Nevertheless, MLA strategies can reduce the impact of static loads on the final design in favour of gust loads, underlining the importance of considering such load-cases in the optimisation. In both cases, blending does not strongly affect the load criticality and retrieve a slightly heavier design. Finally, blending constraints confirmed their significant influence on the final discrete design and their capability to produce more manufacturable structures.

Loads analysis and structural design are core steps of the aircraft design process. To reduce wing loads and with it the wing structural mass, methods of passive and active loads alleviation have been researched in recent years. However, those methods are currently implemented without the consideration of dynamic simulations or unsteady aerodynamics in the optimization process in aircraft predesign. The purpose of this research is to investigate the influence of passive and active loads alleviation methods on the structural mass in aircraft preliminary design. The methods have been applied on the wing of a Generic Mid-Range (GMR) aircraft configuration. The models have been created with ModGen, an in-house program at DLR Institute of Aeroelasticity. The models comprise FE-models for the structure and masses, as well as DLM (Doublet-Lattice-Method) model for the aerodynamics. For the investigation of the influence of the loads alleviation systems, a loop of loads analysis and subsequent structure optimization has been conducted. The loads analysis consists of gust and maneuver simulations. For the passive loads alleviation, an aeroelastic tailoring of the wing structure has been implemented, whereas for the active loads alleviation the ailerons are deflected to redistribute lift during maneuvers and to partially compensate lift increment during gust encounters. With the implemented methods, a first quantification of the influence of loads alleviation methods on the structural mass in aircraft predesign is possible.

In the present paper the authors want to investigate the effect of different load configuration in order to identify the ones driving the optimization. A set of static loads, gust loads and static loads with maneuver load alleviation (MLA) are tested. Gust loads have been included in the optimization via an equivalent static load (ESL). Composite blending is tackled by means of continuous constraints and a two phases approach is proposed to find a blended stacking sequence table. Results show that region of influence can be identified for specific loads and that MLA can be beneficial for structural weight reduction. Finally, the blending constraints prove their effectiveness by significantly reducing the error in retrieving a blended stacking sequence.

This paper summarises the design of a gust generator and the comparison between high fidelity numerical results and experimental results. The gust generator has been designed for a low subsonic wind tunnel in order to perform gust response experiments on wings and assess load alleviation. Special attention has been given to the different design parameters that influence the shape of the gust velocity profile by means of CFD simulations. Design parameters include frequency of actuation, flow speed, maximum deflection, chord length and gust vane spacing. The numerical results are compared to experimental results obtained using a hot-wire anemometer and flow visualisation by means of a tuft and smoke. The first assessment of the performance of the gust generator showed proper operation of the gust generator across the entire range of interest.

A detailed performance investigation of the gust generator built for the Open Jet Facility wind tunnel at TU Delft is summarised in this paper. The influence of various parameters such as reduced frequency, measurement location, and excitation amplitude on the generated gust profile was quantified. In addition, unsteady lift measurements were performed using a rigid wing exposed to various gust profiles. In addition, unsteady incremental lift was compared with the DLM method which showed good agreement.