Markus Kintscher

DESIGN OF A SMART LEADING EDGE DEVICE FOR LOW SPEED WIND TUNNEL TESTS IN THE EUROPEAN PROJECT SADE

Purpose – The purpose of this paper is to describe the pre‐design and sizing of a smart leading edge section which is developed in the project SADE (Smart High Lift Devices for Next Generation Wings), which is part of the seventh framework program of the EU.Design/methodology/approach – The development of morphing technologies in SADE concentrates on the leading and trailing edge high‐lift devices. At the leading edge a smart gap and step‐less droop nose device is developed. For the landing flap a smart trailing edge of the flap is in the focus of the research activities. The main path in SADE follows the development of the leading edge section and the subsequent wind tunnel testing of a five meter span full‐scale section with a chord length of three meters in the wind tunnel T‐101 at the Russian central aero‐hydrodynamic institute (TsAGI) in Moscow.Findings – The presented paper gives an overview over the desired performance and requirements of a smart leading edge device, its aerodynamic design for the ...

Design of a Smart Droop Nose as Leading Edge High Lift System for Transportation Aircrafts

A seamless and gapless high lift device at the wing’s leading edge has the potential for reduction of airframe noise as well as for drag. A concept of a smart leading edge device was developed, which, due to systems solutions, delivers an alternative to the droop nose device as used for the A380. The main emphasis of this new device is to realize a structure/system solution for a smooth leading surface, which can be deflected into a typical high lift application. With respect to the fact that laminarity is the only technology which has the potential for step changes in drag reduction within a suitable timeframe, smart seamless and gapless high lift devices are a mandatory enabler for future wings of significantly increased aerodynamic efficiency

Assessment of the SARISTU Enhanced Adaptive Droop Nose

For the application of laminar flow on commercial aircraft wings, the high-lift devices at the leading edge play a major role. Since conventional leading edge devices like slats do not comply with the high surface quality requirements needed for laminar flow, alternative concepts must be developed. Besides the conventional Krueger device that enables laminar flow on the upper side of the airfoil and additionally implicates an insect shielding functionality, smart droop nose devices are currently being investigated. However, the research on such morphing devices that can deform to a given target shape and provide a smooth, high-quality surface has to give answers to questions of fundamental industrial requirements like erosion protection, anti-/de-icing, lightning strike protection, and bird strike protection. The integration of these functionalities into a given baseline design of a morphing structure is a key challenge for the realization of such devices in the future. This paper focuses on the design drivers, system interdependencies, and effects of the integration of the mentioned functionalities into a smart droop nose device.

Design of a Smart Leading Edge Device

To make use of low-drag future generation wings with high aspect ratio and low sweep for natural laminar flow, new high lift devices have to be developed [ACARE (Addendum to the Strategic Research Agenda, 2008), Horstmann (TELFONA, Contribution to Laminar Wing Development for Future Transport Aircraft, 2006)]. At the wing leading edge a smart e.g. morphing high lift device is being developed which provides a high-quality surface without gaps and steps. Due to the low maturity of morphing skins (Thill et al. (The Aeronautical Journal, 112:117–138)) the challenge of high strains has to be solved by an adequate design and sizing process. The presented design process comprises the requirements of a smart leading edge device, the structural pre-design and sizing of a full-scale leading edge section for wind tunnel tests.

Groundtest of a Composite Smart Droop Nose

The future generation of high lift devices for transport aircrafts has to contribute to the reduction of noise during landing and a reduction of drag during cruise flight. Also it has to be compatible with affords for natural laminar flow on the wing. A smart gapless droop nose would be an alternative to today’s slats and promises to contribute to those goals. A consortium of Airbus, EADS-IW, CASSIDIAN and DLR developed such a smart leading edge in the framework of the fourth German national research program in aeronautics. This paper describes a 1:1 3D fiber reinforced flexible smart droop nose and its ground test. The results of these tests will finally be compared with the results of the finite element simulation.

Morphing Value Assessment on Overall Aircraft Level

In order to assess the benefit of the morphing devices developed in the framework of SARISTU, integration in an overall aircraft model is required. For this purpose, the relevant input data regarding the adaptive leading-edge, trailing-edge and winglet devices are gathered with specific focus on weight and aerodynamic performance. Different levels of detail are applied. For weight and actuation power, the methods range from geometry (e.g. span and chord)-dependent methods to absolute delta values which are for instance subtracted from components weights as wing structure weight. Methods for aerodynamic data reach from subtractions of absolute values from the lift to drag ratio, constant for the flight phases (i.e. climb, cruise, decent), towards changes to the induced drag polars specific for each mission increment and dependent on the explicit lift coefficient. For an objective assessment, several aircraft models are compared. The assessment and comparison of these aircraft AC models take place on standard overall aircraft-level parameters as block fuel or maximum take-off weight.

Experimental and finite element analyses of multifunctional skins for morphing wing applications

As a consequence of operational efficiency because of rising energy costs, future transport systems need to be mission-adaptive. Especially in aircraft design the limits of lightweight construction, reduced aerodynamic drag and optimized propulsion are pushed further and further. The first two aspects can be addressed by using a morphing leading edge. Great economic advantages can be expected as a result of gapless surfaces which feature longer areas of laminar flow. Instead of focusing on the kinematics, which are already published in a great number of varieties, this paper emphasizes as major challenge, the qualification of a multi-material layup which meets the compromise of needed stiffness, flexibility and essential functions to match the flight worthiness requirements, such as erosion shielding, impact safety, lighting protection and de-icing. It is the aim to develop an gapless leading edge device and to prepare the path for higher technology readiness levels resulting in an airborne application. During several national and European projects the DLR developed a gapless smart droop nose concept, which functionality was successfully demonstrated using a two-dimensional 5 m in span prototype in low speed (up to 50 m/s) wind tunnel tests. The basic structure is made of commercially available and certified glass-fiber reinforced plastics (GFRP, Hexcel Hexply 913). This paper presents 4-point bending tests to characterize the composite with its integrated functions. The integrity and aging/fatigue issues of different material combinations are analyzed by experiments. It can be demonstrated that only by adding functional layers the mentioned requirements such as erosion-shielding or de-icing can be satisfied. The total thickness of the composite skin increases by more than 100 % when required functions are integrated as additional layers. This fact has a tremendous impact on the maximum strain of the outer surface if it features a complete monolithic build-up. Based on experimental results a numerical model can be set up for further structural optimizaton of the multi-functional laminate.

The preparation of a composite structure for a first large scale ground test of a smart and gapless wing leading edge

At the Institute of Composite Structures and Adaptive Systems (FA, Prof. Wiedemann) of the DLR the structure of a flexible and gapless wing leading edge has been developed for testing in large scale structure-system ground tests. The absence of gaps in a flexible wing leading edge allows for a significant noise reduction and provides an additional key technology for realizing wings with a fully natural laminar flow. In the years 2009 and 2010 the work in the project SmartLED within the 4th German Aviation Research Program (LuFo) was focused on the preparation and realization of the first ground test of the in the project developed overall system. The overall smart droop nose concept arose from the cooperation of Airbus and EADS, whereas the DLR Institute FA dealt with the structural design, the test of the material systems, the simulation of the overall system, and the development of manufacturing technologies for the composite structures to be employed in the planned tests. The detailed presentation of this work forms the content of this paper which has been made possible through the application of the process chain for composite structures established at the Institute FA of the DLR.

Structural Concept of an Adaptive Shock Control Bump Spoiler

Drag reduction technologies in aircraft design are the key enabler for reducing emissions and for sustainable growth of Commercial aviation. Laminar wing technologies promise a significant benefit by drag reduction and are therefore under investigation in various European projects. However, of the established moveable concepts and high-lift systems, thus far most do not cope with the requirements for natural laminar flow wings. To this aim new leading edge high-lift systems have been the focus of research activities in the last five years. Such leading edge devices investigated in projects include a laminar flow-compatible Kruger flap and the Droop Nose concept and these can be considered as alternatives to the conventional slat. Hybrid laminar flow concepts are also under investigation at several research institutes in Europe. Another challenge associated with laminar wings aside from the development of leading edge moveables is the need to address the control of aerodynamic Shocks and buffeting as laminar wings are sensitive to high flow speeds. One possible method of decreasing the wave drag caused by the aerodynamic shock is through the use of shock control bumps (SCBs). The objective of SCBs is the conversion of a single strong shock into several smaller and weaker shocks resulting in a drag benefit when deployed correctly. A particular desirable characteristic of SCBs is that they would be adaptable in position and height as the shock position changes with varying conditions such as speed, altitude, and angle of attack during the flight. However, as fixed case, SCBs can also help to control laminar buffeting by fixing the shock into given positions at the SCBs ocation. In this paper a concept for an adaptive shock ontrol bump spoiler is presented. Based on a concept of a fixed SCB-spoiler an adaptive spoiler design with two conventional actuators is presented. Design drivers and interdependencies of important design parameters are iscussed. The presented design is simple and aims for a high TRL without adding much complexity to the spoiler. It is robust and able to form a bump with a height of 0.6% which position can be adapted in a range of 10% chord.

Characterization of multifunctional skin-material for morphing leading-edge applications

Former research on morphing droop-nose applications revealed great economical and social ecological advantages in terms of providing gapless surfaces for long areas of laminar flow. Furthermore a droop-nose for laminar flow applications provides a low noise exposing high-lift system at the leading-edge. Various kinematic concepts for the active deployment of such devices are already published but the major challenge is still an open issue: a skin material which meets the compromise of needed stiffness and flexibility. Moreover additional functions have to be added to keep up with standard systems. As a result of several national and European projects the DLR developed a gapless 3D smart droop-nose concept, which was successfully analyzed in a low speed wind tunnel test under relevant loads to prove the functionality and efficiency. The main structure of this concept is made of commercial available glass fiber reinforced plastics (GRFP). This paper presents elementary tests to characterize material lay-ups and their integrity by applying different loads under extreme thermal conditions using aged specimens. On the one hand the presented work is focused on the integrity of material-interfaces and on the other hand the efficiency and feasibility of embedded functions. It can be concluded that different preparations, different adhesives and used materials have their significant influence to the interface stability and mechanical property of the whole lay-up. Especially the laminate design can be optimized due to the e. g. mechanical exploitation of the added systems beyond their main function in order to reduce structural mass.