The numerical three-dimensional structural design of a large-displacement flexible morphing wing leading edge, otherwise known as a droop nose, is presented in this article. The droop nose is an essential component of a novel internally blown high-lift system for a transport aircraft to delay stall and reduce internal compressor requirements. A design chain consisting of optimization procedures was used to arrive at the structural design of the droop nose composed of a composite fiberglass skin with integral stringers and supporting kinematic mechanisms. The optimization tools aim to produce a design with minimal error to the critical target shapes. A maximum final error of 10.09 mm between calculated and target trajectories of the stringers was found after the kinematic optimization stage. After inputting the kinematic optimization results into the skin optimization stage and solving, a maximum error in the order of 13 mm and curvature difference 0.0028 1/mm were calculated, occurring in the outboard region. Prior two-dimensional analyses with similar shape deviations showed 0.4% lift reduction though further three-dimensional investigations are required. Concepts for integrating industrial requirements abrasion and lightning strike protection and in-flight de-icing into a multifunctional skin show promise and the resulting aerodynamic surface quality was found to be adequate.

Drag reduction plays a major role in future aircraft design in order to lower emissions in aviation. In transonic flight, the transonic shock induces wave drag and thus increases the overall aircraft drag and hence emissions. In the past decades, shock control has been investigated intensively from an aerodynamic point of view and has proven its efficacy in terms of reducing wave drag. Furthermore, a number of concepts for shock control bumps (SCBs) that can adapt their position and height have been introduced. The implementation of adaptive SCBs requires a trade-off between aerodynamic benefits, system complexity and overall robustness. The challenge is to find a system with low complexity which still generates sufficient aerodynamic improvement to attain an overall system benefit. The objectives of this paper are to summarize adaptive concepts for shock control, and to evaluate and compare them in terms of their advantages and challenges of their system integrity so as to offer a basis for robust comparisons. The investigated concepts include different actuation systems as conventional spoiler actuators, shape memory alloys (SMAs) or pressurized elements. Near-term applications are seen for spoiler actuator concepts while highest controllability is identified for concepts several with smaller actuators such as SMAs.

A design for a new high lift system that features a morphing wing leading edge “droop nose” has the potential to generate high lift coefficients whilst mitigating airframe noise emissions. This seamless, continuous, and stepless flexible droop nose potentially offers improvements to stall and compressor requirements for an internally-blown active Coandă trailing edge flap. A full-scale, span-trimmed three-dimensional droop nose was manufactured and ground-tested based on results obtained from new design synthesis tools. A new component of the droop nose is the hybrid fiberglass-elastomeric skin that is tailored in stiffness to meet morphing curvature requirements and spanwise bending resistance. A manufacturing concept of the novel skin was established that led to an adequate manufacturing quality. The skin was driven and supported by two optimized kinematic ribs and conventional actuators and overall shape results show good agreement apart from the region closest to the leading edge. Kinematic trajectory measurements showed that the kinematics met the target trajectories well, with and without the influence of the skin, and it was deemed that the error in curvature is due to a higher than expected skin stiffness in the hybrid layer. Calculated actuator torque levels and strain measurements corroborate this inference. The lessons learned show that means of adjustment post-assembly are needed, and a reduction of torque, energy and a better curvature distribution may be achieved if the skin at the spar junction is allowed to move relative to the main wing. Careful aerodynamic, structural, actuation and manufacturing trade-off studies would be needed to determine the overall performance benefit.

This paper presents some of the progress in research on efficient high-lift systems for future civil aircraft achieved by the Coordinated Research Centre CRC 880 sponsored by the German Research Foundation. Several new approaches to increasing the lift are applied as part of the design of a reference aircraft with short take-off and landing capability: The numerically predicted positive effect of Coanda jet blowing at the trailing edge \ud flap is validated in water tunnel experiments. Robust miniature pressure and hot-fi�lm sensors are developed for the closed-loop control of a piezo-actuated blowing lip. A flexible leading-edge device utilizes composite materials, for which new structural designs are developed. Additionally, a potential de-icing system, as well as a lightning-strike protection are presented. A high power-density electrically driven compressor with a broad operating range is designed to provide the blowing air\ud ow. Different propulsion systems for the reference aircraft are evaluated. An ultra-high bypass ratio engine is considered\ud to be most promising, and thus a preliminary fan stage design process is established. The rotor dynamic influences of the engine on the aircraft structure are investigated through a hybrid approach using a multibody model and modal reduction