Aeronautic and aerospace engineering is recently moving in the direction of developing morphing wing devices, with the aim of making adaptable the aerodynamic shapes to different operational conditions. Those devices may be classified according to two different conceptual architectures: kinematic or compliant systems. Both of them embed within their body all the active components (actuators and sensors), necessary to their operations. In the first case, the geometry variation is achieved through an augmented classical mechanism, while in the second case the form modification is due to a special arrangement of the inner structure creating a distributed elastic hinges arrangement. Whatever is the choice, novel design schemes are introduced. Then, it is almost trivial to conclude that standard methods and techniques cannot be applied easily to these innovative layouts. In other words, because new architectures are produced, the former construction paradigms cannot be maintained as they are but shall be somehow transformed and assimilated by the design engineers’ community. In the meantime, the realization process should go on and morphing elements shall be realized, irrespectively of the full maturity of the associated concepts. Therefore, if optimization methods are important for the better exploitation of usual constructions, they become absolutely necessary for the technological demonstration of the capability of such breakthrough systems. In fact, standing their aim of improving the effectiveness of the aircraft flight and reducing then its overall weight, mass impact plays a fundamental role. Promised benefits could completely vanish if the added should overcome the saved weight!
In the study herein presented, the design process of a morphing winglet is reported. The research is collocated within the Clean Sky 2 Regional Aircraft IADP, a large European programme targeting the development of novel technologies for the next generation regional aircraft. The ultimate scope concerns the definition of an adaptive system for alleviating the gust loads and possibly modifying the wing load distribution in the sense of minimizing the attachment momentum (the parameter that governs the wing sizing). The proposed kinematic system is characterized by movable surfaces, each with its own domain authority, sustained by a winglet skeleton and completely integrated with a devoted actuation system. Preliminary aeroelastic investigations did already establish the robustness of the referred structural layout. This paper summarizes the activities relating to the optimization of the envisaged morphing system architecture. Moving from a standard configuration, a process is carried out to identify the lighter adaptive layout that can bear the external and internal loads without experiencing excessive stress levels for its safe operation. The most severe loads are taken into account for this process, as provided by the industrial partner, showing the reliability of the proposed solution on-board of a standard commercial aircraft. The optimization process produces interesting, sometime surprising, results that promise to reduce the weight impact of the structural skeleton for more than 40% with exclusive reference to the regions undergoing the optimization process. Such figure reduces to 15% if the complete structure is taken into account, and 12% if the skin contribution is included. The innovative outcomes are discussed in detail. Results are verified with a dedicated study that proves the consistency of the procedure and the trustworthiness of the computations.
Variation of trailing edge camber proved to be one of the easiest and most effective ways to modify aerofoil shape to match different aircraft operational weights, with benefits approaching 3% of fuel savings or, equivalently, range extension. This is particularly the case of commercial planes, where both initial take-off conditions (because of the unpredictable payload or the specific required mission – transfer flight, for instance) and in-flight states (for the kerosene consumption) can undergo significant differences. Several studies (like the European Research Programs SARISTU or JTI-GRA) demonstrated that the most sensible region for installing an adaptive trailing edge system for those aims is towards the wing tip. This is unfortunately a very delicate area where usually ailerons are deployed and where significant mass insertions could affect the aeroelastic response with some risks of instabilities. Furthermore, the volume available are really limited so that the installation of a fully embedded system is challenging.
Moving from the experience taken in many former projects as the cited ones, the authors faced the problem of installing a fully integrated adaptive trailing edge system within the existing structural skeleton of a reference aileron and defined a design strategy to take into account the aeroelastic modifications due to the installation of such a device. Besides, the architecture preserved the original function of that control surface so that it could work as a standard aileron (classical rigid tab movement) with the augmented function of a deformable, quasi-static shape. In this sense, the proposed system exhibited a double functionality: a conventional rigid aileron with augmented shape modification capability plus a continuous, slow change of the trailing edge, occurring during flight for compensating aircraft weight variation.
The research was carried out within the Italian-Canadian program MDO-505 and led to the realisation of a multifunctional aileron with two operational motor systems (one for the classical aileron working and the other for the morphing enforcement), completely integrated so that no external element was visible or affected the aerodynamics of the wing. The manufacture of this device was possible thanks to the development of a suitable design process that allowed taking into account both the structural and the aeroelastic response of the integrated architecture. This system was part of an adaptive wing section that was completed with the realisations made by the ETS of Montreal, the Quebecoise Consortium for Aerospace Research and Innovation (CRIAQ) and the IAR-NRC, supported by Bombardier and Thales Canada. The joint demonstrator was tested in the wind tunnel at the NRC facilities in Ottawa and gave confirmation of the aerodynamic, aeroelastic and structural predictions.
The paper that is herein presented deals therefore with the design process and the manufacture of an adaptive trailing edge, installed within the existing aileron system of a wing segment, to undergo wind tunnel tests. The resulting device considers the definition of the kinematic structural system, the development of the integrated actuator system, their integration and the assessment of their static and dynamic structural response, and the verification of a safe aeroelastic behavior. Numerical and experimental results are presented, achieved in lab and wind tunnel environments.
The development of adaptive morphing wings has been individuated as one of the crucial topics in the
greening of the next generation air transport. Research programs have been lunched and are still running
worldwide to exploit the potentials of morphing concepts in the optimization of aircraft efficiency and in the
consequent reduction of fuel burn. In the framework of CRIAQ MDO 505, a joint Canadian and Italian
research project, an innovative camber morphing architecture was proposed for the aileron of a reference
civil transportation aircraft; aileron shape adaptation was conceived to increase roll control effectiveness as
well as to maximize overall wing efficiency along a typical flight mission. Implemented structural solutions
and embedded systems were duly validated by means of ground tests carried out on a true scale prototype.
Relying upon the experimental modes of the device in free-free conditions, a rational analysis was carried out
in order to investigate the impacts of the morphing aileron on the aeroelastic stability of the reference
aircraft. Flutter analyses were performed in compliance with EASA CS-25 airworthiness requirements and
referring -at first- to nominal aileron functioning. In this way, safety values for aileron control harmonic and
degree of mass-balance were defined to avoid instabilities within the flight envelope. Trade-off analyses were
finally addressed to justify the robustness of the adopted massbalancing as well as the persistence of the
flutter clearance in case of relevant failures/malfunctions of the morphing system components.
Like any other technology, morphing has to demonstrate system level performance benefits prior to implementation onto a real aircraft. The current status of morphing structures research efforts (as the ones, sponsored by the European Union) involves the design of several subsystems which have to be individually tested in order to consolidate their general performance in view of the final integration into a flyable device. This requires a fundamental understanding of the interaction between aerodynamic, structure and control systems. Important worldwide research collaborations were born in order to exchange acquired experience and better investigate innovative technologies devoted to morphing structures. The “Adaptive Aileron” project represents a joint cooperation between Canadian and Italian research centers and leading industries. In this framework, an overview of the design, manufacturing and testing of a variable camber aileron for a regional aircraft is presented. The key enabling technology for the presented morphing aileron is the actuation structural system, integrating a suitable motor and a load-bearing architecture. The paper describes the lab test campaign of the developed device. The implementation of a distributed actuation system fulfills the actual tendency of the aeronautical research to move toward the use of electrical power to supply non-propulsive systems. The aileron design features are validated by targeted experimental tests, demonstrating both its adaptive capability and robustness under operative loads and its dynamic behavior for further aeroelastic analyses. The experimental results show a satisfactory correlation with the numerical expectations thus validating the followed design approach.
The study herein described is aimed at investigating the feasibility of an innovative full-scale camber morphing
aileron device. In the framework of the “Adaptive Aileron” project, an international cooperation between Italy and
Canada, this goal was carried out with the integration of different morphing concepts in a wing-tip prototype. As
widely demonstrated in recent European projects such as Clean Sky JTI and SARISTU, wing trailing edge morphing
may lead to significant drag reduction (up to 6%) in off-design flight points by adapting chord-wise camber
variations in cruise to compensate A/C weight reduction following fuel consumption. Those researches focused on
the flap region as the most immediate solution to implement structural adaptations. However, there is also a growing
interest in extending morphing functionalities to the aileron region preserving its main functionality in controlling
aircraft directional stability. In fact, the external region of the wing seems to be the most effective in producing “lift
over drag” improvements by morphing. Thus, the objective of the presented research is to achieve a certain drag
reduction in off-design flight points by adapting wing shape and lift distribution following static deflections. In
perspective, the developed device could also be used as a load alleviation system to reduce gust effects, augmenting
its frequency bandwidth. In this paper, the preliminary design of the adaptive aileron is first presented, assessed on
the base of the external aerodynamic loads. The primary structure is made of 5 segmented ribs, distributed along 4
bays, each splitted into three consecutive parts, connected with spanwise stringers. The aileron shape modification is
then implemented by means of an actuation system, based on a classical quick-return mechanism, opportunely
suited for the presented application. Finite element analyses were assessed for properly sizing the load-bearing
structure and actuation systems and for characterizing their dynamic behavior. Obtained results are reported and