Stefan Storm

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

Feasibility Study of a Hybrid Ice Protection System

A key design factor impacting the use of electrical power to drive aircraft systems and subsystems is energy efficiency. With the design of an all-electric, hybrid ice protection system, energy consumption can be reduced to a large extent. The hybridization is achieved through an intentional partitioning of the ice at the stagnation line by melting via surface heating and ice shedding in the unheated regions of the airfoil surface via an electromechanical deicing system based on piezoelectric multilayer actuators. To further reduce energy consumption, the adhesion forces between the ice and the airfoil surface can be reduced using an ultrasmooth, nanostructured surface with water- and ice-repellent properties that encourages ice shedding. Experimental investigations, performed in a laboratory-scale icing wind tunnel for a small-scale configuration, reveal that the hybrid approach for ice protection reliably sheds the ice accreted on the airfoil surface. Compared with an all-thermoelectric system for ice p...

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, Optimization, Testing, Verification, and Validation of the Wingtip Active Trailing Edge

Within the scope of the SARISTU project (smart intelligent aircraft structures), a wingtip active trailing edge (WATE) is developed. Winglets are intended to improve the aircraft’s efficiency aerodynamically, but simultaneously they introduce important loads into the main wing structure. These additional loads lead to heavier wing structure and can thus diminish the initial benefit. Preliminary investigations have shown that a wingtip active trailing edge can significantly reduce these loads at critical flight points (active load alleviation). Additionally, it can provide adapted winglet geometry in off-design flight conditions to further improve aerodynamic efficiency. The idea of the active winglet has been successfully treated in several theoretical studies and small-scale experiments. However, there is a big step towards bringing this concept to a real flight application. In this project, a full-scale outer wing and winglet are currently being manufactured and will be tested, both structurally and at low speed in a wind tunnel. The scope for eventual EASA CS25 certification of a civil transport aircraft with such a winglet control device will then be assessed. In particular, a load alleviation system requires a minimum operational reliability to take effect on the applicable flight load envelope for structural design. Therefore, the potential failure modes are assessed, and a fault tree analysis is performed to draw key requirements for the system architecture design. In order to assess the overall system benefit, manufacturing, operation, and maintenance requirements are taken into account. The confined space inside the winglet loft-line presents a significant challenge for integration of an active control system. It is shown how small changes to the aerodynamic surface have both reduced the aerodynamic hinge moments (leading to lighter actuators) and created additional internal space for systems, whilst maintaining an equivalent overall drag level. The potential for reducing wing and winglet loads with a winglet control device is assessed. The kinematic design challenge of delivering the necessary power in a confined space is described. Actuation is accomplished by a single electromechanical actuator which is housed inside the CFRP winglet.

Towards the Industrial Application of Morphing Aircraft Wings—Development of the Actuation Kinematics of a Droop Nose

This paper describes the design process of a simple actuation system capable of deforming an extensive flexible skin of a leading edge droop nose designated for laminar wings. Special note has to be taken of a least complex actuation system which has to be smoothly modified between the shape for high-lift and cruise flight. To meet the joint aviation requirements a separation of actuation and skin is mandatory. The design of the kinematics is therefore a key element for the development of a droop nose. The SARISTU project (Smart Intelligent Aircraft Structures‚ EU-FP7 project-consortium‚ [1]) utilizes a planform with a wing span of 16 m from which a 4 m outboard segment was selected for detailed studies. To deform the flexible skin in this region seven kinematic stations with different-sized lever kinematics are required. The objective is to develop an interconnected mechanical kinematic system actuated with a single actuator, taking into account the need of simultaneous and uniform deformation of the skin. For optimization purposes the kinematic system is simplified to a reduced subsystem that consists of a single load introduction point linked by a crank mechanism with the actuation system. Its interconnection is achieved by equal rotational angle of each main lever. The possible kinematic points lie along a straight line, which is exclusively depending on the selected rotational angle of the main lever and is named therefore isogonic line. A geometrical methodology to generate the isogonic line is described for the case that the movement of all kinematic points are in-plane, and also for the general case that rotational movement and linked trajectories are arbitrarily arranged in a three-dimensional space. This newly developed methodology enables not only to find a very precise kinematic solution for interconnected crank mechanisms in a convenient way, but shows the impact of parameter variation which are coming along with inaccuracy of production. A full-scale demonstrator of the enhanced adaptive droop nose was designed with this geometrical construction method and its functionality verified in a wind tunnel under realistic flow conditions and during a life-cycle ground test.

Chapter 26 – Synergic Effects of Passive and Active Ice Protection Systems

Abstract Ice accretion on aerodynamic surfaces can catastrophically impact the safety of an aircraft; it leads to a sudden lift drop and a relevant drag rise, compromising the aircrafts flight capability. Typical ice protection systems (IPS) are either concurrently or alternately hampering the ice accretion (anti-icing) or removing the ice itself before it achieves a dangerous consistency (deicing). Thermoelectric-resistance, pneumatic, and mechanic-hydraulic IPSs are among the most common devices currently implemented on aircraft. Those IPSs require a consistent amount of power and need sufficient room inside the leading edge, the critical wing zone for ice protection. For this reason, more and more research departments, aerospace industries and airline companies are devoting efforts worldwide to the study of ice generation and growth phenomena, with the goal of developing safer, simpler, and cheaper IPSs. The work at hand focuses on three different IPS solutions and how they can be combined for energy-efficient ice protection. The first was a passive technique, implementing a nanostructured surface that reduces the actual wetted surface, thus limiting droplet adhesion. The other two were based on a forced heat transfer to hinder ice formation on the leading edge at the stagnation line, and a mechanical device using piezoelectric actuators to induce ice fragmentation aft of the heated zone. Combined, these devices may need only limited electrical power. The design process used computational fluid dynamics (CFD) numerical tools to describe the ice development and its interaction with the aerodynamic flow. In particular, the ice melting due to thermoelectrical system action was modeled with its downstream motion, illustrating how the melting particles give rise to ice reformation once they move far from the heated zone. The aerodynamic action necessary to ultimately produce ice detachment in this region was then estimated; this information is used to size the piezoelectric actuator system, in terms of actuator thickness, extension, location, and excitation conditions. The icephobic surface characteristics were defined to minimize the wet surface and facilitate the removal action of the aerodynamic and mechanical forces. Laboratory tests were carried out on a scaled airfoil model to estimate the adhesion strength of both rime and glazed ice on both a conventional surface and on a nanostructured icephobic surface. This parameter was used to set the numerical tools. Experiments were then conducted in a wind tunnel environment. There, the ices behavior was observed from formation and throughout its evolution: from its melting at the stagnation point, the downstream movement of the resulting particles, and its reassembly, until its final removal via flow action. The results were compared with the theoretical predictions, appreciating and quantifying the combined action of the three elements of the energy-efficient IPS.

Winglet Design, Manufacturing, and Testing

With respect to the SARISTU project (Smart Intelligent Aircraft Structures), a wingtip active trailing edge (WATE) within the application scenario AS03 has been developed. Full-scale demonstrator has been manufactured and successfully tested to prove the maturity of such a device and its technology. This paper contributes to the overview of design, manufacturing, and testing aspects of WATE demonstrator.